Science.gov

Sample records for light transport-heat diffusion

  1. Coupled light transport-heat diffusion model for laser dosimetry with dynamic optical properties

    SciTech Connect

    London, R.A.; Glinsky, M.E.; Zimmerman, G.B.; Eder, D.C.; Jacques, S.L.

    1995-03-01

    The effect of dynamic optical properties on the spatial distribution of light in laser therapy is studied via numerical simulations. A two-dimensional, time dependent computer program called LATIS is used. Laser light transport is simulated with a Monte Carlo technique including anisotropic scattering and absorption. Thermal heat transport is calculated with a finite difference algorithm. Material properties are specified on a 2-D mesh and can be arbitrary functions of space and time. Arrhenius rate equations are solved for tissue damage caused by elevated temperatures. Optical properties are functions of tissue damage, as determined by previous measurements. Results are presented for the time variation of the light distribution and damage within the tissue as the optical properties of the tissue are altered.

  2. Light diffusing fiber optic chamber

    DOEpatents

    Maitland, Duncan J.

    2002-01-01

    A light diffusion system for transmitting light to a target area. The light is transmitted in a direction from a proximal end to a distal end by an optical fiber. A diffusing chamber is operatively connected to the optical fiber for transmitting the light from the proximal end to the distal end and transmitting said light to said target area. A plug is operatively connected to the diffusing chamber for increasing the light that is transmitted to the target area.

  3. Interference of diffusive light waves.

    PubMed

    Schmitt, J M; Knüttel, A; Knutson, J R

    1992-10-01

    We examine interference effects resulting from the superposition of photon-density waves produced by coherently modulated light incident upon a turbid medium. Photon-diffusion theory is used to derive expressions for the ac magnitude and phase of the aggregate diffusive wave produced in full- and half-space volumes by two sources. Using a frequency-domain spectrometer operating at 410 MHz, we verify interference patterns predicted by the model in scattering samples having optical properties similar to those of skin tissue. Potential imaging applications of interfering diffusive waves are discussed in the context of the theoretical and experimental results.

  4. Transmitting and reflecting diffuser. [for ultraviolet light

    NASA Technical Reports Server (NTRS)

    Keafer, L. S., Jr.; Burcher, E. E.; Kopia, L. P. (Inventor)

    1973-01-01

    A near-Lambertian diffuser is described which transmits and reflects ultraviolet light. An ultraviolet grade fused silica substrate is coated with vaporized fuse silica. The coating thickness is controlled, one thickness causing ultraviolet light to diffuse and another thickness causing ultraviolet light to reflect a near Lambertian pattern.

  5. Using light transmission to watch hydrogen diffuse

    PubMed Central

    Pálsson, Gunnar K.; Bliersbach, Andreas; Wolff, Max; Zamani, Atieh; Hjörvarsson, Björgvin

    2012-01-01

    Because of its light weight and small size, hydrogen exhibits one of the fastest diffusion rates in solid materials, comparable to the diffusion rate of liquid water molecules at room temperature. The diffusion rate is determined by an intricate combination of quantum effects and dynamic interplay with the displacement of host atoms that is still only partially understood. Here we present direct observations of the spatial and temporal changes in the diffusion-induced concentration profiles in a vanadium single crystal and we show that the results represent the experimental counterpart of the full time and spatial solution of Fick's diffusion equation. We validate the approach by determining the diffusion rate of hydrogen in a single crystal vanadium (001) film, with net diffusion in the [110] direction. PMID:22692535

  6. Visual perception through the diffusion of light

    NASA Astrophysics Data System (ADS)

    Ung, Timothy

    Human perception of the visual world is limited through the homogeneity of design and the standardization of materials. After constructing a lighting apparatus made of steel and thousands of transparent thread, a small amount of light will be directed onto the apparatus and reflected and refracted multiple times, spreading light over a large area. However, visual perception of the light reflecting and refracting through the apparatus will change according to an observer's location in relation to the apparatus. Ultimately, the goal of this thesis is to engage one's perception of the visual world using properties of transparent materials to maximize the diffusion of light.

  7. Light distribution modulated diffuse reflectance spectroscopy.

    PubMed

    Huang, Pin-Yuan; Chien, Chun-Yu; Sheu, Chia-Rong; Chen, Yu-Wen; Tseng, Sheng-Hao

    2016-06-01

    Typically, a diffuse reflectance spectroscopy (DRS) system employing a continuous wave light source would need to acquire diffuse reflectances measured at multiple source-detector separations for determining the absorption and reduced scattering coefficients of turbid samples. This results in a multi-fiber probe structure and an indefinite probing depth. Here we present a novel DRS method that can utilize a few diffuse reflectances measured at one source-detector separation for recovering the optical properties of samples. The core of innovation is a liquid crystal (LC) cell whose scattering property can be modulated by the bias voltage. By placing the LC cell between the light source and the sample, the spatial distribution of light in the sample can be varied as the scattering property of the LC cell modulated by the bias voltage, and this would induce intensity variation of the collected diffuse reflectance. From a series of Monte Carlo simulations and phantom measurements, we found that this new light distribution modulated DRS (LDM DRS) system was capable of accurately recover the absorption and scattering coefficients of turbid samples and its probing depth only varied by less than 3% over the full bias voltage variation range. Our results suggest that this LDM DRS platform could be developed to various low-cost, efficient, and compact systems for in-vivo superficial tissue investigation. PMID:27375931

  8. Light distribution modulated diffuse reflectance spectroscopy

    PubMed Central

    Huang, Pin-Yuan; Chien, Chun-Yu; Sheu, Chia-Rong; Chen, Yu-Wen; Tseng, Sheng-Hao

    2016-01-01

    Typically, a diffuse reflectance spectroscopy (DRS) system employing a continuous wave light source would need to acquire diffuse reflectances measured at multiple source-detector separations for determining the absorption and reduced scattering coefficients of turbid samples. This results in a multi-fiber probe structure and an indefinite probing depth. Here we present a novel DRS method that can utilize a few diffuse reflectances measured at one source-detector separation for recovering the optical properties of samples. The core of innovation is a liquid crystal (LC) cell whose scattering property can be modulated by the bias voltage. By placing the LC cell between the light source and the sample, the spatial distribution of light in the sample can be varied as the scattering property of the LC cell modulated by the bias voltage, and this would induce intensity variation of the collected diffuse reflectance. From a series of Monte Carlo simulations and phantom measurements, we found that this new light distribution modulated DRS (LDM DRS) system was capable of accurately recover the absorption and scattering coefficients of turbid samples and its probing depth only varied by less than 3% over the full bias voltage variation range. Our results suggest that this LDM DRS platform could be developed to various low-cost, efficient, and compact systems for in-vivo superficial tissue investigation. PMID:27375931

  9. Far-ultraviolet diffuse galactic light

    NASA Technical Reports Server (NTRS)

    Henry, R. C.

    1981-01-01

    Diffuse galactic light is detected at very low galactic latitudes, and useful upper limits are obtained at moderate and high galactic latitudes. Together, these data indicate that the albedo of the interstellar grains is high (a greater than 0.5) and that the grains very strongly (g greater than 0.7) forward-scatter far-ultraviolet radiation.

  10. Quasiparticle Diffusion in CRESST Light Detectors

    NASA Astrophysics Data System (ADS)

    Angloher, G.; Bauer, P.; Ferreiro, N.; Hauff, D.; Tanzke, A.; Strauss, R.; Kiefer, M.; Petricia, F.; Reindl, F.; Seidel, W.; Pröbst, F.; Wüstrich, M.

    2016-07-01

    CRESST-II is a direct dark matter experiment that uses scintillating calorimeters to detect WIMP-induced nuclear scatter processes. Heat and light signals are read out with tungsten transition edge sensors (TESs) that are optimized toward their sensitivity to non-thermal phonons. The usage of superconducting thin film structures (e.g., aluminum) serving as phonon collectors to increase the collection area for this signal component is an approach to improve the sensitivity of the TES. The performance of the phonon collectors depends on the material properties and the quality achieved in the production process. We optimized the size of the phonon collectors for the given quality of CRESST-II light detectors. The diffusion lengths measured in this work are mathcal {O}(1 mm) and show a strong correlation to the Residual Resistivity Ratio of the respective films. First tests of CRESST-II light detectors with larger as well as thicker phonon collectors individually show improvements in the measured pulse height of 30 %.

  11. Do epidermal lens cells facilitate the absorptance of diffuse light?

    PubMed

    Brodersen, Craig R; Vogelmann, Thomas C

    2007-07-01

    Many understory plants rely on diffuse light for photosynthesis because direct light is usually scattered by upper canopy layers before it strikes the forest floor. There is a considerable gap in the literature concerning the interaction of direct and diffuse light with leaves. Some understory plants have well-developed lens-shaped epidermal cells, which have long been thought to increase the absorption of diffuse light. To assess the role of epidermal cell shape in capturing direct vs. diffuse light, we measured leaf reflectance and transmittance with an integrating sphere system using leaves with flat (Begonia erythrophylla, Citrus reticulata, and Ficus benjamina) and lens-shaped epidermal cells (B. bowerae, Colocasia esculenta, and Impatiens velvetea). In all species examined, more light was absorbed when leaves were irradiated with direct as opposed to diffuse light. When leaves were irradiated with diffuse light, more light was transmitted and more was reflected in both leaf types, resulting in absorptance values 2-3% lower than in leaves irradiated with direct light. These data suggest that lens-shaped epidermal cells do not aid the capture of diffuse light. Palisade and mesophyll cell anatomy and leaf thickness appear to have more influence in the capture and absorption of light than does epidermal cell shape.

  12. The Impact of Diffuse Light on Terrestrial Carbon Uptake

    NASA Astrophysics Data System (ADS)

    Cheng, S. J.; Bohrer, G.; Steiner, A. L.; Nadelhoffer, K. J.; Fotis, A.

    2013-12-01

    Clouds and aerosols influence the strength of the terrestrial carbon sink by changing environmental conditions that control rates of photosynthesis and ecosystem gross primary productivity (GPP). Although clouds and aerosols can reduce GPP by lowering the amount of light entering ecosystems, they also create scattered, diffuse light that can penetrate deeper into plant canopies. This can potentially increase lower-canopy light absorption and photosynthesis, sometimes enough to compensate for any decreases in upper canopy photosynthesis under reduced light levels. To identify how strongly diffuse light influences ecosystem GPP, we analyze the relationship between diffuse light and GPP at Ameriflux sites with at least 3 years of diffuse photosynthetically active radiation (PAR) and GPP data. We also compare the effects of diffuse light across deciduous broadleaf forests, mixed forests, croplands, and grasslands. Preliminary results show a positive relationship between diffuse PAR and GPP, with the magnitude of the relationship dependent on zenith angle and vegetation type. The relationship remains positive for low zenith angles after taking into account the effect of direct light availability on GPP. Additionally, we use NASA Moderate Resolution Imaging Spectroradiometer (MODIS) data to analyze how the diffuse light effect on GPP changes under high cloud and aerosol optical depths. Quantifying the effects of diffuse light on GPP for different ecosystem types and determining how they change under different atmospheric conditions will expand our understanding of how changing cloud and aerosol conditions may alter local ecosystem carbon cycling and the magnitude of the terrestrial carbon sink.

  13. Use of diffusive optical fibers for plant lighting

    NASA Technical Reports Server (NTRS)

    Kozai, T.; Kitaya, Y.; Fujiwara, K.; Kino, S.; Kinowaki, M.

    1994-01-01

    Lighting is one of the most critical aspects in plant production and environmental research with plants. Much research has been repeated on the effect of light intensity, spectral distribution of light and lighting cycle, but comparatively little research done on the effect of lighting direction on the growth, development and morphology of plants. When plants are grown with lamps above, light is directed downward to the plants. Downward or overhead lighting is utilized in almost all cases. However, downward lighting does not always give the best result in terms of lighting efficiency, growth, development and morphology of plants. In the present study, a sideward lighting system was developed using diffusive optical fiber belts. More higher quality tissue-cultured transplants could be produced in a reduced space with the sideward lighting system than with a downward lighting system. An application of the sideward lighting system using diffusive optical fiber belts is described and the advantages and disadvantages are discussed.

  14. Diffuse Reflection of Laser Light From Clouds

    NASA Technical Reports Server (NTRS)

    Cahalan, R. F.; Davis, A.; McGill, M.

    1999-01-01

    Laser light reflected from an aqueous suspension of particles or "cloud" with known thickness and particle size distribution defines the "cloud radiative Green's function", G. G is sensitive to cloud thickness, allowing retrieval of that important quantity. We describe a laboratory simulation of G, useful in design of an offbeam Lidar instrument for remote sensing of cloud thickness. Clouds of polystyrene microspheres suspended in water are analogous to real clouds of water droplets suspended in air. The size distribution extends from 0.5 microns to 25 microns, roughly lognormal, similar to real clouds. Density of suspended spheres is adjusted so photon mean-free-path is about 10 cm, 1000 times smaller than in real clouds. The light source is a Nd:YAG laser at 530 nm. Detectors are flux and photon-counting PMTs, with a glass probe for precise positioning. A Labview 5 VI controls position and data acquisition, via an NI Motion Control board connected to a stepper motor driving an Edmund linear slider,and a 16-channel 16-bit NI-DAQ board. The stepper motor is accurate to 10 microns. Step size is selectable. Far from the beam, the rate of exponential increase in the beam direction scales as expected from diffusion theory, linearly with cloud thickness, and inversely as the square root of the reduced optical thickness, independent of particle size. Nearer the beam the signal increases faster than exponential and depends on particle size. Results verify 3D Monte Carlo simulations that demonstrate detectability of remotely sensed offbeam returns, without filters at night, with narrow bandpass filter in day.

  15. Invisibility cloaking in the diffusive-light limit (presentation video)

    NASA Astrophysics Data System (ADS)

    Schittny, Robert; Kadic, Muamer; Wegener, Martin

    2014-09-01

    Albert Einstein's theory of relativity imposes stringent limitations to making macroscopic objects invisible with respect to electromagnetic light waves propagating in vacuum. These limitations are not relevant though for propagation of light in diffusive media like fog or milk because the effective energy speed is significantly lower than in vacuum due to multiple scattering events. Here, by exploiting the close mathematical analogy between the electrostatic or near-field limit of optics on the one hand and light diffusion on the other hand, we design, fabricate, and characterize simple core-shell cloaking structures for diffusive light propagation in cylindrical and spherical geometry.

  16. Diffuse optical light in galaxy clusters

    NASA Astrophysics Data System (ADS)

    Krick, Jessica E.

    We have measured the flux, profile, color, and substructure in the diffuse intracluster light (ICL) in a sample of ten galaxy clusters that have varying mass, morphology, redshift, and density. Deep, wide-field observations for this project were made in two bands at the one meter Swope and 2.5 meter du Pont telescope at Las Campanas Observatory. Careful attention in reduction and analysis was paid to the illumination correction, background subtraction, point spread function determination, galaxy subtraction, and ICL flux determination. ICL flux is detected in both r - and either B - or V - band in all ten clusters ranging from 7.6 × 10 10 to 7.0 × 10 11 [Special characters omitted.] in r - and 1.4 × 10 10 to 1.2 × 10 11 [Special characters omitted.] in the B -band. These fluxes account for 6 to 22% of the total cluster light within one quarter of the virial radius in r - and 4 to 21% in the B - band. ICL B - r colors range from 1.49 to 2.75 when k and evolution corrected to the present epoch. ICL profiles extend to 28-29 mag arcsec -2 and radii up to 600 [Special characters omitted.] kpc, and are well fit by exponential, deVaucouleurs, and Hubble Reynolds profiles (substitute for an NFW density profile). Low surface brightness features are present in the clusters as evidence of ongoing tidal interactions. We find that the ICL forms in group environments and remains with those groups as they are in-falling into the cluster environment. Our sample, having been selected from the Abell sample, is incomplete. The sample does not include high redshift clusters with low density, low flux, or low mass, and it does not include low redshift clusters with high flux, mass, or density. Given this selection bias between ICL properties and cluster properties we do find that the presence of a cD galaxy corresponds to both centrally concentrated galaxy profiles and centrally concentrated ICL profiles. This is consistent with ICL either forming from galaxy interactions at the

  17. Diffusion filter eliminates fringe effects of coherent laser light source

    NASA Technical Reports Server (NTRS)

    Olsasky, M. J.

    1970-01-01

    Diffusion filter comprised of small particles in colloidal suspension reduces the coherence of a laser beam used as a photographic light source. Interference patterns which obscure details in photographic film are eliminated, the intensity and collimation are moderately affected.

  18. Control of light diffusion in a disordered photonic waveguide

    SciTech Connect

    Sarma, Raktim; Cao, Hui; Golubev, Timofey; Yamilov, Alexey

    2014-07-28

    We control the diffusion of light in a disordered photonic waveguide by modulating the waveguide geometry. In a single waveguide of varying cross-section, the diffusion coefficient changes spatially in two dimensions due to localization effects. The intensity distribution inside the waveguide agrees with the prediction of the self-consistent theory of localization. Our work shows that wave diffusion can be efficiently manipulated without modifying the structural disorder.

  19. Light shaping diffusers{trademark} improve aircraft inspection

    SciTech Connect

    Shagam, R.N.; Shie, R.; Lerner, J.

    1994-11-01

    Physical Optical Corporation has introduced a Light Shaping Diffuser{trademark} (LSD) for the specialized illumination requirements of aircraft inspection. Attached to a handheld, battery-powered flashlight, this light-weight, holographic diffuser element provides bright, even illumination as aircraft inspectors perform the important task of visually examining aircraft for possible structural defects. Field trials conducted by the Aging Aircraft Program at Sandia National Laboratories confirm that the LSD-equipped flashlights are preferred by visual inspectors over stock flashlights.

  20. System for diffusing light from an optical fiber or light guide

    DOEpatents

    Maitland, Duncan J [Pleasant Hill, CA; Wilson, Thomas S [San Leandro, CA; Benett, William J [Livermore, CA; Small, IV, Ward [

    2008-06-10

    A system for diffusing light from an optical fiber wherein the optical fiber is coupled to a light source, comprising forming a polymer element adapted to be connected to the optical fiber and incorporating a scattering element with the polymer element wherein the scattering element diffuses the light from the polymer element. The apparatus of the present invention comprises a polymer element operatively connected to the optical fiber and a scattering element operatively connected with the shape polymer element that diffuses the light from the polymer element.

  1. Novel light diffusing fiber for use in medical applications

    NASA Astrophysics Data System (ADS)

    Klubben, W. Spencer; Logunov, Stephan L.; Fewkes, Edward J.; Mooney, Jeff; Then, Paul M.; Wigley, Peter G.; Schreiber, Horst; Matias, Kaitlyn; Wilson, Cynthia J.; Ocampo, Manuela

    2016-03-01

    Fiber-based cylindrical light diffusers are often used in photodynamic therapy to illuminate a luminal organ, such as the esophagus. The diffusers are often made of plastic and suffer from short diffusion lengths and low transmission efficiencies over a broad spectrum. We have developed FibranceTM, a glass-based fiber optic cylindrical diffuser which can illuminate a fiber from 0.5 cm to 10 meters over a broad wavelength range. With these longer illumination lengths, a variety of other medical applications are possible beyond photodynamic therapy. We present a number of applications for Fibrance ranging from in situ controllable illumination for Photodynamic Therapy to light guided anatomy highlighting for minimally invasive surgery to mitigating hospital acquired infections and more.

  2. Light diffusion in quenched disorder: role of step correlations.

    PubMed

    Svensson, Tomas; Vynck, Kevin; Adolfsson, Erik; Farina, Andrea; Pifferi, Antonio; Wiersma, Diederik S

    2014-02-01

    We present a theoretical and experimental study of light transport in disordered media with strongly heterogeneous distribution of scatterers formed via nonscattering regions. Step correlations induced by quenched disorder are found to prevent diffusivity from diverging with increasing heterogeneity scale, contrary to expectations from annealed models. Spectral diffusivity is measured for a porous ceramic where nanopores act as scatterers and macropores render their distribution heterogeneous. Results agree well with Monte Carlo simulations and a proposed analytical model.

  3. Diffusion of light in two-dimensional granular materials

    NASA Astrophysics Data System (ADS)

    Sadjadi, Zeinab; Miri, MirFaez

    2013-06-01

    We study diffusive light transport in a two dimensional packing of monodisperse disks. Ray optics approximation is employed to follow a light beam or photon as it is transmitted or reflected by the grains. We present an analytic expression for the transport-mean-free path based on persistent random walk of photons in a packing of disks and express the diffusion constant of photons in terms of the refractive indices of grains and host medium, grain diameter, and packing fraction. Our analytical results are examined with numerical simulations. The derived results are beneficial for better understanding of the dynamics of granular systems.

  4. LLNL SMP Light Diffuser Fabrication and Preliminary Data

    SciTech Connect

    Small IV, W

    2006-06-02

    We are developing a cylindrical light diffuser using shape memory polymer (SMP) whose diameter, length, stiffness, and diffusion profile can be tailored to suit a particular application. The cylindrical SMP diffuser is made by casting SMP around the end of a glass optical fiber using a teflon tube as the casting mold, and abrading the cured SMP surface to cause the light to leak radially outward. The inner diameter of the casting tube is slightly larger than the fiber diameter. A smaller teflon tube is positioned over the fiber (between the fiber and the casting tube) to approximately center the fiber tip in the casting tube. As the SMP cures, it bonds with the optical fiber, creating a strong joint without the need for additional adhesives or mechanical fixtures. A close-up of the SMP-fiber joint and the finished SMP diffuser are shown in Fig.1. The SMP formulation (developed in-house) was specifically designed to be optically transparent in the visible and near-infrared regions; the spectral absorption of the SMP is shown in Fig. 2. The low absorption is important because (1) it allows the light to travel the length of the diffuser without suffering excessive loss due to absorption and (2) it permits delivery of up to 7 W (300 {micro}m SMP rod on 100 {micro}m core multimode fiber) of laser power into the diffuser without damaging the diffuser. SMP is a good wave guiding material with a refractive index of approximately 1.5. Also, the SMP stiffness can be tailored from stiff (e.g. acrylic, Ea {approx} 10{sup 9} Pa) to very flexible (e.g. silicon rubber, Ea {approx} 10{sup 6} Pa). Finally, since SMP can self-actuate, the SMP diffuser could be designed to actuate into a shape other than a straight rod (e.g. 2D or 3D coil).

  5. Calculating model of light transmission efficiency of diffusers attached to a lighting cavity.

    PubMed

    Sun, Ching-Cherng; Chien, Wei-Ting; Moreno, Ivan; Hsieh, Chih-To; Lin, Mo-Cha; Hsiao, Shu-Li; Lee, Xuan-Hao

    2010-03-15

    A lighting cavity is a reflecting box with light sources inside. Its exit side is covered with a diffuser plate to mix and distribute light, which addresses a key issue of luminaires, display backlights, and other illumination systems. We derive a simple but precise formula for the optical efficiency of diffuser plates attached to a light cavity. We overcome the complexity of the scattering theory and the difficulty of the multiple calculations involved, by carrying out the calculation with a single ray of light that statistically represents all the scattered rays. We constructed and tested several optical cavities using light-emitting diodes, bulk-scattering diffusers, white scatter sheets, and silver coatings. All measurements are in good agreement with predictions from our optical model.

  6. Sol-Gel Glass Holographic Light-Shaping Diffusers

    NASA Technical Reports Server (NTRS)

    Yu, Kevin; Lee, Kang; Savant, Gajendra; Yin, Khin Swe (Lillian)

    2005-01-01

    Holographic glass light-shaping diffusers (GLSDs) are optical components for use in special-purpose illumination systems (see figure). When properly positioned with respect to lamps and areas to be illuminated, holographic GLSDs efficiently channel light from the lamps onto specified areas with specified distributions of illumination for example, uniform or nearly uniform irradiance can be concentrated with intensity confined to a peak a few degrees wide about normal incidence, over a circular or elliptical area. Holographic light diffusers were developed during the 1990s. The development of the present holographic GLSDs extends the prior development to incorporate sol-gel optical glass. To fabricate a holographic GLSD, one records a hologram on a sol-gel silica film formulated specially for this purpose. The hologram is a quasi-random, micro-sculpted pattern of smoothly varying changes in the index of refraction of the glass. The structures in this pattern act as an array of numerous miniature lenses that refract light passing through the GLSD, such that the transmitted light beam exhibits a precisely tailored energy distribution. In comparison with other light diffusers, holographic GLSDs function with remarkably high efficiency: they typically transmit 90 percent or more of the incident lamp light onto the designated areas. In addition, they can withstand temperatures in excess of 1,000 C. These characteristics make holographic GLSDs attractive for use in diverse lighting applications that involve high temperatures and/or requirements for high transmission efficiency for ultraviolet, visible, and near-infrared light. Examples include projectors, automobile headlights, aircraft landing lights, high-power laser illuminators, and industrial and scientific illuminators.

  7. Diffuse galactic light in the 1500-4200 angstrom region

    NASA Technical Reports Server (NTRS)

    Witt, A. N.; Lillie, C. F.

    1972-01-01

    Diffuse galactic light has been observed with the four stellar photometers of the OAO-2 in 29 of Kapteyn's selected areas. The data can be understood in terms of a wavelength dependent albedo of the interstellar grains with a pronounced minimum around 2200 A with a rapid increase towards unity at wavelengths below 2000 A.

  8. Diffuse galactic light observations at 206 selected areas.

    NASA Astrophysics Data System (ADS)

    Toller, G. N.

    1989-12-01

    Space-based, observational diffuse galactic light (DGL) levels at 4400 Å are presented as a function of galactic latitude. The results presented here have been used to characterize the interstellar dust in the general interstellar medium. A galaxy model that reproduces observed brightness levels was used to compare theoretical and observed DGL values.

  9. New design of textile light diffusers for photodynamic therapy.

    PubMed

    Cochrane, Cédric; Mordon, Serge R; Lesage, Jean Claude; Koncar, Vladan

    2013-04-01

    A homogeneous and reproducible fluence delivery rate during clinical photodynamic therapy (PDT) plays a determinant role in preventing under- or overtreatment. PDT applied in dermatology has been carried out with a wide variety of light sources delivering a broad range of more or less adapted light doses. Due to the complexities of the human anatomy, these light sources do not in fact deliver a uniform light distribution to the skin. Therefore, the development of flexible light sources would considerably improve the homogeneity of light delivery. The integration of plastic optical fiber (POF) into textile structures could offer an interesting alternative. In this article, a textile light diffuser (TLD) has been developed using POF and Polyester yarns. Predetermined POF macrobending leads to side emission of light when the critical angle is exceeded. Therefore, a specific pattern based on different satin weaves has been developed in order to improve light emission homogeneity and to correct the decrease of side emitted radiation intensity along POF. The prototyped fabrics (approximately 100 cm(2): 5×20 cm) were woven using a hand loom, then both ends of the POF were coupled to a laser diode (5 W, 635 nm). The fluence rate (mW/ cm(2)) and the homogeneity of light delivery by the TLD were evaluated. Temperature evolution, as a function of time, was controlled with an infrared thermographic camera. When using a power source of 5 W, the fluence rate of the TLD was 18±2.5 mw/cm(2). Due to the high efficiency of the TLD, the optical losses were very low. The TLD temperature elevation was 0.6 °C after 10 min of illumination. Our TLD meets the basic requirements for PDT: homogeneous light distribution and flexibility. It also proves that large (500 cm(2)) textile light diffusers adapted to skin, but also to peritoneal or pleural cavity, PDTs can be easily produced by textile manufacturing processes.

  10. Light scattering and optical diffusion from willemite spherulites

    NASA Astrophysics Data System (ADS)

    Knowles, Kevin M.; Butt, Haider; Batal, Afif; Sabouri, Aydin; Anthony, Carl J.

    2016-02-01

    Willemite is a zinc silicate mineral used in modern day pottery as a decorative feature within glazes. It is produced by controlled heat treatment of zinc oxide-containing ceramic glazes. The heat-treated glazes devitrify, producing thin nanoscale needle-like willemite crystals growing in spherulitic morphologies through branching of the needles. We show here that this resulting morphology of willemite crystals in an inorganic glass matrix has a previously unreported strong interaction with light, displaying remarkable optical diffraction patterns. Thin sections of such spherulites act as optical diffusers, enabling light beams to be spread up to 160° in width. Analysis of the interaction between the willemite spherulites and light suggests that the high density of willemite crystals in the spherulites and the length scales associated with both the thickness of the needles and the spacings between branches are together responsible for this optical diffusion behaviour.

  11. Spectroscopy and Imaging of Tissues with Diffusing Light

    NASA Astrophysics Data System (ADS)

    Yodh, Arjun

    2000-06-01

    Optical methods offer a range of spectoscopies useful for characterization of a wide variety of samples. The optical spectroscopies are rigorous, and work well in simple, homogenous, optically thin samples. Unfortunately many practical materials are not so simple. Human tissues, for example, are highly scattering media. Light penetration in tissues is limited, and generally the effects of tissue absorption and internal motion must be separated from the effects of tissue scattering. Nevertheless, the use of light to investigate the human body interior has grown enormously in recent years, in part as a result in advances in our fundamental understanding about light transport in highly scattering materials, and in part as a result of technological innovations in optics [1]. Using examples from my laboratory I will discuss the basic physical ideas that underly diffusing light probes, as well as some of their applications. [1] See for example, Spectroscopy and Imaging with Diffusing Light (Arjun Yodh and Britton Chance), Physics Today, Volume 48, No. 3, 34-40 (1995).

  12. Morphologic tomography of nonspherical particles using multispectral diffusing light measurements

    PubMed Central

    Hajihashemi, Mohammad Reza; Li, Xiaoqi; Jiang, Huabei

    2011-01-01

    A series of phantom experiments are conducted to demonstrate the ability of a T-matrix–based inverse algorithm for tomographic recovery of morphologic characteristics of nonspherical particles embedded in heterogeneous turbid media. Diffusely scattered light at several wavelengths along the boundary of the phantom are collected and analyzed to allow for simultaneous extraction of the size, concentration, and aspect ratio of the spheroidal particles. PMID:22112119

  13. Diffuse Galactic light at high Galactic latitude: nature and interpretation

    NASA Astrophysics Data System (ADS)

    Zagury, Frédéric

    2006-08-01

    The hypothesis of an extended red emission (ERE) in diffuse Galactic light (DGL) has been put forward in 1998 by Gordon, Witt & Friedmann who found that scattered starlight was not enough to explain the amount of DGL in the R band, in some high Galactic latitude directions. This paper re-investigates, for high Galactic latitudes, the brightnesses and colours of DGL, integrated star and galaxy light (ISGL), and of the total extrasolar light (ISGL+DGL) measured by Pioneer. Under the traditional assumption that DGL is forward scattering of background starlight by interstellar dust on the line of sight, ISGL and Pioneer have very close colours, as it is found by Gordon, Witt & Friedmann. Pioneer observations at high |b| thus accept an alternative and simple interpretation, with no involvement of ERE in DGL.

  14. Trap-controlled hydrogen diffusion and the mechanism of light-enhanced diffusion in a-Si:H

    NASA Astrophysics Data System (ADS)

    Branz, Howard M.; Asher, Sally E.; Nelson, Brent P.

    1992-12-01

    We review our recent high-depth-resolution secondary ion mass spectrometry studies of hydrogen diffusion in amorphous silicon. We describe the trap-controlled H diffusion model supported by the experiments. Recent results on light enhancement of H diffusion in a-Si:H are also discussed.

  15. Light Diffusion in the Tropical Dry Forest of Costa Rica

    NASA Astrophysics Data System (ADS)

    Calvo-Rodriguez, S.; Sanchez-Azofeifa, G. A.

    2016-06-01

    Leaf Area Index (LAI) has been defined as the total leaf area (one-sided) in relation to the ground. LAI has an impact on tree growth and recruitment through the interception of light, which in turn affects primary productivity. Even though many instruments exist for estimating LAI from ground, they are often laborious and costly to run continuously. Measurements of LAI from the field using traditional sensors (e.g., LAI-2000) require multiple visits to the field under very specific sky conditions, making them unsuitable to operate in inaccessible areas and forests with dense vegetation, as well as areas where persistent sunny conditions are the norm like tropical dry forests. With this context, we proposed a methodology to characterize light diffusion based on NDVI and LAI measurements taken from the field in two successional stages in the tropical dry forest of Santa Rosa National Park in Costa Rica. We estimate a "K" coefficient to characterize light diffusion by the canopy, based on field NDVI measurements derived from optical phenology instruments and MODIS NDVI. From the coefficients determined, we estimated LAI values and compared them with ground measurements of LAI. In both successional stages ground measurements of LAI had no significant difference to the tower-derived LAI and the estimated LAI from MODIS NDVI.

  16. Diffuse optical imaging of the breast using structured-light

    NASA Astrophysics Data System (ADS)

    Kwong, Jessica; Nouizi, Farouk; Cho, Jaedu; Zheng, Jie; Li, Yifan; Chen, Jeon-hor; Su, Min-Ying; Gulsen, Gultekin

    2015-03-01

    Diffuse optical imaging with structured-light illumination and detection can provide rapid, wide-field anatomical and functional imaging of the breast with an application for breast cancer screening. Our aims for this study were to test the feasibility of structured-light, test our pattern set, and develop and optimize our image reconstruction algorithm. For our phantom studies, we created an agar phantom with dimensions similar to a compressed breast. A cubic inclusion of 30mm by 30mm by 25mm with twice the amount of absorption contrast than the background was placed at the center. Near-infrared light of eleven patterns including a full illumination and single stripes was illuminated onto the breast phantom and detected with a CCD camera, with integration of the signals according to the patterns performed post-data acquisition, with a total of 121 measurements. These measurements were then used in our reconstruction algorithm that iteratively minimized the difference between the collected data and the estimation from our FEM-based forward model of photon diffusion to calculate the absorption values. Reconstructions of the 3D absorption maps detect an inclusion at the center and indicate that our selected set of patterns may be sufficient for structured-light imaging. We are currently improving our instrumentation and testing with additional phantom studies, while also performing simulations of numerical breast phantoms created from MR images to test structured-light's ability to image complex and realistic breast tissue composition. We hope to use this technique as optical method to image molecular markers, such as hemoglobin, water and lipid, within the breast.

  17. Specular, diffuse, and polarized light scattered by two wheat canopies

    NASA Technical Reports Server (NTRS)

    Vanderbilt, V. C.; Grant, L.; Biehl, L. L.; Robinson, B. F.

    1985-01-01

    Using polarization measurements, the reflectance factor of two wheat canopies is divided into components due to specularly and diffusely reflected light. The data show that two key angles may be predicted, the angle of the polarizer for minimum flux and the angle of incidence of sunlight specularly reflected by a leaf to a sensor. The results show that specular reflection is a key aspect to radiation transfer by two canopies. Results suggest that the advent of heading in wheat may be remotely sensed from polarization measurements of the canopy reflectance.

  18. Double-layer anisotropic light diffusion films fabricated using a two-step UV curing technique

    NASA Astrophysics Data System (ADS)

    Kusama, Kentaro; Ishinabe, Takahiro; Katagiri, Baku; Orui, Tomoo; Shoshi, Satoru; Fujikake, Hideo

    2016-04-01

    We developed a novel light diffusion film with a double diffusion layer structure for high reflectivity and a wide diffusion angle range. We demonstrated that the internal layer structure of the light diffusion film is controlled by the diffusion angle of the ultraviolet (UV) light used for photopolymerization. We successfully fabricated two different diffusion layers in a single polymer film using a two-step UV curing process and achieved a wide diffusion angle range and high reflectivity normal to the film surface. Our light diffusion film can control the distribution of diffused light, and should contribute to the development of future low-power reflective displays with high reflectivity similar to the white paper.

  19. Diffuse light tomography to detect blood vessels using Tikhonov regularization

    NASA Astrophysics Data System (ADS)

    Kazanci, Huseyin O.; Jacques, Steven L.

    2016-04-01

    Detection of blood vessels within light-scattering tissues involves detection of subtle shadows as blood absorbs light. These shadows are diffuse but measurable by a set of source-detector pairs in a spatial array of sources and detectors on the tissue surface. The measured shadows can reconstruct the internal position(s) of blood vessels. The tomographic method involves a set of Ns sources and Nd detectors such that Nsd = Ns x Nd source-detector pairs produce Nsd measurements, each interrogating the tissue with a unique perspective, i.e., a unique region of sensitivity to voxels within the tissue. This tutorial report describes the reconstruction of the image of a blood vessel within a soft tissue based on such source-detector measurements, by solving a matrix equation using Tikhonov regularization. This is not a novel contribution, but rather a simple introduction to a well-known method, demonstrating its use in mapping blood perfusion.

  20. The Photosynthetic Trade-off Between Direct and Diffuse Light, the Problem with Diffuse Fraction and a Proposed Solution.

    NASA Astrophysics Data System (ADS)

    Stine, A.; Swann, A. L. S.; Huybers, P. J.

    2014-12-01

    Increases in atmospheric scatterers change the light environment at the surface both by decreasing total solar illumination and by converting direct radiation to diffuse radiation. In general, diffuse light is more efficient at driving photosynthesis than direct light, leading to disagreements in the net effect of changes in scattering on terrestrial photosynthesis, particularly in the context of large explosive volcanic eruptions. Standard analytical approaches for treating the trade-off between direct and diffuse radiation compare the changes in light against the fraction of light which is diffuse. Here we show that use of diffuse fraction as the independent variable in light trade-off calculations leads to results that are generally biased because the dependent variable (be it direct, diffuse or total radiation) functionally covaries with the independent variable, irrespective of the physical relationship between direct and diffuse radiation. This bias appears to dominate the results of published calculations. We develop a new method for quantifying the trade-off between direct and diffuse radiation on photosynthesis that is not subject to this artifact and demonstrate its use at four Atmospheric Radiation Measurement (ARM) sites.

  1. Advantages of diffuse light for horticultural production and perspectives for further research

    PubMed Central

    Li, Tao; Yang, Qichang

    2015-01-01

    Plants use diffuse light more efficiently than direct light, which is well established due to diffuse light penetrates deeper into the canopy and photosynthetic rate of a single leaf shows a non-linear response to the light flux density. Diffuse light also results in a more even horizontal and temporal light distribution in the canopy, which plays substantial role for crop photosynthesis enhancement as well as production improvement. Here we show some of the recent findings about the effect of diffuse light on light distribution over the canopy and its direct and indirect effects on crop photosynthesis and plant growth, and suggest some perspectives for further research which could strengthen the scientific understanding of diffuse light modulate plant processes and its application in horticultural production. PMID:26388890

  2. Diffuse optical imaging using spatially and temporally modulated light

    PubMed Central

    O’Sullivan, Thomas D.; Cerussi, Albert E.; Cuccia, David J.

    2012-01-01

    Abstract. The authors describe the development of diffuse optical imaging (DOI) technologies, specifically the use of spatial and temporal modulation to control near infrared light propagation in thick tissues. We present theory and methods of DOI focusing on model-based techniques for quantitative, in vivo measurements of endogenous tissue absorption and scattering properties. We specifically emphasize the common conceptual framework of the scalar photon density wave for both temporal and spatial frequency-domain approaches. After presenting the history, theoretical foundation, and instrumentation related to these methods, we provide a brief review of clinical and preclinical applications from our research as well as our outlook on the future of DOI technology. PMID:22894472

  3. Diffusing light photography of solitons and capillary-wave turbulence

    SciTech Connect

    Wright, W.; Budak, R.; Putterman, S. )

    1994-11-01

    The attenuation of light propagating through a slab of water (containing a dilute concentration of polyballs) is approximately proportional to its thickness. Application of this insight to the local elevation of a fluid surface has enabled us to use photography to determine the instantaneous global topography of the surface of a fluid in motion. Use of diffusing light enables us to obtain images that are free of the caustics which plague shadowgraphs. Applications include breather solitons and wave turbulence which results from the nonlinear interaction of a broadband spectrum of high amplitude surface ripples. Measurements indicate that as the amplitude of excitation of the surface of water is increased the wave number of the capillary motion displays a transition to a broadband spectrum. The temporal response of a single pixel yields the power spectrum of the surface height as a function of frequency [ital f].'' The numerous harmonics which can be seen at low amplitude merge at high amplitude into a broadband spectrum which goes as 1/[ital f][sup 3]. This technique should permit the measurement of turbulent parameters which go beyond the purported range of current theories. [Work supported by US DOE Division of Engineering and Geophysics and NASA Microgravity.

  4. Diffuse galactic light observations at 206 selected areas

    NASA Technical Reports Server (NTRS)

    Toller, Gary N.

    1989-01-01

    Space-based, observational diffuse galactic light (DGL) levels at 4400 A are presented as a function of galactic latitude (b). A peak in the ratio of DGL to direct starlight is apparent at the absolute value of b = 5 to 15 deg, where one third of the celestial brightness is due to scattered light. Another salient feature is the general decrease in the relative contribution of the DGL at intermediate and high galactic latitudes. The relationship DGL (S sub 10(V)sub G2V, 4400 A) = 2.4 x 10 (exp -20 N(sub H I) atoms/sq cm may be used to estimate the brightness of DGL from neutral hydrogen column densities when N(sub H I) is less than 2 x 10(exp 21) atoms/sq cm. The results presented here have been used to characterize the interstellar dust in the general interstellar medium. A galaxy model that reproduces observed brightness levels was used to compare theoretical and observed DGL values. This determines two grain parameters - the albedo and the asymmetry of the scattering phase function (g). The results are albedo = .61 + or - .07, and g = .6 + or - .2.

  5. A transmitting and reflecting diffuser for ultraviolet light

    NASA Technical Reports Server (NTRS)

    Keafer, L. S., Jr.; Burcher, E. E.; Kopia, L. P.

    1972-01-01

    Fabrication of ultraviolet radiation diffusing layer in configuration that uses ultraviolet properties of fused silica condensate is discussed. Construction and operation of the device are described. Diagram of reflecting diffuser to show construction and method of operation is included.

  6. The contribution of the diffuse light component to the topographic effect on remotely sensed data

    NASA Technical Reports Server (NTRS)

    Justice, C.; Holben, B.

    1980-01-01

    The topographic effect is measured by the difference between the global radiance from inclined surfaces as a function of their orientation relative to the sensor position and light source. The short wave radiant energy incident on a surface is composed of direct sunlight, scattered skylight, and light reflected from surrounding terrain. The latter two components are commonly known as the diffuse component. The contribution of the diffuse light component to the topographic effect was examined and the significance of this diffuse component with respect to two direct radiance models was assessed. Diffuse and global spectral radiances were measured for a series of slopes and aspects of a uniform and surface in the red and photographic infrared parts of the spectrum, using a nadir pointing two channel handheld radiometer. The diffuse light was found to produce a topographic effect which varied from the topographic effect for direct light. The topographic effect caused by diffuse light was found to increase slightly with solar elevation and wavelength for the channels examined. The correlations between data derived from two simple direct radiance simulation models and the field data were not significantly affected when the diffuse component was removed from the radiances. Radiances from a 60 percent reflective surface, assuming no atmospheric path radiance, the diffuse light topographic effect contributed a maximum range of 3 pixel values in simulated LANDSAT data from all aspects with slopes up to 30 degrees.

  7. Optimal nitrogen distribution within a leaf canopy under direct and diffuse light.

    PubMed

    Hikosaka, Kouki

    2014-09-01

    Nitrogen distribution within a leaf canopy is an important determinant of canopy carbon gain. Previous theoretical studies have predicted that canopy photosynthesis is maximized when the amount of photosynthetic nitrogen is proportionally allocated to the absorbed light. However, most of such studies used a simple Beer's law for light extinction to calculate optimal distribution, and it is not known whether this holds true when direct and diffuse light are considered together. Here, using an analytical solution and model simulations, optimal nitrogen distribution is shown to be very different between models using Beer's law and direct-diffuse light. The presented results demonstrate that optimal nitrogen distribution under direct-diffuse light is steeper than that under diffuse light only. The whole-canopy carbon gain is considerably increased by optimizing nitrogen distribution compared with that in actual canopies in which nitrogen distribution is not optimized. This suggests that optimization of nitrogen distribution can be an effective target trait for improving plant productivity.

  8. Fibreoptic diffuse-light irradiators of biological tissues

    SciTech Connect

    Volkov, Vladimir V; Loshchenov, V B; Konov, Vitalii I; Kononenko, Vitalii V

    2010-10-15

    We report techniques for the fabrication of laser radiation diffusers for interstitial photodynamic therapy. Using chemical etching of the distal end of silica fibre with a core diameter of 200 - 600 {mu}m, we have obtained long (up to 40 mm) diffusers with good scattering uniformity. Laser ablation has been used to produce cylindrical diffusers with high emission contrast and a scattering uniformity no worse than {approx}10 % in their middle part. The maximum length of the diffusers produced by this method is 20 - 25 mm. (laser applications and other topics in quantum electronics)

  9. THE SPECTRUM OF THE DIFFUSE GALACTIC LIGHT: THE MILKY WAY IN SCATTERED LIGHT

    SciTech Connect

    Brandt, Timothy D.; Draine, B. T.

    2012-01-10

    We measure the optical spectrum of the diffuse Galactic light (DGL)-the local Milky Way in reflection-using 92,000 blank sky spectra from the Sloan Digital Sky Survey (SDSS). We correlate the SDSS optical intensity in regions of blank sky against 100 {mu}m intensity independently measured by the Cosmic Background Explorer and Infrared Astronomy satellites, which provides a measure of the dust column density times the intensity of illuminating starlight. The spectrum of scattered light is very blue and shows a clear 4000 A break and broad Mg b absorption. This is consistent with scattered starlight, and the continuum of the DGL is well reproduced by a simple radiative transfer model of the Galaxy. We also detect line emission in H{alpha}, H{beta}, [N II], and [S II], consistent with scattered light from the local interstellar medium. The strength of [N II] and [S II], combined with upper limits on [O III] and He I, indicates a relatively soft ionizing spectrum. We find that our measurements of the DGL can constrain dust models, favoring a grain size distribution with relatively few large grains. We also estimate the fraction of high-latitude H{alpha} which is scattered to be 19% {+-} 4%.

  10. The Spectrum of the Diffuse Galactic Light: The Milky Way in Scattered Light

    NASA Astrophysics Data System (ADS)

    Brandt, Timothy D.; Draine, B. T.

    2012-01-01

    We measure the optical spectrum of the diffuse Galactic light (DGL)—the local Milky Way in reflection—using 92,000 blank sky spectra from the Sloan Digital Sky Survey (SDSS). We correlate the SDSS optical intensity in regions of blank sky against 100 μm intensity independently measured by the Cosmic Background Explorer and Infrared Astronomy satellites, which provides a measure of the dust column density times the intensity of illuminating starlight. The spectrum of scattered light is very blue and shows a clear 4000 Å break and broad Mg b absorption. This is consistent with scattered starlight, and the continuum of the DGL is well reproduced by a simple radiative transfer model of the Galaxy. We also detect line emission in Hα, Hβ, [N II], and [S II], consistent with scattered light from the local interstellar medium. The strength of [N II] and [S II], combined with upper limits on [O III] and He I, indicates a relatively soft ionizing spectrum. We find that our measurements of the DGL can constrain dust models, favoring a grain size distribution with relatively few large grains. We also estimate the fraction of high-latitude Hα which is scattered to be 19% ± 4%.

  11. Light diffusing effects of nano and micro-structures on OLED with microcavity.

    PubMed

    Cho, Doo-Hee; Shin, Jin-Wook; Joo, Chul Woong; Lee, Jonghee; Park, Seung Koo; Moon, Jaehyun; Cho, Nam Sung; Chu, Hye Yong; Lee, Jeong-Ik

    2014-10-20

    We examined the light diffusing effects of nano and micro-structures on microcavity designed OLEDs. The results of FDTD simulations and experiments showed that the pillar shaped nano-structure was more effective than the concave micro-structure for light diffusing of microcavity OLEDs. The sharp luminance distribution of the microcavity OLED was changed to near Lambertian luminance distribution by the nano-structure, and light diffusing effects increased with the height of the nano-structure. Furthermore, the nano-structure has advantages including light extraction of the substrate mode, reproducibility of manufacturing process, and minimizing pixel blur problems in an OLED display panel. The nano-structure is a promising candidate for a light diffuser, resolving the viewing angle problems in microcavity OLEDs.

  12. Modelling the effect of diffuse light on canopy photosynthesis in controlled environments.

    PubMed

    Cavazzoni, James; Volk, Tyler; Tubiello, Francesco; Monje, Oscar

    2002-01-01

    A layered canopy model was used to analyze the effects of diffuse light on canopy gross photosynthesis in controlled environment plant growth chambers, where, in contrast to the field, highly diffuse light can occur at high irradiance. The model suggests that high diffuse light fractions (approximately 0.7) and irradiance (1400 micromoles m-2 s-1) may enhance crop life-cycle canopy gross photosynthesis for hydroponic wheat by about 20% compared to direct light at the same irradiance. Our simulations suggest that high accuracy is not needed in specifying diffuse light fractions in chambers between approximately 0.7 and 1, because simulated photosynthesis for closed canopies plateau in this range. We also examined the effect of leaf angle distribution on canopy photosynthesis under growth chamber conditions, as these distributions determine canopy extinction coefficients for direct and diffuse light. We show that the spherical leaf angle distribution is not suitable for modeling photosynthesis of planophile canopies (e.g., soybean and peanut) in growth chambers. Also, the absorption of the light reflected from the surface below the canopy should generally be included in model simulations, as the corresponding albedo values in the photosynthetically active range may be quite high in growth chambers (e.g., approximately 0.5). In addition to the modeling implications, our results suggest that diffuse light conditions should be considered when drawing conclusions from experiments in controlled environments.

  13. Modelling the effect of diffuse light on canopy photosynthesis in controlled environments

    NASA Technical Reports Server (NTRS)

    Cavazzoni, James; Volk, Tyler; Tubiello, Francesco; Monje, Oscar; Janes, H. W. (Principal Investigator)

    2002-01-01

    A layered canopy model was used to analyze the effects of diffuse light on canopy gross photosynthesis in controlled environment plant growth chambers, where, in contrast to the field, highly diffuse light can occur at high irradiance. The model suggests that high diffuse light fractions (approximately 0.7) and irradiance (1400 micromoles m-2 s-1) may enhance crop life-cycle canopy gross photosynthesis for hydroponic wheat by about 20% compared to direct light at the same irradiance. Our simulations suggest that high accuracy is not needed in specifying diffuse light fractions in chambers between approximately 0.7 and 1, because simulated photosynthesis for closed canopies plateau in this range. We also examined the effect of leaf angle distribution on canopy photosynthesis under growth chamber conditions, as these distributions determine canopy extinction coefficients for direct and diffuse light. We show that the spherical leaf angle distribution is not suitable for modeling photosynthesis of planophile canopies (e.g., soybean and peanut) in growth chambers. Also, the absorption of the light reflected from the surface below the canopy should generally be included in model simulations, as the corresponding albedo values in the photosynthetically active range may be quite high in growth chambers (e.g., approximately 0.5). In addition to the modeling implications, our results suggest that diffuse light conditions should be considered when drawing conclusions from experiments in controlled environments.

  14. Modelling the effect of diffuse light on canopy photosynthesis in controlled environments.

    PubMed

    Cavazzoni, James; Volk, Tyler; Tubiello, Francesco; Monje, Oscar

    2002-01-01

    A layered canopy model was used to analyze the effects of diffuse light on canopy gross photosynthesis in controlled environment plant growth chambers, where, in contrast to the field, highly diffuse light can occur at high irradiance. The model suggests that high diffuse light fractions (approximately 0.7) and irradiance (1400 micromoles m-2 s-1) may enhance crop life-cycle canopy gross photosynthesis for hydroponic wheat by about 20% compared to direct light at the same irradiance. Our simulations suggest that high accuracy is not needed in specifying diffuse light fractions in chambers between approximately 0.7 and 1, because simulated photosynthesis for closed canopies plateau in this range. We also examined the effect of leaf angle distribution on canopy photosynthesis under growth chamber conditions, as these distributions determine canopy extinction coefficients for direct and diffuse light. We show that the spherical leaf angle distribution is not suitable for modeling photosynthesis of planophile canopies (e.g., soybean and peanut) in growth chambers. Also, the absorption of the light reflected from the surface below the canopy should generally be included in model simulations, as the corresponding albedo values in the photosynthetically active range may be quite high in growth chambers (e.g., approximately 0.5). In addition to the modeling implications, our results suggest that diffuse light conditions should be considered when drawing conclusions from experiments in controlled environments. PMID:12882223

  15. Light-element diffusion in Mg using first-principles calculations: Anisotropy and elastodiffusion

    NASA Astrophysics Data System (ADS)

    Agarwal, Ravi; Trinkle, Dallas R.

    2016-08-01

    The light-elemental solutes B, C, N, and O can penetrate the surface of Mg alloys and diffuse during heat treatment or high temperature application, forming undesirable compounds. We investigate the diffusion of these solutes by determining their stable interstitial sites and the interpenetrating network formed by these sites. We use density functional theory (DFT) to calculate the site energies, migration barriers, and attempt frequencies for these networks to inform our analytical model for bulk diffusion. Due to the nature of the networks, O diffuses isotropically, while B, C, and N diffuse anisotropically. We compute the elastodiffusion tensor which quantifies changes in diffusivity due to small strains that perturb the diffusion network geometry and the migration barriers. The DFT-computed elastic dipole tensor which quantifies the change in site energies and migration barriers due to small strains is used as an input to determine the elastodiffusion tensor. We employ the elastodiffusion tensor to determine the effect of thermal strains on interstitial diffusion and find that B, C, and N diffusivity increases on crystal expansion, while O diffusivity decreases. From the elastodiffusion and compliance tensors we calculate the activation volume of diffusion and find that it is positive and anisotropic for B, C, and N diffusion, whereas it is negative and isotropic for O diffusion.

  16. Stray light analysis of the Diffuse Infrared Background Experiment (DIRBE)

    NASA Technical Reports Server (NTRS)

    Breault, R. P.

    1984-01-01

    The straylight analysis of the diffuse infrared background experiment (DIRBE) on the cosmic background explorer (COBE) mission is discussed. From the statement of work (SOW), the purpose of DIRBE is to measure, or set upper limits on, the spectral and spatial character of the diffuse extra galactic infrared radiation. Diffuse infrared sources within our own galaxy are measured. The required reduction of the unwanted radiation imposes severe design and operating restrictions on the DIRBE instrument. To accomplish its missions, it will operate at a multitude of wavelengths ranging from 1.25 um out to 200 to 300 microns. The operating bands and the required point source normalized irradiance transmittance (PSNIT) are shown. The important straylight concepts in the DIRBE design are reviewed. The model and assumptions used in APART analysis are explained. The limitations due to the scalar theory used in the analysis are outlined.

  17. Fabrication and Characterization of Cylindrical Light Diffusers Comprised of Shape Memory Polymer

    SciTech Connect

    Small IV, W; Buckley, P R; Wilson, T S; Loge, J M; Maitland, K D; Maitland, D J

    2007-01-29

    We have developed a technique for constructing light diffusing devices comprised of a flexible shape memory polymer (SMP) cylindrical diffuser attached to the tip of an optical fiber. Devices were fabricated by casting an SMP rod over the cleaved tip of an optical fiber and media blasting the SMP rod to create a light diffusing surface. The axial and polar emission profiles and circumferential (azimuthal) uniformity were characterized for various blasting pressures, nozzle-to-sample distances, and nozzle translation speeds. The diffusers were generally strongly forward-directed and consistently withstood over 8 W of incident infrared laser light without suffering damage when immersed in water. These devices are suitable for various endoluminal and interstitial biomedical applications.

  18. Estimation of diffuse attenuation of ultraviolet light in optically shallow Florida Keys waters from MODIS measurements

    EPA Science Inventory

    Diffuse attenuation of solar light (Kd, m−1) determines the percentage of light penetrating the water column and available for benthic organisms. Therefore, Kd can be used as an index of water quality for coastal ecosystems that are dependent on photosynthesis, such as the coral ...

  19. Silkworm Gut Fiber of Bombyx mori as an Implantable and Biocompatible Light-Diffusing Fiber.

    PubMed

    Cenis, Jose Luis; Aznar-Cervantes, Salvador D; Lozano-Pérez, Antonio Abel; Rojo, Marta; Muñoz, Juan; Meseguer-Olmo, Luis; Arenas, Aurelio

    2016-07-16

    This work describes a new approach to the delivery of light in deeper tissues, through a silk filament that is implantable, biocompatible, and biodegradable. In the present work, silkworm gut fibers (SGFs) of Bombyx mori L., are made by stretching the silk glands. Morphological, structural, and optical properties of the fibers have been characterized and the stimulatory effect of red laser light diffused from the fiber was assayed in fibroblast cultures. SGFs are formed by silk fibroin (SF) mainly in a β-sheet conformation, a stable and non-soluble state in water or biological fluids. The fibers showed a high degree of transparency to visible and infrared radiation. Using a red laser (λ = 650 nm) as source, the light was efficiently diffused along the fiber wall, promoting a significant increment in the cell metabolism 5 h after the irradiation. SGFs have shown their excellent properties as light-diffusing optical fibers with a stimulatory effect on cells.

  20. Silkworm Gut Fiber of Bombyx mori as an Implantable and Biocompatible Light-Diffusing Fiber

    PubMed Central

    Cenis, Jose Luis; Aznar-Cervantes, Salvador D.; Lozano-Pérez, Antonio Abel; Rojo, Marta; Muñoz, Juan; Meseguer-Olmo, Luis; Arenas, Aurelio

    2016-01-01

    This work describes a new approach to the delivery of light in deeper tissues, through a silk filament that is implantable, biocompatible, and biodegradable. In the present work, silkworm gut fibers (SGFs) of Bombyx mori L., are made by stretching the silk glands. Morphological, structural, and optical properties of the fibers have been characterized and the stimulatory effect of red laser light diffused from the fiber was assayed in fibroblast cultures. SGFs are formed by silk fibroin (SF) mainly in a β-sheet conformation, a stable and non-soluble state in water or biological fluids. The fibers showed a high degree of transparency to visible and infrared radiation. Using a red laser (λ = 650 nm) as source, the light was efficiently diffused along the fiber wall, promoting a significant increment in the cell metabolism 5 h after the irradiation. SGFs have shown their excellent properties as light-diffusing optical fibers with a stimulatory effect on cells. PMID:27438824

  1. Silkworm Gut Fiber of Bombyx mori as an Implantable and Biocompatible Light-Diffusing Fiber.

    PubMed

    Cenis, Jose Luis; Aznar-Cervantes, Salvador D; Lozano-Pérez, Antonio Abel; Rojo, Marta; Muñoz, Juan; Meseguer-Olmo, Luis; Arenas, Aurelio

    2016-01-01

    This work describes a new approach to the delivery of light in deeper tissues, through a silk filament that is implantable, biocompatible, and biodegradable. In the present work, silkworm gut fibers (SGFs) of Bombyx mori L., are made by stretching the silk glands. Morphological, structural, and optical properties of the fibers have been characterized and the stimulatory effect of red laser light diffused from the fiber was assayed in fibroblast cultures. SGFs are formed by silk fibroin (SF) mainly in a β-sheet conformation, a stable and non-soluble state in water or biological fluids. The fibers showed a high degree of transparency to visible and infrared radiation. Using a red laser (λ = 650 nm) as source, the light was efficiently diffused along the fiber wall, promoting a significant increment in the cell metabolism 5 h after the irradiation. SGFs have shown their excellent properties as light-diffusing optical fibers with a stimulatory effect on cells. PMID:27438824

  2. Photosensitizer and light diffusion through dentin in photodynamic therapy

    NASA Astrophysics Data System (ADS)

    Nogueira, Ana C.; Graciano, Ariane X.; Nagata, Juliana Y.; Fujimaki, Mitsue; Terada, Raquel S. S.; Bento, Antonio C.; Astrath, Nelson G. C.; Baesso, Mauro L.

    2013-05-01

    Photodynamic therapy has been considered a potential antimicrobial modality against oral infections, including dental caries. A model to estimate the penetration of both photosensitizers and light through human dentin, a factor of interest in photodynamic therapy, is proposed. The photoacoustic spectroscopy technique was used to evaluate in vitro dentin permeability of three different photosensitizers. Using the dentin optical absorption and scattering coefficients, it was possible to propose a semi-quantitative model predicting both photosensitizer and light doses within dentin. The graphic illustrations obtained provided guidelines that may be useful in photodynamic therapy protocols used as antimicrobial tools in caries lesions.

  3. Searching for diffuse light in the M96 galaxy group

    SciTech Connect

    Watkins, Aaron E.; Mihos, J. Christopher; Harding, Paul; Feldmeier, John J.

    2014-08-10

    We present deep, wide-field imaging of the M96 galaxy group (also known as the Leo I Group). Down to surface brightness limits of μ{sub B} = 30.1 and μ{sub V} = 29.5, we find no diffuse, large-scale optical counterpart to the 'Leo Ring', an extended H I ring surrounding the central elliptical M105 (NGC 3379). However, we do find a number of extremely low surface brightness (μ{sub B} ≳ 29) small-scale streamlike features, possibly tidal in origin, two of which may be associated with the Ring. In addition, we present detailed surface photometry of each of the group's most massive members—M105, NGC 3384, M96 (NGC 3368), and M95 (NGC 3351)—out to large radius and low surface brightness, where we search for signatures of interaction and accretion events. We find that the outer isophotes of both M105 and M95 appear almost completely undisturbed, in contrast to NGC 3384 which shows a system of diffuse shells indicative of a recent minor merger. We also find photometric evidence that M96 is accreting gas from the H I ring, in agreement with H I data. In general, however, interaction signatures in the M96 Group are extremely subtle for a group environment, and provide some tension with interaction scenarios for the formation of the Leo H I Ring. The lack of a significant component of diffuse intragroup starlight in the M96 Group is consistent with its status as a loose galaxy group in which encounters are relatively mild and infrequent.

  4. Phosphorous Diffuser Diverged Blue Laser Diode for Indoor Lighting and Communication

    NASA Astrophysics Data System (ADS)

    Chi, Yu-Chieh; Hsieh, Dan-Hua; Lin, Chung-Yu; Chen, Hsiang-Yu; Huang, Chia-Yen; He-Hau, Jr.; Ooi, Boon; Denbaars, Steven P.; Nakamura, Shuji; Kuo, Hao-Chung; Lin, Gong-Ru

    2015-12-01

    An advanced light-fidelity (Li-Fi) system based on the blue Gallium nitride (GaN) laser diode (LD) with a compact white-light phosphorous diffuser is demonstrated for fusing the indoor white-lighting and visible light communication (VLC). The phosphorous diffuser adhered blue GaN LD broadens luminescent spectrum and diverges beam spot to provide ample functionality including the completeness of Li-Fi feature and the quality of white-lighting. The phosphorous diffuser diverged white-light spot covers a radiant angle up to 120o with CIE coordinates of (0.34, 0.37). On the other hand, the degradation on throughput frequency response of the blue LD is mainly attributed to the self-feedback caused by the reflection from the phosphor-air interface. It represents the current state-of-the-art performance on carrying 5.2-Gbit/s orthogonal frequency-division multiplexed 16-quadrature-amplitude modulation (16-QAM OFDM) data with a bit error rate (BER) of 3.1 × 10-3 over a 60-cm free-space link. This work aims to explore the plausibility of the phosphorous diffuser diverged blue GaN LD for future hybrid white-lighting and VLC systems.

  5. Phosphorous Diffuser Diverged Blue Laser Diode for Indoor Lighting and Communication

    PubMed Central

    Chi, Yu-Chieh; Hsieh, Dan-Hua; Lin, Chung-Yu; Chen, Hsiang-Yu; Huang, Chia-Yen; He, Jr-Hau; Ooi, Boon; DenBaars, Steven P.; Nakamura, Shuji; Kuo, Hao-Chung; Lin, Gong-Ru

    2015-01-01

    An advanced light-fidelity (Li-Fi) system based on the blue Gallium nitride (GaN) laser diode (LD) with a compact white-light phosphorous diffuser is demonstrated for fusing the indoor white-lighting and visible light communication (VLC). The phosphorous diffuser adhered blue GaN LD broadens luminescent spectrum and diverges beam spot to provide ample functionality including the completeness of Li-Fi feature and the quality of white-lighting. The phosphorous diffuser diverged white-light spot covers a radiant angle up to 120o with CIE coordinates of (0.34, 0.37). On the other hand, the degradation on throughput frequency response of the blue LD is mainly attributed to the self-feedback caused by the reflection from the phosphor-air interface. It represents the current state-of-the-art performance on carrying 5.2-Gbit/s orthogonal frequency-division multiplexed 16-quadrature-amplitude modulation (16-QAM OFDM) data with a bit error rate (BER) of 3.1 × 10−3 over a 60-cm free-space link. This work aims to explore the plausibility of the phosphorous diffuser diverged blue GaN LD for future hybrid white-lighting and VLC systems. PMID:26687289

  6. Influence of cloud optical thickness on surface diffuse light and carbon uptake in forests and croplands

    NASA Astrophysics Data System (ADS)

    Cheng, S. J.; Steiner, A. L.; Nadelhoffer, K. J.

    2014-12-01

    Accurately modeling atmospheric CO2 removal by terrestrial ecosystems requires an understanding of how atmospheric conditions change the rate of photosynthesis across major vegetation types. Diffuse light, which is created from interactions between incident solar radiation and atmospheric aerosols and clouds, has been postulated to increase carbon uptake in terrestrial ecosystems. To determine how cloud conditions affect carbon uptake through its influence on diffuse light, we quantify the relationship between cloud optical thickness, which indicates surface light attenuation by clouds, and surface diffuse light. We then examine the relationship between cloud optical thickness and gross primary productivity (GPP) to determine whether cloud properties could modulate GPP in temperate ecosystems. Surface diffuse light and GPP data are obtained from publically available Ameriflux data (Mead Crop sites, University of Michigan Biological Station, Morgan Monroe, and Howland Forest) and cloud optical thickness data over the Ameriflux sites are retrieved from NASA's Moderate Resolution Imaging Spetroradiometer. We compare the response of GPP to cloud optical thickness between croplands and forests, as well as within ecosystem types to determine ecosystem-specific responses and the role of plant community composition on ecosystem-level GPP under varying cloud conditions. By linking atmospheric cloud properties to surface light conditions and ecosystem carbon fluxes, we refine understanding of land-atmosphere carbon cycling and how changes in atmospheric cloud conditions may influence the future of the land carbon sink.

