WorldWideScience

Sample records for unit optical depth

  1. Comparative Time Series Analysis of Aerosol Optical Depth over Sites in United States and China Using ARIMA Modeling

    Science.gov (United States)

    Li, X.; Zhang, C.; Li, W.

    2017-12-01

    Long-term spatiotemporal analysis and modeling of aerosol optical depth (AOD) distribution is of paramount importance to study radiative forcing, climate change, and human health. This study is focused on the trends and variations of AOD over six stations located in United States and China during 2003 to 2015, using satellite-retrieved Moderate Resolution Imaging Spectrometer (MODIS) Collection 6 retrievals and ground measurements derived from Aerosol Robotic NETwork (AERONET). An autoregressive integrated moving average (ARIMA) model is applied to simulate and predict AOD values. The R2, adjusted R2, Root Mean Square Error (RMSE), Mean Absolute Error (MAE), Mean Absolute Percentage Error (MAPE), and Bayesian Information Criterion (BIC) are used as indices to select the best fitted model. Results show that there is a persistent decreasing trend in AOD for both MODIS data and AERONET data over three stations. Monthly and seasonal AOD variations reveal consistent aerosol patterns over stations along mid-latitudes. Regional differences impacted by climatology and land cover types are observed for the selected stations. Statistical validation of time series models indicates that the non-seasonal ARIMA model performs better for AERONET AOD data than for MODIS AOD data over most stations, suggesting the method works better for data with higher quality. By contrast, the seasonal ARIMA model reproduces the seasonal variations of MODIS AOD data much more precisely. Overall, the reasonably predicted results indicate the applicability and feasibility of the stochastic ARIMA modeling technique to forecast future and missing AOD values.

  2. Aerosol Optical Depth Over India

    Science.gov (United States)

    David, Liji Mary; Ravishankara, A. R.; Kodros, John K.; Venkataraman, Chandra; Sadavarte, Pankaj; Pierce, Jeffrey R.; Chaliyakunnel, Sreelekha; Millet, Dylan B.

    2018-04-01

    Tropospheric aerosol optical depth (AOD) over India was simulated by Goddard Earth Observing System (GEOS)-Chem, a global 3-D chemical-transport model, using SMOG (Speciated Multi-pOllutant Generator from Indian Institute of Technology Bombay) and GEOS-Chem (GC) (current inventories used in the GEOS-Chem model) inventories for 2012. The simulated AODs were 80% (SMOG) and 60% (GC) of those measured by the satellites (Moderate Resolution Imaging Spectroradiometer and Multi-angle Imaging SpectroRadiometer). There is no strong seasonal variation in AOD over India. The peak AOD values are observed/simulated during summer. The simulated AOD using SMOG inventory has particulate black and organic carbon AOD higher by a factor 5 and 3, respectively, compared to GC inventory. The model underpredicted coarse-mode AOD but agreed for fine-mode AOD with Aerosol Robotic Network data. It captured dust only over Western India, which is a desert, and not elsewhere, probably due to inaccurate dust transport and/or noninclusion of other dust sources. The calculated AOD, after dust correction, showed the general features in its observed spatial variation. Highest AOD values were observed over the Indo-Gangetic Plain followed by Central and Southern India with lowest values in Northern India. Transport of aerosols from Indo-Gangetic Plain and Central India into Eastern India, where emissions are low, is significant. The major contributors to total AOD over India are inorganic aerosol (41-64%), organic carbon (14-26%), and dust (7-32%). AOD over most regions of India is a factor of 5 or higher than over the United States.

  3. Aerosol optical properties in the southeastern United States in summer – Part 2: Sensitivity of aerosol optical depth to relative humidity and aerosol parameters

    Directory of Open Access Journals (Sweden)

    C. A. Brock

    2016-04-01

    Full Text Available Aircraft observations of meteorological, trace gas, and aerosol properties were made between May and September 2013 in the southeastern United States (US. Regionally representative aggregate vertical profiles of median and interdecile ranges of the measured parameters were constructed from 37 individual aircraft profiles made in the afternoon when a well-mixed boundary layer with typical fair-weather cumulus was present (Wagner et al., 2015. We use these 0–4 km aggregate profiles and a simple model to calculate the sensitivity of aerosol optical depth (AOD to changes in dry aerosol mass, relative humidity, mixed-layer height, the central diameter and width of the particle size distribution, hygroscopicity, and dry and wet refractive index, while holding the other parameters constant. The calculated sensitivity is a result of both the intrinsic sensitivity and the observed range of variation in these parameters. These observationally based sensitivity studies indicate that the relationship between AOD and dry aerosol mass in these conditions in the southeastern US can be highly variable and is especially sensitive to relative humidity (RH. For example, calculated AOD ranged from 0.137 to 0.305 as the RH was varied between the 10th and 90th percentile profiles with dry aerosol mass held constant. Calculated AOD was somewhat less sensitive to aerosol hygroscopicity, mean size, and geometric standard deviation, σg. However, some chemistry–climate models prescribe values of σg substantially larger than we or others observe, leading to potential high biases in model-calculated AOD of  ∼  25 %. Finally, AOD was least sensitive to observed variations in dry and wet aerosol refractive index and to changes in the height of the well-mixed surface layer. We expect these findings to be applicable to other moderately polluted and background continental air masses in which an accumulation mode between 0.1–0.5 µm diameter dominates

  4. Factors controlling contrail cirrus optical depth

    Directory of Open Access Journals (Sweden)

    B. Kärcher

    2009-08-01

    Full Text Available Aircraft contrails develop into contrail cirrus by depositional growth and sedimentation of ice particles and horizontal spreading due to wind shear. Factors controlling this development include temperature, ice supersaturation, thickness of ice-supersaturated layers, and vertical gradients in the horizontal wind field. An analytical microphysical cloud model is presented and validated that captures these processes. Many individual contrail cirrus are simulated that develop differently owing to the variability in the controlling factors, resulting in large samples of cloud properties that are statistically analyzed. Contrail cirrus development is studied over the first four hours past formation, similar to the ages of line-shaped contrails that were tracked in satellite imagery on regional scales. On these time scales, contrail cirrus optical depth and microphysical variables exhibit a marked variability, expressed in terms of broad and skewed probability distribution functions. Simulated mean optical depths at a wavelength of 0.55 μm range from 0.05-0.5 and a substantial fraction 20-50% of contrail cirrus stay subvisible (optical depth <0.02, depending on meteorological conditions.

    A detailed analysis based on an observational case study over the continental USA suggests that previous satellite measurements of line-shaped persistent contrails have missed about 89%, 50%, and 11% of contrails with optical depths 0-0.05, 0.05-0.1, and 0.1-0.2, respectively, amounting to 65% of contrail coverage of all optical depths. When comparing observations with simulations and when estimating the contrail cirrus climate impact, not only mean values but also the variability in optical depth and microphysical properties need to be considered.

  5. Extended depth of field imaging through multicore optical fibers.

    Science.gov (United States)

    Orth, Antony; Ploschner, Martin; Maksymov, Ivan S; Gibson, Brant C

    2018-03-05

    Compact microendoscopes use multicore optical fibers (MOFs) to visualize hard-to-reach regions of the body. These devices typically have a large numerical aperture (NA) and are fixed-focus, leading to blurry images from a shallow depth of field with little focus control. In this work, we demonstrate a method to digitally adjust the collection aperture and therefore extend the depth of field of lensless MOF imaging probes. We show that the depth of field can be more than doubled for certain spatial frequencies, and observe a resolution enhancement of up to 78% at a distance of 50μm from the MOF facet. Our technique enables imaging of complex 3D objects at a comparable working distance to lensed MOFs, but without the requirement of lenses, scan units or transmission matrix calibration. Our approach is implemented in post processing and may be used to improve contrast in any microendoscopic probe utilizing a MOF and incoherent light.

  6. Multichannel optical mapping: investigation of depth information

    Science.gov (United States)

    Sase, Ichiro; Eda, Hideo; Seiyama, Akitoshi; Tanabe, Hiroki C.; Takatsuki, Akira; Yanagida, Toshio

    2001-06-01

    Near infrared (NIR) light has become a powerful tool for non-invasive imaging of human brain activity. Many systems have been developed to capture the changes in regional brain blood flow and hemoglobin oxygenation, which occur in the human cortex in response to neural activity. We have developed a multi-channel reflectance imaging system, which can be used as a `mapping device' and also as a `multi-channel spectrophotometer'. In the present study, we visualized changes in the hemodynamics of the human occipital region in multiple ways. (1) Stimulating left and right primary visual cortex independently by showing sector shaped checkerboards sequentially over the contralateral visual field, resulted in corresponding changes in the hemodynamics observed by `mapping' measurement. (2) Simultaneous measurement of functional-MRI and NIR (changes in total hemoglobin) during visual stimulation showed good spatial and temporal correlation with each other. (3) Placing multiple channels densely over the occipital region demonstrated spatial patterns more precisely, and depth information was also acquired by placing each pair of illumination and detection fibers at various distances. These results indicate that optical method can provide data for 3D analysis of human brain functions.

  7. Hyperspectral aerosol optical depths from TCAP flights

    Energy Technology Data Exchange (ETDEWEB)

    Shinozuka, Yohei [NASA Ames Research Center (ARC), Moffett Field, Mountain View, CA (United States); Bay Area Environmental REsearch Institute; Johnson, Roy R [NASA Ames Research Center (ARC), Moffett Field, Mountain View, CA (United States); Flynn, Connor J [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Russell, Philip B [NASA Ames Research Center (ARC), Moffett Field, Mountain View, CA (United States); Schmid, Beat [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2016-06-01

    4STAR (Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research), a hyperspectral airborne sunphotometer, acquired aerosol optical depths (AOD) at 1 Hz during all July 2012 flights of the Two Column Aerosol Project (TCAP). Root-mean-square differences from AERONET ground-based observations were 0.01 at wavelengths between 500-1020 nm, 0.02 at 380 and 1640 nm and 0.03 at 440 nm in four clear-sky fly-over events, and similar in ground side-by-side comparisons. Changes in the above-aircraft AOD across 3- km-deep spirals were typically consistent with integrals of coincident in situ (on DOE Gulfstream 1 with 4STAR) and lidar (on NASA B200) extinction measurements within 0.01, 0.03, 0.01, 0.02, 0.02, 0.02 at 355, 450, 532, 550, 700, 1064 nm, respectively, despite atmospheric variations and combined measurement uncertainties. Finer vertical differentials of the 4STAR measurements matched the in situ ambient extinction profile within 14% for one homogeneous column. For the AOD observed between 350-1660 nm, excluding strong

  8. Optical cryptography with biometrics for multi-depth objects.

    Science.gov (United States)

    Yan, Aimin; Wei, Yang; Hu, Zhijuan; Zhang, Jingtao; Tsang, Peter Wai Ming; Poon, Ting-Chung

    2017-10-11

    We propose an optical cryptosystem for encrypting images of multi-depth objects based on the combination of optical heterodyne technique and fingerprint keys. Optical heterodyning requires two optical beams to be mixed. For encryption, each optical beam is modulated by an optical mask containing either the fingerprint of the person who is sending, or receiving the image. The pair of optical masks are taken as the encryption keys. Subsequently, the two beams are used to scan over a multi-depth 3-D object to obtain an encrypted hologram. During the decryption process, each sectional image of the 3-D object is recovered by convolving its encrypted hologram (through numerical computation) with the encrypted hologram of a pinhole image that is positioned at the same depth as the sectional image. Our proposed method has three major advantages. First, the lost-key situation can be avoided with the use of fingerprints as the encryption keys. Second, the method can be applied to encrypt 3-D images for subsequent decrypted sectional images. Third, since optical heterodyning scanning is employed to encrypt a 3-D object, the optical system is incoherent, resulting in negligible amount of speckle noise upon decryption. To the best of our knowledge, this is the first time optical cryptography of 3-D object images has been demonstrated in an incoherent optical system with biometric keys.

  9. An optical fiber expendable seawater temperature/depth profile sensor

    Science.gov (United States)

    Zhao, Qiang; Chen, Shizhe; Zhang, Keke; Yan, Xingkui; Yang, Xianglong; Bai, Xuejiao; Liu, Shixuan

    2017-10-01

    Marine expendable temperature/depth profiler (XBT) is a disposable measuring instrument which can obtain temperature/depth profile data quickly in large area waters and mainly used for marine surveys, scientific research, military application. The temperature measuring device is a thermistor in the conventional XBT probe (CXBT)and the depth data is only a calculated value by speed and time depth calculation formula which is not an accurate measurement result. Firstly, an optical fiber expendable temperature/depth sensor based on the FBG-LPG cascaded structure is proposed to solve the problems of the CXBT, namely the use of LPG and FBG were used to detect the water temperature and depth, respectively. Secondly, the fiber end reflective mirror is used to simplify optical cascade structure and optimize the system performance. Finally, the optical path is designed and optimized using the reflective optical fiber end mirror. The experimental results show that the sensitivity of temperature and depth sensing based on FBG-LPG cascade structure is about 0.0030C and 0.1%F.S. respectively, which can meet the requirements of the sea water temperature/depth observation. The reflectivity of reflection mirror is in the range from 48.8% to 72.5%, the resonant peak of FBG and LPG are reasonable and the whole spectrum are suitable for demodulation. Through research on the optical fiber XBT (FXBT), the direct measurement of deep-sea temperature/depth profile data can be obtained simultaneously, quickly and accurately. The FXBT is a new all-optical seawater temperature/depth sensor, which has important academic value and broad application prospect and is expected to replace the CXBT in the future.

  10. Assessment and statistical modeling of the relationship between remotely sensed aerosol optical depth and PM2.5 in the eastern United States.

    Science.gov (United States)

    Paciorek, Christopher J; Liu, Yang

    2012-05-01

    Research in scientific, public health, and policy disciplines relating to the environment increasingly makes use of high-dimensional remote sensing and the output of numerical models in conjunction with traditional observations. Given the public health and resultant public policy implications of the potential health effects of particulate matter (PM*) air pollution, specifically fine PM with an aerodynamic diameter work has been rare, in part because discrepancies necessarily exist between satellite-retrieved estimates of AOD, which is an atmospheric-column average, and ground-level PM2.5. In this report, we summarize the results of a number of empirical analyses and of the development of statistical models for the use of proxy information, in particular satellite AOD, in predicting PM2.5 concentrations in the eastern United States. We analyzed the spatiotemporal structure of the relationship between PM2.5 and AOD, first using simple correlations both before and after calibration based on meteorology, as well as large-scale spatial and temporal calibration to account for discrepancies between AOD and PM2.5. We then used both raw and calibrated AOD retrievals in statistical models to predict PM2.5 concentrations, accounting for AOD in two ways: primarily as a separate data source contributing a second likelihood to a Bayesian statistical model, as well as a data source on which we could directly regress. Previous consideration of satellite AOD has largely focused on the National Aeronautics and Space Administration (NASA) moderate resolution imaging spectroradiometer (MODIS) and multiangle imaging spectroradiometer (MISR) instruments. One contribution of our work is more extensive consideration of AOD derived from the Geostationary Operational Environmental Satellite East Aerosol/Smoke Product (GOES GASP) AOD and its relationship with PM2.5. In addition to empirically assessing the spatiotemporal relationship between GASP AOD and PM2.5, we considered new statistical

  11. Study of total column atmospheric aerosol optical depth, ozone and ...

    Indian Academy of Sciences (India)

    Extensive observations of the columnar aerosol optical depth (AOD), total column ozone (TCO) and precipitable water content (PWC) have been carried out using the on-line, multi-band solar radiometers onboard ORV Sagar Kanya (Cruise#SK 147B) over Bay of Bengal during 11th-28th August 1999. Aerosol optical and ...

  12. Variations of aerosol optical depth and Angstrom parameters at a ...

    Indian Academy of Sciences (India)

    In this paper, aerosol optical properties including aerosol optical depth (AOD), Angstrom exponent () and Angstrom turbidity coefficient () have been investigated during December 2009 to October 2010, in a suburban area of Zanjan (36°N, 43°E, 1700 m), in the north–west of Iran, using meteorological and sun ...

  13. Optics in the United kingdom.

    Science.gov (United States)

    Ditchburn, R W

    1969-10-01

    Optics is interpreted to include x-ray optics, electronic optics, and short wave radiooptics as well as the more conventional visible, uv, and ir optics. Recent work in Britain on x-ray optics (applied to molecular biology), on scanning electron microscopy, and in radioastronomy (discovery of pulsars) is mentioned. In the optics of the visible and ir there is an increasing interest in over-all systems design. .The formation of large industrial units capable of carrying through major design program, requiring advanced mechanical and electronic design associated with new lens systems, is welcomed.

  14. Importance of representing optical depth variability for estimates of global line-shaped contrail radiative forcing.

    Science.gov (United States)

    Kärcher, Bernd; Burkhardt, Ulrike; Ponater, Michael; Frömming, Christine

    2010-11-09

    Estimates of the global radiative forcing by line-shaped contrails differ mainly due to the large uncertainty in contrail optical depth. Most contrails are optically thin so that their radiative forcing is roughly proportional to their optical depth and increases with contrail coverage. In recent assessments, the best estimate of mean contrail radiative forcing was significantly reduced, because global climate model simulations pointed at lower optical depth values than earlier studies. We revise these estimates by comparing the probability distribution of contrail optical depth diagnosed with a climate model with the distribution derived from a microphysical, cloud-scale model constrained by satellite observations over the United States. By assuming that the optical depth distribution from the cloud model is more realistic than that from the climate model, and by taking the difference between the observed and simulated optical depth over the United States as globally representative, we quantify uncertainties in the climate model's diagnostic contrail parameterization. Revising the climate model results accordingly increases the global mean radiative forcing estimate for line-shaped contrails by a factor of 3.3, from 3.5 mW/m(2) to 11.6 mW/m(2) for the year 1992. Furthermore, the satellite observations and the cloud model point at higher global mean optical depth of detectable contrails than often assumed in radiative transfer (off-line) studies. Therefore, we correct estimates of contrail radiative forcing from off-line studies as well. We suggest that the global net radiative forcing of line-shaped persistent contrails is in the range 8-20 mW/m(2) for the air traffic in the year 2000.

  15. Aerosol optical depth trend over the Middle East

    KAUST Repository

    Klingmü ller, Klaus; Pozzer, Andrea; Metzger, Swen; Stenchikov, Georgiy L.; Lelieveld, Jos

    2016-01-01

    We use the combined Dark Target/Deep Blue aerosol optical depth (AOD) satellite product of the moderate-resolution imaging spectroradiometer (MODIS) collection 6 to study trends over the Middle East between 2000 and 2015. Our analysis corroborates a

  16. Variations of aerosol optical depth and Angstrom parameters at a ...

    Indian Academy of Sciences (India)

    E, 1700 m), in the north–west of Iran, using meteorological and sun .... However, a few works have been carried out in the Middle-East region .... 3.1.2 Diurnal behaviour of AOD ... work, showed a prevailing pattern of the optical depth in which ...

  17. Research of detection depth for graphene-based optical sensor

    Science.gov (United States)

    Yang, Yong; Sun, Jialve; Liu, Lu; Zhu, Siwei; Yuan, Xiaocong

    2018-03-01

    Graphene-based optical sensors have been developed for research into the biological intercellular refractive index (RI) because they offer greater detection depths than those provided by the surface plasmon resonance technique. In this Letter, we propose an experimental approach for measurement of the detection depth in a graphene-based optical sensor system that uses transparent polydimethylsiloxane layers with different thicknesses. The experimental results show that detection depths of 2.5 μm and 3 μm can be achieved at wavelengths of 532 nm and 633 nm, respectively. These results prove that graphene-based optical sensors can realize long-range RI detection and are thus promising for use as tools in the biological cell detection field. Additionally, we analyze the factors that influence the detection depth and provide a feasible approach for detection depth control based on adjustment of the wavelength and the angle of incidence. We believe that this approach will be useful in RI tomography applications.

  18. Ion induced optical emission for surface and depth profile analysis

    International Nuclear Information System (INIS)

    White, C.W.

    1977-01-01

    Low-energy ion bombardment of solid surfaces results in the emission of infrared, visible, and ultraviolet radiation produced by inelastic ion-solid collision processes. The emitted optical radiation provides important insight into low-energy particle-solid interactions and provides the basis for an analysis technique which can be used for surface and depth profile analysis with high sensitivity. The different kinds of collision induced optical radiation emitted as a result of low-energy particle-solid collisions are reviewed. Line radiation arising from excited states of sputtered atoms or molecules is shown to provide the basis for surface and depth profile analysis. The spectral characteristics of this type of radiation are discussed and applications of the ion induced optical emission technique are presented. These applications include measurements of ion implant profiles, detection sensitivities for submonolayer quantities of impurities on elemental surfaces, and the detection of elemental impurities on complex organic substrates

  19. Signal filtering algorithm for depth-selective diffuse optical topography

    International Nuclear Information System (INIS)

    Fujii, M; Nakayama, K

    2009-01-01

    A compact filtered backprojection algorithm that suppresses the undesirable effects of skin circulation for near-infrared diffuse optical topography is proposed. Our approach centers around a depth-selective filtering algorithm that uses an inverse problem technique and extracts target signals from observation data contaminated by noise from a shallow region. The filtering algorithm is reduced to a compact matrix and is therefore easily incorporated into a real-time system. To demonstrate the validity of this method, we developed a demonstration prototype for depth-selective diffuse optical topography and performed both computer simulations and phantom experiments. The results show that the proposed method significantly suppresses the noise from the shallow region with a minimal degradation of the target signal.

  20. Optical programmable Boolean logic unit.

    Science.gov (United States)

    Chattopadhyay, Tanay

    2011-11-10

    Logic units are the building blocks of many important computational operations likes arithmetic, multiplexer-demultiplexer, radix conversion, parity checker cum generator, etc. Multifunctional logic operation is very much essential in this respect. Here a programmable Boolean logic unit is proposed that can perform 16 Boolean logical operations from a single optical input according to the programming input without changing the circuit design. This circuit has two outputs. One output is complementary to the other. Hence no loss of data can occur. The circuit is basically designed by a 2×2 polarization independent optical cross bar switch. Performance of the proposed circuit has been achieved by doing numerical simulations. The binary logical states (0,1) are represented by the absence of light (null) and presence of light, respectively.

  1. Derivation of Aerosol Columnar Mass from MODIS Optical Depth

    Science.gov (United States)

    Gasso, Santiago; Hegg, Dean A.

    2003-01-01

    In order to verify performance, aerosol transport models (ATM) compare aerosol columnar mass (ACM) with those derived from satellite measurements. The comparison is inherently indirect since satellites derive optical depths and they use a proportionality constant to derive the ACM. Analogously, ATMs output a four dimensional ACM distribution and the optical depth is linearly derived. In both cases, the proportionality constant requires a direct intervention of the user by prescribing the aerosol composition and size distribution. This study introduces a method that minimizes the direct user intervention by making use of the new aerosol products of MODIS. A parameterization is introduced for the derivation of columnar aerosol mass (AMC) and CCN concentration (CCNC) and comparisons between sunphotometer, MODIS Airborne Simulator (MAS) and in-measurements are shown. The method still relies on the scaling between AMC and optical depth but the proportionality constant is dependent on the MODIS derived r$_{eff}$,\\eta (contribution of the accumulation mode radiance to the total radiance), ambient RH and an assumed constant aerosol composition. The CCNC is derived fkom a recent parameterization of CCNC as a function of the retrieved aerosol volume. By comparing with in-situ data (ACE-2 and TARFOX campaigns), it is shown that retrievals in dry ambient conditions (dust) are improved when using a proportionality constant dependent on r$ {eff}$ and \\eta derived in the same pixel. In high humidity environments, the improvement inthe new method is inconclusive because of the difficulty in accounting for the uneven vertical distribution of relative humidity. Additionally, two detailed comparisons of AMC and CCNC retrieved by the MAS algorithm and the new method are shown. The new method and MAS retrievals of AMC are within the same order of magnitude with respect to the in-situ measurements of aerosol mass. However, the proposed method is closer to the in-situ measurements than

  2. Accuracy assessment of Terra-MODIS aerosol optical depth retrievals

    International Nuclear Information System (INIS)

    Safarpour, Sahabeh; Abdullah, Khiruddin; Lim, Hwee San; Dadras, Mohsen

    2014-01-01

    Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol products have been widely used to address environment and climate change subjects with daily global coverage. Aerosol optical depth (AOD) is retrieved by different algorithms based on the pixel surface, determining between land and ocean. MODIS-Terra and Global Aerosol Robotic Network (AERONET) products can be obtained from the Multi-sensor Aerosol Products Sampling System (MAPSS) for coastal regions during 2000-2010. Using data collected from 83 coastal stations worldwide from AERONET from 2000-2010, accuracy assessments are made for coastal aerosol optical depth (AOD) retrieved from MODIS aboard the Terra satellite. AOD retrieved from MODIS at 0.55μm wavelength has been compared With the AERONET derived AOD, because it is reliable with the major wavelength used by many chemistry transport and climate models as well as previous MODIS validation studies. After removing retrievals with quality flags below1 for Ocean algorithm and below 3 for Land algorithm, The accuracy of AOD retrieved from MODIS Dark Target Ocean algorithms (correlation coefficient R 2 is 0.844 and a regression equation of τ M = 0.91·τ A + 0.02 (where subscripts M and A represent MODIS and AERONET respectively), is the greater than the MODIS Dark Target Land algorithms (correlation coefficient R 2 is 0.764 and τ M = 0.95·τ A + 0.03) and the Deep Blue algorithm (correlation coefficient R 2 is 0.652 and τ M = 0.81·τ A + 0.04). The reasons of the retrieval error in AOD are found to be the various underlying surface reflectance. Therefore, the aerosol models and underlying surface reflectance are the dominant factors which influence the accuracy of MODIS retrieval performance. Generally the MODIS Land algorithm implements better than the Ocean algorithm for coastal sites

  3. Multiscale periodicities in aerosol optical depth over India

    International Nuclear Information System (INIS)

    Ramachandran, S; Ghosh, Sayantan; Verma, Amit; Panigrahi, P K

    2013-01-01

    Aerosols exhibit periodic or cyclic variations depending on natural and anthropogenic sources over a region, which can become modulated by synoptic meteorological parameters such as winds, rainfall and relative humidity, and long-range transport. Information on periodicity and phase in aerosol properties assumes significance in prediction as well as examining the radiative and climate effects of aerosols including their association with changes in cloud properties and rainfall. Periodicity in aerosol optical depth, which is a columnar measure of aerosol distribution, is determined using continuous wavelet transform over 35 locations (capitals of states and union territories) in India. Continuous wavelet transform is used in the study because continuous wavelet transform is better suited to the extraction of the periodic and local modulations present in various frequency ranges when compared to Fourier transform. Monthly mean aerosol optical depths (AODs) from the Moderate Resolution Imaging Spectroradiometer (MODIS) on board the Terra satellite at 1° × 1° resolution from January 2001 to December 2012 are used. Annual and quasi-biennial oscillations (QBOs) in AOD are evident in addition to the weak semi-annual (5–6 months) and quasi-triennial oscillations (∼40 months). The semi-annual and annual oscillations are consistent with the seasonal and yearly cycle of variations in AODs. The QBO type periodicity in AOD is found to be non-stationary while the annual period is stationary. The 40 month periodicity indicates the presence of long term correlations in AOD. The observed periodicities in MODIS Terra AODs are also evident in the ground-based AOD measurements made over Kanpur in the Indo-Gangetic Plain. The phase of the periodicity in AOD is stable in the mid-frequency range, while local disturbances in the high-frequency range and long term changes in the atmospheric composition give rise to unstable phases in the low-frequency range. The presence of phase

  4. Can MODIS detect trends in aerosol optical depth over land?

    Science.gov (United States)

    Fan, Xuehua; Xia, Xiang'ao; Chen, Hongbin

    2018-02-01

    The Moderate Resolution Imaging Spectroradiometer (MODIS) sensor onboard NASA's Aqua satellite has been collecting valuable data about the Earth system for more than 14 years, and one of the benefits of this is that it has made it possible to detect the long-term variation in aerosol loading across the globe. However, the long-term aerosol optical depth (AOD) trends derived from MODIS need careful validation and assessment, especially over land. Using AOD products with at least 70 months' worth of measurements collected during 2002-15 at 53 Aerosol Robotic Network (AERONET) sites over land, Mann-Kendall (MK) trends in AOD were derived and taken as the ground truth data for evaluating the corresponding results from MODIS onboard Aqua. The results showed that the AERONET AOD trends over all sites in Europe and North America, as well as most sites in Africa and Asia, can be reproduced by MODIS/Aqua. However, disagreement in AOD trends between MODIS and AERONET was found at a few sites in Australia and South America. The AOD trends calculated from AERONET instantaneous data at the MODIS overpass times were consistent with those from AERONET daily data, which suggests that the AOD trends derived from satellite measurements of 1-2 overpasses may be representative of those from daily measurements.

  5. Aerosol optical depth in the European Brewer Network

    Science.gov (United States)

    López-Solano, Javier; Redondas, Alberto; Carlund, Thomas; Rodriguez-Franco, Juan J.; Diémoz, Henri; León-Luis, Sergio F.; Hernández-Cruz, Bentorey; Guirado-Fuentes, Carmen; Kouremeti, Natalia; Gröbner, Julian; Kazadzis, Stelios; Carreño, Virgilio; Berjón, Alberto; Santana-Díaz, Daniel; Rodríguez-Valido, Manuel; De Bock, Veerle; Moreta, Juan R.; Rimmer, John; Smedley, Andrew R. D.; Boulkelia, Lamine; Jepsen, Nis; Eriksen, Paul; Bais, Alkiviadis F.; Shirotov, Vadim; Vilaplana, José M.; Wilson, Keith M.; Karppinen, Tomi

    2018-03-01

    Aerosols play an important role in key atmospheric processes and feature high spatial and temporal variabilities. This has motivated scientific interest in the development of networks capable of measuring aerosol properties over large geographical areas in near-real time. In this work we present and discuss results of an aerosol optical depth (AOD) algorithm applied to instruments of the European Brewer Network. This network is comprised of close to 50 Brewer spectrophotometers, mostly located in Europe and adjacent areas, although instruments operating at, for example, South America and Australia are also members. Although we only show results for instruments calibrated by the Regional Brewer Calibration Center for Europe, the implementation of the AOD algorithm described is intended to be used by the whole network in the future. Using data from the Brewer intercomparison campaigns in the years 2013 and 2015, and the period in between, plus comparisons with Cimel sun photometers and UVPFR instruments, we check the precision, stability, and uncertainty of the Brewer AOD in the ultraviolet range from 300 to 320 nm. Our results show a precision better than 0.01, an uncertainty of less than 0.05, and, for well-maintained instruments, a stability similar to that of the ozone measurements. We also discuss future improvements to our algorithm with respect to the input data, their processing, and the characterization of the Brewer instruments for the measurement of AOD.

  6. Wind Speed Influences on Marine Aerosol Optical Depth

    Directory of Open Access Journals (Sweden)

    Colin O'Dowd

    2010-01-01

    Full Text Available The Mulcahy (Mulcahy et al., 2008 power-law parameterization, derived at the coastal Atlantic station Mace Head, between clean marine aerosol optical depth (AOD and wind speed is compared to open ocean MODIS-derived AOD versus wind speed. The reported AOD versus wind speed (U was a function of ∼U2. The open ocean MODIS-derived AOD at 550 nm and 860 nm wavelengths, while in good agreement with the general magnitude of the Mulcahy parameterization, follows a power-law with the exponent ranging from 0.72 to 2.47 for a wind speed range of 2–18 m s−1. For the four cases examined, some MODIS cases underestimated AOD while other cases overestimated AOD relative to the Mulcahy scheme. Overall, the results from MODIS support the general power-law relationship of Mulcahy, although some linear cases were also encountered in the MODIS dataset. Deviations also arise between MODIS and Mulcahy at higher wind speeds (>15 m s−1, where MODIS-derived AOD returns lower values as compared to Mulcahy. The results also support the suggestion than wind generated sea spray, under moderately high winds, can rival anthropogenic pollution plumes advecting out into marine environments with wind driven AOD contributing to AOD values approaching 0.3.

  7. Optical Instruments Synergy in Determination of Optical Depth of Thin Clouds

    Energy Technology Data Exchange (ETDEWEB)

    Vladutescu, Daniela V.; Schwartz, Stephen E.

    2017-06-25

    Optically thin clouds have a strong radiative effect and need to be represented accurately in climate models. Cloud optical depth of thin clouds was retrieved using high resolution digital photography, lidar, and a radiative transfer model. The Doppler Lidar was operated at 1.5 μm, minimizing return from Rayleigh scattering, emphasizing return from aerosols and clouds. This approach examined cloud structure on scales 3 to 5 orders of magnitude finer than satellite products, opening new avenues for examination of cloud structure and evolution.

  8. Realization of arbitrarily long focus-depth optical vortices with spiral area-varying zone plates

    Science.gov (United States)

    Zheng, Chenglong; Zang, Huaping; Du, Yanli; Tian, Yongzhi; Ji, Ziwen; Zhang, Jing; Fan, Quanping; Wang, Chuanke; Cao, Leifeng; Liang, Erjun

    2018-05-01

    We provide a methodology to realize an optical vortex with arbitrarily long focus-depth. With a technique of varying each zone area of a phase spiral zone plate one can obtain optics capable of generating ultra-long focus-depth optical vortex from a plane wave. The focal property of such optics was analysed using the Fresnel diffraction theory, and an experimental demonstration was performed to verify its effectiveness. Such optics may bring new opportunity and benefits for optical vortex application such as optical manipulation and lithography.

  9. Secchi depth analysis using bio-optical parameters measured in the Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Suresh, T.; Naik, P.; Bandishte, M.; Desa, E.; Mascarenhas, A.A.M.Q.; Matondkar, S.G.P.

    spatial and temporal variability of Secchi depth and their dependence on the optical properties beam attenuation and diffuse attenuation the biological parameter of Chlorophyll. The in-situ measured inherent and apparent optical properties have been used...

  10. Diagnosing causes of extreme aerosol optical depth events

    Science.gov (United States)

    Bernstein, D. N.; Sullivan, R.; Crippa, P.; Thota, A.; Pryor, S. C.

    2017-12-01

    Aerosol burdens and optical properties exhibit substantial spatiotemporal variability, and simulation of current and possible future aerosol burdens and characteristics exhibits relatively high uncertainty due to uncertainties in emission estimates and in chemical and physical processes associated with aerosol formation, dynamics and removal. We report research designed to improve understanding of the causes and characteristics of extreme aerosol optical depth (AOD) at the regional scale, and diagnose and attribute model skill in simulating these events. Extreme AOD events over the US Midwest are selected by identifying all dates on which AOD in a MERRA-2 reanalysis grid cell exceeds the local seasonally computed 90th percentile (p90) value during 2004-2016 and then finding the dates on which the highest number of grid cells exceed their local p90. MODIS AOD data are subsequently used to exclude events dominated by wildfires. MERRA-2 data are also analyzed within a synoptic classification to determine in what ways the extreme AOD events are atypical and to identify possible meteorological `finger-prints' that can be detected in regional climate model simulations of future climate states to project possible changes in the occurrence of extreme AOD. Then WRF-Chem v3.6 is applied at 12-km resolution and regridded to the MERRA-2 resolution over eastern North America to quantify model performance, and also evaluated using in situ measurements of columnar AOD (AERONET) and near-surface PM2.5 (US EPA). Finally the sensitivity to (i) spin-up time (including procedure used to spin-up the chemistry), (ii) modal versus sectional aerosol schemes, (iii) meteorological nudging, (iv) chemistry initial and boundary conditions, and (v) anthropogenic emissions is quantified. Despite recent declines in mean AOD, supraregional (> 1000 km) extreme AOD events continue to occur. During these events AOD exceeds 0.6 in many Midwestern grid cells for multiple consecutive days. In all

  11. Depth-resolved ballistic imaging in a low-depth-of-field optical Kerr gated imaging system

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Yipeng; Tan, Wenjiang, E-mail: tanwenjiang@mail.xjtu.edu.cn; Si, Jinhai; Ren, YuHu; Xu, Shichao; Hou, Xun [Key Laboratory for Physical Electronics and Devices of the Ministry of Education and Shaanxi Key Lab of Information Photonic Technique, School of Electronics and Information Engineering, Xi' an Jiaotong University, Xianning-xilu 28, Xi' an 710049 (China); Tong, Junyi [Departments of Applied Physics, Xi' an University of Technology, Xi' an 710048 (China)

    2016-09-07

    We demonstrate depth-resolved imaging in a ballistic imaging system, in which a heterodyned femtosecond optical Kerr gate is introduced to extract useful imaging photons for detecting an object hidden in turbid media and a compound lens is proposed to ensure both the depth-resolved imaging capability and the long working distance. Two objects of about 15-μm widths hidden in a polystyrene-sphere suspension have been successfully imaged with approximately 600-μm depth resolution. Modulation-transfer-function curves with the object in and away from the object plane have also been measured to confirm the depth-resolved imaging capability of the low-depth-of-field (low-DOF) ballistic imaging system. This imaging approach shows potential for application in research of the internal structure of highly scattering fuel spray.

  12. MODIS Retrieval of Aerosol Optical Depth over Turbid Coastal Water

    Directory of Open Access Journals (Sweden)

    Yi Wang

    2017-06-01

    Full Text Available We present a new approach to retrieve Aerosol Optical Depth (AOD using the Moderate Resolution Imaging Spectroradiometer (MODIS over the turbid coastal water. This approach supplements the operational Dark Target (DT aerosol retrieval algorithm that currently does not conduct AOD retrieval in shallow waters that have visible sediments or sea-floor (i.e., Class 2 waters. Over the global coastal water regions in cloud-free conditions, coastal screening leads to ~20% unavailability of AOD retrievals. Here, we refine the MODIS DT algorithm by considering that water-leaving radiance at 2.1 μm to be negligible regardless of water turbidity, and therefore the 2.1 μm reflectance at the top of the atmosphere is sensitive to both change of fine-mode and coarse-mode AODs. By assuming that the aerosol single scattering properties over coastal turbid water are similar to those over the adjacent open-ocean pixels, the new algorithm can derive AOD over these shallow waters. The test algorithm yields ~18% more MODIS-AERONET collocated pairs for six AERONET stations in the coastal water regions. Furthermore, comparison of the new retrieval with these AERONET observations show that the new AOD retrievals have equivalent or better accuracy than those retrieved by the MODIS operational algorithm’s over coastal land and non-turbid coastal water product. Combining the new retrievals with the existing MODIS operational retrievals yields an overall improvement of AOD over those coastal water regions. Most importantly, this refinement extends the spatial and temporal coverage of MODIS AOD retrievals over the coastal regions where 60% of human population resides. This expanded coverage is crucial for better understanding of impact of anthropogenic aerosol particles on coastal air quality and climate.

  13. Aerosol optical depth trend over the Middle East

    KAUST Repository

    Klingmüller, Klaus

    2016-04-22

    We use the combined Dark Target/Deep Blue aerosol optical depth (AOD) satellite product of the moderate-resolution imaging spectroradiometer (MODIS) collection 6 to study trends over the Middle East between 2000 and 2015. Our analysis corroborates a previously identified positive AOD trend over large parts of the Middle East during the period 2001 to 2012. We relate the annual AOD to precipitation, soil moisture and surface winds to identify regions where these attributes are directly related to the AOD over Saudi Arabia, Iraq and Iran. Regarding precipitation and soil moisture, a relatively small area in and surrounding Iraq turns out to be of prime importance for the AOD over these countries. Regarding surface wind speed, the African Red Sea coastal area is relevant for the Saudi Arabian AOD. Using multiple linear regression we show that AOD trends and interannual variability can be attributed to soil moisture, precipitation and surface winds, being the main factors controlling the dust cycle. Our results confirm the dust driven AOD trends and variability, supported by a decreasing MODIS-derived Ångström exponent and a decreasing AERONET-derived fine mode fraction that accompany the AOD increase over Saudi Arabia. The positive AOD trend relates to a negative soil moisture trend. As a lower soil moisture translates into enhanced dust emissions, it is not needed to assume growing anthropogenic aerosol and aerosol precursor emissions to explain the observations. Instead, our results suggest that increasing temperature and decreasing relative humidity in the last decade have promoted soil drying, leading to increased dust emissions and AOD; consequently an AOD increase is expected due to climate change.

  14. Estimates of the aerosol optical depth over Pretoria using the CSIR mobile lidar

    CSIR Research Space (South Africa)

    Shikwambana, L

    2013-09-01

    Full Text Available This study shows the estimates of aerosol optical depth measured over Pretoria, South Africa, using the CSIR-NLC mobile LIDAR. The measurements are also compared with observations from the Level-3 MODIS aerosol optical depth (AOD) data...

  15. The matter power spectrum from the Ly alpha forest : an optical depth estimate

    NARCIS (Netherlands)

    Zaroubi, S; Nusser, A; Haehnelt, M; Kim, TS; Viel, M.

    2006-01-01

    We measure the matter power spectrum from 31 Ly alpha spectra spanning the redshift range of 1.6-3.6. The optical depth, tau, for Ly alpha absorption of the intergalactic medium is obtained from the flux using the inversion method of Nusser & Haehnelt. The optical depth is converted to density by

  16. Validation of MODIS aerosol optical depth over the Mediterranean Coast

    Science.gov (United States)

    Díaz-Martínez, J. Vicente; Segura, Sara; Estellés, Víctor; Utrillas, M. Pilar; Martínez-Lozano, J. Antonio

    2013-04-01

    Atmospheric aerosols, due to their high spatial and temporal variability, are considered one of the largest sources of uncertainty in different processes affecting visibility, air quality, human health, and climate. Among their effects on climate, they play an important role in the energy balance of the Earth. On one hand they have a direct effect by scattering and absorbing solar radiation; on the other, they also have an impact in precipitation, modifying clouds, or affecting air quality. The application of remote sensing techniques to investigate aerosol effects on climate has advanced significatively over last years. In this work, the products employed have been obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS). MODIS is a sensor located onboard both Earth Observing Systems (EOS) Terra and Aqua satellites, which provide almost complete global coverage every day. These satellites have been acquiring data since early 2000 (Terra) and mid 2002 (Aqua) and offer different products for land, ocean and atmosphere. Atmospheric aerosol products are presented as level 2 products with a pixel size of 10 x 10 km2 in nadir. MODIS aerosol optical depth (AOD) is retrieved by different algorithms depending on the pixel surface, distinguishing between land and ocean. For its validation, ground based sunphotometer data from AERONET (Aerosol Robotic Network) has been employed. AERONET is an international operative network of Cimel CE318 sky-sunphotometers that provides the most extensive aerosol data base globally available of ground-based measurements. The ground sunphotometric technique is considered the most accurate for the retrieval of radiative properties of aerosols in the atmospheric column. In this study we present a validation of MODIS C051 AOD employing AERONET measurements over different Mediterranean coastal sites centered over an area of 50 x 50 km2, which includes both pixels over land and ocean. The validation is done comparing spatial

  17. Spatial Interpolation of Aerosol Optical Depth Pollution: Comparison of Methods for the Development of Aerosol Distribution

    Science.gov (United States)

    Safarpour, S.; Abdullah, K.; Lim, H. S.; Dadras, M.

    2017-09-01

    Air pollution is a growing problem arising from domestic heating, high density of vehicle traffic, electricity production, and expanding commercial and industrial activities, all increasing in parallel with urban population. Monitoring and forecasting of air quality parameters are important due to health impact. One widely available metric of aerosol abundance is the aerosol optical depth (AOD). The AOD is the integrated light extinction coefficient over a vertical atmospheric column of unit cross section, which represents the extent to which the aerosols in that vertical profile prevent the transmission of light by absorption or scattering. Seasonal aerosol optical depth (AOD) values at 550 nm derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor onboard NASA's Terra satellites, for the 10 years period of 2000 - 2010 were used to test 7 different spatial interpolation methods in the present study. The accuracy of estimations was assessed through visual analysis as well as independent validation based on basic statistics, such as root mean square error (RMSE) and correlation coefficient. Based on the RMSE and R values of predictions made using measured values from 2000 to 2010, Radial Basis Functions (RBFs) yielded the best results for spring, summer and winter and ordinary kriging yielded the best results for fall.

  18. SPATIAL INTERPOLATION OF AEROSOL OPTICAL DEPTH POLLUTION: COMPARISON OF METHODS FOR THE DEVELOPMENT OF AEROSOL DISTRIBUTION

    Directory of Open Access Journals (Sweden)

    S. Safarpour

    2017-09-01

    Full Text Available Air pollution is a growing problem arising from domestic heating, high density of vehicle traffic, electricity production, and expanding commercial and industrial activities, all increasing in parallel with urban population. Monitoring and forecasting of air quality parameters are important due to health impact. One widely available metric of aerosol abundance is the aerosol optical depth (AOD. The AOD is the integrated light extinction coefficient over a vertical atmospheric column of unit cross section, which represents the extent to which the aerosols in that vertical profile prevent the transmission of light by absorption or scattering. Seasonal aerosol optical depth (AOD values at 550 nm derived from the Moderate Resolution Imaging Spectroradiometer (MODIS sensor onboard NASA’s Terra satellites, for the 10 years period of 2000 - 2010 were used to test 7 different spatial interpolation methods in the present study. The accuracy of estimations was assessed through visual analysis as well as independent validation based on basic statistics, such as root mean square error (RMSE and correlation coefficient. Based on the RMSE and R values of predictions made using measured values from 2000 to 2010, Radial Basis Functions (RBFs yielded the best results for spring, summer and winter and ordinary kriging yielded the best results for fall.

  19. Application of simple all-sky imagers for the estimation of aerosol optical depth

    Science.gov (United States)

    Kazantzidis, Andreas; Tzoumanikas, Panagiotis; Nikitidou, Efterpi; Salamalikis, Vasileios; Wilbert, Stefan; Prahl, Christoph

    2017-06-01

    Aerosol optical depth is a key atmospheric constituent for direct normal irradiance calculations at concentrating solar power plants. However, aerosol optical depth is typically not measured at the solar plants for financial reasons. With the recent introduction of all-sky imagers for the nowcasting of direct normal irradiance at the plants a new instrument is available which can be used for the determination of aerosol optical depth at different wavelengths. In this study, we are based on Red, Green and Blue intensities/radiances and calculations of the saturated area around the Sun, both derived from all-sky images taken with a low-cost surveillance camera at the Plataforma Solar de Almeria, Spain. The aerosol optical depth at 440, 500 and 675nm is calculated. The results are compared with collocated aerosol optical measurements and the mean/median difference and standard deviation are less than 0.01 and 0.03 respectively at all wavelengths.

  20. Global Annual Average PM2.5 Grids from MODIS and MISR Aerosol Optical Depth (AOD)

    Data.gov (United States)

    National Aeronautics and Space Administration — Global Annual PM2.5 Grids from MODIS and MISR Aerosol Optical Depth (AOD) data set represents a series of annual average grids (2001-2010) of fine particulate matter...

  1. Global Annual Average PM2.5 Grids from MODIS and MISR Aerosol Optical Depth (AOD)

    Data.gov (United States)

    National Aeronautics and Space Administration — Global Annual PM2.5 Grids from MODIS and MISR Aerosol Optical Depth (AOD) data sets represent a series of annual average grids (2001-2010) of fine particulate matter...

  2. Depth-of-field effects in wiggler radiation sources: Geometrical versus wave optics

    Directory of Open Access Journals (Sweden)

    Richard P. Walker

    2017-02-01

    Full Text Available A detailed analysis is carried out of the optical properties of synchrotron radiation emitted by multipole wigglers, concentrating on the effective source size and brightness and the so-called “depth of field” effects, concerning which there has been some controversy in the literature. By comparing calculations made with both geometrical optics and wave optics methods we demonstrate that the two approaches are not at variance, and that the wave optics results tend towards those of geometrical optics under well-defined conditions.

  3. Temperature dependence of the optical conductivity and penetration depth in superconductor MgB2 film

    International Nuclear Information System (INIS)

    Moarrefi, M.; Yavari, H.; Elahi, M.

    2010-01-01

    By using Green's function method the temperature dependence of the optical conductivity and penetration depth of high-quality MgB 2 film are calculated in the framework of the two-band model. We compare our results with experimental data and we argue that the single gap model is insufficient to describe the optical and penetration depth behavior, but the two-band model with different symmetries describes the data rather well. In the two gap model we consider that the both components of optical conductivity are a weighted sum of the contribution from σ and π bonds and hybridization between them is negligible.

  4. Laser backlight unit based on a leaky optical fiber

    Science.gov (United States)

    Okuda, Yuuto; Onoda, Kousuke; Fujieda, Ichiro

    2012-07-01

    A backlight unit is constructed by laying out an optical fiber on a two-dimensional plane and letting the light leak out in a controlled manner. In experiment, we formed multiple grooves on the surface of a plastic optical fiber by pressing a heated knife edge. The depth of the groove determined the percentage of the optical power leaking out. The optical fiber with multiple grooves was embedded in an acrylic plate with a spiral trench, and a diffuser sheet was placed over it. When we injected laser light into the end of the optical fiber, this configuration successfully worked as an area illuminator. However, the coherent nature of the laser light caused severe speckle noise. We evaluated the speckle contrast under darkness, and it varied from 80% to 23%, depending on the lens aperture used to capture the images of the illuminator. We glued an ultrasound generator to the optical fiber to introduce phase modulation for the light propagating inside the optical fiber. In this way, the speckle contrast was reduced by a factor of seven to four. Under room lighting, the speckle noise was made barely noticeable by turning on the ultrasound generator.

  5. Constraining the CMB optical depth through the dispersion measure of cosmological radio transients

    International Nuclear Information System (INIS)

    Fialkov, A.; Loeb, A.

    2016-01-01

    The dispersion measure of extragalactic radio transients can be used to measure the column density of free electrons in the intergalactic medium. The same electrons also scatter the Cosmic Microwave Background (CMB) photons, affecting precision measurements of cosmological parameters. We explore the connection between the dispersion measure of radio transients existing during the Epoch of Reionization (EoR) and the total optical depth for the CMB showing that the existence of such transients would provide a new sensitive probe of the CMB optical depth. As an example, we consider the population of FRBs. Assuming they exist during the EoR, we show that: (i) such sources can probe the reionization history by measuring the optical depth to sub-percent accuracy, and (ii) they can be detected with high significance by an instrument such as the Square Kilometer Array.

  6. Constraining the CMB optical depth through the dispersion measure of cosmological radio transients

    Energy Technology Data Exchange (ETDEWEB)

    Fialkov, A.; Loeb, A., E-mail: anastasia.fialkov@cfa.harvard.edu, E-mail: aloeb@cfa.harvard.edu [Institute for Teory and Computation, Harvard University, 60 Garden Street, MS-51, Cambridge, MA, 02138 (United States)

    2016-05-01

    The dispersion measure of extragalactic radio transients can be used to measure the column density of free electrons in the intergalactic medium. The same electrons also scatter the Cosmic Microwave Background (CMB) photons, affecting precision measurements of cosmological parameters. We explore the connection between the dispersion measure of radio transients existing during the Epoch of Reionization (EoR) and the total optical depth for the CMB showing that the existence of such transients would provide a new sensitive probe of the CMB optical depth. As an example, we consider the population of FRBs. Assuming they exist during the EoR, we show that: (i) such sources can probe the reionization history by measuring the optical depth to sub-percent accuracy, and (ii) they can be detected with high significance by an instrument such as the Square Kilometer Array.

  7. Fog Density Estimation and Image Defogging Based on Surrogate Modeling for Optical Depth.

    Science.gov (United States)

    Jiang, Yutong; Sun, Changming; Zhao, Yu; Yang, Li

    2017-05-03

    In order to estimate fog density correctly and to remove fog from foggy images appropriately, a surrogate model for optical depth is presented in this paper. We comprehensively investigate various fog-relevant features and propose a novel feature based on the hue, saturation, and value color space which correlate well with the perception of fog density. We use a surrogate-based method to learn a refined polynomial regression model for optical depth with informative fog-relevant features such as dark-channel, saturation-value, and chroma which are selected on the basis of sensitivity analysis. Based on the obtained accurate surrogate model for optical depth, an effective method for fog density estimation and image defogging is proposed. The effectiveness of our proposed method is verified quantitatively and qualitatively by the experimental results on both synthetic and real-world foggy images.

  8. Depth-sensitive optical spectroscopy for noninvasive diagnosis of oral neoplasia

    Science.gov (United States)

    Schwarz, Richard Alan

    Oral cancer is the 11th most common cancer in the world. Cancers of the oral cavity and oropharynx account for more than 7,500 deaths each year in the United States alone. Major advances have been made in the management of oral cancer through the combined use of surgery, radiotherapy and chemotherapy, improving the quality of life for many patients; however, these advances have not led to a significant increase in survival rates, primarily because diagnosis often occurs at a late stage when treatment is more difficult and less successful. Accurate, objective, noninvasive methods for early diagnosis of oral neoplasia are needed. Here a method is presented to noninvasively evaluate oral lesions using depth-sensitive optical spectroscopy (DSOS). A ball lens coupled fiber-optic probe was developed to enable preferential targeting of different depth regions in the oral mucosa. Clinical studies of the diagnostic performance of DSOS in 157 subjects were carried out in collaboration with the University of Texas M. D. Anderson Cancer Center. An overall sensitivity of 90% and specificity of 89% were obtained for nonkeratinized oral tissue relative to histopathology. Based on these results a compact, portable version of the clinical DSOS device with real-time automated diagnostic capability was developed. The portable device was tested in 47 subjects and a sensitivity of 82% and specificity of 83% were obtained for nonkeratinized oral tissue. The diagnostic potential of multimodal platforms incorporating DSOS was explored through two pilot studies. A pilot study of DSOS in combination with widefield imaging was carried out in 29 oral cancer patients, resulting in a combined sensitivity of 94% and specificity of 69%. Widefield imaging and spectroscopy performed slightly better in combination than each method performed independently. A pilot study of DSOS in combination with the optical contrast agents 2-NBDG, EGF-Alexa 647, and proflavine was carried out in resected tissue

  9. Four-dimensional Microscope-Integrated Optical Coherence Tomography to Visualize Suture Depth in Strabismus Surgery.

    Science.gov (United States)

    Pasricha, Neel D; Bhullar, Paramjit K; Shieh, Christine; Carrasco-Zevallos, Oscar M; Keller, Brenton; Izatt, Joseph A; Toth, Cynthia A; Freedman, Sharon F; Kuo, Anthony N

    2017-02-14

    The authors report the use of swept-source microscope-integrated optical coherence tomography (SS-MIOCT), capable of live four-dimensional (three-dimensional across time) intraoperative imaging, to directly visualize suture depth during lateral rectus resection. Key surgical steps visualized in this report included needle depth during partial and full-thickness muscle passes along with scleral passes. [J Pediatr Ophthalmol Strabismus. 2017;54:e1-e5.]. Copyright 2017, SLACK Incorporated.

  10. Robust calibration of an optical-lattice depth based on a phase shift

    Science.gov (United States)

    Cabrera-Gutiérrez, C.; Michon, E.; Brunaud, V.; Kawalec, T.; Fortun, A.; Arnal, M.; Billy, J.; Guéry-Odelin, D.

    2018-04-01

    We report on a method to calibrate the depth of an optical lattice. It consists of triggering the intrasite dipole mode of the cloud by a sudden phase shift. The corresponding oscillatory motion is directly related to the interband frequencies on a large range of lattice depths. Remarkably, for a moderate displacement, a single frequency dominates the oscillation of the zeroth and first orders of the interference pattern observed after a sufficiently long time of flight. The method is robust against atom-atom interactions and the exact value of the extra weak external confinement superimposed to the optical lattice.

  11. Remote sensing of atmospheric optical depth using a smartphone sun photometer.

    Science.gov (United States)

    Cao, Tingting; Thompson, Jonathan E

    2014-01-01

    In recent years, smart phones have been explored for making a variety of mobile measurements. Smart phones feature many advanced sensors such as cameras, GPS capability, and accelerometers within a handheld device that is portable, inexpensive, and consistently located with an end user. In this work, a smartphone was used as a sun photometer for the remote sensing of atmospheric optical depth. The top-of-the-atmosphere (TOA) irradiance was estimated through the construction of Langley plots on days when the sky was cloudless and clear. Changes in optical depth were monitored on a different day when clouds intermittently blocked the sun. The device demonstrated a measurement precision of 1.2% relative standard deviation for replicate photograph measurements (38 trials, 134 datum). However, when the accuracy of the method was assessed through using optical filters of known transmittance, a more substantial uncertainty was apparent in the data. Roughly 95% of replicate smart phone measured transmittances are expected to lie within ±11.6% of the true transmittance value. This uncertainty in transmission corresponds to an optical depth of approx. ±0.12-0.13 suggesting the smartphone sun photometer would be useful only in polluted areas that experience significant optical depths. The device can be used as a tool in the classroom to present how aerosols and gases effect atmospheric transmission. If improvements in measurement precision can be achieved, future work may allow monitoring networks to be developed in which citizen scientists submit acquired data from a variety of locations.

  12. An aerosol optical depth climatology for NOAA's national surface radiation budget network (SURFRAD)

    Science.gov (United States)

    Augustine, John A.; Hodges, Gary B.; Dutton, Ellsworth G.; Michalsky, Joseph J.; Cornwall, Christopher R.

    2008-06-01

    A series of algorithms developed to process spectral solar measurements for aerosol optical depth (AOD) for the National Oceanic and Atmospheric Administration's (NOAA) national surface radiation budget network (SURFRAD) is summarized, and decadal results are presented. AOD is a measure of the extinction of the Sun's beam due to aerosols. Daily files of AOD for five spectral measurements in the visible and near-infrared have been produced for 1997-2006. Comparisons of SURFRAD daily AOD averages to NASA's Aerosol Robotic Network product at two of the stations were generally good. An AOD climatology for each SURFRAD station is presented as an annual time series of composite monthly means that represents a typical intra-annual AOD variation. Results are similar to previous U.S. climatologies in that the highest AOD magnitude and greatest variability occur in summer, the lowest AOD levels are in winter, and geographically, the highest-magnitude AOD is in the eastern United States. Springtime Asian dust intrusions show up as a secondary maximum at the western stations. A time series of nationwide annual means shows that 500-nm AOD has decreased over the United States by about 0.02 AOD units over the 10-year period. However, this decline is not statistically significant nor geographically consistent within the country. The eastern U.S. stations and westernmost station at Desert Rock, Nevada, show decreasing AOD, whereas the other two western stations show an increase that is attributed to an upsurge in wildfire activity in the last half of the decade.

  13. Femtosecond laser excitation of dielectric materials: experiments and modeling of optical properties and ablation depths

    DEFF Research Database (Denmark)

    Wædegaard, Kristian Juncher; Frislev, Martin Thomas; Balling, Peter

    2013-01-01

    Modeling of the interaction between a dielec- tric material and ultrashort laser pulses provides the tem- poral evolution of the electronic excitation and the optical properties of the dielectric. Experimentally determined re- flectances and ablation depths for sapphire are compared...... to the calculations. A decrease in reflectance at high fluences is observed experimentally, which demonstrates the neces- sity of a temperature-dependent electron scattering rate in the model. The comparison thus provides new constraints on the optical parameters of the model....

  14. Relative skills of soil moisture and vegetation optical depth retrievals for agricultural drought monitoring

    Science.gov (United States)

    Soil moisture condition is an important indicator for agricultural drought monitoring. Through the Land Parameter Retrieval Model (LPRM), vegetation optical depth (VOD) as well as surface soil moisture (SM) can be retrieved simultaneously from brightness temperature observations from the Advanced Mi...

  15. Retrieval of Aerosol Optical Depth over Land using two-angle view Satellite Radiometry during TARFOX

    NARCIS (Netherlands)

    Veefkind, J.P.; Leeuw, G. de; Durkee, P.H.

    1998-01-01

    A new aerosol optical depth retrieval algorithm is presented that uses the two-angle view capability of the Along Track Scanning Radiometer 2 (ATSR-2). By combining the two-angle view and the spectral information this so-called dual view algorithm separates between aerosol and surface contributions

  16. Empirical Relationship between particulate matter and Aerosol Optical Depth over Northern Tien-Shan, Central Asia

    Science.gov (United States)

    Measurements were obtained at two sites in northern Tien-Shan in Central Asia during a 1-year period beginning July 2008 to examine the statistical relationship between aerosol optical depth (AOD) and of fine [PM2.5, particles less than 2.5 μm aerodynamic diameter (AD)] and coars...

  17. Retrieval of Aerosol Optical Depth Over Land by Inverse Modeling of Multi-Source Satellite Data

    NARCIS (Netherlands)

    Wu, Y.

    2018-01-01

    The Aerosol Optical Depth (AOD), a measure of the scattering and absorption of light by aerosols, has been extensively used for scientific research such as monitoring air quality near the surface due to fine particles aggregated, aerosol radiative forcing (cooling effect against the warming effect

  18. Optical depth sectioning in the aberration-corrected scanning transmission and scanning confocal electron microscope

    International Nuclear Information System (INIS)

    Behan, G; Nellist, P D

    2008-01-01

    The use of spherical aberration correctors in the scanning transmission electron microscope (STEM) has the effect of reducing the depth of field of the microscope, making three-dimensional imaging of a specimen possible by optical sectioning. Depth resolution can be improved further by placing aberration correctors and lenses pre and post specimen to achieve an imaging mode known as scanning confocal electron microscopy (SCEM). We present the calculated incoherent point spread functions (PSF) and optical transfer functions (OTF) of a STEM and SCEM. The OTF for a STEM is shown to have a missing cone region which results in severe blurring along the optic axis, which can be especially severe for extended objects. We also present strategies for reconstruction of experimental data, such as three-dimensional deconvolution of the point spread function.

  19. Extending the Effective Ranging Depth of Spectral Domain Optical Coherence Tomography by Spatial Frequency Domain Multiplexing

    Directory of Open Access Journals (Sweden)

    Tong Wu

    2016-11-01

    Full Text Available We present a spatial frequency domain multiplexing method for extending the imaging depth range of a spectral domain optical coherence tomography (SDOCT system without any expensive device. This method uses two galvo scanners with different pivot-offset distances in two independent reference arms for spatial frequency modulation and multiplexing. The spatial frequency contents corresponding to different depth regions of the sample can be shifted to different frequency bands. The spatial frequency domain multiplexing SDOCT system provides an approximately 1.9-fold increase in the effective ranging depth compared with that of a conventional full-range SDOCT system. The reconstructed images of phantom and biological tissue demonstrate the expected increase in ranging depth. The parameters choice criterion for this method is discussed.

  20. Spherical aberration of an optical system and its influence on depth of focus.

    Science.gov (United States)

    Mikš, Antonín; Pokorný, Petr

    2017-06-10

    This paper analyzes the influence of spherical aberration on the depth of focus of symmetrical optical systems for imaging of axial points. A calculation of a beam's caustics is discussed using ray equations in the image plane and considering longitudinal spherical aberration as well. Concurrently, the influence of aberration coefficients on extremes of such a curve is presented. Afterwards, conditions for aberration coefficients are derived if the Strehl definition should be the same in two symmetrically placed planes with respect to the paraxial image plane. Such conditions for optical systems with large aberrations are derived with the use of geometric-optical approximation where the gyration diameter of the beam in given planes of the optical system is evaluated. Therefore, one can calculate aberration coefficients in such a way that the optical system generates a beam of rays that has the gyration radius in a given interval smaller than the defined limit value. Moreover, one can calculate the maximal depth of focus of the optical system respecting the aforementioned conditions.

  1. An Optical Fibre Depth (Pressure) Sensor for Remote Operated Vehicles in Underwater Applications

    Science.gov (United States)

    Duraibabu, Dinesh Babu; Poeggel, Sven; Omerdic, Edin; Capocci, Romano; Lewis, Elfed; Newe, Thomas; Leen, Gabriel; Toal, Daniel; Dooly, Gerard

    2017-01-01

    A miniature sensor for accurate measurement of pressure (depth) with temperature compensation in the ocean environment is described. The sensor is based on an optical fibre Extrinsic Fabry-Perot interferometer (EFPI) combined with a Fibre Bragg Grating (FBG). The EFPI provides pressure measurements while the Fibre Bragg Grating (FBG) provides temperature measurements. The sensor is mechanically robust, corrosion-resistant and suitable for use in underwater applications. The combined pressure and temperature sensor system was mounted on-board a mini remotely operated underwater vehicle (ROV) in order to monitor the pressure changes at various depths. The reflected optical spectrum from the sensor was monitored online and a pressure or temperature change caused a corresponding observable shift in the received optical spectrum. The sensor exhibited excellent stability when measured over a 2 h period underwater and its performance is compared with a commercially available reference sensor also mounted on the ROV. The measurements illustrates that the EFPI/FBG sensor is more accurate for depth measurements (depth of ~0.020 m). PMID:28218727

  2. Techniques of surface optical breakdown prevention for low-depths femtosecond waveguides writing

    International Nuclear Information System (INIS)

    Bukharin, M A; Skryabin, N N; Ganin, D V; Khudyakov, D V; Vartapetov, S.K.

    2016-01-01

    We demonstrated technique of direct femtosecond waveguide writing at record low depth (2-15 μm) under surface of lithium niobate, that play a key role in design of electrooptical modulators with low operating voltage. To prevent optical breakdown of crystal surface we used high numerical aperture objectives for focusing of light and non-thermal regime of inscription in contrast to widespread femtosecond writing technique at depths of tens micrometers or higher. Surface optical breakdown threshold was measured for both x- and z- cut crystals. Inscribed waveguides were examined for intrinsic microstructure. It also reported sharp narrowing of operating pulses energy range with writing depth under the surface of crystal, that should be taken in account when near-surface waveguides design. Novelty of the results consists in reduction of inscription depth under the surface of crystals that broadens applications of direct femtosecond writing technique to full formation of near-surface waveguides and postproduction precise geometry correction of near-surfaces optical integrated circuits produced with proton-exchanged technique. (paper)

  3. Fiber-optic annular detector array for large depth of field photoacoustic macroscopy

    Directory of Open Access Journals (Sweden)

    Johannes Bauer-Marschallinger

    2017-03-01

    Full Text Available We report on a novel imaging system for large depth of field photoacoustic scanning macroscopy. Instead of commonly used piezoelectric transducers, fiber-optic based ultrasound detection is applied. The optical fibers are shaped into rings and mainly receive ultrasonic signals stemming from the ring symmetry axes. Four concentric fiber-optic rings with varying diameters are used in order to increase the image quality. Imaging artifacts, originating from the off-axis sensitivity of the rings, are reduced by coherence weighting. We discuss the working principle of the system and present experimental results on tissue mimicking phantoms. The lateral resolution is estimated to be below 200 μm at a depth of 1.5 cm and below 230 μm at a depth of 4.5 cm. The minimum detectable pressure is in the order of 3 Pa. The introduced method has the potential to provide larger imaging depths than acoustic resolution photoacoustic microscopy and an imaging resolution similar to that of photoacoustic computed tomography.

  4. Fiber-optic annular detector array for large depth of field photoacoustic macroscopy.

    Science.gov (United States)

    Bauer-Marschallinger, Johannes; Höllinger, Astrid; Jakoby, Bernhard; Burgholzer, Peter; Berer, Thomas

    2017-03-01

    We report on a novel imaging system for large depth of field photoacoustic scanning macroscopy. Instead of commonly used piezoelectric transducers, fiber-optic based ultrasound detection is applied. The optical fibers are shaped into rings and mainly receive ultrasonic signals stemming from the ring symmetry axes. Four concentric fiber-optic rings with varying diameters are used in order to increase the image quality. Imaging artifacts, originating from the off-axis sensitivity of the rings, are reduced by coherence weighting. We discuss the working principle of the system and present experimental results on tissue mimicking phantoms. The lateral resolution is estimated to be below 200 μm at a depth of 1.5 cm and below 230 μm at a depth of 4.5 cm. The minimum detectable pressure is in the order of 3 Pa. The introduced method has the potential to provide larger imaging depths than acoustic resolution photoacoustic microscopy and an imaging resolution similar to that of photoacoustic computed tomography.

  5. MODA: a new algorithm to compute optical depths in multidimensional hydrodynamic simulations

    Science.gov (United States)

    Perego, Albino; Gafton, Emanuel; Cabezón, Rubén; Rosswog, Stephan; Liebendörfer, Matthias

    2014-08-01

    Aims: We introduce the multidimensional optical depth algorithm (MODA) for the calculation of optical depths in approximate multidimensional radiative transport schemes, equally applicable to neutrinos and photons. Motivated by (but not limited to) neutrino transport in three-dimensional simulations of core-collapse supernovae and neutron star mergers, our method makes no assumptions about the geometry of the matter distribution, apart from expecting optically transparent boundaries. Methods: Based on local information about opacities, the algorithm figures out an escape route that tends to minimize the optical depth without assuming any predefined paths for radiation. Its adaptivity makes it suitable for a variety of astrophysical settings with complicated geometry (e.g., core-collapse supernovae, compact binary mergers, tidal disruptions, star formation, etc.). We implement the MODA algorithm into both a Eulerian hydrodynamics code with a fixed, uniform grid and into an SPH code where we use a tree structure that is otherwise used for searching neighbors and calculating gravity. Results: In a series of numerical experiments, we compare the MODA results with analytically known solutions. We also use snapshots from actual 3D simulations and compare the results of MODA with those obtained with other methods, such as the global and local ray-by-ray method. It turns out that MODA achieves excellent accuracy at a moderate computational cost. In appendix we also discuss implementation details and parallelization strategies.

  6. Measurement of Optic Disc Cup Surface Depth Using Cirrus HD-OCT.

    Science.gov (United States)

    Kim, Young Kook; Ha, Ahnul; Lee, Won June; Jeoung, Jin Wook; Park, Ki Ho

    2017-12-01

    To introduce the measurement method of optic disc cup surface depth using spectral-domain optical coherence tomography (SD-OCT) and then evaluate the rates of cup surface depression at 3 different stages of glaucoma. We retrospectively identified 52 eyes with preperimetric glaucoma, 56 with mild-or-moderate glaucoma and 50 with severe glaucoma and followed them for at least 48 months. Eyes were imaged using SD-OCT (Cirrus HD-OCT) at 12-month intervals. The mean cup surface depth was calculated using the following formula: Cup volume/(disc area×average cup-to-disc ratio)-200 μm. The rates of mean cup surface depression (μm/y) were significantly greater in mild-or-moderate glaucoma (-7.96±1.03) than in preperimetric (-3.11±0.61) and severe glaucoma (-0.70±0.12; all Pcup surface depression (%/y) were significantly greater than those of average of retinal nerve fiber layer (RNFL) thinning (%/y) in preperimetric glaucoma (-1.64±0.12 vs. -1.11±0.07; Pcup surface depth changed slower than did average RNFL thickness (-0.64±0.06 vs. -0.75±0.08%/y; Pcup surface depth changed faster than did the RNFL thickness. These results signify the possibility that SD-OCT-based estimation of cup surface depth might be useful for monitoring of glaucoma development and progression.

  7. Remote sensing of atmospheric optical depth using a smartphone sun photometer.

    Directory of Open Access Journals (Sweden)

    Tingting Cao

    Full Text Available In recent years, smart phones have been explored for making a variety of mobile measurements. Smart phones feature many advanced sensors such as cameras, GPS capability, and accelerometers within a handheld device that is portable, inexpensive, and consistently located with an end user. In this work, a smartphone was used as a sun photometer for the remote sensing of atmospheric optical depth. The top-of-the-atmosphere (TOA irradiance was estimated through the construction of Langley plots on days when the sky was cloudless and clear. Changes in optical depth were monitored on a different day when clouds intermittently blocked the sun. The device demonstrated a measurement precision of 1.2% relative standard deviation for replicate photograph measurements (38 trials, 134 datum. However, when the accuracy of the method was assessed through using optical filters of known transmittance, a more substantial uncertainty was apparent in the data. Roughly 95% of replicate smart phone measured transmittances are expected to lie within ±11.6% of the true transmittance value. This uncertainty in transmission corresponds to an optical depth of approx. ±0.12-0.13 suggesting the smartphone sun photometer would be useful only in polluted areas that experience significant optical depths. The device can be used as a tool in the classroom to present how aerosols and gases effect atmospheric transmission. If improvements in measurement precision can be achieved, future work may allow monitoring networks to be developed in which citizen scientists submit acquired data from a variety of locations.

  8. Optical reversible programmable Boolean logic unit.

    Science.gov (United States)

    Chattopadhyay, Tanay

    2012-07-20

    Computing with reversibility is the only way to avoid dissipation of energy associated with bit erase. So, a reversible microprocessor is required for future computing. In this paper, a design of a simple all-optical reversible programmable processor is proposed using a polarizing beam splitter, liquid crystal-phase spatial light modulators, a half-wave plate, and plane mirrors. This circuit can perform 16 logical operations according to three programming inputs. Also, inputs can be easily recovered from the outputs. It is named the "reversible programmable Boolean logic unit (RPBLU)." The logic unit is the basic building block of many complex computational operations. Hence the design is important in sense. Two orthogonally polarized lights are defined here as two logical states, respectively.

  9. Optical depth retrievals from Delta-T SPN1 measurements of broadband solar irradiance at ground

    Science.gov (United States)

    Estelles, Victor; Serrano, David; Segura, Sara; Wood, John; Webb, Nick

    2016-04-01

    The SPN1 radiometer, manufactured by Delta-T Devices Ltd., is an instrument designed for the measurement of global solar irradiance and its components (diffuse, direct) at ground level. In the present study, the direct irradiance component has been used to retrieve an effective total optical depth, by applying the Beer-Lambert law to the broadband measurements. The results have been compared with spectral total optical depths derived from two Cimel CE318 and Prede POM01 sun-sky radiometers, located at the Burjassot site in Valencia (Spain), during years 2013 - 2015. The SPN1 is an inexpensive and versatile instrument for the measurement of the three components of the solar radiation without any mobile part and without any need to azimuthally align the instrument to track the sun (http://www.delta-t.co.uk). The three components of the solar radiation are estimated from a combination of measurements performed by 7 different miniature thermopiles. In turn, the Beer-Lambert law has been applied to the broadband direct solar component to obtain an effective total optical depth, representative of the total extinction in the atmosphere. For the assessment of the total optical depth values retrieved with the SPN1, two different sun-sky radiometers (Cimel CE318 and Prede POM01L) have been employed. Both instruments belong to the international networks AERONET and SKYNET. The modified SUNRAD package has been applied in both Cimel and Prede instruments. Cloud affected data has been removed by applying the Smirnov cloud-screening procedure in the SUNRAD algorithm. The broadband SPN1 total optical depth has been analysed by comparison with the spectral total optical depth from the sun-sky radiometer measurements at wavelengths 440, 500, 675, 870 and 1020 nm. The slopes and intercepts have been estimated to be 0.47 - 0.98 and 0.055 - 0.16 with increasing wavelength. The average correlation coefficients and RMSD were 0.80 - 0.83 and 0.034 - 0.036 for all the channels. The

  10. Diffuse optical microscopy for quantification of depth-dependent epithelial backscattering in the cervix

    Science.gov (United States)

    Bodenschatz, Nico; Lam, Sylvia; Carraro, Anita; Korbelik, Jagoda; Miller, Dianne M.; McAlpine, Jessica N.; Lee, Marette; Kienle, Alwin; MacAulay, Calum

    2016-06-01

    A fiber optic imaging approach is presented using structured illumination for quantification of almost pure epithelial backscattering. We employ multiple spatially modulated projection patterns and camera-based reflectance capture to image depth-dependent epithelial scattering. The potential diagnostic value of our approach is investigated on cervical ex vivo tissue specimens. Our study indicates a strong backscattering increase in the upper part of the cervical epithelium caused by dysplastic microstructural changes. Quantization of relative depth-dependent backscattering is confirmed as a potentially useful diagnostic feature for detection of precancerous lesions in cervical squamous epithelium.

