Science.gov

Sample records for absorption path length

  1. Light absorption cell combining variable path and length pump

    DOEpatents

    Prather, William S.

    1993-01-01

    A device for use in making spectrophotometric measurements of fluid samples. In particular, the device is a measurement cell containing a movable and a fixed lens with a sample of the fluid therebetween and through which light shines. The cell is connected to a source of light and a spectrophotometer via optic fibers. Movement of the lens varies the path length and also pumps the fluid into and out of the cell. Unidirectional inlet and exit valves cooperate with the movable lens to assure a one-way flow of fluid through the cell. A linear stepper motor controls the movement of the lens and cycles it from a first position closer to the fixed lens and a second position farther from the fixed lens, preferably at least 10 times per minute for a nearly continuous stream of absorption spectrum data.

  2. Light absorption cell combining variable path and length pump

    DOEpatents

    Prather, W.S.

    1993-12-07

    A device is described for use in making spectrophotometric measurements of fluid samples. In particular, the device is a measurement cell containing a movable and a fixed lens with a sample of the fluid there between and through which light shines. The cell is connected to a source of light and a spectrophotometer via optic fibers. Movement of the lens varies the path length and also pumps the fluid into and out of the cell. Unidirectional inlet and exit valves cooperate with the movable lens to assure a one-way flow of fluid through the cell. A linear stepper motor controls the movement of the lens and cycles it from a first position closer to the fixed lens and a second position farther from the fixed lens, preferably at least 10 times per minute for a nearly continuous stream of absorption spectrum data. 2 figures.

  3. Calibration of effective optical path length for hollow-waveguide based gas cell using absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Liu, Lin; Du, Zhenhui; Li, Jinyi

    2016-10-01

    The Hollow Waveguide (HWG) has emerged as a novel tool to transmit laser power. Owing to its long Effective Optical Path Length (EOPL) within a relatively small volume, it is suitable for the application as a gas cell in concentration measurement by using laser spectroscopy. The measurement of effective optical path length for a hollow waveguide, which possesses the physical length of 284.0 cm, by using Tunable Diode Laser Absorption Spectroscopy (TDLAS) was demonstrated. Carbon dioxide was used as a sample gas for a hollow waveguide calibration. A 2004 nm Distributed Feed-Back (DFB) laser was used as the light source to cover a CO2 line near 2003 nm, which was selected as the target line in the measurement. The reference direct absorption spectroscopy signal was obtained by delivering CO2 into a reference cell possessing a length of 29.4 cm. Then the effective optical path length of HWG was calculated by least-squares fitting the measured absorption signal to the reference absorption signal. The measured EOPL of HWG was 282.8 cm and the repeatability error of effective optical path length was calculated as 0.08 cm. A detection limit of 0.057 cm (with integral time 5 s) characterized by the Allan variance, was derived. The effective optical path length is obtained as the significant parameter to calculate the concentration of gases and it is of great importance to precise measurement of absorption spectroscopy.

  4. Cesium oscillator strengths measured with a multiple-path-length absorption cell

    NASA Technical Reports Server (NTRS)

    Exton, R. J.

    1976-01-01

    Absorption-oscillator-strength measurements for the principal series in cesium were measured using a multiple-path-length cell. The optical arrangement included a movable transverse path for checking the uniformity of the alkali density along the length of the cell and which also allowed strength measurements to be made simultaneously on both strong and weak lines. The strengths measured on the first 10 doublets indicate an increasing trend in the doublet ratio. The individual line strengths are in close agreement with the high resolution measurements of Pichler (1974) and with the calculations of Norcross (1973).

  5. Suppression of infrared absorption in nanostructured metals by controlling Faraday inductance and electron path length.

    PubMed

    Han, Sang Eon

    2016-02-08

    Nanostructured metals have been intensively studied for optical applications over the past few decades. However, the intrinsic loss of metals has limited the optical performance of the metal nanostructures in diverse applications. In particular, light concentration in metals by surface plasmons or other resonances causes substantial absorption in metals. Here, we avoid plasmonic excitations for low loss and investigate methods to further suppress loss in nanostructured metals. We demonstrate that parasitic absorption in metal nanostructures can be significantly reduced over a broad band by increasing the Faraday inductance and the electron path length. For an example structure, the loss is reduced in comparison to flat films by more than an order of magnitude over most of the very broad spectrum between short and long wavelength infrared. For a photodetector structure, the fraction of absorption in the photoactive material increases by two orders of magnitude and the photoresponsivity increases by 15 times because of the selective suppression of metal absorption. These findings could benefit many metal-based applications that require low loss such as photovoltaics, photoconductive detectors, solar selective surfaces, infrared-transparent defrosting windows, and other metamaterials.

  6. Assessment of optical path length in tissue using neodymium and water absorptions for application to near-infrared spectroscopy.

    PubMed

    Nighswander-Rempel, Stephen P; Kupriyanov, Valery V; Shaw, R Anthony

    2005-01-01

    Quantitative analysis of blood oxygen saturation using near-IR spectroscopy is made difficult by uncertainties in both the absolute value and the wavelength dependence of the optical path length. We introduce a novel means of assessing the wavelength dependence of path length, exploiting the relative intensities of several absorptions exhibited by an exogenous contrast agent (neodymium). Combined with a previously described method that exploits endogenous water absorptions, the described technique estimates the absolute path length at several wavelengths throughout the visible/near-IR range of interest. Isolated rat hearts (n = 11) are perfused separately with Krebs-Henseleit buffer (KHB) and a KHB solution to which neodymium had been added, and visible/near-IR spectra are acquired using an optical probe made up of emission and collection fibers in concentric rings of diameters 1 and 3 mm, respectively. Relative optical path lengths at 520, 580, 679, 740, 800, 870, and 975 nm are 0.41+/-0.13, 0.49+/-0.21, 0.90+/-0.09, 0.94+/-0.01, 1.00, 0.84+/-0.01, and 0.78+/-0.08, respectively. The absolute path length at 975 nm is estimated to be 3.8+/-0.6 mm, based on the intensity of the water absorptions and the known tissue water concentration. These results are strictly valid only for the experimental geometry applied here.

  7. Monitoring of Atmospheric Hydrogen Peroxide in Houston Using Long Path-Length Laser-Based Absorption Spectroscopy

    NASA Astrophysics Data System (ADS)

    Sanchez, N. P.; Cao, Y.; Jiang, W.; Tittel, F. K.; Griffin, R. J.

    2014-12-01

    Hydrogen peroxide (H2O2) is a relevant atmospheric species mainly formed by recombination of hydroperoxyl radicals. H2O2 participates in the formation of sulfate aerosol by in-cloud oxidation of S(IV) to S(VI) and has been associated with the generation of multi-functional water soluble organic compounds in atmospheric particulate matter. Furthermore, H2O2 plays an important role in the oxidative capacity of the atmosphere as it acts as a reservoir for HOx radicals (OH and HO2). Particular conditions in the Houston area (e.g. extensive presence of petrochemical industry and high ozone and humidity levels) indicate the potential relevance of this species at this location. Despite its atmospheric relevance, no reports on the levels of H2O2 in Houston have been presented previously in the scientific literature. Determination of atmospheric H2O2 usually has been conducted based on transfer of the gas-phase H2O2 to the liquid phase prior to quantification by techniques such as fluorescence spectroscopy. Although these methods allow detection of H2O2 at the sub-ppb level, they present some limitations including the interference from other atmospheric constituents and potential sampling artifacts. In this study, a high sensitivity sensor based on long-path absorption spectroscopy using a distributed-feedback quantum cascade laser was developed and used to conduct direct gas-phase H2O2 monitoring in Houston. The sensor, which targets a strong H2O2 absorption line (~7.73 μm) with no interference from other atmospheric species, was deployed at a ground level monitoring station near the University of Houston main campus during summer 2014. The performance of this novel sensor was evaluated by side-by-side comparison with a fluorescence-based instrument typically used for atmospheric monitoring of H2O2. H2O2 levels were determined, and time series of H2O2 mixing ratios were generated allowing insight into the dynamics, trends, and atmospheric inter-relations of H2O2 in the

  8. Photon path length retrieval from GOSAT observations

    NASA Astrophysics Data System (ADS)

    Kremmling, Beke; Penning de Vries, Marloes; Deutschmann, Tim; Wagner, Thomas

    2013-04-01

    The influence of clouds on the atmospheric radiation budget is investigated, focussing on the photon path length distributions of the scattered sunlight. Apart from the reflection of incoming solar radiation at the cloud top, clouds can also introduce a large number of additional scattering events causing an enhancement of the photon paths. In certain cloud formations, these scattering events also result in a ``ping-pong`` behaviour between different cloud patches and cloud layers. It has been shown from ground based measurements that it is possible to retrieve photon path lengths by analysis of high resolution oxygen A-band spectra (O. Funk et al.). This study uses similar space based measurements of the oxygen A-band for the path length retrieval. The oxygen A-band spectra are retrieved from the Japanese Greenhouse Gases Observing Satellite (GOSAT) which was successfully launched in 2009. The high spectral resolution of the GOSAT TANSO-FTS instrument allows to almost completely resolve the individual absorption lines. The considered spectral range is particularly suitable for this study because it shows clear absorption structures of different strength. From the analysis of the spectral signatures, cloud properties and the underlying path length distributions can be derived. The retrieval is done by analysis and comparison of the extracted TANSO-FTS spectra with simulations from the Monte Carlo radiative transfer Model McArtim. The model permits modelling of altitude dependent oxygen absorption cross sections and three-dimensional cloud patterns. Case studies of clear and cloudy sky scenarios will be presented. Future studies will focus on more complicated cloud structures, especially considering three-dimensional geometries and heterogeneities.

  9. Dependence of the absorption of pulsed CO2-laser radiation by silane on wavenumber, fluence, pulse duration, temperature, optical path length, and pressure of absorbing and nonabsorbing gases

    NASA Astrophysics Data System (ADS)

    Bl/aŻejowski, Jerzy; Gruzdiewa, Ludwika; Rulewski, Jacek; Lampe, Frederick W.

    1995-05-01

    The absorption of three lines [P(20), 944.2 cm-1; P(14), 949.2 cm-1; and R(24), 978.5 cm-1] of the pulsed CO2 laser (0001-1000 transition) by SiH4 was measured at various pulse energy, pulse duration, temperature, optical path length, and pressure of the compound and nonabsorbing foreign gases. In addition, low intensity infrared absorption spectrum of silane was compared with high intensity absorption characteristics for all lines of the pulsed CO2 laser. The experimental dependencies show deviations from the phenomenological Beer-Lambert law which can be considered as arising from the high intensity of an incident radiation and collisions of absorbing molecules with surroundings. These effects were included into the expression, being an extended form of the Beer-Lambert law, which reasonably approximates all experimental data. The results, except for extending knowledge on the interaction of a high power laser radiation with matter, can help understanding and planning processes leading to preparation of silicon-containing technologically important materials.

  10. Variable path length spectrophotometric probe

    DOEpatents

    O'Rourke, Patrick E.; McCarty, Jerry E.; Haggard, Ricky A.

    1992-01-01

    A compact, variable pathlength, fiber optic probe for spectrophotometric measurements of fluids in situ. The probe comprises a probe body with a shaft having a polished end penetrating one side of the probe, a pair of optic fibers, parallel and coterminous, entering the probe opposite the reflecting shaft, and a collimating lens to direct light from one of the fibers to the reflecting surface of the shaft and to direct the reflected light to the second optic fiber. The probe body has an inlet and an outlet port to allow the liquid to enter the probe body and pass between the lens and the reflecting surface of the shaft. A linear stepper motor is connected to the shaft to cause the shaft to advance toward or away from the lens in increments so that absorption measurements can be made at each of the incremental steps. The shaft is sealed to the probe body by a bellows seal to allow freedom of movement of the shaft and yet avoid leakage from the interior of the probe.

  11. Utilization of path length fuzing in the Peacekeeper Weapon System

    NASA Astrophysics Data System (ADS)

    Jackson, A. D.

    This paper presents a discussion of the utilization and implementation of path length fuzing in the Peacekeeper Weapon System. Some background information which introduces the concept of path length fuzing and discusses its applicability to the Peacekeeper is first presented. Mathematical modeling of path length fuzing is discussed, and some novel algorithms and techniques developed by the author for implementation of path length fuzing in the Peacekeeper Operational Flight Program are presented. The scope of this paper is confined to the flight software and targeting aspects of path length fuzing; details of of the fuze hardware and electronics are not addressed.

  12. UV laser long-path absorption spectroscopy

    NASA Technical Reports Server (NTRS)

    Dorn, Hans-Peter; Brauers, Theo; Neuroth, Rudolf

    1994-01-01

    Long path Differential Optical Absorption Spectroscopy (DOAS) using a picosecond UV laser as a light source was developed in our institute. Tropospheric OH radicals are measured by their rotational absorption lines around 308 nm. The spectra are obtained using a high resolution spectrograph. The detection system has been improved over the formerly used optomechanical scanning device by application of a photodiode array which increased the observed spectral range by a factor of 6 and which utilizes the light much more effectively leading to a considerable reduction of the measurement time. This technique provides direct measurements of OH because the signal is given by the product of the absorption coefficient and the OH concentration along the light path according to Lambert-Beers law. No calibration is needed. Since the integrated absorption coefficient is well known the accuracy of the measurement essentially depends on the extent to which the OH absorption pattern can be detected in the spectra. No interference by self generated OH radicals in the detection lightpath has been observed. The large bandwidth (greater than 0.15 nm) and the high spectral resolution (1.5 pm) allows absolute determination of interferences by other trace gas absorptions. The measurement error is directly accessible from the absorption-signal to baseline-noise ratio in the spectra. The applicability of the method strongly depends on visibility. Elevated concentrations of aerosols lead to considerable attenuation of the laser light which reduces the S/N-ratio. In the moderately polluted air of Julich, where we performed a number of OH measurement spectra. In addition absorption features of unidentified species were frequently detected. A quantitative deconvolution even of the known species is not easy to achieve and can leave residual structures in the spectra. Thus interferences usually increase the noise and deteriorate the OH detection sensitivity. Using diode arrays for sensitive

  13. Modified Sagnac interferometer for contact-free length measurement of a direct absorption cell.

    PubMed

    Elandaloussi, Hadj; Rouillé, Christian; Marie-Jeanne, Patrick; Janssen, Christof

    2016-03-10

    Accurate path length measurements in absorption cells are recurrent requirements in quantitative molecular absorption spectroscopy. A new twin path laser interferometer for length measurements in a simple direct path absorption geometry is presented, along with a full uncertainty budget. The path in an absorption cell is determined by measuring the optical path length change due to the diminution of the refractive index when the cell originally filled with nitrogen gas is evacuated. The performance of the instrument based on a stabilized HeNe laser is verified by comparison with the results of direct mechanical length measurements of a roughly 45 mm long, specially designed absorption cell. Due to a resolution of about 1/300 of a HeNe fringe, an expanded (coverage factor k=2) uncertainty of 16 μm in the length measurement is achieved, providing an expanded relative uncertainty of 3.6·10⁻⁴ for the length of our test absorption cell. This value is about 8 times lower than what has been reported previously. The instrument will be useful for precision measurements of absorption cross sections of strong absorbers which require short light paths, such as ozone, halogen oxides, sulfur dioxide, and volatile organic compounds in the UV.

  14. 47 CFR 101.143 - Minimum path length requirements.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... SERVICES FIXED MICROWAVE SERVICES Technical Standards § 101.143 Minimum path length requirements. (a) The... carrier fixed point-to-point microwave services must equal or exceed the value set forth in the...

  15. 47 CFR 101.143 - Minimum path length requirements.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... SERVICES FIXED MICROWAVE SERVICES Technical Standards § 101.143 Minimum path length requirements. (a) The... carrier fixed point-to-point microwave services must equal or exceed the value set forth in the...

  16. 47 CFR 101.143 - Minimum path length requirements.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... SERVICES FIXED MICROWAVE SERVICES Technical Standards § 101.143 Minimum path length requirements. (a) The... carrier fixed point-to-point microwave services must equal or exceed the value set forth in the...

  17. 47 CFR 101.143 - Minimum path length requirements.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... SERVICES FIXED MICROWAVE SERVICES Technical Standards § 101.143 Minimum path length requirements. (a) The... carrier fixed point-to-point microwave services must equal or exceed the value set forth in the...

  18. 47 CFR 101.143 - Minimum path length requirements.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... SERVICES FIXED MICROWAVE SERVICES Technical Standards § 101.143 Minimum path length requirements. (a) The... carrier fixed point-to-point microwave services must equal or exceed the value set forth in the...

  19. Light path-length distributions within the retina.

    PubMed

    Rodmell, Paul I; Crowe, John A; Gorman, Alastair; Harvey, Andrew R; Muyo, Gonzalo; Mordant, David J; McNaught, Andy I; Morgan, Stephen P

    2014-03-01

    A Monte Carlo simulation of light propagation through the retina has been developed to understand the path-length distributions within the retinal vessel. For full-field illumination, the path-length distribution within the vessel comprises directly backscattered light and light that has passed once or twice through the vessel. The origins of these light path-length distributions can be better understood by investigating different combinations of single-point illumination and detection positions. Perhaps the most significant observation is that illumination at the edges of the vessel, rather than over the whole field of view, and detection directly above the vessel capture only the light that has taken a single pass through the vessel. This path-length distribution is tightly constrained around the diameter of the vessel and can potentially provide enhancements for oxygen saturation imaging. The method could be practically implemented using an offset-pinhole confocal imaging system or structured light illumination.

  20. Unobtrusive interferometer tracking by path length oscillation for multidimensional spectroscopy.

    PubMed

    Lee, Kevin F; Bonvalet, Adeline; Nuernberger, Patrick; Joffre, Manuel

    2009-07-20

    We track the path difference between interferometer arms with few-nanometer accuracy without adding optics to the beam path. We measure the interference of a helium-neon beam that copropagates through the interferometer with midinfrared pulses used for multidimensional spectroscopy. This can indicate motion, but not direction. By oscillating the path length of one arm with a mirror on a piezoelectric stack and monitoring the oscillations of the recombined helium-neon beam, the direction can be calculated, and the path delay can be continuously tracked.

  1. All-optical, thermo-optical path length modulation based on the vanadium-doped fibers.

    PubMed

    Matjasec, Ziga; Campelj, Stanislav; Donlagic, Denis

    2013-05-20

    This paper presents an all-fiber, fully-optically controlled, optical-path length modulator based on highly absorbing optical fiber. The modulator utilizes a high-power 980 nm pump diode and a short section of vanadium-co-doped single mode fiber that is heated through absorption and a non-radiative relaxation process. The achievable path length modulation range primarily depends on the pump's power and the convective heat-transfer coefficient of the surrounding gas, while the time response primarily depends on the heated fiber's diameter. An absolute optical length change in excess of 500 µm and a time-constant as short as 11 ms, were demonstrated experimentally. The all-fiber design allows for an electrically-passive and remote operation of the modulator. The presented modulator could find use within various fiber-optics systems that require optical (remote) path length control or modulation.

  2. [Research on the blood components detecting by multi-optical path length spectroscopy technique].

    PubMed

    Li, Gang; Zhao, Zhe; Liu, Rui; Wang, Hui-quan; Wu, Hong-jie; Lin, Ling

    2010-09-01

    To discuss the feasibility of using the serum's multi-optical path length spectroscopy information for measuring the concentration of the human blood components, the automatic micro-displacement measuring device was designed, which can obtain the near-infrared multi-optical path length from 0 to 4.0 mm (interval is 0.2 mm) spectra of 200 serum samples with multioptical path length spectrum of serum participated in building the quantitative analysis model of four components of the human blood: glucose (GLU), total cholesterol (TC), total protein (TP) and albumin (ALB), by mean of the significant non-linear spectral characteristic of blood. Partial least square (PLS) was used to set up the calibration models of the multi-optical path length near-infrared absorption spectrum of 160 experimental samples against the biochemical analysis results of them. The blood components of another 40 samples were predicted according to the model. The prediction effect of four blood components was favorable, and the correlation coefficient (r) of predictive value and biochemical analysis value were 0.9320, 0.9712, 0.9462 and 0.9483, respectively. All of the results proved the feasibility of the multi-optical path length spectroscopy technique for blood components analysis. And this technique established the foundation of detecting the components of blood and other liquid conveniently and rapidly.

  3. Depth-resolved photothermal optical coherence tomography by local optical path length change measurement (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Makita, Shuichi; Hong, Young-Joo; Li, En; Yasuno, Yoshiaki

    2016-03-01

    Photothermal OCT has been emerged to contrast absorbers in biological tissues. The tissues response to photothermal excitation as change of thermal strain and refractive index. To resolve the depth of absorption agents, the measurements of the local thermal strain change and local refractive index change due to photothermal effect is required. In this study, we developed photothermal OCT for depth-resolved absorption contrast imaging. The phase-resolved OCT can measure the axial strain change and local refractive index change as local optical path length change. A swept-source OCT system is used with a wavelength swept laser at 1310 nm with a scanning rate of 50 kHz. The sensitivity of 110 dB is achieved. At the sample arm, the excitation beam from a fiber-coupled laser diode of 406 nm wavelength is combined with the OCT probe beam co-linearly. The slowly modulated excitation beam around 300 Hz illuminate biological tissues. M-mode scan is applied during one-period modulation duration. The local optical path length change is measured by temporal and axial phase difference. The theoretical prediction of the photothermal response is derived and in good agreement with experimental results. In the case of slow modulation, the delay of photothermal response can be neglected. The local path length changes are averaged over the half period of the excitation modulation, and then demodulated. This method exhibits 3-dB gain in the sensitivity of the local optical path length change measurement over the direct Fourier transform method. In vivo human skin imaging of endogenous absorption agent will be demonstrated.

  4. Parallel optical-path-length-shifting digital holography.

    PubMed

    Awatsuji, Yasuhiro; Koyama, Takamasa; Tahara, Tatsuki; Ito, Kenichi; Shimozato, Yuki; Kaneko, Atsushi; Nishio, Kenzo; Ura, Shogo; Kubota, Toshihiro; Matoba, Osamu

    2009-12-01

    The authors propose an optical-path-length-shifting digital holography as a technique capable of single-shot recording of three-dimensional information of objects. With a single image sensor, the proposed technique can simultaneously record all of the holograms required for the in-line digital holography that reconstruct the image of an object from two intensity measurements at different planes. The technique can be optically implemented by using an optical-path-length-shifting array device located in the common path of the reference and object waves. The array device has periodic structure of two-step optical-path difference. The configuration of the array device of the proposed technique is simpler than the phase-shifting array device required for parallel phase-shifting digital holographies. Therefore, the optical system of the proposed technique is more suitable for the realization of a single-shot in-line digital holography system that removes the conjugate image from the reconstructed image. The authors conducted both a numerical simulation and a preliminary experiment of the proposed technique. The reconstructed images were quantitatively evaluated by using root mean squared error. In comparison to single-shot digital holography using the Fresnel transform alone, with the proposed technique the root mean squared errors of the technique were reduced to less than 1/6 in amplitude and 1/3 in phase. Also the results of the simulation and experiment agreed well with the images of an object. Thus the effectiveness of the proposed technique is verified.

  5. Path Length Fluctuations Derived from Site Testing Interferometer Data

    NASA Technical Reports Server (NTRS)

    Acosta, Roberto J.; Nessel, James A.; Morse, Jacquelynne R.

    2010-01-01

    To evaluate possible sites for NASA's proposed Ka-band antenna array, the NASA Glenn Research Center has constructed atmospheric phase monitors (APM) which directly measure the tropospheric phase stability. These instruments observe an unmodulated 20.2 GHz beacon signal broadcast from a geostationary satellite (Anik F2) and measure the phase difference between the signals received by the two antennas. Two APM's have been deployed, one at the NASA Deep Space Network (DSN) Tracking Complex in Goldstone, California, and the other at the NASA White Sands Complex, in Las Cruces, New Mexico. Two station-years of atmospheric phase fluctuation data have been collected at Goldstone since operations commenced in May 2007 and 0.5 station-years of data have been collected at White Sands since operations began February 2009. With identical instruments operating simultaneously, we can directly compare the phase stability at the two sites. Phase stability is analyzed statistically in terms of the root-mean-square (rms) of the tropospheric path length fluctuations over 10 min blocks. Correlation between surface wind speed and relative humidity with interferometer phase are discussed. For 2 years, the path length fluctuations at the DSN site in Goldstone, California, have been better than 757 micrometer (with reference to a 300 m baseline and to Zenith) for 90 percent of the time. For the 6 months of data collected at White Sands, New Mexico, the path length fluctuations have been better than 830 micrometers (with reference to a 300 m baseline and to Zenith) for 90 percent of the time. This type of data analysis, as well as many other site quality characteristics (e.g., rain attenuation, infrastructure, etc.), will be used to determine the suitability of both sites for NASA s future communication services at Ka-band using an array of antennas.

  6. Photon path length distributions for cloudy atmospheres from GOSAT satellite measurements

    NASA Astrophysics Data System (ADS)

    Kremmling, Beke; Penning de Vries, Marloes; Wagner, Thomas

    2014-05-01

    The presence of clouds in the atmosphere has significant influence on the photon paths of the scattered sunlight. Besides reflections of radiation at the cloud top, additional scattering events inside the cloud may occur and thus lengthening or shortening of the photon path in the atmosphere. Clouds consisting of multiple layers or patches may lead to a "ping pong" behaviour of the photons due to reflections at the individual surfaces. The objective of our study is the retrieval of photon path length distributions for various atmospheric cloud situations which will lead to a better understanding of the influence of clouds on the atmospheric radiative transport. Following principles from ground based photon path length retrieval (Funk et al., 2003), our research uses the combination of space based measurements of the oxygen A-band and radiative transfer simulations. The experimental spectra originate from the Japanese Greenhouse gases Observing SATellite (GOSAT), more precisely the Fourier Transform Spectrometer TANSO-FTS. Its high spectral resolution allows to almost completely resolve the individual absorption lines which is a prerequisite to our study. The Monte Carlo radiative transfer model McArtim (Deutschmann et al., 2011) is used to model the measured spectra. This model allows user-defined input for the altitude dependent cross sections and furthermore the incorporation of three dimensional cloud shapes and properties. From the simulation output and the sun-satellite geometry, photon path length distributions can be obtained. Distributions of photon path lengths are presented for a selection of GOSAT observations of entirely cloud covered atmospheres with similar measurement geometries.

  7. Quantification of optical Doppler broadening and optical path lengths of multiply scattered light by phase modulated low coherence interferometry

    NASA Astrophysics Data System (ADS)

    Varghese, B.; Rajan, V.; van Leeuwen, T. G.; Steenbergen, W.

    2007-07-01

    We show experimental validation of a novel technique to measure optical path length distributions and path length resolved Doppler broadening in turbid media for different reduced scattering coefficients and anisotropies. The technique involves a phase modulated low coherence Mach-Zehnder interferometer, with separate fibers for illumination and detection. Water suspensions of Polystyrene microspheres with high scattering and low absorption levels are used as calibrated scattering phantoms. The path length dependent diffusion broadening or Doppler broadening of scattered light is shown to agree with Diffusive Wave Spectroscopy within 5%. The optical path lengths are determined experimentally from the zero order moment of the phase modulation peak around the modulation frequency in the power spectrum and the results are validated with Monte Carlo simulations.

  8. Quantification of optical Doppler broadening and optical path lengths of multiply scattered light by phase modulated low coherence interferometry.

    PubMed

    Varghese, B; Rajan, V; van Leeuwen, T G; Steenbergen, W

    2007-07-23

    We show experimental validation of a novel technique to measure optical path length distributions and path length resolved Doppler broadening in turbid media for different reduced scattering coefficients and anisotropies. The technique involves a phase modulated low coherence Mach-Zehnder interferometer, with separate fibers for illumination and detection. Water suspensions of Polystyrene microspheres with high scattering and low absorption levels are used as calibrated scattering phantoms. The path length dependent diffusion broadening or Doppler broadening of scattered light is shown to agree with Diffusive Wave Spectroscopy within 5%. The optical path lengths are determined experimentally from the zero order moment of the phase modulation peak around the modulation frequency in the power spectrum and the results are validated with Monte Carlo simulations.

  9. Automation of long-path absorption cell measurements.

    PubMed

    Watkins, W R; Dixon, R G

    1979-01-01

    Recent advances have been made in the operation of long-path absorption cells which make them easier to align and improve the accuracy of measurements made with them. Only one person is required now for routine measurements of low absorption coefficients of atmospheric absorbers. Unique gear designs for the adjustment of the cell mirrors are described which utilize low-torque linear drives and make possible rapid changes in pathlength and precision repositioning of the cell output beam at long pathlengths. Automation of cell operation by the use of remote Selsyn controls is described. Several techniques are discussed for precision optical alignment of long-path absorption cells, including the use of infrared radiation sources. The system accuracy which results from these refinements in operation is included.

  10. Active-passive path-length encoded (APPLE) Doppler OCT

    PubMed Central

    Wartak, Andreas; Haindl, Richard; Trasischker, Wolfgang; Baumann, Bernhard; Pircher, Michael; Hitzenberger, Christoph K.

    2016-01-01

    We present a novel active-passive path-length encoded (APPLE) swept source Doppler optical coherence tomography (DOCT) approach, enabling three-dimensional velocity vector reconstruction of moving particles without prior knowledge of the orientation of motion. The developed APPLE DOCT setup allows for non-invasive blood flow measurements in vivo and was primarily designed for quantitative human ocular blood flow investigations. The system’s performance was demonstrated by in vitro flow phantom as well as in vivo retinal vessel bifurcation measurements. Furthermore, total retinal blood flow – a biomarker aiding in diagnosis and monitoring of major ocular diseases such as glaucoma, diabetic retinopathy or central/branch retinal vein occlusion – was determined in the eyes of healthy human volunteers. PMID:28018739

  11. Signal absorption effects on HF radio paths near Sodankyla observatory (Finland)

    NASA Astrophysics Data System (ADS)

    Blagoveshchenskii, D. V.

    2015-05-01

    Studies were performed on three oblique ionospheric sounding (OIS) paths: Gor'kovskaya-Lovozero (St. Petersburg) with a length of 890 km, Sodankyla-Gor'kovskaya (800 km), and Sodankyla-Lovozero (360 km). The data for March 17 and April 14, 2012, the days during the recovery phase of the corresponding magnetic storms, have been analyzed. According to the observations performed at Sodankyla, riometer absorption in the morning-daytime hours was high against a background of very weak magnetic disturbances registered with a magnetometer; a high absorption level was also typical of the second day but during a substantial magnetic disturbance. The signal propagation mode structure and intensity on different paths were compared for the indicated days. The main results achieved are as follows. The OIS signal mode structure at weak (for April 14, 2012) and strong (for March 17, 2012) absorption substantially differed when magnetic disturbances were weak at the same instant. Diffuse reflections from the F2 layer were observed on the first two paths during a magnetic disturbance at night of April 14, 2012. At the same time, diffusivity was absent on the same paths under quiet magnetic conditions in the morning and daytime hours on March 17, 2012. A short-term abrupt increase in the maximum observed frequency of the Es layer (MOF Es) by 30-80% was registered half an hour before a substantial absorption burst on the first path. Signal reflections from the sporadic Es layer were observed only on the first path on March 17, 2012, and April 14, 2012, during the absorption maximum ( A = 6 dB) according to the Sodankyla data, and the signal characteristics differed on those days.

  12. Infrared Pulse-laser Long-path Absorption Measurement of Carbon Dioxide Using a Raman-shifted Dye Laser

    NASA Technical Reports Server (NTRS)

    Minato, Atsushi; Sugimoto, Nobuo; Sasano, Yasuhiro

    1992-01-01

    A pulsed laser source is effective in infrared laser long-path absorption measurements when the optical path length is very long or the reflection from a hard target is utilized, because higher signal-to-noise ratio is obtained in the detection of weak return signals. We have investigated the performance of a pulse-laser long-path absorption system using a hydrogen Raman shifter and a tunable dye laser pumped by a Nd:YAG laser, which generates second Stokes radiation in the 2-micron region.

  13. Optical Path Switching Based Differential Absorption Radiometry for Substance Detection

    NASA Technical Reports Server (NTRS)

    Sachse, Glen W. (Inventor)

    2000-01-01

    A system and method are provided for detecting one or more substances. An optical path switch divides sample path radiation into a time series of alternating first polarized components and second polarized components. The first polarized components are transmitted along a first optical path and the second polarized components along a second optical path. A first gasless optical filter train filters the first polarized components to isolate at least a first wavelength band thereby generating first filtered radiation. A second gasless optical filter train filters the second polarized components to isolate at least a second wavelength band thereby generating second filtered radiation. The first wavelength band and second wavelength band are unique. Further, spectral absorption of a substance of interest is different at the first wavelength band as compared to the second wavelength band. A beam combiner combines the first and second filtered radiation to form a combined beam of radiation. A detector is disposed to monitor magnitude of at least a portion of the combined beam alternately at the first wavelength band and the second wavelength band as an indication of the concentration of the substance in the sample path.

  14. Derivatives of optical path length: from mathematical formulation to applications.

    PubMed

    Lin, Psang Dain

    2015-05-01

    The optical path length (OPL) of an optical system is a highly important parameter since it determines the phase of the light passing through the system and governs the interference and diffraction of the rays as they propagate. The Jacobian and Hessian matrices of the OPL are of fundamental importance in tuning the performance of a system. However, the OPL varies as a recursive function of the incoming ray and the boundary variable vector, and hence computing the Jacobian and Hessian matrices is extremely challenging. In an earlier study by the present group, this problem was addressed by deriving the Jacobian matrix of the OPL with respect to all of the independent system variables of a nonaxially symmetric system. In the present study, the proposed method is extended to the Hessian matrix of a nonaxially symmetric optical system. The proposed method facilitates the cross-sensitivity analysis of the OPL with respect to arbitrary system variables and provides an ideal basis for automatic optical system design applications in which the merit function is defined in terms of wavefront aberrations. An illustrative example is given. It is shown that the proposed method requires fewer iterations than that based on the Jacobian matrix and yields a more reliable and precise optimization performance.

  15. Ray tracing based path-length calculations for polarized light tomographic imaging

    NASA Astrophysics Data System (ADS)

    Manjappa, Rakesh; Kanhirodan, Rajan

    2015-09-01

    A ray tracing based path length calculation is investigated for polarized light transport in a pixel space. Tomographic imaging using polarized light transport is promising for applications in optical projection tomography of small animal imaging and turbid media with low scattering. Polarized light transport through a medium can have complex effects due to interactions such as optical rotation of linearly polarized light, birefringence, di-attenuation and interior refraction. Here we investigate the effects of refraction of polarized light in a non-scattering medium. This step is used to obtain the initial absorption estimate. This estimate can be used as prior in Monte Carlo (MC) program that simulates the transport of polarized light through a scattering medium to assist in faster convergence of the final estimate. The reflectance for p-polarized (parallel) and s-polarized (perpendicular) are different and hence there is a difference in the intensities that reach the detector end. The algorithm computes the length of the ray in each pixel along the refracted path and this is used to build the weight matrix. This weight matrix with corrected ray path length and the resultant intensity reaching the detector for each ray is used in the algebraic reconstruction (ART) method. The proposed method is tested with numerical phantoms for various noise levels. The refraction errors due to regions of different refractive index are discussed, the difference in intensities with polarization is considered. The improvements in reconstruction using the correction so applied is presented. This is achieved by tracking the path of the ray as well as the intensity of the ray as it traverses through the medium.

  16. Interferometric Characterisation of Path Length Errors Resulting from Mirror Surface Topography with Sub-nm Reproducibility

    NASA Astrophysics Data System (ADS)

    Kögel, H.; Gohlke, M.; Pijnenburg, J.; Gerardi, D.; Schuldt, T.; Johann, U.; Braxmaier, C.; Weise, D.

    2013-01-01

    We present the results of our experimental characterisation of path length errors, caused by beamwalk over the surface topography of laser mirrors. These path length errors can have a major influence on the accuracy of the LISA measurement instrument in Astrium's alternative payload concept with In-Field Pointing. Our measurement setup uses a highly sensitive heterodyne interferometer for measuring the path length error amplitudes, generated by the topography of a moving, λ/10 test mirror.

  17. Laser Metrology for an Optical-Path-Length Modulator

    NASA Technical Reports Server (NTRS)

    Gursel, Yekta

    2005-01-01

    Laser gauges have been developed to satisfy requirements specific to monitoring the amplitude of the motion of an optical-path-length modulator that is part of an astronomical interferometer. The modulator includes a corner-cube retroreflector driven by an electromagnetic actuator. During operation of the astronomical interferometer, the electromagnet is excited to produce linear reciprocating motion of the corner-cube retroreflector at an amplitude of 2 to 4 mm at a frequency of 250, 750, or 1,250 Hz. Attached to the corner-cube retroreflector is a small pick-off mirror. To suppress vibrations, a counterweight having a mass equal to that of the corner-cube retroreflector and pick-off mirror is mounted on another electromagnetic actuator that is excited in opposite phase. Each gauge is required to measure the amplitude of the motion of the pick-off mirror, assuming that the motions of the pick-off mirror and the corner-cube retroreflector are identical, so as to measure the amplitude of motion of the corner- cube retroreflector to within an error of the order of picometers at each excitation frequency. Each gauge is a polarization-insensitive heterodyne interferometer that includes matched collimators, beam separators, and photodiodes (see figure). The light needed for operation of the gauge comprises two pairs of laser beams, the beams in each pair being separated by a beat frequency of 80 kHz. The laser beams are generated by an apparatus, denoted the heterodyne plate, that includes stabilized helium-neon lasers, acousto-optical modulators, and associated optical and electronic subsystems. The laser beams are coupled from the heterodyne plate to the collimators via optical fibers.

  18. Estimation of partial optical path length in the brain in subject-specific head models for near-infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Nakamura, Kotaro; Kurihara, Kazuki; Kawaguchi, Hiroshi; Obata, Takayuki; Ito, Hiroshi; Okada, Eiji

    2016-04-01

    Three-dimensional head models with the structures constructed from the MR head images of 40 volunteers were constructed to analyze light propagation in the subject-specific head models. The mean optical path length in the head and the partial optical path length in the brain at 13 fiducial points for each volunteer were estimated to evaluate the intersubject and spatial variability in the optical path lengths. Although the intersubject variability in the optical path lengths is very high, the spatial variability in the average of the mean optical path length and partial optical path length is similar to the previously reported data. The mean optical path length in the head increases, whereas the partial optical path length in the brain decreases with an increase in the depth of the brain surface. The partial optical path length is highly correlated with the depth of the brain surface in comparison to the mean optical path length in the head.

  19. 47 CFR 78.108 - Minimum path lengths for fixed links.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 4 2013-10-01 2013-10-01 false Minimum path lengths for fixed links. 78.108 Section 78.108 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES CABLE TELEVISION RELAY SERVICE Technical Regulations § 78.108 Minimum path lengths for fixed links....

  20. 47 CFR 78.108 - Minimum path lengths for fixed links.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false Minimum path lengths for fixed links. 78.108 Section 78.108 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES CABLE TELEVISION RELAY SERVICE Technical Regulations § 78.108 Minimum path lengths for fixed links....

  1. 47 CFR 78.108 - Minimum path lengths for fixed links.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Minimum path lengths for fixed links. 78.108 Section 78.108 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES CABLE TELEVISION RELAY SERVICE Technical Regulations § 78.108 Minimum path lengths for fixed links....

  2. 47 CFR 78.108 - Minimum path lengths for fixed links.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false Minimum path lengths for fixed links. 78.108 Section 78.108 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES CABLE TELEVISION RELAY SERVICE Technical Regulations § 78.108 Minimum path lengths for fixed links....

  3. 47 CFR 78.108 - Minimum path lengths for fixed links.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 false Minimum path lengths for fixed links. 78.108 Section 78.108 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES CABLE TELEVISION RELAY SERVICE Technical Regulations § 78.108 Minimum path lengths for fixed links....

  4. A fast and accurate algorithm for high-frequency trans-ionospheric path length determination

    NASA Astrophysics Data System (ADS)

    Wijaya, Dudy D.

    2015-12-01

    This paper presents a fast and accurate algorithm for high-frequency trans-ionospheric path length determination. The algorithm is merely based on the solution of the Eikonal equation that is solved using the conformal theory of refraction. The main advantages of the algorithm are summarized as follows. First, the algorithm can determine the optical path length without iteratively adjusting both elevation and azimuth angles and, hence, the computational time can be reduced. Second, for the same elevation and azimuth angles, the algorithm can simultaneously determine the phase and group of both ordinary and extra-ordinary optical path lengths for different frequencies. Results from numerical simulations show that the computational time required by the proposed algorithm to accurately determine 8 different optical path lengths is almost 17 times faster than that required by a 3D ionospheric ray-tracing algorithm. It is found that the computational time to determine multiple optical path lengths is the same with that for determining a single optical path length. It is also found that the proposed algorithm is capable of determining the optical path lengths with millimeter level of accuracies, if the magnitude of the squared ratio of the plasma frequency to the transmitted frequency is less than 1.33× 10^{-3}, and hence the proposed algorithm is applicable for geodetic applications.

  5. Comparison Between Path Lengths Traveled by Solar Electrons and Ions in Ground-Level Enhancement Events

    NASA Technical Reports Server (NTRS)

    Tan, Lun C.; Malandraki, Olga E.; Reames, Donald; NG, Chee K.; Wang, Linghua; Patsou, Ioanna; Papaioannou, Athanasios

    2013-01-01

    We have examined the Wind/3DP/SST electron and Wind/EPACT/LEMT ion data to investigate the path length difference between solar electrons and ions in the ground-level enhancement (GLE) events in solar cycle 23. Assuming that the onset time of metric type II or decameter-hectometric (DH) type III radio bursts is the solar release time of non-relativistic electrons, we have found that within an error range of plus or minus 10% the deduced path length of low-energy (approximately 27 keV) electrons from their release site near the Sun to the 1 AU observer is consistent with the ion path length deduced by Reames from the onset time analysis. In addition, the solar longitude distribution and IMF topology of the GLE events examined are in favor of the coronal mass ejection-driven shock acceleration origin of observed non-relativistic electrons.We have also found an increase of electron path lengths with increasing electron energies. The increasing rate of path lengths is correlated with the pitch angle distribution (PAD) of peak electron intensities locally measured, with a higher rate corresponding to a broader PAD. The correlation indicates that the path length enhancement is due to the interplanetary scattering experienced by first arriving electrons. The observed path length consistency implies that the maximum stable time of magnetic flux tubes, along which particles transport, could reach 4.8 hr.

  6. Optical study of thin-film photovoltaic cells with apparent optical path length

    NASA Astrophysics Data System (ADS)

    Cho, Changsoon; Jeong, Seonju; Lee, Jung-Yong

    2016-09-01

    Extending the insufficient optical path length (OPL) in thin-film photovoltaic cells (PVs) is the key to achieving a high power conversion efficiency (PCE) in devices. Here, we introduce the apparent OPL (AOPL) as a figure of merit for light absorbing capability in thin-film PVs. The optical characteristics such as the structural effects and angular responses in thin-film PVs were analyzed in terms of the AOPL. Although the Lambertian scattering surface yields a broadband absorption enhancement in thin-film PVs, the enhancement is not as effective as in thick-film PVs. On the other hand, nanophotonic schemes are introduced as an approach to increasing the single-pass AOPL by inducing surface plasmon resonance. The scheme using periodic metal gratings is proved to increase the AOPL in a narrow wavelength range and specific polarization, overcoming the Yablonovitch limit. The AOPL calculation can be also adopted in the experimental analysis and a maximum AOPL of 4.15d (where d is the active layer thickness) is exhibited in the absorption band edge region of PTB7:PC70BM-based polymer PVs.

  7. Experimental prediction of the wavelength-dependent path-length factor for optical intrinsic signal analysis.

    PubMed

    Sakaguchi, Koichiro; Tachibana, Tomoya; Furukawa, Shunsuke; Katsura, Takushige; Yamazaki, Kyoko; Kawaguchi, Hideo; Maki, Atsushi; Okada, Eiji

    2007-05-10

    Analysis of the optical intrinsic signal of an exposed cortex has been applied to measurement of functional brain activation. It is important for accurate measurement of concentration changes in oxygenated hemoglobin and deoxygenated hemoglobin to consider the wavelength dependence of the mean optical path lengths for the reflectance of cortical tissue. A method is proposed to experimentally estimate the wavelength dependence of the mean optical path length in cortical tissue from the multispectral reflectance of the exposed cortex without any additional instruments. The trend in the wavelength dependence of the mean optical path length estimated by the proposed method agrees with that estimated by the model-based prediction, whereas the magnitude of the wavelength dependence predicted by the proposed method is greater than that of the model-based prediction. The experimentally predicted mean optical path length minimizes the difference in the measured changes in the concentrations of the oxygenated hemoglobin and deoxygenated hemoglobin calculated from different wavelength pairs.

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

    NASA Astrophysics Data System (ADS)

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

    1999-03-01

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

  9. A microfabricated fixed path length silicon sample holder improves background subtraction for cryoSAXS

    PubMed Central

    Hopkins, Jesse B.; Katz, Andrea M.; Meisburger, Steve P.; Warkentin, Matthew A.; Thorne, Robert E.; Pollack, Lois

    2015-01-01

    The application of small-angle X-ray scattering (SAXS) for high-throughput characterization of biological macromolecules in solution is limited by radiation damage. By cryocooling samples, radiation damage and required sample volumes can be reduced by orders of magnitude. However, the challenges of reproducibly creating the identically sized vitrified samples necessary for conventional background subtraction limit the widespread adoption of this method. Fixed path length silicon sample holders for cryoSAXS have been microfabricated to address these challenges. They have low background scattering and X-ray absorption, require only 640 nl of sample, and allow reproducible sample cooling. Data collected in the sample holders from a nominal illuminated sample volume of 2.5 nl are reproducible down to q ≃ 0.02 Å−1, agree with previous cryoSAXS work and are of sufficient quality for reconstructions that match measured crystal structures. These sample holders thus allow faster, more routine cryoSAXS data collection. Additional development is required to reduce sample fracturing and improve data quality at low q. PMID:26089749

  10. Pillar cuvettes: capillary-filled, microliter quartz cuvettes with microscale path lengths for optical spectroscopy.

    PubMed

    Holzner, Gregor; Kriel, Frederik Hermanus; Priest, Craig

    2015-05-05

    The goal of most analytical techniques is to reduce the lower limit of detection; however, it is sometimes necessary to do the opposite. High sample concentrations or samples with high molar absorptivity (e.g., dyes and metal complexes) often require multiple dilution steps or laborious sample preparation prior to spectroscopic analysis. Here, we demonstrate dilution-free, one-step UV-vis spectroscopic analysis of high concentrations of platinum(IV) hexachloride in a micropillar array, that is, "pillar cuvette". The cuvette is spontaneously filled by wicking of the liquid sample into the micropillar array. The pillar height (thus, the film thickness) defines the optical path length, which was reduced to between 10 and 20 μm in this study (3 orders of magnitude smaller than in a typical cuvette). Only one small droplet (∼2 μL) of sample is required, and the dispensed volume need not be precise or even known to the analyst for accurate spectroscopy measurements. For opaque pillars, we show that absorbance is linearly related to platinum concentration (the Beer-Lambert Law). For fully transparent or semitransparent pillars, the measured absorbance was successfully corrected for the fractional surface coverage of the pillars and the transmittance of the pillars and reference. Thus, both opaque and transparent pillars can be applied to absorbance spectroscopy of high absorptivity, microliter samples. It is also shown here that the pillar array has a useful secondary function as an integrated (in-cuvette) filter for particulates. For pillar cuvette measurements of platinum solutions spiked with 6 μm diameter polystyrene spheres, filtered and unfiltered samples gave identical spectra.

  11. Monte Carlo analysis of single fiber reflectance spectroscopy: photon path length and sampling depth.

    PubMed

    Kanick, S C; Robinson, D J; Sterenborg, H J C M; Amelink, A

    2009-11-21

    Single fiber reflectance spectroscopy is a method to noninvasively quantitate tissue absorption and scattering properties. This study utilizes a Monte Carlo (MC) model to investigate the effect that optical properties have on the propagation of photons that are collected during the single fiber reflectance measurement. MC model estimates of the single fiber photon path length (L(SF)) show excellent agreement with experimental measurements and predictions of a mathematical model over a wide range of optical properties and fiber diameters. Simulation results show that L(SF) is unaffected by changes in anisotropy (g epsilon [0.8, 0.9, 0.95]), but is sensitive to changes in phase function (Henyey-Greenstein versus modified Henyey-Greenstein). A 20% decrease in L(SF) was observed for the modified Henyey-Greenstein compared with the Henyey-Greenstein phase function; an effect that is independent of optical properties and fiber diameter and is approximated with a simple linear offset. The MC model also returns depth-resolved absorption profiles that are used to estimate the mean sampling depth (Z(SF)) of the single fiber reflectance measurement. Simulated data are used to define a novel mathematical expression for Z(SF) that is expressed in terms of optical properties, fiber diameter and L(SF). The model of sampling depth indicates that the single fiber reflectance measurement is dominated by shallow scattering events, even for large fibers; a result that suggests that the utility of single fiber reflectance measurements of tissue in vivo will be in the quantification of the optical properties of superficial tissues.

  12. Visual target distance, but not visual cursor path length produces shifts in motor behavior.

    PubMed

    Wendker, Nike; Sack, Oliver S; Sutter, Christine

    2014-01-01

    When using tools effects in body space and distant space often do not correspond. Findings so far demonstrated that in this case visual feedback has more impact on action control than proprioceptive feedback. The present study varies the dimensional overlap between visual and proprioceptive action effects and investigates its impact on aftereffects in motor responses. In two experiments participants perform linear hand movements on a covered digitizer tablet to produce ∩-shaped cursor trajectories on the display. The shape of hand motion and cursor motion (linear vs. curved) is dissimilar and therefore does not overlap. In one condition the length of hand amplitude and visual target distance is similar and constant while the length of the cursor path is dissimilar and varies. In another condition the length of the hand amplitude varies while the lengths of visual target distance (similar or dissimilar) and cursor path (dissimilar) are constant. First, we found that aftereffects depended on the relation between hand path length and visual target distance, and not on the relation between hand and cursor path length. Second, increasing contextual interference did not reveal larger aftereffects. Finally, data exploration demonstrated a considerable benefit from gain repetitions across trials when compared to gain switches. In conclusion, dimensional overlap between visual and proprioceptive action effects modulates human information processing in visually controlled actions. However, adjustment of the internal model seems to occur very fast for this kind of simple linear transformation, so that the impact of prior visual feedback is fleeting.

  13. Optical path switching based differential absorption radiometry for substance detection

    NASA Technical Reports Server (NTRS)

    Sachse, Glen W. (Inventor)

    2005-01-01

    An optical path switch divides sample path radiation into a time series of alternating first polarized components and second polarized components. The first polarized components are transmitted along a first optical path and the second polarized components along a second optical path. A first gasless optical filter train filters the first polarized components to isolate at least a first wavelength band thereby generating first filtered radiation. A second gasless optical filter train filters the second polarized components to isolate at least a second wavelength band thereby generating second filtered radiation. A beam combiner combines the first and second filtered radiation to form a combined beam of radiation. A detector is disposed to monitor magnitude of at least a portion of the combined beam alternately at the first wavelength band and the second wavelength band as an indication of the concentration of the substance in the sample path.

  14. Optical path switching based differential absorption radiometry for substance detection

    NASA Technical Reports Server (NTRS)

    Sachse, Glen W. (Inventor)

    2003-01-01

    An optical path switch divides sample path radiation into a time series of alternating first polarized components and second polarized components. The first polarized components are transmitted along a first optical path and the second polarized components along a second optical path. A first gasless optical filter train filters the first polarized components to isolate at least a first wavelength band thereby generating first filtered radiation. A second gasless optical filter train filters the second polarized components to isolate at least a second wavelength band thereby generating second filtered radiation. A beam combiner combines the first and second filtered radiation to form a combined beam of radiation. A detector is disposed to monitor magnitude of at least a portion of the combined beam alternately at the first wavelength band and the second wavelength band as an indication of the concentration of the substance in the sample path.

  15. 47 CFR 74.644 - Minimum path lengths for fixed links.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... fixed link must equal or exceed the value set forth in the table below or the EIRP must be reduced in...,990-7,125 17 12,200-13,250 5 Above 17,700 n/a (b) For paths shorter than those specified in the Table... = Maximum EIRP as set forth in the Table in § 74.636 of this part. A = Minimum path length from the...

  16. 47 CFR 74.644 - Minimum path lengths for fixed links.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... fixed link must equal or exceed the value set forth in the table below or the EIRP must be reduced in...,990-7,125 17 12,200-13,250 5 Above 17,700 n/a (b) For paths shorter than those specified in the Table... = Maximum EIRP as set forth in the Table in § 74.636 of this part. A = Minimum path length from the...

  17. Relations between ac-dc components and optical path length in photoplethysmography

    NASA Astrophysics Data System (ADS)

    Lee, Chungkeun; Sik Shin, Hang; Lee, Myoungho

    2011-07-01

    Photoplethysmography is used in various areas such as vital sign measurement, vascular characteristics analysis, and autonomic nervous system assessment. Photoplethysmographic signals are composed of ac and dc, but it is difficult to find research about the interaction of photoplethysmographic components. This study suggested a model equation combining two Lambert-Beer equations at the onset and peak points of photoplethysmography to evaluate ac characteristics, and verified the model equation through simulation and experiment. In the suggested equation, ac was dependent on dc and optical path length. In the simulation, dc was inversely proportionate to ac sensitivity (slope), and ac and optical path length were proportionate. When dc increased from 10% to 90%, stabilized ac decreased from 1 to 0.89 +/- 0.21, and when optical path length increased from 10% to 90%, stabilized ac increased from 1 to 1.53 +/- 0.40.

  18. Analysis of light propagation in highly scattering media by path-length-assigned Monte Carlo simulations

    NASA Astrophysics Data System (ADS)

    Ishii, Katsuhiro; Nishidate, Izumi; Iwai, Toshiaki

    2014-05-01

    Numerical analysis of optical propagation in highly scattering media is investigated when light is normally incident to the surface and re-emerges backward from the same point. This situation corresponds to practical light scattering setups, such as in optical coherence tomography. The simulation uses the path-length-assigned Monte Carlo method based on an ellipsoidal algorithm. The spatial distribution of the scattered light is determined and the dependence of its width and penetration depth on the path-length is found. The backscattered light is classified into three types, in which ballistic, snake, and diffuse photons are dominant.

  19. Fourier optics analysis of phase-mask-based path-length-multiplexed optical coherence tomography.

    PubMed

    Yin, Biwei; Dwelle, Jordan; Wang, Bingqing; Wang, Tianyi; Feldman, Marc D; Rylander, Henry G; Milner, Thomas E

    2015-11-01

    Optical coherence tomography (OCT) is an imaging technique that constructs a depth-resolved image by measuring the optical path-length difference between broadband light backscattered from a sample and a reference surface. For many OCT sample arm optical configurations, sample illumination and backscattered light detection share a common path. When a phase mask is placed in the sample path, features in the detected signal are observed, which suggests that an analysis of a generic common path OCT imaging system is warranted. In this study, we present a Fourier optics analysis using a Fresnel diffraction approximation of an OCT system with a path-length-multiplexing element (PME) inserted in the sample arm optics. The analysis may be generalized for most phase-mask-based OCT systems. A radial-angle-diverse PME is analyzed in detail, and the point spread function, coherent transfer function, sensitivity of backscattering angular diversity detection, and signal formation in terms of sample spatial frequency are simulated and discussed. The analysis reveals important imaging features and application limitations of OCT imaging systems with a phase mask in the sample path optics.

  20. Achromatic recirculated chicane with fixed geometry and independently variable path length and momentum compaction

    DOEpatents

    Douglas, David R.; Neil, George R.

    2005-04-26

    A particle beam recirculated chicane geometry that, through the inducement of a pair of 180 degree bends directed by the poles of a pair of controllable magnetic fields allows for variation of dipole position, return loop radii and steering/focussing, thereby allowing the implementation of independent variation of path length and momentum compaction.

  1. On the determination of atmospheric path length by passive microwave radiometer

    NASA Technical Reports Server (NTRS)

    Webster, W. J., Jr.

    1975-01-01

    Microwave radiometer techniques were evaluated for use in atmospheric path length correction of Pacific Plate Motion Experiment interferometer measurements. It is shown that passive microwave radiometry allows precise measurement of the brightness temperature of the sky. It is also noted that the technological requirements of radiometers are very different from the requirements of radio astronomy. The technology was used in the construction of radiometers which are sufficient for use in the path length correction problem. A simulation study shows that, when combined with surface meteorology data, passive microwave radiometer data would allow a determination of the path length correction to better than 2 cm at the zenith. By a careful choice of frequencies, a dual frequency system would allow a measurement of the path length correction to better than 4 cm at zenith angles as great as 60 deg. Because of the wide range of weather conditions to be expected for the PPME sites (which include Alaska, Hawaii and Massachusetts), it will probably be necessary to use a separate correction algorithm for each site.

  2. Easy transition path sampling methods: flexible-length aimless shooting and permutation shooting.

    PubMed

    Mullen, Ryan Gotchy; Shea, Joan-Emma; Peters, Baron

    2015-06-09

    We present new algorithms for conducting transition path sampling (TPS). Permutation shooting rigorously preserves the total energy and momentum of the initial trajectory and is simple to implement even for rigid water molecules. Versions of aimless shooting and permutation shooting that use flexible-length trajectories have simple acceptance criteria and are more computationally efficient than fixed-length versions. Flexible-length permutation shooting and inertial likelihood maximization are used to identify the reaction coordinate for vacancy migration in a two-dimensional trigonal crystal of Lennard-Jones particles. The optimized reaction coordinate eliminates nearly all recrossing of the transition state dividing surface.

  3. A Variable Path Length Cell for Transverse Acoustic Studies of Superfluid 3He

    NASA Astrophysics Data System (ADS)

    Collett, C. A.; Nguyen, M. D.; Li, J. I. A.; Zimmerman, A. M.; Halperin, W. P.; Davis, J. P.

    2015-03-01

    Transverse sound has recently emerged as an effective probe of the order parameter of superfluid 3He. Both the transverse acoustic impedance and attenuation have been shown to couple to surface bound states in 3He- B, which are predicted to be Majorana states in the specular scattering limit. In order to measure the attenuation at different path lengths to separate surface from bulk effects, as well as reduce the cavity size to the micron scale where transverse sound propagation should be measurable in the normal state, we have constructed a variable path length cell. Using a 4He-actuated diaphragm we demonstrate in-situ changes to the cavity length at dilution temperatures, and report our progress in deploying the cell at sub-mK temperatures. This research was supported by the National Science Foundation grant DMR-1103625.

  4. Tapered laser rods as a means of minimizing the path length of trapped barrel mode rays

    DOEpatents

    Beach, Raymond J.; Honea, Eric C.; Payne, Stephen A.; Mercer, Ian; Perry, Michael D.

    2005-08-30

    By tapering the diameter of a flanged barrel laser rod over its length, the maximum trapped path length of a barrel mode can be dramatically reduced, thereby reducing the ability of the trapped spontaneous emission to negatively impact laser performance through amplified spontaneous emission (ASE). Laser rods with polished barrels and flanged end caps have found increasing application in diode array end-pumped laser systems. The polished barrel of the rod serves to confine diode array pump light within the rod. In systems utilizing an end-pumping geometry and such polished barrel laser rods, the pump light that is introduced into one or both ends of the laser rod, is ducted down the length of the rod via the total internal reflections (TIRs) that occur when the light strikes the rod's barrel. A disadvantage of using polished barrel laser rods is that such rods are very susceptible to barrel mode paths that can trap spontaneous emission over long path lengths. This trapped spontaneous emission can then be amplified through stimulated emission resulting in a situation where the stored energy available to the desired lasing mode is effectively depleted, which then negatively impacts the laser's performance, a result that is effectively reduced by introducing a taper onto the laser rod.

  5. Multibeam long-path differential optical absorption spectroscopy instrument: a device for simultaneous measurements along multiple light paths.

    PubMed

    Pundt, Irene; Mettendorf, Kai Uwe

    2005-08-10

    A novel long-path differential optical absorption spectroscopy (DOAS) apparatus for measuring tropospheric trace gases and the first results from its use are presented: We call it the multibeam instrument. It is the first active DOAS device that emits several light beams simultaneously through only one telescope and with only one lamp as a light source, allowing simultaneous measurement along multiple light paths. In contrast to conventional DOAS instruments, several small mirrors are positioned near the lamp, creating multiple virtual light sources that emit one light beam each in one specific direction. The possibility of error due to scattering between the light beams is negligible. The trace-gas detection limits of NO2, SO2, O3, and H2CO are similar to those of the traditional long-path DOAS instrument.

  6. Modeling the average shortest-path length in growth of word-adjacency networks

    NASA Astrophysics Data System (ADS)

    Kulig, Andrzej; DroŻdŻ, Stanisław; Kwapień, Jarosław; OświÈ©cimka, Paweł

    2015-03-01

    We investigate properties of evolving linguistic networks defined by the word-adjacency relation. Such networks belong to the category of networks with accelerated growth but their shortest-path length appears to reveal the network size dependence of different functional form than the ones known so far. We thus compare the networks created from literary texts with their artificial substitutes based on different variants of the Dorogovtsev-Mendes model and observe that none of them is able to properly simulate the novel asymptotics of the shortest-path length. Then, we identify the local chainlike linear growth induced by grammar and style as a missing element in this model and extend it by incorporating such effects. It is in this way that a satisfactory agreement with the empirical result is obtained.

  7. Round-Trip System Available to Measure Path Length Variation in Korea VLBI System for Geodesy

    NASA Technical Reports Server (NTRS)

    Oh, Hongjong; Kondo, Tetsuro; Lee, Jinoo; Kim, Tuhwan; Kim, Myungho; Kim, Suchul; Park, Jinsik; Ju, Hyunhee

    2010-01-01

    The construction project of Korea Geodetic VLBI officially started in October 2008. The construction of all systems will be completed by the end of 2011. The project was named Korea VLBI system for Geodesy (KVG), and its main purpose is to maintain the Korea Geodetic Datum. In case of the KVG system, an observation room with an H-maser frequency standard is located in a building separated from the antenna by several tens of meters. Therefore KVG system will adopt a so-called round-trip system to transmit reference signals to the antenna with reduction of the effect of path length variations. KVG s round-trip system is designed not only to use either metal or optical fiber cables, but also to measure path length variations directly. We present this unique round trip system for KVG.

  8. A Graduated Cylinder Colorimeter: An Investigation of Path Length and the Beer-Lambert Law

    NASA Astrophysics Data System (ADS)

    Gordon, James; Harman, Stephanie

    2002-05-01

    A 10-mL graduated cylinder was used to construct a colorimeter to investigate the relationship between absorbance and path length found in the Beer-Lambert law. Light-emitting diodes (LEDs) were used as the light sources and filter monochromators. The experiments were conducted on intensely colored permanganate and tetraamminecopper(II) solutions. The device also was useful for demonstrating the relationship between absorbance and concentration.

  9. Measurement of optical path length change following pulsed laser irradiation using differential phase optical coherence tomography.

    PubMed

    Kim, Jihoon; Oh, Junghwan; Milner, Thomas E

    2006-01-01

    Differential phase optical coherence tomography (DPOCT) is introduced to measure optical path length changes in response to pulsed laser irradiation (585 nm). An analytical equation that includes thermoelastic surface displacement and thermorefractive index change is derived to predict optical path length change in response to pulsed laser irradiation for both "confined surface" and "free surface" model systems. The derived equation is tested by comparing predicted values with data recorded from experiments using two model systems. Thermorefractive index change and the thermal expansion coefficient are deduced from differential phase change (dDeltaphi) and temperature increase (DeltaT0) measurements. The measured n(T0)beta(T0)+dndT[=1.7410(-4)+/-1.710(-6) (1K)] in the free surface experiment matches with the National Institute of Standards and Technology (NIST) data value [=1.7710(-4) (1K)]. Exclusion of lateral thermal expansion in the analytical model for the confined surface experiment causes difference between the measured dndT[=-2.310(-4)+/-7.310(-6)(1K)] and the NIST value [=-9.4510(-5) (1K)]. In spite of the difference in the confined surface experiment, results of our studies indicate DPOCT can detect dynamic optical path length change in response to pulsed laser irradiation with high sensitivity, and applications to tissue diagnostics may be possible.

