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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. 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

  4. Using light transmission to watch hydrogen diffuse.

    PubMed

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

    2012-06-12

    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.

  5. 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

  6. 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.

  7. The relevance of light diffusion profiles for interstitial PDT using light-diffusing optical fibers

    NASA Astrophysics Data System (ADS)

    Stringasci, Mirian D.; Fortunato, Thereza C.; Moriyama, Lilian T.; Vollet Filho, José Dirceu; Bagnato, Vanderlei S.; Kurachi, Cristina

    2017-02-01

    Photodynamic therapy (PDT) is a technique used for several tumor types treatment. Light penetration on biological tissue is one limiting factor for PDT applied to large tumors. An alternative is using interstitial PDT, in which optical fibers are inserted into tumors. Cylindrical diffusers have been used in interstitial PDT. Light emission of different diffusers depends on the manufacturing process, size and optical properties of fibers, which make difficult to establish an adequate light dosimetry, since usually light profile is not designed for direct tissue-fiber contact. This study discusses the relevance of light distribution by a cylindrical diffuser into a turbid lipid emulsion solution, and how parts of a single diffuser contribute to illumination. A 2 cm-long cylindrical diffuser optical fiber was connected to a diode laser (630 nm), and the light spatial distribution was measured by scanning the solution with a collection probe. From the light field profile generated by a 1 mm-long intermediary element of a 20 mm-long cylindrical diffuser, recovery of light distribution for the entire diffuser was obtained. PDT was performed in rat healthy liver for a real treatment outcome analysis. By using computational tools, a typical necrosis profile generated by the irradiation with such a diffuser fiber was reconstructed. The results showed that it was possible predicting theoretically the shape of a necrosis profile in a healthy, homogeneous tissue with reasonable accuracy. The ability to predict the necrosis profile obtained from an interstitial illumination by optical diffusers has the potential improve light dosimetry for interstitial PDT.

  8. Phase Transitions in Diffusion of Light

    NASA Astrophysics Data System (ADS)

    Rezvani Naraghi, Roxana; Dogariu, Aristide

    2016-12-01

    It has been a long time belief that, with increasing the scattering strength of multiple scattering media, the transport of light gradually slows down and, eventually, comes to a halt corresponding to a localized state. Here we present experimental evidence that different stages emerge in this evolution, which cannot be described by classical diffusion with conventional scaling arguments. A microscopic model captures the relevant aspects of electromagnetic wave propagation and explains the competing mechanisms that prevent the three-dimensional wave localization. We demonstrate that strong evanescent-field couplings hinder the localization of wave resonances and, therefore, impede the slowing down of diffusion. The emerging out of equilibrium steady-state process resembles the diffusion of classical particles in spatially correlated random potentials and the thermalization of matter waves due to atomic collisions.

  9. The metallicity of diffuse intrahalo light

    NASA Astrophysics Data System (ADS)

    Purcell, Chris W.; Bullock, James S.; Zentner, Andrew R.

    2008-12-01

    We make predictions for the metallicity of diffuse stellar components in systems ranging from small spiral galaxies to rich galaxy clusters. We extend the formalism of Purcell, Bullock & Zentner, in which diffuse stellar mass is produced via galaxy disruption, and we convolve this result with the observed mass-metallicity relation for galaxies in order to analyse the chemical abundance of intrahalo light (IHL) in host haloes with virial mass 1010.5 <= Mhost <= 1015Msolar. We predict a steep rise of roughly 2 dex in IHL metallicity from the scales of small to large spiral galaxies. In terms of the total dynamical mass Mhost of the host systems under consideration, we predict diffuse light metallicities ranging from ZIHL <~ -2.5 for Mhost ~ 1011Msolar to ZIHL ~ -1.0 for Mhost ~ 1012Msolar. In larger systems, we predict a more shallow rise in this trend with ZIHL ~ -0.4 for Mhost ~ 1013Msolar, increasing to ZIHL ~ 0.1 for Mhost ~ 1015Msolar. This behaviour is coincident with a narrowing of the intrahalo metallicity distribution as host mass increases. The observable distinction in surface brightness between old, metal-poor IHL stars and more metal rich, dynamically younger tidal streams is of crucial importance when estimating the chemical abundance of an intrahalo population with multiple origins.

  10. The Diffuse Light of the Universe

    NASA Astrophysics Data System (ADS)

    Bonnet-Bidaud, Jean-Marc

    2017-06-01

    In 1965, the discovery of a new type of uniform radiation, located between radiowaves and infrared light, was accidental. Known today as Cosmic Microwave background (CMB), this diffuse radiation is commonly interpreted as a fossil light released in an early hot and dense universe and constitutes today the main 'pilar' of the big bang cosmology. Considerable efforts have been devoted to derive fundamental cosmological parameters from the characteristics of this radiation that led to a surprising universe that is shaped by at least three major unknown components: inflation, dark matter and dark energy. This is an important weakness of the present consensus cosmological model that justifies raising several questions on the CMB interpretation. Can we consider its cosmological nature as undisputable? Do other possible interpretations exist in the context of other cosmological theories or simply as a result of other physical mechanisms that could account for it? In an effort to questioning the validity of scientific hypotheses and the under-determination of theories compared to observations, we examine here the difficulties that still exist on the interpretation of this diffuse radiation and explore other proposed tracks to explain its origin. We discuss previous historical concepts of diffuse radiation before and after the CMB discovery and underline the limit of our present understanding.

  11. Human vision is attuned to the diffuseness of natural light

    PubMed Central

    Morgenstern, Yaniv; Geisler, Wilson S.; Murray, Richard F.

    2014-01-01

    All images are highly ambiguous, and to perceive 3-D scenes, the human visual system relies on assumptions about what lighting conditions are most probable. Here we show that human observers' assumptions about lighting diffuseness are well matched to the diffuseness of lighting in real-world scenes. We use a novel multidirectional photometer to measure lighting in hundreds of environments, and we find that the diffuseness of natural lighting falls in the same range as previous psychophysical estimates of the visual system's assumptions about diffuseness. We also find that natural lighting is typically directional enough to override human observers' assumption that light comes from above. Furthermore, we find that, although human performance on some tasks is worse in diffuse light, this can be largely accounted for by intrinsic task difficulty. These findings suggest that human vision is attuned to the diffuseness levels of natural lighting conditions. PMID:25139864

  12. 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 %.

  13. Photoacoustic-guided convergence of light through optically diffusive media.

    PubMed

    Kong, Fanting; Silverman, Ronald H; Liu, Liping; Chitnis, Parag V; Lee, Kotik K; Chen, Y C

    2011-06-01

    We demonstrate that laser beams can be converged toward a light-absorbing target through optically diffusive media by using photoacoustic-guided interferometric focusing. The convergence of light is achieved by shaping the wavefront of the incident light with a deformable mirror to maximize the photoacoustic signal, which is proportional to the scattered light intensity at the light absorber.

  14. Photoacoustic-guided convergence of light through optically diffusive media

    PubMed Central

    Kong, Fanting; Silverman, Ronald H.; Liu, Liping; Chitnis, Parag V.; Lee, Kotik K.; Chen, Y. C.

    2012-01-01

    We demonstrate that laser beams can be converged toward a light-absorbing target through optically diffusive media by using photoacoustic-guided interferometric focusing. The convergence of light is achieved by shaping the wavefront of the incident light with a deformable mirror to maximize the photoacoustic signal, which is propor tional to the scattered light intensity at the light absorber. PMID:21633446

  15. 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.

  16. Use of diffusive optical fibers for plant lighting

    NASA Astrophysics Data System (ADS)

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

    1994-03-01

    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.

  17. 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.

  18. 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.

  19. The faint galaxy contribution to the diffuse extragalactic background light

    NASA Technical Reports Server (NTRS)

    Cole, Shaun; Treyer, Marie-Agnes; Silk, Joseph

    1992-01-01

    Models of the faint galaxy contribution to the diffuse extragalactic background light are presented, which are consistent with current data on faint galaxy number counts and redshifts. The autocorrelation function of surface brightness fluctuations in the extragalactic diffuse light is predicted, and the way in which these predictions depend on the cosmological model and assumptions of biasing is determined. It is confirmed that the recent deep infrared number counts are most compatible with a high density universe (Omega-0 is approximately equal to 1) and that the steep blue counts then require an extra population of rapidly evolving blue galaxies. The faintest presently detectable galaxies produce an interesting contribution to the extragalactic diffuse light, and still fainter galaxies may also produce a significant contribution. These faint galaxies still only produce a small fraction of the total optical diffuse background light, but on scales of a few arcminutes to a few degrees, they produce a substantial fraction of the fluctuations in the diffuse light.

  20. 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.

  1. 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.

  2. 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.

  3. Use of diffusive optical fibers for plant lighting

    SciTech Connect

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

    1994-12-31

    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. Kitaya et al. (1988) developed a lighting system in which two rooting beds were arranged; one above and the other under fluorescent lamps. Lettuce plants grew normally in the lower bed and suspended upside-down under the upper bed. The lettuce plants suspended upside-down were given the light in upward direction (upward lighting). No significant difference in growth, development and morphology was found between the lettuce plants grown by the downward and upward lighting. Combining upward and downward lighting, improved spacing efficiency and reduced electricity cost per plant compared with conventional, downward lighting. From the above example, when designing a lighting system for plants with lamps more lighting direction should be considered. 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 reduced space with sideward lighting system than with a downward lighting system. An application of the sideward lighting system using diffusive optical fiber belts is described and advantages and disadvantages are discussed.

  4. Study of diffuse light in cD galaxy clusters

    NASA Astrophysics Data System (ADS)

    Scheick, Xania Nettie

    1993-01-01

    Conventionally, the gravitational potential of galaxy clusters has been mapped using the galaxies themselves or x-rays as test particles. Using the intra-cluster medium or diffuse light instead has the obvious advantage in sheer number of particles, i.e. better counting statistics. Analysis of diffuse light in two cD clusters (A2670 and A2029) is described. Deep R-band CCD images of these clusters were procured at the KPNO 36 in. and 2.1 m telescopes. On large scales, the diffuse light is well fit by a de Vaucouleurs' profile. This 'smoothness' is surprising in light of current cluster evolution theory which relies on violent interactions among cluster members. Thus we are motivated to study the diffuse light on small scales, expecting a priori to see clumpiness in the medium due to collisional or tidal stripping mechanisms or the affects of dynamical friction. Using a statistical approach, we have determined the source of the diffuse light to be numerous low luminosity objects. The clumpiness of the diffuse light in both clusters is described by auto correlations of the residual images (after diffuse light has been removed). From this analysis, we can determine a spatial scale of the clumps and attempt to place some constraints on the faint end of the cluster luminosity function. For A2670, we compute a differential luminosity function in the cluster center that suggests real differences in the luminosity function within the cluster center from a universal cluster luminosity function. We measure the V-R color of the cD and cluster galaxies and the color gradient across the halo of A2670. In A2029, we find structures associated with five galaxies suggestive of wakes, i.e. the gravitational response of the medium to galactic passage. The apparent lack of significant small-scale structure poses a curious problem for cluster evolution models.

  5. Impact of ultraviolet light during rapid thermal diffusion

    NASA Astrophysics Data System (ADS)

    Noël, S.; Ventura, L.; Slaoui, A.; Muller, J. C.; Groh, B.; Schindler, R.; Fröschle, B.; Theiler, T.

    1998-05-01

    Rapid thermal processing for junction formation is emerging as a low cost technique for solar cell as well as for other semiconductor device production. Compared to conventional furnace processing, process differences are not only in very high heating and cooling rates, but also in the incoherent emitted radiation spectrum, which can act on dopant diffusion. The photons emitted from tungsten halogen lamps go from far ultraviolet, over visible to infrared light. In this work additional mercury ultraviolet lamps are used during rapid thermal annealing to analyze the influence of high energetic photons on diffusion mechanisms. The diffusion results are discussed in terms of radiation spectrum, involving analysis of diffusion profiles and sheet resistances.

  6. Metamaterials. Invisibility cloaking in a diffusive light scattering medium.

    PubMed

    Schittny, Robert; Kadic, Muamer; Bückmann, Tiemo; Wegener, Martin

    2014-07-25

    In vacuum, air, and other surroundings that support ballistic light propagation according to Maxwell's equations, invisibility cloaks that are macroscopic, three-dimensional, broadband, passive, and that work for all directions and polarizations of light are not consistent with the laws of physics. We show that the situation is different for surroundings leading to multiple light scattering, according to Fick's diffusion equation. We have fabricated cylindrical and spherical invisibility cloaks made of thin shells of polydimethylsiloxane doped with melamine-resin microparticles. The shells surround a diffusively reflecting hollow core, in which arbitrary objects can be hidden. We find good cloaking performance in a water-based diffusive surrounding throughout the entire visible spectrum and for all illumination conditions and incident polarizations of light. Copyright © 2014, American Association for the Advancement of Science.

  7. 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.

  8. Cloaking and anamorphism for light and mass diffusion

    NASA Astrophysics Data System (ADS)

    Guenneau, Sébastien; Diatta, André; Puvirajesinghe, Tania M.; Farhat, Mohamed

    2017-10-01

    We first review classical results on cloaking and mirage effects for electromagnetic waves. We then show that transformation optics allows the masking of objects or produces mirages in diffusive regimes. In order to achieve this, we consider the equation for diffusive photon density in transformed coordinates, which is valid for diffusive light in scattering media. More precisely, generalizing transformations for star domains introduced in (Diatta and Guenneau J. Opt. 13 024012) for matter waves, we numerically demonstrate that infinite conducting objects of different shapes scatter diffusive light in exactly the same way. We also propose a design of an external light-diffusion cloak with spatially varying sign-shifting parameters that hides a finite size scatterer outside the cloak. We next analyze non-physical parameters in the transformed Fick’s equation derived in (Guenneau and Puvirajesinghe R. Soc. Interface 10 20130106), and propose the use of a non-linear transform that overcomes this problem. We finally investigate other forms of invariant transformed diffusion-like equations in the time domain, and touch upon conformal mappings and non-Euclidean cloaking applied to diffusion processes.

  9. Pressure injury prediction using diffusely scattered light

    NASA Astrophysics Data System (ADS)

    Diaz, David; Lafontant, Alec; Neidrauer, Michael; Weingarten, Michael S.; DiMaria-Ghalili, Rose Ann; Scruggs, Ericka; Rece, Julianne; Fried, Guy W.; Kuzmin, Vladimir L.; Zubkov, Leonid

    2017-02-01

    Pressure injuries (PIs) originate beneath the surface of the skin at the interface between bone and soft tissue. We used diffuse correlation spectroscopy (DCS) and diffuse near-infrared spectroscopy (DNIRS) to predict the development of PIs by measuring dermal and subcutaneous red cell motion and optical absorption and scattering properties in 11 spinal cord injury subjects with only nonbleachable redness in the sacrococcygeal area in a rehabilitation hospital and 20 healthy volunteers. A custom optical probe was developed to obtain continuous DCS and DNIRS data from sacrococcygeal tissue while the subjects were placed in supine and lateral positions to apply pressure from body weight and to release pressure, respectively. Rehabilitation patients were measured up to four times over a two-week period. Three rehabilitation patients developed open PIs (POs) within four weeks and eight patients did not (PNOs). Temporal correlation functions in the area of redness were significantly different (p<0.01) during both baseline and applied pressure stages for POs and PNOs. The results show that our optical method may be used for the early prediction of ulcer progression.

  10. The role of natural lighting diffuseness in human visual perception

    NASA Astrophysics Data System (ADS)

    Morgenstern, Yaniv; Geisler, Wilson S.; Murray, Richard F.

    2015-03-01

    The pattern of the light that falls on the retina is a conflation of real-world sources such as illumination and reflectance. Human observers often contend with the inherent ambiguity of the underlying sources by making assumptions about what real-world sources are most likely. Here we examine whether the visual system's assumptions about illumination match the statistical regularities of the real world. We used a custom-built multidirectional photometer to capture lighting relevant to the shading of Lambertian surfaces in hundreds of real-world scenes. We quantify the diffuseness of these lighting measurements, and compare them to previous biases in human visual perception. We find that (1) natural lighting diffuseness falls over the same range as previous psychophysical estimates of the visual system's assumptions on diffuseness, and (2) natural lighting almost always provides lighting direction cues that are strong enough to override the human visual system's well known assumption that light tends to come from above. A consequence of these findings is that what seem to be errors in visual perception are often actually byproducts of the visual system knowing about and using reliable properties of real-world lighting when contending with ambiguous retinal images.

  11. 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.

  12. Real-time diameter measurement using diffuse light

    NASA Astrophysics Data System (ADS)

    Luo, Xiaohe; Hui, Mei; Zhu, Qiudong; Wang, Shanshan

    2016-09-01

    A method for on-line rapid determination of the diameter of metallic cylinder is introduced in this paper. Under the radiation of diffuse light, there is a bright area close to the margin of metallic cylinder, and the method of this paper is based on the intensity distribution of the bright area. In this paper, with the radiation by a diffuse plane light with special shape, we present the relation expression of the distance between the peak point and the real edge of the cylinder and the distance between the diffuse light and the pinhole aperture of the camera. With the expression, the diameter of the cylinder to be measured can be calculated. In the experiments, monochromatic LED uniting with ground glass forms the diffuse light source, then the light irradiates the tested cylinder. After the cylinder, we use a lens with a front pinhole stop to choose the light into CMOS, then a computer is used to analyze images and export the measurement results. The measuring system using this method is very easily implemented, so it can realize the on-line rapid measurement. Experimental results are presented for six metallic cylinders with the diameter in 5 18mm range and roughness in Ra- 0.02um, and the precision reaches 3um.

  13. 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.

  14. 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).

  15. 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.

  16. Diffused ČERENKOV Light Measurements for the Euso Project

    NASA Astrophysics Data System (ADS)

    Vallania, P.; Cappa, A.; Fava, L.; Galeotti, P.; Saavedra, O.; Vigorito, C.; Chauvin, J.; Lebrun, D.; Moreggia, S.; Stassi, P.; Assis, P.; Brogueira, P.; Espirito-Santo, M. C.; Melo, L.; Pimenta, M.; Silva, J. C.; Tomé, B.; Agnetta, G.; Biondo, B.; Catalano, O.; D'Alí Staiti, G.; Giarrusso, S.; Gugliotta, G.; La Rosa, G.; Mangano, A.; Russo, F.; Scarsi, P.; Zora, M.

    The aim of the EUSO (Extreme Universe Space Observatory) experiment is to measure from space the fluorescent light produced by the interaction of Extreme Energy Cosmic Rays (EECRs) with the Earth atmosphere. Besides the fluorescent signal, a huge amount of Čerenkov photons is emitted in a narrow cone hitting the Earth surface, where it is partially diffused. The detection of this diffused signal, in a delayed coincidence with the fluorescent signal, allows the absolute positioning of the EECR track, while the knowledge of the diffusing properties of the surface gives an independent indication of the shower energy. Measuring simultaneously on ground the electromagnetic component, the direct Čerenkov light, and the diffused Čerenkov light over different surfaces, we aim to characterize the emitted signal as a function of the energy and the arrival direction of the Extensive Air Shower (EAS), and to evaluate its possible detection from space. This is implemented by the ULTRA (Uv Light Transmission and Reflection in the Atmosphere) experiment composed by a small EAS array and a UltraViolet (UV) telescope. The experimental setups used in the first runs at sea level and at 1970 m a.s.l. are described and the first preliminary results are presented.

  17. 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.

  18. Light source distribution and scattering phase function influence light transport in diffuse multi-layered media

    NASA Astrophysics Data System (ADS)

    Vaudelle, Fabrice; L'Huillier, Jean-Pierre; Askoura, Mohamed Lamine

    2017-06-01

    Red and near-Infrared light is often used as a useful diagnostic and imaging probe for highly scattering media such as biological tissues, fruits and vegetables. Part of diffusively reflected light gives interesting information related to the tissue subsurface, whereas light recorded at further distances may probe deeper into the interrogated turbid tissues. However, modelling diffusive events occurring at short source-detector distances requires to consider both the distribution of the light sources and the scattering phase functions. In this report, a modified Monte Carlo model is used to compute light transport in curved and multi-layered tissue samples which are covered with a thin and highly diffusing tissue layer. Different light source distributions (ballistic, diffuse or Lambertian) are tested with specific scattering phase functions (modified or not modified Henyey-Greenstein, Gegenbauer and Mie) to compute the amount of backscattered and transmitted light in apple and human skin structures. Comparisons between simulation results and experiments carried out with a multispectral imaging setup confirm the soundness of the theoretical strategy and may explain the role of the skin on light transport in whole and half-cut apples. Other computational results show that a Lambertian source distribution combined with a Henyey-Greenstein phase function provides a higher photon density in the stratum corneum than in the upper dermis layer. Furthermore, it is also shown that the scattering phase function may affect the shape and the magnitude of the Bidirectional Reflectance Distribution (BRDF) exhibited at the skin surface.

  19. Polarized light diffusely scattered under smooth and rough interfaces

    NASA Astrophysics Data System (ADS)

    Germer, Thomas A.

    2003-12-01

    We develop models for light scattering appropriate for glossy and matte paints. Volume scattering is treated in the single scattering regime and the diffusive scattering regime. In the single scattering regime, scattering is treated in the Rayleigh-Gans approximation, using a Henyey-Greenstein phase function. Interaction of the light with the smooth or rough interface is treated in the facet approximation. The theory for transmissive light scattering by a rough interface in the facet approximation is presented. To treat volume scattering under a rough interface, a Monte Carlo approach is used, where light is allowed to interact with the surface twice, once upon entering the material and once upon exiting. We compare the polarization and intensity predicted by the models with experimental data from glossy and matte paint samples. The results indicate that the new models are an improvement over the Maxwell-Beard model.

  20. Resolution limits for imaging through turbid media with diffuse light

    NASA Astrophysics Data System (ADS)

    Moon, J. A.; Mahon, R.; Duncan, M. D.; Reintjes, J.

    1993-10-01

    For the achievable resolution for imaging through a turbid medium with multiply scattered light in the diffusion limit, the authors present analytic expressions. The spatial resolution R (the half-width of the point-spread function) scales with thickness d of the sample as R = (0.2 +/- 0.04)d over 10 order of magnitude in input intensity and transport length are found for detectable levels of light. The experiments with a time-gated stimulated Raman amplifier are in good agreement with the calculations.

  1. Light reflection visualization to determine solute diffusion into clays.

    PubMed

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

    2014-06-01

    Light reflection visualization (LRV) experiments were performed to investigate solute diffusion in low-permeability porous media using a well-controlled two-dimensional flow chamber with a domain composed of two layers (one sand and one clay). Two different dye tracers (Brilliant Blue FCF and Ponceau 4R) and clay domains (kaolinite and montmorillonite) were used. The images obtained through the LRV technique were processed to monitor two-dimensional concentration distributions in the low-permeability zone by applying calibration curves that related light intensity to equilibrium concentrations for each dye tracer in the clay. One dimensional experimentally-measured LRV concentration profiles in the clay were found to be in very good agreement with those predicted from a one-dimensional analytical solution, with coefficient of efficiency values that exceeded 0.97. The retardation factors (R) for both dyes were relatively large, leading to slow diffusive penetration into the clays. At a relative concentration C/C0=0.1, Brilliant Blue FCF in kaolinite (R=11) diffused approximately 10 mm after 21 days of source loading, and Ponceau 4R in montmorillonite (R=7) diffused approximately 12 mm after 23 days of source loading. The LRV experimentally-measured two-dimensional concentration profiles in the clay were also well described by a simple analytical solution. The results from this study demonstrate that the LRV approach is an attractive non-invasive tool to investigate the concentration distribution of dye tracers in clays in laboratory experiments.

  2. 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

  3. Modeling diffuse reflectance measurements of light scattered by layered tissues

    NASA Astrophysics Data System (ADS)

    Rohde, Shelley B.

    In this dissertation, we first present a model for the diffuse reflectance due to a continuous beam incident normally on a half space composed of a uniform scattering and absorbing medium. This model is the result of an asymptotic analysis of the radiative transport equation for strong scattering, weak absorption and a defined beam width. Through comparison with the diffuse reflectance computed using the numerical solution of the radiative transport equation, we show that this diffuse reflectance model gives results that are accurate for small source-detector separation distances. We then present an explicit model for the diffuse reflectance due to a collimated beam of light incident normally on layered tissues. This model is derived using the corrected diffusion approximation applied to a layered medium, and it takes the form of a convolution with an explicit kernel and the incident beam profile. This model corrects the standard diffusion approximation over all source-detector separation distances provided the beam is sufficiently wide compared to the scattering mean-free path. We validate this model through comparison with Monte Carlo simulations. Then we use this model to estimate the optical properties of an epithelial layer from Monte Carlo simulation data. Using measurements at small source-detector separations and this model, we are able to estimate the absorption coefficient, scattering coefficient and anisotropy factor of epithelial tissues efficiently with reasonable accuracy. Finally, we present an extension of the corrected diffusion approximation for an obliquely incident beam. This model is formed through a Fourier Series representation in the azimuthal angle which allows us to exhibit the break in axisymmetry when combined with the previous analysis. We validate this model with Monte Carlo simulations. This model can also be written in the form of a convolution of an explicit kernel with the incident beam profile. Additionally, it can be used to

  4. DiffusionKit: A light one-stop solution for diffusion MRI data analysis.

    PubMed

    Xie, Sangma; Chen, Liangfu; Zuo, Nianming; Jiang, Tianzi

    2016-11-01

    Diffusion magnetic resonance imaging (dMRI) techniques are receiving increasing attention due to their ability to characterize the arrangement map of white matter in vivo. However, the existing toolkits for dMRI analysis that have accompanied this surge possess noticeable limitations, such as large installation size, an incomplete pipeline, and a lack of cross-platform support. In this work, we developed a light, one-stop, cross-platform solution for dMRI data analysis, called DiffusionKit. It delivers a complete pipeline, including data format conversion, dMRI preprocessing, local reconstruction, white matter fiber tracking, fiber statistical analyses and various visualization schemes. Furthermore, DiffusionKit is a self-contained executable toolkit, without the need to install any other software. The DiffusionKit package is implemented in C/C++ and Qt/VTK, is freely available at http://diffusion.brainnetome.org and https://www.nitrc.org/projects/diffusionkit. The website of DiffusionKit includes test data, a complete tutorial and a series of tutorial examples. A mailing list has also been established for update notification and questions and answers. DiffusionKit provides a full-function pipeline for dMRI data analysis, including data processing, modeling and visualization. Additionally, it provides both a graphical user interface (GUI) and command-line functions, which are helpful for batch processing. The standalone installation package has a small size and cross-platform support. DiffusionKit provides a complete pipeline with cutting-edge methods for dMRI data analysis, including both a GUI interface and command-line functions. The rich functions for both data analysis and visualization will facilitate and benefit dMRI research. Copyright © 2016 Elsevier B.V. All rights reserved.

  5. Diffuse-light all-solid-state invisibility cloak.

    PubMed

    Schittny, Robert; Niemeyer, Andreas; Kadic, Muamer; Bückmann, Tiemo; Naber, Andreas; Wegener, Martin

    2015-09-15

    An ideal invisibility cloak makes arbitrary macroscopic objects within the cloak indistinguishable from its surrounding—for all directions, illumination patterns, polarizations, and colors of visible light. Recently, we have approached such an ideal cloak for the diffusive regime of light propagation using a core-shell geometry and a mixture of water and white wall paint as the surrounding. Here, we present an all-solid-state version based on polydimethylsiloxane doped with titania nanoparticles for the surrounding/shell and on a high-reflectivity microporous ceramic for the core. By virtue of reduced effects of absorption, especially from the core, the cloaking performance and the overall light throughput are improved significantly.

  6. Diffusive-light invisibility cloak for transient illumination

    NASA Astrophysics Data System (ADS)

    Orazbayev, B.; Beruete, M.; Martínez, A.; García-Meca, C.

    2016-12-01

    Invisibility in a diffusive-light-scattering medium has been recently demonstrated by employing a scattering-cancellation core-shell cloak. Unlike nondiffusive cloaks, such a device can be simultaneously macroscopic, broadband, passive, polarization independent, and omnidirectional. Unfortunately, it has been verified that this cloak, as well as more sophisticated ones based on transformation optics, fail under pulsed illumination, invalidating their use for a variety of applications. Here, we introduce a different approach based on unimodular transformations that enables the construction of unidirectional diffusive-light cloaks exhibiting a perfect invisibility effect, even under transient conditions. Moreover, we demonstrate that a polygonal cloak can extend this functionality to multiple directions with a nearly ideal behavior, while preserving all other features. We propose and numerically verify a simple cloak realization based on a layered stack of two isotropic materials. The studied devices have several applications not addressable by any of the other cloaks proposed to date, including shielding from pulse-based detection techniques, cloaking undesired scattering elements in time-of-flight imaging or high-speed communication systems for diffusive environments, and building extreme optical security features. The discussed cloaking strategy could also be applied to simplify the implementation of thermal cloaks.

  7. 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.

  8. 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.

  9. 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.

  10. Diffuse optical imaging using spatially and temporally modulated light

    NASA Astrophysics Data System (ADS)

    O'Sullivan, Thomas D.; Cerussi, Albert E.; Cuccia, David J.; Tromberg, Bruce J.

    2012-07-01

    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.

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. Excess Diffuse Light Absorption in Upper Mesophyll Limits CO2 Drawdown and Depresses Photosynthesis.

    PubMed

    Earles, J Mason; Théroux-Rancourt, Guillaume; Gilbert, Matthew E; McElrone, Andrew J; Brodersen, Craig R

    2017-06-01

    In agricultural and natural systems, diffuse light can enhance plant primary productivity due to deeper penetration into and greater irradiance of the entire canopy. However, for individual sun-grown leaves from three species, photosynthesis is actually less efficient under diffuse compared with direct light. Despite its potential impact on canopy-level productivity, the mechanism for this leaf-level diffuse light photosynthetic depression effect is unknown. Here, we investigate if the spatial distribution of light absorption relative to electron transport capacity in sun- and shade-grown sunflower (Helianthus annuus) leaves underlies its previously observed diffuse light photosynthetic depression. Using a new one-dimensional porous medium finite element gas-exchange model parameterized with light absorption profiles, we found that weaker penetration of diffuse versus direct light into the mesophyll of sun-grown sunflower leaves led to a more heterogenous saturation of electron transport capacity and lowered its CO2 concentration drawdown capacity in the intercellular airspace and chloroplast stroma. This decoupling of light availability from photosynthetic capacity under diffuse light is sufficient to generate an 11% decline in photosynthesis in sun-grown but not shade-grown leaves, primarily because thin shade-grown leaves similarly distribute diffuse and direct light throughout the mesophyll. Finally, we illustrate how diffuse light photosynthetic depression could overcome enhancement in canopies with low light extinction coefficients and/or leaf area, pointing toward a novel direction for future research. © 2017 American Society of Plant Biologists. All Rights Reserved.

  16. Excess Diffuse Light Absorption in Upper Mesophyll Limits CO2 Drawdown and Depresses Photosynthesis1[OPEN

    PubMed Central

    Gilbert, Matthew E.; McElrone, Andrew J.

    2017-01-01

    In agricultural and natural systems, diffuse light can enhance plant primary productivity due to deeper penetration into and greater irradiance of the entire canopy. However, for individual sun-grown leaves from three species, photosynthesis is actually less efficient under diffuse compared with direct light. Despite its potential impact on canopy-level productivity, the mechanism for this leaf-level diffuse light photosynthetic depression effect is unknown. Here, we investigate if the spatial distribution of light absorption relative to electron transport capacity in sun- and shade-grown sunflower (Helianthus annuus) leaves underlies its previously observed diffuse light photosynthetic depression. Using a new one-dimensional porous medium finite element gas-exchange model parameterized with light absorption profiles, we found that weaker penetration of diffuse versus direct light into the mesophyll of sun-grown sunflower leaves led to a more heterogenous saturation of electron transport capacity and lowered its CO2 concentration drawdown capacity in the intercellular airspace and chloroplast stroma. This decoupling of light availability from photosynthetic capacity under diffuse light is sufficient to generate an 11% decline in photosynthesis in sun-grown but not shade-grown leaves, primarily because thin shade-grown leaves similarly distribute diffuse and direct light throughout the mesophyll. Finally, we illustrate how diffuse light photosynthetic depression could overcome enhancement in canopies with low light extinction coefficients and/or leaf area, pointing toward a novel direction for future research. PMID:28432257

  17. Diffuse Stellar Light at 100 KPC Scales in M87

    NASA Astrophysics Data System (ADS)

    Weil, Melinda L.; Bland-Hawthorn, Jonathan; Malin, David F.

    1997-01-01

    In a new survey of nearby galaxies from stacked photographic images, seemingly regular galaxies of several types show amorphous, often asymmetrical features at very faint levels (28 mag arcsec-2). In M87, a diffuse fan of stellar material extends along the projected SE (major) axis out to about 100 kpc. We suggest that accretion of a small spheroidal galaxy into a larger potential is the most likely explanation for the diffuse structure. The orbit is required to pass close to the center of the potential to produce a fan which nearly aligns with the major axis and has a large opening angle, as seen in M87. Our simulations include a rigid primary potential with characteristics similar to those derived for M87 and a populated secondary potential. We investigate the structure of the dark matter at large galactic radii by representing M87 with different potentials. The morphologies of the debris of intruder spheres and disks of different masses and orbital parameters limit the possible accretion scenarios. The total luminosity of the fan and the kinematics of debris in the center of the primary potential are analyzed and compared with substructure in M87. The short lifetimes (t(fan) approx. less than 5 x 108 years) of the simulated diffuse fans and lack of observed shells indicates that either we are seeing M87 at a 'special time' during its evolution or that infall from small intruder galaxies is common. Our simulations indicate that several accretion events could be hidden in galaxies. For many orbits, intruder material is quickly spread out to very low light levels. Observations of the high specific frequency of globular clusters in M87 provide evidence that the galaxy may experience frequent accretions of this type.

