Ultraviolet to optical diffuse sky emission as seen by the Hubble Space Telescope Faint Object Spectrograph

NASA Astrophysics Data System (ADS)

Kawara, Kimiaki; Matsuoka, Yoshiki; Sano, Kei; Brandt, Timothy D.; Sameshima, Hiroaki; Tsumura, Kohji; Oyabu, Shinki; Ienaka, Nobuyuki

2017-04-01

We present an analysis of the blank-sky spectra observed with the Faint Object Spectrograph on board the Hubble Space Telescope. We study the diffuse sky emission from ultraviolet to optical wavelengths, which is composed of zodiacal light (ZL), diffuse Galactic light (DGL), and residual emission. The observations were performed towards 54 fields distributed widely over the sky, with spectral coverage from 0.2 to 0.7 μm. In order to avoid contaminating light from earthshine, we use the data collected only in orbital nighttime. The observed intensity is decomposed into the ZL, DGL, and residual emission, in eight photometric bands spanning our spectral coverage. We found that the derived ZL reflectance spectrum is flat in the optical, which indicates major contribution of C-type asteroids to the interplanetary dust (IPD). In addition, the ZL reflectance spectrum has an absorption feature at ∼0.3 μm. The shape of the DGL spectrum is consistent with those found in earlier measurements and model predictions. While the residual emission contains a contribution from the extragalactic background light, we found that the spectral shape of the residual looks similar to the ZL spectrum. Moreover, its optical intensity is much higher than that measured from beyond the IPD cloud by Pioneer 10/11, and also than that of the integrated galaxy light. These findings may indicate the presence of an isotropic ZL component, which is missed in the conventional ZL models.

Method for Calculating the Optical Diffuse Reflection Coefficient for the Ocular Fundus

NASA Astrophysics Data System (ADS)

Lisenko, S. A.; Kugeiko, M. M.

2016-07-01

We have developed a method for calculating the optical diffuse reflection coefficient for the ocular fundus, taking into account multiple scattering of light in its layers (retina, epithelium, choroid) and multiple refl ection of light between layers. The method is based on the formulas for optical "combination" of the layers of the medium, in which the optical parameters of the layers (absorption and scattering coefficients) are replaced by some effective values, different for cases of directional and diffuse illumination of the layer. Coefficients relating the effective optical parameters of the layers and the actual values were established based on the results of a Monte Carlo numerical simulation of radiation transport in the medium. We estimate the uncertainties in retrieval of the structural and morphological parameters for the fundus from its diffuse reflectance spectrum using our method. We show that the simulated spectra correspond to the experimental data and that the estimates of the fundus parameters obtained as a result of solving the inverse problem are reasonable.

On the Spectral Hardening at gsim300 keV in Solar Flares

NASA Astrophysics Data System (ADS)

Li, G.; Kong, X.; Zank, G.; Chen, Y.

2013-05-01

It has long been noted that the spectra of observed continuum emissions in many solar flares are consistent with double power laws with a hardening at energies gsim300 keV. It is now widely believed that at least in electron-dominated events, the hardening in the photon spectrum reflects an intrinsic hardening in the source electron spectrum. In this paper, we point out that a power-law spectrum of electrons with a hardening at high energies can be explained by the diffusive shock acceleration of electrons at a termination shock with a finite width. Our suggestion is based on an early analytical work by Drury et al., where the steady-state transport equation at a shock with a tanh profile was solved for a p-independent diffusion coefficient. Numerical simulations with a p-dependent diffusion coefficient show hardenings in the accelerated electron spectrum that are comparable with observations. One necessary condition for our proposed scenario to work is that high-energy electrons resonate with the inertial range of the MHD turbulence and low-energy electrons resonate with the dissipation range of the MHD turbulence at the acceleration site, and the spectrum of the dissipation range ~k -2.7. A ~k -2.7 dissipation range spectrum is consistent with recent solar wind observations.

Simultaneous estimation of transcutaneous bilirubin, hemoglobin, and melanin based on diffuse reflectance spectroscopy

NASA Astrophysics Data System (ADS)

Nishidate, Izumi; Abdul, Wares MD.; Ohtsu, Mizuki; Nakano, Kazuya; Haneishi, Hideaki

2018-02-01

We propose a method to estimate transcutaneous bilirubin, hemoglobin, and melanin based on the diffuse reflectance spectroscopy. In the proposed method, the Monte Carlo simulation-based multiple regression analysis for an absorbance spectrum in the visible wavelength region (460-590 nm) is used to specify the concentrations of bilirubin (Cbil), oxygenated hemoglobin (Coh), deoxygenated hemoglobin (Cdh), and melanin (Cm). Using the absorbance spectrum calculated from the measured diffuse reflectance spectrum as a response variable and the extinction coefficients of bilirubin, oxygenated hemoglobin, deoxygenated hemoglobin, and melanin, as predictor variables, multiple regression analysis provides regression coefficients. Concentrations of bilirubin, oxygenated hemoglobin, deoxygenated hemoglobin, and melanin, are then determined from the regression coefficients using conversion vectors that are numerically deduced in advance by the Monte Carlo simulations for light transport in skin. Total hemoglobin concentration (Cth) and tissue oxygen saturation (StO2) are simply calculated from the oxygenated hemoglobin and deoxygenated hemoglobin. In vivo animal experiments with bile duct ligation in rats demonstrated that the estimated Cbil is increased after ligation of bile duct and reaches to around 20 mg/dl at 72 h after the onset of the ligation, which corresponds to the reference value of Cbil measured by a commercially available transcutaneous bilirubin meter. We also performed in vivo experiments with rats while varying the fraction of inspired oxygen (FiO2). Coh and Cdh decreased and increased, respectively, as FiO2 decreased. Consequently, StO2 was dramatically decreased. The results in this study indicate potential of the method for simultaneous evaluation of multiple chromophores in skin tissue.

Reconstructing in-vivo reflectance spectrum of pigmented skin lesion by Monte Carlo simulation

NASA Astrophysics Data System (ADS)

Wang, Shuang; He, Qingli; Zhao, Jianhua; Lui, Harvey; Zeng, Haishan

2012-03-01

In dermatology applications, diffuse reflectance spectroscopy has been extensively investigated as a promising tool for the noninvasive method to distinguish melanoma from benign pigmented skin lesion (nevus), which is concentrated with the skin chromophores like melanin and hemoglobin. We carried out a theoretical study to examine melanin distribution in human skin tissue and establish a practical optical model for further pigmented skin investigation. The theoretical simulation was using junctional nevus as an example. A multiple layer skin optical model was developed on established anatomy structures of skin, the published optical parameters of different skin layers, blood and melanin. Monte Carlo simulation was used to model the interaction between excitation light and skin tissue and rebuild the diffuse reflectance process from skin tissue. A testified methodology was adopted to determine melanin contents in human skin based on in vivo diffuse reflectance spectra. The rebuild diffuse reflectance spectra were investigated by adding melanin into different layers of the theoretical model. One of in vivo reflectance spectra from Junctional nevi and their surrounding normal skin was studied by compare the ratio between nevus and normal skin tissue in both the experimental and simulated diffuse reflectance spectra. The simulation result showed a good agreement with our clinical measurements, which indicated that our research method, including the spectral ratio method, skin optical model and modifying the melanin content in the model, could be applied in further theoretical simulation of pigmented skin lesions.

Characterization of LANDSAT Panels Using the NIST BRDF Scale from 1100 nm to 2500 nm

NASA Technical Reports Server (NTRS)

Markham, Brian; Tsai, Benjamin K.; Allen, David W.; Cooksey, Catherine; Yoon, Howard; Hanssen, Leonard; Zeng, Jinan; Fulton, Linda; Biggar, Stuart; Markham, Brian

2010-01-01

Many earth observing sensors depend on white diffuse reflectance standards to derive scales of radiance traceable to the St Despite the large number of Earth observing sensors that operate in the reflective solar region of the spectrum, there has been no direct method to provide NIST traceable BRDF measurements out to 2500 rim. Recent developments in detector technology have allowed the NIST reflectance measurement facility to expand the operating range to cover the 250 nm to 2500 nm range. The facility has been modified with and additional detector using a cooled extended range indium gallium arsenide (Extended InGaAs) detector. Measurements were made for two PTFE white diffuse reflectance standards over the 1100 nm to 2500 nm region at a 0' incident and 45' observation angle. These two panels will be used to support the OLI calibration activities. An independent means of verification was established using a NIST radiance transfer facility based on spectral irradiance, radiance standards and a diffuse reflectance plaque. An analysis on the results and associated uncertainties will be discussed.

[Comparative study of reflectance spectroscopy of women's acupoints around menstruation].

PubMed

Jiang, Xing-Hui; Liu, Han-Ping; Guo, Zhou-Yi; Meng, Yao-Yong; Zeng, Chang-Chun; Liu, Song-Hao

2010-12-01

Acupoint was reaction of viscera and its optical parameter was an important characteristic of tissue. In the present work, in order to discuss specificity of acupuncture on the response of qi and blood in human body, we compared the diffuse reflectance of Taichong (LV3), Taibai (SP3), and Chongyang (ST42) before, during and after menstruation. All the acupoints had the same shape of the spectrum and troughs were all at 423.16, 544.06 and 577.47 nm. The values of reflectance during menstruation were greater than before and after menstruation, especially for SP3 and ST42 (P < 0.05). SP3 and ST42 were more sensitive to the changes of qi and blood than LV3, and it was asymmetric and we found no evidence for the imbalance of the left side and right. These results indicated that acupoint diffuse reflectance changed with qi and blood, and that SP3 and ST42 had close relationship with menstruation. Diffuse reflectance may be possibly used in the quantitative analysis of qi and blood.

Half-collision analysis of far-wing diffuse structure in Cs-Xe

NASA Technical Reports Server (NTRS)

Exton, R. J.; Hillard, M. E.; Lempert, W. R.

1987-01-01

Laser excitation in the far red wing of the second principal series doublet of Cs mixed with Xe revealed a diffuse structure associated with the 2P(3/2) component. The structure is thought to originate from a reflection type of spectrum between the weakly bound E 2Sigma(1/2) excited state and the X 2Sigma(1/2) repulsive ground state of CsXe.

Method for calculation of light field characteristics in optical diagnosis problems and personalized laser treatment of biological tissues

NASA Astrophysics Data System (ADS)

Lisenko, S. A.; Kugeiko, M. M.

2013-05-01

We have developed a simple method for solving the radiation transport equation, permitting us to rapidly calculate (with accuracy acceptable in practice) the diffuse reflection coeffi cient for a broad class of biological tissues in the spectral region of strong and weak absorption of light, and also the light flux distribution over the depth of the tissue. We show that it is feasible to use the proposed method for quantitative estimates of tissue parameters from its diffuse reflectance spectrum and also for selecting the irradiation dose which is optimal for a specifi c patient in laser therapy for various diseases.

Green method by diffuse reflectance infrared spectroscopy and spectral region selection for the quantification of sulphamethoxazole and trimethoprim in pharmaceutical formulations.

PubMed

da Silva, Fabiana E B; Flores, Érico M M; Parisotto, Graciele; Müller, Edson I; Ferrão, Marco F

2016-03-01

An alternative method for the quantification of sulphametoxazole (SMZ) and trimethoprim (TMP) using diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS) and partial least square regression (PLS) was developed. Interval Partial Least Square (iPLS) and Synergy Partial Least Square (siPLS) were applied to select a spectral range that provided the lowest prediction error in comparison to the full-spectrum model. Fifteen commercial tablet formulations and forty-nine synthetic samples were used. The ranges of concentration considered were 400 to 900 mg g-1SMZ and 80 to 240 mg g-1 TMP. Spectral data were recorded between 600 and 4000 cm-1 with a 4 cm-1 resolution by Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). The proposed procedure was compared to high performance liquid chromatography (HPLC). The results obtained from the root mean square error of prediction (RMSEP), during the validation of the models for samples of sulphamethoxazole (SMZ) and trimethoprim (TMP) using siPLS, demonstrate that this approach is a valid technique for use in quantitative analysis of pharmaceutical formulations. The selected interval algorithm allowed building regression models with minor errors when compared to the full spectrum PLS model. A RMSEP of 13.03 mg g-1for SMZ and 4.88 mg g-1 for TMP was obtained after the selection the best spectral regions by siPLS.

Assessing human skin with diffuse reflectance spectroscopy and colorimetry

NASA Astrophysics Data System (ADS)

Seo, InSeok; Liu, Yang; Bargo, Paulo R.; Kollias, Nikiforos

2012-02-01

Colorimetry has been used as an objective measure of perceived skin color by human eye to document and score physiological responses of the skin from external insults. CIE color space values (L*, a* and b*) are the most commonly used parameters to correlate visually perceived color attributes such as L* for pigment, a* for erythema, and b* for sallowness of the skin. In this study, we investigated the relation of Lab color scale to the amount of major skin chromophores (oxy-, deoxyhemoglobin and melanin) calculated from diffuse reflectance spectroscopy. Thirty two healthy human subjects with ages from 20 to 70 years old, skin types I-VI, were recruited for the study. DRS and colorimetry measurements were taken from the left and right cheeks, and on the right upper inner arm. The melanin content calculated from 630-700 nm range of DRS measurements was shown to correlate with the lightness of skin (L*) for most skin types. For subjects with medium-to-light complexion, melanin measured at the blue part spectrum and hemoglobin interfered on the relation of lightness of the skin color to the melanin content. The sallowness of the skin that is quantified by the melanin contribution at the blue part spectrum of DRS was found to be related to b* scale. This study demonstrates the importance of documenting skin color by assessing individual skin chromophores with diffuse reflectance spectroscopy, in comparison to colorimetry assessment.

On mimicking diffuse reflectance spectra in the visible and near-infrared ranges for tissue-like phantom design

NASA Astrophysics Data System (ADS)

Debernardi, N.; Dunias, P.; van El, B.; Statham, A. E.

2014-03-01

A novel methodology is presented to mimic diffuse reflectance spectra of arbitrary biological tissues in the visible and near-infrared ranges. The prerequisite for this method is that the spectral information of basic components is sufficient to mimic an arbitrary tissue. Using a sterile disposable fiber optic probe the diffuse reflectance spectrum of a tissue (either in vivo or ex vivo) is measured, which forms the target spectrum. With the same type of fiber probe, a wide variety of basic components (ingredients) has been previously measured and all together forms a spectral database. A "recipe" for the optimal mixture of ingredients can then be derived using an algorithm that fits the absorption and scattering behavior of the target spectrum using the spectra of the basic components in the database. The spectral mimicking accuracy refines by adding more ingredients to the database. The validity of the principle is demonstrated by mimicking an arbitrary mixture of components. The method can be applied with different kinds of materials, e.g. gelatins, waxes and silicones, thus providing the possibility of mimicking the mechanical properties of target tissues as well. The algorithm can be extended from single point contact spectral measurement to contactless multi- and hyper-spectral camera acquisition. It can be applied to produce portable and durable tissue-like phantoms that provides consistent results over time for calibration, demonstration, comparison of instruments or other such tasks. They are also more readily available than living tissue or a cadaver and are not so limited by ease of handling and legislation; hence they are highly useful when developing new devices.

Development of a theory of the spectral reflectance of minerals, part 3

NASA Technical Reports Server (NTRS)

Aronson, J. R.; Emslie, A. G.; Roach, L. H.; Smith, E. M.; Vonthuena, P. C.

1972-01-01

Significant refinements were made in the theory of the diffuse reflectance of particulate media. The theory predicts the opposite trends of reflectance with particle size in regions of the spectrum in which the particles are semi-transparent and those in which they are opaque. Enhanced absorption caused by wave-optical effects of small surface asperities and edges was used to improve the theory. The same mechanism remedies the theory to account for the data in spectral regions of anomalous dispersion.

Fluorescence spectroscopy for endogenous porphyrins in human facial skin

NASA Astrophysics Data System (ADS)

Seo, I.; Tseng, S. H.; Cula, G. O.; Bargo, P. R.; Kollias, N.

2009-02-01

The activity of certain bacteria in skin is known to correlate to the presence of porphyrins. In particular the presence of coproporphyrin produced by P.acnes inside plugged pores has been correlated to acne vulgaris. Another porphyrin encountered in skin is protoporphyrin IX, which is produced by the body in the pathway for production of heme. In the present work, a fluorescence spectroscopy system was developed to measure the characteristic spectrum and quantify the two types of porphyrins commonly present in human facial skin. The system is comprised of a Xe lamp both for fluorescence excitation and broadband light source for diffuse reflectance measurements. A computer-controlled filter wheel enables acquisition of sequential spectra, first excited by blue light at 405 nm then followed by the broadband light source, at the same location. The diffuse reflectance spectrum was used to correct the fluorescence spectrum due to the presence of skin chromophores, such as blood and melanin. The resulting fluorescence spectra were employed for the quantification of porphyrin concentration in a population of healthy subjects. The results show great variability on the concentration of these porphyrins and further studies are being conducted to correlate them with skin conditions such as inflammation and acne vulgaris.

New noninvasive approach assessing in vivo sun protection factor (SPF) using diffuse reflectance spectroscopy (DRS) and in vitro transmission.

PubMed

Ruvolo Junior, Eduardo; Kollias, Nikiforos; Cole, Curtis

2014-08-01

In the past 56 years, many different in vitro methodologies have been developed and published to assess the sun protection factor (SPF) of products, but there is no method that has 1:1 correlation with in vivo measurements. Spectroscopic techniques have been used to noninvasively assess the UVA protection factor with good correlation to in vivo UVA-PF methodologies. To assess the SPF of sunscreen product by diffuse reflectance spectroscopy (DRS) technique, it is necessary to also determine the absorbance spectrum of the test material in the UVB portion of the spectrum (290-320 nm). However, because of the high absorbance characteristics of the stratum corneum and epidermis, the human skin does not remit enough UVB radiation to be used to measure the absorption spectrum of the applied product on skin. In this work, we present a new method combining the evaluation of the absolute UVA absorption spectrum, as measured by DRS with the spectral absorbance 'shape' of the UVB absorbance of the test material as determined with current in vitro thin film spectroscopy. The measurement of the in vivo UVA absorption spectrum involves the assessment of the remitted intensity of monochromatic UVA radiation (320-400 nm) before and after a sunscreen product was applied on skin using a spectrofluorimeter Fluorolog 3, FL3-22 (Yvon Horiba, Edison, NJ, USA). The probe geometry assures that light scattering products as well as colored products may be correctly assessed. This methodology has been extensively tested, validated, and reported in the literature. The in vitro absorption spectrum of the sunscreen samples and polyvinyl chloride (PVC) films 'surrogate' sunscreen standards were measured using Labsphere® UV-2000S (Labsphere, North Sutton, NH, USA). Sunscreens samples were tested using PMMA Helioplates (Helioscience, Marseille, France) as substrates. The UVB absorbance spectrum (Labsphere) is 'attached' to the UVA absorbance spectrum (diffuse reflectance) with the UVB absorbance matched to the UVA absorbance at 340 nm to complete the full spectral absorbance from which an estimate the SPF of the product can be calculated. Seventeen test materials with known in vivo SPF values were tested. Two of the tested products were PVC sunscreen thin films with 10-15 micrometers thickness and were used to investigate the absorption spectrum of these films when applied on different reflectance surfaces. Similar to the human in vivo SPF test, the developed methodology suggests limiting the use on Fitzpatrick skin phototypes I to III. The correlation of this new method with in vivo clinical SPF values was 0.98 (r2) with a slope of 1.007. This new methodology provides a new approach to determine SPF values without the extensive UV irradiation procedures (and biological responses) currently used to establish sunscreen efficacy. Further work will be conducted to establish methods for evaluation of products that are not photostable. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Modeling of Light Reflection from Human Skin

NASA Astrophysics Data System (ADS)

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

2006-09-01

In this work a two-layer model is used to simulate the spectral reflectance of adult human skin. We report and discuss diffuse reflectance spectra of this model for three values of the volume fraction of melanosomes fme, namely a) lightly pigmented skin fme = 4%, b) moderately pigmented skin fme = 14% and c) heavily pigmented skin fme = 30% at a volume fraction of blood fbl = 0.2%. We also considered the modeling of reflectance spectra for two values of fbl (0.2% and 1%) with fme = 4%. Both simulations were done in the 400-700 nm spectral range using the Monte Carlo simulation code MCML in standard C. Results showed that the principal signatures of human skin reflectance spectrum are obtained with this model and that it could be of valuable use to made predictions of diffuse reflectance of human skin for different values of the parameters related to skin characterization. These parameters can be associated to distinct medical conditions, such as erythema, jaundice, etc.

Epithelial cancers and photon migration: Monte Carlo simulations and diffuse reflectance measurements

NASA Astrophysics Data System (ADS)

Tubiana, Jerome; Kass, Alex J.; Newman, Maya Y.; Levitz, David

2015-07-01

Detecting pre-cancer in epithelial tissues such as the cervix is a challenging task in low-resources settings. In an effort to achieve low cost cervical cancer screening and diagnostic method for use in low resource settings, mobile colposcopes that use a smartphone as their engine have been developed. Designing image analysis software suited for this task requires proper modeling of light propagation from the abnormalities inside tissues to the camera of the smartphones. Different simulation methods have been developed in the past, by solving light diffusion equations, or running Monte Carlo simulations. Several algorithms exist for the latter, including MCML and the recently developed MCX. For imaging purpose, the observable parameter of interest is the reflectance profile of a tissue under some specific pattern of illumination and optical setup. Extensions of the MCX algorithm to simulate this observable under these conditions were developed. These extensions were validated against MCML and diffusion theory for the simple case of contact measurements, and reflectance profiles under colposcopy imaging geometry were also simulated. To validate this model, the diffuse reflectance profiles of tissue phantoms were measured with a spectrometer under several illumination and optical settings for various homogeneous tissues phantoms. The measured reflectance profiles showed a non-trivial deviation across the spectrum. Measurements of an added absorber experiment on a series of phantoms showed that absorption of dye scales linearly when fit to both MCX and diffusion models. More work is needed to integrate a pupil into the experiment.

Reflectance Spectroscopy of Palagonite and Iron-Rich Montmorillonite Clay Mixtures: Implications for the Surface Composition of Mars

NASA Technical Reports Server (NTRS)

Orenberg, James; Handy, Jonathan

1992-01-01

Mixtures of a Hawaiian palagonite and an iron-rich, montmorillonite clay (15.8 +/- 0.4 wt% Fe as Fe2O3) were evaluated as Mars surface spectral analogs from their diffuse reflectance spectra. The presence of the 2.2 microns absorption band in the reflectance spectrum of clays and its absence in the Mars spectrum have been interpreted as indicating that highly crystalline aluminous hydroxylated clays cannot be a major mineral component of the soil on Mars. The palagonite sample used in this study does not show this absorption feature in its spectrum. In mixtures of palagonite and iron-rich montmorillonite, the 2.2 microns Al-OH clay lattice band is not seen below 15 wt% montmorillonite. This suggests the possibility that iron-rich montmorillonite clay may be present in the soil of Mars at up to 15 wt% in combination with palagonite, and remain undetected in remotely sensed spectra of Mars.

A Multispectral Bidirectional Reflectance Distribution Function Study of Human Skin for Improved Dismount Detection

DTIC Science & Technology

2011-03-01

electromagnetic spectrum. With the availability of multispectral and hyperspectral systems, both spatial and spectral information for a scene are...an image. The boundary conditions for NDGRI and NDSI are set from diffuse spectral reflectance values for the range of skin types determined in [28...wearing no standard uniform and blending into the urban population. To assist with enemy detection and tracking, imaging systems that acquire spectral

Diffuse reflectance spectroscopy from 400-1600 nm to evaluate tumor resection margins during head and neck surgery (Conference Presentation)

NASA Astrophysics Data System (ADS)

Brouwer de Koning, Susan G.; Baltussen, E. J. M.; Karakullukcu, M. Baris; Smit, L.; van Veen, R. L. P.; Hendriks, Benno H. W.; Sterenborg, H. J. C. M.; Ruers, Theo J. M.

2017-02-01

This ex vivo study evaluates the feasibility of diffuse reflectance spectroscopy (DRS) for discriminating tumor from healthy oral tissue, with the aim to develop a technique that can be used to determine a complete excision of tumor through intraoperative margin assessment. DRS spectra were acquired on fresh surgical specimens from patients with an oral squamous cell carcinoma. The spectra represent a measure of diffuse light reflectance (wavelength range of 400-1600 nm), detected after illuminating tissue with a source fiber at 1.0 and 2.0 mm distances from a detection fiber. Spectra were obtained from 23 locations of tumor tissue and 16 locations of healthy muscle tissue. Biopsies were taken from all measured locations to facilitate an optimal correlation between spectra and pathological information. The area under the spectrum was used as a parameter to classify spectra of tumor and healthy tissue. Next, a receiver operating characteristics (ROC) analysis was performed to provide the area under the receiver operating curve (AUROC) as a measure for discriminative power. The area under the spectrum between 650 and 750 nm was used in the ROC analysis and provided AUROC values of 0.99 and 0.97, for distances of 1 mm and 2 mm between source and detector fiber, respectively. DRS can discriminate tumor from healthy oral tissue in an ex vivo setting. More specimens are needed to further evaluate this technique with component analyses and classification methods, prior to in vivo patient measurements.

Determination of the Ability to Measure Traces of Water in Dehydrated Residues of Waste Water by IR Diffuse Reflectance Spectra

NASA Astrophysics Data System (ADS)

Pratsenka, S. V.; Voropai, E. S.; Belkin, V. G.

2018-01-01

Rapid measurement of the moisture content of dehydrated residues is a critical problem, the solution of which will increase the efficiency of treatment facilities and optimize the process of applying flocculants. The ability to determine the moisture content of dehydrated residues using a meter operating on the IR reflectance principle was confirmed experimentally. The most suitable interference filters were selected based on an analysis of the obtained diffuse reflectance spectrum of the dehydrated residue in the range 1.0-2.7 μm. Calibration curves were constructed and compared for each filter set. A measuring filter with a transmittance maximum at 1.19 μm and a reference filter with a maximum at 1.3 μm gave the best agreement with the laboratory measurements.

Investigation of optical properties of nickel oxide nanostructures using photoluminescence and diffuse reflectance spectroscopy

NASA Astrophysics Data System (ADS)

Siddique, M. Naseem; Ahmed, Ateeq; Ali, T.; Tripathi, P.

2018-05-01

Nickel oxide (NiO) nanoparticles with a crystal size of around 16.26 nm have been synthesized via sol-gel method. The synthesized precursor was calcined at 600 °C for 4 hours to obtain the nickel oxide nanoparticles. The XRD analysis result indicated that the calcined sample has a cubic structure without any impurity phases. The FTIR analysis result confirmed the formation of NiO. The NiO nanoparticle exhibited absorption band edge at 277.27 nm and the optical band gap have been estimated approximately 4.47 eV using diffuse reflectance spectroscopy and photoluminescence emission spectrum of our as-synthesized sample showed strong peak at 3.65 eV attributed to the band edge transition.

Analysis of hemodynamics in human skin using photothermal radiometry and diffuse reflectance spectroscopy

NASA Astrophysics Data System (ADS)

Verdel, Nina; Marin, Ana; Vidovič, Luka; Milanič, Matija; Majaron, Boris

2017-07-01

We present a novel methodology for quantitative analysis of hemodynamics in human skin in vivo. Our approach combines pulsed photothermal radiometry (i.e., time-resolved measurements of midinfrared emission from sample surface after exposure to a short light pulse) and diffuse reflectance spectroscopy in visible part of the spectrum. Experimental data are fitted with predictions of a numerical model of light transport in a four-layer skin model (i.e., inverse Monte Carlo), which allows assessment of the layer thicknesses, chromophore contents (e.g., melanin, oxy- and deoxy-hemoglobin), as well as scattering properties. The performance is tested in comparison analysis of healthy skin before and during application of a blood pressure cuff (at 200 mm Hg) for 5 minutes.

Adaptive technique for matching the spectral response in skin lesions' images

NASA Astrophysics Data System (ADS)

Pavlova, P.; Borisova, E.; Pavlova, E.; Avramov, L.

2015-03-01

The suggested technique is a subsequent stage for data obtaining from diffuse reflectance spectra and images of diseased tissue with a final aim of skin cancer diagnostics. Our previous work allows us to extract patterns for some types of skin cancer, as a ratio between spectra, obtained from healthy and diseased tissue in the range of 380 - 780 nm region. The authenticity of the patterns depends on the tested point into the area of lesion, and the resulting diagnose could also be fixed with some probability. In this work, two adaptations are implemented to localize pixels of the image lesion, where the reflectance spectrum corresponds to pattern. First adapts the standard to the personal patient and second - translates the spectrum white point basis to the relative white point of the image. Since the reflectance spectra and the image pixels are regarding to different white points, a correction of the compared colours is needed. The latest is done using a standard method for chromatic adaptation. The technique follows the steps below: -Calculation the colorimetric XYZ parameters for the initial white point, fixed by reflectance spectrum from healthy tissue; -Calculation the XYZ parameters for the distant white point on the base of image of nondiseased tissue; -Transformation the XYZ parameters for the test-spectrum by obtained matrix; -Finding the RGB values of the XYZ parameters for the test-spectrum according sRGB; Finally, the pixels of the lesion's image, corresponding to colour from the test-spectrum and particular diagnostic pattern are marked with a specific colour.

Analytical model of diffuse reflectance spectrum of skin tissue

NASA Astrophysics Data System (ADS)

Lisenko, S. A.; Kugeiko, M. M.; Firago, V. A.; Sobchuk, A. N.

2014-01-01

We have derived simple analytical expressions that enable highly accurate calculation of diffusely reflected light signals of skin in the spectral range from 450 to 800 nm at a distance from the region of delivery of exciting radiation. The expressions, taking into account the dependence of the detected signals on the refractive index, transport scattering coefficient, absorption coefficient and anisotropy factor of the medium, have been obtained in the approximation of a two-layer medium model (epidermis and dermis) for the same parameters of light scattering but different absorption coefficients of layers. Numerical experiments on the retrieval of the skin biophysical parameters from the diffuse reflectance spectra simulated by the Monte Carlo method show that commercially available fibre-optic spectrophotometers with a fixed distance between the radiation source and detector can reliably determine the concentration of bilirubin, oxy- and deoxyhaemoglobin in the dermis tissues and the tissue structure parameter characterising the size of its effective scatterers. We present the examples of quantitative analysis of the experimental data, confirming the correctness of estimates of biophysical parameters of skin using the obtained analytical expressions.

An optically transparent metasurface for broadband microwave antireflection

NASA Astrophysics Data System (ADS)

Zhao, Jie; Zhang, Cheng; Cheng, Qiang; Yang, Jin; Cui, Tie Jun

2018-02-01

Metamaterial absorbers and diffusers provide powerful routes to decrease the backward reflection significantly with advantages of ultrathin profile and customized bandwidth. Simultaneous control of the absorption and scattering behaviors of the metamaterials which helps to improve the suppression capabilities of backward reflection, however, still remains a challenge. Aiming at this goal, we propose a metasurface constituted by two kinds of elements in a pseudorandom arrangement. By the use of indium tin oxide with moderate sheet resistance in the meta-atoms, enhanced absorption of energy can be achieved in a broad spectrum when interacted with illuminated waves. In the meanwhile, electromagnetic diffusion will be invoked from the destructive interference among the elements, giving rise to significant reduction of specular reflection as a result. Excellent agreements are observed between simulation and experiment with pronounced reflection suppression from 6.8 GHz to 19.4 GHz. In addition, the optical transparence of the patterns and substrates makes the proposed metasurface a promising candidate for future applications like photovoltaic solar cells and electromagnetic shielding glasses.

Holographic humidity response of slanted gratings in moisture-absorbing acrylamide photopolymer.

PubMed

Yu, Dan; Liu, Hongpeng; Mao, Dongyao; Geng, Yaohui; Wang, Weibo; Sun, Liping; Lv, Jiang

2015-08-01

Holographic humidity response is characterized in detail using transmission and reflection geometry in moisture-absorbing acrylamide photopolymer. The diffraction spectrum and its temporal evolution at various relative humidity are measured and analyzed. The quantitative relations between relative humidity and holographic properties of slanted gratings are determined. The responsibility of holographic gratings for various relative humidity is observed by the spectrum response of gratings. The extracted humidity constants reflect the applicability of reflection and transmission gratings at different humidity regions. The humidity reversibility experiment is achieved for confirming repeatability of the sensor. These experiments provide a probability for improving the applicability of a holographic humidity sensor. Finally, the extended diffusion model is derived by introducing the expansion coefficient to describe the dynamic swelling process. This work can accelerate development of the holographic sensor and provide a novel strategy for exploring the swelling mechanism of photopolymer.

Prediction of erodibility in Oxisols using iron oxides, soil color and diffuse reflectance spectroscopy

NASA Astrophysics Data System (ADS)

Arantes Camargo, Livia; Marques, José, Jr.

2015-04-01

The prediction of erodibility using indirect methods such as diffuse reflectance spectroscopy could facilitate the characterization of the spatial variability in large areas and optimize implementation of conservation practices. The aim of this study was to evaluate the prediction of interrill erodibility (Ki) and rill erodibility (Kr) by means of iron oxides content and soil color using multiple linear regression and diffuse reflectance spectroscopy (DRS) using regression analysis by least squares partial (PLSR). The soils were collected from three geomorphic surfaces and analyzed for chemical, physical and mineralogical properties, plus scanned in the spectral range from the visible and infrared. Maps of spatial distribution of Ki and Kr were built with the values calculated by the calibrated models that obtained the best accuracy using geostatistics. Interrill-rill erodibility presented negative correlation with iron extracted by dithionite-citrate-bicarbonate, hematite, and chroma, confirming the influence of iron oxides in soil structural stability. Hematite and hue were the attributes that most contributed in calibration models by multiple linear regression for the prediction of Ki (R2 = 0.55) and Kr (R2 = 0.53). The diffuse reflectance spectroscopy via PLSR allowed to predict Interrill-rill erodibility with high accuracy (R2adj = 0.76, 0.81 respectively and RPD> 2.0) in the range of the visible spectrum (380-800 nm) and the characterization of the spatial variability of these attributes by geostatistics.

Holographic spectrum-splitting optical systems for solar photovoltaics

NASA Astrophysics Data System (ADS)

Zhang, Deming

Solar energy is the most abundant source of renewable energy available. The relatively high cost prevents solar photovoltaic (PV) from replacing fossil fuel on a larger scale. In solar PV power generation the cost is reduced with more efficient PV technologies. In this dissertation, methods to improve PV conversion efficiency with holographic optical components are discussed. The tandem multiple-junction approach has achieved very high conversion efficiency. However it is impossible to manufacture tandem PV cells at a low cost due to stringent fabrication standards and limited material types that satisfy lattice compatibility. Current produced by the tandem multi-junction PV cell is limited by the lowest junction due to series connection. Spectrum-splitting is a lateral multi-junction concept that is free of lattice and current matching constraints. Each PV cell can be optimized towards full absorption of a spectral band with tailored light-trapping schemes. Holographic optical components are designed to achieve spectrum-splitting PV energy conversion. The incident solar spectrum is separated onto multiple PV cells that are matched to the corresponding spectral band. Holographic spectrum-splitting can take advantage of existing and future low-cost technologies that produces high efficiency thin-film solar cells. Spectrum-splitting optical systems are designed and analyzed with both transmission and reflection holographic optical components. Prototype holograms are fabricated and high optical efficiency is achieved. Light-trapping in PV cells increases the effective optical path-length in the semiconductor material leading to improved absorption and conversion efficiency. It has been shown that the effective optical path length can be increased by a factor of 4n2 using diffusive surfaces. Ultra-light-trapping can be achieved with optical filters that limit the escape angle of the diffused light. Holographic reflection gratings have been shown to act as angle-wavelength selective filters that can function as ultra-light-trapping filters. Results from an experimental reflection hologram are used to model the absorption enhancement factor for a silicon solar cell and light-trapping filter. The result shows a significant improvement in current generation for thin-film silicon solar cells under typical operating conditions.

Preliminary study of a solar selective coating system using black cobalt oxide for high temperature solar collectors

NASA Technical Reports Server (NTRS)

Mcdonald, G.

1980-01-01

Black cobalt oxide coatings (high solar absorptance layer) were deposited on thin layers of silver or gold (low emittance layer) which had been previously deposited on oxidized (diffusion barrier layer) stainless steel substrates. The reflectance properties of these coatings were measured at various thicknesses of cobalt for integrated values of the solar and infrared spectrum. The values of absorptance and emittance were calculated from the measured reflectance values, before and after exposure in air at 650 C for approximately 1000 hours. Absorptance and emittance were interdependent functions of the weight of cobalt oxide. Also, these cobalt oxide/noble metal/oxide diffusion barrier coatings have absorptances greater than 0.90 and emittances of approximately 0.20 even after about 1000 hours at 650 C.

Diffuse Reflectance Infrared Fourier Transform Spectroscopy for the Determination of Asbestos Species in Bulk Building Materials

PubMed Central

Accardo, Grazia; Cioffi, Raffaeke; Colangelo, Francesco; d’Angelo, Raffaele; De Stefano, Luca; Paglietti, Fderica

2014-01-01

Diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy is a well-known technique for thin film characterization. Since all asbestos species exhibit intense adsorptions peaks in the 4000–400 cm−1 region of the infrared spectrum, a quantitative analysis of asbestos in bulk samples by DRIFT is possible. In this work, different quantitative analytical procedures have been used to quantify chrysotile content in bulk materials produced by building requalification: partial least squares (PLS) chemometrics, the Linear Calibration Curve Method (LCM) and the Method of Additions (MoA). Each method has its own pros and cons, but all give affordable results for material characterization: the amount of asbestos (around 10%, weight by weight) can be determined with precision and accuracy (errors less than 0.1). PMID:28788467

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

NASA Technical Reports Server (NTRS)

Justice, C.; Holben, B.

1980-01-01

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

Monte Carlo Simulation of Visible Light Diffuse Reflection in Neonatal Skin

NASA Astrophysics Data System (ADS)

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

2008-04-01

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

Reference-free spectroscopic determination of fat and protein in milk in the visible and near infrared region below 1000nm using spatially resolved diffuse reflectance fiber probe.

PubMed

Bogomolov, Andrey; Belikova, Valeria; Galyanin, Vladislav; Melenteva, Anastasiia; Meyer, Hans

2017-05-15

New technique of diffuse reflectance spectroscopic analysis of milk fat and total protein content in the visible (Vis) and adjacent near infrared (NIR) region (400-995nm) has been developed and tested. Sample analysis was performed through a probe having eight 200-µm fiber channels forming a linear array. One of the end fibers was used for the illumination and other seven - for the spectroscopic detection of diffusely reflected light. One of the detection channels was used as a reference to normalize the spectra and to convert them into absorbance-equivalent units. The method has been tested experimentally using a designed sample set prepared from industrial raw milk standards with widely varying fat and protein content. To increase the modelling robustness all milk samples were measured in three different homogenization degrees. Comprehensive data analysis has shown the advantage of combining both spectral and spatial resolution in the same measurement and revealed the most relevant channels and wavelength regions. The modelling accuracy was further improved using joint variable selection and preprocessing optimization method based on the genetic algorithm. The root mean-square errors of different validation methods were below 0.10% for fat and below 0.08% for total protein content. Based on the present experimental data, it was computationally shown that the full-spectrum analysis in this method can be replaced by a sensor measurement at several specific wavelengths, for instance, using light-emitting diodes (LEDs) for illumination. Two optimal sensor configurations have been suggested: with nine LEDs for the analysis of fat and seven - for protein content. Both simulated sensors exhibit nearly the same component determination accuracy as corresponding full-spectrum analysis. Copyright © 2017 Elsevier B.V. All rights reserved.

Theoretical studies of floating-reference method for NIR blood glucose sensing

NASA Astrophysics Data System (ADS)

Shi, Zhenzhi; Yang, Yue; Zhao, Huijuan; Chen, Wenliang; Liu, Rong; Xu, Kexin

2011-03-01

Non-invasive blood glucose monitoring using NIR light has been suffered from the variety of optical background that is mainly caused by the change of human body, such as the change of temperature, water concentration, and so on. In order to eliminate these internal influence and external interference a so called floating-reference method has been proposed to provide an internal reference. From the analysis of the diffuse reflectance spectrum, a position has been found where diffuse reflection of light is not sensitive to the glucose concentrations. Our previous work has proved the existence of reference position using diffusion equation. However, since glucose monitoring generally use the NIR light in region of 1000-2000nm, diffusion equation is not valid because of the high absorption coefficient and small source-detector separations. In this paper, steady-state high-order approximate model is used to further investigate the existence of the floating reference position in semi-infinite medium. Based on the analysis of different optical parameters on the impact of spatially resolved reflectance of light, we find that the existence of the floating-reference position is the result of the interaction of optical parameters. Comparing to the results of Monte Carlo simulation, the applicable region of diffusion approximation and higher-order approximation for the calculation of floating-reference position is discussed at the wavelength of 1000nm-1800nm, using the intralipid solution of different concentrations. The results indicate that when the reduced albedo is greater than 0.93, diffusion approximation results are more close to simulation results, otherwise the high order approximation is more applicable.

An introduction to the water recovery x-ray rocket

NASA Astrophysics Data System (ADS)

Miles, Drew M.; McEntaffer, Randall L.; Schultz, Ted B.; Donovan, Benjamin D.; Tutt, James H.; Yastishock, Daniel; Steiner, Tyler; Hillman, Christopher R.; McCoy, Jake A.; Wages, Mitchell; Hull, Sam; Falcone, Abe; Burrows, David N.; Chattopadhyay, Tanmoy; Anderson, Tyler; McQuaide, Maria

2017-08-01

The Water Recovery X-ray Rocket (WRXR) is a sounding rocket payload that will launch from the Kwajalein Atoll in April 2018 and seeks to be the first astrophysics sounding rocket payload to be water recovered by NASA. WRXR's primary instrument is a grating spectrometer that consists of a mechanical collimator, X-ray reflection gratings, grazing-incidence mirrors, and a hybrid CMOS detector. The instrument will obtain a spectrum of the diffuse soft X-ray emission from the northern part of the Vela supernova remnant and is optimized for 3rd and 4th order OVII emission. Utilizing a field of view of 3.25° × 3.25° and resolving power of λ/δλ ≍40-50 in the lines of interest, the WRXR spectrometer aims to achieve the most highly-resolved spectrum of Vela's diffuse soft X-ray emission. This paper presents introductions to the payload and the science target.

Diffuse Reflectance Spectroscopy and Colorimetry as a Diagnostic Tool for Acanthosis Nigricans

NASA Astrophysics Data System (ADS)

Pattamadilok, Bensachee; Devpura, Suneetha; Syed, Zain U.; Vemulapalli, Pranita; Henderson, Marsha; Rehse, Steven J.; Hamzavi, Iltefat; Mahmoud, Bassel H.; Lim, Henry W.; Naik, Ratna

2011-03-01

The purpose of this study was to quantify skin color changes due to Acanthosis Nigricans, a disorder common among prediabetic and obese individuals. The non-invasive optical technique diffuse reflectance spectroscopy (DRS) was used to determine skin melanin, oxyhemoglobin and deoxyhemoglobin content through the measured absorption spectrum. Colorimetery was used to measure skin color based on the standard Tristimulus values (L*, a*, and b*). Data was obtained from eight patients, spanning eight months of treatment. Measurements were obtained from lesion tissue on the neck and healthy skin was used as a control. L*, a* and b* values showed significant differences between lesion and normal controls, whereas melanin was the only parameter which showed statistical significant differences in DRS measurements. Future work will use more sensitive chemometric methods to increase diagnostic accuracy based on the raw spectra of the DRS.

EPR and optical investigations of LaMgAl{sub 11}O{sub 19}:Cr{sup 3+} phosphor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, Vijay, E-mail: vijayjiin2006@yahoo.com; Sivaramaiah, G.; Rao, J.L.

2014-12-15

Graphical abstract: The EPR spectrum of as-prepared LaMgAl{sub 11}O{sub 19}:Cr{sup 3+} phosphor at 110 K. - Highlights: • Using the combustion synthesis, LaMgAl{sub 11}O{sub 19}:Cr{sup 3+} phosphor has been prepared in a few minutes. • Optical investigation indicates that Cr{sup 3+} ions are present in octahedral symmetry. • The EPR signals indicate that exchange coupled Cr{sup 3+}–Cr{sup 3+} ion pairs in weakly distorted sites. - Abstract: The LaMgAl{sub 11}O{sub 19}:Cr{sup 3+} phosphor has been prepared by a low-temperature combustion synthesis method. As-prepared combustion synthesized powder was characterized using powder X-ray diffraction (XRD), diffuse reflectance (DRS), electron paramagnetic resonance (EPR) andmore » photoluminescence (PL) studies. The X-ray diffraction pattern reveals crystalline hexagonal phases. The UV–vis diffuse reflectance spectrum exhibits three broad bands characteristic of Cr{sup 3+} ions in octahedral symmetry. The EPR spectrum exhibits several resonance signals. The signals with the effective g values at g = 4.84, 3.64 and 2.26 have been attributed to the isolated Cr{sup 3+} ions. The signal with the effective g value at g = 1.94 has been attributed to exchange coupled Cr{sup 3+}–Cr{sup 3+} ion pairs. The PL studies exhibit several bands characteristic of Cr{sup 3+} ions in octahedral symmetry.« less

SWIR calibration of Spectralon reflectance factor

NASA Astrophysics Data System (ADS)

Georgiev, Georgi T.; Butler, James J.; Cooksey, Catherine; Ding, Leibo; Thome, Kurtis J.