  11. Study of temperature increase and optic depth penetration in photo irradiated human tissues

    International Nuclear Information System (INIS)

    Stolik, Suren; Delgado, Jose A.; Perez, Arllene M.; Anasagasti, Lorenzo

    2009-01-01

    Optical radiation is widely applied in the treatment and diagnosis of different pathologies. If the power density of the incident light is sufficiently high to induce a significant temperature rise in the irradiated tissue, then it is also needed the knowledge of the thermal properties of the tissue for a complete understanding of the therapeutic effects. The thermal penetration depth of several human tissues has been measured applying the diffusion approximation of the radiative transfer equation for the distribution of optical radiation. The method, the experimental setup and the results are presented and discussed. (Author)

  12. Aerosol Optical Depth Distribution in Extratropical Cyclones over the Northern Hemisphere Oceans

    Science.gov (United States)

    Naud, Catherine M.; Posselt, Derek J.; van den Heever, Susan C.

    2016-01-01

    Using Moderate Resolution Imaging Spectroradiometer and an extratropical cyclone database,the climatological distribution of aerosol optical depth (AOD) in extratropical cyclones is explored based solely on observations. Cyclone-centered composites of aerosol optical depth are constructed for the Northern Hemisphere mid-latitude ocean regions, and their seasonal variations are examined. These composites are found to be qualitatively stable when the impact of clouds and surface insolation or brightness is tested. The larger AODs occur in spring and summer and are preferentially found in the warm frontal and in the post-cold frontal regions in all seasons. The fine mode aerosols dominate the cold sector AODs, but the coarse mode aerosols display large AODs in the warm sector. These differences between the aerosol modes are related to the varying source regions of the aerosols and could potentially have different impacts on cloud and precipitation within the cyclones.

  13. Evaluation of sulfate aerosol optical depths over the North Atlantic and comparison with satellite observations

    International Nuclear Information System (INIS)

    Berkowitz, C.M.; Ghan, S.J.; Benkovitz, C.M.; Wagener, R.; Nemesure, S.; Schwartz, S.E.

    1993-11-01

    It has been postulated that scattering of sunlight by aerosols can significantly reduce the amount of solar energy absorbed by the climate system. Aerosol measurement programs alone cannot provide all the information needed to evaluate the radiative forcing due to anthropogenic aerosols. Thus, comprehensive global-scale aerosol models, properly validated against surface-based and satellite measurements, are a fundamental tool for evaluating the impacts of aerosols on the planetary radiation balance. Analyzed meteorological fields from the European Centre for Medium-Range Weather Forecasts are used to drive a modified version of the PNL Global Chemistry Model, applied to the atmospheric sulfur cycle. The resulting sulfate fields are used to calculate aerosol optical depths, which in turn are compared to estimates of aerosol optical depth based on satellite observations

  14. Depth estimation of laser glass drilling based on optical differential measurements of acoustic response

    Science.gov (United States)

    Gorodesky, Niv; Ozana, Nisan; Berg, Yuval; Dolev, Omer; Danan, Yossef; Kotler, Zvi; Zalevsky, Zeev

    2016-09-01

    We present the first steps of a device suitable for characterization of complex 3D micro-structures. This method is based on an optical approach allowing extraction and separation of high frequency ultrasonic sound waves induced to the analyzed samples. Rapid, non-destructive characterization of 3D micro-structures are limited in terms of geometrical features and optical properties of the sample. We suggest a method which is based on temporal tracking of secondary speckle patterns generated when illuminating a sample with a laser probe while applying known periodic vibration using an ultrasound transmitter. In this paper we investigated lasers drilled through glass vias. The large aspect ratios of the vias possess a challenge for traditional microscopy techniques in analyzing depth and taper profiles of the vias. The correlation of the amplitude vibrations to the vias depths is experimentally demonstrated.

  15. Analysis of aerosol optical depth evaluation in polar regions and associated uncertainties

    Directory of Open Access Journals (Sweden)

    P. Ortiz de Galisteo

    2008-04-01

    Full Text Available Some available processing algorithms used to calculate the aerosol optical depth from radiometric measurements were tested. The aim was to evaluate the associated uncertainties in polar regions due to the data processing, in order to adjust the methodology of the calculation and illustrate the importance of these error sources. The measurements were obtained during a sun photometer campaign in Ny-Ålesund within the framework of the POLAR-AOD project.

  16. Analysis od aerosol optical depth retrieved by MODIS and MERIS and comparison with photometer data

    International Nuclear Information System (INIS)

    Bocci, E.; Bonafoni, S.; Basili, P.; Biondi, R.; Arino, O.

    2009-01-01

    In this work a validation of aerosol optical depth (AOD) value provided by two different satellite sensor (MODIS and MERIS) is proposed. A comparison between satellite and ground-based AERONET data is carried out to verify the reliability of space borne instruments. Finally the behavior of AOD is analyzed monitoring particular events such as desert dust transport occurred on the 9 of October 2004 over the Mediterranean [it

  17. Effective aerosol optical depth from pyranometer measurements of surface solar radiation (global radiation) at Thessaloniki, Greece

    OpenAIRE

    Lindfors, A. V.; Kouremeti, N.; Arola, A.; Kazadzis, S.; Bais, A. F.; Laaksonen, A.

    2013-01-01

    Pyranometer measurements of the solar surface radiation (SSR) are available at many locations worldwide, often as long time series covering several decades into the past. These data constitute a potential source of information on the atmospheric aerosol load. Here, we present a method for estimating the aerosol optical depth (AOD) using pyranometer measurements of the SSR together with total water vapor column information. The method, which is based on radiative transfer simulations, w...

  18. Extended depth of focus adaptive optics spectral domain optical coherence tomography

    Science.gov (United States)

    Sasaki, Kazuhiro; Kurokawa, Kazuhiro; Makita, Shuichi; Yasuno, Yoshiaki

    2012-01-01

    We present an adaptive optics spectral domain optical coherence tomography (AO-SDOCT) with a long focal range by active phase modulation of the pupil. A long focal range is achieved by introducing AO-controlled third-order spherical aberration (SA). The property of SA and its effects on focal range are investigated in detail using the Huygens-Fresnel principle, beam profile measurement and OCT imaging of a phantom. The results indicate that the focal range is extended by applying SA, and the direction of extension can be controlled by the sign of applied SA. Finally, we demonstrated in vivo human retinal imaging by altering the applied SA. PMID:23082278

  19. Measurements and estimation of the columnar optical depth of tropospheric aerosols in the UV spectral region

    Directory of Open Access Journals (Sweden)

    V. E. Cachorro

    2002-04-01

    Full Text Available We report values of the columnar tropospheric aerosol optical depth at UV wavelengths based on experimental measurements of the direct spectral irradiances carried out by a commercial spectroradiometer (Li1800 of Licor company covering the range from 300–1100 nm at two stations with different climate characteristics in Spain. The first station is located in a rural site in north central Spain with continental climate. The data extend from March to the end of October of 1995. The other station is a coastal site in the Gulf of Cádiz (southwest Spain of maritime climate type. This study is mainly focused on the capability of estimating aerosol optical depth values in the UV region based on the extracted information in the visible and near infrared ranges. A first method has been used based on the Ångström turbidity parameters. However, since this method requires detailed spectral information, a second method has also been used, based on the correlation between wavelengths. A correlation has been established between the experimental aerosol optical depth values at 350 nm and 500 nm wavelengths. Although the type of aerosol seems to be the key factor that determines the quality of these estimations, the evaluation of the associated error is necessary to know the behaviour of these estimations in each area of study.Key words. Atmospheric composition and structure (aerosols and particles; transmission and scattering of radiation; troposphere – composition and chemistry

  20. Relating Line Width and Optical Depth for CO Emission in the Large Mgellanic Cloud

    Science.gov (United States)

    Wojciechowski, Evan; Wong, Tony; Bandurski, Jeffrey; MC3 (Mapping CO in Molecular Clouds in the Magellanic Clouds) Team

    2018-01-01

    We investigate data produced from ALMA observations of giant molecular clouds (GMCs) located in the Large Magellanic Cloud (LMC), using 12CO(2–1) and 13CO(2–1) emission. The spectral line width is generally interpreted as tracing turbulent rather than thermal motions in the cloud, but could also be affected by optical depth, especially for the 12CO line (Hacar et al. 2016). We compare the spectral line widths of both lines with their optical depths, estimated from an LTE analysis, to evaluate the importance of optical depth effects. Our cloud sample includes two regions recently published by Wong et al. (2017, submitted): the Tarantula Nebula or 30 Dor, an HII region rife with turbulence, and the Planck cold cloud (PCC), located in a much calmer environment near the fringes of the LMC. We also include four additional LMC clouds, which span intermediate levels of star formation relative to these two clouds, and for which we have recently obtained ALMA data in Cycle 4.

  1. Measurements and estimation of the columnar optical depth of tropospheric aerosols in the UV spectral region

    Directory of Open Access Journals (Sweden)

    V. E. Cachorro

    Full Text Available We report values of the columnar tropospheric aerosol optical depth at UV wavelengths based on experimental measurements of the direct spectral irradiances carried out by a commercial spectroradiometer (Li1800 of Licor company covering the range from 300–1100 nm at two stations with different climate characteristics in Spain. The first station is located in a rural site in north central Spain with continental climate. The data extend from March to the end of October of 1995. The other station is a coastal site in the Gulf of Cádiz (southwest Spain of maritime climate type. This study is mainly focused on the capability of estimating aerosol optical depth values in the UV region based on the extracted information in the visible and near infrared ranges. A first method has been used based on the Ångström turbidity parameters. However, since this method requires detailed spectral information, a second method has also been used, based on the correlation between wavelengths. A correlation has been established between the experimental aerosol optical depth values at 350 nm and 500 nm wavelengths. Although the type of aerosol seems to be the key factor that determines the quality of these estimations, the evaluation of the associated error is necessary to know the behaviour of these estimations in each area of study.

    Key words. Atmospheric composition and structure (aerosols and particles; transmission and scattering of radiation; troposphere – composition and chemistry

  2. Preliminary results of the aerosol optical depth retrieval in Johor, Malaysia

    International Nuclear Information System (INIS)

    Lim, H Q; Lau, A M S; Kanniah, K D

    2014-01-01

    Monitoring of atmospheric aerosols over the urban area is important as tremendous amounts of pollutants are released by industrial activities and heavy traffic flow. Air quality monitoring by satellite observation provides better spatial coverage, however, detailed aerosol properties retrieval remains a challenge. This is due to the limitation of aerosol retrieval algorithm on high reflectance (bright surface) areas. The aim of this study is to retrieve aerosol optical depth over urban areas of Iskandar Malaysia; the main southern development zone in Johor state, using Moderate Resolution Imaging Spectroradiometer (MODIS) 500 m resolution data. One of the important steps is the aerosol optical depth retrieval is to characterise different types of aerosols in the study area. This information will be used to construct a Look Up Table containing the simulated aerosol reflectance and corresponding aerosol optical depth. Thus, in this study we have characterised different aerosol types in the study area using Aerosol Robotic Network (AERONET) data. These data were processed using cluster analysis and the preliminary results show that the area is consisting of coastal urban (65%), polluted urban (27.5%), dust particles (6%) and heavy pollution (1.5%) aerosols

  3. Underwater Inherent Optical Properties Estimation Using a Depth Aided Deep Neural Network

    Directory of Open Access Journals (Sweden)

    Zhibin Yu

    2017-01-01

    Full Text Available Underwater inherent optical properties (IOPs are the fundamental clues to many research fields such as marine optics, marine biology, and underwater vision. Currently, beam transmissometers and optical sensors are considered as the ideal IOPs measuring methods. But these methods are inflexible and expensive to be deployed. To overcome this problem, we aim to develop a novel measuring method using only a single underwater image with the help of deep artificial neural network. The power of artificial neural network has been proved in image processing and computer vision fields with deep learning technology. However, image-based IOPs estimation is a quite different and challenging task. Unlike the traditional applications such as image classification or localization, IOP estimation looks at the transparency of the water between the camera and the target objects to estimate multiple optical properties simultaneously. In this paper, we propose a novel Depth Aided (DA deep neural network structure for IOPs estimation based on a single RGB image that is even noisy. The imaging depth information is considered as an aided input to help our model make better decision.

  4. Underwater Inherent Optical Properties Estimation Using a Depth Aided Deep Neural Network.

    Science.gov (United States)

    Yu, Zhibin; Wang, Yubo; Zheng, Bing; Zheng, Haiyong; Wang, Nan; Gu, Zhaorui

    2017-01-01

    Underwater inherent optical properties (IOPs) are the fundamental clues to many research fields such as marine optics, marine biology, and underwater vision. Currently, beam transmissometers and optical sensors are considered as the ideal IOPs measuring methods. But these methods are inflexible and expensive to be deployed. To overcome this problem, we aim to develop a novel measuring method using only a single underwater image with the help of deep artificial neural network. The power of artificial neural network has been proved in image processing and computer vision fields with deep learning technology. However, image-based IOPs estimation is a quite different and challenging task. Unlike the traditional applications such as image classification or localization, IOP estimation looks at the transparency of the water between the camera and the target objects to estimate multiple optical properties simultaneously. In this paper, we propose a novel Depth Aided (DA) deep neural network structure for IOPs estimation based on a single RGB image that is even noisy. The imaging depth information is considered as an aided input to help our model make better decision.

  5. Novel optical waveguides by in-depth controlled electronic damage with swift ions

    Science.gov (United States)

    Olivares, J.; García-Navarro, A.; Méndez, A.; Agulló-López, F.; García, G.; García-Cabañes, A.; Carrascosa, M.

    2007-04-01

    We review recent results on a novel method to modify crystalline dielectric materials and fabricate optical waveguides and integrated optics devices. It relies on irradiation with medium-mass high-energy ions (2-50 MeV) where the electronic stopping power is dominant over that one associated to nuclear collisions. By exploiting the processing capabilities of the method, novel optical structures can be achieved at moderate (1014 cm-2) and even low and ultralow (1012 cm-2) fluences. In particular, step-like waveguides with a high index jump Δn ∼ 0.1-0.2, guiding both ordinary and extraordinary modes, have been prepared with F and O ions (20 MeV) at moderate fluences. They present good non-linear and electrooptic perfomance and low losses. (1 dB/cm). Moreover, useful optical waveguiding has been also achieved at ultralow frequencies (isolated track regime), using Cl and Si ions (40-45 MeV). In this latter case, the individual amorphous nanotracks, whose radius increases with depth, create an effective optical medium causing optical trapping.

  6. Novel optical waveguides by in-depth controlled electronic damage with swift ions

    International Nuclear Information System (INIS)

    Olivares, J.; Garcia-Navarro, A.; Mendez, A.; Agullo-Lopez, F.; Garcia, G.; Garcia-Cabanes, A.; Carrascosa, M.

    2007-01-01

    We review recent results on a novel method to modify crystalline dielectric materials and fabricate optical waveguides and integrated optics devices. It relies on irradiation with medium-mass high-energy ions (2-50 MeV) where the electronic stopping power is dominant over that one associated to nuclear collisions. By exploiting the processing capabilities of the method, novel optical structures can be achieved at moderate (10 14 cm -2 ) and even low and ultralow (10 12 cm -2 ) fluences. In particular, step-like waveguides with a high index jump Δn ∼ 0.1-0.2, guiding both ordinary and extraordinary modes, have been prepared with F and O ions (20 MeV) at moderate fluences. They present good non-linear and electrooptic perfomance and low losses. (1 dB/cm). Moreover, useful optical waveguiding has been also achieved at ultralow frequencies (isolated track regime), using Cl and Si ions (40-45 MeV). In this latter case, the individual amorphous nanotracks, whose radius increases with depth, create an effective optical medium causing optical trapping

  7. A Neural Network Approach to Infer Optical Depth of Thick Ice Clouds at Night

    Science.gov (United States)

    Minnis, P.; Hong, G.; Sun-Mack, S.; Chen, Yan; Smith, W. L., Jr.

    2016-01-01

    One of the roadblocks to continuously monitoring cloud properties is the tendency of clouds to become optically black at cloud optical depths (COD) of 6 or less. This constraint dramatically reduces the quantitative information content at night. A recent study found that because of their diffuse nature, ice clouds remain optically gray, to some extent, up to COD of 100 at certain wavelengths. Taking advantage of this weak dependency and the availability of COD retrievals from CloudSat, an artificial neural network algorithm was developed to estimate COD values up to 70 from common satellite imager infrared channels. The method was trained using matched 2007 CloudSat and Aqua MODIS data and is tested using similar data from 2008. The results show a significant improvement over the use of default values at night with high correlation. This paper summarizes the results and suggests paths for future improvement.

  8. Improvement of Aerosol Optical Depth Retrieval over Hong Kong from a Geostationary Meteorological Satellite Using Critical Reflectance with Background Optical Depth Correction

    Science.gov (United States)

    Kim, Mijin; Kim, Jhoon; Wong, Man Sing; Yoon, Jongmin; Lee, Jaehwa; Wu, Dong L.; Chan, P.W.; Nichol, Janet E.; Chung, Chu-Yong; Ou, Mi-Lim

    2014-01-01

    Despite continuous efforts to retrieve aerosol optical depth (AOD) using a conventional 5-channelmeteorological imager in geostationary orbit, the accuracy in urban areas has been poorer than other areas primarily due to complex urban surface properties and mixed aerosol types from different emission sources. The two largest error sources in aerosol retrieval have been aerosol type selection and surface reflectance. In selecting the aerosol type from a single visible channel, the season-dependent aerosol optical properties were adopted from longterm measurements of Aerosol Robotic Network (AERONET) sun-photometers. With the aerosol optical properties obtained fromthe AERONET inversion data, look-up tableswere calculated by using a radiative transfer code: the Second Simulation of the Satellite Signal in the Solar Spectrum (6S). Surface reflectance was estimated using the clear sky composite method, awidely used technique for geostationary retrievals. Over East Asia, the AOD retrieved from the Meteorological Imager showed good agreement, although the values were affected by cloud contamination errors. However, the conventional retrieval of the AOD over Hong Kong was largely underestimated due to the lack of information on the aerosol type and surface properties. To detect spatial and temporal variation of aerosol type over the area, the critical reflectance method, a technique to retrieve single scattering albedo (SSA), was applied. Additionally, the background aerosol effect was corrected to improve the accuracy of the surface reflectance over Hong Kong. The AOD retrieved froma modified algorithmwas compared to the collocated data measured by AERONET in Hong Kong. The comparison showed that the new aerosol type selection using the critical reflectance and the corrected surface reflectance significantly improved the accuracy of AODs in Hong Kong areas,with a correlation coefficient increase from0.65 to 0.76 and a regression line change from tMI [basic algorithm] = 0

  9. Depth-resolved imaging of colon tumor using optical coherence tomography and fluorescence laminar optical tomography (Conference Presentation)

    Science.gov (United States)

    Tang, Qinggong; Frank, Aaron; Wang, Jianting; Chen, Chao-wei; Jin, Lily; Lin, Jon; Chan, Joanne M.; Chen, Yu

    2016-03-01

    Early detection of neoplastic changes remains a critical challenge in clinical cancer diagnosis and treatment. Many cancers arise from epithelial layers such as those of the gastrointestinal (GI) tract. Current standard endoscopic technology is unable to detect those subsurface lesions. Since cancer development is associated with both morphological and molecular alterations, imaging technologies that can quantitative image tissue's morphological and molecular biomarkers and assess the depth extent of a lesion in real time, without the need for tissue excision, would be a major advance in GI cancer diagnostics and therapy. In this research, we investigated the feasibility of multi-modal optical imaging including high-resolution optical coherence tomography (OCT) and depth-resolved high-sensitivity fluorescence laminar optical tomography (FLOT) for structural and molecular imaging. APC (adenomatous polyposis coli) mice model were imaged using OCT and FLOT and the correlated histopathological diagnosis was obtained. Quantitative structural (the scattering coefficient) and molecular imaging parameters (fluorescence intensity) from OCT and FLOT images were developed for multi-parametric analysis. This multi-modal imaging method has demonstrated the feasibility for more accurate diagnosis with 87.4% (87.3%) for sensitivity (specificity) which gives the most optimal diagnosis (the largest area under receiver operating characteristic (ROC) curve). This project results in a new non-invasive multi-modal imaging platform for improved GI cancer detection, which is expected to have a major impact on detection, diagnosis, and characterization of GI cancers, as well as a wide range of epithelial cancers.

  10. Prediction of lake depth across a 17-state region in the United States

    Science.gov (United States)

    Oliver, Samantha K.; Soranno, Patricia A.; Fergus, C. Emi; Wagner, Tyler; Winslow, Luke A.; Scott, Caren E.; Webster, Katherine E.; Downing, John A.; Stanley, Emily H.

    2016-01-01

    Lake depth is an important characteristic for understanding many lake processes, yet it is unknown for the vast majority of lakes globally. Our objective was to develop a model that predicts lake depth using map-derived metrics of lake and terrestrial geomorphic features. Building on previous models that use local topography to predict lake depth, we hypothesized that regional differences in topography, lake shape, or sedimentation processes could lead to region-specific relationships between lake depth and the mapped features. We therefore used a mixed modeling approach that included region-specific model parameters. We built models using lake and map data from LAGOS, which includes 8164 lakes with maximum depth (Zmax) observations. The model was used to predict depth for all lakes ≥4 ha (n = 42 443) in the study extent. Lake surface area and maximum slope in a 100 m buffer were the best predictors of Zmax. Interactions between surface area and topography occurred at both the local and regional scale; surface area had a larger effect in steep terrain, so large lakes embedded in steep terrain were much deeper than those in flat terrain. Despite a large sample size and inclusion of regional variability, model performance (R2 = 0.29, RMSE = 7.1 m) was similar to other published models. The relative error varied by region, however, highlighting the importance of taking a regional approach to lake depth modeling. Additionally, we provide the largest known collection of observed and predicted lake depth values in the United States.

  11. Empirical analysis of aerosol and thin cloud optical depth effects on CO2 retrievals from GOSAT

    Science.gov (United States)

    Saha, A.; O'Neill, N. T.; Strong, K.; Nakajima, T.; Uchino, O.; Shiobara, M.

    2014-12-01

    Ground-based sunphotometer observations of aerosol and cloud optical properties at AEROCAN / AERONET sites co-located with TCCON (Total Carbon Column Observing Network) high resolution Fourier Transform Spectrometers (FTS) were used to investigate the aerosol and cloud influence on column-averaged dry-air mole fraction of carbon dioxide (XCO2) retrieved from the TANSO-FTS (Thermal And Near-infrared Sensor for carbon Observation - FTS) of GOSAT (Greenhouse gases Observing SATellite). This instrument employs high resolution spectra measured in the Short-Wavelength InfraRed (SWIR) band to retrieve XCO2estimates. GOSAT XCO2 retrievals are nominally corrected for the contaminating backscatter influence of aerosols and thin clouds. However if the satellite-retrieved aerosol and thin cloud optical depths applied to the CO2 correction is biased then the correction and the retrieved CO2 values will be biased. We employed independent ground based estimates of both cloud screened and non cloud screened AOD (aerosol optical depth) in the CO2 SWIR channel and compared this with the GOSAT SWIR-channel OD retrievals to see if that bias was related to variations in the (generally negative) CO2 bias (ΔXCO2= XCO2(GOSAT) - XCO2(TCCON)). Results are presented for a number of TCCON validation sites.

  12. The impact of molecular emission in compositional depth profiling using Glow Discharge-Optical Emission Spectroscopy

    International Nuclear Information System (INIS)

    Bengtson, Arne

    2008-01-01

    The scope of this paper is to investigate and discuss how molecular emission can affect elemental analysis in glow discharge optical emission (GD-OES), particularly in compositional depth profiling (CDP) applications. Older work on molecular emission in glow discharges is briefly reviewed, and the nature of molecular emission spectra described. Work on the influence of hydrogen in the plasma, in particular elevated background due to a continuum spectrum, is discussed. More recent work from sputtering of polymers and other materials with a large content of light elements in a Grimm type source is reviewed, where substantial emission has been observed from several light diatomic molecules (CO, CH, OH, NH, C 2 ). It is discussed how the elevated backgrounds from such molecular emission can lead to significant analytical errors in the form of 'false' depth profile signals of several atomic analytical lines. Results from a recent investigation of molecular emission spectra from mixed gases in a Grimm type glow discharge are presented. An important observation is that dissociation and subsequent recombination processes occur, leading to formation of molecular species not present in the original plasma gas. Experimental work on depth profiling of a polymer coating and a thin silicate film, using a spectrometer equipped with channels for molecular emission lines, is presented. The results confirm that molecular emission gives rise to apparent depth profiles of elements not present in the sample. The possibilities to make adequate corrections for such molecular emission in CDP of organic coatings and very thin films are discussed

  13. Optical coherence tomography to evaluate variance in the extent of carious lesions in depth.

    Science.gov (United States)

    Park, Kyung-Jin; Schneider, Hartmut; Ziebolz, Dirk; Krause, Felix; Haak, Rainer

    2018-05-03

    Evaluation of variance in the extent of carious lesions in depth at smooth surfaces within the same ICDAS code group using optical coherence tomography (OCT) in vitro and in vivo. (1) Verification/validation of OCT to assess non-cavitated caries: 13 human molars with ICDAS code 2 at smooth surfaces were imaged using OCT and light microscopy. Regions of interest (ROI) were categorized according to the depth of carious lesions. Agreement between histology and OCT was determined by unweighted Cohen's Kappa and Wilcoxon test. (2) Assessment of 133 smooth surfaces using ICDAS and OCT in vitro, 49 surfaces in vivo. ROI were categorized according to the caries extent (ICDAS: codes 0-4, OCT: scoring based on lesion depth). A frequency distribution of the OCT scores for each ICDAS code was determined. (1) Histology and OCT agreed moderately (κ = 0.54, p ≤ 0.001) with no significant difference between both methods (p = 0.25). The lesions (76.9% (10 of 13)) _were equally scored. (2) In vitro, OCT revealed caries in 42% of ROI clinically assessed as sound. OCT detected dentin-caries in 40% of ROIs visually assessed as enamel-caries. In vivo, large differences between ICDAS and OCT were observed. Carious lesions of ICDAS codes 1 and 2 vary largely in their extent in depth.

  14. Tree-based solvers for adaptive mesh refinement code FLASH - I: gravity and optical depths

    Science.gov (United States)

    Wünsch, R.; Walch, S.; Dinnbier, F.; Whitworth, A.

    2018-04-01

    We describe an OctTree algorithm for the MPI parallel, adaptive mesh refinement code FLASH, which can be used to calculate the gas self-gravity, and also the angle-averaged local optical depth, for treating ambient diffuse radiation. The algorithm communicates to the different processors only those parts of the tree that are needed to perform the tree-walk locally. The advantage of this approach is a relatively low memory requirement, important in particular for the optical depth calculation, which needs to process information from many different directions. This feature also enables a general tree-based radiation transport algorithm that will be described in a subsequent paper, and delivers excellent scaling up to at least 1500 cores. Boundary conditions for gravity can be either isolated or periodic, and they can be specified in each direction independently, using a newly developed generalization of the Ewald method. The gravity calculation can be accelerated with the adaptive block update technique by partially re-using the solution from the previous time-step. Comparison with the FLASH internal multigrid gravity solver shows that tree-based methods provide a competitive alternative, particularly for problems with isolated or mixed boundary conditions. We evaluate several multipole acceptance criteria (MACs) and identify a relatively simple approximate partial error MAC which provides high accuracy at low computational cost. The optical depth estimates are found to agree very well with those of the RADMC-3D radiation transport code, with the tree-solver being much faster. Our algorithm is available in the standard release of the FLASH code in version 4.0 and later.

  15. Retrieval of Aerosol Optical Depth Above Clouds from OMI Observations: Sensitivity Analysis, Case Studies

    Science.gov (United States)

    Torres, O.; Jethva, H.; Bhartia, P. K.

    2012-01-01

    A large fraction of the atmospheric aerosol load reaching the free troposphere is frequently located above low clouds. Most commonly observed aerosols above clouds are carbonaceous particles generally associated with biomass burning and boreal forest fires, and mineral aerosols originated in arid and semi-arid regions and transported across large distances, often above clouds. Because these aerosols absorb solar radiation, their role in the radiative transfer balance of the earth atmosphere system is especially important. The generally negative (cooling) top of the atmosphere direct effect of absorbing aerosols, may turn into warming when the light-absorbing particles are located above clouds. The actual effect depends on the aerosol load and the single scattering albedo, and on the geometric cloud fraction. In spite of its potential significance, the role of aerosols above clouds is not adequately accounted for in the assessment of aerosol radiative forcing effects due to the lack of measurements. In this paper we discuss the basis of a simple technique that uses near-UV observations to simultaneously derive the optical depth of both the aerosol layer and the underlying cloud for overcast conditions. The two-parameter retrieval method described here makes use of the UV aerosol index and reflectance measurements at 388 nm. A detailed sensitivity analysis indicates that the measured radiances depend mainly on the aerosol absorption exponent and aerosol-cloud separation. The technique was applied to above-cloud aerosol events over the Southern Atlantic Ocean yielding realistic results as indicated by indirect evaluation methods. An error analysis indicates that for typical overcast cloudy conditions and aerosol loads, the aerosol optical depth can be retrieved with an accuracy of approximately 54% whereas the cloud optical depth can be derived within 17% of the true value.

  16. [In-depth interviews and the Kano model to determine user requirements in a burns unit].

    Science.gov (United States)

    González-Revaldería, J; Holguín-Holgado, P; Lumbreras-Marín, E; Núñez-López, G

    To determine the healthcare requirements of patients in a Burns Unit, using qualitative techniques, such us in-depth personal interviews and Kano's methodology. Qualitative methodology using in-depth personal interviews (12 patients), Kano's conceptual model, and the SERVQHOS questionnaire (24 patients). All patients had been hospitalised in the last 12 months in the Burns Unit. Using Kano's methodology, service attributes were grouped by affinity diagrams, and classified as follows: must-be, attractive (unexpected, great satisfaction), and one-dimensional (linked to the degree of functionality of the service). The outcomes were compared with those obtained with SERVQHOS questionnaire. From the analysis of in-depth interviews, 11 requirements were obtained, referring to hotel aspects, information, need for closer staff relationship, and organisational aspects. The attributes classified as must-be were free television and automatic TV disconnection at midnight. Those classified as attractive were: individual room for more privacy, information about dressing change times in order to avoid anxiety, and additional staff for in-patients. The results were complementary to those obtained with the SERVQHOS questionnaire. In-depth personal interviews provide extra knowledge about patient requirements, complementing the information obtained with questionnaires. With this methodology, a more active patient participation is achieved and the companion's opinion is also taken into account. Copyright © 2016 SECA. Publicado por Elsevier España, S.L.U. All rights reserved.

  17. Photoirradiation system with depth optical dosimetry control in initial oxygen saturation measurement

    International Nuclear Information System (INIS)

    Quintanar, L.; Stolik, S.; Rosa, J. de la; Moreno, E.

    2012-01-01

    Photodynamic Therapy is a technique in which a photosensitizing substance is applied that is activated by light and it generates reactive oxygen species which cause selective cell destruction. The efficiency of the therapy is affected by the parameters dose. In this work it is shown a photo-irradiation system for superficial Photodynamic Therapy, using as a light source a light emitting diode with an automatic control of optical power based on a model of the distribution of light in depth that was tested in tissue phantoms. It also has a reflective pulse oximeter for the measurement of the initial oxygen saturation. (Author)

  18. A comparison of two methods to measure choroidal thickness by enhanced depth imaging optical coherence tomography

    DEFF Research Database (Denmark)

    Lundberg, Lars Kristian; Vestergaard, Anders Højslet; Vergmann, Anna Stage

    Introduction The choroid is believed to be involved in the pathophysiology of several vision threatening diseases such as age-related macular degeneration, central serous chorioretinopathy, inflammatory disorders and myopic macular degeneration. Enhanced depth imaging spectral-domain optical...... millimeter in each direction of fovea. Only the horizontal and vertical sections were selected for analysis. A total of 9 targets per eye that represented anatomically different choroidal locations were analysed for every subject. We used 2 different methods from the Heidelberg Explorer software to measure...

  19. Wave like signatures in aerosol optical depth and associated radiative impacts over the central Himalayan region

    Energy Technology Data Exchange (ETDEWEB)

    Shukla, K. K.; Phanikumar, D. V.; Kumar, K.  Niranjan; Reddy, Kishore; Kotamarthi, V. R.; Newsom, Rob K.; Ouarda, Taha B. M. J.

    2015-10-01

    Doppler Lidar and Multi-Filter Rotating Shadowband Radiometer (MFRSR) observations are utilized to show wave like signatures in aerosol optical depth (AOD) during daytime boundary layer evolution over the Himalayan region. Fourier analysis depicted 60–80 min periods dominant during afternoon hours, implying that observed modulations could be plausible reason for the AOD forenoon–afternoon asymmetry which was previously reported. Inclusion of wave amplitude in diurnal variation of aerosol radiative forcing estimates showed ~40% additional warming in the atmosphere relative to mean AOD. The present observations emphasize the importance of wave induced variations in AOD and radiation budget over the site.

  20. Daily snow depth measurements from 195 stations in the United States

    Energy Technology Data Exchange (ETDEWEB)

    Allison, L.J. [ed.] [Oak Ridge National Lab., TN (United States). Carbon Dioxide Information Analysis Center; Easterling, D.R.; Jamason, P.; Bowman, D.P.; Hughes, P.Y.; Mason, E.H. [National Oceanic and Atmospheric Administration, Asheville, NC (United States). National Climatic Data Center

    1997-02-01

    This document describes a database containing daily measurements of snow depth at 195 National Weather Service (NWS) first-order climatological stations in the United States. The data have been assembled and made available by the National Climatic Data Center (NCDC) in Asheville, North Carolina. The 195 stations encompass 388 unique sampling locations in 48 of the 50 states; no observations from Delaware or Hawaii are included in the database. Station selection criteria emphasized the quality and length of station records while seeking to provide a network with good geographic coverage. Snow depth at the 388 locations was measured once per day on ground open to the sky. The daily snow depth is the total depth of the snow on the ground at measurement time. The time period covered by the database is 1893--1992; however, not all station records encompass the complete period. While a station record ideally should contain daily data for at least the seven winter months (January through April and October through December), not all stations have complete records. Each logical record in the snow depth database contains one station`s daily data values for a period of one month, including data source, measurement, and quality flags.

  1. Estimating the maritime component of aerosol optical depth and its dependency on surface wind speed using satellite data

    Directory of Open Access Journals (Sweden)

    Y. Lehahn

    2010-07-01

    Full Text Available Six years (2003–2008 of satellite measurements of aerosol parameters from the Moderate Resolution Imaging Spectroradiometer (MODIS and surface wind speeds from Quick Scatterometer (QuikSCAT, the Advanced Microwave Scanning Radiometer (AMSR-E, and the Special Sensor Microwave Imager (SSM/I, are used to provide a comprehensive perspective on the link between surface wind speed and marine aerosol optical depth over tropical and subtropical oceanic regions. A systematic comparison between the satellite derived fields in these regions allows to: (i separate the relative contribution of wind-induced marine aerosol to the aerosol optical depth; (ii extract an empirical linear equation linking coarse marine aerosol optical depth and wind intensity; and (iii identify a time scale for correlating marine aerosol optical depth and surface wind speed. The contribution of wind induced marine aerosol to aerosol optical depth is found to be dominated by the coarse mode elements. When wind intensity exceeds 4 m/s, coarse marine aerosol optical depth is linearly correlated with the surface wind speed, with a remarkably consistent slope of 0.009±0.002 s/m. A detailed time scale analysis shows that the linear correlation between the fields is well kept within a 12 h time frame, while sharply decreasing when the time lag between measurements is longer. The background aerosol optical depth, associated with aerosols that are not produced in-situ through wind driven processes, can be used for estimating the contributions of terrestrial and biogenic marine aerosol to over-ocean satellite retrievals of aerosol optical depth.

  2. Results from the Fourth WMO Filter Radiometer Comparison for aerosol optical depth measurements

    Science.gov (United States)

    Kazadzis, Stelios; Kouremeti, Natalia; Diémoz, Henri; Gröbner, Julian; Forgan, Bruce W.; Campanelli, Monica; Estellés, Victor; Lantz, Kathleen; Michalsky, Joseph; Carlund, Thomas; Cuevas, Emilio; Toledano, Carlos; Becker, Ralf; Nyeki, Stephan; Kosmopoulos, Panagiotis G.; Tatsiankou, Viktar; Vuilleumier, Laurent; Denn, Frederick M.; Ohkawara, Nozomu; Ijima, Osamu; Goloub, Philippe; Raptis, Panagiotis I.; Milner, Michael; Behrens, Klaus; Barreto, Africa; Martucci, Giovanni; Hall, Emiel; Wendell, James; Fabbri, Bryan E.; Wehrli, Christoph

    2018-03-01

    This study presents the results of the Fourth Filter Radiometer Comparison that was held in Davos, Switzerland, between 28 September and 16 October 2015. Thirty filter radiometers and spectroradiometers from 12 countries participated including reference instruments from global aerosol networks. The absolute differences of all instruments compared to the reference have been based on the World Meteorological Organization (WMO) criterion defined as follows: 95% of the measured data has to be within 0.005 ± 0.001/m (where m is the air mass). At least 24 out of 29 instruments achieved this goal at both 500 and 865 nm, while 12 out of 17 and 13 out of 21 achieved this at 368 and 412 nm, respectively. While searching for sources of differences among different instruments, it was found that all individual differences linked to Rayleigh, NO2, ozone, water vapor calculations and related optical depths and air mass calculations were smaller than 0.01 in aerosol optical depth (AOD) at 500 and 865 nm. Different cloud-detecting algorithms used have been compared. Ångström exponent calculations showed relatively large differences among different instruments, partly because of the high calculation uncertainty of this parameter in low AOD conditions. The overall low deviations of these AOD results and the high accuracy of reference aerosol network instruments demonstrated a promising framework to achieve homogeneity, compatibility and harmonization among the different spectral AOD networks in the near future.

  3. Method of optical coherence tomography with parallel depth-resolved signal reception and fibre-optic phase modulators

    Energy Technology Data Exchange (ETDEWEB)

    Morozov, A N; Turchin, I V [Institute of Applied Physics, Russian Academy of Sciences, Nizhnii Novgorod (Russian Federation)

    2013-12-31

    The method of optical coherence tomography with the scheme of parallel reception of the interference signal (P-OCT) is developed on the basis of spatial paralleling of the reference wave by means of a phase diffraction grating producing the appropriate time delay in the Mach–Zehnder interferometer. The absence of mechanical variation of the optical path difference in the interferometer essentially reduces the time required for 2D imaging of the object internal structure, as compared to the classical OCT that uses the time-domain method of the image construction, the sensitivity and the dynamic range being comparable in both approaches. For the resulting field of the interfering object and reference waves an analytical expression is derived that allows the calculation of the autocorrelation function in the plane of photodetectors. For the first time a method of linear phase modulation by 2π is proposed for P-OCT systems, which allows the use of compact high-frequency (a few hundred kHz) piezoelectric cell-based modulators. For the demonstration of the P-OCT method an experimental setup was created, using which the images of the inner structure of biological objects at the depth up to 1 mm with the axial spatial resolution of 12 μm were obtained. (optical coherence tomography)

  4. Retrieval of Saharan desert dust optical depth from thermal infrared measurements by IASI

    Science.gov (United States)

    Vandenbussche, S.; Kochenova, S.; Vandaele, A.-C.; Kumps, N.; De Mazière, M.

    2012-04-01

    Aerosols are a major actor in the climate system. They are responsible for climate forcing by both direct (by emission, absorption and scattering) and indirect effects (for example, by altering cloud microphysics). A better knowledge of aerosol optical properties, of the atmospheric aerosol load and of aerosol sources and sinks may therefore significantly improve the modeling of climate changes. Aerosol optical depth and other properties are retrieved on an operational basis from daytime measurements in the visible and near infrared spectral range by a number of instruments, like the satellite instruments MODIS, CALIOP, POLDER, MISR and ground-based sunphotometers. Aerosol retrievals from day and night measurements at thermal infrared (TIR) wavelengths (for example, from SEVIRI, AIRS and IASI satellite instruments) are less common, but they receive growing interest in more recent years. Among those TIR measuring instruments, IASI on METOP has one major advantage for aerosol retrievals: its large continuous spectral coverage, allowing to better capture the broadband signature of aerosols. Furthermore, IASI has a high spectral resolution (0.5cm-1 after apodization) which allows retrieving a large number of trace gases at the same time, it will nominally be in orbit for 15 years and offers a quasi global Earth coverage twice a day. Here we will show recently obtained results of desert aerosol properties (concentration, altitude, optical depth) retrieved from IASI TIR measurements, using the ASIMUT software (BIRA-IASB, Belgium) linked to (V)LIDORT (R. Spurr, RTsolutions Inc, US) and to SPHER (M. Mishchenko, NASA GISS, USA). In particular, we will address the case of Saharan desert dust storms, which are a major source of desert dust particles in the atmosphere. Those storms frequently transport sand to Europe, Western Asia or even South America. We will show some test-case comparisons between our retrievals and measurements from other instruments like those listed

  5. Black carbon's contribution to aerosol absorption optical depth over S. Korea

    Science.gov (United States)

    Lamb, K.; Perring, A. E.; Beyersdorf, A. J.; Anderson, B. E.; Segal-Rosenhaimer, M.; Redemann, J.; Holben, B. N.; Schwarz, J. P.

    2017-12-01

    Aerosol absorption optical depth (AAOD) monitored by ground-based sites (AERONET, SKYNET, etc.) is used to constrain climate radiative forcing from black carbon (BC) and other absorbing aerosols in global models, but few validation studies between in situ aerosol measurements and ground-based AAOD exist. AAOD is affected by aerosol size distributions, composition, mixing state, and morphology. Megacities provide appealing test cases for this type of study due to their association with very high concentrations of anthropogenic aerosols. During the KORUS-AQ campaign in S. Korea, which took place in late spring and early summer of 2016, in situ aircraft measurements over the Seoul Metropolitan Area and Taehwa Research Forest (downwind of Seoul) were repeated three times per flight over a 6 week period, providing significant temporal coverage of vertically resolved aerosol properties influenced by different meteorological conditions and sources. Measurements aboard the NASA DC-8 by the NOAA Humidified Dual Single Particle Soot Photometers (HD-SP2) quantified BC mass, size distributions, mixing state, and the hygroscopicity of BC containing aerosols. The in situ BC mass vertical profiles are combined with estimated absorption enhancement calculated from observed optical size and hygroscopicity using Mie theory, and then integrated over the depth of the profile to calculate BC's contribution to AAOD. Along with bulk aerosol size distributions and hygroscopicity, bulk absorbing aerosol optical properties, and on-board sky radiance measurements, these measurements are compared with ground-based AERONET site measurements of AAOD to evaluate closure between in situ vertical profiles of BC and AAOD measurements. This study will provide constraints on the relative importance of BC (including lensing and hygroscopicity effects) and non-BC components to AAOD over S. Korea.

  6. Relative humidity and its effect on aerosol optical depth in the vicinity of convective clouds

    International Nuclear Information System (INIS)

    Altaratz, O; Bar-Or, R Z; Wollner, U; Koren, I

    2013-01-01

    The hygroscopic growth of aerosols is controlled by the relative humidity (RH) and changes the aerosols’ physical and hence optical properties. Observational studies of aerosol–cloud interactions evaluate the aerosol concentration using optical parameters, such as the aerosol optical depth (AOD), which can be affected by aerosol humidification. In this study we evaluate the RH background and variance values, in the lower cloudy atmosphere, an additional source of variance in AOD values beside the natural changes in aerosol concentration. In addition, we estimate the bias in RH and AOD, related to cloud thickness. This provides the much needed range of RH-related biases in studies of aerosol–cloud interaction. Twelve years of radiosonde measurements (June–August) in thirteen globally distributed stations are analyzed. The estimated non-biased AOD variance due to day-to-day changes in RH is found to be around 20% and the biases linked to cloud development around 10%. Such an effect is important and should be considered in direct and indirect aerosol effect estimations but it is inadequate to account for most of the AOD trend found in observational studies of aerosol–cloud interactions. (letter)

  7. Depth discrimination in acousto-optic cerebral blood flow measurement simulation

    Science.gov (United States)

    Tsalach, A.; Schiffer, Z.; Ratner, E.; Breskin, I.; Zeitak, R.; Shechter, R.; Balberg, M.

    2016-03-01

    Monitoring cerebral blood flow (CBF) is crucial, as inadequate perfusion, even for relatively short periods of time, may lead to brain damage or even death. Thus, significant research efforts are directed at developing reliable monitoring tools that will enable continuous, bed side, simple and cost-effective monitoring of CBF. All existing non invasive bed side monitoring methods, which are mostly NIRS based, such as Laser Doppler or DCS, tend to underestimate CBF in adults, due to the indefinite effect of extra-cerebral tissues on the obtained signal. If those are to find place in day to day clinical practice, the contribution of extra-cerebral tissues must be eliminated and data from the depth (brain) should be extracted and discriminated. Recently, a novel technique, based on ultrasound modulation of light was developed for non-invasive, continuous CBF monitoring (termed ultrasound-tagged light (UTL or UT-NIRS)), and shown to correlate with readings of 133Xe SPECT and laser Doppler. We have assembled a comprehensive computerized simulation, modeling this acousto-optic technique in a highly scattering media. Using the combination of light and ultrasound, we show how depth information may be extracted, thus distinguishing between flow patterns taking place at different depths. Our algorithm, based on the analysis of light modulated by ultrasound, is presented and examined in a computerized simulation. Distinct depth discrimination ability is presented, suggesting that using such method one can effectively nullify the extra-cerebral tissues influence on the obtained signals, and specifically extract cerebral flow data.

  8. The impact of molecular emission in compositional depth profiling using Glow Discharge-Optical Emission Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Bengtson, Arne [Corrosion and Metals Research Institute, Dr. Kristinas vaeg 48, Stockholm (Sweden)], E-mail: arne.bengtson@kimab.com

    2008-09-15

    The scope of this paper is to investigate and discuss how molecular emission can affect elemental analysis in glow discharge optical emission (GD-OES), particularly in compositional depth profiling (CDP) applications. Older work on molecular emission in glow discharges is briefly reviewed, and the nature of molecular emission spectra described. Work on the influence of hydrogen in the plasma, in particular elevated background due to a continuum spectrum, is discussed. More recent work from sputtering of polymers and other materials with a large content of light elements in a Grimm type source is reviewed, where substantial emission has been observed from several light diatomic molecules (CO, CH, OH, NH, C{sub 2}). It is discussed how the elevated backgrounds from such molecular emission can lead to significant analytical errors in the form of 'false' depth profile signals of several atomic analytical lines. Results from a recent investigation of molecular emission spectra from mixed gases in a Grimm type glow discharge are presented. An important observation is that dissociation and subsequent recombination processes occur, leading to formation of molecular species not present in the original plasma gas. Experimental work on depth profiling of a polymer coating and a thin silicate film, using a spectrometer equipped with channels for molecular emission lines, is presented. The results confirm that molecular emission gives rise to apparent depth profiles of elements not present in the sample. The possibilities to make adequate corrections for such molecular emission in CDP of organic coatings and very thin films are discussed.

  9. Comparison of cloud optical depth and cloud mask applying BRDF model-based background surface reflectance

    Science.gov (United States)

    Kim, H. W.; Yeom, J. M.; Woo, S. H.

    2017-12-01

    Over the thin cloud region, satellite can simultaneously detect the reflectance from thin clouds and land surface. Since the mixed reflectance is not the exact cloud information, the background surface reflectance should be eliminated to accurately distinguish thin cloud such as cirrus. In the previous research, Kim et al (2017) was developed the cloud masking algorithm using the Geostationary Ocean Color Imager (GOCI), which is one of significant instruments for Communication, Ocean, and Meteorology Satellite (COMS). Although GOCI has 8 spectral channels including visible and near infra-red spectral ranges, the cloud masking has quantitatively reasonable result when comparing with MODIS cloud mask (Collection 6 MYD35). Especially, we noticed that this cloud masking algorithm is more specialized in thin cloud detections through the validation with Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) data. Because this cloud masking method was concentrated on eliminating background surface effects from the top-of-atmosphere (TOA) reflectance. Applying the difference between TOA reflectance and the bi-directional reflectance distribution function (BRDF) model-based background surface reflectance, cloud areas both thick cloud and thin cloud can be discriminated without infra-red channels which were mostly used for detecting clouds. Moreover, when the cloud mask result was utilized as the input data when simulating BRDF model and the optimized BRDF model-based surface reflectance was used for the optimized cloud masking, the probability of detection (POD) has higher value than POD of the original cloud mask. In this study, we examine the correlation between cloud optical depth (COD) and its cloud mask result. Cloud optical depths mostly depend on the cloud thickness, the characteristic of contents, and the size of cloud contents. COD ranges from less than 0.1 for thin clouds to over 1000 for the huge cumulus due to scattering by droplets. With

  10. Large depth of focus dynamic micro integral imaging for optical see-through augmented reality display using a focus-tunable lens.

    Science.gov (United States)

    Shen, Xin; Javidi, Bahram

    2018-03-01

    We have developed a three-dimensional (3D) dynamic integral-imaging (InIm)-system-based optical see-through augmented reality display with enhanced depth range of a 3D augmented image. A focus-tunable lens is adopted in the 3D display unit to relay the elemental images with various positions to the micro lens array. Based on resolution priority integral imaging, multiple lenslet image planes are generated to enhance the depth range of the 3D image. The depth range is further increased by utilizing both the real and virtual 3D imaging fields. The 3D reconstructed image and the real-world scene are overlaid using an optical see-through display for augmented reality. The proposed system can significantly enhance the depth range of a 3D reconstructed image with high image quality in the micro InIm unit. This approach provides enhanced functionality for augmented information and adjusts the vergence-accommodation conflict of a traditional augmented reality display.

  11. High resolution coherence domain depth-resolved nailfold capillaroscopy based on correlation mapping optical coherence tomography

    Science.gov (United States)

    Subhash, Hrebesh M.; O'Gorman, Sean; Neuhaus, Kai; Leahy, Martin

    2014-03-01

    In this paper we demonstrate a novel application of correlation mapping optical coherence tomography (cm-OCT) for volumetric nailfold capillaroscopy (NFC). NFC is a widely used non-invasive diagnostic method to analyze capillary morphology and microvascular abnormalities of nailfold area for a range of disease conditions. However, the conventional NFC is incapable of providing volumetric imaging, when volumetric quantitative microangiopathic parameters such as plexus morphology, capillary density, and morphologic anomalies of the end row loops most critical. cm-OCT is a recently developed well established coherence domain magnitude based angiographic modality, which takes advantage of the time-varying speckle effect, which is normally dominant in the vicinity of vascular regions compared to static tissue region. It utilizes the correlation coefficient as a direct measurement of decorrelation between two adjacent B-frames to enhance the visibility of depth-resolved microcirculation.

  12. Optical gesture sensing and depth mapping technologies for head-mounted displays: an overview

    Science.gov (United States)

    Kress, Bernard; Lee, Johnny

    2013-05-01

    Head Mounted Displays (HMDs), and especially see-through HMDs have gained renewed interest in recent time, and for the first time outside the traditional military and defense realm, due to several high profile consumer electronics companies presenting their products to hit market. Consumer electronics HMDs have quite different requirements and constrains as their military counterparts. Voice comments are the de-facto interface for such devices, but when the voice recognition does not work (not connection to the cloud for example), trackpad and gesture sensing technologies have to be used to communicate information to the device. We review in this paper the various technologies developed today integrating optical gesture sensing in a small footprint, as well as the various related 3d depth mapping sensors.

  13. Intercomparison of Aerosol Optical Depth from Brewer Ozone spectrophotometers and CIMEL sunphotometers measurements

    Directory of Open Access Journals (Sweden)

    A. Cheymol

    2009-01-01

    Full Text Available The Langley plot method applied on the Brewer Ozone measurements can provide accurate Aerosol Optical Depth (AOD in the UV-B. We present seven intercomparisons between AOD retrieved from Brewer Ozone measurements at 320 nm and AOD measured by CIMEL sunphotometer at 340 nm or 440 nm (shifted to 320 nm in using the Angström's law, which are stored in the international AERONET database. Only the intercomparisons between co-located instruments can be used to validate the Langley Plot Method applied to the Brewer measurements: in this case, all the correlation coefficients are above 0.82. If the instruments are not at the same site, the correlation between the AOD retrieved by both instruments is much lower. In applying the Angström's law the intercomparison is improved compared to previous study.

  14. Hemispheric aerosol vertical profiles: anthropogenic impacts on optical depth and cloud nuclei.

    Science.gov (United States)

    Clarke, Antony; Kapustin, Vladimir

    2010-09-17

    Understanding the effect of anthropogenic combustion upon aerosol optical depth (AOD), clouds, and their radiative forcing requires regionally representative aerosol profiles. In this work, we examine more than 1000 vertical profiles from 11 major airborne campaigns in the Pacific hemisphere and confirm that regional enhancements in aerosol light scattering, mass, and number are associated with carbon monoxide from combustion and can exceed values in unperturbed regions by more than one order of magnitude. Related regional increases in a proxy for cloud condensation nuclei (CCN) and AOD imply that direct and indirect aerosol radiative effects are coupled issues linked globally to aged combustion. These profiles constrain the influence of combustion on regional AOD and CCN suitable for challenging climate model performance and informing satellite retrievals.

  15. Measurements of UV aerosol optical depth in the French Southern Alps

    Directory of Open Access Journals (Sweden)

    J. Lenoble

    2008-11-01

    Full Text Available Routine measurements of global and diffuse UV irradiances at Briançon station (1310 m a.s.l. are used to retrieve the direct solar irradiance and the aerosol optical depth (AOD, for cloudless days. Data of three years (2003, 2004, 2005 are analyzed; the results confirm those of a preliminary analysis for 2001, 2002.

    The atmosphere is very clear in winter, with AODs between 0.05 and 0.1. The turbidity increases slowly in spring, starting end of February, with AODs around 0.2–0.3 in mid summer, some values reaching 0.4. A similar behaviour is observed for all years, with somewhat higher values in late summer for the year 2003.

  16. Evaluating the impact of aerosol particles above cloud on cloud optical depth retrievals from MODIS

    Science.gov (United States)

    Alfaro-Contreras, Ricardo; Zhang, Jianglong; Campbell, James R.; Holz, Robert E.; Reid, Jeffrey S.

    2014-05-01

    Using two different operational Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) cloud optical depth (COD) retrievals (0.86 versus 1.6 µm), we evaluate the impact of above-cloud smoke aerosol particles on near-IR (0.86 µm) COD retrievals. Aerosol Index (AI) from the collocated Ozone Monitoring Instrument (OMI) are used to identify above-cloud aerosol particle loading over the southern Atlantic Ocean, including both smoke and dust from the African subcontinent. Collocated Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation data constrain cloud phase and provide contextual above-cloud aerosol optical depth. The frequency of occurrence of above-cloud aerosol events is depicted on a global scale for the spring and summer seasons from OMI and Cloud Aerosol Lidar with Orthogonal Polarization. Seasonal frequencies for smoke-over-cloud off the southwestern Africa coastline reach 20-50% in boreal summer. We find a corresponding low COD bias of 10-20% for standard MODIS COD retrievals when averaged OMI AI are larger than 1. No such bias is found over the Saharan dust outflow region off northern Africa, since both MODIS 0.86 and 1.6 µm channels are vulnerable to radiance attenuation due to dust particles. A similar result is found for a smaller domain, in the Gulf of Tonkin region, from smoke advection over marine stratocumulus clouds and outflow into the northern South China Sea in spring. This study shows the necessity of accounting for the above-cloud aerosol events for future studies using standard MODIS cloud products in biomass burning outflow regions, through the use of collocated OMI AI and supplementary MODIS 1.6 µm COD products.

  17. Evaluating the impact of above-cloud aerosols on cloud optical depth retrievals from MODIS

    Science.gov (United States)

    Alfaro, Ricardo

    Using two different operational Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) cloud optical depth (COD) retrievals (visible and shortwave infrared), the impacts of above-cloud absorbing aerosols on the standard COD retrievals are evaluated. For fine-mode aerosol particles, aerosol optical depth (AOD) values diminish sharply from the visible to the shortwave infrared channels. Thus, a suppressed above-cloud particle radiance aliasing effect occurs for COD retrievals using shortwave infrared channels. Aerosol Index (AI) from the spatially and temporally collocated Ozone Monitoring Instrument (OMI) are used to identify above-cloud aerosol particle loading over the southern Atlantic Ocean, including both smoke and dust from the African sub-continent. MODIS and OMI Collocated Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) data are used to constrain cloud phase and provide contextual above-cloud AOD values. The frequency of occurrence of above-cloud aerosols is depicted on a global scale for the spring and summer seasons from OMI and CALIOP, thus indicating the significance of the problem. Seasonal frequencies for smoke-over-cloud off the southwestern Africa coastline reach 20--50% in boreal summer. We find a corresponding low COD bias of 10--20% for standard MODIS COD retrievals when averaged OMI AI are larger than 1.0. No such bias is found over the Saharan dust outflow region off northern Africa, since both MODIS visible and shortwave in channels are vulnerable to dust particle aliasing, and thus a COD impact cannot be isolated with this method. A similar result is found for a smaller domain, in the Gulf of Tonkin region, from smoke advection over marine stratocumulus clouds and outflow into the northern South China Sea in spring. This study shows the necessity of accounting for the above-cloud aerosol events for future studies using standard MODIS cloud products in biomass burning outflow regions, through the use of

  18. Influence of water vapour and permanent gases on the atmospheric optical depths and transmittance

    Science.gov (United States)

    Badescu, V.

    1991-05-01

    The influence of the atmospheric state on the extinction of direct solar radiation has been studied by using a four layer atmospheric model. Simple analytical formulae are established for the spectral optical depths of permanent gases and water vapour. These formulae use the ground level values of air pressure, temperature and relative huniidity. An additional parameter, related to the vertical distribution of the hunmidity content, is used for a better estimation of the water vapour optical depth. Good agreement between theory and measurements is found. The paper shows the dependence of the atmospheric spectral transmittance on the above mentioned parameters. L'influence de l'état atmosphérique sur l'extinction de la radiation solaire directe a été étudiée à l'aide d'un modèle atmosphérique développé antérieurement par l'auteur. Des formules simples ont été établies pour l'épaisseur optique spectrale des gaz et de la vapeur d'eau. Ces formules utilisent les valeurs de la pression atmosphérique, de la température et de l'humidité relative, mesurées au niveau du sol. Un paramètre supplémentaire, lié à la distribution verticale du contenu d'humidité, est utilisé pour calculer l'épaisseur optique due à la vapeur d'eau. La théorie est en bon accord avec les résultats des mesures. Le travail montre la dépendance de la transmittance atmosphérique spectrale en fonction des paramètres spécifiés ci-dessus.

  19. Optical Estimation of Depth and Current in a Ebb Tidal Delta Environment

    Science.gov (United States)

    Holman, R. A.; Stanley, J.

    2012-12-01

    A key limitation to our ability to make nearshore environmental predictions is the difficulty of obtaining up-to-date bathymetry measurements at a reasonable cost and frequency. Due to the high cost and complex logistics of in-situ methods, research into remote sensing approaches has been steady and has finally yielded fairly robust methods like the cBathy algorithm for optical Argus data that show good performance on simple barred beach profiles and near immunity to noise and signal problems. In May, 2012, data were collected in a more complex ebb tidal delta environment during the RIVET field experiment at New River Inlet, NC. The presence of strong reversing tidal currents led to significant errors in cBathy depths that were phase-locked to the tide. In this paper we will test methods for the robust estimation of both depths and vector currents in a tidal delta domain. In contrast to previous Fourier methods, wavenumber estimation in cBathy can be done on small enough scales to resolve interesting nearshore features.

  20. Motionless active depth from defocus system using smart optics for camera autofocus applications

    Science.gov (United States)

    Amin, M. Junaid; Riza, Nabeel A.

    2016-04-01

    This paper describes a motionless active Depth from Defocus (DFD) system design suited for long working range camera autofocus applications. The design consists of an active illumination module that projects a scene illuminating coherent conditioned optical radiation pattern which maintains its sharpness over multiple axial distances allowing an increased DFD working distance range. The imager module of the system responsible for the actual DFD operation deploys an electronically controlled variable focus lens (ECVFL) as a smart optic to enable a motionless imager design capable of effective DFD operation. An experimental demonstration is conducted in the laboratory which compares the effectiveness of the coherent conditioned radiation module versus a conventional incoherent active light source, and demonstrates the applicability of the presented motionless DFD imager design. The fast response and no-moving-parts features of the DFD imager design are especially suited for camera scenarios where mechanical motion of lenses to achieve autofocus action is challenging, for example, in the tiny camera housings in smartphones and tablets. Applications for the proposed system include autofocus in modern day digital cameras.

  1. Black Carbon, Aerosol optical depth and Angstrom Exponent in São Paulo, Brazil

    Science.gov (United States)

    Miranda, R. M.; Perez-Martinez, P. J.; Andrade, M. D. F.

    2017-12-01

    Black carbon (BC) is a major absorber of solar radiation, and its impact on the radiative balance is therefore considered important. Fossil fuel combustion processes and biomass burning result in the emission of BC. Black carbon is being monitored since 2014 with a Multi-Angle Absorption Photometer-MAAP (5012; Thermo Scientific) in the East Zone of São Paulo, Brazil. São Paulo Metropolitan Area with more than 19 million inhabitants, 7 million vehicles, has high concentrations of air pollutants, especially in the winter. Vehicles can be considered the principal source of particles emitted to the atmosphere. Concentration of the pollutant had an average of 1.95 ug.m-3 ± 2.06 and a maximum value of 19.93 ug.m-3. These large variations were due to meteorological effects and to the influence of anthropogenic activities, since samples were collected close to important highways. Winds coming from the East part predominate. Higher concentrations were found in the winter months (June, July and August). Optical data from AERONET (Aerosol Optical Depth-AOD 550 nm and Angstrom Exponent 440-675 nm) were related to BC concentrations for the period from August, 2016. Average values of AOD at 500 nm and Angstrom Parameter (440-675nm) were 0.16±0.11 and 1.44±0.23, respectively. Higher BC concentrations were related to lower Angstrom values.

  2. Assessing the relationship between microwave vegetation optical depth and gross primary production

    Science.gov (United States)

    Teubner, Irene E.; Forkel, Matthias; Jung, Martin; Liu, Yi Y.; Miralles, Diego G.; Parinussa, Robert; van der Schalie, Robin; Vreugdenhil, Mariette; Schwalm, Christopher R.; Tramontana, Gianluca; Camps-Valls, Gustau; Dorigo, Wouter A.

    2018-03-01

    At the global scale, the uptake of atmospheric carbon dioxide by terrestrial ecosystems through photosynthesis is commonly estimated through vegetation indices or biophysical properties derived from optical remote sensing data. Microwave observations of vegetated areas are sensitive to different components of the vegetation layer than observations in the optical domain and may therefore provide complementary information on the vegetation state, which may be used in the estimation of Gross Primary Production (GPP). However, the relation between GPP and Vegetation Optical Depth (VOD), a biophysical quantity derived from microwave observations, is not yet known. This study aims to explore the relationship between VOD and GPP. VOD data were taken from different frequencies (L-, C-, and X-band) and from both active and passive microwave sensors, including the Advanced Scatterometer (ASCAT), the Soil Moisture Ocean Salinity (SMOS) mission, the Advanced Microwave Scanning Radiometer for Earth Observation System (AMSR-E) and a merged VOD data set from various passive microwave sensors. VOD data were compared against FLUXCOM GPP and Solar-Induced chlorophyll Fluorescence (SIF) from the Global Ozone Monitoring Experiment-2 (GOME-2). FLUXCOM GPP estimates are based on the upscaling of flux tower GPP observations using optical satellite data, while SIF observations present a measure of photosynthetic activity and are often used as a proxy for GPP. For relating VOD to GPP, three variables were analyzed: original VOD time series, temporal changes in VOD (ΔVOD), and positive changes in VOD (ΔVOD≥0). Results show widespread positive correlations between VOD and GPP with some negative correlations mainly occurring in dry and wet regions for active and passive VOD, respectively. Correlations between VOD and GPP were similar or higher than between VOD and SIF. When comparing the three variables for relating VOD to GPP, correlations with GPP were higher for the original VOD time

  3. The World Optical Depth Research and Calibration Center (WORCC) quality assurance and quality control of GAW-PFR AOD measurements

    Science.gov (United States)

    Kazadzis, Stelios; Kouremeti, Natalia; Nyeki, Stephan; Gröbner, Julian; Wehrli, Christoph

    2018-02-01

    The World Optical Depth Research Calibration Center (WORCC) is a section within the World Radiation Center at Physikalisches-Meteorologisches Observatorium (PMOD/WRC), Davos, Switzerland, established after the recommendations of the World Meteorological Organization for calibration of aerosol optical depth (AOD)-related Sun photometers. WORCC is mandated to develop new methods for instrument calibration, to initiate homogenization activities among different AOD networks and to run a network (GAW-PFR) of Sun photometers. In this work we describe the calibration hierarchy and methods used under WORCC and the basic procedures, tests and processing techniques in order to ensure the quality assurance and quality control of the AOD-retrieved data.

  4. Fast and automatic depth control of iterative bone ablation based on optical coherence tomography data

    Science.gov (United States)

    Fuchs, Alexander; Pengel, Steffen; Bergmeier, Jan; Kahrs, Lüder A.; Ortmaier, Tobias

    2015-07-01

    Laser surgery is an established clinical procedure in dental applications, soft tissue ablation, and ophthalmology. The presented experimental set-up for closed-loop control of laser bone ablation addresses a feedback system and enables safe ablation towards anatomical structures that usually would have high risk of damage. This study is based on combined working volumes of optical coherence tomography (OCT) and Er:YAG cutting laser. High level of automation in fast image data processing and tissue treatment enables reproducible results and shortens the time in the operating room. For registration of the two coordinate systems a cross-like incision is ablated with the Er:YAG laser and segmented with OCT in three distances. The resulting Er:YAG coordinate system is reconstructed. A parameter list defines multiple sets of laser parameters including discrete and specific ablation rates as ablation model. The control algorithm uses this model to plan corrective laser paths for each set of laser parameters and dynamically adapts the distance of the laser focus. With this iterative control cycle consisting of image processing, path planning, ablation, and moistening of tissue the target geometry and desired depth are approximated until no further corrective laser paths can be set. The achieved depth stays within the tolerances of the parameter set with the smallest ablation rate. Specimen trials with fresh porcine bone have been conducted to prove the functionality of the developed concept. Flat bottom surfaces and sharp edges of the outline without visual signs of thermal damage verify the feasibility of automated, OCT controlled laser bone ablation with minimal process time.

  5. Enhanced depth imaging optical coherence tomography of the sclera in dome-shaped macula.

    Science.gov (United States)

    Imamura, Yutaka; Iida, Tomohiro; Maruko, Ichiro; Zweifel, Sandrine A; Spaide, Richard F

    2011-02-01

    To examine the posterior anatomic structure of eyes with dome-shaped macula using enhanced depth imaging spectral-domain optical coherence tomography (EDI-OCT). Retrospective observational case series. Patients with dome-shaped macula, a condition defined as convex elevation of the macula as compared with the surrounding staphylomatous region in a highly myopic eye, were identified through routine examinations using optical coherence tomography (OCT). EDI-OCT was used to examine their posterior anatomic changes. The scleral thickness was measured from the outer border of the choroid to the outer scleral border under the fovea and 3000 μm temporal to the fovea. The mean age of the 15 patients (23 eyes) was 59.3 (± 12.2) years, and the mean refractive error was -13.6 (± 5.0) diopters. The best-corrected visual acuity ranged from 20/15 to 20/800 (median: 20/30). Eight patients (53%) had dome-shaped macula bilaterally. The mean subfoveal scleral thickness in 23 eyes with dome-shaped macula was 570 (± 221) μm, and that in 25 eyes of 15 myopic patients with staphyloma but without dome-shaped macula was 281 (± 85) μm (P macula is the result of a relative localized thickness variation of the sclera under the macula in highly myopic patients, and it cannot be categorized into any of the known types of staphyloma. This finding suggests the ocular expansion in myopia may be more complex than previously thought. Copyright © 2011 Elsevier Inc. All rights reserved.

  6. Reducing Multisensor Satellite Monthly Mean Aerosol Optical Depth Uncertainty: 1. Objective Assessment of Current AERONET Locations

    Science.gov (United States)

    Li, Jing; Li, Xichen; Carlson, Barbara E.; Kahn, Ralph A.; Lacis, Andrew A.; Dubovik, Oleg; Nakajima, Teruyuki

    2016-01-01

    Various space-based sensors have been designed and corresponding algorithms developed to retrieve aerosol optical depth (AOD), the very basic aerosol optical property, yet considerable disagreement still exists across these different satellite data sets. Surface-based observations aim to provide ground truth for validating satellite data; hence, their deployment locations should preferably contain as much spatial information as possible, i.e., high spatial representativeness. Using a novel Ensemble Kalman Filter (EnKF)- based approach, we objectively evaluate the spatial representativeness of current Aerosol Robotic Network (AERONET) sites. Multisensor monthly mean AOD data sets from Moderate Resolution Imaging Spectroradiometer, Multiangle Imaging Spectroradiometer, Sea-viewing Wide Field-of-view Sensor, Ozone Monitoring Instrument, and Polarization and Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar are combined into a 605-member ensemble, and AERONET data are considered as the observations to be assimilated into this ensemble using the EnKF. The assessment is made by comparing the analysis error variance (that has been constrained by ground-based measurements), with the background error variance (based on satellite data alone). Results show that the total uncertainty is reduced by approximately 27% on average and could reach above 50% over certain places. The uncertainty reduction pattern also has distinct seasonal patterns, corresponding to the spatial distribution of seasonally varying aerosol types, such as dust in the spring for Northern Hemisphere and biomass burning in the fall for Southern Hemisphere. Dust and biomass burning sites have the highest spatial representativeness, rural and oceanic sites can also represent moderate spatial information, whereas the representativeness of urban sites is relatively localized. A spatial score ranging from 1 to 3 is assigned to each AERONET site based on the uncertainty

  7. Aerosol optical depth in a western Mediterranean site: An assessment of different methods

    Science.gov (United States)

    Sanchez-Romero, A.; González, J. A.; Calbó, J.; Sanchez-Lorenzo, A.; Michalsky, J.

    2016-06-01

    Column aerosol optical properties were derived from multifilter rotating shadowing radiometer (MFRSR) observations carried out at Girona (northeast Spain) from June 2012 to June 2014. We used a technique that allows estimating simultaneously aerosol optical depth (AOD) and Ångström exponent (AE) at high time-resolution. For the period studied, mean AOD at 500 nm was 0.14, with a noticeable seasonal pattern, i.e. maximum in summer and minimum in winter. Mean AE from 500 to 870 nm was 1.2 with a strong day-to-day variation and slightly higher values in summer. So, the summer increase in AOD seems to be linked with an enhancement in the number of fine particles. A radiative closure experiment, using the SMARTS2 model, was performed to confirm that the MFRSR-retrieved aerosol optical properties appropriately represent the continuously varying atmospheric conditions in Girona. Thus, the calculated broadband values of the direct flux show a mean absolute difference of less than 5.9 W m- 2 (0.77%) and R = 0.99 when compared to the observed fluxes. The sensitivity of the achieved closure to uncertainties in AOD and AE was also examined. We use this MFRSR-based dataset as a reference for other ground-based and satellite measurements that might be used to assess the aerosol properties at this site. First, we used observations obtained from a 100 km away AERONET station; despite a general similar behavior when compared with the in-situ MFRSR observations, certain discrepancies for AOD estimates in the different channels (R < 0.84 and slope < 1) appear. Second, AOD products from MISR and MODIS satellite observations were compared with our ground-based retrievals. Reasonable agreements are found for the MISR product (R = 0.92), with somewhat poorer agreement for the MODIS product (R = 0.70). Finally, we apply all these methods to study in detail the aerosol properties during two singular aerosol events related to a forest fire and a desert dust intrusion.

  8. Evaluation of the MODIS C6 Aerosol Optical Depth Products over Chongqing, China

    Directory of Open Access Journals (Sweden)

    Guangming Shi

    2017-11-01

    Full Text Available The Moderate Resolution Imaging Spectroradiometer (MODIS Collection 6 (C6 aerosol optical depth (AOD products from the 10/3 km Dark Target (DT and Deep Blue (DB algorithms are firstly evaluated using ground observed AODs by the sun photometer in Chongqing, a mountainous mega-city in southwest China. The validation results show that MODIS AODs from 10/3 km DT algorithm are comparable with those of the sun photometer, although there are slight overestimations. However, the DB algorithm substantially underestimates MODIS AODs when comparing with those of the sun photometer. Error analyses imply that the bias of surface reflectance estimation is the main error source for both algorithms. The cloud screening scheme of the DT algorithm is more effective than the DB algorithm. The cloud vicinity effect should be considered in the quality control processes for both of the algorithms. A sensitivity test suggests that in complex terrain area, like Chongqing, the collocation method in the validation of satellite products should be carefully selected according to local circumstances. When comparing the monthly mean AODs of MODIS products with sun photometer observations, it shows that the Terra MODIS AOD products are valid to represent the mean statuses in summer and autumn, but the monthly mean of Aqua MODIS AODs are limited in Chongqing.

  9. Aerosol Optical Depth investigated with satellite remote sensing observations in China

    International Nuclear Information System (INIS)

    Die, Hu; Lei, Zhang; Hongbin, Wang

    2014-01-01

    In this study, Aerosol Optical Depth (AOD) at 550nm from the MODIS sensor on board the Terra/Aqua satellites were compared with sun photometer (CE-318) measurements from 11 AERONET stations in China. The average correlation coefficient (R) value from the AOD product, using the Aqua-MODIS Deep Blue algorithm, in the Hexi Corridor was 0.67. The MODIS Dark Target algorithm AOD product is superior to Deep Blue algorithm AOD products in SACOL of the Semi-arid regions of the Loess Plateau. These two kinds of algorithm are not applicable to sites in Lanzhou city. The average R value of Dark Target algorithm AOD MODIS products is 0.91 for Terra and 0.88 for Aqua in the eastern part of China. According to the analysis of spatial and temporal characteristics of the two MODIS AOD products in China, high value areas are mainly distributed in the southern part of Xinjiang (0.5∼0.8), Sichuan Basin (0.8∼0.9), North China (0.6∼0.8) and the middle and lower reaches of the Changjiang River (0.8∼1.0). The Deep Blue algorithm for Aqua-MODIS is a good supplement for the retrieval of AOD above bright surfaces of deserts in Northwest China

  10. A characterization of Arctic aerosols on the basis of aerosol optical depth and black carbon measurements

    Directory of Open Access Journals (Sweden)

    R. S. Stone

    2014-06-01

    Full Text Available Abstract Aerosols, transported from distant source regions, influence the Arctic surface radiation budget. When deposited on snow and ice, carbonaceous particles can reduce the surface albedo, which accelerates melting, leading to a temperature-albedo feedback that amplifies Arctic warming. Black carbon (BC, in particular, has been implicated as a major warming agent at high latitudes. BC and co-emitted aerosols in the atmosphere, however, attenuate sunlight and radiatively cool the surface. Warming by soot deposition and cooling by atmospheric aerosols are referred to as “darkening” and “dimming” effects, respectively. In this study, climatologies of spectral aerosol optical depth AOD (2001–2011 and Equivalent BC (EBC (1989–2011 from three Arctic observatories and from a number of aircraft campaigns are used to characterize Arctic aerosols. Since the 1980s, concentrations of BC in the Arctic have decreased by more than 50% at ground stations where in situ observations are made. AOD has increased slightly during the past decade, with variations attributed to changing emission inventories and source strengths of natural aerosols, including biomass smoke and volcanic aerosol, further influenced by deposition rates and airflow patterns.