  10. Effect of repetitive pecking at working length for glide path preparation using G-file

    PubMed Central

    Ha, Jung-Hong; Jeon, Hyo-Jin; Abed, Rashid El; Chang, Seok-Woo; Kim, Sung-Kyo

    2015-01-01

    Objectives Glide path preparation is recommended to reduce torsional failure of nickel-titanium (NiTi) rotary instruments and to prevent root canal transportation. This study evaluated whether the repetitive insertions of G-files to the working length maintain the apical size as well as provide sufficient lumen as a glide path for subsequent instrumentation. Materials and Methods The G-file system (Micro-Mega) composed of G1 and G2 files for glide path preparation was used with the J-shaped, simulated resin canals. After inserting a G1 file twice, a G2 file was inserted to the working length 1, 4, 7, or 10 times for four each experimental group, respectively (n = 10). Then the canals were cleaned by copious irrigation, and lubricated with a separating gel medium. Canal replicas were made using silicone impression material, and the diameter of the replicas was measured at working length (D0) and 1 mm level (D1) under a scanning electron microscope. Data was analysed by one-way ANOVA and post-hoc tests (p = 0.05). Results The diameter at D0 level did not show any significant difference between the 1, 2, 4, and 10 times of repetitive pecking insertions of G2 files at working length. However, 10 times of pecking motion with G2 file resulted in significantly larger canal diameter at D1 (p < 0.05). Conclusions Under the limitations of this study, the repetitive insertion of a G2 file up to 10 times at working length created an adequate lumen for subsequent apical shaping with other rotary files bigger than International Organization for Standardization (ISO) size 20, without apical transportation at D0 level. PMID:25984473

  11. Visibility oscillation in a multimode laser interferometer signal and its use in optimizing path lengths.

    PubMed

    Ruden, E L; Camacho, J F; Lynn, A G

    2013-10-01

    The interference signal visibility V (difference to sum ratio of intensities at maximum and minimum interference) of an interferometer that uses a multimode laser is here derived for a given laser gain profile and spectral mode separation as a function of the difference Z(S) between the probe and reference beam optical path lengths and the spectral separation k(S) between the center of the laser gain profile and the nearest laser mode of higher frequency. k(S) has a significant effect on V for a given Z(S). This parameter, in lasers where it sweeps freely across the gain profile, and other effects, such as various misalignments and optical coupling inefficiencies, render V alone an unreliable parameter for quantifying Z(S) (for the purpose of reducing it, say). However, the difference to sum ratio of the maximum and minimum V due to variations in k(S) for a given Z(S) is an intrinsic property of the laser insensitive to configurational details. Parameter W so defined, therefore, proves very useful for balancing path lengths. This is of particular importance for systems where probe and/or reference beams are transmitted via long single mode optical fibers, so this application is detailed. Optical path lengths within such fibers often cannot be measured to sufficient accuracy by spatial path length measurements due to fiber nonuniformity resulting in variations in the mode's group velocity (needed to convert to optical path length). Two examples are provided using different makes and models of 0.633 μm HeNe lasers with similar specifications. In the first case, the function W(Z(S)) is calculated directly from the laser's published gain profile and mode separation. In the second case, W is determined empirically for a range of Z(S)values for a laser with an unknown gain profile in a (heterodyned) interferometer whose interference signal oscillates between maximum and minimum intensity at 80 MHz due to the reference beam's optical frequency being acousto

  12. Length Dependent Thermal Conductivity Measurements Yield Phonon Mean Free Path Spectra in Nanostructures

    PubMed Central

    Zhang, Hang; Hua, Chengyun; Ding, Ding; Minnich, Austin J.

    2015-01-01

    Thermal conductivity measurements over variable lengths on nanostructures such as nanowires provide important information about the mean free paths (MFPs) of the phonons responsible for heat conduction. However, nearly all of these measurements have been interpreted using an average MFP even though phonons in many crystals possess a broad MFP spectrum. Here, we present a reconstruction method to obtain MFP spectra of nanostructures from variable-length thermal conductivity measurements. Using this method, we investigate recently reported length-dependent thermal conductivity measurements on SiGe alloy nanowires and suspended graphene ribbons. We find that the recent measurements on graphene imply that 70% of the heat in graphene is carried by phonons with MFPs longer than 1 micron. PMID:25764977

  13. Optical path-length modulation for three-dimensional particle measurement in mirror-embedded microchannels.

    PubMed

    Choi, Sungyoung; Kim, Seung-Hoon; Park, Je-Kyun

    2010-02-07

    Simple and low-cost implementation of three-dimensional (3D) particle measurement is vital for designing and characterizing microfluidic devices that show spatiotemporally varying characteristics in three dimensions. However, the conventional 3D particle image velocimetry or particle streak velocimetry has proven difficult to address the needs, requiring complex and expensive equipment, precise alignment between optical components, and specialized image-processing algorithms. Here, we report mirror-embedded microchannels and a method of optical path-length (OPL) modulation for 3D particle measurement in the channels. The mirror, ideally at 45 degrees, reflects the side view of the channels and enables 3D positional information to be obtained easily from two different orthogonal-axis images with different optical paths. To offset the optical path difference between two image views, we utilized a cover glass as a medium of high refractive index and placed it in the light path through which the side-view image propagates, thereby prolonging the OPL of the side view and simultaneously shifting its depth of field (DOF) range. This modulation ensures imaging of in-focus side view as well as top view. This 3D imaging principle was verified by observing 3D positions of 6 mum-sized beads in the linear and grooved microchannels. The mirror-embedded scheme can be readily fabricated with existing microfluidic designs, and offer easy and simple implementation of 3D particle measurement.

  14. Determinants of daily path length in black and gold howler monkeys (Alouatta caraya) in northeastern Argentina.

    PubMed

    Raño, Mariana; Kowalewski, Martin M; Cerezo, Alexis M; Garber, Paul A

    2016-08-01

    Models used to explain the social organization of primates suggest that variation in daily path length (DPL) is a response to variation in resource distribution and the intensity of intragroup feeding competition. However, daily path length may be affected by a number of other factors including the availability and distribution of nutritionally complementary food items, temperature which can influence activity budget, patterns of subgrouping, and the frequency and function of intergroup encounters. In this 6-month study (total 495 hr of quantitative data), we examined daily path lengths in two neighboring groups of black and gold howler monkeys (Alouatta caraya) inhabiting a semi-deciduous gallery forest in San Cayetano (27° 30'S, 58° 41'W), in the northwest province of Corrientes, Argentina. Both study groups were of similar size and composition. We identified relationships across groups between time spent feeding on fruits, leaves, and flowers, the number of trees visited, group spread, frequency of intergroup encounters, mean daily temperature, and DPL. Our results suggest that variation in food availability had a significant impact on howler ranging behavior by increasing DPL under conditions of high immature and mature fruit availability, and by decreasing DPL with increased availability and increased time invested in feeding on mature leaves. These results do not support the contention that a reduction in food availability or an increase in within-group feeding competition increased DPL in black and gold howler monkeys. DPL in black and gold howlers is influenced by several interrelated factors. In this regard we suggest that models of socio-ecology and ecological constraints need to reconsider how factors such as individual nutritional requirements, social tolerance and group cohesion, and the spatial and temporal availability of preferred and nearby food resources influence primate ranging behavior. Am. J. Primatol. 78:825-837, 2016. © 2016 Wiley

  15. Evaluation of a multimode fiber optic low coherence interferometer for path length resolved Doppler measurements of diffuse light

    NASA Astrophysics Data System (ADS)

    Varghese, Babu; Rajan, Vinayakrishnan; Van Leeuwen, Ton G.; Steenbergen, Wiendelt

    2007-12-01

    The performance of a graded index multimode fiber optic low coherence Mach-Zehnder interferometer with phase modulation is analyzed. Investigated aspects were its ability to measure path length distributions and to perform path length resolved Doppler measurements of multiple scattered photons in a turbid suspension of particles undergoing Brownian and translational motion. The path length resolution of this instrument is compared with a system using single mode fibers for illumination and detection. The optical path lengths are determined from the zero order moment of the phase modulation peak in the power spectrum. The weighted first moment, which is equal to the average Doppler shift, shows a linear response for different mean flow velocities within the physiological range.

  16. Contact surface motion paths associated with leg length inequality following unilateral total hip replacement.

    PubMed

    Budenberg, Sarah; Redmond, Anthony; White, Derek; Grainger, Andrew; O'Connor, Philip; Stone, Martin H; Stewart, Todd D

    2012-12-01

    In the past, there has been little research into leg length inequality (LLI) and its effect on hip arthroplasty bearing longevity. This investigation aimed to determine the effects of post-operative LLI on hip motions during gait and to postulate the subsequent influence on the wear of the artificial hip joint replacement. Motion data from a clinical gait analysis were processed with an in-house computational model to plot graphs showing the movement of loci of 20 points on the femoral head during one gait cycle for two cohorts: 19 LLI patients and 38 normal healthy patients. Loci paths were quantified by calculating the aspect ratio (AR) of the path shape. It was found that on average, LLI patients had a reduction in flexion/extension and abduction/adduction. Furthermore, the AR of LLI patients was found to be 8% smaller than the normal group. The shorter, more multidirectional, motion paths in LLI patients would suggest the potential for greater wear in a polyethylene bearing compared to an asymptomatic, non-LLI patient. The results have potential implications towards preclinical wear testing of joint replacements.

  17. New method for path-length equalization of long single-mode fibers for interferometry

    NASA Astrophysics Data System (ADS)

    Anderson, M.; Monnier, J. D.; Ozdowy, K.; Woillez, J.; Perrin, G.

    2014-07-01

    The ability to use single mode (SM) fibers for beam transport in optical interferometry offers practical advantages over conventional long vacuum pipes. One challenge facing fiber transport is maintaining constant differential path length in an environment where environmental thermal variations can lead to cm-level variations from day to night. We have fabricated three composite cables of length 470 m, each containing 4 copper wires and 3 SM fibers that operate at the astronomical H band (1500-1800 nm). Multiple fibers allow us to test performance of a circular core fiber (SMF28), a panda-style polarization-maintaining (PM) fiber, and a lastly a specialty dispersion-compensated PM fiber. We will present experimental results using precision electrical resistance measurements of the of a composite cable beam transport system. We find that the application of 1200 W over a 470 m cable causes the optical path difference in air to change by 75 mm (+/- 2 mm) and the resistance to change from 5.36 to 5.50Ω. Additionally, we show control of the dispersion of 470 m of fiber in a single polarization using white light interference fringes (λc=1575 nm, Δλ=75 nm) using our method.

  18. A volumetric approach to path-length measurements is essential when treating radiotherapy with modulated beams

    SciTech Connect

    Forde, Elizabeth; Booth, Jeremy; Leech, Michelle

    2014-07-01

    The established dosimetric benefits of intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy have lead to their increased use in prostate radiotherapy. Complimenting these techniques, volumetric image guidance has supported increased positional accuracy. In addition, 3-dimensional image guidance has also allowed for assessment of potential dosimetric variation that can be attributed to a deformation of either internal or external structures, such as rectal distension or body contour. Compounding these issues is the variation of tissue density through which the new field position passes and also the variation of dose across a modulated beam. Despite the growing level of interest in this area, there are only a limited number of articles that examine the effect of a variation in beam path length, particularly across a modulated field. IMRT and volumetric-modulated radiation therapy (VMAT) fields are dynamic in nature, and the dose gradient within these fields is variable. Assessment of variation of path length away from the beam's central axis and across the entire field is vital where there is considerable variation of dose within the field, such as IMRT and VMAT. In these cases, reliance on the traditional central axis to focus skin distances is no longer appropriate. This article discusses these more subtle challenges that may have a significant clinical effect if left unrecognized and undervalued.

  19. Measurement of the optical path length difference in an interferometer using a sinusoidally frequency-modulated light source.

    PubMed

    Shimada, Shumpei; Shizuka, Makoto; Hayashi, Neisei; Mizuno, Yosuke; Nakamura, Kentaro

    2016-04-10

    We develop a technique for measuring the optical path length difference (OPLD) in an interferometer using a frequency-modulated light source. Compared with conventional methods, this technique offers a high sampling rate, high precision, and cost efficiency, and is capable of determining which of the two optical paths is longer. In addition, we show that this technique works properly even when the OPLD is significantly longer than the coherence length of the light source.

  20. Auto-elimination of fiber optical path-length drift in a frequency scanning interferometer for absolute distance measurements

    NASA Astrophysics Data System (ADS)

    Tao, Long; Liu, Zhigang; Zhang, Weibo

    2015-09-01

    Because of its compact size and portability, optical fiber has been wildly used as optical paths in frequency-scanning interferometers for high-precision absolute distance measurements. However, since the fiber is sensitive to ambient temperature, its length and refractive index change with temperature, resulting in an optical path length drift that influences the repeatability of measurements. To improve the thermal stability of the measurement system, a novel frequency-scanning interferometer composed of two Michelson-type interferometers sharing a common fiber optical path is proposed. One interferometer defined as origin interferometer is used to monitor the drift of the measurement origin due to the optical path length drift of the optical fiber under on-site environment. The other interferometer defined as measurement interferometer is used to measure the distance to the target. Because the optical path length drift of the fiber appears in both interferometers, its influence can be eliminated by subtracting the optical path difference of the origin interferometer from the optical path difference of the measurement interferometer. A prototype interferometer was developed in our research, and experimental results demonstrate its robustness and stability. Under on-site environment, an accuracy about 4 μm was achieved for a distance of about 1 m.

  1. Error Reduction Methods for Integrated-path Differential-absorption Lidar Measurements

    NASA Technical Reports Server (NTRS)

    Chen, Jeffrey R.; Numata, Kenji; Wu, Stewart T.

    2012-01-01

    We report new modeling and error reduction methods for differential-absorption optical-depth (DAOD) measurements of atmospheric constituents using direct-detection integrated-path differential-absorption lidars. Errors from laser frequency noise are quantified in terms of the line center fluctuation and spectral line shape of the laser pulses, revealing relationships verified experimentally. A significant DAOD bias is removed by introducing a correction factor. Errors from surface height and reflectance variations can be reduced to tolerable levels by incorporating altimetry knowledge and "log after averaging", or by pointing the laser and receiver to a fixed surface spot during each wavelength cycle to shorten the time of "averaging before log".

  2. Effect of fiber length of carbon nanotubes on the absorption of erythropoietin from rat small intestine.

    PubMed

    Ito, Yukako; Venkatesan, Natarajan; Hirako, Noriko; Sugioka, Nobuyuki; Takada, Kanji

    2007-06-07

    Erythropoietin (EPO) loaded carbon nanotubes (CNTs) with surfactant as an absorption enhancer were prepared for the oral delivery of EPO using two types of CNTs, long and short fiber length CNTs, and the effect of CNT fiber length on the absorption efficiency of EPO was studied. After Labrasol, PEG-8 caprylic/capric glycerides, as absorption enhancer was adsorbed into long fiber CNTs of which mean fiber length was 20-80 microm, as a carrier, EPO and casein as protease inhibitor and Explotab (sodium starch glycolate) as a disintegrating agent, were mixed. The resulting solid preparation was administered into the rat jejunum and serum EPO levels were measured by ELISA. The dose of EPO, CNTs, casein and Explotab were 100 IU/kg, 5mg/kg, 25mg/kg and 2.5mg/kg, respectively. Serum EPO level reached to C(max), 69.0+/-3.9 mIU/ml, at 3.5+/-0.1h and AUC was 175.7+/-13.8 mIU h/ml. These values were approximately half of that obtained with short fiber length CNTs of which C(max) was 143.1+/-15.2 mIU/ml and AUC was 256.3+/-9.7 mIU h/ml. When amphoteric surfactant, Lipomin LA, sodium beta-alkylaminopropionic acid, was used to accelerate the disaggregation of long fiber length CNTs, C(max) was 36.0+/-4.9 and AUC was 96.9+/-11.9, which showed less bioavailability (BA) of EPO. These results suggest that the short fiber length CNTs deliver more both EPO and absorption enhancer to the absorptive cells of the rat small intestine and the aggregation of CNTs is not the critical factor for the oral delivery of EPO.

  3. A 2-Micron Pulsed Integrated Path Differential Absorption Lidar Development For Atmospheric CO2 Concentration Measurements

    NASA Technical Reports Server (NTRS)

    Yu, Jirong; Petros, Mulugeta; Reithmaier, Karl; Bai, Yingxin; Trieu, Bo C.; Refaat, Tamer F.; Kavaya, Michael J.; Singh, Upendra N.

    2012-01-01

    A 2-micron pulsed, Integrated Path Differential Absorption (IPDA) lidar instrument for ground and airborne atmospheric CO2 concentration measurements via direct detection method is being developed at NASA Langley Research Center. This instrument will provide an alternate approach to measure atmospheric CO2 concentrations with significant advantages. A high energy pulsed approach provides high-precision measurement capability by having high signal-to-noise level and unambiguously eliminates the contamination from aerosols and clouds that can bias the IPDA measurement.

  4. Calculated slant-path absorption and distribution of atmospheric water vapor.

    PubMed

    Calfee, R F; Gates, D M

    1966-02-01

    A procedure is described for determining the amount and distribution of water vapor along a slant path through the atmosphere above 13.7 km. A multilayer analysis is used in which the transmittance of each layer is calculated and the accumulative effect obtained at the altitude of observation. The method depends upon the contribution of each line to the absorptance in a finite spectral region.

  5. Monitoring of atmospheric nitrogen dioxide by long-path pulsed differential optical absorption spectroscopy using two different light paths.

    PubMed

    Kambe, Yasuaki; Yoshii, Yotsumi; Takahashi, Kenshi; Tonokura, Kenichi

    2012-03-01

    Measurements of the local distribution of atmospheric nitrogen dioxide (NO(2)) by long-path pulsed differential optical absorption spectroscopy (LP-PDOAS) in Tokyo during August 2008 are presented. Two LP-PDOAS systems simultaneously measured average NO(2) temporal mixing ratios along two different paths from a single observation point. Two flashing aviation obstruction lights, located 7.0 km north and 6.3 km east from the observation point, were used as light sources, allowing spatiotemporal variations of NO(2) in Tokyo to be inferred. The LP-PDOAS data were compared with ground-based data measured using chemiluminescence. Surface wind data indicated that large inhomogeneities were present in the spatial NO(2) distributions under southerly wind conditions, while northerly wind conditions displayed greater homogeneity between the two systems. The higher correlation in the NO(2) mixing ratio between the two LP-PDOAS systems was observed under northerly wind conditions with a correlation factor R(2) = 0.88. We demonstrated that the combined deployment of two LP-PDOAS systems oriented in different directions provides detailed information on the spatial distribution of NO(2).

  6. DIC image reconstruction using an energy minimization framework to visualize optical path length distribution.

    PubMed

    Koos, Krisztian; Molnár, József; Kelemen, Lóránd; Tamás, Gábor; Horvath, Peter

    2016-07-25

    Label-free microscopy techniques have numerous advantages such as low phototoxicity, simple setup and no need for fluorophores or other contrast materials. Despite their advantages, most label-free techniques cannot visualize specific cellular compartments or the location of proteins and the image formation limits quantitative evaluation. Differential interference contrast (DIC) is a qualitative microscopy technique that shows the optical path length differences within a specimen. We propose a variational framework for DIC image reconstruction. The proposed method largely outperforms state-of-the-art methods on synthetic, artificial and real tests and turns DIC microscopy into an automated high-content imaging tool. Image sets and the source code of the examined algorithms are made publicly available.

  7. Computationally efficient gradient matrix of optical path length in axisymmetric optical systems.

    PubMed

    Hsueh, Chun-Che; Lin, Psang-Dain

    2009-02-10

    We develop a mathematical method for determining the optical path length (OPL) gradient matrix relative to all the system variables such that the effects of variable changes can be evaluated in a single pass. The approach developed avoids the requirement for multiple ray-tracing operations and is, therefore, more computationally efficient. By contrast, the effects of variable changes on the OPL of an optical system are generally evaluated by utilizing a ray-tracing approach to determine the OPL before and after the variable change and then applying a finite-difference (FD) approximation method to estimate the OPL gradient with respect to each individual variable. Utilizing a Petzval lens system for verification purposes, it is shown that the approach developed reduces the computational time by around 90% compared to that of the FD method.

  8. Beam splitter and method for generating equal optical path length beams

    DOEpatents

    Qian, Shinan; Takacs, Peter

    2003-08-26

    The present invention is a beam splitter for splitting an incident beam into first and second beams so that the first and second beams have a fixed separation and are parallel upon exiting. The beam splitter includes a first prism, a second prism, and a film located between the prisms. The first prism is defined by a first thickness and a first perimeter which has a first major base. The second prism is defined by a second thickness and a second perimeter which has a second major base. The film is located between the first major base and the second major base for splitting the incident beam into the first and second beams. The first and second perimeters are right angle trapezoidal shaped. The beam splitter is configured for generating equal optical path length beams.

  9. Determining average path length and average trapping time on generalized dual dendrimer

    NASA Astrophysics Data System (ADS)

    Li, Ling; Guan, Jihong

    2015-03-01

    Dendrimer has wide number of important applications in various fields. In some cases during transport or diffusion process, it transforms into its dual structure named Husimi cactus. In this paper, we study the structure properties and trapping problem on a family of generalized dual dendrimer with arbitrary coordination numbers. We first calculate exactly the average path length (APL) of the networks. The APL increases logarithmically with the network size, indicating that the networks exhibit a small-world effect. Then we determine the average trapping time (ATT) of the trapping process in two cases, i.e., the trap placed on a central node and the trap is uniformly distributed in all the nodes of the network. In both case, we obtain explicit solutions of ATT and show how they vary with the networks size. Besides, we also discuss the influence of the coordination number on trapping efficiency.

  10. DIC image reconstruction using an energy minimization framework to visualize optical path length distribution

    PubMed Central

    Koos, Krisztian; Molnár, József; Kelemen, Lóránd; Tamás, Gábor; Horvath, Peter

    2016-01-01

    Label-free microscopy techniques have numerous advantages such as low phototoxicity, simple setup and no need for fluorophores or other contrast materials. Despite their advantages, most label-free techniques cannot visualize specific cellular compartments or the location of proteins and the image formation limits quantitative evaluation. Differential interference contrast (DIC) is a qualitative microscopy technique that shows the optical path length differences within a specimen. We propose a variational framework for DIC image reconstruction. The proposed method largely outperforms state-of-the-art methods on synthetic, artificial and real tests and turns DIC microscopy into an automated high-content imaging tool. Image sets and the source code of the examined algorithms are made publicly available. PMID:27453091

  11. Interferometer with Continuously Varying Path Length Measured in Wavelengths to the Reference Mirror

    NASA Technical Reports Server (NTRS)

    Ohara, Tetsuo (Inventor)

    2016-01-01

    An interferometer in which the path length of the reference beam, measured in wavelengths, is continuously changing in sinusoidal fashion and the interference signal created by combining the measurement beam and the reference beam is processed in real time to obtain the physical distance along the measurement beam between the measured surface and a spatial reference frame such as the beam splitter. The processing involves analyzing the Fourier series of the intensity signal at one or more optical detectors in real time and using the time-domain multi-frequency harmonic signals to extract the phase information independently at each pixel position of one or more optical detectors and converting the phase information to distance information.

  12. Correlations between psychometric schizotypy, scan path length, fixations on the eyes and face recognition.

    PubMed

    Hills, Peter J; Eaton, Elizabeth; Pake, J Michael

    2016-01-01

    Psychometric schizotypy in the general population correlates negatively with face recognition accuracy, potentially due to deficits in inhibition, social withdrawal, or eye-movement abnormalities. We report an eye-tracking face recognition study in which participants were required to match one of two faces (target and distractor) to a cue face presented immediately before. All faces could be presented with or without paraphernalia (e.g., hats, glasses, facial hair). Results showed that paraphernalia distracted participants, and that the most distracting condition was when the cue and the distractor face had paraphernalia but the target face did not, while there was no correlation between distractibility and participants' scores on the Schizotypal Personality Questionnaire (SPQ). Schizotypy was negatively correlated with proportion of time fixating on the eyes and positively correlated with not fixating on a feature. It was negatively correlated with scan path length and this variable correlated with face recognition accuracy. These results are interpreted as schizotypal traits being associated with a restricted scan path leading to face recognition deficits.

  13. Multispectral reflectance imaging of brain activation in rodents: methodological study of the differential path length estimations and first in vivo recordings in the rat olfactory bulb

    NASA Astrophysics Data System (ADS)

    Renaud, Rémi; Martin, Claire; Gurden, Hirac; Pain, Frédéric

    2012-01-01

    Dynamic maps of relative changes in blood volume and oxygenation following brain activation are obtained using multispectral reflectance imaging. The technique relies on optical absorption modifications linked to hemodynamic changes. The relative variation of hemodynamic parameters can be quantified using the modified Beer-Lambert Law if changes in reflected light intensities are recorded at two wavelengths or more and the differential path length (DP) is known. The DP is the mean path length in tissues of backscattered photons and varies with wavelength. It is usually estimated using Monte Carlo simulations in simplified semi-infinite homogeneous geometries. Here we consider the use of multilayered models of the somatosensory cortex (SsC) and olfactory bulb (OB), which are common physiological models of brain activation. Simulations demonstrate that specific DP estimation is required for SsC and OB, specifically for wavelengths above 600 nm. They validate the hypothesis of a constant path length during activation and show the need for specific DP if imaging is performed in a thinned-skull preparation. The first multispectral reflectance imaging data recorded in vivo during OB activation are presented, and the influence of DP on the hemodynamic parameters and the pattern of oxymetric changes in the activated OB are discussed.

  14. The distribution of path lengths of self avoiding walks on Erdős-Rényi networks

    NASA Astrophysics Data System (ADS)

    Tishby, Ido; Biham, Ofer; Katzav, Eytan

    2016-07-01

    We present an analytical and numerical study of the paths of self avoiding walks (SAWs) on random networks. Since these walks do not retrace their paths, they effectively delete the nodes they visit, together with their links, thus pruning the network. The walkers hop between neighboring nodes, until they reach a dead-end node from which they cannot proceed. Focusing on Erdős-Rényi networks we show that the pruned networks maintain a Poisson degree distribution, {p}t(k), with an average degree, < k{> }t, that decreases linearly in time. We enumerate the SAW paths of any given length and find that the number of paths, {n}T({\\ell }), increases dramatically as a function of {\\ell }. We also obtain analytical results for the path-length distribution, P({\\ell }), of the SAW paths which are actually pursued, starting from a random initial node. It turns out that P({\\ell }) follows the Gompertz distribution, which means that the termination probability of an SAW path increases with its length.

  15. Airborne Measurements of CO2 Column Absorption and Range Using a Pulsed Direct-Detection Integrated Path Differential Absorption Lidar

    NASA Technical Reports Server (NTRS)

    Abshire, James B.; Riris, Haris; Weaver, Clark J.; Mao, Jianping; Allan, Graham R.; Hasselbrack, William E.; Browell, Edward V.

    2013-01-01

    We report on airborne CO2 column absorption measurements made in 2009 with a pulsed direct-detection lidar operating at 1572.33 nm and utilizing the integrated path differential absorption technique. We demonstrated these at different altitudes from an aircraft in July and August in flights over four locations in the central and eastern United States. The results show clear CO2 line shape and absorption signals, which follow the expected changes with aircraft altitude from 3 to 13 km. The lidar measurement statistics were also calculated for each flight as a function of altitude. The optical depth varied nearly linearly with altitude, consistent with calculations based on atmospheric models. The scatter in the optical depth measurements varied with aircraft altitude as expected, and the median measurement precisions for the column varied from 0.9 to 1.2 ppm. The altitude range with the lowest scatter was 810 km, and the majority of measurements for the column within it had precisions between 0.2 and 0.9 ppm.

  16. NO2 measurements in Hong Kong using LED based long path differential optical absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Chan, K. L.; Pöhler, D.; Kuhlmann, G.; Hartl, A.; Platt, U.; Wenig, M. O.

    2012-05-01

    In this study we present the first long term measurements of atmospheric nitrogen dioxide (NO2) using a LED based Long Path Differential Optical Absorption Spectroscopy (LP-DOAS) instrument. This instrument is measuring continuously in Hong Kong since December 2009, first in a setup with a 550 m absorption path and then with a 3820 m path at about 30 m to 50 m above street level. The instrument is using a high power blue light LED with peak intensity at 450 nm coupled into the telescope using a Y-fibre bundle. The LP-DOAS instrument measures NO2 levels in the Kowloon Tong and Mongkok district of Hong Kong and we compare the measurement results to mixing ratios reported by monitoring stations operated by the Hong Kong Environmental Protection Department in that area. Hourly averages of coinciding measurements are in reasonable agreement (R = 0.74). Furthermore, we used the long-term data set to validate the Ozone Monitoring Instrument (OMI) NO2 data product. Monthly averaged LP-DOAS and OMI measurements correlate well (R = 0.84) when comparing the data for the OMI overpass time. We analyzed weekly patterns in both data sets and found that the LP-DOAS detects a clear weekly cycle with a reduction on weekends during rush hour peaks, whereas OMI is not able to observe this weekly cycle due to its fix overpass time (13:30-14:30 LT - local time).

  17. Finding the biased-shortest path with minimal congestion in networks via linear-prediction of queue length

    NASA Astrophysics Data System (ADS)

    Shen, Yi; Ren, Gang; Liu, Yang

    2016-06-01

    In this paper, we propose a biased-shortest path method with minimal congestion. In the method, we use linear-prediction to estimate the queue length of nodes, and propose a dynamic accepting probability function for nodes to decide whether accept or reject the incoming packets. The dynamic accepting probability function is based on the idea of homogeneous network flow and is developed to enable nodes to coordinate their queue length to avoid congestion. A path strategy incorporated with the linear-prediction of the queue length and the dynamic accepting probability function of nodes is designed to allow packets to be automatically delivered on un-congested paths with short traveling time. Our method has the advantage of low computation cost because the optimal paths are dynamically self-organized by nodes in the delivering process of packets with local traffic information. We compare our method with the existing methods such as the efficient path method (EPS) and the optimal path method (OPS) on the BA scale-free networks and a real example. The numerical computations show that our method performs best for low network load and has minimum run time due to its low computational cost and local routing scheme.

  18. Minority carrier diffusion lengths and absorption coefficients in silicon sheet material

    NASA Technical Reports Server (NTRS)

    Dumas, K. A.; Swimm, R. T.

    1980-01-01

    Most of the methods which have been developed for the measurement of the minority carrier diffusion length of silicon wafers require that the material have either a Schottky or an ohmic contact. The surface photovoltage (SPV) technique is an exception. The SPV technique could, therefore, become a valuable diagnostic tool in connection with current efforts to develop low-cost processes for the production of solar cells. The technique depends on a knowledge of the optical absorption coefficient. The considered investigation is concerned with a reevaluation of the absorption coefficient as a function of silicon processing. A comparison of absorption coefficient values showed these values to be relatively consistent from sample to sample, and independent of the sample growth method.

  19. Mapping optical path length and image enhancement using quantitative orientation-independent differential interference contrast microscopy

    NASA Astrophysics Data System (ADS)

    Shribak, Michael; Larkin, Kieran G.; Biggs, David

    2017-01-01

    We describe the principles of using orientation-independent differential interference contrast (OI-DIC) microscopy for mapping optical path length (OPL). Computation of the scalar two-dimensional OPL map is based on an experimentally received map of the OPL gradient vector field. Two methods of contrast enhancement for the OPL image, which reveal hardly visible structures and organelles, are presented. The results obtained can be used for reconstruction of a volume image. We have confirmed that a standard research grade light microscope equipped with the OI-DIC and 100×/1.3 NA objective lens, which was not specially selected for minimum wavefront and polarization aberrations, provides OPL noise level of ˜0.5 nm and lateral resolution if ˜300 nm at a wavelength of 546 nm. The new technology is the next step in the development of the DIC microscopy. It can replace standard DIC prisms on existing commercial microscope systems without modification. This will allow biological researchers that already have microscopy setups to expand the performance of their systems.

  20. Continuous correction of differential path length factor in near-infrared spectroscopy

    PubMed Central

    Moore, Jason H.; Diamond, Solomon G.

    2013-01-01

    Abstract. In continuous-wave near-infrared spectroscopy (CW-NIRS), changes in the concentration of oxyhemoglobin and deoxyhemoglobin can be calculated by solving a set of linear equations from the modified Beer-Lambert Law. Cross-talk error in the calculated hemodynamics can arise from inaccurate knowledge of the wavelength-dependent differential path length factor (DPF). We apply the extended Kalman filter (EKF) with a dynamical systems model to calculate relative concentration changes in oxy- and deoxyhemoglobin while simultaneously estimating relative changes in DPF. Results from simulated and experimental CW-NIRS data are compared with results from a weighted least squares (WLSQ) method. The EKF method was found to effectively correct for artificially introduced errors in DPF and to reduce the cross-talk error in simulation. With experimental CW-NIRS data, the hemodynamic estimates from EKF differ significantly from the WLSQ (p<0.001). The cross-correlations among residuals at different wavelengths were found to be significantly reduced by the EKF method compared to WLSQ in three physiologically relevant spectral bands 0.04 to 0.15 Hz, 0.15 to 0.4 Hz and 0.4 to 2.0 Hz (p<0.001). This observed reduction in residual cross-correlation is consistent with reduced cross-talk error in the hemodynamic estimates from the proposed EKF method. PMID:23640027

  1. The enigma of effective path length for (18) O enrichment in leaf water of conifers.

    PubMed

    Roden, John; Kahmen, Ansgar; Buchmann, Nina; Siegwolf, Rolf

    2015-12-01

    The Péclet correction is often used to predict leaf evaporative enrichment and requires an estimate of effective path length (L). Studies to estimate L in conifer needles have produced unexpected patterns based on Péclet theory and leaf anatomy. We exposed seedlings of six conifer species to different vapour pressure deficits (VPD) in controlled climate chambers to produce steady-state leaf water enrichment (in (18) O). We measured leaf gas exchange, stable oxygen isotopic composition (δ(18) O) of input and plant waters as well as leaf anatomical characteristics. Variation in bulk needle water δ(18) O was strongly related to VPD. Conifer needles had large amounts of water within the vascular strand that was potentially unenriched (up to 40%). Both standard Craig-Gordon and Péclet models failed to accurately predict conifer leaf water δ(18) O without taking into consideration the unenriched water in the vascular strand and variable L. Although L was linearly related to mesophyll thickness, large within-species variation prevented the development of generalizations that could allow a broader use of the Péclet effect in predictive models. Our results point to the importance of within needle water pools and isolating mechanisms that need further investigation in order to integrate Péclet corrections with 'two compartment' leaf water concepts.

  2. Continuous correction of differential path length factor in near-infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Talukdar, Tanveer; Moore, Jason H.; Diamond, Solomon G.

    2013-05-01

    In continuous-wave near-infrared spectroscopy (CW-NIRS), changes in the concentration of oxyhemoglobin and deoxyhemoglobin can be calculated by solving a set of linear equations from the modified Beer-Lambert Law. Cross-talk error in the calculated hemodynamics can arise from inaccurate knowledge of the wavelength-dependent differential path length factor (DPF). We apply the extended Kalman filter (EKF) with a dynamical systems model to calculate relative concentration changes in oxy- and deoxyhemoglobin while simultaneously estimating relative changes in DPF. Results from simulated and experimental CW-NIRS data are compared with results from a weighted least squares (WLSQ) method. The EKF method was found to effectively correct for artificially introduced errors in DPF and to reduce the cross-talk error in simulation. With experimental CW-NIRS data, the hemodynamic estimates from EKF differ significantly from the WLSQ (p<0.001). The cross-correlations among residuals at different wavelengths were found to be significantly reduced by the EKF method compared to WLSQ in three physiologically relevant spectral bands 0.04 to 0.15 Hz, 0.15 to 0.4 Hz and 0.4 to 2.0 Hz (p<0.001). This observed reduction in residual cross-correlation is consistent with reduced cross-talk error in the hemodynamic estimates from the proposed EKF method.

  3. Simultaneous water vapor and dry air optical path length measurements and compensation with the large binocular telescope interferometer

    NASA Astrophysics Data System (ADS)

    Defrère, D.; Hinz, P.; Downey, E.; Böhm, M.; Danchi, W. C.; Durney, O.; Ertel, S.; Hill, J. M.; Hoffmann, W. F.; Mennesson, B.; Millan-Gabet, R.; Montoya, M.; Pott, J.-U.; Skemer, A.; Spalding, E.; Stone, J.; Vaz, A.

    2016-08-01

    The Large Binocular Telescope Interferometer uses a near-infrared camera to measure the optical path length variations between the two AO-corrected apertures and provide high-angular resolution observations for all its science channels (1.5-13 microns). There is however a wavelength dependent component to the atmospheric turbulence, which can introduce optical path length errors when observing at a wavelength different from that of the fringe sensing camera. Water vapor in particular is highly dispersive and its effect must be taken into account for high-precision infrared interferometric observations as described previously for VLTI/MIDI or the Keck Interferometer Nuller. In this paper, we describe the new sensing approach that has been developed at the LBT to measure and monitor the optical path length fluctuations due to dry air and water vapor separately. After reviewing the current performance of the system for dry air seeing compensation, we present simultaneous H-, K-, and N-band observations that illustrate the feasibility of our feedforward approach to stabilize the path length fluctuations seen by the LBTI nuller.

  4. A Multi-Baseline 12 GHz Atmospheric Phase Interferometer with One Micron Path Length Sensitivity

    NASA Astrophysics Data System (ADS)

    Kimberk, Robert S.; Hunter, Todd R.; Leiker, Patrick S.; Blundell, Raymond; Nystrom, George U.; Petitpas, Glen R.; Test, John; Wilson, Robert W.; Yamaguchi, Paul; Young, Kenneth H.

    2012-12-01

    We have constructed a five station 12 GHz atmospheric phase interferometer (API) for the Submillimeter Array (SMA) located near the summit of Mauna Kea, Hawaii. Operating at the base of unoccupied SMA antenna pads, each station employs a commercial low noise mixing block coupled to a 0.7 m off-axis satellite dish which receives a broadband, white noise-like signal from a geostationary satellite. The signals are processed by an analog correlator to produce the phase delays between all pairs of stations with projected baselines ranging from 33-261 m. Each baseline's amplitude and phase is measured continuously at a rate of 8 kHz, processed, averaged and output at 10 Hz. Further signal processing and data reduction is accomplished with a Linux computer, including the removal of the diurnal motion of the target satellite. The placement of the stations below ground level with an environmental shield combined with the use of low temperature coefficient, buried fiber optic cables provides excellent system stability. The sensitivity in terms of rms path length is 1.3 microns which corresponds to phase deviations of about 1° of phase at the highest operating frequency of the SMA. The two primary data products are: (1) standard deviations of observed phase over various time scales, and (2) phase structure functions. These real-time statistical data measured by the API in the direction of the satellite provide an estimate of the phase front distortion experienced by the concurrent SMA astronomical observations. The API data also play an important role, along with the local opacity measurements and weather predictions, in helping to plan the scheduling of science observations on the telescope.

  5. Temperature dependences of optical path length in fluorine-doped silica glass and bismuthate glass

    NASA Astrophysics Data System (ADS)

    Koike, Akio; Sugimoto, Naoki

    2006-02-01

    Temperature dependences of optical path length (dS/dT; calculated using the equation, dS/dT = dn/dT + na, where a is coefficient of thermal expansion, n is refractive index and dn/dT is temperature coefficient of refractive index) in various oxide glasses were investigated. The dS/dT is generally difficult to adjust by change of glass composition because dn/dT and a are interrelated. However, low dS/dT materials are desired for optical applications such as athermal devices, and high dS/dT materials can be used for thermo-optic devices. Pure silica glass is well-known as a typical low dS/dT material but still not sufficient. Fluorine-doped silica glass showed a lower dS/dT than that of pure silica glass. By fluorine-doping in silica glass, refractive index and dn/dT decreased but a near room temperature stayed at the same level. As a result, the dS/dT decreased with increasing fluorine concentration. On the other hand, bismuthate glass showed the highest dS/dT in this study. Most glasses having high a such as tellurite glass showed negative dn/dT. However, bismuthate glasses showed positive dn/dT in spite of high a. As a result, bismuthate glasses showed quite high dS/dT. These results indicate that dS/dT of the glass can be controllable and that fluorine doped silica glass and bismuthate glass are appropriate candidate materials for optical applications.

  6. Efficient computation of the angularly resolved chord length distributions and lineal path functions in large microstructure datasets

    NASA Astrophysics Data System (ADS)

    Turner, David M.; Niezgoda, Stephen R.; Kalidindi, Surya R.

    2016-10-01

    Chord length distributions (CLDs) and lineal path functions (LPFs) have been successfully utilized in prior literature as measures of the size and shape distributions of the important microscale constituents in the material system. Typically, these functions are parameterized only by line lengths, and thus calculated and derived independent of the angular orientation of the chord or line segment. We describe in this paper computationally efficient methods for estimating chord length distributions and lineal path functions for 2D (two dimensional) and 3D microstructure images defined on any number of arbitrary chord orientations. These so called fully angularly resolved distributions can be computed for over 1000 orientations on large microstructure images (5003 voxels) in minutes on modest hardware. We present these methods as new tools for characterizing microstructures in a statistically meaningful way.

  7. [Open-path online monitoring of ambient atmospheric CO2 based on laser absorption spectrum].

    PubMed

    He, Ying; Zhang, Yu-Jun; Kan, Rui-Feng; Xia, Hui; Geng, Hui; Ruan, Jun; Wang, Min; Cui, Xiao-Juan; Liu, Wen-Qing

    2009-01-01

    With the conjunction of tunable diode laser absorption spectroscopy technology (TDLAS) and the open long optical path technology, the system designing scheme of CO2 on-line monitoring based on near infrared tunable diode laser absorption spectroscopy technology was discussed in detail, and the instrument for large-range measurement was set up. By choosing the infrared absorption line of CO2 at 1.57 microm whose line strength is strong and suitable for measurement, the ambient atmospheric CO2 was measured continuously with a 30 s temporal resolution at an suburb site in the autumn of 2007. The diurnal atmospheric variations of CO2 and continuous monitoring results were presented. The results show that the variation in CO2 concentration has an obvious diurnal periodicity in suburb where the air is free of interference and contamination. The general characteristic of diurnal variation is that the concentration is low in the daytime and high at night, so it matches the photosynthesis trend. The instrument can detect gas concentration online with high resolution, high sensitivity, high precision, short response time and many other advantages, the monitoring requires no gas sampling, the calibration is easy, and the detection limit is about 4.2 x 10(-7). It has been proved that the system and measurement project are feasible, so it is an effective method for gas flux continuous online monitoring of large range in ecosystem based on TDLAS technology.

  8. Development of a Pulsed 2-Micron Integrated Path Differential Absorption Lidar for CO2 Measurement

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta; Refaat, Tamer; Refaat, Tamer

    2013-01-01

    Atmospheric carbon dioxide (CO2) is an important greenhouse gas that significantly contributes to the carbon cycle and global radiation budget on Earth. Active remote sensing of CO2 is important to address several limitations that contend with passive sensors. A 2-micron double-pulsed, Integrated Path Differential Absorption (IPDA) lidar instrument for ground and airborne atmospheric CO2 concentration measurements via direct detection method is being developed at NASA Langley Research Center. This active remote sensing instrument will provide an alternate approach of measuring atmospheric CO2 concentrations with significant advantages. A high energy pulsed approach provides high-precision measurement capability by having high signal-to-noise ratio level and unambiguously eliminates the contamination from aerosols and clouds that can bias the IPDA measurement. Commercial, on the shelf, components are implemented for the detection system. Instrument integration will be presented in this paper as well as a background for CO2 measurement at NASA Langley research Center

  9. Development of a pulsed 2-micron integrated path differential absorption lidar for CO2 measurement

    NASA Astrophysics Data System (ADS)

    Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta; Refaat, Tamer; Reithmaier, Karl

    2013-09-01

    Atmospheric carbon dioxide (CO2) is an important greenhouse gas that significantly contributes to the carbon cycle and global radiation budget on Earth. Active remote sensing of CO2 is important to address several limitations that contend with passive sensors. A 2-micron double-pulsed, Integrated Path Differential Absorption (IPDA) lidar instrument for ground and airborne atmospheric CO2 concentration measurements via direct detection method is being developed at NASA Langley Research Center. This active remote sensing instrument will provide an alternate approach of measuring atmospheric CO2 concentrations with significant advantages. A high energy pulsed approach provides high-precision measurement capability by having high signal-to-noise ratio level and unambiguously eliminates the contamination from aerosols and clouds that can bias the IPDA measurement. Commercial, on the shelf, components are implemented for the detection system. Instrument integration will be presented in this paper as well as a background for CO2 measurement at NASA Langley research Center.

  10. Development of a portable active long-path differential optical absorption spectroscopy system for volcanic gas measurements

    USGS Publications Warehouse

    Vita, Fabio; Kern, Christoph; Inguaggiato, Salvatore

    2014-01-01

    Active long-path differential optical absorption spectroscopy (LP-DOAS) has been an effective tool for measuring atmospheric trace gases for several decades. However, instruments were large, heavy and power-inefficient, making their application to remote environments extremely challenging. Recent developments in fibre-coupling telescope technology and the availability of ultraviolet light emitting diodes (UV-LEDS) have now allowed us to design and construct a lightweight, portable, low-power LP-DOAS instrument for use at remote locations and specifically for measuring degassing from active volcanic systems. The LP-DOAS was used to measure sulfur dioxide (SO2) emissions from La Fossa crater, Vulcano, Italy, where column densities of up to 1.2 × 1018 molec cm−2 (~ 500 ppmm) were detected along open paths of up to 400 m in total length. The instrument's SO2 detection limit was determined to be 2 × 1016 molec cm−2 (~ 8 ppmm), thereby making quantitative detection of even trace amounts of SO2 possible. The instrument is capable of measuring other volcanic volatile species as well. Though the spectral evaluation of the recorded data showed that chlorine monoxide (ClO) and carbon disulfide (CS2) were both below the instrument's detection limits during the experiment, the upper limits for the X / SO2 ratio (X = ClO, CS2) could be derived, and yielded 2 × 10−3 and 0.1, respectively. The robust design and versatility of the instrument make it a promising tool for monitoring of volcanic degassing and understanding processes in a range of volcanic systems.

  11. Experimental validation of Monte Carlo and finite-element methods for the estimation of the optical path length in inhomogeneous tissue

    NASA Astrophysics Data System (ADS)

    Okada, Eiji; Schweiger, Martin; Arridge, Simon R.; Firbank, Michael; Delpy, David T.

    1996-07-01

    To validate models of light propagation in biological tissue, experiments to measure the mean time of flight have been carried out on several solid cylindrical layered phantoms. The optical properties of the inner cylinders of the phantoms were close to those of adult brain white matter, whereas a range of scattering or absorption coefficients was chosen for the outer layer. Experimental results for the mean optical path length have been compared with the predictions of both an exact Monte Carlo (MC) model and a diffusion equation, with two differing boundary conditions implemented in a finite-element method (FEM). The MC and experimental results are in good agreement despite poor statistics for large fiber spacings, whereas good agreement with the FEM prediction requires a careful choice of proper boundary conditions. measurement, Monte Carlo method, finite-element method.

  12. Optimal symmetric networks in terms of minimizing average shortest path length and their sub-optimal growth model

    NASA Astrophysics Data System (ADS)

    Xuan, Qi; Li, Yanjun; Wu, Tie-Jun

    2009-04-01

    Homogeneous entangled networks characterized by small world, large girths, and no community structure have attracted much attention due to some of their favorable performances. However, the optimization algorithm proposed by Donetti et al. is very time-consuming and will lose its efficiency when the size of the target network becomes large. In this paper, an alternative optimization algorithm is provided to get optimal symmetric networks by minimizing the average shortest path length. It is shown that the synchronizability of a symmetric network is enhanced when the average shortest path length of the network is shortened as the optimization proceeds, which suggests that the optimal symmetric networks in terms of minimizing average shortest path length will be very close to those entangled networks. In order to overcome the time-consuming obstacle of the optimization algorithms proposed by us and Donetti et al., a growth model is proposed to get large scale sub-optimal symmetric networks. Numerical simulations show that the symmetric networks derived by our growth model will have small-world property, and besides, these networks will have many other similar favorable performances as entangled networks, e.g., robustness against errors and attacks, very good load balancing ability, and strong synchronizability.

  13. Path length tunable light-matter interaction in magnetic nanofluid based field-induced photonic crystal-glass structure

    NASA Astrophysics Data System (ADS)

    Laskar, Junaid M.; Raj, Baldev; Philip, John

    2016-10-01

    The ability to control the light-matter interaction and the simultaneous tuning of both the structural order and disorder in materials, although important in photonics, remain major challenges. In this paper, we demonstrate that path length dictates light-matter interaction for the same crystal structure, formed by the ordering of magnetic nanoparticle self-assembled columns inside magnetic nanofluid under applied field. When the path length is shorter (L=80 μ {{m}}), the condition for maintaining temporal coherence for the constructive interference is therefore satisfied, resulting in the formation of a concentric diffraction ring pattern; while for a longer path length (L=1 {{mm}}), only a corona ring of scattered light is observed. Analysis of diffraction ring pattern suggests the formation of 3D hexagonal crystal structure, where the longitudinal and lateral inter-column spacings are 5.281 μm and 7.344 μm, respectively. Observation of speckles and diffuse scattering background within the diffraction ring pattern confirms the presence of certain degree of crystal disorder, which can be tuned by controlling the applied field strength, nanoparticle size and particle volume fraction. Our results provide a new approach to develop next generation of tunable photonic devices, e.g. tunable random laser, based on simultaneous harnessing of the properties of disordered photonic glass and 3D photonic crystal.

  14. Enhancing light absorption within the carrier transport length in quantum junction solar cells.

    PubMed

    Fu, Yulan; Hara, Yukihiro; Miller, Christopher W; Lopez, Rene

    2015-09-10

    Colloidal quantum dot (CQD) solar cells have attracted tremendous attention because of their tunable absorption spectrum window and potentially low processing cost. Recently reported quantum junction solar cells represent a promising approach to building a rectifying photovoltaic device that employs CQD layers on each side of the p-n junction. However, the ultimate efficiency of CQD solar cells is still highly limited by their high trap state density in both p- and n-type CQDs. By modeling photonic structures to enhance the light absorption within the carrier transport length and by ensuring that the carrier generation and collection efficiencies were both augmented, our work shows that overall device current density could be improved. We utilized a two-dimensional numerical model to calculate the characteristics of patterned CQD solar cells based on a simple grating structure. Our calculation predicts a short circuit current density as high as 31  mA/cm2, a value nearly 1.5 times larger than that of the conventional flat design, showing the great potential value of patterned quantum junction solar cells.

  15. Measurement of Urban Air Quality by an Open-Path Quantum Cascade Laser Absorption Spectrometer in Beijing During Summer 2008

    NASA Astrophysics Data System (ADS)

    Michel, A. P.; Liu, P. Q.; Yeung, J. K.; Zhang, Y.; Baeck, M. L.; Pan, X.; Dong, H.; Wang, Z.; Smith, J. A.; Gmachl, C. F.

    2009-05-01

    The 2008 Olympic Games focused attention on the air quality of Beijing, China and served as an important test-bed for developing, deploying, and testing new technologies for analysis of air quality and regional climate in urban environments. Poor air quality in urban locations has a significant detrimental effect on the health of residents while also impacting both regional and global climate change. As a result, there exists a great need for highly sensitive trace gas sensors for studying the atmosphere of the urban environment. Open-path remote sensors are of particular interest as they can obtain data on spatial scales similar to those used in regional climate models. Quantum cascade lasers (QCLs) can be designed for operation in the mid-infrared (mid-IR) with a central wavelength anywhere between 3 to 24 μm and made tunable over a wavelength interval of over 0.1 μm. The Quantum Cascade Laser Open-Path System (QCLOPS) is a mid-infrared laser absorption spectrometer that uses a tunable, thermoelectrically cooled, pulsed Daylight Solutions Inc. QCL for measurement of trace gases. The system is aimed at applications with path lengths ranging from approximately 0.1 to 1.0 km. The system is designed to continuously monitor multiple trace gases [water vapor (H2O), ozone (O3), ammonia (NH3), and carbon dioxide (CO2)] in the lower atmosphere. A field campaign from July to September 2008 in Beijing used QCLOPS to study trace gas concentrations before, during, and after the Olympic Games in an effort to capture changes induced by emissions reduction methods. QCLOPS was deployed at the Institute of Atmospheric Physics - Chinese Academy of Sciences on the roof of a two-story building, at an approximate distance of 2 miles from the Olympic National Stadium ("The Bird's Nest.") QCLOPS operated with an open-path round trip distance of approximately 75 m. The system ran with minimal human interference, twenty-four hours per day for the full campaign period. In order to

  16. RF Path and Absorption Loss Estimation for Underwater Wireless Sensor Networks in Different Water Environments

    PubMed Central

    Qureshi, Umair Mujtaba; Shaikh, Faisal Karim; Aziz, Zuneera; Shah, Syed M. Zafi S.; Sheikh, Adil A.; Felemban, Emad; Qaisar, Saad Bin

    2016-01-01

    Underwater Wireless Sensor Network (UWSN) communication at high frequencies is extremely challenging. The intricacies presented by the underwater environment are far more compared to the terrestrial environment. The prime reason for such intricacies are the physical characteristics of the underwater environment that have a big impact on electromagnetic (EM) signals. Acoustics signals are by far the most preferred choice for underwater wireless communication. Because high frequency signals have the luxury of large bandwidth (BW) at shorter distances, high frequency EM signals cannot penetrate and propagate deep in underwater environments. The EM properties of water tend to resist their propagation and cause severe attenuation. Accordingly, there are two questions that need to be addressed for underwater environment, first what happens when high frequency EM signals operating at 2.4 GHz are used for communication, and second which factors affect the most to high frequency EM signals. To answer these questions, we present real-time experiments conducted at 2.4 GHz in terrestrial and underwater (fresh water) environments. The obtained results helped in studying the physical characteristics (i.e., EM properties, propagation and absorption loss) of underwater environments. It is observed that high frequency EM signals can propagate in fresh water at a shallow depth only and can be considered for a specific class of applications such as water sports. Furthermore, path loss, velocity of propagation, absorption loss and the rate of signal loss in different underwater environments are also calculated and presented in order to understand why EM signals cannot propagate in sea water and oceanic water environments. An optimal solk6ution for underwater communication in terms of coverage distance, bandwidth and nature of communication is presented, along with possible underwater applications of UWSNs at 2.4 GHz. PMID:27322263

  17. Evaluating the thermal stability of multi-pass cells' effective optical path length using optical frequency domain reflectometer

    NASA Astrophysics Data System (ADS)

    Gao, Hong; Cao, Xiuhan; Li, Jinyi; Du, Zhenhui

    2016-10-01

    Multi-pass cells (MPCs) are commonly used to improve the sensitivity for trace gas detection using spectroscopy technologies. The determination of Effective Optical Path Length (EOPL) of a MPC is very important and challenging in applications which aim at absolute measurements. It is well-known that the temperature changing will exercise some influence on the MPCs' spatial structure, however, measurements of the influence haven't been reported which might due to the limitation of measuring method. In this paper, we used a direct high-precision measuring method with Optical Frequency Domain Reflectometer (OFDR) to evaluate the thermal stability of a multi-pass cell. To simulate the environment with a large range of temperature changing, this paper gave a series of experiments by setting the temperature control unit in system from 25 to 175 degree Celsius, and the MPC's EOPL was measured simultaneously for the investigation of temperature response. The results showed that the effective optical path length increase monotonically along with the variation of the temperature, and the rising rate is 0.5 mm/ºC with the total length of about 3 meters which should be pay attention to when the ultra-high accuracy results are demanded. To stabilize the EOPL of the system, if it is possible, the environment temperature of gas cell can be controlled with a constant temperature. In practical applications, the real-time monitoring of EOPL with a direct measuring method may be necessary.

  18. Airborne 2-Micron Double-Pulsed Integrated Path Differential Absorption Lidar for Column CO2 Measurement

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta; Refaat, Tamer F.; Remus, Ruben G.; Fay, James J.; Reithmaier, Karl

    2014-01-01

    Double-pulse 2-micron lasers have been demonstrated with energy as high as 600 millijouls and up to 10 Hz repetition rate. The two laser pulses are separated by 200 microseconds and can be tuned and locked separately. Applying double-pulse laser in DIAL system enhances the CO2 measurement capability by increasing the overlap of the sampled volume between the on-line and off-line. To avoid detection complicity, integrated path differential absorption (IPDA) lidar provides higher signal-to-noise ratio measurement compared to conventional range-resolved DIAL. Rather than weak atmospheric scattering returns, IPDA rely on the much stronger hard target returns that is best suited for airborne platforms. In addition, the IPDA technique measures the total integrated column content from the instrument to the hard target but with weighting that can be tuned by the transmitter. Therefore, the transmitter could be tuned to weight the column measurement to the surface for optimum CO2 interaction studies or up to the free troposphere for optimum transport studies. Currently, NASA LaRC is developing and integrating a double-Pulsed 2-micron direct detection IPDA lidar for CO2 column measurement from an airborne platform. The presentation will describe the development of the 2-micron IPDA lidar system and present the airborne measurement of column CO2 and will compare to in-situ measurement for various ground target of different reflectivity.

  19. Airborne 2-micron double-pulsed integrated path differential absorption lidar for column CO2 measurement

    NASA Astrophysics Data System (ADS)

    Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta; Refaat, Tamer F.; Remus, Ruben G.; Fay, James J.; Reithmaier, Karl

    2014-10-01

    Double-pulse 2-micron lasers have been demonstrated with energy as high as 600 mJ and up to 10 Hz repetition rate. The two laser pulses are separated by 200 µs and can be tuned and locked separately. Applying double-pulse laser in DIAL system enhances the CO2 measurement capability by increasing the overlap of the sampled volume between the on-line and off-line. To avoid detection complicity, integrated path differential absorption (IPDA) lidar provides higher signal-to-noise ratio measurement compared to conventional range-resolved DIAL. Rather than weak atmospheric scattering returns, IPDA rely on the much stronger hard target returns that is best suited for airborne platforms. In addition, the IPDA technique measures the total integrated column content from the instrument to the hard target but with weighting that can be tuned by the transmitter. Therefore, the transmitter could be tuned to weight the column measurement to the surface for optimum CO2 interaction studies or up to the free troposphere for optimum transport studies. Currently, NASA LaRC is developing and integrating a double-Pulsed 2-µm direct detection IPDA lidar for CO2 column measurement from an airborne platform. The presentation will describe the development of the 2-μm IPDA lidar system and present the airborne measurement of column CO2 and will compare to in-situ measurement for various ground target of different reflectivity.

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

    PubMed

    Merten, André; Tschritter, Jens; Platt, Ulrich

    2011-02-10

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

  1. Atmospheric absorption cell characterization

    NASA Astrophysics Data System (ADS)

    1982-06-01

    The measurement capability of the Avionics Laboratory IR Facility was used to evaluate an absorption cell that will be used to simulate atmospheric absorption over horizontal paths of 1 - 10 km in length. Band models were used to characterize the transmittance of carbon dioxide (CO2), nitrogen (N2), and nitrous oxide (N2O) in the cell. The measured transmittance was compared to the calculated values. Nitrous oxide is important in the 4 - 4.5 micron range in shaping the weak line absorption of carbon dioxide. The absorption cell is adequate for simulating atmospheric absorption over these paths.

  2. Phrase Length Matters: The Interplay between Implicit Prosody and Syntax in Korean "Garden Path" Sentences

    ERIC Educational Resources Information Center

    Hwang, Hyekyung; Steinhauer, Karsten

    2011-01-01

    In spoken language comprehension, syntactic parsing decisions interact with prosodic phrasing, which is directly affected by phrase length. Here we used ERPs to examine whether a similar effect holds for the on-line processing of written sentences during silent reading, as suggested by theories of "implicit prosody." Ambiguous Korean sentence…

  3. Radiometric correction of atmospheric path length fluctuations in interferometric experiments. [in radio astronomy

    NASA Technical Reports Server (NTRS)

    Resch, G. M.; Hogg, D. E.; Napier, P. J.

    1984-01-01

    To support very long baseline interferometric experiments, a system has been developed for estimating atmospheric water vapor path delay. The system consists of dual microwave radiometers, one operating at 20.7 GHz and the other at 31.4 GHz. The measured atmospheric brightness temperatures at these two frequencies yield the estimate of the precipitable water present in both vapor and droplets. To determine the accuracy of the system, a series of observations were undertaken, comparing the outputs of two water vapor radiometers with the phase variation observed with two connected elements of the very large array (VLA). The results show that: (1) water vapor fluctuations dominate the residual VLA phase and (2) the microwave radiometers can measure and correct these effects. The rms phase error after correction is typically 15 deg at a wavelength of 6 cm, corresponding to an uncertainty in the path delay of 0.25 cm. The residual uncertainty is consistent with the stability of the microwave radiometer but is still considerably larger than the stability of the VLA. The technique is less successful under conditions of heavy cloud.

  4. Simulating the Effect of Modulated Tool-Path Chip Breaking On Surface Texture and Chip Length

    SciTech Connect

    Smith, K.S.; McFarland, J.T.; Tursky, D. A.; Assaid, T. S.; Barkman, W. E.; Babelay, Jr., E. F.

    2010-04-30

    One method for creating broken chips in turning processes involves oscillating the cutting tool in the feed direction utilizing the CNC machine axes. The University of North Carolina at Charlotte and the Y-12 National Security Complex have developed and are refining a method to reliably control surface finish and chip length based on a particular machine's dynamic performance. Using computer simulations it is possible to combine the motion of the machine axes with the geometry of the cutting tool to predict the surface characteristics and map the surface texture for a wide range of oscillation parameters. These data allow the selection of oscillation parameters to simultaneously ensure broken chips and acceptable surface characteristics. This paper describes the machine dynamic testing and characterization activities as well as the computational method used for evaluating and predicting chip length and surface texture.

  5. Evaluation on the detection limit of blood hemoglobin using photolepthysmography based on path-length optimization

    NASA Astrophysics Data System (ADS)

    Sun, Di; Guo, Chao; Zhang, Ziyang; Han, Tongshuai; Liu, Jin

    2016-10-01

    The blood hemoglobin concentration's (BHC) measurement using Photoplethysmography (PPG), which gets blood absorption to near infrared light from the instantaneous pulse of transmitted light intensity, has not been applied to the clinical use due to the non-enough precision. The main challenge might be caused of the non-enough stable pulse signal when it's very weak and it often varies in different human bodies or in the same body with different physiological states. We evaluated the detection limit of BHC using PPG as the measurement precision level, which can be considered as a best precision result because we got the relative stable subject's pulse signals recorded by using a spectrometer with high signal-to-noise ratio (SNR) level, which is about 30000:1 in short term. Moreover, we optimized the used pathlength using the theory based on optimum pathlength to get a better sensitivity to the absorption variation in blood. The best detection limit was evaluated as about 1 g/L for BHC, and the best SNR of pulse for in vivo measurement was about 2000:1 at 1130 and 1250 nm. Meanwhile, we conclude that the SNR of pulse signal should be better than 400:1 when the required detection limit is set to 5 g/L. Our result would be a good reference to the BHC measurement to get a desired BHC measurement precision of real application.

  6. Ground-based integrated path coherent differential absorption lidar measurement of CO2: foothill target return

    NASA Astrophysics Data System (ADS)

    Ishii, S.; Koyama, M.; Baron, P.; Iwai, H.; Mizutani, K.; Itabe, T.; Sato, A.; Asai, K.

    2013-05-01

    The National Institute of Information and Communications Technology (NICT) has made a great deal of effort to develop a coherent 2 μm differential absorption and wind lidar (Co2DiaWiL) for measuring CO2 and wind speed. First, coherent Integrated Path Differential Absorption (IPDA) lidar experiments were conducted using the Co2DiaWiL and a foothill target (tree and ground surface) located about 7.12 km south of NICT on 11, 27, and 28 December 2010. The detection sensitivity of a 2 μm IPDA lidar was examined in detail using the CO2 concentration measured by the foothill reflection. The precisions of CO2 measurements for the foothill target and 900, 4500 and 27 000 shot pairs were 6.5, 2.8, and 1.2%, respectively. The results indicated that a coherent IPDA lidar with a laser operating at a high pulse repetition frequency of a few tens of KHz is necessary for XCO2 (column-averaged dry air mixing ratio of CO2) measurement with a precision of 1-2 ppm in order to observe temporal and spatial variations in the CO2. Statistical comparisons indicated that, although a small amount of in situ data and the fact that they were not co-located with the foothill target made comparison difficult, the CO2 volume mixing ratio obtained by the Co2DiaWiL measurements for the foothill target and atmospheric returns was about -5 ppm lower than the 5 min running averages of the in situ sensor. Not only actual difference of sensing volume or the natural variability of CO2 but also the fluctuations of temperature could cause this difference. The statistical results indicated that there were no biases between the foothill target and atmospheric return measurements. The 2 μm coherent IPDA lidar can detect the CO2 volume mixing ratio change of 3% in the 5 min signal integration. In order to detect the position of the foothill target, to measure a range with a high SNR (signal-to-noise ratio), and to reduce uncertainty due to the presence of aerosols and clouds, it is important to make a

  7. Triple-Pulsed Two-Micron Integrated Path Differential Absorption Lidar: A New Active Remote Sensing Capability with Path to Space

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Refaat, Tamer F.; Petros, Mulugeta; Yu, Jirong

    2015-01-01

    The two-micron wavelength is suitable for monitoring atmospheric water vapor and carbon dioxide, the two most dominant greenhouse gases. Recent advances in 2-micron laser technology paved the way for constructing state-of-the-art lidar transmitters for active remote sensing applications. In this paper, a new triple-pulsed 2-micron integrated path differential absorption lidar is presented. This lidar is capable of measuring either two species or single specie with two different weighting functions, simultaneously and independently. Development of this instrument is conducted at NASA Langley Research Center. Instrument scaling for projected future space missions will be discussed.

  8. Chiral-index resolved length mapping of carbon nanotubes in solution using electric-field induced differential absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, Wenshan; Hennrich, Frank; Flavel, Benjamin S.; Kappes, Manfred M.; Krupke, Ralph

    2016-09-01

    The length of single-walled carbon nanotubes (SWCNTs) is an important metric for the integration of SWCNTs into devices and for the performance of SWCNT-based electronic or optoelectronic applications. In this work we propose a rather simple method based on electric-field induced differential absorption spectroscopy to measure the chiral-index-resolved average length of SWCNTs in dispersions. The method takes advantage of the electric-field induced length-dependent dipole moment of nanotubes and has been verified and calibrated by atomic force microscopy. This method not only provides a low cost, in situ approach for length measurements of SWCNTs in dispersion, but due to the sensitivity of the method to the SWCNT chiral index, the chiral index dependent average length of fractions obtained by chromatographic sorting can also be derived. Also, the determination of the chiral-index resolved length distribution seems to be possible using this method.