2011-11-01

Satellite instruments operating in the reflective solar wavelength region require accurate and precise determination of the Bidirectional Reflectance Factor (BRF) of laboratory-based diffusers used in their pre-flight and on-orbit radiometric calibrations. BRF measurements are required throughout the reflected-solar spectrum from the ultraviolet through the shortwave infrared. Spectralon diffusers are commonly used as a reflectance standard for bidirectional and hemispherical geometries. The Diffuser Calibration Laboratory (DCaL) at NASA's Goddard Space Flight Center is a secondary calibration facility with reflectance measurements traceable to those made by the Spectral Tri-function Automated Reference Reflectometer (STARR) facility at the National Institute of Standards and Technology (NIST). For more than two decades, the DCaL has provided numerous NASA projects with BRF data in the ultraviolet (UV), visible (VIS) and the Near InfraRed (NIR) spectral regions. Presented in this paper are measurements of BRF from 1475 nm to 1625 nm obtained using an indium gallium arsenide detector and a tunable coherent light source. The sample was a 50.8 mm (2 in) diameter, 99% white Spectralon target. The BRF results are discussed and compared to empirically generated data from a model based on NIST certified values of 6°directional-hemispherical spectral reflectance factors from 900 nm to 2500 nm. Employing a new NIST capability for measuring bidirectional reflectance using a cooled, extended InGaAs detector, BRF calibration measurements of the same sample were also made using NIST's STARR from 1475 nm to 1625 nm at an incident angle of 0° and at viewing angle of 45°. The total combined uncertainty for BRF in this ShortWave Infrared (SWIR) range is less than 1%. This measurement capability will evolve into a BRF calibration service in SWIR region in support of NASA remote sensing missions.

Handheld dual fluorescence and reflection spectroscopy system for monitoring topical low dose ALA-PDT of actinic keratoses (AK)

NASA Astrophysics Data System (ADS)

Charamisinau, Ivan; Keymel, Kenneth; Potter, William; Oseroff, Allan R.

2006-02-01

Photodynamic therapy is an effective, minimally invasive skin cancer treatment modality with few side effects. Improved therapeutic selectivity and efficacy is expected if treatment is optimized individually for each patient based on detailed measurements prior and during the treatment. The handheld system presented allows measuring optical properties of the skin, the rate of photosensitizer photobleaching during the ALA PDT and oxygen saturation in the tissue. The photobleaching rate is monitored using fluorescence spectroscopy, where protoporphyrin IX in tissue is exited by 410 nm (blue) or 532 nm (green) laser light, and fluorescence in the 580-800 nm range is monitored. The photobleaching rate is calculated by correlating the measured spectrum with known protoporphyrin IX, photoproduct and nonspecific tissue autofluorescence spectra using correlation analysis. Double-wavelength excitation allows a rough estimation of the depth of the fluorescence source due to the significant difference in penetration depth for blue and green light. Blood concentration and oxygenation in the tissue are found from the white light reflectance spectrum in the 460-800 nm range. Known spectra for the oxy- and deoxyhemoglobin, melanin, and tissue baseline absorption and tissue scattering are substituted in nonlinear equations to find the penetration depth and diffuse reflectance coefficient. The nonlinear equation for the diffuse reflectance coefficient is solved for blood and melanin concentrations and blood oxygenation values that provide the best fit to the measured spectrum. The optical properties of the tissue obtained from the reflectance spectroscopy are used to correct the fluorescence data. A noncontact probe with 5 fibers (3 excitation and 2 detection) focused to the same 5 mm diameter spot: 2 excitation lasers, a white light lamp and a two-channel spectrometer are used. A LabView program with custom nonlinear equation solvers written in C++ automatically performs the measurements and calculations, and writes data to a database. The system is currently used in a clinical trial to find the relationship between skin pigmentation, oxygen saturation in blood, photobleaching rate and optimal fluence rate for skin cancer treatment of actinic keratoses.

Noninvasive evaluation of collagen and hemoglobin contents and scattering property of in vivo keloid scars and normal skin using diffuse reflectance spectroscopy: pilot study

NASA Astrophysics Data System (ADS)

Tseng, Sheng-Hao; Hsu, Chao-Kai; Yu-Yun Lee, Julia; Tzeng, Shih-Yu; Chen, Wan-Rung; Liaw, Yu-Kai

2012-07-01

Collagen is a rich component in skin that provides skin structure integrity; however, its contribution to the absorption and scattering properties of various types of skin has not been extensively studied. We considered the contribution of the collagen to the absorption spectrum of in vivo normal skin and keloids of 12 subjects derived from our diffuse reflectance spectroscopy (DRS) system in the wavelength range from 550 to 860 nm. It was found that the collagen concentration, the hemoglobin oxygen saturation, and the reduced scattering coefficient of keloids were remarkably different from that of normal skin. Our results suggest that our DRS system could assist clinicians in understanding the functional and structural condition of keloid scars. In the future, we will evaluate the accuracy of our system in the keloid diagnosis and investigate the applicability of our system for other skin-collagen-related studies.

Optical properties of cells with melanin

NASA Astrophysics Data System (ADS)

Rohde, Barukh; Coats, Israel; Krueger, James; Gareau, Dan

2014-02-01

The optical properties of pigmented lesions have been studied using diffuse reflectance spectroscopy in a noninvasive configuration on optically thick samples such as skin in vivo. However, it is difficult to un-mix the effects of absorption and scattering with diffuse reflectance spectroscopy techniques due to the complex anatomical distributions of absorbing and scattering biomolecules. We present a device and technique that enables absorption and scattering measurements of tissue volumes much smaller than the optical mean-free path. Because these measurements are taken on fresh-frozen sections, they are direct measurements of the optical properties of tissue, albeit in a different hydration state than in vivo tissue. Our results on lesions from 20 patients including melanomas and nevi show the absorption spectrum of melanin in melanocytes and basal keratinocytes. Our samples consisted of fresh frozen sections that were unstained. Fitting the spectrum as an exponential decay between 500 and 1100 nm [mua = A*exp(-B*(lambda-C)) + D], we report on the fit parameters of and their variation due to biological heterogeneity as A = 4.20e4 +/- 1.57e5 [1/cm], B = 4.57e-3 +/- 1.62e-3 [1/nm], C = 210 +/- 510 [nm] , D = 613 +/- 534 [1/cm]. The variability in these results is likely due to highly heterogeneous distributions of eumelanin and pheomelanin.

Multiplexed Colorimetric Solid-Phase Extraction

NASA Technical Reports Server (NTRS)

Gazda, Daniel B.; Fritz, James S.; Porter, Marc D.

2009-01-01

Multiplexed colorimetric solid-phase extraction (MC-SPE) is an extension of colorimetric solid-phase extraction (C-SPE) an analytical platform that combines colorimetric reagents, solid phase extraction, and diffuse reflectance spectroscopy to quantify trace analytes in water. In CSPE, analytes are extracted and complexed on the surface of an extraction membrane impregnated with a colorimetric reagent. The analytes are then quantified directly on the membrane surface using a handheld diffuse reflectance spectrophotometer. Importantly, the use of solid-phase extraction membranes as the matrix for impregnation of the colorimetric reagents creates a concentration factor that enables the detection of low concentrations of analytes in small sample volumes. In extending C-SPE to a multiplexed format, a filter holder that incorporates discrete analysis channels and a jig that facilitates the concurrent operation of multiple sample syringes have been designed, enabling the simultaneous determination of multiple analytes. Separate, single analyte membranes, placed in a readout cartridge create unique, analyte-specific addresses at the exit of each channel. Following sample exposure, the diffuse reflectance spectrum of each address is collected serially and the Kubelka-Munk function is used to quantify each water quality parameter via calibration curves. In a demonstration, MC-SPE was used to measure the pH of a sample and quantitate Ag(I) and Ni(II).

Use of a multiseparation fiber optic probe for the optical diagnosis of breast cancer.

PubMed

Zhu, Changfang; Palmer, Gregory M; Breslin, Tara M; Xu, Fushen; Ramanujam, Nirmala

2005-01-01

We explore the effects of the illumination and collection geometry on optical spectroscopic diagnosis of breast cancer. Fluorescence and diffuse reflectance spectroscopy in the UV-visible spectral range are made with a multiseparation probe at three illumination-collection separations of 735, 980, and 1225 microm, respectively, from 13 malignant and 34 nonmalignant breast tissues. Statistical analysis is carried out on two types of data inputs: (1) the fluorescence and diffuse reflectance spectra recorded at each of the three illumination-collection separations and (2) the integrated fluorescence (at each excitation wavelength) or diffuse reflectance over the entire spectrum at all three illumination-collection separations. The results show that using the integrated fluorescence intensities recorded at a single excitation wavelength at all three illumination-collection separations can discriminate malignant from nonmalignant breast tissues with similar classification accuracy to that using spectral data measured at several excitation wavelengths with a single illumination-collection separation. These findings have significant implications with respect to the design of an optical system for breast cancer diagnosis. Examining the intensity attenuation at a single wavelength rather than spectral intensities at multiple wavelengths can significantly reduce the measurement and data processing time in a clinical setting as well as the cost and complexity of the optical system. Copyright 2005 Society of Photo-Optical Instrumentation Engineers.

Ocean Observations with EOS/MODIS: Algorithm Development and Post Launch Studies

NASA Technical Reports Server (NTRS)

Gordon, Howard R.

1997-01-01

Significant accomplishments made during the present reporting period are as follows: (1) We developed a new method for identifying the presence of absorbing aerosols and, simultaneously, performing atmospheric correction. The algorithm consists of optimizing the match between the top-of-atmosphere radiance spectrum and the result of models of both the ocean and aerosol optical properties; (2) We developed an algorithm for providing an accurate computation of the diffuse transmittance of the atmosphere given an aerosol model. A module for inclusion into the MODIS atmospheric-correction algorithm was completed; (3) We acquired reflectance data for oceanic whitecaps during a cruise on the RV Ka'imimoana in the Tropical Pacific (Manzanillo, Mexico to Honolulu, Hawaii). The reflectance spectrum of whitecaps was found to be similar to that for breaking waves in the surf zone measured by Frouin, Schwindling and Deschamps, however, the drop in augmented reflectance from 670 to 860 nm was not as great, and the magnitude of the augmented reflectance was significantly less than expected; and (4) We developed a method for the approximate correction for the effects of the MODIS polarization sensitivity. The correction, however, requires adequate characterization of the polarization sensitivity of MODIS prior to launch.

Elimination of single-beam substitution error in diffuse reflectance measurements using an integrating sphere.

PubMed

Vidovic, Luka; Majaron, Boris

2014-02-01

Diffuse reflectance spectra (DRS) of biological samples are commonly measured using an integrating sphere (IS). To account for the incident light spectrum, measurement begins by placing a highly reflective white standard against the IS sample opening and collecting the reflected light. After replacing the white standard with the test sample of interest, DRS of the latter is determined as the ratio of the two values at each involved wavelength. However, such a substitution may alter the fluence rate inside the IS. This leads to distortion of measured DRS, which is known as single-beam substitution error (SBSE). Barring the use of more complex experimental setups, the literature states that only approximate corrections of the SBSE are possible, e.g., by using look-up tables generated with calibrated low-reflectivity standards. We present a practical method for elimination of SBSE when using IS equipped with an additional reference port. Two additional measurements performed at this port enable a rigorous elimination of SBSE. Our experimental characterization of SBSE is replicated by theoretical derivation. This offers an alternative possibility of computational removal of SBSE based on advance characterization of a specific DRS setup. The influence of SBSE on quantitative analysis of DRS is illustrated in one application example.

Resonance spectra of a paramagnetic probe dissolved in a viscous medium

NASA Technical Reports Server (NTRS)

Kaplan, J. I.; Gelerinter, E.; Fryburg, G. C.

1972-01-01

A model is presented for calculating the paramagnetic resonance (EPR) spectrum of vanadyl acetylacetonate (VAAC) dissolved in either a liquid crystal or isotropic solvent. It employs density matrix formulation in the rotating reference frame. The molecules occupy several discrete angles with respect to the magnetic field and can relax to neighboring positions in a characteristic time tau(theta). The form of tau(theta) is found from a diffusion approach, and the magnitude of tau(theta) is a measure of how freely the VAAC probe tumbles in the solvent. Spectra are predicted for values of tau between 10 to the minus 11th power sec and 10 to the minus 7th power sec. The EPR spectrum, in the isotropic case, is obtained be summing the contributions from the allowed angles weighted by the polar volume element, sin theta. When applying the model to the nematic liquid crystal case it is also necessary to multiply by the Saupe distribution function. For this case tau(theta) is obtained from the diffusion approach in which two diffusion constants are employed to reflect the difference in the parallel and perpendicular components of the viscosity.

Diffuse reflectance study of the effects of bleaching agents in damaged dental pieces

NASA Astrophysics Data System (ADS)

Bante-Guerra, J.; Trejo-Tzab, R.; Macias, J. D.; Quintana, P.; Alvarado-Gil, J. J.

2011-03-01

One of the most important subjects of interest in dentistry and teeth preservation is related to the effects of bleaching agents on the integrity of the dental pieces. This is especially crucial when teeth surface has received some damage, generated by chemical, biological and mechanical agents or weathering in the case of dental pieces recovered from burial sites. In this work the time evolution of the effects of bleaching agents on the surface of dental pieces is monitored using diffuse reflectance in the visible spectrum is reported. The effects were monitored in teeth previously subject to chemical agents. Bleaching was induced using commercial whitening products. It is shown that the time evolution of the reflectance depends strongly on the condition of the surface as well as on the thickness of enamel. Additionally the colorimetric analysis of the samples during the bleaching is presented. This is especially useful in for comparing with previous studies. In order to complement our studies, the effects of the bleaching on the surface of the teeth were monitored by scanning electron microscopy.

Steady state and time resolved optical characterization studies of Zn 2SnO 4 nanowires for solar cell applications

DOE PAGES

Yakami, Baichhabi R.; Poudyal, Uma; Nandyala, Shashank R.; ...

2016-10-25

Nanowires are a promising option for sensitized solar cells, sensors, and display technology. Most of the work thus far has focused on binary oxides for these nanowires, but ternary oxides have advantages in additional control of optical and electronic properties. Here, we report on the diffuse reflectance, Low Temperature and Room Temperature Photoluminescence (PL), PL excitation spectrum, and Time Resolved PL (TRPL) of Zinc Tin Oxide (ZTO) nanowires grown by Chemical Vapor Deposition. The PL from the ZTO nanowires does not exhibit any band gap or near gap emission, and the diffuse reflectance measurement confirms that these ZTO nanowires havemore » a direct forbidden transition. The broad PL spectrum reveals two Gaussian peaks centered at 1.86 eV (red) and 2.81 eV (blue), representing two distinct defect states or complexes. The PL spectra were further studied by the Time Resolved Emission Spectrum and intensity dependent PL and TRPL. The time resolved measurements show complex non-exponential decays at all wavelengths, indicative of defect to defect transitions, and the red emissive states decay much slower than the blue emissive states. The effects of annealing in air and vacuum are studied to investigate the origin of the defect states in the nanowires, showing that the blue states are related to oxygen vacancies. We propose an energy band model for the nanowires containing defect states within the band gap and the associated transitions between these states that are consistent with our measurements.« less

Steady state and time resolved optical characterization studies of Zn 2SnO 4 nanowires for solar cell applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yakami, Baichhabi R.; Poudyal, Uma; Nandyala, Shashank R.

Nanowires are a promising option for sensitized solar cells, sensors, and display technology. Most of the work thus far has focused on binary oxides for these nanowires, but ternary oxides have advantages in additional control of optical and electronic properties. Here, we report on the diffuse reflectance, Low Temperature and Room Temperature Photoluminescence (PL), PL excitation spectrum, and Time Resolved PL (TRPL) of Zinc Tin Oxide (ZTO) nanowires grown by Chemical Vapor Deposition. The PL from the ZTO nanowires does not exhibit any band gap or near gap emission, and the diffuse reflectance measurement confirms that these ZTO nanowires havemore » a direct forbidden transition. The broad PL spectrum reveals two Gaussian peaks centered at 1.86 eV (red) and 2.81 eV (blue), representing two distinct defect states or complexes. The PL spectra were further studied by the Time Resolved Emission Spectrum and intensity dependent PL and TRPL. The time resolved measurements show complex non-exponential decays at all wavelengths, indicative of defect to defect transitions, and the red emissive states decay much slower than the blue emissive states. The effects of annealing in air and vacuum are studied to investigate the origin of the defect states in the nanowires, showing that the blue states are related to oxygen vacancies. We propose an energy band model for the nanowires containing defect states within the band gap and the associated transitions between these states that are consistent with our measurements.« less

jasonSWIR Calibration of Spectralon Reflectance Factor

NASA Technical Reports Server (NTRS)

Georgiev, Georgi T.; Butler, James J.; Cooksey, Cahterine; Ding, Leibo; Thome, Kurtis J.

2011-01-01

Satellite instruments operating in the reflective solar wavelength region require accurate and precise determination of the Bidirectional Reflectance Factor (BRF) of laboratory-based diffusers used in their pre-flight and on-orbit radiometric calibrations. BRF measurements are required throughout the reflected-solar spectrum from the ultraviolet through the shortwave infrared. Spectralon diffusers are commonly used as a reflectance standard for bidirectional and hemispherical geometries. The Diffuser Calibration Laboratory (DCaL) at NASA's Goddard Space Flight Center is a secondary calibration facility with reflectance measurements traceable to those made by the Spectral Tri-function Automated Reference Reflectometer (STARR) facility at the National Institute of Standards and Technology (NIST). For more than two decades, the DCaL has provided numerous NASA projects with BRF data in the ultraviolet (UV), visible (VIS) and the Near infraRed (NIR) spectral regions. Presented in this paper are measurements of BRF from 1475nm to 1625nm obtained using an indium gallium arsenide detector and a tunable coherent light source. The sample was a 2 inch diameter, 99% white Spectralon target. The BRF results are discussed and compared to empirically generated data from a model based on NIST certified values of 6deg directional/hemispherical spectral reflectance factors from 900nm to 2500nm. Employing a new NIST capability for measuring bidirectional reflectance using a cooled, extended InGaAs detector, BRF calibration measurements of the same sample were also made using NIST's STARR from 1475nm to 1625nm at an incident angle of 0deg and at viewing angles of 40deg, 45deg, and 50deg. The total combined uncertainty for BRF in this ShortWave Infrared (SWIR) range is less than 1%. This measurement capability will evolve into a BRF calibration service in SWIR region in support of NASA remote sensing missions. Keywords: BRF, BRDF, Calibration, Spectralon, Reflectance, Remote Sensing.

Model of bidirectional reflectance distribution function for metallic materials

NASA Astrophysics Data System (ADS)

Wang, Kai; Zhu, Jing-Ping; Liu, Hong; Hou, Xun

2016-09-01

Based on the three-component assumption that the reflection is divided into specular reflection, directional diffuse reflection, and ideal diffuse reflection, a bidirectional reflectance distribution function (BRDF) model of metallic materials is presented. Compared with the two-component assumption that the reflection is composed of specular reflection and diffuse reflection, the three-component assumption divides the diffuse reflection into directional diffuse and ideal diffuse reflection. This model effectively resolves the problem that constant diffuse reflection leads to considerable error for metallic materials. Simulation and measurement results validate that this three-component BRDF model can improve the modeling accuracy significantly and describe the reflection properties in the hemisphere space precisely for the metallic materials.

Calculation of Transfer Functions of Multilayer Biotissues in the Problems of Correction of Their Fluorescence Spectra

NASA Astrophysics Data System (ADS)

Lysenko, S. A.

2018-01-01

A method for rapid calculation of a flux of stimulated fluorescence of a multilayer optically dense medium with inhomogeneous distribution of the fluorophore has been developed. The light field in the medium at the excitation wavelength of fluorescence is represented by a superposition of incident collimated, incident diffuse, and reflected diffuse fluxes. A two-stream approximation is used to describe the light field in the medium at the wavelength of emission of the fluorescence. Fluxes in adjacent elementary layers of the medium and on its surface are connected by simple matrix operators that are obtained using a combination of engineering approaches of radiation-transfer theory and single-scattering approximation. The calculations of fluorescence fluxes of a four-layer biotissue that are excited and recorded at 400-800 nm are compared with their Monte Carlo simulation with a discrepancy of 1%. The effect of the propagation medium on the fluorescence spectra of 5-ALA-induced protoporphyrin IX that are recorded from human skin was studied, and a technique for their correction that is based on measurements and quantitative analysis of the diffuse reflectance spectrum of skin was proposed.

Noninvasive spectral imaging of skin chromophores based on multiple regression analysis aided by Monte Carlo simulation

NASA Astrophysics Data System (ADS)

Nishidate, Izumi; Wiswadarma, Aditya; Hase, Yota; Tanaka, Noriyuki; Maeda, Takaaki; Niizeki, Kyuichi; Aizu, Yoshihisa

2011-08-01

In order to visualize melanin and blood concentrations and oxygen saturation in human skin tissue, a simple imaging technique based on multispectral diffuse reflectance images acquired at six wavelengths (500, 520, 540, 560, 580 and 600nm) was developed. The technique utilizes multiple regression analysis aided by Monte Carlo simulation for diffuse reflectance spectra. Using the absorbance spectrum as a response variable and the extinction coefficients of melanin, oxygenated hemoglobin, and deoxygenated hemoglobin as predictor variables, multiple regression analysis provides regression coefficients. Concentrations of melanin and total blood are then determined from the regression coefficients using conversion vectors that are deduced numerically in advance, while oxygen saturation is obtained directly from the regression coefficients. Experiments with a tissue-like agar gel phantom validated the method. In vivo experiments with human skin of the human hand during upper limb occlusion and of the inner forearm exposed to UV irradiation demonstrated the ability of the method to evaluate physiological reactions of human skin tissue.

Spectral properties of plant leaves pertaining to urban landscape design of broad-spectrum solar ultraviolet radiation reduction

NASA Astrophysics Data System (ADS)

Yoshimura, Haruka; Zhu, Hui; Wu, Yunying; Ma, Ruijun

2010-03-01

Human exposure to harmful ultraviolet (UV) radiation has important public health implications. Actual human exposure to solar UV radiation depends on ambient UV irradiance, and the latter is influenced by ground reflection. In urban areas with higher reflectivity, UV exposure occurs routinely. To discover the solar UV radiation regulation mechanism of vegetation, the spectral reflectance and transmittance of plant leaves were measured with a spectrophotometer. Typically, higher plants have low leaf reflectance (around 5%) and essentially zero transmittance throughout the UV region regardless of plant species and seasonal change. Accordingly, incident UV radiation decreases to 5% by being reflected and is reduced to zero by passing through a leaf. Therefore, stratified structures of vegetation are working as another terminator of UV rays, protecting whole terrestrial ecosystems, while vegetation at waterfronts contributes to protect aquatic ecosystems. It is possible to protect the human population from harmful UV radiation by urban landscape design of tree shade and the botanical environment. Even thin but uniformly distributed canopy is effective in attenuating UV radiation. To intercept diffuse radiation, UV screening by vertical structures such as hedges should be considered. Reflectivity of vegetation is around 2%, as foliage surfaces reduce incident UV radiation via reflection, while also eliminating it by transmittance. Accordingly, vegetation reduces incident UV radiation to around 2% by reflection. Vegetation influence on ambient UV radiation is broad-spectrum throughout the UV region. Only trees provide cool UV protective shade. Urban landscapes aimed at abating urban heat islands integrated with a reduction of human UV over-exposure would contribute to mitigation of climate change.

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

NASA Astrophysics Data System (ADS)

Yokokawa, Takumi; Nishidate, Izumi

2016-04-01

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

Fuji apple storage time rapid determination method using Vis/NIR spectroscopy.

PubMed

Liu, Fuqi; Tang, Xuxiang

2015-01-01

Fuji apple storage time rapid determination method using visible/near-infrared (Vis/NIR) spectroscopy was studied in this paper. Vis/NIR diffuse reflection spectroscopy responses to samples were measured for 6 days. Spectroscopy data were processed by stochastic resonance (SR). Principal component analysis (PCA) was utilized to analyze original spectroscopy data and SNR eigen value. Results demonstrated that PCA could not totally discriminate Fuji apples using original spectroscopy data. Signal-to-noise ratio (SNR) spectrum clearly classified all apple samples. PCA using SNR spectrum successfully discriminated apple samples. Therefore, Vis/NIR spectroscopy was effective for Fuji apple storage time rapid discrimination. The proposed method is also promising in condition safety control and management for food and environmental laboratories.

Fuji apple storage time rapid determination method using Vis/NIR spectroscopy

PubMed Central

Liu, Fuqi; Tang, Xuxiang

2015-01-01

Fuji apple storage time rapid determination method using visible/near-infrared (Vis/NIR) spectroscopy was studied in this paper. Vis/NIR diffuse reflection spectroscopy responses to samples were measured for 6 days. Spectroscopy data were processed by stochastic resonance (SR). Principal component analysis (PCA) was utilized to analyze original spectroscopy data and SNR eigen value. Results demonstrated that PCA could not totally discriminate Fuji apples using original spectroscopy data. Signal-to-noise ratio (SNR) spectrum clearly classified all apple samples. PCA using SNR spectrum successfully discriminated apple samples. Therefore, Vis/NIR spectroscopy was effective for Fuji apple storage time rapid discrimination. The proposed method is also promising in condition safety control and management for food and environmental laboratories. PMID:25874818

A preliminary verification of the floating reference measurement method for non-invasive blood glucose sensing

NASA Astrophysics Data System (ADS)

Min, Xiaolin; Liu, Rong; Fu, Bo; Xu, Kexin

2017-06-01

In the non-invasive sensing of blood glucose by near-infrared diffuse reflectance spectroscopy, the spectrum is highly susceptible to the unstable and complicated background variations from the human body and the environment. In in vitro analyses, background variations are usually corrected by the spectrum of a standard reference sample that has similar optical properties to the analyte of interest. However, it is hard to find a standard sample for the in vivo measurement. Therefore, the floating reference measurement method is proposed to enable relative measurements in vivo, where the spectra under some special source-detector distance, defined as the floating reference position, are insensitive to the changes in glucose concentration due to the absorption effect and scattering effect. Because the diffuse reflectance signals at the floating reference positions only reflect the information on background variations during the measurement, they can be used as the internal reference. In this paper, the theoretical basis of the floating reference positions in a semi-infinite turbid medium was discussed based on the steady-state diffusion equation and its analytical solutions in a semi-infinite turbid medium (under the extrapolated boundary conditions). Then, Monte-Carlo (MC) simulations and in vitro experiments based on a custom-built continuous-moving spatially resolving double-fiber NIR measurement system, configured with two types of light source, a super luminescent diode (SLD) and a super-continuum laser, were carried out to verify the existence of the floating reference position in 5%, 10% and 20% Intralipid solutions. The results showed that the simulation values of the floating reference positions are close to the theoretical results, with a maximum deviation of approximately 0.3 mm in 1100-1320 nm. Great differences can be observed in 1340-1400 nm because the optical properties of Intralipid in this region don not satisfy the conditions of the steady-state diffusion equation. For the in vitro experiments, floating reference positions exist in 1220 nm and 1320 nm under two types of light source, and the results are quite close. However, the reference positions obtained from experiments are further from the light source compared with those obtained in the MC simulation. For the turbid media and the wavelengths investigated, the difference is up to 1 mm. This study is important for the design of optical fibers to be applied in the floating reference measurement.

Constraints on Particle Sizes in Saturn's G Ring from Ring Plane Crossing Observations

NASA Astrophysics Data System (ADS)

Throop, H. B.; Esposito, L. W.

1996-09-01

The ring plane crossings in 1995--96 allowed earth-based observations of Saturn's diffuse rings (Nicholson et al., Nature 272, 1996; De Pater et al. Icarus 121, 1996) at a phase angle of alpha ~ 5 deg . We calculate the G ring reflectance for steady state distributions of dust to km-sized bodies from a range of physical models which track the evolution of the G ring from its initial formation following the disruption of a progenitor satellite (Canup & Esposito 1996, \\ Icarus,\\ in press). We model scattering from the ring's small particles using an exact T-matrix method for nonspherical, absorptive particles (Mishchenko et al. 1996, \\ JGR Atmo., in press), large particles using the phase function and spectrum of Europa, and intermediate particles using a linear combination of the small and large limits. Two distinct particle size distributions from the CE96 model fit the observed spectrum. The first is that of a dusty ring, with the majority of ring reflectance in dust particles of relatedly shallow power law size distribution exponent q ~ 2.5. The second has equal reflectances from a) dust in the range q ~ 3.5 -- 6.5 and b) macroscopic bodies > 1 mm. In this second case, the respective slightly blue and red components combine to form the observed relatively flat spectrum. Although light scattering in backscatter is not sufficient to completely constrain the G ring size distribution, the distributions predicted by the CE96 model can explain the earth-based observations.

Effect of upstream ULF waves on the energetic ion diffusion at the earth's foreshock: Theory, Simulation, and Observations

NASA Astrophysics Data System (ADS)

Otsuka, F.; Matsukiyo, S.; Kis, A.; Hada, T.

2017-12-01

Spatial diffusion of energetic particles is an important problem not only from a fundamental physics point of view but also for its application to particle acceleration processes at astrophysical shocks. Quasi-linear theory can provide the spatial diffusion coefficient as a function of the wave turbulence spectrum. By assuming a simple power-law spectrum for the turbulence, the theory has been successfully applied to diffusion and acceleration of cosmic rays in the interplanetary and interstellar medium. Near the earth's foreshock, however, the wave spectrum often has an intense peak, presumably corresponding to the upstream ULF waves generated by the field-aligned beam (FAB). In this presentation, we numerically and theoretically discuss how the intense ULF peak in the wave spectrum modifies the spatial parallel diffusion of energetic ions. The turbulence is given as a superposition of non-propagating transverse MHD waves in the solar wind rest frame, and its spectrum is composed of a piecewise power-law spectrum with different power-law indices. The diffusion coefficients are then estimated by using the quasi-linear theory and test particle simulations. We find that the presence of the ULF peak produces a concave shape of the diffusion coefficient when it is plotted versus the ion energy. The results above are used to discuss the Cluster observations of the diffuse ions at the Earth's foreshock. Using the density gradients of the energetic ions detected by the Cluster spacecraft, we determine the e-folding distances, equivalently, the spatial diffusion coefficients, of ions with their energies from 10 to 32 keV. The observed e-folding distances are significantly smaller than those estimated in the past statistical studies. This suggests that the particle acceleration at the foreshock can be more efficient than considered before. Our test particle simulation explains well the small estimate of the e-folding distances, by using the observed wave turbulence spectrum near the shock.

Syntheses, characterization and nonlinear optical properties of sodium-scandium carbonate Na5Sc(CO3)4·2H2O

NASA Astrophysics Data System (ADS)

Chen, Jie; Luo, Min; Ye, Ning

2014-10-01

A novel nonlinear optical (NLO) material Na5Sc(CO3)4·2H2O has been synthesized under a subcritical hydrothermal condition. The structure is determined by single-crystal X-ray diffraction and further characterized by TG analyses and UV-vis-NIR diffuse reflectance spectrum. It crystallizes in the tetragonal space group P-421c, with a = b = 7.4622(6) Å, C = 11.5928(15) Å. The Second-harmonic generation (SHG) on polycrystalline samples was measured using the Kurtz and Perry technique, which indicated that Na5Sc(CO3)4·2H2O was a phase-matchable material, and its measured SHG coefficient was about 1.8 times as large as that of d36 (KDP). The results from the UV-vis diffuse reflectance spectroscopy study of the powder samples indicated that the short-wavelength absorption edges of Na5Sc(CO3)4·2H2O is about 220 nm, suggesting that this crystal is a promising UV nonlinear optical (NLO) materials.

Procedure for measuring simultaneously the solar and visible properties of glazing with complex internal or external structures.

PubMed

Gentle, A R; Smith, G B

2014-10-20

Accurate solar and visual transmittances of materials in which surfaces or internal structures are complex are often not easily amenable to standard procedures with laboratory-based spectrophotometers and integrating spheres. Localized "hot spots" of intensity are common in such materials, so data on small samples is unreliable. A novel device and simple protocols have been developed and undergone validation testing. Simultaneous solar and visible transmittance and reflectance data have been acquired for skylight components and multilayer polycarbonate roof panels. The pyranometer and lux sensor setups also directly yield "light coolness" in lumens/watt. Sample areas must be large, and, although mainly in sheet form, some testing has been done on curved panels. The instrument, its operation, and the simple calculations used are described. Results on a subset of diffuse and partially diffuse materials with no hot spots have been cross checked using 150 mm integrating spheres with a spectrophotometer and the Air Mass 1.5 spectrum. Indications are that results are as good or better than with such spheres for transmittance, but reflectance techniques need refinement for some sample types.

A non-invasive diffuse reflectance calibration-free method for absolute determination of exogenous biochemicals concentration in biological tissues

NASA Astrophysics Data System (ADS)

Lappa, Alexander V.; Kulikovskiy, Artem N.; Busarov, Oleg G.

2014-03-01

The paper presents a new method for distant non-destructive determination of concentration of light absorbing admixtures in turbid media. In particular, it is intended for non-invasive in vivo control of accumulation in patient tissues of various biochemicals introduced to the patients for chemotherapy, photodynamic therapy or diagnostics. It is require that the admixture absorption spectrum should have a clearly marked peak in the wavelength region where the pure medium one varies regularly. Fluorescence of admixtures is not required. The method uses the local diffuse reflectance spectroscopy with optical fiber probe including one emitting and two reading There are several features in the method: the value to be determined is absolute concentration of admixtures; the method needs no calibration measurements on phantoms; it needs no reference measurements on sample with zero admixture concentration; it uses a two parametric kinetic light propagation model and original algorithms to resolve direct and inverse tasks of radiation transport theory. Experimental testing passed with tissue equivalent phantoms and different admixtures, including a chlorine photosensitizer, showed accuracy under 10% in all cases.

Phosphorous Diffuser Diverged Blue Laser Diode for Indoor Lighting and Communication

PubMed Central

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

2015-01-01

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

Phosphorous Diffuser Diverged Blue Laser Diode for Indoor Lighting and Communication

NASA Astrophysics Data System (ADS)

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

2015-12-01

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

A method for operative quantitative interpretation of multispectral images of biological tissues

NASA Astrophysics Data System (ADS)

Lisenko, S. A.; Kugeiko, M. M.

2013-10-01

A method for operative retrieval of spatial distributions of biophysical parameters of a biological tissue by using a multispectral image of it has been developed. The method is based on multiple regressions between linearly independent components of the diffuse reflection spectrum of the tissue and unknown parameters. Possibilities of the method are illustrated by an example of determining biophysical parameters of the skin (concentrations of melanin, hemoglobin and bilirubin, blood oxygenation, and scattering coefficient of the tissue). Examples of quantitative interpretation of the experimental data are presented.

A high resolution spectrum of the diffuse soft X-ray background

NASA Astrophysics Data System (ADS)

Crowder, S. Gwynne

Galactic contributions to the diffuse X-ray background were believed to largely come from thermal emission of hot gas and models of the Galactic neighborhood within ˜ 100 pc reflected this belief. However, recent observations led to the realization that emission from charge exchange within the Solar System might produce comparable intensities to that of thermal emission. A high resolution spectrum of the diffuse X-ray background from 0.1 to 1 keV was obtained for a ˜ 1 sr region of the sky centered at l = 90°, b = +60° in May 2008 using a 36 pixel array of microcalorimeters flown on a sounding rocket. With an energy resolution of 11 eV FWHM below 1 keV, the spectrum can be used to separate charge exchange contributions originating within the heliosphere from thermal emission of hot gas in the interstellar medium. The X-ray sensitivity below 1 keV was reduced about a factor of four by contamination that occurred early in the flight, limiting the significance of the results. The observed ratio of helium-like O VII forbidden plus intercombination to resonance lines is 1.2 +/- 1.2 at 90% confidence. This indicates that at least 67% of the emission is thermal. On the other hand, the observed ratio of C VI Lygamma to Lyalpha is 0.3+0.3-0.2 , requiring at least a 33% contribution from charge exchange. In addition to these astrophysical results, I present experimental improvements from the addition of a gold coating to the detector array substrate which greatly reduces extraneous signals and from the use of silicon support meshes which improves blocking filter robustness. I also detail a new optimal filtering analysis technique that preserves spectral resolution and live time in the presence of pulse overlap.

Influence of humidity on spectral performance for near-infrared detection of fruit

NASA Astrophysics Data System (ADS)

Zhou, Ying; Fu, Xiaping; Ying, Yibin

2006-10-01

Spectral performance would be affected by many factors such as temperature, equipment parameters and so on. Humidity fluctuations may occur in practice because of varying weather conditions. The objective of this research was to find out whether the change of humidity would influence the near infrared spectrum of samples. In this trial, an airproof, humidity-controllable test-bed was established to change the humidity of the mini environment. At 40%, 50%, 60%, 70% and 80% degrees of humidity, each sample's final spectrum was attained by removing the background's spectrum from the sample's. For whether the influence of the sample's and the background's spectrum are equal was not known, This trial was divided into two groups: detecting background and sample at each degree of humidity (group 1) and background's detecting just happened at 40% degree of humidity (group 2). This research was based on the hardware of NEXUS intelligent FT-IR spectrometer, made by Nicolet instrument company U.S.A, with using fiber optic diffuse reflectance accessory. The final spectrum was analysed using single variance analysis and Mahalanobis Distance methods. The result shows that neither in group 1 nor 2, humidity had little influence on NIR.

Spatial frequency domain spectroscopy of two layer media

NASA Astrophysics Data System (ADS)

Yudovsky, Dmitry; Durkin, Anthony J.

2011-10-01

Monitoring of tissue blood volume and oxygen saturation using biomedical optics techniques has the potential to inform the assessment of tissue health, healing, and dysfunction. These quantities are typically estimated from the contribution of oxyhemoglobin and deoxyhemoglobin to the absorption spectrum of the dermis. However, estimation of blood related absorption in superficial tissue such as the skin can be confounded by the strong absorption of melanin in the epidermis. Furthermore, epidermal thickness and pigmentation varies with anatomic location, race, gender, and degree of disease progression. This study describes a technique for decoupling the effect of melanin absorption in the epidermis from blood absorption in the dermis for a large range of skin types and thicknesses. An artificial neural network was used to map input optical properties to spatial frequency domain diffuse reflectance of two layer media. Then, iterative fitting was used to determine the optical properties from simulated spatial frequency domain diffuse reflectance. Additionally, an artificial neural network was trained to directly map spatial frequency domain reflectance to sets of optical properties of a two layer medium, thus bypassing the need for iteration. In both cases, the optical thickness of the epidermis and absorption and reduced scattering coefficients of the dermis were determined independently. The accuracy and efficiency of the iterative fitting approach was compared with the direct neural network inversion.

Model-free and analytical EAP reconstruction via spherical polar Fourier diffusion MRI.

PubMed

Cheng, Jian; Ghosh, Aurobrata; Jiang, Tianzi; Deriche, Rachid

2010-01-01

How to estimate the diffusion Ensemble Average Propagator (EAP) from the DWI signals in q-space is an open problem in diffusion MRI field. Many methods were proposed to estimate the Orientation Distribution Function (ODF) that is used to describe the fiber direction. However, ODF is just one of the features of the EAP. Compared with ODF, EAP has the full information about the diffusion process which reflects the complex tissue micro-structure. Diffusion Orientation Transform (DOT) and Diffusion Spectrum Imaging (DSI) are two important methods to estimate the EAP from the signal. However, DOT is based on mono-exponential assumption and DSI needs a lot of samplings and very large b values. In this paper, we propose Spherical Polar Fourier Imaging (SPFI), a novel model-free fast robust analytical EAP reconstruction method, which almost does not need any assumption of data and does not need too many samplings. SPFI naturally combines the DWI signals with different b-values. It is an analytical linear transformation from the q-space signal to the EAP profile represented by Spherical Harmonics (SH). We validated the proposed methods in synthetic data, phantom data and real data. It works well in all experiments, especially for the data with low SNR, low anisotropy, and non-exponential decay.

The role of boundary variability in polycrystalline grain-boundary diffusion

NASA Astrophysics Data System (ADS)

Moghadam, M. M.; Rickman, J. M.; Harmer, M. P.; Chan, H. M.

2015-01-01

We investigate the impact of grain-boundary variability on mass transport in a polycrystal. More specifically, we perform both numerical and analytical studies of steady-state diffusion in prototypical microstructures in which there is either a discrete spectrum of grain-boundary activation energies or else a complex distribution of grain-boundary character, and hence a continuous spectrum of boundary activation energies. An effective diffusivity is calculated for these structures using simplified multi-state models and, for the case of a continuous spectrum, employing experimentally obtained grain-boundary energy data. We identify different diffusive regimes for these cases and quantify deviations from Arrhenius behavior using effective medium theory. Finally, we examine the diffusion kinetics of a simplified model of an interfacial layering (i.e., complexion) transition.

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

DTIC Science & Technology

2016-12-22

reflective inverse diffusion, which was a proof-of-concept experiment that used phase modulation to shape the wavefront of a laser causing it to refocus...after reflection from a rough surface. By refocusing the light, reflective inverse diffusion has the potential to eliminate the complex radiometric model...photography. However, the initial reflective inverse diffusion experiments provided no mathematical background and were conducted under the premise that the

Resolving the Origin of the Diffuse Soft X-ray Background

NASA Technical Reports Server (NTRS)

Smith, Randall K.; Foster, Adam R.; Edgar, Ricard J.; Brickhouse, Nancy S.; Sanders, Wilton T.

2012-01-01

In January 1993, the Diffuse X-ray Spectrometer (DXS) measured the first high-resolution spectrum of the diffuse soft X-ray background between 44-80A. A line-dominated spectrum characteristic of a 10(exp 6)K collisionally ionized plasma' was expected but while the observed spectrum was clearly line-dominated, no model would fit. Then in 2003 the Cosmic Hot Interstellar Plasma Spectrometer (CHIPS) launched and observed the diffuse extreme-ultraviolet (EUV) spectrum between 90- 265A. Although many emission lines were again expected; only Fe IX at 171.1A was detected. The discovery of X-rays from comets led to the realization that heavy ions (Z=6-28) in the solar wind will emit soft X-rays as the ions interact via charge exchange with neutral atoms in the heliosphere and geocorona. Using a new model for solar wind charge exchange (SWCX) emission, we show that the diffuse soft X-ray background can be understood as a combination of emission from charge exchange onto the slow and fast solar wind together with a more distant and diffuse hot (10(exp 6)K) plasma.

Holographic lens spectrum splitting photovoltaic system for increased diffuse collection and annual energy yield

NASA Astrophysics Data System (ADS)

Vorndran, Shelby D.; Wu, Yuechen; Ayala, Silvana; Kostuk, Raymond K.

2015-09-01

Concentrating and spectrum splitting photovoltaic (PV) modules have a limited acceptance angle and thus suffer from optical loss under off-axis illumination. This loss manifests itself as a substantial reduction in energy yield in locations where a significant portion of insulation is diffuse. In this work, a spectrum splitting PV system is designed to efficiently collect and convert light in a range of illumination conditions. The system uses a holographic lens to concentrate shortwavelength light onto a smaller, more expensive indium gallium phosphide (InGaP) PV cell. The high efficiency PV cell near the axis is surrounded with silicon (Si), a less expensive material that collects a broader portion of the solar spectrum. Under direct illumination, the device achieves increased conversion efficiency from spectrum splitting. Under diffuse illumination, the device collects light with efficiency comparable to a flat-panel Si module. Design of the holographic lens is discussed. Optical efficiency and power output of the module under a range of illumination conditions from direct to diffuse are simulated with non-sequential raytracing software. Using direct and diffuse Typical Metrological Year (TMY3) irradiance measurements, annual energy yield of the module is calculated for several installation sites. Energy yield of the spectrum splitting module is compared to that of a full flat-panel Si reference module.

Accurate wavelength measurements of a putative standard for near-infrared diffuse reflection spectrometry.

PubMed

Isaksson, Tomas; Yang, Husheng; Kemeny, Gabor J; Jackson, Richard S; Wang, Qian; Alam, M Kathleen; Griffiths, Peter R

2003-02-01

The diffuse reflection (DR) spectrum of a sample consisting of a mixture of rare earth oxides and talc was measured at 2 cm-1 resolution, using five different accessories installed on five different Fourier transform near-infrared (FT-NIR) spectrometers from four manufacturers. Peak positions for 37 peaks were determined using two peak-picking algorithms: center-of-mass and polynomial fitting. The wavenumber of the band center reported by either of these techniques was sensitive to the slope of the baseline, and so the baseline of the spectra was corrected using either a polynomial fit or conversion to the second derivative. Significantly different results were obtained with one combination of spectrometer and accessory than the others. Apparently, the beam path through the interferometer and DR accessory was different for this accessory than for any of the other measurements, causing a severe degradation of the resolution. Spectra measured on this instrument were removed as outliers. For measurements made on FT-NIR spectrometers, it is shown that it is important to check the resolution at which the spectrum has been measured using lines in the vibration-rotation spectrum of atmospheric water vapor and to specify the peak-picking and baseline-correction algorithms that are used to process the measured spectra. The variance between the results given by the four different methods of peak-picking and baseline correction was substantially larger than the variance between the remaining five measurements. Certain bands were found to be more suitable than others for use as wavelength standards. A band at 5943.13 cm-1 (1682.62 nm) was found to be the most stable band between the four methods and the six measurements. A band at 5177.04 cm-1 (1931.61 nm) has the highest precision between different measurements when polynomial baseline correction and polynomial peak-picking algorithms are used.