  11. Interference of Heavy Aerosol Loading on the VIIRS Aerosol Optical Depth (AOD Retrieval Algorithm

    Directory of Open Access Journals (Sweden)

    Yang Wang

    2017-04-01

    Full Text Available Aerosol optical depth (AOD has been widely used in climate research, atmospheric environmental observations, and other applications. However, high AOD retrieval remains challenging over heavily polluted regions, such as the North China Plain (NCP. The Visible Infrared Imaging Radiometer Suite (VIIRS, which was designed as a successor to the Moderate Resolution Imaging Spectroradiometer (MODIS, will undertake the aerosol observations mission in the coming years. Using the VIIRS AOD retrieval algorithm as an example, we analyzed the influence of heavy aerosol loading through the 6SV radiative transfer model (RTM with a focus on three aspects: cloud masking, ephemeral water body tests, and data quality estimation. First, certain pixels were mistakenly screened out as clouds and ephemeral water bodies because of heavy aerosols, resulting in the loss of AOD retrievals. Second, the greenness of the surface could not be accurately identified by the top of atmosphere (TOA index, and the quality of the aggregation data may be artificially high. Thus, the AOD retrieval algorithm did not perform satisfactorily, indicated by the low availability of data coverage (at least 37.97% of all data records were missing according to ground-based observations and overestimation of the data quality (high-quality data increased from 63.42% to 80.97% according to radiative simulations. To resolve these problems, the implementation of a spatial variability cloud mask method and surficial index are suggested in order to improve the algorithm.

  12. A Review on Predicting Ground PM2.5 Concentration Using Satellite Aerosol Optical Depth

    Directory of Open Access Journals (Sweden)

    Yuanyuan Chu

    2016-10-01

    Full Text Available This study reviewed the prediction of fine particulate matter (PM2.5 from satellite aerosol optical depth (AOD and summarized the advantages and limitations of these predicting models. A total of 116 articles were included from 1436 records retrieved. The number of such studies has been increasing since 2003. Among these studies, four predicting models were widely used: Multiple Linear Regression (MLR (25 articles, Mixed-Effect Model (MEM (23 articles, Chemical Transport Model (CTM (16 articles and Geographically Weighted Regression (GWR (10 articles. We found that there is no so-called best model among them and each has both advantages and limitations. Regarding the prediction accuracy, MEM performs the best, while MLR performs worst. CTM predicts PM2.5 better on a global scale, while GWR tends to perform well on a regional level. Moreover, prediction performance can be significantly improved by combining meteorological variables with land use factors of each region, instead of only considering meteorological variables. In addition, MEM has advantages in dealing with the AOD data with missing values. We recommend that with the help of higher resolution AOD data, future works could be focused on developing satellite-based predicting models for the prediction of historical PM2.5 and other air pollutants.

  13. Effective aerosol optical depth from pyranometer measurements of surface solar radiation (global radiation at Thessaloniki, Greece

    Directory of Open Access Journals (Sweden)

    A. V. Lindfors

    2013-04-01

    Full Text Available Pyranometer measurements of the solar surface radiation (SSR are available at many locations worldwide, often as long time series covering several decades into the past. These data constitute a potential source of information on the atmospheric aerosol load. Here, we present a method for estimating the aerosol optical depth (AOD using pyranometer measurements of the SSR together with total water vapor column information. The method, which is based on radiative transfer simulations, was developed and tested using recent data from Thessaloniki, Greece. The effective AOD calculated using this method was found to agree well with co-located AERONET measurements, exhibiting a correlation coefficient of 0.9 with 2/3 of the data found within ±20% or ±0.05 of the AERONET AOD. This is similar to the performance of current satellite aerosol methods. Differences in the AOD as compared to AERONET can be explained by variations in the aerosol properties of the atmosphere that are not accounted for in the idealized settings used in the radiative transfer simulations, such as variations in the single scattering albedo and Ångström exponent. Furthermore, the method is sensitive to calibration offsets between the radiative transfer simulations and the pyranometer SSR. The method provides an opportunity of extending our knowledge of the atmospheric aerosol load to locations and times not covered by dedicated aerosol measurements.

  14. Automatic segmentation of the choroid in enhanced depth imaging optical coherence tomography images.

    Science.gov (United States)

    Tian, Jing; Marziliano, Pina; Baskaran, Mani; Tun, Tin Aung; Aung, Tin

    2013-03-01

    Enhanced Depth Imaging (EDI) optical coherence tomography (OCT) provides high-definition cross-sectional images of the choroid in vivo, and hence is used in many clinical studies. However, the quantification of the choroid depends on the manual labelings of two boundaries, Bruch's membrane and the choroidal-scleral interface. This labeling process is tedious and subjective of inter-observer differences, hence, automatic segmentation of the choroid layer is highly desirable. In this paper, we present a fast and accurate algorithm that could segment the choroid automatically. Bruch's membrane is detected by searching the pixel with the biggest gradient value above the retinal pigment epithelium (RPE) and the choroidal-scleral interface is delineated by finding the shortest path of the graph formed by valley pixels using Dijkstra's algorithm. The experiments comparing automatic segmentation results with the manual labelings are conducted on 45 EDI-OCT images and the average of Dice's Coefficient is 90.5%, which shows good consistency of the algorithm with the manual labelings. The processing time for each image is about 1.25 seconds.

  15. Moderate Imaging Resolution Spectroradiometer (MODIS) Aerosol Optical Depth Retrieval for Aerosol Radiative Forcing

    Science.gov (United States)

    Asmat, A.; Jalal, K. A.; Ahmad, N.

    2018-02-01

    The present study uses the Aerosol Optical Depth (AOD) retrieved from Moderate Imaging Resolution Spectroradiometer (MODIS) data for the period from January 2011 until December 2015 over an urban area in Kuching, Sarawak. The results show the minimum AOD value retrieved from MODIS is -0.06 and the maximum value is 6.0. High aerosol loading with high AOD value observed during dry seasons and low AOD monitored during wet seasons. Multi plane regression technique used to retrieve AOD from MODIS (AODMODIS) and different statistics parameter is proposed by using relative absolute error for accuracy assessment in spatial and temporal averaging approach. The AODMODIS then compared with AOD derived from Aerosol Robotic Network (AERONET) Sunphotometer (AODAERONET) and the results shows high correlation coefficient (R2) for AODMODIS and AODAERONET with 0.93. AODMODIS used as an input parameters into Santa Barbara Discrete Ordinate Radiative Transfer (SBDART) model to estimate urban radiative forcing at Kuching. The observed hourly averaged for urban radiative forcing is -0.12 Wm-2 for top of atmosphere (TOA), -2.13 Wm-2 at the surface and 2.00 Wm-2 in the atmosphere. There is a moderate relationship observed between urban radiative forcing calculated using SBDART and AERONET which are 0.75 at the surface, 0.65 at TOA and 0.56 in atmosphere. Overall, variation in AOD tends to cause large bias in the estimated urban radiative forcing.

  16. Variability of aerosol optical depth and Angstrom wavelength exponent derived from AERONET observations in recent decades

    International Nuclear Information System (INIS)

    Xia Xiangao

    2011-01-01

    Using aerosol loading data from 79 Aerosol Robotic Network (AERONET) stations with observations from more than six years, changes in aerosol optical depth (AOD) and Angstrom wavelength exponent (AWE) were studied. A statistical method was developed to determine whether AOD changes were due to increased background AOD values and/or an increased number of high AOD events. AOD decreased significantly at AERONET sites in northeastern North American and in Western Europe, which was accompanied by decreased AWE. Reduction of AOD there was mainly due to a decreased frequency of high AOD events and an increased frequency of background AOD events. In addition, decreased AOD values for high AOD events also accounted for ∼ 16–32% of the AOD reduction. This is indicative of significant meteorological effects on AOD variability. AOD trends in other regions were marginal and most were not significant; however, AOD increased significantly at one site in the Sahel and another in Saudi Arabia, predominantly due to the increased frequency of high AOD events and their average AOD.

  17. Wave like signatures in aerosol optical depth and associated radiative impacts over the central Himalayan region

    Energy Technology Data Exchange (ETDEWEB)

    Shukla, K. K.; Phanikumar, D. V.; Kumar, K.  Niranjan; Reddy, Kishore; Kotamarthi, V. R.; Newsom, Rob K.; Ouarda, Taha B. M. J.

    2015-10-01

    In this study, we present a case study on 16 October 2011 to show the first observational evidence of the influence of short period gravity waves in aerosol transport during daytime over the central Himalayan region. The Doppler lidar data has been utilized to address the daytime boundary layer evolution and related aerosol dynamics over the site. Mixing layer height is estimated by wavelet covariance transform method and found to be ~ 0.7 km, AGL. Aerosol optical depth observations during daytime revealed an asymmetry showing clear enhancement during afternoon hours as compared to forenoon. Interestingly, Fourier and wavelet analysis of vertical velocity and attenuated backscatter showed similar 50-90 min short period gravity wave signatures during afternoon hours. Moreover, our observations showed that gravity waves are dominant within the boundary layer implying that the daytime boundary layer dynamics is playing a vital role in transporting the aerosols from surface to the top of the boundary layer. Similar modulations are also evident in surface parameters like temperature, relative humidity and wind speed indicating these waves are associated with the dynamical aspects over Himalayan region. Finally, time evolution of range-23 height indicator snapshots during daytime showed strong upward velocities especially during afternoon hours implying that convective processes through short period gravity waves plays a significant role in transporting aerosols from the nearby valley region to boundary layer top over the site. These observations also establish the importance of wave induced daytime convective boundary layer dynamics in the lower Himalayan region.

  18. Comparison of Aerosol optical depth (AOD) derived from AERONET sunphotometer and Lidar system

    International Nuclear Information System (INIS)

    Khor, Wei Ying; Hee, Wan Shen; Tan, Fuyi; Lim, Hwee San; Jafri, Mohamad Zubir Mat; Holben, Brent

    2014-01-01

    Aerosol optical depth (AOD) is the measure of aerosols distributed within a column of air from the instrument or Earth's surface to the top of the atmosphere. In this paper, we compared the AOD measured by the Raymetrics Lidar system and AERONET sunphotometer. A total of 6 days data which was collected by both instruments were compiled and compared. Generally, AOD value calculated from Lidar data are higher than that calculated from AERONET data. Differences and similarities in the AOD data trend were observed and the corresponding explanations were done. Level 1.5 data of AERONET is estimated to have an accuracy of ±0.03, thus the Lidar data should follow the trend of the AERONET. But in this regards, this study was conducted less than one month and was very difficult to justify the differences and similarities between AOD measured by the Raymetrics Lidar system and AERONET sunphotometer. So further studies for an extended period will be needed and performed with more comprehensive LIDAR measurements. The slope of the best-fit straight line for the data points between the AOD values retrieved from LIDAR and the AERONET measurements is the closest to unity and the coefficient of determination is high (above 0. 6692). Factors which affect AOD data were discussed. As a conclusion, the trends of the AOD of both systems are similar. Yet due to some external factors, the trend will be slightly different

  19. Impact of the optical depth of field on cytogenetic image quality

    Science.gov (United States)

    Qiu, Yuchen; Chen, Xiaodong; Li, Yuhua; Zheng, Bin; Li, Shibo; Chen, Wei R.; Liu, Hong

    2012-09-01

    In digital pathology, clinical specimen slides are converted into digital images by microscopic image scanners. Since random vibration and mechanical drifting are unavoidable on even high-precision moving stages, the optical depth of field (DOF) of microscopic systems may affect image quality, in particular when using an objective lens with high magnification power. The DOF of a microscopic system was theoretically analyzed and experimentally validated using standard resolution targets under 60× dry and 100× oil objective lenses, respectively. Then cytogenetic samples were imaged at in-focused and off-focused states to analyze the impact of DOF on the acquired image qualities. For the investigated system equipped with the 60× dry and 100× oil objective lenses, the theoretical estimation of the DOF are 0.855 μm and 0.703 μm, and the measured DOF are 3.0 μm and 1.8 μm, respectively. The observation reveals that the chromosomal bands of metaphase cells are distinguishable when images are acquired up to approximately 1.5 μm or 1 μm out of focus using the 60× dry and 100× oil objective lenses, respectively. The results of this investigation provide important designing trade-off parameters to optimize the digital microscopic image scanning systems in the future.

  20. Total Volcanic Stratospheric Aerosol Optical Depths and Implications for Global Climate Change

    Science.gov (United States)

    Ridley, D. A.; Solomon, S.; Barnes, J. E.; Burlakov, V. D.; Deshler, T.; Dolgii, S. I.; Herber, A. B.; Nagai, T.; Neely, R. R., III; Nevzorov, A. V.; hide

    2014-01-01

    Understanding the cooling effect of recent volcanoes is of particular interest in the context of the post-2000 slowing of the rate of global warming. Satellite observations of aerosol optical depth above 15 km have demonstrated that small-magnitude volcanic eruptions substantially perturb incoming solar radiation. Here we use lidar, Aerosol Robotic Network, and balloon-borne observations to provide evidence that currently available satellite databases neglect substantial amounts of volcanic aerosol between the tropopause and 15 km at middle to high latitudes and therefore underestimate total radiative forcing resulting from the recent eruptions. Incorporating these estimates into a simple climate model, we determine the global volcanic aerosol forcing since 2000 to be 0.19 +/- 0.09W/sq m. This translates into an estimated global cooling of 0.05 to 0.12 C. We conclude that recent volcanic events are responsible for more post-2000 cooling than is implied by satellite databases that neglect volcanic aerosol effects below 15 km.

  1. Electron beam and optical depth profiling of quasibulk GaN

    International Nuclear Information System (INIS)

    Chernyak, L.; Osinsky, A.; Nootz, G.; Schulte, A.; Jasinski, J.; Benamara, M.; Liliental-Weber, Z.; Look, D. C.; Molnar, R. J.

    2000-01-01

    Electron beam and optical depth profiling of thick (5.5--64 μm) quasibulk n-type GaN samples, grown by hydride vapor-phase epitaxy, were carried out using electron beam induced current (EBIC), microphotoluminescence (PL), and transmission electron microscopy (TEM). The minority carrier diffusion length, L, was found to increase linearly from 0.25 μm, at a distance of about 5 μm from the GaN/sapphire interface, to 0.63 μm at the GaN surface, for a 36-μm-thick sample. The increase in L was accompanied by a corresponding increase in PL band-to-band radiative transition intensity as a function of distance from the GaN/sapphire interface. We attribute the latter changes in PL intensity and minority carrier diffusion length to a reduced carrier mobility and lifetime at the interface, due to scattering at threading dislocations. The results of EBIC and PL measurements are in good agreement with the values for dislocation density obtained using TEM

  2. Prediction of daily fine particulate matter concentrations using aerosol optical depth retrievals from the Geostationary Operational Environmental Satellite (GOES).

    Science.gov (United States)

    Chudnovsky, Alexandra A; Lee, Hyung Joo; Kostinski, Alex; Kotlov, Tanya; Koutrakis, Petros

    2012-09-01

    Although ground-level PM2.5 (particulate matter with aerodynamic diameter < 2.5 microm) monitoring sites provide accurate measurements, their spatial coverage within a given region is limited and thus often insufficient for exposure and epidemiological studies. Satellite data expand spatial coverage, enhancing our ability to estimate location- and/or subject-specific exposures to PM2.5. In this study, the authors apply a mixed-effects model approach to aerosol optical depth (AOD) retrievals from the Geostationary Operational Environmental Satellite (GOES) to predict PM2.5 concentrations within the New England area of the United States. With this approach, it is possible to control for the inherent day-to-day variability in the AOD-PM2.5 relationship, which depends on time-varying parameters such as particle optical properties, vertical and diurnal concentration profiles, and ground surface reflectance. The model-predicted PM2.5 mass concentration are highly correlated with the actual observations, R2 = 0.92. Therefore, adjustment for the daily variability in AOD-PM2.5 relationship allows obtaining spatially resolved PM2.5 concentration data that can be of great value to future exposure assessment and epidemiological studies. The authors demonstrated how AOD can be used reliably to predict daily PM2.5 mass concentrations, providing determination of their spatial and temporal variability. Promising results are found by adjusting for daily variability in the AOD-PM2.5 relationship, without the need to account for a wide variety of individual additional parameters. This approach is of a great potential to investigate the associations between subject-specific exposures to PM2.5 and their health effects. Higher 4 x 4-km resolution GOES AOD retrievals comparing with the conventional MODerate resolution Imaging Spectroradiometer (MODIS) 10-km product has the potential to capture PM2.5 variability within the urban domain.

  3. First test model of the optical microscope which images the whole vertical particle tracks without any depth scanning

    International Nuclear Information System (INIS)

    Soroko, L.M.

    2001-01-01

    The first test model of the optical microscope which produces the in focus image of the whole vertical particle track without depth scanning is described. The in focus image of the object consisting of the linear array of the point-like elements was obtained. A comparison with primary out of focus image of such an object has been made

  4. Retrieval of Surface Lambert Albedos and Aerosols Optical Depths Using OMEGA Near-IR EPF Observations of Mars

    Science.gov (United States)

    Vincendon, M.; Langevin, Y.; Poulet, F.; Bibring, J.-P.; Gondet, B.

    2007-03-01

    We have analyzed five EPF sequences acquired by OMEGA/Mars Express in the near-IR over ice-free and ice-covered surfaces to retrieve simultaneously the Lambert albedo of the surface and the optical depth of aerosols.

  5. PROCEDURE ENABLING SIMULATION AND IN-DEPTH ANALYSIS OF OPTICAL EFFECTS IN CAMERA-BASED TIME-OF-FLIGHT SENSORS

    Directory of Open Access Journals (Sweden)

    M. Baumgart

    2018-05-01

    Full Text Available This paper presents a simulation approach for Time-of-Flight cameras to estimate sensor performance and accuracy, as well as to help understanding experimentally discovered effects. The main scope is the detailed simulation of the optical signals. We use a raytracing-based approach and use the optical path length as the master parameter for depth calculations. The procedure is described in detail with references to our implementation in Zemax OpticStudio and Python. Our simulation approach supports multiple and extended light sources and allows accounting for all effects within the geometrical optics model. Especially multi-object reflection/scattering ray-paths, translucent objects, and aberration effects (e.g. distortion caused by the ToF lens are supported. The optical path length approach also enables the implementation of different ToF senor types and transient imaging evaluations. The main features are demonstrated on a simple 3D test scene.

  6. Enhanced depth imaging optical coherence tomography and fundus autofluorescence findings in bilateral choroidal osteoma: a case report

    Energy Technology Data Exchange (ETDEWEB)

    Erol, Muhammet Kazim; Coban, Deniz Turgut; Ceran, Basak Bostanci; Bulut, Mehmet, E-mail: muhammetkazimerol@gmail.com [Kazim Erol. Antalya Training and Research Hospital, Ophthalmology Department, Antalya (Turkey)

    2013-11-01

    The authors present enhanced depth imaging optical coherence tomography (EDI OCT) and fundus autofluorescence (FAF) characteristics of a patient with bilateral choroidal osteoma and try to make a correlation between two imaging techniques. Two eyes of a patient with choroidal osteoma underwent complete ophthalmic examination. Enhanced depth imaging optical coherence tomography revealed a cage-like pattern, which corresponded to the calcified region of the tumor. Fundus autofluorescence imaging of the same area showed slight hyperautofluorescence. Three different reflectivity patterns in the decalcified area were defined. In the areas of subretinal fluid, outer segment elongations similar to central serous chorioretinopathy were observed. Hyperautofluorescent spots were evident in fundus autofluorescence in the same area. Calcified and decalcified portions of choroidal osteoma as well as the atrophy of choriocapillaris demonstrated different patterns with enhanced depth imaging and fundus autofluorescence imaging. Both techniques were found to be beneficial in the diagnosis and follow-up of choroidal osteoma. (author)

  7. Enhanced depth imaging optical coherence tomography and fundus autofluorescence findings in bilateral choroidal osteoma: a case report

    International Nuclear Information System (INIS)

    Erol, Muhammet Kazim; Coban, Deniz Turgut; Ceran, Basak Bostanci; Bulut, Mehmet

    2013-01-01

    The authors present enhanced depth imaging optical coherence tomography (EDI OCT) and fundus autofluorescence (FAF) characteristics of a patient with bilateral choroidal osteoma and try to make a correlation between two imaging techniques. Two eyes of a patient with choroidal osteoma underwent complete ophthalmic examination. Enhanced depth imaging optical coherence tomography revealed a cage-like pattern, which corresponded to the calcified region of the tumor. Fundus autofluorescence imaging of the same area showed slight hyperautofluorescence. Three different reflectivity patterns in the decalcified area were defined. In the areas of subretinal fluid, outer segment elongations similar to central serous chorioretinopathy were observed. Hyperautofluorescent spots were evident in fundus autofluorescence in the same area. Calcified and decalcified portions of choroidal osteoma as well as the atrophy of choriocapillaris demonstrated different patterns with enhanced depth imaging and fundus autofluorescence imaging. Both techniques were found to be beneficial in the diagnosis and follow-up of choroidal osteoma. (author)

  8. Enhanced depth imaging optical coherence tomography and fundus autofluorescence findings in bilateral choroidal osteoma: a case report

    Directory of Open Access Journals (Sweden)

    Muhammet Kazim Erol

    2013-06-01

    Full Text Available The authors present enhanced depth imaging optical coherence tomography (EDI OCT and fundus autofluorescence (FAF characteristics of a patient with bilateral choroidal osteoma and try to make a correlation between two imaging techniques. Two eyes of a patient with choroidal osteoma underwent complete ophthalmic examination. Enhanced depth imaging optical coherence tomography revealed a cage-like pattern, which corresponded to the calcified region of the tumor. Fundus autofluorescence imaging of the same area showed slight hyperautofluorescence. Three different reflectivity patterns in the decalcified area were defined. In the areas of subretinal fluid, outer segment elongations similar to central serous chorioretinopathy were observed. Hyperautofluorescent spots were evident in fundus autofluorescence in the same area. Calcified and decalcified portions of choroidal osteoma as well as the atrophy of choriocapillaris demonstrated different patterns with enhanced depth imaging and fundus autofluorescence imaging. Both techniques were found to be beneficial in the diagnosis and follow-up of choroidal osteoma.

  9. Estimating nocturnal opaque ice cloud optical depth from MODIS multispectral infrared radiances using a neural network method

    Science.gov (United States)

    Minnis, Patrick; Hong, Gang; Sun-Mack, Szedung; Smith, William L.; Chen, Yan; Miller, Steven D.

    2016-05-01

    Retrieval of ice cloud properties using IR measurements has a distinct advantage over the visible and near-IR techniques by providing consistent monitoring regardless of solar illumination conditions. Historically, the IR bands at 3.7, 6.7, 11.0, and 12.0 µm have been used to infer ice cloud parameters by various methods, but the reliable retrieval of ice cloud optical depth τ is limited to nonopaque cirrus with τ < 8. The Ice Cloud Optical Depth from Infrared using a Neural network (ICODIN) method is developed in this paper by training Moderate Resolution Imaging Spectroradiometer (MODIS) radiances at 3.7, 6.7, 11.0, and 12.0 µm against CloudSat-estimated τ during the nighttime using 2 months of matched global data from 2007. An independent data set comprising observations from the same 2 months of 2008 was used to validate the ICODIN. One 4-channel and three 3-channel versions of the ICODIN were tested. The training and validation results show that IR channels can be used to estimate ice cloud τ up to 150 with correlations above 78% and 69% for all clouds and only opaque ice clouds, respectively. However, τ for the deepest clouds is still underestimated in many instances. The corresponding RMS differences relative to CloudSat are ~100 and ~72%. If the opaque clouds are properly identified with the IR methods, the RMS differences in the retrieved optical depths are ~62%. The 3.7 µm channel appears to be most sensitive to optical depth changes but is constrained by poor precision at low temperatures. A method for estimating total optical depth is explored for estimation of cloud water path in the future. Factors affecting the uncertainties and potential improvements are discussed. With improved techniques for discriminating between opaque and semitransparent ice clouds, the method can ultimately improve cloud property monitoring over the entire diurnal cycle.

  10. DESIGNING FEATURES OF POWER OPTICAL UNITS FOR TECHNOLOGICAL EQUIPMENT

    Directory of Open Access Journals (Sweden)

    M. Y. Afanasiev

    2016-03-01

    Full Text Available This paper considers the question of an optical unit designing for transmitting power laser radiation through an optical fiber. The aim of this work is designing a simple construction unit with minimized reflection losses. The source of radiation in the optical unit described below is an ultraviolet laser with diode pumping. We present the general functioning scheme and designing features for the three main parts: laser beam deflecting system, laser beam dump and optical unit control system. The described laser beam deflection system is composed of a moving flat mirror and a spherical scattering mirror. Comparative analysis of the production technology for such mirrors was carried out, and, as a result, the decision was made to produce both mirrors of 99.99 % pure molybdenum without coating. A moving mirror deflects laser emission from a source through a fiber or deflects it on a spherical mirror and into the laser beam dump, moreover, switching from one position to another occurs almost immediately. It is shown that a scattering mirror is necessary, otherwise, the absorbing surface of the beam dump is being worn out irregularly. The laser beam dump is an open conical cavity, in which the conical element with its spire turned to the emission source is placed. Special microgeometry of the internal surface of the beam dump is suggested for the better absorption effect. An optical unit control system consists of a laser beam deflection system, laser temperature sensor, deflection system solenoid temperature sensor, and deflection mirror position sensor. The signal processing algorithm for signals coming from the sensors to the controller is described. The optical unit will be used in special technological equipment.

  11. Congestion estimation technique in the optical network unit registration process.

    Science.gov (United States)

    Kim, Geunyong; Yoo, Hark; Lee, Dongsoo; Kim, Youngsun; Lim, Hyuk

    2016-07-01

    We present a congestion estimation technique (CET) to estimate the optical network unit (ONU) registration success ratio for the ONU registration process in passive optical networks. An optical line terminal (OLT) estimates the number of collided ONUs via the proposed scheme during the serial number state. The OLT can obtain congestion level among ONUs to be registered such that this information may be exploited to change the size of a quiet window to decrease the collision probability. We verified the efficiency of the proposed method through simulation and experimental results.

  12. Reflector antenna analysis using physical optics on Graphics Processing Units

    DEFF Research Database (Denmark)

    Borries, Oscar Peter; Sørensen, Hans Henrik Brandenborg; Dammann, Bernd

    2014-01-01

    The Physical Optics approximation is a widely used asymptotic method for calculating the scattering from electrically large bodies. It requires significant computational work and little memory, and is thus well suited for application on a Graphics Processing Unit. Here, we investigate the perform......The Physical Optics approximation is a widely used asymptotic method for calculating the scattering from electrically large bodies. It requires significant computational work and little memory, and is thus well suited for application on a Graphics Processing Unit. Here, we investigate...

  13. Spatiotemporal fusion of multiple-satellite aerosol optical depth (AOD) products using Bayesian maximum entropy method

    Science.gov (United States)

    Tang, Qingxin; Bo, Yanchen; Zhu, Yuxin

    2016-04-01

    Merging multisensor aerosol optical depth (AOD) products is an effective way to produce more spatiotemporally complete and accurate AOD products. A spatiotemporal statistical data fusion framework based on a Bayesian maximum entropy (BME) method was developed for merging satellite AOD products in East Asia. The advantages of the presented merging framework are that it not only utilizes the spatiotemporal autocorrelations but also explicitly incorporates the uncertainties of the AOD products being merged. The satellite AOD products used for merging are the Moderate Resolution Imaging Spectroradiometer (MODIS) Collection 5.1 Level-2 AOD products (MOD04_L2) and the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) Deep Blue Level 2 AOD products (SWDB_L2). The results show that the average completeness of the merged AOD data is 95.2%,which is significantly superior to the completeness of MOD04_L2 (22.9%) and SWDB_L2 (20.2%). By comparing the merged AOD to the Aerosol Robotic Network AOD records, the results show that the correlation coefficient (0.75), root-mean-square error (0.29), and mean bias (0.068) of the merged AOD are close to those (the correlation coefficient (0.82), root-mean-square error (0.19), and mean bias (0.059)) of the MODIS AOD. In the regions where both MODIS and SeaWiFS have valid observations, the accuracy of the merged AOD is higher than those of MODIS and SeaWiFS AODs. Even in regions where both MODIS and SeaWiFS AODs are missing, the accuracy of the merged AOD is also close to the accuracy of the regions where both MODIS and SeaWiFS have valid observations.

  14. An algorithm for estimating aerosol optical depth from HIMAWARI-8 data over Ocean

    Science.gov (United States)

    Lee, Kwon Ho

    2016-04-01

    The paper presents currently developing algorithm for aerosol detection and retrieval over ocean for the next generation geostationary satellite, HIMAWARI-8. Enhanced geostationary remote sensing observations are now enables for aerosol retrieval of dust, smoke, and ash, which began a new era of geostationary aerosol observations. Sixteen channels of the Advanced HIMAWARI Imager (AHI) onboard HIMAWARI-8 offer capabilities for aerosol remote sensing similar to those currently provided by the Moderate Resolution Imaging Spectroradiometer (MODIS). Aerosols were estimated in detection processing from visible and infrared channel radiances, and in retrieval processing using the inversion-optimization of satellite-observed radiances with those calculated from radiative transfer model. The retrievals are performed operationally every ten minutes for pixel sizes of ~8 km. The algorithm currently under development uses a multichannel approach to estimate the effective radius, aerosol optical depth (AOD) simultaneously. The instantaneous retrieved AOD is evaluated by the MODIS level 2 operational aerosol products (C006), and the daily retrieved AOD was compared with ground-based measurements from the AERONET databases. The results show that the detection of aerosol and estimated AOD are in good agreement with the MODIS data and ground measurements with a correlation coefficient of ˜0.90 and a bias of 4%. These results suggest that the proposed method applied to the HIMAWARI-8 satellite data can accurately estimate continuous AOD. Acknowledgments This work was supported by "Development of Geostationary Meteorological Satellite Ground Segment(NMSC-2014-01)" program funded by National Meteorological Satellite Centre(NMSC) of Korea Meteorological Administration(KMA).

  15. The Relationship of Temporal Variations in SMAP Vegetation Optical Depth to Plant Hydraulic Behavior

    Science.gov (United States)

    Konings, A. G.

    2016-12-01

    The soil emissions measured by L-band radiometers such as that on the NASA Soil Moisture Active/Passive mission are modulated by vegetation cover as quantified by the soil scattering albedo and the vegetation optical depth (VOD). The VOD is linearly proportional to the total vegetation water content, which is dependent on both the biomass and relative water content of the plant. Biomass is expected to vary more slowly than water content. Variations in vegetation water content are highly informative as they are directly indicative of the degree of hydraulic stress (or lack thereof) experienced by the plant. However, robust retrievals are needed in order for SMAP VOD observations to be useful. This is complicated by the fact that multiple unknowns (soil moisture, VOD, and albedo) need to be determined from two highly correlated polarizations. This presentation will discuss the application to SMAP of a recently developed timeseries algorithm for VOD and albedo retrieval - the Multi-Temporal Dual Channel Algorithm MTDCA, and its interpretation for plant hydraulic applications. The MT-DCA is based on the assumption that, for consecutive overpasses at a given time of day, VOD varies more slowly than soil moisture. A two-overpass moving average can then be used to determine variations in VOD that are less sensitive to high-frequency noise than classical dual-channel algorithms. Seasonal variations of SMAP VOD are presented and compared to expected patterns based on rainfall and radiation seasonality. Taking advantage of the large diurnal variation (relative to the seasonal variation) of canopy water potention, diurnal variations (between 6AM and 6PM observations) of SMAP VOD are then used to calculate global variations in ecosystem-scale isohydricity - the degree of stomatal closure and xylem conductivity loss in response to water stress. Lastly, the effect of satellite sensing frequency and overpass time on water content across canopies of different height will be

  16. Determination of Thermal Equilibrium in a Sealed Cell Based on Optical Depth

    Energy Technology Data Exchange (ETDEWEB)

    Zou, Sheng; Zhang, Hong; Chen, Xi-yuan [Southeast University, Nanjing (China); Shan, Guang-cun; Quan, Wei [Beihang University, Beijing (China)

    2017-01-15

    An effective method based on optical depth (OD) is presented to measure thermal equilibrium in a cell. First, the principle of determining the temperature distribution in the cell by using the OD is demonstrated. Subsequently, relevant experiments are carried out. Original experimental results showed that some gradients of OD distributions in the cell at different wavelengths and variations of the OD increased slowly along the direction of motion of the beam at a fixed wavelength. At a wavelength of 766.6839 nm, which is about 7 GHz blue shifted with respect to the potassium resonance, the average value of the OD was about 0.764 and the maximal and the minimum inhomogeneity biases among all location points were about 6.07% and 0.56%, respectively. As for the corresponding wavelengths of 766.67785 nm and 766.73004 nm, some deviations from previous results, which were caused by different absorptions of the alkali-metal atoms at different frequencies of the laser beam, were observed. The nonuniform OD values along the direction of motion of the beam reflected an inhomogeneous distribution of the temperature in the cell, which may have been caused by layout of the oven. When the layout of the oven was modified, comparative experiments comparable to these with the previous layout of the oven demonstrated that the uniformity of the temperature distribution in the cell was improved and that thermal equilibrium time was shorter by about 10 minutes. This method played an important role in determining the thermal equilibrium time in the cell.

  17. Choroidal vasculature characteristics based choroid segmentation for enhanced depth imaging optical coherence tomography images

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Qiang; Niu, Sijie [School of Computer Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); Yuan, Songtao; Fan, Wen, E-mail: fanwen1029@163.com; Liu, Qinghuai [Department of Ophthalmology, The First Affiliated Hospital with Nanjing Medical University, Nanjing 210029 (China)

    2016-04-15

    Purpose: In clinical research, it is important to measure choroidal thickness when eyes are affected by various diseases. The main purpose is to automatically segment choroid for enhanced depth imaging optical coherence tomography (EDI-OCT) images with five B-scans averaging. Methods: The authors present an automated choroid segmentation method based on choroidal vasculature characteristics for EDI-OCT images with five B-scans averaging. By considering the large vascular of the Haller’s layer neighbor with the choroid-sclera junction (CSJ), the authors measured the intensity ascending distance and a maximum intensity image in the axial direction from a smoothed and normalized EDI-OCT image. Then, based on generated choroidal vessel image, the authors constructed the CSJ cost and constrain the CSJ search neighborhood. Finally, graph search with smooth constraints was utilized to obtain the CSJ boundary. Results: Experimental results with 49 images from 10 eyes in 8 normal persons and 270 images from 57 eyes in 44 patients with several stages of diabetic retinopathy and age-related macular degeneration demonstrate that the proposed method can accurately segment the choroid of EDI-OCT images with five B-scans averaging. The mean choroid thickness difference and overlap ratio between the authors’ proposed method and manual segmentation drawn by experts were −11.43 μm and 86.29%, respectively. Conclusions: Good performance was achieved for normal and pathologic eyes, which proves that the authors’ method is effective for the automated choroid segmentation of the EDI-OCT images with five B-scans averaging.

  18. Improving Satellite Quantitative Precipitation Estimation Using GOES-Retrieved Cloud Optical Depth

    Energy Technology Data Exchange (ETDEWEB)

    Stenz, Ronald; Dong, Xiquan; Xi, Baike; Feng, Zhe; Kuligowski, Robert J.

    2016-02-01

    To address significant gaps in ground-based radar coverage and rain gauge networks in the U.S., geostationary satellite quantitative precipitation estimates (QPEs) such as the Self-Calibrating Multivariate Precipitation Retrievals (SCaMPR) can be used to fill in both the spatial and temporal gaps of ground-based measurements. Additionally, with the launch of GOES-R, the temporal resolution of satellite QPEs may be comparable to that of Weather Service Radar-1988 Doppler (WSR-88D) volume scans as GOES images will be available every five minutes. However, while satellite QPEs have strengths in spatial coverage and temporal resolution, they face limitations particularly during convective events. Deep Convective Systems (DCSs) have large cloud shields with similar brightness temperatures (BTs) over nearly the entire system, but widely varying precipitation rates beneath these clouds. Geostationary satellite QPEs relying on the indirect relationship between BTs and precipitation rates often suffer from large errors because anvil regions (little/no precipitation) cannot be distinguished from rain-cores (heavy precipitation) using only BTs. However, a combination of BTs and optical depth (τ) has been found to reduce overestimates of precipitation in anvil regions (Stenz et al. 2014). A new rain mask algorithm incorporating both τ and BTs has been developed, and its application to the existing SCaMPR algorithm was evaluated. The performance of the modified SCaMPR was evaluated using traditional skill scores and a more detailed analysis of performance in individual DCS components by utilizing the Feng et al. (2012) classification algorithm. SCaMPR estimates with the new rain mask applied benefited from significantly reduced overestimates of precipitation in anvil regions and overall improvements in skill scores.

  19. Choroidal vasculature characteristics based choroid segmentation for enhanced depth imaging optical coherence tomography images

    International Nuclear Information System (INIS)

    Chen, Qiang; Niu, Sijie; Yuan, Songtao; Fan, Wen; Liu, Qinghuai

    2016-01-01

    Purpose: In clinical research, it is important to measure choroidal thickness when eyes are affected by various diseases. The main purpose is to automatically segment choroid for enhanced depth imaging optical coherence tomography (EDI-OCT) images with five B-scans averaging. Methods: The authors present an automated choroid segmentation method based on choroidal vasculature characteristics for EDI-OCT images with five B-scans averaging. By considering the large vascular of the Haller’s layer neighbor with the choroid-sclera junction (CSJ), the authors measured the intensity ascending distance and a maximum intensity image in the axial direction from a smoothed and normalized EDI-OCT image. Then, based on generated choroidal vessel image, the authors constructed the CSJ cost and constrain the CSJ search neighborhood. Finally, graph search with smooth constraints was utilized to obtain the CSJ boundary. Results: Experimental results with 49 images from 10 eyes in 8 normal persons and 270 images from 57 eyes in 44 patients with several stages of diabetic retinopathy and age-related macular degeneration demonstrate that the proposed method can accurately segment the choroid of EDI-OCT images with five B-scans averaging. The mean choroid thickness difference and overlap ratio between the authors’ proposed method and manual segmentation drawn by experts were −11.43 μm and 86.29%, respectively. Conclusions: Good performance was achieved for normal and pathologic eyes, which proves that the authors’ method is effective for the automated choroid segmentation of the EDI-OCT images with five B-scans averaging.

  20. Retrieval of Aerosol Optical Depth in the Arid or Semiarid Region of Northern Xinjiang, China

    Directory of Open Access Journals (Sweden)

    Xinpeng Tian

    2018-01-01

    Full Text Available Satellite remote sensing has been widely used to retrieve aerosol optical depth (AOD, which is an indicator of air quality as well as radiative forcing. The dark target (DT algorithm is applied to low reflectance areas, such as dense vegetation, and the deep blue (DB algorithm is adopted for bright-reflecting regions. However, both DT and DB algorithms ignore the effect of surface bidirectional reflectance. This paper provides a method for AOD retrieval in arid or semiarid areas, in which the key points are the accurate estimation of surface reflectance and reasonable assumptions of the aerosol model. To reduce the uncertainty in surface reflectance, a minimum land surface reflectance database at the spatial resolution of 500 m for each month was constructed based on the moderate-resolution imaging spectroradiometer (MODIS surface reflectance product. Furthermore, a bidirectional reflectance distribution function (BRDF correction model was adopted to compensate for the effect of surface reflectance anisotropy. The aerosol parameters, including AOD, single scattering albedo, asymmetric factor, Ångström exponent and complex refractive index, are determined based on the observation of two sunphotometers installed in northern Xinjiang from July to August 2014. The AOD retrieved from the MODIS images was validated with ground-based measurements and the Terra-MODIS aerosol product (MOD04. The 500 m AOD retrieved from the MODIS showed high consistency with ground-based AOD measurements, with an average correlation coefficient of ~0.928, root mean square error (RMSE of ~0.042, mean absolute error (MAE of ~0.032, and the percentage falling within the expected error (EE of the collocations is higher than that for the MOD04 DB product. The results demonstrate that the new AOD algorithm is more suitable to represent aerosol conditions over Xinjiang than the DB standard product.

  1. Monocular display unit for 3D display with correct depth perception

    Science.gov (United States)

    Sakamoto, Kunio; Hosomi, Takashi

    2009-11-01

    A study of virtual-reality system has been popular and its technology has been applied to medical engineering, educational engineering, a CAD/CAM system and so on. The 3D imaging display system has two types in the presentation method; one is a 3-D display system using a special glasses and the other is the monitor system requiring no special glasses. A liquid crystal display (LCD) recently comes into common use. It is possible for this display unit to provide the same size of displaying area as the image screen on the panel. A display system requiring no special glasses is useful for a 3D TV monitor, but this system has demerit such that the size of a monitor restricts the visual field for displaying images. Thus the conventional display can show only one screen, but it is impossible to enlarge the size of a screen, for example twice. To enlarge the display area, the authors have developed an enlarging method of display area using a mirror. Our extension method enables the observers to show the virtual image plane and to enlarge a screen area twice. In the developed display unit, we made use of an image separating technique using polarized glasses, a parallax barrier or a lenticular lens screen for 3D imaging. The mirror can generate the virtual image plane and it enlarges a screen area twice. Meanwhile the 3D display system using special glasses can also display virtual images over a wide area. In this paper, we present a monocular 3D vision system with accommodation mechanism, which is useful function for perceiving depth.

  2. Modeling the South American regional smoke plume: aerosol optical depth variability and surface shortwave flux perturbation

    Directory of Open Access Journals (Sweden)

    N. E. Rosário

    2013-03-01

    Full Text Available Intra-seasonal variability of smoke aerosol optical depth (AOD and downwelling solar irradiance at the surface during the 2002 biomass burning season in South America was modeled using the Coupled Chemistry-Aerosol-Tracers Transport model with the Brazilian developments on the Regional Atmospheric Modeling System (CCATT-BRAMS. Measurements of total and fine mode fraction (FMF AOD from the AErosol RObotic NETwork (AERONET and solar irradiance at the surface from the Solar Radiation Network (SolRad-NET were used to evaluate model results. In general, the major features associated with AOD evolution over the southern part of the Amazon basin and cerrado ecosystem are captured by the model. The main discrepancies were found for high aerosol loading events. In the northeastern portion of the Amazon basin the model systematically underestimated total AOD, as expected, since smoke contribution is not dominant as it is in the southern portion and emissions other than smoke were not considered in the simulation. Better agreement was obtained comparing the model results with observed FMF AOD, which pointed out the relevance of coarse mode aerosol emission in that region. Likewise, major discrepancies over cerrado during high AOD events were found to be associated with coarse mode aerosol omission in our model. The issue of high aerosol loading events in the southern part of the Amazon was related to difficulties in predicting the smoke AOD field, which was discussed in the context of emissions shortcomings. The Cuiabá cerrado site was the only one where the highest quality AERONET data were unavailable for both total and FMF AOD. Thus, lower quality data were used. Root-mean-square error (RMSE between the model and observed FMF AOD decreased from 0.34 to 0.19 when extreme AOD events (FMF AOD550 nm ≥ 1.0 and Cuiabá were excluded from the analysis. Downward surface solar irradiance comparisons also followed similar trends when extreme AOD were excluded

  3. Rattlesnake Mountain Observator (46.4{degrees}N, 119.6{degrees}W) multispectral optical depth measurements, 1979--1994

    Energy Technology Data Exchange (ETDEWEB)

    Daniels, R.C. [ed.

    1995-09-22

    Surface measurements of solar irradiance of the atmosphere were made by a multipurpose computer-controlled scanning photometer at the Rattlesnake Mountain Observatory. The observatory is located at 46.4{degrees}N, 119.6{degrees}W at an elevation of 1088 m above mean sea level. The photometer measures the attenuation of direct solar radiation for different wavelengths using 12 filters. Five of these filters (ie., at 428 nm, 486 nm, 535 nm, 785 nm, and 1010 nm, with respective half-power widths of 2, 2, 3, 18, and 28 nm) are suitable for monitoring variations in the total optical depth of the atmosphere. Total optical depths for the five wavelength bands were derived from solar irradiance measurements taken at the observatory from August 5, 1979, to September 2, 1994; these total optical depth data are distributed with this numeric data package (NDP). To determine the contribution of atmospheric aerosols to the total optical depths, the effects of Rayleigh scattering and ozone absorption were subtracted (other molecular scattering was minimal for the five filters) to obtain total column aerosol optical depths. The total aerosol optical depths were further decomposed into tropospheric and stratospheric components by calculating a robustly smoothed mean background optical depth (tropospheric component) for each wavelength using data obtained during periods of low stratospheric aerosol loading. By subtracting the smoothed background tropospheric aerosol optical depths from the total aerosol optical depths, residual aerosol optical depths were obtained. These residuals are good estimates of the stratospheric aerosol optical depth at each wavelength and may be used to monitor the long-term effects of volcanic eruptions on the atmosphere. These data are available as an NDP from the Carbon Dioxide Information Analysis Center (CDIAC), and the NDP consists of this document and a set of computerized data files.

  4. Sub?40?fs, 1060?nm Yb?fiber laser enhances penetration depth in nonlinear optical microscopy of human skin

    OpenAIRE

    Balu, Mihaela; Saytashev, Ilyas; Hou, Jue; Dantus, Marcos; Tromberg, Bruce J.

    2015-01-01

    © 2015 The Authors. Advancing the practical utility of nonlinear optical microscopy requires continued improvement in imaging depth and contrast. We evaluated second-harmonic generation (SHG) and third-harmonic generation images from ex vivo human skin and showed that a sub-40 fs, 1060-nm Yb-fiber laser can enhance SHG penetration depth by up to 80% compared to a > 100 fs, 800 nm Ti:sapphire source. These results demonstrate the potential of fiber-based laser systems to address a key perform...

  5. Planck early results. XIX. All-sky temperature and dust optical depth from Planck and IRAS. Constraints on the "dark gas" in our Galaxy

    DEFF Research Database (Denmark)

    Poutanen, T.; Natoli, P.; Polenta, G.

    2011-01-01

    An all sky map of the apparent temperature and optical depth of thermal dust emission is constructed using the Planck-HFI (350μm to 2 mm) andIRAS(100μm) data. The optical depth maps are correlated with tracers of the atomic (Hi) and molecular gas traced by CO. The correlation with the column dens...

  6. Optical Depth Estimates and Effective Critical Densities of Dense Gas Tracers in the Inner Parts of Nearby Galaxy Discs

    OpenAIRE

    Jimenez-Donaire, M. J.; Bigiel, F.; Leroy, A. K.; Cormier, D.; Gallagher, M.; Usero, A.; Bolatto, A.; Colombo, D.; Garcia-Burillo, S.; Hughes, A.; Kramer, C.; Krumholz, M. R.; Meier, D. S.; Murphy, E.; Pety, J.

    2016-01-01

    High critical density molecular lines like HCN(1-0) or HCO+(1-0) represent our best tool to study currently star-forming, dense molecular gas at extragalactic distances. The optical depth of these lines is a key ingredient to estimate the effective density required to excite emission. However, constraints on this quantity are even scarcer in the literature than measurements of the high density tracers themselves. Here, we combine new observations of HCN, HCO+ and HNC(1-0) and their optically ...

  7. Prediction of Aerosol Optical Depth in West Asia: Machine Learning Methods versus Numerical Models

    Science.gov (United States)

    Omid Nabavi, Seyed; Haimberger, Leopold; Abbasi, Reyhaneh; Samimi, Cyrus

    2017-04-01

    Dust-prone areas of West Asia are releasing increasingly large amounts of dust particles during warm months. Because of the lack of ground-based observations in the region, this phenomenon is mainly monitored through remotely sensed aerosol products. The recent development of mesoscale Numerical Models (NMs) has offered an unprecedented opportunity to predict dust emission, and, subsequently Aerosol Optical Depth (AOD), at finer spatial and temporal resolutions. Nevertheless, the significant uncertainties in input data and simulations of dust activation and transport limit the performance of numerical models in dust prediction. The presented study aims to evaluate if machine-learning algorithms (MLAs), which require much less computational expense, can yield the same or even better performance than NMs. Deep blue (DB) AOD, which is observed by satellites but also predicted by MLAs and NMs, is used for validation. We concentrate our evaluations on the over dry Iraq plains, known as the main origin of recently intensified dust storms in West Asia. Here we examine the performance of four MLAs including Linear regression Model (LM), Support Vector Machine (SVM), Artificial Neural Network (ANN), Multivariate Adaptive Regression Splines (MARS). The Weather Research and Forecasting model coupled to Chemistry (WRF-Chem) and the Dust REgional Atmosphere Model (DREAM) are included as NMs. The MACC aerosol re-analysis of European Centre for Medium-range Weather Forecast (ECMWF) is also included, although it has assimilated satellite-based AOD data. Using the Recursive Feature Elimination (RFE) method, nine environmental features including soil moisture and temperature, NDVI, dust source function, albedo, dust uplift potential, vertical velocity, precipitation and 9-month SPEI drought index are selected for dust (AOD) modeling by MLAs. During the feature selection process, we noticed that NDVI and SPEI are of the highest importance in MLAs predictions. The data set was divided

  8. Variation in MERRA-2 aerosol optical depth over the Yangtze River Delta from 1980 to 2016

    Science.gov (United States)

    Sun, Enwei; Che, Huizheng; Xu, Xiaofeng; Wang, Zhenzhu; Lu, Chunsong; Gui, Ke; Zhao, Hujia; Zheng, Yu; Wang, Yaqiang; Wang, Hong; Sun, Tianze; Liang, Yuanxin; Li, Xiaopan; Sheng, Zhizhong; An, Linchang; Zhang, Xiaoye; Shi, Guangyu

    2018-05-01

    In this study, 765 instantaneous MERRA-2 (second Modern-Era Retrospective analysis for Research and Applications) aerosol optical depth (AOD) values at 550 nm were compared with those of a sky radiometer in Hefei (31.90° N, 117.17° E) for the different seasons from March 2007 to February 2010. The correlation coefficients (R) were 0.88, 0.83, 0.88, and 0.80 in spring, summer, autumn, and winter, respectively. The MERRA-2 AOD is also compared with MODIS Aqua AOD in the entire Yangtze River Delta, and good agreement has been obtained. The MERRA-2 AOD product was used to analyze the spatial distribution and temporal variation of the annual, seasonal and monthly means of the AOD over the Yangtze River Delta region from 1980 to 2016 (37 years). The mean values of the MERRA-2 AOD during the study period show that the AOD (between 0.45 and 0.55) in the northern area of the Yangtze River Delta was higher than that (between 0.30 and 0.45) of the southern area. The northwest part of the Yangtze River Delta had the highest mean AOD values (between 0.50 and 0.55). The AOD increased slowly in the 1980s and 1990s, followed by a rapid increase between 2001 and 2010. An AOD decrease can be seen from 2011 to 2016. The mean AOD in each month is discussed. High AOD was observed in March, April, and June, while low AOD could be seen in September, October, November, and December. Three different area types (large cities, medium-sized cities, and remote areas) had nearly the same annual AOD variation. Large cities had the highest AOD (about 0.48), while remote areas had the lowest (about 0.42). In summer, the AOD in remote areas was much lower than that in cities. The AOD variational trend over the Yangtze River Delta was studied during two periods. The increasing trend could be seen over the entire Yangtze River Delta in each month from 1980 to 2009. A decreasing trend was found all over the Yangtze River Delta in January, February, March, July, October, and November, whereas in

  9. Trends in aerosol optical depth in the Russian Arctic and their links with synoptic climatology

    International Nuclear Information System (INIS)

    Shahgedanova, Maria; Lamakin, Mikhail

    2005-01-01

    Temporal and spatial variability of aerosol optical depth (AOD) are examined using observations of direct solar radiation in the Eurasian Arctic for 1940-1990. AOD is estimated using empirical methods for 14 stations located between 66.2 deg N and 80.6 deg N, from the Kara Sea to the Chukchi Sea. While AOD exhibits a well-known springtime maximum and summertime minimum at all stations, atmospheric turbidity is higher in spring in the western (Kara-Laptev) part of the Eurasian Arctic. Between June and August, the eastern (East Siberian-Chukchi) sector experiences higher transparency than the western part. A statistically significant positive trend in AOD was observed in the Kara-Laptev sector between the late 1950s and the early 1980s predominantly in spring when pollution-derived aerosol dominates the Arctic atmosphere but not in the eastern sector. Although all stations are remote, those with positive trends are located closer to the anthropogenic sources of air pollution. By contrast, a widespread decline in AOD was observed between 1982 and 1990 in the eastern Arctic in spring but was limited to two sites in the western Arctic. These results suggest that the post-1982 decline in anthropogenic emissions in Europe and the former Soviet Union has had a limited effect on aerosol load in the Arctic. The post-1982 negative trends in AOD in summer, when marine aerosol is present in the atmosphere, were more common in the west. The relationships between AOD and atmospheric circulation are examined using a synoptic climatology approach. In spring, AOD depends primarily on the strength and direction of air flow. Thus strong westerly and northerly flows result in low AOD values in the East Siberian-Chukchi sector. By contrast, strong southerly flow associated with the passage of depressions results in high AOD in the Kara-Laptev sector and trajectory analysis points to the contribution of industrial regions of the sub-Arctic. In summer, low pressure gradient or

  10. Influence of observed diurnal cycles of aerosol optical depth on aerosol direct radiative effect

    Directory of Open Access Journals (Sweden)

    A. Arola

    2013-08-01

    Full Text Available The diurnal variability of aerosol optical depth (AOD can be significant, depending on location and dominant aerosol type. However, these diurnal cycles have rarely been taken into account in measurement-based estimates of aerosol direct radiative forcing (ADRF or aerosol direct radiative effect (ADRE. The objective of our study was to estimate the influence of diurnal aerosol variability at the top of the atmosphere ADRE estimates. By including all the possible AERONET sites, we wanted to assess the influence on global ADRE estimates. While focusing also in more detail on some selected sites of strongest impact, our goal was to also see the possible impact regionally. We calculated ADRE with different assumptions about the daily AOD variability: taking the observed daily AOD cycle into account and assuming diurnally constant AOD. Moreover, we estimated the corresponding differences in ADREs, if the single AOD value for the daily mean was taken from the the Moderate Resolution Imaging Spectroradiometer (MODIS Terra or Aqua overpass times, instead of accounting for the true observed daily variability. The mean impact of diurnal AOD variability on 24 h ADRE estimates, averaged over all AERONET sites, was rather small and it was relatively small even for the cases when AOD was chosen to correspond to the Terra or Aqua overpass time. This was true on average over all AERONET sites, while clearly there can be much stronger impact in individual sites. Examples of some selected sites demonstrated that the strongest observed AOD variability (the strongest morning afternoon contrast does not typically result in a significant impact on 24 h ADRE. In those cases, the morning and afternoon AOD patterns are opposite and thus the impact on 24 h ADRE, when integrated over all solar zenith angles, is reduced. The most significant effect on daily ADRE was induced by AOD cycles with either maximum or minimum AOD close to local noon. In these cases, the impact on

  11. Interacting Effects of Leaf Water Potential and Biomass on Vegetation Optical Depth

    Science.gov (United States)

    Momen, M.; Wood, J. D.; Novick, K. A.; Pockman, W.; Konings, A. G.

    2017-12-01

    Remotely-sensed microwave observations of vegetation optical depth (VOD) have been widely used to examine vegetation responses to climate. Such studies have alternately found that VOD is sensitive to both biomass and canopy water content. However, the relative impacts of changes in phenology or water stress on VOD have not been disentangled. In particular, understanding whether leaf water potential (LWP) affects VOD may permit the assimilation of satellite observations into new large-scale plant hydraulic models. Despite extensive validation of the relationship between satellite-derived VOD estimates and vegetation density, relatively few studies have explicitly sought to validate the sensitivity of VOD to canopy water status, and none have studied the effect of variations in LWP on VOD. In this work, we test the sensitivity of VOD to variations in LWP, and present a conceptual framework which relates VOD to a combination of leaf water potential and total biomass including leaves, whose dynamics can be measured through leaf area index, and woody biomass. We used in-situ measurements of LWP data to validate the conceptual model in mixed deciduous forests in Indiana and Missouri, as well as a pinion-juniper woodland in New Mexico. Observed X-band VOD from the AMSR-E and AMSR2 satellites showed dynamics similar to those reconstructed VOD signals based on the new conceptual model which employs in-situ LWP data (R2=0.60-0.80). Because LWP data are not available at global scales, we further estimated ecosystem LWP based on remotely sensed surface soil moisture to better understand the sensitivity of VOD across ecosystems. At the global scale, incorporating a combination of biomass and water potential in the reconstructed VOD signal increased correlations with VOD about 15% compared to biomass alone and about 30% compared to water potential alone. In wetter regions with denser and taller canopy heights, VOD has a higher correlation with leaf area index than with water

  12. Spatial Factor Analysis for Aerosol Optical Depth in Metropolises in China with Regard to Spatial Heterogeneity

    Directory of Open Access Journals (Sweden)

    Hui Shi

    2018-04-01

    Full Text Available A substantial number of studies have analyzed how driving factors impact aerosols, but they have been little concerned with the spatial heterogeneity of aerosols and the factors that impact aerosols. The spatial distributions of the aerosol optical depth (AOD retrieved by Moderate Resolution Imaging Spectrometer (MODIS data at 550-nm and 3-km resolution for three highly developed metropolises, the Beijing-Tianjin-Hebei (BTH region, the Yangtze River Delta (YRD, and the Pearl River Delta (PRD, in China during 2015 were analyzed. Different degrees of spatial heterogeneity of the AOD were found, which were indexed by Moran’s I index giving values of 0.940, 0.715, and 0.680 in BTH, YRD, and PRD, respectively. For the spatial heterogeneity, geographically weighted regression (GWR was employed to carry out a spatial factor analysis, where terrain, climate condition, urban development, and vegetation coverage were taken as the potential driving factors. The results of the GWR imply varying relationships between the AOD and the factors. The results were generally consistent with existing studies, but the results suggest the following: (1 Elevation increase would more likely lead to a strong negative impact on aerosols (with most of the coefficients ranging from −1.5~0 in the BTH, −1.5~0 in the YRD, and −1~0 in the PRD in the places with greater elevations where the R-squared values are always larger than 0.5. However, the variation of elevations cannot explain the variation of aerosols in the places with relatively low elevations (with R-squared values approximately 0.1, ranging from 0 to 0.3, and approximately 0.1 in the BTH, YRD, and PRD, such as urban areas in the BTH and YRD. (2 The density of the built-up areas made a strong and positive impact on aerosols in the urban areas of the BTH (R-squared larger than 0.5, while the R-squared dropped to 0.1 in the places far away from the urban areas. (3 The vegetation coverage led to a stronger

  13. Aerosol Robotic Network (AERONET) Version 3 Aerosol Optical Depth and Inversion Products

    Science.gov (United States)

    Giles, D. M.; Holben, B. N.; Eck, T. F.; Smirnov, A.; Sinyuk, A.; Schafer, J.; Sorokin, M. G.; Slutsker, I.

    2017-12-01

    The Aerosol Robotic Network (AERONET) surface-based aerosol optical depth (AOD) database has been a principal component of many Earth science remote sensing applications and modelling for more than two decades. During this time, the AERONET AOD database had utilized a semiautomatic quality assurance approach (Smirnov et al., 2000). Data quality automation developed for AERONET Version 3 (V3) was achieved by augmenting and improving upon the combination of Version 2 (V2) automatic and manual procedures to provide a more refined near real time (NRT) and historical worldwide database of AOD. The combined effect of these new changes provides a historical V3 AOD Level 2.0 data set comparable to V2 Level 2.0 AOD. The recently released V3 Level 2.0 AOD product uses Level 1.5 data with automated cloud screening and quality controls and applies pre-field and post-field calibrations and wavelength-dependent temperature characterizations. For V3, the AERONET aerosol retrieval code inverts AOD and almucantar sky radiances using a full vector radiative transfer called Successive ORDers of scattering (SORD; Korkin et al., 2017). The full vector code allows for potentially improving the real part of the complex index of refraction and the sphericity parameter and computing the radiation field in the UV (e.g., 380nm) and degree of linear depolarization. Effective lidar ratio and depolarization ratio products are also available with the V3 inversion release. Inputs to the inversion code were updated to the accommodate H2O, O3 and NO2 absorption to be consistent with the computation of V3 AOD. All of the inversion products are associated with estimated uncertainties that include the random error plus biases due to the uncertainty in measured AOD, absolute sky radiance calibration, and retrieved MODIS BRDF for snow-free and snow covered surfaces. The V3 inversion products use the same data quality assurance criteria as V2 inversions (Holben et al. 2006). The entire AERONET V3

  14. Effects of Optical Combiner and IPD Change for Convergence on Near-Field Depth Perception in an Optical See-Through HMD.

    Science.gov (United States)

    Lee, Sangyoon; Hu, Xinda; Hua, Hong

    2016-05-01

    Many error sources have been explored in regards to the depth perception problem in augmented reality environments using optical see-through head-mounted displays (OST-HMDs). Nonetheless, two error sources are commonly neglected: the ray-shift phenomenon and the change in interpupillary distance (IPD). The first source of error arises from the difference in refraction for virtual and see-through optical paths caused by an optical combiner, which is required of OST-HMDs. The second occurs from the change in the viewer's IPD due to eye convergence. In this paper, we analyze the effects of these two error sources on near-field depth perception and propose methods to compensate for these two types of errors. Furthermore, we investigate their effectiveness through an experiment comparing the conditions with and without our error compensation methods applied. In our experiment, participants estimated the egocentric depth of a virtual and a physical object located at seven different near-field distances (40∼200 cm) using a perceptual matching task. Although the experimental results showed different patterns depending on the target distance, the results demonstrated that the near-field depth perception error can be effectively reduced to a very small level (at most 1 percent error) by compensating for the two mentioned error sources.

  15. Sub-40 fs, 1060-nm Yb-fiber laser enhances penetration depth in nonlinear optical microscopy of human skin

    Science.gov (United States)

    Balu, Mihaela; Saytashev, Ilyas; Hou, Jue; Dantus, Marcos; Tromberg, Bruce J.

    2015-12-01

    Advancing the practical utility of nonlinear optical microscopy requires continued improvement in imaging depth and contrast. We evaluated second-harmonic generation (SHG) and third-harmonic generation images from ex vivo human skin and showed that a sub-40 fs, 1060-nm Yb-fiber laser can enhance SHG penetration depth by up to 80% compared to a >100 fs, 800 nm Ti:sapphire source. These results demonstrate the potential of fiber-based laser systems to address a key performance limitation related to nonlinear optical microscopy (NLOM) technology while providing a low-barrier-to-access alternative to Ti:sapphire sources that could help accelerate the movement of NLOM into clinical practice.

  16. Fine Particulate Matter Predictions Using High Resolution Aerosol Optical Depth (AOD) Retrievals

    Science.gov (United States)

    Chudnovsky, Alexandra A.; Koutrakis, Petros; Kloog, Itai; Melly, Steven; Nordio, Francesco; Lyapustin, Alexei; Wang, Jujie; Schwartz, Joel

    2014-01-01

    To date, spatial-temporal patterns of particulate matter (PM) within urban areas have primarily been examined using models. On the other hand, satellites extend spatial coverage but their spatial resolution is too coarse. In order to address this issue, here we report on spatial variability in PM levels derived from high 1 km resolution AOD product of Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm developed for MODIS satellite. We apply day-specific calibrations of AOD data to predict PM(sub 2.5) concentrations within the New England area of the United States. To improve the accuracy of our model, land use and meteorological variables were incorporated. We used inverse probability weighting (IPW) to account for nonrandom missingness of AOD and nested regions within days to capture spatial variation. With this approach we can control for the inherent day-to-day variability in the AOD-PM(sub 2.5) relationship, which depends on time-varying parameters such as particle optical properties, vertical and diurnal concentration profiles and ground surface reflectance among others. Out-of-sample "ten-fold" cross-validation was used to quantify the accuracy of model predictions. Our results show that the model-predicted PM(sub 2.5) mass concentrations are highly correlated with the actual observations, with out-of- sample R(sub 2) of 0.89. Furthermore, our study shows that the model captures the pollution levels along highways and many urban locations thereby extending our ability to investigate the spatial patterns of urban air quality, such as examining exposures in areas with high traffic. Our results also show high accuracy within the cities of Boston and New Haven thereby indicating that MAIAC data can be used to examine intra-urban exposure contrasts in PM(sub 2.5) levels.

  17. Reconstructing the Gamma-Ray Photon Optical Depth of the Universe To Z Approx. 4 from Multiwavelength Galaxy Survey Data

    Science.gov (United States)

    Helgason, Kari; Kashlinsky, Alexander

    2012-01-01

    Reconstructing the Gamma-Ray Photon Optical Depth of the Universe To Z Approx. 4fFrom Multiwavelength Galaxy Survey Data We reconstruct the gamma-ray opacity of the universe out to z approx. photons already at z approx. < 0.2 and reaching tau approx 10 at z = 1. Comparing with the currently available Fermi/LAT gamma-ray burst and blazar data shows that there is room for significant emissions originating in the first stars era.

  18. Using high-resolution satellite aerosol optical depth to estimate daily PM2.5 geographical distribution in Mexico City

    OpenAIRE

    Just, Allan C.; Wright, Robert O.; Schwartz, Joel; Coull, Brent A.; Baccarelli, Andrea A.; Tellez-Rojo, Martha María; Moody, Emily; Wang, Yujie; Lyapustin, Alexei; Kloog, Itai

    2015-01-01

    Recent advances in estimating fine particle (PM2.5) ambient concentrations use daily satellite measurements of aerosol optical depth (AOD) for spatially and temporally resolved exposure estimates. Mexico City is a dense megacity that differs from other previously modeled regions in several ways: it has bright land surfaces, a distinctive climatological cycle, and an elevated semi-enclosed air basin with a unique planetary boundary layer dynamic. We extend our previous satellite methodology to...

  19. Retrieval of Cirrus Cloud Optical Depth under Day and Night Conditions from MODIS Collection 6 Cloud Property Data

    Directory of Open Access Journals (Sweden)

    Andrew K. Heidinger

    2015-06-01

    Full Text Available This paper presents a technique to generate cirrus optical depth and particle effective size estimates from the cloud emissivities at 8.5, 11 and 12 μm contained in the Collection-6 (C6 MYD06 cloud product. This technique employs the latest scattering models and scattering radiative transfer approximations to estimate cloud optical depth and particle effective size using efficient analytical formulae. Two scattering models are tested. The first is the same scattering model as that used in the C6 MYD06 solar reflectance products. The second model is an empirical model derived from radiometric consistency. Both models are shown to generate optical depths that compare well to those from constrained CALIPSO retrievals and MYD06. In terms of effective radius retrievals, the results from the radiometric empirical model agree more closely with MYD06 than those from the C6 model. This analysis is applied to AQUA/MODIS data collocated with CALIPSO/CALIOP during January 2010.

  20. Preliminary Analysis of Night-time Aerosol Optical Depth Retrievals at a Rural, Near-urban Site in Southern Canada

    International Nuclear Information System (INIS)

    Baibakov, K.; O'Neill, N. T.; Firanski, B.; Strawbridge, K.

    2009-01-01

    In the summer of 2007, a SPSTAR03 starphotometer was installed at Egbert, Canada (44 deg. 13' N, 79 deg. 45' W, alt 264 m) and a continuous series of initial measurements was performed between August 26 and September 19. Several sunphotometry parameters such as the aerosol optical depth (AOD) and the 'fine' and 'coarse' optical depths were extracted from the SPSTAR03 extinction spectra. The SPSTAR03 data was analyzed in conjunction with sunphotometry and zenith-pointing lidar data acquired during the same time period. Preliminary results show coarse continuity between the day- and night time AOD values (with the mean difference between the measured and the interpolated values being 0.05) as well as a qualitative correlation between the 'fine' and 'coarse' optical depths and the normalized lidar backscatter coefficient profiles. It was also found that the spectra produced with the differential two-star measurement method were sensitive to non-horizontally homogeneous differences in the line-of-sight conditions of both stars. The one-star method helps to reduce the uncertainties but requires the determination of a calibration constant.

  1. Assembling optically active and nonactive metamaterials with chiral units

    Directory of Open Access Journals (Sweden)

    Xiang Xiong

    2012-12-01

    Full Text Available Metamaterials constructed with chiral units can be either optically active or nonactive depending on the spatial configuration of the building blocks. For a class of chiral units, their effective induced electric and magnetic dipoles, which originate from the induced surface electric current upon illumination of incident light, can be collinear at the resonant frequency. This feature provides significant advantage in designing metamaterials. In this paper we concentrate on several examples. In one scenario, chiral units with opposite chiralities are used to construct the optically nonactive metamaterial structure. It turns out that with linearly polarized incident light, the pure electric or magnetic resonance (and accordingly negative permittivity or negative permeability can be selectively realized by tuning the polarization of incident light for 90°. Alternatively, units with the same chirality can be assembled as a chiral metamaterial by taking the advantage of the collinear induced electric and magnetic dipoles. It follows that for the circularly polarized incident light, negative refractive index can be realized. These examples demonstrate the unique approach to achieve certain optical properties by assembling chiral building blocks, which could be enlightening in designing metamaterials.

  2. Evaluating Nighttime CALIOP 0.532 micron Aerosol Optical Depth and Extinction Coefficient Retrievals

    Science.gov (United States)

    Campbell, J. R.; Tackett, J. L.; Reid, J. S.; Zhang, J.; Curtis, C. A.; Hyer, E. J.; Sessions, W. R.; Westphal, D. L.; Prospero, J. M.; Welton, E. J.; hide

    2012-01-01

    NASA Cloud Aerosol Lidar with Orthogonal Polarization (CALIOP) Version 3.01 5-km nighttime 0.532 micron aerosol optical depth (AOD) datasets from 2007 are screened, averaged and evaluated at 1 deg X 1 deg resolution versus corresponding/co-incident 0.550 micron AOD derived using the US Navy Aerosol Analysis and Prediction System (NAAPS), featuring two-dimensional variational assimilation of quality-assured NASA Moderate Resolution Imaging Spectroradiometer (MODIS) and Multi-angle Imaging Spectroradiometer (MISR) AOD. In the absence of sunlight, since passive radiometric AOD retrievals rely overwhelmingly on scattered radiances, the model represents one of the few practical global estimates available from which to attempt such a validation. Daytime comparisons, though, provide useful context. Regional-mean CALIOP vertical profiles of night/day 0.532 micron extinction coefficient are compared with 0.523/0.532 micron ground-based lidar measurements to investigate representativeness and diurnal variability. In this analysis, mean nighttime CALIOP AOD are mostly lower than daytime (0.121 vs. 0.126 for all aggregated data points, and 0.099 vs. 0.102 when averaged globally per normalised 1 deg. X 1 deg. bin), though the relationship is reversed over land and coastal regions when the data are averaged per normalised bin (0.134/0.108 vs. 0140/0.112, respectively). Offsets assessed within single bins alone approach +/- 20 %. CALIOP AOD, both day and night, are higher than NAAPS over land (0.137 vs. 0.124) and equal over water (0.082 vs. 0.083) when averaged globally per normalised bin. However, for all data points inclusive, NAAPS exceeds CALIOP over land, coast and ocean, both day and night. Again, differences assessed within single bins approach 50% in extreme cases. Correlation between CALIOP and NAAPS AOD is comparable during both day and night. Higher correlation is found nearest the equator, both as a function of sample size and relative signal magnitudes inherent at

  3. Nanometric resolution in glow discharge optical emission spectroscopy and Rutherford backscattering spectrometry depth profiling of metal (Cr, Al) nitride multilayers

    International Nuclear Information System (INIS)

    Escobar Galindo, R.; Gago, R.; Fornies, E.; Munoz-Martin, A.; Climent Font, A.; Albella, J.M.

    2006-01-01

    In this work, we address the capability of glow discharge optical emission spectroscopy (GDOES) for fast and accurate depth profiling of multilayer nitride coatings down to the nanometer range. This is shown by resolving the particular case of CrN/AlN structures with individual thickness ranging from hundreds to few nanometers. In order to discriminate and identify artefacts in the GDOES depth profile due to the sputtering process, the layered structures were verified by Rutherford backscattering spectrometry (RBS) and scanning electron microscopy (SEM). The interfaces in the GDOES profiles for CrN/AlN structures are sharper than the ones measured for similar metal multilayers due to the lower sputtering rate of the nitrides. However, as a consequence of the crater shape, there is a linear degradation of the depth resolution with depth (approximately 40 nm/μm), saturating at a value of approximately half the thickness of the thinner layer. This limit is imposed by the simultaneous sputtering of consecutive layers. The ultimate GDOES depth resolution at the near surface region was estimated to be of 4-6 nm

  4. Simultaneous reconstruction of multiple depth images without off-focus points in integral imaging using a graphics processing unit.

    Science.gov (United States)

    Yi, Faliu; Lee, Jieun; Moon, Inkyu

    2014-05-01

    The reconstruction of multiple depth images with a ray back-propagation algorithm in three-dimensional (3D) computational integral imaging is computationally burdensome. Further, a reconstructed depth image consists of a focus and an off-focus area. Focus areas are 3D points on the surface of an object that are located at the reconstructed depth, while off-focus areas include 3D points in free-space that do not belong to any object surface in 3D space. Generally, without being removed, the presence of an off-focus area would adversely affect the high-level analysis of a 3D object, including its classification, recognition, and tracking. Here, we use a graphics processing unit (GPU) that supports parallel processing with multiple processors to simultaneously reconstruct multiple depth images using a lookup table containing the shifted values along the x and y directions for each elemental image in a given depth range. Moreover, each 3D point on a depth image can be measured by analyzing its statistical variance with its corresponding samples, which are captured by the two-dimensional (2D) elemental images. These statistical variances can be used to classify depth image pixels as either focus or off-focus points. At this stage, the measurement of focus and off-focus points in multiple depth images is also implemented in parallel on a GPU. Our proposed method is conducted based on the assumption that there is no occlusion of the 3D object during the capture stage of the integral imaging process. Experimental results have demonstrated that this method is capable of removing off-focus points in the reconstructed depth image. The results also showed that using a GPU to remove the off-focus points could greatly improve the overall computational speed compared with using a CPU.

  5. Orderly recruitment of motor units under optical control in vivo.

    Science.gov (United States)

    Llewellyn, Michael E; Thompson, Kimberly R; Deisseroth, Karl; Delp, Scott L

    2010-10-01

    A drawback of electrical stimulation for muscle control is that large, fatigable motor units are preferentially recruited before smaller motor units by the lowest-intensity electrical cuff stimulation. This phenomenon limits therapeutic applications because it is precisely the opposite of the normal physiological (orderly) recruitment pattern; therefore, a mechanism to achieve orderly recruitment has been a long-sought goal in physiology, medicine and engineering. Here we demonstrate a technology for reliable orderly recruitment in vivo. We find that under optical control with microbial opsins, recruitment of motor units proceeds in the physiological recruitment sequence, as indicated by multiple independent measures of motor unit recruitment including conduction latency, contraction and relaxation times, stimulation threshold and fatigue. As a result, we observed enhanced performance and reduced fatigue in vivo. These findings point to an unanticipated new modality of neural control with broad implications for nervous system and neuromuscular physiology, disease research and therapeutic innovation.