  7. Light-induced atomic desorption and diffusion of Rb from porous alumina

    SciTech Connect

    Villalba, S.; Failache, H.; Lezama, A.

    2010-03-15

    We present a study of light-induced atom desorption (LIAD) of an alkali-metal atom (Rb) in porous alumina. We observe the variation due to LIAD of the rubidium density in a vapor cell as a function of illumination time, intensity, and wavelength. The simple and regular structure of the alumina pores allows a description of the atomic diffusion in the porous medium in which the diffusion constant only depends on the known pore geometry and the atomic sticking time to the pore wall. A simple one-dimensional theoretical model is presented which reproduces the essential features of the observed signals. Fitting of the model to the experimental data gives access to the diffusion constant and consequently the atom-wall sticking time and its dependence on light intensity and wavelength. The nonmonotonic dependence of the LIAD yield on the illumination light frequency is indicative of the existence of Rb clusters in the porous medium.

  8. Nanocellulose-based Translucent Diffuser for Optoelectronic Device Applications with Dramatic Improvement of Light Coupling.

    PubMed

    Wu, Wei; Tassi, Nancy G; Zhu, Hongli; Fang, Zhiqiang; Hu, Liangbing

    2015-12-01

    Nanocellulose is a biogenerated and biorenewable organic material. Using a process based on 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)/NaClO/NaBr system, a highly translucent and light-diffusive film consisting of many layers of nanocellulose fibers and wood pulp microfibers was made. The film demonstrates a combination of large optical transmittance of ∼90% and tunable diffuse transmission of up to ∼78% across the visible and near-infrared spectra. The detailed characterizations of the film indicate the combination of high optical transmittance and haze is due to the film's large packing density and microstructured surface. The superior optical properties make the film a translucent light diffuser and applicable for improving the efficiencies of optoelectronic devices such as thin-film silicon solar cells and organic light-emitting devices. PMID:26572592

  9. Measuring tissue blood flow using ultrasound modulated diffused light

    NASA Astrophysics Data System (ADS)

    Ron, A.; Racheli, N.; Breskin, I.; Metzger, Y.; Silman, Z.; Kamar, M.; Nini, A.; Shechter, R.; Balberg, M.

    2012-02-01

    We demonstrate the ability of a novel device employing ultrasound modulation of near infrared light (referred as "Ultrasound tagged light" or UTL) to perform non-invasive monitoring of blood flow in the microvascular level in tissue. Monitoring microcirculatory blood flow is critical in clinical situations affecting flow to different organs, such as the brain or the limbs. . However, currently there are no non-invasive devices that measure microcirculatory blood flow in deep tissue continuously. Our prototype device (Ornim Medical, Israel) was used to monitor tissue blood flow on anesthetized swine during controlled manipulations of increased and decreased blood flow. Measurements were done on the calf muscle and forehead of the animal and compared with Laser Doppler (LD). ROC analysis of the sensitivity and specificity for detecting an increase in blood flow on the calf muscle, demonstrated AUC = 0.951 for 23 systemic manipulations of cardiac output by Epinephrine injection, which is comparable to AUC = 0.943 using laser Doppler. Some examples of cerebral blood flow monitoring are presented, along with their individual ROC curves. UTL flowmetry is shown to be effective in detecting changes in cerebral and muscle blood flow in swine, and has merit in clinical applications.

  10. METHOD OF AND APPARATUS FOR WITHDRAWING LIGHT ISOTOPIC PRODUCT FROM A LIQUID THERMAL DIFFUSION PLANT

    DOEpatents

    Dole, M.

    1959-09-22

    An improved process and apparatus are described for removing enriched product from the columns of a thermal diffusion plant for separation of isotopes. In the removal cycle, light product at the top cf the diffusion columns is circulated through the column tops and a shipping cylinder connected thereto unttl the concertation of enriched product in the cylinder reaches the desired point. During the removal, circulation through the bottoms is blocked bv freezing. in the diffusion cycle, the bottom portion is unfrozen, fresh feed is distributed to the bottoms of the columns, ard heavy product is withdrawn from the bottoms, while the tops of the columns are blocked by freezing.

  11. Wavelength-selective and anisotropic light-diffusing scale on the wing of the Morpho butterfly.

    PubMed Central

    Yoshioka, Shinya; Kinoshita, Shuichi

    2004-01-01

    We have found that cover scales on the wing of the butterfly Morpho didius possess specially designed microscopic structures for wavelength-selective reflection and contribute considerably to the brilliant blue colour of the wing. In addition, the cover scale functions as an anisotropic optical diffuser which diffuses light only in one plane, while it makes the range of reflection narrower in the orthogonal plane. The quantitative analyses for the wavelength-selection mechanism and the peculiar optical diffuser are given and the role of such a special optical effect is discussed from physical and biological viewpoints. PMID:15156915

  12. Improving the light quantification of near infrared (NIR) diffused light optical tomography with ultrasound localization

    NASA Astrophysics Data System (ADS)

    Ardeshirpour, Yasaman

    According to the statistics published by the American Cancer Society, currently breast cancer is the second most common cancer after skin cancer and the second cause of cancer death after lung cancer in the female population. Diffuse optical tomography (DOT) using near-infrared (NIR) light, guided by ultrasound localization, has shown great promise in distinguishing benign from malignant breast tumors and in assessing the response of breast cancer to chemotherapy. Our ultrasound-guided DOT system is based on reflection geometry, with patients scanned in supine position using a hand-held probe. For patients with chest-wall located at a depth shallower than 1 to 2cm, as in about 10% of our clinical cases, the semi-infinite imaging medium is not a valid assumption and the chest-wall effect needs to be considered in the imaging reconstruction procedure. In this dissertation, co-registered ultrasound images were used to model the breast-tissue and chest-wall as a two-layer medium. The effect of the chest wall on breast lesion reconstruction was systematically investigated. The performance of the two-layer model-based reconstruction, using the Finite Element Method, was evaluated by simulation, phantom experiments and clinical studies. The results show that the two-layer model can improve the accuracy of estimated background optical properties, the reconstructed absorption map and the total hemoglobin concentration of the lesion. For patients' data affected by chest wall, the perturbation, which is the difference between measurements obtained at lesion and normal reference sites, may include the information of background mismatch between these two sites. Because the imaging reconstruction is based on the perturbation approach, the effect of this mismatch between the optical properties at the two sites on reconstructed optical absorption was studied and a guideline for imaging procedure was developed to reduce these effects during data capturing. To reduce the artifacts

  13. Fiberoptic Microneedles: Novel Optical Diffusers for Interstitial Delivery of Therapeutic Light

    PubMed Central

    Kosoglu, Mehmet A.; Hood, Robert L.; Rossmeisl, John H.; Grant, David C.; Xu, Yong; Robertson, John L.; Rylander, M. Nichole; Rylander, Christopher G.

    2012-01-01

    Background and Objectives Photothermal therapies have limited efficacy and application due to the poor penetration depth of light inside tissue. In earlier work, we described the development of novel fiberoptic microneedles to provide a means to mechanically penetrate dermal tissue and deliver light directly into a localized target area. This paper presents an alternate fiberoptic microneedle design with the capability of delivering more diffuse, but therapeutically useful photothermal energy. Laser lipolysis is envisioned as a future clinical application for this design. Materials and Methods A novel fiberoptic microneedle was developed using hydrofluoric acid etching of optical fiber to permit diffuse optical delivery. Microneedles etched for 10, 30, and 50 minutes, and an optical fiber control were compared with three techniques. First, red light delivery from the microneedles was evaluated by imaging the reflectance of the light from a white paper. Second, spatial temperature distribution of the paper in response to near-IR light (1064 nm, 1 W CW) was recorded using infrared thermography. Third, ex vivo adipose tissue response during 1064 nm, (5 W CW) irradiation was recorded with bright field microscopy. Results The acid etching exposed a 3 mm length of the fiber core, allowing circumferential delivery of light along this length. Increasing etching time decreased microneedle diameter, resulting in increased uniformity of red and 1064 nm light delivery along the microneedle axis. For equivalent total energy delivery, thinner microneedles reduced carbonization in the adipose tissue experiments. Conclusions We developed novel microscale optical diffusers that provided a more homogeneous light distribution from their surfaces, and compared performance to a flat-cleaved fiber, a device currently utilized in clinical practice. These fiberoptic microneedles can potentially enhance clinical laser procedures by providing direct delivery of diffuse light to target

  14. Diffusion injected multi-quantum well light-emitting diode structure

    SciTech Connect

    Riuttanen, L. Nykänen, H.; Svensk, O.; Suihkonen, S.; Sopanen, M.; Kivisaari, P.; Oksanen, J.; Tulkki, J.

    2014-02-24

    The attention towards light-emitting diode (LED) structures based on nanowires, surface plasmon coupled LEDs, and large-area high-power LEDs has been increasing for their potential in increasing the optical output power and efficiency of LEDs. In this work we demonstrate an alternative way to inject charge carriers into the active region of an LED, which is based on completely different current transport mechanism compared to conventional current injection approaches. The demonstrated structure is expected to help overcoming some of the challenges related to current injection with conventional structures. A functioning III-nitride diffusion injected light-emitting diode structure, in which the light-emitting active region is located outside the pn-junction, is realized and characterized. In this device design, the charge carriers are injected into the active region by bipolar diffusion, which could also be utilized to excite otherwise challenging to realize light-emitting structures.

  15. Molecular Simulation of Solubility and Diffusion of Hindered-Amine Light Stabilizers (HALS) in Polyethylene

    NASA Astrophysics Data System (ADS)

    Nath, Shyamal K.; de Pablo, Juan J.; Debellis, Anthony

    1997-03-01

    Hindered-amine light stabilizers (HALS) are some of the most common additives employed for prevention of photooxidation in polymers. One of the major problems encountered in polymer stabilization is that of physical loss of the additives. Such loss limits the life of the polymer and, more importantly, it can have serious consequences when the polymer is to be used for food packaging and other toxicity-sensitive applications. The loss of additives is related to their solubility and diffusion coefficient in polymers. In this work, a novel Monte Carlo formalism is proposed to determine the solubility of commercially available HALS (Tinuvin 770) in polyethylene. Diffusion coefficients is also determined by conventional molecular dynamics simulations. We report results for the solubility and diffusion of HALS in polyethylene as a function of temperature, pressure and density. We also examine the effects of branching on these quantities, and we use our findings to propose HALS structures with attractive compatibility and diffusive characteristics.

  16. Effects of Diffuse Light on Radiation Use Efficiency of Two Anthurium Cultivars Depend on the Response of Stomatal Conductance to Dynamic Light Intensity

    PubMed Central

    Li, Tao; Kromdijk, Johannes; Heuvelink, Ep; van Noort, F. R.; Kaiser, Elias; Marcelis, Leo F. M.

    2016-01-01

    The stimulating effect of diffuse light on radiation use efficiency (RUE) of crops is often explained by the more homogeneous spatial light distribution, while rarely considering differences in temporal light distribution at leaf level. This study investigated whether diffuse light effects on crop RUE can be explained by dynamic responses of leaf photosynthesis to temporal changes of photosynthetic photon flux density (PPFD). Two Anthurium andreanum cultivars (‘Pink Champion’ and ‘Royal Champion’) were grown in two glasshouses covered by clear (control) and diffuse glass, with similar light transmission. On clear days, diffusing the light resulted in less temporal fluctuations of PPFD. Stomatal conductance (gs) varied strongly in response to transient PPFD in ‘Royal Champion,’ whereas it remained relatively constant in ‘Pink Champion.’ Instantaneous net leaf photosynthesis (Pn) in both cultivars approached steady state Pn in diffuse light treatment. In control treatment this only occurred in ‘Pink Champion.’ These cultivar differences were reflected by a higher RUE (8%) in ‘Royal Champion’ in diffuse light treatment compared with control, whereas no effect on RUE was observed in ‘Pink Champion.’ We conclude that the stimulating effect of diffuse light on RUE depends on the stomatal response to temporal PPFD fluctuations, which response is cultivar dependent. PMID:26870071

  17. Effects of Diffuse Light on Radiation Use Efficiency of Two Anthurium Cultivars Depend on the Response of Stomatal Conductance to Dynamic Light Intensity.

    PubMed

    Li, Tao; Kromdijk, Johannes; Heuvelink, Ep; van Noort, F R; Kaiser, Elias; Marcelis, Leo F M

    2016-01-01

    The stimulating effect of diffuse light on radiation use efficiency (RUE) of crops is often explained by the more homogeneous spatial light distribution, while rarely considering differences in temporal light distribution at leaf level. This study investigated whether diffuse light effects on crop RUE can be explained by dynamic responses of leaf photosynthesis to temporal changes of photosynthetic photon flux density (PPFD). Two Anthurium andreanum cultivars ('Pink Champion' and 'Royal Champion') were grown in two glasshouses covered by clear (control) and diffuse glass, with similar light transmission. On clear days, diffusing the light resulted in less temporal fluctuations of PPFD. Stomatal conductance (g s) varied strongly in response to transient PPFD in 'Royal Champion,' whereas it remained relatively constant in 'Pink Champion.' Instantaneous net leaf photosynthesis (P n) in both cultivars approached steady state P n in diffuse light treatment. In control treatment this only occurred in 'Pink Champion.' These cultivar differences were reflected by a higher RUE (8%) in 'Royal Champion' in diffuse light treatment compared with control, whereas no effect on RUE was observed in 'Pink Champion.' We conclude that the stimulating effect of diffuse light on RUE depends on the stomatal response to temporal PPFD fluctuations, which response is cultivar dependent.

  18. Induced dipole-dipole interactions in light diffusion from point dipoles

    NASA Astrophysics Data System (ADS)

    Cherroret, Nicolas; Delande, Dominique; van Tiggelen, Bart A.

    2016-07-01

    We develop a perturbative treatment of induced dipole-dipole interactions in the diffusive transport of electromagnetic waves through disordered atomic clouds. The approach is exact at order 2 in the atomic density and accounts for the vector character of light. It is applied to the calculations of the electromagnetic energy stored in the atomic cloud, which modifies the energy transport velocity, and of the light scattering and transport mean free paths. Results are compared to those obtained from a purely scalar model for light.

  19. Intrauterine device for laser light diffusion and method of using the same

    DOEpatents

    Tadir, Yona; Berns, Michael W.; Svaasand, Lars O.; Tromberg, Bruce J.

    1995-01-01

    An improved device for delivery of photoenergy from a light source, such as a laser, into a uterine cavity for photodynamic therapy is comprised of a plurality of optic fibers, which are bundled together and inserted into the uterine cavity by means of a uterine cannula. The cannula is positioned within the uterine cavity at a preferred location and then withdrawn thereby allowing the plurality of optic fibers to splay or diverge one from the other within the cavity. Different portions of the distal tip of the optic fiber is provided with a light diffusing tip, the remainder being provided with a nondiffusing tip portion. The fiber optic shape, as well as the segment which is permitted to actively diffuse light through the tip, is selected in order to provide a more uniform exposure intensity of the photo energy or at least sufficient radiation directed to each segment of the uterine walls.

  20. Intrauterine device for laser light diffusion and method of using the same

    DOEpatents

    Tadir, Y.; Berns, M.W.; Svaasand, L.O.; Tromberg, B.J.

    1995-12-26

    An improved device for delivery of photoenergy from a light source, such as a laser, into a uterine cavity for photodynamic therapy is comprised of a plurality of optic fibers, which are bundled together and inserted into the uterine cavity by means of a uterine cannula. The cannula is positioned within the uterine cavity at a preferred location and then withdrawn thereby allowing the plurality of optic fibers to splay or diverge one from the other within the cavity. Different portions of the distal tip of the optic fiber is provided with a light diffusing tip, the remainder being provided with a nondiffusing tip portion. The fiber optic shape, as well as the segment which is permitted to actively diffuse light through the tip, is selected in order to provide a more uniform exposure intensity of the photo energy or at least sufficient radiation directed to each segment of the uterine walls. 5 figs.

  1. Coupling of light into the fundamental diffusion mode of a scattering medium (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Ojambati, Oluwafemi S.; Yılmaz, Hasan; Lagendijk, Ad; Mosk, Allard P.; Vos, Willem L.

    2016-03-01

    Diffusion equation describes the energy density inside a scattering medium such as biological tissues and paint [1]. The solution of the diffusion equation is a sum over a complete set of eigensolutions that shows a characteristic linear decrease with depth in the medium. It is of particular interest if one could launch energy in the fundamental eigensolution, as this opens the opportunity to achieve a much greater internal energy density. For applications in optics, an enhanced energy density is vital for solid-state lighting, light harvesting in solar cells, low-threshold random lasers, and biomedical optics. Here we demonstrate the first ever selective coupling of optical energy into a diffusion eigensolution of a scattering medium of zinc oxide (ZnO) paint. To this end, we exploit wavefront shaping to selectively couple energy into the fundamental diffusion mode, employing fluorescence of nanoparticles randomly positioned inside the medium as a probe of the energy density. We observe an enhanced fluorescence in case of optimized incident wavefronts, and the enhancement increases with sample thickness, a typical mesoscopic control parameter. We interpret successfully our result by invoking the fundamental eigensolution of the diffusion equation, and we obtain excellent agreement with our observations, even in absence of adjustable parameters [2]. References [1] R. Pierrat, P. Ambichl, S. Gigan, A. Haber, R. Carminati, and R. Rotter, Proc. Natl. Acad. Sci. U.S.A. 111, 17765 (2014). [2] O. S. Ojambati, H. Yilmaz, A. Lagendijk, A. P. Mosk, and W. L. Vos, arXiv:1505.08103.

  2. Vertical excitation profile in diffusion injected multi-quantum well light emitting diode structure

    NASA Astrophysics Data System (ADS)

    Riuttanen, L.; Kivisaari, P.; Svensk, O.; Vasara, T.; Myllys, P.; Oksanen, J.; Suihkonen, S.

    2015-03-01

    Due to their potential to improve the performance of light-emitting diodes (LEDs), novel device structures based on nanowires, surface plasmons, and large-area high-power devices have received increasing amount of interest. These structures are almost exclusively based on the double hetero junction (DHJ) structure, that has remained essentially unchanged for decades. In this work we study a III-nitride diffusion injected light-emitting diode (DILED), in which the active region is located outside the pn-junction and the excitation of the active region is based on bipolar diffusion of charge carriers. This unorthodox approach removes the need of placing the active region in the conventional current path and thus enabling carrier injection in device structures, which would be challenging to realize with the conventional DHJ design. The structure studied in this work is has 3 indium gallium nitride / gallium nitride (InGaN/GaN) quantum wells (QWs) under a GaN pn-junction. The QWs are grown at diferent growth temperatures for obtaining distinctive luminescence peaks. This allows to obtain knowledge on the carrier diffusion in the structure. When the device is biased, all QWs emit light indicating a significant diffusion current into the QW stack.

  3. Growth of highly bright-white silica nanowires as diffusive reflection coating in LED lighting.

    PubMed

    Xi, Shuang; Shi, Tielin; Zhang, Lei; Liu, Dan; Lai, Wuxing; Tang, Zirong

    2011-12-19

    Large quantities of silica nanowires were synthesized through thermal treatment of silicon wafer in the atmosphere of N(2)/H(2)(5%) under 1200 °C with Cu as catalyst. These nanowires grew to form a natural bright-white mat, which showed highly diffusive reflectivity over the UV-visible range, with more than 60% at the whole range and up to 88% at 350 nm. The utilization of silica nanowires in diffusive coating on the reflector cup of LED is demonstrated, which shows greatly improved light distribution comparing with the specular reflector cup. It is expected that these nanowires can be promising coating material for optoelectronic applications.

  4. Characterization of highly scattering media by measurement of diffusely backscattered polarized light

    DOEpatents

    Hielscher, Andreas H.; Mourant, Judith R.; Bigio, Irving J.

    2000-01-01

    An apparatus and method for recording spatially dependent intensity patterns of polarized light that is diffusely backscattered from highly scattering media are described. These intensity patterns can be used to differentiate different turbid media, such as polystyrene-sphere and biological-cell suspensions. Polarized light from a He-Ne laser (.lambda.=543 nm) is focused onto the surface of the scattering medium, and a surface area of approximately 4.times.4 cm centered on the light input point is imaged through polarization analysis optics onto a CCD camera. A variety of intensity patterns may be observed by varying the polarization state of the incident laser light and changing the analyzer configuration to detect different polarization components of the backscattered light. Experimental results for polystyrene-sphere and Intralipid suspensions demonstrate that the radial and azimuthal variations of the observed pattern depend on the concentration, size, and anisotropy factor, g, of the particles constituting the scattering medium. Measurements performed on biological cell suspensions show that intensity patterns can be used to differentiate between suspensions of cancerous and non-cancerous cells. Introduction of the Mueller-matrix for diffusely backscattered light, permits the selection of a subset of measurements which comprehensively describes the optical properties of backscattering media.

  5. Hybrid diffusion and two-flux approximation for multilayered tissue light propagation modeling.

    PubMed

    Yudovsky, Dmitry; Durkin, Anthony J

    2011-07-20

    Accurate and rapid estimation of fluence, reflectance, and absorbance in multilayered biological media has been essential in many biophotonics applications that aim to diagnose, cure, or model in vivo tissue. The radiative transfer equation (RTE) rigorously models light transfer in absorbing and scattering media. However, analytical solutions to the RTE are limited even in simple homogeneous or plane media. Monte Carlo simulation has been used extensively to solve the RTE. However, Monte Carlo simulation is computationally intensive and may not be practical for applications that demand real-time results. Instead, the diffusion approximation has been shown to provide accurate estimates of light transport in strongly scattering tissue. The diffusion approximation is a greatly simplified model and produces analytical solutions for the reflectance and absorbance in tissue. However, the diffusion approximation breaks down if tissue is strongly absorbing, which is common in the visible part of the spectrum or in applications that involve darkly pigmented skin and/or high local volumes of blood such as port-wine stain therapy or reconstructive flap monitoring. In these cases, a model of light transfer that can accommodate both strongly and weakly absorbing regimes is required. Here we present a model of light transfer through layered biological media that represents skin with two strongly scattering and one strongly absorbing layer.

  6. Hybrid diffusion and two-flux approximation for multilayered tissue light propagation modeling

    NASA Astrophysics Data System (ADS)

    Yudovsky, Dmitry; Durkin, Anthony J.

    2011-07-01

    Accurate and rapid estimation of fluence, reflectance, and absorbance in multilayered biological media has been essential in many biophotonics applications that aim to diagnose, cure, or model in vivo tissue. The radiative transfer equation (RTE) rigorously models light transfer in absorbing and scattering media. However, analytical solutions to the RTE are limited even in simple homogeneous or plane media. Monte Carlo simulation has been used extensively to solve the RTE. However, Monte Carlo simulation is computationally intensive and may not be practical for applications that demand real-time results. Instead, the diffusion approximation has been shown to provide accurate estimates of light transport in strongly scattering tissue. The diffusion approximation is a greatly simplified model and produces analytical solutions for the reflectance and absorbance in tissue. However, the diffusion approximation breaks down if tissue is strongly absorbing, which is common in the visible part of the spectrum or in applications that involve darkly pigmented skin and/or high local volumes of blood such as port-wine stain therapy or reconstructive flap monitoring. In these cases, a model of light transfer that can accommodate both strongly and weakly absorbing regimes is required. Here we present a model of light transfer through layered biological media that represents skin with two strongly scattering and one strongly absorbing layer.

  7. Diffuse light scattering from a dense and cold microscopic 87Rb sample

    NASA Astrophysics Data System (ADS)

    Kemp, Kasie; Roof, S. J.; Havey, M. D.; Sokolov, I. M.; Kupriyanov, D. V.

    2015-05-01

    We report investigation of near-resonance light scattering from a cold atomic sample of 87Rb. Measurements are made on the F = 2 -->F' = 3 nearly closed hyperfine transition for atomic densities ranging from ~1010 to ~1013 atoms/cm3. The sample, initially prepared in a magneto-optical trap, is loaded into a far-off-resonance trap (FORT) in which the ensemble has a temperature ~100 μK and initial Gaussian radii of ~3 μm and ~280 μm in the transverse and longitudinal directions, respectively. The experimental geometry consists of projecting a near-resonance collimated laser beam onto the entire volume of the FORT and detecting the diffusely scattered light. The measured scattered light intensity as a function of detuning, atomic density, and sample size suggests that collective light scattering plays an important role in the experimental results. This research is supported by the National Science Foundation (Grant No. NSF-PHY-1068159).

  8. Separation of ballistic and diffusive fluorescence photons in confocal Light-Sheet Microscopy of Arabidopsis roots.

    PubMed

    Meinert, Tobias; Tietz, Olaf; Palme, Klaus J; Rohrbach, Alexander

    2016-01-01

    Image quality in light-sheet fluorescence microscopy is strongly affected by the shape of the illuminating laser beam inside embryos, plants or tissue. While the phase of Gaussian or Bessel beams propagating through thousands of cells can be partly controlled holographically, the propagation of fluorescence light to the detector is difficult to control. With each scatter process a fluorescence photon loses information necessary for the image generation. Using Arabidopsis root tips we demonstrate that ballistic and diffusive fluorescence photons can be separated by analyzing the image spectra in each plane without a priori knowledge. We introduce a theoretical model allowing to extract typical scattering parameters of the biological material. This allows to attenuate image contributions from diffusive photons and to amplify the relevant image contributions from ballistic photons through a depth dependent deconvolution. In consequence, image contrast and resolution are significantly increased and scattering artefacts are minimized especially for Bessel beams with confocal line detection. PMID:27553506

  9. Separation of ballistic and diffusive fluorescence photons in confocal Light-Sheet Microscopy of Arabidopsis roots

    PubMed Central

    Meinert, Tobias; Tietz, Olaf; Palme, Klaus J.; Rohrbach, Alexander

    2016-01-01

    Image quality in light-sheet fluorescence microscopy is strongly affected by the shape of the illuminating laser beam inside embryos, plants or tissue. While the phase of Gaussian or Bessel beams propagating through thousands of cells can be partly controlled holographically, the propagation of fluorescence light to the detector is difficult to control. With each scatter process a fluorescence photon loses information necessary for the image generation. Using Arabidopsis root tips we demonstrate that ballistic and diffusive fluorescence photons can be separated by analyzing the image spectra in each plane without a priori knowledge. We introduce a theoretical model allowing to extract typical scattering parameters of the biological material. This allows to attenuate image contributions from diffusive photons and to amplify the relevant image contributions from ballistic photons through a depth dependent deconvolution. In consequence, image contrast and resolution are significantly increased and scattering artefacts are minimized especially for Bessel beams with confocal line detection. PMID:27553506

  10. First Detection of Galactic Latitude Dedpendence of Near-infrared Diffuse Galactic Light from DIRBE Renalysis

    NASA Astrophysics Data System (ADS)

    Sano, K.; Matsuura, S.; Tsumura, K.; Arai, T.; Shirahata, M.; Onishi, Y.

    2016-04-01

    Observational study on near-infrared (IR) scattering properties of interstellar dust grains has been limited due to its faintness. Using all-sky maps obtained from the Diffuse Infrared Background Experiment, we investigate the scattering property from diffuse Galactic light (DGL) measurements at 1.25, 2.2, and 3.5 μ {{m}}, in addition to our recent analyses of diffuse near-IR emission. As a result, we first find that the intensity ratios of near-IR DGL to 100 μ {{m}} emission increase toward low Galactic latitudes at 1.25 and 2.2 μ {{m}}. The derived latitude dependence can be reproduced by a scattered light model of interstellar dust with a large scattering asymmetry factor g\\equiv < {cos}θ > of {0.8}-0.3+0.2 at 1.25 and 2.2 μ {{m}}, assuming an infinite Galaxy disk as an illuminating source. The derived asymmetry factor is comparable to the values obtained in the optical, but several times larger than that expected from a recent dust model. Since a possible latitude dependence of ultraviolet-excited dust emission at 1.25 and 2.2 μ {{m}} would reduce the large asymmetry factor to the reasonable value, our result may indicate the first detection of such an additional emission component in the diffuse interstellar medium.

  11. Comment on ''Light-induced atomic desorption and diffusion of Rb from porous alumina''

    SciTech Connect

    RePbilas, Krzysztof

    2010-11-15

    In a recent article [Phys. Rev. A 81, 037801 (2010)] a theory of light-induced atomic desorption for Rb in porous alumina is proposed. We point out that both the main assumption of this theory (the diffusion inside the pores treated as a random walk with the adsorption to the inner surface of the pores at any step) and several further hypotheses supporting the theoretical model require a revision.

  12. Spectroscopy of diffuse light in dust clouds. Scattered light and the solar neighbourhood radiation field

    NASA Astrophysics Data System (ADS)

    Lehtinen, K.; Mattila, K.

    2013-01-01

    Context. The optical surface brightness of dark nebulae is mainly due to scattering of integrated starlight by classical dust grains. It contains information on the impinging interstellar radiation field, cloud structure, and grain scattering properties. We have obtained spectra of the scattered light from 3500 to 9000 Å in two globules, the Thumbprint Nebula and DC 303.8-14.2. Aims. We use observations of the scattered light to study the impinging integrated starlight spectrum as well as the scattered Hα and other line emissions from all over the sky. We search also for the presence of other than scattered light in the two globules. Methods. We obtained long-slit spectra encompassing the whole globule plus adjacent sky in a one-slit setting, thus enabling efficient elimination of airglow and other foreground sky components. We calculated synthetic integrated starlight spectra for the solar neighbourhood using HIPPARCOS-based stellar distributions and the spectral library of Pickles. Results. Spectra are presented separately for the bright rims and dark cores of the globules. The continuum spectral energy distributions and absorption line spectra can be well modelled with the synthetic integrated starlight spectra. Emission lines of Hα +[N II], Hβ, and [S II] are detected and are interpreted in terms of scattered light plus an in situ warm ionized medium component behind the globules. We detected an excess of emission over the wavelength range 5200-8000 Å in DC 303.8-14.2 but the nature of this emission remains open. Based on observations collected at the European Southern Observatory, Chile, under programme ESO No. 073.C-0239(A). Appendix A is available in electronic form at http://www.aanda.org.

  13. Study of microparticles' anomalous diffusion in active bath using speckle light fields (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Pince, Ercag; Sabareesh, Sabareesh K. P.; Volpe, Giorgio; Gigan, Sylvain; Volpe, Giovanni S.

    2015-08-01

    Particles undergoing a stochastic motion within a disordered medium is a ubiquitous physical and biological phenomenon. Examples can be given from organelles as molecular machines of cells performing physical tasks in a populated cytoplasm to human mobility in patchy environment at larger scales. Our recent results showed that it is possible to use the disordered landscape generated by speckle light fields to perform advanced manipulation tasks at the microscale. Here, we use speckle light fields to study the anomalous diffusion of micron size silica particles (5 μm) in the presence of active microswimmers. The microswimmers we used in the experiments are motile bacteria, Escherichia coli (E.coli). They constitute an active background constantly agitating passive silica particles within complex optical potentials. The speckle fields are generated by mode mixing inside a multimode optical fiber where a small amount of incident laser power (maximum power = 12 μW/μm2) is needed to obtain an effective random landscape pattern for the purpose of optical manipulation. We experimentally show how complex potentials contribute to the anomalous diffusion of silica particles undergoing collisions with swimming bacteria. We observed an enhanced diffusion of particles interacting with the active bath of E.coli inside speckle light fields: this effect can be tuned and controlled by varying the intensity and the statistical properties of the speckle pattern. Potentially, these results could be of interest for many technological applications, such as the manipulation of microparticles inside optically disordered media of biological interests.

  14. The Role of Triplet Exciton Diffusion in Light-Upconverting Polymer Glasses.

    PubMed

    Raišys, Steponas; Kazlauskas, Karolis; Juršėnas, Saulius; Simon, Yoan C

    2016-06-22

    Light upconversion (UC) via triplet-triplet annihilation (TTA) by using noncoherent photoexcitation at subsolar irradiance power densities is extremely attractive, particularly for enhanced solar energy harvesting. Unfortunately, practical TTA-UC application is hampered by low UC efficiency of upconverting polymer glasses, which is commonly attributed to poor exciton diffusion of the triplet excitons across emitter molecules. The present study addresses this issue by systematically evaluating triplet exciton diffusion coefficients and diffusion lengths (LD) in a UC model system based on platinum-octaethylporphyrin-sensitized poly(methyl methacrylate)/diphenylanthracene (emitter) films as a function of emitter concentration (15-40 wt %). For this evaluation time-resolved photoluminescence bulk-quenching technique followed by Stern-Volmer-type quenching analysis of experimental data was employed. The key finding is that although increasing emitter concentration in the disordered PMMA/DPA/PtOEP films improves triplet exciton diffusion, and thus LD, this does not result in enhanced UC quantum yield. Conversely, improved LD accompanied by the accelerated decay of UC intensity on millisecond time scale degrades TTA-UC performance at high emitter loadings (>25 wt %) and suggests that diffusion-enhanced nonradiative decay of triplet excitons is the major limiting factor. PMID:27219281

  15. Intragroup diffuse light in compact groups of galaxies: HCG 79, 88 and 95

    NASA Astrophysics Data System (ADS)

    Da Rocha, C.; Mendes de Oliveira, C.

    2005-12-01

    Deep B and R images of three Hickson Compact Groups, HCG 79, 88 and 95, have been analysed using a new wavelet technique to measure possible intragroup diffuse light present in these systems. The method used, OV_WAV, is a wavelet technique particularly suitable for detecting low surface brightness extended structures, down to a signal-to-noise ratio (S/N) = 0.1 per pixel, which corresponds to a 5σ detection level in wavelet space. The three groups studied are in different evolutionary stages, as can be judged by their very different fractions of the total light contained in their intragroup haloes: 46 +/- 11 per cent for HCG 79 and 11 +/- 26 per cent for HCG 95, in the B band, and HCG 88 had no component detected down to a limiting surface brightness of 29.1B mag arcsec-2. For HCG 95, the intragroup light (IGL) is red, similar to the mean colours of the group galaxies themselves, suggesting that it is formed by an old population with no significant ongoing star formation. For HCG 79, however, the intragroup material has a significantly bluer colour than the mean colour of the group galaxies, suggesting that the diffuse light may, at least in part, come from stripping of dwarf galaxies which dissolved into the group potential well.

  16. Intragroup diffuse light in compact groups of galaxies - II. HCG 15, 35 and 51

    NASA Astrophysics Data System (ADS)

    Da Rocha, C.; Ziegler, B. L.; Mendes de Oliveira, C.

    2008-08-01

    This continuing study of intragroup light in compact groups of galaxies aims to establish new constraints to models of formation and evolution of galaxy groups, specially of compact groups, which are a key part in the evolution of larger structures, such as clusters. In this paper we present three additional groups (HCG 15, 35 and 51) using deep wide-field B- and R-band images observed with the LAICA camera at the 3.5-m telescope at the Calar Alto observatory (CAHA). This instrument provides us with very stable flat-fielding, a mandatory condition for reliably measuring intragroup diffuse light. The images were analysed with the OV_WAV package, a wavelet technique that allows us to uncover the intragroup component in an unprecedented way. We have detected that 19, 15 and 26 per cent of the total light of HCG 15, 35 and 51, respectively, are in the diffuse component, with colours that are compatible with old stellar populations and with mean surface brightness that can be as low as 28.4 B mag arcsec-2. Dynamical masses, crossing times and mass-to-light ratios were recalculated using the new group parameters. Also tidal features were analysed using the wavelet technique.

  17. Three-dimensional surface reconstruction within noncontact diffuse optical tomography using structured light

    NASA Astrophysics Data System (ADS)

    Baum, Kirstin; Hartmann, Raimo; Bischoff, Tobias; Oelerich, Jan O.; Finkensieper, Stephan; Heverhagen, Johannes T.

    2012-12-01

    A main field in biomedical optics research is diffuse optical tomography, where intensity variations of the transmitted light traversing through tissue are detected. Mathematical models and reconstruction algorithms based on finite element methods and Monte Carlo simulations describe the light transport inside the tissue and determine differences in absorption and scattering coefficients. Precise knowledge of the sample's surface shape and orientation is required to provide boundary conditions for these techniques. We propose an integrated method based on structured light three-dimensional (3-D) scanning that provides detailed surface information of the object, which is usable for volume mesh creation and allows the normalization of the intensity dispersion between surface and camera. The experimental setup is complemented by polarization difference imaging to avoid overlaying byproducts caused by inter-reflections and multiple scattering in semitransparent tissue.

  18. Impact of diffuse light on isoprene and monoterpene emissions from a mixed temperate forest

    NASA Astrophysics Data System (ADS)

    Laffineur, Q.; Aubinet, M.; Schoon, N.; Amelynck, C.; Müller, J.-F.; Dewulf, J.; Steppe, K.; Heinesch, B.

    2013-08-01

    This study investigated the impact of diffuse light on canopy scale emission of isoprene and monoterpenes measured continuously above a mixed temperate forest, using the disjunct eddy-covariance by mass scanning technique with a proton transfer reaction-mass spectrometer (PTR-MS) instrument. To assess this impact, the relationship between emissions/radiation and emissions/gross primary production (GPP) under clear sky and cloudy conditions were analysed. Under cloudy conditions (high proportion of diffuse radiation), the isoprene and monoterpene fluxes were enhanced compared to clear sky conditions (low proportion of diffuse radiation) at equivalent temperature and above-canopy total radiation. The whole-canopy enzymatic activity of the metabolic isoprene production pathway, however, was suggested to be lower under cloudy conditions than under clear sky conditions at equivalent temperature. The mechanisms behind these observations are probably linked to the better penetration of diffuse radiation in the canopy. Shade leaves/needles receive more radiation in cloudy conditions than in clear sky conditions, thereby inducing the observed effects.

  19. GPU-Accelerated Finite Element Method for Modelling Light Transport in Diffuse Optical Tomography

    PubMed Central

    Schweiger, Martin

    2011-01-01

    We introduce a GPU-accelerated finite element forward solver for the computation of light transport in scattering media. The forward model is the computationally most expensive component of iterative methods for image reconstruction in diffuse optical tomography, and performance optimisation of the forward solver is therefore crucial for improving the efficiency of the solution of the inverse problem. The GPU forward solver uses a CUDA implementation that evaluates on the graphics hardware the sparse linear system arising in the finite element formulation of the diffusion equation. We present solutions for both time-domain and frequency-domain problems. A comparison with a CPU-based implementation shows significant performance gains of the graphics accelerated solution, with improvements of approximately a factor of 10 for double-precision computations, and factors beyond 20 for single-precision computations. The gains are also shown to be dependent on the mesh complexity, where the largest gains are achieved for high mesh resolutions. PMID:22013431

  20. GPU-Accelerated Finite Element Method for Modelling Light Transport in Diffuse Optical Tomography.

    PubMed

    Schweiger, Martin

    2011-01-01

    We introduce a GPU-accelerated finite element forward solver for the computation of light transport in scattering media. The forward model is the computationally most expensive component of iterative methods for image reconstruction in diffuse optical tomography, and performance optimisation of the forward solver is therefore crucial for improving the efficiency of the solution of the inverse problem. The GPU forward solver uses a CUDA implementation that evaluates on the graphics hardware the sparse linear system arising in the finite element formulation of the diffusion equation. We present solutions for both time-domain and frequency-domain problems. A comparison with a CPU-based implementation shows significant performance gains of the graphics accelerated solution, with improvements of approximately a factor of 10 for double-precision computations, and factors beyond 20 for single-precision computations. The gains are also shown to be dependent on the mesh complexity, where the largest gains are achieved for high mesh resolutions.

  1. Diffuse light and building history of the galaxy cluster Abell 2667

    NASA Astrophysics Data System (ADS)

    Covone, G.; Adami, C.; Durret, F.; Kneib, J.-P.; Lima Neto, G. B.; Slezak, E.

    2006-12-01

    Aims.We searched for diffuse intracluster light in the galaxy cluster Abell 2667 (z=0.233) from HST images in three broad band-filters. Methods: .We applied an iterative multi-scale wavelet analysis and reconstruction technique to these images, which allows to subtract stars and galaxies from the original images. Results: .We detect a zone of diffuse emission southwest of the cluster center (DS1) and a second faint object (ComDif) within DS1. Another diffuse source (DS2) may be detected at lower confidence level northeast of the center. These sources of diffuse light contribute to 10-15% of the total visible light in the cluster. Whether they are independent entities or part of the very elliptical external envelope of the central galaxy remains unclear. Deep VLT VIMOS integral field spectroscopy reveals a faint continuum at the positions of DS1 and ComDif but do not allow a redshift to be computed, so we conclude if these sources are part of the central galaxy or not. A hierarchical substructure detection method reveals the presence of several galaxy pairs and groups defining a similar direction to the one drawn by the DS1 - central galaxy - DS2 axis. The analysis of archive XMM-Newton and Chandra observations shows X-ray emission elongated in the same direction. The X-ray temperature map shows the presence of a cool core, a broad cool zone stretching from north to south, and hotter regions towards the northeast, southwest, and northwest. This might suggest shock fronts along these directions produced by infalling material, even if uncertainties remain quite large on the temperature determination far from the center. Conclusions: .These various data are consistent with a picture in which diffuse sources are concentrations of tidal debris and harassed matter expelled from infalling galaxies by tidal stripping and undergoing an accretion process onto the central cluster galaxy; as such, they are expected to be found along the main infall directions. Note, however

  2. Diffuse Galactic Light in the Field of the Translucent High Galactic Latitude Cloud MBM32

    NASA Astrophysics Data System (ADS)

    Ienaka, N.; Kawara, K.; Matsuoka, Y.; Sameshima, H.; Oyabu, S.; Tsujimoto, T.; Peterson, B. A.

    2013-04-01

    We have conducted B-, g-, V-, and R-band imaging in a 45' × 40' field containing part of the high Galactic latitude translucent cloud MBM32, and correlated the intensity of diffuse optical light S ν(λ) with that of 100 μm emission S ν(100 μm). A χ2 minimum analysis is applied to fit a linear function to the measured correlation and derive the slope parameter b(λ) = ΔS ν(λ)/ΔS ν(100 μm) of the best-fit linear function. Compiling a sample by combining our b(λ) and published ones, we show that the b(λ) strength varies from cloud to cloud by a factor of four. Finding that b(λ) decreases as S ν(100 μm) increases in the sample, we suggest that a nonlinear correlation including a quadratic term of S ν(100 μm)2 should be fitted to the measured correlation. The variation of optical depth, which is AV = 0.16-2.0 in the sample, can change b(λ) by a factor of 2-3. There would be some contribution to the large b(λ) variation from the forward-scattering characteristic of dust grains which is coupled to the non-isotropic interstellar radiation field (ISRF). Models of the scattering of diffuse Galactic light (DGL) underestimate the b(λ) values by a factor of two. This could be reconciled by deficiency in UV photons in the ISRF or by a moderate increase in dust albedo. Our b(λ) spectrum favors a contribution from extended red emission (ERE) to the diffuse optical light; b(λ) rises from B to V faster than the models, seems to peak around 6000 Å and decreases toward long wavelengths. Such a characteristic is expected from the models in which the DGL is combined with ERE.

  3. Toward subdiffraction transmission microscopy of diffuse materials with silver nanoparticle white-light beacons.

    PubMed

    Chaudhuri, Debansu; Galusha, Jeremy W; Walter, Manfred J; Borys, Nicholas J; Bartl, Michael H; Lupton, John M

    2009-03-01

    We demonstrate high resolution transmission microscopy in a conventional two-photon wide-field fluorescence microscope by exploiting nonlinear white light generation from clusters of silver nanoparticles placed beneath the specimen. Surface-enhanced two-photon luminescence occurs at nanoparticle hot spots in the form of spectrally broad, spatially confined light which can be exploited to determine the transmission properties of a sample placed on the silver nanoparticles. We demonstrate the versatility of the technique by revealing individual crystalline domains formed in the diffuse biological photonic crystals of the scales of a beetle. We can identify submicron changes between photonic crystal facets as well as the occurrence of stacked domains invisible to surface-sensitive methods. Control over wavelength, polarization, and pulse shape promises selective addressing of hot spots in nanoparticle assemblies for motionless spatial scanning of the transmission properties with subdiffraction resolution.

  4. Light scattering by a rough surface of human skin. 2. Diffuse reflectance

    SciTech Connect

    Barun, V V; Ivanov, A P

    2013-10-31

    Based on the previously calculated luminance factors, we have investigated the integral characteristics of light reflection from a rough surface of the skin with large-scale inhomogeneities under various conditions of the skin illumination. Shadowing of incident and scattered beams by relief elements is taken into account. Diffuse reflectances by the Gaussian and the quasi-periodic surfaces are compared and, in general, both these roughness models are shown to give similar results. We have studied the effect of the angular structure of radiation multiply scattered deep in the tissue and the refraction of rays as they propagate from the dermis to the surface of the stratum corneum on the reflection characteristics of the skin surface. The importance of these factors is demonstrated. The algorithms constructed can be included in the schemes of calculation of the light fields inside and outside the medium in solving various direct and inverse problems of optics of biological tissues. (biophotonics)

  5. Time-resolved diffuse optical tomography with patterned-light illumination and detection.

    PubMed

    Chen, Jin; Venugopal, Vivek; Lesage, Frederic; Intes, Xavier

    2010-07-01

    This investigation explores the feasibility of performing diffuse optical tomography based on time-domain wide-field illumination and detection strategies. Wide-field patterned excitation and detection schemes are investigated in transmittance geometry with time-gated detection channels. A Monte Carlo forward model is employed to compute the time-resolved Jacobians for rigorous light propagation modeling. We demonstrate both in silico and experimentally that reconstructions of absorption structures based on wide-field patterned-light strategies are feasible and outperform classical point excitation schemes for similar data set sizes. Moreover, we demonstrate that time-domain information is retained even though large spatial areas are illuminated. The enhanced time-domain data set allows for quantitative three-dimensional imaging in thick tissue based on relatively small data sets associated with much shorter acquisition times.

  6. Light-emitting diode-based multiwavelength diffuse optical tomography system guided by ultrasound

    PubMed Central

    Yuan, Guangqian; Alqasemi, Umar; Chen, Aaron; Yang, Yi; Zhu, Quing

    2014-01-01

    Abstract. Laser diodes are widely used in diffuse optical tomography (DOT) systems but are typically expensive and fragile, while light-emitting diodes (LEDs) are cheaper and are also available in the near-infrared (NIR) range with adequate output power for imaging deeply seated targets. In this study, we introduce a new low-cost DOT system using LEDs of four wavelengths in the NIR spectrum as light sources. The LEDs were modulated at 20 kHz to avoid ambient light. The LEDs were distributed on a hand-held probe and a printed circuit board was mounted at the back of the probe to separately provide switching and driving current to each LED. Ten optical fibers were used to couple the reflected light to 10 parallel photomultiplier tube detectors. A commercial ultrasound system provided simultaneous images of target location and size to guide the image reconstruction. A frequency-domain (FD) laser-diode-based system with ultrasound guidance was also used to compare the results obtained from those of the LED-based system. Results of absorbers embedded in intralipid and inhomogeneous tissue phantoms have demonstrated that the LED-based system provides a comparable quantification accuracy of targets to the FD system and has the potential to image deep targets such as breast lesions. PMID:25473884

  7. Non-invasive imaging of breast cancer with diffusing near-infrared light

    NASA Astrophysics Data System (ADS)

    Konecky, Soren D.

    Diffuse optical tomography (DOT) is a new medical imaging technique that combines biomedical optics with the principles of computed tomography. We use DOT to quantitatively reconstruct images of complex phantoms with millimeter sized features located centimeters deep within a highly-scattering medium. A non-contact instrument is employed to collect large data sets consisting of greater than 107 source-detector pairs. Images are reconstructed using a fast image reconstruction algorithm based on an analytic solution to the inverse scattering problem for diffuse light. We also describe a next generation DOT breast imaging device for frequency domain transmission data acquisition in the parallel plate geometry. Frequency domain heterodyne measurements are made by intensity modulating a continuous wave laser source with an electro-optic modulator (EOM) and detecting the transmitted light with a gain-modulated image intensifier coupled to a CCD. Finally, we acquire and compare three-dimensional tomographic breast images of three females with suspicious masses using DOT and Positron Emission Tomography (PET). Co-registration of DOT and PET images is facilitated by a mutual information maximization algorithm. We also compare DOT and whole-body PET images of 14 patients with breast abnormalities. Positive correlations are found between both total hemoglobin concentration and tissue scattering, and fluorodeoxyglucose (18F-FDG) uptake.

  8. Light illumination and detection patterns for fluorescence diffuse optical tomography based on compressive sensing.

    PubMed

    Jin, An; Yazici, Birsen; Ntziachristos, Vasilis

    2014-06-01

    Fluorescence diffuse optical tomography (FDOT) is an emerging molecular imaging modality that uses near infrared light to excite the fluorophore injected into tissue; and to reconstruct the fluorophore concentration from boundary measurements. The FDOT image reconstruction is a highly ill-posed inverse problem due to a large number of unknowns and limited number of measurements. However, the fluorophore distribution is often very sparse in the imaging domain since fluorophores are typically designed to accumulate in relatively small regions. In this paper, we use compressive sensing (CS) framework to design light illumination and detection patterns to improve the reconstruction of sparse fluorophore concentration. Unlike the conventional FDOT imaging where spatially distributed light sources illuminate the imaging domain one at a time and the corresponding boundary measurements are used for image reconstruction, we assume that the light sources illuminate the imaging domain simultaneously several times and the corresponding boundary measurements are linearly filtered prior to image reconstruction. We design a set of optical intensities (illumination patterns) and a linear filter (detection pattern) applied to the boundary measurements to improve the reconstruction of sparse fluorophore concentration maps. We show that the FDOT sensing matrix can be expressed as a columnwise Kronecker product of two matrices determined by the excitation and emission light fields. We derive relationships between the incoherence of the FDOT forward matrix and these two matrices, and use these results to reduce the incoherence of the FDOT forward matrix. We present extensive numerical simulation and the results of a real phantom experiment to demonstrate the improvements in image reconstruction due to the CS-based light illumination and detection patterns in conjunction with relaxation and greedy-type reconstruction algorithms.

  9. Hybrid model of light propagation in random media based on the time-dependent radiative transfer and diffusion equations

    NASA Astrophysics Data System (ADS)

    Fujii, Hiroyuki; Okawa, Shinpei; Yamada, Yukio; Hoshi, Yoko

    2014-11-01

    Numerical modeling of light propagation in random media has been an important issue for biomedical imaging, including diffuse optical tomography (DOT). For high resolution DOT, accurate and fast computation of light propagation in biological tissue is desirable. This paper proposes a space-time hybrid model for numerical modeling based on the radiative transfer and diffusion equations (RTE and DE, respectively) in random media under refractive-index mismatching. In the proposed model, the RTE and DE regions are separated into space and time by using a crossover length and the time from the ballistic regime to the diffusive regime, ρDA~10/μt‧ and tDA~20/vμt‧ where μt‧ and v represent a reduced transport coefficient and light velocity, respectively. The present model succeeds in describing light propagation accurately and reduces computational load by a quarter compared with full computation of the RTE.

  10. Photoluminescence studies of organic phosphor coated diffusing surface using blue inorganic light-emitting diode as excitation source

    NASA Astrophysics Data System (ADS)

    Singh, Gyanendra; Singh Mehta, Dalip

    2013-02-01

    We report the studies on photoluminescence (PL) of organic phosphor coated on a diffusing surface using a blue inorganic light-emitting diode (LED) array as an excitation source. The organic phosphor composite coated diffuser was used to scatter the directional blue light from the LED array. Some of the blue light is absorbed by the organic phosphor composite and the phosphor molecules are excited and re-emit light at longer wavelengths due to the PL process. The output light consists of scattered blue light plus phosphor generated broadband yellow light, thus making white light. The diffuser was made up of a plastic substrate coated with an organic composite of small molecule fluorescent material zinc(II)bis(8-hydroxyquinoline) (Znq2) doped with different percentages of electro-phosphorescent metal complex iridium(III)bis(2-methyldibenzo-[f, h] quinoxaline) (acetylacetonate) ([Ir(MDQ)2(acac)]). By means of changing the concentration and the thickness of the phosphor composite material the colour coordinates of white light were achieved. The CIE coordinates and correlated colour temperature were calculated for various thicknesses and phosphor composite concentrations and the results are reported.

  11. Accuracy of RGD approximation for computing light scattering properties of diffusing and motile bacteria.

    PubMed

    Kotlarchyk, M; Chen, S H; Asano, S

    1979-07-15

    The quasi-elastic light scattering has become an established technique for a rapid and quantitative characterization of an average motility pattern of motile bacteria in suspensions. Essentially all interpretations of the measured light scattering intensities and spectra so far are based on the Rayleigh-Gans-Debye (RGD) approximation. Since the range of sizes of bacteria of interest is generally larger than the wavelength of light used in the measurement, one is not certain of the justification for the use of the RGD approximation. In this paper we formulate a method by which both the scattering intensity and the quasi-elastic light scattering spectra can be calculated from a rigorous scattering theory. For a specific application we study the case of bacteria Escherichia coli (about 1 microm in size) by using numerical solutions of the scattering field amplitudes from a prolate spheroid, which is known to simulate optical properties of the bacteria well. We have computed (1) polarized scattered light intensity vs scattering angle for a randomly oriented bacteria population; (2) polarized scattered field correlation functions for both a freely diffusing bacterium and for a bacterium undergoing a straight line motion in random directions and with a Maxwellian speed distribution; and (3) the corresponding depolarized scattered intensity and field correlation functions. In each case sensitivity of the result to variations of the index of refraction and size of the bacterium is investigated. The conclusion is that within a reasonable range of parameters applicable to E. coli, the accuracy of the RGD is good to within 10% at all angles for the properties (1) and (2), and the depolarized contributions in (3) are generally very small. PMID:20212685

  12. Validation of diffusion tensor MRI in the central nervous system using light microscopy: quantitative comparison of fiber properties.

    PubMed

    Choe, A S; Stepniewska, I; Colvin, D C; Ding, Z; Anderson, A W

    2012-07-01

    Diffusion tensor imaging (DTI) provides an indirect measure of tissue structure on a microscopic scale. To date, DTI is the only imaging method that provides such information in vivo, and has proven to be a valuable tool in both research and clinical settings. In this study, we investigated the relationship between white matter structure and diffusion parameters measured by DTI. We used micrographs from light microscopy of fixed, myelin-stained brain sections as a gold standard for direct comparison with data from DTI. Relationships between microscopic tissue properties observed with light microscopy (fiber orientation, density and coherence) and fiber properties observed by DTI (tensor orientation, diffusivities and fractional anisotropy) were investigated. Agreement between the major eigenvector of the tensor and myelinated fibers was excellent in voxels with high fiber coherence. In addition, increased fiber spread was strongly associated with increased radial diffusivity (p = 6 × 10(-6)) and decreased fractional anisotropy (p = 5 × 10(-8)), and was weakly associated with decreased axial diffusivity (p = 0.07). Increased fiber density was associated with increased fractional anisotropy (p = 0.03), and weakly associated with decreased radial diffusivity (p < 0.06), but not with axial diffusivity (p = 0.97). The mean diffusivity was largely independent of fiber spread (p = 0.24) and fiber density (p = 0.34).

  13. DIFFUSE GALACTIC LIGHT IN THE FIELD OF THE TRANSLUCENT HIGH GALACTIC LATITUDE CLOUD MBM32

    SciTech Connect

    Ienaka, N.; Kawara, K.; Matsuoka, Y.; Oyabu, S.; Sameshima, H.; Tsujimoto, T.; Peterson, B. A.

    2013-04-10

    We have conducted B-, g-, V-, and R-band imaging in a 45' Multiplication-Sign 40' field containing part of the high Galactic latitude translucent cloud MBM32, and correlated the intensity of diffuse optical light S{sub {nu}}({lambda}) with that of 100 {mu}m emission S{sub {nu}}(100 {mu}m). A {chi}{sup 2} minimum analysis is applied to fit a linear function to the measured correlation and derive the slope parameter b({lambda}) = {Delta}S{sub {nu}}({lambda})/{Delta}S{sub {nu}}(100 {mu}m) of the best-fit linear function. Compiling a sample by combining our b({lambda}) and published ones, we show that the b({lambda}) strength varies from cloud to cloud by a factor of four. Finding that b({lambda}) decreases as S{sub {nu}}(100 {mu}m) increases in the sample, we suggest that a nonlinear correlation including a quadratic term of S{sub {nu}}(100 {mu}m){sup 2} should be fitted to the measured correlation. The variation of optical depth, which is A{sub V} = 0.16-2.0 in the sample, can change b({lambda}) by a factor of 2-3. There would be some contribution to the large b({lambda}) variation from the forward-scattering characteristic of dust grains which is coupled to the non-isotropic interstellar radiation field (ISRF). Models of the scattering of diffuse Galactic light (DGL) underestimate the b({lambda}) values by a factor of two. This could be reconciled by deficiency in UV photons in the ISRF or by a moderate increase in dust albedo. Our b({lambda}) spectrum favors a contribution from extended red emission (ERE) to the diffuse optical light; b({lambda}) rises from B to V faster than the models, seems to peak around 6000 A and decreases toward long wavelengths. Such a characteristic is expected from the models in which the DGL is combined with ERE.

  14. Instrument for fluorescence sensing of circulating cells with diffuse light in mice in vivo

    PubMed Central

    Zettergren, Eric; Vickers, Dwayne; Runnels, Judith; Murthy, Shashi K.; Lin, Charles P.

    2012-01-01

    Abstract. Accurate quantification of circulating cell populations in mice is important in many areas of preclinical biomedical research. Normally, this is done either by extraction and analysis of small blood samples or, more recently, by using microscopy-based in vivo fluorescence flow cytometry. We describe a new technological approach to this problem using detection of diffuse fluorescent light from relatively large blood vessels in vivo. The diffuse fluorescence flow cytometer (DFFC) uses a laser to illuminate a mouse limb and an array of optical fibers coupled to a high-sensitivity photomultiplier tube array operating in photon counting mode to detect weak fluorescence signals from cells. We first demonstrate that the DFFC instrument is capable of detecting fluorescent microspheres and Vybrant-DiD-labeled cells in a custom-made optical flow phantom with similar size, optical properties, linear flow rates, and autofluorescence as a mouse limb. We also present preliminary data demonstrating that the DFFC is capable of detecting circulating cells in nude mice in vivo. In principle, this device would allow interrogation of the whole blood volume of a mouse in minutes, with sensitivity improvement by several orders of magnitude compared to current approaches. PMID:22502573

  15. Simple Multi-level Microchannel Fabrication by Pseudo-Grayscale Backside Diffused Light Lithography.

    PubMed

    Lai, David; Labuz, Joseph M; Kim, Jiwon; Luker, Gary D; Shikanov, Ariella; Takayama, Shuichi

    2013-11-14

    Photolithography of multi-level channel features in microfluidics is laborious and/or costly. Grayscale photolithography is mostly used with positive photoresists and conventional front side exposure, but the grayscale masks needed are generally costly and positive photoresists are not commonly used in microfluidic rapid prototyping. Here we introduce a simple and inexpensive alternative that uses pseudo-grayscale (pGS) photomasks in combination with backside diffused light lithography (BDLL) and the commonly used negative photoresist, SU-8. BDLL can produce smooth multi-level channels of gradually changing heights without use of true grayscale masks because of the use of diffused light. Since the exposure is done through a glass slide, the photoresist is cross-linked from the substrate side up enabling well-defined and stable structures to be fabricated from even unspun photoresist layers. In addition to providing unique structures and capabilities, the method is compatible with the "garage microfluidics" concept of creating useful tools at low cost since pGS BDLL can be performed with the use of only hot plates and a UV transilluminator: equipment commonly found in biology labs. Expensive spin coaters or collimated UV aligners are not needed. To demonstrate the applicability of pGS BDLL, a variety of weir-type cell traps were constructed with a single UV exposure to separate cancer cells (MDA-MB-231, 10-15 μm in size) from red blood cells (RBCs, 2-8 μm in size) as well as follicle clusters (40-50 μm in size) from cancer cells (MDA-MB-231, 10-15 μm in size). PMID:24976950

  16. Sunlight Transmission through Desert Dust and Marine Aerosols: Diffuse Light Corrections to Sun Photometry and Pyrheliometry

    NASA Technical Reports Server (NTRS)

    Russell, P. B.; Livingston, J. M.; Dubovik, O.; Ramirez, S. A.; Wang, J.; Redemann, J.; Schmid, B.; Box, M.; Holben, B. N.

    2003-01-01

    Desert dust and marine aerosols are receiving increased scientific attention because of their prevalence on intercontinental scales and their potentially large effects on Earth radiation and climate, as well as on other aerosols, clouds, and precipitation. The relatively large size of desert dust and marine aerosols produces scattering phase functions that are strongly forward- peaked. Hence, Sun photometry and pyrheliometry of these aerosols are more subject to diffuse-light errors than is the case for smaller aerosols. Here we quantify these diffuse-light effects for common Sun photometer and pyrheliometer fields of view (FOV), using a data base on dust and marine aerosols derived from (1) AERONET measurements of sky radiance and solar beam transmission and (2) in situ measurements of aerosol layer size distribution and chemical composition. Accounting for particle non-sphericity is important when deriving dust size distribution from both AERONET and in situ aerodynamic measurements. We express our results in terms of correction factors that can be applied to Sun photometer and pyrheliometer measurements of aerosol optical depth (AOD). We find that the corrections are negligible (less than approximately 1% of AOD) for Sun photometers with narrow FOV (half-angle eta less than degree), but that they can be as large as 10% of AOD at 354 nm wavelength for Sun photometers with eta = 1.85 degrees. For pyrheliometers (which can have eta up to approximately 2.8 degrees), corrections can be as large as 16% at 354 nm. We find that AOD correction factors are well correlated with AOD wavelength dependence (hence Angstrom exponent). We provide best-fit equations for determining correction factors from Angstrom exponents of uncorrected AOD spectra, and we demonstrate their application to vertical profiles of multiwavelength AOD.

  17. Parameterized source term in the diffusion approximation for enhanced near-field modeling of collimated light

    NASA Astrophysics Data System (ADS)

    Jia, Mengyu; Wang, Shuang; Chen, Xueying; Gao, Feng; Zhao, Huijuan

    2016-03-01

    Most analytical methods for describing light propagation in turbid medium exhibit low effectiveness in the near-field of a collimated source. Motivated by the Charge Simulation Method in electromagnetic theory as well as the established discrete source based modeling, we have reported on an improved explicit model, referred to as "Virtual Source" (VS) diffuse approximation (DA), to inherit the mathematical simplicity of the DA while considerably extend its validity in modeling the near-field photon migration in low-albedo medium. In this model, the collimated light in the standard DA is analogously approximated as multiple isotropic point sources (VS) distributed along the incident direction. For performance enhancement, a fitting procedure between the calculated and realistic reflectances is adopted in the nearfield to optimize the VS parameters (intensities and locations). To be practically applicable, an explicit 2VS-DA model is established based on close-form derivations of the VS parameters for the typical ranges of the optical parameters. The proposed VS-DA model is validated by comparing with the Monte Carlo simulations, and further introduced in the image reconstruction of the Laminar Optical Tomography system.

  18. Strengthening TiN diffusion barriers for Cu metallization by lightly doping Al

    NASA Astrophysics Data System (ADS)

    Yang, L. C.; Hsu, C. S.; Chen, G. S.; Fu, C. C.; Zuo, J. M.; Lee, B. Q.

    2005-09-01

    Thin films of Ti1-xAlxN were deposited on (100) Si by ultrahigh-vacuum dual-target reactive sputtering, and the impact of lightly doping Al of x as small as 0.09 on altering the films's microstructure upon thermal annealing, and hence the performance of the films (40nm thick) as diffusion barriers for Cu metallization was evaluated. The results of transmission electron microscopy, Rutherford backscattering spectroscopy, and grazing-incidence x-ray diffraction show that the TiN barrier layer gives the commonly observed voided, columnar grains composed of 5nm sized subgrains. Upon annealing, the subgrains tend to coalesce into 20nm sized equiaxed grains full of crystalline defects, initiating an inward penetration of Cu and a partial dissociation of TiN, transforming themselves, respectively, into pyramidal (or columnar) Cu3Si precipitates and a dendritic Ti5Si3 layer just after 550°C, 10min annealing. However, the lightly doped Al not only overrides the tendency to form intercolumnar voids inherent in sputter deposition by self-shadowing and statistical roughening, but also substantially enhances the microstructural and thermochemical stability, hence significantly improving barrier property, as evidenced from an annealing test at an elevated temperature (600°C) for a prolonged period of 30min.

  19. Extraction of quasi-straightforward-propagating photons from diffused light transmitting through a scattering medium by polarization modulation

    NASA Astrophysics Data System (ADS)

    Horinaka, Hiromichi; Hashimoto, Koji; Wada, Kenji; Cho, Yoshio; Osawa, Masahiko

    1995-07-01

    The utilization of light polarization is proposed to extract quasi-straightforward-propagating photons from diffused light transmitting through a scattering medium under continuously operating conditions. Removal of a floor level normally appearing on the dynamic range over which the extraction capability is maintained is demonstrated. By use of pulse-based observations this cw scheme of extraction of quasi-straightforward-propagating photons is directly shown to be equivalent to the use of a temporal gate in the pulse-based operation.