Diffuse reflectance relations based on diffusion dipole theory for large absorption and reduced scattering

NASA Astrophysics Data System (ADS)

Bremmer, Rolf H.; van Gemert, Martin J. C.; Faber, Dirk J.; van Leeuwen, Ton G.; Aalders, Maurice C. G.

2013-08-01

Diffuse reflectance spectra are used to determine the optical properties of biological samples. In medicine and forensic science, the turbid objects under study often possess large absorption and/or scattering properties. However, data analysis is frequently based on the diffusion approximation to the radiative transfer equation, implying that it is limited to tissues where the reduced scattering coefficient dominates over the absorption coefficient. Nevertheless, up to absorption coefficients of 20 m at reduced scattering coefficients of 1 and 11.5 mm-1, we observed excellent agreement (r2=0.994) between reflectance measurements of phantoms and the diffuse reflectance equation proposed by Zonios et al. [Appl. Opt. 38, 6628-6637 (1999)], derived as an approximation to one of the diffusion dipole equations of Farrell et al. [Med. Phys. 19, 879-888 (1992)]. However, two parameters were fitted to all phantom experiments, including strongly absorbing samples, implying that the reflectance equation differs from diffusion theory. Yet, the exact diffusion dipole approximation at high reduced scattering and absorption also showed agreement with the phantom measurements. The mathematical structure of the diffuse reflectance relation used, derived by Zonios et al. [Appl. Opt. 38, 6628-6637 (1999)], explains this observation. In conclusion, diffuse reflectance relations derived as an approximation to the diffusion dipole theory of Farrell et al. can analyze reflectance ratios accurately, even for much larger absorption than reduced scattering coefficients. This allows calibration of fiber-probe set-ups so that the object's diffuse reflectance can be related to its absorption even when large. These findings will greatly expand the application of diffuse reflection spectroscopy. In medicine, it may allow the use of blue/green wavelengths and measurements on whole blood, and in forensic science, it may allow inclusion of objects such as blood stains and cloth at crime scenes.

Vibronic Origin for the Diffuse Band Spectrum

NASA Astrophysics Data System (ADS)

Duley, W. W.

1983-09-01

The two arguments outlined by Nuth and Donn (1983) against an interpretation of the diffuse band spectrum between 677 and 536 nm as vibronic systems associated with forbidden origins at 14321, 15153, and 15343 cm-1 (Duley, 1982) are controverted. It is concluded that the vibronic analysis presented by Duley, 1983 for the diffuse band spectrum is in keeping with current spectroscopic practice. The identification of a forbidden origin for 19 of these bands at 14321 cm-1 strongly suggests the involvement of Cr3+ ions in MgO solids in the production of these features.

Measurement and Modeling of the Optical Scattering Properties of Crop Canopies

NASA Technical Reports Server (NTRS)

Vanderbilt, V. C. (Principal Investigator)

1985-01-01

The specular reflection process is shown to be a key aspect of radiation transfer by plant canopies. Polarization measurements are demonstrated as the tool for determining the specular and diffuse portions of the canopy radiance. The magnitude of the specular fraction of the reflectance is significant compared to the magnitude of the diffuse fraction. Therefore, it is necessary to consider specularly reflected light in developing and evaluating light-canopy interaction models for wheat canopies. Models which assume leaves are diffuse reflectors correctly predict only the diffuse fraction of the canopy reflectance factor. The specular reflectance model, when coupled with a diffuse leaf model, would predict both the specular and diffuse portions of the reflectance factor. The specular model predicts and the data analysis confirms that the single variable, angle of incidence of specularly reflected sunlight on the leaf, explains much of variation in the polarization data as a function of view-illumination directions.

An improved method to estimate reflectance parameters for high dynamic range imaging

NASA Astrophysics Data System (ADS)

Li, Shiying; Deguchi, Koichiro; Li, Renfa; Manabe, Yoshitsugu; Chihara, Kunihiro

2008-01-01

Two methods are described to accurately estimate diffuse and specular reflectance parameters for colors, gloss intensity and surface roughness, over the dynamic range of the camera used to capture input images. Neither method needs to segment color areas on an image, or to reconstruct a high dynamic range (HDR) image. The second method improves on the first, bypassing the requirement for specific separation of diffuse and specular reflection components. For the latter method, diffuse and specular reflectance parameters are estimated separately, using the least squares method. Reflection values are initially assumed to be diffuse-only reflection components, and are subjected to the least squares method to estimate diffuse reflectance parameters. Specular reflection components, obtained by subtracting the computed diffuse reflection components from reflection values, are then subjected to a logarithmically transformed equation of the Torrance-Sparrow reflection model, and specular reflectance parameters for gloss intensity and surface roughness are finally estimated using the least squares method. Experiments were carried out using both methods, with simulation data at different saturation levels, generated according to the Lambert and Torrance-Sparrow reflection models, and the second method, with spectral images captured by an imaging spectrograph and a moving light source. Our results show that the second method can estimate the diffuse and specular reflectance parameters for colors, gloss intensity and surface roughness more accurately and faster than the first one, so that colors and gloss can be reproduced more efficiently for HDR imaging.

Effects of ionizing radiations on a pharmaceutical compound, chloramphenicol

NASA Astrophysics Data System (ADS)

Varshney, L.; Patel, K. M.

1994-05-01

Chloramphenicol, a broad spectrum antibiotic, has been irradiated using Cobalt-60 γ radiation and electron beam at graded radiation doses upto 100 kGy. Several degradation products and free radicals are formed on irradiation. Purity, degradation products, free radicals, discolouration, crystallinity, solubility and entropy of radiation processing have been investigated. Aqueous solutions undergo extensive radiolysis even at low doses. Physico-chemical, microbiological and toxicological tests do not show significant degradation at sterilization dose. High performance liquid chromatography (HPLC), differential scanning calorimetry (DSC), UV-spectrophotometry, diffuse reflectance spectroscopy (DRS) and electron spin resonance spectroscopy (ESR) techniques were employed for the investigations.

Bone optical spectroscopy for the measurement of hemoglobin content

NASA Astrophysics Data System (ADS)

Hollmann, Joseph L.; Arambel, Paula; Piet, Judith; Shefelbine, Sandra; Markovic, Stacey; Niedre, Mark; DiMarzio, Charles A.

2014-05-01

Osteoporosis is a common side effect of spinal cord injuries. Blood perfusion in the bone provides an indication of bone health and may help to evaluate therapies addressing bone loss. Current methods for measuring blood perfusion of bone use dyes and ionizing radiation, and yield qualitative results. We present a device capable of measuring blood oxygenation in the tibia. The device illuminates the skin directly over the tibia with a white light source and measures the diffusely reflected light in the near infrared spectrum. Multiple source-detector distances are utilized so that the blood perfusion in skin and bone may be differentiated.

Cadmium Telluride-Titanium Dioxide Nanocomposite for Photodegradation of Organic Substance.

PubMed

Ontam, Areeporn; Khaorapapong, Nithima; Ogawa, Makoto

2015-12-01

Cadmium telluride-titanium dioxide nanocomposite was prepared by hydrothermal reaction of sol-gel derived titanium dioxide and organically modified cadmium telluride. The crystallinity of titanium dioxide in the nanocomposite was higher than that of pure titanium dioxide obtained by the reaction under the same temperature and pressure conditions, showing that cadmium telluride induced the crystallization of titanium dioxide. Diffuse reflectance spectrum of the nanocomposite showed the higher absorption efficiency in the UV-visible region due to band-gap excitation of titanium dioxide. The nanocomposite significantly showed the improvement of photocatalytic activity for 4-chlorophenol with UV light.

In situ nondestructive imaging of functional pigments in Micro-Tom tomato fruits by multi spectral imaging based on Wiener estimation method

NASA Astrophysics Data System (ADS)

Nishidate, Izumi; Ooe, Shintaro; Todoroki, Shinsuke; Asamizu, Erika

2013-05-01

To evaluate the functional pigments in the tomato fruits nondestructively, we propose a method based on the multispectral diffuse reflectance images estimated by the Wiener estimation for a digital RGB image. Each pixel of the multispectral image is converted to the absorbance spectrum and then analyzed by the multiple regression analysis to visualize the contents of chlorophyll a, lycopene and β-carotene. The result confirms the feasibility of the method for in situ imaging of chlorophyll a, β-carotene and lycopene in the tomato fruits.

Leaf absorbance and photosynthesis

NASA Technical Reports Server (NTRS)

Schurer, Kees

1994-01-01

The absorption spectrum of a leaf is often thought to contain some clues to the photosynthetic action spectrum of chlorophyll. Of course, absorption of photons is needed for photosynthesis, but the reverse, photosynthesis when there is absorption, is not necessarily true. As a check on the existence of absorption limits we measured spectra for a few different leaves. Two techniques for measuring absorption have been used, viz. the separate determination of the diffuse reflectance and the diffuse transmittance with the leaf at a port of an integrating sphere and the direct determination of the non-absorbed fraction with the leaf in the sphere. In a cross-check both methods yielded the same results for the absorption spectrum. The spectrum of a Fuchsia leaf, covering the short-wave region from 350 to 2500 nm, shows a high absorption in UV, blue and red, the well known dip in the green and a steep fall-off at 700 nm. Absorption drops to virtually zero in the near infrared, with subsequent absorptions, corresponding to the water absorption bands. In more detailed spectra, taken at 5 nm intervals with a 5 nm bandwidth, differences in chlorophyll content show in the different depths of the dip around 550 nm and in a small shift of the absorption edge at 700 nm. Spectra for Geranium (Pelargonium zonale) and Hibiscus (with a higher chlorophyll content) show that the upper limit for photosynthesis can not be much above 700 nm. No evidence, however, is to be seen of a lower limit for photosynthesis and, in fact, some experiments down to 300 nm still did not show a decrease of the absorption although it is well recognized that no photosynthesis results with 300 nm wavelengths.

Angular distribution of diffuse reflectance from incoherent multiple scattering in turbid media.

PubMed

Gao, M; Huang, X; Yang, P; Kattawar, G W

2013-08-20

The angular distribution of diffuse reflection is elucidated with greater understanding by studying a homogeneous turbid medium. We modeled the medium as an infinite slab and studied the reflection dependence on the following three parameters: the incident direction, optical depth, and asymmetry factor. The diffuse reflection is produced by incoherent multiple scattering and is solved through radiative transfer theory. At large optical depths, the angular distribution of the diffuse reflection with small incident angles is similar to that of a Lambertian surface, but, with incident angles larger than 60°, the angular distributions have a prominent reflection peak around the specular reflection angle. These reflection peaks are found originating from the scattering within one transport mean free path in the top layer of the medium. The maximum reflection angles for different incident angles are analyzed and can characterize the structure of angular distributions for different asymmetry factors and optical depths. The properties of the angular distribution can be applied to more complex systems for a better understanding of diffuse reflection.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aparnadevi, N.; Department of Nuclear Physics, University of Madras, Guindy Campus, Chennai 600 025; Saravana Kumar, K.

Phase pure NdFeO{sub 3} has been achieved using high energy ball milling of oxide precursors with subsequent sintering. It is established that structural arrangement of NdFeO{sub 3} regulates the multifunctional feature of the material. Rietveld refinement of the room temperature X-ray diffraction pattern shows that the Fe-O-Fe bond angle significantly favors the super exchange interaction, which is predominantly antiferromagnetic in nature. Magnetization measurement illustrates antiferromagnetic behaviour with a weak ferromagnetic component caused by the canted nature of the Fe{sup 3+} spins at room temperature. Absorption bands in the visible ambit, apparent from the UV-Vis diffuse reflectance studies, is found duemore » to the crystal ligand field of octahedral oxygen environment of Fe{sup 3+} ions. The direct band gap is estimated to be 2.39 eV from the diffuse reflectance spectrum. The lossy natured ferroelectric loop having a maximum polarization of 0.23 μC/cm{sup 2} at room temperature is found to be driven by the non-collinear magnetic structure with reverse Dzyaloshinskii–Moriya effect. Magnetic field has influence on the dielectric constant as evident from the impedance spectroscopy, indicating the strong coupling between ferroelectric and the magnetic structure of NdFeO{sub 3}.« less

Defect-detection algorithm for noncontact acoustic inspection using spectrum entropy

NASA Astrophysics Data System (ADS)

Sugimoto, Kazuko; Akamatsu, Ryo; Sugimoto, Tsuneyoshi; Utagawa, Noriyuki; Kuroda, Chitose; Katakura, Kageyoshi

2015-07-01

In recent years, the detachment of concrete from bridges or tunnels and the degradation of concrete structures have become serious social problems. The importance of inspection, repair, and updating is recognized in measures against degradation. We have so far studied the noncontact acoustic inspection method using airborne sound and the laser Doppler vibrometer. In this method, depending on the surface state (reflectance, dirt, etc.), the quantity of the light of the returning laser decreases and optical noise resulting from the leakage of light reception arises. Some influencing factors are the stability of the output of the laser Doppler vibrometer, the low reflective characteristic of the measurement surface, the diffused reflection characteristic, measurement distance, and laser irradiation angle. If defect detection depends only on the vibration energy ratio since the frequency characteristic of the optical noise resembles white noise, the detection of optical noise resulting from the leakage of light reception may indicate a defective part. Therefore, in this work, the combination of the vibrational energy ratio and spectrum entropy is used to judge whether a measured point is healthy or defective or an abnormal measurement point. An algorithm that enables more vivid detection of a defective part is proposed. When our technique was applied in an experiment with real concrete structures, the defective part could be extracted more vividly and the validity of our proposed algorithm was confirmed.

SAS-2 observations of celestial diffuse gamma radiation above 30 MeV

NASA Technical Reports Server (NTRS)

Thompson, D. J.; Fichtel, C. E.; Kniffen, D. A.; Hartman, R. C.

1974-01-01

The small astronomy satellite, SAS-2, used a 32-deck magnetic core digitized spark chamber to study gamma rays with energies above 30 MeV. Data for four regions of the sky away from the galactic plane were analyzed. These regions show a finite, diffuse flux of gamma rays with a steep energy spectrum, and the flux is uniform over all the regions. Represented by a power law, the differential energy spectrum shows an index of 2.5 + or - 0.4. The steep SAS-2 spectrum and the lower energy data are reasonably consistent with a neutral pion gamma-ray spectrum which was red-shifted (such as that proposed by some cosmological theories). It is concluded that the diffuse celestial gamma ray spectrum observed presents the possibility of cosmological studies and possible evidence for a residual cosmic ray density, and supports the galactic superclusters of matter and antimatter remaining from baryon-symmetric big bang.

Measurement of fluorophore concentrations and fluorescence quantum yield in tissue-simulating phantoms using three diffusion models of steady-state spatially resolved fluorescence.

PubMed

Diamond, Kevin R; Farrell, Thomas J; Patterson, Michael S

2003-12-21

Steady-state diffusion theory models of fluorescence in tissue have been investigated for recovering fluorophore concentrations and fluorescence quantum yield. Spatially resolved fluorescence, excitation and emission reflectance Carlo simulations, and measured using a multi-fibre probe on tissue-simulating phantoms containing either aluminium phthalocyanine tetrasulfonate (AlPcS4), Photofrin meso-tetra-(4-sulfonatophenyl)-porphine dihydrochloride The accuracy of the fluorophore concentration and fluorescence quantum yield recovered by three different models of spatially resolved fluorescence were compared. The models were based on: (a) weighted difference of the excitation and emission reflectance, (b) fluorescence due to a point excitation source or (c) fluorescence due to a pencil beam excitation source. When literature values for the fluorescence quantum yield were used for each of the fluorophores, the fluorophore absorption coefficient (and hence concentration) at the excitation wavelength (mu(a,x,f)) was recovered with a root-mean-square accuracy of 11.4% using the point source model of fluorescence and 8.0% using the more complicated pencil beam excitation model. The accuracy was calculated over a broad range of optical properties and fluorophore concentrations. The weighted difference of reflectance model performed poorly, with a root-mean-square error in concentration of about 50%. Monte Carlo simulations suggest that there are some situations where the weighted difference of reflectance is as accurate as the other two models, although this was not confirmed experimentally. Estimates of the fluorescence quantum yield in multiple scattering media were also made by determining mu(a,x,f) independently from the fitted absorption spectrum and applying the various diffusion theory models. The fluorescence quantum yields for AlPcS4 and TPPS4 were calculated to be 0.59 +/- 0.03 and 0.121 +/- 0.001 respectively using the point source model, and 0.63 +/- 0.03 and 0.129 +/- 0.002 using the pencil beam excitation model. These results are consistent with published values.

Restriction spectrum imaging reveals decreased neurite density in patients with temporal lobe epilepsy

PubMed Central

Loi, Richard Q.; Leyden, Kelly M.; Balachandra, Akshara; Uttarwar, Vedang; Hagler, Donald J.; Paul, Brianna M.; Dale, Anders M.; White, Nathan S.; McDonald, Carrie R.

2016-01-01

Objective Diffusion tensor imaging (DTI) has become a popular tool for delineating the location and extent of white matter injury in temporal lobe epilepsy (TLE). However, DTI yields nonspecific measures that are confounded by changes occurring within both the intracellular and extracellular environments. This study investigated whether an advanced diffusion method, restriction spectrum imaging (RSI) could provide a more robust measure of white matter injury in TLE relative to DTI due to RSI’s ability to separate intra-axonal diffusion (i.e., neurite density; ND) from diffusion associated with extra-axonal factors (e.g., inflammation; crossing fibers). Methods RSI and DTI scans were obtained on 21 patients with TLE and 11 age-matched controls. RSI-derived maps of ND, isotropic hindered (IH) and free (IF) water, and crossing fibers (CF) were compared to DTI-derived fractional anisotropy (FA) maps. Voxelwise and tract-based analyses were performed comparing patients with TLE to controls on each diffusion metric. Results Reductions in FA were seen primarily in frontotemporal white matter in TLE and were most pronounced proximal to the seizure focus. Reductions in ND corresponded to those seen in the FA maps; however, ND reductions were greater in magnitude, more lateralized to the epileptogenic hemisphere, and showed a broader pattern. Increases in IF/IH and effects from CFs also contributed to reduced FA in the ipsilateral parahippocampal cingulum and fornix, with decreases in IH extending into extratemporal regions. Reduced ND of the uncinate fasciculus was associated with longer disease duration, whereas FA was not associated with any clinical variables. Significance RSI may provide a more specific measure of white matter pathology in TLE, distinguishing regions primarily affected by axonal/myelin loss from those where CFs and increases in extracellular water also play a role. By providing a more specific measure of axonal/myelin loss, RSI-derived ND may better reflect overall white matter burden in epilepsy. PMID:27735051

Restriction spectrum imaging reveals decreased neurite density in patients with temporal lobe epilepsy.

PubMed

Loi, Richard Q; Leyden, Kelly M; Balachandra, Akshara; Uttarwar, Vedang; Hagler, Donald J; Paul, Brianna M; Dale, Anders M; White, Nathan S; McDonald, Carrie R

2016-11-01

Diffusion tensor imaging (DTI) has become a popular tool for delineating the location and extent of white matter injury in temporal lobe epilepsy (TLE). However, DTI yields nonspecific measures that are confounded by changes occurring within both the intracellular and extracellular environments. This study investigated whether an advanced diffusion method, restriction spectrum imaging (RSI) could provide a more robust measure of white matter injury in TLE relative to DTI due to RSI's ability to separate intraaxonal diffusion (i.e., neurite density; ND) from diffusion associated with extraaxonal factors (e.g., inflammation; crossing fibers). RSI and DTI scans were obtained on 21 patients with TLE and 11 age-matched controls. RSI-derived maps of ND, isotropic-hindered (IH) and isotropic-free (IF) water, and crossing fibers (CFs) were compared to DTI-derived fractional anisotropy (FA) maps. Voxelwise and tract-based analyses were performed comparing patients with TLE to controls on each diffusion metric. Reductions in FA were seen primarily in frontotemporal white matter in TLE, and they were most pronounced proximal to the seizure focus. Reductions in ND corresponded to those seen in the FA maps; however, ND reductions were greater in magnitude, more lateralized to the epileptogenic hemisphere, and showed a broader pattern. Increases in IF/IH and effects from CFs also contributed to reduced FA in the ipsilateral parahippocampal cingulum and fornix, with decreases in IH extending into extratemporal regions. Reduced ND of the uncinate fasciculus was associated with longer disease duration, whereas FA was not associated with any clinical variables. RSI may provide a more specific measure of white matter pathology in TLE, distinguishing regions primarily affected by axonal/myelin loss from those where CFs and increases in extracellular water also play a role. By providing a more specific measure of axonal/myelin loss, RSI-derived ND may better reflect overall white matter burden in epilepsy. Wiley Periodicals, Inc. © 2016 International League Against Epilepsy.

Fermi-Compton scattering due to magnetopause surface fluctuations in Jupiter's magnetospheric cavity

NASA Technical Reports Server (NTRS)

Barbosa, D. D.

1981-01-01

The effects of boundary surface fluctuations on a spectrum of electromagnetic radiation trapped in a high Q (quality) cavity are considered. Undulating walls introduce small frequency shifts at reflection to the radiation, and it is argued that the process is entirely analogous to both Fermi (particle) acceleration and inverse Compton scattering. A Fokker-Planck formalism is pursued; it yields a diffusion equation in frequency for which the Green's function and steady-state solutions are found. Applying this analysis to the Jovian continuum radiation discovered by Voyager spacecraft, it is suggested that characteristic diffusion times are greater than 1 year, and that in order to account for the steep frequency spectra observed, an unidentified loss mechanism must operate in the cavity with a decay time constant approximately equal to the characteristic diffusion time divided by 28. A radiator-reactor model of the cavity is investigated to provide an estimate for the intrinsic luminosity of the low frequency (approximately 100 Hz) continuum source whose power is approximately 7 x 10 to the 6th W.

Application of a two-stream radiative transfer model for leaf lignin and cellulose concentrations from spectral reflectance measurements, part 2

NASA Technical Reports Server (NTRS)

Conel, James E.; Vandenbosch, Jeannette; Grove, Cindy I.

1993-01-01

We used the Kubelka-Munk theory of diffuse spectral reflectance in layers to analyze influences of multiple chemical components in leaves. As opposed to empirical approaches to estimation of plant chemistry, the full spectral resolution of laboratory reflectance data was retained in an attempt to estimate lignin or other constituent concentrations from spectral band positions. A leaf water reflectance spectrum was derived from theoretical mixing rules, reflectance observations, and calculations from theory of intrinsic k- and s-functions. Residual reflectance bands were then isolated from spectra of fresh green leaves. These proved hard to interpret for composition in terms of simple two component mixtures such as lignin and cellulose. We next investigated spectral and dilution influences of other possible components (starch, protein). These components, among others, added to cellulose in hypothetical mixtures, produce band displacements similar to lignin, but will disguise by dilution the actual abundance of lignin present in a multicomponent system. This renders interpretation of band positions problematical. Knowledge of end-members and their spectra, and a more elaborate mixture analysis procedure may be called for. Good observational atmospheric and instrumental conditions and knowledge thereof are required for retrieval of expected subtle reflectance variations present in spectra of green vegetation.

Quantification of changes in language-related brain areas in autism spectrum disorders using large-scale network analysis.

PubMed

Goch, Caspar J; Stieltjes, Bram; Henze, Romy; Hering, Jan; Poustka, Luise; Meinzer, Hans-Peter; Maier-Hein, Klaus H

2014-05-01

Diagnosis of autism spectrum disorders (ASD) is difficult, as symptoms vary greatly and are difficult to quantify objectively. Recent work has focused on the assessment of non-invasive diffusion tensor imaging-based biomarkers that reflect the microstructural characteristics of neuronal pathways in the brain. While tractography-based approaches typically analyze specific structures of interest, a graph-based large-scale network analysis of the connectome can yield comprehensive measures of larger-scale architectural patterns in the brain. Commonly applied global network indices, however, do not provide any specificity with respect to functional areas or anatomical structures. Aim of this work was to assess the concept of network centrality as a tool to perform locally specific analysis without disregarding the global network architecture and compare it to other popular network indices. We create connectome networks from fiber tractographies and parcellations of the human brain and compute global network indices as well as local indices for Wernicke's Area, Broca's Area and the Motor Cortex. Our approach was evaluated on 18 children suffering from ASD and 18 typically developed controls using magnetic resonance imaging-based cortical parcellations in combination with diffusion tensor imaging tractography. We show that the network centrality of Wernicke's area is significantly (p<0.001) reduced in ASD, while the motor cortex, which was used as a control region, did not show significant alterations. This could reflect the reduced capacity for comprehension of language in ASD. The betweenness centrality could potentially be an important metric in the development of future diagnostic tools in the clinical context of ASD diagnosis. Our results further demonstrate the applicability of large-scale network analysis tools in the domain of region-specific analysis with a potential application in many different psychological disorders.

Refractive index dependence of Papilio Ulysses butterfly wings reflectance spectra

NASA Astrophysics Data System (ADS)

Isnaeni, Muslimin, Ahmad Novi; Birowosuto, Muhammad Danang

2016-02-01

We have observed and utilized butterfly wings of Papilio Ulysses for refractive index sensor. We noticed this butterfly wings have photonic crystal structure, which causes blue color appearance on the wings. The photonic crystal structure, which consists of cuticle and air void, is approximated as one dimensional photonic crystal structure. This photonic crystal structure opens potential to several optical devices application, such as refractive index sensor. We have utilized small piece of Papilio Ulysses butterfly wings to characterize refractive index of several liquid base on reflectance spectrum of butterfly wings in the presence of sample liquid. For comparison, we simulated reflectance spectrum of one dimensional photonic crystal structure having material parameter based on real structure of butterfly wings. We found that reflectance spectrum peaks shifted as refractive index of sample changes. Although there is a slight difference in reflectance spectrum peaks between measured spectrum and calculated spectrum, the trend of reflectance spectrum peaks as function of sample's refractive index is the similar. We assume that during the measurement, the air void that filled by sample liquid is expanded due to liquid pressure. This change of void shape causes non-similarity between measured spectrum and calculated spectrum.

Left-Hemispheric Microstructural Abnormalities in Children With High Functioning Autism Spectrum Disorder

PubMed Central

Peterson, Daniel; Mahajan, Rajneesh; Crocetti, Deana; Mejia, Amanda; Mostofsky, Stewart

2014-01-01

Current theories of the neurobiological basis of Autism Spectrum Disorder (ASD) posit an altered pattern of connectivity in large-scale brain networks. Here we used Diffusion Tensor Imaging to investigate the microstructural properties of the white matter that mediates inter-regional connectivity in 36 high-functioning children with ASD (HF-ASD), as compared to 37 controls. By employing an atlas-based analysis using LDDMM registration, a widespread, but left-lateralized pattern of abnormalities was revealed. The Mean Diffusivity (MD) of water in the white matter of HF-ASD children was significantly elevated throughout the left hemisphere, particularly in the outer-zone cortical white matter. Across diagnostic groups there was a significant effect of age on left hemisphere MD, with a similar reduction in MD during childhood in both TD and HF-ASD children. The increased MD in children with HF-ASD suggests hypomyelination, and may reflect increased short-range cortico-cortical connections subsequent to early white matter overgrowth. These findings also highlight left hemispheric connectivity as relevant to the pathophysiology of ASD, and indicate that the spatial distribution of microstructural abnormalities in HF-ASD is widespread, and left-lateralized. This altered left-hemispheric connectivity may contribute to deficits in communication and praxis observed in ASD. PMID:25256103

Applicability of a Diffuse Reflectance Infrared Fourier Transform handheld spectrometer to perform in situ analyses on Cultural Heritage materials

NASA Astrophysics Data System (ADS)

Arrizabalaga, Iker; Gómez-Laserna, Olivia; Aramendia, Julene; Arana, Gorka; Madariaga, Juan Manuel

2014-08-01

This work studies the applicability of a Diffuse Reflectance Infrared Fourier Transform handheld device to perform in situ analyses on Cultural Heritage assets. This portable diffuse reflectance spectrometer has been used to characterise and diagnose the conservation state of (a) building materials of the Guevara Palace (15th century, Segura, Basque Country, Spain) and (b) different 19th century wallpapers manufactured by the Santa Isabel factory (Vitoria-Gasteiz, Basque Country, Spain) and by the well known Dufour and Leroy manufacturers (Paris, France), all of them belonging to the Torre de los Varona Castle (Villanañe, Basque Country, Spain). In all cases, in situ measurements were carried out and also a few samples were collected and measured in the laboratory by diffuse reflectance spectroscopy (DRIFT) in order to validate the information obtained by the handheld instrument. In the analyses performed in situ, distortions in the diffuse reflectance spectra can be observed due to the presence of specular reflection, showing the inverted bands caused by the Reststrahlen effect, in particular on those IR bands with the highest absorption coefficients. This paper concludes that the results obtained in situ by a diffuse reflectance handheld device are comparable to those obtained with laboratory diffuse reflectance spectroscopy equipment and proposes a few guidelines to acquire good spectra in the field, minimising the influence caused by the specular reflection.

Monitoring bruise age using visible diffuse reflectance spectroscopy

NASA Astrophysics Data System (ADS)

McMurdy, John W.; Duffy, Susan; Crawford, Gregory P.

2007-02-01

The ability to determine the age of a bruise of unknown age mechanism is important in matters of domestic and child abuse and forensics. While physicians are asked to make clinical judgment on the age of a bruise using color and tenderness, studies have shown that a physicians estimate is highly inaccurate and in cases no better than chance alone. We present here the temporal progression of reflection spectrum collected from accidentally inflicted contusions in adult and child study participants with a synopsis of the observed phenomena. Reflection spectra collected using a portable fiber optic reflection spectrometer can track the increase in extravasated hemoglobin from trauma caused blood vessel rupture and subsequent removal of this hemoglobin occurring concurrent with an increase in the absorption attributed to the breakdown product bilirubin. We hypothesize that this time dependent pattern can be used to determine the age of an unknown bruise in an individual provided rate constant information for the patient can be determined in a controlled calibration bruise. Using reflection spectra to estimate bruise age can provide a rapid and noninvasive method to improve the ability of physicians in dating the age of a contusion.

Automated test-site radiometer for vicarious calibration

NASA Astrophysics Data System (ADS)

Li, Xin; Yin, Ya-peng; Liu, En-chao; Zhang, Yan-na; Xun, Li-na; Wei, Wei; Zhang, Zhi-peng; Qiu, Gang-gang; Zhang, Quan; Zheng, Xiao-bing

2014-11-01

In order to realize unmanned vicarious calibration, Automated Test-site Radiometer (ATR) was developed for surface reflectance measurements. ATR samples the spectrum from 400nm-1600 nm with 8 interference filters coupled with silicon and InGaAs detectors. The field of view each channel is 10 ° with parallel optical axis. One SWIR channel lies in the center and the other seven VNIR channels are on the circle of 4.8cm diameters which guarantee each channel to view nearly the same section of ground. The optical head as a whole is temperature controlled utilizing a TE cooler for greater stability and lower noise. ATR is powered by a solar panel and transmit its data through a BDS (China's BeiDou Navigation Satellite System) terminator for long-term measurements without personnel in site. ATR deployed in Dunhuang test site with ground field about 30-cm-diameter area for multi-spectral reflectance measurements. Other instruments at the site include a Cimel sunphotometer and a diffuser-to-globe irradiance meter for atmosphere observations. The methodology for band-averaged reflectance retrieval and hyperspectral reflectance fitting process are described. Then the hyperspectral reflectance and atmospheric parameters are put into 6s code to predict TOA radiance which compare with MODIS radiance.

Polarization impacts on the water-leaving radiance retrieval from above-water radiometric measurements.

PubMed

Harmel, Tristan; Gilerson, Alexander; Tonizzo, Alberto; Chowdhary, Jacek; Weidemann, Alan; Arnone, Robert; Ahmed, Sam

2012-12-10

Above-water measurements of water-leaving radiance are widely used for water-quality monitoring and ocean-color satellite data validation. Reflected skylight in above-water radiometry needs to be accurately estimated prior to derivation of water-leaving radiance. Up-to-date methods to estimate reflection of diffuse skylight on rough sea surfaces are based on radiative transfer simulations and sky radiance measurements. But these methods neglect the polarization state of the incident skylight, which is generally highly polarized. In this paper, the effects of polarization on the sea surface reflectance and the subsequent water-leaving radiance estimation are investigated. We show that knowledge of the polarization field of the diffuse skylight significantly improves above-water radiometry estimates, in particular in the blue part of the spectrum where the reflected skylight is dominant. A newly developed algorithm based on radiative transfer simulations including polarization is described. Its application to the standard Aerosol Robotic Network-Ocean Color and hyperspectral radiometric measurements of the 1.5-year dataset acquired at the Long Island Sound site demonstrates the noticeable importance of considering polarization for water-leaving radiance estimation. In particular it is shown, based on time series of collocated data acquired in coastal waters, that the azimuth range of measurements leading to good-quality data is significantly increased, and that these estimates are improved by more than 12% at 413 nm. Full consideration of polarization effects is expected to significantly improve the quality of the field data utilized for satellite data validation or potential vicarious calibration purposes.

Cutaneous tumors in vivo investigations using fluorescence and diffuse reflectance techniques

NASA Astrophysics Data System (ADS)

Borisova, E.; Troyanova, P.; Nikolova, E.; Avramov, L.

2008-06-01

In the recent years, there has been growing interest in the common use of laser-induced autofluorescence (LIAF) and reflectance spectroscopy (RS) to differentiate disease from normal surrounding tissue - so called optical biopsy method. Painless, instant diagnoses from optical biopsies will soon be a reality. These forms of optical diagnoses are preferable to the removal of several square millimeters of tissue surface - common in traditional biopsies - followed by delays while samples are sent for clinical analysis. The goal of this work was investigation of cutaneous benign and malignant lesions by the methods of LIAFS and RS. A nitrogen laser at 337 nm was applied for the needs of autofluorescence excitation. Broad-spectrum halogen lamp (from 400 to 900 nm) was applied for diffuse reflectance measurements. An associated microspectrometer detected in vivo the fluorescence and reflectance signals from human skin. The main spectral features of benign lesions - compound nevus, dysplastic nevi, heamangioma and basal cell papilloma and malignant lesions - pigmented, amelanotic and secondary malignant melanoma, as well as basal cell carcinoma are discussed and their possible origins are indicated. Spectra from healthy skin areas near to the lesion were detected to be used posteriori to reveal changes between healthy and lesion skin spectra. Influence of the main skin pigments on the spectra detected is discussed and evaluation of possibilities for differentiation between malignant and benign lesions is made based on their spectral properties. This research shows that non-invasive and high-sensitive in vivo detection by means of appropriate light sources and detectors should be possible, related to real-time determination of existing pathological conditions.

Quantifying white matter tract diffusion parameters in the presence of increased extra-fiber cellularity and vasogenic edema

PubMed Central

Chiang, Chia-Wen; Wang, Yong; Sun, Peng; Lin, Tsen-Hsuan; Trinkaus, Kathryn; Cross, Anne H.; Song, Sheng-Kwei

2014-01-01

The effect of extra-fiber structural and pathological components confounding diffusion tensor imaging (DTI) computation was quantitatively investigated using data generated by both Monte-Carlo simulations and tissue phantoms. Increased extent of vasogenic edema, by addition of various amount of gel to fixed normal mouse trigeminal nerves or by increasing non-restricted isotropic diffusion tensor components in Monte-Carlo simulations, significantly decreased fractional anisotropy (FA), increased radial diffusivity, while less significantly increased axial diffusivity derived by DTI. Increased cellularity, mimicked by graded increase of the restricted isotropic diffusion tensor component in Monte-Carlo simulations, significantly decreased FA and axial diffusivity with limited impact on radial diffusivity derived by DTI. The MC simulation and tissue phantom data were also analyzed by the recently developed diffusion basis spectrum imaging (DBSI) to simultaneously distinguish and quantify the axon/myelin integrity and extra-fiber diffusion components. Results showed that increased cellularity or vasogenic edema did not affect the DBSI-derived fiber FA, axial or radial diffusivity. Importantly, the extent of extra-fiber cellularity and edema estimated by DBSI correlated with experimentally added gel and Monte-Carlo simulations. We also examined the feasibility of applying 25-direction diffusion encoding scheme for DBSI analysis on coherent white matter tracts. Results from both phantom experiments and simulations suggested that the 25-direction diffusion scheme provided comparable DBSI estimation of both fiber diffusion parameters and extra-fiber cellularity/edema extent as those by 99-direction scheme. An in vivo 25-direction DBSI analysis was performed on experimental autoimmune encephalomyelitis (EAE, an animal model of human multiple sclerosis) optic nerve as an example to examine the validity of derived DBSI parameters with post-imaging immunohistochemistry verification. Results support that in vivo DBSI using 25-direction diffusion scheme correctly reflect the underlying axonal injury, demyelination, and inflammation of optic nerves in EAE mice. PMID:25017446

Mildly obscured active galaxies and the cosmic X-ray background

NASA Astrophysics Data System (ADS)

Esposito, V.; Walter, R.

2016-05-01

Context. The diffuse cosmic X-ray background (CXB) is the sum of the emission of discrete sources, mostly massive black-holes accreting matter in active galactic nuclei (AGN). The CXB spectrum differs from the integration of the spectra of individual sources, calling for a large population, undetected so far, of strongly obscured Compton-thick AGN. Such objects are predicted by unified models, which attribute most of the AGN diversity to their inclination on the line of sight, and play an important role for the understanding of the growth of black holes in the early Universe. Aims: The percentage of strongly obscured Compton-thick AGN at low redshift can be derived from the observed CXB spectrum, if we assume AGN spectral templates and luminosity functions. Methods: We show that high signal-to-noise stacked hard X-ray spectra, derived from more than a billion seconds of effective exposure time with the Swift/BAT instrument, imply that mildly obscured Compton-thin AGN feature a strong reflection and contribute massively to the CXB. Results: A population of Compton-thick AGN larger than that which is effectively detected is not required to reproduce the CXB spectrum, since no more than 6% of the CXB flux can be attributed to them. The stronger reflection observed in mildly obscured AGN suggests that the covering factor of the gas and dust surrounding their central engines is a key factor in shaping their appearance. These mildly obscured AGN are easier to study at high redshift than Compton-thick sources are.

Improved backward ray tracing with stochastic sampling

NASA Astrophysics Data System (ADS)

Ryu, Seung Taek; Yoon, Kyung-Hyun

1999-03-01

This paper presents a new technique that enhances the diffuse interreflection with the concepts of backward ray tracing. In this research, we have modeled the diffuse rays with the following conditions. First, as the reflection from the diffuse surfaces occurs in all directions, it is impossible to trace all of the reflected rays. We confined the diffuse rays by sampling the spherical angle out of the reflected rays around the normal vector. Second, the traveled distance of reflected energy from the diffuse surface differs according to the object's property, and has a comparatively short reflection distance. Considering the fact that the rays created on the diffuse surfaces affect relatively small area, it is very inefficient to trace all of the sampled diffused rays. Therefore, we set a fixed distance as the critical distance and all the rays beyond this distance are ignored. The result of this research is that as the improved backward ray tracing can model the illumination effects such as the color bleeding effects, we can replace the radiosity algorithm under the limited environment.

Diffuse Galactic Continuum Gamma Rays. A Model Compatible with EGRET Data and Cosmic-ray Measurements

NASA Technical Reports Server (NTRS)

Strong, Andrew W.; Moskalenko, Igor V.; Reimer, Olaf

2004-01-01

We present a study of the compatibility of some current models of the diffuse Galactic continuum gamma-rays with EGRET data. A set of regions sampling the whole sky is chosen to provide a comprehensive range of tests. The range of EGRET data used is extended to 100 GeV. The models are computed with our GALPROP cosmic-ray propagation and gamma-ray production code. We confirm that the "conventional model" based on the locally observed electron and nucleon spectra is inadequate, for all sky regions. A conventional model plus hard sources in the inner Galaxy is also inadequate, since this cannot explain the GeV excess away from the Galactic plane. Models with a hard electron injection spectrum are inconsistent with the local spectrum even considering the expected fluctuations; they are also inconsistent with the EGRET data above 10 GeV. We present a new model which fits the spectrum in all sky regions adequately. Secondary antiproton data were used to fix the Galactic average proton spectrum, while the electron spectrum is adjusted using the spectrum of diffuse emission it- self. The derived electron and proton spectra are compatible with those measured locally considering fluctuations due to energy losses, propagation, or possibly de- tails of Galactic structure. This model requires a much less dramatic variation in the electron spectrum than models with a hard electron injection spectrum, and moreover it fits the y-ray spectrum better and to the highest EGRET energies. It gives a good representation of the latitude distribution of the y-ray emission from the plane to the poles, and of the longitude distribution. We show that secondary positrons and electrons make an essential contribution to Galactic diffuse y-ray emission.

Transmitting and reflecting diffuser. [for ultraviolet light

NASA Technical Reports Server (NTRS)

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

1973-01-01

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

Tailoring growth conditions for efficient tuning of band edge of CdS nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Susha, N.; Nair, Swapna S., E-mail: swapna.s.nair@gmail.com; Aravind, P. B.

2015-06-24

CdS nanoparticles are successively synthesized by chemical precipitation method. The samples prepared at different reaction time and temperature are characterized by X-ray diffraction, Diffuse reflectance spectroscopy, Photoluminescence spectroscopy ans Energy dispersive x-ray analysis. Visible color variation is noted from light yellow to orange, indicates the quantum confinement effect and the results are again got confirmed from the optical studies. A shift in absorption peak is observed towards the lower region of the visible spectra - the “blue shift”- upon decrease in reaction time and temperature. Blue emission observed in the photoluminescence spectrum confirms the grain size induced confinement.

Simultaneous Multi-Scale Diffusion Estimation and Tractography Guided by Entropy Spectrum Pathways

PubMed Central

Galinsky, Vitaly L.; Frank, Lawrence R.

2015-01-01

We have developed a method for the simultaneous estimation of local diffusion and the global fiber tracts based upon the information entropy flow that computes the maximum entropy trajectories between locations and depends upon the global structure of the multi-dimensional and multi-modal diffusion field. Computation of the entropy spectrum pathways requires only solving a simple eigenvector problem for the probability distribution for which efficient numerical routines exist, and a straight forward integration of the probability conservation through ray tracing of the convective modes guided by a global structure of the entropy spectrum coupled with a small scale local diffusion. The intervoxel diffusion is sampled by multi b-shell multi q-angle DWI data expanded in spherical waves. This novel approach to fiber tracking incorporates global information about multiple fiber crossings in every individual voxel and ranks it in the most scientifically rigorous way. This method has potential significance for a wide range of applications, including studies of brain connectivity. PMID:25532167

Applicability of a Diffuse Reflectance Infrared Fourier Transform handheld spectrometer to perform in situ analyses on Cultural Heritage materials.

PubMed

Arrizabalaga, Iker; Gómez-Laserna, Olivia; Aramendia, Julene; Arana, Gorka; Madariaga, Juan Manuel

2014-08-14

This work studies the applicability of a Diffuse Reflectance Infrared Fourier Transform handheld device to perform in situ analyses on Cultural Heritage assets. This portable diffuse reflectance spectrometer has been used to characterise and diagnose the conservation state of (a) building materials of the Guevara Palace (15th century, Segura, Basque Country, Spain) and (b) different 19th century wallpapers manufactured by the Santa Isabel factory (Vitoria-Gasteiz, Basque Country, Spain) and by the well known Dufour and Leroy manufacturers (Paris, France), all of them belonging to the Torre de los Varona Castle (Villanañe, Basque Country, Spain). In all cases, in situ measurements were carried out and also a few samples were collected and measured in the laboratory by diffuse reflectance spectroscopy (DRIFT) in order to validate the information obtained by the handheld instrument. In the analyses performed in situ, distortions in the diffuse reflectance spectra can be observed due to the presence of specular reflection, showing the inverted bands caused by the Reststrahlen effect, in particular on those IR bands with the highest absorption coefficients. This paper concludes that the results obtained in situ by a diffuse reflectance handheld device are comparable to those obtained with laboratory diffuse reflectance spectroscopy equipment and proposes a few guidelines to acquire good spectra in the field, minimising the influence caused by the specular reflection. Copyright © 2014 Elsevier B.V. All rights reserved.

Effects of hydrogen peroxide on the light reflectance and morphology of bovine enamel.

PubMed

Kwon, Y H; Huo, M S; Kim, K H; Kim, S K; Kim, Y J

2002-05-01

The purpose of this study was to examine the effects of a bleaching agent (30% hydrogen peroxide) on the surface of bovine enamel using a scanning electron microscope and a UV-VIS-NIR spectrophotometer. Five non-carious bovine incisors were bleached for 0, 1, 2 and 3 days using 30% hydrogen peroxide. The light reflectance spectrum was measured using a spectrophotometer with diffuse reflectance mode. Colour values and colour differences in the teeth were evaluated from the reflectance measurements with the CIE L*a*b* colour coordinate system. Surface alterations in the bleached and unbleached teeth were studied using a scanning electron microscope. The change of reflectance in the teeth was related to the change of colour. Most reflectance change occurred within a 1-day bleaching, and this result was confirmed by a CIE L*a*b* colour coordinate system. The colour differences in the bleached teeth were significant enough to be perceived by the observer's eye. The comparison of bleached to unbleached bovine enamel revealed that the bleached surface showed non-uniform slight morphological alterations, and it developed varying degrees of surface porosity. This study indicates that the bleached bovine teeth showed apparent colour differences as well as slight morphological alterations after bleaching.