  18. Hydrogen peroxide diffusion with and without light activation.

    PubMed

    Llena, Carmen; Forner, Leopoldo; Vazquez, María

    The aim of this study was to assess the dental bleaching efficacy of 37.5% hydrogen peroxide (HP), with and without light activation, in HP-exposed and unexposed areas. 28 bovine teeth were selected and divided into two groups (n = 14). Crowns were detached and stained with tea. The gingival half was covered with a gingival barrier. In the incisal half, 37.5% HP (Pola Office+, SDI) was applied three times, with a 1-week interval between applications. In HP-A group, the bleaching agent was activated for 3 min with a LED lamp. No light activation was applied in HP-N group. Dental color variation was determined through a spectrophotometer in both halves. Statistical analysis between groups was performed with an ANOVA test, and intragroup differences were evaluated, with an ANOVA test for paired data, with a significance level of P < 0.05. An increase in lightness and a decrease in chroma were found in both groups and halves. No significant differences in ΔE between groups (P > 0.5) were detected in the incisal half. After treatment, a significantly higher ΔE was found in the gingival half for HP-A group (P < 0.05). For the same group, a significantly higher bleaching effect was found in the gingival half, compared with the incisal half (P < 0.05). LED activation did not have a significant effect in terms of bleaching in the incisal half, but increased clearance in the gingival half. HP light activation does not significantly increase the whitening effect, but it can improve the bleaching diffusion to areas where it has not been directly applied.

  19. 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.

  20. Enhancement of crop photosynthesis by diffuse light: quantifying the contributing factors.

    PubMed

    Li, T; Heuvelink, E; Dueck, T A; Janse, J; Gort, G; Marcelis, L F M

    2014-07-01

    Plants use diffuse light more efficiently than direct light. However, experimental comparisons between diffuse and direct light have been obscured by co-occurring differences in environmental conditions (e.g. light intensity). This study aims to analyse the factors that contribute to an increase in crop photosynthesis in diffuse light and to quantify their relative contribution under different levels of diffuseness at similar light intensities. The hypothesis is that the enhancement of crop photosynthesis in diffuse light results not only from the direct effects of more uniform vertical and horizontal light distribution in the crop canopy, but also from crop physiological and morphological acclimation. Tomato (Solanum lycopersicum) crops were grown in three greenhouse compartments that were covered by glass with different degrees of light diffuseness (0, 45 and 71 % of the direct light being converted into diffuse light) while maintaining similar light transmission. Measurements of horizontal and vertical photosynthetic photon flux density (PPFD) distribution in the crop, leaf photosynthesis light response curves and leaf area index (LAI) were used to quantify each factor's contribution to an increase in crop photosynthesis in diffuse light. In addition, leaf temperature, photoinhibition, and leaf biochemical and anatomical properties were studied. The highest degree of light diffuseness (71 %) increased the calculated crop photosynthesis by 7·2 %. This effect was mainly attributed to a more uniform horizontal (33 % of the total effect) and vertical PPFD distribution (21 %) in the crop. In addition, plants acclimated to the high level of diffuseness by gaining a higher photosynthetic capacity of leaves in the middle of the crop and a higher LAI, which contributed 23 and 13 %, respectively, to the total increase in crop photosynthesis in diffuse light. Moreover, diffuse light resulted in lower leaf temperatures and less photoinhibition at the top of the canopy when

  1. Enhancement of crop photosynthesis by diffuse light: quantifying the contributing factors

    PubMed Central

    Li, T.; Heuvelink, E.; Dueck, T. A.; Janse, J.; Gort, G.; Marcelis, L. F. M.

    2014-01-01

    Background and Aims Plants use diffuse light more efficiently than direct light. However, experimental comparisons between diffuse and direct light have been obscured by co-occurring differences in environmental conditions (e.g. light intensity). This study aims to analyse the factors that contribute to an increase in crop photosynthesis in diffuse light and to quantify their relative contribution under different levels of diffuseness at similar light intensities. The hypothesis is that the enhancement of crop photosynthesis in diffuse light results not only from the direct effects of more uniform vertical and horizontal light distribution in the crop canopy, but also from crop physiological and morphological acclimation. Methods Tomato (Solanum lycopersicum) crops were grown in three greenhouse compartments that were covered by glass with different degrees of light diffuseness (0, 45 and 71 % of the direct light being converted into diffuse light) while maintaining similar light transmission. Measurements of horizontal and vertical photosynthetic photon flux density (PPFD) distribution in the crop, leaf photosynthesis light response curves and leaf area index (LAI) were used to quantify each factor's contribution to an increase in crop photosynthesis in diffuse light. In addition, leaf temperature, photoinhibition, and leaf biochemical and anatomical properties were studied. Key Results The highest degree of light diffuseness (71 %) increased the calculated crop photosynthesis by 7·2 %. This effect was mainly attributed to a more uniform horizontal (33 % of the total effect) and vertical PPFD distribution (21 %) in the crop. In addition, plants acclimated to the high level of diffuseness by gaining a higher photosynthetic capacity of leaves in the middle of the crop and a higher LAI, which contributed 23 and 13 %, respectively, to the total increase in crop photosynthesis in diffuse light. Moreover, diffuse light resulted in lower leaf temperatures and less

  2. Detection of diffuse sea floor venting using structured light imaging

    NASA Astrophysics Data System (ADS)

    Inglis, G.; Smart, C.; Roman, C.; Carey, S.

    2011-12-01

    Efficiently identifying and localizing diffuse sea floor venting at hydrothermal and cold seep sites is often difficult. Actively venting fluids are usually identified by a temperature induced optical shimmering seen during direct visual inspections or in video data collected by vehicles working close to the sea floor. Relying on such direct methods complicates establishing spatial relations between areas within a survey covering a broad area. Our recent work with a structured light laser system has shown that venting can also be detected in the image data in an automated fashion. A structured light laser system consists of a camera and sheet laser projected at the sea floor. The camera and laser are fixed to a rigid calibrated mount such that the optical axis of the camera and the laser plane intersect at some distance away from the camera, typically 2 to 5 meters. The position of the laser line, visible on the sea floor in the image, can be extracted using standard computer vision techniques (Fig. 1) and used to determine the height of the bottom along the laser line. By collecting images in a survey pattern at a high frame rate, typically 20 to 30 Hz, a bathymetric map can be produced using the individual profiles. In the presence of venting, temperature anomalies refract the laser sheet such that it does not project a crisp and clear line on the sea floor. The laser will instead appear blurred and visible over a larger section of the image. By processing the images to segment out clear laser lines from refracted lines it is possible to identify areas of venting. Our initial approach uses calculated image moments relative to the peak intensity level detected in each column of the image matrix. In the presence of venting the calculated moments differ from those of the undistorted laser shining on the sea floor. Test results from the Kolumbo submarine volcano near Santorini, Greece demonstrate this approach and show the utility of the method for survey work. Test

  3. Tailoring the light distribution of liquid crystal display with freeform engineered diffuser.

    PubMed

    Zhu, Ruidong; Hong, Qi; Gao, Yating; Luo, Zhenyue; Wu, Shin-Tson; Li, Ming-Chun; Lee, Seok-Lyul; Tsai, Wen-Ching

    2015-06-01

    We propose a versatile design approach of engineered diffuser based on freeform optics that can tailor the light distribution of a liquid crystal display (LCD) to meet different applications. The proposed LCD system consists of a quasi-directional backlight, liquid crystal panel, and an engineered diffuser. It offers high efficiency, wide view, high contrast, as well as low ambient light reflection. For large size LCDs, we design a wide view diffuser to match the light distribution with state-of-the-art organic light emitting diode (OLED) TV. For mobile displays, we design a diffuser to replicate current LCD performance. Our design can also provide flattop light intensity distribution for privacy protection. These exemplary designs prove that our engineered diffuser is versatile for different applications.

  4. 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.

  5. 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)

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Excess diffuse light absorption in upper mesophyll limits CO2 drawdown and depresses photosynthesis

    USDA-ARS?s Scientific Manuscript database

    Sun-grown and shade-grown leaves of some species absorb direct and diffuse light differently. Sun-grown leaves can photosynthesize ~10-15% less under diffuse compared to direct irradiance, while shade-grown leaves do not exhibit this sensitivity. In this study, we investigate if the spatial differen...

  12. 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.

  13. Modeling boundary measurements of scattered light using the corrected diffusion approximation

    PubMed Central

    Lehtikangas, Ossi; Tarvainen, Tanja; Kim, Arnold D.

    2012-01-01

    We study the modeling and simulation of steady-state measurements of light scattered by a turbid medium taken at the boundary. In particular, we implement the recently introduced corrected diffusion approximation in two spatial dimensions to model these boundary measurements. This implementation uses expansions in plane wave solutions to compute boundary conditions and the additive boundary layer correction, and a finite element method to solve the diffusion equation. We show that this corrected diffusion approximation models boundary measurements substantially better than the standard diffusion approximation in comparison to numerical solutions of the radiative transport equation. PMID:22435102

  14. Large-sized light field three-dimensional display using multi-projectors and directional diffuser

    NASA Astrophysics Data System (ADS)

    Peng, Yi-fan; Li, Hai-feng; Zhong, Qing; Xia, Xin-xing; Liu, Xu

    2013-01-01

    A scalable system to achieve large-sized light field three-dimensional display using multi-projectors and directional diffuser is presented. The system mainly employs an array of mini-projectors projecting images onto a special cylindrical directional diffuser screen. The principle of light field reconstruction, configuration of multi-projectors style, and characteristics of directional diffuser are explicitly analyzed, respectively. A prototype of a piece of equipment in mini-cinema class is proposed, with 100 mini-projectors and a special cylindrical directional diffuser performing different diffuse angles in horizontal and vertical directions. Bright and large-sized three-dimensional images displayed by the system can be observed at different horizontal viewing positions around the cylindrical display area with stereo parallax and motion parallax.

  15. 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.

  16. 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 ...

  17. 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 ...

  18. Light-dependent changes in outer retinal water diffusion in rats in vivo

    PubMed Central

    Bissig, David

    2012-01-01

    Purpose To test the hypothesis that in rats, intraretinal light-dependent changes on diffusion-weighted magnetic resonance imaging (MRI) in vivo are consistent with known retinal layer-specific physiology. Methods In male Sprague-Dawley rats, retinal morphology (thickness, extent, surface area, volume) and intraretinal profiles of the apparent diffusion coefficient (ADC, i.e., water mobility) parallel and perpendicular to the optic nerve were measured in vivo using quantitative MRI methods during light and dark stimulation. Results The parallel ADC in the posterior half of the avascular, photoreceptor-dominated outer retina was significantly higher in light than dark, and this pattern was reversed (dark>light) in the anterior outer retina. The perpendicular ADC in the posterior outer retina was similar in light and dark, but was significantly higher in dark than light in the anterior outer retina. No light-dark changes in the inner retina were noted. Conclusions We identified light-dependent intraretinal diffusion changes that reflected established stimulation-based changes in outer retinal hydration. These findings are expected to motivate future applications of functional diffusion-based MRI in blinding disorders of the outer retina. PMID:23129976

  19. Transfer of diffuse astronomical light and airglow in scattering Earth atmosphere

    NASA Astrophysics Data System (ADS)

    Hong, S. S.; Kwon, S. M.; Park, Y.-S.; Park, C.

    1998-06-01

    To understand an observed distribution of atmospheric diffuse light (ADL) over an entire meridian, we have solved rigorously, with the quasi-diffusion method, the problem of radiative transfer in an anisotropically scattering spherical atmosphere of the earth. In addition to the integrated starlight and the zodiacal light we placed a narrow layer of airglow emission on top of the scattering earth atmosphere. The calculated distribution of the ADL brightness over zenith distance shows good agreement with the observed one. The agreement can be utilized in deriving the zodiacal light brightness at small solar elongations from the night sky brightness observed at large zenith distances.

  20. Universal sensitivity of speckle intensity correlations to wavefront change in light diffusers

    NASA Astrophysics Data System (ADS)

    Kim, Kyungduk; Yu, Hyeonseung; Lee, Kyeoreh; Park, Yongkeun

    2017-03-01

    Here, we present a concept based on the realization that a complex medium can be used as a simple interferometer. Changes in the wavefront of an incident coherent beam can be retrieved by analyzing changes in speckle patterns when the beam passes through a light diffuser. We demonstrate that the spatial intensity correlations of the speckle patterns are independent of the light diffusers, and are solely determined by the phase changes of an incident beam. With numerical simulations using the random matrix theory, and an experimental pressure-driven wavefront-deforming setup using a microfluidic channel, we theoretically and experimentally confirm the universal sensitivity of speckle intensity correlations, which is attributed to the conservation of optical field correlation despite multiple light scattering. This work demonstrates that a light diffuser works as a simple interferometer, and presents opportunities to retrieve phase information of optical fields with a compact scattering layer in various applications in metrology, analytical chemistry, and biomedicine.

  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

    2016-07-16

    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.

  2. 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

  3. Universal sensitivity of speckle intensity correlations to wavefront change in light diffusers

    PubMed Central

    Kim, KyungDuk; Yu, Hyeonseung; Lee, KyeoReh; Park, YongKeun

    2017-01-01

    Here, we present a concept based on the realization that a complex medium can be used as a simple interferometer. Changes in the wavefront of an incident coherent beam can be retrieved by analyzing changes in speckle patterns when the beam passes through a light diffuser. We demonstrate that the spatial intensity correlations of the speckle patterns are independent of the light diffusers, and are solely determined by the phase changes of an incident beam. With numerical simulations using the random matrix theory, and an experimental pressure-driven wavefront-deforming setup using a microfluidic channel, we theoretically and experimentally confirm the universal sensitivity of speckle intensity correlations, which is attributed to the conservation of optical field correlation despite multiple light scattering. This work demonstrates that a light diffuser works as a simple interferometer, and presents opportunities to retrieve phase information of optical fields with a compact scattering layer in various applications in metrology, analytical chemistry, and biomedicine. PMID:28322268

  4. 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.

  5. Searching for Diffuse Light in the M96 Galaxy Group

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

    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 B = 30.1 and μ 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 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.

  6. 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.

  7. 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

  8. 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.

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

    PubMed

    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

    2015-12-21

    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 120(o) 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.

  10. Total light approach of time-domain fluorescence diffuse optical tomography.

    PubMed

    Marjono, Andhi; Yano, Akira; Okawa, Shinpei; Gao, Feng; Yamada, Yukio

    2008-09-15

    In this study, time-domain fluorescence diffuse optical tomography in biological tissue is numerically investigated using a total light approach. Total light is a summation of excitation light and zero-lifetime emission light divided by quantum yield. The zero-lifetime emission light is an emitted fluorescence light calculated by assuming that the fluorescence lifetime is zero. The zero-lifetime emission light is calculated by deconvolving the actually measured emission light with a lifetime function, an exponential function for fluorescence decay. The object for numerical simulation is a 2-D 10 mm-radius circle with the optical properties simulating biological tissues for near infrared light, and contains regions with fluorophore. The inverse problem of fluorescence diffuse optical tomography is solved using time-resolved simulated measurement data of the excitation and total lights for reconstructing the bsorption coefficient and fluorophore concentration simultaneously. The mean time of flight is used as the featured data-type extracted from the time-resolved data. The reconstructed images of fluorophore concentration show good quantitativeness and spatial reproducibility. By use of the total light approach, computation is performed much faster than the conventional ones.

  11. Diffuse-light two-dimensional line-of-sight attenuation for soot concentration measurements

    NASA Astrophysics Data System (ADS)

    Thomson, Kevin A.; Johnson, Matthew R.; Snelling, David R.; Smallwood, Gregory J.

    2008-02-01

    A technique of diffuse-light two-dimensional line-of-sight attenuation (diffuse 2D-LOSA) is described and demonstrated that achieves very high levels of sensitivity in transmissivity measurements (optical thicknesses down to 0.001) while effectively mitigating interferences due to beam steering. An optical system is described in which an arc lamp coupled with an integrating sphere is used as a source of diffuse light that is imaged to the center of the particulate laden medium. The center of the medium is then imaged onto a CCD detector with 1:1 magnification. Comparative measurements with collimated 2D-LOSA in nonpremixed flames demonstrate the accuracy and improved optical noise rejection of the technique. Tests in weakly sooting, nonpremixed methane-air flames, and in high pressure methane-air flames, reveal the excellent sensitivity of diffuse 2D-LOSA, which is primarily limited by the shot noise of the lamp and CCD detector.

  12. 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.

  13. 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.

  14. 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

    2015-12-09

    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.

  15. Effect of diffusion of light on thin-film photovoltaic laminates

    NASA Astrophysics Data System (ADS)

    Mohanty, Lipi; Wittkopf, Stephen K.

    A large fraction of the daylight incident on building-integrated photovoltaic (BIPV) laminates is diffuse irradiance. In this study, fabrics of various weaves were used to simulate combinations of direct and diffuse irradiance on façade-mounted PV. The scattering of light achieved with the fabrics at varying angles of incidence was measured with a goniophotometer. The transmittance distribution was used to quantify the percentage of diffusion created by the fabrics. A photovoltaic (PV) laminate was shaded with the fabrics to simulate diffuse irradiance and the short circuit current of the module was measured. The experimental results indicate fabrics of different porosity can be used to simulate various combinations of direct and diffuse irradiance. However, these fabrics can affect the module output. Preliminary results show that the proximity of the fabric to the thin-film PV laminate during the test skews the measured electrical parameters.

  16. Sensing and enumerating rare circulating cells with diffuse light

    NASA Astrophysics Data System (ADS)

    Zettergren, Eric; Vickers, Dwayne; Niedre, Mark

    2011-02-01

    Detection and quantification of circulating cells in live animals is a challenging and important problem in many areas of biomedical research. Current methods involve extraction of blood samples and counting of cells ex-vivo. Since only small blood volumes are analyzed at specific time points, monitoring of changes in cell populations over time is difficult and rare cells often escape detection. The goal of this research is to develop a method for enumerating very rare circulating cells in the bloodstream non-invasively. This would have many applications in biomedical research, including monitoring of cancer metastasis and tracking of hematopoietic stem cells. In this work we describe the optical configuration of our instrument which allows fluorescence detection of single cells in diffusive media at the mesoscopic scale. Our instrument design consists of two continuous wave laser diode sources and an 8-channel fiber coupled multi-anode photon counting PMT. Fluorescence detector fibers were arranged circularly around the target in a miniaturized ring configuration. Cell-simulating fluorescent microspheres and fluorescently-labeled cells were passed through a limb mimicking phantom with similar optical properties and background fluorescence as a limb of a mouse. Our data shows that we are able to successfully detect and count these with high quantitative accuracy. Future work includes characterization of our instrument using fluorescently labeled cells in-vivo. If successful, this technique would allow several orders of magnitude in vivo detection sensitivity improvement versus current approaches.

  17. 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.

  18. Reflection of diffuse light from dielectric one-dimensional rough surfaces.

    PubMed

    González-Alcalde, Alma K; Méndez, Eugenio R; Terán, Emiliano; Cuppo, Fabio L S; Olivares, J A; García-Valenzuela, Augusto

    2016-03-01

    We study the reflection of diffuse light from 1D randomly rough dielectric interfaces. Results for the reflectance under diffuse illumination are obtained by rigorous numerical simulations and then contrasted with those obtained for flat surfaces. We also explore the possibility of using perturbation theories and conclude that they are limited for this type of study. Numerical techniques based on Kirchhoff approximation and reduced Rayleigh equations yield better results. We find that, depending on the refractive index contrast and nature of the irregularities, the roughness can increase or decrease the diffuse reflectance of the surface.

  19. Chromatographic determination of the diffusion coefficients of light hydrocarbons in polymers

    NASA Astrophysics Data System (ADS)

    Yakubenko, E. E.; Korolev, A. A.; Chapala, P. P.; Bermeshev, M. V.; Kanat'eva, A. Yu.; Kurganov, A. A.

    2017-01-01

    Gas-chromatographic determination of the diffusion coefficients that allows for the compressibility of the mobile phase has been suggested. The diffusion coefficients were determined for light hydrocarbons C1-C4 in four polymers with a high free volume, which are candidates for use as gas-separating membranes. The diffusion coefficients calculated from chromatographic data were shown to be one or two orders of magnitude smaller than the values obtained by the membrane method. This may be due to the presence of an additional flow through the membrane caused by the pressure gradient across the membrane in membrane methods.

  20. First derivative of NIR light diffuse reflectance spectra as an approach to analyze muscle tissue chromophores and light pathlength

    NASA Astrophysics Data System (ADS)

    Gussakovsky, Eugene

    2009-02-01

    Diffuse reflectance was applied to the biomedical studies (muscles, cardiac tissues etc.) in a form of either a direct pseudo-optical spectrum or its second derivative. The first derivative adopts advantages of both direct spectrum (high signal-to-noise ratio) and its second derivative (simplifying the consideration of light scattering contribution, S). In contrast to spectrophotometry of solutions, diffuse reflectance application to the analysis of turbid medium chromophores leads to non-trivial problems of contribution of light scattering, the choice of reference, and light pathlength. Under certain conditions, the first approximation of the Taylor series of S results in the known linear dependence of S on wavelength in the 650-1050 nm wavelength range. Then the light scattering contribution to the first derivative becomes a wavelength-independent offset. In contrast to the second derivative, the information on light scattering inside the tissue is not lost. Effect of reference on the measured spectra becomes negligible. Application of the first derivative allowed (i) determination of NIR light pathlength in muscle tissue, and (ii) quantification of hemoglobin + myoglobin absolute concentration (in mM) in cardiac tissue during open-heart surgery. The first derivative approach may in general be applied to any chromophores in turbid (biological) media.

  1. 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

  2. Scale-Up of flat plate photobioreactors considering diffuse and direct light characteristics.

    PubMed

    Quinn, Jason C; Turner, Chris W; Bradley, Thomas H

    2012-02-01

    This study investigates the scaling of photobioreactor productivity based on the growth of Nannochloropsis salina incorporating the effects of direct and diffuse light. The scaling and optimization of photobioreactor geometry was analyzed by determining the growth response of a small-scale system designed to represent a core sample of a large-scale photobioreactor. The small-scale test apparatus was operated at a variety of light intensities on a batch time scale to generate a photosynthetic irradiance (PI) growth dataset, ultimately used to inform a PI growth model. The validation of the scalability of the PI growth model to predict productivity in large-scale systems was done by comparison with experimental growth data collected from two geometrically different large-scale photobioreactors operated at a variety of light intensities. For direct comparison, the small-scale and large-scale experimental systems presented were operated similarly and in such a way to incorporate cultivation relevant time scales, light intensities, mixing, and nutrient loads. Validation of the scalability of the PI growth model enables the critical evaluation of different photobioreactor geometries and design optimization incorporating growth effects from diffuse and direct light. Discussion focuses on the application of the PI growth model to assess the effect of diffuse light growth compared to direct light growth for the evaluation of photobioreactors followed by the use of the model for photobioreactor geometry optimization on the metric of areal productivity. Copyright © 2011 Wiley Periodicals, Inc.

  3. 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.

  4. Numerical and experimental study of excited light and auto-fluorescence diffusion in teeth

    NASA Astrophysics Data System (ADS)

    Chen, Q. G.; Lin, B.; Chen, Z. B.

    2010-10-01

    Excited light and corresponding intrinsic fluorescence diffusion inside teeth tissue are an essential problem for light-based carious lesion detection. Based on finite element numerical analysis of diffusion equation, the photon density distribution of both excited light and autofluorescence of 2D premolar teeth model is obtained. The dependence of excited light and autofluorescence density distribution inside the teeth model on the scattering coefficient of enamel (5-25 mm-1) and dentine (100-140 mm-1) is numerically simulated and analyzed. The fitted results reveal that fluorescence intensity decreases exponentially. Optical penetration depth and fluorescence relative depth declined with the increment of scattering coefficient of enamel. And the dentine had the opposite effect. Finally, the experiment of measurement of fluorescence intensity on the teeth surface is conducted and the result is compared with the numerical computation.

  5. Evaluating fibre orientation dispersion in white matter: Comparison of diffusion MRI, histology and polarized light imaging.

    PubMed

    Mollink, Jeroen; Kleinnijenhuis, Michiel; Cappellen van Walsum, Anne-Marie van; Sotiropoulos, Stamatios N; Cottaar, Michiel; Mirfin, Christopher; Heinrich, Mattias P; Jenkinson, Mark; Pallebage-Gamarallage, Menuka; Ansorge, Olaf; Jbabdi, Saad; Miller, Karla L

    2017-08-15

    Diffusion MRI is an exquisitely sensitive probe of tissue microstructure, and is currently the only non-invasive measure of the brain's fibre architecture. As this technique becomes more sophisticated and microstructurally informative, there is increasing value in comparing diffusion MRI with microscopic imaging in the same tissue samples. This study compared estimates of fibre orientation dispersion in white matter derived from diffusion MRI to reference measures of dispersion obtained from polarized light imaging and histology. Three post-mortem brain specimens were scanned with diffusion MRI and analyzed with a two-compartment dispersion model. The specimens were then sectioned for microscopy, including polarized light imaging estimates of fibre orientation and histological quantitative estimates of myelin and astrocytes. Dispersion estimates were correlated on region - and voxel-wise levels in the corpus callosum, the centrum semiovale and the corticospinal tract. The region-wise analysis yielded correlation coefficients of r = 0.79 for the diffusion MRI and histology comparison, while r = 0.60 was reported for the comparison with polarized light imaging. In the corpus callosum, we observed a pattern of higher dispersion at the midline compared to its lateral aspects. This pattern was present in all modalities and the dispersion profiles from microscopy and diffusion MRI were highly correlated. The astrocytes appeared to have minor contribution to dispersion observed with diffusion MRI. These results demonstrate that fibre orientation dispersion estimates from diffusion MRI represents the tissue architecture well. Dispersion models might be improved by more faithfully incorporating an informed mapping based on microscopy data. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

  6. 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

  7. Interface morphologies and interlayer diffusions in organic light emitting device by x-ray scattering

    NASA Astrophysics Data System (ADS)

    Lee, Young Joo; Park, Seong-Sik; Kim, Jinwoo; Kim, Hyunjung

    2009-06-01

    Surface and interface morphologies with thermal expansions and interlayer diffusions in organic light emitting device [LiF/tris-(8-hydroxyquinoline) aluminum (Alq3)/N,N'-bis(naphthalen-1-yl)-N ,N'-bis(phenyl)benzidine (NPB)/copper phthalocyanine (CuPc)/indium tin oxide/SiO2/glass] were studied by synchrotron x-ray scattering. Interface sharpness and roughness correlation are held under annealing at 100 °C up to 1 h and at 120 °C up to 0.25 h in spite of thermal expansions and interlayer diffusions of NPB and Alq3 layers. The roughness correlation at the interfaces was recovered partially when the interlayer diffusions reach quasisaturation. Crystallization of NPB is hindered due to the interlayer diffusions and appears at much higher temperature than its glass transition.

  8. 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.

  9. 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.

  10. Study of CCT varying by volume scattering diffuser with moving and rotating white light LED

    NASA Astrophysics Data System (ADS)

    Ma, Shih-Hsin; Chen, Liang-Shiun; Huang, Wen-Chao

    2014-09-01

    In this study, the corrected color temperature (CCT) of white light, which originates from a white light LED (WLLED) and passes through a volume-scattering diffuser (VSD), is investigated. The VSD with thickness of 2mm is fabricated by mixing the 2um-sized PMMA scattering particles and the epoxy glue with different concentration values. Moreover, in order to understand the influences of the illuminated area and the scattering path of VSD on CCT values, the bulletheaded and lambertian-type WLLEDs are assembled for different positions and distinct orientations along the optical axis in a black cavity. A detailed comparison between results regarding the white light with and without passing through the VSD is offered. The results of this research will help to improve the colorful consistency of the LED lamps which use diffusers.

  11. 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.

  12. Predicting diffuse light-enhancement of GPP from plant functional traits: A multi-site synthesis

    NASA Astrophysics Data System (ADS)

    O'Halloran, T. L.; Barr, J. G.; Cook, B.; Goeckede, M.; Law, B. E.; Kueppers, L. M.; Riley, W. J.

    2013-12-01

    Diffuse light enhances canopy-scale photosynthesis because isotropic diffuse light penetrates deeper into the canopy, involves more leaf area in photosynthesis, and prevents the top of the canopy from becoming light saturated. However, the observational and modeling communities still have little understanding of how the 'Diffuse light Enhancement Effect' (DEE) varies across plant functional types or is constrained by factors such as nitrogen availability and plant structure. So far, variability in the strength of DEE across plant functional types (PFTs) remains poorly constrained, but canopy models indicate leaf area index (LAI) is a primary controller. While the very few existing multi-site, measurement-based syntheses of the DEE have provided valuable information on the variability of the DEE across a few plant functional types, no study has correlated measured metrics of DEE magnitude with direct measurements of canopy physical traits across a wide range of plant functional types. Here we report a new metric that is suitable for quantifying the DEE in both flux measurements and land surface models. We also present, for the first time, an examination of the relationship between the DEE metric and plant functional traits. Results from our 70+ site AmeriFlux and FLUXNET synthesis indicate that LAI is the strongest controller of the DEE across sites and PFTs, with less significant influences from foliar nitrogen, canopy height, and mean annual precipitation. Our results will enable direct evaluation and improvement of remote sensing algorithms and light use efficiency models (e.g. MODIS GPP), which to this point regard diffuse light fraction as a source of noise. Additionally, improving resolution of the DEE in prognostic land surface models, such as the Community Land Model (CLM), will greatly improve our ability to forecast future feedbacks to terrestrial carbon sequestration from changes in cloudiness and aerosol amount.

  13. 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.

  14. 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.

  15. Mutual diffusion in binary mixtures of ionic liquids and molecular liquids by dynamic light scattering (DLS).

    PubMed

    Rausch, Michael Heinrich; Lehmann, Julia; Leipertz, Alfred; Fröba, Andreas Paul

    2011-05-28

    The present study shows that dynamic light scattering (DLS) is capable of measuring mutual diffusion coefficients for binary mixtures of ionic liquids (ILs) with different molecular liquids over the complete composition range. Evidence is given that the light scattering signals are related to true molecular binary diffusion. The method stands out due to its ability to work non-invasively in macroscopic thermodynamic equilibrium with reasonable accuracy and within convenient measurement periods. Compared with other techniques, mixtures with distinctly higher viscosities can be probed. For exemplary binary mixtures of 1-ethyl-3-methylimidazolium ethylsulfate ([EMIM][EtSO(4)]) with acetone, acetonitrile, dichloromethane, ethanol, or water as well as of 1-ethyl-3-methylimidazolium methanesulfonate ([EMIM][MeSO(3)]) with acetone, water, or methanol, mutual diffusivity data were measured over a wide range of composition at a temperature of 293.15 K. In general, the mutual diffusivity increases with increasing mole fraction of the molecular liquid and similarities to aqueous solutions of classical inorganic salts can be found. The characteristic behavior of the mutual diffusion coefficients is influenced by the nature of the chosen molecular liquid. For IL water mixtures, low light scattering intensities were observed despite the large refractive index difference of the pure components. The reason for this behavior may be the existence of water clusters in the mixtures. Additional measurements for IL acetone mixtures at temperatures ranging from 278.15 K to 323.15 K showed that the temperature dependence of the mutual diffusivity can be represented by Arrhenius functions and is increasing for decreasing mole fractions of acetone.

  16. 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.

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

    SciTech Connect

    Hielscher, A.H.; Mourant, J.R.; Bigio, I.J.

    2000-01-04

    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 x 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.

  18. Diffusion of light gases in advanced nanoporous membranes and catalysts via NMR diffusometry

    NASA Astrophysics Data System (ADS)

    Mueller, Robert A.

    Diffusion in nanoporous gas separation membranes and catalysts plays an important role in their selectivity and performance. As a result, there is an intense effort towards development of novel membranes and catalysts with microstructures tailored for improved transport properties. Fundamental understanding and prediction of the mass transport properties of these materials can be obtained by studies of mass transport on a broad range of microscopic length scales. In this dissertation, a novel NMR diffusometry technique is employed to study the influence of the pore network properties on light gas diffusion for several nanoporous systems, which represent promising advanced gas separation membranes and catalysts. The following systems were investigated: (i) carbon molecular sieve membranes, (ii) mixed-matrix membranes and (iii) rare-earth aerogel catalysts. For carbon molecular sieve membranes, the self-diffusion properties of several light gases of industrial importance are characterized by investigating the dependences of the self diffusivity on displacement length scale, temperature, sorbate loading and composition. Analysis of these dependences and comparison of the measured microscopic transport data with the corresponding results of membrane permeation enabled the determination of membrane structural properties which lead to the remarkable diffusion selectivity of these membranes. For mixed-matrix membranes, detailed measurements of light gas sorbate diffusion over a broad range of microscopic length scales enables resolution of the different modes of sorbate self-diffusion inside mixed-matrix membranes. Finally for samaria-aerogel catalyst, the influence of catalyst packing is explored based on detailed microscopic diffusion measurements over a broad range of sorbate loading pressures and detailed data analysis. These studies were enabled by application of a novel pulsed-field gradient nuclear magnetic resonance technique, developed in part by this work

  19. 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.

  20. Memory-Assisted Exciton Diffusion in the Chlorosome Light-Harvesting Antenna of Green Sulfur Bacteria.

    PubMed

    Fujita, Takatoshi; Brookes, Jennifer C; Saikin, Semion K; Aspuru-Guzik, Alán

    2012-09-06

    Chlorosomes are likely the largest and most efficient natural light-harvesting photosynthetic antenna systems. They are composed of large numbers of bacteriochlorophylls organized into supramolecular aggregates. We explore the microscopic origin of the fast excitation energy transfer in the chlorosome using the recently resolved structure and atomistic-detail simulations. Despite the dynamical disorder effects on the electronic transitions of the bacteriochlorophylls, our simulations show that the exciton delocalizes over the entire aggregate in about 200 fs. The memory effects associated to the dynamical disorder assist the exciton diffusion through the aggregates and enhance the diffusion coefficients as a factor of 2 as compared to the model without memory. Furthermore, exciton diffusion in the chlorosome is found to be highly anisotropic with the preferential transfer toward the baseplate, which is the next functional element in the photosynthetic system.

  1. Stimulated concentration (diffusion) light scattering on nanoparticles in a liquid suspension

    NASA Astrophysics Data System (ADS)

    Burkhanov, I. S.; Krivokhizha, S. V.; Chaikov, L. L.

