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Sample records for densities refractive indices

  1. Densities and refractive indices for acetone + methanol + 1-propanol at 298.15 K

    SciTech Connect

    Iglesias, M.; Orge, B.; Tojo, J.

    1996-03-01

    Densities and refractive indices at 298.15 K for acetone + methanol + 1-propanol and the binary acetone + 1-propanol and methanol + 1-propanol mixtures have been measured as a function of the mole fraction at atmospheric pressure. Parameters of analytical expressions which represent the composition dependences of physical properties and excess values are reported. The refractive index results are compared with estimation methods. The excess properties for the ternary mixture are compared with those estimated on the basis of binary property contributions.

  2. Densities and refractive indices of acetone + methanol + 2-methyl-2-butanol at 298.15 K

    SciTech Connect

    Orge, B.; Iglesias, M.; Tojo, J.; Legido, J.L.

    1995-11-01

    Densities and refractive indices at 298.15 K for acetone + methanol + 2-methyl-2-butanol and the binary acetone + 2-methyl-2-butanol and methanol + 2-methyl-2-butanol mixtures have been measured as a function of the mole fraction at atmospheric pressure. Results have been correlated with analytical expressions.

  3. Indices of refraction for the HITRAN compilation

    NASA Technical Reports Server (NTRS)

    Massie, S. T.

    1994-01-01

    Indices of refraction of sulfuric acid solutions, water, and ice, which will become part of the HITRAN database, are discussed. Representative calculations are presented for the sulfate aerosol, to illustrate the broadband spectral features of i.r. aerosol extinction spectra. Values of the sulfuric acid mass density are used in an application of the Lorentz-Lorenz equation, which is used to estimate the sensitivity of extinction coefficients to temperature dependent refractive indices.

  4. Densities, viscosities, and refractive indices of the binary liquid systems n-alkanes + isomers of hexane at 298.15 K

    SciTech Connect

    Aucejo, A.; Burguet, M.C.; Munoz, R.; Marques, J.L.

    1995-07-01

    In this paper the viscosities, densities, and refractive indices of nine binary liquid systems containing n-alkane + isomers of hexane have been determined at 298.15 K. The viscosity values were fitted to the McAllister three-body model and the Redlich-Kister-type equation. The results with these models agree with experimental data with an average absolute deviation of less than 0.6%. The nine binary liquid systems studied were hexadecane with 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, and 2,3-dimethylbutane; dodecane with 2-methylpentane, 2,2-dimethylbutane, and 2,3-dimethylbutane; and tetradecane with 2-methylpentane and 2,3-dimethylbutane.

  5. The real part of the refractive indices and effective densities for chemically segregated ambient aerosols in Guangzhou by a single particle aerosol mass spectrometer

    NASA Astrophysics Data System (ADS)

    Zhang, G.; Bi, X.; Qiu, N.; Han, B.; Lin, Q.; Peng, L.; Chen, D.; Wang, X.; Peng, P.; Sheng, G.; Zhou, Z.

    2015-12-01

    Microphysical properties of atmospheric aerosols are essential to better evaluate their radiative forcing. This paper first presents an estimate of the real part of the refractive indices (n) and effective densities (ρeff) of chemically segregated atmospheric aerosols in China. Vacuum aerodynamic diameter, chemical compositions, and light scattering intensities of individual particles were simultaneously measured by a single particle aerosol mass spectrometer (SPAMS) during fall of 2012 in Guangzhou. On the basis of Mie theory, n and ρeff were estimated for 17 particle types in four categories: organics (OC), elemental carbon (EC), internally mixed EC and OC (ECOC), and metal rich, respectively. Results indicate the presence of spherical or nearly spherical shape for majority of particle types, whose partial scattering cross section vs. sizes were well fitted to Mie theoretical modeling results. While sharing n in a narrow range (1.47-1.53), majority of particle types exhibited a wide range of ρeff (0.87-1.51 g cm-3). OC group is associated with the lowest ρeff (0.87-1.07 g cm-3), while metal rich group with the highest ones (1.29-1.51 g cm-3). It is noteworthy that a specific EC type exhibits a complex scattering curve vs. size due to the presence of both compact and irregularly shape particles. Overall, the results on detailed relationship between physical and chemical properties benefits future researches on the impact of aerosols on visibility and climate.

  6. Refractive Indices of Gases at Microwave Frequencies

    ERIC Educational Resources Information Center

    Goodhead, D. T.; And Others

    1976-01-01

    Describes a simple microwave interferometer capable of measuring small phase shifts. Proposes laboratory exercises involving the use of the interferometer in the determination of refractive indices of gases and the analysis of the reflection in a test chamber. (Author/CP)

  7. The real part of the refractive indices and effective densities for chemically segregated ambient aerosols in Guangzhou measured by a single-particle aerosol mass spectrometer

    NASA Astrophysics Data System (ADS)

    Zhang, Guohua; Bi, Xinhui; Qiu, Ning; Han, Bingxue; Lin, Qinhao; Peng, Long; Chen, Duohong; Wang, Xinming; Peng, Ping'an; Sheng, Guoying; Zhou, Zhen

    2016-03-01

    Knowledge on the microphysical properties of atmospheric aerosols is essential to better evaluate their radiative forcing. This paper presents an estimate of the real part of the refractive indices (n) and effective densities (ρeff) of chemically segregated atmospheric aerosols in Guangzhou, China. Vacuum aerodynamic diameter, chemical compositions, and light-scattering intensities of individual particles were simultaneously measured by a single-particle aerosol mass spectrometer (SPAMS) during the fall of 2012. On the basis of Mie theory, n at a wavelength of 532 nm and ρeff were estimated for 17 particle types in four categories: organics (OC), elemental carbon (EC), internally mixed EC and OC (ECOC), and Metal-rich. The results indicate the presence of spherical or nearly spherical shapes for the majority of particle types, whose partial scattering cross-section versus sizes were well fitted to Mie theoretical modeling results. While sharing n in a narrow range (1.47-1.53), majority of particle types exhibited a wide range of ρeff (0.87-1.51 g cm-3). The OC group is associated with the lowest ρeff (0.87-1.07 g cm-3), and the Metal-rich group with the highest ones (1.29-1.51 g cm-3). It is noteworthy that a specific EC type exhibits a complex scattering curve versus size due to the presence of both compact and irregularly shaped particles. Overall, the results on the detailed relationship between physical and chemical properties benefits future research on the impact of aerosols on visibility and climate.

  8. Densities, viscosities, refractive indices, and speeds of sound of the binary mixtures of bis(2-methoxyethyl) ether with nonane, decane, dodecane, tetradecane, and hexadecane at 298. 15, 308. 15, and 318. 15 K

    SciTech Connect

    Aminabhavi, T.M.; Gopalkrishna, B. . Dept. of Chemistry)

    1994-07-01

    Densities, viscosities, refractive indices, and speeds of sound for the boundary mixtures of bis(2-methoxyethyl) ether with nonane, decane, dodecane, tetradecane, and hexadecane have been measured at 298.15, 308.15, and 318.15 K over the entire range of mole fractions. From these results, the excess molar volumes and deviations in viscosity, refractivity, speed of sound, and isentropic compressibility have been calculated. These results are fitted to the Redlich-Kister polynomial relation to estimate the binary interaction parameters. The excess molar volumes and deviations in isentropic compressibility are positive, while the deviations in viscosity, speed of sound, and molar refractivity are negative. The results show a trend with the chain length of the alkanes.

  9. EDITORIAL: Sensitive structures: refractive indices in nanotechnology Sensitive structures: refractive indices in nanotechnology

    NASA Astrophysics Data System (ADS)

    Demming, Anna

    2012-12-01

    Refractive index effects using nanoscale systems are frequently applied in new imaging, sensing and even visibility cloaking technology. In this issue, researchers in Japan use simulations and experiments to describe the confinement of optical vortices in nanoscale fin structures and the sensitivity of these systems to the refractive index of the surrounding media [1]. The effects of refraction as light rays pass between different media were recorded as long ago as the first century AD, by Ptolemy [2]. Over the following centuries the phenomena inspired Ibn Sahl in 984 [3], Thomas Harriot in 1602 [4], Willebrord Snellius in 1621 [5] and Rene Descartes in 1637 [6] to independently derive the more accurate and elegant equation for refraction so familiar to us today. Recent studies of the interactions between light and matter continue to reveal a wealth of phenomena that originate in the effects of the refractive indices of materials. Nanostructures can be used to manipulate conditions that affect the refractive indices of materials, such as temperature. A E Aliev et al at the University of Texas reported a striking demonstration of temperature-dependent refractive index effects using a free-standing, highly aligned carbon nanotube aerogel sheet [7]. They used the extremely low thermal capacitance and high heat transfer ability of transparent carbon nanotube sheets to enable high-frequency modulation of the sheet temperature over an enormous temperature range. The resulting sharp, rapidly changing gradient of the refractive index in the surrounding liquid or gas makes objects seem to disappear and can be used for visibility cloaking. Light-matter interaction resonances, where light is confined at the nanoscale, can be extremely sensitive to changes in the refractive index of the surrounding media [8], even allowing single-molecule detection [9]. Plasmons, the collective oscillations of electrons in response to incident light, are a typical example. Researchers at Rice

  10. Measuring Variable Refractive Indices Using Digital Photos

    ERIC Educational Resources Information Center

    Lombardi, S.; Monroy, G.; Testa, I.; Sassi, E.

    2010-01-01

    A new procedure for performing quantitative measurements in teaching optics is presented. Application of the procedure to accurately measure the rate of change of the variable refractive index of a water-denatured alcohol mixture is described. The procedure can also be usefully exploited for measuring the constant refractive index of distilled…

  11. EDITORIAL: Sensitive structures: refractive indices in nanotechnology Sensitive structures: refractive indices in nanotechnology

    NASA Astrophysics Data System (ADS)

    Demming, Anna

    2012-12-01

    Refractive index effects using nanoscale systems are frequently applied in new imaging, sensing and even visibility cloaking technology. In this issue, researchers in Japan use simulations and experiments to describe the confinement of optical vortices in nanoscale fin structures and the sensitivity of these systems to the refractive index of the surrounding media [1]. The effects of refraction as light rays pass between different media were recorded as long ago as the first century AD, by Ptolemy [2]. Over the following centuries the phenomena inspired Ibn Sahl in 984 [3], Thomas Harriot in 1602 [4], Willebrord Snellius in 1621 [5] and Rene Descartes in 1637 [6] to independently derive the more accurate and elegant equation for refraction so familiar to us today. Recent studies of the interactions between light and matter continue to reveal a wealth of phenomena that originate in the effects of the refractive indices of materials. Nanostructures can be used to manipulate conditions that affect the refractive indices of materials, such as temperature. A E Aliev et al at the University of Texas reported a striking demonstration of temperature-dependent refractive index effects using a free-standing, highly aligned carbon nanotube aerogel sheet [7]. They used the extremely low thermal capacitance and high heat transfer ability of transparent carbon nanotube sheets to enable high-frequency modulation of the sheet temperature over an enormous temperature range. The resulting sharp, rapidly changing gradient of the refractive index in the surrounding liquid or gas makes objects seem to disappear and can be used for visibility cloaking. Light-matter interaction resonances, where light is confined at the nanoscale, can be extremely sensitive to changes in the refractive index of the surrounding media [8], even allowing single-molecule detection [9]. Plasmons, the collective oscillations of electrons in response to incident light, are a typical example. Researchers at Rice

  12. Removing singular refractive indices with sculpted surfaces

    PubMed Central

    Horsley, S. A. R.; Hooper, I. R.; Mitchell–Thomas, R. C.; Quevedo–Teruel, O.

    2014-01-01

    The advent of Transformation Optics established the link between geometry and material properties, and has resulted in a degree of control over electromagnetic fields that was previously impossible. For waves confined to a surface it is known that there is a simpler, but related, geometrical equivalence between the surface shape and the refractive index, and here we demonstrate that conventional devices possessing a singularity — that is, the requirement of an infinite refractive index — can be realised for waves confined to an appropriately sculpted surface. In particular, we redesign three singular omnidirectional devices: the Eaton lens, the generalized Maxwell Fish–Eye, and the invisible sphere. Our designs perfectly reproduce the behaviour of these singular devices, and can be achieved with simple isotropic media of low refractive index contrast. PMID:24786649

  13. Silica nanorod-array films with very low refractive indices.

    PubMed

    Xi, J Q; Kim, Jong Kyu; Schubert, E F

    2005-07-01

    The refractive-index contrast is an important figure of merit for dielectric multilayer structures, optical resonators, and photonic crystals. This represents a strong driving force for novel materials that have refractive indices lower than those of conventional optically transparent materials. Silica nanorod-array dielectric films with unprecedented low refractive indices of 1.08 are demonstrated and shown to have viable optical properties including enhanced reflectivity of a single-pair distributed Bragg reflector.

  14. Lens Design Using Group Indices of Refraction

    NASA Technical Reports Server (NTRS)

    Vaughan, A. H.

    1995-01-01

    An approach to lens design is described in which the ratio of the group velocity to the speed of light (the group index) in glass is used, in conjunction with the more familiar phase index of refraction, to control certain chromatic properties of a system of thin lenses in contact. The first-order design of thin-lens systems is illustrated by examples incorporating the methods described.

  15. Interferometric Methods of Measuring Refractive Indices and Double-Refraction of Fibres.

    ERIC Educational Resources Information Center

    Hamza, A. A.; El-Kader, H. I. Abd

    1986-01-01

    Presents two methods used to measure the refractive indices and double-refraction of fibers. Experiments are described, with one involving the use of Pluta microscope in the double-beam interference technique, the other employing the multiple-beam technique. Immersion liquids are discussed that can be used in the experiments. (TW)

  16. Intermolecular interaction in plant oils from refractive and density measurements

    NASA Astrophysics Data System (ADS)

    Andriyevsky, B.; Andriyevska, L.; Piecuch, T.

    2010-12-01

    Refractive indices n and density ρ of three plant oils (Anise, Nigelle, and Juniper berries) have been measured in the temperature range of 10-60°C. The model of the effective electric field E' acting on a molecule in the material, E' = E + x4π P, with the unlimited value of the coefficient of polarization input x has been applied to the analysis of the results obtained. The value x of the oils studied have been found to be in the range of 0.193-0.269, which is smaller than a similar value for water ( x water > 0.3), known as a strong polar liquid.

  17. Effective refractive indices of three-phase optical coatings

    NASA Astrophysics Data System (ADS)

    Ma, Yushieh; Varadan, Vijay K.; Varadan, Vasundara V.

    1991-11-01

    To obtain the effective refractive indices of three-phase coating materials, in which multiple scattering can also occur between the two different discrete phases, a multiple scattering formalism for two-phase systems is modified to include the third phase. Numerical results for different refractive indices of various arrangements are presented for a paint coating in which some of the TiO2 pigment particles are replaced by microbubbles.

  18. Calculation of refraction indices of triple chalcogenide crystals

    NASA Astrophysics Data System (ADS)

    Kamenshchikov, V. N.; Suslikov, L. M.

    2015-04-01

    We use Harrison's bond-orbital method to calculate high frequency refraction indices of AgGaS2, CdGa2S4, and CdGa2Se4 crystals. We demonstrate a satisfactory agreement between obtained results and experimental data.

  19. Refractive indices of metal working fluid emulsion components

    NASA Astrophysics Data System (ADS)

    Glasse, Benjamin; Zerwas, Alexander; Guardani, Roberto; Fritsching, Udo

    2014-03-01

    Metal working fluids (MWF) used in machining processes are typically formulated as oil-in-water emulsions, consisting of an aqueous base with an emulsified oleous phase and additives. These emulsions degenerate over their lifetime leading to changed physical attributes, for instance increased droplet size or concentration. This temporal change may be monitored via optical measurement techniques, which require knowledge of the refractive index of the aqueous and oleous phases for the droplet size measurement. The optical dispersion of the aqueous phase is widely documented in the literature; however, there are no proper references available for the oleous phase for MWF. Thus, in this study the dependence of refractive indices on the wavelength of light of oils that are typically used for the formulation of MWF was determined. The measurements were performed using an Abbe refractometer at room temperature (22 ± 2 °C) in the visible light range at wavelengths between 430 and 680 nm. The results were fitted to the Cauchy dispersion equation describing the optical dispersion of the systems.

  20. Comparison of Methods for Predicting the Compositional Dependence of the Density and Refractive Index of Organic-Aqueous Aerosols.

    PubMed

    Cai, Chen; Miles, Rachael E H; Cotterell, Michael I; Marsh, Aleksandra; Rovelli, Grazia; Rickards, Andrew M J; Zhang, Yun-Hong; Reid, Jonathan P

    2016-08-25

    Representing the physicochemical properties of aerosol particles of complex composition is of crucial importance for understanding and predicting aerosol thermodynamic, kinetic, and optical properties and processes and for interpreting and comparing analysis methods. Here, we consider the representations of the density and refractive index of aqueous-organic aerosol with a particular focus on the dependence of these properties on relative humidity and water content, including an examination of the properties of solution aerosol droplets existing at supersaturated solute concentrations. Using bulk phase measurements of density and refractive index for typical organic aerosol components, we provide robust approaches for the estimation of these properties for aerosol at any intermediate composition between pure water and pure solute. Approximately 70 compounds are considered, including mono-, di- and tricarboxylic acids, alcohols, diols, nitriles, sulfoxides, amides, ethers, sugars, amino acids, aminium sulfates, and polyols. We conclude that the molar refraction mixing rule should be used to predict the refractive index of the solution using a density treatment that assumes ideal mixing or, preferably, a polynomial dependence on the square root of the mass fraction of solute, depending on the solubility limit of the organic component. Although the uncertainties in the density and refractive index predictions depend on the range of subsaturated compositional data available for each compound, typical errors for estimating the solution density and refractive index are less than ±0.1% and ±0.05%, respectively. Owing to the direct connection between molar refraction and the molecular polarizability, along with the availability of group contribution models for predicting molecular polarizability for organic species, our rigorous testing of the molar refraction mixing rule provides a route to predicting refractive indices for aqueous solutions containing organic molecules

  1. Comparison of Methods for Predicting the Compositional Dependence of the Density and Refractive Index of Organic-Aqueous Aerosols.

    PubMed

    Cai, Chen; Miles, Rachael E H; Cotterell, Michael I; Marsh, Aleksandra; Rovelli, Grazia; Rickards, Andrew M J; Zhang, Yun-Hong; Reid, Jonathan P

    2016-08-25

    Representing the physicochemical properties of aerosol particles of complex composition is of crucial importance for understanding and predicting aerosol thermodynamic, kinetic, and optical properties and processes and for interpreting and comparing analysis methods. Here, we consider the representations of the density and refractive index of aqueous-organic aerosol with a particular focus on the dependence of these properties on relative humidity and water content, including an examination of the properties of solution aerosol droplets existing at supersaturated solute concentrations. Using bulk phase measurements of density and refractive index for typical organic aerosol components, we provide robust approaches for the estimation of these properties for aerosol at any intermediate composition between pure water and pure solute. Approximately 70 compounds are considered, including mono-, di- and tricarboxylic acids, alcohols, diols, nitriles, sulfoxides, amides, ethers, sugars, amino acids, aminium sulfates, and polyols. We conclude that the molar refraction mixing rule should be used to predict the refractive index of the solution using a density treatment that assumes ideal mixing or, preferably, a polynomial dependence on the square root of the mass fraction of solute, depending on the solubility limit of the organic component. Although the uncertainties in the density and refractive index predictions depend on the range of subsaturated compositional data available for each compound, typical errors for estimating the solution density and refractive index are less than ±0.1% and ±0.05%, respectively. Owing to the direct connection between molar refraction and the molecular polarizability, along with the availability of group contribution models for predicting molecular polarizability for organic species, our rigorous testing of the molar refraction mixing rule provides a route to predicting refractive indices for aqueous solutions containing organic molecules

  2. Optical constants of ammonium sulfate in the infrared. [stratospheric aerosol refractive and absorption indices

    NASA Technical Reports Server (NTRS)

    Downing, H. D.; Pinkley, L. W.; Sethna, P. P.; Williams, D.

    1977-01-01

    The infrared spectral reflectance at near normal incidence has been measured for 3.2 M, 2.4 M, and 1.6 M solutions of ammonium sulfate, an aerosol abundant in the stratosphere and also present in the troposphere. Kramers-Kronig analysis was used to determine values of the refractive and absorption indices from the measured spectral reflectance. A synthetic spectrum of crystalline ammonium sulfate was obtained by extrapolation of the absorption index obtained for the solution to the absorber number densities of the NH4 and SO4 ions characteristic of the crystal.

  3. Aqueous ammonium thiocyanate solutions as refractive index-matching fluids with low density and viscosity

    NASA Astrophysics Data System (ADS)

    Borrero-Echeverry, D.; Morrison, B. C. A.

    2016-07-01

    We show that aqueous solutions of ammonium thiocyanate ({NH}4{SCN}) can be used to match the index of refraction of several transparent materials commonly used in experiments, while maintaining low viscosity and density compared to other common refractive index-matching liquids. We present empirical models for estimating the index of refraction, density, and kinematic viscosity of these solutions as a function of temperature and concentration. Finally, we summarize the chemical compatibility of ammonium thiocyanate with materials commonly used in apparatus.

  4. Construction of Lines of Constant Density and Constant Refractive Index for Ternary Liquid Mixtures.

    ERIC Educational Resources Information Center

    Tasic, Aleksandar Z.; Djordjevic, Bojan D.

    1983-01-01

    Demonstrates construction of density constant and refractive index constant lines in triangular coordinate system on basis of systematic experimental determinations of density and refractive index for both homogeneous (single-phase) ternary liquid mixtures (of known composition) and the corresponding binary compositions. Background information,…

  5. Refractive indices of (NH{sub 4}){sub 2}SO{sub 4} crystals under uniaxial pressure

    SciTech Connect

    Stadnyk, V. Yo. Romanyuk, M. O.; Andrievskii, B. V.; Tuzyak, N. R.

    2009-03-15

    The effect of uniaxial pressure {sigma}{sub m} {<=} 200 bar on the spectral (300-800 nm) and temperature (300-77 K) dependences of the refractive indices of(NH{sub 4}){sub 2}SO{sub 4} crystals has been investigated. The baric dependences of the electronic polarizability, specific refraction, and parameters of the Sellmeier formula have been calculated. It is established that uniaxial pressure increases the refractive indices, mainly because of the narrowing of the band gap, increase in the oscillator density, and redshift of the UV absorption band maximum. The anomalies arising as a result of ferroelectric phase transition are related to the occurrence of spontaneous deformation and polarization (the latter is a superposition of two sublattice polarizations). The spectral and temperature dependences of the piezooptic constants are analyzed and the values of electro-optic coefficients are estimated.

  6. Refractive Indices of Asian Dust in Mid-Infrared Region

    NASA Astrophysics Data System (ADS)

    Lee, K.; Park, J.

    2013-12-01

    Optical constants of Asian dust are determined based on mineral compositions of aerosols sampled at Seoul, Korea. Complex refractive index for labradorite (plagioclase) and orthoclase (K-feldspar), which are component minerals of Asian dust, are calculated from the dispersion theory using reflectance data of the Advanced Spaceborne Thermal Emission Reflection Radiometer (ASTER). The optical constants of Asian dust are compared with those of other dust aerosols. Simulated brightness temperatures of satellite measurement using the present optical constants for a typical loading of Asian dust aerosols show spectral features of the Atmospheric Infrared Sounder (AIRS) data for an Asian dust storm. Measured and simulated spectral locations of the maximum brightness temperature are in good agreement. Simulated data show the negative slope in the region of 800-1000 cm-1. Brightness temperature of AIRS near 1233 cm-1 being lower than the maximum near 832 cm-1 can also be simulated using the optical constants of Asian dust.

  7. Frequency dependent complex refractive indices of supercooled liquid water and ice determined from aerosol extinction spectra.

    PubMed

    Zasetsky, A Y; Khalizov, A F; Earle, M E; Sloan, J J

    2005-03-31

    Complex refractive indices of supercooled liquid water at 240, 253, 263, and 273 K, and ice at 200, 210, and 235 K in the mid infrared from 460 to 4000 cm(-1) are reported. The results were obtained from the extinction spectra of small (micron-size) aerosol particles, recorded using the cryogenic flow tube technique. An improved iterative procedure for retrieving complex refractive indices from extinction measurements is described. The refractive indices of ice determined in the present study are in good agreement with data reported earlier. The temperature region and range of states covered in the present work are relevant to the study of upper tropospheric and stratospheric aerosols and clouds.

  8. Refractive indices of aerosols in the upper troposhere and lower stratosphere

    SciTech Connect

    Baumgardner, D.; Dye, J.E.; Gandrud, B.; Barr, K.

    1996-04-01

    A new instrument for simultaneously measuring aerosol diameter from 0.4-1.4 {mu}m and the refractive index between 1.30-1.60 has recently been flown on the NASA ER-2 aircraft during a stratospheric measurement campaign. Average stratospheric refractive indices varied from 1.40 to 1.46 over a vertical range from 4-20 km. The measured stratospheric refractive indices do not agree well with theoretical predictions and vertical profiles suggest the presence of non-spherical or absorbing particles in the altitude range of 7-9 km. 17 refs., 4 fig.

  9. Complex refractive indices in the infrared of nitric acid trihydrate aerosols

    SciTech Connect

    Richwine, L.J.; Clapp, M.L.; Miller, R.E.

    1995-10-01

    The refractive indices of nitric acid trihydrate (NAT) have been determined from the infrared spectra of laboratory generated aerosols. The aerosols are formed via homogeneous nucleation in a flow cell with separate regions for nucleation and observation, allowing for independent control of the temperature conditions in these regions. A spectrum of small, non-scattering particles is recorded to determine the frequency dependent imaginary refractive index, within a scaling factor. A subtractive Kramers-Kronig routine is then used to calculate the real index. The scaling factor for the imaginary indices is determined by fitting a spectrum associated with larger, scattering particles, which depends on both the real and imaginary portions of the refractive indices. The complex refractive indices of NAT are reported over the range 700 cm{sup -1} to 4000 cm{sup -1}. While in good qualitative agreement with previously reported results, there are significant quantitative differences which are discussed. 21 refs., 3 figs.

  10. Stratospheric aerosol acidity, density, and refractive index deduced from SAGE 2 and NMC temperature data

    NASA Technical Reports Server (NTRS)

    Yue, G. K.; Poole, L. R.; Wang, P.-H.; Chiou, E. W.

    1994-01-01

    Water vapor concentrations obtained by the Stratospheric Aerosol and Gas Experiment 2 (SAGE 2) and collocated temperatures provided by the National Meteorological Center (NMC) from 1986 to 1990 are used to deduce seasonally and zonally averaged acidity, density, and refractive index of stratospheric aerosols. It is found that the weight percentage of sulfuric acid in the aerosols increases from about 60 just above the tropopause to about 86 at 35 km. The density increases from about 1.55 to 1.85 g/cu cm between the same altitude limits. Some seasonal variations of composition and density are evident at high latitudes. The refractive indices at 1.02, 0.694, and 0.532 micrometers increase, respectively, from about 1.425, 1.430, and 1.435 just above the tropopause to about 1.445, 1.455, and 1.458 at altitudes above 27 km, depending on the season and latitude. The aerosol properties presented can be used in models to study the effectiveness of heterogeneous chemistry, the mass loading of stratospheric aerosols, and the extinction and backscatter of aerosols at different wavelengths. Computed aerosol surface areas, rate coefficients for the heterogeneous reaction ClONO2 + H2O yields HOCl + HNO3 and aerosol mass concentrations before and after the Pinatubo eruption in June 1991 are shown as sample applications.

  11. The effect of impurity on temperature variations in the refractive indices and thickness of TGS crystals

    NASA Astrophysics Data System (ADS)

    Stadnyk, V. Yo.; Andriyevsky, B. V.; Gaba, V. M.; Kogut, Z. A.

    2016-06-01

    Temperature dependences of optical path difference δΔi and the relative changes in thickness δ l i/ l of TGS crystals doped with L-valine are studied. Temperature dependences of the relative changes in refractive indices δ n i/( n-1) are calculated. The anisotropy coefficients of refractive indices An-1(T) and linear expansion Aα(T) are calculated, and a characteristic minimum of these dependences is found near the phase transition temperature.

  12. The Temperature Changes of Refractive Indices and Thickness of Doped Triglycine Sulfate Crystals

    NASA Astrophysics Data System (ADS)

    Kurlyak, V. Yu.; Stadnyk, V. Y.; Gaba, V. M.; Kohut, Z. O.; Matviishyn, I. M.

    2016-07-01

    The temperature dependences of the optical path difference δΔi and the relative changes in the thickness δli/l of TGS crystals doped with L-threonine are studied. The temperature dependences of the relative changes in the refractive indices δni/(n - 1), coefficients of anisotropy for refractive indices, and linear expansion have been calculated. Characteristic minimum has been detected on these curves near the phase transition temperature.

  13. Fiber-type sensor of refractive indices and concentration of liquids

    NASA Astrophysics Data System (ADS)

    Zhang, Weigang; Xu, Zhaowen; Yang, Xiang-Peng; Kai, Guiyun; Yuan, Shou-Zhong; Dong, Xiaoyi

    2001-10-01

    A portable and practical fiber-type sensor, with which can determine the refractive index and the concentration of the liquid, has been designed and realized. The method combines simplicity of structure, facility of operation, wide range of measurement and low price. It can be used either by immersing the liquid or by pouring one drop of liquid into the sensing head. The measuring resolution of the refractive index is 1.41 X 10-4 for the refractive indices of 1.33 - 1.70, and the measuring resolution of the concentration is 2.67 X 10-4 for the salt solution and the sugar solution.

  14. Age-dependence of the average and equivalent refractive indices of the crystalline lens

    PubMed Central

    Charman, W. Neil; Atchison, David A.

    2013-01-01

    Lens average and equivalent refractive indices are required for purposes such as lens thickness estimation and optical modeling. We modeled the refractive index gradient as a power function of the normalized distance from lens center. Average index along the lens axis was estimated by integration. Equivalent index was estimated by raytracing through a model eye to establish ocular refraction, and then backward raytracing to determine the constant refractive index yielding the same refraction. Assuming center and edge indices remained constant with age, at 1.415 and 1.37 respectively, average axial refractive index increased (1.408 to 1.411) and equivalent index decreased (1.425 to 1.420) with age increase from 20 to 70 years. These values agree well with experimental estimates based on different techniques, although the latter show considerable scatter. The simple model of index gradient gives reasonable estimates of average and equivalent lens indices, although refinements in modeling and measurements are required. PMID:24466474

  15. Age-dependence of the average and equivalent refractive indices of the crystalline lens.

    PubMed

    Charman, W Neil; Atchison, David A

    2013-12-01

    Lens average and equivalent refractive indices are required for purposes such as lens thickness estimation and optical modeling. We modeled the refractive index gradient as a power function of the normalized distance from lens center. Average index along the lens axis was estimated by integration. Equivalent index was estimated by raytracing through a model eye to establish ocular refraction, and then backward raytracing to determine the constant refractive index yielding the same refraction. Assuming center and edge indices remained constant with age, at 1.415 and 1.37 respectively, average axial refractive index increased (1.408 to 1.411) and equivalent index decreased (1.425 to 1.420) with age increase from 20 to 70 years. These values agree well with experimental estimates based on different techniques, although the latter show considerable scatter. The simple model of index gradient gives reasonable estimates of average and equivalent lens indices, although refinements in modeling and measurements are required. PMID:24466474

  16. Investigative Studies of Refractive Indices of Liquids and a Demonstration of Refraction by the Use of a Laser Pointer and a Lazy Susan

    ERIC Educational Resources Information Center

    Wong, Siu Ling; Mak, Se-yuen

    2008-01-01

    We describe the design of a simple homemade apparatus for the measurement of the refractive indices of liquids and demonstration of refraction. A circular transparent plastic tank and a lazy Susan are held concentrically. A laser pointer is mounted on the lazy Susan with its laser beam pointing radially through the centre of the plastic tank.…

  17. Spectral absorption coefficients and imaginary parts of refractive indices of Saharan dust during SAMUM-1

    NASA Astrophysics Data System (ADS)

    Müller, T.; Schladitz, A.; Massling, A.; Kaaden, N.; Kandler, K.; Wiedensohler, A.

    2009-02-01

    ABSTRACT During the SAMUM-1 experiment, absorption coefficients and imaginary parts of refractive indices of mineral dust particles were investigated in southern Morocco. Main absorbing constituents of airborne samples were identified to be iron oxide and soot. Spectral absorption coefficients were measured using a spectral optical absorption photometer (SOAP) in the wavelength range from 300 to 800 nm with a resolution of 50 nm. A new method that accounts for a loading-dependent correction of fibre filter based absorption photometers, was developed. The imaginary part of the refractive index was determined using Mie calculations from 350 to 800 nm. The spectral absorption coefficient allowed a separation between dust and soot absorption. A correlation analysis showed that the dust absorption coefficient is correlated (R2 up to 0.55) with the particle number concentration for particle diameters larger than 0.5 μm, whereas the coefficient of determination R2 for smaller particles is below 0.1. Refractive indices were derived for both the total aerosol and a dust aerosol that was corrected for soot absorption. Average imaginary parts of refractive indices of the entire aerosol are 7.4 × 10-3, 3.4 × 10-3 and 2.0 × 10-3 at wavelengths of 450, 550 and 650 nm. After a correction for the soot absorption, imaginary parts of refractive indices are 5.1 × 10-3, 1.6 × 10-3 and 4.5 × 10-4.

  18. Determination of the Dispersion of the Principal Refractive Indices for Birefringent Polypropylene Films

    NASA Astrophysics Data System (ADS)

    Bezruchenko, V. S.; Murauski, An. A.; Muravsky, Al. A.

    2014-07-01

    We present a novel method for determining the dispersion of the refractive indices of birefringent films, based on treatment of transmission spectra, in which we observe interference of light. The dispersion curves n x (λ) and n y (λ) were determined by treatment of transmission spectra obtained for normal incidence of radiation on a P2-25 birefringent fi lm, and n z (λ) was determined for oblique incidence of radiation. From the results of determination of the dispersions of the principal refractive indices of a birefringent P2-25 polypropylene film (Mogilevkhimvolokno OAO, Belarus), we established that the sample is a negative biaxial retarder with N z = 2.9.

  19. Measurement of Single Cell Refractive Index, Dry Mass, Volume, and Density Using a Transillumination Microscope

    NASA Astrophysics Data System (ADS)

    Phillips, Kevin G.; Jacques, Steven L.; McCarty, Owen J. T.

    2012-09-01

    Phase contrast microscopy has become ubiquitous in the field of biology, particularly in qualitative investigations of cellular morphology. However, the use of quantitative phase retrieval methods and their connection to cellular refractive index and dry mass density remain under utilized. This is due in part to the restriction of phase and cellular mass determination to custom built instruments, involved mathematical analysis, and prohibitive sample perturbations. We introduce tomographic bright field imaging, an accessible optical imaging technique enabling the three dimensional measurement of cellular refractive index and dry mass density using a standard transillumination optical microscope. The validity of the technique is demonstrated on polystyrene spheres. The technique is then applied to the measurement of the refractive index, dry mass, volume, and density of red blood cells. This optical technique enables a simple and robust means to perform quantitative investigations of engineered and biological specimens in three dimensions using standard optical microscopes.

  20. Refractive indices in the whole transmission range of partially deuterated KDP crystals

    SciTech Connect

    Zhu, Lili; Zhang, Xiang; Xu, Mingxia; Liu, Baoan; Ji, Shaohua; Zhang, Lisong; Liu, Fafu; Wang, Zhengping E-mail: zpwang@sdu.edu.cn; Sun, Xun E-mail: zpwang@sdu.edu.cn; Zhou, Hailiang

    2013-11-15

    Refractive indices of partially deuterated potassium dihydrogen phosphate (DKDP) crystals with 55%, 70% and 80% deuterium contents were measured by auto-collimation method at 293 K between 0.254 to 1.529 μm. Dependence of refractive indices of DKDP on deuterium content show different trend in the infrared region as in uv-visible region. Dependence of n{sup 2} (the square of refractive index) on the mole fraction of deuterium shows a difference between pure KDP and partially deuterated KDP. The Sellmeier equations were obtained by the least square method. The non-critical phase matching angles calculated from the fitted formula were in good agreement with laser experiment results, by which the reliability of these Sellmeier equations was confirmed.

  1. Indication of advanced orthokeratology as an additional treatment after refractive surgeries

    NASA Astrophysics Data System (ADS)

    Mitsui, Iwane; Yamada, Yoshida

    2005-04-01

    Ortho-K was indicated for twenty-three eyes of thirteen patients after refractive surgeries such as RK(1) ,PRK(2), and LASIK(3). The average of their Uncorrective Visual Acuity (UCVA) after surgeries was 20/30 or worse, and mean spherical equivalent (SE) was -2.42D. They were followed at least two years wearing of Advanced Ortho-K lenses during night. The following studies were examined on their auto-refraction, auto-keratometry, uncorrected and corrected visual acuity, intra-ocular pressure, corneal endothelium, corneal thickness, corneal curvature, and corneal shape for more than two years. 95% of the patients improved in UCVA up to 20/20 or better, 86% of them improved up to 20/15 or better, and 76% of them improved up to 20/10. The mean SEs improved to -1.20+/-1.02D during six months, - 1.03+/-0.83D during one year, and -0.73+/-0.64D during two years. Astigmatism also slightly decreased. Ophthalmologic examinations showed no abnormalities including flap formation, intra-ocular pressure, and endothelium. Among the refractive surgeries as well as RK and PRK, LASIK has been most popularly spread all over the world. However, patient's quality of vision is not always satisfied during and/or after refractive surgeries, because of several complications such as instability of flap formation, unexpected keratoectasia, diffuse lamellar keratitis, epithelial ingrowth, irregularity of corneal surface which caused myopia regression. In such cases, additional surgical procedures should not be indicated easily. However, Ortho-K is safe and effective enough to correct refractive errors still remained or re-appeared after refractive surgeries. It enables to restore the corneal irregularity to the ideal shape.

  2. XUV complex refractive indices of aerosols in the atmospheres of Titan and the primitive Earth

    NASA Astrophysics Data System (ADS)

    Gavilan, Lisseth; Neumann, Maciej; Bulkin, Pavel; Popescu, Horia; Steffan, Martin; Esser, Norbert; Carrasco, Nathalie

    2016-10-01

    The complex refractive indices of tholins, simulating aerosols in the atmosphere of Titan and the primitive earth, have been measured over a wide spectral range, including the soft X-ray, vacuum-ultraviolet (VUV), and UV-Visible. The soft X-ray and VUV spectral ranges are in particular relevant to radiative transfer models of solar irradiation of primitive atmospheres (Lammer et al. 2008) and may elucidate the (anti-)greenhouse potential of photochemical aerosols.Thin films were grown using the PAMPRE capacitively coupled plasma setup (Szopa et al. 2006; Carrasco et al. 2009). Gas mixtures consisting of CH4/N2 with 5:95 ratios were used to simulate Titan's atmospheric composition. For the primitive Earth, gas mixtures of N2/CO2/H2 and N2/CO2/CH4 were used as described in Fleury et al. (2014).State-of-the-art laboratory techniques were used to determine the refractive indices of such tholin films. These include VUV ellipsometry (performed in collaboration with the Metrology Light Source in Berlin) and synchrotron X-ray spectroscopy (performed at the SEXTANTS beamline of the SOLEIL synchrotron). While VUV spectroscopy reveals new electronic transitions due to plasmon resonances in tholins, X-ray spectra reveal the C and O absorption edges of these solids. The refractive indices are compared to results from Khare et al. (1984). Implications on the optical properties of these aerosol analogs on the radiative modeling of primitive atmospheres will be discussed.

  3. Airborne Lidar Point Cloud Density Indices

    NASA Astrophysics Data System (ADS)

    Shih, P. T.; Huang, C.-M.

    2006-12-01

    Airborne lidar is useful for collecting a large volume and high density of points with three dimensional coordinates. Among these points are terrain points, as well as those points located aboveground. For DEM production, the density of the terrain points is an important quality index. While the penetration rate of laser points is dependent on the surface type characteristics, there are also different ways to present the point density. Namely, the point density could be measured by subdividing the surveyed area into cells, then computing the ratio of the number of points in each respective cell to its area. In this case, there will be one density value for each cell. The other method is to construct the TIN, and count the number of triangles in the cell, divided by the area of the cell. Aside from counting the number of triangles, the area of the largest, or the 95% ranking, triangle, could be used as an index as well. The TIN could also be replaced by Voronoi diagrams (Thiessen Polygon), and a polygon with even density could be derived from human interpretation. The nature of these indices is discussed later in this research paper. Examples of different land cover types: bare earth, built-up, low vegetation, low density forest, and high density forest; are extracted from point clouds collected in 2005 by ITRI under a contract from the Ministry of the Interior. It is found that all these indices are capable of reflecting the differences of the land cover type. However, further investigation is necessary to determine which the most descriptive one is.

  4. Indices of refraction of AlGaAsSb by an optical waveguide technique

    NASA Astrophysics Data System (ADS)

    Mozume, T.; Simoyama, T.; Ishikawa, H.

    2007-12-01

    Nearly lattice-matched AlxGa1-xAsySb1-y alloys with Al composition x >0.7 were grown by molecular beam epitaxy. The indices of refraction for a series of alloy compositions were measured. The Al composition was determined by x-ray diffraction (XRD) measurements assuming that the AlxGa1-xAs film that was grown prior to the growth of the AlxGa1-xAsySb1-y layer has the same Al composition. The arsenic to antimony ratio was determined by (004) symmetrical and (115) asymmetric reflection XRD rocking curve measurements. The refractive index and thickness were obtained by prism coupler measurements. A symmetric 75° Si prism coupler was employed to excite the waveguide modes with wavelengths of 1319 and 1540 nm. The shift in the measured indices of refraction from that of the calculated values revealed a deviation from the interpolating scheme based on the binary or ternary alloy data.

  5. QSPR study on refractive indices of solvents commonly used in polymer chemistry using flexible molecular descriptors.

    PubMed

    Fioressi, S E; Bacelo, D E; Cui, W P; Saavedra, L M; Duchowicz, P R

    2015-06-01

    A predictive Quantitative Structure-Property Relationship (QSPR) for the refractive indices of 370 solvents commonly used in the processing and analysis of polymers is presented, using as chemical information descriptors the simplified molecular input line entry system (SMILES). The model employs a flexible molecular descriptor and a conformation-independent approach. Various well-known techniques, such as the use of an external test set of compounds, the cross-validation method, and Y-randomization were used to test and validate the established equations. The predicted values were finally compared with published results from the literature. The simple model proposed correlates the refractive index values with good accuracy, and it is not dependent on 3D-molecular geometries. PMID:26223885

  6. Binary and Ternary Mixtures of Biopolymers and Water: Viscosity, Refractive Index, and Density

    NASA Astrophysics Data System (ADS)

    Silva, Bárbara Louise L. D.; Costa, Bernardo S.; Garcia-Rojas, Edwin E.

    2016-08-01

    Biopolymers have been the focus of intense research because of their wide applicability. The thermophysical properties of solutions containing biopolymers have fundamental importance for engineering calculations, as well as for thermal load calculations, energy expenditure, and development of new products. In this work, the thermophysical properties of binary and ternary solutions of carboxymethylcellulose and/or high methoxylation pectin and water at different temperatures have been investigated taking into consideration different biopolymer concentrations. The experimental data related to the thermophysical properties were correlated to obtain empirical models that can describe the temperature-concentration combined effect on the density, refractive index, and dynamic viscosity. From data obtained from the experiments, the density, refractive index, and dynamic viscosity increase with increasing biopolymer concentration and decrease with increasing temperature. The polynomial models showed a good fit to the experimental data and high correlation coefficients (R2ge 0.98) for each studied system.

  7. Nanoscale dielectric-graphene-dielectric tunable infrared waveguide with ultrahigh refractive indices.

    PubMed

    Zhu, Bofeng; Ren, Guobin; Zheng, Siwen; Lin, Zhen; Jian, Shuisheng

    2013-07-15

    We propose in this paper a dielectric-graphene-dielectric tunable infrared waveguide based on multilayer metamaterials with ultrahigh refractive indices. The waveguide modes with different orders are systematically analyzed with numerical simulations based on both multilayer structures and effective medium approach. The waveguide shows hyperbolic dispersion properties from mid-infrared to far-infrared wavelength, which means the modes with ultrahigh mode indices could be supported in the waveguide. Furthermore, the optical properties of the waveguide modes could be tuned by the biased voltages on graphene layers. The waveguide may have various promising applications in the quantum cascade lasers and bio-sensing.

  8. Z-scan measurements of the nonlinear refractive indices of novel Yb-doped laser crystal hosts

    NASA Astrophysics Data System (ADS)

    Major, A.; Aitchison, J. S.; Smith, P. W. E.; Druon, F.; Georges, P.; Viana, B.; Aka, G. P.

    2005-02-01

    We report on the z-scan characterization of the nonlinear refractive indices of three borate crystals (GdCOB, YCOB, and BOYS), which are new promising Yb-doped laser hosts. The results indicate the possibility of substantial Kerr-lensing and self-phase modulation effects in femtosecond oscillators and amplifiers. High values of the nonlinear refractive indices suggest possible KLM operation of such lasers.

  9. Quantitative Mass Density Image Reconstructed from the Complex X-Ray Refractive Index

    PubMed Central

    Mukaide, Taihei; Iida, Atsuo; Watanabe, Masatoshi; Takada, Kazuhiro; Noma, Takashi

    2015-01-01

    We demonstrate a new analytical X-ray computed tomography technique for visualizing and quantifying the mass density of materials comprised of low atomic number elements with unknown atomic ratios. The mass density was obtained from the experimentally observed ratio of the imaginary and real parts of the complex X-ray refractive index. An empirical linear relationship between the X-ray mass attenuation coefficient of the materials and X-ray energy was found for X-ray energies between 8 keV and 30 keV. The mass density image of two polymer fibers was quantified using the proposed technique using a scanning-type X-ray microbeam computed tomography system equipped with a wedge absorber. The reconstructed mass density agrees well with the calculated one. PMID:26114770

  10. Computation of Mass Density Images from X-ray Refraction-Angle Images

    SciTech Connect

    Wernick,M.; Yang, Y.; Mondal, I.; Chapman, D.; Hasnah, M.; Parham, C.; Pisano, E.; Zhong, Z.

    2006-01-01

    In this paper, we investigate the possibility of computing quantitatively accurate images of mass density variations in soft tissue. This is a challenging task, because density variations in soft tissue, such as the breast, can be very subtle. Beginning from an image of refraction angle created by either diffraction-enhanced imaging (DEI) or multiple-image radiography (MIR), we estimate the mass-density image using a constrained least squares (CLS) method. The CLS algorithm yields accurate density estimates while effectively suppressing noise. Our method improves on an analytical method proposed by Hasnah et al (2005 Med. Phys. 32 549-52), which can produce significant artifacts when even a modest level of noise is present. We present a quantitative evaluation study to determine the accuracy with which mass density can be determined in the presence of noise. Based on computer simulations, we find that the mass-density estimation error can be as low as a few per cent for typical density variations found in the breast. Example images computed from less-noisy real data are also shown to illustrate the feasibility of the technique. We anticipate that density imaging may have application in assessment of water content of cartilage resulting from osteoarthritis, in evaluation of bone density, and in mammographic interpretation.

  11. Aqueous ammonium thiocyanate solutions as refractive index-matching fluids with low density and viscosity

    NASA Astrophysics Data System (ADS)

    Morrison, Benjamin C.; Borrero-Echeverry, Daniel

    2015-11-01

    Index-matching fluids play an important role in many fluid dynamics experiments, particularly those involving particle tracking, as they can be used to minimize errors due to distortion from the refraction of light across interfaces of the apparatus. Common index-matching fluids, such as sodium iodide solutions or mineral oils, often have densities or viscosities very different from those of water. This can make them undesirable for use as a working fluid when using commercially available tracer particles or at high Reynolds numbers. A solution of ammonium thiocyanate (NH4SCN) can be used for index-matching common materials such as borosilicate glass and acrylic, and has material properties similar to those of water (ν ~ 1 . 6 cSt and ρ ~ 1 . 1 g/cc). We present an empirical model for predicting the refractive index of aqueous NH4SCN solutions as a function of temperature and NH4SCN concentration that allows experimenters to develop refractive index matching solutions for various common materials. This work was supported by the National Science Foundation (CBET-0853691) and by the James Borders Physics Student Fellowship at Reed College.

  12. Structural properties of aqueous metoprolol succinate solutions. Density, viscosity, and refractive index at 311 K

    NASA Astrophysics Data System (ADS)

    Deosarkar, S. D.; Kalyankar, T. M.

    2013-06-01

    Density, viscosity and refractive index of aqueous solutions of metoprolol succinate of different concentrations (0.005-0.05 mol dm-3) were measured at 38°C. Apparent molar volume of resultant solutions were calculated and fitted to the Masson's equation and apparent molar volume at infinite dilution was determined graphically. Viscosity data of solutions has been fitted to the Jone-Dole equation and viscosity A- and B-coefficients were determined graphically. Physicochemical data obtained were discussed in terms of molecular interactions.

  13. Baric changes in refractive indices of K2ZnCl4 crystals

    NASA Astrophysics Data System (ADS)

    Stadnyk, V. Yo.; Romanyuk, M. O.; Andrievsky, B. V.; Kogut, Z. O.

    2010-05-01

    The influence of uniaxial pressure applied along the principal crystallophysical directions on the dispersion and temperature dependences of the refractive indices n i of K2ZnCl4 crystals has been investigated. The n i values are found to be fairly sensitive to uniaxial pressure, whereas an uniaxial stress does not change the behavior of the dispersion and temperature dependences of n i . The baric changes in n i have been studied. The electronic polarizability α i , refractions R, and parameters of UV oscillators (λ0 i , B 1 i ) of mechanically deformed K2ZnCl4 crystals have been calculated. The contributions of UV and IR oscillators to n i (λ) have been estimated for different temperatures, spectral regions, and stresses. A significant baric shift of the points of the paraelectric phase-incommensurate phase-commensurate phase transitions to different temperature ranges, depending on the direction of pressure application, is found; this shift is due to the effect of uniaxial stress on the K2ZnCl4 crystal structure.

  14. Modulation instability in a zigzag array of nonlinear waveguides with alternating positive and negative refractive indices

    SciTech Connect

    Dovgiy, A A

    2014-12-31

    The modulation instability is analytically investigated in a zigzag array of tunnel-coupled optical waveguides with alternating refractive indices and Kerr nonlinearity. Particular solutions to a system of coupled nonlinear equations are found. They describe the propagation of electromagnetic waves that are uniform along the waveguide and their instability is studied. It is shown that the coupling coefficient between the waveguides, which are non-nearest neighbours, has a significant effect on the instability of the waves in question. When the coupling coefficient exceeds a certain threshold, the modulation instability disappears regardless of the radiation power. The influence of the ratio of the wave amplitudes in adjacent waveguides to the instability of the particular solutions is studied. Different variants of the nonlinear response in waveguides are considered. The studies performed present a new unusual type of the modulation instability in nonlinear periodic systems. (metamaterials)

  15. Nonlinear waves in an array of zigzag waveguides with alternating positive and negative refractive indices

    SciTech Connect

    Kazantseva, E V; Maimistov, A I

    2013-09-30

    Interaction of coupled waves propagating in a system of waveguides with alternating positive and negative refractive indices is studied theoretically. The zigzag configuration of the waveguides in the array allows communication not only between the nearest neighbours, but also with the waveguides beyond them. It is shown that the spectrum of linear waves in such a waveguide system has a bandgap. Partial solutions are found to the system of coupled waves corresponding to a stationary electromagnetic field pulse that propagates along the array of tunnel-coupled waveguides as a whole. Investigation of the interaction of nonlinear solitary waves has demonstrated numerically the stability of their relatively weak disturbances and collisions with each other. (nanogradient dielectric coatings and metamaterials)

  16. Surface plasmon resonance biosensor as a tool for the measurement of complex refractive indices.

    PubMed

    Filion-Cote, Sandrine; Tabrizian, Maryam; Kirk, Andrew G

    2015-01-01

    Optical characterisation of liquids through the measurement of their complex refractive index is critical in environmental monitoring, food industry and medicine. While surface plasmon resonance is widely used for measurement of the real part of the refractive index there have been few studies to date on measurement of complex refractive index with this method. We present a systematic study which highlights the challenges associated with this approach. Instrument design and data analysis techniques are presented together with preliminary experimental results. PMID:26737760

  17. Low hazard refractive index and density-matched fluid for quantitative imaging of concentrated suspensions of particles

    NASA Astrophysics Data System (ADS)

    Zhu, W.; Knapp, Y.; Deplano, V.

    2016-05-01

    A novel refractive index and density-matched liquid-solid suspension system taking into account chemical hazard and health concerns was developed and characterized. The solid phase is made of PMMA spheres, the refractive index of which being adapted with a mixture of 2,2'-thiodiethanol and phosphate-buffered saline (PBS), while the density is adapted with a mixture of PBS and glycerol. The proposed chemicals present low hazard characteristics in comparison with former solutions. Data collected from density and refractive index measurements of the solid phase and of the different fluid constituents are used to define a specific ternary mixture adapted to commercial grade micron-size particles. The defined mixture is validated in a micron-sized granular flow experiment. The described method can be applied to other low-density solids.

  18. Determination of polar stratospheric cloud particle refractive indices by use of in situ optical measurements and T-matrix calculations.

    PubMed

    Scarchilli, Claudio; Adriani, Alberto; Cairo, Francesco; Di Donfrancesco, Guido; Buontempo, Carlo; Snels, Marcel; Moriconi, Maria Luisa; Deshler, Terry; Larsen, Niels; Luo, Beiping; Mauersberger, Konrad; Ovarlez, Joelle; Rosen, Jim; Schreiner, Jochen

    2005-06-01

    A new algorithm to infer structural parameters such as refractive index and asphericity of cloud particles has been developed by use of in situ observations taken by a laser backscattersonde and an optical particle counter during balloon stratospheric flights. All three main particles, liquid, ice, and a no-ice solid (NAT, nitric acid trihydrate) of polar stratospheric clouds, were observed during two winter flights performed from Kiruna, Sweden. The technique is based on use of the T-matrix code developed for aspherical particles to calculate the backscattering coefficient and particle depolarizing properties on the basis of size distribution and concentration measurements. The results of the calculations are compared with observations to estimated refractive indices and particle asphericity. The method has also been used in cases when the liquid and solid phases coexist with comparable influence on the optical behavior of the cloud to estimate refractive indices. The main results prove that the index of refraction for NAT particles is in the range of 1.37-1.45 at 532 nm. Such particles would be slightly prolate spheroids. The calculated refractive indices for liquid and ice particles are 1.51-1.55 and 1.31-1.33, respectively. The results for solid particles confirm previous measurements taken in Antarctica during 1992 and obtained by a comparison of lidar and optical particle counter data.

  19. Real refractive indices of infrared-characterized nitric-acid/ice films: Implications for optical measurements of polar stratospheric clouds

    NASA Technical Reports Server (NTRS)

    Middlebrook, Ann M.; Berland, Brian S.; George, Steven M.; Tolbert, Margaret A.; Toon, Owen B.

    1994-01-01

    The infrared spectra of nitric-acid/ice films representative of polar stratospheric clouds (PSCs) were collected with simultaneous optical interference measurements to determine the real refractive indices at lambda = 632 nm. Ice and amphorous nitric-acid/ice films were prepared by condensation of water and nitric acid vapors onto a wedged Al2O3 substrate. The real refractive indices of these films were determined from the optical interference of a reflected helium-neon laser during film growth. The indices of the amphorous films varied smoothly from n = 1.30 for ice to n = 1.49 for nitric acid, similar to observations in previous work. We were unable to obtain the refractive index of crystlline films during adsorption because of optical scattering caused by surface roughness. Therefore crystlline nitric acid hydrate films were prepared by annealing amphorous nitric-acid/ice films. Further heating caused desorption of the crystalline hydrate films. During desorption, the refractive indices for ice, NAM (nitric acid monohydrate), alpha- and beta-NAT (nitric acid trihydrate) films were measured using the optical interference technique. In agreement with earlier data, the real refractive indices for ice and NAM determined in desorption were n = 1.30 +/- 0.01 and n = 1.53 +/- 0.03, respectively. The real refractive indices for alpha- and beta-NAT were found to be n = 1.51 +/- 0.01 and n greater than or equal to 1.46, respectively. Our measurements also suggest that the shape of crystalline nitric acid particles may depend on whether they nucleate from the liquid or by vapor deposition. If confirmed by future studies, this observation may provide a means of distinguishing the nucleation mechanism of crystalline PSCs.

  20. General expressions for the refractive indices of absorbing biaxial media as a function of the angle of incidence.

    PubMed

    Alberdi, C; Diñeiro, J M; Hernández, B; Sáenz, C

    2015-02-01

    In this work we obtain general expressions for the complex refractive indices of refracted waves as a function of the angle of incidence in the case of an electromagnetic wave propagating in a transparent isotropic medium that reaches an interface with a biaxial absorbing medium. The biaxial absorbing medium is only required to have a diagonalizable complex dielectric tensor. Obtained expressions can be applied to any orientation of the principal axes and can be specialized for isotropic, uniaxial or biaxial, or transparent or absorbing media. By using these expressions we have also obtained the surface of indices and the surface of absorption coefficients for an example of a biaxial absorbing medium.

  1. Determination of the anisotropy complex refractive indices of chicken tissues in vitro at 650 nm

    NASA Astrophysics Data System (ADS)

    Sun, P.; Sun, H.

    2010-07-01

    The anisotropy complex refractive index of tissue is an important parameter in understanding the behavior of light, including its transportation in and interaction with tissues. We used the specular reflection method to investigate the anisotropy complex refractive index of chicken tissue with fibrous structures in vitro at a wavelength of 650 nm. The measurement data were highly consistent with the Fesnell equations. The results showed that the real refractive index was higher along the orientation of the fibers than along the cross section, but the imaginary refractive index was nearly identical. Furthermore, the fiber orientation was in the direction of the optic axis of the chicken tissue and the chicken tissue section was similar to a negative uniaxial crystal wafer.

  2. Anisotropic light absorption, refractive indices, and orientational order parameter of unidirectionally aligned columnar liquid crystal films.

    PubMed

    Charlet, Emilie; Grelet, Eric

    2008-10-01

    The anisotropic optical properties of thermotropic columnar liquid crystals absorbing in the visible range are investigated for different discotic compounds unidirectionally oriented in open supported thin films. Two methods to monitor the alignment of columnar mesophases in thin films are reported, making possible to achieve either homeotropic anchoring (columns normal to the substrate) by a specific thermal annealing, or unidirectional planar orientation (columns parallel to the substrate) by using a rubbed Teflon coating. The columnar liquid crystal anchoring is found to depend on the nature of the compound, either parallel or perpendicular to the Teflon orientation. Based on this control of the mesophase alignment, the dichroic ratio and the orientational order parameter of oriented samples are measured, and a high order parameter of 0.9 is found in the case of parallel alignment. From the polarized absorption data of the columnar liquid crystal films, the light wavelength dependence of the birefringence and of the real and imaginary parts (refractive index and extinction coefficient, respectively) of the anisotropic optical indices are determined over the whole visible range. PMID:18999445

  3. Accurate Measurements of Refractive Indices for Dielectrics in an Undergraduate Optics Laboratory for Science and Engineering Students

    ERIC Educational Resources Information Center

    Hsu, Wei-Tai; Bahrim, Cristian

    2009-01-01

    Based on our novel method recently published in the "Am. J. Phys." 77 337-43 (2009) for finding precise values of the indices of refraction for dielectrics from measurements of the polarized light reflected by the surface, in this paper we propose an improved technique for finding Brewster angles with a better precision, of 0.001 degrees, using…

  4. A novel inverse method for determining the refractive indices of medium and dispersed particles simultaneously by turbidity measurement.

    PubMed

    Xu, Shenghua; Liu, Jie; Sun, Zhiwei; Zhang, Pu

    2008-10-01

    The refractive indices of particles and dispersion medium are important parameters in many colloidal experiments using optical techniques, such as turbidity and light scattering measurements. These data are in general wavelength-dependent and may not be available at some wavelengths fitting to the experimental requirement. In this study we present a novel approach to inversely determine the refractive indices of particles and dispersion medium by examining the consistency of measured extinction cross sections of particles with their theoretical values using a series of trial values of the refractive indices. The colloidal suspension of polystyrene particles dispersed in water was used as an example to demonstrate how this approach works and the data obtained via such a method are compared with those reported in literature, showing a good agreement between both. Furthermore, the factors that affect the accuracy of measurements are discussed. We also present some data of the refractive indices of polystyrene over a range of wavelengths smaller than 400 nm that have been not reported in the available literature.

  5. Hamiltonian indices and rational spectral densities

    NASA Technical Reports Server (NTRS)

    Byrnes, C. I.; Duncan, T. E.

    1980-01-01

    Several (global) topological properties of various spaces of linear systems, particularly symmetric, lossless, and Hamiltonian systems, and multivariable spectral densities of fixed McMillan degree are announced. The study is motivated by a result asserting that on a connected but not simply connected manifold, it is not possible to find a vector field having a sink as its only critical point. In the scalar case, this is illustrated by showing that only on the space of McMillan degree = /Cauchy index/ = n, scalar transfer functions can one define a globally convergent vector field. This result holds both in discrete-time and for the nonautonomous case. With these motivations in mind, theorems of Bochner and Fogarty are used in showing that spaces of transfer functions defined by symmetry conditions are, in fact, smooth algebraic manifolds.

  6. The Effects of Experimental Conditions on the Refractive Index and Density of Low-temperature Ices: Solid Carbon Dioxide

    NASA Astrophysics Data System (ADS)

    Loeffler, M. J.; Moore, M. H.; Gerakines, P. A.

    2016-08-01

    We present the first study on the effects of the deposition technique on the measurements of the visible refractive index and the density of a low-temperature ice using solid carbon dioxide (CO2) at 14-70 K as an example. While our measurements generally agree with previous studies that show a dependence of index and density on temperature below 50 K, we also find that the measured values depend on the method used to create each sample. Below 50 K, we find that the refractive index varied by as much as 4% and the density by as much as 16% at a single temperature depending on the deposition method. We also show that the Lorentz-Lorenz approximation is valid for solid CO2 across the full 14-70 K temperature range, regardless of the deposition method used. Since the refractive index and density are important in calculations of optical constants and infrared (IR) band strengths of materials, our results suggest that the deposition method must be considered in cases where n vis and ρ are not measured in the same experimental setup where the IR spectral measurements are made.

  7. The Effects of Experimental Conditions on the Refractive Index and Density of Low-temperature Ices: Solid Carbon Dioxide

    NASA Astrophysics Data System (ADS)

    Loeffler, M. J.; Moore, M. H.; Gerakines, P. A.

    2016-08-01

    We present the first study on the effects of the deposition technique on the measurements of the visible refractive index and the density of a low-temperature ice using solid carbon dioxide (CO2) at 14–70 K as an example. While our measurements generally agree with previous studies that show a dependence of index and density on temperature below 50 K, we also find that the measured values depend on the method used to create each sample. Below 50 K, we find that the refractive index varied by as much as 4% and the density by as much as 16% at a single temperature depending on the deposition method. We also show that the Lorentz–Lorenz approximation is valid for solid CO2 across the full 14–70 K temperature range, regardless of the deposition method used. Since the refractive index and density are important in calculations of optical constants and infrared (IR) band strengths of materials, our results suggest that the deposition method must be considered in cases where n vis and ρ are not measured in the same experimental setup where the IR spectral measurements are made.

  8. Moiré deflectometry using the Talbot-Lau interferometer as refraction diagnostic for High Energy Density plasmas at energies below 10 keV

    SciTech Connect

    Valdivia, M. P.; Stutman, D.; Finkenthal, M.

    2014-07-15

    The highly localized density gradients expected in High Energy Density (HED) plasma experiments can be characterized by x-ray phase-contrast imaging in addition to conventional attenuation radiography. Moiré deflectometry using the Talbot-Lau grating interferometer setup is an attractive HED diagnostic due to its high sensitivity to refraction induced phase shifts. We report on the adaptation of such a system for operation in the sub-10 keV range by using a combination of free standing and ultrathin Talbot gratings. This new x-ray energy explored matches well the current x-ray backlighters used for HED experiments, while also enhancing phase effects at lower electron densities. We studied the performance of the high magnification, low energy Talbot-Lau interferometer, for single image phase retrieval using Moiré fringe deflectometry. Our laboratory and simulation studies indicate that such a device is able to retrieve object electron densities from phase shift measurements. Using laboratory x-ray sources from 7 to 15 μm size we obtained accurate simultaneous measurements of refraction and attenuation for both sharp and mild electron density gradients.