Non-Lambertian effects on remote sensing of surface reflectance and vegetation index

NASA Technical Reports Server (NTRS)

Lee, T. Y.; Kaufman, Y. J.

1986-01-01

This paper discusses the effects of non-Lambertian reflection from a homogeneous surface on remote sensing of the surface reflectance and vegetation index from a satellite. Remote measurement of the surface characteristics is perturbed by atmospheric scattering of sun light. This scattering tends to smooth the angular dependence of non-Lambertian surface reflectances, an effect that is not present in the case of Lambertian surfaces. This effect is calculated to test the validity of a Lambertian assumption used in remote sensing. For the three types of vegetations considered in this study, the assumption of Lambertian surface can be used satisfactorily in the derivation of surface reflectance from remotely measured radiance for a view angle outside the backscattering region. Within the backscattering region, however, the use of the assumption can result in a considerable error in the derived surface reflectance. Accuracy also deteriorates with increasing solar zenith angle. The angular distribution of the surface reflectance derived from remote measurements is smoother than that at the surface. The effect of surface non-Lambertianity on remote sensing of vegetation index is very weak. Since the effect is similiar in the visible and near infrared part of the solar spectrum for the vegetations treated in this study, it is canceled in deriving the vegetation index. The effect of the diffuse skylight on surface reflectance measurements at ground level is also discussed.

Quantitative broadband absorption and scattering spectroscopy in turbid media by combined frequency-domain and steady state methodologies

DOEpatents

Tromberg, Bruce J [Irvine, CA; Berger, Andrew J [Rochester, NY; Cerussi, Albert E [Lake Forest, CA; Bevilacqua, Frederic [Costa Mesa, CA; Jakubowski, Dorota [Irvine, CA

2008-09-23

A technique for measuring broadband near-infrared absorption spectra of turbid media that uses a combination of frequency-domain and steady-state reflectance methods. Most of the wavelength coverage is provided by a white-light steady-state measurement, whereas the frequency-domain data are acquired at a few selected wavelengths. Coefficients of absorption and reduced scattering derived from the frequency-domain data are used to calibrate the intensity of the steady-state measurements and to determine the reduced scattering coefficient at all wavelengths in the spectral window of interest. The absorption coefficient spectrum is determined by comparing the steady-state reflectance values with the predictions of diffusion theory, wavelength by wavelength. Absorption spectra of a turbid phantom and of human breast tissue in vivo, derived with the combined frequency-domain and steady-state technique, agree well with expected reference values.

In-vivo Reflectance Measurements from Human Skin

NASA Astrophysics Data System (ADS)

Delgado, J. A.; Cornejo, A.; Cunill, M.; Báez, J. J.; Matos, R.; Anasagasti, L.; Santiago, C.

2006-09-01

We evaluate the potential of using a standard commercial spectrophotometer, specifically designed to meet the growing requirement for color control in the digital-imaging application field, to perform in-vivo diffuse reflectance measurements from adult human skin. We report and discuss diffuse reflectance spectra for three practical situations: a) reflectance versus skin type, b) reflectance from normal skin with different grade of solar exposition, c) reflectance from normal skin versus reflectance from seborrheic keratosis. Results show, that using the above spectrophotometer we can easily differentiate two sites of different solar exposition. Besides, significant differences are found in the normal skin diffuse reflectance for patients with different skin types.

Diffuse reflectance spectroscopy of pre- and post-treated oral submucous fibrosis: an in vivo study

NASA Astrophysics Data System (ADS)

Sivabalan, S.; Ponranjini Vedeswari, C.; Jayachandran, S.; Koteeswaran, D.; Pravda, C.; Aruna, P.; Ganesan, S.

2010-02-01

Oral submucous fibrosis (OSF) is a high risk precancerous condition characterized by changes in the connective tissue fibers of the lamina propria and deeper parts leading to stiffness of the mucosa and restricted mouth opening, fibrosis of the lining mucosa of the upper digestive tract involving the oral cavity, oro- and hypo-pharynx and the upper two-thirds of the oesophagus. Optical reflectance measurements have been used to extract diagnostic information from a variety of tissue types, in vivo. We apply diffuse reflectance spectroscopy to quantitatively monitor tumour response to chemotherapy. Twenty patients with submucous fibrosis were diagnosed with diffuse reflectance spectroscopy and treated with the chemotherapy drug, Dexamethasone sodium phosphate and Hyaluronidase injection for seven weeks and after the treatment they were again subjected to the diffuse reflectance spectroscopy. The major observed spectral alterations on pre and post treated submucous fibrosis is an increase in the diffuse reflectance from 450 to 600 nm. Normal mucosa has showed higher reflectance when compared to the pre and post-treated cases. The spectral changes were quantified and correlated to conventional diagnostic results viz., maximum mouth opening, tongue protrusion and burning sensation. The results of this study suggest that the diffuse reflectance spectroscopy may also be considered as complementary optical techniques to monitor oral tissue transformation.

Spectrum of the isotropic diffuse gamma-ray emission derived from first-year Fermi Large Area Telescope data.

PubMed

Abdo, A A; Ackermann, M; Ajello, M; Atwood, W B; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Baughman, B M; Bechtol, K; Bellazzini, R; Berenji, B; Blandford, R D; Bloom, E D; Bonamente, E; Borgland, A W; Bregeon, J; Brez, A; Brigida, M; Bruel, P; Burnett, T H; Buson, S; Caliandro, G A; Cameron, R A; Caraveo, P A; Casandjian, J M; Cavazzuti, E; Cecchi, C; Celik, O; Charles, E; Chekhtman, A; Cheung, C C; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Cominsky, L R; Conrad, J; Cutini, S; Dermer, C D; de Angelis, A; de Palma, F; Digel, S W; Di Bernardo, G; do Couto e Silva, E; Drell, P S; Drlica-Wagner, A; Dubois, R; Dumora, D; Farnier, C; Favuzzi, C; Fegan, S J; Focke, W B; Fortin, P; Frailis, M; Fukazawa, Y; Funk, S; Fusco, P; Gaggero, D; Gargano, F; Gasparrini, D; Gehrels, N; Germani, S; Giebels, B; Giglietto, N; Giommi, P; Giordano, F; Glanzman, T; Godfrey, G; Grenier, I A; Grondin, M-H; Grove, J E; Guillemot, L; Guiriec, S; Gustafsson, M; Hanabata, Y; Harding, A K; Hayashida, M; Hughes, R E; Itoh, R; Jackson, M S; Jóhannesson, G; Johnson, A S; Johnson, R P; Johnson, T J; Johnson, W N; Kamae, T; Katagiri, H; Kataoka, J; Kawai, N; Kerr, M; Knödlseder, J; Kocian, M L; Kuehn, F; Kuss, M; Lande, J; Latronico, L; Lemoine-Goumard, M; Longo, F; Loparco, F; Lott, B; Lovellette, M N; Lubrano, P; Madejski, G M; Makeev, A; Mazziotta, M N; McConville, W; McEnery, J E; Meurer, C; Michelson, P F; Mitthumsiri, W; Mizuno, T; Moiseev, A A; Monte, C; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Nolan, P L; Norris, J P; Nuss, E; Ohsugi, T; Omodei, N; Orlando, E; Ormes, J F; Paneque, D; Panetta, J H; Parent, D; Pelassa, V; Pepe, M; Pesce-Rollins, M; Piron, F; Porter, T A; Rainò, S; Rando, R; Razzano, M; Reimer, A; Reimer, O; Reposeur, T; Ritz, S; Rochester, L S; Rodriguez, A Y; Roth, M; Ryde, F; Sadrozinski, H F-W; Sanchez, D; Sander, A; Saz Parkinson, P M; Scargle, J D; Sellerholm, A; Sgrò, C; Shaw, M S; Siskind, E J; Smith, D A; Smith, P D; Spandre, G; Spinelli, P; Starck, J-L; Strickman, M S; Strong, A W; Suson, D J; Tajima, H; Takahashi, H; Takahashi, T; Tanaka, T; Thayer, J B; Thayer, J G; Thompson, D J; Tibaldo, L; Torres, D F; Tosti, G; Tramacere, A; Uchiyama, Y; Usher, T L; Vasileiou, V; Vilchez, N; Vitale, V; Waite, A P; Wang, P; Winer, B L; Wood, K S; Ylinen, T; Ziegler, M

2010-03-12

We report on the first Fermi Large Area Telescope (LAT) measurements of the so-called "extragalactic" diffuse gamma-ray emission (EGB). This component of the diffuse gamma-ray emission is generally considered to have an isotropic or nearly isotropic distribution on the sky with diverse contributions discussed in the literature. The derivation of the EGB is based on detailed modeling of the bright foreground diffuse Galactic gamma-ray emission, the detected LAT sources, and the solar gamma-ray emission. We find the spectrum of the EGB is consistent with a power law with a differential spectral index gamma = 2.41 +/- 0.05 and intensity I(>100 MeV) = (1.03 +/- 0.17) x 10(-5) cm(-2) s(-1) sr(-1), where the error is systematics dominated. Our EGB spectrum is featureless, less intense, and softer than that derived from EGRET data.

X-ray Reflection

NASA Astrophysics Data System (ADS)

Fabian, A. C.; Ross, R. R.

2010-12-01

Material irradiated by X-rays produces backscattered radiation which is commonly known as the Reflection Spectrum. It consists of a structured continuum, due at high energies to the competition between photoelectric absorption and electron scattering enhanced at low energies by emission from the material itself, together with a complex line spectrum. We briefly review the history of X-ray reflection in astronomy and discuss various methods for computing the reflection spectrum from cold and ionized gas, illustrated with results from our own work reflionx. We discuss how the reflection spectrum can be used to obtain the geometry of the accretion flow, particularly the inner regions around black holes and neutron stars.

Influence of diffuse reflectance measurement accuracy on the scattering coefficient in determination of optical properties with integrating sphere optics (a secondary publication).

PubMed

Horibe, Takuro; Ishii, Katsunori; Fukutomi, Daichi; Awazu, Kunio

2015-12-30

An estimation error of the scattering coefficient of hemoglobin in the high absorption wavelength range has been observed in optical property calculations of blood-rich tissues. In this study, the relationship between the accuracy of diffuse reflectance measurement in the integrating sphere and calculated scattering coefficient was evaluated with a system to calculate optical properties combined with an integrating sphere setup and the inverse Monte Carlo simulation. Diffuse reflectance was measured with the integrating sphere using a small incident port diameter and optical properties were calculated. As a result, the estimation error of the scattering coefficient was improved by accurate measurement of diffuse reflectance. In the high absorption wavelength range, the accuracy of diffuse reflectance measurement has an effect on the calculated scattering coefficient.

Discrimination of periodontal diseases using diffuse reflectance spectral intensity ratios

NASA Astrophysics Data System (ADS)

Chandra Sekhar, Prasanth; Betsy, Joseph; Presanthila, Janam; Subhash, Narayanan

2012-02-01

This clinical study was to demonstrate the applicability of diffuse reflectance (DR) intensity ratio R620/R575 in the quantification and discrimination of periodontitis and gingivitis from healthy gingiva. DR spectral measurements were carried out with white-light illumination from 70 healthy sites in 30 healthy volunteers, and 63 gingivitis- and 58 periodontitis-infected sites in 60 patients. Clinical parameters such as probing pocket depth, clinical attachment level, and gingival index were recorded in patient population. Diagnostic accuracies for discrimination of gingivitis and periodontitis from healthy gingiva were determined by comparison of spectral signatures with clinical parameters. Divergence of average DR spectral intensity ratio between control and test groups was studied using analysis of variance. The mean DR spectrum on normalization at 620 nm showed marked differences between healthy tissue, gingivitis, and periodontitis. Hemoglobin concentration and apparent SO2 (oxygen saturation) were also calculated for healthy, gingivitis, and periodontitis sites. DR spectral intensities at 545 and 575 nm showed a decreasing trend with progression of disease. Among the various DR intensity ratios studied, the R620/R575 ratio provided a sensitivity of 90% and specificity of 94% for discrimination of healthy tissues from gingivitis and a sensitivity of 91% and specificity of 100% for discrimination of gingivitis from periodontitis.

[Progressive damage monitoring of corrugated composite skins by the FBG spectral characteristics].

PubMed

Zhang, Yong; Wang, Bang-Feng; Lu, Ji-Yun; Gu, Li-Li; Su, Yong-Gang

2014-03-01

In the present paper, a method of monitoring progressive damage of composite structures by non-uniform fiber Bragg grating (FBG) reflection spectrum is proposed. Due to the finite element analysis of corrugated composite skins specimens, the failure process under tensile load and corresponding critical failure loads of corrugated composite skin was predicated. Then, the non-uniform reflection spectrum of FBG sensor could be reconstructed and the corresponding relationship between layer failure order sequence of corrugated composite skin and FBG sensor reflection spectrums was acquired. A monitoring system based on FBG non-uniform reflection spectrum, which can be used to monitor progressive damage of corrugated composite skins, was built. The corrugated composite skins were stretched under this FBG non-uniform reflection spectrum monitoring system. The results indicate that real-time spectrums acquired by FBG non-uniform reflection spectrum monitoring system show the same trend with the reconstruction reflection spectrums. The maximum error between the corresponding failure and the predictive value is 8.6%, which proves the feasibility of using FBG sensor to monitor progressive damage of corrugated composite skin. In this method, the real-time changes in the FBG non-uniform reflection spectrum within the scope of failure were acquired through the way of monitoring and predicating, and at the same time, the progressive damage extent and layer failure sequence of corru- gated composite skin was estimated, and without destroying the structure of the specimen, the method is easy and simple to operate. The measurement and transmission section of the system are completely composed of optical fiber, which provides new ideas and experimental reference for the field of dynamic monitoring of smart skin.

Applications of fourier transform infrared spectroscopy to surface analysis problems 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Powell, G.L.; Milosevic, M.

Applications of infrared spectroscopy to surface analysis are described in terms of the combined use of a number of techniques to solve specific surface analysis problems involving both qualitative and quantitative analysis of surface species. Emphasis is placed on the characterization of both the substrate and the surface species and the application of this to the monitoring of surface processes and the inspection of manufactured items. Lithium Hydride has been studied using remote analysis by diffuse reflectance in glove boxes containing very pure argon or controlled moisture levels with robot-operated gravimetric monitoring. These experiments are supported by internal reflectance andmore » diffuse reflectance measurements in spectrometer sample compartments to characterize the reactants. Beryllium oxide has been studied using an evacuable diffuse reflectance cell to determine the effects of vacuum baking reexposure to moisture on the surface hydroxyl species. Diffuse reflectance and emission measurements have been used to monitor the curing and reaction of environmental gases with composite materials such as graphite-expoxy structures. A direct comparison of diffuse reflectance and emission spectra was done using a barrel ellipsoid diffuse reflectance/emission detector and Spectropus optical transfer system. Grazing-incidence external-reflectance with p-polarized light was used to study the oxidation in room air of polished uranium coupons. The absorption band at 570 cm{sup {minus}1} was used to monitor the extent of oxidation with a resolution of approximately one monolayer of UO{sub 2} and to distinguish the parabolic, linear, and breakaway corrosion domains. External reflectance is compared with diffuse reflectance as a method for stain analysis and for measuring the effects of H{sub 2}O in UO{sub 2} corrosion films.« less

Applications of fourier transform infrared spectroscopy to surface analysis problems 2. Revision 1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Powell, G.L.; Milosevic, M.

Applications of infrared spectroscopy to surface analysis are described in terms of the combined use of a number of techniques to solve specific surface analysis problems involving both qualitative and quantitative analysis of surface species. Emphasis is placed on the characterization of both the substrate and the surface species and the application of this to the monitoring of surface processes and the inspection of manufactured items. Lithium Hydride has been studied using remote analysis by diffuse reflectance in glove boxes containing very pure argon or controlled moisture levels with robot-operated gravimetric monitoring. These experiments are supported by internal reflectance andmore » diffuse reflectance measurements in spectrometer sample compartments to characterize the reactants. Beryllium oxide has been studied using an evacuable diffuse reflectance cell to determine the effects of vacuum baking reexposure to moisture on the surface hydroxyl species. Diffuse reflectance and emission measurements have been used to monitor the curing and reaction of environmental gases with composite materials such as graphite-expoxy structures. A direct comparison of diffuse reflectance and emission spectra was done using a barrel ellipsoid diffuse reflectance/emission detector and Spectropus optical transfer system. Grazing-incidence external-reflectance with p-polarized light was used to study the oxidation in room air of polished uranium coupons. The absorption band at 570 cm{sup {minus}1} was used to monitor the extent of oxidation with a resolution of approximately one monolayer of UO{sub 2} and to distinguish the parabolic, linear, and breakaway corrosion domains. External reflectance is compared with diffuse reflectance as a method for stain analysis and for measuring the effects of H{sub 2}O in UO{sub 2} corrosion films.« less

Tract-Specific Analyses of Diffusion Tensor Imaging Show Widespread White Matter Compromise in Autism Spectrum Disorder

ERIC Educational Resources Information Center

Shukla, Dinesh K.; Keehn, Brandon; Muller, Ralph-Axel

2011-01-01

Background: Previous diffusion tensor imaging (DTI) studies have shown white matter compromise in children and adults with autism spectrum disorder (ASD), which may relate to reduced connectivity and impaired function of distributed networks. However, tract-specific evidence remains limited in ASD. We applied tract-based spatial statistics (TBSS)…

White Matter Compromise of Callosal and Subcortical Fiber Tracts in Children with Autism Spectrum Disorder: A Diffusion Tensor Imaging Study

ERIC Educational Resources Information Center

Shukla, Dinesh K.; Keehn, Brandon; Lincoln, Alan J.; Muller, Ralph-Axel

2010-01-01

Objective: Autism spectrum disorder (ASD) is increasingly viewed as a disorder of functional networks, highlighting the importance of investigating white matter and interregional connectivity. We used diffusion tensor imaging (DTI) to examine white matter integrity for the whole brain and for corpus callosum, internal capsule, and middle…

A New Proof of the Expected Frequency Spectrum under the Standard Neutral Model.

PubMed

Hudson, Richard R

2015-01-01

The sample frequency spectrum is an informative and frequently employed approach for summarizing DNA variation data. Under the standard neutral model the expectation of the sample frequency spectrum has been derived by at least two distinct approaches. One relies on using results from diffusion approximations to the Wright-Fisher Model. The other is based on Pólya urn models that correspond to the standard coalescent model. A new proof of the expected frequency spectrum is presented here. It is a proof by induction and does not require diffusion results and does not require the somewhat complex sums and combinatorics of the derivations based on urn models.

Motion of charged particles normal to an irregular magnetic field. [astrophysical plasmas

NASA Technical Reports Server (NTRS)

Jokipii, J. R.

1975-01-01

The motion is analyzed of charged particles in a fluctuating magnetic field which varies only in directions normal to its mean direction, such as that which would be generated by an ensemble of magnetosonic waves propagating normal to an ambient magnetic field. The appropriate generalization of gradient-drift motion is derived in terms of the power spectrum of the magnetic fluctuations, and an effective spatial diffusion coefficient is obtained. Several special cases are considered, including a Gaussian power spectrum, a power-law spectrum with a cutoff, and a general power-law spectrum. A possible magnitude is calculated for the spatial diffusion coefficient of the solar wind.

Analyzing the performance of PROSPECT model inversion based on different spectral information for leaf biochemical properties retrieval

NASA Astrophysics Data System (ADS)

Sun, Jia; Shi, Shuo; Yang, Jian; Du, Lin; Gong, Wei; Chen, Biwu; Song, Shalei

2018-01-01

Leaf biochemical constituents provide useful information about major ecological processes. As a fast and nondestructive method, remote sensing techniques are critical to reflect leaf biochemistry via models. PROSPECT model has been widely applied in retrieving leaf traits by providing hemispherical reflectance and transmittance. However, the process of measuring both reflectance and transmittance can be time-consuming and laborious. Contrary to use reflectance spectrum alone in PROSPECT model inversion, which has been adopted by many researchers, this study proposes to use transmission spectrum alone, with the increasing availability of the latter through various remote sensing techniques. Then we analyzed the performance of PROSPECT model inversion with (1) only transmission spectrum, (2) only reflectance and (3) both reflectance and transmittance, using synthetic datasets (with varying levels of random noise and systematic noise) and two experimental datasets (LOPEX and ANGERS). The results show that (1) PROSPECT-5 model inversion based solely on transmission spectrum is viable with results generally better than that based solely on reflectance spectrum; (2) leaf dry matter can be better estimated using only transmittance or reflectance than with both reflectance and transmittance spectra.

Multimodal fiber-probe spectroscopy for the diagnostics and classification of bladder tumors

NASA Astrophysics Data System (ADS)

Anand, Suresh; Cicchi, Riccardo; Fantechi, Riccardo; Gacci, Mauro; Nesi, Gabriella; Carini, Marco; Pavone, Francesco S.

2017-02-01

The gold standard for the detection of bladder cancer is white light cystoscopy, followed by an invasive biopsy and pathological examination. Tissue pathology is time consuming and often prone to sampling errors. Recently, optical spectroscopy techniques have evolved as promising techniques for the detection of neoplasia. The specific goal of this study is to evaluate the application of combined auto-fluorescence (excited using 378 nm and 445 nm wavelengths) and diffuse reflectance spectroscopy to discriminate normal bladder tissue from tumor at different grades. The fluorescence spectrum at both excitation wavelengths showed an increased spectral intensity in tumors with respect to normal tissues. Reflectance data indicated an increased reflectance in the wavelength range 610 nm - 700 nm for different grades of tumors, compared to normal tissues. The spectral data were further analyzed using principal component analysis for evaluating the sensitivity and specificity for diagnosing tumor. The spectral differences observed between various grades of tumors provides a strong genesis for the future evaluation on a larger patient population to achieve statistical significance. This study indicates that a combined spectroscopic strategy, incorporating fluorescence and reflectance spectroscopy, could improve the capability for diagnosing bladder tumor as well as for differentiating tumors in different grades.

Improved mathematical and computational tools for modeling photon propagation in tissue

NASA Astrophysics Data System (ADS)

Calabro, Katherine Weaver

Light interacts with biological tissue through two predominant mechanisms: scattering and absorption, which are sensitive to the size and density of cellular organelles, and to biochemical composition (ex. hemoglobin), respectively. During the progression of disease, tissues undergo a predictable set of changes in cell morphology and vascularization, which directly affect their scattering and absorption properties. Hence, quantification of these optical property differences can be used to identify the physiological biomarkers of disease with interest often focused on cancer. Diffuse reflectance spectroscopy is a diagnostic tool, wherein broadband visible light is transmitted through a fiber optic probe into a turbid medium, and after propagating through the sample, a fraction of the light is collected at the surface as reflectance. The measured reflectance spectrum can be analyzed with appropriate mathematical models to extract the optical properties of the tissue, and from these, a set of physiological properties. A number of models have been developed for this purpose using a variety of approaches -- from diffusion theory, to computational simulations, and empirical observations. However, these models are generally limited to narrow ranges of tissue and probe geometries. In this thesis, reflectance models were developed for a much wider range of measurement parameters, and influences such as the scattering phase function and probe design were investigated rigorously for the first time. The results provide a comprehensive understanding of the factors that influence reflectance, with novel insights that, in some cases, challenge current assumptions in the field. An improved Monte Carlo simulation program, designed to run on a graphics processing unit (GPU), was built to simulate the data used in the development of the reflectance models. Rigorous error analysis was performed to identify how inaccuracies in modeling assumptions can be expected to affect the accuracy of extracted optical property values from experimentally-acquired reflectance spectra. From this analysis, probe geometries that offer the best robustness against error in estimation of physiological properties from tissue, are presented. Finally, several in vivo studies demonstrating the use of reflectance spectroscopy for both research and clinical applications are presented.

Reduction of skylight reflection effects in the above-water measurement of diffuse marine reflectance.

PubMed

Fougnie, B; Frouin, R; Lecomte, P; Deschamps, P Y

1999-06-20

Reflected skylight in above-water measurements of diffuse marine reflectance can be reduced substantially by viewing the surface through an analyzer transmitting the vertically polarized component of incident radiance. For maximum reduction of effects, radiometric measurements should be made at a viewing zenith angle of approximately 45 degrees (near the Brewster angle) and a relative azimuth angle between solar and viewing directions greater than 90 degrees (backscattering), preferably 135 degrees. In this case the residual reflected skylight in the polarized signal exhibits minimum sensitivity to the sea state and can be corrected to within a few 10(-4) in reflectance units. For most oceanic waters the resulting relative error on the diffuse marine reflectance in the blue and green is less than 1%. Since the water body polarizes incident skylight, the measured polarized reflectance differs from the total reflectance. The difference, however, is small for the considered geometry. Measurements made at the Scripps Institution of Oceanography pier in La Jolla, Calif., with a specifically designed scanning polarization radiometer, confirm the theoretical findings and demonstrate the usefulness of polarization radiometry for measuring diffuse marine reflectance.

Biomimetic light-harvesting funnels for re-directioning of diffuse light.

PubMed

Pieper, Alexander; Hohgardt, Manuel; Willich, Maximilian; Gacek, Daniel Alexander; Hafi, Nour; Pfennig, Dominik; Albrecht, Andreas; Walla, Peter Jomo

2018-02-14

Efficient sunlight harvesting and re-directioning onto small areas has great potential for more widespread use of precious high-performance photovoltaics but so far intrinsic solar concentrator loss mechanisms outweighed the benefits. Here we present an antenna concept allowing high light absorption without high reabsorption or escape-cone losses. An excess of randomly oriented pigments collects light from any direction and funnels the energy to individual acceptors all having identical orientations and emitting ~90% of photons into angles suitable for total internal reflection waveguiding to desired energy converters (funneling diffuse-light re-directioning, FunDiLight). This is achieved using distinct molecules that align efficiently within stretched polymers together with others staying randomly orientated. Emission quantum efficiencies can be >80% and single-foil reabsorption <0.5%. Efficient donor-pool energy funneling, dipole re-orientation, and ~1.5-2 nm nearest donor-acceptor transfer occurs within hundreds to ~20 ps. Single-molecule 3D-polarization experiments confirm nearly parallel emitters. Stacked pigment selection may allow coverage of the entire solar spectrum.

Effect of Organic Substrates on the Photocatalytic Reduction of Cr(VI) by Porous Hollow Ga2O3 Nanoparticles

PubMed Central

Liu, Jin; Gan, Huihui; Wu, Hongzhang; Zhang, Xinlei; Zhang, Jun; Li, Lili; Wang, Zhenling

2018-01-01

Porous hollow Ga2O3 nanoparticles were successfully synthesized by a hydrolysis method followed by calcination. The prepared samples were characterized by field emission scanning electron microscope, transmission electron microscope, thermogravimetry and differential scanning calorimetry, UV-vis diffuse reflectance spectra and Raman spectrum. The porous structure of Ga2O3 nanoparticles can enhance the light harvesting efficiency, and provide lots of channels for the diffusion of Cr(VI) and Cr(III). Photocatalytic reduction of Cr(VI), with different initial pH and degradation of several organic substrates by porous hollow Ga2O3 nanoparticles in single system and binary system, were investigated in detail. The reduction rate of Cr(VI) in the binary pollutant system is markedly faster than that in the single Cr(VI) system, because Cr(VI) mainly acts as photogenerated electron acceptor. In addition, the type and concentration of organic substrates have an important role in the photocatalytic reduction of Cr(VI). PMID:29690548

Method for estimating optimal spectral and energy parameters of laser irradiation in photodynamic therapy of biological tissue

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lisenko, S A; Kugeiko, M M

We have solved the problem of layer-by-layer laser-light dosimetry in biological tissues and of selecting an individual therapeutic dose in laser therapy. A method is proposed for real-time monitoring of the radiation density in tissue layers in vivo, concentrations of its endogenous (natural) and exogenous (specially administered) chromophores, as well as in-depth distributions of the spectrum of light action on these chromophores. As the background information use is made of the spectrum of diffuse light reflected from a patient's tissue, measured by a fibre-optic spectrophotometer. The measured spectrum is quantitatively analysed by the method of approximating functions for fluxes ofmore » light multiply scattered in tissue and by a semi-analytical method for calculating the in-depth distribution of the light flux in a multi-layered medium. We have shown the possibility of employing the developed method for monitoring photosensitizer and oxyhaemoglobin concentrations in tissue, light power absorbed by chromophores in tissue layers at different depths and laser-induced changes in the tissue morphology (vascular volume content and ratios of various forms of haemoglobin) during photodynamic therapy. (biophotonics)« less

Circumnuclear starbursts in Seyfert galaxies

NASA Technical Reports Server (NTRS)

Wilson, Andrew S.

1987-01-01

Observational diagnostics for the recognition of circumnuclear star formation in Seyfert galaxies are described and illustrated. These methods include: (1) spatially resolved optical spectroscopy, which allows the emission lines for HII regions to be separated from those originating in gas ionized by the Seyfert nucleus; (2) radio continuum mapping, where the linear radio sources characteristic of the nuclear activity may be distinguished from the diffuse morphology of multiple supernova remnants generated in a starburst; (3) infrared spectroscopic searches for emission features of dust, which are seen in starbursts but not in Seyfert nuclei; (4) the shape of the IRAS spectrum. These various diagnostics agree well as to the presence or absence of ongoing star formation. The IRAS spectra of a significant fraction of Seyferts are dominated by emission from dust heated by stars, not the Seyfert nucleus itself. In these cases, the spectrum is curved, being steep between 25 and 60 microns and flatter between 60 and 100 microns. When the Seyfert nucleus dominates, the 25 to 100 micron spectrum is much flatter. It is suggested that the location of a Seyfert galaxy in the IRAS color-color diagram reflects primarily the relative contributions of the active nucleus and dust heated by stars to the infrared fluxes.

Methods for quantitative infrared directional-hemispherical and diffuse reflectance measurements using an FTIR and a commercial integrating sphere

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blake, Thomas A.; Johnson, Timothy J.; Tonkyn, Russell G.

Infrared integrating sphere measurements of solid samples are important in providing reference data for contact, standoff and remote sensing applications. At the Pacific Northwest National Laboratory (PNNL) we have developed protocols to measure both the directional-hemispherical ( and diffuse (d) reflectances of powders, liquids, and disks of powders and solid materials using a commercially available, matte gold-coated integrating sphere and Fourier transform infrared spectrometer. Detailed descriptions of the sphere alignment and its use for making these reflectance measurements are given. Diffuse reflectance values were found to be dependent on the bidirectional reflection distribution function (BRDF) of the sample and themore » solid angle intercepted by the sphere’s specular exclusion port. To determine how well the sphere and protocols produce quantitative reflectance data, measurements were made of three diffuse and two specular standards prepared by the National institute of Standards and Technology (NIST, USA), LabSphere Infragold and Spectralon standards, hand-loaded sulfur and talc powder samples, and water. The five NIST standards behaved as expected: the three diffuse standards had a high degree of “diffuseness,” d/ = D > 0.9, whereas the two specular standards had D ≤ 0.03. The average absolute differences between the NIST and PNNL measurements of the NIST standards for both directional-hemispherical and diffuse reflectances are on the order of 0.01 reflectance units. Other quantitative differences between the PNNL-measured and calibration (where available) or literature reflectance values for these standards and materials are given and the possible origins of discrepancies are discussed. Random uncertainties and estimates of systematic uncertainties are presented. Corrections necessary to provide better agreement between the PNNL reflectance values as measured for the NIST standards and the NIST reflectance values for these same standards are also discussed.« less

Optimised mounting conditions for poly (ether sulfone) in radiation detection.

PubMed

Nakamura, Hidehito; Shirakawa, Yoshiyuki; Sato, Nobuhiro; Yamada, Tatsuya; Kitamura, Hisashi; Takahashi, Sentaro

2014-09-01

Poly (ether sulfone) (PES) is a candidate for use as a scintillation material in radiation detection. Its characteristics, such as its emission spectrum and its effective refractive index (based on the emission spectrum), directly affect the propagation of light generated to external photodetectors. It is also important to examine the presence of background radiation sources in manufactured PES. Here, we optimise the optical coupling and surface treatment of the PES, and characterise its background. Optical grease was used to enhance the optical coupling between the PES and the photodetector; absorption by the grease of short-wavelength light emitted from PES was negligible. Diffuse reflection induced by surface roughening increased the light yield for PES, despite the high effective refractive index. Background radiation derived from the PES sample and its impurities was negligible above the ambient, natural level. Overall, these results serve to optimise the mounting conditions for PES in radiation detection. Copyright © 2014 Elsevier Ltd. All rights reserved.

[Studies on the brand traceability of milk powder based on NIR spectroscopy technology].

PubMed

Guan, Xiao; Gu, Fang-Qing; Liu, Jing; Yang, Yong-Jian

2013-10-01

Brand traceability of several different kinds of milk powder was studied by combining near infrared spectroscopy diffuse reflectance mode with soft independent modeling of class analogy (SIMCA) in the present paper. The near infrared spectrum of 138 samples, including 54 Guangming milk powder samples, 43 Netherlands samples, and 33 Nestle samples and 8 Yili samples, were collected. After pretreatment of full spectrum data variables in training set, principal component analysis was performed, and the contribution rate of the cumulative variance of the first three principal components was about 99.07%. Milk powder principal component regression model based on SIMCA was established, and used to classify the milk powder samples in prediction sets. The results showed that the recognition rate of Guangming milk powder, Netherlands milk powder and Nestle milk powder was 78%, 75% and 100%, the rejection rate was 100%, 87%, and 88%, respectively. Therefore, the near infrared spectroscopy combined with SIMCA model can classify milk powder with high accuracy, and is a promising identification method of milk powder variety.

Photoluminescence and thermoluminescence properties of BaGa2O4

NASA Astrophysics Data System (ADS)

Noto, L. L.; Poelman, D.; Orante-Barrón, V. R.; Swart, H. C.; Mathevula, L. E.; Nyenge, R.; Chithambo, M.; Mothudi, B. M.; Dhlamini, M. S.

2018-04-01

Rare-Earth free luminescent materials are fast becoming important as the cost of rare earth ions gradually increases. In this work, a Rare-Earth free BaGa2O4 luminescent compound was prepared by solid state chemical reaction, which was confirmed to have a single phase by X-ray Diffraction. The Backscattered Electron image and Energy Dispersive X-ray spectroscopy maps confirmed irregular particle and homogeneous compound formation, respectively. The Photoluminescence spectrum displayed broad emission between 350 to 650 nm, which was deconvoluted into two components. The photoluminescence excitation peak was positioned at 254 nm, which corresponds with the band-to-band position observed from the diffuse reflectance spectrum. The band gap was extrapolated to 4.65 ± 0.02 eV using the Kubelka-Munk model. The preliminary thermoluminescence results indicated that the kinetics involved were neither of first nor second order. Additionally, the activation energy of the electrons within the trap centres was approximated to 0.61 ± 0.01 eV using the Initial Rise model.

Li3Ge3Se6: the first ternary lithium germanium selenide with interesting ∞[Ge6Se12]n chains constructed by ethane-like [Ge2Se6]6- clusters.

PubMed

Li, Guangmao; Zhen, Ni; Chu, Yu; Zhou, Zhongxiang

2017-12-21

Li 3 Ge 3 Se 6 , the first compound of the ternary Li/Ge/Se system, has been synthesized. Note that interesting 1D ∞ [Ge 6 Se 12 ] n chains constructed by ethane-like [Ge 2 Se 6 ] 6- clusters were discovered in its structure. Investigations on the structures of all the [Ge 2 Se 6 ] 6- cluster-containing compounds have shown that only in Li 3 Ge 3 Se 6 are there 1D chains composed of [Ge 2 Se 6 ] 6- clusters, which result from the space limitation within the tunnels surrounded by LiSe 6 octahedra. Raman spectrum was obtained to demonstrate the existence of Ge-Ge bonds. UV-visible-NIR diffuse reflection spectrum showed an optical bandgap of 2.08 eV. Theoretical calculations based on first principles have also been performed for its band structure and density of states to analyze its structure-property relationship.

Abnormal Corpus Callosum Connectivity, Socio-Communicative Deficits, and Motor Deficits in Children with Autism Spectrum Disorder: A Diffusion Tensor Imaging Study

ERIC Educational Resources Information Center

Hanaie, Ryuzo; Mohri, Ikuko; Kagitani-Shimono, Kuriko; Tachibana, Masaya; Matsuzaki, Junko; Watanabe, Yoshiyuki; Fujita, Norihiko; Taniike, Masako

2014-01-01

In addition to social and communicative deficits, many studies have reported motor deficits in autism spectrum disorder (ASD). This study investigated the macro and microstructural properties of the corpus callosum (CC) of 18 children with ASD and 12 typically developing controls using diffusion tensor imaging tractography. We aimed to explore…

Remote Detection of Saline Intrusion in a Coastal Aquifer Using Borehole Measurements of Self-Potential

NASA Astrophysics Data System (ADS)

MacAllister, DJ.; Jackson, M. D.; Butler, A. P.; Vinogradov, J.

2018-03-01

Two years of self-potential (SP) measurements were made in a monitoring borehole in the coastal UK Chalk aquifer. The borehole SP data showed a persistent gradient with depth, and temporal variations with a tidal power spectrum consistent with ocean tides. No gradient with depth was observed at a second coastal monitoring borehole ca. 1 km further inland, and no gradient or tidal power spectrum were observed at an inland site ca. 80 km from the coast. Numerical modeling suggests that the SP gradient recorded in the coastal monitoring borehole is dominated by the exclusion-diffusion potential, which arises from the concentration gradient across a saline front in close proximity to, but not intersecting, the base of the borehole. No such saline front is present at the two other monitoring sites. Modeling further suggests that the ocean tidal SP response in the borehole, measured prior to breakthrough of saline water, is dominated by the exclusion-diffusion potential across the saline front, and that the SP fluctuations are due to the tidal movement of the remote front. The electrokinetic potential, caused by changes in hydraulic head across the tide, is one order of magnitude too small to explain the observed SP data. The results suggest that in coastal aquifers, the exclusion-diffusion potential plays a dominant role in borehole SP when a saline front is nearby. The SP gradient with depth indicates the close proximity of the saline front to the borehole and changes in SP at the borehole reflect changes in the location of the saline front. Thus, SP monitoring can be used to facilitate more proactive management of abstraction and saline intrusion in coastal aquifers.

Spectral properties of Dy3+ doped ZnAl2O4 phosphor

NASA Astrophysics Data System (ADS)

Prakash, Ram; Kumar, Sandeep; Mahajan, Rubby; Khajuria, Pooja; Kumar, Vinay; Choudhary, R. J.; Phase, D. M.

2018-05-01

Herein, Dy3+ doped ZnAl2O4 phosphor was synthesized by the solution combustion method. The synthesized phosphor was characterized by X-ray diffraction (XRD), photoluminescence (PL) spectroscopy, UV-Vis spectroscopy and X-ray photoelectron spectroscopy (XPS). The phase purity of the phosphor was confirmed by the XRD studies that showed cubic symmetry of the synthesized phosphor. Under UV excitation (388 nm) the PL emission spectrum of the phosphor shows characteristic transition from the Dy3+ ion. A band gap of 5.2 eV was estimated from the diffused reflectance spectroscopy. The surface properties of the phosphor were studied using the X-ray photoelectron spectroscopy.

Growth, structural, spectroscopic and optical characterization of barium doped calcium tartrate

NASA Astrophysics Data System (ADS)

Verma, Seema; Raina, Bindu; Gupta, Vandana; Bamzai, K. K.

2018-05-01

Barium doped calcium tartrates synthesized by controlled diffusion using silica gel technique at ambient temperature was characterized by single crystal X-ray diffraction which establishes monoclinic crystal system with volume of the unit cell 923.97(10) Ǻ3 and the space group being P21. UV - Vis characterization gives various linear optical constants like absorption, transmittance, reflectance, band gap, extinction coefficient, urbach energy, complex dielectric constant, optical and electrical conductivity. These constants are considered to be essential in characterizing materials that are used in various applications like fabrication of optoelectronic devices. FTIR spectrum establishes the presence of various bands of functional groups expected from metal tartrate with water of crystallization.

Special report, diffuse reflectivity of the lunar surface

NASA Technical Reports Server (NTRS)

Fastie, W. G.

1972-01-01

The far ultraviolet diffuse reflectivity of samples of lunar dust material is determined. Equipment for measuring the diffuse reflectivity of materials (e.g. paint samples) is already in existence and requires only minor modification for the proposed experiment which will include the measurement of the polarizing properties of the lunar samples. Measurements can be made as a function of both illumination angle and angle of observation.

Characteristic power spectrum of diffusive interface dynamics in the two-dimensional Ising model

NASA Astrophysics Data System (ADS)

Masumoto, Yusuke; Takesue, Shinji

2018-05-01

We investigate properties of the diffusive motion of an interface in the two-dimensional Ising model in equilibrium or nonequilibrium situations. We focused on the relation between the power spectrum of a time sequence of spins and diffusive motion of an interface which was already clarified in one-dimensional systems with a nonequilibrium phase transition like the asymmetric simple exclusion process. It is clarified that the interface motion is a diffusion process with a drift force toward the higher-temperature side when the system is in contact with heat reservoirs at different temperatures and heat transfers through the system. Effects of the width of the interface are also discussed.

Spectrum of the Isotropic Diffuse Gamma-Ray Emission Derived from First-Year Fermi Large Area Telescope Data

DOE PAGES

Abdo, A. A.

2010-03-08

Here, we report on the first Fermi Large Area Telescope (LAT) measurements of the so-called “extragalactic” diffuse γ -ray emission (EGB). This component of the diffuse γ -ray emission is generally considered to have an isotropic or nearly isotropic distribution on the sky with diverse contributions discussed in the literature. The derivation of the EGB is based on detailed modeling of the bright foreground diffuse Galactic γ -ray emission, the detected LAT sources, and the solar γ -ray emission. We also find the spectrum of the EGB is consistent with a power law with a differential spectral index γ =more » 2.41 ± 0.05 and intensity I ( > 100 MeV ) = ( 1.03 ± 0.17 ) × 10 - 5 cm -2 s - 1 sr - 1 , where the error is systematics dominated. The EGB spectrum, presented here, is featureless, less intense, and softer than that derived from EGRET data.« less

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arai, T.; Matsuura, S.; Sano, K.

2015-06-10

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

[Application of BaSO4 diffuser plate in 250-400 nm spectral radiance calibration].

PubMed

Jia, Hui; Li, Fu-tian

2004-01-01

Sprayed BaSO4 diffuser plate is the most Lambertian surface actually used in spectral radiance calibration known by now. Its hemispheric reflectance and Bi-directional Reflectance Distribution Functions (BRDF) were measured in the experiment. Its diffuse characteristics were compared with Lambertian surface. In order to calibrate spectral radiance more accurately, the small variation of diffuser's BRDF with scattered angles and the nonuniformity of spectral irradiance on diffuser surface illuminated by the standard lamp should be considered. By integrating the radiation flux reflected by the element area and that entering the entrance slit within the viewing area of spectrometer, the measured spectral radiance can be calculated. Furthermore, the spectral radiance of Lambertian surface whose BRDF was derived from hemispheric reflectance was compared with that from the average of the measured BRDF.

Diffuse and specular characteristics of leaf reflectance

NASA Technical Reports Server (NTRS)

Grant, Lois

1987-01-01

In this paper, the evolution of current understanding of the mechanisms of leaf reflectance is reviewed. The use of measurements of polarized reflectance to separate leaf reflectance into diffuse and specular components is discussed. A section on the factors influencing leaf reflectance - leaf structure and physiological disturbances - is included along with discussion on the manner in which these influences are manifested.

Contamination and UV ageing of diffuser targets used in satellite inflight and ground reference test site calibrations

NASA Astrophysics Data System (ADS)

Vaskuri, Anna; Greenwell, Claire; Hessey, Isabel; Tompkins, Jordan; Woolliams, Emma

2018-02-01

Diffuser reflectance targets are key components in in-orbit calibrations and for verifying ground reference test sites. In this work, Spectralon, Diffusil, and Heraeus diffusers were exposed to exhaust gases and ultraviolet (UV) radiation in the ambient air conditions and their degradations were monitored by measuring changes in spectral reflectances. Spectralon is a state-of-the-art diffuser made of polytetrafluoroethylene, and Diffusil and Heraeus diffusers are made of fused silica with gas bubbles inside. Based on the contamination tests, Spectralon degrades faster than fused silica diffusers. For the samples exposed to contamination for 20 minutes, the 250 nm - 400 nm total diffuse spectral reflectance of Spectralon degraded 3-5 times more when exposed to petrol-like emission and 16-23 times more when exposed to diesel-like emission, compared with Diffusil. When the reflectance changes of Spectralon were compared with those of Heraeus, Spectralon degraded 3-4 times more when exposed to petrol-like emission for 20 minutes and 5-7 times more when exposed to diesel-like emission for 7.5 minutes. When the samples contaminated were exposed to UV radiation in the ambient air, their reflectance gradually restored back to the original level. In conclusion, fused silica diffusers are more resistant to hydrocarbon contaminants present in ground reference test sites, and thus more stable under UV radiation in the air.

The angular distribution of diffusely backscattered light

NASA Astrophysics Data System (ADS)

Vera, M. U.; Durian, D. J.