    2016-06-01

    A nonlinear growth of the light scattering intensity has been observed and the frequency shift of the spectral line of scattered light has been measured in light backscattered in suspensions of diamond and latex nanoparticles in water. The shift corresponds to the HWHM of the line of spontaneous scattering on particles. We may conclude that there exists stimulated concentration (diffusion) light scattering on variations of the particle concentration, which is also called the stimulated Mie scattering. In a fibre probe scheme, the growth of the shift of the scattered spectral line is observed with an increase in the exciting beam power. The variation of the frequency shift with an increase in the exciting power is explained by convection in liquid.

  2. 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

  3. Brownian Motion in a Speckle Light Field: Tunable Anomalous Diffusion and Selective Optical Manipulation

    PubMed Central

    Volpe, Giorgio; Volpe, Giovanni; Gigan, Sylvain

    2014-01-01

    The motion of particles in random potentials occurs in several natural phenomena ranging from the mobility of organelles within a biological cell to the diffusion of stars within a galaxy. A Brownian particle moving in the random optical potential associated to a speckle pattern, i.e., a complex interference pattern generated by the scattering of coherent light by a random medium, provides an ideal model system to study such phenomena. Here, we derive a theory for the motion of a Brownian particle in a speckle field and, in particular, we identify its universal characteristic timescale. Based on this theoretical insight, we show how speckle light fields can be used to control the anomalous diffusion of a Brownian particle and to perform some basic optical manipulation tasks such as guiding and sorting. Our results might broaden the perspectives of optical manipulation for real-life applications. PMID:24496461

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

    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.

  5. Parallel heterodyne detection of dynamic light-scattering spectra from gold nanoparticles diffusing in viscous fluids.

    PubMed

    Atlan, Michael; Desbiolles, Pierre; Gross, Michel; Coppey-Moisan, Maïté

    2010-03-01

    We developed a microscope intended to probe, using a parallel heterodyne receiver, the fluctuation spectrum of light quasi-elastically scattered by gold nanoparticles diffusing in viscous fluids. The cutoff frequencies of the recorded spectra scale up linearly with those expected from single-scattering formalism in a wide range of dynamic viscosities (1 to 15 times water viscosity at room temperature). Our scheme enables ensemble-averaged optical fluctuations measurements over multispeckle recordings in low light, at temporal frequencies up to 10 kHz, with a 12 Hz framerate array detector.

  6. 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.

  7. Highly transparent sapphire micro-grating structures with large diffuse light scattering.

    PubMed

    Ko, Yeong Hwan; Yu, Jae Su

    2011-08-01

    The highly transparent micro-grating structures (MGSs) of sapphire substrate with large diffuse light scattering were theoretically and experimentally studied. From the finite difference time domain simulation, it was found that the degree of diffuse light scattering is strongly dependent on the size of grating structures. For a highly transparent property, the sapphire MGSs were optimally designed by the theoretical calculations using the rigorous coupled wave analysis method. The order of taper, geometry (i.e., width and height), and pitch length of MGSs were optimized to maximize their average total transmittance over a wide wavelength range of 300-1800 nm. Additionally, the influence of the deposition of low-refractive index material such as SiO2 onto sapphire MGSs on the transmittance characteristics was investigated. To verify experimentally the feasibility, the sapphire MGSs were fabricated by the conventional lithography and dry etching processes. The SiO2 deposited sapphire MGS exhibited a further increase in the total transmittance due to its relatively more graded refractive index profile while maintaining a significantly enhanced diffuse light scattering. The experimental data were in a reasonable agreement with the theoretical results.

  8. Detection of the Cherenkov light diffused by Sea Water with the ULTRA Experiment

    NASA Astrophysics Data System (ADS)

    ULTRA Collaboration

    The study of Ultra High Energy Cosmic Rays represents one of the most challenging topic in this field. The interaction of primary particles with atmospheric nuclei produces a huge Extensive Air Shower together with isotropic emission of UV fluorescence light and highly directional Cherenkov photons, that are reflected/diffused isotropically by the impact on the Earth's surface or on high optical depth clouds. For space-based observations, detecting the reflected Cherenkov signal in a delayed coincidence with the fluorescence light allows to measure the shower maximum, giving a strong signature for discriminating hadrons and neutrinos, and allowing to estimate the primary chemical composition. Since the Earth's surface is mostly covered by water, the ULTRA (UV Light Transmission and Reflection in the Atmosphere) experiment has been designed to provide the diffusing properties of sea water, overcoming the lack of information in this specific field. A small EAS array, made of 5 particle detectors, and an UV optical device, have been coupled to detect in coincidence both electromagnetic and UV components. The detector was in operation from May to December, 2005, in a small private harbour in Capo Granitola (Italy); the results of these measurements in terms of diffusion coefficient and threshold energy are presented.

  9. Spatial-mode conversion using random diffuser and spatial light modulator for reduction of modal crosstalk

    NASA Astrophysics Data System (ADS)

    Ishii, Koki; Okamoto, Atsushi; Tsuritani, Takehiro; Wakayama, Yuta; Goto, Yuta; Tomita, Akihisa

    2016-02-01

    The mode-division multiplexing (MDM) technique enables the transmission of multiple signals within a multi-mode fiber (MMF) or a few-mode fiber (FMF). To construct an efficient and flexible MDM network in the same way as a wavelength-division multiplexing network, a mode conversion method with low modal crosstalk is required for switching between arbitrary spatial modes. However, in general, modal crosstalk is strongly dependent on the intensity pattern before mode conversion, and it is increased particularly for higher order modes. In order to reduce modal crosstalk, we propose a method using a random diffuser and a spatial light modulator (SLM). In the proposed method, firstly, the input spatial mode is dispersed uniformly by the random diffuser. Subsequently, the diffused phase distribution is canceled and converted into the desired spatial mode by the SLM, which displays phase difference between desired and diffused modes. Consequently, every spatial mode can be evenly converted into a desired mode. Here, we numerically simulate and confirm that the proposed method can reduce modal crosstalk compared to the conversion method without the random diffuser.

  10. 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.

  11. Advances in detection of diffuse seafloor venting using structured light imaging.

    NASA Astrophysics Data System (ADS)

    Smart, C.; Roman, C.; Carey, S.

    2016-12-01

    Systematic, remote detection and high resolution mapping of low temperature diffuse hydrothermal venting is inefficient and not currently tractable using traditional remotely operated vehicle (ROV) mounted sensors. Preliminary results for hydrothermal vent detection using a structured light laser sensor were presented in 2011 and published in 2013 (Smart) with continual advancements occurring in the interim. As the structured light laser passes over active venting, the projected laser line effectively blurs due to the associated turbulence and density anomalies in the vent fluid. The degree laser disturbance is captured by a camera collecting images of the laser line at 20 Hz. Advancements in the detection of the laser and fluid interaction have included extensive normalization of the collected laser data and the implementation of a support vector machine algorithm to develop a classification routine. The image data collected over a hydrothermal vent field is then labeled as seafloor, bacteria or a location of venting. The results can then be correlated with stereo images, bathymetry and backscatter data. This sensor is a component of an ROV mounted imaging suite which also includes stereo cameras and a multibeam sonar system. Originally developed for bathymetric mapping, the structured light laser sensor, and other imaging suite components, are capable of creating visual and bathymetric maps with centimeter level resolution. Surveys are completed in a standard mowing the lawn pattern completing a 30m x 30m survey with centimeter level resolution in under an hour. Resulting co-registered data includes, multibeam and structured light laser bathymetry and backscatter, stereo images and vent detection. This system allows for efficient exploration of areas with diffuse and small point source hydrothermal venting increasing the effectiveness of scientific sampling and observation. Recent vent detection results collected during the 2013-2015 E/V Nautilus seasons will be

  12. A facile fabrication of light diffusing film with LDP/polyacrylates composites coating for anti-glare LED application

    NASA Astrophysics Data System (ADS)

    Song, Shisen; Sun, Yaojie; Lin, Yandan; You, Bo

    2013-05-01

    In this paper, we present a facile coating technique to fabricate the light diffusing film with hemispherical surface convex micro-structure. The coating was prepared by different ratio of light-diffusing particles (LDP)/polyacrylates composites via in situ radical polymerization, with the H2SO4 and vinyl triethoxysilane (A-151) pretreatment made the LDP better dispersed and incorporated with polyacrylate polymer chains. When the mass ratio (LDP/polyacrylate) was 0.5, the film obtained the highest light-diffusing effect and more than 90% transmittance due to the formation of hemispherical surface convex micro-structure. The light diffusing films have excellent anti-glare property if applied to LED light system.

  13. Generation of diffuser dot patterns for light guides using fuzzy scheme strategy

    NASA Astrophysics Data System (ADS)

    Zhao, Heng; Fang, Suping; Yang, Qing; Shang, Bo

    2009-12-01

    We propose a fuzzy scheme strategy for the generation of the diffuser dot patterns in the light guide of an edge-lit backlight. The fuzzy scheme strategy is based on fuzzy logic and rules, which are closely related to the physical luminance properties of the light guide. During the process of generating diffuser dot patterns, two inputs are the dot radius and the distance from dots to a light source, and one output is the luminance of the light guide panel. This strategy converts the linguistic strategy based on expert knowledge the optimal dot-generation strategy. Furthermore, this study includes the discussion of fuzzification and defuzzification strategies, the derivation of fuzzy logic rules, and the analysis of fuzzy reasoning mechanisms. Experiment results reveal that the proposed strategy can achieve an even luminance condition by establishing dot patterns. Compared to conventional methods, the fuzzy scheme strategy has two advantages. It effectively integrates the dot generation scheme into the subsequent optical design phase to make dot patterns more efficient and easy to control. Moreover, optimized dot patterns realize sufficient luminance uniformity.

  14. The focusing of light scattered from diffuse reflectors using phase modulation

    NASA Astrophysics Data System (ADS)

    Schafer, Jessica M.; Marciniak, Michael A.

    2012-10-01

    "Indirect photography" was recently demonstrated for imaging hidden scene information through the collection and radiometric modeling of light reflecting off of visible reflecting surfaces. The ability to focus the beam that reflects off the visible surface to a tight spot on the hidden object is theorized to simulate a direct line of sight from the light source to the object, reducing the radiometric model to that of the previously demonstrated "dual photography." Experiments involving the focusing of light transmitted through highly scattering media have been adapted to the case of reflection. The focusing of a HeNe laser reflected off diffusely scattering surfaces to a tight spot is demonstrated using phase control. A liquid crystal spatial light modulator assigns pixelated phase delay to the beam to conjugate the scattering properties of the reflector. Intensity enhancement values between 13.8 and 122.3 are achieved for the surfaces studied. Samples with relatively strong specular reflection achieve higher enhancement for a given geometry. More diffusely reflecting materials achieve higher enhancement in regions of nonspecular scatter, facilitating non-mechanical beam steering.

  15. Neurite density from magnetic resonance diffusion measurements at ultrahigh field: comparison with light microscopy and electron microscopy.

    PubMed

    Jespersen, Sune N; Bjarkam, Carsten R; Nyengaard, Jens R; Chakravarty, M Mallar; Hansen, Brian; Vosegaard, Thomas; Østergaard, Leif; Yablonskiy, Dmitriy; Nielsen, Niels Chr; Vestergaard-Poulsen, Peter

    2010-01-01

    Due to its unique sensitivity to tissue microstructure, diffusion-weighted magnetic resonance imaging (MRI) has found many applications in clinical and fundamental science. With few exceptions, a more precise correspondence between physiological or biophysical properties and the obtained diffusion parameters remain uncertain due to lack of specificity. In this work, we address this problem by comparing diffusion parameters of a recently introduced model for water diffusion in brain matter to light microscopy and quantitative electron microscopy. Specifically, we compare diffusion model predictions of neurite density in rats to optical myelin staining intensity and stereological estimation of neurite volume fraction using electron microscopy. We find that the diffusion model describes data better and that its parameters show stronger correlation with optical and electron microscopy, and thus reflect myelinated neurite density better than the more frequently used diffusion tensor imaging (DTI) and cumulant expansion methods. Furthermore, the estimated neurite orientations capture dendritic architecture more faithfully than DTI diffusion ellipsoids.

  16. Charactrisation of particle assemblies by 3D cross correlation light scattering and diffusing wave spectroscopy

    NASA Astrophysics Data System (ADS)

    Scheffold, Frank

    2014-08-01

    To characterize the structural and dynamic properties of soft materials and small particles, information on the relevant mesoscopic length scales is required. Such information is often obtained from traditional static and dynamic light scattering (SLS/DLS) experiments in the single scattering regime. In many dense systems, however, these powerful techniques frequently fail due to strong multiple scattering of light. Here I will discuss some experimental innovations that have emerged over the last decade. New methods such as 3D static and dynamic light scattering (3D LS) as well as diffusing wave spectroscopy (DWS) can cover a much extended range of experimental parameters ranging from dilute polymer solutions, colloidal suspensions to extremely opaque viscoelastic emulsions.

  17. Light diffusion through composite restorations added with spherical glass mega fillers

    PubMed Central

    BASSI, M. ANDREASI; BASSI, S. ANDREASI; ANDRISANI, C.; LICO, S.; BAGGI, L.; LAURITANO, D.

    2016-01-01

    SUMMARY Purpose Evaluate how the spherical glass mega fillers (SGMFs) can positively interfere with light diffusion when incorporated in a composite restoration. Materials and methods 30 samples (Ss) were performed, applying 2 composite layers of 3 mm each: 6 were made with composite only; 6 with a layer of SGMFs of O1.5mm within the first layer of composite; 6 with 2 overlapping layers of SGMFs of O1.5mm; 6 with a layer of SGMFs of O2mm; 6 with 2 overlapping layers of SGMFs of O2mm. The curing time was set at 40s for the first layer, and 120s for the second layer, transilluminated through the first layer. Digital pictures were taken, in standardized settings, during the transillumination, and the light intensity was measured with a digital image analysis software. Results From a lateral view the Ss with a single layer of SGMFs of O1.5mm and O2mm, the relative increments of light intensity, were of 24.37% and 33.33% respectively. Concerning the Ss made with 2 layers of SGMFs, the relative increments were of 67.99% and 66.4% respectively. In front view has emerged a relative increase rate of light intensity of 53.66% and 79.58%, in the Ss with a single layer of SGMFs of O1.5mm and of O2mm respectively. Furthermore, in the Ss with two layers of SGMFs of O1.5mm and O2mm the relative increments were of 267.53 and 319.63% respectively. Conclusion The SGMFs are reliable in facilitating light diffusion within the light-curing composite resins. PMID:28280536

  18. Studying complex fluids and crystal formation using Dynamic Light Scattering and Optical Probe Diffusion

    NASA Astrophysics Data System (ADS)

    Streletzky, Kiril A.

    2004-10-01

    Dynamic light scattering (DLS) spectroscopy provides non-destructive analytic technique for probing structure and dynamics of polymer solutions, colloids, micellar systems, liquid crystals, and, in some cases, observation of nucleation and crystal growth. The method of optical probe diffusion uses DLS to measure transport of dilute mesoscopic probes in a complex fluid solution. If tracer particles are the dominant scatterers in solution, their diffusion provides important information for inferring physical properties of the complex fluid. In situ nature of DLS allows non-invasive studies of different chemical and physical processes such as polymer and colloidal diffusion, gelation, micellar aggregation and dynamics. DLS is also useful for studying critical behavior of liquid crystals and for observing crystallization from clear solutions. The highlights of our results obtained using DLS and optical probe diffusion are presented. These examples include: a) research on polymer dynamics in dilute and concentrated solutions of a neutral HPC polymer; b) project on aggregation and transport of spherical Tx-100 micelles; c) study of crystallization of molecular sieve zeolite NaA.

  19. Diffusivities of Ternary Mixtures of n-Alkanes with Dissolved Gases by Dynamic Light Scattering.

    PubMed

    Heller, Andreas; Giraudet, Cédric; Makrodimitri, Zoi A; Fleys, Matthieu S H; Chen, Jiaqi; van der Laan, Gerard P; Economou, Ioannis G; Rausch, Michael H; Fröba, Andreas P

    2016-10-12

    Theoretical approaches suggest that dynamic light scattering (DLS) signals from low-molecular-weight ternary mixtures are governed by fluctuations in temperature as well as two individual contributions from fluctuations in concentration that are related to the eigenvalues of the Fick diffusion matrix. Until now, this could not be proven experimentally in a conclusive way. In the present study, a detailed analysis of DLS signals in ternary mixtures consisting of n-dodecane (n-C12H26) and n-octacosane (n-C28H58) with dissolved hydrogen (H2), carbon monoxide (CO), or water (H2O) as well as of n-C12H26 or n-C28H58 with dissolved H2 and CO is given for temperatures up to 523 K and pressures up to 4.1 MPa. Thermal diffusivities of pure n-C12H26 and n-C28H58 as well as thermal and mutual diffusivities of their binary mixtures being the basis for the ternary mixtures with dissolved gas were studied for comparison purposes. For the investigated ternary mixtures, three individual signals could be distinguished in the time-resolved analysis of scattered light intensity by using photon correlation spectroscopy (PCS). For the first time, it could be evidenced that these signals are clearly associated with hydrodynamic modes. In most cases, the fastest mode observable for ternary mixtures is associated with the thermal diffusivity. The two further modes obviously related to the molecular mass transport are observable on different time scales and comparable to the modes associated with the concentration fluctuations in the respective binary mixtures. Comparison of the experimental data with results from molecular dynamics simulations revealed very good agreement.

  20. Radiative Energy Budgets of Phototrophic Surface-Associated Microbial Communities and their Photosynthetic Efficiency Under Diffuse and Collimated Light

    PubMed Central

    Lichtenberg, Mads; Brodersen, Kasper E.; Kühl, Michael

    2017-01-01

    We investigated the radiative energy budgets of a heterogeneous photosynthetic coral reef sediment and a compact uniform cyanobacterial biofilm on top of coastal sediment. By combining electrochemical, thermocouple and fiber-optic microsensor measurements of O2, temperature and light, we could calculate the proportion of the absorbed light energy that was either dissipated as heat or conserved by photosynthesis. We show, across a range of different incident light regimes, that such radiative energy budgets are highly dominated by heat dissipation constituting up to 99.5% of the absorbed light energy. Highest photosynthetic energy conservation efficiency was found in the coral sediment under low light conditions and amounted to 18.1% of the absorbed light energy. Additionally, the effect of light directionality, i.e., diffuse or collimated light, on energy conversion efficiency was tested on the two surface-associated systems. The effects of light directionality on the radiative energy budgets of these phototrophic communities were not unanimous but, resulted in local spatial differences in heat-transfer, gross photosynthesis, and light distribution. The light acclimation index, Ek, i.e., the irradiance at the onset of saturation of photosynthesis, was >2 times higher in the coral sediment compared to the biofilm and changed the pattern of photosynthetic energy conservation under light-limiting conditions. At moderate to high incident irradiances, the photosynthetic conservation of absorbed energy was highest in collimated light; a tendency that changed in the biofilm under sub-saturating incident irradiances, where higher photosynthetic efficiencies were observed under diffuse light. The aim was to investigate how the physical structure and light propagation affected energy budgets and light utilization efficiencies in loosely organized vs. compact phototrophic sediment under diffuse and collimated light. Our results suggest that the optical properties and the

  1. Radiative Energy Budgets of Phototrophic Surface-Associated Microbial Communities and their Photosynthetic Efficiency Under Diffuse and Collimated Light.

    PubMed

    Lichtenberg, Mads; Brodersen, Kasper E; Kühl, Michael

    2017-01-01

    We investigated the radiative energy budgets of a heterogeneous photosynthetic coral reef sediment and a compact uniform cyanobacterial biofilm on top of coastal sediment. By combining electrochemical, thermocouple and fiber-optic microsensor measurements of O2, temperature and light, we could calculate the proportion of the absorbed light energy that was either dissipated as heat or conserved by photosynthesis. We show, across a range of different incident light regimes, that such radiative energy budgets are highly dominated by heat dissipation constituting up to 99.5% of the absorbed light energy. Highest photosynthetic energy conservation efficiency was found in the coral sediment under low light conditions and amounted to 18.1% of the absorbed light energy. Additionally, the effect of light directionality, i.e., diffuse or collimated light, on energy conversion efficiency was tested on the two surface-associated systems. The effects of light directionality on the radiative energy budgets of these phototrophic communities were not unanimous but, resulted in local spatial differences in heat-transfer, gross photosynthesis, and light distribution. The light acclimation index, Ek, i.e., the irradiance at the onset of saturation of photosynthesis, was >2 times higher in the coral sediment compared to the biofilm and changed the pattern of photosynthetic energy conservation under light-limiting conditions. At moderate to high incident irradiances, the photosynthetic conservation of absorbed energy was highest in collimated light; a tendency that changed in the biofilm under sub-saturating incident irradiances, where higher photosynthetic efficiencies were observed under diffuse light. The aim was to investigate how the physical structure and light propagation affected energy budgets and light utilization efficiencies in loosely organized vs. compact phototrophic sediment under diffuse and collimated light. Our results suggest that the optical properties and the

  2. Spatial cross modulation method using a random diffuser and phase-only spatial light modulator for constructing arbitrary complex fields.

    PubMed

    Shibukawa, Atsushi; Okamoto, Atsushi; Takabayashi, Masanori; Tomita, Akihisa

    2014-02-24

    We propose a spatial cross modulation method using a random diffuser and a phase-only spatial light modulator (SLM), by which arbitrary complex-amplitude fields can be generated with higher spatial resolution and diffraction efficiency than off-axis and double-phase computer-generated holograms. Our method encodes the original complex object as a phase-only diffusion image by scattering the complex object using a random diffuser. In addition, all incoming light to the SLM is consumed for a single diffraction order, making a diffraction efficiency of more than 90% possible. This method can be applied for holographic data storage, three-dimensional displays, and other such applications.

  3. 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)

  4. Extensive air showers and diffused Cherenkov light detection: The ULTRA experiment

    NASA Astrophysics Data System (ADS)

    Agnetta, G.; Assis, P.; Biondo, B.; Brogueira, P.; Cappa, A.; Catalano, O.; Chauvin, J.; D'Alí Staiti, G.; Dattoli, M.; Espirito-Santo, M. C.; Fava, L.; Galeotti, P.; Giarrusso, S.; Gugliotta, G.; La Rosa, G.; Lebrun, D.; Maccarone, M. C.; Mangano, A.; Melo, L.; Moreggia, S.; Pimenta, M.; Russo, F.; Saavedra, O.; Segreto, A.; Silva, J. C.; Stassi, P.; Tomè, B.; Vallania, P.; Vigorito, C.; ULTRA Collaboration

    2007-01-01

    The Uv Light Transmission and Reflection in the Atmosphere (ULTRA) experiment has been designed to provide quantitative measurements of the backscattered Cherenkov signal associated to the Extensive Air Showers (EAS) at the impact point on the Earth surface. The knowledge of such information will test the possibility to detect the diffused Cherenkov light spot from space within the Ultra high-energy cosmic ray observation. The Cherenkov signal is necessary to give an absolute reference for the track, allowing the measurement of the shower maximum and easing the separation between neutrino and hadronic showers. In this paper we discuss the experimental set-up with detailed information on the detection method; the in situ and laboratory calibrations; the simulation of the expected detector response and finally the preliminary results on the detector performance.

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

    NASA Astrophysics Data System (ADS)

    Barun, V. V.; Ivanov, A. P.

    2013-10-01

    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.

  6. Iterative positioning algorithm to reduce the impact of diffuse reflection on an indoor visible light positioning system

    NASA Astrophysics Data System (ADS)

    Huang, Heqing; Feng, Lihui; Guo, Peng; Yang, Aiying; Ni, Guoqiang

    2016-06-01

    Recently, indoor visible light localization has become attractive. Unfortunately, its performance is limited by diffuse reflection. The diffuse reflection is estimated by the bilinear interpolation-based method. A received signal strength-based iterative visible light positioning algorithm is proposed to reduce the influence of diffuse reflection by subtracting the estimated diffuse reflection signal from the received signal. Simulations are made to evaluate the proposed iterative positioning algorithm in a typical scenario with different parameters of the field-of-view (FOV) of the receiver and the reflectivity of the wall. Results show that the proposed algorithm can reduce the average positioning error by 12 times in a typical scenario and can reduce the positioning error greatly with various FOV of the receiver and the reflectivity of the wall. The proposed algorithm is effective and robust to reduce the degradation caused by diffuse reflection in a positioning system and will have many potential applications in indoor localization scenarios.

  7. Scaling property of the diffusion equation for light in a turbid medium with varying refractive index.

    PubMed

    Shendeleva, Margarita L; Molloy, John A

    2007-09-01

    A spatially varying refractive index leads to the bending of photon paths in a medium, which complicates the Monte Carlo modeling of a photon random walk. We show that the process of photon diffusion in a turbid medium with varying refractive index and curved photon paths can be mapped to the diffusion process in a medium with straight photon paths and modified optical properties. Specifically, the diffusion coefficient, the absorption, and the refractive index of the second medium should differ from the corresponding properties of the first medium by the factor of the squared refractive index of the first medium. The specific intensity of light in the second medium will then be equal to the specific intensity in the first medium divided by the same factor, which also means that the photon density distributions in the two media will be identical. In a Monte Carlo simulation the scaling property suggests that two different algorithms can be used to obtain the photon density distribution, namely, the algorithm with curved photon paths and given optical properties and the algorithm with straight photon paths and modified optical properties.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    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.

  9. 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

  10. 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.

  11. 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.

  12. 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 / v μt‧ 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.

  13. Systematic analysis of diffuse rear reflectors for enhanced light trapping in silicon solar cells

    SciTech Connect

    Pfeffer, Florian; Eisenlohr, Johannes; Basch, Angelika; Hermle, Martin; Lee, Benjamin G.; Goldschmidt, Jan Christoph

    2016-04-08

    Simple diffuse rear reflectors can enhance the light path length of weakly absorbed near infrared light in silicon solar cells and set a benchmark for more complex and expensive light trapping structures like dielectric gratings or plasmonic particles. We analyzed such simple diffuse rear reflectors systematically by optical and electrical measurements. We applied white paint, TiO2 nanoparticles, white backsheets and a silver mirror to bifacial silicon solar cells and measured the enhancement of the external quantum efficiency for three different solar cell geometries: planar front and rear side, textured front and planar rear side, and textured front and rear side. We showed that an air-gap between the solar cell and the reflector decreases the absorption enhancement significantly, thus white paint and TiO2 nanoparticles directly applied to the rear cell surface lead to the highest short circuit current density enhancements. Here, the short circuit current density gains for a 200 um thick planar solar cell reached up to 1.8 mA/cm2, compared to a non-reflecting black rear side and up to 0.8 mA/cm2 compared to a high-quality silver mirror rear side. For solar cells with textured front side the short circuit current density gains are in the range between 0.5 and 1.0 mA/cm2 compared to a non-reflecting black rear side and do not significantly depend on the angular characteristic of the rear side reflector but mainly on its absolute reflectance.

  14. Systematic analysis of diffuse rear reflectors for enhanced light trapping in silicon solar cells

    SciTech Connect

    Pfeffer, Florian; Eisenlohr, Johannes; Basch, Angelika; Hermle, Martin; Lee, Benjamin G.; Goldschmidt, Jan Christoph

    2016-08-01

    Simple diffuse rear reflectors can enhance the light path length of weakly absorbed near infrared light in silicon solar cells and set a benchmark for more complex and expensive light trapping structures like dielectric gratings or plasmonic particles. We analyzed such simple diffuse rear reflectors systematically by optical and electrical measurements. We applied white paint, TiO2 nanoparticles, white backsheets and a silver mirror to bifacial silicon solar cells and measured the enhancement of the external quantum efficiency for three different solar cell geometries: planar front and rear side, textured front and planar rear side, and textured front and rear side. We showed that an air-gap between the solar cell and the reflector decreases the absorption enhancement significantly, thus white paint and TiO2 nanoparticles directly applied to the rear cell surface lead to the highest short circuit current density enhancements. The short circuit current density gains for a 200 um thick planar solar cell reached up to 1.8 mA/cm2, compared to a non-reflecting black rear side and up to 0.8 mA/cm2 compared to a high-quality silver mirror rear side. For solar cells with textured front side the short circuit current density gains are in the range between 0.5 and 1.0 mA/cm2 compared to a non-reflecting black rear side and do not significantly depend on the angular characteristic of the rear side reflector but mainly on its absolute reflectance.

  15. Systematic analysis of diffuse rear reflectors for enhanced light trapping in silicon solar cells

    DOE PAGES

    Pfeffer, Florian; Eisenlohr, Johannes; Basch, Angelika; ...

    2016-04-08

    Simple diffuse rear reflectors can enhance the light path length of weakly absorbed near infrared light in silicon solar cells and set a benchmark for more complex and expensive light trapping structures like dielectric gratings or plasmonic particles. We analyzed such simple diffuse rear reflectors systematically by optical and electrical measurements. We applied white paint, TiO2 nanoparticles, white backsheets and a silver mirror to bifacial silicon solar cells and measured the enhancement of the external quantum efficiency for three different solar cell geometries: planar front and rear side, textured front and planar rear side, and textured front and rear side.more » We showed that an air-gap between the solar cell and the reflector decreases the absorption enhancement significantly, thus white paint and TiO2 nanoparticles directly applied to the rear cell surface lead to the highest short circuit current density enhancements. Here, the short circuit current density gains for a 200 um thick planar solar cell reached up to 1.8 mA/cm2, compared to a non-reflecting black rear side and up to 0.8 mA/cm2 compared to a high-quality silver mirror rear side. For solar cells with textured front side the short circuit current density gains are in the range between 0.5 and 1.0 mA/cm2 compared to a non-reflecting black rear side and do not significantly depend on the angular characteristic of the rear side reflector but mainly on its absolute reflectance.« less

  16. Flow visualization in an artificial heart using diffuse and planar laser lighting.

    PubMed

    Mussivand, T; Navarro, R; Chen, J F; Braun, J; Harasaki, H; Kiraly, R; Batur, C; McMillin, C; Nosé, Y

    1988-01-01

    The purpose of the study was to characterize flow properties within a clinical pusher plate type artificial heart. Dual camera video tape and synchronized still photographs were used to study flow patterns. Diffused light and a planar laser source provided illumination. The laser light was turned into a plane of light with a thickness varying from 0.1 to 10 mm, and magnesium oxide and Amberlite particles were used as tracers. Qualitative and quantitative analyses were performed by the examination and digitization of flow patterns. Inflow, outflow, pneumatic drive and after-load pressure, diaphragm motion, cardiac output, and heart rate were measured and recorded. An electrical circuit was developed to synchronize pump diaphragm motion with captured images of flow trajectories. Trajectories were then digitized, and velocities, turbulence, and shear stresses were calculated. As the result of these experiments, disturbed, recirculating, and stagnation zones were identified and global and local turbulence values were determined. Simultaneous turbulence, stasis, recirculation, and laminar flow patterns were observed during most phases of the pumping cycle. Velocities obtained varied from 2 cm/sec to 145 cm/sec; total local shear stresses of 12 to 897 dynes/cm2 were seen.

  17. 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).

  18. 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.

  19. Method of measuring blood oxygenation based on spectroscopy of diffusely scattered light

    NASA Astrophysics Data System (ADS)

    Kleshnin, M. S.; Orlova, A. G.; Kirillin, M. Yu.; Golubyatnikov, G. Yu.; Turchin, I. V.

    2017-05-01

    A new approach to the measurement of blood oxygenation is developed and implemented, based on an original two-step algorithm reconstructing the relative concentration of biological chromophores (haemoglobin, water, lipids) from the measured spectra of diffusely scattered light at different distances from the radiation source. The numerical experiments and approbation of the proposed approach using a biological phantom have shown the high accuracy of the reconstruction of optical properties of the object in question, as well as the possibility of correct calculation of the haemoglobin oxygenation in the presence of additive noises without calibration of the measuring device. The results of the experimental studies in animals agree with the previously published results obtained by other research groups and demonstrate the possibility of applying the developed method to the monitoring of blood oxygenation in tumour tissues.

  20. Diffuse reflectors for improving light management in solar cells: a review and outlook

    NASA Astrophysics Data System (ADS)

    Barugkin, Chog; Beck, Fiona J.; Catchpole, Kylie R.

    2017-01-01

    Pigment based diffuse reflectors (DRs) have several advantages over metal reflectors such as good stability, high reflectivity, and low parasitic absorption. As such, DRs have the potential to be applied on high efficiency silicon solar cells and further increase the power conversion efficiency. In this paper, we perform a thorough review on the notable achievements to date of DRs’ application for photovoltaics. We outline unique attributes of these technologies and discuss the theoretical and laboratory development working towards overcoming the challenges of transferring to high efficiency silicon solar cells. In order to understand the potential of DRs for high efficiency silicon solar cells, we provide a qualitative analysis of the impact of front reflection, rear absorption and the angular distribution on the useful light absorption in silicon wafers. By including this discussion, we provide an outlook for the application of DR in reaching maximum photo-current for high efficiency silicon solar cells.

  1. Perturbative diffusion theory formalism for interpreting temporal light intensity changes during laser interstitial thermal therapy.

    PubMed

    Chin, Lee C L; Whelan, William M; Vitkin, I Alex

    2007-03-21

    In an effort to understand dynamic optical changes during laser interstitial thermal therapy (LITT), we utilize the perturbative solution of the diffusion equation in heterogeneous media to formulate scattering weight functions for cylindrical line sources. The analysis explicitly shows how changes in detected interstitial light intensity are associated with the extent and location of the volume of thermal coagulation during treatment. Explanations for previously reported increases in optical intensity observed early during laser heating are clarified using the model and demonstrated with experimental measurements in ex vivo bovine liver tissue. This work provides an improved understanding of interstitial optical signal changes during LITT and indicates the sensitivity and potential of interstitial optical monitoring of thermal damage.