  9. Simultaneous Retrieval of Effective Refractive Index and Density from Size Distribution and Light Scattering Data: Weakly-Absorbing Aerosol

    SciTech Connect

    Kassianov, Evgueni I.; Barnard, James C.; Pekour, Mikhail S.; Berg, Larry K.; Shilling, John E.; Flynn, Connor J.; Mei, Fan; Jefferson, Anne

    2014-10-01

    We propose here a novel approach for retrieving in parallel the effective density and real refractive index of weakly absorbing aerosol from optical and size distribution measurements. Here we define “weakly absorbing” as aerosol single-scattering albedos that exceed 0.95 at 0.5 um.The required optical measurements are the scattering coefficient and the hemispheric backscatter fraction, obtained in this work from an integrating nephelometer. The required size spectra come from a Scanning Mobility Particle Sizer and an Aerodynamic Particle Sizer. The performance of this approach is first evaluated using a sensitivity study with synthetically generated but measurement-related inputs. The sensitivity study reveals that the proposed approach is robust to random noise; additionally the uncertainties of the retrieval are almost linearly proportional to the measurement errors, and these uncertainties are smaller for the real refractive index than for the effective density. Next, actual measurements are used to evaluate our approach. These measurements include the optical, microphysical, and chemical properties of weakly absorbing aerosol which are representative of a variety of coastal summertime conditions observed during the Two-Column Aerosol Project (TCAP; http://campaign.arm.gov/tcap/). The evaluation includes calculating the root mean square error (RMSE) between the aerosol characteristics retrieved by our approach, and the same quantities calculated using the conventional volume mixing rule for chemical constituents. For dry conditions (defined in this work as relative humidity less than 55%) and sub-micron particles, a very good (RMSE~3%) and reasonable (RMSE~28%) agreement is obtained for the retrieved real refractive index (1.49±0.02) and effective density (1.68±0.21), respectively. Our approach permits discrimination between the retrieved aerosol characteristics of sub-micron and sub-10micron particles. The evaluation results also reveal that the

  10. Simultaneous retrieval of effective refractive index and density from size distribution and light scattering data: weakly absorbing aerosol

    NASA Astrophysics Data System (ADS)

    Kassianov, E.; Barnard, J.; Pekour, M.; Berg, L. K.; Shilling, J.; Flynn, C.; Mei, F.; Jefferson, A.

    2014-05-01

    We propose here a novel approach for retrieving in parallel the effective density and real refractive index of weakly absorbing aerosol from optical and size distribution measurements. Here we define "weakly absorbing" as aerosol single-scattering albedos that exceed 0.95 at 0.5 μm. The required optical measurements are the scattering coefficient and the hemispheric backscatter fraction, obtained in this work from an integrating nephelometer. The required size spectra come from a Scanning Mobility Particle Sizer and an Aerodynamic Particle Sizer. The performance of this approach is first evaluated using a sensitivity study with synthetically generated but measurement-related inputs. The sensitivity study reveals that the proposed approach is robust to random noise; additionally the uncertainties of the retrieval are almost linearly proportional to the measurement errors, and these uncertainties are smaller for the real refractive index than for the effective density. Next, actual measurements are used to evaluate our approach. These measurements include the optical, microphysical, and chemical properties of weakly absorbing aerosol which are representative of a variety of coastal summertime conditions observed during the Two-Column Aerosol Project (TCAP; http://campaign.arm.gov/tcap/). The evaluation includes calculating the root mean square error (RMSE) between the aerosol characteristics retrieved by our approach, and the same quantities calculated using the conventional volume mixing rule for chemical constituents. For dry conditions (defined in this work as relative humidity less than 55%) and sub-micron particles, a very good (RMSE ~ 3%) and reasonable (RMSE ~ 28%) agreement is obtained for the retrieved real refractive index (1.49 ± 0.02) and effective density (1.68 ± 0.21), respectively. Our approach permits discrimination between the retrieved aerosol characteristics of sub-micron and sub-10

  11. [Retrieval of dust fraction of atmospheric aerosols based on spectra characteristics of refractive indices obtained from remote sensing measurements].

    PubMed

    Wang, Ling; Li, Zheng-Qiang; Li, Dong-Hui; Li, Kai-Tao; Tian, Qing-Jiu; Li, Li; Zhang, Ying; Lü, Yang; Gu, Xing-Fa

    2012-06-01

    Mineral dust is an important chemical component of aerosol, which has a significant impact on the climate and environmental changes. The spectral behavior of aerosol refractive indices at four wavelengths from 440 to 1 020 nm was analyzed based on one year observation obtained from Beijing AERONET site. The real parts of refractive index (n) in each band did not differ greatly, however the imaginary parts (k) showed a significant difference due to the absorption of mineral dust in aerosol. From 440 to 670 nm k decreased rapidly, while from 670 to 1 020 nm featured a lower, constant value. Accordingly, k(440 nm) could be considered separately with other three bands. Hence, we added mineral dust into the currently used three-component aerosol chemical model to form a new four-component model (i. e. BC, AS, dust and water) which is more suitable to represent the aerosol chemical composition. Then we presented a method to retrieve dust content in aerosols using this four-component model and refractive indices obtained from the sunphotometer measurements. Finally the dust content in aerosol was investigated under different weather conditions, i. e. clear, haze and dust in Beijing. The results showed that volume fractions of the dust component were 88%, 37% and 48% for clear, hazy and dusty day respectively, which was consistent with the coarse mode proportion in aerosols calculated from aerosol size distributions.

  12. Antimony orthophosphate glasses with large nonlinear refractive indices, low two-photon absorption coefficients, and ultrafast response

    SciTech Connect

    Falcao-Filho, E.L.; Araujo, Cid B. de; Bosco, C.A.C.; Maciel, G.S.; Acioli, L.H.; Nalin, M.; Messaddeq, Y.

    2005-01-01

    Antimony glasses based on the composition Sb{sub 2}O{sub 3}-SbPO{sub 4} were prepared and characterized. The samples present high refractive index, good transmission from 380 to 2000 nm, and high thermal stability. The nonlinear refractive index, n{sub 2}, of the samples was studied using the optical Kerr shutter technique at 800 nm. The third-order correlation signals between pump and probe pulses indicate ultrafast response (<100 fs) for all compositions. Enhancement of n{sub 2} was observed by adding lead oxide to the Sb{sub 2}O{sub 3}-SbPO{sub 4} composition. Large values of n{sub 2}{approx_equal}10{sup -14} cm{sup 2}/W and negligible two-photon absorption coefficients (smaller than 0.01 cm/GW) were determined for all samples. The glass compositions studied present appropriate figure-of-merit for all-optical switching applications.

  13. Temperature dependence of nu3 and nu4 bandwidths and complex refractive indices for crystalline methane

    NASA Astrophysics Data System (ADS)

    Ngoh, M. A.; Khanna, R. K.; Fox, K.

    1993-03-01

    Infrared spectra of thin films of pure CH4 have been measured for a range of temperatures from 22 to 68 K. The bandwidth for the fundamental nu3 near 3000/cm varies from 12.7 to 33.2/cm, while that for nu4 near 1300/cm varies from 6.2 to 16.0/cm. The real and imaginary parts of the index of refraction also exhibit significant dependence on temperature. These broadband measurements at low temperatures are useful for an understanding of clouds and hazes in the atmosphere of Uranus, clouds and ices in the atmosphere of Titan, and ices on the surfaces of Pluto and Triton.

  14. Dependence on pressure of the refractive indices of wurtzite ZnO, GaN, and AlN

    SciTech Connect

    Goni, AR; Kaess, F; Reparaz, JS; Alonso, MI; Garriga, M; Callsen, G; Wagner, MR; Hoffmann, A; Sitar, Z

    2014-07-25

    We have measured both the ordinary and extraordinary refractive index of m-plane cuts of wurtzite ZnO, GaN, and AlN single crystals at room temperature and as a function of hydrostatic pressure up to 8 GPa. For that purpose we have developed an alternative optical interference method, called bisected-beam method, which leads, in general, to high contrast interference fringes. Its main feature, however, is to be particularly suitable for high pressure experiments with the diamond anvil cell, when the refractive index of the sample is low and similar to that of diamond and/or the pressure transmitting medium, as is the case here. For all three wide-gap materials we observe a monotonous decrease of the ordinary and extraordinary refractive indices with increasing pressure, being most pronounced for GaN, less marked for ZnO, and the smallest for AlN. The frequency dependence of the refractive indices was extrapolated to zero energy using a critical-point-plus-Lorentz-oscillator model of the ordinary and extraordinary dielectric function. In this way, we determined the variation with pressure of the electronic part (no-phonon contribution) of the static dielectric constant epsilon(infinity). Its volume derivative, r = d ln epsilon(infinity)/d ln V, serves as single scaling coefficient for comparison with experimental and/or theoretical results for other semiconductors, regarding the pressure effects on the dielectric properties. We have obtained an ordinary/extraordinary average value (r) over bar of 0.49(15) for ZnO, 1.22(9) for GaN, and 0.32(4) for AlN. With the values for the ordinary and extraordinary case being within experimental uncertainty, there is thus no apparent change in dielectric anisotropy under pressure for these wurtzite semiconductors. Results are discussed in terms of the pressure-dependent electronic band structure of the materials.

  15. Electromagnetic diffraction of light focused through a planar interface between materials of mismatched refractive indices: structure of the electromagnetic field. I

    NASA Astrophysics Data System (ADS)

    Török, P.; Varga, P.; Booker, G. R.

    1995-10-01

    We consider the diffraction occurring when light is focused by a lens without spherical aberration through a planar interface between materials of mismatched refractive indices, which focusing produces spherical aberration. By means of a rigorous vectorial electromagnetic treatment that was previously developed for this problem [Torok et al., J. Opt. Soc. Am. A 12, 325 (1995)], the diffraction integrals are transformed into a form that is computable. Time-averaged electric energy density distributions in the region of the focused probe are numerically evaluated for air-glass and air-silicon interfaces as a function of lens numerical aperture and probe depth corresponding to a wide range of spherical aberration. Two-dimensional lateral ( x - y ) and meridional ( x - z ) electric energy density plots show how the energy, the size, and the position of the various axial and lateral maxima changed, providing new information concerning the

  16. Direct optical measurements of far- and deep-ultraviolet surface plasmon resonance with different refractive indices.

    PubMed

    Tanabe, Ichiro; Tanaka, Yoshito Y; Ryoki, Takayuki; Watari, Koji; Goto, Takeyoshi; Kikawada, Masakazu; Inami, Wataru; Kawata, Yoshimawa; Ozaki, Yukihiro

    2016-09-19

    The surface plasmon resonance (SPR) of Al thin films was investigated by varying the refractive index of the environment near the films in the far-ultraviolet (FUV, 120-200 nm) and deep-ultraviolet (DUV, 200-300 nm) regions. An original FUV-DUV spectrometer that adopts an attenuated total reflectance (ATR) system was used. The measurable wavelength range was down to the 180 nm, and the environment near the Al surface could be controlled. The resultant spectra enabled the dispersion relationship of Al-SPR in the FUV and DUV regions to be obtained. In the presence of 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) on the Al film, the angle and wavelength of the SPR became larger and longer, respectively, compared to those in air. These shifts correspond well with the results of simulations performed using Fresnel equations.

  17. Direct optical measurements of far- and deep-ultraviolet surface plasmon resonance with different refractive indices.

    PubMed

    Tanabe, Ichiro; Tanaka, Yoshito Y; Ryoki, Takayuki; Watari, Koji; Goto, Takeyoshi; Kikawada, Masakazu; Inami, Wataru; Kawata, Yoshimawa; Ozaki, Yukihiro

    2016-09-19

    The surface plasmon resonance (SPR) of Al thin films was investigated by varying the refractive index of the environment near the films in the far-ultraviolet (FUV, 120-200 nm) and deep-ultraviolet (DUV, 200-300 nm) regions. An original FUV-DUV spectrometer that adopts an attenuated total reflectance (ATR) system was used. The measurable wavelength range was down to the 180 nm, and the environment near the Al surface could be controlled. The resultant spectra enabled the dispersion relationship of Al-SPR in the FUV and DUV regions to be obtained. In the presence of 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) on the Al film, the angle and wavelength of the SPR became larger and longer, respectively, compared to those in air. These shifts correspond well with the results of simulations performed using Fresnel equations. PMID:27661924

  18. Measurements of refractive indices and thermo-optical coefficients using a white-light Michelson interferometer.

    PubMed

    Rocha, A C P; Silva, J R; Lima, S M; Nunes, L A O; Andrade, L H C

    2016-08-20

    A dispersive white-light Michelson interferometer was used to determine the wavelength dependence of the refractive index (n) in the visible range from 425 to 775 nm and the thermo-optical coefficient (dn/dT) of fused silica (FS) and borosilicate glass (BK7). For FS, the values obtained for n and dn/dT at 546 nm were 1.46079 and 11.3×10-6  K-1, respectively, while the values for BK7 glass were 1.51825 and 2.2×10-6  K-1, respectively, which is in good agreement with the literature. The accuracy of the methodology used for n was almost 10-6, enabling precise spectroscopic characterization of materials across a wide spectral range. PMID:27556983

  19. Infrared band extinctions and complex refractive indices of crystalline C2H2 and C4H2

    NASA Technical Reports Server (NTRS)

    Khanna, R. K.; Ospina, Mario J.; Zhao, Guizhi

    1988-01-01

    Thermal IR absorption intensities are obtained for thin films of crystalline C2H2 and C4H2 at 70 K, and their n and k complex refractive indices are ascertained by separating true film absorption from interface reflection on the basis of an analysis of the transmission spectrum ratio for two sample thicknesses. This method significantly simplifies the n and k iteration process. The n and k values determined in the laboratory will in most cases reproduce a given sample thickness' observed transmission to within + or - 5 percent.

  20. Crystalline sulfur dioxide: Crystal field splittings, absolute band intensities and complex refractive indices derived from infrared spectra

    NASA Technical Reports Server (NTRS)

    Khanna, R. K.; Zhao, Guizhi

    1986-01-01

    The infrared absorption spectra of thin crystalline films of sulfur dioxide at 90 K are reported in the 2700 to 450/cm region. The observed multiplicity of the spectral features in the regions of fundamentals is attributed to factor group splittings of the modes in a biaxial crystal lattice and the naturally present minor S-34, S-36, and O-18 isotopic species. Complex refractive indices determined by an iterative Kramers-Kronig analysis of the extinction data, and absolute band strengths derived from them, are also reported in this region.

  1. Determination of the complex refractive indices of Titan haze analogs using photothermal deflection spectroscopy

    NASA Astrophysics Data System (ADS)

    Vuitton, Véronique; Tran, Buu N.; Persans, Peter D.; Ferris, James P.

    2009-10-01

    The spectrometers of the Cassini mission to the Saturn system have detected haze layers reaching up to 800 km in Titan's atmosphere. Knowledge of the complex refractive index ( k) of the haze is important for modeling the surface and atmosphere of Titan and retrieving some information about the functional groups present in the aerosols. Plasma discharges or ultraviolet radiation are commonly used to drive the formation of solid organics assumed to be good analogs of the Titan aerosols. [Tran, B.N., Ferris, J.P., Chera, J.J., 2003a. The photochemical formation of a Titan haze analog. Structural analysis by X-ray photoelectron and infrared spectroscopy. Icarus 162, 114-124; Tran, B.N., Force, M., Briggs, R., Ferris J.P., Persans, P., Chera, J.J., 2008. Photochemical processes on Titan: Irradiation of mixtures of gases that simulate Titan's atmosphere. Icarus 177, 106-115] reported the index of refraction of analogs synthesized by far ultraviolet irradiation of various gas mixtures. k was determined in the 200-800 nm wavelength range from transmission and reflection spectroscopy. However, this technique is limited by (i) uncertainties in the absorption values because of the small amounts of organics available, (ii) light scattering by the surface roughness and particulates in the sample. These limitations prompted us to perform new measurements using photothermal deflection spectroscopy (PDS), a technique based on the conversion of absorbed light into heat in the material of interest. By combining traditional spectroscopy ( λ < 500 nm) and PDS ( λ > 500 nm), we determined values of k over the 375-1550 nm range. k values as low as 10 -4 above 1000 nm were determined. This is one order of magnitude lower than the measurements generally used as a reference for Titan's aerosols analogs [Khare, B.N., Sagan, C., Arakawa, E.T., Suits, F., Callicott, T.A., Williams, M.W., 1984. Optical-constants of organic Tholins produced in a simulated Titanian atmosphere—from soft

  2. Simultaneous retrieval of effective refractive index and density from size distribution and light-scattering data: weakly absorbing aerosol

    NASA Astrophysics Data System (ADS)

    Kassianov, E.; Barnard, J.; Pekour, M.; Berg, L. K.; Shilling, J.; Flynn, C.; Mei, F.; Jefferson, A.

    2014-10-01

    We propose here a novel approach for retrieving in parallel the effective density and real refractive index of weakly absorbing aerosol from optical and size distribution measurements. Here we define "weakly absorbing" as aerosol single-scattering albedos that exceed 0.95 at 0.5 μm. The required optical measurements are the scattering coefficient and the hemispheric backscatter fraction, obtained in this work from an integrating nephelometer. The required size spectra come from mobility and aerodynamic particle size spectrometers commonly referred to as a scanning mobility particle sizer and an aerodynamic particle sizer. The performance of this approach is first evaluated using a sensitivity study with synthetically generated but measurement-related inputs. The sensitivity study reveals that the proposed approach is robust to random noise; additionally the uncertainties of the retrieval are almost linearly proportional to the measurement errors, and these uncertainties are smaller for the real refractive index than for the effective density. Next, actual measurements are used to evaluate our approach. These measurements include the optical, microphysical, and chemical properties of weakly absorbing aerosol which are representative of a variety of coastal summertime conditions observed during the Two-Column Aerosol Project (TCAP; http://campaign.arm.gov/tcap/). The evaluation includes calculating the root mean square error (RMSE) between the aerosol characteristics retrieved by our approach, and the same quantities calculated using the conventional volume mixing rule for chemical constituents. For dry conditions (defined in this work as relative humidity less than 55%) and sub-micron particles, a very good (RMSE ~ 3%) and reasonable (RMSE ~ 28%) agreement is obtained for the retrieved real refractive index (1.49 ± 0.02) and effective density (1.68 ± 0.21), respectively. Our approach permits discrimination between the

  3. Study of the physical properties of a mesogenic mixture showing induced smectic A(d) phase by refractive index, density and x-ray diffraction measurements.

    PubMed

    Roy, P D; Prasad, A; Das, M K

    2009-02-18

    The binary mixture of 4-n-pentyl phenyl 4-n'-hexyloxy benzoate (ME6O.5) and p-cyanophenyl trans-4-pentyl cyclohexane carboxylate (CPPCC) shows the presence of an induced smectic A(d) phase in a certain concentration range 0.03refractive indices, densities and x-ray diffraction measurements are reported here. In general, the change in birefringence is continuous at the smectic A(d) to nematic phase transition for mixtures with x>0.33, whereas there is a discontinuity in these values for mixtures with x<0.33, consistent with the density and transition entropy measurements done on this system. The orientational order parameter, measured from x-ray diffraction studies, are somewhat smaller than those obtained from refractive index measurement in the induced smectic phase for all the mixtures. In the smectic phase, the OOP values initially increases with molar concentration up to x = 0.24 and then decreases showing a broad minima around x = 0.4. The variation of layer thickness in the induced smectic phase with composition has been explained by assuming the formation of homo- and heterodimers. We conclude that the possible packing of molecules in the induced smectic A(d) phase stabilizes the layers but increases the orientational free volume, consistent with the lower orientational order parameter.

  4. Concentration dependences of density, viscosity, refractive index, and other derived properties of metoclopramide aqueous solutions at 303.15 K

    NASA Astrophysics Data System (ADS)

    Sawale, R. T.; Deosarkar, S. D.; Kalyankar, T. M.

    2015-07-01

    Density ( ρ), viscosity ( η) and refractive index ( n D) of an antiemetic drug metoclopramide (4-amino-5-chloro- N-(2-(diethylamino)ethyl)-2-methoxybenzamide hydrochloride) solutions containing amino acids (glycine, D-alanine, L-cystine and L-histidine) were measured in the concentration range 0.01-0.17 mol/dm3 at 303.15 K. The apparent molar volume (φv) of this drug in aqueous amino acid solutions was calculated from the density data and fitted to the Massons relation, and the partial molar volume φ{v/0} of the drug was determined graphically. The partial molar volumes of transfer (Δtrφ{v/0}) of drug at infinite dilution from pure water to aqueous amino acid solutions were calculated and interpreted in terms of different interactions between the drug and amino acids.

  5. Statistical quality indicators for electron-density maps

    SciTech Connect

    Tickle, Ian J.

    2012-04-01

    A likelihood-based metric for scoring the local agreement of a structure model with the observed electron density is described. The commonly used validation metrics for the local agreement of a structure model with the observed electron density, namely the real-space R (RSR) and the real-space correlation coefficient (RSCC), are reviewed. It is argued that the primary goal of all validation techniques is to verify the accuracy of the model, since precision is an inherent property of the crystal and the data. It is demonstrated that the principal weakness of both of the above metrics is their inability to distinguish the accuracy of the model from its precision. Furthermore, neither of these metrics in their usual implementation indicate the statistical significance of the result. The statistical properties of electron-density maps are reviewed and an improved alternative likelihood-based metric is suggested. This leads naturally to a χ{sup 2} significance test of the difference density using the real-space difference density Z score (RSZD). This is a metric purely of the local model accuracy, as required for effective model validation and structure optimization by practising crystallographers prior to submission of a structure model to the PDB. A new real-space observed density Z score (RSZO) is also proposed; this is a metric purely of the model precision, as a substitute for other precision metrics such as the B factor.

  6. Statistical quality indicators for electron-density maps.

    PubMed

    Tickle, Ian J

    2012-04-01

    The commonly used validation metrics for the local agreement of a structure model with the observed electron density, namely the real-space R (RSR) and the real-space correlation coefficient (RSCC), are reviewed. It is argued that the primary goal of all validation techniques is to verify the accuracy of the model, since precision is an inherent property of the crystal and the data. It is demonstrated that the principal weakness of both of the above metrics is their inability to distinguish the accuracy of the model from its precision. Furthermore, neither of these metrics in their usual implementation indicate the statistical significance of the result. The statistical properties of electron-density maps are reviewed and an improved alternative likelihood-based metric is suggested. This leads naturally to a χ(2) significance test of the difference density using the real-space difference density Z score (RSZD). This is a metric purely of the local model accuracy, as required for effective model validation and structure optimization by practising crystallographers prior to submission of a structure model to the PDB. A new real-space observed density Z score (RSZO) is also proposed; this is a metric purely of the model precision, as a substitute for other precision metrics such as the B factor.

  7. Real refractive indices and formation yields of secondary organic aerosol generated from photooxidation of limonene and α-pinene: the effect of the HC/NO(x) ratio.

    PubMed

    Kim, Hwajin; Barkey, Brian; Paulson, Suzanne E

    2012-06-21

    The refractive index is an important property affecting aerosol optical properties, which in turn help determine the aerosol direct effect and satellite retrieval results. Here, we investigate the real refractive indices (m(r)) of secondary organic aerosols (SOA) generated from the photooxidation of limonene and α-pinene with different HC/NO(x) ratios. Refractive indices were obtained from polar nephelometer data using parallel and perpendicular polarized 532 nm light combined with measured size distributions, and retrievals were performed using a genetic algorithm and Mie-Lorenz scattering theory. The absolute error associated with the m(r) retrieval is ±0.03, and reliable retrievals are possible for mass concentrations above 5-20 μg/m(3) depending on particle size. The limonene SOA data suggest the most important factor controlling the refractive index is the HC/NO(x) ratio; the refractive index is much less sensitive to the aerosol age or mass concentration. The refractive index ranges from about 1.34 to 1.56 for limonene and from 1.36 to 1.52 for α-pinene, and generally decreases as the HC/NO(x) ratio increases. Especially for limonene, the particle diameter is also inversely related to the HC/NO(x) ratio; the final size mode increases from 220 to 330 nm as the HC/NO(x) ratio decreases from 33 to 6. In an effort to explore the ability of models from the literature to explain the observed refractive indices, a recent limonene oxidation mechanism was combined with SOA partitioning and a structure-property relationship for estimating refractive indices of condensing species. The resulting refractive indices fell in a much narrower range (1.475 ± 0.02) of m(r) than observed experimentally. We hypothesize the experimentally observed high m(r) values are due to oligomerization and the low values to water uptake, small soluble molecules such as glyoxal and other factors, each of which is not included in the oxidation mechanism. Aerosol formation yields were

  8. Density and refractive index of the binary mixtures of cyclohexane with dodecane, tridecane, tetradecane, and pentadecane at (298.15, 303.15, and 308.15) K

    SciTech Connect

    Aminabhavi, T.M.; Patil, V.B.; Aralaguppi, M.I.; Ortego, J.D.; Hansen, K.C.

    1996-05-01

    Experimental values of density and refractive index are presented for the binary mixtures of cyclohexane with dodecane, tridecane, tetradecane, and pentadecane over the whole range of mixture compositions at (298.15, 303.15, and 308.15) K. These data are used to calculate the excess molar volume and deviations in molar refractivity. The excess quantities are fitted to the Redlich-Kister equation to estimate the values of the binary interaction parameters and values of the standard errors. The excess molar volume data at 298.15 K have been compared with the available literature findings for the mixtures of cyclohexane with dodecane and tetradecane.

  9. Benchmarking density functional perturbation theory to enable high-throughput screening of materials for dielectric constant and refractive index

    NASA Astrophysics Data System (ADS)

    Petousis, Ioannis; Chen, Wei; Hautier, Geoffroy; Graf, Tanja; Schladt, Thomas D.; Persson, Kristin A.; Prinz, Fritz B.

    2016-03-01

    We demonstrate a high-throughput density functional perturbation theory (DFPT) methodology capable of screening compounds for their dielectric properties. The electronic and ionic dielectric tensors are calculated for 88 compounds, where the eigenvalues of the total dielectric tensors are compared with single crystal and polycrystalline experimental values reported in the literature. We find that GGA/PBE has a smaller mean average deviation from experiments (MARD=16.2 %) when compared to LDA. The prediction accuracy of DFPT is lowest for compounds that exhibit complex structural relaxation effects (e.g., octahedra rotation in perovskites) and/or strong anharmonicity. Despite some discrepancies between DFPT results and reported experimental values, the high-throughput methodology is found to be useful in identifying interesting compounds by ranking. This is demonstrated by the high Spearman correlation factor (ρ =0.92 ). Finally, we demonstrate that DFPT provides a good estimate for the refractive index of a compound without calculating the frequency dependence of the dielectric matrix (MARD=5.7 %).

  10. Real refractive indices and volatility of secondary organic aerosol generated from photooxidation and ozonolysis of limonene, α-pinene and toluene

    NASA Astrophysics Data System (ADS)

    Kim, H.; Paulson, S. E.

    2013-08-01

    Thermodenuding particles can provide insights into aerosol composition and may be a way to create particles in laboratory chambers that better mimic the atmosphere. The relative volatility of secondary organic aerosol (SOA) was investigated by evaporating organics from the particles using a thermodenuder (TD) at temperatures between ∼60 and 100 °C. Volatility was influenced by the parent hydrocarbon, oxidation chemistry and relative humidity (RH). For SOA generated from ozonolysis, limonene had lower volatility than α-pinene, and OH scavengers had no influence on volatility. For photooxidation, α-pinene SOA was slightly more volatile than limonene SOA. Increasing RH also modestly increased volatility, while toluene SOA was unaffected by heating to 98 °C. For both α-pinene and limonene, the concentration of NOx and the HC / NOx ratio had no discernible effect on SOA volatility. Refractive indices for the original and denuded particles were retrieved from polar nephelometer measurements using parallel and perpendicular polarized 532 nm light. Retrievals were performed with a genetic algorithm method using Mie-Lorenz scattering theory and measured particle size distributions. Retrieved refractive indices for the SOA before thermodenuding varied between 1.35 and 1.61 depending on several factors, including parent hydrocarbon, oxidation chemistry, and SOA generation temperature. For high NOx SOA, as particles shrink, their refractive index returns to the value of the corresponding size particles before heating (limonene) or slightly higher (α-pinene). For low NOx however, the resulting refractive index is 0.05 ± 0.02 lower than the corresponding size undenuded particles. Additionally, for α-pinene SOA from ozonolysis with OH radical scavenger, resulting refractive indices were higher by about 0.03 after heating. Consistent with no change in size, refractive indices of toluene SOA were unaffected by heating. Finally, refractive index data available to date

  11. Real refractive indices and volatility of secondary organic aerosol generated from photooxidation and ozonolysis of limonene, α-pinene and toluene

    NASA Astrophysics Data System (ADS)

    Kim, H.; Paulson, S. E.

    2013-01-01

    Thermodenuding particles can provide insights into aerosol composition, and may be a way to create particles in laboratory chambers that better mimic the atmosphere. The volatility of secondary organic aerosol (SOA) was investigated by evaporating organics from the particles using a thermodenuder (TD) at temperatures between ~ 60 and 100 °C. Volatility was influenced by the parent hydrocarbon, oxidation chemistry and relative humidity (RH). For SOA generated from ozonolysis, limonene had lower volatility than α-pinene, and OH scavengers had no influence on volatility. For photooxidation, α-pinene SOA was slightly more volatile than limonene SOA and increasing RH also modestly increased volatility, while toluene SOA was unaffected by heating to 98 °C. For both α-pinene and limonene, the concentration of NOx and the HC/NOx ratio had no discernible effect on SOA volatility. Refractive indices for the original and denuded particles were retrieved from polar nephelometer measurements using parallel and perpendicular polarized 532 nm light. Retrievals were performed with a genetic algorithm method using Mie-Lorenz scattering theory and measured particle size distributions. Retrieved refractive indices for the SOA before thermodenuding varied between 1.35 and 1.61 depending on several factors, including parent hydrocarbon, oxidation chemistry, and SOA generation temperature. For high NOx SOA, as particles shrink, their refractive index returns to the value of the corresponding size particles before heating (limonene) or slightly higher (α-pinene). For low NOx however, the resulting refractive index is 0.05 ± 0.02 lower than the corresponding size undenuded particles. Additionally, for α-pinene SOA from ozonolysis with OH radical scavenger, resulting refractive indices were higher by about 0.03 after heating. Consistent with no change in size, refractive indices of toluene SOA were unaffected by heating. Finally, refractive index data available to date are reviewed

  12. Finite frequency f-sum rule for assessment of number density of gold nanoparticles (AuNPs) and Kramers-Kronig relation for refractive index of colloidal gold.

    PubMed

    Kontturi, Ville; Silfsten, Pertti; Peiponen, Kai-Erik

    2011-07-01

    Absorption spectra from colloids containing different concentrations of spherical gold nanoparticles in water were measured with a spectrophotometer. The absorption spectra were used to calculate the number density of nanoparticles (NPs) with the aid of an unconventional finite spectral band f-sum rule applied for gold colloid. Good correlation between the number density of dispersion electrons, obtained from the f-sum rule, and the number density of nanoparticles was found. The effective absolute refractive index of the gold colloid was obtained with the aid of a singly subtractive Kramers-Kronig relation, and in addition the refractive index change due to the nanoparticles was obtained with the aid of a conventional Kramers-Kronig relation. Such optical properties are valuable in studies of light interaction with nanoparticles.

  13. Complex refractive indices in the near-ultraviolet spectral region of biogenic secondary organic aerosol aged with ammonia

    SciTech Connect

    Flores, J. M.; Washenfelder, Rebecca; Adler, Gabriela; Lee, H-J; Segev, Lior; Laskin, Julia; Laskin, Alexander; Nizkorodov, Sergey; Brown, Steven; Rudich, Yinon

    2014-05-14

    Atmospheric absorption by brown carbon aerosol may play an important role in global radiative forcing. Brown carbon arises from both primary and secondary sources, but the mechanisms and reactions for the latter are highly uncertain. One proposed mechanism is the reaction of ammonia or amino acids with carbonyl products in secondary organic aerosol (SOA). We generated SOA in situ by reacting biogenic alkenes (α-pinene, limonene, and α-humulene) with excess ozone, humidifying the resulting aerosol, and reacting the humidified aerosol with gaseous ammonia. We determined the complex refractive indices (RI) in the 360 – 420 nm range for these aerosols using broadband cavity enhanced spectroscopy (BBCES). The average real part (n) of the measured spectral range of the NH3-aged α-pinene SOA increased from n = 1.50 (±0.01) for the unreacted SOA to n = 1.57 (± 0.01) after a 1.5h exposure to 1.9 ppm NH3; whereas,the imaginary component (k) remained below k < 0.001 (± 0.002). For the limonene and α-humulene SOA the real part did not change significantly, and we observed a small change in the imaginary component of the RI. The imaginary component increased from k = 0.0 to an average k= 0.029 (± 0.021) for α-humulene SOA, and from k < 0.001 (± 0.002) to an average k = 0.032 (±0.019) for limonene SOA after a 1.5 h exposure to 1.3 and 1.9 ppm of NH3, respectively. Collected filter samples of the aged and unreacted α-pinene SOA and limonene SOA were analyzed off-line with nanospray desorption electrospray ionization high resolution mass spectrometry (nano-DESI/HR-MS), and in-situ with a Time-of-Fligh Aerosol Mass Spectrometer, confirming that the SOA reacted and that various nitrogen-containing reaction products formed. If we assume that NH3 aging reactions scale linearly with time and concentration, then a 1.5 h reaction with 1 ppm NH3 in the laboratory is equivalent to 24 h reaction with 63 ppbv NH3, indicating that the observed aerosol absorption will be limited

  14. Atmospheric refraction: a history.

    PubMed

    Lehn, Waldemar H; van der Werf, Siebren

    2005-09-20

    We trace the history of atmospheric refraction from the ancient Greeks up to the time of Kepler. The concept that the atmosphere could refract light entered Western science in the second century B.C. Ptolemy, 300 years later, produced the first clearly defined atmospheric model, containing air of uniform density up to a sharp upper transition to the ether, at which the refraction occurred. Alhazen and Witelo transmitted his knowledge to medieval Europe. The first accurate measurements were made by Tycho Brahe in the 16th century. Finally, Kepler, who was aware of unusually strong refractions, used the Ptolemaic model to explain the first documented and recognized mirage (the Novaya Zemlya effect).

  15. Atmospheric refraction: a history

    NASA Astrophysics Data System (ADS)

    Lehn, Waldemar H.; van der Werf, Siebren

    2005-09-01

    We trace the history of atmospheric refraction from the ancient Greeks up to the time of Kepler. The concept that the atmosphere could refract light entered Western science in the second century B.C. Ptolemy, 300 years later, produced the first clearly defined atmospheric model, containing air of uniform density up to a sharp upper transition to the ether, at which the refraction occurred. Alhazen and Witelo transmitted his knowledge to medieval Europe. The first accurate measurements were made by Tycho Brahe in the 16th century. Finally, Kepler, who was aware of unusually strong refractions, used the Ptolemaic model to explain the first documented and recognized mirage (the Novaya Zemlya effect).

  16. Phase conjugate Twyman-Green interferometer for testing spherical surfaces and lenses and for measuring refractive indices of liquids or solid transparent materials

    NASA Astrophysics Data System (ADS)

    Shukla, R. P.; Dokhanian, Mostafa; Venkateswarlu, Putcha; George, M. C.

    1990-09-01

    The present paper describes an application of a phase conjugate Twyman-Green interferometer using barium titanate as a self-pumping mirror for testing optical components like concave and convex spherical mirrors and lenses. The aberrations introduced by the beam splitter while testing concave or convex spherical mirrors of large aperture are automatically eliminated due to self-focussing property of the phase conjugate mirror. There is no necessity for a good spherical surface as a reference surface unlike in classical Twyman-Green interferometer or Williams interferometer. The phase conjugate Twyman Green interferometer with a divergent illumination can be used as a test plate for checking spherical surfaces. A nondestructive technique for measuring the refractive indices of a Fabry Perot etalon by using a phase conjugate interferometer is also suggested. The interferometer is found to be useful for measuring the refractive indices of liquids and solid transparent materials with an accuracy of the order of + or - 0.0004.

  17. Phase conjugate Twyman-Green interferometer for testing spherical surfaces and lenses and for measuring refractive indices of liquids or solid transparent materials

    NASA Technical Reports Server (NTRS)

    Shukla, R. P.; Dokhanian, Mostafa; Venkateswarlu, Putcha; George, M. C.

    1990-01-01

    The present paper describes an application of a phase conjugate Twyman-Green interferometer using barium titanate as a self-pumping mirror for testing optical components like concave and convex spherical mirrors and lenses. The aberrations introduced by the beam splitter while testing concave or convex spherical mirrors of large aperture are automatically eliminated due to self-focussing property of the phase conjugate mirror. There is no necessity for a good spherical surface as a reference surface unlike in classical Twyman-Green interferometer or Williams interferometer. The phase conjugate Twyman Green interferometer with a divergent illumination can be used as a test plate for checking spherical surfaces. A nondestructive technique for measuring the refractive indices of a Fabry Perot etalon by using a phase conjugate interferometer is also suggested. The interferometer is found to be useful for measuring the refractive indices of liquids and solid transparent materials with an accuracy of the order of + or - 0.0004.

  18. Spectral particle absorption coefficients, single scattering albedos and imaginary parts of refractive indices from ground based in situ measurements at Cape Verde Island during SAMUM-2

    NASA Astrophysics Data System (ADS)

    Müller, T.; Schladitz, A.; Kandler, K.; Wiedensohler, A.

    2011-09-01

    During the SAMUM-2 experiment, spectral absorption coefficients, single scattering albedos and imaginary parts of refractive indices of mineral dust particles were investigated at the Cape Verde Islands. Main absorbing constituents of airborne samples were mineral dust and soot. PM10 spectral absorption coefficients were measured using a Spectral Optical Absorption Photometer (SOAP) covering the wavelength range from 300 to 960 nm with a resolution of 25 nm. From SOAP, also information on the particle scattering coefficients could be retrieved. Spectral single scattering albedos were obtained in the wavelength range from 350 to 960 nm. Imaginary parts of the refractive index were inferred from measured particle number size distributions and absorption coefficients using Mie scattering theory. Imaginary parts for a dust case were 0.012, 0.0047 and 0.0019 at the wavelengths 450, 550 and 950 nm, respectively, and the single scattering albedos were 0.91, 0.96 and 0.98 at the same wavelengths. During a marine case, the imaginary parts of the refractive indices were 0.0045, 0.0040 and 0.0036 and single scattering albedos were 0.93, 0.95 and 0.96 at the wavelengths given above.

  19. Refractive Errors

    MedlinePlus

    ... and lens of your eye helps you focus. Refractive errors are vision problems that happen when the shape ... cornea, or aging of the lens. Four common refractive errors are Myopia, or nearsightedness - clear vision close up ...

  20. Refractive keratoplasty

    SciTech Connect

    Schwab, I.R. )

    1987-01-01

    This book contains 12 chapters. Some of the titles are: Perspectives on refractive surgery; Radial keratotomy; The refractive aspects of corneal transplantation; Wedge resection and relating incisions; Laser surgery of the cornea; and All plastic corneal lenses.

  1. Direct measurements of the optical cross sections and refractive indices of individual volatile and hygroscopic aerosol particles.

    PubMed

    Mason, B J; Cotterell, M I; Preston, T C; Orr-Ewing, A J; Reid, J P

    2015-06-01

    We present measurements of the evolving extinction cross sections of individual aerosol particles (spanning 700-2500 nm in radius) during the evaporation of volatile components or hygroscopic growth using a combination of a single particle trap formed from a Bessel light beam and cavity ring-down spectroscopy. For single component organic aerosol droplets of 1,2,6-hexanetriol, polyethylene glycol 400, and glycerol, the slow evaporation of the organic component (over time scales of 1000 to 10,000 s) leads to a time-varying size and extinction cross section that can be used to estimate the refractive index of the droplet. Measurements on binary aqueous-inorganic aerosol droplets containing one of the inorganic solutes ammonium bisulfate, ammonium sulfate, sodium nitrate, or sodium chloride (over time scales of 1000 to 15,000 s) under conditions of changing relative humidity show that extinction cross-section measurements are consistent with expectations from accepted models for the variation in droplet refractive index with hygroscopic growth. In addition, we use these systems to establish an experimental protocol for future single particle extinction measurements. The advantages of mapping out the evolving light extinction cross-section of an individual particle over extended time frames accompanied by hygroscopic cycling or component evaporation are discussed.

  2. Gradient Refractive Index Lenses.

    ERIC Educational Resources Information Center

    Morton, N.

    1984-01-01

    Describes the nature of gradient refractive index (GRIN) lenses, focusing on refraction in these materials, focal length of a thin Wood lens, and on manufacturing of such lenses. Indicates that GRIN lenses of small cross section are in limited production with applications suggested for optical communication and photocopying fields. (JN)

  3. Absorption intensities and complex refractive indices of crystalline HCN, HC3N, and C4N2 in the infrared region

    NASA Technical Reports Server (NTRS)

    Masterson, C. M.; Khanna, R. K.

    1990-01-01

    IR absorption intensities are presented for thin crystalline films of HCN, HC3N, and C4N2, together with n and k complex refractive indices determined on the basis of an iterative program for the Kramers-Konig integral via a least-squares, point-by-point fitting of the experimental transmission data. It is established that the transmission spectra generated by means of these n and k values can reproduce the experimental transmission observation values to within + or - 2 percent.

  4. Marine seismic refraction data indicate Mesozoic syn-rift volcanism and seafloor-spreading in the northwestern Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Eddy, Drew; van Avendonk, Harm; Christeson, Gail; Norton, Ian; Karner, Garry; Johnson, Chris; Kneller, Erik; Snedden, John

    2013-04-01

    The Gulf of Mexico is a small ocean basin that formed by continental rifting and seafloor-spreading between North America and the Yucatan Block during the Jurassic to early Cretaceous. The lack of good, deeply-penetrating geophysical data in the Gulf of Mexico has precluded prior reconstructions of the timing and location of the transition from rifting to seafloor-spreading, as well as the degree to which magmatism influenced these geological processes. To illuminate the deep structure of this enigmatic region, we acquired four marine seismic refraction profiles in the northern Gulf of Mexico from the shelf to deep water as part of the Fall 2010 Gulf of Mexico Basin Opening (GUMBO) project. Here, we present the data and resulting seismic velocity structures of two GUMBO profiles in the northwestern Gulf of Mexico. GUMBO Line 1 extends ~330 km offshore south Texas from Matagorda Island across Alaminos Canyon to the central Gulf. GUMBO Line 2 extends ~400 km from the shelf offshore western Louisiana across the Sigsbee Escarpment. On both lines, ocean-bottom seismometers at 10-km spacing recorded 150m-spaced airgun shots over offsets up to 80 km. We use travel times from these long-offset reflections and refractions to image seismic velocities in the sediments, crystalline crust, and upper mantle using a tomographic inversion. On average, seismic velocities increase with depth from 2 km/s near the seafloor to 5 km/s near the interpreted base of salt. On both profiles we observe a large amount of lateral heterogeneity in the sediments due to salt tectonics. The deeper seismic velocity structure along GUMBO Line 1 also exhibits substantial lateral heterogeneity (4.5 km/s to 7 km/s) that may be consistent with crystallization of thin, ultraslow-spreading oceanic crust alternating with emplacement of exhumed mantle lithosphere. If the basement here is indeed oceanic, the prominent magnetic anomaly along the Texas coastline may represent the expression of synrift volcanism

  5. Derivation of the density and refractive index of organic matter and elemental carbon from closure between physical and chemical aerosol properties.

    PubMed

    Schmid, Otmar; Chand, Duli; Karg, Erwin; Guyon, Pascal; Frank, Goran P; Swietlicki, Erik; Andreae, Meinrat O

    2009-02-15

    Information on the density (rho) and refractive index m (=n-ik) of elemental carbon (ECa) and organic matter (OMa), the main carbon components of atmospheric aerosols, has frequently been obtained from closure calculations between physical and chemical aerosol properties. However, this approach has suffered from large uncertainties since there were more unknown (or poorly known) parameters than defining equations. In this study, we propose a method that avoids this ambiguity mainly by considering both optical and mass closure and by expressing the three ECa parameters (rho(ECa), n(ECa), k(ECa)) by a single (unknown) parameter. This allows mathematically rigorous determination of rho(Eca), m(ECa), rho(OMa) and m(OMa) from standard physico-chemical aerosol data and rigorous error analysis. The results are unambiguous and self-consistent, i.e., there is no difference between the chemically and physically derived p and m values of the atmospheric aerosol. Application of this method to our previously published data on biomass burning particles from Amazonia yields rho(ECa) = 1.8(+/-0.2) g/cm3, m(ECa) = 1.9(+/-0.1)-i0.20(-0.04/+0.02), rho(OMa) = 1.39(+/-0.13) g/cm3 and m(OMa) = 1.46(+/-0.02), where the launcertainty limits given in parenthesis are based on the principles of error propagation. The relatively low imaginary part of m(ECa) indicates the presence of only partially graphitized elemental carbon, which is consistentwith biomass burning aerosol dominated by smoldering combustion conditions.

  6. Atmospheric microwave refractivity and refraction

    NASA Technical Reports Server (NTRS)

    Yu, E.; Hodge, D. B.

    1980-01-01

    The atmospheric refractivity can be expressed as a function of temperature, pressure, water vapor content, and operating frequency. Based on twenty-year meteorological data, statistics of the atmospheric refractivity were obtained. These statistics were used to estimate the variation of dispersion, attenuation, and refraction effects on microwave and millimeter wave signals propagating along atmospheric paths. Bending angle, elevation angle error, and range error were also developed for an exponentially tapered, spherical atmosphere.

  7. Implantable collamer lens for residual refractive error after corneal refractive surgery

    PubMed Central

    Chen, Xun; Wang, Xiao-Ying; Zhang, Xi; Chen, Zhi; Zhou, Xing-Tao

    2016-01-01

    AIM To assess the safety, efficacy, predictability and stability of implantable collamer lens (ICL) for residual refractive error after corneal refractive surgery. METHODS This study evaluated 19 eyes of 12 patients who underwent ICL implantation after corneal refractive surgeries. They were followed up for 1y to 5y of uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refractive error, flat and steep K value, axial length, intraocular pressure, corneal endothelial cell density, adverse events after ICL surgery. RESULTS The mean follow-up period was 39.05±19.22 mo (range, 1-5y). Spherical equivalent refractive error changed from -7.45±3.02 D preoperatively to -0.85±1.10 D 1wk to 1mo after ICL implantation, with the safety and efficacy indices being 1.12 and 1.15, respectively. A total of 52.63% of eyes were within ±0.5 D of the predicted spherical equivalents, 73.68% were within ±1.0 D. A trend of mild regression towards myopia with axial elongation after 5y was observed. One eye with mild anterior capsule opacity and retinal detachment 1y after surgery were observed. CONCLUSION ICL implantation is safe and effective for the correction of residual refractive error after corneal refractive surgeries, especially in moderate to high residual myopia. PMID:27803858

  8. Simultaneous retrieval of the complex refractive indices of the core and shell of coated aerosol particles from extinction measurements using simulated annealing.

    PubMed

    Erlick, Carynelisa; Haspel, Mitch; Rudich, Yinon

    2011-08-01

    Simultaneously retrieving the complex refractive indices of the core and shell of coated aerosol particles given the measured extinction efficiency as a function of particle dimensions (core diameter and coated diameter) is much more difficult than retrieving the complex refractive index of homogeneous aerosol particles. Not only must the minimization be performed over a four-parameter space, making it less efficient, but in addition the absolute value of the difference between the measured extinction and the calculated extinction does not have an easily distinguished global minimum. Rather, there are a number of local minima to which almost all conventional retrieval algorithms converge. In this work, we develop a new (to our knowledge) retrieval algorithm that employs the numerical method known as simulated annealing with an innovative "temperature" schedule. This study is limited only to spherical particles with a concentric shell and to cases in which the diameter of both the core and the coated particle are known. We find that when the top ranking particle sizes according to their information content are combined from separate experiments to make up the particle size distribution, the simulated annealing retrieval algorithm is quite robust and by far superior to a greedy random perturbation approach often used.

  9. Comparison of refractive indices measured by m-lines and ellipsometry: application to polymer blend and ceramic thin films for gas sensors

    NASA Astrophysics Data System (ADS)

    Wood, Thomas; Le Rouzo, Judikaël.; Flory, François; Coudray, Paul; Mastelaro, Valmor R.; Pelissari, Pedro; Zilio, Sérgio

    2012-10-01

    Two optical techniques, "m-lines" and spectroscopic ellipsometry, are compared for their suitability for obtaining the wavelength and temperature dispersion of the refractive index of thin film layers used in gas detector devices. Two types of materials often integrated into gas sensors are studied: a polymer organic-inorganic blend deposited by spin-coating typically used in near infra-red waveguides and the ceramic semiconductor SrTi1-xFexO3 (strontium titanate) doped with iron at concentrations x = 0.075 and 0.1 deposited by electron beam deposition. In this paper, we will compare the refractive index dispersion obtained by m-lines and ellipsometry, and comment on the differences between the measured parameters for the two materials. The chromatic dispersion will be represented by a three term Cauchy law. An intuitive method of verifying the measured indices using an integrating sphere and reflexion coefficient modelling techniques will also be demonstrated. Thermo-optic coefficients of the order of -1×10-4/K for both materials are reported, and very low chromatic dispersions are also measured thanks to the high sensitivity of the m-lines technique.

  10. Atmospheric refraction: a history.

    PubMed

    Lehn, Waldemar H; van der Werf, Siebren

    2005-09-20

    We trace the history of atmospheric refraction from the ancient Greeks up to the time of Kepler. The concept that the atmosphere could refract light entered Western science in the second century B.C. Ptolemy, 300 years later, produced the first clearly defined atmospheric model, containing air of uniform density up to a sharp upper transition to the ether, at which the refraction occurred. Alhazen and Witelo transmitted his knowledge to medieval Europe. The first accurate measurements were made by Tycho Brahe in the 16th century. Finally, Kepler, who was aware of unusually strong refractions, used the Ptolemaic model to explain the first documented and recognized mirage (the Novaya Zemlya effect). PMID:16201423

  11. Uncorrected refractive errors.

    PubMed

    Naidoo, Kovin S; Jaggernath, Jyoti

    2012-01-01

    Global estimates indicate that more than 2.3 billion people in the world suffer from poor vision due to refractive error; of which 670 million people are considered visually impaired because they do not have access to corrective treatment. Refractive errors, if uncorrected, results in an impaired quality of life for millions of people worldwide, irrespective of their age, sex and ethnicity. Over the past decade, a series of studies using a survey methodology, referred to as Refractive Error Study in Children (RESC), were performed in populations with different ethnic origins and cultural settings. These studies confirmed that the prevalence of uncorrected refractive errors is considerably high for children in low-and-middle-income countries. Furthermore, uncorrected refractive error has been noted to have extensive social and economic impacts, such as limiting educational and employment opportunities of economically active persons, healthy individuals and communities. The key public health challenges presented by uncorrected refractive errors, the leading cause of vision impairment across the world, require urgent attention. To address these issues, it is critical to focus on the development of human resources and sustainable methods of service delivery. This paper discusses three core pillars to addressing the challenges posed by uncorrected refractive errors: Human Resource (HR) Development, Service Development and Social Entrepreneurship. PMID:22944755

  12. Broadband optical extinction measurements and complex refractive indices in the ultraviolet spectral region for biogenic secondary organic aerosol exposed to ammonia

    NASA Astrophysics Data System (ADS)

    Flores, J.; Washenfelder, R. A.; Lee, H.; Segev, L.; Nizkorodov, S.; Brown, S. S.; Rudich, Y.

    2013-12-01

    The interaction between aerosols and sunlight plays an important role in the radiative balance of Earth's atmosphere. Aerosols can both scatter and absorb solar radiation causing surface cooling and heating of the atmosphere. These interactions depend on the optical properties of the aerosols (i.e., complex refractive index). Secondary organic aerosol (SOA) account for a significant fraction of the tropospheric aerosol. However, their chemical, physical, and optical properties, especially as they are processed in the atmosphere (aging), are still poorly understood. In this study, SOA formed by the ozonolysis of various biogenic volatile organic compound (BVOC) precursors (α-pinene, limonene, and α-humulene) were exposed to humid air containing various concentrations of gaseous ammonia which has been shown to cause the biogenic SOA to ';brown' on filters. The extent of absorption of the SOA in the aerosol phase cause by the exposure to gaseous ammonia was measured by a newly developed instrument to measure aerosol extinction as a function of wavelength using Broadband Cavity Enhanced Spectroscopy (BBCES) with a broadband light source. Size-selected measurements of the humid SOA exposed to NH3 for about 1.5 hours were used to derive complex refractive indices (RI) as a function of wavelength in the UV spectral region (from 360 - 420nm). The imaginary part of the refractive index did not exceed 0.05 in the 360 - 420 nm range for SOA formed from the three BVOCs even at high concentrations of NH3 (>1ppm), allowing to place an upper limit of k = 0.05. Furthermore, the small k values are consistent with bulk UV-VIS measurements. However, for the α-pinene SOA, the real part of the RI slightly increased from n = 1.49 to n = 1.55 with negligible spectral dependence. For limonene and α-humulene the real part remind constant within error calculations. Based on these observations, reactive uptake of gaseous ammonia is not expected to significantly affect absorption and

  13. Spectroscopic refractive indices of monoclinic single crystal and ceramic Lutetium oxyorthosilicate (LSO) from 200 to 850 nm

    SciTech Connect

    Jellison Jr, Gerald Earle; Specht, Eliot D; Boatner, Lynn A; Singh, David J; Melcher, Charles L

    2012-01-01

    The four real values of the dielectric function tensor of the monoclinic crystal Lu2SiO5 or lutetium oxyorthosilicate (LSO) have been determined using generalized ellipsometry from 200 to 850 nm. The three principal values are fit to the Sellmeier model, and they indicate that the band gap of LSO is less than ~9 eV. The off-diagonal element 12 is non-zero over the entire spectrum, but it is very close to zero for wavelengths longer than ~400 nm, indicating that structurally monoclinic LSO is nearly optically orthorhombic in this wavelength region. The spectroscopic dielectric functions of three isotropic ceramic LSO samples are presented, which are consistent with the dielectric functions of single-crystal LSO when the effects of porosity are included. As a comparison, the dielectric functions are also determined using relativistic electronic structure and optical calculations based on the recently developed potential functional of Tran and Blaha (Phys. Rev. Lett. 102, 226401 (2009).)

  14. Multiple scattering induced negative refraction of matter waves

    PubMed Central

    Pinsker, Florian

    2016-01-01

    Starting from fundamental multiple scattering theory it is shown that negative refraction indices are feasible for matter waves passing a well-defined ensemble of scatterers. A simple approach to this topic is presented and explicit examples for systems of scatterers in 1D and 3D are stated that imply negative refraction for a generic incoming quantum wave packet. Essential features of the effective scattering field, densities and frequency spectrum of scatterers are considered. Additionally it is shown that negative refraction indices allow perfect transmission of the wave passing the ensemble of scatterers. Finally the concept of the superlens is discussed, since it is based on negative refraction and can be extended to matter waves utilizing the observations presented in this paper which thus paves the way to ‘untouchable’ quantum systems in analogy to cloaking devices for electromagnetic waves. PMID:26857266

  15. Multiple scattering induced negative refraction of matter waves.

    PubMed

    Pinsker, Florian

    2016-02-09

    Starting from fundamental multiple scattering theory it is shown that negative refraction indices are feasible for matter waves passing a well-defined ensemble of scatterers. A simple approach to this topic is presented and explicit examples for systems of scatterers in 1D and 3D are stated that imply negative refraction for a generic incoming quantum wave packet. Essential features of the effective scattering field, densities and frequency spectrum of scatterers are considered. Additionally it is shown that negative refraction indices allow perfect transmission of the wave passing the ensemble of scatterers. Finally the concept of the superlens is discussed, since it is based on negative refraction and can be extended to matter waves utilizing the observations presented in this paper which thus paves the way to 'untouchable' quantum systems in analogy to cloaking devices for electromagnetic waves.

  16. Multiple scattering induced negative refraction of matter waves.

    PubMed

    Pinsker, Florian

    2016-01-01

    Starting from fundamental multiple scattering theory it is shown that negative refraction indices are feasible for matter waves passing a well-defined ensemble of scatterers. A simple approach to this topic is presented and explicit examples for systems of scatterers in 1D and 3D are stated that imply negative refraction for a generic incoming quantum wave packet. Essential features of the effective scattering field, densities and frequency spectrum of scatterers are considered. Additionally it is shown that negative refraction indices allow perfect transmission of the wave passing the ensemble of scatterers. Finally the concept of the superlens is discussed, since it is based on negative refraction and can be extended to matter waves utilizing the observations presented in this paper which thus paves the way to 'untouchable' quantum systems in analogy to cloaking devices for electromagnetic waves. PMID:26857266

  17. Sensitivity of condition indices to changing density in a white-tailed deer population

    USGS Publications Warehouse

    Sams, M.G.; Lochmiller, R.L.; Qualls, C.W.; Leslie, David M.

    1998-01-01

    The ways in which comprehensive condition profiles, incorporating morphometric, histologic, physiologic, and diet quality indices, responded to changes in density of a white-tailed deer (Odocoileus virginianus) population were examined. Changes in these condition indices were monitored in a northeastern Oklahoma deer herd as density declined from peaks of 80 and 72 deer/km2 in 1989 and 1990 (high-density) to lows of 39 and 41 deer/km2 in 1991 and 1992 (reduced-density), respectively. Compared to a reference population (6 deer/km2), deer sampled during high-density exhibited classic signs of nutritional stress such as low body and visceral organ masses (except elevated adrenal gland mass), low fecal nitrogen levels, reduced concentrations of serum albumin, elevated serum creatinine concentrations, and a high prevalence of parasitic infections. Although density declined by one half over the 4-yr study, gross indices of condition (in particular body mass and size) remained largely unchanged. However, selected organ masses, serum albumin and non-protein nitrogen constituents, and fecal nitrogen indices reflected improvements in nutritional status with reductions in density. Many commonly used indices of deer condition (fat reserves, hematocrit, total serum protein, and blood urea nitrogen) were not responsive to fluctuations in density. ?? Wildlife Disease Association 1998.

  18. Cryogenic Refractive Indices of S-LAH55, S-LAH55V, S-LAH59, S-LAM3, S-NBM51, S-NPH2, S-PHM52, and S-TIH14 Glasses

    NASA Technical Reports Server (NTRS)

    Miller, Kevin H.; Quijada, Manuel A.; Leviton, Doug

    2015-01-01

    The Transiting Exoplanet Survey Satellite (TESS) is an explorer-class planet finder, whose principal goal is to detect small planets with bright host starts in the solar neighborhood. The TESS payload consists of four identical cameras with seven optical elements each that include various types of Ohara glass substrates. The successful implementation both panchromatic and thermal lens assembly designs for these cameras requires a fairly accurate (up to 1E-6) knowledge of the temperature and wavelength dependence of the refractive index in the wavelength and temperature range of operation. Hence, this paper is devoted to report on measurements of the refractive index over the wavelength range of 0.42-1.15 um and temperature range of 110-310 K for the following Ohara glasses: S-LAH55, S-LAH55V, SLAH59, S-LAM3, S-NBM51, S-NPH2, S-PHM52, and S-TIH14. The measurements were performed utilizing the Cryogenic High Accuracy Refraction Measuring System (CHARMS) facility at NASA's Goddard Space Flight Center. A dense coverage of the absolute refractive index for the title substrates in the aforementioned wavelength and temperature ranges was used to determine the thermo-optic coefficient (dn/dT) and dispersion relation (dn/d lambda) as a function of wavelength and temperature. A comparison of the measured indices with literature values, specifically the temperature-dependent refractive indices of S-PHM52 and S-TIH14, will be presented.

  19. Applications of the Conceptual Density Functional Theory Indices to Organic Chemistry Reactivity.

    PubMed

    Domingo, Luis R; Ríos-Gutiérrez, Mar; Pérez, Patricia

    2016-01-01

    Theoretical reactivity indices based on the conceptual Density Functional Theory (DFT) have become a powerful tool for the semiquantitative study of organic reactivity. A large number of reactivity indices have been proposed in the literature. Herein, global quantities like the electronic chemical potential μ, the electrophilicity ω and the nucleophilicity N indices, and local condensed indices like the electrophilic P k + and nucleophilic P k - Parr functions, as the most relevant indices for the study of organic reactivity, are discussed. PMID:27294896

  20. Applications of the Conceptual Density Functional Theory Indices to Organic Chemistry Reactivity.

    PubMed

    Domingo, Luis R; Ríos-Gutiérrez, Mar; Pérez, Patricia

    2016-06-09

    Theoretical reactivity indices based on the conceptual Density Functional Theory (DFT) have become a powerful tool for the semiquantitative study of organic reactivity. A large number of reactivity indices have been proposed in the literature. Herein, global quantities like the electronic chemical potential μ, the electrophilicity ω and the nucleophilicity N indices, and local condensed indices like the electrophilic P k + and nucleophilic P k - Parr functions, as the most relevant indices for the study of organic reactivity, are discussed.

  1. Method of producing optical quality glass having a selected refractive index

    DOEpatents

    Poco, John F.; Hrubesh, Lawrence W.

    2000-01-01

    Optical quality glass having a selected refractive index is produced by a two stage drying process. A gel is produced using sol-gel chemistry techniques and first dried by controlled evaporation until the gel volume reaches a pre-selected value. This pre-selected volume determines the density and refractive index of the finally dried gel. The gel is refilled with solvent in a saturated vapor environment, and then dried again by supercritical extraction of the solvent to form a glass. The glass has a refractive index less than the full density of glass, and the range of achievable refractive indices depends on the composition of the glass. Glasses having different refractive indices chosen from an uninterrupted range of values can be produced from a single precursor solution.

  2. Mass-specific optical absorption coefficients and imaginary part of the complex refractive indices of mineral dust components measured by a multi-wavelength photoacoustic spectrometer

    NASA Astrophysics Data System (ADS)

    Utry, N.; Ajtai, T.; Pintér, M.; Tombácz, E.; Illés, E.; Bozóki, Z.; Szabó, G.

    2015-01-01

    Mass-specific optical absorption coefficients (MACs) and the imaginary part (κ) of the refractive indices of various mineral dust components including silicate clays (illite, kaolin and bentonite), oxides (quartz, hematite and rutile), and carbonate (limestone) were determined at the wavelengths of 1064, 532, 355 and 266 nm. The MAC values were calculated from aerosol optical absorption coefficients measured by a multi-wavelength photoacoustic (PA) instrument, the mass concentration and the number size distribution of the generated aerosol samples as well as the size transfer functions of the measuring instruments. Values of κ were calculated from the measured and particle-loss-corrected data by using a Mie-theory-based retrieval algorithm. The determined values could be used for comparisons with calculated wavelength-dependent κ values typically deduced from bulk-phase measurements by using indirect measurement methods. Accordingly, the presented comparison of the measured and calculated aerosol optical absorption spectra revealed the strong need for standardized sample preparation and measurement methodology in case of bulk-phase measurements.

  3. Investigation of influences of the paraformaldehyde fixation and paraffin embedding removal process on refractive indices and scattering properties of epithelial cells

    NASA Astrophysics Data System (ADS)

    Su, Jing-Wei; Hsu, Wei-Chen; Tjiu, Jeng-Wei; Chiang, Chun-Pin; Huang, Chao-Wei; Sung, Kung-Bin

    2014-07-01

    The scattering properties and refractive indices (RI) of tissue are important parameters in tissue optics. These parameters can be determined from quantitative phase images of thin slices of tissue blocks. However, the changes in RI and structure of cells due to fixation and paraffin embedding might result in inaccuracies in the estimation of the scattering properties of tissue. In this study, three-dimensional RI distributions of cells were measured using digital holographic microtomography to obtain total scattering cross sections (TSCS) of the cells based on the first-order Born approximation. We investigated the slight loss of dry mass and drastic shrinkage of cells due to paraformaldehyde fixation and paraffin embedding removal processes. We propose a method to compensate for the correlated changes in volume and RI of cells. The results demonstrate that the TSCS of live cells can be estimated using restored cells. The percentage deviation of the TSCS between restored cells and live cells was only -8%. Spatially resolved RI and scattering coefficients of unprocessed oral epithelium ranged from 1.35 to 1.39 and from 100 to 450 cm-1, respectively, estimated from paraffin-embedded oral epithelial tissue after restoration of RI and volume.

  4. Investigation of influences of the paraformaldehyde fixation and paraffin embedding removal process on refractive indices and scattering properties of epithelial cells.