  9. The azimuthal path of myosin V and its dependence on lever-arm length.

    PubMed

    Lewis, John H; Beausang, John F; Sweeney, H Lee; Goldman, Yale E

    2012-02-01

    Myosin V (myoV) is a two-headed myosin capable of taking many successive steps along actin per diffusional encounter, enabling it to transport vesicular and ribonucleoprotein cargos in the dense and complex environment within cells. To better understand how myoV navigates along actin, we used polarized total internal reflection fluorescence microscopy to examine angular changes of bifunctional rhodamine probes on the lever arms of single myoV molecules in vitro. With a newly developed analysis technique, the rotational motions of the lever arm and the local orientation of each probe relative to the lever arm were estimated from the probe's measured orientation. This type of analysis could be applied to similar studies on other motor proteins, as well as other proteins with domains that undergo significant rotational motions. The experiments were performed on recombinant constructs of myoV that had either the native-length (six IQ motifs and calmodulins [CaMs]) or truncated (four IQ motifs and CaMs) lever arms. Native-length myoV-6IQ mainly took straight steps along actin, with occasional small azimuthal tilts around the actin filament. Truncated myoV-4IQ showed an increased frequency of azimuthal steps, but the magnitudes of these steps were nearly identical to those of myoV-6IQ. The results show that the azimuthal deflections of myoV on actin are more common for the truncated lever arm, but the range of these deflections is relatively independent of its lever-arm length.

  10. Challenges and Solutions for Frequency and Energy References for Spaceborne and Airborne Integrated Path Differential Absorption Lidars

    NASA Astrophysics Data System (ADS)

    Fix, Andreas; Quatrevalet, Mathieu; Witschas, Benjamin; Wirth, Martin; Büdenbender, Christian; Amediek, Axel; Ehret, Gerhard

    2016-06-01

    The stringent requirements for both the frequency stability and power reference represent a challenging task for Integrated Path Differential Absorption Lidars (IPDA) to measure greenhouse gas columns from satellite or aircraft. Currently, the German-French methane mission MERLIN (Methan Remote Lidar Mission) is prepared. At the same time CHARM-F, an aircraft installed system has been developed at DLR as an airborne demonstrator for a spaceborne greenhouse gas mission. The concepts and realization of these important sub-systems are discussed.

  11. Ground-based Photon Path Measurements from Solar Absorption Spectra of the O2 A-band

    NASA Technical Reports Server (NTRS)

    Yang, Z.; Wennberg, P. O.; Cageao, R. P.; Pongetti, T. J.; Toon, G. C.; Sander, S. P.

    2005-01-01

    High-resolution solar absorption spectra obtained from Table Mountain Facility (TMF, 34.38degN, 117.68degW, 2286 m elevation) have been analyzed in the region of the O2 A-band. The photon paths of direct sunlight in clear sky cases are retrieved from the O2 absorption lines and compared with ray-tracing calculations based on the solar zenith angle and surface pressure. At a given zenith angle, the ratios of retrieved to geometrically derived photon paths are highly precise (approx.0.2%), but they vary as the zenith angle changes. This is because current models of the spectral lineshape in this band do not properly account for the significant absorption that exists far from the centers of saturated lines. For example, use of a Voigt function with Lorentzian far wings results in an error in the retrieved photon path of as much as 5%, highly correlated with solar zenith angle. Adopting a super-Lorentz function reduces, but does not completely eliminate this problem. New lab measurements of the lineshape are required to make further progress.

  12. Large stroke MOEMS actuators for optical path length modulation in miniaturized FTIR spectrometers

    NASA Astrophysics Data System (ADS)

    Sandner, Thilo; Drabe, Christian; Schenk, Harald; Kenda, Andreas

    2009-05-01

    In this paper we present a novel translatory MOEMS device with extraordinary large stroke especially designed for fast optical path modulation in an improved miniaturized Fourier-transform infrared (FTIR) spectrometer capable to perform time resolved measurements from NIR to MIR. Recently, we presented a first MOEMS based FTIR system using a different translatory MOEMS actuator with bending suspensions of the mirror plate and +/-100μm oscillation amplitude resulting in a limited spectral resolution of 30 cm-1. For the novel MOEMS actuator an advanced pantograph suspension of the mirror plate was used to guarantee an extraordinary large stroke of up to 500 μm required for an improved spectral resolution. To optimize the optical throughput of the spectrometer the mirror aperture was increased to 7 mm2. The MOEMS actuators are driven electro statically resonant using out-of-plane comb drives and operate at a resonant frequency of 500 (1000) Hz, respectively. Hence, this enables to realize an improved MOEMS based FTIR-spectrometer with a spectral resolution of up to 10 cm-1, a SNR of > 1000:1 and an acquisition time of 1 ms per spectrum of the miniaturized FTIR-system. In this article we discuss in detail the design and the experimental characteristics of the novel large stroke translatory MOEMS device. The application and system integration, especially the optical vacuum packaging, of this MOEMS device in an improved miniaturized MOEMS based FTIR spectrometer enabling ultra rapid measurements in the NIRMIR spectral region with 12cm-1 spectral resolution is discussed in a separate paper submitted to this conference.

  13. The cosmic-ray path length (age) distribution in the Galaxy - Experimental limits on the deviation from an exponential

    NASA Technical Reports Server (NTRS)

    Webber, W. R.

    1993-01-01

    A systematic examination is presented of the observational effects that can provide information on the departure of the cosmic-ray path length distribution (PLD) for propagation in the Galaxy from a simple exponential distribution. The possible physical causes for this departure are examined in order to set realistic limits on how well a simple exponential PLD actually describes the distribution of sources and propagation of cosmic rays in the galaxy. From the findings, it is argued that the cosmic ray source distribution must be quite uniform, probably on a scale of about 50 pc or less near the sun. Extending this uniformity to the Galaxy as a whole would imply more than 100,000 active sources. The cosmic-ray propagation can be described quite well by a leaky box model which is equivalent to observing the particles through a dense fog.

  14. Leaf morphological effects predict effective path length and enrichment of 18O in leaf water of different Eucalyptus species

    NASA Astrophysics Data System (ADS)

    Kahmen, A.; Merchant, A.; Callister, A.; Dawson, T. E.; Arndt, S. K.

    2006-12-01

    Stable isotopes have been a valuable tool to study water or carbon fluxes of plants and ecosystems. In particular oxygen isotopes (δ18O) in leaf water or plant organic material are now beginning to be established as a simple and integrative measure for plant - water relations. Current δ18O models, however, are still limited in their application to a broad range of different species and ecosystems. It remains for example unclear, if species-specific effects such as different leaf morphologies need to be included in the models for a precise understanding and prediction of δ18O signals. In a common garden experiment (Currency Creek Arboretum, South Australia), where over 900 different Eucalyptus species are cultivated in four replicates, we tested effects of leaf morphology and anatomy on δ18O signals in leaf water of 25 different species. In particular, we determined for all species enrichment in 18O of mean lamina leaf water above source water (Δ18O) as related to leaf physiology as well as leaf thickness, leaf area, specific leaf area and weight and selected anatomical properties. Our data revealed that diurnal Δ18O in leaf water at steady state was significantly different among the investigated species and with differences up to 10% at midday. Fitting factors (effective path length) of leaf water Δ18O models were also significantly different among the investigated species and were highly affected by species-specific morphological parameters. For example, leaf area explained a high percentage of the differences in effective path length observed among the investigated species. Our data suggest that leaf water δ18O can act as powerful tool to estimate plant - water relations in comparative studies but that additional leaf morphological parameters need to be considered in existing δ18O models for a better interpretation of the observed δ18O signals.

  15. Long term NO2 measurements in Hong Kong using LED based Long Path Differential Optical Absorption Spectroscopy

    NASA Astrophysics Data System (ADS)

    Chan, K. L.; Pöhler, D.; Kuhlmann, G.; Hartl, A.; Platt, U.; Wenig, M. O.

    2011-11-01

    In this study we present the first long term measurements of atmospheric nitrogen dioxide (NO2) using a LED based Long Path Differential Optical Absorption Spectroscopy (LP-DOAS) instrument. This instrument is measuring continuously in Hong Kong since December 2009, first in a setup with a 550 m absorption path and then with a 3820 m path at about 30 m to 50 m above street level. The instrument is using a high power blue light LED with peak intensity at 450 nm coupled into the telescope using a Y-fibre bundle. The LP-DOAS instrument measures NO2 concentrations in the Kowloon Tong and Mong Kok district of Hong Kong and we compare the measurement results to concentrations reported by monitoring stations operated by the Hong Kong Environmental Protection Department in that area. Hourly averages of coinciding measurements are in reasonable agreement (R = 0.74). Furthermore, we used the long-term data set to validate the Ozone Monitoring Instrument (OMI) NO2 data product. Monthly averaged LP-DOAS and OMI measurements correlate well (R = 0.84) when comparing the data for the OMI overpass time. We analyzed weekly patterns in both data sets and found that the LP-DOAS detects a clear weekly cycle with a reduction on weekends during rush hour peaks, whereas OMI is not able to observe this weekly cycle due to its fix overpass time.

  16. Analysis of Atmospheric Composition and Tropospheric Variability With Integrated Open- Path and Ground-Based Solar Infrared Absorption Spectroscopy

    NASA Astrophysics Data System (ADS)

    Steill, J. D.; Compton, R. N.; Hager, J. S.

    2006-12-01

    Ground-based solar infrared absorption spectroscopy coupled with open-path spectroscopy provides a means for analysis of the highly variable contribution of the boundary layer to problems of radiative transfer and atmospheric chemistry. This is of particular importance in geographic regions of significant local anthropogenic influence and large tropospheric fluctuations in general. A Bomem DA8 FT-IR integrated with a sun-tracking and open-path system (~0.5 km) is located at The University of Tennessee, in downtown Knoxville and near The Great Smoky Mountains National Park, an area known for problematic air quality. From atmospheric absorption spectra, boundary layer concentrations as well as total column abundances and vertical concentration profiles are derived. A record of more than 1000 solar-sourced atmospheric spectra covering a period greater than three years in duration is under analysis to characterize the limit of precision in total column abundance determinations for many gases such as O3, CO, CH4, N2O, HF and CO2. Initial efforts using atmospheric O2 as a calibration indicate the solar-sourced spectra may not meet the precision required for the highly accurate atmospheric CO2 quantification by such global efforts as the OCO and NDSC. However, the determined variability of CO2 and other gas concentrations is statistically significant and is indicative of local concentration fluxes pertinent to the regional atmospheric chemistry. This is therefore an important data record in the southeastern United States, a somewhat under- sampled geographic region. In addition to providing a means to improve the analysis of solar spectra, the open-path data is useful for elucidation of seasonal and diurnal trends in the trace gas concentrations. This provides an urban air quality monitor in addition to improving the description of the total atmospheric composition, as the open-path system is stable and permanent.

  17. OPEN PATH TUNABLE DIODE LASER ABSORPTION SPECTROSCOPY FOR ACQUISITION OF FUGITIVE EMISSION FLUX DATA

    EPA Science Inventory

    Air pollutant emission from unconfined sources is an increasingly important environmental issue. The U.S. EPA has developed a gorund-based optical remote sensing method that enables direct measurement of fugitive emission flux from large area sources. Open-path Fourier transfor...

  18. Review and analysis of VHF/UHF field strength measurements: Measurements at VHF over path lengths greater than 100 km

    NASA Astrophysics Data System (ADS)

    Sandell, R. S.; Bell, C. P.; Taplin, D. W.

    1986-12-01

    In 1983 CCIRIWP 5/5 put forward a number of proposals for improvements to the field strength prediction methods of CCIR Recommendation 370 and associated Report 239, as used for international planning negotiations in the VHF and UHF Broadcast Bands. Described are the results of studies carried out by the BBC, in conjunction with other propagation investigations, to assess the validity of those proposals of IWP 5/5 which relate to propagation over path lengths in excess of about 100 km in the VHF Bands. It is concluded that these proposals can be supported with only one exception, relating to an addition of 7 dB to beyond-horizon oversea curves. Subsequently, the VHF proposals (excepting the one relating to the 7 dB correction) have been endorsed by CCIR Study Group 5 and adopted by the Plenar Meeting in 1986 for inclusion as modifications to Recommendation 370. Even so, limitations in the exsiting methods are identified and further work is proposed.

  19. In vivo quantification of photosensitizer concentration using fluorescence differential path-length spectroscopy: influence of photosensitizer formulation and tissue location

    NASA Astrophysics Data System (ADS)

    de Visscher, Sebastiaan A. H. J.; Witjes, Max J. H.; Kaščáková, Slávka; Sterenborg, Henricus J. C. M.; Robinson, Dominic J.; Roodenburg, Jan L. N.; Amelink, Arjen

    2012-06-01

    In vivo measurement of photosensitizer concentrations may optimize clinical photodynamic therapy (PDT). Fluorescence differential path-length spectroscopy (FDPS) is a non-invasive optical technique that has been shown to accurately quantify the concentration of Foscan® in rat liver. As a next step towards clinical translation, the effect of two liposomal formulations of mTHPC, Fospeg® and Foslip®, on FDPS response was investigated. Furthermore, FDPS was evaluated in target organs for head-and-neck PDT. Fifty-four healthy rats were intravenously injected with one of the three formulations of mTHPC at 0.15 mg kg-1. FDPS was performed on liver, tongue, and lip. The mTHPC concentrations estimated using FDPS were correlated with the results of the subsequent harvested and chemically extracted organs. An excellent goodness of fit (R2) between FDPS and extraction was found for all formulations in the liver (R2=0.79). A much lower R2 between FDPS and extraction was found in lip (R2=0.46) and tongue (R2=0.10). The lower performance in lip and in particular tongue was mainly attributed to the more layered anatomical structure, which influences scattering properties and photosensitizer distribution.

  20. Measurements of atmospheric NO3 radicals in Hefei using LED-based long path differential optical absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Xue, Lu; Min, Qin; Pin-Hua, Xie; Jun, Duan; Wu, Fang; Liu-Yi, Ling; Lan-Lan, Shen; Jian-Guo, Liu; Wen-Qing, Liu

    2016-02-01

    NO3 radicals accumulate during the night, thereby being the most critical night oxidant. Owing to the low concentration and dramatic variation, the detection of atmospheric NO3 radicals is still challenging. In this paper, an LED-based Long Path Differential Optical Absorption Spectroscopy (LPDOAS) instrument is developed for measuring the atmospheric NO3 radicals. This instrument is composed of a Schmidt-Cassegrain telescope, a combined emitting and receiving fiber, and a red LED equipped with a thermostat, and has a center wavelength of 660 nm, covering the NO3 strongest absorption peak (662 nm). The influence of LED temperature fluctuations is discussed. The temperature of the LED lamp with a home-made thermostat is tested, showing a stability of ±0.1 °C. The principle and fitting analyses of LED-LPDOAS are presented. A retrieval example and a time series of NO3 radical concentrations with good continuity for one night are shown. The detection limit of NO3 for 2.6-km optical path is about 10 ppt. Project supported by the “Strategic Priority Research Program” of the Chinese Academy of Sciences (Grant Nos. XDB05040200 and XDB05010500).

  1. An indoor test campaign of the tomography long path differential optical absorption spectroscopy technique.

    PubMed

    Mettendorf, K U; Hartl, A; Pundt, I

    2006-02-01

    In this study we validate the two-dimensional long path DOAS tomography measurement technique by means of an indoor experiment with well-known concentration distributions. The experiment was conducted over an area of 10 m x 15 m using one and two cylindrical polycarbonate containers of diameter 2 m, respectively, filled with NO2. The setup was realized with three of the multibeam instruments recently developed by Pundt and Mettendorf (Appl. Opt., 2005, in press), which allow the simultaneous measurement along at least four light paths each. The configuration consisted of twelve simultaneous light beams, 39 horizontal light paths in total, and 18 different cylinder positions inside the field. It was found that for the discretization and inversion technique shown here reconstructions of the concentration distributions from experimental data agree well with simulated reconstructions. In order to draw conclusions for atmospheric applications, numerical studies including instrumental errors were carried out. It was found that with the presented measurement setup it is possible to measure and reconstruct one or two NO2 plumes of 600 m diameter and average concentrations above 4.2 ppbv each, on a scale of 13.5 km2. Theoretical investigations show that it should be possible to localize and quantify 600 m diameter plumes of SO2 > 1.5 ppbv, H2CO > 6.3 ppbv, HONO > 3.2 ppbv, and ozone > 46.2 ppbv. Larger plumes can be measured with higher precision.

  2. Detection of hydrogen peroxide based on long-path absorption spectroscopy using a CW EC-QCL

    NASA Astrophysics Data System (ADS)

    Sanchez, N. P.; Yu, Y.; Dong, L.; Griffin, R.; Tittel, F. K.

    2016-02-01

    A sensor system based on a CW EC-QCL (mode-hop-free range 1225-1285 cm-1) coupled with long-path absorption spectroscopy was developed for the monitoring of gas-phase hydrogen peroxide (H2O2) using an interference-free absorption line located at 1234.055 cm-1. Wavelength modulation spectroscopy (WMS) with second harmonic detection was implemented for data processing. Optimum levels of pressure and modulation amplitude of the sensor system led to a minimum detection limit (MDL) of 25 ppb using an integration time of 280 sec. The selected absorption line for H2O2, which exhibits no interference from H2O, makes this sensor system suitable for sensitive and selective monitoring of H2O2 levels in decontamination and sterilization processes based on Vapor Phase Hydrogen Peroxide (VPHP) units, in which a mixture of H2O and H2O2 is generated. Furthermore, continuous realtime monitoring of H2O2 concentrations in industrial facilities employing this species can be achieved with this sensing system in order to evaluate average permissible exposure levels (PELs) and potential exceedances of guidelines established by the US Occupational Safety and Health Administration for H2O2.

  3. The Influence of Research Designs in Understanding the Control of Morphological Patterns on Bedload Path Lengths in gravel-bed rivers

    NASA Astrophysics Data System (ADS)

    Lamarre, H.; Roy, A.

    2009-05-01

    There may be a strong association between particle path length and the morphologic scale of prevailing pool- bar channel patterns in gravel-bed rivers. It has been shown that tracers introduced in a pool during channel- forming discharges have downstream path length frequency distributions that are symmetrical, with modes coinciding with pool-bar spacing. Evidence to support this hypothesis comes mostly from flume studies and there is only a limited support based on field data. For the past seven years, we have conducted field experiments in streams with gradients ranging from constricted pool and pool-bar systems to step-pools and cascades in order to link displacement distances of tracing particles to the spacing between bed features. Results showed that clast movements could not be predicted from morphological length scales. The objective of this paper is to define why the control of morphological patterns on bedload path lengths could not be seen from our dataset. We have tested hypotheses for which the limited predictive capacity of the morphological length scale results from 1) the identification of some bed units that may have been ambiguous along the bed profiles or 2) the selection of sampling parameters. The experiment was carried out in seven reaches located in Quebec and in the French Alps. The slopes ranged between 0.011 and 0.43 and the representative particle size (d50) from 42 to 110 mm. Detailed topographic maps of the bed were produced in order to describe the morphological patterns. We used passive transponders inserted into clasts to measure displacement distances. Between 100 and 450 clasts of different sizes were tagged in each reach between 2003 and 2008. The tracking was carried out at low flow using a portable antenna. In identifying morphological entities that represent no ambiguity from both field observations and long profiles, we did not observe significant evidence of a morphological control on the path lengths. The results show that

  4. Development of a sensitive long path absorption photometer to quantify peroxides in aerosol particles (Peroxide-LOPAP)

    NASA Astrophysics Data System (ADS)

    Mertes, P.; Pfaffenberger, L.; Dommen, J.; Kalberer, M.; Baltensperger, U.

    2012-10-01

    A new off-line instrument to quantify peroxides in aerosol particles using iodometry in long path absorption spectroscopy has been developed and is called peroxide long path absorption photometer (Peroxide-LOPAP). The new analytical setup features important technical innovations compared to hitherto published iodometric peroxide measurements. Firstly, the extraction, chemical conversion and measurement of the aerosol samples are performed in a closed oxygen-free (~ 1 ppb) environment. Secondly, a 50-cm optical detection cell is used for an increased photometric sensitivity. The limit of detection was 0.1 μM peroxide in solution or 0.25 nmol m-3 with respect to an aerosol sample volume of 1 m3. The test reaction was done at a constant elevated temperature of 40 °C and the reaction time was 60 min. Calibration experiments showed that the test reaction with all reactive peroxides, i.e. hydrogen peroxide (H2O2), peracids and peroxides with vicinal carbonyl groups (e.g. lauroyl peroxide) goes to completion and their sensitivity (slope of calibration curve) varies by only ±5%. However, very inert peroxides have a lower sensitivity. For example, tert-butyl hydroperoxide shows only 37% sensitivity compared to H2O2 after 1 h. A kinetic study revealed that even after 5 h only 85% of this inert compound had reacted. The time trends of the peroxide content in secondary organic aerosol (SOA) from the ozonolysis and photo-oxidation of α-pinene in smog chamber experiments were measured. The highest mass fraction of peroxides with 34% (assuming a molecular weight of 300 g mol-1) was found in freshly generated SOA from α-pinene ozonolysis. Mass fractions decreased with increasing NO levels in the photo-oxidation experiments. A decrease of the peroxide content was also observed with aging of the aerosol, indicating a decomposition of peroxides in the particles.

  5. Comparison of path integral molecular dynamics methods for the infrared absorption spectrum of liquid water

    NASA Astrophysics Data System (ADS)

    Habershon, Scott; Fanourgakis, George S.; Manolopoulos, David E.

    2008-08-01

    The ring polymer molecular dynamics (RPMD) and partially adiabatic centroid molecular dynamics (PA-CMD) methods are compared and contrasted in an application to the infrared absorption spectrum of a recently parametrized flexible, polarizable, Thole-type potential energy model for liquid water. Both methods predict very similar spectra in the low-frequency librational and intramolecular bending region at wavenumbers below 2500 cm-1. However, the RPMD spectrum is contaminated in the high-frequency O-H stretching region by contributions from the internal vibrational modes of the ring polymer. This problem is avoided in the PA-CMD method, which adjusts the elements of the Parrinello-Rahman mass matrix so as to shift the frequencies of these vibrational modes beyond the spectral range of interest. PA-CMD does not require any more computational effort than RPMD and it is clearly the better of the two methods for simulating vibrational spectra.

  6. Förster resonance energy transfer, absorption and emission spectra in multichromophoric systems. III. Exact stochastic path integral evaluation

    SciTech Connect

    Moix, Jeremy M.; Ma, Jian; Cao, Jianshu

    2015-03-07

    A numerically exact path integral treatment of the absorption and emission spectra of open quantum systems is presented that requires only the straightforward solution of a stochastic differential equation. The approach converges rapidly enabling the calculation of spectra of large excitonic systems across the complete range of system parameters and for arbitrary bath spectral densities. With the numerically exact absorption and emission operators, one can also immediately compute energy transfer rates using the multi-chromophoric Förster resonant energy transfer formalism. Benchmark calculations on the emission spectra of two level systems are presented demonstrating the efficacy of the stochastic approach. This is followed by calculations of the energy transfer rates between two weakly coupled dimer systems as a function of temperature and system-bath coupling strength. It is shown that the recently developed hybrid cumulant expansion (see Paper II) is the only perturbative method capable of generating uniformly reliable energy transfer rates and emission spectra across a broad range of system parameters.

  7. NitroMAC: An instrument for the measurement of HONO and intercomparison with a long-path absorption photometer.

    PubMed

    Afif, Charbel; Jambert, Corinne; Michoud, Vincent; Colomb, Aurélie; Eyglunent, Gregory; Borbon, Agnès; Daële, Véronique; Doussin, Jean-François; Perros, Pascal

    2016-02-01

    NitroMAC (French acronym for continuous atmospheric measurements of nitrogenous compounds) is an instrument which has been developed for the semi-continuous measurement of atmospheric nitrous acid (HONO). This instrument relies on wet chemical sampling and detection using high performance liquid chromatography (HPLC)-visible absorption at 540 nm. Sampling proceeds by dissolution of gaseous HONO in a phosphate buffer solution followed by derivatization with sulfanilamide/N-(1-naphthyl)-ethylenediamine. The performance of this instrument was found to be as follows: a detection limit of around 3 ppt with measurement uncertainty of 10% over an analysis time of 10 min. Intercomparison was made between the instrument and a long-path absorption photometer (LOPAP) during two experiments in different environments. First, air was sampled in a smog chamber with concentrations up to 18 ppb of nitrous acid. NitroMAC and LOPAP measurements showed very good agreement. Then, in a second experiment, ambient air with HONO concentrations below 250 ppt was sampled. While NitroMAC showed its capability of measuring HONO in moderate and highly polluted environments, the intercomparison results in ambient air highlighted that corrections must be made for minor interferences when low concentrations are measured.

  8. Förster resonance energy transfer, absorption and emission spectra in multichromophoric systems. III. Exact stochastic path integral evaluation.

    PubMed

    Moix, Jeremy M; Ma, Jian; Cao, Jianshu

    2015-03-07

    A numerically exact path integral treatment of the absorption and emission spectra of open quantum systems is presented that requires only the straightforward solution of a stochastic differential equation. The approach converges rapidly enabling the calculation of spectra of large excitonic systems across the complete range of system parameters and for arbitrary bath spectral densities. With the numerically exact absorption and emission operators, one can also immediately compute energy transfer rates using the multi-chromophoric Förster resonant energy transfer formalism. Benchmark calculations on the emission spectra of two level systems are presented demonstrating the efficacy of the stochastic approach. This is followed by calculations of the energy transfer rates between two weakly coupled dimer systems as a function of temperature and system-bath coupling strength. It is shown that the recently developed hybrid cumulant expansion (see Paper II) is the only perturbative method capable of generating uniformly reliable energy transfer rates and emission spectra across a broad range of system parameters.

  9. Integrated Path Differential Absorption Lidar Optimizations Based on Pre-Analyzed Atmospheric Data for ASCENDS Mission Applications

    NASA Technical Reports Server (NTRS)

    Pliutau, Denis; Prasad, Narasimha S.

    2012-01-01

    In this paper a modeling method based on data reductions is investigated which includes pre analyzed MERRA atmospheric fields for quantitative estimates of uncertainties introduced in the integrated path differential absorption methods for the sensing of various molecules including CO2. This approach represents the extension of our existing lidar modeling framework previously developed and allows effective on- and offline wavelength optimizations and weighting function analysis to minimize the interference effects such as those due to temperature sensitivity and water vapor absorption. The new simulation methodology is different from the previous implementation in that it allows analysis of atmospheric effects over annual spans and the entire Earth coverage which was achieved due to the data reduction methods employed. The effectiveness of the proposed simulation approach is demonstrated with application to the mixing ratio retrievals for the future ASCENDS mission. Independent analysis of multiple accuracy limiting factors including the temperature, water vapor interferences, and selected system parameters is further used to identify favorable spectral regions as well as wavelength combinations facilitating the reduction in total errors in the retrieved XCO2 values.

  10. Monitoring complex trace-gas mixtures by long-path laser absorption spectrometry. [in long duration manned mission closed environments

    NASA Technical Reports Server (NTRS)

    Green, B. D.; Steinfeld, J. I.

    1976-01-01

    Laser-based spectrophotometric methods, which have been proposed for the detection of trace concentrations of gaseous contaminants, include Raman and passive radiometry. The paper discusses a simple long-path laser absorption method which is capable of resolving complex mixtures of closely related trace contaminants at ppm levels. A number of species were selected which are most likely to accumulate in closed environments, such as submarines or long-duration manned space flights. Absorption coefficients at CO2 laser wavelengths were measured, accurate to + 3 per cent or better, for each of these species. This data base was then used to determine the presence and concentration of the contaminants in prepared mixtures of 12 to 15 gases. Computer programs have been developed which will permit a real-time analysis of the monitored atmosphere. Minimum detectable concentrations for individual species are generally in the ppm range, and are not seriously degraded by interferences even in complex mixtures. Estimates of the dynamic range of this monitoring technique for various system configurations and comparison with other methods of analysis are discussed

  11. Delivery Path Length and Holding Tree Minimization Method of Securities Delivery among the Registration Agencies Connected as Non-Tree

    NASA Astrophysics Data System (ADS)

    Shimamura, Atsushi; Moritsu, Toshiyuki; Someya, Harushi

    To dematerialize the securities such as stocks or cooporate bonds, the securities were registered to account in the registration agencies which were connected as tree. This tree structure had the advantage in the management of the securities those were issued large amount and number of brands of securities were limited. But when the securities such as account receivables or advance notes are dematerialized, number of brands of the securities increases extremely. In this case, the management of securities with tree structure becomes very difficult because of the concentration of information to root of the tree. To resolve this problem, using the graph structure is assumed instead of the tree structure. When the securities are kept with tree structure, the delivery path of securities is unique, but when securities are kept with graph structure, path of delivery is not unique. In this report, we describe the requirement of the delivery path of securities, and we describe selecting method of the path.

  12. Observation of halogen species in the Amundsen Gulf, Arctic, by active long-path differential optical absorption spectroscopy

    PubMed Central

    Pöhler, Denis; Vogel, Leif; Frieß, Udo; Platt, Ulrich

    2010-01-01

    In the polar tropospheric boundary layer, reactive halogen species (RHS) are responsible for ozone depletion as well as the oxidation of elemental mercury and dimethyl sulphide. After polar sunrise, air masses enriched in reactive bromine cover areas of several million square kilometers. Still, the source and release mechanisms of halogens are not completely understood. We report measurements of halogen oxides performed in the Amundsen Gulf, Arctic, during spring 2008. Active long-path differential optical absorption spectroscopy (LP-DOAS) measurements were set up offshore, several kilometers from the coast, directly on the sea ice, which was never done before. High bromine oxide concentrations were detected frequently during sunlight hours with a characteristic daily cycle showing morning and evening maxima and a minimum at noon. The, so far, highest observed average mixing ratio in the polar boundary layer of 41 pmol/mol (equal to pptv) was detected. Only short sea ice contact is required to release high amounts of bromine. An observed linear decrease of maximum bromine oxide levels with ambient temperature during sunlight, between -24 °C and -15 °C, provides indications on the conditions required for the emission of RHS. In addition, the data indicate the presence of reactive chlorine in the Arctic boundary layer. In contrast to Antarctica, iodine oxide was not detected above a detection limit of 0.3 pmol/mol. PMID:20160121

  13. Ultra-High Resolution Ion Mobility Separations Utilizing Traveling Waves in a 13 m Serpentine Path Length Structures for Lossless Ion Manipulations Module.

    PubMed

    Deng, Liulin; Ibrahim, Yehia M; Hamid, Ahmed M; Garimella, Sandilya V B; Webb, Ian K; Zheng, Xueyun; Prost, Spencer A; Sandoval, Jeremy A; Norheim, Randolph V; Anderson, Gordon A; Tolmachev, Aleksey V; Baker, Erin S; Smith, Richard D

    2016-09-20

    We report the development and initial evaluation of a 13 m path length Structures for Lossless Manipulations (SLIM) module for achieving high resolution separations using traveling waves (TW) with ion mobility (IM) spectrometry. The TW SLIM module was fabricated using two mirror-image printed circuit boards with appropriately configured RF, DC, and TW electrodes and positioned with a 2.75 mm intersurface gap. Ions were effectively confined in field-generated conduits between the surfaces by RF-generated pseudopotential fields and moved losslessly through a serpentine path including 44 "U" turns using TWs. The ion mobility resolution was characterized at different pressures, gaps between the SLIM surfaces, and TW and RF parameters. After initial optimization, the SLIM IM-MS module provided about 5-fold higher resolution separations than present commercially available drift tube or traveling wave IM-MS platforms. Peak capacity and peak generation rates achieved were 246 and 370 s(-1), respectively, at a TW speed of 148 m/s. The high resolution achieved in the TW SLIM IM-MS enabled, e.g., isomeric sugars (lacto-N-fucopentaose I and lacto-N-fucopentaose II) to be baseline resolved, and peptides from an albumin tryptic digest were much better resolved than with existing commercial IM-MS platforms. The present work also provides a foundation for the development of much higher resolution SLIM devices based upon both considerably longer path lengths and multipass designs.

  14. Ultra-High Resolution Ion Mobility Separations Utilizing Traveling Waves in a 13 m Serpentine Path Length Structures for Lossless Ion Manipulations Module

    SciTech Connect

    Deng, Liulin; Ibrahim, Yehia M.; Hamid, Ahmed M.; Garimella, Sandilya V. B.; Webb, Ian K.; Zheng, Xueyun; Prost, Spencer A.; Sandoval, Jeremy A.; Norheim, Randolph V.; Anderson, Gordon A.; Tolmachev, Aleksey V.; Baker, Erin S.; Smith, Richard D.

    2016-09-20

    We report the development and initial evaluation of a 13-m path length Structures for Lossless Manipulations (SLIM) module for achieving high resolution separations using traveling waves (TW) with ion mobility (IM) spectrometry. The TW SLIM module was fabricated using two mirror-image printed circuit boards with appropriately configured RF, DC and TW electrodes and positioned with a 2.75-mm inter-surface gap. Ions were effective confined between the surfaces by RF-generated pseudopotential fields and moved losslessly through a serpentine path including 44 “U” turns using TWs. The ion mobility resolution was characterized at different pressures, gaps between the SLIM surfaces, TW and RF parameters. After initial optimization the SLIM IM-MS module provided about 5-fold higher resolution separations than present commercially available drift tube or traveling wave IM-MS platforms. Peak capacity and peak generation rates achieved were 246 and 370 s-1, respectively, at a TW speed of 148 m/s. The high resolution achieved in the TW SLIM IM-MS enabled e.g., isomeric sugars (Lacto-N-fucopentaose I and Lacto-N-fucopentaose II) to be baseline resolved, and peptides from a albumin tryptic digest much better resolved than with existing commercial IM-MS platforms. The present work also provides a foundation for the development of much higher resolution SLIM devices based upon both considerably longer path lengths and multi-pass designs.

  15. Global observations of atmospheric CH4 by Integrated Path Differential-Absorption Lidar: the French-German Climate Monitoring Initiative

    NASA Astrophysics Data System (ADS)

    Ehret, Gerhard; Flamant, Pierre; Ciais, Philippe; Fabien, Gibert; Amediek, Axel; Kiemle, Christoph; Fix, Andreas; Quatrevalet, Mathieu; Wirth, Martin

    Atmospheric methane (CH4) is a powerful greenhouse gas, which has a Greenhouse Warming Potential (GWP) of 25 relative to CO2 on a time scale of 100 years. Despite the fact that the imbalance between the sources and sinks has decreased in the early 1990's to an insignificant value, a significant renewal of the CH4 growth is reported in recent years. Questions arise whether an increase of atmospheric CH4 might be fostered through melting of permafrost soil in the Arctic region or arise from changes of the tropical wetlands which comprise the biggest natural methane source. Another reason could be the change in the agro-industrial era of predominant human influence or the very large deposits of CH4 as gas hydrates on ocean shelves that are vulnerable to ocean warming. The French-German Climate Monitoring Initiative, which has recently been selected to undergo Phase0/A studies in a joint project by the space agencies CNES (France)and DLR (Germany), targets on satellite observations of atmospheric CH4 for the improvement of our knowledge on regional to synoptic scale CH4 sources on a global basis. As a novel feature, the observational instrument of this mission will be an Integrated Path Differential-Absorption (IPDA) Lidar system embarked on board of the French Myriade platform for the measurement of the column-weighted dry-air mixing ratio of CH4 in a nadir viewing configuration. This data will be provided by the lidar technique with no bias due to particles scattering in the light path and can directly be used as input for flux inversion models. In our presentation we will discuss the observational principle and the sampling strategy of the envisaged mission in connection to the needs for CH4 flux inversion experiments. In addition, we report on supporting campaign activities on airborne measurements of Lidar reflectivity data in the respective spectral region. The airborne data is of prime interest for the generation of pseudo CH4 data examples using the satellite

  16. Relationships and Transformations Between Concentration-Path-Length (CL), Agents Containing Particles per Liter of Air (ACPLA), and the Number of Spores (N spores)

    DTIC Science & Technology

    2005-11-01

    Bacillus atrophaeus Vegetative Cell Bacillus anthracis (SPECIAL) Endospore 0 Slaphylococcus aureus Staphylococcus epidermidis Escherichia co/i o i 2...bacteria and spores. 15. SUBJECT TERMS ACPLA Spores Bacteria Bacillus subtilus Concentration-path-Length CL Bioaerosols Aerosol size distribution Standoff...x 2 x 10’I(cm3) x t.3 2 (g/cn3)X 100(m) x 106 = 2 .6 mg liter r 2 • Density of Bacillus subtilis BG spores. Only a few references to the density of

  17. Double-pulse 2-μm integrated path differential absorption lidar airborne validation for atmospheric carbon dioxide measurement.

    PubMed

    Refaat, Tamer F; Singh, Upendra N; Yu, Jirong; Petros, Mulugeta; Remus, Ruben; Ismail, Syed

    2016-05-20

    Field experiments were conducted to test and evaluate the initial atmospheric carbon dioxide (CO2) measurement capability of airborne, high-energy, double-pulsed, 2-μm integrated path differential absorption (IPDA) lidar. This IPDA was designed, integrated, and operated at the NASA Langley Research Center on-board the NASA B-200 aircraft. The IPDA was tuned to the CO2 strong absorption line at 2050.9670 nm, which is the optimum for lower tropospheric weighted column measurements. Flights were conducted over land and ocean under different conditions. The first validation experiments of the IPDA for atmospheric CO2 remote sensing, focusing on low surface reflectivity oceanic surface returns during full day background conditions, are presented. In these experiments, the IPDA measurements were validated by comparison to airborne flask air-sampling measurements conducted by the NOAA Earth System Research Laboratory. IPDA performance modeling was conducted to evaluate measurement sensitivity and bias errors. The IPDA signals and their variation with altitude compare well with predicted model results. In addition, off-off-line testing was conducted, with fixed instrument settings, to evaluate the IPDA systematic and random errors. Analysis shows an altitude-independent differential optical depth offset of 0.0769. Optical depth measurement uncertainty of 0.0918 compares well with the predicted value of 0.0761. IPDA CO2 column measurement compares well with model-driven, near-simultaneous air-sampling measurements from the NOAA aircraft at different altitudes. With a 10-s shot average, CO2 differential optical depth measurement of 1.0054±0.0103 was retrieved from a 6-km altitude and a 4-GHz on-line operation. As compared to CO2 weighted-average column dry-air volume mixing ratio of 404.08 ppm, derived from air sampling, IPDA measurement resulted in a value of 405.22±4.15  ppm with 1.02% uncertainty and

  18. Analyzing Water's Optical Absorption

    NASA Technical Reports Server (NTRS)

    2002-01-01

    A cooperative agreement between World Precision Instruments (WPI), Inc., and Stennis Space Center has led the UltraPath(TM) device, which provides a more efficient method for analyzing the optical absorption of water samples at sea. UltraPath is a unique, high-performance absorbance spectrophotometer with user-selectable light path lengths. It is an ideal tool for any study requiring precise and highly sensitive spectroscopic determination of analytes, either in the laboratory or the field. As a low-cost, rugged, and portable system capable of high- sensitivity measurements in widely divergent waters, UltraPath will help scientists examine the role that coastal ocean environments play in the global carbon cycle. UltraPath(TM) is a trademark of World Precision Instruments, Inc. LWCC(TM) is a trademark of World Precision Instruments, Inc.

  19. Ion Mobility Separations of Isomers based upon Long Path Length Structures for Lossless Ion Manipulations Combined with Mass Spectrometry

    SciTech Connect

    Deng, Liulin; Ibrahim, Yehia M.; Baker, Erin S.; Aly, Noor A.; Hamid, Ahmed M.; Zhang, Xing; Zheng, Xueyun; Garimella, Sandilya V. B.; Webb, Ian K.; Prost, Spencer A.; Sandoval, Jeremy A.; Norheim, Randolph V.; Anderson, Gordon A.; Tolmachev, Aleksey V.; Smith, Richard D.

    2016-07-01

    Mass spectrometry (MS)-based multi-omic measurements, including proteomics, metabolomics, lipidomics, and glycomics, are increasingly transforming our ability to characterize and understand biological systems, but, presently have limitations due to the chemical diversity and range of abundances of biomolecules in complex samples. Advances addressing these challenges increasingly are based upon the ability to quickly separate, react and otherwise manipulate sample components for analysis by MS. Here we report on a new approach using Structures for Lossless Ion Manipulations (SLIM) to enable long serpentine path ion mobility spectrometry (IMS) separations followed by MS analyses. This approach provides previously unachieved mobility biomolecule isomer separations for biomolecular species, in conjunction with more effective ion utilization, and producing a basis for the improved characterization of very small samples.

  20. The influence of NDT-Bobath and PNF methods on the field support and total path length measure foot pressure (COP) in patients after stroke.

    PubMed

    Krukowska, Jolanta; Bugajski, Marcin; Sienkiewicz, Monika; Czernicki, Jan

    In stroke patients, the NDT - (Bobath - Neurodevelopmental Treatment) and PNF (Proprioceptive Neuromuscular Facilitation) methods are used to achieve the main objective of rehabilitation, which aims at the restoration of maximum patient independence in the shortest possible period of time (especially the balance of the body). The aim of the study is to evaluate the effect of the NDT-Bobath and PNF methods on the field support and total path length measure foot pressure (COP) in patients after stroke. The study included 72 patients aged from 20 to 69 years after ischemic stroke with Hemiparesis. The patients were divided into 4 groups by a simple randomization. The criteria for this division were: the body side (right or left) affected by paresis and the applied rehabilitation methods. All the patients were applied the recommended kinesitherapeutic method (randomized), 35 therapy sessions, every day for a period of six weeks. Before initiation of therapy and after 6 weeks was measured the total area of the support and path length (COP (Center Of Pressure) measure foot pressure) using stabilometer platform - alpha. The results were statistically analyzed. After treatment studied traits decreased in all groups. The greatest improvement was obtained in groups with NDT-Bobath therapy. NDT-Bobath method for improving the balance of the body is a more effective method of treatment in comparison with of the PNF method. In stroke patients, the effectiveness of NDT-Bobath method does not depend on hand paresis.

  1. Light extinction and absorption by arbitrarily oriented finite circular cylinders by use of geometrical path statistics of rays.

    PubMed

    Xu, Min

    2003-11-20

    From the geometrical path statistics of rays in an anomalous-diffraction theory (ADT) [Opt. Lett. 28, 179 (2003)] closed-form expressions for the geometrical path distribution of rays and analytical formulas for the optical efficiencies of finite circular cylinders oriented in an arbitrary direction with respect to the incident light are derived. The characteristics of the shapes of the cylinders produce unique features in the geometrical path distributions of the cylinders compared with spheroids. Gaussian ray approximations, which depend only on the mean and the mean-squared geometrical paths of rays, of the optical efficiencies of finite circular cylinders and spheroids are compared with the exact optical efficiencies in ADT. The influence of the difference in shape between cylinders and spheroids on the optical efficiencies in ADT is illustrated by their respective geometrical path distributions of rays.

  2. Inhibition of Ileal Water Absorption by Intraluminal Fatty Acids INFLUENCE OF CHAIN LENGTH, HYDROXYLATION, AND CONJUGATION OF FATTY ACIDS

    PubMed Central

    Ammon, Helmut V.; Phillips, Sidney F.

    1974-01-01

    The influence of fatty acids on ileal absorption of water, electrolytes, glucose, and taurocholate was examined in Thirty-Vella fistulas in five mongrel dogs. Fatty acid absorption also was measured. Segments of terminal ileum were perfused at steady state with isotonic electrolyte solutions containing 11.2 mM glucose, 4.5 mM taurocholate, and 0.1-5.0 mM fatty acid. Three C18 fatty acids, oleic acid, 10(9)-hydroxystearic acid, and ricinoleic acid, completely inhibited water absorption at 5 mM. Sodium, chloride, and potassium absorptions were inhibited in parallel with absorption of water. Differences between the potencies of C18 fatty acids were apparent when lesser concentrations were perfused. Dodecanoic and decanoic acids were as effective as C18 fatty acids at 5 mM but octanoic and hexanoic acids were ineffective. The polar group of C18 fatty acids was modified by conjugating oleic and ricinoleic acids with taurine. When these compounds and a substituted C18 fatty acid, p-n-decylbenzenesulfonate, were perfused, water absorption was also inhibited. Short-chain fatty acids (C3 and C4) and their hydroxylated derivatives were ineffective at 5 mM. When water absorption was inhibited, absorption of glucose and taurocholate was decreased. We speculate that the phenomenon of inhibition of water and electrolyte absorption by fatty acids may be relevant to steatorrhea and diarrhea in man. Images PMID:4808636

  3. Synchrotron radiation and long path cryogenic cells: New tools and results for modelling SF6 absorption in the 10μm atmospheric window

    NASA Astrophysics Data System (ADS)

    Faye, Mbaye; Boudon, Vincent; Loete, Michel; Roy, Pascale; Manceron, Laurent

    2015-04-01

    Sulfur hexa?uoride (SF6) is a heavy and stable molecule used in many sectors, such as the electrical industry, but also as a gas tracer to model air masse motions in the Earth atmosphere. This anthropogenic species is also an atmospheric pollutant owing to its greenhouse effect capability. Although its six fundamental modes have been largely studied up to now, it is not the case for the numerous hot bands that represent the most important part of the SF6 spectrum at room temperature. So, to model correctly the SF6 atmospheric absorption requires the knowledge of the spectroscopic parameters of all states involved in these hot bands. Nevertheless, due to their overlapping, a direct analysis of the hot bands near the 10,5μm absorption of SF6 in the atmospheric window is not possible. It is necessary to use another strategy, gathering information in the far and mid infrared regions on initial and final states to recompute the relevant total absorption. Here, we present new results of an analysis of spectra recorded at the AILES beam line at the SOLEIL Synchrotron facility. For these measurements, we used a IFS125HR interferometer in the 100 - 3200 cm-1 range, coupled to a cryogenic multiple pass cell [1]. The optical path length was adjusted to 93m; the SF6 sample was cooled down to 153 K. We could record 17 rovibrational bands of SF6 in this region with a resolution of 0.0025 cm-1. These results allowed us to perform the detailed analysis of several bands. Adding to previous knowledge on ν3, ν2, 2ν3 and new results on 3ν3, 2ν1 + ν3, ν1 + ν3, ν2 + ν3, ν3 - ν2 , ν3 - ν1 , we developed a global fit of the ν1, ν2, ν3 parameters, thus permitting the modelling of the ν3 + ν1 - ν1, ν3 + ν2 - ν2 hot bands. New information has also been obtained on ν6 and ν3 + ν5 and another strategy will be detailed to model the more important ν3 + ν5 - ν5 and ν3 + ν6 - ν6 hot band contributions. Including these new parameters in the XTDS model [2], we

  4. Adjusting the tasseled cap brightness and greenness factors for atmospheric path radiance and absorption on a pixel by pixel basis

    NASA Technical Reports Server (NTRS)

    Jackson, R. D.; Slater, P. N.; Pinter, P. J. (Principal Investigator)

    1982-01-01

    A radiative transfer model was used to convert ground measured reflectances into the radiance at the top of the atmosphere, for several levels of atmospheric path radiance. The radiance in MSS7 (0.8 to 1.1 m) was multiplied by the transmission fraction for atmospheres having different levels of precipitable water. The radiance values were converted to simulated LANDSAT digital counts for four path radiance levels and four levels of precipitable water. These values were used to calculate the Kauth-Thomas brightness, greenness, yellowness, and nonsuch factors. Brightness was affected by surface conditions and path radiance. Greenness was affected by surface conditions, path radiance, and precipitable water. Yellowness was affected by path radiance and nonsuch by precipitable water, and both factors changed only slightly with surface conditions. Yellowness and nonsuch were used to adjust brightness and greenness to produce factors that were affected only by surface conditions such as soils and vegetation, and not by path radiance and precipitable water.

  5. Application of maximum likelihood estimator in nano-scale optical path length measurement using spectral-domain optical coherence phase microscopy

    PubMed Central

    Motaghian Nezam, S. M. R.; Joo, C; Tearney, G. J.; de Boer, J. F.

    2009-01-01

    Spectral-domain optical coherence phase microscopy (SD-OCPM) measures minute phase changes in transparent biological specimens using a common path interferometer and a spectrometer based optical coherence tomography system. The Fourier transform of the acquired interference spectrum in spectral-domain optical coherence tomography (SD-OCT) is complex and the phase is affected by contributions from inherent random noise. To reduce this phase noise, knowledge of the probability density function (PDF) of data becomes essential. In the present work, the intensity and phase PDFs of the complex interference signal are theoretically derived and the optical path length (OPL) PDF is experimentally validated. The full knowledge of the PDFs is exploited for optimal estimation (Maximum Likelihood estimation) of the intensity, phase, and signal-to-noise ratio (SNR) in SD-OCPM. Maximum likelihood (ML) estimates of the intensity, SNR, and OPL images are presented for two different scan modes using Bovine Pulmonary Artery Endothelial (BPAE) cells. To investigate the phase accuracy of SD-OCPM, we experimentally calculate and compare the cumulative distribution functions (CDFs) of the OPL standard deviation and the square root of the Cramér-Rao lower bound (1/2SNR) over 100 BPAE images for two different scan modes. The correction to the OPL measurement by applying ML estimation to SD-OCPM for BPAE cells is demonstrated. PMID:18957999

  6. Earth-satellite-Earth laser long-path absorption experiment using the Retroreflector in Space (RIS) on the Advanced Earth Observing Satellite (ADEOS)

    NASA Astrophysics Data System (ADS)

    Sugimoto, Nobuo; Koga, Nobuhiko; Matsui, Ichiro; Sasano, Yasuhiro; Minato, Atsushi; Ozawa, Kenichi; Saito, Yasunori; Nomura, Akio; Aoki, Tetsuo; Itabe, Toshikazu; Kunimori, Hiroo; Murata, Isao; Fukunishi, Hiroshi

    1999-03-01

    This paper reports the results of the laser long-path absorption experiments carried out with the Retroreflector in Space (RIS) on the Advanced Earth Observing Satellite (ADEOS). The RIS is a 0.5 m diameter single-element hollow retroreflector with a unique optical design which uses a curved mirror surface to correct velocity aberrations caused by the satellite movement. In the RIS experiments a laser beam was transmitted from a ground station, reflected by the RIS, and received back at the ground station. The absorption of the intervening atmosphere was measured in the round-trip optical path. After the launch of the ADEOS in August 1996, the optical characteristics of the RIS were tested, and it was confirmed that the RIS worked well in orbit. The spectroscopic measurement was carried out with the single-longitudinal-mode TEA 1464-4258/1/2/015/img12 lasers by means of the method utilizing the Doppler shift of the reflected beam caused by the movement of the satellite. The spectrum of ozone was successfully measured in the 1464-4258/1/2/015/img13 region, and the measurement of the column contents of ozone was validated with the simultaneous heterodyne spectrometer measurement. In June 1997, however, the experiment with the RIS was discontinued due to the malfunction of the ADEOS solar paddle.

  7. Seismic scattering and absorption mapping of debris flows, feeding paths, and tectonic units at Mount St. Helens volcano

    NASA Astrophysics Data System (ADS)

    De Siena, L.; Calvet, M.; Watson, K. J.; Jonkers, A. R. T.; Thomas, C.

    2016-05-01

    Frequency-dependent peak-delay times and coda quality factors have been used jointly to separate seismic absorption from scattering quantitatively in Earth media at regional and continental scale; to this end, we measure and map these two quantities at Mount St. Helens volcano. The results show that we can locate and characterize volcanic and geological structures using their unique contribution to seismic attenuation. At 3 Hz a single high-scattering and high-absorption anomaly outlines the debris flows that followed the 1980 explosive eruption, as deduced by comparison with remote sensing imagery. The flows overlay a NNW-SSE interface, separating rocks of significant varying properties down to 2-4 km, and coinciding with the St. Helens Seismic Zone. High-scattering and high-absorption anomalies corresponding to known locations of magma emplacement follow this signature under the volcano, showing the important interconnections between its feeding systems and the regional tectonic boundaries. With frequency increasing from 6 to 18 Hz the NNW-SSE tectonic/feeding trends rotate around an axis centered on the volcano in the direction of the regional-scale magmatic arc (SW-NE). While the aseismic high-scattering region WSW of the volcano shows no evidence of high absorption, the regions of highest-scattering and absorption are consistently located at all frequencies under either the eastern or the south-eastern flank of the volcanic edifice. From the comparison with the available geological and geophysical information we infer that these anomalies mark both the location and the trend of the main feeding systems at depths greater than 4 km.

  8. Seismic scattering and absorption mapping of debris flows, feeding paths, and tectonic units at Mount St. Helens volcano

    NASA Astrophysics Data System (ADS)

    De Siena, Luca; Calvet, Marie; Watson, Keira J.; Jonkers, Art R. D.; Thomas, Christine

    2016-04-01

    Frequency-dependent peak-delay times and coda quality factors have been used jointly to separate seismic absorption from scattering quantitatively in Earth media at regional and lithospheric scale; to this end, we measure and map these two quantities at Mount St. Helens volcano. The results show that we can locate and characterise volcanic and geological structures using their unique contribution to seismic attenuation. At 3 Hz a single high-scattering and high-absorption anomaly outlines the debris flows that followed the 1980 explosive eruption, as deduced by comparison with remote sensing imagery. The flows overlay a NNW-SSE interface, separating rocks of significant varying properties down to 2-4 km, and coinciding with the Saint Helens Seismic Zone. High-scattering and high-absorption anomalies corresponding to known locations of magma emplacement follow this signature under the volcano, showing the important interconnections between its feeding systems and the regional tectonic boundaries. With frequency increasing from 6 to 18 Hz the NNW-SSE tectonic/feeding trends rotate around an axis centered on the volcano in the direction of the regional-scale magmatic arc (SW-NE). While the aseismic high-scattering region WSW of the volcano shows no evidence of high absorption, the regions of highest-scattering and absorption are consistently located at all frequencies under either the eastern or the south-eastern flank of the volcanic edifice. From the comparison with the available geological and geophysical information we infer that these anomalies mark both the location and the trend of the main feeding systems at depths greater than 4 km.

  9. Transpiration rate relates to within- and across-species variations in effective path length in a leaf water model of oxygen isotope enrichment.

    PubMed

    Song, Xin; Barbour, Margaret M; Farquhar, Graham D; Vann, David R; Helliker, Brent R

    2013-07-01

    Stable oxygen isotope ratio of leaf water (δ(18)O(L)) yields valuable information on many aspects of plant-environment interactions. However, current understanding of the mechanistic controls on δ(18)O(L) does not provide complete characterization of effective path length (L) of the Péclet effect,--a key component of the leaf water model. In this study, we collected diurnal and seasonal series of leaf water enrichment and estimated L in six field-grown angiosperm and gymnosperm tree species. Our results suggest a pivotal role of leaf transpiration rate (E) in driving both within- and across-species variations in L. Our observation of the common presence of an inverse scaling of L with E in the different species therefore cautions against (1) the conventional treatment of L as a species-specific constant in leaf water or cellulose isotope (δ(18)O(p)) modelling; and (2) the use of δ(18)O(p) as a proxy for gs or E under low E conditions. Further, we show that incorporation of a multi-species L-E scaling into the leaf water model has the potential to both improve the prediction accuracy and simplify parameterization of the model when compared with the conventional approach. This has important implications for future modelling of oxygen isotope ratios.

  10. Water equivalent path length calculations using scatter-corrected head and neck CBCT images to evaluate patients for adaptive proton therapy

    NASA Astrophysics Data System (ADS)

    Kim, Jihun; Park, Yang-Kyun; Sharp, Gregory; Busse, Paul; Winey, Brian

    2017-01-01

    Proton therapy has dosimetric advantages due to the well-defined range of the proton beam over photon radiotherapy. When the proton beams, however, are delivered to the patient in fractionated radiation treatment, the treatment outcome is affected by delivery uncertainties such as anatomic change in the patient and daily patient setup error. This study aims at establishing a method to evaluate the dosimetric impact of the anatomic change and patient setup error during head and neck proton therapy. Range variations due to the delivery uncertainties were assessed by calculating water equivalent path length (WEPL) to the distal edge of tumor volume using planning CT and weekly treatment cone-beam CT (CBCT) images. Specifically, mean difference and root mean squared deviation (RMSD) of the distal WEPLs were calculated as the weekly range variations. To accurately calculate the distal WEPLs, an existing CBCT scatter correction algorithm was used. An automatic rigid registration was used to align the planning CT and treatment CBCT images, simulating a six degree-of-freedom couch correction at treatments. The authors conclude that the dosimetric impact of the anatomic change and patient setup error was reasonably captured in the differences of the distal WEPL variation with a range calculation uncertainty of 2%. The proposed method to calculate the distal WEPL using the scatter-corrected CBCT images can be an essential tool to decide the necessity of re-planning in adaptive proton therapy.

  11. Development of formulae for estimating amylose content, amylopectin chain length distribution, and resistant starch content based on the iodine absorption curve of rice starch.

    PubMed

    Nakamura, Sumiko; Satoh, Hikaru; Ohtsubo, Ken'ichi

    2015-01-01

    Not only amylose but also amylopectin greatly affects the gelatinization properties of rice starch and the quality of cooked rice grains. We here characterized the starches of 32 rice cultivars and evaluated the relationship between their iodine absorption curve, apparent amylose content (AAC), pasting property, resistant starch (RS) content, and chain length distribution of amylopectin. We found that the iodine absorption curve differed among the various sample rice cultivars. Using the wavelength at which absorbance becomes maximum on iodine staining of starch (λmax), we propose a novel index, "new λmax" (AAC/(λmax of sample rice starches-λmax of glutinous rice starch)). We developed the novel estimation formulae for AAC, RS contents, and amylopectin fractions with the use of λmax and "new λmax." These formulae would lead to the improved method for estimating starch properties using an easy and rapid iodine colorimetric method.

  12. Determination of bond lengths from extended X-ray absorption fine structure in cobalt(III)-oxo cubane-like clusters

    NASA Astrophysics Data System (ADS)

    Nitin Nair, N.; Shrivastava, B. D.; Das, Birinchi Kumar

    2016-10-01

    The extended X-ray absorption fine structure (EXAFS) at the K-edge of cobalt has been studied in two cobalt complexes having Co(III)-oxo cubane-like clusters of the type Co4O4(O2CR)4L4 where R is CH3 and L is pyridine (py) in one of the complex and ammonia (NH3) in the other complex. The spectra have been recorded at BL-9 scanning EXAFS beamline at the 2.5-GeV INDUS-2 Synchrotron, RRCAT, Indore, India. The positions of EXAFS maxima and minima have been reported. Using this data, the bond length has been determined by simple bond determination methods, viz., Levy's, Lytle's and Lytle, Sayers and Stern's (LSS) methods. The normalized EXAFS spectra have been Fourier transformed and the value of the bond length has also been determined from the position of the first peak in the Fourier transform. This distance is the phase-uncorrected bond length. LSS method also gives such bond length. The results obtained from Fourier transform and LSS methods have been found to be comparable to each other. For the pyridine complex, the value obtained from Levy's method has been found to be in agreement with the available crystallographic value.

  13. Open-path quantum cascade laser-based system for simultaneous remote sensing of methane, nitrous oxide, and water vapor using chirped-pulse differential optical absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Castillo, Paulo; Diaz, Adrian; Thomas, Benjamin; Gross, Barry; Moshary, Fred

    2015-10-01

    Methane and Nitrous Oxide are long-lived greenhouse gases in the atmosphere with significant global warming effects. We report on application of chirped-pulsed quantum cascade lasers (QCLs) to simultaneous measurements of these trace gases in both open-path fence-line and backscatter systems. The intra-pulse thermal frequency chip in a QCL can be time resolved and calibrated to allow for high resolution differential optical absorption spectroscopy over the spectral window of the chip, which for a DFB-QCL can be reach ~2cm-1 for a 500 nsec pulse. The spectral line-shape of the output from these lasers are highly stable from pulse to pulse over long period of time (> 1 day), and the system does not require frequent calibrations.

  14. 2-micron triple-pulse integrated path differential absorption lidar development for simultaneous airborne column measurements of carbon dioxide and water vapor in the atmosphere

    NASA Astrophysics Data System (ADS)

    Singh, Upendra N.; Petros, Mulugeta; Refaat, Tamer F.; Yu, Jirong

    2016-05-01

    For more than 15 years, NASA Langley Research Center (LaRC) has contributed in developing several 2-micron carbon dioxide active remote sensors using the DIAL technique. Currently, an airborne 2-micron triple-pulse integrated path differential absorption (IPDA) lidar is under development at NASA LaRC. This paper focuses on the advancement of the 2-micron triple-pulse IPDA lidar development. Updates on the state-of-the-art triple-pulse laser transmitter will be presented including the status of wavelength control, packaging and lidar integration. In addition, receiver development updates will also be presented, including telescope integration, detection systems and data acquisition electronics. Future plan for IPDA lidar system for ground integration, testing and flight validation will be presented.

  15. 2-Micron Triple-Pulse Integrated Path Differential Absorption Lidar Development for Simultaneous Airborne Column Measurements of Carbon Dioxide and Water Vapor in the Atmosphere

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Petros, Mulugeta; Refaat, Tamer F.; Yu, Jirong

    2016-01-01

    For more than 15 years, NASA Langley Research Center (LaRC) has contributed in developing several 2-micron carbon dioxide active remote sensors using the DIAL technique. Currently, an airborne 2-micron triple-pulse integrated path differential absorption (IPDA) lidar is under development at NASA LaRC. This paper focuses on the advancement of the 2-micron triple-pulse IPDA lidar development. Updates on the state-of-the-art triple-pulse laser transmitter will be presented including the status of wavelength control, packaging and lidar integration. In addition, receiver development updates will also be presented, including telescope integration, detection systems and data acquisition electronics. Future plan for IPDA lidar system for ground integration, testing and flight validation will be presented.

  16. SU-E-J-141: Activity-Equivalent Path Length Approach for the 3D PET-Based Dose Reconstruction in Proton Therapy

    SciTech Connect

    Attili, A; Vignati, A; Giordanengo, S; Kraan, A; Dalmasso, F; Battistoni, G

    2015-06-15

    Purpose: Ion beam therapy is sensitive to uncertainties from treatment planning and dose delivery. PET imaging of induced positron emitter distributions is a practical approach for in vivo, in situ verification of ion beam treatments. Treatment verification is usually done by comparing measured activity distributions with reference distributions, evaluated in nominal conditions. Although such comparisons give valuable information on treatment quality, a proper clinical evaluation of the treatment ultimately relies on the knowledge of the actual delivered dose. Analytical deconvolution methods relating activity and dose have been studied in this context, but were not clinically applied. In this work we present a feasibility study of an alternative approach for dose reconstruction from activity data, which is based on relating variations in accumulated activity to tissue density variations. Methods: First, reference distributions of dose and activity were calculated from the treatment plan and CT data. Then, the actual measured activity data were cumulatively matched with the reference activity distributions to obtain a set of activity-equivalent path lengths (AEPLs) along the rays of the pencil beams. Finally, these AEPLs were used to deform the original dose distribution, yielding the actual delivered dose. The method was tested by simulating a proton therapy treatment plan delivering 2 Gy on a homogeneous water phantom (the reference), which was compared with the same plan delivered on a phantom containing inhomogeneities. Activity and dose distributions were were calculated by means of the FLUKA Monte Carlo toolkit. Results: The main features of the observed dose distribution in the inhomogeneous situation were reproduced using the AEPL approach. Variations in particle range were reproduced and the positions, where these deviations originated, were properly identified. Conclusions: For a simple inhomogeneous phantom the 3D dose reconstruction from PET

  17. Correlation of electron path lengths observed in the highly wound outer region of magnetic clouds with the slab fraction of magnetic turbulence in the dissipation range

    SciTech Connect

    Tan, Lun C.; Shao, Xi; Reames, Donald V.; Ng, Chee K.; Wang, Linghua

    2014-05-10

    Three magnetic cloud events, in which solar impulsive electron events occurred in their outer region, are employed to investigate the difference of path lengths L {sub 0eIII} traveled by non-relativistic electrons from their release site near the Sun to the observer at 1 AU, where L {sub 0eIII} = v {sub l} × (t {sub l} – t {sub III}), v {sub l} and t {sub l} being the velocity and arrival time of electrons in the lowest energy channel (∼27 keV) of the Wind/3DP/SST sensor, respectively, and t {sub III} being the onset time of type III radio bursts. The deduced L {sub 0eIII} value ranges from 1.3 to 3.3 AU. Since a negligible interplanetary scattering level can be seen in both L {sub 0eIII} > 3 AU and ∼1.2 AU events, the difference in L {sub 0eIII} could be linked to the turbulence geometry (slab or two-dimensional) in the solar wind. By using the Wind/MFI magnetic field data with a time resolution of 92 ms, we examine the turbulence geometry in the dissipation range. In our examination, ∼6 minutes of sampled subintervals are used in order to improve time resolution. We have found that, in the transverse turbulence, the observed slab fraction is increased with an increasing L {sub 0eIII} value, reaching ∼100% in the L {sub 0eIII} > 3 AU event. Our observation implies that when only the slab spectral component exists, magnetic flux tubes (magnetic surfaces) are closed and regular for a very long distance along the transport route of particles.

  18. Absorption and metabolization of sex hormones and their transformation into contraceptive technologies: the paths taken by medical thought in Brazil.