  2. Transcranial measurement of diffuse light reflectance from brain edema in rats: effect of change in the blood flow

    NASA Astrophysics Data System (ADS)

    Ueda, Yoshinori; Sato, Shunichi; Ooigawa, Hidetoshi; Nawashiro, Hiroshi; Saitoh, Daizoh; Shima, Katsuji; Okada, Yoshiaki; Ashida, Hiroshi; Obara, Minoru

    2005-04-01

    We assumed that edema causes a decrease in the scattering coefficient of brain tissue and hence a decrease in the intensity of diffuse reflectance from the brain. On the basis of this assumption, we attempted to transcranially detect a formation of brain edema by measuring diffuse light reflectance. In rats, edema was induced by making a cold injury in the brain. The skull was irradiated with 633-nm and 532-nm laser light delivered through an optical fiber, and the diffuse light reflectance from the brain was collected with another optical fiber. We observed that reflectance intensities were significantly decreased around the cold injury both at 633 nm and 532 nm, suggesting that scattering coefficient of brain tissue was reduced due to a formation of edema in this area. In the injury, reflectance intensity was increased at 532 nm, indicating that cerebral blood volume was decreased in this region.

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

    NASA Astrophysics Data System (ADS)

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

    2012-03-01

    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.

  4. 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.

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

    PubMed Central

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

    2014-01-01

    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

  6. 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.

  7. Sub-diffusive spatial frequency domain imaging: light scattering as a biomarker (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    McClatchy, David M.; Rizzo, Elizabeth J.; Kanick, Stephen C.; Krishnaswamy, Venkataramanan; Elliott, Jonathan T.; Wells, Wendy A.; Paulsen, Keith D.; Pogue, Brian W.

    2017-02-01

    In spatial frequency domain imaging (SFDI), a spatially modulated intensity pattern is projected on to tissue, with the demodulated reflectance having more superficial sensitivity with increasing spatial modulation frequency. With sub-diffusive SFDI, very high (>0.5 mm-1) spatial modulation frequencies are projected yielding sensitivity to the directionality of light scattering with only few scattering events occurring and sub-millimeter penetration depth and spatial resolution. This technique has been validated in a series of phantom experiments, where fractal distributions of polystyrene spheres were imaged, and through a model based inversion, the size scale distribution versus overall density of these particles could be separated and visualized in spatially resolved maps. With sensitivity to localized light scattering over a wide field of view (11 cm x 14 cm), this technique is being translated for the application of intraoperative breast tumor margin assessment. To test sensitivity to changes in human breast tissue morphology, a cohort of over 30 freshly excised human breast tissue specimens, including adipose, fibroglandular, fibroadenoma, and invasive carcinoma, have been imaged and co-registered to whole specimen histology. Statistical analysis of the distributions of both textual raw reflectance parameters and model based optical properties for each type of tissue will be presented. Furthermore, classification algorithm development and analysis to predicted likelihood of cancer on the surface of the tissue will also be presented. Reflectance maps, optical property maps, and probability likelihood maps of spatially heterogeneous samples with multiple tissue types will also be shown.

  8. 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.

  9. 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.

  10. 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.

  11. Power output uniformity and power output capabilities of a guidewire-compatible cylindrical light-diffusing catheter

    NASA Astrophysics Data System (ADS)

    Anderson, Steven C.; Narciso, Hugh L., Jr.; Mai, David; Doiron, Daniel R.

    1994-07-01

    Cardiovascular Photodynamic Therapy requires the uniform application of laser energy over the length of an atherosclerotic lesion, thus ensuring equal treatment to all parts of the lesion. The total amount of laser energy delivered to the lesion also affects the results of the treatment. Uniform light distribution both radially and axially of a cylindrical diffuser during Photodynamic Therapy prevents miscalculated dosimetry and uneven treatment. Maximizing the amount of laser power delivered to the cylindrical diffuser tip (without inducing temperature elevation) minimizes the exposure time thus reducing the overall treatment time. Power output uniformity and power output capabilities are thus crucial factors in the design of a cardiovascular cylindrical diffuser. This paper will discuss the output characteristics and performance of six guidewire compatible cylindrical diffusers. Each diffuser consists of an array of fiber optics surrounding an inner guidewire lumen. This assembly is covered by an outer sheath. The fibers launch into an elastomer which contains a scattering medium. In this way a light diffusing tip is created. The total length of the fiber system is 3.0 meters. The total length of the difffuser tip is 2.0 cm.

  12. 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.

  13. 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.

  14. Influence of incident light offset on diffuse reflectance measurement for curved object: a Monte Carlo-based study

    NASA Astrophysics Data System (ADS)

    Ding, Chizhu

    2016-10-01

    Diffuse reflectance spectroscopy in the near-infrared (NIR) spectral ranges is a widely used technique for nondestructive inspection of biological tissues. The optical properties, such as absorption and scattering coefficients, can be inversely deduced from the measured quantities and then be used to speculate on some related chemical and physical properties of the tissue. Most studies consider biological tissues as homogeneous semi-infinite turbid media or infinitelywide planar layered turbid media. However, the biological tissues have various geometries, and nearly all of them have curved surfaces. The position and direction of the incident light relative to the tissue surface affect the diffuse reflectance. In this work, we study the influence of incident light offset on the measured diffuse reflectance signals based on the Monte Carlo (MC) simulation. The MC method are regarded as golden standard for light propagation in turbid media and can be used without the limitations of complex tissue geometries. A model for diffuse reflectance spectroscopy measurement using optic fiber probe is built. The incident light is assumed to be an infinitely narrow photon beam. The tissue under detection is assumed to be spherical described by its curvature radius. A series of Monte Carlo simulation are carried out with varying incident directions. Simulation results are analyzed and discussed to assess the influence on the measurements for tissues with different curvature radii. This study may aid in achieving more accurate and effective measurement without extensive experiments.

  15. Study of Mass Diffusion and Relaxation Processes in Polymer Systems by Laser Induced Holographic Grating Relaxation and Dynamic Light Scattering.

    NASA Astrophysics Data System (ADS)

    Xia, Jiulin

    The diffusion of dye molecules in various polymer systems is studied using the Laser Induced Holographic Grating Relaxation technique. The diffusion coefficients of camphorquinone (CQ), thymoquinone (TQ), diacetyl (DA) and azo compounds in these polymers are studied as a function of temperature, properties of both the polymers and the dye molecules. The effects of additives are also investigated. Due to the chemical reversibility of the azo compounds, the kinetics of their chemical processes are also analyzed. The mutual diffusion coefficients in poly(methyl methacrylate) (PMMA) and poly(ethylene oxide) (PEO) compatible polymer blends are measured by dynamic light scattering as a function of the molecular weight of PEO while keeping the molecular weight of PMMA fixed. The polymer chain relaxation processes of poly(isobornyl methacrylate) (PIMA) are also studied by using dynamic light scattering.

  16. 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

  17. 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

  18. Diffusion equation derived from the space-time transport equation and light pulse propagation through thick clouds

    NASA Astrophysics Data System (ADS)

    Furutsu, K.; Ito, S.

    1981-11-01

    The diffusion equation is derived from the ordinary space-time transport equation and is shown to be given necessarily in the first order in time, as in cases of the diffusion equations derived from the Fokker-Planck and Boltzmann equations. The systematic way of obtaining the higher-order diffusion equations also has been shown elsewhere. The boundary equations on the boundary of free space are obtained and applied to the light pulse propagation through thick clouds. The explicit expression is obtained for the pulse broadening and is found to be considerably affected by a slight absorption of the medium, especially when the diffusion distances are large. With the experimental value of absorption for stratocumulus clouds, as suggested by Danielson et al., the theoretical values of pulse broadening are compared to those of experiments observed by Bucher and Lerner to show a good agreement.

  19. 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.

  20. Hydrogel patterning by diffusion through the matrix and subsequent light-triggered chemical immobilization.

    PubMed

    Yi, Zheyi; Zhang, Yu; Kootala, Sujit; Hilborn, Jöns; Ossipov, Dmitri A

    2015-01-21

    A novel approach to hyaluronic acid (HA) hydrogel with a chemical gradient of the matrix-linked bisphosphonate (BP) groups is presented. The method consists of two steps, including initial generation of physical gradient patterns of BPs by diffusion of BP acrylamide reagent into HA matrix carrying thiol groups and subsequent chemical immobilization of the BP groups by UV light-triggered thiol-ene addition reaction. This gradient hydrogel permits spatial three-dimensional regulation of secondary interactions of different molecules with the polymer matrix. In particular, graded amounts of cytochrome c (cyt c) were reversibly absorbed in the hydrogel, thus enabling the subsequent spatially controlled release of the therapeutic protein. The obtained patterned hydrogel acts also as a unique reactor in which peroxidase-catalyzed oxidation of a substrate is determined by spatial position of the enzyme (cyt c) in the matrix resulting in a range of product concentrations. As an example, matrix template-assisted oxidation of 3,3',5,5'-tetarmethylbenzydine (TMB) in the presence of H2O2 occurs simultaneously at different rates within the gradient hydrogel. Moreover, calcium binding to the gradient HABP hydrogel reflects the pattern of immobilized BP groups eventually leading to the graded biomineralization of the matrix. This approach opens new possibilities for use of hydrogels as dynamic models for biologic three-dimensional structures such as extracellular matrix.

  1. Computer simulation of bulk and surface chemical diffusion of light atoms in metals

    SciTech Connect

    Murch, G.E.

    1981-01-01

    The lattice gas as a model for interstitial solid solution and adsorption systems is reviewed with emphasis on the generation of ordered structures. Then, as a prelude to the main discourse on chemical diffusion, the tracer diffusion coefficient is discussed in conjunction with the presentation of Monte Carlo results. Next, chemical diffusion is treated in detail with emphasis on the Danken equation. Monte Carlo results are then presented for the chemical diffusion coefficient. The large maximum in the chemical diffusivity observed within the ordered phase is traced back to the very strong driving force provided by the chemical potential derivative.

  2. Decreasing lateral diffusion of photo-generated carriers for light-addressable potentiometric array by using meshed working electrode

    NASA Astrophysics Data System (ADS)

    Chen, Dong; Liu, ShiBin; Yin, ShiMin; Liang, JinTao

    2016-09-01

    Lateral diffusion of photon-generated carriers is a critical factor affecting the signal stability and spatial resolution of light-addressable potentiometric sensor (LAPS) array. LAPS with meshed working electrode for rejecting lateral diffusion is presented. Simulation shows that using meshed working electrode can resist the lateral distribution. In an experiment, the inhibition of lateral distribution and the signal stability was studied. Results showed, using the meshed working electrode, the ability to reject the lateral distribution and the signal stability is obviously enhanced. Research in this paper may help to enhance spatial resolution and detection stability of LAPS.

  3. 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.

  4. Modeling of light propagation in the human neck for diagnoses of thyroid cancers by diffuse optical tomography.

    PubMed

    Fujii, H; Yamada, Y; Kobayashi, K; Watanabe, M; Hoshi, Y

    2017-05-01

    Diffuse optical tomography using near-infrared light in a wavelength range from 700 to 1000 nm has the potential to enable non-invasive diagnoses of thyroid cancers; some of which are difficult to detect by conventional methods such as ultrasound tomography. Diffuse optical tomography needs to be based on a physically accurate model of light propagation in the neck, because it reconstructs tomographic images of the optical properties in the human neck by inverse analysis. Our objective here was to investigate the effects of three factors on light propagation in the neck using the 2D time-dependent radiative transfer equation: (1) the presence of the trachea, (2) the refractive-index mismatch at the trachea-tissue interface, and (3) the effect of neck organs other than the trachea (spine, spinal cord, and blood vessels). There was a significant influence of reflection and refraction at the trachea-tissue interface on the light intensities in the region between the trachea and the front of the neck surface. Organs other than the trachea showed little effect on the light intensities measured at the front of the neck surface although these organs affected the light intensities locally. These results indicated the necessity of modeling the refractive-index mismatch at the trachea-tissue interface and the possibility of modeling other neck organs simply as a homogeneous medium when the source and detectors were far from large blood vessels. Copyright © 2016 John Wiley & Sons, Ltd.

  5. Diffusivity measurement using compact low cost field portable device based on light deflection

    NASA Astrophysics Data System (ADS)

    Chhaniwal, Vani; Mahajan, Swapnil; Trivedi, Vismay; Anand, Arun

    2015-05-01

    Imaging and measurement of diffusion process in liquid solutions is a challenging and interesting problem. Especially the mixing of binary liquid solutions in real-time provides an insight into the physics of diffusion as well as leads to measurement of diffusion coefficient, which is the most important parameter of a diffusing liquid solution. Accurate measurement of diffusion coefficient is important in areas ranging from oil extraction to pollution control. Interferometric methods provides very accurate measurement of diffusion coefficients albeit they impose very stringent optical conditions. Here we describe the development of a compact, easy to implement, easy to use and inexpensive device for imaging and quantification of the diffusion process. This technique does not require the stringent optical conditions of interferometric techniques. It computes the diffusivity values by measuring the amount of deflection happening to a line pattern printed on a paper and projected through the sample cell. The measured diffusivity values varied by less than 1%, with the values of diffusivities reported in literature.

  6. LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS Fibreoptic diffuse-light irradiators of biological tissues

    NASA Astrophysics Data System (ADS)

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

    2010-10-01

    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 μm, 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 ~10 % in their middle part. The maximum length of the diffusers produced by this method is 20 — 25 mm.

  7. 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

  8. Galerkin analysis of light-induced patterns in the chlorine dioxide-iodine-malonic acid reaction-diffusion system

    NASA Astrophysics Data System (ADS)

    Ghosh, Pushpita; Sen, Shrabani; Riaz, Syed Shahed; Ray, Deb Shankar

    2009-05-01

    The photosensitive chlorine dioxide-iodine-malonic acid reaction-diffusion system has been an experimental paradigm for the study of Turing pattern over the last several years. When subjected to illumination of varied intensity by visible light the patterns undergo changes from spots to stripes, vice versa, and their mixture. We carry out a nonlinear analysis of the underlying model in terms of a Galerkin scheme with finite number of modes to explore the nature of the stability and existence of various modes responsible for the type and crossover of the light-induced patterns.

  9. Light-induced hydrogen evolution from hydrogenated amorphous silicon: Hydrogen diffusion by formation of bond centered hydrogen

    NASA Astrophysics Data System (ADS)

    Tanimoto, H.; Arai, H.; Mizubayashi, H.; Yamanaka, M.; Sakata, I.

    2014-02-01

    The light-induced hydrogen evolution (LIHE) from amorphous (a-) Si:H by the order of at. % is observed during white light soaking (WLS) of 100-400 mW/cm2 at 350-500 K or ultra violet light soaking (UVLS) of 30-120 mW/cm2 at 305-320 K in a vacuum. The thermal desorption spectroscopy indicates that LIHE originated from bonded hydrogen takes place through the diffusion of light-induced mobile hydrogen (LIMH) with the activation energy of 0.5 eV. LIMH is assigned to bond centered hydrogen and the hydrogen diffusion process becomes prominent when LIMH can leave from a-Si:H such under light soaking in a vacuum above room temperature. For H2 in microvoids, the hydrogen evolution rate is governed by the surface barrier and its activation energy of 1.0 eV in dark decreases to 0.4 eV under WLS or UVLS.

  10. Influence of particle size and concentration on the diffuse backscattering of polarized light from tissue phantoms and biological cell suspensions

    SciTech Connect

    Hielscher, A.H.; Mourant, J.R.; Bigio, I.J.

    1997-01-01

    We present experimental results that show the spatial variations of the diffuse-backscattered intensity when linearly polarized light is incident upon highly scattering media. Experiments on polystyrene-sphere and Intralipid suspensions demonstrate that the radial and azimuthal variations of the observed pattern depend on the concentration, and anisotropy factor {ital g} of the particles that constitute the scattering medium. Measurements performed on biological-cell suspensions show the potential of this method for cell characterization. {copyright} 1997 Optical Society of America

  11. Reflection Matrix Method for Controlling Light After Reflection From a Diffuse Scattering Surface

    DTIC Science & Technology

    2016-12-22

    policy or position of the United States Air Force, the United States Department of Defense or the United States Government. This material is declared a...for Reflective Inverse Diffusion . . . . . . . . . . . . . . . . . . . . . 16 3.1 Enhancement for Reflective Inverse Diffusion...66 5.4.4 Predicted vs Measured Enhancement

  12. 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.

  13. Lighting analysis of diffusely illuminated tableaus in realist paintings: an application to detecting "compositing" in the portraits of Garth Herrick

    NASA Astrophysics Data System (ADS)

    Stork, David G.; Johnson, Micah K.

    2009-02-01

    The problem of estimating the direction of point-source illumination in digital photographs has been studied extensively, and the cast-shadow and occluding-contour algorithms have been used to detect tampering and compositing; differences between the lighting directions estimated from different objects indicate that at least one of them was composited into the image. Such methods have also been applied to the analysis of realist paintings to estimate the position of illuminants within a tableau and thereby test for artists' use of optical aids. Recently, the occluding-contour algorithm has been enhanced to address the case of diffuse illumination, for instance from light passing through several windows, from multiple lamps, and so forth. Here, the pattern of lightness along the occluding contour of an object is expressed as a weighted sum of spherical harmonics. Significant differences between the coefficients extracted from different objects indicates that they were recorded under different illumination conditions, and thus that one or more was likely composited into the image. We apply this technique to the analysis of diffuse lighting in realist paintings, focussing on the portraits of the contemporary American realist Garth Herrick. Herrick often works with multiple photographs as referents, for instance a photograph of the portrait subject and a different photograph of the background. There is no guarantee that the two lighting conditions are the same, nor that Herrick can perceive or compensate for such lighting discrepancies when executing his painting. We tested for lighting consistency throughout two of his paintings: one based on a single photographic referent, and another "composited," i.e., based on two photographic referents. Our algorithms found great illumination consistency in the first painting and significant inconsistencies in the second painting-inconsistencies difficult to discern by eye. As such, our methods reveal this artist's working

  14. Real-time convolution method for generating light diffusion profiles of layered turbid media.

    PubMed

    Kim, Hoe-Min; Ko, Kwang Hee; Lee, Kwan H

    2011-06-01

    In this paper we present a technique to obtain a diffusion profile of layered turbid media in real time by using the quasi fast Hankel transform (QFHT) and the latest graphics processing unit technique. We apply the QFHT to convolve the diffusion profiles of each layer so as to dramatically reduce the time for the convolution step while maintaining the accuracy. In addition, we also introduce an accelerated technique to generate individual discrete diffusion profiles for each layer through parallel processing. The proposed method is 2 orders of magnitude faster than the existing method, and we validate its efficiency by comparing it with Monte Carlo simulation and another relevant methods.

  15. Methanol conversion to light olefins over SAPO-34. Sorption, diffusion, and catalytic reactions

    SciTech Connect

    Chen, D.; Rebo, H.P.; Moljord, K.; Holmen, A.

    1999-11-01

    The catalytic conversion of methanol to lower olefins (MTO) is a way of converting natural gas and coal to chemicals via methanol. The effects of adsorption and diffusion of the reactants on methanol to olefins (MTO) and propene conversion over SAPO-34 have been studied in an oscillating microbalance reactor. The adsorption parameters of methanol and propene at reaction conditions (698 K) were determined by a pulse method, and the results were identical to the values obtained by extrapolation from low temperatures (323--398 K). Inverse uptake diffusion times were calculated form adsorption data at low temperatures, and these results were dependent on the temperature and the adsorbed amount. The inverse steady-state diffusion times calculated form the inverse uptake diffusion times were independent of the temperature and the adsorbed amount. The influence of diffusion on the reaction rates was estimated on the basis of the inverse steady-state diffusion times, using the Weisz-Prater criterion. The methanol conversion over SAPO-34 was influenced by diffusion of the reactant, while the propene conversion was not. A kinetic study revealed that both the rate constant and the site coverage of propene were much lower than that of methanol at 698 K. The deactivation behavior during the MTO reaction over SAPO-34 was studied by measuring both the adsorbed amount of methanol and the conversion at different coke contents. Catalyst deactivation was proposed to be due to a decreasing number of sites available for adsorption at high coke contents and a lower diffusivity, hence a lower effectiveness factor due to coke deposition.

  16. 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.

  17. Lateral CO2 diffusion inside dicotyledonous leaves can be substantial: quantification in different light intensities.

    PubMed

    Morison, James I L; Lawson, Tracy; Cornic, Gabriel

    2007-11-01

    Substantial lateral CO(2) diffusion rates into leaf areas where stomata were blocked by grease patches were quantified by gas exchange and chlorophyll a fluorescence imaging in different species across the full range of photosynthetic photon flux densities (PPFD). The lateral CO(2) flux rate over short distances was substantial and very similar in five dicotyledonous species with different vascular anatomies (two species with bundle sheath extensions, sunflower [Helianthus annuus] and dwarf bean [Phaseolus vulgaris]; and three species without bundle sheath extensions, faba bean [Vicia faba], petunia [Petunia hybrida], and tobacco [Nicotiana tabacum]). Only in the monocot maize (Zea mays) was there little or no evident lateral CO(2) flux. Lateral diffusion rates were low when PPFD <300 micromol m(-2) s(-1) but approached saturation in moderate PPFD (300 micromol m(-2) s(-1)) when lateral CO(2) diffusion represented 15% to 24% of the normal CO(2) assimilation rate. Smaller patches and higher ambient CO(2) concentration increased lateral CO(2) diffusion rates. Calculations with a two-dimensional diffusion model supported these observations that lateral CO(2) diffusion over short distances inside dicotyledonous leaves can be important to photosynthesis. The results emphasize that supply of CO(2) from nearby stomata usually dominates assimilation, but that lateral supply over distances up to approximately 1 mm can be important if stomata are blocked, particularly when assimilation rate is low.

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

    SciTech Connect

    Parkhomenko, A I; Shalagin, A M

    2015-02-28

    We study theoretically how the dependences of transport collision frequencies ν{sub i}, 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 ν{sub i}(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 ν{sub i}(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. (nonlinear optical phenomena)

  19. 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.

  20. A new approach to evaluating the effects of pharmacologic vitreolysis on vitreous diffusion coefficients using dynamic light scattering

    NASA Astrophysics Data System (ADS)

    Ansari, Rafat R.; Suh, Kwang I.; Sebag, J.

    2006-02-01

    PURPOSE: Pharmacologic vitreolysis is a new approach to improve vitreo-retinal surgery. Ultimately, the development of drugs to liquefy and detach vitreous from retina should prevent disease by mitigating the contribution of vitreous to retinopathy and eliminate the need for surgery. However, the mechanism of action of pharmacologic vitreolysis remains unclear. The technique of Dynamic light scattering (DLS) was used to evaluate the effects of microplasmin by following the diffusion coefficients of spherical polystyrene nano-particles injected with microplasmin into the vitreous. METHODS: Diffusion coefficients in dissected (n=9) porcine eyes were measured in vitro. DLS was performed on all specimens at 37°C as often as every 10 minutes for up to 6 hours following injections of human recombinant microplasmin at doses ranging from 0.125 mg to 0.8 mg, with 20 nm diameter tracer nanospheres. RESULTS: DLS findings in untreated porcine vitreous were similar to the previously described findings in bovine and human vitreous, demonstrating a fast (early) component, resulting from the flexible hyaluronan molecules, and a slow (late) component, resulting form the stiff collagen molecules. Microplasmin increased porcine vitreous diffusion coefficients. A new approach was developed to use DLS measurements of vitreous diffusion coefficients to evaluate the effects of microplasmin in intact eyes. CONCLUSIONS: Pharmacologic vitreolysis with human recombinant microplasmin increases vitreous diffusion coefficients in vitro. The results of these studies indicate that this new approach using DLS to measure vitreous diffusion coefficients can be used to study the effects of pharmacologic vitreolysis using microplasmin and other agents in intact eyes and ultimately in vivo.

  1. The Diffuse Light of the Universe - On the Microwave Background Before and After Its Discovery: Open Questions

    NASA Astrophysics Data System (ADS)

    Bonnet-Bidaud, Jean-Marc

    2016-12-01

    In 1965, the discovery of a new type of uniform radiation, located between radiowaves and infrared light, was accidental. Known today as Cosmic Microwave background (CMB), this diffuse radiation is commonly interpreted as a fossil light released in an early hot and dense universe and constitutes today the main 'pilar' of the big bang cosmology. Considerable efforts have been devoted to derive fundamental cosmological parameters from the characteristics of this radiation that led to a surprising universe that is shaped by at least three major unknown components: inflation, dark matter and dark energy. This is an important weakness of the present consensus cosmological model that justifies raising several questions on the CMB interpretation. Can we consider its cosmological nature as undisputable? Do other possible interpretations exist in the context of other cosmological theories or simply as a result of other physical mechanisms that could account for it? In an effort to questioning the validity of scientific hypotheses and the under-determination of theories compared to observations, we examine here the difficulties that still exist on the interpretation of this diffuse radiation and explore other proposed tracks to explain its origin. We discuss previous historical concepts of diffuse radiation before and after the CMB discovery and underline the limit of our present understanding.

  2. Impacts of Diffuse Radiation on Light Use Efficiency across Terrestrial Ecosystems Based on Eddy Covariance Observation in China

    PubMed Central

    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≤R2≤0.85), especially at the Changbaishan temperate forest ecosystem (R2 = 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. PMID:25393629

  3. 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.

  4. 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.

  5. Revealing the ultrafast light-to-matter energy conversion before heat diffusion in a layered Dirac semimetal

    NASA Astrophysics Data System (ADS)

    Ishida, Y.; Masuda, H.; Sakai, H.; Ishiwata, S.; Shin, S.

    2016-03-01

    There is still no general consensus on how one can describe the out-of-equilibrium phenomena in matter induced by an ultrashort light pulse. We investigate the pulse-induced dynamics in a layered Dirac semimetal SrMnBi2 by pump-and-probe photoemission spectroscopy. At ≲1 ps, the electronic recovery slowed upon increasing the pump power. Such a bottleneck-type slowing is expected in a two-temperature model (TTM) scheme, although opposite trends have been observed to date in graphite and in cuprates. Subsequently, an unconventional power-law cooling took place at ˜100 ps, indicating that spatial heat diffusion is still ill defined at ˜100 ps . We identify that the successive dynamics before the emergence of heat diffusion is a canonical realization of a TTM scheme. Criteria for the applicability of the scheme is also provided.

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. Effect of chlorine-containing bleaching agents on diffuse reflection of light by cellulose pulp

    NASA Astrophysics Data System (ADS)

    Belov, N. P.; Pokoptseva, O. K.; Sherstobitova, A. S.; Yas'kov, A. D.

    2010-07-01

    We have studied diffuse reflectance in the spectral range λ = 380-760 nm of sulfate cellulose pulp with initial hardness G = 30-70 after it was treated with a chlorine-containing bleaching agent with active chlorine concentration C = 0%-10% for different time intervals. We determined the general behavior and basic features of the concentration and time dependences of the brightness B and the diffuse reflectance spectral ratio ( R 437/ R 650)ṡ100% at λ = 457 nm and 650 nm. Based on the data obtained, we propose an optimal algorithm for using optical spectral technologies for metered addition of chlorine-containing bleaching agents.

  11. Improved optical properties of silica/UV-cured polymer composite films made of hollow silica nanoparticles with a hierarchical structure for light diffuser film applications.

    PubMed

    Suthabanditpong, W; Takai, C; Fuji, M; Buntem, R; Shirai, T

    2016-06-28

    This study successfully improved the optical properties of silica/UV-cured polymer composite films made of hollow silica nanoparticles having a hierarchical structure. The particles were synthesized by an inorganic particle method, which involves two steps of sol-gel silica coating around the template and acid dissolution removal of the template. The pH of the acid was varied to achieve different hierarchical structures of the particles. The morphologies and surface properties of the obtained particles were characterized before dispersing in a UV-curable acrylate monomer solution to prepare dispersions for fabricating light diffuser films. The optical properties and the light diffusing ability of the fabricated films were studied. The results revealed that the increased pH of the acid provides the particles with a thinner shell, a larger hollow interior and a higher specific surface area. Moreover, the films with these particles exhibit a better light diffusing ability and a higher diffuse transmittance value when compared to those without particles. Therefore, the composite films can be used as light diffuser films, which is an essential part of optical diffusers in the back-light unit of LCDs. In addition, utilizing the hierarchical particles probably reduces the number of back-light units in the LCDs leading to energy-savings and subsequently lightweight LCDs.

  12. 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.

  13. The Focusing of Light Scattered from Diffuse Reflectors Using Phase Modulation

    DTIC Science & Technology

    2012-03-22

    in Visual Studio 2010. In a single iteration, a matrix of pixel values was loaded onto the SLM, the camera was called to capture an image with a 100...proof of concept for adapting transmissive inverse diffusion to the case of reflection, particularly in geo - metric setups which are practical within

  14. Solubility and diffusivity study for light gases in heavy oil and its fractions

    NASA Astrophysics Data System (ADS)

    Ganapathi, Rajkumar

    Solvent-based recovery (VAPEX) is one of the most promising alternatives to thermal techniques to enhance heavy oil/bitumen recovery. Knowledge of the phase behavior and diffusion coefficients of gases in heavy oil is very important when designing recovery operations and facilities. In this work, a gravimetric microbalance was used to measure the solubility of carbon dioxide, ethane, propane and butane in a Lloydminster heavy oil and its fractions. Measurements were carried out on carbon dioxide and ethane at (290, 298 and 313) K over a pressure range from (200 to 2000) kPa. Similar measurements were performed on propane and butane below their vapor pressures. The Peng-Robinson equation of state was used to correlate the experimental results. The Solubility Parameter Theory was used to predict the solubility of CO2 and propane in heavy oil/bitumen over a wide range of pressures and temperatures. The associated Henry's Law constants for carbon dioxide, ethane and propane in heavy oil, its saturate fractions and aromatic fractions, were also determined from the absorption data. The gases had higher solubilities and the strongest interactions at lower temperatures in the heavy oil and its fractions. The diffusion coefficients of carbon dioxide, ethane and propane in heavy oil, its saturate and aromatic fractions were calculated using a simple diffusion model. The diffusion coefficient of carbon dioxide, ethane, propane and butane in heavy oil were calculated at different pressures. Estimated values were in agreement with published results and were found satisfactory.

  15. Tomographic imaging of absolute optical absorption coefficient in turbid media using combined photoacoustic and diffusing light measurements.

    PubMed

    Yin, Lu; Wang, Qiang; Zhang, Qizhi; Jiang, Huabei

    2007-09-01

    We present a new method that can provide high resolution images of absolute optical absorption coefficient in heterogeneous turbid media. In this method, acoustic measurements in conventional photoacoustic tomography are combined with diffusing light measurements to separate the product of absorption coefficient and optical fluence or photon density. We validate this method using a series of tissuelike phantom experiments. The experimental results show that targets as small as 0.5 mm in diameter with optical absorption contrasts as low as 1.5 relative to a 50 mm diameter scattering background medium can be clearly detected.

  16. 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

  17. Artificial lighting as a vector attractant and cause of disease diffusion.

    PubMed

    Barghini, Alessandro; de Medeiros, Bruno A S

    2010-11-01

    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. 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. 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. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Diffuse reflection of light by cellulose pulp and optical absorption of aqueous residual lignin solutions

    NASA Astrophysics Data System (ADS)

    Belov, N. P.; Sherstobitova, A. S.; Yaskov, A. D.

    2011-03-01

    Within Kubelka-Munk theory using the Lorenz relations, we have determined the correlation between the optical diffuse reflectance spectra R(λ) of cellulose pulp in the visible range (380-760 nm) and ultraviolet absorption (λ = 200-400 nm) of aqueous solutions containing residual lignins. The data obtained can be used to monitor and predict the results of digestion and bleach plants in the paper and pulp industry.

  2. 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.

  3. 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. Copyright © 2014 Elsevier B.V. All rights reserved.

  4. 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.

  5. 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.

  6. Sorption and diffusion of light hydrocarbons on Na-Y zeolites

    SciTech Connect

    Palmas, S.; Polcaro, A.M.; Carta, R.; Tola, G. )

    1991-01-01

    This paper reports on the adsorption isotherms that were determined on zeolite Na-Y at 298, 313, and 333 K for propane and propylene and at 298 K for butane, trans-butene, 1-butene, and cis-butene. The pressure of the experiments ranged from 5 {times} 10{sup {minus}2} to 30 kPa. The weight of adsorbed hydrocarbons was determined by a gravimetric method with a vacuum microbalance. The Henry constants were evaluated from the equilibrium measurements in the low-concentration range, and their sequence propane {lt} butane {lt} trans-butene {lt} propylene {lt} 1-butene {lt} cis-butene, was discussed in terms of the different adsorbate-adsorbent interactions. Equilibrium data, over the whole pressure range, were correlated by using the simplified model by Ruthven, based on statistical thermodynamics, and the appropriate parameters are reported. For C4 hydrocarbons, the intracrystalline diffusion process was also investigated and the Darken equation was used to correlate the uptake curves at the higher pressures. The diffusion coefficients were found in the order butane {gt} trans-butene {gt} 1-butene {gt} cis-butene and were compared to the available values in literature.

  7. The Burrell Schmidt Deep Virgo Survey: Tidal Debris, Galaxy Halos, and Diffuse Intracluster Light in the Virgo Cluster

    NASA Astrophysics Data System (ADS)

    Mihos, J. Christopher; Harding, Paul; Feldmeier, John J.; Rudick, Craig; Janowiecki, Steven; Morrison, Heather; Slater, Colin; Watkins, Aaron

    2017-01-01

    We present the results of a deep imaging survey of the Virgo cluster of galaxies, concentrated around the cores of Virgo subclusters A and B. The goal of this survey was to detect and study very low surface brightness features present in Virgo, including discrete tidal features, the faint halos of luminous galaxies, and the diffuse intracluster light (ICL). Our observations span roughly 16 degrees2 in two filters, reaching a 3σ limiting depth of {μ }B = 29.5 and {μ }V = 28.5 mag arcsec-2. At these depths, our limiting systematic uncertainties are astrophysical: variations in faint background sources as well as scattered light from galactic dust. We show that this dust-scattered light is well traced by deep far-infrared imaging, making it possible to separate it from true diffuse light in Virgo. We use our imaging to trace and measure the color of the diffuse tidal streams and ICL in the Virgo core near M87, in fields adjacent to the core including the M86/M84 region, and to the south of the core around M49 and subcluster B, along with the more distant W{}\\prime cloud around NGC 4365. Overall, the bulk of the projected ICL is found in the Virgo core and within the W{}\\prime cloud; we find little evidence for an extensive ICL component in the field around M49. The bulk of the ICL we detect is fairly red in color (B - V = 0.7-0.9), indicative of old, evolved stellar populations. Based on the luminosity of the observed ICL features in the cluster, we estimate a total Virgo ICL fraction of 7%-15%. This value is somewhat smaller than that expected for massive, evolved clusters, suggesting that Virgo is still in the process of growing its extended ICL component. We also trace the shape of M87's extremely boxy outer halo out to ˜150 kpc, and show that the current tidal stripping rate from low luminosity galaxies is insufficient to have built M87's outer halo over a Hubble time. We identify a number of previously unknown low surface brightness structures around

  8. 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.