    PubMed

    Su, Jing-Wei; Hsu, Wei-Chen; Tjiu, Jeng-Wei; Chiang, Chun-Pin; Huang, Chao-Wei; Sung, Kung-Bin

    2014-01-01

    The scattering properties and refractive indices (RI) of tissue are important parameters in tissue optics. These parameters can be determined from quantitative phase images of thin slices of tissue blocks. However, the changes in RI and structure of cells due to fixation and paraffin embedding might result in inaccuracies in the estimation of the scattering properties of tissue. In this study, three-dimensional RI distributions of cells were measured using digital holographic microtomography to obtain total scattering cross sections (TSCS) of the cells based on the first-order Born approximation. We investigated the slight loss of dry mass and drastic shrinkage of cells due to paraformaldehyde fixation and paraffin embedding removal processes. We propose a method to compensate for the correlated changes in volume and RI of cells. The results demonstrate that the TSCS of live cells can be estimated using restored cells. The percentage deviation of the TSCS between restored cells and live cells was only −8%. Spatially resolved RI and scattering coefficients of unprocessed oral epithelium ranged from 1.35 to 1.39 and from 100 to 450 cm−1, respectively, estimated from paraffinembedded oral epithelial tissue after restoration of RI and volume.

  5. Investigation of influences of the paraformaldehyde fixation and paraffin embedding removal process on refractive indices and scattering properties of epithelial cells.

    PubMed

    Su, Jing-Wei; Hsu, Wei-Chen; Tjiu, Jeng-Wei; Chiang, Chun-Pin; Huang, Chao-Wei; Sung, Kung-Bin

    2014-01-01

    The scattering properties and refractive indices (RI) of tissue are important parameters in tissue optics. These parameters can be determined from quantitative phase images of thin slices of tissue blocks. However, the changes in RI and structure of cells due to fixation and paraffin embedding might result in inaccuracies in the estimation of the scattering properties of tissue. In this study, three-dimensional RI distributions of cells were measured using digital holographic microtomography to obtain total scattering cross sections (TSCS) of the cells based on the first-order Born approximation. We investigated the slight loss of dry mass and drastic shrinkage of cells due to paraformaldehyde fixation and paraffin embedding removal processes. We propose a method to compensate for the correlated changes in volume and RI of cells. The results demonstrate that the TSCS of live cells can be estimated using restored cells. The percentage deviation of the TSCS between restored cells and live cells was only −8%. Spatially resolved RI and scattering coefficients of unprocessed oral epithelium ranged from 1.35 to 1.39 and from 100 to 450 cm−1, respectively, estimated from paraffinembedded oral epithelial tissue after restoration of RI and volume. PMID:25069007

  6. Serengeti real estate: density vs. fitness-based indicators of lion habitat quality.

    PubMed

    Mosser, Anna; Fryxell, John M; Eberly, Lynn; Packer, Craig

    2009-10-01

    Habitat quality is typically inferred by assuming a direct relationship between consumer density and resource abundance, although it has been suggested that consumer fitness may be a more accurate measure of habitat quality. We examined density vs. fitness-based measures of habitat quality for lions in the Serengeti National Park, Tanzania. A 40-year average of female reproductive success (yearling cubs per female) was best explained by proximity to river confluences, whereas patterns of productivity (yearling cubs per km(2)) and adult female density (individuals per km(2)) were associated with more general measures of habitat quality and areas of shelter in poor habitat. This suggests that density may not accurately distinguish between high-quality 'source' areas and low-quality sites that merely provide refuges for effectively non-reproductive individuals. Our results indicate that density may be a misleading indicator of real estate value, particularly for populations that do not conform to an ideal free distribution.

  7. Use of burrow entrances to indicate densities of Townsend's ground squirrels

    USGS Publications Warehouse

    Van Horne, Beatrice; Schooley, R.L.; Knick, Steven T.; Olson, G.S.; Burnham, K.P.

    1997-01-01

    Counts of burrow entrances have been positively correlated with densities of semi-fossorial rodents and used as an index of densities. We evaluated their effectiveness in indexing densities of Townsend's ground squirrels (Spermophilus townsendii) in the Snake River Birds of Prey National Conservation Area (SRBOPNCA), Idaho, by comparing burrow entrance densities to densities of ground squirrels estimated from livetrapping in 2 consecutive years over which squirrel populations declined by >75%. We did not detect a consistent relation between burrow entrance counts and ground squirrel density estimates within or among habitat types. Scatter plots indicated that burrow entrances had little predictive power at intermediate densities. Burrow entrance counts did not reflect the magnitude of a between-year density decline. Repeated counts of entrances late in the squirrels' active season varied in a manner that would be difficult to use for calibration of transects sampled only once during this period. Annual persistence of burrow entrances varied between habitats. Trained observers were inconsistent in assigning active-inactive status to entrances. We recommend that burrow entrance counts not be used as measures or indices of ground squirrel densities in shrubsteppe habitats, and that the method be verified thoroughly before being used in other habitats.

  8. The N III and O IV intersystem multiplets as density indicators for solar plasmas

    NASA Technical Reports Server (NTRS)

    Feldman, U.; Doschek, G. A.

    1979-01-01

    The usefulness of the relative intensities of lines within the N III intersystem multiplet near 1750 A as an electron density indicator for solar plasmas is discussed. Although the relative intensities of lines in the multiplet are density sensitive, the intensity ratios should at present be used with caution. Errors of the order of 20% in transition probabilities and excitation rate coefficients can lead to order of magnitude errors in density determinations. It is demonstrated that the intensity ratio of one of the N III intersystem lines and an allowed line from a different ion may also be used as a density indicator in the 10 to the 9th to 10 to the 11th per cu cm regime.

  9. A New Empirical Thermospheric Density Model JB2006 using New Solar Indices

    NASA Technical Reports Server (NTRS)

    Bowman, Bruce R.; Tobiska, W. Kent; Marcos, Frank A.

    2006-01-01

    A new empirical atmospheric density model is developed using the CIRA72 (Jacchia 71) model as the basis for the diffusion equations. New solar indices based on orbit based sensor data are used for the solar irradiances in the extreme and far ultraviolet wavelengths. New exospheric temperature and semiannual density equations are employed to represent the major thermospheric density variations. Temperature correction equations are also developed for diurnal and latitudinal effects, and finally density correction factors are used for model corrections required at high altitude (1500-4000 km). The new model, Jacchia-Bowman 2006, is validated through comparisons of accurate daily density drag data previously computed for numerous satellite. For 400 km altitude the standard deviation of 16% for the standard Jacchia model is reduced to 10% for the new JB2006 model for periods of low geomagnetic storm activity.

  10. Digital orthopantomograms in osteoporosis detection: mandibular density and mandibular radiographic indices as skeletal BMD predictors

    PubMed Central

    Savic Pavicin, I; Jukic, T; Badel, T; Badanjak, A

    2014-01-01

    Objectives: To determine the correlation of skeletal bone mineral density (BMD) with mandibular density and mandibular radiographic indices estimated on digital panoramic radiographs. Methods: Study comprised 112 female subjects older than 45 years. Digital panoramic radiographs were taken, and patients were referred to densitometric measuring (dual energy X-ray absorptiometry) of BMD in the hip bones and lumbar spine regions (L1–L4). On the radiographs, mandibular bone density was estimated and the following indices were measured by the DIGORA® software (Soredex, Tuusula, Finland): mental index (MI), gonial index (GI), antegonial index (AI), panoramic mandibular index (PMI) and alveolar crest resorption degree (M/M). Mandibular cortical index (MCI) was visually estimated. Results: Mandibular density and visual index MCI are significant predictors of hip and spine BMD. Mandibular density was marked by a significant square trend: it decreased until the age of 54 years and remained constant until the age of 64 years when it started to increase. Significant correlations were found between MI, AI and PMI values and BMD in the hip but not in the lumbar spine region. The GI and M/M values did not show statistically significant correlations with BMD of either region. Conclusions: Mandibular bone density and mandibular radiographic indices are useful in detecting patients with decreased BMD. The applicability of orthopantomograms in diagnosing osteoporosis/osteopenia should be recognized as the potential greatest benefit of this everyday diagnostic method in dental practice. PMID:24969554

  11. Cryogenic Refractive Indices of S-LAH55, S-LAH55V, S-LAH59, S-LAM3, S-NBM51, S-NPH2, S-PHM52, and S-TIH14 Glasses

    NASA Technical Reports Server (NTRS)

    Miller, Kevin H.; Quijada, Manuel A.; Leviton, Douglas B.

    2015-01-01

    The Transiting Exoplanet Survey Satellite (TESS) is an explorer-class planet finder, whose principal goal is to detect small planets with bright host starts in the solar neighborhood. The TESS payload consists of four identical cameras and a Data Handling Unit (DHU) fitted with CCD detectors and associated electronics. Each camera consist of a lens assembly with seven optical elements that include various types of Ohara glass substrates. The successful implementation of a panchromatic and a thermal lens assembly design for these cameras requires a fairly accurate (up to 0.000001 (1e-6)) knowledge of the temperature- and wavelength-dependent of the refractive index in the wavelength and temperature range of operation. Hence, this paper is devoted to report on measurements of the refractive index over the wavelength range of 0.42-1.15 micrometers and temperature range of 110-300 K for the following Ohara glasses: S-LAH55, S-LAH55V, S-LAH59, S-LAM3, S-NBM51, S-NPH2, S-PHM52, and S-TIH14. The measurements were performed utilizing the Cryogenic High Accuracy Refraction Measuring System (CHARMS) facility at NASA's Goddard Space Flight Center. A dense coverage of the absolute refractive index for all these substrates in the aforementioned wavelength and temperature ranges was used to determine the thermo-optic coefficient (dndT) and dispersion relation (dnd) as a function of wavelength and temperature. A comparison of the measured indices with literature values, specifically the temperature-dependent refractive indices of S-PHM52 and S-TIH14 reported by Yamamuro et al. [Yamamuro et al., Opt. Eng. 45(8), 083401 (2006)], will be presented.

  12. Effects of refractive index mismatch in optical CT imaging of polymer gel dosimeters

    SciTech Connect

    Manjappa, Rakesh; Makki S, Sharath; Kanhirodan, Rajan; Kumar, Rajesh

    2015-02-15

    Purpose: Proposing an image reconstruction technique, algebraic reconstruction technique-refraction correction (ART-rc). The proposed method takes care of refractive index mismatches present in gel dosimeter scanner at the boundary, and also corrects for the interior ray refraction. Polymer gel dosimeters with high dose regions have higher refractive index and optical density compared to the background medium, these changes in refractive index at high dose results in interior ray bending. Methods: The inclusion of the effects of refraction is an important step in reconstruction of optical density in gel dosimeters. The proposed ray tracing algorithm models the interior multiple refraction at the inhomogeneities. Jacob’s ray tracing algorithm has been modified to calculate the pathlengths of the ray that traverses through the higher dose regions. The algorithm computes the length of the ray in each pixel along its path and is used as the weight matrix. Algebraic reconstruction technique and pixel based reconstruction algorithms are used for solving the reconstruction problem. The proposed method is tested with numerical phantoms for various noise levels. The experimental dosimetric results are also presented. Results: The results show that the proposed scheme ART-rc is able to reconstruct optical density inside the dosimeter better than the results obtained using filtered backprojection and conventional algebraic reconstruction approaches. The quantitative improvement using ART-rc is evaluated using gamma-index. The refraction errors due to regions of different refractive indices are discussed. The effects of modeling of interior refraction in the dose region are presented. Conclusions: The errors propagated due to multiple refraction effects have been modeled and the improvements in reconstruction using proposed model is presented. The refractive index of the dosimeter has a mismatch with the surrounding medium (for dry air or water scanning). The algorithm

  13. QPCR Determined Fecal Indicator Bacterial Densities in Marine Waters from Two Recreational Beaches

    EPA Science Inventory

    The use of real-time qPCR to determine fecal indicator bacteria (FIB) densities is currently being investigated by the U.S. EPA. The present recreational water quality guidelines, based on culturable FIB, prevent same day determinations of water quality whereas results from the ...

  14. Effects of stocking density on behavior, productivity, and comfort indices of lactating dairy cows.

    PubMed

    Wang, F X; Shao, D F; Li, S L; Wang, Y J; Azarfar, A; Cao, Z J

    2016-05-01

    The objective of this study was to investigate the effects of different stocking densities of 82 (0.82 cows per freestall and feed bin), 100, and 129% on behavior, productivity, and comfort indices of lactating Holstein dairy cows. Twenty-seven lactating cows (15 primiparous and 12 multiparous) were assigned to 1 of the 3 treatments, which were balanced for parity, milk yield, days in milk, and body weight in a 3×3 Latin square design with 14-d periods. After 7 d of adaptation to the treatments, lying time and bouts were recorded at 1-min intervals for 3 d, DMI and feeding time were monitored electronically by feed bins, and rumination time was quantified at 2-h periods for 5 d during each period. The cow comfort index, stall standing index, stall perching index, and stall use index (SUI) were calculated using 10-min scan samples of video recording from d 8 to 10 of each period. Milk yield was recorded from d 8 to 12 and milk composition was determined from composite samples on d 12 in each period. Daily lying time, lying bouts, and bout duration did not differ among the stocking densities. The ratio of lying time ≥12 h/d (the number of cows with daily lying time ≥12 h/d divided by number of cows per pen) was higher for cows housed at 82% stocking density compared with those housed at 100% stocking density, with stocking density of 129% intermediate. Hourly lying time was lower at 100% stocking density compared with 82 and 129% stocking densities during the peak period (2300-0400 h), determined based on diurnal pattern of lying time. Daily dry matter intake, feeding time, and feeding rate were not affected by stocking density. After morning milking, dry matter intake and feeding time was reduced at 129 versus 82% stocking density during peak feeding time (0600-0800 h), determined based on diurnal patterns of feeding behavior. Stocking density had no effect on rumination time, milk yield and milk composition. The ratio of SUI ≥85% (mean of the number of SUI

  15. Effects of stocking density on behavior, productivity, and comfort indices of lactating dairy cows.

    PubMed

    Wang, F X; Shao, D F; Li, S L; Wang, Y J; Azarfar, A; Cao, Z J

    2016-05-01

    The objective of this study was to investigate the effects of different stocking densities of 82 (0.82 cows per freestall and feed bin), 100, and 129% on behavior, productivity, and comfort indices of lactating Holstein dairy cows. Twenty-seven lactating cows (15 primiparous and 12 multiparous) were assigned to 1 of the 3 treatments, which were balanced for parity, milk yield, days in milk, and body weight in a 3×3 Latin square design with 14-d periods. After 7 d of adaptation to the treatments, lying time and bouts were recorded at 1-min intervals for 3 d, DMI and feeding time were monitored electronically by feed bins, and rumination time was quantified at 2-h periods for 5 d during each period. The cow comfort index, stall standing index, stall perching index, and stall use index (SUI) were calculated using 10-min scan samples of video recording from d 8 to 10 of each period. Milk yield was recorded from d 8 to 12 and milk composition was determined from composite samples on d 12 in each period. Daily lying time, lying bouts, and bout duration did not differ among the stocking densities. The ratio of lying time ≥12 h/d (the number of cows with daily lying time ≥12 h/d divided by number of cows per pen) was higher for cows housed at 82% stocking density compared with those housed at 100% stocking density, with stocking density of 129% intermediate. Hourly lying time was lower at 100% stocking density compared with 82 and 129% stocking densities during the peak period (2300-0400 h), determined based on diurnal pattern of lying time. Daily dry matter intake, feeding time, and feeding rate were not affected by stocking density. After morning milking, dry matter intake and feeding time was reduced at 129 versus 82% stocking density during peak feeding time (0600-0800 h), determined based on diurnal patterns of feeding behavior. Stocking density had no effect on rumination time, milk yield and milk composition. The ratio of SUI ≥85% (mean of the number of SUI

  16. Bone Geometry, Density and Strength Indices of the Distal Radius Reflect Loading via Childhood Gymnastic Activity

    PubMed Central

    Dowthwaite, Jodi N.; Flowers, Portia P.E.; Spadaro, Joseph A.; Scerpella, Tamara A.

    2007-01-01

    The distal radius bears unique forces during gymnastic activity. Its relatively simple anatomy, minimal soft tissue envelope and varied composition make the distal radius ideal for evaluating the effects of loading on bone properties. For 56 premenarcheal gymnasts and non-gymnasts, ultradistal and 1/3 distal radius DXA scans measured bone mineral content (BMC), areal bone mineral density and projected area. Simplified geometric models were used to generate bone mineral apparent density (BMAD), geometric indices, strength indices and fall strength ratios. Ratios of regional BMC vs. total body fat free mass (FFM) were calculated. Separate Tanner I and II analyses of covariance adjusted bone parameters for age and height. Ratios were compared using maturity-matched analyses of variance. At the 1/3 region, periosteal width, BMC, cortical cross-sectional area, and section modulus were greater in gymnasts than non-gymnasts (p<0.05); 1/3 BMAD means were equivalent. Ultradistal BMAD, BMC and index for structural strength in axial compression were higher in gymnasts than non-gymnasts; ultradistal periosteal width was only larger in Tanner I gymnasts. Fall strength ratios and BMC/FFM ratios were greater in gymnasts (p<0.05). Geometric and volumetric responses to mechanical loading are site-specific during late childhood and early adolescence. The distal radius bears unique forces during gymnastic activity, and fan beam magnification error is negligible at this site, making it ideal for DXA evaluation of associated bone properties. For 56 premenarcheal gymnasts and non-gymnasts, ultradistal and 1/3 distal radius DXA scans measured bone mineral content, areal bone mineral density and projected area. Simplified geometric models were used to generate bone mineral apparent density, geometric indices, strength indices and fall strength ratios. Ratios of regional bone mineral content vs. total body fat free mass were calculated. Separate Tanner I and II analyses of covariance

  17. Amphipod densities and indices of wetland quality across the upper-Midwest, USA

    USGS Publications Warehouse

    Anteau, M.J.; Afton, A.D.

    2008-01-01

    Nutritional, behavioral, and diet data for lesser scaup (Aythya affinis [Eyton, 1838]) indicates that there has been a decrease in amphipod (Gammarus lacustris [G. O. Sars, 1863] and Hyalella azteca [Saussure, 1858]) density and wetland quality throughout the upper-Midwest, USA. Accordingly, we estimated densities of Gammarus and Hyalella in six eco-physiographic regions of Iowa, Minnesota, and North Dakota; 356 randomly selected semipermanent and permanent wetlands were sampled during springs 2004 and 2005. We also examined indices of wetland quality (e.g., turbidity, fish communities, aquatic vegetation) among regions in a random subset of these wetlands (n = 267). Gammarus and Hyalella were present in 19% and 54% of wetlands sampled, respectively. Gammarus and Hyalella densities in North Dakota were higher than those in Iowa and Minnesota. Although historical data are limited, our regional mean (1 to 12 m-3) amphipod densities (Gammarus + Hyalella) were markedly lower than any of the historical density estimates. Fish, important predators of amphipods, occurred in 31%-45% of wetlands in North Dakota, 84% of wetlands in the Red River Valley, and 74%-84% of wetlands in Iowa and Minnesota. Turbidity in wetlands of Minnesota Morainal (4.0 NTU geometric mean) and Red River Valley (6.1 NTU) regions appeared low relative to that of the rest of the upper-Midwest (13.2-17.5 NTU). We conclude that observed estimates of amphipods, fish, and turbidity are consistent with low wetland quality, which has resulted in lower food availability for various wildlife species, especially lesser scaup, which use these wetlands in the upper-Midwest. ?? 2008, The Society of Wetland Scientists.

  18. Graphene nano-ribbon waveguides of record-small mode area and ultra-high effective refractive indices for future VLSI.

    PubMed

    He, Sailing; Zhang, Xizhou; He, Yingran

    2013-12-16

    Electronics circuits keep shrinking in dimensions, as requested by Moore's law. In contrast, photonic waveguides and circuit elements still have lateral dimensions on the order of the wavelength. A key to make photonics have a microelectronics-like development is a drastic reduction of size. To achieve this, we need a low-loss nanoscale waveguide with a drastically reduced mode area and an ultra-high effective refractive index. For this purpose, we propose here several low-loss waveguide structures based on graphene nano-ribbons. An extremely small mode area (~10(-7)λ(0)(2), one order smaller than the smallest mode area of any waveguide that has ever been reported in the literature; here λ(0) is the operating wavelength in vacuum) and an extremely large effective refractive index (several hundreds) are achieved. As a device example, a nano-ring cavity of ultra-small size (with a diameter of ~10(-2)λ(0)) is designed. Our study paves the way for future VLSI (very-large-scale integration) optoelectronics.

  19. Negative refraction in molybdenum disulfide.

    PubMed

    Wang, Wenhui; Cui, Xudong; Yang, Erchan; Fan, Quanping; Xiang, Bin

    2015-08-24

    Recently, negative refractions have been demonstrated in uniaxial crystals with no necessary of negative permittivity and permeability. However, the small anisotropy parameterγin the uniaxial crystals limits the negative refraction occurrence only in a small range of the incident light angle, retarding its practical applications. In this paper, we report negative refraction induced by a pronounced anisotropic behavior in the bulk MoS(2). Using the first-principles, the dielectric function and refractive index calculations confirm a uniaxial trait of MoS(2) with a calculated anisotropy parameterγlarger than 2.5 in the entire range of visible wavelength. The critical incident angle to trigger a negative refraction in the bulk MoS(2) is calculated up to 90°. The finite-difference time-domain simulations prove that the incident light with a density of 59.5% can be negatively refracted in a MoS(2) slab with a thickness of 0.1 µm. Our results open up a new pathway for MoS(2)-like materials to a novel field of optical integration.

  20. Negative refraction in one-dimensional photonic crystals

    NASA Astrophysics Data System (ADS)

    Lugo, J. E.; Doti, Rafael; Faubert, J.

    2012-10-01

    Photonic crystals are artificial structures that have periodic dielectric components with different refractive indices. Under certain conditions, they abnormally refract the light, a phenomenon called negative refraction. Here, we discuss recent theoretical and simulation results that showed that negative refraction could be present near the low frequency edge of at least the second, fourth and sixth bandgaps of a lossless one-dimensional photonic crystals (1DPC) structure. That is, negative refraction is a multiband phenomenon. We also discuss the negative refraction correctness condition that gives the angular region where negative refraction occurs. We compare two current negative refraction theoretical models with recent experimental results. In order to succeed, an output refraction correction is utilized. The correction uses Snell's law and an effective refractive index based on two effective dielectric constants. We found good agreement between experiment and both theoretical models in the negative refraction zone.

  1. Plant root tortuosity: an indicator of root path formation in soil with different composition and density

    PubMed Central

    Popova, Liyana; van Dusschoten, Dagmar; Nagel, Kerstin A.; Fiorani, Fabio; Mazzolai, Barbara

    2016-01-01

    Background and Aims Root soil penetration and path optimization are fundamental for root development in soil. We describe the influence of soil strength on root elongation rate and diameter, response to gravity, and root-structure tortuosity, estimated by average curvature of primary maize roots. Methods Soils with different densities (1·5, 1·6, 1·7 g cm−3), particle sizes (sandy loam; coarse sand mixed with sandy loam) and layering (monolayer, bilayer) were used. In total, five treatments were performed: Mix_low with mixed sand low density (three pots, 12 plants), Mix_medium - mixed sand medium density (three pots, 12 plants), Mix_high - mixed sand high density (three pots, ten plants), Loam_low sandy loam soil low density (four pots, 16 plants), and Bilayer with top layer of sandy loam and bottom layer mixed sand both of low density (four pots, 16 plants). We used non-invasive three-dimensional magnetic resonance imaging to quantify effects of these treatments. Key Results Roots grew more slowly [root growth rate (mm h–1); decreased 50 %] with increased diameters [root diameter (mm); increased 15 %] in denser soils (1·7 vs. 1·5 g cm–3). Root response to gravity decreased 23 % with increased soil compaction, and tortuosity increased 10 % in mixed sand. Response to gravity increased 39 % and tortuosity decreased 3 % in sandy loam. After crossing a bilayered–soil interface, roots grew more slowly, similar to roots grown in soil with a bulk density of 1·64 g cm–3, whereas the actual experimental density was 1·48±0·02 g cm–3. Elongation rate and tortuosity were higher in Mix_low than in Loam_low. Conclusions The present study increases our existing knowledge of the influence of physical soil properties on root growth and presents new assays for studying root growth dynamics in non-transparent media. We found that root tortuosity is indicative of root path selection, because it could result from both mechanical deflection and

  2. The dipole moment of the spin density as a local indicator for phase transitions

    PubMed Central

    Schmitz, D.; Schmitz-Antoniak, C.; Warland, A.; Darbandi, M.; Haldar, S.; Bhandary, S.; Eriksson, O.; Sanyal, B.; Wende, H.

    2014-01-01

    The intra-atomic magnetic dipole moment - frequently called 〈Tz〉 term - plays an important role in the determination of spin magnetic moments by x-ray absorption spectroscopy for systems with nonspherical spin density distributions. In this work, we present the dipole moment as a sensitive monitor to changes in the electronic structure in the vicinity of a phase transiton. In particular, we studied the dipole moment at the Fe2+ and Fe3+ sites of magnetite as an indicator for the Verwey transition by a combination of x-ray magnetic circular dichroism and density functional theory. Our experimental results prove that there exists a local change in the electronic structure at temperatures above the Verwey transition correlated to the known spin reorientation. Furthermore, it is shown that measurement of the dipole moment is a powerful tool to observe this transition in small magnetite nanoparticles for which it is usually screened by blocking effects in classical magnetometry. PMID:25041757

  3. The dipole moment of the spin density as a local indicator for phase transitions

    NASA Astrophysics Data System (ADS)

    Schmitz, D.; Schmitz-Antoniak, C.; Warland, A.; Darbandi, M.; Haldar, S.; Bhandary, S.; Eriksson, O.; Sanyal, B.; Wende, H.

    2014-07-01

    The intra-atomic magnetic dipole moment - frequently called term - plays an important role in the determination of spin magnetic moments by x-ray absorption spectroscopy for systems with nonspherical spin density distributions. In this work, we present the dipole moment as a sensitive monitor to changes in the electronic structure in the vicinity of a phase transiton. In particular, we studied the dipole moment at the Fe2+ and Fe3+ sites of magnetite as an indicator for the Verwey transition by a combination of x-ray magnetic circular dichroism and density functional theory. Our experimental results prove that there exists a local change in the electronic structure at temperatures above the Verwey transition correlated to the known spin reorientation. Furthermore, it is shown that measurement of the dipole moment is a powerful tool to observe this transition in small magnetite nanoparticles for which it is usually screened by blocking effects in classical magnetometry.

  4. Refractive index of rigid contact lens materials.

    PubMed

    Tranoudis, I; Efron, N

    1998-01-01

    A simple hand-held refractometer was used to measure the refractive index of 27 rigid gas permeable contact lens materials. As a general rule, lenses with refractive indices lower than 1.458 are made from fluorosilicone acrylates; lenses with refractive indices in the range of 1.458 to 1.469 are made from either fluorosilicone acrylates or silicone acrylates; and lenses with refractive indices greater than 1.469 are made from silicone acrylates. It is demonstrated how refractometry can be used by contact lens practitioners for the identification and verification of rigid contact lenses.

  5. Refraction characteristics of phononic crystals

    NASA Astrophysics Data System (ADS)

    Nemat-Nasser, Sia

    2015-08-01

    Some of the most interesting refraction properties of phononic crystals are revealed by examining the anti-plane shear waves in doubly periodic elastic composites with unit cells containing rectangular and/or elliptical multi-inclusions. The corresponding band structure, group velocity, and energy-flux vector are calculated using a powerful mixed variational method that accurately and efficiently yields all the field quantities over multiple frequency pass-bands. The background matrix and the inclusions can be anisotropic, each having distinct elastic moduli and mass densities. Equifrequency contours and energy-flux vectors are readily calculated as functions of the wave-vector components. By superimposing the energy-flux vectors on equifrequency contours in the plane of the wave-vector components, and supplementing this with a three-dimensional graph of the corresponding frequency surface, a wealth of information is extracted essentially at a glance. This way it is shown that a composite with even a simple square unit cell containing a central circular inclusion can display negative or positive energy and phase velocity refractions, or simply performs a harmonic vibration (standing wave), depending on the frequency and the wave-vector. Moreover, that the same composite when interfaced with a suitable homogeneous solid can display: (1) negative refraction with negative phase velocity refraction; (2) negative refraction with positive phase velocity refraction; (3) positive refraction with negative phase velocity refraction; (4) positive refraction with positive phase velocity refraction; or even (5) complete reflection with no energy transmission, depending on the frequency, and direction and the wavelength of the plane-wave that is incident from the homogeneous solid to the interface. For elliptical and rectangular inclusion geometries, analytical expressions are given for the key calculation quantities. Expressions for displacement, velocity, linear momentum

  6. Kernel density surface modelling as a means to identify significant concentrations of vulnerable marine ecosystem indicators.

    PubMed

    Kenchington, Ellen; Murillo, Francisco Javier; Lirette, Camille; Sacau, Mar; Koen-Alonso, Mariano; Kenny, Andrew; Ollerhead, Neil; Wareham, Vonda; Beazley, Lindsay

    2014-01-01

    The United Nations General Assembly Resolution 61/105, concerning sustainable fisheries in the marine ecosystem, calls for the protection of vulnerable marine ecosystems (VME) from destructive fishing practices. Subsequently, the Food and Agriculture Organization (FAO) produced guidelines for identification of VME indicator species/taxa to assist in the implementation of the resolution, but recommended the development of case-specific operational definitions for their application. We applied kernel density estimation (KDE) to research vessel trawl survey data from inside the fishing footprint of the Northwest Atlantic Fisheries Organization (NAFO) Regulatory Area in the high seas of the northwest Atlantic to create biomass density surfaces for four VME indicator taxa: large-sized sponges, sea pens, small and large gorgonian corals. These VME indicator taxa were identified previously by NAFO using the fragility, life history characteristics and structural complexity criteria presented by FAO, along with an evaluation of their recovery trajectories. KDE, a non-parametric neighbour-based smoothing function, has been used previously in ecology to identify hotspots, that is, areas of relatively high biomass/abundance. We present a novel approach of examining relative changes in area under polygons created from encircling successive biomass categories on the KDE surface to identify "significant concentrations" of biomass, which we equate to VMEs. This allows identification of the VMEs from the broader distribution of the species in the study area. We provide independent assessments of the VMEs so identified using underwater images, benthic sampling with other gear types (dredges, cores), and/or published species distribution models of probability of occurrence, as available. For each VME indicator taxon we provide a brief review of their ecological function which will be important in future assessments of significant adverse impact on these habitats here and elsewhere.

  7. Kernel Density Surface Modelling as a Means to Identify Significant Concentrations of Vulnerable Marine Ecosystem Indicators

    PubMed Central

    Kenchington, Ellen; Murillo, Francisco Javier; Lirette, Camille; Sacau, Mar; Koen-Alonso, Mariano; Kenny, Andrew; Ollerhead, Neil; Wareham, Vonda; Beazley, Lindsay

    2014-01-01

    The United Nations General Assembly Resolution 61/105, concerning sustainable fisheries in the marine ecosystem, calls for the protection of vulnerable marine ecosystems (VME) from destructive fishing practices. Subsequently, the Food and Agriculture Organization (FAO) produced guidelines for identification of VME indicator species/taxa to assist in the implementation of the resolution, but recommended the development of case-specific operational definitions for their application. We applied kernel density estimation (KDE) to research vessel trawl survey data from inside the fishing footprint of the Northwest Atlantic Fisheries Organization (NAFO) Regulatory Area in the high seas of the northwest Atlantic to create biomass density surfaces for four VME indicator taxa: large-sized sponges, sea pens, small and large gorgonian corals. These VME indicator taxa were identified previously by NAFO using the fragility, life history characteristics and structural complexity criteria presented by FAO, along with an evaluation of their recovery trajectories. KDE, a non-parametric neighbour-based smoothing function, has been used previously in ecology to identify hotspots, that is, areas of relatively high biomass/abundance. We present a novel approach of examining relative changes in area under polygons created from encircling successive biomass categories on the KDE surface to identify “significant concentrations” of biomass, which we equate to VMEs. This allows identification of the VMEs from the broader distribution of the species in the study area. We provide independent assessments of the VMEs so identified using underwater images, benthic sampling with other gear types (dredges, cores), and/or published species distribution models of probability of occurrence, as available. For each VME indicator taxon we provide a brief review of their ecological function which will be important in future assessments of significant adverse impact on these habitats here and

  8. Kernel density surface modelling as a means to identify significant concentrations of vulnerable marine ecosystem indicators.

    PubMed

    Kenchington, Ellen; Murillo, Francisco Javier; Lirette, Camille; Sacau, Mar; Koen-Alonso, Mariano; Kenny, Andrew; Ollerhead, Neil; Wareham, Vonda; Beazley, Lindsay

    2014-01-01

    The United Nations General Assembly Resolution 61/105, concerning sustainable fisheries in the marine ecosystem, calls for the protection of vulnerable marine ecosystems (VME) from destructive fishing practices. Subsequently, the Food and Agriculture Organization (FAO) produced guidelines for identification of VME indicator species/taxa to assist in the implementation of the resolution, but recommended the development of case-specific operational definitions for their application. We applied kernel density estimation (KDE) to research vessel trawl survey data from inside the fishing footprint of the Northwest Atlantic Fisheries Organization (NAFO) Regulatory Area in the high seas of the northwest Atlantic to create biomass density surfaces for four VME indicator taxa: large-sized sponges, sea pens, small and large gorgonian corals. These VME indicator taxa were identified previously by NAFO using the fragility, life history characteristics and structural complexity criteria presented by FAO, along with an evaluation of their recovery trajectories. KDE, a non-parametric neighbour-based smoothing function, has been used previously in ecology to identify hotspots, that is, areas of relatively high biomass/abundance. We present a novel approach of examining relative changes in area under polygons created from encircling successive biomass categories on the KDE surface to identify "significant concentrations" of biomass, which we equate to VMEs. This allows identification of the VMEs from the broader distribution of the species in the study area. We provide independent assessments of the VMEs so identified using underwater images, benthic sampling with other gear types (dredges, cores), and/or published species distribution models of probability of occurrence, as available. For each VME indicator taxon we provide a brief review of their ecological function which will be important in future assessments of significant adverse impact on these habitats here and elsewhere

  9. Bone geometry, density, and strength indices of the distal radius reflect loading via childhood gymnastic activity.

    PubMed

    Dowthwaite, Jodi N; Flowers, Portia P E; Spadaro, Joseph A; Scerpella, Tamara A

    2007-01-01

    The distal radius bears unique forces during gymnastic activity. Its relatively simple anatomy, minimal soft tissue envelope, and varied composition make the distal radius ideal for evaluating the effects of loading on bone properties. For 56 premenarcheal gymnasts and nongymnasts, ultradistal and 1/3 distal radius DXA scans measured bone mineral content (BMC), areal bone mineral density, and projected area. Simplified geometric models were used to generate bone mineral apparent density (BMAD), geometric indices, strength indices, and fall strength ratios. Ratios of regional BMC vs total body fat-free mass (FFM) were calculated. Separate Tanner I and II analyses of covariance adjusted bone parameters for age and height. Ratios were compared using maturity-matched analyses of variance. At the 1/3 region, periosteal width, BMC, cortical cross-sectional area, and section modulus were greater in gymnasts than nongymnasts (p<0.05); 1/3 BMAD means were equivalent. Ultradistal BMAD, BMC, and index for structural strength in axial compression were higher in gymnasts than nongymnasts; ultradistal periosteal width was only larger in Tanner I gymnasts. Fall strength ratios and BMC/FFM ratios were greater in gymnasts (p<0.05). Geometric and volumetric responses to mechanical loading are site specific during late childhood and early adolescence.

  10. Refractive index of plant cell walls

    NASA Technical Reports Server (NTRS)

    Gausman, H. W.; Allen, W. A.; Escobar, D. E.

    1974-01-01

    Air was replaced with media of higher refractive indices by vacuum infiltration in leaves of cucumber, blackeye pea, tomato, and string bean plants, and reflectance of noninfiltrated and infiltrated leaves was spectrophotometrically measured. Infiltrated leaves reflected less light than noninfiltrated leaves over the 500-2500-nm wavelength interval because cell wall-air interfaces were partly eliminated. Minimal reflectance should occur when the average refractive index of plant cell walls was matched by the infiltrating fluid. Although refractive indices that resulted in minimal reflectance differed among the four plant genera, an average value of 1.425 approximates the refractive index of plant cell walls for the four plant genera.

  11. Influence of wastewater disinfection on densities of culturable fecal indicator bacteria and genetic markers.

    PubMed

    Chern, Eunice C; Brenner, Kristen; Wymer, Larry; Haugland, Richard A

    2014-09-01

    The US Environmental Protection Agency has proposed the use of quantitative polymerase chain reaction (qPCR) as a rapid alternative analytical method for monitoring recreational water quality at beaches. For qPCR to be considered for other Clean Water Act purposes, such as inclusion in discharge permits and use in Total Maximum Daily Load calculations, it is necessary to understand how qPCR detectable genetic markers are influenced by wastewater disinfection. This study investigated genetic markers for Escherichia coli, Enterococcus, Clostridium spp., Bacteroides, total Bacteroidales, as well as the human-associated Bacteroides markers, HF183 and HumM2, to determine which, if any, were influenced by disinfection (chlorination or ultraviolet light) of effluents from secondary wastewater treatment in different seasons. The effects of disinfection on culturable enterococci, E. coli, Bacteroides, and C. perfringens were also compared to their associated genetic markers. Disinfection of secondary treatment effluents significantly reduced culturable fecal indicator bacteria (FIB) but not genetic marker densities. No significant differences were observed in the responses of FIB culture and genetic marker densities to type of disinfection (chlorination vs UV) or season. Results of this study provide evidence that qPCR may not be suitable for monitoring efficacy of wastewater disinfection on the inactivation of bacterial pathogens. PMID:25252344

  12. Influence of wastewater disinfection on densities of culturable fecal indicator bacteria and genetic markers.

    PubMed

    Chern, Eunice C; Brenner, Kristen; Wymer, Larry; Haugland, Richard A

    2014-09-01

    The US Environmental Protection Agency has proposed the use of quantitative polymerase chain reaction (qPCR) as a rapid alternative analytical method for monitoring recreational water quality at beaches. For qPCR to be considered for other Clean Water Act purposes, such as inclusion in discharge permits and use in Total Maximum Daily Load calculations, it is necessary to understand how qPCR detectable genetic markers are influenced by wastewater disinfection. This study investigated genetic markers for Escherichia coli, Enterococcus, Clostridium spp., Bacteroides, total Bacteroidales, as well as the human-associated Bacteroides markers, HF183 and HumM2, to determine which, if any, were influenced by disinfection (chlorination or ultraviolet light) of effluents from secondary wastewater treatment in different seasons. The effects of disinfection on culturable enterococci, E. coli, Bacteroides, and C. perfringens were also compared to their associated genetic markers. Disinfection of secondary treatment effluents significantly reduced culturable fecal indicator bacteria (FIB) but not genetic marker densities. No significant differences were observed in the responses of FIB culture and genetic marker densities to type of disinfection (chlorination vs UV) or season. Results of this study provide evidence that qPCR may not be suitable for monitoring efficacy of wastewater disinfection on the inactivation of bacterial pathogens.

  13. Density, refractive index, interfacial tension, and viscosity of ionic liquids [EMIM][EtSO4], [EMIM][NTf2], [EMIM][N(CN)2], and [OMA][NTf2] in dependence on temperature at atmospheric pressure.

    PubMed

    Fröba, Andreas P; Kremer, Heiko; Leipertz, Alfred

    2008-10-01

    The density, refractive index, interfacial tension, and viscosity of ionic liquids (ILs) [EMIM][EtSO 4] (1-ethyl-3-methylimidazolium ethylsulfate), [EMIM][NTf 2] (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide), [EMIM][N(CN) 2] (1-ethyl-3-methylimidazolium dicyanimide), and [OMA][NTf 2] (trioctylmethylammonium bis(trifluoromethylsulfonyl)imide) were studied in dependence on temperature at atmospheric pressure both by conventional techniques and by surface light scattering (SLS). A vibrating tube densimeter was used for the measurement of density at temperatures from (273.15 to 363.15) K and the results have an expanded uncertainty ( k = 2) of +/-0.02%. Using an Abbe refractometer, the refractive index was measured for temperatures between (283.15 and 313.15) K with an expanded uncertainty ( k = 2) of about +/-0.0005. The interfacial tension was obtained from the pendant drop technique at a temperature of 293.15 K with an expanded uncertainty ( k = 2) of +/-1%. For higher and lower temperatures, the interfacial tension was estimated by an adequate prediction scheme based on the datum at 293.15 K and the temperature dependence of density. For the ILs studied within this work, at a first order approximation, the quantity directly accessible by the SLS technique was the ratio of surface tension to dynamic viscosity. By combining the experimental results of the SLS technique with density and interfacial tension from conventional techniques, the dynamic viscosity could be obtained for temperatures between (273.15 and 333.15) K with an estimated expanded uncertainty ( k = 2) of less than +/-3%. The measured density, refractive index, and viscosity are represented by interpolating expressions with differences between the experimental and calculated values that are comparable with but always smaller than the expanded uncertainties ( k = 2). Besides a comparison with the literature, the influence of structural variations on the thermophysical properties of the

  14. Refraction near the horizon

    NASA Technical Reports Server (NTRS)

    Schaefer, Bradley E.; Liller, William

    1990-01-01

    Variations in astronomical refraction near the horizon are examined. Sunset timings, a sextant mounted on a tripod, and a temperature profile are utilized to derive the variations in refraction data, collected from 7 locations. It is determined that the refraction ranges from 0.234 to 1.678 deg with an rms deviation of 0.16, and it is observed that the variation is larger than previously supposed. Some applications for the variation of refraction value are discussed.

  15. Refractive error blindness.

    PubMed Central

    Dandona, R.; Dandona, L.

    2001-01-01

    Recent data suggest that a large number of people are blind in different parts of the world due to high refractive error because they are not using appropriate refractive correction. Refractive error as a cause of blindness has been recognized only recently with the increasing use of presenting visual acuity for defining blindness. In addition to blindness due to naturally occurring high refractive error, inadequate refractive correction of aphakia after cataract surgery is also a significant cause of blindness in developing countries. Blindness due to refractive error in any population suggests that eye care services in general in that population are inadequate since treatment of refractive error is perhaps the simplest and most effective form of eye care. Strategies such as vision screening programmes need to be implemented on a large scale to detect individuals suffering from refractive error blindness. Sufficient numbers of personnel to perform reasonable quality refraction need to be trained in developing countries. Also adequate infrastructure has to be developed in underserved areas of the world to facilitate the logistics of providing affordable reasonable-quality spectacles to individuals suffering from refractive error blindness. Long-term success in reducing refractive error blindness worldwide will require attention to these issues within the context of comprehensive approaches to reduce all causes of avoidable blindness. PMID:11285669

  16. Borehole density on the surface of living Porites corals as an indicator of sedimentation in Hong Kong.

    PubMed

    Xie, James Y; Wong, Jane C Y; Dumont, Clement P; Goodkin, Nathalie; Qiu, Jian-Wen

    2016-07-15

    Borehole density on the surface of Porites has been used as an indicator of water quality in the Great Barrier Reef. We assessed the relationship between borehole density on Porites and eight water quality parameters across 26 sites in Hong Kong. We found that total borehole densities on the surface of Porites at 16 of the studied sites were high (>1000individualsm(-2)), with polychaetes being the dominant bioeroders. Sedimentation rate was correlated positively with total borehole density and polychaete borehole density, with the latter relationship having a substantially higher correlation of determination. None of the environmental factors used were significantly correlated with bivalve borehole density. These results provide a baseline for assessing future changes in coral bioerosion in Hong Kong. This present study also indicates that polychaete boreholes can be used as a bioindicator of sedimentation in the South China Sea region where polychaetes are numerically dominant bioeroders. PMID:27179996

  17. Borehole density on the surface of living Porites corals as an indicator of sedimentation in Hong Kong.

    PubMed

    Xie, James Y; Wong, Jane C Y; Dumont, Clement P; Goodkin, Nathalie; Qiu, Jian-Wen

    2016-07-15

    Borehole density on the surface of Porites has been used as an indicator of water quality in the Great Barrier Reef. We assessed the relationship between borehole density on Porites and eight water quality parameters across 26 sites in Hong Kong. We found that total borehole densities on the surface of Porites at 16 of the studied sites were high (>1000individualsm(-2)), with polychaetes being the dominant bioeroders. Sedimentation rate was correlated positively with total borehole density and polychaete borehole density, with the latter relationship having a substantially higher correlation of determination. None of the environmental factors used were significantly correlated with bivalve borehole density. These results provide a baseline for assessing future changes in coral bioerosion in Hong Kong. This present study also indicates that polychaete boreholes can be used as a bioindicator of sedimentation in the South China Sea region where polychaetes are numerically dominant bioeroders.

  18. Refraction of coastal ocean waves

    NASA Technical Reports Server (NTRS)

    Shuchman, R. A.; Kasischke, E. S.

    1981-01-01

    Refraction of gravity waves in the coastal area off Cape Hatteras, NC as documented by synthetic aperture radar (SAR) imagery from Seasat orbit 974 (collected on September 3, 1978) is discussed. An analysis of optical Fourier transforms (OFTs) from more than 70 geographical positions yields estimates of wavelength and wave direction for each position. In addition, independent estimates of the same two quantities are calculated using two simple theoretical wave-refraction models. The OFT results are then compared with the theoretical results. A statistical analysis shows a significant degree of linear correlation between the data sets. This is considered to indicate that the Seasat SAR produces imagery whose clarity is sufficient to show the refraction of gravity waves in shallow water.

  19. Decay of aftershock density with distance indicates triggering by dynamic stress.

    PubMed

    Felzer, K R; Brodsky, E E

    2006-06-01

    The majority of earthquakes are aftershocks, yet aftershock physics is not well understood. Many studies suggest that static stress changes trigger aftershocks, but recent work suggests that shaking (dynamic stresses) may also play a role. Here we measure the decay of aftershocks as a function of distance from magnitude 2-6 mainshocks in order to clarify the aftershock triggering process. We find that for short times after the mainshock, when low background seismicity rates allow for good aftershock detection, the decay is well fitted by a single inverse power law over distances of 0.2-50 km. The consistency of the trend indicates that the same triggering mechanism is working over the entire range. As static stress changes at the more distant aftershocks are negligible, this suggests that dynamic stresses may be triggering all of these aftershocks. We infer that the observed aftershock density is consistent with the probability of triggering aftershocks being nearly proportional to seismic wave amplitude. The data are not fitted well by models that combine static stress change with the evolution of frictionally locked faults.

  20. Decay of aftershock density with distance indicates triggering by dynamic stress

    USGS Publications Warehouse

    Felzer, K.R.; Brodsky, E.E.

    2006-01-01

    The majority of earthquakes are aftershocks, yet aftershock physics is not well understood. Many studies suggest that static stress changes trigger aftershocks, but recent work suggests that shaking (dynamic stresses) may also play a role. Here we measure the decay of aftershocks as a function of distance from magnitude 2-6 mainshocks in order to clarify the aftershock triggering process. We find that for short times after the mainshock, when low background seismicity rates allow for good aftershock detection, the decay is well fitted by a single inverse power law over distances of 0.2-50 km. The consistency of the trend indicates that the same triggering mechanism is working over the entire range. As static stress changes at the more distant aftershocks are negligible, this suggests that dynamic stresses may be triggering all of these aftershocks. We infer that the observed aftershock density is consistent with the probability of triggering aftershocks being nearly proportional to seismic wave amplitude. The data are not fitted well by models that combine static stress change with the evolution of frictionally locked faults. ?? 2006 Nature Publishing Group.

  1. Solar energetic particle track densities as an indicator of the origin of interplanetary dust

    NASA Technical Reports Server (NTRS)

    Blanford, George E.

    1994-01-01

    An examination of the relation of track densities from solar energetic particles in interplanetary dust grains (IDP's) to the orbital elements of source bodies is made and the positive and negative aspects of using track densities to determine the origin of IDP's are reported. It is found from calculations that predicted track densities for a particle of given size are related logarithmically to the minimum semimajor axis of the source body. Consequently, although track densities measurements may not be capable of distinguishing cometary from asteroidal sources, they should give information on the minimum semimajor axis of the originating bodies.

  2. Determination of total nitrogen content, pH, density, refractive index, and brix in Thai fish sauces and their classification by near-infrared spectroscopy with searching combination moving window partial least squares.

    PubMed

    Ritthiruangdej, Pitiporn; Kasemsumran, Sumaporn; Suwonsichon, Thongchai; Haruthaithanasan, Vichai; Thanapase, Warunee; Ozaki, Yukihiro

    2005-10-01

    Near-infrared (NIR) transflectance spectra in the region of 1100-2500 nm were measured for 100 Thai fish sauces. Quantitative analyses of total nitrogen (TN) content, pH, refractive index, density and brix in the Thai fish sauces and their qualitative analyses were carried out by multivariate analyses with the aid of wavelength interval selection method named searching combination moving window partial least squares (SCMWPLS). The optimized informative region for TN selected by SCMWPLS was the region of 2264-2428 nm. A PLS calibration model, which used this region, yielded the lowest root mean square error of prediction (RMSEP) of 0.100% w/v for the PLS factor of 5. This prediction result is significantly better than those obtained by using the whole spectral region or informative regions selected by moving window partial least squares regression (MWPLSR). As for pH, density, refractive index and brix, the 1698-1722, and 2222-2258 nm regions, the 1358-1438 nm region, the 1774-1846, and 2078-2114 nm regions, and the 1322-1442, and 2000-2076 nm regions were selected by SCMWPLS as the optimized regions. The best prediction results were always obtained by use of the optimized regions selected by SCMWPLS. The lowest RMSEP for pH, density, refractive index and brix were 0.170, 0.007 g cm(-3), 0.0079 and 0.435 degrees Brix, respectively. Qualitative models were developed by using four supervised pattern recognitions, linear discriminant analysis (LDA), factor analysis-linear discriminant analysis (FA-LDA), soft independent modeling of class analog (SIMCA), and K neareat neighbors (KNN) for the optimized combination of informative regions of the NIR spectra of fish sauces to classify fish sauces into three groups based on TN. All the developed models can potentially classify the fish sauces with the correct classification rate of more than 82%, and the KNN classified model has the highest correct classification rate (95%). The present study has demonstrated that NIR

  3. Path integrals for electronic densities, reactivity indices, and localization functions in quantum systems.

    PubMed

    Putz, Mihai V

    2009-11-10

    The density matrix theory, the ancestor of density functional theory, provides the immediate framework for Path Integral (PI) development, allowing the canonical density be extended for the many-electronic systems through the density functional closure relationship. Yet, the use of path integral formalism for electronic density prescription presents several advantages: assures the inner quantum mechanical description of the system by parameterized paths; averages the quantum fluctuations; behaves as the propagator for time-space evolution of quantum information; resembles Schrödinger equation; allows quantum statistical description of the system through partition function computing. In this framework, four levels of path integral formalism were presented: the Feynman quantum mechanical, the semiclassical, the Feynman-Kleinert effective classical, and the Fokker-Planck non-equilibrium ones. In each case the density matrix or/and the canonical density were rigorously defined and presented. The practical specializations for quantum free and harmonic motions, for statistical high and low temperature limits, the smearing justification for the Bohr's quantum stability postulate with the paradigmatic Hydrogen atomic excursion, along the quantum chemical calculation of semiclassical electronegativity and hardness, of chemical action and Mulliken electronegativity, as well as by the Markovian generalizations of Becke-Edgecombe electronic focalization functions - all advocate for the reliability of assuming PI formalism of quantum mechanics as a versatile one, suited for analytically and/or computationally modeling of a variety of fundamental physical and chemical reactivity concepts characterizing the (density driving) many-electronic systems.

  4. Path Integrals for Electronic Densities, Reactivity Indices, and Localization Functions in Quantum Systems

    PubMed Central

    Putz, Mihai V.

    2009-01-01

    The density matrix theory, the ancestor of density functional theory, provides the immediate framework for Path Integral (PI) development, allowing the canonical density be extended for the many-electronic systems through the density functional closure relationship. Yet, the use of path integral formalism for electronic density prescription presents several advantages: assures the inner quantum mechanical description of the system by parameterized paths; averages the quantum fluctuations; behaves as the propagator for time-space evolution of quantum information; resembles Schrödinger equation; allows quantum statistical description of the system through partition function computing. In this framework, four levels of path integral formalism were presented: the Feynman quantum mechanical, the semiclassical, the Feynman-Kleinert effective classical, and the Fokker-Planck non-equilibrium ones. In each case the density matrix or/and the canonical density were rigorously defined and presented. The practical specializations for quantum free and harmonic motions, for statistical high and low temperature limits, the smearing justification for the Bohr’s quantum stability postulate with the paradigmatic Hydrogen atomic excursion, along the quantum chemical calculation of semiclassical electronegativity and hardness, of chemical action and Mulliken electronegativity, as well as by the Markovian generalizations of Becke-Edgecombe electronic focalization functions – all advocate for the reliability of assuming PI formalism of quantum mechanics as a versatile one, suited for analytically and/or computationally modeling of a variety of fundamental physical and chemical reactivity concepts characterizing the (density driving) many-electronic systems. PMID:20087467

  5. Developing a bubble number-density paleoclimatic indicator for glacier ice

    USGS Publications Warehouse

    Spencer, M.K.; Alley, R.B.; Fitzpatrick, J.J.

    2006-01-01

    Past accumulation rate can be estimated from the measured number-density of bubbles in an ice core and the reconstructed paleotemperature, using a new technique. Density increase and grain growth in polar firn are both controlled by temperature and accumulation rate, and the integrated effects are recorded in the number-density of bubbles as the firn changes to ice. An empirical model of these processes, optimized to fit published data on recently formed bubbles, reconstructs accumulation rates using recent temperatures with an uncertainty of 41% (P < 0.05). For modern sites considered here, no statistically significant trend exists between mean annual temperature and the ratio of bubble number-density to grain number-density at the time of pore close-off; optimum modeled accumulation-rate estimates require an eventual ???2.02 ?? 0.08 (P < 0.05) bubbles per close-off grain. Bubble number-density in the GRIP (Greenland) ice core is qualitatively consistent with independent estimates for a combined temperature decrease and accumulation-rate increase there during the last 5 kyr.

  6. Fully 3D refraction correction dosimetry system

    NASA Astrophysics Data System (ADS)

    Manjappa, Rakesh; Sharath Makki, S.; Kumar, Rajesh; Mohan Vasu, Ram; Kanhirodan, Rajan

    2016-02-01

    The irradiation of selective regions in a polymer gel dosimeter results in an increase in optical density and refractive index (RI) at those regions. An optical tomography-based dosimeter depends on rayline path through the dosimeter to estimate and reconstruct the dose distribution. The refraction of light passing through a dose region results in artefacts in the reconstructed images. These refraction errors are dependant on the scanning geometry and collection optics. We developed a fully 3D image reconstruction algorithm, algebraic reconstruction technique-refraction correction (ART-rc) that corrects for the refractive index mismatches present in a gel dosimeter scanner not only at the boundary, but also for any rayline refraction due to multiple dose regions inside the dosimeter. In this study, simulation and experimental studies have been carried out to reconstruct a 3D dose volume using 2D CCD measurements taken for various views. The study also focuses on the effectiveness of using different refractive-index matching media surrounding the gel dosimeter. Since the optical density is assumed to be low for a dosimeter, the filtered backprojection is routinely used for reconstruction. We carry out the reconstructions using conventional algebraic reconstruction (ART) and refractive index corrected ART (ART-rc) algorithms. The reconstructions based on FDK algorithm for cone-beam tomography has also been carried out for comparison. Line scanners and point detectors, are used to obtain reconstructions plane by plane. The rays passing through dose region with a RI mismatch does not reach the detector in the same plane depending on the angle of incidence and RI. In the fully 3D scanning setup using 2D array detectors, light rays that undergo refraction are still collected and hence can still be accounted for in the reconstruction algorithm. It is found that, for the central region of the dosimeter, the usable radius using ART-rc algorithm with water as RI matched

  7. Fully 3D refraction correction dosimetry system.

    PubMed

    Manjappa, Rakesh; Makki, S Sharath; Kumar, Rajesh; Vasu, Ram Mohan; Kanhirodan, Rajan

    2016-02-21

    The irradiation of selective regions in a polymer gel dosimeter results in an increase in optical density and refractive index (RI) at those regions. An optical tomography-based dosimeter depends on rayline path through the dosimeter to estimate and reconstruct the dose distribution. The refraction of light passing through a dose region results in artefacts in the reconstructed images. These refraction errors are dependant on the scanning geometry and collection optics. We developed a fully 3D image reconstruction algorithm, algebraic reconstruction technique-refraction correction (ART-rc) that corrects for the refractive index mismatches present in a gel dosimeter scanner not only at the boundary, but also for any rayline refraction due to multiple dose regions inside the dosimeter. In this study, simulation and experimental studies have been carried out to reconstruct a 3D dose volume using 2D CCD measurements taken for various views. The study also focuses on the effectiveness of using different refractive-index matching media surrounding the gel dosimeter. Since the optical density is assumed to be low for a dosimeter, the filtered backprojection is routinely used for reconstruction. We carry out the reconstructions using conventional algebraic reconstruction (ART) and refractive index corrected ART (ART-rc) algorithms. The reconstructions based on FDK algorithm for cone-beam tomography has also been carried out for comparison. Line scanners and point detectors, are used to obtain reconstructions plane by plane. The rays passing through dose region with a RI mismatch does not reach the detector in the same plane depending on the angle of incidence and RI. In the fully 3D scanning setup using 2D array detectors, light rays that undergo refraction are still collected and hence can still be accounted for in the reconstruction algorithm. It is found that, for the central region of the dosimeter, the usable radius using ART-rc algorithm with water as RI matched

  8. Refractive Index of Sodium Iodide

    SciTech Connect

    Jellison Jr, Gerald Earle; Boatner, Lynn A; Ramey, Joanne Oxendine; Kolopus, James A; Ramey, Lucas A; Singh, David J

    2012-01-01

    The refractive index of sodium iodide, an important scintillator material that is widely used for radiation detection, is based on a single measurement made by Spangenberg at one wavelength using the index-matching liquid immersion method (Z. Kristallogr., 57, 494-534 (1923)). In the present paper, we present new results for the refractive index of sodium iodide as measured by the minimum deviation technique at six wavelengths between 436 nm (n=1.839 0.002) and 633 nm (n=1.786 0.002). These 6 measurements can be fit to a Sellmeier model, resulting in a 2 of 1.02, indicating a good fit to the data. In addition, we report on ellipsometry measurements, which suggest that the near-surface region of the air sensitive NaI crystal seriously degrades, even in a moisture-free environment, resulting in a significantly lower value of the refractive index near the surface. First-principles theoretical calculations of the NaI refractive index that agree with the measured values within 0.025-0.045 are also presented and discussed.

  9. Reduced Bone Density and Cortical Bone Indices in Female Adiponectin-Knockout Mice.

    PubMed

    Naot, Dorit; Watson, Maureen; Callon, Karen E; Tuari, Donna; Musson, David S; Choi, Ally J; Sreenivasan, Dharshini; Fernandez, Justin; Tu, Pao Ting; Dickinson, Michelle; Gamble, Greg D; Grey, Andrew; Cornish, Jillian

    2016-09-01

    A positive association between fat and bone mass is maintained through a network of signaling molecules. Clinical studies found that the circulating levels of adiponectin, a peptide secreted from adipocytes, are inversely related to visceral fat mass and bone mineral density, and it has been suggested that adiponectin contributes to the coupling between fat and bone. Our study tested the hypothesis that adiponectin affects bone tissue by comparing the bone phenotype of wild-type and adiponectin-knockout (APN-KO) female mice between the ages of 8-37 weeks. Using a longitudinal study design, we determined body composition and bone density using dual energy x-ray absorptiometry. In parallel, groups of animals were killed at different ages and bone properties were analyzed by microcomputed tomography, dynamic histomorphometry, 3-point bending test, nanoindentation, and computational modelling. APN-KO mice had reduced body fat and decreased whole-skeleton bone mineral density. Microcomputed tomography analysis identified reduced cortical area fraction and average cortical thickness in APN-KO mice in all the age groups and reduced trabecular bone volume fraction only in young APN-KO mice. There were no major differences in bone strength and material properties between the 2 groups. Taken together, our results demonstrate a positive effect of adiponectin on bone geometry and density in our mouse model. Assuming adiponectin has similar effects in humans, the low circulating levels of adiponectin associated with increased fat mass are unlikely to contribute to the parallel increase in bone mass. Therefore, adiponectin does not appear to play a role in the coupling between fat and bone tissue. PMID:27384302

  10. Isaac Newton and the astronomical refraction.

    PubMed

    Lehn, Waldemar H

    2008-12-01

    In a short interval toward the end of 1694, Isaac Newton developed two mathematical models for the theory of the astronomical refraction and calculated two refraction tables, but did not publish his theory. Much effort has been expended, starting with Biot in 1836, in the attempt to identify the methods and equations that Newton used. In contrast to previous work, a closed form solution is identified for the refraction integral that reproduces the table for his first model (in which density decays linearly with elevation). The parameters of his second model, which includes the exponential variation of pressure in an isothermal atmosphere, have also been identified by reproducing his results. The implication is clear that in each case Newton had derived exactly the correct equations for the astronomical refraction; furthermore, he was the first to do so.

  11. Anomalies of free mantle surface for Asia region as an indicator of subcrustal density inhomogeneities

    NASA Astrophysics Data System (ADS)

    Senachin, V. N.; Baranov, A. A.

    2009-04-01

    Free mantle surface (FMS) is one of the important characteristics of the isostatic state of the Earth. FMS shows the degree of uplifting of the crust about the normal level, which corresponds to the homogeneous upper mantle. The FMS anomaly study can provide important information about the different geodynamic processes that responsible for the density heterogeneities in the upper mantle and the changing isostatic state of the lithosphere. Investigations of the FMS (Artemjev et. al, 1986) revealed main dependencies for the depth of the FMS under the continents and oceans. For the continental lithosphere it was found that the FMS depth depends on the thickness of the crust. Subsequently, the same dependence was revealed for the oceanic lithosphere using CRUST 2.0 model for all Earth (Senachin, 2008). In this study we present the updated FMS anomaly map for the Central and Southern Asia calculated using the crustal model AsCRUST-08 (Baranov, 2008), which has the resolution of 1x1 degree. We used the Moho map and density for upper, middle, and lower layers of crystalline crust for calculating the FSM anomalies. The Southern and Central Asia is tectonically complex region characterized by the great collision between the Asian and Indian plates, anomalously thick uplifted crust, and the large extensional zones near the southern and eastern margins of Asia. The evolution of the entire region is also strongly related to the active subduction along the Pacific border. The crustal model AsCRUST-08 provides substantially more detailed FMS data for the Asia region. We can see anomalous uplifting of the FMS up to 3 km in the extensional zones (Red Sea) and in the deep seafloor areas. Arabian Peninsula has the FMS depth about 6 km, which can be attributed to rather high density of the upper mantle. For Tibet region we reveal quite complex dependence between the FMS depth and the thickness of the crust. The central part with crustal thickness more then 45 km has elevated FMS

  12. Density and Porosity of Shower Meteorites as Indicators of Meter-scale Asteroid Homogeneity

    NASA Astrophysics Data System (ADS)

    Macke, Robert; Britt, D.; Consolmagno, G.

    2008-09-01

    Meteorite showers containing multiple stones from the same event provide clues to the homogeneity of meteorite parent bodies over decimeter to meter scales. Small bodies that have been studied in detail show a high degree of surface mineralogical homogeneity in reflectance spectra (Abe et al., 2006a; Veverka et al., 2001) and no detectable large scale density variations (Abe et al., 2006b; Thomas et al., 2002). Large meteorite showers provide a direct sample of the possible variations in physical properties of small bodies. We present the results of density, porosity, and magnetic susceptibility measurements of at least ten stones each from seven meteorite showers in the collection at the Smithsonian Institution's National Museum of Natural History. This includes three carbonaceous chondrites (Allende, Murchison and Murray) and four ordinary chondrites. We find strong homogeneity within showers. For example, the mass-weighted average grain density of Allende we measured as 3.60 g/cm3, with individual stones ranging from 3.59 to 3.62 g/cm3 and typical uncertainties 0.03 or 0.04 g/cm3. Allende porosities averaged 18.8% and ranged from 17.8% to 19.5% with typical uncertainties of about 1.2%. We also studied one weathered find (Gold Basin) for clues regarding the uniformity of chondrite weathering. For five showers, we compare results with measurements made on additional stones at the Vatican Observatory and the American Museum of Natural History. This work was supported in part by a Smithsonian Institution Graduate Student Fellowship. Veverka, J. et al., 2001. Science 289, 2088. Abe S. et al., 2006b. Science 312, 1344. Abe M. et al., 2006a. Science 312, 1334. Thomas P. et al., 2002. Icarus 155, 18.