  20. Light-induced autofluorescence and diffuse reflectance spectroscopy in clinical diagnosis of skin cancer

    NASA Astrophysics Data System (ADS)

    Borisova, E.; Pavlova, E.; Kundurjiev, T.; Troyanova, P.; Genova, Ts.; Avramov, L.

    2014-05-01

    We investigated more than 500 clinical cases to receive the spectral properties of basal cell (136 patients) and squamous cell carcinoma (28), malignant melanoma (41) and different cutaneous dysplastic and benign cutaneous lesions. Excitation at 365, 385 and 405 nm using LEDs sources is applied to obtain autofluorescence spectra, and broad-band illumination in the region of 400-900 nm is used to detect diffuse reflectance spectra of all pathologies investigated. USB4000 microspectrometer (Ocean Optics Inc, USA) is applied as a detector and fiber-optic probe is used for delivery of the light. In the case of in vivo tumor measurements spectral shape and intensity changes are observed that are specific for a given type of lesion. Autofluorescence origins of the signals coming from skin tissues are mainly due to proteins, such as collagen, elastin, keratin, their cross-links, co-enzimes - NADH and flavins and endogenous porphyrins. Spectral features significant into diffuse spectroscopy diagnosis are related to the effects of re-absorption of hemoglobin and its forms, as well as melanin and its concentration in different pathologies. We developed significant database and revealed specific features for a large class of cutaneous neoplasia, using about 30 different spectral peculiarities to differentiate cutaneous tumors. Sensitivity and specificity obtained exceed 90%, which make optical biopsy very useful tool for clinical practice. These results are obtained in the frames of clinical investigations for development of significant "spectral features" database for the most common cutaneous malignant, dysplastic and benign lesions. In the forthcoming plans, our group tries to optimize the existing experimental system for optical biopsy of skin, and to introduce it and the diagnostic algorithms developed into clinical practice, based on the high diagnostic accuracy achieved.

  1. Sub-diffuse structured light imaging provides macroscopic maps of microscopic tissue structure (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Kanick, Stephen C.

    2016-03-01

    The onset and progression of cancer introduces changes to the intra-cellular ultrastructural components and to the morphology of the extracellular matrix. While previous work has shown that localized scatter imaging is sensitive to pathology-induced differences in these aspects of tissue microstructure, wide adaptation this knowledge for surgical guidance is limited by two factors. First, the time required to image with confocal-level localization of the remission signal can be substantial. Second, localized (i.e. sub-diffuse) scatter remission intensity is influenced interchangeably by parameters that define scattering frequency and anisotropy. This similarity relationship must be carefully considered in order to obtain unique estimates of biomarkers that define either the scatter density or features that describe the distribution (e.g. shape, size, and orientation) of scatterers. This study presents a novel approach that uses structured light imaging to address both of these limitations. Monte Carlo data were used to model the reflectance intensity over a wide range of spatial frequencies, reduced scattering coefficients, absorption coefficients, and a metric of the scattering phase function that directly maps to the fractal dimension of scatter sizes. The approach is validated in tissue-simulating phantoms constructed with user-tuned scattering phase functions. The validation analysis shows that the phase function can be described in the presence of different scatter densities or background absorptions. Preliminary data from clinical tissue specimens show quantitative images of both the scatter density and the tissue fractal dimension for various tissue types and pathologies. These data represent a novel wide-field quantitative approach to mapping microscopic structural biomarkers that cannot be obtained with standard diffuse imaging. Implications for the use of this approach to assess surgical margins will be discussed.

  2. 3D structure tensor analysis of light microscopy data for validating diffusion MRI.

    PubMed

    Khan, Ahmad Raza; Cornea, Anda; Leigland, Lindsey A; Kohama, Steven G; Jespersen, Sune Nørhøj; Kroenke, Christopher D

    2015-05-01

    Diffusion magnetic resonance imaging (d-MRI) is a powerful non-invasive and non-destructive technique for characterizing brain tissue on the microscopic scale. However, the lack of validation of d-MRI by independent experimental means poses an obstacle to accurate interpretation of data acquired using this method. Recently, structure tensor analysis has been applied to light microscopy images, and this technique holds promise to be a powerful validation strategy for d-MRI. Advantages of this approach include its similarity to d-MRI in terms of averaging the effects of a large number of cellular structures, and its simplicity, which enables it to be implemented in a high-throughput manner. However, a drawback of previous implementations of this technique arises from it being restricted to 2D. As a result, structure tensor analyses have been limited to tissue sectioned in a direction orthogonal to the direction of interest. Here we describe the analytical framework for extending structure tensor analysis to 3D, and utilize the results to analyze serial image "stacks" acquired with confocal microscopy of rhesus macaque hippocampal tissue. Implementation of 3D structure tensor procedures requires removal of sources of anisotropy introduced in tissue preparation and confocal imaging. This is accomplished with image processing steps to mitigate the effects of anisotropic tissue shrinkage, and the effects of anisotropy in the point spread function (PSF). In order to address the latter confound, we describe procedures for measuring the dependence of PSF anisotropy on distance from the microscope objective within tissue. Prior to microscopy, ex vivo d-MRI measurements performed on the hippocampal tissue revealed three regions of tissue with mutually orthogonal directions of least restricted diffusion that correspond to CA1, alveus and inferior longitudinal fasciculus. We demonstrate the ability of 3D structure tensor analysis to identify structure tensor orientations that

  3. 3D structure tensor analysis of light microscopy data for validating diffusion MRI

    PubMed Central

    Khan, Ahmad Raza; Cornea, Anda; Leigland, Lindsey A.; Kohama, Steven G.; Jespersen, Sune Nørhøj; Kroenke, Christopher D.

    2015-01-01

    Diffusion magnetic resonance imaging (d-MRI) is a powerful non-invasive and non-destructive technique for characterizing brain tissue on the microscopic scale. However, the lack of validation of d-MRI by independent experimental means poses an obstacle to accurate interpretation of data acquired using this method. Recently, structure tensor analysis has been applied to light microscopy images, and this technique holds promise to be a powerful validation strategy for d-MRI. Advantages of this approach include its similarity to d-MRI in terms of averaging the effects of a large number of cellular structures, and its simplicity, which enables it to be implemented in a high-throughput manner. However, a drawback of previous implementations of this technique arises from it being restricted to 2D. As a result, structure tensor analyses have been limited to tissue sectioned in a direction orthogonal to the direction of interest. Here we describe the analytical framework for extending structure tensor analysis to 3D, and utilize the results to analyze serial image “stacks” acquired with confocal microscopy of rhesus macaque hippocampal tissue. Implementation of 3D structure tensor procedures requires removal of sources of anisotropy introduced in tissue preparation and confocal imaging. This is accomplished with image processing steps to mitigate the effects of anisotropic tissue shrinkage, and the effects of anisotropy in the point spread function (PSF). In order to address the latter confound, we describe procedures for measuring the dependence of PSF anisotropy on distance from the microscope objective within tissue. Prior to microscopy, ex vivo d-MRI measurements performed on the hippocampal tissue revealed three regions of tissue with mutually orthogonal directions of least restricted diffusion that correspond to CA1, alveus and inferior longitudinal fasciculus. We demonstrate the ability of 3D structure tensor analysis to identify structure tensor orientations

  4. The influence of diffuse scattered light. II. Observations of galaxy haloes and thick discs and hosts of blue compact galaxies

    NASA Astrophysics Data System (ADS)

    Sandin, Christer

    2015-05-01

    Studies of deep photometry of galaxies have presented discoveries of excess light in surface-brightness and colour profiles at large radii in the form of diffuse faint haloes and thick discs. In a majority of the cases, it has seemed necessary to use exotic stellar populations or alternative physical solutions to explain the excess. Few studies have carefully scrutinized the role of scattered light in this context. I explore the influence of scattered light on ground-based observations of haloes and thick discs around edge-on galaxies, haloes around face-on disc galaxies, host galaxies around blue compact galaxies (BCGs), and haloes around elliptical galaxies. Surface-brightness structures of all considered types of galaxies are modelled and analysed to compare scattered-light haloes and thick discs with measurements. I simulate the influence of scattered light and accurate sky subtraction on simplified Sérsic-type and face-on disc galaxy models. All galaxy models are convolved with both lower-limit and brighter point spread functions (PSFs); for a few galaxies it was possible to use dedicated PSFs. The results show bright scattered-light haloes and high amounts of red excess at large radii and faint surface brightnesses for nearly all types of galaxies; exceptions are the largest elliptical-type galaxies where the influence of scattered light is smaller. Studies have underestimated the role of scattered light to explain their surface-brightness profiles. My analysis shows surface-brightness profiles that include scattered light that are very similar to and overlap measurements at all radii. The derivation of physical properties of haloes, thick discs, and BCG hosts from diffuse data is misleading since accurate and radially extended PSFs are non-existent. Significantly improved analyses that include new measurements of PSFs are required to study diffuse faint structures further.

  5. Diffuse optical tomography with structured-light patterns to quantify breast density

    NASA Astrophysics Data System (ADS)

    Kwong, Jessica; Nouizi, Farouk; Cho, Jaedu; Zheng, Jie; Li, Yifan; Chen, Jeon-hor; Su, Min-Ying; Gulsen, Gultekin

    2016-02-01

    Breast density is an independent risk factor for breast cancer, where women with denser breasts are more likely to develop cancer. By identifying women at higher risk, healthcare providers can suggest screening at a younger age to effectively diagnose and treat breast cancer in its earlier stages. Clinical risk assessment models currently do not incorporate breast density, despite its strong correlation with breast cancer. Current methods to measure breast density rely on mammography and MRI, both of which may be difficult to use as a routine risk assessment tool. We propose to use diffuse optical tomography with structured-light to measure the dense, fibroglandular (FGT) tissue volume, which has a different chromophore signature than the surrounding adipose tissue. To test the ability of this technique, we performed simulations by creating numerical breast phantoms from segmented breast MR images. We looked at two different cases, one with a centralized FGT distribution and one with a dispersed distribution. As expected, the water and lipid volumes segmented at half-maximum were overestimated for the dispersed case. However, it was noticed that the recovered water and lipid concentrations were lower and higher, respectively, than the centralized case. This information may provide insight into the morphological distribution of the FGT and can be a correction in estimating the breast density.

  6. Light polarization measurements - A method to determine the specular and diffuse light-scattering properties of both leaves and plant canopies

    NASA Technical Reports Server (NTRS)

    Vanderbilt, V. C.; Grant, L.

    1984-01-01

    The contributions of diffuse and specular reflection to the total canopy reflection of sunlight are determined experimentally for wheat at two stages of development using spectroradiometer measurements obtained at 13 wavelengths in the 480-720-nm range with a polarizing film in maximum and minimum signal-amplitude positions. The data and computation techniques are presented in tables, diagrams, and graphs, and the need to take specular reflection into account in constructing models of light/canopy interaction is stressed.

  7. Monte-Carlo Radiative Transfer Model of the Diffuse Galactic Light

    NASA Astrophysics Data System (ADS)

    Seon, Kwang-Il

    2015-02-01

    Monte-Carlo radiative models of the diffuse Galactic light (DGL) in our Galaxy are calcu-lated using the dust radiative transfer code MoCafe, which is three-dimensional and takes full account of multiple scattering. The code is recently updated to use a fast voxel traversal algorithm, which has dramatically increased the computing speed. The radiative transfer models are calculated with the gen-erally accepted dust scale-height of 0.1 kpc. The stellar scale-heights are assumed to be 0.1 or 0.35 kpc, appropriate for far-ultraviolet (FUV) and optical wavelengths, respectively. The face-on optical depth, measured perpendicular to the Galactic plane, is also varied from 0.2 to 0.6, suitable to the optical to FUV wavelengths, respectively. We find that the DGL at high Galactic latitudes is mostly due to backward or large-angle scattering of starlight originating from the local stars within a radial distance of r < 0.5 kpc from the Earth. On the other hand, the DGL measured in the Galactic plane is mostly due to stars at a distance range that corresponds to an optical depth of -1 measured from the Earth. Therefore, the low-latitude DGL at the FUV wavelength band would be mostly caused by the stars located at a distance of r . 0.5 kpc and the optical DGL near the Galactic plane mainly originates from stars within a distance range of 1 . r . 2 kpc. We also calculate the radiative transfer models in a clumpy two-phase medium. The clumpy two-phase models provide lower intensities at high Galactic latitudes compared to the uniform density models, because of the lower effective optical depth in clumpy media. However, no significant difference in the intensity at the Galactic plane is found.

  8. Monitoring and Scoring Counter-Diffusion Protein Crystallization Experiments in Capillaries by in situ Dynamic Light Scattering

    PubMed Central

    Oberthuer, Dominik; Melero-García, Emilio; Dierks, Karsten; Meyer, Arne; Betzel, Christian; Garcia-Caballero, Alfonso; Gavira, Jose A.

    2012-01-01

    In this paper, we demonstrate the feasibility of using in situ Dynamic Light Scattering (DLS) to monitor counter-diffusion crystallization experiments in capillaries. Firstly, we have validated the quality of the DLS signal in thin capillaries, which is comparable to that obtained in standard quartz cuvettes. Then, we have carried out DLS measurements of a counter-diffusion crystallization experiment of glucose isomerase in capillaries of different diameters (0.1, 0.2 and 0.3 mm) in order to follow the temporal evolution of protein supersaturation. Finally, we have compared DLS data with optical recordings of the progression of the crystallization front and with a simulation model of counter-diffusion in 1D. PMID:22675464

  9. Diffuse-light absorption spectroscopy by fiber optics for detecting and quantifying the adulteration of extra virgin olive oil

    NASA Astrophysics Data System (ADS)

    Mignani, A. G.; Ciaccheri, L.; Ottevaere, H.; Thienpont, H.; Conte, L.; Marega, M.; Cichelli, A.; Attilio, C.; Cimato, A.

    2010-09-01

    A fiber optic setup for diffuse-light absorption spectroscopy in the wide 400-1700 nm spectral range is experimented for detecting and quantifying the adulteration of extra virgin olive oil caused by lower-grade olive oils. Absorption measurements provide spectral fingerprints of authentic and adulterated oils. A multivariate processing of spectroscopic data is applied for discriminating the type of adulterant and for predicting its fraction.

  10. Diffusion of myosin light chain kinase on actin: A mechanism to enhance myosin phosphorylation rates in smooth muscle.

    PubMed

    Hong, Feng; Brizendine, Richard K; Carter, Michael S; Alcala, Diego B; Brown, Avery E; Chattin, Amy M; Haldeman, Brian D; Walsh, Michael P; Facemyer, Kevin C; Baker, Josh E; Cremo, Christine R

    2015-10-01

    Smooth muscle myosin (SMM) light chain kinase (MLCK) phosphorylates SMM, thereby activating the ATPase activity required for muscle contraction. The abundance of active MLCK, which is tightly associated with the contractile apparatus, is low relative to that of SMM. SMM phosphorylation is rapid despite the low ratio of MLCK to SMM, raising the question of how one MLCK rapidly phosphorylates many SMM molecules. We used total internal reflection fluorescence microscopy to monitor single molecules of streptavidin-coated quantum dot-labeled MLCK interacting with purified actin, actin bundles, and stress fibers of smooth muscle cells. Surprisingly, MLCK and the N-terminal 75 residues of MLCK (N75) moved on actin bundles and stress fibers of smooth muscle cell cytoskeletons by a random one-dimensional (1-D) diffusion mechanism. Although diffusion of proteins along microtubules and oligonucleotides has been observed previously, this is the first characterization to our knowledge of a protein diffusing in a sustained manner along actin. By measuring the frequency of motion, we found that MLCK motion is permitted only if acto-myosin and MLCK-myosin interactions are weak. From these data, diffusion coefficients, and other kinetic and geometric considerations relating to the contractile apparatus, we suggest that 1-D diffusion of MLCK along actin (a) ensures that diffusion is not rate limiting for phosphorylation, (b) allows MLCK to locate to areas in which myosin is not yet phosphorylated, and (c) allows MLCK to avoid getting "stuck" on myosins that have already been phosphorylated. Diffusion of MLCK along actin filaments may be an important mechanism for enhancing the rate of SMM phosphorylation in smooth muscle.

  11. Diffusion of myosin light chain kinase on actin: A mechanism to enhance myosin phosphorylation rates in smooth muscle

    PubMed Central

    Hong, Feng; Brizendine, Richard K.; Carter, Michael S.; Alcala, Diego B.; Brown, Avery E.; Chattin, Amy M.; Haldeman, Brian D.; Walsh, Michael P.; Facemyer, Kevin C.; Baker, Josh E.

    2015-01-01

    Smooth muscle myosin (SMM) light chain kinase (MLCK) phosphorylates SMM, thereby activating the ATPase activity required for muscle contraction. The abundance of active MLCK, which is tightly associated with the contractile apparatus, is low relative to that of SMM. SMM phosphorylation is rapid despite the low ratio of MLCK to SMM, raising the question of how one MLCK rapidly phosphorylates many SMM molecules. We used total internal reflection fluorescence microscopy to monitor single molecules of streptavidin-coated quantum dot–labeled MLCK interacting with purified actin, actin bundles, and stress fibers of smooth muscle cells. Surprisingly, MLCK and the N-terminal 75 residues of MLCK (N75) moved on actin bundles and stress fibers of smooth muscle cell cytoskeletons by a random one-dimensional (1-D) diffusion mechanism. Although diffusion of proteins along microtubules and oligonucleotides has been observed previously, this is the first characterization to our knowledge of a protein diffusing in a sustained manner along actin. By measuring the frequency of motion, we found that MLCK motion is permitted only if acto–myosin and MLCK–myosin interactions are weak. From these data, diffusion coefficients, and other kinetic and geometric considerations relating to the contractile apparatus, we suggest that 1-D diffusion of MLCK along actin (a) ensures that diffusion is not rate limiting for phosphorylation, (b) allows MLCK to locate to areas in which myosin is not yet phosphorylated, and (c) allows MLCK to avoid getting “stuck” on myosins that have already been phosphorylated. Diffusion of MLCK along actin filaments may be an important mechanism for enhancing the rate of SMM phosphorylation in smooth muscle. PMID:26415568

  12. A compact, multi-wavelength, and high frequency response light source for diffuse optical spectroscopy and imaging

    NASA Astrophysics Data System (ADS)

    Park, Kyoungsu; Lee, Minseok; Lee, Seung-ha; Cerussi, Albert E.; Chung, Phil-sang; Kim, Sehwan

    2015-03-01

    Many biomedical applications require an efficient combination and localization of multiple discrete light sources. In this paper, we present a compact six-channel combiner of optical sub-assembly type that couples the output of independent solid-state light sources into a single 400 μm diameter optical fiber. It is equipped with six discrete laser diodes, 658, 690, 705, 785, 830, and 850 nm for the measurement of the tissue optical properties from optical spectroscopy and imaging. We demonstrate coupling efficiencies ≥ 77% and output optical power ≥ 20 mW for each of the 6 laser diodes installed into the prototype. The design supports the use of continuous wave and intensity modulated laser diodes (with bandwidth ≥ 3 GHz). The developed light source could be used to construct custom multi-wavelength sources for tissue oximeters, diffuse optical imaging, and molecular imaging technologies.

  13. Spectral shape of a signal in light-induced diffusive pulling (pushing) of particles into a light beam

    NASA Astrophysics Data System (ADS)

    Parkhomenko, A. I.; Shalagin, A. M.

    2015-02-01

    We study theoretically how the dependences of transport collision frequencies νi, collision broadening γ and collision shift Δ of the levels on the velocity v of resonant particles influence lightinduced diffusive pulling (pushing) (LDP) effects in the framework of a generalised model of strong collisions in the case of velocitydependent collision rates (so-called kangaroo model). It is found that allowance for the dependences νi(v), γ(v) and Δ(v) does not change the spectral shape of an LDP signal. In particular, in the case of low-intensity radiation, the spectral dependence of the LDP signal coincides with the absorption line shape. It is shown that the magnitude of the LDP effect is proportional to the difference between the diffusion coefficients of particles in the excited and ground states. It is found that the spectral anomalies previously predicted in the LDP effect [Gel'mukhanov F.Kh. JETP Lett., 55, 214 (1992)] for an idealised model of the Lorentz gas (the limiting case of heavy buffer particles), which arise due to the dependences νi(v), γ(v) and Δ(v), are typical only for this gas. At a realistic ratio of the masses of absorbing and buffer particles, spectral anomalies do not occur in the LDP effect.

  14. Impacts of diffuse radiation on light use efficiency across terrestrial ecosystems based on Eddy covariance observation in China.

    PubMed

    Huang, Kun; Wang, Shaoqiang; Zhou, Lei; Wang, Huimin; Zhang, Junhui; Yan, Junhua; Zhao, Liang; Wang, Yanfen; Shi, Peili

    2014-01-01

    Ecosystem light use efficiency (LUE) is a key factor of production models for gross primary production (GPP) predictions. Previous studies revealed that ecosystem LUE could be significantly enhanced by an increase on diffuse radiation. Under large spatial heterogeneity and increasing annual diffuse radiation in China, eddy covariance flux data at 6 sites across different ecosystems from 2003 to 2007 were used to investigate the impacts of diffuse radiation indicated by the cloudiness index (CI) on ecosystem LUE in grassland and forest ecosystems. Our results showed that the ecosystem LUE at the six sites was significantly correlated with the cloudiness variation (0.24 ≤ R(2) ≤ 0.85), especially at the Changbaishan temperate forest ecosystem (R(2) = 0.85). Meanwhile, the CI values appeared more frequently between 0.8 and 1.0 in two subtropical forest ecosystems (Qianyanzhou and Dinghushan) and were much larger than those in temperate ecosystems. Besides, cloudiness thresholds which were favorable for enhancing ecosystem carbon sequestration existed at the three forest sites, respectively. Our research confirmed that the ecosystem LUE at the six sites in China was positively responsive to the diffuse radiation, and the cloudiness index could be used as an environmental regulator for LUE modeling in regional GPP prediction.

  15. METHOD FOR REMOVAL OF LIGHT ISOTOPE PRODUCT FROM LIQUID THERMAL DIFFUSION UNITS

    DOEpatents

    Hoffman, J.D.; Ballou, J.K.

    1957-11-19

    A method and apparatus are described for removing the lighter isotope of a gaseous-liquid product from a number of diffusion columns of a liquid thermal diffusion system in two stages by the use of freeze valves. The subject liquid flows from the diffusion columns into a heated sloping capsule where the liquid is vaporized by the action of steam in a heated jacket surrounding the capsule. When the capsule is filled the gas flows into a collector. Flow between the various stages is controlled by freeze valves which are opened and closed by the passage of gas and cool water respectively through coils surrounding portions of the pipes through which the process liquid is passed. The use of the dual stage remover-collector and the freeze valves is an improvement on the thermal diffusion separation process whereby the fraction containing the lighter isotope many be removed from the tops of the diffusion columns without intercolumn flow, or prior stage flow while the contents of the capsule is removed to the final receiver.

  16. Light propagation through weakly scattering media: a study of Monte Carlo vs. diffusion theory with application to neuroimaging

    NASA Astrophysics Data System (ADS)

    Ancora, Daniele; Zacharopoulos, Athanasios; Ripoll, Jorge; Zacharakis, Giannis

    2015-07-01

    One of the major challenges within Optical Imaging, photon propagation through clear layers embedded between scattering tissues, can be now efficiently modelled in real-time thanks to the Monte Carlo approach based on GPU. Because of its nature, the photon propagation problem can be very easily parallelized and ran on low cost hardware, avoiding the need for expensive Super Computers. A comparison between Diffusion and MC photon propagation theory is presented in this work with application to neuroimaging, investigating low scattering regions in a mouse-like phantom. Regions such as the Cerebral Spinal Fluid, are currently not taken into account in the classical computational models because of the impossibility to accurately simulate light propagation using fast Diffusive Equation approaches, leading to inaccuracies during the reconstruction process. The goal of the study presented here, is to reduce and further improve the computation accuracy of the reconstructed solution in a highly realistic scenario in the case of neuroimaging in preclinical mouse models.

  17. The Origin of the Excess Near-Infrared Diffuse Sky Brightness: Population III Stars or Zodiacal Light?

    NASA Technical Reports Server (NTRS)

    Dwek, Eli

    2006-01-01

    The intensity of the diffuse 1 to 5 micron sky emission from which solar system and Galactic foregrounds have been subtracted is in excess of that expected from energy released by galaxies and stars that formed during the z < 5 redshift interval. The spectral signature of this excess near-infrared background light (NIRBL) component is almost identical to that of reflected sunlight from the interplanetary dust cloud, and could therefore be the result of the incomplete subtraction of this foreground emission component from the diffuse sky maps. Alternatively, this emission component could be extragalactic. Its spectral signature is consistent with that of redshifted continuum and recombination line emission from H-II regions formed by the first generation of very massive stars. In this talk I will present the implications of this excess emission for our understanding of the zodiacal dust cloud, the formation rate of Pop III stars, and the TeV gamma-ray opacity to nearby blazars.

  18. Method for estimating closed-form solutions of the light diffusion equation for turbid media of any boundary shape

    PubMed Central

    Alqasemi, Umar; Salehi, Hassan S.; Zhu, Quing

    2016-01-01

    This paper reports a method of estimating an approximate closed-form solution to the light diffusion equation for any type of geometry involving Dirichlet’s boundary condition with known source location. It is based on estimating the optimum locations of multiple imaginary point sources to cancel the fluence at the extrapolated boundary by constrained optimization using a genetic algorithm. The mathematical derivation of the problem to approach the optimum solution for the direct-current type of diffuse optical systems is described in detail. Our method is first applied to slab geometry and compared with a truncated series solution. After that, it is applied to hemispherical geometry and compared with Monte Carlo simulation results. The method provides a fast and sufficiently accurate fluence distribution for optical reconstruction. PMID:26831771

  19. Enhanced intensity variation for multiple-plane phase retrieval using a spatial light modulator as a convenient tunable diffuser.

    PubMed

    Almoro, Percival F; Pham, Quang Duc; Serrano-Garcia, David Ignacio; Hasegawa, Satoshi; Hayasaki, Yoshio; Takeda, Mitsuo; Yatagai, Toyohiko

    2016-05-15

    In the multiple-plane phase retrieval method, a tedious-to-fabricate phase diffuser plate is used to increase the axial intensity variation for a nonstagnating iterative reconstruction of a smooth object wavefront. Here we show that a spatial light modulator (SLM) can be used as an easily controllable diffuser for phase retrieval. The polarization modulation at the SLM facilitates independent formation of orthogonally polarized scattered and specularly reflected beams. Through an analyzer, the polarization states are filtered enabling beam interference, thereby efficiently encoding the phase information in the axially diverse speckle intensity measurements. The technique is described using wave propagation and Jones calculus, and demonstrated experimentally on technical and biological samples. PMID:27176952

  20. Selective mode excitation in finite size plasma crystals by diffusely reflected laser light

    SciTech Connect

    Schablinski, Jan; Block, Dietmar

    2015-02-15

    The possibility to use diffuse reflections of a laser beam to exert a force on levitating dust particles is studied experimentally. Measurements and theoretical predictions are found to be in good agreement. Further, the method is applied to test the selective excitation of breathing-like modes in finite dust clusters.

  1. Artificial Lighting as a Vector Attractant and Cause of Disease Diffusion

    PubMed Central

    Barghini, Alessandro; de Medeiros, Bruno A. S.

    2010-01-01

    Background Traditionally, epidemiologists have considered electrification to be a positive factor. In fact, electrification and plumbing are typical initiatives that represent the integration of an isolated population into modern society, ensuring the control of pathogens and promoting public health. Nonetheless, electrification is always accompanied by night lighting that attracts insect vectors and changes people’s behavior. Although this may lead to new modes of infection and increased transmission of insect-borne diseases, epidemiologists rarely consider the role of night lighting in their surveys. Objective We reviewed the epidemiological evidence concerning the role of lighting in the spread of vector-borne diseases to encourage other researchers to consider it in future studies. Discussion We present three infectious vector-borne diseases—Chagas, leishmaniasis, and malaria—and discuss evidence that suggests that the use of artificial lighting results in behavioral changes among human populations and changes in the prevalence of vector species and in the modes of transmission. Conclusion Despite a surprising lack of studies, existing evidence supports our hypothesis that artificial lighting leads to a higher risk of infection from vector-borne diseases. We believe that this is related not only to the simple attraction of traditional vectors to light sources but also to changes in the behavior of both humans and insects that result in new modes of disease transmission. Considering the ongoing expansion of night lighting in developing countries, additional research on this subject is urgently needed. PMID:20675268

  2. Diffuse and local effects of light adaptation in photoreceptors of the honey bee drone.

    PubMed

    Bader, C R; Baumann, F; Bertrand, D; Carreras, J; Fuortes, G

    1982-01-01

    Intracellular recordings from drone photoreceptors were made by means of glass microelectrodes in superfused retinae. Exposure of a small portion of a cell to white light decreased the amplitude of responses to a small stimulus subsequently applied at different sites of the photoreceptor cell, i.e. light adaptation occurred throughout the cell. After 7 min of darkness, the responses had completely recovered. When a violet light (404 nm) was used to adapt a small portion of the cell, the responses at the site of exposure to the adapting stimulus remained depressed for at least 30 min. Illumination at the site of the violet adapting stimulus with green light (585 nm) caused an immediate recovery of the amplitude of the response. These results can be explained by the existence of two processes responsible for light adaptation: one is localized and persistent and appears to be due to changes in concentration of rhodopsin. The other affects the whole cell, is spontaneously reversible and depends upon the ability of the light to produce a receptor potential but not on any lasting change in rhodopsin concentration.

  3. Doppler shift generated by a moving diffraction grating under incidence by polychromatic diffuse light

    NASA Astrophysics Data System (ADS)

    Dossou, Kokou B.

    2016-05-01

    We consider the spectral response of moving diffraction gratings, in which the incident light extends over a broad angular range and where the diffracted light is observed from a specific angle. We show that the dispersion relation between the frequency perceived by an observer who is looking at a moving grating and the incident frequency can exhibit some unique features, such as a flat band (i.e., a local minimum). An observer can see the light diffracted into a non-specular diffraction order from a multitude of incident light rays and the angle of incidence of each ray is frequency-dependent, as a consequence, when the grating is moving, each incident ray experiences a Doppler shift in frequency that depends on its angle of incidence. We find that remarkable features appear near a Wood anomaly where the angle of incidence, for a given diffraction angle, can change very quickly with frequency. This means that light of multiple frequencies and incident from multiple angles can be mixed by the motion of the grating into the same diffracted ray and their frequencies can be compressed into a narrower range. The existence of a flat band means that a moving grating can be used as a device to increase the intensity of the perceived diffracted light due to spectral compression. The properties of a grating in motion in sunlight can also be relevant to the study of naturally occurring gratings which are typically in oscillatory motion.

  4. Doppler shift generated by a moving diffraction grating under incidence by polychromatic diffuse light.

    PubMed

    Dossou, Kokou B

    2016-05-20

    We consider the spectral response of moving diffraction gratings, in which the incident light extends over a broad angular range and where the diffracted light is observed from a specific angle. We show that the dispersion relation between the frequency perceived by an observer who is looking at a moving grating and the incident frequency can exhibit some unique features, such as a flat band (i.e., a local minimum). An observer can see the light diffracted into a nonspecular diffraction order from a multitude of incident light rays, and the angle of incidence of each ray is frequency dependent; as a consequence, when the grating is moving, each incident ray experiences a Doppler shift in frequency that depends on its angle of incidence. We find that remarkable features appear near a Wood anomaly where the angle of incidence, for a given diffraction angle, can change very quickly with frequency. This means that light of multiple frequencies and incident from multiple angles can be mixed by the motion of the grating into the same diffracted ray and their frequencies can be compressed into a narrower range. The existence of a flat band means that a moving grating can be used as a device to increase the intensity of the perceived diffracted light due to spectral compression. The properties of a grating in motion in sunlight can also be relevant to the study of naturally occurring gratings which are typically in oscillatory motion.

  5. Arctic canopy photosynthetic efficiency enhanced under diffuse light, linked to a reduction in the fraction of the canopy in deep shade.

    PubMed

    Williams, Mathew; Rastetter, Edward B; Van der Pol, Laura; Shaver, Gaius R

    2014-06-01

    We investigated how radiation conditions within a tundra canopy were linked to canopy photosynthesis, and how this linkage explained photosynthetic sensitivity to sky conditions, that is total radiation and its diffuse fraction. We measured within canopy radiation at leaf scales and net CO2 exchanges at canopy scales, under varied total irradiance and diffuse fraction, in Alaskan shrub tundra. Normalised mean radiation profiles within canopies showed no significant differences with varied diffuse fractions. However, radiation density distribution was non-normal, being more unimodal under diffuse conditions and distinctly bimodal under direct sunlight. There was a nearly three-fold increase in the proportion of the canopy in deep shade under direct illumination, compared to diffuse conditions. Under diffuse conditions the canopy had higher light-use efficiency (LUE), resulting in up to 17% greater photosynthesis. The enhancement in LUE under diffuse illumination was not related to differences in the mean light profiles, but instead was due to significant shifts in the density distribution of light at leaf scales, in particular a reduced fraction of the canopy in deep shade under diffuse illumination. These results provide unique information for testing radiative transfer schemes in canopy models, and for better understanding canopy structure and trait variation within plant canopies.

  6. How diffusivity, thermocline and incident light intensity modulate the dynamics of deep chlorophyll maximum in Tyrrhenian Sea.

    PubMed

    Valenti, Davide; Denaro, Giovanni; Spagnolo, Bernardo; Conversano, Fabio; Brunet, Christophe

    2015-01-01

    During the last few years theoretical works have shed new light and proposed new hypotheses on the mechanisms which regulate the spatio-temporal behaviour of phytoplankton communities in marine pelagic ecosystems. Despite this, relevant physical and biological issues, such as effects of the time-dependent mixing in the upper layer, competition between groups, and dynamics of non-stationary deep chlorophyll maxima, are still open questions. In this work, we analyze the spatio-temporal behaviour of five phytoplankton populations in a real marine ecosystem by using a one-dimensional reaction-diffusion-taxis model. The study is performed, taking into account the seasonal variations of environmental variables, such as light intensity, thickness of upper mixed layer and profiles of vertical turbulent diffusivity, obtained starting from experimental findings. Theoretical distributions of phytoplankton cell concentration was converted in chlorophyll concentration, and compared with the experimental profiles measured in a site of the Tyrrhenian Sea at four different times (seasons) of the year, during four different oceanographic cruises. As a result we find a good agreement between theoretical and experimental distributions of chlorophyll concentration. In particular, theoretical results reveal that the seasonal changes of environmental variables play a key role in the phytoplankton distribution and determine the properties of the deep chlorophyll maximum. This study could be extended to other marine ecosystems to predict future changes in the phytoplankton biomass due to global warming, in view of devising strategies to prevent the decline of the primary production and the consequent decrease of fish species.

  7. Size and diffusion phenomena of AOT/alcohol/water system in the presence of morin by dynamic light scattering.

    PubMed

    Bhattarai, Ajaya; Wilczura-Wachnik, Hanna

    2015-01-30

    Presented paper is a continuation of our studies on morin interaction with AOT (sodium bis(2-ethylhexyl) sulfosuccinate) reversed micelles solutions in two solvents: ethanol and n-decanol. Now we focused on morin influence on size and diffusion phenomena in the system morin/solvent/AOT/water. In this paper precise measurements of dynamic light scattering (DLS) of the effects of temperature, solvents (alcohols), water on the size and diffusion of AOT reversed micelles in the morin/AOT/alcohol/water system are reported. The concentrations of AOT were varied from 0.51 to 0.78mol/L. Morin concentration in during auto-correlation function registration was not the same in each solvent because of its different solubility depending on the solvent. Water concentration in the studied systems was defined by R parameter according to relation: R=(H2O)/(AOT) and was equal 0 and 30 in ethanol, and 0 in n-decanol. DLS measurements were done at 298.15 and 308.15K. DLS experiment involved on detection two relaxation modes (fast and slow) in the systems containing AOT reversed micelles, water, morin and solvents (ethanol and n-decanol). The DLS data clearly show the solvent influence as well as morin presence on AOT reversed micelles size and consequently their diffusion coefficients. Contrary to n-decanol strong competition between morin and ethanol molecules in AOT reversed micelles palisade layer has been found. It suggests that morin molecules replaced ethanol in AOT reversed micelles and locate in their palisade layer strongly increasing AOT reversed micelles size. Furthermore, it was found a sharp increase in correlation radii of slow modes of AOT reversed micelles containing morin molecules and their diffusion coefficients diminishing.

  8. Reply to Comment on Light-induced atomic desorption and diffusion of Rb from porous alumina

    SciTech Connect

    Villalba, S.; Failache, H.; Lezama, A.

    2010-11-15

    We argue that the model used in our paper [Phys. Rev. A 81, 032901 (2010)] for the analysis of the experimental study of light-induced atomic desorption in porous alumina is the simplest consistent approach to a previously unexplored physical system.

  9. Monte Carlo Simulation of Visible Light Diffuse Reflection in Neonatal Skin

    NASA Astrophysics Data System (ADS)

    Atencio, J. A. Delgado; Rodríguez, E. E.; Rodríguez, A. Cornejo; Rivas-Silva, J. F.

    2008-04-01

    Neonatal jaundice is a medical condition that happens commonly in newborns as result of desbalance between the production and the elimination of the bilirubin. Around 50% of newborns in term and something more of 60% of the near-term becomes jaundiced in the first week of life. This excess of bilirubin in the blood is exhibited in the skin, the sclera of the eyes and the mucous of mouth like a characteristic yellow coloration. In this work we make several numerical simulations of the spectral diffuse reflection for the skin of newborns that present different values of the biological parameters (bilirubin content, grade of pigmentation and content of blood) that characterize it. These simulations will allow us to evaluate the influence of these parameters on the experimental determination of bilirubin by noninvasive optical methods. The simulations are made in the spectral range of 400-700 nm using the Monte Carlo code MCML and two programs developed in LabVIEW by the authors. We simulated the diffuse reflection spectrum of neonatal skin for concentrations of bilirubin in skin that covers an ample range: from physiological to harmful numbers. We considered the influence of factors such as grade of pigmentation and content of blood.

  10. Light diffuse reflectance for detection and differentiation of teeth caries lesions

    NASA Astrophysics Data System (ADS)

    Borisova, E.; Uzunov, Tz.; Valkanov, S.; Avramov, L.

    2007-05-01

    One of the goals of the contemporary dentistry is differentiation between carious stages that must be fast, non-invasive procedure, which will allow to the dentists to make reliable judgments. One suitable candidate for such method is reflectance spectroscopy. The objectives of current study are to determine the feasibility of applying the light reflectance spectroscopy technique for detection of different carious stages; therefore reflectance spectra of teeth illuminated at 450- 900 nm light were recorded. There are obtained reflectance signals from the healthy enamel, dentine and different lesion stages of the investigated teeth. These spectra are compared to that, obtained by non-carious tooth lesions - fluorosa and odontolithiasis, resembling on initial carious stages. There is observed a significant decrease of the intensity of the reflected light in blue region in the case of caries. Reflectance signals, obtained from non-carious lesions also have significantly different character and could be used for differentiation between them and initial carious stages. An algorithm for differentiation between carious stages is proposed with diagnostic accuracy achieved up to 86,1% between precarious stage and sound tooth and 100% for determination of deep cavitation. Some comments about role of teeth enamel structure and anisotropy factor of dental layers on the results obtained are also made.

  11. Contact and contactless diffuse reflectance spectroscopy: potential for recovery monitoring of vascular lesions after intense pulsed light treatment

    NASA Astrophysics Data System (ADS)

    Kuzmina, Ilona; Diebele, Ilze; Spigulis, Janis; Valeine, Lauma; Berzina, Anna; Abelite, Anita

    2011-04-01

    Optical fiber contact probe diffuse reflectance spectroscopy and remote multispectral imaging methods in the spectral range of 400 to 1100 nm were used for skin vascular malformation assessment and recovery tracing after treatment by intense pulsed light. The results confirmed that oxy-hemoglobin relative changes and the optical density difference between lesion and healthy skin in the spectral region 500 to 600 nm may be successfully used for objective appraisal of the therapy effect. Color redness parameter a* = 2 is suggested as a diagnostic border to distinguish healthy skin and vascular lesions, and as the indicator of phototreatment efficiency. Valuable diagnostic information on large area (>5 mm) lesions and lesions with uncertain borders can be proved by the multispectral imaging method.

  12. Lithium isotopes and light lithophile element abundances in shergottites: Evidence for both magmatic degassing and subsolidus diffusion

    NASA Astrophysics Data System (ADS)

    Udry, Arya; McSween, Harry Y.; Hervig, Richard L.; Taylor, Lawrence A.

    2016-01-01

    Degassed magmatic water was potentially the major source of surficial water on Mars. We measured Li, B, and Be abundances and Li isotope profiles in pyroxenes, olivines, and maskelynite from four compositionally different shergottites—Shergotty, QUE 94201, LAR 06319, and Tissint—using secondary ion mass spectrometry (SIMS). All three light lithophile elements (LLE) are incompatible: Li and B are soluble in H2O-rich fluids, whereas Be is insoluble. In the analyzed shergottites, Li concentration decreases and Be concentration increases from cores to rims in pyroxenes. However, B concentrations do not vary consistently with Li and Be abundances, except in QUE 94201 pyroxenes. Additionally, abundances of these three elements in olivines show a normal igneous-fractionation trend consistent with the crystallization of olivine before magma ascent and degassing. We expect that kinetic effects would lead to fractionation of 6Li in the vapor phase compared to 7Li during degassing. The Li isotope profiles, with increasing δ7Li from cores to rims, as well as Li and B profiles indicate possible degassing of hydrous fluids only for the depleted shergottite QUE 94201, as also supported by degassing models. Conversely, Shergotty, LAR 06319, and Tissint appear to have been affected by postcrystallization diffusion, based on their LLE and Li isotope profiles, accompanied by diffusion models. This process may represent an overlay on a degassing pattern. The LLE profiles and isotope profiles in QUE 94201 support the hypothesis that degassing of some basaltic shergottite magmas provided water to the Martian surface, although evidence may be obscured by subsolidus diffusion processes.

  13. Sub-diffusive scattering parameter maps recovered using wide-field high-frequency structured light imaging

    PubMed Central

    Kanick, Stephen Chad; McClatchy, David M.; Krishnaswamy, Venkataramanan; Elliott, Jonathan T.; Paulsen, Keith D.; Pogue, Brian W.

    2014-01-01

    This study investigates the hypothesis that structured light reflectance imaging with high spatial frequency patterns (fx) can be used to quantitatively map the anisotropic scattering phase function distribution (P(θs)) in turbid media. Monte Carlo simulations were used in part to establish a semi-empirical model of demodulated reflectance (Rd) in terms of dimensionless scattering (μs′fx−1) and γ, a metric of the first two moments of the P(θs) distribution. Experiments completed in tissue-simulating phantoms showed that simultaneous analysis of Rd spectra sampled at multiple fx in the frequency range [0.05-0.5] mm−1 allowed accurate estimation of both μs′(λ) in the relevant tissue range [0.4-1.8] mm−1, and γ(λ) in the range [1.4-1.75]. Pilot measurements of a healthy volunteer exhibited γ-based contrast between scar tissue and surrounding normal skin, which was not as apparent in wide field diffuse imaging. These results represent the first wide-field maps to quantify sub-diffuse scattering parameters, which are sensitive to sub-microscopic tissue structures and composition, and therefore, offer potential for fast diagnostic imaging of ultrastructure on a size scale that is relevant to surgical applications. PMID:25360357

  14. How Diffusivity, Thermocline and Incident Light Intensity Modulate the Dynamics of Deep Chlorophyll Maximum in Tyrrhenian Sea

    PubMed Central

    Valenti, Davide; Denaro, Giovanni; Spagnolo, Bernardo; Conversano, Fabio; Brunet, Christophe

    2015-01-01

    During the last few years theoretical works have shed new light and proposed new hypotheses on the mechanisms which regulate the spatio-temporal behaviour of phytoplankton communities in marine pelagic ecosystems. Despite this, relevant physical and biological issues, such as effects of the time-dependent mixing in the upper layer, competition between groups, and dynamics of non-stationary deep chlorophyll maxima, are still open questions. In this work, we analyze the spatio-temporal behaviour of five phytoplankton populations in a real marine ecosystem by using a one-dimensional reaction-diffusion-taxis model. The study is performed, taking into account the seasonal variations of environmental variables, such as light intensity, thickness of upper mixed layer and profiles of vertical turbulent diffusivity, obtained starting from experimental findings. Theoretical distributions of phytoplankton cell concentration was converted in chlorophyll concentration, and compared with the experimental profiles measured in a site of the Tyrrhenian Sea at four different times (seasons) of the year, during four different oceanographic cruises. As a result we find a good agreement between theoretical and experimental distributions of chlorophyll concentration. In particular, theoretical results reveal that the seasonal changes of environmental variables play a key role in the phytoplankton distribution and determine the properties of the deep chlorophyll maximum. This study could be extended to other marine ecosystems to predict future changes in the phytoplankton biomass due to global warming, in view of devising strategies to prevent the decline of the primary production and the consequent decrease of fish species. PMID:25629963

  15. How diffusivity, thermocline and incident light intensity modulate the dynamics of deep chlorophyll maximum in Tyrrhenian Sea.

    PubMed

    Valenti, Davide; Denaro, Giovanni; Spagnolo, Bernardo; Conversano, Fabio; Brunet, Christophe

    2015-01-01

    During the last few years theoretical works have shed new light and proposed new hypotheses on the mechanisms which regulate the spatio-temporal behaviour of phytoplankton communities in marine pelagic ecosystems. Despite this, relevant physical and biological issues, such as effects of the time-dependent mixing in the upper layer, competition between groups, and dynamics of non-stationary deep chlorophyll maxima, are still open questions. In this work, we analyze the spatio-temporal behaviour of five phytoplankton populations in a real marine ecosystem by using a one-dimensional reaction-diffusion-taxis model. The study is performed, taking into account the seasonal variations of environmental variables, such as light intensity, thickness of upper mixed layer and profiles of vertical turbulent diffusivity, obtained starting from experimental findings. Theoretical distributions of phytoplankton cell concentration was converted in chlorophyll concentration, and compared with the experimental profiles measured in a site of the Tyrrhenian Sea at four different times (seasons) of the year, during four different oceanographic cruises. As a result we find a good agreement between theoretical and experimental distributions of chlorophyll concentration. In particular, theoretical results reveal that the seasonal changes of environmental variables play a key role in the phytoplankton distribution and determine the properties of the deep chlorophyll maximum. This study could be extended to other marine ecosystems to predict future changes in the phytoplankton biomass due to global warming, in view of devising strategies to prevent the decline of the primary production and the consequent decrease of fish species. PMID:25629963

  16. Near-infrared background anisotropies from diffuse intrahalo light of galaxies.

    PubMed

    Cooray, Asantha; Smidt, Joseph; De Bernardis, Francesco; Gong, Yan; Stern, Daniel; Ashby, Matthew L N; Eisenhardt, Peter R; Frazer, Christopher C; Gonzalez, Anthony H; Kochanek, Christopher S; Kozłowski, Szymon; Wright, Edward L

    2012-10-25

    Unresolved anisotropies of the cosmic near-infrared background radiation are expected to have contributions from the earliest galaxies during the epoch of reionization and from faint, dwarf galaxies at intermediate redshifts. Previous measurements were unable to pinpoint conclusively the dominant origin because they did not sample spatial scales that were sufficiently large to distinguish between these two possibilities. Here we report a measurement of the anisotropy power spectrum from subarcminute to one-degree angular scales, and find the clustering amplitude to be larger than predicted by the models based on the two existing explanations. As the shot-noise level of the power spectrum is consistent with that expected from faint galaxies, a new source population on the sky is not necessary to explain the observations. However, a physical mechanism that increases the clustering amplitude is needed. Motivated by recent results related to the extended stellar light profile in dark-matter haloes, we consider the possibility that the fluctuations originate from intrahalo stars of all galaxies. We find that the measured power spectrum can be explained by an intrahalo light fraction of 0.07 to 0.2 per cent relative to the total luminosity in dark-matter haloes of 10(9) to 10(12) solar masses at redshifts of about 1 to 4.

  17. Implementation of cost-effective diffuse light source mechanism to reduce specular reflection and halo effects for resistor-image processing

    NASA Astrophysics Data System (ADS)

    Chen, Yung-Sheng; Wang, Jeng-Yau

    2015-09-01

    Light source plays a significant role to acquire a qualified image from objects for facilitating the image processing and pattern recognition. For objects possessing specular surface, the phenomena of reflection and halo appearing in the acquired image will increase the difficulty of information processing. Such a situation may be improved by the assistance of valuable diffuse light source. Consider reading resistor via computer vision, due to the resistor's specular reflective surface it will face with a severe non-uniform luminous intensity on image yielding a higher error rate in recognition without a well-controlled light source. A measurement system including mainly a digital microscope embedded in a replaceable diffuse cover, a ring-type LED embedded onto a small pad carrying a resistor for evaluation, and Arduino microcontrollers connected with PC, is presented in this paper. Several replaceable cost-effective diffuse covers made by paper bowl, cup and box inside pasted with white paper are presented for reducing specular reflection and halo effects and compared with a commercial diffuse some. The ring-type LED can be flexibly configured to be a full or partial lighting based on the application. For each self-made diffuse cover, a set of resistors with 4 or 5 color bands are captured via digital microscope for experiments. The signal-to-noise ratio from the segmented resistor-image is used for performance evaluation. The detected principal axis of resistor body is used for the partial LED configuration to further improve the lighting condition. Experimental results confirm that the proposed mechanism can not only evaluate the cost-effective diffuse light source but also be extended as an automatic recognition system for resistor reading.

  18. Sub-nanosecond time resolved light emission study for diffuse discharges in air under steep high voltage pulses

    NASA Astrophysics Data System (ADS)

    Tardiveau, P.; Magne, L.; Marode, E.; Ouaras, K.; Jeanney, P.; Bournonville, B.

    2016-10-01

    Pin-to-plane discharges in centimetre air gaps and standard conditions of pressure and temperature are generated under very high positive nanosecond scale voltage pulses. The experimental study is based on recordings of sub-nanosecond time resolved and Abel-processed light emission profiles and their complete correlation to electrical current waveforms. The effects of the voltage pulse features (amplitude between 20 and 90 kV, rise time between 2 and 5.2 ns, and time rate between 4 and 40 kV · ns‑1) and the electrode configuration (gap distance between 10 and 30 mm, pin radius between 10 and 200 µm, copper, molybdenum or tungsten pin material) are described. A three time period development can be found: a glow-like structure with monotonic light profiles during the first 1.5 ns whose size depends on time voltage rate, a shell-like structure with bimodal profiles whose duration and extension in space depends on rise time, and either diffuse or multi-channel regime for the connection to the cathode plane according to gap distance. The transition of the light from monotonic to bimodal patterns reveals the relative effects and dynamics of streamer space charge and external laplacian field. A classical 2D-fluid model for streamer propagation has been used and adapted for very high and steep voltage pulses. It shows the formation of a strong space charge (streamer) very close to the pin, but also a continuity of emission between the pin and the streamer, and electric fields higher than the critical ionization field (28 kV · cm‑1 in air) almost in the whole gap and very early in the discharge propagation.

  19. Mutual and Self-Diffusivities in Binary Mixtures of [EMIM][B(CN)4] with Dissolved Gases by Using Dynamic Light Scattering and Molecular Dynamics Simulations.

    PubMed

    Koller, Thomas M; Heller, Andreas; Rausch, Michael H; Wasserscheid, Peter; Economou, Ioannis G; Fröba, Andreas P

    2015-07-01

    Ionic liquids (ILs) are possible working fluids for the separation of carbon dioxide (CO2) from flue gases. For evaluating their performance in such processes, reliable mutual-diffusivity data are required for mixtures of ILs with relevant flue gas components. In the present study, dynamic light scattering (DLS) and molecular dynamics (MD) simulations were used for the investigation of the molecular diffusion in binary mixtures of the IL 1-ethyl-3-methylimidazolium tetracyanoborate ([EMIM][B(CN)4]) with the dissolved gases carbon dioxide, nitrogen, carbon monoxide, hydrogen, methane, oxygen, and hydrogen sulfide at temperatures from 298.15 to 363.15 K and pressures up to 63 bar. At conditions approaching infinite dilution of a gas, the Fick mutual diffusivity of the mixture measured by DLS and the self-diffusivity of the corresponding gas calculated by MD simulations match, which could be generally found within combined uncertainties. The obtained diffusivities are in agreement with literature data for the same or comparable systems as well as with the general trend of increasing diffusivities for decreasing IL viscosities. The DLS and MD results reveal distinctly larger molecular diffusivities for [EMIM][B(CN)4]-hydrogen mixtures compared to mixtures with all other gases. This behavior results in the failure of an empirical correlation with the molar volumes of the gases at their normal boiling points. The DLS experiments also showed that there is no noticeable influence of the dissolved gas and temperature on the thermal diffusivity of the studied systems. PMID:26075680

  20. Lighting.

    SciTech Connect

    United States. Bonneville Power Administration.

    1992-09-01

    Since lighting accounts for about one-third of the energy used in commercial buildings, there is opportunity to conserve. There are two ways to reduce lighting energy use: modify lighting systems so that they used less electricity and/or reduce the number of hours the lights are used. This booklet presents a number of ways to do both. Topics covered include: reassessing lighting levels, reducing lighting levels, increasing bulb & fixture efficiency, using controls to regulate lighting, and taking advantage of daylight.

  1. Characterization of light transport in scattering media at sub-diffusion length scales with Low-coherence Enhanced Backscattering.

    PubMed

    Turzhitsky, Vladimir; Rogers, Jeremy D; Mutyal, Nikhil N; Roy, Hemant K; Backman, Vadim

    2010-01-01

    Low-coherence enhanced backscattering (LEBS) is a technique that has recently shown promise for tissue characterization and the detection of early pre-cancer. Although several Monte Carlo models of LEBS have been described, these models have not been accurate enough to predict all of the experimentally observed LEBS features. We present an appropriate Monte Carlo model to simulate LEBS peak properties from polystyrene microsphere suspensions in water. Results show that the choice of the phase function greatly impacts the accuracy of the simulation when the transport mean free path (ls*) is much greater than the spatial coherence length (L(SC)). When ls* < L(SC), a diffusion approximation based model of LEBS is sufficiently accurate. We also use the Monte Carlo model to validate that LEBS can be used to measure the radial scattering probability distribution (radial point spread function), p(r), at small length scales and demonstrate LEBS measurements of p(r) from biological tissue. In particular, we show that pre-cancerous and benign mucosal tissues have different small length scale light transport properties.

  2. Characterization of light transport in scattering media at sub-diffusion length scales with Low-coherence Enhanced Backscattering

    PubMed Central

    Turzhitsky, Vladimir; Rogers, Jeremy D.; Mutyal, Nikhil N.; Roy, Hemant K.; Backman, Vadim

    2009-01-01

    Low-coherence enhanced backscattering (LEBS) is a technique that has recently shown promise for tissue characterization and the detection of early pre-cancer. Although several Monte Carlo models of LEBS have been described, these models have not been accurate enough to predict all of the experimentally observed LEBS features. We present an appropriate Monte Carlo model to simulate LEBS peak properties from polystyrene microsphere suspensions in water. Results show that the choice of the phase function greatly impacts the accuracy of the simulation when the transport mean free path (ls*) is much greater than the spatial coherence length (LSC). When ls* < LSC, a diffusion approximation based model of LEBS is sufficiently accurate. We also use the Monte Carlo model to validate that LEBS can be used to measure the radial scattering probability distribution (radial point spread function), p(r), at small length scales and demonstrate LEBS measurements of p(r) from biological tissue. In particular, we show that pre-cancerous and benign mucosal tissues have different small length scale light transport properties. PMID:21037980

  3. Active optical remote sensing of dense clouds with diffusing light : Early results, present implementations, and the challenges ahead

    SciTech Connect

    Davis, A. B.; Cahalan, R. F.; Winker, D. M.

    2002-01-01

    We survey the rapid progress of 'off-beam' cloud lidar, from inception to validation via laboratory-scale simulations. Cloud observations from ground, aircraft and even space are covered. Finally, we describe future work in this instrument development effort born out of pure theory in the mid-1990s. We foresee a bright future for off-beam lidar which is, in essence, an atmospheric application of the general principles of optical diffuse-light tomography. The physical cloud-boundary information it delivers is, in principle, the same as given from ground or space (upcoming CloudSat mission) obtained by mm-radar. And mm-radar gives some information about internal variability. However, radar reflectivities quite often disagree with optical estimates of cloud base and optical thickness for well-understood reasons. So optical and microwave cloud probes are now considered as complimentary rather then competitive in our efforts to better understand cloud radiative properties in the context of climate research. We are confident that off-beam lidar will be a valuable and, ultimately, cost-effective source of information about cloud processes. In this, we include direct insight into the present issues in large-scale short-wave absorption based on unambiguous geometrical pathlength statistics, a unique capability of off-beam cloud lidar.

  4. Theoretical and experimental study of the diffuse transmission of light through highly concentrated absorbing and scattering materials. Part I: Monte-Carlo simulations

    NASA Astrophysics Data System (ADS)

    Bressel, L.; Reich, O.

    2014-10-01

    In many technical materials and commercial products like sunscreen or paint high particle and absorber concentrations are present. An important parameter for slabs of these materials is the diffuse transmission of light, which quantifies the total amount of directly and diffusely transmitted light. Due to the high content of scattering particles not only multiple scattering but also additional dependent scattering occurs. Hence, simple analytical models cannot be applied to calculate the diffuse transmission. In this work a Monte-Carlo program for the calculation of the diffuse transmission of light through dispersions in slab-like geometry containing high concentrations of scattering particles and absorbers is presented and discussed in detail. Mie theory is applied for the calculation of the scattering properties of the samples. Additionally, dependent scattering is considered in two different models, the well-known hard sphere model in the Percus-Yevick approximation (HSPYA) and the Yukawa model in the Mean Spherical Approximation (YMSA). Comparative experiments will show the accurateness of the program as well as its applicability to real samples [1].

  5. Characteristics of Optical Diffusers for Light-Emitting Diodes Backlight Unit Prepared by Melt-Extrusion Process

    NASA Astrophysics Data System (ADS)

    Kim, Hyo Jin; Kim, Dong Won; Kim, Seong Woo

    2013-10-01

    Using extrusion compounding followed by compression molding processes, polycarbonate-based optical diffusers with uniform dispersion of diffusing particles could be prepared for application in direct-lit LED backlight unit. Inorganic porous silica and organic silicone microsphere particles were employed as diffusing agents. The inclusion of diffusing particles up to 3 wt % substantially improved the luminance uniformity with respect to both location and viewing angle, and the effect was shown to be more prominent for the silicone particles. Alternatively, inorganic silica particles could yield diffusers with enhanced absolute luminance and thermal resistance property. The thermo-mechanical property of the elastic modulus was revealed to be improved upon addition of diffusing particles of silica and silicone with cross-linked structure.

  6. Principles of stray light suppression and conceptual application to the design of the Diffuse Infrared Background Experiment for NASA's Cosmic Background Explorer

    NASA Technical Reports Server (NTRS)

    Evans, D. C.

    1983-01-01

    The Diffuse Infrared Background Experiment (DIRBE) is a 10 band filter photometer that will operate at superfluid helium temperatures. Diffuse galactic and extragalactic infrared radiation in the 1-300 micrometer wavelength region will be measured by the instrument. Polarization measurements will be made for 3 bands in the 1-4 micrometer spectral region. The main sources of unwanted radiation are the sun, earth, thermal radiation from an external sun shield, the moon, the brighter planets and stars, and sky light itself from outside the instrument's nominal one degree square field of view. The system level engineering concepts and the principles of stray light suppression that resulted in the instrument design are presented.

  7. MEASUREMENTS OF THE MEAN DIFFUSE GALACTIC LIGHT SPECTRUM IN THE 0.95–1.65 μm BAND FROM CIBER

    SciTech Connect

    Arai, T.; Matsuura, S.; Sano, K.; Matsumoto, T.; Nakagawa, T.; Onishi, Y.; Bock, J.; Lanz, A.; Korngut, P.; Zemcov, M.; Cooray, A.; Smidt, J.; Kim, M. G.; Lee, H. M.; Lee, D. H.; Shirahata, M.; Tsumura, K.

    2015-06-10

    We report measurements of the diffuse galactic light (DGL) spectrum in the near-infrared, spanning the wavelength range 0.95–1.65 μm by the Cosmic Infrared Background ExpeRiment. Using the low-resolution spectrometer calibrated for absolute spectro-photometry, we acquired long-slit spectral images of the total diffuse sky brightness toward six high-latitude fields spread over four sounding rocket flights. To separate the DGL spectrum from the total sky brightness, we correlated the spectral images with a 100 μm intensity map, which traces the dust column density in optically thin regions. The measured DGL spectrum shows no resolved features and is consistent with other DGL measurements in the optical and at near-infrared wavelengths longer than 1.8 μm. Our result implies that the continuum is consistently reproduced by models of scattered starlight in the Rayleigh scattering regime with a few large grains.

  8. Measurements of the Mean Diffuse Galactic Light Spectrum in the 0.95-1.65 μm Band from CIBER

    NASA Astrophysics Data System (ADS)

    Arai, T.; Matsuura, S.; Bock, J.; Cooray, A.; Kim, M. G.; Lanz, A.; Lee, D. H.; Lee, H. M.; Sano, K.; Smidt, J.; Matsumoto, T.; Nakagawa, T.; Onishi, Y.; Korngut, P.; Shirahata, M.; Tsumura, K.; Zemcov, M.

    2015-06-01

    We report measurements of the diffuse galactic light (DGL) spectrum in the near-infrared, spanning the wavelength range 0.95-1.65 μm by the Cosmic Infrared Background ExpeRiment. Using the low-resolution spectrometer calibrated for absolute spectro-photometry, we acquired long-slit spectral images of the total diffuse sky brightness toward six high-latitude fields spread over four sounding rocket flights. To separate the DGL spectrum from the total sky brightness, we correlated the spectral images with a 100 μm intensity map, which traces the dust column density in optically thin regions. The measured DGL spectrum shows no resolved features and is consistent with other DGL measurements in the optical and at near-infrared wavelengths longer than 1.8 μm. Our result implies that the continuum is consistently reproduced by models of scattered starlight in the Rayleigh scattering regime with a few large grains.

  9. Diagnosing isopycnal diffusivity in an eddying, idealized midlatitude ocean basin via Lagrangian, in Situ, Global, High-Performance Particle Tracking (LIGHT)

    SciTech Connect

    Wolfram, Phillip J.; Ringler, Todd D.; Maltrud, Mathew E.; Jacobsen, Douglas W.; Petersen, Mark R.

    2015-08-01

    Isopycnal diffusivity due to stirring by mesoscale eddies in an idealized, wind-forced, eddying, midlatitude ocean basin is computed using Lagrangian, in Situ, Global, High-Performance Particle Tracking (LIGHT). Simulation is performed via LIGHT within the Model for Prediction across Scales Ocean (MPAS-O). Simulations are performed at 4-, 8-, 16-, and 32-km resolution, where the first Rossby radius of deformation (RRD) is approximately 30 km. Scalar and tensor diffusivities are estimated at each resolution based on 30 ensemble members using particle cluster statistics. Each ensemble member is composed of 303 665 particles distributed across five potential density surfaces. Diffusivity dependence upon model resolution, velocity spatial scale, and buoyancy surface is quantified and compared with mixing length theory. The spatial structure of diffusivity ranges over approximately two orders of magnitude with values of O(105) m2 s–1 in the region of western boundary current separation to O(103) m2 s–1 in the eastern region of the basin. Dominant mixing occurs at scales twice the size of the first RRD. Model resolution at scales finer than the RRD is necessary to obtain sufficient model fidelity at scales between one and four RRD to accurately represent mixing. Mixing length scaling with eddy kinetic energy and the Lagrangian time scale yield mixing efficiencies that typically range between 0.4 and 0.8. In conclusion, a reduced mixing length in the eastern region of the domain relative to the west suggests there are different mixing regimes outside the baroclinic jet region.

  10. Diagnosing isopycnal diffusivity in an eddying, idealized midlatitude ocean basin via Lagrangian, in Situ, Global, High-Performance Particle Tracking (LIGHT)

    DOE PAGESBeta

    Wolfram, Phillip J.; Ringler, Todd D.; Maltrud, Mathew E.; Jacobsen, Douglas W.; Petersen, Mark R.