    PubMed

    Bonan, Claudia; Teixeira, Luiz Antonio; Nakano, Andreza Rodrigues

    2017-01-01

    The article analyses knowledge assimilation and the development of clinical and research practices relating to sex hormones among Brazilian gynaecologists. It discusses the paths taken by medical thought from the reception of the hormones to their transformation into contraceptives. Our objective is to comprehend styles of introducing and disseminating medical technologies in the area of reproductive health in Brazil. It uses methods of historical analysis and takes as its source the Anais Brasileiros de Ginecologia, a journal published between 1936 and 1970. From the outset, the accompaniment of scientific breakthroughs in relation to sex hormones and their use to treat diverse female illnesses played a key role in the rapid medical acceptance of hormonal contraception. Scientific and technical questions (side effects, dosages) and the demographic issue formed part of the majority of the debates. Objections from the Catholic Church were considered but did not set the agenda of medical thought on contraceptives. The quest to consolidate gynaecology as a scientific, modern and cosmopolitan area of expertise, along with sanitary and demographic motives that allowed contraceptives to be classed as ethical drugs, are identified as processes underlying the assimilation and metabolization of sex hormones as hormonal contraceptives.

  19. Probing grain boundary sink strength at the nanoscale: Energetics and length scales of vacancy and interstitial absorption by grain boundaries in α-Fe

    SciTech Connect

    Tschopp, Mark A.; Solanki, K. N.; Gao, Fei; Sun, Xin; Khaleel, Mohammad A.; Horstemeyer, Mark

    2012-02-10

    The energetics and length scales associated with the interaction between point defects (vacancies and self-interstitial atoms) and grain boundaries in bcc Fe was explored. Molecular statics simulations were used to generate a grain boundary structure database that contained {approx}170 grain boundaries with varying tilt and twist character. Then, vacancy and self-interstitial atom formation energies were calculated at all potential grain boundary sites within 15 {angstrom} of the boundary. The present results provide detailed information about the interaction energies of vacancies and self-interstitial atoms with symmetric tilt grain boundaries in iron and the length scales involved with absorption of these point defects by grain boundaries. Both low- and high-angle grain boundaries were effective sinks for point defects, with a few low-{Sigma} grain boundaries (e.g., the {Sigma}3{l_brace}112{r_brace} twin boundary) that have properties different from the rest. The formation energies depend on both the local atomic structure and the distance from the boundary center. Additionally, the effect of grain boundary energy, disorientation angle, and {Sigma} designation on the boundary sink strength was explored; the strongest correlation occurred between the grain boundary energy and the mean point defect formation energies. Based on point defect binding energies, interstitials have {approx}80% more grain boundary sites per area and {approx}300% greater site strength than vacancies. Last, the absorption length scale of point defects by grain boundaries is over a full lattice unit larger for interstitials than for vacancies (mean of 6-7 {angstrom} versus 10-11 {angstrom} for vacancies and interstitials, respectively).

  20. Molar Absorptivity Measurements in Absorbing Solvents: Impact on Solvent Absorptivity Values.

    PubMed

    Bohman, Ariel; Arnold, Mark A

    2016-10-18

    Molar absorptivity is a fundamental molecular property that quantifies absorption strength as a function of wavelength. Absolute measurements of molar absorptivity demand accounting for all mechanisms of light attenuation, including reflective losses at interfaces associated with the sample. Ideally, such measurements are performed in nonabsorbing solvents and reflective losses can be determined in a straightforward manner from Fresnel equations or effectively accounted for by path length difference methods. At near-infrared wavelengths, however, many solvents, including water, are absorbing which complicates the quantification of reflective losses. Here, generalized equations are developed for calculating absolute molar absorptivities of neat liquids wherein the dependency of reflective loss on absorption properties of the liquid are considered explicitly. The resulting equations are used to characterize sensitivity of absolute molar absorptivity measurements for solvents to the absorption strength of the solvent as well as the path length of the measurement. Methods are derived from these equations to properly account for reflective losses in general and the effectiveness of these methods is demonstrated for absolute molar absorptivity measurements for water over the combination region (5000-4000 cm(-1)) of the near-infrared spectrum. Results indicate that ignoring solvent absorption effects can incorporate wide ranging systematic errors depending upon experimental conditions. As an example, systematic errors range from 0 to 10% for common conditions used in the measurement of absolute molar absorptivity of water over the combination region of the near-infrared spectrum.

  1. Comparing different light-emitting diodes as light sources for long path differential optical absorption spectroscopy NO2 and SO2 measurements

    NASA Astrophysics Data System (ADS)

    Chan, Ka-Lok; Ling, Liu-Yi; Andreas, Hartl; Zheng, Ni-Na; Gerrit, Kuhlmann; Qin, Min; Sun, You-Wen; Xie, Pin-Hua; Liu, Wen-Qing; Mark, Wenig

    2012-11-01

    In this paper, we present a comparison of different light-emitting diodes (LEDs) as the light source for long path differential optical absorption spectroscopy (LP-DOAS) atmospheric trace gas measurements. In our study, we use a fiberoptic design, where high power LEDs used as the light source are coupled into the telescope using a Y shape fiber bundle. Two blue and one ultraviolet (UV) LEDs with different emission wavelength ranges are tested for NO2 and SO2 measurements. The detailed description of the instrumental setup, the NO2 and SO2 retrieval procedure, the error analysis, and the preliminary results from the measurements carried out in Science Island, Hefei, Anhui, China are presented. Our first measurement results show that atmospheric NO2 and SO2 have strong temporal variations in that area and that the measurement accuracy is strongly dependent on the visibility conditions. The measured NO2 and SO2 data are compared to the Ozone Monitoring Instrument (OMI) satellite observations. The results show that the OMI NO2 product underestimates the ground level NO2 by 45%, while the OMI SO2 data are highly influenced by clouds and aerosols, which can lead to large biases in the ground level concentrations. During the experiment, the mixing ratios of the atmospheric NO2 and SO2 vary from 8 ppbv to 36 ppbv and from 3 ppbv to 18 ppbv, respectively.

  2. Self-Calibration and Laser Energy Monitor Validations for a Double-Pulsed 2-Micron CO2 Integrated Path Differential Absorption Lidar Application

    NASA Technical Reports Server (NTRS)

    Refaat, Tamer F.; Singh, Upendra N.; Petros, Mulugeta; Remus, Ruben; Yu, Jirong

    2015-01-01

    Double-pulsed 2-micron integrated path differential absorption (IPDA) lidar is well suited for atmospheric CO2 remote sensing. The IPDA lidar technique relies on wavelength differentiation between strong and weak absorbing features of the gas normalized to the transmitted energy. In the double-pulse case, each shot of the transmitter produces two successive laser pulses separated by a short interval. Calibration of the transmitted pulse energies is required for accurate CO2 measurement. Design and calibration of a 2-micron double-pulse laser energy monitor is presented. The design is based on an InGaAs pin quantum detector. A high-speed photo-electromagnetic quantum detector was used for laser-pulse profile verification. Both quantum detectors were calibrated using a reference pyroelectric thermal detector. Calibration included comparing the three detection technologies in the single-pulsed mode, then comparing the quantum detectors in the double-pulsed mode. In addition, a self-calibration feature of the 2-micron IPDA lidar is presented. This feature allows one to monitor the transmitted laser energy, through residual scattering, with a single detection channel. This reduces the CO2 measurement uncertainty. IPDA lidar ground validation for CO2 measurement is presented for both calibrated energy monitor and self-calibration options. The calibrated energy monitor resulted in a lower CO2 measurement bias, while self-calibration resulted in a better CO2 temporal profiling when compared to the in situ sensor.

  3. New Results from Frequency and Energy Reference Measurements during the first Test Flight with the Airborne Integrated Path Differential Absorption Lidar System CHARM-F

    NASA Astrophysics Data System (ADS)

    Ehret, G.; Fix, A.; Amediek, A.; Quatrevalet, M.

    2015-12-01

    The Integrated Path Differential Absorption Lidar (IPDA) technique is regarded as a suitable means for the measurement of methane and carbon dioxide columns from satellite or aircraft platforms with unprecedented accuracy. Currently, the German-French methane mission MERLIN (Methan Remote Lidar Mission) is prepared. At the same time CHARM-F, an aircraft installed system has been developed at DLR as an airborne demonstrator for a spaceborne greenhouse gas mission. Both use e.g. optical parametric oscillators (OPOs) in a double-pulse mode as the transmitter. Of particular importance for both instruments are the sub-modules required for the frequency stabilization of the transmitter wavelength and, since the IPDA technique, in contrast to DIAL, requires the exact knowledge of the energy ratio of outgoing on-line. The coherence of the lidar transmitter gives rise to speckle effects which have to be considered for the monitoring of the energy ratio of outgoing on- and off-line pulses. For the frequency reference of CHARM-F, a very successful stabilization scheme has been developed which will also serve as the reference for MERLIN. In Spring 2015, CHARM-F was flown aboard the German HALO aircraft for the first time which enables a detailed view on the performance of both the energy calibration and frequency reference subsystems under real flight conditions. As an initial quality check we will compared the airborne results to previous lab measurements which have been performed under stable environmental conditions.

  4. Changes in Search Path Complexity and Length During Learning of a Virtual Water Maze: Age Differences and Differential Associations with Hippocampal Subfield Volumes.

    PubMed

    Daugherty, Ana M; Bender, Andrew R; Yuan, Peng; Raz, Naftali

    2016-06-01

    Impairment of hippocampus-dependent cognitive processes has been proposed to underlie age-related deficits in navigation. Animal studies suggest a differential role of hippocampal subfields in various aspects of navigation, but that hypothesis has not been tested in humans. In this study, we examined the association between volume of hippocampal subfields and age differences in virtual spatial navigation. In a sample of 65 healthy adults (age 19-75 years), advanced age was associated with a slower rate of improvement operationalized as shortening of the search path over 25 learning trials on a virtual Morris water maze task. The deficits were partially explained by greater complexity of older adults' search paths. Larger subiculum and entorhinal cortex volumes were associated with a faster decrease in search path complexity, which in turn explained faster shortening of search distance. Larger Cornu Ammonis (CA)1-2 volume was associated with faster distance shortening, but not in path complexity reduction. Age differences in regional volumes collectively accounted for 23% of the age-related variance in navigation learning. Independent of subfield volumes, advanced age was associated with poorer performance across all trials, even after reaching the asymptote. Thus, subiculum and CA1-2 volumes were associated with speed of acquisition, but not magnitude of gains in virtual maze navigation.

  5. Self-calibration and laser energy monitor validations for a double-pulsed 2-μm CO2 integrated path differential absorption lidar application.

    PubMed

    Refaat, Tamer F; Singh, Upendra N; Petros, Mulugeta; Remus, Ruben; Yu, Jirong

    2015-08-20

    Double-pulsed 2-μm integrated path differential absorption (IPDA) lidar is well suited for atmospheric CO2 remote sensing. The IPDA lidar technique relies on wavelength differentiation between strong and weak absorbing features of the gas normalized to the transmitted energy. In the double-pulse case, each shot of the transmitter produces two successive laser pulses separated by a short interval. Calibration of the transmitted pulse energies is required for accurate CO2 measurement. Design and calibration of a 2-μm double-pulse laser energy monitor is presented. The design is based on an InGaAs pin quantum detector. A high-speed photoelectromagnetic quantum detector was used for laser-pulse profile verification. Both quantum detectors were calibrated using a reference pyroelectric thermal detector. Calibration included comparing the three detection technologies in the single-pulsed mode, then comparing the quantum detectors in the double-pulsed mode. In addition, a self-calibration feature of the 2-μm IPDA lidar is presented. This feature allows one to monitor the transmitted laser energy, through residual scattering, with a single detection channel. This reduces the CO2 measurement uncertainty. IPDA lidar ground validation for CO2 measurement is presented for both calibrated energy monitor and self-calibration options. The calibrated energy monitor resulted in a lower CO2 measurement bias, while self-calibration resulted in a better CO2 temporal profiling when compared to the in situ sensor.

  6. Comparison of methods for transfer of calibration models in near-infared spectroscopy: a case study based on correcting path length differences using fiber-optic transmittance probes in in-line near-infrared spectroscopy.

    PubMed

    Sahni, Narinder Singh; Isaksson, Tomas; Naes, Tormod

    2005-04-01

    This article addresses problems related to transfer of calibration models due to variations in distance between the transmittance fiber-optic probes. The data have been generated using a mixture design and measured at five different probe distances. A number of techniques reported in the literature have been compared. These include multiplicative scatter correction (MSC), path length correction (PLC), finite impulse response (FIR), orthogonal signal correction (OSC), piecewise direct standardization (PDS), and robust calibration. The quality of the predictions was expressed in terms of root mean square error of prediction (RMSEP). Robust calibration gave good calibration transfer results, while the other methods did not give acceptable results.

  7. Low-Absorption Liquid Crystals for Infrared Beam Steering

    DTIC Science & Technology

    2013-10-22

    clearing point of 51.5 "C and its melting point is lower than -10 °C due to super-cooling effect . We also measured its transmission spectrum in the...thickness (or effective optical path length) increases, then the absorption will increase exponentially, as Eq. (1) indicates. To improve transmittance... effective mass (m) as: (0 = -yjic/m. (3) As the effective mass increases the vibration frequency decreases, i.e., the absorption band shifts toward a

  8. Method and apparatus for background signal reduction in opto-acoustic absorption measurement

    NASA Technical Reports Server (NTRS)

    Rosengren, L. G. (Inventor)

    1976-01-01

    The sensitivity of an opto-acoustic absorption detector is increased to make it possible to measure trace amounts of constituent gases. A second beam radiation path is created through the sample cell identical to a first path except as to length, alternating the beam through the two paths and minimizing the detected pressure difference for the two paths while the beam wavelength is tuned away from the absorption lines of the sample. Then with the beam wavelength tuned to the absorption line of any constituent of interest, the pressure difference is a measure of trace amounts of the constituent. The same improved detector may also be used for measuring the absorption coefficient of known concentrations of absorbing gases.

  9. Integration of Fluorescence Differential Path-Length Spectroscopy to Photodynamic Therapy of the Head and Neck Tumors is Useful in Monitoring Clinical Outcome

    NASA Astrophysics Data System (ADS)

    Karakullukcu, Baris; Kanick, Stephen; Aans, Jan Bonne; Sterenborg, Henricus; Tan, Bing; Amelink, Arjen; Robinson, Dominic

    2015-04-01

    The use of fluorescence differential pathlength spectroscopy (FDPS) has the potential to provide real-time information on photosensitiser pharmacokinetics, vascular physiology and photosensitizer photobleaching based dosimetry of tumors in the oral cavity receiving m-tetrahydroxyphenylchlorin (mTHPC) photodynamic therapy (PDT). Reflectance spectra can be used provide quantitative values of oxygen saturation, blood volume fraction, blood vessel diameter, and to determine the local optical properties that can be used to correct raw fluorescence for tissue absorption. Patients and methods: Twenty-seven lesions in the oral cavity, either dysplasias or cancer were interrogated using FDPS, before and immediately after the therapeutic illumination. The average tumor center to normal mucosa ratio of fluorescence was 1.50 ± 0.66. mTHPC photobleaching was observed in 24 of the lesions treated. The average extent of photobleaching was 81% ± 17%. Information from FDPS spectroscopy coupled with the clinical results of the treatment identified 3 types of correctable errors in the application of mTHPC-PDT: Two patients exhibited very low concentrations of photosensitizer in tumour center, indicating an ineffective i.v. injection of photosensitiser or an erroneous systemic distribution of mTHPC. In one in tumor we observed no photobleaching accompanied by a high blood volume fraction in the illuminated tissue, suggesting that the presence of blood prevented therapeutic light reaching the target tissue. All 3 of the these lesions had no clinical response to PDT. In four patients we observed less than 50% photobleaching at the tumor margins , suggesting a possible geographic miss. One patient in this group had a recurrence within 2 months after PDT even though the initial response was good. The integration of FDPS to clinical PDT yields data on tissue physiology, photosensitiser content and photobleaching that can help identify treatment errors that can potentially be corrected.

  10. Azimuthal Anisotropy of pi Production in Au+Au Collisions at s_NN = 200 GeV: Path-length Dependence of Jet-Quenching and the Role of Initial Geometry

    SciTech Connect

    Adare, A.; Awes, Terry C; Cianciolo, Vince; Efremenko, Yuri; Enokizono, Akitomo; Read Jr, Kenneth F; Silvermyr, David O; Sorensen, Soren P; Stankus, Paul W; PHENIX, Collaboration

    2010-01-01

    We have measured the azimuthal anisotropy of {pi}{sup 0} production for 1 < p{sub T} < 18 GeV/c for Au+Au collisions at {radical}s{sub NN} = 200 GeV. The observed anisotropy shows a gradual decrease for 3 {approx}< p {approx}< 7-10 GeV/c, but remains positive beyond 10 GeV/c. The magnitude of this anisotropy is underpredicted, up to at least {approx}10 GeV/c, by current perturbative QCD (PQCD) energy-loss model calculations. An estimate of the increase in anisotropy expected from initial-geometry modification due to gluon saturation effects and fluctuations is insufficient to account for this discrepancy. Calculations that implement a path-length dependence steeper than what is implied by current PQCD energy-loss models show reasonable agreement with the data.

  11. In situ Gas Temperature Measurements by UV-Absorption Spectroscopy

    NASA Astrophysics Data System (ADS)

    Fateev, A.; Clausen, S.

    2009-02-01

    The absorption spectrum of the NO A2Σ+ ← X2Πγ-system can be used for in situ evaluation of gas temperature. Experiments were performed with a newly developed atmospheric-pressure high-temperature flow gas cell at highly uniform and stable gas temperatures over a 0.533 m path in the range from 23 °C to 1,500 °C. The gas temperature was evaluated (1) from the analysis of the structure of selected NO high-resolution γ-absorption bands and (2) from the analysis of vibrational distribution in the NO γ-absorption system in the (211-238) nm spectral range. The accuracy of both methods is discussed. Validation of the classical Lambert-Beer law has been demonstrated at NO concentrations up to 500 ppm and gas temperatures up to 1,500 °C over an optical absorption path length of 0.533 m.

  12. Path Finder

    SciTech Connect

    Rigdon, J. Brian; Smith, Marcus Daniel; Mulder, Samuel A

    2014-01-07

    PathFinder is a graph search program, traversing a directed cyclic graph to find pathways between labeled nodes. Searches for paths through ordered sequences of labels are termed signatures. Determining the presence of signatures within one or more graphs is the primary function of Path Finder. Path Finder can work in either batch mode or interactively with an analyst. Results are limited to Path Finder whether or not a given signature is present in the graph(s).

  13. Broadband transient absorption spectroscopy with 1- and 2-photon excitations: Relaxation paths and cross sections of a triphenylamine dye in solution

    SciTech Connect

    Moreno, J.; Dobryakov, A. L.; Hecht, S. E-mail: skovale@chemie.hu-berlin.de; Kovalenko, S. A. E-mail: skovale@chemie.hu-berlin.de; Ioffe, I. N.; Granovsky, A. A.

    2015-07-14

    1-photon (382 nm) and 2-photon (752 nm) excitations to the S{sub 1} state are applied to record and compare transient absorption spectra of a push-pull triphenylamine (TrP) dye in solution. After 1-photon excitation, ultrafast vibrational and structural molecular relaxations are detected on a 0.1 ps time scale in nonpolar hexane, while in polar acetonitrile, the spectral evolution is dominated by dipolar solvation. Upon 2-photon excitation, transient spectra in hexane reveal an unexpected growth of stimulated emission (SE) and excited-state absorption (ESA) bands. The behavior is explained by strong population transfer S{sub 1} → S{sub n} due to resonant absorption of a third pump photon. Subsequent S{sub n} → S{sub 1} internal conversion (with τ{sub 1} = 1 ps) prepares a very hot S{sub 1} state which cools down with τ{sub 2} = 13 ps. The pump pulse energy dependence proves the 2-photon origin of the bleach signal. At the same time, SE and ESA are strongly affected by higher-order pump absorptions that should be taken into account in nonlinear fluorescence applications. The 2-photon excitation cross sections σ{sup (2)} = 32 ⋅ 10{sup −50} cm{sup 4} s at 752 nm are evaluated from the bleach signal.

  14. Broadband transient absorption spectroscopy with 1- and 2-photon excitations: Relaxation paths and cross sections of a triphenylamine dye in solution.

    PubMed

    Moreno, J; Dobryakov, A L; Ioffe, I N; Granovsky, A A; Hecht, S; Kovalenko, S A

    2015-07-14

    1-photon (382 nm) and 2-photon (752 nm) excitations to the S1 state are applied to record and compare transient absorption spectra of a push-pull triphenylamine (TrP) dye in solution. After 1-photon excitation, ultrafast vibrational and structural molecular relaxations are detected on a 0.1 ps time scale in nonpolar hexane, while in polar acetonitrile, the spectral evolution is dominated by dipolar solvation. Upon 2-photon excitation, transient spectra in hexane reveal an unexpected growth of stimulated emission (SE) and excited-state absorption (ESA) bands. The behavior is explained by strong population transfer S1 → Sn due to resonant absorption of a third pump photon. Subsequent Sn → S1 internal conversion (with τ1 = 1 ps) prepares a very hot S1 state which cools down with τ2 = 13 ps. The pump pulse energy dependence proves the 2-photon origin of the bleach signal. At the same time, SE and ESA are strongly affected by higher-order pump absorptions that should be taken into account in nonlinear fluorescence applications. The 2-photon excitation cross sections σ(2) = 32 ⋅ 10(-50) cm(4) s at 752 nm are evaluated from the bleach signal.

  15. Diode laser-based sensor system for long-path absorption measurements of atmospheric concentration and near-IR molecular spectral parameters

    SciTech Connect

    Goldstein, N.; Lee, J.; Adler-Golden, S.M.; Bien, F.

    1993-12-31

    Line-locked near-IR diode lasers and a simple retroreflector/telescope system were used for remote sensing of atmospheric constituents over long atmospheric paths. The experimental configuration used in preliminary measurements of atmospheric water vapor and oxygen with AlGaAs diode lasers is presented. A prototype field sensor system currently under development shares the same basic configuration but incorporates interchangeable AlGaAs and InGaAsP diode-laser modules for monitoring a variety of atmospheric gases.

  16. Global sampling of the photochemical reaction paths of bromoform by ultrafast deep-UV through near-IR transient absorption and ab initio multiconfigurational calculations

    NASA Astrophysics Data System (ADS)

    Pal, S. K.; Mereshchenko, A. S.; Butaeva, E. V.; El-Khoury, P. Z.; Tarnovsky, A. N.

    2013-03-01

    Ultrafast deep-ultraviolet through near infrared (210-950 nm) transient absorption spectroscopy complemented by ab initio multiconfigurational calculations offers a global description of the photochemical reaction pathways of bromoform following 255-nm excitation in methylcyclohexane and acetonitrile solutions. Photoexcitation of CHBr3 leads to the ground-state iso-CHBr3 product in a large quantum yield (˜35%), formed through two different mechanisms: concerted excited-state isomerization and cage-induced isomerization through the recombination of the nascent radical pair. These two processes take place on different time scales of tens of femtoseconds and several picoseconds, respectively. The novel ultrafast direct isomerization pathway proposed herein is consistent with the occurrence of a conical intersection between the first excited singlet state of CHBr3 and the ground electronic state of iso-CHBr3. Complete active space self-consistent field calculations characterize this singularity in the vicinity of a second order saddle point on the ground state which connects the two isomer forms. For cage-induced isomerization, both the formation of the nascent radical pair and its subsequent collapse into ground-state iso-CHBr3 are directly monitored through the deep-ultraviolet absorption signatures of the radical species. In both mechanisms, the optically active (i.e., those with largest Franck-Condon factors) C-Br-Br bending and Br-Br stretching modes of ground-state iso-CHBr3 have the largest projection on the reaction coordinate, enabling us to trace the structural changes accompanying vibrational relaxation of the non-equilibrated isomers through transient absorption dynamics. The iso-CHBr3 photoproduct is stable in methylcyclohexane, but undergoes either facile thermal isomerization to the parent CHBr3 structure through a cyclic transition state stabilized by the polar acetonitrile medium (˜300-ps lifetime), and hydrolysis in the presence of water.

  17. Development of an Airborne Triple-Pulse 2-Micron Integrated Path Differential Absorption Lidar (IPDA) for Simultaneous Airborne Column Measurements of Carbon Dioxide and Water Vapor in the Atmosphere

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Petros, Mulugeta; Refaat, Tamer F.; Yu, Jirong; Antill, Charles W.; Remus, Ruben

    2016-01-01

    This presentation will provide status and details of an airborne 2-micron triple-pulse integrated path differential absorption (IPDA) lidar being developed at NASA Langley Research Center with support from NASA ESTO Instrument Incubator Program. The development of this active optical remote sensing IPDA instrument is targeted for measuring both atmospheric carbon dioxide and water vapor in the atmosphere from an airborne platform. This presentation will focus on the advancement of the 2-micron triple-pulse IPDA lidar development. Updates on the state-of-the-art triple-pulse laser transmitter will be presented including the status of seed laser locking, wavelength control, receiver and detector upgrades, laser packaging and lidar integration. Future plan for IPDA lidar system for ground integration, testing and flight validation will also be presented.

  18. Optical path control in the MAM testbed

    NASA Technical Reports Server (NTRS)

    Regehr, M. W.; Hines, B.; Holmes, B.

    2003-01-01

    Future space-based optical interferometers will require control of the optical path delay to accomplish some or all of the three objectives: balancing the optical path in the two arms to within a tolerance corresponding to the coherence length of the star light being observed, modulating the optical path in order to observe the phase of the star light interference fringe, and modulating the path length in order to reduce the effect of cyclic errors in the laser metrology system used to measure the optical path length in the two arms of the interferometer.

  19. Ligand binding at the A-cluster in full-length or truncated acetyl-CoA synthase studied by X-ray absorption spectroscopy

    PubMed Central

    Schrapers, Peer; Ilina, Julia; Gregg, Christina M.; Mebs, Stefan; Jeoung, Jae-Hun; Dau, Holger; Dobbek, Holger; Haumann, Michael

    2017-01-01

    Bacteria integrate CO2 reduction and acetyl coenzyme-A (CoA) synthesis in the Wood-Ljungdal pathway. The acetyl-CoA synthase (ACS) active site is a [4Fe4S]-[NiNi] complex (A-cluster). The dinickel site structure (with proximal, p, and distal, d, ions) was studied by X-ray absorption spectroscopy in ACS variants comprising all three protein domains or only the C-terminal domain with the A-cluster. Both variants showed two square-planar Ni(II) sites and an OH- bound at Ni(II)p in oxidized enzyme and a H2O at Ni(I)p in reduced enzyme; a Ni(I)p-CO species was induced by CO incubation and a Ni(II)-CH3- species with an additional water ligand by a methyl group donor. These findings render a direct effect of the N-terminal and middle domains on the A-cluster structure unlikely. PMID:28178309

  20. Ligand binding at the A-cluster in full-length or truncated acetyl-CoA synthase studied by X-ray absorption spectroscopy.

    PubMed

    Schrapers, Peer; Ilina, Julia; Gregg, Christina M; Mebs, Stefan; Jeoung, Jae-Hun; Dau, Holger; Dobbek, Holger; Haumann, Michael

    2017-01-01

    Bacteria integrate CO2 reduction and acetyl coenzyme-A (CoA) synthesis in the Wood-Ljungdal pathway. The acetyl-CoA synthase (ACS) active site is a [4Fe4S]-[NiNi] complex (A-cluster). The dinickel site structure (with proximal, p, and distal, d, ions) was studied by X-ray absorption spectroscopy in ACS variants comprising all three protein domains or only the C-terminal domain with the A-cluster. Both variants showed two square-planar Ni(II) sites and an OH- bound at Ni(II)p in oxidized enzyme and a H2O at Ni(I)p in reduced enzyme; a Ni(I)p-CO species was induced by CO incubation and a Ni(II)-CH3- species with an additional water ligand by a methyl group donor. These findings render a direct effect of the N-terminal and middle domains on the A-cluster structure unlikely.

  1. An introduction to critical paths.

    PubMed

    Coffey, Richard J; Richards, Janet S; Remmert, Carl S; LeRoy, Sarah S; Schoville, Rhonda R; Baldwin, Phyllis J

    2005-01-01

    A critical path defines the optimal sequencing and timing of interventions by physicians, nurses, and other staff for a particular diagnosis or procedure. Critical paths are developed through collaborative efforts of physicians, nurses, pharmacists, and others to improve the quality and value of patient care. They are designed to minimize delays and resource utilization and to maximize quality of care. Critical paths have been shown to reduce variation in the care provided, facilitate expected outcomes, reduce delays, reduce length of stay, and improve cost-effectiveness. The approach and goals of critical paths are consistent with those of total quality management (TQM) and can be an important part of an organization's TQM process.

  2. The dependence of the ultrafast relaxation kinetics of the S2 and S1 states in β-carotene homologs and lycopene on conjugation length studied by femtosecond time-resolved absorption and Kerr-gate fluorescence spectroscopies

    NASA Astrophysics Data System (ADS)

    Kosumi, Daisuke; Fujiwara, Masazumi; Fujii, Ritsuko; Cogdell, Richard J.; Hashimoto, Hideki; Yoshizawa, Masayuki

    2009-06-01

    The ultrafast relaxation kinetics of all-trans-β-carotene homologs with varying numbers of conjugated double bonds n(n =7-15) and lycopene (n =11) has been investigated using femtosecond time-resolved absorption and Kerr-gate fluorescence spectroscopies, both carried out under identical excitation conditions. The nonradiative relaxation rates of the optically allowed S2(1Bu+1) state were precisely determined by the time-resolved fluorescence. The kinetics of the optically forbidden S1(2Ag-1) state were observed by the time-resolved absorption measurements. The dependence of the S1 relaxation rates upon the conjugation length is adequately described by application of the energy gap law. In contrast to this, the nonradiative relaxation rates of S2 have a minimum at n =9 and show a reverse energy gap law dependence for values of n above 11. This anomalous behavior of the S2 relaxation rates can be explained by the presence of an intermediate state (here called the Sx state) located between the S2 and S1 states at large values of n (such as n =11). The presence of such an intermediate state would then result in the following sequential relaxation pathway S2→Sx→S1→S0. A model based on conical intersections between the potential energy curves of these excited singlet states can readily explain the measured relationships between the decay rates and the energy gaps.

  3. The dependence of the ultrafast relaxation kinetics of the S(2) and S(1) states in beta-carotene homologs and lycopene on conjugation length studied by femtosecond time-resolved absorption and Kerr-gate fluorescence spectroscopies.

    PubMed

    Kosumi, Daisuke; Fujiwara, Masazumi; Fujii, Ritsuko; Cogdell, Richard J; Hashimoto, Hideki; Yoshizawa, Masayuki

    2009-06-07

    The ultrafast relaxation kinetics of all-trans-beta-carotene homologs with varying numbers of conjugated double bonds n(n=7-15) and lycopene (n=11) has been investigated using femtosecond time-resolved absorption and Kerr-gate fluorescence spectroscopies, both carried out under identical excitation conditions. The nonradiative relaxation rates of the optically allowed S(2)(1(1)B(u) (+)) state were precisely determined by the time-resolved fluorescence. The kinetics of the optically forbidden S(1)(2(1)A(g) (-)) state were observed by the time-resolved absorption measurements. The dependence of the S(1) relaxation rates upon the conjugation length is adequately described by application of the energy gap law. In contrast to this, the nonradiative relaxation rates of S(2) have a minimum at n=9 and show a reverse energy gap law dependence for values of n above 11. This anomalous behavior of the S(2) relaxation rates can be explained by the presence of an intermediate state (here called the S(x) state) located between the S(2) and S(1) states at large values of n (such as n=11). The presence of such an intermediate state would then result in the following sequential relaxation pathway S(2)-->S(x)-->S(1)-->S(0). A model based on conical intersections between the potential energy curves of these excited singlet states can readily explain the measured relationships between the decay rates and the energy gaps.

  4. Path Pascal

    NASA Technical Reports Server (NTRS)

    Campbell, R. H.; Kolstad, R. B.; Holle, D. F.; Miller, T. J.; Krause, P.; Horton, K.; Macke, T.

    1983-01-01

    Path Pascal is high-level experimental programming language based on PASCAL, which incorporates extensions for systems and real-time programming. Pascal is extended to treat real-time concurrent systems.

  5. Computer programs for absorption spectrophotometry.

    PubMed

    Jones, R N

    1969-03-01

    Brief descriptions are given of twenty-two modular computer programs for performing the basic numerical computations of absorption spectrophotometry. The programs, written in Fortran IV for card input and output, are available from the National Research Council of Canada. The input and output formats are standardized to permit easy interfacing to yield more complex data processing systems. Though these programs were developed for ir spectrophotometry, they are readily modified for use with digitized visual and uv spectrophotometers. The operations covered include ordinate and abscissal unit and scale interconversions, ordinate addition and subtraction, location of band maxima and minima, smoothing and differentiation, slit function convolution and deconvolution, band profile analysis and asymmetry quantification, Fourier transformation to time correlation curves, multiple overlapping band separation in terms of Cauchy (Lorentz), Gauss, Cauchy-Gauss product, and Cauchy-Gauss sum functions and cell path length determination from fringe spacing analysis.

  6. Intracavity absorption with a continuous wave dye laser - Quantification for a narrowband absorber

    NASA Technical Reports Server (NTRS)

    Brobst, William D.; Allen, John E., Jr.

    1987-01-01

    An experimental investigation of the dependence of intracavity absorption on factors including transition strength, concentration, absorber path length, and pump power is presented for a CW dye laser with a narrow-band absorber (NO2). A Beer-Lambert type relationship is found over a small but useful range of these parameters. Quantitative measurement of intracavity absorption from the dye laser spectral profiles showed enhancements up to 12,000 (for pump powers near lasing threshold) when compared to extracavity measurements. The definition of an intracavity absorption coefficient allowed the determination of accurate transition strength ratios, demonstrating the reliability of the method.

  7. Time optimal paths for high speed maneuvering

    SciTech Connect

    Reister, D.B.; Lenhart, S.M.

    1993-01-01

    Recent theoretical results have completely solved the problem of determining the minimum length path for a vehicle with a minimum turning radius moving from an initial configuration to a final configuration. Time optimal paths for a constant speed vehicle are a subset of the minimum length paths. This paper uses the Pontryagin maximum principle to find time optimal paths for a constant speed vehicle. The time optimal paths consist of sequences of axes of circles and straight lines. The maximum principle introduces concepts (dual variables, bang-bang solutions, singular solutions, and transversality conditions) that provide important insight into the nature of the time optimal paths. We explore the properties of the optimal paths and present some experimental results for a mobile robot following an optimal path.

  8. Completely automated open-path FT-IR spectrometry.

    PubMed

    Griffiths, Peter R; Shao, Limin; Leytem, April B

    2009-01-01

    Atmospheric analysis by open-path Fourier-transform infrared (OP/FT-IR) spectrometry has been possible for over two decades but has not been widely used because of the limitations of the software of commercial instruments. In this paper, we describe the current state-of-the-art of the hardware and software that constitutes a contemporary OP/FT-IR spectrometer. We then describe advances that have been made in our laboratory that have enabled many of the limitations of this type of instrument to be overcome. These include not having to acquire a single-beam background spectrum that compensates for absorption features in the spectra of atmospheric water vapor and carbon dioxide. Instead, an easily measured "short path-length" background spectrum is used for calculation of each absorbance spectrum that is measured over a long path-length. To accomplish this goal, the algorithm used to calculate the concentrations of trace atmospheric molecules was changed from classical least-squares regression (CLS) to partial least-squares regression (PLS). For calibration, OP/FT-IR spectra are measured in pristine air over a wide variety of path-lengths, temperatures, and humidities, ratioed against a short-path background, and converted to absorbance; the reference spectrum of each analyte is then multiplied by randomly selected coefficients and added to these background spectra. Automatic baseline correction for small molecules with resolved rotational fine structure, such as ammonia and methane, is effected using wavelet transforms. A novel method of correcting for the effect of the nonlinear response of mercury cadmium telluride detectors is also incorporated. Finally, target factor analysis may be used to detect the onset of a given pollutant when its concentration exceeds a certain threshold. In this way, the concentration of atmospheric species has been obtained from OP/FT-IR spectra measured at intervals of 1 min over a period of many hours with no operator intervention.

  9. Spreading paths in partially observed social networks

    PubMed Central

    Onnela, Jukka-Pekka; Christakis, Nicholas A.

    2012-01-01

    Understanding how and how far information, behaviors, or pathogens spread in social networks is an important problem, having implications for both predicting the size of epidemics, as well as for planning effective interventions. There are, however, two main challenges for inferring spreading paths in real-world networks. One is the practical difficulty of observing a dynamic process on a network, and the other is the typical constraint of only partially observing a network. Using a static, structurally realistic social network as a platform for simulations, we juxtapose three distinct paths: (1) the stochastic path taken by a simulated spreading process from source to target; (2) the topologically shortest path in the fully observed network, and hence the single most likely stochastic path, between the two nodes; and (3) the topologically shortest path in a partially observed network. In a sampled network, how closely does the partially observed shortest path (3) emulate the unobserved spreading path (1)? Although partial observation inflates the length of the shortest path, the stochastic nature of the spreading process also frequently derails the dynamic path from the shortest path. We find that the partially observed shortest path does not necessarily give an inflated estimate of the length of the process path; in fact, partial observation may, counterintuitively, make the path seem shorter than it actually is. PMID:22587148

  10. Multi-Criteria Path Finding

    NASA Astrophysics Data System (ADS)

    Mohammadi, E.; Hunter, A.

    2012-07-01

    Path finding solutions are becoming a major part of many GIS applications including location based services and web-based GIS services. Most traditional path finding solutions are based on shortest path algorithms that tend to minimize the cost of travel from one point to another. These algorithms make use of some cost criteria that is usually an attribute of the edges in the graph network. Providing one shortest path limits user's flexibility when choosing a possible route, especially when more than one parameter is utilized to calculate cost (e.g., when length, number of traffic lights, and number of turns are used to calculate network cost.) K shortest path solutions tend to overcome this problem by providing second, third, and Kth shortest paths. These algorithms are efficient as long as the graphs edge weight does not change dynamically and no other parameters affect edge weights. In this paper we try to go beyond finding shortest paths based on some cost value, and provide all possible paths disregarding any parameter that may affect total cost. After finding all possible paths, we can rank the results by any parameter or combination of parameters, without a substantial increase in time complexity.

  11. Highly sensitive detection using Herriott cell for laser absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhao, Chongyi; Song, Guangming; Du, Yang; Zhao, Xiaojun; Wang, Wenju; Zhong, Liujun; Hu, Mai

    2016-11-01

    The tunable diode laser absorption spectroscopy combined with the long absorption path technique is a significant method to detect harmful gas. The long optical path could come true by Herriott cell reducing the size of the spectrometers. A 15 cm long Herriott cell with 28.8 m optical absorption path after 96 times reflection was designed that enhanced detection sensitivity of absorption spectroscopy. According to the theory data of calculation, Herriott cell is analyzed and simulated by softwares Matlab and Lighttools.

  12. Relationships between molecular structure and kinetic and thermodynamic controls in lipid systems. Part II: Phase behavior and transformation paths of SSS, PSS and PPS saturated triacylglycerols--effect of chain length mismatch.

    PubMed

    Bouzidi, Laziz; Narine, Suresh S

    2012-01-01

    The kinetic phase behavior and phase transformation paths of purified tristearoylglycerol (SSS), 3-palmitoyl-1,2-distearoyl-sn-glycerol (PSS) and 1,2-dipalmitoyl-3-stearoyl-sn-glycerol (PPS) were investigated in terms of polymorphism, crystallization and melting. The details of the phase transformation paths were obtained using the heating cycles of two sets of experiments: (a) cooling rate was varied and heating rate fixed and (b) cooling rate was fixed and heating rate varied. Kinetic effects were manifest in all measured properties, underscoring the complexity of the phase transformation paths for each TAG, and the intricate thermodynamics-molecular relationships. For the first time, XRD data obtained for SSS, PSS and PPS TAGs, cooled at rates higher than 0.5°C/min, suggested the formation of a transient structure similar to the so-called α(2)-phase which has been observed in mixed saturated-unsaturated TAGs quenched from the melt. The more stable phases (β' in PSS and PPS, and β in SSS) were only observed for cooling rates lower than 1.0°C/min. The kinetic and thermodynamic differences observed in the crystallization, structure and melting of SSS, PSS and PPS are proposed to be mainly due to the disturbances introduced at the "terrace" level via methyl-end group interactions, i.e., the missing of two or four CH(2) groups compared to SSS. The symmetrical SSS with a relatively flat "terrace" crystallizes preferably in the most stable β-form. Two missing CH(2) groups at the sn-1 position (PSS) introduces enough structural disturbances to promote the relative prevalence and persistence of the β'-phase, and four missing CH(2) groups at the sn-1 and sn-2 positions (PPS) is relatively too large of a disturbance and therefore favors the α-form.

  13. PG 1411 + 442 - The nearest broad absorption line quasar

    NASA Technical Reports Server (NTRS)

    Malkan, Matthew A.; Green, Richard F.; Hutchings, John B.

    1987-01-01

    IUE observations reveal strong, moderately broad absorption troughs in the blue wings of the C IV and N V emission lines of the quasar PG 1411 + 442. No absorption from weakly ionized gas is detected. The emission-line strengths and overall shape of the ultraviolet/optical/near-infrared/far-infrared continuum of the new broad absorption line quasar are within the range normally measured in quasars. Its redshift is low enough to allow the morphology of the host galaxy to be studied in deep broad-band and intermediate-band CCD images. The galaxy appears to be a large spiral with a very long arm or tail. The inclination angle is 57 deg, which rules out the possibility that the line of sight to the nucleus intersects a large path length in a galactic disk.

  14. Mid-Infrared Laser Absorption Diagnostics for Combustion and Propulsion Applications

    DTIC Science & Technology

    2010-12-01

    mW), narrow line width, single- frequency, and tunable mid-IR laser radiation required for sensitive detection of gas-phase species [7-8]. As QCLs...been described numerous times; for example, see [24]. The absorption of monochromatic radiation along a line-of-sight is governed by the Beer...Lambert relation l_ TQ\\V where / and /0 are the transmitted and incident intensities, L the optical path length, i/the frequency of radiation , aj. the

  15. Ground-based, integrated path differential absorption LIDAR measurement of CO2, CH4, and H2O near 1.6  μm.

    PubMed

    Wagner, Gerd A; Plusquellic, David F

    2016-08-10

    A ground-based, integrated path, differential absorption light detection and ranging (IPDA LIDAR) system is described and characterized for a series of nighttime studies of CO2, CH4, and H2O. The transmitter is based on an actively stabilized, continuous-wave, single-frequency external-cavity diode laser (ECDL) operating from 1.60 to 1.65 μm. The fixed frequency output of the ECDL is microwave sideband tuned using an electro-optical phase modulator driven by an arbitrary waveform generator and filtered using a confocal cavity to generate a sequence of 123 frequencies separated by 300 MHz. The scan sequence of single sideband frequencies of 600 ns duration covers a 37 GHz region at a spectral scan rate of 10 kHz (100 μs per scan). Simultaneously, an eye-safe backscatter LIDAR system at 1.064 μm is used to monitor the atmospheric boundary layer. IPDA LIDAR measurements of the CO2 and CH4 dry air mixing ratios are presented in comparison with those from a commercial cavity ring-down (CRD) instrument. Differences between the IPDA LIDAR and CRD concentrations in several cases appear to be well correlated with the atmospheric aerosol structure from the backscatter LIDAR measurements. IPDA LIDAR dry air mixing ratios of CO2 and CH4 are determined with fit uncertainties of 2.8 μmol/mol (ppm) for CO2 and 22 nmol/mol (ppb) for CH4 over 30 s measurement periods. For longer averaging times (up to 1200 s), improvements in these detection limits by up to 3-fold are estimated from Allan variance analyses. Two sources of systematic error are identified and methods to remove them are discussed, including speckle interference from wavelength decorrelation and the seed power dependence of amplified spontaneous emission. Accuracies in the dry air retrievals of CO2 and CH4 in a 30 s measurement period are estimated at 4 μmol/mol (1% of ambient levels) and 50

  16. Water (H2O and D2O) molar absorptivity in the 1000-4000 cm-1 range and quantitative infrared spectroscopy of aqueous solutions.

    PubMed

    Venyaminov SYu; Prendergast, F G

    1997-06-01

    Water (H2O and D2O) molar absorptivity was measured by Fourier transform infrared transmission spectroscopy in the 1000-4000 cm-1 range at 25 degrees C. A series of assembled cells with path lengths from 1.2 to 120.5 microns was used for these measurements. The optimal path length (the path length of aqueous solution at which the IR spectrum of solute, corrected for water absorbance, has the highest signal-to-noise ratio) was calculated for all water absorbance bands. The results presented here show that the optimal path length does not depend on solute properties and is inversely proportional to the solvent (water) molar absorptivity. The maximal signal-to-noise ratio for measurements of IR spectra of aqueous solution in the 1650 cm-1 spectral region, of primary interest in biological applications, can be obtained at an optimal cell path lengths of 3-4 microns (H2O) and 40-60 microns (D2O). As an example, the signal-to-noise ratio was calculated as a function of the cell path length for the amide I (H2O) and amide I' (D2O) bands of an aqueous lysozyme solution. The molar absorptivities of water bands are several orders of magnitude weaker than those of the strongest bands of biological macromolecules in the same spectral regions. High net water absorbance in aqueous solutions is due simply to the very high molar concentration of water. A method is proposed for the quantitative measuring of the path length of the cell which exploits the molar absorptivity of the strongest water bands (stretching vibrations) or of bands which do not overlap with solute absorbance. A path length in the range from approximately 0.01 micron to approximately 1.0 mm can be determined with high precision using this technique for a samples of known concentration. Problems involved in the proper correction of strong water absorbance in IR spectra of aqueous solutions of biomolecules are discussed, including multiple reflections within the cell, the effects of pH, temperature, and

  17. A Random Walk on a Circular Path

    ERIC Educational Resources Information Center

    Ching, W.-K.; Lee, M. S.

    2005-01-01

    This short note introduces an interesting random walk on a circular path with cards of numbers. By using high school probability theory, it is proved that under some assumptions on the number of cards, the probability that a walker will return to a fixed position will tend to one as the length of the circular path tends to infinity.

  18. Ultraviolet absorption hygrometer

    DOEpatents

    Gersh, Michael E.; Bien, Fritz; Bernstein, Lawrence S.

    1986-01-01

    An ultraviolet absorption hygrometer is provided including a source of pulsed ultraviolet radiation for providing radiation in a first wavelength region where water absorbs significantly and in a second proximate wavelength region where water absorbs weakly. Ultraviolet radiation in the first and second regions which has been transmitted through a sample path of atmosphere is detected. The intensity of the radiation transmitted in each of the first and second regions is compared and from this comparison the amount of water in the sample path is determined.

  19. Ultraviolet absorption hygrometer

    DOEpatents

    Gersh, M.E.; Bien, F.; Bernstein, L.S.

    1986-12-09

    An ultraviolet absorption hygrometer is provided including a source of pulsed ultraviolet radiation for providing radiation in a first wavelength region where water absorbs significantly and in a second proximate wavelength region where water absorbs weakly. Ultraviolet radiation in the first and second regions which has been transmitted through a sample path of atmosphere is detected. The intensity of the radiation transmitted in each of the first and second regions is compared and from this comparison the amount of water in the sample path is determined. 5 figs.

  20. Influence of the cavity parameters on the output intensity in incoherent broadband cavity-enhanced absorption spectroscopy.

    PubMed

    Fiedler, Sven E; Hese, Achim; Heitmann, Uwe

    2007-07-01

    The incoherent broadband cavity-enhanced absorption spectroscopy is a technique in measuring small absorptions over a broad wavelength range. The setup consists of a conventional absorption spectrometer using an incoherent lamp and a charge coupled device detector, as well as a linear optical cavity placed around the absorbing sample, which enhances the effective path length through the sample. In this work the consequences of cavity length, mirror curvature, reflectivity, different light injection geometries, and spot size of the light source on the output intensity are studied and the implications to the signal-to-noise ratio of the absorption measurement are discussed. The symmetric confocal resonator configuration is identified as a special case with optimum imaging characteristics but with higher requirements for mechanical stability. Larger spot sizes of the light source were found to be favorable in order to reduce the negative effects of aberrations on the intensity.

  1. Towards quantitative atmospheric water vapor profiling with differential absorption lidar.

    PubMed

    Dinovitser, Alex; Gunn, Lachlan J; Abbott, Derek

    2015-08-24

    Differential Absorption Lidar (DIAL) is a powerful laser-based technique for trace gas profiling of the atmosphere. However, this technique is still under active development requiring precise and accurate wavelength stabilization, as well as accurate spectroscopic parameters of the specific resonance line and the effective absorption cross-section of the system. In this paper we describe a novel master laser system that extends our previous work for robust stabilization to virtually any number of multiple side-line laser wavelengths for the future probing to greater altitudes. In this paper, we also highlight the significance of laser spectral purity on DIAL accuracy, and illustrate a simple re-arrangement of a system for measuring effective absorption cross-section. We present a calibration technique where the laser light is guided to an absorption cell with 33 m path length, and a quantitative number density measurement is then used to obtain the effective absorption cross-section. The same absorption cell is then used for on-line laser stabilization, while microwave beat-frequencies are used to stabilize any number of off-line lasers. We present preliminary results using ∼300 nJ, 1 μs pulses at 3 kHz, with the seed laser operating as a nanojoule transmitter at 822.922 nm, and a receiver consisting of a photomultiplier tube (PMT) coupled to a 356 mm mirror.

  2. Spectral Fingerprinting of Individual Cells Visualized by Cavity-Reflection-Enhanced Light-Absorption Microscopy

    PubMed Central

    Arai, Yoshiyuki; Yamamoto, Takayuki; Minamikawa, Takeo; Takamatsu, Tetsuro; Nagai, Takeharu

    2015-01-01

    The absorption spectrum of light is known to be a “molecular fingerprint” that enables analysis of the molecular type and its amount. It would be useful to measure the absorption spectrum in single cell in order to investigate the cellular status. However, cells are too thin for their absorption spectrum to be measured. In this study, we developed an optical-cavity-enhanced absorption spectroscopic microscopy method for two-dimensional absorption imaging. The light absorption is enhanced by an optical cavity system, which allows the detection of the absorption spectrum with samples having an optical path length as small as 10 μm, at a subcellular spatial resolution. Principal component analysis of various types of cultured mammalian cells indicates absorption-based cellular diversity. Interestingly, this diversity is observed among not only different species but also identical cell types. Furthermore, this microscopy technique allows us to observe frozen sections of tissue samples without any staining and is capable of label-free biopsy. Thus, our microscopy method opens the door for imaging the absorption spectra of biological samples and thereby detecting the individuality of cells. PMID:25950513

  3. Spectral fingerprinting of individual cells visualized by cavity-reflection-enhanced light-absorption microscopy.

    PubMed

    Arai, Yoshiyuki; Yamamoto, Takayuki; Minamikawa, Takeo; Takamatsu, Tetsuro; Nagai, Takeharu

    2015-01-01

    The absorption spectrum of light is known to be a "molecular fingerprint" that enables analysis of the molecular type and its amount. It would be useful to measure the absorption spectrum in single cell in order to investigate the cellular status. However, cells are too thin for their absorption spectrum to be measured. In this study, we developed an optical-cavity-enhanced absorption spectroscopic microscopy method for two-dimensional absorption imaging. The light absorption is enhanced by an optical cavity system, which allows the detection of the absorption spectrum with samples having an optical path length as small as 10 μm, at a subcellular spatial resolution. Principal component analysis of various types of cultured mammalian cells indicates absorption-based cellular diversity. Interestingly, this diversity is observed among not only different species but also identical cell types. Furthermore, this microscopy technique allows us to observe frozen sections of tissue samples without any staining and is capable of label-free biopsy. Thus, our microscopy method opens the door for imaging the absorption spectra of biological samples and thereby detecting the individuality of cells.

  4. Time-resolved detection of temperature, concentration, and pressure in a shock tube by intracavity absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Fjodorow, Peter; Fikri, Mustapha; Schulz, Christof; Hellmig, Ortwin; Baev, Valery M.

    2016-06-01

    In this paper, we demonstrate the first application of intracavity absorption spectroscopy (ICAS) for monitoring species concentration, total pressure, and temperature in shock-tube experiments. ICAS with a broadband Er3+-doped fiber laser is applied to time-resolved measurements of absorption spectra of shock-heated C2H2. The measurements are performed in a spectral range between 6512 and 6542 cm-1, including many absorption lines of C2H2, with a time resolution of 100 µs and an effective absorption path length of 15 m. Up to 18-times increase of the total pressure and a temperature rise of up to 1200 K have been monitored. Due to the ability of simultaneously recording many absorption lines in a broad spectral range, the presented technique can also be applied to multi-component analysis of transient single-shot processes in reactive gas mixtures in shock tubes, pulse detonation engines, or explosions.

  5. Automatic Control Of Length Of Welding Arc

    NASA Technical Reports Server (NTRS)

    Iceland, William F.

    1991-01-01

    Nonlinear relationships among current, voltage, and length stored in electronic memory. Conceptual microprocessor-based control subsystem maintains constant length of welding arc in gas/tungsten arc-welding system, even when welding current varied. Uses feedback of current and voltage from welding arc. Directs motor to set position of torch according to previously measured relationships among current, voltage, and length of arc. Signal paths marked "calibration" or "welding" used during those processes only. Other signal paths used during both processes. Control subsystem added to existing manual or automatic welding system equipped with automatic voltage control.

  6. Absorption enhancement by textured InP in solar cells

    NASA Astrophysics Data System (ADS)

    Yun, Seokhun; Ji, Taeksoo

    2016-03-01

    III-V compound semiconductors seem to be the ideal materials for photovoltaic devices because they exhibit fast carrier velocity. III-V compound semiconductors, however, are unfavorable materials to be commercialized on large scale photovoltaic devices because of their high material cost. The textured surface shows the potential to increase the performance of solar cells because of the properties such as high absorption and longer light path length. These properties can overcome the disadvantage of the III-V compound semiconductors through thin thickness use when producing solar cells. In this study, we demonstrate that textured surfaces on InP formed by nano-sphere lithography and plasma etching process can enhance the absorption effectively in comparison with planar surface. The power conversion efficiency of InP solar cells using the textured InP and the aluminum doped zinc oxide was achieved up to 8%.

  7. Opportunity's Path

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This Long Term Planning graphic was created from a mosaic of navigation camera images overlain by a polar coordinate grid with the center point as Opportunity's original landing site. The blue dots represent the rover position at various locations.

    The red dots represent the center points of the target areas for the instruments on the rover mast (the panoramic camera and miniature thermal emission spectrometer). Opportunity visited Stone Mountain on Feb. 5. Stone Mountain was named after the southernmost point of the Appalachian Mountains outside of Atlanta, Ga. On Earth, Stone Mountain is the last big mountain before the Piedmont flatlands, and on Mars, Stone Mountain is at one end of Opportunity Ledge. El Capitan is a target of interest on Mars named after the second highest peak in Texas in Guadaloupe National Park, which is one of the most visited outcrops in the United States by geologists. It has been a training ground for students and professional geologists to understand what the layering means in relation to the formation of Earth, and scientists will study this prominent point of Opportunity Ledge to understand what the layering means on Mars.

    The yellow lines show the midpoint where the panoramic camera has swept and will sweep a 120-degree area from the three waypoints on the tour of the outcrop. Imagine a fan-shaped wedge from left to right of the yellow line.

    The white contour lines are one meter apart, and each drive has been roughly about 2-3 meters in length over the last few sols. The large white blocks are dropouts in the navigation camera data.

    Opportunity is driving along and taking a photographic panorama of the entire outcrop. Scientists will stitch together these images and use the new mosaic as a 'base map' to decide on geology targets of interest for a more detailed study of the outcrop using the instruments on the robotic arm. Once scientists choose their targets of interest, they plan to study the outcrop for roughly five to

  8. Pathfinder: Visual Analysis of Paths in Graphs

    PubMed Central

    Partl, C.; Gratzl, S.; Streit, M.; Wassermann, A. M.; Pfister, H.; Schmalstieg, D.; Lex, A.

    2016-01-01

    The analysis of paths in graphs is highly relevant in many domains. Typically, path-related tasks are performed in node-link layouts. Unfortunately, graph layouts often do not scale to the size of many real world networks. Also, many networks are multivariate, i.e., contain rich attribute sets associated with the nodes and edges. These attributes are often critical in judging paths, but directly visualizing attributes in a graph layout exacerbates the scalability problem. In this paper, we present visual analysis solutions dedicated to path-related tasks in large and highly multivariate graphs. We show that by focusing on paths, we can address the scalability problem of multivariate graph visualization, equipping analysts with a powerful tool to explore large graphs. We introduce Pathfinder (Figure 1), a technique that provides visual methods to query paths, while considering various constraints. The resulting set of paths is visualized in both a ranked list and as a node-link diagram. For the paths in the list, we display rich attribute data associated with nodes and edges, and the node-link diagram provides topological context. The paths can be ranked based on topological properties, such as path length or average node degree, and scores derived from attribute data. Pathfinder is designed to scale to graphs with tens of thousands of nodes and edges by employing strategies such as incremental query results. We demonstrate Pathfinder's fitness for use in scenarios with data from a coauthor network and biological pathways. PMID:27942090

  9. A cryogenic circulating advective multi-pass absorption cell

    NASA Astrophysics Data System (ADS)

    Stockett, M. H.; Lawler, J. E.

    2012-03-01

    A novel absorption cell has been developed to enable a spectroscopic survey of a broad range of polycyclic aromatic hydrocarbons (PAH) under astrophysically relevant conditions and utilizing a synchrotron radiation continuum to test the still controversial hypothesis that these molecules or their ions could be carriers of the diffuse interstellar bands. The cryogenic circulating advective multi-pass absorption cell resembles a wind tunnel; molecules evaporated from a crucible or injected using a custom gas feedthrough are entrained in a laminar flow of cryogenically cooled buffer gas and advected into the path of the synchrotron beam. This system includes a multi-pass optical White cell enabling absorption path lengths of hundreds of meters and a detection sensitivity to molecular densities on the order of 107 cm-3. A capacitively coupled radio frequency dielectric barrier discharge provides ionized and metastable buffer gas atoms for ionizing the candidate molecules via charge exchange and the Penning effect. Stronger than expected clustering of PAH molecules has slowed efforts to record gas phase PAH spectra at cryogenic temperatures, though such clusters may play a role in other interstellar phenomena.

  10. A cryogenic circulating advective multi-pass absorption cell.

    PubMed

    Stockett, M H; Lawler, J E

    2012-03-01

    A novel absorption cell has been developed to enable a spectroscopic survey of a broad range of polycyclic aromatic hydrocarbons (PAH) under astrophysically relevant conditions and utilizing a synchrotron radiation continuum to test the still controversial hypothesis that these molecules or their ions could be carriers of the diffuse interstellar bands. The cryogenic circulating advective multi-pass absorption cell resembles a wind tunnel; molecules evaporated from a crucible or injected using a custom gas feedthrough are entrained in a laminar flow of cryogenically cooled buffer gas and advected into the path of the synchrotron beam. This system includes a multi-pass optical White cell enabling absorption path lengths of hundreds of meters and a detection sensitivity to molecular densities on the order of 10(7) cm(-3). A capacitively coupled radio frequency dielectric barrier discharge provides ionized and metastable buffer gas atoms for ionizing the candidate molecules via charge exchange and the Penning effect. Stronger than expected clustering of PAH molecules has slowed efforts to record gas phase PAH spectra at cryogenic temperatures, though such clusters may play a role in other interstellar phenomena.

  11. A cryogenic circulating advective multi-pass absorption cell

    SciTech Connect

    Stockett, M. H.; Lawler, J. E.

    2012-03-15

    A novel absorption cell has been developed to enable a spectroscopic survey of a broad range of polycyclic aromatic hydrocarbons (PAH) under astrophysically relevant conditions and utilizing a synchrotron radiation continuum to test the still controversial hypothesis that these molecules or their ions could be carriers of the diffuse interstellar bands. The cryogenic circulating advective multi-pass absorption cell resembles a wind tunnel; molecules evaporated from a crucible or injected using a custom gas feedthrough are entrained in a laminar flow of cryogenically cooled buffer gas and advected into the path of the synchrotron beam. This system includes a multi-pass optical White cell enabling absorption path lengths of hundreds of meters and a detection sensitivity to molecular densities on the order of 10{sup 7} cm{sup -3}. A capacitively coupled radio frequency dielectric barrier discharge provides ionized and metastable buffer gas atoms for ionizing the candidate molecules via charge exchange and the Penning effect. Stronger than expected clustering of PAH molecules has slowed efforts to record gas phase PAH spectra at cryogenic temperatures, though such clusters may play a role in other interstellar phenomena.

  12. Atmospheric absorption of high frequency noise and application to fractional-octave bands

    NASA Technical Reports Server (NTRS)

    Shields, F. D.; Bass, H. E.

    1977-01-01

    Pure tone sound absorption coefficients were measured at 1/12 octave intervals from 4 to 100 KHz at 5.5K temperature intervals between 255.4 and 310.9 K and at 10 percent relative humidity increments between 0 percent and saturation in a large cylindrical tube (i.d., 25.4 cm; length, 4.8 m). Special solid-dielectric capacitance transducers, one to generate bursts of sound waves and one to terminate the sound path and detect the tone bursts, were constructed to fit inside the tube. The absorption was measured by varying the transmitter receiver separation from 1 to 4 m and observing the decay of multiple reflections or change in amplitude of the first received burst. The resulting absorption was compared with that from a proposed procedure for computing sound absorption in still air. Absorption of bands of noise was numerically computed by using the pure tone results. The results depended on spectrum shape, on filter type, and nonlinearly on propagation distance. For some of the cases considered, comparison with the extrapolation of ARP-866A showed a difference as large as a factor of 2. However, for many cases, the absorption for a finite band was nearly equal to the pure tone absorption at the center frequency of the band. A recommended prediction procedure is described for 1/3 octave band absorption coefficients.

  13. Optimization of A 2-Micron Laser Frequency Stabilization System for a Double-Pulse CO2 Differential Absorption Lidar

    NASA Technical Reports Server (NTRS)

    Chen, Songsheng; Yu, Jirong; Bai, Yingsin; Koch, Grady; Petros, Mulugeta; Trieu, Bo; Petzar, Paul; Singh, Upendra N.; Kavaya, Michael J.; Beyon, Jeffrey

    2010-01-01

    A carbon dioxide (CO2) Differential Absorption Lidar (DIAL) for accurate CO2 concentration measurement requires a frequency locking system to achieve high frequency locking precision and stability. We describe the frequency locking system utilizing Frequency Modulation (FM), Phase Sensitive Detection (PSD), and Proportional Integration Derivative (PID) feedback servo loop, and report the optimization of the sensitivity of the system for the feed back loop based on the characteristics of a variable path-length CO2 gas cell. The CO2 gas cell is characterized with HITRAN database (2004). The method can be applied for any other frequency locking systems referring to gas absorption line.

  14. Soliton absorption spectroscopy

    PubMed Central

    Kalashnikov, V. L.; Sorokin, E.

    2010-01-01

    We analyze optical soliton propagation in the presence of weak absorption lines with much narrower linewidths as compared to the soliton spectrum width using the novel perturbation analysis technique based on an integral representation in the spectral domain. The stable soliton acquires spectral modulation that follows the associated index of refraction of the absorber. The model can be applied to ordinary soliton propagation and to an absorber inside a passively modelocked laser. In the latter case, a comparison with water vapor absorption in a femtosecond Cr:ZnSe laser yields a very good agreement with experiment. Compared to the conventional absorption measurement in a cell of the same length, the signal is increased by an order of magnitude. The obtained analytical expressions allow further improving of the sensitivity and spectroscopic accuracy making the soliton absorption spectroscopy a promising novel measurement technique. PMID:21151755

  15. Extended X-ray absorption fine structure studies of Zn/sub 2/Fe/sub 2/ hybrid hemoglobins: absence of heme bond length changes in half-ligated species

    SciTech Connect

    Simolo, K.; Korszun, Z.R.; Stucky, G.; Moffat, K.; McLendon, G.

    1986-07-01

    Metal hybrid hemoglobins, in which Zn(II) replaces Fe(II), have been structurally characterized by extended X-ray absorption structure (EAFS) studies. Since Zn and Fe have very different K absorption edge energies, the structures of the ligated (Fe) and unligated (Zn) sites could be examined independently within a single molecule that mimics an intermediate ligation state. The observed EXAFS spectra and associated structural parameters are compared among the ligand free (..cap alpha..Zn)/sub 2/(..beta..Zn)/sub 2/, half-ligated (..cap alpha..FeCO)/sub 2/(..beta..Zn)/sub 2/ and (..cap alpha..Zn)/sub 2/(..beta..FeCO)/sub 2/, and fully ligated (..cap alpha..FeCO)/sub 2/(..beta..FeCO)/sub 2/ systems.

  16. Continuously variable focal length lens

    DOEpatents

    Adams, Bernhard W; Chollet, Matthieu C

    2013-12-17

    A material preferably in crystal form having a low atomic number such as beryllium (Z=4) provides for the focusing of x-rays in a continuously variable manner. The material is provided with plural spaced curvilinear, optically matched slots and/or recesses through which an x-ray beam is directed. The focal length of the material may be decreased or increased by increasing or decreasing, respectively, the number of slots (or recesses) through which the x-ray beam is directed, while fine tuning of the focal length is accomplished by rotation of the material so as to change the path length of the x-ray beam through the aligned cylindrical slows. X-ray analysis of a fixed point in a solid material may be performed by scanning the energy of the x-ray beam while rotating the material to maintain the beam's focal point at a fixed point in the specimen undergoing analysis.