  13. Randomised controlled trial of vitamin D supplementation on bone density and biochemical indices in preterm infants

    PubMed Central

    Backstrom, M; Maki, R; Kuusela, A; Sievanen, H; Koivisto, A; Ikonen, R; Kouri, T; Maki, M

    1999-01-01

    AIMS—To test the hypothesis that a vitamin D dose of 200 IU/kg, maximum 400 IU/day, given to preterm infants will maintain normal vitamin D status and will result in as high a bone mineral density as that attained with the recommended dose of 960 IU/day.
METHODS—Thirty nine infants of fewer than 33 weeks of gestational age were randomly allocated to receive vitamin D 200 IU/kg of body weight/day up to a maximum of 400 IU/day or 960 IU/day until 3months old. Vitamin D metabolites, bone mineral content and density were determined by dual energy x-ray absorptiometry, and plasma ionised calcium, plasma alkaline phosphatase, and intact parahormone measurements were used to evaluate outcomes.
RESULTS—The 25 hydroxy vitamin D concentrations tended to be higher in infants receiving 960 IU/day, but the differences did not reach significance at any age. There was no difference between the infants receiving low or high vitamin D dose in bone mineral content nor in bone mineral density at 3 and 6 months corrected age, even after taking potential risk factors into account.
CONCLUSIONS—A vitamin D dose of 200 IU/kg of body weight/day up to a maximum of 400 IU/day maintains normal vitamin D status and as good a bone mineral accretion as the previously recommended higher dose of 960 IU/day. Vitamin D is a potent hormone which affects organs other than bone and should not be given in excess to preterm infants.

 PMID:10212074

  14. Distribution characteristics of coronal electric current density as an indicator for the occurrence of a solar flare

    NASA Astrophysics Data System (ADS)

    Kang, Jihye; Magara, Tetsuya; Inoue, Satoshi; Kubo, Yuki; Nishizuka, Naoto

    2016-10-01

    In this paper we investigate the distribution characteristics of the coronal electric current density in a flare-producing active region (AR12158; SOL2014-09-10) by reconstructing nonlinear force-free (NLFF) fields from photospheric magnetic field data. A time series of NLFF fields shows the spatial distribution and its temporal development of coronal current density in this active region. A fractal dimensional analysis shows that a concentrated coronal current forms a structure of fractal spatiality. Furthermore, the distribution function of coronal current density is featured with a double power-law profile, and the value of electric current density at the breaking point of a double power-law fitting function shows a noticeable time variation toward the onset of an X-class flare. We discuss that this quantity will be a useful indicator for the occurrence of a flare.

  15. Relation of initial spacing and relative stand density indices to stand characteristics in a Douglas-fir plantation spacing trial

    USGS Publications Warehouse

    Curtis, Robert O.; Bansal, Sheel; Harrington, Constance A.

    2016-01-01

    This report presents updated information on a 1981 Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii) plantation spacing trial at 33 years from planting. Stand statistics at the most recent measurement were compared for initial spacing of 1 through 6 meters and associated relative densities. There was no clear relationship of spacing to top height. Diameter, live crown ratio, and percent survival increased with spacing; basal area and relative density decreased with increase in spacing. Volume in trees ≥ 4 cm diameter was greatest at 2 m spacing, while utilizable volume (trees ≥20 cm dbh) was greatest at 4 m spacing. Live crown ratio decreased and total crown projectional area increased with increasing relative density indices. Total crown projectional area was more closely related to relative density than to basal area.

  16. Raman spectroscopic investigation on high refractive index glasses prepared from local quartz sand

    NASA Astrophysics Data System (ADS)

    Dararutana, P.; Pongkrapan, S.; Sirikulrat, N.; Thawornmongkolkij, M.; Wathanakul, P.

    2009-08-01

    High refractive index (RI) glasses prepared from local quartz sand and compounds of heavy elements, such as, barium carbonate, lead oxide, and bismuth oxide as major ingredients were investigated using Raman spectroscopy. The results showed changes in glass structures of different doping elements, namely, Ba, Pb, and Bi. Refractive indices, densities, and UV-vis-NIR spectra of the glass samples were also measured. The Raman spectroscopy can be used to investigate and/or identify heavy glasses, local ancient glasses as well as glass jewelry.

  17. Hydrometeorological variables predict fecal indicator bacteria densities in freshwater: data-driven methods for variable selection.

    PubMed

    Jones, Rachael M; Liu, Li; Dorevitch, Samuel

    2013-03-01

    Statistical models of microbial water quality inform risk management for water recreation. Current research focuses on resource-intensive, location-specific data collection and water quality modeling, but this approach may be cost-prohibitive for risk managers responsible for numerous recreation sites. As an alternative, we tested the ability of two data-driven models, tree regression and random forests with conditional inference trees, to select readily available hydrometeorological variables for use in linear mixed effects (LME) models predicting bacterial density. The study included the Chicago Area Waterway System (CAWS) and Lake Michigan beaches and harbors in Chicago, Illinois, at which Escherichia coli and enterococci were measured seasonally in 2007-2009. Tree regression node variables reduced data dimensionality by >50 %. Variable importance ranks from random forests were used in a forward-step selection based on R (2) and root mean squared prediction error (RMSPE). We found two to three variables explained bacteria densities well relative to random forests with all variables. LME models with tree- or forest-selected variables performed reasonably well (0.335 < R (2) < 0.658). LME models for Lake Michigan had good prediction accuracy with respect to the single sample maximum standard (72-77 %), but limited sensitivity (23-62 %). Results suggest that our alternative approach is feasible and performs similarly to more resource-intensive approaches.

  18. Optofluidic two-dimensional grating volume refractive index sensor.

    PubMed

    Sarkar, Anirban; Shivakiran Bhaktha, B N; Khastgir, Sugata Pratik

    2016-09-10

    We present an optofluidic reservoir with a two-dimensional grating for a lab-on-a-chip volume refractive index sensor. The observed diffraction pattern from the device resembles the analytically obtained fringe pattern. The change in the diffraction pattern has been monitored in the far-field for fluids with different refractive indices. Reliable measurements of refractive index variations, with an accuracy of 6×10-3 refractive index units, for different fluids establishes the optofluidic device as a potential on-chip tool for monitoring dynamic refractive index changes. PMID:27661360

  19. Optofluidic two-dimensional grating volume refractive index sensor.

    PubMed

    Sarkar, Anirban; Shivakiran Bhaktha, B N; Khastgir, Sugata Pratik

    2016-09-10

    We present an optofluidic reservoir with a two-dimensional grating for a lab-on-a-chip volume refractive index sensor. The observed diffraction pattern from the device resembles the analytically obtained fringe pattern. The change in the diffraction pattern has been monitored in the far-field for fluids with different refractive indices. Reliable measurements of refractive index variations, with an accuracy of 6×10-3 refractive index units, for different fluids establishes the optofluidic device as a potential on-chip tool for monitoring dynamic refractive index changes.

  20. Refractive index measurement by prism autocollimation

    NASA Astrophysics Data System (ADS)

    Cheng, Chao-Chia

    2014-03-01

    An autocollimation-based method for measuring the refractive indices of solid or liquids using a Littrow prism is presented. Measurement accuracy is enhanced by use of a telescope. In solids, the refractive index is accurate to three decimal places. Similar accuracy is obtained in liquids by correcting for the wedge angle of the liquid container window. The proposed prismatic method confers high accuracy, compactness, and automation. It is suitable for index measurement applications in undergraduate laboratories.

  1. Refractive surgery for keratoconus.

    PubMed

    Ormonde, Sue

    2013-03-01

    Traditionally, keratoconus has been managed with glasses when mild, contact lenses when moderate and keratoplasty when severe. When cornea-based refractive surgery was first developed it appeared to be a useful option for keratoconus until reports of post-operative progressive ectasia emerged and thus keratoconus was considered a contraindication to refractive surgery. However, improvements in older techniques and the development of new techniques mean that there are now several viable options to avoid keratoplasty in contact lens-intolerant patients. This review discusses the risks and benefits of excimer laser refractive procedures, both with and without corneal collagen cross linking, as well as intra-corneal ring segments, phakic intraocular lenses and refractive lens exchange with toric intraocular lens implantation. PMID:23496655

  2. Refractive evaluation in thalidomide embryopathy.

    PubMed

    Strömland, K; Miller, M T

    1992-01-01

    To evaluate the ocular findings associated with thalidomide embryopathy, we examined 86 of 100 Swedes who had a proven correlation between birth defects and the mother's intake of thalidomide during pregnancy. Cycloplegic refraction, keratometry, and axial length measurements were performed. The subjects were divided into four groups according to their physical malformations, giving a time frame for when in gestation the insult occurred (the sensitive phase for thalidomide is 20-36 days after conception). The results indicate a trend toward shorter and longer axial lengths, high refractive errors, and corneal astigmatism in thalidomide embryopathy compared to controls, and in addition there was a tendency for those anomalies to occur in the group with the earliest thalidomide-induced defects. It is suggested that thalidomide disturbs the growth and shape of the eye and that this effect is exerted early in its teratogenic period.

  3. Survival analysis for the missing censoring indicator model using kernel density estimation techniques.

    PubMed

    Subramanian, Sundarraman

    2006-01-01

    This article concerns asymptotic theory for a new estimator of a survival function in the missing censoring indicator model of random censorship. Specifically, the large sample results for an inverse probability-of-non-missingness weighted estimator of the cumulative hazard function, so far not available, are derived, including an almost sure representation with rate for a remainder term, and uniform strong consistency with rate of convergence. The estimator is based on a kernel estimate for the conditional probability of non-missingness of the censoring indicator. Expressions for its bias and variance, in turn leading to an expression for the mean squared error as a function of the bandwidth, are also obtained. The corresponding estimator of the survival function, whose weak convergence is derived, is asymptotically efficient. A numerical study, comparing the performances of the proposed and two other currently existing efficient estimators, is presented. PMID:18953423

  4. Nonlinear Refractive Properties

    NASA Technical Reports Server (NTRS)

    Vikram, Chandra S.; Witherow, William K.

    2001-01-01

    Using nonlinear refractive properties of a salt-water solution at two wavelengths, numerical analysis has been performed to extract temperature and concentration from interferometric fringe data. The theoretical study, using a commercially available equation solving software, starts with critical fringe counting needs and the role of nonlinear refractive properties in such measurements. Finally, methodology of the analysis, codes, fringe counting accuracy needs, etc. is described in detail.

  5. ON THE SOURCE OF ASTROMETRIC ANOMALOUS REFRACTION

    SciTech Connect

    Taylor, M. Suzanne; McGraw, John T.; Zimmer, Peter C.; Pier, Jeffrey R.

    2013-03-15

    More than a century ago, astronomers using transit telescopes to determine precise stellar positions were hampered by an unexplained periodic shifting of the stars they were observing. With the advent of CCD transit telescopes in the past three decades, this unexplained motion, termed 'anomalous refraction' by these early astronomers, is again being observed. Anomalous refraction is described as a low-frequency, large angular scale ({approx}2 Degree-Sign ) motion of the entire image plane with respect to the celestial coordinate system as observed and defined by astrometric catalogs. These motions, of typically several tenths of an arcsecond amplitude with timescales on the order of 10 minutes, are ubiquitous to ground-based drift-scan astrometric measurements regardless of location or telescopes used and have been attributed to the effect of tilting of equal-density layers of the atmosphere. The cause of this tilting has often been attributed to atmospheric gravity waves, but this cause has never been confirmed. Although theoretical models of atmospheric refraction show that atmospheric gravity waves are a plausible cause of anomalous refraction, an observational campaign specifically directed at defining this relationship provides clear evidence that anomalous refraction is not consistent with the passage of atmospheric gravity waves. The source of anomalous refraction is found to be meter-scale, slowly evolving quasi-coherent dynamical structures in the boundary layer below 60 m above ground level.

  6. Density functional theory of chemical reactivity indices in some ion-molecule reaction systems

    SciTech Connect

    Tachibana, Akitoma; Kawauchi, Susumu; Nakamura, Koichi; Inaba, Hideyuki

    1996-02-15

    Three isoelectronic reactions, proton transfer (PT), hydrogen abstraction (HA), and electron transfer (ET), of NH{sub 3}{sup +} with NH{sub 3}, H{sub 2}O, and HF have been studied using ab initio molecular orbital calculations. For the reaction of NH{sub 3}{sup +} + H{sub 2}O, the energy of the transition state (TS) is higher than that of the reactants. This is consistent with the experimental observation that the rate constant is less than the average dipole orientation (ADO) rate constant. It seems reasonable that the reaction rate for the reaction NH{sub 3}{sup +} + H{sub 2}O would hardly depend on the V{sub 2} mode of NH{sub 3}{sup +} at least for low-lying excited states (E{sub int}{le} 0.714 eV) of the V{sub 2} mode, because the V{sub 2} contributes mainly to the normal mode orthogonal to the reaction coordinate at the TS. This is consistent with experimental observation. A similiar prediction can be made for the NH{sub 3}{sup +} + HF reaction. The electron transfer processes for the HA reactions have been examined in terms of the intrinsic reaction coordinate (IRC). The order of reactivity with NH{sub 3}{sup +} is NH{sub 3}>H{sub 2}O>HF. It is found that the degree of the electron transfer and the reactivity are correlated with the absolute hardness {eta} of NH{sub 3}, H{sub 2}O, and HF. this is accord with the softness as the chemical reactivity index in the density functional theory. 25 refs., 6 fig., 4 tab.

  7. Influence of refractive correction on ocular dominance

    NASA Astrophysics Data System (ADS)

    Nakayama, Nanami; Kawamorita, Takushi; Uozato, Hiroshi

    2010-07-01

    We investigated the effects of refractive correction and refractive defocus on the assessment of sensory ocular dominance. In 25 healthy subjects (4 males and 21 females) aged between 20 and 31 years, a quantitative measurement of sensory ocular dominance was performed with refractive correction and the addition of a positive lens on the dominant eye. Sensory ocular dominance was measured with a chart using binocular rivalry targets. The reversal point changed after the addition of a +1.00 D lens on the dominant eye in all subjects. However, sighting ocular dominance and stereopsis did not change after the addition of a positive lens on the dominant eye ( P > 0:05, Wilcoxon test). These results suggest that refractive correction affects sensory ocular dominance, indicating the possible development of a new type of occlusion for amblyopia in the future.

  8. Broadband giant-refractive-index material based on mesoscopic space-filling curves.

    PubMed

    Chang, Taeyong; Kim, Jong Uk; Kang, Seung Kyu; Kim, Hyowook; Kim, Do Kyung; Lee, Yong-Hee; Shin, Jonghwa

    2016-01-01

    The refractive index is the fundamental property of all optical materials and dictates Snell's law, propagation speed, wavelength, diffraction, energy density, absorption and emission of light in materials. Experimentally realized broadband refractive indices remain <40, even with intricately designed artificial media. Herein, we demonstrate a measured index >1,800 resulting from a mesoscopic crystal with a dielectric constant greater than three million. This gigantic enhancement effect originates from the space-filling curve concept from mathematics. The principle is inherently very broad band, the enhancement being nearly constant from zero up to the frequency of interest. This broadband giant-refractive-index medium promises not only enhanced resolution in imaging and raised fundamental absorption limits in solar energy devices, but also compact, power-efficient components for optical communication and increased performance in many other applications. PMID:27573337

  9. Broadband giant-refractive-index material based on mesoscopic space-filling curves.

    PubMed

    Chang, Taeyong; Kim, Jong Uk; Kang, Seung Kyu; Kim, Hyowook; Kim, Do Kyung; Lee, Yong-Hee; Shin, Jonghwa

    2016-08-30

    The refractive index is the fundamental property of all optical materials and dictates Snell's law, propagation speed, wavelength, diffraction, energy density, absorption and emission of light in materials. Experimentally realized broadband refractive indices remain <40, even with intricately designed artificial media. Herein, we demonstrate a measured index >1,800 resulting from a mesoscopic crystal with a dielectric constant greater than three million. This gigantic enhancement effect originates from the space-filling curve concept from mathematics. The principle is inherently very broad band, the enhancement being nearly constant from zero up to the frequency of interest. This broadband giant-refractive-index medium promises not only enhanced resolution in imaging and raised fundamental absorption limits in solar energy devices, but also compact, power-efficient components for optical communication and increased performance in many other applications.

  10. Broadband giant-refractive-index material based on mesoscopic space-filling curves

    NASA Astrophysics Data System (ADS)

    Chang, Taeyong; Kim, Jong Uk; Kang, Seung Kyu; Kim, Hyowook; Kim, Do Kyung; Lee, Yong-Hee; Shin, Jonghwa

    2016-08-01

    The refractive index is the fundamental property of all optical materials and dictates Snell's law, propagation speed, wavelength, diffraction, energy density, absorption and emission of light in materials. Experimentally realized broadband refractive indices remain <40, even with intricately designed artificial media. Herein, we demonstrate a measured index >1,800 resulting from a mesoscopic crystal with a dielectric constant greater than three million. This gigantic enhancement effect originates from the space-filling curve concept from mathematics. The principle is inherently very broad band, the enhancement being nearly constant from zero up to the frequency of interest. This broadband giant-refractive-index medium promises not only enhanced resolution in imaging and raised fundamental absorption limits in solar energy devices, but also compact, power-efficient components for optical communication and increased performance in many other applications.

  11. Broadband giant-refractive-index material based on mesoscopic space-filling curves

    PubMed Central

    Chang, Taeyong; Kim, Jong Uk; Kang, Seung Kyu; Kim, Hyowook; Kim, Do Kyung; Lee, Yong-Hee; Shin, Jonghwa

    2016-01-01

    The refractive index is the fundamental property of all optical materials and dictates Snell's law, propagation speed, wavelength, diffraction, energy density, absorption and emission of light in materials. Experimentally realized broadband refractive indices remain <40, even with intricately designed artificial media. Herein, we demonstrate a measured index >1,800 resulting from a mesoscopic crystal with a dielectric constant greater than three million. This gigantic enhancement effect originates from the space-filling curve concept from mathematics. The principle is inherently very broad band, the enhancement being nearly constant from zero up to the frequency of interest. This broadband giant-refractive-index medium promises not only enhanced resolution in imaging and raised fundamental absorption limits in solar energy devices, but also compact, power-efficient components for optical communication and increased performance in many other applications. PMID:27573337

  12. Decay of aftershock density with distance does not indicate triggering by dynamic stress

    USGS Publications Warehouse

    Richards-Dinger, K.; Stein, R.S.; Toda, S.

    2010-01-01

    Resolving whether static or dynamic stress triggers most aftershocks and subsequent mainshocks is essential to understand earthquake interaction and to forecast seismic hazard. Felzer and Brodsky examined the distance distribution of earthquakes occurring in the first five minutes after 2 ≤ M  M  M ≥ 2 aftershocks showed a uniform power-law decay with slope −1.35 out to 50 km from the mainshocks. From this they argued that the distance decay could be explained only by dynamic triggering. Here we propose an alternative explanation for the decay, and subject their hypothesis to a series of tests, none of which it passes. At distances more than 300 m from the 2 ≤  M< 3 mainshocks, the seismicity decay 5 min before the mainshocks is indistinguishable from the decay five minutes afterwards, indicating that the mainshocks have no effect at distances outside their static triggering range. Omori temporal decay, the fundamental signature of aftershocks, is absent at distances exceeding 10 km from the mainshocks. Finally, the distance decay is found among aftershocks that occur before the arrival of the seismic wave front from the mainshock, which violates causality. We argue that Felzer and Brodsky implicitly assume that the first of two independent aftershocks along a fault rupture triggers the second, and that the first of two shocks in a creep- or intrusion-driven swarm triggers the second, when this need not be the case.

  13. Halogen bonding from a hard and soft acids and bases perspective: investigation by using density functional theory reactivity indices.

    PubMed

    Pinter, Balazs; Nagels, Nick; Herrebout, Wouter A; De Proft, Frank

    2013-01-01

    Halogen bonds between the trifluoromethyl halides CF(3)Cl, CF(3)Br and CF(3)I, and dimethyl ether, dimethyl sulfide, trimethylamine and trimethyl phosphine were investigated using Pearson's hard and soft acids and bases (HSAB) concept with conceptual DFT reactivity indices, the Ziegler-Rauk-type energy-decomposition analysis, the natural orbital for chemical valence (NOCV) framework and the non-covalent interaction (NCI) index. It is found that the relative importance of electrostatic and orbital (charge transfer) interactions varies as a function of both the donor and acceptor molecules. Hard and soft interactions were distinguished and characterised by atomic charges, electrophilicity and local softness indices. Dual-descriptor plots indicate an orbital σ hole on the halogen similar to the electrostatic σ hole manifested in the molecular electrostatic potential. The predicted high halogen-bond-acceptor affinity of N-heterocyclic carbenes was evidenced in the highest complexation energy for the hitherto unknown CF(3) I·NHC complex. The dominant NOCV orbital represents an electron-density deformation according to a n→σ*-type interaction. The characteristic signal found in the reduced density gradient versus electron-density diagram corresponds to the non-covalent interaction between contact atoms in the NCI plots, which is the manifestation of halogen bonding within the NCI theory. The unexpected C-X bond strengthening observed in several cases was rationalised within the molecular orbital framework.

  14. Halogen bonding from a hard and soft acids and bases perspective: investigation by using density functional theory reactivity indices.

    PubMed

    Pinter, Balazs; Nagels, Nick; Herrebout, Wouter A; De Proft, Frank

    2013-01-01

    Halogen bonds between the trifluoromethyl halides CF(3)Cl, CF(3)Br and CF(3)I, and dimethyl ether, dimethyl sulfide, trimethylamine and trimethyl phosphine were investigated using Pearson's hard and soft acids and bases (HSAB) concept with conceptual DFT reactivity indices, the Ziegler-Rauk-type energy-decomposition analysis, the natural orbital for chemical valence (NOCV) framework and the non-covalent interaction (NCI) index. It is found that the relative importance of electrostatic and orbital (charge transfer) interactions varies as a function of both the donor and acceptor molecules. Hard and soft interactions were distinguished and characterised by atomic charges, electrophilicity and local softness indices. Dual-descriptor plots indicate an orbital σ hole on the halogen similar to the electrostatic σ hole manifested in the molecular electrostatic potential. The predicted high halogen-bond-acceptor affinity of N-heterocyclic carbenes was evidenced in the highest complexation energy for the hitherto unknown CF(3) I·NHC complex. The dominant NOCV orbital represents an electron-density deformation according to a n→σ*-type interaction. The characteristic signal found in the reduced density gradient versus electron-density diagram corresponds to the non-covalent interaction between contact atoms in the NCI plots, which is the manifestation of halogen bonding within the NCI theory. The unexpected C-X bond strengthening observed in several cases was rationalised within the molecular orbital framework. PMID:23169478

  15. Decay of aftershock density with distance does not indicate triggering by dynamic stress.

    PubMed

    Richards-Dinger, Keith; Stein, Ross S; Toda, Shinji

    2010-09-30

    Resolving whether static or dynamic stress triggers most aftershocks and subsequent mainshocks is essential to understand earthquake interaction and to forecast seismic hazard. Felzer and Brodsky examined the distance distribution of earthquakes occurring in the first five minutes after 2 ≤ M < 3 and 3 ≤ M < 4 mainshocks and found that their magnitude M ≥ 2 aftershocks showed a uniform power-law decay with slope -1.35 out to 50 km from the mainshocks. From this they argued that the distance decay could be explained only by dynamic triggering. Here we propose an alternative explanation for the decay, and subject their hypothesis to a series of tests, none of which it passes. At distances more than 300 m from the 2 ≤ M < 3 mainshocks, the seismicity decay 5 min before the mainshocks is indistinguishable from the decay five minutes afterwards, indicating that the mainshocks have no effect at distances outside their static triggering range. Omori temporal decay, the fundamental signature of aftershocks, is absent at distances exceeding 10 km from the mainshocks. Finally, the distance decay is found among aftershocks that occur before the arrival of the seismic wave front from the mainshock, which violates causality. We argue that Felzer and Brodsky implicitly assume that the first of two independent aftershocks along a fault rupture triggers the second, and that the first of two shocks in a creep- or intrusion-driven swarm triggers the second, when this need not be the case.

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

    NASA Astrophysics Data System (ADS)

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

    2013-01-01

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

  17. Negative refraction and superconductivity

    NASA Astrophysics Data System (ADS)

    Amariti, Antonio; Forcella, Davide; Mariotti, Alberto; Siani, Massimo

    2011-10-01

    We discuss exotic properties of charged hydrodynamical systems, in the broken superconducting phase, probed by electromagnetic waves. Motivated by general arguments from hydrodynamics, we observe that negative refraction, namely the propagation in opposite directions of the phase velocities and of the energy flux, is expected for low enough frequencies. We corroborate this general idea by analyzing a holographic superconductor in the AdS/CFT correspondence, where the response functions can be explicitly computed. We study the dual gravitational theory both in the probe and in the backreacted case. We find that, while in the first case the refractive index is positive at every frequency, in the second case there is negative refraction at low enough frequencies. This is in agreement with hydrodynamic considerations.

  18. Negative refraction using Raman transitions and chirality

    SciTech Connect

    Sikes, D. E.; Yavuz, D. D.

    2011-11-15

    We present a scheme that achieves negative refraction with low absorption in far-off resonant atomic systems. The scheme utilizes Raman resonances and does not require the simultaneous presence of an electric-dipole transition and a magnetic-dipole transition near the same wavelength. We show that two interfering Raman tran-sitions coupled to a magnetic-dipole transition can achieve a negative index of refraction with low absorption through magnetoelectric cross-coupling. We confirm the validity of the analytical results with exact numerical simulations of the density matrix. We also discuss possible experimental implementations of the scheme in rare-earth metal atomic systems.

  19. Refraction corrections for surveying

    NASA Technical Reports Server (NTRS)

    Lear, W. M.

    1979-01-01

    Optical measurements of range and elevation angle are distorted by the earth's atmosphere. High precision refraction correction equations are presented which are ideally suited for surveying because their inputs are optically measured range and optically measured elevation angle. The outputs are true straight line range and true geometric elevation angle. The 'short distances' used in surveying allow the calculations of true range and true elevation angle to be quickly made using a programmable pocket calculator. Topics covered include the spherical form of Snell's Law; ray path equations; and integrating the equations. Short-, medium-, and long-range refraction corrections are presented in tables.

  20. Index of Refraction Measurements Using a Laser Distance Meter

    ERIC Educational Resources Information Center

    Ochoa, Romulo; Fiorillo, Richard; Ochoa, Cris

    2014-01-01

    We present a simple method to determine the refractive indices of transparent media using a laser distance meter. Indices of refraction have been obtained by measuring the speed of light in materials. Some speed of light techniques use time-of-flight measurements in which pulses are emitted by lasers and the time interval is measured for the pulse…

  1. Comparison of flow characteristics around refractive and right-angled groins in barotropic and baroclinic conditions

    NASA Astrophysics Data System (ADS)

    Omdehghiasi, Hamed; Mojtahedi, Alireza; Lotfollahi-Yaghin, Mohammad Ali

    2015-12-01

    Groins are employed to prevent nearshore areas from erosion and to control the direction of flow. However, the groin structure and its associated flow characteristics are the main causes of local erosion. In this study, we investigate the flow patterns around refractive and right-angle groins. In particular, we analytically compare the flow characteristics around a refractive groin and study the degree of accuracy that can be achieved by using a right-angle groin of various projected lengths. To compare the flow characteristics, we replaced the right-angle groin with an approximation of a refractive groin. This replacement had the least effect on the maximum velocity of flow in the channel. Moreover, we investigated the distribution of the density variables of temperature and salinity, and their effects on the flow characteristics around the right-angle groin. A comparison of the flow analysis results in baroclinic and barotropic conditions reveals that the flow characteristic values are very similar for both the refractive and right-angle groins. The geometry of the groin, i.e., right-angle or refractive, has little effect on the maximum speed to relative average speed. Apart from the angular separation, the arm length of the groin in downstream refractive groins has less effect on other flow characteristics than do upstream refractive groins. We also correlated a number of non-dimensional variables with respect to various flow characteristics and groin geometry. These comparisons indicate that the correlation between the thalweg height and width of the channel and groin arm's length to projection length have been approximated using linear and nonlinear formulas regardless of inner velocity in the subcritical flow.

  2. Refraction corrections for surveying

    NASA Technical Reports Server (NTRS)

    Lear, W. M.

    1980-01-01

    Optical measurements of range and elevation angles are distorted by refraction of Earth's atmosphere. Theoretical discussion of effect, along with equations for determining exact range and elevation corrections, is presented in report. Potentially useful in optical site surveying and related applications, analysis is easily programmed on pocket calculator. Input to equation is measured range and measured elevation; output is true range and true elevation.

  3. Conceptualization of Light Refraction

    ERIC Educational Resources Information Center

    Sokolowski, Andrzej

    2013-01-01

    There have been a number of papers dealing quantitatively with light refraction. Yet the conceptualization of the phenomenon that sets the foundation for a more rigorous math analysis is minimized. The purpose of this paper is to fill that gap. (Contains 3 figures.)

  4. Perfect imaging with positive refraction

    NASA Astrophysics Data System (ADS)

    Leonhardt, Ulf; Tyc, Tomáš; Danner, Aaron

    2010-10-01

    We present several refractive index profiles for perfect imaging with positive refraction other than Maxwell's fish eye. Numerical simulations show that these profiles may transfer images with, in principle, unlimited resolution. Such profiles could overcome the fundamental limitations of perfect imaging with negative refraction and find practical applications in nanolithography.

  5. Effect of dietary probiotic and high stocking density on the performance, carcass yield, gut microflora, and stress indicators of broilers.

    PubMed

    Cengiz, Özcan; Köksal, Bekir H; Tatlı, Onur; Sevim, Ömer; Ahsan, Umair; Üner, Aykut G; Ulutaş, Pınar A; Beyaz, Devrim; Büyükyörük, Sadık; Yakan, Akın; Önol, Ahmet G

    2015-10-01

    A study was carried out to evaluate the effect of dietary probiotic supplementation and stocking density on the performance, relative carcass yield, gut microflora, and stress markers of broilers. One-day-old Ross 308 male broiler chickens (n = 480) were allocated to 4 experimental groups for 42 d. Each treatment had 8 replicates of 15 chicks each. Two groups were subjected to a high stocking density (HSD) of 20 birds/m² and the other 2 groups were kept at low stocking density (LSD) of 10 birds/m². A basal diet supplemented with probiotic 1 and 0.5 g/kg of diet (in starter and finisher diets, respectively) was fed to 2 treatments, one with HSD and the other with LSD, thereby making a 2 × 2 factorial arrangement. There was no interaction between stocking density (LSD and HSD) and dietary probiotic (supplemented and unsupplemented) for all the variables. Feed intake and weight gain were significantly low and feed conversion ratio was poor in broilers at HSD. Dietary probiotic significantly enhanced the feed intake and weight gain in starter phase only. Dietary probiotic supplementation had no effect (P > 0.05) on total aerobs, Salmonella sp., and Lactobacilli populations in the intestines of broilers. However, HSD reduced the Lactobacilli population only (P < 0.05). Relative breast yields were significantly higher in broilers reared at LSD than HSD. Thigh meat yield was higher in broilers in HSD group compared to LSD. Dietary probiotic did not affect the relative carcass yield and weight of lymphoid organs. Serum malondialdehyde, corticosterone, nitric oxide, and plasma heterophil:lymphocyte ratio were not affected either by stocking density or dietary probiotic supplementation. In conclusion, HSD negatively affected the performance and intestinal Lactobacilli population of broilers only, whereas probiotic supplementation enhanced the performance of broilers during the starter phase only. Total aerobes, Salmonella, Lactobacilli carcass yield, and stress indicators

  6. Theoretical schemes for negative refraction and enhanced refractive index in atomic systems

    NASA Astrophysics Data System (ADS)

    Sikes, Daniel E.

    In this thesis we present a scheme for negative refraction in atomic systems. Negative refraction was predicted over 4 decades ago and recently experimentally demonstrated in the field of metamaterials. We seek a new approach for negative refraction using laser driven transition resonances in atomic systems. By utilizing atomic resonances we hope to achieve negative refraction in short wavelength regimes, such as visible and ultra-violet, and eliminate absorption by quantum interference. This scheme is based on the experimentally demonstrated "refractive index enhancement with vanishing absorption" technique, in which closely spaced absorptive and amplifying transitions are interfered. Our scheme utilizes Raman transitions and is able to drive an electric resonance while far-detuned from an electric-dipole transition. This far-off resonance feature allows our scheme to be adaptable to various atomic energy level structures, in that it does not require the simultaneous presence of an electric-dipole and a magnetic-dipole transition near the same wavelength. We show that two interfering Raman transitions coupled to a magnetic-dipole transition can achieve a negative index of refraction with low absorption through magnetoelectric cross coupling. Analytical predictions have been made for a model atomic system and their validity has been confirmed with exact numerical simulations of the density matrix. We consider possible experimental implementations of the scheme in rare-earth atomic systems, such as ultracold vapors and doped crystals. We also discuss applications of negative and enhanced refractive index for imaging. A fundamental challenge of imaging systems is the diffraction limit, which causes spatial features of an object smaller than the light wavelength to be lost in the image. Achieving negative refraction with vanishing absorption is important for near-perfect imaging systems based on Pendry's suggestion for a negative index perfect lens. A perfect lens is

  7. Fermat's principle and the formal equivalence of local light-ray rotation and refraction at the interface between homogeneous media with a complex refractive index ratio.

    PubMed

    Sundar, Bhuvanesh; Hamilton, Alasdair C; Courtial, Johannes

    2009-02-01

    We derive a formal description of local light-ray rotation in terms of complex refractive indices. We show that Fermat's principle holds, and we derive an extended Snell's law. The change in the angle of a light ray with respect to the normal of a refractive index interface is described by the modulus of the refractive index ratio; the rotation around the interface normal is described by the argument of the refractive index ratio. PMID:19183663

  8. Water quality, weather and environmental factors associated with fecal indicator organism density in beach sand at two recreational marine beaches.

    PubMed

    Heaney, Christopher D; Exum, Natalie G; Dufour, Alfred P; Brenner, Kristen P; Haugland, Richard A; Chern, Eunice; Schwab, Kellogg J; Love, David C; Serre, Marc L; Noble, Rachel; Wade, Timothy J

    2014-11-01

    Recent studies showing an association between fecal indicator organisms (FIOs) in sand and gastrointestinal (GI) illness among beachgoers with sand contact have important public health implications because of the large numbers of people who recreate at beaches and engage in sand contact activities. Yet, factors that influence fecal pollution in beach sand remain unclear. During the 2007 National Epidemiological and Environmental Assessment of Recreational (NEEAR) Water Study, sand samples were collected at three locations (60 m apart) on weekend days (Sat, Sun) and holidays between June and September at two marine beaches - Fairhope Beach, AL and Goddard Beach, RI - with nearby publicly-owned treatment works (POTWs) outfalls. F(+) coliphage, enterococci, Bacteroidales, fecal Bacteroides spp., and Clostridium spp. were measured in sand using culture and qPCR-based calibrator-cell equivalent methods. Water samples were also collected on the same days, times and transects as the 144 sand samples and were assayed using the same FIO measurements. Weather and environmental data were collected at the time of sample collection. Mean FIO concentrations in sand varied over time, but not space. Enterococci CFU and CCE densities in sand were not correlated, although other FIOs in sand were. The strongest correlation between FIO density in sand and water was fecal Bacteroides CCE, followed by enterococci CFU, Clostridium spp. CCE, and Bacteroidales CCE. Overall, the factors associated with FIO concentrations in sand were related to the sand-water interface (i.e., sand-wetting) and included daily average densities of FIOs in water, rainfall, and wave height. Targeted monitoring that focuses on daily trends of sand FIO variability, combined with information about specific water quality, weather, and environmental factors may inform beach monitoring and management decisions to reduce microbial burdens in beach sand. The views expressed in this paper are those of the authors and do

  9. Water quality, weather and environmental factors associated with fecal indicator organism density in beach sand at two recreational marine beaches

    PubMed Central

    Heaney, Christopher D.; Exum, Natalie G.; Dufour, Alfred P.; Brenner, Kristen P.; Haugland, Richard A.; Chern, Eunice; Schwab, Kellogg J.; Love, David C.; Serre, Marc L.; Noble, Rachel; Wade, Timothy J.

    2015-01-01

    Recent studies showing an association between fecal indicator organisms (FIOs) in sand and gastrointestinal (GI) illness among beachgoers with sand contact have important public health implications because of the large numbers of people who recreate at beaches and engage in sand contact activities. Yet, factors that influence fecal pollution in beach sand remain unclear. During the 2007 National Epidemiological and Environmental Assessment of Recreational (NEEAR) Water Study, sand samples were collected at three locations (60 m apart) on weekend days (Sat, Sun) and holidays between June and September at two marine beaches — Fairhope Beach, AL and Goddard Beach, RI — with nearby publicly-owned treatment works (POTWs) outfalls. F+ coliphage, enterococci, Bacteroidales, fecal Bacteroides spp., and Clostridium spp. were measured in sand using culture and qPCR-based calibrator-cell equivalent methods. Water samples were also collected on the same days, times and transects as the 144 sand samples and were assayed using the same FIO measurements. Weather and environmental data were collected at the time of sample collection. Mean FIO concentrations in sand varied over time, but not space. Enterococci CFU and CCE densities in sand were not correlated, although other FIOs in sand were. The strongest correlation between FIO density in sand and water was fecal Bacteroides CCE, followed by enterococci CFU, Clostridium spp. CCE, and Bacteroidales CCE. Overall, the factors associated with FIO concentrations in sand were related to the sand–water interface (i.e., sand-wetting) and included daily average densities of FIOs in water, rainfall, and wave height. Targeted monitoring that focuses on daily trends of sand FIO variability, combined with information about specific water quality, weather, and environmental factors may inform beach monitoring and management decisions to reduce microbial burdens in beach sand. The views expressed in this paper are those of the authors

  10. How Common are Refractive Effects in Pulsar Scintillation?

    NASA Astrophysics Data System (ADS)

    Stinebring, D. R.; Hole, K.; Foster, S. R.

    1998-05-01

    Refractive effects have been noticed in pulsar observations for more than twenty years, although they have not always been identified as such. These effects include pulsar flux variations on time scales of days to years, tilted scintles and fringe patterns in dynamic spectra, and elongation of VLBI images of pulsars. Of particular interest are those phenomena, such as fringing or multiple-imaging, that indicate an excess of fluctuation power at the refractive size scale compared to that expected from a Kolmogorov extrapolation from the diffractive size scale. The frequency of occurrence of such events has not been well characterized. Recently, Rickett, Lyne, and Gupta (1997, MNRAS, 287, 739) underscored the remarkable sensitivity of dynamic spectra observations for probing multiple-imaging effects. They found an instance of multiple imaging in which the flux density from the secondary ray path was only 0.0016 times the flux density of the primary ray path, and the separation between the ray directions was more than 10 times larger than the diffractive image size! How prevalent are such remarkable events? We have applied a similar secondary spectrum analysis to a data set of dynamic spectra obtained by one of us (RSF) in 1991-92 at the NRAO 42-m telescope. A total of 22 pulsars were observed at 8 quarterly epochs over these two years at both 800 MHz and 1330 MHz. We have analyzed these data paying particular attention to weak features in the secondary spectra. We will present the results of this analysis in an effort to quantify how often strong refractive effects are present in pulsar scintillation data.

  11. Evaluation of a quantitative structure-property relationship (QSPR) for predicting mid-visible refractive index of secondary organic aerosol (SOA).

    PubMed

    Redmond, Haley; Thompson, Jonathan E

    2011-04-21

    In this work we describe and evaluate a simple scheme by which the refractive index (λ = 589 nm) of non-absorbing components common to secondary organic aerosols (SOA) may be predicted from molecular formula and density (g cm(-3)). The QSPR approach described is based on three parameters linked to refractive index-molecular polarizability, the ratio of mass density to molecular weight, and degree of unsaturation. After computing these quantities for a training set of 111 compounds common to atmospheric aerosols, multi-linear regression analysis was conducted to establish a quantitative relationship between the parameters and accepted value of refractive index. The resulting quantitative relationship can often estimate refractive index to ±0.01 when averaged across a variety of compound classes. A notable exception is for alcohols for which the model consistently underestimates refractive index. Homogenous internal mixtures can conceivably be addressed through use of either the volume or mole fraction mixing rules commonly used in the aerosol community. Predicted refractive indices reconstructed from chemical composition data presented in the literature generally agree with previous reports of SOA refractive index. Additionally, the predicted refractive indices lie near measured values we report for λ = 532 nm for SOA generated from vapors of α-pinene (R.I. 1.49-1.51) and toluene (R.I. 1.49-1.50). We envision the QSPR method may find use in reconstructing optical scattering of organic aerosols if mass composition data is known. Alternatively, the method described could be incorporated into in models of organic aerosol formation/phase partitioning to better constrain organic aerosol optical properties.

  12. Urban aerosol refractive index prediction by partial molar refraction approach

    SciTech Connect

    Stelson, A.W. )

    1990-11-01

    The ambient aerosol of the polluted troposphere is a complex mixture of water, electrolytes, ionic solids, metal oxides and glasses, and carbonaceous material. Prediction of the refractive indexes of these inhomogeneous mixtures can be a formidable task. Contained within this paper is the necessary parameterization to estimate the mean real aerosol refractive index based on aerosol chemical composition and the partial molar refraction approach. This approach assumes all chemical constituents are homogeneously distributed throughout the aerosol phase. Consistency of the data is discussed, and this approach is verified by prediction of refractive indexes of NaOH-Si-O{sub 2}-H{sub 2}O mixtures. Finally, aerosol chemical composition data from the Los Angeles Basin are used to predict mean real aerosol refractive indexes. These values are compared to urban aerosol refractive indexes calculated via other techniques (light scattering).

  13. Mechanism of the photoinduced refractive index increase in polymethyl methacrylate.

    PubMed

    Bowden, M J; Chandross, E A; Kaminow, I P

    1974-01-01

    Polymethyl methacrylate prepared under special circumstances exhibits a substantial increase in refractive index after irradiation with uv light. The essential step in the preparation is peroxidation of the monomer prior to polymerization. This increase in refractive index results from a photoinduced polymerization of unreacted monomer (1-2%) within the film which produces an increase in density (and hence refractive index) in the irradiated region. It is believed that peroxides, both polymeric and monomeric, act as photoinitiators. Sensitivity depends on the concentration of photoinitiator, but the absolute value of Deltan depends on the amount of unreacte monomer.

  14. Traffic air pollution and lung cancer in females in Taiwan: petrol station density as an indicator of disease development.

    PubMed

    Chang, Chih-Ching; Tsai, Shang-Shyue; Chiu, Hui-Fen; Wu, Trong-Neng; Yang, Chun-Yuh

    2009-01-01

    To investigate the relationship between traffic air pollution exposure and development of lung cancer in females, studies were conducted using a matched cancer case-control model into deaths that occurred in Taiwan from 1997 through 2006. Data on all eligible lung cancer deaths in females were obtained from the Bureau of Vital Statistics of the Taiwan Provincial Department of Health. The control group consisted of women who died from causes other than neoplasms or diseases that were associated with respiratory problems. The controls were pair matched to the cancer cases by year of birth and year of death. Each matched control was selected randomly from the set of possible controls for each case. Data on the number of petrol stations in study municipalities were collected from the two major petroleum supply companies, Chinese Petroleum Corporation (CPC) and Formosa Petrochemical Corporation (FPCC). The petrol station density (per square kilometer; PSD) for study municipalities was used as an indicator of a subject's exposure to benzene and other hydrocarbons present in ambient evaporative losses of petrol or to air emissions from motor vehicles. The subjects were divided into tertiles according to PSD in their residential municipality. The results showed that there was a significant exposure-response relationship between PSD and risk of lung cancer in females after controlling for possible confounders. The findings of this study warrant further investigation of the role of traffic air pollution exposure in the etiology of lung cancer. PMID:19308850

  15. Colored Flag by Double Refraction.

    ERIC Educational Resources Information Center

    Reid, Bill

    1994-01-01

    Describes various demonstrations that illustrate double refraction and rotation of the plane of polarization in stressed, transparent plastics, with the consequent production of colored designs. (ZWH)

  16. Real-space indicators for chemical bonding. Experimental and theoretical electron density studies of four deltahedral boranes.

    PubMed

    Mebs, Stefan; Kalinowski, Roman; Grabowsky, Simon; Förster, Diana; Kickbusch, Rainer; Justus, Eugen; Morgenroth, Wolfgang; Paulmann, Carsten; Luger, Peter; Gabel, Detlef; Lentz, Dieter

    2011-01-01

    In an approach combining high-resolution X-ray diffraction at low temperatures with density functional theory calculations, two closo-borates, B(12)H(12)(2-) (1) and B(10)H(10)(2-) (2), and two arachno-boranes, B(10)H(12)L(2) [L = amine (3) or acetonitrile (4)], were analyzed by means of the atoms-in-molecules (AIM) theory and electron localizability indicator (ELI-D). The two-electron three-center (2e3c) bonds of the borane cages are investigated with the focus on real-space indicators for chemical bonding and electron delocalization. In compound 2, only two of the three expected bond critical points (bcp's) are found. However, a weakly populated ELI-D basin is found for this pair of adjacent B atoms and the delocalization index and the Source contributions are on the same order of magnitude as those for the other pairs. The opposite situation is found in the arachno-boranes, where no ELI-D basins are found for two types of B-B pairs, which, in turn, exhibit a bcp. However, again the delocalization index is on the same order of magnitude for this bonding interaction. The results show that an unambiguous real-space criterion for chemical bonding is not given yet for this class of compounds. The arachno-boranes carry a special B-B bond, which is the edge of the crown-shaped molecule. This bond is very long and extremely curved inward the B-B-B ring. Nevertheless, the corresponding bond ellipticity is quite small and the ELI-D value at the attractor position of the disynaptic valence basin is remarkably larger than those for all other B-B valence basins. Furthermore, the value of the ED is large in relation to the B-B bond length, so that only this bond type does not follow a linear relationship of the ED value at the bcp versus B-B bond distances, which is found for all other B-B bcp's. The results indicate that both 2e2c and 2e3c bonding play a distinct role in borane chemistry. PMID:21114266

  17. CHARMS: The Cryogenic, High-Accuracy Refraction Measuring System

    NASA Technical Reports Server (NTRS)

    Frey, Bradley; Leviton, Douglas

    2004-01-01

    The success of numerous upcoming NASA infrared (IR) missions will rely critically on accurate knowledge of the IR refractive indices of their constituent optical components at design operating temperatures. To satisfy the demand for such data, we have built a Cryogenic, High-Accuracy Refraction Measuring System (CHARMS), which, for typical 1R materials. can measure the index of refraction accurate to (+ or -) 5 x 10sup -3 . This versatile, one-of-a-kind facility can also measure refractive index over a wide range of wavelengths, from 0.105 um in the far-ultraviolet to 6 um in the IR, and over a wide range of temperatures, from 10 K to 100 degrees C, all with comparable accuracies. We first summarize the technical challenges we faced and engineering solutions we developed during the construction of CHARMS. Next we present our "first light," index of refraction data for fused silica and compare our data to previously published results.

  18. Perfect imaging without refraction?

    NASA Astrophysics Data System (ADS)

    Blaikie, R. J.

    2011-12-01

    Recent work suggesting that ‘perfect’ far-field imaging is possible using Maxwell's fish-eye lens (Leonhardt 2009 New J. Phys. 11 093040) has raised a number of questions and controversies about the nature of imaging and field localization in inhomogeneous media. In this brief paper we present analogous results for a purely reflector-based imaging system—an elliptical cavity. With a source at one focus of the ellipse we show that sub-wavelength field localization can be achieved at the other focus when an active ‘drain’ is present there, but not without it. Does this show that far-field ‘perfect’ imaging is possible even without refraction (negative or positive)? Unfortunately not, giving further evidence that these are solely drain-induced effects.

  19. GRAVSAT/GEOPAUSE refraction study

    NASA Technical Reports Server (NTRS)

    Llewellyn, S. K.

    1977-01-01

    A ground station network tracked a high altitude spacecraft which in turn tracked a low orbiting satellite. Orbit data are relayed back to the ground stations. A refraction study was performed on this configuration to compute ionospheric and tropospheric refraction effects along the satellite and ground links.

  20. An 'electromagnetic wiggler' originating from refraction of waves at the side edge of a Bragg reflector

    NASA Astrophysics Data System (ADS)

    Iorsh, I. V.; Kaliteevski, M. A.; Brand, S.; Abram, R. A.; Kaliteevskaya, N. A.

    2011-05-01

    Calculations are reported which predict that light incident on the side edge of a Bragg reflector can show varied and unusual refraction behaviour, including a rapid transition from positive to negative refraction. Although under certain conditions negative refraction can occur, it is concluded that perfect lensing based on it is unlikely to be realised in practice. However, it is shown that light incident obliquely on the structure can be made to propagate normal to the interface after refraction while exhibiting lateral oscillations of its Poynting vector, an effect that could possibly find application in an 'electromagnetic wiggler'. It is also shown that negative group velocity rather than negative effective mass is required for the observation of the negative refraction, and in the case of low refractive index contrast, negative refraction occurs only when the size of the illumination spot exceeds a critical value, which is inversely proportional to the contrast of the refractive indices.

  1. Comparison of capture-recapture and visual count indices of prairie dog densities in black-footed ferret habitat

    USGS Publications Warehouse

    Fagerstone, Kathleen A.; Biggins, Dean E.

    1986-01-01

    Black-footed ferrets (Mustela nigripes) are dependent on prairie dogs (Cynomys spp.) for food and on their burrows for shelter and rearing young. A stable prairie dog population may therefore be the most important factor determining the survival of ferrets. A rapid method of determining prairie dog density would be useful for assessing prairie dog density in colonies currently occupied by ferrets and for selecting prairie dog colonies in other areas for ferret translocation. This study showed that visual counts can provide a rapid density estimate. Visual counts of white-tailed prairie dogs (Cynomys leucurus) were significantly correlated (r = 0.95) with mark-recapture population density estimates on two study areas near Meeteetse, Wyoming. Suggestions are given for use of visual counts.

  2. The inverse problem of refraction travel times, part II: Quantifying refraction nonuniqueness using a three-layer model

    USGS Publications Warehouse

    Ivanov, J.; Miller, R.D.; Xia, J.; Steeples, D.

    2005-01-01

    . Insufficient a priori information during the inversion is the reason why refraction methods often may not produce desired results or even fail. This work also demonstrates that the application of the smoothing constraints, typical when solving ill-posed inverse problems, has a dual and contradictory role when applied to the ill-posed inverse problem of refraction travel times. This observation indicates that smoothing constraints may play such a two-fold role when applied to other inverse problems. Other factors that contribute to inverse-refraction-problem nonuniqueness are also considered, including indeterminacy, statistical data-error distribution, numerical error and instability, finite data, and model parameters. ?? Birkha??user Verlag, Basel, 2005.

  3. The effects of measurement error on previously reported mathematical relationships between indicator organism density and swimming-associated illness: a quantitative estimate of the resulting bias.

    PubMed

    Fleisher, J M

    1990-12-01

    Several recent epidemiological studies seeking associations between swimming in recreational waters contaminated with domestic sewage and increased illness among such swimmers have reported mathematical relationships relating indicator organism densities to illness among swimmers. Common to the design of all of these studies is the failure to adequately control for large amounts of measurement error contained in estimates of exposure, i.e. estimated indicator organism densities. The limited precision of current methods of indicator organism enumeration, coupled with temporal and spacial variation in indicator organism densities at the locations studied, are responsible for a substantial portion of this measurement error. The failure to control adequately for these sources of measurement error has resulted in a significant amount of bias being present in the mathematical relationships reported by these previously published epidemiological studies. In order to explore the magnitude and direction of this bias, computer simulations were conducted using data in which estimation of indicator organism density was obtained by the two most widely used techniques of enumeration: the Multiple Tube Fermentation Technique and the Membrane Filtration Technique. The results of the computer simulations show that the bias caused by this measurement error is non-differential causing the mathematical relationships between indicator organism density and swimming-associated illness reported in previous epidemiological studies to underestimate true risk by a minimum of approximately 14%, and that this underestimate could range as high as approximately 30 to 57%. This study also demonstrates that substantial reduction of this bias can be easily accomplished by incorporating a formal water quality sampling strategy, based on statistical principles of experimental design and analysis, into the design of future epidemiological studies seeking mathematical relationships between indicator

  4. Acoustical Imaging with Negative Refraction

    NASA Astrophysics Data System (ADS)

    Gan, W. S.

    It is well known that the resolution limit of acoustical images is limited by diffraction to λ/2 where λ is the sound wavelength. Negative refraction proposed by Veselago in 1968 shows possibility of defeating the diffraction limit. His work is for electromagnetic waves. Recently it has been shown experimentally that negative refraction can be achieved for both electromagnetic waves and sound waves by using photonic crystals and phononic crystals respectively. John Pendry proposed the concept of `perfect lens' using negative refraction for electromagnetic waves. In this paper, we propose a `perfect lens' for sound waves and an acoustical imaging system incorporating the `perfect lens' is also outlined

  5. Photoresist Exposure Parameter Extraction from Refractive Index Change during Exposure

    NASA Astrophysics Data System (ADS)

    Sohn, Young-Soo; Sung, Moon-Gyu; Lee, Young-Mi; Lee, Eun-Mi; Oh, Jin-Kyung; Byun, Sung-Hwan; Jeong, Yeon-Un; Oh, Hye-Keun; An, Ilsin; Lee, Kun-Sang; Park, In-Ho; Cho, Joon-Yeon; Lee, Sang-Ho

    1998-12-01

    The refractive indices of photoresist are usually measured byan ellipsometer or spectrophotometer, but the values are limited to pre-exposure. It is known thatthe real and imaginary indices are changed during the exposure.But there is little report on these variations since itis difficult to measure this refractive index change at deep ultraviolet. The DillABC parameters show a significant variation with the resist and substrate thicknessas well as the experimental conditions.A method is suggested to extract the parameters from the refractive index changes.We can get the refractive index change and extract the Dill ABC exposure parameters from that.The multiple thin film interference calculation is used to fit the measured transmittance data.The results of our experiments and calculations for several resists including193 nm chemically amplified resists are compared with other methods.The results are agreed well with the full multilayer thin film simulation.

  6. Dielectric Optical-Controllable Magnifying Lens by Nonlinear Negative Refraction

    PubMed Central

    Cao, Jianjun; Shang, Ce; Zheng, Yuanlin; Feng, Yaming; Chen, Xianfeng; Liang, Xiaogan; Wan, Wenjie

    2015-01-01

    A simple optical lens plays an important role for exploring the microscopic world in science and technology by refracting light with tailored spatially varying refractive indices. Recent advancements in nanotechnology enable novel lenses, such as, superlens and hyperlens, with sub-wavelength resolution capabilities by specially designed materials’ refractive indices with meta-materials and transformation optics. However, these artificially nano- or micro-engineered lenses usually suffer high losses from metals and are highly demanding in fabrication. Here, we experimentally demonstrate, for the first time, a nonlinear dielectric magnifying lens using negative refraction by degenerate four-wave mixing in a plano-concave glass slide, obtaining magnified images. Moreover, we transform a nonlinear flat lens into a magnifying lens by introducing transformation optics into the nonlinear regime, achieving an all-optical controllable lensing effect through nonlinear wave mixing, which may have many potential applications in microscopy and imaging science. PMID:26149952

  7. Dielectric Optical-Controllable Magnifying Lens by Nonlinear Negative Refraction.

    PubMed

    Cao, Jianjun; Shang, Ce; Zheng, Yuanlin; Feng, Yaming; Chen, Xianfeng; Liang, Xiaogan; Wan, Wenjie

    2015-01-01

    A simple optical lens plays an important role for exploring the microscopic world in science and technology by refracting light with tailored spatially varying refractive indices. Recent advancements in nanotechnology enable novel lenses, such as, superlens and hyperlens, with sub-wavelength resolution capabilities by specially designed materials' refractive indices with meta-materials and transformation optics. However, these artificially nano- or micro-engineered lenses usually suffer high losses from metals and are highly demanding in fabrication. Here, we experimentally demonstrate, for the first time, a nonlinear dielectric magnifying lens using negative refraction by degenerate four-wave mixing in a plano-concave glass slide, obtaining magnified images. Moreover, we transform a nonlinear flat lens into a magnifying lens by introducing transformation optics into the nonlinear regime, achieving an all-optical controllable lensing effect through nonlinear wave mixing, which may have many potential applications in microscopy and imaging science. PMID:26149952

  8. Dielectric Optical-Controllable Magnifying Lens by Nonlinear Negative Refraction

    NASA Astrophysics Data System (ADS)

    Cao, Jianjun; Shang, Ce; Zheng, Yuanlin; Feng, Yaming; Chen, Xianfeng; Liang, Xiaogan; Wan, Wenjie

    2015-07-01

    A simple optical lens plays an important role for exploring the microscopic world in science and technology by refracting light with tailored spatially varying refractive indices. Recent advancements in nanotechnology enable novel lenses, such as, superlens and hyperlens, with sub-wavelength resolution capabilities by specially designed materials’ refractive indices with meta-materials and transformation optics. However, these artificially nano- or micro-engineered lenses usually suffer high losses from metals and are highly demanding in fabrication. Here, we experimentally demonstrate, for the first time, a nonlinear dielectric magnifying lens using negative refraction by degenerate four-wave mixing in a plano-concave glass slide, obtaining magnified images. Moreover, we transform a nonlinear flat lens into a magnifying lens by introducing transformation optics into the nonlinear regime, achieving an all-optical controllable lensing effect through nonlinear wave mixing, which may have many potential applications in microscopy and imaging science.

  9. Is the decrease of the total electron energy density a covalence indicator in hydrogen and halogen bonds?

    PubMed

    Angelina, Emilio L; Duarte, Darío J R; Peruchena, Nélida M

    2013-05-01

    In this work, halogen bonding (XB) and hydrogen bonding (HB) complexes were studied with the aim of analyzing the variation of the total electronic energy density H(r b ) with the interaction strengthening. The calculations were performed at the MP2/6-311++G(2d,2p) level of approximation. To explain the nature of such interactions, the atoms in molecules theory (AIM) in conjunction with reduced variational space self-consistent field (RVS) energy decomposition analysis were carried out. Based on the local virial theorem, an equation to decompose the total electronic energy density H(r b ) in two energy densities, (-G(r b )) and 1/4∇(2)ρ(r b ), was derived. These energy densities were linked with the RVS interaction energy components. Through the connection between both decomposition schemes, it was possible to conclude that the decrease in H(r b ) with the interaction strengthening observed in the HB as well as the XB complexes, is mainly due to the increase in the attractive electrostatic part of the interaction energy and in lesser extent to the increase in its covalent character, as is commonly considered. PMID:23187685

  10. Is the decrease of the total electron energy density a covalence indicator in hydrogen and halogen bonds?

    PubMed

    Angelina, Emilio L; Duarte, Darío J R; Peruchena, Nélida M

    2013-05-01

    In this work, halogen bonding (XB) and hydrogen bonding (HB) complexes were studied with the aim of analyzing the variation of the total electronic energy density H(r b ) with the interaction strengthening. The calculations were performed at the MP2/6-311++G(2d,2p) level of approximation. To explain the nature of such interactions, the atoms in molecules theory (AIM) in conjunction with reduced variational space self-consistent field (RVS) energy decomposition analysis were carried out. Based on the local virial theorem, an equation to decompose the total electronic energy density H(r b ) in two energy densities, (-G(r b )) and 1/4∇(2)ρ(r b ), was derived. These energy densities were linked with the RVS interaction energy components. Through the connection between both decomposition schemes, it was possible to conclude that the decrease in H(r b ) with the interaction strengthening observed in the HB as well as the XB complexes, is mainly due to the increase in the attractive electrostatic part of the interaction energy and in lesser extent to the increase in its covalent character, as is commonly considered.

  11. Complex refractive index of starch acetate used as a biodegradable pigment and filler of paper

    NASA Astrophysics Data System (ADS)

    Karvinen, Petri; Oksman, Antti; Silvennoinen, Raimo; Mikkonen, Hannu

    2007-05-01

    Complex refractive index of strongly depolarizing starch acetate is investigated as a function of bulk package density, which is compulsory parameter in analysis of light scattering from nanoscale starch acetate pigments and fillers. The measurements were made using a laser-goniometer and spectrophotometer to gain data for refractive index analysis according to the Brewster's law and Fresnel equations. The real part of refractive index was verified by microscopic immersion method.

  12. Designing refractive beam shapers via aberration theory

    NASA Astrophysics Data System (ADS)

    Laskin, Alexander; Shealy, David

    2014-10-01

    In this paper, we use aberration theory to design a refractive laser beam shaper in the configuration of two-aspheric lenses, whose analytical equations are known, but rather complicated. Specifically, we use results from third order aberration theory to obtain the parameters of the refracting laser beam shaper from the transverse aberration, which are then used as a starting point for further optimization by using optical design software. This approach was developed during the beginning of the twentieth century, works well for systems with a low numerical aperture, and allows one to define the following parameters of an optical system: radii of curvature, indices of refraction, thicknesses or air gaps, and conic constants of second order aspheric surfaces. We shall consider surfaces of the second-order spherical and conic sections and shall consider the example of designing of a two-lens beam shaper of the Keplerian 1-to-1 telescopic design providing a theoretical flat phase front and a flat-top irradiance profile of the output beam, where the ray mapping function from the input aperture to the output aperture is known from the literature. Explicit expression for third order longitudinal aberration and the Seidel coefficients are expressed in terms beam waist and input beam geometrical parameter, indices, lens radii and conic constants.

  13. Transverse chromatic aberration after corneal refractive surgery

    NASA Astrophysics Data System (ADS)

    Anera, R. G.; Jiménez, J. R.; Jiménez del Barco, L.; Hita, E.

    2005-05-01

    An expression has been deduced theoretically from a schematic-eye model, for the transverse or lateral chromatic aberration (TCA) after refractive surgery. The aim was to investigate analytically how chromatic aberration varies after the emmetropization process. These changes in the TCA have been characterized from changes in corneal asphericity. The results indicate that TCA after refractive surgery diminishes as the degree of myopia increases, a trend contrary to that occurring with monochromatic aberrations, such as spherical or coma. These results can explain the fact that the real deterioration of the visual function under photopic conditions detected in those operated on for myopia is less than expected when only monochromatic aberrations are taken into account.

  14. Optical electronegativity and refractive index of materials

    NASA Astrophysics Data System (ADS)

    Reddy, R. R.; Nazeer Ahammed, Y.; Rama Gopal, K.; Raghuram, D. V.

    1998-05-01

    Simple correlations between the energy gap, optical electronegativity and the refractive index are given for various classes of materials such as semiconductors, insulators and oxides. There has been no report in the literature on the direct estimation of optical electronegativity for the wide variety of materials using energy gap values. The present method performance is compared with Moss and Ravindra's relationships. A simple analysis on the average percentage deviation for low and high n value materials is also presented. The average percentage deviation in the present approach reveals that the method proposed proves its identity and soundness compared to that of Moss and Ravindra's relationships. A good agreement is observed between the computed and literature values of refractive indices.

  15. Nonlinear refraction in vitreous humor.

    PubMed

    Rockwell, B A; Roach, W P; Rogers, M E; Mayo, M W; Toth, C A; Cain, C P; Noojin, G D

    1993-11-01

    We extend the application of the z-scan technique to determine the nonlinear refractive index (n(2)) for human and rabbit vitreous humor, water, and physiological saline. In these measurements there were nonlinear contributions to the measured signal from the aqueous samples and the quartz cell that held the sample. Measurements were made with 60-ps pulses at 532 nm. To our knowledge, this is the first measurement of the nonlinear refractive properties of biological material. PMID:19829406

  16. Spatial variation in density and size structure indicate habitat selection throughout life stages of two Southwestern Atlantic snappers.

    PubMed

    Aschenbrenner, Alexandre; Hackradt, Carlos Werner; Ferreira, Beatrice Padovani

    2016-02-01

    The early life history of Lutjanus alexandrei and Lutjanus jocu in Southwestern Atlantic is still largely unknown. Habitat use of different life stages (i.e. size categories and densities) of the Brazilian snapper (L. alexandrei) and dog snapper (L. jocu) was examined in a tropical portion of NE coast of Brazil. Visual surveys were conducted in different shallow habitats (mangroves and reefs). Both snapper species showed higher densities in early life stages in mangrove habitat, with a clear increase in fish size from mangrove to adjacent reefs. Post-settler individuals were exclusively found in mangroves for both species. Juveniles of L. alexandrei were also registered only in mangroves, while sub-adult individuals were associated with both mangrove and reef habitats. Mature individuals of L. alexandrei were only observed in reef habitats. Juvenile and sub-adult individuals of the dog snapper were both associated with mangrove and reef habitats, with high densities registered in mangroves. Mature individuals of L. jocu were not registered in the study area. This pattern suggests preference for mangrove habitat in early life stages for both species. Ontogenetic movement between habitats was also recorded. This pattern denotes habitat selection across different life cycle of both species. Such information highlights the importance of directing management and conservation efforts to these habitats to secure the continuity of contribution to adult populations.