    2015-08-01

    Isopycnal diffusivity due to stirring by mesoscale eddies in an idealized, wind-forced, eddying, midlatitude ocean basin is computed using Lagrangian, in Situ, Global, High-Performance Particle Tracking (LIGHT). Simulation is performed via LIGHT within the Model for Prediction across Scales Ocean (MPAS-O). Simulations are performed at 4-, 8-, 16-, and 32-km resolution, where the first Rossby radius of deformation (RRD) is approximately 30 km. Scalar and tensor diffusivities are estimated at each resolution based on 30 ensemble members using particle cluster statistics. Each ensemble member is composed of 303 665 particles distributed across five potential density surfaces. Diffusivity dependence upon modelmore » resolution, velocity spatial scale, and buoyancy surface is quantified and compared with mixing length theory. The spatial structure of diffusivity ranges over approximately two orders of magnitude with values of O(105) m2 s–1 in the region of western boundary current separation to O(103) m2 s–1 in the eastern region of the basin. Dominant mixing occurs at scales twice the size of the first RRD. Model resolution at scales finer than the RRD is necessary to obtain sufficient model fidelity at scales between one and four RRD to accurately represent mixing. Mixing length scaling with eddy kinetic energy and the Lagrangian time scale yield mixing efficiencies that typically range between 0.4 and 0.8. In conclusion, a reduced mixing length in the eastern region of the domain relative to the west suggests there are different mixing regimes outside the baroclinic jet region.« less

  11. Maskless direct laser writing with visible light: Breaking through the optical resolving limit with cooperative manipulations of nonlinear reverse saturation absorption and thermal diffusion

    SciTech Connect

    Wei, Jingsong; Wang, Rui

    2014-03-28

    In this work, the resolving limit of maskless direct laser writing is overcome by cooperative manipulation from nonlinear reverse saturation absorption and thermal diffusion, where the nonlinear reverse saturation absorption can induce the formation of below diffraction-limited energy absorption spot, and the thermal diffusion manipulation can make the heat quantity at the central region of energy absorption spot propagate along the thin film thickness direction. The temperature at the central region of energy absorption spot transiently reaches up to melting point and realizes nanolithography. The sample “glass substrate/AgInSbTe” is prepared, where AgInSbTe is taken as nonlinear reverse saturation absorption thin film. The below diffraction-limited energy absorption spot is simulated theoretically and verified experimentally by near-field spot scanning method. The “glass substrate/Al/AgInSbTe” sample is prepared, where the Al is used as thermal conductive layer to manipulate the thermal diffusion channel because the thermal diffusivity coefficient of Al is much larger than that of AgInSbTe. The direct laser writing is conducted by a setup with a laser wavelength of 650 nm and a converging lens of NA=0.85, the lithographic marks with a size of about 100 nm are obtained, and the size is only about 1/10 the incident focused spot. The experimental results indicate that the cooperative manipulation from nonlinear reverse saturation absorption and thermal diffusion is a good method to realize nanolithography in maskless direct laser writing with visible light.

  12. Linear and nonlinear light scattering and absorption in free-electron nanoclusters with diffuse surface: General considerations and linear response

    SciTech Connect

    Fomichev, S. V.; Becker, W.

    2010-06-15

    Both linear and nonlinear scattering and absorption of a laser pulse by spherical nanoclusters with free electrons and with a diffuse surface are considered in the collisionless hydrodynamics approximation. The developed model of forced collective motion of electrons confined to a cluster permits one consistently to introduce into the theory all the sources of nonlinearity, as well as the inhomogeneity of the cluster near its boundary. Two different perturbation theories corresponding to different laser intensity ranges are developed in this context, and both cold metal clusters and hot laser-heated or -ionized clusters are considered within the same approach. In the present article, after developing the full nonlinear model, the linear response to the laser field of the free-electron cluster with diffuse surface is investigated in detail, especially the properties of the linear Mie resonance (width and position). Under certain conditions, depending on the various cluster parameters secondary resonances are found. The properties of resonance-enhanced third-order harmonic generation and nonlinear laser absorption and their dependence on the shape of the diffuse surface will be presented separately.

  13. Built-in hyperspectral camera for smartphone in visible, near-infrared and middle-infrared lights region (second report): sensitivity improvement of Fourier-spectroscopic imaging to detect diffuse reflection lights from internal human tissues for healthcare sensors

    NASA Astrophysics Data System (ADS)

    Kawashima, Natsumi; Hosono, Satsuki; Ishimaru, Ichiro

    2016-05-01

    We proposed the snapshot-type Fourier spectroscopic imaging for smartphone that was mentioned in 1st. report in this conference. For spectroscopic components analysis, such as non-invasive blood glucose sensors, the diffuse reflection lights from internal human skins are very weak for conventional hyperspectral cameras, such as AOTF (Acousto-Optic Tunable Filter) type. Furthermore, it is well known that the spectral absorption of mid-infrared lights or Raman spectroscopy especially in long wavelength region is effective to distinguish specific biomedical components quantitatively, such as glucose concentration. But the main issue was that photon energies of middle infrared lights and light intensities of Raman scattering are extremely weak. For improving sensitivity of our spectroscopic imager, the wide-field-stop & beam-expansion method was proposed. Our line spectroscopic imager introduced a single slit for field stop on the conjugate objective plane. Obviously to increase detected light intensities, the wider slit width of the field stop makes light intensities higher, regardless of deterioration of spatial resolutions. Because our method is based on wavefront-division interferometry, it becomes problems that the wider width of single slit makes the diffraction angle narrower. This means that the narrower diameter of collimated objective beams deteriorates visibilities of interferograms. By installing the relative inclined phaseshifter onto optical Fourier transform plane of infinity corrected optical systems, the collimated half flux of objective beams derived from single-bright points on objective surface penetrate through the wedge prism and the cuboid glass respectively. These two beams interfere each other and form the infererogram as spatial fringe patterns. Thus, we installed concave-cylindrical lens between the wider slit and objective lens as a beam expander. We successfully obtained the spectroscopic characters of hemoglobin from reflected lights from

  14. Far-ultraviolet studies. VI - Further limits on diffuse galactic light scattered at large angles by dust

    NASA Technical Reports Server (NTRS)

    Anderson, R. C.; Henry, R. C.; Fastie, W. G.

    1982-01-01

    The Apollo 17 wide-field far-ultraviolet spectrometer was used to scan six large bands of the sky during trans-earth coast. After accounting for internal scattered light and the light expected from stars in the field of view, no significant residual flux remains. This imposes important constraints on the scattering properties of the interstellar dust grains: either the grains are extremely strongly forward scattering, or the albedo of the grains is low. The absence of a scattered light signal from dusty, moderate galactic latitude regions of the sky indicates that the high galactic latitude flux reported by Henry et al. (1977) and by Anderson et al. (1979) does not represent starlight backscattered by dust.

  15. The effect of humidity and light on cellular water relations and diffusion conductance of leaves ofTradescantia virginiana L.

    PubMed

    Frensch, J; Schulze, E D

    1988-12-01

    Turgor (Ψp) and osmotic potential (Ψs) in epidermal and mesophyll cells, in-situ xylem water potential (Ψ-xyl) and gas exchange were measured during changes of air humidity and light in leaves ofTradescantia virginiana L., Turgor of single cells was determined using the pressure probe. Sap of individual cells was collected with the probe for measuring the freezing-point depression in a nanoliter osmometer. Turgor pressure was by 0.2 to 0.4 MPa larger in mesophyll cells than in epidermal cells. A water-potential gradient, which was dependent on the rate of transpiration, was found between epidermis and mesophyll and between tip and base of the test leaf. Step changes of humidity or light resulted in changes of epidermal and mesophyll turgor (Ψp-epi, Ψp-mes) and could be correlated with the transpiration rate. Osmotic potential was not affected by a step change of humidity or light. For the humidity-step experiments, stomatal conductance (g) increased with increasing epidermal turgor.Δg/Ψp-epi appeared to be constant over a wide range of epidermal turgor pressures. In light-step experiments this type of response was not found and stomatal conductance could increase while epidermal turgor decreased. PMID:24226693

  16. Lighting

    SciTech Connect

    Audin, L.

    1994-12-31

    EPAct covers a vast territory beyond lighting and, like all legislation, also contains numerous {open_quotes}favors,{close_quotes} compromises, and even some sleight-of-hand. Tucked away under Title XIX, for example, is an increase from 20% to 28% tax on gambling winnings, effective January 1, 1993 - apparently as a way to help pay for new spending listed elsewhere in the bill. Overall, it is a landmark piece of legislation, about a decade overdue. It remains to be seen how the Federal Government will enforce upgrading of state (or even their own) energy codes. There is no mention of funding for {open_quotes}energy police{close_quotes} in EPAct. Merely creating such a national standard, however, provides a target for those who sincerely wish to create an energy-efficient future.

  17. Stray light in cone beam optical computed tomography: I. Measurement and reduction strategies with planar diffuse source

    NASA Astrophysics Data System (ADS)

    Granton, Patrick V.; Dekker, Kurtis H.; Battista, Jerry J.; Jordan, Kevin J.

    2016-04-01

    Optical cone-beam computed tomographic (CBCT) scanning of 3D radiochromic dosimeters may provide a practical method for 3D dose verification in radiation therapy. However, in cone-beam geometry stray light contaminates the projection images, degrading the accuracy of reconstructed linear attenuation coefficients. Stray light was measured using a beam pass aperture array (BPA) and structured illumination methods. The stray-to-primary ray ratio (SPR) along the central axis was found to be 0.24 for a 5% gelatin hydrogel, representative of radiochromic hydrogels. The scanner was modified by moving the spectral filter from the detector to the source, changing the light’s spatial fluence pattern and lowering the acceptance angle by extending distance between the source and object. These modifications reduced the SPR significantly from 0.24 to 0.06. The accuracy of the reconstructed linear attenuation coefficients for uniform carbon black liquids was compared to independent spectrometer measurements. Reducing the stray light increased the range of accurate transmission readings. In order to evaluate scanner performance for the more challenging application to small field dosimetry, a carbon black finger gel phantom was prepared. Reconstructions of the phantom from CBCT and fan-beam CT scans were compared. The modified source resulted in improved agreement. Subtraction of residual stray light, measured with BPA or structured illumination from each projection further improved agreement. Structured illumination was superior to BPA for measuring stray light for the smaller 1.2 and 0.5 cm diameter phantom fingers. At the costs of doubling the scanner size and tripling the number of scans, CBCT reconstructions of low-scattering hydrogel dosimeters agreed with those of fan-beam CT scans.

  18. Diffuse light propagation in a turbid medium with varying refractive index: Monte Carlo modeling in a spherically symmetrical geometry.

    PubMed

    Shendeleva, Margarita L; Molloy, John A

    2006-09-20

    We report on the development of Monte Carlo software that can model media with spatially varying scattering coefficient, absorption, and refractive index. The varying refractive index is implemented by calculating curved photon paths in the medium. The results of the numerical simulations are compared with analytical solutions obtained using the diffusion approximation. The model under investigation is a scattering medium that contains a spherically symmetrical inclusion (inhomogeneity) created by variation in optical properties and having no sharp boundaries. The following steady-state cases are considered: (a) a nonabsorbing medium with a spherically symmetrical varying refractive index, (b) an inclusion with varying absorption and scattering coefficients and constant refractive index, and (c) an inclusion with varying absorption, scattering, and refractive index. In the latter case it is shown that the interplay between the absorption coefficient and the refractive index may create the effect of a hidden inclusion.

  19. Specific features of diffuse reflection of human face skin for laser and non-laser sources of visible and near-IR light

    SciTech Connect

    Dolotov, L E; Sinichkin, Yu P; Tuchin, Valerii V; Al'tshuler, G B; Yaroslavskii, I V

    2011-04-30

    The specific features of diffuse reflection from different areas of human face skin for laser and non-laser sources of visible and near-IR light have been investigated to localise the closed-eye (eyelid) region. In the visible spectral range the reflection from the eyelid skin surface can be differentiated by measuring the slope of the spectral dependence of the effective optical density of skin in the wavelength range from 650 to 700nm. In the near-IR spectral range the reflectances of the skin surface at certain wavelengths, normalised to the forehead skin reflectance, can be used as a criterion for differentiating the eyelid skin. In this case, a maximum discrimination is obtained when measuring the skin reflectances at laser wavelengths of 1310 and 1470nm, which correspond to the spectral ranges of maximum and minimum water absorption. (optical technologies in biophysics and medicine)

  20. Specific features of diffuse reflection of human face skin for laser and non-laser sources of visible and near-IR light

    NASA Astrophysics Data System (ADS)

    Dolotov, L. E.; Sinichkin, Yu P.; Tuchin, Valerii V.; Al'tshuler, G. B.; Yaroslavskii, I. V.

    2011-04-01

    The specific features of diffuse reflection from different areas of human face skin for laser and non-laser sources of visible and near-IR light have been investigated to localise the closed-eye (eyelid) region. In the visible spectral range the reflection from the eyelid skin surface can be differentiated by measuring the slope of the spectral dependence of the effective optical density of skin in the wavelength range from 650 to 700nm. In the near-IR spectral range the reflectances of the skin surface at certain wavelengths, normalised to the forehead skin reflectance, can be used as a criterion for differentiating the eyelid skin. In this case, a maximum discrimination is obtained when measuring the skin reflectances at laser wavelengths of 1310 and 1470nm, which correspond to the spectral ranges of maximum and minimum water absorption.

  1. Barrier performance optimization of atomic layer deposited diffusion barriers for organic light emitting diodes using x-ray reflectivity investigations

    SciTech Connect

    Singh, Aarti Schröder, Uwe; Klumbies, Hannes; Müller-Meskamp, Lars; Leo, Karl; Geidel, Marion; Knaut, Martin; Hoßbach, Christoph; Albert, Matthias; Mikolajick, Thomas

    2013-12-02

    The importance of O{sub 3} pulse duration for encapsulation of organic light emitting diodes (OLEDs) with ultra thin inorganic atomic layer deposited Al{sub 2}O{sub 3} layers is demonstrated for deposition temperatures of 50 °C. X-ray reflectivity (XRR) measurements show that O{sub 3} pulse durations longer than 15 s produce dense and thin Al{sub 2}O{sub 3} layers. Correspondingly, black spot growth is not observed in OLEDs encapsulated with such layers during 91 days of aging under ambient conditions. This implies that XRR can be used as a tool for process optimization of OLED encapsulation layers leading to devices with long lifetimes.

  2. Evaluation of light scattering properties and chromophore concentrations in skin tissue based on diffuse reflectance signals at isosbestic wavelengths of hemoglobin

    NASA Astrophysics Data System (ADS)

    Yokokawa, Takumi; Nishidate, Izumi

    2016-04-01

    We investigate a method to evaluate light-scattering properties and chromophore concentrations in human skin tissue through diffuse reflectance spectroscopy using the reflectance signals acquired at isosbestic wavelengths of hemoglobin (420, 450, 500, and 585 nm). In the proposed method, Monte Carlo simulation-based empirical formulas are used to specify the scattering parameters of skin tissue, such as the scattering amplitude a and the scattering power b, as well as the concentration of melanin C m and the total blood concentration C tb. The use of isosbestic wavelengths of hemoglobin enables the values of C m, C tb, a, and b to be estimated independently of the oxygenation of hemoglobin. The spectrum of the reduced scattering coefficient is reconstructed from the scattering parameters. Experiments using in vivo human skin tissues were performed to confirm the feasibility of the proposed method for evaluating the changes in scattering properties and chromophore concentrations in skin tissue. The experimental results revealed that light scattering is significantly reduced by the application of a glycerol solution, which indicates an optical clearing effect due to osmotic dehydration and the matching of the refractive indices of scatterers in the epidermis.

  3. Quantificaion of ion diffusion in gallium arsenide-based spintronic Light-Emitting Diode devices using time-of-flight secondary ion mass spectrometry

    NASA Astrophysics Data System (ADS)

    Cogswell, Jeffrey Ryan

    Depth profiling using Secondary Ion Mass Spectrometry (SIMS) is a direct method to measure diffusion of atomic or molecular species that have migrated distances of nanometers/micrometers in a specific material. For this research, the diffusion of Mn, sequentially Ga ions, in Gallium Arsenide (GaAs)-based spin Light Emitting Diode (LED) devices is studied by quantitative Time-of-Flight (ToF) SIMS. The goal is to prove conclusively the driving force and mechanism behind Mn diffusion in GaAs by quantifying the diffusion of these ions in each device. Previous work has identified two competing processes for the movement of Mn in GaAs: diffusion and phase separation. The process is dependent on the temperature the sample is exposed to, either by post-annealing, or during the molecular beam epitaxy (MBE) growth process. The hypothesis is that Manganese Arsenide (MnAs) is thermodynamically more stable than randomly distributed Mn ions in GaAs, and that by annealing at a certain temperature, a pure MnAs layer can be produced from a GaMnAs layer in a working spin LED device. Secondly, the spin efficiencies will be measured and the difference will be related to the formation of a pure MnAs layer. The first chapter of this dissertation discusses the history of spintronic devices, including details on the established methods for characterization, the importance for potential application to the semiconductor industry, and the requirements for the full implementation of spintronic devices in modern-day computers. MnAs and GaMnAs devices are studied, their preparation and properties are described, and the study's experimental design is covered in the latter part of Chapter 1. Chapter 2 includes a review of diffusion in semiconductors, including the types of diffusion, mechanisms they follow, and the different established experimental methods for studying diffusion. The later sections include summaries of Mn diffusion and previous studies investigating Mn diffusion in different

  4. Structure and phase diagram of an adhesive colloidal dispersion under high pressure: A small angle neutron scattering, diffusing wave spectroscopy, and light scattering study

    NASA Astrophysics Data System (ADS)

    Vavrin, R.; Kohlbrecher, J.; Wilk, A.; Ratajczyk, M.; Lettinga, M. P.; Buitenhuis, J.; Meier, G.

    2009-04-01

    We have applied small angle neutron scattering (SANS), diffusing wave spectroscopy (DWS), and dynamic light scattering (DLS) to investigate the phase diagram of a sterically stabilized colloidal system consisting of octadecyl grafted silica particles dispersed in toluene. This system is known to exhibit gas-liquid phase separation and percolation, depending on temperature T, pressure P, and concentration φ. We have determined by DLS the pressure dependence of the coexistence temperature and the spinodal temperature to be dP /dT=77 bar/K. The gel line or percolation limit was measured by DWS under high pressure using the condition that the system became nonergodic when crossing it and we determined the coexistence line at higher volume fractions from the DWS limit of turbid samples. From SANS measurements we determined the stickiness parameter τB(P,T,φ) of the Baxter model, characterizing a polydisperse adhesive hard sphere, using a global fit routine on all curves in the homogenous regime at various temperatures, pressures, and concentrations. The phase coexistence and percolation line as predicted from τB(P,T,φ) correspond with the determinations by DWS and were used to construct an experimental phase diagram for a polydisperse sticky hard sphere model system. A comparison with theory shows good agreement especially concerning the predictions for the percolation threshold. From the analysis of the forward scattering we find a critical scaling law for the susceptibility corresponding to mean field behavior. This finding is also supported by the critical scaling properties of the collective diffusion.

  5. A tantalum diffusion barrier layer for improving the output performance of AlGaInP-based light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Kim, Dae-Hyun; Park, Jae-Seong; Kang, Daesung; Seong, Tae-Yeon

    2016-03-01

    We have investigated the effect of a Ta diffusion barrier layer on the electrical characteristics of AuBe/Au contacts on a p-GaP window layer for AlGaInP-based light-emitting diodes (LEDs). It was shown that after annealing at 500 °C, the AuBe/Ta/Au contacts exhibited nearly 2 orders of magnitude lower specific contact resistance (2.8 × 10-6 Ω·cm2) than the AuBe/Au contacts (1.0 × 10-4 Ω·cm2). The LEDs with and without the Ta diffusion barrier layer showed an external quantum efficiency of 14.03 and 13.5% at 50 mA, respectively. After annealing at 500 °C, the AuBe/Ta/Au contacts showed a higher reflectance (92.8% at 617 nm) than that of the AuBe/Au contacts (87.7%). X-ray photoemission spectroscopy (XPS) results showed that the Ga 2p core level for the annealed AuBe/Au samples shifted to higher binding energies, while this level shifted towards lower binding energies for the AuBe/Ta/Au samples. Depth profiles using Auger electron spectroscopy (AES) showed that annealing of the AuBe/Au samples caused the outdiffusion of both Be and P atoms into the metal contact, while for the AuBe/Ta/Au samples, the outdiffusion of Be atoms was blocked by the Ta barrier layer and more Be atoms were indiffused into GaP. The annealing-induced electrical degradation and ohmic contact formation are described and discussed based on the XPS and electrical results.

  6. Instrumentation in Diffuse Optical Imaging

    PubMed Central

    Zhang, Xiaofeng

    2014-01-01

    Diffuse optical imaging is highly versatile and has a very broad range of applications in biology and medicine. It covers diffuse optical tomography, fluorescence diffuse optical tomography, bioluminescence, and a number of other new imaging methods. These methods of diffuse optical imaging have diversified instrument configurations but share the same core physical principle – light propagation in highly diffusive media, i.e., the biological tissue. In this review, the author summarizes the latest development in instrumentation and methodology available to diffuse optical imaging in terms of system architecture, light source, photo-detection, spectral separation, signal modulation, and lastly imaging contrast. PMID:24860804

  7. Diffuse light in z˜0.25 galaxy clusters: constraining tidal damage and the faint end of the luminosity function

    NASA Astrophysics Data System (ADS)

    Zibetti, Stefano; White, Simon D. M.

    The starlight coming from the intergalactic space in galaxy clusters and groups witnesses the violent tidal interactions that galaxies experience in these dense environments. Such interactions may be (at least partly) responsible for the transformation of normal star-forming galaxies into passive dwarf ellipticals (dEs).In this contribution we present the first systematic study of the IntraCluster Light (ICL) for a statistically representative sample (Zibetti et al. 2005), which comprises 683 clusters selected between z=0.2 and 0.3 from {˜}1500 °2 in the SDSS. Their ICL is studied by stacking the images in the g-, r-, and i-band after masking out all galaxies and polluting sources. In this way a very uniform background illumination is obtained, that allows us to measure surface brightnesses as faint as 31 mag arcsec-2 and to trace the ICL out to 700 kpc from the central galaxy. We find that the local fraction of light contributed by intracluster stars rapidly decreases as a function of the clustercentric distance, from ˜40% at 100 kpc to ˜5% at 500 kpc. By comparing the distribution and colours of the ICL and of the clusters galaxies, we find indication that the main source of ICL are the stars stripped from galaxies that plunge deeply into the cluster potential well along radial orbits. Thus, if dEs are the remnants of these stripped progenitors we should expect similar radial orbital anisotropies and correlations between the dE luminosity function and the amount of ICL in different clusters.The diffuse emission we measure is contaminated by faint unresolved galaxies: this makes our flux estimate depend to some extent on the assumed luminosity function, but, on the other hand, allows us to constrain the number of faint galaxies. Our present results disfavour steep (α) faint-end powerlaw slopes.

  8. Investigation of in-flame soot optical properties in laminar coflow diffusion flames using thermophoretic particle sampling and spectral light extinction

    NASA Astrophysics Data System (ADS)

    Kempema, Nathan J.; Ma, Bin; Long, Marshall B.

    2016-09-01

    Soot optical properties are essential to the noninvasive study of the in-flame evolution of soot particles since they allow quantitative interpretation of optical diagnostics. Such experimental data are critical for comparison to results from computational models and soot sub-models. In this study, the thermophoretic sampling particle diagnostic (TSPD) technique is applied along with data from a previous spectrally resolved line-of-sight light attenuation experiment to determine the soot volume fraction and absorption function. The TSPD technique is applied in a flame stabilized on the Yale burner, and the soot scattering-to-absorption ratio is calculated using the Rayleigh-Debye-Gans theory for fractal aggregates and morphology information from a previous sampling experiment. The soot absorption function is determined as a function of wavelength and found to be in excellent agreement with previous in-flame measurements of the soot absorption function in coflow laminar diffusion flames. Two-dimensional maps of the soot dispersion exponent are calculated and show that the soot absorption function may have a positive or negative exponential wavelength dependence depending on the in-flame location. Finally, the wavelength dependence of the soot absorption function is related to the ratio of soot absorption functions, as would be found using two-excitation-wavelength laser-induced incandescence.

  9. Low-Resolution Spectrum of the Diffuse Galactic Light and 3.3 μm PAH Emission with the AKARI InfraRed Camera

    NASA Astrophysics Data System (ADS)

    Tsumura, Kohji; Matsumoto, Toshio; Matsuura, Shuji; Sakon, Itsuki; Tanaka, Masahiro; Wada, Takehiko

    2013-12-01

    We first obtained the spectrum of the diffuse Galactic light (DGL) at general interstellar space in the 1.8-5.3μm wavelength region with the low-resolution prism spectroscopy mode of the AKARI Infra-Red Camera (IRC) NIR channel. The 3.3μm m PAH band is detected in the DGL spectrum at Galactic latitude |b| < 15˚, and its correlations with the Galactic dust and gas are confirmed. The correlation between the 3.3μm PAH band and the thermal emission from the Galactic dust is expressed not by a simple linear correlation, but by a relation with extinction. Using this correlation, the spectral shape of DGL at an optically thin region (5˚ < |b| < 15˚) was derived as a template spectrum. Assuming that the spectral shape of this template spectrum is uniform at any position, the DGL spectrum can be estimated by scaling this template spectrum using the correlation between the 3.3μm PAH band and the thermal emission from the Galactic dust.

  10. Diffuse Optical Intracluster Light as a Measure of Stellar Tidal Stripping: The Cluster CL0024+17 at z ~ 0.4 Observed at the Large Binocular Telescope

    NASA Astrophysics Data System (ADS)

    Giallongo, E.; Menci, N.; Grazian, A.; Gallozzi, S.; Castellano, M.; Fiore, F.; Fontana, A.; Pentericci, L.; Boutsia, K.; Paris, D.; Speziali, R.; Testa, V.

    2014-01-01

    We have evaluated the diffuse intracluster light (ICL) in the central core of the galaxy cluster CL0024+17 at z ~ 0.4 observed with the prime focus camera (Large Binocular Camera) at the Large Binocular Telescope. The measure required an accurate removal of the galaxies' light within ~200 kpc from the center. The residual background intensity has then been integrated in circular apertures to derive the average ICL intensity profile. The latter shows an approximate exponential decline as expected from theoretical cold dark matter models where the ICL is due to the integrated contribution of light from stars that are tidally stripped from the halo of their host galaxies due to encounters with other galaxies in the cluster cold dark matter (CDM) potential. The radial profile of the ICL over the galaxies intensity ratio (ICL fraction) is increasing with decreasing radius, but near the cluster center it starts to bend and then decreases where the overlap of the halos of the brightest cluster galaxies becomes dominant. Theoretical expectations in a simplified CDM scenario show that the ICL fraction profile can be estimated from the stripped over galaxy stellar mass ratio in the cluster. It is possible to show that the latter quantity is almost independent of the properties of the individual host galaxies but mainly depends on the average cluster properties. The predicted ICL fraction profile is thus very sensitive to the assumed CDM profile, total mass, and concentration parameter of the cluster. Adopting values very similar to those derived from the most recent lensing analysis in CL0024+17, we find a good agreement with the observed ICL fraction profile. The galaxy counts in the cluster core have then been compared with that derived from composite cluster samples in larger volumes, up to the clusters virial radius. The galaxy counts in the CL0024+17 core appear flatter and the amount of bending with respect to the average cluster galaxy counts imply a loss of total

  11. An analysis of diffuse light attenuation in the northern Gulf of Mexico hypoxic zone using the SeaWiFS satellite data record

    EPA Science Inventory

    The water column diffuse attenuation coefficient (Kd) of the Louisiana Continental Shelf (LCS) was examined during ten years to characterize the spatial and temporal variations on monthly scales from 1998 to 2007. This region is well-known for summer hypoxia (dissolved oxygen < 2...

  12. Diffusion MRI

    NASA Astrophysics Data System (ADS)

    Fukuyama, Hidenao

    Recent advances of magnetic resonance imaging have been described, especially stressed on the diffusion sequences. We have recently applied the diffusion sequence to functional brain imaging, and found the appropriate results. In addition to the neurosciences fields, diffusion weighted images have improved the accuracies of clinical diagnosis depending upon magnetic resonance images in stroke as well as inflammations.

  13. Diffusion of polyelectrolytes in polyelectrolyte gels

    NASA Astrophysics Data System (ADS)

    Rahalkar, Anand; Muthukumar, Murugappan

    2015-03-01

    Using dynamic light scattering, we have investigated the diffusion coefficient of sodium poly(styrene sulfonate) in a matrix of poly(acrylamide-co-acrylate) gels. The diffusion coefficient of the probe polyelectrolyte exhibits a crossover behavior from a particle-diffusion to entropic-barrier dominated diffusion, as the molecular weight is increased. The effect of electrostatics, by varying the charge density of the matrix, on probe diffusion constant will be presented.

  14. Designing Au Surface-Modified Nanoporous-Single-Crystalline SrTiO3 to Optimize Diffusion of Surface Plasmon Resonance-Induce Photoelectron toward Enhanced Visible-Light Photoactivity.

    PubMed

    Lu, Da; Ouyang, Shuxin; Xu, Hua; Li, Dewang; Zhang, Xueliang; Li, Yunxiang; Ye, Jinhua

    2016-04-13

    Nanoporous single-crystalline SrTiO3 is fabricated at a low temperature of 60 °C via a novel approach of sol-gel alkali-dissolution-exothermal reaction. The plasmon-active metal Au is loaded on the nanoporous single-crystalline SrTiO3 material to construct a new kind of plasmonic photocatalyst. Due to the single-crystalline nature and the space confinement effect of pores for Au growing, not only the promoted diffusion efficiency of surface plasmon resonance (SPR)-induce photoelectron is achieved, but also the diffusion region are well optimized via changing the loading amount of Au. Therefore, an optimal sample with 4.8 wt % Au loading exhibits a more than 40-fold photoactivity enhancement under visible-light irradiation compared to the common nanosized SrTiO3 (a commercially available sample) loaded with 5.3 wt % Au which was prepared under the same condition. Furthermore, combining the special nanostructure of Au surface-modified nanoporous-single-crystalline SrTiO3 with photocatalytic properties, estimation of the diffusion mean free path of SPR-induce photoelectron can be achieved. This study proposes an alternative approach to enhance the photoactivity of plasmonic photocatalyst via fine designing the semiconductor substrate. PMID:27007490

  15. Light-Induced Increase of Electron Diffusion Length in a p-n Junction Type CH3NH3PbBr3 Perovskite Solar Cell.

    PubMed

    Kedem, Nir; Brenner, Thomas M; Kulbak, Michael; Schaefer, Norbert; Levcenko, Sergiu; Levine, Igal; Abou-Ras, Daniel; Hodes, Gary; Cahen, David

    2015-07-01

    High band gap, high open-circuit voltage solar cells with methylammonium lead tribromide (MAPbBr3) perovskite absorbers are of interest for spectral splitting and photoelectrochemical applications, because of their good performance and ease of processing. The physical origin of high performance in these and similar perovskite-based devices remains only partially understood. Using cross-sectional electron-beam-induced current (EBIC) measurements, we find an increase in carrier diffusion length in MAPbBr3(Cl)-based solar cells upon low intensity (a few percent of 1 sun intensity) blue laser illumination. Comparing dark and illuminated conditions, the minority carrier (electron) diffusion length increases about 3.5 times from Ln = 100 ± 50 nm to 360 ± 22 nm. The EBIC cross section profile indicates a p-n structure between the n-FTO/TiO2 and p-perovskite, rather than the p-i-n structure, reported for the iodide derivative. On the basis of the variation in space-charge region width with varying bias, measured by EBIC and capacitance-voltage measurements, we estimate the net-doping concentration in MAPbBr3(Cl) to be 3-6 × 10(17) cm(-3).

  16. Combination Light

    NASA Technical Reports Server (NTRS)

    1990-01-01

    The Rayovac TANDEM is an advanced technology combination work light and general purpose flashlight that incorporates several NASA technologies. The TANDEM functions as two lights in one. It features a long range spotlight and wide angle floodlight; simple one-hand electrical switching changes the beam from spot to flood. TANDEM developers made particular use of NASA's extensive research in ergonomics in the TANDEM's angled handle, convenient shape and different orientations. The shatterproof, water resistant plastic casing also draws on NASA technology, as does the shape and beam distance of the square diffused flood. TANDEM's heavy duty magnet that permits the light to be affixed to any metal object borrows from NASA research on rare earth magnets that combine strong magnetic capability with low cost. Developers used a NASA-developed ultrasonic welding technique in the light's interior.

  17. Diffuse Optics for Tissue Monitoring and Tomography

    PubMed Central

    Durduran, T; Choe, R; Baker, W B; Yodh, A G

    2015-01-01

    This review describes the diffusion model for light transport in tissues and the medical applications of diffuse light. Diffuse optics is particularly useful for measurement of tissue hemodynamics, wherein quantitative assessment of oxy- and deoxy-hemoglobin concentrations and blood flow are desired. The theoretical basis for near-infrared or diffuse optical spectroscopy (NIRS or DOS, respectively) is developed, and the basic elements of diffuse optical tomography (DOT) are outlined. We also discuss diffuse correlation spectroscopy (DCS), a technique whereby temporal correlation functions of diffusing light are transported through tissue and are used to measure blood flow. Essential instrumentation is described, and representative brain and breast functional imaging and monitoring results illustrate the workings of these new tissue diagnostics. PMID:26120204

  18. Devitrite-based optical diffusers.

    PubMed

    Butt, Haider; Knowles, Kevin M; Montelongo, Yunuen; Amaratunga, Gehan A J; Wilkinson, Timothy D

    2014-03-25

    Devitrite is a novel material produced by heat treatment of commercial soda-lime-silica glass. It consists of fans of needle-like crystals which can extend up to several millimeters and have interspacings of up to a few hundred nanometers. To date, only the material properties of devitrite have been reported, and there has been a distinct lack of research on using it for optical applications. In this study, we demonstrate that randomly oriented fans of devitrite crystals can act as highly efficient diffusers for visible light. Devitrite crystals produce phase modulation of light because of their relatively high anisotropy. The nanoscale spacings between these needles enable light to be diffused to large scattering angles. Experimentally measured results suggest that light diffusion patterns with beam widths of up to 120° are produced. Since devitrite is an inexpensive material to produce, it has the potential to be used in a variety of commercial applications.

  19. Exciton quenching by diffusion of 2,3,5,6-tetrafluoro-7,7',8,8'-tetra cyano quino dimethane and its consequences on joule heating and lifetime of organic light-emitting diodes.

    PubMed

    Tyagi, Priyanka; Kumar, Arunandan; Giri, Lalat Indu; Dalai, Manas Kumar; Tuli, Suneet; Kamalasanan, M N; Srivastava, Ritu

    2013-10-01

    In this Letter, the effect of F(4)-TCNQ insertion at the anode/hole transport layer (HTL) interface was studied on joule heating and the lifetime of organic light-emitting diodes (OLEDs). Joule heating was found to reduce significantly (pixel temperature decrease by about 10 K at a current density of 40 mA/cm(2)) by this insertion. However, the lifetime was found to reduce significantly with a 1 nm thick F(4)-TCNQ layer, and it improved by increasing the thickness of this layer. Thermal diffusion of F(4)-TCNQ into HTL leads to F(4)-TCNQ ionization by charge transfer, and drift of these molecules into the emissive layer caused faster degradation of the OLEDs. This drift was found to reduce with an increase in the thickness of F(4)-TCNQ. PMID:24081070

  20. Vaneless diffusers

    NASA Astrophysics Data System (ADS)

    Senoo, Y.

    The influence of vaneless diffusers on flow in centrifugal compressors, particularly on surge, is discussed. A vaneless diffuser can demonstrate stable operation in a wide flow range only if it is installed with a backward leaning blade impeller. The circumferential distortion of flow in the impeller disappears quickly in the vaneless diffuser. The axial distortion of flow at the diffuser inlet does not decay easily. In large specific speed compressors, flow out of the impeller is distorted axially. Pressure recovery of diffusers at distorted inlet flow is considerably improved by half guide vanes. The best height of the vanes is a little 1/2 diffuser width. In small specific speed compressors, flow out of the impeller is not much distorted and pressure recovery can be predicted with one-dimensional flow analysis. Wall friction loss is significant in narrow diffusers. The large pressure drop at a small flow rate can cause the positive gradient of the pressure-flow rate characteristic curve, which may cause surging.

  1. Apparatus for diffusion separation

    DOEpatents

    Nierenberg, William A.; Pontius, Rex B.

    1976-08-10

    1. The method of testing the separation efficiency of porous permeable membranes which comprises causing a stream of a gaseous mixture to flow into contact with one face of a finely porous permeable membrane under such conditions that a major fraction of the mixture diffuses through the membrane, maintaining a rectangular cross section of the gaseous stream so flowing past said membrane, continuously recirculating the gas that diffuses through said membrane and continuously withdrawing the gas that does not diffuse through said membrane and maintaining the volume of said recirculating gas constant by continuously introducing into said continuously recirculating gas stream a mass of gas equivalent to that which is continuously withdrawn from said gas stream and comparing the concentrations of the light component in the entering gas, the withdrawn gas and the recirculated gas in order to determine the efficiency of said membrane.

  2. Diffuse light reflectance signals as potential indicators of loss of viability in brain tissue due to hypoxia: charge-coupled-device-based imaging and fiber-based measurement

    NASA Astrophysics Data System (ADS)

    Kawauchi, Satoko; Nishidate, Izumi; Uozumi, Yoichi; Nawashiro, Hiroshi; Ashida, Hiroshi; Sato, Shunichi

    2013-01-01

    Brain tissue is highly vulnerable to ischemia/hypoxia, and real-time monitoring of its viability is important. By fiber-based measurements for rat brain, we previously observed a unique triphasic reflectance change (TRC) after a certain period of time after hypoxia. After TRC, rats could not be rescued, suggesting that TRC can be used as an indicator of loss of brain tissue viability. In this study, we investigated this diffuse-reflectance change due to hypoxia in three parts. First, we developed and validated a theoretical method to quantify changes in the absorption and reduced scattering coefficients involved in TRC. Second, we performed charge-coupled-device-based reflectance imaging of the rat brain during hypoxia followed by reoxygenation to examine spatiotemporal characteristics of the reflectance and its correlation with reversibility of brain tissue damage. Third, we made simultaneous imaging and fiber-based measurement of the reflectance for the rat to compare signals obtained by these two modalities. We observed a nontriphasic reflectance change by the imaging, and it was associated with brain tissue viability. We found that TRC measured by the fibers preceded the reflectance-signal change captured by the imaging. This time difference is attributable to the different observation depths in the brain with these two methods.

  3. Diffusion-Controlled Rotation of Triptycene in a Metal–Organic Framework (MOF) Sheds Light on the Viscosity of MOF-Confined Solvent

    PubMed Central

    2016-01-01

    Artificial molecular machines are expected to operate under conditions of very low Reynolds numbers with inertial forces orders of magnitude smaller than viscous forces. While these conditions are relatively well understood in bulk fluids, opportunities to assess the role of viscous forces in confined crystalline media are rare. Here we report one such example of diffusion-controlled rotation in crystals and its application as a probe for viscosity of MOF-confined solvent. We describe the preparation and characterization of three pillared paddlewheel MOFs, with 9,10-bis(4-pyridylethynyl)triptycene 3 as a pillar and molecular rotator, and three axially substituted dicarboxylate linkers with different lengths and steric bulk. The noncatenated structure with a bulky dicarboxylate linker (UCLA-R3) features a cavity filled by 10 molecules of N,N-dimethylformamide (DMF). Solid-state 2H NMR analysis performed between 293 and 343 K revealed a fast 3-fold rotation of the pillar triptycene group with the temperature dependence consistent with a site exchange process determined by rotator-solvent interactions. The dynamic viscosity of the MOF-confined solvent was estimated to be 13.3 N·s/m2 (or Pa·s), which is 4 orders of magnitude greater than that of bulk DMF (8.2 × 10–4 N·s/m2), and comparable to that of honey. PMID:27725958

  4. Diffuse radiation

    NASA Technical Reports Server (NTRS)

    1981-01-01

    A diffuse celestial radiation which is isotropic at least on a course scale were measured from the soft X-ray region to about 150 MeV, at which energy the intensity falls below that of the galactic emission for most galactic latitudes. The spectral shape, the intensity, and the established degree of isotropy of this diffuse radiation already place severe constraints on the possible explanations for this radiation. Among the extragalactic theories, the more promising explanations of the isotropic diffuse emission appear to be radiation from exceptional galaxies from matter antimatter annihilation at the boundaries of superclusters of galaxies of matter and antimatter in baryon symmetric big bang models. Other possible sources for extragalactic diffuse gamma radiation are discussed and include normal galaxies, clusters of galaxies, primordial cosmic rays interacting with intergalactic matter, primordial black holes, and cosmic ray leakage from galaxies.

  5. Diffusion barriers

    NASA Technical Reports Server (NTRS)

    Nicolet, M. A.

    1983-01-01

    The choice of the metallic film for the contact to a semiconductor device is discussed. One way to try to stabilize a contact is by interposing a thin film of a material that has low diffusivity for the atoms in question. This thin film application is known as a diffusion barrier. Three types of barriers can be distinguished. The stuffed barrier derives its low atomic diffusivity to impurities that concentrate along the extended defects of a polycrystalline layer. Sacrificial barriers exploit the fact that some (elemental) thin films react in a laterally uniform and reproducible fashion. Sacrificial barriers have the advantage that the point of their failure is predictable. Passive barriers are those most closely approximating an ideal barrier. The most-studied case is that of sputtered TiN films. Stuffed barriers may be viewed as passive barriers whose low diffusivity material extends along the defects of the polycrystalline host.

  6. Monitoring hemodynamic and morphologic responses to closed head injury in a mouse model using orthogonal diffuse near-infrared light reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Abookasis, David; Shochat, Ariel; Mathews, Marlon S.

    2013-04-01

    The authors' aim is to assess and quantitatively measure brain hemodynamic and morphological variations during closed-head injury (CHI) in mice using orthogonal diffuse near-infrared reflectance spectroscopy (o-DRS). CHI is a type of injury to the head that does not penetrate the skull. Usually, it is caused by mechanical blows to the head and frequently occurs in traffic accidents, falls, and assaults. Measurements of brain optical properties, namely absorption and reduced scattering coefficients in the wavelength range from 650 to 1000 nm were carried out by employing different source-detector distance and locations to provide depth sensitivity on an intact scalp over the duration of the whole experiment. Furthermore, alteration in both cortical hemodynamics and morphologic markers, i.e., scattering power and amplitude properties were derived. CHI was induced in anesthetized male mice by a weight-drop model using ˜50 g cylindrical metal falling from a height of 90 cm onto the intact scalp producing an impact of 4500 g cm. With respect to baseline, difference in brain physiological properties was observed following injury up to 1 h post-trauma. Additionally, the reduced scattering spectral shapes followed Mie scattering theory was quantified and clearly shows changes in both scattering amplitude and power from baseline indicating structural variations likely from evolving cerebral edema during CHI. We further demonstrate high correlation between scattering amplitude and scattering power, with more than 20% difference in slope in comparison to preinjury. This result indicates the possibility of using the slope also as a marker for detection of structural changes. Finally, experiments investigating brain function during the first 20 min postinjury were conducted and changes in chromophore concentrations and scattering were observed. Overall, our experiments demonstrate the potential of using the proposed technique as a valuable quantitative noninvasive tool for

  7. Demonstrating Diffusion

    ERIC Educational Resources Information Center

    Foy, Barry G.

    1977-01-01

    Two demonstrations are described. Materials and instructions for demonstrating movement of molecules into cytoplasm using agar blocks, phenolphthalein, and sodium hydroxide are given. A simple method for demonstrating that the rate of diffusion of a gas is inversely proportional to its molecular weight is also presented. (AJ)

  8. Relativistic diffusion

    NASA Astrophysics Data System (ADS)

    Haba, Z.

    2009-02-01

    We discuss relativistic diffusion in proper time in the approach of Schay (Ph.D. thesis, Princeton University, Princeton, NJ, 1961) and Dudley [Ark. Mat. 6, 241 (1965)]. We derive (Langevin) stochastic differential equations in various coordinates. We show that in some coordinates the stochastic differential equations become linear. We obtain momentum probability distribution in an explicit form. We discuss a relativistic particle diffusing in an external electromagnetic field. We solve the Langevin equations in the case of parallel electric and magnetic fields. We derive a kinetic equation for the evolution of the probability distribution. We discuss drag terms leading to an equilibrium distribution. The relativistic analog of the Ornstein-Uhlenbeck process is not unique. We show that if the drag comes from a diffusion approximation to the master equation then its form is strongly restricted. The drag leading to the Tsallis equilibrium distribution satisfies this restriction whereas the one of the Jüttner distribution does not. We show that any function of the relativistic energy can be the equilibrium distribution for a particle in a static electric field. A preliminary study of the time evolution with friction is presented. It is shown that the problem is equivalent to quantum mechanics of a particle moving on a hyperboloid with a potential determined by the drag. A relation to diffusions appearing in heavy ion collisions is briefly discussed.

  9. Defusing Diffusion

    ERIC Educational Resources Information Center

    Dou, Remy; Hogan, DaNel; Kossover, Mark; Spuck, Timothy; Young, Sarah

    2013-01-01

    Diffusion has often been taught in science courses as one of the primary ways by which molecules travel, particularly within organisms. For years, classroom teachers have used the same common demonstrations to illustrate this concept (e.g., placing drops of food coloring in a beaker of water). Most of the time, the main contributor to the motion…

  10. Relativistic diffusion.

    PubMed

    Haba, Z

    2009-02-01

    We discuss relativistic diffusion in proper time in the approach of Schay (Ph.D. thesis, Princeton University, Princeton, NJ, 1961) and Dudley [Ark. Mat. 6, 241 (1965)]. We derive (Langevin) stochastic differential equations in various coordinates. We show that in some coordinates the stochastic differential equations become linear. We obtain momentum probability distribution in an explicit form. We discuss a relativistic particle diffusing in an external electromagnetic field. We solve the Langevin equations in the case of parallel electric and magnetic fields. We derive a kinetic equation for the evolution of the probability distribution. We discuss drag terms leading to an equilibrium distribution. The relativistic analog of the Ornstein-Uhlenbeck process is not unique. We show that if the drag comes from a diffusion approximation to the master equation then its form is strongly restricted. The drag leading to the Tsallis equilibrium distribution satisfies this restriction whereas the one of the Jüttner distribution does not. We show that any function of the relativistic energy can be the equilibrium distribution for a particle in a static electric field. A preliminary study of the time evolution with friction is presented. It is shown that the problem is equivalent to quantum mechanics of a particle moving on a hyperboloid with a potential determined by the drag. A relation to diffusions appearing in heavy ion collisions is briefly discussed.

  11. Effective photocatalytic disinfection of E. coli K-12 using AgBr-Ag-Bi2WO6 nanojunction system irradiated by visible light: the role of diffusing hydroxyl radicals.

    PubMed

    Zhang, Li-Sha; Wong, Kin-Hang; Yip, Ho-Yin; Hu, Chun; Yu, Jimmy C; Chan, Chiu-Yeung; Wong, Po-Keung

    2010-02-15

    Urgent development of effective and low-cost disinfecting technologies is needed to address the problems caused by an outbreak of harmful microorganisms. In this work, we report an effective photocatalytic disinfection of E. coli K-12 by using a AgBr-Ag-Bi(2)WO(6) nanojunction system as a catalyst under visible light (lambda >or= 400 nm) irradiation. The visible-light-driven (VLD) AgBr-Ag-Bi(2)WO(6) nanojunction could completely inactivate 5 x 10(7) cfu mL(-1) E. coli K-12 within 15 min, which was superior to other VLD photocatalysts such as Bi(2)WO(6) superstructure, Ag-Bi(2)WO(6) and AgBr-Ag-TiO(2) composite. Moreover, the photochemical mechanism of bactericidal action for the AgBr-Ag-Bi(2)WO(6) nanojunction was investigated by using different scavengers. It was found that the diffusing hydroxyl radicals generated both by the oxidative pathway and the reductive pathway play an important role in the photocatalytic disinfection. Moreover, direct contact between the AgBr-Ag-Bi(2)WO(6) nanojunction and bacterial cells was not necessary for the photocatalytic disinfection of E. coli K-12. Finally, the photocatalytic destruction of the bacterial cells was directly observed by TEM images and further confirmed by the determination of potassium ion (K(+)) leakage from the killed bacteria. This work provides a potential effective VLD photocatalyst to disinfect the bacterial cells, even to destruct the biofilm that can provide shelter and substratum for microorganisms and resist to disinfection.

  12. Effective photocatalytic disinfection of E. coli K-12 using AgBr-Ag-Bi2WO6 nanojunction system irradiated by visible light: the role of diffusing hydroxyl radicals.

    PubMed

    Zhang, Li-Sha; Wong, Kin-Hang; Yip, Ho-Yin; Hu, Chun; Yu, Jimmy C; Chan, Chiu-Yeung; Wong, Po-Keung

    2010-02-15

    Urgent development of effective and low-cost disinfecting technologies is needed to address the problems caused by an outbreak of harmful microorganisms. In this work, we report an effective photocatalytic disinfection of E. coli K-12 by using a AgBr-Ag-Bi(2)WO(6) nanojunction system as a catalyst under visible light (lambda >or= 400 nm) irradiation. The visible-light-driven (VLD) AgBr-Ag-Bi(2)WO(6) nanojunction could completely inactivate 5 x 10(7) cfu mL(-1) E. coli K-12 within 15 min, which was superior to other VLD photocatalysts such as Bi(2)WO(6) superstructure, Ag-Bi(2)WO(6) and AgBr-Ag-TiO(2) composite. Moreover, the photochemical mechanism of bactericidal action for the AgBr-Ag-Bi(2)WO(6) nanojunction was investigated by using different scavengers. It was found that the diffusing hydroxyl radicals generated both by the oxidative pathway and the reductive pathway play an important role in the photocatalytic disinfection. Moreover, direct contact between the AgBr-Ag-Bi(2)WO(6) nanojunction and bacterial cells was not necessary for the photocatalytic disinfection of E. coli K-12. Finally, the photocatalytic destruction of the bacterial cells was directly observed by TEM images and further confirmed by the determination of potassium ion (K(+)) leakage from the killed bacteria. This work provides a potential effective VLD photocatalyst to disinfect the bacterial cells, even to destruct the biofilm that can provide shelter and substratum for microorganisms and resist to disinfection. PMID:20085257

  13. Diffusion bonding

    DOEpatents

    Anderson, Robert C.

    1976-06-22

    1. A method for joining beryllium to beryllium by diffusion bonding, comprising the steps of coating at least one surface portion of at least two beryllium pieces with nickel, positioning a coated surface portion in a contiguous relationship with an other surface portion, subjecting the contiguously disposed surface portions to an environment having an atmosphere at a pressure lower than ambient pressure, applying a force upon the beryllium pieces for causing the contiguous surface portions to abut against each other, heating the contiguous surface portions to a maximum temperature less than the melting temperature of the beryllium, substantially uniformly decreasing the applied force while increasing the temperature after attaining a temperature substantially above room temperature, and maintaining a portion of the applied force at a temperature corresponding to about maximum temperature for a duration sufficient to effect the diffusion bond between the contiguous surface portions.

  14. Diffuse optical intracluster light as a measure of stellar tidal stripping: The cluster CL0024+17 at z ∼ 0.4 observed at the large binocular telescope

    SciTech Connect

    Giallongo, E.; Menci, N.; Grazian, A.; Gallozzi, S.; Castellano, M.; Fiore, F.; Fontana, A.; Pentericci, L.; Boutsia, K.; Paris, D.; Speziali, R.; Testa, V.

    2014-01-20

    We have evaluated the diffuse intracluster light (ICL) in the central core of the galaxy cluster CL0024+17 at z ∼ 0.4 observed with the prime focus camera (Large Binocular Camera) at the Large Binocular Telescope. The measure required an accurate removal of the galaxies' light within ∼200 kpc from the center. The residual background intensity has then been integrated in circular apertures to derive the average ICL intensity profile. The latter shows an approximate exponential decline as expected from theoretical cold dark matter models where the ICL is due to the integrated contribution of light from stars that are tidally stripped from the halo of their host galaxies due to encounters with other galaxies in the cluster cold dark matter (CDM) potential. The radial profile of the ICL over the galaxies intensity ratio (ICL fraction) is increasing with decreasing radius, but near the cluster center it starts to bend and then decreases where the overlap of the halos of the brightest cluster galaxies becomes dominant. Theoretical expectations in a simplified CDM scenario show that the ICL fraction profile can be estimated from the stripped over galaxy stellar mass ratio in the cluster. It is possible to show that the latter quantity is almost independent of the properties of the individual host galaxies but mainly depends on the average cluster properties. The predicted ICL fraction profile is thus very sensitive to the assumed CDM profile, total mass, and concentration parameter of the cluster. Adopting values very similar to those derived from the most recent lensing analysis in CL0024+17, we find a good agreement with the observed ICL fraction profile. The galaxy counts in the cluster core have then been compared with that derived from composite cluster samples in larger volumes, up to the clusters virial radius. The galaxy counts in the CL0024+17 core appear flatter and the amount of bending with respect to the average cluster galaxy counts imply a loss of total

  15. Modeling of hydrogen-air diffusion flame

    NASA Technical Reports Server (NTRS)

    Isaac, K. M.

    1988-01-01

    Work performed during the first six months of the project duration for NASA Grant (NAG-1-861) is reported. An analytical and computational study of opposed jet diffusion flame for the purpose of understanding the effects of contaminants in the reactants and thermal diffusion of light species on extinction and reignition of diffusion flames is in progress. The methodologies attempted so far are described.

  16. Flexible textile light diffuser for photodynamic therapy

    NASA Astrophysics Data System (ADS)

    Selm, Barbel; Camenzind, Martin

    2005-03-01

    In this article a new medical application is introduced using textile production techniques to deliver a defined radiation dose. The advantage for photodynamic therapy (PDT) is that a flat luminous textile structure can homogeneously illuminate unequal body surfaces. The optical properties of this two-dimensional luminous pad are characterized with a set of bench-scale tests. In vitro investigations on petri dishes with cultivated cells and first clinical tests on animal patients are promising. In addition first measurement results are presented together with an outlook to future developments.

  17. DIFFUSION PUMP

    DOEpatents

    Levenson, L.

    1963-09-01

    A high-vacuum diffusion pump is described, featuring a novel housing geometry for enhancing pumping speed. An upright, cylindrical lower housing portion is surmounted by a concentric, upright, cylindrical upper housing portion of substantially larger diameter; an uppermost nozzle, disposed concentrically within the upper portion, is adapted to eject downwardly a conical sheet of liquid outwardly to impinge upon the uppermost extremity of the interior wall of the lower portion. Preferably this nozzle is mounted upon a pedestal rising coaxially from within the lower portion and projecting up into said upper portion. (AEC)

  18. Optical diffusers based on silicone emulsions

    NASA Astrophysics Data System (ADS)

    Wang, Jui-Hao; Lien, Shui-Yang; Ho, Jeng-Rong; Shih, Teng-Kai; Chen, Chia-Fu; Chen, Chien-Chung; Whang, Wha-Tzong

    2009-12-01

    The present study provides an experimental approach for fabricating optical diffuser films based on silicone emulsions. The silicone emulsion consisting of silicone polymer (Sylgard 184) and NaCl aq. solution was used as the optical material of diffusers, wherein NaCl aq. solution was severed as surfactant to stabilize the emulsions. After stirring mechanically, microscaled water drop with various sizes distributed randomly in silicone polymer, wherein water drop was used as scattering diffusion particles. To modulate the volume of NaCl aq. solution, the diffusing performance of diffusers could be change by different amount drop particles. Thereafter, an optical examination was carried out to characterize optical properties, transmittance, and light diffusivity of volumetric diffuser films.

  19. Modeling of hydrogen-air diffusion flame

    NASA Technical Reports Server (NTRS)

    Isaac, K. M.

    1989-01-01

    An analytical and computational study of opposed jet diffusion flame for the purpose of understanding the effects of contaminants in the reactants and thermal diffusion of light species on extinction and reignition of diffusion flames is in progress. The methodologies that have been attempted so far are described. Results using a simple, one-step reaction for the hydrogen-air counterflow diffusion flame are presented. These results show the correct trends in the profiles of chemical species and temperature. The extinction limit can be clearly seen in the plot of temperature vs. Damkohler number.

  20. Cloaking through cancellation of diffusive wave scattering

    NASA Astrophysics Data System (ADS)

    Farhat, M.; Chen, P. Y.; Guenneau, S.; Bağc, H.; Salama, K. N.; Alù, A.

    2016-08-01

    A new cloaking mechanism, which makes enclosed objects invisible to diffusive photon density waves, is proposed. First, diffusive scattering from a basic core-shell geometry, which represents the cloaked structure, is studied. The conditions of scattering cancellation in a quasi-static scattering regime are derived. These allow for tailoring the diffusivity constant of the shell enclosing the object so that the fields scattered from the shell and the object cancel each other. This means that the photon flow outside the cloak behaves as if the cloaked object were not present. Diffusive light invisibility may have potential applications in hiding hot spots in infrared thermography or tissue imaging.

  1. Bili lights

    MedlinePlus

    Phototherapy for jaundice; Bilirubin - bili lights; Neonatal care - bili lights; Newborn care - bili lights ... Phototherapy involves shining fluorescent light from the bili lights on bare skin. A specific wavelength of light can break down bilirubin into a form that ...

  2. Perturbative thermal diffusivity from partial sawtooth crashes in Alcator C-Mod

    NASA Astrophysics Data System (ADS)

    Creely, A. J.; White, A. E.; Edlund, E. M.; Howard, N. T.; Hubbard, A. E.

    2016-03-01

    Perturbative thermal diffusivity has been measured on Alcator C-Mod via the use of the extended-time-to-peak method on heat pulses generated by partial sawtooth crashes. Perturbative thermal diffusivity governs the propagation of heat pulses through a plasma. It differs from power balance thermal diffusivity, which governs steady state thermal transport. Heat pulses generated by sawtooth crashes have been used extensively in the past to study heat pulse thermal diffusivity (Lopes Cardozo 1995 Plasma Phys. Control. Fusion 37 799), but the details of the sawtooth event typically lead to non-diffusive ‘ballistic’ transport, making them an unreliable measure of perturbative diffusivity on many tokamaks (Fredrickson et al 2000 Phys. Plasmas 7 5051). Partial sawteeth are common on numerous tokamaks, and generate a heat pulse without the ‘ballistic’ transport that often accompanies full sawteeth (Fredrickson et al 2000 Phys. Plasmas 7 5051). This is the first application of the extended-time-to-peak method of diffusivity calculation (Tubbing et al 1987 Nucl. Fusion 27 1843) to partial sawtooth crashes. This analysis was applied to over 50 C-Mod shots containing both L- and I-Mode. Results indicate correlations between perturbative diffusivity and confinement regime (L- versus I-mode), as well as correlations with local temperature, density, the associated gradients, and gradient scale lengths (a/L Te and a/L n ). In addition, diffusivities calculated from partial sawteeth are compared to perturbative diffusivities calculated with the nonlinear gyrokinetic code GYRO. We find that standard ion-scale simulations (ITG/TEM turbulence) under-predict the perturbative thermal diffusivity, but new multi-scale (ITG/TEM coupled with ETG) simulations can match the experimental perturbative diffusivity within error bars for an Alcator C-Mod L-mode plasma. Perturbative diffusivities extracted from heat pulses due to partial sawteeth provide a new constraint that can be used to

  3. OLED lighting devices having multi element light extraction and luminescence conversion layer

    DOEpatents

    Krummacher, Benjamin Claus; Antoniadis, Homer

    2010-11-16

    An apparatus such as a light source has a multi element light extraction and luminescence conversion layer disposed over a transparent layer of the light source and on the exterior of said light source. The multi-element light extraction and luminescence conversion layer includes a plurality of light extraction elements and a plurality of luminescence conversion elements. The light extraction elements diffuses the light from the light source while luminescence conversion elements absorbs a first spectrum of light from said light source and emits a second spectrum of light.

  4. Device structure for OLED light device having multi element light extraction and luminescence conversion layer

    DOEpatents

    Antoniadis; Homer , Krummacher; Benjamin Claus

    2008-01-22

    An apparatus such as a light source has a multi-element light extraction and luminescence conversion layer disposed over a transparent layer of the light source and on the exterior of said light source. The multi-element light extraction and luminescence conversion layer includes a plurality of light extraction elements and a plurality of luminescence conversion elements. The light extraction elements diffuses the light from the light source while luminescence conversion elements absorbs a first spectrum of light from said light source and emits a second spectrum of light.

  5. Optical processing furnace with quartz muffle and diffuser plate

    DOEpatents

    Sopori, Bhushan L.

    1996-01-01

    An optical furnace for annealing a process wafer comprising a source of optical energy, a quartz muffle having a door to hold the wafer for processing, and a quartz diffuser plate to diffuse the light impinging on the quartz muffle; a feedback system with a light sensor located in the wall of the muffle is also provided for controlling the source of optical energy.

  6. Self-diffusion of interacting micelles: FRAPP study of micelles self-diffusion

    NASA Astrophysics Data System (ADS)

    Chatenay, D.; Urbach, W.; Messager, R.; Langevin, D.

    1987-02-01

    We have studied self-diffusion in DTAB micellar systems at three different salinities with fluorescence photobleaching experiments. In order to characterize interactions in these systems, we have also performed light scattering experiments. Despite of the strong variation of the interactions with salinities, almost no salinity variation in self-diffusion coefficients vs droplets volume fraction curves has been observed. A clear difference between the friction coefficients involved in self- and mutual diffusion have been evidenced.

  7. NIST Diffusion Data Center

    National Institute of Standards and Technology Data Gateway

    NIST Diffusion Data Center (Web, free access)   The NIST Diffusion Data Center is a collection of over 14,100 international papers, theses, and government reports on diffusion published before 1980.

  8. Parallel flow diffusion battery

    DOEpatents

    Yeh, H.C.; Cheng, Y.S.

    1984-01-01

    A parallel flow diffusion battery for determining the mass distribution of an aerosol has a plurality of diffusion cells mounted in parallel to an aerosol stream, each diffusion cell including a stack of mesh wire screens of different density.

  9. Parallel flow diffusion battery

    DOEpatents

    Yeh, Hsu-Chi; Cheng, Yung-Sung

    1984-08-07

    A parallel flow diffusion battery for determining the mass distribution of an aerosol has a plurality of diffusion cells mounted in parallel to an aerosol stream, each diffusion cell including a stack of mesh wire screens of different density.

  10. Laser activated diffuse discharge switch

    DOEpatents

    Christophorou, Loucas G.; Hunter, Scott R.

    1988-01-01

    The invention is a gas mixture for a diffuse discharge switch which is capable of changing from a conducting state to an insulating state in the presence of electrons upon the introduction of laser light. The mixture is composed of a buffer gas such as nitrogen or argon and an electron attaching gas such as C.sub.6 H.sub.5 SH, C.sub.6 H.sub.5 SCH.sub.3, CH.sub.3 CHO and CF.sub.3 CHO wherein the electron attachment is brought on by indirect excitation of molecules to long-lived states by exposure to laser light.

  11. 46 CFR 129.410 - Lighting fixtures.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 4 2013-10-01 2013-10-01 false Lighting fixtures. 129.410 Section 129.410 Shipping... INSTALLATIONS Lighting Systems § 129.410 Lighting fixtures. (a) Each globe, lens, or diffuser of a lighting fixture must have a high-strength guard or be made of high-strength material, except in...

  12. 46 CFR 129.410 - Lighting fixtures.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 4 2014-10-01 2014-10-01 false Lighting fixtures. 129.410 Section 129.410 Shipping... INSTALLATIONS Lighting Systems § 129.410 Lighting fixtures. (a) Each globe, lens, or diffuser of a lighting fixture must have a high-strength guard or be made of high-strength material, except in...

  13. 46 CFR 129.410 - Lighting fixtures.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 4 2011-10-01 2011-10-01 false Lighting fixtures. 129.410 Section 129.410 Shipping... INSTALLATIONS Lighting Systems § 129.410 Lighting fixtures. (a) Each globe, lens, or diffuser of a lighting fixture must have a high-strength guard or be made of high-strength material, except in...

  14. 46 CFR 129.410 - Lighting fixtures.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Lighting fixtures. 129.410 Section 129.410 Shipping... INSTALLATIONS Lighting Systems § 129.410 Lighting fixtures. (a) Each globe, lens, or diffuser of a lighting fixture must have a high-strength guard or be made of high-strength material, except in...

  15. Isotopic fractionation by diffusion in groundwater

    NASA Astrophysics Data System (ADS)

    Labolle, Eric M.; Fogg, Graham E.; Eweis, Juana B.; Gravner, Janko; Leaist, Derek G.

    2008-07-01

    During the last decade, isotopic fractionation has gained acceptance as an indicator of microbiological and chemical transformations of contaminants in groundwater. These transformation processes typically favor isotopically light, compared to isotopically heavy, contaminants, resulting in enrichment of the latter in the residual aqueous phase. In these isotope applications, it has been generally presumed that physical transport processes in groundwater have a negligible effect on isotopic enrichment. It is well known, however, that aqueous phase diffusion generally proceeds faster for isotopically light, compared to isotopically heavy, solute molecules, often resulting in isotopic fractionation in groundwater. This paper considers the potential for isotopic fractionation during transport in groundwater resulting from minute isotopic effects on aqueous diffusion coefficients. Analyses of transport in heterogeneous systems delimit the viable range of isotopic fractionation by diffusion in groundwater. Results show that diffusion can result in similar degrees of depletion and enrichment of isotopically heavy solutes during transport in heterogeneous systems with significant diffusion rate-limited mass transfer between fast- and slow-flow zones. Additional analyses and examples explore conditions that attenuate the development of significant fractionation. Examples are presented for 13C methyl tertiary butyl ether and deuterated and nondeuterated isopropanol and tertiary butyl alcohol using aqueous diffusion coefficients measured by the Taylor dispersion method with refractive index profiling as a part of this study. Examples elucidate the potential for diffusive fractionation as a confounder in isotope applications and emphasize the importance of hydrogeologic analysis for assessing the role of diffusive fractionation in isotope applications at contaminant field sites.

  16. Diffusing Diffusivity: A Model for Anomalous, yet Brownian, Diffusion

    NASA Astrophysics Data System (ADS)

    Chubynsky, Mykyta V.; Slater, Gary W.

    2014-08-01

    Wang et al. [Proc. Natl. Acad. Sci. U.S.A. 106, 15160 (2009)] have found that in several systems the linear time dependence of the mean-square displacement (MSD) of diffusing colloidal particles, typical of normal diffusion, is accompanied by a non-Gaussian displacement distribution G(x ,t), with roughly exponential tails at short times, a situation they termed "anomalous yet Brownian" diffusion. The diversity of systems in which this is observed calls for a generic model. We present such a model where there is diffusivity memory but no direction memory in the particle trajectory, and we show that it leads to both a linear MSD and a non-Gaussian G(x ,t) at short times. In our model, the diffusivity is undergoing a (perhaps biased) random walk, hence the expression "diffusing diffusivity". G(x ,t) is predicted to be exactly exponential at short times if the distribution of diffusivities is itself exponential, but an exponential remains a good fit for a variety of diffusivity distributions. Moreover, our generic model can be modified to produce subdiffusion.