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

    PubMed

    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.

  10. An Analysis of Diffuse Light Attenuation in the Northern Gulf of Mexico Hypoxic Zone Using the SeaWiFS Satellite Data Record

    DTIC Science & Technology

    2011-01-01

    from the Mississippi and Atchafalaya River Basin. SeaWiFS daily integrated surface photosynthetically active radiation (PAR, 400 -700 nm) and diffuse...speed, nutrient loading, and river discharge from the Mississippi and Atchafalaya River Basin. SeaWiFS daily integrated surface photosynthetically ...the hypoxic zone. In this paper we examine shelf-wide synoptic estimates of diffuse light attenuation, absolute daily integrated photosynthetically

  11. 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.

  12. Anisotropy of collagen fibre alignment in bovine cartilage: comparison of polarised light microscopy and spatially resolved diffusion-tensor measurements.

    PubMed

    de Visser, S K; Bowden, J C; Wentrup-Byrne, E; Rintoul, L; Bostrom, T; Pope, J M; Momot, K I

    2008-06-01

    To compare collagen fibre alignment angles obtained from polarised light microscopy (PLM) and diffusion-tensor imaging (DTI) in bovine articular cartilage. Five samples of bovine articular cartilage from five different animals were studied using magnetic resonance imaging and PLM techniques. T(2)-weighted, diffusion-tensor (DT), and PLM images were acquired for each sample and average depth profiles of the PLM and DTI angles, as well as the banding patterns observed in T(2)-weighted magnetic resonance (MR) images, were compared. Statistical properties of the distributions of the DTI and PLM angles were examined. The samples exhibited a range of alignment morphologies. In the samples with the "conventional" three-zone alignment pattern, a correlation between the PLM and DTI alignment zones and the banding in T(2)-weighted MR images was observed. The shapes of the depth profiles of the PLM and DTI alignment angles were qualitatively similar for each sample. Three samples showed good quantitative correlation between the DT and PLM alignment angles. The correlation between the diffusion and PLM alignment angles was best in the regions of low degree of disorder of fibre alignment. This study provides the first quantitative comparison of DTI of cartilage with the more established PLM techniques. The correlation between alignment angles derived from PLM and DTI data was evident across a wide range of alignment morphologies. The results support the use of DTI for the quantitative measurement of collagen fibre alignment. The microscopic-scale (~10 microm) dispersion of fibre alignment angles appears to be an important factor for understanding the extent of quantitative correlation between PLM and DTI results.

  13. High-resolution characterization of the diffusion of light chemical elements in metallic components by scanning microwave microscopy

    NASA Astrophysics Data System (ADS)

    Optasanu, Virgil; Bourillot, Eric; Vitry, Pauline; Plassard, Cédric; Beaurenaut, Laure; Jacquinot, Pierre; Herbst, Frédéric; Berger, Pascal; Lesniewska, Eric; Montessin, Tony

    2014-11-01

    An original sub-surface, high spatial resolution tomographic technique based on scanning microwave microscopy (SMM) is used to visualize in-depth materials with different chemical compositions. A significant phase difference in SMM between aluminum and chromium buried patterns has been observed. Moreover this technique was used to characterize a solid solution of a light chemical element (oxygen) in a metal lattice (zirconium). The large solubility of the oxygen in zirconium leads to modifications of the properties of the solid solution that can be measured by the phase shift signal in the SMM technique. The signal obtained in cross-section of an oxidized Zr sample shows the excellent agreement between phase shift profiles measured at different depths. Such a profile can reveal the length of diffusion of the oxygen in zirconium under the surface. The comparison with the oxygen concentration measured by nuclear reaction analysis shows excellent agreement in terms of length of diffusion and spatial distribution of the oxygen. A rapid calibration shows a linear dependence between the phase shift and the oxygen concentration. The SMM method opens up new possibilities for indirect measurements of the oxygen concentration dissolved in the metal lattice.

  14. Quantitative full-colour transmitted light microscopy and dyes for concentration mapping and measurement of diffusion coefficients in microfluidic architectures.

    PubMed

    Werts, Martinus H V; Raimbault, Vincent; Texier-Picard, Rozenn; Poizat, Rémi; Français, Olivier; Griscom, Laurent; Navarro, Julien R G

    2012-02-21

    A simple and versatile methodology has been developed for the simultaneous measurement of multiple concentration profiles of colourants in transparent microfluidic systems, using a conventional transmitted light microscope, a digital colour (RGB) camera and numerical image processing combined with multicomponent analysis. Rigorous application of the Beer-Lambert law would require monochromatic probe conditions, but in spite of the broad spectral bandwidths of the three colour channels of the camera, a linear relation between the measured optical density and dye concentration is established under certain conditions. An optimised collection of dye solutions for the quantitative optical microscopic characterisation of microfluidic devices is proposed. Using the methodology for optical concentration measurement we then implement and validate a simplified and robust method for the microfluidic measurement of diffusion coefficients using an H-filter architecture. It consists of measuring the ratio of the concentrations of the two output channels of the H-filter. It enables facile determination of the diffusion coefficient, even for non-fluorescent molecules and nanoparticles, and is compatible with non-optical detection of the analyte.

  15. 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

  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. 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.

  19. 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.

  20. Average Path-Length Parameter of Diffuse Light in Scattering Media

    NASA Astrophysics Data System (ADS)

    Arancibia-Bulnes, Camilo A.; Ruiz-Suárez, Jesús C.

    1999-03-01

    We use Monte Carlo simulations to study in detail the propagation of light in a plane-parallel medium containing scattering particles. In particular, we compute the forward and backward average path-length parameters (FAPP and BAPP, respectively) of four-flux radiative transfer models as functions of the optical depth. Strong dependence on the single scattering albedo and phase function asymmetry is found for both quantities. In general the values of the FAPP decrease with increasing absorption, whereas the opposite occurs for the BAPP. A similar effect is produced when changing from isotropic phase functions to phase functions with a large asymmetry in the forward direction. We present analytical results for the asymptotic values of the FAPP and BAPP as functions of albedo for the particular case of isotropic scattering. Our results differ markedly from the predictions obtained recently with two multiple-scattering models by Vargas and Niklasson J. Opt. Soc. Am. A 14, 2243 (1997); Appl. Opt. 36, 3735 (1997) . The differences found point out the intrinsic limitations of these models.

  1. Computer vision on color-band resistor and its cost-effective diffuse light source design

    NASA Astrophysics Data System (ADS)

    Chen, Yung-Sheng; Wang, Jeng-Yau

    2016-11-01

    Color-band resistor possessing specular surface is worthy of studying in the area of color image processing and color material recognition. The specular reflection and halo effects appearing in the acquired resistor image will result in the difficulty of color band extraction and recognition. A computer vision system is proposed to detect the resistor orientation, segment the resistor's main body, extract and identify the color bands, as well as recognize the color code sequence and read the resistor value. The effectiveness of reducing the specular reflection and halo effects are confirmed by several cheap covers, e.g., paper bowl, cup, or box inside pasted with white paper combining with a ring-type LED controlled automatically by the detected resistor orientation. The calibration of the microscope used to acquire the resistor image is described and the proper environmental light intensity is suggested. Experiments are evaluated by 200 4-band and 200 5-band resistors comprising 12 colors used on color-band resistors and show the 90% above correct rate of reading resistor. The performances reported by the failed number of horizontal alignment, color band extraction, color identification, as well as color code sequence flip over checking confirm the feasibility of the presented approach.

  2. 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

    2015-07-09

    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.

  3. Design and implementation of ultra-high resolution, large bandwidth, and compact diffuse light spectrometers

    NASA Astrophysics Data System (ADS)

    Badieirostami, Majid

    such as finite difference time-domain or the finite element techniques is not possible due to the excessive requirement of memory and simulation time. Added to the complexity of the problem is the diffuse (or spatially incoherent) nature of the optical beams in the state-of-the-art spectroscopy applications. In my Ph.D. research, I developed new approximate modeling tools for both the modeling of incoherent sources in nanophotonics, and for the propagation of such optical beams inside the 3D nanophotonic structures of interest with several orders of magnitude improvement in the simulation speed for practical size devices without sacrificing accuracy. I believe the tools developed in my research enable us to look into new structures and functionalities that we were not able to analyze simply before. To enable new dispersive properties using a single nanophotonic structure, I have focused in my Ph.D. research into polymer-based 3D photonic crystals, which can be engineered using their geometrical features to demonstrate unique dispersive properties in three dimensions that cannot be matched by any bulk material even with orders of magnitude larger sizes. I have demonstrated the possibilities of using a very compact structure for wavelength demultiplexing and also for spectroscopy without adding any other device. The range of applications that can be enabled by having a material system with a wide range of 3D dispersive properties is very wide covering spectroscopy and sensing, dispersion management, diffraction compensation, pulse shaping, and many others. I am very interested in using this material platform and extend my current research into 3D heterostructures in which each portion of the structure is engineered to optimize a subset of optical functionalities. The simplest version of such heterostructures is the integration of interferometry and spectroscopy in a single structure. The most general view of such engineered nanostructures is to consider them as a 3D

  4. Modeling of diffuse reflectance of light in heterogeneous biological tissue to analysis of the effects of multiple scattering on reflectance pulse oximetry

    NASA Astrophysics Data System (ADS)

    Mehrabi, Mohsen; Setayeshi, Saeed; Ardehali, Seyed Hossein; Arabalibeik, Hossein

    2017-01-01

    Fingertip-type pulse oximeters are popular, but their inconvenience for long-term monitoring in daily life means that other types of wearable pulse oximeters, such as reflectance pulse oximeters, need to be developed. For the purpose of developing reflection pulse oximetry, we have analyzed the light propagation in tissue to calculate and estimate the measured intensities of reflected light using the analytical and numerical solutions of the diffusion approximation equation. The reflectance of light from the biological tissue is investigated from theoretical and experimental perspectives, for light in the visible and near-infrared wavelengths. To establish the model, the calculated curves were compared with the analytical solution (AS) of the diffusion approximation equation in biological tissue. The results validated that the diffusion approximation equation could resolve the heterogeneous advanced tissue and the finite element method (FEM) could offer the simulation with higher efficiency and accuracy. Our aim has been to demonstrate the power of the FEM and AS in modeling of the steady-state diffusion approximation in a heterogeneous medium. Also, experimental data and the Monte Carlo model as a gold standard were used to verify the effectiveness of these methods.

  5. Immunoglobulin heavy chain/light chain pair measurement is associated with survival in diffuse large B-cell lymphoma.

    PubMed

    Jardin, Fabrice; Delfau-Larue, Marie Hélène; Molina, Thierry Jo; Copie-Bergman, Christiane; Brière, Josette; Petrella, Tony; Canioni, Danielle; Fabiani, Bettina; Jais, Jean-Philippe; Figeac, Martin; Leroy, Karen; Mareschal, Sylvain; Salles, Gilles André; Coiffier, Bertrand; Delarue, Richard; Peyrade, Frédéric; Bosly, André; André, Marc; Ketterer, Nicolas; Haioun, Corinne; Tilly, Hervé

    2013-09-01

    Elevated serum free light chains (FLCs) have been associated with an unfavorable prognosis in diffuse large B-cell lymphoma (DLBCL). The aim of this study was to determine the clinical relevance of a quantitative assessment of intact circulating immunoglobulin (Ig), using serum Ig heavy chain/light chain pair (HLC) measurements in patients with DLBCL. FLC and HLC were measured in 409 serum samples of patients with DLBCL included in the LNH03-B clinical trial program of the Groupe d'Etudes des Lymphomes de l'Adulte (GELA). Patients with an abnormal IgMκ/IgMλ ratio or an abnormal FLC ratio more frequently displayed adverse clinical characteristics. Patients with abnormal IgMκ/IgMλ ratios had inferior progression-free survival (PFS) and overall survival (OS) as compared to patients with a normal ratio in the overall cohort (5-year PFS 44.9% vs. 69.3%, p = 0.0003 and 5-year OS 50.8% vs. 78.1%, p = 0.0003) and in the R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, prednisone) cohort (5-year OS 43.5% vs. 70.3%, p = 0.003). In multivariate analysis, including elevated FLC/HLC and International Prognostic Index (IPI), an abnormal IgMκ/IgMλ ratio (hazard ratio [HR] = 1.54, 95% confidence interval [CI] 1.03-2.3, p = 0.03) remained predictive of shorter progression-free survival. Gene expression profile experiments and immunohistochemistry indicate that this measurement is at least partially related to tumor cell secretion. Both elevated serum FLCs and an abnormal IgMκ/IgMλ ratio are associated with unfavorable outcomes in patients with DLBCL treated by R-CHOP.

  6. 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

  7. Complex adjustments of photosynthetic potentials and internal diffusion conductance to current and previous light availabilities and leaf age in Mediterranean evergreen species Quercus ilex.

    PubMed

    Niinemets, Ulo; Cescatti, Alessandro; Rodeghiero, Mirco; Tosens, Tiina

    2006-06-01

    Mature non-senescent leaves of evergreen species become gradually shaded as new foliage develops and canopy expands, but the interactive effects of integrated light during leaf formation (Q(int)G), current light (Q(int)C) and leaf age on foliage photosynthetic competence are poorly understood. In Quercus ilex L., we measured the responses of leaf structural and physiological variables to Q(int)C and Q(int)G for four leaf age classes. Leaf aging resulted in increases in leaf dry mass per unit area (M(A)), and leaf dry to fresh mass ratio (D(F)) and decreases in N content per dry mass (N(M)). N content per area (N(A)) was independent of age, indicating that decreases in N(M) reflected dilution of leaf N because of accumulation of dry mass (NA = N(M) M(A)). M(A), D(F) and N(A) scaled positively with irradiance, whereas these age-specific correlations were stronger with leaf growth light than with current leaf light. Area-based maximum ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) carboxylase activity (V(cmax)A), capacity for photosynthetic electron transport (J(max)A) and the rate of non-photorespiratory respiration in light (R(d)A) were also positively associated with irradiance. Differently from leaf structural characteristics, for all data pooled, these relationships were stronger with current light with little differences among leaves of different age. Acclimation to current leaf light environment was achieved by light-dependent partitioning of N in rate-limiting proteins. Mass-based physiological activities decreased with increasing leaf age, reflecting dilution of leaf N and a larger fraction of non-photosynthetic N in older leaves. This resulted in age-dependent modification of leaf photosynthetic potentials versus N relationships. Internal diffusion conductance (g(m)) per unit area (g(m)A) increased curvilinearly with increasing irradiance for two youngest leaf age classes and was independent of light for older leaves. In contrast, g(m) per dry

  8. 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].

  9. Target sites for transcallosal fibers in human visual cortex - A combined diffusion and polarized light imaging study.

    PubMed

    Caspers, Svenja; Axer, Markus; Caspers, Julian; Jockwitz, Christiane; Jütten, Kerstin; Reckfort, Julia; Grässel, David; Amunts, Katrin; Zilles, Karl

    2015-11-01

    Transcallosal fibers of the visual system have preferential target sites within the occipital cortex of monkeys. These target sites coincide with vertical meridian representations of the visual field at borders of retinotopically defined visual areas. The existence of preferential target sites of transcallosal fibers in the human brain at the borders of early visual areas was claimed, but controversially discussed. Hence, we studied the distribution of transcallosal fibers in human visual cortex, searching for an organizational principle across early and higher visual areas. In-vivo high angular resolution diffusion imaging data of 28 subjects were used for probabilistic fiber tracking using a constrained spherical deconvolution approach. The fiber architecture within the target sites was analyzed at microscopic resolution using 3D polarized light imaging in a post-mortem human hemisphere. Fibers through a seed in the splenium of the corpus callosum reached the occipital cortex via the forceps major and the tapetum. We found target sites of these transcallosal fibers at borders of cytoarchitectonically defined occipital areas not only between early visual areas V1 and V2, V3d and V3A, and V3v and V4, but also between higher extrastriate areas, namely V4 (ventral) and posterior fusiform area FG1 as well as posterior fusiform area FG2 and lateral occipital cortex. In early visual areas, the target sites coincided with the vertical meridian representations of retinotopic maps. The spatial arrangement of the fibers in the 'border tuft' region at the V1/V2 border was found to be more complex than previously observed in myeloarchitectonic studies. In higher visual areas, our results provided additional evidence for a hemi-field representation in human area V4. The fiber topography in posterior fusiform gyrus indicated that additional retinotopic areas might exist, located between the recently identified retinotopic representations phPITv/phPITd and PHC-1/PHC-2 in lateral

  10. Light

    NASA Astrophysics Data System (ADS)

    Vernon, C. G.

    2016-09-01

    Preface; 1. Historical; 2. Waves and wave-motion; 3. The behaviour of ripples; 4. The behaviour of light; 5. Refraction through glass blocks and prisms; 6. The imprinting of curvatures; 7. Simple mathematical treatment; 8. More advanced mathematical treatment; 9. The velocity of light; 10. The spectrum and colour; 11. Geometrical optics; 12. The eye and optical instruments; 13. Sources of light; 14. Interference, diffraction and polarisation; 15. Suggestions for class experiments; Index.

  11. Developmental changes in mesophyll diffusion conductance and photosynthetic capacity under different light and water availabilities in Populus tremula: how structure constrains function.

    PubMed

    Tosens, Tiina; Niinemets, Ulo; Vislap, Vivian; Eichelmann, Hillar; Castro Díez, Pilar

    2012-05-01

    Finite mesophyll diffusion conductance (g(m) ) significantly constrains net assimilation rate (A(n) ), but g(m) variations and variation sources in response to environmental stresses during leaf development are imperfectly known. The combined effects of light and water limitations on g(m) and diffusion limitations of photosynthesis were studied in saplings of Populus tremula L. An one-dimensional diffusion model was used to gain insight into the importance of key anatomical traits in determining g(m) . Leaf development was associated with increases in dry mass per unit area, thickness, density, exposed mesophyll (S(mes) /S) and chloroplast (S(c) /S) to leaf area ratio, internal air space (f(ias) ), cell wall thickness and chloroplast dimensions. Development of S(mes) /S and S(c) /S was delayed under low light. Reduction in light availability was associated with lower S(c) /S, but with larger f(ias) and chloroplast thickness. Water stress reduced S(c) /S and increased cell wall thickness under high light. In all treatments, g(m) and A(n) increased and CO(2) drawdown because of g(m) , C(i) -C(c) , decreased with increasing leaf age. Low light and drought resulted in reduced g(m) and A(n) and increased C(i) -C(c) . These results emphasize the importance of g(m) and its components in determining A(n) variations during leaf development and in response to stress. © 2011 Blackwell Publishing Ltd.

  12. Enhancement of the diffusion of oxygen and boron in silicon crystals under irradiation of infrared laser light

    SciTech Connect

    Liu Lijun; Tanahashi, Katsutoshi; Yamada-Kaneta, Hiroshi; Kangawa, Y.; Kakimoto, Koichi

    2006-04-01

    Numerical and experimental analyses revealed the enhancement of diffusion of oxygen and boron by laser irradiation. We studied the effect of laser irradiation on the enhancement of diffusion of boron and oxygen including both isotopes of {sup 16}O and {sup 18}O. The study clarified that the diffusion of the impurities was enhanced by laser irradiation by about 2.5-8 times more than that in the case without laser irradiation in the temperature range from 990 to 1200 deg. C. We confirmed from temperature measurements of the samples that such enhancement was not based on temperature increase caused by laser irradiation but was based on the effect of irradiation of the laser. The effect of frequency of the laser on the diffusion was observed by changing the wavelength of the laser.

  13. Temperature and Loading-Dependent Diffusion of Light Hydrocarbons in ZIF-8 as Predicted Through Fully Flexible Molecular Simulations.

    PubMed

    Verploegh, Ross J; Nair, Sankar; Sholl, David S

    2015-12-23

    Accurate and efficient predictions of hydrocarbon diffusivities in zeolitic imidazolate frameworks (ZIFs) are challenging, due to the small pore size of materials such as ZIF-8 and the wide range of diffusion time scales of hydrocarbon molecules in ZIFs. Here we have computationally measured the hopping rates of 15 different molecules (kinetic diameters of 2.66-5.10 Å) in ZIF-8 via dynamically corrected transition state theory (dcTST). Umbrella sampling combined with the one-dimensional weighted histogram analysis method (WHAM) was used to calculate the diffusion free energy barriers. Both the umbrella sampling and dynamical correction calculations included ZIF-8 flexibility, which is found to be critical in accurately describing molecular diffusion in this material. Comparison of the computed diffusivities to extant experimental results shows remarkable agreement within an order of magnitude for all the molecules. The dcTST method was also applied to study the effect of hydrocarbon loadings. Self and transport diffusion coefficients of methane, ethane, ethylene, propane, propylene, n-butane, and 1-butene in ZIF-8 are reported over a temperature range of 0-150 °C and loadings from infinite dilution to liquid-like loadings.

  14. Improved accuracy of brain oxygen metabolism measurements using multi-distance diffuse correlation spectroscopy and near infrared spectroscopy together with a Monte Carlo light transport model (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Carp, Stefan A.; Boas, David A.; Selb, Juliette J.

    2017-02-01

    Diffuse correlation spectroscopy (DCS) is being employed alongside near-infrared spectroscopy (NIRS) measurements to track the cerebral oxygen metabolic rate (CMRO2). However, both techniques employ diffusely reflected light that has traveled mostly through extracerebral tissues. Recent studies indicate that depth sensitivity profiles are different for NIRS vs DCS measurements, with DCS appearing to be more sensitive to the brain than NIRS methods for a given source-detector separation. This mismatch can lead to erroneous conclusions with respect to the amount and perhaps even the direction of change in CMRO2. Recently, our group and others have demonstrated the use of Monte Carlo (MC) based multi-layer, multi-distance fitting, which offers increased accuracy for complex tissue structures such as the adult brain. In this paper we employ a Monte Carlo light transport model based on a realistic head geometry that can be derived from MRI scans (if available) or approximated from head shape measurements. We consider DCS and CW-NIRS measurements taken at two or more distances and analyze simulated data generated using a fully segmented adult brain MRI scan. Through simulations, we explore the improvements offered by our method vs. processing the same measurements with a semi-infinite diffusion model and estimate the impact of errors in geometry and optical properties on relative blood flow and CMRO2 changes.

  15. Diffusivities of lysozyme in aqueous MgCl2 solutions from dynamic light-scattering data:  Effect of protein and salt concentrations

    SciTech Connect

    Grigsby, J. J.; Blanch, H. W.; Prausnitz, J. M.

    2000-03-25

    Dynamic light-scattering (DLS) studies are reported for lysozyme in aqueous magnesium chloride solutions at ionic strengths 0.6, 0.8, and 1.0 M for a temperature range 10–30 °C at pH 4.0. The diffusion coefficient of lysozyme was calculated as a function of protein concentration, salt concentration, temperature, and scattering angle. A Zimm-plot analysis provided the infinitely-dilute diffusion coefficient and the protein-concentration dependence of the diffusion coefficient. The hydrodynamic radius of a lysozyme monomer was obtained from the Stokes–Einstein equation; it is 18.6 ± 1.0 Å. The difference (1.4 Å) between the hydrodynamic and the crystal-structure radius is attributed to binding of Mg2+ ions to the protein surface and subsequent water structuring. The effect of protein concentration on the diffusion coefficient indicates that attractive interactions increase as the temperature falls at fixed salt concentration. However, when plotted against ionic strength, attractive interactions exhibit a maximum at ionic strength 0.84 M, probably because Mg2+–protein binding and water structuring become increasingly important as the concentration of magnesium ion rises. Finally, the present work suggests that inclusion of ion binding and water structuring at the protein surface in a pair-potential model is needed to achieve accurate predictions of protein-solution phase behavior.

  16. Color Tuning of Poly(N-vinylcarbazole)-Based Light-Emitting Devices through Maskless Dye-Diffusion Technique Using Phosphorescent Dyes

    NASA Astrophysics Data System (ADS)

    Tada, Kazuya; Onoda, Mitsuyoshi

    2008-02-01

    The maskless dye-diffusion technique, a method for the local color tuning of polymer light-emitting devices employing thermal dye transfer, is applied to introduce a phosphorescent dye into poly(N-vinylcarbazole) (PVK). It is mentioned that the maskless diffusion of various phosphorescent dyes, such as iridium(III)-bis[2-(2'-benzothienyl)-pyridinato-N,C3'](acetylacetonate) (BtpIr), iridium(III)-tris[2-(4-tolyl)pyridinato-N,C2] [Ir(tpy)3], and iridium(III)-bis[2-(4,6-difluoropheny)pyridinato-N,C2'] picolinate (FIrpic), into PVK results in red-, green-, and sky-blue-emitting devices. The quantum efficiency of the devices fabricated using dye diffusion was much higher than that of the device fabricated using pristine PVK; however, the emission onset voltages were almost the same for all the devices. It was also found that there was a red-shift in the emission spectrum due to prolonged FIrpic diffusion.

  17. 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.

  18. 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.

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

    DOE PAGES

    Wolfram, Phillip J.; Ringler, Todd D.; Maltrud, Mathew E.; ...

    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

  20. 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.

  1. 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.

  2. Accuracy of RGD approximation for computing light scattering properties of diffusing and motile bacteria. [Rayleigh-Gans-Debye

    NASA Technical Reports Server (NTRS)

    Kottarchyk, M.; Chen, S.-H.; Asano, S.

    1979-01-01

    The study tests the accuracy of the Rayleigh-Gans-Debye (RGD) approximation against a rigorous scattering theory calculation for a simplified model of E. coli (about 1 micron in size) - a solid spheroid. A general procedure is formulated whereby the scattered field amplitude correlation function, for both polarized and depolarized contributions, can be computed for a collection of particles. An explicit formula is presented for the scattered intensity, both polarized and depolarized, for a collection of randomly diffusing or moving particles. Two specific cases for the intermediate scattering functions are considered: diffusing particles and freely moving particles with a Maxwellian speed distribution. The formalism is applied to microorganisms suspended in a liquid medium. Sensitivity studies revealed that for values of the relative index of refraction greater than 1.03, RGD could be in serious error in computing the intensity as well as correlation functions.

  3. A nanoporous polymer film as a diffuser as well as a light extraction component for top emitting organic light emitting diodes with a strong microcavity structure

    NASA Astrophysics Data System (ADS)

    Pyo, Beom; Joo, Chul Woong; Kim, Hyung Suk; Kwon, Byoung-Hwa; Lee, Jeong-Ik; Lee, Jonghee; Suh, Min Chul

    2016-04-01

    To improve the viewing angle characteristic as well as the light extraction effect of strong microcavity devices, we fabricated a nanoporous polymer film (NPF) as a scattering medium as well as a light extraction component. We designed two types of organic light emitting diodes (OLEDs) with a strong microcavity effect by changing the thickness of the hole transport layer (HTL; e.g. 30 nm and 60 nm) to investigate two different scattering effects of the NPF. Very interestingly, we could observe a significant enhancement of the external quantum efficiency (EQE) for each device (30 nm thick HTL: 18.0%, 60 nm thick HTL: 31.6%) when we attached a NPF formed on a 125 μm thick PET film coated with the NPF. Furthermore, the NPF successfully suppressed the viewing angle dependence to realize ideal angular emission even in the two extreme microcavity conditions although they are still different from that of a Lambertian distribution.To improve the viewing angle characteristic as well as the light extraction effect of strong microcavity devices, we fabricated a nanoporous polymer film (NPF) as a scattering medium as well as a light extraction component. We designed two types of organic light emitting diodes (OLEDs) with a strong microcavity effect by changing the thickness of the hole transport layer (HTL; e.g. 30 nm and 60 nm) to investigate two different scattering effects of the NPF. Very interestingly, we could observe a significant enhancement of the external quantum efficiency (EQE) for each device (30 nm thick HTL: 18.0%, 60 nm thick HTL: 31.6%) when we attached a NPF formed on a 125 μm thick PET film coated with the NPF. Furthermore, the NPF successfully suppressed the viewing angle dependence to realize ideal angular emission even in the two extreme microcavity conditions although they are still different from that of a Lambertian distribution. Electronic supplementary information (ESI) available: The theoretical backgrounds associated with designing of microcavity

  4. 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

  5. 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.

  6. 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.

  7. Light and CO2 do not affect the mesophyll conductance to CO2 diffusion in wheat leaves.

    PubMed

    Tazoe, Youshi; von Caemmerer, Susanne; Badger, Murray R; Evans, John R

    2009-01-01

    In C(3) plants, diffusion of CO(2) into leaves is restricted by stomata and subsequently by the intercellular airspaces and liquid phase into chloroplasts. While considerable information exists on the effect of environmental conditions on stomatal conductance (g(s)), little is known on whether the mesophyll conductance to CO(2) diffusion (g(m)) changes with respect to photon flux density (PFD) and CO(2) partial pressure (pCO(2)). In this study, the effects of PFD and/or pCO(2) on g(m) were examined in wheat leaves by combining gas exchange with carbon isotope discrimination measurements using a membrane inlet mass spectrometer. Measurements were made in 2% O(2) to reduce the fractionation associated with photorespiration. The magnitude of g(m) was estimated using the observed carbon isotope discrimination (Delta), ambient and intercellular pCO(2), CO(2) assimilation and respiration rates, either from an individual measurement made under one environmental condition or from a global fit to multiple measurements where PFD was varied. It was found that respiration made a significant and variable contribution to the observed discrimination, which associated with the difference in isotopic composition between CO(2) in the greenhouse and that used for gas exchange measurements. In wheat, g(m) was independent of PFD between 200 and 1500 micromol m(-2) s(-1) and was independent of p(i) between 80 and 500 microbar.

  8. Detection of the value of consecutive serum total light chain (sTLC) in patients diagnosed with diffuse large B cell lymphoma.

    PubMed

    Zhai, Linzhu; Zhao, Yuanyuan; Peng, Songguo; Zhu, Ke; Yu, Rongjian; Chen, Hailong; Lin, Tongyu; Lin, Lizhu

    2016-12-01

    There are limited data on serum total light chain (sTLC) in lymphoma and its relative role on the outcome of diffuse large B cell lymphoma (DLBCL) patients. Blood samples from 46 cases newly diagnosed with DLBCL were collected consecutively during chemotherapy to detect sTLC, IgG, IgA, and IgM levels. Clinical data and survival outcomes were analyzed according to the results of sTLC measurements. In summary, 22 patients (47.8 %) had abnormal k or λ light chain, respectively, and 6 patients (13.0 %) had both abnormal k and λ light chains before chemotherapy. Patients with elevated k light chain more frequently displayed multiple extra-nodal organ involvement (P = 0.01) and had an inferior overall survival (OS) (P = 0.041) and progression-free survival (PFS) (P = 0.044) compared to patients with normal level of k light chain. Furthermore, patients with elevated level of both k and λ also exhibited significant association with shorter OS (P = 0.002) and PFS (P = 0.009). Both elevated k alone and concurrent elevated k and λ had independent adverse effects on PFS (P = 0.031 and P = 0.019, respectively). sTLC level was reduced gradually by treatment in this study and reached the lowest point after the fourth cycle of chemotherapy, which was consistent with the disease behavior during chemotherapy. Considering the small sample size of this study, these results should be confirmed in a larger prospective study.

  9. LIGHT SCATTERING: Axial and diffusion models of the laser pulse propagation in a highly-scattering medium

    NASA Astrophysics Data System (ADS)

    Tereshchenko, Sergei A.; Danilov, Arsenii A.; Podgaetskii, Vitalii M.; Vorob'ev, Nikolai S.

    2004-06-01

    The propagation of laser radiation through a layer of a highly-scattering medium (HSM) is considered on the basis of two theoretical models: a nonstationary axial (two-flux) model and a nonstationary diffusion model. Analytic expressions for the temporal distributions of the photons of an ultrashort laser pulse transmitted through the HSM are presented. Experimental temporal distributions are used to obtain the parameters of models corresponding to an HSM, to determine the theoretical temporal distributions, and to compare them with the experimental curves. These two theoretical models are compared quantitatively for the first time. Their advantages and drawbacks that must be considered in the development of HSM transmission optical tomography are pointed out.

  10. 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.

  11. 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)

  12. The Impact of Diffuse Sunlight and Shortwave Dimming on Canopy Light-use Efficiency and net Carbon Exchange in 3 Forest Biomes.

    NASA Astrophysics Data System (ADS)

    Alton, P.; North, P.; Los, S.

    2006-05-01

    The latter half of the 20th century has seen a 5-10% fall in mean global insolation with reductions of up to 20% regionally (Stanhill & Cohen 2001). Anthropogenic aerosols, by their propensity to increase the optical depth of clouds, are cited as the major factor in this trend (Liepert 2002). By evaluating observed carbon flow, we estimate the impact of reduced downwelling shortwave radiation (SW) on 3 forest biomes (sparse Boreal needleleaf, temperate deciduous broadleaf and dense tropical broadleaf). We are careful to account for the increased proportion of diffuse sky radiation that accompanies obscuration by cloud (Roderick et al 2001). We find that canopy light-use efficiency (LUE) is enhanced at all 3 study sites when diffuse rather than direct sunlight predominates. The increase spans 6-33%. Intepretation with the land-surface model JULES, modified to take account of sunfleck penetration, indicates that increased sharing of the radiation-load across the foliage is the primary factor responsible for this LUE-enhancement. The increase in LUE, however, is insufficient to offset the reduction in GPP associated with attenuated SW. Greatest sensitivity is exhibited by the Boreal site, Zotino, where net ecosystem exchange (NEE) falls by 12±6% for a reduction of 20% in SW. (Part of this work has just appeared in JGR (110, D23209) and was accorded very favourable reviews.)