  17. Plasmas with index of refraction greater than one

    SciTech Connect

    Nilsen, J; Scofield, J H

    2004-06-23

    Over the last decade, X-ray lasers in the wavelength range14 - 47 nm have been used to do interferometry of plasmas. Just as for optical interferometry of plasmas, the experimental analysis assumed that the index of refraction is due only to the free electrons. This makes the index of refraction less then one. Recent experiments in Al plasmas have observed fringe lines bend the wrong way as though the electron density is negative. We show how the bound electrons can dominate the index of refraction in many plasmas and make the index greater than one or enhance the index such that one would greatly overestimate the density of the plasma using interferometry.

  18. Biexciton induced refractive index changes in a semiconductor quantum dot

    NASA Astrophysics Data System (ADS)

    Shojaei, S.

    2015-06-01

    We present a detailed theoretical study of linear and third order nonlinear refractive index changes in a optically driven disk-like GaN quantum dot. In our numerical calculations, we consider the three level system containing biexciton, exciton, and ground states and use the compact density matrix formalism and iterative method to obtain refractive index changes. Variational method through effective mass approximation are employed to calculate the ground state energy of biexciton and exciton states. The evolution of refractive index changes around one, two and three photon resonance is investigated and discussed for different quantum dot sizes and light intensities. Size-dependent three-photon nonlinear refractive index change versus incident photon energy compared to that of two-photon is obtained and analyzed. As main result, we found that around resonance frequency at exciton-biexciton transition the quantum confinement has great influence on the linear change in refractive index so that for very large quantum dots, it decreases. Moreover, it was found that third order refractive index changes for three photon process is strongly dependent on QD size and light intensity. Our study reveals that considering our simple model leads to results which are in good agreement with other rare numerical results. Comparison with experimental results has been done.

  19. Empirical estimates of cumulative refraction errors associated with procedurally constrained levelings based on the Gaithersburg- Tucson refraction tests of the National Geodetic Survey.

    USGS Publications Warehouse

    Castle, R.O.; Gilmore, T.D.; Mark, R.K.; Shaw, R.H.

    1985-01-01

    Analyses of results of the National Geodetic Survey's leveling refraction tests indicate that the standard deviation about the mean (sigma) for high-scale minus low-scale rod readings closely correlates with measured refraction error. Use of this relation in conjunction with values for sigma obtained from routinely constrainted surveys provides a basis for estimating the refraction error associated with levelings of stipulated order and class. -Authors

  20. Computational imaging using lightweight diffractive-refractive optics.

    PubMed

    Peng, Yifan; Fu, Qiang; Amata, Hadi; Su, Shuochen; Heide, Felix; Heidrich, Wolfgang

    2015-11-30

    Diffractive optical elements (DOE) show great promise for imaging optics that are thinner and more lightweight than conventional refractive lenses while preserving their light efficiency. Unfortunately, severe spectral dispersion currently limits the use of DOEs in consumer-level lens design. In this article, we jointly design lightweight diffractive-refractive optics and post-processing algorithms to enable imaging under white light illumination. Using the Fresnel lens as a general platform, we show three phase-plate designs, including a super-thin stacked plate design, a diffractive-refractive-hybrid lens, and a phase coded-aperture lens. Combined with cross-channel deconvolution algorithm, both spherical and chromatic aberrations are corrected. Experimental results indicate that using our computational imaging approach, diffractive-refractive optics is an alternative candidate to build light efficient and thin optics for white light imaging.

  1. Tissue refractive index as marker of disease

    NASA Astrophysics Data System (ADS)

    Wang, Zhuo; Tangella, Krishnarao; Balla, Andre; Popescu, Gabriel

    2011-11-01

    The gold standard in histopathology relies on manual investigation of stained tissue biopsies. A sensitive and quantitative method for in situ tissue specimen inspection is highly desirable, as it would allow early disease diagnosis and automatic screening. Here we demonstrate that quantitative phase imaging of entire unstained biopsies has the potential to fulfill this requirement. Our data indicates that the refractive index distribution of histopathology slides, which contains information about the molecular scale organization of tissue, reveals prostate tumors and breast calcifications. These optical maps report on subtle, nanoscale morphological properties of tissues and cells that cannot be recovered by common stains, including hematoxylin and eosin. We found that cancer progression significantly alters the tissue organization, as exhibited by consistently higher refractive index variance in prostate tumors versus normal regions. Furthermore, using the quantitative phase information, we obtained the spatially resolved scattering mean free path and anisotropy factor g for entire biopsies and demonstrated their direct correlation with tumor presence. In essence, our results show that the tissue refractive index reports on the nanoscale tissue architecture and, in principle, can be used as an intrinsic marker for cancer diagnosis.

  2. Age-Related Shifts in the Density and Distribution of Genetic Marker Water Quality Indicators in Cow and Calf Feces

    EPA Science Inventory

    Recent studies have shown that different adult bovine animal feeding practices dramatically influence fecal indicator bacteria shedding, however very little is known about juvenile milk-fed calves. Calves (≤ 6 months of age) make up about 16% of the current bovine population in ...

  3. Water Quality, Weather and Environmental Factors Associated with Fecal Indicator Organism Density in Beach Sand at Two Recreational Marine Beaches

    EPA Science Inventory

    Recent studies showing an association between fecal indicator organisms (FIOs and gastrointestinal (GI) illness among beachgoers wit sand contact have important public health implicatons because of the large numbers of people who recreate at beaches and engage in sand contact act...

  4. Determination of the index of refraction for [alpha]-NTO and DAAF using the Becke test

    SciTech Connect

    Oldenborg, M. R.; Peterson, P. D.; Lee, K. Y.

    2004-01-01

    NTO and DAAF are insensitive high explosives developed at Los Alamos National Laboratory. Both the defense and civilian sectors have particular interest in these types of materials for applications ranging from weapons to air bag design. The performance of explosives is highly dependent on particle size. Many common techniques for measuring particle size distributions require knowledge of the material's index of refraction. To-date the principle refractive indices of {alpha}-NTO and DAAF have not been determined. We present the three principle indices of refraction for the triclinic explosive {alpha}-NTO and an averaged index of refraction for DAAF found using the Becke Test. In addition, by comparing particle size distributions based on different refractive indices we show the importance of using the true index of refraction in measuring fine particles.

  5. Ammonia Levels and Urine-Spot Characteristics as Cage-Change Indicators for High-Density Individually Ventilated Mouse Cages.

    PubMed

    Washington, Ida M; Payton, Mark E

    2016-01-01

    Mouse cage and bedding changes are potentially stressful to mice and are also labor- and resource-intensive. These changes are often performed on a calendar-based schedule to maintain a clean microenvironment and limit the concentrations of ammonia to which mice and workers are exposed. The current study sought to establish a performance-based approach to mouse cage-changing that uses urine spot characteristics as visual indicators of intracage ammonia levels. Colorimetric ammonia indicators were used to measure ammonia levels in individually-ventilated cages (IVC) housing male or female mice (n =5 per cage) of various strains at 1 to 16 d after cage change. Urine spot characteristics were correlated with ammonia levels to create a visual indicator of the cage-change criterion of 25 ppm ammonia. Results demonstrated a consistent increase in ammonia levels with days since cage change, with cages reaching the cage-change criterion at approximately 10 d for IVC containing male mice and 16 d for those with female mice. Ammonia levels were higher for male than female mice but were not correlated with mouse age. However, urine spot diameter, color, and edge characteristics were strongly correlated with ammonia levels. Husbandry practices based on using urine spot characteristics as indicators of ammonia levels led to fewer weekly cage changes and concomitant savings in labor and resources. Therefore, urine spot characteristics can be used as visual indicators of intracage ammonia levels for use of a performance (urine spot)-based approach to cage-changing frequency that maintains animal health and wellbeing. PMID:27177558

  6. Effects of combined sewer overflow and stormwater on indicator bacteria concentrations in the Tama River due to the high population density of Tokyo Metropolitan area.

    PubMed

    Ham, Young-Sik; Kobori, Hiromi; Takasago, Masahisa

    2009-05-01

    The indicator bacteria (standard plate count, total coliform, and fecal coliform bacteria) concentrations have been investigated using six ambient habitats (population density, percent sewer penetration, stream flow rate (m(3)/sec), percent residential area, percent forest area and percent agricultural area) in the Tama River basin in Tokyo, Japan during June 2003 to January 2005. The downstream and tributary Tama River showed higher concentrations of TC and FC bacteria than the upstream waters, which exceeded an environmental quality standard for rivers and a bathing water quality criterion. It was estimated that combined sewer overflow (CSO) and stormwater effluents contributed -4-23% to the indicator bacteria concentrations of the Tama River. The results of multiple regression analyses show that the indicator bacteria concentrations of Tama River basin are significantly affected by population density. It is concluded that the Tama River received a significant bacterial contamination load originating from the anthropogenic source.

  7. Are growth and density quantitative indicators of essential fish habitat quality? An application to the common sole Solea solea nursery grounds

    NASA Astrophysics Data System (ADS)

    Gilliers, C.; Le Pape, O.; Désaunay, Y.; Morin, J.; Guérault, D.; Amara, R.

    2006-08-01

    Bio-indicators were measured on juvenile fish to assess the quality of eight coastal and estuarine nursery grounds in the Eastern English Channel and in the Bay of Biscay during 3 years. Growth (size and otolith daily increment width), body condition (morphometric index) and abundance of juvenile common soles were analysed together with xenobiotic concentrations (heavy metals and organic contaminants). Condition indices displayed important variations and did not allow relevant estimation of environmental quality. On the contrary, growth and density indicators showed good steadiness above years but varied among sites. In spite of difficulties of interpreting these indicators on such a meso-scale approach, analyses highlighted the estuaries of Seine and Gironde. In these nursery areas, the levels of contamination were especially high, and the combination of fish growth performances and density was significantly lower than in other sites. The combination of these variables appears to provide reliable indicators of habitat quality and anthropogenic pressure on nursery grounds, especially highlighting contaminated areas. Such indicators may thus contribute to improve assessment of environmental quality of essential fish habitats with the aim of a sustainable management of fisheries resources. A study at a different scale, from this meso-scale nursery approach with more precise analyses, on local habitats, will nevertheless be necessary to optimize the relevance of these indicators for the assessment of essential fish habitat quality.

  8. Spatial and temporal heterogeneities of Aedes albopictus density in La Reunion Island: rise and weakness of entomological indices.

    PubMed

    Boyer, Sebastien; Foray, Coralie; Dehecq, Jean-Sebastien

    2014-01-01

    Following the 2006 Chikungunya disease in La Reunion, questions were raised concerning the monitoring survey of Aedes albopictus populations and the entomological indexes used to evaluate population abundance. The objectives of the present study were to determine reliable productivity indexes using a quantitative method to improve entomological surveys and mosquito control measures on Aedes albopictus. Between 2007 and 2011, 4 intervention districts, 24 cities, 990 areas and over 850,000 houses were used to fulfil those objectives. Four indexes including the classical Stegomyia index (House Index, Container Index, Breteau Index) plus an Infested Receptacle Index were studied in order to determine whether temporal (year, month, week) and/or spatial (districts, cities, areas) heterogeneities existed. Temporal variations have been observed with an increase of Ae. albopictus population density over the years, and a seasonality effect with a highest population during the hot and wet season. Spatial clustering was observed at several scales with an important autocorrelation at the area scale. Moreover, the combination among these results and the breeding site productivity obtained during these 5 years allowed us to propose recommendations to monitor Aedes albopictus by eliminating not the most finding sites but the most productive ones. As the other strategies failed in La Reunion, this new approach should should work better.

  9. Characterizing conical refraction optical tweezers.

    PubMed

    McDonald, C; McDougall, C; Rafailov, E; McGloin, D

    2014-12-01

    Conical refraction occurs when a beam of light travels through an appropriately cut biaxial crystal. By focusing the conically refracted beam through a high numerical aperture microscope objective, conical refraction optical tweezers can be created, allowing for particle manipulation in both Raman spots, and in the Lloyd/Poggendorff rings. We present a thorough quantification of the trapping properties of such a beam, focusing on the trap stiffness, and how this varies with trap power and trapped particle location. We show that the lower Raman spot can be thought of as a single-beam optical gradient force trap, while radiation pressure dominates in the upper Raman spot, leading to optical levitation rather than trapping. Particles in the Lloyd/Poggendorff rings experience a lower trap stiffness than particles in the lower Raman spot, but benefit from rotational control. PMID:25490654

  10. A Newtonian approach to extraordinarily strong negative refraction.

    PubMed

    Yoon, Hosang; Yeung, Kitty Y M; Umansky, Vladimir; Ham, Donhee

    2012-08-01

    Metamaterials with negative refractive indices can manipulate electromagnetic waves in unusual ways, and can be used to achieve, for example, sub-diffraction-limit focusing, the bending of light in the 'wrong' direction, and reversed Doppler and Cerenkov effects. These counterintuitive and technologically useful behaviours have spurred considerable efforts to synthesize a broad array of negative-index metamaterials with engineered electric, magnetic or optical properties. Here we demonstrate another route to negative refraction by exploiting the inertia of electrons in semiconductor two-dimensional electron gases, collectively accelerated by electromagnetic waves according to Newton's second law of motion, where this acceleration effect manifests as kinetic inductance. Using kinetic inductance to attain negative refraction was theoretically proposed for three-dimensional metallic nanoparticles and seen experimentally with surface plasmons on the surface of a three-dimensional metal. The two-dimensional electron gas that we use at cryogenic temperatures has a larger kinetic inductance than three-dimensional metals, leading to extraordinarily strong negative refraction at gigahertz frequencies, with an index as large as -700. This pronounced negative refractive index and the corresponding reduction in the effective wavelength opens a path to miniaturization in the science and technology of negative refraction.

  11. The Optics of Refractive Substructure

    NASA Astrophysics Data System (ADS)

    Johnson, Michael D.; Narayan, Ramesh

    2016-08-01

    Newly recognized effects of refractive scattering in the ionized interstellar medium have broad implications for very long baseline interferometry (VLBI) at extreme angular resolutions. Building upon work by Blandford & Narayan, we present a simplified, geometrical optics framework, which enables rapid, semi-analytic estimates of refractive scattering effects. We show that these estimates exactly reproduce previous results based on a more rigorous statistical formulation. We then derive new expressions for the scattering-induced fluctuations of VLBI observables such as closure phase, and we demonstrate how to calculate the fluctuations for arbitrary quantities of interest using a Monte Carlo technique.

  12. A refracting radio telescope. [using ionosphere as lens

    NASA Technical Reports Server (NTRS)

    Bernhardt, P.; Da Rosa, A. V.

    1977-01-01

    Observations of extraterrestrial radio sources at the lower end of the radio frequency spectrum are limited by reflection of waves from the topside ionosphere and by the large size of antenna apertures necessary for the realization of narrow beamwidths. The use of the ionosphere as a lens is considered. The lens is formed by the release of chemicals such as H2 and H2O at the F2-layer peak. These chemicals promote dissociative recombination of O(+) in the ionosphere resulting in a local reduction in plasma density. Gradients in electron density in the vicinity of the gas release tend to focus rays propagating through the depleted region. Preliminary calculations indicate that a lens capable of focusing cosmic radio waves in the 1 to 10 MHz frequency range may be produced by the release of 100 kg of H2 at the peak of the nighttime F layer. The beamwidth of a refracting radio telescope using this lens may be less than 1/5 degree.

  13. Atmospheric refraction effects on baseline error in satellite laser ranging systems

    NASA Technical Reports Server (NTRS)

    Im, K. E.; Gardner, C. S.

    1982-01-01

    Because of the mathematical complexities involved in exact analyses of baseline errors, it is not easy to isolate atmospheric refraction effects; however, by making certain simplifying assumptions about the ranging system geometry, relatively simple expressions can be derived which relate the baseline errors directly to the refraction errors. The results indicate that even in the absence of other errors, the baseline error for intercontinental baselines can be more than an order of magnitude larger than the refraction error.

  14. REFLECTION AND REFRACTION, VOLUME 2.

    ERIC Educational Resources Information Center

    KLAUS, DAVID J.; AND OTHERS

    THIS VOLUME 2 OF A TWO-VOLUME SET PROVIDES AUTOINSTRUCTION IN PHYSICS. THE UNITS COVERED IN THIS VOLUME ARE (1) REFLECTION OF LIGHT, (2) PHOTOMETRY, (3) POLARIZATION, (4) REFRACTION OF LIGHT, (5) SNELL'S LAW, (6) LENSES, FOCUS, AND FOCAL POINTS, (7) IMAGE FORMATION, AND (8) ABERRATIONS, THE EYE, AND MAGNIFICATION. THE INTRODUCTION AND UNITS ON…

  15. Index of Refraction without Geometry

    ERIC Educational Resources Information Center

    Farkas, N.; Henriksen, P. N.; Ramsier, R. D.

    2006-01-01

    This article presents several activities that permit students to determine the index of refraction of transparent solids and liquids using simple equipment without the need for geometrical relationships, special lighting or optical instruments. Graphical analysis of the measured data is shown to be a useful method for determining the index of…

  16. Fiber optic refractive index monitor

    DOEpatents

    Weiss, Jonathan David

    2002-01-01

    A sensor for measuring the change in refractive index of a liquid uses the lowest critical angle of a normal fiber optic to achieve sensitivity when the index of the liquid is significantly less than the index of the fiber core. Another embodiment uses a liquid filled core to ensure that its index is approximately the same as the liquid being measured.

  17. Morphometric evaluation of the Afşin-Elbistan lignite basin using kernel density estimation and Getis-Ord's statistics of DEM derived indices, SE Turkey

    NASA Astrophysics Data System (ADS)

    Sarp, Gulcan; Duzgun, Sebnem

    2015-11-01

    A morphometric analysis of river network, basins and relief using geomorphic indices and geostatistical analyses of Digital Elevation Model (DEM) are useful tools for discussing the morphometric evolution of the basin area. In this study, three different indices including valley floor width to height ratio (Vf), stream gradient (SL), and stream sinuosity were applied to Afşin-Elbistan lignite basin to test the imprints of tectonic activity. Perturbations of these indices are usually indicative of differences in the resistance of outcropping lithological units to erosion and active faulting. To map the clusters of high and low indices values, the Kernel density estimation (K) and the Getis-Ord Gi∗ statistics were applied to the DEM-derived indices. The K method and Gi∗ statistic highlighting hot spots and cold spots of the SL index, the stream sinuosity and the Vf index values helped to identify the relative tectonic activity of the basin area. The results indicated that the estimation by the K and Gi∗ including three conceptualization of spatial relationships (CSR) for hot spots (percent volume contours 50 and 95 categorized as high and low respectively) yielded almost similar results in regions of high tectonic activity and low tectonic activity. According to the K and Getis-Ord Gi∗ statistics, the northern, northwestern and southern parts of the basin indicates a high tectonic activity. On the other hand, low elevation plain in the central part of the basin area shows a relatively low tectonic activity.

  18. Refractive Errors - Multiple Languages: MedlinePlus

    MedlinePlus

    ... Are Here: Home → Multiple Languages → All Health Topics → Refractive Errors URL of this page: https://medlineplus.gov/languages/ ... V W XYZ List of All Topics All Refractive Errors - Multiple Languages To use the sharing features on ...

  19. Emmetropisation and the aetiology of refractive errors

    PubMed Central

    Flitcroft, D I

    2014-01-01

    The distribution of human refractive errors displays features that are not commonly seen in other biological variables. Compared with the more typical Gaussian distribution, adult refraction within a population typically has a negative skew and increased kurtosis (ie is leptokurtotic). This distribution arises from two apparently conflicting tendencies, first, the existence of a mechanism to control eye growth during infancy so as to bring refraction towards emmetropia/low hyperopia (ie emmetropisation) and second, the tendency of many human populations to develop myopia during later childhood and into adulthood. The distribution of refraction therefore changes significantly with age. Analysis of the processes involved in shaping refractive development allows for the creation of a life course model of refractive development. Monte Carlo simulations based on such a model can recreate the variation of refractive distributions seen from birth to adulthood and the impact of increasing myopia prevalence on refractive error distributions in Asia. PMID:24406411

  20. Evidence for subwavelength imaging with positive refraction

    NASA Astrophysics Data System (ADS)

    Gui Ma, Yun; Sahebdivan, Sahar; Ong, C. K.; Tyc, Tomáš; Leonhardt, Ulf

    2011-03-01

    The resolution of lenses is normally limited by the wave nature of light. Imaging with perfect resolution was believed to rely on negative refraction, but here we present experimental evidence for subwavelength imaging with positive refraction.

  1. Refractive-index measurements by moire deflectometry.

    PubMed

    Karny, Z; Kafri, O

    1982-09-15

    A novel method for measuring refractive index of gases and liquids is presented based on moire deflectometry. We demonstrate this technique by measuring the refractive index of diluted sucrose solutions and of air at atmospheric pressure.

  2. Relationships among oil density, gross composition, and thermal maturity indicators in northeastern Williston basin oils and their significance for expulsion thresholds and migration pathways

    SciTech Connect

    Osadetz, K.G.; Snowdon, L.R.; Brooks, P.W. )

    1991-06-01

    Oil density ({degree}API), gross composition, and biological market thermal maturity variations in northeastern Williston basin have stratigraphic and geographic significance controlled by migration pathways and source rock composition as it affects hydrocarbon generation and expulsion characteristics. When the depth and density of oil pools is compared to relationships predicted using the correlation between source rock thermal maturity and oil density, several different migration pathways can be inferred. Winnipegosis source oils indicate four paths. Most small pinnacle reef pools are sourced locally, but larger coalesced reefs contain oils migrated long distances through the Lower Member Winnipegosis Formation. Among oils that have migrated past Prairie salts, both locally sourced oils, like those on the flank of the Hummingbird Trough, and more mature, longer migrated oils in Saskatchewan Group reservoirs can be identified. Bakken oils have the longest migration pathways, controlled primarily by a lowstand shoreline sandstone on the eastern side of the basin. Lodgepole-sourced oils dominate Madison Group plays. Northwest of Steelman field, oil density increases primarily due to thermal maturity differences but also because of increasing biodegradation and water-washing that affect the western edge of the play trend. Along the margin of the Hummingbird Trough are a number of deep, medium-gravity pools whose oil compositions are entirely attributable to low thermal maturity and local migration pathways.

  3. Highly tunable refractive index visible-light metasurface from block copolymer self-assembly

    NASA Astrophysics Data System (ADS)

    Kim, Ju Young; Kim, Hyowook; Kim, Bong Hoon; Chang, Taeyong; Lim, Joonwon; Jin, Hyeong Min; Mun, Jeong Ho; Choi, Young Joo; Chung, Kyungjae; Shin, Jonghwa; Fan, Shanhui; Kim, Sang Ouk

    2016-09-01

    The refractive index of natural transparent materials is limited to 2-3 throughout the visible wavelength range. Wider controllability of the refractive index is desired for novel optical applications such as nanoimaging and integrated photonics. We report that metamaterials consisting of period and symmetry-tunable self-assembled nanopatterns can provide a controllable refractive index medium for a broad wavelength range, including the visible region. Our approach exploits the independent control of permeability and permittivity with nanoscale objects smaller than the skin depth. The precise manipulation of the interobject distance in block copolymer nanopatterns via pattern shrinkage increased the effective refractive index up to 5.10. The effective refractive index remains above 3.0 over more than 1,000 nm wavelength bandwidth. Spatially graded and anisotropic refractive indices are also obtained with the design of transitional and rotational symmetry modification.

  4. Highly tunable refractive index visible-light metasurface from block copolymer self-assembly

    PubMed Central

    Kim, Ju Young; Kim, Hyowook; Kim, Bong Hoon; Chang, Taeyong; Lim, Joonwon; Jin, Hyeong Min; Mun, Jeong Ho; Choi, Young Joo; Chung, Kyungjae; Shin, Jonghwa; Fan, Shanhui; Kim, Sang Ouk

    2016-01-01

    The refractive index of natural transparent materials is limited to 2–3 throughout the visible wavelength range. Wider controllability of the refractive index is desired for novel optical applications such as nanoimaging and integrated photonics. We report that metamaterials consisting of period and symmetry-tunable self-assembled nanopatterns can provide a controllable refractive index medium for a broad wavelength range, including the visible region. Our approach exploits the independent control of permeability and permittivity with nanoscale objects smaller than the skin depth. The precise manipulation of the interobject distance in block copolymer nanopatterns via pattern shrinkage increased the effective refractive index up to 5.10. The effective refractive index remains above 3.0 over more than 1,000 nm wavelength bandwidth. Spatially graded and anisotropic refractive indices are also obtained with the design of transitional and rotational symmetry modification. PMID:27683077

  5. Fully interferometric controllable anomalous refraction efficiency using cross modulation with plasmonic metasurfaces.

    PubMed

    Liu, Zhaocheng; Chen, Shuqi; Li, Jianxiong; Cheng, Hua; Li, Zhancheng; Liu, Wenwei; Yu, Ping; Xia, Ji; Tian, Jianguo

    2014-12-01

    We present a method of fully interferometric, controllable anomalous refraction efficiency by introducing cross-modulated incident light based on plasmonic metasurfaces. Theoretical analyses and numerical simulations indicate that the anomalous and ordinary refracted beams generated from two opposite-helicity incident beams and following the generalized Snell's law will have a superposition for certain incident angles, and the anomalous refraction efficiency can be dynamically controlled by changing the relative phase of the incident sources. As the incident wavelength nears the resonant wavelength of the plasmonic metasurfaces, two equal-amplitude incident beams with opposite helicity can be used to control the anomalous refraction efficiency. Otherwise, two unequal-amplitude incident beams with opposite helicity can be used to fully control the anomalous refraction efficiency. This Letter may offer a further step in the development of controllable anomalous refraction.

  6. Optical refractive index of massive particles and physical meanings of left-handed media [rapid communication

    NASA Astrophysics Data System (ADS)

    Shen, Jian Qi

    2005-09-01

    In this Letter the expression for the refractive index of de Broglie wave in the presence of a potential field is obtained and based on this, the physical meanings of negative index of refraction is revealed. We demonstrate that the electromagnetic wave propagation in a left-handed medium with negative refractive index behaves just like that of antiphotons, which is required of the complex vector field theory. It is believed that the complex vector field theory is helpful in considering the wave propagation and photonic band gap structures in the left-handed medium photonic crystals with a periodicity in negative and positive indices of refraction.

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

    NASA Technical Reports Server (NTRS)

    Gardner, C. S.

    1976-01-01

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

  8. Measurement of the refractive index of human teeth by optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Meng, Zhuo; Yao, X. Steve; Yao, Hui; Liang, Yan; Liu, Tiegen; Li, Yanni; Wang, Guanhua; Lan, Shoufeng

    2009-05-01

    We describe a novel method based on optical coherence tomography (OCT) for the accurate measurement of the refractive index of in vitro human teeth. We obtain the refractive indices of enamel, dentin, and cementum to be 1.631+/-0.007, 1.540+/-0.013, and 1.582+/-0.010, respectively. The profile of the refractive index is readily obtained via an OCT B scan across a tooth. This method can be used to study the refractive index changes caused by dental decay and therefore has great potential for the clinical diagnosis of early dental caries.

  9. Electro-refractive photonic device

    SciTech Connect

    Zortman, William A.; Watts, Michael R.

    2015-06-09

    The various technologies presented herein relate to phase shifting light to facilitate any of light switching, modulation, amplification, etc. Structures are presented where a second layer is juxtaposed between a first layer and a third layer with respective doping facilitating formation of p-n junctions at the interface between the first layer and the second layer, and between the second layer and the third layer. Application of a bias causes a carrier concentration change to occur at the p-n junctions which causes a shift in the effective refractive index per incremental change in an applied bias voltage. The effective refractive index enhancement can occur in both reverse bias and forward bias. The structure can be incorporated into a waveguide, an optical resonator, a vertical junction device, a horizontal junction device, a Mach-Zehnder interferometer, a tuneable optical filter, etc.

  10. The Reality of Negative Refraction

    NASA Astrophysics Data System (ADS)

    Smith, David

    2004-03-01

    Negative refraction, a phenomenon first hypothesized by Victor Veselago in 1968 to occur in materials whose permittivity and permeability are simultaneously negative, has now been confirmed in several independent studies. These experiments demonstrate that it is indeed possible to design and fabricate an artificial material - now known as a "metamaterial" - having an index-of-refraction that is negative over some finite band of frequencies. The positive confirmations of the phenomenon of negative refraction represent an important first step. As applications are considered that take advantage of negative index materials, the ability to meet the needed specifications is the next step, since the viability of applications is ultimately tied to the quality, reproducibility and cost of the underlying materials. Some of the more striking or exotic wave propagation behavior predicted to occur in negative index materials, such as reflectionless compact lenses, near-field refocusing, "perfect" lensing, phase compensation and novel wave-guiding phenomena - place challenging demands on the material parameters. In this talk, I will discuss our efforts to fabricate and characterize negative index metamaterials, and how the current material limitations impact a variety of proposed applications.

  11. Measuring the refractive index of thin transparent films using an extended cavity diode laser

    NASA Astrophysics Data System (ADS)

    Luetjen, Christopher; Hallsted, Jonathan; Kleinert, Michaela

    2013-12-01

    We report on a novel method for determining refractive indices of thin layers of liquids or gases, based on the use of extended cavity diode lasers. Measurements for air, water, and vegetable oil show excellent agreement with accepted values. Applications in determining the refractive index of thin optical coatings and biological cells are discussed.

  12. Measurement of Refractive Index Gradients by Deflection of a Laser Beam

    ERIC Educational Resources Information Center

    Barnard, A. J.; Ahlborn, B.

    1975-01-01

    In this simple experiment for an undergraduate laboratory a laser beam is passed through the mixing zone of two liquids with different refractive indices. The spatial variation of the refractive index, at different times during the mixing, can be determined from the observed deflection of the beam. (Author)

  13. Water absorption in a refractive index model for bacterial spores

    NASA Astrophysics Data System (ADS)

    Siegrist, K. M.; Thrush, E.; Airola, M.; Carr, A. K.; Limsui, D. M.; Boggs, N. T.; Thomas, M. E.; Carter, C. C.

    2009-05-01

    The complexity of biological agents can make it difficult to identify the important factors impacting scattering characteristics among variables such as size, shape, internal structure and biochemical composition, particle aggregation, and sample additives. This difficulty is exacerbated by the environmentally interactive nature of biological organisms. In particular, bacterial spores equilibrate with environmental humidity by absorption/desorption of water which can affect both the complex refractive index and the size/shape distributions of particles - two factors upon which scattering characteristics depend critically. Therefore accurate analysis of experimental data for determination of refractive index must take account of particle water content. First, spectral transmission measurements to determine visible refractive index done on suspensions of bacterial spores must account for water (or other solvent) uptake. Second, realistic calculations of aerosol scattering cross sections should consider effects of atmospheric humidity on particle water content, size and shape. In this work we demonstrate a method for determining refractive index of bacterial spores bacillus atropheus (BG), bacillus thuringiensis (BT) and bacillus anthracis Sterne (BAs) which accounts for these effects. Visible index is found from transmission measurements on aqueous and DMSO suspensions of particles, using an anomalous diffraction approximation. A simplified version of the anomalous diffraction theory is used to eliminate the need for knowledge of particle size. Results using this approach indicate the technique can be useful in determining the visible refractive index of particles when size and shape distributions are not well known but fall within the region of validity of anomalous dispersion theory.

  14. Empirical modelling to predict the refractive index of human blood

    NASA Astrophysics Data System (ADS)

    Yahya, M.; Saghir, M. Z.

    2016-02-01

    Optical techniques used for the measurement of the optical properties of blood are of great interest in clinical diagnostics. Blood analysis is a routine procedure used in medical diagnostics to confirm a patient’s condition. Measuring the optical properties of blood is difficult due to the non-homogenous nature of the blood itself. In addition, there is a lot of variation in the refractive indices reported in the literature. These are the reasons that motivated the researchers to develop a mathematical model that can be used to predict the refractive index of human blood as a function of concentration, temperature and wavelength. The experimental measurements were conducted on mimicking phantom hemoglobin samples using the Abbemat Refractometer. The results analysis revealed a linear relationship between the refractive index and concentration as well as temperature, and a non-linear relationship between refractive index and wavelength. These results are in agreement with those found in the literature. In addition, a new formula was developed based on empirical modelling which suggests that temperature and wavelength coefficients be added to the Barer formula. The verification of this correlation confirmed its ability to determine refractive index and/or blood hematocrit values with appropriate clinical accuracy.

  15. Empirical modelling to predict the refractive index of human blood.

    PubMed

    Yahya, M; Saghir, M Z

    2016-02-21

    Optical techniques used for the measurement of the optical properties of blood are of great interest in clinical diagnostics. Blood analysis is a routine procedure used in medical diagnostics to confirm a patient's condition. Measuring the optical properties of blood is difficult due to the non-homogenous nature of the blood itself. In addition, there is a lot of variation in the refractive indices reported in the literature. These are the reasons that motivated the researchers to develop a mathematical model that can be used to predict the refractive index of human blood as a function of concentration, temperature and wavelength. The experimental measurements were conducted on mimicking phantom hemoglobin samples using the Abbemat Refractometer. The results analysis revealed a linear relationship between the refractive index and concentration as well as temperature, and a non-linear relationship between refractive index and wavelength. These results are in agreement with those found in the literature. In addition, a new formula was developed based on empirical modelling which suggests that temperature and wavelength coefficients be added to the Barer formula. The verification of this correlation confirmed its ability to determine refractive index and/or blood hematocrit values with appropriate clinical accuracy.

  16. [Some physiological and biochemical indicators of underyearling Laxman's shrews (Sorex cecutiens Laxmann) and even-toothed shrews (Sorex isodon Turov) under conditions of different population densities].

    PubMed

    Kiselev, S V; Lazutkin, A N; Yamborko, A V

    2013-01-01

    Based on the results of a study conducted in 2006-2010 in the Buyunda River basin (a feeder of the Kolyma River), the influence of the population density of common shrews (Sorex) on some of the physiological and biochemical parameters (glycogen and lipids in the liver, the relative weight of the spleen, the white and brown adipose tissue cellularity of bone and brain tissue) was investigated. The content of energy reserve substances was correlated with the number of animals (fat deposits had a negative correlation; the glycogen content in the liver had a direct correlation). For the rest of the physiological-biochemical parameters, no significant correlation with the population density was detected, although for the content of brown fat and cellularity of bone marrow tissue in Sorex isodon, as well as the relative weight of the spleen in both species of shrews, a trend was observed. We suggest that the identified physiological changes indicate irregular feeding of animals in years with higher population densities. PMID:24459854

  17. Low-loss polymer films with adjustable refractive index.

    PubMed

    Ramaswamy, V; Weber, H P

    1973-07-01

    Solution-deposited polymer films with continuously adjustable refractive index (1.489-1.563) are made by blending in solution two polymers: polymethyl methacrylate (PMMA) and styrene-acrylonitrile copolymer (SAN). The dependence of index of refraction on composition was found to be linear, indicating the compatibility of the two polymers on a molecular basis. In films ~2 microm thick losses less than 0.2 dB/cm were measured. For thicker films (3.5 microm) an increased scattering loss was observed in high SAN content films.

  18. Laser refractive tomography of phase objects

    SciTech Connect

    Raskovskaya, I L

    2013-06-30

    The principles are outlined of laser refractive tomography - a method for reconstructing the values of the refractive index in the cross sections of phase objects, which involves the use of three-dimensional refractive images (3D refractograms) of structured laser radiation. A simulation algorithm is realised and examples are provided of characteristic 3D refractograms obtained by solving the direct problem of refraction of structured radiation. A method was developed for reconstructing the values of refractive index under conditions of strong refraction, which is based on the visualisation of ray trajectories inside an optically inhomogeneous medium. A classification is made of possible approaches to the solution of the inverse problem of refraction based on the visualisation of ray trajectories. Examples are given of cross section reconstruction and quantitative diagnostics of phase objects. (laser imaging)

  19. Optical negative refraction by four-wave mixing in thin metallic nanostructures.

    PubMed

    Palomba, Stefano; Zhang, Shuang; Park, Yongshik; Bartal, Guy; Yin, Xiaobo; Zhang, Xiang

    2012-01-01

    The law of refraction first derived by Snellius and later introduced as the Huygens-Fermat principle, states that the incidence and refracted angles of a light wave at the interface of two different materials are related to the ratio of the refractive indices in each medium. Whereas all natural materials have a positive refractive index and therefore exhibit refraction in the positive direction, artificially engineered negative index metamaterials have been shown capable of bending light waves negatively. Such a negative refractive index is the key to achieving a perfect lens that is capable of imaging well below the diffraction limit. However, negative index metamaterials are typically lossy, narrow band, and require complicated fabrication processes. Recently, an alternative approach to obtain negative refraction from a very thin nonlinear film has been proposed and experimentally demonstrated in the microwave region. However, such approaches use phase conjugation, which makes optical implementations difficult. Here, we report a simple but different scheme to demonstrate experimentally nonlinear negative refraction at optical frequencies using four-wave mixing in nanostructured metal films. The refractive index can be designed at will by simply tuning the wavelengths of the interacting waves, which could have potential impact on many important applications, such as superlens imaging.

  20. Optical negative refraction by four-wave mixing in thin metallic nanostructures

    NASA Astrophysics Data System (ADS)

    Palomba, Stefano; Zhang, Shuang; Park, Yongshik; Bartal, Guy; Yin, Xiaobo; Zhang, Xiang

    2012-01-01

    The law of refraction first derived by Snellius and later introduced as the Huygens-Fermat principle, states that the incidence and refracted angles of a light wave at the interface of two different materials are related to the ratio of the refractive indices in each medium. Whereas all natural materials have a positive refractive index and therefore exhibit refraction in the positive direction, artificially engineered negative index metamaterials have been shown capable of bending light waves negatively. Such a negative refractive index is the key to achieving a perfect lens that is capable of imaging well below the diffraction limit. However, negative index metamaterials are typically lossy, narrow band, and require complicated fabrication processes. Recently, an alternative approach to obtain negative refraction from a very thin nonlinear film has been proposed and experimentally demonstrated in the microwave region. However, such approaches use phase conjugation, which makes optical implementations difficult. Here, we report a simple but different scheme to demonstrate experimentally nonlinear negative refraction at optical frequencies using four-wave mixing in nanostructured metal films. The refractive index can be designed at will by simply tuning the wavelengths of the interacting waves, which could have potential impact on many important applications, such as superlens imaging.

  1. Two-dimensional scanning focused refractive-index microscopy and applications to refractive-index profiling of optical fibers.

    PubMed

    Wang, Xiaowan; Ye, Qing; Sun, Tengqian; Wang, Jin; Deng, Zhichao; Mei, Jianchun; Zhou, Wenyuan; Zhang, Chunping; Tian, Jianguo

    2015-01-01

    The refractive-index profile (RIP) of optical fibers is of fundamental significance in determining critical fiber properties. Here, we present the application of a two-dimensional (2-D) scanning focused refractive-index microscopy (SFRIM) to accurately obtain the 2-D RIP of a graded-index optical fiber. Some modifications are made to SFRIM for better 2-D measurement. Quantitative RIP of the fiber is obtained with derivative total reflection method. The refractive-index accuracy is 0.002. The measured result is in good agreement with theoretical expectation. This method is straightforward, simple, repeatable, and free from signal distortion. This technique is suitable for symmetric and asymmetric optical fibers. The results indicate that this technique can be applied to obtain the RIPs of a wide range of materials and has broad application prospect in many fields.

  2. Refraction effects in soft x-ray multilayer blazed gratings.

    PubMed

    Voronov, D L; Salmassi, F; Meyer-Ilse, J; Gullikson, E M; Warwick, T; Padmore, H A

    2016-05-30

    A 2500 lines/mm Multilayer Blazed Grating (MBG) optimized for the soft x-ray wavelength range was fabricated and tested. The grating coated with a W/B4C multilayer demonstrated a record diffraction efficiency in the 2nd blazed diffraction order in the energy range from 500 to 1200 eV. Detailed investigation of the diffraction properties of the grating demonstrated that the diffraction efficiency of high groove density MBGs is not limited by the normal shadowing effects that limits grazing incidence x-ray grating performance. Refraction effects inherent in asymmetrical Bragg diffraction were experimentally confirmed for MBGs. The refraction affects the blazing properties of the MBGs and results in a shift of the resonance wavelength of the gratings and broadening or narrowing of the grating bandwidth depending on diffraction geometry. The true blaze angle of the MBGs is defined by both the real structure of the multilayer stack and by asymmetrical refraction effects. Refraction effects can be used as a powerful tool in providing highly efficient suppression of high order harmonics.

  3. A Simple Theory to Predict Small Changes in Volume and Refractivity During Mixing of a Two-Component Liquid System.

    ERIC Educational Resources Information Center

    Aminabhavi, Tejraj M.

    1983-01-01

    Discusses a set of relations (addressing changes in volume and refractivity) for use in the study of binary systems. Suggests including such an experiment in undergraduate physical chemistry courses (measuring density/refractive index of pure compounds and their mixtures) to predict even small changes occurring during mixing process. (Author/JN)

  4. Automation, Operation, and Data Analysis in the Cryogenic, High Accuracy, Refraction Measuring System (CHARMS)

    NASA Technical Reports Server (NTRS)

    Frey, Bradley J.; Leviton, Douglas B.

    2005-01-01

    The Cryogenic High Accuracy Refraction Measuring System (CHARMS) at NASA's Goddard Space Flight Center has been enhanced in a number of ways in the last year to allow the system to accurately collect refracted beam deviation readings automatically over a range of temperatures from 15 K to well beyond room temperature with high sampling density in both wavelength and temperature. The engineering details which make this possible are presented. The methods by which the most accurate angular measurements are made and the corresponding data reduction methods used to reduce thousands of observed angles to a handful of refractive index values are also discussed.

  5. Automation, Operation, and Data Analysis in the Cryogenic, High Accuracy, Refraction Measuring System (CHARMS)

    NASA Technical Reports Server (NTRS)

    Frey, Bradley; Leviton, Duoglas

    2005-01-01

    The Cryogenic High Accuracy Refraction Measuring System (CHARMS) at NASA s Goddard Space Flight Center has been enhanced in a number of ways in the last year to allow the system to accurately collect refracted beam deviation readings automatically over a range of temperatures from 15 K to well beyond room temperature with high sampling density in both wavelength and temperature. The engineering details which make this possible are presented. The methods by which the most accurate angular measurements are made and the corresponding data reduction methods used to reduce thousands of observed angles to a handful of refractive index values are also discussed.

  6. Photoinduced anisotropy of the refractive index of an azopolymer with liquid-crystal properties

    SciTech Connect

    Andreeva, M S; Shmalgauzen, V I

    2004-01-31

    The formation of a photoinduced refractive-index grating in a photosensitive azopolymer with liquid-crystal (LC) properties is theoretically studied. Equations for photoinduced additions to the refractive index of the LC and amorphous polymers are obtained from balance equations for the distribution densities of trans- and cis-isomers of azodyes. The frequency characteristics of the response of the refractive index to a harmonic perturbation are calculated for different values of the LC order parameter. (interaction of laser radiation with matter. laser plasma)

  7. Barriers to Use of Refractive Services in Mozambique

    PubMed Central

    Thompson, Stephen; Naidoo, Kovin; Gonzalez-Alvarez, Carmen; Harris, Geoff; Chinanayi, Farai; Loughman, James

    2015-01-01

    ABSTRACT Purpose Uncorrected refractive error remains a leading cause of visual impairment (VI) across the globe with Mozambique being no exception. The establishment of an optometry profession in Mozambique that is integrated into the public health system denotes significant progress with refractive services becoming available to the population. As the foundations of a comprehensive refractive service have now been established, this article seeks to understand what barriers may limit their uptake by the general population and inform decision making on improved service delivery. Methods A community-based cross-sectional study using two-stage cluster sampling was conducted. Participants with VI were asked to identify barriers that were reflective of their experiences and perceptions of accessing refractive services. A total of 4601 participants were enumerated from 76 clusters in Nampula, Mozambique. Results A total of 1087 visually impaired participants were identified (884 with near and 203 with distance impairment). Cost was the most frequently cited barrier, identified by more than one in every two participants (53%). Other barriers identified included lack of felt need (20%), distance to travel (15%), and lack of awareness (13%). In general, no significant influence of sex or type of VI on barrier selection was found. Location had a significant impact on the selection of several barriers. Pearson χ2 analysis indicated that participants from rural areas were found to feel disadvantaged regarding the distance to services (p ≤ 0.001) and adequacy of hospital services (p = 0.001). Conclusions For a comprehensive public sector refractive service to be successful in Mozambique, those planning its implementation must consider cost and affordability. A clear strategy for overcoming lack of felt need will also be needed, possibly in the form of improved advocacy and health promotion. The delivery of refractive services in more remote rural areas merits careful and

  8. Nonlinear refraction in aqueous colloidal gold

    NASA Astrophysics Data System (ADS)

    Mehendale, S. C.; Mishra, S. R.; Bindra, K. S.; Laghate, M.; Dhami, T. S.; Rustagi, K. C.

    1997-02-01

    Nonlinear refraction in aqueous colloidal gold at 527 nm was studied using the z-scan technique. While a z-scan with a 35 ns laser showed a large negative lensing, a z-scan with a 4 ps laser showed no measurable refraction. The observed nonlinear refraction is shown to be of thermal origin resulting from energy transfer from gold particles to the water molecules.

  9. Centration axis in refractive surgery.

    PubMed

    Arba Mosquera, Samuel; Verma, Shwetabh; McAlinden, Colm

    2015-01-01

    The human eye is an asymmetric optical system and the real cornea is not a rotationally symmetrical volume. Each optical element in the eye has its own optical and neural axes. Defining the optimum center for laser ablation is difficult with many available approaches. We explain the various centration approaches (based on these reference axes) in refractive surgery and review their clinical outcomes. The line-of-sight (LOS) (the line joining the entrance pupil center with the fixation point) is often the recommended reference axis for representing wavefront aberrations of the whole eye (derived from the definition of chief ray in geometrical optics); however pupil centration can be unstable and change with the pupil size. The corneal vertex (CV) represents a stable preferable morphologic reference which is the best approximate for alignment to the visual axis. However, the corneal light reflex can be considered as non-constant, but dependent on the direction of gaze of the eye with respect to the light source. A compromise between the pupil and CV centered ablations is seen in the form of an asymmetric offset where the manifest refraction is referenced to the CV while the higher order aberrations are referenced to the pupil center. There is a need for a flexible choice of centration in excimer laser systems to design customized and non-customized treatments optimally. PMID:26605360

  10. Statistical Analysis of Refractivity in UAE

    NASA Astrophysics Data System (ADS)

    Al-Ansari, Kifah; Al-Mal, Abdulhadi Abu; Kamel, Rami

    2007-07-01

    This paper presents the results of the refractivity statistics in the UAE (United Arab Emirates) for a period of 14 years (1990-2003). Six sites have been considered using meteorological surface data (Abu Dhabi, Dubai, Sharjah, Al-Ain, Ras Al-Kaimah, and Al-Fujairah). Upper air (radiosonde) data were available at one site only, Abu Dhabi airport, which has been considered for the refractivity gradient statistics. Monthly and yearly averages are obtained for the two parameters, refractivity and refractivity gradient. Cumulative distributions are also provided.

  11. Material and Optical Densities

    ERIC Educational Resources Information Center

    Gluck, Paul

    2007-01-01

    The bending of a laser beam in a medium with a density and refractive index gradient in the same direction has been described previously. When a transparent container is half filled with a salt or sugar solution and an equal amount of water is floated on top of it, then diffusion will create a concentration gradient from top to bottom. A laser…

  12. Refractive index change during exposure for 193-nm chemically amplified resists

    NASA Astrophysics Data System (ADS)

    Oh, Hye-Keun; Sohn, Young-Soo; Sung, Moon-Gyu; Lee, Young-Mi; Lee, Eun-Mi; Byun, Sung Hwan; An, Ilsin; Lee, Kun-Sang; Park, In-Ho

    1999-06-01

    Some of the important areas to be improved for lithography simulation are getting correct exposure parameters and determining the change of refractive index. It is known that the real and imaginary refractive indices are changed during exposure. We obtained these refractive index changes during exposure for 193 nm chemically amplified resists. The variations of the transmittance as well as the resist thickness were measured during ArF excimer laser exposure. We found that the refractive index change is directly related to the concentration of the photo acid generator and de-protected resin. It is important to know the exact values of acid concentration from the exposure parameters since a small difference in acid concentration magnifies the variation in the amplified de-protection during post exposure bake. We developed and used a method to extract Dill ABC exposure parameters for 193 nm chemically amplified resist from the refractive index change upon exposure.

  13. Detection of analyte refractive index and concentration using liquid-core photonic Bragg fibers

    NASA Astrophysics Data System (ADS)

    Li, Jingwen; Qu, Hang; Skorobogatiy, Maksim

    2016-03-01

    We demonstrate detection of liquid analyte refractive index by using a hollow-core photonic Bragg fiber. We apply this fiber sensor to monitor concentrations of commercial cooling oil. The sensor operates on a spectral modality. Variation in the analyte refractive index modifies the bandgap guidance of a fiber, leading to spectral shifts in the fiber transmission spectrum. The sensitivity of the sensor to changes in the analyte refractive index filling in the fiber core is found to be 1460nm/Refractive index unit (RIU). By using the spectral modality and effective medium theory, we determine the concentrations of commercial fluid from the measured refractive indices with an accuracy of ~0.42%. The presented fiber sensor can be used for on-line monitoring of concentration of many industrial fluids and dilutions with sub-1%v accuracy.

  14. Decoupling the refractive index from the electrical properties of transparent conducting oxides via periodic superlattices

    NASA Astrophysics Data System (ADS)

    Caffrey, David; Norton, Emma; Coileáin, Cormac Ó.; Smith, Christopher M.; Bulfin, Brendan; Farrell, Leo; Shvets, Igor V.; Fleischer, Karsten

    2016-09-01

    We demonstrate an alternative approach to tuning the refractive index of materials. Current methodologies for tuning the refractive index of a material often result in undesirable changes to the structural or optoelectronic properties. By artificially layering a transparent conducting oxide with a lower refractive index material the overall film retains a desirable conductivity and mobility while acting optically as an effective medium with a modified refractive index. Calculations indicate that, with our refractive index change of 0.2, a significant reduction of reflective losses could be obtained by the utilisation of these structures in optoelectronic devices. Beyond this, periodic superlattice structures present a solution to decouple physical properties where the underlying electronic interaction is governed by different length scales.

  15. Decoupling the refractive index from the electrical properties of transparent conducting oxides via periodic superlattices

    PubMed Central

    Caffrey, David; Norton, Emma; Coileáin, Cormac Ó; Smith, Christopher M.; Bulfin, Brendan; Farrell, Leo; Shvets, Igor V.; Fleischer, Karsten

    2016-01-01

    We demonstrate an alternative approach to tuning the refractive index of materials. Current methodologies for tuning the refractive index of a material often result in undesirable changes to the structural or optoelectronic properties. By artificially layering a transparent conducting oxide with a lower refractive index material the overall film retains a desirable conductivity and mobility while acting optically as an effective medium with a modified refractive index. Calculations indicate that, with our refractive index change of 0.2, a significant reduction of reflective losses could be obtained by the utilisation of these structures in optoelectronic devices. Beyond this, periodic superlattice structures present a solution to decouple physical properties where the underlying electronic interaction is governed by different length scales. PMID:27623228

  16. Refractive index sensor based on a polymer fiber directional coupler for low index sensing.

    PubMed

    Lee, Kwang Jo; Liu, Xiaoqi; Vuillemin, Nelly; Lwin, Richard; Leon-Saval, Sergio G; Argyros, Alexander; Kuhlmey, Boris T

    2014-07-14

    We propose, numerically analyze and experimentally demonstrate a novel refractive index sensor specialized for low index sensing. The device is based on a directional coupler architecture implemented in a single microstructured polymer optical fiber incorporating two waveguides within it: a single-mode core and a satellite waveguide consisting of a hollow high-index ring. This hollow channel is filled with fluid and the refractive index of the fluid is detected through changes to the wavelength at which resonant coupling occurs between the two waveguides. The sensor design was optimized for both higher sensitivity and lower detection limit, with simulations and experiments demonstrating a sensitivity exceeding 1.4 × 10(3) nm per refractive index unit. Simulations indicate a detection limit of ~2 × 10(-6) refractive index units is achievable. We also numerically investigate the performance for refractive index changes localized at the surface of the holes, a case of particular importance for biosensing.

  17. Decoupling the refractive index from the electrical properties of transparent conducting oxides via periodic superlattices.

    PubMed

    Caffrey, David; Norton, Emma; Coileáin, Cormac Ó; Smith, Christopher M; Bulfin, Brendan; Farrell, Leo; Shvets, Igor V; Fleischer, Karsten

    2016-09-13

    We demonstrate an alternative approach to tuning the refractive index of materials. Current methodologies for tuning the refractive index of a material often result in undesirable changes to the structural or optoelectronic properties. By artificially layering a transparent conducting oxide with a lower refractive index material the overall film retains a desirable conductivity and mobility while acting optically as an effective medium with a modified refractive index. Calculations indicate that, with our refractive index change of 0.2, a significant reduction of reflective losses could be obtained by the utilisation of these structures in optoelectronic devices. Beyond this, periodic superlattice structures present a solution to decouple physical properties where the underlying electronic interaction is governed by different length scales.

  18. Decoupling the refractive index from the electrical properties of transparent conducting oxides via periodic superlattices.

    PubMed

    Caffrey, David; Norton, Emma; Coileáin, Cormac Ó; Smith, Christopher M; Bulfin, Brendan; Farrell, Leo; Shvets, Igor V; Fleischer, Karsten

    2016-01-01

    We demonstrate an alternative approach to tuning the refractive index of materials. Current methodologies for tuning the refractive index of a material often result in undesirable changes to the structural or optoelectronic properties. By artificially layering a transparent conducting oxide with a lower refractive index material the overall film retains a desirable conductivity and mobility while acting optically as an effective medium with a modified refractive index. Calculations indicate that, with our refractive index change of 0.2, a significant reduction of reflective losses could be obtained by the utilisation of these structures in optoelectronic devices. Beyond this, periodic superlattice structures present a solution to decouple physical properties where the underlying electronic interaction is governed by different length scales. PMID:27623228

  19. Refractive index determination using the central focal masking technique with dispersion colors.

    USGS Publications Warehouse

    Wilcox, R.E.

    1983-01-01

    The procedures, precision, advantages and limitations of central focal masking ("dispersion staining'), a technique for determining the refractive indices of microfragments by the immersion method and for distinguishing between minerals in an immersion mount, are described. -J.A.Z.

  20. Effect of parallel refraction on magnetospheric upper hybrid waves

    NASA Technical Reports Server (NTRS)

    Engel, J.; Kennel, C. F.

    1984-01-01

    Large amplitude (not less than 10 mV/m) electrostatic plasma waves near the upper hybrid (UH) frequency have been observed from 0 to 50 deg magnetic latitude (MLAT) during satellite plasma-pause crossings. A three-dimensional numerical ray-tracing calculation, based on an electron distribution measured during a GEOS 1 dayside intense upper-hybrid wave event, suggests how UH waves might achieve such large amplitudes away from the geomagnetic equator. Refractive effects largely control the wave amplification and, in particular, the unavoidable refraction due to parallel geomagnetic field gradients restricts growth to levels below those observed. However, a cold electron density gradient parallel to the field can lead to upper hybrid wave growth that can account for the observed emission levels.

  1. Strong refraction near the Venus surface - Effects observed by descent probes

    NASA Technical Reports Server (NTRS)

    Croft, T. A.

    1982-01-01

    The telemetry signals from Pioneer Venus probes indicated the strong downward refraction of radio waves. As the probes descended, the strength of the direct signal decreased because of absorption and refractive defocusing. During the last 30 km of descent there was a second measured component in addition to the direct signal. Strong atmospheric reaction is important in strengthening echoes that are scattered toward the earth. Such surface-reflected signals are good indicators of horizontal winds.

  2. Experimental determination of the refractive index of metamaterials

    NASA Astrophysics Data System (ADS)

    Nielsen, Michael G.; Pors, Anders; Albrektsen, Ole; Willatzen, Morten; Bozhevolnyi, Sergey I.

    2011-05-01

    We present a simple experimental technique based on diffraction for determining the complex refractive index of metamaterials, and demonstrate it with metamaterials that consist of detuned electrical dipoles (DEDs), mimicking the dressed-state picture of electromagnetically induced transparency (EIT). The metamaterials are realized by fabricating lithographically defined gold nanorods on a silica substrate, covered with a ~ 15 µm thick polymer layer, and feature EIT-like transmission spectra with transparency windows centered at wavelengths near ~ 800 nm. The refractive indices are determined for wavelengths where the DED metamaterials exhibit enhanced transmission. Thereby, we experimentally demonstrate normal dispersion in the transmission window and estimate the group refractive index to ~ 3.6. Furthermore, finite-element simulations are conducted on a monolayer of DED unit cells, which similarly exhibit the EIT-like behavior in terms of enhanced transmission revealed in the transmission spectra. Simulated transmission and reflection spectra are utilized for calculations of the real and imaginary parts of the metamaterial refractive index, showing consistent trends with those obtained experimentally.

  3. S-wave refraction survey of alluvial aggregate

    USGS Publications Warehouse

    Ellefsen, Karl J.; Tuttle, Gary J.; Williams, Jackie M.; Lucius, Jeffrey E.

    2005-01-01

    An S-wave refraction survey was conducted in the Yampa River valley near Steamboat Springs, Colo., to determine how well this method could map alluvium, a major source of construction aggregate. At the field site, about 1 m of soil overlaid 8 m of alluvium that, in turn, overlaid sedimentary bedrock. The traveltimes of the direct and refracted S-waves were used to construct velocity cross sections whose various regions were directly related to the soil, alluvium, and bed-rock. The cross sections were constrained to match geologic logs that were developed from drill-hole data. This constraint minimized the ambiguity in estimates of the thickness and the velocity of the alluvium, an ambiguity that is inherent to the S-wave refraction method. In the cross sections, the estimated S-wave velocity of the alluvium changed in the horizontal direction, and these changes were attributed to changes in composition of the alluvium. The estimated S-wave velocity of the alluvium was practically constant in the vertical direc-tion, indicating that the fine layering observed in the geologic logs could not be detected. The S-wave refraction survey, in conjunction with independent information such as geologic logs, was found to be suitable for mapping the thickness of the alluvium.

  4. Polymers for refractive index change in intraocular lenses: a novel approach for photoinduced tuning of focal length

    NASA Astrophysics Data System (ADS)

    Träger, Jens; Kim, Hee-Cheol; Hampp, Norbert

    2006-02-01

    Before an intraocular lens (IOL) is implanted during cataract surgery, biometric data of the patient's eye have to be determined to calculate the thickness and shape of the IOL. In particular the postoperative anterior chamber depth is an important parameter to predict the correct shape of the IOL. This value, however, cannot be measured without significant uncertainities. We present a solution to this problem, describe novel polymers suitable for IOLs which refractive indices can be changed non-invasively in a photo-induced process. The focal length can be modified by about 2 D, which is sufficient to achive ideal acuteness of vision for almost all patients with implanted IOLs. The change in refractive index is accomplished by linking or cleaving bonds between a sufficiently large number of side groups of the polymer main chain in a photoinduced cyloaddition or cycloreversion, respectively. The photochemical reaction can also be triggered by a two-photon process (TPA) using a pulsed laser system, i.e. the energy required for bond breaking is provided by two photons in the visible range. Light in the UV as well as the visible range of the spectrum cannot induce undesired changes of the refractive index owing to the strong UV-absorption of the cornea and photon densities much too low for TPA, respectively. Due to the excellent spatial resolution that can be achieved with two-photon processes not only modification of the refractive index of the entire lens but also selectively in well defined areas is possible enabling the correction for aberrations such as astigmatism.

  5. Retinal Image Simulation of Subjective Refraction Techniques.

    PubMed

    Perches, Sara; Collados, M Victoria; Ares, Jorge

    2016-01-01

    Refraction techniques make it possible to determine the most appropriate sphero-cylindrical lens prescription to achieve the best possible visual quality. Among these techniques, subjective refraction (i.e., patient's response-guided refraction) is the most commonly used approach. In this context, this paper's main goal is to present a simulation software that implements in a virtual manner various subjective-refraction techniques--including Jackson's Cross-Cylinder test (JCC)--relying all on the observation of computer-generated retinal images. This software has also been used to evaluate visual quality when the JCC test is performed in multifocal-contact-lens wearers. The results reveal this software's usefulness to simulate the retinal image quality that a particular visual compensation provides. Moreover, it can help to gain a deeper insight and to improve existing refraction techniques and it can be used for simulated training.

  6. Refraction in electrically thin inhomogeneous media.

    PubMed

    Ruphuy, Miguel; Ramahi, Omar M

    2016-04-01

    This work presents a new formulation for refraction from flat electrically thin lenses and reflectors comprised of inhomogeneous material. Inhomogeneous electrically thin flat lenses and reflectors cannot make use of the Snell law since this classical formulation works solely at interfaces of planar homogeneous media. The refraction of a perpendicularly incident plane wave at a planar interface is physically explained through the phase advance of the rays within the medium. The Huygens principle is then used to construct the refracted wavefront. The formulation is validated using numerical full wave simulation for several examples where the refractive angle is predicted with good accuracy. Furthermore, the formulation gives a physical insight of the phenomenon of refraction from electrically thin inhomogeneous media.

  7. Retinal Image Simulation of Subjective Refraction Techniques

    PubMed Central

    Perches, Sara; Collados, M. Victoria; Ares, Jorge

    2016-01-01

    Refraction techniques make it possible to determine the most appropriate sphero-cylindrical lens prescription to achieve the best possible visual quality. Among these techniques, subjective refraction (i.e., patient’s response-guided refraction) is the most commonly used approach. In this context, this paper’s main goal is to present a simulation software that implements in a virtual manner various subjective-refraction techniques—including Jackson’s Cross-Cylinder test (JCC)—relying all on the observation of computer-generated retinal images. This software has also been used to evaluate visual quality when the JCC test is performed in multifocal-contact-lens wearers. The results reveal this software’s usefulness to simulate the retinal image quality that a particular visual compensation provides. Moreover, it can help to gain a deeper insight and to improve existing refraction techniques and it can be used for simulated training. PMID:26938648

  8. Traffic air pollution and risk of death from gastric cancer in Taiwan: petrol station density as an indicator of air pollutant exposure.

    PubMed

    Chiu, Hui-Fen; Tsai, Shang-Shyue; Chen, Pei-Shih; Liao, Yen-Hsiung; Liou, Saou-Hsing; Wu, Trong-Neng; Yang, Chun-Yuh

    2011-01-01

    To investigate the relationship between air pollution and risk of death attributed to gastric cancer, a matched cancer case-control study was conducted using deaths that occurred in Taiwan from 2004 through 2008. Data for all eligible gastric cancer deaths were obtained and compared to a control group consisting of individuals who died from causes other than neoplasms and diseases that were associated with gastrointestinal (GIT) disorders. The controls were pair-matched to the cancer cases by gender, year of birth, and year of death. Each matched control was randomly selected from the set of possible controls for each cancer case. Data for the number of petrol stations in study municipalities were collected from two major petroleum supply companies. The petrol station density (per square kilometer) (PSD) for study municipalities was used as an indicator of a subject's exposure to benzene and other hydrocarbons present in ambient evaporative losses of petrol or to air emissions from motor vehicles. The exposed individuals were subdivided into three categories (≤25th percentile; 25th-75th percentile; >75th percentile) according to PSD in the residential municipality. Results showed that individuals who resided in municipalities with the highest PSD were at an increased risk of death attributed to gastric cancer compared to those subjects living in municipalities with the lowest PSD. The findings of this study warrant further investigation of the role of traffic air pollution exposure in the etiology of gastric cancer.

  9. The association of very low-density lipoprotein receptor (VLDLR) haplotypes with egg production indicates VLDLR is a candidate gene for modulating egg production

    PubMed Central

    Wang, ZhePeng; Meng, GuoHua; Li, Na; Yu, MingFen; Liang, XiaoWei; Min, YuNa; Liu, FuZhu; Gao, YuPeng

    2016-01-01

    Abstract The very low-density lipoprotein receptor (VLDLR) transports egg yolk precursors into oocytes. However, our knowledge of the distribution patterns of VLDLR variants among breeds and their relationship to egg production is still incomplete. In this study, eight single nucleotide polymorphisms (SNPs) that account for 87% of all VLDLR variants were genotyped in Nick Chick (NC, n=91), Lohmann Brown (LohB, n=50) and Lueyang (LY, n=381) chickens, the latter being an Chinese indigenous breed. Egg production by NC and LY chickens was recorded from 17 to 50 weeks. Only four similar haplotypes were found in NC and LohB, of which two accounted for 100% of all NC haplotypes and 92.5% of LohB haplotypes. In contrast, there was considerable haplotypic diversity in LY. Comparison of egg production in LY showed that hens with NC-like haplotypes had a significantly higher production (p < 0.05) than those without the haplotypes. However, VLDLR expression was not significantly different between the haplotypes. These findings indicate a divergence in the distribution of VLDLR haplotypes between selected and non-selected breeds and suggest that the near fixation of VLDLR variants in NC and LohB is compatible with signature of selection. These data also support VLDLR as a candidate gene for modulating egg production. PMID:27560838

  10. The association of very low-density lipoprotein receptor (VLDLR) haplotypes with egg production indicates VLDLR is a candidate gene for modulating egg production.