  17. Lighting: Green Light.

    ERIC Educational Resources Information Center

    Maniccia, Dorine

    2003-01-01

    Explains that by using sustainable (green) building practices, schools and universities can make their lighting systems more efficient, noting that embracing green design principles can help schools attract students. Discusses lighting-control technologies (occupancy sensing technology, daylighting technology, and scheduling based technologies),…

  18. Handheld Diffusion Test Cells

    NASA Technical Reports Server (NTRS)

    2001-01-01

    This photo shows the Handheld Diffusion Test Cell (HH-DTC) apparatus flown on the Space Shuttle. Similar cells (inside the plastic box) will be used in the Observable Protein Crystal Growth Apparatus (OPCGA) to be operated aboard the International Space Station (ISS). The principal investigator is Dr. Alex McPherson of the University of California, Irvine. Each individual cell comprises two sample chambers with a rotating center section that isolates the two from each other until the start of the experiment and after it is completed. The cells are made from optical-quality quartz glass to allow photography and interferometric observations. Each cell has a small light-emitting diode and lens to back-light the solution. In protein crystal growth experiments, a precipitating agent such as a salt solution is used to absorb and hold water but repel the protein molecules. This increases the concentration of protein until the molecules nucleate to form crystals. This cell is one of 96 that make up the experiment module portion of the OPCGA.

  19. Handheld Diffusion Test Cells

    NASA Technical Reports Server (NTRS)

    2001-01-01

    This photo shows an individual cell from the Handheld Diffusion Test Cell (HH-DTC) apparatus flown on the Space Shuttle. Similar cells will be used in the Observable Protein Crystal Growth Apparatus (OPCGA) to be operated aboard the International Space Station (ISS). The principal investigator is Dr. Alex McPherson of the University of California, Irvine. Each individual cell comprises two sample chambers with a rotating center section that isolates the two from each other until the start of the experiment and after it is completed. The cells are made from optical-quality quartz glass to allow photography and interferometric observations. Each cell has a small light-emitting diode and lens to back-light the solution. In protein crystal growth experiments, a precipitating agent such as a salt solution is used to absorb and hold water but repel the protein molecules. This increases the concentration of protein until the molecules nucleate to form crystals. This cell is one of 96 that make up the experiment module portion of the OPCGA.

  20. Diffusing-wave polarimetry for tissue diagnostics

    NASA Astrophysics Data System (ADS)

    Macdonald, Callum; Doronin, Alexander; Peña, Adrian F.; Eccles, Michael; Meglinski, Igor

    2014-03-01

    We exploit the directional awareness of circularly and/or elliptically polarized light propagating within media which exhibit high numbers of scattering events. By tracking the Stokes vector of the detected light on the Poincaŕe sphere, we demonstrate its applicability for characterization of anisotropy of scattering. A phenomenological model is shown to have an excellent agreement with the experimental data and with the results obtained by the polarization tracking Monte Carlo model, developed in house. By analogy to diffusing-wave spectroscopy we call this approach diffusing-wave polarimetry, and illustrate its utility in probing cancerous and non-cancerous tissue samplesin vitro for diagnostic purposes.

  1. Optical processing furnace with quartz muffle and diffuser plate

    DOEpatents

    Sopori, Bhushan L.

    1995-01-01

    An optical furnace for annealing a process wafer comprising a source of optical energy, a quartz muffle having a door to hold the wafer for processing, and a quartz diffuser plate to diffuse the light impinging on the quartz muffle; a feedback system with a light sensor located in the door or wall of the muffle is also provided for controlling the source of optical energy. The quartz for the diffuser plate is surface etched (to give the quartz diffusive qualities) in the furnace during a high intensity burn-in process.

  2. Rare earth element diffusion in apatite

    NASA Astrophysics Data System (ADS)

    Cherniak, D. J.

    2000-11-01

    Diffusion of rare earth elements (REEs) in natural and synthetic fluorapatite has been characterized under anhydrous conditions. Three types of experiments were run. In the first set of experiments, Sm was introduced into the apatite by means of ion implantation, with diffusivities extracted through measurement of the "relaxation" of the implanted profile after diffusion anneals. The second group consisted of "in diffusion" experiments, in which apatite was immersed in reservoirs of synthetic REE apatite analogs of various compositions. The final set of experiments was "out-diffusion" experiments run on synthetic Nd-doped apatite immersed in a reservoir of synthetic (undoped) fluorapatite. REE depth profiles in all cases were measured with Rutherford Backscattering Spectrometry. Diffusion rates for the REE vary significantly among these sets of experiments. For the ion-implantation experiments, the following Arrhenius relation was obtained for Sm, over the temperature range 750°C to 1100°C: D imp=6.3×10-7exp(-298±17 kJ/mol/RT) m2/s Diffusion of a series of REE, from light to heavy, was investigated in the "in-diffusion" experiments. Over the temperature range 800°C to 1250°C, the following Arrhenius relations are obtained for La, Nd, Dy, and Yb, for in-diffusion experiments using REE silicate oxyapatite sources: D La=2.6×10-7exp(-324±9 kJ/mol/RT) m2/sD Nd=2.4×10-6exp(-348±13 kJ/mol/RT) m2/sD Dy=9.7×10-7exp(-340±11 kJ/mol/RT) m2/sD Yb=1.3×10-8exp(-292±23 kJ/mol/RT) m2/s Diffusivities of the REE in these "in-diffusion" experiments are all quite similar, suggesting little difference in diffusion rates in apatite with increasing ionic radii of the REEs. The "out-diffusion" experiments on the Nd-doped synthetic apatite, over the temperature range 950°C to 1400°C, yield the Arrhenius law: D out=9.3×10-6exp(-392±31 kJ/mol/RT) m2/s The differences in REE diffusion among these three sets of experiments (i.e., ion implantation, in-diffusion, and out-diffusion

  3. Microfabricated diffusion source

    DOEpatents

    Oborny, Michael C.; Frye-Mason, Gregory C.; Manginell, Ronald P.

    2008-07-15

    A microfabricated diffusion source to provide for a controlled diffusion rate of a vapor comprises a porous reservoir formed in a substrate that can be filled with a liquid, a headspace cavity for evaporation of the vapor therein, a diffusion channel to provide a controlled diffusion of the vapor, and an outlet to release the vapor into a gas stream. The microfabricated diffusion source can provide a calibration standard for a microanalytical system. The microanalytical system with an integral diffusion source can be fabricated with microelectromechanical systems technologies.

  4. Hybrid Diffusion Imaging

    PubMed Central

    Wu, Yu-Chien; Alexander, Andrew L.

    2007-01-01

    Diffusion measurements in the human central nervous system are complex to characterize and a broad spectrum of methods have been proposed. In this study, a comprehensive diffusion encoding and analysis approach, Hybrid Diffusion Imaging (HYDI), is described. The HYDI encoding scheme is composed of multiple concentric “shells” of constant diffusion-weighting, which may be used to characterize the signal behavior with low, moderate and high diffusion-weighting. HYDI facilitates the application of multiple data-analyses strategies including diffusion tensor imaging (DTI), multi-exponential diffusion measurements, diffusion spectrum imaging (DSI) and q-ball imaging (QBI). These different analysis strategies may provide complementary information. DTI measures (mean diffusivity and fractional anisotropy) may be estimated from either data in the inner shells or the entire HYDI data. Fast and slow diffusivities were estimated using a nonlinear least-squares bi-exponential fit on geometric means of the HYDI shells. DSI measurements from the entire HYDI data yield empirical model-independent diffusion information and are well-suited for characterizing tissue regions with complex diffusion behavior. DSI measurements were characterized using the zero displacement probability and the mean squared displacement. The outermost HYDI shell was analyzed using QBI analysis to estimate the orientation distribution function (ODF), which is useful for characterizing the directions of multiple fiber groups within a voxel. In this study, a HYDI encoding scheme with 102 diffusion-weighted measurements was obtained over most of the human cerebrum in under 30 minutes. PMID:17481920

  5. Diffusion bonding aeroengine components

    NASA Astrophysics Data System (ADS)

    Fitzpatrick, G. A.; Broughton, T.

    1988-10-01

    The use of diffusion bonding processes at Rolls-Royce for the manufacture of titanium-alloy aircraft engine components and structures is described. A liquid-phase diffusion bonding process called activated diffusion bonding has been developed for the manufacture of the hollow titanium wide chord fan blade. In addition, solid-state diffusion bonding is being used in the manufacture of hollow vane/blade airfoil constructions mainly in conjunction with superplastic forming and hot forming techniques.

  6. Updating applied diffusion models

    SciTech Connect

    Weil, J.C.

    1985-11-01

    Most diffusion models currently used in air quality applications are substantially out of date with understanding of turbulence and diffusion in the planetary boundary layer. Under a Cooperative Agreement with the Environmental Protection Agency, the American Meteorological Society organized a workshop to help improve the basis of such models, their physics and hopefuly their performance. Reviews and recommendations were made on models in three areas: diffusion in the convective boundary layer (CBL), diffusion in the stabe boundary layer (SBL), and model uncertainty.

  7. 46 CFR 129.410 - Lighting fixtures.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) OFFSHORE SUPPLY VESSELS ELECTRICAL INSTALLATIONS Lighting Systems § 129.410 Lighting fixtures. (a) Each globe, lens, or diffuser of a lighting fixture must have a high-strength guard or be made of high-strength material, except in...

  8. Diffusion Strategy Guide.

    ERIC Educational Resources Information Center

    McCutcheon, James R.; Sanders, John R.

    A methodology is presented for planning and managing the spread of educational innovations. The first portion of the guide develops a theoretical framework for diffusion which summarizes and capitalizes on the latest marketing and on the latest marketing and diffusion research findings. Major stages in the diffusion paradigm discussed include…

  9. Reduce Confusion about Diffusion.

    ERIC Educational Resources Information Center

    Hebrank, Mary R.

    1997-01-01

    Presents activities that allow students to explore the fundamental but poorly understood concept of diffusion by appealing to their kinesthetic senses first, then challenging their analytical skills as they try to deduce the mathematical principle involved. Presents a computer simulation of diffusion and discusses diffusion's limitations and…

  10. Handbook on atmospheric diffusion

    SciTech Connect

    Hanna, S.R.; Briggs, G.A.; Hosker, R.P. Jr.

    1982-01-01

    Basic meteorological concepts are covered as well as plume rise, source effects, and diffusion models. Chapters are included on cooling tower plumes and urban diffusion. Suggestions are given for calculating diffusion in special situations, such as for instantaneous releases over complex terrain, over long distances, and during times when chemical reactions or dry or wet deposition are important. (PSB)

  11. Photoacoustic thermal diffusion flowmetry

    PubMed Central

    Sheinfeld, Adi; Eyal, Avishay

    2012-01-01

    Thermal Diffusion Flowmetry (TDF) (also called Heat Clearance Method or Thermal Clearance Method) is a longstanding technique for measuring blood flow or blood perfusion in living tissues. Typically, temperature transients and/or gradients are induced in a volume of interest and the temporal and/or spatial temperature variations which follow are measured and used for calculation of the flow. In this work a new method for implementing TDF is studied theoretically and experimentally. The heat deposition which is required for TDF is implemented photothermally (PT) and the measurement of the induced temperature variations is done by photoacoustic (PA) thermometry. Both excitation light beams (the PT and the PA) are produced by directly modulated 830 nm laser diodes and are conveniently delivered to the volume under test by the same optical fiber. The method was tested experimentally using a blood-filled phantom vessel and the results were compared with a theoretical prediction based on the heat and the photoacoustic equations. The fitting of a simplified lumped thermal model to the experimental data yielded estimated values of the blood velocity at different flow rates. By combining additional optical sources at different wavelengths it will be possible to utilize the method for non-invasive simultaneous measurement of blood flow and oxygen saturation using a single fiber probe. PMID:22574267

  12. Diffusing Wave Spectroscopy Used to Study Foams

    NASA Technical Reports Server (NTRS)

    Zimmerli, Gregory A.; Durian, Douglas J.

    2000-01-01

    The white appearance of familiar objects such as clouds, snow, milk, or foam is due to the random scattering of light by the sample. As we all know, pure water is clear and easily passes a beam of light. However, tiny water droplets, such as those in a cloud, scatter light because the air and water droplet have different indexes of refraction. When many droplets, or scattering sites, are present, the incident light is scattered in random directions and the sample takes on a milky white appearance. In a glass of milk, the scattering is due to small colloidal particles. The white appearance of shaving cream, or foam, is due to the scattering of light at the water-bubble interface. Diffusing wave spectroscopy (DWS) is a laser light-scattering technique used to noninvasively probe the particle dynamics in systems that strongly scatter light. The technique takes advantage of the diffuse nature of light, which is reflected or transmitted from samples such as foams, dense colloidal suspensions (such as paint and milk), emulsions, liquid crystals, sandpiles, and even biological tissues.

  13. Light Pollution

    ERIC Educational Resources Information Center

    Riegel, Kurt W.

    1973-01-01

    Outdoor lighting is light pollution which handicaps certain astronomical programs. Protective measures must be adopted by the government to aid observational astronomy without sacrificing legitimate outdoor lighting needs. (PS)

  14. Light Duty.

    ERIC Educational Resources Information Center

    Rogers, Jeff

    1996-01-01

    Discusses multipurpose athletic-field lighting specifications to enhance lighting quality and reduce costs. Topics discussed include lamp choice, lighting spillover and glare prevention, luminary assemblies and poles, and the electrical dimming and switching systems. (GR)

  15. Mapping intracellular diffusion distribution using single quantum dot tracking: compartmentalized diffusion defined by endoplasmic reticulum.

    PubMed

    Li, Hui; Dou, Shuo-Xing; Liu, Yu-Ru; Li, Wei; Xie, Ping; Wang, Wei-Chi; Wang, Peng-Ye

    2015-01-14

    The crowded intracellular environment influences the diffusion-mediated cellular processes, such as metabolism, signaling, and transport. The hindered diffusion of macromolecules in heterogeneous cytoplasm has been studied over years, but the detailed diffusion distribution and its origin still remain unclear. Here, we introduce a novel method to map rapidly the diffusion distribution in single cells based on single-particle tracking (SPT) of quantum dots (QDs). The diffusion map reveals the heterogeneous intracellular environment and, more importantly, an unreported compartmentalization of QD diffusions in cytoplasm. Simultaneous observations of QD motion and green fluorescent protein-tagged endoplasmic reticulum (ER) dynamics provide direct evidence that the compartmentalization results from micron-scale domains defined by ER tubules, and ER cisternae form perinuclear areas that restrict QDs to enter. The same phenomenon was observed using fluorescein isothiocyanate-dextrans, further confirming the compartmentalized diffusion. These results shed new light on the diffusive movements of macromolecules in the cell, and the mapping of intracellular diffusion distribution may be used to develop strategies for nanoparticle-based drug deliveries and therapeutics.

  16. Diffusion of excitons in materials for optoelectronic device applications

    NASA Astrophysics Data System (ADS)

    Singh, Jai; Narayan, Monishka Rita; Ompong, David

    2015-06-01

    The diffusion of singlet excitonsis known to occur through the Förster resonance energy transfer (FRET) mechanism and that of singlet and triplet excitonscan occur through the Dexter carrier transfer mechanism. It is shown here that if a material possesses the strong exciton-spin-orbit-photon interaction then triplet excitonscan also be transported /diffused through a mechanism like FRET. The theory is applicable to the diffusion of excitonsin optoelectronic devices like organic solar cells, organic light emitting devices and inorganic scintillators.

  17. A Guide to the Librarian's Responsibility in Achieving Quality in Lighting and Ventilation.

    ERIC Educational Resources Information Center

    Mason, Ellsworth

    1967-01-01

    Quality, not intensity, is the keystone to good library lighting. The single most important problem in lighting is glare caused by extremely intense centers of light. Multiple interfiling of light rays is a factor required in library lighting. A fixture that diffuses light well is basic when light emerges from the fixture. It scatters widely,…

  18. Mapping Spatio-Temporal Diffusion inside the Human Brain Using a Numerical Solution of the Diffusion Equation

    PubMed Central

    Zhan, Wang; Jiang, Li; Loew, Murray; Yang, Yihong

    2008-01-01

    Diffusion is an important mechanism for molecular transport in living biological tissues. Diffusion magnetic resonance imaging (dMRI) provides a unique probe to examine microscopic structures of the tissues in vivo, but current dMRI techniques usually ignore the spatio-temporal evolution process of the diffusive medium. In the present study, we demonstrate the feasibility to reveal the spatio-temporal diffusion process inside the human brain based on a numerical solution of the diffusion equation. Normal human subjects were scanned with a diffusion tensor imaging (DTI) technique on a 3-Tesla MRI scanner, and the diffusion tensor in each voxel was calculated from the DTI data. The diffusion equation, a partial-derivative description of Fick’s Law for the diffusion process, was discretized into equivalent algebraic equations. A finite-difference method was employed to obtain the numerical solution of the diffusion equation with a Crank-Nicholson iteration scheme to enhance the numerical stability. By specifying boundary and initial conditions, the spatio-temporal evolution of the diffusion process inside the brain can be virtually reconstructed. Our results exhibit similar medium profiles and diffusion coefficients as those of light fluorescence dextrans measured in integrative optical imaging experiments. The proposed method highlights the feasibility to non-invasively estimate the macroscopic diffusive transport time for a molecule in a given region of the brain. PMID:18440744

  19. Li diffusion in zircon

    NASA Astrophysics Data System (ADS)

    Cherniak, D. J.; Watson, E. B.

    2010-09-01

    Diffusion of Li under anhydrous conditions at 1 atm and under fluid-present elevated pressure (1.0-1.2 GPa) conditions has been measured in natural zircon. The source of diffusant for 1-atm experiments was ground natural spodumene, which was sealed under vacuum in silica glass capsules with polished slabs of zircon. An experiment using a Dy-bearing source was also conducted to evaluate possible rate-limiting effects on Li diffusion of slow-diffusing REE+3 that might provide charge balance. Diffusion experiments performed in the presence of H2O-CO2 fluid were run in a piston-cylinder apparatus, using a source consisting of a powdered mixture of spodumene, quartz and zircon with oxalic acid added to produce H2O-CO2 fluid. Nuclear reaction analysis (NRA) with the resonant nuclear reaction 7Li(p,γ)8Be was used to measure diffusion profiles for the experiments. The following Arrhenius parameters were obtained for Li diffusion normal to the c-axis over the temperature range 703-1.151°C at 1 atm for experiments run with the spodumene source: D_{text{Li}} = 7.17 × 10^{ - 7} { exp }( - 275 ± 11 {text{kJmol}}^{ - 1} /{text{RT}}){text{m}}2 {text{s}}^{ - 1}. Diffusivities are similar for transport parallel to the c-axis, indicating little anisotropy for Li diffusion in zircon. Similar Li diffusivities were also found for experiments run under fluid-present conditions and for the experiment run with the Dy-bearing source. Li diffusion is considerably faster than diffusion of other cations in zircon, with a smaller activation energy for diffusion. Although Li diffusion in zircon is comparatively rapid, zircons will be moderately retentive of Li signatures at mid-crustal metamorphic temperatures, but they are unlikely to retain this information for geologically significant times under high-grade metamorphism.

  20. Optical processing furnace with quartz muffle and diffuser plate

    DOEpatents

    Sopori, B.L.

    1996-11-19

    An optical furnace for annealing a process wafer is disclosed comprising a source of optical energy, a quartz muffle having a door to hold the wafer for processing, and a quartz diffuser plate to diffuse the light impinging on the quartz muffle; a feedback system with a light sensor located in the wall of the muffle is also provided for controlling the source of optical energy. 5 figs.

  1. L(alpha)-induced two-photon absorption of visible light emitted from an O-type star by H2(+) ions located near the surface of the Stromgren sphere surrounding the star: A possible explanation for the diffuse interstellar absorption bands (DIDs)

    NASA Technical Reports Server (NTRS)

    Glownia, James H.; Sorokin, Peter P.

    1994-01-01

    In this paper, a new model is proposed to account for the DIB's (Diffuse Interstellar Bands). In this model, the DIB's result from a non-linear effect: resonantly-enhanced two-photon absorption of H(2+) ions located near the surface of the Stromgren sphere that surrounds an O- or B- type star. The strong light that is required to 'drive' the two-photon transition is provided by L(alpha) light emerging from the Stromgren sphere that bounds the H II region surrounding the star. A value of approximately 100 micro W/sq cm is estimated for the L(alpha) flux at the Stromgren radius, R(s), of a strong (O5) star. It is shown that a c.w. L(alpha) flux of this intensity should be sufficient to induce a few percent absorption for visible light radiated by the same star at a frequency (omega2) that completes an allowed two-photon transition, provided (1) the L(alpha) radiation happens to be nearly resonant with the frequency of a fully-allowed absorber transition that effectively represents the first step in the two-photon transition, and (2) an effective column density approximately 10(sup18)/sq cm of the absorber is present near the Stromgren sphere radius, R(sub s).

  2. Updating applied diffusion models

    SciTech Connect

    Weil, J.C.

    1985-01-01

    Most diffusion models currently used in air-quality applications are substantially out of date with understanding of turbulence and diffusion in the planetary boundary layer. Under a Cooperative Agreement with the Environmental Protection Agency, the American Meteorological Society organized a workshop to help improve the basis of such models, their physics and hopefully their performance. Reviews and recommendations were made on models in three areas: diffusion in the convective boundary layer (CBL), diffusion in the stable boundary layer (SBL), and model uncertainty. Progress has been made in all areas, but it is most significant and ready for application to practical models in the case of the CBL. This has resulted from a clear understanding of the vertical structure and diffusion in the CBL, as demonstrated by laboratory experiments, numerical simulations, and field observations. Understanding of turbulence structure and diffusion in the SBL is less complete and not yet ready for general use in applications.

  3. Gaseous diffusion system

    DOEpatents

    Garrett, George A.; Shacter, John

    1978-01-01

    1. A gaseous diffusion system comprising a plurality of diffusers connected in cascade to form a series of stages, each of said diffusers having a porous partition dividing it into a high pressure chamber and a low pressure chamber, and means for combining a portion of the enriched gas from a succeeding stage with a portion of the enriched gas from the low pressure chamber of each stage and feeding it into one extremity of the high pressure chamber thereof.

  4. Spectralon diffuser calibration for MERIS

    NASA Astrophysics Data System (ADS)

    Olij, Carina; Schaarsberg, Jos G.; Werij, Henri G.; Zoutman, Erik; Baudin, Gilles; Chommeloux, Beatrice; Bezy, Jean-Loup; Gourmelon, Georges

    1997-12-01

    One of the key payload instruments of ESA's ENVISAT polar platform is the medium resolution imaging spectrometer (MERIS), aiming at improved knowledge of our planet in the fields of bio-optical oceanography, and atmospheric and land surface processes. MERIS, which is built under responsibility of Aerospatiale, will monitor the solar irradiation scattered by the Earth by employing five cameras which simultaneously record data in 15 visible and near-infrared programmable spectral bands with very low degree of polarization sensitivity. The combined field-of-view of the five cameras spans a range of 68.5 degrees. Crucial for obtaining the desired high accuracy during a four-years lifetime, is the on- board calibration unit. This calibration unit contains a set of Spectralon diffusers, which were manufactured having in mind excellent in-flight stability as well as spectral and spatial uniformity. Preflight calibration of the Spectralon diffusers was carried out at TNO-TPD. This calibration includes the measurement of the bidirectional reflectance distribution function (BRDF) for applicable angles and wavelengths, i.e., while varying angle of incidence, angle of observation, observation area on the elongated diffusers, wavelength and polarization. The diffuser calibration was performed in a class 100 cleanroom. For these measurements the TPD calibration facility, which is described in detail, has been adapted, so that it now has five geometrical degrees of freedom. Detectors have been optimized to minimize stray light. Due to extensive commissioning of the calibration setup the absolute error (1 sigma) of these measurements amounts to less than 0.5%; relative errors are in the 0.3 - 0.4% range.

  5. Inpainting using airy diffusion

    NASA Astrophysics Data System (ADS)

    Lorduy Hernandez, Sara

    2015-09-01

    One inpainting procedure based on Airy diffusion is proposed, implemented via Maple and applied to some digital images. Airy diffusion is a partial differential equation with spatial derivatives of third order in contrast with the usual diffusion with spatial derivatives of second order. Airy diffusion generates the Airy semigroup in terms of the Airy functions which can be rewritten in terms of Bessel functions. The Airy diffusion can be used to smooth an image with the corresponding noise elimination via convolution. Also the Airy diffusion can be used to erase objects from an image. We build an algorithm using the Maple package ImageTools and such algorithm is tested using some images. Our results using Airy diffusion are compared with the similar results using standard diffusion. We observe that Airy diffusion generates powerful filters for image processing which could be incorporated in the usual packages for image processing such as ImageJ and Photoshop. Also is interesting to consider the possibility to incorporate the Airy filters as applications for smartphones and smart-glasses.

  6. Multicomponent diffusion revisited

    NASA Astrophysics Data System (ADS)

    Lam, S. H.

    2006-07-01

    The derivation of the multicomponent diffusion law is revisited. Following Furry [Am. J. Phys. 16, 63 (1948)], Williams [Am. J. Phys. 26, 467 (1958); Combustion Theory, 2nd ed. (Benjamin/Cummings , Menlo Park, CA,1985)] heuristically rederived the classical kinetic theory results using macroscopic equations, and pointed out that the dynamics of the mixture fluid had been assumed inviscid. This paper generalizes the derivation, shows that the inviscid assumption can easily be relaxed to add a new term to the classical diffusion law, and the thermal diffusion term can also be easily recovered. The nonuniqueness of the multicomponent diffusion coefficient matrix is emphasized and discussed.

  7. Experimental study of vortex diffusers

    SciTech Connect

    Shakerin, S.; Miller, P.L.

    1995-11-01

    This report documents experimental research performed on vortex diffusers used in ventilation and air-conditioning systems. The main objectives of the research were (1) to study the flow characteristics of isothermal jets issuing from vortex diffusers, (2) to compare the vortex diffuser`s performance with that of a conventional diffuser, and (3) to prepare a report that disseminates the results to the designers of ventilation and air-conditioning systems. The researchers considered three diffusers: a conventional round ceiling diffuser and two different styles of vortex diffusers. Overall, the vortex diffusers create slightly more induction of ambient air in comparison to the conventional diffuser.

  8. SIRTF stray light analysis

    NASA Technical Reports Server (NTRS)

    Elliott, David G.; Dinger, Ann S.

    1991-01-01

    The Space Infrared Telescope Facility (SIRTF) is a 1-meter cryogenic infrared telescope. Stray light is kept below the natural background by restrictions on sun, Earth, and moon off-axis angles; by conservative baffle design; by the use of advanced diffuse black coatings; and by superfluid helium cooling. The aperture stop is located at the primary mirror rather than at the secondary mirror to increase the aperture and reduce the central obscuration. Stray light from off-axis sources is greater with the aperture stop at the primary than with the aperture stop at the secondary, but the modulation of the signal produced by tilting of the secondary mirror for chopping is less. Stray light from telescope thermal emission is lower with the aperture stop at the primary.

  9. Light emitting ceramic device

    DOEpatents

    Valentine, Paul; Edwards, Doreen D.; Walker, Jr., William John; Slack, Lyle H.; Brown, Wayne Douglas; Osborne, Cathy; Norton, Michael; Begley, Richard

    2010-05-18

    A light-emitting ceramic based panel, hereafter termed "electroceramescent" panel, is herein claimed. The electroceramescent panel is formed on a substrate providing mechanical support as well as serving as the base electrode for the device. One or more semiconductive ceramic layers directly overlay the substrate, and electrical conductivity and ionic diffusion are controlled. Light emitting regions overlay the semiconductive ceramic layers, and said regions consist sequentially of a layer of a ceramic insulation layer and an electroluminescent layer, comprised of doped phosphors or the equivalent. One or more conductive top electrode layers having optically transmissive areas overlay the light emitting regions, and a multi-layered top barrier cover comprising one or more optically transmissive non-combustible insulation layers overlay said top electrode regions.

  10. Slanted liquid microlens array by using diffuser

    NASA Astrophysics Data System (ADS)

    Shin, DooSeub; Kim, JunOh; Lee, JunSik; Kim, CheolJoong; Koo, GyoHyun; Won, Yong Hyub

    2016-03-01

    This paper aims to describe a slanted liquid microlens array using diffusers. Ordinary liquid microlens has vertical side walls. The shape of it, however, has several weaknesses such as a low value of diopter and a difficulty in evaporating electrode. The diffuser causes UV light to spread slantly not straightly. This research shows a result of a slanted liquid micro lens having side walls with an angle of 74 degrees and verifies a high value of diopter and a well-filmed electrode. In order to achieve a high percentage of fill factor, it also presents matching values for refractive indices of the two media, oil and chamber.

  11. Sunlight Diffusing Tent for Lunar Worksite

    NASA Technical Reports Server (NTRS)

    Burleson, Blair; Clark, Todd; Deese, Todd; Gentry, Ernest; Samad, Abdul

    1990-01-01

    The purpose is to provide a solution to problems astronauts encounter with sunlight on the lunar surface. Due to the absence of an atmosphere the Moon is subjected to intense sunlight creating problems with color and contrast. This problem can be overcome by providing a way to reduce intensity and diffuse the light in a working environment. The solution to the problem utilizes an umbrella, tent-like structure covered with a diffusing material. The design takes into account structural materials, stresses, fabrics, and deployment.

  12. Light Visor

    NASA Technical Reports Server (NTRS)

    1993-01-01

    Seasonal Affective Disorder is a form of depression brought on by reduced light. For some people, this can lead to clinical depression. NASA has conducted research in light therapy and employs it to help astronauts adjust internal rhythms during orbital flight. Dr. George Brainard, a medical researcher and NASA consultant, has developed a portable light therapy device, which is commercially available. The Light Visor allows continuous light therapy and can be powered by either batteries or electricity. Dr. Brainard continues to research various aspects of light therapy.

  13. Cosmology with matter diffusion

    SciTech Connect

    Calogero, Simone; Velten, Hermano E-mail: velten@cce.ufes.br

    2013-11-01

    We construct a viable cosmological model based on velocity diffusion of matter particles. In order to ensure the conservation of the total energy-momentum tensor in the presence of diffusion, we include a cosmological scalar field φ which we identify with the dark energy component of the universe. The model is characterized by only one new degree of freedom, the diffusion parameter σ. The standard ΛCDM model can be recovered by setting σ = 0. If diffusion takes place (σ > 0) the dynamics of the matter and of the dark energy fields are coupled. We argue that the existence of a diffusion mechanism in the universe may serve as a theoretical motivation for interacting models. We constrain the background dynamics of the diffusion model with Supernovae, H(z) and BAO data. We also perform a perturbative analysis of this model in order to understand structure formation in the universe. We calculate the impact of diffusion both on the CMB spectrum, with particular attention to the integrated Sachs-Wolfe signal, and on the matter power spectrum P(k). The latter analysis places strong constraints on the magnitude of the diffusion mechanism but does not rule out the model.

  14. Speckle reducing anisotropic diffusion.

    PubMed

    Yu, Yongjian; Acton, Scott T

    2002-01-01

    This paper provides the derivation of speckle reducing anisotropic diffusion (SRAD), a diffusion method tailored to ultrasonic and radar imaging applications. SRAD is the edge-sensitive diffusion for speckled images, in the same way that conventional anisotropic diffusion is the edge-sensitive diffusion for images corrupted with additive noise. We first show that the Lee and Frost filters can be cast as partial differential equations, and then we derive SRAD by allowing edge-sensitive anisotropic diffusion within this context. Just as the Lee and Frost filters utilize the coefficient of variation in adaptive filtering, SRAD exploits the instantaneous coefficient of variation, which is shown to be a function of the local gradient magnitude and Laplacian operators. We validate the new algorithm using both synthetic and real linear scan ultrasonic imagery of the carotid artery. We also demonstrate the algorithm performance with real SAR data. The performance measures obtained by means of computer simulation of carotid artery images are compared with three existing speckle reduction schemes. In the presence of speckle noise, speckle reducing anisotropic diffusion excels over the traditional speckle removal filters and over the conventional anisotropic diffusion method in terms of mean preservation, variance reduction, and edge localization.

  15. Galactic Diffuse Emissions

    SciTech Connect

    Digel, Seth W.; /SLAC

    2007-10-25

    Interactions of cosmic rays with interstellar nucleons and photons make the Milky Way a bright, diffuse source of high-energy {gamma}-rays. Observationally, the results from EGRET, COMPTEL, and OSSE have now been extended to higher energies by ground-based experiments, with detections of diffuse emission in the Galactic center reported by H.E.S.S. in the range above 100 GeV and of diffuse emission in Cygnus by MILAGRO in the TeV range. In the range above 100 keV, INTEGRAL SPI has found that diffuse emission remains after point sources are accounted for. I will summarize current knowledge of diffuse {gamma}-ray emission from the Milky Way and review some open issues related to the diffuse emission -- some old, like the distribution of cosmic-ray sources and the origin of the 'excess' of GeV emission observed by EGRET, and some recently recognized, like the amount and distribution of molecular hydrogen not traced by CO emission -- and anticipate some of the advances that will be possible with the Large Area Telescope on GLAST. We plan to develop an accurate physical model for the diffuse emission, which will be useful for detecting and accurately characterizing emission from Galactic point sources as well as any Galactic diffuse emission from exotic processes, and for studying the unresolved extragalactic emission.

  16. Investigating Diffusion with Technology

    ERIC Educational Resources Information Center

    Miller, Jon S.; Windelborn, Augden F.

    2013-01-01

    The activities described here allow students to explore the concept of diffusion with the use of common equipment such as computers, webcams and analysis software. The procedure includes taking a series of digital pictures of a container of water with a webcam as a dye slowly diffuses. At known time points, measurements of the pixel densities…

  17. Anatomy of Particle Diffusion

    ERIC Educational Resources Information Center

    Bringuier, E.

    2009-01-01

    The paper analyses particle diffusion from a thermodynamic standpoint. The main goal of the paper is to highlight the conceptual connection between particle diffusion, which belongs to non-equilibrium statistical physics, and mechanics, which deals with particle motion, at the level of third-year university courses. We start out from the fact…

  18. Combustor diffuser interaction program

    NASA Technical Reports Server (NTRS)

    Srinivasan, Ram; Thorp, Daniel

    1986-01-01

    Advances in gas turbine engine performance are achieved by using compressor systems with high stage loading and low part count, which result in high exit Mach numbers. The diffuser and combustor systems in such engines should be optimized to reduce system pressure loss and to maximize the engine thrust-to-weight ratio and minimize length. The state-of-the-art combustor-diffuser systems do not meet these requirements. Detailed understanding of the combustor-diffuser flow field interaction is required for designing advanced gas turbine engines. An experimental study of the combustor-diffuser interaction (CDI) is being conducted to obtain data for the evaluation and improvement of analytical models applicable to a wide variety of diffuser designs. The CDI program consists of four technical phases: Literature Search; Baseline Configuration; Parametric Configurations; and Performance Configurations. Phase 2 of the program is in progress.

  19. Diffusion in Coulomb crystals.

    PubMed

    Hughto, J; Schneider, A S; Horowitz, C J; Berry, D K

    2011-07-01

    Diffusion in Coulomb crystals can be important for the structure of neutron star crusts. We determine diffusion constants D from molecular dynamics simulations. We find that D for Coulomb crystals with relatively soft-core 1/r interactions may be larger than D for Lennard-Jones or other solids with harder-core interactions. Diffusion, for simulations of nearly perfect body-centered-cubic lattices, involves the exchange of ions in ringlike configurations. Here ions "hop" in unison without the formation of long lived vacancies. Diffusion, for imperfect crystals, involves the motion of defects. Finally, we find that diffusion, for an amorphous system rapidly quenched from Coulomb parameter Γ=175 to Coulomb parameters up to Γ=1750, is fast enough that the system starts to crystalize during long simulation runs. These results strongly suggest that Coulomb solids in cold white dwarf stars, and the crust of neutron stars, will be crystalline and not amorphous. PMID:21867316

  20. Diffusion in Coulomb crystals.

    PubMed

    Hughto, J; Schneider, A S; Horowitz, C J; Berry, D K

    2011-07-01

    Diffusion in Coulomb crystals can be important for the structure of neutron star crusts. We determine diffusion constants D from molecular dynamics simulations. We find that D for Coulomb crystals with relatively soft-core 1/r interactions may be larger than D for Lennard-Jones or other solids with harder-core interactions. Diffusion, for simulations of nearly perfect body-centered-cubic lattices, involves the exchange of ions in ringlike configurations. Here ions "hop" in unison without the formation of long lived vacancies. Diffusion, for imperfect crystals, involves the motion of defects. Finally, we find that diffusion, for an amorphous system rapidly quenched from Coulomb parameter Γ=175 to Coulomb parameters up to Γ=1750, is fast enough that the system starts to crystalize during long simulation runs. These results strongly suggest that Coulomb solids in cold white dwarf stars, and the crust of neutron stars, will be crystalline and not amorphous.

  1. Innovation Diffusion Model in Higher Education: Case Study of E-Learning Diffusion

    ERIC Educational Resources Information Center

    Buc, Sanjana; Divjak, Blaženka

    2015-01-01

    The diffusion of innovation (DOI) is critical for any organization and especially nowadays for higher education institutions (HEIs) in the light of vast pressure of emerging educational technologies as well as of the demand of economy and society. DOI takes into account the initial and the implementation phase. The conceptual model of DOI in…

  2. A universal, easy-to-apply light-quality index based on natural light spectrum resemblance

    NASA Astrophysics Data System (ADS)

    Jou, Jwo-Huei; Chou, Kun-Yi; Yang, Fu-Chin; Agrawal, Abhishek; Chen, Sun-Zen; Tseng, Jing-Ru; Lin, Ching-Chiao; Chen, Po-Wei; Wong, Ken-Tsung; Chi, Yun

    2014-05-01

    Light-quality is extremely crucial for any light source to be used for illumination. However, a proper light-quality index is still missing although numerous electricity-driven lighting measures have been introduced since past 150 yr. We present in this communication a universal and easy-to-apply index for quantifying the quality of any given lighting source, which is based on direct comparison of its lumen spectrum with the natural light counterpart having the same color temperature. A general principle for creating high quality pseudo-natural light is accordingly derived. By using organic light-emitting diode technology, for example, daylight-style emission with a 96% natural light resemblance is obtained as a high number of organic emitters with diffused colors spanning throughout the entire visible range are employed. The same principle can be extended to other lighting technology such as light-emitting diode to generate natural light-style emission.

  3. Diffusive fractionation of trace elements in basaltic melt

    NASA Astrophysics Data System (ADS)

    Holycross, Megan E.; Bruce Watson, E.

    2016-10-01

    The chemical diffusivities of 25 trace elements (Sc, V, Rb, Sr, Y, Zr, Nb, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Lu, Hf, Ta, Th, and U) in basaltic melt were measured in diffusion couple experiments performed at 1 GPa pressure and temperatures from 1250 to 1500 °C. Trace element concentration gradients developed in the glasses were simultaneously characterized using laser ablation ICP/MS to create an internally consistent data set. A ratio-fitting technique was employed to accurately determine the relative diffusivities of the rare earth elements (REE). All diffusion coefficients conform to the expected Arrhenius relation D = D 0exp(- E a /RT), where the constant log( D 0, m2/s) ranges from -3.81 to -5.11 and E a ranges from 161.73 to 223.81 kJ/mol. The slowest diffusivities are obtained for the high-field-strength elements; the fastest diffusivities are obtained for the low-field-strength elements. Trace element diffusion in MORB follows the compensation law, where log D 0 is linearly correlated with E a. Arrhenius parameters for diffusion of trivalent REE monotonically increase from La to Lu and are near-linear functions of bond strength (the variation in Arrhenius parameters means that the diffusivities decrease monotonically from La to Lu at a given T). The new data for trace element diffusion in basaltic melt can be used to explore the potential for diffusive fractionation of trace elements using kinetic models. Concentrations of the slower-diffusing heavy REE may be altered relative to those of the faster-diffusing light REE as a diffusive boundary layer develops in melt-melt and crystal-melt systems. The results indicate that diffusion in basalt can be an effective mechanism to fractionate trace elements from one another.

  4. Light Reflector

    NASA Technical Reports Server (NTRS)

    1988-01-01

    Ultra Sales, Inc.'s fluorescent lighting fixture gets a boost in reflectivity through installation of Lightdriver, a thin tough thermoplastic film plated with aluminum, capable of reflecting 95 percent of visible light striking it. Lightdriver increases brightness without adding bulbs, and allows energy savings by removing some bulbs because the mirrorlike surface cuts light loss generally occasioned by conventional low reflectivity white painted surface above the bulbs in many fluorescent fixtures. Forty-five percent reduction in lighting electricity is attainable.

  5. Helium Diffusion in Olivine

    NASA Astrophysics Data System (ADS)

    Cherniak, D. J.; Watson, E. B.

    2011-12-01

    Diffusion of helium has been characterized in natural Fe-bearing olivine (~Fo90) and synthetic forsterite. Polished, oriented slabs of olivine were implanted with 3He, at 100 keV at a dose of 5x1015/cm2 or at 3.0 MeV at a dose of 1x1016/cm2. A set of experiments on the implanted olivine were run in 1-atm furnaces. In addition to the one-atm experiments, experiments on implanted samples were also run at higher pressures (2.6 and 2.7 GPa) to assess the potential effects of pressure on He diffusion and the applicability of the measured diffusivities in describing He transport in the mantle. The high-pressure experiments were conducted in a piston-cylinder apparatus using an "ultra-soft" pressure cell, with the diffusion sample directly surrounded by AgCl. 3He distributions following experiments were measured with Nuclear Reaction Analysis using the reaction 3He(d,p)4He. This direct profiling method permits us to evaluate anisotropy of diffusion, which cannot be easily assessed using bulk-release methods. For diffusion in forsterite parallel to c we obtain the following Arrhenius relation over the temperatures 250-950°C: D = 3.91x10-6exp(-159 ± 4 kJ mol-1/RT) m2/sec. The data define a single Arrhenius line spanning more than 7 orders of magnitude in D and 700°C in temperature. Diffusion parallel to a appears slightly slower, yielding an activation energy for diffusion of 135 kJ/mol and a pre-exponential factor of 3.73x10-8 m2/sec. Diffusion parallel to b is slower than diffusion parallel to a (by about two-thirds of a log unit); for this orientation an activation energy of 138 kJ/mol and a pre-exponential factor of 1.34x10-8 m2/sec are obtained. This anisotropy is broadly consistent with observations for diffusion of Ni and Fe-Mg in olivine. Diffusion in Fe-bearing olivine (transport parallel to b) agrees within uncertainty with findings for He diffusion in forsterite. The higher-pressure experiments yield diffusivities in agreement with those from the 1-atm

  6. Lighting Utilization.

    ERIC Educational Resources Information Center

    Crank, Ron

    This instructional unit is one of 10 developed by students on various energy-related areas that deals specifically with lighting utilization. Its objective is for the student to be able to outline the development of lighting use and conservation and identify major types and operating characteristics of lamps used in electric lighting. Some topics…

  7. SCHOOL LIGHTING

    ERIC Educational Resources Information Center

    1965

    SEVERAL ARTICLES ON SCHOOL LIGHTING ARE CONTAINED IN THIS JOURNAL. THE TITLES AND AUTHORS INCLUDED ARE AS FOLLOWS--(1) "TODAY'S CONCEPTS IN SCHOOL LIGHTING" BY CHARLES D. GIBSON, (2) "CHALLENGE OF TOMMORROW'S LIGHTING" BY S.K. GUTH AND E.H. WITTE, (3) "PEEK PREVIEW OF THE WINDOWLESS SCHOOL" BY JAMES J. MORISSEAU, (4) "MAINTENANCE BEGINS BEFORE…

  8. Back diffusion from thin low permeability zones.

    PubMed

    Yang, Minjune; Annable, Michael D; Jawitz, James W

    2015-01-01

    Aquitards can serve as long-term contaminant sources to aquifers when contaminant mass diffuses from the aquitard following aquifer source mass depletion. This study describes analytical and experimental approaches to understand reactive and nonreactive solute transport in a thin aquitard bounded by an adjacent aquifer. A series of well-controlled laboratory experiments were conducted in a two-dimensional flow chamber to quantify solute diffusion from a high-permeability sand into and subsequently out of kaolinite clay layers of vertical thickness 15 mm, 20 mm, and 60 mm. One-dimensional analytical solutions were developed for diffusion in a finite aquitard with mass exchange with an adjacent aquifer using the method of images. The analytical solutions showed very good agreement with measured breakthrough curves and aquitard concentration distributions measured in situ by light reflection visualization. Solutes with low retardation accumulated more stored mass with greater penetration distance in the aquitard compared to high-retardation solutes. However, because the duration of aquitard mass release was much longer, high-retardation solutes have a greater long-term back diffusion risk. The error associated with applying a semi-infinite domain analytical solution to a finite diffusion domain increases as a function of the system relative diffusion length scale, suggesting that the solutions using image sources should be applied in cases with rapid solute diffusion and/or thin clay layers. The solutions presented here can be extended to multilayer aquifer/low-permeability systems to assess the significance of back diffusion from thin layers.

  9. Back diffusion from thin low permeability zones.

    PubMed

    Yang, Minjune; Annable, Michael D; Jawitz, James W

    2015-01-01

    Aquitards can serve as long-term contaminant sources to aquifers when contaminant mass diffuses from the aquitard following aquifer source mass depletion. This study describes analytical and experimental approaches to understand reactive and nonreactive solute transport in a thin aquitard bounded by an adjacent aquifer. A series of well-controlled laboratory experiments were conducted in a two-dimensional flow chamber to quantify solute diffusion from a high-permeability sand into and subsequently out of kaolinite clay layers of vertical thickness 15 mm, 20 mm, and 60 mm. One-dimensional analytical solutions were developed for diffusion in a finite aquitard with mass exchange with an adjacent aquifer using the method of images. The analytical solutions showed very good agreement with measured breakthrough curves and aquitard concentration distributions measured in situ by light reflection visualization. Solutes with low retardation accumulated more stored mass with greater penetration distance in the aquitard compared to high-retardation solutes. However, because the duration of aquitard mass release was much longer, high-retardation solutes have a greater long-term back diffusion risk. The error associated with applying a semi-infinite domain analytical solution to a finite diffusion domain increases as a function of the system relative diffusion length scale, suggesting that the solutions using image sources should be applied in cases with rapid solute diffusion and/or thin clay layers. The solutions presented here can be extended to multilayer aquifer/low-permeability systems to assess the significance of back diffusion from thin layers. PMID:25478850

  10. Intragroup and Intracluster Light

    NASA Astrophysics Data System (ADS)

    Mihos, J. Christopher

    2016-08-01

    The largest stellar halos in the universe are found in massive galaxy clusters, where interactions and mergers of galaxies, along with the cluster tidal field, all act to strip stars from their host galaxies and feed the diffuse intracluster light (ICL) and extended halos of brightest cluster galaxies (BCGs). Studies of the nearby Virgo Cluster reveal a variety of accretion signatures imprinted in the morphology and stellar populations of its ICL. While simulations suggest the ICL should grow with time, attempts to track this evolution across clusters spanning a range of mass and redshift have proved difficult due to a variety of observational and definitional issues. Meanwhile, studies of nearby galaxy groups reveal the earliest stages of ICL formation: the extremely diffuse tidal streams formed during interactions in the group environment.

  11. Tungsten diffusion in silicon

    SciTech Connect

    De Luca, A.; Texier, M.; Burle, N.; Oison, V.; Pichaud, B.; Portavoce, A.; Grosjean, C.

    2014-01-07

    Two doses (10{sup 13} and 10{sup 15} cm{sup −2}) of tungsten (W) atoms were implanted in different Si(001) wafers in order to study W diffusion in Si. The samples were annealed or oxidized at temperatures between 776 and 960 °C. The diffusion profiles were measured by secondary ion mass spectrometry, and defect formation was studied by transmission electron microscopy and atom probe tomography. W is shown to reduce Si recrystallization after implantation and to exhibit, in the temperature range investigated, a solubility limit close to 0.15%–0.2%, which is higher than the solubility limit of usual metallic impurities in Si. W diffusion exhibits unusual linear diffusion profiles with a maximum concentration always located at the Si surface, slower kinetics than other metals in Si, and promotes vacancy accumulation close to the Si surface, with the formation of hollow cavities in the case of the higher W dose. In addition, Si self-interstitial injection during oxidation is shown to promote W-Si clustering. Taking into account these observations, a diffusion model based on the simultaneous diffusion of interstitial W atoms and W-Si atomic pairs is proposed since usual models used to model diffusion of metallic impurities and dopants in Si cannot reproduce experimental observations.

  12. Tungsten diffusion in olivine

    NASA Astrophysics Data System (ADS)

    Cherniak, D. J.; Van Orman, J. A.

    2014-03-01

    Diffusion of tungsten has been characterized in synthetic forsterite and natural olivine (Fo90) under dry conditions. The source of diffusant was a mixture of magnesium tungstate and olivine powders. Experiments were prepared by sealing the source material and polished olivine under vacuum in silica glass ampoules with solid buffers to buffer at NNO or IW. Prepared capsules were annealed in 1 atm furnaces for times ranging from 45 min to several weeks, at temperatures from 1050 to 1450 °C. Tungsten distributions in the olivine were profiled by Rutherford Backscattering Spectrometry (RBS). The following Arrhenius relation is obtained for W diffusion in forsterite: D=1.0×10-8exp(-365±28 kJ mol/RT) m s Diffusivities for the synthetic forsterite and natural Fe-bearing olivine are similar, and tungsten diffusion in olivine shows little dependence on crystallographic orientation or oxygen fugacity. The slow diffusivities measured for W in olivine indicate that Hf-W ages in olivine-metal systems will close to diffusive exchange at higher temperatures than other chronometers commonly used in cosmochronology, and that tungsten isotopic signatures will be less likely to be reset by subsequent thermal events.

  13. Light Source

    NASA Technical Reports Server (NTRS)

    1993-01-01

    Research on food growth for long duration spacecraft has resulted in a light source for growing plants indoors known as Qbeam, a solid state light source consisting of a control unit and lamp. The light source, manufactured by Quantum Devices, Inc., is not very hot, although it generates high intensity radiation. When Ron Ignatius, an industrial partner of WCSAR, realized that terrestrial plant research lighting was not energy efficient enough for space use, he and WCSAR began to experiment with light emitting diodes. A line of LED products was developed, and QDI was formed to market the technology. An LED-based cancer treatment device is currently under development.

  14. Diffusion Flame Stabilization

    NASA Technical Reports Server (NTRS)

    Takahashi, Fumiaki; Katta, V. R.

    2006-01-01

    Diffusion flames are commonly used for industrial burners in furnaces and flares. Oxygen/fuel burners are usually diffusion burners, primarily for safety reasons, to prevent flashback and explosion in a potentially dangerous system. Furthermore, in most fires, condensed materials pyrolyze, vaporize, and burn in air as diffusion flames. As a result of the interaction of a diffusion flame with burner or condensed-fuel surfaces, a quenched space is formed, thus leaving a diffusion flame edge, which plays an important role in flame holding in combustion systems and fire spread through condensed fuels. Despite a long history of jet diffusion flame studies, lifting/blowoff mechanisms have not yet been fully understood, compared to those of premixed flames. In this study, the structure and stability of diffusion flames of gaseous hydrocarbon fuels in coflowing air at normal earth gravity have been investigated experimentally and computationally. Measurements of the critical mean jet velocity (U(sub jc)) of methane, ethane, or propane at lifting or blowoff were made as a function of the coflowing air velocity (U(sub a)) using a tube burner (i.d.: 2.87 mm). By using a computational fluid dynamics code with 33 species and 112 elementary reaction steps, the internal chemical-kinetic structures of the stabilizing region of methane and propane flames were investigated. A peak reactivity spot, i.e., reaction kernel, is formed in the flame stabilizing region due to back-diffusion of heat and radical species against an oxygen-rich incoming flow, thus holding the trailing diffusion flame. The simulated flame base moved downstream under flow conditions close to the measured stability limit.

  15. Diffusion Flame Stabilization

    NASA Technical Reports Server (NTRS)

    Takahashi, Fumiaki; Katta, Viswanath R.

    2007-01-01

    Diffusion flames are commonly used for industrial burners in furnaces and flares. Oxygen/fuel burners are usually diffusion burners, primarily for safety reasons, to prevent flashback and explosion in a potentially dangerous system. Furthermore, in most fires, condensed materials pyrolyze, vaporize, and burn in air as diffusion flames. As a result of the interaction of a diffusion flame with burner or condensed-fuel surfaces, a quenched space is formed, thus leaving a diffusion flame edge, which plays an important role in flame holding in combustion systems and fire spread through condensed fuels. Despite a long history of jet diffusion flame studies, lifting/blowoff mechanisms have not yet been fully understood, compared to those of premixed flames. In this study, the structure and stability of diffusion flames of gaseous hydrocarbon fuels in coflowing air at normal earth gravity have been investigated experimentally and computationally. Measurements of the critical mean jet velocity (U(sub jc)) of methane, ethane, or propane at lifting or blowoff were made as a function of the coflowing air velocity (U(sub a)) using a tube burner (i.d.: 2.87 mm) (Fig. 1, left). By using a computational fluid dynamics code with 33 species and 112 elementary reaction steps, the internal chemical-kinetic structures of the stabilizing region of methane and propane flames were investigated (Fig. 1, right). A peak reactivity spot, i.e., reaction kernel, is formed in the flame stabilizing region due to back-diffusion of heat and radical species against an oxygen-rich incoming flow, thus holding the trailing diffusion flame. The simulated flame base moved downstream under flow conditions close to the measured stability limit.

  16. HD/H2 as a Probe of the Roles of Gas, Dust, Light, Metallicity, and Cosmic Rays in Promoting the Growth of Molecular Hydrogen in the Diffuse Interstellar Medium

    NASA Astrophysics Data System (ADS)

    Liszt, H. S.

    2015-01-01

    We modeled recent observations of UV absorption of HD and {H_2} in the Milky Way and toward damped/subdamped Lyα systems at z = 0.18 and z >1.7. N(HD)/N({H_2}) ratios reflect the separate self-shieldings of HD and {H_2} and the coupling introduced by deuteration chemistry. Locally, observations are explained by diffuse molecular gas with 16 cm-3 <~ n(H) <~ 128 cm-3 if the cosmic-ray ionization rate per H nucleus ζ H =2 × 10-16 s-1, as inferred from H3 + and OH+. The dominant influence on N(HD)/N({H_2}) is the cosmic-ray ionization rate with a much weaker downward dependence on n(H) at solar metallicity, but dust extinction can drive N(HD) higher as with N({H_2}). At z > 1.7, N(HD) is comparable to the Galaxy but with 10 times smaller N({H_2}) and somewhat smaller N({H_2})/N(H I). Comparison of our Galaxy with the Magellanic Clouds shows that smaller {H_2}/H is expected at subsolar metallicity, and we show by modeling that HD/{H_2} increases with density at low metallicity, opposite to the Milky Way. Observations of HD would be explained with higher n(H) at low metallicity, but high-z systems have high HD/{H_2} at metallicity 0.04 <~ Z <~ 2 solar. In parallel, we trace dust extinction and self-shielding effects. The abrupt {H_2} transition to {H_2}/H ≈ 1%-10% occurs mostly from self-shielding, although it is assisted by extinction for n(H) <~ 16 cm-3. Interior {H_2} fractions are substantially increased by dust extinction below <~ 32 cm-3. At smaller n(H), ζ H , small increases in {H_2} triggered by dust extinction can trigger abrupt increases in N(HD).

  17. HD/H{sub 2} AS A PROBE OF THE ROLES OF GAS, DUST, LIGHT, METALLICITY, AND COSMIC RAYS IN PROMOTING THE GROWTH OF MOLECULAR HYDROGEN IN THE DIFFUSE INTERSTELLAR MEDIUM

    SciTech Connect

    Liszt, H. S.

    2015-01-20

    We modeled recent observations of UV absorption of HD and H{sub 2} in the Milky Way and toward damped/subdamped Lyα systems at z = 0.18 and z >1.7. N(HD)/N(H{sub 2}) ratios reflect the separate self-shieldings of HD and H{sub 2} and the coupling introduced by deuteration chemistry. Locally, observations are explained by diffuse molecular gas with 16 cm{sup –3} ≲ n(H) ≲ 128 cm{sup –3} if the cosmic-ray ionization rate per H nucleus ζ {sub H} =2 × 10{sup –16} s{sup –1}, as inferred from H{sub 3} {sup +} and OH{sup +}. The dominant influence on N(HD)/N(H{sub 2}) is the cosmic-ray ionization rate with a much weaker downward dependence on n(H) at solar metallicity, but dust extinction can drive N(HD) higher as with N(H{sub 2}). At z > 1.7, N(HD) is comparable to the Galaxy but with 10 times smaller N(H{sub 2}) and somewhat smaller N(H{sub 2})/N(H I). Comparison of our Galaxy with the Magellanic Clouds shows that smaller H{sub 2}/H is expected at subsolar metallicity, and we show by modeling that HD/H{sub 2} increases with density at low metallicity, opposite to the Milky Way. Observations of HD would be explained with higher n(H) at low metallicity, but high-z systems have high HD/H{sub 2} at metallicity 0.04 ≲ Z ≲ 2 solar. In parallel, we trace dust extinction and self-shielding effects. The abrupt H{sub 2} transition to H{sub 2}/H ≈ 1%-10% occurs mostly from self-shielding, although it is assisted by extinction for n(H) ≲ 16 cm{sup –3}. Interior H{sub 2} fractions are substantially increased by dust extinction below ≲ 32 cm{sup –3}. At smaller n(H), ζ {sub H}, small increases in H{sub 2} triggered by dust extinction can trigger abrupt increases in N(HD)

  18. Diffuse-Illumination Systems for Growing Plants

    NASA Technical Reports Server (NTRS)

    May, George; Ryan, Robert

    2010-01-01

    Agriculture in both terrestrial and space-controlled environments relies heavily on artificial illumination for efficient photosynthesis. Plant-growth illumination systems require high photon flux in the spectral range corresponding with plant photosynthetic active radiation (PAR) (400 700 nm), high spatial uniformity to promote uniform growth, and high energy efficiency to minimize electricity usage. The proposed plant-growth system takes advantage of the highly diffuse reflective surfaces on the interior of a sphere, hemisphere, or other nearly enclosed structure that is coated with highly reflective materials. This type of surface and structure uniformly mixes discrete light sources to produce highly uniform illumination. Multiple reflections from within the domelike structures are exploited to obtain diffuse illumination, which promotes the efficient reuse of photons that have not yet been absorbed by plants. The highly reflective surfaces encourage only the plant tissue (placed inside the sphere or enclosure) to absorb the light. Discrete light sources, such as light emitting diodes (LEDs), are typically used because of their high efficiency, wavelength selection, and electronically dimmable properties. The light sources are arranged to minimize shadowing and to improve uniformity. Different wavelengths of LEDs (typically blue, green, and red) are used for photosynthesis. Wavelengths outside the PAR range can be added for plant diagnostics or for growth regulation

  19. Relativistic diffusion processes and random walk models

    SciTech Connect

    Dunkel, Joern; Talkner, Peter; Haenggi, Peter

    2007-02-15

    The nonrelativistic standard model for a continuous, one-parameter diffusion process in position space is the Wiener process. As is well known, the Gaussian transition probability density function (PDF) of this process is in conflict with special relativity, as it permits particles to propagate faster than the speed of light. A frequently considered alternative is provided by the telegraph equation, whose solutions avoid superluminal propagation speeds but suffer from singular (noncontinuous) diffusion fronts on the light cone, which are unlikely to exist for massive particles. It is therefore advisable to explore other alternatives as well. In this paper, a generalized Wiener process is proposed that is continuous, avoids superluminal propagation, and reduces to the standard Wiener process in the nonrelativistic limit. The corresponding relativistic diffusion propagator is obtained directly from the nonrelativistic Wiener propagator, by rewriting the latter in terms of an integral over actions. The resulting relativistic process is non-Markovian, in accordance with the known fact that nontrivial continuous, relativistic Markov processes in position space cannot exist. Hence, the proposed process defines a consistent relativistic diffusion model for massive particles and provides a viable alternative to the solutions of the telegraph equation.

  20. Hereditary Diffuse Gastric Cancer

    MedlinePlus

    ... with the syndrome is recommended. What are the estimated cancer risks associated with HDGC? Not everyone who ... the lifetime risk for diffuse gastric cancer is estimated to be 70% to 80% for men and ...

  1. Multinomial Diffusion Equation

    SciTech Connect

    Balter, Ariel I.; Tartakovsky, Alexandre M.

    2011-06-01

    We have developed a novel stochastic, space/time discrete representation of particle diffusion (e.g. Brownian motion) based on discrete probability distributions. We show that in the limit of both very small time step and large concentration, our description is equivalent to the space/time continuous stochastic diffusion equation. Being discrete in both time and space, our model can be used as an extremely accurate, efficient, and stable stochastic finite-difference diffusion algorithm when concentrations are so small that computationally expensive particle-based methods are usually needed. Through numerical simulations, we show that our method can generate realizations that capture the statistical properties of particle simulations. While our method converges converges to both the correct ensemble mean and ensemble variance very quickly with decreasing time step, but for small concentration, the stochastic diffusion PDE does not, even for very small time steps.

  2. Lung diffusion testing

    MedlinePlus

    Lung diffusion testing measures how well the lungs exchange gases. This is an important part of lung testing , because ... gases do not move normally across the lung tissues into the blood vessels of the lung. This ...

  3. Investigating diffusion with technology

    NASA Astrophysics Data System (ADS)

    Miller, Jon S.; Windelborn, Augden F.

    2013-07-01

    The activities described here allow students to explore the concept of diffusion with the use of common equipment such as computers, webcams and analysis software. The procedure includes taking a series of digital pictures of a container of water with a webcam as a dye slowly diffuses. At known time points, measurements of the pixel densities (darkness) of the digital pictures are recorded and then plotted on a graph. The resulting graph of darkness versus time allows students to see the results of diffusion of the dye over time. Through modification of the basic lesson plan, students are able to investigate the influence of a variety of variables on diffusion. Furthermore, students are able to expand the boundaries of their thinking by formulating hypotheses and testing their hypotheses through experimentation. As a result, students acquire a relevant science experience through taking measurements, organizing data into tables, analysing data and drawing conclusions.

  4. Hydrogen Diffusion in Forsterite

    NASA Astrophysics Data System (ADS)

    Demouchy, S.; Mackwell, S.

    2002-12-01

    Physical and chemical properties of Earth's mantle are readily modified by interaction with volatiles, such as water. Thus, characterization of solubility and kinetics of incorporation for water in nominally anhydrous minerals is important in order to understand the behavior of Earth's interior under hydrous conditions. Experimental studies on the olivine-water system indicate that significant amounts of OH can dissolve within olivine as point defects (Bell and Rossman, 1992; Kohlstedt et al. 1996). Extending Kohlstedt and Mackwell's (1998) work, our study concerns the kinetics of hydrogen transport in the iron-free olivine-water system. This study is based on hydrogenation of forsterite samples during piston-cylinder and TZM cold-seal vessel experiments. We use infrared analyses in order to constrain the speciation of the mobile water-derived defects in forsterite single-crystal sample, and the rates of diffusion of such species under uppermost mantle conditions (0.2 to 1.5 GPa, 900 to 1100° C). Hydrogen defect transport in single crystals of forsterite is investigated for diffusion parallel to each crystallographic axis. Defect diffusivities are obtained by fitting a diffusion law to the OH content as a function of position in the sample. Our current results indicate that incorporation of hydroxyl species into iron-free olivine is a one-stage process with hydrogen diffusion linked to magnesium vacancy self-diffusion DV, such that DV = D~/3 = 10-12 m2/s at 1000° C parallel to [001], where D~ represents the chemical diffusivity. Those diffusion rates are slightly lower than in iron-bearing olivine for the same incorporation mechanism. The different concentration profiles show a clear anisotropy of diffusion, with fastest diffusion parallel to [001] as in iron-bearing olivine. Thus, while hydrogen solubilities are dependent on iron content, the rate of incorporation of water-derived species in olivine is not strongly coupled to the concentration of iron. This

  5. Nodal Diffusion & Transport Theory

    1992-02-19

    DIF3D solves multigroup diffusion theory eigenvalue, adjoint, fixed source, and criticality (concentration, buckling, and dimension search) problems in 1, 2, and 3-space dimensions for orthogonal (rectangular or cylindrical), triangular, and hexagonal geometries. Anisotropic diffusion theory coefficients are permitted. Flux and power density maps by mesh cell and regionwise balance integrals are provided. Although primarily designed for fast reactor problems, upscattering and internal black boundary conditions are also treated.

  6. A Simple Single Step diffusion and Emitter Etching Process for High Efficiency Gallium Antimonide Thermophotovoltaic Devices

    SciTech Connect

    G. Rajagopalan; N.S. Reddy; E. Ehsani; I.B. Bhat; P.S. Dutta; R.J. Gutmann; G. Nichols; G.W. Charache; O. Sulima

    2003-08-29

    A single step diffusion followed by precise etching of the diffused layer has been developed to obtain a diffusion profile appropriate for high efficiency GaSb thermophotovoltaic cells. The junction depth was controlled through monitoring of light current-voltage (I-V) curves (photovoltaic response) during the post diffusion emitter etching process. The measured photoresponses (prior to device fabrication) have been correlated with the quantum efficiencies and the open circuit voltages in the fabricated devices. An optimum junction depth for obtaining highest quantum efficiency and open circuit voltage is presented based on diffusion lengths (or monitoring carrier lifetimes), carrier mobility and typical diffused impurity profile in GaSb.