  6. THE ORIGIN AND OPTICAL DEPTH OF IONIZING RADIATION IN THE 'GREEN PEA' GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Jaskot, A. E.; Oey, M. S. [Department of Astronomy, University of Michigan, 830 Dennison Building, Ann Arbor, MI 48109 (United States)

    2013-04-01

    Although Lyman-continuum (LyC) radiation from star-forming galaxies likely drove the reionization of the universe, observations of star-forming galaxies at low redshift generally indicate low LyC escape fractions. However, the extreme [O III]/[O II] ratios of the z = 0.1-0.3 Green Pea galaxies may be due to high escape fractions of ionizing radiation. To analyze the LyC optical depths and ionizing sources of these rare, compact starbursts, we compare nebular photoionization and stellar population models with observed emission lines in the Peas' Sloan Digital Sky Survey (SDSS) spectra. We focus on the six most extreme Green Peas, the galaxies with the highest [O III]/[O II] ratios and the best candidates for escaping ionizing radiation. The Balmer line equivalent widths and He I {lambda}3819 emission in the extreme Peas support young ages of 3-5 Myr, and He II {lambda}4686 emission in five extreme Peas signals the presence of hard ionizing sources. Ionization by active galactic nuclei or high-mass X-ray binaries is inconsistent with the Peas' line ratios and ages. Although stacked spectra reveal no Wolf-Rayet (WR) features, we tentatively detect WR features in the SDSS spectra of three extreme Peas. Based on the Peas' ages and line ratios, we find that WR stars, chemically homogeneous O stars, or shocks could produce the observed He II emission. If hot stars are responsible, then the Peas' optical depths are ambiguous. However, accounting for emission from shocks lowers the inferred optical depth and suggests that the Peas may be optically thin. The Peas' ages likely optimize the escape of LyC radiation; they are old enough for supernovae and stellar winds to reshape the interstellar medium, but young enough to possess large numbers of UV-luminous O or WR stars.

  7. Quality parameters analysis of optical imaging systems with enhanced focal depth using the Wigner distribution function

    Science.gov (United States)

    Zalvidea; Colautti; Sicre

    2000-05-01

    An analysis of the Strehl ratio and the optical transfer function as imaging quality parameters of optical elements with enhanced focal length is carried out by employing the Wigner distribution function. To this end, we use four different pupil functions: a full circular aperture, a hyper-Gaussian aperture, a quartic phase plate, and a logarithmic phase mask. A comparison is performed between the quality parameters and test images formed by these pupil functions at different defocus distances.

  8. Extended focused imaging and depth map reconstruction in optical scanning holography.

    Science.gov (United States)

    Ren, Zhenbo; Chen, Ni; Lam, Edmund Y

    2016-02-10

    In conventional microscopy, specimens lying within the depth of field are clearly recorded whereas other parts are blurry. Although digital holographic microscopy allows post-processing on holograms to reconstruct multifocus images, it suffers from defocus noise as a traditional microscope in numerical reconstruction. In this paper, we demonstrate a method that can achieve extended focused imaging (EFI) and reconstruct a depth map (DM) of three-dimensional (3D) objects. We first use a depth-from-focus algorithm to create a DM for each pixel based on entropy minimization. Then we show how to achieve EFI of the whole 3D scene computationally. Simulation and experimental results involving objects with multiple axial sections are presented to validate the proposed approach.

  9. Aerosol spectral optical depths and size characteristics at a coastal industriallocation in India - effect of synoptic and mesoscale weather

    Directory of Open Access Journals (Sweden)

    K. Niranjan

    2004-06-01

    Full Text Available The aerosol spectral optical depths at ten discrete channels in the visible and near IR bands, obtained from a ground-based passive multi-wavelength solar radiometer at a coastal industrial location, Visakhapatnam, on the east coast of India, are used to study the response of the aerosol optical properties and size distributions to the changes in atmospheric humidity, wind speed and direction. It is observed that during high humidity conditions, the spectral optical depths show about 30% higher growth factors, and the size distributions show the generation of a typical new mode around 0.4 microns. The surface wind speed and direction also indicate the formation of new particles when the humid marine air mass interacts with the industrial air mass. This is interpreted in terms of new particle formation and subsequent particle growth by condensation and self-coagulation. The results obtained on the surface-size segregated aerosol mass distribution from a co-located Quartz Crystal Microbalance during different humidity conditions also show a large mass increase in the sub-micron size range with an increase in atmospheric humidity, indicating new particle formation at the sub-micron size range.

  10. Distributed multi-hypothesis coding of depth maps using texture motion information and optical flow

    DEFF Research Database (Denmark)

    Salmistraro, Matteo; Zamarin, Marco; Rakêt, Lars Lau

    2013-01-01

    Distributed Video Coding (DVC) is a video coding paradigm allowing a shift of complexity from the encoder to the decoder. Depth maps are images enabling the calculation of the distance of an object from the camera, which can be used in multiview coding in order to generate virtual views, but also...

  11. Depth Estimation of Submerged Aquatic Vegetation in Clear Water Streams Using Low-Altitude Optical Remote Sensing.

    Science.gov (United States)

    Visser, Fleur; Buis, Kerst; Verschoren, Veerle; Meire, Patrick

    2015-09-30

    UAVs and other low-altitude remote sensing platforms are proving very useful tools for remote sensing of river systems. Currently consumer grade cameras are still the most commonly used sensors for this purpose. In particular, progress is being made to obtain river bathymetry from the optical image data collected with such cameras, using the strong attenuation of light in water. No studies have yet applied this method to map submergence depth of aquatic vegetation, which has rather different reflectance characteristics from river bed substrate. This study therefore looked at the possibilities to use the optical image data to map submerged aquatic vegetation (SAV) depth in shallow clear water streams. We first applied the Optimal Band Ratio Analysis method (OBRA) of Legleiter et al. (2009) to a dataset of spectral signatures from three macrophyte species in a clear water stream. The results showed that for each species the ratio of certain wavelengths were strongly associated with depth. A combined assessment of all species resulted in equally strong associations, indicating that the effect of spectral variation in vegetation is subsidiary to spectral variation due to depth changes. Strongest associations (R²-values ranging from 0.67 to 0.90 for different species) were found for combinations including one band in the near infrared (NIR) region between 825 and 925 nm and one band in the visible light region. Currently data of both high spatial and spectral resolution is not commonly available to apply the OBRA results directly to image data for SAV depth mapping. Instead a novel, low-cost data acquisition method was used to obtain six-band high spatial resolution image composites using a NIR sensitive DSLR camera. A field dataset of SAV submergence depths was used to develop regression models for the mapping of submergence depth from image pixel values. Band (combinations) providing the best performing models (R²-values up to 0.77) corresponded with the OBRA

  12. Enhanced depth-of-field of an integral imaging microscope using a bifocal holographic optical element-micro lens array.

    Science.gov (United States)

    Kwon, Ki-Chul; Lim, Young-Tae; Shin, Chang-Won; Erdenebat, Munkh-Uchral; Hwang, Jae-Moon; Kim, Nam

    2017-08-15

    We propose and implement an integral imaging microscope with extended depth-of-field (DoF) using a bifocal holographic micro lens array (MLA). The properties of the two MLAs are switched via peristrophic multiplexing, where different properties of the MLA are recorded onto the single holographic optical element (HOE). The recorded MLA properties are perpendicular to each other: after the first mode is recorded, the HOE is rotated by 90° clockwise, and the second mode is recorded. The experimental results confirm that the DoF of the integral imaging microscopy system is extended successfully by using the bifocal MLA.

  13. Active probing of cloud multiple scattering, optical depth, vertical thickness, and liquid water content using wide-angle imaging lidar

    Science.gov (United States)

    Love, Steven P.; Davis, Anthony B.; Rohde, Charles A.; Tellier, Larry; Ho, Cheng

    2002-09-01

    At most optical wavelengths, laser light in a cloud lidar experiment is not absorbed but merely scattered out of the beam, eventually escaping the cloud via multiple scattering. There is much information available in this light scattered far from the input beam, information ignored by traditional 'on-beam' lidar. Monitoring these off-beam returns in a fully space- and time-resolved manner is the essence of our unique instrument, Wide Angle Imaging Lidar (WAIL). In effect, WAIL produces wide-field (60-degree full-angle) 'movies' of the scattering process and records the cloud's radiative Green functions. A direct data product of WAIL is the distribution of photon path lengths resulting from multiple scattering in the cloud. Following insights from diffusion theory, we can use the measured Green functions to infer the physical thickness and optical depth of the cloud layer, and, from there, estimate the volume-averaged liquid water content. WAIL is notable in that it is applicable to optically thick clouds, a regime in which traditional lidar is reduced to ceilometry. Here we present recent WAIL data on various clouds and discuss the extension of WAIL to full diurnal monitoring by means of an ultra-narrow magneto-optic atomic line filter for daytime measurements.

  14. Active probing of cloud multiple scattering, optical depth, vertical thickness, and liquid water content using wide-angle imaging LIDAR

    International Nuclear Information System (INIS)

    Love, Steven P.; Davis, Anthony B.; Rohde, Charles A.; Tellier, Larry L.; Ho, Cheng

    2002-01-01

    At most optical wavelengths, laser light in a cloud lidar experiment is not absorbed but merely scattered out of the beam, eventually escaping the cloud via multiple scattering. There is much information available in this light scattered far from the input beam, information ignored by traditional 'on-beam' lidar. Monitoring these off-beam returns in a fully space- and time-resolved manner is the essence of our unique instrument, Wide Angle Imaging Lidar (WAIL). In effect, WAIL produces wide-field (60-degree full-angle) 'movies' of the scattering process and records the cloud's radiative Green functions. A direct data product of WAIL is the distribution of photon path lengths resulting from multiple scattering in the cloud. Following insights from diffusion theory, we can use the measured Green functions to infer the physical thickness and optical depth of the cloud layer, and, from there, estimate the volume-averaged liquid water content. WAIL is notable in that it is applicable to optically thick clouds, a regime in which traditional lidar is reduced to ceilometry. Here we present recent WAIL data oti various clouds and discuss the extension of WAIL to full diurnal monitoring by means of an ultra-narrow magneto-optic atomic line filter for daytime measurements.

  15. NOAA JPSS Visible Infrared Imaging Radiometer Suite (VIIRS) Aerosol Optical Depth and Aerosol Particle Size Distribution Environmental Data Record (EDR) from NDE

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This dataset contains a high quality operational Environmental Data Record (EDR) of aerosol optical depth (AOD) and particle size from the Visible Infrared Imaging...

  16. Quantitatively Measured Anatomic Location and Volume of Optic Disc Drusen: An Enhanced Depth Imaging Optical Coherence Tomography Study

    DEFF Research Database (Denmark)

    Malmqvist, Lasse; Lindberg, Anne-Sofie Wessel; Dahl, Vedrana Andersen

    2017-01-01

    function using automated perimetric mean deviation (MD) and multifocal visual evoked potentials. Increased age (P = 0.015); larger ODD volume (P = 0.002); and more superficial anatomic ODD location (P = 0.007) were found in patients with ODD visible by ophthalmoscopy compared to patients with buried ODD.......025) and had a higher effect on MD when compared to retinal nerve fiber layer thickness. Large ODD volume is associated with optic nerve dysfunction. The worse visual field defects associated with visible ODD should only be ascribed to larger ODD volume and not to a more superficial anatomic ODD location....

  17. Ocean Color Patterns Help to Predict Depth of Optical Layers in Coastal Marine Waters

    Science.gov (United States)

    2012-02-09

    Space Center, NASA, MS 39529, USA 3Institut des Sciences de la Mer, Universite du Quebec a Rimouski, Canada, *E-mail: martin_montes@uqar. qc. ca...depth was derived from CTD variables (i.e., temperature and conductivity without pressure correction) and using the standard UNESCO polynomial equation... la y *,es^ S Si es ti m at ed nt er re y B a n an d up ), th e up pe r te d in w h i 5112 ^ "a :*J ? tf?^ •a Mis a a •S M ^ « a fo

  18. Ion beam energy attenuation for fabrication of buried, variable-depth, optical waveguides

    International Nuclear Information System (INIS)

    Bibra, M.L. von; Roberts, A.; Dods, S.D.

    2000-01-01

    Buried waveguides with graded depths have been fabricated using a focussed ion beam, direct-write process in fused silica by irradiation with 3 MeV protons through a tapered film varying in thickness from 5 to 40 μm. The resulting waveguides ramp uniformly from 25 to 80 μm below the substrate surface. The waveguides are also uniform in cross-section along their lengths. This demonstrates the potential for this fabrication technique to direct-write three-dimensional waveguide devices within a substrate

  19. Aerosol Optical Depths over Oceans: a View from MISR Retrievals and Collocated MAN and AERONET in Situ Observations

    Science.gov (United States)

    Witek, Marcin L.; Garay, Michael J.; Diner, David J.; Smirnov, Alexander

    2013-01-01

    In this study, aerosol optical depths over oceans are analyzed from satellite and surface perspectives. Multiangle Imaging SpectroRadiometer (MISR) aerosol retrievals are investigated and validated primarily against Maritime Aerosol Network (MAN) observations. Furthermore, AErosol RObotic NETwork (AERONET) data from 19 island and coastal sites is incorporated in this study. The 270 MISRMAN comparison points scattered across all oceans were identified. MISR on average overestimates aerosol optical depths (AODs) by 0.04 as compared to MAN; the correlation coefficient and root-mean-square error are 0.95 and 0.06, respectively. A new screening procedure based on retrieval region characterization is proposed, which is capable of substantially reducing MISR retrieval biases. Over 1000 additional MISRAERONET comparison points are added to the analysis to confirm the validity of the method. The bias reduction is effective within all AOD ranges. Setting a clear flag fraction threshold to 0.6 reduces the bias to below 0.02, which is close to a typical ground-based measurement uncertainty. Twelve years of MISR data are analyzed with the new screening procedure. The average over ocean AOD is reduced by 0.03, from 0.15 to 0.12. The largest AOD decrease is observed in high latitudes of both hemispheres, regions with climatologically high cloud cover. It is postulated that the screening procedure eliminates spurious retrieval errors associated with cloud contamination and cloud adjacency effects. The proposed filtering method can be used for validating aerosol and chemical transport models.

  20. PRECISE MEASUREMENT OF THE REIONIZATION OPTICAL DEPTH FROM THE GLOBAL 21 cm SIGNAL ACCOUNTING FOR COSMIC HEATING

    Energy Technology Data Exchange (ETDEWEB)

    Fialkov, Anastasia; Loeb, Abraham, E-mail: anastasia.fialkov@cfa.harvard.edu, E-mail: aloeb@cfa.harvard.edu [Department of Astronomy, Harvard University, 60 Garden Street, MS-51, Cambridge, MA 02138 (United States)

    2016-04-10

    As a result of our limited data on reionization, the total optical depth for electron scattering, τ, limits precision measurements of cosmological parameters from the Cosmic Microwave Background (CMB). It was recently shown that the predicted 21 cm signal of neutral hydrogen contains enough information to reconstruct τ with sub-percent accuracy, assuming that the neutral gas was much hotter than the CMB throughout the entire epoch of reionization (EoR). Here we relax this assumption and use the global 21 cm signal alone to extract τ for realistic X-ray heating scenarios. We test our model-independent approach using mock data for a wide range of ionization and heating histories and show that an accurate measurement of the reionization optical depth at a sub-percent level is possible in most of the considered scenarios even when heating is not saturated during the EoR, assuming that the foregrounds are mitigated. However, we find that in cases where heating sources had hard X-ray spectra and their luminosity was close to or lower than what is predicted based on low-redshift observations, the global 21 cm signal alone is not a good tracer of the reionization history.

  1. Effect of Wind Speed on Aerosol Optical Depth over Remote Oceans, Based on Data from the Maritime Aerosol Network

    Science.gov (United States)

    Smirnov, A.; Sayer, A. M.; Holben, B. N.; Hsu, N. C.; Sakerin, S. M.; Macke, A.; Nelson, N. B.; Courcoux, Y.; Smyth, T. J.; Croot, P.; hide

    2012-01-01

    The Maritime Aerosol Network (MAN) has been collecting data over the oceans since November 2006. The MAN archive provides a valuable resource for aerosol studies in maritime environments. In the current paper we investigate correlations between ship-borne aerosol optical depth (AOD) and near-surface wind speed, either measured (onboard or from satellite) or modeled (NCEP). According to our analysis, wind speed influences columnar aerosol optical depth, although the slope of the linear regression between AOD and wind speed is not steep (approx. 0.004 - 0.005), even for strong winds over 10m/s. The relationships show significant scatter (correlation coefficients typically in the range 0.3 - 0.5); the majority of this scatter can be explained by the uncertainty on the input data. The various wind speed sources considered yield similar patterns. Results are in good agreement with the majority of previously published relationships between surface wind speed and ship-based or satellite-based AOD measurements. The basic relationships are similar for all the wind speed sources considered; however, the gradient of the relationship varies by around a factor of two depending on the wind data used

  2. PRECISE MEASUREMENT OF THE REIONIZATION OPTICAL DEPTH FROM THE GLOBAL 21 cm SIGNAL ACCOUNTING FOR COSMIC HEATING

    International Nuclear Information System (INIS)

    Fialkov, Anastasia; Loeb, Abraham

    2016-01-01

    As a result of our limited data on reionization, the total optical depth for electron scattering, τ, limits precision measurements of cosmological parameters from the Cosmic Microwave Background (CMB). It was recently shown that the predicted 21 cm signal of neutral hydrogen contains enough information to reconstruct τ with sub-percent accuracy, assuming that the neutral gas was much hotter than the CMB throughout the entire epoch of reionization (EoR). Here we relax this assumption and use the global 21 cm signal alone to extract τ for realistic X-ray heating scenarios. We test our model-independent approach using mock data for a wide range of ionization and heating histories and show that an accurate measurement of the reionization optical depth at a sub-percent level is possible in most of the considered scenarios even when heating is not saturated during the EoR, assuming that the foregrounds are mitigated. However, we find that in cases where heating sources had hard X-ray spectra and their luminosity was close to or lower than what is predicted based on low-redshift observations, the global 21 cm signal alone is not a good tracer of the reionization history

  3. Validation of new satellite aerosol optical depth retrieval algorithm using Raman lidar observations at radiative transfer laboratory in Warsaw

    Science.gov (United States)

    Zawadzka, Olga; Stachlewska, Iwona S.; Markowicz, Krzysztof M.; Nemuc, Anca; Stebel, Kerstin

    2018-04-01

    During an exceptionally warm September of 2016, the unique, stable weather conditions over Poland allowed for an extensive testing of the new algorithm developed to improve the Meteosat Second Generation (MSG) Spinning Enhanced Visible and Infrared Imager (SEVIRI) aerosol optical depth (AOD) retrieval. The development was conducted in the frame of the ESA-ESRIN SAMIRA project. The new AOD algorithm aims at providing the aerosol optical depth maps over the territory of Poland with a high temporal resolution of 15 minutes. It was tested on the data set obtained between 11-16 September 2016, during which a day of relatively clean atmospheric background related to an Arctic airmass inflow was surrounded by a few days with well increased aerosol load of different origin. On the clean reference day, for estimating surface reflectance the AOD forecast available on-line via the Copernicus Atmosphere Monitoring Service (CAMS) was used. The obtained AOD maps were validated against AODs available within the Poland-AOD and AERONET networks, and with AOD values obtained from the PollyXT-UW lidar. of the University of Warsaw (UW).

  4. Utilizing the ratio and the summation of two spectral lines for estimation of optical depth: Focus on thick plasmas

    Science.gov (United States)

    Rezaei, Fatemeh; Tavassoli, Seyed Hassan

    2016-11-01

    In this paper, a study is performed on the spectral lines of plasma radiations created from focusing of the Nd:YAG laser on Al standard alloys at atmospheric air pressure. A new theoretical method is presented to investigate the evolution of the optical depth of the plasma based on the radiative transfer equation, in LTE condition. This work relies on the Boltzmann distribution, lines broadening equations, and as well as the self-absorption relation. Then, an experimental set-up is devised to extract some of plasma parameters such as temperature from modified line ratio analysis, electron density from Stark broadening mechanism, line intensities of two spectral lines in the same order of ionization from similar species, and the plasma length from the shadowgraphy section. In this method, the summation and the ratio of two spectral lines are considered for evaluation of the temporal variations of the plasma parameters in a LIBS homogeneous plasma. The main advantage of this method is that it comprises the both of thin and thick laser induced plasmas without straight calculation of self-absorption coefficient. Moreover, the presented model can also be utilized for evaluation the transition of plasma from the thin condition to the thick one. The results illustrated that by measuring the line intensities of two spectral lines at different evolution times, the plasma cooling and the growth of the optical depth can be followed.

  5. Multimodal adaptive optics for depth-enhanced high-resolution ophthalmic imaging

    Science.gov (United States)

    Hammer, Daniel X.; Mujat, Mircea; Iftimia, Nicusor V.; Lue, Niyom; Ferguson, R. Daniel

    2010-02-01

    We developed a multimodal adaptive optics (AO) retinal imager for diagnosis of retinal diseases, including glaucoma, diabetic retinopathy (DR), age-related macular degeneration (AMD), and retinitis pigmentosa (RP). The development represents the first ever high performance AO system constructed that combines AO-corrected scanning laser ophthalmoscopy (SLO) and swept source Fourier domain optical coherence tomography (SSOCT) imaging modes in a single compact clinical prototype platform. The SSOCT channel operates at a wavelength of 1 μm for increased penetration and visualization of the choriocapillaris and choroid, sites of major disease activity for DR and wet AMD. The system is designed to operate on a broad clinical population with a dual deformable mirror (DM) configuration that allows simultaneous low- and high-order aberration correction. The system also includes a wide field line scanning ophthalmoscope (LSO) for initial screening, target identification, and global orientation; an integrated retinal tracker (RT) to stabilize the SLO, OCT, and LSO imaging fields in the presence of rotational eye motion; and a high-resolution LCD-based fixation target for presentation to the subject of stimuli and other visual cues. The system was tested in a limited number of human subjects without retinal disease for performance optimization and validation. The system was able to resolve and quantify cone photoreceptors across the macula to within ~0.5 deg (~100-150 μm) of the fovea, image and delineate ten retinal layers, and penetrate to resolve targets deep into the choroid. In addition to instrument hardware development, analysis algorithms were developed for efficient information extraction from clinical imaging sessions, with functionality including automated image registration, photoreceptor counting, strip and montage stitching, and segmentation. The system provides clinicians and researchers with high-resolution, high performance adaptive optics imaging to help

  6. Calculation of optical properties of dental composites as a basis for determining color impression and penetration depth of laser light

    Science.gov (United States)

    Weniger, Kirsten K.; Muller, Gerhard J.

    2005-03-01

    In order to achieve esthetic dental restorations, there should be no visible difference between restorative material and treated teeth. This requires a match of the optical properties of both restorative material and natural teeth. These optical properties are determined by absorption and scattering of light emerging not only on the surface but also inside the material. Investigating different dental composites in several shades, a method has been developed to calculate the optical parameters absorption coefficient μa, scattering coefficient μs, anisotropy factor g and reduced scattering coefficient μs'. The method includes sample preparation and measurements of transmittance and reflectance in an integrating sphere spectrometer, followed by inverse Monte Carlo simulations. Determination of optical properties is more precise and comprehensive than with the previously used Kubelka Munk theory because scattering can be looked at separated into pure scattering with the scattering coefficient μs and its direction with the anisotropy factor g. Moreover the use of the inverse Monte Carlo simulation not only minimizes systematic errors and considers the scattering phase function, but also takes into account the measuring geometry. The compilation of a data pool of optical parameters now enables the application of further calculation models as a basis for optimization of the composition of new materials. For example, a prediction of the general color impression for multiple layers can be carried out as well as the calculation of the wavelength dependent penetration depths of light with regard to photo polymerization. Further applications are possible in the area of laser ablation.

  7. Creating Actionable Data from an Optical Depth Measurement Network using RDF

    Science.gov (United States)

    Freemantle, J. R.; O'Neill, N. T.; Lumb, L. I.; Abboud, I.; McArthur, B.

    2010-12-01

    The AEROCAN sunphotometery network has, for more than a decade, generated optical indicators of aerosol concentration and size on a regional and national scale. We believe this optical information can be rendered more “actionable” to the health care community by developing a technical and interpretative information-sharing geospatial strategy with that community. By actionable data we mean information that is presented in manner that can be understood and then used in the decision making process. The decision may be that of a technical professional, a policy maker or a machine. The information leading up to a decision may come from many sources; this means it is particularly important that data are well defined across knowledge fields, in our case atmospheric science and respiratory health science. As part of the AEROCAN operational quality assurance (QA) methodology we have written automatic procedures to make some of the AEROCAN data more accessible or “actionable”. Tim Berners-Lee has advocated making datasets, “Linked Data”, available on the web with a proper structural description (metadata). We have been using RDF (Resource Description Framework) to enhance the utility of our sunphotometer data; the resulting self-describing representation is structured so that it is machine readable. This allows semantically based queries (e.g., via SPARQL) on our dataset that in the past were only viewable as passive Web tables of data.

  8. Collagen Content Limits Optical Coherence Tomography Image Depth in Porcine Vocal Fold Tissue.

    Science.gov (United States)

    Garcia, Jordan A; Benboujja, Fouzi; Beaudette, Kathy; Rogers, Derek; Maurer, Rie; Boudoux, Caroline; Hartnick, Christopher J

    2016-11-01

    Vocal fold scarring, a condition defined by increased collagen content, is challenging to treat without a method of noninvasively assessing vocal fold structure in vivo. The goal of this study was to observe the effects of vocal fold collagen content on optical coherence tomography imaging to develop a quantifiable marker of disease. Excised specimen study. Massachusetts Eye and Ear Infirmary. Porcine vocal folds were injected with collagenase to remove collagen from the lamina propria. Optical coherence tomography imaging was performed preinjection and at 0, 45, 90, and 180 minutes postinjection. Mean pixel intensity (or image brightness) was extracted from images of collagenase- and control-treated hemilarynges. Texture analysis of the lamina propria at each injection site was performed to extract image contrast. Two-factor repeated measure analysis of variance and t tests were used to determine statistical significance. Picrosirius red staining was performed to confirm collagenase activity. Mean pixel intensity was higher at injection sites of collagenase-treated vocal folds than control vocal folds (P Fold change in image contrast was significantly increased in collagenase-treated vocal folds than control vocal folds (P = .002). Picrosirius red staining in control specimens revealed collagen fibrils most prominent in the subepithelium and above the thyroarytenoid muscle. Specimens treated with collagenase exhibited a loss of these structures. Collagen removal from vocal fold tissue increases image brightness of underlying structures. This inverse relationship may be useful in treating vocal fold scarring in patients. © American Academy of Otolaryngology—Head and Neck Surgery Foundation 2016.

  9. Aerosol optical depth (AOD) and Angstrom exponent of aerosols observed by the Chinese Sun Hazemeter Network from August 2004 to September 2005

    Science.gov (United States)

    Jinyuan Xin; Yuesi Wang; Zhanqing Li; Pucai Wang; Wei Min Hao; Bryce L. Nordgren; Shigong Wang; Guangren Lui; Lili Wang; Tianxue Wen; Yang Sun; Bo Hu

    2007-01-01

    To reduce uncertainties in the quantitative assessment of aerosol effects on regional climate and environmental changes, extensive measurements of aerosol optical properties were made with handheld Sun photometers in the Chinese Sun Hazemeter Network (CSHNET) starting in August 2004. Regional characteristics of the aerosol optical depth (AOD) at 500 nm and Angstrom...

  10. Photothermal optical coherence tomography for depth-resolved imaging of mesenchymal stem cells via single wall carbon nanotubes

    Science.gov (United States)

    Subhash, Hrebesh M.; Connolly, Emma; Murphy, Mary; Barron, Valerie; Leahy, Martin

    2014-03-01

    The progress in stem cell research over the past decade holds promise and potential to address many unmet clinical therapeutic needs. Tracking stem cell with modern imaging modalities are critically needed for optimizing stem cell therapy, which offers insight into various underlying biological processes such as cell migration, engraftment, homing, differentiation, and functions etc. In this study we report the feasibility of photothermal optical coherence tomography (PT-OCT) to image human mesenchymal stem cells (hMSCs) labeled with single-walled carbon nanotubes (SWNTs) for in vitro cell tracking in three dimensional scaffolds. PT-OCT is a functional extension of conventional OCT with extended capability of localized detection of absorbing targets from scattering background to provide depth-resolved molecular contrast imaging. A 91 kHz line rate, spectral domain PT-OCT system at 1310nm was developed to detect the photothermal signal generated by 800nm excitation laser. In general, MSCs do not have obvious optical absorption properties and cannot be directly visualized using PT-OCT imaging. However, the optical absorption properties of hMSCs can me modified by labeling with SWNTs. Using this approach, MSC were labeled with SWNT and the cell distribution imaged in a 3D polymer scaffold using PT-OCT.

  11. International review of Kursk unit 1 in-depth safety analysis report

    International Nuclear Information System (INIS)

    Chouha, M.; Bolshov, L.; Butcher, P.; Janke, R.; Parsons, T.; Weber, J.P.

    2004-01-01

    The paper presents the objectives, organisation, main findings and conclusions of the international review of the Kursk unit 1 safety analysis report (K1IRSR). The K1IRSR was administered by RISKAUDIT IRSN/GRS international and carried out by international experts from 7 western countries plus the Russian Federation, under the supervision of the safety review group (SRG) of the European bank for reconstruction and development (EBRD). The project was financed by the nuclear safety account (NSA) administered by the EBRD. The Russian experts worked under a contract with IBRAE financed by Rosenergoatom. The main conclusions were that the SAR followed a correct approach, broadly in line with Russian and international guidance documents, but needed improvement in structure and content. It established that the safety level of the unit has been increased significantly by the modernisation programme. The important deviations of the unit from current Russian regulations and the IAEA safety issues for RBMK are either fully resolved or are being addressed to the extent possible by compensatory measures to further reduce the risk. The K1IRSR experts have made a number of recommendations for improvement of the K1SAR. The authors agreed to take the recommendations into account in future revision of the K1SAR. (orig.)

  12. Depth probing of the hydride formation process in thin Pd films by combined electrochemistry and fiber optics-based in situ UV/vis spectroscopy.

    Science.gov (United States)

    Wickman, Björn; Fredriksson, Mattias; Feng, Ligang; Lindahl, Niklas; Hagberg, Johan; Langhammer, Christoph

    2015-07-15

    We demonstrate a flexible combined electrochemistry and fiber optics-based in situ UV/vis spectroscopy setup to gain insight into the depth evolution of electrochemical hydride and oxide formation in Pd films with thicknesses of 20 and 100 nm. The thicknesses of our model systems are chosen such that the films are thinner or significantly thicker than the optical skin depth of Pd to create two distinctly different situations. Low power white light is irradiated on the sample and analyzed in three different configurations; transmittance through, and, reflectance from the front and the back side of the film. The obtained optical sensitivities correspond to fractions of a monolayer of adsorbed or absorbed hydrogen (H) and oxygen (O) on Pd. Moreover, a combined simultaneous readout obtained from the different optical measurement configurations provides mechanistic insights into the depth-evolution of the studied hydrogenation and oxidation processes.

  13. Analysis of dust and marine aerosol optical depth spectral-curvature information in the UV to SWIR (Short Wave Infrared) wavelength regions.

    Science.gov (United States)

    O'Neill, N. T.; Smirnov, A.; Eck, T. F.; Sakerin, S.; Kabanov, D.

    2005-12-01

    Traditional sunphotometry in the UV, visible and very NIR (Near Infrared) spectral regions is weighted, in terms of spectral information content, towards sub-micron (fine mode) particles. Sunphotometry in the NIR and SWIR increases the diversity and information content of spectral aerosol optical depth (AOD) measurements for supermicron (coarse mode) particles. Two data sets representing dust aerosols from the UAE (United Arab Emirates) region and marine aerosols from the northern, tropical and southern Atlantic Ocean were analyzed in terms of their spectral curvature diversity and information content. The former data set was acquired using NIR-enhanced CIMEL sunphotometers (340, 340, 380, 440, 500, 670, 870, 1020, 1640 nm) as part of the August to October, 2004 UAE2 field campaign while the latter data set was acquired using an automated Russian UV to SWIR SP-5 sunphotometer (339, 423, 438, 484, 552, 633, 677, 777, 869, 1241, 1560, 2148, 4000 nm) as part of a October/December 2004 cruise campaign in the northern, tropical and south Atlantic Ocean. A Microtops hand-held sunphotometer was also employed to acquire VIS to NIR AOD spectra during the latter field campaign. Results will be presented in terms of robust micro-physical and spectral curvature parameters which characterize super-micron aerosols and, in a more general sense, in terms of what universal/fundamental optical inferences can be drawn from the two disperse data sets.

  14. [Comparison of atmospheric particulate matter and aerosol optical depth in Beijing City].

    Science.gov (United States)

    Lin, Hai-Feng; Xin, Jin-Yuan; Zhang, Wen-Yu; Wang, Yue-Si; Liu, Zi-Rui; Chen, Chuan-Lei

    2013-03-01

    The pollution of particulate matter was serious in Beijing City from the synchronous observation of particulate matter mass concentration and aerosol optical characteristics in 2009. The annual mean concentrations of PM2.5 and PM10 were (65 +/- 14) microg x m(-3) and (117 +/- 31) microg x m(-3), respectively, which exceeded the national ambient air quality annual standards to be implemented in 2016. There were 35% and 26% days of 2009 that the daily standards were exceeded. There was a significant correlation between fine particulate (PM2.5) and inhalable particle (PM10), with a correlation coefficient (R) of approximately 0.90 (P 500 nm) and Angstrom exponent were (0.55 +/- 0.1) and (1.12 +/- 0.08), respectively. There were significant correlations between PM2.5, PM10 and AOD in the four seasons and the whole year, and the correlation coefficients were greater than or equal to 0.50. Furthermore, the correlation functions and coefficients had seasonal variations. The correlations were more significant in summer and autumn than in spring and winter. The annual correlation could cover up the seasonal systematic differences. The correlations between AOD revised by Mixed Layer Height and PM2.5 PM10 revised by Relative Humidity became stronger, and the exponential correlations were superior to the linear correlations.

  15. Using the OMI aerosol index and absorption aerosol optical depth to evaluate the NASA MERRA Aerosol Reanalysis

    Science.gov (United States)

    Buchard, V.; da Silva, A. M.; Colarco, P. R.; Darmenov, A.; Randles, C. A.; Govindaraju, R.; Torres, O.; Campbell, J.; Spurr, R.

    2015-05-01

    A radiative transfer interface has been developed to simulate the UV aerosol index (AI) from the NASA Goddard Earth Observing System version 5 (GEOS-5) aerosol assimilated fields. The purpose of this work is to use the AI and aerosol absorption optical depth (AAOD) derived from the Ozone Monitoring Instrument (OMI) measurements as independent validation for the Modern Era Retrospective analysis for Research and Applications Aerosol Reanalysis (MERRAero). MERRAero is based on a version of the GEOS-5 model that is radiatively coupled to the Goddard Chemistry, Aerosol, Radiation, and Transport (GOCART) aerosol module and includes assimilation of aerosol optical depth (AOD) from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor. Since AI is dependent on aerosol concentration, optical properties and altitude of the aerosol layer, we make use of complementary observations to fully diagnose the model, including AOD from the Multi-angle Imaging SpectroRadiometer (MISR), aerosol retrievals from the AErosol RObotic NETwork (AERONET) and attenuated backscatter coefficients from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) mission to ascertain potential misplacement of plume height by the model. By sampling dust, biomass burning and pollution events in 2007 we have compared model-produced AI and AAOD with the corresponding OMI products, identifying regions where the model representation of absorbing aerosols was deficient. As a result of this study over the Saharan dust region, we have obtained a new set of dust aerosol optical properties that retains consistency with the MODIS AOD data that were assimilated, while resulting in better agreement with aerosol absorption measurements from OMI. The analysis conducted over the southern African and South American biomass burning regions indicates that revising the spectrally dependent aerosol absorption properties in the near-UV region improves the modeled-observed AI comparisons

  16. Outer Retinal and Choroidal Evaluation in Multiple Evanescent White Dot Syndrome (MEWDS): An Enhanced Depth Imaging Optical Coherence Tomography Study.

    Science.gov (United States)

    Fiore, Tito; Iaccheri, Barbara; Cerquaglia, Alessio; Lupidi, Marco; Torroni, Giovanni; Fruttini, Daniela; Cagini, Carlo

    2018-01-01

    To perform an analysis of optical coherence tomography (OCT) abnormalities in patients with MEWDS, during the acute and recovery stages, using enhanced depth imaging-OCT (EDI-OCT). A retrospective case series of five patients with MEWDS was included. EDI-OCT imaging was evaluated to detect retinal and choroidal features. In the acute phase, focal impairment of the ellipsoid zone and external limiting membrane, hyperreflective dots in the inner choroid, and full-thickness increase of the choroidal profile were observed in the affected eye; disappearance of these findings and restoration of the choroidal thickness (p = 0.046) was appreciated in the recovery phase. No OCT abnormalities were assessed in the unaffected eye. EDI-OCT revealed transient outer retinal layer changes and inner choroidal hyperreflective dots. A transient increased thickness of the whole choroid was also identified. This might confirm a short-lasting inflammatory involvement of the whole choroidal tissue in the active phase of MEWDS.

  17. Enhanced-Depth Imaging Optical Coherence Tomography of the Human Choroid In Vivo Compared With Histology After Enucleation

    DEFF Research Database (Denmark)

    Li, Xiao Qiang; Heegaard, Steffen; Kiilgaard, Jens Folke

    2016-01-01

    PURPOSE: This study compared in vivo enhanced-depth imaging optical coherence tomography (EDI-OCT) with ex vivo histology of the choroid in human eyes. METHODS: Three eyes in three patients with advanced iris melanoma without posterior segment involvement underwent EDI-OCT less than 24 hours prior...... to enucleation and, in one eye, immediately after enucleation. Following fixation in 4% buffered formaldehyde and paraffin embedding, serial sections of the whole eye were cut horizontally, mounted, stained with hematoxylin-eosin and digitized. Alignment between histology and EDI-OCT was made on landmarks...... and subfoveal choroid thickness reduced to 56%, 45%, and 56%, respectively, of its in vivo thickness on EDI-OCT. CONCLUSIONS: There were no identifiable discrepancies in choroidal structural patterns between clinical EDI-OCT and histologic sections except that after enucleation and histologic fixation choroidal...

  18. The effect of aerosol optical depth on rainfall with reference to meteorology over metro cities in India.

    Science.gov (United States)

    Gunaseelan, Indira; Bhaskar, B Vijay; Muthuchelian, K

    2014-01-01

    Rainfall is a key link in the global water cycle and a proxy for changing climate; therefore, proper assessment of the urban environment's impact on rainfall will be increasingly important in ongoing climate diagnostics and prediction. Aerosol optical depth (AOD) measurements on the monsoon seasons of the years 2008 to 2010 were made over four metro regional hotspots in India. The highest average of AOD was in the months of June and July for the four cities during 3 years and lowest was in September. Comparing the four regions, Kolkata was in the peak of aerosol contamination and Chennai was in least. Pearson correlation was made between AOD with climatic parameters. Some changes in the parameters were found during drought year. Temperature, cloud parameters, and humidity play an important role for the drought conditions. The role of aerosols, meteorological parameters, and their impacts towards the precipitation during the monsoon was studied.

  19. About microlensing optical depth and rates for free-floating planets towards the Kepler's field of view

    International Nuclear Information System (INIS)

    Hafizi, M; Hamolli, L

    2012-01-01

    In this work we examine the possibility of observing microlensing events in the Kepler space observatory field of view, caused by brown dwarfs or free-floating planets. We calculate the optical depth towards the field of view of the Kepler satellite and the rate of these events based on latest results about mass distribution of astrophysical objects from brown dwarf down to Earth mass order. With the current data, the probability of such events is insignificant, due to the small number of stars observed by this instrument compared to other experiments devoted to the microlensing method. Nevertheless, this probability may increase significantly in the case of a higher presence of free-floating planets, whose number is poorly defined so far.

  20. Determination of the columnar aerosol size distribution by inversion of spectral aerosol optical depth measurements at different areas in Egypt

    International Nuclear Information System (INIS)

    EI-Metwally, M.; Madkour, M.A.

    2006-01-01

    Aerosols have a great effects on nuclear safety calculations and atmospheric environment. The aerosol optical depth measurements are carried out at four areas in Egypt: Cairo and Helwan as urban/industrial areas, Aswan as an arid area and Mansoura as an agricultural area covering the period from Jun 1992 to May 1993. These measurements were recorded by ground-based pyrheliometers with large band-pass filters. Monthly average values of aerosol optical depth (AOD) showed a pronounced temporal trend, with a maximum AOD during summer and the transition seasons (spring and autumn) at all sites. Levels of AODs are higher at both urban and industrial areas than at other areas. Variation of Angstrom exponent a with the AOD was clear at most sites and the a value depends on the spectral range used in its determination. The mean contribution of anthropogenic sources to AOD over Cairo was at the range of 25.1-54.3%, whereas those values in Helwan were at the range of 34.5-59.8%. Finally, columnar aerosol size distributions have been inferred by inverting particularly AOD measurements as a function of wavelength. The Junge (type I) and bimodal (type III) distributions are dominant at urban and arid areas (Cairo and Aswan), whereas mono dispersion distribution (type II) are dominant in industrial and agricultural areas (Helwan and Mansoura). In Cairo and Aswan, the peak of columnar size distribution for the fine mode at radius r is around 0.1 and 0.2 μm respectively, while it is around 1.0 and 2.0 μm for the coarse mode. .Also, the peak of size distribution for the mono dispersion mode was marked at radius around 0.2 μm at both Helwan and Mansoura. A comprehensive comparison of our results with literature size distributions is very sparse, nevertheless, our size distributions in general agree with them

  1. Optical modeling of a corneal inlay in real eyes to increase depth of focus: optimum centration and residual defocus.

    Science.gov (United States)

    Tabernero, Juan; Artal, Pablo

    2012-02-01

    To determine the optimum position to center a small-aperture corneal inlay and the effect of residual defocus in the surgical eye to maximize depth of focus. Laboratorio de Óptica, Universidad de Murcia, Murcia, Spain. Cohort study. Personalized eye models were built using actual data (corneal topography, eye length, ocular aberrations, and eye alignment). A small aperture 1.6 mm in diameter was placed at the corneal plane in each model. The monochromatic and polychromatic Strehl ratios were calculated as a function of the pinhole position. Different residual defocus values were also incorporated into the models, and the through-focus Strehl ratios were calculated. Sixteen eye models were built. For most subjects, the optimum location of the aperture for distance vision was close to the corneal reflex position. For a given optimized centration of the aperture, the best compromise of depth of focus was obtained when the eyes had some residual myopic defocus (range -0.75 to -1.00 diopter [D]). Strehl ratio values were over 0.1 for far distance, which led to visual acuities better than 20/20. The depth of focus was 2.50 D with a mean near visual acuity of Jaeger 1 or better. In eyes with little astigmatism and aberrations, the optimum centration of the small aperture was near the corneal reflex position. To improve optical outcomes with the inlay, some small residual myopia and correction of corneal astigmatism might be required. Copyright © 2011 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  2. Effects on stratospheric moistening by rates of change of aerosol optical depth and ozone due to solar activity in extra-tropics

    Science.gov (United States)

    Saha, U.; Maitra, A.

    2014-11-01

    The solar-induced changes in ozone and aerosol optical depth have relative effects on stratospheric moistening at upper troposphere/lower stratosphere region. Wavelet-based multi-scale principal component analysis technique has been applied to de-noise component of quasi-biennial oscillation and El Niño-Southern Oscillation from ozone and aerosol optical depth variations. Rate of change of aerosol optical depth sharply increases indicating a positive gradient whereas rate of change of ozone sharply decreases indicating a negative gradient with solar activity during the years 2004-2010. It is also observed that with increase of rate of change of aerosol optical depth, there is a sharp increase of stratospheric moistening caused by enhanced deep convection. On the contrary, with the increase of stratospheric moistening, there is a sharp decrease of rate of change of ozone resulting in a cross-over between the two parameters. An increase in aerosol optical depth may cause a significant increase in the gradient of vertical temperature profile, as well as formation of cloud condensation nuclei, clouds and hence rainfall. This may lead to formation of strong convective system in the atmosphere that is essential for vertical transfer of water vapour in the tropics percolating tropical tropopause layer and depleting stratospheric ozone in the extra-tropics.

  3. The spatial-temporal evolution of aerosol optical depth and the analysis of influence factors in Bohai Rim

    International Nuclear Information System (INIS)

    Hou, Chunliang; Jiang, Hong; Wang, Xiaoyan; Pei, Huan

    2014-01-01

    Aerosol Optical Depth (AOD) is an important parameter of aerosol optical properties and it is an important physical parameter quantity to understanding the atmospheric environment. Bohai Rim is one of the three major urban agglomeration regions with rapidly developing economy in China. The study of AOD over this region is important to understand the environment and climate in Bohai Rim. Firstly, aerosol product data from 2000 to 2010, published by NASA, were used to analyze the temporal-spatial evolution of AOD in Bohai Rim with precision evaluation. The results showed that the spatial distribution of AOD had an obvious regional characteristic. The spatial distribution characterized that a much high value existed at urban areas and plain areas. On the contrary, the low value data existed in some mountainous regions which had higher percentages of forest coverage. The AOD values fluctuated somewhat each year in the region, from the minimum annual mean in 2003 to the maximum in 2009. Generally, the highest AOD value was in summer, followed by spring, autumn and winter. In terms of monthly variation, the value of AOD reached its peak in June and the lowest value was in December. This study analyzed the relation between AOD and some influence factors such as land use types, elevation, and distribution of urban agglomeration and so on. These results provide an important basic dataset for climate and environmental research

  4. All-optical in-depth detection of the acoustic wave emitted by a single gold nanorod

    Science.gov (United States)

    Xu, Feng; Guillet, Yannick; Ravaine, Serge; Audoin, Bertrand

    2018-04-01

    A single gold nanorod dropped on the surface of a silica substrate is used as a transient optoacoustic source of gigahertz hypersounds. We demonstrate the all-optical detection of the as-generated acoustic wave front propagating in the silica substrate. For this purpose, time-resolved femtosecond pump-probe experiments are performed in a reflection configuration. The fundamental breathing mode of the nanorod is detected at 23 GHz by interferometry, and the longitudinal acoustic wave radiated in the silica substrate is detected by time-resolved Brillouin scattering. By tuning the optical probe wavelength from 750 to 900 nm, hypersounds with wavelengths of 260-315 nm are detected in the silica substrate, with corresponding acoustic frequencies in the range of 19-23 GHz. To confirm the origin of these hypersounds, we theoretically analyze the influence of the acoustic excitation spectrum on the temporal envelope of the transient reflectivity. This analysis proves that the acoustic wave detected in the silica substrate results from the excitation of the breathing mode of the nanorod. These results pave the way for performing local in-depth elastic nanoscopy.

  5. Characterizing the Breadth and Depth of Volunteer Water Monitoring Programs in the United States

    Science.gov (United States)

    Stepenuck, Kristine F.; Genskow, Kenneth D.

    2018-01-01

    A survey of 345 volunteer water monitoring programs in the United States was conducted to document their characteristics, and perceived level of support for data to inform natural resource management or policy decisions. The response rate of 86% provided information from 46 states. Programs represented a range of ages, budgets, objectives, scopes, and level of quality assurance, which influenced data uses and perceived support by sponsoring agency administrators and external decision makers. Most programs focused on rivers, streams, and lakes. Programs had not made substantial progress to develop EPA or state-approved quality assurance plans since 1998, with only 48% reporting such plans. Program coordinators reported feeling slightly more support for data to be used for management as compared to policy decisions. Programs with smaller budgets may be at particular risk of being perceived to lack credibility due to failure to develop quality assurance plans. Over half of programs identified as collaborative, in that volunteers assisted scientists in program design, data analysis and/or dissemination of results. Just under a third were contributory, in which volunteers primarily collected data in a scientist-defined program. Recommendations to improve perceived data credibility, and to augment limited budgets include developing quality assurance plans and gaining agency approval, and developing partnerships with other organizations conducting monitoring in the area to share resources and knowledge. Funding agencies should support development of quality assurance plans to help ensure data credibility. Service providers can aid in plan development by providing training to program staff over time to address high staff turnover rates.

  6. Comparison between a New Optical Biometry Device and an Anterior Segment Optical Coherence Tomographer for Measuring Central Corneal Thickness and Anterior Chamber Depth

    Directory of Open Access Journals (Sweden)

    Jinhai Huang

    2016-01-01

    Full Text Available Purpose. To compare between a new optical biometer (AL-Scan, Nidek Co., Aichi, Japan and an anterior segment optical coherence tomographer (Visante AS-OCT, Carl Zeiss Meditec, Dublin, USA for measuring central corneal thickness (CCT, anterior chamber depth (ACD, and aqueous depth (AD. Methods. Sixty-three eyes of 63 normal subjects were examined with AL-Scan and Visante AS-OCT in this prospective study. One eye per subject was measured three times with both devices to record their CCT, ACD, and AD. All procedures were performed by the same operator. Agreement between the two devices was assessed using paired t-tests, Bland-Altman plots, and 95% limits of agreement (LoA. Results. The mean CCT, ACD, and AD measured by AL-Scan were 538.59±27.37 μm, 3.70±0.30 mm, and 3.16±0.30 mm, respectively. The mean values obtained by the Visante OCT were 536.14±26.61 μm for CCT, 3.71±0.29 mm for ACD, and 3.17±0.29 mm for AD. The mean CCT by the AL-Scan was higher than that obtained by the Visante AS-OCT (difference = 2.45±6.07 μm, P<0.05. The differences in ACD and AD measurements were not statistically significant. The 95% LoA of CCT, ACD, and AD were between −9.44 and 14.35 μm, −0.15 and 0.12 mm, and −0.15 and 0.12 mm, respectively. Conclusions. Since these two devices were comparable for measuring CCT, ACD, and AD, their results can be interchangeably used in the clinic.

  7. Area- and depth- weighted averages of selected SSURGO variables for the conterminous United States and District of Columbia

    Science.gov (United States)

    Wieczorek, Michael

    2014-01-01

    This digital data release consists of seven data files of soil attributes for the United States and the District of Columbia. The files are derived from National Resources Conservations Service’s (NRCS) Soil Survey Geographic database (SSURGO). The data files can be linked to the raster datasets of soil mapping unit identifiers (MUKEY) available through the NRCS’s Gridded Soil Survey Geographic (gSSURGO) database (http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/survey/geo/?cid=nrcs142p2_053628). The associated files, named DRAINAGECLASS, HYDRATING, HYDGRP, HYDRICCONDITION, LAYER, TEXT, and WTDEP are area- and depth-weighted average values for selected soil characteristics from the SSURGO database for the conterminous United States and the District of Columbia. The SSURGO tables were acquired from the NRCS on March 5, 2014. The soil characteristics in the DRAINAGE table are drainage class (DRNCLASS), which identifies the natural drainage conditions of the soil and refers to the frequency and duration of wet periods. The soil characteristics in the HYDRATING table are hydric rating (HYDRATE), a yes/no field that indicates whether or not a map unit component is classified as a "hydric soil". The soil characteristics in the HYDGRP table are the percentages for each hydrologic group per MUKEY. The soil characteristics in the HYDRICCONDITION table are hydric condition (HYDCON), which describes the natural condition of the soil component. The soil characteristics in the LAYER table are available water capacity (AVG_AWC), bulk density (AVG_BD), saturated hydraulic conductivity (AVG_KSAT), vertical saturated hydraulic conductivity (AVG_KV), soil erodibility factor (AVG_KFACT), porosity (AVG_POR), field capacity (AVG_FC), the soil fraction passing a number 4 sieve (AVG_NO4), the soil fraction passing a number 10 sieve (AVG_NO10), the soil fraction passing a number 200 sieve (AVG_NO200), and organic matter (AVG_OM). The soil characteristics in the TEXT table are

  8. Depth dependent modification of optical constants arising from H+ implantation in n-type 4H-SiC measured using coherent acoustic phonons

    Directory of Open Access Journals (Sweden)

    Andrey Baydin

    2016-06-01

    Full Text Available Silicon carbide (SiC is a promising material for new generation electronics including high power/high temperature devices and advanced optical applications such as room temperature spintronics and quantum computing. Both types of applications require the control of defects particularly those created by ion bombardment. In this work, modification of optical constants of 4H-SiC due to hydrogen implantation at 180 keV and at fluences ranging from 1014 to 1016 cm−2 is reported. The depth dependence of the modified optical constants was extracted from coherent acoustic phonon spectra. Implanted spectra show a strong dependence of the 4H-SiC complex refractive index depth profile on H+ fluence. These studies provide basic insight into the dependence of optical properties of 4H silicon carbide on defect densities created by ion implantation, which is of relevance to the fabrication of SiC-based photonic and optoelectronic devices.

  9. The Two-Column Aerosol Project: Phase I—Overview and impact of elevated aerosol layers on aerosol optical depth

    Science.gov (United States)

    Berg, Larry K.; Fast, Jerome D.; Barnard, James C.; Burton, Sharon P.; Cairns, Brian; Chand, Duli; Comstock, Jennifer M.; Dunagan, Stephen; Ferrare, Richard A.; Flynn, Connor J.; Hair, Johnathan W.; Hostetler, Chris A.; Hubbe, John; Jefferson, Anne; Johnson, Roy; Kassianov, Evgueni I.; Kluzek, Celine D.; Kollias, Pavlos; Lamer, Katia; Lantz, Kathleen; Mei, Fan; Miller, Mark A.; Michalsky, Joseph; Ortega, Ivan; Pekour, Mikhail; Rogers, Ray R.; Russell, Philip B.; Redemann, Jens; Sedlacek, Arthur J.; Segal-Rosenheimer, Michal; Schmid, Beat; Shilling, John E.; Shinozuka, Yohei; Springston, Stephen R.; Tomlinson, Jason M.; Tyrrell, Megan; Wilson, Jacqueline M.; Volkamer, Rainer; Zelenyuk, Alla; Berkowitz, Carl M.

    2016-01-01

    The Two-Column Aerosol Project (TCAP), conducted from June 2012 through June 2013, was a unique study designed to provide a comprehensive data set that can be used to investigate a number of important climate science questions, including those related to aerosol mixing state and aerosol radiative forcing. The study was designed to sample the atmosphere between and within two atmospheric columns; one fixed near the coast of North America (over Cape Cod, MA) and a second moveable column over the Atlantic Ocean several hundred kilometers from the coast. The U.S. Department of Energy's (DOE) Atmospheric Radiation Measurement (ARM) Mobile Facility (AMF) was deployed at the base of the Cape Cod column, and the ARM Aerial Facility was utilized for the summer and winter intensive observation periods. One important finding from TCAP is that four of six nearly cloud-free flight days had aerosol layers aloft in both the Cape Cod and maritime columns that were detected using the nadir pointing second-generation NASA high-spectral resolution lidar (HSRL-2). These layers contributed up to 60% of the total observed aerosol optical depth (AOD). Many of these layers were also intercepted by the aircraft configured for in situ sampling, and the aerosol in the layers was found to have increased amounts of biomass burning material and nitrate compared to aerosol found near the surface. In addition, while there was a great deal of spatial and day-to-day variability in the aerosol chemical composition and optical properties, no systematic differences between the two columns were observed.

  10. The Two-Column Aerosol Project: Phase I - Overview and Impact of Elevated Aerosol Layers on Aerosol Optical Depth

    Science.gov (United States)

    Berg, Larry K.; Fast, Jerome D.; Barnard, James C.; Burton, Sharon P.; Cairns, Brian; Chand, Duli; Comstock, Jennifer M.; Dunagan, Stephen; Ferrare, Richard A.; Flynn, Connor J.; hide

    2015-01-01

    The Two-Column Aerosol Project (TCAP), conducted from June 2012 through June 2013, was a unique study designed to provide a comprehensive data set that can be used to investigate a number of important climate science questions, including those related to aerosol mixing state and aerosol radiative forcing. The study was designed to sample the atmosphere be tween and within two atmospheric columns; one fixed near the coast of North America (over Cape Cod, MA) and a second moveable column over the Atlantic Ocean several hundred kilometers from the coast. The U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Mobile Facility (AMF) was deployed at the base of the Cape Cod column, and the ARM Aerial Facility was utilized for the summer and winter intensive observation periods. One important finding from TCAP is that four of six nearly cloud-free flight days had aerosol layers aloft in both the Cape Cod and maritime columns that were detected using the nadir pointing second-generation NASA high-spectral resolution lidar (HSRL-2).These layer s contributed up to 60 of the total observed aerosol optical depth (AOD). Many of these layers were also intercepted by the aircraft configured for in situ sampling, and the aerosol in the layers was found to have increased amounts of biomass burning material and nitrate compared to aerosol found near the surface. In addition, while there was a great deal of spatial and day-to-day variability in the aerosol chemical composition and optical properties, no systematic differences between the two columns were observed.

  11. Depth from Optical Turbulence

    Science.gov (United States)

    2012-01-01

    Dagobert, and C. Franchis . Atmospheric tur- bulence restoration by diffeomorphic image registration and blind deconvolution. In ACIVS, 2008. 1 [4] S...20] V. Tatarskii. Wave Propagation in a Turbulent Medium. McGraw-Hill Books, 1961. 2 [21] Y. Tian and S. Narasimhan. A globally optimal data-driven

  12. Fast ray-tracing of human eye optics on Graphics Processing Units.

    Science.gov (United States)

    Wei, Qi; Patkar, Saket; Pai, Dinesh K

    2014-05-01

    We present a new technique for simulating retinal image formation by tracing a large number of rays from objects in three dimensions as they pass through the optic apparatus of the eye to objects. Simulating human optics is useful for understanding basic questions of vision science and for studying vision defects and their corrections. Because of the complexity of computing such simulations accurately, most previous efforts used simplified analytical models of the normal eye. This makes them less effective in modeling vision disorders associated with abnormal shapes of the ocular structures which are hard to be precisely represented by analytical surfaces. We have developed a computer simulator that can simulate ocular structures of arbitrary shapes, for instance represented by polygon meshes. Topographic and geometric measurements of the cornea, lens, and retina from keratometer or medical imaging data can be integrated for individualized examination. We utilize parallel processing using modern Graphics Processing Units (GPUs) to efficiently compute retinal images by tracing millions of rays. A stable retinal image can be generated within minutes. We simulated depth-of-field, accommodation, chromatic aberrations, as well as astigmatism and correction. We also show application of the technique in patient specific vision correction by incorporating geometric models of the orbit reconstructed from clinical medical images. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  13. Climatology of the Aerosol Optical Depth by Components from the Multi-Angle Imaging Spectroradiometer (MISR) and Chemistry Transport Models

    Science.gov (United States)

    Lee, Huikyo; Kalashnikova, Olga V.; Suzuki, Kentaroh; Braverman, Amy; Garay, Michael J.; Kahn, Ralph A.

    2016-01-01

    The Multi-angle Imaging Spectroradiometer (MISR) Joint Aerosol (JOINT_AS) Level 3 product has provided a global, descriptive summary of MISR Level 2 aerosol optical depth (AOD) and aerosol type information for each month over 16+ years since March 2000. Using Version 1 of JOINT_AS, which is based on the operational (Version 22) MISR Level 2 aerosol product, this study analyzes, for the first time, characteristics of observed and simulated distributions of AOD for three broad classes of aerosols: spherical nonabsorbing, spherical absorbing, and nonspherical - near or downwind of their major source regions. The statistical moments (means, standard deviations, and skew-nesses) and distributions of AOD by components derived from the JOINT_AS are compared with results from two chemistry transport models (CTMs), the Goddard Chemistry Aerosol Radiation and Transport (GOCART) and SPectral RadIatioN-TrAnSport (SPRINTARS). Overall, the AOD distributions retrieved from MISR and modeled by GOCART and SPRINTARS agree with each other in a qualitative sense. Marginal distributions of AOD for each aerosol type in both MISR and models show considerable high positive skewness, which indicates the importance of including extreme AOD events when comparing satellite retrievals with models. The MISR JOINT_AS product will greatly facilitate comparisons between satellite observations and model simulations of aerosols by type.

  14. MODIS derived fire characteristics and aerosol optical depth variations during the agricultural residue burning season, north India

    International Nuclear Information System (INIS)

    Vadrevu, Krishna Prasad; Ellicott, Evan; Badarinath, K.V.S.; Vermote, Eric

    2011-01-01

    Agricultural residue burning is one of the major causes of greenhouse gas emissions and aerosols in the Indo-Ganges region. In this study, we characterize the fire intensity, seasonality, variability, fire radiative energy (FRE) and aerosol optical depth (AOD) variations during the agricultural residue burning season using MODIS data. Fire counts exhibited significant bi-modal activity, with peak occurrences during April-May and October-November corresponding to wheat and rice residue burning episodes. The FRE variations coincided with the amount of residues burnt. The mean AOD (2003-2008) was 0.60 with 0.87 (+1σ) and 0.32 (-1σ). The increased AOD during the winter coincided well with the fire counts during rice residue burning season. In contrast, the AOD-fire signal was weak during the summer wheat residue burning and attributed to dust and fossil fuel combustion. Our results highlight the need for 'full accounting of GHG's and aerosols', for addressing the air quality in the study area. - Highlights: → MODIS data could capture rice and wheat residue burning events. → The total FRP was high during the rice burning season than the wheat. → MODIS AOD variations coincided well with rice burning events than wheat. → AOD values exceeding one suggested intense air pollution. - This research work highlights the satellite derived fire products and their potential in characterizing the agricultural residue burning events and air pollution.

  15. Comparison of slitlamp optical coherence tomography and scanning peripheral anterior chamber depth analyzer to evaluate angle closure in Asian eyes.

    Science.gov (United States)

    Wong, Hon-Tym; Chua, Jocelyn L L; Sakata, Lisandro M; Wong, Melissa H Y; Aung, Han T; Aung, Tin

    2009-05-01

    To evaluate the effectiveness of slitlamp optical coherence tomography (SL-OCT) and Scanning Peripheral Anterior Chamber depth analyzer (SPAC) in detecting angle closure, using gonioscopy as the reference standard. A total of 153 subjects underwent gonioscopy, SL-OCT, and SPAC. The anterior chamber angle (ACA) was classified as closed on gonioscopy if the posterior trabecular meshwork could not be seen; with SL-OCT, closure was determined by contact between the iris and angle wall anterior to the scleral spur; and with SPAC by a numerical grade of 5 or fewer and/or a categorical grade of suspect or potential. A closed ACA was identified in 51 eyes with gonioscopy, 86 eyes with SL-OCT, and 61 eyes with SPAC (gonioscopy vs SL-OCT, P gonioscopy vs SPAC, P = .10; SL-OCT vs SPAC, P gonioscopy, SL-OCT detected a closed ACA in 43, whereas SPAC identified 41 (P = .79). An open angle in all 4 quadrants was observed in 102 eyes with gonioscopy, but SL-OCT and SPAC identified 43 and 20 of these eyes, respectively, as having angle closure. The overall sensitivity and specificity for SL-OCT were 84% and 58% vs 80% and 80% for SPAC. Using gonioscopy as the reference, SL-OCT and SPAC showed good sensitivity for detecting eyes at risk of angle closure.

  16. High Resolution Trajectory-Based Smoke Forecasts Using VIIRS Aerosol Optical Depth and NUCAPS Carbon Monoxide Retrievals

    Science.gov (United States)

    Pierce, R. B.; Smith, N.; Barnet, C.; Barnet, C. D.; Kondragunta, S.; Davies, J. E.; Strabala, K.

    2016-12-01

    We use Suomi National Polar-orbiting Partnership (S-NPP) Visible Infrared Imaging Radiometer Suite (VIIRS) Aerosol Optical Depth (AOD) and combined Cross-track Infrared Sounder (CrIS) and Advanced Technology Microwave Sounder (ATMS) NOAA-Unique CrIS-ATMS Processing System (NUCAPS) carbon monoxide (CO) retrievals to initialize trajectory-based, high spatial resolution North American smoke dispersion forecasts during the May 2016 Fort McMurray wildfire in northern Alberta and the July 2016 Soberanes Fire in Northern California. These two case studies illustrate how long range transport of wild fire smoke can adversely impact surface air quality thousands of kilometers downwind and how local topographic flow can lead to complex transport patterns near the wildfire source region. The NUCAPS CO retrievals are shown to complement the high resolution VIIRS AOD retrievals by providing retrievals in partially cloudy scenes and also providing information on the vertical distribution of the wildfire smoke. This work addresses the need for low latency, web-based, high resolution forecasts of smoke dispersion for use by NWS Incident Meteorologists (IMET) to support on-site decision support services for fire incident management teams. The primary user community for the IDEA-I smoke forecasts is the Western regions of the NWS and US EPA due to the significant impacts of wildfires in these regions. Secondary users include Alaskan NWS offices and Western State and Local air quality management agencies such as the Western Regional Air Partnership (WRAP).

  17. Comparison of peripapillary choroidal thickness measurements via spectral domain optical coherence tomography with and without enhanced depth imaging.

    Science.gov (United States)

    Ayyildiz, Onder; Kucukevcilioglu, Murat; Ozge, Gokhan; Koylu, Mehmet Talay; Ozgonul, Cem; Gokce, Gokcen; Mumcuoglu, Tarkan; Durukan, Ali Hakan; Mutlu, Fatih Mehmet

    2016-05-01

    To compare peripapillary choroidal thickness (PP-CT) measurements using a spectral domain optical coherence tomography (SD-OCT) device with and without enhanced depth imaging (EDI). Sixty healthy subjects aged from 18 to 40 years were included in this study. PP-CTs were measured in the right eyes by manual segmentation via SD-OCT both with and without EDI. The intraclass correlation coefficient (ICC) for each technique and comparison of PP-CT measurements between two techniques were evaluated. The correlation between retinal nerve fiber layer (RNFL) thickness and PP-CT was also explored on images of SD-OCT without EDI. The PP-CT measurements of 55 subjects were evaluated. The ICC was 0.999 (95% CI: 0.998-1.0, p  0.05). Additionally, there was no correlation between RNFL thickness and PP-CT (r = -0.109; p = 0.335). The PP-CT measurements via SD-OCT without EDI were consistent with the measurements via SD-OCT with EDI. Ophthalmologists who do not have access to EDI technology can use images of SD-OCT without EDI to measure the peripapillary choroid for research purposes. However, thicker peripapillary choroids cannot be measured using this technique and require further modifications or newer technologies, such as SD-OCT with EDI.

  18. Investigating the relationship between Aerosol Optical Depth and Precipitation over Southeast Asia with Relative Humidity as an influencing factor.

    Science.gov (United States)

    Ng, Daniel Hui Loong; Li, Ruimin; Raghavan, Srivatsan V; Liong, Shie-Yui

    2017-10-17

    Atmospheric aerosols influence precipitation by changing the earth's energy budget and cloud properties. A number of studies have reported correlations between aerosol properties and precipitation data. Despite previous research, it is still hard to quantify the overall effects that aerosols have on precipitation as multiple influencing factors such as relative humidity (RH) can distort the observed relationship between aerosols and precipitation. Thus, in this study, both satellite-retrieved and reanalysis data were used to investigate the relationship between aerosols and precipitation in the Southeast Asia region from 2001 to 2015, with RH considered as a possible influencing factor. Different analyses in the study indicate that a positive correlation was present between Aerosol Optical Depth (AOD) and precipitation over northern Southeast Asia region during the autumn and the winter seasons, while a negative correlation was identified over the Maritime Continent during the autumn season. Subsequently, a partial correlation analysis revealed that while RH influences the long-term negative correlations between AOD and precipitation, it did not significantly affect the positive correlations seen in the winter season. The result of this study provides additional evidence with respect to the critical role of RH as an influencing factor in AOD-precipitation relationship over Southeast Asia.

  19. Statistical variability comparison in MODIS and AERONET derived aerosol optical depth over Indo-Gangetic Plains using time series modeling.

    Science.gov (United States)

    Soni, Kirti; Parmar, Kulwinder Singh; Kapoor, Sangeeta; Kumar, Nishant

    2016-05-15

    A lot of studies in the literature of Aerosol Optical Depth (AOD) done by using Moderate Resolution Imaging Spectroradiometer (MODIS) derived data, but the accuracy of satellite data in comparison to ground data derived from ARrosol Robotic NETwork (AERONET) has been always questionable. So to overcome from this situation, comparative study of a comprehensive ground based and satellite data for the period of 2001-2012 is modeled. The time series model is used for the accurate prediction of AOD and statistical variability is compared to assess the performance of the model in both cases. Root mean square error (RMSE), mean absolute percentage error (MAPE), stationary R-squared, R-squared, maximum absolute percentage error (MAPE), normalized Bayesian information criterion (NBIC) and Ljung-Box methods are used to check the applicability and validity of the developed ARIMA models revealing significant precision in the model performance. It was found that, it is possible to predict the AOD by statistical modeling using time series obtained from past data of MODIS and AERONET as input data. Moreover, the result shows that MODIS data can be formed from AERONET data by adding 0.251627 ± 0.133589 and vice-versa by subtracting. From the forecast available for AODs for the next four years (2013-2017) by using the developed ARIMA model, it is concluded that the forecasted ground AOD has increased trend. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. Three-dimensional variational assimilation of MODIS aerosol optical depth: Implementation and application to a dust storm over East Asia

    Science.gov (United States)

    Liu, Zhiquan; Liu, Quanhua; Lin, Hui-Chuan; Schwartz, Craig S.; Lee, Yen-Huei; Wang, Tijian

    2011-12-01

    Assimilation of the Moderate Resolution Imaging Spectroradiometer (MODIS) total aerosol optical depth (AOD) retrieval products (at 550 nm wavelength) from both Terra and Aqua satellites have been developed within the National Centers for Environmental Prediction (NCEP) Gridpoint Statistical Interpolation (GSI) three-dimensional variational (3DVAR) data assimilation system. This newly developed algorithm allows, in a one-step procedure, the analysis of 3-D mass concentration of 14 aerosol variables from the Goddard Chemistry Aerosol Radiation and Transport (GOCART) module. The Community Radiative Transfer Model (CRTM) was extended to calculate AOD using GOCART aerosol variables as input. Both the AOD forward model and corresponding Jacobian model were developed within the CRTM and used in the 3DVAR minimization algorithm to compute the AOD cost function and its gradient with respect to 3-D aerosol mass concentration. The impact of MODIS AOD data assimilation was demonstrated by application to a dust storm from 17 to 24 March 2010 over East Asia. The aerosol analyses initialized Weather Research and Forecasting/Chemistry (WRF/Chem) model forecasts. Results indicate that assimilating MODIS AOD substantially improves aerosol analyses and subsequent forecasts when compared to MODIS AOD, independent AOD observations from the Aerosol Robotic Network (AERONET) and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) instrument, and surface PM10 (particulate matter with diameters less than 10 μm) observations. The newly developed AOD data assimilation system can serve as a tool to improve simulations of dust storms and general air quality analyses and forecasts.

  1. Using High-Resolution Satellite Aerosol Optical Depth To Estimate Daily PM2.5 Geographical Distribution in Mexico City.

    Science.gov (United States)

    Just, Allan C; Wright, Robert O; Schwartz, Joel; Coull, Brent A; Baccarelli, Andrea A; Tellez-Rojo, Martha María; Moody, Emily; Wang, Yujie; Lyapustin, Alexei; Kloog, Itai

    2015-07-21

    Recent advances in estimating fine particle (PM2.5) ambient concentrations use daily satellite measurements of aerosol optical depth (AOD) for spatially and temporally resolved exposure estimates. Mexico City is a dense megacity that differs from other previously modeled regions in several ways: it has bright land surfaces, a distinctive climatological cycle, and an elevated semi-enclosed air basin with a unique planetary boundary layer dynamic. We extend our previous satellite methodology to the Mexico City area, a region with higher PM2.5 than most U.S. and European urban areas. Using a novel 1 km resolution AOD product from the MODIS instrument, we constructed daily predictions across the greater Mexico City area for 2004-2014. We calibrated the association of AOD to PM2.5 daily using municipal ground monitors, land use, and meteorological features. Predictions used spatial and temporal smoothing to estimate AOD when satellite data were missing. Our model performed well, resulting in an out-of-sample cross-validation R(2) of 0.724. Cross-validated root-mean-squared prediction error (RMSPE) of the model was 5.55 μg/m(3). This novel model reconstructs long- and short-term spatially resolved exposure to PM2.5 for epidemiological studies in Mexico City.

  2. Major Optical Depth Perturbations to the Stratosphere from Volcanic Eruptions: Stellar-Extinction Period, 1961-1978

    Science.gov (United States)

    Stothers, Richard B.; Hansen, James E. (Technical Monitor)

    2001-01-01

    A revised chronology of stratospheric aerosol extinction due to volcanic eruptions has been assembled for the period 1961-1978, which immediately precedes the era of dedicated satellite measurements. On the whole, the most accurate data consist of published observations of stellar extinction, supplemented in part by other kinds of observational data. The period covered encompasses the important eruptions of Agung (1963) and Fuego (1974), whose dust veils are discussed with respect to their transport, decay, and total mass. The effective (area-weighted mean) radii of the aerosols for both eruptions are found to be 0.3-0.4 microns. It is confirmed that, among known tropical eruptions, Agung's dust was unique for a low-latitude eruption in remaining almost entirely confined to the hemisphere of its production. A new table of homogeneous visual optical depth perturbations, listed by year and by hemisphere, is provided for the whole period 1881-1978, including the pyrheliometric period before 1961 that was investigated previously.

  3. Towards identification of relevant variables in the observed aerosol optical depth bias between MODIS and AERONET observations

    Science.gov (United States)

    Malakar, N. K.; Lary, D. J.; Gencaga, D.; Albayrak, A.; Wei, J.

    2013-08-01

    Measurements made by satellite remote sensing, Moderate Resolution Imaging Spectroradiometer (MODIS), and globally distributed Aerosol Robotic Network (AERONET) are compared. Comparison of the two datasets measurements for aerosol optical depth values show that there are biases between the two data products. In this paper, we present a general framework towards identifying relevant set of variables responsible for the observed bias. We present a general framework to identify the possible factors influencing the bias, which might be associated with the measurement conditions such as the solar and sensor zenith angles, the solar and sensor azimuth, scattering angles, and surface reflectivity at the various measured wavelengths, etc. Specifically, we performed analysis for remote sensing Aqua-Land data set, and used machine learning technique, neural network in this case, to perform multivariate regression between the ground-truth and the training data sets. Finally, we used mutual information between the observed and the predicted values as the measure of similarity to identify the most relevant set of variables. The search is brute force method as we have to consider all possible combinations. The computations involves a huge number crunching exercise, and we implemented it by writing a job-parallel program.

  4. Chemical data assimilation of geostationary aerosol optical depth and PM surface observations on regional aerosol modeling over the Korean Peninsula during KORUS-AQ campaign

    Science.gov (United States)

    Jung, J.; Choi, Y.; Souri, A.; Jeon, W.

    2017-12-01

    Particle matter(PM) has played a significantly deleterious role in affecting human health and climate. Recently, continuous high concentrations of PM in Korea attracted public attention to this critical issue, and the Korea-United States Air Quality Study(KORUS-AQ) campaign in 2016 was conducted to investigate the causes. For this study, we adjusted the initial conditions in the chemical transport model(CTM) to improve its performance over Korean Peninsula during KORUS-AQ period, using the campaign data to evaluate our model performance. We used the Optimal Interpolation(OI) approach and used hourly surface air quality measurement data from the Air Quality Monitoring Station(AQMS) by NIER and the aerosol optical depth(AOD) measured by a GOCI sensor from the geostationary orbit onboard the Communication Ocean and Meteorological Satellite(COMS). The AOD at 550nm has a 6km spatial resolution and broad coverage over East Asia. After assimilating the surface air quality observation data, the model accuracy significantly improved compared to base model result (without assimilation). It reported very high correlation value (0.98) and considerably decreased mean bias. Especially, it well captured some high peaks which was underpredicted by the base model. To assimilate satellite data, we applied AOD scaling factors to quantify each specie's contribution to total PM concentration and find-mode fraction(FMF) to define vertical distribution. Finally, the improvement showed fairly good agreement.