  17. Competition for shortest paths on sparse graphs.

    PubMed

    Yeung, Chi Ho; Saad, David

    2012-05-18

    Optimal paths connecting randomly selected network nodes and fixed routers are studied analytically in the presence of a nonlinear overlap cost that penalizes congestion. Routing becomes more difficult as the number of selected nodes increases and exhibits ergodicity breaking in the case of multiple routers. The ground state of such systems reveals nonmonotonic complex behaviors in average path length and algorithmic convergence, depending on the network topology, and densities of communicating nodes and routers. A distributed linearly scalable routing algorithm is also devised.

  18. [Research on VOC concentration detection by photoelastic modulation infrared spectrum absorption method].

    PubMed

    Hu, Miao; Wang, Tai-yong; Qiao, Zhi-feng; Geng, Bo; Xiao, Xin-hua

    2011-12-01

    In order to ensure high stability and strong anti-interference ability in static interference system for qualitative and quantitative analysis of gas, a static scans interference detection system was designed based on photoelastic modulation infrared spectrum absorption system. The system consists of infrared laser, polarizer, photoelastic modulator, polarization analyzer and CCD components. By photoelastic modulator the principal refractive index of optical crystal will change cyclically by the modulation signal, producing cyclical changes in the optical path difference. With the calculation of modulation phase variation, the authors can get the function of the crystal length, the modulation cycle, and the range of optical path difference. Based on phase delay value and the energy distribution of interference pattern, the authors got the formula for the corresponding interference light intensity. The experiment used ZnSe crystal as the photoelastic modulation crystal, the polarizer uses the DOP3212 polarizer, and the detector uses the TCD5390AP array CCD. The five groups have different concentrations with three common VOC gases (formaldehyde, benzene and xylene) for detecting the concentrations of gases. The experimental results with the traditional infrared absorption were compared with the test results of photoelastic modulation infrared spectrum absorption method. The method of photoelastic modulation infrared spectrum absorption had high stability and real-time features, while the detection accuracy is better than the traditional infrared absorption method.

  19. Propagation path length variations due to bending of optical fibers

    NASA Technical Reports Server (NTRS)

    Lau, K. Y.

    1981-01-01

    The geometric effect and material stress effects are included. Calculations are shown that put an upper limit on the expected phase shift in single mode fibers. The fractional change in propagation constant is presented. Moding effects in multimode fibers cause extraneous phase shifts of unusually high magnitude. This does not occur in single mode fibers, rendering them very insensitive to bending with a theoretical limit given by the above relation.

  20. Reflectance-mode interferometric near-infrared spectroscopy quantifies brain absorption, scattering, and blood flow index in vivo.

    PubMed

    Borycki, Dawid; Kholiqov, Oybek; Srinivasan, Vivek J

    2017-02-01

    Interferometric near-infrared spectroscopy (iNIRS) is a new technique that measures time-of-flight- (TOF-) resolved autocorrelations in turbid media, enabling simultaneous estimation of optical and dynamical properties. Here, we demonstrate reflectance-mode iNIRS for noninvasive monitoring of a mouse brain in vivo. A method for more precise quantification with less static interference from superficial layers, based on separating static and dynamic components of the optical field autocorrelation, is presented. Absolute values of absorption, reduced scattering, and blood flow index (BFI) are measured, and changes in BFI and absorption are monitored during a hypercapnic challenge. Absorption changes from TOF-resolved iNIRS agree with absorption changes from continuous wave NIRS analysis, based on TOF-integrated light intensity changes, an effective path length, and the modified Beer-Lambert Law. Thus, iNIRS is a promising approach for quantitative and noninvasive monitoring of perfusion and optical properties in vivo.

  1. Scramjet Performance Assessment Using Water Absorption Diagnostics (U)

    NASA Technical Reports Server (NTRS)

    Cavolowsky, John A.; Loomis, Mark P.; Deiwert, George

    1995-01-01

    Simultaneous multiple path measurements of temperature and H2O concentration will be presented for the AIMHYE test entries in the NASA Ames 16-Inch Shock Tunnel. Monitoring the progress of high temperature chemical reactions that define scramjet combustor efficiencies is a task uniquely suited to nonintrusive optical diagnostics. One application strategy to overcome the many challenges and limitations of nonintrusive measurements is to use laser absorption spectroscopy coupled with optical fibers. Absorption spectroscopic techniques with rapidly tunable lasers are capable of making simultaneous measurements of mole fraction, temperature, pressure, and velocity. The scramjet water absorption diagnostic was used to measure combustor efficiency and was compared to thrust measurements using a nozzle force balance and integrated nozzle pressures to develop a direct technique for evaluating integrated scramjet performance. Tests were initially performed with a diode laser tuning over a water absorption feature at 1391.7 nm. A second diode laser later became available at a wavelength near 1343.3 nm covering an additional water absorption feature and was incorporated in the system for a two-wavelength technique. Both temperature and mole fraction can be inferred from the lineshape analysis using this approach. Additional high temperature spectroscopy research was conducted to reduce uncertainties in the scramjet application. The lasers are optical fiber coupled to ports at the combustor exit and in the nozzle region. The output from the two diode lasers were combined in a single fiber, and the resultant two-wavelength beam was subsequently split into four legs. Each leg was directed through 60 meters of optical fiber to four combustor exit locations for measurement of beam intensity after absorption by the water within the flow. Absorption results will be compared to 1D combustor analysis using RJPA and nozzle CFD computations as well as to data from a nozzle metric

  2. The absolute path command

    SciTech Connect

    Moody, A.

    2012-05-11

    The ap command traveres all symlinks in a given file, directory, or executable name to identify the final absolute path. It can print just the final path, each intermediate link along with the symlink chan, and the permissions and ownership of each directory component in the final path. It has functionality similar to "which", except that it shows the final path instead of the first path. It is also similar to "pwd", but it can provide the absolute path to a relative directory from the current working directory.

  3. Influence of absorption induced thermal initiation pathway on irradiance threshold for laser induced breakdown

    PubMed Central

    Varghese, Babu; Bonito, Valentina; Jurna, Martin; Palero, Jonathan; Verhagen, Margaret Hortonand Rieko

    2015-01-01

    We investigated the influence of thermal initiation pathway on the irradiance threshold for laser induced breakdown in transparent, absorbing and scattering phantoms. We observed a transition from laser-induced optical breakdown to laser-induced thermal breakdown as the absorption coefficient of the medium is increased. We found that the irradiance threshold after correction for the path length dependent absorption and scattering losses in the medium is lower due to the thermal pathway for the generation of seed electrons compared to the laser-induced optical breakdown. Furthermore, irradiance threshold gradually decreases with the increase in the absorption properties of the medium. Creating breakdown with lower irradiance threshold that is specific at the target chromophore can provide intrinsic target selectivity and improve safety and efficacy of skin treatment methods that use laser induced breakdown. PMID:25909007

  4. Continuous in-situ methane measurements at paddy fields in a rural area of India with poor electric infrastructure, using a low-cost instrument based on open-path near-IR laser absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Hidemori, T.; Matsumi, Y.; Nakayama, T.; Kawasaki, M.; Sasago, H.; Takahashi, K.; Imasu, R.; Takeuchi, W.; Adachi, M.; Machida, T.; Terao, Y.; Nomura, S.; Dhaka, S. K.; Singh, J.

    2015-12-01

    In southeast and south Asia, the previous satellite observations suggest that the methane emission from rice paddies is significant and important source of methane during rainy season. Since it is difficult to measure methane stably and continuously at rural areas such as the paddy fields in terms of infrastructures and maintenances, there are large uncertainties in quantitative estimation of methane emission in these areas and there are needs for more certification between satellite and ground based measurements. To measure methane concentrations continuously at difficult situations such as the center of paddy fields and wetlands, we developed the continuous in-situ measurement system, not to look for your lost keys under the streetlight. The methane gas sensor is used an open-path laser based measurement instrument (LaserMethane, ANRITSU CORPORATION), which can quickly and selectively detect average methane concentrations on the optical path of the laser beam. The developed system has the power supply and telecommunication system to run the laser gas sensor in rural areas with poor electricity infrastructure.The methane measurement system was installed at paddy fields of Sonepat, Haryana on the north of Delhi in India and has been operated from the end of 2014. The air sampling along with our measurement has been carried out once a week during daytime to calibrate the laser instrument. We found that the seasonal variation of methane concentrations was different from the satellite observations and there were significant diurnal variations, which it was difficult to detect from occasional air samplings. We will present details of the measurement system and recent results of continuous methane measurements in India.

  5. Earth's Atmospheric CO2 Saturated IR Absorption

    NASA Astrophysics Data System (ADS)

    Wall, Ernst

    2008-10-01

    Using the on-line SpectraCalc IR absorption simulator, the amount of IR absorption by the 15 μ line of the current atmospheric CO2 was obtained and compared with that of twice the amount of CO2. The simulation required a fixed density equivalent for the atmospheric path length. This was obtained by numerically integrating the NOAA Standard Atmospheric model. While the current line is saturated, doubling the CO2 will cause a slight width increase. Using this and the blackbody radiation curve plus considering the effects of water vapor, the temperature rise of the Earth will be less than 2.5 deg. C. Integrating a NASA Martian atmospheric model, we find that the Martian atmosphere has 45 times more CO2 to penetrate than Earth, and yet, the Martian diurnal temperature swings exceed those of the Sahara desert. I.e., large amounts of CO2 alone do not necessarily cause planetary warming. As the oceans warm from any cause, more CO2 is boiled out, but if they cool, they will absorb more CO2 just as a carbonated drink does, so that temperature and CO2 density will correlate. It is to be noted that the Earth's known petroleum reserves contain only enough CO2 to increase the atmospheric CO2 by some 15%.

  6. Evaluation of ammonia absorption coefficients by photoacoustic spectroscopy for detection of ammonia levels in human breath

    NASA Astrophysics Data System (ADS)

    Dumitras, D. C.; Dutu, D. C.; Matei, C.; Cernat, R.; Banita, S.; Patachia, M.; Bratu, A. M.; Petrus, M.; Popa, C.

    2011-04-01

    Photoacoustic spectroscopy represents a powerful technique for measuring extremely low absorptions independent of the path length and offers a degree of parameter control that cannot be attained by other methods. We report precise measurements of the ammonia absorption coefficients at the CO2 laser wavelengths by using a photoacoustic (PA) cell in an extracavity configuration and we compare our results with other values reported in the literature. Ammonia presents a clear fingerprint spectrum and high absorption strengths in the CO2 wavelengths region. Because more than 250 molecular gases of environmental concern for atmospheric, industrial, medical, military, and scientific spheres exhibit strong absorption bands in the region 9.2-10.8 μm, we have chosen a frequency tunable CO2 laser. In the present work, ammonia absorption coefficients were measured at both branches of the CO2 laser lines by using a calibrated mixture of 10 ppm NH3 in N2. We found the maximum absorption in the 9 μm region, at 9R(30) line of the CO2 laser. One of the applications based on the ammonia absorption coefficients is used to measure the ammonia levels in exhaled human breath. This can be used to determine the exact time necessary at every session for an optimal degree of dialysis at patients with end-stage renal disease.

  7. Time-Resolved Broadband Cavity-Enhanced Absorption Spectroscopy behind Shock Waves.

    PubMed

    Matsugi, Akira; Shiina, Hiroumi; Oguchi, Tatsuo; Takahashi, Kazuo

    2016-04-07

    A fast and sensitive broadband absorption technique for measurements of high-temperature chemical kinetics and spectroscopy has been developed by applying broadband cavity-enhanced absorption spectroscopy (BBCEAS) in a shock tube. The developed method has effective absorption path lengths of 60-200 cm, or cavity enhancement factors of 12-40, over a wavelength range of 280-420 nm, and is capable of simultaneously recording absorption time profiles over an ∼32 nm spectral bandpass in a single experiment with temporal and spectral resolutions of 5 μs and 2 nm, respectively. The accuracy of the kinetic and spectroscopic measurements was examined by investigating high-temperature reactions and absorption spectra of formaldehyde behind reflected shock waves using 1,3,5-trioxane as a precursor. The rate constants obtained for the thermal decomposition reactions of 1,3,5-trioxane (to three formaldehyde molecules) and formaldehyde (to HCO + H) agreed well with the literature data. High-temperature absorption cross sections of formaldehyde between 280 and 410 nm have been determined at the post-reflected-shock temperatures of 955, 1265, and 1708 K. The results demonstrate the applicability of the BBCEAS technique to time- and wavelength-resolved sensitive absorption measurements at high temperatures.

  8. Two-path plasmonic interferometer with integrated detector

    DOEpatents

    Dyer, Gregory Conrad; Shaner, Eric A.; Aizin, Gregory

    2016-03-29

    An electrically tunable terahertz two-path plasmonic interferometer with an integrated detection element can down convert a terahertz field to a rectified DC signal. The integrated detector utilizes a resonant plasmonic homodyne mixing mechanism that measures the component of the plasma waves in-phase with an excitation field that functions as the local oscillator in the mixer. The plasmonic interferometer comprises two independently tuned electrical paths. The plasmonic interferometer enables a spectrometer-on-a-chip where the tuning of electrical path length plays an analogous role to that of physical path length in macroscopic Fourier transform interferometers.

  9. A multiple path photonic lab on a chip for parallel protein concentration measurements.

    PubMed

    Rodríguez-Ruiz, Isaac; Conejero-Muriel, Mayte; Ackermann, Tobias N; Gavira, José A; Llobera, Andreu

    2015-02-21

    We propose a PDMS-based photonic system for the accurate measurement of protein concentration with minute amounts of the sample. As opposed to the state of the art approach, in the multiple path photonic lab on a chip (MPHIL), analyte concentration or molar absorptivity is obtained with a single injection step, by performing simultaneous parallel optical measurements varying the optical path length. Also, as opposed to the standard calibration protocol, the MPHIL approach does not require a series of measurements at different concentrations. MPHIL has three main advantages: firstly the possibility of dynamically selecting the path length, always working in the absorbance vs. concentration linear range for each target analyte. Secondly, a dramatic reduction of the total volume of the sample required to obtain statistically reliable results. Thirdly, since only one injection is required, the measurement time is minimized, reducing both contamination and signal drifts. These characteristics are clearly advantageous when compared to commercial micro-spectrophotometers. The MPHIL concept was validated by testing three commercial proteins, lysozyme (HEWL), glucose isomerase (d-xylose-ketol-isomerase, GI) and Aspergillus sp. lipase L (BLL), as well as two proteins expressed and purified for this study, B. cereus formamidase (FASE) and dihydropyrimidinase from S. meliloti CECT41 (DHP). The use of MPHIL is also proposed for any spectrophotometric measurement in the UV-VIS range, as well as for its integration as a concentration measurement platform in more advanced photonic lab on a chip systems.

  10. CO2 LIDAR measurements over a 20-km slant path

    NASA Astrophysics Data System (ADS)

    Senft, Daniel C.; Fox, Marsha J.; Gonglewski, John D.; Dowling, James A.; Highland, Ronald G.; Shilko, Michael L.

    1997-01-01

    The Air Force Phillips Laboratory conducted a series of measurements in February, May and August 1995 at the Air Force Maui Optical Station (AMOS) facility on Maui, Hawaii, to determine system requirements for an airborne long path CO(subscript 2) DIAL system. The lidar incorporates a cavity-matched mode-locked 3-J laser with the 60 cm diameter AMOS Beam Director Telescope. The one-way beam propagation path length was 21.3 km, originating at the AMOS facility on Haleakala at an altitude of 3.050 km ASL, and terminating at a target site near sea level. Both heterodyne and direct detection techniques are compared with respect to radiometric performance and signal statistics. Minimum detectable absorption levels for DIAL systems using both detection techniques and a variety of targets are estimated from long- range measurements with controlled absorbers. The signal correlation as a function of interpulse temporal separation was determined for long-range direct detection measurements. Radiometric models including system optical characteristics, beam propagation considerations, target reflectivity characteristics,a nd atmospheric effects have been developed and validated experimentally. A new receiver system is currently being fabricated and the laser transmitter is being upgraded for pulse-to-pulse wavelength agility, prior to incorporation into a C-135E airborne platform for future flight experiments.

  11. Cooperative organic mine avoidance path planning

    NASA Astrophysics Data System (ADS)

    McCubbin, Christopher B.; Piatko, Christine D.; Peterson, Adam V.; Donnald, Creighton R.; Cohen, David

    2005-06-01

    The JHU/APL Path Planning team has developed path planning techniques to look for paths that balance the utility and risk associated with different routes through a minefield. Extending on previous years' efforts, we investigated real-world Naval mine avoidance requirements and developed a tactical decision aid (TDA) that satisfies those requirements. APL has developed new mine path planning techniques using graph based and genetic algorithms which quickly produce near-minimum risk paths for complicated fitness functions incorporating risk, path length, ship kinematics, and naval doctrine. The TDA user interface, a Java Swing application that obtains data via Corba interfaces to path planning databases, allows the operator to explore a fusion of historic and in situ mine field data, control the path planner, and display the planning results. To provide a context for the minefield data, the user interface also renders data from the Digital Nautical Chart database, a database created by the National Geospatial-Intelligence Agency containing charts of the world's ports and coastal regions. This TDA has been developed in conjunction with the COMID (Cooperative Organic Mine Defense) system. This paper presents a description of the algorithms, architecture, and application produced.

  12. Path optimization with limited sensing ability

    SciTech Connect

    Kang, Sung Ha Kim, Seong Jun Zhou, Haomin

    2015-10-15

    We propose a computational strategy to find the optimal path for a mobile sensor with limited coverage to traverse a cluttered region. The goal is to find one of the shortest feasible paths to achieve the complete scan of the environment. We pose the problem in the level set framework, and first consider a related question of placing multiple stationary sensors to obtain the full surveillance of the environment. By connecting the stationary locations using the nearest neighbor strategy, we form the initial guess for the path planning problem of the mobile sensor. Then the path is optimized by reducing its length, via solving a system of ordinary differential equations (ODEs), while maintaining the complete scan of the environment. Furthermore, we use intermittent diffusion, which converts the ODEs into stochastic differential equations (SDEs), to find an optimal path whose length is globally minimal. To improve the computation efficiency, we introduce two techniques, one to remove redundant connecting points to reduce the dimension of the system, and the other to deal with the entangled path so the solution can escape the local traps. Numerical examples are shown to illustrate the effectiveness of the proposed method.

  13. Quantification and parametrization of non-linearity effects by higher-order sensitivity terms in scattered light differential optical absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Puķīte, Jānis; Wagner, Thomas

    2016-05-01

    We address the application of differential optical absorption spectroscopy (DOAS) of scattered light observations in the presence of strong absorbers (in particular ozone), for which the absorption optical depth is a non-linear function of the trace gas concentration. This is the case because Beer-Lambert law generally does not hold for scattered light measurements due to many light paths contributing to the measurement. While in many cases linear approximation can be made, for scenarios with strong absorptions non-linear effects cannot always be neglected. This is especially the case for observation geometries, for which the light contributing to the measurement is crossing the atmosphere under spatially well-separated paths differing strongly in length and location, like in limb geometry. In these cases, often full retrieval algorithms are applied to address the non-linearities, requiring iterative forward modelling of absorption spectra involving time-consuming wavelength-by-wavelength radiative transfer modelling. In this study, we propose to describe the non-linear effects by additional sensitivity parameters that can be used e.g. to build up a lookup table. Together with widely used box air mass factors (effective light paths) describing the linear response to the increase in the trace gas amount, the higher-order sensitivity parameters eliminate the need for repeating the radiative transfer modelling when modifying the absorption scenario even in the presence of a strong absorption background. While the higher-order absorption structures can be described as separate fit parameters in the spectral analysis (so-called DOAS fit), in practice their quantitative evaluation requires good measurement quality (typically better than that available from current measurements). Therefore, we introduce an iterative retrieval algorithm correcting for the higher-order absorption structures not yet considered in the DOAS fit as well as the absorption dependence on

  14. TATP stand-off detection with open path: FTIR techniques

    NASA Astrophysics Data System (ADS)

    Fischer, C.; Pohl, T.; Weber, K.; Vogel, A.; van Haren, G.; Schweikert, W.

    2012-10-01

    TATP is a very easy to synthesize [9], sensitive, high explosive [10] and high volatile explosive [1, 3, 7] with great absorption in the IR Spectra [4, 5, 6]. In this project we detect TATP gas traces with open path FTIR - techniques. The first project phase was to construct and build a heatable multi-reflection cell with adjustable optical path length and a heatable intake to evaporate solid TATP samples. In this cell reference TATP - spectra were collected under controlled conditions with a Bruker FTIR system (Typ OPAG 33). The next step was to find out how the TATP gas will be diluted in the ambient air and validate some physical properties which are described inconsistently in literature e.g. evaporation rates. We constructed a special double - T shaped chamber with stabile air conditions. In this chamber the dispersion kinetics of the TATP vapour could be tested. It turned out that the TATP vapours has the tendency to drop down. Therefore the highest TATP - concentrations were measured below the TATP sample. During the investigation for this study it turned out, that some materials scrub the TATP- vapour out of the air, e.g. Metals, fabric, leather. In the second phase of the project successful open path FTIR- measurements were taken in ambient air and will be continued with different system configurations of the OPAG 33 to lower the detection limits. Also successful measurements were taken in indoor ambient air with a Hyper spectral camera (passive FTIR with array sensor) to detect TATP in solid and gaseous phase. This technique allows detecting TATP and identifying the TATP source. The poster shows some selected results of the continued research.

  15. Distributed multiple path routing in complex networks

    NASA Astrophysics Data System (ADS)

    Chen, Guang; Wang, San-Xiu; Wu, Ling-Wei; Mei, Pan; Yang, Xu-Hua; Wen, Guang-Hui

    2016-12-01

    Routing in complex transmission networks is an important problem that has garnered extensive research interest in the recent years. In this paper, we propose a novel routing strategy called the distributed multiple path (DMP) routing strategy. For each of the O-D node pairs in a given network, the DMP routing strategy computes and stores multiple short-length paths that overlap less with each other in advance. And during the transmission stage, it rapidly selects an actual routing path which provides low transmission cost from the pre-computed paths for each transmission task, according to the real-time network transmission status information. Computer simulation results obtained for the lattice, ER random, and scale-free networks indicate that the strategy can significantly improve the anti-congestion ability of transmission networks, as well as provide favorable routing robustness against partial network failures.

  16. Robot path planning using a genetic algorithm

    NASA Technical Reports Server (NTRS)

    Cleghorn, Timothy F.; Baffes, Paul T.; Wang, Liu

    1988-01-01

    Robot path planning can refer either to a mobile vehicle such as a Mars Rover, or to an end effector on an arm moving through a cluttered workspace. In both instances there may exist many solutions, some of which are better than others, either in terms of distance traversed, energy expended, or joint angle or reach capabilities. A path planning program has been developed based upon a genetic algorithm. This program assumes global knowledge of the terrain or workspace, and provides a family of good paths between the initial and final points. Initially, a set of valid random paths are constructed. Successive generations of valid paths are obtained using one of several possible reproduction strategies similar to those found in biological communities. A fitness function is defined to describe the goodness of the path, in this case including length, slope, and obstacle avoidance considerations. It was found that with some reproduction strategies, the average value of the fitness function improved for successive generations, and that by saving the best paths of each generation, one could quite rapidly obtain a collection of good candidate solutions.

  17. The universal path integral

    NASA Astrophysics Data System (ADS)

    Lloyd, Seth; Dreyer, Olaf

    2016-02-01

    Path integrals calculate probabilities by summing over classical configurations of variables such as fields, assigning each configuration a phase equal to the action of that configuration. This paper defines a universal path integral, which sums over all computable structures. This path integral contains as sub-integrals all possible computable path integrals, including those of field theory, the standard model of elementary particles, discrete models of quantum gravity, string theory, etc. The universal path integral possesses a well-defined measure that guarantees its finiteness. The probabilities for events corresponding to sub-integrals can be calculated using the method of decoherent histories. The universal path integral supports a quantum theory of the universe in which the world that we see around us arises out of the interference between all computable structures.

  18. Multilayer Active Control For Structural Damping And Optical-Path Regulation

    NASA Technical Reports Server (NTRS)

    Rahman, Zahidul H.; Spanos, John T.; Fanson, James L.

    1995-01-01

    Two active-control concepts incorporated into system for suppression of vibrations in truss structure and regulation of length of optical path on structure to nanometer level. Optical-path-length-control subsystem contains two feedback control loops to obtain active damping in wide amplitude-and-frequency range. Concept described in more detail in number of previous articles, including "Stabilizing Optical-Path Length on a Vibrating Structure" (NPO-19040), "Controllable Optical Delay Line for Stellar Interferometry" (NPO-18686), "Test Bed for Control of Optical-Path Lengths" (NPO-18487).

  19. Pulled Motzkin paths

    NASA Astrophysics Data System (ADS)

    Janse van Rensburg, E. J.

    2010-08-01

    In this paper the models of pulled Dyck paths in Janse van Rensburg (2010 J. Phys. A: Math. Theor. 43 215001) are generalized to pulled Motzkin path models. The generating functions of pulled Motzkin paths are determined in terms of series over trinomial coefficients and the elastic response of a Motzkin path pulled at its endpoint (see Orlandini and Whittington (2004 J. Phys. A: Math. Gen. 37 5305-14)) is shown to be R(f) = 0 for forces pushing the endpoint toward the adsorbing line and R(f) = f(1 + 2cosh f))/(2sinh f) → f as f → ∞, for forces pulling the path away from the X-axis. In addition, the elastic response of a Motzkin path pulled at its midpoint is shown to be R(f) = 0 for forces pushing the midpoint toward the adsorbing line and R(f) = f(1 + 2cosh (f/2))/sinh (f/2) → 2f as f → ∞, for forces pulling the path away from the X-axis. Formal combinatorial identities arising from pulled Motzkin path models are also presented. These identities are the generalization of combinatorial identities obtained in directed paths models to their natural trinomial counterparts.

  20. Path Integrals and Hamiltonians

    NASA Astrophysics Data System (ADS)

    Baaquie, Belal E.

    2014-03-01

    1. Synopsis; Part I. Fundamental Principles: 2. The mathematical structure of quantum mechanics; 3. Operators; 4. The Feynman path integral; 5. Hamiltonian mechanics; 6. Path integral quantization; Part II. Stochastic Processes: 7. Stochastic systems; Part III. Discrete Degrees of Freedom: 8. Ising model; 9. Ising model: magnetic field; 10. Fermions; Part IV. Quadratic Path Integrals: 11. Simple harmonic oscillators; 12. Gaussian path integrals; Part V. Action with Acceleration: 13. Acceleration Lagrangian; 14. Pseudo-Hermitian Euclidean Hamiltonian; 15. Non-Hermitian Hamiltonian: Jordan blocks; 16. The quartic potential: instantons; 17. Compact degrees of freedom; Index.

  1. Quantitative infrared absorption cross sections of isoprene for atmospheric measurements

    SciTech Connect

    Brauer, Carolyn S.; Blake, Thomas A.; Guenther, Alex B.; Sharpe, Steven W.; Sams, Robert L.; Johnson, Timothy J.

    2014-11-19

    The OH- and O3- initiated oxidations of isoprene, which is one of the primary volatile organic compounds produced by vegetation, are a major source of atmospheric formaldehyde and other oxygenated organics, yet little quantitative IR data exists for isoprene. We thus report absorption coefficients and integrated band intensities for isoprene in the 600 - 6500 cm-1 region. The pressure-broadened (1 atmosphere N2) spectra were recorded at 278, 298 and 323 K in a 19.96 cm path length cell at 0.112 cm-1 resolution, using a Bruker 66V FTIR. Composite spectra are derived from a minimum of seven pressures at each temperature.

  2. Diffuse reflectance spectroscopy characterization of hemoglobin and intralipid solutions: in vitro measurements with continuous variation of absorption and scattering.

    PubMed

    Hernández, Sergio E; Rodríguez, Vicente D; Pérez, Justo; Martín, Felipe A; Castellano, Miguel A; Gonzalez-Mora, Jose Luis

    2009-01-01

    Absorption and scattering processes in biological tissues are studied through reflectance spectroscopy in tissue-like phantoms. For this aim, an experimental setup is designed to independently control both processes in hemoglobin and intralipid solutions. From the analysis of the obtained spectra, a simple empirical power law equation is found that relates absorbance with scattering and absorption coefficients. This relationship includes three wavelength independent parameters, which can be determined geometry from in vitro measurements for each particular optical optode. The dependence of the optical path length on the absorption and scattering coefficients is also analyzed, and estimations of this parameter for physiological conditions are presented. This study is useful to better understand the scattering phenomena in biological tissue, and to obtain absolute concentration of absorber particles when a homogeneous medium can be assumed.

  3. PERITONEAL ABSORPTION

    PubMed Central

    Hahn, P. F.; Miller, L. L.; Robscheit-Robbins, F. S.; Bale, W. F.; Whipple, G. H.

    1944-01-01

    The absorption of red cells from the normal peritoneum of the dog can be demonstrated by means of red cells labeled with radio-iron incorporated in the hemoglobin of these red cells. Absorption in normal dogs runs from 20 to 100 per cent of the amount given within 24 hours. Dogs rendered anemic by bleeding absorb red cells a little less rapidly—ranging from 5 to 80 per cent of the injected red cells. Doubly depleted dogs (anemic and hypoproteinemic) absorb even less in the three experiments recorded. This peritoneal absorption varies widely in different dogs and even in the same dog at different times. We do not know the factors responsible for these variations but there is no question about active peritoneal absorption. The intact red cells pass readily from the peritoneal cavity into lymph spaces in diaphragm and other areas of the peritoneum. The red cells move along the lymphatics and through the lymph glands with little or no phagocytosis and eventually into the large veins through the thoracic ducts. PMID:19871404

  4. Nutrient absorption.

    PubMed

    Rubin, Deborah C

    2004-03-01

    Our understanding of nutrient absorption continues to grow, from the development of unique animal models and from studies in which cutting-edge molecular and cellular biologic approaches have been used to analyze the structure and function of relevant molecules. Studies of the molecular genetics of inherited disorders have also provided many new insights into these processes. A major advance in lipid absorption has been the cloning and characterization of several intestinal acyl CoA:monoacylglycerol acyltransferases; these may provide new targets for antiobesity drug therapy. Studies of intestinal cholesterol absorption and reverse cholesterol transport have encouraged the development of novel potential treatments for hyperlipidemia. Observations in genetically modified mice and in humans with mutations in glucose transporter 2 suggest the importance of a separate microsomal membrane transport pathway for glucose transport. The study of iron metabolism has advanced greatly with the identification of the hemochromatosis gene and the continued examination of the genetic regulation of iron absorptive pathways. Several human thiamine transporters have been identified, and their specific roles in different tissues are being explored.

  5. Impact of the magnetic superstorm on March 17-19, 2015 on subpolar HF radio paths: Experiment and modeling

    NASA Astrophysics Data System (ADS)

    Blagoveshchensky, D. V.; Maltseva, O. A.; Anishin, M. M.; Sergeeva, M. A.; Rogov, D. D.

    2016-09-01

    The ionospheric phenomena which significantly influenced radio propagation during March 17-19, 2015 are considered in the study. The data of oblique ionospheric sounding (OIS) were analyzed at six radio paths. These paths are located in the zone of North Siberia in Russia and have different lengths: from 1000 to 5000 km. The results are the following. The magnetic storm drastically changed the character of radio propagation at all the considered paths: in most cases the reflections from the ionospheric F2-layer were changed by the reflections only from the sporadic Es-layer. The parameters of movement of the disturbance front were estimated on the basis of OIS data of the paths. The average velocity of the front movements from east to west was about V = 440 m/s. Even the moderate growth of riometer absorption within the region of radio paths' locations, resulted in loss of multihop modes in the signal reflections from sporadic layers. It also resulted in a sharp decrease of signal strength at the paths. Real distance-frequency characteristics (DFC) of the paths were compared to DFC calculated on the basis of International Reference Ionosphere (IRI) model. It was revealed that on a quiet day of March, 15th, the real and the calculated DFC are similar or coincide in the majority of cases. During the disturbed days of March, 17-19, most commonly observed are the significant differences between the calculated and the experimental data. The most pronounced difference is revealed while estimating the character of OIS signals' reflections from Es-layers.

  6. Tornado intensity estimated from damage path dimensions.

    PubMed

    Elsner, James B; Jagger, Thomas H; Elsner, Ian J

    2014-01-01

    The Newcastle/Moore and El Reno tornadoes of May 2013 are recent reminders of the destructive power of tornadoes. A direct estimate of a tornado's power is difficult and dangerous to get. An indirect estimate on a categorical scale is available from a post-storm survery of the damage. Wind speed bounds are attached to the scale, but the scale is not adequate for analyzing trends in tornado intensity separate from trends in tornado frequency. Here tornado intensity on a continuum is estimated from damage path length and width, which are measured on continuous scales and correlated to the EF rating. The wind speeds on the EF scale are treated as interval censored data and regressed onto the path dimensions and fatalities. The regression model indicates a 25% increase in expected intensity over a threshold intensity of 29 m s(-1) for a 100 km increase in path length and a 17% increase in expected intensity for a one km increase in path width. The model shows a 43% increase in the expected intensity when fatalities are observed controlling for path dimensions. The estimated wind speeds correlate at a level of .77 (.34, .93) [95% confidence interval] with a small sample of wind speeds estimated independently from a doppler radar calibration. The estimated wind speeds allow analyses to be done on the tornado database that are not possible with the categorical scale. The modeled intensities can be used in climatology and in environmental and engineering applications. Research is needed to understand the upward trends in path length and width.

  7. Apparatus and method for quantitative measurement of small differences in optical absorptivity between two samples using differential interferometry and the thermooptic effect

    DOEpatents

    Cremers, D.A.; Keller, R.A.

    1984-05-08

    An apparatus and method for the measurement of small differences in optical absorptivity of weakly absorbing solutions using differential interferometry and the thermooptic effect have been developed. Two sample cells are placed in each arm of an interferometer and are traversed by colinear probe and heating laser beams. The interrogation probe beams are recombined forming a fringe pattern, the intensity of which can be related to changes in optical path length of these laser beams through the cells. This in turn can be related to small differences in optical absorptivity which results in different amounts of sample heating when the heating laser beams are turned on, by the fact that the index of refraction of a liquid is temperature dependent. A critical feature of this invention is the stabilization of the optical path of the probe beams against drift. Background (solvent) absorption can then be suppressed by a factor of approximately 400. Solute absorptivities of about 10[sup [minus]5] cm[sup [minus]1] can then be determined in the presence of background absorptions in excess of 10[sup [minus]3] cm[sup [minus]1]. In addition, the smallest absorption measured with the instant apparatus and method is about 5 [times] 10[sup [minus]6] cm[sup [minus]1]. 6 figs.

  8. Oceanic Path Effects of Microseismic Waves

    NASA Astrophysics Data System (ADS)

    Chen, X.; Wen, L.

    2015-12-01

    Microseismic surface waves originating from sources in ocean would propagate along parts of oceanic path before being recorded by on-land seismic stations. Studying the path effects on waveform, travel-time, magnitude and other properties of these microseismic signals is important in accurately determining the location, strength and generating mechanism of the sources. Strong effects are observed in the microseismic signals generated by Hurricane Sandy in 2012, and verified by synthetic seismograms. We find that Sandy-related seismic signals are significantly affected by oceanic path: only seismic signals share a similar length of oceanic path are cross-correlated and a large portion of the correlated signals can be traced back to sources at the ocean-continent boundary within a narrow azimuthal range from the hurricane center. In this presentation, we report that these observations can be explained by strong path effect of wave propagation from a seismic source in the hurricane center. The strong directionality of waveform cross-correlation can be explained by the propagation effect that waveform characteristics of Rayleigh wave are mostly controlled by transitional propagating path from ocean to the continental region, resulting in seismic signals being correlated only among stations sharing similar length of oceanic path; the sources at the ocean-continent boundary can be attributed to strong seismic scattering in the ocean-continent boundary, generating apparent seismic "sources" there. We also compare the synthetic vertical/transverse magnitude ratio of Rayleigh waves in an anisotropic velocity model with observations. Our results indicate that these types of seismic observations would be particularly useful for studying seismic structure of crust and upper mantle in the ocean-continent area.

  9. A novel dual-LED based long-path DOAS instrument for the measurement of aromatic hydrocarbons

    NASA Astrophysics Data System (ADS)

    Stutz, Jochen; Hurlock, Stephen C.; Colosimo, Santo F.; Tsai, Catalina; Cheung, Ross; Festa, James; Pikelnaya, Olga; Alvarez, Sergio; Flynn, James H.; Erickson, Matthew H.; Olaguer, Eduardo P.

    2016-12-01

    Aromatic hydrocarbons are well known air toxics which are regulated by the US EPA and other air quality agencies. Accurate, long-term monitoring of these compounds at low part-per-billion levels, as well as identifying emission point sources is therefore crucial to protect human health in neighborhoods near large emission sources. Here we present a new long-path differential optical absorption spectroscopy (LP-DOAS) instrument specifically designed to monitor aromatic hydrocarbons. The system is based on a novel dual - light emitting diode (LED) light source, which eliminates the requirement to suppress spectrometer stray light. This light source, together with a high stability fiber-based sending/receiving telescope, allows the measurement of aromatic hydrocarbons on once-folded absorptions paths of 200-1200 m length. The new instrument shows very good agreement with simultaneous in-situ measurements if inhomogeneities of the trace gas spatial distributions are considered. The new instrument performed well during a three-month field test as an automated fence-line monitor at a refinery, successfully distinguishing upwind background levels of ∼1 ppb from emissions reflected in elevated mixing ratios of 3-4 ppb. A two-dimensional measurement network based on two identical LP-DOAS instruments operating on seven crossed light paths was operated successfully in Houston, TX. Qualitative and quantitative analysis of two events with toluene and xylene plumes demonstrate how this setup can be used to derive the spatial distribution of aromatic hydrocarbons, and identify point sources.

  10. Minimal entropy probability paths between genome families.

    PubMed

    Ahlbrandt, Calvin; Benson, Gary; Casey, William

    2004-05-01

    We develop a metric for probability distributions with applications to biological sequence analysis. Our distance metric is obtained by minimizing a functional defined on the class of paths over probability measures on N categories. The underlying mathematical theory is connected to a constrained problem in the calculus of variations. The solution presented is a numerical solution, which approximates the true solution in a set of cases called rich paths where none of the components of the path is zero. The functional to be minimized is motivated by entropy considerations, reflecting the idea that nature might efficiently carry out mutations of genome sequences in such a way that the increase in entropy involved in transformation is as small as possible. We characterize sequences by frequency profiles or probability vectors, in the case of DNA where N is 4 and the components of the probability vector are the frequency of occurrence of each of the bases A, C, G and T. Given two probability vectors a and b, we define a distance function based as the infimum of path integrals of the entropy function H( p) over all admissible paths p(t), 0 < or = t< or =1, with p(t) a probability vector such that p(0)=a and p(1)=b. If the probability paths p(t) are parameterized as y(s) in terms of arc length s and the optimal path is smooth with arc length L, then smooth and "rich" optimal probability paths may be numerically estimated by a hybrid method of iterating Newton's method on solutions of a two point boundary value problem, with unknown distance L between the abscissas, for the Euler-Lagrange equations resulting from a multiplier rule for the constrained optimization problem together with linear regression to improve the arc length estimate L. Matlab code for these numerical methods is provided which works only for "rich" optimal probability vectors. These methods motivate a definition of an elementary distance function which is easier and faster to calculate, works on non

  11. Effect of radiometric errors on accuracy of temperature-profile measurement by spectral scanning using absorption-emission pyrometry

    NASA Technical Reports Server (NTRS)

    Buchele, D. R.

    1972-01-01

    The spectral-scanning method may be used to determine the temperature profile of a jet- or rocket-engine exhaust stream by measurements of gas radiation and transmittance, at two or more wavelengths. A single, fixed line of sight is used, using immobile radiators outside of the gas stream, and there is no interference with the flow. At least two sets of measurements are made, each set consisting of the conventional three radiometric measurements of absorption-emission pyrometry, but each set is taken over a different spectral interval that gives different weight to the radiation from a different portion of the optical path. Thereby, discrimination is obtained with respect to location along the path. A given radiometric error causes an error in computed temperatures. The ratio between temperature error and radiometric error depends on profile shape, path length, temperature level, and strength of line absorption, and the absorption coefficient and its temperature dependency. These influence the choice of wavelengths, for any given gas. Conditions for minimum temperature error are derived. Numerical results are presented for a two-wavelength measurement on a family of profiles that may be expected in a practical case of hydrogen-oxygen combustion. Under favorable conditions, the fractional error in temperature approximates the fractional error in radiant-flux measurement.

  12. On-column double-beam laser absorption detection for capillary electrophoresis

    SciTech Connect

    Xue, Y.; Yeung, E.S. )

    1993-08-01

    Double-beam laser absorption detection in capillary electrophoresis (CE) has been developed. This is based on the direct subtraction of reference and signal photocurrents by an electronic circuit, under feedback control, to reduce background noise. A simple equation for calculating concentrations has been proposed and was confirmed by experimental results. A practical noise-to-signal ratio of 1 [times] 10[sup [minus]5] in intensity is achieved. This is 5 times lower than that of commercial CE systems. For absorbance detection, as low as 2 [times] 10[sup [minus]8] M malachite green can be detected. This corresponds to a 25-fold improvement of detection limit over commercial systems. This gain in detectability results from both a reduction in intensity fluctuations (noise) and an increase in the effective absorption path length (signal). 22 refs., 6 figs.

  13. Arc Length Gone Global

    ERIC Educational Resources Information Center

    Boudreaux, Gregory M.; Wells, M. Scott

    2007-01-01

    Everyone with a thorough knowledge of single variable calculus knows that integration can be used to find the length of a curve on a given interval, called its arc length. Fortunately, if one endeavors to pose and solve more interesting problems than simply computing lengths of various curves, there are techniques available that do not require an…

  14. Portable 4.6 Micrometers Laser Absorption Spectrometer for Carbon Monoxide Monitoring and Fire Detection

    NASA Technical Reports Server (NTRS)

    Briggs, Ryan M.; Frez, Clifford; Forouhar, Siamak; May, Randy D.; Ruff, Gary A.

    2013-01-01

    The air quality aboard manned spacecraft must be continuously monitored to ensure crew safety and identify equipment malfunctions. In particular, accurate real-time monitoring of carbon monoxide (CO) levels helps to prevent chronic exposure and can also provide early detection of combustion-related hazards. For long-duration missions, environmental monitoring grows in importance, but the mass and volume of monitoring instruments must be minimized. Furthermore, environmental analysis beyond low-Earth orbit must be performed in-situ, as sample return becomes impractical. Due to their small size, low power draw, and performance reliability, semiconductor-laser-based absorption spectrometers are viable candidates for this purpose. To reduce instrument form factor and complexity, the emission wavelength of the laser source should coincide with strong fundamental absorption lines of the target gases, which occur in the 3 to 5 micrometers wavelength range for most combustion products of interest, thereby reducing the absorption path length required for low-level concentration measurements. To address the needs of current and future NASA missions, we have developed a prototype absorption spectrometer using a semiconductor quantum cascade laser source operating near 4.6 micrometers that can be used to detect low concentrations of CO with a compact single-pass absorption cell. In this study, we present the design of the prototype instrument and report on measurements of CO emissions from the combustion of a variety of aerospace plastics.

  15. Near-IR diode laser absorption for measurement of tropospheric HO2

    NASA Technical Reports Server (NTRS)

    Stanton, Alan C.

    1994-01-01

    The possibility of using tunable lead salt diode lasers in the infrared for measurement of tropospheric HO2 has been frequently considered. Although the sensitivity of diode laser absorption has been improved through the use of high frequency detection techniques, nature has been unkind in that the HO2 absorption cross sections are weak. Even using the most optimistic assumptions about attainable path length and detectable absorbance, measurement of tropospheric HO2 by diode laser absorption in the mid-IR appears marginal. A possible alternative method for measuring HO2 is by absorption at near-infrared wavelengths. Several absorption bands of HO2 occur in the wavelength region between 1.2 and 1.6 micron due to electronic transitions and overtones of the fundamental vibrational modes. InGaAsP diode lasers operate in this wavelength region and can be used for high resolution spectroscopy in a manner analogous to the lead salt lasers. A diode laser system in the near-IR offers some advantages.

  16. A Path to Discovery

    ERIC Educational Resources Information Center

    Stegemoller, William; Stegemoller, Rebecca

    2004-01-01

    The path taken and the turns made as a turtle traces a polygon are examined to discover an important theorem in geometry. A unique tool, the Angle Adder, is implemented in the investigation. (Contains 9 figures.)

  17. Tortuous path chemical preconcentrator

    DOEpatents

    Manginell, Ronald P.; Lewis, Patrick R.; Adkins, Douglas R.; Wheeler, David R.; Simonson, Robert J.

    2010-09-21

    A non-planar, tortuous path chemical preconcentrator has a high internal surface area having a heatable sorptive coating that can be used to selectively collect and concentrate one or more chemical species of interest from a fluid stream that can be rapidly released as a concentrated plug into an analytical or microanalytical chain for separation and detection. The non-planar chemical preconcentrator comprises a sorptive support structure having a tortuous flow path. The tortuosity provides repeated twists, turns, and bends to the flow, thereby increasing the interfacial contact between sample fluid stream and the sorptive material. The tortuous path also provides more opportunities for desorption and readsorption of volatile species. Further, the thermal efficiency of the tortuous path chemical preconcentrator is comparable or superior to the prior non-planar chemical preconcentrator. Finally, the tortuosity can be varied in different directions to optimize flow rates during the adsorption and desorption phases of operation of the preconcentrator.

  18. Topological analysis of polymeric melts: Chain-length effects and fast-converging estimators for entanglement length

    NASA Astrophysics Data System (ADS)

    Hoy, Robert S.; Foteinopoulou, Katerina; Kröger, Martin

    2009-09-01

    Primitive path analyses of entanglements are performed over a wide range of chain lengths for both bead spring and atomistic polyethylene polymer melts. Estimators for the entanglement length Ne which operate on results for a single chain length N are shown to produce systematic O(1/N) errors. The mathematical roots of these errors are identified as (a) treating chain ends as entanglements and (b) neglecting non-Gaussian corrections to chain and primitive path dimensions. The prefactors for the O(1/N) errors may be large; in general their magnitude depends both on the polymer model and the method used to obtain primitive paths. We propose, derive, and test new estimators which eliminate these systematic errors using information obtainable from the variation in entanglement characteristics with chain length. The new estimators produce accurate results for Ne from marginally entangled systems. Formulas based on direct enumeration of entanglements appear to converge faster and are simpler to apply.

  19. Path integration in tactile perception of shapes.

    PubMed

    Moscatelli, Alessandro; Naceri, Abdeldjallil; Ernst, Marc O

    2014-11-01

    Whenever we move the hand across a surface, tactile signals provide information about the relative velocity between the skin and the surface. If the system were able to integrate the tactile velocity information over time, cutaneous touch may provide an estimate of the relative displacement between the hand and the surface. Here, we asked whether humans are able to form a reliable representation of the motion path from tactile cues only, integrating motion information over time. In order to address this issue, we conducted three experiments using tactile motion and asked participants (1) to estimate the length of a simulated triangle, (2) to reproduce the shape of a simulated triangular path, and (3) to estimate the angle between two-line segments. Participants were able to accurately indicate the length of the path, whereas the perceived direction was affected by a direction bias (inward bias). The response pattern was thus qualitatively similar to the ones reported in classical path integration studies involving locomotion. However, we explain the directional biases as the result of a tactile motion aftereffect.

  20. Gas analysis in the UV region using a long-length hollow core waveguide

    NASA Astrophysics Data System (ADS)

    Kotschau, R.; Eckhardt, Hanns-S.; Klein, Karl-Friedrich; Behler, Klaus; Hillrichs, Georg

    2003-07-01

    In the DUV-region and MIR-region, the so-called Hollow-Core-Waveguide is an alternative for light-delivery systems, because flexible silica-based fibers are no lnoger useable due to the high intrinsic absorption of silica. In additionl to light-transportation, only the HCW can be used as an intrinsic sensor: due to the long path-length through the HCW with similar intensity profiles at the input and output, the spectral absorption of the gas under test can easily be monitored. Up to now, the gases are analyzed in the MIR-region, mainly. However, the UV-region offers a lot of advantages. Using commercially available components for the UV-light source and the detector-system, the whole system with UV hollow-core-waveguides has to be studied in the wavelength-region from 170 nm up to 350 nm. With this experimental system, it is obvious to observe the UV-absorption of air and carbon dioxide below 200 nm, using nitrogen as a reference gas. In addition, ozone generated by the deuterium-lamp itself and several gas mixtures (e.g. 2 ppm toluene or xylene in cabon dioxide) were studied in detail.

  1. A Faster, Unbiased Path Opening by Upper Skeletonization and Weighted Adjacency Graphs.

    PubMed

    Asplund, Teo; Luengo Hendriks, Cris L

    2016-12-01

    The path opening is a filter that preserves bright regions in the image in which a path of a certain length L fits. A path is a (not necessarily straight) line defined by a specific adjacency relation. The most efficient implementation known scales as O(min(L, d, Q) N) with the length of the path, L , the maximum possible path length, d , the number of graylevels, Q , and the image size, N . An approximation exists (parsimonious path opening) that has an execution time independent of path length. This is achieved by preselecting paths, and applying 1D openings along these paths. However, the preselected paths can miss important structures, as described by its authors. Here, we propose a different approximation, in which we preselect paths using a grayvalue skeleton. The skeleton follows all ridges in the image, meaning that no important line structures will be missed. An H-minima transform simplifies the image to reduce the number of branches in the skeleton. A graph-based version of the traditional path opening operates only on the pixels in the skeleton, yielding speedups up to one order of magnitude, depending on image size and filter parameters. The edges of the graph are weighted in order to minimize bias. Experiments show that the proposed algorithm scales linearly with image size, and that it is often slightly faster for longer paths than for shorter paths. The algorithm also yields the most accurate results-as compared with a number of path opening variants-when measuring length distributions.

  2. Demonstration of scan path optimization in proton therapy

    SciTech Connect

    Kang, Joanne H.; Wilkens, Jan J.; Oelfke, Uwe

    2007-09-15

    A three-dimensional (3D) intensity modulated proton therapy treatment plan to be delivered by magnetic scanning may comprise thousands of discrete beam positions. This research presents the minimization of the total scan path length by application of a fast simulated annealing (FSA) optimization algorithm. Treatment plans for clinical prostate and head and neck cases were sequenced for continuous raster scanning in two ways, and the resulting scan path lengths were compared: (1) A simple back-and-forth, top-to-bottom (zigzag) succession, and (2) an optimized path produced as a solution of the FSA algorithm. Using a first approximation of the scanning dynamics, the delivery times for the scan sequences before and after path optimization were calculated for comparison. In these clinical examples, the FSA optimization shortened the total scan path length for the 3D target volumes by approximately 13%-56%. The number of extraneous spilled particles was correspondingly reduced by about 13%-54% due to the more efficient scanning maps that eliminated multiple crossings through regions of zero fluence. The relative decrease in delivery time due to path length minimization was estimated to be less than 1%, due to both a high scanning speed and time requirements that could not be altered by optimization (e.g., time required to change the beam energy). In a preliminary consideration of application to rescanning techniques, the decrease in delivery time was estimated to be 4%-20%.

  3. ABSORPTION ANALYZER

    DOEpatents

    Brooksbank, W.A. Jr.; Leddicotte, G.W.; Strain, J.E.; Hendon, H.H. Jr.

    1961-11-14

    A means was developed for continuously computing and indicating the isotopic assay of a process solution and for automatically controlling the process output of isotope separation equipment to provide a continuous output of the desired isotopic ratio. A counter tube is surrounded with a sample to be analyzed so that the tube is exactly in the center of the sample. A source of fast neutrons is provided and is spaced from the sample. The neutrons from the source are thermalized by causing them to pass through a neutron moderator, and the neutrons are allowed to diffuse radially through the sample to actuate the counter. A reference counter in a known sample of pure solvent is also actuated by the thermal neutrons from the neutron source. The number of neutrons which actuate the detectors is a function of a concentration of the elements in solution and their neutron absorption cross sections. The pulses produced by the detectors responsive to each neu tron passing therethrough are amplified and counted. The respective times required to accumulate a selected number of counts are measured by associated timing devices. The concentration of a particular element in solution may be determined by utilizing the following relation: T2/Ti = BCR, where B is a constant proportional to the absorption cross sections, T2 is the time of count collection for the unknown solution, Ti is the time of count collection for the pure solvent, R is the isotopic ratlo, and C is the molar concentration of the element to be determined. Knowing the slope constant B for any element and when the chemical concentration is known, the isotopic concentration may be readily determined, and conversely when the isotopic ratio is known, the chemical concentrations may be determined. (AEC)

  4. Neandertal clavicle length

    PubMed Central

    Trinkaus, Erik; Holliday, Trenton W.; Auerbach, Benjamin M.

    2014-01-01

    The Late Pleistocene archaic humans from western Eurasia (the Neandertals) have been described for a century as exhibiting absolutely and relatively long clavicles. This aspect of their body proportions has been used to distinguish them from modern humans, invoked to account for other aspects of their anatomy and genetics, used in assessments of their phylogenetic polarities, and used as evidence for Late Pleistocene population relationships. However, it has been unclear whether the usual scaling of Neandertal clavicular lengths to their associated humeral lengths reflects long clavicles, short humeri, or both. Neandertal clavicle lengths, along with those of early modern humans and latitudinally diverse recent humans, were compared with both humeral lengths and estimated body masses (based on femoral head diameters). The Neandertal do have long clavicles relative their humeri, even though they fall within the ranges of variation of early and recent humans. However, when scaled to body masses, their humeral lengths are relatively short, and their clavicular lengths are indistinguishable from those of Late Pleistocene and recent modern humans. The few sufficiently complete Early Pleistocene Homo clavicles seem to have relative lengths also well within recent human variation. Therefore, appropriately scaled clavicular length seems to have varied little through the genus Homo, and it should not be used to account for other aspects of Neandertal biology or their phylogenetic status. PMID:24616525

  5. Mobile transporter path planning

    NASA Technical Reports Server (NTRS)

    Baffes, Paul; Wang, Lui

    1990-01-01

    The use of a genetic algorithm (GA) for solving the mobile transporter path planning problem is investigated. The mobile transporter is a traveling robotic vehicle proposed for the space station which must be able to reach any point of the structure autonomously. Elements of the genetic algorithm are explored in both a theoretical and experimental sense. Specifically, double crossover, greedy crossover, and tournament selection techniques are examined. Additionally, the use of local optimization techniques working in concert with the GA are also explored. Recent developments in genetic algorithm theory are shown to be particularly effective in a path planning problem domain, though problem areas can be cited which require more research.

  6. Electromagnetic wave absorption properties of composites with ultrafine hollow magnetic fibers

    NASA Astrophysics Data System (ADS)

    Yi, Jin Woo; Lee, Sang Bok; Kim, Jin Bong; Lee, Sang Kwan; Park, O. Ok

    2014-06-01

    Ultrafine hollow magnetic fibers were prepared by electroless plating using hydrolyzed polyester fiber as a sacrificial substrate. These hollow fibers can be served for lightweight and efficient electromagnetic (EM) absorbing materials. As observed from SEM and EDS analysis, hollow structures consisting of Ni inner layer and Fe or Fe-Co outer layer were obtained. By introducing Co onto Fe, oxidation of the Fe layer was successfully prevented making it possible to enhance the complex permeability compared to a case in which only Fe was used. Polymeric composites containing the hollow fibers with different weight fractions and fiber lengths were prepared by a simple mixing process. The electromagnetic wave properties of the composites were measured by a vector network analyzer and it was found that the hollow magnetic fibers show a clear resonance peak of the complex permittivity around the X-band range (8-12 GHz) and the resonance frequency strongly depends on the fiber concentration and length. A possible explanation for the unique resonance is that the hollow fibers possess relatively low electrical conductivity and a long mean free path due to their oxidized phase and hollow structure. The calculated EM wave absorption with the measured EM wave properties showed that the composite containing 30 wt% hollow Ni/Fe-Co (7:3) fibers in length of 180 μm exhibited multiple absorbance peaks resulting in a broad absorption bandwidth of 4.2 GHz. It is obvious that this multiple absorbance is attributed to the resonance characteristic of the composite.

  7. Broadband Phase Spectroscopy over Turbulent Air Paths.

    PubMed

    Giorgetta, Fabrizio R; Rieker, Gregory B; Baumann, Esther; Swann, William C; Sinclair, Laura C; Kofler, Jon; Coddington, Ian; Newbury, Nathan R

    2015-09-04

    Broadband atmospheric phase spectra are acquired with a phase-sensitive dual-frequency-comb spectrometer by implementing adaptive compensation for the strong decoherence from atmospheric turbulence. The compensation is possible due to the pistonlike behavior of turbulence across a single spatial-mode path combined with the intrinsic frequency stability and high sampling speed associated with dual-comb spectroscopy. The atmospheric phase spectrum is measured across 2 km of air at each of the 70,000 comb teeth spanning 233  cm(-1) across hundreds of near-infrared rovibrational resonances of CO(2), CH(4), and H(2)O with submilliradian uncertainty, corresponding to a 10(-13) refractive index sensitivity. Trace gas concentrations extracted directly from the phase spectrum reach 0.7 ppm uncertainty, demonstrated here for CO(2). While conventional broadband spectroscopy only measures intensity absorption, this approach enables measurement of the full complex susceptibility even in practical open path sensing.

  8. Broadband Phase Spectroscopy over Turbulent Air Paths

    NASA Astrophysics Data System (ADS)

    Giorgetta, Fabrizio R.; Rieker, Gregory B.; Baumann, Esther; Swann, William C.; Sinclair, Laura C.; Kofler, Jon; Coddington, Ian; Newbury, Nathan R.

    2015-09-01

    Broadband atmospheric phase spectra are acquired with a phase-sensitive dual-frequency-comb spectrometer by implementing adaptive compensation for the strong decoherence from atmospheric turbulence. The compensation is possible due to the pistonlike behavior of turbulence across a single spatial-mode path combined with the intrinsic frequency stability and high sampling speed associated with dual-comb spectroscopy. The atmospheric phase spectrum is measured across 2 km of air at each of the 70 000 comb teeth spanning 233 cm-1 across hundreds of near-infrared rovibrational resonances of CO2 , CH4 , and H2O with submilliradian uncertainty, corresponding to a 10-13 refractive index sensitivity. Trace gas concentrations extracted directly from the phase spectrum reach 0.7 ppm uncertainty, demonstrated here for CO2 . While conventional broadband spectroscopy only measures intensity absorption, this approach enables measurement of the full complex susceptibility even in practical open path sensing.

  9. Parallel rail electromagnetic launcher with multiple current path armature

    SciTech Connect

    Kemeny, G. A.

    1984-12-04

    Electromagnetic projectile launchers utilize multiple current path armatures in an internally series augmented conductor rail configuration or an internally augmented system connected to multiple power supplies. The current paths include plasmas, conductors or combinations of both. Plasma separation is maintained by trailing insulating plasma dividers extending toward the launcher breech from arc driving faces on a projectile sabot. Arc length and/or plama volume is reduced by conductive assemblies adjacent to the arc driving faces.

  10. An Unplanned Path

    ERIC Educational Resources Information Center

    McGarvey, Lynn M.; Sterenberg, Gladys Y.; Long, Julie S.

    2013-01-01

    The authors elucidate what they saw as three important challenges to overcome along the path to becoming elementary school mathematics teacher leaders: marginal interest in math, low self-confidence, and teaching in isolation. To illustrate how these challenges were mitigated, they focus on the stories of two elementary school teachers--Laura and…

  11. Gas path seal

    NASA Technical Reports Server (NTRS)

    Bill, R. C.; Johnson, R. D. (Inventor)

    1979-01-01

    A gas path seal suitable for use with a turbine engine or compressor is described. A shroud wearable or abradable by the abrasion of the rotor blades of the turbine or compressor shrouds the rotor bades. A compliant backing surrounds the shroud. The backing is a yieldingly deformable porous material covered with a thin ductile layer. A mounting fixture surrounds the backing.

  12. Use of radial symmetry for the calculation of cylindrical absorption coefficients and optimal capillary loadings

    DOE PAGES

    Khalifah, Peter

    2015-02-01

    The problem of numerically evaluating absorption correction factors for cylindrical samples has been revisited using a treatment that fully takes advantage of the sample symmetry. It is shown that the path lengths for all points within the sample at all possible diffraction angles can be trivially determined once the angle-dependent distance distribution for a single line of points is calculated. This provides advantages in both computational efficiency and in gaining an intuitive understanding of the effects of absorption on diffraction data. A matrix of absorption coefficients calculated for µR products between 0 and 20 for diffraction angles θD of 0°more » to 90° were used to examine the influence of (1) capillary diameter and of (2) sample density on the overall scattered intensity as a function of diffraction angle, where µ is the linear absorption coefficient for the sample and R is the capillary radius. Based on this analysis, the optimal sample loading for a capillary experiment to maximize diffraction at angles of 0 – 50° is in general expected to be achieved when the maximum radius capillary compatible with the beam is used, and when the sample density is adjusted to be 3/(4µR) of its original density.« less

  13. Light trapping and near-unity solar absorption in a three-dimensional photonic-crystal.

    PubMed

    Kuang, Ping; Deinega, Alexei; Hsieh, Mei-Li; John, Sajeev; Lin, Shawn-Yu

    2013-10-15

    We report what is to our knowledge the first observation of the effect of parallel-to-interface-refraction (PIR) in a three-dimensional, simple-cubic photonic-crystal. PIR is an acutely negative refraction of light inside a photonic-crystal, leading to light-bending by nearly 90 deg over broad wavelengths (λ). The consequence is a longer path length of light in the medium and an improved light absorption beyond the Lambertian limit. As an illustration of the effect, we show near-unity total absorption (≥98%) in λ=520-620 nm and an average absorption of ~94% over λ=400-700 nm for our α-Si:H photonic-crystal sample of an equivalent bulk thickness of t˜=450 nm. Furthermore, we have achieved an ultra-wide angular acceptance of light over θ=0°-80°. This demonstration opens up a new door for light trapping and near-unity solar absorption over broad λs and wide angles.

  14. Tunable Diode Laser Atomic Absorption Spectroscopy for Detection of Potassium under Optically Thick Conditions.

    PubMed

    Qu, Zhechao; Steinvall, Erik; Ghorbani, Ramin; Schmidt, Florian M

    2016-04-05

    Potassium (K) is an important element related to ash and fine-particle formation in biomass combustion processes. In situ measurements of gaseous atomic potassium, K(g), using robust optical absorption techniques can provide valuable insight into the K chemistry. However, for typical parts per billion K(g) concentrations in biomass flames and reactor gases, the product of atomic line strength and absorption path length can give rise to such high absorbance that the sample becomes opaque around the transition line center. We present a tunable diode laser atomic absorption spectroscopy (TDLAAS) methodology that enables accurate, calibration-free species quantification even under optically thick conditions, given that Beer-Lambert's law is valid. Analyte concentration and collisional line shape broadening are simultaneously determined by a least-squares fit of simulated to measured absorption profiles. Method validation measurements of K(g) concentrations in saturated potassium hydroxide vapor in the temperature range 950-1200 K showed excellent agreement with equilibrium calculations, and a dynamic range from 40 pptv cm to 40 ppmv cm. The applicability of the compact TDLAAS sensor is demonstrated by real-time detection of K(g) concentrations close to biomass pellets during atmospheric combustion in a laboratory reactor.

  15. Use of radial symmetry for the calculation of cylindrical absorption coefficients and optimal capillary loadings

    SciTech Connect

    Khalifah, Peter

    2015-02-01

    The problem of numerically evaluating absorption correction factors for cylindrical samples has been revisited using a treatment that fully takes advantage of the sample symmetry. It is shown that the path lengths for all points within the sample at all possible diffraction angles can be trivially determined once the angle-dependent distance distribution for a single line of points is calculated. This provides advantages in both computational efficiency and in gaining an intuitive understanding of the effects of absorption on diffraction data. A matrix of absorption coefficients calculated for µR products between 0 and 20 for diffraction angles θD of 0° to 90° were used to examine the influence of (1) capillary diameter and of (2) sample density on the overall scattered intensity as a function of diffraction angle, where µ is the linear absorption coefficient for the sample and R is the capillary radius. Based on this analysis, the optimal sample loading for a capillary experiment to maximize diffraction at angles of 0 – 50° is in general expected to be achieved when the maximum radius capillary compatible with the beam is used, and when the sample density is adjusted to be 3/(4µR) of its original density.

  16. [Concentration retrieving method of SO2 using differential optical absorption spectroscopy based on statistics].

    PubMed

    Liu, Bin; Sun, Chang-Ku; Zhang, Chi; Zhao, Yu-Mei; Liu, Jun-Ping

    2011-01-01

    A concentration retrieving method using statistics is presented, which is applied in differential optical absorption spectroscopy (DOAS) for measuring the concentration of SO2. The method uses the standard deviation of the differential absorption to represents the gas concentration. Principle component analysis (PCA) method is used to process the differential absorption spectrum. In the method, the basis data for the concentration retrieval of SO2 is the combination of the PCA processing result, the correlation coefficient, and the standard deviation of the differential absorption. The method is applied to a continuous emission monitoring system (CEMS) with optical path length of 0.3 m. Its measuring range for SO2 concentration is 0-5 800 mg x m(-3). The nonlinear calibration and the temperature compensation for the system were executed. The full scale error of the retrieving concentration is less than 0.7% FS. And the measuring result is -4.54 mg x m(-3) when the concentration of SO2 is zero.