  7. Advanced manufacturing: Technology diffusion

    SciTech Connect

    Tesar, A.

    1995-12-01

    In this paper we examine how manufacturing technology diffuses rom the developers of technology across national borders to those who do not have the capability or resources to develop advanced technology on their own. None of the wide variety of technology diffusion mechanisms discussed in this paper are new, yet the opportunities to apply these mechanisms are growing. A dramatic increase in technology diffusion occurred over the last decade. The two major trends which probably drive this increase are a worldwide inclination towards ``freer`` markets and diminishing isolation. Technology is most rapidly diffusing from the US In fact, the US is supplying technology for the rest of the world. The value of the technology supplied by the US more than doubled from 1985 to 1992 (see the Introduction for details). History shows us that technology diffusion is inevitable. It is the rates at which technologies diffuse to other countries which can vary considerably. Manufacturers in these countries are increasingly able to absorb technology. Their manufacturing efficiency is expected to progress as technology becomes increasingly available and utilized.

  8. Emergency Lighting

    NASA Technical Reports Server (NTRS)

    1977-01-01

    A lighting system originally developed for NASA's Apollo and Skylab manned spacecraft resulted in a industrial spinoff and creation of a whole new company to produce and market the product line. The company is UDEC Corp., Waltham, Mass. UDEC's "Multi-Mode" electronic lighting systems are designed for plant emergency and supplemental use, such as night lighting, "always-on" stairwell lights and illuminated exit signs. Their advantages stem from the qualities demanded for spacecraft installation: extremely high fight output with very low energy drain, compactness, light weight, and high reliability. The Multi-Mode system includes long-life fluorescent lamps operated by electronic circuitry, a sealed battery that needs no maintenance for 10 years, and a solid-state battery charger. A typical emergency installation consists of a master module with battery and an eight watt lamp, together with four remote "Satellight" modules powered by the master's battery. As a night lighting system for maintenance or I security, UDEC fixtures can bypass the battery and 1 operate on normal current at a fraction of the energy 1 demand of conventional night lighting. Industrial customers have realized savings of better than ninety percent with UDEC night lights. UDEC started as a basement industry in 1972 but the company has already sold more than 1,000 lighting systems to building operators.

  9. Multispecies diffusion models: A study of uranyl species diffusion

    SciTech Connect

    Liu, Chongxuan; Shang, Jianying; Zachara, John M.

    2011-12-14

    Rigorous numerical description of multi-species diffusion requires coupling of species, charge, and aqueous and surface complexation reactions that collectively affect diffusive fluxes. The applicability of a fully coupled diffusion model is, however, often constrained by the availability of species self-diffusion coefficients, as well as by computational complication for imposing charge conservation. In this study, several diffusion models with variable complexity in charge and species coupling were formulated and compared to describe reactive multi-species diffusion in groundwater. Diffusion of uranyl [U(VI)] species was used as an example in demonstrating the effectiveness of the models in describing multi-species diffusion. Numerical simulations found that a diffusion model with a single, common diffusion coefficient for all species was sufficient to describe multi-species U(VI) diffusion under steady-state condition of major chemical composition, but not under transient chemical conditions. Simulations revealed that a fully coupled diffusion model can be well approximated by a component-based diffusion model, which considers difference in diffusion coefficients between chemical components, but not between the species within each chemical component. This treatment significantly enhanced computational efficiency at the expense of minor charge conservation. The charge balance in the component-based diffusion model can be rigorously enforced, if necessary, by adding an artificial kinetic reaction term induced by the charge separation. The diffusion models were applied to describe U(VI) diffusive mass transfer in intragranular domains in two sediments collected from US Department of Energy's Hanford 300A where intragrain diffusion is a rate-limiting process controlling U(VI) adsorption and desorption. The grain-scale reactive diffusion model was able to describe U(VI) adsorption/desorption kinetics that has been described using a semi-empirical, multi-rate model

  10. Permanganate diffusion and reaction in sedimentary rocks.

    PubMed

    Huang, Qiuyuan; Dong, Hailiang; Towne, Rachael M; Fischer, Timothy B; Schaefer, Charles E

    2014-04-01

    In situ chemical oxidation using permanganate has frequently been used to treat chlorinated solvents in fractured bedrock aquifers. However, in systems where matrix back-diffusion is an important process, the ability of the oxidant to migrate and treat target contaminants within the rock matrix will likely determine the overall effectiveness of this remedial approach. In this study, a series of diffusion experiments were performed to measure the permanganate diffusion and reaction in four different types of sedimentary rocks (dark gray mudstone, light gray mudstone, red sandstone, and tan sandstone). Results showed that, within the experimental time frame (~2 months), oxidant migration into the rock was limited to distances less than 500 μm. The observed diffusivities for permanganate into the rock matrices ranged from 5.3 × 10(-13) to 1.3 × 10(-11) cm(2)/s. These values were reasonably predicted by accounting for both the rock oxidant demand and the effective diffusivity of the rock. Various Mn minerals formed as surface coatings from reduction of permanganate coupled with oxidation of total organic carbon (TOC), and the nature of the formed Mn minerals was dependent upon the rock type. Post-treatment tracer testing showed that these Mn mineral coatings had a negligible impact on diffusion through the rock. Overall, our results showed that the extent of permanganate diffusion and reaction depended on rock properties, including porosity, mineralogy, and organic carbon. These results have important implications for our understanding of long-term organic contaminant remediation in sedimentary rocks using permanganate.

  11. Permanganate diffusion and reaction in sedimentary rocks.

    PubMed

    Huang, Qiuyuan; Dong, Hailiang; Towne, Rachael M; Fischer, Timothy B; Schaefer, Charles E

    2014-04-01

    In situ chemical oxidation using permanganate has frequently been used to treat chlorinated solvents in fractured bedrock aquifers. However, in systems where matrix back-diffusion is an important process, the ability of the oxidant to migrate and treat target contaminants within the rock matrix will likely determine the overall effectiveness of this remedial approach. In this study, a series of diffusion experiments were performed to measure the permanganate diffusion and reaction in four different types of sedimentary rocks (dark gray mudstone, light gray mudstone, red sandstone, and tan sandstone). Results showed that, within the experimental time frame (~2 months), oxidant migration into the rock was limited to distances less than 500 μm. The observed diffusivities for permanganate into the rock matrices ranged from 5.3 × 10(-13) to 1.3 × 10(-11) cm(2)/s. These values were reasonably predicted by accounting for both the rock oxidant demand and the effective diffusivity of the rock. Various Mn minerals formed as surface coatings from reduction of permanganate coupled with oxidation of total organic carbon (TOC), and the nature of the formed Mn minerals was dependent upon the rock type. Post-treatment tracer testing showed that these Mn mineral coatings had a negligible impact on diffusion through the rock. Overall, our results showed that the extent of permanganate diffusion and reaction depended on rock properties, including porosity, mineralogy, and organic carbon. These results have important implications for our understanding of long-term organic contaminant remediation in sedimentary rocks using permanganate. PMID:24566296

  12. Freeform microstructure linear light emitter design for a natural light illumination system.

    PubMed

    Chen, Bo-Jian; Gao, Bo-Yuan; Ullah, Irfan; Chen, Kuan-Yu; Chou, Chun-Han; Lin, Chia-Min; Chang, Cheng-Ming; Jhan, Kai-Cyuan; Whang, Allen Jong-Woei

    2015-10-01

    The major factors of an illuminative environment are a high rendering index and uniformity. The natural light illumination system (NLIS) is used to guide sunlight for indoor illumination. The NLIS consists of three subsystems: collecting, transmitting, and emitting. Nowadays, a variety of light emitters are available for different illuminative environments. This paper proposes a linear microstructure to diffuse parallel light for indoor illumination. To increase uniformity and promote the illuminative area, the light emitter includes two microstructures for the distribution of light. Finally, the proposed light emitter gives illuminance uniformity and efficiency of 0.55% and 74.18%, respectively. PMID:26479647

  13. Freeform microstructure linear light emitter design for a natural light illumination system.

    PubMed

    Chen, Bo-Jian; Gao, Bo-Yuan; Ullah, Irfan; Chen, Kuan-Yu; Chou, Chun-Han; Lin, Chia-Min; Chang, Cheng-Ming; Jhan, Kai-Cyuan; Whang, Allen Jong-Woei

    2015-10-01

    The major factors of an illuminative environment are a high rendering index and uniformity. The natural light illumination system (NLIS) is used to guide sunlight for indoor illumination. The NLIS consists of three subsystems: collecting, transmitting, and emitting. Nowadays, a variety of light emitters are available for different illuminative environments. This paper proposes a linear microstructure to diffuse parallel light for indoor illumination. To increase uniformity and promote the illuminative area, the light emitter includes two microstructures for the distribution of light. Finally, the proposed light emitter gives illuminance uniformity and efficiency of 0.55% and 74.18%, respectively.

  14. Dynamic light scattering optical coherence tomography

    PubMed Central

    Lee, Jonghwan; Wu, Weicheng; Jiang, James Y.; Zhu, Bo; Boas, David A.

    2012-01-01

    We introduce an integration of dynamic light scattering (DLS) and optical coherence tomography (OCT) for high-resolution 3D imaging of heterogeneous diffusion and flow. DLS analyzes fluctuations in light scattered by particles to measure diffusion or flow of the particles, and OCT uses coherence gating to collect light only scattered from a small volume for high-resolution structural imaging. Therefore, the integration of DLS and OCT enables high-resolution 3D imaging of diffusion and flow. We derived a theory under the assumption that static and moving particles are mixed within the OCT resolution volume and the moving particles can exhibit either diffusive or translational motion. Based on this theory, we developed a fitting algorithm to estimate dynamic parameters including the axial and transverse velocities and the diffusion coefficient. We validated DLS-OCT measurements of diffusion and flow through numerical simulations and phantom experiments. As an example application, we performed DLS-OCT imaging of the living animal brain, resulting in 3D maps of the absolute and axial velocities, the diffusion coefficient, and the coefficient of determination. PMID:23037374

  15. Anomalous Diffusion Near Resonances

    SciTech Connect

    Sen, Tanaji; /Fermilab

    2010-05-01

    Synchro-betatron resonances can lead to emittance growth and the loss of luminosity. We consider the detailed dynamics of a bunch near such a low order resonance driven by crossing angles at the collision points. We characterize the nature of diffusion and find that it is anomalous and sub-diffusive. This affects both the shape of the beam distribution and the time scales for growth. Predictions of a simplified anomalous diffusion model are compared with direct simulations. Transport of particles near resonances is still not a well understood phenomenon. Often, without justification, phase space motion is assumed to be a normal diffusion process although at least one case of anomalous diffusion in beam dynamics has been reported [1]. Here we will focus on the motion near synchro-betatron resonances which can be excited by several means, including beams crossing at an angle at the collision points as in the LHC. We will consider low order resonances which couple the horizontal and longitudinal planes, both for simplicity and to observe large effects over short time scales. While the tunes we consider are not practical for a collider, nonetheless the transport mechanisms we uncover are also likely to operate at higher order resonances.

  16. Light-induced atomic desorption: recent developments

    NASA Astrophysics Data System (ADS)

    Mariotti, E.; Atutov, S. N.; Biancalana, Valerio; Bocci, S.; Burchianti, A.; Marinelli, C.; Nasyrov, K. A.; Pieragnoli, B.; Moi, L.

    2001-04-01

    Light induced atomic desorption (LIAD) is an impressive manifestation of a new class of phenomena involving alkali atoms, dielectric films and light. LIAD consists of a huge emission of alkali atoms (experimentally proved for sodium, potassium, rubidium and cesium) from siloxane films when illuminated by laser or ordinary light. Most of the experiments have been performed in glass cells suitably coated by a thin film (of the order of 10 micrometer) either of poly - (dimethylsiloxane) (PDMS), a polymer, or of octamethylcyclotetrasiloxane (OCT), a crown molecule. LIAD is a combination of two processes: direct photo-desorption from the surface and diffusion within the siloxane layer. The photo-desorbed atoms are replaced by fresh atoms diffusing to the surface. Moreover, from the experimental data it comes out that the desorbing light increases atomic diffusion and hence the diffusion coefficient. To our knowledge this is the first time that such an effect is clearly observed, measured and discussed: LIAD represents a new class of photo-effects characterized by two simultaneous phenomena due to the light: surface desorption and fastened bulk diffusion.

  17. Cesium diffusion in graphite

    SciTech Connect

    Evans, R.B. III; Davis, W. Jr.; Sutton, A.L. Jr.

    1980-05-01

    Experiments on diffusion of /sup 137/Cs in five types of graphite were performed. The document provides a completion of the report that was started and includes a presentation of all of the diffusion data, previously unpublished. Except for data on mass transfer of /sup 137/Cs in the Hawker-Siddeley graphite, analyses of experimental results were initiated but not completed. The mass transfer process of cesium in HS-1-1 graphite at 600 to 1000/sup 0/C in a helium atmosphere is essentially pure diffusion wherein values of (E/epsilon) and ..delta..E of the equation D/epsilon = (D/epsilon)/sub 0/ exp (-..delta..E/RT) are about 4 x 10/sup -2/ cm/sup 2//s and 30 kcal/mole, respectively.

  18. Diffusion model of the non-stoichiometric uranium dioxide

    SciTech Connect

    Moore, Emily; Guéneau, Christine; Crocombette, Jean-Paul

    2013-07-15

    Uranium dioxide (UO{sub 2}), which is used in light water reactors, exhibits a large range of non-stoichiometry over a wide temperature scale up to 2000 K. Understanding diffusion behavior of uranium oxides under such conditions is essential to ensure safe reactor operation. The current understanding of diffusion properties is largely limited by the stoichiometric deviations inherent to the fuel. The present DICTRA-based model considers diffusion across non-stoichiometric ranges described by experimentally available data. A vacancy and interstitial model of diffusion is applied to the U–O system as a function of its defect structure derived from CALPHAD-type thermodynamic descriptions. Oxygen and uranium self and tracer diffusion coefficients are assessed for the construction of a mobility database. Chemical diffusion coefficients of oxygen are derived with respect to the Darken relation and migration energies of defects are evaluated as a function of stoichiometric deviation. - Graphical abstract: Complete description of Oxygen–Uranium diffusion as a function of composition at various temperatures according to the developed Dictra model. - Highlights: • Assessment of a uranium–oxygen diffusion model with Dictra. • Complete description of U–O diffusion over wide temperature and composition range. • Oxygen model includes terms for interstitial and vacancy migration. • Interaction terms between defects help describe non-stoichiometric domain of UO{sub 2±x}. • Uranium model is separated into mobility terms for the cationic species.

  19. EDITORIAL: Slow light Slow light

    NASA Astrophysics Data System (ADS)

    Boyd, Robert; Hess, Ortwin; Denz, Cornelia; Paspalakis, Emmanuel

    2010-10-01

    Research into slow light began theoretically in 1880 with the paper [1] of H A Lorentz, who is best known for his work on relativity and the speed of light. Experimental work started some 60 years later with the work of S L McCall and E L Hahn [2] who explored non-linear self-induced transparency in ruby. This field of research has burgeoned in the last 10 years, starting with the work of L Vestergaard Hau and coworkers on slow light via electromagnetically induced transparency in a Bose-Einstein condensate [3]. Many groups are now able to slow light down to a few metres per second or even stop the motion of light entirely [4]. Today, slow light - or more often `slow and fast light' - has become its own vibrant field with a strongly increasing number of publications. In broad scope, slow light research can be categorized in terms of the sort of physical mechanism used to slow down the light. One sort of slow light makes use of material dispersion. This dispersion can be the natural dispersion of the ordinary refractive index or can be the frequency dependence of some nonlinear optical process, such as electromagnetically induced transparency, coherent population oscillations, stimulated light scattering, or four-wave mixing processes. The second sort of slow light makes use of the wavelength dependence of artificially structured materials, such as photonic crystals, optical waveguides, and collections of microresonators. Material systems in which slow light has been observed include metal vapours, rare-earth-doped materials, Raman and Brillioun gain media, photonic crystals, microresonators and, more recently, metamaterials. A common feature of all of these schemes is the presence of a sharp single resonance or multiple resonances produced by an atomic transition, a resonance in a photonic structure, or in a nonlinear optical process. Current applications of slow light include a series of attractive topics in optical information processing, such as optical data

  20. Hydrogen diffusion in Zircon

    NASA Astrophysics Data System (ADS)

    Ingrin, Jannick; Zhang, Peipei

    2016-04-01

    Hydrogen mobility in gem quality zircon single crystals from Madagascar was investigated through H-D exchange experiments. Thin slices were annealed in a horizontal furnace flushed with a gas mixture of Ar/D2(10%) under ambient pressure between 900 ° C to 1150 ° C. FTIR analyses were performed on oriented slices before and after each annealing run. H diffusion along [100] and [010] follow the same diffusion law D = D0exp[-E /RT], with log D0 = 2.24 ± 1.57 (in m2/s) and E = 374 ± 39 kJ/mol. H diffusion along [001] follows a slightly more rapid diffusion law, with log D0 = 1.11 ± 0.22 (in m2/s) and E = 334 ± 49 kJ/mol. H diffusion in zircon has much higher activation energy and slower diffusivity than other NAMs below 1150 ° C even iron-poor garnets which are known to be among the slowest (Blanchard and Ingrin, 2004; Kurka et al. 2005). During H-D exchange zircon incorporates also deuterium. This hydration reaction involves uranium reduction as it is shown from the exchange of U5+ and U4+ characteristic bands in the near infrared region during annealing. It is the first time that a hydration reaction U5+ + OH‑ = U4+ + O2‑ + 1/2H2, is experimentally reported. The kinetics of deuterium incorporation is slightly slower than hydrogen diffusion, suggesting that the reaction is limited by hydrogen mobility. Hydrogen isotopic memory of zircon is higher than other NAMs. Zircons will be moderately retentive of H signatures at mid-crustal metamorphic temperatures. At 500 ° C, a zircon with a radius of 300 μm would retain its H isotopic signature over more than a million years. However, a zircon is unable to retain this information for geologically significant times under high-grade metamorphism unless the grain size is large enough. Refrences Blanchard, M. and Ingrin, J. (2004) Hydrogen diffusion in Dora Maira pyrope. Physics and Chemistry of Minerals, 31, 593-605. Kurka, A., Blanchard, M. and Ingrin, J. (2005) Kinetics of hydrogen extraction and deuteration in

  1. Hydrogen diffusion in Zircon

    NASA Astrophysics Data System (ADS)

    Ingrin, Jannick; Zhang, Peipei

    2016-04-01

    Hydrogen mobility in gem quality zircon single crystals from Madagascar was investigated through H-D exchange experiments. Thin slices were annealed in a horizontal furnace flushed with a gas mixture of Ar/D2(10%) under ambient pressure between 900 ° C to 1150 ° C. FTIR analyses were performed on oriented slices before and after each annealing run. H diffusion along [100] and [010] follow the same diffusion law D = D0exp[-E /RT], with log D0 = 2.24 ± 1.57 (in m2/s) and E = 374 ± 39 kJ/mol. H diffusion along [001] follows a slightly more rapid diffusion law, with log D0 = 1.11 ± 0.22 (in m2/s) and E = 334 ± 49 kJ/mol. H diffusion in zircon has much higher activation energy and slower diffusivity than other NAMs below 1150 ° C even iron-poor garnets which are known to be among the slowest (Blanchard and Ingrin, 2004; Kurka et al. 2005). During H-D exchange zircon incorporates also deuterium. This hydration reaction involves uranium reduction as it is shown from the exchange of U5+ and U4+ characteristic bands in the near infrared region during annealing. It is the first time that a hydration reaction U5+ + OH- = U4+ + O2- + 1/2H2, is experimentally reported. The kinetics of deuterium incorporation is slightly slower than hydrogen diffusion, suggesting that the reaction is limited by hydrogen mobility. Hydrogen isotopic memory of zircon is higher than other NAMs. Zircons will be moderately retentive of H signatures at mid-crustal metamorphic temperatures. At 500 ° C, a zircon with a radius of 300 μm would retain its H isotopic signature over more than a million years. However, a zircon is unable to retain this information for geologically significant times under high-grade metamorphism unless the grain size is large enough. Refrences Blanchard, M. and Ingrin, J. (2004) Hydrogen diffusion in Dora Maira pyrope. Physics and Chemistry of Minerals, 31, 593-605. Kurka, A., Blanchard, M. and Ingrin, J. (2005) Kinetics of hydrogen extraction and deuteration in

  2. Multispecies diffusion models: A study of uranyl species diffusion

    NASA Astrophysics Data System (ADS)

    Liu, Chongxuan; Shang, Jianying; Zachara, John M.

    2011-12-01

    Rigorous numerical description of multispecies diffusion requires coupling of species, charge, and aqueous and surface complexation reactions that collectively affect diffusive fluxes. The applicability of a fully coupled diffusion model is, however, often constrained by the availability of species self-diffusion coefficients, as well as by computational complication in imposing charge conservation. In this study, several diffusion models with variable complexity in charge and species coupling were formulated and compared to describe reactive multispecies diffusion in groundwater. Diffusion of uranyl [U(VI)] species was used as an example in demonstrating the effectiveness of the models in describing multispecies diffusion. Numerical simulations found that a diffusion model with a single, common diffusion coefficient for all species was sufficient to describe multispecies U(VI) diffusion under a steady state condition of major chemical composition, but not under transient chemical conditions. Simulations revealed that for multispecies U(VI) diffusion under transient chemical conditions, a fully coupled diffusion model could be well approximated by a component-based diffusion model when the diffusion coefficient for each chemical component was properly selected. The component-based diffusion model considers the difference in diffusion coefficients between chemical components, but not between the species within each chemical component. This treatment significantly enhanced computational efficiency at the expense of minor charge conservation. The charge balance in the component-based diffusion model can be enforced, if necessary, by adding a secondary migration term resulting from model simplification. The effect of ion activity coefficient gradients on multispecies diffusion is also discussed. The diffusion models were applied to describe U(VI) diffusive mass transfer in intragranular domains in two sediments collected from U.S. Department of Energy's Hanford 300A

  3. Detection of a diffusive cloak via second-order statistics

    NASA Astrophysics Data System (ADS)

    Koirala, Milan; Yamilov, Alexey

    2016-08-01

    We propose a scheme to detect the diffusive cloak proposed by Schittny et al [Science 345, 427 (2014)]. We exploit the fact that diffusion of light is an approximation that disregards wave interference. The long-range contribution to intensity correlation is sensitive to locations of paths crossings and the interference inside the medium, allowing one to detect the size and position, including the depth, of the diffusive cloak. Our results also suggest that it is possible to separately manipulate the first- and the second-order statistics of wave propagation in turbid media.

  4. Improved Optics For Quasi-Elastic Light Scattering

    NASA Technical Reports Server (NTRS)

    Cheung, Harry Michael

    1995-01-01

    Improved optical train devised for use in light-scattering measurements of quasi-elastic light scattering (QELS) and laser spectroscopy. Measurements performed on solutions, microemulsions, micellular solutions, and colloidal dispersions. Simultaneous measurements of total intensity and fluctuations in total intensity of light scattered from sample at various angles provides data used, in conjunction with diffusion coefficients, to compute sizes of particles in sample.

  5. Specular, diffuse and polarized imagery of an oat canopy

    NASA Technical Reports Server (NTRS)

    Vanderbilt, Vern C.; De Venecia, Kurt J.

    1988-01-01

    Light, polarized by specular reflection, has been found to be an important part of the light scattered by several measured plant canopies. The authors investigate for one canopy the relative importance of specularly reflected sunlight, specularly reflected light from other sources including skylight, and diffusely upwelling light. Polarization images are used to gain increased understanding of the radiation transfer process in a plant canopy. Analysis of the results suggests that properly analyzed polarized remotely sensed data, acquired under specific atmospheric conditions by a specially designed sensor, potentially provide measures of physiological and morphological states of plants in a canopy.

  6. Thermal diffusivity measurement by lock-in photothermal shadowgraph method

    NASA Astrophysics Data System (ADS)

    Cifuentes, A.; Alvarado, S.; Cabrera, H.; Calderón, A.; Marín, E.

    2016-04-01

    Here, we present a novel application of the shadowgraph technique for obtaining the thermal diffusivity of an opaque solid sample, inspired by the orthogonal skimming photothermal beam deflection technique. This new variant utilizes the shadow projected by the sample when put against a collimated light source. The sample is then heated periodically by another light beam, giving rise to thermal waves, which propagate across it and through its surroundings. Changes in the refractive index of the surrounding media due to the heating distort the shadow. This phenomenon is recorded and lock-in amplified in order to determine the sample's thermal diffusivity.

  7. Oscillatory Extinction Of Spherical Diffusion Flames

    NASA Technical Reports Server (NTRS)

    Law, C. K.; Yoo, S. W.; Christianson, E. W.

    2003-01-01

    Since extinction has been observed in an oscillatory manner in Le greater than 1 premixed flames, it is not unreasonable to expect that extinction could occur in an unsteady manner for diffusion flames. Indeed, near-limit oscillations have been observed experimentally under microgravity conditions for both candle flames and droplet flames. Furthermore, the analysis of Cheatham and Matalon on the unsteady behavior of diffusion flames with heat loss, identified an oscillatory regime which could be triggered by either a sufficiently large Lewis number (even without heat loss) or an appreciable heat loss (even for Le=1). In light of these recent understanding, the present investigation aims to provide a well-controlled experiment that can unambiguously demonstrate the oscillation of diffusion flames near both the transport- and radiation-induced limits. That is, since candle and jet flames are stabilized through flame segments that are fundamentally premixed in nature, and since premixed flames are prone to oscillate, there is the possibility that the observed oscillation of these bulk diffusion flames could be triggered and sustained by the oscillation of the premixed flame segments. Concerning the observed oscillatory droplet extinction, it is well-known that gas-phase oscillation in heterogeneous burning can be induced by and is thereby coupled with condensed-phase unsteadiness. Consequently, a convincing experiment on diffusion flame oscillation must exclude any ingredients of premixed flames and other sources that may either oscillate themselves or promote the oscillation of the diffusion flame. The present experiment on burner-generated spherical flames with a constant reactant supply endeavored to accomplish this goal. The results are further compared with those from computational simulation for further understanding and quantification of the flame dynamics and extinction.

  8. The visual light field in real scenes

    PubMed Central

    Xia, Ling; Pont, Sylvia C.; Heynderickx, Ingrid

    2014-01-01

    Human observers' ability to infer the light field in empty space is known as the “visual light field.” While most relevant studies were performed using images on computer screens, we investigate the visual light field in a real scene by using a novel experimental setup. A “probe” and a scene were mixed optically using a semitransparent mirror. Twenty participants were asked to judge whether the probe fitted the scene with regard to the illumination intensity, direction, and diffuseness. Both smooth and rough probes were used to test whether observers use the additional cues for the illumination direction and diffuseness provided by the 3D texture over the rough probe. The results confirmed that observers are sensitive to the intensity, direction, and diffuseness of the illumination also in real scenes. For some lighting combinations on scene and probe, the awareness of a mismatch between the probe and scene was found to depend on which lighting condition was on the scene and which on the probe, which we called the “swap effect.” For these cases, the observers judged the fit to be better if the average luminance of the visible parts of the probe was closer to the average luminance of the visible parts of the scene objects. The use of a rough instead of smooth probe was found to significantly improve observers' abilities to detect mismatches in lighting diffuseness and directions. PMID:25926970

  9. Multicomponent diffusion in molten salt NaF-ZrF4: Dynamical correlations and Maxwell-Stefan diffusivities

    NASA Astrophysics Data System (ADS)

    Baig, Mohammad Saad; Chakraborty, Brahmananda; Ramaniah, Lavanya M.

    2016-05-01

    NaF-ZrF4 is used as a waste incinerator and as a coolant in Generation IV reactors.Structural and dynamical properties of molten NaF-ZrF4 system were studied along with Onsagercoefficients and Maxwell-Stefan (MS) Diffusivities applying Green-Kubo formalism and molecular dynamics (MD) simulations. The zirconium ions are found to be 8 fold coordinated with fluoride ions for all temperatures and concentrations. All the diffusive flux correlations show back-scattering. Even though the MS diffusivities are expected to depend very lightly on the composition because of decoupling of thermodynamic factor, the diffusivity ĐNa-F shows interesting behavior with the increase in concentration of ZrF4. This is because of network formation in NaF-ZrF4. Positive entropy constraints have been plotted to authenticate negative diffusivities observed.

  10. Light Learning.

    ERIC Educational Resources Information Center

    Cutshall, Sandy

    2002-01-01

    Describes a career and technical education program on photonics, the study, research, and development of equipment and concepts used in the transmission of information through light, including fiber optics and experimental laser technologies. (JOW)

  11. Osmosis and Diffusion

    ERIC Educational Resources Information Center

    Sack, Jeff

    2005-01-01

    OsmoBeaker is a CD-ROM designed to enhance the learning of diffusion and osmosis by presenting interactive experimentation to the student. The software provides several computer simulations that take the student through different scenarios with cells, having different concentrations of solutes in them.

  12. Thermodynamics of diffusion

    NASA Astrophysics Data System (ADS)

    Matuszak, Daniel

    Diffusion is the migration of molecules in the reference frame of a system's center of mass and it is a physical process that occurs in all chemical and biological systems. Diffusion generally involves intermolecular interactions that lead to clustering, adsorption, and phase transitions; as such, it is difficult to describe theoretically on a molecular level in systems containing both intermolecular repulsions and attractions. This work describes a simple thermodynamic approach that accounts for intermolecular attractions and repulsions (much like how the van der Waals equation does) to model and help provide an understanding of diffusion. The approach is an extension of the equilibrium Lattice Density Functional Theory of Aranovich and Donohue; it was developed with Mason and Lonsdale's guidelines on how to construct and test a transport theory. In the framework of lattice fluids, this new approach gives (a) correct equilibrium limits, (b) Fickian behavior for non-interacting systems, (c) correct departures from Fickian behavior in non-ideal systems, (d) the correct Maxwell-Stefan formulation, (e) symmetry behavior upon re-labeling species, (f) reasonable non-equilibrium phase behavior, (g) agreement with Molecular Dynamics simulations, (h) agreement with the theory of non-equilibrium thermodynamics, (i) a vanishing diffusive flux at the critical point, and (j) other qualitatively-correct behaviors when applied to problems in porous membranes and in packed beds.

  13. Water vapor diffusion membranes

    NASA Technical Reports Server (NTRS)

    Holland, F. F., Jr.; Smith, J. K.

    1974-01-01

    The program is reported, which was designed to define the membrane technology of the vapor diffusion water recovery process and to test this technology using commercially available or experimental membranes. One membrane was selected, on the basis of the defined technology, and was subjected to a 30-day demonstration trial.

  14. Light's twist

    PubMed Central

    Padgett, Miles

    2014-01-01

    That light travels in straight lines is a statement of the obvious. However, the energy and momentum flow within light beams can twist to form vortices such as eddies in a stream. These twists carry angular momentum, which can make microscopic objects spin, be used to encode extra information in communication systems, enable the design of novel imaging systems and allow new tests of quantum mechanics. PMID:25484612

  15. Ti Diffusion in Zircon

    NASA Astrophysics Data System (ADS)

    Cherniak, D. J.; Watson, E. B.

    2006-12-01

    Diffusion of Ti under anhydrous conditions at 1 atmosphere and under fluid-present conditions at 1.1-1.2 GPa has been measured in natural zircon. The source of diffusant for 1-atm experiments was a ZrO2- TiO2-ZrSiO4 mixture, with experiments run in Pt capsules. Diffusion experiments conducted in the presence of H2O-CO2 fluid were run in a piston-cylinder apparatus, using a source of ground TiO2, ZrSiO4 and SiO2, with oxalic acid added to produce H2O-CO2 vapor and partially melt the solid source material, yielding an assemblage of rutile + zircon + melt + vapor. Resonant nuclear reaction analysis (NRA) with the nuclear reaction ^{48}Ti(p,Γ)^{49}V was used to measure diffusion profiles for both sets of experiments. The following Arrhenius relation was obtained for Ti diffusion normal to c over the temperature range 1350-1550C at one atmosphere: DTi = 3.3x102 exp(-754 ± 56 kJ mol-1 /RT) m2sec-1 Ti diffusivities were found to be similar for experiments run under fluid-present conditions. A fit to all of the data yields the Arrhenius relation D = 1.3x103 exp(-741 ± 46 kJ mol-1 /RT) m2sec-1. These data suggest that zircon should be extremely retentive of Ti chemical signatures, indicating that the recently developed Ti-in-zircon crystallization geothermometer (Watson and Harrison, 2005; Watson et al., 2006) will be quite robust in preserving temperatures of zircon crystallization. Titanium diffuses somewhat faster in zircon than larger tetravalent cations U, Th, and Hf, but considerably more slowly than Pb, the REE, and oxygen; hence Ti crystallization temperatures may be retained under circumstances when radiometric ages or other types of geochemical information are lost. Watson EB, Harrison TM (2005) Science 308, 841-844. Watson EB, Wark DA, Thomas JB (2006) CMP(in press).

  16. Controlling Light Harvesting with Light.

    PubMed

    Gwizdala, Michal; Berera, Rudi; Kirilovsky, Diana; van Grondelle, Rienk; Krüger, Tjaart P J

    2016-09-14

    When exposed to intense sunlight, all organisms performing oxygenic photosynthesis implement various photoprotective strategies to prevent potentially lethal photodamage. The rapidly responding photoprotective mechanisms, occurring in the light-harvesting pigment-protein antennae, take effect within tens of seconds, while the dramatic and potentially harmful light intensity fluctuations manifest also on shorter time scales. Here we show that, upon illumination, individual phycobilisomes from Synechocystis PCC 6803, which, in vivo under low-light conditions, harvest solar energy, and have the built-in capacity to switch rapidly and reversibly into light-activated energy-dissipating states. Simultaneously measured fluorescence intensity, lifetime, and spectra, compared with a multicompartmental kinetic model, revealed that essentially any subunit of a phycobilisome can be quenched, and that the core complexes were targeted most frequently. Our results provide the first evidence for fluorescence blinking from a biologically active system at physiological light intensities and suggest that the light-controlled switches to intrinsically available energy-dissipating states are responsible for a novel type of photoprotection in cyanobacteria. We anticipate other photosynthetic organisms to employ similar strategies to respond instantly to rapid solar light intensity fluctuations. A detailed understanding of the photophysics of photosynthetic antenna complexes is of great interest for bioinspired solar energy technologies. PMID:27546794

  17. Controlling Light Harvesting with Light.

    PubMed

    Gwizdala, Michal; Berera, Rudi; Kirilovsky, Diana; van Grondelle, Rienk; Krüger, Tjaart P J

    2016-09-14

    When exposed to intense sunlight, all organisms performing oxygenic photosynthesis implement various photoprotective strategies to prevent potentially lethal photodamage. The rapidly responding photoprotective mechanisms, occurring in the light-harvesting pigment-protein antennae, take effect within tens of seconds, while the dramatic and potentially harmful light intensity fluctuations manifest also on shorter time scales. Here we show that, upon illumination, individual phycobilisomes from Synechocystis PCC 6803, which, in vivo under low-light conditions, harvest solar energy, and have the built-in capacity to switch rapidly and reversibly into light-activated energy-dissipating states. Simultaneously measured fluorescence intensity, lifetime, and spectra, compared with a multicompartmental kinetic model, revealed that essentially any subunit of a phycobilisome can be quenched, and that the core complexes were targeted most frequently. Our results provide the first evidence for fluorescence blinking from a biologically active system at physiological light intensities and suggest that the light-controlled switches to intrinsically available energy-dissipating states are responsible for a novel type of photoprotection in cyanobacteria. We anticipate other photosynthetic organisms to employ similar strategies to respond instantly to rapid solar light intensity fluctuations. A detailed understanding of the photophysics of photosynthetic antenna complexes is of great interest for bioinspired solar energy technologies.

  18. Feasibility of interstitial diffuse optical tomography using cylindrical diffusing fiber for prostate PDT

    PubMed Central

    Liang, Xing; Wang, Ken Kang-Hsin; Zhu, Timothy C.

    2013-01-01

    Interstitial diffuse optical tomography (DOT) has been used to characterize spatial distribution of optical properties for prostate photodynamic therapy (PDT) dosimetry. We have developed an interstitial DOT method using cylindrical diffuse fibers (CDFs) as light sources, so that the same light sources can be used for both DOT measurement and PDT treatment. In this novel interstitial CDF-DOT method, absolute light fluence per source strength (in unit of 1/cm2) is used to separate absorption and scattering coefficients. A mathematical phantom and a solid prostate phantom including anomalies with known optical properties were used, respectively, to test the feasibility of reconstructing optical properties using interstitial CDF-DOT. Three dimension spatial distributions of the optical properties were reconstructed for both scenarios. Our studies show that absorption coefficient can be reliably extrapolated while there are some cross talks between absorption and scattering properties. Even with the suboptimal reduced scattering coefficients, the reconstructed light fluence rate agreed with the measured values to within ±10%, thus the proposed CDF-DOT allows greatly improved light dosimetry calculation for interstitial PDT. PMID:23629149

  19. Diffusion in solids with holographic interferometry

    NASA Astrophysics Data System (ADS)

    Liu, Dingyu

    1996-12-01

    It is of great importance for the formation of p-n junction in semiconductors by penetrating some impurities through the depth near the surface, so it has long been paid attention to control the concentration distribution of impurities during the diffusion process. In recent years, ionic carburizing, and ion bombardment penetration etc. for the treatment of metal surface have also attracted by material sciences. It requires that the diffusion depth and the diffusion time of the impurities should be under precise control. Different methods, such as the method of radioisotopic detection and the method of chemical analysis have been adopted, however, the reports of different workers are very different, especially in the real time measurement, so, finding new method is never ending. In 1984, H. Fenichel have performed experiments on the solutions of table salt and sugar with the method of holographic interferometry. As for metals which are opaque for the visible light, but they become transparent by making them into a very thin film so that, in principle, the diffusion of atoms within a film is capable of measure by holographic interferometry. Alternatively, the electromagnetic waves within 1 - 70 micrometers wavelengths may be utilized, some materials, such as high purified germanium and silicon are good materials for infrared transmission. Some fluorides of alkaline-earth metals have high transmittance in the range of 1 - 8 micrometers , the concentration of impurities in the semiconductor and metal surface treatment are of 1015 - 1020 atoms per cubic cm, which is capable of detection.

  20. Erbium diffusion in silicon dioxide

    SciTech Connect

    Lu Yingwei; Julsgaard, B.; Petersen, M. Christian; Jensen, R. V. Skougaard; Pedersen, T. Garm; Pedersen, K.; Larsen, A. Nylandsted

    2010-10-04

    Erbium diffusion in silicon dioxide layers prepared by magnetron sputtering, chemical vapor deposition, and thermal growth has been investigated by secondary ion mass spectrometry, and diffusion coefficients have been extracted from simulations based on Fick's second law of diffusion. Erbium diffusion in magnetron sputtered silicon dioxide from buried erbium distributions has in particular been studied, and in this case a simple Arrhenius law can describe the diffusivity with an activation energy of 5.3{+-}0.1 eV. Within a factor of two, the erbium diffusion coefficients at a given temperature are identical for all investigated matrices.

  1. Direct visualization of surface-plasmon bandgaps in the diffuse background of metallic gratings.

    PubMed

    Depine, Ricardo A; Ledesma, Silvia

    2004-10-01

    When a surface plasmon propagates along a microrough grating, it interacts with the periodic plus the random roughness and emits light into the diffuse background, which can present intensity maxima called diffuse light bands. We reexamine previous studies on these bands within the framework of recent studies on photonic surfaces and show that the phenomenon of diffuse light provides an experimental technique for directly imaging the dispersion relation of surface plasmons, including the gap that, under appropriate circumstances, opens in the reciprocal grating space.

  2. Numerical modelling and image reconstruction in diffuse optical tomography

    PubMed Central

    Dehghani, Hamid; Srinivasan, Subhadra; Pogue, Brian W.; Gibson, Adam

    2009-01-01

    The development of diffuse optical tomography as a functional imaging modality has relied largely on the use of model-based image reconstruction. The recovery of optical parameters from boundary measurements of light propagation within tissue is inherently a difficult one, because the problem is nonlinear, ill-posed and ill-conditioned. Additionally, although the measured near-infrared signals of light transmission through tissue provide high imaging contrast, the reconstructed images suffer from poor spatial resolution due to the diffuse propagation of light in biological tissue. The application of model-based image reconstruction is reviewed in this paper, together with a numerical modelling approach to light propagation in tissue as well as generalized image reconstruction using boundary data. A comprehensive review and details of the basis for using spatial and structural prior information are also discussed, whereby the use of spectral and dual-modality systems can improve contrast and spatial resolution. PMID:19581256

  3. A SIGNATURE OF CHEMICAL SEPARATION IN THE COOLING LIGHT CURVES OF TRANSIENTLY ACCRETING NEUTRON STARS

    SciTech Connect

    Medin, Zach; Cumming, Andrew E-mail: cumming@physics.mcgill.ca

    2014-03-01

    We show that convection driven by chemical separation can significantly affect the cooling light curves of accreting neutron stars after they go into quiescence. We calculate the thermal relaxation of the neutron star ocean and crust including the thermal and compositional fluxes due to convection. After the inward propagating cooling wave reaches the base of the neutron star ocean, the ocean begins to freeze, driving chemical separation. The resulting convection transports heat inward, giving much faster cooling of the surface layers than found assuming the ocean cools passively. The light curves including convection show a rapid drop in temperature weeks after outburst. Identifying this signature in observed cooling curves would constrain the temperature and composition of the ocean as well as offer a real time probe of the freezing of a classical multicomponent plasma.

  4. Pose estimation using time-resolved inversion of diffuse light.

    PubMed

    Raviv, Dan; Barsi, Christopher; Naik, Nikhil; Feigin, Micha; Raskar, Ramesh

    2014-08-25

    We present a novel approach for evaluation of position and orientation of geometric shapes from scattered time-resolved data. Traditionally, imaging systems treat scattering as unwanted and are designed to mitigate the effects. Instead, we show here that scattering can be exploited by implementing a system based on a femtosecond laser and a streak camera. The result is accurate estimation of object pose, which is a fundamental tool in analysis of complex scenarios and plays an important role in our understanding of physical phenomena. Here, we experimentally show that for a given geometry, a single incident illumination point yields enough information for pose estimation and tracking after multiple scattering events. Our technique can be used for single-shot imaging behind walls or through turbid media.

  5. Remote sensing of prefrontal cortex function with diffusive light

    NASA Astrophysics Data System (ADS)

    Zhao, Zhongyao; Wang, Xin C.; Chance, Britton

    2004-12-01

    A data bank on prefrontal imaging under stressful conditions including deceit, has been gathered over several years on National and International populations using a contact imager pad consisting of 16 detectors and 4 sources, validating the concept of imaging prefrontal responses to stress, not only following the response of the PFC to imaging stress but especially of precognitive activations. We designed a new portable and non-invasive optical detecting system for remote sensing of deceit at 1~2m distance. The signals of pre- and post-cognitive function in deceit can be detected with very high sensitivity for blood volume and blood oxygenation detection at depths sufficient for PFC imaging and sensitivities of sub-micromolar oxy-hemoglobin and blood concentration detection. Thus, remote imaging of the process of decision making seems possible and examples will be presented using both contact and flying spot remote sensing.

  6. Diffuse Cystic Lung Diseases: Diagnostic Considerations.

    PubMed

    Xu, Kai-Feng; Feng, Ruie; Cui, Han; Tian, Xinlun; Wang, Hanping; Zhao, Jing; Huang, Hui; Zhang, Weihong; Lo, Bee Hong

    2016-06-01

    Diffuse cystic lung disease (DCLD) is a group of heterogeneous diseases that present as diffuse cystic changes in the lung on computed tomography of the chest. Most DCLD diseases are rare, although they might resemble common diseases such as emphysema and bronchiectasis. Main causes of DCLD include lymphangioleiomyomatosis, Birt-Hogg-Dubé syndrome, pulmonary Langerhans cell histiocytosis, lymphoid interstitial pneumonia, amyloidosis, light-chain deposition disease, Sjögren syndrome, and primary or metastatic neoplasm. We discuss clinical factors that are helpful in the differential diagnosis of DCLDsuch as sex and age, symptoms and signs, extrapulmonary presentations, cigarette smoking, and family history. Investigations for DCLD include high-resolution computed tomography, biochemical and histopathological studies, genetic tests, pulmonary function tests, and bronchoscopic and video-assisted thoracoscopic biopsies. A proposed diagnostic algorithm would enhance ease of diagnosing most cases of DCLD. PMID:27231867

  7. Diffuse Cystic Lung Disease. Part II.

    PubMed

    Gupta, Nishant; Vassallo, Robert; Wikenheiser-Brokamp, Kathryn A; McCormack, Francis X

    2015-07-01

    The diffuse cystic lung diseases have a broad differential diagnosis. A wide variety of pathophysiological processes spanning the spectrum from airway obstruction to lung remodeling can lead to multifocal cyst development in the lung. Although lymphangioleiomyomatosis and pulmonary Langerhans cell histiocytosis are perhaps more frequently seen in the clinic, disorders such as Birt-Hogg-Dubé syndrome, lymphocytic interstitial pneumonia, follicular bronchiolitis, and light-chain deposition disease are increasingly being recognized. Obtaining an accurate diagnosis can be challenging, and management approaches are highly disease dependent. Unique imaging features, genetic tests, serum studies, and clinical features provide invaluable clues that help clinicians distinguish among the various etiologies, but biopsy is often required for definitive diagnosis. In part II of this review, we present an overview of the diffuse cystic lung diseases caused by lymphoproliferative disorders, genetic mutations, or aberrant lung development and provide an approach to aid in their diagnosis and management.

  8. Numerical investigations of gaseous spherical diffusion flames

    NASA Astrophysics Data System (ADS)

    Lecoustre, Vivien R.

    Spherical diffusion flames have several unique characteristics that make them attractive from experimental and theoretical perspectives. They can be modeled with one spatial dimension, which frees computational resources for detailed chemistry, transport, and radiative loss models. This dissertation is a numerical study of two classes of spherical diffusion flames: hydrogen micro-diffusion flames, emphasizing kinetic extinction, and ethylene diffusion flames, emphasizing sooting limits. The flames were modeled using a one-dimensional, time-accurate diffusion flame code with detailed chemistry and transport. Radiative losses from products were modeled using a detailed absorption/emission statistical narrow band model and the discrete ordinates method. During this work the code has been enhanced by the implementation of a soot formation/oxidation model using the method of moments. Hydrogen micro-diffusion flames were studied experimentally and numerically. The experiments involved gas jets of hydrogen. At their quenching limits, these flames had heat release rates of 0.46 and 0.25 W in air and in oxygen, respectively. These are the weakest flames ever observed. The modeling results confirmed the quenching limits and revealed high rates of reactant leakage near the limits. The effects of the burner size and mass flow rate were predicted to have a significant impact on the flame chemistry and species distribution profiles, favoring kinetic extinction. Spherical ethylene diffusion flames at their sooting limits were also examined. Seventeen normal and inverse spherical flames were considered. Initially sooty, these flames were experimentally observed to reach their sooting limits 2 s after ignition. Structure of the flames at 2 s was considered, with an emphasis on the relationships among local temperature, carbon to oxygen atom ratio (C/O), and scalar dissipation rate. A critical C/O ratio was identified, along with two different sooting limit regimes. Diffusion flames

  9. High-Speed Three-Dimensional Nodal Diffusion Code System.

    2001-03-21

    Version 00 MOSRA-Light is a three-dimensional diffusion calculation code for X-Y-Z geometry. It can be used in: validation of discontinuity factor for adjoint problem; benchmark on discontinuity factor (forward & adjoint cal.); DVP BWR Benchmark (2D,2G calculation); and void reactivity effect benchmark; etc. A utility code called More-MOSRA provides many useful functions with the file produced by MOSRA-Light.

  10. Detection of Extended Red Emission in the Diffuse Interstellar Medium

    NASA Astrophysics Data System (ADS)

    Gordon, Karl Douglas

    1997-12-01

    Extended Red Emission (ERE) has been detected in many dusty astrophysical objects and this raises the question: Is ERE present only in discrete objects or is it an observational feature of all dust, i.e. present in the diffuse interstellar medium? In order to answer this question, we determined the blue and red intensities of the radiation from the diffuse interstellar medium (ISM) and examined the red intensity for the presence of an excess above that expected for scattered light. The diffuse ISM blue and red intensities were obtained by subtracting the integrated star and galaxy intensities from the blue and red measurements made by the Imaging Photopolarimeter (IPP) aboard the Pioneer 10 and 11 spacecraft. The unique characteristic of the Pioneer measurements is that they were taken outside the zodiacal dust cloud and, therefore, are free from zodiacal light. The color of the diffuse ISM was found to be redder than the Pioneer intensities. If the diffuse ISM intensities were entirely due to scattering from dust (i.e. Diffuse Galactic Light or DGL), the color of the diffuse ISM would be bluer than the Pioneer intensities. Finding a redder color implies the presence of an excess red intensity. Using a model for the DGL, the blue diffuse ISM intensity was found to be entirely attributable to the DGL. The red DGL was calculated using the blue diffuse ISM intensities and the approximately invariant color of the DGL calculated with the DGL model. Subtracting the calculated red DGL from the red diffuse ISM intensities resulted in the detection of an excess red intensity with an average value of ~10/ S10(V)G2V. This represents the detection of ERE in the diffuse ISM since Hα emission cannot account for the strength of this excess and the only other known emission process applicable to the diffuse ISM is ERE. Thus, ERE appears to be a general characteristic of dust. The correlation between NHI and ERE intensity is (1.43± 0.31)× 10-29 ergs s-1/A-1/ sr-1/ H/ atom-1 from

  11. Detection of Extended Red Emission in the Diffuse Interstellar Medium

    NASA Astrophysics Data System (ADS)

    Gordon, Karl D.; Witt, Adolf N.; Friedmann, Brian C.

    1998-05-01

    Extended red emission (ERE) has been detected in many dusty astrophysical objects, raising the question of whether ERE is present only in discrete objects or if it is an observational feature of all dust, i.e., present in the diffuse interstellar medium. In order to answer this question, we determined the blue and red intensities of the radiation from the diffuse interstellar medium (ISM) and examined the red intensity for the presence of an excess above that expected for scattered light. The diffuse ISM blue and red intensities were obtained by subtracting the integrated star and galaxy intensities from the blue and red measurements made by the Imaging Photopolarimeters (IPPs) aboard the Pioneer 10 and 11 spacecraft. The unique characteristic of the Pioneer measurements is that they were taken outside the zodiacal dust cloud and, therefore, are free from zodiacal light. The color of the diffuse ISM was found to be redder than the Pioneer intensities. If the diffuse ISM intensities were entirely caused by scattering from dust (i.e., diffuse Galactic light or DGL), the color of the diffuse ISM would be bluer than the Pioneer intensities. Finding a redder color implies the presence of an excess red intensity. Using a model for the DGL, we found the blue diffuse ISM intensity to be entirely attributable to the DGL. The red DGL was calculated using the blue diffuse ISM intensities and the approximately invariant color of the DGL calculated with the DGL model. Subtracting the calculated red DGL from the red diffuse ISM intensities resulted in the detection of an excess red intensity with an average value of ~10 S10(V)G2 V. This represents the likely detection of ERE in the diffuse ISM since Hα emission cannot account for the strength of this excess and the only other known emission process applicable to the diffuse ISM is ERE. Thus, ERE appears to be a general characteristic of dust. The correlation between NH I and ERE intensity is (1.43 +/- 0.31) × 10-29 ergs s-1

  12. Detection of Extended Red Emission in the Diffuse Interstellar Medium

    NASA Astrophysics Data System (ADS)

    Gordon, K.

    1997-10-01

    Extended Red Emission (ERE) has been detected in many dusty astrophysical objects and this raises the question: Is ERE present only in discrete objects or is it an observational feature of all dust, i.e. present in the diffuse interstellar medium? In order to answer this question, we determined the blue and red intensities of the radiation from the diffuse interstellar medium (ISM) and examined the red intensity for the presence of an excess above that expected for scattered light. The diffuse ISM blue and red intensities were obtained by subtracting the integrated star and galaxy intensities from the blue and red measurements made by the Imaging Photopolarimeter (IPP) aboard the Pioneer 10 and 11 spacecraft. The unique characteristic of the Pioneer measurements is that they were taken outside the zodiacal dust cloud and, therefore, are free from zodiacal light. The color of the diffuse ISM was found to be redder than the Pioneer intensities. If the diffuse ISM intensities were entirely due to scattering from dust (i.e. Diffuse Galactic Light or DGL), the color of the diffuse ISM would be bluer than the Pioneer intensities. Finding a redder color implies the presence of an excess red intensity. Using a model for the DGL, the blue diffuse ISM intensity was found to be entirely attributable to the DGL. The red DGL was calculated using the blue diffuse ISM intensities and the approximately invariant color of the DGL calculated with the DGL model. Subtracting the calculated red DGL from the red diffuse ISM intensities resulted in the detection of an excess red intensity with an average value of ~ 10 S10(V)_A0V. This represents the detection of ERE in the diffuse ISM since Hα emission cannot account for the strength of this excess and the only other known emission process applicable to the diffuse ISM is ERE. Thus, ERE appears to be a general characteristic of dust. The correlation between NHI and ERE intensity is (1.43 +/- 0.31)x 10(-29) ergs s(-1) Angstroms(-1) sr(-1

  13. Light source design for machine vision

    NASA Astrophysics Data System (ADS)

    Sieczka, Eric J.; Harding, Kevin G.

    1992-03-01

    There is a lack of commercially available white light sources for machine vision applications. Current commercial sources are typically expensive and primarily designed for workbench use. Because of their benchtop design, these light sources cannot be easily integrated into the inspection system. In most cases a light source must be custom designed and built to suit the needs of the particular machine vision application. The materials being inspected can vary from highly specular to highly diffuse, thus requiring a broad range of illumination levels. Other issues important in machine vision light sources include efficiency, light divergence, spectral content, source size, and packaging. This paper discusses the issues that must be overcome when designing a light source for machine vision applications, and describes the work done by ITI to produce an efficient white light source with computer controlled illumination level.

  14. Light's Darkness

    ScienceCinema

    Padgett, Miles [University of Glasgow, Glasgow, Scotland

    2016-07-12

    Optical vortices and orbital angular momentum are currently topical subjects in the optics literature. Although seemingly esoteric, they are, in fact, the generic state of light and arise whenever three or more plane waves interfere. To be observed by eye the light must be monochromatic. Laser speckle is one such example, where the optical energy circulates around each black spot, giving a local orbital angular momentum. This talk with report three on-going studies. First, when considering a volume of interfering waves, the laser specs map out threads of complete darkness embedded in the light. Do these threads form loops? Links? Or even knots? Second, when looking through a rapidly spinning window, the image of the world on the other side is rotated: true or false? Finally, the entanglement of orbital angular momentum states means measuring how the angular position of one photons sets the angular momentum of another: is this an angular version of the EPR (Einstein, Podolsky, and Rosen) paradox?

  15. Lighting installations

    NASA Technical Reports Server (NTRS)

    Schurer, Kees

    1994-01-01

    Model computations that give the lay-out of a lighting installation have to be implemented in the real world. There, deviations from the ideal performance of just about every element of the installation will be felt. A list of possible sources of non-ideal behavior, based on practical experience, are: lamps, ballasts, reflectors, mounting position, sagging of lamps, and soiling. It is clear that with all possible deviations from the ideal the homogeneity of a real lighting installation can never be as good as the one computed. The only way to make sure it is nearly as good is by measurement of the actual light distribution. Then, an occasional adjustment or replacement may often yield a satisfactory result. This measurement should really be part of the installation contract.

  16. Fractal model of anomalous diffusion.

    PubMed

    Gmachowski, Lech

    2015-12-01

    An equation of motion is derived from fractal analysis of the Brownian particle trajectory in which the asymptotic fractal dimension of the trajectory has a required value. The formula makes it possible to calculate the time dependence of the mean square displacement for both short and long periods when the molecule diffuses anomalously. The anomalous diffusion which occurs after long periods is characterized by two variables, the transport coefficient and the anomalous diffusion exponent. An explicit formula is derived for the transport coefficient, which is related to the diffusion constant, as dependent on the Brownian step time, and the anomalous diffusion exponent. The model makes it possible to deduce anomalous diffusion properties from experimental data obtained even for short time periods and to estimate the transport coefficient in systems for which the diffusion behavior has been investigated. The results were confirmed for both sub and super-diffusion.

  17. Turbo fluid machinery and diffusers

    NASA Technical Reports Server (NTRS)

    Sakurai, T.

    1984-01-01

    The general theory behind turbo devices and diffusers is explained. Problems and the state of research on basic equations of flow and experimental and measuring methods are discussed. Conventional centrifugation-type compressor and fan diffusers are considered in detail.

  18. Diffuse UV Background Radiation

    NASA Astrophysics Data System (ADS)

    Conn Henry, Richard; Murthy, J.

    2012-01-01

    The diffuse UV sky is expected to glow with significant amounts of starlight that is scattered from the interstellar dust. The albedo and scattering pattern of the dust in the ultraviolet are both well established, and are both fairly independent of wavelength from 912 Å to 3000 Å. We present 1943 Voyager spectra of the diffuse cosmic background radiation from 500 Å to 1200 Å, and we compare their brightnesses, and their distribution on the sky, to those observed (Murthy et al., ApJ 724, 1389, 2010) from the GALEX mission at longer wavelengths (1530 Å). Significant differences appear, suggesting that background radiation components in addition to dust-scattered starlight may be present in both spectral regions.

  19. Nonlocal electrical diffusion equation

    NASA Astrophysics Data System (ADS)

    Gómez-Aguilar, J. F.; Escobar-Jiménez, R. F.; Olivares-Peregrino, V. H.; Benavides-Cruz, M.; Calderón-Ramón, C.

    2016-07-01

    In this paper, we present an analysis and modeling of the electrical diffusion equation using the fractional calculus approach. This alternative representation for the current density is expressed in terms of the Caputo derivatives, the order for the space domain is 0<β≤1 and for the time domain is 0<γ≤2. We present solutions for the full fractional equation involving space and time fractional derivatives using numerical methods based on Fourier variable separation. The case with spatial fractional derivatives leads to Levy flight type phenomena, while the time fractional equation is related to sub- or super diffusion. We show that the mathematical concept of fractional derivatives can be useful to understand the behavior of semiconductors, the design of solar panels, electrochemical phenomena and the description of anomalous complex processes.

  20. Diffusion dans les liquides

    NASA Astrophysics Data System (ADS)

    Dianoux, A. J.

    2003-09-01

    Après une brève introduction qui rappelle les concepts détaillés dans le cours de M. Bée, nous présentons un aperçu de trois de nos travaux sur l'étude de la diffusion. Tout d'abord la dynamique de l'eau, dans son état normal ou surfondu, révèle la complexité apportée par le réseau de liaisons hydrogène. Ensuite l'effet du confinement sur la dynamique de l'eau sera étudié dans le cas de la membrane Nafion. Enfin la diffusion dans les phases nématique et smectique A d'un cristal liquide permet d'obtenir la valeur du potentiel qui maintient les couches dans la phase smectique.

  1. Orientability and Diffusion Maps

    PubMed Central

    Singer, Amit; Wu, Hau-tieng

    2010-01-01

    One of the main objectives in the analysis of a high dimensional large data set is to learn its geometric and topological structure. Even though the data itself is parameterized as a point cloud in a high dimensional ambient space ℝp, the correlation between parameters often suggests the “manifold assumption” that the data points are distributed on (or near) a low dimensional Riemannian manifold ℳd embedded in ℝp, with d ≪ p. We introduce an algorithm that determines the orientability of the intrinsic manifold given a sufficiently large number of sampled data points. If the manifold is orientable, then our algorithm also provides an alternative procedure for computing the eigenfunctions of the Laplacian that are important in the diffusion map framework for reducing the dimensionality of the data. If the manifold is non-orientable, then we provide a modified diffusion mapping of its orientable double covering. PMID:21765628

  2. Galactic Diffuse Polarized Emission

    NASA Astrophysics Data System (ADS)

    Carretti, Ettore

    2011-12-01

    Diffuse polarized emission by synchrotron is a key tool to investigate magnetic fields in the Milky Way, particularly the ordered component of the large scale structure. Key observables are the synchrotron emission itself and the RM is by Faraday rotation. In this paper the main properties of the radio polarized diffuse emission and its use to investigate magnetic fields will be reviewed along with our current understanding of the galactic magnetic field and the data sets available. We will then focus on the future perspective discussing RM-synthesis - the new powerful instrument devised to unlock the information encoded in such an emission - and the surveys currently in progress like S-PASS and GMIMS.

  3. Thermal diffusivity imaging

    NASA Astrophysics Data System (ADS)

    Gfroerer, Tim; Phillips, Ryan; Rossi, Peter

    2015-11-01

    The tip of a rod is heated with a torch and brought into contact with the center of a metal sheet. A thermal camera is then used to image the temperature profile of the surface as a function of time. The infrared camera is capable of recording radiometric data with 1 mK resolution in nearly 105 pixels, so thermal diffusion can be monitored with unprecedented precision. With a frame rate of approximately 10 Hz, the pace of the data acquisition minimizes the loss of accuracy due to inevitable cooling mechanisms. We report diffusivity constants equal to 1.23 ± 0.06 cm2/s in copper and 0.70 ± 0.05 cm2/s in aluminum. The behavior is modeled with a straightforward but oddly under-utilized one-dimensional finite difference method.

  4. Mass transport by diffusion

    NASA Technical Reports Server (NTRS)

    Baird, James K.

    1987-01-01

    For the purpose of determining diffusion coefficients as required for electrodeposition studies and other applications, a diaphragm cell and an isothermal water bath were constructed. the calibration of the system is discussed. On the basis of three calibration runs on the diaphram cell, researchers concluded that the cell constant beta equals 0.12 cm -2 . Other calibration runs in progress should permit the cell constant to be determined with an accuracy of one percent.

  5. Peridynamic thermal diffusion

    SciTech Connect

    Oterkus, Selda; Madenci, Erdogan; Agwai, Abigail

    2014-05-15

    This study presents the derivation of ordinary state-based peridynamic heat conduction equation based on the Lagrangian formalism. The peridynamic heat conduction parameters are related to those of the classical theory. An explicit time stepping scheme is adopted for numerical solution of various benchmark problems with known solutions. It paves the way for applying the peridynamic theory to other physical fields such as neutronic diffusion and electrical potential distribution.

  6. Random diffusion model.

    PubMed

    Mazenko, Gene F

    2008-09-01

    We study the random diffusion model. This is a continuum model for a conserved scalar density field varphi driven by diffusive dynamics. The interesting feature of the dynamics is that the bare diffusion coefficient D is density dependent. In the simplest case, D=D[over ]+D_{1}deltavarphi , where D[over ] is the constant average diffusion constant. In the case where the driving effective Hamiltonian is quadratic, the model can be treated using perturbation theory in terms of the single nonlinear coupling D1 . We develop perturbation theory to fourth order in D1 . The are two ways of analyzing this perturbation theory. In one approach, developed by Kawasaki, at one-loop order one finds mode-coupling theory with an ergodic-nonergodic transition. An alternative more direct interpretation at one-loop order leads to a slowing down as the nonlinear coupling increases. Eventually one hits a critical coupling where the time decay becomes algebraic. Near this critical coupling a weak peak develops at a wave number well above the peak at q=0 associated with the conservation law. The width of this peak in Fourier space decreases with time and can be identified with a characteristic kinetic length which grows with a power law in time. For stronger coupling the system becomes metastable and then unstable. At two-loop order it is shown that the ergodic-nonergodic transition is not supported. It is demonstrated that the critical properties of the direct approach survive, going to higher order in perturbation theory.

  7. Diffusive Shock Acceleration

    NASA Astrophysics Data System (ADS)

    Baring, Matthew

    2003-04-01

    The process of diffusive acceleration of charged particles in shocked plasmas is widely invoked in astrophysics to account for the ubiquitous presence of signatures of non-thermal relativistic electrons and ions in the universe. This statistical energization mechanism, manifested in turbulent media, was first posited by Enrico Fermi in 1949 to explain the observed cosmic ray population, which exhibits an almost power-law distribution in rigidity. The absence of a momentum scale is a key characteristic of diffusive shock acceleration, and astrophysical systems generally only impose scales at the injection (low energy) and loss (high energy) ends of the particle spectrum. The existence of structure in the cosmic ray spectrum (the "knee") at around 3000 TeV has promoted contentions that there are at least two origins for cosmic rays, a galactic one supplying those up to the knee, and perhaps an extragalactic one that can explain even the ultra-high energy cosmic rays (UHECRs) seen at 1-300 EeV. Accounting for the UHECRs with familiar astrophysical sites of acceleration has historically proven difficult due to the need to assume high magnetic fields in order to reduce the shortest diffusive acceleration timescale, the ion gyroperiod, to meaningful values. Yet active galaxies and gamma-ray bursts remain strong and interesting candidate sources for UHECRs, turning the theoretical focus to relativistic shocks. This review summarizes properties of diffusive shock acceleration that are salient to the issue of UHECR generation. These include spectral indices, anisotropies, acceleration efficencies and timescales, as functions of the shock speed and mean field orientation, and also the degree of field turbulence. Astrophysical sites for UHECR production are also critiqued.

  8. Photovoltaic structures having a light scattering interface layer and methods of making the same

    SciTech Connect

    Liu, Xiangxin; Compaan, Alvin D.; Paudel, Naba Raj

    2015-10-13

    Photovoltaic (PV) cell structures having an integral light scattering interface layer configured to diffuse or scatter light prior to entering a semiconductor material and methods of making the same are described.