    PubMed

    Wang, ZhePeng; Meng, GuoHua; Li, Na; Yu, MingFen; Liang, XiaoWei; Min, YuNa; Liu, FuZhu; Gao, YuPeng

    2016-01-01

    The very low-density lipoprotein receptor (VLDLR) transports egg yolk precursors into oocytes. However, our knowledge of the distribution patterns of VLDLR variants among breeds and their relationship to egg production is still incomplete. In this study, eight single nucleotide polymorphisms (SNPs) that account for 87% of all VLDLR variants were genotyped in Nick Chick (NC, n=91), Lohmann Brown (LohB, n=50) and Lueyang (LY, n=381) chickens, the latter being an Chinese indigenous breed. Egg production by NC and LY chickens was recorded from 17 to 50 weeks. Only four similar haplotypes were found in NC and LohB, of which two accounted for 100% of all NC haplotypes and 92.5% of LohB haplotypes. In contrast, there was considerable haplotypic diversity in LY. Comparison of egg production in LY showed that hens with NC-like haplotypes had a significantly higher production (p < 0.05) than those without the haplotypes. However, VLDLR expression was not significantly different between the haplotypes. These findings indicate a divergence in the distribution of VLDLR haplotypes between selected and non-selected breeds and suggest that the near fixation of VLDLR variants in NC and LohB is compatible with signature of selection. These data also support VLDLR as a candidate gene for modulating egg production.

  11. The association of very low-density lipoprotein receptor (VLDLR) haplotypes with egg production indicates VLDLR is a candidate gene for modulating egg production.

    PubMed

    Wang, ZhePeng; Meng, GuoHua; Li, Na; Yu, MingFen; Liang, XiaoWei; Min, YuNa; Liu, FuZhu; Gao, YuPeng

    2016-01-01

    The very low-density lipoprotein receptor (VLDLR) transports egg yolk precursors into oocytes. However, our knowledge of the distribution patterns of VLDLR variants among breeds and their relationship to egg production is still incomplete. In this study, eight single nucleotide polymorphisms (SNPs) that account for 87% of all VLDLR variants were genotyped in Nick Chick (NC, n=91), Lohmann Brown (LohB, n=50) and Lueyang (LY, n=381) chickens, the latter being an Chinese indigenous breed. Egg production by NC and LY chickens was recorded from 17 to 50 weeks. Only four similar haplotypes were found in NC and LohB, of which two accounted for 100% of all NC haplotypes and 92.5% of LohB haplotypes. In contrast, there was considerable haplotypic diversity in LY. Comparison of egg production in LY showed that hens with NC-like haplotypes had a significantly higher production (p < 0.05) than those without the haplotypes. However, VLDLR expression was not significantly different between the haplotypes. These findings indicate a divergence in the distribution of VLDLR haplotypes between selected and non-selected breeds and suggest that the near fixation of VLDLR variants in NC and LohB is compatible with signature of selection. These data also support VLDLR as a candidate gene for modulating egg production. PMID:27560838

  12. Simulation of imperfections in plastic lenses - transferring local refractive index changes into surface shape modifications

    NASA Astrophysics Data System (ADS)

    Arasa, Josep; Pizarro, Carles; Blanco, Patricia

    2016-06-01

    Injection molded plastic lenses have continuously improved their performance regarding optical quality and nowadays are as usual as glass lenses in image forming devices. However, during the manufacturing process unavoidable fluctuations in material density occur, resulting in local changes in the distribution of refractive index, which degrade the imaging properties of the polymer lens. Such material density fluctuations correlate to phase delays, which opens a path for their mapping. However, it is difficult to transfer the measured variations in refractive index into conventional optical simulation tool. Thus, we propose a method to convert the local variations in refractive index into local changes of one surface of the lens, which can then be described as a free-form surface, easy to introduce in conventional simulation tools. The proposed method was tested on a commercial gradient index (GRIN) lens for a set of six different object positions, using the MTF sagittal and tangential cuts to compare the differences between the real lens and a lens with homogenous refractive index, and the last surface converted into a free-form shape containing the internal refractive index changes. The same procedure was used to reproduce the local refractive index changes of an injected plastic lens with local index changes measured using an in-house built polariscopic arrangement, showing the capability of the method to provide successful results.

  13. Vacuum birefringence in strong magnetic fields: (II) Complex refractive index from the lowest Landau level

    SciTech Connect

    Hattori, Koichi; Itakura, Kazunori

    2013-07-15

    We compute the refractive indices of a photon propagating in strong magnetic fields on the basis of the analytic representation of the vacuum polarization tensor obtained in our previous paper. When the external magnetic field is strong enough for the fermion one-loop diagram of the polarization tensor to be approximated by the lowest Landau level, the propagating mode in parallel to the magnetic field is subject to modification: The refractive index deviates from unity and can be very large, and when the photon energy is large enough, the refractive index acquires an imaginary part indicating decay of a photon into a fermion–antifermion pair. We study dependences of the refractive index on the propagating angle and the magnetic-field strength. It is also emphasized that a self-consistent treatment of the equation which defines the refractive index is indispensable for accurate description of the refractive index. This self-consistent treatment physically corresponds to consistently including the effects of back reactions of the distorted Dirac sea in response to the incident photon. -- Highlights: •Vacuum birefringence and photon decay are described by the complex refractive index. •Resummed photon vacuum polarization tensor in the lowest Landau level is used. •Back reactions from the distorted Dirac sea are self-consistently taken into account. •Self-consistent treatment drastically changes structure in photon energy dependence. •Dependences on photon propagation angle and magnetic-field strength are presented.

  14. DISCRIMINATING BETWEEN CLOUDY, HAZY, AND CLEAR SKY EXOPLANETS USING REFRACTION

    SciTech Connect

    Misra, Amit K.; Meadows, Victoria S.

    2014-11-01

    We propose a method to distinguish between cloudy, hazy, and clear sky (free of clouds and hazes) exoplanet atmospheres that could be applicable to upcoming large aperture space- and ground-based telescopes such as the James Webb Space Telescope (JWST) and the European Extremely Large Telescope (E-ELT). These facilities will be powerful tools for characterizing transiting exoplanets, but only after a considerable amount of telescope time is devoted to a single planet. A technique that could provide a relatively rapid means of identifying haze-free targets (which may be more valuable targets for characterization) could potentially increase the science return for these telescopes. Our proposed method utilizes broadband observations of refracted light in the out-of-transit spectrum. Light refracted through an exoplanet atmosphere can lead to an increase of flux prior to ingress and subsequent to egress. Because this light is transmitted at pressures greater than those for typical cloud and haze layers, the detection of refracted light could indicate a cloud- or haze-free atmosphere. A detection of refracted light could be accomplished in <10 hr for Jovian exoplanets with JWST and <5 hr for super-Earths/mini-Neptunes with E-ELT. We find that this technique is most effective for planets with equilibrium temperatures between 200 and 500 K, which may include potentially habitable planets. A detection of refracted light for a potentially habitable planet would strongly suggest the planet was free of a global cloud or haze layer, and therefore a promising candidate for follow-up observations.

  15. Temperature-dependent Refractive Index of Silicon and Germanium

    NASA Technical Reports Server (NTRS)

    Frey, Bradley J.; Leviton, Douglas B.; Madison, Timothy J.

    2006-01-01

    Silicon and germanium are perhaps the two most well-understood semiconductor materials in the context of solid state device technologies and more recently micromachining and nanotechnology. Meanwhile, these two materials are also important in the field of infrared lens design. Optical instruments designed for the wavelength range where these two materials are transmissive achieve best performance when cooled to cryogenic temperatures to enhance signal from the scene over instrument background radiation. In order to enable high quality lens designs using silicon and germanium at cryogenic temperatures, we have measured the absolute refractive index of multiple prisms of these two materials using the Cryogenic, High-Accuracy Refraction Measuring System (CHARMS) at NASA's Goddard Space Flight Center, as a function of both wavelength and temperature. For silicon, we report absolute refractive index and thermo-optic coefficient (dn/dT) at temperatures ranging from 20 to 300 K at wavelengths from 1.1 to 5.6 pin, while for germanium, we cover temperatures ranging from 20 to 300 K and wavelengths from 1.9 to 5.5 microns. We compare our measurements with others in the literature and provide temperature-dependent Sellmeier coefficients based on our data to allow accurate interpolation of index to other wavelengths and temperatures. Citing the wide variety of values for the refractive indices of these two materials found in the literature, we reiterate the importance of measuring the refractive index of a sample from the same batch of raw material from which final optical components are cut when absolute accuracy greater than k5 x 10" is desired.

  16. Negative refractive index, perfect lenses and checkerboards: Trapping and imaging effects in folded optical spaces

    NASA Astrophysics Data System (ADS)

    Guenneau, Sébastien; Ramakrishna, S. Anantha

    2009-06-01

    Newly discovered metamaterials have opened new vistas for better control of light via negative refraction, whereby light refracts in the "wrong" manner. These are dielectric and metallic composite materials structured at subwavelength lengthscales. Their building blocks consist of local resonators such as conducting thin bars and split rings driving the material parameters such as the dielectric permittivity and magnetic permeability to negative (complex) values. Combined together, these structural elements can bring about a (complex valued) negative effective refractive index for the Snell-Descartes law and result in negative refraction of radiation. Negative refractive index materials can support a host of surface plasmon states for both polarizations of light. This makes possible unique effects such as imaging with subwavelength image resolution through the Pendry-Veselago slab lens. Other geometries have also been investigated, such as cylindrical or spherical lenses that enable a magnification of images with subwavelength resolution. Superlenses of three-fold (equilateral triangle), four-fold (square) and six-fold (hexagonal) geometry allow for multiple images, respectively two, three, and five. Generalization to rectangular and triangular checkerboards consisting of alternating cells of positive and negative refractive index represents a very singular situation in which the density of modes diverges at the corners, with an infinity of images. Sine-cosecant anisotropic heterogeneous square and triangular checkerboards can be respectively mapped onto three-dimensional cubic and icosahedral corner lenses consisting of alternating positive and negative refractive regions. All such systems with corners between negative and positive refractive media display very singular behavior with the local density of states becoming infinitely large at the corner, in the limit of no dissipation. We investigate all of these, using the unifying viewpoint of transformation optics

  17. An examination of the southern California field test for the systematic accumulation of the optical refraction error in geodetic leveling.

    USGS Publications Warehouse

    Castle, R.O.; Brown, B.W., Jr.; Gilmore, T.D.; Mark, R.K.; Wilson, R.C.

    1983-01-01

    Appraisals of the two levelings that formed the southern California field test for the accumulation of the atmospheric refraction error indicate that random error and systematic error unrelated to refraction competed with the systematic refraction error and severely complicate any analysis of the test results. If the fewer than one-third of the sections that met less than second-order, class I standards are dropped, the divergence virtually disappears between the presumably more refraction contaminated long-sight-length survey and the less contaminated short-sight-length survey. -Authors

  18. Ray tracing evaluation of a technique for correcting the refraction errors in satellite tracking data

    NASA Technical Reports Server (NTRS)

    Gardner, C. S.; Rowlett, J. R.; Hendrickson, B. E.

    1978-01-01

    Errors may be introduced in satellite laser ranging data by atmospheric refractivity. Ray tracing data have indicated that horizontal refractivity gradients may introduce nearly 3-cm rms error when satellites are near 10-degree elevation. A correction formula to compensate for the horizontal gradients has been developed. Its accuracy is evaluated by comparing it to refractivity profiles. It is found that if both spherical and gradient correction formulas are employed in conjunction with meteorological measurements, a range resolution of one cm or less is feasible for satellite elevation angles above 10 degrees.

  19. Negative Refraction experiments in Photonic Crystal prisms

    NASA Astrophysics Data System (ADS)

    Vodo, Plarenta; Parimi, Patanjali. V.; Lu, Wentao. T.; di Gennaro, Emiliano; Sridhar, Srinivas

    2004-03-01

    We have experimentally demonstrated negative refraction in metallic photonic crystal (PC) prisms [1]. The refracted fields in the parallel plate waveguide (PPW) are measured by an automated dipole antenna, which scans the desired area, while the free space (FS) measurements, performed in a anechoic chamber, are measured by a rectangular X-band horn that swings in an arc in far field area. Both TE and TM excitation modes are used in FS experiments. Numerical calculations of the band structure and equi-frequency surface simulations are used to determine frequency regions of negative refraction of the triangular lattice PC. Angle of refraction determined by theoretical simulations and experimental results, are in exceptional good agreement, yielding the negative refraction index. FS and PPW refraction experimental results agree remarkably with simulations. 1. "Negative Refraction and Left-handed electromagnetism in Microwave Photonic Crystals", P.V Parimi, W.T Lu, P.Vodo J. Sokoloff and S.Sridhar, cond-mat/0306109 (2003)

  20. Failure Analysis of Sapphire Refractive Secondary Concentrators

    NASA Technical Reports Server (NTRS)

    Salem, Jonathan A.; Quinn, George D.

    2009-01-01

    Failure analysis was performed on two sapphire, refractive secondary concentrators (RSC) that failed during elevated temperature testing. Both concentrators failed from machining/handling damage on the lens face. The first concentrator, which failed during testing to 1300 C, exhibited a large r-plane twin extending from the lens through much of the cone. The second concentrator, which was an attempt to reduce temperature gradients and failed during testing to 649 C, exhibited a few small twins on the lens face. The twins were not located at the origin, but represent another mode of failure that needs to be considered in the design of sapphire components. In order to estimate the fracture stress from fractographic evidence, branching constants were measured on sapphire strength specimens. The fractographic analysis indicated radial tensile stresses of 44 to 65 MPa on the lens faces near the origins. Finite element analysis indicated similar stresses for the first RSC, but lower stresses for the second RSC. Better machining and handling might have prevented the fractures, however, temperature gradients and resultant thermal stresses need to be reduced to prevent twinning.

  1. J. B. Biot and Refraction Calculations

    NASA Astrophysics Data System (ADS)

    Young, A. T.

    2000-12-01

    The Auer-Standish (AJ 119, 2472, 2000) algorithm, recommended in the revised Explanatory Supplement for calculating refraction in an arbitrary model atmosphere, was derived and used by J. B. Biot (Conn. des Tems pour l'An 1839) a century and a half earlier, using Newton's (wrong) emission theory, and the clumsy notation of Laplace's Mécanique Céleste, which Biot had proof-read. Newton, Laplace, and Biot all describe refraction in terms of the trajectories of ``luminous molecules'' attracted by a central force exerted by the atmosphere; this explains why Laplace considered refraction a topic in celestial mechanics. Fortunately for these authors, the only optics required is Snel's law of refraction, which was discovered before Newton's birth, and which Newton's corpuscular optics was rigged to reproduce. Thus Biot's ``derivation'' of the refractive invariant nr sin z by Laplace's method is a circular and unnecessary argument. While Auer & Standish were reinventing Biot's method, the historian D. T. Whiteside (Centaurus 24, 288, 1980) noticed the mathematical similarity of the refraction theories of Newton and Biot to modern ones, and rashly concluded that ``working astronomers still find computational advantage in maintaining the fiction of a Newtonian emission theory'' --- which is absurd nonsense! Despite being an emissionist, Biot understood atmospheric refraction much better than most astronomers do today: he knew why refraction is almost independent of atmospheric structure, except within a few degrees of the horizon, and that refraction at the horizon depends mostly on the local temperature gradient. His work --- together with that of Lord Rayleigh, who derived his eponymous scattering law from the elastic-solid theory of the luminiferous \\ae ther --- reminds us that a theory's correct results do not make it true. This work was supported by NSF grant ATM-9714357.

  2. Formation of bulk refractive index structures

    DOEpatents

    Potter, Jr., Barrett George; Potter, Kelly Simmons; Wheeler, David R.; Jamison, Gregory M.

    2003-07-15

    A method of making a stacked three-dimensional refractive index structure in photosensitive materials using photo-patterning where first determined is the wavelength at which a photosensitive material film exhibits a change in refractive index upon exposure to optical radiation, a portion of the surfaces of the photosensitive material film is optically irradiated, the film is marked to produce a registry mark. Multiple films are produced and aligned using the registry marks to form a stacked three-dimensional refractive index structure.

  3. The refraction in the atmospheric surface layer

    NASA Astrophysics Data System (ADS)

    Golitsyn, G. S.

    1982-12-01

    An analytical theory of refraction for the atmospheric layer is developed in which the vertical profiles of the refraction are calculated based on the theory of Monin and Obukhov (1954). A similarity parameter is found for the refraction in such conditions. These results are used to clarify the idea of Moroz (1976) that the nearness of the horizon as recorded by the automatic stations on the surface of Venus can be explained by the decrease in the temperature at the very surface of the planet. In addition, several other optical phenomena which occur near the surface of the earth are examined.

  4. Atmospheric refraction errors in laser ranging systems

    NASA Technical Reports Server (NTRS)

    Gardner, C. S.; Rowlett, J. R.

    1976-01-01

    The effects of horizontal refractivity gradients on the accuracy of laser ranging systems were investigated by ray tracing through three dimensional refractivity profiles. The profiles were generated by performing a multiple regression on measurements from seven or eight radiosondes, using a refractivity model which provided for both linear and quadratic variations in the horizontal direction. The range correction due to horizontal gradients was found to be an approximately sinusoidal function of azimuth having a minimum near 0 deg azimuth and a maximum near 180 deg azimuth. The peak to peak variation was approximately 5 centimeters at 10 deg elevation and decreased to less than 1 millimeter at 80 deg elevation.

  5. Complex Refractive Index of Ammonium Nitrate in the 2-20 micron Spectral Range

    NASA Technical Reports Server (NTRS)

    Jarzembski, Maurice A.; Norman, Mark L.; Fuller, Kirk A.; Srivastava, Vandana; Cutten, Dean R.

    2002-01-01

    Using high resolution Fourier Transform Infrared Spectroscopy (FTIR) absorbance/transmittance spectral data for ammonium sulfate (AMS), calcium carbonate (CAC) and ammonium nitrate (AMN), comparisons were made with previously published complex refractive indices data for AMS and CAC to infer experimental parameters to determine the imaginary refractive index for AMN in the infrared wavelength range from 2 to 20 microns. Kramers-Kronig mathematical relations were applied to calculate the real refractive index for the three compositions. Excellent agreement for AMS and CAC with the published values was found, validating the complex refractive indices obtained for AMN. Backscatter calculations using a lognormal size distribution for AMS, AMN, and CAC aerosols were performed to show differences in their backscattered spectra.

  6. Radiative transfer in nonuniformly refracting layered media: atmosphere-ocean system.

    PubMed

    Jin, Z; Stamnes, K

    1994-01-20

    We have applied the discrete-ordinate method to solve the radiative-transfer problem pertaining to a system consisting of two strata with different indices of refraction. The refraction and reflection at the interface are taken into account. The relevant changes (as compared with the standard problem with a constant index of refraction throughout the medium) in formulation and solution of the radiative-transfer equation, including the proper application of interface and boundary conditions, are described. Appropriate quadrature points (streams) and weights are chosen for the interface-continuity relations. Examples of radiative transfer in the coupled atmosphere-ocean system are provided. To take into account the region of total reflection in the ocean, additional angular quadrature points are required, compared with those used in the atmosphere and in the refractive region of the ocean that communicates directly with the atmosphere. To verify the model we have tested for energy conservation. We also discuss the effect of the number of streams assigned to the refractive region and the total reflecting region on the convergence. Our results show that the change in the index of refraction between the two strata significantly affects the radiation field. The radiative-transfer model we present is designed for application to the atmosphere-ocean system, but it can be applied to other systems that need to consider the change in the index of refraction between two strata. PMID:20862035

  7. Determination of Diameter and Index of Refraction of Textile Fibers by Laser Backscattering

    SciTech Connect

    H. Okuda; B. Stratton; L. Meixler; P. Efthimion; D.Mansfield

    2003-07-24

    A new method was developed to determine both diameters and indices of refraction and hence the birefringence of cylindrical textile and industrial fibers and bundles by measuring intensity patterns of the scattered light over an interval of scattering angles. The measured intensity patterns are compared with theoretical predictions (Mie theory) to determine fiber diameter and index of refraction. It is shown that the method is simple and accurate and may be useful as an on-line, noncontact diagnostic tool in real time.

  8. Refractive index measurement using comparative interferometry

    NASA Astrophysics Data System (ADS)

    Bojan, Mihaela; Apostol, D.; Damian, V.; Logofatu, P. C.; Garoi, F.; Iordache, Iuliana

    2007-05-01

    The refractive index of a material medium is an important optical parameter since it exhibits the optical properties of the material. The adulteration problem is increasing day by day and hence simple, automatic and accurate measurement of the refractive index of materials is of great importance these days. For solid thin films materials Abeles method was reconsidered. Quick, measurements of refractive index using simple techniques and refractometers can help controlling adulteration of liquids of common use to a greater extent. Very simple interferometric set-up using Fizeau fringe patterns compares the fringe pitch as obtained in a cell with two levels: one down level with the unknown refractive index liquids and the upper level with gas air. A CCD matrix and a PC can handle the data and produce the results up to for digits.

  9. A New Expression for Astronomical Refraction

    NASA Astrophysics Data System (ADS)

    Yan, Haojian

    1996-09-01

    In this paper, new sophisticated computing formulas for astronomical refraction have been developed based on the generator function method of atmospheric refractive integrals proposed by Yan & Ping (1995, AJ, 110, 934). The accuracies of the expressions have been numerically improved about one order of magnitude in comparison with those commonly used. A significant advantage of using a calibrated continued fraction mapping function for the astronomical refraction correction is to extend the coverage of the formulas to rather lower elevation observations with high accuracy. The corrections related to the finite distances of objects have been considered in detail. We have briefly analyzed the influences of the errors of atmospheric profile and of the deviation of atmospheric parameters. in order to match different requirements in astrometry and geodesy, we have considered the corrections at both radio and optical frequencies, respectively. The dispersion of signals at optical frequencies plays a primary role in astronomical refraction computation.

  10. The refractive index of relic gravitons

    NASA Astrophysics Data System (ADS)

    Giovannini, Massimo

    2016-06-01

    The dynamical evolution of the refractive index of the tensor modes of the geometry produces a specific class of power spectra characterized by a blue (i.e. slightly increasing) slope which is directly determined by the competition of the slow-roll parameter and of the rate of variation of the refractive index. Throughout the conventional stages of the inflationary and post-inflationary evolution, the microwave background anisotropies measurements, the pulsar timing limits and the big-bang nucleosynthesis constraints set stringent bounds on the refractive index and on its rate of variation. Within the physically allowed region of the parameter space the cosmic background of relic gravitons leads to a potentially large signal for the ground-based detectors (in their advanced version) and for the proposed space-borne interferometers. Conversely, the lack of direct detection of the signal will set a qualitatively new bound on the dynamical variation of the refractive index.

  11. Nonlinear negative refraction by difference frequency generation

    NASA Astrophysics Data System (ADS)

    Cao, Jianjun; Shen, Dongyi; Feng, Yaming; Wan, Wenjie

    2016-05-01

    Negative refraction has attracted much interest for its promising capability in imaging applications. Such an effect can be implemented by negative index meta-materials, however, which are usually accompanied by high loss and demanding fabrication processes. Recently, alternative nonlinear approaches like phase conjugation and four wave mixing have shown advantages of low-loss and easy-to-implement, but associated problems like narrow accepting angles can still halt their practical applications. Here, we demonstrate theoretically and experimentally a scheme to realize negative refraction by nonlinear difference frequency generation with wide tunability, where a thin Beta barium borate slice serves as a negative refraction layer bending the input signal beam to the idler beam at a negative angle. Furthermore, we realize optical focusing effect using such nonlinear negative refraction, which may enable many potential applications in imaging science.

  12. REFractions: The Representing Equivalent Fractions Game

    ERIC Educational Resources Information Center

    Tucker, Stephen I.

    2014-01-01

    Stephen Tucker presents a fractions game that addresses a range of fraction concepts including equivalence and computation. The REFractions game also improves students' fluency with representing, comparing and adding fractions.

  13. [Is there a relation between weight in rats, bone density, ash weight and histomorphometric indicators of trabecular volume and thickness in the bones of extremities?].

    PubMed

    Zák, J; Kapitola, J; Povýsil, C

    2003-01-01

    Authors deal with question, if there is possibility to infer bone histological structure (described by histomorphometric parameters of trabecular bone volume and trabecular thickness) from bone density, ash weight or even from weight of animal (rat). Both tibias of each of 30 intact male rats, 90 days old, were processed. Left tibia was utilized to the determination of histomorphometric parameters of undecalcified bone tissue patterns by automatic image analysis. Right tibia was used to the determination of values of bone density, using Archimedes' principle. Values of bone density, ash weight, ash weight related to bone volume and animal weight were correlated with histomorphometric parameters (trabecular bone volume, trabecular thickness) by Pearson's correlation test. One could presume the existence of relation between data, describing bone mass at the histological level (trabecular bone of tibia) and other data, describing mass of whole bone or even animal mass (weight). But no statistically significant correlation was found. The reason of the present results could be in the deviations of trabecular density in marrow of tibia. Because of higher trabecular bone density in metaphyseal and epiphyseal regions, the histomorphometric analysis of trabecular bone is preferentially done in these areas. It is possible, that this irregularity of trabecular tibial density could be the source of the deviations, which could influence the results of correlations determined. The values of bone density, ash weight and animal weight do not influence trabecular bone volume and vice versa: static histomorphometric parameters of trabecular bone do not reflect bone density, ash weight and weight of animal. PMID:15224536

  14. Refractive index and birefringence of 2H silicon carbide

    NASA Technical Reports Server (NTRS)

    Powell, J. A.

    1972-01-01

    The refractive indices of 2H SiC were measured over the wavelength range 435.8 to 650.9 nm by the method of minimum deviation. At the wavelength lambda = 546.1 nm, the ordinary index n sub 0 was 2.6480 and the extraordinary index n sub e was 2.7237. The estimated error (standard deviation) in the measured values is 0.0006 for n sub 0 and 0.0009 for n sub e. The experimental data were curve fitted to the Cauchy equation for the index of refraction as a function of wavelength. The birefringence of 2H SiC was found to vary from 0.0719 at lambda = 650.9 nm to 0.0846 at lambda = 435.8 nm.

  15. Imaging based refractometer for hyperspectral refractive index detection

    SciTech Connect

    Baba, Justin S.; Boudreaux, Philip R.

    2015-11-24

    Refractometers for simultaneously measuring refractive index of a sample over a range of wavelengths of light include dispersive and focusing optical systems. An optical beam including the range of wavelengths is spectrally spread along a first axis and focused along a second axis so as to be incident to an interface between the sample and a prism at a range of angles of incidence including a critical angle for at least one wavelength. An imaging detector is situated to receive the spectrally spread and focused light from the interface and form an image corresponding to angle of incidence as a function of wavelength. One or more critical angles are identified and corresponding refractive indices are determined.

  16. Does negative refraction make a perfect lens?

    NASA Astrophysics Data System (ADS)

    Ramm, A. G.

    2008-10-01

    A discussion of a question, studied earlier by Veselago in 1967 and by Pendry in 2000, is given. The question is: can a slab of the material with negative refraction make a perfect lens? Pendry's conclusion was: yes, it can. Our conclusion is: no, in practice it cannot, because of the fluctuations of the refraction coefficient of the slab. Resolution ability of linear isoplanatic optical instruments is discussed.

  17. Two Color Interferometry with Nonlinear Refractive Properties

    NASA Technical Reports Server (NTRS)

    Vikram, Chandra S.; Witherow, William K.

    2002-01-01

    Using nonlinear refractive properties of salt-water solution at two wavelengths, numerical analysis has been performed to extract temperature and concentration from virtual interferometric fringe data. The theoretical study, using a commercially available equation solving tool, starts with critical fringe counting needs and the role of nonlinear refractive properties in such measurements. Finally, methodology of the analysis, developed codes, and fringe counting accuracy needs are described in detail.

  18. Low scatter edge blackening compounds for refractive optical elements

    SciTech Connect

    Lewis, I.T.; Telkamp, A.R. ); Ledebuhr, A.G. )

    1989-07-25

    Perkin-Elmer's Applied Optics Operation recently delivered several prototype wide-field-of-view (WFOV), F/2.8, 250 mm efl, near diffraction limited, concentric refractive lenses to Lawrence Livermore National Laboratory (LLNL). In these lenses, special attention was paid to reducing stray light to allow viewing of very dim objects. Because of the very large FOV, the use of a long baffle to eliminate direct illumination of lens edges was not practical. With the existing relatively short baffle design, one-bounce stray light paths off the element edges are possible. The scattering off the inside edges thus had to be kept to an absolute minimum. While common means for blackening the edges of optical elements are easy to apply and quite cost effective for normal lens assemblies, their blackening effect is limited by the Fresnel reflection due to the index of refraction mismatch at the glass boundary. At high angles of incidence, total internal reflection (TIR) might occur ruining the effect of the blackening process. An index-matched absorbing medium applied to the edges of such elements is the most effective approach for reducing the amount of undesired light reflected or scattered off these edges. The presence of such a medium provides an extended path outside the glass boundary in which an absorptive non-scattering dye can be used to eliminate light that might otherwise have propagated to the focal plane. Perkin-Elmer and LLNL undertook a program to develop epoxy-based dye carrier compounds with refractive indices corresponding to the glass types used in the WFOV lens. This program involved the measuring of the refractive index of a number of epoxy compounds and catalysts, the experimental combination of epoxies to match our glass indices, and the identification of a suitable non-scattering absorptive dye. 10 figs., 3 tabs.

  19. Direct determination of the second refractivity virial coefficient of methane, nitrogen, and five of their mixtures

    NASA Astrophysics Data System (ADS)

    Achterman, H. J.; Bose, T. K.; Jaeschke, M.; St-Arnaud, J. M.

    1986-03-01

    The experimental technique for the direct determination of the second refractivity virial coefficient is described. The absolute measurement of the refractive index n combined with an expansion technique for obtaining the higher-order coefficients of the Lorentz-Lorenz expansion 10765_2004_Article_BF00500161_TeX2GIFE1.gif {text{LL = [(}}n^2 - 1)/(n^2 + 2)]{text{ }}ρ ^{ - 1} {text{ = }}A_n {text{ }} + {text{ }}B_n ρ {text{ }} + {text{ }}C_n ρ ^2 {text{ + }} \\cdot \\cdot \\cdot leads to precise values of density ρ. A nis the ideal molar refractivity, which is readily determined from the absolute measurements of n in terms of pressure, whereas B n, C n,... are the higher-order molar refractivity virial coefficients, which are obtained from expansion experiments. The expansion method consists in measuring the sum of optical path lengths of two similar cells: one of them is filled with the gas at density ρ, and the other is evacuated. After the expansion the density is nearly halved and one measures again the optical path lengths. In order to cancel the small differences in volume and path lengths between the two cells, the process is reversed. Because the linear term in density remains the same before and after the expansion and only the quadratic and higher-order terms change, we can determine the refractivity virial coefficients B n, C n,... from the change in the optical path lengths. The measurements for the determination of B nand C nfor methane, nitrogen, and five mixtures were carried out at 323.15 K and pressures up to 450 bar. The mixed-interaction constant for methane and nitrogen derived from the experimental second refractivity virial coefficient is compared with those obtained from the geometric and linear mixing rule as well as Lorentz combination.

  20. Electromagnetic waves: Negative refraction by photonic crystals

    NASA Astrophysics Data System (ADS)

    Ozbay, Ekmel

    2004-03-01

    Recently left-handed materials (LHM) attracted great attention since these materials exhibit negative effective index, which is due to simultaneously negative permeability and permittivity. Pendry proposed that negative effective index in left-handed materials can be used for constructing a perfect lens, which is not limited by diffraction(J. B. Pendry, Negative refraction makes a perfect lens, Phys. Rev. Lett. vol. 85, 3966 (2000)). Negative refraction is also achievable in a dielectric photonic crystal (PC) that has a periodically modulated positive permittivity and a permeability of unity. Luo et al. has studied negative refraction and subwavelength imaging in photonic crystals(C. Luo, S. G. Johnson, J. D. Joannopoulos, J. B. Pendry, Subwavelength Imaging in Photonic Crystals Phys. Rev. B 68, 045115 (2003)). In this presentation, we report our experimental and theoretical investigation of negative refraction and subwavelength focusing of electromagnetic waves in a 2D PC. Our structure consists of a square array of dielectric rods in air. Transmission measurements are performed for experimentally verifying the predicted negative refraction behavior in our structure. Negative index of refraction determined from the experiment is -1.94 which is very close to the theoretical value of -2.06. Negative refraction is observed for the incidence angles of > 20°(Ertugrul Cubukcu, Koray Aydin, Ekmel Ozbay, S. Foteinopolou, and Costas Soukoulis, Negative Refraction by Photonic Crystals, Nature, vol. 423, 604 (2003)). Since we know the optimum frequency for a broad angle negative refraction, we can use our crystal to test the superlensing effect that was predicted for negative refractive materials. Scanning transmission measurement technique is used to measure the spatial power distribution of the focused electromagnetic waves that radiate from a point source. Full width at half maximum of the focused beam is measured to be 0.21λ, which is in good agreement with the finite

  1. Comparison of modeled and observed astronomical refraction of the setting sun.

    PubMed

    Sampson, Russell D; Lozowski, Edward P; Peterson, Arthur E

    2003-01-20

    In this study a ray-tracing model that uses atmospheric data from VIZ and Vaisala RS80 rawinsondes is compared with the observed astronomical refraction presented by the setting Sun as seen from Stony Plain, Alberta, Canada. Photogrammetric measurements taken from photographs of the setting Sun show good agreement with the model for the 14 and 22 December 1998 sunsets. The poorer model results for the 8 December sunset appear to be caused by an obsolete and possibly defective VIZ rawinsonde. The results suggest that the ray-tracing model can produce improved refraction values when compared with the Pulkovo tables [Pulkovo Observatory, Refraction Tables of the Pulkovo Observatory, 5th ed. (Nauka, Leningrad, 1985)]. However, they also indicate that the inverse solution (i.e., extracting the temperature profile from refraction measurements) may produce no improvement on U.S. Standard Atmosphere adjusted to the surface conditions.

  2. A single-element interferometer for measuring refractive index of transparent liquids

    NASA Astrophysics Data System (ADS)

    Zhang, Tao; Feng, Guoying; Song, Zheyi; Zhou, Shouhuan

    2014-12-01

    A simple and stable method based on a single-element interferometer for accurately measuring refractive index of transparent liquids was demonstrated. The refractive index is measured by rotating a rectangular optical glass cell which contains sample liquid and air simultaneously, and by calculating interference fringe shift number which is detected from an interferogram. This method was successfully used to measure the refractive indices of various transparent liquids including distilled water, ethanol and NaCl-water and ethanol-water solutions at various concentrations. The temperature- dependent refractive index of distilled water was also measured. Furthermore, our method is simple to implement, vibration insensitive, and of high accuracy up to 10-4.

  3. Methods for Prediction of Refractive Index in Glasses for the Infrared

    SciTech Connect

    McCloy, John S.

    2011-06-14

    It is often useful to obtain custom glasses that meet particular requirements of refractive index and dispersion for high-end optical design and applications. In the case of infrared glasses, limited experimental data are available due to difficulties in processing of these glasses and also measuring refractive indices accurately. This paper proposes methods to estimate refractive index and dispersion as a function of composition for selected infrared-transmitting glasses. Methods for refractive index determination are reviewed and evaluated, including Gladstone-Dale, Wemple-DiDomenico single oscillator, Optical basicity, and Lorentz-Lorenz total polarizability. Various estimates for a set of PbO-Bi2O3-Ga2O3 (heavy metal oxide) and As-S (chalcogenide) glasses will be compared with measured values of index and dispersion.

  4. Surface antireflection properties of GaN nanostructures with various effective refractive index profiles.

    PubMed

    Han, Lu; Zhao, Hongping

    2014-12-29

    GaN nanostructures with various effective refractive index profiles (Linear, Cubic, and Quintic functions) were numerically studied as broadband omnidirectional antireflection structures for concentrator photovoltaics by using three-dimensional finite difference time domain (3D-FDTD) method. Effective medium theory was used to design the surface structures corresponding to different refractive index profiles. Surface antireflection properties were calculated and analyzed for incident light with wavelength, polarization and angle dependences. The surface antireflection properties of GaN nanostructures based on six-sided pyramid with both uniform and non-uniform patterns were also investigated. Results indicate a significant dependence of the surface antireflection on the refractive index profiles of surface nanostructures as well as their pattern uniformity. The GaN nanostructures with linear refractive index profile show the best performance to be used as broadband omnidirectional antireflection structures.

  5. Porous anodic alumina with low refractive index for broadband graded-index antireflection coatings.

    PubMed

    Chen, Junwu; Wang, Biao; Yang, Yi; Shi, Yuanyuan; Xu, Gaojie; Cui, Ping

    2012-10-01

    Materials with very low refractive index are essential to prepare broadband graded-index antireflection (AR) coatings. However, the availability of such materials is very limited. In this study, large-area (4 cm×4 cm) low refractive index porous anodic alumina (PAA) coatings on glass substrate were prepared successfully by electron-beam evaporation, electrochemical oxidation, and chemical etching method. The nanopore size of PAA film is smaller than 40 nm, and the refractive index of PAA film is n=1.08. Besides, five-layered graded-index broadband PAA coatings with refractive indices following the Gaussian profile were also prepared to noticeably eliminate the reflectance of glass over a broadband wavelength, and the lowest reflectivity is 0.64% at the wavelength of 534 nm at normal incidence. The PAA AR coatings having an omnidirectional nature are likely to have practical applications in photovoltaic cells and optical devices.

  6. Physics of negative refractive index materials

    NASA Astrophysics Data System (ADS)

    Ramakrishna, S. Anantha

    2005-02-01

    In the past few years, new developments in structured electromagnetic materials have given rise to negative refractive index materials which have both negative dielectric permittivity and negative magnetic permeability in some frequency ranges. The idea of a negative refractive index opens up new conceptual frontiers in photonics. One much-debated example is the concept of a perfect lens that enables imaging with sub-wavelength image resolution. Here we review the fundamental concepts and ideas of negative refractive index materials. First we present the ideas of structured materials or meta-materials that enable the design of new materials with a negative dielectric permittivity, negative magnetic permeability and negative refractive index. We discuss how a variety of resonance phenomena can be utilized to obtain these materials in various frequency ranges over the electromagnetic spectrum. The choice of the wave-vector in negative refractive index materials and the issues of dispersion, causality and energy transport are analysed. Various issues of wave propagation including nonlinear effects and surface modes in negative refractive materials (NRMs) are discussed. In the latter part of the review, we discuss the concept of a perfect lens consisting of a slab of a NRM. This perfect lens can image the far-field radiative components as well as the near-field evanescent components, and is not subject to the traditional diffraction limit. Different aspects of this lens such as the surface modes acting as the mechanism for the imaging of the evanescent waves, the limitations imposed by dissipation and dispersion in the negative refractive media, the generalization of this lens to optically complementary media and the possibility of magnification of the near-field images are discussed. Recent experimental developments verifying these ideas are briefly covered.

  7. Anomalous refraction, diffraction, and imaging in metamaterials

    NASA Astrophysics Data System (ADS)

    Paul, Thomas; Rockstuhl, Carsten; Menzel, Christoph; Lederer, Falk

    2009-03-01

    In the past several years, optical metamaterials (MMs) have attracted a considerable deal of interest because it may be anticipated that their properties can be shaped to an unprecedented extent relieving optics from some of its natural limitations. An inevitable first step toward this goal is the evaluation of the optical properties of specifically designed MMs. To date, apart from identifying chiral properties of very specific configurations, this is primarily done in retrieving an effective refractive index—mostly—only for normal incidence. On this basis suggestions for a perfect lens, exploiting this negative refractive index have been put forward by taking advantage of geometrical optics arguments. We show that this approach is pointless for realistic MMs. Instead we prove that the dispersion relation of normal modes in these MMs provides all the required information. Most of the relevant optical parameters, such as refraction and diffraction coefficients, can be derived from this relation. Imaging properties follow straightforwardly from that data. This general approach holds for any optical material, in particular, for all MMs in question. As an example, we apply it to the fishnet structure: one of the most prominent and best studied design approaches to date. We show that both refraction and diffraction properties are strongly spatially and temporally dispersive and they can even change sign. In detail, we study the effect of these peculiarities on imaging and refraction of finite beams. In particular, we discuss both the effect of the specific dispersion relation and the losses on the imaging properties. All our physical predictions are backed by rigorous numerical calculations and the agreement is almost perfect. Ultimately the main conclusion to be drawn is that a negative index of refraction is by no means a sufficient criterion to achieve negative refraction and/or perfect imaging.

  8. Age-Related Shifts in the Density and Distribution of Genetic Marker Water Quality Indicators in Cow and Calf Feces (Journal)

    EPA Science Inventory

    Calves (≤ 226 kg body mass) make up about 16% of the current bovine population in the United States and can excrete high levels of human pathogens. We describe the density and distribution of genetic markers from 11 PCR- and real-time quantitative PCR-based assays including CF...

  9. Refraction-Enhanced X-ray Radiography for Inertial Confinement Fusion and Laser-Produced Plasma Applications

    SciTech Connect

    Koch, J A; Landen, O L; Kozioziemski, B J; Izumi, N; Dewald, E L; Salmonson, J D; Hammel, B A

    2008-08-26

    We explore various laser-produced plasma and inertial-confinement fusion (ICF) applications of phase-contrast x-ray radiography, and we show how the main features of these enhancements can be considered from a geometrical optics perspective as refraction enhancements. This perspective simplifies the analysis, and often permits simple analytical formulae to be derived that predict the enhancements. We explore a raytrace approach to various material interface applications, and we explore a more general example of refractive bending of x-rays by an implosion plasma. We find that refraction-enhanced x-ray radiography of implosions may provide a means to quantify density differences across shock fronts as well as density variations caused by local heating due to high-Z dopants. We also point out that refractive bending by implosions plasmas can blur fine radiograph features, and can also provide misleading contrast information in area-backlit pinhole imaging experiments unless its effects are taken into consideration.

  10. Design of acid-lead battery stage-of-charge detection system based on refractive index detection technology

    NASA Astrophysics Data System (ADS)

    Chen, Junyao; Yang, Kecheng; Xia, Min; Li, Lei; Zeng, Xianjiang

    2015-10-01

    Based on optical total reflection critical Angle method, we have designed a refractive index measurement system. It adopted a divergent light source and a CCD camera as the occurrence and receiver of the signal. The divergent light source sent out a bunch of tapered beam, exposure to the interface of optical medium and sulfuric acid solution. Light intensity reflected from the interface could be detected by the CCD camera and then sent to the embedded system. In the DSP embedded system, we could obtain the critical edge position through the light intensity distribution curve and converted it to critical angle. Through experiment, we concluded the relation between liquid refractive index and the critical angle edge position. In this system, the detecting precision of the refractive index of sulfuric acid solution reached 10-4. Finally, through the conversion of the refractive index and density, we achieved high accuracy online measurement of electrolyte density in lead-acid battery.

  11. Refractive index of r-cut sapphire under shock pressure range 5 to 65 GPa

    SciTech Connect

    Cao, Xiuxia; Li, Jiabo; Li, Jun; Li, Xuhai; Xu, Liang; Wang, Yuan; Zhu, Wenjun; Meng, Chuanmin; Zhou, Xianming

    2014-09-07

    High-pressure refractive index of optical window materials not only can provide information on electronic polarizability and band-gap structure, but also is important for velocity correction in particle-velocity measurement with laser interferometers. In this work, the refractive index of r-cut sapphire window at 1550 nm wavelength was measured under shock pressures of 5–65 GPa. The refractive index (n) decreases linearly with increasing shock density (ρ) for shock stress above the Hugoniot elastic limit (HEL): n = 2.0485 (± 0.0197) − 0.0729 (± 0.0043)ρ, while n remains nearly a constant for elastic shocks. This behavior is attributed to the transition from elastic (below HEL) to heterogeneous plastic deformation (above HEL). Based on the obtained refractive index-density relationship, polarizability of the shocked sapphire was also obtained.

  12. Refraction Correction in 3D Transcranial Ultrasound Imaging

    PubMed Central

    Lindsey, Brooks D.; Smith, Stephen W.

    2014-01-01

    We present the first correction of refraction in three-dimensional (3D) ultrasound imaging using an iterative approach that traces propagation paths through a two-layer planar tissue model, applying Snell’s law in 3D. This approach is applied to real-time 3D transcranial ultrasound imaging by precomputing delays offline for several skull thicknesses, allowing the user to switch between three sets of delays for phased array imaging at the push of a button. Simulations indicate that refraction correction may be expected to increase sensitivity, reduce beam steering errors, and partially restore lost spatial resolution, with the greatest improvements occurring at the largest steering angles. Distorted images of cylindrical lesions were created by imaging through an acrylic plate in a tissue-mimicking phantom. As a result of correcting for refraction, lesions were restored to 93.6% of their original diameter in the lateral direction and 98.1% of their original shape along the long axis of the cylinders. In imaging two healthy volunteers, the mean brightness increased by 8.3% and showed no spatial dependency. PMID:24275538

  13. Computed estimation of visual acuity after laser refractive keratectomy

    NASA Astrophysics Data System (ADS)

    Rol, Pascal O.; Parel, Jean-Marie A.; Hanna, Khalil

    1991-06-01

    A number of surgical techniques has been developed to correct ametropia (refractive defaults) of the eye by changing the anterior corneal radius. Because the air-cornea interface makes up for about two-third of the refractive power of the eye, a refractive correction is obtained by a suitable photoablation of the cornea. For this purpose, e.g., an ArF excimer laser which emits a wavelength of 193 nm is being used. After a mechanical removal of the epithelium, the Bowman's layer and the corneal stroma are photoablated on typically 50% of the central surface of the cornea with various precomputed shapes. Methods using a variable diaphragm1 or a scanning slit2 are being utilized. After regrowth of the epithelium, a smooth interface with air develops itself, which can be attributed to a mechanical equilibration. Yet, SEM studies have shown that with such kind of treatments, irregularities can remain in the new stromal surface (Fig. 1). A possible explanation for this effect is associated with an inhomogeneous energy distribution of the laser beam profile3. To some extent, the stromal surface is equalized by the epithelial layer during healing& However, as the corneal epithelium and stroma have different refractive indices, a scatter of the incident light may result causing a haze in the cornea and a blur of the image at the retina. In such a case the resolution and the contrast performance of the eye which is expected from a successful operation, may be reduced. This study is an attempt to quantify the vision blur as a function of the deformation observed at the epithelium-stroma interface.

  14. Refraction data survey: 2nd generation correlation of myopia.

    PubMed

    Greene, Peter R; Medina, Antonio

    2016-10-01

    The objective herein is to provide refraction data, myopia progression rate, prevalence, and 1st and 2nd generation correlations, relevant to whether myopia is random or inherited. First- and second-generation ocular refraction data are assembled from N = 34 families, average of 2.8 children per family. From this group, data are available from N = 165 subjects. Inter-generation regressions are performed on all the data sets, including correlation coefficient r, and myopia prevalence [%]. Prevalence of myopia is [M] = 38.5 %. Prevalence of high myopes with |R| >6 D is [M-] = 20.5 %. Average refraction is  = -1.84 D ± 3.22 (N = 165). For the high myopes, |R| >6 D, prevalence for the parents is [M-] = 25 %, for the 2nd generation [M-] = 16.5 %. Average myopia level for the high myopes, both generations, is  = -7.52 D ± 1.31 D (N = 33). Regression parameters are calculated for all the data sets, yielding correlation coefficients in the range r = 0.48-0.72 for some groups of myopes and high myopes, fathers to daughters, and mothers to sons. Also of interest, some categories show essentially no correlation, -0.20 < r < 0.20, indicating that the refractive errors occur randomly. Time series results show myopia diopter rates = -0.50 D/year.

  15. Negative Refraction and Imaging with Quasicrystals

    NASA Astrophysics Data System (ADS)

    Zhang, Xiangdong; Feng, Zhifang; Wang, Yiquan; Li, Zhi-Yuan; Cheng, Bingying; Zhang, Dao-Zhong

    Recently, negative refraction of electromagnetic waves in photonic crystals was demonstrated experimentally and subwavelength images were observed. However, these investigations all focused on the periodic structure. In fact, the negative refraction exists not only in periodic structure, but also in nonperiodic structures such as quasicrystalline arrangement of dielectric. Here, we discuss the negative refraction and imaging based on some transparent quasicrystalline photonic structures. The high-symmetric photonic quasicrystals (PQCs) can exhibit an effective refractive index close to -1 in a certain frequency window. The index shows small spatial dispersion, consistent with the nearly homogeneous geometry of the quasicrystal. Thus, a flat lens based on the 2D PQCs can form a non-near-field image whose position varies with the thickness of the sample and the source distance. At the same time, the focus and image for both polarized waves at the same structure and parameters can also be realized by such a flat lens. In addition, the negative refraction behaviors of acoustic wave in phononic quasicrystal are also discussed.

  16. Refractive error sensing from wavefront slopes.

    PubMed

    Navarro, Rafael

    2010-01-01

    The problem of measuring the objective refractive error with an aberrometer has shown to be more elusive than expected. Here, the formalism of differential geometry is applied to develop a theoretical framework of refractive error sensing. At each point of the pupil, the local refractive error is given by the wavefront curvature, which is a 2 × 2 symmetric matrix, whose elements are directly related to sphere, cylinder, and axis. Aberrometers usually measure the local gradient of the wavefront. Then refractive error sensing consists of differentiating the gradient, instead of integrating as in wavefront sensing. A statistical approach is proposed to pass from the local to the global (clinically meaningful) refractive error, in which the best correction is assumed to be the maximum likelihood estimation. In the practical implementation, this corresponds to the mode of the joint histogram of the 3 different elements of the curvature matrix. Results obtained both in computer simulations and with real data provide a close agreement and consistency with the main optical image quality metrics such as the Strehl ratio.

  17. Refractive error sensing from wavefront slopes.

    PubMed

    Navarro, Rafael

    2010-01-01

    The problem of measuring the objective refractive error with an aberrometer has shown to be more elusive than expected. Here, the formalism of differential geometry is applied to develop a theoretical framework of refractive error sensing. At each point of the pupil, the local refractive error is given by the wavefront curvature, which is a 2 × 2 symmetric matrix, whose elements are directly related to sphere, cylinder, and axis. Aberrometers usually measure the local gradient of the wavefront. Then refractive error sensing consists of differentiating the gradient, instead of integrating as in wavefront sensing. A statistical approach is proposed to pass from the local to the global (clinically meaningful) refractive error, in which the best correction is assumed to be the maximum likelihood estimation. In the practical implementation, this corresponds to the mode of the joint histogram of the 3 different elements of the curvature matrix. Results obtained both in computer simulations and with real data provide a close agreement and consistency with the main optical image quality metrics such as the Strehl ratio. PMID:21149305

  18. Refractive Secondary Concentrators for Solar Thermal Applications

    NASA Technical Reports Server (NTRS)

    Wong, Wayne A.; Macosko, Robert P.

    1999-01-01

    The NASA Glenn Research Center is developing technologies that utilize solar energy for various space applications including electrical power conversion, thermal propulsion, and furnaces. Common to all of these applications is the need for highly efficient, solar concentration systems. An effort is underway to develop the innovative single crystal refractive secondary concentrator, which uses refraction and total internal reflection to efficiently concentrate and direct solar energy. The refractive secondary offers very high throughput efficiencies (greater than 90%), and when used in combination with advanced primary concentrators, enables very high concentration ratios (10,0(X) to 1) and very high temperatures (greater than 2000 K). Presented is an overview of the refractive secondary concentrator development effort at the NASA Glenn Research Center, including optical design and analysis techniques, thermal modeling capabilities, crystal materials characterization testing, optical coatings evaluation, and component testing. Also presented is a discussion of potential future activity and technical issues yet to be resolved. Much of the work performed to date has been in support of the NASA Marshall Space Flight Center's Solar Thermal Propulsion Program. The many benefits of a refractive secondary concentrator that enable efficient, high temperature thermal propulsion system designs, apply equally well to other solar applications including furnaces and power generation systems such as solar dynamics, concentrated thermal photovoltaics, and thermionics.

  19. Interferometric determination of refraction and dispersion of human blood-serum, saliva, sweat and urine

    NASA Astrophysics Data System (ADS)

    El-Zaiat, S. Y.

    2003-02-01

    Multiple-beam interference fringes of equal chromatic order are produced in air and liquid sample interferometric gaps. The two gaps are of the same thickness and simultaneously enclosed in a wedge interferometer. A single shot interferogram containing fringes in the two gaps is sufficient to deduce the needed experimental data. Locations of the fringe maxima, in the two gaps, are introduced in a non-numerical procedure for determining the gap thickness and the liquid-phase refractive indices across the visible spectrum. The method has been used for measuring the phase refractive indices of human blood-serum, saliva, sweat, urine and water liquids. A third-order polynomial dispersion relation is applied for fitting the measured phase indices. Group refractive indices have been derived and fitted to the same dispersion formula.

  20. Prediction of child health by household density and asset-based indices in impoverished indigenous villages in rural Panamá.

    PubMed

    Halpenny, Carli M; Koski, Kristine G; Valdés, Victoria E; Scott, Marilyn E

    2012-02-01

    Chronic infection over a 16-month period and stunting of preschool children were compared between more spatially dense versus dispersed households in rural Panamá. Chronic protozoan infection was associated with higher household density, lower household wealth index, poor household water quality, yard defecation, and the practice of not washing hands with soap before eating. Models for chronic diarrhea confirmed the importance of household wealth, water quality, sanitation, and hygiene practices. Furthermore, chronic protozoan infection was an important predictor for low height-for-age, along with low household wealth index scores, but not household density. Thus, despite better access to health related infrastructure in the more densely populated households, chronic protozoan infection was more common, and was associated with higher rates of child stunting, compared with more dispersed households. PMID:22302864

  1. Prediction of Child Health by Household Density and Asset-Based Indices in Impoverished Indigenous Villages in Rural Panamá

    PubMed Central

    Halpenny, Carli M.; Koski, Kristine G.; Valdés, Victoria E.; Scott, Marilyn E.

    2012-01-01

    Chronic infection over a 16-month period and stunting of preschool children were compared between more spatially dense versus dispersed households in rural Panamá. Chronic protozoan infection was associated with higher household density, lower household wealth index, poor household water quality, yard defecation, and the practice of not washing hands with soap before eating. Models for chronic diarrhea confirmed the importance of household wealth, water quality, sanitation, and hygiene practices. Furthermore, chronic protozoan infection was an important predictor for low height-for-age, along with low household wealth index scores, but not household density. Thus, despite better access to health related infrastructure in the more densely populated households, chronic protozoan infection was more common, and was associated with higher rates of child stunting, compared with more dispersed households. PMID:22302864

  2. Determining the refractive index of a {lambda}/4 thin film on a thick substrate from a transmittance measurement

    SciTech Connect

    Chow, R.; Loomis, G.E.; Biltoft, P.

    1993-06-01

    The refractive index is a key optical constant required by optical thin film designers. The coater-designer team must constantly verify the refractive indices of the non-absorbing optical thin films since the refractive index of a deposited material can vary by switching coating systems or operators as well as expected changes during the course of a coating run. A transmittance measurement on a spectrophotometer is an easy and accurate (usually to within {+-}0.5% spread) method of determining the refractive index. In one technique, the refractive index is obtained from visually curve-fitting a calculated (using a thin film design program and selecting the refractive index) transmittance spectrum to the measured transmittance spectrum. There are two other techniques which are discussed in this report: A quick, approximate method vs. the exact derivation. What the authors have not been able to find in the literature is the exact transmittance dependence as a function of the refractive indices (layers) through which the light passes and which accounts for the substrate back reflections. There are undocumented approximation methods as well as one in the literature by Cheremukhin and Rozhnox. Otherwise, most texts either derive the transmittances through optical multilayers or just the effect of back reflections on the transmittance for thick substrates. Without correcting for substrate back reflections, the derived refractive indices from the measured transmittances are in error by as much as 10%. In this work, the authors have utilized both an exact and an approximate method of determining the refractive index of the film. It is found that both the exact and approximate methods of determining the refractive index of thin optical coatings are within the measurement errors of commercially available spectrophotometers.

  3. Determination of the refractive index of microparticles by utilizing light dispersion properties of the particle and an immersion liquid.

    PubMed

    Niskanen, I; Räty, J; Peiponen, K E

    2013-10-15

    The knowledge of the refractive index of a particle is important in sensing and imaging applications, e.g., in biology, medicine and process industry. The refractive index of tiny solid particles such as microsize particles can be determined by the so-called liquid immersion technique. This study deals with three different types of interrogation methods to get the refractive index of a particle in a liquid matrix. These methods utilize thermo-optical properties and wavelength-dependent refractive index of the particle and the immersion liquids, as well as, the classical method using a set of in advance prepared set of immersion liquids with different refractive indices. The emphasis is on a method to get especially the wavelength-dependent refractive index of microparticles and exploiting different wavelength-dependences of immersion liquid and a solid particle because identification of a particle is more reliable if the refractive index of the particle is known at several wavelengths. In this study glycerol-water mixtures served as immersion liquids to obtain the refractive index of CaF2 at several discrete wavelengths in the spectral range 200-500 nm. The idea is to find the maximum value of light transmission of suspension by scanning the wavelength of a commercial spectrophotometer. The light dispersion-based method is suggested as a relatively easy, economic and fast method to determine the refractive index of a particle by a spectrophotometer at several wavelengths of light. The accuracy of the detection of the refractive index is suggested to be better than ± 0.005 refractive index units.

  4. Adjustable hybrid diffractive/refractive achromatic lens.

    PubMed

    Valley, Pouria; Savidis, Nickolaos; Schwiegerling, Jim; Dodge, Mohammad Reza; Peyman, Gholam; Peyghambarian, N

    2011-04-11

    We demonstrate a variable focal length achromatic lens that consists of a flat liquid crystal diffractive lens and a pressure-controlled fluidic refractive lens. The diffractive lens is composed of a flat binary Fresnel zone structure and a thin liquid crystal layer, producing high efficiency and millisecond switching times while applying a low ac voltage input. The focusing power of the diffractive lens is adjusted by electrically modifying the sub-zones and re-establishing phase wrapping points. The refractive lens includes a fluid chamber with a flat glass surface and an opposing elastic polydimethylsiloxane (PDMS) membrane surface. Inserting fluid volume through a pump system into the clear aperture region alters the membrane curvature and adjusts the refractive lens' focal position. Primary chromatic aberration is remarkably reduced through the coupling of the fluidic and diffractive lenses at selected focal lengths. Potential applications include miniature color imaging systems, medical and ophthalmic devices, or any design that utilizes variable focal length achromats.

  5. Seismic refraction analysis: the path forward

    USGS Publications Warehouse

    Haines, Seth S.; Zelt, Colin; Doll, William

    2012-01-01

    Seismic Refraction Methods: Unleashing the Potential and Understanding the Limitations; Tucson, Arizona, 29 March 2012 A workshop focused on seismic refraction methods took place on 29 May 2012, associated with the 2012 Symposium on the Application of Geophysics to Engineering and Environmental Problems. This workshop was convened to assess the current state of the science and discuss paths forward, with a primary focus on near-surface problems but with an eye on all applications. The agenda included talks on these topics from a number of experts interspersed with discussion and a dedicated discussion period to finish the day. Discussion proved lively at times, and workshop participants delved into many topics central to seismic refraction work.

  6. Refractive index of air. 2. Group index.

    PubMed

    Ciddor, P E; Hill, R J

    1999-03-20

    In a previous paper [Appl. Opt. 35, 1566 (1996)] one of us presented new equations for evaluation of the phase refractive index of air over a range of wavelengths and atmospheric parameters. That paper also gave an incorrect, although sufficiently accurate, procedure for calculating the group refractive index. Here we describe the results of a more rigorous derivation of the group index that takes proper account of the Lorentz-Lorenz formula, and we demonstrate that deviations from the Lorentz-Lorenz formula are insignificant to within a foreseeable precision of dispersion measurements for atmospheric conditions. We also derive and evaluate a simplification of the resultant equation that is useful for exploratory calculations. We clarify the limits of validity of the standard equation for the group refractive index and correct some minor errors in the previous paper.

  7. Interferometric atmospheric refractive-index environmental monitor.

    PubMed

    Ludman, J E; Ludman, J J; Callahan, H; Caulfield, H J; Watt, D; Sampson, J L; Robinson, J; Davis, S; Hunt, A

    1995-06-20

    Long, open-path, outdoor interferometric measurement of the index of refraction as a function of wavelength (spectral refractivity) requires a number of innovations. These include active compensation for vibration and turbulence. The use of electronic compensation produces an electronic signal that is ideal for extracting data. This allows the appropriate interpretation of those data and the systematic and fast scanning of the spectrum by the use of bandwidths that are intermediate between lasers (narrow bandwidth) and white light (broad bandwidth). An Environmental Interferometer that incorporates these features should be extremely valuable in both pollutant detection and pollutant identification. Spectral refractivity measurements complement the information available from spectral absorption instruments (e.g., a Fourier-transform infrared spectrometer). The Environmental Interferometer currently uses an electronic compensating device with a 1-kHz response time, and therefore rapid spectral scans are feasibe so that it is possible to monitor the time evolution of pollutant events.

  8. Refraction of microwave signals by water vapor

    NASA Technical Reports Server (NTRS)

    Goldfinger, A. D.

    1980-01-01

    Tropospheric water vapor causes a refractive path length effect which is typically 5-10% of the 'dry' tropospheric effect and as large as several meters at elevation angles below 5 deg. The vertical water vapor profile is quite variable, and measurements of intensive atmospheric parameters such as temperature and humidity limited to the surface do not adequately predict the refractive effect. It is suggested that a water vapor refraction model that is a function of the amount of precipitable water alone can be successful at low elevation angles. From an extensive study of numerical ray tracings through radiosonde balloon data, such a model has been constructed. The model predicts the effect at all latitudes and elevation angles between 2 and 10 deg to an accuracy of better than 4% (11 cm at 3 deg elevation angle).

  9. Fiber optic liquid refractive index sensor

    NASA Astrophysics Data System (ADS)

    Bhardwaj, Vanita; Gangwar, Rahul Kumar; Singh, Vinod Kumar

    2015-08-01

    In this present work we report fabrication of fiber optic liquid refractive index (RI) measurement sensor based on Michelson Interferometer method. This sensor was assembled by using graded index multimode (MM) fiber with core diameter 50 µm and the cladding of fiber was removed by simple chemical method. To perform this experiment a 2×2 3dB coupler is used. The fiber ends are then immersed in solvent and solution to provide reference and refractive index measurements, respectively. This method was successfully used to measure refractive index of Sodium Chloride (NaCl)-Water solution at different concentrations. The fringe contrast sensitivity of device is 92.90 dB/RIU measured in the RI range from 1.34 to 1.42 which is better than Mach-Zehnder Interferometer sensor [1] and Fabry perot based sensor [2]. The fabrication of sensor is simple, low cost and highly sensitive.

  10. Refractive acoustic devices for airborne sound.

    PubMed

    Cervera, F; Sanchis, L; Sánchez-Pérez, J V; Martínez-Sala, R; Rubio, C; Meseguer, F; López, C; Caballero, D; Sánchez-Dehesa, J

    2002-01-14

    We show that a sonic crystal made of periodic distributions of rigid cylinders in air acts as a new material which allows the construction of refractive acoustic devices for airborne sound. It is demonstrated that, in the long-wave regime, the crystal has low impedance and the sound is transmitted at subsonic velocities. Here, the fabrication and characterization of a convergent lens are presented. Also, an example of a Fabry-Perot interferometer based on this crystal is analyzed. It is concluded that refractive devices based on sonic crystals behave in a manner similar to that of optical systems.

  11. A Liquid Prism for Refractive Index Studies

    NASA Astrophysics Data System (ADS)

    Edmiston, Michael D.

    2001-11-01

    A hollow glass prism filled with liquid becomes a "liquid prism". A simple method for constructing hollow glass prisms is presented. A method is given for a demonstration that uses the liquid prism with a laser or laser pointer so the audience can observe differences in refractive index for various liquids. The demonstration provides a quick and easy determination of the sugar content of soft drinks and juices. The prism makes it easy to determine a numerical value for the refractive index of a liquid.

  12. Plasmonic crystal enhanced refractive index sensing

    SciTech Connect

    Stein, Benedikt; Devaux, Eloïse; Genet, Cyriaque Ebbesen, Thomas W.