  17. Mid-infrared laser absorption spectroscopy of NO2 at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Sur, Ritobrata; Peng, Wen Yu; Strand, Christopher; Mitchell Spearrin, R.; Jeffries, Jay B.; Hanson, Ronald K.; Bekal, Anish; Halder, Purbasha; Poonacha, Samhitha P.; Vartak, Sameer; Sridharan, Arun K.

    2017-01-01

    A mid-infrared quantum cascade laser absorption sensor was developed for in-situ detection of NO2 in high-temperature gas environments. A cluster of spin-split transitions near 1599.9 cm-1 from the ν3 absorption band of NO2 was selected due to the strength of these transitions and the low spectral interference from water vapor within this region. Temperature- and species-dependent collisional broadening parameters of ten neighboring NO2 transitions with Ar, O2, N2, CO2 and H2O were measured and reported. The spectral model was validated through comparisons with direct absorption spectroscopy measurements of NO2 seeded in various bath gases. The performance of the scanned wavelength modulation spectroscopy (WMS)-based sensor was demonstrated in a combustion exhaust stream seeded with varying flow rates of NO2, achieving reliable detection of 1.45 and 1.6 ppm NO2 by mole at 600 K and 800 K, respectively, with a measurement uncertainty of ±11%. 2σ noise levels of 360 ppb and 760 ppb were observed at 600 K and 800 K, respectively, in an absorption path length of 1.79 m.

  18. A new calibration system for lightweight, compact and mobile Cavity-Enhanced Differential Optical Absorption Spectroscopy instruments

    NASA Astrophysics Data System (ADS)

    Zielcke, Johannes; Horbanski, Martin; Pöhler, Denis; Frieß, Udo; Platt, Ulrich

    2013-04-01

    Absorption Spectroscopy has been employed for several decades now to study the earth's atmosphere. While the focus has been on remote sensing for a long time, lately there has been a renewed interest in in-situ methods, as point measurements allow an easier interpretation for highly inhomogeneous distributions of gases of interest compared to the integration approach of most remote sensing methods. One comparatively new method offering both advantages of in-situ measurements as well as being contactless is open-path Cavity-Enhanced Differential Optical Absorption Spectroscopy (CE-DOAS). Broadband open-path CE-DOAS instruments have been used for ten years now, and in the meantime allow the measurement of numerous atmospheric trace gases (e.g. NO2, NO3, IO, CHOCHO, HCHO). While those instruments were bulky and not very mobile at first, recent developments resulted in relatively lightweight (< 30 kg) instruments with a relatively low power consumption allowing mobile open-path measurements at remote field locations. An important operational issue has been the path length calibration in the field, necessary for the determination of the concentration of measured gases. Until now, often calibration gases were used with different scattering properties than air or known concentrations. However this methods has several major shortcomings, being rather inconvenient and cumbersome in the field with the need for compressed gas cylinders, as well as time consuming, preventing a quick check of the state of the instrument in the field after changing measurement locations. Here we present a new wavelength-resolved method for broadband CE-DOAS path length calibration. A small, custom made ring-down system is employed with a pulsed LED as light source. The wavelength is then resolved by tilting a narrow band interference filter. The system not only allows quick, automated path length calibrations without physical interaction on the instrument, but also saves weight, space and the

  19. Myofilament length dependent activation.

    PubMed

    de Tombe, Pieter P; Mateja, Ryan D; Tachampa, Kittipong; Ait Mou, Younss; Farman, Gerrie P; Irving, Thomas C

    2010-05-01

    The Frank-Starling law of the heart describes the interrelationship between end-diastolic volume and cardiac ejection volume, a regulatory system that operates on a beat-to-beat basis. The main cellular mechanism that underlies this phenomenon is an increase in the responsiveness of cardiac myofilaments to activating Ca(2+) ions at a longer sarcomere length, commonly referred to as myofilament length-dependent activation. This review focuses on what molecular mechanisms may underlie myofilament length dependency. Specifically, the roles of inter-filament spacing, thick and thin filament based regulation, as well as sarcomeric regulatory proteins are discussed. Although the "Frank-Starling law of the heart" constitutes a fundamental cardiac property that has been appreciated for well over a century, it is still not known in muscle how the contractile apparatus transduces the information concerning sarcomere length to modulate ventricular pressure development.

  20. Coefficients of Effective Length.

    ERIC Educational Resources Information Center

    Edwards, Roger H.

    1981-01-01

    Under certain conditions, a validity Coefficient of Effective Length (CEL) can produce highly misleading results. A modified coefficent is suggested for use when empirical studies indicate that underlying assumptions have been violated. (Author/BW)

  1. Myofilament length dependent activation

    SciTech Connect

    de Tombe, Pieter P.; Mateja, Ryan D.; Tachampa, Kittipong; Mou, Younss Ait; Farman, Gerrie P.; Irving, Thomas C.

    2010-05-25

    The Frank-Starling law of the heart describes the interrelationship between end-diastolic volume and cardiac ejection volume, a regulatory system that operates on a beat-to-beat basis. The main cellular mechanism that underlies this phenomenon is an increase in the responsiveness of cardiac myofilaments to activating Ca{sup 2+} ions at a longer sarcomere length, commonly referred to as myofilament length-dependent activation. This review focuses on what molecular mechanisms may underlie myofilament length dependency. Specifically, the roles of inter-filament spacing, thick and thin filament based regulation, as well as sarcomeric regulatory proteins are discussed. Although the 'Frank-Starling law of the heart' constitutes a fundamental cardiac property that has been appreciated for well over a century, it is still not known in muscle how the contractile apparatus transduces the information concerning sarcomere length to modulate ventricular pressure development.

  2. Length Paradox in Relativity

    ERIC Educational Resources Information Center

    Martins, Roberto de A.

    1978-01-01

    Describes a thought experiment using a general analysis approach with Lorentz transformations to show that the apparent self-contradictions of special relativity concerning the length-paradox are really non-existant. (GA)

  3. Differential optoacoustic absorption detector

    NASA Technical Reports Server (NTRS)

    Shumate, M. S. (Inventor)

    1978-01-01

    A differential optoacoustic absorption detector employed two tapered cells in tandem or in parallel. When operated in tandem, two mirrors were used at one end remote from the source of the beam of light directed into one cell back through the other, and a lens to focus the light beam into the one cell at a principal focus half way between the reflecting mirror. Each cell was tapered to conform to the shape of the beam so that the volume of one was the same as for the other, and the volume of each received maximum illumination. The axes of the cells were placed as close to each other as possible in order to connect a differential pressure detector to the cells with connecting passages of minimum length. An alternative arrangement employed a beam splitter and two lenses to operate the cells in parallel.

  4. Length of Stay

    PubMed Central

    Gustafson, David H.

    1968-01-01

    Five methodologies for predicting hospital length of stay were developed and compared. Two—a subjective Bayesian forecaster and a regression forecaster—also measured the relative importance of the symptomatic and demographic factors in predicting length of stay. The performance of the methodologies was evaluated with several criteria of effectiveness and one of cost. The results should provide encouragement for those interested in computer applications to utilization review and to scheduling inpatient admissions. PMID:5673664

  5. Observations on oesophageal length.

    PubMed Central

    Kalloor, G J; Deshpande, A H; Collis, J L

    1976-01-01

    The subject of oesophageal length is discussed. The great variations in the length of the oesophagus in individual patients is noted, and the practical use of its recognition in oesophageal surgery is stressed. An apprasial of the various methods available for this measurement is made; this includes the use of external chest measurement, endoscopic measurement, and the measurement of the level of the electrical mucosal potential change. Correlative studies of these various methods are made, and these show a very high degree of significance. These studies involved simultaneous measurement of external and internal oesophageal length in 26 patients without a hiatal hernia or gastro-oesophageal length in 26 patients without a hiatal hernia or gastro-oesophageal reflux symptoms, 42 patients with sliding type hiatal hernia, and 17 patients with a peptic stricture in association with hiatal hernia. The method of measuring oesophageal length by the use of the external chest measurement, that is, the distance between the lower incisor teeth and the xiphisternum, measured with the neck fully extended and the patient lying supine, is described in detail, its practical application in oesophageal surgery is illustrated, and its validity tested by internal measurements. The findings of this study demonstrate that the external chest measurement provides a mean of assessing the true static length of the oesophagus, corrected for the size of the individual. Images PMID:941114

  6. Editorial: Redefining Length

    SciTech Connect

    Sprouse, Gene D.

    2011-07-15

    Technological changes have moved publishing to electronic-first publication where the print version has been relegated to simply another display mode. Distribution in HTML and EPUB formats, for example, changes the reading environment and reduces the need for strict pagination. Therefore, in an effort to streamline the calculation of length, the APS journals will no longer use the printed page as the determining factor for length. Instead the journals will now use word counts (or word equivalents for tables, figures, and equations) to establish length; for details please see http://publish.aps.org/authors/length-guide. The title, byline, abstract, acknowledgment, and references will not be included in these counts allowing authors the freedom to appropriately credit coworkers, funding sources, and the previous literature, bringing all relevant references to the attention of readers. This new method for determining length will be easier for authors to calculate in advance, and lead to fewer length-associated revisions in proof, yet still retain the quality of concise communication that is a virtue of short papers.

  7. Analysis for nonlinear inversion technique developed to estimate depth-distribution of absorption by spatially resolved backscattering measurement

    NASA Astrophysics Data System (ADS)

    Nishida, Kazuhiro; Namita, Takeshi; Kato, Yuji; Shimizu, Koichi

    2015-03-01

    We have proposed a new nonlinear inversion technique to estimate the spatial distribution of the absorption coefficient (μa) in the depth direction of a turbid medium by spatially resolved backscattering measurement. With this technique, we can obtain cross-sectional image of μa as deep as the backscattered light traveled even when the transmitted light through the medium cannot be detected. In this technique, the depth distribution of absorption coefficient is determined by iterative calculation using the spatial path-length distribution (SPD) of traveled photons as a function of source-detector distance. In this calculation, the variance of path-length of many photons in each layer is also required. The SPD and the variance of path-length are obtained by Monte Carlo simulation using a known reduced scattering coefficient (μs'). Therefore, we need to know the μs' of the turbid medium beforehand. We have shown in computer simulation that this technique works well when the μs' is the typical values of mammalian body tissue, or 1.0 /mm. In this study, the accuracy of the μa estimation was analyzed and its dependence on the μs' was clarified quantitatively in various situations expected in practice. 10% deviations in μs' resulted in about 30% error in μa estimation, in average. This suggested that the measurement or the appropriate estimation of μs' is required to utilize the proposed technique effectively. Through this analysis, the effectiveness and the limitation of the newly proposed technique were clarified, and the problems to be solved were identified.

  8. Higher-Order Airy Scaling in Deformed Dyck Paths

    NASA Astrophysics Data System (ADS)

    Haug, Nils; Olde Daalhuis, Adri; Prellberg, Thomas

    2017-03-01

    We introduce a deformed version of Dyck paths (DDP), where additional to the steps allowed for Dyck paths, `jumps' orthogonal to the preferred direction of the path are permitted. We consider the generating function of DDP, weighted with respect to their half-length, area and number of jumps. This represents the first example of an exactly solvable two-dimensional lattice vesicle model showing a higher-order multicritical point. Applying the generalized method of steepest descents, we see that the associated two-variable scaling function is given by the logarithmic derivative of a generalized (higher-order) Airy integral.

  9. APPLYING OPEN-PATH OPTICAL SPECTROSCOPY TO HEAVY-DUTY DIESEL EMISSIONS

    EPA Science Inventory

    Non-dispersive infrared absorption has been used to measure gaseous emissions for both stationary and mobile sources. Fourier transform infrared spectroscopy has been used for stationary sources as both extractive and open-path methods. We have applied the open-path method for bo...

  10. On the significant enhancement of the continuum-collision induced absorption in H2O+CO2 mixtures

    NASA Astrophysics Data System (ADS)

    Baranov, Yu. I.

    2016-05-01

    The IR spectra of water vapor-carbon dioxide mixtures as well as the spectra of pure gas samples have been recorded using a Fourier-transform infrared spectrometer at a resolution of 0.1 cm-1 in order to explore the effect of colliding CO2 and H2O molecules on their continuum absorptions. The sample temperatures were 294, 311, 325 and 339 K. Measurements have been conducted at several different water vapor partial pressures depending on the cell temperature. Carbon dioxide pressures were kept close to the three values of 103, 207 and 311 kPa (1.02, 2.04 and 3.07 atm). The path length used in the study was 100 m. It was established that, in the region around 1100 cm-1, the continuum absorption coefficient C H2 O + CO2 is about 20 times stronger than the water-nitrogen continuum absorption coefficient CH2O+N2. On the other hand, in the far wing region (2500 cm-1) of the ν3 CO2 fundamental band, the binary absorption coefficient CCO2+H2O appears to be about one order of magnitude stronger than the absorption coefficient CCO2+CO2 in pure carbon dioxide. The continuum interpretation and the main problem of molecular band shape formation are discussed in light of these experimental facts.

  11. Entanglement by Path Identity.

    PubMed

    Krenn, Mario; Hochrainer, Armin; Lahiri, Mayukh; Zeilinger, Anton

    2017-02-24

    Quantum entanglement is one of the most prominent features of quantum mechanics and forms the basis of quantum information technologies. Here we present a novel method for the creation of quantum entanglement in multipartite and high-dimensional systems. The two ingredients are (i) superposition of photon pairs with different origins and (ii) aligning photons such that their paths are identical. We explain the experimentally feasible creation of various classes of multiphoton entanglement encoded in polarization as well as in high-dimensional Hilbert spaces-starting only from nonentangled photon pairs. For two photons, arbitrary high-dimensional entanglement can be created. The idea of generating entanglement by path identity could also apply to quantum entities other than photons. We discovered the technique by analyzing the output of a computer algorithm. This shows that computer designed quantum experiments can be inspirations for new techniques.

  12. Entanglement by Path Identity

    NASA Astrophysics Data System (ADS)

    Krenn, Mario; Hochrainer, Armin; Lahiri, Mayukh; Zeilinger, Anton

    2017-02-01

    Quantum entanglement is one of the most prominent features of quantum mechanics and forms the basis of quantum information technologies. Here we present a novel method for the creation of quantum entanglement in multipartite and high-dimensional systems. The two ingredients are (i) superposition of photon pairs with different origins and (ii) aligning photons such that their paths are identical. We explain the experimentally feasible creation of various classes of multiphoton entanglement encoded in polarization as well as in high-dimensional Hilbert spaces—starting only from nonentangled photon pairs. For two photons, arbitrary high-dimensional entanglement can be created. The idea of generating entanglement by path identity could also apply to quantum entities other than photons. We discovered the technique by analyzing the output of a computer algorithm. This shows that computer designed quantum experiments can be inspirations for new techniques.

  13. Nonadiabatic transition path sampling

    NASA Astrophysics Data System (ADS)

    Sherman, M. C.; Corcelli, S. A.

    2016-07-01

    Fewest-switches surface hopping (FSSH) is combined with transition path sampling (TPS) to produce a new method called nonadiabatic path sampling (NAPS). The NAPS method is validated on a model electron transfer system coupled to a Langevin bath. Numerically exact rate constants are computed using the reactive flux (RF) method over a broad range of solvent frictions that span from the energy diffusion (low friction) regime to the spatial diffusion (high friction) regime. The NAPS method is shown to quantitatively reproduce the RF benchmark rate constants over the full range of solvent friction. Integrating FSSH within the TPS framework expands the applicability of both approaches and creates a new method that will be helpful in determining detailed mechanisms for nonadiabatic reactions in the condensed-phase.

  14. PathMaster

    PubMed Central

    Mattie, Mark E.; Staib, Lawrence; Stratmann, Eric; Tagare, Hemant D.; Duncan, James; Miller, Perry L.

    2000-01-01

    Objective: Currently, when cytopathology images are archived, they are typically stored with a limited text-based description of their content. Such a description inherently fails to quantify the properties of an image and refers to an extremely small fraction of its information content. This paper describes a method for automatically indexing images of individual cells and their associated diagnoses by computationally derived cell descriptors. This methodology may serve to better index data contained in digital image databases, thereby enabling cytologists and pathologists to cross-reference cells of unknown etiology or nature. Design: The indexing method, implemented in a program called PathMaster, uses a series of computer-based feature extraction routines. Descriptors of individual cell characteristics generated by these routines are employed as indexes of cell morphology, texture, color, and spatial orientation. Measurements: The indexing fidelity of the program was tested after populating its database with images of 152 lymphocytes/lymphoma cells captured from lymph node touch preparations stained with hematoxylin and eosin. Images of “unknown” lymphoid cells, previously unprocessed, were then submitted for feature extraction and diagnostic cross-referencing analysis. Results: PathMaster listed the correct diagnosis as its first differential in 94 percent of recognition trials. In the remaining 6 percent of trials, PathMaster listed the correct diagnosis within the first three “differentials.” Conclusion: PathMaster is a pilot cell image indexing program/search engine that creates an indexed reference of images. Use of such a reference may provide assistance in the diagnostic/prognostic process by furnishing a prioritized list of possible identifications for a cell of uncertain etiology. PMID:10887168

  15. PATHS groundwater hydrologic model

    SciTech Connect

    Nelson, R.W.; Schur, J.A.

    1980-04-01

    A preliminary evaluation capability for two-dimensional groundwater pollution problems was developed as part of the Transport Modeling Task for the Waste Isolation Safety Assessment Program (WISAP). Our approach was to use the data limitations as a guide in setting the level of modeling detail. PATHS Groundwater Hydrologic Model is the first level (simplest) idealized hybrid analytical/numerical model for two-dimensional, saturated groundwater flow and single component transport; homogeneous geology. This document consists of the description of the PATHS groundwater hydrologic model. The preliminary evaluation capability prepared for WISAP, including the enhancements that were made because of the authors' experience using the earlier capability is described. Appendixes A through D supplement the report as follows: complete derivations of the background equations are provided in Appendix A. Appendix B is a comprehensive set of instructions for users of PATHS. It is written for users who have little or no experience with computers. Appendix C is for the programmer. It contains information on how input parameters are passed between programs in the system. It also contains program listings and test case listing. Appendix D is a definition of terms.

  16. Upper Extremity Length Equalization

    PubMed Central

    DeCoster, Thomas A.; Ritterbusch, John; Crawford, Mark

    1992-01-01

    Significant upper extremity length inequality is uncommon but can cause major functional problems. The ability to position and use the hand may be impaired by shortness of any of the long bones of the upper extremity. In many respects upper and lower extremity length problems are similar. They most commonly occur after injury to a growing bone and the treatment modalities utilized in the lower extremity may be applied to the upper extremity. These treatment options include epiphysiodesis, shortening osteotomy, angulatory correction osteotomy and lengthening. This report reviews the literature relative to upper extremity length inequality and equalization and presents an algorithm for evaluation and planning appropriate treatment for patients with this condition. This algorithm is illustrated by two clinical cases of posttraumatic shortness of the radius which were effectively treated. ImagesFigure 1Figure 2Figure 3

  17. Relativistic Length Agony Continued

    NASA Astrophysics Data System (ADS)

    Redzic, D. V.

    2014-06-01

    We made an attempt to remedy recent confusing treatments of some basic relativistic concepts and results. Following the argument presented in an earlier paper (Redzic 2008b), we discussed the misconceptions that are recurrent points in the literature devoted to teaching relativity such as: there is no change in the object in Special Relativity, illusory character of relativistic length contraction, stresses and strains induced by Lorentz contraction, and related issues. We gave several examples of the traps of everyday language that lurk in Special Relativity. To remove a possible conceptual and terminological muddle, we made a distinction between the relativistic length reduction and relativistic FitzGerald-Lorentz contraction, corresponding to a passive and an active aspect of length contraction, respectively; we pointed out that both aspects have fundamental dynamical contents. As an illustration of our considerations, we discussed briefly the Dewan-Beran-Bell spaceship paradox and the 'pole in a barn' paradox.

  18. "Albedo dome": a method for measuring spectral flux-reflectance in a laboratory for media with long optical paths.

    PubMed

    Light, Bonnie; Carns, Regina C; Warren, Stephen G

    2015-06-10

    A method is presented for accurate measurement of spectral flux-reflectance (albedo) in a laboratory, for media with long optical path lengths, such as snow and ice. The approach uses an acrylic hemispheric dome, which, when placed over the surface being studied, serves two functions: (i) it creates an overcast "sky" to illuminate the target surface from all directions within a hemisphere, and (ii) serves as a platform for measuring incident and backscattered spectral radiances, which can be integrated to obtain fluxes. The fluxes are relative measurements and because their ratio is used to determine flux-reflectance, no absolute radiometric calibrations are required. The dome and surface must meet minimum size requirements based on the scattering properties of the surface. This technique is suited for media with long photon path lengths since the backscattered illumination is collected over a large enough area to include photons that reemerge from the domain far from their point of entry because of multiple scattering and small absorption. Comparison between field and laboratory albedo of a portable test surface demonstrates the viability of this method.

  19. The path planning of UAV based on orthogonal particle swarm optimization

    NASA Astrophysics Data System (ADS)

    Liu, Xin; Wei, Haiguang; Zhou, Chengping; Li, Shujing

    2013-10-01

    To ensure the attack mission success rate, a trajectory with high survivability and accepted path length and multiple paths with different attack angles must be planned. This paper proposes a novel path planning algorithm based on orthogonal particle swarm optimization, which divides population individual and speed vector into independent orthogonal parts, velocity and individual part update independently, this improvement advances optimization effect of traditional particle swarm optimization in the field of path planning, multiple paths are produced by setting different attacking angles, this method is simulated on electronic chart, the simulation result shows the effect of this method.

  20. Surface Roughness Lengths

    DTIC Science & Technology

    1993-08-01

    m trees 110 - 170 Thom 1972 Pine forest - 20 m trees 128 DeBruin and Moore 1985 Forested plateau, rolling 120 - 130 Ming et al. 1983 Rolling terrain...H. A. R., and C. J. Moore , 1985 , "Zero-Plane Displacement and Roughness Length for Tall Vegetation, Derived from a Simple Mass Conservation

  1. Sampling by Length.

    ERIC Educational Resources Information Center

    Handley, John C.

    1991-01-01

    Discussion of sampling methods used in information science research focuses on Fussler's method for sampling catalog cards and on sampling by length. Highlights include simple random sampling, sampling with probability equal to size without replacement, sampling with replacement, and examples of estimating the number of books on shelves in certain…

  2. Method for Veterbi decoding of large constraint length convolutional codes

    NASA Technical Reports Server (NTRS)

    Hsu, In-Shek (Inventor); Truong, Trieu-Kie (Inventor); Reed, Irving S. (Inventor); Jing, Sun (Inventor)

    1988-01-01

    A new method of Viterbi decoding of convolutional codes lends itself to a pipline VLSI architecture using a single sequential processor to compute the path metrics in the Viterbi trellis. An array method is used to store the path information for NK intervals where N is a number, and K is constraint length. The selected path at the end of each NK interval is then selected from the last entry in the array. A trace-back method is used for returning to the beginning of the selected path back, i.e., to the first time unit of the interval NK to read out the stored branch metrics of the selected path which correspond to the message bits. The decoding decision made in this way is no longer maximum likelihood, but can be almost as good, provided that constraint length K in not too small. The advantage is that for a long message, it is not necessary to provide a large memory to store the trellis derived information until the end of the message to select the path that is to be decoded; the selection is made at the end of every NK time unit, thus decoding a long message in successive blocks.

  3. Tracking hurricane paths

    NASA Technical Reports Server (NTRS)

    Prabhakaran, Nagarajan; Rishe, Naphtali; Athauda, Rukshan

    1997-01-01

    The South East coastal region experiences hurricane threat for almost six months in every year. To improve the accuracy of hurricane forecasts, meteorologists would need the storm paths of both the present and the past. A hurricane path can be established if we could identify the correct position of the storm at different times right from its birth to the end. We propose a method based on both spatial and temporal image correlations to locate the position of a storm from satellite images. During the hurricane season, the satellite images of the Atlantic ocean near the equator are examined for the hurricane presence. This is accomplished in two steps. In the first step, only segments with more than a particular value of cloud cover are selected for analysis. Next, we apply image processing algorithms to test the presence of a hurricane eye in the segment. If the eye is found, the coordinate of the eye is recorded along with the time stamp of the segment. If the eye is not found, we examine adjacent segments for the existence of hurricane eye. It is probable that more than one hurricane eye could be found from different segments of the same period. Hence, the above process is repeated till the entire potential area for hurricane birth is exhausted. The subsequent/previous position of each hurricane eye will be searched in the appropriate adjacent segments of the next/previous period to mark the hurricane path. The temporal coherence and spatial coherence of the images are taken into account by our scheme in determining the segments and the associated periods required for analysis.

  4. Critical Path Web Site

    NASA Technical Reports Server (NTRS)

    Robinson, Judith L.; Charles, John B.; Rummel, John A. (Technical Monitor)

    2000-01-01

    Approximately three years ago, the Agency's lead center for the human elements of spaceflight (the Johnson Space Center), along with the National Biomedical Research Institute (NSBRI) (which has the lead role in developing countermeasures) initiated an activity to identify the most critical risks confronting extended human spaceflight. Two salient factors influenced this activity: first, what information is needed to enable a "go/no go" decision to embark on extended human spaceflight missions; and second, what knowledge and capabilities are needed to address known and potential health, safety and performance risks associated with such missions. A unique approach was used to first define and assess those risks, and then to prioritize them. This activity was called the Critical Path Roadmap (CPR) and it represents an opportunity to develop and implement a focused and evolving program of research and technology designed from a "risk reduction" perspective to prevent or minimize the risks to humans exposed to the space environment. The Critical Path Roadmap provides the foundation needed to ensure that human spaceflight, now and in the future, is as safe, productive and healthy as possible (within the constraints imposed on any particular mission) regardless of mission duration or destination. As a tool, the Critical Path Roadmap enables the decisionmaker to select from among the demonstrated or potential risks those that are to be mitigated, and the completeness of that mitigation. The primary audience for the CPR Web Site is the members of the scientific community who are interested in the research and technology efforts required for ensuring safe and productive human spaceflight. They may already be informed about the various space life sciences research programs or they may be newcomers. Providing the CPR content to potential investigators increases the probability of their delivering effective risk mitigations. Others who will use the CPR Web Site and its content

  5. Critical Path Web Site

    NASA Technical Reports Server (NTRS)

    Robinson, Judith L.; Charles, John B.; Rummel, John A. (Technical Monitor)

    2000-01-01

    Approximately three years ago, the Agency's lead center for the human elements of spaceflight (the Johnson Space Center), along with the National Biomedical Research Institute (NSBRI) (which has the lead role in developing countermeasures) initiated an activity to identify the most critical risks confronting extended human spaceflight. Two salient factors influenced this activity: first, what information is needed to enable a "go/no go" decision to embark on extended human spaceflight missions; and second, what knowledge and capabilities are needed to address known and potential health, safety and performance risks associated with such missions. A unique approach was used to first define and assess those risks, and then to prioritize them. This activity was called the Critical Path Roadmap (CPR) and it represents an opportunity to develop and implement a focused and evolving program of research and technology designed from a "risk reduction" perspective to prevent or minimize the risks to humans exposed to the space environment. The Critical Path Roadmap provides the foundation needed to ensure that human spaceflight, now and in the future, is as safe, productive and healthy as possible (within the constraints imposed on any particular mission) regardless of mission duration or destination. As a tool, the Critical Path Roadmap enables the decision maker to select from among the demonstrated or potential risks those that are to be mitigated, and the completeness of that mitigation. The primary audience for the CPR Web Site is the members of the scientific community who are interested in the research and technology efforts required for ensuring safe and productive human spaceflight. They may already be informed about the various space life sciences research programs or they may be newcomers. Providing the CPR content to potential investigators increases the probability of their delivering effective risk mitigations. Others who will use the CPR Web Site and its

  6. Far-from-equilibrium measurements of thermodynamic length

    SciTech Connect

    Feng, Edward H.; Crooks, Gavin E.

    2008-11-05

    Thermodynamic length is a path function that generalizes the notion of length to the surface of thermodynamic states. Here, we show how to measure thermodynamic length in far-from-equilibrium experiments using the work fluctuation relations. For these microscopic systems, it proves necessary to define the thermodynamic length in terms of the Fisher information. Consequently, the thermodynamic length can be directly related to the magnitude of fluctuations about equilibrium. The work fluctuation relations link the work and the free energy change during an external perturbation on a system. We use this result to determine equilibrium averages at intermediate points of the protocol in which the system is out-of-equilibrium. This allows us to extend Bennett's method to determine the potential of mean force, as well as the thermodynamic length, in single molecule experiments.

  7. JAVA PathFinder

    NASA Technical Reports Server (NTRS)

    Mehhtz, Peter

    2005-01-01

    JPF is an explicit state software model checker for Java bytecode. Today, JPF is a swiss army knife for all sort of runtime based verification purposes. This basically means JPF is a Java virtual machine that executes your program not just once (like a normal VM), but theoretically in all possible ways, checking for property violations like deadlocks or unhandled exceptions along all potential execution paths. If it finds an error, JPF reports the whole execution that leads to it. Unlike a normal debugger, JPF keeps track of every step how it got to the defect.

  8. Portage and Path Dependence*

    PubMed Central

    Bleakley, Hoyt; Lin, Jeffrey

    2012-01-01

    We examine portage sites in the U.S. South, Mid-Atlantic, and Midwest, including those on the fall line, a geomorphological feature in the southeastern U.S. marking the final rapids on rivers before the ocean. Historically, waterborne transport of goods required portage around the falls at these points, while some falls provided water power during early industrialization. These factors attracted commerce and manufacturing. Although these original advantages have long since been made obsolete, we document the continuing importance of these portage sites over time. We interpret these results as path dependence and contrast explanations based on sunk costs interacting with decreasing versus increasing returns to scale. PMID:23935217

  9. Probing local structure of pyrochlore lead zinc niobate with synchrotron x-ray absorption spectroscopy technique

    NASA Astrophysics Data System (ADS)

    Kanchiang, Kanokwan; Pramchu, Sittichain; Yimnirun, Rattikorn; Pakawanit, Phakkhananan; Ananta, Supon; Laosiritaworn, Yongyut

    2013-08-01

    Local structure of lead zinc niobate (PZN) ceramic, synthesized via B-site oxide precursor route in atmospheric pressure, was investigated using synchrotron x-ray absorption spectroscopy (XAS) technique. The x-ray absorption near-edge structure (XANES) simulation was first carried out. The XANES simulation results indicate that the PZN ceramic is in pyrochlore phase having Zn2+ substituted on Nb5+ site. Afterwards, the extended x-ray absorption fine structure (EXAFS) analysis was performed to extract the bond length information between Zn2+ and its neighboring atoms. From the EXAFS fitting, the bond length between Zn2+ and Pb2+ in the pyrochlore phase was found to be longer than the previously reported bond length in the perovskite phase. Further, with the radial distribution information of Zn2+'s neighboring atoms, the formation energies along the precursor-to-pyrochlore and precursor-to-perovskite reaction paths were calculated using the density functional theory (DFT). The calculated results show that the formation energy of the perovskite phase is noticeably higher than that of the pyrochlore phase, which is influenced by the presence of energetic Pb2+ lone pair, as the perovskite phase has shorter Zn2+ to Pb2+ bonding. This therefore suggests the steric hindrance of Pb2+ lone pair and the mutual interactions between Pb2+ lone pair and Zn2+ are main causes of the instability of lead zinc niobate in the perovskite structure and confirm the efficacy of XAS and DFT analysis in revealing local structural details of complex pyrochlore materials.

  10. Not-so-resonant, resonant absorption

    NASA Astrophysics Data System (ADS)

    Brunel, F.

    1987-07-01

    When an intense electromagnetic wave is incident obliquely on a sharply bounded overdense plasma, strong energy absorption can be accounted for by the electrons that are dragged into the vacuum and sent back into the plasma with velocities v~=vosc. This mechanism is more efficient than usual resonant absorption for vosc/ω>L, with L being the density gradient length. In the very high-intensity CO2-laser-target interaction, this mechanism may account for most of the energy absorption.

  11. [On using tunable diode laser absorption spectroscopy to determine gas fluxes over cropland].

    PubMed

    Tian, Yong-zhi; Liu, Jian-guo; Zhang, Yu-jun; Lu, Yi-huai; He, Ying

    2012-04-01

    Tunable diode laser absorption spectroscopy (TDLAS) is a compact, automated, high precision technique and fit for in-situ or field measurements. Two spectroscopy measurement systems, TDLAS and NDIR (non-dispersive infrared spectroscopy), were used to monitor trace gas emission over cropland at Fengqiu Agricultural Ecology Experimental Station for one month. The fluxes of carbon dioxide were estimated by flux-gradient and eddy covariance method, respectively. A footprint model was developed during experiment. Based on this model, the source areas of TDLAS and NDIR were investigated. The effects of different factors on the flux measurement were also analyzed. The authors concluded that the source areas for the two techniques are discrepant in most of the cases. The source areas increase with path length and detecting height. This result will help the installation of instruments.

  12. Long-range open-path greenhouse gas monitoring using mid-infrared laser dispersion spectroscopy

    NASA Astrophysics Data System (ADS)

    Daghestani, Nart; Brownsword, Richard; Weidmann, Damien

    2015-04-01

    Accurate and sensitive methods of monitoring greenhouse gas (GHG) emission over large areas has become a pressing need to deliver improved estimates of both human-made and natural GHG budgets. These needs relate to a variety of sectors including environmental monitoring, energy, oil and gas industry, waste management, biogenic emission characterization, and leak detection. To address the needs, long-distance open-path laser spectroscopy methods offer significant advantages in terms of temporal resolution, sensitivity, compactness and cost effectiveness. Path-integrated mixing ratio measurements stemming from long open-path laser spectrometers can provide emission mapping when combined with meteorological data and/or through tomographic approaches. Laser absorption spectroscopy is the predominant method of detecting gasses over long integrated path lengths. The development of dispersion spectrometers measuring tiny refractive index changes, rather than optical power transmission, may offer a set of specific advantages1. These include greater immunity to laser power fluctuations, greater dynamic range due to the linearity of dispersion, and ideally a zero baseline signal easing quantitative retrievals of path integrated mixing ratios. Chirped laser dispersion spectrometers (CLaDS) developed for the monitoring of atmospheric methane and carbon dioxide will be presented. Using quantum cascade laser as the source, a minimalistic and compact system operating at 7.8 μm has been developed and demonstrated for the monitoring of atmospheric methane over a 90 meter open path2. Through full instrument modelling and error propagation analysis, precision of 3 ppm.m.Hz-0.5 has been established (one sigma precision for atmospheric methane normalized over a 1 m path and 1 s measurement duration). The system was fully functional in the rain, sleet, and moderate fog. The physical model and system concept of CLaDS can be adapted to any greenhouse gas species. Currently we are

  13. [The development of acetylene on-line monitoring technology based on laser absorption spectrum].

    PubMed

    He, Ying; Zhang, Yu-jun; Kan, Rui-feng; Xia, Hui; Wang, Min; Cui, Xiao-juan; Chen, Jiu-ying; Chen, Dong; Liu, Wen-qing; Liu, Jian-guo

    2008-10-01

    As one of the materials in organic chemical industry, acetylene has been used in many aspects of chemical industry. But acetylene is a very dangerous inflammable and explosive gas, so it needs in-situ monitoring during industrial storage and production. Tunable diode laser absorption spectroscopy (TDLAS) technology has been widely used in atmospheric trace gases detection, because it has a lot of advantageous characteristics, such as high sensitivity, good selectivity, and rapid time response. The distribution characteristics of absorption lines of acetylene in near infrared band were studied, and then the system designing scheme of acetylene on-line monitoring based on near infrared tunable diode laser absorption spectroscopy technology was discussed in detail. Moreover, the system of experiment measurement was set up and the method of signal detection and the algorithm of concentration inversion were studied. In addition, the sample cell with a path length of 10 cm, and the acetylene of different known concentrations were measured. As a result, the detection limit obtained reached 1.46 cm3 x m(-3). Finally the dynamic detection experiment was carried out, and the measurement result is stable and reliable, so the design of the system is practicable through experiment analysis. On-line acetylene leakage monitoring system was developed based on the experiment, and it is suitable for giving a leakage alarm of acetylene during its storage, transportation and use.

  14. Near infrared cavity enhanced absorption spectra of atmospherically relevant ether-1, 4-Dioxane

    NASA Astrophysics Data System (ADS)

    Chandran, Satheesh; Varma, Ravi

    2016-01-01

    1, 4-Dioxane (DX) is a commonly found ether in industrially polluted atmosphere. The near infrared absorption spectra of this compound has been recorded in the region 5900-8230 cm- 1 with a resolution of 0.08 cm- 1 using a novel Fourier transform incoherent broadband cavity-enhanced absorption spectrometer (FT-IBBCEAS). All recorded spectra were found to contain regions that are only weakly perturbed. The possible combinations of fundamental modes and their overtone bands corresponding to selected regions in the measured spectra are tabulated. Two interesting spectral regions were identified as 5900-6400 cm- 1 and 8100-8230 cm- 1. No significant spectral interference due to presence of water vapor was observed suggesting the suitability of these spectral signatures for spectroscopic in situ detection of DX. The technique employed here is much more sensitive than standard Fourier transform spectrometer measurements on account of long effective path length achieved. Hence significant enhancement of weaker absorption lines above the noise level was observed as demonstrated by comparison with an available measurement from database.

  15. Enhancement of the photocatalytic activity of TiO2 through spatial structuring and particle size control: from subnanometric to submillimetric length scale.

    PubMed

    Aprile, Carmela; Corma, Avelino; Garcia, Hermenegildo

    2008-02-14

    This review summarizes the physical approaches towards enhancement of the photocatalytic activity of titanium dioxide by controlling this semiconductor in a certain length scale from subnanometric to submillimetric distances and provides examples in which the photocatalytic activity of TiO2 is not promoted by doping or changes in the chemical composition, but rather by application of physical concepts and spatial structuring of the semiconductor. Thus, encapsulation inside the micropores and cavities of zeolites (about 1 nm) renders small titanium oxide clusters with harnessed photocatalytic activity. On the other hand, nanometric titanium particles can be ordered forming structured periodic mesoporous materials with high specific surface area and well defined porosity. Titiania nanotubes of micrometric length, either independent or forming a membrane, also exhibit unique photocatalytic activity as consequence of the long diffusion length of charge carriers along the nanotube axis. Finally, photonic crystals with an inverse opal structure and the even more powerful concept of photonic sponges can serve to slow down visible light photons inside the material, increasing the effective optical path in such a way that light absorption near the absorption onset of the material is enhanced considerably. All these physical-based approaches have shown their potential in enhancing the photocatalytic activity of titania, paving the way for a new generation of novel structured photocatalysts in which physical and chemical concepts are combined.

  16. Quantum cascade laser-based multipass absorption system for hydrogen peroxide detection

    NASA Astrophysics Data System (ADS)

    Cao, Yingchun; Sanchez, Nancy P.; Jiang, Wenzhe; Ren, Wei; Lewicki, Rafal; Jiang, Dongfang; Griffin, Robert J.; Tittel, Frank K.

    2015-01-01

    Hydrogen peroxide (H2O2) is a relevant molecular trace gas species, that is related to the oxidative capacity of the atmosphere, the production of radical species such as OH, the generation of sulfate aerosol via oxidation of S(IV) to S(VI), and the formation of acid rain. The detection of atmospheric H2O2 involves specific challenges due to its high reactivity and low concentration (ppbv to sub-ppbv level). Traditional methods for measuring atmospheric H2O2 concentration are often based on wet-chemistry methods that require a transfer from the gas- to liquid-phase for a subsequent determination by techniques such as fluorescence spectroscopy, which can lead to problems such as sampling artifacts and interference by other atmospheric constituents. A quartz-enhanced photoacoustic spectroscopy-based system for the measurement of atmospheric H2O2 with a detection limit of 75 ppb for 1-s integration time was previously reported. In this paper, an updated H2O2 detection system based on long-optical-path-length absorption spectroscopy by using a distributed feedback quantum cascade laser (DFB-QCL) will be described. A 7.73-μm CW-DFB-QCL and a thermoelectrically cooled infrared detector, optimized for a wavelength of 8 μm, are employed for theH2O2 sensor system. A commercial astigmatic Herriott multi-pass cell with an effective optical path-length of 76 m is utilized for the reported QCL multipass absorption system. Wavelength modulation spectroscopy (WMS) with second harmonic detection is used for enhancing the signal-to-noise-ratio. A minimum detection limit of 13.4 ppb is achieved with a 2 s sampling time. Based on an Allan-Werle deviation analysis the minimum detection limit can be improved to 1.5 ppb when using an averaging time of 300 s.

  17. 757 Path Loss Measurements

    NASA Technical Reports Server (NTRS)

    Horton, Kent; Huffman, Mitch; Eppic, Brian; White, Harrison

    2005-01-01

    Path Loss Measurements were obtained on three (3) GPS equipped 757 aircraft. Systems measured were Marker Beacon, LOC, VOR, VHF (3), Glide Slope, ATC (2), DME (2), TCAS, and GPS. This data will provide the basis for assessing the EMI (Electromagnetic Interference) safety margins of comm/nav (communication and navigation) systems to portable electronic device emissions. These Portable Electronic Devices (PEDs) include all devices operated in or around the aircraft by crews, passengers, servicing personnel, as well as the general public in the airport terminals. EMI assessment capability is an important step in determining if one system-wide PED EMI policy is appropriate. This data may also be used comparatively with theoretical analysis and computer modeling data sponsored by NASA Langley Research Center and others.

  18. Interactive cutting path analysis programs

    NASA Technical Reports Server (NTRS)

    Weiner, J. M.; Williams, D. S.; Colley, S. R.

    1975-01-01

    The operation of numerically controlled machine tools is interactively simulated. Four programs were developed to graphically display the cutting paths for a Monarch lathe, Cintimatic mill, Strippit sheet metal punch, and the wiring path for a Standard wire wrap machine. These programs are run on a IMLAC PDS-ID graphic display system under the DOS-3 disk operating system. The cutting path analysis programs accept input via both paper tape and disk file.

  19. Development of a Near-Ir Cavity Enhanced Absorption Spectrometer for the Detection of Atmospheric Oxidation Products and Organoamines

    NASA Astrophysics Data System (ADS)

    Eddingsaas, Nathan C.; Jewell, Breanna; Thurnherr, Emily

    2014-06-01

    An estimated 10,000 to 100,000 different compounds have been measured in the atmosphere, each one undergoes many oxidation reactions that may or may not degrade air quality. To date, the fate of even some of the most abundant hydrocarbons in the atmosphere is poorly understood. One difficulty is the detection of atmospheric oxidation products that are very labile and decompose during analysis. To study labile species under atmospheric conditions, a highly sensitive, non-destructive technique is needed. Here we describe a near-IR incoherent broadband cavity enhanced absorption spectroscopy (IBBCEAS) setup that we are developing to meet this end. We have chosen to utilize the near-IR, where vibrational overtone absorptions are observed, due to the clean spectral windows and better spectral separation of absorption features. In one spectral window we can simultaneously and continuously monitor the composition of alcohols, hydroperoxides, and carboxylic acids in an air mass. In addition, we have used our CEAS setup to detect organoamines. The long effective path length of CEAS allows for low detection limits, even of the overtone absorption features, at ppb and ppt levels.

  20. Design of a simple cryogenic system for ultraviolet-visible absorption spectroscopy with a back-reflectance fiber optic probe.

    PubMed

    Vinyard, Andrew; Hansen, Kaj A; Byrd, Ross; Stuart, Douglas A; Hansen, John E

    2014-01-01

    We report a convenient and inexpensive technique for the rapid acquisition of absorption spectra from small samples at cryogenic temperatures using a home built cryostat with novel collection optics. A cylindrical copper block was constructed with a coaxial bore to hold a 4.00 mm diameter electron paramagnetic resonance (EPR) tube and mounted on a copper feed in thermal contact with liquid nitrogen. A 6.35 mm diameter hole was bored into the side of the cylinder so a fiber optic cable bundle could be positioned orthogonally to the EPR tube. The light passing through the sample is reflected off of the opposing surfaces of the EPR tube and surrounding copper, back through the sample. The emergent light is then collected using the fiber optic bundle and analyzed using a dispersive spectrometer. Absorption spectra for KMnO4 were measured between 400 and 700 nm. Absorption intensity at 506, 525, 545, and 567 nm was found to be proportional to concentration, displaying Beer's law-like behavior. The EPR tube had an internal diameter of 3.2 mm; the double pass of the probe beam through the sample affords a central path length of about 6.4 mm. Comparing these measurements with those recorded on a conventional tabletop spectrometer using a cuvette with a 10.00 mm path length, we consistently found a ratio between intensities of 0.58 rather than the anticipated 0.64. These 6% smaller values we attribute to the curvature of the EPR tube and transmission/reflection losses. This system is particularly well-suited to studying the kinetics and dynamics of chemical reactions at cryogenic temperatures. The rapid response (100 ms) and multiplex advantage provided the opportunity of recording simultaneous time courses at several wavelengths following initiation of a chemical reaction with a pulsed laser source.

  1. Length of stain dosimeter

    NASA Technical Reports Server (NTRS)

    Lueck, Dale E. (Inventor)

    1994-01-01

    Payload customers for the Space Shuttle have recently expressed concerns about the possibility of their payloads at an adjacent pad being contaminated by plume effluents from a shuttle at an active pad as they await launch on an inactive pad. As part of a study to satisfy such concerns a ring of inexpensive dosimeters was deployed around the active pad at the inter-pad distance. However, following a launch, dosimeters cannot be read for several hours after the exposure. As a consequence factors such as different substrates, solvent systems, and possible volatilization of HCl from the badges were studied. This observation led to the length of stain (LOS) dosimeters of this invention. Commercial passive LOS dosimeters are sensitive only to the extent of being capable of sensing 2 ppm to 20 ppm if the exposure is 8 hours. To map and quantitate the HCl generated by Shuttle launches, and in the atmosphere within a radius of 1.5 miles from the active pad, a sensitivity of 2 ppm HCl in the atmospheric gases on an exposure of 5 minutes is required. A passive length of stain dosimeter has been developed having a sensitivity rendering it capable of detecting a gas in a concentration as low as 2 ppm on an exposure of five minutes.

  2. An advanced open-path atmospheric monitor design

    SciTech Connect

    Taylor, L.; Suhre, D.; Mech, S.

    1996-05-01

    The conceptual design of an open-path atmospheric monitor combines an acousto-optic tunable filter for emission spectroscopy (3-14 {mu}m) with a mid-IR (4.6-5.4 {mu}m) for absorption spectroscopy. It utilizes mostly commercially available components, covers a large area ({approximately}4 km radius), measures the distance to any reflecting object, can take measurements along any line-of-sight, and is eye safe. Of twenty test pollutants it is to detect, the concentrations of all twenty will be measurable via emission spectroscopy and ten by the more sensitive absorption spectroscopy.

  3. Path ensembles and a tradeoff between communication efficiency and resilience in the human connectome.

    PubMed

    Avena-Koenigsberger, Andrea; Mišić, Bratislav; Hawkins, Robert X D; Griffa, Alessandra; Hagmann, Patric; Goñi, Joaquín; Sporns, Olaf

    2017-01-01

    Computational analysis of communication efficiency of brain networks often relies on graph-theoretic measures based on the shortest paths between network nodes. Here, we explore a communication scheme that relaxes the assumption that information travels exclusively through optimally short paths. The scheme assumes that communication between a pair of brain regions may take place through a path ensemble comprising the k-shortest paths between those regions. To explore this approach, we map path ensembles in a set of anatomical brain networks derived from diffusion imaging and tractography. We show that while considering optimally short paths excludes a significant fraction of network connections from participating in communication, considering k-shortest path ensembles allows all connections in the network to contribute. Path ensembles enable us to assess the resilience of communication pathways between brain regions, by measuring the number of alternative, disjoint paths within the ensemble, and to compare generalized measures of path length and betweenness centrality to those that result when considering only the single shortest path between node pairs. Furthermore, we find a significant correlation, indicative of a trade-off, between communication efficiency and resilience of communication pathways in structural brain networks. Finally, we use k-shortest path ensembles to demonstrate hemispherical lateralization of efficiency and resilience.

  4. Automated continuous monitoring of inorganic and total mercury in wastewater and other waters by flow-injection analysis and cold-vapour atomic absorption spectrometry

    PubMed Central

    Birnie, S. E.

    1988-01-01

    An automated continuous monitoring system for the determination of inorganic and total mercury by flow-injection analysis followed by cold-vapour atomic absorption spectrometry is described. The method uses a typical flow-injection manifold where digestion and reduction of the injected sample takes place. Mercury is removed by aeration from the flowing stream in a specially designed air-liquid separator and swept into a silica cell for absorption measurement at a wavelength of 253.7 nm. A calibration curve up to 10 μg Hg ml-1 using three different path length cells is obtained with a detection limit of 0.02 μg Hg ml-1. The sampling rate of an injection every 3 min produces 20 results per hour from a flowing stream. PMID:18925201

  5. Optically generated small electron and hole polarons in nominally undoped and Fe-doped KNbO3 investigated by transient absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Torbrügge, S.; Imlau, M.; Schoke, B.; Merschjann, C.; Schirmer, O. F.; Vernay, S.; Gross, A.; Wesemann, V.; Rytz, D.

    2008-09-01

    Transient light-induced absorption in nominally undoped and Fe-doped KNbO3 crystals is observed in the visible and infrared spectral ranges after single pulse illumination with λ=532nm . For nominally undoped KNbO3 the decay of the light-induced absorption in a single step can be explained by incoherent hopping transport of optically generated small bound O- hole and small free Nb4+ electron polarons and their mutual recombination. Iron doping causes an additional slow decay component and, remarkably, accelerates the initial decay process. A consistent model for the formation, hopping, and recombination paths of hole and electron polarons is deduced from the experimental data set for both nominally undoped and Fe-doped KNbO3 . The decrease in the polaron hopping-transport length in Fe-doped samples is attributed to the increased number densities of optically generated hole polarons by additional one-quantum excitations.

  6. Path Analysis: A Brief Introduction.

    ERIC Educational Resources Information Center

    Carducci, Bernardo J.

    Path analysis is presented as a technique that can be used to test on a priori model based on a theoretical conceptualization involving a network of selected variables. This being an introductory source, no previous knowledge of path analysis is assumed, although some understanding of the fundamentals of multiple regression analysis might be…

  7. Estimation of microwave absorption in the Jupiter atmosphere

    NASA Technical Reports Server (NTRS)

    Coombs, W. C.

    1971-01-01

    A procedure for estimating the microwave absorption loss of the Jupiter atmosphere is presented. Estimation of microwave absorption by planetary atmospheres involves two different investigative disciplines (1) the determination of an acceptable model of the atmosphere itself and (2) the determination of the microwave attenuation rate applicable to each different volume sample of the atmosphere, and the integration of this loss over the varying radio propagation path for any given entry trajectory to obtain the total loss.

  8. Quantitative infrared absorption cross sections of isoprene for atmospheric measurements

    DOE PAGES

    Brauer, C. S.; Blake, T. A.; Guenther, A. B.; ...

    2014-11-19

    Isoprene (C5H8, 2-methyl-1,3-butadiene) is a volatile organic compound (VOC) and is one of the primary contributors to annual global VOC emissions. Isoprene is produced primarily by vegetation as well as anthropogenic sources, and its OH- and O3-initiated oxidations are a major source of atmospheric oxygenated organics. Few quantitative infrared studies have been reported for isoprene, limiting the ability to quantify isoprene emissions via remote or in situ infrared detection. We thus report absorption cross sections and integrated band intensities for isoprene in the 600–6500 cm-1 region. The pressure-broadened (1 atmosphere N2) spectra were recorded at 278, 298, and 323 Kmore » in a 19.94 cm path-length cell at 0.112 cm-1 resolution, using a Bruker IFS 66v/S Fourier transform infrared (FTIR) spectrometer. Composite spectra are derived from a minimum of seven isoprene sample pressures, each at one of three temperatures, and the number densities are normalized to 296 K and 1 atm.« less

  9. Reconfigurable data path processor

    NASA Technical Reports Server (NTRS)

    Donohoe, Gregory (Inventor)

    2005-01-01

    A reconfigurable data path processor comprises a plurality of independent processing elements. Each of the processing elements advantageously comprising an identical architecture. Each processing element comprises a plurality of data processing means for generating a potential output. Each processor is also capable of through-putting an input as a potential output with little or no processing. Each processing element comprises a conditional multiplexer having a first conditional multiplexer input, a second conditional multiplexer input and a conditional multiplexer output. A first potential output value is transmitted to the first conditional multiplexer input, and a second potential output value is transmitted to the second conditional multiplexer output. The conditional multiplexer couples either the first conditional multiplexer input or the second conditional multiplexer input to the conditional multiplexer output, according to an output control command. The output control command is generated by processing a set of arithmetic status-bits through a logical mask. The conditional multiplexer output is coupled to a first processing element output. A first set of arithmetic bits are generated according to the processing of the first processable value. A second set of arithmetic bits may be generated from a second processing operation. The selection of the arithmetic status-bits is performed by an arithmetic-status bit multiplexer selects the desired set of arithmetic status bits from among the first and second set of arithmetic status bits. The conditional multiplexer evaluates the select arithmetic status bits according to logical mask defining an algorithm for evaluating the arithmetic status bits.

  10. Absorption-induced trapping in an anisotropic magneto-optical trap.

    PubMed

    Greenberg, Joel A; Oriá, M; Dawes, Andrew M C; Gauthier, Daniel J

    2007-12-24

    We report on a simple anisotropic magneto-optical trap for neutral atoms that produces a large sample of cold atoms confined in a cylindrically-shaped volume with a high aspect ratio (100:1). Due to the large number of trapped atoms, the laser beams that propagate along the optically thick axis of the trap to cool the atoms are substantially attenuated. We demonstrate that the resulting intensity imbalance produces a net force that spatially localizes the atoms. This limits both the trap length and the total number of trapped atoms. Rotating the cooling beams by a small angle relative to the trap axis avoids the problem of attenuation, and atoms can be trapped throughout the entire available trapping volume. Numerical and experimental results are reported that demonstrate the effects of absorption in an anisotropic trap, and a steady-state, line-center optical path length of 55 is measured for a probe beam propagating along the length of the trap.

  11. Extremely sensitive detection of NO₂ employing off-axis integrated cavity output spectroscopy coupled with multiple-line integrated absorption spectroscopy.

    PubMed

    Rao, Gottipaty N; Karpf, Andreas

    2011-05-01

    We report on the development of a new sensor for NO₂ with ultrahigh sensitivity of detection. This has been accomplished by combining off-axis integrated cavity output spectroscopy (OA-ICOS) (which can provide large path lengths of the order of several kilometers in a small volume cell) with multiple-line integrated absorption spectroscopy (MLIAS) (where we integrate the absorption spectra over a large number of rotational-vibrational transitions of the molecular species to further improve the sensitivity). Employing an external cavity quantum cascade laser operating in the 1601-1670 cm⁻¹ range and a high-finesse optical cavity, the absorption spectra of NO₂ over 100 transitions in the R band have been recorded. From the observed linear relationship between the integrated absorption versus concentration of NO₂ and the standard deviation of the integrated absorption signal, we report an effective sensitivity of detection of approximately 28 ppt (parts in 10¹²) for NO₂ To the best of our knowledge, this is among the most sensitive levels of detection of NO₂ to date.

  12. Ultrasensitive, real-time analysis of biomarkers in breath using tunable external cavity laser and off-axis cavity-enhanced absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Bayrakli, Ismail; Akman, Hatice

    2015-03-01

    A robust biomedical sensor for ultrasensitive detection of biomarkers in breath based on a tunable external cavity laser (ECL) and an off-axis cavity-enhanced absorption spectroscopy (OA-CEAS) using an amplitude stabilizer is developed. A single-mode, narrow-linewidth, tunable ECL is demonstrated. A broadly coarse wavelength tuning range of 720 cm-1 for the spectral range between 6890 and 6170 cm-1 is achieved by rotating the diffraction grating forming a Littrow-type external-cavity configuration. A mode-hop-free tuning range of 1.85 cm-1 is obtained. The linewidths below 140 kHz are recorded. The ECL is combined with an OA-CEAS to perform laser chemical sensing. Our system is able to detect any molecule in breath at concentrations to the ppbv range that have absorption lines in the spectral range between 1450 and 1620 nm. Ammonia is selected as target molecule to evaluate the performance of the sensor. Using the absorption line of ammonia at 6528.76 cm-1, a minimum detectable absorption coefficient of approximately 1×10-8 cm-1 is demonstrated for 256 averages. This is achieved for a 1.4-km absorption path length and a 2-s data-acquisition time. These results yield a detection sensitivity of approximately 8.6×10-10 cm-1 Hz-1/2. Ammonia in exhaled breath is analyzed and found in a concentration of 870 ppb for our example.

  13. Infrared absorption of carbon dioxide at high densitites with application to the atmosphere of Venus. Ph.D. Thesis - Columbia Univ.

    NASA Technical Reports Server (NTRS)

    Moore, J. F.

    1971-01-01

    Several new infrared absorptions were found in carbon dioxide. All are normally forbidden, and were collision-induced in an absorbing cell whose combination of pressure and path length has a unique sensitivity for induced absorptions. The new absorptions in the 2.3 micron region are attributed to transitions from ground to the 3(1)1 Fermi pair at 4248 and 4391/cm. Other absorptions are attributed to simultaneous CO2-N2 transitions and to the 00(0)0-00(0)2 transition in CO2 polarizability derivatives and regular progressions in strength versus increasing quantum number. The spectra were used to predict the radiative transfer in a dry CO2 model of the lower Venus atmosphere. The results indicate that the radiation balance in the lower atmosphere is adequately explained by a dry massive atmosphere of CO2 with a layer of infrared-opaque clouds. The absorptions in the 2.3 micron region are significant in accounting for the opacity to sustain Venus' 768 K surface temperature.

  14. Collabortive Authoring of Walden's Paths

    SciTech Connect

    Li, Yuanling; Bogen II, Paul Logasa; Pogue, Daniel; Furuta, Richard Keith; Shipman, Frank Major

    2012-01-01

    This paper presents a prototype of an authoring tool to allow users to collaboratively build, annotate, manage, share and reuse collections of distributed resources from the World Wide Web. This extends on the Walden’s Path project’s work to help educators bring resources found on the World Wide Web into a linear contextualized structure. The introduction of collaborative authoring feature fosters collaborative learning activities through social interaction among participants, where participants can coauthor paths in groups. Besides, the prototype supports path sharing, branching and reusing; specifically, individual participant can contribute to the group with private collections of knowledge resources; paths completed by group can be shared among group members, such that participants can tailor, extend, reorder and/or replace nodes to have sub versions of shared paths for different information needs.

  15. Cavity ring-down spectroscopy (CRDS) system for measuring atmospheric mercury using differential absorption

    NASA Astrophysics Data System (ADS)

    Pierce, A.; Obrist, D.; Moosmuller, H.; Moore, C.

    2012-04-01

    Atmospheric elemental mercury (Hg0) is a globally pervasive element that can be transported and deposited to remote ecosystems where it poses — particularly in its methylated form — harm to many organisms including humans. Current techniques for measurement of atmospheric Hg0 require several liters of sample air and several minutes for each analysis. Fast-response (i.e., 1 second or faster) measurements would improve our ability to understand and track chemical cycling of mercury in the atmosphere, including high frequency Hg0 fluctuations, sources and sinks, and chemical transformation processes. We present theory, design, challenges, and current results of our new prototype sensor based on cavity ring-down spectroscopy (CRDS) for fast-response measurement of Hg0 mass concentrations. CRDS is a direct absorption technique that implements path-lengths of multiple kilometers in a compact absorption cell using high-reflectivity mirrors, thereby improving sensitivity and reducing sample volume compared to conventional absorption spectroscopy. Our sensor includes a frequency-doubled, dye-laser emitting laser pulses tunable from 215 to 280 nm, pumped by a Q-switched, frequency tripled Nd:YAG laser with a pulse repetition rate of 50 Hz. We present how we successfully perform automated wavelength locking and stabilization of the laser to the peak Hg0 absorption line at 253.65 nm using an external isotopically-enriched mercury (202Hg0) cell. An emphasis of this presentation will be on the implementation of differential absorption measurement whereby measurements are alternated between the peak Hg0 absorption wavelength and a nearby wavelength "off" the absorption line. This can be achieved using a piezo electric tuning element that allows for pulse-by-pulse tuning and detuning of the laser "online" and "offline" of the Hg absorption line, and thereby allows for continuous correction of baseline extinction losses. Unexpected challenges with this approach included

  16. Slip length crossover on a graphene surface

    SciTech Connect

    Liang, Zhi; Keblinski, Pawel

    2015-04-07

    Using equilibrium and non-equilibrium molecular dynamics simulations, we study the flow of argon fluid above the critical temperature in a planar nanochannel delimited by graphene walls. We observe that, as a function of pressure, the slip length first decreases due to the decreasing mean free path of gas molecules, reaches the minimum value when the pressure is close to the critical pressure, and then increases with further increase in pressure. We demonstrate that the slip length increase at high pressures is due to the fact that the viscosity of fluid increases much faster with pressure than the friction coefficient between the fluid and the graphene. This behavior is clearly exhibited in the case of graphene due to a very smooth potential landscape originating from a very high atomic density of graphene planes. By contrast, on surfaces with lower atomic density, such as an (100) Au surface, the slip length for high fluid pressures is essentially zero, regardless of the nature of interaction between fluid and the solid wall.

  17. Long path CO{sub 2} lidar measurements

    SciTech Connect

    Senft, D.C.; Fox, M.J.; Gonglewski, J.D.

    1996-11-01

    The Air Force Phillips Laboratory conducted a series of measurements in February, May and August 1995 at the Air Force Maui Optical Station (AMOS) facility on Maui, Hawaii, to determine system requirements for an airborne long path CO{sub 2} DIAL system. The lidar incorporates a cavity-matched mode-locked 3-J laser with the 60 cm diameter AMOS Beam Director Telescope. The one-way beam propagation path length was 21.3 km, originating at the AMOS facility on Haleakala at an altitude of 3.050 km ASL, and terminating at a target site enar sea level. 5 refs., 8 figs., 1 tab.

  18. Effect of idler absorption in pulsed optical parametric oscillators.

    PubMed

    Rustad, Gunnar; Arisholm, Gunnar; Farsund, Øystein

    2011-01-31

    Absorption at the idler wavelength in an optical parametric oscillator (OPO) is often considered detrimental. We show through simulations that pulsed OPOs with significant idler absorption can perform better than OPOs with low idler absorption both in terms of conversion efficiency and beam quality. The main reason for this is reduced back conversion. We also show how the beam quality depends on the beam width and pump pulse length, and present scaling relations to use the example simulations for other pulsed nanosecond OPOs.

  19. Coherent perfect absorption and reflection in slow-light waveguides.

    PubMed

    Gutman, Nadav; Sukhorukov, Andrey A; Chong, Y D; de Sterke, C Martijn

    2013-12-01

    We identify a family of unusual slow-light modes occurring in lossy multimode grating waveguides, for which either the forward or backward mode components, or both, are degenerate. In the fully degenerate case, the response can be modulated between coherent perfect absorption (zero reflection) and perfect reflection by varying the wave amplitudes in a uniform input waveguide. The perfectly absorbed wave has anomalously short absorption length, scaling as the inverse one-third power of the absorptivity.

  20. Long-path atmospheric measurements using dual frequency comb measurements

    NASA Astrophysics Data System (ADS)

    Waxman, Eleanor; Cossel, Kevin; Truong, Gar-Wing; Giorgetta, Fabrizio; Swann, William; Coddington, Ian; Newbury, Nathan

    2016-04-01

    The dual frequency comb spectrometer is a new tool for performing atmospheric trace gas measurements. This instrument is capable of measuring carbon dioxide, methane, and water with extremely high resolution in the region between 1.5 and 2.1 microns in the near-IR. It combines the high resolution of a laboratory-based FTIR instrument with the portability of a long-path DOAS system. We operate this instrument at path lengths of a few kilometers, thus bridging the spatial resolution of in-situ point sensors and the tens of square kilometer footprints of satellites. This spatial resolution is ideal for measuring greenhouse gas emissions from cities. Here we present initial long-path integrated column measurements of the greenhouse gases water, carbon dioxide, and methane in an urban environment. We present a time series with 5 minute time resolution over a 2 kilometer path in Boulder, Colorado at the urban-rural interface. We validate this data via a comparison with an in-situ greenhouse gas monitor co-located along the measurement path and show that we agree well on the baseline concentration but that we are significantly less sensitive to local point source emission that have high temporal variability, making this instrument ideal for measurements of average city-wide emissions. We additionally present progress towards measurements over an 11 kilometer path over downtown Boulder to measure the diurnal flux of greenhouse gases across the city.