  9. Solute diffusion in liquid metals

    NASA Technical Reports Server (NTRS)

    Bhat, B. N.

    1973-01-01

    A gas model of diffusion in liquid metals is presented. In this model, ions of liquid metals are assumed to behave like the molecules in a dense gas. Diffusion coefficient of solute is discussed with reference to its mass, ionic size, and pair potential. The model is applied to the case of solute diffusion in liquid silver. An attempt was made to predict diffusion coefficients of solutes with reasonable accuracy.

  10. LED lamp or bulb with remote phosphor and diffuser configuration with enhanced scattering properties

    SciTech Connect

    Tong, Tao; Le Toquin, Ronan; Keller, Bernd; Tarsa, Eric; Youmans, Mark; Lowes, Theodore; Medendorp, Jr., Nicholas W; Van De Ven, Antony; Negley, Gerald

    2014-11-11

    An LED lamp or bulb is disclosed that comprises a light source, a heat sink structure and an optical cavity. The optical cavity comprises a phosphor carrier having a conversions material and arranged over an opening to the cavity. The phosphor carrier comprises a thermally conductive transparent material and is thermally coupled to the heat sink structure. An LED based light source is mounted in the optical cavity remote to the phosphor carrier with light from the light source passing through the phosphor carrier. A diffuser dome is included that is mounted over the optical cavity, with light from the optical cavity passing through the diffuser dome. The properties of the diffuser, such as geometry, scattering properties of the scattering layer, surface roughness or smoothness, and spatial distribution of the scattering layer properties may be used to control various lamp properties such as color uniformity and light intensity distribution as a function of viewing angle.

  11. Percolation of interaction diffusing particles

    NASA Technical Reports Server (NTRS)

    Selinger, Robin Blumberg; Stanley, H. Eugene

    1990-01-01

    The connectivity properties of systems of diffusing interacting particles with the blind and myopic diffusion rules are studied. It is found that the blind rule case is equivalent to the lattice gas with J = 0 in all dimensions. The connectivity properties of blind rule diffusion are described by random site percolation due to the fact that the density on neighboring sites is uncorrelated.

  12. Ex vivo laser lipolysis assisted with radially diffusing optical applicator

    NASA Astrophysics Data System (ADS)

    Hwang, Jieun; Hau, Nguyen Trung; Park, Sung Yeon; Rhee, Yun-Hee; Ahn, Jin-Chul; Kang, Hyun Wook

    2016-05-01

    Laser-assisted lipolysis has been implemented to reduce body fat in light of thermal interactions with adipose tissue. However, using a flat fiber with high irradiance often needs rapid cannula movements and even undesirable thermal injury due to direct tissue contact. The aim of the current study was to explore the feasibility of a radially diffusing optical applicator to liquefy the adipose tissue for effective laser lipolysis. The proposed diffuser was evaluated with a flat fiber in terms of temperature elevation and tissue liquefaction after laser lipolysis with a 980-nm wavelength. Given the same power (20 W), the diffusing applicator generated a 30% slower temperature increase with a 25% lower maximum temperature (84±3.2°C in 1 min p<0.001) in the tissue, compared with the flat fiber. Under the equivalent temperature development, the diffuser induced up to fivefold larger area of the adipose liquefaction due to radial light emission than the flat fiber. Ex vivo tissue tests for 5-min irradiation demonstrated that the diffuser (1.24±0.15 g) liquefied 66% more adipose tissue than the flat fiber (0.75±0.05 g). The proposed diffusing applicator can be a feasible therapeutic device for laser lipolysis due to low temperature development and wide coverage of thermal treatment.

  13. Ex vivo laser lipolysis assisted with radially diffusing optical applicator

    NASA Astrophysics Data System (ADS)

    Hwang, Jieun; Hau, Nguyen Trung; Park, Sung Yeon; Rhee, Yun-Hee; Ahn, Jin-Chul; Kang, Hyun Wook

    2016-05-01

    Laser-assisted lipolysis has been implemented to reduce body fat in light of thermal interactions with adipose tissue. However, using a flat fiber with high irradiance often needs rapid cannula movements and even undesirable thermal injury due to direct tissue contact. The aim of the current study was to explore the feasibility of a radially diffusing optical applicator to liquefy the adipose tissue for effective laser lipolysis. The proposed diffuser was evaluated with a flat fiber in terms of temperature elevation and tissue liquefaction after laser lipolysis with a 980-nm wavelength. Given the same power (20 W), the diffusing applicator generated a 30% slower temperature increase with a 25% lower maximum temperature (84±3.2°C in 1 min p<0.001) in the tissue, compared with the flat fiber. Under the equivalent temperature development, the diffuser induced up to fivefold larger area of the adipose liquefaction due to radial light emission than the flat fiber. Ex vivo tissue tests for 5-min irradiation demonstrated that the diffuser (1.24±0.15 g) liquefied 66% more adipose tissue than the flat fiber (0.75±0.05 g). The proposed diffusing applicator can be a feasible therapeutic device for laser lipolysis due to low temperature development and wide coverage of thermal treatment.

  14. School Lighting.

    ERIC Educational Resources Information Center

    Rennhackkamp, W. M. H.

    Research gathered by the Functional Efficiency Division of the National Building Research Institute, South Africa, is aimed at providing lighting conditions under which the school child can produce his maximum effort with the least strain and fatigue. These favorable conditions are outlined along with specific examples of their realization in…

  15. Polarized light scanning for cultural heritage investigation

    NASA Astrophysics Data System (ADS)

    Toque, Jay Arre; Murayama, Yusuke; Matsumoto, Yohei; Ide-Ektessabi, Ari

    2011-03-01

    Numerous cultural heritage art works have shiny surfaces resulting form gold, silver, and other metallic pigments. In addition varnish overlayer on oil paintings makes it challenging to retrieve true color information. This is due to the great effect of lighting condition when images are acquired and viewed. The reflection of light from such surfaces is a combination of the surface's specular and diffused light reflections. In this paper, this specific problems encountered when digitizing cultural heritage were discussed. Experimental results using the images acquired with a high-resolution large flat bed scanner, together with a mathematical method for processing the captured images were presented and discussed in detail. Focus was given in separating the diffused and specular components of the reflected light for the purpose of analytical imaging. The mathematical algorithm developed in this study enables imaging of cultural heritage with shiny and glossy surfaces effectively and efficiently.

  16. Light collection device for flame emission detectors

    DOEpatents

    Woodruff, Stephen D.; Logan, Ronald G.; Pineault, Richard L.

    1990-01-01

    A light collection device for use in a flame emission detection system such as an on-line, real-time alkali concentration process stream monitor is disclosed which comprises a sphere coated on its interior with a highly diffuse reflective paint which is positioned over a flame emission source, and one or more fiber optic cables which transfer the light generated at the interior of the sphere to a detecting device. The diffuse scattering of the light emitted by the flame uniformly distributes the light in the sphere, and the collection efficiency of the device is greater than that obtainable in the prior art. The device of the present invention thus provides enhanced sensitivity and reduces the noise associated with flame emission detectors, and can achieve substantial improvements in alkali detection levels.

  17. Solar light bulb

    SciTech Connect

    Smith, D.A.

    1983-07-26

    A system for generating light directly using solar energy is provided herein. It includes a concentrator and accumulator for the sun's rays to generate a concentrated beam of visible solar radiation. A distributor shaft is provided for distributing the beam of visible solar radiation. A fork is provided in the distributor shaft to define a plurality of branch lines, each provided with a mirror at the intersection to direct the beam down the respective branch line to permit parallel fractions of the beam to be reflected off the respective mirrors and to pass down the respective branch line. A solar bulb is provided including a double walled upper bulbous portion including the inlet from the branch line and a pair of heat outlet tubes, and a double walled lower bulbous portion, the upper portion thereof being divergently reflective, with the lower portion having walls which are either transparent or translucent to provide greater light diffusion, and the space between the two walls being maintained under vacuum to provide heat insulation values. A structure is provided within the solar bulb for the absorption and radiation of the concentrated beam of visible solar radiation. Preferably structure is provided connected to the solar bulb to draw in outside air in the summer to direct it past the solar bulb and to air vent hot air produced at the solar bulb to the outside, thereby providing light with minimal heat in the summer. The same structure is operated in the winter to draw in household air to direct it past the solar bulb and to recirculate such heated air produced at the solar bulb to the house, thereby providing light and heat in the winter.

  18. Particle diffusion in a spheromak

    SciTech Connect

    Meyerhofer, D.D.; Levinton, F.M.; Yamada, M.

    1988-01-01

    The local carbon particle diffusion coefficient was measured in the Proto S-1/C spheromak using a test particle injection scheme. When the plasma was not in a force-free Taylor state, and when there were pressure gradients in the plasma, the particle diffusion was five times that predicted by Bohm and was consistent with collisional drift wave diffusion. The diffusion appears to be driven by correlations of the fluctuating electric field and density. During the decay phase of the discharge when the plasma was in the Taylor state, the diffusion coefficient of the carbon was classical. 23 refs., 4 figs.

  19. Bioluminescent signals spatially amplified by wavelength-specific diffusion through the shell of a marine snail

    PubMed Central

    Deheyn, Dimitri D.; Wilson, Nerida G.

    2011-01-01

    Some living organisms produce visible light (bioluminescence) for intra- or interspecific visual communication. Here, we describe a remarkable bioluminescent adaptation in the marine snail Hinea brasiliana. This species produces a luminous display in response to mechanical stimulation caused by encounters with other motile organisms. The light is produced from discrete areas on the snail's body beneath the snail's shell, and must thus overcome this structural barrier to be viewed by an external receiver. The diffusion and transmission efficiency of the shell is greater than a commercial diffuser reference material. Most strikingly, the shell, although opaque and pigmented, selectively diffuses the blue-green wavelength of the species bioluminescence. This diffusion generates a luminous display that is enlarged relative to the original light source. This unusual shell thus allows spatially amplified outward transmission of light communication signals from the snail, while allowing the animal to remain safely inside its hard protective shell. PMID:21159673

  20. Trace-Element Diffusion Coefficients in Olivine

    NASA Astrophysics Data System (ADS)

    Spandler, C.; O'Neill, H. S.

    2006-12-01

    We have undertaken chemical diffusion experiments at 1300°C to determine both crystal/melt partition coefficients and diffusion coefficients for a wide range of trace elements in forsteritic olivine. Experiments were conducted at 1 atm under controlled fO2 for up to 25 days using synthetic melts made to a composition in equilibrium with olivine for major elements, and doped with selected trace elements. The melt was put into a 5 mm diameter cylindrical hole in gem quality San Carlos olivine crystals drilled paralell to the a axis. Diffusion profiles were obtained both for trace elements that were added to the starting material and diffuse into the olivine, and also for several trace elements present at natural abundances in the olivine that diffuse out. The profiles were measured across sections perpendicular to crystal/melt boundary at a variety of crystallographic orientations (confirmed by EBSD) by laser-ablation ICP-MS. A thin laser slit oriented parallel to the crystal/melt interface was traversed from the melt through the crystal. Element concentrations were fitted to the diffusion equation to obtain both diffusion coefficients and concentrations at the crystal/melt interface, and hence partition coefficients. Calculated diffusivities for many trace elements (Ca, REE, Y, Sc, V, Cr, Ni, Co, Mn, Na, Li, Be, Ti) are relatively fast (D = 10-16 to 10^{-13 m2/s at 1300°C). The diffusion of Li in olivine (approx. D = 10^{-15} m2/s) is only slightly slower than REEs and similar to divalent cations, in good agreement with inferences from zoning profiles in natural olivine [1]. This rate is considerably slower than for plagioclase and clinopyroxene [2], a result which has important implications for interpreting Li isotopic data from mantle-derived rocks. The fastest diffusing trace element we observe is Be. Applying our diffusion and partition coefficients to the model of Qin et al. [3], we calculate that the REEs of olivine-hosted melt inclusions in the mantle will

  1. Diffuse, Warm Ionized Gas

    NASA Astrophysics Data System (ADS)

    Haffner, L. M.

    2002-05-01

    Over the past decade, new high-sensitivity observations have significantly advanced our knowledge of the diffuse, ionized gas in spiral galaxies. This component of the interstellar medium, often referred to as Warm Ionized Medium (WIM) or Diffuse Ionized Gas (DIG), plays an important role in the complex stellar-interstellar matter and energy cycle. In examining the distribution and physical properties of this gas, we learn not only about the conditions of the medium but also about processes providing heating and ionization in the halos of spiral galaxies. For the Milky Way, three new Hα surveys are available providing large sky coverage, arc-minute spatial resolution, and the ability to kinematically resolve this prominent optical emission line. These new, global views show that the Warm Ionized Medium of the Galaxy is ubiquitous as previously suspected, is rich with filamentary structure down to current resolution limits, and can be traced into the halo at large distances from the Galactic plane. Observations of additional optical emission lines are beginning to probe the physical conditions of the WIM. Early results suggest variations in the temperature and ionization state of the gas which are not adequately explained by Lyman continuum stellar photoionization alone. In parallel with this intensive work in the Milky Way have been numerous studies about the diffuse, ionized gas in other spiral galaxies. Here, deep, face-on spiral investigations provide some of the best maps of the global DIG distribution in a galaxy and begin to allow a probe of the local link between star formation and the powering of ionized gas. In addition, ionized gas has been traced out to impressive distances (z > 3 kpc) in edge-on spirals, revealing out large-scale changes in the physical conditions and kinematics of galactic halos.

  2. No-Light Light Bulbs

    ERIC Educational Resources Information Center

    Modern Schools, 1976

    1976-01-01

    A thumbnail sketch of some of the light bulbs manufactured for a purpose other than seeing. These "dark" lamps perform varied tasks including keeping food fresh, detecting and preventing disease, spurring plant growth, heating, and copying printed material. (Author/MLF)

  3. Diffusion in silicon isotope heterostructures

    SciTech Connect

    Silvestri, Hughes Howland

    2004-05-14

    The simultaneous diffusion of Si and the dopants B, P, and As has been studied by the use of a multilayer structure of isotopically enriched Si. This structure, consisting of 5 pairs of 120 nm thick natural Si and {sup 28}Si enriched layers, enables the observation of {sup 30}Si self-diffusion from the natural layers into the {sup 28}Si enriched layers, as well as dopant diffusion from an implanted source in an amorphous Si cap layer, via Secondary Ion Mass Spectrometry (SIMS). The dopant diffusion created regions of the multilayer structure that were extrinsic at the diffusion temperatures. In these regions, the Fermi level shift due to the extrinsic condition altered the concentration and charge state of the native defects involved in the diffusion process, which affected the dopant and self-diffusion. The simultaneously recorded diffusion profiles enabled the modeling of the coupled dopant and self-diffusion. From the modeling of the simultaneous diffusion, the dopant diffusion mechanisms, the native defect charge states, and the self- and dopant diffusion coefficients can be determined. This information is necessary to enhance the physical modeling of dopant diffusion in Si. It is of particular interest to the modeling of future electronic Si devices, where the nanometer-scale features have created the need for precise physical models of atomic diffusion in Si. The modeling of the experimental profiles of simultaneous diffusion of B and Si under p-type extrinsic conditions revealed that both species are mediated by neutral and singly, positively charged Si self-interstitials. The diffusion of As and Si under extrinsic n-type conditions yielded a model consisting of the interstitialcy and vacancy mechanisms of diffusion via singly negatively charged self-interstitials and neutral vacancies. The simultaneous diffusion of P and Si has been modeled on the basis of neutral and singly negatively charged self-interstitials and neutral and singly positively charged P

  4. Accelerated stochastic diffusion processes

    NASA Astrophysics Data System (ADS)

    Garbaczewski, Piotr

    1990-07-01

    We give a purely probabilistic demonstration that all effects of non-random (external, conservative) forces on the diffusion process can be encoded in the Nelson ansatz for the second Newton law. Each random path of the process together with a probabilistic weight carries a phase accumulation (complex valued) weight. Random path summation (integration) of these weights leads to the transition probability density and transition amplitude respectively between two spatial points in a given time interval. The Bohm-Vigier, Fenyes-Nelson-Guerra and Feynman descriptions of the quantum particle behaviours are in fact equivalent.

  5. Turbulent forced diffusion flames

    SciTech Connect

    Arpaci, V.S.; Li, C.Y.

    1995-07-01

    It is the purpose of this study to introduce a turbulent microscale appropriate for forced diffusion flames and to propose models for fuel consumption and skin friction in terms of this scale. The study consists of four sections. Following the introduction, Section 2 recapitulates the laminar theories of reacting boundary layers in terms of dimensional arguments and proposes models for fuel consumption and skin friction. Section 3 extends these arguments by introducing a microscale appropriate for turbulent flames and, in terms of this scale, develops models for fuel consumption and skin friction, correlates the experimental data on skin friction, and Section 4 concludes the study.

  6. Diffusion from solid cylinders

    SciTech Connect

    Nestor, C.W. Jr.

    1980-01-01

    The problem considered is the diffusion of material from a solid cylinder initially containng a uniform concentration and immersed in a well-stirred bath which maintains the external concentration at zero. The Fourier-Bessel series form of the fraction of the original material removed from the cylinder as a function of time converges very slowly for small time. An alternate form was obtained, which converges reasonably rapidly for small time. The convergence acceleration method of P. Wynn was also used to provide an efficient method for computation. Numerical examples and program listings are included.

  7. Vapor Diffusion Apparatus

    NASA Technical Reports Server (NTRS)

    2001-01-01

    Vapor Diffusion Apparatus (VDA and VDA-2) was developed by the University of Alabama in Birmingham for NASA's Marshall Space Flight Center. In the original VDA, a protein solution and a precipitant are extruded by two plungers onto the tip of a small syringe and allowed to evaporate, raising the concentration and prompting protein molecules to crystallize. In the VDA-2 version, a third plunger was added to mix the two solutions before returning the mix to the syringe tip. The principal investigator is Dr. Larry Delucas of the University of Alabama in Birmingham

  8. Vapor Diffusion Apparatus

    NASA Technical Reports Server (NTRS)

    2001-01-01

    Vapor Diffusion Apparatus (VDA-2) was developed by the University of Alabama in Birmingham for NASA's Marshall Space Flight Center. In the original VDA, a protein solution and a precipitant are extruded by two plungers onto the tip of a small syringe and allowed to evaporate, raising the concentration and prompting protein molecules to crystallize. In the VDA-2 version, a third plunger was added to mix the two solutions before returning the mix to the syringe tip. The principal investigator is Dr. Larry Delucas of the University of Alabama in Birmingham.

  9. Light Sources and Lighting Circuits

    NASA Astrophysics Data System (ADS)

    Honda, Hisashi; Suwa, Takumi; Yasuda, Takeo; Ohtani, Yoshihiko; Maehara, Akiyoshi; Okada, Atsunori; Komatsu, Naoki; Mannami, Tomoaki

    According to the Machinery Statistics of the Ministry of Economy, Trade and Industry, the production of incandescent lamps in Japan in 2007 was 990 million units (90.0% of the previous year's total), in which the production of incandescent lamps for general lighting was 110 million units (90.0% of the previous year's total) and of tungsten-halogen lamps was 44 million units (96.6% of the previous year's total). The production of fluorescent lamps was 927 million units (93.9% of the previous year's total), in which general fluorescent lamps, excluding those for LCD back lighting, was 320 million units (87.2% of the previous year's total). Also, the production of HID lamps was 10 million units (101.5% of the previous year's total). On the other hand, when the numbers of sales are compared with the sales of the previous year, incandescent lamps for general use was 99.8%, tungsten-halogen lamps was 96.9%, fluorescent lamps was 95.9%, and HID lamps was 98.9%. Self-ballasted fluorescent lamps alone showed an increase in sales as strong as 29 million units, or 121.7% of the previous year's sales. It is considered that the switchover of incandescent lamps to HID lamps was promoted for energy conservation and carbon dioxide reduction with the problem of global warming in the background. In regard to exhibitions, Lighting Fair 2007 was held in Tokyo in March, and LIGHTFAIR INTERNATIONAL 2007 was held in New York in May. Regarding academic conferences, LS:11 (the 11th International Symposium on the Science & Technology of Light Sources) was held in Shanghai in May, and the First International Conference on White LEDs and Solid State Lighting was held in Tokyo in November. Both conferences suggested that there are strong needs and concerns now about energy conservation, saving natural resources, and restrictions of hazardous materials. In regard to incandescent lamps, the development of products aiming at higher efficacy, electric power savings, and longer life was advanced by

  10. EDITORIAL: Controlling light with light

    NASA Astrophysics Data System (ADS)

    Hesselink, Lambertus; Feinberg, Jack; Roosen, Gerald

    2008-11-01

    The field of photorefractive physics and optics is mature and, although there is no significant commercial activity using photorefractive media, researchers in the field have had an extraordinary impact on many related areas of research and development. For example, in the late 1990s many of the telecom innovations and products were based on the interaction between light and matter. Examples include optical switches, filters, gratings, routers and light sources. The theory of multiple interacting beams of light inside a photosensitive medium, many of which were developed or further explored in photorefractive media, has found application in medicine, engineering, communication systems, displays and other photonics devices. On the occasions of the 30th anniversary of the theory of coupled wave analysis and the 10th anniversary of the meetings on Photorefractive Effects and Devices, it seemed appropriate to the meeting organizers of PR'07 to broaden the scope to include other related fields. The name of the meeting was changed to Controlling Light with Light: Photorefractive Effects, Photosensitivity, Fiber Gratings, Photonic Materials and More to attract a larger audience than traditionally would attend the more narrowly focused photorefractive meeting. To further disseminate the results of the 2007 meeting, Gerald Roosen proposed a special publication of original full research articles arising from key presentations at the meeting. The selection of papers in this Cluster Issue of Journal of Physics D: Applied Physics is the result of that initiative. We would like to thank all the authors for their contributions, the committee members for their valuable insight and efforts in helping to organize the meeting, and the Optical Society of America for their professional assistance throughout the preparation period of the meeting as well as during the three beautiful days in Lake Tahoe, CA.

  11. High intensity portable fluorescent light

    NASA Technical Reports Server (NTRS)

    Kendall, F. B.

    1972-01-01

    Eight high intensity portable fluorescent lights were produced. Three prototype lights were also produced, two of which were subsequently updated to the physical and operational configuration of the qualification and flight units. Positioning of lamp apertures and reflectors in these lights is such that the light is concentrated and intensified in a specific pattern rather than widely diffused. Indium amalgam control of mercury vapor pressure in the lamp gives high output at lamp ambient temperatures up to 105 C. A small amount of amalgam applied to each electrode stem helps to obtain fast warm-up. Shrinking a Teflon sleeve on the tube and potting metal caps on each end of the lamp minimizes dispersion of mercury vapor and glass particles in the event of accidental lamp breakage. Operation at 20 kHz allows the lamps to consume more power than at low frequency, thus increasing their light output and raising their efficiency. When used to expose color photographic film, light from the lamps produces results approximately equal to sunlight.

  12. Static diffusion cloud chambers

    NASA Technical Reports Server (NTRS)

    Ayers, G.

    1981-01-01

    The chamber geometry and optical arrangement are described. The supersaturation range is given and consists of readings taken at five fixed points: 0.25%, 0.5%, 0.75%, 1.0%, and 1.25%. The detection system is described including light source, cameras, and photocell detectors. The temperature control and the calibration of the chamber are discussed.

  13. Elastomeric Photopolymers: Shaping Polymer Gels with Light

    NASA Astrophysics Data System (ADS)

    Kornfield, Julia

    2008-03-01

    Polymer gels that possess a latent ability to change shape, which can be triggered in a spatially resolved manner using light---``elastomeric photopolymers''---have been developed to meet the need for materials that can be reshaped without direct contact, e.g., to non-invasively adjust an implanted lens in the human eye. The physics of diffusion and swelling in elastomers are applied to create a transparent silicone suitable for making a foldable intraocular lens that can be reshaped using near ultraviolet light. A crosslinked silicone matrix dictates the initial shape of the lens, while ``macromers''--short silicone chains with polymerizable end groups—and photoinitiator enable shape adjustment using light: polymerization of the macromer in the irradiated regions, followed by diffusion of free macromer causes local swelling. To predict shape change directly from irradiation profile, a theoretical treatment is presented that captures 1. shape change with no external forces, 2. coupling between diffusion and deformation, and 3. connection between thermodynamics, constitutive equations and equations of motion. Using continuum mechanics complemented with thermodynamics within the auspices of the finite element method, we develop a steady-state model which successfully captures the coupling between diffusion and deformation. Parameter values are drawn from our prior experimental studies of the mechanical properties, equilibrium swelling, penetrant diffusivities and interaction parameters in systematically varied polydimethylsiloxane (PDMS) networks and acrylate endcapped PDMS macromers. Preliminary computational studies show qualitative agreement with experimentally observed phenomena.

  14. Impact of osmotic stress on protein diffusion in Lactococcus lactis.

    PubMed

    Mika, Jacek T; Schavemaker, Paul E; Krasnikov, Victor; Poolman, Bert

    2014-11-01

    We measured translational diffusion of proteins in the cytoplasm and plasma membrane of the Gram-positive bacterium Lactococcus lactis and probed the effect of osmotic upshift. For cells in standard growth medium the diffusion coefficients for cytosolic proteins (27 and 582 kDa) and 12-transmembrane helix membrane proteins are similar to those in Escherichia coli. The translational diffusion of GFP in L. lactis drops by two orders of magnitude when the medium osmolality is increased by ∼ 1.9 Osm, and the decrease in mobility is partly reversed in the presence of osmoprotectants. We find a large spread in diffusion coefficients over the full population of cells but a smaller spread if only sister cells are compared. While in general the diffusion coefficients we measure under normal osmotic conditions in L. lactis are similar to those reported in E. coli, the decrease in translational diffusion upon osmotic challenge in L. lactis is smaller than in E. coli. An even more striking difference is that in L. lactis the GFP diffusion coefficient drops much more rapidly with volume than in E. coli. We discuss these findings in the light of differences in turgor, cell volume, crowding and cytoplasmic structure of Gram-positive and Gram-negative bacteria.

  15. Diffusion behavior of lipid vesicles in entangled polymer solutions.

    PubMed Central

    Cao, X; Bansil, R; Gantz, D; Moore, E W; Niu, N; Afdhal, N H

    1997-01-01

    Dynamic light scattering was used to follow the tracer diffusion of phospholipid/cholesterol vesicles in aqueous polyacrylamide solutions and compared with the diffusive behavior of polystyrene (PS) latex spheres of comparable diameters. Over the range of the matrix concentration examined (Cp = 0.1-10 mg/ml), the diffusivities of the PS spheres and the large multilamellar vesicles exhibited the Stokes-Einstein (SE) relation, while the diffusivity of the unilamellar vesicles did not follow the increase of the solution's viscosity caused by the presence of the matrix molecules. The difference between the diffusion behaviors of unilamellar vesicles and hard PS spheres of similar size is possibly due to the flexibility of the lipid bilayer of the vesicles. The unilamellar vesicles are capable of changing their shape to move through the entangled polymer solution so that the hindrance to their diffusion due to the presence of the polymer chains is reduced, while the rigid PS spheres have little flexibility and they encounter greater resistance. The multilamellar vesicles are less flexible, thus their diffusion is similar to the hard PS spheres of similar diameter. Images FIGURE 2 PMID:9336189

  16. Apparatus for diffusion separation

    DOEpatents

    Nierenberg, William A.

    1976-08-10

    1. A diffuser separator apparatus which comprises a plurality of flow channels in a single stage, each of said channels having an inlet port and an outlet port and a constant cross sectional area between said ports, at least a portion of the defining surface of each of said channels being a diffusion separation membrane, and each of said channels having a different cross sectional area, means for connecting said channels in series so that each successive channel of said series has a smaller cross sectional area than the previous channel of said series, a source of gaseous mixture, individual means for flowing said gaseous mixture to the inlet port of each of said channels, gas receiving and analyzing means, individual means for flowing gas passing from each of said outlet ports and means for flowing gas passing through said membranes to said receiving and analyzing means, and individual means for connecting the outlet port of each channel with the inlet port of the channel having the next smaller cross sectional area.

  17. Diffusing obesity myths.

    PubMed

    Ramos Salas, X; Forhan, M; Sharma, A M

    2014-06-01

    Misinformation or myths about obesity can lead to weight bias and obesity stigma. Counteracting myths with facts and evidence has been shown to be effective educational tools to increase an individuals' knowledge about a certain condition and to reduce stigma.The purpose of this study was to identify common obesity myths within the healthcare and public domains and to develop evidence-based counterarguments to diffuse them. An online search of grey literature, media and public health information sources was conducted to identify common obesity myths. A list of 10 obesity myths was developed and reviewed by obesity experts and key opinion leaders. Counterarguments were developed using current research evidence and validated by obesity experts. A survey of obesity experts and health professionals was conducted to determine the usability and potential effectiveness of the myth-fact messages to reduce weight bias. A total of 754 individuals responded to the request to complete the survey. Of those who responded, 464 (61.5%) completed the survey. All 10 obesity myths were identified to be deeply pervasive within Canadian healthcare and public domains. Although the myth-fact messages were endorsed, respondents also indicated that they would likely not be sufficient to reduce weight bias. Diffusing deeply pervasive obesity myths will require multilevel approaches. PMID:25826775

  18. Sampling diffusive transition paths

    SciTech Connect

    F. Miller III, Thomas; Predescu, Cristian

    2006-10-12

    We address the problem of sampling double-ended diffusive paths. The ensemble of paths is expressed using a symmetric version of the Onsager-Machlup formula, which only requires evaluation of the force field and which, upon direct time discretization, gives rise to a symmetric integrator that is accurate to second order. Efficiently sampling this ensemble requires avoiding the well-known stiffness problem associated with sampling infinitesimal Brownian increments of the path, as well as a different type of stiffness associated with sampling the coarse features of long paths. The fine-features sampling stiffness is eliminated with the use of the fast sampling algorithm (FSA), and the coarse-feature sampling stiffness is avoided by introducing the sliding and sampling (S&S) algorithm. A key feature of the S&S algorithm is that it enables massively parallel computers to sample diffusive trajectories that are long in time. We use the algorithm to sample the transition path ensemble for the structural interconversion of the 38-atom Lennard-Jones cluster at low temperature.

  19. Anisotropic Thermal Diffusion

    NASA Astrophysics Data System (ADS)

    Gardiner, Thomas

    2013-10-01

    Anisotropic thermal diffusion in magnetized plasmas is an important physical phenomena for a diverse set of physical conditions ranging from astrophysical plasmas to MFE and ICF. Yet numerically simulating this phenomenon accurately poses significant challenges when the computational mesh is misaligned with respect to the magnetic field. Particularly when the temperature gradients are unresolved, one frequently finds entropy violating solutions with heat flowing from cold to hot zones for χ∥ /χ⊥ >=102 which is substantially smaller than the range of interest which can reach 1010 or higher. In this talk we present a new implicit algorithm for solving the anisotropic thermal diffusion equations and demonstrate its characteristics on what has become a fairly standard set of test problems in the literature. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. SAND2013-5687A.

  20. Diffuse Alveolar Hemorrhage

    PubMed Central

    2013-01-01

    Diffuse alveolar hemorrhage (DAH) is a life-threatening and medical emergency that can be caused by numerous disorders and presents with hemoptysis, anemia, and diffuse alveolar infiltrates. Early bronchoscopy with bronchoalveolar lavage is usually required to confirm the diagnosis and rule out infection. Most cases of DAH are caused by capillaritis associated with systemic autoimmune diseases such as anti-neutrophil cytoplasmic antibody-associated vasculitis, anti-glomerular basement membrane disease, and systemic lupus erythematosus, but DAH may also result from coagulation disorders, drugs, inhaled toxins, or transplantation. The diagnosis of DAH relies on clinical suspicion combined with laboratory, radiologic, and pathologic findings. Early recognition is crucial, because prompt diagnosis and treatment is necessary for survival. Corticosteroids and immunosuppressive agents remain the gold standard. In patients with DAH, biopsy of involved sites can help to identify the cause and to direct therapy. This article aims to provide a general review of the causes and clinical presentation of DAH and to recommend a diagnostic approach and a management plan for the most common causes. PMID:23678356

  1. Diffuse alveolar hemorrhage.

    PubMed

    Park, Moo Suk

    2013-04-01

    Diffuse alveolar hemorrhage (DAH) is a life-threatening and medical emergency that can be caused by numerous disorders and presents with hemoptysis, anemia, and diffuse alveolar infiltrates. Early bronchoscopy with bronchoalveolar lavage is usually required to confirm the diagnosis and rule out infection. Most cases of DAH are caused by capillaritis associated with systemic autoimmune diseases such as anti-neutrophil cytoplasmic antibody-associated vasculitis, anti-glomerular basement membrane disease, and systemic lupus erythematosus, but DAH may also result from coagulation disorders, drugs, inhaled toxins, or transplantation. The diagnosis of DAH relies on clinical suspicion combined with laboratory, radiologic, and pathologic findings. Early recognition is crucial, because prompt diagnosis and treatment is necessary for survival. Corticosteroids and immunosuppressive agents remain the gold standard. In patients with DAH, biopsy of involved sites can help to identify the cause and to direct therapy. This article aims to provide a general review of the causes and clinical presentation of DAH and to recommend a diagnostic approach and a management plan for the most common causes.

  2. Configurational diffusion of coal macromolecules

    SciTech Connect

    Guin, J.A.; Curtis, C.W.; Tarrer, A.R.

    1991-01-01

    It has been reported that the most predominant constituents of coal extract are the polycyclic aromatic hydrocarbons. Yet the experimental values of diffusivity in ethyl acetate for the most of these materials were not available in the literature. Thus, the diffusion coefficients of some of these materials were measured to increase an understanding of the diffusional behavior of coal macromolecules. In an earlier quarterly report, the authors reported the diffusion coefficients of some model coal molecules determined using their diffusion cell with polycarbonate membranes. Subsequently, they have found that these polycarbonate membranes are semi-permeable to some of the model compounds, so that the measured diffusion flux was greater than that through the pores alone. This extra solute flux could result in over estimation of the diffusion coefficients, therefore, they have now re-measured these diffusivities using polyester, rather than polycarbonate, membranes. The polyester material is not permeable to the solute molecules, except through the open pore area. Thus the only diffusion flux is that through the pores, resulting in correct diffusion coefficients as reported herein. The detailed results are presented in the body of this report. Finally in the last section the authors discuss a slight departure in methodology of some of their earlier planned work. This change will have a positive beneficial impact on the results and speed-up the collection of configurational diffusion data in actual tortuous porous media. 12 refs., 3 figs., 4 tabs.

  3. Sucrose diffusion in aqueous solution.

    PubMed

    Price, Hannah C; Mattsson, Johan; Murray, Benjamin J

    2016-07-28

    The diffusion of sugar in aqueous solution is important both in nature and in technological applications, yet measurements of diffusion coefficients at low water content are scarce. We report directly measured sucrose diffusion coefficients in aqueous solution. Our technique utilises a Raman isotope tracer method to monitor the diffusion of non-deuterated and deuterated sucrose across a boundary between the two aqueous solutions. At a water activity of 0.4 (equivalent to 90 wt% sucrose) at room temperature, the diffusion coefficient of sucrose was determined to be approximately four orders of magnitude smaller than that of water in the same material. Using literature viscosity data, we show that, although inappropriate for the prediction of water diffusion, the Stokes-Einstein equation works well for predicting sucrose diffusion under the conditions studied. As well as providing information of importance to the fundamental understanding of diffusion in binary solutions, these data have technological, pharmaceutical and medical implications, for example in cryopreservation. Moreover, in the atmosphere, slow organic diffusion may have important implications for aerosol growth, chemistry and evaporation, where processes may be limited by the inability of a molecule to diffuse between the bulk and the surface of a particle. PMID:27364512

  4. Sucrose diffusion in aqueous solution

    PubMed Central

    Murray, Benjamin J.

    2016-01-01

    The diffusion of sugar in aqueous solution is important both in nature and in technological applications, yet measurements of diffusion coefficients at low water content are scarce. We report directly measured sucrose diffusion coefficients in aqueous solution. Our technique utilises a Raman isotope tracer method to monitor the diffusion of non-deuterated and deuterated sucrose across a boundary between the two aqueous solutions. At a water activity of 0.4 (equivalent to 90 wt% sucrose) at room temperature, the diffusion coefficient of sucrose was determined to be approximately four orders of magnitude smaller than that of water in the same material. Using literature viscosity data, we show that, although inappropriate for the prediction of water diffusion, the Stokes–Einstein equation works well for predicting sucrose diffusion under the conditions studied. As well as providing information of importance to the fundamental understanding of diffusion in binary solutions, these data have technological, pharmaceutical and medical implications, for example in cryopreservation. Moreover, in the atmosphere, slow organic diffusion may have important implications for aerosol growth, chemistry and evaporation, where processes may be limited by the inability of a molecule to diffuse between the bulk and the surface of a particle. PMID:27364512

  5. Contrast Enhancement by Nonlinear Diffusion Filtering.

    PubMed

    Liang, Zhetong; Liu, Weijian; Yao, Ruohe

    2016-02-01

    To enhance the visual quality of an image that is degraded by uneven light, an effective method is to estimate the illumination component and compress it. Some previous methods have either defects of halo artifacts or contrast loss in the enhanced image due to incorrect estimation. In this paper, we discuss this problem and propose a novel method to estimate the illumination. The illumination is obtained by iteratively solving a nonlinear diffusion equation. During the diffusion process, surround suppression is embedded in the conductance function to specially enhance the diffusive strength in textural areas of the image. The proposed estimation method has the following two merits: 1) the boundary areas are preserved in the illumination, and thus halo artifacts are prevented and 2) the textural details are preserved in the reflectance to not suffer from illumination compression, which contributes to the contrast enhancement in the result. Experimental results show that the proposed algorithm achieves excellent performance in artifact removal and local contrast enhancement. PMID:26685234

  6. Apparatus and method for a light direction sensor

    NASA Technical Reports Server (NTRS)

    Leviton, Douglas B. (Inventor)

    2011-01-01

    The present invention provides a light direction sensor for determining the direction of a light source. The system includes an image sensor; a spacer attached to the image sensor, and a pattern mask attached to said spacer. The pattern mask has a slit pattern that as light passes through the slit pattern it casts a diffraction pattern onto the image sensor. The method operates by receiving a beam of light onto a patterned mask, wherein the patterned mask as a plurality of a slit segments. Then, diffusing the beam of light onto an image sensor and determining the direction of the light source.

  7. Diffusion length in nanoporous TiO{sub 2} films under above-band-gap illumination

    SciTech Connect

    Park, J. D.; Son, B. H.; Park, J. K.; Kim, Sang Yong; Park, Ji-Yong; Lee, Soonil; Ahn, Y. H.

    2014-06-15

    We determined the carrier diffusion lengths in TiO{sub 2} nanoporous layers of dye-sensitized solar cells by using scanning photocurrent microscopy using an ultraviolet laser. Here, we excited the carrier directly in the nanoporous layers where the diffusion lengths were found to 140 μm as compared to that of visible illumination measured at 90 μm. The diffusion length decreased with increasing laser modulation frequency, in which we determined the electron lifetimes and the diffusion coefficients for both visible and UV illuminations. The diffusion lengths have been studied in terms of the sintering temperatures for both cells with and without binding molecules. We found a strong correlation between the diffusion length and the overall light-to-current conversion efficiency, proving that improving the diffusion length and hence the interparticle connections, is key to improving cell efficiency.

  8. Polychromatic Speckle Reduction in Laser Pico-Projectors Using Stationary Dual Hadamard Diffusers

    NASA Astrophysics Data System (ADS)

    Thomas, W.; Middlebrook, C.

    2014-12-01

    Speckle from coherent light sources continues to be a limiting factor in the design and manufacturing of laser projectors. Utilizing diffractive diffusers has been an effective method for reducing monochromatic speckle contrast. Color laser projection devices require the use of red, green, and blue laser sources therefore; using a monochromatic diffractive diffuser may not be optimal for color speckle contrast reduction. A new static dual-diffuser system utilizing Hadamard matrices has been designed to reduce full color speckle. This paper analyzes the effectiveness of the new Hadamard diffusers in reducing speckle using three separate RGB laser diodes. A simulation of the Hadamard diffusers is conducted to determine the optimum spacing between the two diffusers for polychromatic speckle reduction. Experimental measured results are presented using the optimal spacing of Hadamard diffusers for RGB color speckle reduction showing 60% reduction in contrast.

  9. The Harrison Diffusion Kinetics Regimes in Solute Grain Boundary Diffusion

    SciTech Connect

    Belova, Irina; Fiedler, T; Kulkarni, Nagraj S; Murch, Prof. Graeme

    2012-01-01

    Knowledge of the limits of the principal Harrison kinetics regimes (Type-A, B and C) for grain boundary diffusion is very important for the correct analysis of the depth profiles in a tracer diffusion experiment. These regimes for self-diffusion have been extensively studied in the past by making use of the phenomenological Lattice Monte Carlo (LMC) method with the result that the limits are now well established. The relationship of those self-diffusion limits to the corresponding ones for solute diffusion in the presence of solute segregation to the grain boundaries remains unclear. In the present study, the influence of solute segregation on the limits is investigated with the LMC method for the well-known parallel grain boundary slab model by showing the equivalence of two diffusion models. It is shown which diffusion parameters are useful for identifying the limits of the Harrison kinetics regimes for solute grain boundary diffusion. It is also shown how the measured segregation factor from the diffusion experiment in the Harrison Type-B kinetics regime may differ from the global segregation factor.

  10. Diffusing Diffusivity: Survival in a Crowded Rearranging and Bounded Domain.

    PubMed

    Jain, Rohit; Sebastian, Kizhakeyil L

    2016-09-01

    We consider a particle diffusing in a bounded, crowded, rearranging medium. The rearrangement happens on a time scale longer than the typical time scale of diffusion of the particle; as a result, effectively, the diffusion coefficient of the particle varies as a stochastic function of time. What is the probability that the particle will survive within the bounded region, given that it is absorbed the first time it hits the boundary of the region in which it diffuses? This question is of great interest in a variety of chemical and biological problems. If the diffusion coefficient is a constant, then analytical solutions for a variety of cases are available in the literature. However, there is no solution available for the case in which the diffusion coefficient is a random function of time. We discuss a class of models for which it is possible to find analytical solutions to the problem. We illustrate the method for a circular, two-dimensional region, but our methods are easy to apply to diffusion in arbitrary dimensions and spherical/rectangular regions. Our solution shows that if the dimension of the region is large, then only the average value of the diffusion coefficient determines the survival probability. However, for smaller-sized regions, one would be able to see the effects of the stochasticity of the diffusion coefficient. We also give generalizations of the results to N dimensions. PMID:27478982

  11. Diffuse radiation increases global ecosystem-level water-use efficiency

    NASA Astrophysics Data System (ADS)

    Moffat, A. M.; Reichstein, M.; Cescatti, A.; Knohl, A.; Zaehle, S.

    2012-12-01

    Current environmental changes lead not only to rising atmospheric CO2 levels and air temperature but also to changes in air pollution and thus the light quality of the solar radiation reaching the land-surface. While rising CO2 levels are thought to enhance photosynthesis and closure of stomata, thus leading to relative water savings, the effect of diffuse radiation on transpiration by plants is less clear. It has been speculated that the stimulation of photosynthesis by increased levels of diffuse light may be counteracted by higher transpiration and consequently water depletion and drought stress. Ultimately, in water co-limited systems, the overall effect of diffuse radiation will depend on the sensitivity of canopy transpiration versus photosynthesis to diffuse light, i.e. whether water-use efficiency changes with relative levels of diffuse light. Our study shows that water-use efficiency increases significantly with higher fractions of diffuse light. It uses the ecosystem-atmosphere gas-exchange observations obtained with the eddy covariance method at 29 flux tower sites. In contrast to previous global studies, the analysis is based directly on measurements of diffuse radiation. Its effect on water-use efficiency was derived by analyzing the multivariate response of carbon and water fluxes to radiation and air humidity using a purely empirical approach based on artificial neural networks. We infer that per unit change of diffuse fraction the water-use efficiency increases up to 40% depending on diffuse fraction levels and ecosystem type. Hence, in regions with increasing diffuse radiation positive effects on primary production are expected even under conditions where water is co-limiting productivity.

  12. Is anomalous transport diffusive

    SciTech Connect

    Rewoldt, G.

    1989-09-01

    It has often been assumed that the anomalous transport from saturated plasma instabilities is diffusive'' in the sense that the particle flux, {Gamma}, the electron energy flux, q{sub e}, and the ion energy flux, q{sub i}, can be written in forms that are linear in the density gradient, dn/dr, the electron temperature gradient, dT{sub e}/dr, and the ion temperature gradient dT{sub i}/dr. In the simplest form, {Gamma} = {minus} D{sub n}{sup n}(dn/dr), q{sub e} = {minus} D{sub e}{sup e}n(dT{sub e}/dr), and q{sub i} = {minus}D{sub i}{sup i}n(dT{sub i}/dr). A possible generalization of this is to include so-called off-diagonal'' terms, with {Gamma} = nV{sub n} {minus} D{sub n}{sup n}(dn/dr) {minus} D{sub n}{sup e}(n/T{sub e})(dT{sub e}/dr) {minus} D{sub n}{sup i}(n/T{sub i})(dT{sub i}/dr), with corresponding forms for the energy fluxes. Here, general results for the quasilinear particle and energy fluxes, resulting from tokamak linear microinstabilities, are evaluated to assess the relative importance of the diagonal and the off-diagonal terms. A further possible generatlization is to include also contributions to the fluxes from higher powers of the gradients, specifically quadratic'' contributions proportional to (dn/dr){sup 2}, (dn/dr)(dT{sub e}/dr), and so on. A procedure is described for evaluating the corresponding coefficients, and results are presented for illustrative realistic tokamak cases. Qualitatively, it is found that the off-diagonal diffusion coefficients can be as big as the diagonal ones, and that the quadratic terms can be larger than the linear ones. The results thus strongly suggest that the commonly used diffusive'' approximation with only diagonal terms, {Gamma} = {minus}D{sub n}{sup n}(dn/dr), and correspondingly for the energy fluxes, is not adequate in practice. 9 refs., 1 tabs.

  13. Apoplastic diffusion barriers in Arabidopsis.

    PubMed

    Nawrath, Christiane; Schreiber, Lukas; Franke, Rochus Benni; Geldner, Niko; Reina-Pinto, José J; Kunst, Ljerka

    2013-12-27

    During the development of Arabidopsis and other land plants, diffusion barriers are formed in the apoplast of specialized tissues within a variety of plant organs. While the cuticle of the epidermis is the primary diffusion barrier in the shoot, the Casparian strips and suberin lamellae of the endodermis and the periderm represent the diffusion barriers in the root. Different classes of molecules contribute to the formation of extracellular diffusion barriers in an organ- and tissue-specific manner. Cutin and wax are the major components of the cuticle, lignin forms the early Casparian strip, and suberin is deposited in the stage II endodermis and the periderm. The current status of our understanding of the relationships between the chemical structure, ultrastructure and physiological functions of plant diffusion barriers is discussed. Specific aspects of the synthesis of diffusion barrier components and protocols that can be used for the assessment of barrier function and important barrier properties are also presented.

  14. Apoplastic Diffusion Barriers in Arabidopsis

    PubMed Central

    Schreiber, Lukas; Franke, Rochus Benni; Geldner, Niko; Reina-Pinto, José J.; Kunst, Ljerka

    2013-01-01

    During the development of Arabidopsis and other land plants, diffusion barriers are formed in the apoplast of specialized tissues within a variety of plant organs. While the cuticle of the epidermis is the primary diffusion barrier in the shoot, the Casparian strips and suberin lamellae of the endodermis and the periderm represent the diffusion barriers in the root. Different classes of molecules contribute to the formation of extracellular diffusion barriers in an organ- and tissue-specific manner. Cutin and wax are the major components of the cuticle, lignin forms the early Casparian strip, and suberin is deposited in the stage II endodermis and the periderm. The current status of our understanding of the relationships between the chemical structure, ultrastructure and physiological functions of plant diffusion barriers is discussed. Specific aspects of the synthesis of diffusion barrier components and protocols that can be used for the assessment of barrier function and important barrier properties are also presented. PMID:24465172

  15. Osmosis and diffusion conceptual assessment.

    PubMed

    Fisher, Kathleen M; Williams, Kathy S; Lineback, Jennifer Evarts

    2011-01-01

    Biology student mastery regarding the mechanisms of diffusion and osmosis is difficult to achieve. To monitor comprehension of these processes among students at a large public university, we developed and validated an 18-item Osmosis and Diffusion Conceptual Assessment (ODCA). This assessment includes two-tiered items, some adopted or modified from the previously published Diffusion and Osmosis Diagnostic Test (DODT) and some newly developed items. The ODCA, a validated instrument containing fewer items than the DODT and emphasizing different content areas within the realm of osmosis and diffusion, better aligns with our curriculum. Creation of the ODCA involved removal of six DODT item pairs, modification of another six DODT item pairs, and development of three new item pairs addressing basic osmosis and diffusion concepts. Responses to ODCA items testing the same concepts as the DODT were remarkably similar to responses to the DODT collected from students 15 yr earlier, suggesting that student mastery regarding the mechanisms of diffusion and osmosis remains elusive.

  16. Light fantastic

    NASA Astrophysics Data System (ADS)

    2010-05-01

    The laser has become so ubiquitous that it would be impossible to acknowledge everyone who has played a role in its success. As Roy Glauber said at the 2005 Nobel-prize banquet, when it comes to lasers, "many hands make light work". And he should know: the prize Glauber shared with fellow optics pioneers John Hall and Theodore Hänsch is one of more than 10 Nobels awarded (so far!) for laser-related research. This timeline marking 50 years of the laser contains Physics World's pick of events from laser history, including prizes (gold text), applications (green) and "firsts" (blue).

  17. Diffusion Coefficients in White Dwarfs

    NASA Astrophysics Data System (ADS)

    Saumon, D.; Starrett, C. E.; Daligault, J.

    2015-06-01

    Models of diffusion in white dwarfs universally rely on the coefficients calculated by Paquette et al. (1986). We present new calculations of diffusion coefficients based on an advanced microscopic theory of dense plasmas and a numerical simulation approach that intrinsically accounts for multiple collisions. Our method is validated against a state-of-the-art method and we present results for the diffusion of carbon ions in a helium plasma.

  18. Diffusion in Jammed Particle Packs.

    PubMed

    Bolintineanu, Dan S; Grest, Gary S; Lechman, Jeremy B; Silbert, Leonardo E

    2015-08-21

    Using random walk simulations we explore diffusive transport through monodisperse sphere packings over a range of packing fractions ϕ in the vicinity of the jamming transition at ϕ(c). Various diffusion properties are computed over several orders of magnitude in both time and packing pressure. Two well-separated regimes of normal "Fickian" diffusion, where the mean squared displacement is linear in time, are observed. The first corresponds to diffusion inside individual spheres, while the latter is the long-time bulk diffusion. The intermediate anomalous diffusion regime and the long-time value of the diffusion coefficient are both shown to be controlled by particle contacts, which in turn depend on proximity to ϕ(c). The time required to recover normal diffusion t* scales as (ϕ-ϕ(c))(-0.5) and the long-time diffusivity D(∞)∼(ϕ-ϕ(c))0.5, or D(∞)∼1/t*. It is shown that the distribution of mean first passage times associated with the escape of random walkers between neighboring particles controls both t* and D(∞) in the limit ϕ→ϕ(c).

  19. Enthalpy Diffusion in Multicomponent Flows

    SciTech Connect

    Cook, A W

    2009-01-20

    The conclusions of this paper are: (1) Enthalpy diffusion preserves the second law. (2) Euler solvers will not produce correct temperatures in mixing regions. (3) Navier-Stokes solvers will only produce correct temperatures if q{sub d} is included. (4) Errors from neglecting enthalpy diffusion are most severe when differences in molecular weights are large. (5) In addition to temperature, enthalpy diffusion affects density, dilatation and other fields in subtle ways. (6) Reacting flow simulations that neglect the term are a dubious proposition. (7) Turbulence models for RANS and LES closures should preserve consistency between energy and species diffusion.

  20. Diffusion rates for elevated releases

    SciTech Connect

    Ramsdell, J.V.

    1983-11-01

    A search of the literature related to diffusion from elevated sources has determined that an adequate data base exists for use in developing parameterizations for estimating diffusion rates for material released from free standing stacks at nuclear power plants. A review of published data analyses indicates that a new parameterization of horizontal diffusion rates specifically for elevated releases is not likely to significantly change the magnitudes of horizontal diffusion coefficients on the average. However, the uncertainties associated with horizontal diffusion coefficient estimates under any given set of atmospheric conditions could be reduced by a new parameterization. Similarly, a new parameterization of vertical diffusion rates would be unlikely to significantly alter the magnitudes of diffusion coefficients for unstable atmospheric conditons. However, for neutral and stable atmospheric conditions, a new parameterization of vertical diffusion rates might increase vertical diffusion coefficients significantly. The increase would move ground-level time-integrated concentration maxima closer to the plant and would increase the maxima. 55 references, 2 figures, 4 tables.

  1. Diffusion in Jammed Particle Packs.

    PubMed

    Bolintineanu, Dan S; Grest, Gary S; Lechman, Jeremy B; Silbert, Leonardo E

    2015-08-21

    Using random walk simulations we explore diffusive transport through monodisperse sphere packings over a range of packing fractions ϕ in the vicinity of the jamming transition at ϕ(c). Various diffusion properties are computed over several orders of magnitude in both time and packing pressure. Two well-separated regimes of normal "Fickian" diffusion, where the mean squared displacement is linear in time, are observed. The first corresponds to diffusion inside individual spheres, while the latter is the long-time bulk diffusion. The intermediate anomalous diffusion regime and the long-time value of the diffusion coefficient are both shown to be controlled by particle contacts, which in turn depend on proximity to ϕ(c). The time required to recover normal diffusion t* scales as (ϕ-ϕ(c))(-0.5) and the long-time diffusivity D(∞)∼(ϕ-ϕ(c))0.5, or D(∞)∼1/t*. It is shown that the distribution of mean first passage times associated with the escape of random walkers between neighboring particles controls both t* and D(∞) in the limit ϕ→ϕ(c). PMID:26340211

  2. Diffusion in the Formation of Photopolymer Holograms

    NASA Astrophysics Data System (ADS)

    Lanteigne, David John

    The research presented in this dissertation shows that the formation of holographic gratings in the Polaroid DMP-128 photopolymer medium is largely a result of the diffusion of lithium acrylate monomer within the medium. DMP -128 and other similar holographic photopolymers are capable of recording volume phase gratings by means of the physical and chemical changes that occur in the media when they are exposed to an optical interference pattern. In the presence of light, the absorption of photons by a sensitizing dye leads to the formation of free radicals. The free radicals, in turn, catalyze the linkage of simple monomer molecules into long-chain polymer molecules. The chemical reaction alters the molar refraction, and thus the index of refraction of the medium. If the illumination is spatially periodic, as when due to the interference of two plane waves, the chemical reaction also induces periodic variations in the concentration of monomer. The result is the diffusion of monomer from dark fringes, where little polymerization occurred, to bright fringes, where monomer was depleted by the photochemical reaction. This diffusion causes a periodic modulation of the mass density, which also modulates the index of refraction of the medium, according to the Lorentz-Lorenz relationship. A mathematical model developed in this research predicts that the amplitude of the periodic concentration decays exponentially with time; the time constant varies quadratically with the period of the grating. A detectable grating is formed in DMP-128 immediately upon holographic exposure. Experiment revealed that when the grating period was 25 microns or more, the effect of diffusion was insignificant, and the diffraction efficiency continued to increase long after exposure ended, due to residual free radical in the system. Shorter grating periods led to progressively more rapid decay of diffraction efficiency after exposure. The decay can be explained by assuming that the index modulation

  3. Turing instability in reaction-diffusion systems with nonlinear diffusion

    NASA Astrophysics Data System (ADS)

    Zemskov, E. P.

    2013-10-01

    The Turing instability is studied in two-component reaction-diffusion systems with nonlinear diffusion terms, and the regions in parametric space where Turing patterns can form are determined. The boundaries between super- and subcritical bifurcations are found. Calculations are performed for one-dimensional brusselator and oregonator models.

  4. Turing instability in reaction-diffusion systems with nonlinear diffusion

    SciTech Connect

    Zemskov, E. P.

    2013-10-15

    The Turing instability is studied in two-component reaction-diffusion systems with nonlinear diffusion terms, and the regions in parametric space where Turing patterns can form are determined. The boundaries between super- and subcritical bifurcations are found. Calculations are performed for one-dimensional brusselator and oregonator models.

  5. A light blanket for intraoperative photodynamic therapy

    NASA Astrophysics Data System (ADS)

    Hu, Yida; Wang, Ken; Zhu, Timothy C.

    2009-06-01

    A novel light source - light blanket composed of a series of parallel cylindrical diffusing fibers (CDF) is designed to substitute the hand-held point source in the PDT treatment of the malignant pleural or intraperitoneal diseases. It achieves more uniform light delivery and less operation time in operating room. The preliminary experiment was performed for a 9cmx9cm light blanket composed of 8 9-cm CDFs. The linear diffusers were placed in parallel fingerlike pockets. The blanket is filled with 0.2 % intralipid scattering medium to improve the uniformity of light distribution. 0.3-mm aluminum foil is used to shield and reflect the light transmission. The full width of the profile of light distribution at half maximum along the perpendicular direction is 7.9cm and 8.1cm with no intralipid and with intralipid. The peak value of the light fluence rate profiles per input power is 11.7mW/cm2/W and 8.6mW/cm2/W respectively. The distribution of light field is scanned using the isotropic detector and the motorized platform. The average fluence rate per input power is 8.6 mW/cm2/W and the standard deviation is 1.6 mW/cm2/W for the scan in air, 7.4 mW/cm2/W and 1.1 mW/cm2/W for the scan with the intralipid layer. The average fluence rate per input power and the standard deviation are 20.0 mW/cm2/W and 2.6 mW/cm2/W respectively in the tissue mimic phantom test. The light blanket design produces a reasonably uniform field for effective light coverage and is flexible to confirm to anatomic structures in intraoperative PDT. It also has great potential value for superficial PDT treatment in clinical application.

  6. Speckle in a thick diffuser

    NASA Astrophysics Data System (ADS)

    Chang, Nien-An

    Theory and experiments on speckle generated from a thick diffuser are presented in this thesis. An overview of speckle from a diffuser in a 4F optical processor gives a basic understanding of the speckle formation and properties. The speckle size depends on the F number of the system, while the interior properties of a diffuser are evident in the wavelength dependence of speckle. We then move on to analyzing speckle from a thick diffuser, which is composed of particles embedded in a host medium. Emphasis on the theory is placed on solving for the wavelength decorrelation of speckle in a thick diffuser. A brief overview of the scattering theory for a particle using the Lorenz-Mie theory is included. Then we present a careful analysis of the speckle created by propagation through a thick diffuser. In the analysis we use an angular spectrum approach that is valid in the non-paraxial case together with a decomposition of the thick diffuser into a cascade of many screens. This calculation is well-suited to numerical analysis and an original computer software program has been provided as an Appendix in this thesis. By adding the scattered field from the randomly-located particles on any screen and propagating through a free space between each screen, one can generate a speckled field after going through the whole cascade. The theoretical predictions are summarized and later compared with experimental results on a series of opal milk glass diffusers. In many practical applications it is particularly advantageous to have mild thick diffusers of controllable diffusivity. We have extensively studied a new diffuser series fabricated using polystyrene spheres of various diameters embedded in gelatin. Theory and experiments are in good agreement.

  7. A microscale turbine driven by diffusive mass flux.

    PubMed

    Yang, Mingcheng; Liu, Rui; Ripoll, Marisol; Chen, Ke

    2015-10-01

    An external diffusive mass flux is shown to be able to generate a mechanical torque on a microscale object based on anisotropic diffusiophoresis. In light of this finding, we propose a theoretical prototype micro-turbine driven purely by diffusive mass flux, which is in strong contrast to conventional turbines driven by convective mass flows. The rotational velocity of the proposed turbine is determined by the external concentration gradient, the geometry and the diffusiophoretic properties of the turbine. This scenario is validated by performing computer simulations. Our finding thus provides a new type of chemo-mechanical response which could be used to exploit existing chemical energies at small scales.

  8. Al and Zn Impurity Diffusion in Binary and Ternary Magnesium Solid-Solutions

    SciTech Connect

    Kammerer, Catherine; Kulkarni, Nagraj S; Warmack, Robert J Bruce; Sohn, Yong Ho

    2014-01-01

    Magnesium alloys are considered for implementation into structural components where energy-efficiency and light-weighting are important. Two of the most common alloying elements in magnesium alloys are Aluminum and Zinc. The present work examines impurity diffusion coefficients of Al and Zn in Mg(Zn) and Mg(Al) binary solid solutions, respectively. Experimental investigation is carried out with ternary diffusion couples with polycrystalline alloys. Concentration profiles were measured by electron microprobe micro-analysis and the impurity diffusion coefficients were determined by the Hall Method. Results of Al and Zn impurity diffusion in Mg solid solutions are reported, and examined as a function of composition of Mg solid solution.

  9. Validation of practical diffusion approximation for virtual near infrared spectroscopy using a digital head phantom

    NASA Astrophysics Data System (ADS)

    Oki, Yosuke; Kawaguchi, Hiroshi; Okada, Eiji

    2009-03-01

    Light propagation in the digital head phantom for virtual near infrared spectroscopy and imaging is calculated by diffusion theory. In theory, diffusion approximation is not valid in a low-scattering cerebrospinal fluid (CSF) layer around the brain. The optical path length and spatial sensitivity profile predicted by the finite element method based upon the diffusion theory are compared with those predicted by the Monte Carlo method to validate a practical implementation of diffusion approximation to light propagation in an adult head. The transport scattering coefficient of the CSF layer is varied from 0.01 to 1.0 mm-1 to evaluate the influence of that layer on the error caused by diffusion approximation. The error is practically ignored and the geometry of the brain surface such as the sulcus structure in the digital head phantom scarcely affects the error when the transport scattering coefficient of the CSF layer is greater than 0.3 mm-1.

  10. Diffusion in jammed particle packs

    NASA Astrophysics Data System (ADS)

    Bolintineanu, Dan S.; Silbert, Leonardo E.; Grest, Gary S.; Lechman, Jeremy B.

    2015-03-01

    Diffusive transport in jammed particle packs is of interest for a number of applications, as well as being a potential indicator of structural properties near the jamming point. To this end, we report stochastic simulations of equilibrium diffusion through monodisperse sphere packs near the jamming point in the limit of a perfectly insulating surrounding medium. The time dependence of various diffusion properties is resolved over several orders of magnitude. Two time regimes of expected Fickian diffusion are observed, separated by an intermediate regime of anomalous diffusion. This intermediate regime grows as the particle volume fraction approaches the critical jamming transition. The diffusion behavior is fully controlled by the extent of the contacts between neighboring particles, which in turn depend on proximity to the jamming point. In particular, the mean first passage time associated with the escape of random walkers between neighboring particles is shown to control both the time to recover Fickian diffusion and the long time diffusivity. Scaling laws are established that relate these quantities to the difference between the actual and critical jamming volume fractions. Sandia National Laboratories is a multiprogram laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's NNSA under Contract DE- AC04-94AL85000.

  11. Fractional diffusion on bounded domains

    SciTech Connect

    Defterli, Ozlem; D'Elia, Marta; Du, Qiang; Gunzburger, Max Donald; Lehoucq, Richard B.; Meerschaert, Mark M.

    2015-03-13

    We found that the mathematically correct specification of a fractional differential equation on a bounded domain requires specification of appropriate boundary conditions, or their fractional analogue. In this paper we discuss the application of nonlocal diffusion theory to specify well-posed fractional diffusion equations on bounded domains.

  12. Osmosis and Diffusion Conceptual Assessment

    ERIC Educational Resources Information Center

    Fisher, Kathleen M.; Williams, Kathy S.; Lineback, Jennifer Evarts

    2011-01-01

    Biology student mastery regarding the mechanisms of diffusion and osmosis is difficult to achieve. To monitor comprehension of these processes among students at a large public university, we developed and validated an 18-item Osmosis and Diffusion Conceptual Assessment (ODCA). This assessment includes two-tiered items, some adopted or modified…

  13. Teaching Diffusion with a Coin

    ERIC Educational Resources Information Center

    Haddad, Hamilton; Baldo, Marcus Vinicius Chrysostomo

    2010-01-01

    In this article, the authors describe an inexpensive and simple way to make students intuitively experience the probabilistic nature and nonorientated motion of diffusing particles. This understanding allows students to realize why diffusion works so well over short distances and becomes increasingly and rapidly less effective as the distances…

  14. Demonstrating Diffusion: Why the Confusion?

    ERIC Educational Resources Information Center

    Panizzon, Debra Lee

    1998-01-01

    Examines the principles of diffusion and how it may be confused with convection. Suggests that educators may be misleading students and clouding their understanding of the process. Provides two contemporary examples to explain the process of diffusion and how it differs from convection. (Author/CCM)

  15. The Diffusion of New Math.

    ERIC Educational Resources Information Center

    Ready, Patricia M.

    The life cycle of "new math" is fertile ground for the study of the diffusion of an innovation. New math arrived in 1958 to save the day for America after the Soviet Union launched Sputnik, the first successful space flight in 1957. In a period of 16 years an entire diffusion cycle was completed throughout the entire educational system of the…

  16. Thermal diffusivity of diamond films

    NASA Technical Reports Server (NTRS)

    Albin, Sacharia; Winfree, William P.; Crews, B. Scott

    1990-01-01

    A laser pulse technique to measure the thermal diffusivity of diamond films deposited on a silicon substrate is developed. The effective thermal diffusivity of diamond film on silicon was measured by observing the phase and amplitude of the cyclic thermal waves generated by the laser pulses. An analytical model is developed to calculate the effective in-plane (face-parallel) diffusivity of a two layer system. The model is used to reduce the effective thermal diffusivity of the diamond/silicon sample to a value for the thermal diffusivity and conductivity of the diamond film. Phase and amplitude measurements give similar results. The thermal conductivity of the films is found to be better than that of type 1a natural diamond.