1997-03-01

The diffusion approximation predicts the angular distribution of light diffusely transmitted through an opaque slab to depend only on boundary reflectivity, independent of scattering anisotropy, and this has been verified by experiment(M.U. Vera and D.J. Durian, Phys. Rev. E 53) 3215 (1996). Here, by contrast, we demonstrate that the angular distribution of diffusely backscattered light depends on scattering anisotropy as well as boundary reflectivity. To model this observation scattering anisotropy is added to the diffusion approximation by a discontinuity in the photon concentration at the source point that is proportional to the average cosine of the scattering angle. We compare the resulting predictions with random walk simulations and with measurements of diffusely backscattered intensity versus angle for glass frits and aqueous suspensions of polystyrene spheres held in air or immersed in a water bath. Increasing anisotropy and boundary reflectivity each tend to flatten the predicted distributions, and for different combinations of anisotropy and reflectivity the agreement between data and predictions ranges from qualitatively to quantitatively good.

Design and evaluation of an imaging spectrophotometer incorporating a uniform light source.

PubMed

Noble, S D; Brown, R B; Crowe, T G

2012-03-01

Accounting for light that is diffusely scattered from a surface is one of the practical challenges in reflectance measurement. Integrating spheres are commonly used for this purpose in point measurements of reflectance and transmittance. This solution is not directly applicable to a spectral imaging application for which diffuse reflectance measurements are desired. In this paper, an imaging spectrophotometer design is presented that employs a uniform light source to provide diffuse illumination. This creates the inverse measurement geometry to the directional illumination/diffuse reflectance mode typically used for point measurements. The final system had a spectral range between 400 and 1000 nm with a 5.2 nm resolution, a field of view of approximately 0.5 m by 0.5 m, and millimeter spatial resolution. Testing results indicate illumination uniformity typically exceeding 95% and reflectance precision better than 1.7%.

From Vulcanian explosions to sustained explosive eruptions: The role of diffusive mass transfer in conduit flow dynamics

NASA Astrophysics Data System (ADS)

Mason, R. M.; Starostin, A. B.; Melnik, O. E.; Sparks, R. S. J.

2006-05-01

Magmatic explosive eruptions are influenced by mass transfer processes of gas diffusion into bubbles caused by decompression. Melnik and Sparks [Melnik, O.E., Sparks, R.S.J. 2002, Modelling of conduit flow dynamic during explosive activity at Soufriere Hills Volcano, Montserrat. In: Druitt, T.H., Kokelaar, B.P. (eds). The Eruption of Soufriere Hills Volcano, Montserrat, from 1995 to 1999. Geological Society, London, Memoirs, 21, 307-317] proposed two end member cases corresponding to complete equilibrium and complete disequilibrium. In the first case, diffusion is fast enough to maintain the system near equilibrium and a long-lived explosive eruption develops. In the latter case, pre-existing bubbles expand under conditions of explosive eruption and decompression, but diffusive gas transfer is negligible. This leads to a much shorter eruption. Here we develop this model to consider the role of mass transfer by investigating transient flows at the start of an explosive eruption triggered by a sudden decompression. The simulations reveal a spectrum of behaviours from sustained to short-lived highly non-equilibrium Vulcanian-style explosions lasting a few tens of seconds, through longer lasting eruptions that can be sustained for tens of minutes and finally to eruptions that can last hours or even days. Behaviour is controlled by a mass-transfer parameter, ω, which equals n*2/3D, where n* is the bubble number density and D is the diffusivity. The parameter ω is expected to vary between 10 - 5 and 1 s - 1 in nature and reflects a time-scale for efficient diffusion. The spectrum of model behaviours is consistent with variations in styles of explosive eruptions of silicic volcanoes. In the initial stages peak discharges occur over 10-20 s and then decline to low discharges. If a critical bubble overpressure is assumed to be the criterion for fragmentation then fragmentation may stop and start several times in the declining period causing several pulses of high-intensity discharge. For the cases of strong disequilibria, the fluxes can decrease to negligible values where other processes, such as gas escape through permeable magma, prevents explosive conditions becoming re-established so that explosive activity stops and dome growth can start. For cases closer to the equilibrium the eruption can evolve towards a quasi-steady sustained flow, never declining sufficiently for gas escape to become dominant.

Including scattering within the room acoustics diffusion model: An analytical approach.

PubMed

Foy, Cédric; Picaut, Judicaël; Valeau, Vincent

2016-10-01

Over the last 20 years, a statistical acoustic model has been developed to predict the reverberant sound field in buildings. This model is based on the assumption that the propagation of the reverberant sound field follows a transport process and, as an approximation, a diffusion process that can be easily solved numerically. This model, initially designed and validated for rooms with purely diffuse reflections, is extended in the present study to mixed reflections, with a proportion of specular and diffuse reflections defined by a scattering coefficient. The proposed mathematical developments lead to an analytical expression of the diffusion constant that is a function of the scattering coefficient, but also on the absorption coefficient of the walls. The results obtained with this extended diffusion model are then compared with the classical diffusion model, as well as with a sound particles tracing approach considering mixed wall reflections. The comparison shows a good agreement for long rooms with uniform low absorption (α = 0.01) and uniform scattering. For a larger absorption (α = 0.1), the agreement is moderate, due to the fact that the proposed expression of the diffusion coefficient does not vary spatially. In addition, the proposed model is for now limited to uniform diffusion and should be extended in the future to more general cases.

The grand unified photon spectrum: A coherent view of the diffuse extragalactic background radiation

NASA Technical Reports Server (NTRS)

Ressell, M. Ted; Turner, Michael S.

1989-01-01

The spectrum of diffuse extragalactic background radiation (DEBRA) at wavelengths from 10(exp 5) to 10(exp -24) cm is presented in a coherent fashion. Each wavelength region, from the radio to ultra-high energy photons and cosmic rays, is treated both separately and as part of the grand unified photon spectrum (GUPS). A discussion of, and references to, the relevant literature for each wavelength region is included. This review should provide a useful tool for those interested in diffuse backgrounds, the epoch of galaxy formation, astrophysical/cosmological constraints to particle properties, exotic early Universe processes, and many other astrophysical and cosmological enterprises. As a worked example, researchers derive the cosmological constraints to an unstable-neutrino spies (with arbitrary branching ratio to a radiative decay mode) that follow from the GUPS.

Characterizing the reflectivity of handheld display devices.

PubMed

Liu, Peter; Badano, Aldo

2014-08-01

With increased use of handheld and tablet display devices for viewing medical images, methods for consistently measuring reflectivity of the devices are needed. In this note, the authors report on the characterization of diffuse reflections for handheld display devices including mobile phones and tablets using methods recommended by the American Association of Physicists in Medicine Task Group 18 (TG18). The authors modified the diffuse reflectance coefficient measurement method outlined in the TG18 report. The authors measured seven handheld display devices (two phones and five tablets) and three workstation displays. The device was attached to a black panel with Velcro. To study the effect of the back surface on the diffuse reflectance coefficient, the authors created Styrofoam masks with different size square openings and placed it in front of the device. Overall, for each display device, measurements of illuminance and reflected luminance on the display screen were taken. The authors measured with no mask, with masks of varying size, and with display-size masks, and calculated the corresponding diffuse reflectance coefficient. For all handhelds, the diffuse reflectance coefficient measured with no back panel were lower than measurements performed with a mask. The authors found an overall increase in reflectivity as the size of the mask decreases. For workstations displays, diffuse reflectance coefficients were higher when no back panel was used, and higher than with masks. In all cases, as luminance increased, illuminance increased, but not at the same rate. Since the size of handheld displays is smaller than that of workstation devices, the TG18 method suffers from a dependency on illumination condition. The authors show that the diffuse reflection coefficients can vary depending on the nature of the back surface of the illuminating box. The variability in the diffuse coefficient can be as large as 20% depending on the size of the mask. For all measurements, both luminance and illuminance increased as the size of the display window decreased. The TG18 method does not account for this variability. The authors conclude that the method requires a definitive description of the back panel used in the light source setup. The methods described in the TG18 document may need to be improved to provide consistent comparisons of desktop monitors, phones, and tablets.

Tissue differentiation by diffuse reflectance spectroscopy for automated oral and maxillofacial laser surgery: ex vivo pilot study

NASA Astrophysics Data System (ADS)

Zam, Azhar; Stelzle, Florian; Tangermann-Gerk, Katja; Adler, Werner; Nkenke, Emeka; Schmidt, Michael; Douplik, Alexandre

2010-02-01

Remote laser surgery lacks of haptic feedback during the laser ablation of tissue. Hence, there is a risk of iatrogenic damage or destruction of anatomical structures like nerves or salivary glands. Diffuse reflectance spectroscopy provides a straightforward and simple approach for optical tissue differentiation. We measured diffuse reflectance from seven various tissue types ex vivo. We applied Linear Discriminant Analysis (LDA) to differentiate the seven tissue types and computed the area under the ROC curve (AUC). Special emphasis was taken on the identification of nerves and salivary glands as the most crucial tissue for maxillofacial surgery. The results show a promise for differentiating tissues as guidance for oral and maxillofacial laser surgery by means of diffuse reflectance.

Determining biological tissue optical properties via integrating sphere spatial measurements

DOEpatents

Baba, Justin S [Knoxville, TN; Letzen, Brian S [Coral Springs, FL

2011-01-11

An optical sample is mounted on a spatial-acquisition apparatus that is placed in or on an enclosure. An incident beam is irradiated on a surface of the sample and the specular reflection is allowed to escape from the enclosure through an opening. The spatial-acquisition apparatus is provided with a light-occluding slider that moves in front of the sample to block portions of diffuse scattering from the sample. As the light-occluding slider moves across the front of the sample, diffuse light scattered into the area of the backside of the light-occluding slider is absorbed by back side surface of the light-occluding slider. By measuring a baseline diffuse reflectance without a light-occluding slider and subtracting measured diffuse reflectance with a light-occluding slider therefrom, diffuse reflectance for the area blocked by the light-occluding slider can be calculated.

Autism Spectrum Disorder: Does Neuroimaging Support the DSM-5 Proposal for a Symptom Dyad? A Systematic Review of Functional Magnetic Resonance Imaging and Diffusion Tensor Imaging Studies

ERIC Educational Resources Information Center

Pina-Camacho, Laura; Villero, Sonia; Fraguas, David; Boada, Leticia; Janssen, Joost; Navas-Sanchez, Francisco J.; Mayoral, Maria; Llorente, Cloe; Arango, Celso; Parellada, Mara

2012-01-01

A systematic review of 208 studies comprising functional magnetic resonance imaging and diffusion tensor imaging data in patients with "autism spectrum disorder" (ASD) was conducted, in order to determine whether these data support the forthcoming DSM-5 proposal of a social communication and behavioral symptom dyad. Studies consistently reported…

A Diffusion Cloud Chamber Study of Very Slow Mesons. II. Beta Decay of the Muon

DOE R&D Accomplishments Database

Lederman, L. M.; Sargent, C. P.; Rinehart, M.; Rogers, K.

1955-03-01

The spectrum of electrons arising from the decay of the negative mu meson has been determined. The muons are arrested in the gas of a high pressure hydrogen filled diffusion cloud chamber. The momenta of the decay electrons are determined from their curvature in a magnetic field of 7750 gauss. The spectrum of 415 electrons has been analyzed according to the theory of Michel.

SeaWiFS long-term solar diffuser reflectance and sensor noise analyses.

PubMed

Eplee, Robert E; Patt, Frederick S; Barnes, Robert A; McClain, Charles R

2007-02-10

The NASA Ocean Biology Processing Group's Calibration and Validation (Cal/Val) team has undertaken an analysis of the mission-long Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) solar calibration time series to assess the long-term degradation of the solar diffuser reflectance over 9 years on orbit. The SeaWiFS diffuser is an aluminum plate coated with YB71 paint. The bidirectional reflectance distribution function of the diffuser was not fully characterized before launch, so the Cal/Val team has implemented a regression of the solar incidence angles and the drift in the node of the satellite's orbit against the diffuser time series to correct for solar incidence angle effects. An exponential function with a time constant of 200 days yields the best fit to the diffuser time series. The decrease in diffuser reflectance over the mission is wavelength dependent, ranging from 9% in the blue (412 nm) to 5% in the red and near infrared (670-865 nm). The Cal/Val team has developed a methodology for computing the signal-to-noise ratio (SNR) for SeaWiFS on orbit from the diffuser time series corrected for both the varying solar incidence angles and the diffuser reflectance degradation. A sensor noise model is used to compare on-orbit SNRs computed for radiances reflected from the diffuser with prelaunch SNRs measured at typical radiances specified for the instrument. To within the uncertainties in the measurements, the SNRs for SeaWiFS have not changed over the mission. The on-orbit performance of the SeaWiFS solar diffuser should offer insight into the long-term on-orbit performance of solar diffusers on other instruments, such as the Moderate-Resolution Imaging Spectrometer [currently flying on the Earth Observing System (EOS) Terra and Aqua satellites], the Visible and Infrared Radiometer Suite [scheduled to fly on the NASA National Polar-orbiting Operational Environmental Satellite System (NPOESS) and NPOESS Preparatory Project (NPP) satellites] and the Advanced Baseline Imager [scheduled to fly on the National Oceanic and Atmospheric Administration Geostationary Environmental Operational Satellite Series R (GOES-R) satellites].

SeaWiFS long-term solar diffuser reflectance and sensor noise analyses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eplee, Robert E. Jr.; Patt, Frederick S.; Barnes, Robert A.

The NASA Ocean Biology Processing Group's Calibration and Validation(Cal/Val) team has undertaken an analysis of the mission-long Sea-Viewing Wide Field-of-View Sensor (SeaWiFS)solar calibration time series to assess the long-term degradation of the solar diffuser reflectance over 9 years on orbit. The SeaWiFS diffuser is an aluminum plate coated with YB71 paint. The bidirectional reflectance distribution function of the diffuser was not fully characterized before launch,so the Cal/Val team has implemented a regression of the solar incidence angles and the drift in the node of the satellite's orbit against the diffuser time series to correct for solar incidence angle effects. Anmore » exponential function with a time constant of 200 days yields the best fit to the diffuser time series.The decrease in diffuser reflectance over the mission is wavelength dependent,ranging from 9% in the blue(412 nm) to 5% in the red and near infrared(670-865 nm). The Cal/Val team has developed a methodology for computing the signal-to-noise ratio (SNR) for SeaWiFS on orbit from the diffuser time series corrected for both the varying solar incidence angles and the diffuser reflectance degradation. A sensor noise model is used to compare on-orbit SNRs computed for radiances reflected from the diffuser with prelaunch SNRs measured at typical radiances specified for the instrument. To within the uncertainties in the measurements, the SNRs for SeaWiFS have not changed over the mission. The on-orbit performance of the SeaWiFS solar diffuser should offer insight into the long-term on-orbit performance of solar diffusers on other instruments, such as the Moderate-Resolution Imaging Spectrometer [currently flying on the Earth Observing System (EOS) Terra and Aqua satellites], the Visible and Infrared Radiometer Suite [scheduled to fly on the NASA National Polar-orbiting Operational Environmental Satellite System (NPOESS) and NPOESS Preparatory Project (NPP) satellites] and the Advanced Baseline Imager [scheduled to fly on the National Oceanic and Atmospheric Administration Geostationary Environmental Operational Satellite Series R (GOES-R) satellites].« less

SeaWiFS long-term solar diffuser reflectance and sensor noise analyses

NASA Astrophysics Data System (ADS)

Eplee, Robert E., Jr.; Patt, Frederick S.; Barnes, Robert A.; McClain, Charles R.

2007-02-01

The NASA Ocean Biology Processing Group's Calibration and Validation (Cal/Val) team has undertaken an analysis of the mission-long Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) solar calibration time series to assess the long-term degradation of the solar diffuser reflectance over 9 years on orbit. The SeaWiFS diffuser is an aluminum plate coated with YB71 paint. The bidirectional reflectance distribution function of the diffuser was not fully characterized before launch, so the Cal/Val team has implemented a regression of the solar incidence angles and the drift in the node of the satellite's orbit against the diffuser time series to correct for solar incidence angle effects. An exponential function with a time constant of 200 days yields the best fit to the diffuser time series. The decrease in diffuser reflectance over the mission is wavelength dependent, ranging from 9% in the blue (412 nm) to 5% in the red and near infrared (670-865 nm). The Cal/Val team has developed a methodology for computing the signal-to-noise ratio (SNR) for SeaWiFS on orbit from the diffuser time series corrected for both the varying solar incidence angles and the diffuser reflectance degradation. A sensor noise model is used to compare on-orbit SNRs computed for radiances reflected from the diffuser with prelaunch SNRs measured at typical radiances specified for the instrument. To within the uncertainties in the measurements, the SNRs for SeaWiFS have not changed over the mission. The on-orbit performance of the SeaWiFS solar diffuser should offer insight into the long-term on-orbit performance of solar diffusers on other instruments, such as the Moderate-Resolution Imaging Spectrometer [currently flying on the Earth Observing System (EOS) Terra and Aqua satellites], the Visible and Infrared Radiometer Suite [scheduled to fly on the NASA National Polar-orbiting Operational Environmental Satellite System (NPOESS) and NPOESS Preparatory Project (NPP) satellites] and the Advanced Baseline Imager [scheduled to fly on the National Oceanic and Atmospheric Administration Geostationary Environmental Operational Satellite Series R (GOES-R) satellites].

Volumetric Visualization of Human Skin

NASA Astrophysics Data System (ADS)

Kawai, Toshiyuki; Kurioka, Yoshihiro

We propose a modeling and rendering technique of human skin, which can provide realistic color, gloss and translucency for various applications in computer graphics. Our method is based on volumetric representation of the structure inside of the skin. Our model consists of the stratum corneum and three layers of pigments. The stratum corneum has also layered structure in which the incident light is reflected, refracted and diffused. Each layer of pigment has carotene, melanin or hemoglobin. The density distributions of pigments which define the color of each layer can be supplied as one of the voxel values. Surface normals of upper-side voxels are fluctuated to produce bumps and lines on the skin. We apply ray tracing approach to this model to obtain the rendered image. Multiple scattering in the stratum corneum, reflective and absorptive spectrum of pigments are considered. We also consider Fresnel term to calculate the specular component for glossy surface of skin. Some examples of rendered images are shown, which can successfully visualize a human skin.

Ultra-broadband and planar sound diffuser with high uniformity of reflected intensity

NASA Astrophysics Data System (ADS)

Fan, Xu-Dong; Zhu, Yi-Fan; Liang, Bin; Yang, Jing; Yang, Jun; Cheng, Jian-Chun

2017-09-01

Schroeder diffusers, as a classical design of acoustic diffusers proposed over 40 years ago, play key roles in many practical scenarios ranging from architectural acoustics to noise control to particle manipulation. Despite the great success of conventional acoustic diffusers, it is still worth pursuing ideal acoustic diffusers that are essentially expected to produce perfect sound diffuse reflection within the unlimited bandwidth. Here, we propose a different mechanism for designing acoustic diffusers to overcome the basic limits in intensity uniformity and working bandwidth in the previous designs and demonstrate a practical implementation by acoustic metamaterials with dispersionless phase-steering capability. In stark contrast to the existing production of diffuse fields relying on random scattering of sound energy by using a specific mathematical number sequence of periodically distributed unit cells, we directly mold the reflected wavefront into the desired shape by precisely manipulating the local phases of individual subwavelength metastructures. We also benchmark our design via numerical simulation with a commercially available Schroeder diffuser, and the results verify that our proposed diffuser scatters incident acoustic energy into all directions more uniformly within an ultra-broad band regardless of the incident angle. Furthermore, our design enables further improvement of the working bandwidth just by simply downscaling each individual element. With ultra-broadband functionality and high uniformity of reflected intensity, our metamaterial-based production of the diffusive field opens a route to the design and application of acoustic diffusers and may have a significant impact on various fields such as architectural acoustics and medical ultrasound imaging/treatment.

Infrared reflectance spectra: effects of particle size, provenance and preparation

NASA Astrophysics Data System (ADS)

Su, Yin-Fong; Myers, Tanya L.; Brauer, Carolyn S.; Blake, Thomas A.; Forland, Brenda M.; Szecsody, J. E.; Johnson, Timothy J.

2014-10-01

We have recently developed methods for making more accurate infrared total and diffuse directional - hemispherical reflectance measurements using an integrating sphere. We have found that reflectance spectra of solids, especially powders, are influenced by a number of factors including the sample preparation method, the particle size and morphology, as well as the sample origin. On a quantitative basis we have investigated some of these parameters and the effects they have on reflectance spectra, particularly in the longwave infrared. In the IR the spectral features may be observed as either maxima or minima: In general, upward-going peaks in the reflectance spectrum result from strong surface scattering, i.e. rays that are reflected from the surface without bulk penetration, whereas downward-going peaks are due to either absorption or volume scattering, i.e. rays that have penetrated or refracted into the sample interior and are not reflected. The light signals reflected from solids usually encompass all such effects, but with strong dependencies on particle size and preparation. This paper measures the reflectance spectra in the 1.3 - 16 micron range for various bulk materials that have a combination of strong and weak absorption bands in order to observe the effects on the spectral features: Bulk materials were ground with a mortar and pestle and sieved to separate the samples into various size fractions between 5 and 500 microns. The median particle size is demonstrated to have large effects on the reflectance spectra. For certain minerals we also observe significant spectral change depending on the geologic origin of the sample. All three such effects (particle size, preparation and provenance) result in substantial change in the reflectance spectra for solid materials; successful identification algorithms will require sufficient flexibility to account for these parameters.

Melanin and blood concentration in human skin studied by multiple regression analysis: experiments

NASA Astrophysics Data System (ADS)

Shimada, M.; Yamada, Y.; Itoh, M.; Yatagai, T.

2001-09-01

Knowledge of the mechanism of human skin colour and measurement of melanin and blood concentration in human skin are needed in the medical and cosmetic fields. The absorbance spectrum from reflectance at the visible wavelength of human skin increases under several conditions such as a sunburn or scalding. The change of the absorbance spectrum from reflectance including the scattering effect does not correspond to the molar absorption spectrum of melanin and blood. The modified Beer-Lambert law is applied to the change in the absorbance spectrum from reflectance of human skin as the change in melanin and blood is assumed to be small. The concentration of melanin and blood was estimated from the absorbance spectrum reflectance of human skin using multiple regression analysis. Estimated concentrations were compared with the measured one in a phantom experiment and this method was applied to in vivo skin.

On the cosmic ray diffusion in a violent interstellar medium

NASA Technical Reports Server (NTRS)

Bykov, A. M.; Toptygin, I. N.

1985-01-01

A variety of the available observational data on the cosmic ray (CR) spectrum, anisotropy and composition are in good agreement with a suggestion on the diffusion propagation of CR with energy below 10(15) eV in the interstellar medium. The magnitude of the CR diffusion coefficient and its energy dependence are determined by interstellar medium (ISM) magnetic field spectra. Direct observational data on magnetic field spectra are still absent. A theoretical model to the turbulence generation in the multiphase ISM is resented. The model is based on the multiple generation of secondary shocks and concomitant large-scale rarefactions due to supernova shock interactions with interstellar clouds. The distribution function for ISM shocks are derived to include supernova statistics, diffuse cloud distribution, and various shock wave propagation regimes. This permits calculation of the ISM magnetic field fluctuation spectrum and CR diffusion coefficient for the hot phase of ISM.

Hazard calculations of diffuse reflected laser radiation for the SELENE program

NASA Technical Reports Server (NTRS)

Miner, Gilda A.; Babb, Phillip D.

1993-01-01

The hazards from diffuse laser light reflections off water clouds, ice clouds, and fog and from possible specular reflections off ice clouds were assessed with the American National Standards (ANSI Z136.1-1986) for the free-electron-laser parameters under consideration for the Segmented Efficient Laser Emission for Non-Nuclear Electricity (SELENE) Program. Diffuse laser reflection hazards exist for water cloud surfaces less than 722 m in altitude and ice cloud surfaces less than 850 m in altitude. Specular reflections from ice crystals in cirrus clouds are not probable; however, any specular reflection is a hazard to ground observers. The hazard to the laser operators and any ground observers during heavy fog conditions is of such significant magnitude that the laser should not be operated in fog.

Improved algorithm for estimating optical properties of food and biological materials using spatially-resolved diffuse reflectance

USDA-ARS?s Scientific Manuscript database

In this research, the inverse algorithm for estimating optical properties of food and biological materials from spatially-resolved diffuse reflectance was optimized in terms of data smoothing, normalization and spatial region of reflectance profile for curve fitting. Monte Carlo simulation was used ...

Nanostructured Antireflective and Thermoisolative Cicada Wings.

PubMed

Morikawa, Junko; Ryu, Meguya; Seniutinas, Gediminas; Balčytis, Armandas; Maximova, Ksenia; Wang, Xuewen; Zamengo, Massimiliano; Ivanova, Elena P; Juodkazis, Saulius

2016-05-10

Inter-related mechanical, thermal, and optical macroscopic properties of biomaterials are defined at the nanoscale by their constituent structures and patterns, which underpin complex functions of an entire bio-object. Here, the temperature diffusivity of a cicada (Cyclochila australasiae) wing with nanotextured surfaces was measured using two complementary techniques: a direct contact method and IR imaging. The 4-6-μm-thick wing section was shown to have a thermal diffusivity of α⊥ = (0.71 ± 0.15) × 10(-7) m(2)/s, as measured by the contact temperature wave method along the thickness of the wing; it corresponds to the inherent thermal property of the cuticle. The in-plane thermal diffusivity value of the wing was determined by IR imaging and was considerably larger at α∥ = (3.6 ± 0.2) × 10(-7) m(2)/s as a result of heat transport via air. Optical properties of wings covered with nanospikes were numerically simulated using an accurate 3D model of the wing pattern and showed that light is concentrated between spikes where intensity is enhanced by up to 3- to 4-fold. The closely packed pattern of nanospikes reduces the reflectivity of the wing throughout the visible light spectrum and over a wide range of incident angles, hence acting as an antireflection coating.

Diffuse attenuation coefficient for downwelling irradiance at 490 nm and its spectral characteristics in the Black Sea upper layer: modeling, in situ measurements and ocean color data

NASA Astrophysics Data System (ADS)

Suslin, V. V.; Slabakova, V. K.; Churilova, T. Ya.

2017-11-01

Vertical diffuse attenuation coefficient, Kd(490), is one of the key parameter required for water quality modeling, hydrodynamic and biological processes in the sea. We showed that standard level-2 product of Kd(490) was underestimated in comparison with Kd(490) values simulated by the regional model during the diatom bloom in the Black Sea. Using data of SeaWiFS, MERIS and MODIS color scanners, a regional relationship between the model value of Kd(490) and the ratio of remote sensing reflectances has been obtained. Based on the bulgarian argo-bio-buoy dataset, the relationship between the attenuation coefficient of photosynthetically active radiation and attenuation coefficient at a wavelength of 490 nm is obtained. The simplified model, below as the S-model, of the diffuse attenuation coefficient spectrum for downwelling irradiance in the Black Sea upper layer is described. As a consequence of the S-model, the link between the depth of the euphotic zone and Kd(490) has been obtained. It is shown that the Kd(490) values, retrieved from ocean color data with using the regional link and from argo-bio-buoy measurements at depths between 6-20 m, are close to each other.

Properties of seismic absorption induced reflections

NASA Astrophysics Data System (ADS)

Zhao, Haixia; Gao, Jinghuai; Peng, Jigen

2018-05-01

Seismic reflections at an interface are often regarded as the variation of the acoustic impedance (product of seismic velocity and density) in a medium. In fact, they can also be generated due to the difference in absorption of the seismic energy. In this paper, we investigate the properties of such reflections. Based on the diffusive-viscous wave equation and elastic diffusive-viscous wave equation, we investigate the dependency of the reflection coefficients on frequency, and their variations with incident angles. Numerical results at a boundary due to absorption contrasts are compared with those resulted from acoustic impedance variation. It is found that, the reflection coefficients resulted from absorption depend significantly on the frequency especially at lower frequencies, but vary very slowly at small incident angles. At the higher frequencies, the reflection coefficients of diffusive-viscous wave and elastic diffusive-viscous wave are close to those of acoustic and elastic cases, respectively. On the other hand, the reflections caused by acoustic impedance variation are independent of frequency but vary distinctly with incident angles before the critical angle. We also investigate the difference between the seismograms generated in the two different media. The numerical results show that the amplitudes of these reflected waves are attenuated and their phases are shifted. However, the reflections obtained by acoustic impedance contrast, show no significant amplitude attenuation and phase shift.

Spectral reflectance properties of black chrome for use as a solar selective coating

NASA Technical Reports Server (NTRS)

Mcdonald, G. E.

1974-01-01

The NASA-Lewis Research Center has determined that a widely available commercially electroplated decorative finish known as black chrome has desirable solar selective properties. Black chrome electroplated coating has high absorbtance in the solar spectrum and low emissivity in the 250 F blackbody thermal spectrum. The spectral reflectance properties of a commercially prepared black chrome on steel have been measured. Values are presented for reflectance of the black chrome, and compared with the reflectance of black paint and with two available samples of black nickel which had been prepared for solar selective properties. The reflectance of black chrome, of the two black nickels, and of black paint integrated over the solar spectrum for air mass 2 were 0.132, 0.123, 0.133, and 0.033, respectively. The reflectance of the black chrome, two black nickels, and of the black paint integrated over the blackbody spectrum for 250 F from 3 to 15 microns are 0.912, 0.934, 0.891, and 0.033, respectively. These reflectance measurements indicate absorptivity-to-emissivity values of 9.8, 13.8, 8.0, and 1.00, respectively.

Reflectance and fluorescence spectroscopies in photodynamic therapy

NASA Astrophysics Data System (ADS)

Finlay, Jarod C.

In vivo fluorescence spectroscopy during photodynamic therapy (PDT) has the potential to provide information on the distribution and degradation of sensitizers, the formation of fluorescent photoproducts and changes in tissue autofluorescence induced by photodynamic treatment. Reflectance spectroscopy allows quantification of light absorption and scattering in tissue. We present the results of several related studies of fluorescence and reflectance spectroscopy and their applications to photodynamic dosimetry. First, we develop and test an empirical method for the correction of the distortions imposed on fluorescence spectra by absorption and scattering in turbid media. We characterize the irradiance dependence of the in vivo photobleaching of three sensitizers, protoporphyrin IX (PpIX), Photofrin and mTHPC, in a rat skin model. The photobleaching and photoproduct formation of PpIX exhibit irradiance dependence consistent with singlet oxygen (1O2)-mediated bleaching. The bleaching of mTHPC occurs in two phases, only one of which is consistent with a 1O 2-mediated mechanism. Photofrin's bleaching is independent of irradiance, although its photoproduct formation is not. This can be explained by a mixed-mechanism bleaching model. Second, we develop an algorithm for the determination of tissue optical properties using diffuse reflectance spectra measured at a single source-detector separation and demonstrate the recovery of the hemoglobin oxygen dissociation curve from tissue-simulating phantoms containing human erythrocytes. This method is then used to investigate the heterogeneity of oxygenation response in murine tumors induced by carbogen inhalation. We find that while the response varies among animals and within each tumor, the majority of tumors exhibit an increase in blood oxygenation during carbogen breathing. We present a forward-adjoint model of fluorescence propagation that uses the optical property information acquired from reflectance spectroscopy to obtain the undistorted fluorescence spectrum over a wide range of optical properties. Finally, we investigate the ability of the forward-adjoint theory to extract undistorted fluorescence and optical property information simultaneously from a single measured fluorescence spectrum. This method can recover the hemoglobin oxygen dissociation curve in tissue-simulating phantoms with an accuracy comparable to that of reflectance-based methods while correcting distortions in the fluorescence over a wide range of absorption and scattering coefficients.

The evaluation of the photocatalytic activity of magnetic and non-magnetic polymorphs of Fe2O3 in natural sunlight exposure: A comparison of photocatalytic activity

NASA Astrophysics Data System (ADS)

Aslam, M.; Qamar, M. Tariq; Rehman, Ateeq Ur; Soomro, M. Tahir; Ali, Shahid; Ismail, I. M. I.; Hameed, A.

2018-09-01

The non-magnetic and magnetic polymorphs of iron oxide (Fe2O3) namely: α-Fe2O3 (hematite) and γ-Fe2O3 (maghemite) respectively, were synthesized by a facile surfactant aided hydrogel route. The synthesized polymorphs were characterized by diffuse reflectance, photoluminescence and raman spectroscopy for optical properties whereas the morphological, structural, chemical and electronic state evaluation were performed by FESEM, HRTEM, XRD, and XPS. The charge transport and the stability of the materials were examined electrochemically. The photocatalytic activity of the synthesized polymorphs was evaluated for the degradation of 2-chlorophenol and 2-nitrophenol in the exposure of the visible region and complete spectrum natural sunlight. Both the polymorphs exhibited a significantly high activity for the degradation of the phenolic substrate in the exposure of the complete spectrum of sunlight, however, the activity in the visible region of the sunlight was relatively lower. A substantial increase in the activity in the visible region was noticed when the polymorphs were exposed to complete spectrum sunlight prior to the photocatalytic experiments. The comparison of the exposed and unexposed samples revealed the induction of defects that served as traps for the excited electrons and increased activity of the polymorphs.

Intensity-Value Corrections for Integrating Sphere Measurements of Solid Samples Measured Behind Glass

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Timothy J.; Bernacki, Bruce E.; Redding, Rebecca L.

2014-11-01

Accurate and calibrated directional-hemispherical reflectance spectra of solids are important for both in situ and remote sensing. Many solids are in the form of powders or granules and to measure their diffuse reflectance spectra in the laboratory, it is often necessary to place the samples behind a transparent medium such as glass for the ultraviolet (UV), visible, or near-infrared spectral regions. Using both experimental methods and a simple optical model, we demonstrate that glass (fused quartz in our case) leads to artifacts in the reflectance values. We report our observations that the measured reflectance values, for both hemispherical and diffusemore » reflectance, are distorted by the additional reflections arising at the air–quartz and sample–quartz interfaces. The values are dependent on the sample reflectance and are offset in intensity in the hemispherical case, leading to measured values up to ~6% too high for a 2% reflectance surface, ~3.8% too high for 10% reflecting surfaces, approximately correct for 40–60% diffuse-reflecting surfaces, and ~1.5% too low for 99% reflecting Spectralon® surfaces. For the case of diffuse-only reflectance, the measured values are uniformly too low due to the polished glass, with differences of nearly 6% for a 99% reflecting matte surface. The deviations arise from the added reflections from the quartz surfaces, as verified by both theory and experiment, and depend on sphere design. Finally, empirical correction factors were implemented into post-processing software to redress the artifact for hemispherical and diffuse reflectance data across the 300–2300 nm range.« less

Infrared reflectance spectra: Effects of particle size, provenance and preparation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Su, Yin-Fong; Myers, Tanya L.; Brauer, Carolyn S.

2014-09-22

We have recently developed methods for making more accurate infrared total and diffuse directional - hemispherical reflectance measurements using an integrating sphere. We have found that reflectance spectra of solids, especially powders, are influenced by a number of factors including the sample preparation method, the particle size and morphology, as well as the sample origin. On a quantitative basis we have investigated some of these parameters and the effects they have on reflectance spectra, particularly in the longwave infrared. In the IR the spectral features may be observed as either maxima or minima: In general, upward-going peaks in the reflectancemore » spectrum result from strong surface scattering, i.e. rays that are reflected from the surface without bulk penetration, whereas downward-going peaks are due to either absorption or volume scattering, i.e. rays that have penetrated or refracted into the sample interior and are not reflected. The light signals reflected from solids usually encompass all such effects, but with strong dependencies on particle size and preparation. This paper measures the reflectance spectra in the 1.3 – 16 micron range for various bulk materials that have a combination of strong and weak absorption bands in order to observe the effects on the spectral features: Bulk materials were ground with a mortar and pestle and sieved to separate the samples into various size fractions between 5 and 500 microns. The median particle size is demonstrated to have large effects on the reflectance spectra. For certain minerals we also observe significant spectral change depending on the geologic origin of the sample. All three such effects (particle size, preparation and provenance) result in substantial change in the reflectance spectra for solid materials; successful identification algorithms will require sufficient flexibility to account for these parameters.« less

Identification of oil residues in Roman amphorae (Monte Testaccio, Rome): a comparative FTIR spectroscopic study of archeological and artificially aged samples.

PubMed

Tarquini, Gabriele; Nunziante Cesaro, Stella; Campanella, Luigi

2014-01-01

The application of Fourier Transform InfraRed (FTIR) spectroscopy to the analysis of oil residues in fragments of archeological amphorae (3rd century A.D.) from Monte Testaccio (Rome, Italy) is reported. In order to check the possibility to reveal the presence of oil residues in archeological pottery using microinvasive and\\or not invasive techniques, different approaches have been followed: firstly, FTIR spectroscopy was used to study oil residues extracted from roman amphorae. Secondly, the presence of oil residues was ascertained analyzing microamounts of archeological fragments with the Diffuse Reflectance Infrared Spectroscopy (DRIFT). Finally, the external reflection analysis of the ancient shards was performed without preliminary treatments evidencing the possibility to detect oil traces through the observation of the most intense features of its spectrum. Incidentally, the existence of carboxylate salts of fatty acids was also observed in DRIFT and Reflectance spectra of archeological samples supporting the roman habit of spreading lime over the spoil heaps. The data collected in all steps were always compared with results obtained on purposely made replicas. © 2013 Elsevier B.V. All rights reserved.

New mounting improves solar-cell efficiency

NASA Technical Reports Server (NTRS)

Shepard, N. F., Jr.

1980-01-01

Method boosts output by about 20 percent by trapping and redirecting solar radiation without increasing module depth. Mounted solar-cell array is covered with internally reflecting plate. Plate is attached to each cell by transparent adhesive, and space between cells is covered with layer of diffusely reflecting material. Solar energy falling on space between cells is diffused and reflected internally by plate until it is reflected onto solar cell.

Diffuse reflectance of TiO 2 pigmented paints: Spectral dependence of the average pathlength parameter and the forward scattering ratio

NASA Astrophysics Data System (ADS)

Vargas, William E.; Amador, Alvaro; Niklasson, Gunnar A.

2006-05-01

Diffuse reflectance spectra of paint coatings with different pigment concentrations, normally illuminated with unpolarized radiation, have been measured. A four-flux radiative transfer approach is used to model the diffuse reflectance of TiO2 (rutile) pigmented coatings through the solar spectral range. The spectral dependence of the average pathlength parameter and of the forward scattering ratio for diffuse radiation, are explicitly incorporated into this four-flux model from two novel approximations. The size distribution of the pigments has been taken into account to obtain the averages of the four-flux parameters: scattering and absorption cross sections, forward scattering ratios for collimated and isotropic diffuse radiation, and coefficients involved in the expansion of the single particle phase function in terms of Legendre polynomials.

Selective radiative cooling with MgO and/or LiF layers

DOEpatents

Berdahl, P.H.

1984-09-14

A selective radiation cooling material which is absorptive only in the 8 to 13 microns wavelength range is accomplished by placing ceramic magnesium oxide and/or polycrystalline lithium fluoride on an infrared-reflective substrate. The reflecting substrate may be a metallic coating, foil or sheet, such as aluminum, which reflects all atmospheric radiation from 0.3 to 8 microns, the magnesium oxide and lithium fluoride being nonabsorptive at those wavelengths. <10% of submicron voids in the material is permissible in which case the MgO and/or LiF layer is diffusely scattering, but still nonabsorbing, in the wavelength range of 0.3 to 8 microns. At wavelengths from 8 to 13 microns, the magnesium oxide and lithium fluoride radiate power through the ''window'' in the atmosphere, and thus remove heat from the reflecting sheet of material and the attached object to be cooled. At wavelengths longer than 13 microns, the magnesium oxide and lithium fluoride reflects the atmospheric radiation back into the atmosphere. This high reflectance is only obtained if the surface is sufficiently smooth: roughness on a scale of 1 micron is permissible but roughness on a scale of 10 microns is not. An infrared-transmitting cover or shield is mounted in spaced relationship to the material to reduce convective heat transfer. If this is utilized in direct sunlight, the infrared transmitting cover or shield should be opaque in the solar spectrum of 0.3 to 3 microns.

The study of frequency-scan photothermal reflectance technique for thermal diffusivity measurement

DOE PAGES

Hua, Zilong; Ban, Heng; Hurley, David H.

2015-05-05

A frequency scan photothermal reflectance technique to measure thermal diffusivity of bulk samples is studied in this manuscript. Similar to general photothermal reflectance methods, an intensity-modulated heating laser and a constant intensity probe laser are used to determine the surface temperature response under sinusoidal heating. The approach involves fixing the distance between the heating and probe laser spots, recording the phase lag of reflected probe laser intensity with respect to the heating laser frequency modulation, and extracting thermal diffusivity using the phase lag – (frequency) 1/2 relation. The experimental validation is performed on three samples (SiO 2, CaF 2 andmore » Ge), which have a wide range of thermal diffusivities. The measured thermal diffusivity values agree closely with literature values. Lastly, compared to the commonly used spatial scan method, the experimental setup and operation of the frequency scan method are simplified, and the uncertainty level is equal to or smaller than that of the spatial scan method.« less

The study of frequency-scan photothermal reflectance technique for thermal diffusivity measurement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hua, Zilong; Ban, Heng; Hurley, David H.

A frequency scan photothermal reflectance technique to measure thermal diffusivity of bulk samples is studied in this manuscript. Similar to general photothermal reflectance methods, an intensity-modulated heating laser and a constant intensity probe laser are used to determine the surface temperature response under sinusoidal heating. The approach involves fixing the distance between the heating and probe laser spots, recording the phase lag of reflected probe laser intensity with respect to the heating laser frequency modulation, and extracting thermal diffusivity using the phase lag – (frequency) 1/2 relation. The experimental validation is performed on three samples (SiO 2, CaF 2 andmore » Ge), which have a wide range of thermal diffusivities. The measured thermal diffusivity values agree closely with literature values. Lastly, compared to the commonly used spatial scan method, the experimental setup and operation of the frequency scan method are simplified, and the uncertainty level is equal to or smaller than that of the spatial scan method.« less

Soft tissue differentiation by diffuse reflectance spectroscopy

NASA Astrophysics Data System (ADS)

Zam, Azhar; Stelzle, Florian; Nkenke, Emeka; Tangermann-Gerk, Katja; Schmidt, Michael; Adler, Werner; Douplik, Alexandre

2009-07-01

Laser surgery gives the possibility to work remotely which leads to high precision, little trauma and high level sterility. However these advantages are coming with the lack of haptic feedback during the laser ablation of tissue. Therefore additional means are required to control tissue-specific ablation during laser surgery supporting the surgeon regardless of experience and skills. Diffuse Reflectance Spectroscopy provides a straightforward and simple approach for optical tissue differentiation. We measured diffuse reflectance from four various tissue types ex vivo. We applied Linear Discriminant Analysis (LDA) to differentiate the four tissue types and computed the area under the ROC curve (AUC). Special emphasis was taken on the identification of nerve as the most crucial tissue for maxillofacial surgery. The results show a promise for differentiating soft tissues as guidance for tissue-specific laser surgery by means of the diffuse reflectance.

[A Method to Reconstruct Surface Reflectance Spectrum from Multispectral Image Based on Canopy Radiation Transfer Model].

PubMed

Zhao, Yong-guang; Ma, Ling-ling; Li, Chuan-rong; Zhu, Xiao-hua; Tang, Ling-li

2015-07-01

Due to the lack of enough spectral bands for multi-spectral sensor, it is difficult to reconstruct surface retlectance spectrum from finite spectral information acquired by multi-spectral instrument. Here, taking into full account of the heterogeneity of pixel from remote sensing image, a method is proposed to simulate hyperspectral data from multispectral data based on canopy radiation transfer model. This method first assumes the mixed pixels contain two types of land cover, i.e., vegetation and soil. The sensitive parameters of Soil-Leaf-Canopy (SLC) model and a soil ratio factor were retrieved from multi-spectral data based on Look-Up Table (LUT) technology. Then, by combined with a soil ratio factor, all the parameters were input into the SLC model to simulate the surface reflectance spectrum from 400 to 2 400 nm. Taking Landsat Enhanced Thematic Mapper Plus (ETM+) image as reference image, the surface reflectance spectrum was simulated. The simulated reflectance spectrum revealed different feature information of different surface types. To test the performance of this method, the simulated reflectance spectrum was convolved with the Landsat ETM + spectral response curves and Moderate Resolution Imaging Spectrometer (MODIS) spectral response curves to obtain the simulated Landsat ETM+ and MODIS image. Finally, the simulated Landsat ETM+ and MODIS images were compared with the observed Landsat ETM+ and MODIS images. The results generally showed high correction coefficients (Landsat: 0.90-0.99, MODIS: 0.74-0.85) between most simulated bands and observed bands and indicated that the simulated reflectance spectrum was well simulated and reliable.

Surface Temperature Measurement Using Hematite Coating

NASA Technical Reports Server (NTRS)

Bencic, Timothy J. (Inventor)

2015-01-01

Systems and methods that are capable of measuring temperature via spectrophotometry principles are discussed herein. These systems and methods are based on the temperature dependence of the reflection spectrum of hematite. Light reflected from these sensors can be measured to determine a temperature, based on changes in the reflection spectrum discussed herein.