    2014-06-23

    We demonstrate experimentally how the local anisotropy of the dispersion relation of surface plasmon modes propagating over periodic metal gratings can lead to an enhancement of the figure of merit of refractive index sensors. Exploiting the possibility to acquire defocused images of the Fourier space of a highly stable leakage radiation microscope, we report a twofold increase in sensing sensitivity close to the band gap of a one-dimensional plasmonic crystal where the anisotropy of the band structure is the most important. A practical sensing resolution of O(10{sup −6}) refractive index units is demonstrated.

  13. Refractive acoustic devices for airborne sound.

    PubMed

    Cervera, F; Sanchis, L; Sánchez-Pérez, J V; Martínez-Sala, R; Rubio, C; Meseguer, F; López, C; Caballero, D; Sánchez-Dehesa, J

    2002-01-14

    We show that a sonic crystal made of periodic distributions of rigid cylinders in air acts as a new material which allows the construction of refractive acoustic devices for airborne sound. It is demonstrated that, in the long-wave regime, the crystal has low impedance and the sound is transmitted at subsonic velocities. Here, the fabrication and characterization of a convergent lens are presented. Also, an example of a Fabry-Perot interferometer based on this crystal is analyzed. It is concluded that refractive devices based on sonic crystals behave in a manner similar to that of optical systems. PMID:11801014

  14. Modeling of mouse eye and errors in ocular parameters affecting refractive state

    NASA Astrophysics Data System (ADS)

    Bawa, Gurinder

    Rodents eye are particularly used to study refractive error state of an eye and development of refractive eye. Genetic organization of rodents is similar to that of humans, which makes them interesting candidates to be researched upon. From rodents family mice models are encouraged over rats because of availability of genetically engineered models. Despite of extensive work that has been performed on mice and rat models, still no one is able to quantify an optical model, due to variability in the reported ocular parameters. In this Dissertation, we have extracted ocular parameters and generated schematics of eye from the raw data from School of Medicine, Detroit. In order to see how the rays would travel through an eye and the defects associated with an eye; ray tracing has been performed using ocular parameters. Finally we have systematically evaluated the contribution of various ocular parameters, such as radii of curvature of ocular surfaces, thicknesses of ocular components, and refractive indices of ocular refractive media, using variational analysis and a computational model of the rodent eye. Variational analysis revealed that variation in all the ocular parameters does affect the refractive status of the eye, but depending upon the magnitude of the impact those parameters are listed as critical or non critical. Variation in the depth of the vitreous chamber, thickness of the lens, radius of the anterior surface of the cornea, radius of the anterior surface of the lens, as well as refractive indices for the lens and vitreous, appears to have the largest impact on the refractive error and thus are categorized as critical ocular parameters. The radii of the posterior surfaces of the cornea and lens have much smaller contributions to the refractive state, while the radii of the anterior and posterior surfaces of the retina have no effect on the refractive error. These data provide the framework for further refinement of the optical models of the rat and mouse

  15. Constraining Subsurface Structure and Composition Using Seismic Refraction Surveys of Proglacial Valleys in the Cordillera Blanca, Peru

    NASA Astrophysics Data System (ADS)

    Glas, R. L.; Lautz, L.; McKenzie, J. M.; Mark, B. G.; Baker, E. A.; Aubry-Wake, C.; Somers, L. D.; Wigmore, O.

    2015-12-01

    As tropical glaciers rapidly recede in response to climate change, the storage and discharge of groundwater will play an increasing role in regulating river baseflow, particularly during the dry season, when stream flow is currently sustained predominantly by glacial melt. Little is understood regarding the hydrogeologic processes controlling base flow characteristics of low-gradient proglacial valleys of the Cordillera Blanca in Northwestern Peru, which has the world's highest density of tropical glaciers. To better understand the processes of groundwater storage and discharge in proglacial meadows, we completed seismic refraction surveys in three representative valleys of the Cordillera Blanca range: the Quilcayhuanca, Yanamarey, and Pachacoto valleys. The locations of survey transects were chosen based on locations of previous sediment core sampling, GPR lines, and quantification of groundwater-surface water interaction derived from dye and temperature tracing experiments. The seismic surveys consisted of 48 vertical component geophones with 2.5 m spacing. Across the three representative valleys a total of 15 surveys were conducted, covering a distance of 1800 m in cross, down, and oblique-valley directions. Preliminary interpretation of the seismic refraction data indicates a maximum imaging depth of 16 m below land surface, and a transition from glacio-lacustrine sediments to buried saturated talus at a depth of 6 m in the Quilcayhuanca valley. The organic-rich glacio-lacustrine sediments in the Yanamarey valley have seismic velocities ranging from 300 to 800 m/s and are >16 m in thickness at mid- valley. Weathered metasedimentary bedrock in the Pachacoto valley was imaged at ~5 m below the valley surface, exhibiting a p-wave velocity of 3400 m/s. The knowledge of hydrogeologic structure derived from seismic refraction surveys will provide crucial boundary conditions for future groundwater models of the valleys of the Cordillera Blanca.

  16. Compositional dependence of optical band gap and refractive index in lead and bismuth borate glasses

    SciTech Connect

    Mallur, Saisudha B.; Czarnecki, Tyler; Adhikari, Ashish; Babu, Panakkattu K.

    2015-08-15

    Highlights: • Refractive indices increase with increasing PbO/Bi{sub 2}O{sub 3} content. • Optical band gap arises due to direct forbidden transition. • Optical band gaps decrease with increasing PbO/Bi{sub 2}O{sub 3} content. • New empirical relation between the optical band gap and the refractive index. - Abstract: We prepared a series of lead and bismuth borate glasses by varying PbO/Bi{sub 2}O{sub 3} content and studied refractive index and optical band gap as a function of glass composition. Refractive indices were measured very accurately using a Brewster’s angle set up while the optical band gaps were determined by analyzing the optical absorption edge using the Mott–Davis model. Using the Lorentz–Lorentz method and the effective medium theory, we calculated the refractive indices and then compared them with the measured values. Bismuth borate glasses show better agreement between the calculated values of the refractive index and experimental values. We used a differential method based on Mott–Davis model to obtain the type of transition and optical band gap (E{sub opt}) which in turn was compared with the value of E{sub opt} obtained using the extinction coefficient. Our analysis shows that in both lead and bismuth borate glasses, the optical band gap arises due to direct forbidden transition. With increasing PbO/Bi{sub 2}O{sub 3} content, the absorption edge shifts toward longer wavelengths and the optical band gap decreases. This behavior can be explained in terms of changes to the Pb−O/Bi−O chemical bonds with glass composition. We obtained a new empirical relation between the optical band gap and the refractive index which can be used to accurately determine the electronic oxide polarizability in lead and bismuth oxide glasses.

  17. Refractive index of air: 3. The roles of CO2, H2O, and refractivity virials.

    PubMed

    Ciddor, Philip E

    2002-04-20

    The author's recent studies of the refractive index of air are extended, and several assumptions made therein are further examined. It is shown that the alternative dispersion equations for CO2, which are due to Edlen [Metrologia 2, 71 (1966)] and Old et al. [J. Opt. Soc. Am. 61, 89 (1971)] result in differences of less than 2 x 10(-9) in the phase refractive index and less than 3 x 10(-9) in the group refractive index for current and predicted concentrations of CO2. However, because the dispersion equation given by Old et al. is consistent with experimental data in the near infrared, it is preferable to the equation used by Edlen, which is valid only in the ultraviolet and the visible. The classical measurement by Barrell and Sears [Philos. Trans. R. Soc. London Ser. A 238, 1 (1939)] on the refractivity of moist air is shown to have some procedural errors in addition to the one discussed by Birch and Downs [Metrologia 30, 155 (1993)]. It is shown that for normal atmospheric conditions the higher refractivity virial coefficients related to the Lorentz-Lorenz relation are adequately incorporated into the empirically determined first refractivity virial. As a guide to users the practical limits to the calculation of the refractive index of the atmosphere that result from the uncertainties in the measurement of the various atmospheric parameters are summarized.

  18. Effects of Long-Wavelength Lighting on Refractive Development in Infant Rhesus Monkeys

    PubMed Central

    Smith, Earl L.; Hung, Li-Fang; Arumugam, Baskar; Holden, Brien A.; Neitz, Maureen; Neitz, Jay

    2015-01-01

    Purpose Differences in the spectral composition of lighting between indoor and outdoor scenes may contribute to the higher prevalence of myopia in children who spend low amounts of time outdoors. Our goal was to determine whether environments dominated by long-wavelength light promote the development of myopia. Methods Beginning at 25 ± 2 days of age, infant monkeys were reared with long-wavelength-pass (red) filters in front of one (MRL, n = 6) or both eyes (BRL, n = 7). The filters were worn continuously until 146 ± 7 days of age. Refractive development, corneal power, and vitreous chamber depth were assessed by retinoscopy, keratometry, and ultrasonography, respectively. Control data were obtained from 6 monkeys reared with binocular neutral density (ND) filters and 33 normal monkeys reared with unrestricted vision under typical indoor lighting. Results At the end of the filter-rearing period, the median refractive error for the BRL monkeys (+4.25 diopters [D]) was significantly more hyperopic than that for the ND (+2.22 D; P = 0.003) and normal monkeys (+2.38 D; P = 0.0001). Similarly, the MRL monkeys exhibited hyperopic anisometropias that were larger than those in normal monkeys (+1.70 ± 1.55 vs. −0.013 ± 0.33 D, P < 0.0001). The relative hyperopia in the treated eyes was associated with shorter vitreous chambers. Following filter removal, the filter-reared monkeys recovered from the induced hyperopic errors. Conclusions The observed hyperopic shifts indicate that emmetropization does not necessarily target the focal plane that maximizes luminance contrast and that reducing potential chromatic cues can interfere with emmetropization. There was no evidence that environments dominated by long wavelengths necessarily promote myopia development. PMID:26447984

  19. Characterization of a novel ultra low refractive index material for biosensor application.

    PubMed

    Memisevic, Jasenka; Korampally, Venumadhav; Gangopadhyay, Shubhra; Grant, Sheila A

    2009-08-18

    Nanoporous materials can provide significant benefits to the field of biosensors. Their size and porous structure makes them an ideal tool for improving sensor performance. This study characterized a novel ultra low index of refraction nanoporous organosilicate (NPO) material for use as an optical platform for fluorescence-based optical biosensors. While serving as the low index cladding material, the novel coating based on organosilicate nanoparticles also provides an opportunity for a high surface area coating that can be utilized for immobilizing biological probes. Biological molecules were immobilized onto NPO, which was spin-coated on silicon and glass substrates. The biological molecule was composed of Protein A conjugated to AlexaFluor 546 fluorophore and then immobilized onto the NPO substrate via silanization. Sample analysis consisted of spectrofluorometry, FT-IR spectroscopy, scanning electron microscopy, contact angle measurement and ellipsometry. The results showed the presence of emission peaks at 574 nm, indicating that the immobilization of Protein A to the NPO material is possible. When compared to Si and glass substrates not coated with NPO, the results showed a 100X and 10X increase in packing density with the NPO coated films respectively. Ellipsometric analysis, FT-IR, contact angle, and SEM imaging of the surface immobilized NPO films suggested that while the surface modifications did induce some damage, it did not incur significant changes to its unique characteristics, i.e., pore structure, wettability and index of refraction. It was concluded that NPO films would be a viable sensor substrate to enhance sensitivity and improve sensor performance. PMID:20161155

  20. Calculations of atmospheric refraction for spacecraft remote-sensing applications

    NASA Technical Reports Server (NTRS)

    Chu, W. P.

    1983-01-01

    Analytical solutions to the refraction integrals appropriate for ray trajectories along slant paths through the atmosphere are derived in this paper. This type of geometry is commonly encountered in remote-sensing applications utilizing an occultation technique. The solutions are obtained by evaluating higher-order terms from expansion of the refraction integral and are dependent on the vertical temperature distributions. Refraction parameters such as total refraction angles, air masses, and path lengths can be accurately computed. It is also shown that the method can be used for computing refraction parameters in astronomical refraction geometry for large zenith angles.

  1. High Refraction Index Polysiloxanes via Organometallic Routes - An Overview

    NASA Astrophysics Data System (ADS)

    Stańzyk, Włodzimierz A.; Czech, Anna; Duczmal, Wojciech; Ganicz, Tomasz; Noskowska, Małgorzata; Szeląg, Anna

    Processes based on four organometallic routes leading to phenylethenyl substituted siloxanes are reviewed. Such materials, exhibiting high refraction indices, can be made by hydrosilylation of phenylacetylenes with Si-H moieties containing siloxane oligomers and polymers. On the other hand reactions between vinyl containing siloxanes with haloaryls or styrenes lead to the same systems via Heck or metathetic and silylative coupling. The effectiveness of the catalytic processes is analyzed from the point of view of side reactions, required catalyst concentration and reaction conditions. At the current state of knowledge the Heck coupling offers synthesis of the desired phenylethenyl substituted silicone fluids using technologically most attractive pathway.

  2. Index of refraction measurements and window corrections for PMMA under shock compression

    NASA Astrophysics Data System (ADS)

    Chapman, David James; Eakins, Daniel E.; Williamson, David Martin; Proud, William

    2012-03-01

    Symmetric plate impact experiments were performed to investigate the change in the refractive index of Polymethylmethacrylate (PMMA) under shock loading. Flyer and target geometries allowed the measurement of shock velocity, particle velocity, and refractive index in the shocked state, using a Het-V system (1550 nm). The change in refractive index of PMMA as a function of density is generally considered to be well described by the Gladstone-Dale relationship, meaning that the "apparent" velocity measured by a laser velocity interferometer is the "true" velocity, and hence there is no window correction. The results presented here demonstrate that the behaviour of PMMA deviates from an ideal Gladstone-Dale description, requiring a small velocity correction of order 1% at peak stresses up to 1.9 GPa. These results are consistent with literature values measured using a wavelength of 632.8 nm by [1].

  3. Exploring negative refraction conditions for quantum cascade semiconductor metamaterials in the terahertz spectral range

    NASA Astrophysics Data System (ADS)

    Daničić, A.; Radovanović, J.; Ramović, S.; Milanović, V.

    2016-03-01

    In order to avoid losses in metamaterial unit cells at frequencies of interest, caused by metallic inclusions, an active medium design has been proposed. As candidate structures for this active medium, we have chosen quantum cascade lasers because of their high output gain. Here we analyze and compare two quantum cascade structures that emit at 4.6 THz and 3.9 THz, respectively, placed under the influence of a strong magnetic field. We first solve the full system of rate equations for all relevant Landau levels, and obtain the necessary information about carrier distribution among the levels, after which we are able to evaluate the permittivity component along the growth direction of the structure. With these data one can determine the conditions under which negative refraction occurs, and calculate the values of the refractive index of the structure, as well as the range of frequencies at which the structure exhibits negative refraction for a predefined total electron sheet density.

  4. Wave propagation in pulsar magnetospheres - Refraction of rays in the open flux zone

    NASA Technical Reports Server (NTRS)

    Barnard, J. J.; Arons, J.

    1986-01-01

    The propagation of waves through a relativistically outflowing electron-positron plasma in a very strong dipolar magnetic field, conditions expected in pulsar magnetospheres, is investigated. Halmilton's equations is derived for the propagation of rays through a plasma which is inhomogeneous in density, magnetic field directions, and Lorentz factor. These equations are solved for rays propagating through the plasmas outflowing along the 'open' dipolar field lines in which the density decreases inversely as the radius cubed and in the case where gradients transverse to the radial direction exist. In the radial case, the effects of refraction on pulse profiles, spectrum, and polarization are examined, and the effects of a transverse gradient are indicated. Attention is given to models in which the observed broad bandwidth in the radio emission has its origin in a radius to frequency map. Models with broad-band emission at a single radius are also studied. These are compared to observations of pulse width and pulse component separation as a function of frequency. The origin of 'orthogonal modes' is discussed.

  5. Joint analysis of refractions with surface waves: An inverse solution to the refraction-traveltime problem

    USGS Publications Warehouse

    Ivanov, J.; Miller, R.D.; Xia, J.; Steeples, D.; Park, C.B.

    2006-01-01

    We describe a possible solution to the inverse refraction-traveltime problem (IRTP) that reduces the range of possible solutions (nonuniqueness). This approach uses a reference model, derived from surface-wave shear-wave velocity estimates, as a constraint. The application of the joint analysis of refractions with surface waves (JARS) method provided a more realistic solution than the conventional refraction/tomography methods, which did not benefit from a reference model derived from real data. This confirmed our conclusion that the proposed method is an advancement in the IRTP analysis. The unique basic principles of the JARS method might be applicable to other inverse geophysical problems. ?? 2006 Society of Exploration Geophysicists.

  6. Influence of refractive index on the accuracy of size determination of aerosol particles with light-scattering aerosol counters.

    PubMed

    Quenzel, H

    1969-01-01

    The scattering properties of single aerosol particles with different indices of refraction have been computed from the Mie theory considering the spectral response of light-scattering aerosol counters commercially available. It is demonstrated that high resolution of the aerosol size distribution is impossible, particularly because of the different refractive indices of the atmospheric aerosol particles. By using other ranges of scattering angle for the measurement, one may, in some cases, obtain better results.

  7. Meta-atom cluster acoustic metamaterial with broadband negative effective mass density

    SciTech Connect

    Chen, Huaijun; Zhai, Shilong; Ding, Changlin; Liu, Song; Luo, Chunrong; Zhao, Xiaopeng

    2014-02-07

    We design a resonant meta-atom cluster, via which a two-dimensional (2D) acoustic metamaterial (AM) with broadband negative effective mass density from 1560 Hz to 5580 Hz is fabricated. Experimental results confirm that there is only weak interaction among the meta-atoms in the cluster. And then the meta-atoms in the cluster independently resonate, resulting in the cluster becoming equivalent to a broadband resonance unit. Extracted effective refractive indices from reflection and transmission measurements of the 2D AM appear to be negative from 1500 Hz to 5480 Hz. The broadband negative refraction has also been demonstrated by our further experiments. We expect that this meta-atom cluster AM will significantly contribute to the design of broadband negative effective mass density AM.

  8. Three-Dimensional Holographic Refractive-Index Measurement of Continuously Flowing Cells in a Microfluidic Channel

    NASA Astrophysics Data System (ADS)

    Sung, Yongjin; Lue, Niyom; Hamza, Bashar; Martel, Joseph; Irimia, Daniel; Dasari, Ramachandra R.; Choi, Wonshik; Yaqoob, Zahid; So, Peter

    2014-02-01

    The refractive index of biological specimens is a source of intrinsic contrast that can be explored without any concerns of photobleaching or harmful effects caused by extra contrast agents. In addition, the refractive index contains rich information related to the metabolism of cells at the cellular and subcellular levels. Here, we report a no-moving-parts approach that provides three-dimensional refractive-index maps of biological samples continuously flowing in a microfluidic channel. Specifically, we use line illumination and off-axis digital holography to record the angular spectra of light scattered from flowing samples at high speed. Applying the scalar diffraction theory, we obtain accurate refractive-index maps of the samples from the measured spectra. Using this method, we demonstrate label-free three-dimensional imaging of live RKO human colon cancer cells and RPMI8226 multiple myeloma cells, and obtain the volume, dry mass, and density of these cells from the measured three-dimensional refractive-index maps. Our results show that the reported method, alone or in combination with the existing flow cytometry techniques, shows promise as a quantitative tool for stain-free characterization of a large number of cells.

  9. Tropospheric wet refractivity tomography based on the BeiDou satellite system

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoying; Wang, Xianliang; Dai, Ziqiang; Ke, Fuyang; Cao, Yunchang; Wang, Feifei; Song, Lianchun

    2014-03-01

    This paper presents a novel approach for assessing the precision of the wet refractivity field using BDS (BeiDou navigation satellite system) simulations only, GPS, and BDS+GPS for the Shenzhen and Hongkong GNSS network. The simulations are carried out by adding artificial noise to a real observation dataset. Instead of using the d and s parameters computed from slant wet delay, as in previous studies, we employ the Bias and RMS parameters, computed from the tomography results of total voxels, in order to obtain a more direct and comprehensive evaluation of the precision of the refractivity field determination. The results show that: (1) the precision of tropospheric wet refractivity estimated using BDS alone (only 9 satellites used) is basically comparable to that of GPS; (2) BDS+GPS (as of current operation) may not be able to significantly improve the data's spatial density for the application of refractivity tomography; and (3) any slight increase in the precision of refractivity tomography, particularly in the lower atmosphere, bears great significance for any applications dependent on the Chinese operational meteorological service.

  10. Blending History with Physics: Acoustic Refraction.

    ERIC Educational Resources Information Center

    Ross, Charles D.

    2000-01-01

    Argues that the study of refraction of sound waves, although usually neglected, is an excellent ancillary to the normal optical approach in physics courses. Discusses the historical context of interest in the science behind outdoor sound propagation, particularly during the Civil War in the United States. (WRM)

  11. A Mechanical Analogue of the Refracting Telescope

    ERIC Educational Resources Information Center

    Vannoni, Maurizio; Molesini, Giuseppe; Sordini, Andrea; Straulino, Samuele

    2011-01-01

    The recent celebration of the discoveries made by Galileo four centuries ago has attracted new attention to the refracting telescope and to its use as an instrument for the observation of the night sky. This has offered the opportunity for addressing in the classroom the basic principles explaining the operation of the telescope. When doing so, a…

  12. Validation of Ray Tracing Code Refraction Effects

    NASA Technical Reports Server (NTRS)

    Heath, Stephanie L.; McAninch, Gerry L.; Smith, Charles D.; Conner, David A.

    2008-01-01

    NASA's current predictive capabilities using the ray tracing program (RTP) are validated using helicopter noise data taken at Eglin Air Force Base in 2007. By including refractive propagation effects due to wind and temperature, the ray tracing code is able to explain large variations in the data observed during the flight test.

  13. Nonlinear negative refraction in reorientational soft matter

    NASA Astrophysics Data System (ADS)

    Alberucci, Alessandro; Jisha, Chandroth P.; Assanto, Gaetano

    2015-09-01

    We analyze the propagation of self-trapped optical beams close to the Fréedericksz threshold in nematic liquid crystals. Accounting for power-dependent changes in walk-off due to the all-optical response, we demonstrate that light beams can switch from positive to negative refraction according to the excitation.

  14. Compound refractive X-ray lens

    DOEpatents

    Nygren, David R.; Cahn, Robert; Cederstrom, Bjorn; Danielsson, Mats; Vestlund, Jonas

    2000-01-01

    An apparatus and method for focusing X-rays. In one embodiment, his invention is a commercial-grade compound refractive X-ray lens. The commercial-grade compound refractive X-ray lens includes a volume of low-Z material. The volume of low-Z material has a first surface which is adapted to receive X-rays of commercially-applicable power emitted from a commercial-grade X-ray source. The volume of low-Z material also has a second surface from which emerge the X-rays of commercially-applicable power which were received at the first surface. Additionally, the commercial-grade compound refractive X-ray lens includes a plurality of openings which are disposed between the first surface and the second surface. The plurality of openings are oriented such that the X-rays of commercially-applicable power which are received at the first surface, pass through the volume of low-Z material and through the plurality openings. In so doing, the X-rays which emerge from the second surface are refracted to a focal point.

  15. Gradient Refractive Index Optics IOL: Theoretical Background and Clinical Results

    PubMed Central

    Malyugin, Boris; Morozova, Tatiana; Cherednik, Valentin

    2014-01-01

    Purpose: To present the theoretical optical background and clinical results of a new multifocal intraocular lens (MIOL) concept–gradient refractive index optics (Gradiol). Patients and Methods: Original mathematical modeling software was used to calculate optimal construction of the MIOL optic constructed from two polymer materials with different refractive indices. Gradiol lenses were manufactured from hydrophobic acrylic utilizing original step-by-step polymerization technology with the final power difference of of 3.5 D between optic components. Non-comparative prospective clinical study included 26 patients (29 eyes) who were candidates for MIOL implantation. All surgeries were performed at the S. Fyodorov Eye Microsurgery Complex State Institution, Moscow, Russia. After implantation of the Gradiol lenses, the postoperative evaluations included distance (best corrected visual acuity (BCVA)) and near visual acuity (NVA), contrast sensitivity (CS), and amplitude of pseudoaccommodation. Subjective patient's satisfaction was assessed using a questionnaire (VF-14). Results: The mean age of the patients was 62.5 ± 5.7 years (range 27-82 years). All surgical procedures were uneventful. At 6 months postoperatively, the mean uncorrected distance VA was 0.73 ± 0.18, mean uncorrected near VA was 0.57 ± 0.19, mean corrected distance VA was 0.89 ± 0.15, mean corrected near VA was 0.84 ± 0.07, and amplitude of pseudoaccommodation was 4.75 ± 0.5 D. Eighty-six percent of patients were spectacle independent for daily activities and reading. Optical disturbances that were functionally significant were reported by 10.7% of patients postoperatively. Conclusion: The clinical outcomes of this study confirmed the theoretical calculations of constructing MIOL optics from materials with different refractive indices. PMID:24669143

  16. Pg shingles: preliminary results from the onshore GLIMPCE refraction experiment

    NASA Astrophysics Data System (ADS)

    Mereu, R. F.; Epili, D.; Green, A. G.

    1990-02-01

    In 1986, a series of near vertical Seismic reflection lines and coincident Seismic refraction lines were recorded across the Great Lakes in the GLIMPCE experiment. From a refraction point of view this experiment was unique as this was the first time in North America that long range refraction lines up to 350 km were recorded with a trace spacing of less than 100 metres. The source of energy was a large air gun. Some preliminary results of the nature of the onshore recordings made by the University of Western Ontario are presented in this paper. Observations of many of the in-line profiles show that the character of the Pg crustal phase is not simple but has a "shingle-like" pattern which may be caused by wide-angle reflection effects from numerous long and short reflectors within the crust. Theoretical studies indicate that the amplitudes of the wide-angle reflected signals from thin high-velocity layers are in general much larger than those from thin low-velocity layers. Supercritical reflected waves are not possible from the top of a low-velocity layer. The closely spaced traces show in minute detail the manner in which one travel-time branch fades and the next one arrives. The results seem to indicate that the Pg phase in our data set has little direct wave component but, instead, is made up of a whole series of "shingled or fish-scaled" wide-angle reflection components, each with successively larger apparent velocities. These results are in agreement with the findings of the near-vertical reflection component of the experiment.

  17. Ultrafast refractive index control of a terahertz graphene metamaterial

    PubMed Central

    Lee, Seung Hoon; Choi, Jeongmook; Kim, Hyeon-Don; Choi, Hyunyong; Min, Bumki

    2013-01-01

    Modulation of the refractive index of materials is elementary, yet it is crucial for the manipulation of electromagnetic waves. Relying on the inherent properties of natural materials, it has been a long-standing challenge in device engineering to increase the index-modulation contrast. Here, we demonstrate a significant amount of ultrafast index modulation by optically exciting non-equilibrium Dirac fermions in the graphene layer integrated onto a high-index metamaterial. Furthermore, an extremely-large electrical modulation of refractive index up to Δn ~ −3.4 (at 0.69 THz) is achieved by electrical tuning of the density of the equilibrium Dirac fermion in the graphene metamaterial. This manifestation, otherwise remaining elusive in conventional semiconductor devices, fully exploits the characteristic ultrafast charge relaxation in graphene as well as the strong capacitive response of the metamaterial, both of which enable us to drastically increase the light-matter interaction of graphene and the corresponding index contrast in the graphene metamaterials. PMID:23823715

  18. Ultrafast refractive index control of a terahertz graphene metamaterial.

    PubMed

    Lee, Seung Hoon; Choi, Jeongmook; Kim, Hyeon-Don; Choi, Hyunyong; Min, Bumki

    2013-01-01

    Modulation of the refractive index of materials is elementary, yet it is crucial for the manipulation of electromagnetic waves. Relying on the inherent properties of natural materials, it has been a long-standing challenge in device engineering to increase the index-modulation contrast. Here, we demonstrate a significant amount of ultrafast index modulation by optically exciting non-equilibrium Dirac fermions in the graphene layer integrated onto a high-index metamaterial. Furthermore, an extremely-large electrical modulation of refractive index up to Δn ~ -3.4 (at 0.69 THz) is achieved by electrical tuning of the density of the equilibrium Dirac fermion in the graphene metamaterial. This manifestation, otherwise remaining elusive in conventional semiconductor devices, fully exploits the characteristic ultrafast charge relaxation in graphene as well as the strong capacitive response of the metamaterial, both of which enable us to drastically increase the light-matter interaction of graphene and the corresponding index contrast in the graphene metamaterials. PMID:23823715

  19. Relocation of Groningen seismicity using refracted waves

    NASA Astrophysics Data System (ADS)

    Ruigrok, E.; Trampert, J.; Paulssen, H.; Dost, B.

    2015-12-01

    The Groningen gas field is a giant natural gas accumulation in the Northeast of the Netherlands. The gas is in a reservoir at a depth of about 3 km. The naturally-fractured gas-filled sandstone extends roughly 45 by 25 km laterally and 140 m vertically. Decades of production have led to significant compaction of the sandstone. The (differential) compaction is thought to have reactivated existing faults and being the main driver of induced seismicity. Precise earthquake location is difficult due to a complicated subsurface, and that is the likely reason, the current hypocentre estimates do not clearly correlate with the well-known fault network. The seismic velocity model down to reservoir depth is quite well known from extensive seismic surveys and borehole data. Most to date earthquake detections, however, were made with a sparse pre-2015 seismic network. For shallow seismicity (<5 km depth) horizontal source-receiver distances tend to be much larger than vertical distances. Consequently, preferred source-receiver travel paths are refractions over high-velocity layers below the reservoir. However, the seismic velocities of layers below the reservoir are poorly known. We estimated an effective velocity model of the main refracting layer below the reservoir and use this for relocating past seismicity. We took advantage of vertical-borehole recordings for estimating precise P-wave (refraction) onset times and used a tomographic approach to find the laterally varying velocity field of the refracting layer. This refracting layer is then added to the known velocity model, and the combined model is used to relocate the past seismicity. From the resulting relocations we assess which of the faults are being reactivated.

  20. Refractive Turbulence, Transient Propagation Disturbances, and Space Situational Awareness

    NASA Astrophysics Data System (ADS)

    Cote, O.; Wroblewski, D.; Hacker, J.

    This paper examines the proposition that mission limiting space situational awareness (SSA) has important and fundamental turbulence and propagation physics issues to be investigated. We propose to call these aspects, propagation situational awareness (PSA). Transient disturbances can be present in communication to and from ground stations and satellites and in the performance of ground based and space based optical and infra-red imaging and tracking systems. Propagation frequency is important in characterizing whether the source of the disturbance lay in the electron density fluctuations of ionosphere or the refractive turbulence of the neutral atmosphere. Over the past ten years high altitude airborne measurements of clear air and refractive turbulence were made in Australia to support design and performance evaluations of the Airborne Laser. More recently in collaboration with the Australian Defence Science & Technology Organization (DSTO) smaller aircraft were used to investigate the effect of ducting layers on the signal strength of an airborne emitter as a low cost simulation of potential for loss of track in the coverage pattern of an airborne radar. From 2002 onward we were also tasked to do fundamental investigations of clear air turbulence for flight safety evaluations of both manned and unmanned high altitude surveillance aircraft. These investigations covered a wide spread in frequency, from infra-red to microwave. Most of these investigations were confined to measurement days and altitudes where strong turbulence was expected. The decision to measure was based on predictions of the location of jet streams relative to the measurement area as well as bulk gradient Richardson (Ri) vertical profiles derived from radio sound measurements from stations surround the potential measurement location. We will show how all these analyses and decision aids, including the Ri profiles, can be used to estimate potential for propagation disturbances to SSA. Current DOD

  1. Specific features of measuring the optical power of artificial refractive and diffractive-refractive eye lenses

    NASA Astrophysics Data System (ADS)

    Lenkova, G. A.

    2016-08-01

    Methods for monitoring the optical power of artificial refractive eye lenses (intraocular lenses) based on measuring focal lengths in air and in medium are analyzed. The methods for determining the refraction of diffractive-refractive lenses (in particular, of MIOL-Akkord type), with allowance for the specific features of the diffractive structure, are considered. A computer simulation of the measurement of the focal length of MIOL-Akkord lenses is performed. The effective optical power of the diffractive component of these lenses is shown to depend on the diaphragm diameter. The optimal diaphragm diameter, at which spherical aberrations do not affect the position of foci, is found to be 3 mm. Possible errors in measuring the focal lengths are analyzed, and the necessary corrections that must be introduced into measurement results and calculations of refractions are determined.

  2. Electrodynamics of moving media inducing positive and negative refraction

    SciTech Connect

    Grzegorczyk, Tomasz M.; Kong, Jin Au

    2006-07-15

    Negative refraction is a phenomenon that has been recently reported with left-handed media (either isotropic or not), photonic crystals, and rotated uniaxial media. In this Brief Report, we identify another origin of negative refraction, due to the motion of the transmitted medium parallel to the interface at which refraction occurs. Previous works in this domain have concentrated on media velocities that are above the Cerenkov limit, while we show here that negative refraction is in fact achievable at any velocities of the transmitted medium. A possible experimental implementation is proposed to verify this effect. Next, we consider an isotropic frequency-dispersive medium for which the index of refraction can take negative values, and we study the wave refraction phenomenon as a function of frequency and medium velocity. It is found that the motion of the medium induces a rotation of refraction, which can either enhance or attenuate the natural negative refraction of the medium.

  3. Automatic Refraction: How It Is Done: Some Clinical Results

    ERIC Educational Resources Information Center

    Safir, Aran; And Others

    1973-01-01

    Compaired are methods of determining visual refraction needs of young children or other unreliable observers by means of retinosocopy or the Opthalmetron, an automatic instrument which can be operated by a technician with no knowledge of refraction. (DB)

  4. Design of Amphoteric Refraction Models Using WAVICA and RAYICA

    NASA Technical Reports Server (NTRS)

    Su, Richard

    2004-01-01

    The phenomenon of refraction of light is due to refractive index mismatches in two different media. However, to achieve this effect, a finite reflection loss is inevitable. A recent finding presented a unique type of interface, ferroelastic materials, that enables refraction without any reflection for either an electron or a light beam. This property is called total refraction. The same type of interface that yields total refraction can also yield amphoteric refraction, where the index of refraction can be either positive or negative depending on the incident angle. This interface could potentially be used to steer light without reflections which could have major applications in high power optics. My goal this summer is to first familiarize myself with the Mathematica software, especially the Wavica and Rayica packages. I will then model the amphoteric refraction by either modifying the Wavica and Rayica packages or using the built-in functions in these packages.

  5. Is LASIK for Me? A Patient's Guide to Refractive Surgery

    MedlinePlus

    ... were developed with the help of the Federal Trade Commission and the American Society of Cataract and Refractive Surgery. For the complete guidelines, see: www.aao.org/about/policy/upload/Guidelines-for-Refractive-Surgery- Advertising-3-26- ...

  6. Negative refraction of elastic waves at the deep-subwavelength scale in a single-phase metamaterial.

    PubMed

    Zhu, R; Liu, X N; Hu, G K; Sun, C T; Huang, G L

    2014-11-24

    Negative refraction of elastic waves has been studied and experimentally demonstrated in three- and two-dimensional phononic crystals, but Bragg scattering is impractical for low-frequency wave control because of the need to scale the structures to manageable sizes. Here we present an elastic metamaterial with chiral microstructure made of a single-phase solid material that aims to achieve subwavelength negative refraction of elastic waves. Both negative effective mass density and modulus are observed owing to simultaneous translational and rotational resonances. We experimentally demonstrate negative refraction of the longitudinal elastic wave at the deep-subwavelength scale in the metamaterial fabricated in a stainless steel plate. The experimental measurements are in good agreement with numerical simulations. Moreover, wave mode conversion related with negative refraction is revealed and discussed. The proposed elastic metamaterial may thus be used as a flat lens for elastic wave focusing.

  7. Methods to retrieve the complex refractive index of aquatic suspended particles: going beyond simple shapes

    NASA Astrophysics Data System (ADS)

    Sánchez, Albert-Miquel; Piera, Jaume

    2016-07-01

    The scattering properties of aquatic suspended particles have many optical applications. Several data inversion methods have been proposed to estimate important features of particles, such as their size distribution or their refractive index. Most of the proposed methods are based on the Lorenz-Mie theory to solve Maxwell's equations, where particles are considered homogeneous spheres. A generalization that allows consideration of more complex-shaped particles is the T-matrix method. Although this approach imposes some geometrical restrictions (particles must be rotationally symmetrical) it is applicable to many life forms of phytoplankton. In this paper, three different scenarios are considered in order to compare the performance of several inversion methods for retrieving refractive indices. The error associated with each method is discussed and analyzed. The results suggest that inverse methods using the T-matrix approach are useful to accurately retrieve the refractive indices of particles with complex shapes, such as for many phytoplankton organisms.

  8. [Results of refractive surgery in hyperopic and combined astigmatism].

    PubMed

    Vlaicu, Valeria

    2013-01-01

    The refractive surgery includes a lot of procedures for changing the refraction of the eye to obtain a better visual acuity with no glasses or contact lenses. LASIK is the most commonly performed laser refractive surgery today. The goal is to present the postoperative evolution of the refraction and visual acuity after LASIK for Mixed and Hyperopic Astigmatism. The results show that LASIK is safe and predictible if we have well performed interventions and well-selected patients.

  9. Wavelength dependence of refractive index in lead-free Na0.5Bi0.5TiO3-BaTiO3 single crystals

    NASA Astrophysics Data System (ADS)

    He, Chongjun; Yi, Xiujie; Wu, Tong; Wang, Jiming; Zhu, Kongjun; Liu, Youwen

    2014-10-01

    Refractive indices of (1-x)Na0.5Bi0.5TiO3-xBaTiO3 (NBT-xBT, x = 0, 0.06 and 0.08) single crystals were measured at room temperature after poled along pseudo-cubic crystallographic direction [0 0 1]. The refractive indices decrease dramatically when the wavelength increases for all crystals. At the same wavelength, refractive indices of NBT-xBT single crystals decrease with increasing BT content. Sellmeier dispersion equations were obtained by least square fitting, which can be used to calculate the refractive indices in low absorption wavelength range. Parameters connected to the energy band structure were determined by fitting single-oscillator dispersion equation. Similar to most oxygen-octahedral ferroelectrics, NBT-xBT crystals have the same dispersion behavior described by the refractive-index dispersion parameter. Dispersion energies take on covalent crystal values.

  10. Low Scatter Edge Blackening Compounds For Refractive Optical Elements

    NASA Astrophysics Data System (ADS)

    Lewis, Isabella T.; Telkamp, Arthur R.; Ledebuhr, Arno G.

    1990-01-01

    Perkin-Elmer's Applied Optics Operation recently delivered several prototype wide-field-of-view (WFOV), F/2.8, 250 mm efl, near diffraction limited, concentric refractive lenses to Lawrence Livermore National Laboratory (LLNL). In these lenses, special attention was paid to reducing stray light to allow viewing of very dim objects. Because of the very large FOV, the use of a long baffle to eliminate direct illumination of lens edges was not practical. With the existing relatively short baffle design, one-bounce stray light paths off the element edges are possible. The scattering off the inside edges thus had to be kept to an absolute minimum. While common means for blackening the edges of optical elements are easy to apply and quite cost effective for normal lens assemblies, their blackening effect is limited by the Fresnel reflection due to the index of refraction mismatch at the glass boundary. At high angles of incidence, total internal reflection (TIR) might occur ruining the effect of the blackening process. An index-matched absorbing medium applied to the edges of such elements is the most effective approach for reducing the amount of undesired light reflected or scattered off these edges. The presence of such a medium provides an extended path outside the glass boundary in which an absorptive non-scattering dye can be used to eliminate light that might otherwise have propagated to the focal plane. Perkin-Elmer and LLNL undertook a program to develop epoxy-based dye carrier compounds with refractive indices corresponding to the glass types used in the WFOV lens. This program involved the measuring of the refractive index of a number of epoxy compounds and catalysts, the experimental combination of epoxies to match our glass indices, and the identification of a suitable non-scattering absorptive dye. Measurements on these blacks showed Bidirectional Reflectance Distribution Functions (BRDFs) between 1.4 and 3.1 orders of magnitude lower than Perkin

  11. Shuttle program: Computing atmospheric scale height for refraction corrections

    NASA Technical Reports Server (NTRS)

    Lear, W. M.

    1980-01-01

    Methods for computing the atmospheric scale height to determine radio wave refraction were investigated for different atmospheres, and different angles of elevation. Tables of refractivity versus altitude are included. The equations used to compute the refraction corrections are given. It is concluded that very accurate corrections are determined with the assumption of an exponential atmosphere.

  12. Optical Enhancement in Optoelectronic Devices Using Refractive Index Grading Layers.

    PubMed

    Lee, Illhwan; Park, Jae Yong; Gim, Seungo; Kim, Kisoo; Cho, Sang-Hwan; Choi, Chung Sock; Song, Seung-Yong; Lee, Jong-Lam

    2016-02-10

    We enhanced the optical transmittance of a multilayer barrier film by inserting a refractive index grading layer (RIGL). The result indicates that the Fresnel reflection, induced by the difference of refractive indices between Si(x)N(y) and SiO2, is reduced by the RIGL. To eliminate the Fresnel reflection while maintaining high transmittance, the optimized design of grading structures with the RIGL was conducted using an optical simulator. With the RIGL, we achieved averaged transmittance in the visible wavelength region by 89.6%. It is found that the optimized grading structure inserting the multilayer barrier film has a higher optical transmittance (89.6%) in the visible region than that of a no grading sample (82.6%). Furthermore, luminance is enhanced by 14.5% (from 10,190 to 11,670 cd m(-2) at 30 mA cm(-2)) when the grading structure is applied to organic light-emitting diodes. Finally, the results offer new opportunities in development of multilayer barrier films, which assist industrialization of very cost-effective flexible organic electronic devices.

  13. A new target reconstruction method considering atmospheric refraction

    NASA Astrophysics Data System (ADS)

    Zuo, Zhengrong; Yu, Lijuan

    2015-12-01

    In this paper, a new target reconstruction method considering the atmospheric refraction is presented to improve 3D reconstruction accuracy in long rang surveillance system. The basic idea of the method is that the atmosphere between the camera and the target is partitioned into several thin layers radially in which the density is regarded as uniform; Then the reverse tracking of the light propagation path from sensor to target was carried by applying Snell's law at the interface between layers; and finally the average of the tracked target's positions from different cameras is regarded as the reconstructed position. The reconstruction experiments were carried, and the experiment results showed that the new method have much better reconstruction accuracy than the traditional stereoscopic reconstruction method.

  14. Dependence of the Radiation Pressure on the Background Refractive Index

    NASA Astrophysics Data System (ADS)

    Webb, Kevin J.

    2013-07-01

    The 1978 experiments by Jones and Leslie showing that the radiation pressure on a mirror depends on the background medium refractive index have yet to be adequately explained using a force model and have provided a leading challenge to the Abraham form of the electromagnetic momentum. Those experimental results are predicted for the first time using a force representation that incorporates the Abraham momentum by utilizing the power calibration method employed in the Jones and Leslie experiments. With an extension of the same procedure, the polarization and angle independence of the experimental data are also explained by this model. Prospects are good for this general form of the electromagnetic force density to be effective in predicting other experiments with macroscopic materials. Furthermore, the rigorous representation of material dispersion makes the representation important for metamaterials that operate in the vicinity of homogenized material resonances.

  15. High Prevalence of Refractive Errors in 7 Year Old Children in Iran

    PubMed Central

    HASHEMI, Hassan; YEKTA, Abbasali; JAFARZADEHPUR, Ebrahim; OSTADIMOGHADDAM, Hadi; ETEMAD, Koorosh; ASHARLOUS, Amir; NABOVATI, Payam; KHABAZKHOOB, Mehdi

    2016-01-01

    Background: The latest WHO report indicates that refractive errors are the leading cause of visual impairment throughout the world. The aim of this study was to determine the prevalence of myopia, hyperopia, and astigmatism in 7 yr old children in Iran. Methods: In a cross-sectional study in 2013 with multistage cluster sampling, first graders were randomly selected from 8 cities in Iran. All children were tested by an optometrist for uncorrected and corrected vision, and non-cycloplegic and cycloplegic refraction. Refractive errors in this study were determined based on spherical equivalent (SE) cyloplegic refraction. Results: From 4614 selected children, 89.0% participated in the study, and 4072 were eligible. The prevalence rates of myopia, hyperopia and astigmatism were 3.04% (95% CI: 2.30–3.78), 6.20% (95% CI: 5.27–7.14), and 17.43% (95% CI: 15.39–19.46), respectively. Prevalence of myopia (P=0.925) and astigmatism (P=0.056) were not statistically significantly different between the two genders, but the odds of hyperopia were 1.11 (95% CI: 1.01–2.05) times higher in girls (P=0.011). The prevalence of with-the-rule astigmatism was 12.59%, against-the-rule was 2.07%, and oblique 2.65%. Overall, 22.8% (95% CI: 19.7–24.9) of the schoolchildren in this study had at least one type of refractive error. Conclusion: One out of every 5 schoolchildren had some refractive error. Conducting multicenter studies throughout the Middle East can be very helpful in understanding the current distribution patterns and etiology of refractive errors compared to the previous decade. PMID:27114984

  16. Refractive Error, Axial Length, and Relative Peripheral Refractive Error before and after the Onset of Myopia

    PubMed Central

    Mutti, Donald O.; Hayes, John R.; Mitchell, G. Lynn; Jones, Lisa A.; Moeschberger, Melvin L.; Cotter, Susan A.; Kleinstein, Robert N.; Manny, Ruth E.; Twelker, J. Daniel; Zadnik, Karla

    2009-01-01

    Purpose To evaluate refractive error, axial length, and relative peripheral refractive error before, during the year of, and after the onset of myopia in children who became myopic compared with emmetropes. Methods Subjects were 605 children 6 to 14 years of age who became myopic (at least −0.75 D in each meridian) and 374 emmetropic (between −0.25 D and + 1.00 D in each meridian at all visits) children participating between 1995 and 2003 in the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error (CLEERE) Study. Axial length was measured annually by A-scan ultrasonography. Relative peripheral refractive error (the difference between the spherical equivalent cycloplegic autorefraction 30° in the nasal visual field and in primary gaze) was measured using either of two autorefractors (R-1; Canon, Lake Success, NY [no longer manufactured] or WR 5100-K; Grand Seiko, Hiroshima, Japan). Refractive error was measured with the same autorefractor with the subjects under cycloplegia. Each variable in children who became myopic was compared to age-, gender-, and ethnicity-matched model estimates of emmetrope values for each annual visit from 5 years before through 5 years after the onset of myopia. Results In the sample as a whole, children who became myopic had less hyperopia and longer axial lengths than did emmetropes before and after the onset of myopia (4 years before through 5 years after for refractive error and 3 years before through 5 years after for axial length; P < 0.0001 for each year). Children who became myopic had more hyperopic relative peripheral refractive errors than did emmetropes from 2 years before onset through 5 years after onset of myopia (P < 0.002 for each year). The fastest rate of change in refractive error, axial length, and relative peripheral refractive error occurred during the year before onset rather than in any year after onset. Relative peripheral refractive error remained at a consistent level of hyperopia each

  17. Refractive index measurement of the mouse crystalline lens using optical coherence tomography.

    PubMed

    Chakraborty, Ranjay; Lacy, Kip D; Tan, Christopher C; Park, Han Na; Pardue, Machelle T

    2014-08-01

    In recent years, there has been a growing interest for using mouse models in refractive development and myopia research. The crystalline lens is a critical optical component of the mouse eye that occupies greater than 50% of the ocular space, and significant increases in thickness with age. However, changes in refractive index of the mouse crystalline lens are less known. In this study, we examined the changes in thickness and refractive index of the mouse crystalline lens for two different strains, wild-type (WT) and a nyx mutant (nob) over the course of normal visual development or after form deprivation. Refractive index and lens thickness measurements were made on ex vivo lenses using spectral domain optical coherence tomography (SD-OCT). Comparison of refractive index measurements on 5 standard ball lenses using the SD-OCT and their known refractive indices (manufacturer provided) indicated good precision (intra-class correlation coefficient, 0.998 and Bland-Altman coefficient of repeatability, 0.116) of the SD-OCT to calculate mouse lens refractive index ex vivo. During normal visual development, lens thickness increased significantly with age for three different cohorts of mice, aged 4 (average thickness from both eyes; WT: 1.78 ± 0.03, nob: 1.79 ± 0.08 mm), 10 (WT: 2.02 ± 0.05, nob: 2.01 ± 0.04 mm) and 16 weeks (WT: 2.12 ± 0.06, nob: 2.09 ± 0.06 mm, p < 0.001). Lens thickness was not significantly different between the two strains at any age (p = 0.557). For mice with normal vision, refractive index for isolated crystalline lenses in nob mice was significantly greater than WT mice (mean for all ages; WT: 1.42 ± 0.01, nob: 1.44 ± 0.001, p < 0.001). After 4 weeks of form deprivation to the right eye using a skull-mounted goggling apparatus, a thinning of the crystalline lens was observed in both right and left eyes of goggled animals compared to their naïve controls (average from both the right and the left eye) for both

  18. Refractive index determination by coherence scanning interferometry.

    PubMed

    Yoshino, H; Kaminski, P M; Smith, R; Walls, J M; Mansfield, D

    2016-05-20

    Coherence scanning interferometry is established as a powerful noncontact, three-dimensional, metrology technique used to determine accurate surface roughness and topography measurements with subnanometer precision. The helical complex field (HCF) function is a topographically defined helix modulated by the electrical field reflectance, originally developed for the measurement of thin films. An approach to extend the capability of the HCF function to determine the spectral refractive index of a substrate or absorbing film has recently been proposed. In this paper, we confirm this new capability, demonstrating it on surfaces of silicon, gold, and a gold/palladium alloy using silica and zirconia oxide thin films. These refractive index dispersion measurements show good agreement with those obtained by spectroscopic ellipsometry. PMID:27411157

  19. Babinet's principle in double-refraction systems

    NASA Astrophysics Data System (ADS)

    Ropars, Guy; Le Floch, Albert

    2014-06-01

    Babinet's principle applied to systems with double refraction is shown to involve spatial interchanges between the ordinary and extraordinary patterns observed through two complementary screens. As in the case of metamaterials, the extraordinary beam does not follow the Snell-Descartes refraction law, the superposition principle has to be applied simultaneously at two points. Surprisingly, by contrast to the intuitive impression, in the presence of the screen with an opaque region, we observe that the emerging extraordinary photon pattern, which however has undergone a deviation, remains fixed when a natural birefringent crystal is rotated while the ordinary one rotates with the crystal. The twofold application of Babinet's principle implies intensity and polarization interchanges but also spatial and dynamic interchanges which should occur in birefringent metamaterials.

  20. Refractive scintillation in the interstellar medium

    NASA Astrophysics Data System (ADS)

    Coles, W. A.; Rickett, B. J.; Codona, J. L.; Frehlich, R. G.

    1987-04-01

    The slow variation in the apparent intensity of pulsars on time scales of days to months was recently shown to be due to a large-scale component of interstellar scintillation (Rickett, Coles, and Bourgois). These variations are greater than one would expect if the turbulence spectrum were a simple Kolmogorov power law. It is shown that this large-scale component can be greatly enhanced when the turbulence spectrum has a limiting "inner scale" of the order of 109m. The authors present a solution for the covariance of refractive scintillation of an extended source in an extended medium. The results show that refractive scintillations are also responsible for slow variations in "low-frequency variables".

  1. Neutrino refraction by the cosmic neutrino background

    NASA Astrophysics Data System (ADS)

    Díaz, J. S.; Klinkhamer, F. R.

    2016-03-01

    We have determined the dispersion relation of a neutrino test particle propagating in the cosmic neutrino background. Describing the relic neutrinos and antineutrinos from the hot big bang as a dense medium, a matter potential or refractive index is obtained. The vacuum neutrino mixing angles are unchanged, but the energy of each mass state is modified. Using a matrix in the space of neutrino species, the induced potential is decomposed into a part which produces signatures in beta-decay experiments and another part which modifies neutrino oscillations. The low temperature of the relic neutrinos makes a direct detection extremely challenging. From a different point of view, the identified refractive effects of the cosmic neutrino background constitute an ultralow background for future experimental studies of nonvanishing Lorentz violation in the neutrino sector.

  2. Emerging Technology in Refractive Cataract Surgery

    PubMed Central

    Saraiva, João; Neatrour, Kristin; Waring IV, George O.

    2016-01-01

    Technology in cataract surgery is constantly evolving to meet the goals of both surgeons and patients. Recent major advances in refractive cataract surgery include innovations in preoperative and intraoperative diagnostics, femtosecond laser-assisted cataract surgery (FLACS), and a new generation of intraocular lenses (IOLs). This paper presents the latest technologies in each of these major categories and discusses how these contributions serve to improve cataract surgery outcomes in a safe, effective, and predictable manner. PMID:27433353

  3. Comment on 'Perfect imaging without negative refraction'

    NASA Astrophysics Data System (ADS)

    Blaikie, R. J.

    2010-05-01

    The prediction of 'perfect' imaging without negative refraction for Maxwell's fish-eye lens (Leonhardt U 2009 New J. Phys. 11 093040) is a consequence of imposing an active localized 'drain' at the image point rather than being a general property of the lens. This work then becomes analogous to other work using time-reversal symmetry and/or structured antennae to achieve super-resolution, which can be applied to many types of imaging system beyond the fish-eye lens.

  4. Nonlinear refraction and reflection travel time tomography

    USGS Publications Warehouse

    Zhang, Jiahua; ten Brink, U.S.; Toksoz, M.N.

    1998-01-01

    We develop a rapid nonlinear travel time tomography method that simultaneously inverts refraction and reflection travel times on a regular velocity grid. For travel time and ray path calculations, we apply a wave front method employing graph theory. The first-arrival refraction travel times are calculated on the basis of cell velocities, and the later refraction and reflection travel times are computed using both cell velocities and given interfaces. We solve a regularized nonlinear inverse problem. A Laplacian operator is applied to regularize the model parameters (cell slownesses and reflector geometry) so that the inverse problem is valid for a continuum. The travel times are also regularized such that we invert travel time curves rather than travel time points. A conjugate gradient method is applied to minimize the nonlinear objective function. After obtaining a solution, we perform nonlinear Monte Carlo inversions for uncertainty analysis and compute the posterior model covariance. In numerical experiments, we demonstrate that combining the first arrival refraction travel times with later reflection travel times can better reconstruct the velocity field as well as the reflector geometry. This combination is particularly important for modeling crustal structures where large velocity variations occur in the upper crust. We apply this approach to model the crustal structure of the California Borderland using ocean bottom seismometer and land data collected during the Los Angeles Region Seismic Experiment along two marine survey lines. Details of our image include a high-velocity zone under the Catalina Ridge, but a smooth gradient zone between. Catalina Ridge and San Clemente Ridge. The Moho depth is about 22 km with lateral variations. Copyright 1998 by the American Geophysical Union.

  5. The ionospheric refraction at 38 MHz.

    NASA Astrophysics Data System (ADS)

    Milogradov-Turin, J.

    The investigation of the observed shift of the North Polar Spur (NPS) at the 38 MHz survey of Milogradov-Turin and Smith (1973) in respect to the position of the NPS on the survey at 408 MHz convolved to the same resolution (Haslam and Salter 1977) has shown that there is no dependence of the NPS position on frequency and that the ionospheric refraction should be larger than believed.

  6. Matched Index of Refraction Flow Facility

    SciTech Connect

    Mcllroy, Hugh

    2010-01-01

    What's 27 feet long, 10 feet tall and full of mineral oil (3000 gallons' worth)? If you said INL's Matched Index of Refraction facility, give yourself a gold star. Scientists use computers to model the inner workings of nuclear reactors, and MIR helps validate those models. INL's Hugh McIlroy explains in this video. You can learn more about INL energy research at the lab's facebook site http://www.facebook.com/idahonationallaboratory.

  7. Matched Index of Refraction Flow Facility

    ScienceCinema

    Mcllroy, Hugh

    2016-07-12

    What's 27 feet long, 10 feet tall and full of mineral oil (3000 gallons' worth)? If you said INL's Matched Index of Refraction facility, give yourself a gold star. Scientists use computers to model the inner workings of nuclear reactors, and MIR helps validate those models. INL's Hugh McIlroy explains in this video. You can learn more about INL energy research at the lab's facebook site http://www.facebook.com/idahonationallaboratory.

  8. Autonomous satellite navigation by stellar refraction

    NASA Technical Reports Server (NTRS)

    Gounley, R.; White, R.; Gai, E.

    1983-01-01

    This paper describes an error analysis of an autonomous navigator using refraction measurements of starlight passing through the upper atmosphere. The analysis is based on a discrete linear Kalman filter. The filter generated steady-state values of navigator performance for a variety of test cases. Results of these simulations show that in low-earth orbit position-error standard deviations of less than 0.100 km may be obtained using only 40 star sightings per orbit.

  9. Emerging Technology in Refractive Cataract Surgery.

    PubMed

    Saraiva, João; Neatrour, Kristin; Waring Iv, George O

    2016-01-01

    Technology in cataract surgery is constantly evolving to meet the goals of both surgeons and patients. Recent major advances in refractive cataract surgery include innovations in preoperative and intraoperative diagnostics, femtosecond laser-assisted cataract surgery (FLACS), and a new generation of intraocular lenses (IOLs). This paper presents the latest technologies in each of these major categories and discusses how these contributions serve to improve cataract surgery outcomes in a safe, effective, and predictable manner. PMID:27433353

  10. Refraction effects of atmosphere on geodetic measurements to celestial bodies

    NASA Technical Reports Server (NTRS)

    Joshi, C. S.

    1973-01-01

    The problem is considered of obtaining accurate values of refraction corrections for geodetic measurements of celestial bodies. The basic principles of optics governing the phenomenon of refraction are defined, and differential equations are derived for the refraction corrections. The corrections fall into two main categories: (1) refraction effects due to change in the direction of propagation, and (2) refraction effects mainly due to change in the velocity of propagation. The various assumptions made by earlier investigators are reviewed along with the basic principles of improved models designed by investigators of the twentieth century. The accuracy problem for various quantities is discussed, and the conclusions and recommendations are summarized.

  11. Laser refractive surgery: a review and current status

    NASA Astrophysics Data System (ADS)

    Ren, Qiushi; Keates, Richard H.; Hill, Richard A.; Berns, Michael W.

    1995-03-01

    The aim of corneal refractive surgery is to modify the anterior surface of the cornea for the correction of myopia, hyperopia, and astigmatism. The air-tear film interface is a powerful refractive surface. Small changes in the curvature can induce large shifts in refractive power. The exquisite nature of laser-tissue interaction with corneal tissue allows successful application of lasers for refractive surgery. Numerous systems have been developed for clinical applications. An overview is provided of the current clinical and research status of laser refractive surgery.

  12. Scanning focused refractive-index microscopy

    NASA Astrophysics Data System (ADS)

    Sun, Teng-Qian; Ye, Qing; Wang, Xiao-Wan; Wang, Jin; Deng, Zhi-Chao; Mei, Jian-Chun; Zhou, Wen-Yuan; Zhang, Chun-Ping; Tian, Jian-Guo

    2014-07-01

    We present a novel scanning focused refractive-index microscopy (SFRIM) technique to obtain the refractive index (RI) profiles of objects. The method uses a focused laser as the light source, and combines the derivative total reflection method (DTRM), projection magnification, and scanning technique together. SFRIM is able to determine RIs with an accuracy of 0.002, and the central spatial resolution achieved is 1 µm, which is smaller than the size of the focal spot. The results of measurements carried out on cedar oil and a gradient-refractive-index (GRIN) lens agree well with theoretical expectations, verifying the accuracy of SFRIM. Furthermore, using SFRIM, to the best of our knowledge we have extracted for the first time the RI profile of a periodically modulated photosensitive gelatin sample. SFRIM is the first RI profile-resolved reflected light microscopy technique that can be applied to scattering and absorbing samples. SFRIM enables the possibility of performing RI profile measurements in a variety of applications, including optical waveguides, photosensitive materials and devices, photorefractive effect studies, and RI imaging in biomedical fields.

  13. Scanning focused refractive-index microscopy

    PubMed Central

    Sun, Teng-Qian; Ye, Qing; Wang, Xiao-Wan; Wang, Jin; Deng, Zhi-Chao; Mei, Jian-Chun; Zhou, Wen-Yuan; Zhang, Chun-Ping; Tian, Jian-Guo

    2014-01-01

    We present a novel scanning focused refractive-index microscopy (SFRIM) technique to obtain the refractive index (RI) profiles of objects. The method uses a focused laser as the light source, and combines the derivative total reflection method (DTRM), projection magnification, and scanning technique together. SFRIM is able to determine RIs with an accuracy of 0.002, and the central spatial resolution achieved is 1 µm, which is smaller than the size of the focal spot. The results of measurements carried out on cedar oil and a gradient-refractive-index (GRIN) lens agree well with theoretical expectations, verifying the accuracy of SFRIM. Furthermore, using SFRIM, to the best of our knowledge we have extracted for the first time the RI profile of a periodically modulated photosensitive gelatin sample. SFRIM is the first RI profile-resolved reflected light microscopy technique that can be applied to scattering and absorbing samples. SFRIM enables the possibility of performing RI profile measurements in a variety of applications, including optical waveguides, photosensitive materials and devices, photorefractive effect studies, and RI imaging in biomedical fields. PMID:25008374

  14. Scanning focused refractive-index microscopy.

    PubMed

    Sun, Teng-Qian; Ye, Qing; Wang, Xiao-Wan; Wang, Jin; Deng, Zhi-Chao; Mei, Jian-Chun; Zhou, Wen-Yuan; Zhang, Chun-Ping; Tian, Jian-Guo

    2014-01-01

    We present a novel scanning focused refractive-index microscopy (SFRIM) technique to obtain the refractive index (RI) profiles of objects. The method uses a focused laser as the light source, and combines the derivative total reflection method (DTRM), projection magnification, and scanning technique together. SFRIM is able to determine RIs with an accuracy of 0.002, and the central spatial resolution achieved is 1 µm, which is smaller than the size of the focal spot. The results of measurements carried out on cedar oil and a gradient-refractive-index (GRIN) lens agree well with theoretical expectations, verifying the accuracy of SFRIM. Furthermore, using SFRIM, to the best of our knowledge we have extracted for the first time the RI profile of a periodically modulated photosensitive gelatin sample. SFRIM is the first RI profile-resolved reflected light microscopy technique that can be applied to scattering and absorbing samples. SFRIM enables the possibility of performing RI profile measurements in a variety of applications, including optical waveguides, photosensitive materials and devices, photorefractive effect studies, and RI imaging in biomedical fields. PMID:25008374

  15. Advanced interferometric profile measurements through refractive media

    SciTech Connect

    Koev, Stephan T.; Ghodssi, Reza

    2008-09-15

    Optical profilers are valuable tools for the characterization of microelectromechanical systems (MEMSs). They use phase sifting interferometry (PSI) or vertical scanning interferometry to measure the topography of microscale structures with nanometer resolution. However, for many emerging MEMS applications, the sample needs to be imaged while placed in a liquid or in a package with a glass window. The increased refractive index of the transparent medium degrades the interference image contrast and prevents any measurement of the sample. We report on the modification of a Veeco NT1100 optical profiler to enable PSI measurements through refractive media. This approach can be applied to any other optical profiler with PSI capability. The modification consists in replacing the original illumination source with a custom-built narrow linewidth source, which increases the coherence length of the light and the contrast of the interference image. We present measurements taken with the modified configuration on samples covered with 3 mm water or 500 {mu}m glass, and we compare them to measurements of uncovered samples. We show that the measurement precision is only slightly reduced by the water and glass, and that it is still sufficiently high for typical MEMS applications. The described method can be readily used for measuring through other types and thicknesses of refractive materials.

  16. Compound Refractive Lenses for Thermal Neutron Applications

    SciTech Connect

    Gary, Charles K.

    2013-11-12

    This project designed and built compound refractive lenses (CRLs) that are able to focus, collimate and image using thermal neutrons. Neutrons are difficult to manipulate compared to visible light or even x rays; however, CRLs can provide a powerful tool for focusing, collimating and imaging neutrons. Previous neutron CRLs were limited to long focal lengths, small fields of view and poor resolution due to the materials available and manufacturing techniques. By demonstrating a fabrication method that can produce accurate, small features, we have already dramatically improved the focal length of thermal neutron CRLs, and the manufacture of Fresnel lens CRLs that greatly increases the collection area, and thus efficiency, of neutron CRLs. Unlike a single lens, a compound lens is a row of N lenslets that combine to produce an N-fold increase in the refraction of neutrons. While CRLs can be made from a variety of materials, we have chosen to mold Teflon lenses. Teflon has excellent neutron refraction, yet can be molded into nearly arbitrary shapes. We designed, fabricated and tested Teflon CRLs for neutrons. We demonstrated imaging at wavelengths as short as 1.26 ? with large fields of view and achieved resolution finer than 250 μm which is better than has been previously shown. We have also determined designs for Fresnel CRLs that will greatly improve performance.