  17. Enthalpy Diffusion in Multicomponent Flows

    SciTech Connect

    Cook, A W

    2008-11-12

    The enthalpy diffusion flux in the multicomponent energy equation is a well known yet frequently neglected term. It accounts for energy changes, associated with compositional changes, resulting from species diffusion. Enthalpy diffusion is important in flows where significant mixing occurs between species of dissimilar molecular weight. The term plays a critical role in preventing local violations of the entropy condition. In simulations of nonpremixed combustion, omission of the enthalpy flux can lead to anomalous temperature gradients, which may cause mixing regions to exceed ignition conditions. The term can also play a role in generating acoustic noise in turbulent mixing layers. Euler solvers that rely on numerical diffusion to mix fluids cannot accurately predict the temperature in mixed regions. On the other hand, Navier-Stokes solvers that incorporate enthalpy diffusion can provide much more accurate results.

  18. Heat transfer, diffusion, and evaporation

    NASA Technical Reports Server (NTRS)

    Nusselt, Wilhelm

    1954-01-01

    Although it has long been known that the differential equations of the heat-transfer and diffusion processes are identical, application to technical problems has only recently been made. In 1916 it was shown that the speed of oxidation of the carbon in iron ore depends upon the speed with which the oxygen of the combustion air diffuses through the core of gas surrounding the carbon surface. The identity previously referred to was then used to calculate the amount of oxygen diffusing to the carbon surface on the basis of the heat transfer between the gas stream and the carbon surface. Then in 1921, H. Thoma reversed that procedure; he used diffusion experiments to determine heat-transfer coefficients. Recently Lohrisch has extended this work by experiment. A technically very important application of the identity of heat transfer and diffusion is that of the cooling tower, since in this case both processes occur simultaneously.

  19. Portable vapor diffusion coefficient meter

    DOEpatents

    Ho, Clifford K.

    2007-06-12

    An apparatus for measuring the effective vapor diffusion coefficient of a test vapor diffusing through a sample of porous media contained within a test chamber. A chemical sensor measures the time-varying concentration of vapor that has diffused a known distance through the porous media. A data processor contained within the apparatus compares the measured sensor data with analytical predictions of the response curve based on the transient diffusion equation using Fick's Law, iterating on the choice of an effective vapor diffusion coefficient until the difference between the predicted and measured curves is minimized. Optionally, a purge fluid can forced through the porous media, permitting the apparatus to also measure a gas-phase permeability. The apparatus can be made lightweight, self-powered, and portable for use in the field.

  20. Ammonia diffusion through Nalophan™ bags.

    PubMed

    Sironi, Selena; Eusebio, Lidia; Dentoni, Licinia; Capelli, Laura; Del Rosso, Renato

    2014-01-01

    The aim of the work is to verify the diffusion rate of ammonia through the Nalophan™ film that constitutes the sampling bag, considering storage times ranging from 1 to 26 h. The ammonia decay over time was evaluated using gas-chromatography for the quantification of ammonia concentration inside the bag. The research assesses the roles of both of ammonia and water concentration gradients at the polymeric film interface on the diffusion process. The results show that both the ammonia concentration gradient and, in a less pronounced way, the water concentration gradient are the main 'engines' of ammonia diffusion. Double bags seem to represent a simple solution for preventing ammonia losses during storage. Another interesting result concerns the role of the bag surface on the ammonia diffusion rate: the higher the surface/volume (S/V) ratio, the higher the ammonia diffusion rate through the polymeric film.

  1. Diffusion of childbearing within cohabitation.

    PubMed

    Vitali, Agnese; Aassve, Arnstein; Lappegård, Trude

    2015-04-01

    The article analyzes the diffusion of childbearing within cohabitation in Norway, using municipality data over a 24-year period (1988-2011). Research has found substantial spatial heterogeneity in this phenomenon but also substantial spatial correlation, and the prevalence of childbearing within cohabitation has increased significantly over time. We consider several theoretical perspectives and implement a spatial panel model that allows accounting for autocorrelation not only on the dependent variable but also on key explanatory variables, and hence identifies the key determinants of diffusion of childbearing within cohabitation across space and over time. We find only partial support for the second demographic transition as a theory able to explain the diffusion of childbearing within cohabitation. Our results show that at least in the first phase of the diffusion (1988-1997), economic difficulties as measured by increased unemployment among men contributed to the diffusion of childbearing within cohabitation. However, the most important driver for childbearing within cohabitation is expansion in education for women.

  2. Microfiberoptic fluorescence photobleaching reveals size-dependent macromolecule diffusion in extracellular space deep in brain.

    PubMed

    Zador, Zsolt; Magzoub, Mazin; Jin, Songwan; Manley, Geoffrey T; Papadopoulos, Marios C; Verkman, A S

    2008-03-01

    Diffusion in brain extracellular space (ECS) is important for nonsynaptic intercellular communication, extracellular ionic buffering, and delivery of drugs and metabolites. We measured macromolecular diffusion in normally light-inaccessible regions of mouse brain by microfiberoptic epifluorescence photobleaching, in which a fiberoptic with a micron-size tip is introduced deep in brain tissue. In brain cortex, the diffusion of a noninteracting molecule [fluorescein isothiocyanate (FITC)-dextran, 70 kDa] was slowed 4.5 +/- 0.5-fold compared with its diffusion in water (D(o)/D), and was depth-independent down to 800 microm from the brain surface. Diffusion was significantly accelerated (D(o)/D of 2.9+/-0.3) in mice lacking the glial water channel aquaporin-4. FITC-dextran diffusion varied greatly in different regions of brain, with D(o)/D of 3.5 +/- 0.3 in hippocampus and 7.4 +/- 0.3 in thalamus. Remarkably, D(o)/D in deep brain was strongly dependent on solute size, whereas diffusion in cortex changed little with solute size. Mathematical modeling of ECS diffusion required nonuniform ECS dimensions in deep brain, which we call "heterometricity," to account for the size-dependent diffusion. Our results provide the first data on molecular diffusion in ECS deep in brain in vivo and demonstrate previously unrecognized hindrance and heterometricity for diffusion of large macromolecules in deep brain.

  3. Assessing PDT response with diffuse optical spectroscopies

    NASA Astrophysics Data System (ADS)

    Rohrbach, Daniel J.

    Photodynamic therapy (PDT) is used to treat a variety of conditions including cancer. Effective PDT requires three components: a photosensitizer (PS), light of a specific wavelength to activate the PS and oxygen. When all three are present in a lesion it leads to cell death and vascular destruction. Optical techniques such as diffuse reflectance spectroscopy (DRS), diffuse fluorescence spectroscopy (DFS) and diffuse correlation spectroscopy (DCS) can be used to quantify vascular parameters and photosensitizer content before and after PDT, providing valuable information for assessing response. For the quantification of vascular parameters, a probe-specific empirical light transport model was developed. A look-up-table was constructed using tissue simulating phantoms made of Intralipid to control the scattering, India Ink to control the absorption and water. The empirical model allowed the quantification of optical properties as well as the vascular parameters blood volume fraction (BVf) and blood oxygen saturation (SO2) with DRS. Blood flow was measured using DCS. For the quantification of PS content two techniques were used. DRS was used to fit the absorption of the PS and DFS measured the fluorescence of the PS. For quantification of PS content from measured fluorescence, a correction factor was developed using Monte Carlo simulations to account for the optical properties at the excitation and emission wavelengths. The three techniques were used to assess PDT response in pre-clinical and clinical studies. For the preclinical study, mice were treated with HPPH-PDT and blood flow was measured continuously with DCS. Blood flow variables were compared to STAT3 crosslinking (a molecular marker for PDT photoreaction) and CD31 staining (to visualize intact endothelial cells after PDT). For the clinical study, patients in a clinical trial for HPPH-PDT were measured with DRS, DFS and DCS before and after treatment. Multiple parameters were compared to the clinical response

  4. The global structure of the visual light field and its relation to the physical light field.

    PubMed

    Kartashova, Tatiana; Sekulovski, Dragan; de Ridder, Huib; Pas, Susan F Te; Pont, Sylvia C

    2016-08-01

    Human observers have been demonstrated to be sensitive to the local (physical) light field, or more precisely, to the primary direction, intensity, and diffuseness of the light at a point in a space. In the present study we focused on the question of whether it is possible to reconstruct the global visual light field, based on observers' inferences of the local light properties. Observers adjusted the illumination on a probe in order to visually fit it in three diversely lit scenes. For each scene they made 36 settings on a regular grid. The global structure of the first order properties of the light field could then indeed be reconstructed by interpolation of light vectors coefficients representing the local settings. We demonstrate that the resulting visual light fields (individual and averaged) can be visualized and we show how they can be compared to physical measurements in the same scenes. Our findings suggest that human observers have a robust impression of the light field that is simplified with respect to the physical light field. In particular, the subtle spatial variations of the physical light fields are largely neglected and the visual light fields were more similar to simple diverging fields than to the actual physical light fields. PMID:27548087

  5. Diffusion in membranes: Toward a two-dimensional diffusion map

    NASA Astrophysics Data System (ADS)

    Toppozini, Laura; Garcia-Sakai, Victoria; Bewley, Robert; Dalgliesh, Robert; Perring, Toby; Rheinstädter, Maikel C.

    2015-01-01

    For decades, quasi-elastic neutron scattering has been the prime tool for studying molecular diffusion in membranes over relevant nanometer distances. These experiments are essential to our current understanding of molecular dynamics of lipids, proteins and membrane-active molecules. Recently, we presented experimental evidence from X-ray diffraction and quasi-elastic neutron scattering demonstrating that ethanol enhances the permeability of membranes. At the QENS 2014/WINS 2014 conference we presented a novel technique to measure diffusion across membranes employing 2-dimensional quasi-elastic neutron scattering. We present results from our preliminary analysis of an experiment on the cold neutron multi-chopper spectrometer LET at ISIS, where we studied the self-diffusion of water molecules along lipid membranes and have the possibility of studying the diffusion in membranes. By preparing highly oriented membrane stacks and aligning them horizontally in the spectrometer, our aim is to distinguish between lateral and transmembrane diffusion. Diffusion may also be measured at different locations in the membranes, such as the water layer and the hydrocarbon membrane core. With a complete analysis of the data, 2-dimensional mapping will enable us to determine diffusion channels of water and ethanol molecules to quantitatively determine nanoscale membrane permeability.

  6. Diffusion with optimal resetting

    NASA Astrophysics Data System (ADS)

    Evans, Martin R.; Majumdar, Satya N.

    2011-10-01

    We consider the mean time to absorption by an absorbing target of a diffusive particle with the addition of a process whereby the particle is reset to its initial position with rate r. We consider several generalizations of the model of Evans and Majumdar (2011 Phys. Rev. Lett.106 160601): (i) a space-dependent resetting rate r(x); (ii) resetting to a random position z drawn from a resetting distribution { P}(z); and (iii) a spatial distribution for the absorbing target PT(x). As an example of (i) we show that the introduction of a non-resetting window around the initial position can reduce the mean time to absorption provided that the initial position is sufficiently far from the target. We address the problem of optimal resetting, that is, minimizing the mean time to absorption for a given target distribution. For an exponentially decaying target distribution centred at the origin we show that a transition in the optimal resetting distribution occurs as the target distribution narrows.

  7. Diffuse gamma radiation

    NASA Technical Reports Server (NTRS)

    Fichtel, C. E.; Simpson, G. A.; Thompson, D. J.

    1977-01-01

    An examination of the intensity, energy spectrum, and spatial distribution of the diffuse gamma-radiation observed by SAS-2 satellite away from the galactic plane in the energy range above 35 MeV has shown that it consists of two components. One component is generally correlated with galactic latitudes, the atomic hydrogen column density was deduced from 21 cm measurements, and the continuum radio emission, believed to be synchrotron emission. It has an energy spectrum similar to that in the plane and joins smoothly to the intense radiation from the plane. It is therefore presumed to be of galactic origin. The other component is apparently isotropic, at least on a coarse scale, and has a steep energy spectrum. No evidence is found for a cosmic ray halo surrounding the galaxy in the shape of a sphere or oblate spheroid with galactic dimensions. Constraints for a halo model with significantly larger dimensions are set on the basis of an upper limit to the gamma-ray anisotropy.

  8. Diffuse Microwave Emission Survey

    NASA Astrophysics Data System (ADS)

    Shafer, R. A.; Mather, J.; Kogut, A.; Fixsen, D. J.; Seiffert, M.; Lubin, P. M.; Levin, S. M.

    1996-12-01

    The Diffuse Microwave Emission Survey (DIMES) is a mission concept selected by NASA in 1995 to answer fundamental questions about the content and history of the universe. DIMES will use a set of absolutely calibrated cryogenic radiometers from a space platform to measure the frequency spectrum of the cosmic microwave background (CMB) at wavelengths 15--0.3 cm (frequency 2--100 GHz) to precision 0.1 mK or better. Measurements at centimeter wavelengths probe different physical processes than the COBE-FIRAS spectra at shorter wavelengths, and complement the anisotropy measurements from DMR, balloon and ground-based instruments, and the planned MAP and COBRAS/SAMBA satellites. DIMES will observe the free-free signal from early photoionization to establish the precise epoch of structure formation, and will measure or limit energy release at redshift 10(4) < z < 10(7) by measuring the chemical potential distortion of the CMB spectrum. Both are likely under current cosmological theory and allowed by current measurement limits; even an upper limit at the expected sensitivity 10(-5) MJy/sr will place important constraints on the matter content, structure, and evolution of the universe. Detecting these distortions or showing that they do not exist constitutes the last frontier of CMB observations.

  9. A model for ultrasound modulated light in a turbid medium

    NASA Astrophysics Data System (ADS)

    Hollmann, Joseph L.; Horstmeyer, Roarke; Yang, Changhuei; DiMarzio, Charles A.

    2014-03-01

    The ability to focus light in most tissue degrades quickly with depth due to high optical scattering. Researchers have investigated using both ultrasound (US) and light synergistically to overcome this difficulty. Ultrasound has been utilized to modulated light within tissue to create a diffusive wave at that is modulated at the US frequency. Recently, there has been interest in the modulated sidebands which reside at optical frequency plus or minus the US frequency. This paper will discuss a model for US-light interactions in a scattering medium. We will use this model to relate the radiance in the probe beam to the radiance in the diffusive wave. We will then employ the P-1 approximation to the radiative transport equation to find the fluence and flux of the modulated wave. We will use these parameters to write a diffusion equation for the modulated wave that can be described in terms of the incoming optical power, and the US intensity and geometry.

  10. Multicomponent diffusion in molten salt LiF-BeF2: Dynamical correlations and Maxwell-Stefan diffusivities

    NASA Astrophysics Data System (ADS)

    Chakraborty, Brahmananda; Ramaniah, Lavanya M.

    2015-06-01

    Applying Green-Kubo formalism and equilibrium molecular dynamics (MD) simulations, we have studied the dynamic correlation, Onsager coeeficients and Maxwell-Stefan (MS) Diffusivities of molten salt LiF-BeF2, which is used as coolant in high temperature reactor. All the diffusive flux correlations show back-scattering or cage dynamics which becomes pronouced at higher temperature. Although the MS diffusivities are expected to depend very lightly on the composition due to decoupling of thermodynamic factor, the diffusivity ĐLi-F and ĐBe-F decreases sharply for higher concentration of LiF and BeF2 respectively. Interestingly, all three MS diffusivities have highest magnitude for eutectic mixture at 1000K (except ĐBe-F at lower LiF mole fraction) which is desirable from coolant point of view. Although the diffusivity for positive-positive ion pair is negative it is not in violation of the second law of thermodynamics as it satisfies the non-negative entropic constraints.

  11. Multicomponent diffusion in molten salt LiF-BeF{sub 2}: Dynamical correlations and Maxwell–Stefan diffusivities

    SciTech Connect

    Chakraborty, Brahmananda Ramaniah, Lavanya M.

    2015-06-24

    Applying Green–Kubo formalism and equilibrium molecular dynamics (MD) simulations, we have studied the dynamic correlation, Onsager coeeficients and Maxwell–Stefan (MS) Diffusivities of molten salt LiF-BeF{sub 2}, which is used as coolant in high temperature reactor. All the diffusive flux correlations show back-scattering or cage dynamics which becomes pronouced at higher temperature. Although the MS diffusivities are expected to depend very lightly on the composition due to decoupling of thermodynamic factor, the diffusivity Đ{sub Li-F} and Đ{sub Be-F} decreases sharply for higher concentration of LiF and BeF{sub 2} respectively. Interestingly, all three MS diffusivities have highest magnitude for eutectic mixture at 1000K (except Đ{sub Be-F} at lower LiF mole fraction) which is desirable from coolant point of view. Although the diffusivity for positive-positive ion pair is negative it is not in violation of the second law of thermodynamics as it satisfies the non-negative entropic constraints.

  12. Lighting the Learning Environment.

    ERIC Educational Resources Information Center

    Fielding, Randall

    2000-01-01

    Explores the benefits and pitfalls of day lighting, indirect light, and full-spectrum lamps for general illumination and accent lighting in classrooms. Discussions include lighting considerations in areas where computers are used and fixture cost factors versus efficiency. (GR)

  13. Transdermal diffusion of xenon in vitro using diffusion cells

    NASA Astrophysics Data System (ADS)

    Verkhovsky, A.; Petrov, E.

    2015-11-01

    The aim of this research was to study the diffusion rate of xenon through guinea pig skin and how viscosity of cosmetic component capryl/capric triglyceride (CCT) facilitates to deliver xenon to surface of skin patches. They were placed in Franz cell for 24 hours and diffusion rate and permeability of xenon were calculated. Thus diffusion rate was 0.031 mg/hour*cm2 and permeability was 0.003 cm/hour. Using Brookfield viscometer it was shown that viscosity of CCT decreased upon increasing xenon concentration. Obtained results can be utilized in developing of new xenon containing drugs for topical administration.

  14. Cost effective flat plate photovoltaic modules using light trapping

    NASA Technical Reports Server (NTRS)

    Bain, C. N.; Gordon, B. A.; Knasel, T. M.; Malinowski, R. L.

    1981-01-01

    Work in optical trapping in 'thick films' is described to form a design guide for photovoltaic engineers. A thick optical film can trap light by diffusive reflection and total internal reflection. Light can be propagated reasonably long distances compared with layer thicknesses by this technique. This makes it possible to conduct light from inter-cell and intra-cell areas now not used in photovoltaic modules onto active cell areas.

  15. Traffic Lights: Red Light Spells Danger.

    ERIC Educational Resources Information Center

    Reed, Chris

    2001-01-01

    A "traffic light" model provides youth groups with a means to evaluate the risk level of specific behaviors and agree upon the management of such behaviors. Designed for outdoor pursuits, the model may be used in other environments. Suggestions for ways to discuss red-light, yellow-light, and green-light behaviors are included. (SV)

  16. Classical momentum diffusion in double-{delta}-kicked particles

    SciTech Connect

    Stocklin, M. M. A.; Monteiro, T. S.

    2006-08-15

    We investigate the classical chaotic diffusion of atoms subjected to pairs of closely spaced pulses ('kicks') from standing waves of light (the 2{delta}-KP). Recent experimental studies with cold atoms implied an underlying classical diffusion of a type very different from the well-known paradigm of Hamiltonian chaos, the standard map. The kicks in each pair are separated by a small time interval {epsilon}<<1, which together with the kick strength K, characterizes the transport. Phase space for the 2{delta}-KP is partitioned into momentum 'cells' partially separated by momentum-trapping regions where diffusion is slow. We present here an analytical derivation of the classical diffusion for a 2{delta}-KP including all important correlations which were used to analyze the experimental data. We find an asymptotic (t{yields}{infinity}) regime of 'hindered' diffusion: while for the standard map the diffusion rate, for K>>1, D{approx}K{sup 2}/2[1-2J{sub 2}(K){center_dot}{center_dot}{center_dot}] oscillates about the uncorrelated rate D{sub 0}=K{sup 2}/2, we find analytically, that the 2{delta}-KP can equal, but never diffuses faster than, a random walk rate. We argue this is due to the destruction of the important classical 'accelerator modes' of the standard map. We analyze the experimental regime 0.1 < or approx. K{epsilon} < or approx. 1, where quantum localization lengths L{approx}({Dirac_h}/2{pi}){sup -0.75} are affected by fractal cell boundaries. We find an approximate asymptotic diffusion rate D{proportional_to}K{sup 3}{epsilon}, in correspondence to a D{proportional_to}K{sup 3} regime in the standard map associated with the 'golden-ratio' cantori.

  17. Diffusivity Measurements Made Instant and Easy

    NASA Technical Reports Server (NTRS)

    Rashidnia, Nasser

    2001-01-01

    A compact common path interferometer (CPI) system has been developed to measure the diffusivity of liquid pairs. The CPI is an optical technique that can be used to measure changes in the gradient of the refraction index of transparent materials. It uses a shearing interferometer that shares the same optical path from a laser light source to the final imaging plane. The molecular diffusion coefficient of liquids can be determined from the physical relations between changes in the optical path length and liquid phase properties. When the data obtained by using the CPI have been compared with similar results from other techniques, the instrument has been demonstrated to be far superior to other instruments for measuring the diffusivity of miscible liquids while staying very compact and robust (ref. 1). Because of its compactness and ease of use, the CPI has been adopted for use in studies of interface dynamics as well as other diffusion-controlled process applications (ref. 2). This progress will permit experiments in microgravity that can quantitatively answer basic science questions about mass and thermal diffusion and their effect in transport processes. This instrument is a spinoff of a diagnostic development for microgravity fluid physics experiments at the NASA Glenn Research Center that has used optics and electronics existing in the fluid physics laboratory for feasibility studies. Optical diagnostic techniques have become an integral part of many areas of measurement applications in industrial and research laboratories. Many types of interferometers and their phase-shifted versions have been used as instruments for measuring optical wave fronts for lens testing and combustion and fluid flow diagnostics. One of these, the point diffraction interferometer, is considered to be robust (see, for example, ref. 3) because it has a common-path design. The point diffraction interferometer is difficult to align and has a limited measurement range for liquid

  18. Multiple Light Scattering Probes of Soft Materials

    NASA Astrophysics Data System (ADS)

    Scheffold, Frank

    2007-02-01

    I will discuss both static and dynamic properties of diffuse waves. In practical applications the optical properties of colloidal systems play an important role, for example in commercial products such as sunscreen lotions, food (drinks), coatings but also in medicine for example in cataract formation (eye lens turbidity). It is thus of importance to know the key parameters governing optical turbidity from the single to the multiple scattering regime. Temporal fluctuations of multiply scattered light are studied with photon correlation spectroscopy (Diffusing Wave Spectroscopy). This DWS method and its various implementations will be treated.

  19. Single file diffusion in microtubules

    NASA Astrophysics Data System (ADS)

    Rutenberg, Andrew; Farrell, Spencer; Brown, Aidan

    2015-03-01

    We investigate the single file diffusion (SFD) of large particles entering a confined tubular geometry, such as luminal diffusion of proteins inside microtubules or flagella. While single-file effects have no effect on particle density, we report significant single-file effects for individually-tracked tracer particle motion. Both exact and approximate ordering statistics of particles entering semi-infinite tubes agree well with our stochastic simulations. Considering initially empty semi-infinite tubes, with particles entering at one end starting from an initial time t = 0 , tracked particles display super-diffusive effective exponents just after they enter the system and trends towards diffusive exponents at later times. Equivalently, if diffusive exponents are assumed the effective diffusivity is reduced at early times and enhanced at later times through a logarithmic factor logN , where N is the number of particles in the tube. When we number each particle from the first (n = 1) to the most recent (n = N), we find good scaling collapse of the effective diffusivity for all n. Techniques that track individual particles, or local groups of particles, such as photo-activation or photobleaching, will exhibit single-file effects.

  20. Cytoplasmic hydrogen ion diffusion coefficient.

    PubMed Central

    al-Baldawi, N F; Abercrombie, R F

    1992-01-01

    The apparent cytoplasmic proton diffusion coefficient was measured using pH electrodes and samples of cytoplasm extracted from the giant neuron of a marine invertebrate. By suddenly changing the pH at one surface of the sample and recording the relaxation of pH within the sample, an apparent diffusion coefficient of 1.4 +/- 0.5 x 10(-6) cm2/s (N = 7) was measured in the acidic or neutral range of pH (6.0-7.2). This value is approximately 5x lower than the diffusion coefficient of the mobile pH buffers (approximately 8 x 10(-6) cm2/s) and approximately 68x lower than the diffusion coefficient of the hydronium ion (93 x 10(-6) cm2/s). A mobile pH buffer (approximately 15% of the buffering power) and an immobile buffer (approximately 85% of the buffering power) could quantitatively account for the results at acidic or neutral pH. At alkaline pH (8.2-8.6), the apparent proton diffusion coefficient increased to 4.1 +/- 0.8 x 10(-6) cm2/s (N = 7). This larger diffusion coefficient at alkaline pH could be explained quantitatively by the enhanced buffering power of the mobile amino acids. Under the conditions of these experiments, it is unlikely that hydroxide movement influences the apparent hydrogen ion diffusion coefficient. PMID:1617134

  1. Enhanced diffusion of oxygen depending on Fermi level position in heavily boron-doped silicon

    SciTech Connect

    Torigoe, Kazuhisa Fujise, Jun; Ono, Toshiaki; Nakamura, Kozo

    2014-11-21

    The enhanced diffusivity of oxygen in heavily boron doped silicon was obtained by analyzing oxygen out-diffusion profile changes found at the interface between a lightly boron-doped silicon epitaxial layer and a heavily boron-doped silicon substrate by secondary ion mass spectrometry. It was found that the diffusivity is proportional to the square root of boron concentration in the range of 10{sup 18 }cm{sup −3}–10{sup 19 }cm{sup −3} at temperatures from 750 °C to 950 °C. The model based on the diffusion of oxygen dimers in double positive charge state could explain the enhanced diffusion. We have concluded that oxygen diffusion enhanced in heavily boron-doped silicon is attributed to oxygen dimers ionized depending on Fermi level position.

  2. Sulphur diffusion in β-NiAl and effect of Pt additive: an ab initio study

    NASA Astrophysics Data System (ADS)

    Chen, Kuiying

    2016-02-01

    Diffusivities of detrimental impurity sulfur (S) in stoichiometric and Pt doped β-NiAl were evaluated using density functional theory calculations. The apparent activation energy and the pre-exponential factor of diffusivity via the next nearest neighbour (NNN) and interstitial jumps were evaluated to identify possible preferred diffusion mechanism(s). By calculating the electron localization function (ELF), the bonding characteristics of S with its surrounding atoms were assessed for the diffusion process. By comparison with the experimental results, the S diffusion through the NNN vacancy-mediated mechanism is found to be favoured. Addition of Pt in β-NiAl was found to significantly reduce the S diffusivity, and an associated electronic effect was explored. The elucidation of the above mechanisms may shed light on the development of new Pt-modified doped β-NiAl bond coats that can extend the life of oxidation resistant and thermal barrier coatings.

  3. Amplitude equations for reaction-diffusion systems with cross diffusion

    NASA Astrophysics Data System (ADS)

    Zemskov, Evgeny P.; Vanag, Vladimir K.; Epstein, Irving R.

    2011-09-01

    Using Taylor series expansion, multiscaling, and further expansion in powers of a small parameter, we develop general amplitude equations for two-variable reaction-diffusion systems with cross-diffusion terms in the cases of Hopf and Turing instabilities. We apply this analysis to the Oregonator and Brusselator models and find that inhibitor cross diffusion induced by the activator and activator cross diffusion induced by the inhibitor have opposite effects in the two models as a result of the different structure of their community matrices. Our analysis facilitates finding regions of supercritical and subcritical bifurcations, as well as wave and antiwave domains and domains of turbulent waves in the case of Hopf instability.

  4. Amplitude equations for reaction-diffusion systems with cross diffusion.

    PubMed

    Zemskov, Evgeny P; Vanag, Vladimir K; Epstein, Irving R

    2011-09-01

    Using Taylor series expansion, multiscaling, and further expansion in powers of a small parameter, we develop general amplitude equations for two-variable reaction-diffusion systems with cross-diffusion terms in the cases of Hopf and Turing instabilities. We apply this analysis to the Oregonator and Brusselator models and find that inhibitor cross diffusion induced by the activator and activator cross diffusion induced by the inhibitor have opposite effects in the two models as a result of the different structure of their community matrices. Our analysis facilitates finding regions of supercritical and subcritical bifurcations, as well as wave and antiwave domains and domains of turbulent waves in the case of Hopf instability. PMID:22060484

  5. Turing instabilities in reaction-diffusion systems with cross diffusion

    NASA Astrophysics Data System (ADS)

    Fanelli, Duccio; Cianci, Claudia; Di Patti, Francesca

    2013-04-01

    The Turing instability paradigm is revisited in the context of a multispecies diffusion scheme derived from a self-consistent microscopic formulation. The analysis is developed with reference to the case of two species. These latter share the same spatial reservoir and experience a degree of mutual interference due to the competition for the available resources. Turing instability can set in for all ratios of the main diffusivities, also when the (isolated) activator diffuses faster then the (isolated) inhibitor. This conclusion, at odd with the conventional vision, is here exemplified for the Brusselator model and ultimately stems from having assumed a generalized model of multispecies diffusion, fully anchored to first principles, which also holds under crowded conditions.

  6. Fick's Insights on Liquid Diffusion

    SciTech Connect

    Narasimhan, T.N.

    2004-10-07

    In 1855, Adolph Fick published ''On Liquid Diffusion'', mathematically treating salt movements in liquids as a diffusion process, analogous to heat diffusion. Less recognized is the fact that Fick also provided a detailed account of the implications of salt diffusion to transport through membranes. A careful look at Fick (1855) shows that his conceptualization of molecular diffusion was more comprehensive than could be captured with the mathematical methods available to him, and therefore his expression, referred to as Fick's Law, dealt only with salt flux. He viewed salt diffusion in liquids as a binary process, with salt moving in one way and water moving in the other. Fick's analysis of the consequences of such a binary process operating in a hydrophilic pore in a membrane offers insights that are relevant to earth systems. This paper draws attention to Fick's rationale, and its implications to hydrogeological systems. Fick (1829-1901; Figure 1), a gifted scientist, published the first book on medical physics (Fick, 1858), discussing the application of optics, solid mechanics, gas diffusion, and heat budget to biological systems. Fick's paper is divisible into two parts. The first describes his experimental verification of the applicability of Fourier's equation to liquid diffusion. The second is a detailed discussion of diffusion through a membrane. Although Fick's Law specifically quantifies solute flux, Fick visualized a simultaneous movement of water and stated, ''It is evident that a volume of water equal to that of the salt passes simultaneously out of the upper stratum into the lower.'' (Fick, 1855, p.30). Fick drew upon Fourier's model purely by analogy. He assumed that concentration gradient impelled salt movement, without inquiring why concentration gradient should constitute a driving force. As for water movement, he stated intuitively, ''a force of suction comes into play on each side of the membrane, proportional to the difference of concentration

  7. Soft bounds on diffusion produce skewed distributions and Gompertz growth.

    PubMed

    Mandrà, Salvatore; Lagomarsino, Marco Cosentino; Gherardi, Marco

    2014-09-01

    Constraints can affect dramatically the behavior of diffusion processes. Recently, we analyzed a natural and a technological system and reported that they perform diffusion-like discrete steps displaying a peculiar constraint, whereby the increments of the diffusing variable are subject to configuration-dependent bounds. This work explores theoretically some of the revealing landmarks of such phenomenology, termed "soft bound." At long times, the system reaches a steady state irreversibly (i.e., violating detailed balance), characterized by a skewed "shoulder" in the density distribution, and by a net local probability flux, which has entropic origin. The largest point in the support of the distribution follows a saturating dynamics, expressed by the Gompertz law, in line with empirical observations. Finally, we propose a generic allometric scaling for the origin of soft bounds. These findings shed light on the impact on a system of such "scaling" constraint and on its possible generating mechanisms.

  8. Soft bounds on diffusion produce skewed distributions and Gompertz growth

    NASA Astrophysics Data System (ADS)

    Mandrà, Salvatore; Lagomarsino, Marco Cosentino; Gherardi, Marco

    2014-09-01

    Constraints can affect dramatically the behavior of diffusion processes. Recently, we analyzed a natural and a technological system and reported that they perform diffusion-like discrete steps displaying a peculiar constraint, whereby the increments of the diffusing variable are subject to configuration-dependent bounds. This work explores theoretically some of the revealing landmarks of such phenomenology, termed "soft bound." At long times, the system reaches a steady state irreversibly (i.e., violating detailed balance), characterized by a skewed "shoulder" in the density distribution, and by a net local probability flux, which has entropic origin. The largest point in the support of the distribution follows a saturating dynamics, expressed by the Gompertz law, in line with empirical observations. Finally, we propose a generic allometric scaling for the origin of soft bounds. These findings shed light on the impact on a system of such "scaling" constraint and on its possible generating mechanisms.

  9. A diffuse interface Lox/hydrogen transcritical flame model

    NASA Astrophysics Data System (ADS)

    Gaillard, Pierre; Giovangigli, Vincent; Matuszewski, Lionel

    2016-05-01

    We present a diffuse-interface all-pressure flame model that transitions smoothly between subcritical and supercritical conditions. The model involves a non-equilibrium liquid/gas diffuse interface of van der Waals/Korteweg type embedded into a non-ideal multicomponent reactive fluid. The multicomponent transport fluxes are evaluated in their thermodynamic form in order to avoid singularities at thermodynamic mechanical stability limits. The model also takes into account condensing liquid water in order to avoid thermodynamic chemical instabilities. The resulting equations are used to investigate the interface between cold dense and hot light oxygen as well as the structure of diffusion flames between cold dense oxygen and gaseous-like hydrogen at all pressures, either subcritical or supercritical.

  10. History of Diffuse Optical Spectroscopy of Human Tissue

    NASA Astrophysics Data System (ADS)

    Huppert, Theodore J.

    Diffuse optical spectroscopy is a noninvasive method that uses low levels of near-infrared light to measure blood oxygenation in the brain. Over the last 35 years, the number of diffuse optical studies and the range of clinical and research applications have grown steadily. Compared to other neuroimaging methods to measure cerebral blood oxygenation, such as magnetic resonance imaging or positron emission tomography, diffuse optical imaging (DOI) is more cost effective and often uses small portable instrumentation. Wireless and bedside optical systems are currently produced commercially. The portability of these instruments has extended the use of optical methods into several unique applications including brain imaging in infants and children, studies of the brain during ambulatory tasks such as walking or balance, and interoperative brain assessments. This chapter will introduce the history and basic principles of DOI including discussion of the factors contributing to the optical properties of tissue, instrumentation, and an overview of applications of the technology.

  11. ALUMINUM IMPURITY DIFFUSION IN MAGNESIUM

    SciTech Connect

    Brennan, Sarah; Warren, Andrew; Coffey, Kevin; Kulkarni, Nagraj S; Todd, Peter J; Sohn, Yong Ho; Klimov, Mikhail

    2012-01-01

    The Al impurity diffusion in polycrystalline Mg (99.9%) via depth profiling with secondary ion mass spectrometry was studied in the temperature range of 673-573K, utilizing the thin film method and thin film solution to the diffusion equation. Multiple samples were utilized and multiple profiles were obtained to determine statistically confident coefficient with maximum standard deviation of 16%. Activation energy and pre-exponential factor of Al impurity diffusion in Mg was determined as 155 kJ/mole and 3.9 x 10-3 m2/sec.

  12. BEAM DIFFUSION MEASUREMENTS AT RHIC.

    SciTech Connect

    FLILLER,R.P.,IIIDREES,A.GASSNER,D.MCINTYRE,G.PEGGS,S.TRBOJEVIC,D.

    2003-05-12

    During a store, particles from the beam core continually diffuse outwards into the halo through a variety of mechanisms. Understanding the diffusion rate as a function of particle amplitude can help discover which processes are important to halo growth. A collimator can be used to measure the amplitude growth rate as a function of the particle amplitude. In this paper we present results of diffusion measurements performed at the Relativistic Heavy Ion Collider (RHIC) with fully stripped gold ions, deuterons, and protons. We compare these results with measurements from previous years, and simulations, and discuss any factors that relate to beam growth in RHIC.

  13. Diffuser for augmenting a wind turbine

    DOEpatents

    Foreman, Kenneth M.; Gilbert, Barry L.

    1984-01-01

    A diffuser for augmenting a wind turbine having means for energizing the boundary layer at several locations along the diffuser walls is improved by the addition of a short collar extending radially outward from the outlet of the diffuser.

  14. Improved diffuser for augmenting a wind turbine

    DOEpatents

    Foreman, K.M.; Gilbert, B.L.

    A diffuser for augmenting a wind turbine having means for energizing the boundary layer at several locations along the diffuser walls is improved by the addition of a short collar extending radially outward from the outlet of the diffuser.

  15. Floating-diffusion electrometer with adjustable sensitivity

    NASA Technical Reports Server (NTRS)

    Tower, John R. (Inventor)

    1989-01-01

    The effective capacitance of the floating diffusion in a floating-diffusion electrometer is modified to adjust electrometer sensitivity. This is done by changing the direct potential applied to a gate electrode proximate to the floating diffusion.

  16. Characterization and modeling of thermal diffusion and aggregation in nanofluids.

    SciTech Connect

    Gharagozloo, Patricia E.; Goodson, Kenneth E.

    2010-05-01

    Fluids with higher thermal conductivities are sought for fluidic cooling systems in applications including microprocessors and high-power lasers. By adding high thermal conductivity nanoscale metal and metal oxide particles to a fluid the thermal conductivity of the fluid is enhanced. While particle aggregates play a central role in recent models for the thermal conductivity of nanofluids, the effect of particle diffusion in a temperature field on the aggregation and transport has yet to be studied in depth. The present work separates the effects of particle aggregation and diffusion using parallel plate experiments, infrared microscopy, light scattering, Monte Carlo simulations, and rate equations for particle and heat transport in a well dispersed nanofluid. Experimental data show non-uniform temporal increases in thermal conductivity above effective medium theory and can be well described through simulation of the combination of particle aggregation and diffusion. The simulation shows large concentration distributions due to thermal diffusion causing variations in aggregation, thermal conductivity and viscosity. Static light scattering shows aggregates form more quickly at higher concentrations and temperatures, which explains the increased enhancement with temperature reported by other research groups. The permanent aggregates in the nanofluid are found to have a fractal dimension of 2.4 and the aggregate formations that grow over time are found to have a fractal dimension of 1.8, which is consistent with diffusion limited aggregation. Calculations show as aggregates grow the viscosity increases at a faster rate than thermal conductivity making the highly aggregated nanofluids unfavorable, especially at the low fractal dimension of 1.8. An optimum nanoparticle diameter for these particular fluid properties is calculated to be 130 nm to optimize the fluid stability by reducing settling, thermal diffusion and aggregation.

  17. Diffusing Wave Spectroscopy: Application for Blood Diagnostics

    NASA Astrophysics Data System (ADS)

    Meglinski, Igor; Tuchin, Valery V.

    This chapter describes the application of diffusing wave spectroscopy (DWS) for noninvasive characterization of skin blood flow and skin blood microcirculation in vivo. The DWS is a simple but ingenious approach, utilizing the loss of correlation of scattered laser light to observe the structural changes and displacement of scattering particles, such as red blood cells (RBC) within the biological tissues. This approach has the potential to be so specific that it can revolutionize the currently developed techniques for blood flow monitoring. Developments in DWS are likely to lead it to be used for characterization of skin blood microcirculation, to assess burn depth, to diagnose atherosclerotic disease, and investigate mechanisms of photodynamic therapy for cancer treatment, as well as to monitor pharmacological intervention for failing surgical skin flaps or replants.

  18. Blood oxygenation monitoring by diffuse optical tomography

    SciTech Connect

    Patachia, M; Dutu, D.C.A.; Dumitras, D.C.

    2011-01-24

    Diffuse optical tomography (DOT) makes it possible to reconstruct, in two or three dimensions, the internal structure of the biological tissues based on the distribution of the absorption coefficient and the reduced scattering coefficient, using optical measurements at multiple source - detector positions on the tissue surface. The measurement of the light intensity transmitted through the tissue can be also used to compute the haemoglobin and oxyhaemoglobin concentrations, measuring the selective absorption of the main blood chromophores by near infrared spectroscopy (NIRS). The spectral selectivity of the system and the evaluation of the blood volume and blood oxygenation (BV and OXY distributions), together with the reconstruction of the inner structure of the tissue, can improve the accuracy of early cancer diagnosis, based on the tissue angiogenesis characterisation. (application of lasers and laser-optical methods in life sciences)

  19. Time-resolved optical diffusion tomography

    NASA Astrophysics Data System (ADS)

    Appledorn, C. Robert; Kruger, Robert A.; Liu, Pingyu

    1994-05-01

    A mathematical model is proposed describing time-resolved output measurements obtained on the surface of a diffusely scattering body due to an input pulse of near-IR light at a different location also on the surface. Such measurements can be obtained using a pulsed near-IR laser coupled with a CCD streak camera. The scattering body is assumed to exhibit homogenous scattering and spatially varying absorption. Using this model, an iterative algorithm is derived using maximum likelihood methods that allows the reconstruction of the spatial absorption pattern from a set of time-resolved tomographic measurements. The methodology places no restrictions upon the time-of-arrival of the detected photons, thus permitting the entire time-resolved signal to be used in the reconstruction process. The reconstruction algorithm is easily initialized and preliminary results indicate that stable reconstructions can be performed.

  20. Region-of-interest diffuse optical tomography system

    NASA Astrophysics Data System (ADS)

    Saikia, Manob Jyoti; Kanhirodan, Rajan

    2016-01-01

    Diffuse optical tomography (DOT) using near-infrared light is a promising tool for non-invasive imaging of deep tissue. This technique is capable of quantitative reconstruction of absorption (μa) and scattering coefficient (μs) inhomogeneities in the tissue. The rationale for reconstructing the optical property map is that the absorption coefficient variation provides diagnostic information about metabolic and disease states of the tissue. The aim of DOT is to reconstruct the internal tissue cross section with good spatial resolution and contrast from noisy measurements non-invasively. We develop a region-of-interest scanning system based on DOT principles. Modulated light is injected into the phantom/tissue through one of the four light emitting diode sources. The light traversing through the tissue gets partially absorbed and scattered multiple times. The intensity and phase of the exiting light are measured using a set of photodetectors. The light transport through a tissue is diffusive in nature and is modeled using radiative transfer equation. However, a simplified model based on diffusion equation (DE) can be used if the system satisfies following conditions: (a) the optical parameter of the inhomogeneity is close to the optical property of the background, and (b) μs of the medium is much greater than μa (μs > > μa). The light transport through a highly scattering tissue satisfies both of these conditions. A discrete version of DE based on finite element method is used for solving the inverse problem. The depth of probing light inside the tissue depends on the wavelength of light, absorption, and scattering coefficients of the medium and the separation between the source and detector locations. Extensive simulation studies have been carried out and the results are validated using two sets of experimental measurements. The utility of the system can be further improved by using multiple wavelength light sources. In such a scheme, the spectroscopic

  1. On the detection of rubidium in diffuse interstellar clouds

    NASA Technical Reports Server (NTRS)

    Federman, S. R.; Sneden, C.; Schempp, W. V.; Smith, W. H.

    1985-01-01

    A search for absorption from neutral rubidium at 7800 A was conducted. No evidence for absorption to a 3 sigma limit of less than 1.5 mA was seen in the diffuse interstellar gas toward the stars omicron Persei, zeta Persei, and zeta Ophiuchi. Present results do not confirm the detection by Jura and Smith (1981) toward zeta Oph. A possible reason for the discrepancy is presented. In light of the present measurements, the abundance of interstellar rubidium in reconsidered.

  2. Diffusive suppression of AC-Stark shifts in atomic magnetometers

    PubMed Central

    Sulai, I. A.; Wyllie, R.; Kauer, M.; Smetana, G. S.; Wakai, R. T.; Walker, T. G.

    2016-01-01

    In atomic magnetometers, the vector AC-Stark shift associated with circularly polarized light generates spatially varying effective magnetic fields, which limit the magnetometer response and serve as sources of noise. We describe a scheme whereby optically pumping a small subvolume of the magnetometer cell and relying on diffusion to transport polarized atoms allows a magnetometer to be operated with minimal sensitivity to the AC-Stark field. © 2013 Optical Society of America PMID:23503278

  3. Influence of Diffused Solar Radiation on the Solar Concentrating System of a Plant Shoot Configuration

    NASA Astrophysics Data System (ADS)

    Obara, Shin'ya

    Investigation of a plant shoot configuration is used to obtain valuable information concerning the received light system. Additionally, analysis results concerning a plant shoot configuration interaction with direct solar radiation were taken from a past study. However, in order to consider a plant shoot as a received sunlight system, it is necessary to understand the received light characteristics of both direct solar radiation and diffused solar radiation. Under a clear sky, the ratio of direct solar radiation to diffused solar radiation is large. However, under a clouded sky, the amount of diffused solar radiation becomes larger. Therefore, in this paper, we investigate the received light characteristics of a plant shoot configuration under the influence of diffused solar radiation. As a result, we clarify the relationship between the amount of diffused solar radiation and the amount of received light as a function of the characteristics of the plant shoot configuration. In order to obtain diffused solar radiation, it is necessary to correspond to the radiation of the multi-directions. In the analysis, the characteristic of the difference in arrangement of the top leaf and the other leaf was obtained. Therefore, in analysis, leaves other than the top were distributed in the wide range.

  4. Flow development through interturbine diffusers

    SciTech Connect

    Dominy, R.G.; Kirkham, D.A.; Smith, A.D.

    1998-04-01

    Interturbine diffusers offer the potential advantage of reducing the flow coefficient in the following stages, leading to increased efficiency. The flows associated with these ducts differ from those in simple annular diffusers both as a consequence of their high-curvature S-shaped geometry and of the presence of wakes created by the upstream turbine. Experimental data and numerical simulations clearly reveal the generation of significant secondary flows as the flow develops through the diffuser in the presence of cross-passage pressure gradients. The further influence of inlet swirl is also demonstrated. Data from experimental measurements with and without an upstream turbine are discussed and computational simulations are shown not only to give a good prediction of the flow development within the diffuser but also to demonstrate the importance of modeling the fully three-dimensional nature of the flow.

  5. Diffusion technique stabilizes resistor values

    NASA Technical Reports Server (NTRS)

    Gallagher, R. C.; Giuliano, M. N.

    1966-01-01

    Reduction of the contact resistance stabilizes the values, over a broad temperature range, of resistors used in linear integrated circuits. This reduction is accomplished by p-plus diffusion under the alloyed aluminum contacts.

  6. Geometric diffusion of quantum trajectories.

    PubMed

    Yang, Fan; Liu, Ren-Bao

    2015-07-16

    A quantum object can acquire a geometric phase (such as Berry phases and Aharonov-Bohm phases) when evolving along a path in a parameter space with non-trivial gauge structures. Inherent to quantum evolutions of wavepackets, quantum diffusion occurs along quantum trajectories. Here we show that quantum diffusion can also be geometric as characterized by the imaginary part of a geometric phase. The geometric quantum diffusion results from interference between different instantaneous eigenstate pathways which have different geometric phases during the adiabatic evolution. As a specific example, we study the quantum trajectories of optically excited electron-hole pairs in time-reversal symmetric insulators, driven by an elliptically polarized terahertz field. The imaginary geometric phase manifests itself as elliptical polarization in the terahertz sideband generation. The geometric quantum diffusion adds a new dimension to geometric phases and may have applications in many fields of physics, e.g., transport in topological insulators and novel electro-optical effects.

  7. Fractional-calculus diffusion equation

    PubMed Central

    2010-01-01

    Background Sequel to the work on the quantization of nonconservative systems using fractional calculus and quantization of a system with Brownian motion, which aims to consider the dissipation effects in quantum-mechanical description of microscale systems. Results The canonical quantization of a system represented classically by one-dimensional Fick's law, and the diffusion equation is carried out according to the Dirac method. A suitable Lagrangian, and Hamiltonian, describing the diffusive system, are constructed and the Hamiltonian is transformed to Schrodinger's equation which is solved. An application regarding implementation of the developed mathematical method to the analysis of diffusion, osmosis, which is a biological application of the diffusion process, is carried out. Schrödinger's equation is solved. Conclusions The plot of the probability function represents clearly the dissipative and drift forces and hence the osmosis, which agrees totally with the macro-scale view, or the classical-version osmosis. PMID:20492677

  8. Uphill diffusion in multicomponent mixtures.

    PubMed

    Krishna, Rajamani

    2015-05-21

    Molecular diffusion is an omnipresent phenomena that is important in a wide variety of contexts in chemical, physical, and biological processes. In the majority of cases, the diffusion process can be adequately described by Fick's law that postulates a linear relationship between the flux of any species and its own concentration gradient. Most commonly, a component diffuses down the concentration gradient. The major objective of this review is to highlight a very wide variety of situations that cause the uphill transport of one constituent in the mixture. Uphill diffusion may occur in multicomponent mixtures in which the diffusion flux of any species is strongly coupled to that of its partner species. Such coupling effects often arise from strong thermodynamic non-idealities. For a quantitative description we need to use chemical potential gradients as driving forces. The transport of ionic species in aqueous solutions is coupled with its partner ions because of the electro-neutrality constraints; such constraints may accelerate or decelerate a specific ion. When uphill diffusion occurs, we observe transient overshoots during equilibration; the equilibration process follows serpentine trajectories in composition space. For mixtures of liquids, alloys, ceramics and glasses the serpentine trajectories could cause entry into meta-stable composition zones; such entry could result in phenomena such as spinodal decomposition, spontaneous emulsification, and the Ouzo effect. For distillation of multicomponent mixtures that form azeotropes, uphill diffusion may allow crossing of distillation boundaries that are normally forbidden. For mixture separations with microporous adsorbents, uphill diffusion can cause supra-equilibrium loadings to be achieved during transient uptake within crystals; this allows the possibility of over-riding adsorption equilibrium for achieving difficult separations.

  9. Boron diffusion in silicon devices

    DOEpatents

    Rohatgi, Ajeet; Kim, Dong Seop; Nakayashiki, Kenta; Rounsaville, Brian

    2010-09-07

    Disclosed are various embodiments that include a process, an arrangement, and an apparatus for boron diffusion in a wafer. In one representative embodiment, a process is provided in which a boric oxide solution is applied to a surface of the wafer. Thereafter, the wafer is subjected to a fast heat ramp-up associated with a first heating cycle that results in a release of an amount of boron for diffusion into the wafer.

  10. Visualization of Diffusion within Nanoarrays.

    PubMed

    Liu, Yang; Holzinger, Angelika; Knittel, Peter; Poltorak, Lukasz; Gamero-Quijano, Alonso; Rickard, William D A; Walcarius, Alain; Herzog, Grégoire; Kranz, Christine; Arrigan, Damien W M

    2016-07-01

    The direct experimental characterization of diffusion processes at nanoscale remains a challenge that could help elucidate processes in biology, medicine and technology. In this report, two experimental approaches were employed to visualize ion diffusion profiles at the orifices of nanopores (radius (ra) of 86 ± 6 nm) in array format: (1) electrochemically assisted formation of silica deposits based on surfactant ion transfer across nanointerfaces between two immiscible electrolyte solutions (nanoITIES); (2) combined atomic force - scanning electrochemical microscopy (AFM-SECM) imaging of topography and redox species diffusion through the nanopores. The nature of the diffusion zones formed around the pores is directly related to the interpore distance within the array. Nanopore arrays with different ratios of pore center-to-center separation (rc) to pore radius (ra) were fabricated by focused ion beam (FIB) milling of silicon nitride (SiN) membranes, with 100 pores in a hexagonal arrangement. The ion diffusion profiles determined by the two visualization methods indicated the formation of overlapped or independent diffusion profiles at nanopore arrays with rc/ra ratios of 21 ± 2 and 91 ± 7, respectively. In particular, the silica deposition method resulted in formation of a single deposit encompassing the complete array with closer nanopore arrangement, whereas individual silica deposits were formed around each nanopore within the more widely spaced array. The methods reveal direct experimental evidence of diffusion zones at nanopore arrays and provide practical illustration that the pore-pore separation within such arrays has a significant impact on diffusional transport as the pore size is reduced to the nanoscale. These approaches to nanoscale diffusion zone visualization open up possibilities for better understanding of molecular transport processes within miniaturized systems. PMID:27264360

  11. Uphill diffusion in multicomponent mixtures.

    PubMed

    Krishna, Rajamani

    2015-05-21

    Molecular diffusion is an omnipresent phenomena that is important in a wide variety of contexts in chemical, physical, and biological processes. In the majority of cases, the diffusion process can be adequately described by Fick's law that postulates a linear relationship between the flux of any species and its own concentration gradient. Most commonly, a component diffuses down the concentration gradient. The major objective of this review is to highlight a very wide variety of situations that cause the uphill transport of one constituent in the mixture. Uphill diffusion may occur in multicomponent mixtures in which the diffusion flux of any species is strongly coupled to that of its partner species. Such coupling effects often arise from strong thermodynamic non-idealities. For a quantitative description we need to use chemical potential gradients as driving forces. The transport of ionic species in aqueous solutions is coupled with its partner ions because of the electro-neutrality constraints; such constraints may accelerate or decelerate a specific ion. When uphill diffusion occurs, we observe transient overshoots during equilibration; the equilibration process follows serpentine trajectories in composition space. For mixtures of liquids, alloys, ceramics and glasses the serpentine trajectories could cause entry into meta-stable composition zones; such entry could result in phenomena such as spinodal decomposition, spontaneous emulsification, and the Ouzo effect. For distillation of multicomponent mixtures that form azeotropes, uphill diffusion may allow crossing of distillation boundaries that are normally forbidden. For mixture separations with microporous adsorbents, uphill diffusion can cause supra-equilibrium loadings to be achieved during transient uptake within crystals; this allows the possibility of over-riding adsorption equilibrium for achieving difficult separations. PMID:25761383

  12. Diffusion in silicate melts: III. Empirical models for multicomponent diffusion

    NASA Astrophysics Data System (ADS)

    Yan, Liang; Richter, Frank M.; Chamberlin, Laurinda

    1997-12-01

    Empirical models for multicomponent diffusion in an isotropic fluid were derived by splitting the component's dispersion velocity into two parts: (a) an intrinsic velocity which is proportional to each component's electrochemical potential gradient and independent of reference frame and (b) a net interaction velocity which is both model and reference frame dependent. Simple molecules (e.g., M pO q) were chosen as endmember components. The interaction velocity is assumed to be either the same for each component (leading to a common relaxation velocity U) or proportional to a common interaction force ( F). U or F is constrained by requiring no local buildup in either volume or charge. The most general form of the model-derived diffusion matrix [ D] can be written as a product of a model-dependent kinetic matrix [ L] and a model independent thermodynamic matrix [ G], [ D] = [ L] · [ G]. The elements of [ G] are functions of derivatives of chemical potential with respect to concentration. The elements of [ L] are functions of concentration and partial molar volume of the endmember components, Cio and Vio, and self diffusivity Di, and charge number zi of individual diffusing species. When component n is taken as the dependent variable they can be written in a common form L ij = D jδ ij + C io[V noD n - V joD j)A i + (p nz nD n - p jz jD j)B i] where the functional forms of the scaling factors Ai and Bi depend on the model considered. The off-diagonal element Lij ( i ≠ j) is directly proportional to the concentration of component i, and thus negligible when i is a dilute component. The salient feature of kinetic interaction or relaxation is to slow down larger (volume or charge) and faster diffusing components and to speed up smaller (volume or charge) and slower moving species, in order to prevent local volume or charge buildup. Empirical models for multicomponent diffusion were tested in the ternary system CaOAl 2O 3SiO 2 at 1500°C and 1 GPa over a large

  13. Lipid diffusion in alcoholic environment.

    PubMed

    Rifici, Simona; Corsaro, Carmelo; Crupi, Cristina; Nibali, Valeria Conti; Branca, Caterina; D'Angelo, Giovanna; Wanderlingh, Ulderico

    2014-08-01

    We have studied the effects of a high concentration of butanol and octanol on the phase behavior and on the lateral mobility of 1,2-palmitoyl-sn-glycero-3-phosphocholine (DPPC) by means of differential scanning calorimetry and pulsed-gradient stimulated-echo (PGSTE) NMR spectroscopy. A lowering of the lipid transition from the gel to the liquid-crystalline state for the membrane-alcohol systems has been observed. NMR measurements reveal three distinct diffusions in the DPPC-alcohol systems, characterized by a high, intermediate, and slow diffusivity, ascribed to the water, the alcohol, and the lipid, respectively. The lipid diffusion process is promoted in the liquid phase while it is hindered in the interdigitated phase due to the presence of alcohols. Furthermore, in the interdigitated phase, lipid lateral diffusion coefficients show a slight temperature dependence. To the best of our knowledge, this is the first time that lateral diffusion coefficients on alcohol with so a long chain, and at low temperatures, are reported. By the Arrhenius plots of the temperature dependence of the diffusion coefficients, we have evaluated the apparent activation energy in both the liquid and in the interdigitated phase. The presence of alcohol increases this value in both phases. An explanation in terms of a free volume model that takes into account also for energy factors is proposed.

  14. Gibbs Ringing in Diffusion MRI

    PubMed Central

    Veraart, Jelle; Fieremans, Els; Jelescu, Ileana O.; Knoll, Florian; Novikov, Dmitry S.

    2016-01-01

    Purpose To study and reduce the effect of Gibbs ringing artifact on computed diffusion parameters. Methods We reduce the ringing by extrapolating the k-space of each diffusion weighted image beyond the measured part by selecting an adequate regularization term. We evaluate several regularization terms and tune the regularization parameter to find the best compromise between anatomical accuracy of the reconstructed image and suppression of the Gibbs artifact. Results We demonstrate empirically and analytically that the Gibbs artifact, which is typically observed near sharp edges in magnetic resonance images, has a significant impact on the quantification of diffusion model parameters, even for infinitesimal diffusion weighting. We find the second order total generalized variation to be a good choice for the penalty term to regularize the extrapolation of the k-space, as it provides a parsimonious representation of images, a practically full suppression of Gibbs ringing, and the absence of staircasing artifacts typical for total variation methods. Conclusions Regularized extrapolation of the k-space data significantly reduces truncation artifacts without compromising spatial resolution in comparison to the default option of window filtering. In particular, accuracy of estimating diffusion tensor imaging and diffusion kurtosis imaging parameters improves so much that unconstrained fits become possible. PMID:26257388

  15. Osmosis and Diffusion Conceptual Assessment

    PubMed Central

    Fisher, Kathleen M.; Williams, Kathy S.; Lineback, Jennifer Evarts

    2011-01-01

    Biology student mastery regarding the mechanisms of diffusion and osmosis is difficult to achieve. To monitor comprehension of these processes among students at a large public university, we developed and validated an 18-item Osmosis and Diffusion Conceptual Assessment (ODCA). This assessment includes two-tiered items, some adopted or modified from the previously published Diffusion and Osmosis Diagnostic Test (DODT) and some newly developed items. The ODCA, a validated instrument containing fewer items than the DODT and emphasizing different content areas within the realm of osmosis and diffusion, better aligns with our curriculum. Creation of the ODCA involved removal of six DODT item pairs, modification of another six DODT item pairs, and development of three new item pairs addressing basic osmosis and diffusion concepts. Responses to ODCA items testing the same concepts as the DODT were remarkably similar to responses to the DODT collected from students 15 yr earlier, suggesting that student mastery regarding the mechanisms of diffusion and osmosis remains elusive. PMID:22135375

  16. Functional imaging of small tissue volumes with diffuse optical tomography

    NASA Astrophysics Data System (ADS)

    Klose, Alexander D.; Hielscher, Andreas H.

    2006-03-01

    Imaging of dynamic changes in blood parameters, functional brain imaging, and tumor imaging are the most advanced application areas of diffuse optical tomography (DOT). When dealing with the image reconstruction problem one is faced with the fact that near-infrared photons, unlike X-rays, are highly scattered when they traverse biological tissue. Image reconstruction schemes are required that model the light propagation inside biological tissue and predict measurements on the tissue surface. By iteratively changing the tissue-parameters until the predictions agree with the real measurements, a spatial distribution of optical properties inside the tissue is found. The optical properties can be related to the tissue oxygenation, inflammation, or to the fluorophore concentration of a biochemical marker. If the model of light propagation is inaccurate, the reconstruction process will lead to an inaccurate result as well. Here, we focus on difficulties that are encountered when DOT is employed for functional imaging of small tissue volumes, for example, in cancer studies involving small animals, or human finger joints for early diagnosis of rheumatoid arthritis. Most of the currently employed image reconstruction methods rely on the diffusion theory that is an approximation to the equation of radiative transfer. But, in the cases of small tissue volumes and tissues that contain low scattering regions diffusion theory has been shown to be of limited applicability Therefore, we employ a light propagation model that is based on the equation of radiative transfer, which promises to overcome the limitations.

  17. Brightness property of micro-capsules diffuser screen in laser projection display

    NASA Astrophysics Data System (ADS)

    Kondo, Jun; Okagaki, Satoru; Kojima, Kuniko; Nakano, Yuzo; Miyata, Akihisa

    2016-03-01

    In recent years, the development of displays, projectors, and the like which use laser light sources have been advanced. As a laser light source is used, it provide wide color gamut and compact an optical system; on the other hand, the speckle noise is generated. We make a proposal about the microcapsule diffuser screen with the purpose of reducing the speckle noise on a laser rear projection display. This microcapsule diffuser screen has a screen surface in which microcapsules (~100um) containing charged diffuser particles are applied; where an electric field is charged from the outside and, thus, the diffuser particles in the capsule are randomly agitated to reduce the speckle noise. We have separately reported the effect of reducing speckle in relation to the driving parameters. The previous report, however, did not discuss how the configuration parameters within the microcapsule would affect the brightness, diffusion characteristics and other particulars. In this report, the authors used the Monte Carlo ray tracing method to study the diffusion characteristics of the microcapsule diffuser sheet with reference to the refractive index and diameters of the diffuser particles. The study confirmed that while the diffusion characteristics lowered with the diffuser particle diameter being 3.0μm or smaller the optical loss of the transmitting light significantly increased. Where designing the capsule profile based on the simulation model, a simple spherical profile failed to see that the actual measurement and calculated values did not agree with the other. The optical simulation model created based on a microscopic image confirmed that both values agreed. Thus, the authors confirmed that the latter was suitable for an optical simulation model.

  18. Enhanced photocoagulation with catheter-based diffusing optical device

    NASA Astrophysics Data System (ADS)

    Kang, Hyun Wook; Kim, Jeehyun; Oh, Jungwhan

    2012-11-01

    A novel balloon catheter-based diffusing optical device was designed and evaluated to assist in treating excessive menstrual bleeding. A synthetic fused-silica fiber was micro-machined precisely to create scattering segments on a 25 mm long fiber tip for uniform light distribution. A visible wavelength (λ=532 nm) was used to specifically target the endometrium due to the high vascularity of the uterine wall. Optical simulation presented 30% wider distribution of photons along with approximately 40% higher irradiance induced by addition of a glass cap to the diffuser tip. Incorporation of the optical diffuser with a polyurethane balloon catheter considerably enhanced coagulation depth and area (i.e., 3.5 mm and 18.9 cm2 at 1 min irradiation) in tissue in vitro. The prototype device demonstrated the coagulation necrosis of 2.8±1.2 mm (n=18) and no thermal damage to myometrium in in vivo caprine models. A prototype 5 cm long balloon catheter-assisted optical diffuser was also evaluated with a cadaveric human uterus to confirm the coagulative response of the uterine tissue as well as to identify the further design improvement and clinical applicability. The proposed catheter-based diffusing optical device can be a feasible therapeutic tool to photocoagulate endometrial cell layers in an efficient and safe manner.

  19. Rewiring the network. What helps an innovation to diffuse?

    NASA Astrophysics Data System (ADS)

    Sznajd-Weron, Katarzyna; Szwabiński, Janusz; Weron, Rafał; Weron, Tomasz

    2014-03-01

    A fundamental question related to innovation diffusion is how the structure of the social network influences the process. Empirical evidence regarding real-world networks of influence is very limited. On the other hand, agent-based modeling literature reports different, and at times seemingly contradictory, results. In this paper we study innovation diffusion processes for a range of Watts-Strogatz networks in an attempt to shed more light on this problem. Using the so-called Sznajd model as the backbone of opinion dynamics, we find that the published results are in fact consistent and allow us to predict the role of network topology in various situations. In particular, the diffusion of innovation is easier on more regular graphs, i.e. with a higher clustering coefficient. Moreover, in the case of uncertainty—which is particularly high for innovations connected to public health programs or ecological campaigns—a more clustered network will help the diffusion. On the other hand, when social influence is less important (i.e. in the case of perfect information), a shorter path will help the innovation to spread in the society and—as a result—the diffusion will be easiest on a random graph.

  20. Lighting Options for Homes.

    SciTech Connect

    Baker, W.S.

    1991-04-01

    This report covers many aspects of various lighting options for homes. Types of light sources described include natural light, artificial light, incandescent lamps, fluorescent lamps, and high intensity discharge lamps. A light source selection guide gives the physical characteristics of these, design considerations, and common applications. Color, strategies for efficient lighting, and types of lighting are discussed. There is one section giving tips for various situations in specific rooms. Rooms and types of fixtures are shown on a matrix with watts saved by using the recommended type lighting for that room and room location. A major emphasis of this report is saving energy by utilizing the most suitable, recommended lighting option. (BN)