Translational Imaging Spectroscopy for Proximal Sensing

PubMed Central

Rogass, Christian; Koerting, Friederike M.; Mielke, Christian; Brell, Maximilian; Boesche, Nina K.; Bade, Maria; Hohmann, Christian

2017-01-01

Proximal sensing as the near field counterpart of remote sensing offers a broad variety of applications. Imaging spectroscopy in general and translational laboratory imaging spectroscopy in particular can be utilized for a variety of different research topics. Geoscientific applications require a precise pre-processing of hyperspectral data cubes to retrieve at-surface reflectance in order to conduct spectral feature-based comparison of unknown sample spectra to known library spectra. A new pre-processing chain called GeoMAP-Trans for at-surface reflectance retrieval is proposed here as an analogue to other algorithms published by the team of authors. It consists of a radiometric, a geometric and a spectral module. Each module consists of several processing steps that are described in detail. The processing chain was adapted to the broadly used HySPEX VNIR/SWIR imaging spectrometer system and tested using geological mineral samples. The performance was subjectively and objectively evaluated using standard artificial image quality metrics and comparative measurements of mineral and Lambertian diffuser standards with standard field and laboratory spectrometers. The proposed algorithm provides highly qualitative results, offers broad applicability through its generic design and might be the first one of its kind to be published. A high radiometric accuracy is achieved by the incorporation of the Reduction of Miscalibration Effects (ROME) framework. The geometric accuracy is higher than 1 μpixel. The critical spectral accuracy was relatively estimated by comparing spectra of standard field spectrometers to those from HySPEX for a Lambertian diffuser. The achieved spectral accuracy is better than 0.02% for the full spectrum and better than 98% for the absorption features. It was empirically shown that point and imaging spectrometers provide different results for non-Lambertian samples due to their different sensing principles, adjacency scattering impacts on the signal and anisotropic surface reflection properties. PMID:28800111

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Huafeng; Colabello, Diane M.; Sklute, Elizabeth C.

The absolute absorption coefficient, α(E), is a critical design parameter for devices using semiconductors for light harvesting associated with renewable energy production, both for classic technologies such as photovoltaics and for emerging technologies such as direct solar fuel production. While α(E) is well-known for many classic simple semiconductors used in photovoltaic applications, the absolute values of α(E) are typically unknown for the complex semiconductors being explored for solar fuel production due to the absence of single crystals or crystalline epitaxial films that are needed for conventional methods of determining α(E). In this work, a simple self-referenced method for estimating bothmore » the refractive indices, n(E), and absolute absorption coefficients, α(E), for loose powder samples using diffuse reflectance data is demonstrated. In this method, the sample refractive index can be deduced by refining n to maximize the agreement between the relative absorption spectrum calculated from bidirectional reflectance data (calculated through a Hapke transform which depends on n) and integrating sphere diffuse reflectance data (calculated through a Kubleka–Munk transform which does not depend on n). This new method can be quickly used to screen the suitability of emerging semiconductor systems for light-harvesting applications. The effectiveness of this approach is tested using the simple classic semiconductors Ge and Fe 2O 3 as well as the complex semiconductors La 2MoO 5 and La 4Mo 2O 11. The method is shown to work well for powders with a narrow size distribution (exemplified by Fe 2O 3) and to be ineffective for semiconductors with a broad size distribution (exemplified by Ge). As such, it provides a means for rapidly estimating the absolute optical properties of complex solids which are only available as loose powders.« less

Color Vision Losses in Autism Spectrum Disorders

PubMed Central

Zachi, Elaine C.; Costa, Thiago L.; Barboni, Mirella T. S.; Costa, Marcelo F.; Bonci, Daniela M. O.; Ventura, Dora F.

2017-01-01

Autism spectrum disorders (ASDs) are neurodevelopmental conditions characterized by impairments in social/communication abilities and restricted behaviors. The present study aims to examine color vision discrimination in ASD children and adolescents without intellectual disability. The participants were also subdivided in order to compare color vision thresholds of autistic participants and those who achieved diagnostic criteria for Asperger Syndrome (AS). Nine subjects with autism, 11 participants with AS and 36 typically developing children and adolescents participated in the study. Color vision was assessed by the Cambridge Color Test (CCT). The Trivector protocol was administered to determine color discrimination thresholds along the protan, deutan, and tritan color confusion lines. Data from ASD participants were compared to tolerance limits for 90% of the population with 90% probability obtained from controls thresholds. Of the 20 ASD individuals examined, 6 (30%) showed color vision losses. Elevated color discrimination thresholds were found in 3/9 participants with autism and in 3/11 AS participants. Diffuse and tritan deficits were found. Mechanisms for chromatic losses may be either at the retinal level and/or reflect reduced cortical integration. PMID:28713324

Density Convection near Radiating ICRF Antennas and its Effect on the Coupling of Lower Hybrid Waves

NASA Astrophysics Data System (ADS)

Ekedahl, A.; Colas, L.; Mayoral, M.-L.; Beaumont, B.; Bibet, Ph.; Brémond, S.; Kazarian, F.; Mailloux, J.; Noterdaeme, J.-M.; Efda-Jet Contributors

2003-12-01

Combined operation of Lower Hybrid (LH) and Ion Cyclotron Resonance Frequency (ICRF) waves can result in a degradation of the LH wave coupling, as observed both in the Tore Supra and JET tokamaks. The reflection coefficient on the part of the LH launcher magnetically connected to the powered ICRF antenna increases, suggesting a local decrease in the electron density in the connecting flux tubes. This has been confirmed by Langmuir probe measurements on the LH launchers in the latest Tore Supra experiments. Moreover, recent experiments in JET indicate that the LH coupling degradation depends on the ICRF power and its launched k//-spectrum. The 2D density distribution around the Tore Supra ICRF antennas has been modelled with the CELLS-code, balancing parallel losses with diffusive transport and sheath induced E×B convection, obtained from RF field mapping using the ICANT-code. The calculations are in qualitative agreement with the experimental observations, i.e. density depletion is obtained, localised mainly in the antenna shadow, and dependent on ICRF power and antenna spectrum.

Improved full analytical polygon-based method using Fourier analysis of the three-dimensional affine transformation.

PubMed

Pan, Yijie; Wang, Yongtian; Liu, Juan; Li, Xin; Jia, Jia

2014-03-01

Previous research [Appl. Opt.52, A290 (2013)] has revealed that Fourier analysis of three-dimensional affine transformation theory can be used to improve the computation speed of the traditional polygon-based method. In this paper, we continue our research and propose an improved full analytical polygon-based method developed upon this theory. Vertex vectors of primitive and arbitrary triangles and the pseudo-inverse matrix were used to obtain an affine transformation matrix representing the spatial relationship between the two triangles. With this relationship and the primitive spectrum, we analytically obtained the spectrum of the arbitrary triangle. This algorithm discards low-level angular dependent computations. In order to add diffusive reflection to each arbitrary surface, we also propose a whole matrix computation approach that takes advantage of the affine transformation matrix and uses matrix multiplication to calculate shifting parameters of similar sub-polygons. The proposed method improves hologram computation speed for the conventional full analytical approach. Optical experimental results are demonstrated which prove that the proposed method can effectively reconstruct three-dimensional scenes.

Method for Estimating Bilirubin Isomerization Efficiency in Phototherapy to Treat Neonatal Jaundice

NASA Astrophysics Data System (ADS)

Lisenko, S. A.; Kugeiko, M. M.

2014-11-01

We propose a method for quantitative assessment of the efficacy of phototherapy to treat neonatal jaundice using the diffuse reflectance spectrum for the newborn's skin, based on the analytical dependence of the measured spectrum on the structural and morphological parameters of the skin, affecting the optical conditions in the medium, and an algorithm for rapid calculation of the bilirubin photoisomerization rate in the skin tissues as a function of the structural and morphological parameters of the skin and the wavelength of the exciting radiation. From the results of a numerical simulation of the process of radiation transport in the skin, we assess the stability of our method to variations in the scattering properties of the skin and the concentrations of its optically active chromophores (melanin, oxyhemoglobin, deoxyhemoglobin). We show that in order to achieve the maximum efficacy of phototherapy, we should use light from the range 484-496 nm. In this case, the intensity of the exciting radiation should be selected individually for each newborn according to the bilirubin photoisomerization rate characteristic for it.

Absorption spectra and light penetration depth of normal and pathologically altered human skin

NASA Astrophysics Data System (ADS)

Barun, V. V.; Ivanov, A. P.; Volotovskaya, A. V.; Ulashchik, V. S.

2007-05-01

A three-layered skin model (stratum corneum, epidermis, and dermis) and engineering formulas for radiative transfer theory are used to study absorption spectra and light penetration depths of normal and pathologically altered skin. The formulas include small-angle and asymptotic approximations and a layer-addition method. These characteristics are calculated for wavelengths used for low-intensity laser therapy. We examined several pathologies such as vitiligo, edema, erythematosus lupus, and subcutaneous wound, for which the bulk concentrations of melanin and blood vessels or tissue structure (for subcutaneous wound) change compared with normal skin. The penetration depth spectrum is very similar to the inverted blood absorption spectrum. In other words, the depth is minimal at blood absorption maxima. The calculated absorption spectra enable the power and irradiation wavelength providing the required light effect to be selected. Relationships between the penetration depth and the diffuse reflectance coefficient of skin (unambiguously expressed through the absorption coefficient) are analyzed at different wavelengths. This makes it possible to find relationships between the light fields inside and outside the tissue.

The color of the Martian sky and its influence on the illumination of the Martian surface

USGS Publications Warehouse

Thomas, N.; Markiewicz, W.J.; Sablotny, R.M.; Wuttke, M.W.; Keller, H.U.; Johnson, J. R.; Reid, R.J.; Smith, R.H.

1999-01-01

The dust in the atmosphere above the Mars Pathfinder landing site produced a bright, red sky that increases in redness toward the horizon at midday. There is also evidence for an absorption band in the scattered light from the sky at 860 nm. A model of the sky brightness has been developed [Markiewicz et al., this issue] and tested against Imager for Mars Pathfinder (IMP) observations of calibration targets on the lander. The resulting model has been used to quantify the total diffuse flux onto a surface parallel to the local level for several solar elevation angles and optical depths. The model shows that the diffuse illumination in shadowed areas is strongly reddened while areas illuminated directly by the Sun (and the blue forward scattering peak) see a more solar-type spectrum, in agreement with Viking and IMP observations. Quantitative corrections for the reddening in shadowed areas are demonstrated. It is shown quantitatively that the unusual appearance of the rock Yogi (the east face of which appeared relatively blue in images taken during the morning but relatively red during the afternoon) can be explained purely by the changing illumination geometry. We conclude that any spectrophotometric analysis of surfaces on Mars must take into account the diffuse flux. Specifically, the reflectances of surfaces viewed under different illumination geometries cannot be investigated for spectral diversity unless a correction has been applied which removes the influence of the reddened diffuse flux. Copyright 1999 by the American Geophysical Union.

Converting Multi-Shell and Diffusion Spectrum Imaging to High Angular Resolution Diffusion Imaging

PubMed Central

Yeh, Fang-Cheng; Verstynen, Timothy D.

2016-01-01

Multi-shell and diffusion spectrum imaging (DSI) are becoming increasingly popular methods of acquiring diffusion MRI data in a research context. However, single-shell acquisitions, such as diffusion tensor imaging (DTI) and high angular resolution diffusion imaging (HARDI), still remain the most common acquisition schemes in practice. Here we tested whether multi-shell and DSI data have conversion flexibility to be interpolated into corresponding HARDI data. We acquired multi-shell and DSI data on both a phantom and in vivo human tissue and converted them to HARDI. The correlation and difference between their diffusion signals, anisotropy values, diffusivity measurements, fiber orientations, connectivity matrices, and network measures were examined. Our analysis result showed that the diffusion signals, anisotropy, diffusivity, and connectivity matrix of the HARDI converted from multi-shell and DSI were highly correlated with those of the HARDI acquired on the MR scanner, with correlation coefficients around 0.8~0.9. The average angular error between converted and original HARDI was 20.7° at voxels with signal-to-noise ratios greater than 5. The network topology measures had less than 2% difference, whereas the average nodal measures had a percentage difference around 4~7%. In general, multi-shell and DSI acquisitions can be converted to their corresponding single-shell HARDI with high fidelity. This supports multi-shell and DSI acquisitions over HARDI acquisition as the scheme of choice for diffusion acquisitions. PMID:27683539

Quantitative analysis of binary polymorphs mixtures of fusidic acid by diffuse reflectance FTIR spectroscopy, diffuse reflectance FT-NIR spectroscopy, Raman spectroscopy and multivariate calibration.

PubMed

Guo, Canyong; Luo, Xuefang; Zhou, Xiaohua; Shi, Beijia; Wang, Juanjuan; Zhao, Jinqi; Zhang, Xiaoxia

2017-06-05

Vibrational spectroscopic techniques such as infrared, near-infrared and Raman spectroscopy have become popular in detecting and quantifying polymorphism of pharmaceutics since they are fast and non-destructive. This study assessed the ability of three vibrational spectroscopy combined with multivariate analysis to quantify a low-content undesired polymorph within a binary polymorphic mixture. Partial least squares (PLS) regression and support vector machine (SVM) regression were employed to build quantitative models. Fusidic acid, a steroidal antibiotic, was used as the model compound. It was found that PLS regression performed slightly better than SVM regression in all the three spectroscopic techniques. Root mean square errors of prediction (RMSEP) were ranging from 0.48% to 1.17% for diffuse reflectance FTIR spectroscopy and 1.60-1.93% for diffuse reflectance FT-NIR spectroscopy and 1.62-2.31% for Raman spectroscopy. The results indicate that diffuse reflectance FTIR spectroscopy offers significant advantages in providing accurate measurement of polymorphic content in the fusidic acid binary mixtures, while Raman spectroscopy is the least accurate technique for quantitative analysis of polymorphs. Copyright © 2017 Elsevier B.V. All rights reserved.

Frontal networks in adults with autism spectrum disorder

PubMed Central

Catani, Marco; Dell’Acqua, Flavio; Budisavljevic, Sanja; Howells, Henrietta; Thiebaut de Schotten, Michel; Froudist-Walsh, Seán; D’Anna, Lucio; Thompson, Abigail; Sandrone, Stefano; Bullmore, Edward T.; Suckling, John; Baron-Cohen, Simon; Lombardo, Michael V.; Wheelwright, Sally J.; Chakrabarti, Bhismadev; Lai, Meng-Chuan; Ruigrok, Amber N. V.; Leemans, Alexander; Ecker, Christine; Consortium, MRC AIMS; Craig, Michael C.

2016-01-01

Abstract It has been postulated that autism spectrum disorder is underpinned by an ‘atypical connectivity’ involving higher-order association brain regions. To test this hypothesis in a large cohort of adults with autism spectrum disorder we compared the white matter networks of 61 adult males with autism spectrum disorder and 61 neurotypical controls, using two complementary approaches to diffusion tensor magnetic resonance imaging. First, we applied tract-based spatial statistics, a ‘whole brain’ non-hypothesis driven method, to identify differences in white matter networks in adults with autism spectrum disorder. Following this we used a tract-specific analysis, based on tractography, to carry out a more detailed analysis of individual tracts identified by tract-based spatial statistics. Finally, within the autism spectrum disorder group, we studied the relationship between diffusion measures and autistic symptom severity. Tract-based spatial statistics revealed that autism spectrum disorder was associated with significantly reduced fractional anisotropy in regions that included frontal lobe pathways. Tractography analysis of these specific pathways showed increased mean and perpendicular diffusivity, and reduced number of streamlines in the anterior and long segments of the arcuate fasciculus, cingulum and uncinate—predominantly in the left hemisphere. Abnormalities were also evident in the anterior portions of the corpus callosum connecting left and right frontal lobes. The degree of microstructural alteration of the arcuate and uncinate fasciculi was associated with severity of symptoms in language and social reciprocity in childhood. Our results indicated that autism spectrum disorder is a developmental condition associated with abnormal connectivity of the frontal lobes. Furthermore our findings showed that male adults with autism spectrum disorder have regional differences in brain anatomy, which correlate with specific aspects of autistic symptoms. Overall these results suggest that autism spectrum disorder is a condition linked to aberrant developmental trajectories of the frontal networks that persist in adult life. PMID:26912520

Frontal networks in adults with autism spectrum disorder.

PubMed

Catani, Marco; Dell'Acqua, Flavio; Budisavljevic, Sanja; Howells, Henrietta; Thiebaut de Schotten, Michel; Froudist-Walsh, Seán; D'Anna, Lucio; Thompson, Abigail; Sandrone, Stefano; Bullmore, Edward T; Suckling, John; Baron-Cohen, Simon; Lombardo, Michael V; Wheelwright, Sally J; Chakrabarti, Bhismadev; Lai, Meng-Chuan; Ruigrok, Amber N V; Leemans, Alexander; Ecker, Christine; Consortium, Mrc Aims; Craig, Michael C; Murphy, Declan G M

2016-02-01

It has been postulated that autism spectrum disorder is underpinned by an 'atypical connectivity' involving higher-order association brain regions. To test this hypothesis in a large cohort of adults with autism spectrum disorder we compared the white matter networks of 61 adult males with autism spectrum disorder and 61 neurotypical controls, using two complementary approaches to diffusion tensor magnetic resonance imaging. First, we applied tract-based spatial statistics, a 'whole brain' non-hypothesis driven method, to identify differences in white matter networks in adults with autism spectrum disorder. Following this we used a tract-specific analysis, based on tractography, to carry out a more detailed analysis of individual tracts identified by tract-based spatial statistics. Finally, within the autism spectrum disorder group, we studied the relationship between diffusion measures and autistic symptom severity. Tract-based spatial statistics revealed that autism spectrum disorder was associated with significantly reduced fractional anisotropy in regions that included frontal lobe pathways. Tractography analysis of these specific pathways showed increased mean and perpendicular diffusivity, and reduced number of streamlines in the anterior and long segments of the arcuate fasciculus, cingulum and uncinate--predominantly in the left hemisphere. Abnormalities were also evident in the anterior portions of the corpus callosum connecting left and right frontal lobes. The degree of microstructural alteration of the arcuate and uncinate fasciculi was associated with severity of symptoms in language and social reciprocity in childhood. Our results indicated that autism spectrum disorder is a developmental condition associated with abnormal connectivity of the frontal lobes. Furthermore our findings showed that male adults with autism spectrum disorder have regional differences in brain anatomy, which correlate with specific aspects of autistic symptoms. Overall these results suggest that autism spectrum disorder is a condition linked to aberrant developmental trajectories of the frontal networks that persist in adult life. © The Author (2016). Published by Oxford University Press on behalf of the Guarantors of Brain.

In vivo soft tissue differentiation by diffuse reflectance spectroscopy: preliminary results

NASA Astrophysics Data System (ADS)

Zam, Azhar; Stelzle, Florian; Tangermann-Gerk, Katja; Adler, Werner; Nkenke, Emeka; Neukam, Friedrich Wilhelm; Schmidt, Michael; Douplik, Alexandre

Remote laser surgery does not provide haptic feedback to operate layer by layer and preserve vulnerable anatomical structures like nerve tissue or blood vessels. The aim of this study is identification of soft tissue in vivo by diffuse reflectance spectroscopy to set the base for a feedback control system to enhance nerve preservation in oral and maxillofacial laser surgery. Various soft tissues can be identified by diffuse reflectance spectroscopy in vivo. The results may set the base for a feedback system to prevent nerve damage during oral and maxillofacial laser surgery.

In Search of Multi-Peaked Reflective Spectrum with Optic Fiber Bragg Grating Sensor for Dynamic Strain Measurement

NASA Technical Reports Server (NTRS)

Tai, Hsiang

2006-01-01

In a typical optic fiber Bragg grating (FBG) strain measurement, unless in an ideal static laboratory environment, the presence of vibration or often disturbance always exists, which often creates spurious multiple peaks in the reflected spectrum, resulting in a non-unique determination of strain value. In this report we attempt to investigate the origin of this phenomenon by physical arguments and simple numerical simulation. We postulate that the fiber gratings execute small amplitude transverse vibrations changing the optical path in which the reflected light traverses slightly and non-uniformly. Ultimately, this causes the multi-peak reflected spectrum.

Optical device for thermal diffusivity determination in liquids by reflection of a thermal wave

NASA Astrophysics Data System (ADS)

Sánchez-Pérez, C.; De León-Hernández, A.; García-Cadena, C.

2017-08-01

In this work, we present a device for determination of the thermal diffusivity using the oblique reflection of a thermal wave within a solid slab that is in contact with the medium to be characterized. By using the reflection near a critical angle under the assumption that thermal waves obey Snell's law of refraction with the square root of the thermal diffusivities, the unknown thermal diffusivity is obtained by simple formulae. Experimentally, the sensor response is measured using the photothermal beam deflection technique within a slab that results in a compact device with no contact of the laser probing beam with the sample. We describe the theoretical basis and provide experimental results to validate the proposed method. We determine the thermal diffusivity of tridistilled water and glycerin solutions with an error of less than 0.5%.

[Spectral Study on the Effects of Angle-Tuned Filter Wedge Angle Parameter to Reflecting Characteristics].

PubMed

Yu, Kan; Huang, De-xiu; Yin, Juan-juan; Bao, Jia-qi

2015-08-01

Three-port tunable optical filter is a key device in the all-optic intelligent switching network and dense wavelength division multiplexing system. The characteristics of the reflecting spectrum, especially the reflectivity and the isolation degree are very important to the three-port filter. Angle-tuned thin film filter is widely used as a three-port tunable filter for its high rectangular degree and good temperature stability. The characteristics of the reflecting spectrum are greatly influenced not only by the incident angle, but also by the wedge angle parameter of the non-paralleled wedge thin film filter. In the present paper, the influences of the wedge angle parameter to the reflectivity and the half bandwidth are analyzed, and the reflecting spectrum characterstics are simulationed in different wedge angle parameter and polarity. The wedge angle-tuned thin film filter with 0.8° wedge angle parameter is fabricated. The experimental results show that keeping the wedge angle the same orientation to the incident angle will worsen the reflectivity and the rectangular degree of the reflecting spectrum. However, keeping the wedge angle orientation reverse to the incident angle will enhance the reflectivity and decrease the bandwidth, which will give higher reflectivity and isolation degree to the three-port filter than that of high parallel degree angle-tuned thin film filter.

Fermi LAT Search for Dark Matter in Gamma-Ray Lines and the Inclusive Photon Spectrum

NASA Technical Reports Server (NTRS)

Ackermann, M.; Ajello, M.; Albert, A.; Baldini, L.; Barbiellini, G.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Blandford, R. D.; Bloom, E. D.;

Fermi LAT search for dark matter in gamma-ray lines and the inclusive photon spectrum

DOE PAGES

Ackermann, M.

2012-07-05

Dark matter particle annihilation or decay can produce monochromatic gamma-ray lines and contribute to the diffuse gamma-ray background. Furthermore, we present the flux upper limits for gamma-ray spectral lines from 7 to 200 GeV and for the diffuse gamma-ray background from 4.8 GeV to 264 GeV obtained from two years of Fermi Large Area Telescope data integrated over most of the sky. Here, we give cross-section upper limits and decay lifetime lower limits for dark matter models that produce gamma-ray lines or contribute to the diffuse spectrum, including models proposed as explanations of the PAMELA and Fermi cosmic-ray data.

Using reflectance spectroscopy to predict beef tenderness.

PubMed

Bowling, M B; Vote, D J; Belk, K E; Scanga, J A; Tatum, J D; Smith, G C

2009-05-01

A study was conducted to determine if reflectance measurements made in the near-infrared region of the spectrum were additive to reflectance measurements made in the visible region of the spectrum for predicting Warner-Bratzler shear force (WBSF) values. Eighty seven strip loins were collected following fabrication over 3d at a commercial beef processing facility from heifer carcasses with Slight or Traces marbling scores. Spectroscopic measurements were made at approximately 50h postmortem using a Hunter-Lab UltraScan. Subsequently, all strip loins were aged for 14d, cooked to an internal temperature of 70°C, and sheared to obtain WBSF values. Reflectance measurements obtained in the near-infrared region of the spectrum were correlated with WBSF values, however, these measurements were not additive to the predictive ability of reflectance measurements (R(2) values did not differ) made in the visible portion of the spectrum when the use of broad-band wavelength filters were simulated. It was therefore determined, that both the visible and near-infrared spectra measure reflectance and that both methods are acceptable methods of tenderness prediction.

A method of online quantitative interpretation of diffuse reflection profiles of biological tissues

NASA Astrophysics Data System (ADS)

Lisenko, S. A.; Kugeiko, M. M.

2013-02-01

We have developed a method of combined interpretation of spectral and spatial characteristics of diffuse reflection of biological tissues, which makes it possible to determine biophysical parameters of the tissue with a high accuracy in real time under conditions of their general variability. Using the Monte Carlo method, we have modeled a statistical ensemble of profiles of diffuse reflection coefficients of skin, which corresponds to a wave variation of its biophysical parameters. On its basis, we have estimated the retrieval accuracy of biophysical parameters using the developed method and investigated the stability of the method to errors of optical measurements. We have showed that it is possible to determine online the concentrations of melanin, hemoglobin, bilirubin, oxygen saturation of blood, and structural parameters of skin from measurements of its diffuse reflection in the spectral range 450-800 nm at three distances between the radiation source and detector.

Combination of acoustical radiosity and the image source method.

PubMed

Koutsouris, Georgios I; Brunskog, Jonas; Jeong, Cheol-Ho; Jacobsen, Finn

2013-06-01

A combined model for room acoustic predictions is developed, aiming to treat both diffuse and specular reflections in a unified way. Two established methods are incorporated: acoustical radiosity, accounting for the diffuse part, and the image source method, accounting for the specular part. The model is based on conservation of acoustical energy. Losses are taken into account by the energy absorption coefficient, and the diffuse reflections are controlled via the scattering coefficient, which defines the portion of energy that has been diffusely reflected. The way the model is formulated allows for a dynamic control of the image source production, so that no fixed maximum reflection order is required. The model is optimized for energy impulse response predictions in arbitrary polyhedral rooms. The predictions are validated by comparison with published measured data for a real music studio hall. The proposed model turns out to be promising for acoustic predictions providing a high level of detail and accuracy.

Optical diffuse reflectance accessory for measurements of skin tissue by near-infrared spectroscopy

NASA Astrophysics Data System (ADS)

Marbach, R.; Heise, H. M.

1995-02-01

An optimized accessory for measuring the diffuse reflectance spectra of human skin tissue in the near-infrared spectral range is presented. The device includes an on-axis ellipsoidal collecting mirror with efficient illumination optics for small sampling areas of bulky body specimens. The optical design is supported by the results of a Monte Carlo simulation study of the reflectance characteristics of skin tissue. Because the results evolved from efforts to measure blood glucose noninvasively, the main emphasis is placed on the long-wavelength near-infrared range where sufficient penetration depth for radiation into tissue is still available. The accessory is applied for in vivo diffuse reflectance measurements.

Numerical analyses for thinned fiber Bragg grating under uneven surrounding refractive index environment

NASA Astrophysics Data System (ADS)

Luo, Bin-bin; Zhao, Ming-fu; Zhou, Xiao-jun; Huang, De-yi; Wang, Shao-fei; Cao, Xue-mei

2011-12-01

Based on the fiber waveguide models, a modified transfer matrix method was utilized to calculate the reflection spectrum of the thinned fiber Bragg grating (ThFBG) under the uneven surrounding refractive index (SRI) environment. Tow SRI ranges, including the high SRI region (from 1.42 to the fiber cladding index) and the low ones (from 1.33 to about 1.36), were considered. Numerical results showed that the responsive characteristics of the reflectance spectrum of the ThFBG were closely related to the properties of the SRI distribution, first, the original reflection spectrum of the ThFBG would split into many tinny resonant peaks and the reflectance spectrums are asymmetric since the uneven SRI distributions, second, the number of the resonant peaks, the decline of the amplitude, and the degree of the asymmetric of the reflectance spectrums would increase as the increase in the SRI gradient and the D-value of the SRI between the tow ends of the ThFBG. The same numerical approach could be used to analyze the responsive characteristics of the ThFBG under the uneven medium environment where the SRI distribution was any other functions.

Expanding Lorentz and spectrum corrections to large volumes of reciprocal space for single-crystal time-of-flight neutron diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Michels-Clark, Tara M.; Savici, Andrei T.; Lynch, Vickie E.

Evidence is mounting that potentially exploitable properties of technologically and chemically interesting crystalline materials are often attributable to local structure effects, which can be observed as modulated diffuse scattering (mDS) next to Bragg diffraction (BD). BD forms a regular sparse grid of intense discrete points in reciprocal space. Traditionally, the intensity of each Bragg peak is extracted by integration of each individual reflection first, followed by application of the required corrections. In contrast, mDS is weak and covers expansive volumes of reciprocal space close to, or between, Bragg reflections. For a representative measurement of the diffuse scattering, multiple sample orientationsmore » are generally required, where many points in reciprocal space are measured multiple times and the resulting data are combined. The common post-integration data reduction method is not optimal with regard to counting statistics. A general and inclusive data processing method is needed. In this contribution, a comprehensive data analysis approach is introduced to correct and merge the full volume of scattering data in a single step, while correctly accounting for the statistical weight of the individual measurements. Lastly, development of this new approach required the exploration of a data treatment and correction protocol that includes the entire collected reciprocal space volume, using neutron time-of-flight or wavelength-resolved data collected at TOPAZ at the Spallation Neutron Source at Oak Ridge National Laboratory.« less

Facile fabrication of mesoporous Fe-Ti-SBA15 silica with enhanced visible-light-driven simultaneous photocatalytic degradation and reduction reactions

NASA Astrophysics Data System (ADS)

Chang, Fei; Jiao, Mingzhi; Xu, Quan; Deng, Baoqing; Hu, Xuefeng

2018-03-01

A series of mesoporous iron-titanium-containing silica Fe-TiO2-SBA15 (FTS) were constructed via a facile one-pot hydrothermal route and subsequently characterized by X-ray diffraction patterns, UV-vis diffuse reflection spectroscopy, transmission electron microscopy, scanning electron microscopy, nitrogen adsorption-desorption, X-ray photoelectron spectroscopy, and X-ray energy dispersion spectroscopy. By analyses, these samples possessed ordered two-dimensional hexagonal mesoporous structures, mainly involving mixed dual-phases of anatase and rutile TiO2, like commercial titania P25. The UV-vis diffuse reflection spectra demonstrated the presence of Fe species that was further confirmed by the X-ray photoelectron spectra and X-ray energy dispersion spectrum. The existence of Fe species in form of Fe3+ cations played an important role on the phase composition and electronic structure of these samples. With structural and morphological merits, these samples exhibited relatively high photocatalytic efficiency toward the degradation of dye methylene blue (MB) and reduction of Cr(VI) under visible-light irradiation, comparing with P25. In addition, among all candidates, the sample with a Fe/Si molar ratio of 0.03 showed the highest catalytic performance under optimal conditions, especially in the coexistence of both MB and Cr(VI), revealing an obviously synergistic effect when the consumption of both contaminants occurred. Finally, a primary catalytic mechanism was speculated on basis of active species capture experiments.

Expanding Lorentz and spectrum corrections to large volumes of reciprocal space for single-crystal time-of-flight neutron diffraction

DOE PAGES

Michels-Clark, Tara M.; Savici, Andrei T.; Lynch, Vickie E.; ...

2016-03-01

Evidence is mounting that potentially exploitable properties of technologically and chemically interesting crystalline materials are often attributable to local structure effects, which can be observed as modulated diffuse scattering (mDS) next to Bragg diffraction (BD). BD forms a regular sparse grid of intense discrete points in reciprocal space. Traditionally, the intensity of each Bragg peak is extracted by integration of each individual reflection first, followed by application of the required corrections. In contrast, mDS is weak and covers expansive volumes of reciprocal space close to, or between, Bragg reflections. For a representative measurement of the diffuse scattering, multiple sample orientationsmore » are generally required, where many points in reciprocal space are measured multiple times and the resulting data are combined. The common post-integration data reduction method is not optimal with regard to counting statistics. A general and inclusive data processing method is needed. In this contribution, a comprehensive data analysis approach is introduced to correct and merge the full volume of scattering data in a single step, while correctly accounting for the statistical weight of the individual measurements. Lastly, development of this new approach required the exploration of a data treatment and correction protocol that includes the entire collected reciprocal space volume, using neutron time-of-flight or wavelength-resolved data collected at TOPAZ at the Spallation Neutron Source at Oak Ridge National Laboratory.« less

Preliminary Assessment of Suomi-NPP VIIRS On-orbit Radiometric Performance

NASA Technical Reports Server (NTRS)

Oudrari, Hassan; DeLuccia, Frank; McIntire, Jeff; Moyer, David; Chiang, Vincent; Xiong, Xiao-xiong; Butler, James

2012-01-01

The Visible-Infrared Imaging Radiometer Suite (VIIRS) is a key instrument on-board the Suomi National Polar-orbiting Partnership (NPP) spacecraft that was launched on October 28th 2011. VIIRS was designed to provide moderate and imaging resolution of most of the globe twice daily. It is a wide-swath (3,040 km) cross-track scanning radiometer with spatial resolutions of 370.and 740 m at nadir for imaging and moderate bands, respectively. It has 22 spectral bands covering the spectrum between 0.412 11m and 12.01 11m, including 14 reflective solar bands (RSB), 7 thermal emissive bands (TEB), and 1 day-night band (ON B). VIIRS observations are used to generate 22 environmental data products (EORs). This paper will briefly describe NPP VIIRS calibration strategies performed by the independent government team, for the initial on-orbit Intensive Calibration and Validation (ICV) activities. In addition, this paper will provide an early assessment of the sensor on-orbit radiometric performance, such as the sensor signal to noise ratios (SNRs), dual gain transition verification, dynamic range and linearity, reflective bands calibration based on the solar diffuser (SO) and solar diffuser stability monitor (SOSM), and emissive bands calibration based on the on-board blackbody calibration (OBC). A comprehensive set of performance metrics generated during the pre-launch testing program will be compared to VIIRS on-orbit early performance, and a plan for future cal/val activities and performance enhancements will be presented.

Beyond colour: consistent variation in near infrared and solar reflectivity in sunbirds (Nectariniidae)

NASA Astrophysics Data System (ADS)

Shawkey, Matthew D.; Igic, Branislav; Rogalla, Svana; Goldenberg, Jonathan; Clusella-Trullas, Susana; D'Alba, Liliana

2017-10-01

The visible spectrum represents a fraction of the sun's radiation, a large portion of which is within the near infrared (NIR). However, wavelengths outside of the visible spectrum that are reflected by coloured tissues have rarely been considered, despite their potential significance to thermal effects. Here, we report the reflectivity from 300 to 2100 nm of differently coloured feathers. We measured reflectivity across the UV-Vis-NIR spectra of different (a) body parts, (b) colour-producing mechanisms and (c) sexes for 252 individuals of 68 sunbird (family: Nectariniidae) species. Breast plumage was the most reflective and cap plumage the least. Female plumage had greater reflectivity than males. Carotenoid-based colours had the greatest reflectivity, followed by non-iridescent and iridescent melanin-based colours. As ordered arrays of melanin-filled organelles (melanosomes) produce iridescent colours, this suggests that nanostructuring may affect reflectance across the spectrum. Our results indicate that differently coloured feathers consistently vary in their thermal, as well as obvious visual, properties.

In vivo imaging of scattering and absorption properties of exposed brain using a digital red-green-blue camera

NASA Astrophysics Data System (ADS)

Nishidate, Izumi; Yoshida, Keiichiro; Kawauchi, Satoko; Sato, Shunichi; Sato, Manabu

2014-03-01

We investigate a method to estimate the spectral images of reduced scattering coefficients and the absorption coefficients of in vivo exposed brain tissues in the range from visible to near-infrared wavelength (500-760 nm) based on diffuse reflectance spectroscopy using a digital RGB camera. In the proposed method, the multi-spectral reflectance images of in vivo exposed brain are reconstructed from the digital red, green blue images using the Wiener estimation algorithm. The Monte Carlo simulation-based multiple regression analysis for the absorbance spectra is then used to specify the absorption and scattering parameters of brain tissue. In this analysis, the concentration of oxygenated hemoglobin and that of deoxygenated hemoglobin are estimated as the absorption parameters whereas the scattering amplitude a and the scattering power b in the expression of μs'=aλ-b as the scattering parameters, respectively. The spectra of absorption and reduced scattering coefficients are reconstructed from the absorption and scattering parameters, and finally, the spectral images of absorption and reduced scattering coefficients are estimated. The estimated images of absorption coefficients were dominated by the spectral characteristics of hemoglobin. The estimated spectral images of reduced scattering coefficients showed a broad scattering spectrum, exhibiting larger magnitude at shorter wavelengths, corresponding to the typical spectrum of brain tissue published in the literature. In vivo experiments with exposed brain of rats during CSD confirmed the possibility of the method to evaluate both hemodynamics and changes in tissue morphology due to electrical depolarization.

Cosmic ray injection spectrum at the galactic sources

NASA Astrophysics Data System (ADS)

Lagutin, Anatoly; Tyumentsev, Alexander; Volkov, Nikolay

The spectra of cosmic rays measured at Earth are different from their source spectra. A key to understanding this difference, being crucial for solving the problem of cosmic-ray origin, is the determination of how cosmic-ray (CR) particles propagate through the turbulent interstellar medium (ISM). If the medium is a quasi-homogeneous the propagation process can be described by a normal diffusion model. However, during a last few decades many evidences, both from theory and observations, of the existence of multiscale structures in the Galaxy have been found. Filaments, shells, clouds are entities widely spread in the ISM. In such a highly non-homogeneous (fractal-like) ISM the normal diffusion model certainly is not kept valid. Generalization of this model leads to what is known as "anomalous diffusion". The main goal of the report is to retrieve the cosmic ray injection spectrum at the galactic sources in the framework of the anomalous diffusion (AD) model. The anomaly in this model results from large free paths ("Levy flights") of particles between galactic inhomogeneities. In order to evaluate the CR spectrum at the sources, we carried out new calculation of the CR spectra at Earth. AD equation in terms of fractional derivatives have been used to describe CR propagation from the nearby (r≤1 kpc) young (t≤ 1 Myr) and multiple old distant (r > 1 kpc) sources. The assessment of the key model parameters have been based on the results of the particles diffusion in the cosmic and laboratory plasma. We show that in the framework of the anomalous diffusion model the locally observed basic features of the cosmic rays (difference between spectral exponents of proton, He and other nuclei, "knee" problem, positron to electron ratio) can be explained if the injection spectrum at the main galactic sources of cosmic rays has spectral exponent p˜ 2.85. The authors acknowledge support from The Russian Foundation for Basic Research grant No. 14-02-31524.

Correction for the Hematocrit Bias in Dried Blood Spot Analysis Using a Nondestructive, Single-Wavelength Reflectance-Based Hematocrit Prediction Method.

PubMed

Capiau, Sara; Wilk, Leah S; De Kesel, Pieter M M; Aalders, Maurice C G; Stove, Christophe P

2018-02-06

The hematocrit (Hct) effect is one of the most important hurdles currently preventing more widespread implementation of quantitative dried blood spot (DBS) analysis in a routine context. Indeed, the Hct may affect both the accuracy of DBS methods as well as the interpretation of DBS-based results. We previously developed a method to determine the Hct of a DBS based on its hemoglobin content using noncontact diffuse reflectance spectroscopy. Despite the ease with which the analysis can be performed (i.e., mere scanning of the DBS) and the good results that were obtained, the method did require a complicated algorithm to derive the total hemoglobin content from the DBS's reflectance spectrum. As the total hemoglobin was calculated as the sum of oxyhemoglobin, methemoglobin, and hemichrome, the three main hemoglobin derivatives formed in DBS upon aging, the reflectance spectrum needed to be unmixed to determine the quantity of each of these derivatives. We now simplified the method by only using the reflectance at a single wavelength, located at a quasi-isosbestic point in the reflectance curve. At this wavelength, assuming 1-to-1 stoichiometry of the aging reaction, the reflectance is insensitive to the hemoglobin degradation and only scales with the total amount of hemoglobin and, hence, the Hct. This simplified method was successfully validated. At each quality control level as well as at the limits of quantitation (i.e., 0.20 and 0.67) bias, intra- and interday imprecision were within 10%. Method reproducibility was excellent based on incurred sample reanalysis and surpassed the reproducibility of the original method. Furthermore, the influence of the volume spotted, the measurement location within the spot, as well as storage time and temperature were evaluated, showing no relevant impact of these parameters. Application to 233 patient samples revealed a good correlation between the Hct determined on whole blood and the predicted Hct determined on venous DBS. The bias obtained with Bland and Altman analysis was -0.015 and the limits of agreement were -0.061 and 0.031, indicating that the simplified, noncontact Hct prediction method even outperforms the original method. In addition, using caffeine as a model compound, it was demonstrated that this simplified Hct prediction method can effectively be used to implement a Hct-dependent correction factor to DBS-based results to alleviate the Hct bias.

Effect of the diffusion parameters on the observed γ-ray spectrum of sources and their contribution to the local all-electron spectrum: The EDGE code

NASA Astrophysics Data System (ADS)

López-Coto, R.; Hahn, J.; BenZvi, S.; Dingus, B.; Hinton, J.; Nisa, M. U.; Parsons, R. D.; Greus, F. Salesa; Zhang, H.; Zhou, H.

2018-11-01

The positron excess measured by PAMELA and AMS can only be explained if there is one or several sources injecting them. Moreover, at the highest energies, it requires the presence of nearby ( ∼ hundreds of parsecs) and middle age (maximum of ∼ hundreds of kyr) sources. Pulsars, as factories of electrons and positrons, are one of the proposed candidates to explain the origin of this excess. To calculate the contribution of these sources to the electron and positron flux at the Earth, we developed EDGE (Electron Diffusion and Gamma rays to the Earth), a code to treat the propagation of electrons and compute their diffusion from a central source with a flexible injection spectrum. Using this code, we can derive the source's gamma-ray spectrum, spatial extension, the all-electron density in space, the electron and positron flux reaching the Earth and the positron fraction measured at the Earth. We present in this paper the foundations of the code and study how different parameters affect the gamma-ray spectrum of a source and the electron flux measured at the Earth. We also studied the effect of several approximations usually performed in these studies. This code has been used to derive the results of the positron flux measured at the Earth in [1].

Annual Research Review: Reaction time variability in ADHD and autism spectrum disorders: measurement and mechanisms of a proposed trans-diagnostic phenotype

PubMed Central

Karalunas, Sarah L.; Geurts, Hilde M.; Konrad, Kerstin; Bender, Stephan; Nigg, Joel T.

2014-01-01

Background Intraindividual variability in reaction time (RT) has received extensive discussion as an indicator of cognitive performance, a putative intermediate phenotype of many clinical disorders, and a possible trans-diagnostic phenotype that may elucidate shared risk factors for mechanisms of psychiatric illnesses. Scope and Methodology Using the examples of attention deficit hyperactivity disorder (ADHD) and autism spectrum disorders (ASD), we discuss RT variability. We first present a new meta-analysis of RT variability in ASD with and without comorbid ADHD. We then discuss potential mechanisms that may account for RT variability and statistical models that disentangle the cognitive processes affecting RTs. We then report a second meta-analysis comparing ADHD and non-ADHD children on diffusion model parameters. We consider how findings inform the search for neural correlates of RT variability. Findings Results suggest that RT variability is increased in ASD only when children with comorbid ADHD are included in the sample. Furthermore, RT variability in ADHD is explained by moderate to large increases (d = 0.63–0.99) in the ex-Gaussian parameter τ and the diffusion parameter drift rate, as well as by smaller differences (d = 0.32) in the diffusion parameter of nondecision time. The former may suggest problems in state regulation or arousal and difficulty detecting signal from noise, whereas the latter may reflect contributions from deficits in motor organization or output. The neuroimaging literature converges with this multicomponent interpretation and also highlights the role of top-down control circuits. Conclusion We underscore the importance of considering the interactions between top-down control, state regulation (e.g. arousal), and motor preparation when interpreting RT variability and conclude that decomposition of the RT signal provides superior interpretive power and suggests mechanisms convergent with those implicated using other cognitive paradigms. We conclude with specific recommendations for the field for next steps in the study of RT variability in neurodevelopmental disorders. PMID:24628425

The Water Recovery X-ray Rocket (WRX-R)

NASA Astrophysics Data System (ADS)

Miles, Drew

2017-08-01

The Water Recovery X-ray Rocket (WRX-R) is a diffuse soft X-ray spectrometer that will launch on a sounding rocket from the Kwajalein Atoll. WRX-R has a field of view of >10 deg2 and will observe the Vela supernova remnant. A mechanical collimator, state-of-the-art off-plane reflection grating array and hybrid CMOS detector will allow WRX to achieve the most highly-resolved spectrum of the Vela SNR ever recorded. In addition, this payload will fly a hard X-ray telescope that is offset from the soft X-ray spectrometer in order to observe the pulsar at the center of the remnant. We present here an introduction to the instrument, the expected science return, and an update on the state of the payload as we work towards launch.

UV-Vis-NIR luminescence properties and energy transfer mechanism of LiSrPO4:Eu2+, Pr3+ suitable for solar spectral convertor.

PubMed

Chen, Yan; Wang, Jing; Liu, Chunmeng; Tang, Jinke; Kuang, Xiaojun; Wu, Mingmei; Su, Qiang

2013-02-11

An efficient near-infrared (NIR) phosphor LiSrPO(4):Eu(2+), Pr(3+) is synthesized by solid-state reaction and systematically investigated using x-ray diffraction, diffuse reflection spectrum, photoluminescence spectra at room temperature and 3 K, and the decay curves. The UV-Vis-NIR energy transfer mechanism is proposed based on these results. The results demonstrate Eu(2+) can be an efficient sensitizer for harvesting UV photon and greatly enhancing the NIR emission of Pr(3+) between 960 and 1060 nm through efficient energy feeding by allowed 4f-5d absorption of Eu(2+) with high oscillator strength. Eu(2+)/Pr(3+) may be an efficient donor-acceptor pair as solar spectral converter for Si solar cells.