  13. Small-angle X-ray and light scattering analysis of multi-layered Curdlan gels prepared by a diffusion method.

    PubMed

    Maki, Yasuyuki; Furusawa, Kazuya; Dobashi, Toshiaki; Sugimoto, Yasunobu; Wakabayashi, Katsuzo

    2017-01-02

    Curdlan, a microbial polysaccharide, forms a multi-layered gel consisting of four layers with different turbidity when its alkaline solution is dialyzed against aqueous solutions containing Ca(2+) (diffusion-set gel). The present study clarified the microstructure of each layer of the diffusion-set Curdlan gel by small-angle X-ray scattering (SAXS) and small-angle light scattering (SALS). The SAXS data showed that Curdlan chains assume a helical ordered conformation in the gel and that the gel consists of the fibrils formed by the association of Curdlan chains and the aggregates of fibrils. The SAXS results also indicated that the gelation is induced by the formation of a network of Ca(2+)-cross-linked fibrils in the outer region of the gel, whereas by the network formation of the aggregation of fibrils in the neutralization process in the inner region of the gel. A structural anisotropy of the gel was investigated by analysis of two-dimensional SAXS images, showing that the fibril is oriented circumferentially in the outer region of the cylindrical gel, whereas it is oriented randomly in the inner region of the gel. The SALS data showed that a characteristic length of an inhomogeneous structure in the turbid layers is of the order of micrometers. The observed spatial variation of the microscopic structure is caused by the difference in the paths of pH and [Ca(2+)] traced in the gelation process. Copyright © 2016 Elsevier Ltd. All rights reserved.

  14. Non-invasive measurements of hemoglobin + myoglobin, their oxygenation and NIR light pathlength in heart in vivo by diffuse reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Gussakovsky, Eugene; Jilkina, Olga; Yang, Yanmin; Kupriyanov, Valery

    2009-02-01

    The existing non-invasive optical methods of the hemoglobin (Hb) and myoglobin (Mb) estimation in cardiac tissues imply knowledge of the light pathlength (L) when various modifications of Lambert-Beer law for either spectrophotometry or light diffuse reflectance is applied. For Hb and/or Mb quantification in tissue, a few invasive (biochemical) approaches were applied. For L (differential pathlength factor; DPF) determination in tissue, special optical methods were used. No approaches have been proposed to simultaneously and non-invasively determine Hb/Mb and L in cardiac or other muscle tissues. In the present study, the first derivative of the NIR diffuse reflectance spectrum is shown to be effective in simultaneous determination of Hb+Mb concentration (in mM) and L (in mm) in cardiac tissue in vivo. The results showed that measured in a few minutes in a normal pig heart in vivo the total Hb+Mb concentration was 0.9-1.2 mM of heme, tissue oxygen saturation parameter (OSP) was approximately 65%, and DPF at 700-965 nm was of 2.7-2.8. At the experimental ischemia, total [Hb+Mb] decreased by 25%, OSP reduced to zero, while DPF did not change. These results correlated with the previously published. The method may be applied during open-heart surgery, heart studies ex vivo or to any muscle tissue to continuously and non-invasively monitor the [Hb+Mb] content and oxygenation as well as L, which may reflect the changes in tissue structure.

  15. Optical rotation and linear and circular depolarization rates in diffusively scattered light from chiral, racemic, and achiral turbid media.

    PubMed

    Hadley, Kevin C; Vitkin, I Alex

    2002-07-01

    The polarization properties of light scattered in a lateral direction from turbid media were studied. Polarization modulation and synchronous detection were used to measure, and Mueller calculus to model and derive, the degrees of surviving linear and circular polarization and the optical rotation induced by turbid samples. Polystyrene microspheres were used as scatterers in water solutions containing dissolved chiral, racemic, and achiral molecules. The preservation of circular polarization was found to exceed the linear polarization preservation for all samples examined. The optical rotation induced increased with the chiral molecule concentration only, whereas both linear and circular polarizations increased with an increase in the concentrations of chiral, racemic, and achiral molecules. This latter effect was shown to stem solely from the refractive index matching mechanism induced by the solute molecules, independent of their chiral nature.

  16. 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.

  17. Effect of Diffuse Luminance Flicker Light Stimulation on Total Retinal Blood Flow Assessed With Dual-Beam Bidirectional Doppler OCT.

    PubMed

    Aschinger, Gerold C; Schmetterer, Leopold; Fondi, Klemens; Aranha Dos Santos, Valentin; Seidel, Gerald; Garhöfer, Gerhard; Werkmeister, René M

    2017-02-01

    We assess the increase in total retinal blood flow (TRBF) induced by flicker stimulation of the human retina in vivo and investigate the flicker induced hyperemia by means of a vascular flow model of the retinal circulation to study neurovascular coupling (NC). In six healthy subjects, TRBF was measured before and during stimulation with diffuse luminance flicker. Blood flow velocities in retinal vessels were measured via dual-beam bidirectional Doppler Fourier-domain optical coherence tomography (FD-OCT), retinal vessel diameters were assessed based on FD-OCT phase data. This allowed for the calculation of TRBF before and during visual stimulation. Additionally, a mathematical flow model for the retinal vasculature was adapted to study the implications of diameter variations on retinal perfusion. Measured and simulated perfusion was compared to draw conclusions on the diameter variations in different layers of the vascular tree. The measured mean baseline flow was 36.4 ± 6.5 μl/min while the mean flow during flicker stimulation was 53.4% ± 8.3 μl/min. The individual increase in TRBF during flicker stimulation ranged between 34% and 66%. The average increase in TRBF over all measured subjects was 47.6% ± 12.6%. Dual-beam bidirectional Doppler FD-OCT allowed quantifying NC in the human retina in vivo and may be a promising method for monitoring alterations in NC caused by various pathologies. The comparison of the measured data with the results obtained in the simulated vasculature indicates that the vasodilation induced by NC is more pronounced in smaller vessels.

  18. 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.

  19. 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

  20. 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.

  1. 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

  2. Binary diffusion coefficients for mixtures of ionic liquids [EMIM][N(CN)2], [EMIM][NTf2], and [HMIM][NTf2] with acetone and ethanol by dynamic light scattering (DLS).

    PubMed

    Rausch, Michael H; Hopf, Lisa; Heller, Andreas; Leipertz, Alfred; Fröba, Andreas P

    2013-02-28

    Mutual diffusivities for binary mixtures of the ionic liquids (ILs) [EMIM][N(CN)2] (1-ethyl-3-methylimidazolium dicyanimide), [EMIM][NTf2] (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide), and [HMIM][NTf2] (1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) with acetone and ethanol were studied in dependence on composition in the temperature range from 283.15 to 323.15 K, applying dynamic light scattering (DLS). The influence of experimental parameters on the achievable uncertainties was analyzed to ensure the acquisition of accurate data in adequate measurement times. For all probed systems, increasing binary diffusion coefficients were found for increasing temperatures. The systematic variation of anion and cation of the investigated ILs as well as a comparison with the literature data demonstrates the considerable influence of different ions on the resulting binary diffusion coefficients. Mutual diffusivities were found to be lower for the mixtures with ethanol than for those with acetone, which could be related to the formation of hydrogen bonds between ethanol and the ions. Most of the investigated IL solvent mixtures show increasing binary diffusion coefficients with increasing solvent concentration. For the mixtures of [EMIM][NTf2] with ethanol, however, a minimum of the mutual diffusivities was found in the ethanol mole fraction range from 0.7 to 0.8, which may hint at the vicinity of a critical demixing point. The viscosity of the pure ILs turned out to be no reliable indicator for the mutual diffusivity in mixtures with the same solvent.

  3. Ionic liquid containing microemulsions: probe by conductance, dynamic light scattering, diffusion-ordered spectroscopy NMR measurements, and study of solvent relaxation dynamics.

    PubMed

    Pramanik, Rajib; Sarkar, Souravi; Ghatak, Chiranjib; Rao, Vishal Govind; Sarkar, Nilmoni

    2011-03-17

    Room-temperature ionic liquid (RTIL), N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide ([P(13)][Tf(2)N]), was substituted for polar water and formed nonaqueous microemulsions with benzene by the aid of nonionic surfactant TX-100. The phase behavior of the ternary system was investigated, and microregions of [P(13)][Tf(2)N]-in-benzene (IL/O), bicontinuous, and benzene-in-[P(13)][Tf(2)N] (O/IL) were identified by traditional electrical conductivity measurements. Dynamic light scattering (DLS) revealed the formation of these IL microemulsions because with gradual increase of RTIL contents the droplet sizes of the microemulsions are also gradually increasing. Pulsed-field gradient spin-echo NMR have been studied to measure the diffusion coefficients of neat [P(13)][Tf(2)N] and [P(13)][Tf(2)N] in microemulsions which indicate ionic liquid containing microemulsions is formed. Moreover, the dynamics of solvent relaxation have been investigated in [P(13)][Tf(2)N]/TX100/benzene microemulsions using steady-state and time-resolved fluorescence spectroscopy using coumarin 153 (C-153) and coumarin 480 (C-480) fluorescence probe with variation of RTIL contents in microemulsions. For both of the probes with increasing amount of ionic liquids in microemulsions the relative contribution of the fast components increases and the slow components contribution decreases; therefore the average solvation time decreases. © 2011 American Chemical Society

  4. 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.

  5. Diffusion Cross Sections for Potassium 4(2)P(3/2) and 4(2)P(1/2) Levels in Rare Gases and Anomalous Light - Drift of Potassium in Neon + Rare Gas Mixtures.

    NASA Astrophysics Data System (ADS)

    Yahyaei-Moayyed, Frazaneh

    We have used a light-induced drift (LID) experiment to determine ratios of cross sections for diffusion of potassium in the excited rm4^2P_ {3/2}, 4^2P_{1/2} and the ground rm4^2S_ {1/2} levels in five rare gases, He, Ne, Ar, Kr, and Xe. The measured ratios are combined with the ground state cross sections and statistically averaged excited cross sections, available from a previously reported light-induced diffusive pulling experiment, to obtain the absolute cross sections for individual fine structure levels. We also report calculated cross-sections based on available potential curves and a coupled-channel theory. Rough qualitative agreement is generally found between the absolute cross sections inferred from experiment and the theoretical values. The light-induced drift experiments, however, measure ratios of cross section differences that are highly sensitive to the potential curves. It is found that the available theoretical potential curves are not adequate for predicting these measured ratios. A new method, using light-induced drift experiment, to measure the ground state diffusion coefficient of potassium vapor in Ar as a buffer gas is also studied and the results are compared to the previous results from the light-induced diffusive pulling experiment. Finally, we report anomalous light-induced drift of potassium vapor in mixtures of Ne with another rare gas (He, Ar, Kr, or Xe). This is the first observation of anomalous light-induced drift in an atomic system. The drift velocity versus laser frequency curve shows a strong deviation from the dispersion curve predicted by the standard theory of light-induced drift based on velocity-independent collision rates. The observed drift velocity versus frequency curves have three zero-crossings. For qualitatively relating the results to the collisional interaction, a strong collision model with different velocity-dependent collision rates is used. The partial pressures that cancel normal light -induced drift also

  6. 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

  7. Mutual and thermal diffusivity of binary mixtures of the ionic liquids [BMIM][C(CN)3] and [BMIM][B(CN)4] with dissolved CO2 by dynamic light scattering.

    PubMed

    Rausch, Michael H; Heller, Andreas; Herbst, Jonas; Koller, Thomas M; Bahlmann, Matthias; Schulz, Peter S; Wasserscheid, Peter; Fröba, Andreas P

    2014-05-01

    Ionic liquids (ILs) are promising solvents for gas separation processes such as carbon dioxide (CO2) capture from flue gases. For the design of corresponding processes and apparatus, thermophysical properties of ILs containing dissolved gases are required. In the present study, it is demonstrated that with a single optical setup, mutual and thermal diffusivities as well as refractive indices can be measured quasi-simultaneously for such mixtures. Dynamic light scattering (DLS) from bulk fluids was applied to determine mutual and thermal diffusivities for mixtures of 1-butyl-3-methylimidazolium tricyanomethanide ([BMIM][C(CN)3]) or 1-butyl-3-methylimidazolium tetracyanoborate ([BMIM][B(CN)4]) with dissolved CO2 at temperatures from 303.15 to 333.15 K and pressures between 2 and 26 bar in macroscopic thermodynamic equilibrium. Good agreement with literature data and only slight differences between the diffusivities measured for the two systems at the same temperature and comparable mole fractions of CO2 were found. Increasing mutual diffusivities with increasing mole fractions of CO2 are consistent with decreasing viscosities reported for other IL-CO2 mixtures in the literature and can be attributed to weakening of molecular interactions by the dissolved gas. For the conditions studied, no dependence of the thermal diffusivity on the temperature or the mole fraction of CO2 could be found.

  8. Monoclonal and polyclonal gammopathy measured by serum free light chain and immunofixation subdivide the clinical outcomes of diffuse large B-cell lymphoma according to molecular classification.

    PubMed

    Kim, Yu Ri; Kim, Soo-Jeong; Cheong, June-Won; Kim, Yundeok; Jang, Ji Eun; Lee, Jung Yeon; Min, Yoo Hong; Song, Jae-Woo; Yang, Woo Ick; Kim, Jin Seok

    2014-11-01

    Elevated serum free light chain (FLC) is known to be an adverse prognostic factor for diffuse large B-cell lymphoma (DLBCL). We hypothesized that monoclonal gammopathy (MG; elevated kappa [κ] or lambda [λ] FLC with an abnormal κ/λ ratio or a positive IF [immunofixation]) and polyclonal gammopathy (PG; elevated κ and/or λ FLC with a normal κ/λ ratio and a negative IF) would have different clinical outcome according to the molecular classification of DLBCL. In addition, MG would be a poor prognostic factor in patients with activated B-cell like type of DLBCL. Molecular classification of DLBCL, such as germinal center B-cell (GCB) type and non-GCB type, was performed according to the Hans algorithm. Among 175 newly diagnosed DLBCL patients, 96 (54.9 %) patients had an elevated FLC. MG and PG were observed in 34 and 68 patients, respectively. The 2-year overall survival (OS) and event-free survival (EFS) rates were 79.0 % and 71.6 %, respectively. In multivariate analysis, high-intermediate/high International Prognostic Index score and elevated FLC were significant for the OS (P = 0.002, P = 0.005, respectively) and EFS (P < 0.002, P = 0.010, respectively). MG and PG were also associated with inferior OS (P = 0.002, P = 0.011, respectively) and EFS (P = 0.002, P = 0.013, respectively). Ninety-six patients from a total 133 evaluable patients were classified to the non-GCB type. Patients with PG showed inferior clinical outcome for OS and EFS in patients with the GCB type (P = 0.006, P = 0.035, respectively). MG was a significant poor prognostic factor for OS and EFS in patients with the non-GCB type (P = 0.017, P = 0.004, respectively). MG was a poor prognostic maker in patients with the non-GCB type and PG was a poor prognostic indicator for the GCB type of DLBCL who were treated with R-CHOP.

  9. 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...

  10. 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...

  11. 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.

  12. Plasmapause diffusion

    NASA Technical Reports Server (NTRS)

    Horwitz, J. L.

    1983-01-01

    The Bohm diffusion coefficient and observed electrostatic wave scattering are used as the bases of estimates of the smoothing effect that diffusion may have on steep plasmapause density gradients. The estimate for diffusion resulting from scattering by observed electrostatic waves is found to be much lower than that of the perpendicular Bohm diffusion coefficient for characteristic plasma temperatures and magnetic fields. This diffusion rate estimate may be too small, however, if the wave amplitudes are significantly higher for steep plasmapauses. The effects are therefore negligible for most considerations of macroscopic plasmapause dynamics, but may be significant in limiting drift wave instabilities and similar phenomena driven by the steepness of the plasmapause density gradient.

  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. High power red-light GaInP/AlGaInP laser diodes with nonabsorbing windows based on Zn diffusion-induced quantum well intermixing

    NASA Astrophysics Data System (ADS)

    Zheng, Kai; Lin, Tao; Jiang, Li; Wang, Jun; Liu, Suping; Wei, Xin; Zhang, Guangze; Ma, Xiaoyu

    2006-01-01

    The layer structure of GaInP/AlGaInP quantum well laser diodes (LDs) was grown on GaAs substrate using low-pressure metalorganic chemical vapor deposition (LP-MOCVD) technique. In order to improve the catastrophic optical damage (COD) level of devices, a nonabsorbing window (NAW), which was based on Zn diffusion-induced quantum well intermixing, was fabricated near the both ends of the cavities. Zn diffusions were respectively carried out at 480, 500, 520, 540, and 580 Celsius degree for 20 minutes. The largest energy blue shift of 189.1 meV was observed in the window regions at 580 Celsius degree. When the blue shift was 24.7 meV at 480 Celsius degree, the COD power for the window LD was 86.7% higher than the conventional LD.

  15. Novel Diffusivity Measurement Technique

    NASA Technical Reports Server (NTRS)

    Rashidnia, Nasser

    2001-01-01

    A common-path interferometer (CPI) system was 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. This system uses a shearing interferometer that shares the same optical path from a laser light source to the final imaging plane. Hence, the molecular diffusion coefficient of liquids can be determined using the physical relations between changes in the optical path length and the liquid phase properties. The data obtained with this interferometer were compared with similar results from other techniques and demonstrated that the instrument is superior in measuring the diffusivity of miscible liquids while keeping the system very compact and robust. CPI can also be used for studies in interface dynamics and other diffusion-dominated-process applications.

  16. Griffith diffusers

    NASA Technical Reports Server (NTRS)

    Yang, T.-T.; Nelson, C. D.

    1979-01-01

    Contoured wall diffusers are designed by using an inverse method. The prescribed wall velocity distribution(s) was taken from the high lift airfoil designed by A. A. Griffith in 1938; therefore, such diffusers are named Griffith diffusers. First the formulation of the inverse problem and the method of solution are outlined. Then the typical contour of a two-dimensional diffuser and velocity distributions across the flow channel at various stations are presented. For a Griffith diffuser to operate as it is designed, boundary layer suction is necessary. Discussion of the percentage of through-flow required to be removed for the purpose of boundary layer control is given. Finally, reference is made to the latest version of a computer program for a two-dimensional diffuser requiring only area ratio, nondimensional length and suction percentage as inputs.

  17. Griffith diffusers

    NASA Technical Reports Server (NTRS)

    Yang, T.-T.; Nelson, C. D.

    1979-01-01

    Contoured wall diffusers are designed by using an inverse method. The prescribed wall velocity distribution(s) was taken from the high lift airfoil designed by A. A. Griffith in 1938; therefore, such diffusers are named Griffith diffusers. First the formulation of the inverse problem and the method of solution are outlined. Then the typical contour of a two-dimensional diffuser and velocity distributions across the flow channel at various stations are presented. For a Griffith diffuser to operate as it is designed, boundary layer suction is necessary. Discussion of the percentage of through-flow required to be removed for the purpose of boundary layer control is given. Finally, reference is made to the latest version of a computer program for a two-dimensional diffuser requiring only area ratio, nondimensional length and suction percentage as inputs.

  18. Combination Light

    NASA Astrophysics Data System (ADS)

    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.

  19. 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

  20. 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.

  1. Light induced diffusion driven self assembly of Ag nanoparticles in a-Se/Ag bi-layer thin film with ultrafast optical response

    NASA Astrophysics Data System (ADS)

    Bapna, Mukund; Sharma, Rituraj; Barik, A. R.; Khan, Pritam; Ranjan Kumar, Rakesh; Adarsh, K. V.

    2013-05-01

    In this Letter, we demonstrate that femtosecond light-induced interdiffusion of Ag driven by the electrostatic attraction between photo-excited Ag+ ions and negatively charged amorphous layer can act as an efficient single step method for hybrid integration of spatially ordered and interconnected nanoparticles on the surface of amorphous films. Such self assembled complex hybrid structures of silver nanoparticles via bottom-up nano-construction method on a-Se thin film show an ultrafast optical response over an unusually broad wavelength range that can be used to construct optical modulators operating at switching speed of ˜5 ps.

  2. 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.

  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. 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.

  5. 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.

  6. A numerical study of primary production related to vertical turbulent diffusion with special reference to vertical motions of the phytoplankton cells in nutrient and light fields

    NASA Astrophysics Data System (ADS)

    Zakardjian, Bruno; Prieur, Louis

    1994-08-01

    Assuming stationary physical processes, in particular the light field and turbulent activity [ K( z)], we described steady-state and convergent solutions obtained from a simple time-dependent vertical model of phytoplankton dynamics. Simulations included vertical turbulent motions experienced by the cells in the light and nutrient fields. Parallel simulations made with a classical formulation of phytoplankton growth, i.e., neglecting vertical turbulent motions, are discussed. From two typical situations of stratification in the Western Mediterranean, we identified two distinct systems of new production, as the consequence of Low (LTR) and High Turbulent Regime (HTR) in the photic zone respectively. Data from the Prolig-II (1985) and Almofront-I (1991) cruises supported the LTR system of new production. The results of the second part of the Mediprod-I (1969) cruise show several patterns that specifically appeared in the HTR simulation. Regenerated production was not influenced by the turbulent activity situation. In natural conditions, regenerated production depends on the specific phytoplankton-grazers system that develops according to the level of new production; such ecological dynamics were not considered in our model. Differences with the reference model changed the relationships between the vertical distributions of biomass and new production. Particularly, the HTR simulation led to distinct vertical distribution of biomass and new production. Such a pattern did not occur with the reference model. Although the vertical turbulent motions affected both the level and vertical distribution of new production, a significant effect on the depth-integrated production finally depends on how the phytoplankton biomass interacts with its environmental conditions. It is shown that the minimum of K( z) in the euphotic zone determined the system of new production, whereas its values below the euphotic zone scaled the production and biomass levels. The two distinct systems of

  7. 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

  8. Facilitated Diffusion of Transcription Factor Proteins with Anomalous Bulk Diffusion.

    PubMed

    Liu, Lin; Cherstvy, Andrey G; Metzler, Ralf

    2017-02-16

    What are the physical laws of the diffusive search of proteins for their specific binding sites on DNA in the presence of the macromolecular crowding in cells? We performed extensive computer simulations to elucidate the protein target search on DNA. The novel feature is the viscoelastic non-Brownian protein bulk diffusion recently observed experimentally. We examine the influence of the protein-DNA binding affinity and the anomalous diffusion exponent on the target search time. In all cases an optimal search time is found. The relative contribution of intermittent three-dimensional bulk diffusion and one-dimensional sliding of proteins along the DNA is quantified. Our results are discussed in the light of recent single molecule tracking experiments, aiming at a better understanding of the influence of anomalous kinetics of proteins on the facilitated diffusion mechanism.

  9. Diffuser Test

    NASA Image and Video Library

    2007-09-13

    Tests begun at Stennis Space Center's E Complex Sept. 13 evaluated a liquid oxygen lead for engine start performance, part of the A-3 Test Facility Subscale Diffuser Risk Mitigation Project at SSC's E-3 Test Facility. Phase 1 of the subscale diffuser project, completed Sept. 24, was a series of 18 hot-fire tests using a 1,000-pound liquid oxygen and gaseous hydrogen thruster to verify maximum duration and repeatability for steam generation supporting the A-3 Test Stand project. The thruster is a stand-in for NASA's developing J-2X engine, to validate a 6 percent scale version of A-3's exhaust diffuser. Testing the J-2X at altitude conditions requires an enormous diffuser. Engineers will generate nearly 4,600 pounds per second of steam to reduce pressure inside A-3's test cell to simulate altitude conditions. A-3's exhaust diffuser has to be able to withstand regulated pressure, temperatures and the safe discharge of the steam produced during those tests. Before the real thing is built, engineers hope to work out any issues on the miniature version. Phase 2 testing is scheduled to begin this month.

  10. The prognostic utility and the association of serum light chains (free and total) and absolute lymphocyte count in patients with newly diagnosed diffuse large B-cell lymphoma.

    PubMed

    Han, Xiaohong; Wang, Jianfei; Zhang, Ningning; Yao, Jiarui; Feng, Yun; Li, Dan; Liu, Peng; Yang, Jianliang; Zhou, Shengyu; Qin, Yan; Yang, Sheng; Gui, Lin; He, Xiaohui; Shi, Yuankai

    2014-11-01

    In this study, serum free and total light chains (sFLC/sTLC) were measured in 108 serum samples of therapy-naïve patients with DLBCL. Clinicopathologic data and survival outcomes were analyzed according to the results of sFLC/sTLC measurements. Moreover, the association of sFLC/sTLC with absolute monocyte count (AMC) and absolute lymphocyte count (ALC) was evaluated. Elevated sFLC and abnormal κ/λ ratio was present in 42.6% (51/108) and 4.6% (5/108) of patients, respectively. sTLC was successfully measured in 107 serum samples, abnormal sTLC and abnormal κ/λ ratio was found in 28.0% (30/107) and 26.2% (28/107) of patients, respectively. Patients with elevated sFLC more frequently displayed adverse clinical characteristics, including age (P=0.001), B symptoms (P=0.022), low ALC (P=0.024) and hyperglobulinemia (P=0.012). Patients with elevated sFLC had an inferior overall survival (OS) (P=0.012) and tended to have shorter progression-free survival (PFS) (P=0.061) compared to patients with normal sFLC. Abnormal sTLC or abnormal sTLC ratio showed no significant association with clinical outcomes, with exception of abnormal concurrent κ and λ. Only association of sFLC and ALC with survival remained significant after adjusting for the International Prognostic Index (IPI). The measurement of sFLC and ALC at diagnosis might be useful for the prognostic stratification of patients and sTLC measurement was of little prognostic utility in DLBCL.

  11. 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…

  12. 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)

  13. 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…

  14. 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)

  15. 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

  16. 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.

  17. 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.

  18. 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.

  19. 46 CFR 129.410 - Lighting fixtures.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 4 2012-10-01 2012-10-01 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... lighting fixture may be used as a connection box for a circuit other than the branch circuit supplying the...

  20. 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... lighting fixture may be used as a connection box for a circuit other than the branch circuit supplying the...

  1. 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... lighting fixture may be used as a connection box for a circuit other than the branch circuit supplying the...

  2. 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... lighting fixture may be used as a connection box for a circuit other than the branch circuit supplying the...

  3. 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... lighting fixture may be used as a connection box for a circuit other than the branch circuit supplying the...

  4. 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)

  5. Double Diffusive Plumes

    NASA Astrophysics Data System (ADS)

    Sutherland, Bruce; Lee, Brace

    2008-11-01

    Sour gas flares attempt to dispose of deadly H2S gas through combustion. What does not burn rises as a buoyant plume. But the gas is heavier than air at room temperature, so as the rising gas cools eventually it becomes negatively buoyant and descends back to the ground. Ultimately, our intent is to predict the concentrations of the gas at ground level in realistic atmospheric conditions. As a first step towards this goal we have performed laboratory experiments examining the structure of a steady state plume of hot and salty water that rises buoyantly near the source and descends as a fountain after it has cooled sufficiently. We call this a double-diffusive plume because its evolution is dictated by the different (turbulent) diffusivities of heat and salt. A temperature and conductivity probe measures both the salinity and temperature along the centreline of the plume. The supposed axisymmetric structure of the salinity concentration as it changes with height is determined by light-attenuation methods. To help interpret the results, a theory has been successfully adapted from the work of Bloomfield and Kerr (2000), who developed coupled equations describing the structure of fountains. Introducing a new empirical parameter for the relative rates of turbulent heat and salt diffusion, the predictions are found to agree favourably with experimental results.

  6. Transmitting and reflecting diffuser. [using ultraviolet grade fused silica coatings

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

    An ultraviolet grade fused silica substrate is coated with vaporized fused 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.

  7. 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

  8. 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 ...

  9. Cloaking through cancellation of diffusive wave scattering

    PubMed Central

    Chen, P. Y.; Guenneau, S.; Bağcı, H.; Salama, K. N.; Alù, A.

    2016-01-01

    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. PMID:27616925

  10. 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.

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

    DOEpatents

    Antoniadis,; Homer, Krummacher [Mountain View, CA; Claus, Benjamin [Regensburg, DE

    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.

  12. 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.

  13. Background Light Bluer Than Expected

    NASA Image and Video Library

    2014-11-06

    This plot shows data from the Cosmic Infrared Background Experiment, or CIBER, rockets launched in 2010 and 2012. The experiment measures a diffuse glow of infrared light in the sky, known as the cosmic infrared background.

  14. Measuring Diffusion and Recombination in Polycrystalline Silicon

    NASA Technical Reports Server (NTRS)

    Zook, J. D.

    1983-01-01

    Light-beam-induced currents yield information about solar cell material. Apparatus measures short-circuit current generated when spot of concentrated light is scanned across grains and grain boundaries in material under test. Technique used to evaluate SOC samples for diffusion and recombination effects of cell processing and chemical and structural defects.

  15. 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.

  16. Diffusion archeology for diffusion progression history reconstruction.

    PubMed

    Sefer, Emre; Kingsford, Carl

    2016-11-01

    Diffusion through graphs can be used to model many real-world processes, such as the spread of diseases, social network memes, computer viruses, or water contaminants. Often, a real-world diffusion cannot be directly observed while it is occurring - perhaps it is not noticed until some time has passed, continuous monitoring is too costly, or privacy concerns limit data access. This leads to the need to reconstruct how the present state of the diffusion came to be from partial diffusion data. Here, we tackle the problem of reconstructing a diffusion history from one or more snapshots of the diffusion state. This ability can be invaluable to learn when certain computer nodes are infected or which people are the initial disease spreaders to control future diffusions. We formulate this problem over discrete-time SEIRS-type diffusion models in terms of maximum likelihood. We design methods that are based on submodularity and a novel prize-collecting dominating-set vertex cover (PCDSVC) relaxation that can identify likely diffusion steps with some provable performance guarantees. Our methods are the first to be able to reconstruct complete diffusion histories accurately in real and simulated situations. As a special case, they can also identify the initial spreaders better than the existing methods for that problem. Our results for both meme and contaminant diffusion show that the partial diffusion data problem can be overcome with proper modeling and methods, and that hidden temporal characteristics of diffusion can be predicted from limited data.

  17. 46 CFR 120.410 - Lighting fixtures.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 4 2011-10-01 2011-10-01 false Lighting fixtures. 120.410 Section 120.410 Shipping... PASSENGERS OR WITH OVERNIGHT ACCOMMODATIONS FOR MORE THAN 49 PASSENGERS ELECTRICAL INSTALLATION Lighting Systems § 120.410 Lighting fixtures. (a) Each lighting fixture globe, lens, or diffuser must have a guard...

  18. 46 CFR 120.410 - Lighting fixtures.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 4 2012-10-01 2012-10-01 false Lighting fixtures. 120.410 Section 120.410 Shipping... PASSENGERS OR WITH OVERNIGHT ACCOMMODATIONS FOR MORE THAN 49 PASSENGERS ELECTRICAL INSTALLATION Lighting Systems § 120.410 Lighting fixtures. (a) Each lighting fixture globe, lens, or diffuser must have a guard...

  19. 46 CFR 120.410 - Lighting fixtures.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 4 2014-10-01 2014-10-01 false Lighting fixtures. 120.410 Section 120.410 Shipping... PASSENGERS OR WITH OVERNIGHT ACCOMMODATIONS FOR MORE THAN 49 PASSENGERS ELECTRICAL INSTALLATION Lighting Systems § 120.410 Lighting fixtures. (a) Each lighting fixture globe, lens, or diffuser must have a guard...

  20. 46 CFR 120.410 - Lighting fixtures.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 4 2013-10-01 2013-10-01 false Lighting fixtures. 120.410 Section 120.410 Shipping... PASSENGERS OR WITH OVERNIGHT ACCOMMODATIONS FOR MORE THAN 49 PASSENGERS ELECTRICAL INSTALLATION Lighting Systems § 120.410 Lighting fixtures. (a) Each lighting fixture globe, lens, or diffuser must have a guard...

  1. 46 CFR 120.410 - Lighting fixtures.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Lighting fixtures. 120.410 Section 120.410 Shipping... PASSENGERS OR WITH OVERNIGHT ACCOMMODATIONS FOR MORE THAN 49 PASSENGERS ELECTRICAL INSTALLATION Lighting Systems § 120.410 Lighting fixtures. (a) Each lighting fixture globe, lens, or diffuser must have a guard...

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. FRACTIONAL PEARSON DIFFUSIONS.

    PubMed

    Leonenko, Nikolai N; Meerschaert, Mark M; Sikorskii, Alla

    2013-07-15

    Pearson diffusions are governed by diffusion equations with polynomial coefficients. Fractional Pearson diffusions are governed by the corresponding time-fractional diffusion equation. They are useful for modeling sub-diffusive phenomena, caused by particle sticking and trapping. This paper provides explicit strong solutions for fractional Pearson diffusions, using spectral methods. It also presents stochastic solutions, using a non-Markovian inverse stable time change.

  7. FRACTIONAL PEARSON DIFFUSIONS

    PubMed Central

    Leonenko, Nikolai N.; Meerschaert, Mark M.

    2013-01-01

    Pearson diffusions are governed by diffusion equations with polynomial coefficients. Fractional Pearson diffusions are governed by the corresponding time-fractional diffusion equation. They are useful for modeling sub-diffusive phenomena, caused by particle sticking and trapping. This paper provides explicit strong solutions for fractional Pearson diffusions, using spectral methods. It also presents stochastic solutions, using a non-Markovian inverse stable time change. PMID:23626377

  8. 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),…

  9. 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),…

  10. 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.

  11. Nanosecond pulsed laser texturing of optical diffusers

    NASA Astrophysics Data System (ADS)

    Alqurashi, Tawfiq; Sabouri, Aydin; Yetisen, Ali K.; Butt, Haider

    2017-02-01

    High-quality optical glass diffusers have applications in aerospace, displays, imaging systems, medical devices, and optical sensors. The development of rapid and accurate fabrication techniques is highly desirable for their production. Here, a micropatterning method for the fast fabrication of optical diffusers by means of nanosecond pulsed laser ablation is demonstrated (λ=1064 nm, power=7.02, 9.36 and 11.7 W and scanning speed=200 and 800 mm s-1). The experiments were carried out by point-to-point texturing of a glass surface in spiral shape. The laser machining parameters, the number of pulses and their power had significant effect on surface features. The optical characteristics of the diffusers were characterized at different scattering angles. The features of the microscale structures influenced average roughness from 0.8 μm to 1.97 μm. The glass diffusers scattered light at angles up to 20° and their transmission efficiency were measured up to ˜97% across the visible spectrum. The produced optical devices diffuse light less but do so with less scattering and energy losses as compared to opal diffusing glass. The presented fabrication method can be applied to any other transparent material to create optical diffusers. It is anticipated that the optical diffusers presented in this work will have applications in the production of LED spotlights and imaging devices.