  1. Finding reaction paths using the potential energy as reaction coordinate.

    PubMed

    Aguilar-Mogas, Antoni; Giménez, Xavier; Bofill, Josep Maria

    2008-03-14

    The intrinsic reaction coordinate curve (IRC), normally proposed as a representation of a reaction path, is parametrized as a function of the potential energy rather than the arc-length. This change in the parametrization of the curve implies that the values of the energy of the potential energy surface points, where the IRC curve is located, play the role of reaction coordinate. We use Caratheodory's relation to derive in a rigorous manner the proposed parametrization of the IRC path. Since this Caratheodory's relation is the basis of the theory of calculus of variations, then this fact permits to reformulate the IRC model from this mathematical theory. In this mathematical theory, the character of the variational solution (either maximum or minimum) is given through the Weierstrass E-function. As proposed by Crehuet and Bofill [J. Chem. Phys. 122, 234105 (2005)], we use the minimization of the Weierstrass E-function, as a function of the potential energy, to locate an IRC path between two minima from an arbitrary curve on the potential energy surface, and then join these two minima. We also prove, from the analysis of the Weierstrass E-function, the mathematical bases for the algorithms proposed to locate the IRC path. The proposed algorithm is applied to a set of examples. Finally, the algorithm is used to locate a discontinuous, or broken, IRC path, namely, when the path connects two first order saddle points through a valley-ridged inflection point.

  2. Preliminary assignments of 2 ν 3 - ν 4 hot band of 12 CH 4 in the 2 μm transparency window from long-path FTS spectra

    NASA Astrophysics Data System (ADS)

    Nikitin, A. V.; Daumont, L.; Thomas, X.; Régalia, L.; Rey, M.; Tyuterev, Vl. G.; Brown, L. R.

    2011-07-01

    New measurements and assignments for the rovibrational transitions of the hot band 2 v3- v4 of 12CH 4 are reported from 4600 to 4880 cm -1 and refer to lower part of the 2 μm methane transparency window. Three long-path spectra were recorded with a Fourier transform spectrometer (FTS) in Reims using an L = 1603 m absorption path length at 1, 7, 34 h Pa for the natural samples of CH 4; a spectrum of enriched 13CH 4 was also used. Assignments were made for 196 lines of 2 v3(F 2,E)- v4. These transitions had an integrated intensity of 5 × 10 -24 cm/molecule at 296 K and improved the overall description of absorption in the 2.1 μm region. The empirical upper state levels of these assignments belong to Tetradecad (4800-6200 cm -1). The new analysis provided much better accuracies of badly blended positions of 2 v3(F 2)-ground state manifolds at 1.66 μm.

  3. Precision distance measurement using a two-photon absorption process in a silicon avalanche photodiode with saw-tooth phase modulation.

    PubMed

    Tanaka, Yosuke; Tominaka, Seiji; Kurokawa, Takashi

    2015-10-01

    We present a novel configuration of a precision laser distance measurement based on the two-photon absorption (TPA) photocurrent from a silicon avalanche photodiode (Si-APD). The proposed system uses saw-tooth phase modulation, known as serrodyne modulation, in order to shift the frequency of the reference light from that of the probe light. It suppresses the coherent interference noise between the probe and the reference. The serrodyne modulation also enables lock-in detection of the TPA photocurrent. Furthermore, it contributes to the reduction of the system components. The precision measurement is experimentally demonstrated by measuring a fiber length difference of 2.6 m with a standard deviation of 27 μm under constant temperature. The high-precision displacement measurement is also demonstrated by measuring the temperature-induced change in the optical path length difference of a fiber interferometer.

  4. High pressure in situ x-ray absorption spectroscopy cell for studying simultaneously the liquid phase and the solid-liquid interface

    SciTech Connect

    Grunwaldt, Jan-Dierk; Ramin, Michael; Rohr, Markus; Michailovski, Alexej; Patzke, Greta R.; Baiker, Alfons

    2005-05-15

    A high pressure in situ x-ray absorption spectroscopy cell with two different path lengths and path positions is presented for studying element-specifically both the liquid phase and the solid-liquid interface at pressures up to 250 bar and temperatures up to 220 deg. C. For this purpose, one x-ray path probes the bottom, while the other x-ray path penetrates through the middle of the in situ cell. The basic design of the cell resembles a 10 ml volume batch reactor, which is equipped with in- and outlet lines to dose compressed gases and liquids as well as a stirrer for good mixing. Due to the use of a polyetheretherketone inset it is also suitable for measurements under corrosive conditions. The characteristic features of the cell are illustrated using case studies from catalysis and solid state chemistry: (a) the ruthenium-catalyzed formylation of an amine in 'supercritical' carbon dioxide in the presence of hydrogen; (b) the cycloaddition of carbon dioxide to propylene oxide in the presence of a solid Zn-based catalyst, and (c) the solvothermal synthesis of MoO{sub 3} nanorods from MoO{sub 3}-2H{sub 2}O.

  5. High pressure in situ x-ray absorption spectroscopy cell for studying simultaneously the liquid phase and the solid/liquid interface

    NASA Astrophysics Data System (ADS)

    Grunwaldt, Jan-Dierk; Ramin, Michael; Rohr, Markus; Michailovski, Alexej; Patzke, Greta R.; Baiker, Alfons

    2005-05-01

    A high pressure in situ x-ray absorption spectroscopy cell with two different path lengths and path positions is presented for studying element-specifically both the liquid phase and the solid/liquid interface at pressures up to 250 bar and temperatures up to 220 °C. For this purpose, one x-ray path probes the bottom, while the other x-ray path penetrates through the middle of the in situ cell. The basic design of the cell resembles a 10 ml volume batch reactor, which is equipped with in- and outlet lines to dose compressed gases and liquids as well as a stirrer for good mixing. Due to the use of a polyetheretherketone inset it is also suitable for measurements under corrosive conditions. The characteristic features of the cell are illustrated using case studies from catalysis and solid state chemistry: (a) the ruthenium-catalyzed formylation of an amine in "supercritical" carbon dioxide in the presence of hydrogen; (b) the cycloaddition of carbon dioxide to propylene oxide in the presence of a solid Zn-based catalyst, and (c) the solvothermal synthesis of MoO3 nanorods from MoO3•2H2O.

  6. Mathematical model for path selection by ants between nest and food source.

    PubMed

    Bodnar, Marek; Okińczyc, Natalia; Vela-Pérez, M

    2017-03-01

    Several models have been proposed to describe the behavior of ants when moving from nest to food sources. Most of these studies where based on numerical simulations with no mathematical justification. In this paper, we propose a mechanism for the formation of paths of minimal length between two points by a collection of individuals undergoing reinforced random walks taking into account not only the lengths of the paths but also the angles (connected to the preference of ants to move along straight lines). Our model involves reinforcement (pheromone accumulation), persistence (tendency to preferably follow straight directions in absence of any external effect) and takes into account the bifurcation angles of each edge (represented by a probability of willingness of choosing the path with the smallest angle). We describe analytically the results for 2 ants and different path lengths and numerical simulations for several ants.

  7. An algorithm to find critical execution paths of software based on complex network

    NASA Astrophysics Data System (ADS)

    Huang, Guoyan; Zhang, Bing; Ren, Rong; Ren, Jiadong

    2015-01-01

    The critical execution paths play an important role in software system in terms of reducing the numbers of test date, detecting the vulnerabilities of software structure and analyzing software reliability. However, there are no efficient methods to discover them so far. Thus in this paper, a complex network-based software algorithm is put forward to find critical execution paths (FCEP) in software execution network. First, by analyzing the number of sources and sinks in FCEP, software execution network is divided into AOE subgraphs, and meanwhile, a Software Execution Network Serialization (SENS) approach is designed to generate execution path set in each AOE subgraph, which not only reduces ring structure's influence on path generation, but also guarantees the nodes' integrity in network. Second, according to a novel path similarity metric, similarity matrix is created to calculate the similarity among sets of path sequences. Third, an efficient method is taken to cluster paths through similarity matrices, and the maximum-length path in each cluster is extracted as the critical execution path. At last, a set of critical execution paths is derived. The experimental results show that the FCEP algorithm is efficient in mining critical execution path under software complex network.

  8. Application of multilayer feed-forward neural networks to automated compound identification in low-resolution open-path FT-IR spectrometry.

    PubMed

    Yang, H; Griffiths, P R

    1999-02-01

    A drawback of current open-path Fourier transform infrared (OP/FT-IR) systems is that they need a human expert to determine those compounds that may be quantified from a given spectrum. In this work, multilayer feed-forward neural networks with one hidden layer were used to automatically recognize compounds in an OP/FT-IR spectrum without compensation of absorption lines due to atmospheric H2O and CO2. The networks were trained by fast-back-propagation. The training set comprised spectra that were synthesized by digitally adding randomly scaled reference spectra to actual open-path background spectra measured over a variety of path lengths and temperatures. The reference spectra of 109 compounds were used to synthesize the training spectra. Each neural network was trained to recognize only one compound in the presence of up to 10 other interferences in an OP/FT-IR spectrum. Every compound in a database of vaporphase reference spectra can be encoded in an independent neural network so that a neural network library can be established. When these networks are used for the identification of compounds, the process is analogous to spectral library searching. The effect of learning rate and band intensities on the convergence of network training was examined. The networks were successfully used to recognize five alcohols and two chlorinated compounds in field-measured controlled-release OP/FT-IR spectra of mixtures of these compounds.

  9. Significant improvement of signal-to-noise ratio in capillary electrophoresis through optimization of aperture width for UV absorption detection.

    PubMed

    Kitagishi, K; Sato, Y

    2001-10-01

    In capillary electrophoresis (CE), light flux passes through a capillary cell and is in most cases detected photometrically. Due to the thinness of the cell, a part of the light passes through the wall and misses hitting the sample. In most CE apparatuses, incident light is focused by converging lenses in order to condense light beams passing through the capillary. Considering the aberration of lenses and lens effects of capillary, we assumed that light beams inside were approximately parallel. Although the path lengths of light beams vary depending on their tracks, we could estimate the virtual light path length, L, by measuring absorbance when concentration and molar absorptivity of the sample solution were known. A light-restricting device consisting of narrow slits makes effectively L longer and signal intensity higher. On the other hand, noise increases as light width narrows. The signal-to-noise ratio showed a maximum at 68 microm of light width for a capillary with diameter of 75 microm. The optimized L was evaluated by the simulation. The experimental data verified it even in indirect UV detection. Our approach could help to design the optics of CE apparatuses.

  10. Length-adaptive graph search for automatic segmentation of pathological features in optical coherence tomography images

    NASA Astrophysics Data System (ADS)

    Keller, Brenton; Cunefare, David; Grewal, Dilraj S.; Mahmoud, Tamer H.; Izatt, Joseph A.; Farsiu, Sina

    2016-07-01

    We introduce a metric in graph search and demonstrate its application for segmenting retinal optical coherence tomography (OCT) images of macular pathology. Our proposed "adjusted mean arc length" (AMAL) metric is an adaptation of the lowest mean arc length search technique for automated OCT segmentation. We compare this method to Dijkstra's shortest path algorithm, which we utilized previously in our popular graph theory and dynamic programming segmentation technique. As an illustrative example, we show that AMAL-based length-adaptive segmentation outperforms the shortest path in delineating the retina/vitreous boundary of patients with full-thickness macular holes when compared with expert manual grading.

  11. Keeping track of the distance from home by leaky integration along veering paths.

    PubMed

    Lappe, Markus; Stiels, Maren; Frenz, Harald; Loomis, Jack M

    2011-07-01

    When humans use vision to gauge the travel distance of an extended forward movement, they often underestimate the movement's extent. This underestimation can be explained by leaky path integration, an integration of the movement to obtain distance. Distance underestimation occurs because this integration is imperfect and contains a leak that increases with distance traveled. We asked human observers to estimate the distance from a starting location for visually simulated movements in a virtual environment. The movements occurred along curved paths that veered left and right around a central forward direction. In this case, the distance that has to be integrated (i.e., the beeline distance between origin and endpoint) and the distance that is traversed (the path length along the curve) are distinct. We then tested whether the leak accumulated with distance from the origin or with traversed distance along the curved path. Leaky integration along the path makes the seemingly counterintuitive prediction that the estimated origin-to-endpoint distance should decrease with increasing veering, because the length of the path over which the integration occurs increases, leading to a larger leak effect. The results matched the prediction: movements of identical origin-to-endpoint distance were judged as shorter when the path became longer. We conclude that leaky path integration from visual motion is performed along the traversed path even when a straight beeline distance is calculated.

  12. Transition Path Theory

    NASA Astrophysics Data System (ADS)

    vanden-Eijnden, E.

    The dynamical behavior of many systems arising in physics, chemistry, biology, etc. is dominated by rare but important transition events between long lived states. For over 70 years, transition state theory (TST) has provided the main theoretical framework for the description of these events [17,33,34]. Yet, while TST and evolutions thereof based on the reactive flux formalism [1, 5] (see also [30,31]) give an accurate estimate of the transition rate of a reaction, at least in principle, the theory tells very little in terms of the mechanism of this reaction. Recent advances, such as transition path sampling (TPS) of Bolhuis, Chandler, Dellago, and Geissler [3, 7] or the action method of Elber [15, 16], may seem to go beyond TST in that respect: these techniques allow indeed to sample the ensemble of reactive trajectories, i.e. the trajectories by which the reaction occurs. And yet, the reactive trajectories may again be rather uninformative about the mechanism of the reaction. This may sound paradoxical at first: what more than actual reactive trajectories could one need to understand a reaction? The problem, however, is that the reactive trajectories by themselves give only a very indirect information about the statistical properties of these trajectories. This is similar to why statistical mechanics is not simply a footnote in books about classical mechanics. What is the probability density that a trajectory be at a given location in state-space conditional on it being reactive? What is the probability current of these reactive trajectories? What is their rate of appearance? These are the questions of interest and they are not easy to answer directly from the ensemble of reactive trajectories. The right framework to tackle these questions also goes beyond standard equilibrium statistical mechanics because of the nontrivial bias that the very definition of the reactive trajectories imply - they must be involved in a reaction. The aim of this chapter is to

  13. A Two Micron Coherent Differential Absorption Lidar Development

    NASA Technical Reports Server (NTRS)

    Yu, Jirong; Petros, Mulugeta; Chen, Songsheng; Bai, Yingxin; Petzar, Paul J.; Trieu, Bo C.; Koch, Grady J.; Beyon, Jeffrey Y.; VanValkenburg, Randal L.; Kavaya, Michael J.; Singh, Upendra N.

    2010-01-01

    A pulsed, 2-micron coherent Differential Absorption Lidar (DIAL)/Integrated Path Differential Absorption (IPDA) transceiver, developed under the Laser Risk Reduction Program (LRRP) at NASA, is integrated into a fully functional lidar instrument. This instrument measures atmospheric CO2 profiles (by DIAL) from a ground platform. It allows the investigators to pursue subsequent in science-driven deployments, and provides a unique tool for Active Sensing of CO2 Emissions over Night, Days, and Seasons (ASCENDS) validation that was strongly advocated in the recent ASCENDS Workshop. Keywords: Differential Absorption Lidar, Near Infrared Laser,

  14. Stochastic method for determining the coherence length of a TEA CO2 laser

    NASA Astrophysics Data System (ADS)

    Codnia, J.; Gómez, N. D.; Azcárate, M. L.

    2013-12-01

    In this work the results of the measurement of the coherence length of a TEA CO2 laser developed in DEILAP are presented. A Michelson interferometer of about 5 m of optical path length difference was built for this purpose. A motorized translation optical mount was placed in one arm in order to enable the variation of the optical path length in many wavelengths. The length of the other arm was varied manually in steps of several tens of centimeters. Spatial filtering forced the laser to oscillate in a single transverse mode, TEM00. An innovative stochastic technique for data analysis allowed determining the amount of longitudinal modes, the amplitude and the individual average coherence length of each mode as well as the global coherence length of the laser. This technique was later compared with a method based on the analysis of the Fourier transform of the time series obtained at the interferometer input.

  15. An investigation of a mathematical model for atmospheric absorption spectra

    NASA Technical Reports Server (NTRS)

    Niple, E. R.

    1979-01-01

    A computer program that calculates absorption spectra for slant paths through the atmosphere is described. The program uses an efficient convolution technique (Romberg integration) to simulate instrument resolution effects. A brief information analysis is performed on a set of calculated spectra to illustrate how such techniques may be used to explore the quality of the information in a spectrum.

  16. Conjugation Length Distribution in Poly(p-phenylenevinylene) (PPV) Films.

    PubMed

    da Silva, Marcelo C; Cassemiro, Sandra de M; Machado, Angelita M; Alves, Joniel C F; Nogueira, Sandra L; Jarrosson, Thibault; Serein-Spirau, Françoise; Akcelrud, Leni; Tozoni, José R; Silva, Raigna A; Freire, José A; Marletta, Alexandre

    2016-12-15

    We studied the absorption line-shape of poly(p-phenylenevinylene) (PPV) films deposited via spin coating and Langmuir-Blodgett techniques with the intent of identifying the conjugation length distribution in these two types of films, a key morphological aspect of conjugated polymer films. We treated the excitons in the polymer as independent oligomer excitons and modeled the absorption spectra of the individual oligomers using simple expressions for the oligomer size dependence of the gap energy, the line-broadening factor, the transition dipole moment and the Huang-Rhys parameter. We validated these expressions by independent measurements on phenyl-based oligomers and Density Functional Theory calculations. Our results show clear evidence that, for both types of PPV films, the conjugation length distribution depends exponentially on the segment size. Our results also set a lower limit, of about ten repeat units, for the maximum exciton length of three different phenyl-based oligomers.

  17. Coaxial atomizer liquid intact lengths

    NASA Technical Reports Server (NTRS)

    Eroglu, Hasan; Chigier, Norman; Farago, Zoltan

    1991-01-01

    Average intact lengths of round liquid jets generated by airblast coaxial atomizer were measured from over 1500 photographs. The intact lengths were studied over a jet Reynolds number range of 18,000 and Weber number range of 260. Results are presented for two different nozzle geometries. The intact lengths were found to be strongly dependent on Re and We numbers. An empirical equation was derived as a function of these parameters. A comparison of the intact lengths for round jets and flat sheets shows that round jets generate shorter intact lengths.

  18. An Introduction to Path Analysis

    ERIC Educational Resources Information Center

    Wolfe, Lee M.

    1977-01-01

    The analytical procedure of path analysis is described in terms of its use in nonexperimental settings in the social sciences. The description assumes a moderate statistical background on the part of the reader. (JKS)

  19. Scattering theory with path integrals

    SciTech Connect

    Rosenfelder, R.

    2014-03-15

    Starting from well-known expressions for the T-matrix and its derivative in standard nonrelativistic potential scattering, I rederive recent path-integral formulations due to Efimov and Barbashov et al. Some new relations follow immediately.

  20. Fourier transform infrared absorption spectroscopy characterization of gaseous atmospheric pressure plasmas with 2 mm spatial resolution

    SciTech Connect

    Laroche, G.; Vallade, J.; Bazinette, R.; Hernandez, E.; Hernandez, G.; Massines, F.; Nijnatten, P. van

    2012-10-15

    This paper describes an optical setup built to record Fourier transform infrared (FTIR) absorption spectra in an atmospheric pressure plasma with a spatial resolution of 2 mm. The overall system consisted of three basic parts: (1) optical components located within the FTIR sample compartment, making it possible to define the size of the infrared beam (2 mm Multiplication-Sign 2 mm over a path length of 50 mm) imaged at the site of the plasma by (2) an optical interface positioned between the spectrometer and the plasma reactor. Once through the plasma region, (3) a retro-reflector module, located behind the plasma reactor, redirected the infrared beam coincident to the incident path up to a 45 Degree-Sign beamsplitter to reflect the beam toward a narrow-band mercury-cadmium-telluride detector. The antireflective plasma-coating experiments performed with ammonia and silane demonstrated that it was possible to quantify 42 and 2 ppm of these species in argon, respectively. In the case of ammonia, this was approximately three times less than this gas concentration typically used in plasma coating experiments while the silane limit of quantification was 35 times lower. Moreover, 70% of the incoming infrared radiation was focused within a 2 mm width at the site of the plasma, in reasonable agreement with the expected spatial resolution. The possibility of reaching this spatial resolution thus enabled us to measure the gaseous precursor consumption as a function of their residence time in the plasma.

  1. Fourier transform infrared absorption spectroscopy characterization of gaseous atmospheric pressure plasmas with 2 mm spatial resolution.

    PubMed

    Laroche, G; Vallade, J; Bazinette, R; van Nijnatten, P; Hernandez, E; Hernandez, G; Massines, F

    2012-10-01

    This paper describes an optical setup built to record Fourier transform infrared (FTIR) absorption spectra in an atmospheric pressure plasma with a spatial resolution of 2 mm. The overall system consisted of three basic parts: (1) optical components located within the FTIR sample compartment, making it possible to define the size of the infrared beam (2 mm × 2 mm over a path length of 50 mm) imaged at the site of the plasma by (2) an optical interface positioned between the spectrometer and the plasma reactor. Once through the plasma region, (3) a retro-reflector module, located behind the plasma reactor, redirected the infrared beam coincident to the incident path up to a 45° beamsplitter to reflect the beam toward a narrow-band mercury-cadmium-telluride detector. The antireflective plasma-coating experiments performed with ammonia and silane demonstrated that it was possible to quantify 42 and 2 ppm of these species in argon, respectively. In the case of ammonia, this was approximately three times less than this gas concentration typically used in plasma coating experiments while the silane limit of quantification was 35 times lower. Moreover, 70% of the incoming infrared radiation was focused within a 2 mm width at the site of the plasma, in reasonable agreement with the expected spatial resolution. The possibility of reaching this spatial resolution thus enabled us to measure the gaseous precursor consumption as a function of their residence time in the plasma.

  2. Torsional and cyclic fatigue resistances of glide path preparation instruments: G-file and PathFile.

    PubMed

    Sung, Sang Yup; Ha, Jung-Hong; Kwak, Sang-Won; Abed, Rashid El; Byeon, Kyeongmin; Kim, Hyeon-Cheol

    2014-01-01

    This study aimed to compare cyclic fatigue and torsional resistances of glide path creating instruments with different tapers and tip sizes. Two sizes (G1 and G2) from G-File system and three sizes (PathFile #1, #2, and #3) from PathFile system were used for torsional resistance and cyclic fatigue resistance tests (n = 10). The torsional resistance was evaluated at 2-, 3-, 4-, 5-, and 6-mm from the file tip by plotting the torsional load changes until fracture by rotational loading of 2 rpm. The cyclic fatigue resistance was compared by measuring the number of cycles to failure. Data were analyzed statistically using one-way ANOVA and Duncan's post-hoc comparison. The length of the fractured file fragment was also measured. All fractured fragments were observed under a scanning electron microscope (SEM). Although G-2 file showed a lower torsional strength than PathFile #3 at 2- and 3-mm levels (p < 0.05), they had similar ultimate strengths at 4-, 5-, and 6-mm levels (p > 0.05). The smaller files of each brand had a significantly higher cyclic fatigue resistance than the bigger ones (p < 0.05). PathFile #1 and #2 had higher fatigue resistances than G-files (p < 0.05). While G-1 had a similar fatigue resistance as PathFile #3, G-2 showed the lowest and PathFile #1 showed the highest resistances among the tested groups (p < 0.05). The SEM examination showed typical appearances of cyclic fatigue and torsional fractures, regardless of the tested levels. Clinicians may consider the instruments' sizes for each clinical case in order to get efficient glide path with minimal risk of fracture.

  3. Formal language constrained path problems

    SciTech Connect

    Barrett, C.; Jacob, R.; Marathe, M.

    1997-07-08

    In many path finding problems arising in practice, certain patterns of edge/vertex labels in the labeled graph being traversed are allowed/preferred, while others are disallowed. Motivated by such applications as intermodal transportation planning, the authors investigate the complexity of finding feasible paths in a labeled network, where the mode choice for each traveler is specified by a formal language. The main contributions of this paper include the following: (1) the authors show that the problem of finding a shortest path between a source and destination for a traveler whose mode choice is specified as a context free language is solvable efficiently in polynomial time, when the mode choice is specified as a regular language they provide algorithms with improved space and time bounds; (2) in contrast, they show that the problem of finding simple paths between a source and a given destination is NP-hard, even when restricted to very simple regular expressions and/or very simple graphs; (3) for the class of treewidth bounded graphs, they show that (i) the problem of finding a regular language constrained simple path between source and a destination is solvable in polynomial time and (ii) the extension to finding context free language constrained simple paths is NP-complete. Several extensions of these results are presented in the context of finding shortest paths with additional constraints. These results significantly extend the results in [MW95]. As a corollary of the results, they obtain a polynomial time algorithm for the BEST k-SIMILAR PATH problem studied in [SJB97]. The previous best algorithm was given by [SJB97] and takes exponential time in the worst case.

  4. NOAA Aeronomy Laboratory long-path OH experiment, Fritz Peak Observatory, Colorado

    NASA Technical Reports Server (NTRS)

    Mount, George H.

    1994-01-01

    Long path absorption of laser light over a 20.6 km path at Fritz Peak Observatory 17 km west of Boulder is described: elevation 2800 m, average beam height above terrain approximately 250 m, and operational since March 1991. System runs at maximum signal to noise with integration times longer than 64 seconds. Most of the data obtained to date are 15-minute averages due to the lengthy data analysis required.

  5. Constructing Overlay Networks with Short Paths and Low Communication Cost

    NASA Astrophysics Data System (ADS)

    Makikawa, Fuminori; Tsuchiya, Tatsuhiro; Kikuno, Tohru

    A Peer-To-Peer (P2P) application uses an overlay network which is a virtual network constructed over the physical network. Traditional overlay construction methods do not take physical location of nodes into consideration, resulting in a large amount of redundant traffic. Some proximity-aware construction methods have been proposed to address this problem. These methods typically connect nearby nodes in the physical network. However, as the number of nodes increases, the path length of a route between two distant nodes rapidly increases. To alleviate this problem, we propose a technique which can be incorporated in existing overlay construction methods. The idea behind this technique is to employ long links to directly connect distant nodes. Through simulation experiments, we show that using our proposed technique, networks can achieve small path length and low communication cost while maintaining high resiliency to failures.

  6. Multi-channel absolute distance measurement system with sub ppm-accuracy and 20 m range using frequency scanning interferometry and gas absorption cells.

    PubMed

    Dale, John; Hughes, Ben; Lancaster, Andrew J; Lewis, Andrew J; Reichold, Armin J H; Warden, Matthew S

    2014-10-06

    We present an implementation of an absolute distance measurement system which uses frequency scanning interferometry (FSI). The technique, referred to as dynamic FSI, uses two frequency scanning lasers, a gas absorption cell and a reference interferometer to determine the unknown optical path length difference (OPD) of one or many measurement interferometers. The gas absorption cell is the length reference for the measurement system and is traceable to international standards through knowledge of the frequencies of its absorption features. The OPD of the measurement interferometers can vary during the measurement and the variation is measured at the sampling rate of the system (2.77 MHz in the system described here). The system is shown to measure distances from 0.2 m to 20 m with a combined relative uncertainty of 0.41 × 10⁻⁶ at the two sigma level (k = 2). It will be shown that within a scan the change in OPD of the measurement interferometer can be determined to a resolution of 40 nm.

  7. Precision Neutron Scattering Length Measurements with Neutron Interferometry

    NASA Astrophysics Data System (ADS)

    Huber, M. G.; Arif, M.; Jacobson, D. L.; Pushin, D. A.; Abutaleb, M. O.; Shahi, C. B.; Wietfeldt, F. E.; Black, T. C.

    2011-10-01

    Since its inception, single-crystal neutron interferometry has often been utilized for precise neutron scattering length, b, measurements. Scattering length data of light nuclei is particularly important in the study of few nucleon interactions as b can be predicted by two + three nucleon interaction (NI) models. As such they provide a critical test of the accuracy 2+3 NI models. Nuclear effective field theories also make use of light nuclei b in parameterizing mean-field behavior. The NIST neutron interferometer and optics facility has measured b to less than 0.8% relative uncertainty in polarized 3He and to less than 0.1% relative uncertainty in H, D, and unpolarized 3He. A neutron interferometer consists of a perfect silicon crystal machined such that there are three separate blades on a common base. Neutrons are Bragg diffracted in the blades to produce two spatially separate (yet coherent) beam paths much like an optical Mach-Zehnder interferometer. A gas sample placed in one of the beam paths of the interferometer causes a phase difference between the two paths which is proportional to b. This talk will focus on the latest scattering length measurement for n-4He which ran at NIST in Fall/Winter 2010 and is currently being analyzed.

  8. Computing Path Tables for Quickest Multipaths In Computer Networks

    SciTech Connect

    Grimmell, W.C.

    2004-12-21

    We consider the transmission of a message from a source node to a terminal node in a network with n nodes and m links where the message is divided into parts and each part is transmitted over a different path in a set of paths from the source node to the terminal node. Here each link is characterized by a bandwidth and delay. The set of paths together with their transmission rates used for the message is referred to as a multipath. We present two algorithms that produce a minimum-end-to-end message delay multipath path table that, for every message length, specifies a multipath that will achieve the minimum end-to-end delay. The algorithms also generate a function that maps the minimum end-to-end message delay to the message length. The time complexities of the algorithms are O(n{sup 2}((n{sup 2}/logn) + m)min(D{sub max}, C{sub max})) and O(nm(C{sub max} + nmin(D{sub max}, C{sub max}))) when the link delays and bandwidths are non-negative integers. Here D{sub max} and C{sub max} are respectively the maximum link delay and maximum link bandwidth and C{sub max} and D{sub max} are greater than zero.

  9. Characterizing Reactive Flow Paths in Fractured Cement

    NASA Astrophysics Data System (ADS)

    Wenning, Q. C.; Huerta, N. J.; Hesse, M. A.; Bryant, S. L.

    2011-12-01

    Geologic carbon sequestration can be a viable method for reducing anthropogenic CO2 flux into the atmosphere. However, the technology must be economically feasible and pose acceptable risk to stakeholders. One key risk is CO2 leakage out of the storage reservoir. Potential driving forces for leakage are the overpressure due to CO2 injection and the buoyancy of free phase CO2. Potential hazards of leakage are contamination of Underground Sources of Drinking Water or the atmosphere and would be deemed an unacceptable risk. Wells potentially provide a fast path for leakage from the reservoir. While the well's cement casing is reactive with CO2 and CO2-saturated brine, the low cement matrix permeability and slow diffusion rate make it unlikely that CO2 will escape through a properly constructed wellbore. However, highly permeable fractures with micrometer scale apertures can occur in cement casings. Reactions that occur in the flow in these fractures can either be self-limiting or self-enhancing. Therefore, understanding the reactive flow is critical to understanding of leakage evolution through these fractures. The goal of our work is to characterize the modification of the flow paths in the fracture due to reaction with acidic brine. With this aim we have characterized both the initial flow path of un-reactive flow and the final flow path after introduction of low-pH acid along the same fracture. Class H cement cores 3-6 cm in length and 2.5 cm diameter are created and a single natural and unique fracture is produced in each core using the Brazilian method. Our experimental fluid is injected at a constant rate into the cement core housed in a Hassler Cell under confining pressure. A solution of red dye and deionized water is pumped through the fracture to stain the un-reactive flow paths. Deionized water is then pumped through the core to limit diffusion of the dye into non-flowing portions of the fracture. After staining the initial flow path, low pH water due to

  10. Logarithmic Sobolev Inequalities on Path Spaces Over Riemannian Manifolds

    NASA Astrophysics Data System (ADS)

    Hsu, Elton P.

    Let Wo(M) be the space of paths of unit time length on a connected, complete Riemannian manifold M such that γ(0) =o, a fixed point on M, and ν the Wiener measure on Wo(M) (the law of Brownian motion on M starting at o).If the Ricci curvature is bounded by c, then the following logarithmic Sobolev inequality holds:

  11. Vehicle path-planning in three dimensions using optics analogs for optimizing visibility and energy cost

    NASA Technical Reports Server (NTRS)

    Rowe, Neil C.; Lewis, David H.

    1989-01-01

    Path planning is an important issue for space robotics. Finding safe and energy-efficient paths in the presence of obstacles and other constraints can be complex although important. High-level (large-scale) path planning for robotic vehicles was investigated in three-dimensional space with obstacles, accounting for: (1) energy costs proportional to path length; (2) turn costs where paths change trajectory abruptly; and (3) safety costs for the danger associated with traversing a particular path due to visibility or invisibility from a fixed set of observers. Paths optimal with respect to these cost factors are found. Autonomous or semi-autonomous vehicles were considered operating either in a space environment around satellites and space platforms, or aircraft, spacecraft, or smart missiles operating just above lunar and planetary surfaces. One class of applications concerns minimizing detection, as for example determining the best way to make complex modifications to a satellite without being observed by hostile sensors; another example is verifying there are no paths (holes) through a space defense system. Another class of applications concerns maximizing detection, as finding a good trajectory between mountain ranges of a planet while staying reasonably close to the surface, or finding paths for a flight between two locations that maximize the average number of triangulation points available at any time along the path.

  12. Dynamic behavior of shortest path routing algorithms for communication networks

    NASA Astrophysics Data System (ADS)

    Bertsekas, D. P.

    1980-06-01

    Several proposed routing algorithms for store and forward communication networks, including one currently in operation in the ARPANET, route messages along shortest paths computed by using some set of link lengths. When these lengths depend on current traffic conditions as they must in an adaptive algorithm, dynamic behavior questions such as stability convergence, and speed of convergence are of interest. This paper is the first attempt to analyze systematically these issues. It is shown that minimum queuing delay path algorithms tend to exhibit violent oscillatory behavior in the absence of a damping mechanism. The oscillations can be damped by means of several types of schemes, two of which are analyzed in this paper. In the first scheme a constant bias is added to the queuing delay thereby providing a preference towards paths with a small number of links. In the second scheme the effects of several past routings are averaged as, for example, when the link lengths are computed and communicated asynchronously throughout the network.

  13. Propagation and absorption of high-intensity femtosecond laser radiation in diamond

    SciTech Connect

    Kononenko, V V; Konov, V I; Gololobov, V M; Zavedeev, E V

    2014-12-31

    Femtosecond interferometry has been used to experimentally study the photoexcitation of the electron subsystem of diamond exposed to femtosecond laser pulses of intensity 10{sup 11} to 10{sup 14} W cm{sup -2}. The carrier concentration has been determined as a function of incident intensity for three harmonics of a Ti : sapphire laser (800, 400 and 266 nm). The results demonstrate that, in a wide range of laser fluences (up to those resulting in surface and bulk graphitisation), a well-defined multiphoton absorption prevails. We have estimated nonlinear absorption coefficients for pulsed radiation at λ = 800 nm (four-photon transition) and at 400 and 266 nm (indirect and direct two-photon transitions, respectively). It has also been shown that, at any considerable path length of a femtosecond pulse in diamond (tens of microns or longer), the laser beam experiences a severe nonlinear transformation, determining the amount of energy absorbed by the lattice, which is important for the development of technology for diamond photostructuring by ultrashort pulses. The competition between wave packet self-focusing and the plasma defocusing effect is examined as a major mechanism governing the propagation of intense laser pulses in diamond. (interaction of laser radiation with matter. laser plasma)

  14. Measuring the scattering mean free path of Rayleigh waves on a volcano from spatial phase decoherence

    NASA Astrophysics Data System (ADS)

    Obermann, Anne; Larose, Eric; Margerin, Ludovic; Rossetto, Vincent

    2014-04-01

    We analyse the statistics of phase fluctuations of seismic signals obtained from a temporary small aperture array deployed on a volcano in the French Auvergne. We demonstrate that the phase field satisfies Circular Gaussian statistics. We then determine the scattering mean free path of Rayleigh waves from the spatial phase decoherence. This phenomenon, observed for diffuse wavefields, is found to yield a good approximation of the scattering mean free path. Contrary to the amplitude, spatial phase decoherence is free from absorption effects and provides direct access to the scattering mean free path.

  15. A Hot Gaseous Galaxy Halo Candidate with Mg X Absorption

    NASA Astrophysics Data System (ADS)

    Qu, Zhijie; Bregman, Joel N.

    2016-12-01

    The hot gas in galaxy halos may account for a significant fraction of missing baryons in galaxies, and some of these gases can be traced by high ionization absorption systems in QSO UV spectra. Using high S/N Hubble Space Telescope/Cosmic Origins Spectrograph spectra, we discovered a high ionization state system at z = 1.1912 in the sightline toward LBQS 1435-0134, and two-component absorption lines are matched for Mg x, Ne viii, Ne vi, O vi, Ne v, O v, Ne iv, O iv, N iv, O iii, and H i. Mg x, detected for the first time (5.8σ), is a particularly direct tracer of hot galactic halos, as its peak ion fraction occurs near 106.1 K, about the temperature of a virialized hot galaxy halo of mass ˜ 0.5{M}* . With Mg x and Ne viii, a photoionization model cannot reproduce the observed column densities with path lengths of galaxy halos. For collisional ionization models, one or two-temperature models do not produce acceptable fits, but a three-temperature model or a power-law model can produce the observed results. In the power-law model, {dN}/{dT}={10}4.4+/- 2.2-[Z/X]{T}1.55+/- 0.41 with temperatures in the range of {10}4.39+/- 0.13 {{K}}\\lt T\\lt {10}6.04+/- 0.05 {{K}}, the total hydrogen column density is 8.2× {10}19(0.3 {Z}⊙ /Z) {{cm}}-2 and the positive power-law index indicates most of the mass is at the high temperature end. We suggest that this absorption system is a hot volume-filled galaxy halo rather than interaction layers between the hot halo and cool clouds. The temperature dependence of the column density is likely due to the local mixture of multiple phase gases.

  16. What is the right time for path integrals?

    NASA Astrophysics Data System (ADS)

    Jones, Eric; Bach, Roger; Batelaan, Herman

    2013-05-01

    The Feynman path integral formulation of quantum mechanics has proven to be a powerful tool for calculations in matter optics. It is natural to introduce the path integral in the context of Young's double slit experiment for matter waves as Feynman did, perhaps after discussing the analogous situation for optics. While intuitive, this approach can lead to a pedagogical misrepresentation of the theory, namely in the phase accumulated along single free-particle trajectories. How is the use of the accumulated phase, 2 πL /λdB , along a path of length L justified? The free-particle action gives a phase that differs by a factor of two. The guiding principle that interference occurs only for two paths that are indistinguishable from one another provides a correct solution: interfering paths must originate and terminate at equal times. We will present several simple thought experiments to illustrate incorrect and correct methods for determining phase shifts. We gratefully acknowledge support from NSF and the DoE GAANN. We thank Ron Cappelletti for interesting discussions.

  17. The Edge-Disjoint Path Problem on Random Graphs by Message-Passing

    PubMed Central

    2015-01-01

    We present a message-passing algorithm to solve a series of edge-disjoint path problems on graphs based on the zero-temperature cavity equations. Edge-disjoint paths problems are important in the general context of routing, that can be defined by incorporating under a unique framework both traffic optimization and total path length minimization. The computation of the cavity equations can be performed efficiently by exploiting a mapping of a generalized edge-disjoint path problem on a star graph onto a weighted maximum matching problem. We perform extensive numerical simulations on random graphs of various types to test the performance both in terms of path length minimization and maximization of the number of accommodated paths. In addition, we test the performance on benchmark instances on various graphs by comparison with state-of-the-art algorithms and results found in the literature. Our message-passing algorithm always outperforms the others in terms of the number of accommodated paths when considering non trivial instances (otherwise it gives the same trivial results). Remarkably, the largest improvement in performance with respect to the other methods employed is found in the case of benchmarks with meshes, where the validity hypothesis behind message-passing is expected to worsen. In these cases, even though the exact message-passing equations do not converge, by introducing a reinforcement parameter to force convergence towards a sub optimal solution, we were able to always outperform the other algorithms with a peak of 27% performance improvement in terms of accommodated paths. On random graphs, we numerically observe two separated regimes: one in which all paths can be accommodated and one in which this is not possible. We also investigate the behavior of both the number of paths to be accommodated and their minimum total length. PMID:26710102

  18. Solar absorption surface panel

    DOEpatents

    Santala, Teuvo J.

    1978-01-01

    A composite metal of aluminum and nickel is used to form an economical solar absorption surface for a collector plate wherein an intermetallic compound of the aluminum and nickel provides a surface morphology with high absorptance and relatively low infrared emittance along with good durability.

  19. Rectal absorption of propylthiouracil.

    PubMed

    Bartle, W R; Walker, S E; Silverberg, J D

    1988-06-01

    The rectal absorption of propylthiouracil (PTU) was studied and compared to oral absorption in normal volunteers. Plasma levels of PTU after administration of suppositories of PTU base and PTU diethanolamine were significantly lower compared to the oral route. Elevated plasma reverse T3 levels were demonstrated after each treatment, however, suggesting a desirable therapeutic effect at this dosage level for all preparations.

  20. Petawatt laser absorption bounded

    PubMed Central

    Levy, Matthew C.; Wilks, Scott C.; Tabak, Max; Libby, Stephen B.; Baring, Matthew G.

    2014-01-01

    The interaction of petawatt (1015 W) lasers with solid matter forms the basis for advanced scientific applications such as table-top particle accelerators, ultrafast imaging systems and laser fusion. Key metrics for these applications relate to absorption, yet conditions in this regime are so nonlinear that it is often impossible to know the fraction of absorbed light f, and even the range of f is unknown. Here using a relativistic Rankine-Hugoniot-like analysis, we show for the first time that f exhibits a theoretical maximum and minimum. These bounds constrain nonlinear absorption mechanisms across the petawatt regime, forbidding high absorption values at low laser power and low absorption values at high laser power. For applications needing to circumvent the absorption bounds, these results will accelerate a shift from solid targets, towards structured and multilayer targets, and lead the development of new materials. PMID:24938656

  1. Collisionless absorption in sharp-edged plasmas

    SciTech Connect

    Gibbon, P. ); Bell, A.R. )

    1992-03-09

    The absorption of subpicosecond, obliquely incident laser light is studied using a 11/2D particle-in-cell code. Density scale lengths from {ital L}/{lambda}=0.01 to 2 and laser irradiances between {ital I}{lambda}{sup 2}=10{sup 14} and 10{sup 18} W cm{sup {minus}2} {mu}m{sup 2} are considered. Vacuum heating'' (F. Brunel, Phys. Rev. Lett. 59, 52 (1987)) dominates over resonance absorption for scale lengths {ital L}/{lambda}{lt}0.1, and is most efficient when {ital v}{sub osc}/{ital c}{congruent}3.1({ital L}/{lambda}){sup 2}. Absorbed energy is carried mainly by a superhot'' electron population with {ital U}{sub hot}{similar to}({ital I}{lambda}{sup 2}){sup 1/3--1/2}.

  2. Monte Carlo Simulation of the Optical Absorption of Hydrogenated Nanocrystalline Silicon Thin Films

    NASA Astrophysics Data System (ADS)

    Besahraoui, Fatiha; Sib, Jamal Dine; Bouizem, Yahia; Chahed, Larbi

    2008-05-01

    The optical absorption coefficient measured by Constant Photocurrent Method (CPM) for nanotextured silicon thin films is apparent affected by light scattering produced in these heterogeneous materials. A detailed Monte Carlo simulation of the absorption spectra and the random optical paths traveled by the scattered photons is presented for the case of nano-Si:H layers. The calculated values of apparent absorption coefficient and the mean optical path depend mainly on the variation of the included nanocrystallites fraction, which favors bulk light scattering phenomena. The particular structure of these materials is a key characteristic of efficient thin films solar cells.

  3. Absorption enhancement and total absorption in a graphene-waveguide hybrid structure

    NASA Astrophysics Data System (ADS)

    Guo, Jun; Wu, Leiming; Dai, Xiaoyu; Xiang, Yuanjiang; Fan, Dianyuan

    2017-02-01

    We propose a graphene/planar waveguide hybrid structure, and demonstrate total absorption in the visible wavelength range by means of attenuated total reflectance. The excitation of planar waveguide mode, which has strong near field enhancement and increased light interaction length with graphene, plays a vital role in total absorption. We analyze the origin and physical insight of total absorption theoretically by using an approximated reflectance, and show how to design such hybrid structure numerically. Utilizing the tunability of doped graphene, we discuss the possible application in optical modulators. We also achieve broadband absorption enhancement in near-IR range by cascading multiple graphene-waveguide hybrid structures. We believe our results will be useful not only for potential applications in optical devices, but also for studying other two-dimension materials.

  4. Gas-path seal technology

    NASA Technical Reports Server (NTRS)

    Zuk, J.

    1976-01-01

    Improved gas-path seals are needed for better fuel economy, longer performance retention, and lower maintenance, particularly in advanced, high-performance gas turbine engines. Problems encountered in gas-path sealing are described, as well as new blade-tip sealing approaches for high-pressure compressors and turbines. These include a lubricant coating for conventional, porous-metal, rub-strip materials used in compressors. An improved hot-press metal alloy shows promise to increase the operating surface temperatures of high-pressure-turbine, blade-tip seals to 1450 K (2150 F). Three ceramic seal materials are also described that have the potential to allow much higher gas-path surface operating temperatures than are possible with metal systems.

  5. Line Lengths and Starch Scores.

    ERIC Educational Resources Information Center

    Moriarty, Sandra E.

    1986-01-01

    Investigates readability of different line lengths in advertising body copy, hypothesizing a normal curve with lower scores for shorter and longer lines, and scores above the mean for lines in the middle of the distribution. Finds support for lower scores for short lines and some evidence of two optimum line lengths rather than one. (SKC)

  6. Super-Resonant Intracavity Coherent Absorption

    NASA Astrophysics Data System (ADS)

    Malara, P.; Campanella, C. E.; Giorgini, A.; Avino, S.; de Natale, P.; Gagliardi, G.

    2016-07-01

    The capability of optical resonators to extend the effective radiation-matter interaction length originates from a multipass effect, hence is intrinsically limited by the resonator’s quality factor. Here, we show that this constraint can be overcome by combining the concepts of resonant interaction and coherent perfect absorption (CPA). We demonstrate and investigate super-resonant coherent absorption in a coupled Fabry-Perot (FP)/ring cavity structure. At the FP resonant wavelengths, the described phenomenon gives rise to split modes with a nearly-transparent peak and a peak whose transmission is exceptionally sensitive to the intracavity loss. For small losses, the effective interaction pathlength of these modes is proportional respectively to the ratio and the product of the individual finesse coefficients of the two resonators. The results presented extend the conventional definition of resonant absorption and point to a way of circumventing the technological limitations of ultrahigh-quality resonators in spectroscopy and optical sensing schemes.

  7. Innovative development path of ethnomedicines: the interpretation of the path.

    PubMed

    Zhu, Zhaoyun; Fu, Dehuan; Gui, Yali; Cui, Tao; Wang, Jingkun; Wang, Ting; Yang, Zhizhong; Niu, Yanfei; She, Zhennan; Wang, Li

    2017-03-01

    One of the primary purposes of the innovative development of ethnomedicines is to use their excellent safety and significant efficacy to serve a broader population. To achieve this purpose, modern scientific and technological means should be referenced, and relevant national laws and regulations as well as technical guides should be strictly followed to develop standards and to perform systemic research in producing ethnomedicines. Finally, ethnomedicines, which are applied to a limited extent in ethnic areas, can be transformed into safe, effective, and quality-controllable medical products to relieve the pain of more patients. The innovative development path of ethnomedicines includes the following three primary stages: resource study, standardized development research, and industrialization of the achievements and efforts for internationalization. The implementation of this path is always guaranteed by the research and development platform and the talent team. This article is based on the accumulation of long-term practice and is combined with the relevant disciplines, laws and regulations, and technical guidance from the research and development of ethnomedicines. The intention is to perform an in-depth analysis and explanation of the major research thinking, methods, contents, and technical paths involved in all stages of the innovative development path of ethnomedicines to provide useful references for the development of proper ethnomedicine use.

  8. Gestation length in farmed reindeer.

    PubMed

    Shipka, M P; Rowell, J E

    2010-01-01

    Reindeer (Rangifer tarandus tarundus) are the only cervids indigenous to the arctic environment. In Alaska, reindeer are a recognized agricultural species and an economic mainstay for many native populations. Traditionally raised in extensive free-ranging systems, a recent trend toward intensive farming requires a more in-depth knowledge of reproductive management. Reported gestation length in reindeer varies, ranging from 198 to 229 d in studies performed at the University of Alaska Fairbanks. A switchback study that manipulated only breeding date demonstrated a mean increase in gestation length of 8.5 d among females bred early in the season. The negative correlation between conception date and gestation length is consistent with reindeer research at other locations and reports of variable gestation length in a growing number of domestic and non-domestic species. This paper reviews the phenomenon in reindeer and discusses some of the factors known to affect gestation length as well as possible areas for future research.

  9. Speckle Imaging Over Horizontal Paths

    SciTech Connect

    Carrano, C J

    2002-05-21

    Atmospheric aberrations reduce the resolution and contrast in surveillance images recorded over horizontal or slant paths. This paper describes our recent horizontal and slant path imaging experiments of extended scenes as well as the results obtained using speckle imaging. The experiments were performed with an 8-inch diameter telescope placed on either a rooftop or hillside and cover ranges of interest from 0.5 km up to 10 km. The scenery includes resolution targets, people, vehicles, and other structures. The improvement in image quality using speckle imaging is dramatic in many cases, and depends significantly upon the atmospheric conditions. We quantify resolution improvement through modulation transfer function measurement comparisons.

  10. Multiple paths in complex tasks

    NASA Technical Reports Server (NTRS)

    Galanter, Eugene; Wiegand, Thomas; Mark, Gloria

    1987-01-01

    The relationship between utility judgments of subtask paths and the utility of the task as a whole was examined. The convergent validation procedure is based on the assumption that measurements of the same quantity done with different methods should covary. The utility measures of the subtasks were obtained during the performance of an aircraft flight controller navigation task. Analyses helped decide among various models of subtask utility combination, whether the utility ratings of subtask paths predict the whole tasks utility rating, and indirectly, whether judgmental models need to include the equivalent of cognitive noise.

  11. Ultrasensitive near-infrared integrated cavity output spectroscopy technique for detection of CO at 1.57 μm: new sensitivity limits for absorption measurements in passive optical cavities

    NASA Astrophysics Data System (ADS)

    Engel, Gregory S.; Drisdell, Walter S.; Keutsch, Frank N.; Moyer, Elisabeth J.; Anderson, James G.

    2006-12-01

    A robust absorption spectrometer using the off-axis integrated cavity output spectroscopy (ICOS) technique in a passive cavity is presented. The observed sensitivity, conceptually the detection threshold for the absorption cross section (cm2) multiplied by the concentration (cm-3) and normalized by the averaging time, is measured to be 1.9×10-12 (1/cm√Hz). This high sensitivity arises from using the optical cavity to amplify the observed path length in the spectrometer while avoiding cavity resonances by careful design of the spot pattern within the cavity. The instrument is ideally suited for routine monitoring of trace gases in the near-infrared region. A spectrum showing ambient carbon monoxide at 1.57 μm is presented.

  12. Quasar Absorption Studies

    NASA Technical Reports Server (NTRS)

    Mushotzky, Richard (Technical Monitor); Elvis, Martin

    2004-01-01

    The aim of the proposal is to investigate the absorption properties of a sample of inter-mediate redshift quasars. The main goals of the project are: Measure the redshift and the column density of the X-ray absorbers; test the correlation between absorption and redshift suggested by ROSAT and ASCA data; constrain the absorber ionization status and metallicity; constrain the absorber dust content and composition through the comparison between the amount of X-ray absorption and optical dust extinction. Unanticipated low energy cut-offs where discovered in ROSAT spectra of quasars and confirmed by ASCA, BeppoSAX and Chandra. In most cases it was not possible to constrain adequately the redshift of the absorber from the X-ray data alone. Two possibilities remain open: a) absorption at the quasar redshift; and b) intervening absorption. The evidences in favour of intrinsic absorption are all indirect. Sensitive XMM observations can discriminate between these different scenarios. If the absorption is at the quasar redshift we can study whether the quasar environment evolves with the Cosmic time.

  13. Localization and phase coherence length in the Lloyd model

    NASA Astrophysics Data System (ADS)

    Rodrigues, D. E.; Pastawski, H. M.; Weisz, J. F.

    1986-12-01

    The coefficient for exponential attenuation of the averaged Green function [limδ-->0~av~e-κR] is calculated for several infinite lattices in one, two, and three dimensions with a diagonal Lorentzian disorder of site energies (Lloyd model). In the limit of extended states, l=κ-1 coincidences with the phase coherence length and with the mean free path associated with ||k> states. In the opposite limit, that of strongly localized states, the inequality κ>=γ is almost satisfied as an equality where γ is the inverse localization length. Our results for κ are the same as those calculated by Johnston and Kunz who associate their results with γ, that is, with the localization length. This leads us to reinterpret their results and to conclude that, when the dimensionality is higher than 2, there is still a strong possibility of a mobility edge in this model.

  14. Method for path imbalance measurement of the two-arm fiber-optic interferometer.

    PubMed

    Huang, Shih-Chu; Lin, Hermann

    2008-10-01

    The path imbalance (PI) of the two-arm fiber-optic interferometric sensor is a substantial parameter; a precise value of millimeters is required. Currently the precision reflectometry and the millimeter optical time-domain reflectometry are used to measure the tiny optical path difference, but the performances of these measurements are limited from the length and the resolution of the PI. We propose a new method accomplished by interferometer to accurately measure millimeters to within a few decimeters of the PI.

  15. Career Paths in Environmental Sciences

    EPA Science Inventory

    Career paths, current and future, in the environmental sciences will be discussed, based on experiences and observations during the author's 40 + years in the field. An emphasis will be placed on the need for integrated, transdisciplinary systems thinking approaches toward achie...

  16. SSME propellant path leak detection

    NASA Technical Reports Server (NTRS)

    Crawford, Roger; Shohadaee, Ahmad Ali

    1989-01-01

    The complicated high-pressure cycle of the space shuttle main engine (SSME) propellant path provides many opportunities for external propellant path leaks while the engine is running. This mode of engine failure may be detected and analyzed with sufficient speed to save critical engine test hardware from destruction. The leaks indicate hardware failures which will damage or destroy an engine if undetected; therefore, detection of both cryogenic and hot gas leaks is the objective of this investigation. The primary objective of this phase of the investigation is the experimental validation of techniques for detecting and analyzing propellant path external leaks which have a high probability of occurring on the SSME. The selection of candidate detection methods requires a good analytic model for leak plumes which would develop from external leaks and an understanding of radiation transfer through the leak plume. One advanced propellant path leak detection technique is obtained by using state-of-the-art technology infrared (IR) thermal imaging systems combined with computer, digital image processing, and expert systems for the engine protection. The feasibility of IR leak plume detection is evaluated on subscale simulated laboratory plumes to determine sensitivity, signal to noise, and general suitability for the application.

  17. Career Path of School Superintendents.

    ERIC Educational Resources Information Center

    Mertz, Norma T.; McNeely, Sonja R.

    This study of the career paths of 147 Tennessee school superintendents sought to determine to what extent coaching and principalships are routes to that office. The majority of respondents were white males; only one was black, and 10 were female. The data were analyzed by group, race, sex, years in office, and method of selection (elected or…

  18. Employer Resource Manual. Project Path.

    ERIC Educational Resources Information Center

    Kane, Karen R.; Del George, Eve

    Project Path at Illinois' College of DuPage was established to provide pre-employment training and career counseling for disabled students. To encourage the integration of qualified individuals with disabilities into the workplace, the project compiled this resource manual for area businesses, providing tips for interacting with disabled people…

  19. Perceived Shrinkage of Motion Paths

    ERIC Educational Resources Information Center

    Sinico, Michele; Parovel, Giulia; Casco, Clara; Anstis, Stuart

    2009-01-01

    We show that human observers strongly underestimate a linear or circular trajectory that a luminous spot follows in the dark. At slow speeds, observers are relatively accurate, but, as the speed increases, the size of the path is progressively underestimated, by up to 35%. The underestimation imposes little memory load and does not require…

  20. Minimum length-maximum velocity

    NASA Astrophysics Data System (ADS)

    Panes, Boris

    2012-03-01

    We study a framework where the hypothesis of a minimum length in space-time is complemented with the notion of reference frame invariance. It turns out natural to interpret the action of the obtained reference frame transformations in the context of doubly special relativity. As a consequence of this formalism we find interesting connections between the minimum length properties and the modified velocity-energy relation for ultra-relativistic particles. For example, we can predict the ratio between the minimum lengths in space and time using the results from OPERA on superluminal neutrinos.

  1. Fluid absorption solar energy receiver

    NASA Technical Reports Server (NTRS)

    Bair, Edward J.

    1993-01-01

    A conventional solar dynamic system transmits solar energy to the flowing fluid of a thermodynamic cycle through structures which contain the gas and thermal energy storage material. Such a heat transfer mechanism dictates that the structure operate at a higher temperature than the fluid. This investigation reports on a fluid absorption receiver where only a part of the solar energy is transmitted to the structure. The other part is absorbed directly by the fluid. By proportioning these two heat transfer paths the energy to the structure can preheat the fluid, while the energy absorbed directly by the fluid raises the fluid to its final working temperature. The surface temperatures need not exceed the output temperature of the fluid. This makes the output temperature of the gas the maximum temperature in the system. The gas can have local maximum temperatures higher than the output working temperature. However local high temperatures are quickly equilibrated, and since the gas does not emit radiation, local high temperatures do not result in a radiative heat loss. Thermal radiation, thermal conductivity, and heat exchange with the gas all help equilibrate the surface temperature.

  2. Advanced Sine Wave Modulation of Continuous Wave Laser System for Atmospheric CO2 Differential Absorption Measurements

    NASA Technical Reports Server (NTRS)

    Campbell, Joel F.; Lin, Bing; Nehrir, Amin R.

    2014-01-01

    NASA Langley Research Center in collaboration with ITT Exelis have been experimenting with Continuous Wave (CW) laser absorption spectrometer (LAS) as a means of performing atmospheric CO2 column measurements from space to support the Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) mission.Because range resolving Intensity Modulated (IM) CW lidar techniques presented here rely on matched filter correlations, autocorrelation properties without side lobes or other artifacts are highly desirable since the autocorrelation function is critical for the measurements of lidar return powers, laser path lengths, and CO2 column amounts. In this paper modulation techniques are investigated that improve autocorrelation properties. The modulation techniques investigated in this paper include sine waves modulated by maximum length (ML) sequences in various hardware configurations. A CW lidar system using sine waves modulated by ML pseudo random noise codes is described, which uses a time shifting approach to separate channels and make multiple, simultaneous online/offline differential absorption measurements. Unlike the pure ML sequence, this technique is useful in hardware that is band pass filtered as the IM sine wave carrier shifts the main power band. Both amplitude and Phase Shift Keying (PSK) modulated IM carriers are investigated that exibit perfect autocorrelation properties down to one cycle per code bit. In addition, a method is presented to bandwidth limit the ML sequence based on a Gaussian filter implemented in terms of Jacobi theta functions that does not seriously degrade the resolution or introduce side lobes as a means of reducing aliasing and IM carrier bandwidth.

  3. Absorption heat pump system

    DOEpatents

    Grossman, G.

    1982-06-16

    The efficiency of an absorption heat pump system is improved by conducting liquid from a second stage evaporator thereof to an auxiliary heat exchanger positioned downstream of a primary heat exchanger in the desorber of the system.

  4. Compounds affecting cholesterol absorption

    NASA Technical Reports Server (NTRS)

    Hua, Duy H. (Inventor); Koo, Sung I. (Inventor); Noh, Sang K. (Inventor)

    2004-01-01

    A class of novel compounds is described for use in affecting lymphatic absorption of cholesterol. Compounds of particular interest are defined by Formula I: ##STR1## or a pharmaceutically acceptable salt thereof.

  5. Absorption heat pump system

    DOEpatents

    Grossman, Gershon

    1984-01-01

    The efficiency of an absorption heat pump system is improved by conducting liquid from a second stage evaporator thereof to an auxiliary heat exchanger positioned downstream of a primary heat exchanger in the desorber of the system.

  6. Optical absorption measurement system

    DOEpatents

    Draggoo, Vaughn G.; Morton, Richard G.; Sawicki, Richard H.; Bissinger, Horst D.

    1989-01-01

    The system of the present invention contemplates a non-intrusive method for measuring the temperature rise of optical elements under high laser power optical loading to determine the absorption coefficient. The method comprises irradiating the optical element with a high average power laser beam, viewing the optical element with an infrared camera to determine the temperature across the optical element and calculating the absorption of the optical element from the temperature.

  7. Solar selective absorption coatings

    DOEpatents

    Mahoney, Alan R.; Reed, Scott T.; Ashley, Carol S.; Martinez, F. Edward

    2003-10-14

    A new class of solar selective absorption coatings are disclosed. These coatings comprise a structured metallic overlayer such that the overlayer has a sub-micron structure designed to efficiently absorb solar radiation, while retaining low thermal emissivity for infrared thermal radiation. A sol-gel layer protects the structured metallic overlayer from mechanical, thermal, and environmental degradation. Processes for producing such solar selective absorption coatings are also disclosed.

  8. Solar selective absorption coatings

    DOEpatents

    Mahoney, Alan R.; Reed, Scott T.; Ashley, Carol S.; Martinez, F. Edward

    2004-08-31

    A new class of solar selective absorption coatings are disclosed. These coatings comprise a structured metallic overlayer such that the overlayer has a sub-micron structure designed to efficiently absorb solar radiation, while retaining low thermal emissivity for infrared thermal radiation. A sol-gel layer protects the structured metallic overlayer from mechanical, thermal, and environmental degradation. Processes for producing such solar selective absorption coatings are also disclosed.

  9. Intranasal absorption of oxymorphone.

    PubMed

    Hussain, M A; Aungst, B J

    1997-08-01

    The nasal bioavailability of oxymorphone HCI was determined. Rats were surgically prepared to isolate the nasal cavity, into which a solution of oxymorphone was administered. A reference group of rats was administered oxymorphone HCl intravenously. Plasma oxymorphone concentrations were determined by HPLC. Nasal absorption was rapid, nasal bioavailability was 43%, and the iv and nasal elimination profiles were similar. Oxymorphone HCI appears to have the solubility, potency, and absorption properties required for efficient nasal delivery, which is an alternative to injections.

  10. Definition of Magnetic Exchange Length

    SciTech Connect

    Abo, GS; Hong, YK; Park, J; Lee, J; Lee, W; Choi, BC

    2013-08-01

    The magnetostatic exchange length is an important parameter in magnetics as it measures the relative strength of exchange and self-magnetostatic energies. Its use can be found in areas of magnetics including micromagnetics, soft and hard magnetic materials, and information storage. The exchange length is of primary importance because it governs the width of the transition between magnetic domains. Unfortunately, there is some confusion in the literature between the magnetostatic exchange length and a similar distance concerning magnetization reversal mechanisms in particles known as the characteristic length. This confusion is aggravated by the common usage of two different systems of units, SI and cgs. This paper attempts to clarify the situation and recommends equations in both systems of units.

  11. Electronic Stroke CarePath: Integrated Approach to Stroke Care.

    PubMed

    Katzan, Irene L; Fan, Youran; Speck, Micheal; Morton, Johanna; Fromwiller, Lauren; Urchek, John; Uchino, Ken; Griffith, Sandra D; Modic, Michael

    2015-10-01

    We describe the development, implementation, and outcomes of the first 2 years of the Electronic Stroke CarePath, an initiative developed for management of ischemic stroke patients in an effort to improve efficiency and quality of care for patients. The CarePath consists of care pathways for ischemic stroke that are integrated within the electronic health record. Patient-reported outcomes are collected using an external software platform. Documentation tools, order sets, and clinical decision support were designed to improve efficiency, optimize process measure adherence, and produce clinical data as a byproduct of care that are available for future analyses. Inpatient mortality and length of stay were compared before and after CarePath implementation in ischemic stroke patients after adjustment for case-mix. Postdischarge functional outcomes of patients with ischemic stroke were compared between the first 3 months of rollout and remainder of the study period. From January 2011 to December 2012, there were 1106 patients with ischemic stroke on the CarePath. There was a decline in inpatient mortality in patients with ischemic stroke, but not in control patients with intracerebral or subarachnoid hemorrhage. Completion rate of patient-reported questionnaires at postdischarge stroke follow-up was 72.9%. There was a trend toward improved functional outcomes at follow-up with CarePath implementation. Implementation of the Electronic Stroke CarePath is feasible and may be associated with a benefit in multiple different outcomes after ischemic stroke. This approach may be an important strategy for optimizing stroke care in the future.

  12. Open-path cavity ring-down spectroscopy sensor for atmospheric ammonia

    NASA Astrophysics Data System (ADS)

    Shadman, Soran; Rose, Charles; Yalin, Azer P.

    2016-07-01

    An open-path cavity ring-down spectroscopy (CRDS) sensor has been developed for measurement of atmospheric ammonia (NH3) and represents the first use of open-path CRDS in the mid-infrared region. The sensor uses a continuous-wave distributed feedback quantum cascade laser at 10.33 μm to target strong absorption features. The optical cavity is constructed with two high-reflectivity mirrors ( R = 0.9995). The open-path configuration removes inlet effects, which are very challenging for closed-path instruments, and can be enabling for compact, low-power designs. Sensor performance was validated in the laboratory by measuring known concentrations in a closed-path configuration. The open-path configuration was validated by comparison against a commercial closed-path CRDS instrument for outdoor measurements at a small feed lot. Ammonia concentrations from the two instruments showed good agreement with slope of 0.990 ( R 2 = 0.92), for 5-min averages. The precision of the open-path instrument was found from Allan variance studies as 1.2 ppb (2-σ) for 3-s measurement durations.