Structural and optical characterization of bismuth sulphide nanorods

NASA Astrophysics Data System (ADS)

Shah, N. M.; Poria, K. C.

2017-05-01

In this work Bismuth sulfide (Bi2S3) nanorods with a high order of crystallinity is synthesized via hydrothermal method from aqueous solution of Bismuth Nitrate Pentahydrate and elemental Sulphur using Triethanolamine (TEA) as capping agent. The microstructures of Bi2S3 nanorods were investigated by X-ray diffraction (XRD) analysis. The positions and relative intensities of all the peaks in XRD pattern are in good agreement with those of the orthorhombic crystal structure of Bi2S3. TEM images shows that synthesized Bi2S3 has morphology of nanorods while selected area electron diffraction pattern indicates single crystalline nature. The analysis of diffuse reflectance (DR) spectrum of as synthesized Bi2S3 using Kubelka - Munk theory suggests direct energy band gap of 1.5 eV.

[Spectrum studies on titania photocatalysts].

PubMed

Su, W; Fu, X; Wei, K; Zhang, H; Lin, H; Wang, X; Li, D

2001-02-01

The nano-sized TiO2 photocatalysts were prepared by sol-gel method and characterized by FTIR spectroscopy, FT-Raman spectroscopy and diffuse reflectance spectroscopy(DRS). Photocatalytic degradation of oleic acid over the TiO2 catalysts was investigated. The result showed that calcination temperature has strong effect on crystal structure, energy band structure, optical adsorption and photocatalytic activity of the TiO2 catalysts. It was found that the TiO2 photocatalyst calcined at 400 degrees C has the best apparent optical adsorption, the biggest band edge position and the highest photoactivity. The effect of calcination temperature on photocatalytic activity of TiO2 catalysts has been ascribed to the changes in structure and optical property of catalyst such as crystal size, content of rutile, residual NO3-, and band-edge position of light adsorption.

Application of a neural network for reflectance spectrum classification

NASA Astrophysics Data System (ADS)

Yang, Gefei; Gartley, Michael

2017-05-01

Traditional reflectance spectrum classification algorithms are based on comparing spectrum across the electromagnetic spectrum anywhere from the ultra-violet to the thermal infrared regions. These methods analyze reflectance on a pixel by pixel basis. Inspired by high performance that Convolution Neural Networks (CNN) have demonstrated in image classification, we applied a neural network to analyze directional reflectance pattern images. By using the bidirectional reflectance distribution function (BRDF) data, we can reformulate the 4-dimensional into 2 dimensions, namely incident direction × reflected direction × channels. Meanwhile, RIT's micro-DIRSIG model is utilized to simulate additional training samples for improving the robustness of the neural networks training. Unlike traditional classification by using hand-designed feature extraction with a trainable classifier, neural networks create several layers to learn a feature hierarchy from pixels to classifier and all layers are trained jointly. Hence, the our approach of utilizing the angular features are different to traditional methods utilizing spatial features. Although training processing typically has a large computational cost, simple classifiers work well when subsequently using neural network generated features. Currently, most popular neural networks such as VGG, GoogLeNet and AlexNet are trained based on RGB spatial image data. Our approach aims to build a directional reflectance spectrum based neural network to help us to understand from another perspective. At the end of this paper, we compare the difference among several classifiers and analyze the trade-off among neural networks parameters.

Picosecond dynamics of excited singlet states in organic microcrystals: Diffuse reflectance laser photolysis study

NASA Astrophysics Data System (ADS)

Ikeda, Noriaki; Koshioka, Masanori; Masuhara, Hiroshi; Yoshihara, Keitaro

1988-09-01

Absorption spectra and picosecond dynamics of the singlet exciton states of benzil and p-terphenyl in a microcrystal have been measured for the first time by analyzing the diffuse reflected spectra of the picosecond continuum.

Regression-based model of skin diffuse reflectance for skin color analysis

NASA Astrophysics Data System (ADS)

Tsumura, Norimichi; Kawazoe, Daisuke; Nakaguchi, Toshiya; Ojima, Nobutoshi; Miyake, Yoichi

2008-11-01

A simple regression-based model of skin diffuse reflectance is developed based on reflectance samples calculated by Monte Carlo simulation of light transport in a two-layered skin model. This reflectance model includes the values of spectral reflectance in the visible spectra for Japanese women. The modified Lambert Beer law holds in the proposed model with a modified mean free path length in non-linear density space. The averaged RMS and maximum errors of the proposed model were 1.1 and 3.1%, respectively, in the above range.

Light distribution modulated diffuse reflectance spectroscopy.

PubMed

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

2016-06-01

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

Design and validation of a diffuse reflectance and spectroscopic microendoscope with poly(dimethylsioxane)-based phantoms

PubMed Central

Greening, Gage J.; Powless, Amy J.; Hutcheson, Joshua A.; Prieto, Sandra P.; Majid, Aneeka A.; Muldoon, Timothy J.

2015-01-01

Many cases of epithelial cancer originate in basal layers of tissue and are initially undetected by conventional microendoscopy techniques. We present a bench-top, fiber-bundle microendoscope capable of providing high resolution images of surface cell morphology. Additionally, the microendoscope has the capability to interrogate deeper into material by using diffuse reflectance and broadband diffuse reflectance spectroscopy. The purpose of this multimodal technique was to overcome the limitation of microendoscopy techniques that are limited to only visualizing morphology at the tissue or cellular level. Using a custom fiber optic probe, high resolution surface images were acquired using topical proflavine to fluorescently stain non-keratinized epithelia. A 635 nm laser coupled to a 200 μm multimode fiber delivers light to the sample and the diffuse reflectance signal was captured by a 1 mm image guide fiber. Finally, a tungsten-halogen lamp coupled to a 200 μm multimode fiber delivers broadband light to the sample to acquire spectra at source-detector separations of 374, 729, and 1051 μm. To test the instrumentation, a high resolution proflavine-induced fluorescent image of resected healthy mouse colon was acquired. Additionally, five monolayer poly(dimethylsiloxane)-based optical phantoms with varying absorption and scattering properties were created to acquire diffuse reflectance profiles and broadband spectra. PMID:25983372

Light distribution modulated diffuse reflectance spectroscopy

PubMed Central

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

2016-01-01

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

Influence of Acoustic Reflection on the Inertial Cavitation Dose in a Franz Diffusion Cell.

PubMed

Robertson, Jeremy; Becker, Sid

2018-05-01

The exposure of the skin to low-frequency (20-100 kHz) ultrasound is a well-established method for increasing its permeability to drugs. The mechanism underlying this permeability increase has been found to be inertial cavitation within the coupling fluid. This study investigated the influence of acoustic reflections on the inertial cavitation dose during low-frequency (20 kHz) exposure in an in vitro skin sonoporation setup. This investigation was conducted using a passive cavitation detector that monitored the broadband noise emission within a modified Franz diffusion cell. Two versions of this diffusion cell were employed. One version had acoustic conditions that were similar to those of a standard Franz diffusion cell surrounded by air, whereas the second was designed to greatly reduce the acoustic reflection by submerging the diffusion cell in a water bath. The temperature of the coupling fluid in both setups was controlled using a novel thermoelectric cooling system. At an ultrasound intensity of 13.6 W/cm 2 , the median inertial cavitation dose when the acoustic reflections were suppressed, was found to be only about 15% lower than when reflections were not suppressed. Copyright © 2018 World Federation for Ultrasound in Medicine and Biology. Published by Elsevier Inc. All rights reserved.

Spectrophotometric Method for Differentiation of Human Skin Melanoma. II. Diagnostic Characteristics

NASA Astrophysics Data System (ADS)

Petruk, V. G.; Ivanov, A. P.; Kvaternyuk, S. M.; Barunb, V. V.

2016-05-01

Experimental data on the spectral dependences of the optical diffuse reflection coefficient for skin from different people with melanoma or nevus are presented in the form of the probability density of the diffuse reflection coefficient for the corresponding pigmented lesions. We propose a noninvasive technique for differentiating between malignant and benign tumors, based on measuring the diffuse reflection coefficient for a specific patient and comparing the value obtained with a pre-set threshold. If the experimental result is below the threshold, then it is concluded that the person has melanoma; otherwise, no melanoma is present. As an example, we consider the wavelength 870 nm. We determine the risk of malignant transformation of a nevus (its transition to melanoma) for different measured diffuse reflection coefficients. We have studied the errors in the method, its operating characteristics and probability characteristics as the threshold diffuse reflection coefficient is varied. We find that the diagnostic confidence, sensitivity, specificity, and effectiveness (accuracy) parameters are maximum (>0.82) for a threshold of 0.45-0.47. The operating characteristics for the proposed technique exceed the corresponding parameters for other familiar optical approaches to melanoma diagnosis. Its distinguishing feature is operation at only one wavelength, and consequently implementation of the experimental technique is simplified and made less expensive.

Hyperspectral diffuse reflectance for determination of the optical properties of milk and fruit and vegetable juices

NASA Astrophysics Data System (ADS)

Qin, Jianwei; Lu, Renfu

2005-11-01

Absorption and reduced scattering coefficients are two fundamental optical properties for turbid biological materials. This paper presents the technique and method of using hyperspectral diffuse reflectance for fast determination of the optical properties of fruit and vegetable juices and milks. A hyperspectral imaging system was used to acquire spatially resolved steady-state diffuse reflectance over the spectral region between 530 and 900 nm from a variety of fruit and vegetable juices (citrus, grapefruit, orange, and vegetable) and milks with different fat levels (full, skim and mixed). The system collected diffuse reflectance in the source-detector separation range from 1.1 to 10.0 mm. The hyperspectral reflectance data were analyzed by using a diffusion theory model for semi-infinite homogeneous media. The absorption and reduced scattering coefficients of the fruit and vegetable juices and milks were extracted by inverse algorithms from the scattering profiles for wavelengths of 530-900 nm. Values of the absorption and reduced scattering coefficient at 650 nm were highly correlated to the fat content of the milk samples with the correlation coefficient of 0.990 and 0.989, respectively. The hyperspectral imaging technique can be extended to the measurement of other liquid and solid foods in which light scattering is dominant.

Design and validation of a diffuse reflectance and spectroscopic microendoscope with poly(dimethylsiloxane)-based phantoms

NASA Astrophysics Data System (ADS)

Greening, Gage J.; Powless, Amy J.; Hutcheson, Joshua A.; Prieto, Sandra P.; Majid, Aneeka A.; Muldoon, Timothy J.

2015-03-01

Many cases of epithelial cancer originate in basal layers of tissue and are initially undetected by conventional microendoscopy techniques. We present a bench-top, fiber-bundle microendoscope capable of providing high resolution images of surface cell morphology. Additionally, the microendoscope has the capability to interrogate deeper into material by using diffuse reflectance and broadband diffuse reflectance spectroscopy. The purpose of this multimodal technique was to overcome the limitation of microendoscopy techniques that are limited to only visualizing morphology at the tissue or cellular level. Using a custom fiber optic probe, high resolution surface images were acquired using topical proflavine to fluorescently stain non-keratinized epithelia. A 635 nm laser coupled to a 200 μm multimode fiber delivers light to the sample and the diffuse reflectance signal was captured by a 1 mm image guide fiber. Finally, a tungsten-halogen lamp coupled to a 200 μm multimode fiber delivers broadband light to the sample to acquire spectra at source-detector separations of 374, 729, and 1051 μm. To test the instrumentation, a high resolution proflavine-induced fluorescent image of resected healthy mouse colon was acquired. Additionally, five monolayer poly(dimethylsiloxane)-based optical phantoms with varying absorption and scattering properties were created to acquire diffuse reflectance profiles and broadband spectra.

SO2 frost - UV-visible reflectivity and Io surface coverage

NASA Technical Reports Server (NTRS)

Nash, D. B.; Fanale, F. P.; Nelson, R. M.

1980-01-01

The reflectance spectrum in the range 0.24-0.85 microns of SO2 frost is measured in light of the discovery of SO2 gas in the atmosphere of Io and the possible discovery of the frost on its surface. Frost deposits up to 1.5 mm thick were grown in vacuum at 130 K and bi-directional reflectance spectra were obtained. Typical SO2 frost is found to exhibit very low reflectivity (2-5%) at 0.30 microns, rising steeply at 0.32 microns to attain a maximum reflectivity (75-80%) at 4.0 microns and uniformly high reflectivity throughout the visible and near infrared. Comparison with the full disk spectrum of Io reveals that no more than 20% of the surface can be covered with optically thick SO2 frost. Combinations of surface materials including SO2 frost which can produce the observed spectrum are indicated.

The X-ray Emitting Components towards l = 111 deg: The Local Hot Bubble and Beyond

NASA Technical Reports Server (NTRS)

Kuntz, K. D.; Snowden, S. L.

2006-01-01

We have obtained an XMM-Newton spectrum of the diffuse X-ray emission towards (l, b) = (111.14,1.11), a line of sight with a relatively simple distribution of absorbing clouds; > 9 x 10(exp 19)/sq cm at R>170 pc, a 6 x 10(exp 21)/sq cm molecular cloud at 2.5-3.3 kpc, and a total column of 1.2 x 10(exp 22)/sq cm. We find that the analysis of the XMM-Newton spectrum in conjunction with the RASS spectral energy distribution for the same direction requires three thermal components to be well fit: a "standard" Local Hot Bubble component with kT = 0.089, a component beyond the molecular cloud with kT = 0.59, and a component before the molecular cloud with kT = 0.21. The strength of the O VII 0.56 keV line from the Local Hot Bubble, 2.1+/-0.7 photons/sq cm/s/sr, is consistent with other recent measures. The 0.21 keV component has an emission measure of 0.0022+/-0.0006 pc and is not localized save as diffuse emission within the Galactic plane; it is the best candidate for a pervasive hot medium. The spatial separation of the approx. 0.2 keV component from the approx. 0.6 keV component suggests that the spectral decompositions of the emission from late-type spiral disks found in the literature do represent real temperature components rather than reflecting more complex temperature distributions.

Scientific results from COBE

NASA Technical Reports Server (NTRS)

Bennett, C. L.; Boggess, N. W.; Cheng, E. S.; Hauser, M. G.; Kelsall, T.; Mather, J. C.; Moseley, S. H., Jr.; Murdock, T. L.; Shafer, R. A.; Silverberg, R. F.

1993-01-01

NASA's Cosmic Background Explorer (COBE) carries three scientific instruments to make precise measurements of the spectrum and anisotropy of the cosmic microwave background (CMB) radiation on angular scales greater than 7 deg and to conduct a search for a diffuse cosmic infrared background (CIB) radiation with 0.7 deg angular resolution. Data from the Far-Infrared Absolute Spectrophotometer (FIRAS) show that the spectrum of the CMB is that of a blackbody of temperature T = 2.73 +/- 0.06 K, with no deviation from a blackbody spectrum greater than 0.25% of the peak brightness. The first year of data from the Differential Microwave Radiometers (DMR) show statistically significant CMB anisotropy. The anisotropy is consistent with a scale invariant primordial density fluctuation spectrum. Infrared sky brightness measurements from the Diffuse Infrared Background Experiment (DIRBE) provide new conservative upper limits to the CIB. Extensive modeling of solar system and galactic infrared foregrounds is required for further improvement in the CIB limits.

Reflectance spectrum of plasmon waveguide interband cascade lasers and observation of the Berreman effect

NASA Astrophysics Data System (ADS)

Hinkey, Robert T.; Tian, Zhaobing; Yang, Rui Q.; Mishima, Tetsuya D.; Santos, Michael B.

2011-08-01

Noninvasive infrared reflectance measurements have been explored as a method for studying the optical properties of Si-doped cladding layers of plasmon waveguide interband cascade lasers. Measurements and theoretical simulations of the reflectance spectra were carried out on both the laser structures themselves, as well as highly doped InAs films grown on GaAs substrates. We have found that there is a sharp drop in the signal of the reflectance spectrum for p-polarized light oscillating near the plasma frequency. This is a manifestation of the so-called Berreman effect, which occurs at frequencies where the dielectric function approaches zero. This is distinct from the plasma edge feature seen in the reflectance spectrum of thick samples. The plasma frequencies of the highly doped layers were obtained by identifying the Berreman feature in the measured spectrum and fitting the spectrum to a modeled curve. Using a model for the effective mass, we were able to obtain measurements of the conduction electron concentration (in a range from 1018 to 1019 cm-3) in the waveguide cladding layers with values that were in good agreement with those found using Hall effect and SIMS measurements. The reflectance data was effectively used to achieve better calibration of the Si-doping during the growth of the n++-type InAs layers in the plasmon waveguide laser structures.

Transverse particle acceleration and diffusion in a planetary magnetic field

NASA Technical Reports Server (NTRS)

Barbosa, D. D.

1994-01-01

A general model of particle acceleration by plasma waves coupled with adiabatic radial diffusion in a planetary magnetic field is developed. The model assumes that a spectrum of lower hybird waves is present to resonantly accelerate ions transverse to the magnetic field. The steady state Green's function for the combined radial diffusion and wave acceleration equation is found in terms of a series expansion. The results provide a rigorous demonstration of how a quasi-Maxwellian distribution function is formed in the absence of particle collisons and elucidate the nature of turbulent heating of magnetospheric plasmas. The solution is applied to the magnetosphere of Neptune for which a number of examples are given illustrating how the spectrum of pickup N(+) ions from Triton evolves.

NIST High Accuracy Reference Reflectometer-Spectrophotometer

PubMed Central

Proctor, James E.; Yvonne Barnes, P.

1996-01-01

A new reflectometer-spectrophotometer has been designed and constructed using state-of-the-art technology to enhance optical properties of materials measurements over the ultraviolet, visible, and near-infrared (UV-Vis-NIR) wavelength range (200 nm to 2500 nm). The instrument, Spectral Tri-function Automated Reference Reflectometer (STARR), is capable of measuring specular and diffuse reflectance, bidirectional reflectance distribution function (BRDF) of diffuse samples, and both diffuse and non-diffuse transmittance. Samples up to 30 cm by 30 cm can be measured. The instrument and its characterization are described. PMID:27805081

Wavelength Coded Image Transmission and Holographic Optical Elements.

DTIC Science & Technology

1984-08-20

system has been designed and built for transmitting images of diffusely reflecting objects through optical fibers and displaying those images at a...passive components at the end of a fiber-optic designed to transmit high-resolution images of diffusely imaging system as described in this paper... designing a system for viewing diffusely reflecting The authors are with University of Minnesota. Electrical Engi- objects, one must consider that a

Measurement and Interpretation of Diffuse Scattering in X-Ray Diffraction for Macromolecular Crystallography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wall, Michael E.

X-ray diffraction from macromolecular crystals includes both sharply peaked Bragg reflections and diffuse intensity between the peaks. The information in Bragg scattering reflects the mean electron density in the unit cells of the crystal. The diffuse scattering arises from correlations in the variations of electron density that may occur from one unit cell to another, and therefore contains information about collective motions in proteins.

To See the World in a Grain of Sand: Recognizing the Origin of Sand Specimens by Diffuse Reflectance Infrared Fourier Transform Spectroscopy and Multivariate Exploratory Data Analysis

ERIC Educational Resources Information Center

Pezzolo, Alessandra De Lorenzi

2011-01-01

The diffuse reflectance infrared Fourier transform (DRIFT) spectra of sand samples exhibit features reflecting their composition. Basic multivariate analysis (MVA) can be used to effectively sort subsets of homogeneous specimens collected from nearby locations, as well as pointing out similarities in composition among sands of different origins.…

Renormalization of the diffusion tensor for high-frequency, electromagnetic modes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Litwin, C.; Sudan, R.N.

The resonance broadening theory is used to derive the diffusion tensor for resonant particles in a spectrum of electromagnetic modes propagating parallel to the magnetic field. The magnetic trapping limit for saturation of wave amplitudes is discussed.

Relationship between reflection spectra of breast adipose tissue with histologic grade

NASA Astrophysics Data System (ADS)

Muñoz Morales, Aarón; Vázquez Y Montiel, Sergio; Reigosa, Aldo

2011-08-01

Optical spectroscopy allows the characterization, recognition and differentiation of subcutaneous tissues healthy and no-healthy, to facilitate the diagnosis or early detection for breast cancer are studied white adipose tissue by the subcutaneous region with the help of the diffuse reflection spectroscopy in the visible areas (400 to 700 nm) of electromagnetic spectrum for them using a spectrometer portable of integrating sphere, Hunter lab Model Mini-Scan. The problem to be solved for cancer detection by optical techniques is to find the solution to the inverse problem of scattering of radiation in tissue where it is necessary to solve the equation of energy transfer. us through the trigonometric interpolation and by the data adjustment by least squares using Fourier series expansion to parameterize the spectral response curves of each sample of breast adipose tissue then correlated with histological grades established by the optical biopsy for each one of the samples, allowing use this technique to the study of anomalies in White Adipose Tissue Breast, changes are evident in the spectral response for Breast Adipose Tissue carcinogens with respect to healthy tissues and for the different histological grades.

Shared neuroanatomical substrates of impaired phonological working memory across reading disability and autism

PubMed Central

Lu, Chunming; Qi, Zhenghan; Harris, Adrianne; Weil, Lisa Wisman; Han, Michelle; Halverson, Kelly; Perrachione, Tyler K.; Kjelgaard, Margaret; Wexler, Kenneth; Tager-Flusberg, Helen; Gabrieli, John D. E.

2015-01-01

Background Individuals with reading disability or individuals with autism spectrum disorder (ASD) are characterized, respectively, by their difficulties in reading or social communication, but both groups often have impaired phonological working memory (PWM). It is not known whether the impaired PWM reflects distinct or shared neuroanatomical abnormalities in these two diagnostic groups. Methods White-matter structural connectivity via diffusion weighted imaging was examined in sixty-four children, ages 5-17 years, with reading disability, ASD, or typical development (TD), who were matched in age, gender, intelligence, and diffusion data quality. Results Children with reading disability and children with ASD exhibited reduced PWM compared to children with TD. The two diagnostic groups showed altered white-matter microstructure in the temporo-parietal portion of the left arcuate fasciculus (AF) and in the temporo-occipital portion of the right inferior longitudinal fasciculus (ILF), as indexed by reduced fractional anisotropy and increased radial diffusivity. Moreover, the structural integrity of the right ILF was positively correlated with PWM ability in the two diagnostic groups, but not in the TD group. Conclusions These findings suggest that impaired PWM is transdiagnostically associated with shared neuroanatomical abnormalities in ASD and reading disability. Microstructural characteristics in left AF and right ILF may play important roles in the development of PWM. The right ILF may support a compensatory mechanism for children with impaired PWM. PMID:26949750

Shared neuroanatomical substrates of impaired phonological working memory across reading disability and autism.

PubMed

Lu, Chunming; Qi, Zhenghan; Harris, Adrianne; Weil, Lisa Wisman; Han, Michelle; Halverson, Kelly; Perrachione, Tyler K; Kjelgaard, Margaret; Wexler, Kenneth; Tager-Flusberg, Helen; Gabrieli, John D E

2016-03-01

Individuals with reading disability or individuals with autism spectrum disorder (ASD) are characterized, respectively, by their difficulties in reading or social communication, but both groups often have impaired phonological working memory (PWM). It is not known whether the impaired PWM reflects distinct or shared neuroanatomical abnormalities in these two diagnostic groups. White-matter structural connectivity via diffusion weighted imaging was examined in sixty-four children, ages 5-17 years, with reading disability, ASD, or typical development (TD), who were matched in age, gender, intelligence, and diffusion data quality. Children with reading disability and children with ASD exhibited reduced PWM compared to children with TD. The two diagnostic groups showed altered white-matter microstructure in the temporo-parietal portion of the left arcuate fasciculus (AF) and in the temporo-occipital portion of the right inferior longitudinal fasciculus (ILF), as indexed by reduced fractional anisotropy and increased radial diffusivity. Moreover, the structural integrity of the right ILF was positively correlated with PWM ability in the two diagnostic groups, but not in the TD group. These findings suggest that impaired PWM is transdiagnostically associated with shared neuroanatomical abnormalities in ASD and reading disability. Microstructural characteristics in left AF and right ILF may play important roles in the development of PWM. The right ILF may support a compensatory mechanism for children with impaired PWM.

[The study of aluminium diffuser calibration in the UV].

PubMed

Li, Cong; Wang, Yong-Mei; Zhang, Zhong-Mou

2008-04-01

A bi-directional reflectance distribution function (BRDF) measurement setup in the ultraviolet spectral range was established. The BRDF of the aluminium diffusers at a given orientation was measured. The relative accuracy of the BRDF measurement is better than 2.5%. The hemispheric reflectance of the aluminium diffusers was measured in the wavelength range from 250 to 650 nm. It increases with the wavelength, and changes about 6% from 300 to 360 nm. It decreases with the time. Since the diffuser was made (about one year ago), from 250 to 300 nm, the peak decrease in the hemispheric reflectance can reach 2.6%, and the average decrease is 1.5%. From 300 to 360 nm, it has an average decrease of 0.9% decrease, and 0.8% when wavelength is longer than 360 nm.

Spectral and geometrical variation of the bidirectional reflectance distribution function of diffuse reflectance standards.

PubMed

Ferrero, Alejandro; Rabal, Ana María; Campos, Joaquín; Pons, Alicia; Hernanz, María Luisa

2012-12-20

A study on the variation of the spectral bidirectional reflectance distribution function (BRDF) of four diffuse reflectance standards (matte ceramic, BaSO(4), Spectralon, and white Russian opal glass) is accomplished through this work. Spectral BRDF measurements were carried out and, using principal components analysis, its spectral and geometrical variation respect to a reference geometry was assessed from the experimental data. Several descriptors were defined in order to compare the spectral BRDF variation of the four materials.

Comparison of the Radiative Two-Flux and Diffusion Approximations

NASA Technical Reports Server (NTRS)

Spuckler, Charles M.

2006-01-01

Approximate solutions are sometimes used to determine the heat transfer and temperatures in a semitransparent material in which conduction and thermal radiation are acting. A comparison of the Milne-Eddington two-flux approximation and the diffusion approximation for combined conduction and radiation heat transfer in a ceramic material was preformed to determine the accuracy of the diffusion solution. A plane gray semitransparent layer without a substrate and a non-gray semitransparent plane layer on an opaque substrate were considered. For the plane gray layer the material is semitransparent for all wavelengths and the scattering and absorption coefficients do not vary with wavelength. For the non-gray plane layer the material is semitransparent with constant absorption and scattering coefficients up to a specified wavelength. At higher wavelengths the non-gray plane layer is assumed to be opaque. The layers are heated on one side and cooled on the other by diffuse radiation and convection. The scattering and absorption coefficients were varied. The error in the diffusion approximation compared to the Milne-Eddington two flux approximation was obtained as a function of scattering coefficient and absorption coefficient. The percent difference in interface temperatures and heat flux through the layer obtained using the Milne-Eddington two-flux and diffusion approximations are presented as a function of scattering coefficient and absorption coefficient. The largest errors occur for high scattering and low absorption except for the back surface temperature of the plane gray layer where the error is also larger at low scattering and low absorption. It is shown that the accuracy of the diffusion approximation can be improved for some scattering and absorption conditions if a reflectance obtained from a Kubelka-Munk type two flux theory is used instead of a reflection obtained from the Fresnel equation. The Kubelka-Munk reflectance accounts for surface reflection and radiation scattered back by internal scattering sites while the Fresnel reflection only accounts for surface reflections.

Spectral reflectance characteristics of different snow and snow-covered land surface objects and mixed spectrum fitting

USGS Publications Warehouse

Zhang, J.-H.; Zhou, Z.-M.; Wang, P.-J.; Yao, F.-M.; Yang, L.

2011-01-01

The field spectroradiometer was used to measure spectra of different snow and snow-covered land surface objects in Beijing area. The result showed that for a pure snow spectrum, the snow reflectance peaks appeared from visible to 800 nm band locations; there was an obvious absorption valley of snow spectrum near 1030 nm wavelength. Compared with fresh snow, the reflection peaks of the old snow and melting snow showed different degrees of decline in the ranges of 300~1300, 1700~1800 and 2200~2300 nm, the lowest was from the compacted snow and frozen ice. For the vegetation and snow mixed spectral characteristics, it was indicated that the spectral reflectance increased for the snow-covered land types(including pine leaf with snow and pine leaf on snow background), due to the influence of snow background in the range of 350~1300 nm. However, the spectrum reflectance of mixed pixel remained a vegetation spectral characteristic. In the end, based on the spectrum analysis of snow, vegetation, and mixed snow/vegetation pixels, the mixed spectral fitting equations were established, and the results showed that there was good correlation between spectral curves by simulation fitting and observed ones(correlation coefficient R2=0.9509).

Exploring the Effects of Disk Thickness on the Black Hole Reflection Spectrum

NASA Astrophysics Data System (ADS)

Taylor, Corbin; Reynolds, Christopher S.

2018-03-01

The relativistically broadened reflection spectrum, observed in both AGN and X-ray binaries, has proven to be a powerful probe of the properties of black holes and the environments in which they reside. Emitted from the innermost regions of the accretion disk, this X-ray spectral component carries with it information not only about the plasma that resides in these extreme conditions, but also the black hole spin, a marker of the formation and accretion history of these objects. The models currently used to interpret the reflection spectrum are often simplistic, however, approximating the disk as an infinitely thin, optically thick plane of material orbiting in circular Keplerian orbits around the central object. Using a new relativistic ray-tracing suite (Fenrir) that allows for more complex disk approximations, we examine the effects that disk thickness may have on the reflection spectrum. Assuming a lamppost corona, we find that finite disk thickness can have a variety of effects on the reflection spectrum, including a truncation of the blue wing (from self-shadowing of the accretion disk) and an enhancement of the red wing (from the irradiation of the central “eye wall” of the inner disk). We deduce the systematic errors on black hole spin and height that may result from neglecting these effects.

In vivo burn diagnosis by camera-phone diffuse reflectance laser speckle detection.

PubMed

Ragol, S; Remer, I; Shoham, Y; Hazan, S; Willenz, U; Sinelnikov, I; Dronov, V; Rosenberg, L; Bilenca, A

2016-01-01

Burn diagnosis using laser speckle light typically employs widefield illumination of the burn region to produce two-dimensional speckle patterns from light backscattered from the entire irradiated tissue volume. Analysis of speckle contrast in these time-integrated patterns can then provide information on burn severity. Here, by contrast, we use point illumination to generate diffuse reflectance laser speckle patterns of the burn. By examining spatiotemporal fluctuations in these time-integrated patterns along the radial direction from the incident point beam, we show the ability to distinguish partial-thickness burns in a porcine model in vivo within the first 24 hours post-burn. Furthermore, our findings suggest that time-integrated diffuse reflectance laser speckle can be useful for monitoring burn healing over time post-burn. Unlike conventional diffuse reflectance laser speckle detection systems that utilize scientific or industrial-grade cameras, our system is designed with a camera-phone, demonstrating the potential for burn diagnosis with a simple imager.

In vivo burn diagnosis by camera-phone diffuse reflectance laser speckle detection

PubMed Central

Ragol, S.; Remer, I.; Shoham, Y.; Hazan, S.; Willenz, U.; Sinelnikov, I.; Dronov, V.; Rosenberg, L.; Bilenca, A.

2015-01-01

Burn diagnosis using laser speckle light typically employs widefield illumination of the burn region to produce two-dimensional speckle patterns from light backscattered from the entire irradiated tissue volume. Analysis of speckle contrast in these time-integrated patterns can then provide information on burn severity. Here, by contrast, we use point illumination to generate diffuse reflectance laser speckle patterns of the burn. By examining spatiotemporal fluctuations in these time-integrated patterns along the radial direction from the incident point beam, we show the ability to distinguish partial-thickness burns in a porcine model in vivo within the first 24 hours post-burn. Furthermore, our findings suggest that time-integrated diffuse reflectance laser speckle can be useful for monitoring burn healing over time post-burn. Unlike conventional diffuse reflectance laser speckle detection systems that utilize scientific or industrial-grade cameras, our system is designed with a camera-phone, demonstrating the potential for burn diagnosis with a simple imager. PMID:26819831

Polarization properties and microfacet-based modelling of white, grey and coloured matte diffuse reflection standards

NASA Astrophysics Data System (ADS)

Quast, T.; Schirmacher, A.; Hauer, K.-O.; Koo, A.

2018-02-01

To elucidate the influence of polarization in diffuse reflectometry, we performed a series of measurements in several bidirectional geometries and determined the Stokes parameters of the diffusely reflected radiation. Different types of matte reflection standards were used, including several common white standards and ceramic colour standards. The dependence of the polarization on the sample type, wavelength and geometry have been studied systematically, the main influence factors have been identified: The effect is largest at large angles of incidence or detection and at wavelengths where the magnitude of the reflectance is small. The results for the colour standards have been modelled using a microfacet-based reflection theory which is derived from the well-known model of Torrance and Sparrow. Although the theory is very simple and only has three free parameters, the agreement with the measured data is very good, all essential features of the data can be reproduced by the model.

Reduction of shading-derived artifacts in skin chromophore imaging without measurements or assumptions about the shape of the subject

NASA Astrophysics Data System (ADS)

Yoshida, Kenichiro; Nishidate, Izumi; Ojima, Nobutoshi; Iwata, Kayoko

2014-01-01

To quantitatively evaluate skin chromophores over a wide region of curved skin surface, we propose an approach that suppresses the effect of the shading-derived error in the reflectance on the estimation of chromophore concentrations, without sacrificing the accuracy of that estimation. In our method, we use multiple regression analysis, assuming the absorbance spectrum as the response variable and the extinction coefficients of melanin, oxygenated hemoglobin, and deoxygenated hemoglobin as the predictor variables. The concentrations of melanin and total hemoglobin are determined from the multiple regression coefficients using compensation formulae (CF) based on the diffuse reflectance spectra derived from a Monte Carlo simulation. To suppress the shading-derived error, we investigated three different combinations of multiple regression coefficients for the CF. In vivo measurements with the forearm skin demonstrated that the proposed approach can reduce the estimation errors that are due to shading-derived errors in the reflectance. With the best combination of multiple regression coefficients, we estimated that the ratio of the error to the chromophore concentrations is about 10%. The proposed method does not require any measurements or assumptions about the shape of the subjects; this is an advantage over other studies related to the reduction of shading-derived errors.

Motion of glossy objects does not promote separation of lighting and surface colour

PubMed Central

2017-01-01

The surface properties of an object, such as texture, glossiness or colour, provide important cues to its identity. However, the actual visual stimulus received by the eye is determined by both the properties of the object and the illumination. We tested whether operational colour constancy for glossy objects (the ability to distinguish changes in spectral reflectance of the object, from changes in the spectrum of the illumination) was affected by rotational motion of either the object or the light source. The different chromatic and geometric properties of the specular and diffuse reflections provide the basis for this discrimination, and we systematically varied specularity to control the available information. Observers viewed animations of isolated objects undergoing either lighting or surface-based spectral transformations accompanied by motion. By varying the axis of rotation, and surface patterning or geometry, we manipulated: (i) motion-related information about the scene, (ii) relative motion between the surface patterning and the specular reflection of the lighting, and (iii) image disruption caused by this motion. Despite large individual differences in performance with static stimuli, motion manipulations neither improved nor degraded performance. As motion significantly disrupts frame-by-frame low-level image statistics, we infer that operational constancy depends on a high-level scene interpretation, which is maintained in all conditions. PMID:29291113

Radial q-space sampling for DSI.

PubMed

Baete, Steven H; Yutzy, Stephen; Boada, Fernando E

2016-09-01

Diffusion spectrum imaging (DSI) has been shown to be an effective tool for noninvasively depicting the anatomical details of brain microstructure. Existing implementations of DSI sample the diffusion encoding space using a rectangular grid. Here we present a different implementation of DSI whereby a radially symmetric q-space sampling scheme for DSI is used to improve the angular resolution and accuracy of the reconstructed orientation distribution functions. Q-space is sampled by acquiring several q-space samples along a number of radial lines. Each of these radial lines in q-space is analytically connected to a value of the orientation distribution functions at the same angular location by the Fourier slice theorem. Computer simulations and in vivo brain results demonstrate that radial diffusion spectrum imaging correctly estimates the orientation distribution functions when moderately high b-values (4000 s/mm2) and number of q-space samples (236) are used. The nominal angular resolution of radial diffusion spectrum imaging depends on the number of radial lines used in the sampling scheme, and only weakly on the maximum b-value. In addition, the radial analytical reconstruction reduces truncation artifacts which affect Cartesian reconstructions. Hence, a radial acquisition of q-space can be favorable for DSI. Magn Reson Med 76:769-780, 2016. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

Cosmic-ray effects on diffuse gamma-ray measurements.

NASA Technical Reports Server (NTRS)

Fishman, G. J.

1972-01-01

Evaluation of calculations and experimental evidence from 600-MeV proton irradiation indicating that cosmic-ray-induced radioactivity in detectors used to measure the diffuse gamma-ray background produces a significant counting rate in the energy region around 1 MeV. It is concluded that these counts may be responsible for the observed flattening of the diffuse photon spectrum at this energy.

Artificial neural networks for retrieving absorption and reduced scattering spectra from frequency-domain diffuse reflectance spectroscopy at short source-detector separation

PubMed Central

Chen, Yu-Wen; Chen, Chien-Chih; Huang, Po-Jung; Tseng, Sheng-Hao

2016-01-01

Diffuse reflectance spectroscopy (DRS) based on the frequency-domain (FD) technique has been employed to investigate the optical properties of deep tissues such as breast and brain using source to detector separation up to 40 mm. Due to the modeling and system limitations, efficient and precise determination of turbid sample optical properties from the FD diffuse reflectance acquired at a source-detector separation (SDS) of around 1 mm has not been demonstrated. In this study, we revealed that at SDS of 1 mm, acquiring FD diffuse reflectance at multiple frequencies is necessary for alleviating the influence of inevitable measurement uncertainty on the optical property recovery accuracy. Furthermore, we developed artificial neural networks (ANNs) trained by Monte Carlo simulation generated databases that were capable of efficiently determining FD reflectance at multiple frequencies. The ANNs could work in conjunction with a least-square optimization algorithm to rapidly (within 1 second), accurately (within 10%) quantify the sample optical properties from FD reflectance measured at SDS of 1 mm. In addition, we demonstrated that incorporating the steady-state apparatus into the FD DRS system with 1 mm SDS would enable obtaining broadband absorption and reduced scattering spectra of turbid samples in the wavelength range from 650 to 1000 nm. PMID:27446671

The Nustar Spectrum of Mrk 335: Extreme Relativistic Effects Within Two Gravitational Radii of the Event Horizon?

NASA Technical Reports Server (NTRS)

Parker, M. L.; Wilkins, D. R.; Fabian, A. C.; Grupe, D.; Dauser, T.; Matt, G.; Harrison, F. A.; Brenneman, L.; Boggs, S. E.; Christensen, F. E.;

Thin-film thickness measurement method based on the reflection interference spectrum

NASA Astrophysics Data System (ADS)

Jiang, Li Na; Feng, Gao; Shu, Zhang

2012-09-01

A method is introduced to measure the thin-film thickness, refractive index and other optical constants. When a beam of white light shines on the surface of the sample film, the reflected lights of the upper and the lower surface of the thin-film will interfere with each other and reflectivity of the film will fluctuate with light wavelength. The reflection interference spectrum is analyzed with software according to the database, while the thickness and refractive index of the thin-film is measured.

Effect of temperature on the spectrum of fiber Bragg grating sensors embedded in polymer composite

NASA Astrophysics Data System (ADS)

Anoshkin, A. N.; Shipunov, G. S.; Voronkov, A. A.; Shardakov, I. N.

2017-12-01

This work presents the experimental results on the effect of temperature on the spectrum of fiber Bragg grating (FBG) sensors embedded in a polymer composite material manufactured by the prepreg method. The tests are carried out for flat bar specimens made of fiberglass with five embedded FBG sensors. For measuring the reflected wave power, the ASTRO X322 Interrogator is used. It is shown that embedding leads to the occurrence of an additional power peak and decreases the reflection spectrum signal by 10-12 dB. This is due to the effect of transverse compression force and the anisotropic character of the thermal expansion coefficient of the material. In heating, the reflected spectrum is close to the initial state of the material, but it has a less power.

SeaWiFS long-term solar diffuser reflectance trend analysis

NASA Astrophysics Data System (ADS)

Eplee, Robert E., Jr.; Patt, Frederick S.; Barnes, Robert A.; McClain, Charles R.

2006-08-01

The NASA Ocean Biology Processing Group's Calibration and Validation (Cal/Val) Team implemented daily solar calibrations of SeaWiFS to look for step-function changes in the instrument response and has used these calibrations to supplement the monthly lunar calibrations in monitoring the radiometric stability of SeaWiFS during its first year of on-orbit operations. The Team has undertaken an analysis of the mission-long solar calibration time series, with the lunar-derived radiometric corrections over time applied, to assess the long-term degradation of the solar diffuser reflectance over nine years on orbit. The SeaWiFS diffuser is an aluminum plate coated with YB71 paint. The bidirectional reflectance distribution function of the diffuser was not fully characterized before launch, so the Cal/Val Team has implemented a regression of the solar incidence angles and the drift in the node of the satellite's orbit against the diffuser time series to correct for solar incidence angle effects. An exponential function with a time constant of 200 days yields the best fit to the diffuser time series. The decrease in diffuser reflectance over the mission is wavelength-dependent, ranging from 9% in the blue (412 nm) to 5% in the red and near infrared (670-865 nm). The degradation of diffuser reflctance is similar to that observed for SeaWiFS radiometric response itself from lunar calibration time series for bands 1-5 (412-555 nm), though the magnitude of the change is four times larger for the diffuser. Evidently, the same optical degradation process has affected both the telescope optics and the solar diffuser in the blue and green. The Cal/Val Team has developed a methodology for computing the signal-to-noise ratio (SNR) for SeaWiFS on orbit from the diffuser time series. The on-orbit change in the SNR for each band over the nine-year mission is less than 7%. The on-orbit performance of the SeaWiFS solar diffuser should offer insight into the long-term on-orbit performance of solar diffusers on other instruments, such as MODIS, VIIRS, and ABI.

An ASCA GIS spectrum of S5 0014+813 AT z = 3.384

NASA Technical Reports Server (NTRS)

Elvis, Martin; Matsuoka, M.; Siemiginowska, A.; Fiore, F.; Mihara, T.; Brinkmann, W.

1994-01-01

ASCA has detected the z = 3.384 quasar S5 0014+813 up to energies of 34 keV in the quasar rest frame using the two gas imaging spectrometer (GIS) instruments. The combined X-ray spectrum has a signal-to-noise ratio of over 50 sigma and is consistent with a single power law of energy slope 0.63 +/- 0.03 over the 0.8-8 keV (observed) energy range. The spectrum is also well fitted with a simple thermal bremsstrahlung model of kT = 40 +/- 4 keV (in the quasar frame), which raises obvious possibilities for contributions to the diffuse X-ray background. A maximum solid angle of Omega(sub d)/2(pi) = 0.4(90% confidence) can be placed on the strength of a Compton reflection component above the energy of the Fe K-edge. The Fe K 6.4 keV fluorescence line has a rest frame equivalent width less than 120 eV (90% confidence) at its redshifted energy of 1.46 keV. The weakness of these features differentiates this high-luminosity, high-redshift quasar from the majority of Seyfert galaxies using its X-ray spectrum alone. The GIS slope is consistent with the slope derived by the ROSAT Position Sensitive Proportional Counter (PSPC). The normalization at 1 keV in the ASCA observation is, however, a factor 30%-40% higher than in the ROSAT observation, suggesting a significant increase in the 1 keV (observed) flux over the 31.5 months between the two observations (7.2 months, rest frame).

Parameterization and sensitivity analyses of a radiative transfer model for remote sensing plant canopies

NASA Astrophysics Data System (ADS)

Hall, Carlton Raden

A major objective of remote sensing is determination of biochemical and biophysical characteristics of plant canopies utilizing high spectral resolution sensors. Canopy reflectance signatures are dependent on absorption and scattering processes of the leaf, canopy properties, and the ground beneath the canopy. This research investigates, through field and laboratory data collection, and computer model parameterization and simulations, the relationships between leaf optical properties, canopy biophysical features, and the nadir viewed above-canopy reflectance signature. Emphasis is placed on parameterization and application of an existing irradiance radiative transfer model developed for aquatic systems. Data and model analyses provide knowledge on the relative importance of leaves and canopy biophysical features in estimating the diffuse absorption a(lambda,m-1), diffuse backscatter b(lambda,m-1), beam attenuation alpha(lambda,m-1), and beam to diffuse conversion c(lambda,m-1 ) coefficients of the two-flow irradiance model. Data sets include field and laboratory measurements from three plant species, live oak (Quercus virginiana), Brazilian pepper (Schinus terebinthifolius) and grapefruit (Citrus paradisi) sampled on Cape Canaveral Air Force Station and Kennedy Space Center Florida in March and April of 1997. Features measured were depth h (m), projected foliage coverage PFC, leaf area index LAI, and zenith leaf angle. Optical measurements, collected with a Spectron SE 590 high sensitivity narrow bandwidth spectrograph, included above canopy reflectance, internal canopy transmittance and reflectance and bottom reflectance. Leaf samples were returned to laboratory where optical and physical and chemical measurements of leaf thickness, leaf area, leaf moisture and pigment content were made. A new term, the leaf volume correction index LVCI was developed and demonstrated in support of model coefficient parameterization. The LVCI is based on angle adjusted leaf thickness Ltadj, LAI, and h (m). Its function is to translate leaf level estimates of diffuse absorption and backscatter to the canopy scale allowing the leaf optical properties to directly influence above canopy estimates of reflectance. The model was successfully modified and parameterized to operate in a canopy scale and a leaf scale mode. Canopy scale model simulations produced the best results. Simulations based on leaf derived coefficients produced calculated above canopy reflectance errors of 15% to 18%. A comprehensive sensitivity analyses indicated the most important parameters were beam to diffuse conversion c(lambda, m-1), diffuse absorption a(lambda, m-1), diffuse backscatter b(lambda, m-1), h (m), Q, and direct and diffuse irradiance. Sources of error include the estimation procedure for the direct beam to diffuse conversion and attenuation coefficients and other field and laboratory measurement and analysis errors. Applications of the model include creation of synthetic reflectance data sets for remote sensing algorithm development, simulations of stress and drought on vegetation reflectance signatures, and the potential to estimate leaf moisture and chemical status.