  12. 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.

  13. Diffusing diffusivity: Rotational diffusion in two and three dimensions

    NASA Astrophysics Data System (ADS)

    Jain, Rohit; Sebastian, K. L.

    2017-06-01

    We consider the problem of calculating the probability distribution function (pdf) of angular displacement for rotational diffusion in a crowded, rearranging medium. We use the diffusing diffusivity model and following our previous work on translational diffusion [R. Jain and K. L. Sebastian, J. Phys. Chem. B 120, 3988 (2016)], we show that the problem can be reduced to that of calculating the survival probability of a particle undergoing Brownian motion, in the presence of a sink. We use the approach to calculate the pdf for the rotational motion in two and three dimensions. We also propose new dimensionless, time dependent parameters, αr o t ,2 D and αr o t ,3 D, which can be used to analyze the experimental/simulation data to find the extent of deviation from the normal behavior, i.e., constant diffusivity, and obtain explicit analytical expressions for them, within our model.

  14. 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.

  15. 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.

  16. Nanoparticle Diffusion in Polymer Nanocomposites

    SciTech Connect

    Kalathi, Jagannathan; Yamamoto, Umi; Schweizer, Kenneth; Grest, Gary S.; Kumar, Sanat

    2014-01-01

    Large-scale molecular dynamics simulations show that nanoparticle (NP) diffusivity in weakly interacting mixtures of NPs and polymer melts has two very different classes of behavior depending on their size. NP relaxation times and their diffusivities are completely described by the local, Rouse dynamics of the polymer chains for NPs smaller than the polymer entanglement mesh size. The motion of larger NPs, which are comparable to the entanglement mesh size, is significantly slowed by chain entanglements, and is not describable by the Stokes-Einstein relationship. Our results are in essentially quantitative agreement with a force-level generalized Langevin equation theory for all the NP sizes and chain lengths explored, and imply that for these lightly entangled systems, activated NP hopping is not important.

  17. 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.

  18. Acoustic diffusers III

    NASA Astrophysics Data System (ADS)

    Bidondo, Alejandro

    2002-11-01

    This acoustic diffusion research presents a pragmatic view, based more on effects than causes and 15 very useful in the project advance control process, where the sound field's diffusion coefficient, sound field diffusivity (SFD), for its evaluation. Further research suggestions are presented to obtain an octave frequency resolution of the SFD for precise design or acoustical corrections.

  19. 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…

  20. A Student Diffusion Activity

    ERIC Educational Resources Information Center

    Kutzner, Mickey; Pearson, Bryan

    2017-01-01

    Diffusion is a truly interdisciplinary topic bridging all areas of STEM education. When biomolecules are not being moved through the body by fluid flow through the circulatory system or by molecular motors, diffusion is the primary mode of transport over short distances. The direction of the diffusive flow of particles is from high concentration…

  1. Diffusion of tungsten hexafluoride

    NASA Astrophysics Data System (ADS)

    Winkelmann, J.

    This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of tungsten hexafluoride

  2. 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…

  3. 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)

  4. 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…

  5. Diffusion of uranium hexafluoride

    NASA Astrophysics Data System (ADS)

    Winkelmann, J.

    This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of uranium hexafluoride

  6. A Student Diffusion Activity

    NASA Astrophysics Data System (ADS)

    Kutzner, Mickey; Pearson, Bryan

    2017-02-01

    Diffusion is a truly interdisciplinary topic bridging all areas of STEM education. When biomolecules are not being moved through the body by fluid flow through the circulatory system or by molecular motors, diffusion is the primary mode of transport over short distances. The direction of the diffusive flow of particles is from high concentration toward low concentration.

  7. Dim and diffuse

    NASA Image and Video Library

    2017-07-17

    Tucked away in the small northern constellation of Canes Venatici (The Hunting Dogs) is the galaxy NGC 4242, shown here as seen by the NASA/ESA Hubble Space Telescope. The galaxy lies some 30 million light-years from us. At this distance from Earth, actually not all that far on a cosmic scale, NGC 4242 is visible to anyone armed with even a basic telescope (as British astronomer William Herschel found when he discovered the galaxy in 1788). This image shows the galaxy’s bright centre and the surrounding dimmer and more diffuse “fuzz”. Despite appearing to be relatively bright in this image, studies have found that NGC 4242 is actually relatively dim (it has a moderate-to-low surface brightness and low luminosity) and also supports a low rate of star formation. The galaxy also seems to have a weak bar of stars cutting through its asymmetric centre, and a very faint and poorly-defined spiral structure throughout its disc. But if NGC 4242 is not all that remarkable, as with much of the Universe, it is still a beautiful and ethereal sight.

  8. 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)

  9. 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)

  10. 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)

  11. 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)

  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. 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,…

  14. 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.

  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. 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.

  17. 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).

  18. Lighting Conservation

    ERIC Educational Resources Information Center

    Arnold, Frank D.

    1975-01-01

    With the energy crisis has come an awareness of wasteful consumption practices. One area where research is being done is in lighting conservation. Information in this article is concerned with finding more effective and efficient lighting designs which include daylight utilization, task-oriented lighting, and lighting controls. (MA)

  19. 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.

  20. Hereditary Diffuse Infiltrating Retinoblastoma.

    PubMed

    Schedler, Katharina J E; Traine, Peter G; Lohmann, Dietmar R; Haritoglou, Christos; Metz, Klaus A; Rodrigues, Eduardo B

    2016-01-01

    Retinoblastoma is one of the most common childhood cancers. The diffuse infiltrating retinoblastoma is a rare subtype of this neoplasm. The majority of cases of diffuse infiltrating retinoblastoma are unilateral and occur sporadically. Herein we report on a family with three children affected by retinoblastoma, among them one girl with diffuse infiltrating retinoblastoma. This girl was diagnosed at the age of 8 years with a unilateral diffuse infiltrating retinoblastoma. By contrast, the two brothers became clinically apparent in the first 2 years of life with bilateral retinoblastoma. The parents were clinically unremarkable. Genetic analysis of RB1 gene was performed. The girl with diffuse infiltrating RB was found to be heterozygous for an oncogenic mutation in the RB1 gene that was also carried by both brothers and the father of the family. These results show that diffuse infiltrating retinoblastoma can develop on the background of a hereditary predisposition to retinoblastoma.

  1. Correlated diffusion imaging

    PubMed Central

    2013-01-01

    Background Prostate cancer is one of the leading causes of cancer death in the male population. Fortunately, the prognosis is excellent if detected at an early stage. Hence, the detection and localization of prostate cancer is crucial for diagnosis, as well as treatment via targeted focal therapy. New imaging techniques can potentially be invaluable tools for improving prostate cancer detection and localization. Methods In this study, we introduce a new form of diffusion magnetic resonance imaging called correlated diffusion imaging, where the tissue being imaged is characterized by the joint correlation of diffusion signal attenuation across multiple gradient pulse strengths and timings. By taking into account signal attenuation at different water diffusion motion sensitivities, correlated diffusion imaging can provide improved delineation between cancerous tissue and healthy tissue when compared to existing diffusion imaging modalities. Results Quantitative evaluation using receiver operating characteristic (ROC) curve analysis, tissue class separability analysis, and visual assessment by an expert radiologist were performed to study correlated diffusion imaging for the task of prostate cancer diagnosis. These results are compared with that obtained using T2-weighted imaging and standard diffusion imaging (via the apparent diffusion coefficient (ADC)). Experimental results suggest that correlated diffusion imaging provide improved delineation between healthy and cancerous tissue and may have potential as a diagnostic tool for cancer detection and localization in the prostate gland. Conclusions A new form of diffusion magnetic resonance imaging called correlated diffusion imaging (CDI) was developed for the purpose of aiding radiologists in cancer detection and localization in the prostate gland. Preliminary results show CDI shows considerable promise as a diagnostic aid for radiologists in the detection and localization of prostate cancer. PMID:23924150

  2. 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.

  3. 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.

  4. Phase singularity diffusion.

    PubMed

    Cheng, Xiaojun; Lockerman, Yitzchak; Genack, Azriel Z

    2014-06-01

    We follow the trajectories of phase singularities at nulls of intensity in the speckle pattern of waves transmitted through random media as the frequency of the incident radiation is scanned in microwave experiments and numerical simulations. Phase singularities are observed to diffuse with a linear increase of the square displacement 〈R2〉 with frequency shift. The product of the diffusion coefficient of phase singularities in the transmitted speckle pattern and the photon diffusion coefficient through the random medium is proportional to the square of the effective sample length. This provides the photon diffusion coefficient and a method for characterizing the motion of dynamic material systems.

  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. 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.

  7. 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.

  8. Scalar Potential Model of light

    NASA Astrophysics Data System (ADS)

    Hodge, John

    2008-04-01

    Some observations of light are inconsistent with a wave--like model. Other observations of light are inconsistent with a particle--like model. A model of light is proposed wherein Newton's and Democritus's speculations are combined with the cosmological scalar potential model (SPM). The SPM was tested by confrontation with observations of galaxy HI rotation curves (RCs), asymmetric RCs, redshift, discrete redshift, galaxy central mass, and central velocity dispersion; and with observations of the Pioneer Anomaly. The resulting model of light will be tested by numerical simulation of a photon behaving in a wave-like manner such as diffusion, interference, reflection, spectrography, and the Afshar experiment. Although the SPM light model requires more work, early results are beginning to emerge that suggest possible tests because a few predictions are inconsistent with both the current particle and wave models of light and that suggest a re-interpretation of the equations of quantum mechanics.

  9. 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.

  10. Diffuse interstellar bands in reflection nebulae

    NASA Technical Reports Server (NTRS)

    Fischer, O.; Henning, Thomas; Pfau, Werner; Stognienko, R.

    1994-01-01

    A Monte Carlo code for radiation transport calculations is used to compare the profiles of the lambda lambda 5780 and 6613 Angstrom diffuse interstellar bands in the transmitted and the reflected light of a star embedded within an optically thin dust cloud. In addition, the behavior of polarization across the bands were calculated. The wavelength dependent complex indices of refraction across the bands were derived from the embedded cavity model. In view of the existence of different families of diffuse interstellar bands the question of other parameters of influence is addressed in short.

  11. Review of Light Scattering Literature

    DTIC Science & Technology

    1994-06-01

    Homopolymers ......................................... 3 2.2. Polyelectrolytes...and Sphere Diffusion .................................................................... 7 3.3. Homopolymer Solutions 3.3.1. Flexible Polymers...static light scattering of polymers. 2.1. Dilute Solution Properties of Homopolymers A Mark-Houwink-Sakurada (M-H-S) equation for polyurethane in benzene

  12. A light-scattering characterization of membrane vesicles.

    PubMed Central

    Selser, J C; Yeh, Y; Baskin, R J

    1976-01-01

    A technique has been developed in this paper which enables quasi-elastic laser light scattering to be used to accurately and quantitatively measure the average vesicle diffusion coefficient and the relative dispersion in the diffusion coefficient about this average for dilute polydisperse vesicle suspensions. This technique relies on a theoretical analysis of a modified form of the Z-averaged diffusion coefficient. This modified Z-averaged diffusion coefficient explicitly incorporates vesicle size, structure, and polydispersity in a description of the scattered light autocorrelation spectrum. Light-scattering experiments were performed on a dilute, lobster sarcoplasmic reticulum vesicle suspension and the measured average diffusion coefficient and the diffusion coefficient relative dispersion about this average were determined with accuracies of 2 and 10%, respectively. A comparison of vesicle size inferred from light-scattering results was made with size results from electron microscopic analysis of the same sample. Images FIGURE 2 FIGURE 3 FIGURE 4 PMID:1252585

  13. Light Motives.

    ERIC Educational Resources Information Center

    Filler, Martin

    1979-01-01

    The new energy consciousness has led to a thorough reevaluation of how artificial lighting can be used wisely, while other researchers have explored the potential of daylighting as an alternative interior light source. (Author/MLF)

  14. Muonium quantum diffusion and localization in cryocrystals

    SciTech Connect

    Storchak, V.; Brewer, J.H.; Morris, G.D.

    1995-08-01

    The authors review their recent study of atomic muonium ({mu}{sup +}e{sup {minus}} or Mu, a light isotope of the hydrogen atom) diffusion in the simplest solids--Van der Walls cryocrystals. They give experimental evidence of the quantum-mechanical nature of the Mu diffusion in these solids. The results are compared with the current theories of quantum diffusion in insulators. The predicted T{sup {+-}7} power-law temperature dependence of the Mu hop rate is observed directly for the first time in solid nitrogen ({delta}-N{sub 2}) and is taken as confirmation of a two-phonon scattering mechanism. In solid xenon and krypton, by contrast, the one-phonon interaction is dominant in the whole temperature range under investigation due to the extremely low values of the Debye temperatures in those solids. Particular attention is devoted to processes of inhomogeneous quantum diffusion and Mu localization. It is shown that at low temperatures static crystal disorder results in an inhomogeneity of the Mu quantum diffusion which turns out to be inconsistent with diffusion models using a single correlation time {tau}{sub c}. Conventional trapping mechanisms are shown to be ineffective at low temperatures in insulators. Muonium localization effects are studied in detail in solid Kr. In all the cryocrystals studied, muonium atoms turn out to be localized at the lowest temperatures.

  15. 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.

  16. 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…

  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. 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…

  19. Adaptation and Cultural Diffusion.

    ERIC Educational Resources Information Center

    Ormrod, Richard K.

    1992-01-01

    Explores the role of adaptation in cultural diffusion. Explains that adaptation theory recognizes the lack of independence between innovations and their environmental settings. Discusses testing and selection, modification, motivation, and cognition. Suggests that adaptation effects are pervasive in cultural diffusion but require a broader, more…

  20. Diffusion of Botulinum Toxins

    PubMed Central

    Brodsky, Matthew A.; Swope, David M.; Grimes, David

    2012-01-01

    Background It is generally agreed that diffusion of botulinum toxin occurs, but the extent of the spread and its clinical importance are disputed. Many factors have been suggested to play a role but which have the most clinical relevance is a subject of much discussion. Methods This review discusses the variables affecting diffusion, including protein composition and molecular size as well as injection factors (e.g., volume, dose, injection method). It also discusses data on diffusion from comparative studies in animal models and human clinical trials that illustrate differences between the available botulinum toxin products (onabotulinumtoxinA, abobotulinumtoxinA, incobotulinumtoxinA, and rimabotulinumtoxinB). Results Neither molecular weight nor the presence of complexing proteins appears to affect diffusion; however, injection volume, concentration, and dose all play roles and are modifiable. Both animal and human studies show that botulinum toxin products are not interchangeable, and that some products are associated with greater diffusion and higher rates of diffusion-related adverse events than others. Discussion Each of the botulinum toxins is a unique pharmacologic entity. A working knowledge of the different serotypes is essential to avoid unwanted diffusion-related adverse events. In addition, clinicians should be aware that the factors influencing diffusion may range from properties intrinsic to the drug to accurate muscle selection as well as dilution, volume, and dose injected. PMID:23440162

  1. 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.

  2. The Diffusion of Innovation

    NASA Technical Reports Server (NTRS)

    Earabino, Gerard J.; Heyl, G. Christopher; Percorini, Thomas J.

    1987-01-01

    New ideas encounter obstacles on way to becoming products. Report examines process by which new ideas become products, processes, or accepted standards. Sequence of events called "the diffusion of innovation." Focuses on development of material processing in low gravity as case study in diffusion of innovation.

  3. 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…

  4. 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.

  5. 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…

  6. 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…

  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. 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…

  9. 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.

  10. 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.

  11. Diffusion in Coulomb crystals

    SciTech Connect

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

    2011-07-15

    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 {Gamma}=175 to Coulomb parameters up to {Gamma}=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.

  12. Establishing the diffuse correlation spectroscopy signal relationship with blood flow.

    PubMed

    Boas, David A; Sakadžić, Sava; Selb, Juliette; Farzam, Parisa; Franceschini, Maria Angela; Carp, Stefan A

    2016-07-01

    Diffuse correlation spectroscopy (DCS) measurements of blood flow rely on the sensitivity of the temporal autocorrelation function of diffusively scattered light to red blood cell (RBC) mean square displacement (MSD). For RBCs flowing with convective velocity [Formula: see text], the autocorrelation is expected to decay exponentially with [Formula: see text], where [Formula: see text] is the delay time. RBCs also experience shear-induced diffusion with a diffusion coefficient [Formula: see text] and an MSD of [Formula: see text]. Surprisingly, experimental data primarily reflect diffusive behavior. To provide quantitative estimates of the relative contributions of convective and diffusive movements, we performed Monte Carlo simulations of light scattering through tissue of varying vessel densities. We assumed laminar vessel flow profiles and accounted for shear-induced diffusion effects. In agreement with experimental data, we found that diffusive motion dominates the correlation decay for typical DCS measurement parameters. Furthermore, our model offers a quantitative relationship between the RBC diffusion coefficient and absolute tissue blood flow. We thus offer, for the first time, theoretical support for the empirically accepted ability of the DCS blood flow index ([Formula: see text]) to quantify tissue perfusion. We find [Formula: see text] to be linearly proportional to blood flow, but with a proportionality modulated by the hemoglobin concentration and the average blood vessel diameter.

  13. 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.

  14. 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.

  15. 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

  16. Helium diffusion in carbonates

    NASA Astrophysics Data System (ADS)

    Amidon, W. H.; Cherniak, D. J.; Watson, E. B.; Hobbs, D.

    2013-12-01

    The abundance and large grain size of carbonate minerals make them a potentially attractive target for 4He thermochronology and 3He cosmogenic dating, although the diffusive properties of helium in carbonates remain poorly understood. This work characterizes helium diffusion in calcite and dolomite to better understand the crystal-chemical factors controlling He transport and retentivity. Slabs of cleaved natural calcite and dolomite, and polished sections of calcite cut parallel or normal to c, were implanted with 3He at 3 MeV with a dose of 5x1015/cm2. Implanted carbonates were heated in 1-atm furnaces, and 3He distributions following diffusion anneals were profiled with Nuclear Reaction Analysis using the reaction 3He(d,p)4He. For 3He transport normal to cleavage surfaces in calcite, we obtain the following Arrhenius relation over the temperature range 78-300°C: Dcalcite = 9.0x10-9exp(-55 × 6 kJ mol-1/RT) m2sec-1. Diffusion in calcite exhibits marked anisotropy, with diffusion parallel to c about two orders of magnitude slower than diffusion normal to cleavage faces. He diffusivities for transport normal to the c-axis are similar in value to those normal to cleavage surfaces. Our findings are broadly consistent with helium diffusivities from step-heating measurements of calcite by Copeland et al. (2007); these bulk degassing data may reflect varying effects of diffusional anisotropy. Helium diffusion normal to cleavage surfaces in dolomite is significantly slower than diffusion in calcite, and has a much higher activation energy for diffusion. For dolomite, we obtain the following Arrhenius relation for He diffusion over the temperature range 150-400°C: Ddolomite = 9.0x10-8exp(-92 × 9 kJ mol-1/RT) m2sec-1. The role of crystallographic structure in influencing these differences among diffusivities was evaluated using the maximum aperture approach of Cherniak and Watson (2011), in which crystallographic structures are sectioned along possible diffusion

  17. Thorium Diffusion in Monazite

    NASA Astrophysics Data System (ADS)

    Cherniak, D. J.

    2006-05-01

    Diffusion of thorium has been characterized in synthetic monazite under dry conditions. The synthetic monazites (either pure CePO4, NdPO4, or a mixed LREE phosphate containing Ce, Nd, and Sm) were grown via a Na2CO3-MoO3 flux method. The source of diffusant for the experiments were either synthesized ThSiO4 or CaTh(PO4)2 powders. Experiments were performed by placing source and monazite in Pt capsules and annealing capsules in 1 atm furnaces for times ranging from 10 days to a few hours, at temperatures from 1400 to 1550C. The Th distributions in the monazite were profiled by Rutherford Backscattering Spectrometry (RBS). The following Arrhenius relation was obtained for diffusion in monazite: DSm = 7.2x103 exp(-814 kJ mol-1/RT) m2sec-1 The diffusivity of Th was similar for monazites containing a single REE and the mixed LREE phosphates. Th diffusion was also similar for experiments run using the Th silicate and Ca-Th phosphate sources, suggesting that the substitutional mechanism for Th in monazite, i.e, Th+4 + Si+4 for REE+3 + P+5 with the ThSiO4 source, and Th+4 + Ca+2 for 2REE+3 with the CaTh(PO4)2 source, does not significantly affect Th diffusivities, and that Th is likely the rate-limiting species. Th diffusion in monazite is about 4 orders of magnitude slower than Pb diffusion (Cherniak et al., 2004). This contrasts with findings of Gardes et al. (2005) who determined that Pb, Th and REE diffusivities in monazite are similar. Th diffusion in zircon (Cherniak et al., 1997) is about an order of magnitude slower than in monazite, but with similar activation energy for diffusion. The smaller diffusivities in zircon may be a consequence of the larger disparity in size between Th and the Zr site in zircon as compared with Th and the REE site in monazite. Nonetheless, Th is essentially immobile in monazite with respect to exchange by volume diffusion under most geologic conditions; these findings may have implications for containment of high- level actinide

  18. Hybrid radiative-transfer-diffusion model for optical tomography

    NASA Astrophysics Data System (ADS)

    Tarvainen, Tanja; Vauhkonen, Marko; Kolehmainen, Ville; Kaipio, Jari P.

    2005-02-01

    A hybrid radiative-transfer-diffusion model for optical tomography is proposed. The light propagation is modeled with the radiative-transfer equation in the vicinity of the laser sources, and the diffusion approximation is used elsewhere in the domain. The solution of the radiative-transfer equation is used to construct a Dirichlet boundary condition for the diffusion approximation on a fictitious interface within the object. This boundary condition constitutes an approximative distributed source model for the diffusion approximation in the remaining area. The results from the proposed approach are compared with finite-element solutions of the radiative-transfer equation and the diffusion approximation and Monte Carlo simulation. The results show that the method improves the accuracy of the forward model compared with the conventional diffusion model.

  19. 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)

  20. 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.

  1. 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.

  2. 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.

  3. Infrared diffuse interstellar bands

    NASA Astrophysics Data System (ADS)

    Galazutdinov, G. A.; Lee, Jae-Joon; Han, Inwoo; Lee, Byeong-Cheol; Valyavin, G.; Krełowski, J.

    2017-05-01

    We present high-resolution (R ˜ 45 000) profiles of 14 diffuse interstellar bands in the ˜1.45 to ˜2.45 μm range based on spectra obtained with the Immersion Grating INfrared Spectrograph at the McDonald Observatory. The revised list of diffuse bands with accurately estimated rest wavelengths includes six new features. The diffuse band at 15 268.2 Å demonstrates a very symmetric profile shape and thus can serve as a reference for finding the 'interstellar correction' to the rest wavelength frame in the H range, which suffers from a lack of known atomic/molecular lines.

  4. Diffusion in monodisperse ferrofluids

    NASA Astrophysics Data System (ADS)

    Peredo-Ortíz, R.; Hernández-Contreras, M.; Hernández Gómez, R.

    2017-01-01

    The diffusion coefficients characterizing the translational and rotational Brownian motion of a particle in a concentrated suspension were determined in the long time diffusive regime for a ferrofluid suspension with the use of a Langevin equation approach. These dynamical properties depend on the equilibrium micro-structural information of the suspension and take into account the effect of direct anisotropic inter-particle's interactions on self-diffusion. The comparison of this theory with Brownian dynamic simulations results is made in terms of colloid density and dipole interaction strength.

  5. A volume scanner for diffuse imaging

    NASA Astrophysics Data System (ADS)

    Vafa, Elham; Roberts, Nicolas; Sharafutdinova, Galiya; Holdsworth, John

    2016-11-01

    Non-invasive optical screening mammography has a significant barrier in the extreme scatter of human tissue at optical wavelengths. A volume scanner suited for high numerical aperture capture of scattered light from diffuse media has been designed, modelled using Trace Pro software and experimentally constructed. Modelling results indicate the presence of an embedded volume with different scatter properties from the bulk yields a measurable difference in the overall scatter pattern and intensity recorded. Work towards a full tomographic reconstruction from scattered light recorded on the two dimensional array detector is currently underway.

  6. 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

  7. Digital micromirror device as amplitude diffuser for multiple-plane phase retrieval

    NASA Astrophysics Data System (ADS)

    Abregana, Timothy Joseph T.; Hermosa, Nathaniel P.; Almoro, Percival F.

    2017-06-01

    Previous implementations of the phase diffuser used in the multiple-plane phase retrieval method included a diffuser glass plate with fixed optical properties or a programmable yet expensive spatial light modulator. Here a model for phase retrieval based on a digital micromirror device as amplitude diffuser is presented. The technique offers programmable, convenient and low-cost amplitude diffuser for a non-stagnating iterative phase retrieval. The technique is demonstrated in the reconstructions of smooth object wavefronts.

  8. 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.

  9. Diffusion of eccentric microswimmers.

    PubMed

    Debnath, Debajyoti; Ghosh, Pulak K; Li, Yunyun; Marchesoni, Fabio; Li, Baowen

    2016-02-21

    We model the two-dimensional diffusive dynamics of an eccentric artificial microswimmer in a highly viscous medium. We assume that the swimmer's propulsion results from an effective force applied to a center distinct from its center of mass, both centers resting on a body's axis parallel to its average self-propulsion velocity. Moreover, we allow for angular fluctuations of the velocity about the body's axis. We prove, both analytically and numerically, that the ensuing active diffusion of the swimmer is suppressed to an extent that strongly depends on the model parameters. In particular, the active diffusion constant undergoes a transition from a quadratic to a linear dependence on the self-propulsion speed, with practical consequences on the interpretation of the experimental data. Finally, we extend our model to describe the diffusion of chiral eccentric swimmers.

  10. Factorized Diffusion Map Approximation

    PubMed Central

    Amizadeh, Saeed; Valizadegan, Hamed; Hauskrecht, Milos

    2013-01-01

    Diffusion maps are among the most powerful Machine Learning tools to analyze and work with complex high-dimensional datasets. Unfortunately, the estimation of these maps from a finite sample is known to suffer from the curse of dimensionality. Motivated by other machine learning models for which the existence of structure in the underlying distribution of data can reduce the complexity of estimation, we study and show how the factorization of the underlying distribution into independent subspaces can help us to estimate diffusion maps more accurately. Building upon this result, we propose and develop an algorithm that can automatically factorize a high dimensional data space in order to minimize the error of estimation of its diffusion map, even in the case when the underlying distribution is not decomposable. Experiments on both the synthetic and real-world datasets demonstrate improved estimation performance of our method over the standard diffusion-map framework. PMID:25309676

  11. 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

  12. WOW: light print, light propel, light point

    NASA Astrophysics Data System (ADS)

    Glückstad, Jesper; Bañas, Andrew; Aabo, Thomas; Palima, Darwin

    2012-10-01

    We are presenting so-called Wave-guided Optical Waveguides (WOWs) fabricated by two-photon polymerization and capable of being optically manipulated into any arbitrary orientation. By integrating optical waveguides into the structures we have created freestanding waveguides which can be positioned anywhere in a sample at any orientation using real-time 3D optical micromanipulation with six degrees of freedom. One of the key aspects of our demonstrated WOWs is the change in direction of in-coupled light and the marked increase in numerical aperture of the out-coupled light. Hence, each light propelled WOW can tap from a relatively broad incident beam and generate a much more tightly confined light at its tip. The presentation contains both numerical simulations related to the propagation of light through a WOW and preliminary experimental demonstrations on our BioPhotonics Workstation. In a broader context, this research shows that optically trapped micro-fabricated structures can potentially help bridge the diffraction barrier. This structure-mediated paradigm may be carried forward to open new possibilities for exploiting beams from far-field optics down to the sub-wavelength domain.

  13. Guide tube flow diffuser

    SciTech Connect

    Berringer, R.T.; Myron, D.L.

    1980-11-04

    A nuclear reactor upper internal guide tube has a flow diffuser integral with its bottom end. The guide tube provides guidance for control rods during their ascent or descent from the reactor core. The flow diffuser serves to divert the upward flow of reactor coolant around the outside of the guide tube thereby limiting the amount of coolant flow and turbulence within the guide tube, thus enhancing the ease of movement of the control rods.

  14. 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.

  15. 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.

  16. Brownian yet Non-Gaussian Diffusion: From Superstatistics to Subordination of Diffusing Diffusivities

    NASA Astrophysics Data System (ADS)

    Chechkin, Aleksei V.; Seno, Flavio; Metzler, Ralf; Sokolov, Igor M.

    2017-04-01

    A growing number of biological, soft, and active matter systems are observed to exhibit normal diffusive dynamics with a linear growth of the mean-squared displacement, yet with a non-Gaussian distribution of increments. Based on the Chubinsky-Slater idea of a diffusing diffusivity, we here establish and analyze a minimal model framework of diffusion processes with fluctuating diffusivity. In particular, we demonstrate the equivalence of the diffusing diffusivity process with a superstatistical approach with a distribution of diffusivities, at times shorter than the diffusivity correlation time. At longer times, a crossover to a Gaussian distribution with an effective diffusivity emerges. Specifically, we establish a subordination picture of Brownian but non-Gaussian diffusion processes, which can be used for a wide class of diffusivity fluctuation statistics. Our results are shown to be in excellent agreement with simulations and numerical evaluations.

  17. Theoretical model of blood flow measurement by diffuse correlation spectroscopy

    NASA Astrophysics Data System (ADS)

    Sakadžić, Sava; Boas, David A.; Carp, Stefan

    2017-02-01

    Diffuse correlation spectroscopy (DCS) is a noninvasive method to quantify tissue perfusion from measurements of the intensity temporal autocorrelation function of diffusely scattered light. However, DCS autocorrelation function measurements in tissue better match theoretical predictions based on the diffusive motion of the scatterers than those based on a model where the advective nature of blood flow dominates the stochastic properties of the scattered light. We have recently shown using Monte Carlo (MC) simulations and assuming a simplistic vascular geometry and laminar flow profile that the diffusive nature of the DCS autocorrelation function decay is likely a result of the shear-induced diffusion of the red blood cells. Here, we provide theoretical derivations supporting and generalizing the previous MC results. Based on the theory of diffusing-wave spectroscopy, we derive an expression for the autocorrelation function along the photon path through a vessel that takes into account both diffusive and advective scatterer motion, and we provide the solution for the DCS autocorrelation function in a semi-infinite geometry. We also derive the correlation diffusion and correlation transfer equation, which can be applied for an arbitrary sample geometry. Further, we propose a method to take into account realistic vascular morphology and flow profile.

  18. Diffusion in natural ilmenite

    NASA Astrophysics Data System (ADS)

    Stenhouse, Iona; O'Neill, Hugh; Lister, Gordon

    2010-05-01

    Diffusion rates in natural ilmenite of composition Fe0.842+ Fe0.163+Mn0.07Mg0.01Ti 0.92O3 from the Vishnevye Mountains (Urals, Russia) have been measured at 1000° C. Experiments were carried out in a one atmosphere furnace with oxygen fugacity controlled by flow of a CO-CO2 gas mixture, over a period of four hours. The diffusant source was a synthetic ilmenite (FeTiO3) powder doped with trace amounts of Mg, Co, Ni, Zr, Hf, V, Nb, Ta, Al, Cr, Ga and Y. Since, the natural ilmenite crystal contained Mn it was also possible to study diffusion of Mn from the ilmenite crystal. The experiments were analysed using the electron microprobe and scanning laser ablation ICP-MS. Diffusion profiles were measured for Al, Mg, Mn, Co, Ni, Ga, and Y. Diffusion of Cr, Hf, Zr, V, Nb and Ta was too slow to allow diffusion profiles to be accurately measured for the times and temperatures studied so far. The preliminary results show that diffusion in ilmenite is fast, with the diffusivity determined in this study on the order of 10-13 to 10-16 m2s-1. For comparison, Chakraborty (1997) found interdiffusion of Fe and Mg in olivine at 1000° C on the order of 10-17 to 10-18m2s-1 and Dieckmann (1998) found diffusivity of Fe, Mg, Co in magnetite at 1200° C to be on the order of 10-13 to 10-14 m2s-1. The order in which the diffusivity of the elements decreases is Mn > Co > Mg ≥ Ni > Al ≥ Y ≥ Ga, that is to say that Mn diffuses the fastest and Ga the slowest. Overall, this study intends to determine diffusion parameters such as frequency factor, activation energy and activation volume as a function of temperature and oxygen fugacity. This research is taking place in the context of a larger study focusing on the use of the garnet-ilmenite system as a geospeedometer. Examination of the consequences of simultaneous diffusion of multiple elements is a necessity if we are to develop an understanding of the crystal-chemical controls on diffusion (cf Spandler & O'Neill, in press). Chakraborty

  19. Measuring the diffusion of linguistic change.

    PubMed

    Nerbonne, John

    2010-12-12

    We examine situations in which linguistic changes have probably been propagated via normal contact as opposed to via conquest, recent settlement and large-scale migration. We proceed then from two simplifying assumptions: first, that all linguistic variation is the result of either diffusion or independent innovation, and, second, that we may operationalize social contact as geographical distance. It is clear that both of these assumptions are imperfect, but they allow us to examine diffusion via the distribution of linguistic variation as a function of geographical distance. Several studies in quantitative linguistics have examined this relation, starting with Séguy (Séguy 1971 Rev. Linguist. Romane 35, 335-357), and virtually all report a sublinear growth in aggregate linguistic variation as a function of geographical distance. The literature from dialectology and historical linguistics has mostly traced the diffusion of individual features, however, so that it is sensible to ask what sort of dynamic in the diffusion of individual features is compatible with Séguy's curve. We examine some simulations of diffusion in an effort to shed light on this question.