  13. Enzymatic reaction paths as determined by transition path sampling

    NASA Astrophysics Data System (ADS)

    Masterson, Jean Emily

    Enzymes are biological catalysts capable of enhancing the rates of chemical reactions by many orders of magnitude as compared to solution chemistry. Since the catalytic power of enzymes routinely exceeds that of the best artificial catalysts available, there is much interest in understanding the complete nature of chemical barrier crossing in enzymatic reactions. Two specific questions pertaining to the source of enzymatic rate enhancements are investigated in this work. The first is the issue of how fast protein motions of an enzyme contribute to chemical barrier crossing. Our group has previously identified sub-picosecond protein motions, termed promoting vibrations (PVs), that dynamically modulate chemical transformation in several enzymes. In the case of human heart lactate dehydrogenase (hhLDH), prior studies have shown that a specific axis of residues undergoes a compressional fluctuation towards the active site, decreasing a hydride and a proton donor--acceptor distance on a sub-picosecond timescale to promote particle transfer. To more thoroughly understand the contribution of this dynamic motion to the enzymatic reaction coordinate of hhLDH, we conducted transition path sampling (TPS) using four versions of the enzymatic system: a wild type enzyme with natural isotopic abundance; a heavy enzyme where all the carbons, nitrogens, and non-exchangeable hydrogens were replaced with heavy isotopes; and two versions of the enzyme with mutations in the axis of PV residues. We generated four separate ensembles of reaction paths and analyzed each in terms of the reaction mechanism, time of barrier crossing, dynamics of the PV, and residues involved in the enzymatic reaction coordinate. We found that heavy isotopic substitution of hhLDH altered the sub-picosecond dynamics of the PV, changed the favored reaction mechanism, dramatically increased the time of barrier crossing, but did not have an effect on the specific residues involved in the PV. In the mutant systems

  14. Length Invisibilization of Tachyonic Neutrinos

    NASA Astrophysics Data System (ADS)

    Estakhr, Ahmad Reza

    2016-09-01

    Faster than the speed of light particle such as tachyonic neutrino due to its superluminal nature disapper and is undetectable. L = iΩ-1Lo where, i =√{ - 1 } is imaginary Number, Ω = 1 /√{βs2 - 1 } is Estakhr's Omega factor, L is the Superluminal Length, Lo is the proper length, βs =Vs / c > 1 is superluminal speed parameter, Vs is Superluminal velocity and c is speed of light.

  15. Space diversity performance prediction for earth-satellite paths using radar modeling techniques

    NASA Technical Reports Server (NTRS)

    Goldhirsh, J.

    1982-01-01

    Space diversity performance is examined on the basis of radar modeling techniques. Radar-derived joint probability distributions are calculated for determining path attenuation and statistical formulation. The computational aspects of the model are discussed in terms of the data base, determining path length and converting statistics to other path angles. The results are presented in terms of prediction accuracy, predicted joint probability distributions, diversity gain, and the autocorrection function. When compared to other models, this model's rain-derived relative diversity gain shows good agreement.

  16. 47 CFR 74.644 - Minimum path lengths for fixed links.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... paragraph (b): For transmitters using Automatic Transmitter Power Control, EIRP corresponds to the maximum transmitter power available, not the coordinated transmit power or the nominal transmit power. Note 2 to...BW Where: EIRP = The new maximum EIRP (equivalent isotropically radiated power) in dBW....

  17. On the Distribution of Free Path Lengths for the Periodic Lorentz Gas III

    NASA Astrophysics Data System (ADS)

    Caglioti, Emanuele; Golse, François

    For r(0,1), let Zr={xR2|dist(x,Z2)>r/2} and define τr(x,v)=inf{t>0|x+tv∂Zr}. Let Φr(t) be the probability that τr(x,v)>=t for x and v uniformly distributed in Zr and §1 respectively. We prove in this paper that as t-->+∞. This result improves upon the bounds on Φr in Bourgain-Golse-Wennberg [Commun. Math. Phys. 190, 491-508 (1998)]. We also discuss the applications of this result in the context of kinetic theory.

  18. Long-path-length experimental studies of longitudinal phenomena in intense beams

    NASA Astrophysics Data System (ADS)

    Beaudoin, Brian

    2015-11-01

    Intense charged particle beams are nonneutral plasmas and they can support a host of plasma waves and instabilities. For a long beam bunch, the longitudinal physics can often be reasonably described by a 1-D cold-fluid model, with a geometry factor to account for the transverse effects. The plasma physics of such beams has been extensively studied theoretically and computationally for decades, but until recently, the only experimental measurements were carried out on relatively short linacs. This work reviews experimental studies over the past 5 years on the U. Maryland Electron Ring, investigating longitudinal phenomena, for the first time, over time scales of hundreds and thousands of plasma periods. These results are in good agreement with theory and simulation. Topics that will be discussed are: Longitudinal confinement of a long bunch using barrier fields. The generation of space charge waves from barrier field mismatches, their propagation along the bunch and reflection at the beam ends, as well as their long-term dissipation. The characterization of solitary waves from density/velocity perturbations in the center of the bunch. Compression of solitary wave trains with velocity ``tilts'' (head-to-tail gradient). Observation of a multi-stream instability driven by the longitudinal merging of bunches and the characterization of the onset of the instability with a PIC code. The shock-wave compression of a bunch using rapidly-moving barrier fields.

  19. Experimental simulation of beam propagation over long path lengths using radio-frequency and magnetic traps

    NASA Astrophysics Data System (ADS)

    Okamoto, H.; Endo, M.; Fukushima, K.; Higaki, H.; Ito, K.; Moriya, K.; Yamaguchi, S.; Lund, S. M.

    2014-01-01

    An overview is given of the novel beam-dynamics experiments based on compact non-neutral plasma traps at Hiroshima University. We have designed and constructed two different classes of trap systems, one of which uses a radio-frequency electric field (Paul trap) and the other uses an axial magnetic field (Penning trap) for transverse plasma confinement. These systems are called "S-POD" (Simulator for Particle Orbit Dynamics). The S-POD systems can approximately reproduce the collective motion of a charged-particle beam propagating through long alternating-gradient (AG) quadrupole focusing channels using the Paul trap and long continuous focusing channels using the Penning trap. This allows us to study various beam-dynamics issues in compact and inexpensive experiments without relying on large-scale accelerators. So far, the linear Paul traps have been applied for the study of resonance-related issues including coherent-resonance-induced stop bands and their dependence on AG lattice structures, resonance crossing in fixed-field AG accelerators, ultralow-emittance beam stability, etc. The Penning trap with multi-ring electrodes has been employed primarily for the study of beam halo formation driven by initial distribution perturbations. In this paper, we briefly overview the S-POD systems, and then summarize recent experimental results on resonance effects and halo formation.

  20. Tail Asymptotics of Free Path Lengths for the Periodic Lorentz Process: On Dettmann's Geometric Conjectures

    NASA Astrophysics Data System (ADS)

    Nándori, Péter; Szász, Domokos; Varjú, Tamás

    2014-10-01

    In the simplest case, consider a -periodic ( d ≥ 3) arrangement of balls of radii < 1/2, and select a random direction and point (outside the balls). According to Dettmann's first conjecture, the probability that the so determined free flight (until the first hitting of a ball) is larger than t > > 1 is , where C is explicitly given by the geometry of the model. In its simplest form, Dettmann's second conjecture is related to the previous case with tangent balls (of radii 1/2). The conjectures are established in a more general setup: for -periodic configuration of—possibly intersecting—convex bodies with being a non-degenerate lattice. These questions are related to Pólya's visibility problem (Arch Math Phys Ser 2:135-142,1918), to theories of Bourgain et al. (Commun Math Phys 190:491-508,1998), and of Marklof-Strömbergsson (Ann Math 172:1949-2033,2010). The results also provide the asymptotic covariance of the periodic Lorentz process assuming it has a limit in the super-diffusive scaling, a fact if d = 2 and the horizon is infinite.

  1. Information flow in interaction networks II: channels, path lengths, and potentials.

    PubMed

    Stojmirović, Aleksandar; Yu, Yi-Kuo

    2012-04-01

    In our previous publication, a framework for information flow in interaction networks based on random walks with damping was formulated with two fundamental modes: emitting and absorbing. While many other network analysis methods based on random walks or equivalent notions have been developed before and after our earlier work, one can show that they can all be mapped to one of the two modes. In addition to these two fundamental modes, a major strength of our earlier formalism was its accommodation of context-specific directed information flow that yielded plausible and meaningful biological interpretation of protein functions and pathways. However, the directed flow from origins to destinations was induced via a potential function that was heuristic. Here, with a theoretically sound approach called the channel mode, we extend our earlier work for directed information flow. This is achieved by constructing a potential function facilitating a purely probabilistic interpretation of the channel mode. For each network node, the channel mode combines the solutions of emitting and absorbing modes in the same context, producing what we call a channel tensor. The entries of the channel tensor at each node can be interpreted as the amount of flow passing through that node from an origin to a destination. Similarly to our earlier model, the channel mode encompasses damping as a free parameter that controls the locality of information flow. Through examples involving the yeast pheromone response pathway, we illustrate the versatility and stability of our new framework.

  2. [Theoretical analysis of the single optical path spectrum detection in biological tissue].

    PubMed

    Chen, Yun; Du, Zhen-hui; Chen, Feng; Xu, Ke-xin

    2008-06-01

    The technology of spectrum detection with high sensitivity is of significance in clinic diagnosis and tissue optical parameter measurement. A new method of difference-modulated laser spectrum detection was developed in the present paper. The measuring light and the reference light are separated from the lasing light source in this method. After passing through the tissue, the measuring light interferes with the reference light, and the frequency character of spectrum includes the information of the difference of optical path-length between the measuring light and reference light. By using the phase sensitive detector, the spectrum signal with different frequency can be separated, and consequently the measuring light passed through the tissue with different optical length will be apart. The mechanism of difference-modulated laser spectrum was analyzed and the value of dominant frequency of spectrum was deduced. Based on the theory of the optical path distribution in biological tissue, the spectrum signature of measuring light was discussed also. The distribution of dominant frequency component is decided by the difference of optical path-length between measuring light and reference light when the modulation parameters are invariable, and the magnitude of tissue' s modulus decay will effect the energy distribution of spectrum frequencies component. Theoretical analysis showed that the method of difference modulation can be used to separate lights according to the optical path-length and realize the single optical path measurement in biological tissue.

  3. Seven-effect absorption refrigeration

    DOEpatents

    DeVault, R.C.; Biermann, W.J.

    1989-05-09

    A seven-effect absorption refrigeration cycle is disclosed utilizing three absorption circuits. In addition, a heat exchanger is used for heating the generator of the low absorption circuit with heat rejected from the condenser and absorber of the medium absorption circuit. A heat exchanger is also provided for heating the generator of the medium absorption circuit with heat rejected from the condenser and absorber of the high absorption circuit. If desired, another heat exchanger can also be provided for heating the evaporator of the high absorption circuit with rejected heat from either the condenser or absorber of the low absorption circuit. 1 fig.

  4. Seven-effect absorption refrigeration

    DOEpatents

    DeVault, Robert C.; Biermann, Wendell J.

    1989-01-01

    A seven-effect absorption refrigeration cycle is disclosed utilizing three absorption circuits. In addition, a heat exchanger is used for heating the generator of the low absorption circuit with heat rejected from the condenser and absorber of the medium absorption circuit. A heat exchanger is also provided for heating the generator of the medium absorption circuit with heat rejected from the condenser and absorber of the high absorption circuit. If desired, another heat exchanger can also be provided for heating the evaporator of the high absorption circuit with rejected heat from either the condenser or absorber of the low absorption circuit.

  5. Aircraft flight path angle display system

    NASA Technical Reports Server (NTRS)

    Lambregts, Antonius A. (Inventor)

    1991-01-01

    A display system for use in an aircraft control wheel steering system provides the pilot with a single, quickened flight path angle display to overcome poor handling qualities due to intrinsic flight path angle response lags, while avoiding multiple information display symbology. The control law for the flight path angle control system is designed such that the aircraft's actual flight path angle response lags the pilot's commanded flight path angle by a constant time lag .tau., independent of flight conditions. The synthesized display signal is produced as a predetermined function of the aircraft's actual flight path angle, the time lag .tau. and command inputs from the pilot's column.

  6. Walking on inclines: how do desert ants monitor slope and step length

    PubMed Central

    Seidl, Tobias; Wehner, Rüdiger

    2008-01-01

    Background During long-distance foraging in almost featureless habitats desert ants of the genus Cataglyphis employ path-integrating mechanisms (vector navigation). This navigational strategy requires an egocentric monitoring of the foraging path by incrementally integrating direction, distance, and inclination of the path. Monitoring the latter two parameters involves idiothetic cues and hence is tightly coupled to the ant's locomotor behavior. Results In a kinematic study of desert ant locomotion performed on differently inclined surfaces we aimed at pinpointing the relevant mechanisms of estimating step length and inclination. In a behavioral experiment with ants foraging on slippery surfaces we broke the otherwise tightly coupled relationship between stepping frequency and step length and examined the animals' ability to monitor distances covered even under those adverse conditions. We show that the ants' locomotor system is not influenced by inclined paths. After removing the effect of speed, slope had only marginal influence on kinematic parameters. Conclusion From the obtained data we infer that the previously proposed monitoring of angles of the thorax-coxa joint is not involved in inclinometry. Due to the tiny variations in cycle period, we also argue that an efference copy of the central pattern generator coding the step length in its output frequency will most likely not suffice for estimating step length and complementing the pedometer. Finally we propose that sensing forces acting on the ant's legs could provide the desired neuronal correlate employed in monitoring inclination and step length. PMID:18518946

  7. Handbook for the estimation of microwave propagation effects: Link calculations for earth-space paths (path loss and noise estimation)

    NASA Technical Reports Server (NTRS)

    Crane, R. K.; Blood, D. W.

    1979-01-01

    A single model for a standard of comparison for other models when dealing with rain attenuation problems in system design and experimentation is proposed. Refinements to the Global Rain Production Model are incorporated. Path loss and noise estimation procedures as the basic input to systems design for earth-to-space microwave links operating at frequencies from 1 to 300 GHz are provided. Topics covered include gaseous absorption, attenuation by rain, ionospheric and tropospheric scintillation, low elevation angle effects, radome attenuation, diversity schemes, link calculation, and receiver noise emission by atmospheric gases, rain, and antenna contributions.

  8. Correlation of solar energetic protons and polar cap absorption

    NASA Astrophysics Data System (ADS)

    Patterson, J. D.; Armstrong, T. P.; Laird, C. M.; Detrick, D. L.; Weatherwax, A. T.

    2001-01-01

    This study shows the results of a model of polar cap absorption events (PCAs) using solar energetic proton flux as an input. The proton data are recorded by the Charged Particle Measurement Experiment (CPME) on board the IMP 8 satellite and are collected by the Applied Physics Laboratory at Johns Hopkins University. The IMP 8 satellite orbits the Earth at distances between 30 and 35 Earth radii, which places it in the solar energetic particle environment throughout most of its orbit. It has been shown in previous studies that these solar energetic particles have direct and immediate access to the polar atmosphere [Reid, 1970]. Our model shows that the majority of the ionization resulting from the influx of solar energetic protons occurs in the altitude range from ~50-90 km. Excess ionization at these altitudes causes enhanced absorption of cosmic HF radio waves. The levels of absorption used for comparison in this study were measured directly by the riometer at South Pole station, Antarctica. The results show a very strong correlation between the incident proton flux and measured path-integrated cosmic HF radio noise absorption for significant events, involving absorptions greater than 1.0 dB. For absorption levels lower than this it is obvious that other phenomena dominate. For HF radio waves the primary contributors to PCA are protons with energies near 20 MeV. This study extends the correlated observations of interplanetary particles and PCA throughout a 9-year period. The close quantitative agreement between the measured and calculated values of absorption supports the validity of the assumptions and suppositions made by this model. The data also suggest a method by which the path-integrated cosmic noise absorption may be used to probe the E and D layers of the ionosphere to determine the effective ion-electron recombination coefficients within these regions.

  9. Long-path Atmospheric Measurements Using Dual Frequency Comb Spectroscopy

    NASA Astrophysics Data System (ADS)

    Cossel, K.; Truong, G. W.; Waxman, E.; Baumann, E.; Giorgetta, F.; Rieker, G. B.; Sinclair, L.; Swann, W.; Coddington, I.; Newbury, N.

    2015-12-01

    Dual frequency comb (DFC) spectroscopy is a new technique that combines broad spectral bandwidth, high spectral resolution, rapid data acquisition, and high sensitivity. In addition, unlike standard Fourier-transform spectroscopy, it has an almost ideal instrument lineshape function and does not require recalibration. These features make DFC spectroscopy well suited for accurate measurements of multiple species simultaneously. We have recently demonstrated DFC-based open-path measurements of several greenhouse gases in the 1.6-1.67 μm (6250-6000 cm-1) spectral region with 2 km of path length [Rieker et al, 2014]. This initial demonstration used laboratory-based lasers and achieved a sensitivity of 2.3 ppbv for CH4, 1 ppmv for CO2, and <1 ppmv for H2O and HDO with 5 minute measurement times. We are currently developing a portable system that will cover a wider spectral region (about 1.3-2.1 μm or 7700-4750 cm-1) with improved sensitivity. In this talk, we will provide an introduction to dual frequency comb spectroscopy and then discuss ongoing improvements to the open-path system. G. B. Rieker, F. R. Giorgetta, W. C. Swann, J. Kofler, A. M. Zolot, L. C. Sinclair, E. Baumann, C. Cromer, G. Petron, C. Sweeney, P. P. Tans, I. Coddington, and N. R. Newbury (2014), Frequency-comb-based remote sensing of greenhouse gases over kilometer air paths, Optica, 1(5), 290-298.

  10. Long gain length solar pumped box laser

    NASA Technical Reports Server (NTRS)

    Deyoung, R. J.

    1986-01-01

    A solar pumped laser has its lasing path lengthened by forming a square loop in the lasing path by means of bending mirrors. Solar radiation is collected and concentrated into a donut shaped intensity pattern. This intensity pattern is directed onto the lasing path such that there is a maximum fit of the solar intensity pattern to the square loop laser cavity.

  11. Quantum Entanglement Molecular Absorption Spectrum Simulator

    NASA Technical Reports Server (NTRS)

    Nguyen, Quang-Viet; Kojima, Jun

    2006-01-01

    Quantum Entanglement Molecular Absorption Spectrum Simulator (QE-MASS) is a computer program for simulating two photon molecular-absorption spectroscopy using quantum-entangled photons. More specifically, QE-MASS simulates the molecular absorption of two quantum-entangled photons generated by the spontaneous parametric down-conversion (SPDC) of a fixed-frequency photon from a laser. The two-photon absorption process is modeled via a combination of rovibrational and electronic single-photon transitions, using a wave-function formalism. A two-photon absorption cross section as a function of the entanglement delay time between the two photons is computed, then subjected to a fast Fourier transform to produce an energy spectrum. The program then detects peaks in the Fourier spectrum and displays the energy levels of very short-lived intermediate quantum states (or virtual states) of the molecule. Such virtual states were only previously accessible using ultra-fast (femtosecond) laser systems. However, with the use of a single-frequency continuous wave laser to produce SPDC photons, and QEMASS program, these short-lived molecular states can now be studied using much simpler laser systems. QE-MASS can also show the dependence of the Fourier spectrum on the tuning range of the entanglement time of any externally introduced optical-path delay time. QE-MASS can be extended to any molecule for which an appropriate spectroscopic database is available. It is a means of performing an a priori parametric analysis of entangled photon spectroscopy for development and implementation of emerging quantum-spectroscopic sensing techniques. QE-MASS is currently implemented using the Mathcad software package.

  12. Physarum can compute shortest paths.

    PubMed

    Bonifaci, Vincenzo; Mehlhorn, Kurt; Varma, Girish

    2012-09-21

    Physarum polycephalum is a slime mold that is apparently able to solve shortest path problems. A mathematical model has been proposed by Tero et al. (Journal of Theoretical Biology, 244, 2007, pp. 553-564) to describe the feedback mechanism used by the slime mold to adapt its tubular channels while foraging two food sources s(0) and s(1). We prove that, under this model, the mass of the mold will eventually converge to the shortest s(0)-s(1) path of the network that the mold lies on, independently of the structure of the network or of the initial mass distribution. This matches the experimental observations by Tero et al. and can be seen as an example of a "natural algorithm", that is, an algorithm developed by evolution over millions of years.

  13. Path similarity skeleton graph matching.

    PubMed

    Bai, Xiang; Latecki, Longin Jan

    2008-07-01

    This paper presents a novel framework to for shape recognition based on object silhouettes. The main idea is to match skeleton graphs by comparing the shortest paths between skeleton endpoints. In contrast to typical tree or graph matching methods, we completely ignore the topological graph structure. Our approach is motivated by the fact that visually similar skeleton graphs may have completely different topological structures. The proposed comparison of shortest paths between endpoints of skeleton graphs yields correct matching results in such cases. The skeletons are pruned by contour partitioning with Discrete Curve Evolution, which implies that the endpoints of skeleton branches correspond to visual parts of the objects. The experimental results demonstrate that our method is able to produce correct results in the presence of articulations, stretching, and occlusion.

  14. Squeezed states and path integrals

    NASA Technical Reports Server (NTRS)

    Daubechies, Ingrid; Klauder, John R.

    1992-01-01

    The continuous-time regularization scheme for defining phase-space path integrals is briefly reviewed as a method to define a quantization procedure that is completely covariant under all smooth canonical coordinate transformations. As an illustration of this method, a limited set of transformations is discussed that have an image in the set of the usual squeezed states. It is noteworthy that even this limited set of transformations offers new possibilities for stationary phase approximations to quantum mechanical propagators.

  15. Microwave absorption by nanoresonator vibrations tuned with surface modification

    NASA Astrophysics Data System (ADS)

    Krivosudský, Ondrej; Cifra, Michal

    2016-08-01

    Elucidating the physical and chemical parameters that govern viscous damping of nanoresonator vibrations and their coupling to electromagnetic radiation is important for understanding the behavior of matter at the nanoscale. Here we develop an analytical model of microwave absorption of a longitudinally oscillating and electrically polar rod-like nanoresonator embedded in a viscoelastic fluid. We show that the slip length, which can be tuned via surface modifications, controls the quality factor and coupling of nanoresonator vibration modes to microwave radiation. We demonstrate that the larger slip length brings the sharper frequency response of the nanoresonator vibration and electromagnetic absorption. Our findings contribute to design guidelines of fluid embedded nanoresonator devices.

  16. Accelerating cleanup: Paths to closure

    SciTech Connect

    Edwards, C.

    1998-06-30

    This document was previously referred to as the Draft 2006 Plan. As part of the DOE`s national strategy, the Richland Operations Office`s Paths to Closure summarizes an integrated path forward for environmental cleanup at the Hanford Site. The Hanford Site underwent a concerted effort between 1994 and 1996 to accelerate the cleanup of the Site. These efforts are reflected in the current Site Baseline. This document describes the current Site Baseline and suggests strategies for further improvements in scope, schedule and cost. The Environmental Management program decided to change the name of the draft strategy and the document describing it in response to a series of stakeholder concerns, including the practicality of achieving widespread cleanup by 2006. Also, EM was concerned that calling the document a plan could be misconstrued to be a proposal by DOE or a decision-making document. The change in name, however, does not diminish the 2006 vision. To that end, Paths to Closure retains a focus on 2006, which serves as a point in time around which objectives and goals are established.

  17. Path planning under spatial uncertainty.

    PubMed

    Wiener, Jan M; Lafon, Matthieu; Berthoz, Alain

    2008-04-01

    In this article, we present experiments studying path planning under spatial uncertainties. In the main experiment, the participants' task was to navigate the shortest possible path to find an object hidden in one of four places and to bring it to the final destination. The probability of finding the object (probability matrix) was different for each of the four places and varied between conditions. Givensuch uncertainties about the object's location, planning a single path is not sufficient. Participants had to generate multiple consecutive plans (metaplans)--for example: If the object is found in A, proceed to the destination; if the object is not found, proceed to B; and so on. The optimal solution depends on the specific probability matrix. In each condition, participants learned a different probability matrix and were then asked to report the optimal metaplan. Results demonstrate effective integration of the probabilistic information about the object's location during planning. We present a hierarchical planning scheme that could account for participants' behavior, as well as for systematic errors and differences between conditions.

  18. Active stabilization of a fiber-optic two-photon interferometer using continuous optical length control.

    PubMed

    Cho, Seok-Beom; Kim, Heonoh

    2016-05-16

    The practical realization of long-distance entanglement-based quantum communication systems strongly rely on the observation of highly stable quantum interference between correlated single photons. This task must accompany active stabilization of the optical path lengths within the single-photon coherence length. Here, we provide two-step interferometer stabilization methods employing continuous optical length control and experimentally demonstrate two-photon quantum interference using an actively stabilized 6-km-long fiber-optic Hong-Ou-Mandel interferometer. The two-step active control techniques are applied for measuring highly stable two-photon interference fringes by scanning the optical path-length difference. The obtained two-photon interference visibilities with and without accidental subtraction are found to be approximately 90.7% and 65.4%, respectively.

  19. Electron Inelastic-Mean-Free-Path Database

    National Institute of Standards and Technology Data Gateway

    SRD 71 NIST Electron Inelastic-Mean-Free-Path Database (PC database, no charge)   This database provides values of electron inelastic mean free paths (IMFPs) for use in quantitative surface analyses by AES and XPS.

  20. Recovery of acetylene absorption line profile basing on tunable diode laser spectroscopy with intensity modulation and photoacoustic spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, Li; Thursby, Graham; Stewart, George; Arsad, Norhana; Uttamchandani, Deepak; Culshaw, Brian; Wang, Yiding

    2010-04-01

    A novel and direct absorption line recovery technique based on tunable diode laser spectroscopy with intensity modulation is presented. Photoacoustic spectroscopy is applied for high sensitivity, zero background and efficient acoustic enhancement at a low modulation frequency. A micro-electromechanical systems (MEMS) mirror driven by an electrothermal actuator is used for generating laser intensity modulation (without wavelength modulation) through the external reflection. The MEMS mirror with 10μm thick structure material layer and 100nm thick gold coating is formed as a circular mirror of 2mm diameter attached to an electrothermal actuator and is fabricated on a chip that is wire-bonded and placed on a PCB holder. Low modulation frequency is adopted (since the resonant frequencies of the photoacoustic gas cell and the electrothermal actuator are different) and intrinsic high signal amplitude characteristics in low frequency region achieved from measured frequency responses for the MEMS mirror and the gas cell. Based on the property of photoacoustic spectroscopy and Beer's law that detectable sensitivity is a function of input laser intensity in the case of constant gas concentration and laser path length, a Keopsys erbium doped fibre amplifier (EDFA) with opto-communication C band and high output power up to 1W is chosen to increase the laser power. High modulation depth is achieved through adjusting the MEMS mirror's reflection position and driving voltage. In order to scan through the target gas absorption line, the temperature swept method is adopted for the tunable distributed feed-back (DFB) diode laser working at 1535nm that accesses the near-infrared vibration-rotation spectrum of acetylene. The profile of acetylene P17 absorption line at 1535.39nm is recovered ideally for ~100 parts-per-million (ppm) acetylene balanced by nitrogen. The experimental signal to noise ratio (SNR) of absorption line recovery for 500mW laser power was ~80 and hence the

  1. Multiple Paths to Encephalization and Technical Civilizations

    NASA Astrophysics Data System (ADS)

    Schwartzman, David; Middendorf, George

    2011-12-01

    We propose consideration of at least two possible evolutionary paths for the emergence of intelligent life with the potential for technical civilization. The first is the path via encephalization of homeothermic animals; the second is the path to swarm intelligence of so-called superorganisms, in particular the social insects. The path to each appears to be facilitated by environmental change: homeothermic animals by decreased climatic temperature and for swarm intelligence by increased oxygen levels.

  2. Path-Based Supports for Hypergraphs

    NASA Astrophysics Data System (ADS)

    Brandes, Ulrik; Cornelsen, Sabine; Pampel, Barbara; Sallaberry, Arnaud

    A path-based support of a hypergraph H is a graph with the same vertex set as H in which each hyperedge induces a Hamiltonian subgraph. While it is NP-complete to compute a path-based support with the minimum number of edges or to decide whether there is a planar path-based support, we show that a path-based tree support can be computed in polynomial time if it exists.

  3. When Does Length Cause the Word Length Effect?

    ERIC Educational Resources Information Center

    Jalbert, Annie; Neath, Ian; Bireta, Tamra J.; Surprenant, Aimee M.

    2011-01-01

    The word length effect, the finding that lists of short words are better recalled than lists of long words, has been termed one of the benchmark findings that any theory of immediate memory must account for. Indeed, the effect led directly to the development of working memory and the phonological loop, and it is viewed as the best remaining…

  4. IMF Length Scales and Predictability: The Two Length Scale Medium

    NASA Technical Reports Server (NTRS)

    Collier, Michael R.; Szabo, Adam; Slavin, James A.; Lepping, R. P.; Kokubun, S.

    1999-01-01

    We present preliminary results from a systematic study using simultaneous data from three spacecraft, Wind, IMP 8 (Interplanetary Monitoring Platform) and Geotail to examine interplanetary length scales and their implications on predictability for magnetic field parcels in the typical solar wind. Time periods were selected when the plane formed by the three spacecraft included the GSE (Ground Support Equipment) x-direction so that if the parcel fronts were strictly planar, the two adjacent spacecraft pairs would determine the same phase front angles. After correcting for the motion of the Earth relative to the interplanetary medium and deviations in the solar wind flow from radial, we used differences in the measured front angle between the two spacecraft pairs to determine structure radius of curvature. Results indicate that the typical radius of curvature for these IMF parcels is of the order of 100 R (Sub E). This implies that there are two important IMF (Interplanetary Magnetic Field) scale lengths relevant to predictability: (1) the well-established scale length over which correlations observed by two spacecraft decay along a given IMF parcel, of the order of a few tens of Earth radii and (2) the scale length over which two spacecraft are unlikely to even observe the same parcel because of its curvature, of the order of a hundred Earth radii.

  5. CEBAF Upgrade Bunch Length Measurements

    SciTech Connect

    Ahmad, Mahmoud

    2016-05-01

    Many accelerators use short electron bunches and measuring the bunch length is important for efficient operations. CEBAF needs a suitable bunch length because bunches that are too long will result in beam interruption to the halls due to excessive energy spread and beam loss. In this work, bunch length is measured by invasive and non-invasive techniques at different beam energies. Two new measurement techniques have been commissioned; a harmonic cavity showed good results compared to expectations from simulation, and a real time interferometer is commissioned and first checkouts were performed. Three other techniques were used for measurements and comparison purposes without modifying the old procedures. Two of them can be used when the beam is not compressed longitudinally while the other one, the synchrotron light monitor, can be used with compressed or uncompressed beam.

  6. Spatio-Temporal Structure, Path Characteristics, and Perceptual Grouping in Immediate Serial Spatial Recall

    PubMed Central

    De Lillo, Carlo; Kirby, Melissa; Poole, Daniel

    2016-01-01

    Immediate serial spatial recall measures the ability to retain sequences of locations in short-term memory and is considered the spatial equivalent of digit span. It is tested by requiring participants to reproduce sequences of movements performed by an experimenter or displayed on a monitor. Different organizational factors dramatically affect serial spatial recall but they are often confounded or underspecified. Untangling them is crucial for the characterization of working-memory models and for establishing the contribution of structure and memory capacity to spatial span. We report five experiments assessing the relative role and independence of factors that have been reported in the literature. Experiment 1 disentangled the effects of spatial clustering and path-length by manipulating the distance of items displayed on a touchscreen monitor. Long-path sequences segregated by spatial clusters were compared with short-path sequences not segregated by clusters. Recall was more accurate for sequences segregated by clusters independently from path-length. Experiment 2 featured conditions where temporal pauses were introduced between or within cluster boundaries during the presentation of sequences with the same paths. Thus, the temporal structure of the sequences was either consistent or inconsistent with a hierarchical representation based on segmentation by spatial clusters but the effect of structure could not be confounded with effects of path-characteristics. Pauses at cluster boundaries yielded more accurate recall, as predicted by a hierarchical model. In Experiment 3, the systematic manipulation of sequence structure, path-length, and presence of path-crossings of sequences showed that structure explained most of the variance, followed by the presence/absence of path-crossings, and path-length. Experiments 4 and 5 replicated the results of the previous experiments in immersive virtual reality navigation tasks where the viewpoint of the observer changed

  7. The Development of Diode Laser Infrared Absorption Spectroscopy as a Plasma Diagnostic.

    NASA Astrophysics Data System (ADS)

    McClain, Robert Leslie

    A high resolution infrared spectrometer based on a tunable lead salt diode laser has been interfaced to both a DC glow discharge and to the downstream region of an ECR plasma etcher. In each case high sensitivity is achieved by multi-passing the infrared beam, using a Herriott type optical arrangement consisting of two facing spherical mirrors. In the DC discharge a 1 m long by 15 cm diameter section of the positive column is sampled using typically 42 passes between 10 cm mirrors roughly 2 m apart. In the ECR device a region approximately 50 cm downstream from the ECR layer of a 0-1 kW ASTeX source is sampled. Effective path lengths of about 9 m are achieved with 30 passes. The abundance of CF_2 in discharges of CF_4 and mixtures of CF _4 and either 0_2 or CHF_3 has been obtained by measuring the fractional absorption in several rotational lines of the upsilon_3 band (asymmetric stretch) near 1095 cm^{-1} (9.1 mu). Rotational temperatures are determined only approximately, but are close to room temperature as expected. The derived concentration of CF_2 is 1.75 times 10^{11} cm ^{-3} in a CF_4 plasma in the ECR etcher at 800 W excitation and 2 mTorr pressure, while in the DC discharge positive column at 20 mTorr and 40 mA it is 1.11 times 10^{12} cm^ {-3}. Dependence on pressure and excitation has been determined over a limited range. In the ECR etcher, the concentration of CF_3 has been determined from the measured fractional absorption of a selected R-branch transition of the upsilon _3 band at 1266.714 cm^{ -1}. The density is 9.5 times 10^{11} cm ^{-3} in a CF_4 plasma at 2 mTorr and 800 W. The CF_3 density has also been monitored over a limited range of excitation power, pressure, and gas composition. Absorption lines of the parent species CF_4 are also easily observed and followed, and those of the polymerization product C_2F _6 were detected in the DC discharge. In the ECR plasma, which uses a quartz liner in the source to mitigate sputtering, strong

  8. Modelling and implementation of a fixed-length-extension to measure fluorescent intensity in bioprocesses using an optical sensor

    NASA Astrophysics Data System (ADS)

    Sardesai, Neha; Al-Adhami, Mustafa; Rao, Govind; Kostov, Yordan

    2016-05-01

    Fluorescent proteins are often used as reporters of protein concentration in biology and biomedicine applications. They can be detected using a fluorimeter equipped with fiber optics for ease of access. However, small changes in the path length due to change in the position, or immersion depth of the optical fiber results in large changes in readings. To alleviate the situation, the fiber is equipped with a fixed-length-extension that provides constant path length. The operation of the fiber equipped fluorimeter is theoretically modelled and practically verified in this paper.

  9. Performance Analysis of Path Planning Modeling

    NASA Astrophysics Data System (ADS)

    Wang, Zhirui; Li, Shuanghong; Zhang, Ying; Du, Qiaoling

    Ant colony system (ACS) algorithm was applied to the path planning for the robot. In the same working environment, path planning based on MAKLINK graph theory and Voronoi diagram were simulated and compared. MAKLINK graph theory is appropriate to apply to precise searching in small-scale district, and Voronoi diagram is suitable for fast path planning in a large area.

  10. Evaluation of the Learning Path Specification

    ERIC Educational Resources Information Center

    Janssen, Jose; Berlanga, Adriana J.; Koper, Rob

    2011-01-01

    Flexible lifelong learning requires that learners can compare and select learning paths that best meet individual needs, not just in terms of learning goals, but also in terms of planning, costs etc. To this end a learning path specification was developed, which describes both the contents and the structure of any learning path, be it formal,…

  11. Time-multiplexed open-path TDLAS spectrometer for dynamic, sampling-free, interstitial H2 18O and H2 16O vapor detection in ice clouds

    NASA Astrophysics Data System (ADS)

    Kühnreich, B.; Wagner, S.; Habig, J. C.; Möhler, O.; Saathoff, H.; Ebert, V.

    2015-04-01

    An advanced in situ diode laser hygrometer for simultaneous, sampling-free detection of interstitial H2 16O and H2 18O vapor was developed and tested in the aerosol interaction and dynamics in atmosphere (AIDA) cloud chamber during dynamic cloud formation processes. The spectrometer to measure isotope-resolved water vapor concentrations comprises two rapidly time-multiplexed DFB lasers near 1.4 and 2.7 µm and an open-path White cell with 227-m absorption path length and 4-m mirror separation. A dynamic water concentration range from 2.6 ppb to 87 ppm for H2 16O and 87 ppt to 3.6 ppm for H2 18O could be achieved and was used to enable a fast and direct detection of dynamic isotope ratio changes during ice cloud formation in the AIDA chamber at temperatures between 190 and 230 K. Relative changes in the H2 18O/H2 16O isotope ratio of 1 % could be detected and resolved with a signal-to-noise ratio of 7. This converts to an isotope ratio resolution limit of 0.15 % at 1-s time resolution.

  12. Absorption heat pump system

    DOEpatents

    Grossman, Gershon; Perez-Blanco, Horacio

    1984-01-01

    An improvement in an absorption heat pump cycle is obtained by adding adiabatic absorption and desorption steps to the absorber and desorber of the system. The adiabatic processes make it possible to obtain the highest temperature in the absorber before any heat is removed from it and the lowest temperature in the desorber before heat is added to it, allowing for efficient utilization of the thermodynamic availability of the heat supply stream. The improved system can operate with a larger difference between high and low working fluid concentrations, less circulation losses, and more efficient heat exchange than a conventional system.

  13. Absorption Heat Pump Cycles

    NASA Astrophysics Data System (ADS)

    Kunugi, Yoshifumi; Kashiwagi, Takao

    Various advanced absorption cycles are studied, developed and invented. In this paper, their cycles are classified and arranged using the three categories: effect, stage and loop, then an outline of the cycles are explained on the Duehring diagram. Their cycles include high COP cycles for refrigerations and heat pumps, high temperature lift cycles for heat transformer, absorption-compression hybrid cycles and heat pump transformer cycle. The highest COPi is attained by the seven effect cycle. In addition, the cycles for low temperature are invented and explained. Furthermore the power generation • refrigeration cycles are illustrated.

  14. Stress-induced crack path in Aji granite under tensile stress

    NASA Astrophysics Data System (ADS)

    Kudo, Yozo; Sano, Osam; Murashige, Naokuni; Mizuta, Yoshiaki; Nakagawa, Koji

    1992-12-01

    The double-torsion test using Aji granite was carried out to investigate the interaction between stress-induced crack path and mineral grains. Crack velocities were controlled at range 10-7 m/s to 10-1 m/s. After the stressed specimens were dyed, we checked the crack path by thin section analysis, using an optical microscope. The stress-induced crack path was divided into two types, transgranular and intergranular cracks, and each path was subdivided with respect to mineral grains. In spite of the extensive range of crack velocities, the ratios between the transgranular and intergranular crack lengths did not change. The crack paths were all jagged, and often showed detour around the grain boundary when faced with obstacles like hard grains or preexisting cracks. That is to say, quartz grain played an important role as an obstacle. Feldspar grain could change the crack path because of its cleavage plane. Biolite grain had a serious effect on the path even if its constitution ratio is very small. Fractal dimensions of the crack paths were calculated by three methods, as indicators of surface roughness. The fractal dimensions were shown in a slight trend with the change of crack velocity. This trend can be explained from the point of limited cracking rate in stress corrosion.

  15. Continuous lengths of oxide superconductors

    DOEpatents

    Kroeger, Donald M.; List, III, Frederick A.

    2000-01-01

    A layered oxide superconductor prepared by depositing a superconductor precursor powder on a continuous length of a first substrate ribbon. A continuous length of a second substrate ribbon is overlaid on the first substrate ribbon. Sufficient pressure is applied to form a bound layered superconductor precursor powder between the first substrate ribbon and the second substrate ribbon. The layered superconductor precursor is then heat treated to establish the oxide superconducting phase. The layered oxide superconductor has a smooth interface between the substrate and the oxide superconductor.

  16. FTIR-spectrometer-determined absorption coefficients of seven hydrazine fuel gases - Implications for laser remote sensing

    NASA Technical Reports Server (NTRS)

    Molina, L. T.; Grant, W. B.

    1984-01-01

    The absorption spectra of three hydrazines and four of their air-oxidation products were measured in the 9-12-micron spectral region with a Fourier transform infrared (FTIR) spectrometer with a 0.05-kayser resolution to determine absorption coefficients at CO2 and tunable diode laser wavelengths. The measurements agreed well with published CO2 laser determinations for many of the absorption coefficients, except where the published values are thought to be in error. The coefficients were then used to estimate the sensitivity for remote detection of these gases using CO2 and tunable diode lasers in long-path differential absorption measurements.

  17. Path Relaxation: Path Planning for a Mobile Robot.

    DTIC Science & Technology

    1984-04-01

    15213 April 1984 JUN 5 1984 Copyright © 1984 Mobile Robot Laboratory, Carnegie-Mellon University The CMU Rover has been supported at the Carnegie-Mellon...particular robot or mission. Path Relaxation is part of Fido, the vision and navigation system of the CM L Rover mol)ile robot. [29, 411 The Rover , under...their 31) positions relative to the Rover . The Rover will then move about half a meter, take a new pair of pictires, find the 40 tracked points in each of

  18. Z-path SAW RFID tag.

    PubMed

    Härmä, Sanna; Plessky, Victor P; Hartmann, Clinton S; Steichen, William

    2008-01-01

    Surface acoustic wave (SAW) radio-frequency identification (RFID) tags are soon expected to be produced in very high volumes. The size and cost of a SAW RFID tag will be key parameters for many applications. Therefore, it is of primary importance to reduce the chip size. In this work, we describe the design principles of a 2.4-GHz SAW RFID tag that is significantly smaller than earlier reported tags. We also present simulated and experimental results. The coded signal should arrive at the reader with a certain delay (typically about 1 micros), i.e., after the reception of environmental echoes. If the tag uses a bidirectional interdigital transducer (IDT), space for the initial delay is needed on both sides of the IDT. In this work, we replace the bidirectional IDT by a unidirectional one. This halves the space required by the initial delay because all the code reflectors must now be placed on the same side of the IDT. We reduce tag size even further by using a Z-path geometry in which the same space in x-direction is used for both the initial delay and the code reflectors. Chip length is thus determined only by the space required by the code reflectors.

  19. Tunable optical-path correlator for distributed strain or temperature-sensing application.

    PubMed

    Yuan, Yonggui; Wu, Bing; Yang, Jun; Yuan, Libo

    2010-10-15

    Based on a cavity-length tunable fiber-loop resonator, a multibeam optical path difference is generated. It can be used to match and correlate the reflective signals from the partial reflective ends of each sensing fiber gauge. The correlation signals correspond to the sensing gauge lengths, and the shift of the correlation peak is related with the fiber sensing gauge elongation caused by strain or temperature. Therefore, it can be used to measure distributed strain or deformation for smart structural monitoring.

  20. Incubation length of dabbling ducks

    USGS Publications Warehouse

    Wells-Berlin, A. M.; Prince, H.H.; Arnold, T.W.

    2005-01-01

    We collected unincubated eggs from wild Mallard (Anas platyrhynchos), Gadwall (A. strepera), Blue-winged Teal (A. discors), and Northern Shoveler (A. clypeata) nests and artificially incubated them at 37.5??C. Average incubation lengths of Mallard, Gadwall, and Northern Shoveler eggs did not differ from their wild-nesting counterparts, but artificially incubated Blue-winged Teal eggs required an additional 1.7 days to hatch, suggesting that wild-nesting teal incubated more effectively. A small sample of Mallard, Gadwall, and Northern Shoveler eggs artificially incubated at 38.3??C hatched 1 day sooner, indicating that incubation temperature affected incubation length. Mean incubation length of Blue-winged Teal declined by 1 day for each 11-day delay in nesting, but we found no such seasonal decline among Mallards, Gadwalls, or Northern Shovelers. There is no obvious explanation for the seasonal reduction in incubation length for Blue-winged Teal eggs incubated in a constant environment, and the phenomenon deserves further study. ?? The Cooper Ornithological Society 2005.

  1. Finite length Taylor Couette flow

    NASA Technical Reports Server (NTRS)

    Streett, C. L.; Hussaini, M. Y.

    1987-01-01

    Axisymmetric numerical solutions of the unsteady Navier-Stokes equations for flow between concentric rotating cylinders of finite length are obtained by a spectral collocation method. These representative results pertain to two-cell/one-cell exchange process, and are compared with recent experiments.

  2. Persistent Criminality and Career Length

    ERIC Educational Resources Information Center

    Haapanen, Rudy; Britton, Lee; Croisdale, Tim

    2007-01-01

    This study is an examination of persistent offending and its implications for the understanding and investigation of desistance and career length. Persistence, especially as it is operationalized using official measures, is characterized as fundamentally a measure of resistance to formal social control: continued crime in the face of increasingly…

  3. Two-Phonon Absorption

    ERIC Educational Resources Information Center

    Hamilton, M. W.

    2007-01-01

    A nonlinear aspect of the acousto-optic interaction that is analogous to multi-photon absorption is discussed. An experiment is described in which the second-order acousto-optically scattered intensity is measured and found to scale with the square of the acoustic intensity. This experiment using a commercially available acousto-optic modulator is…

  4. Characterizing the Evolutionary Path(s) to Early Homo

    PubMed Central

    Schroeder, Lauren; Roseman, Charles C.; Cheverud, James M.; Ackermann, Rebecca R.

    2014-01-01

    Numerous studies suggest that the transition from Australopithecus to Homo was characterized by evolutionary innovation, resulting in the emergence and coexistence of a diversity of forms. However, the evolutionary processes necessary to drive such a transition have not been examined. Here, we apply statistical tests developed from quantitative evolutionary theory to assess whether morphological differences among late australopith and early Homo species in Africa have been shaped by natural selection. Where selection is demonstrated, we identify aspects of morphology that were most likely under selective pressure, and determine the nature (type, rate) of that selection. Results demonstrate that selection must be invoked to explain an Au. africanus—Au. sediba—Homo transition, while transitions from late australopiths to various early Homo species that exclude Au. sediba can be achieved through drift alone. Rate tests indicate that selection is largely directional, acting to rapidly differentiate these taxa. Reconstructions of patterns of directional selection needed to drive the Au. africanus—Au. sediba—Homo transition suggest that selection would have affected all regions of the skull. These results may indicate that an evolutionary path to Homo without Au. sediba is the simpler path and/or provide evidence that this pathway involved more reliance on cultural adaptations to cope with environmental change. PMID:25470780

  5. Characteristic length of glass transition

    NASA Astrophysics Data System (ADS)

    Donth, E.

    1996-03-01

    The characteristic length of the glass transition (ξ _α ) is based on the concept of cooperatively rearranging regions (CRR's) by Adam & Gibbs (1965): ξ _α is the diameter of one CRR. In the theoretical part of the talk a formula is derived how this length can be calculated from calorimetric data of the transformation interval. The approach is based on fluctuations in natural functional subsystems. The corresponding thermodynamics is represented e.g. in a book of the author (E. Donth, Relaxation and Thermodynamics in Polymers. Glass Transition, Akademie-Verlag, Berlin 1992). A typical value for this length is 3 nanometers. In the experimental part several examples are reported to enlarge the experimental evidence for such a length: Squeezing the glass transition in the amorphous layers of partially crystallized PET (C. Schick, Rostock), glass transition of small-molecule glass formers in a series of nanoscaled pores of porous glasses (F. Kremer, Leipzig), comparison with a concentration fluctuation model in homogeneous polymer mixtures (E.W. Fischer, Mainz), and, from our laboratory, backscaling to ξ _α across the main transition from the entanglement spacing in several amorphous polymers such as PVAC, PS, NR, and some polymer networks. Rouse backscaling was possible in the α β splitting region of several poly(n alkyl methacrylates) resulting in small characteristic lengths of order 1 nanometer near the onset of α cooperativity. In a speculative outlook a dynamic density pattern is presented, having a cellular structure with higher density and lower mobility of the cell walls. It will be explained, with the aid of different thermal expansion of wall and clusters, how the clusters within the cells maintain a certain mobility far below the glass temperature.

  6. Initial investigation of the wavelength dependence of optical properties measured with a new multi-pass Aerosol Extinction Differential Optical Absorption Spectrometer (AE-DOAS)

    NASA Astrophysics Data System (ADS)

    Chartier, R. T.; Greenslade, M. E.

    2012-04-01

    Atmospheric aerosols directly affect climate by scattering and absorbing radiation. The magnitude of the impact is dependent upon the wavelength of light, but is often estimated near 550 nm. When light scattering and absorption by aerosols is approximated, the wavelength dependence of the refractive index for specific components is lost. As a result, climate models would have inherent uncertainties for aerosol contributions to radiative forcing when considering the entire solar spectrum. An aerosol extinction differential optical absorption spectrometer has been developed to directly measure aerosol extinction at mid-ultraviolet to near infrared wavelengths. The instrument consists of a spectrometer coupled to a closed White-type multi-pass gas cell with an adjustable path length of up to approximately 20 m. Laboratory measurements of various gases are compared with known absorption cross sections. Additionally, the extinction of monodisperse samples of polystyrene latex spheres are measured and compared to Mie theory generated with refractive index values from the literature to validate the new instrument. The polystyrene experiments also emphasize the ability of the new instrument to retrieve the wavelength dependent refractive index, especially in the ultraviolet wavelength regions where variability is expected. The spectrometer will be a significant advancement for determining wavelength dependent complex refractive indices in future laboratory studies as well as provide the ability to monitor ambient aerosol light extinction.

  7. Initial investigation of the wavelength dependence of optical properties measured with a new multi-pass aerosol extinction differential optical absorption spectrometer (AE-DOAS)

    NASA Astrophysics Data System (ADS)

    Chartier, R. T.; Greenslade, M. E.

    2011-10-01

    Atmospheric aerosols directly affect climate by scattering and absorbing radiation. The magnitude of the impact is dependent upon the wavelength of light, but is often estimated near 550 nm. When light scattering and absorption by aerosols is approximated, the wavelength dependence of the refractive index for specific components is lost. As a result, climate models would have inherent uncertainties for aerosol contributions to radiative forcing when considering the entire solar spectrum. An aerosol extinction differential optical absorption spectrometer has been developed to directly measure aerosol extinction at mid-ultraviolet to near infrared wavelengths. The instrument consists of a spectrometer coupled to a closed White-type multi-pass gas cell with an adjustable path length of up to approximately 20 m. Laboratory measurements of various gases are compared with known absorption cross sections. Additionally, the extinction of monodisperse samples of polystyrene latex spheres are measured and compared to Mie theory generated with refractive index values from the literature to validate the new instrument. The polystyrene experiments also emphasize the ability of the new instrument to retrieve the wavelength dependent refractive index, especially in the ultraviolet wavelength regions where variability is expected. The spectrometer will be a significant advancement for determining wavelength dependent complex refractive indices in future laboratory studies as well as provide the ability to monitor ambient aerosol light extinction.

  8. Open Path Trace Gas Laser Sensors for UAV Deployment

    NASA Astrophysics Data System (ADS)

    Shadman, S.; Mchale, L.; Rose, C.; Yalin, A.

    2015-12-01

    Novel trace gas sensors based on open-path Cavity Ring-down Spectroscopy (CRDS) are being developed to enable remote and mobile deployments including on small unmanned aerial systems (UAS). Relative to established closed-path CRDS instruments, the use of open-path configurations allows removal of the bulky and power hungry vacuum and flow system, potentially enabling lightweight and low power instruments with high sensitivity. However, open path operation introduces new challenges including the need to maintain mirror cleanliness, mitigation of particle optical effects, and the need to measure spectral features that are relatively broad. The present submission details open-path CRDS instruments for ammonia and methane and their planned use in UAS studies. The ammonia sensor uses a quantum cascade laser at 10.3 mm in a configuration in which the laser frequency is continuously swept and a trigger circuit and acousto-optic modulator (AOM) extinguish the light when the laser is resonant with the cavity. Ring-down signals are measured with a two-stage thermoelectrically cooled MCT photodetector. The cavity mirrors have reflectivity of 0.9995 and a noise equivalent absorption of 1.5 ppb Hz-1/2 was demonstrated. A first version of the methane sensor operated at 1.7um with a telecom diode laser while the current version operates at 3.6 um with an interband cascade laser (stronger absorption). We have performed validation measurements against known standards for both sensors. Compact optical assemblies are being developed for UAS deployment. For example, the methane sensor head will have target mass of <4 kg and power draw <40 W. A compact single board computer and DAQ system is being designed for sensor control and signal processing with target mass <1 kg and power draw <10 W. The sensor size and power parameters are suitable for UAS deployment on both fixed wing and rotor style UAS. We plan to deploy the methane sensor to measure leakage and emission of methane from

  9. Attention trees and semantic paths

    NASA Astrophysics Data System (ADS)

    Giusti, Christian; Pieroni, Goffredo G.; Pieroni, Laura

    2007-02-01

    In the last few decades several techniques for image content extraction, often based on segmentation, have been proposed. It has been suggested that under the assumption of very general image content, segmentation becomes unstable and classification becomes unreliable. According to recent psychological theories, certain image regions attract the attention of human observers more than others and, generally, the image main meaning appears concentrated in those regions. Initially, regions attracting our attention are perceived as a whole and hypotheses on their content are formulated; successively the components of those regions are carefully analyzed and a more precise interpretation is reached. It is interesting to observe that an image decomposition process performed according to these psychological visual attention theories might present advantages with respect to a traditional segmentation approach. In this paper we propose an automatic procedure generating image decomposition based on the detection of visual attention regions. A new clustering algorithm taking advantage of the Delaunay- Voronoi diagrams for achieving the decomposition target is proposed. By applying that algorithm recursively, starting from the whole image, a transformation of the image into a tree of related meaningful regions is obtained (Attention Tree). Successively, a semantic interpretation of the leaf nodes is carried out by using a structure of Neural Networks (Neural Tree) assisted by a knowledge base (Ontology Net). Starting from leaf nodes, paths toward the root node across the Attention Tree are attempted. The task of the path consists in relating the semantics of each child-parent node pair and, consequently, in merging the corresponding image regions. The relationship detected in this way between two tree nodes generates, as a result, the extension of the interpreted image area through each step of the path. The construction of several Attention Trees has been performed and partial

  10. Cryogenic Absorption Cells Operating Inside a Bruker IFS-125HR: First Results for 13CH4 at 7 Micrometers

    NASA Technical Reports Server (NTRS)

    Sung, K.; Mantz, A. W.; Smith, M. A. H.; Brown, L. R.; Crawford, T. J.; Devi, V. M.; Benner, D. C.

    2010-01-01

    New absorption cells designed specifically to achieve stable temperatures down to 66 K inside the sample compartment of an evacuated Bruker IFS-125HR Fourier transform spectrometer (FTS) were developed at Connecticut College and tested at the Jet Propulsion Laboratory (JPL). The temperature stabilized cryogenic cells with path lengths of 24.29 and 20.38 cm were constructed of oxygen free high conductivity (OFHC) copper and fitted with wedged ZnSe windows using vacuum tight indium seals. In operation, the temperature-controlled cooling by a closed-cycle helium refrigerator achieved stability of 0.01 K. The unwanted absorption features arising from cryodeposits on the cell windows at low temperatures were eliminated by building an internal vacuum shroud box around the cell which significantly minimized the growth of cryodeposits. The effects of vibrations from the closed-cycle helium refrigerator on the FTS spectra were characterized. Using this set up, several high-resolution spectra of methane isotopologues broadened with nitrogen were recorded in the 1200-1800 per centimeter spectral region at various sample temperatures between 79.5 and 296 K. Such data are needed to characterize the temperature dependence of spectral line shapes at low temperatures for remote sensing of outer planets and their moons. Initial analysis of a limited number of spectra in the region of the R(2) manifold of the v4 fundamental band of 13CH4 indicated that an empirical power law used for the temperature dependence of the N2-broadened line widths would fail to fit the observed data in the entire temperature range from 80 to 296 K; instead, it follows a temperature-dependence similar to that reported by Mondelain et al. [17,18]. The initial test was very successful proving that a high precision Fourier transform spectrometer with a completely evacuated optical path can be configured for spectroscopic studies at low temperatures relevant to the planetary atmospheres.

  11. Smart random walkers: the cost of knowing the path.

    PubMed

    Perotti, Juan I; Billoni, Orlando V

    2012-07-01

    In this work we study the problem of targeting signals in networks using entropy information measurements to quantify the cost of targeting. We introduce a penalization rule that imposes a restriction on the long paths and therefore focuses the signal to the target. By this scheme we go continuously from fully random walkers to walkers biased to the target. We found that the optimal degree of penalization is mainly determined by the topology of the network. By analyzing several examples, we have found that a small amount of penalization reduces considerably the typical walk length, and from this we conclude that a network can be efficiently navigated with restricted information.

  12. Multiple order common path spectrometer

    NASA Technical Reports Server (NTRS)

    Newbury, Amy B. (Inventor)

    2010-01-01

    The present invention relates to a dispersive spectrometer. The spectrometer allows detection of multiple orders of light on a single focal plane array by splitting the orders spatially using a dichroic assembly. A conventional dispersion mechanism such as a defraction grating disperses the light spectrally. As a result, multiple wavelength orders can be imaged on a single focal plane array of limited spectral extent, doubling (or more) the number of spectral channels as compared to a conventional spectrometer. In addition, this is achieved in a common path device.

  13. Communication path for extreme environments

    NASA Technical Reports Server (NTRS)

    Jorgensen, Charles C. (Inventor); Betts, Bradley J. (Inventor)

    2010-01-01

    Methods and systems for using one or more radio frequency identification devices (RFIDs), or other suitable signal transmitters and/or receivers, to provide a sensor information communication path, to provide location and/or spatial orientation information for an emergency service worker (ESW), to provide an ESW escape route, to indicate a direction from an ESW to an ES appliance, to provide updated information on a region or structure that presents an extreme environment (fire, hazardous fluid leak, underwater, nuclear, etc.) in which an ESW works, and to provide accumulated thermal load or thermal breakdown information on one or more locations in the region.

  14. Path correlation considered prioritized burst segmentation for quality of service support in optical burst switching networks

    NASA Astrophysics Data System (ADS)

    Hou, Rui; Changyue, Jiana; He, Tingting; Yu, Jianwei; Lei, Bo; Mao, Tengyue

    2013-04-01

    Burst segmentation (BS) is a high-efficiency contention resolution scheme in bufferless optical burst switching (OBS) networks. A prioritized BS scheme for quality of service (QoS) support is developed. Unlike the existing work on the BS scheme, the proposed BS model considers path-correlated factors, such as path length, the adjoining paths carrying traffic on a given path, and the multipriority traffic coming from all paths. Byte loss probability for high-priority and low-priority bursts under the time-based assembly approach and the length-based assembly approach to estimate the performance of the proposed BS scheme by comparing the cumulative distribution function of a burst length in an OBS ingress node (source) with that in an egress node (destination) is introduced. A preemptive BS policy for different priority bursts is proposed to support the QoS of the OBS network. Finally, a simulation is given to validate the proposed analytical model in an existing OBS network with two priority bursts. It is shown that the proposed BS scheme can realize the service differentiation for multipriority traffic under the consideration of network topology-dependent parameters.

  15. Path statistics, memory, and coarse-graining of continuous-time random walks on networks.

    PubMed

    Manhart, Michael; Kion-Crosby, Willow; Morozov, Alexandre V

    2015-12-07

    Continuous-time random walks (CTRWs) on discrete state spaces, ranging from regular lattices to complex networks, are ubiquitous across physics, chemistry, and biology. Models with coarse-grained states (for example, those employed in studies of molecular kinetics) or spatial disorder can give rise to memory and non-exponential distributions of waiting times and first-passage statistics. However, existing methods for analyzing CTRWs on complex energy landscapes do not address these effects. Here we use statistical mechanics of the nonequilibrium path ensemble to characterize first-passage CTRWs on networks with arbitrary connectivity, energy landscape, and waiting time distributions. Our approach can be applied to calculating higher moments (beyond the mean) of path length, time, and action, as well as statistics of any conservative or non-conservative force along a path. For homogeneous networks, we derive exact relations between length and time moments, quantifying the validity of approximating a continuous-time process with its discrete-time projection. For more general models, we obtain recursion relations, reminiscent of transfer matrix and exact enumeration techniques, to efficiently calculate path statistics numerically. We have implemented our algorithm in PathMAN (Path Matrix Algorithm for Networks), a Python script that users can apply to their model of choice. We demonstrate the algorithm on a few representative examples which underscore the importance of non-exponential distributions, memory, and coarse-graining in CTRWs.

  16. Path statistics, memory, and coarse-graining of continuous-time random walks on networks

    PubMed Central

    Kion-Crosby, Willow; Morozov, Alexandre V.

    2015-01-01

    Continuous-time random walks (CTRWs) on discrete state spaces, ranging from regular lattices to complex networks, are ubiquitous across physics, chemistry, and biology. Models with coarse-grained states (for example, those employed in studies of molecular kinetics) or spatial disorder can give rise to memory and non-exponential distributions of waiting times and first-passage statistics. However, existing methods for analyzing CTRWs on complex energy landscapes do not address these effects. Here we use statistical mechanics of the nonequilibrium path ensemble to characterize first-passage CTRWs on networks with arbitrary connectivity, energy landscape, and waiting time distributions. Our approach can be applied to calculating higher moments (beyond the mean) of path length, time, and action, as well as statistics of any conservative or non-conservative force along a path. For homogeneous networks, we derive exact relations between length and time moments, quantifying the validity of approximating a continuous-time process with its discrete-time projection. For more general models, we obtain recursion relations, reminiscent of transfer matrix and exact enumeration techniques, to efficiently calculate path statistics numerically. We have implemented our algorithm in PathMAN (Path Matrix Algorithm for Networks), a Python script that users can apply to their model of choice. We demonstrate the algorithm on a few representative examples which underscore the importance of non-exponential distributions, memory, and coarse-graining in CTRWs. PMID:26646868

  17. Path integration: effect of curved path complexity and sensory system on blindfolded walking.

    PubMed

    Koutakis, Panagiotis; Mukherjee, Mukul; Vallabhajosula, Srikant; Blanke, Daniel J; Stergiou, Nicholas

    2013-02-01

    Path integration refers to the ability to integrate continuous information of the direction and distance traveled by the system relative to the origin. Previous studies have investigated path integration through blindfolded walking along simple paths such as straight line and triangles. However, limited knowledge exists regarding the role of path complexity in path integration. Moreover, little is known about how information from different sensory input systems (like vision and proprioception) contributes to accurate path integration. The purpose of the current study was to investigate how sensory information and curved path complexity affect path integration. Forty blindfolded participants had to accurately reproduce a curved path and return to the origin. They were divided into four groups that differed in the curved path, circle (simple) or figure-eight (complex), and received either visual (previously seen) or proprioceptive (previously guided) information about the path before they reproduced it. The dependent variables used were average trajectory error, walking speed, and distance traveled. The results indicated that (a) both groups that walked on a circular path and both groups that received visual information produced greater accuracy in reproducing the path. Moreover, the performance of the group that received proprioceptive information and later walked on a figure-eight path was less accurate than their corresponding circular group. The groups that had the visual information also walked faster compared to the group that had proprioceptive information. Results of the current study highlight the roles of different sensory inputs while performing blindfolded walking for path integration.

  18. Parametric Study of the Absorption Cross-Section for a Moderately Conducting Thin Cylinder.

    NASA Astrophysics Data System (ADS)

    Gurton, Kristan Peter

    A system has been developed to measure the absorption cross section of a single carbon fiber at 35 GHz as a function of length, orientation, and diameter. Typical lengths considered ranged from 1 to 20 mm, and diameters ranged from 3 to 8 um. The results were compared with the modified integral equation calculations of Waterman and Pedersen that describe the scattering and absorption behavior for a wire of finite length and conductivity. Good agreement was found for all lengths, orientations, and diameters studied.

  19. Parametric study of the absorption cross section for a moderately conducting thin cylinder

    NASA Astrophysics Data System (ADS)

    Gurton, Kristan P.; Bruce, Charles W.

    1995-05-01

    A system has been developed to measure the absorption cross section for a single carbon fiber at 35 GHz as a function of length, orientation, and diameter. Typical lengths of the fibers considered ranged from 1 to 20 mm, and diameters ranged from 3 to 8 mu m. The results were compared with the modified integral equation calculations of Waterman and Pedersen that describe the scattering and absorption behavior for a wire of finite length and conductivity. Good agreement was found for all lengths, orientations, and diameters studied.

  20. An electrical probe of the phonon mean-free path spectrum

    NASA Astrophysics Data System (ADS)

    Ramu, Ashok T.; Halaszynski, Nicole I.; Peters, Jonathan D.; Meinhart, Carl D.; Bowers, John E.

    2016-09-01

    Most studies of the mean-free path accumulation function (MFPAF) rely on optical techniques to probe heat transfer at length scales on the order of the phonon mean-free path. In this paper, we propose and implement a purely electrical probe of the MFPAF that relies on photo-lithographically defined heater-thermometer separation to set the length scale. An important advantage of the proposed technique is its insensitivity to the thermal interfacial impedance and its compatibility with a large array of temperature-controlled chambers that lack optical ports. Detailed analysis of the experimental data based on the enhanced Fourier law (EFL) demonstrates that heat-carrying phonons in gallium arsenide have a much wider mean-free path spectrum than originally thought.