  17. Tissue Refractive Index Fluctuations Report on Cancer Development

    NASA Astrophysics Data System (ADS)

    Popescu, Gabriel

    2012-02-01

    The gold standard in histopathology relies on manual investigation of stained tissue biopsies. A sensitive and quantitative method for in situ tissue specimen inspection is highly desirable, as it will allow early disease diagnosis and automatic screening. Here we demonstrate that quantitative phase imaging of entire unstained biopsies has the potential to fulfill this requirement. Our data indicates that the refractive index distribution of histopathology slides, which contains information about the molecular scale organization of tissue, reveals prostate tumors. These optical maps report on subtle, nanoscale morphological properties of tissues and cells that cannot be recovered by common stains, including hematoxylin and eosin (H&E). We found that cancer progression significantly alters the tissue organization, as exhibited in our refractive index maps. Furthermore, using the quantitative phase information, we obtained the spatially resolved scattering mean free path and anisotropy factor g for entire biopsies and demonstrated their direct correlation with tumor presence. We found that these scattering parameters are able to distinguish between two adjacent grades, which is a difficult task and relevant for determining patient treatment. In essence, our results show that the tissue refractive index reports on the nanoscale tissue architecture and, in principle, can be used as an intrinsic marker for cancer diagnosis. [4pt] [1] Z. Wang, K. Tangella, A. Balla and G. Popescu, Tissue refractive index as marker of disease, Journal of Biomedical Optics, in press).[0pt] [2] Z. Wang, L. J. Millet, M. Mir, H. Ding, S. Unarunotai, J. A. Rogers, M. U. Gillette and G. Popescu, Spatial light interference microscopy (SLIM), Optics Express, 19, 1016 (2011).[0pt] [3] Z. Wang, D. L. Marks, P. S. Carney, L. J. Millet, M. U. Gillette, A. Mihi, P. V. Braun, Z. Shen, S. G. Prasanth and G. Popescu, Spatial light interference tomography (SLIT), Optics Express, 19, 19907-19918 (2011

  18. Influence of saturation on the reflection and refraction at the interface between two semi-infinite poroelastic media

    NASA Astrophysics Data System (ADS)

    Yeh, C.-L.; Lo, W.-C.; Jan, C.-D.; Lee, J.-W.

    2012-04-01

    Based on the theoretical model derived by Yeh et al. (2010), this study simulates and analyzes reflection and refraction of incident elastic waves on a plane interface between two semi-infinite poroelastic half-spaces saturated by two different fluid mixtures. The amplitude and energy ratios of reflected and refracted waves considering the effect of motional modes, inertial and viscous couplings are determined for the first time with respect to water saturation of an incident P1 wave (the first dilatational wave). A plot of amplitude and energy ratios of reflected and refracted waves as a function of water saturation using an illustrative example with Lincoln sand containing an air-water mixture in the lower half-space and Columbia fine sandy loam bearing an oil-water mixture in the upper half-space. Analytical results indicate that the amplitude and energy ratios have the same magnitude order as phase speed, and the ratios of refracted and reflected waves are markedly affected by different physical parameters. This study further elucidates the difference in reflection and refraction between the oblique (30°) and normal (0°) incidences at the interface. The normal incident case have similar trend with the oblique case but no reflected and refracted SV waves exist. The sum of the energy ratio under each degree of water saturation equals unity. Additionally, amplitude and energy ratios of reflected and refracted waves are affected significantly by degree of saturation.

  19. Comparison of the accuracy of aerosol refractive index measurements from single particle and ensemble techniques.

    PubMed

    Mason, Bernard J; King, Simon-John; Miles, Rachael E H; Manfred, Katherine M; Rickards, Andrew M J; Kim, Jin; Reid, Jonathan P; Orr-Ewing, Andrew J

    2012-08-23

    The ability of two techniques, aerosol cavity ring down spectroscopy (A-CRDS) and optical tweezers, to retrieve the refractive index of atmospherically relevant aerosol was compared through analysis of supersaturated sodium nitrate at a range of relative humidities. Accumulation mode particles in the diameter range 300-600 nm were probed using A-CRDS, with optical tweezer measurements performed on coarse mode particles several micrometers in diameter. A correction for doubly charged particles was applied in the A-CRDS measurements. Both techniques were found to retrieve refractive indices in good agreement with previously published results from Tang and Munkelwitz, with a precision of ±0.0012 for the optical tweezers and ±0.02 for the A-CRDS technique. The coarse mode optical tweezer measurements agreed most closely with refractive index predictions made using a mass-weighted linear mixing rule. The uncertainty in the refractive index retrieved by the A-CRDS technique prevented discrimination between predictions using both mass-weighted and volume-weighted linear mixing rules. No efflorescence or kinetic limitations on water transport between the particle and the gas phase were observed at relative humidities down to 14%. The magnitude of the uncertainty in refractive index retrieved using the A-CRDS technique reflects the challenges in determining particle optical properties in the accumulation mode, where the extinction efficiency varies steeply with particle size.

  20. [Comparison of contact and immersion techniques of ultrasound biometry in terms of target postoperative refraction].

    PubMed

    Hrebcová, J; Skorkovská, S; Vasků, A

    2009-07-01

    The success of cataract surgery in terms of the postoperative refractive result depends on the calculation of optimal intraocular lens (IOL) power. The accuracy of preoperative measurements (keratometry, biometry) is of a great importance due to the increasing patients' demands on final refractive results. The purpose of this study was to compare the accuracy of contact and immersion techniques of A - scan ultrasound biometry in terms of target postoperative refraction while using the SRK/T formula. The accuracy of the applied biometric techniques was compared by means of the postoperative spherical equivalent (SE). The prospective longitudinal study included 111 non-paired eyes, and the preoperative biometry was performed by means of an OcuScan ultrasound machine (Alcon).The contact technique was used in 48 eyes whereas the immersion technique was employed in 63 eyes.The mean SE in the group measured by the contact technique was -0.13 D, compared to 0.25 D in the group with the applied immersion technique. No statistically significant difference was found in postoperative spherical equivalents while using both biometric techniques (p > 0.1). In this study the choice of a biometric technique had therefore no influence on the predicted postoperative refraction. The results have indicated that the biometric techniques (contact and immersion) are interchangeable in terms of postoperative refractive results.

  1. High-refractive-index fluids for the next-generation ArF immersion lithography

    NASA Astrophysics Data System (ADS)

    Wang, Yong; Miyamatsu, Takashi; Furukawa, Taiichi; Yamada, Kinji; Tominaga, Tetsuo; Makita, Yutaka; Nakagawa, Hiroki; Nakamura, Atsushi; Shima, Motoyuki; Kusumoto, Shiro; Shimokawa, Tsutomu; Hieda, Katsuhiko

    2006-03-01

    ArF immersion lithography using a high-refractive-index fluid (HIF) is considered to be a promising candidate for the 32nm node or below. At SPIE 2005 we introduced a new immersion fluid, JSR HIL-1, which has a refractive index and transmittance of 1.64 and >98%/mm (193.4nm, 23 °C), respectively. With HIL-1 immersion and a two beam interferometric exposure tool, hp32nm L/S imaging has been demonstrated. In this paper, we will report another novel immersion fluid, HIL-2, which has a transmittance of >99%/mm, which is almost as high as that of water, and a refractive index of 1.65 (193.4nm, 23 °C). Furthermore, an ArF laser irradiation study has shown that the degree of photodecomposition for both HIL-1 and HIL-2 is small enough for immersion lithography application. A "fluid puddle" defect study confirmed that HILs have less tendency to form immersion-specific photoresist defects and the refractive indices of HILs were found constant under laser irradiation. Batch-to-batch variation in refractive index during manufacture of HILs was not observed. By refining prism designs, hp30nm L/S patterns have also been successfully imaged with two interferometric exposure tools and HIL immersion.

  2. Needle-probe system for the measurement of tissue refractive index

    NASA Astrophysics Data System (ADS)

    Zysk, Adam M.; Adie, Steven G.; Armstrong, Julian J.; Leigh, Matthew S.; Paduch, Alexandre; Nguyen, Freddy T.; Sampson, David D.; Boppart, Stephen A.

    2007-02-01

    Needle-based devices, which are in wide clinical use for needle biopsy procedures, may be augmented by suitable optical techniques for the localization and diagnosis of diseased tissue. Tissue refractive index is one optical contrast mechanism with diagnostic potential. In the case of mammary tissue, for example, recent research indicates that refractive index variations between tissue types may be useful for the identification of cancerous tissue. While many coherence-based forward-sensing devices have been developed to detect scattering changes, none have demonstrated refractive index measurement capabilities. We present a novel needle-based device that is capable of simultaneously measuring refractive index and scattering. Coupled to the sample arm of an optical coherence tomography system, the needle device detects the scattering response and optical pathlength through tissue residing in a fixed-width channel. Near-infrared measurements of tissues and materials with known optical properties using a prototype device will be presented. This work demonstrates the feasibility of integrated in vivo measurement of refractive index and scattering in conjunction with existing clinical needle-based devices.

  3. Fiber-optic epoxy composite cure sensor. I. Dependence of refractive index of an autocatalytic reaction epoxy system at 850 nm on temperature and extent of cure

    NASA Astrophysics Data System (ADS)

    Lam, Kai-Yuen; Afromowitz, Martin A.

    1995-09-01

    We discuss the behavior of the refractive index of a typical epoxy-aromatic diamine system. Near 850 nm the index of refraction is found to be largely controlled by the density of the epoxy. Models are derived to describe its dependence on temperature and extent of cure. Within the range of temperatures studied, the refractive index decreases linearly with increasing temperature. In addition, as the epoxy is cured, the refractive index increases linearly with conversion to the gel point. >From then on, shrinkage in the volume of the epoxy is restricted by local viscosity. Therefore the linear relationship between the refractive index and the extent of cure does not hold beyond the gel point.

  4. The Effect of the Refractive Index of the Medium in Fluorescence Correlation Spectroscopy

    NASA Astrophysics Data System (ADS)

    Cha, Seoncheol; Kim, Sung Hyun; Kim, Doseok

    2010-03-01

    Fluorescence correlation spectroscopy (FCS) is a useful tool to study diffusional motion in liquids as it measures resident time of a dye molecule in a small excitation volume made by confocal microscopy. Some reports recently predicted that the measurement result of FCS is affected sensitively by the refractive index of liquid medium. To check for this possibility, several liquids having the same viscosity values but different refractive indices were chosen to dissolve dye molecules. The change in the observed diffusion coefficients in solutions having the same viscosity value manifests that care needs to be taken in the common practice of using sucrose to change the viscosity in the FCS experiment.

  5. Optically transparent bionanofiber composites with low sensitivity to refractive index of the polymer matrix

    NASA Astrophysics Data System (ADS)

    Nogi, Masaya; Handa, Keishin; Nakagaito, Antonio Norio; Yano, Hiroyuki

    2005-12-01

    Transparent polymers were reinforced by bacterial cellulose (BC) nanofibers, which are 10×50nm ribbon-shaped fibers. They exhibited high luminous transmittance at a fiber content as high as 60 wt %, and low sensitivity to a variety of refractive indices of matrix resins. Due to the nanofiber size effect, high transparency was obtained against a wider distribution of refractive index of resins from 1.492 to 1.636 at 20 °C. The optical transparency was also surprisingly insensitive to temperature increases up to 80 °C. As such, BC nanofibers appear to be viable candidates for optically transparent reinforcement.

  6. [Rational performance of femtosecond laser assisted corneal refractive surgery against complication].

    PubMed

    Zhang, Fengju

    2014-04-01

    Many clinical data have shown that the femtosecond assisted corneal refractive surgery is a safe and effective method for ammetropia. The perfect visual quality of post-operation must be achieved due to high price and high expectation from patients. Therefore, surgeons should select the indication carefully, pay more attention on procedure carefully and prevent from complications perioperative period. Some strategies on the key points are stated in this article in order to avoiding the complications related to femtosecond assisted corneal refractive surgery, to eliminating the potential medical trap and approaching to the perfect visual quality. PMID:24931147

  7. On the Determination of Refractive Index and Thickness of Thin Dielectric Films from Measurement of Transmittance

    NASA Astrophysics Data System (ADS)

    Shah, Z. H.; Ahmad, I.; Tahir, Q. A.; Khawaja, E. E.

    2012-12-01

    Refractive index and thickness of a transparent film (ZnS) on a transparent substrate (BK-7 glass) have been determined from measurement of normal incidence transmittance, using different methods. Some of the methods considered here are most widely used, as is apparent from the literature. The outcome of this study could help a researcher in selecting an appropriate method for such an application. The values of the refractive indices determined by different methods were found to be close to each other (within 0.5%). However, large (up to 4.4%) differences existed in the values of the thickness determined by different methods.

  8. Measurement of refractive index distribution of biotissue by scanning focused refractive index microscopy

    NASA Astrophysics Data System (ADS)

    Ye, Qing; Sun, Tengqian; Wang, Jin; Wang, Xiaowan; Deng, Zhichao; Zhou, Wenyuan; Zhang, Chunping; Tian, Jianguo

    2014-03-01

    A novel scanning focused refractive-index microscopy (SFRIM) technique are presented. With a focused laser serves as the light source, we combine the derivative total reflection method (DTRM), microscopy and the scanning technique together to obtain the refractive-index profiles (RIP) of objects. The refractive index (RI) accuracy is 0.002. The central spatial resolution of SFRIM achieves 1 μm , smaller than the size of the focal spot. Results of measurements carried out on cedar oil and a gradient-refractive-index (GRIN) lens agree well with theoretical expectations, thereby verifying the accuracy of SFRIM. Refractive index distribution of biotissue are measured by this microscopy. The use of SFRIM opens up possibilities for RIP measurement in many applications, including optical waveguides, photosensitive materials and devices, the study of the photorefractive effect, and RI imaging in biomedical fields. This research is supported by the Chinese National Key Basic Research Special Fund (Grant No.2011CB922003), Science and Technology Program of Tianjin (Grant No.11ZCKFSY00500).

  9. Influence of refractive index and solar concentration on optical power absorption in slabs

    NASA Technical Reports Server (NTRS)

    Williams, M. D.

    1988-01-01

    The optical power absorbed by a slab at the focus of a parabolic dish concentrator is calculated. The calculations are plotted versus maximum angle of incidence of irradiation (which corresponds to solar concentration) with absorption coefficient as a parameter for several different indices of refraction that represent real materials.

  10. Influence of refractive index dispersion on pulse shaping in white-light interferometry

    NASA Astrophysics Data System (ADS)

    Lychagov, Vladislav V.; Sdobnov, Anton Y.; Ryabukho, Vladimir P.

    2015-03-01

    Particularities of interference signal shaping in white-light interferometer with uncompensated dispersive layer are discussed. We especially attended to dependence of interference pulse position on the dispersive layer properties. Phase refractive index of the layer tends to be substantially nonlinear function of wavelength within the wide emission band of ultra-low coherence thermal light source. In this case, it is the group refractive index dispersion that is beginning to exert an influence on interference signal formation. It is shown experimentally that influence consists in nonlinear dependence of interference pulse position on geometrical thickness of the dispersive layer. The results show that mismatch of the dispersive layer and compensator refractive indices in the third place can produce interference signal shift on the order of pulse width.

  11. Atmospheric refractivity profiling by the mountain-based GPS and the tomographic method

    NASA Astrophysics Data System (ADS)

    Cao, Yunchang; Guo, Zhimei; Bi, Yanmeng; Tu, Mahong; Zheng, Feifei

    2007-11-01

    Atmospheric refractivity sounding is of great importance to the meteorological and military applications. An experiment was conducted for sounding the atmospheric refractivity on the top of the Wuling Mountain in August, 2005. Profiles of the atmospheric refractivity were obtained by both the mountain-based GPS and the tomographic method. Comparison shows that there is a bias of -3.83N and a standard deviation of 7.03N between the mountain-based GPS and the radiosonde. A bias less than 1% among different receivers proves that the receivers tested can meet the demand of the radio occultation technique. A very good consistence among the profiles by the mountain-based GPS, the tomographic method and the radiosonde suggests the effectiveness of both the mountain-based GPS and the tomographic method, indicating the great potential in the future meteorological application.

  12. Effect of refractive dispersion on the trichromatic correlation of irradiances for atmospheric scintillation.

    PubMed

    Hill, R J; Lataitis, R J

    1989-10-01

    Formulations of the trichromatic correlation of scintillating irradiance are corrected by introducing the cospectrum of the two different refractive indices in place of the refractive index power spectrum. Receiver aperture averaging is included in the formulation. The effect of dispersion on the bichromatic correlation coefficient is studied and quantified for four specific experimental cases. Dispersion of the water vapor refractive index between wavelengths in the visible and 10 microm window is of particular significance in this study. In most cases, the effect of dispersion on the bichromatic correlation coefficient is much less than on the ratio of monochromatic irradiance correlations, and is negligible for practical considerations. The exception is the case of such strong humidity fluctuations that they (as opposed to temperature fluctuations) cause most of the scintillation of the midinfrared radiation.

  13. Band structure and reflectivity of omnidirectional Si-based mirrors with a Gaussian profile refractive index

    NASA Astrophysics Data System (ADS)

    Arriaga, J.; Saldaña, X. I.

    2006-08-01

    Using the transfer matrix method we calculate the band structure for a one-dimensional photonic crystal consisting of alternating layers of two dielectric materials A and B with refractive indices nA and nB, respectively. The refractive index of layer A is constant and the refractive index for layer B varies according to the envelope of a Gaussian function. We find that under certain circumstances it is possible to obtain a 100% reflectivity for both polarizations (TE and TM) and any value of the incident angle of the electromagnetic waves. The interval of maximum reflectivity coincides with the photonic band gap of the structure. By an adequate selection of the parameters forming the structure, it is possible to tune the interval of frequencies with maximum reflectivity. This could be used in the fabrication of the so-called omnidirectional mirrors.

  14. Exact wavefront surface refracted by a smooth arbitrary surface considering a plane wavefront incident

    NASA Astrophysics Data System (ADS)

    Avendaño-Alejo, Maximino M.

    2015-08-01

    We study the formation of wavefronts produced by smooth arbitrary surfaces with symmetry of revolution considering a plane wavefront propagating parallel to the optical axis and impinging on the refracting surface. The wavefronts are obtained by using the Malus-Dupin theorem and they represent the monochromatic aberrations which can be called image errors, furthermore their shapes could be modified by changing the parameters of the lens in such a way that if a caustic surface is vanished the optical system produces a perfect image, on the other hand for a caustic possessing a large area it could be applied to design non-imaging optical systems. The shape of the wavefront depends only on the indices of refraction and geometrical properties of the refracting surface such as the first derivative and their parameters associated. This analytic formula has potential applications in the microscopy field, illumination or corrector plates.

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

    NASA Technical Reports Server (NTRS)

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

    1976-01-01

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

  16. Comparison of Aberrations After Standard and Customized Refractive Surgery

    NASA Astrophysics Data System (ADS)

    Fang, L.; He, X.; Wang, Y.

    2013-09-01

    To detect possible differences in residual wavefront aberrations between standard and customized laser refractive surgery based onmathematical modeling, the residual optical aberrations after conventional and customized laser refractive surgery were compared accordingto the ablation profile with transition zone. The results indicated that ablation profile has a significant impact on the residual aberrations.The amount of residual aberrations for conventional correction is higher than that for customized correction. Additionally, the residualaberrations for high myopia eyes are markedly larger than those for moderate myopia eyes. For a 5 mm pupil, the main residual aberrationterm is coma and yet it is spherical aberration for a 7 mm pupil. When the pupil diameter is the same as optical zone or greater, themagnitudes of residual aberrations is obviously larger than that for a smaller pupil. In addition, the magnitudes of the residual fifth orsixth order aberrations are relatively large, especially secondary coma in a 6 mm pupil and secondary spherical aberration in a 7 mm pupil.Therefore, the customized ablation profile may be superior to the conventional correction even though the transition zone and treatmentdecentration are taken into account. However, the customized ablation profile will still induce significant amount of residual aberrations.

  17. Refractive index of erbium doped GaN thin films

    SciTech Connect

    Alajlouni, S.; Sun, Z. Y.; Li, J.; Lin, J. Y.; Jiang, H. X.; Zavada, J. M.

    2014-08-25

    GaN is an excellent host for erbium (Er) to provide optical emission in the technologically important as well as eye-safe 1540 nm wavelength window. Er doped GaN (GaN:Er) epilayers were synthesized on c-plane sapphire substrates using metal organic chemical vapor deposition. By employing a pulsed growth scheme, the crystalline quality of GaN:Er epilayers was significantly improved over those obtained by conventional growth method of continuous flow of reaction precursors. X-ray diffraction rocking curve linewidths of less than 300 arc sec were achieved for the GaN (0002) diffraction peak, which is comparable to the typical results of undoped high quality GaN epilayers and represents a major improvement over previously reported results for GaN:Er. Spectroscopic ellipsometry was used to determine the refractive index of the GaN:Er epilayers in the 1540 nm wavelength window and a linear dependence on Er concentration was found. The observed refractive index increase with Er incorporation and the improved crystalline quality of the GaN:Er epilayers indicate that low loss GaN:Er optical waveguiding structures are feasible.

  18. Quantum Enhancement of the Index of Refraction in a Bose-Einstein Condensate.

    PubMed

    Bons, P C; de Haas, R; de Jong, D; Groot, A; van der Straten, P

    2016-04-29

    We study the index of refraction of an ultracold bosonic gas in the dilute regime. Using phase-contrast imaging with light detuned from resonance by several tens of linewidths, we image a single cloud of ultracold atoms for 100 consecutive shots, which enables the study of the scattering rate as a function of temperature and density using only a single cloud. We observe that the scattering rate is increased below the critical temperature for Bose-Einstein condensation by a factor of 3 compared to the single-atom scattering rate. We show that current atom-light interaction models to second order of the density show a similar increase, where the magnitude of the effect depends on the model that is used to calculate the pair-correlation function. This confirms that the effect of quantum statistics on the index of refraction is dominant in this regime. PMID:27176521

  19. Quantum Enhancement of the Index of Refraction in a Bose-Einstein Condensate.

    PubMed

    Bons, P C; de Haas, R; de Jong, D; Groot, A; van der Straten, P

    2016-04-29

    We study the index of refraction of an ultracold bosonic gas in the dilute regime. Using phase-contrast imaging with light detuned from resonance by several tens of linewidths, we image a single cloud of ultracold atoms for 100 consecutive shots, which enables the study of the scattering rate as a function of temperature and density using only a single cloud. We observe that the scattering rate is increased below the critical temperature for Bose-Einstein condensation by a factor of 3 compared to the single-atom scattering rate. We show that current atom-light interaction models to second order of the density show a similar increase, where the magnitude of the effect depends on the model that is used to calculate the pair-correlation function. This confirms that the effect of quantum statistics on the index of refraction is dominant in this regime.

  20. A model for the influence of granularity in a negative refractive index metamaterial lens

    NASA Astrophysics Data System (ADS)

    Webb, Kevin; Li, Jia-Han

    2006-03-01

    An important goal in building a negative refractive index metamaterial lens at optical frequencies is the achievement of sub-wavelength image resolution. In assigning an effective medium negative refractive index, the electric and magnetic dipoles (which give rise to negative permittivity and permeability) need to be dense relative to the wavelength, i.e., operation near the center of the first Brillouin zone is a prerequisite. Sub-wavelength imaging requires good performance for a significant portion of the evanescent plane wave spectrum. We use a model comprised of discrete regions with negative permittivity and permeability, calculate the effective medium parameters, and show the impact of granularity level (scatterer density) on the performance of a discrete lens, using the slab lens as a reference. We thus arrive at a measure of metamaterial density required to achieve significant improvement over traditional lensing approaches.

  1. Comparison of Densitometry, Refractive Index, and Classical Permanganate Titration Assay Methods with Commercially Available Rocket-Grade Hydrogen Peroxide

    NASA Astrophysics Data System (ADS)

    McPherson, M. D.

    2004-10-01

    Using classical methods of assay analysis for highly concentrated rocket grade hydrogen peroxide (RGHP, H2O2), comparison and correlation to historical values using currently available commercial-source RGHP is presented. In particular, fluid densities, refractive index, and the potassium permanganate (KMnO4) wet chemical method of analysis are compared. Discussion includes those analytical processes that support field use, with attendant rapid, accurate, and verifiable concentration determinations of RGHP. Method accuracy is ranked as Manual KMnO4 Titration > Refractive Index > Density, based on vendor certifications, with the refractive index method having best precision (+/-0.02%wt H2O2). Results from densitometry data are anomalous, with variability likely due to less mature measurement techniques used in this study.

  2. Deviations of Lambert-Beer's law affect corneal refractive parameters after refractive surgery.

    PubMed

    Jiménez, José R; Rodríguez-Marín, Francisco; Anera, Rosario G; Jiménez Del Barco, Luis

    2006-06-12

    We calculate whether deviations of Lambert-Beer's law, which regulates depth ablation during corneal ablation, significantly influence corneal refractive parameters after refractive surgery and whether they influence visual performance. For this, we compute a point-to-point correction on the cornea while assuming a non-linear (including a quadratic term) fit for depth ablation. Post-surgical equations for refractive parameters using a non-linear fit show significant differences with respect to parameters obtained from a linear fit (Lambert-Beer's law). Differences were also significant for corneal aberrations. These results show that corneal-ablation algorithms should include analytical information on deviations from Lambert-Beer's law for achieving an accurate eye correction.

  3. The measurement of patient-reported outcomes of refractive surgery: the refractive status and vision profile.

    PubMed Central

    Schein, O D

    2000-01-01

    PURPOSE: To develop a questionnaire, the Refractive Status and Vision Profile (RSVP), to assess health-related quality of life associated with refractive error and its correction. METHODS: The published literature on patient report of visual and overall function was reviewed, and the RSVP was self-administered by 550 participants with refractive error. Cross-sectional validation was performed using standard psychometric techniques. The responsiveness of the RSVP to surgical intervention was assessed prospectively in a subset of 176 patients. The principal outcomes measures were scores on the overall RSVP scale (S) and on 8 RSVP subscales (functioning, driving, concern, expectations, symptoms, glare, optical problems, problems with corrective lenses). RESULTS: The RSVP (S) and its subscales demonstrated very good internal consistency (Cronbach's alpha, 0.70-0.93). S and several subscale scores were independently associated with satisfaction with vision and were more correlated with satisfaction with vision than with either visual acuity or refractive error. Higher refractive error was associated with lower scores on S and on 5 subscales. In the prospective surgical cohort, 15% of patients had some worsening in their total RSVP score; however, substantial variation was seen in the individual subscales where worsening ranged from 7% (problems with corrective lenses) to 41% (driving). The effect size (measure of responsiveness) of the RSVP and most of its subscales was very high. Approximately 14% of patients had significant worsening in 3 or more subscales, and this outcome was found to be independently associated with being dissatisfied with vision following surgery (OR, 5.84; 95% CI, 1.88, 8.13). CONCLUSIONS: The RSVP has been validated as a questionnaire that measures patient-reported quality of life related to refractive error and its correction. It is responsive to surgical intervention and provides important information regarding patient outcomes not available

  4. Two-dimensional refractive index profiling of optical fibers by modified refractive near-field technique

    NASA Astrophysics Data System (ADS)

    El Sayed, A.; Pilz, Soenke; Ryser, Manuel; Romano, Valerio

    2016-02-01

    The refractive index distribution in the core-cladding region of an optical fiber plays an important role in determining the transmission and dispersion properties of the waveguide. The refracted near-field technique (RNF) is among the most widespread techniques used for measuring the refractive index profile of optical fibers and is based on illuminating the end-facet of a fiber with a focused beam whose vertex angle greatly exceeds the acceptance angle of the fiber, which is immersed in an index matching liquid. What one observes are then the refracted unguided rays rather than the guided rays. Nevertheless, the standard refracted near-field technique cannot be applied to a wide range of optical fibers e.g. if their shapes are not axially symmetric. In this work we demonstrate a modified method which allows 2-D imaging of the refractive index profile and thereby overcoming the axial symmetric limitation of the standard RNF. The new system is operating at 630 nm and based on the same principle of the RNF, but the optical path is reversed so that the light at the fiber end-facet is collected by an objective lens and detected by a CCD camera. The method does not require scanning over the fiber end-facet. Thus the system is faster and less sensitive to vibrations and external conditions compared to the standard RNF, furthermore it allows averaging to improve the signal to noise ratio. The spatial resolution of the system is determined by the numerical aperture of the objective and by the resolution of the CCD camera. To calibrate the setup, a reference multi-step index fiber provided by National Physical Laboratory was used.

  5. Two-dimensional refractive index profiling of optical fibers by modified refractive near-field technique

    NASA Astrophysics Data System (ADS)

    El Sayed, A.; Pilz, Soenke; Ryser, Manuel; Romano, Valerio

    2016-04-01

    The refractive index distribution in the core-cladding region of an optical fiber plays an important role in determining the transmission and dispersion properties of the waveguide. The refracted near-field technique (RNF) is among the most widespread techniques used for measuring the refractive index profile of optical fibers and is based on illuminating the end-facet of a fiber with a focused beam whose vertex angle greatly exceeds the acceptance angle of the fiber, which is immersed in an index matching liquid. What one observes are then the refracted unguided rays rather than the guided rays. Nevertheless, the standard refracted near-field technique cannot be applied to a wide range of optical fibers e.g. if their shapes are not axially symmetric. In this work we demonstrate a modified method which allows 2-D imaging of the refractive index profile and thereby overcoming the axial symmetric limitation of the standard RNF. The new system is operating at 630 nm and based on the same principle of the RNF, but the optical path is reversed so that the light at the fiber end-facet is collected by an objective lens and detected by a CCD camera. The method does not require scanning over the fiber end-facet. Thus the system is faster and less sensitive to vibrations and external conditions compared to the standard RNF, furthermore it allows averaging to improve the signal to noise ratio. The spatial resolution of the system is determined by the numerical aperture of the objective and by the resolution of the CCD camera. To calibrate the setup, a reference multi-step index fiber provided by National Physical Laboratory was used.

  6. Weighted Essentially Non-Oscillatory Simulations and Modeling of Complex Hydrodynamic Flows Part 1. Regular Shock Refraction

    SciTech Connect

    Schilling, O; Latini, M

    2004-06-18

    Shock refraction is a fundamental shock phenomenon observed when shocks interact with a material interface separating gases with different properties. Following refraction, a transmitted shock enters the second gas and a reflected wave returns back into the first gas. In the case of regular shock refraction all waves meet at a single point called the triple-point, creating five different states for the two gases. Analytical methods based on shock polar analysis [9, 16] have been developed to determine the state of two ideal gases in each of the five refraction regions. Furthermore, shock refraction constitutes a basic example of complex hydrodynamic flows. For this reason, shock refraction is used in this report as one validation of the high-order accurate weighted essentially non-oscillatory (WENO) shock-capturing method, as implemented in the HOPE code. The following two-step validation process is adopted. First, analytical results are obtained for the normal and oblique shock refraction (with shock-interface angle {beta}{sub int} = 75) observed for a Ma = 1.2 shock. To validate the single-fluid and the two-fluid implementations of the WENO method, two pairs of gases, argon/xenon, having equal adiabatic exponents {gamma} and air(acetone)/sulfur hexafluoride, having different adiabatic exponents {gamma}, are considered. Both the light-to-heavy and heavy-to-light configurations are considered. Second, numerical simulations are performed using the fifth-order WENO method and values of the density, pressure, temperature, speed of sound, and flow velocity in each of the five refraction regions are compared with the analytical predictions from shock polar analysis. In all cases considered, excellent agreement between the simulation results and the analytical predictions was found. The results from this investigation suggest that the WENO method is a very useful numerical method for the simulation and modeling of complex hydrodynamic flows.

  7. Tailoring the index of refraction of nanocrystalline hafnium oxide thin films

    SciTech Connect

    Vargas, Mirella; Murphy, N. R.; Ramana, C. V.

    2014-03-10

    Hafnium oxide (HfO{sub 2}) films were grown by sputter-deposition by varying the growth temperature (T{sub s} = 25–700 °C). HfO{sub 2} films grown at T{sub s} < 200 °C were amorphous, while those grown at T{sub s} ≥ 200 °C were monoclinic, nanocrystalline with (1{sup ¯}11) texturing. X-ray reflectivity (XRR) analyses indicate that the film-density (ρ) increases with increasing T{sub s}. The index of refraction (n) profiles derived from spectroscopic ellipsometry analyses follow the Cauchy dispersion relation. Lorentz-Lorenz analysis (n{sub (λ)} = 550 nm) and optical-model adopted agree well with the XRR data/analyses. A direct T{sub s}-ρ-n relationship suggests that tailoring the optical quality is possible by tuning T{sub s} and the microstructure of HfO{sub 2} films.

  8. Optical detection enhancement in porous volumetric microfluidic capture elements using refractive index matching fluids

    PubMed Central

    Wiederoder, M. S.; Peterken, L.; Lu, A. X.; Rahmanian, O. D.; Raghavan, S. R.; DeVoe, D. L.

    2015-01-01

    Porous volumetric capture elements in microfluidic sensors are advantageous compared to planar capture surfaces due to higher reaction site density and decreased diffusion lengths that can reduce detection limits and total assay time. However a mismatch in refractive indices between the capture matrix and fluid within the porous interstices results in scattering of incident, reflected, or emitted light, significantly reducing the signal for optical detection. Here we demonstrate that perfusion of an index-matching fluid within a porous matrix minimizes scattering, thus enhancing optical signal by enabling the entire capture element volume to be probed. Signal enhancement is demonstrated for both fluorescence and absorbance detection, using porous polymer monoliths in a silica capillary and packed beds of glass beads within thermoplastic microchannels, respectively. Fluorescence signal was improved by a factor of 3.5× when measuring emission from a fluorescent compound attached directly to the polymer monolith, and up to 2.6× for a rapid 10 min direct immunoassay. When combining index matching with a silver enhancement step, a detection limit of 0.1 ng/mL human IgG and a 5 log dynamic range was achieved. The demonstrated technique provides a simple method for enhancing optical sensitivity for a wide range of assays, enabling the full benefits of porous detection elements in miniaturized analytical systems to be realized. PMID:26160546

  9. Optical detection enhancement in porous volumetric microfluidic capture elements using refractive index matching fluids.

    PubMed

    Wiederoder, M S; Peterken, L; Lu, A X; Rahmanian, O D; Raghavan, S R; DeVoe, D L

    2015-08-21

    Porous volumetric capture elements in microfluidic sensors are advantageous compared to planar capture surfaces due to higher reaction site density and decreased diffusion lengths that can reduce detection limits and total assay time. However a mismatch in refractive indices between the capture matrix and fluid within the porous interstices results in scattering of incident, reflected, or emitted light, significantly reducing the signal for optical detection. Here we demonstrate that perfusion of an index-matching fluid within a porous matrix minimizes scattering, thus enhancing optical signal by enabling the entire capture element volume to be probed. Signal enhancement is demonstrated for both fluorescence and absorbance detection, using porous polymer monoliths in a silica capillary and packed beds of glass beads within thermoplastic microchannels, respectively. Fluorescence signal was improved by a factor of 3.5× when measuring emission from a fluorescent compound attached directly to the polymer monolith, and up to 2.6× for a rapid 10 min direct immunoassay. When combining index matching with a silver enhancement step, a detection limit of 0.1 ng mL(-1) human IgG and a 5 log dynamic range was achieved. The demonstrated technique provides a simple method for enhancing optical sensitivity for a wide range of assays, enabling the full benefits of porous detection elements in miniaturized analytical systems to be realized. PMID:26160546

  10. Measurement of complex refractive index of turbid media by scanning focused refractive index.

    PubMed

    Sun, Teng-Qian; Ye, Qing; Liu, Shi-Ke; Wang, Xiao-Wan; Wang, Jin; Deng, Zhi-Chao; Mei, Jian-Chun; Zhou, Wen-Yuan; Zhang, Chun-Ping; Tian, Jian-Guo

    2016-08-15

    We present the application of scanning focused refractive index microscopy in the complex refractive index measurement of turbid media. An extra standard scattering layer is placed in front of the detector to perform scattering transformation on the reflected light. The principle of the scattering transformation is elaborated theoretically. The influence of the sample scattering is deeply and effectively suppressed experimentally. As a proof of the feasibility and accuracy of the proposed method, we demonstrate experimental data of 20% and 30% Intralipid solutions that are commonly used as phantom media for light propagation studies.

  11. Refraction of nonlinear beams by localized refractive index changes in nematic liquid crystals

    SciTech Connect

    Assanto, Gaetano; Minzoni, Antonmaria A.; Smyth, Noel F.; Worthy, Annette L.

    2010-11-15

    The propagation of solitary waves in nematic liquid crystals in the presence of localized nonuniformities is studied. These nonuniformities can be caused by external electric fields, other light beams, or any other mechanism which results in a modified director orientation in a localized region of the liquid-crystal cell. The net effect is that the solitary wave undergoes refraction and trajectory bending. A general modulation theory for this refraction is developed, and particular cases of circular, elliptical, and rectangular perturbations are considered. The results are found to be in excellent agreement with numerical solutions.

  12. Retrieval of aerosol refractive index from extinction spectra with a damped harmonic-oscillator band model.

    PubMed

    Thomas, Gareth E; Bass, Stephen F; Grainger, Roy G; Lambert, Alyn

    2005-03-01

    A new method for the retrieval of the spectral refractive indices of micrometer-sized particles from infrared aerosol extinction spectra has been developed. With this method we use a classical damped harmonic-oscillator model of molecular absorption in conjunction with Mie scattering to model extinction spectra, which we then fit to the measurements using a numerical optimal estimation algorithm. The main advantage of this method over the more traditional Kramers-Kronig approach is that it allows the full complex refractive-index spectra, along with the parameters of the particle size distribution, to be retrieved from a single extinction spectrum. The retrieval scheme has been extensively characterized and has been found to provide refractive indices with a maximum uncertainty of approximately 10% (with a minimum of approximately 0.1%). Comparison of refractive indices calculated from measurements of a ternary solution of HNO3, H2SO4, and H2O with those published in J. Phys. Chem. A 104, 783 (2000) show similar differences as found by other authors.

  13. An extension of the Lighthill theory of jet noise to encompass refraction and shielding

    NASA Technical Reports Server (NTRS)

    Ribner, Herbert S.

    1995-01-01

    A formalism for jet noise prediction is derived that includes the refractive 'cone of silence' and other effects; outside the cone it approximates the simple Lighthill format. A key step is deferral of the simplifying assumption of uniform density in the dominant 'source' term. The result is conversion to a convected wave equation retaining the basic Lighthill source term. The main effect is to amend the Lighthill solution to allow for refraction by mean flow gradients, achieved via a frequency-dependent directional factor. A general formula for power spectral density emitted from unit volume is developed as the Lighthill-based value multiplied by a squared 'normalized' Green's function (the directional factor), referred to a stationary point source. The convective motion of the sources, with its powerful amplifying effect, also directional, is already accounted for in the Lighthill format: wave convection and source convection are decoupled. The normalized Green's function appears to be near unity outside the refraction dominated 'cone of silence', this validates our long term practice of using Lighthill-based approaches outside the cone, with extension inside via the Green's function. The function is obtained either experimentally (injected 'point' source) or numerically (computational aeroacoustics). Approximation by unity seems adequate except near the cone and except when there are shrouding jets: in that case the difference from unity quantifies the shielding effect. Further extension yields dipole and monopole source terms (cf. Morfey, Mani, and others) when the mean flow possesses density gradients (e.g., hot jets).

  14. Planar scanning method for detecting refraction characteristics of two-dimensional photonic quasi-crystal wedge-shaped prisms.

    PubMed

    Liu, Jianjun; Tan, Wei; Liu, Exian; Hu, Haili; Fan, Zhigang; Zhang, Tianhua; Zhang, Xiong

    2016-05-01

    In this study, a planar scanning method is proposed. This novel method adapts two monitors moving along double planar tracks that can be used to detect refraction characteristics of two-dimensional (2D) photonic quasi-crystal (PQC) wedge-shaped prisms. Refraction of a decagonal Penrose-type PQC prism is analyzed for a given incident beam and two polarization modes at different incident positions in the prism using this method. Refraction from the prism is irregular, indicating that nonuniformity in the arrangement of scatterers in the prism causes Bragg-like scattering irregularities. Numerical results show that this method can be used for guiding the design of a 2D PQC prism and for the analysis of its refraction characteristics. PMID:27140896

  15. Planar scanning method for detecting refraction characteristics of two-dimensional photonic quasi-crystal wedge-shaped prisms.

    PubMed

    Liu, Jianjun; Tan, Wei; Liu, Exian; Hu, Haili; Fan, Zhigang; Zhang, Tianhua; Zhang, Xiong

    2016-05-01

    In this study, a planar scanning method is proposed. This novel method adapts two monitors moving along double planar tracks that can be used to detect refraction characteristics of two-dimensional (2D) photonic quasi-crystal (PQC) wedge-shaped prisms. Refraction of a decagonal Penrose-type PQC prism is analyzed for a given incident beam and two polarization modes at different incident positions in the prism using this method. Refraction from the prism is irregular, indicating that nonuniformity in the arrangement of scatterers in the prism causes Bragg-like scattering irregularities. Numerical results show that this method can be used for guiding the design of a 2D PQC prism and for the analysis of its refraction characteristics.

  16. Multifrequency radiation diffusion equations for homogeneous, refractive, lossy media and their interface conditions

    SciTech Connect

    Shestakov, Aleksei I.

    2013-06-15

    We derive time-dependent multifrequency diffusion equations for homogeneous, refractive lossy media. The equations are applicable for a domain composed of several materials with distinct refractive indexes. In such applications, the fundamental radiation variable, the intensity I, is discontinuous across material interfaces. The diffusion equations evolve a variable ξ, the integral of I over all directions divided by the square of the refractive index. Attention is focused on boundary and internal interface conditions for ξ. For numerical solutions using finite elements, it is shown that at material interfaces, the usual diffusion coefficient 1/3κ of the multifrequency equation, where κ is the opacity, is modified by a tensor diffusion term consisting of integrals of the reflectivity. Numerical results are presented. For a single material simulation, the ξ equations yield the same result as diffusion equations that evolve the spectral radiation energy density. A second simulation solves a test problem that models radiation transport in a domain comprised of materials with different refractive indexes. Results qualitatively agree with those previously published.

  17. Room-temperature formation of low refractive index silicon oxide films using atmospheric-pressure plasma.

    PubMed

    Nakamura, Kei; Yamaguchi, Yoshihito; Yokoyama, Keiji; Higashida, Kosuke; Ohmi, Hiromasa; Kakiuchi, Hiroaki; Yasutake, Kiyoshi

    2011-04-01

    This study aims to apply atmospheric-pressure (AP) plasma to the fabrication of single-layer anti-reflection (AR) coatings with porous silicon oxide. 150 MHz very high-frequency (VHF) excitation of AP plasma permits to enhance the chemical reactions both in the gas phase and on the film-growing surface, increasing deposition rate significantly. Silicon oxide films were prepared from silane (SiH4) and carbon dioxide (CO2) dual sources diluted with helium. The microstructure and refractive index of the films were studied using infrared absorption and ellipsometry as a function of VHF power density. It was shown that significant increase in deposition rate at room temperature prevented the formation of a dense SiO2 network, decreasing refractive index of the resulting film effectively. As a result, a porous silicon oxide film, which had the lowest refractive index of 1.24 at 632.8 nm, was obtained with a very high deposition rate of 235 nm/s. The reflectance and transmittance spectra showed that the low refractive index film functioned as a quarter-wave AR coating of a glass plate.

  18. Negative refraction makes a perfect lens

    PubMed

    Pendry

    2000-10-30

    With a conventional lens sharpness of the image is always limited by the wavelength of light. An unconventional alternative to a lens, a slab of negative refractive index material, has the power to focus all Fourier components of a 2D image, even those that do not propagate in a radiative manner. Such "superlenses" can be realized in the microwave band with current technology. Our simulations show that a version of the lens operating at the frequency of visible light can be realized in the form of a thin slab of silver. This optical version resolves objects only a few nanometers across.

  19. Negative Refraction Makes a Perfect Lens

    NASA Astrophysics Data System (ADS)

    Pendry, J. B.

    2000-10-01

    With a conventional lens sharpness of the image is always limited by the wavelength of light. An unconventional alternative to a lens, a slab of negative refractive index material, has the power to focus all Fourier components of a 2D image, even those that do not propagate in a radiative manner. Such ``superlenses'' can be realized in the microwave band with current technology. Our simulations show that a version of the lens operating at the frequency of visible light can be realized in the form of a thin slab of silver. This optical version resolves objects only a few nanometers across.

  20. Refraction and absorption of microwaves in wood

    NASA Astrophysics Data System (ADS)

    Ziherl, Saša; Bajc, Jurij; Čepič, Mojca

    2013-03-01

    A demonstration experiment for physics students showing the dependence of the refractive index and absorption coefficient of wood on the direction of microwaves is presented. Wood and microwaves enable study of anisotropic properties, which are typically found in crystals. Wood is used as the persuasive representative of uniaxial anisotropic materials due to its visible structure and its consequent anisotropic properties. Wood can be cut in a general direction and wooden plates a few centimetres thick with well-defined fibre orientation are easily prepared. Microwaves are used because wood is transparent for microwaves and their centimetre-scale wavelength is comparable to the wood structure.

  1. The Alvarez and Lohmann refractive lenses revisited.

    PubMed

    Barbero, Sergio

    2009-05-25

    Alvarez and Lohmann lenses are variable focus optical devices based on lateral shifts of two lenses with cubic-type surfaces. I analyzed the optical performance of these types of lenses computing the first order optical properties (applying wavefront refraction and propagation) without the restriction of the thin lens approximation, and the spot diagram using a ray tracing algorithm. I proposed an analytic and numerical method to select the most optimum coefficients and the specific configuration of these lenses. The results show that Lohmann composite lens is slightly superior to Alvarez one because the overall thickness and optical aberrations are smaller.

  2. Effects of refractive index on glories.

    PubMed

    Laven, Philip

    2008-12-01

    Atmospheric glories are caused by backscattering of sunlight from spherical droplets of water (e.g., from fog or clouds). But what would glories look like if they were caused by scattering from more exotic substances, such as clouds of ethane as found on Titan? Examining backscattering as a function of the refractive index n of spherical droplets leads to the surprising conclusion that a glory's appearance is almost independent of n (at least for 1.03

  3. Critical review on refractive surgical lasers

    NASA Astrophysics Data System (ADS)

    Lin, J. T.

    1995-03-01

    The current status of refractive surgical lasers (including excimer and nonexcimer lasers) is reviewed with an emphasis on photorefractive keratectomy (PRK). The correlation of engineering parameters and the clinical requirements with optimal conditions are presented. The fundamentals of corneal reshaping with formulas for ablation profiles and the advantages of the multizone method are discussed. Updated information on the Mini-Excimer PRK laser system, with an emphasis on the scanning delivery device, is presented. PMMA ablation profiles performed by standard diaphragm and scanning modes are compared for surface ablation quality. Scanning mode ablation patterns for myopia, hyperopia, and regular and irregular astigmatism are presented.

  4. Effects of refractive index on glories.

    PubMed

    Laven, Philip

    2008-12-01

    Atmospheric glories are caused by backscattering of sunlight from spherical droplets of water (e.g., from fog or clouds). But what would glories look like if they were caused by scattering from more exotic substances, such as clouds of ethane as found on Titan? Examining backscattering as a function of the refractive index n of spherical droplets leads to the surprising conclusion that a glory's appearance is almost independent of n (at least for 1.03

  5. Negative refraction characterization in one-dimensional photonic crystals

    NASA Astrophysics Data System (ADS)

    Doti, R.; Lugo, J. E.; Faubert, J.

    2012-10-01

    In this work we present two experiments as evidence of negative refraction in one dimensional photonics crystals (1D PC). Particularly the porous silicon (p-Si) multilayer structure is used as 1D PC since this structure presents periodic dielectric components with specific refraction indexes and under certain conditions it can abnormally refract the light. In the first experiment we show the negative refraction for two different wavelengths, one in the visible, and the other in the infrared regions of the spectrum. In this experiment we use a fixed incidence angle for a conditioned white light beam and we look for the emerging negative refracted beam. In the second experiment we characterize de negative refraction observed for the same material by varying the incidence angle in a wide range. The obtained results are compared with a theoretic prediction according a model proposed by the authors [1]. We present a brief description of the material production and its properties, as well.

  6. Caustics in a field negatively refracted at a plane interface.

    PubMed

    Shendeleva, M L

    2008-03-01

    An electromagnetic field radiated by a line source situated near a plane interface between a medium with positive refractive index and a medium with negative refractive index is considered by using the geometrical optics approach. Rays and wave fronts of the refracted field are constructed using Fermat's principle. It is shown that the negatively refracted rays intersecting in pairs create 2-fold caustics that meet at a cusp point. The cusp of the caustic is directed towards the interface for |n| > 1 and away from the interface for |n| < 1, where n is the relative refractive index. It is also shown that wave fronts of the refracted field propagate towards the interface, in the direction from negative to positive optical path lengths. PMID:18331494

  7. Radio jet refraction in galactic atmospheres with static pressure gradients

    NASA Technical Reports Server (NTRS)

    Henriksen, R. N.; Vallee, J. P.; Bridle, A. H.

    1981-01-01

    A theory of double radio sources which have a 'Z' or 'S' morphology is proposed, based on the refraction of radio jets in the extended atmosphere of an elliptical galaxy. The model describes a collimated jet of supersonic material bending self-consistently under the influence of external static pressure gradients. Gravity and magnetic fields are neglected in the simplest case except insofar as they determine the static pressure distribution. The calculation is a straightforward extension of a method used to calculate a ram-pressure model for twin radio trails ('C' morphology). It may also be described as a continuous-jet version of a buoyancy model proposed in 1973. The model has the added virtue of invoking a galactic atmosphere similar to those already indicated by X-ray measurements of some other radio galaxies and by models for the collimation of other radio jets.

  8. Modeling of saturation and refraction in x-ray lasers

    NASA Astrophysics Data System (ADS)

    Benredjem, D.; Kuba, J.; Möller, C.; Zabaydullin, O. Z.

    2003-04-01

    We model an experiment in which an iron slab target is irradiated by superimposing the six beams of the LULI facility onto a 22 mm×100 μm focal line. The driving laser is composed of two Gaussian pulses of 130-ps duration (full width at half maximum), preceded by a prepulse. A strong enhancement of the 3p-3s 0-1 x-ray line at 25.5 nm in neonlike iron was observed. Saturation is attained for plasma lengths near 1 cm. A ray-trace code working as a postprocessor to a hydroatomic code is used to model the x-ray laser beam refraction due to the variation of the electron density versus the distance to the target surface. Knowing the hydrodynamic conditions, i.e., electron density, and electron and ion temperatures, along the ray paths, the radiative transfer equation, and the population equations are solved self-consistently by using a Maxwell-Bloch approach. A more tractable approach, requiring also the intensity of saturation as a function of time and space, is also presented. In this case, calculation time is much less than in the Maxwell-Bloch approach.

  9. An Approximate Analytic Expression for the Flux Density of Scintillation Light at the Photocathode

    SciTech Connect

    Braverman, Joshua B; Harrison, Mark J; Ziock, Klaus-Peter

    2012-01-01

    The flux density of light exiting scintillator crystals is an important factor affecting the performance of radiation detectors, and is of particular importance for position sensitive instruments. Recent work by T. Woldemichael developed an analytic expression for the shape of the light spot at the bottom of a single crystal [1]. However, the results are of limited utility because there is generally a light pipe and photomultiplier entrance window between the bottom of the crystal and the photocathode. In this study, we expand Woldemichael s theory to include materials each with different indices of refraction and compare the adjusted light spot shape theory to GEANT 4 simulations [2]. Additionally, light reflection losses from index of refraction changes were also taken into account. We found that the simulations closely agree with the adjusted theory.

  10. Calculation of electron wave functions and refractive index of Ne

    NASA Astrophysics Data System (ADS)

    Zhu, Min; Liu, Wei; Zhang, Tao

    2008-10-01

    The radial wave functions of inner electron shell and outer electron shell of a Ne atom were obtained by the approximate analytical method and tested by calculating the ground state energy of the Ne atom. The equivalent volume of electron cloud and the refractive index of Ne were calculated. The calculated refractive index agrees well with the experimental result. Relationship between the refractive index and the wave function of Ne was discovered.

  11. Negative-Refraction Metamaterials: Fundamental Principles and Applications

    NASA Astrophysics Data System (ADS)

    Eleftheriades, G. V.; Balmain, K. G.

    2005-06-01

    Learn about the revolutionary new technology of negative-refraction metamaterials Negative-Refraction Metamaterials: Fundamental Principles and Applications introduces artificial materials that support the unusual electromagnetic property of negative refraction. Readers will discover several classes of negative-refraction materials along with their exciting, groundbreaking applications, such as lenses and antennas, imaging with super-resolution, microwave devices, dispersion-compensating interconnects, radar, and defense. The book begins with a chapter describing the fundamentals of isotropic metamaterials in which a negative index of refraction is defined. In the following chapters, the text builds on the fundamentals by describing a range of useful microwave devices and antennas. Next, a broad spectrum of exciting new research and emerging applications is examined, including: Theory and experiments behind a super-resolving, negative-refractive-index transmission-line lens 3-D transmission-line metamaterials with a negative refractive index Numerical simulation studies of negative refraction of Gaussian beams and associated focusing phenomena Unique advantages and theory of shaped lenses made of negative-refractive-index metamaterials A new type of transmission-line metamaterial that is anisotropic and supports the formation of sharp steerable beams (resonance cones) Implementations of negative-refraction metamaterials at optical frequencies Unusual propagation phenomena in metallic waveguides partially filled with negative-refractive-index metamaterials Metamaterials in which the refractive index and the underlying group velocity are both negative This work brings together the best minds in this cutting-edge field. It is fascinating reading for scientists, engineers, and graduate-level students in physics, chemistry, materials science, photonics, and electrical engineering.

  12. Ultrarefraction and negative refraction in metamaterials

    NASA Astrophysics Data System (ADS)

    Maystre, Daniel R.; Enoch, Stefan; Tayeb, Gerard

    2004-07-01

    In the recent years, many experimental and theoretical achievements have shown that meta-materials can simulate homogeneous materials with optical index less than unity or even negative. For example, a dielectric photonic crystal, used at the edge of a band gap, can generate phenomena of ultra-refraction (positive index less than unity) or negative refraction (negative index). Some applications of these phenomena will be shown, specially the design of directive antenna in the microwaves region. More recently, experimental and theoretical studies have been published on left-handed materials. These materials, which have a permittivity and a permeability equal to -1, have been the subject of controversies about their alleged property of making perfect lenses. It will be shown that such a perfect lens cannot exist. However, this kind of meta-material could be used for making better lenses than the best classical ones, a fact which could explain some experimental results. The vital influence of the size of the elementary cell on the performance of the lens will be pointed out. Finally, it will be shown that surprisingly, a left-handed material can be interpreted as a means to go through the mirror, as Alice in the novel of Lewis Carrol...

  13. Two different looks at Kepler’s refraction experiment

    NASA Astrophysics Data System (ADS)

    Grusche, Sascha; Wagner, Steffen

    2016-11-01

    Most refraction experiments are theory-laden and far from everyday experience. Accordingly, many students fail to apply the law of refraction to phenomena. To guide students from phenomena to theory, teachers can use a refraction experiment proposed by Kepler, where measurements are based on shadow images. For a different look at Kepler’s experiment, one can use the principle of reversibility to get equivalent results, but based on apparent depth. For this reversal, rays of light are reinterpreted as lines of sight, and vice versa. The principle allows students to relate refracted rays to shifted images, and applies to other optical phenomena.

  14. Baseline peripheral refractive error and changes in axial refraction during one year in a young adult population

    PubMed Central

    Hartwig, Andreas; Charman, William Neil; Radhakrishnan, Hema

    2015-01-01

    Purpose To determine whether the initial characteristics of individual patterns of peripheral refraction relate to subsequent changes in refraction over a one-year period. Methods 54 myopic and emmetropic subjects (mean age: 24.9 ± 5.1 years; median 24 years) with normal vision were recruited and underwent conventional non-cycloplegic subjective refraction. Peripheral refraction was also measured at 5° intervals over the central 60° of horizontal visual field, together with axial length. After one year, measurements of subjective refraction and axial length were repeated on the 43 subjects who were still available for examination. Results In agreement with earlier studies, higher myopes tended to show greater relative peripheral hyperopia. There was, however, considerable inter-subject variation in the pattern of relative peripheral refractive error (RPRE) at any level of axial refraction. Across the group, mean one-year changes in axial refraction and axial length did not differ significantly from zero. There was no correlation between changes in these parameters for individual subjects and any characteristic of their RPRE. Conclusion No evidence was found to support the hypothesis that the pattern of RPRE is predictive of subsequent refractive change in this age group. PMID:26188389

  15. Imaginary refractive index and other microphysical properties of volcanic ash, Sarahan dust, and other mineral aerosols

    NASA Astrophysics Data System (ADS)

    Rocha Lima, A.; Martins, J.; Krotkov, N. A.; Artaxo, P.; Todd, M.; Ben Ami, Y.; Dolgos, G.; Espinosa, R.

    2013-12-01

    Aerosol properties are essential to support remote sensing measurements, atmospheric circulation and climate models. This research aims to improve the understanding of the optical and microphysical properties of different types of aerosols particles. Samples of volcanic ash, Saharan dust and other mineral aerosols particles were analyzed by different techniques. Ground samples were sieved down to 45um, de-agglomerated and resuspended in the laboratory using a Fluidized Bed Aerosol Generator (FBAG). Particles were collected on Nuclepore filters into PM10, PM2.5, or PM1.0. and analyzed by different techniques, such as Scanning Electron Microscopy (SEM) for determination of size distribution and shape, spectral reflectance for determination of the optical absorption properties as a function of the wavelength, material density, and X-Ray fluorescence for the elemental composition. The spectral imaginary part of refractive index from the UV to the short wave infrared (SWIR) wavelength was derived empirically from the measurements of the spectral mass absorption coefficient, size distribution and density of the material. Some selected samples were also analyzed with the Polarized Imaging Nephelometer (PI-Neph) instrument for the characterization of the aerosol polarized phase function. This work compares results of the spectral refractive index of different materials obtained by our methodology with those available in the literature. In some cases there are significant differences both in magnitude and spectral dependence of the imaginary refractive index. These differences are evaluated and discussed in this work.

  16. Measurements of the complex refractive index of volcanic ash at 450, 546.7, and 650 nm

    NASA Astrophysics Data System (ADS)

    Ball, J. G. C.; Reed, B. E.; Grainger, R. G.; Peters, D. M.; Mather, T. A.; Pyle, D. M.

    2015-08-01

    The detection and quantification of volcanic ash is extremely important to the aviation industry, civil defense organizations, and those in peril from volcanic ashfall. To exploit the remote sensing techniques that are used to monitor a volcanic cloud and return information on its properties, the effective complex refractive index of the volcanic ash is required. This paper presents the complex refractive index determined in the laboratory at 450.0 nm, 546.7 nm, and 650.0 nm for volcanic ash samples from eruptions of Aso (Japan), Grímsvötn (Iceland), Chaitén (Chile), Etna (Italy), Eyjafjallajökull (Iceland), Tongariro (New Zealand), Askja (Iceland), Nisyros (Greece), Okmok (Alaska), Augustine (Alaska), and Spurr (Alaska). The Becke line method was used to measure the real part of the refractive index with an accuracy of 0.01. The values measured differed between eruptions and were in the range 1.51-1.63 at 450.0 nm, 1.50-1.61 at 546.7 nm, and 1.50-1.59 at 650.0 nm. A novel method is introduced to derive the imaginary part of the refractive index from the attenuation of light by ash. The method has a precision in the range 10-3-10-4. The values for the ash imaginary refractive index ranged 0.22-1.70 × 10-3 at 450.0 nm, 0.16-1.93 × 10-3 at 546.7 nm, and 0.15-2.08 × 10-3 at 650.0 nm. The accuracy of Becke and attenuation methods was assessed by measuring the complex refractive index of Hoya neutral density glass and found to have an accuracy of <0.01 and <2 × 10-5 for the real and imaginary parts of the refractive index, respectively.

  17. Concentration dependent refractive index of CO2/CH4 mixture in gaseous and supercritical phase

    NASA Astrophysics Data System (ADS)

    Giraudet, C.; Marlin, L.; Bégué, D.; Croccolo, F.; Bataller, H.

    2016-04-01

    Carbon dioxide (CO2)/methane (CH4) binary mixtures are investigated at pressure values up to 20 MPa at 303 K in order to investigate the pressure dependence of the optical concentration contrast factor, (" separators=" ∂ n / ∂ c ) P , T , through gaseous and supercritical phase. Refractive index is measured by means of a Michelson interferometer. Refractivities of the mixtures are found in good agreement with Lorentz-Lorenz predictions after density calculations by means of the AGA8-DC92 equation of state. Experimental polarizabilities of pure fluids are compared to quantum calculations of monomers and dimers for each pressure; it results that the quantity of dimers is small in the investigated thermodynamic conditions. Finally, by extending our experimental database with numerical simulations, we evidence that (" separators=" ∂ n / ∂ c ) P , T presents a critical enhancement similar to heat capacity.

  18. Mathematics of Radiation Propagation in Planetary Atmospheres: Absorption, Refraction, Time Delay, Occultation, and Abel Inversion

    NASA Astrophysics Data System (ADS)

    Huestis, D. L.

    Forward integration calculation of air mass, refraction, and time delay requires care even for very smooth model atmospheres. The literature abounds in examples of injudicious approximations, assumptions, transformations, variable substitutions, and failures to verify that the formulas work with unlimited accuracy for simple cases and also survive challenges from mathematically pathological but physically realizable cases. A few years ago we addressed the problem of evaluation of the Chapman function for attenuation along a straight line path in an exponential atmosphere. In this presentation we will describe issues and approaches for integration over light paths curved by refraction. The inverse problem, determining the altitude profile of mass density (index of refraction) or the concentration of an individual chemical species (absorption), from occultation data, also has its mathematically interesting (i.e., difficult) aspects. Now we automatically have noise and thus statistical analysis is just as important as calculus and numerical analysis. Here we will describe a new approach of least-squares fitting occultation data to an expansion over compact basis functions. This approach, which avoids numerical differentiation and singular integrals, was originally developed to analyze laboratory imaging data.Forward integration calculation of air mass, refraction, and time delay requires care even for very smooth model atmospheres. The literature abounds in examples of injudicious approximations, assumptions, transformations, variable substitutions, and failures to verify that the formulas work with unlimited accuracy for simple cases and also survive challenges from mathematically pathological but physically realizable cases. A few years ago we addressed the problem of evaluation of the Chapman function for attenuation along a straight line path in an exponential atmosphere. In this presentation we will describe issues and approaches for integration over light paths

  19. Nanofocusing Parabolic Refractive X-Ray Lenses

    SciTech Connect

    Schroer, C.G.; Kuhlmann, M.; Hunger, U.T.; Guenzler, T.F.; Kurapova, O.; Feste, S.; Lengeler, B.; Drakopoulos, M.; Somogyi, A.; Simionovici, A. S.; Snigirev, A.; Snigireva, I.

    2004-05-12

    Parabolic refractive x-ray lenses with short focal distance can generate intensive hard x-ray microbeams with lateral extensions in the 100nm range even at short distance from a synchrotron radiation source. We have fabricated planar parabolic lenses made of silicon that have a focal distance in the range of a few millimeters at hard x-ray energies. In a crossed geometry, two lenses were used to generate a microbeam with a lateral size of 330nm by 110nm at 25keV in a distance of 41.8m from the synchrotron radiation source. First microdiffraction and fluorescence microtomography experiments were carried out with these lenses. Using diamond as lens material, microbeams with lateral size down to 20nm and below are conceivable in the energy range from 10 to 100keV.

  20. Infrared refractive index of atmospheric aerosol substances.

    PubMed

    Volz, F E

    1972-04-01

    The optical constants in the ir from lambda2.5 microm to 40 microm (4000-250 cm(-1)) of dry natural aerosol substances and of sea salt are presented. The aerosol substances were obtained from rain and snow water: dust and soot by sedimentation, and water soluble salts by evaporation. The spectra of the absorption index n' were derived from our published transmittance measurements of potassium bromide disks. The real part n of the refractive index was calculated from the specular reflectance at near normal incidence of disks of pure aerosol substance. The observed spectral features are being related to chemical constituents, notably sulfates and alcohol soluble organics. Optical constants of composite and wet aerosol are discussed. A simple model confirms the measured transmission of a coarse dry powder of water solubles and shows that the extinction by natural aerosol should have a minimum near 8 microm and a strong maximum near 9 microm.