  5. The impact of aerosol vertical distribution on aerosol optical depth retrieval using CALIPSO and MODIS data : Case study over dust and smoke regions

    NARCIS (Netherlands)

    Wu, Y.; de Graaf, M.; Menenti, M.

    2017-01-01

    Global quantitative aerosol information has been derived from MODerate Resolution Imaging SpectroRadiometer (MODIS) observations for decades since early 2000 and widely used for air quality and climate change research. However, the operational MODIS Aerosol Optical Depth (AOD) products Collection

  6. Comparison of Coincident Multiangle Imaging Spectroradiometer and Moderate Resolution Imaging Spectroradiometer Aerosol Optical Depths over Land and Ocean Scenes Containing Aerosol Robotic Network Sites

    Science.gov (United States)

    Abdou, Wedad A.; Diner, David J.; Martonchik, John V.; Bruegge, Carol J.; Kahn, Ralph A.; Gaitley, Barbara J.; Crean, Kathleen A.; Remer, Lorraine A.; Holben, Brent

    2005-01-01

    The Multiangle Imaging Spectroradiometer (MISR) and the Moderate Resolution Imaging Spectroradiometer (MODIS), launched on 18 December 1999 aboard the Terra spacecraft, are making global observations of top-of-atmosphere (TOA) radiances. Aerosol optical depths and particle properties are independently retrieved from these radiances using methodologies and algorithms that make use of the instruments corresponding designs. This paper compares instantaneous optical depths retrieved from simultaneous and collocated radiances measured by the two instruments at locations containing sites within the Aerosol Robotic Network (AERONET). A set of 318 MISR and MODIS images, obtained during the months of March, June, and September 2002 at 62 AERONET sites, were used in this study. The results show that over land, MODIS aerosol optical depths at 470 and 660 nm are larger than those retrieved from MISR by about 35% and 10% on average, respectively, when all land surface types are included in the regression. The differences decrease when coastal and desert areas are excluded. For optical depths retrieved over ocean, MISR is on average about 0.1 and 0.05 higher than MODIS in the 470 and 660 nm bands, respectively. Part of this difference is due to radiometric calibration and is reduced to about 0.01 and 0.03 when recently derived band-to-band adjustments in the MISR radiometry are incorporated. Comparisons with AERONET data show similar patterns.

  7. Beveled fiber-optic probe couples a ball lens for improving depth-resolved fluorescence measurements of layered tissue: Monte Carlo simulations

    International Nuclear Information System (INIS)

    Jaillon, Franck; Zheng Wei; Huang Zhiwei

    2008-01-01

    In this study, we evaluate the feasibility of designing a beveled fiber-optic probe coupled with a ball lens for improving depth-resolved fluorescence measurements of epithelial tissue using Monte Carlo (MC) simulations. The results show that by using the probe configuration with a beveled tip collection fiber and a flat tip excitation fiber associated with a ball lens, discrimination of fluorescence signals generated in different tissue depths is achievable. In comparison with a flat-tip collection fiber, the use of a large bevel angled collection fiber enables a better differentiation between the shallow and deep tissue layers by changing the excitation-collection fiber separations. This work suggests that the beveled fiber-optic probe coupled with a ball lens has the potential to facilitate depth-resolved fluorescence measurements of epithelial tissues

  8. Correction of fluorescence for depth-specific optical and vascular properties using reflectance and differential path-length spectroscopy during PDT

    Science.gov (United States)

    van Zaane, F.; Middelburg, T. A.; de Bruijn, H. S.; van der Ploeg-van den Heuvel, A.; de Haas, E. R. M.; Sterenborg, H. J. C. M.; Neumann, H. A. M.; Robinson, D. J.

    2009-06-01

    Introduction: The rate of PpIX fluorescence photobleaching is routinely used as a dose metric for ALA-PDT. Diffuse reflection spectroscopy is often used to account for variations in tissue optical properties at the photosensitizer excitation and emission bands. It can be used to quantify changes in vascular parameters, such as blood volume fraction and saturation, and can aid understanding of tissue response to PDT. The volume and(/or) depth over which these signals are acquired are critical. The aim of this study is to use quantitative reflectance spectroscopy (DPS) to correct fluorescence for changes in tissue optical properties and monitor PDT. Materials & Methods: ALA was topically applied to hairless mice skin and the incubated spot was treated with PDT according to fractionated illumination schemes. DPS measurements of vascular parameters and optical properties were performed directly before and after illumination. Both the differential signal, delivery-and-collection-fiber signal and the collection fiber signal, which all probe different measurement volumes, are analyzed. Results & Conclusions: Analysis of DPS measurements shows that at the depth where most fluorescence originates, there is almost no blood present. During PDT vascular parameters at this depth stay constant. In more oxygenated layers of the tissue, the optical properties do change during PDT, suggesting that only a small part of PpIX fluorescence originates from the interesting depths where vascular response occurs. Correcting fluorescence emission spectra for optical changes at specific depths and not for the total of changes in a larger volume, as is usually done now, can improve PpIX photobleaching based treatment monitoring.

  9. Estimation of the Cloud condensation nuclei concentration(CCN) and aerosol optical depth(AOD) relation in the Arctic region

    Science.gov (United States)

    Jung, C. H.; Yoon, Y. J.; Ahn, S. H.; Kang, H. J.; Gim, Y. T.; Lee, B. Y.

    2017-12-01

    Information of the spatial and temporal variations of cloud condensation nuclei (CCN) concentrations is important in estimating aerosol indirect effects. Generally, CCN aerosol is difficult to estimate using remote sensing methods. Although there are many CCN measurements data, extensive measurements of CCN are not feasible because of the complex nature of the operation and high cost, especially in the Arctic region. Thus, there have been many attempts to estimate CCN concentrations from more easily obtainable parameters such as aerosol optical depth (AOD) because AOD has the advantage of being readily observed by remote sensing from space by several sensors. For example, some form of correlation was derived between AOD and the number concentration of cloud condensation nuclei (CCN) through the comparison results from AERONET network and CCN measurements (Andreae 2009). In this study, a parameterization of CCN concentration as a function of AOD at 500 nm is given in the Arctic region. CCN data was collected during the period 2007-2013 at the Zeppelin observatory (78.91° N, 11.89° E, 474 masl). The AERONET network and MODIS AOD data are compared with ground measured CCN measurement and the relations between AOD and CCN are parameterized. The seasonal characteristics as well as long term trends are also considered. Through the measurement, CCN concentration remains high during spring because of aerosol transportation from the mid-latitudes, known as Arctic Haze. Lowest CCN number densities were observed during Arctic autumn and early winter when aerosol long-range transport into the Arctic is not effective and new particle formation ceases. The results show that the relation between AOD and CCN shows a different parameter depending on the seasonal aerosol and CCN characteristics. This seasonal different CCN-AOD relation can be interpreted as many physico-chemical aerosol properties including aerosol size distribution, composition. ReferenceAndreae, M. O. (2009

  10. Comparison of aerosol optical depth from satellite (MODIS), sun photometer and broadband pyrheliometer ground-based observations in Cuba

    Science.gov (United States)

    Antuña-Marrero, Juan Carlos; Cachorro Revilla, Victoria; García Parrado, Frank; de Frutos Baraja, Ángel; Rodríguez Vega, Albeth; Mateos, David; Estevan Arredondo, René; Toledano, Carlos

    2018-04-01

    In the present study, we report the first comparison between the aerosol optical depth (AOD) and Ångström exponent (AE) of the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on the Terra (AODt) and Aqua (AODa) satellites and those measured using a sun photometer (AODSP) at Camagüey, Cuba, for the period 2008 to 2014. The comparison of Terra and Aqua data includes AOD derived with both deep blue (DB) and dark target (DT) algorithms from MODIS Collection 6. Combined Terra and Aqua (AODta) data were also considered. Assuming an interval of ±30 min around the overpass time and an area of 25 km around the sun photometer site, two coincidence criteria were considered: individual pairs of observations and both spatial and temporal mean values, which we call collocated daily means. The usual statistics (root mean square error, RMSE; mean absolute error, MAE; median bias, BIAS), together with linear regression analysis, are used for this comparison. Results show very similar values for both coincidence criteria: the DT algorithm generally displays better statistics and higher homogeneity than the DB algorithm in the behaviour of AODt, AODa, AODta compared to AODSP. For collocated daily means, (a) RMSEs of 0.060 and 0.062 were obtained for Terra and Aqua with the DT algorithm and 0.084 and 0.065 for the DB algorithm, (b) MAE follows the same patterns, (c) BIAS for both Terra and Aqua presents positive and negative values but its absolute values are lower for the DT algorithm; (d) combined AODta data also give lower values of these three statistical indicators for the DT algorithm; (e) both algorithms present good correlations for comparing AODt, AODa, AODta vs. AODSP, with a slight overestimation of satellite data compared to AODSP, (f). The DT algorithm yields better figures with slopes of 0.96 (Terra), 0.96 (Aqua) and 0.96 (Terra + Aqua) compared to the DB algorithm (1.07, 0.90, 0.99), which displays greater variability. Multi-annual monthly means of

  11. The Two-Column Aerosol Project: Phase I - Overview and Impact of Elevated Aerosol Layers on Aerosol Optical Depth

    Energy Technology Data Exchange (ETDEWEB)

    Berg, Larry K.; Fast, Jerome D.; Barnard, James C.; Burton, Sharon; Cairns, Brian; Chand, Duli; Comstock, Jennifer M.; Dunagan, Stephen; Ferrare, Richard A.; Flynn, Connor J.; Hair, John; Hostetler, Chris A.; Hubbe, John M.; Jefferson, Anne; Johnson, Roy; Kassianov, Evgueni I.; Kluzek, Celine D.; Kollias, Pavlos; Lamer, Katia; Lantz, K.; Mei, Fan; Miller, Mark A.; Michalsky, Joseph; Ortega, Ivan; Pekour, Mikhail S.; Rogers, Ray; Russell, P.; Redemann, Jens; Sedlacek, Art; Segal Rozenhaimer, Michal; Schmid, Beat; Shilling, John E.; Shinozuka, Yohei; Springston, Stephen R.; Tomlinson, Jason M.; Tyrrell, Megan; Wilson, Jacqueline; Volkamer, Rainer M.; Zelenyuk, Alla; Berkowitz, Carl M.

    2016-01-08

    The Two-Column Aerosol Project (TCAP), which was conducted from June 2012 through June 2013, was a unique field study that was designed to provide a comprehensive data set that can be used to investigate a number of important climate science questions, including those related to aerosol mixing state and aerosol radiative forcing. The study was designed to sample the atmosphere at a number of altitudes, from near the surface to as high as 8 km, within two atmospheric columns; one located near the coast of North America (over Cape Cod, MA) and a second over the Atlantic Ocean several hundred kilometers from the coast. TCAP included the yearlong deployment of the U.S. Department of Energy’s (DOE) Atmospheric Radiation Measurement (ARM) Mobile Facility (AMF) that was located at the base of the Cape Cod column, as well as summer and winter aircraft intensive observation periods of the ARM Aerial Facility. One important finding from TCAP is the relatively common occurrence (on four of six nearly cloud-free flights) of elevated aerosol layers in both the Cape Cod and maritime columns that were detected using the nadir pointing second-generation NASA high-spectral resolution lidar (HSRL-2). These layers contributed up to 60% of the total aerosol optical depth (AOD) observed in the column. Many of these layers were also intercepted by the aircraft configured for in situ sampling, and the aerosol in the layers was found to have increased amounts of biomass burning aerosol and nitrate compared to the aerosol found near the surface.

  12. The comparison of MODIS-Aqua (C5 and CALIOP (V2 & V3 aerosol optical depth

    Directory of Open Access Journals (Sweden)

    J. Redemann

    2012-03-01

    Full Text Available We assess the consistency between instantaneously collocated level-2 aerosol optical depth (AOD retrievals from MODIS-Aqua (C5 and CALIOP (Version 2 & 3, comparing the standard MODIS AOD (MYD04_L2 data to the AOD calculated from CALIOP aerosol extinction profiles for both the previous release (V2 and the latest release (V3 of CALIOP data. Based on data collected in January 2007, we investigate the most useful criteria for screening the MODIS and CALIOP retrievals to achieve the best agreement between the two data sets. Applying these criteria to eight months of data (Jan, Apr, Jul, Oct 2007 and 2009, we find an order of magnitude increase for the CALIOP V3 data density (by comparison to V2, that is generally accompanied by equal or better agreement with MODIS AOD. Differences in global, monthly mean, over-ocean AOD (532 nm between CALIOP and MODIS range between 0.03 and 0.04 for CALIOP V3, with CALIOP generally biased low, when all available data from both sensors are considered. Root-mean-squares (RMS differences in instantaneously collocated AOD retrievals by the two instruments are reduced from values ranging between 0.14 and 0.19 using the unscreened V3 data to values ranging from 0.09 to 0.1 for the screened data. A restriction to scenes with cloud fractions less than 1% (as defined in the MODIS aerosol retrievals generally results in improved correlation (R2>0.5, except for the month of July when correlations remain relatively lower. Regional assessments show hot spots in disagreement between the two sensors in Asian outflow during April and off the coast of South Africa in July.

  13. A Simplified Method to Measure Choroidal Thickness Using Adaptive Compensation in Enhanced Depth Imaging Optical Coherence Tomography

    Science.gov (United States)

    Gupta, Preeti; Sidhartha, Elizabeth; Girard, Michael J. A.; Mari, Jean Martial; Wong, Tien-Yin; Cheng, Ching-Yu

    2014-01-01

    Purpose To evaluate a simplified method to measure choroidal thickness (CT) using commercially available enhanced depth imaging (EDI) spectral domain optical coherence tomography (SD-OCT). Methods We measured CT in 31 subjects without ocular diseases using Spectralis EDI SD-OCT. The choroid-scleral interface of the acquired images was first enhanced using a post-processing compensation algorithm. The enhanced images were then analysed using Photoshop. Two graders independently graded the images to assess inter-grader reliability. One grader re-graded the images after 2 weeks to determine intra-grader reliability. Statistical analysis was performed using intra-class correlation coefficient (ICC) and Bland-Altman plot analyses. Results Using adaptive compensation both the intra-grader reliability (ICC: 0.95 to 0.97) and inter-grader reliability (ICC: 0.93 to 0.97) were perfect for all five locations of CT. However, with the conventional technique of manual CT measurements using built-in callipers provided with the Heidelberg explorer software, the intra- (ICC: 0.87 to 0.94) and inter-grader reliability (ICC: 0.90 to 0.93) for all the measured locations is lower. Using adaptive compensation, the mean differences (95% limits of agreement) for intra- and inter-grader sub-foveal CT measurements were −1.3 (−3.33 to 30.8) µm and −1.2 (−36.6 to 34.2) µm, respectively. Conclusions The measurement of CT obtained from EDI SD-OCT using our simplified method was highly reliable and efficient. Our method is an easy and practical approach to improve the quality of choroidal images and the precision of CT measurement. PMID:24797674

  14. A simplified method to measure choroidal thickness using adaptive compensation in enhanced depth imaging optical coherence tomography.

    Directory of Open Access Journals (Sweden)

    Preeti Gupta

    Full Text Available PURPOSE: To evaluate a simplified method to measure choroidal thickness (CT using commercially available enhanced depth imaging (EDI spectral domain optical coherence tomography (SD-OCT. METHODS: We measured CT in 31 subjects without ocular diseases using Spectralis EDI SD-OCT. The choroid-scleral interface of the acquired images was first enhanced using a post-processing compensation algorithm. The enhanced images were then analysed using Photoshop. Two graders independently graded the images to assess inter-grader reliability. One grader re-graded the images after 2 weeks to determine intra-grader reliability. Statistical analysis was performed using intra-class correlation coefficient (ICC and Bland-Altman plot analyses. RESULTS: Using adaptive compensation both the intra-grader reliability (ICC: 0.95 to 0.97 and inter-grader reliability (ICC: 0.93 to 0.97 were perfect for all five locations of CT. However, with the conventional technique of manual CT measurements using built-in callipers provided with the Heidelberg explorer software, the intra- (ICC: 0.87 to 0.94 and inter-grader reliability (ICC: 0.90 to 0.93 for all the measured locations is lower. Using adaptive compensation, the mean differences (95% limits of agreement for intra- and inter-grader sub-foveal CT measurements were -1.3 (-3.33 to 30.8 µm and -1.2 (-36.6 to 34.2 µm, respectively. CONCLUSIONS: The measurement of CT obtained from EDI SD-OCT using our simplified method was highly reliable and efficient. Our method is an easy and practical approach to improve the quality of choroidal images and the precision of CT measurement.

  15. Assessment of nocturnal aerosol optical depth from lunar photometry at the Izaña high mountain observatory

    Directory of Open Access Journals (Sweden)

    Á. Barreto

    2017-08-01

    Full Text Available This work is a first approach to correct the systematic errors observed in the aerosol optical depth (AOD retrieved at nighttime using lunar photometry and calibration techniques dependent on the lunar irradiance model. To this end, nocturnal AOD measurements were performed in 2014 using the CE318-T master Sun–sky–lunar photometer (lunar Langley calibrated at the Izaña high mountain observatory. This information has been restricted to 59 nights characterized as clean and stable according to lidar vertical profiles. A phase angle dependence as well as an asymmetry within the Moon's cycle of the Robotic Lunar Observatory (ROLO model could be deduced from the comparison in this 59-night period of the CE318-T calibration performed by means of the lunar Langley calibration and the calibration performed every single night by means of the common Langley technique. Nocturnal AOD has also been compared in the same period with a reference AOD based on daylight AOD extracted from the AErosol RObotic NETwork (AERONET at the same station. Considering stable conditions, the difference ΔAODfit, between AOD from lunar observations and the linearly interpolated AOD (the reference from daylight data, has been calculated. The results show that ΔAODfit values are strongly affected by the Moon phase and zenith angles. This dependency has been parameterized using an empirical model with two independent variables (Moon phase and zenith angles in order to correct the AOD for these residual dependencies. The correction of this parameterized dependency has been checked at four stations with quite different environmental conditions (Izaña, Lille, Carpentras and Dakar showing a significant reduction of the AOD dependence on phase and zenith angles and an improved agreement with daylight reference data. After the correction, absolute AOD differences for day–night–day clean and stable transitions remain below 0.01 for all wavelengths.

  16. Large-scale connection between aerosol optical depth and summer monsoon circulation, and precipitation over northeast Asia

    Science.gov (United States)

    Kim, Sang-Woo; Yoon, Soon-Chang; Choi, Suk-Jin; Choi, In-Jin

    2010-05-01

    We investigated the large-scale connection between columnar aerosol loads and summer monsoon circulation, and also the precipitation over northeast Asia using aerosol optical depth (AOD) data obtained from the 8-year MODIS, AERONET Sun/sky radiometer, and precipitation data acquired under the Global Precipitation Climatology Project (GPCP). These high-quality data revealed the large-scale link between AOD and summer monsoon circulation, precipitation in July over northeast Asian countries, and their distinct spatial and annual variabilities. Compared to the mean AOD for the entire period of 2001-2008, the increase of almost 40-50% in the AOD value in July 2005 and July 2007 was found over the downwind regions of China (Yellow Sea, Korean peninsula, and East Sea), with negative precipitation anomalies. This can be attributable to the strong westerly confluent flows, between cyclone flows by continental thermal low centered over the northern China and anti-cyclonic flows by the western North Pacific High, which transport anthropogenic pollution aerosols emitted from east China to aforementioned downwind high AOD regions along the rim of the Pacific marine airmass. In July 2002, however, the easterly flows transported anthropogenic aerosols from east China to the southwestern part of China in July 2002. As a result, the AOD off the coast of China was dramatically reduced in spite of decreasing rainfall. From the calculation of the cross-correlation coefficient between MODIS-derived AOD anomalies and GPCP precipitation anomalies over the period 2001-2008, we found negative correlations over the areas encompassed by 105-115E and 30-35N and by 120-140E and 35-40N (Yellow Sea, Korean peninsula, and East Sea). This suggests that aerosol loads over these regions are easily influenced by the Asian monsoon flow system and associated precipitation.

  17. Interacting Effects of Leaf Water Potential and Biomass on Vegetation Optical Depth: Effects of LWP and Biomass on VOD

    Energy Technology Data Exchange (ETDEWEB)

    Momen, Mostafa [Department of Earth System Science, Stanford University, Stanford CA USA; Wood, Jeffrey D. [School of Natural Resources, University of Missouri, Columbia MO USA; Novick, Kimberly A. [School of Public and Environmental Affairs, Indiana University-Bloomington, Bloomington IN USA; Pangle, Robert [Department of Biology, University of New Mexico, Albuquerque NM USA; Pockman, William T. [Department of Biology, University of New Mexico, Albuquerque NM USA; McDowell, Nate G. [Pacific Northwest National Laboratory, Richland WA USA; Konings, Alexandra G. [Department of Earth System Science, Stanford University, Stanford CA USA

    2017-11-01

    Remotely sensed microwave observations of vegetation optical depth (VOD) have been widely used for examining vegetation responses to climate. Nevertheless, the relative impacts of phenological changes in leaf biomass and water stress on VOD have not been explicitly disentangled. In particular, determining whether leaf water potential (ψL) affects VOD may allow these data sets as a constraint for plant hydraulic models. Here we test the sensitivity of VOD to variations in ψL and present a conceptual framework that relates VOD to ψL and total biomass including leaves, whose dynamics are measured through leaf area index, and woody components. We used measurements of ψL from three sites across the US—a mixed deciduous forests in Indiana and Missouri and a piñon-juniper woodland in New Mexico—to validate the conceptual model. The temporal dynamics of X-band VOD were similar to those of the VOD signal estimated from the new conceptual model with observed ψL (R2 = 0.6–0.8). At the global scale, accounting for a combination of biomass and estimated ψL (based on satellite surface soil moisture data) increased correlations with VOD by ~ 15% and 30% compared to biomass and water potential, respectively. In wetter regions with denser and taller canopy heights, VOD has a higher correlation with leaf area index than with water stress and vice versa in drier regions. Our results demonstrate that variations in both phenology and ψL must be considered to accurately interpret the dynamics of VOD observations for ecological applications.

  18. Spatial and temporal interpolation of satellite-based aerosol optical depth measurements over North America using B-splines

    Science.gov (United States)

    Pfister, Nicolas; O'Neill, Norman T.; Aube, Martin; Nguyen, Minh-Nghia; Bechamp-Laganiere, Xavier; Besnier, Albert; Corriveau, Louis; Gasse, Geremie; Levert, Etienne; Plante, Danick

    2005-08-01

    Satellite-based measurements of aerosol optical depth (AOD) over land are obtained from an inversion procedure applied to dense dark vegetation pixels of remotely sensed images. The limited number of pixels over which the inversion procedure can be applied leaves many areas with little or no AOD data. Moreover, satellite coverage by sensors such as MODIS yields only daily images of a given region with four sequential overpasses required to straddle mid-latitude North America. Ground based AOD data from AERONET sun photometers are available on a more continuous basis but only at approximately fifty locations throughout North America. The object of this work is to produce a complete and coherent mapping of AOD over North America with a spatial resolution of 0.1 degree and a frequency of three hours by interpolating MODIS satellite-based data together with available AERONET ground based measurements. Before being interpolated, the MODIS AOD data extracted from different passes are synchronized to the mapping time using analyzed wind fields from the Global Multiscale Model (Meteorological Service of Canada). This approach amounts to a trajectory type of simplified atmospheric dynamics correction method. The spatial interpolation is performed using a weighted least squares method applied to bicubic B-spline functions defined on a rectangular grid. The least squares method enables one to weight the data accordingly to the measurement errors while the B-splines properties of local support and C2 continuity offer a good approximation of AOD behaviour viewed as a function of time and space.

  19. Anatomical relationship between the optic nerve and posterior paranasal sinuses on ostiomeatal unit CT

    International Nuclear Information System (INIS)

    Cho, June Il; Kim, Hong In; Seol, Hae Young; Lee, Nam Joon; Kim, Jung Hyuk; Cha, In Ho

    1997-01-01

    To determine the anatomic variations that can lead to optic nerve damage during the sugical treatment of posterior paranasal sinus lesions two hundred optic nerves of 100 persons were examined using ostiomeatal unit CT(OMU CT). The anatomical features of this nerve and posterior paranasal sinuses were classified into four types:the optic nerve adjacent to the sphenoid sinus without indentation of the sinus wall (type 1);the optic nerve adjacent to the sphenoid sinus, causing indentation of the sinus wall (type 2);the optic nerve passing through the sphenoid sinus (type 3);and the optic nerve adjacent to the sphenoid sinus and posterior ethmoid sinus (type 4). Bony dehiscence around the optic nerve and pneumatization of the anterior clinoid process were also evaluated. The anatomical classification of the optic nerve and posterior paranasal sinuses was as follows:type 1, 1326(66%); type 2, 60(30%); type 3, 6(3%), and type 4, 2(1%). Bony dehiscence around the optic nerve had developed in 58 cases (29%) and pneumatization of the anterior clinoid process in 13(6.5%). These conditions were most common in type 3 optic nerve, and second most common in type 2. The 2 and 3 optic nerves, bony dehiscence around the optic nerve and pneumatization of the anterior clinoid process are the anatomic variations that can lead to optic nerve damage during the surgical treatment of posterior paranasal sinus lesions. To prevent optic nerve damage, these factors should be carefully evaluated by OMU CT

  20. Spectral Discrimination of Fine and Coarse Mode Aerosol Optical Depth from AERONET Direct Sun Data of Singapore and South-East Asia

    Science.gov (United States)

    Salinas Cortijo, S.; Chew, B.; Liew, S.

    2009-12-01

    Aerosol optical depth combined with the Angstrom exponent and its derivative, are often used as a qualitative indicator of aerosol particle size, with Angstrom exp. values greater than 2 indicating small (fine mode) particles associated with urban pollution and bio-mass burning. Around this region, forest fires are a regular occurrence during the dry season, specially near the large land masses of Sumatra and Borneo. The practice of clearing land by burning the primary and sometimes secondary forest, results in a smog-like haze covering large areas of regional cities such as cities Singapore, Kuala Lumpur and sometimes the south of Thailand, often reducing visibility and increasing health problems for the local population. In Singapore, the sources of aerosols are mostly from fossil fuel burning (energy stations, incinerators, urban transport etc.) and from the industrial and urban areas. The proximity to the sea adds a possible oceanic source. However, as stated above and depending on the time of the year, there can be a strong bio-mass component coming from forest fires from various regions of the neighboring countries. Bio-mass related aerosol particles are typically characterized by showing a large optical depth and small, sub-micron particle size distributions. In this work, we analyze three years of direct Sun measurements performed with a multi-channel Cimel Sun-Photometer (part of the AERONET network) located at our site. In order to identify bio-mass burning events in this region, we perform a spectral discrimination between coarse and fine mode optical depth; subsequently, the fine mode parameters such as optical depth, optical ratio and fine mode Angstrom exponents (and its derivative) are used to identify possible bio-mass related events within the data set.

  1. Combined in-depth, 3D, en face imaging of the optic disc, optic disc pits and optic disc pit maculopathy using swept-source megahertz OCT at 1050 nm.

    Science.gov (United States)

    Maertz, Josef; Kolb, Jan Philip; Klein, Thomas; Mohler, Kathrin J; Eibl, Matthias; Wieser, Wolfgang; Huber, Robert; Priglinger, Siegfried; Wolf, Armin

    2018-02-01

    To demonstrate papillary imaging of eyes with optic disc pits (ODP) or optic disc pit associated maculopathy (ODP-M) with ultrahigh-speed swept-source optical coherence tomography (SS-OCT) at 1.68 million A-scans/s. To generate 3D-renderings of the papillary area with 3D volume-reconstructions of the ODP and highly resolved en face images from a single densely-sampled megahertz-OCT (MHz-OCT) dataset for investigation of ODP-characteristics. A 1.68 MHz-prototype SS-MHz-OCT system at 1050 nm based on a Fourier-domain mode-locked laser was employed to acquire high-definition, 3D datasets with a dense sampling of 1600 × 1600 A-scans over a 45° field of view. Six eyes with ODPs, and two further eyes with glaucomatous alteration or without ocular pathology are presented. 3D-rendering of the deep papillary structures, virtual 3D-reconstructions of the ODPs and depth resolved isotropic en face images were generated using semiautomatic segmentation. 3D-rendering and en face imaging of the optic disc, ODPs and ODP associated pathologies showed a broad spectrum regarding ODP characteristics. Between individuals the shape of the ODP and the appending pathologies varied considerably. MHz-OCT en face imaging generates distinct top-view images of ODPs and ODP-M. MHz-OCT generates high resolution images of retinal pathologies associated with ODP-M and allows visualizing ODPs with depths of up to 2.7 mm. Different patterns of ODPs can be visualized in patients for the first time using 3D-reconstructions and co-registered high-definition en face images extracted from a single densely sampled 1050 nm megahertz-OCT (MHz-OCT) dataset. As the immediate vicinity to the SAS and the site of intrapapillary proliferation is located at the bottom of the ODP it is crucial to image the complete structure and the whole depth of ODPs. Especially in very deep pits, where non-swept-source OCT fails to reach the bottom, conventional swept-source devices and the MHz-OCT alike are feasible

  2. Refined Use of Satellite Aerosol Optical Depth Snapshots to Constrain Biomass Burning Emissions in the GOCART Model

    Science.gov (United States)

    Petrenko, Mariya; Kahn, Ralph; Chin, Mian; Limbacher, James

    2017-10-01

    Simulations of biomass burning (BB) emissions in global chemistry and aerosol transport models depend on external inventories, which provide location and strength for BB aerosol sources. Our previous work shows that to first order, satellite snapshots of aerosol optical depth (AOD) near the emitted smoke plume can be used to constrain model-simulated AOD, and effectively, the smoke source strength. We now refine the satellite-snapshot method and investigate where applying simple multiplicative emission adjustment factors alone to the widely used Global Fire Emission Database version 3 emission inventory can achieve regional-scale consistency between Moderate Resolution Imaging Spectroradiometer (MODIS) AOD snapshots and the Goddard Chemistry Aerosol Radiation and Transport model. The model and satellite AOD are compared globally, over a set of BB cases observed by the MODIS instrument during the 2004, and 2006-2008 biomass burning seasons. Regional discrepancies between the model and satellite are diverse around the globe yet quite consistent within most ecosystems. We refine our approach to address physically based limitations of our earlier work (1) by expanding the number of fire cases from 124 to almost 900, (2) by using scaled reanalysis-model simulations to fill missing AOD retrievals in the MODIS observations, (3) by distinguishing the BB components of the total aerosol load from background aerosol in the near-source regions, and (4) by including emissions from fires too small to be identified explicitly in the satellite observations. The small-fire emission adjustment shows the complimentary nature of correcting for source strength and adding geographically distinct missing sources. Our analysis indicates that the method works best for fire cases where the BB fraction of total AOD is high, primarily evergreen or deciduous forests. In heavily polluted or agricultural burning regions, where smoke and background AOD values tend to be comparable, this approach

  3. Integration of satellite-induced fluorescence and vegetation optical depth to improve the retrieval of land evaporation

    Science.gov (United States)

    Pagán, B. R.; Martens, B.; Maes, W. H.; Miralles, D. G.

    2017-12-01

    Global satellite-based data sets of land evaporation overcome limitations in coverage of in situ measurements while retaining some observational nature. Although their potential for real world applications are promising, their value during dry conditions is still poorly understood. Most evaporation retrieval algorithms are not directly sensitive to soil moisture. An exception is the Global Land Evaporation Amsterdam Model (GLEAM), which uses satellite surface soil moisture and precipitation to account for land water availability. The existing methodology may greatly benefit from the optimal integration of novel observations of the land surface. Microwave vegetation optical depth (VOD) and near-infrared solar-induced fluorescence (SIF) are expected to reflect different aspects of evaporative stress. While the former is considered to be a proxy of vegetation water content, the latter is indicative of the activity of photosynthetic machinery. As stomata regulate both photosynthesis and transpiration, we expect a relationship between SIF and transpiration. An important motivation to incorporate observations in land evaporation calculations is that plant transpiration - usually the largest component of the flux - is extremely challenging to model due to species-dependent responses to drought. Here we present an innovative integration of VOD and SIF into the GLEAM evaporative stress function. VOD is utilized as a measurement of isohydricity to improve the representation of species specific drought responses. SIF is used for transpiration modelling, a novel application, and standardized by incoming solar radiation to better account for radiation-limited periods. Results are validated with global FLUXNET and International Soil Moisture Network data and demonstrate that the incorporation of VOD and SIF can yield accurate estimates of transpiration over large-scales, which are essential to further understand ecosystem-atmosphere feedbacks and the response of terrestrial

  4. Aerosol data assimilation in the chemical transport model MOCAGE during the TRAQA/ChArMEx campaign: aerosol optical depth

    Science.gov (United States)

    Sič, Bojan; El Amraoui, Laaziz; Piacentini, Andrea; Marécal, Virginie; Emili, Emanuele; Cariolle, Daniel; Prather, Michael; Attié, Jean-Luc

    2016-11-01

    In this study, we describe the development of the aerosol optical depth (AOD) assimilation module in the chemistry transport model (CTM) MOCAGE (Modèle de Chimie Atmosphérique à Grande Echelle). Our goal is to assimilate the spatially averaged 2-D column AOD data from the National Aeronautics and Space Administration (NASA) Moderate-resolution Imaging Spectroradiometer (MODIS) instrument, and to estimate improvements in a 3-D CTM assimilation run compared to a direct model run. Our assimilation system uses 3-D-FGAT (first guess at appropriate time) as an assimilation method and the total 3-D aerosol concentration as a control variable. In order to have an extensive validation dataset, we carried out our experiment in the northern summer of 2012 when the pre-ChArMEx (CHemistry and AeRosol MEditerranean EXperiment) field campaign TRAQA (TRAnsport à longue distance et Qualité de l'Air dans le bassin méditerranéen) took place in the western Mediterranean basin. The assimilated model run is evaluated independently against a range of aerosol properties (2-D and 3-D) measured by in situ instruments (the TRAQA size-resolved balloon and aircraft measurements), the satellite Spinning Enhanced Visible and InfraRed Imager (SEVIRI) instrument and ground-based instruments from the Aerosol Robotic Network (AERONET) network. The evaluation demonstrates that the AOD assimilation greatly improves aerosol representation in the model. For example, the comparison of the direct and the assimilated model run with AERONET data shows that the assimilation increased the correlation (from 0.74 to 0.88), and reduced the bias (from 0.050 to 0.006) and the root mean square error in the AOD (from 0.12 to 0.07). When compared to the 3-D concentration data obtained by the in situ aircraft and balloon measurements, the assimilation consistently improves the model output. The best results as expected occur when the shape of the vertical profile is correctly simulated by the direct model. We

  5. Changes in ground-level PM mass concentration and column aerosol optical depth over East Asia during 2004-2014

    Science.gov (United States)

    Nam, J.; Kim, S. W.; Park, R.; Yoon, S. C.; Sugimoto, N.; Park, J. S.; Hong, J.

    2015-12-01

    Multi-year records of moderate resolution imaging spectroradiometer (MODIS), ground-level particulate matter (PM) mass concentration, cloud-aerosol lidar with orthogonal polarization (CALIOP), and ground-level lidar were analyzed to investigate seasonal and annual changes of aerosol optical depth (AOD) and PM mass concentration over East Asia. Least mean square fit method is applied to detect the trends and their magnitudes for each selected regions and stations. Eleven-year MODIS measurements show generally increasing trends in both AOD (1.18 % yr-1) and Ångström exponent (0.98 % yr-1), especially over the east coastal industrialized region in China. Monthly variation of AOD show maximum value at April-July, which were related to the progress of summer monsoon rain band and stationary continental air mass on the northeast of Asia. Increasing trends of AOD were found for eight cites in China (0.80 % yr-1) and Seoul site, Korea (0.40 % yr-1), whereas no significant change were shown in Gosan background site (0.04 % yr-1) and decreasing trend at five background sites in Japan (-0.42 % yr-1). Contrasting to AOD trend, all fifteen sites in China (-1.28 % yr-1), Korea (-2.77 % yr-1), and Japan (-2.03 % yr-1) showed decreasing trend of PM10 mass concentration. Also, PM2.5 mass concentration at Beijing, Seoul, Rishiri, and Oki show significant decreasing trend of -1.16 % yr-1. To further discuss the opposite trend of surface PM mass concentration and column AOD, we investigate vertical aerosol profile from lidar measurements. AOD estimated for planetary boundary layer (surface~1.5 km altitude; AODPBL) from CALIOP measurements over East China show decreasing trend of -1.71 % yr-1 over the period of 2007-2014, wherever AOD estimated for free troposphere (1.5 km~5 km altitude; AODFT) show increasing trend of 2.92 % yr-1. In addition, ground-level lidar measurements in Seoul show decreasing AODPBL trend of -2.57 % yr-1, whereas, AODFT show no significant change (-0.44 % yr

  6. Prediction of Hourly Particulate Matter Concentrations in Chiangmai, Thailand Using MODIS Aerosol Optical Depth and Ground-Based Meteorological Data

    Directory of Open Access Journals (Sweden)

    Thongchai Kanabkaew

    2013-07-01

    Full Text Available Various extreme events recorded over the world have been recognized as scientific-based evidence from possible climate change and variability. The incidence of increasing forest fires and intensive agricultural field burning in Chiangmai and Northern Thailand due to favor conditions may also due to a likely increase of droughts caused by the changing climate. Smog from biomass burning, particularly particulate matter (PM seriously affects health and the environment. Lack and sparse of ground monitors may cause unreliability for warning information. Satellite remote sensing is now a promising technology for air quality prediction at ground level. This study was to investigate the statistical model for predicting PM concentration using satellite data. Aerosol optical depth (AOD data were gathered from MODIS-Terra platform while hourly PM2.5 and PM10 data were collected from the Pollution Control Department. The relationship between AOD and hourly PM over Chiangmai was addressed by Model I-Simple linear regression and Model II-Multiple linear regression with ground-based meteorological data correction. The data used for the statistical analyses were from smog period in 2012 (January-April. Results revealed that AOD and hourly PM in Model I were positively correlated with the coefficient of determination (R2 of 0.22 and 0.21, respectively for PM2.5 and PM10. The relationship between AOD and hourly PM was improved significantly when correcting with relative humidity and temperature data. The model II gave R2 of 0.77 and 0.71, respectively for PM2.5 and PM10. To investigate the validity of model, the regression equation obtained from Model II was then applied with smog data over Chiangmai in March 2007. The model performed reasonably with R2 of 0.74. The model applications would provide supplementary data to other areas with similar conditions and without air quality monitoring stations, and reduce false warning the level of air pollution associated

  7. Spatiotemporal variability and contribution of different aerosol types to the aerosol optical depth over the Eastern Mediterranean

    Directory of Open Access Journals (Sweden)

    A. K. Georgoulias

    2016-11-01

    Full Text Available This study characterizes the spatiotemporal variability and relative contribution of different types of aerosols to the aerosol optical depth (AOD over the Eastern Mediterranean as derived from MODIS (Moderate Resolution Imaging Spectroradiometer Terra (March 2000–December 2012 and Aqua (July 2002–December 2012 satellite instruments. For this purpose, a 0.1° × 0.1° gridded MODIS dataset was compiled and validated against sun photometric observations from the AErosol RObotic NETwork (AERONET. The high spatial resolution and long temporal coverage of the dataset allows for the determination of local hot spots like megacities, medium-sized cities, industrial zones and power plant complexes, seasonal variabilities and decadal averages. The average AOD at 550 nm (AOD550 for the entire region is ∼ 0.22 ± 0.19, with maximum values in summer and seasonal variabilities that can be attributed to precipitation, photochemical production of secondary organic aerosols, transport of pollution and smoke from biomass burning in central and eastern Europe and transport of dust from the Sahara and the Middle East. The MODIS data were analyzed together with data from other satellite sensors, reanalysis projects and a chemistry–aerosol-transport model using an optimized algorithm tailored for the region and capable of estimating the contribution of different aerosol types to the total AOD550. The spatial and temporal variability of anthropogenic, dust and fine-mode natural aerosols over land and anthropogenic, dust and marine aerosols over the sea is examined. The relative contribution of the different aerosol types to the total AOD550 exhibits a low/high seasonal variability over land/sea areas, respectively. Overall, anthropogenic aerosols, dust and fine-mode natural aerosols account for ∼ 51, ∼ 34 and ∼ 15 % of the total AOD550 over land, while, anthropogenic aerosols, dust and marine aerosols account ∼ 40, ∼ 34

  8. Statistical intercomparison and validation of multisensory aerosol optical depth retrievals over three AERONET sites in Kenya, East Africa

    Science.gov (United States)

    Boiyo, Richard; Kumar, K. Raghavendra; Zhao, Tianliang

    2017-11-01

    Over the last two decades, a number of space-borne sensors have been used to retrieve aerosol optical depth (AOD). The reliability of these datasets over East Africa (EA), however, is an important issue in the interpretation of regional aerosol variability. This study provides an intercomparison and validation of AOD retrievals from the MODIS-Terra (DT and DB), MISR and OMI sensors against ground-based measurements from the AERONET over three sites (CRPSM_Malindi, Nairobi, and ICIPE_Mbita) in Kenya, EA during the periods 2008-2013, 2005-2009 and 2006-2015, respectively. The analysis revealed that MISR performed better over the three sites with about 82.5% of paired AOD data falling within the error envelope (EE). MODIS-DT showed good agreement against AERONET with 59.05% of paired AOD falling within the sensor EE over terrestrial surfaces with relatively high vegetation cover. The comparison between MODIS-DB and AERONET revealed an overall lower performance with lower Gfraction (48.93%) and lower correlation r = 0.58; while AOD retrieved from OMI showed less correspondence with AERONET data with lower Gfraction (68.89%) and lowest correlation r = 0.31. The monthly evaluation of AODs retrieved from the sensors against AERONET AOD indicates that MODIS-DT has the best performance over the three sites with highest correlation (0.71-0.84), lowest RMSE and spread closer to the AERONET. Regarding seasonal analysis, MISR performed well during most seasons over Nairobi and Mbita; while MODIS-DT performed better than all other sensors during most seasons over Malindi. Furthermore, the best seasonal performance of most sensors relative to AERONET data occurred during June-August (JJA) attributed to modulations induced by a precipitation-vegetation factor to AOD satellite retrieval algorithms. The study revealed the strength and weakness of each of the retrieval algorithm and forms the basis for further research on the validation of satellite retrieved aerosol products over EA.

  9. THEORETICAL MODELLING STUDY ON THE RELATIONSHIP BETWEEN MULTI-FREQUENCY MICROWAVE VEGETATION INDEX AND VEGETATION PROPERTIES (OPTICAL DEPTH AND SINGLE SCATTERING ALBEDO

    Directory of Open Access Journals (Sweden)

    S. Talebi

    2018-04-01

    Full Text Available This paper presents a theoretical study of derivation Microwave Vegetation Indices (MVIs in different pairs of frequencies using two methods. In the first method calculating MVI in different frequencies based on Matrix Doubling Model (to take in to account multi scattering effects has been done and analyzed in various soil properties. The second method was based on MVI theoretical basis and its independency to underlying soil surface signals. Comparing the results from two methods with vegetation properties (single scattering albedo and optical depth indicated partial correlation between MVI from first method and optical depth, and full correlation between MVI from second method and vegetation properties. The second method to derive MVI can be used widely in global microwave vegetation monitoring.

  10. Apparent discrepancy between single-unit activity and [14C]deoxyglucose labeling in optic tectum of the rattlesnake

    International Nuclear Information System (INIS)

    Auker, C.R.; Meszler, R.M.; Carpenter, D.O.

    1983-01-01

    Autoradiographic analysis of [1- 14 C]2-deoxy-D-glucose-6-phosphate ([ 14 C]2-DG-P) accumulation in the rattlesnake brain stem and optic tectum was used in an effort to map infrared and visual neuronal pathways. Visual stimulation with a standard stimulus (a heat lamp) resulted in dense labeling of the superficial layers of the optic tectum. Infrared stimulation resulted in labeling at the first synaptic relay, the lateral descending nucleus of the trigeminal tract, but not at higher levels. Responses of infrared units in one hemitectum and visual units in the other were analyzed. There were no clear differences in the number, maximal density, spread, or rates of accommodation of visual units and infrared units, although the locus of maximal density was more superficial for visual units. In general, infrared units generated a greater number of action potentials. All infrared units responded to onset but they varied greatly in their ability to maintain discharge for the duration of the stimulus. Infrared stimuli generated single, large, triphasic on-responses, whereas visual stimulation generated complex multiphasic and long-lasting on- and off-responses. The major infrared-on peak reached maximal amplitude at greater depths and was larger than the major visual-on peak. Amplitude of the infrared peak fell off more rapidly with distance than did amplitude of the visual peak. These observations are consistent with the view that infrared stimulation is effective in discharging neurons but is not associated with intense synaptic excitation. Our observations suggest that 2-deoxy-D-glucose uptake is not necessarily correlated with the degree of action potential activation of specific neuronal pathways. The amount of [ 14 C]2-DG-P labeling may reflect the metabolic requirements for support of synaptic depolarization as well as that supporting action potentials

  11. Application of a multiple scattering model to estimate optical depth, lidar ratio and ice crystal effective radius of cirrus clouds observed with lidar.

    Directory of Open Access Journals (Sweden)

    Gouveia Diego

    2018-01-01

    Full Text Available Lidar measurements of cirrus clouds are highly influenced by multiple scattering (MS. We therefore developed an iterative approach to correct elastic backscatter lidar signals for multiple scattering to obtain best estimates of single-scattering cloud optical depth and lidar ratio as well as of the ice crystal effective radius. The approach is based on the exploration of the effect of MS on the molecular backscatter signal returned from above cloud top.

  12. Neutral Hydrogen Optical Depth near Star-forming Galaxies at z ≈ 2.4 in the Keck Baryonic Structure Survey

    Science.gov (United States)

    Rakic, Olivera; Schaye, Joop; Steidel, Charles C.; Rudie, Gwen C.

    2012-06-01

    We study the interface between galaxies and the intergalactic medium by measuring the absorption by neutral hydrogen in the vicinity of star-forming galaxies at z ≈ 2.4. Our sample consists of 679 rest-frame UV-selected galaxies with spectroscopic redshifts that have impact parameters advantage of all available Lyman series lines. The median optical depth, and hence the median density of atomic hydrogen, drops by more than an order of magnitude around 100 kpc, which is similar to the virial radius of the halos thought to host the galaxies. The median remains enhanced, at the >3σ level, out to at least 2.8 Mpc (i.e., >9 comoving Mpc), but the scatter at a given distance is large compared with the median excess optical depth, suggesting that the gas is clumpy. Within 100 (200) kpc, and over ±165 km s-1, the covering fraction of gas with Lyα optical depth greater than unity is 100+0 - 32% (66% ± 16%). Absorbers with τLyα > 0.1 are typically closer to galaxies than random. The mean galaxy overdensity around absorbers increases with the optical depth and also as the length scale over which the galaxy overdensity is evaluated is decreased. Absorbers with τLyα ~ 1 reside in regions where the galaxy number density is close to the cosmic mean on scales >=0.25 Mpc. We clearly detect two types of redshift space anisotropies. On scales 3σ significance), an effect that we attribute to large-scale infall (i.e., the Kaiser effect). Based on data obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W. M. Keck Foundation.

  13. Application of a multiple scattering model to estimate optical depth, lidar ratio and ice crystal effective radius of cirrus clouds observed with lidar.

    Science.gov (United States)

    Gouveia, Diego; Baars, Holger; Seifert, Patric; Wandinger, Ulla; Barbosa, Henrique; Barja, Boris; Artaxo, Paulo; Lopes, Fabio; Landulfo, Eduardo; Ansmann, Albert

    2018-04-01

    Lidar measurements of cirrus clouds are highly influenced by multiple scattering (MS). We therefore developed an iterative approach to correct elastic backscatter lidar signals for multiple scattering to obtain best estimates of single-scattering cloud optical depth and lidar ratio as well as of the ice crystal effective radius. The approach is based on the exploration of the effect of MS on the molecular backscatter signal returned from above cloud top.

  14. Retrievals of aerosol optical depth and Angström exponent from ground-based Sun-photometer data of Singapore.

    Science.gov (United States)

    Salinas, Santo V; Chew, Boon N; Liew, Soo C

    2009-03-10

    The role of aerosols in climate and climate change is one of the factors that is least understood at the present. Aerosols' direct interaction with solar radiation is a well understood mechanism that affects Earth's net radiative forcing. However, quantifying its magnitude is more problematic because of the temporal and spatial variability of aerosol particles. To enhance our understanding of the radiative effects of aerosols on the global climate, Singapore has joined the AERONET (Aerosol Robotic Network) worldwide network by contributing ground-based direct Sun measurements performed by means of a multiwavelength Sun-photometer instrument. Data are collected on an hourly basis, then are uploaded to be fully screened and quality assured by AERONET. We use a one year data record (level 1.5/2.0) of measured columnar atmospheric optical depth, spanning from November 2006 to October 2007, to study the monthly and seasonal variability of the aerosol optical depth and the Angström exponent. We performed independent retrievals of these parameters (aerosol optical depth and Angström exponent) by using the photometer's six available bands covering the near-UV to near-IR (380-1080 nm). As a validation, our independent retrievals were compared with AERONET 1.5/2.0 level direct Sun product.

  15. UTILIZATION OF FUNDUS AUTOFLUORESCENCE, SPECTRAL DOMAIN OPTICAL COHERENCE TOMOGRAPHY, AND ENHANCED DEPTH IMAGING IN THE CHARACTERIZATION OF BIETTI CRYSTALLINE DYSTROPHY IN DIFFERENT STAGES.

    Science.gov (United States)

    Li, Qian; Li, Yang; Zhang, Xiaohui; Xu, Zhangxing; Zhu, Xiaoqing; Ma, Kai; She, Haicheng; Peng, Xiaoyan

    2015-10-01

    To characterize Bietti crystalline dystrophy (BCD) in different stages using multiple imaging modalities. Sixteen participants clinically diagnosed as BCD were included in the retrospective study and were categorized into 3 stages according to fundus photography. Eleven patients were genetically confirmed. Fundus autofluorescence, spectral domain optical coherence tomography, and enhanced depth imaging features of BCD were analyzed. On fundus autofluorescence, the abnormal autofluorescence was shown to enlarge in area and decrease in intensity with stages. Using spectral domain optical coherence tomography, the abnormalities in Stage 1 were observed to localize in outer retinal layers, whereas in Stage 2 and Stage 3, more extensive retinal atrophy was seen. In enhanced depth imaging, the subfoveal choroidal layers were delineated clearly in Stage 1; in Stage 2, destructions were primarily found in the choriocapillaris with associated alterations in the outer vessels; Stage 3 BCD displayed severe choroidal thinning. Choroidal neovascularization and macular edema were exhibited with high incidence. IVS6-8del17bp/inGC of the CYP4V2 gene was the most common mutant allele. Noninvasive fundus autofluorescence, spectral domain optical coherence tomography, and enhanced depth imaging may help to characterize the chorioretinal pathology of BCD at different degrees, and therefore, we propose staging of BCD depending on those methods. Physicians should be cautious of the vision-threatening complications of the disease.

  16. Observation of depth-dependent atomic displacements related to dislocations in GaN by optical sectioning in the STEM

    International Nuclear Information System (INIS)

    Lozano, J G; Hirsch, P B; Nellist, P D; Guerrero-Lebrero, M P; Galindo, P L; Yasuhara, A; Okinishi, E; Zhang, S; Humphreys, C J

    2014-01-01

    We demonstrate that it is possible to observe depth-dependent atomic displacements in a GaN crystal due to the sufficiently small depth of field achievable in the aberration-corrected scanning transmission electron microscope. The depth-dependent displacements associated with the Eshelby twist of screw dislocations in GaN viewed end on are directly imaged, and makes possible the determination of the sign of the Burgers vector of the dislocation. The experimental results are in good agreement with theoretical images

  17. Depth information in natural environments derived from optic flow by insect motion detection system: A model analysis

    Directory of Open Access Journals (Sweden)

    Alexander eSchwegmann

    2014-08-01

    Full Text Available Knowing the depth structure of the environment is crucial for moving animals in many behavioral contexts, such as collision avoidance, targeting objects, or spatial navigation. An important source of depth information is motion parallax. This powerful cue is generated on the eyes during translatory self-motion with the retinal images of nearby objects moving faster than those of distant ones. To investigate how the visual motion pathway represents motion-based depth information we analyzed its responses to image sequences recorded in natural cluttered environments with a wide range of depth structures. The analysis was done on the basis of an experimentally validated model of the visual motion pathway of insects, with its core elements being correlation-type elementary motion detectors (EMDs. It is the key result of our analysis that the absolute EMD responses, i.e. the motion energy profile, represent the contrast-weighted nearness of environmental structures during translatory self-motion at a roughly constant velocity. In other words, the output of the EMD array highlights contours of nearby objects. This conclusion is largely independent of the scale over which EMDs are spatially pooled and was corroborated by scrutinizing the motion energy profile after eliminating the depth structure from the natural image sequences. Hence, the well-established dependence of correlation-type EMDs on both velocity and textural properties of motion stimuli appears to be advantageous for representing behaviorally relevant information about the environment in a computationally parsimonious way.

  18. Development of a fibre-optic dosemeter to measure the skin dose and percentage depth dose in the build-up region of therapeutic photon beams

    International Nuclear Information System (INIS)

    Kim, K. A.; Yoo, W. J.; Jang, K. W.; Moon, J.; Han, K. T.; Jeon, D.; Park, J. Y.; Cha, E. J.; Lee, B.

    2013-01-01

    In this study, a fibre-optic dosemeter (FOD) using an organic scintillator with a diameter of 0.5 mm for photon-beam therapy dosimetry was fabricated. The fabricated dosemeter has many advantages, including water equivalence, high spatial resolution, remote sensing and real-time measurement. The scintillating light generated from an organic-dosemeter probe embedded in a solid-water stack phantom is guided to a photomultiplier tube and an electrometer via 20 m of plastic optical fibre. Using this FOD, the skin dose and the percentage depth dose in the build-up region according to the depths of a solid-water stack phantom are measured with 6- and 15-MV photon-beam energies with field sizes of 10310 and 20320 cm 2 , respectively. The results are compared with those measured using conventional dosimetry films. It is expected that the proposed FOD can be effectively used in radiotherapy dosimetry for accurate measurement of the skin dose and the depth dose distribution in the build-up region due to its high spatial resolution. (authors)

  19. Motivation with Depth.

    Science.gov (United States)

    DiSpezio, Michael A.

    2000-01-01

    Presents an illusional arena by offering experience in optical illusions in which students must apply critical analysis to their innate information gathering systems. Introduces different types of depth illusions for students to experience. (ASK)

  20. Validating MODIS Above-Cloud Aerosol Optical Depth Retrieved from Color Ratio Algorithm Using Direct Measurements Made by NASA's Airborne AATS and 4STAR Sensors

    Science.gov (United States)

    Jethva, Hiren; Torres, Omar; Remer, Lorraine; Redemann, Jens; Livingston, John; Dunagan, Stephen; Shinozuka, Yohei; Kacenelenbogen, Meloe; Segal Rozenhaimer, Michal; Spurr, Rob

    2016-01-01

    We present the validation analysis of above-cloud aerosol optical depth (ACAOD) retrieved from the color ratio method applied to MODIS cloudy-sky reflectance measurements using the limited direct measurements made by NASAs airborne Ames Airborne Tracking Sunphotometer (AATS) and Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research (4STAR) sensors. A thorough search of the airborne database collection revealed a total of five significant events in which an airborne sun photometer, coincident with the MODIS overpass, observed partially absorbing aerosols emitted from agricultural biomass burning, dust, and wildfires over a low-level cloud deck during SAFARI-2000, ACE-ASIA 2001, and SEAC4RS 2013 campaigns, respectively. The co-located satellite-airborne match ups revealed a good agreement (root-mean-square difference less than 0.1), with most match ups falling within the estimated uncertainties associated with the MODIS retrievals (about -10 to +50 ). The co-retrieved cloud optical depth was comparable to that of the MODIS operational cloud product for ACE-ASIA and SEAC4RS, however, higher by 30-50% for the SAFARI-2000 case study. The reason for this discrepancy could be attributed to the distinct aerosol optical properties encountered during respective campaigns. A brief discussion on the sources of uncertainty in the satellite-based ACAOD retrieval and co-location procedure is presented. Field experiments dedicated to making direct measurements of aerosols above cloud are needed for the extensive validation of satellite based retrievals.

  1. Depth-resolved multilayer pigment identification in paintings: combined use of laser-induced breakdown spectroscopy (LIBS) and optical coherence tomography (OCT).

    Science.gov (United States)

    Kaszewska, Ewa A; Sylwestrzak, Marcin; Marczak, Jan; Skrzeczanowski, Wojciech; Iwanicka, Magdalena; Szmit-Naud, Elżbieta; Anglos, Demetrios; Targowski, Piotr

    2013-08-01

    A detailed feasibility study on the combined use of laser-induced breakdown spectroscopy with optical coherence tomography (LIBS/OCT), aiming at a realistic depth-resolved elemental analysis of multilayer stratigraphies in paintings, is presented. Merging a high spectral resolution LIBS system with a high spatial resolution spectral OCT instrument significantly enhances the quality and accuracy of stratigraphic analysis. First, OCT mapping is employed prior to LIBS analysis in order to assist the selection of specific areas of interest on the painting surface to be examined in detail. Then, intertwined with LIBS, the OCT instrument is used as a precise profilometer for the online determination of the depth of the ablation crater formed by individual laser pulses during LIBS depth-profile analysis. This approach is novel and enables (i) the precise in-depth scaling of elemental concentration profiles, and (ii) the recognition of layer boundaries by estimating the corresponding differences in material ablation rate. Additionally, the latter is supported, within the transparency of the object, by analysis of the OCT cross-sectional views. The potential of this method is illustrated by presenting results on the detailed analysis of the structure of an historic painting on canvas performed to aid planned restoration of the artwork.

  2. Benthic Habitat Mapping by Combining Lyzenga’s Optical Model and Relative Water Depth Model in Lintea Island, Southeast Sulawesi

    Science.gov (United States)

    Hafizt, M.; Manessa, M. D. M.; Adi, N. S.; Prayudha, B.

    2017-12-01

    Benthic habitat mapping using satellite data is one challenging task for practitioners and academician as benthic objects are covered by light-attenuating water column obscuring object discrimination. One common method to reduce this water-column effect is by using depth-invariant index (DII) image. However, the application of the correction in shallow coastal areas is challenging as a dark object such as seagrass could have a very low pixel value, preventing its reliable identification and classification. This limitation can be solved by specifically applying a classification process to areas with different water depth levels. The water depth level can be extracted from satellite imagery using Relative Water Depth Index (RWDI). This study proposed a new approach to improve the mapping accuracy, particularly for benthic dark objects by combining the DII of Lyzenga’s water column correction method and the RWDI of Stumpt’s method. This research was conducted in Lintea Island which has a high variation of benthic cover using Sentinel-2A imagery. To assess the effectiveness of the proposed new approach for benthic habitat mapping two different classification procedures are implemented. The first procedure is the commonly applied method in benthic habitat mapping where DII image is used as input data to all coastal area for image classification process regardless of depth variation. The second procedure is the proposed new approach where its initial step begins with the separation of the study area into shallow and deep waters using the RWDI image. Shallow area was then classified using the sunglint-corrected image as input data and the deep area was classified using DII image as input data. The final classification maps of those two areas were merged as a single benthic habitat map. A confusion matrix was then applied to evaluate the mapping accuracy of the final map. The result shows that the new proposed mapping approach can be used to map all benthic objects in

  3. Remote Access Unit for Optic-to-Wireless Conversion

    DEFF Research Database (Denmark)

    Chorchos, Łukasz; Rommel, Simon; Turkiewicz, J. P.

    . Growing demand for high speed wireless data transmission and new wireless standards like 5G force network operators to find new solutions for backhaul networks. Presently, to meet this need, attention of many researchers and top network vendors has been directed towards millimeter wave radio links....... Operation in the millimeter wave range brings new possibilities for a channel allocation as well as allows wider radio channels to be used. Moreover this frequency range is lighter licensed than regular GSM. This clearly shows a huge potential of millimeter waves for a high speed wireless data transmission...... was proposed and research projects like IPHOBAC-NG were founded. The aim of the mentioned project is to employ novel RAUs featuring opticto-wireless and wireless-to-optic conversion with a speeds of 1-10Gbit/s for broadband wireless access and up to 3Gbit/s for mobile backhaul. The RAU proposed in this paper...

  4. Constraining the optical depth of galaxies and velocity bias with cross-correlation between the kinetic Sunyaev-Zeldovich effect and the peculiar velocity field

    Science.gov (United States)

    Ma, Yin-Zhe; Gong, Guo-Dong; Sui, Ning; He, Ping

    2018-03-01

    We calculate the cross-correlation function between the kinetic Sunyaev-Zeldovich (kSZ) effect and the reconstructed peculiar velocity field using linear perturbation theory, with the aim of constraining the optical depth τ and peculiar velocity bias of central galaxies with Planck data. We vary the optical depth τ and the velocity bias function bv(k) = 1 + b(k/k0)n, and fit the model to the data, with and without varying the calibration parameter y0 that controls the vertical shift of the correlation function. By constructing a likelihood function and constraining the τ, b and n parameters, we find that the quadratic power-law model of velocity bias, bv(k) = 1 + b(k/k0)2, provides the best fit to the data. The best-fit values are τ = (1.18 ± 0.24) × 10-4, b=-0.84^{+0.16}_{-0.20} and y0=(12.39^{+3.65}_{-3.66})× 10^{-9} (68 per cent confidence level). The probability of b > 0 is only 3.12 × 10-8 for the parameter b, which clearly suggests a detection of scale-dependent velocity bias. The fitting results indicate that the large-scale (k ≤ 0.1 h Mpc-1) velocity bias is unity, while on small scales the bias tends to become negative. The value of τ is consistent with the stellar mass-halo mass and optical depth relationship proposed in the literature, and the negative velocity bias on small scales is consistent with the peak background split theory. Our method provides a direct tool for studying the gaseous and kinematic properties of galaxies.

  5. Tunable optical frequency comb enabled scalable and cost-effective multiuser orthogonal frequency-division multiple access passive optical network with source-free optical network units.

    Science.gov (United States)

    Chen, Chen; Zhang, Chongfu; Liu, Deming; Qiu, Kun; Liu, Shuang

    2012-10-01

    We propose and experimentally demonstrate a multiuser orthogonal frequency-division multiple access passive optical network (OFDMA-PON) with source-free optical network units (ONUs), enabled by tunable optical frequency comb generation technology. By cascading a phase modulator (PM) and an intensity modulator and dynamically controlling the peak-to-peak voltage of a PM driven signal, a tunable optical frequency comb source can be generated. It is utilized to assist the configuration of a multiple source-free ONUs enhanced OFDMA-PON where simultaneous and interference-free multiuser upstream transmission over a single wavelength can be efficiently supported. The proposed multiuser OFDMA-PON is scalable and cost effective, and its feasibility is successfully verified by experiment.

  6. Growth, structure, and performance of depth-graded W/Si multilayers for hard x-ray optics

    DEFF Research Database (Denmark)

    Windt, D.L.; Christensen, Finn Erland; Craig, W.W.

    2000-01-01

    that the dominant interface imperfection in these films is interfacial diffuseness; interfacial roughness is minimal (sigma(r)similar to 0.175 nm) in structures prepared under optimal conditions, but can increase under conditions in which the beneficial effects of energetic bombardment during growth are compromised......-graded W/Si multilayer structures, and high-resolution transmission electron microscopy (TEM) and selected area electron diffraction (SAED) to characterize the interface structure and layer morphology as a function of depth in an optimized depth-graded multilayer. From x-ray analysis we find interface......), and somewhat larger interface widths (i.e., sigma=0.35-0.4 nm) for structures grown at higher Ar pressures, higher background pressures, or with larger target-to-substrate distances. We find no variation in interface widths with magnetron power. Nonspecular x-ray reflectance analysis and TEM suggest...

  7. Climatology and trends of aerosol optical depth over the Mediterranean basin during the last 12years (2002-2014) based on Collection 006 MODIS-Aqua data.

    Science.gov (United States)

    Floutsi, A A; Korras-Carraca, M B; Matsoukas, C; Hatzianastassiou, N; Biskos, G

    2016-05-01

    The Mediterranean basin is a region of particular interest for studying atmospheric aerosols due to the large variety of air masses it receives, and its sensitivity to climate change. In this study we use the newest collection (C006) of aerosol optical depth from MODIS-Aqua, from which we also derived the fine-mode fraction and Ångström exponent over the last 12years (i.e., from 2002 to 2014), providing the longest analyzed dataset for this region. The long-term regional optical depth average is 0.20±0.05, with the indicated uncertainty reflecting the inter-annual variability. Overall, the aerosol optical depth exhibits a south-to-north decreasing gradient and an average decreasing trend of 0.0030 per year (19% total decrease over the study period). The correlation between the reported AOD observations with measurements from the ground AERONET stations is high (R=0.76-0.80 depending on the wavelength), with the MODIS-Aqua data being slightly overestimated. Both fine-fraction and Ångström exponent data highlight the dominance of anthropogenic aerosols over the northern, and of desert aerosols over the southern part of the region. Clear intrusions of desert dust over the Eastern Mediterranean are observed principally in spring, and in some cases in winter. Dust intrusions dominate the Western Mediterranean in the summer (and sometimes in autumn), whereas anthropogenic aerosols dominate the sub-region of the Black Sea in all seasons but especially during summer. Fine-mode optical depth is found to decrease over almost all areas of the study region during the 12-year period, marking the decreasing contribution of anthropogenic particulate matter emissions over the study area. Coarse-mode aerosol load also exhibits an overall decreasing trend. However, its decrease is smaller than that of fine aerosols and not as uniformly distributed, underlining that the overall decrease in the region arises mainly from reduced anthropogenic emissions. Copyright © 2016 Elsevier

  8. Biogenic Aerosols – Effects on Climate and Clouds. Cloud Optical Depth (COD) Sensor Three-Waveband Spectrally-Agile Technique (TWST) Field Campaign Report

    Energy Technology Data Exchange (ETDEWEB)

    Niple, E. R. [Aerodyne Research, Inc., Billerica, MA (United States); Scott, H. E. [Aerodyne Research, Inc., Billerica, MA (United States)

    2016-04-01

    This report describes the data collected by the Three-Waveband Spectrally-agile Technique (TWST) sensor deployed at Hyytiälä, Finland from 16 July to 31 August 2014 as a guest on the Biogenic Aerosols Effects on Climate and Clouds (BAECC) campaign. These data are currently available from the Atmospheric Radiation Measurement (ARM) Data Archive website and consists of Cloud Optical Depth (COD) measurements for the clouds directly overhead approximately every second (with some dropouts described below) during the daylight periods. A good range of cloud conditions were observed from clear sky to heavy rainfall.

  9. Quantitative depth resolved microcirculation imaging with optical coherence tomography angiography (Part ΙΙ): Microvascular network imaging.

    Science.gov (United States)

    Gao, Wanrong

    2017-04-17

    In this work, we review the main phenomena that have been explored in OCT angiography to image the vessels of the microcirculation within living tissues with the emphasis on how the different processing algorithms were derived to circumvent specific limitations. Parameters are then discussed that can quantitatively describe the depth-resolved microvascular network for possible clinic diagnosis applications. Finally,future directions in continuing OCT development are discussed. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  10. Evaluation of Optical Depths and Self-Absorption of Strontium and Aluminum Emission Lines in Laser-Induced Breakdown Spectroscopy (LIBS).

    Science.gov (United States)

    Alfarraj, Bader A; Bhatt, Chet R; Yueh, Fang Yu; Singh, Jagdish P

    2017-04-01

    Laser-induced breakdown spectroscopy (LIBS) is a widely used laser spectroscopic technique in various fields, such as material science, forensic science, biological science, and the chemical and pharmaceutical industries. In most LIBS work, the analysis is performed using radiative transitions from atomic emissions. In this study, the plasma temperature and the product [Formula: see text] (the number density N and the absorption path length [Formula: see text]) were determined to evaluate the optical depths and the self-absorption of Sr and Al lines. A binary mixture of strontium nitrate and aluminum oxide was used as a sample, consisting of variety of different concentrations in powder form. Laser-induced breakdown spectroscopy spectra were collected by varying various parameters, such as laser energy, gate delay time, and gate width time to optimize the LIBS signals. Atomic emission from Sr and Al lines, as observed in the LIBS spectra of different sample compositions, was used to characterize the laser induced plasma and evaluate the optical depths and self-absorption of LIBS.

  11. Comparison of Monthly Mean Cloud Fraction and Cloud Optical depth Determined from Surface Cloud Radar, TOVS, AVHRR, and MODIS over Barrow, Alaska

    Science.gov (United States)

    Uttal, Taneil; Frisch, Shelby; Wang, Xuan-Ji; Key, Jeff; Schweiger, Axel; Sun-Mack, Sunny; Minnis, Patrick

    2005-01-01

    A one year comparison is made of mean monthly values of cloud fraction and cloud optical depth over Barrow, Alaska (71 deg 19.378 min North, 156 deg 36.934 min West) between 35 GHz radar-based retrievals, the TOVS Pathfinder Path-P product, the AVHRR APP-X product, and a MODIS based cloud retrieval product from the CERES-Team. The data sets represent largely disparate spatial and temporal scales, however, in this paper, the focus is to provide a preliminary analysis of how the mean monthly values derived from these different data sets compare, and determine how they can best be used separately, and in combination to provide reliable estimates of long-term trends of changing cloud properties. The radar and satellite data sets described here incorporate Arctic specific modifications that account for cloud detection challenges specific to the Arctic environment. The year 2000 was chosen for this initial comparison because the cloud radar data was particularly continuous and reliable that year, and all of the satellite retrievals of interest were also available for the year 2000. Cloud fraction was chosen as a comparison variable as accurate detection of cloud is the primary product that is necessary for any other cloud property retrievals. Cloud optical depth was additionally selected as it is likely the single cloud property that is most closely correlated to cloud influences on surface radiation budgets.

  12. All-fiber probe for optical coherence tomography with an extended depth of focus by a high-efficient fiber-based filter

    Science.gov (United States)

    Qiu, Jianrong; Shen, Yi; Shangguan, Ziwei; Bao, Wen; Yang, Shanshan; Li, Peng; Ding, Zhihua

    2018-04-01

    Although methods have been proposed to maintain high transverse resolution over an increased depth range, it is not straightforward to scale down the bulk-optic solutions to minimized probes of optical coherence tomography (OCT). In this paper, we propose a high-efficient fiber-based filter in an all-fiber OCT probe to realize an extended depth of focus (DOF) while maintaining a high transverse resolution. Mode interference in the probe is exploited to modulate the complex field with controllable radial distribution. The principle of DOF extension by the fiber-based filter is theoretically analyzed. Numerical simulations are conducted to evaluate the performances of the designed probes. A DOF extension ratio of 2.6 over conventional Gaussian beam is obtainable in one proposed probe under a focused beam diameter of 4 . 6 μm. Coupling efficiencies of internal interfaces of the proposed probe are below -40 dB except the last probe-air interface, which can also be depressed to be -44 dB after minor modification in lengths for the filter. Length tolerance of the proposed probe is determined to be - 28 / + 20 μm, which is readily satisfied in fabrication. With the merits of extended-DOF, high-resolution, high-efficiency and easy-fabrication, the proposed probe is promising in endoscopic applications.

  13. Medical diagnosis system and method with multispectral imaging. [depth of burns and optical density of the skin

    Science.gov (United States)

    Anselmo, V. J.; Reilly, T. H. (Inventor)

    1979-01-01

    A skin diagnosis system includes a scanning and optical arrangement whereby light reflected from each incremental area (pixel) of the skin is directed simultaneously to three separate light filters, e.g., IR, red, and green. As a result, the three devices simultaneously produce three signals which are directly related to the reflectance of light of different wavelengths from the corresponding pixel. These three signals for each pixel after processing are used as inputs to one or more output devices to produce a visual color display and/or a hard copy color print, for one usable as a diagnostic aid by a physician.

  14. In-depth imaging and quantification of degenerative changes associated with Achilles ruptured tendons by polarization-sensitive optical coherence tomography

    International Nuclear Information System (INIS)

    Bagnaninchi, P O; Yang, Y; Maffulli, G; El Haj, A; Maffulli, N; Bonesi, M; Meglinski, I; Phelan, C

    2010-01-01

    The objective of this study was to develop a method based on polarization-sensitive optical coherent tomography (PSOCT) for the imaging and quantification of degenerative changes associated with Achilles tendon rupture. Ex vivo PSOCT examinations were performed in 24 patients. The study involved samples from 14 ruptured Achilles tendons, 4 tendinopathic Achilles tendons and 6 patellar tendons (collected during total knee replacement) as non-ruptured controls. The samples were imaged in both intensity and phase retardation modes within 24 h after surgery, and birefringence was quantified. The samples were fixed and processed for histology immediately after imaging. Slides were assessed twice in a blind manner to provide a semi-quantitative histological score of degeneration. In-depth micro structural imaging was demonstrated. Collagen disorganization and high cellularity were observable by PSOCT as the main markers associated with pathological features. Quantitative assessment of birefringence and penetration depth found significant differences between non-ruptured and ruptured tendons. Microstructure abnormalities were observed in the microstructure of two out of four tendinopathic samples. PSOCT has the potential to explore in situ and in-depth pathological change associated with Achilles tendon rupture, and could help to delineate abnormalities in tendinopathic samples in vivo.

  15. Quantum dot imaging in the second near-infrared optical window: studies on reflectance fluorescence imaging depths by effective fluence rate and multiple image acquisition

    Science.gov (United States)

    Jung, Yebin; Jeong, Sanghwa; Nayoun, Won; Ahn, Boeun; Kwag, Jungheon; Geol Kim, Sang; Kim, Sungjee

    2015-04-01

    Quantum dot (QD) imaging capability was investigated by the imaging depth at a near-infrared second optical window (SOW; 1000 to 1400 nm) using time-modulated pulsed laser excitations to control the effective fluence rate. Various media, such as liquid phantoms, tissues, and in vivo small animals, were used and the imaging depths were compared with our predicted values. The QD imaging depth under excitation of continuous 20 mW/cm2 laser was determined to be 10.3 mm for 2 wt% hemoglobin phantom medium and 5.85 mm for 1 wt% intralipid phantom, which were extended by more than two times on increasing the effective fluence rate to 2000 mW/cm2. Bovine liver and porcine skin tissues also showed similar enhancement in the contrast-to-noise ratio (CNR) values. A QD sample was inserted into the abdomen of a mouse. With a higher effective fluence rate, the CNR increased more than twofold and the QD sample became clearly visualized, which was completely undetectable under continuous excitation. Multiple acquisitions of QD images and averaging process pixel by pixel were performed to overcome the thermal noise issue of the detector in SOW, which yielded significant enhancement in the imaging capability, showing up to a 1.5 times increase in the CNR.