  20. Measuring the diffusion of linguistic change

    PubMed Central

    Nerbonne, John

    2010-01-01

    We examine situations in which linguistic changes have probably been propagated via normal contact as opposed to via conquest, recent settlement and large-scale migration. We proceed then from two simplifying assumptions: first, that all linguistic variation is the result of either diffusion or independent innovation, and, second, that we may operationalize social contact as geographical distance. It is clear that both of these assumptions are imperfect, but they allow us to examine diffusion via the distribution of linguistic variation as a function of geographical distance. Several studies in quantitative linguistics have examined this relation, starting with Séguy (Séguy 1971 Rev. Linguist. Romane 35, 335–357), and virtually all report a sublinear growth in aggregate linguistic variation as a function of geographical distance. The literature from dialectology and historical linguistics has mostly traced the diffusion of individual features, however, so that it is sensible to ask what sort of dynamic in the diffusion of individual features is compatible with Séguy's curve. We examine some simulations of diffusion in an effort to shed light on this question. PMID:21041207

  1. 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. Copyright © 2014 Elsevier B.V. All rights reserved.

  2. 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

  3. New Chorus Diffusion Matrix

    NASA Astrophysics Data System (ADS)

    Horne, Richard B.; Kersten, Tobias; Glauert, Sarah A.; Meredith, Nigel P.; Boscher, Daniel; Sicard, Angelica; Maget, Vincent

    2013-04-01

    Whistler mode chorus waves play a major role in the loss and acceleration of electrons in the Earth's radiation belts. While high time resolution satellite data show that these waves are highly structured in frequency and time, at present their effects on the electron distribution can only be assessed on a global scale by using quasi-linear diffusion theory. Here we present new quasi-linear diffusion coefficients for upper and lower band chorus waves for use in global radiation belt models. Using data from DE 1 CRRES, Cluster 1, Double Star TC1 and THEMIS, we have constructed a database of wave properties and used this to construct new diffusion coefficients for L* = 1.5 to 10 in steps of 0.5, 10 latitude bins between 0o and 60o ,8 bins in MLT and 5 levels of geomagnetic activity as measured by Kp. We find that the peak frequency of lower band chorus is close to 0.2 fce, which is lower than that used in previous models. The combined upper and lower band chorus diffusion shows structure that should result in an energy dependent pitch angle anisotropy, particularly between 1 keV and 100 keV. The diffusion rates suggest that wave-particle interactions should still be very important outside geostationary orbit, out to at least L* = 8. We find significant energy diffusion near 1 keV near the loss cone, consistent with wave growth. By including the new chorus diffusion matrix into the BAS radiation belt (BRB) model we compare the effects on the evolution of the radiation belts against previous models.

  4. Diffuser for wellhead isolation tool

    SciTech Connect

    Surjaatmadja, J.B.

    1981-04-21

    An improved diffuser for a wellhead isolation tool which employs a combination of angles in its bore. This improvement reduces the incidence of erosion caused by the flow of fluids through the diffuser, in both the well production tubing adjacent the end of the diffuser and in the diffuser itself.

  5. Multidimensional diffusion MRI

    NASA Astrophysics Data System (ADS)

    Topgaard, Daniel

    2017-02-01

    Principles from multidimensional NMR spectroscopy, and in particular solid-state NMR, have recently been transferred to the field of diffusion MRI, offering non-invasive characterization of heterogeneous anisotropic materials, such as the human brain, at an unprecedented level of detail. Here we revisit the basic physics of solid-state NMR and diffusion MRI to pinpoint the origin of the somewhat unexpected analogy between the two fields, and provide an overview of current diffusion MRI acquisition protocols and data analysis methods to quantify the composition of heterogeneous materials in terms of diffusion tensor distributions with size, shape, and orientation dimensions. While the most advanced methods allow estimation of the complete multidimensional distributions, simpler methods focus on various projections onto lower-dimensional spaces as well as determination of means and variances rather than actual distributions. Even the less advanced methods provide simple and intuitive scalar parameters that are directly related to microstructural features that can be observed in optical microscopy images, e.g. average cell eccentricity, variance of cell density, and orientational order - properties that are inextricably entangled in conventional diffusion MRI. Key to disentangling all these microstructural features is MRI signal acquisition combining isotropic and directional dimensions, just as in the field of multidimensional solid-state NMR from which most of the ideas for the new methods are derived.

  6. Bicarbonate diffusion through mucus.

    PubMed

    Livingston, E H; Miller, J; Engel, E

    1995-09-01

    The mucus layer overlying duodenal epithelium maintains a pH gradient against high luminal acid concentrations. Despite these adverse conditions, epithelial surface pH remains close to neutrality. The exact nature of the gradient-forming barrier remains unknown. The barrier consists of mucus into which HCO3- is secreted. Quantification of the ability of HCO3- to establish and maintain the gradient depends on accurate measurement of this ion's diffusion coefficient through mucus. We describe new experimental and mathematical methods for diffusion measurement and report diffusion coefficients for HCO3- diffusion through saline, 5% mucin solutions, and rat duodenal mucus. The diffusion coefficients were 20.2 +/- 0.10, 3.02 +/- 0.31, and 1.81 +/- 0.12 x 10(-6) cm2/s, respectively. Modeling of the mucobicarbonate layer with this latter value suggests that for conditions of high luminal acid strength the neutralization of acid by HCO3- occurs just above the epithelial surface. Under these conditions the model predicts that fluid convection toward the lumen could be important in maintaining the pH gradient. In support of this hypothesis we were able to demonstrate a net luminal fluid flux of 5 microliters.min-1.cm-2 after perfusion of 0.15 N HCl in the rat duodenum.

  7. Diffusion Influenced Adsorption Kinetics.

    PubMed

    Miura, Toshiaki; Seki, Kazuhiko

    2015-08-27

    When the kinetics of adsorption is influenced by the diffusive flow of solutes, the solute concentration at the surface is influenced by the surface coverage of solutes, which is given by the Langmuir-Hinshelwood adsorption equation. The diffusion equation with the boundary condition given by the Langmuir-Hinshelwood adsorption equation leads to the nonlinear integro-differential equation for the surface coverage. In this paper, we solved the nonlinear integro-differential equation using the Grünwald-Letnikov formula developed to solve fractional kinetics. Guided by the numerical results, analytical expressions for the upper and lower bounds of the exact numerical results were obtained. The upper and lower bounds were close to the exact numerical results in the diffusion- and reaction-controlled limits, respectively. We examined the validity of the two simple analytical expressions obtained in the diffusion-controlled limit. The results were generalized to include the effect of dispersive diffusion. We also investigated the effect of molecular rearrangement of anisotropic molecules on surface coverage.

  8. 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

  9. [A study of brain inner tissue water molecule self-diffusion model based on Monte Carlo simulation].

    PubMed

    Wu, Zhanxiong; Zhu, Shanan; Bin, He

    2010-06-01

    The study of water molecule self-diffusion process is of importance not only for getting anatomical information of brain inner tissue, but also for shedding light on the diffusion process of some medicine in brain tissue. In this paper, we summarized the self-diffusion model of water molecule in brain inner tissue, and calculated the self-diffusion coefficient based on Monte Carlo simulation under different conditions. The comparison between this result and that of Latour model showed that the two self-diffusion coefficients were getting closer when the diffusion time became longer, and that the Latour model was a long time-depended self-diffusion model.

  10. 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.

  11. Memory-controlled diffusion

    NASA Astrophysics Data System (ADS)

    Trimper, Steffen; Zabrocki, Knud; Schulz, Michael

    2004-11-01

    Memory effects require for their incorporation into random-walk models an extension of the conventional equations. The linear Fokker-Planck equation for the probability density p(r⃗,t) is generalized by including nonlinear and nonlocal spatial-temporal memory effects. The realization of the memory kernel is restricted due the conservation of the basic quantity p . A general criteria is given for the existence of stationary solutions. In case the memory kernel depends on p polynomially, transport may be prevented. Owing to the delay effects a finite amount of particles remains localized and the further transport is terminated. For diffusion with nonlinear memory effects we find an exact solution in the long-time limit. Although the mean square displacement exhibits diffusive behavior, higher order cumulants offer differences to diffusion and they depend on the memory strength.

  12. 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.

  13. Positron diffusion in Si

    SciTech Connect

    Nielsen, B.; Lynn, K.G.; Vehanen, A.; Schultz, P.J.

    1985-06-01

    Positron diffusion in Si(100) and Si(111) has been studied using a variable energy positron beam. The positron diffusion coefficient is found to be D/sub +/ = 2.7 +- 0.3 cm/sup 2//sec using a Makhov-type positron implantation profile, which is demonstrated to fit the data more reliably than the more commonly applied exponential profile. The diffusion related parameter, E/sub 0/, which results from the exponential profile, is found to be 4.2 +- 0.2 keV, significantly longer than previously reported values. A drastic reduction in E/sub 0/ is found after annealing the sample at 1300 K, showing that previously reported low values of E/sub 0/ are probably associated with the thermal history of the sample.

  14. 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.

  15. Transverse Spin Diffusion

    NASA Astrophysics Data System (ADS)

    Mullin, William

    2014-05-01

    Transverse spin diffusion is a relatively new transport coefficient and a review of its history and physical basis will be presented. In NMR spin diffusion is often measured by spin echo techniques, which involve spin currents perpendicular to the direction of the magnetization, in contrast with the usual longitudinal case where the current is parallel to the magnetization. The first indication that this involved new physics was the Leggett-Rice effect (1970) in which spin waves, new spin-echo behavior, and an altered spin diffusion coefficient were predicted in liquid 3He. This effect gave the possibility of the first measurement of F1a, the parameter of the Landau Fermi-liquid theory mean-field responsible for the effect. In 1982 Lhuillier and Laloe found a transport equation very similar to the Leggett equation, but valid for highly-polarized dilute Boltzmann Bose and Fermi gases, and describing the ``identical spin rotation effect'' (ISRE), the analog of a Landau mean field. Coincidentally Bashkin and Meyerovich had also given equivalent descriptions of transport in polarized Boltzmann gases. That a mean-field effect could exists in dilute Boltzmann gases was theoretically surprising, but was confirmed experimentally. At low polarization the basic transverse diffusion constant D⊥ coincides with the longitudinal value D∥ however Meyerovich first pointed out that they could differ in highly polarized degenerate gases. Indeed detailed calculations (Jeon and Mullin) showed that, while D∥ is proportional to T-2, D⊥ approaches a constant (depending on polarization) at low T. Considerable controversy existed until experimental verification was achieved in 2004. The importance of ISRE again arose in 2008 as the basis of ``anomalous spin-state segregation'' in Duke and JILA experiments. More recently application of the ideas of transverse spin diffusion to strongly interacting Fermi gases has resulted in the observation of the diffusion constants at the quantum

  16. Lead diffusion in monazite

    NASA Astrophysics Data System (ADS)

    Smith, Harold A.; Giletti, Bruno J.

    1997-03-01

    We have measured the tracer diffusion rate of Pb in natural, annealed, gem-quality monazite from Alexander Co., NC, USA, and Riverside Co., CA, USA. Observations from the literature concerning low T annealing in monazite suggest the possibility that Pb diffusion at geologic conditions occurs, in effect, within a similarly annealed lattice. Our experiments were performed by evaporating an aqueous solution containing 204Pb onto a crystal face and then heating the charge to 1000-1200°C for 4 to 36 days. To the extent that the compositions of the two samples differed, we observed no effect of composition upon the rate of Pb diffusion. We do find that transport parallel to the c-axis is ˜2-5 times slower than that measured perpendicular to c. For Pb diffusion perpendicular to c, the Arrhenius parameters are Q = 180 ± 48 kJ/mol and log D0 = -14.18 ± 1.54 (for D0 in m 2/s). While these parameters now allow for a direct calculation of closure temperatures for monazite, we believe a more useful form of our data for geochronologists is the fraction of Pb lost from crystals, expressed as a function of T, time, and crystal size. We have applied this formalism to discordant monazite UPb ages from the recent literature and find that Pb diffusion at rates extrapolated from our experiments can account for the observed degree of discordancy. We suggest that, rather than employing the concept of closure temperature to evaluate possible Pb loss in monazite, the diffusion data presented here be used in Pb loss models based upon T and duration conditions appropriate for a given geological setting.

  17. Tracer Diffusion of Polyelectrolytes in a Complex Medium

    NASA Astrophysics Data System (ADS)

    Ma, J.; Bruggink, J. L.; Yu, H.

    1997-03-01

    The issue of translational polyelectrolyte diffusion in a complex medium is of both fundamental and practical interest. In our study we examine the diffusion in a gelatin gel as a function of molecular weight and polyelectrolytes concentration. Fractionated, monodisperse gelatin is used as a model matrix. The diffusion of poly(styrene sulfonate) (PSS) and poly (2-acrylamido-2-methylpropane sulfonate) (PAMPS), both in the form of sodium salts, have been studied using fluorescence recovery after photobleaching (FRAP) and dynamic light scattering (DLS) techniques. A series of molecular weights of the two polyelectrolytes and the gelatin have been labeled with fluorescent dyes so that diffusion of each component can be studied individually. By correlating the diffusion of the polyelectrolyte and gelatin, we gain insight into the interactions between the polyelectrolytes and the matrix.

  18. Fractional-order bidirectional diffusion for image up-sampling

    NASA Astrophysics Data System (ADS)

    Ren, Zemin; He, Chuanjiang; Li, Meng

    2012-04-01

    Following the recently proposed total variation (TV) up-sampling method, we present a novel image up-sampling algorithm based on fractional-order bidirectional diffusion. For the bidirectional diffusion, the forward diffusion occurs on the light side of edge, while the backward diffusion proceeds on the dark side. This bidirectional diffusion can reduce the edge width and avoid the appearances of false edge or texture and block effects. Moreover, the fractional-order derivative is used to avoid strong contrast near the edge in the interpolated images. The experiments show that, unlike the TV up-sampling (TVUP) method, the proposed algorithm does not suffer from the drift of edges, block effect in the smooth regions, false edges, and false texture.

  19. Beam splitter for squeezed light

    NASA Astrophysics Data System (ADS)

    Qu, Weizhi; Sun, Jian; Mikhailov, Eugeniy; Novikova, Irina; Shen, Heng; Xiao, Yanhong

    2016-05-01

    A conventional beam splitter can split classical light beams, but when used for squeezed light, the non-classical property is often lost at the beam splitter output. Here, we demonstrate a beam splitter made of moving atoms that can split squeezed light. Squeezed vacuum is generated by a degenerate four-wave-mixing (FWM) process in one location (Ch1) of a wall-coated Rb vapor cell, and then due to coherent diffusion of ground state coherence of the atoms within the cell, squeezed vacuum can be generated in a different location (Ch2) of the cell where no squeezing would exist without the presence of the Ch1, because of a relatively weak laser input. We attribute the phenomenon to FWM enhanced by coherence transfer. This effectively forms a beam splitter for squeezed light. We built a simple model that produces results in qualitative agreement with our experimental observations.

  20. Carbon Diffusion in Zircon

    NASA Astrophysics Data System (ADS)

    Cherniak, D. J.; Watson, E. B.; Boehnke, P.; Harrison, T. M.

    2016-12-01

    With the recent discovery of potentially biogenic carbon in 4.1 billion-year-old zircon (Bell et al., 2015), it is important to understand diffusion of C in zircon in order to assess the potential of these carbonaceous inclusions to preserve isotopic evidence of Earth's early history. In this study, we have characterized carbon diffusion in natural zircon at 1-atm and under high-pressure conditions in the presence of hydrous species. The 1-atm experiments were conducted by implanting 13C into polished, oriented slabs of zircon, with implanted samples heated in air or under buffered conditions in silica glass ampoules sealed under vacuum. High-pressure experiments (1 GPa) were conducted in a piston-cylinder apparatus, using 13C labeled glycine as the starting source (this breaks down at run conditions). In all cases, 13C distributions in zircon were measured by Nuclear Reaction Analysis (NRA) using the reaction 13C(p,γ)14N. In addition to the NRA measurements, we have also conducted analyses of carbon in zircon by ion microprobe. For diffusion parallel to c we obtain a well-constrained Arrhenius relation over the temperature range 600-1100°C. Diffusion normal to c is similar. Data from the high-pressure experiments and those run under buffered conditions also yield similar diffusivities, suggesting that carbon diffusion is not significantly affected by these parameters over the range of conditions studied. Carbon diffuses more rapidly than most cations in zircon, with the exception of lithium, but several orders of magnitude more slowly than helium. Zircon will therefore be moderately retentive of carbon. For example, diffusion distances on Gyr timescales would be on order of nm at 200°C, μm at 350°C and mm at 650°C, suggesting that carbon isotopic signatures contained within carbonaceous inclusions in zircon may be retained over long timeframes if zircons experience only moderate heating. E.A. Bell, P. Boehnke, T. M. Harrison, W.L. Mao (2015) PNAS 47, 14518-14521

  1. [Microbial diffusion and antibiotherapy].

    PubMed

    Vilain, R

    1982-01-01

    Cleaning leg ulcers depends on tissular and microbial enzymes, the production of which depends on good vascularization. When an aetiological treatment is started, the microbes ensure sufficient cleaning, leading to granulation and epidermization. Antibiotherapy is pointless. Sometimes it can be detrimental, replacing a natural growth with alien strains which cause diffusion. Very exceptionally, a short course of antibiotherapy may be necessary to cope with signs of diffusion, usually signifying a Group A streptococcal infection, with seasonal recrudescence. The Blue Pus Microbe has no special pathological significance. It merely indicates that the case has become chronic.

  2. 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

  3. 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

  4. 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

  5. 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)

  6. 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)

  7. Circadian light

    PubMed Central

    2010-01-01

    The present paper reflects a work in progress toward a definition of circadian light, one that should be informed by the thoughtful, century-old evolution of our present definition of light as a stimulus for the human visual system. This work in progress is based upon the functional relationship between optical radiation and its effects on nocturnal melatonin suppression, in large part because the basic data are available in the literature. Discussed here are the fundamental differences between responses by the visual and circadian systems to optical radiation. Brief reviews of photometry, colorimetry, and brightness perception are presented as a foundation for the discussion of circadian light. Finally, circadian light (CLA) and circadian stimulus (CS) calculation procedures based on a published mathematical model of human circadian phototransduction are presented with an example. PMID:20377841

  8. 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.

  9. Reaction-diffusion optoelectronics based on dispersed semiconductors

    NASA Astrophysics Data System (ADS)

    Gradov, O. V.; Gradova, M. A.

    2015-11-01

    Since many dispersed semiconductors are capable of light energy conversion and possess photocatalytic and luminescent properties, and any discreet light-sensitive medium can be applied for the positional-sensitive light flux registration (similar to pixels and voxels in semiconductor-based image recording), the use of chemically active dispersed semiconductors allows to perform a direct signal / image registration based on light-sensitive reaction-diffusion redox systems without conventional CCD / CMOS devices. The image capturing in this case will correspond to the formation of the metastable dissipative structures in the active medium, with their morphological properties determined by the flux gradient and provided by the corresponding dispersed semiconductor medium sensitivity.

  10. 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

  11. Computational analysis of endometrial photocoagulation with diffusing optical device.

    PubMed

    Kwon, Jinhee; Lee, Chang-Yong; Oh, Junghwan; Kang, Hyun Wook

    2013-01-01

    A balloon-catheter optical diffuser for endometrial treatment was evaluated with computational thermal analysis. Various catheter materials and dimensions were implemented to identify the optimal design for the device. Spatial and temporal development of temperature during 30-sec irradiation of 532-nm light demonstrated thermal insulation effects of polyurethane on temperature increase up to 384 K, facilitating the irreversible denaturation. The current model revealed the degree of thermal coagulation 13% thicker than experimental results possibly due to lack of tissue dynamics and light intensity distribution. In combination with photon distribution, the analytical simulation can be a feasible tool to optimize the new optical diffuser for efficient and safe endometrial treatment.

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

    SciTech Connect

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

    2016-04-28

    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.

  13. Deciphering mechanisms of enhanced-retarded oxygen diffusion in doped Si

    NASA Astrophysics Data System (ADS)

    Timerkaeva, Dilyara; Caliste, Damien; Pochet, Pascal

    2013-12-01

    We study enhanced/retarded diffusion of oxygen in doped silicon by means of first principle calculations. We evidence that the migration energy of oxygen dimers cannot be significantly affected by strain, doping type, or concentration. We attribute the enhanced oxygen diffusion in p-doped silicon to reduced monomer migration energy and the retarded oxygen diffusion in Sb-doped to monomer trapping close to a dopant site. These two mechanisms can appear simultaneously for a given dopant leading to contradictory experimental results. More generally, our findings cast a new light on phenomena involving oxygen diffusion: precipitation, thermal donors formation, and light induced degradation.

  14. 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.

  15. Multicomponent diffusion in molten salt NaF-ZrF{sub 4}: Dynamical correlations and Maxwell–Stefan diffusivities

    SciTech Connect

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

    2016-05-23

    NaF-ZrF{sub 4} is used as a waste incinerator and as a coolant in Generation IV reactors.Structural and dynamical properties of molten NaF-ZrF{sub 4} 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 Đ{sub Na-F} shows interesting behavior with the increase in concentration of ZrF{sub 4}. This is because of network formation in NaF-ZrF{sub 4}. Positive entropy constraints have been plotted to authenticate negative diffusivities observed.

  16. 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.

  17. Observations of the diffuse UV radiation field

    NASA Technical Reports Server (NTRS)

    Murthy, Jayant; Henry, R. C.; Feldman, P. D.; Tennyson, P. D.

    1989-01-01

    Spectra are presented for the diffuse UV radiation field between 1250 to 3100 A from eight different regions of the sky, which were obtained with the Johns Hopkins UVX experiment. UVX flew aboard the Space Shuttle Columbia (STS-61C) in January 1986 as part of the Get-Away Special project. The experiment consisted of two 1/4 m Ebert-Fastie spectrometers, covering the spectral range 1250 to 1700 A at 17 A resolution and 1600 to 3100 A at 27 A resolution, respectively, with a field of view of 4 x .25 deg, sufficiently small to pick out regions of the sky with no stars in the line of sight. Values were found for the diffuse cosmic background ranging in intensity from 300 to 900 photons/sq cm/sec/sr/A. The cosmic background is spectrally flat from 1250 to 3100 A, within the uncertainties of each spectrometer. The zodiacal light begins to play a significant role in the diffuse radiation field above 2000 A, and its brightness was determined relative to the solar emission. Observed brightnesses of the zodiacal light in the UV remain almost constant with ecliptic latitude, unlike the declining visible brightnesses, possibly indicating that those (smaller) grains responsible for the UV scattering have a much more uniform distribution with distance from the ecliptic plane than do those grains responsible for the visible scattering.

  18. DEVELOPMENT, DIFFUSION, AND EVALUATION.

    ERIC Educational Resources Information Center

    GUBA, EGON G.

    THE KNOWLEDGE GAP BETWEEN INITIAL RESEARCH AND FINAL USE IS DISCUSSED IN TERMS OF THE FOUR STATES OF THE THEORY-PRACTICE CONTINUUM (RESEARCH, DEVELOPMENT, DIFFUSION, AND ADOPTION). THE TWO MIDDLE STAGES ARE EMPHASIZED. RESEARCH AND DEVELOPMENT CENTERS, REGIONAL EDUCATIONAL LABORATORIES, AND TITLE III PROJECTS ARE SUGGESTED AS AGENCIES RESPONSIBLE…

  19. Diffusion in random networks

    DOE PAGES

    Zhang, Duan Z.; Padrino, Juan C.

    2017-06-01

    The ensemble averaging technique is applied to model mass transport by diffusion in random networks. The system consists of an ensemble of random networks, where each network is made of pockets connected by tortuous channels. Inside a channel, fluid transport is assumed to be governed by the one-dimensional diffusion equation. Mass balance leads to an integro-differential equation for the pocket mass density. The so-called dual-porosity model is found to be equivalent to the leading order approximation of the integration kernel when the diffusion time scale inside the channels is small compared to the macroscopic time scale. As a test problem,more » we consider the one-dimensional mass diffusion in a semi-infinite domain. Because of the required time to establish the linear concentration profile inside a channel, for early times the similarity variable is xt$-$1/4 rather than xt$-$1/2 as in the traditional theory. We found this early time similarity can be explained by random walk theory through the network.« less

  20. Lung diffusion testing

    MedlinePlus

    ... the blood from the lungs, and to allow carbon dioxide to "diffuse" from the blood into the lungs. How the Test is Performed You breathe in (inhale) air containing a very small amount of carbon monoxide and a tracer gas, such as methane ...

  1. 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.

  2. 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.

  3. 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.

  4. Nanocrystal diffusion doping.

    PubMed

    Vlaskin, Vladimir A; Barrows, Charles J; Erickson, Christian S; Gamelin, Daniel R

    2013-09-25

    A diffusion-based synthesis of doped colloidal semiconductor nanocrystals is demonstrated. This approach involves thermodynamically controlled addition of both impurity cations and host anions to preformed seed nanocrystals under equilibrium conditions, rather than kinetically controlled doping during growth. This chemistry allows thermodynamic crystal compositions to be prepared without sacrificing other kinetically trapped properties such as shape, size, or crystallographic phase. This doping chemistry thus shares some similarities with cation-exchange reactions, but proceeds without the loss of host cations and excels at the introduction of relatively unreactive impurity ions that have not been previously accessible using cation exchange. Specifically, we demonstrate the preparation of Cd(1-x)Mn(x)Se (0 ≤ x ≤ ∼0.2) nanocrystals with narrow size distribution, unprecedentedly high Mn(2+) content, and very large magneto-optical effects by diffusion of Mn(2+) into seed CdSe nanocrystals grown by hot injection. Controlling the solution and lattice chemical potentials of Cd(2+) and Mn(2+) allows Mn(2+) diffusion into the internal volumes of the CdSe nanocrystals with negligible Ostwald ripening, while retaining the crystallographic phase (wurtzite or zinc blende), shape anisotropy, and ensemble size uniformity of the seed nanocrystals. Experimental results for diffusion doping of other nanocrystals with other cations are also presented that indicate this method may be generalized, providing access to a variety of new doped semiconductor nanostructures not previously attainable by kinetic routes or cation exchange.

  5. 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

  6. Diffusion on Cu surfaces

    NASA Technical Reports Server (NTRS)

    Karimi, Majid

    1993-01-01

    Understanding surface diffusion is essential in understanding surface phenomena, such as crystal growth, thin film growth, corrosion, physisorption, and chemisorption. Because of its importance, various experimental and theoretical efforts have been directed to understand this phenomena. The Field Ion Microscope (FIM) has been the major experimental tool for studying surface diffusion. FIM have been employed by various research groups to study surface diffusion of adatoms. Because of limitations of the FIM, such studies are only limited to a few surfaces: nickel, platinum, aluminum, iridium, tungsten, and rhodium. From the theoretical standpoint, various atomistic simulations are performed to study surface diffusion. In most of these calculations the Embedded Atom Method (EAM) along with the molecular static (MS) simulation are utilized. The EAM is a semi-empirical approach for modeling the interatomic interactions. The MS simulation is a technique for minimizing the total energy of a system of particles with respect to the positions of its particles. One of the objectives of this work is to develop the EAM functions for Cu and use them in conjunction with the molecular static (MS) simulation to study diffusion of a Cu atom on a perfect as well as stepped Cu(100) surfaces. This will provide a test of the validity of the EAM functions on Cu(100) surface and near the stepped environments. In particular, we construct a terrace-ledge-kink (TLK) model and calculate the migration energies of an atom on a terrace, near a ledge site, near a kink site, and going over a descending step. We have also calculated formation energies of an atom on the bare surface, a vacancy in the surface, a stepped surface, and a stepped-kink surface. Our results are compared with the available experimental and theoretical results.

  7. 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.

  8. OLED lighting: light where it never has been before

    NASA Astrophysics Data System (ADS)

    Klein, M.; Heuser, K.; Schindler, F.; Krummacher, B.; Dobbertin, T.; Pätzold, R.; Gärditz, C.

    2007-02-01

    "Optical Technologies have conquered the world" - their economic key data showed an impressive growth in the past couple of years, and the predictions for the up-coming years keep the expectations high 1, 2. In the case of OLED (Organic Light Emitting Diode) lighting, e.g. IDTechEx is predicting a worldwide market growth from 50 million USD in 2009 to 3.3 billion USD in 2012 3. LED and OLED technology, although both being referred to as solid state lighting, are rather complementary in their characteristics. Whereas LEDs are high efficient point light sources, OLEDs cover large area, diffuse lighting applications which can follow the increased awareness for creation of personalized atmosphere. Ambience and mood lighting can be perfectly realized by the means of OLED large area illumination which will pave the way for applications that up to now could not have been realized. OLED lighting technology rests on three pillars at the same time, the basic performance like efficiency and lifetime, the unique features, and costs. These key challenges and their impact on various applications will be discussed.

  9. 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.

  10. Synchrotron light

    SciTech Connect

    Craievich, A. )

    1990-01-01

    Several developed countries such as the USA, URSS, England, France, Italy, Sweden and Japan have one or more of these synchrotron light facilities operating or under construction. Some developing countries have constructed (China) or are building (Taiwan, India, Korea, Brazil) synchrotron light facilities. The construction of the Brazilian synchrotron source began in June, 1987. After two years of activities, the injector linac for the electron storage ring is in its final stage of construction. These Proceedings contain the Invited Lectures presented at the Workshop by specialists working on synchrotron light applications and related instrumentation and by members of LNLS regarding technical details of the Brazilian project. The II Workshop Synchrotron Light: Applications and Related Instrumentation was dedicated to oral presentations about applications of synchrotron light, most of which were not covered during the I Workshop, organized by LNLS in 1988, and the Proceedings of which were published by World Scientific. The II Workshop included discussions on the application possibilities for the newly designed LNLS 1.15 GeV storage ring, and on the modifications which would eventually be necessary for the work-station and instrumentation projects currently in progress at LNLS and at various external user laboratories.

  11. 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

  12. Diffuse Winter Lighting of the Chasma Boreale Scarp

    NASA Image and Video Library

    2013-08-08

    Sunlight was just starting to reach the high Northern latitudes in late winter when NASA Mars Reconnaissance Orbiter HiRISE camera captured this image of part of the steep scarps around portions of the North Polar layered deposits.

  13. Breast Cancer Diagnosis Using Ultrasound and Diffusive Light

    DTIC Science & Technology

    2004-08-01

    transducer and NIR optical imaging sensors mounted on a hand- held probe. The co-registered ultrasound is used for lesion localization and optical... sensors are used for imaging tumor angiogenesis and tumor hypoxia. With the US localization, the entire imaging volume is thus segmented into lesion...A. Developed the unique technique by simultaneously deploying near infrared sensors and an

  14. 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.

  15. Enhanced Backscattering of Light from Randomly Rough Diffusers. Appendix

    DTIC Science & Technology

    1991-09-01

    Walter Welford, Nick Jackson, the 3 d Year Undergraduate Laboratory staff for the loan of their cylindrical lens (you can have it back now!), and Dionaea ... Muscipula (affection- ately known as Fred) who has been a source of much philosophical inspiration to me. I extend my gratitude to the managers of The

  16. Resolving High Amplitude Surface Motion with Diffusing Light

    NASA Technical Reports Server (NTRS)

    Wright, W.; Budakian, R.; Putterman, Seth J.

    1996-01-01

    A new technique has been developed for the purpose of imaging high amplitude surface motion. With this method one can quantitatively measure the transition to ripple wave turbulence. In addition, one can measure the phase of the turbulent state. These experiments reveal strong coherent structures in turbulent range of motion.

  17. Application of diffusion and photosensitizing techniques in PMMA to optical interconnects

    NASA Astrophysics Data System (ADS)

    Brenner, Karl-Heinz; Kufner, Maria; Kufner, Stefan; Sinzinger, Stefan; Testorf, Markus E.

    1990-07-01

    A new technique for the three dimensional integration of optical components is presented. It is based on diffusion techniques and photoinitiated polymerization. Initial experimental results demonstrate the feasibility and efficiency. DIFFUSION jQ PHOTOINITIATED POLYMERISA11ON We want to combine diffusion with photoinitiated polymerization in order to form passive elements which are necessary for three dimensional integration of optical components for microoptical systems1''2. The production of optical elements by photopolymerization consists of two main steps. First the PMMA is sensitized to ultraviolet light by diffusing a photoinitiator into the substrat. Then the exposure by UV light causes an increase in the thickness and in the refractive index. The structuring can be achieved either by local diffusion and global exposure for stabilization or by global diffusion and local exposure. In the first case metal-masks for the diffusion process are necessary whereas in the second case photo-masks can be used. OPTICAL INTERCONNECFION For realizing a flexible optical interconnection plate3''4 the necessary functions are: light collimation light deflection and beam splitting. Collimation can be achieved by microlenses. For deflection we use a miniaturized prism. For beam splitting an index grating can be used. The components are integrated within a planar PMMA plate. EXPERIMENTAL RESULTS By measuring the phase profile of diffused lenses and prisms we demonstrated that phase shifts of several wavelengths can be achieved by polymerization and diffusion techniques. The main effect results from the

  18. Light- scattering studies of blood sedimentation

    NASA Astrophysics Data System (ADS)

    Grzegorzewski, Bronislaw; Kowalinska, E.

    2002-02-01

    We present the result of investigation of blood sediment formation with the use of three different optical techniques. The angular dependence of scattered light intensity, transmitted light intensity across the sediment's layer and correlation of speckle intensity fluctuations were measure. Two characteristic time periods of the sedimentation process are demonstrated. In the first period three phases can be distinguished: the plasma, the phase of diffuse erythrocytes and the phase of already formed aggregates. In the second period the phase of the diffuse erythrocytes disappears. The results support the hypothesis that a phase transition is associated with the blood sedimentation process.

  19. An automatic light scattering CCN counter

    NASA Technical Reports Server (NTRS)

    Lala, G. G.

    1981-01-01

    The counter is a static thermal diffusion chamber which has been modified to include an optical system for the determination of droplet concentration by the measurement of scattered light. The determination of concentration is made by measurement of the peak scattered light signal from the cloud of growing droplets which is a function of both the droplet concentration and chamber supersaturation. Because the formation of the peak is related to the rate of growth of the droplets and sedimentation, both of which are determined by supersaturation, the system calibration can be uniquely determined by comparison with an absolute counter such as a static diffusion chamber with a photographic recording system.

  20. 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?