  16. Analysis of SMOS brightness temperature and vegetation optical depth data with coupled land surface and radiative transfer models in Southern Germany

    Directory of Open Access Journals (Sweden)

    F. Schlenz

    2012-10-01

    Full Text Available Soil Moisture and Ocean Salinity (SMOS L1c brightness temperature and L2 optical depth data are analysed with a coupled land surface (PROMET and radiative transfer model (L-MEB. The coupled models are validated with ground and airborne measurements under contrasting soil moisture, vegetation and land surface temperature conditions during the SMOS Validation Campaign in May and June 2010 in the SMOS test site Upper Danube Catchment in southern Germany. The brightness temperature root-mean-squared errors are between 6 K and 9 K. The L-MEB parameterisation is considered appropriate under local conditions even though it might possibly be further optimised. SMOS L1c brightness temperature data are processed and analysed in the Upper Danube Catchment using the coupled models in 2011 and during the SMOS Validation Campaign 2010 together with airborne L-band brightness temperature data. Only low to fair correlations are found for this comparison (R between 0.1–0.41. SMOS L1c brightness temperature data do not show the expected seasonal behaviour and are positively biased. It is concluded that RFI is responsible for a considerable part of the observed problems in the SMOS data products in the Upper Danube Catchment. This is consistent with the observed dry bias in the SMOS L2 soil moisture products which can also be related to RFI. It is confirmed that the brightness temperature data from the lower SMOS look angles and the horizontal polarisation are less reliable. This information could be used to improve the brightness temperature data filtering before the soil moisture retrieval. SMOS L2 optical depth values have been compared to modelled data and are not considered a reliable source of information about vegetation due to missing seasonal behaviour and a very high mean value. A fairly strong correlation between SMOS L2 soil moisture and optical depth was found (R = 0.65 even though the two variables are considered independent in the

  17. Multiangle Imaging Spectroradiometer (MISR) Global Aerosol Optical Depth Validation Based on 2 Years of Coincident Aerosol Robotic Network (AERONET) Observations

    Science.gov (United States)

    Kahn, Ralph A.; Gaitley, Barbara J.; Martonchik, John V.; Diner, David J.; Crean, Kathleen A.; Holben, Brent

    2005-01-01

    Performance of the Multiangle Imaging Spectroradiometer (MISR) early postlaunch aerosol optical thickness (AOT) retrieval algorithm is assessed quantitatively over land and ocean by comparison with a 2-year measurement record of globally distributed AERONET Sun photometers. There are sufficient coincident observations to stratify the data set by season and expected aerosol type. In addition to reporting uncertainty envelopes, we identify trends and outliers, and investigate their likely causes, with the aim of refining algorithm performance. Overall, about 2/3 of the MISR-retrieved AOT values fall within [0.05 or 20% x AOT] of Aerosol Robotic Network (AERONET). More than a third are within [0.03 or 10% x AOT]. Correlation coefficients are highest for maritime stations (approx.0.9), and lowest for dusty sites (more than approx.0.7). Retrieved spectral slopes closely match Sun photometer values for Biomass burning and continental aerosol types. Detailed comparisons suggest that adding to the algorithm climatology more absorbing spherical particles, more realistic dust analogs, and a richer selection of multimodal aerosol mixtures would reduce the remaining discrepancies for MISR retrievals over land; in addition, refining instrument low-light-level calibration could reduce or eliminate a small but systematic offset in maritime AOT values. On the basis of cases for which current particle models are representative, a second-generation MISR aerosol retrieval algorithm incorporating these improvements could provide AOT accuracy unprecedented for a spaceborne technique.

  18. Multi year changes of Aerosol Optical Depth in the monsoon region of the Indian Ocean since 1986 as seen in the AVHRR and TOMS data

    Directory of Open Access Journals (Sweden)

    J. P. George

    2008-02-01

    Full Text Available Aerosol Optical Depth (AOD data based on AVHRR and TOMS was analyzed to find out the changes in the Indian Ocean from 1981 to 2004. Four regions covering Indian Ocean north of 10° S were studied in detail. The results strongly suggest that the mean value of AOD in these regions decreased from 1986–1990 to 1995–1999. The Arabian Sea and Bay of Bengal show increase thereafter whereas in the equatorial part it decreased further, during 2000–2004. The drop in AOD from the first to second period is evident in AVHRR and TOMS in the case of the Arabian Sea (North West Indian Ocean. The decrease in this case is prominent in summer. These results in general agree with the recently reported global decrease in AOD, "global brightening" and also the reversal of trend in some of the anthropogenic emissions.

  19. The impact of aerosol vertical distribution on aerosol optical depth retrieval using CALIPSO and MODIS data: Case study over dust and smoke regions

    Science.gov (United States)

    Wu, Yerong; de Graaf, Martin; Menenti, Massimo

    2017-08-01

    Global quantitative aerosol information has been derived from MODerate Resolution Imaging SpectroRadiometer (MODIS) observations for decades since early 2000 and widely used for air quality and climate change research. However, the operational MODIS Aerosol Optical Depth (AOD) products Collection 6 (C6) can still be biased, because of uncertainty in assumed aerosol optical properties and aerosol vertical distribution. This study investigates the impact of aerosol vertical distribution on the AOD retrieval. We developed a new algorithm by considering dynamic vertical profiles, which is an adaptation of MODIS C6 Dark Target (C6_DT) algorithm over land. The new algorithm makes use of the aerosol vertical profile extracted from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) measurements to generate an accurate top of the atmosphere (TOA) reflectance for the AOD retrieval, where the profile is assumed to be a single layer and represented as a Gaussian function with the mean height as single variable. To test the impact, a comparison was made between MODIS DT and Aerosol Robotic Network (AERONET) AOD, over dust and smoke regions. The results show that the aerosol vertical distribution has a strong impact on the AOD retrieval. The assumed aerosol layers close to the ground can negatively bias the retrievals in C6_DT. Regarding the evaluated smoke and dust layers, the new algorithm can improve the retrieval by reducing the negative biases by 3-5%.

  20. Photoflash unit having optical system including aspheric lens to enhance light output

    International Nuclear Information System (INIS)

    English, G.J.

    1984-01-01

    A photoflash unit employing an optical system or apparatus with improved center beam candle power seconds and zonal lumen seconds from the flash lamp therein, said unit also employing a minimized utilization ratio of lamp-to-package cross-sectional area. Each individual lamp capsule comprises a reflective element, a refractive element (lens), and at least one photoflash lamp (light source). The lens provides for lamp shred magnification so as to fill the cell (capsule) width to thus provide maximum transfer of light to the subject on axis. One embodiment has the light source fused (glued) to the reflector and lens while a second embodiment has an air interface between the source and the optical elements. In both embodiments, the lens is aspheric and substantially covers both the reflector and source

  1. Long-term analysis of aerosol optical depth over Northeast Asia using a satellite-based measurement: MI Yonsei Aerosol Retrieval Algorithm (YAER)

    Science.gov (United States)

    Kim, Mijin; Kim, Jhoon; Yoon, Jongmin; Chung, Chu-Yong; Chung, Sung-Rae

    2017-04-01

    In 2010, the Korean geostationary earth orbit (GEO) satellite, the Communication, Ocean, and Meteorological Satellite (COMS), was launched including the Meteorological Imager (MI). The MI measures atmospheric condition over Northeast Asia (NEA) using a single visible channel centered at 0.675 μm and four IR channels at 3.75, 6.75, 10.8, 12.0 μm. The visible measurement can also be utilized for the retrieval of aerosol optical properties (AOPs). Since the GEO satellite measurement has an advantage for continuous monitoring of AOPs, we can analyze the spatiotemporal variation of the aerosol using the MI observations over NEA. Therefore, we developed an algorithm to retrieve aerosol optical depth (AOD) using the visible observation of MI, and named as MI Yonsei Aerosol Retrieval Algorithm (YAER). In this study, we investigated the accuracy of MI YAER AOD by comparing the values with the long-term products of AERONET sun-photometer. The result showed that the MI AODs were significantly overestimated than the AERONET values over bright surface in low AOD case. Because the MI visible channel centered at red color range, contribution of aerosol signal to the measured reflectance is relatively lower than the surface contribution. Therefore, the AOD error in low AOD case over bright surface can be a fundamental limitation of the algorithm. Meanwhile, an assumption of background aerosol optical depth (BAOD) could result in the retrieval uncertainty, also. To estimate the surface reflectance by considering polluted air condition over the NEA, we estimated the BAOD from the MODIS dark target (DT) aerosol products by pixel. The satellite-based AOD retrieval, however, largely depends on the accuracy of the surface reflectance estimation especially in low AOD case, and thus, the BAOD could include the uncertainty in surface reflectance estimation of the satellite-based retrieval. Therefore, we re-estimated the BAOD using the ground-based sun-photometer measurement, and

  2. The disinfection of flexible fibre-optic nasendoscopes out-of-hours: confidential telephone survey of ENT units in England

    NARCIS (Netherlands)

    Kanagalingam, J.; Zainal, A.; Georgalas, C.; Paun, S.; Tolley, N. S.

    2002-01-01

    We present the results of a confidential telephone survey of ENT units in England on the disinfection of flexible fibre-optic nasendoscopes out-of-hours. The on-call residents of 124 units were contacted and questioned. In 35.1 per cent of units surveyed, the on-call resident was primarily

  3. Reliability of Entire Corneal Thickness Mapping in Normal Post-Laser in situ Keratomileusis and Keratoconus Eyes Using Long Scan Depth Spectral Domain Optical Coherence Tomography.

    Science.gov (United States)

    Xu, Zhe; Chen, Sisi; Yang, Chun; Huang, Shenghai; Shen, Meixiao; Wang, Yuanyuan

    2018-01-01

    To investigate the repeatability and reproducibility of mapping the entire corneal thickness using spectral domain optical coherence tomography (SD-OCT). Thirty normal eyes, 30 post-laser in situ keratomileusis (LASIK) surgery eyes, and 30 keratoconus eyes were analyzed. A custom-built long scan depth SD-OCT device was used to obtain entire corneal images. Ten-millimeter-diameter corneal thickness maps were generated by an automated segmentation algorithm. Intraclass correlation coefficients of repeatability (ICC1) and reproducibility (ICC2), and coefficients of repeatability (CoR1) and reproducibility (CoR2), were calculated to quantify the precision and accuracy of corneal pachymetry measurements using the Bland-Altman method. For SD-OCT measurements in healthy subjects, CoR1 and CoR2 were less than 5.00 and 5.53 μm. ICC1 and ICC2 were more than 0.997 and 0.996. For SD-OCT measurements in LASIK patients, CoR1 and CoR2 were less than 5.09 and 5.34 μm. ICC1 and ICC2 were more than 0.997 and 0.996. For SD-OCT measurements in keratoconus patients, CoR1 and CoR2 were less than 11.57 and 10.92 μm. ICC1 and ICC2 were more than 0.995 and 0.996. The measurements of corneal pachymetric mapping by long scan depth SD-OCT can be assessed over the entire corneal area with good repeatability and reproducibility. © 2017 S. Karger AG, Basel.

  4. Extended depth of focus contact lenses vs. two commercial multifocals: Part 1. Optical performance evaluation via computed through-focus retinal image quality metrics.

    Science.gov (United States)

    Bakaraju, Ravi C; Ehrmann, Klaus; Ho, Arthur

    To compare the computed optical performance of prototype lenses designed using deliberate manipulation of higher-order spherical aberrations to extend depth-of-focus (EDOF) with two commercial multifocals. Emmetropic, presbyopic, schematic eyes were coupled with prototype EDOF and commercial multifocal lenses (Acuvue Oasys for presbyopia, AOP, Johnson & Johnson & Air Optix Aqua multifocal, AOMF, Alcon). For each test configuration, the through-focus retinal image quality (TFRIQ) values were computed over 21 vergences, ranging from -0.50 to 2.00D, in 0.125D steps. Analysis was performed considering eyes with three different inherent aberration profiles: five different pupils and five different lens decentration levels. Except the LOW design, the AOP lenses offered 'bifocal' like TFRIQ performance. Lens performance was relatively independent to pupil and aberrations but not centration. Contrastingly, AOMF demonstrated distance centric performance, most dominant in LOW followed by MED and HIGH designs. AOMF lenses were the most sensitive to pupil, aberrations and centration. The prototypes demonstrated a 'lift-off' in the TFRIQ performance, particularly at intermediate and near, without trading performance at distance. When compared with AOP and AOMF, EDOF lenses demonstrated reduced sensitivity to pupil, aberrations and centration. With the through focus retinal image quality as the gauge of optical performance, we demonstrated that the prototype EDOF designs were less susceptible to variations in pupil, inherent ocular aberrations and decentration, compared to the commercial designs. To ascertain whether these incremental improvements translate to a clinically palpable outcome requires investigation through human trials. Copyright © 2017 Spanish General Council of Optometry. Published by Elsevier España, S.L.U. All rights reserved.

  5. Real-time Measurements of an Optical Reconfigurable Radio Access Unit for 5G Wireless Access Networks

    DEFF Research Database (Denmark)

    Rodríguez, Sebastián; Morales Vicente, Alvaro; Rommel, Simon

    2017-01-01

    A reconfigurable radio access unit able to switch wavelength, RF carrier frequency and optical path is experimentally demonstrated. The system is able to do the switching processes correctly, while achieving BER values below FEC limit.......A reconfigurable radio access unit able to switch wavelength, RF carrier frequency and optical path is experimentally demonstrated. The system is able to do the switching processes correctly, while achieving BER values below FEC limit....

  6. Real-time acquisition and display of flow contrast using speckle variance optical coherence tomography in a graphics processing unit.

    Science.gov (United States)

    Xu, Jing; Wong, Kevin; Jian, Yifan; Sarunic, Marinko V

    2014-02-01

    In this report, we describe a graphics processing unit (GPU)-accelerated processing platform for real-time acquisition and display of flow contrast images with Fourier domain optical coherence tomography (FDOCT) in mouse and human eyes in vivo. Motion contrast from blood flow is processed using the speckle variance OCT (svOCT) technique, which relies on the acquisition of multiple B-scan frames at the same location and tracking the change of the speckle pattern. Real-time mouse and human retinal imaging using two different custom-built OCT systems with processing and display performed on GPU are presented with an in-depth analysis of performance metrics. The display output included structural OCT data, en face projections of the intensity data, and the svOCT en face projections of retinal microvasculature; these results compare projections with and without speckle variance in the different retinal layers to reveal significant contrast improvements. As a demonstration, videos of real-time svOCT for in vivo human and mouse retinal imaging are included in our results. The capability of performing real-time svOCT imaging of the retinal vasculature may be a useful tool in a clinical environment for monitoring disease-related pathological changes in the microcirculation such as diabetic retinopathy.

  7. Temporal variation of aerosol optical depth and associated shortwave radiative forcing over a coastal site along the west coast of India.

    Science.gov (United States)

    Menon, Harilal B; Shirodkar, Shilpa; Kedia, Sumita; S, Ramachandran; Babu, Suresh; Moorthy, K Krishna

    2014-01-15

    Optical characterization of aerosol was performed by assessing the columnar aerosol optical depth (AOD) and angstrom wavelength exponent (α) using data from the Microtops II Sunphotometer. The data were collected on cloud free days over Goa, a coastal site along the west coast of India, from January to December 2008. Along with the composite aerosol, the black carbon (BC) mass concentration from the Aethalometer was also analyzed. The AOD0.500 μm and angstrom wavelength exponent (α) were in the range of 0.26 to 0.7 and 0.52 to 1.33, respectively, indicative of a significant seasonal shift in aerosol characteristics during the study period. The monthly mean AOD0.500 μm exhibited a bi-modal distribution, with a primary peak in April (0.7) and a secondary peak in October (0.54), whereas the minimum of 0.26 was observed in May. The monthly mean BC mass concentration varied between 0.31 μg/m(3) and 4.5 μg/m(3), and the single scattering albedo (SSA), estimated using the OPAC model, ranged from 0.87 to 0.97. Modeled aerosol optical properties were used to estimate the direct aerosol shortwave radiative forcing (DASRF) in the wavelength range 0.25 μm4.0 μm. The monthly mean forcing at the surface, at the top of the atmosphere (TOA) and in the atmosphere varied between -14.1 Wm(-2) and -35.6 Wm(-2), -6.7 Wm(-2) and -13.4 Wm(-2) and 5.5 Wm(-2) to 22.5 Wm(-2), respectively. These results indicate that the annual SSA cycle in the atmosphere is regulated by BC (absorbing aerosol), resulting in a positive forcing; however, the surface forcing was governed by the natural aerosol scattering, which yielded a negative forcing. These two conditions neutralized, resulting in a negative forcing at the TOA that remains nearly constant throughout the year. © 2013.

  8. Correcting Measurement Error in Satellite Aerosol Optical Depth with Machine Learning for Modeling PM2.5 in the Northeastern USA

    Directory of Open Access Journals (Sweden)

    Allan C. Just

    2018-05-01

    Full Text Available Satellite-derived estimates of aerosol optical depth (AOD are key predictors in particulate air pollution models. The multi-step retrieval algorithms that estimate AOD also produce quality control variables but these have not been systematically used to address the measurement error in AOD. We compare three machine-learning methods: random forests, gradient boosting, and extreme gradient boosting (XGBoost to characterize and correct measurement error in the Multi-Angle Implementation of Atmospheric Correction (MAIAC 1 × 1 km AOD product for Aqua and Terra satellites across the Northeastern/Mid-Atlantic USA versus collocated measures from 79 ground-based AERONET stations over 14 years. Models included 52 quality control, land use, meteorology, and spatially-derived features. Variable importance measures suggest relative azimuth, AOD uncertainty, and the AOD difference in 30–210 km moving windows are among the most important features for predicting measurement error. XGBoost outperformed the other machine-learning approaches, decreasing the root mean squared error in withheld testing data by 43% and 44% for Aqua and Terra. After correction using XGBoost, the correlation of collocated AOD and daily PM2.5 monitors across the region increased by 10 and 9 percentage points for Aqua and Terra. We demonstrate how machine learning with quality control and spatial features substantially improves satellite-derived AOD products for air pollution modeling.

  9. A long term study of the relations between erythemal UV-B irradiance, total ozone column, and aerosol optical depth at central Argentina

    Science.gov (United States)

    Palancar, Gustavo G.; Olcese, Luis E.; Achad, Mariana; López, María Laura; Toselli, Beatriz M.

    2017-09-01

    Global ultraviolet-B irradiance (UV-B, 280-315 nm) measurements made at the campus of the University of Córdoba, Argentina were analyzed to quantify the effects of ozone and aerosols on surface UV-B erythemal irradiance (UVER). The measurements have been carried out with a YES Pyranometer during the period 2000-2013. The effect of ozone and aerosols has been quantified by means of the Radiation Amplification Factor (RAF) and by an aerosol factor (AF, analogous to RAF), respectively. The overall mean RAF under cloudless conditions was (1.2 ± 0.3) %, ranging from 0.67 to 2.10% depending on solar zenith angle (SZA) and on Aerosol Optical Depth (AOD). The RAF increased with the SZA with a clear trend. Similarly, the aerosol effect under almost-constant ozone and SZA showed that, on average, a 1% increase in AOD forced a decrease of (0.15 ± 0.04) % in the UVER, with a range of 0.06 to 0.27 and no defined trend as a function of the SZA. To analyze the effect of absorbing aerosols, an effective single scattering albedo (SSA) was determined by comparing the experimental UVER with calculations carried out with the TUV radiative transfer model.

  10. Application of Spectral Analysis Techniques in the Intercomparison of Aerosol Data: Part III. Using Combined PCA to Compare Spatiotemporal Variability of MODIS, MISR and OMI Aerosol Optical Depth

    Science.gov (United States)

    Li, Jing; Carlson, Barbara E.; Lacis, Andrew A.

    2014-01-01

    Satellite measurements of global aerosol properties are very useful in constraining aerosol parameterization in climate models. The reliability of different data sets in representing global and regional aerosol variability becomes an essential question. In this study, we present the results of a comparison using combined principal component analysis (CPCA), applied to monthly mean, mapped (Level 3) aerosol optical depth (AOD) product from Moderate Resolution Imaging Spectroradiometer (MODIS), Multiangle Imaging Spectroradiometer (MISR), and Ozone Monitoring Instrument (OMI). This technique effectively finds the common space-time variability in the multiple data sets by decomposing the combined AOD field. The results suggest that all of the sensors capture the globally important aerosol regimes, including dust, biomass burning, pollution, and mixed aerosol types. Nonetheless, differences are also noted. Specifically, compared with MISR and OMI, MODIS variability is significantly higher over South America, India, and the Sahel. MODIS deep blue AOD has a lower seasonal variability in North Africa, accompanied by a decreasing trend that is not found in either MISR or OMI AOD data. The narrow swath of MISR results in an underestimation of dust variability over the Taklamakan Desert. The MISR AOD data also exhibit overall lower variability in South America and the Sahel. OMI does not capture the Russian wild fire in 2010 nor the phase shift in biomass burning over East South America compared to Central South America, likely due to cloud contamination and the OMI row anomaly. OMI also indicates a much stronger (boreal) winter peak in South Africa compared with MODIS and MISR.

  11. Assessing the effectiveness of RegCM4 regional climate model in simulating the aerosol optical depth patterns over the region of Eastern Mediterranean

    Science.gov (United States)

    Georgoulias, Aristeidis K.; Tsikerdekis, Athanasios; Ntogras, Christos; Zanis, Prodromos

    2014-05-01

    In this work, the ability of the regional climate model RegCM4 to simulate the aerosol optical depth (AOD) patterns over the region of Eastern Mediterranean is assessed. Three separate runs were implemented within the framework of the QUADIEEMS project for the time period 2000-2010 at a horizontal resolution of 50km covering the region of Europe. ERA-interim data were used as lateral boundary conditions while the model was driven by emissions from CMIP5. In the first case, the total of the aerosol types that RegCM4 accounts for were included (sulfate, black carbon, sea salt, dust), while in the other two cases only anthropogenic and dust particles were taken into account, respectively. The total AOD patterns were compared against level-2 satellite observations from MODIS TERRA and AQUA and ground-based measurements from 12 AERONET sites located in the region. In addition, the RegCM4 anthropogenic and dust AOD patterns were compared against the anthropogenic and dust component of MODIS AOD which was calculated using a combination of various satellite, model and reanalysis products. Our results indicate a significant underestimation of the anthropogenic AOD, while, on the contrary, the dust AOD fields are simulated in a more efficient way. The QUADIEEMS project is co-financed by the European Social Fund (ESF) and national resources under the operational programme Education and Lifelong Learning (EdLL) within the framework of the Action "Supporting Postdoctoral Researchers".

  12. How do A-train Sensors Inter-Compare in the Retrieval of Above-Cloud Aerosol Optical Depth? A Case Study based Assessment

    Science.gov (United States)

    Jethva, H. T.; Torres, O.; Waquet, F.; Chand, D.

    2013-12-01

    Atmospheric aerosols are known to produce a net cooling effect in the cloud-free conditions. However, when present over the reflective cloud decks, absorbing aerosols such as biomass burning generated smoke and wind-blown dust can potentially exert a large positive forcing through enhanced atmospheric heating resulting from cloud-aerosol radiative interactions. The interest on this aspect of aerosol science has grown significantly in the recent years. Particularly, development of the satellite-based retrieval techniques and unprecedented knowledge on the above-cloud aerosol optical depth (ACAOD) is of great relevance. A direct validation of satellite ACAOD is a difficult task primarily due to lack of ample in situ and/or remote sensing measurements of aerosols above cloud. In these circumstances, a comparative analysis on the inter-satellite ACAOD retrievals can be performed for the sack of consistency check. Here, we inter-compare the ACAOD of biomass burning plumes observed from different A-train sensors, i.e., MODIS [Jethva et al., 2013], CALIOP [Chand et al., 2008], POLDER [Waquet et al., 2009], and OMI [Torres et al., 2012]. These sensors have been shown to acquire sensitivity and independent capabilities to detect and retrieve aerosol loading above marine stratocumulus clouds--a kind of situation often found over the southeastern Atlantic Ocean during dry burning season. A systematic one-to-one comparison reveals that, in general, all passive sensors and CALIOP-based research methods retrieve comparable ACAOD over homogeneous cloud fields. The high-resolution sensors (MODIS and CALIOP) are able to retrieve aerosols over thin clouds but with larger discrepancies. Given the different types of sensor measurements processed with different algorithms, a reasonable agreement between them is encouraging. A direct validation of satellite-based ACAOD remains an open challenge for which dedicated field measurements over the region of frequent aerosol/cloud overlap are

  13. Solution of relativistic quantum optics problems using clusters of graphical processing units

    Energy Technology Data Exchange (ETDEWEB)

    Gordon, D.F., E-mail: daviel.gordon@nrl.navy.mil; Hafizi, B.; Helle, M.H.

    2014-06-15

    Numerical solution of relativistic quantum optics problems requires high performance computing due to the rapid oscillations in a relativistic wavefunction. Clusters of graphical processing units are used to accelerate the computation of a time dependent relativistic wavefunction in an arbitrary external potential. The stationary states in a Coulomb potential and uniform magnetic field are determined analytically and numerically, so that they can used as initial conditions in fully time dependent calculations. Relativistic energy levels in extreme magnetic fields are recovered as a means of validation. The relativistic ionization rate is computed for an ion illuminated by a laser field near the usual barrier suppression threshold, and the ionizing wavefunction is displayed.

  14. Evaluation of white-to-white distance and anterior chamber depth measurements using the IOL Master, slit-lamp adapted optical coherence tomography and digital photographs in phakic eyes.

    Science.gov (United States)

    Wilczyński, Michał; Pośpiech-Zabierek, Aleksandra

    2015-01-01

    The accurate measurement of the anterior chamber internal diameter and depth is important in ophthalmic diagnosis and before some eye surgery procedures. The purpose of the study was to compare the white-to-white distance measurements performed using the IOL-Master and photography with internal anterior chamber diameter determined using slit lamp adapted optical coherence tomography in healthy eyes, and to compare anterior chamber depth measurements by IOL-Master and slit lamp adapted optical coherence tomography. The data were gathered prospectively from a non-randomized consecutive series of patients. The examined group consisted of 46 eyes of 39 patients. White-to-white was measured using IOL-Master and photographs of the eye were taken with a digital camera. Internal anterior chamber diameter was measured with slit-lamp adapted optical coherence tomography. Anterior chamber depth was measured using the IOL Master and slit-lamp adapted optical coherence tomography. Statistical analysis was performed using parametric tests. A Bland-Altman plot was drawn. White-to-white distance by the IOL Master was 11.8 +/- 0.40 mm, on photographs it was 11.29 +/- 0.58 mm and internal anterior chamber diameter by slit-lamp adapted optical coherence tomography was 11.34?0.54 mm. A significant difference was found between IOL-Master and slit-lamp adapted optical coherence tomography (pphotographs (pphotographs (p>0.05). All measurements were correlated (Spearman pphotographs. In order to obtain accurate measurements of the internal anterior chamber diameter and anterior chamber depth, a method involving direct visualization of intraocular structures should be used.

  15. Comparison of aerosol optical depths from the Ozone Monitoring Instrument (OMI on Aura with results from airborne sunphotometry, other space and ground measurements during MILAGRO/INTEX-B

    Directory of Open Access Journals (Sweden)

    J. M. Livingston

    2009-09-01

    Full Text Available Airborne sunphotometer measurements are used to evaluate retrievals of extinction aerosol optical depth (AOD from spatially coincident and temporally near-coincident measurements by the Ozone Monitoring Instrument (OMI aboard the Aura satellite during the March 2006 Megacity Initiative-Local And Global Research Observations/Phase B of the Intercontinental Chemical Transport Experiment (MILAGRO/INTEX-B. The 14-channel NASA Ames Airborne Tracking Sunphotometer (AATS flew on nine missions over the Gulf of Mexico and four in or near the Mexico City area. Retrievals of AOD from near-coincident AATS and OMI measurements are compared for three flights over the Gulf of Mexico for flight segments when the aircraft flew at altitudes 60–70 m above sea level, and for one flight over the Mexico City area where the aircraft was restricted to altitudes ~320–800 m above ground level over the rural area and ~550–750 m over the city. OMI-measured top of atmosphere (TOA reflectances are routinely inverted to yield aerosol products such as AOD and aerosol absorption optical depth (AAOD using two different retrieval algorithms: a near-UV (OMAERUV and a multiwavelength (OMAERO technique. This study uses the archived Collection 3 data products from both algorithms. In particular, AATS and OMI AOD comparisons are presented for AATS data acquired in 20 OMAERUV retrieval pixels (15 over water and 19 OMAERO pixels (also 15 over water. At least four pixels for one of the over-water coincidences and all pixels for the over-land case were cloud-free. Coincident AOD retrievals from 17 pixels of the Moderate Resolution Imaging Spectroradiometer (MODIS aboard Aqua are available for two of the over-water flights and are shown to agree with AATS AODs to within root mean square (RMS differences of 0.00–0.06, depending on wavelength. Near-coincident ground-based AOD measurements from ground-based sun/sky radiometers operated as part of the Aerosol Robotic Network (AERONET

  16. SMAP Multi-Temporal Soil Moisture and Vegetation Optical Depth Retrievals in Vegetated Regions Including Higher-Order Soil-Canopy Interactions

    Science.gov (United States)

    Feldman, A.; Akbar, R.; Konings, A. G.; Piles, M.; Entekhabi, D.

    2017-12-01

    The Soil Moisture Active Passive (SMAP) mission utilizes a zeroth order radiative transfer model, known as the tau-omega model, to retrieve soil moisture from microwave brightness temperature observations. This model neglects first order scattering which is significant at L-Band in vegetated regions, or 30% of land cover. Previous higher order algorithms require extensive in-situ measurements and characterization of canopy layer physical properties. We propose a first order retrieval algorithm that approximately characterizes the eight first order emission pathways using rough surface reflectivity, vegetation optical depth (VOD), and scattering albedo terms. The recently developed Multi-Temporal Dual Channel Algorithm (MT-DCA) then retrieves these three parameters in a forward model without ancillary information under the assumption of temporally static albedo and constant vegetation water content between three day SMAP revisits. The approximated scattering terms are determined to be conservative estimates of analytically derived first order scattering terms. In addition, we find the first order algorithm to be more sensitive to surface emission than the tau-omega model. The simultaneously retrieved VOD, previously demonstrated to be proportional to vegetation water content, can provide insight into vegetation dynamics in regions with significant phenology. Specifically, dry tropical forests exhibit an increase in VOD during the dry season in alignment with prior studies that suggest that certain vegetative species green up during the dry season despite limited water availability. VOD retrieved using the first order algorithm and MT-DCA framework can therefore contribute to understanding of tropical forests' role in the carbon, energy, and water cycles, which has yet to be fully explained.

  17. Intercomparison between CMIP5 model and MODIS satellite-retrieved data of aerosol optical depth, cloud fraction, and cloud-aerosol interactions

    Science.gov (United States)

    Sockol, Alyssa; Small Griswold, Jennifer D.

    2017-08-01

    Aerosols are a critical component of the Earth's atmosphere and can affect the climate of the Earth through their interactions with solar radiation and clouds. Cloud fraction (CF) and aerosol optical depth (AOD) at 550 nm from the Moderate Resolution Imaging Spectroradiometer (MODIS) are used with analogous cloud and aerosol properties from Historical Phase 5 of the Coupled Model Intercomparison Project (CMIP5) model runs that explicitly include anthropogenic aerosols and parameterized cloud-aerosol interactions. The models underestimate AOD by approximately 15% and underestimate CF by approximately 10% overall on a global scale. A regional analysis is then used to evaluate model performance in two regions with known biomass burning activity and absorbing aerosol (South America (SAM) and South Africa (SAF)). In SAM, the models overestimate AOD by 4.8% and underestimate CF by 14%. In SAF, the models underestimate AOD by 35% and overestimate CF by 13.4%. Average annual cycles show that the monthly timing of AOD peaks closely match satellite data in both SAM and SAF for all except the Community Atmosphere Model 5 and Geophysical Fluid Dynamics Laboratory (GFDL) models. Monthly timing of CF peaks closely match for all models (except GFDL) for SAM and SAF. Sorting monthly averaged 2° × 2.5° model or MODIS CF as a function of AOD does not result in the previously observed "boomerang"-shaped CF versus AOD relationship characteristic of regions with absorbing aerosols from biomass burning. Cloud-aerosol interactions, as observed using daily (or higher) temporal resolution data, are not reproducible at the spatial or temporal resolution provided by the CMIP5 models.

  18. Citizen-Enabled Aerosol Measurements for Satellites (CEAMS): A Network for High-Resolution Measurements of PM2.5 and Aerosol Optical Depth

    Science.gov (United States)

    Pierce, J. R.; Volckens, J.; Ford, B.; Jathar, S.; Long, M.; Quinn, C.; Van Zyl, L.; Wendt, E.

    2017-12-01

    Atmospheric particulate matter with diameter smaller than 2.5 μm (PM2.5) is a pollutant that contributes to the development of human disease. Satellite-derived estimates of surface-level PM2.5 concentrations have the potential to contribute greatly to our understanding of how particulate matter affects health globally. However, these satellite-derived PM2.5 estimates are often uncertain due to a lack of information about the ratio of surface PM2.5 to aerosol optical depth (AOD), which is the primary aerosol retrieval made by satellite instruments. While modelling and statistical analyses have improved estimates of PM2.5:AOD, large uncertainties remain in situations of high PM2.5 exposure (such as urban areas and in wildfire-smoke plumes) where the health impacts of PM2.5 may be the greatest. Surface monitoring networks for co-incident PM2.5 and AOD measurements are extremely rare, even in the North America. To provide constraints for the PM2.5:AOD relationship, we have developed a relatively low-cost (application (iOS and Android). Sun photometry is performed across 4 discrete wavelengths that match those reported by the Aerosol Robotic Network (AERONET). Aerosol concentration is reported using both time-integrated filter mass (analyzed in an academic laboratory and reported as a 24-48hr average) and a continuous PM sensor within the instrument. Citizen scientists use the device to report daily AOD and PM2.5 measurements made in their backyards to a central server for data display and download. In this presentation, we provide an overview of (1) AOD and PM2.5 measurement calibration; (2) citizen recruiting and training efforts; and (3) results from our pilot citizen-science measurement campaign.

  19. Interannual variability of summertime aerosol optical depth over East Asia during 2000–2011: a potential influence from El Niño Southern Oscillation

    International Nuclear Information System (INIS)

    Liu, Yikun; Liu, Junfeng; Tao, Shu

    2013-01-01

    Aerosols degrade air quality, perturb atmospheric radiation, and impact regional and global climate. Due to the rapid increase in anthropogenic emissions, aerosol loading over East Asia (EA) is markedly higher than other industrialized regions, which motivates a need to characterize the evolution of aerosols and understand the associated drivers. Based on the MISR satellite data during 2000–2011, a wave-like interannual variation of summertime aerosol optical depth (SAOD) is observed over the highly populated North China Plain (NCP) in East Asia. Specifically, the peak-to-trough ratio of SAOD ranges from 1.4 to 1.6, with a period of 3–4 years. This variation pattern differs apparently from what has been seen in EA emissions, indicating a periodic change in regional climate pattern during the past decade. Investigations of meteorological fields over the region reveal that the high SAOD is generally associated with the enhanced Philippine Sea Anticyclone Anomaly (PSAA) which weakens southeasterlies over northeastern EA and depresses air ventilation. Alternatively, higher temperature and lower relative humidity are found to be coincident with reduced SAOD. The behavior of PSAA has been found previously to be modulated by the El Niño Southern Oscillations (ENSO), therefore ENSO could disturb the EA SAOD as well. Rather than changing coherently with the ENSO activity, the SAOD peaks over NCP are found to be accompanied by the rapid transition of El Niño warm to cold phases developed four months ahead. An index measuring the development of ENSO during January–April is able to capture the interannual variability of SAOD over NCP during 2000–2011. This finding indicates a need to integrate the large-scale periodic climate variability in the design of regional air quality policy. (letter)

  20. Statistical relationship between surface PM10 concentration and aerosol optical depth over the Sahel as a function of weather type, using neural network methodology

    Science.gov (United States)

    Yahi, H.; Marticorena, B.; Thiria, S.; Chatenet, B.; Schmechtig, C.; Rajot, J. L.; Crepon, M.

    2013-12-01

    work aims at assessing the capability of passive remote-sensed measurements such as aerosol optical depth (AOD) to monitor the surface dust concentration during the dry season in the Sahel region (West Africa). We processed continuous measurements of AODs and surface concentrations for the period (2006-2010) in Banizoumbou (Niger) and Cinzana (Mali). In order to account for the influence of meteorological condition on the relationship between PM10 surface concentration and AOD, we decomposed the mesoscale meteorological fields surrounding the stations into five weather types having similar 3-dimensional atmospheric characteristics. This classification was obtained by a clustering method based on nonlinear artificial neural networks, the so-called self-organizing map. The weather types were identified by processing tridimensional fields of meridional and zonal winds and air temperature obtained from European Centre for Medium-Range Weather Forecasts (ECMWF) model output centered on each measurement station. Five similar weather types have been identified at the two stations. Three of them are associated with the Harmattan flux; the other two correspond to northward inflow of the monsoon flow at the beginning or the end of the dry season. An improved relationship has been found between the surface PM10 concentrations and the AOD by using a dedicated statistical relationship for each weather type. The performances of the statistical inversion computed on the test data sets show satisfactory skills for most of the classes, much better than a linear regression. This should permit the inversion of the mineral dust concentration from AODs derived from satellite observations over the Sahel.

  1. Depth Dose Measurement using a Scintillating Fiber Optic Dosimeter for Proton Therapy Beam of the Passive-Scattering Mode Having Range Modulator Wheel

    Science.gov (United States)

    Hwang, Ui-Jung; Shin, Dongho; Lee, Se Byeong; Lim, Young Kyung; Jeong, Jong Hwi; Kim, Hak Soo; Kim, Ki Hwan

    2018-05-01

    To apply a scintillating fiber dosimetry system to measure the range of a proton therapy beam, a new method was proposed to correct for the quenching effect on measuring an spread out Bragg peak (SOBP) proton beam whose range is modulated by a range modulator wheel. The scintillating fiber dosimetry system was composed of a plastic scintillating fiber (BCF-12), optical fiber (SH 2001), photo multiplier tube (H7546), and data acquisition system (PXI6221 and SCC68). The proton beam was generated by a cyclotron (Proteus-235) in the National Cancer Center in Korea. It operated in the double-scattering mode and the spread out of the Bragg peak was achieved by a spinning range modulation wheel. Bragg peak beams and SOBP beams of various ranges were measured, corrected, and compared to the ion chamber data. For the Bragg peak beam, quenching equation was used to correct the quenching effect. On the proposed process of correcting SOBP beams, the measured data using a scintillating fiber were separated by the Bragg peaks that the SOBP beam contained, and then recomposed again to reconstruct an SOBP after correcting for each Bragg peak. The measured depth-dose curve for the single Bragg peak beam was well corrected by using a simple quenching equation. Correction for SOBP beam was conducted with a newly proposed method. The corrected SOBP signal was in accordance with the results measured with an ion chamber. We propose a new method to correct for the SOBP beam from the quenching effect in a scintillating fiber dosimetry system. This method can be applied to other scintillator dosimetry for radiation beams in which the quenching effect is shown in the scintillator.

  2. Estimating ground-level PM2.5 in eastern China using aerosol optical depth determined from the GOCI satellite instrument

    Science.gov (United States)

    Xu, J.-W.; Martin, R. V.; van Donkelaar, A.; Kim, J.; Choi, M.; Zhang, Q.; Geng, G.; Liu, Y.; Ma, Z.; Huang, L.; Wang, Y.; Chen, H.; Che, H.; Lin, P.; Lin, N.

    2015-11-01

    We determine and interpret fine particulate matter (PM2.5) concentrations in eastern China for January to December 2013 at a horizontal resolution of 6 km from aerosol optical depth (AOD) retrieved from the Korean geostationary ocean color imager (GOCI) satellite instrument. We implement a set of filters to minimize cloud contamination in GOCI AOD. Evaluation of filtered GOCI AOD with AOD from the Aerosol Robotic Network (AERONET) indicates significant agreement with mean fractional bias (MFB) in Beijing of 6.7 % and northern Taiwan of -1.2 %. We use a global chemical transport model (GEOS-Chem) to relate the total column AOD to the near-surface PM2.5. The simulated PM2.5 / AOD ratio exhibits high consistency with ground-based measurements in Taiwan (MFB = -0.52 %) and Beijing (MFB = -8.0 %). We evaluate the satellite-derived PM2.5 versus the ground-level PM2.5 in 2013 measured by the China Environmental Monitoring Center. Significant agreement is found between GOCI-derived PM2.5 and in situ observations in both annual averages (r2 = 0.66, N = 494) and monthly averages (relative RMSE = 18.3 %), indicating GOCI provides valuable data for air quality studies in Northeast Asia. The GEOS-Chem simulated chemical composition of GOCI-derived PM2.5 reveals that secondary inorganics (SO42-, NO3-, NH4+) and organic matter are the most significant components. Biofuel emissions in northern China for heating increase the concentration of organic matter in winter. The population-weighted GOCI-derived PM2.5 over eastern China for 2013 is 53.8 μg m-3, with 400 million residents in regions that exceed the Interim Target-1 of the World Health Organization.

  3. Design and implementation of interface units for high speed fiber optics local area networks and broadband integrated services digital networks

    Science.gov (United States)

    Tobagi, Fouad A.; Dalgic, Ismail; Pang, Joseph

    1990-01-01

    The design and implementation of interface units for high speed Fiber Optic Local Area Networks and Broadband Integrated Services Digital Networks are discussed. During the last years, a number of network adapters that are designed to support high speed communications have emerged. This approach to the design of a high speed network interface unit was to implement package processing functions in hardware, using VLSI technology. The VLSI hardware implementation of a buffer management unit, which is required in such architectures, is described.

  4. Depth of Cervical Intraepithelial Neoplasia Grade 3 in Peruvian Women: Implications for Therapeutic Depth of Necrosis.

    Science.gov (United States)

    Taxa, Luis; Jeronimo, Jose; Alonzo, Todd A; Gage, Julia; Castle, Philip E; Cremer, Miriam L; Felix, Juan C

    2018-01-01

    To determine the involvement of cervical intraepithelial neoplasia grade 3 (CIN3) in a population of women in a lower-resource setting. One hundred twelve consecutive cone excision specimens with histological diagnosis of CIN3 were retrieved from the National Institute of Neoplastic Diseases in Lima Peru. Two pathologists independently evaluated each specimen microscopically and confirmed 107 cases that could be measured by optical micrometry. Depth and breadth of the lesions were measured microscopically. The mean maximal depth of cervical involvement by CIN3 was 2 ± 0.13 mm; depth was less than 3.5 mm in 89.7% of cases and less than 5 mm in 93.5%. Mean breadth of CIN3 was 7.3 ± 4.4 mm; breadth was less than 15.9 mm in 95% of cases and less than 20.5 mm in 99.7%. The correlation coefficient between breadth and depth of CIN3 was 0.61. No significant correlation was found between age and depth. Depth of CIN3 involvement in a developing country is significantly deeper than that reported in the United States. Treatment selection for women with CIN3 and risk of treatment failure may vary between developing and developed countries because of the difference in the depth of lesions. Countries with underscreened populations need to consider the increased disease severity in devising treatment strategies.

  5. Integration of agglutination assay for protein detection in microfluidic disc using Blu-ray optical pickup unit and optical fluid scanning

    DEFF Research Database (Denmark)

    Uddin, Rokon; Burger, Robert; Donolato, Marco

    2015-01-01

    We present a novel strategy for thrombin detection by combining a magnetic bead based agglutination assay and low-cost microfluidic disc. The detection method is based on an optomagnetic readout system implemented using a Blu-ray optical pickup unit (OPU) as main optoelectronic component. The ass...

  6. All-optical quantum computing with a hybrid solid-state processing unit

    International Nuclear Information System (INIS)

    Pei Pei; Zhang Fengyang; Li Chong; Song Heshan

    2011-01-01

    We develop an architecture of a hybrid quantum solid-state processing unit for universal quantum computing. The architecture allows distant and nonidentical solid-state qubits in distinct physical systems to interact and work collaboratively. All the quantum computing procedures are controlled by optical methods using classical fields and cavity QED. Our methods have a prominent advantage of the insensitivity to dissipation process benefiting from the virtual excitation of subsystems. Moreover, the quantum nondemolition measurements and state transfer for the solid-state qubits are proposed. The architecture opens promising perspectives for implementing scalable quantum computation in a broader sense that different solid-state systems can merge and be integrated into one quantum processor afterward.

  7. Using NASA Satellite Aerosol Optical Depth to Enhance PM2.5 Concentration Datasets for Use in Human Health and Epidemiology Studies

    Science.gov (United States)

    Huff, A. K.; Weber, S.; Braggio, J.; Talbot, T.; Hall, E.

    2012-12-01

    Fine particulate matter (PM2.5) is a criterion air pollutant, and its adverse impacts on human health are well established. Traditionally, studies that analyze the health effects of human exposure to PM2.5 use concentration measurements from ground-based monitors and predicted PM2.5 concentrations from air quality models, such as the U.S. EPA's Community Multi-scale Air Quality (CMAQ) model. There are shortcomings associated with these datasets, however. Monitors are not distributed uniformly across the U.S., which causes spatially inhomogeneous measurements of pollutant concentrations. There are often temporal variations as well, since not all monitors make daily measurements. Air quality model output, while spatially and temporally uniform, represents predictions of PM2.5 concentrations, not actual measurements. This study is exploring the potential of combining Aerosol Optical Depth (AOD) data from the MODIS instrument on NASA's Terra and Aqua satellites with PM2.5 monitor data and CMAQ predictions to create PM2.5 datasets that more accurately reflect the spatial and temporal variations in ambient PM2.5 concentrations on the metropolitan scale, with the overall goal of enhancing capabilities for environmental public health decision-making. AOD data provide regional information about particulate concentrations that can fill in the spatial and temporal gaps in the national PM2.5 monitor network. Furthermore, AOD is a measurement, so it reflects actual concentrations of particulates in the atmosphere, in contrast to PM2.5 predictions from air quality models. Results will be presented from the Battelle/U.S. EPA statistical Hierarchical Bayesian Model (HBM), which was used to combine three PM2.5 concentration datasets: monitor measurements, AOD data, and CMAQ model predictions. The study is focusing on the Baltimore, MD and New York City, NY metropolitan regions for the period 2004-2006. For each region, combined monitor/AOD/CMAQ PM2.5 datasets generated by the HBM

  8. A New Hybrid Spatio-temporal Model for Estimating Daily Multi-year PM2.5 Concentrations Across Northeastern USA Using High Resolution Aerosol Optical Depth Data

    Science.gov (United States)

    Kloog, Itai; Chudnovsky, Alexandra A.; Just, Allan C.; Nordio, Francesco; Koutrakis, Petros; Coull, Brent A.; Lyapustin, Alexei; Wang, Yujie; Schwartz, Joel

    2014-01-01

    The use of satellite-based aerosol optical depth (AOD) to estimate fine particulate matter PM(sub 2.5) for epidemiology studies has increased substantially over the past few years. These recent studies often report moderate predictive power, which can generate downward bias in effect estimates. In addition, AOD measurements have only moderate spatial resolution, and have substantial missing data. We make use of recent advances in MODIS satellite data processing algorithms (Multi-Angle Implementation of Atmospheric Correction (MAIAC), which allow us to use 1 km (versus currently available 10 km) resolution AOD data.We developed and cross validated models to predict daily PM(sub 2.5) at a 1X 1 km resolution across the northeastern USA (New England, New York and New Jersey) for the years 2003-2011, allowing us to better differentiate daily and long term exposure between urban, suburban, and rural areas. Additionally, we developed an approach that allows us to generate daily high-resolution 200 m localized predictions representing deviations from the area 1 X 1 km grid predictions. We used mixed models regressing PM(sub 2.5) measurements against day-specific random intercepts, and fixed and random AOD and temperature slopes. We then use generalized additive mixed models with spatial smoothing to generate grid cell predictions when AOD was missing. Finally, to get 200 m localized predictions, we regressed the residuals from the final model for each monitor against the local spatial and temporal variables at each monitoring site. Our model performance was excellent (mean out-of-sample R(sup 2) = 0.88). The spatial and temporal components of the out-of-sample results also presented very good fits to the withheld data (R(sup 2) = 0.87, R(sup)2 = 0.87). In addition, our results revealed very little bias in the predicted concentrations (Slope of predictions versus withheld observations = 0.99). Our daily model results show high predictive accuracy at high spatial resolutions

  9. Inter-annual variability of aerosol optical depth over the tropical Atlantic Ocean based on MODIS-Aqua observations over the period 2002-2012

    Science.gov (United States)

    Gkikas, Antonis; Hatzianastassiou, Nikolaos

    2013-04-01

    The tropical Atlantic Ocean is affected by dust and biomass burning aerosol loads transported from the western parts of the Saharan desert and the sub-Sahel regions, respectively. The spatial and temporal patterns of this transport are determined by the aerosol emission rates, their deposition (wet and dry), by the latitudinal shift of the Intertropical Convergence Zone (ITCZ) and the prevailing wind fields. More specifically, in summer, Saharan dust aerosols are transported towards the Atlantic Ocean, even reaching the Gulf of Mexico, while in winter the Atlantic Ocean transport takes place in more southern latitudes, near the equator, sometimes reaching the northern parts of South America. In the later case, dust is mixed with biomass burning aerosols originating from agricultural activities in the sub-Sahel, associated with prevailing north-easterly airflow (Harmattan winds). Satellite observations are the appropriate tool for describing this African aerosol export, which is important to atmospheric, oceanic and climate processes, offering the advantage of complete spatial coverage. In the present study, we use satellite measurements of aerosol optical depth at 550nm (AOD550nm), on a daily and monthly basis, derived from MODIS-Aqua platform, at 1ox1o spatial resolution (Level 3), for the period 2002-2012. The primary objective is to determine the pixel-level and regional mean anomalies of AOD550nm over the entire study period. The regime of the anomalies of African export is interpreted in relation to the aerosol source areas, precipitation, wind patterns and temporal variability of the North Atlantic Oscillation Index (NAOI). In order to ensure availability of AOD over the Sahara desert, MODIS-Aqua Deep Blue products are also used. As for precipitation, Global Precipitation Climatology Project (GPCP) data at 2.5ox2.5o are used. The wind fields are taken from the National Center for Environmental Prediction (NCEP). Apart from the regime of African aerosol export

  10. Verification, improvement and application of aerosol optical depths in China Part 1: Inter-comparison of NPP-VIIRS and Aqua-MODIS

    Science.gov (United States)

    Wei, Jing; Sun, Lin; Huang, Bo; Bilal, Muhammad; Zhang, Zhaoyang; Wang, Lunche

    2018-02-01

    The objective of this study is to evaluate typical aerosol optical depth (AOD) products in China, which experienced seriously increasing atmospheric particulate pollution. For this, the Aqua-MODerate resolution Imaging Spectroradiometer (MODIS) AOD products (MYD04) at 10 km spatial resolution and Visible Infrared Imaging Radiometer Suite (VIIRS) Environmental Data Record (EDR) AOD product at 6 km resolution for different Quality Flags (QF) are obtained for validation against AErosol RObotic NETwork (AERONET) AOD measurements during 2013-2016. Results show that VIIRS EDR similarly Dark Target (DT) and MODIS DT algorithms perform worse with only 45.36% and 45.59% of the retrievals (QF = 3) falling within the Expected Error (EE, ±(0.05 + 15%)) compared to the Deep Blue (DB) algorithm (69.25%, QF ≥ 2). The DT retrievals perform poorly over the Beijing-Tianjin-Hebei (BTH) and Yangtze-River-Delta (YRD) regions, which significantly overestimate the AOD observations, but the performance is better over the Pearl-River-Delta (PRD) region than DB retrievals, which seriously under-estimate the AOD loadings. It is not surprising that the DT algorithm performs better over vegetated areas, while the DB algorithm performs better over bright areas mainly depends on the accuracy of surface reflectance estimation over different land use types. In general, the sensitivity of aerosol to apparent reflectance reduces by about 34% with an increasing surface reflectance by 0.01. Moreover, VIIRS EDR and MODIS DT algorithms perform overall better in the winter as 64.53% and 72.22% of the retrievals are within the EE but with less retrievals. However, the DB algorithm performs worst (57.17%) in summer mainly affected by the vegetation growth but there are overall high accuracies with more than 62% of the collections falling within the EE in other three seasons. Results suggest that the quality assurance process can help improve the overall data quality for MYD04 DB retrievals, but it is

  11. Interannual variation in the fine-mode MODIS aerosol optical depth and its relationship to the changes in sulfur dioxide emissions in China between 2000 and 2010

    Directory of Open Access Journals (Sweden)

    S. Itahashi

    2012-03-01

    Full Text Available Anthropogenic SO2 emissions increased alongside economic development in China at a rate of 12.7% yr−1 from 2000 to 2005. However, under new Chinese government policy, SO2 emissions declined by 3.9% yr−1 between 2005 and 2009. Between 2000 and 2010, we found that the variability in the fine-mode (submicron aerosol optical depth (AOD over the oceans adjacent to East Asia increased by 3–8% yr−1 to a peak around 2005–2006 and subsequently decreased by 2–7% yr−1, based on observations by the Moderate Resolution Imaging Spectroradiometer (MODIS on board NASA's Terra satellite and simulations by a chemical transport model. This trend is consistent with ground-based observations of aerosol particles at a mountainous background observation site in central Japan. These fluctuations in SO2 emission intensity and fine-mode AOD are thought to reflect the widespread installation of fuel-gas desulfurization (FGD devices in power plants in China, because aerosol sulfate is a major determinant of the fine-mode AOD in East Asia. Using a chemical transport model, we confirmed that the contribution of particulate sulfate to the fine-mode AOD is more than 70% of the annual mean and that the abovementioned fluctuation in fine-mode AOD is caused mainly by changes in SO2 emission rather than by other factors such as varying meteorological conditions in East Asia. A strong correlation was also found between satellite-retrieved SO2 vertical column density and bottom-up SO2 emissions, both of which were also consistent with observed fine-mode AOD trends. We propose a simplified approach for evaluating changes in SO2 emissions in China, combining the use of modeled sensitivity coefficients that describe the variation of fine-mode AOD with changes in SO2 emissions and satellite retrieval. Satellite measurements of fine-mode AOD

  12. Validation of MODIS derived aerosol optical depth and an investigation on aerosol transport over the South East Arabian Sea during ARMEX-II

    Directory of Open Access Journals (Sweden)

    M. Aloysius

    2009-06-01

    Full Text Available The influence of wind and humidity on aerosol optical depth (AOD over the Arabian sea is being investigated using MODIS (Moderate Resolution Imaging Spectroradiometer Level 3 (Collection-5 and NCEP (National Centres for Environmental Prediction reanalysis data for the second phase of the Arabian Sea Monsoon Experiment (ARMEX-II over the South East Arabian Sea (SEAS in the pre-monsoon period (14 March–10 April 2003. In order to qualify MODIS data for this study, MODIS aerosol parameters were first compared with ship borne Microtops measurements. This showed correlations 0.96–0.97 in the case of spectral AODs and a correlation 0.72 for the angstrom exponents. The daily AOD data from MODIS and winds from NCEP reveal that the ship observed episodic enhancement and decay of AOD at the TSL (Time Series Location during 23 March–6 April 2003 was caused by the southward drift of an aerosol pocket driven by an intensification and reduction of surface pressure in the North Western Arabian Sea with a low altitude convergence prevailing over SEAS. The AOD increase coincided with a decrease in the Angstrom exponent and the fine mode fraction suggesting the pocket being dominated by coarse mode particles. A partial correlation analysis reveals that the lower altitude wind convergence is the most influential atmospheric variable in modulating AOD over the ARMEX-II domain during the TSL period. However, surface winds at a distant zone in the north/north west upwind direction also had a moderate influence, though with a lag of two days. But this effect was minor since the winds were not strong enough to produce marine aerosols matching with the high AODs over the ARMEX-II domain. These findings and the similarity between MODIS column mass concentration and the ship borne QCM (Quartz Crystal Microbalance measured coarse mode mass concentration, suggest that the aerosol pocket was mostly composed of coarse mode mineral dust in the lower atmospheric altitudes

  13. Mass concentration, optical depth and carbon composition of particulate matter in the major southern West African cities of Cotonou (Benin) and Abidjan (Côte d'Ivoire)

    Science.gov (United States)

    Djossou, Julien; Léon, Jean-François; Barthélemy Akpo, Aristide; Liousse, Cathy; Yoboué, Véronique; Bedou, Mouhamadou; Bodjrenou, Marleine; Chiron, Christelle; Galy-Lacaux, Corinne; Gardrat, Eric; Abbey, Marcellin; Keita, Sékou; Bahino, Julien; Touré N'Datchoh, Evelyne; Ossohou, Money; Awanou, Cossi Norbert

    2018-05-01

    Air quality degradation is a major issue in the large conurbations on the shore of the Gulf of Guinea. We present for the first time PM2.5 time series collected in Cotonou, Benin, and Abidjan, Côte d'Ivoire, from February 2015 to March 2017. Measurements were performed in the vicinity of major combustion aerosol sources: Cotonou/traffic (CT), Abidjan/traffic (AT), Abidjan/landfill (AL) and Abidjan/domestic fires (ADF). We report the weekly PM2.5 mass and carbonaceous content as elemental (EC) and organic (OC) carbon concentrations. We also measure the aerosol optical depth (AOD) and the Ångström exponent in both cities. The average PM2.5 mass concentrations were 32 ± 32, 32 ± 24 and 28 ± 19 µg m-3 at traffic sites CT and AT and landfill site AL, respectively. The domestic fire site shows a concentration of 145 ± 69 µg m-3 due to the contribution of smoking and roasting activities. The highest OC and EC concentrations were also measured at ADF at 71 ± 29 and 15 ± 9 µg m-3, respectively, while the other sites present OC concentration between 8 and 12 µg m-3 and EC concentrations between 2 and 7 µg m-3. The OC / EC ratio is 4.3 at CT and 2.0 at AT. This difference highlights the influence of two-wheel vehicles using gasoline in Cotonou compared to that of four-wheel vehicles using diesel fuel in Abidjan. AOD was rather similar in both cities, with a mean value of 0.58 in Cotonou and of 0.68 in Abidjan. The seasonal cycle is dominated by the large increase in surface mass concentration and AOD during the long dry season (December-February) as expected due to mineral dust advection and biomass burning activities. The lowest concentrations are observed during the short dry season (August-September) due to an increase in surface wind speed leading to a better ventilation. On the other hand, the high PM2.5 / AOD ratio in the short wet season (October-November) indicates the stagnation of local pollution.

  14. Mass concentration, optical depth and carbon composition of particulate matter in the major southern West African cities of Cotonou (Benin and Abidjan (Côte d'Ivoire

    Directory of Open Access Journals (Sweden)

    J. Djossou

    2018-05-01

    Full Text Available Air quality degradation is a major issue in the large conurbations on the shore of the Gulf of Guinea. We present for the first time PM2.5 time series collected in Cotonou, Benin, and Abidjan, Côte d'Ivoire, from February 2015 to March 2017. Measurements were performed in the vicinity of major combustion aerosol sources: Cotonou/traffic (CT, Abidjan/traffic (AT, Abidjan/landfill (AL and Abidjan/domestic fires (ADF. We report the weekly PM2.5 mass and carbonaceous content as elemental (EC and organic (OC carbon concentrations. We also measure the aerosol optical depth (AOD and the Ångström exponent in both cities. The average PM2.5 mass concentrations were 32 ± 32, 32 ± 24 and 28 ± 19 µg m−3 at traffic sites CT and AT and landfill site AL, respectively. The domestic fire site shows a concentration of 145 ± 69 µg m−3 due to the contribution of smoking and roasting activities. The highest OC and EC concentrations were also measured at ADF at 71 ± 29 and 15 ± 9 µg m−3, respectively, while the other sites present OC concentration between 8 and 12 µg m−3 and EC concentrations between 2 and 7 µg m−3. The OC ∕ EC ratio is 4.3 at CT and 2.0 at AT. This difference highlights the influence of two-wheel vehicles using gasoline in Cotonou compared to that of four-wheel vehicles using diesel fuel in Abidjan. AOD was rather similar in both cities, with a mean value of 0.58 in Cotonou and of 0.68 in Abidjan. The seasonal cycle is dominated by the large increase in surface mass concentration and AOD during the long dry season (December–February as expected due to mineral dust advection and biomass burning activities. The lowest concentrations are observed during the short dry season (August–September due to an increase in surface wind speed leading to a better ventilation. On the other hand, the high PM2.5 ∕ AOD ratio in the short wet season (October–November indicates the

  15. PM 2.5 mass concentrations in comparison with aerosol optical depths over the Arabian Sea and Indian Ocean during winter monsoon

    Science.gov (United States)

    Ramachandran, S.

    An analysis of PM 2.5 mass concentrations and 0.5 μm aerosol optical depths (AODs) during the Northeast winter monsoon seasons of 1996-2000 is performed and intercompared. AODs are found to show diurnal variations over Coastal India (CI) (west coast) while they are relatively smooth over the Arabian Sea (AS) (5-20°N) and tropical Indian Ocean (TIO) (5°N-20°S). PM 2.5, PM 10 and total mass concentrations show less variations in a day over these oceanic regions. Columnar AODs are found to increase with an increase in the marine boundary layer aerosol concentrations over CI and AS while an opposite trend is seen over TIO. The yearly-mean AODs and mass concentrations are found to increase over CI and AS, over TIO the mass concentrations increased while the AODs decreased during 1996-2000. It is found from the 7-days air back trajectory analyses that at different altitudes air masses can originate from different source regions leading to changes in chemical, physical and optical characteristics of the aerosol between the surface and column. The differences in the surface and columnar measurements could also occur due to changes in the meteorological conditions, wind patterns, in addition to changes in production and subsequently the transport of aerosols. Least-squares fits to the above intercomparison resulted in intercepts of 0.24 and 0.22 over CI and AS indicating that the background AODs over these oceanic regions are higher. An examination of the daily-mean wind speeds and PM 2.5 mass concentrations yielded an index of wind dependence of 0.04 for AS and 0.07 for TIO. The background PM 2.5 mass concentrations are also found to be high at 36 and 25 μg m -3 over AS and TIO, respectively, indicating a stronger influence from the continent. Frequency distribution figures show that 28% of the PM 2.5 values over CI lie in the 60-80 μg m -3 range. Over AS the dominant mode of distribution is 40-60 μg m -3 with a peak value of 42%. Over TIO PM 2.5 values are found to

  16. The Association of Arsenic With Redox Conditions, Depth, and Ground-Water Age in the Glacial Aquifer System of the Northern United States

    Science.gov (United States)

    Thomas, Mary Ann

    2007-01-01

    More than 800 wells in the glacial aquifer system of the Northern United States were sampled for arsenic as part of U.S. Geological Survey National Water-Quality Assessment (NAWQA) studies during 1991-2003. Elevated arsenic concentrations (greater than or equal to 10 micrograms per liter) were detected in 9 percent of samples. Elevated arsenic concentrations were associated with strongly reducing conditions. Of the samples classified as iron reducing or sulfate reducing, arsenic concentrations were elevated in 19 percent. Of the methanogenic samples, arsenic concentrations were elevated in 45 percent. In contrast, concentrations of arsenic were elevated in only 1 percent of oxic samples. Arsenic concentrations were also related to ground-water age. Elevated arsenic concentrations were detected in 34 percent of old waters (recharged before 1953) as compared to 4 percent of young waters (recharged since 1953). For samples classified as both old and methanogenic, elevated arsenic concentrations were detected in 62 percent of samples, as compared to 1 percent for samples classified as young and oxic. Arsenic concentrations were also correlated with well depth and concentrations of several chemical constituents, including (1) constituents linked to redox processes and (2) anions or oxyanions that sorb to iron oxides. Observations from the glacial aquifer system are consistent with the idea that the predominant source of arsenic is iron oxides and the predominant mechanism for releasing arsenic to the ground water is reductive desorption or reductive dissolution. Arsenic is also released from iron oxides under oxic conditions, but on a more limited basis and at lower concentrations. Logistic regression was used to investigate the relative significance of redox, ground-water age, depth, and other water-quality constituents as indicators of elevated arsenic concentrations in the glacial aquifer system. The single variable that explained the greatest amount of variation in

  17. Trinary arithmetic and logic unit (TALU) using savart plate and spatial light modulator (SLM) suitable for optical computation in multivalued logic

    Science.gov (United States)

    Ghosh, Amal K.; Bhattacharya, Animesh; Raul, Moumita; Basuray, Amitabha

    2012-07-01

    Arithmetic logic unit (ALU) is the most important unit in any computing system. Optical computing is becoming popular day-by-day because of its ultrahigh processing speed and huge data handling capability. Obviously for the fast processing we need the optical TALU compatible with the multivalued logic. In this regard we are communicating the trinary arithmetic and logic unit (TALU) in modified trinary number (MTN) system, which is suitable for the optical computation and other applications in multivalued logic system. Here the savart plate and spatial light modulator (SLM) based optoelectronic circuits have been used to exploit the optical tree architecture (OTA) in optical interconnection network.

  18. Determination of the depth-resolved Stokes parameters of light backscattered from turbid media by use of polarization-sensitive optical coherence tomography

    International Nuclear Information System (INIS)

    Boer, J.F. de; Milner, T.E.; Nelson, J.S.

    1999-01-01

    Polarization-sensitive optical coherence tomography (PS-OCT) was used to characterize completely the polarization state of light backscattered from turbid media. Using a low-coherence light source, one can determine the Stokes parameters of backscattered light as a function of optical path in turbid media. To demonstrate the application of this technique we determined the birefringence and the optical axis in fibrous tissue (rodent muscle) and in vivo rodent skin. PS-OCT has potentially useful applications in biomedical optics by imaging simultaneously the structural properties of turbid biological materials and their effects on the polarization state of backscattered light. This method may also find applications in material science for investigation of polarization properties (e.g., birefringence) in opaque media such as ceramics and crystals. copyright 1999 Optical Society of America

  19. Optics

    CERN Document Server

    Mathieu, Jean Paul

    1975-01-01

    Optics, Parts 1 and 2 covers electromagnetic optics and quantum optics. The first part of the book examines the various of the important properties common to all electromagnetic radiation. This part also studies electromagnetic waves; electromagnetic optics of transparent isotropic and anisotropic media; diffraction; and two-wave and multi-wave interference. The polarization states of light, the velocity of light, and the special theory of relativity are also examined in this part. The second part is devoted to quantum optics, specifically discussing the classical molecular theory of optical p

  20. Beyond MOS and fibers: Optical Fourier-transform Imaging Unit for Cananea Observatory (OFIUCO)

    Science.gov (United States)

    Nieto-Suárez, M. A.; Rosales-Ortega, F. F.; Castillo, E.; García, P.; Escobedo, G.; Sánchez, S. F.; González, J.; Iglesias-Páramo, J.; Mollá, M.; Chávez, M.; Bertone, E.; et al.

    2017-11-01

    Many physical processes in astronomy are still hampered by the lack of spatial and spectral resolution, and also restricted to the field-of-view (FoV) of current 2D spectroscopy instruments available worldwide. It is due to that, many of the ongoing or proposed studies are based on large-scale imaging and/or spectroscopic surveys. Under this philosophy, large aperture telescopes are dedicated to the study of intrinsically faint and/or distance objects, covering small FoVs, with high spatial resolution, while smaller telescopes are devoted to wide-field explorations. However, future astronomical surveys, should be addressed by acquiring un-biases, spatially resolved, high-quality spectroscopic information for a wide FoV. Therefore, and in order to improve the current instrumental offer in the Observatorio Astrofísico Guillermo Haro (OAGH) in Cananea, Mexico (INAOE); and to explore a possible instrument for the future Telescopio San Pedro Mártir (6.5m), we are currently integrating at INAOE an instrument prototype that will provide us with un-biased wide-field (few arcmin) spectroscopic information, and with the flexibility of operating at different spectral resolutions (R 1-20000), with a spatial resolution limited by seeing, and therefore, to be used in a wide range of astronomical problems. This instrument called OFIUCO: Optical Fourier-transform Imaging Unit for Cananea Observatory, will make use of the Fourier Transform Spectroscopic technique, which has been proved to be feasible in the optical wavelength range (350-1000 nm) with designs such as SITELLE (CFHT). We describe here the basic technical description of a Fourier transform spectrograph with important modifications from previous astronomical versions, as well as the technical advantages and weakness, and the science cases in which this instrument can be implemented.

  1. Optics

    CERN Document Server

    Fincham, W H A

    2013-01-01

    Optics: Ninth Edition Optics: Ninth Edition covers the work necessary for the specialization in such subjects as ophthalmic optics, optical instruments and lens design. The text includes topics such as the propagation and behavior of light; reflection and refraction - their laws and how different media affect them; lenses - thick and thin, cylindrical and subcylindrical; photometry; dispersion and color; interference; and polarization. Also included are topics such as diffraction and holography; the limitation of beams in optical systems and its effects; and lens systems. The book is recommen

  2. Optical Coating Performance and Thermal Structure Design for Heat Reflectors of JWST Electronic Control Unit

    Science.gov (United States)

    Quijada, Manuel A.; Threat, Felix; Garrison, Matt; Perrygo, Chuck; Bousquet, Robert; Rashford, Robert

    2008-01-01

    The James Webb Space Telescope (JWST) consists of an infrared-optimized Optical Telescope Element (OTE) that is cooled down to 40 degrees Kelvin. A second adjacent component to the OTE is the Integrated Science Instrument Module, or ISIM. This module includes the electronic compartment, which provides the mounting surfaces and ambient thermally controlled environment for the instrument control electronics. Dissipating the 200 watts generated from the ISIM structure away from the OTE is of paramount importance so that the spacecraft's own heat does not interfere with the infrared light detected from distant cosmic sources. This technical challenge is overcome by a thermal subsystem unit that provides passive cooling to the ISIM control electronics. The proposed design of this thermal radiator consists of a lightweight structure made out of composite materials and low-emittance metal coatings. In this paper, we will present characterizations of the coating emittance, bidirectional reflectance, and mechanical structure design that will affect the performance of this passive cooling system.

  3. Real-time speckle variance swept-source optical coherence tomography using a graphics processing unit.

    Science.gov (United States)

    Lee, Kenneth K C; Mariampillai, Adrian; Yu, Joe X Z; Cadotte, David W; Wilson, Brian C; Standish, Beau A; Yang, Victor X D

    2012-07-01

    Advances in swept source laser technology continues to increase the imaging speed of swept-source optical coherence tomography (SS-OCT) systems. These fast imaging speeds are ideal for microvascular detection schemes, such as speckle variance (SV), where interframe motion can cause severe imaging artifacts and loss of vascular contrast. However, full utilization of the laser scan speed has been hindered by the computationally intensive signal processing required by SS-OCT and SV calculations. Using a commercial graphics processing unit that has been optimized for parallel data processing, we report a complete high-speed SS-OCT platform capable of real-time data acquisition, processing, display, and saving at 108,000 lines per second. Subpixel image registration of structural images was performed in real-time prior to SV calculations in order to reduce decorrelation from stationary structures induced by the bulk tissue motion. The viability of the system was successfully demonstrated in a high bulk tissue motion scenario of human fingernail root imaging where SV images (512 × 512 pixels, n = 4) were displayed at 54 frames per second.

  4. Slug Test Characterization Results for Multi-Test/Depth Intervals Conducted During the Drilling of CERCLA Operable Unit OU ZP-1 Wells 299-W11-43, 299-W15-50, and 299-W18-16

    Energy Technology Data Exchange (ETDEWEB)

    Spane, Frank A.; Newcomer, Darrell R.

    2010-06-21

    The following report presents test descriptions and analysis results for multiple, stress level slug tests that were performed at selected test/depth intervals within three Operable Unit (OU) ZP-1 wells: 299-W11-43 (C4694/Well H), 299-W15-50 (C4302/Well E), and 299-W18-16 (C4303/Well D). These wells are located within south-central region of the Hanford Site 200-West Area (Figure 1.1). The test intervals were characterized as the individual boreholes were advanced to their final drill depths. The primary objective of the hydrologic tests was to provide information pertaining to the areal variability and vertical distribution of hydraulic conductivity with depth at these locations within the OU ZP-1 area. This type of characterization information is important for predicting/simulating contaminant migration (i.e., numerical flow/transport modeling) and designing proper monitor well strategies for OU and Waste Management Area locations.

  5. Slug Test Characterization Results for Multi-Test/Depth Intervals Conducted During the Drilling of CERCLA Operable Unit OU UP-1 Wells 299-W19-48, 699-30-66, and 699-36-70B

    Energy Technology Data Exchange (ETDEWEB)

    Spane, Frank A.; Newcomer, Darrell R.

    2010-06-15

    This report presents test descriptions and analysis results for multiple, stress-level slug tests that were performed at selected test/depth intervals within three Operable Unit (OU) UP-1 wells: 299-W19-48 (C4300/Well K), 699-30-66 (C4298/Well R), and 699-36-70B (C4299/Well P). These wells are located within, adjacent to, and to the southeast of the Hanford Site 200-West Area. The test intervals were characterized as the individual boreholes were advanced to their final drill depths. The primary objective of the hydrologic tests was to provide information pertaining to the areal variability and vertical distribution of hydraulic conductivity with depth at these locations within the OU UP-1 area. This type of characterization information is important for predicting/simulating contaminant migration (i.e., numerical flow/transport modeling) and designing proper monitor well strategies for OU and Waste Management Area locations.

  6. Aerosol optical properties derived from the DRAGON-NE Asia campaign, and implications for a single-channel algorithm to retrieve aerosol optical depth in spring from Meteorological Imager (MI on-board the Communication, Ocean, and Meteorological Satellite (COMS

    Directory of Open Access Journals (Sweden)

    M. Kim

    2016-02-01

    Full Text Available An aerosol model optimized for northeast Asia is updated with the inversion data from the Distributed Regional Aerosol Gridded Observation Networks (DRAGON-northeast (NE Asia campaign which was conducted during spring from March to May 2012. This updated aerosol model was then applied to a single visible channel algorithm to retrieve aerosol optical depth (AOD from a Meteorological Imager (MI on-board the geostationary meteorological satellite, Communication, Ocean, and Meteorological Satellite (COMS. This model plays an important role in retrieving accurate AOD from a single visible channel measurement. For the single-channel retrieval, sensitivity tests showed that perturbations by 4 % (0.926 ± 0.04 in the assumed single scattering albedo (SSA can result in the retrieval error in AOD by over 20 %. Since the measured reflectance at the top of the atmosphere depends on both AOD and SSA, the overestimation of assumed SSA in the aerosol model leads to an underestimation of AOD. Based on the AErosol RObotic NETwork (AERONET inversion data sets obtained over East Asia before 2011, seasonally analyzed aerosol optical properties (AOPs were categorized by SSAs at 675 nm of 0.92 ± 0.035 for spring (March, April, and May. After the DRAGON-NE Asia campaign in 2012, the SSA during spring showed a slight increase to 0.93 ± 0.035. In terms of the volume size distribution, the mode radius of coarse particles was increased from 2.08 ± 0.40 to 2.14 ± 0.40. While the original aerosol model consists of volume size distribution and refractive indices obtained before 2011, the new model is constructed by using a total data set after the DRAGON-NE Asia campaign. The large volume of data in high spatial resolution from this intensive campaign can be used to improve the representative aerosol model for East Asia. Accordingly, the new AOD data sets retrieved from a single-channel algorithm, which uses a precalculated look-up table (LUT with the new aerosol model

  7. Aerosol Optical Properties Derived from the DRAGON-NE Asia Campaign, and Implications for a Single-Channel Algorithm to Retrieve Aerosol Optical Depth in Spring from Meteorological Imager (MI) On-Board the Communication, Ocean, and Meteorological Satellite (COMS)

    Science.gov (United States)

    Kim, M.; Kim, J.; Jeong, U.; Kim, W.; Hong, H.; Holben, B.; Eck, T. F.; Lim, J.; Song, C.; Lee, S.; hide

    2016-01-01

    An aerosol model optimized for northeast Asia is updated with the inversion data from the Distributed Regional Aerosol Gridded Observation Networks (DRAGON)-northeast (NE) Asia campaign which was conducted during spring from March to May 2012. This updated aerosol model was then applied to a single visible channel algorithm to retrieve aerosol optical depth (AOD) from a Meteorological Imager (MI) on-board the geostationary meteorological satellite, Communication, Ocean, and Meteorological Satellite (COMS). This model plays an important role in retrieving accurate AOD from a single visible channel measurement. For the single-channel retrieval, sensitivity tests showed that perturbations by 4 % (0.926 +/- 0.04) in the assumed single scattering albedo (SSA) can result in the retrieval error in AOD by over 20 %. Since the measured reflectance at the top of the atmosphere depends on both AOD and SSA, the overestimation of assumed SSA in the aerosol model leads to an underestimation of AOD. Based on the AErosol RObotic NETwork (AERONET) inversion data sets obtained over East Asia before 2011, seasonally analyzed aerosol optical properties (AOPs) were categorized by SSAs at 675 nm of 0.92 +/- 0.035 for spring (March, April, and May). After the DRAGON-NE Asia campaign in 2012, the SSA during spring showed a slight increase to 0.93 +/- 0.035. In terms of the volume size distribution, the mode radius of coarse particles was increased from 2.08 +/- 0.40 to 2.14 +/- 0.40. While the original aerosol model consists of volume size distribution and refractive indices obtained before 2011, the new model is constructed by using a total data set after the DRAGON-NE Asia campaign. The large volume of data in high spatial resolution from this intensive campaign can be used to improve the representative aerosol model for East Asia. Accordingly, the new AOD data sets retrieved from a single-channel algorithm, which uses a precalculated look-up table (LUT) with the new aerosol model, show

  8. Optics

    CERN Document Server

    Fincham, W H A

    2013-01-01

    Optics: Eighth Edition covers the work necessary for the specialization in such subjects as ophthalmic optics, optical instruments and lens design. The text includes topics such as the propagation and behavior of light; reflection and refraction - their laws and how different media affect them; lenses - thick and thin, cylindrical and subcylindrical; photometry; dispersion and color; interference; and polarization. Also included are topics such as diffraction and holography; the limitation of beams in optical systems and its effects; and lens systems. The book is recommended for engineering st

  9. Extended depth of focus contact lenses vs. two commercial multifocals: Part 1. Optical performance evaluation via computed through-focus retinal image quality metrics

    Directory of Open Access Journals (Sweden)

    Ravi C. Bakaraju

    2018-01-01

    Conclusion: With the through focus retinal image quality as the gauge of optical performance, we demonstrated that the prototype EDOF designs were less susceptible to variations in pupil, inherent ocular aberrations and decentration, compared to the commercial designs. To ascertain whether these incremental improvements translate to a clinically palpable outcome requires investigation through human trials.

  10. Assessment of optical performance of three non-tracking, non-imaging, external compound parabolic concentrators designed for high temperature solar thermal collector units

    OpenAIRE

    Cisneros, Jesus

    2010-01-01

    The objective of this thesis is to perform a preliminary optical assessment of the external compound parabolic concentrator (XCPC) component in three concentrating solar thermal units. Each solar thermal unit consists an optical element (the non-imaging concentrating reflector) and a thermal element (the evacuated glass tube solar absorber). The three concentrating solar thermal units discussed in this work are DEWAR 58, a direct flow all-glass dewar, DEWAR 47 an indirect flow ...

  11. Exploring the Application of Optical Remote Sensing as a Method to Estimate the Depth of Backwater Nursery Habitats of the Colorado Pikeminnow

    Energy Technology Data Exchange (ETDEWEB)

    Hamada, Yuki [Argonne National Lab. (ANL), Argonne, IL (United States); LaGory, Kirk E. [Argonne National Lab. (ANL), Argonne, IL (United States)

    2016-02-01

    Low-velocity channel-margin habitats serve as important nursery habitats for the endangered Colorado pikeminnow (Ptychocheilus lucius) in the middle Green River between Jensen and Ouray, Utah. These habitats, known as backwaters, are associated with emergent sand bars, and are shaped and reformed annually by peak flows. A recent synthesis of information on backwater characteristics and the factors that influence inter-annual variability in those backwaters (Grippo et al. 2015) evaluated detailed survey information collected annually since 2003 on a relatively small sample of backwaters, as well as reach-wide evaluations of backwater surface area from aerial and satellite imagery. An approach is needed to bridge the gap between these detailed surveys, which estimate surface area, volume, and depth, and the reach-wide assessment of surface area to enable an assessment of the amount of habitat that meets the minimum depth requirements for suitable habitat.

  12. Creating diversity by site-selective peptide modification: a customizable unit affords amino acids with high optical purity.

    Science.gov (United States)

    Romero-Estudillo, Ivan; Boto, Alicia

    2013-11-15

    The development of peptide libraries by site-selective modification of a few parent peptides would save valuable time and materials in discovery processes, but still is a difficult synthetic challenge. Herein natural hydroxyproline is introduced as a "convertible" unit for the production of a variety of optically pure amino acids, including expensive N-alkyl amino acids, and to achieve the mild, efficient, and site-selective modification of peptides.

  13. Optical remote sensing of the Gulf of Gabès – relation between turbidity, Secchi depth and total suspended matter

    OpenAIRE

    R. Katlane Essersi; B. Nechad; K. Ruddick; F. Zargouni

    2010-01-01

    Optical remote sensing is used here in the Gulf of Gabès to provide scientific information to support environmental management. The Gulf of Gabès is located in the southern east coast of Tunisia. It is a shallow continental shelf with semi-diurnal tides with average amplitude of 2 m. Industrial activities in this area since the early 1970s may have contributed to the degradation of the biodiversity of the ecosystem with eutrophica...

  14. Black carbon aerosol mixing state, organic aerosols and aerosol optical properties over the United Kingdom

    Science.gov (United States)

    McMeeking, G. R.; Morgan, W. T.; Flynn, M.; Highwood, E. J.; Turnbull, K.; Haywood, J.; Coe, H.

    2011-09-01

    Black carbon (BC) aerosols absorb sunlight thereby leading to a positive radiative forcing and a warming of climate and can also impact human health through their impact on the respiratory system. The state of mixing of BC with other aerosol species, particularly the degree of internal/external mixing, has been highlighted as a major uncertainty in assessing its radiative forcing and hence its climate impact, but few in situ observations of mixing state exist. We present airborne single particle soot photometer (SP2) measurements of refractory BC (rBC) mass concentrations and mixing state coupled with aerosol composition and optical properties measured in urban plumes and regional pollution over the United Kingdom. All data were obtained using instrumentation flown on the UK's BAe-146-301 large Atmospheric Research Aircraft (ARA) operated by the Facility for Airborne Atmospheric Measurements (FAAM). We measured sub-micron aerosol composition using an aerosol mass spectrometer (AMS) and used positive matrix factorization to separate hydrocarbon-like (HOA) and oxygenated organic aerosols (OOA). We found a higher number fraction of thickly coated rBC particles in air masses with large OOA relative to HOA, higher ozone-to-nitrogen oxides (NOx) ratios and large concentrations of total sub-micron aerosol mass relative to rBC mass concentrations. The more ozone- and OOA-rich air masses were associated with transport from continental Europe, while plumes from UK cities had higher HOA and NOx and fewer thickly coated rBC particles. We did not observe any significant change in the rBC mass absorption efficiency calculated from rBC mass and light absorption coefficients measured by a particle soot absorption photometer despite observing significant changes in aerosol composition and rBC mixing state. The contributions of light scattering and absorption to total extinction (quantified by the single scattering albedo; SSA) did change for different air masses, with lower SSA

  15. Black carbon aerosol mixing state, organic aerosols and aerosol optical properties over the United Kingdom

    Directory of Open Access Journals (Sweden)

    G. R. McMeeking

    2011-09-01

    Full Text Available Black carbon (BC aerosols absorb sunlight thereby leading to a positive radiative forcing and a warming of climate and can also impact human health through their impact on the respiratory system. The state of mixing of BC with other aerosol species, particularly the degree of internal/external mixing, has been highlighted as a major uncertainty in assessing its radiative forcing and hence its climate impact, but few in situ observations of mixing state exist. We present airborne single particle soot photometer (SP2 measurements of refractory BC (rBC mass concentrations and mixing state coupled with aerosol composition and optical properties measured in urban plumes and regional pollution over the United Kingdom. All data were obtained using instrumentation flown on the UK's BAe-146-301 large Atmospheric Research Aircraft (ARA operated by the Facility for Airborne Atmospheric Measurements (FAAM. We measured sub-micron aerosol composition using an aerosol mass spectrometer (AMS and used positive matrix factorization to separate hydrocarbon-like (HOA and oxygenated organic aerosols (OOA. We found a higher number fraction of thickly coated rBC particles in air masses with large OOA relative to HOA, higher ozone-to-nitrogen oxides (NOx ratios and large concentrations of total sub-micron aerosol mass relative to rBC mass concentrations. The more ozone- and OOA-rich air masses were associated with transport from continental Europe, while plumes from UK cities had higher HOA and NOx and fewer thickly coated rBC particles. We did not observe any significant change in the rBC mass absorption efficiency calculated from rBC mass and light absorption coefficients measured by a particle soot absorption photometer despite observing significant changes in aerosol composition and rBC mixing state. The contributions of light scattering and absorption to total extinction (quantified by the single scattering albedo; SSA did change for

  16. Spectra from 2.5-15 μm of tissue phantom materials, optical clearing agents and ex vivo human skin: implications for depth profiling of human skin

    International Nuclear Information System (INIS)

    Viator, John A; Choi, Bernard; Peavy, George M; Kimel, Sol; Nelson, J Stuart

    2003-01-01

    Infrared measurements have been used to profile or image biological tissue, including human skin. Usually, analysis of such measurements has assumed that infrared absorption is due to water and collagen. Such an assumption may be reasonable for soft tissue, but introduction of exogenous agents into skin or the measurement of tissue phantoms has raised the question of their infrared absorption spectrum. We used Fourier transform infrared spectroscopy in attenuated total reflection mode to measure the infrared absorption spectra, in the range of 2-15 μm, of water, polyacrylamide, Intralipid, collagen gels, four hyperosmotic clearing agents (glycerol, 1,3-butylene glycol, trimethylolpropane, Topicare TM ), and ex vivo human stratum corneum and dermis. The absorption spectra of the phantom materials were similar to that of water, although additional structure was noted in the range of 6-10 μm. The absorption spectra of the clearing agents were more complex, with molecular absorption bands dominating between 6 and 12 μm. Dermis was similar to water, with collagen structure evident in the 6-10 μm range. Stratum corneum had a significantly lower absorption than dermis due to a lower content of water. These results suggest that the assumption of water-dominated absorption in the 2.5-6 μm range is valid. At longer wavelengths, clearing agent absorption spectra differ significantly from the water spectrum. This spectral information can be used in pulsed photothermal radiometry or utilized in the interpretation of reconstructions in which a constant μ ir is used. In such cases, overestimating μ ir will underestimate chromophore depth and vice versa, although the effect is dependent on actual chromophore depth. (note)

  17. Evaluation of Macular Ganglion Cell-inner Plexiform Layer and Choroid in Psoriasis Patients Using Enhanced Depth Imaging Spectral Domain Optical Coherence Tomography.

    Science.gov (United States)

    Ersan, Ismail; Kilic, Sevilay; Arikan, Sedat; Kara, Selcuk; Işik, Selda; Gencer, Baran; Ogretmen, Zerrin

    2017-08-01

    To evaluate changes in the thickness of the central macula, macular ganglion cell-inner plexiform layer (mGCIPL), and subfoveal choroid in patients with psoriasis using spectral domain optical coherence tomography (SD-OCT). The measurements of macular, mGCIPL thicknesses and subfoveal choroidal thickness (SFCT) obtained by SD-OCT of psoriasis patients (n = 46). These measurements were compared with those of 50 healthy controls. The macular, mGCIPL, and choroidal thicknesses did not differ between the controls and psoriatic subjects (p>0.05). When the patients were divided into two distinct groups, only the SFCT was significantly thicker in the severe psoriasis group compared with the mild psoriasis group (p = 0.003). These findings suggest that choroidal alterations are seen without macular changes in patients with psoriasis. Severe psoriasis appears to be related to increases in SFCT as a consequence of possible inflammatory cascades that are part of the disease's pathogenesis.

  18. Online Simulations of Global Aerosol Distributions in the NASA GEOS-4 Model and Comparisons to Satellite and Ground-Based Aerosol Optical Depth

    Science.gov (United States)

    Colarco, Peter; daSilva, Arlindo; Chin, Mian; Diehl, Thomas

    2010-01-01

    We have implemented a module for tropospheric aerosols (GO CART) online in the NASA Goddard Earth Observing System version 4 model and simulated global aerosol distributions for the period 2000-2006. The new online system offers several advantages over the previous offline version, providing a platform for aerosol data assimilation, aerosol-chemistry-climate interaction studies, and short-range chemical weather forecasting and climate prediction. We introduce as well a methodology for sampling model output consistently with satellite aerosol optical thickness (AOT) retrievals to facilitate model-satellite comparison. Our results are similar to the offline GOCART model and to the models participating in the AeroCom intercomparison. The simulated AOT has similar seasonal and regional variability and magnitude to Aerosol Robotic Network (AERONET), Moderate Resolution Imaging Spectroradiometer, and Multiangle Imaging Spectroradiometer observations. The model AOT and Angstrom parameter are consistently low relative to AERONET in biomass-burning-dominated regions, where emissions appear to be underestimated, consistent with the results of the offline GOCART model. In contrast, the model AOT is biased high in sulfate-dominated regions of North America and Europe. Our model-satellite comparison methodology shows that diurnal variability in aerosol loading is unimportant compared to sampling the model where the satellite has cloud-free observations, particularly in sulfate-dominated regions. Simulated sea salt burden and optical thickness are high by a factor of 2-3 relative to other models, and agreement between model and satellite over-ocean AOT is improved by reducing the model sea salt burden by a factor of 2. The best agreement in both AOT magnitude and variability occurs immediately downwind of the Saharan dust plume.

  19. Microdureza de resina composta: efeito de aparelhos e tempos de polimerização em diferentes profundidades Microhardness of composite resins: effect of photocuring units and polymerization periods in different depths

    Directory of Open Access Journals (Sweden)

    Luciana Aily SANTOS

    2000-03-01

    Full Text Available As propriedades das resinas compostas têm sido estudadas com freqüência, bem como os fatores que podem influenciar seu grau de polimerização. Diante da evolução desses materiais e da necessidade de buscarmos melhora do seu comportamento na cavidade bucal, objetivamos, por meio deste estudo avaliar a eficácia de dois aparelhos fotopolimerizadores do tipo pistola (de alta intensidade de luz, comparando com a de um aparelho a cabo (de baixa intensidade de luz, com tempos de exposição de 20 e de 40 segundos e em profundidades de 1 a 4 milímetros. Os testes avaliaram o grau de polimerização da resina por meio de testes de microdureza Knoop. Os resultados mostraram haver diferença estatisticamente significante entre os tempos, sendo que com 40 segundos a dureza foi maior que com 20 segundos para as 4 diferentes profundidades. Para o fator aparelhos, os dois aparelhos tipo pistola se comportaram superiores ao do tipo cabo Fibralux (Dabi Atlante, e entre eles, o XL 1500 (3M promoveu dureza maior que o Optilight II (Gnatus no tempo de polimerização de 40 segundos. As profundidades de 1, 2, 3 e 4 milímetros mostraram estatisticamente diferença entre si tendo sido encontrada maior dureza para as menores profundidades (p The properties of composite resins have been frequently studied, as well as the factors that might influence the polymerization degree. Considering the evolution of composites and the need to improve their clinical performance, this study intends to evaluate the efficacy of two high-intensity and one low-intensity photocuring units, as a function of exposure time (20 and 40seconds and composite depth (from 1 to 4 millimeters. Composite properties were evaluated via Knoop Microhardness Test. Statistical analysis (1 way ANOVA, p < 0.05 of the obtained results showed that there was statistically significant difference regarding the time factor. The 40-seconds polymerization time showed the best results, for the four depths

  20. Percutaneous dilatational tracheostomy without fiber optic bronchoscopy-Evaluation of 80 intensive care units cases

    NARCIS (Netherlands)

    J.A. Calvache (Jose Andrés); R.A. Molina García (Rodrigo); A.L. Trochez (Adolfo); J. Benitez (Javier); L.A. Flga (Lucía Arroyo)

    2013-01-01

    textabstractBackground: The development of percutaneous dilatational tracheostomy techniques (PDT) has facilitated the procedure in Intensive Care Units (ICU). Objective: To describe the early intra and post-operative complications in ICU patients requiring percutaneous dilatational tracheostomy

  1. Microscopy system of atomic force based on a digital optical reading unit and a buzzer-scanner

    International Nuclear Information System (INIS)

    Dabirian, R.; Loza M, D.; Wang, W. M.; Hwu, E. T.

    2015-01-01

    An astigmatic detection system (Ads) based on a compact disk/digital-versatile-disk (Cd-DVD) astigmatic optical pickup unit is presented. It can achieve a resolution better than 0.3 nm in detection of the vertical displacement and is able to detect the two-dimensional angular tilt of the object surface. Furthermore, a novel scanner design actuated by piezoelectric disk buzzers is presented. The scanner is composed of a quad-rod actuation structure and several piezoelectric disks. It can be driven directly with low-voltage and low-current sources, such as analogue outputs of a data acquisition card and enables a sufficient scanning range of up to μm. In addition, an economic, high-performance streamlined atomic force microscopy (AFM) was constructed, using the buzzer-scanner to move the sample relative to the probe, and using a Cd/DVD optical pickup unit to detect the mechanical resonance of a micro fabricated cantilever. The performance of the AFM is evaluated. The high sensitivity and high bandwidth of the detection system makes the equipment suitable for characterizing nano scale elements. An AFM using our detection system for detecting the deflection of micro fabricated cantilevers can resolve individual atomic steps on graphite surfaces. (Author)

  2. Improvement of Aerosol Optical Depth Retrieval from MODIS Spectral Reflectance over the Global Ocean Using New Aerosol Models Archived from AERONET Inversion Data and Tri-axial Ellipsoidal Dust Database

    Science.gov (United States)

    Lee, J.; Kim, J.; Yang, P.; Hsu, N. C.

    2012-01-01

    New over-ocean aerosol models are developed by integrating the inversion data from the Aerosol Robotic Network (AERONET) sun/sky radiometers with a database for the optical properties of tri-axial ellipsoid particles. The new aerosol models allow more accurate retrieval of aerosol optical depth (AOD) from the Moderate Resolution Imaging Spectroradiometer (MODIS) in the case of high AOD (AOD greater than 0.3). The aerosol models are categorized by using the fine-mode fraction (FMF) at 550 nm and the singlescattering albedo (SSA) at 440 nm from the AERONET inversion data to include a variety of aerosol types found around the globe. For each aerosol model, the changes in the aerosol optical properties (AOPs) as functions of AOD are considered to better represent aerosol characteristics. Comparisons of AODs between AERONET and MODIS for the period from 2003 to 2010 show that the use of the new aerosol models enhances the AOD accuracy with a Pearson coefficient of 0.93 and a regression slope of 0.99 compared to 0.92 and 0.85 calculated using the MODIS Collection 5 data. Moreover, the percentage of data within an expected error of +/-(0.03 + 0.05xAOD) is increased from 62 percent to 64 percent for overall data and from 39 percent to 51 percent for AOD greater than 0.3. Errors in the retrieved AOD are further characterized with respect to the Angstrom exponent (AE), scattering angle, SSA, and air mass factor (AMF). Due to more realistic AOPs assumptions, the new algorithm generally reduces systematic errors in the retrieved AODs compared with the current operational algorithm. In particular, the underestimation of fine-dominated AOD and the scattering angle dependence of dust-dominated AOD are significantly mitigated as results of the new algorithm's improved treatment of aerosol size distribution and dust particle nonsphericity.

  3. Improvement of aerosol optical depth retrieval from MODIS spectral reflectance over the global ocean using new aerosol models archived from AERONET inversion data and tri-axial ellipsoidal dust database

    Directory of Open Access Journals (Sweden)

    J. Lee

    2012-08-01

    Full Text Available New over-ocean aerosol models are developed by integrating the inversion data from the Aerosol Robotic Network (AERONET sun/sky radiometers with a database for the optical properties of tri-axial ellipsoid particles. The new aerosol models allow more accurate retrieval of aerosol optical depth (AOD from the Moderate Resolution Imaging Spectroradiometer (MODIS in the case of high AOD (AOD > 0.3. The aerosol models are categorized by using the fine-mode fraction (FMF at 550 nm and the single-scattering albedo (SSA at 440 nm from the AERONET inversion data to include a variety of aerosol types found around the globe. For each aerosol model, the changes in the aerosol optical properties (AOPs as functions of AOD are considered to better represent aerosol characteristics. Comparisons of AODs between AERONET and MODIS for the period from 2003 to 2010 show that the use of the new aerosol models enhances the AOD accuracy with a Pearson coefficient of 0.93 and a regression slope of 0.99 compared to 0.92 and 0.85 calculated using the MODIS Collection 5 data. Moreover, the percentage of data within an expected error of ± (0.03 + 0.05 × AOD is increased from 62% to 64% for overall data and from 39% to 5% for AOD > 0.3. Errors in the retrieved AOD are further characterized with respect to the Ångström exponent (AE, scattering angle (Θ, SSA, and air mass factor (AMF. Due to more realistic AOPs assumptions, the new algorithm generally reduces systematic errors in the retrieved AODs compared with the current operational algorithm. In particular, the underestimation of fine-dominated AOD and the scattering angle dependence of dust-dominated AOD are significantly mitigated as results of the new algorithm's improved treatment of aerosol size distribution and dust particle nonsphericity.

  4. Distribution in depth of quasars

    International Nuclear Information System (INIS)

    Schmidt, M.; Green, R.F.

    1980-01-01

    The authors discuss the distribution in depth of different kinds of quasars: quasi-stellar radio sources with steep radio spectrum, those with flat radio spectrum, and optically selected quasars. All exhibit an increase of space density with distance to a different degree. The optically selected quasars, in particular, show a steep increase of surface density with magnitude. The steepness of the increase is inconsistent with a uniform distribution of quasars in the local hypothesis. In the cosmological hypothesis the co-moving space density of optically selected quasars increases by a factor of 100,000 to a redshift of 2, and by factors of 1000 and 10 for steep-spectrum and flat-spectrum radio quasars, respectively. (Auth.)

  5. Compact, low-cost, and high-resolution interrogation unit for optical sensors

    International Nuclear Information System (INIS)

    Kiesel, Peter; Schmidt, Oliver; Mohta, Setu; Johnson, Noble; Malzer, Stefan

    2006-01-01

    Compact wavelength detectors that resolve wavelength changes in the subpicometer range over a broad spectral range are presented. A photodiode array or position sensor device is coated with a linear variable filter that converts the wavelength of the incident light into a spatial intensity distribution. The centroid of the spatial distribution is determined by a differential readout of the two elements of the photodiode array or the position sensor device. The device can interrogate any optical sensor that produces a wavelength shift in response to a stimulus. The potential of this device was tested by interrogating fiber-Bragg-grating sensors

  6. A configurable FPGA FEC unit for Tb/s optical communication

    DEFF Research Database (Denmark)

    Andersen, Jakob Dahl; Larsen, Knud J.; Bering Bøgh, Christian

    2017-01-01

    Decoding of FEC (forward error correction) for optical communication beyond 1 Tb/s is investigated. A configurable single FPGA solution is presented having configurations supporting bit-rates in the range from 40 Gb/s to 1.6 Tb/s. The design allows for trade-offs of bit-rate, footprint, and latency...... within the resources of the FPGA. A proof-of-concept lab experiment at 40 Gb/s was conducted and pre-FEC — post-FEC performance validated with simulated results....

  7. Electrical and optical analysis of fast transient discharges in a pulsed corona pilot unit

    NARCIS (Netherlands)

    Blom, P.P.M.; Smulders, H.W.M.; Heesch, van E.J.M.; Laan, van der P.C.T.

    1997-01-01

    We give a detailed analysis of intense pulsed corona dis charges. CCD movies and current, voltage and energy in put measurements are the basis of the description. The discharges are generated in a 1.5 kW pilot unit, which cre ates pulsed corona discharges energized by 100 kV pulses of 200 us width,

  8. Soluble Electrochromic Polymers Incorporating Benzoselenadiazole and Electron Donor Units (Carbazole or Fluorene: Synthesis and Electronic-Optical Properties

    Directory of Open Access Journals (Sweden)

    Jianzhong Xu

    2018-04-01

    Full Text Available A series of π-conjugated polymers containing alternating benzoselenadiazole (BSe-bi(thiophene derivative-carbazole or benzoththiadiazole (BSe-bi(thiophene derivative-fluorene units were designed and synthesized. Thiophene derivatives, namely 3-hexylthiophene, 3,4-bihexyloxythiophene, and 3,4-bioctyloxythiophene, were used as the π-bridges of the polymers. The polymers were characterized in detail in terms of their thermal stabilities, cyclic voltammograms, UV-Vis absorption, spectroelectrochemistry, dynamic switching property and so forth. The alkoxy thiophene π-bridged polymers have lower onset oxidation potentials and bandgaps than that of their corresponding alkyl thiophene π-bridged polymers. The selection of the donor units between the carbazole and the fluorene units has nearly no effect on the bandgaps and colors as well as the onset oxidation potentials of the polymers. The increase in the length of the side alkyl chains on the thiophene ring caused a slight increase in the polymer bandgap, which may be caused by the space hindrance effect. The dynamic switching abilities of the polymers were obtained by the chronoabsorptometry method, and the results also suggested that the alkoxy thiophene-containing polymers (as π-bridges have higher contrast ratios than the corresponding alkyl thiophene-containing polymers. Furthermore, the increase in the length of the side alkyl chain might have a detrimental effect on the optical contrast ratios of the polymers.

  9. Spatial and temporal variability of column-integrated aerosol optical properties in the southern Arabian Gulf and United Arab Emirates in summer

    Science.gov (United States)

    Eck, T. F.; Holben, B. N.; Reid, J. S.; Sinyuk, A.; Dubovik, O.; Smirnov, A.; Giles, D.; O'Neill, N. T.; Tsay, S.-C.; Ji, Q.; Al Mandoos, A.; Ramzan Khan, M.; Reid, E. A.; Schafer, J. S.; Sorokine, M.; Newcomb, W.; Slutsker, I.

    2008-01-01

    A mesoscale network of 14 AERONET Sun photometers was established in the UAE and adjacent Arabian Gulf from August through September 2004 as a component of the United Arab Emirates Unified Aerosol Experiment (UAE2). These measurements allowed for spatial, temporal and spectral characterization of the complex aerosol mixtures present in this environment where coarse mode desert dust aerosols often mix with fine mode pollution aerosols largely produced by the petroleum industry. Aerosol loading was relatively high with 2-month averages of aerosol optical depth (AOD) at 500 nm (τa500) ranging from 0.40 to 0.53. A higher fine mode fraction of AOD was observed over Arabian Gulf island sites with Angstrom exponent at 440-870 nm (α440-870) of 0.77 as compared to an average of 0.64 over coastal sites and 0.50-0.57 at inland desert sites. During pollution events with α440-870 > 1 the retrieved fine mode radius was larger over an island site than a desert site probably because of hygroscopic growth over the humid marine environment. For these same pollution cases, single scattering albedo (ωo) at all wavelengths was ˜0.03 higher (less absorption) over the marine environment than over the desert, also consistent with aerosol humidification growth. At an inland desert location, the ωo at 440 nm remained relatively constant as Angstrom exponent varied since the fine mode pollution and coarse mode dust were both strong absorbers at short wavelengths. However, at longer wavelengths (675-1020 nm) the dust was much less absorbing than the pollution resulting in dynamic ωo as a function of α440-870.

  10. Graphics processing unit accelerated intensity-based optical coherence tomography angiography using differential frames with real-time motion correction.

    Science.gov (United States)

    Watanabe, Yuuki; Takahashi, Yuhei; Numazawa, Hiroshi

    2014-02-01

    We demonstrate intensity-based optical coherence tomography (OCT) angiography using the squared difference of two sequential frames with bulk-tissue-motion (BTM) correction. This motion correction was performed by minimization of the sum of the pixel values using axial- and lateral-pixel-shifted structural OCT images. We extract the BTM-corrected image from a total of 25 calculated OCT angiographic images. Image processing was accelerated by a graphics processing unit (GPU) with many stream processors to optimize the parallel processing procedure. The GPU processing rate was faster than that of a line scan camera (46.9 kHz). Our OCT system provides the means of displaying structural OCT images and BTM-corrected OCT angiographic images in real time.

  11. Energy-efficient optical network units for OFDM PON based on time-domain interleaved OFDM technique.

    Science.gov (United States)

    Hu, Xiaofeng; Cao, Pan; Zhang, Liang; Jiang, Lipeng; Su, Yikai

    2014-06-02

    We propose and experimentally demonstrate a new scheme to reduce the energy consumption of optical network units (ONUs) in orthogonal frequency division multiplexing passive optical networks (OFDM PONs) by using time-domain interleaved OFDM (TI-OFDM) technique. In a conventional OFDM PON, each ONU has to process the complete downstream broadcast OFDM signal with a high sampling rate and a large FFT size to retrieve its required data, even if it employs a portion of OFDM subcarriers. However, in our scheme, the ONU only needs to sample and process one data group from the downlink TI-OFDM signal, effectively reducing the sampling rate and the FFT size of the ONU. Thus, the energy efficiency of ONUs in OFDM PONs can be greatly improved. A proof-of-concept experiment is conducted to verify the feasibility of the proposed scheme. Compared to the conventional OFDM PON, our proposal can save 17.1% and 26.7% energy consumption of ONUs by halving and quartering the sampling rate and the FFT size of ONUs with the use of the TI-OFDM technology.

  12. Application of Spectral Analysis Techniques in the Intercomparison of Aerosol Data: 1. an EOF Approach to the Spatial-Temporal Variability of Aerosol Optical Depth Using Multiple Remote Sensing Data Sets

    Science.gov (United States)

    Li, Jing; Carlson, Barbara E.; Lacis, Andrew A.

    2013-01-01

    Many remote sensing techniques and passive sensors have been developed to measure global aerosol properties. While instantaneous comparisons between pixel-level data often reveal quantitative differences, here we use Empirical Orthogonal Function (EOF) analysis, also known as Principal Component Analysis, to demonstrate that satellite-derived aerosol optical depth (AOD) data sets exhibit essentially the same spatial and temporal variability and are thus suitable for large-scale studies. Analysis results show that the first four EOF modes of AOD account for the bulk of the variance and agree well across the four data sets used in this study (i.e., Aqua MODIS, Terra MODIS, MISR, and SeaWiFS). Only SeaWiFS data over land have slightly different EOF patterns. Globally, the first two EOF modes show annual cycles and are mainly related to Sahara dust in the northern hemisphere and biomass burning in the southern hemisphere, respectively. After removing the mean seasonal cycle from the data, major aerosol sources, including biomass burning in South America and dust in West Africa, are revealed in the dominant modes due to the different interannual variability of aerosol emissions. The enhancement of biomass burning associated with El Niño over Indonesia and central South America is also captured with the EOF technique.

  13. Weighted halfspace depth

    Czech Academy of Sciences Publication Activity Database

    Kotík, Lukáš; Hlubinka, D.; Vencálek, O.

    Vol. 46, č. 1 (2010), s. 125-148 ISSN 0023-5954 Institutional research plan: CEZ:AV0Z10750506 Keywords : data depth * nonparametric multivariate analysis * strong consistency of depth * mixture of distributions Subject RIV: BB - Applied Statistics, Operational Research Impact factor: 0.461, year: 2010 http://library.utia.cas.cz/separaty/2010/SI/kotik-weighted halfspace depth.pdf

  14. Radiation dose measurements of an on-board imager X-ray unit using optically-stimulated luminescence dosimeters

    International Nuclear Information System (INIS)

    Smith, Leon; Haque, Mamoon; Hill, Robin; Morales, Johnny

    2015-01-01

    Cone beam computed tomography (CBCT) is now widely used to image radiotherapy patients prior to treatment for the purpose of accurate patient setup. However each CBCT image delivered to a patient increases the total radiation dose that they receive. The measurement of the dose delivered from the CBCT images is not readily performed in the clinic. In this study, we have used commercially available optically stimulated luminescence (OSLD) dosimeters to measure the dose delivered by the Varian OBI on a radiotherapy linear accelerator. Calibration of the OSLDs was achieved by using a therapeutic X-ray unit. The dose delivered by a head CBCT scan was found to be 3.2 ± 0.3 mGy which is similar in magnitude to the dose of a head computed tomography (CT) scan. The results of this study suggest that the radiation hazard associated with CBCT is of a similar nature to that of conventional CT scans. We have also demonstrated that the OSLDs are suitable for these low X-ray dose measurements.

  15. Complexity and Dynamical Depth

    Directory of Open Access Journals (Sweden)

    Terrence Deacon

    2014-07-01

    Full Text Available We argue that a critical difference distinguishing machines from organisms and computers from brains is not complexity in a structural sense, but a difference in dynamical organization that is not well accounted for by current complexity measures. We propose a measure of the complexity of a system that is largely orthogonal to computational, information theoretic, or thermodynamic conceptions of structural complexity. What we call a system’s dynamical depth is a separate dimension of system complexity that measures the degree to which it exhibits discrete levels of nonlinear dynamical organization in which successive levels are distinguished by local entropy reduction and constraint generation. A system with greater dynamical depth than another consists of a greater number of such nested dynamical levels. Thus, a mechanical or linear thermodynamic system has less dynamical depth than an inorganic self-organized system, which has less dynamical depth than a living system. Including an assessment of dynamical depth can provide a more precise and systematic account of the fundamental difference between inorganic systems (low dynamical depth and living systems (high dynamical depth, irrespective of the number of their parts and the causal relations between them.

  16. Near Real-Time Automatic Data Quality Controls for the AERONET Version 3 Database: An Introduction to the New Level 1.5V Aerosol Optical Depth Data Product

    Science.gov (United States)

    Giles, D. M.; Holben, B. N.; Smirnov, A.; Eck, T. F.; Slutsker, I.; Sorokin, M. G.; Espenak, F.; Schafer, J.; Sinyuk, A.

    2015-12-01

    The Aerosol Robotic Network (AERONET) has provided a database of aerosol optical depth (AOD) measured by surface-based Sun/sky radiometers for over 20 years. AERONET provides unscreened (Level 1.0) and automatically cloud cleared (Level 1.5) AOD in near real-time (NRT), while manually inspected quality assured (Level 2.0) AOD are available after instrument field deployment (Smirnov et al., 2000). The growing need for NRT quality controlled aerosol data has become increasingly important. Applications of AERONET NRT data include the satellite evaluation (e.g., MODIS, VIIRS, MISR, OMI), data synergism (e.g., MPLNET), verification of aerosol forecast models and reanalysis (e.g., GOCART, ICAP, NAAPS, MERRA), input to meteorological models (e.g., NCEP, ECMWF), and field campaign support (e.g., KORUS-AQ, ORACLES). In response to user needs for quality controlled NRT data sets, the new Version 3 (V3) Level 1.5V product was developed with similar quality controls as those applied by hand to the Version 2 (V2) Level 2.0 data set. The AERONET cloud screened (Level 1.5) NRT AOD database can be significantly impacted by data anomalies. The most significant data anomalies include AOD diurnal dependence due to contamination or obstruction of the sensor head windows, anomalous AOD spectral dependence due to problems with filter degradation, instrument gains, or non-linear changes in calibration, and abnormal changes in temperature sensitive wavelengths (e.g., 1020nm) in response to anomalous sensor head temperatures. Other less common AOD anomalies result from loose filters, uncorrected clock shifts, connection and electronic issues, and various solar eclipse episodes. Automatic quality control algorithms are applied to the new V3 Level 1.5 database to remove NRT AOD anomalies and produce the new AERONET V3 Level 1.5V AOD product. Results of the quality control algorithms are presented and the V3 Level 1.5V AOD database is compared to the V2 Level 2.0 AOD database.

  17. A 4-D Climatology (1979-2009) of the Monthly Tropospheric Aerosol Optical Depth Distribution over the Mediterranean Region from a Comparative Evaluation and Blending of Remote Sensing and Model Products

    Science.gov (United States)

    Nabat, P.; Somot, S.; Mallet, M.; Chiapello, I; Morcrette, J. J.; Solomon, F.; Szopa, S.; Dulac, F; Collins, W.; Ghan, S.; hide

    2013-01-01

    Since the 1980s several spaceborne sensors have been used to retrieve the aerosol optical depth (AOD) over the Mediterranean region. In parallel, AOD climatologies coming from different numerical model simulations are now also available, permitting to distinguish the contribution of several aerosol types to the total AOD. In this work, we perform a comparative analysis of this unique multiyear database in terms of total AOD and of its apportionment by the five main aerosol types (soil dust, seasalt, sulfate, black and organic carbon). We use 9 different satellite-derived monthly AOD products: NOAA/AVHRR, SeaWiFS (2 products), TERRA/MISR, TERRA/MODIS, AQUA/MODIS, ENVISAT/MERIS, PARASOL/POLDER and MSG/SEVIRI, as well as 3 more historical datasets: NIMBUS7/CZCS, TOMS (onboard NIMBUS7 and Earth- Probe) and METEOSAT/MVIRI. Monthly model datasets include the aerosol climatology from Tegen et al. (1997), the climate-chemistry models LMDz-OR-INCA and RegCM-4, the multi-model mean coming from the ACCMIP exercise, and the reanalyses GEMS and MACC. Ground-based Level- 2 AERONET AOD observations from 47 stations around the basin are used here to evaluate the model and satellite data. The sensor MODIS (on AQUA and TERRA) has the best average AOD scores over this region, showing a relevant spatio-temporal variability and highlighting high dust loads over Northern Africa and the sea (spring and summer), and sulfate aerosols over continental Europe (summer). The comparison also shows limitations of certain datasets (especially MERIS and SeaWiFS standard products). Models reproduce the main patterns of the AOD variability over the basin. The MACC reanalysis is the closest to AERONET data, but appears to underestimate dust over Northern Africa, where RegCM-4 is found closer to MODIS thanks to its interactive scheme for dust emissions. The vertical dimension is also investigated using the CALIOP instrument. This study confirms differences of vertical distribution between dust

  18. A 4-D climatology (1979–2009 of the monthly tropospheric aerosol optical depth distribution over the Mediterranean region from a comparative evaluation and blending of remote sensing and model products

    Directory of Open Access Journals (Sweden)

    P. Nabat

    2013-05-01

    Full Text Available Since the 1980s several spaceborne sensors have been used to retrieve the aerosol optical depth (AOD over the Mediterranean region. In parallel, AOD climatologies coming from different numerical model simulations are now also available, permitting to distinguish the contribution of several aerosol types to the total AOD. In this work, we perform a comparative analysis of this unique multi-year database in terms of total AOD and of its apportionment by the five main aerosol types (soil dust, sea-salt, sulfate, black and organic carbon. We use 9 different satellite-derived monthly AOD products: NOAA/AVHRR, SeaWiFS (2 products, TERRA/MISR, TERRA/MODIS, AQUA/MODIS, ENVISAT/MERIS, PARASOL/POLDER and MSG/SEVIRI, as well as 3 more historical datasets: NIMBUS7/CZCS, TOMS (onboard NIMBUS7 and Earth-Probe and METEOSAT/MVIRI. Monthly model datasets include the aerosol climatology from Tegen et al. (1997, the climate-chemistry models LMDz-OR-INCA and RegCM-4, the multi-model mean coming from the ACCMIP exercise, and the reanalyses GEMS and MACC. Ground-based Level-2 AERONET AOD observations from 47 stations around the basin are used here to evaluate the model and satellite data. The sensor MODIS (on AQUA and TERRA has the best average AOD scores over this region, showing a relevant spatio-temporal variability and highlighting high dust loads over Northern Africa and the sea (spring and summer, and sulfate aerosols over continental Europe (summer. The comparison also shows limitations of certain datasets (especially MERIS and SeaWiFS standard products. Models reproduce the main patterns of the AOD variability over the basin. The MACC reanalysis is the closest to AERONET data, but appears to underestimate dust over Northern Africa, where RegCM-4 is found closer to MODIS thanks to its interactive scheme for dust emissions. The vertical dimension is also investigated using the CALIOP instrument. This study confirms differences of vertical distribution between

  19. Aerosol optical properties in the southeastern United States in summer – Part 1: Hygroscopic growth

    Directory of Open Access Journals (Sweden)

    C. A. Brock

    2016-04-01

    Full Text Available Aircraft observations of meteorological, trace gas, and aerosol properties were made during May–September 2013 in the southeastern United States (US under fair-weather, afternoon conditions with well-defined planetary boundary layer structure. Optical extinction at 532 nm was directly measured at relative humidities (RHs of  ∼  15,  ∼  70, and  ∼  90 % and compared with extinction calculated from measurements of aerosol composition and size distribution using the κ-Köhler approximation for hygroscopic growth. The calculated enhancement in hydrated aerosol extinction with relative humidity, f(RH, calculated by this method agreed well with the observed f(RH at  ∼  90 % RH. The dominance of organic aerosol, which comprised 65 ± 10 % of particulate matter with aerodynamic diameter  <  1 µm in the planetary boundary layer, resulted in relatively low f(RH values of 1.43 ± 0.67 at 70 % RH and 2.28 ± 1.05 at 90 % RH. The subsaturated κ-Köhler hygroscopicity parameter κ for the organic fraction of the aerosol must have been  <  0.10 to be consistent with 75 % of the observations within uncertainties, with a best estimate of κ  =  0.05. This subsaturated κ value for the organic aerosol in the southeastern US is broadly consistent with field studies in rural environments. A new, physically based, single-parameter representation was developed that better described f(RH than did the widely used gamma power-law approximation.

  20. Injection-depth-locking axial motion guided handheld micro-injector using CP-SSOCT.

    Science.gov (United States)

    Cheon, Gyeong Woo; Huang, Yong; Kwag, Hye Rin; Kim, Ki-Young; Taylor, Russell H; Gehlbach, Peter L; Kang, Jin U

    2014-01-01

    This paper presents a handheld micro-injector system using common-path swept source optical coherence tomography (CP-SSOCT) as a distal sensor with highly accurate injection-depth-locking. To achieve real-time, highly precise, and intuitive freehand control, the system used graphics processing unit (GPU) to process the oversampled OCT signal with high throughput and a smart customized motion monitoring control algorithm. A performance evaluation was conducted with 60-insertions and fluorescein dye injection tests to show how accurately the system can guide the needle and lock to the target depth. The evaluation tests show our system can guide the injection needle into the desired depth with 4.12 um average deviation error while injecting 50 nl of fluorescein dye.

  1. Depth compensating calculation method of computer-generated holograms using symmetry and similarity of zone plates

    Science.gov (United States)

    Wei, Hui; Gong, Guanghong; Li, Ni

    2017-10-01

    Computer-generated hologram (CGH) is a promising 3D display technology while it is challenged by heavy computation load and vast memory requirement. To solve these problems, a depth compensating CGH calculation method based on symmetry and similarity of zone plates is proposed and implemented on graphics processing unit (GPU). An improved LUT method is put forward to compute the distances between object points and hologram pixels in the XY direction. The concept of depth compensating factor is defined and used for calculating the holograms of points with different depth positions instead of layer-based methods. The proposed method is suitable for arbitrary sampling objects with lower memory usage and higher computational efficiency compared to other CGH methods. The effectiveness of the proposed method is validated by numerical and optical experiments.

  2. Prestack depth migration

    International Nuclear Information System (INIS)

    Postma, R.W.

    1991-01-01

    Two lines form the southern North Sea, with known velocity inhomogeneities in the overburden, have been pre-stack depth migrated. The pre-stack depth migrations are compared with conventional processing, one with severe distortions and one with subtle distortions on the conventionally processed sections. The line with subtle distortions is also compared with post-stack depth migration. The results on both lines were very successful. Both have already influenced drilling decisions, and have caused a modification of structural interpretation in the respective areas. Wells have been drilled on each of the lines, and well tops confirm the results. In fact, conventional processing led to incorrect locations for the wells, both of which were dry holes. The depth migrated sections indicate the incorrect placement, and on one line reveals a much better drilling location. This paper reports that even though processing costs are high for pre-stack depth migration, appropriate use can save millions of dollars in dry-hole expense

  3. Depth profile measurement with lenslet images of the plenoptic camera

    Science.gov (United States)

    Yang, Peng; Wang, Zhaomin; Zhang, Wei; Zhao, Hongying; Qu, Weijuan; Zhao, Haimeng; Asundi, Anand; Yan, Lei

    2018-03-01

    An approach for carrying out depth profile measurement of an object with the plenoptic camera is proposed. A single plenoptic image consists of multiple lenslet images. To begin with, these images are processed directly with a refocusing technique to obtain the depth map, which does not need to align and decode the plenoptic image. Then, a linear depth calibration is applied based on the optical structure of the plenoptic camera for depth profile reconstruction. One significant improvement of the proposed method concerns the resolution of the depth map. Unlike the traditional method, our resolution is not limited by the number of microlenses inside the camera, and the depth map can be globally optimized. We validated the method with experiments on depth map reconstruction, depth calibration, and depth profile measurement, with the results indicating that the proposed approach is both efficient and accurate.

  4. Radon depth migration

    International Nuclear Information System (INIS)

    Hildebrand, S.T.; Carroll, R.J.

    1993-01-01

    A depth migration method is presented that used Radon-transformed common-source seismograms as input. It is shown that the Radon depth migration method can be extended to spatially varying velocity depth models by using asymptotic ray theory (ART) to construct wavefield continuation operators. These operators downward continue an incident receiver-array plane wave and an assumed point-source wavefield into the subsurface. The migration velocity model is constrain to have longer characteristic wavelengths than the dominant source wavelength such that the ART approximations for the continuation operators are valid. This method is used successfully to migrate two synthetic data examples: (1) a point diffractor, and (2) a dipping layer and syncline interface model. It is shown that the Radon migration method has a computational advantage over the standard Kirchhoff migration method in that fewer rays are computed in a main memory implementation

  5. Towards direct realisation of the SI unit of sound pressure in the audible hearing range based on optical free-field acoustic particle measurements

    Energy Technology Data Exchange (ETDEWEB)

    Koukoulas, Triantafillos, E-mail: triantafillos.koukoulas@npl.co.uk; Piper, Ben [Acoustics Group, National Physical Laboratory, Hampton Road, Teddington, Middlesex TW11 0LW (United Kingdom)

    2015-04-20

    Since the introduction of the International System of Units (the SI system) in 1960, weights, measures, standardised approaches, procedures, and protocols have been introduced, adapted, and extensively used. A major international effort and activity concentrate on the definition and traceability of the seven base SI units in terms of fundamental constants, and consequently those units that are derived from the base units. In airborne acoustical metrology and for the audible range of frequencies up to 20 kHz, the SI unit of sound pressure, the pascal, is realised indirectly and without any knowledge or measurement of the sound field. Though the principle of reciprocity was originally formulated by Lord Rayleigh nearly two centuries ago, it was devised in the 1940s and eventually became a calibration standard in the 1960s; however, it can only accommodate a limited number of acoustic sensors of specific types and dimensions. International standards determine the device sensitivity either through coupler or through free-field reciprocity but rely on the continuous availability of specific acoustical artefacts. Here, we show an optical method based on gated photon correlation spectroscopy that can measure sound pressures directly and absolutely in fully anechoic conditions, remotely, and without disturbing the propagating sound field. It neither relies on the availability or performance of any measurement artefact nor makes any assumptions of the device geometry and sound field characteristics. Most importantly, the required units of sound pressure and microphone sensitivity may now be experimentally realised, thus providing direct traceability to SI base units.

  6. Measuring depth in boreholes

    International Nuclear Information System (INIS)

    Hodson, G.M.

    1979-01-01

    This invention relates to a method of determining the depth of rock strata and other features of a borehole. It may be employed with particular advantage when access to the top of the borehole is difficult, for example in underwater operations. A radioactive marker, such as a source of gamma rays, is positioned near the top of the riser of a sub-sea wellhead structure. A radiation detector is lowered between the marker and a radioactive stratum and the length of line supplied is measured on the floating platform. This enables the depth of the stratum to be measured irrespective of tidal variations of the height of the platform. (U.K.)

  7. Scene depth estimation using a moving camera

    International Nuclear Information System (INIS)

    Sune, Jean-Luc

    1995-01-01

    This thesis presents a solution of the depth-from-motion problem. The movement of the monocular observer is known. We have focused our research on a direct method which avoid the optical flow estimation required by classical approaches. The direct application of this method is not exploitable. We need to define a validity domain to extract the set of image points where it is possible to get a correct depth value. Also, we use a multi-scale approach to improve the derivatives estimation. The depth estimation for a given scale is obtained by the minimisation of an energy function established in the context of statistic regularization. A fusion operator, merging the various spatial and temporal scales, has been used to estimate the final depth map. A correction-prediction schema is used to integrate the temporal information from an image sequence. The predicted depth map is considered as an additional observation and integrated in the fusion process. At each time, an error depth map is associated to the estimated depth map. (author) [fr

  8. Why bother about depth?

    DEFF Research Database (Denmark)

    Stæhr, Peter A.; Obrador, Biel; Christensen, Jesper Philip

    We present results from a newly developed method to determine depth specific rates of GPP, NEP and R using frequent automated profiles of DO and temperature. Metabolic rate calculations were made for three lakes of different trophic status using a diel DO methodology that integrates rates across...

  9. Defining depth of anesthesia.

    Science.gov (United States)

    Shafer, S L; Stanski, D R

    2008-01-01

    In this chapter, drawn largely from the synthesis of material that we first presented in the sixth edition of Miller's Anesthesia, Chap 31 (Stanski and Shafer 2005; used by permission of the publisher), we have defined anesthetic depth as the probability of non-response to stimulation, calibrated against the strength of the stimulus, the difficulty of suppressing the response, and the drug-induced probability of non-responsiveness at defined effect site concentrations. This definition requires measurement of multiple different stimuli and responses at well-defined drug concentrations. There is no one stimulus and response measurement that will capture depth of anesthesia in a clinically or scientifically meaningful manner. The "clinical art" of anesthesia requires calibration of these observations of stimuli and responses (verbal responses, movement, tachycardia) against the dose and concentration of anesthetic drugs used to reduce the probability of response, constantly adjusting the administered dose to achieve the desired anesthetic depth. In our definition of "depth of anesthesia" we define the need for two components to create the anesthetic state: hypnosis created with drugs such as propofol or the inhalational anesthetics and analgesia created with the opioids or nitrous oxide. We demonstrate the scientific evidence that profound degrees of hypnosis in the absence of analgesia will not prevent the hemodynamic responses to profoundly noxious stimuli. Also, profound degrees of analgesia do not guarantee unconsciousness. However, the combination of hypnosis and analgesia suppresses hemodynamic response to noxious stimuli and guarantees unconsciousness.

  10. Toward understanding atmospheric physics impacting the relationship between columnar aerosol optical depth and near-surface PM2.5 mass concentrations in Nevada and California, U.S.A., during 2013

    Science.gov (United States)

    Loría-Salazar, S. Marcela; Panorska, Anna; Arnott, W. Patrick; Barnard, James C.; Boehmler, Jayne M.; Holmes, Heather A.

    2017-12-01

    Determining the relationship between columnar aerosol optical depth (τext) and surface particulate matter concentrations (PM2.5) is desired to estimate surface aerosol concentrations over broad spatial and temporal scales using satellite remote sensing. However, remote sensing studies incur challenges when surface aerosol pollution (i.e. PM2.5) is not correlated with columnar conditions (i.e., τext). PM2.5 data fusion models that rely on satellite data and statistical relationships of τext and PM2.5 may not be able to capture the physical conditions impacting the relationships that cause columnar and surface aerosols to not be correlated in the western U.S. Therefore, an extensive examination of the atmospheric conditions is required to improve surface estimates of PM2.5 that rely on columnar aerosol measurements. This investigation uses datasets from both routine monitoring networks and models of meteorological variables and aerosol physical parameters to understand the atmospheric conditions under which surface aerosol pollution can be explained by column measurements in California and Nevada during 2013. A novel quadrant method, that utilizes statistical analysis, was developed to investigate the relationship between τext and PM2.5. The results from this investigation show that τext and PM2.5 had a positive association (τext and PM2.5 increase together) when local sources of pollution or wildfires dominated aerosol pollution in the presence of a deep and well-mixed planetary boundary layer (PBL). Moreover, τext and PM2.5 had no association (where the variables are not related) when stable conditions, long-range transport, or entrainment of air from above the PBL were observed. It was found that seasonal categorization of the relationship between τext and PM2.5, an approach commonly used in statistical models to estimate surface concentrations with satellite remote sensing, may not be enough to account for the atmospheric conditions that drive the

  11. Utilization of a new optical sensor unit to monitor the electrochemical elimination of selected dyes in water

    Science.gov (United States)

    Valica, M.; Černá, T.; Hostin, S.

    2017-10-01

    This paper presents results obtained by developed optical sensor, which consist from multi-wavelength LED light source and two photodetectors capable of measuring the change in optical signal along two different optical paths (absorbance and reflectance measurements). Arduino microcomputer was used for light source management and optical signal data measuring and recording. Analytical validation of developed optical sensor is presented in this paper. The performance of the system has been tested with varying water solution of dyes (malachite green, methyl orange, trypan red). These results show strong correlations between the optical signal response and colour change from the dyes. Sensor was used for continual in-situ monitoring of electrochemical elimination of selected dyes (current density 15.7 mA cm-2, electrolyte volume 4 L and NaCl concentration 2 g L-1). Maximum decolorization level varies with each dye. For malachite green was obtain 92,7 % decolorization (25 min); methyl orange 90,8% (8,5 min) and trypan red 84,7% decolorization after 33 min of electrochemical treatment.

  12. Ischemic Optic Neuropathy in Cardiac Surgery: Incidence and Risk Factors in the United States from the National Inpatient Sample 1998 to 2013.

    Science.gov (United States)

    Rubin, Daniel S; Matsumoto, Monica M; Moss, Heather E; Joslin, Charlotte E; Tung, Avery; Roth, Steven

    2017-05-01

    Ischemic optic neuropathy is the most common form of perioperative visual loss, with highest incidence in cardiac and spinal fusion surgery. To date, potential risk factors have been identified in cardiac surgery by only small, single-institution studies. To determine the preoperative risk factors for ischemic optic neuropathy, the authors used the National Inpatient Sample, a database of inpatient discharges for nonfederal hospitals in the United States. Adults aged 18 yr or older admitted for coronary artery bypass grafting, heart valve repair or replacement surgery, or left ventricular assist device insertion in National Inpatient Sample from 1998 to 2013 were included. Risk of ischemic optic neuropathy was evaluated by multivariable logistic regression. A total of 5,559,395 discharges met inclusion criteria with 794 (0.014%) cases of ischemic optic neuropathy. The average yearly incidence was 1.43 of 10,000 cardiac procedures, with no change during the study period (P = 0.57). Conditions increasing risk were carotid artery stenosis (odds ratio, 2.70), stroke (odds ratio, 3.43), diabetic retinopathy (odds ratio, 3.83), hypertensive retinopathy (odds ratio, 30.09), macular degeneration (odds ratio, 4.50), glaucoma (odds ratio, 2.68), and cataract (odds ratio, 5.62). Female sex (odds ratio, 0.59) and uncomplicated diabetes mellitus type 2 (odds ratio, 0.51) decreased risk. The incidence of ischemic optic neuropathy in cardiac surgery did not change during the study period. Development of ischemic optic neuropathy after cardiac surgery is associated with carotid artery stenosis, stroke, and degenerative eye conditions.

  13. Optical tomography of tissues

    International Nuclear Information System (INIS)

    Zimnyakov, D A; Tuchin, Valerii V

    2002-01-01

    Methods of optical tomography of biological tissues are considered, which include pulse-modulation and frequency-modulation tomography, diffusion tomography with the use of cw radiation sources, optical coherent tomography, speckle-correlation tomography of nonstationary media, and optoacoustic tomography. The method for controlling the optical properties of tissues is studied from the point of view of increasing a probing depth in optical coherent tomography. The modern state and prospects of the development of optical tomography are discussed. (review)

  14. Design and construction of a single unit multi-function optical encoder for a six-degree-of-freedom motion error measurement in an ultraprecision linear stage

    International Nuclear Information System (INIS)

    Lee, ChaBum; Kim, Gyu Ha; Lee, Sun-Kyu

    2011-01-01

    This paper presents the method of a six-degree-of-freedom (DOF) posture measurement in a linear stage by employing a single unit of an optical encoder. The proposed optical encoder was constructed to simultaneously measure the posture along the traveling axis; angular errors, pitch, yaw and roll; and translational errors, ΔX, ΔY and ΔZ. It consists of a diffractive optical element, a corner cube, four separate two-dimensional position-sensitive detectors, four photodiodes and auxiliary optics components. The circularly polarizing interferometric technique was integrated to measure the displacement of the stage along the traveling axis in a robust manner and the resolution was estimated to be less than 0.4 nm. Two types of stages were employed for the measurement implementation, the piezoelectric transducer-driven and the ballscrew-driven, and they were feedback-controlled for the traveling axis, respectively. With a single travel of the stage, it provided a six-DOF motion error with a high resolution, less than 0.03 arcsec, 20 nm and 0.4 nm for angular errors, ΔY and ΔZ, and ΔX, respectively, at the same time. As a result, it was seen that motion errors of the stage have relevance to the driving mechanism and the whole construction of the stage

  15. Headaches: In Depth

    Science.gov (United States)

    ... 4):199–208. Kemper KJ, Breuner CC. Complementary, holistic, and integrative medicine: headaches . Pediatrics in Review . 2010; ... based evaluation of complementary health approaches for pain management in the United States. Mayo Clinic Proceedings . September ...

  16. Coastal Secchi Depth Atlas

    Science.gov (United States)

    1985-07-01

    ptical properties 5pley. I(-,8). Table 5. Chart 4-Percentage of one-degree squares. 13 f plankton aleae . 0 Table 6. Global coverage-Percentage of one...optical properties result from (e.g., Colorado River), typical in mountainous (tectonic) regions, 9. Hunghlo (Red)110 Mekong and/or organic sediments...typical in mountainous (tectonic) regions, 9. Hungho (Red) 160 Inadequate 10. Mekong 160 Sufficient larger-sized particles in suspension. The

  17. Depth sectioning using electron energy loss spectroscopy

    International Nuclear Information System (INIS)

    D'Alfonso, A J; Findlay, S D; Allen, L J; Cosgriff, E C; Kirkland, A I; Nellist, P D; Oxley, M P

    2008-01-01

    The continued development of electron probe aberration correctors for scanning transmission electron microscopy has enabled finer electron probes, allowing atomic resolution column-by-column electron energy loss spectroscopy. Finer electron probes have also led to a decrease in the probe depth of focus, facilitating optical slicing or depth sectioning of samples. The inclusion of post specimen aberration corrected image forming lenses allows for scanning confocal electron microscopy with further improved depth resolution and selectivity. We show that in both scanning transmission electron microscopy and scanning confocal electron microscopy geometries, by performing a three dimensional raster scan through a specimen and detecting electrons scattered with a characteristic energy loss, it will be possible to determine the location of isolated impurities embedded within the bulk.

  18. Imaging of the vertical particle tracks without any depth scanning

    International Nuclear Information System (INIS)

    Soroko, L.M.

    2001-01-01

    The principle of a new optical microscope which enables us to get the image of a vertical particle track without any depth scanning is described. This new optical microscope contains a spatial transformer which consists of mirror lamellar elements and which produces a secondary in focus image of the vertical particle track. Properties of such a system are presented. A longitudinal resolution is estimated

  19. Progress in optics

    CERN Document Server

    Wolf, Emil

    2015-01-01

    The Progress in Optics series contains more than 300 review articles by distinguished research workers, which have become permanent records for many important developments, helping optical scientists and optical engineers stay abreast of their fields. Comprehensive, in-depth reviewsEdited by the leading authority in the field

  20. On the possibility of producing true real-time retinal cross-sectional images using a graphics processing unit enhanced master-slave optical coherence tomography system.

    Science.gov (United States)

    Bradu, Adrian; Kapinchev, Konstantin; Barnes, Frederick; Podoleanu, Adrian

    2015-07-01

    In a previous report, we demonstrated master-slave optical coherence tomography (MS-OCT), an OCT method that does not need resampling of data and can be used to deliver en face images from several depths simultaneously. In a separate report, we have also demonstrated MS-OCT's capability of producing cross-sectional images of a quality similar to those provided by the traditional Fourier domain (FD) OCT technique, but at a much slower rate. Here, we demonstrate that by taking advantage of the parallel processing capabilities offered by the MS-OCT method, cross-sectional OCT images of the human retina can be produced in real time. We analyze the conditions that ensure a true real-time B-scan imaging operation and demonstrate in vivo real-time images from human fovea and the optic nerve, with resolution and sensitivity comparable to those produced using the traditional FD-based method, however, without the need of data resampling.

  1. Shave-off depth profiling: Depth profiling with an absolute depth scale

    International Nuclear Information System (INIS)

    Nojima, M.; Maekawa, A.; Yamamoto, T.; Tomiyasu, B.; Sakamoto, T.; Owari, M.; Nihei, Y.

    2006-01-01

    Shave-off depth profiling provides profiling with an absolute depth scale. This method uses a focused ion beam (FIB) micro-machining process to provide the depth profile. We show that the shave-off depth profile of a particle reflected the spherical shape of the sample and signal intensities had no relationship to the depth. Through the introduction of FIB micro-sampling, the shave-off depth profiling of a dynamic random access memory (DRAM) tip was carried out. The shave-off profile agreed with a blue print from the manufacturing process. Finally, shave-off depth profiling is discussed with respect to resolutions and future directions

  2. Optical fiber network of the data acquisition sub system of SIIP Integral Information System of Process, Unit 2

    International Nuclear Information System (INIS)

    Moreno R, J.; Ramirez C, M.J.; Pina O, I.; Cortazar F, S.; Villavicencio R, A.

    1995-01-01

    In this article, a description of the communication network, based in optical fiber, which interlace the data acquisition equipment with the computers of Laguna Verde Nuclear Power Plant of SIIP is made. It is also presented a description of the equipment and accessories which conform the network. The requirements imposed by the Central which stated the selection of optical fiber as interlace mean are also outstanding. SIIP is a computerized, centralized and integrated system which make information functions by means of the acquisition of signals and the required computational process for the continuous evaluation of the nuclear power plant in normal and emergency conditions. Is an exclusive monitoring system with no one action on the generation process; that is to say, it only acquire, process, store information and assist to the personnel in the operational analysis of the nuclear plant. SIIP is a Joint Project with three participant institutions: Federal Electricity Commission/ Electrical Research Institute/ General Electric. (Author)

  3. Rooting depths of plants relative to biological and environmental factors

    International Nuclear Information System (INIS)

    Foxx, T.S.; Tierney, G.D.; Williams, J.M.

    1984-11-01

    In 1981 to 1982 an extensive bibliographic study was completed to document rooting depths of native plants in the United States. The data base presently contains 1034 citations with approximately 12,000 data elements. In this paper the data were analyzed for rooting depths as related to life form, soil type, geographical region, root type, family, root depth to shoot height ratios, and root depth to root lateral ratios. Average rooting depth and rooting frequencies were determined and related to present low-level waste site maintenance

  4. Institutional Strength in Depth

    International Nuclear Information System (INIS)

    Weightman, M.

    2016-01-01

    Much work has been undertaken in order to identify, learn and implement the lessons from the TEPCO Fukushima Daiichi nuclear accident. These have mainly targeted on engineering or operational lessons. Less attention has been paid to the institutional lessons, although there have been some measures to improve individual peer reviews, particularly by the World Association of Nuclear Operators, and the authoritative IAEA report published in 2015 brought forward several important lessons for regulators and advocated a system approach. The report noted that one of the contributing factors the accident was the tendency of stakeholders not to challenge. Additionally, it reported deficiencies in the regulatory authority and system. Earlier, the root cause of the accident was identified by a Japanese independent parliamentary report as being cultural and institutional. The sum total of the institutions, the safety system, was ineffective. While it is important to address the many technical and operational lessons these may not necessary address this more fundamental lesson, and may not serve to provide robust defences against human or institutional failings over a wide variety of possible events and combinations. The overall lesson is that we can have rigorous and comprehensive safety standards and other tools in place to deliver high levels of safety, but ultimately what is important is the ability of the nuclear safety system to ensure that the relevant institutions diligently and effectively apply those standards and tools — to be robust and resilient. This has led to the consideration of applying the principles of the strength in depth philosophy to a nuclear safety system as a way of providing a framework for developing, assessing, reviewing and improving the system. At an IAEA conference in October 2013, a model was presented for a robust national nuclear safety system based on strength in depth philosophy. The model highlighted three main layers: industry, the

  5. Offshore Wind Technology Depth Zones

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Coastal bathymetric depth, measured in meters at depth values of: -30, -60, -900 Shallow Zone (0-30m): Technology has been demonstrated on a commercial scale at...

  6. Enhancing Interpretation of Natural Phenomena through a Mathematical Apparatus: A Proposal of an Interactive Unit in Optics

    Science.gov (United States)

    Sokolowski, Andrzej

    2012-01-01

    This paper integrates technology, in the form of a physics simulation; science concepts, via image formation by lenses; and a mathematics apparatus, in the form of rational functions. All constituents merge into an instructional unit that can be embedded into a high school or undergraduate mathematics or physics course. The cognitive purpose of…

  7. Particulate matter and black carbon optical properties and emission factors from prescribed fires in the southeastern United States

    Science.gov (United States)

    The aerosol emissions from prescribed fires in the Southeastern United States were measured and compared to emissions from laboratory burns with fuels collected from the site. Fine particulate matter (PM2.5), black carbon, and aerosol light scattering and absorption were characte...

  8. Quantitative optical fluorescence microprobe measurements of stresses around indentations in Al2O3 and Al2O3/SiC nanocomposites: The influence of depth resolution and specimen translucency

    International Nuclear Information System (INIS)

    Guo Sheng; Todd, R.I.

    2011-01-01

    Residual stresses around 1 kg Vickers indentations in Al 2 O 3 and Al 2 O 3 /SiC nanocomposites were measured using high-resolution Cr 3+ fluorescence microscopy. Experiments and modelling showed that the use of non-confocal microscopes can lead to significant underestimation of the surface stress in Al 2 O 3 because of the sampling of subsurface regions where the stresses are lower. The nanocomposites were less sensitive to the depth resolution of the microscope because their strong absorption limited the depth from which fluorescent radiation was collected. The use of confocal microscope settings allowed accurate measurements to be made and the indentation stresses were found to be very similar in Al 2 O 3 and the Al 2 O 3 /SiC nanocomposites. The stresses measured were significantly different from the predictions of the Yoffe model for indentation stresses. This was because of indentation cracking, which is not accounted for in the model. Cracking was also considered to be important in determining the plastic zone size in ceramics, which is much smaller relative to the indentation size than in metals.

  9. Wavefield Extrapolation in Pseudo-depth Domain

    KAUST Repository

    Ma, Xuxin

    2011-12-11

    Wave-equation based seismic migration and inversion tools are widely used by the energy industry to explore hydrocarbon and mineral resources. By design, most of these techniques simulate wave propagation in a space domain with the vertical axis being depth measured from the surface. Vertical depth is popular because it is a straightforward mapping of the subsurface space. It is, however, not computationally cost-effective because the wavelength changes with local elastic wave velocity, which in general increases with depth in the Earth. As a result, the sampling per wavelength also increases with depth. To avoid spatial aliasing in deep fast media, the seismic wave is oversampled in shallow slow media and therefore increase the total computation cost. This issue is effectively tackled by using the vertical time axis instead of vertical depth. This is because in a vertical time representation, the "wavelength" is essentially time period for vertical rays. This thesis extends the vertical time axis to the pseudo-depth axis, which features distance unit while preserving the properties of the vertical time representation. To explore the potentials of doing wave-equation based imaging in the pseudo-depth domain, a Partial Differential Equation (PDE) is derived to describe acoustic wave in this new domain. This new PDE is inherently anisotropic because the use of a constant vertical velocity to convert between depth and vertical time. Such anisotropy results in lower reflection coefficients compared with conventional space domain modeling results. This feature is helpful to suppress the low wavenumber artifacts in reverse-time migration images, which are caused by the widely used cross-correlation imaging condition. This thesis illustrates modeling acoustic waves in both conventional space domain and pseudo-depth domain. The numerical tool used to model acoustic waves is built based on the lowrank approximation of Fourier integral operators. To investigate the potential

  10. Information content in spectral dependencies of optical unit volume parameters under action of He-Ne laser on blood

    Science.gov (United States)

    Khairullina, Alphiya Y.; Oleinik, Tatiana V.

    1995-01-01

    Our previous works concerned with the development of methods for studying blood and action of low-intensity laser radiation on blood and erythrocyte suspensions had shown the light- scattering methods gave a large body of information on a medium studied due to the methodological relationship between irradiation processes and techniques for investigations. Detail analysis of spectral diffuse reflectivities and transmissivities of optically thick blood layers, spectral absorptivities calculated on this basis over 600 - 900 nm, by using different approximations, for a pathological state owing to hypoxia testifies to the optical significance of not only hemoglobin derivatives but also products of hemoglobin decomposition. Laser action on blood is specific and related to an initial state of blood absorption due to different composition of chromoproteids. This work gives the interpretation of spectral observations. Analysis of spectral dependencies of the exinction coefficient e, mean cosine m of phase function, and parameter Q equals (epsilon) (1-(mu) )H/(lambda) (H - hematocrit) testifies to decreasing the relative index of refraction of erythrocytes and to morphological changes during laser action under pathology owing to hypoxia. The possibility to obtain physical and chemical information on the state of blood under laser action in vivo is shown to be based on the method proposed by us for calculating multilayered structures modeling human organs and on the technical implementation of this method.

  11. Method and apparatus of prefetching streams of varying prefetch depth

    Science.gov (United States)

    Gara, Alan [Mount Kisco, NY; Ohmacht, Martin [Yorktown Heights, NY; Salapura, Valentina [Chappaqua, NY; Sugavanam, Krishnan [Mahopac, NY; Hoenicke, Dirk [Seebruck-Seeon, DE

    2012-01-24

    Method and apparatus of prefetching streams of varying prefetch depth dynamically changes the depth of prefetching so that the number of multiple streams as well as the hit rate of a single stream are optimized. The method and apparatus in one aspect monitor a plurality of load requests from a processing unit for data in a prefetch buffer, determine an access pattern associated with the plurality of load requests and adjust a prefetch depth according to the access pattern.

  12. TRENDS IN ESTIMATED MIXING DEPTH DAILY MAXIMUMS

    Energy Technology Data Exchange (ETDEWEB)

    Buckley, R; Amy DuPont, A; Robert Kurzeja, R; Matt Parker, M

    2007-11-12

    Mixing depth is an important quantity in the determination of air pollution concentrations. Fireweather forecasts depend strongly on estimates of the mixing depth as a means of determining the altitude and dilution (ventilation rates) of smoke plumes. The Savannah River United States Forest Service (USFS) routinely conducts prescribed fires at the Savannah River Site (SRS), a heavily wooded Department of Energy (DOE) facility located in southwest South Carolina. For many years, the Savannah River National Laboratory (SRNL) has provided forecasts of weather conditions in support of the fire program, including an estimated mixing depth using potential temperature and turbulence change with height at a given location. This paper examines trends in the average estimated mixing depth daily maximum at the SRS over an extended period of time (4.75 years) derived from numerical atmospheric simulations using two versions of the Regional Atmospheric Modeling System (RAMS). This allows for differences to be seen between the model versions, as well as trends on a multi-year time frame. In addition, comparisons of predicted mixing depth for individual days in which special balloon soundings were released are also discussed.

  13. Defence in depth perspectives

    International Nuclear Information System (INIS)

    Veneau, Tania; Ferrier, Agnes; Barbaud, Jean

    2017-01-01

    The Defence in Depth (DiD) concept was introduced to the field of nuclear safety in the sixties and early seventies. Even though it was not well developed at the beginning, the principles rapidly became close to those currently used. The concept was then composed of 3 levels, and was already associated with operating conditions. These principles have progressed over time and now there are five levels, including progressively situations issued from design extension conditions, to cope with severe accidents and dealing with accident management off-site. Indeed, human and organizational features are considered as a part of the safety provisions at all levels in an integrated approach that is not just related to reactor design. That's the current vision from IAEA, addressed first in INSAG 3 then in INSAG 10, and in the IAEA standards requirements currently addressed by SSR-2/1 superseding NS-R-1). These five levels of DiD are also referred to in other texts including WENRA documents in Europe, but also in the national requirements from different countries. Thus, the application of DiD principle has become a recognized international practice. The 2011 Fukushima Daiichi accidents, even if they raised many questions on nuclear safety issues, confirmed the merits of the DiD concept. Indeed, lessons learned from the accidents have reinforced the use of the DiD concept to ensure adequate safety. The discussions focused more on the implementation of the concept (how it has been or can be used in practice) than the concept itself, and in particular on the following subjects: the notion of level robustness, generally addressed separately from the levels definition, but playing an important role for the efficiency of the concept; the notion of levels independence and the need for strengthening them; the role of diversity to achieve levels independence. However, a prescription of additional diversity and independence across all safety levels could result in inappropriately

  14. Optics/Optical Diagnostics Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — The Optics/Optical Diagnostics Laboratory supports graduate instruction in optics, optical and laser diagnostics and electro-optics. The optics laboratory provides...

  15. Evaluation of Depth of Field for depth perception in DVR

    KAUST Repository

    Grosset, A.V.Pascal; Schott, Mathias; Bonneau, Georges-Pierre; Hansen, Charles D.

    2013-01-01

    In this paper we present a user study on the use of Depth of Field for depth perception in Direct Volume Rendering. Direct Volume Rendering with Phong shading and perspective projection is used as the baseline. Depth of Field is then added to see its impact on the correct perception of ordinal depth. Accuracy and response time are used as the metrics to evaluate the usefulness of Depth of Field. The onsite user study has two parts: static and dynamic. Eye tracking is used to monitor the gaze of the subjects. From our results we see that though Depth of Field does not act as a proper depth cue in all conditions, it can be used to reinforce the perception of which feature is in front of the other. The best results (high accuracy & fast response time) for correct perception of ordinal depth occurs when the front feature (out of the two features users were to choose from) is in focus and perspective projection is used. © 2013 IEEE.

  16. Evaluation of Depth of Field for depth perception in DVR

    KAUST Repository

    Grosset, A.V.Pascal

    2013-02-01

    In this paper we present a user study on the use of Depth of Field for depth perception in Direct Volume Rendering. Direct Volume Rendering with Phong shading and perspective projection is used as the baseline. Depth of Field is then added to see its impact on the correct perception of ordinal depth. Accuracy and response time are used as the metrics to evaluate the usefulness of Depth of Field. The onsite user study has two parts: static and dynamic. Eye tracking is used to monitor the gaze of the subjects. From our results we see that though Depth of Field does not act as a proper depth cue in all conditions, it can be used to reinforce the perception of which feature is in front of the other. The best results (high accuracy & fast response time) for correct perception of ordinal depth occurs when the front feature (out of the two features users were to choose from) is in focus and perspective projection is used. © 2013 IEEE.

  17. Fiber optic connector

    Science.gov (United States)

    Rajic, Slobodan; Muhs, Jeffrey D.

    1996-01-01

    A fiber optic connector and method for connecting composite materials within which optical fibers are imbedded. The fiber optic connector includes a capillary tube for receiving optical fibers at opposing ends. The method involves inserting a first optical fiber into the capillary tube and imbedding the unit in the end of a softened composite material. The capillary tube is injected with a coupling medium which subsequently solidifies. The composite material is machined to a desired configuration. An external optical fiber is then inserted into the capillary tube after fluidizing the coupling medium, whereby the optical fibers are coupled.

  18. SDSS-IV MaNGA: identification of active galactic nuclei in optical integral field unit surveys

    Science.gov (United States)

    Wylezalek, Dominika; Zakamska, Nadia L.; Greene, Jenny E.; Riffel, Rogemar A.; Drory, Niv; Andrews, Brett H.; Merloni, Andrea; Thomas, Daniel

    2018-02-01

    In this paper, we investigate 2727 galaxies observed by MaNGA as of 2016 June to develop spatially resolved techniques for identifying signatures of active galactic nuclei (AGNs). We identify 303 AGN candidates. The additional spatial dimension imposes challenges in identifying AGNs due to contamination from diffuse ionized gas, extraplanar gas and photoionization by hot stars. We show that the combination of spatially resolved line diagnostic diagrams and additional cuts on H α surface brightness and H α equivalent width can distinguish between AGN-like signatures and high-metallicity galaxies with low-ionization nuclear emission-line regions-like spectra. Low-mass galaxies with high specific star formation rates are particularly difficult to diagnose and routinely show diagnostic line ratios outside of the standard star formation locus. We develop a new diagnostic - the distance from the standard diagnostic line in the line-ratio space - to evaluate the significance of the deviation from the star formation locus. We find 173 galaxies that would not have been selected as AGN candidates based on single-fibre spectral measurements but exhibit photoionization signatures suggestive of AGN activity in the Mapping Nearby Galaxies at APO resolved observations, underscoring the power of large integral field unit surveys. A complete census of these new AGN candidates is necessary to understand their nature and probe the complex co-evolution of supermassive black holes and their hosts.

  19. ISLSCP II Ecosystem Rooting Depths

    Data.gov (United States)

    National Aeronautics and Space Administration — The goal of this study was to predict the global distribution of plant rooting depths based on data about global aboveground vegetation structure and climate....

  20. ISLSCP II Ecosystem Rooting Depths

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: The goal of this study was to predict the global distribution of plant rooting depths based on data about global aboveground vegetation structure and...

  1. Real-time processing for full-range Fourier-domain optical-coherence tomography with zero-filling interpolation using multiple graphic processing units.

    Science.gov (United States)

    Watanabe, Yuuki; Maeno, Seiya; Aoshima, Kenji; Hasegawa, Haruyuki; Koseki, Hitoshi

    2010-09-01

    The real-time display of full-range, 2048?axial pixelx1024?lateral pixel, Fourier-domain optical-coherence tomography (FD-OCT) images is demonstrated. The required speed was achieved by using dual graphic processing units (GPUs) with many stream processors to realize highly parallel processing. We used a zero-filling technique, including a forward Fourier transform, a zero padding to increase the axial data-array size to 8192, an inverse-Fourier transform back to the spectral domain, a linear interpolation from wavelength to wavenumber, a lateral Hilbert transform to obtain the complex spectrum, a Fourier transform to obtain the axial profiles, and a log scaling. The data-transfer time of the frame grabber was 15.73?ms, and the processing time, which includes the data transfer between the GPU memory and the host computer, was 14.75?ms, for a total time shorter than the 36.70?ms frame-interval time using a line-scan CCD camera operated at 27.9?kHz. That is, our OCT system achieved a processed-image display rate of 27.23 frames/s.

  2. Development and Applications of Time of Flight Neutron Depth Profiling

    International Nuclear Information System (INIS)

    Cady, Bingham; Unlu, Kenan

    2005-01-01

    The depth profiles of intentional or intrinsic constituents of a sample provide valuable information for the characterization of materials. For example, the subtle differences in spatial distribution and composition of many chemical species in the near surface region and across interfacial boundaries can significantly alter the electronic and optical properties of materials. A number of analytical techniques for depth profiling have been developed during the last two decades. neutron Depth Profiling (NDP) is one of the leading analytical techniques. The NDP is a nondestructive near surface technique that utilizes thermal/cold neutron beam to measure the concentration of specific light elements versus their depth in materials. The depth is obtained from the energy loss of protons, alphas or recoil atoms in substrate materials. Since the charged particle energy determination using surface barrier detector is used for NDP, the depth resolution is highly dependent on the detectors an d detection instruments. The depth resolutions of a few tens of nm are achieved with available NDP facilities in the world. However, the performance of NDP needs to be improved in order to obtain a few A depth resolutions

  3. High bit depth infrared image compression via low bit depth codecs

    Science.gov (United States)

    Belyaev, Evgeny; Mantel, Claire; Forchhammer, Søren

    2017-08-01

    Future infrared remote sensing systems, such as monitoring of the Earth's environment by satellites, infrastructure inspection by unmanned airborne vehicles etc., will require 16 bit depth infrared images to be compressed and stored or transmitted for further analysis. Such systems are equipped with low power embedded platforms where image or video data is compressed by a hardware block called the video processing unit (VPU). However, in many cases using two 8-bit VPUs can provide advantages compared with using higher bit depth image compression directly. We propose to compress 16 bit depth images via 8 bit depth codecs in the following way. First, an input 16 bit depth image is mapped into 8 bit depth images, e.g., the first image contains only the most significant bytes (MSB image) and the second one contains only the least significant bytes (LSB image). Then each image is compressed by an image or video codec with 8 bits per pixel input format. We analyze how the compression parameters for both MSB and LSB images should be chosen to provide the maximum objective quality for a given compression ratio. Finally, we apply the proposed infrared image compression method utilizing JPEG and H.264/AVC codecs, which are usually available in efficient implementations, and compare their rate-distortion performance with JPEG2000, JPEG-XT and H.265/HEVC codecs supporting direct compression of infrared images in 16 bit depth format. A preliminary result shows that two 8 bit H.264/AVC codecs can achieve similar result as 16 bit HEVC codec.

  4. Λ and Σ well depth

    International Nuclear Information System (INIS)

    Satoh, Eiji

    1982-01-01

    The Λ well depth was calculated by taking into account the effect of the ΛΣ conversion. Takahashi et al. obtained the separate type of potentials which described the hyperon-nucleon interaction up to p waves. Two types of the potentials among several types they obtained were used to calculate the Λ well depth. The G matrix was easily calculated, and the Λ well depth was obtained by integrating the G matrix in momentum space up to the Fermi surface. The effect of the ΛΣ conversion was given by an equation. The total Λ well depth was estimated to be 9.13 MeV and 49.36 MeV for each type of potential, respectively. It was concluded that the argument by Bodmer et al. was not correct. The Σ well depth was also calculated using the potential obtained by Takahashi et al. for I = 1/2 and the one obtained by Σ + p → Σ + p scattering data for I = 3/2. The obtained value 35.30 MeV may be overestimated, and the experimental value is expected to be in the range from 20 MeV to 30 MeV. (Ito, K.)

  5. Nonlinear optical systems

    CERN Document Server

    Lugiato, Luigi; Brambilla, Massimo

    2015-01-01

    Guiding graduate students and researchers through the complex world of laser physics and nonlinear optics, this book provides an in-depth exploration of the dynamics of lasers and other relevant optical systems, under the umbrella of a unitary spatio-temporal vision. Adopting a balanced approach, the book covers traditional as well as special topics in laser physics, quantum electronics and nonlinear optics, treating them from the viewpoint of nonlinear dynamical systems. These include laser emission, frequency generation, solitons, optically bistable systems, pulsations and chaos and optical pattern formation. It also provides a coherent and up-to-date treatment of the hierarchy of nonlinear optical models and of the rich variety of phenomena they describe, helping readers to understand the limits of validity of each model and the connections among the phenomena. It is ideal for graduate students and researchers in nonlinear optics, quantum electronics, laser physics and photonics.

  6. Optical materials

    International Nuclear Information System (INIS)

    Poker, D.B.; Ortiz, C.

    1989-01-01

    This book reports on: Diamond films, Synthesis of optical materials, Structure related optical properties, Radiation effects in optical materials, Characterization of optical materials, Deposition of optical thin films, and Optical fibers and waveguides

  7. Spectrometric kidney depth measurement method

    International Nuclear Information System (INIS)

    George, P.; Soussaline, F.; Raynaud, C.

    1976-01-01

    The method proposed uses the single posterior surface measurement of the kidney radioactivity distribution. The ratio C/P of the number of scattered photons to the number of primary photons, which is a function of the tissue depth penetrated, is calculated for a given region. The parameters on which the C/P value depends are determined from studies on phantoms. On the basis of these results the kidney depth was measured on a series of 13 patients and a correlation was established between the value thus calculated and that obtained by the profile method. The reproducibility of the method is satisfactory [fr

  8. Heat flow of standard depth

    International Nuclear Information System (INIS)

    Cull, J.P.

    1981-01-01

    Secular and long-term periodic changes in surface temperature cause perturbations to the geothermal gradient which may be significant to depths of at least 1000 m, and major corrections are required to determine absolute values of heat flow from the Earth's interior. However, detailed climatic models remain contentious and estimates of error in geothermal gradients differ widely. Consequently, regions of anomalous heat flow which could contain geothermal resources may be more easily resolved by measuring relative values at a standard depth (e.g. 100 m) so that all data are subject to similar corrections. (orig./ME)

  9. Extreme depth-of-field intraocular lenses

    Science.gov (United States)

    Baker, Kenneth M.

    1996-05-01

    A new technology brings the full aperture single vision pseudophakic eye's effective hyperfocal distance within the half-meter range. A modulated index IOL containing a subsurface zeroth order coherent microlenticular mosaic defined by an index gradient adds a normalizing function to the vergences or parallactic angles of incoming light rays subtended from field object points and redirects them, in the case of near-field images, to that of far-field images. Along with a scalar reduction of the IOL's linear focal range, this results in an extreme depth of field with a narrow depth of focus and avoids the focal split-up, halo, and inherent reduction in contrast of multifocal IOLs. A high microlenticular spatial frequency, which, while still retaining an anisotropic medium, results in a nearly total zeroth order propagation throughout the visible spectrum. The curved lens surfaces still provide most of the refractive power of the IOL, and the unique holographic fabrication technology is especially suitable not only for IOLs but also for contact lenses, artificial corneas, and miniature lens elements for cameras and other optical devices.

  10. Study of total column atmospheric aerosol optical depth, ozone and ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    general circulation models. ... at all wavelengths from initial to later part of observation period due to cloud-scavenging and rain-washout effects as well as signature of coastal aerosol loading. ... important roles in the study of the Earth's climate.

  11. Characteristics of spectral aerosol optical depths over India during ...

    Indian Academy of Sciences (India)

    regions leads to remarkable changes in the magnitude of the AODs and their wavelength depen- dencies during ... climate directly as well as indirectly; though the magnitudes .... analysis have been carried out following a common protocol.

  12. MODIS Aerosol Optical Depth Bias Adjustment Using Machine Learning Algorithms

    Science.gov (United States)

    Albayrak, Arif; Wei, Jennifer; Petrenko, Maksym; Lary, David; Leptoukh, Gregory

    2011-01-01

    To monitor the earth atmosphere and its surface changes, satellite based instruments collect continuous data. While some of the data is directly used, some others such as aerosol properties are indirectly retrieved from the observation data. While retrieved variables (RV) form very powerful products, they don't come without obstacles. Different satellite viewing geometries, calibration issues, dynamically changing atmospheric and earth surface conditions, together with complex interactions between observed entities and their environment affect them greatly. This results in random and systematic errors in the final products.

  13. Aerosol optical depth retrieval over snow using AATSR data

    NARCIS (Netherlands)

    Mei, L.; Xue, Y.; Kokhanovsky, A.A.; Hoyningen-Huene, W. von; Istomina, L.; Leeuw, G. de; Burrows, J.P.; Guang, J.; Jing, Y.

    2013-01-01

    Aerosol observations over the Arctic are important because of the effects of aerosols on Arctic climate, such as their direct and indirect effects on the Earth's radiation balance and on snow albedo. Although information on aerosol properties is available from ground-based measurements, passive

  14. Pursuing the Depths of Knowledge

    Science.gov (United States)

    Boyles, Nancy

    2016-01-01

    Today's state literacy standards and assessments demand deeper levels of knowledge from students. But many teachers ask, "What does depth of knowledge look like on these new, more rigorous assessments? How do we prepare students for this kind of thinking?" In this article, Nancy Boyles uses a sampling of questions from the PARCC and SBAC…

  15. Tunable micro-optics

    CERN Document Server

    Duppé, Claudia

    2015-01-01

    Presenting state-of-the-art research into the dynamic field of tunable micro-optics, this is the first book to provide a comprehensive survey covering a varied range of topics including novel materials, actuation concepts and new imaging systems in optics. Internationally renowned researchers present a diverse range of chapters on cutting-edge materials, devices and subsystems, including soft matter, artificial muscles, tunable lenses and apertures, photonic crystals, and complete tunable imagers. Special contributions also provide in-depth treatment of micro-optical characterisation, scanners, and the use of natural eye models as inspiration for new concepts in advanced optics. With applications extending from medical diagnosis to fibre telecommunications, Tunable Micro-optics equips readers with a solid understanding of the broader technical context through its interdisciplinary approach to the realisation of new types of optical systems. This is an essential resource for engineers in industry and academia,...

  16. Intercomparison On Depth Dose Measurement

    International Nuclear Information System (INIS)

    Rohmah, N; Akhadi, M

    1996-01-01

    Intercomparation on personal dose evaluation system has been carried out between CSRSR-NAEA of Indonesia toward Standard Laboratory of JAERI (Japan) and ARL (Australia). The intercomparison was in 10 amm depth dose measurement , Hp (10), from the intercomparison result could be stated that personal depth dose measurement conducted by CSRSR was sufficiently good. Deviation of dose measurement result using personal dosemeter of TLD BG-1 type which were used by CSRSR in the intercomparison and routine photon personal dose monitoring was still in internationally agreed limit. Maximum deviation of reported doses by CSRSR compared to delivered doses for dosemeter irradiation by JAERI was -10.0 percent and by ARL was +29 percent. Maximum deviation permitted in personal dose monitoring is ± 50 percent

  17. Applications of positron depth profiling

    International Nuclear Information System (INIS)

    Hakvoort, R.A.

    1993-01-01

    In this thesis some contributions of the positron-depth profiling technique to materials science have been described. Following studies are carried out: Positron-annihilation measurements on neon-implanted steel; Void creation in silicon by helium implantation; Density of vacancy-type defects present in amorphous silicon prepared by ion implantation; Measurements of other types of amorphous silicon; Epitaxial cobalt disilicide prepared by cobalt outdiffusion. Positron-annihilation experiments on low-pressure CVD silicon-nitride films. (orig./MM)

  18. Applications of positron depth profiling

    Energy Technology Data Exchange (ETDEWEB)

    Hakvoort, R A

    1993-12-23

    In this thesis some contributions of the positron-depth profiling technique to materials science have been described. Following studies are carried out: Positron-annihilation measurements on neon-implanted steel; Void creation in silicon by helium implantation; Density of vacancy-type defects present in amorphous silicon prepared by ion implantation; Measurements of other types of amorphous silicon; Epitaxial cobalt disilicide prepared by cobalt outdiffusion. Positron-annihilation experiments on low-pressure CVD silicon-nitride films. (orig./MM).

  19. Optic neuritis

    Science.gov (United States)

    Retro-bulbar neuritis; Multiple sclerosis - optic neuritis; Optic nerve - optic neuritis ... The exact cause of optic neuritis is unknown. The optic nerve carries visual information from your eye to the brain. The nerve can swell when ...

  20. Subjective method of refractometry and depth of focus

    Directory of Open Access Journals (Sweden)

    Nikolai M. Sergienko

    2012-04-01

    Conclusion: The traditional method of subjective refractometry with application of trial lenses was developed on the basis of data of large optical aberrations and significant depth of focus which values should be taken into account during interpretation of results of subjective refractometry. Our data regarding to prevalence of emmetropic refraction falls in line with basic science provisions in respect of the physiology of the eye.

  1. Glow discharge depth analysis of metallic elements in steels

    International Nuclear Information System (INIS)

    Berneron, R.

    The glow discharge lamp designed by Grimm gives new possibilities in the optical spectrometry. The plasma produced is a cool emissive source and its advantages are the following: low spectral background, no reabsorption, linear calibration, very stable emission, very high yield. The sputtering produced by ionic bombardment of the sample enables the depth repartition of several elements to be made in the same run [fr

  2. Are galaxy discs optically thick?

    International Nuclear Information System (INIS)

    Disney, Michael; Davies, Jonathan; Phillipps, Steven

    1989-01-01

    We re-examine the classical optical evidence for the low optical depths traditionally assigned to spiral discs and argue that it is highly model-dependent and unconvincing. In particular, layered models with a physically thin but optically thick dust layer behave like optically thin discs. The opposite hypotheses, that such discs are optically thick is then examined in the light of modern evidence. We find it to be consistent with the near-infrared and IRAS observations, with the surface brightnesses, with the HI and CO column densities and with the Hα measurements. (author)

  3. Characterisation of optically cleared paper by optical coherence tomography

    International Nuclear Information System (INIS)

    Fabritius, T; Alarousu, E; Prykaeri, T; Hast, J; Myllylae, Risto

    2006-01-01

    Due to the highly light scattering nature of paper, the imaging depth of optical methods such as optical coherence tomography (OCT) is limited. In this work, we study the effect of refractive index matching on improving the imaging depth of OCT in paper. To this end, four different refractive index matching liquids (ethanol, 1-pentanol, glycerol and benzyl alcohol) with a refraction index between 1.359 and 1.538 were used in experiments. Low coherent light transmission was studied in commercial copy paper sheets, and the results indicate that benzyl alcohol offers the best improvement in imaging depth, while also being sufficiently stable for the intended purpose. Constructed cross-sectional images demonstrate visually that the imaging depth of OCT is considerably improved by optical clearing. Both surfaces of paper sheets can be detected along with information about the sheet's inner structure. (laser applications and other topics in quantum electronics)

  4. Simplicial band depth for multivariate functional data

    KAUST Repository

    López-Pintado, Sara

    2014-03-05

    We propose notions of simplicial band depth for multivariate functional data that extend the univariate functional band depth. The proposed simplicial band depths provide simple and natural criteria to measure the centrality of a trajectory within a sample of curves. Based on these depths, a sample of multivariate curves can be ordered from the center outward and order statistics can be defined. Properties of the proposed depths, such as invariance and consistency, can be established. A simulation study shows the robustness of this new definition of depth and the advantages of using a multivariate depth versus the marginal depths for detecting outliers. Real data examples from growth curves and signature data are used to illustrate the performance and usefulness of the proposed depths. © 2014 Springer-Verlag Berlin Heidelberg.

  5. Optical smart card using semipassive communication.

    Science.gov (United States)

    Glaser, I; Green, Shlomo; Dimkov, Ilan

    2006-03-15

    An optical secure short-range communication system is presented. The mobile unit (optical smart card) of this system utilizes a retroreflector with an optical modulator, using light from the stationary unit; this mobile unit has very low power consumption and can be as small as a credit card. Such optical smart cards offer better security than RF-based solutions, yet do not require physical contact. Results from a feasibility study model are included.

  6. Reconfigurable optical-to-optical frequency conversion method and apparatus

    Science.gov (United States)

    Zortman, William A.; Lentine, Anthony L.

    2017-04-18

    A photonic device is provided for impressing a modulation pattern on an optical carrier. The device includes a unit in which a photodetector and an optical microresonator are monolithically integrated. The device further includes an optical waveguide evanescently coupled to the optical microresonator and having at least an upstream portion configured to carry at least one optical carrier toward the microresonator. The optical microresonator is tunable so as to resonate with the optical carrier frequency. The optical microresonator and the photodetector are mutually coupled such that in operation, charge carriers photogenerated in the photodetector are injected into the microresonator, where the photocurrent changes the resonant conditions. In some embodiments the device is operable as an optical-to-optical frequency converter. In other embodiments the device is operable as an oscillator.

  7. Updating default depths in the ISC bulletin

    Science.gov (United States)

    Bolton, Maiclaire K.; Storchak, Dmitry A.; Harris, James

    2006-09-01

    The International Seismological Centre (ISC) publishes the definitive global bulletin of earthquake locations. In the ISC bulletin, we aim to obtain a free depth, but often this is not possible. Subsequently, the first option is to obtain a depth derived from depth phases. If depth phases are not available, we then use the reported depth from a reputable local agency. Finally, as a last resort, we set a default depth. In the past, common depths of 10, 33, or multiples of 50 km have been assigned. Assigning a more meaningful default depth, specific to a seismic region will increase the consistency of earthquake locations within the ISC bulletin and allow the ISC to publish better positions and magnitude estimates. It will also improve the association of reported secondary arrivals to corresponding seismic events. We aim to produce a global set of default depths, based on a typical depth for each area, from well-constrained events in the ISC bulletin or where depth could be constrained using a consistent set of depth phase arrivals provided by a number of different reporters. In certain areas, we must resort to using other assumptions. For these cases, we use a global crustal model (Crust2.0) to set default depths to half the thickness of the crust.

  8. Optical gyroscope

    Science.gov (United States)

    Seifollahi, Alireza

    It is said that future of the world is based on space exploration which leads us to think more about low cost and light weight instruments. Cheap and sensitive instruments should be de-signed and replace the expensive ones. One of the required instruments in space ships is gyroscope controls the direction of space ship. In this article I am going to give an idea to use optical properties in a new gyroscope which will be cheaper as well as more sensitive in com-pare with most of the being used normal gyroscope nowadays. This instrument uses an optical system to measure the angular changes in the direction of a space craft movements in any of the three axels. Any movement, even very small one, will move a crystal bulb which is lashed by some narrow elastic bands in a fixed box surrounded by three optical sources and light meters. Light meters measure the attitude and the angel of changes in the light beams going through the bulb which is related to the amount of changes in the space craft directions. The system will be very sensitive even against movement around its access. As an electro digital device in connection to a Main Process Unit (MPU) it can be used in Stability Augmentation System (SAS) in a space ship. The sensitivity rate of the instrument will be based on the quality and sensitivity of the light meters.

  9. EOP TDRs (Temperature-Depth-Recordings) Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Temperature-depth-recorders (TDRs) were attached to commercial longline and research Cobb trawl gear to obtain absolute depth and temperature measurement during...

  10. Simplicial band depth for multivariate functional data

    KAUST Repository

    Ló pez-Pintado, Sara; Sun, Ying; Lin, Juan K.; Genton, Marc G.

    2014-01-01

    sample of curves. Based on these depths, a sample of multivariate curves can be ordered from the center outward and order statistics can be defined. Properties of the proposed depths, such as invariance and consistency, can be established. A simulation

  11. Gaspe hole sets depth record

    Energy Technology Data Exchange (ETDEWEB)

    1970-03-09

    The deepest diamond-cored hole in the Western Hemisphere, Gulf Sunnybank No. 1 on the Gaspe Peninsula of Quebec, has been completed at a depth of 11,600 ft. This is the deepest cored hole to be drilled anywhere in search of oil and gas production, and the deepest to be drilled using a wire-line core recovery technique. The well was completed in 183 days, and was cored continuously below the surface casing which was set and cemented at 1,004 ft. After underreaming a portion of the bottom of the hole, intermediate casing was set and cemented at 8,000 ft as a safety precaution against possible high oil or gas-fluid pressure. Actual coring time, after deducting time for underreaming and casing operations, was 152 days. Because of the cost of transporting a conventional oil-drilling rig to the E. location, the 89-ft mining rig was modified for the project. The contractor was Heath and Sherwood Drilling (Western) Ltd.

  12. A new method for depth profiling reconstruction in confocal microscopy

    Science.gov (United States)

    Esposito, Rosario; Scherillo, Giuseppe; Mensitieri, Giuseppe

    2018-05-01

    Confocal microscopy is commonly used to reconstruct depth profiles of chemical species in multicomponent systems and to image nuclear and cellular details in human tissues via image intensity measurements of optical sections. However, the performance of this technique is reduced by inherent effects related to wave diffraction phenomena, refractive index mismatch and finite beam spot size. All these effects distort the optical wave and cause an image to be captured of a small volume around the desired illuminated focal point within the specimen rather than an image of the focal point itself. The size of this small volume increases with depth, thus causing a further loss of resolution and distortion of the profile. Recently, we proposed a theoretical model that accounts for the above wave distortion and allows for a correct reconstruction of the depth profiles for homogeneous samples. In this paper, this theoretical approach has been adapted for describing the profiles measured from non-homogeneous distributions of emitters inside the investigated samples. The intensity image is built by summing the intensities collected from each of the emitters planes belonging to the illuminated volume, weighed by the emitters concentration. The true distribution of the emitters concentration is recovered by a new approach that implements this theoretical model in a numerical algorithm based on the Maximum Entropy Method. Comparisons with experimental data and numerical simulations show that this new approach is able to recover the real unknown concentration distribution from experimental profiles with an accuracy better than 3%.

  13. Measurement of Cerenkov Radiation Induced by the Gamma-Rays of Co-60 Therapy Units Using Wavelength Shifting Fiber

    Directory of Open Access Journals (Sweden)

    Kyoung Won Jang

    2014-04-01

    Full Text Available In this study, a wavelength shifting fiber that shifts ultra-violet and blue light to green light was employed as a sensor probe of a fiber-optic Cerenkov radiation sensor. In order to characterize Cerenkov radiation generated in the developed wavelength shifting fiber and a plastic optical fiber, spectra and intensities of Cerenkov radiation were measured with a spectrometer. The spectral peaks of light outputs from the wavelength shifting fiber and the plastic optical fiber were measured at wavelengths of 500 and 510 nm, respectively, and the intensity of transmitted light output of the wavelength shifting fiber was 22.2 times higher than that of the plastic optical fiber. Also, electron fluxes and total energy depositions of gamma-ray beams generated from a Co-60 therapy unit were calculated according to water depths using the Monte Carlo N-particle transport code. The relationship between the fluxes of electrons over the Cerenkov threshold energy and the energy depositions of gamma-ray beams from the Co-60 unit is a near-identity function. Finally, percentage depth doses for the gamma-ray beams were obtained using the fiber-optic Cerenkov radiation sensor, and the results were compared with those obtained by an ionization chamber. The average dose difference between the results of the fiber-optic Cerenkov radiation sensor and those of the ionization chamber was about 2.09%.

  14. Visual Discomfort and Depth-of-Field

    Directory of Open Access Journals (Sweden)

    Louise O'Hare

    2013-05-01

    Full Text Available Visual discomfort has been reported for certain visual stimuli and under particular viewing conditions, such as stereoscopic viewing. In stereoscopic viewing, visual discomfort can be caused by a conflict between accommodation and convergence cues that may specify different distances in depth. Earlier research has shown that depth-of-field, which is the distance range in depth in the scene that is perceived to be sharp, influences both the perception of egocentric distance to the focal plane, and the distance range in depth between objects in the scene. Because depth-of-field may also be in conflict with convergence and the accommodative state of the eyes, we raised the question of whether depth-of-field affects discomfort when viewing stereoscopic photographs. The first experiment assessed whether discomfort increases when depth-of-field is in conflict with coherent accommodation–convergence cues to distance in depth. The second experiment assessed whether depth-of-field influences discomfort from a pre-existing accommodation–convergence conflict. Results showed no effect of depth-of-field on visual discomfort. These results suggest therefore that depth-of-field can be used as a cue to depth without inducing discomfort in the viewer, even when cue conflicts are large.

  15. CsB{sub 4}O{sub 6}F. A congruent-melting deep-ultraviolet nonlinear optical material by combining superior functional units

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xuefei [Key Lab. of Functional Materials and Devices for Special Environments, Xinjiang Technical Inst. of Physics and Chemistry, Chinese Academy of Sciences, Xinjiang Key Lab. of Electronic Information Materials and Devices, Urumqi (China); University of Chinese Academy of Sciences, Beijing (China); Wang, Ying; Zhang, Bingbing; Zhang, Fangfang; Yang, Zhihua; Pan, Shilie [Key Lab. of Functional Materials and Devices for Special Environments, Xinjiang Technical Inst. of Physics and Chemistry, Chinese Academy of Sciences, Xinjiang Key Lab. of Electronic Information Materials and Devices, Urumqi (China)

    2017-11-06

    The discovery of new nonlinear optical (NLO) materials for coherent light generation in the deep-ultraviolet (DUV, wavelength below 200 nm) region is essential for the development of laser technologies. Herein, we report a new material CsB{sub 4}O{sub 6}F (CBF), which combines the superior structural properties of two well-known NLO materials, β-BaB{sub 2}O{sub 4} (BBO) and KBe{sub 2}BO{sub 3}F{sub 2} (KBBF). CBF exhibits excellent DUV optical properties including a short cutoff edge (155 nm), a large SHG response (∼1.9 x KDP), and a suitable birefringence that enables frequency doubling down to 171.6 nm. Remarkably, CBF melts congruently and shows an improved growth habit. In addition, our rational design strategy will contribute to the discovery of DUV NLO materials. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  16. CsB_4O_6F. A congruent-melting deep-ultraviolet nonlinear optical material by combining superior functional units

    International Nuclear Information System (INIS)

    Wang, Xuefei; Wang, Ying; Zhang, Bingbing; Zhang, Fangfang; Yang, Zhihua; Pan, Shilie

    2017-01-01

    The discovery of new nonlinear optical (NLO) materials for coherent light generation in the deep-ultraviolet (DUV, wavelength below 200 nm) region is essential for the development of laser technologies. Herein, we report a new material CsB_4O_6F (CBF), which combines the superior structural properties of two well-known NLO materials, β-BaB_2O_4 (BBO) and KBe_2BO_3F_2 (KBBF). CBF exhibits excellent DUV optical properties including a short cutoff edge (155 nm), a large SHG response (∼1.9 x KDP), and a suitable birefringence that enables frequency doubling down to 171.6 nm. Remarkably, CBF melts congruently and shows an improved growth habit. In addition, our rational design strategy will contribute to the discovery of DUV NLO materials. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  17. Simulation of excitonic optical line shapes of cyclic oligomers - models for basic units of photosynthetic antenna systems: Transfer integral versus local energy fluctuations with dichotomic coloured noise

    International Nuclear Information System (INIS)

    Barvik, I.; Reineker, P.; Warns, C.; Neidlinger, T.

    1995-08-01

    For Frenkel excitons moving on cyclic and linear molecular chains modeling in part photosynthetic antenna systems we investigate the influence of dynamic and static disorder on their optical line shapes. The dynamic disorder describes the influence of vibrational degrees of freedom and is taken into account by fluctuations of the transfer matrix element between neighbouring molecules. The fluctuations are represented by dichotomic Markov processes with coloured noise. We obtain a closed set of equations of motion for the correlation functions determining the optical line shape which is solved exactly. The line shapes are discussed for various sets of the model parameters and arrangements of molecules and their dipole moments. (author). 63 refs, 10 figs

  18. Microscopy system of atomic force based on a digital optical reading unit and a buzzer-scanner; Sistema de microscopia de fuerza atomica basada en una unidad de lectura optica digital y un escaner-zumbador

    Energy Technology Data Exchange (ETDEWEB)

    Dabirian, R.; Loza M, D. [Universidad de las Fuerzas Armadas-ESPE, Departamento de Ciencias de la Energia y Mecanica, Sangolqui (Ecuador); Wang, W. M.; Hwu, E. T., E-mail: whoand@gmail.com [Academia Sinica, Institute of Physics, Taipei, 11529 Taiwan (China)

    2015-07-01

    An astigmatic detection system (Ads) based on a compact disk/digital-versatile-disk (Cd-DVD) astigmatic optical pickup unit is presented. It can achieve a resolution better than 0.3 nm in detection of the vertical displacement and is able to detect the two-dimensional angular tilt of the object surface. Furthermore, a novel scanner design actuated by piezoelectric disk buzzers is presented. The scanner is composed of a quad-rod actuation structure and several piezoelectric disks. It can be driven directly with low-voltage and low-current sources, such as analogue outputs of a data acquisition card and enables a sufficient scanning range of up to μm. In addition, an economic, high-performance streamlined atomic force microscopy (AFM) was constructed, using the buzzer-scanner to move the sample relative to the probe, and using a Cd/DVD optical pickup unit to detect the mechanical resonance of a micro fabricated cantilever. The performance of the AFM is evaluated. The high sensitivity and high bandwidth of the detection system makes the equipment suitable for characterizing nano scale elements. An AFM using our detection system for detecting the deflection of micro fabricated cantilevers can resolve individual atomic steps on graphite surfaces. (Author)

  19. SMEX03 Atmospheric Aerosol Optical Properties Data: Oklahoma

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set consists of observations of atmospheric parameters including spectral aerosol optical depths, precipitable water, sky radiance distributions and...

  20. Is visual short-term memory depthful?

    Science.gov (United States)

    Reeves, Adam; Lei, Quan

    2014-03-01

    Does visual short-term memory (VSTM) depend on depth, as it might be if information was stored in more than one depth layer? Depth is critical in natural viewing and might be expected to affect retention, but whether this is so is currently unknown. Cued partial reports of letter arrays (Sperling, 1960) were measured up to 700 ms after display termination. Adding stereoscopic depth hardly affected VSTM capacity or decay inferred from total errors. The pattern of transposition errors (letters reported from an uncued row) was almost independent of depth and cue delay. We conclude that VSTM is effectively two-dimensional. Copyright © 2014 Elsevier Ltd. All rights reserved.

  1. Optical tweezers principles and applications

    CERN Document Server

    Jones, Philip; Volpe, Giovanni

    2015-01-01

    Combining state-of-the-art research with a strong pedagogic approach, this text provides a detailed and complete guide to the theory, practice and applications of optical tweezers. In-depth derivation of the theory of optical trapping and numerical modelling of optical forces are supported by a complete step-by-step design and construction guide for building optical tweezers, with detailed tutorials on collecting and analysing data. Also included are comprehensive reviews of optical tweezers research in fields ranging from cell biology to quantum physics. Featuring numerous exercises and problems throughout, this is an ideal self-contained learning package for advanced lecture and laboratory courses, and an invaluable guide to practitioners wanting to enter the field of optical manipulation. The text is supplemented by www.opticaltweezers.org, a forum for discussion and a source of additional material including free-to-download, customisable research-grade software (OTS) for calculation of optical forces, dig...

  2. The variable-depth mobile gammadensitometer (GMPV)

    International Nuclear Information System (INIS)

    Gourdon, J.L.; Davy, M.; Bisson, D.

    1991-01-01

    The continuous control of the density of wearing courses has been common practice in France for nearly twenty years. The instrument used for this purpose, called PSM (Petit Sabot Mobile; the Small Mobile Shoe), consists of a diffusion nucleo-densitometer carried on a mini-tractor. The unit has had to be completely replaced since this equipment is no longer on the market. The new instrument, known as the GMPV, has the following advantages. The depth of measurement is adjustable, so that thin wearing courses can be controlled. The accuracy and reproducibility of measurements are in the neighbourhood of 1% and 0.5% respectively, for a duration of 100 seconds. Handling is easier, thanks to infra-red remote steering of the measuring carriage from the driver's seat, and to a compatible micro-PC making it possible to gather, display, edit and store 200 kilometres of density values per hour. The GMPV is designed for intensive use in strict accordance with safety standards. It is due to be put into normal service in 1991 [fr

  3. Stereoscopic optical viewing system

    Science.gov (United States)

    Tallman, C.S.

    1986-05-02

    An improved optical system which provides the operator with a stereoscopic viewing field and depth of vision, particularly suitable for use in various machines such as electron or laser beam welding and drilling machines. The system features two separate but independently controlled optical viewing assemblies from the eyepiece to a spot directly above the working surface. Each optical assembly comprises a combination of eye pieces, turning prisms, telephoto lenses for providing magnification, achromatic imaging relay lenses and final stage pentagonal turning prisms. Adjustment for variations in distance from the turning prisms to the workpiece, necessitated by varying part sizes and configurations and by the operator's visual accuity, is provided separately for each optical assembly by means of separate manual controls at the operator console or within easy reach of the operator.

  4. The prototype detection unit of the KM3NeT detector

    Energy Technology Data Exchange (ETDEWEB)

    Adrian-Martinez, S.; Ardid, M.; Llorens Alvarez, C.D.; Martinez-Mora, J.A.; Saldana, M. [Universitat Politecnica de Valencia, Instituto de Investigacion para la Gestion Integrada de las Zonas Costeras, Gandia (Spain); Ageron, M.; Bertin, V.; Beurthey, S.; Billault, M.; Brunner, J.; Caillat, L.; Cosquer, A.; Coyle, P.; Destelle, J.J.; Dornic, D.; Henry, S.; Keller, P.; Lamare, P.; Tezier, D.; Theraube, S. [Aix Marseille Universite CNRS/IN2P3, CPPM UMR 7346, Marseille (France); Aharonian, F.; Drury, L. [DIAS, Dublin (Ireland); Aiello, S.; Giordano, V.; Leonora, E.; Randazzo, N.; Sipala, V. [INFN, Sezione di Catania, Catania (Italy); Albert, A.; Drouhin, D.; Racca, C. [GRPHE, Universite de Haute Alsace, IUT de Colmar, Colmar (France); Ameli, F.; Biagioni, A.; De Bonis, G.; Lonardo, A.; Nicolau, C.A.; Simeone, F.; Vicini, P. [INFN, Sezione di Roma, Rome (Italy); Anassontzis, E.G.; Resvanis, L. [National and Kapodistrian University of Athens, Deparment of Physics, Athens (Greece); Androulakis, G.C.; Balasi, K.; Belias, A.; Drakopoulou, E.; Kappos, E.; Manolopoulos, K.; Markou, C.; Pikounis, K.; Rapidis, P.A.; Stavropoulos, G.; Tzamariudaki, E. [Institute of Nuclear Physics, NCSR ' ' Demokritos' ' , Athens (Greece); Anghinolfi, M.; Cereseto, R.; Hugon, C.; Musico, P.; Orzelli, A. [INFN, Sezione di Genova, Genova (Italy); Anton, G.; Classen, L.; Eberl, T.; Gal, T.; Graf, K.; Heid, T.; Herold, B.; Hofestaedt, J.; Hoessl, J.; James, C.W.; Kalekin, O.; Kappes, A.; Katz, U.; Lahmann, R.; Reubelt, J.; Schnabel, J.; Seitz, T.; Stransky, D.; Tselengidou, M. [Friedrich-Alexander-Universitaet Erlangen-Nuernberg, Erlangen Centre for Astroparticle Physics, Erlangen (Germany); Anvar, S.; Chateau, F.; Durand, D.; Le Provost, H.; Louis, F.; Moudden, Y.; Zonca, E. [CEA, Irfu/Sedi, Centre de Saclay, Gif-sur-Yvette (France); Avgitas, T.; Baret, B.; Baron, S.; Boutonnet, C.; Champion, C.; Coleiro, A.; Colonges, S.; Creusot, A.; Galata, S.; Gracia Ruiz, R.; Kouchner, A.; Lindsey Clark, M.; Loucatos, S.; Van Elewyck, V. [APC,Universite Paris Diderot, CNRS/IN2P3 CEA/IRFU, Observatoire de Paris, Sorbonne Paris Cite, Paris (France); Band, H.; Berbee, E.; Berkien, A.; Beveren, V. van; Boer Rookhuizen, H.; Bouwhuis, M.; D' Amico, A.; Gajanana, D.; Gebyehu, M.; Heijboer, A.; Heine, E.; Hoek, M. van der; Hogenbirk, J.; Jansweijer, P.; Jongen, M.; Kieft, G.; Kok, H.; Koopstra, J.; Korporaal, A.; Melis, K.W.; Michael, T.; Mos, S.; Peek, H.; Schmelling, J.; Steijger, J.; Timmer, P.; Vermeulen, J.; Werneke, P.; Wiggers, L.; Zwart, A. [Nikhef, Amsterdam (Netherlands); Barbarino, G.; Barbato, F.; De Rosa, G.; Di Capua, F.; Garufi, F.; Vivolo, D. [INFN, Sezione di Napoli, Naples (Italy); Universita ' Federico II' , Dipartimento di Fisica, Naples (Italy); Barbarito, E.; Ceres, A.; Circella, M.; Mongelli, M.; Sgura, I. [INFN, Sezione di Bari, Bari (Italy); Barrios, J.; Calvo, D.; Hernandez-Rey, J.J.; Real, D.; Zornoza, J.D.; Zuniga, J. [CSIC-Universitat de Valencia, IFIC-Instituto de Fisica Corpuscular, Valencia (Spain); Berg, A.M. van den; Dorosti-Hasankiadeh, Q.; Hevinga, M.A.; Kavatsyuk, O.; Loehner, H.; Wooning, R.H.L. van [KVI-CART, University of Groningen, Groningen (Netherlands); Beverini, N. [INFN, Sezione di Pisa, Pisa (Italy); Universita di Pisa, Dipartimento di Fisica, Pisa (Italy); Biagi, S. [INFN, Laboratori Nazionali del Sud, Catania (Italy); Bianucci, S.; Bouhadef, B.; Calamai, M.; Maccioni, E.; Morganti, M.; Raffaelli, F.; Terreni, G. [Universita di Pisa, Dipartimento di Fisica, Pisa (Italy); Birbas, A.; Bourlis, G.; Christopoulou, B.; Gizani, N.; Leisos, A.; Lenis, D.; Tsirigotis, A.; Tzamarias, S. [Hellenic Open University, School of Science and Technology, Patras (Greece); Bormuth, R.; Jong, M. de; Samtleben, D.F.E. [Nikhef, Amsterdam (Netherlands); Leiden University, Leiden Institute of Physics, Leiden (Netherlands); Bouche, V.; Capone, A.; Fermani, P.; Masullo, R.; Perrina, C. [INFN, Sezione di Roma, Rome (Italy); Universita di Roma La Sapienza, Dipartimento di Fisica, Rome (Italy); Bozza, C.; Grella, G. [Universita ' Federico II' , Dipartimento di Fisica, Naples (Italy); Universita di Salerno, Dipartimento di Fisica, Fisciano (Italy); Bruijn, R.; Koffeman, E.; Wolf, E. de [Nikhef, Amsterdam (Netherlands); University of Amsterdam, Institute of Physics, Amsterdam (Netherlands); Cacopardo, G.; Caruso, F.; Cocimano, R.; Coniglione, R.; Costa, M.; Cuttone, G.; D' Amato, C.; Distefano, C.; Grasso, R.; Grmek, A.; Imbesi, M.; Kulikovskiy, V.; Larosa, G.; Lattuada, D.; Leismueller, K.P.; Migneco, E.; Miraglia, A.; Musumeci, M.; Orlando, A.; Papaleo, R.; Pellegriti, M.G.; Collaboration: KM3NeT Collaboration; and others

    2016-02-15

    A prototype detection unit of the KM3NeT deep-sea neutrino telescope has been installed at 3500m depth 80 km offshore the Italian coast. KM3NeT in its final configuration will contain several hundreds of detection units. Each detection unit is a mechanical structure anchored to the sea floor, held vertical by a submerged buoy and supporting optical modules for the detection of Cherenkov light emitted by charged secondary particles emerging from neutrino interactions. This prototype string implements three optical modules with 31 photomultiplier tubes each. These optical modules were developed by the KM3NeT Collaboration to enhance the detection capability of neutrino interactions. The prototype detection unit was operated since its deployment in May 2014 until its decommissioning in July 2015. Reconstruction of the particle trajectories from the data requires a nanosecond accuracy in the time calibration. A procedure for relative time calibration of the photomultiplier tubes contained in each optical module is described. This procedure is based on the measured coincidences produced in the sea by the {sup 40}K background light and can easily be expanded to a detector with several thousands of optical modules. The time offsets between the different optical modules are obtained using LED nanobeacons mounted inside them. A set of data corresponding to 600 h of livetime was analysed. The results show good agreement with Monte Carlo simulations of the expected optical background and the signal from atmospheric muons. An almost background-free sample of muons was selected by filtering the time correlated signals on all the three optical modules. The zenith angle of the selected muons was reconstructed with a precision of about 3 {sup circle}. (orig.)

  5. The prototype detection unit of the KM3NeT detector

    International Nuclear Information System (INIS)

    Adrian-Martinez, S.; Ardid, M.; Llorens Alvarez, C.D.; Martinez-Mora, J.A.; Saldana, M.; Ageron, M.; Bertin, V.; Beurthey, S.; Billault, M.; Brunner, J.; Caillat, L.; Cosquer, A.; Coyle, P.; Destelle, J.J.; Dornic, D.; Henry, S.; Keller, P.; Lamare, P.; Tezier, D.; Theraube, S.; Aharonian, F.; Drury, L.; Aiello, S.; Giordano, V.; Leonora, E.; Randazzo, N.; Sipala, V.; Albert, A.; Drouhin, D.; Racca, C.; Ameli, F.; Biagioni, A.; De Bonis, G.; Lonardo, A.; Nicolau, C.A.; Simeone, F.; Vicini, P.; Anassontzis, E.G.; Resvanis, L.; Androulakis, G.C.; Balasi, K.; Belias, A.; Drakopoulou, E.; Kappos, E.; Manolopoulos, K.; Markou, C.; Pikounis, K.; Rapidis, P.A.; Stavropoulos, G.; Tzamariudaki, E.; Anghinolfi, M.; Cereseto, R.; Hugon, C.; Musico, P.; Orzelli, A.; Anton, G.; Classen, L.; Eberl, T.; Gal, T.; Graf, K.; Heid, T.; Herold, B.; Hofestaedt, J.; Hoessl, J.; James, C.W.; Kalekin, O.; Kappes, A.; Katz, U.; Lahmann, R.; Reubelt, J.; Schnabel, J.; Seitz, T.; Stransky, D.; Tselengidou, M.; Anvar, S.; Chateau, F.; Durand, D.; Le Provost, H.; Louis, F.; Moudden, Y.; Zonca, E.; Avgitas, T.; Baret, B.; Baron, S.; Boutonnet, C.; Champion, C.; Coleiro, A.; Colonges, S.; Creusot, A.; Galata, S.; Gracia Ruiz, R.; Kouchner, A.; Lindsey Clark, M.; Loucatos, S.; Van Elewyck, V.; Band, H.; Berbee, E.; Berkien, A.; Beveren, V. van; Boer Rookhuizen, H.; Bouwhuis, M.; D'Amico, A.; Gajanana, D.; Gebyehu, M.; Heijboer, A.; Heine, E.; Hoek, M. van der; Hogenbirk, J.; Jansweijer, P.; Jongen, M.; Kieft, G.; Kok, H.; Koopstra, J.; Korporaal, A.; Melis, K.W.; Michael, T.; Mos, S.; Peek, H.; Schmelling, J.; Steijger, J.; Timmer, P.; Vermeulen, J.; Werneke, P.; Wiggers, L.; Zwart, A.; Barbarino, G.; Barbato, F.; De Rosa, G.; Di Capua, F.; Garufi, F.; Vivolo, D.; Barbarito, E.; Ceres, A.; Circella, M.; Mongelli, M.; Sgura, I.; Barrios, J.; Calvo, D.; Hernandez-Rey, J.J.; Real, D.; Zornoza, J.D.; Zuniga, J.; Berg, A.M. van den; Dorosti-Hasankiadeh, Q.; Hevinga, M.A.; Kavatsyuk, O.; Loehner, H.; Wooning, R.H.L. van; Beverini, N.; Biagi, S.; Bianucci, S.; Bouhadef, B.; Calamai, M.; Maccioni, E.; Morganti, M.; Raffaelli, F.; Terreni, G.; Birbas, A.; Bourlis, G.; Christopoulou, B.; Gizani, N.; Leisos, A.; Lenis, D.; Tsirigotis, A.; Tzamarias, S.; Bormuth, R.; Jong, M. de; Samtleben, D.F.E.; Bouche, V.; Capone, A.; Fermani, P.; Masullo, R.; Perrina, C.; Bozza, C.; Grella, G.; Bruijn, R.; Koffeman, E.; Wolf, E. de; Cacopardo, G.; Caruso, F.; Cocimano, R.; Coniglione, R.; Costa, M.; Cuttone, G.; D'Amato, C.; Distefano, C.; Grasso, R.; Grmek, A.; Imbesi, M.; Kulikovskiy, V.; Larosa, G.; Lattuada, D.; Leismueller, K.P.; Migneco, E.; Miraglia, A.; Musumeci, M.; Orlando, A.; Papaleo, R.; Pellegriti, M.G.

    2016-01-01

    A prototype detection unit of the KM3NeT deep-sea neutrino telescope has been installed at 3500m depth 80 km offshore the Italian coast. KM3NeT in its final configuration will contain several hundreds of detection units. Each detection unit is a mechanical structure anchored to the sea floor, held vertical by a submerged buoy and supporting optical modules for the detection of Cherenkov light emitted by charged secondary particles emerging from neutrino interactions. This prototype string implements three optical modules with 31 photomultiplier tubes each. These optical modules were developed by the KM3NeT Collaboration to enhance the detection capability of neutrino interactions. The prototype detection unit was operated since its deployment in May 2014 until its decommissioning in July 2015. Reconstruction of the particle trajectories from the data requires a nanosecond accuracy in the time calibration. A procedure for relative time calibration of the photomultiplier tubes contained in each optical module is described. This procedure is based on the measured coincidences produced in the sea by the 40 K background light and can easily be expanded to a detector with several thousands of optical modules. The time offsets between the different optical modules are obtained using LED nanobeacons mounted inside them. A set of data corresponding to 600 h of livetime was analysed. The results show good agreement with Monte Carlo simulations of the expected optical background and the signal from atmospheric muons. An almost background-free sample of muons was selected by filtering the time correlated signals on all the three optical modules. The zenith angle of the selected muons was reconstructed with a precision of about 3 circle . (orig.)

  6. The prototype detection unit of the KM3NeT detector

    Science.gov (United States)

    Adrián-Martínez, S.; Ageron, M.; Aharonian, F.; Aiello, S.; Albert, A.; Ameli, F.; Anassontzis, E. G.; Androulakis, G. C.; Anghinolfi, M.; Anton, G.; Anvar, S.; Ardid, M.; Avgitas, T.; Balasi, K.; Band, H.; Barbarino, G.; Barbarito, E.; Barbato, F.; Baret, B.; Baron, S.; Barrios, J.; Belias, A.; Berbee, E.; van den Berg, A. M.; Berkien, A.; Bertin, V.; Beurthey, S.; van Beveren, V.; Beverini, N.; Biagi, S.; Biagioni, A.; Bianucci, S.; Billault, M.; Birbas, A.; Boer Rookhuizen, H.; Bormuth, R.; Bouché, V.; Bouhadef, B.; Bourlis, G.; Boutonnet, C.; Bouwhuis, M.; Bozza, C.; Bruijn, R.; Brunner, J.; Cacopardo, G.; Caillat, L.; Calamai, M.; Calvo, D.; Capone, A.; Caramete, L.; Caruso, F.; Cecchini, S.; Ceres, A.; Cereseto, R.; Champion, C.; Château, F.; Chiarusi, T.; Christopoulou, B.; Circella, M.; Classen, L.; Cocimano, R.; Coleiro, A.; Colonges, S.; Coniglione, R.; Cosquer, A.; Costa, M.; Coyle, P.; Creusot, A.; Cuttone, G.; D'Amato, C.; D'Amico, A.; De Bonis, G.; De Rosa, G.; Deniskina, N.; Destelle, J.-J.; Distefano, C.; Di Capua, F.; Donzaud, C.; Dornic, D.; Dorosti-Hasankiadeh, Q.; Drakopoulou, E.; Drouhin, D.; Drury, L.; Durand, D.; Eberl, T.; Elsaesser, D.; Enzenhöfer, A.; Fermani, P.; Fusco, L. A.; Gajanana, D.; Gal, T.; Galatà, S.; Garufi, F.; Gebyehu, M.; Giordano, V.; Gizani, N.; Gracia Ruiz, R.; Graf, K.; Grasso, R.; Grella, G.; Grmek, A.; Habel, R.; van Haren, H.; Heid, T.; Heijboer, A.; Heine, E.; Henry, S.; Hernández-Rey, J. J.; Herold, B.; Hevinga, M. A.; van der Hoek, M.; Hofestädt, J.; Hogenbirk, J.; Hugon, C.; Hößl, J.; Imbesi, M.; James, C. W.; Jansweijer, P.; Jochum, J.; de Jong, M.; Jongen, M.; Kadler, M.; Kalekin, O.; Kappes, A.; Kappos, E.; Katz, U.; Kavatsyuk, O.; Keller, P.; Kieft, G.; Koffeman, E.; Kok, H.; Kooijman, P.; Koopstra, J.; Korporaal, A.; Kouchner, A.; Kreykenbohm, I.; Kulikovskiy, V.; Lahmann, R.; Lamare, P.; Larosa, G.; Lattuada, D.; Le Provost, H.; Leismüller, K. P.; Leisos, A.; Lenis, D.; Leonora, E.; Lindsey Clark, M.; Llorens Alvarez, C. D.; Löhner, H.; Lonardo, A.; Loucatos, S.; Louis, F.; Maccioni, E.; Mannheim, K.; Manolopoulos, K.; Margiotta, A.; Mariş, O.; Markou, C.; Martínez-Mora, J. A.; Martini, A.; Masullo, R.; Melis, K. W.; Michael, T.; Migliozzi, P.; Migneco, E.; Miraglia, A.; Mollo, C. M.; Mongelli, M.; Morganti, M.; Mos, S.; Moudden, Y.; Musico, P.; Musumeci, M.; Nicolaou, C.; Nicolau, C. A.; Orlando, A.; Orzelli, A.; Papaikonomou, A.; Papaleo, R.; Păvălaş, G. E.; Peek, H.; Pellegrino, C.; Pellegriti, M. G.; Perrina, C.; Piattelli, P.; Pikounis, K.; Popa, V.; Pradier, Th.; Priede, M.; Pühlhofer, G.; Pulvirenti, S.; Racca, C.; Raffaelli, F.; Randazzo, N.; Rapidis, P. A.; Razis, P.; Real, D.; Resvanis, L.; Reubelt, J.; Riccobene, G.; Rovelli, A.; Saldaña, M.; Samtleben, D. F. E.; Sanguineti, M.; Santangelo, A.; Sapienza, P.; Schmelling, J.; Schnabel, J.; Sciacca, V.; Sedita, M.; Seitz, T.; Sgura, I.; Simeone, F.; Sipala, V.; Spitaleri, A.; Spurio, M.; Stavropoulos, G.; Steijger, J.; Stolarczyk, T.; Stransky, D.; Taiuti, M.; Terreni, G.; Tézier, D.; Théraube, S.; Thompson, L. F.; Timmer, P.; Trasatti, L.; Trovato, A.; Tselengidou, M.; Tsirigotis, A.; Tzamarias, S.; Tzamariudaki, E.; Vallage, B.; Van Elewyck, V.; Vermeulen, J.; Vernin, P.; Vicini, P.; Viola, S.; Vivolo, D.; Werneke, P.; Wiggers, L.; Wilms, J.; de Wolf, E.; van Wooning, R. H. L.; Zonca, E.; Zornoza, J. D.; Zúñiga, J.; Zwart, A.

    2016-02-01

    A prototype detection unit of the KM3NeT deep-sea neutrino telescope has been installed at 3500m depth 80 km offshore the Italian coast. KM3NeT in its final configuration will contain several hundreds of detection units. Each detection unit is a mechanical structure anchored to the sea floor, held vertical by a submerged buoy and supporting optical modules for the detection of Cherenkov light emitted by charged secondary particles emerging from neutrino interactions. This prototype string implements three optical modules with 31 photomultiplier tubes each. These optical modules were developed by the KM3NeT Collaboration to enhance the detection capability of neutrino interactions. The prototype detection unit was operated since its deployment in May 2014 until its decommissioning in July 2015. Reconstruction of the particle trajectories from the data requires a nanosecond accuracy in the time calibration. A procedure for relative time calibration of the photomultiplier tubes contained in each optical module is described. This procedure is based on the measured coincidences produced in the sea by the ^{40}K background light and can easily be expanded to a detector with several thousands of optical modules. The time offsets between the different optical modules are obtained using LED nanobeacons mounted inside them. A set of data corresponding to 600 h of livetime was analysed. The results show good agreement with Monte Carlo simulations of the expected optical background and the signal from atmospheric muons. An almost background-free sample of muons was selected by filtering the time correlated signals on all the three optical modules. The zenith angle of the selected muons was reconstructed with a precision of about 3°.

  7. Resilience to Changing Snow Depth in a Shrubland Ecosystem.

    Science.gov (United States)

    Loik, M. E.

    2008-12-01

    Snowfall is the dominant hydrologic input for high elevations and latitudes of the arid- and semi-arid western United States. Sierra Nevada snowpack provides numerous important services for California, but is vulnerable to anthropogenic forcing of the coupled ocean-atmosphere system. GCM and RCM scenarios envision reduced snowpack and earlier melt under a warmer climate, but how will these changes affect soil and plant water relations and ecosystem processes? And, how resilient will this ecosystem be to short- and long-term forcing of snow depth and melt timing? To address these questions, our experiments utilize large- scale, long-term roadside snow fences to manipulate snow depth and melt timing in eastern California, USA. Interannual snow depth averages 1344 mm with a CV of 48% (April 1, 1928-2008). Snow fences altered snow melt timing by up to 18 days in high-snowfall years, and affected short-term soil moisture pulses less in low- than medium- or high-snowfall years. Sublimation in this arid location accounted for about 2 mol m- 2 of water loss from the snowpack in 2005. Plant water potential increased after the ENSO winter of 2005 and stayed relatively constant for the following three years, even after the low snowfall of winter 2007. Over the long-term, changes in snow depth and melt timing have impacted cover or biomass of Achnatherum thurberianum, Elymus elemoides, and Purshia tridentata. Growth of adult conifers (Pinus jeffreyi and Pi. contorta) was not equally sensitive to snow depth. Thus, complex interactions between snow depth, soil water inputs, physiological processes, and population patterns help drive the resilience of this ecosystem to changes in snow depth and melt timing.

  8. Theoretical performance model for single image depth from defocus.

    Science.gov (United States)

    Trouvé-Peloux, Pauline; Champagnat, Frédéric; Le Besnerais, Guy; Idier, Jérôme

    2014-12-01

    In this paper we present a performance model for depth estimation using single image depth from defocus (SIDFD). Our model is based on an original expression of the Cramér-Rao bound (CRB) in this context. We show that this model is consistent with the expected behavior of SIDFD. We then study the influence on the performance of the optical parameters of a conventional camera such as the focal length, the aperture, and the position of the in-focus plane (IFP). We derive an approximate analytical expression of the CRB away from the IFP, and we propose an interpretation of the SIDFD performance in this domain. Finally, we illustrate the predictive capacity of our performance model on experimental data comparing several settings of a consumer camera.

  9. Incoherently combining logarithmic aspheric lenses for extended depth of field.

    Science.gov (United States)

    Chu, Kaiqin; George, Nicholas; Chi, Wanli

    2009-10-01

    We describe a method for combining concentric logarithmic aspheric lenses in order to obtain an extended depth of field. Substantial improvement in extending the depth of field is obtained by carefully controlling the optical path difference among the concentric lenses so that their outputs combine incoherently. The system is analyzed through diffraction theory and the point spread function is shown to be highly invariant over a long range of object distances. After testing the image performance on a three-dimensional scene, we found that the incoherently combined logarithmic aspheres can provide a high-quality image over an axial distance corresponding to a defocus of +/- 14(lambda/4). Studies of the images of two-point objects are presented to illustrate the resolution of these lenses.

  10. Optic nerve invasion of uveal melanoma

    DEFF Research Database (Denmark)

    Lindegaard, Jens; Isager, Peter; Prause, Jan Ulrik

    2007-01-01

    in Denmark between 1942 and 2001 were reviewed (n=157). Histopathological characteristics and depth of optic nerve invasion were recorded. The material was compared with a control material from the same period consisting of 85 cases randomly drawn from all choroidal/ciliary body melanomas without optic nerve...... juxtapapillary tumors invading the optic nerve because of simple proximity to the nerve. A neurotropic subtype invades the optic nerve and retina in a diffuse fashion unrelated to tumor size or location. Udgivelsesdato: 2007-Jan...

  11. A mechanical design for a detection unit for a deep-sea neutrino telescope

    Energy Technology Data Exchange (ETDEWEB)

    Berbee, E.M.; Boer Rookhuizen, H.; Heine, E.; Mul, G. [Nikhef, Science Park 105, 1098 XG Amsterdam (Netherlands); Wolf, E. de, E-mail: e.dewolf@nikhef.nl [University of Amsterdam, Science Park 904, 1098 XH Amsterdam (Netherlands); Nikhef, Science Park 105, 1098 XG Amsterdam (Netherlands)

    2013-10-11

    The future KM3NeT neutrino telescope will be built on the seabed of the Mediterranean Sea at a depth between three and five kilometers. The high ambient pressure, but also the fact that the detector is hardly accessible, put severe constraints on the mechanical design of the detection units of the telescope. A detection unit is a vertical structure that supports the optical sensors of the telescope. It has a height of almost 900 m; two data cables run along the full length of the structure. The detection unit will be installed at the seabed as a compact package. Once acoustically released, it unfurls to its full length. The stability of the detection unit during unfurling and during operation is an important requirement for the mechanical design of the structure. We present the evolution of the design of the detection unit for the KM3NeT detector.

  12. A mechanical design for a detection unit for a deep-sea neutrino telescope

    International Nuclear Information System (INIS)

    Berbee, E.M.; Boer Rookhuizen, H.; Heine, E.; Mul, G.; Wolf, E. de

    2013-01-01

    The future KM3NeT neutrino telescope will be built on the seabed of the Mediterranean Sea at a depth between three and five kilometers. The high ambient pressure, but also the fact that the detector is hardly accessible, put severe constraints on the mechanical design of the detection units of the telescope. A detection unit is a vertical structure that supports the optical sensors of the telescope. It has a height of almost 900 m; two data cables run along the full length of the structure. The detection unit will be installed at the seabed as a compact package. Once acoustically released, it unfurls to its full length. The stability of the detection unit during unfurling and during operation is an important requirement for the mechanical design of the structure. We present the evolution of the design of the detection unit for the KM3NeT detector

  13. Handheld White Light Interferometer for Measuring Defect Depth in Windows

    Science.gov (United States)

    Youngquist, Robert; Simmons, Stephen; Cox, Robert

    2010-01-01

    Accurate quantification of defects (scratches and impacts) is vital to the certification of flight hardware and other critical components. The amount of damage to a particular component contributes to the performance, reliability, and safety of a system, which ultimately affects the success or failure of a mission or test. The launch-commit criteria on a Space Shuttle Orbiter window are governed by the depth of the defects that are identified by a visual inspection. This measurement of a defect is not easy to obtain given the environment, size of the defect, and location of the window(s). The determination of depth has typically been performed by taking a mold impression and measuring the impression with an optical profiling instrument. Another method of obtaining an estimate of the depth is by using a refocus microscope. To use a refocus microscope, the surface of the glass and bottom of the defect are, in turn, brought into focus by the operator. The amount of movement between the two points corresponds to the depth of the defect. The refocus microscope requires a skilled operator and has been proven to be unreliable when used on Orbiter windows. White light interferometry was chosen as a candidate to replace the refocus microscope. The White Light Interferometer (WLI) was developed to replace the refocus microscope as the instrument used for measuring the depth of defects in Orbiter windows. The WLI consists of a broadband illumination source, interferometer, detector, motion control, displacement sensor, mechanical housing, and support electronics. The illumination source for the WLI is typically a visible light emitting diode (LED) or a near-infrared superluminescent diode (SLD) with power levels of less than a milliwatt. The interferometer is a Michelson configuration consisting of a 1-in. (2.5-cm) cube beam splitter, a 0.5-in. (1.3-cm) optical window as a movable leg (used to closely match the return intensity of the fixed leg from the window), and a

  14. Subring Depth, Frobenius Extensions, and Towers

    Directory of Open Access Journals (Sweden)

    Lars Kadison

    2012-01-01

    Full Text Available The minimum depth d(B,A of a subring B⊆A introduced in the work of Boltje, Danz and Külshammer (2011 is studied and compared with the tower depth of a Frobenius extension. We show that d(B,A < ∞ if A is a finite-dimensional algebra and Be has finite representation type. Some conditions in terms of depth and QF property are given that ensure that the modular function of a Hopf algebra restricts to the modular function of a Hopf subalgebra. If A⊇B is a QF extension, minimum left and right even subring depths are shown to coincide. If A⊇B is a Frobenius extension with surjective Frobenius, homomorphism, its subring depth is shown to coincide with its tower depth. Formulas for the ring, module, Frobenius and Temperley-Lieb structures are noted for the tower over a Frobenius extension in its realization as tensor powers. A depth 3 QF extension is embedded in a depth 2 QF extension; in turn certain depth n extensions embed in depth 3 extensions if they are Frobenius extensions or other special ring extensions with ring structures on their relative Hochschild bar resolution groups.

  15. Meso-optical Fourier transform microscope - a new device for high energy physics

    International Nuclear Information System (INIS)

    Astakhov, A.Ya.; Batusov, Yu.A.; Bencze, G.L.; Farago, I.; Kisvaradi, A.; Molnar, L.; Soroko, L.M.; Vegh, J.

    1989-01-01

    A new device for high energy physics, the Meso-optical Fourier Transform Microscope (MFTM), designed for observation fo straight line particle tracks in nuclear research emulsion is described. The MFTM works without any mechanical or electronical depth scanning and can be considered as a selectivity viewing 'eye'. The computer controlled system containing MFTM as its main unit is given. This system can be used for a fast search for particle tracks and events produced by high energy neutrinos from particle accelerators. The results of the first experimental test of the computer controlled MFTM are presented. The performance of this system is described and discussed. It is shown that the angular resolution of the MFTM is 1 angular minute and the measurement time is equal to 30 ms per image. As all operations in the MFTM proceed without any depth scanning, this new evaluation system works at least two orders of magnitude faster than any known system with a traditional optical microscope. (orig.)

  16. Free space optical communication

    CERN Document Server

    Kaushal, Hemani; Kar, Subrat

    2017-01-01

    This book provides an in-depth understanding of free space optical (FSO) communication with a particular emphasis on optical beam propagation through atmospheric turbulence. The book is structured in such a way that it provides a basic framework for the beginners and also gives a concise description from a designer’s perspective. The book provides an exposure to FSO technology, fundamental limitations, design methodologies, system trade-offs, acquisition, tracking and pointing (ATP) techniques and link-feasibility analysis. The contents of this book will be of interest to professionals and researchers alike. The book may also be used as a textbook for engineering coursework and professional training.

  17. Handbook of biomedical optics

    CERN Document Server

    Boas, David A

    2011-01-01

    Biomedical optics holds tremendous promise to deliver effective, safe, non- or minimally invasive diagnostics and targeted, customizable therapeutics. Handbook of Biomedical Optics provides an in-depth treatment of the field, including coverage of applications for biomedical research, diagnosis, and therapy. It introduces the theory and fundamentals of each subject, ensuring accessibility to a wide multidisciplinary readership. It also offers a view of the state of the art and discusses advantages and disadvantages of various techniques.Organized into six sections, this handbook: Contains intr

  18. Optical waveguide demultiplexer

    International Nuclear Information System (INIS)

    Gajdaj, Yu.O.; Maslyukyivs'kij, R.M.; Sirota, A.V.

    2009-01-01

    For channels division in fibre-optical networks with wavelength multiplexing, the planar waveguide together with a prism coupler is offered for using. The planar waveguide fulfils a role of a dispersing unit, and prism coupler is the selector of optical channels. The parameters of the planar waveguide which provide maximal space division of adjacent information channels in networks with coarse wavelength multiplexing are calculated

  19. Coding of Depth Images for 3DTV

    DEFF Research Database (Denmark)

    Zamarin, Marco; Forchhammer, Søren

    In this short paper a brief overview of the topic of coding and compression of depth images for multi-view image and video coding is provided. Depth images represent a convenient way to describe distances in the 3D scene, useful for 3D video processing purposes. Standard approaches...... for the compression of depth images are described and compared against some recent specialized algorithms able to achieve higher compression performances. Future research directions close the paper....

  20. High resolution axicon-based endoscopic FD OCT imaging with a large depth range

    Science.gov (United States)

    Lee, Kye-Sung; Hurley, William; Deegan, John; Dean, Scott; Rolland, Jannick P.

    2010-02-01

    Endoscopic imaging in tubular structures, such as the tracheobronchial tree, could benefit from imaging optics with an extended depth of focus (DOF). This optics could accommodate for varying sizes of tubular structures across patients and along the tree within a single patient. In the paper, we demonstrate an extended DOF without sacrificing resolution showing rotational images in biological tubular samples with 2.5 μm axial resolution, 10 ìm lateral resolution, and > 4 mm depth range using a custom designed probe.

  1. GNF Defense in Depth Update

    Energy Technology Data Exchange (ETDEWEB)

    Lingenfelter, Andrew A.; Schneider, Robert J.; Cantonwine, Paul E.; Moore, Brian; Rea, John; Crawford, Douglas C. [Global Nuclear Fuel, P.O. Box 780 M/C H25, Wilmington, NC 28402 (United States)

    2009-06-15

    Global Nuclear Fuel (GNF) has designed, fabricated, and placed into operation more than 9 million fuel rods in approximately 135 thousand assemblies. Customer satisfaction has always compelled GNF to reduce fuel rod failures (defined here as fuel rods that breach or leak in service), However, increasing success with and subsequent expectations for economic performance of nuclear reactor plants have raised broader Industry emphasis on fuel reliability. In 2005, GNF established its Defense-in-Depth (DID) Program for the purpose of focusing attention on the many aspects of fuel design, fabrication, performance, and utilization that affect fuel reliability as well as on the key methods that govern the utilization of GNF fuel. The Program is structured to address each of the identified in-service, fuel failure mechanisms. This paper provides a summary of GNF fuel performance, following previous updates. This paper will discuss recent GNF fuel reliability and channel performance, GNF2 introduction status, and methods. GNF's more recent fuel experience includes approximately 3.8 million GE11/13 (9x9) and GE12/14 (10x10) fuel rods, well over half of which are the GE12/14 design. (Those figures also include roughly 25,000 recently-introduced GNF2 fuel rods.) Reliability, expressed as annual, observed fuel failure rates (i.e., number of rods failed each year divided by the number of opportunities, or fuel rods in service), has improved for each year since 2005. The GNF fuel failure rate for years leading up to 2007 and 2008 has been on the order of 5 to 7 ppm (excluding the corrosion events of 2001-2003), and as of this writing (January 2009) the current in-service failure has decreased to around 1.5 ppm. Failures in GE14 fuel rod failures have been primarily due to debris-fretting (> 60%), with other failures being duty-related or yet undetermined. The only failure observed in GNF2 to date was a single, early-life debris failure in a bundle not equipped with GNF

  2. Depth Perception In Remote Stereoscopic Viewing Systems

    Science.gov (United States)

    Diner, Daniel B.; Von Sydow, Marika

    1989-01-01

    Report describes theoretical and experimental studies of perception of depth by human operators through stereoscopic video systems. Purpose of such studies to optimize dual-camera configurations used to view workspaces of remote manipulators at distances of 1 to 3 m from cameras. According to analysis, static stereoscopic depth distortion decreased, without decreasing stereoscopitc depth resolution, by increasing camera-to-object and intercamera distances and camera focal length. Further predicts dynamic stereoscopic depth distortion reduced by rotating cameras around center of circle passing through point of convergence of viewing axes and first nodal points of two camera lenses.

  3. Directional Joint Bilateral Filter for Depth Images

    Directory of Open Access Journals (Sweden)

    Anh Vu Le

    2014-06-01

    Full Text Available Depth maps taken by the low cost Kinect sensor are often noisy and incomplete. Thus, post-processing for obtaining reliable depth maps is necessary for advanced image and video applications such as object recognition and multi-view rendering. In this paper, we propose adaptive directional filters that fill the holes and suppress the noise in depth maps. Specifically, novel filters whose window shapes are adaptively adjusted based on the edge direction of the color image are presented. Experimental results show that our method yields higher quality filtered depth maps than other existing methods, especially at the edge boundaries.

  4. ACCURACY ANALYSIS OF KINECT DEPTH DATA

    Directory of Open Access Journals (Sweden)

    K. Khoshelham

    2012-09-01

    Full Text Available This paper presents an investigation of the geometric quality of depth data obtained by the Kinect sensor. Based on the mathematical model of depth measurement by the sensor a theoretical error analysis is presented, which provides an insight into the factors influencing the accuracy of the data. Experimental results show that the random error of depth measurement increases with increasing distance to the sensor, and ranges from a few millimetres up to about 4 cm at the maximum range of the sensor. The accuracy of the data is also found to be influenced by the low resolution of the depth measurements.

  5. Modified Linnik microscopic interferometry for quantitative depth evaluation of diffraction-limited microgroove

    Science.gov (United States)

    Ye, Shiwei; Takahashi, Satoru; Michihata, Masaki; Takamasu, Kiyoshi

    2018-05-01

    The quality control of microgrooves is extremely crucial to ensure the performance and stability of microstructures and improve their fabrication efficiency. This paper introduces a novel optical inspection method and a modified Linnik microscopic interferometer measurement system to detect the depth of microgrooves with a width less than the diffraction limit. Using this optical method, the depth of diffraction-limited microgrooves can be related to the near-field optical phase difference, which cannot be practically observed but can be computed from practical far-field observations. Thus, a modified Linnik microscopic interferometer system based on three identical objective lenses and an optical path reversibility principle were developed. In addition, experiments for standard grating microgrooves on the silicon surface were carried out to demonstrate the feasibility and repeatability of the proposed method and developed measurement system.

  6. Nonlinear optics

    International Nuclear Information System (INIS)

    Boyd, R.W.

    1992-01-01

    Nonlinear optics is the study of the interaction of intense laser light with matter. This book is a textbook on nonlinear optics at the level of a beginning graduate student. The intent of the book is to provide an introduction to the field of nonlinear optics that stresses fundamental concepts and that enables the student to go on to perform independent research in this field. This book covers the areas of nonlinear optics, quantum optics, quantum electronics, laser physics, electrooptics, and modern optics

  7. Physical optics

    International Nuclear Information System (INIS)

    Kim Il Gon; Lee, Seong Su; Jang, Gi Wan

    2012-07-01

    This book indicates physical optics with properties and transmission of light, mathematical expression of wave like harmonic wave and cylindrical wave, electromagnetic theory and light, transmission of light with Fermat principle and Fresnel equation, geometrical optics I, geometrical optics II, optical instrument such as stops, glasses and camera, polarized light like double refraction by polarized light, interference, interference by multiple reflections, diffraction, solid optics, crystal optics such as Faraday rotation and Kerr effect and measurement of light. Each chapter has an exercise.

  8. Physical optics

    Energy Technology Data Exchange (ETDEWEB)

    Kim Il Gon; Lee, Seong Su; Jang, Gi Wan

    2012-07-15

    This book indicates physical optics with properties and transmission of light, mathematical expression of wave like harmonic wave and cylindrical wave, electromagnetic theory and light, transmission of light with Fermat principle and Fresnel equation, geometrical optics I, geometrical optics II, optical instrument such as stops, glasses and camera, polarized light like double refraction by polarized light, interference, interference by multiple reflections, diffraction, solid optics, crystal optics such as Faraday rotation and Kerr effect and measurement of light. Each chapter has an exercise.

  9. An Exploration of the Needling Depth in Acupuncture: The Safe Needling Depth and the Needling Depth of Clinical Efficacy

    Directory of Open Access Journals (Sweden)

    Jaung-Geng Lin

    2013-01-01

    Full Text Available Objective. To explore the existing scientific information regarding safe needling depth of acupuncture points and the needling depth of clinical efficacy. Methods. We searched the PubMed, EMBASE, Cochrane, Allied and Complementary Medicine (AMED, The National Center for Complementary and Alternative Medicine (NCCAM, and China National Knowledge Infrastructure (CNKI databases to identify relevant monographs and related references from 1991 to 2013. Chinese journals and theses/dissertations were hand searched. Results. 47 studies were recruited and divided into 6 groups by measuring tools, that is, MRI, in vivo evaluation, CT, ultrasound, dissected specimen of cadavers, and another group with clinical efficacy. Each research was analyzed for study design, definition of safe depth, and factors that would affect the measured depths.