Time-dependent Models for Blazar Emission with the Second-order Fermi Acceleration

NASA Astrophysics Data System (ADS)

Asano, Katsuaki; Takahara, Fumio; Kusunose, Masaaki; Toma, Kenji; Kakuwa, Jun

2014-01-01

The second-order Fermi acceleration (Fermi-II) driven by turbulence may be responsible for the electron acceleration in blazar jets. We test this model with time-dependent simulations. The hard electron spectrum predicted by the Fermi-II process agrees with the hard photon spectrum of 1ES 1101-232. For other blazars that show softer spectra, the Fermi-II model requires radial evolution of the electron injection rate and/or diffusion coefficient in the outflow. Such evolutions can yield a curved electron spectrum, which can reproduce the synchrotron spectrum of Mrk 421 from the radio to the X-ray regime. The photon spectrum in the GeV energy range of Mrk 421 is hard to fit with a synchrotron self-Compton model. However, if we introduce an external radio photon field with a luminosity of 4.9 × 1038 erg s-1, GeV photons are successfully produced via inverse Compton scattering. The temporal variability of the diffusion coefficient or injection rate causes flare emission. The observed synchronicity of X-ray and TeV flares implies a decrease of the magnetic field in the flaring source region.

Magnetic field generation by pointwise zero-helicity three-dimensional steady flow of an incompressible electrically conducting fluid

NASA Astrophysics Data System (ADS)

Rasskazov, Andrey; Chertovskih, Roman; Zheligovsky, Vladislav

2018-04-01

We introduce six families of three-dimensional space-periodic steady solenoidal flows, whose kinetic helicity density is zero at any point. Four families are analytically defined. Flows in four families have zero helicity spectrum. Sample flows from five families are used to demonstrate numerically that neither zero kinetic helicity density nor zero helicity spectrum prohibit generation of large-scale magnetic field by the two most prominent dynamo mechanisms: the magnetic α -effect and negative eddy diffusivity. Our computations also attest that such flows often generate small-scale field for sufficiently small magnetic molecular diffusivity. These findings indicate that kinetic helicity and helicity spectrum are not the quantities controlling the dynamo properties of a flow regardless of whether scale separation is present or not.

Diffuse characteristics study of laser target board using Monte Carlo simulation

NASA Astrophysics Data System (ADS)

Yang, Pengling; Wu, Yong; Wang, Zhenbao; Tao, Mengmeng; Wu, Junjie; Wang, Ping; Yan, Yan; Zhang, Lei; Feng, Gang; Zhu, Jinghui; Feng, Guobin

2013-05-01

In this paper, Torrance-Sparrow and Oren-Nayar model is adopt to study diffuse characteristics of laser target board. The model which based on geometric optics, assumes that rough surfaces are made up of a series of symmetric V-groove cavities with different slopes at microscopic level. The distribution of the slopes of the V-grooves are modeled as beckman distribution function, and every microfacet of the V-groove cavity is assumed to behave like a perfect mirror, which means the reflected ray follows Fresnel law at the microfacet. The masking and shadowing effects of rough surface are also taken into account through geometric attenuation factor. Monte Carlo method is used to simulate the diffuse reflectance distribution of the laser target board with different materials and processing technology, and all the calculated results are verified by experiment. It is shown that the profile of bidirectional reflectance distribution curve is lobe-shaped with the maximum lies along the mirror reflection direction. The width of the profile is narrower for a lower roughness value, and broader for a higher roughness value. The refractive index of target material will also influence the intensity and distribution of diffuse reflectance of laser target surface.

Dual-modality optical biopsy of glioblastomas multiforme with diffuse reflectance and fluorescence: ex vivo retrieval of optical properties

NASA Astrophysics Data System (ADS)

Du Le, Vinh Nguyen; Provias, John; Murty, Naresh; Patterson, Michael S.; Nie, Zhaojun; Hayward, Joseph E.; Farrell, Thomas J.; McMillan, William; Zhang, Wenbin; Fang, Qiyin

2017-02-01

Glioma itself accounts for 80% of all malignant primary brain tumors, and glioblastoma multiforme (GBM) accounts for 55% of such tumors. Diffuse reflectance and fluorescence spectroscopy have the potential to discriminate healthy tissues from abnormal tissues and therefore are promising noninvasive methods for improving the accuracy of brain tissue resection. Optical properties were retrieved using an experimentally evaluated inverse solution. On average, the scattering coefficient is 2.4 times higher in GBM than in low grade glioma (LGG), and the absorption coefficient is 48% higher. In addition, the ratio of fluorescence to diffuse reflectance at the emission peak of 460 nm is 2.6 times higher for LGG while reflectance at 650 nm is 2.7 times higher for GBM. The results reported also show that the combination of diffuse reflectance and fluorescence spectroscopy could achieve sensitivity of 100% and specificity of 90% in discriminating GBM from LGG during ex vivo measurements of 22 sites from seven glioma specimens. Therefore, the current technique might be a promising tool for aiding neurosurgeons in determining the extent of surgical resection of glioma and, thus, improving intraoperative tumor identification for guiding surgical intervention.

Dual-modality optical biopsy of glioblastomas multiforme with diffuse reflectance and fluorescence: ex vivo retrieval of optical properties.

PubMed

Du Le, Vinh Nguyen; Provias, John; Murty, Naresh; Patterson, Michael S; Nie, Zhaojun; Hayward, Joseph E; Farrell, Thomas J; McMillan, William; Zhang, Wenbin; Fang, Qiyin

2017-02-01

Glioma itself accounts for 80% of all malignant primary brain tumors, and glioblastoma multiforme (GBM) accounts for 55% of such tumors. Diffuse reflectance and fluorescence spectroscopy have the potential to discriminate healthy tissues from abnormal tissues and therefore are promising noninvasive methods for improving the accuracy of brain tissue resection. Optical properties were retrieved using an experimentally evaluated inverse solution. On average, the scattering coefficient is 2.4 times higher in GBM than in low grade glioma (LGG), and the absorption coefficient is 48% higher. In addition, the ratio of fluorescence to diffuse reflectance at the emission peak of 460 nm is 2.6 times higher for LGG while reflectance at 650 nm is 2.7 times higher for GBM. The results reported also show that the combination of diffuse reflectance and fluorescence spectroscopy could achieve sensitivity of 100% and specificity of 90% in discriminating GBM from LGG during ex vivo measurements of 22 sites from seven glioma specimens. Therefore, the current technique might be a promising tool for aiding neurosurgeons in determining the extent of surgical resection of glioma and, thus, improving intraoperative tumor identification for guiding surgical intervention.

Determination of the optical properties of semi-infinite turbid media from frequency-domain reflectance close to the source.

PubMed

Kienle, A; Patterson, M S

1997-09-01

We investigate theoretically the errors in determining the reduced scattering and absorption coefficients of semi-infinite turbid media from frequency-domain reflectance measurements made at small distances between the source and the detector(s). The errors are due to the uncertainties in the measurement of the phase, the modulation and the steady-state reflectance as well as to the diffusion approximation which is used as a theoretical model to describe light propagation in tissue. Configurations using one and two detectors are examined for the measurement of the phase and the modulation and for the measurement of the phase and the steady-state reflectance. Three solutions of the diffusion equation are investigated. We show that measurements of the phase and the steady-state reflectance at two different distances are best suited for the determination of the optical properties close to the source. For this arrangement the errors in the absorption coefficient due to typical uncertainties in the measurement are greater than those resulting from the application of the diffusion approximation at a modulation frequency of 200 MHz. A Monte Carlo approach is also examined; this avoids the errors due to the diffusion approximation.

Online high-speed NIR diffuse-reflectance imaging spectroscopy in food quality monitoring

NASA Astrophysics Data System (ADS)

Driver, Richard D.; Didona, Kevin

2009-05-01

The use of hyperspectral technology in the NIR for food quality monitoring is discussed. An example of the use of hyperspectral diffuse reflectance scanning and post-processing with a chemometric model shows discrimination between four pharmaceutical samples comprising Aspirin, Acetaminophen, Vitamin C and Vitamin D.

New closed-form approximation for skin chromophore mapping.

PubMed

Välisuo, Petri; Kaartinen, Ilkka; Tuchin, Valery; Alander, Jarmo

2011-04-01

The concentrations of blood and melanin in skin can be estimated based on the reflectance of light. Many models for this estimation have been built, such as Monte Carlo simulation, diffusion models, and the differential modified Beer-Lambert law. The optimization-based methods are too slow for chromophore mapping of high-resolution spectral images, and the differential modified Beer-Lambert is not often accurate enough. Optimal coefficients for the differential Beer-Lambert model are calculated by differentiating the diffusion model, optimized to the normal skin spectrum. The derivatives are then used in predicting the difference in chromophore concentrations from the difference in absorption spectra. The accuracy of the method is tested both computationally and experimentally using a Monte Carlo multilayer simulation model, and the data are measured from the palm of a hand during an Allen's test, which modulates the blood content of skin. The correlations of the given and predicted blood, melanin, and oxygen saturation levels are correspondingly r = 0.94, r = 0.99, and r = 0.73. The prediction of the concentrations for all pixels in a 1-megapixel image would take ∼ 20 min, which is orders of magnitude faster than the methods based on optimization during the prediction.

Non-Implanted Gallium-Arsenide and its Subsequent Annealing Effects.

NASA Astrophysics Data System (ADS)

Liou, Lih-Yeh

Infrared spectroscopy is used to study ion-implanted GaAs and its subsequent annealing effects. The damage in the implantation region causes a change in dielectric constant resulting in an infrared reflection spectrum which shows the interference pattern of a multilayer structure. Reflection data are fitted by values calculated from a physically realistic model by using computer codes. The first part in this work studies the solid state regrowth of amorphous GaAs made by Be implantation at -100(DEGREES)C. The regrowth temperature is around 200(DEGREES)C. The regrowth starts with a narrowing of the transition region and the transformation of the implanted layer from as-implanted amorphous (a-l) state to thermally-stablized amorphous (a-ll) state. The non-epitaxial recrystallization from both the surface and the interfacial region follows. The final regrown layer has a slightly higher refractive index than the crystalline value, indicating a high residual defect concentration. The temperature dependent regrowth velocity and the activation energy for this process are determined. The second part studies the free carrier activation in Be-implanted GaAs. Free holes are activated with prolonged annealing at 400(DEGREES)C ((TURN)50 hours) or a shorter time at higher temperature. The carrier contribution to the dielectric constant is calculated from the classical model and best fit to the reflection results show that the carrier profile can be approximated by a two half-Gaussians joined smoothly at their peaks. The peak position for the profile occurs deeper than that for the Be impurity profile measured by SIMS. The carrier distribution is speculated to be the result of the Be impurity, Ga vacancy and possible compensating defect distributions. The final part studies the free carrier removal by proton implantation in heavily doped, high carrier density, n-type GaAs. The as-implantation region is highly compensated until annealed at 550(DEGREES)C. After annealing between 300 and 400(DEGREES)C, the infrared results show a partially compensated region diffused deeply into substrate from the as-implanted region. The SIMS measurements show a well correlated hydrogen diffusion layer which suggests that the compensation defect is hydrogen related. After 500(DEGREES)C, the hydrogen diffusion layer is still observed, but the compensation layer has disappeared. The diffusion coefficient of the compensating defect and the activation energy for this process are determined. Carbon -implanted GaAs having a high carrier density substrate is also measured and compared with the H-implanted cases. (Copies available exclusively from Micrographics Department, Doheny Library, USC, Los Angeles, CA 90089 -0182.).

Further laboratory study of the diffuse reflectance spectra of frosts occurring on astronomical objects

NASA Technical Reports Server (NTRS)

Glaser, F. M.

1976-01-01

Oligoclase and bloedite, two mined samples, have been investigated, and the diffuse reflectance spectra are presented. These data are for powdered material, 50 microns to 5 microns size mixture, cooled to 160 K. The reflectivity of the oligoclase sample was also measured at room temperature, about 290 K, and the results at these two temperatures do indicate some tentative differences. A frost of ordinary water was prepared and its spectral reflectance is presented. This result compares reasonably well with measurements made by other investigators.

A simulation study for determination of refractive index dispersion of dielectric film from reflectance spectrum by using Paul wavelet

NASA Astrophysics Data System (ADS)

Tiryaki, Erhan; Coşkun, Emre; Kocahan, Özlem; Özder, Serhat

2017-02-01

In this work, the Continuous Wavelet Transform (CWT) with Paul wavelet was improved as a tool for determination of refractive index dispersion of dielectric film by using the reflectance spectrum of the film. The reflectance spectrum was generated theoretically in the range of 0.8333 - 3.3333 μm wavenumber and it was analyzed with presented method. Obtained refractive index determined from various resolution of Paul wavelet were compared with the input values, and the importance of the tunable resolution with Paul wavelet was discussed briefly. The noise immunity and uncertainty of the method was also studied.

Neodymium(III) Complexes of Dialkylphosphoric and Dialkylphosphonic Acids Relevant to Liquid-Liquid Extraction Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lumetta, Gregg J.; Sinkov, Sergey I.; Krause, Jeanette A.

2016-01-27

The complexes formed during the extraction of neodymium(III) into hydrophobic solvents containing acidic organophosphorus extractants were probed by single-crystal X-ray diffractometry, visible spectrophotometry, and Fourier-transform infrared spectroscopy. The crystal structure of the compound Nd(DMP)3 (1, DMP = dimethyl phosphate) revealed a polymeric arrangement in which each Nd(III) center is surrounded by six DMP oxygen atoms in a pseudo-octahedral environment. Adjacent Nd(III) ions are bridged by (MeO)2POO– anions, forming the polymeric network. The diffuse reflectance visible spectrum of 1 is nearly identical to that of the solid that is formed when an n-dodecane solution of di-(2-ethylhexyl)phosphoric acid (HA) is saturated withmore » Nd(III), indicating a similar coordination environment around the Nd center in the NdA3 solid. The visible spectrum of the HA solution fully loaded with Nd(III) is very similar to that of the NdA3 material, both displaying hypersensitive bands characteristic of an pseudo-octahedral coordination environment around Nd. These spectral characteristics persisted across a wide range of organic Nd concentrations, suggesting that the pseudo-octahedral coordination environment is maintained from dilute to saturated conditions.« less

Neodymium(III) Complexes of Dialkylphosphoric and Dialkylphosphonic Acids Relevant to Liquid-Liquid Extraction Systems.

PubMed

Lumetta, Gregg J; Sinkov, Sergey I; Krause, Jeanette A; Sweet, Lucas E

2016-02-15

The complexes formed during the extraction of neodymium(III) into hydrophobic solvents containing acidic organophosphorus extractants were probed by single-crystal X-ray diffractometry, visible spectrophotometry, and Fourier-transform infrared spectroscopy. The crystal structure of the compound Nd(DMP)3 (1, DMP = dimethyl phosphate) revealed a polymeric arrangement in which each Nd(III) center is surrounded by six DMP oxygen atoms in a pseudo-octahedral environment. Adjacent Nd(III) ions are bridged by (MeO)2POO(-) anions, forming the polymeric network. The diffuse reflectance visible spectrum of 1 is nearly identical to that of the solid that is formed when an n-dodecane solution of di(2-ethylhexyl)phosphoric acid (HA) is saturated with Nd(III), indicating a similar coordination environment around the Nd center in the NdA3 solid. The visible spectrum of the HA solution fully loaded with Nd(III) is very similar to that of the NdA3 material, both displaying hypersensitive bands characteristic of an pseudo-octahedral coordination environment around Nd. These spectral characteristics persisted across a wide range of organic Nd concentrations, suggesting that the pseudo-octahedral coordination environment is maintained from dilute to saturated conditions.

Benign Synthesis of Black Microspheres of Anatase TiO2 with Paramagnetic Oxygen Vacancies through NH3 Treatment.

PubMed

Maqbool, Qysar; Srivastava, Aasheesh

2017-10-09

Coloured TiO 2 is coveted for its ability to extract energy from the visible region of electromagnetic spectrum. Here a facile synthesis of black anatase titania microspheres (B-TiO 2 ) through a two-step process is reported. In the first step, amorphous white TiO 2 microspheres (W-TiO 2 ) are obtained by hydrolysing titanium tetraisopropoxide by ammonia vapours in ethanol. In the second step, the W-TiO 2 is thermally annealed at 500 °C to obtain B-TiO 2 . The diffuse reflectance analysis showed that B-TiO 2 absorbs across visible spectrum with absorption extending well into NIR region. Raman scattering together with EPR analysis showed compelling evidence of the existence of oxygen deficiency within the crystal in B-TiO 2 that induces black colouration in the sample. The defects present in the black anatase sample were confirmed to be single-electron-trapped (or paramagnetic) oxygen vacancies (V o ⋅) by XPS and EPR studies. The magnetic susceptibility studies showed existence of antiferromagnetic interactions between these unpaired electron spins. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Near-band-edge optical responses of solution-processed organic-inorganic hybrid perovskite CH3NH3PbI3 on mesoporous TiO2 electrodes

NASA Astrophysics Data System (ADS)

Yamada, Yasuhiro; Nakamura, Toru; Endo, Masaru; Wakamiya, Atsushi; Kanemitsu, Yoshihiko

2014-03-01

We studied the near-band-edge optical responses of solution-processed CH3NH3PbI3 on mesoporous TiO2 electrodes, which is utilized in mesoscopic heterojunction solar cells. Photoluminescence (PL) and PL excitation spectra peaks appear at 1.60 and 1.64 eV, respectively. The transient absorption spectrum shows a negative peak at 1.61 eV owing to photobleaching at the band-gap energy, indicating a direct band-gap semiconductor. On the basis of the temperature-dependent PL and diffuse reflectance spectra, we clarified that the absorption tail at room temperature is explained in terms of an Urbach tail and consistently determined the band-gap energy to be ˜1.61 eV at room temperature.

NuSTAR and XMM-Newton Observations of the Hard X- Ray Spectrum of Centaurus A

NASA Technical Reports Server (NTRS)

Furst, F.; Muller, C.; Madsen, K. K.; Lanz, L.; Rivers, E.; Brightman, M.; Arevalo, P.; Balokovic, M.; Beuchert, T.; Zhang, W.

2016-01-01

We present simultaneous XMM-Newton and Nuclear Spectroscopic Telescope Array (NuSTAR) observations spanning 3-78 keV of the nearest radio galaxy, Centaurus A (Cen A). The accretion geometry around the central engine in Cen A is still debated, and we investigate possible configurations using detailed X-ray spectral modeling. NuSTAR imaged the central region of Cen A with subarcminute resolution at X-ray energies above 10 keV for the first time, but found no evidence for an extended source or other off-nuclear point sources. The XMM-Newton and NuSTAR spectra agree well and can be described with an absorbed power law with a photon index Gamma = 1.8150 +/- 0.005 and a fluorescent Fe Kaline in good agreement with literature values. The spectrum is greater than 1 MeV. A thermal Comptonization continuum describes the data well, with parameters that agree with values measured by INTEGRAL, in particular an electron temperature kTe between approximately 100-300 keV and seed photon input temperatures between 5 and 50 eV. We do not find evidence for reflection or a broad iron line and put stringent upper limits of R is less than 0.01 on the reflection fraction and accretion disk illumination. We use archival Chandra data to estimate the contribution from diffuse emission, extra-nuclear point sources, and the outer X-ray jet to the observed NuSTAR and XMM-Newton X-ray spectra and find the contribution to be negligible. We discuss different scenarios for the physical origin of the observed hard X-ray spectrum and conclude that the inner disk is replaced by an advection-dominated accretion flow or that the X-rays are dominated by synchrotron self-Compton emission from the inner regions of the radio jet or a combination thereof.

Descent imager/spectral radiometer (DISR) instrument aboard the Huygens probe of Titan

NASA Astrophysics Data System (ADS)

Tomasko, Martin G.; Doose, Lyn R.; Smith, Peter H.; Fellows, C.; Rizk, B.; See, C.; Bushroe, M.; McFarlane, E.; Wegryn, E.; Frans, E.; Clark, R.; Prout, M.; Clapp, S.

1996-10-01

The Huygen's probe of the atmosphere of Saturn's moon Titan includes one optical instrument sensitive to the wavelengths of solar radiation. The goals of this investigation fall into four broad areas: 1) the measurement of the profile of solar heating to support an improved understanding of the thermal balance of Titan and the role of the greenhouse effect in maintaining Titan's temperature structure; 2) the measurement of the size, vertical distribution, and optical properties of the aerosol and cloud particles in Titan's atmosphere to support studies of the origin, chemistry, life cycles, and role in the radiation balance of Titan played by these particles; 3) the composition of the atmosphere, particularly the vertical profile of the mixing ratio of methane, a condensable constituent in Titan's atmosphere; and 4) the physical state, composition, topography, and physical processes at work in determining the nature of the surface of Titan and its interaction with Titan's atmosphere. In order to accomplish these objectives, the Descent Imager/Spectral Radiometer (DISR) instrument makes extensive use of fiber optics to bring the light from several different sets of foreoptics to a silicon CCD detector, to a pair of InGaAs linear array detectors, and to three silicon photometers. Together these detectors permit DISR to make panoramic images of the clouds and surface of Titan, to measure the spectrum of upward and downward streaming sunlight from 350 to 1700 nm at a resolving power of about 200, to measure the reflection spectrum of >= 3000 locations on the surface, to measure the brightness and polarization of the solar aureole between 4 and 30 degrees from the sun at 500 and 935 nm, to separate the direct and diffuse downward solar flux at each wavelength measured, and to measure the continuous reflection spectrum of the ground between 850 and 1600 nm using an onboard lamp in the last 100 m of the descent.

In vivo characterization of structural and optical properties of human skin by combined photothermal radiometry and diffuse reflectance spectroscopy

NASA Astrophysics Data System (ADS)

Verdel, Nina; Marin, Ana; Vidovič, Luka; Milanič, Matija; Majaron, Boris

2017-02-01

We have combined two optical techniques to enable simultaneous assessment of structure and composition of human skin in vivo: Pulsed photothermal radiometry (PPTR), which involves measurements of transient dynamics in midinfrared emission from sample surface after exposure to a light pulse, and diffuse reflectance spectroscopy (DRS) in visible part of the spectrum. Namely, while PPTR is highly sensitive to depth distribution of selected absorbers, DRS provides spectral information and thus enables differentiation between various chromophores. The accuracy and robustness of the inverse analysis is thus considerably improved compared to use of either technique on its own. Our analysis approach is simultaneous multi-dimensional fitting of the measured PPTR signals and DRS with predictions from a numerical model of light-tissue interaction (a.k.a. inverse Monte Carlo). By using a three-layer skin model (epidermis, dermis, and subcutis), we obtain a good match between the experimental and modeling data. However, dividing the dermis into two separate layers (i.e., papillary and reticular dermis) helps to bring all assessed parameter values within anatomically and physiologically plausible intervals. Both the quality of the fit and the assessed parameter values depend somewhat on the assumed scattering properties for skin, which vary in literature and likely depend on subject's age and gender, anatomical site, etc. In our preliminary experience, simultaneous fitting of the scattering properties is possible and leads to considerable improvement of the fit. The described approach may thus have a potential for simultaneous determination of absorption and scattering properties of human skin in vivo.

Raman Spectroscopy Differentiates Each Tissue From the Skin to the Spinal Cord: A Novel Method for Epidural Needle Placement?

PubMed Central

Anderson, T. Anthony; Kang, Jeon Woong; Gubin, Tatyana; Dasari, Ramachandra R.; So, Peter T. C.

2016-01-01

BACKGROUND Neuraxial anesthesia and epidural steroid injection techniques require precise anatomical targeting to ensure successful and safe analgesia. Previous studies suggest that only some of the tissues encountered during these procedures can be identified by spectroscopic methods, and no previous study has investigated the use of Raman, diffuse reflectance, and fluorescence spectroscopies. The authors hypothesized that real-time needle-tip spectroscopy may aid epidural needle placement and tested the ability of spectroscopy to distinguish each of the tissues in the path of neuraxial needles. METHODS For comparison of detection methods, the spectra of individual, dissected ex vivo paravertebral and neuraxial porcine tissues were collected using Raman spectroscopy (RS), diffuse reflectance spectroscopy (DRS), and fluorescence spectroscopy (FS). Real-time spectral guidance was tested using a 2 mm inner diameter fiber optic probe-in-needle device. Raman spectra were collected during the needle’s passage through intact paravertebral and neuraxial porcine tissue and analyzed afterward. The RS tissue signatures were verified as mapping to individual tissue layers using histochemical staining and widefield microscopy. RESULTS Raman spectroscopy revealed a unique spectrum for all ex vivo paravertebral and neuraxial tissue layers; DRS and FS spectra were not distinct for all tissues. Moreover, when accounting for the expected order of tissues, real-time Raman spectra recorded during needle insertion also permitted identification of each paravertebral and neuraxial porcine tissue. CONCLUSIONS This study demonstrates Raman spectroscopy can distinguish the tissues encountered during epidural needle insertion. This technology may prove useful during needle placement by providing evidence of its anatomical localization. PMID:27466032

The spectral energy distribution of the scattered light from dark clouds

NASA Technical Reports Server (NTRS)

Mattila, Kalevi; Schnur, G. F. O.

1989-01-01

A dark cloud is exposed to the ambient radiation field of integrated starlight in the Galaxy. Scattering of starlight by the dust particles gives rise to a diffuse surface brightness of the dark nebula. The intensity and the spectrum of this diffuse radiation can be used to investigate, e.g., the scattering parameters of the dust, the optical thickness of the cloud, and as a probe of the ambient radiation field at the location of the cloud. An understanding of the scattering process is also a prerequisite for the isolation of broad spectral features due to fluorescence or to any other non-scattering origin of the diffuse light. Model calculations are presented for multiple scattering in a spherical cloud. These calculations show that the different spectral shapes of the observed diffuse light can be reproduced with standard dust parameters. The possibility to use the observed spectrum as a diagnostic tool for analyzing the thickness of the cloud and the dust particle is discussed.

Limitations of the commonly used simplified laterally uniform optical fiber probe-tissue interface in Monte Carlo simulations of diffuse reflectance

PubMed Central

Naglič, Peter; Pernuš, Franjo; Likar, Boštjan; Bürmen, Miran

2015-01-01

Light propagation models often simplify the interface between the optical fiber probe tip and tissue to a laterally uniform boundary with mismatched refractive indices. Such simplification neglects the precise optical properties of the commonly used probe tip materials, e.g. stainless steel or black epoxy. In this paper, we investigate the limitations of the laterally uniform probe-tissue interface in Monte Carlo simulations of diffuse reflectance. In comparison to a realistic probe-tissue interface that accounts for the layout and properties of the probe tip materials, the simplified laterally uniform interface is shown to introduce significant errors into the simulated diffuse reflectance. PMID:26504647

[Application of near-infrared diffuse reflectance spectroscopy to the detection and identification of transgenic corn].

PubMed

Rui, Yu-kui; Luo, Yun-bo; Huang, Kun-lun; Wang, Wei-min; Zhang, Lu-da

2005-10-01

With the rapid development of the GMO, more and more GMO food has been pouring into the market. Much attention has been paid to GMO labeling under the controversy of GMO safety. Transgenic corns and their parents were scanned by continuous wave of near infrared diffuse reflectance spectroscopy range of 12000-4000 cm(-1); the resolution was 4 cm(-1); scanning was carried out for 64 times; BP algorithm was applied for data processing. The GMO food was easily resolved. Near-infrared diffuse reflectance spectroscopy is unpolluted and inexpensive compared with PCR and ELISA, so it is a very promising detection method for GMO food.

The color metamerism evaluation of paint based on ocean spectrum

NASA Astrophysics Data System (ADS)

Chen, Zhongwei; Huang, Hao; Liao, Ningfang

2018-03-01

The surface color of the sea is affected by many factors and will be different the due to the material difference in the sea. And the difference will be reflected in the ocean spectrum. If the paint materials of a ship can simulate the ocean surface color and the ocean spectrum at the same time. This will minimize the metamerism. In this paper, the method of metamerism is used to evaluate paint based on ocean spectrum, so that the color of the material affected by the light source will be reflected in the metamerism index.

Quantitative photography of intermittency in surface wave turbulence

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

1997-12-31

At high amplitudes of excitation surface waves on water distribute their energy according to a Kolmogorov type of turbulent power spectrum. We have used diffusing light photography to measure the power spectrum and to quantify the presence of large structures in the turbulent state.

Enhanced photon indistinguishability in pulse-driven quantum emitters

NASA Astrophysics Data System (ADS)

Fotso, Herbert F.

2017-04-01

Photon indistinguishability is an essential ingredient for the realization of scalable quantum networks. For quantum bits in the solid state, this is hindered by spectral diffusion, the uncontrolled random drift of the emission/absorption spectrum as a result of fluctuations in the emitter's environment. We study optical properties of a quantum emitter in the solid state when it is driven by a periodic sequence of optical pulses with finite detuning with respect to the emitter. We find that a pulse sequence can effectively mitigate spectral diffusion and enhance photon indistinguishability. The bulk of the emission occurs at a set target frequency; Photon indistinguishability is enhanced and is restored to its optimal value after every even pulse. Also, for moderate values of the sequence period and of the detuning, both the emission spectrum and the absorption spectrum have lineshapes with little dependence on the detuning. We describe the solution and the evolution of the emission/absorption spectrum as a function time.

Spatial Variation of the 3.29 and 3.40 Micron Emission Bands Within Reflection Nebulae and The Photochemical Evolution of Methylated Polycyclic Aromatic Hydrocarbons

NASA Technical Reports Server (NTRS)

Joblin, C.; Tielens, A. G. G. M.; Allamandola, L. J.; Geballe, T. R.

1996-01-01

Spectra of 3 microns emission features have been obtained at several positions within the reflection nebulae NGC 1333 SVS3 and NGC 2023. Strong variations of the relative intensities of the 3.29 microns feature and its most prominent satellite band at 3.40 microns are found. It is shown that: (1) the 3.40 microns band is too intense with respect to the 3.29 microns band at certain positions to arise from hot band emission alone, (2) the 3.40 microns band can be reasonably well matched by new laboratory spectra of gas-phase polycyclic aromatic hydrocarbons (PAHs) with alkyl (-CH3) side groups, and (3) the variations in the 3.40 microns to 3.29 microns band intensity ratios are consistent with the photochemical erosion of alkylated PAHs. We conclude that the 3.40 microns emission feature is attributable to -CH3 side groups on PAH molecules. We predict a value of 0.5 for the peak intensity ratio of the 3.40 and 3.29 microns emission bands from free PAHs in the diffuse interstellar medium, which would correspond to a proportion of one methyl group for four peripheral hydrogens. We also compare the 3 microns spectrum of the proto-planetary nebula IRAS 05341 + 0852 with the spectrum of the planetary nebula IRAS 21282 + 5050. We suggest that a photochemical evolution of the initial aliphatic and aromatic hydrocarbon mixture formed in the outflow is responsible for the changes observed in the 3 microns emission spectra of these objects.

Spatial variation of the 3.29 and 3.40 micron emission bands within reflection nebulae and the photochemical evolution of methylated polycyclic aromatic hydrocarbons

NASA Technical Reports Server (NTRS)

Joblin, C.; Tielens, A. G.; Allamandola, L. J.; Geballe, T. R.

1996-01-01

Spectra of 3 micrometers emission features have been obtained at several positions within the reflection nebulae NGC 1333 SVS3 and NGC 2023. Strong variations of the relative intensities of the 3.29 micrometers feature and its most prominent satellite band at 3.40 micrometers are found. It is shown that (i) the 3.40 micrometers band is too intense with respect to the 3.29 micrometers band at certain positions to arise from hot band emission alone, (ii) the 3.40 micrometers band can be reasonably well matched by new laboratory spectra of gas-phase polycyclic aromatic hydrocarbons (PAHs) with alkyl (-CH3) side groups, and (iii) the variations in the 3.40 micrometers to 3.29 micrometers band intensity ratios are consistent with the photochemical erosion of alkylated PAHs. We conclude that the 3.40 micrometers emission feature is attributable to -CH3 side groups on PAH molecules. We predict a value of 0.5 for the peak intensity ratio of the 3.40 and 3.29 micrometers emission bands from free PAHs in the diffuse interstellar medium, which would correspond to a proportion of one methyl group for four peripheral hydrogens. We also compare the 3 micrometers spectrum of the proto-planetary nebula IRAS 05341+0852 with the spectrum of the planetary nebula IRAS 21282+5050. We suggest that a photochemical evolution of the initial aliphatic and aromatic hydrocarbon mixture formed in the outflow is responsible for the changes observed in the 3 micrometers emission spectra of these objects.

Analysis on the impact of FBG reflectance spectrum with different optical fiber connection in vacuum thermal environment

NASA Astrophysics Data System (ADS)

Zhang, Jingchuan; Zhang, Wen; Lv, Jianfeng; Liang, Shuo; Wang, Lei; Li, Xiyuan

2018-01-01

To satisfy the application of fiber grating sensor technology in high vacuum thermal environment, FBG on sleeve compactly single model fiber with two typical different kind of connection such as fiber splicing and optical fiber connector are researched. Influence of the different connection to the characteristic of FBG reflectance spectrum in high vacuum thermal environment is analyzed and verified. First, experimental program of influence on FBG reflection spectrum characteristics is designed. Then, a hardware-in-the-loop detection platform is set up. Finally, the influence of temperature and vacuum on the reflection peak power of FBG with two typical different connections under high vacuum thermal environment is studied and verified. Experimental results indicate that: when vacuum varied from normal pressure to 10-4Pa level and then return to normal pressure, temperature of two different single-mode optical fiber connection dropped to -196 °C from room temperature and then returned to room temperature, after 224 hours, the peak power of the FBG reflectance spectrum did not change. It provided the experimental basis for the application of optical fiber sensing technology in high vacuum (pressure about 10-4Pa level) and thermal environment (-196 °C temperature cycle).

Transfer matrix method for four-flux radiative transfer.

PubMed

Slovick, Brian; Flom, Zachary; Zipp, Lucas; Krishnamurthy, Srini

2017-07-20

We develop a transfer matrix method for four-flux radiative transfer, which is ideally suited for studying transport through multiple scattering layers. The model predicts the specular and diffuse reflection and transmission of multilayer composite films, including interface reflections, for diffuse or collimated incidence. For spherical particles in the diffusion approximation, we derive closed-form expressions for the matrix coefficients and show remarkable agreement with numerical Monte Carlo simulations for a range of absorption values and film thicknesses, and for an example multilayer slab.

Diffuse Reflectance Spectroscopy for Total Carbon Analysis of Hawaiian Soils

NASA Astrophysics Data System (ADS)

McDowell, M. L.; Bruland, G. L.; Deenik, J. L.; Grunwald, S.; Uchida, R.

2010-12-01

Accurate assessment of total carbon (Ct) content is important for fertility and nutrient management of soils, as well as for carbon sequestration studies. The non-destructive analysis of soils by diffuse reflectance spectroscopy (DRS) is a potential supplement or alternative to the traditional time-consuming and costly combustion method of Ct analysis, especially in spatial or temporal studies where sample numbers are large. We investigate the use of the visible to near-infrared (VNIR) and mid-infrared (MIR) spectra of soils coupled with chemometric analysis to determine their Ct content. Our specific focus is on Hawaiian soils of agricultural importance. Though this technique has been introduced to the soil community, it has yet to be fully tested and used in practical applications for all soil types, and this is especially true for Hawaii. In short, DRS characterizes and differentiates materials based on the variation of the light reflected by a material at certain wavelengths. This spectrum is dependent on the material’s composition, structure, and physical state. Multivariate chemometric analysis unravels the information in a set of spectra that can help predict a property such as Ct. This study benefits from the remarkably diverse soils of Hawaii. Our sample set includes 216 soil samples from 145 pedons from the main Hawaiian Islands archived at the National Soil Survey Center in Lincoln, NE, along with more than 50 newly-collected samples from Kauai, Oahu, Molokai, and Maui. In total, over 90 series from 10 of the 12 soil orders are represented. The Ct values of these samples range from < 1% - 55%. We anticipate that the diverse nature of our sample set will ensure a model with applicability to a wide variety of soils, both in Hawaii and globally. We have measured the VNIR and MIR spectra of these samples and obtained their Ct values by dry combustion. Our initial analyses are conducted using only samples obtained from the Lincoln archive. In this preliminary case, we use Partial Least Squares (PLS) regression with cross validation to develop a prediction model for soils of unknown carbon content given only their spectral signature. We find R2 values of greater than 0.93 for the MIR spectra and 0.87 for the VNIR spectra, indicating a strong ability to correlate a soil’s spectrum with its Ct content. We build on these encouraging results by continuing chemometric analyses using the full data set, different data subsets, separate model calibration and validation groups, combined VNIR and MIR spectra, and exploring different data pretreatment options and variations to the PLS parameters.

Developing Mirror Self Awareness in Students with Autism Spectrum Disorder

ERIC Educational Resources Information Center

Duff, Christine K.; Flattery, J. J., Jr.

2014-01-01

A teaching methodology and curriculum was designed to develop and increase positive self-awareness in students diagnosed with autism spectrum disorders (ASD). Joint attention (JA) strategies were first utilized to directly teach students about reflected mirror images, and then subsequently, to indirectly teach students about their reflected image.…

Remote sensing-a geophysical perspective.

USGS Publications Warehouse

Watson, K.

1985-01-01

In this review of developments in the field of remote sensing from a geophysical perspective, the subject is limited to the electromagnetic spectrum from 0.4 mu m to 25cm. Three broad energy categories are covered: solar reflected, thermal infrared, and microwave.-from Authorremote sensing electromagnetic spectrum solar reflected thermal infrared microwave geophysics

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

NASA Astrophysics Data System (ADS)

Schablinski, Jan; Block, Dietmar

2015-02-01

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

Diffuse-reflectance fourier-transform mid-infrared spectroscopy as a method of characterizing changes in soil organic matter

USDA-ARS?s Scientific Manuscript database

Diffuse-Reflectance Fourier-Transform Mid-Infrared Spectroscopy (MidIR) can identify the presence of important organic functional groups in soil organic matter (SOM). Soils contain myriad organic and inorganic components that absorb in the MidIR so spectral interpretation needs to be validated in or...

Study of normal, fibrous and calcified aortic valve tissue by Raman and reflectance spectroscopy

NASA Astrophysics Data System (ADS)

Rodrigues, Kátia Calligaris; Munin, Egberto; Alves, Leandro P.; Silveira, Fabrício L.; Junior, Landulfo S.; De Lima, Carlos J.; Lázzaro, João C.; De Souza, Genivaldo C.; Piotto, José A. B.; Pacheco, Marcos T. T.; Zângaro, Renato A.

2007-02-01

Several studies have identified the degree of aortic valve calcification as a strong predictor both for the progression and outcome of aortic stenosis. In industrialized countries, aortic valve stenosis is most frequently caused by progressive calcification and degeneration of aortic cusps. However, there are no accurate methods to quantify the extent of aortic valve calcification. To provide a non-invasive alternative to biopsy, a range of optical methods have been investigated, including Raman and reflectance spectroscopy. A Raman spectrum can be used to access the molecular constitution of a particular tissue and classify it. Raman spectroscopy is largely used in the quantification and evaluation of human atherosclerosis, being a powerful technique for performing biochemical analysis without tissue removal. Nevertheless, increased thickness and disorganization of the collagen fibre network and extracellular matrix are known to affect the diffuse spectral reflectance of the tissue. A catheter with the "6 around 1" configuration, the central fiber transmit laser radiation to the sample and the scattered light is collected by the other six surrounding fibers, was used both for Raman and reflectance spectroscopy. A white light (krypton lamp, flashtube Model FX 1160 Perkin Elmer, USA) excitation was used for reflectance measurements. A Ti-sapphire (785nm, Spectra Physics, model 3900S, USA) laser, pumped by an argon laser (Spectra Physics, model Stabilite 2017, USA) was used as the near infrared Raman set up. Several ex-vivo spectra of aortic valve samples were analyzed. The results show a promising way to differentiate normal, fibrous and calcified tissue in aortic valve.

Interface morphology of Mo/Si multilayer systems with varying Mo layer thickness studied by EUV diffuse scattering.

PubMed

Haase, Anton; Soltwisch, Victor; Braun, Stefan; Laubis, Christian; Scholze, Frank

2017-06-26

We investigate the influence of the Mo-layer thickness on the EUV reflectance of Mo/Si mirrors with a set of unpolished and interface-polished Mo/Si/C multilayer mirrors. The Mo-layer thickness is varied in the range from 1.7 nm to 3.05 nm. We use a novel combination of specular and diffuse intensity measurements to determine the interface roughness throughout the multilayer stack and do not rely on scanning probe measurements at the surface only. The combination of EUV and X-ray reflectivity measurements and near-normal incidence EUV diffuse scattering allows to reconstruct the Mo layer thicknesses and to determine the interface roughness power spectral density. The data analysis is conducted by applying a matrix method for the specular reflection and the distorted-wave Born approximation for diffuse scattering. We introduce the Markov-chain Monte Carlo method into the field in order to determine the respective confidence intervals for all reconstructed parameters. We unambiguously detect a threshold thickness for Mo in both sample sets where the specular reflectance goes through a local minimum correlated with a distinct increase in diffuse scatter. We attribute that to the known appearance of an amorphous-to-crystallization transition at a certain thickness threshold which is altered in our sample system by the polishing.

Time-dependent diffuse reflectance spectroscopy for in vivo characterization of pediatric epileptogenic brain lesions

NASA Astrophysics Data System (ADS)

Oh, Sanghoon; Ragheb, John; Bhatia, Sanjiv; Sandberg, David; Johnson, Mahlon; Fernald, Bradley; Lin, Wei-Chiang

2008-02-01

Optical spectroscopy for in vivo tissue diagnosis is performed traditionally in a static manner; a snap shot of the tissue biochemical and morphological characteristics is captured through the interaction between light and the tissue. This approach does not capture the dynamic nature of a living organ, which is critical to the studies of brain disorders such as epilepsy. Therefore, a time-dependent diffuse reflectance spectroscopy system with a fiber-optic probe was designed and developed. The system was designed to acquire broadband diffuse reflectance spectra (240 ~ 932 nm) at an acquisition rate of 33 Hz. The broadband spectral acquisition feature allows simultaneous monitoring of various physiological characteristics of tissues. The utility of such a system in guiding pediatric epilepsy surgery was tested in a pilot clinical study including 13 epilepsy patients and seven brain tumor patients. The control patients were children undergoing suregery for brain tumors in which measurements were taken from normal brain exposed during the surgery. Diffuse reflectance spectra were acquired for 12 seconds from various parts of the brain of the patients during surgery. Recorded spectra were processed and analyzed in both spectral and time domains to gain insights into the dynamic changes in, for example, hemodynamics of the investigated brain tissue. One finding from this pilot study is that unsynchronized alterations in local blood oxygenation and local blood volume were observed in epileptogenic cortex. These study results suggest the advantage of using a time-dependent diffuse reflectance spectroscopy system to study epileptogenic brain in vivo.

White matter correlates of sensory processing in autism spectrum disorders

PubMed Central

Pryweller, Jennifer R.; Schauder, Kimberly B.; Anderson, Adam W.; Heacock, Jessica L.; Foss-Feig, Jennifer H.; Newsom, Cassandra R.; Loring, Whitney A.; Cascio, Carissa J.

2014-01-01

Autism spectrum disorder (ASD) has been characterized by atypical socio-communicative behavior, sensorimotor impairment and abnormal neurodevelopmental trajectories. DTI has been used to determine the presence and nature of abnormality in white matter integrity that may contribute to the behavioral phenomena that characterize ASD. Although atypical patterns of sensory responding in ASD are well documented in the behavioral literature, much less is known about the neural networks associated with aberrant sensory processing. To address the roles of basic sensory, sensory association and early attentional processes in sensory responsiveness in ASD, our investigation focused on five white matter fiber tracts known to be involved in these various stages of sensory processing: superior corona radiata, centrum semiovale, inferior longitudinal fasciculus, posterior limb of the internal capsule, and splenium. We acquired high angular resolution diffusion images from 32 children with ASD and 26 typically developing children between the ages of 5 and 8. We also administered sensory assessments to examine brain-behavior relationships between white matter integrity and sensory variables. Our findings suggest a modulatory role of the inferior longitudinal fasciculus and splenium in atypical sensorimotor and early attention processes in ASD. Increased tactile defensiveness was found to be related to reduced fractional anisotropy in the inferior longitudinal fasciculus, which may reflect an aberrant connection between limbic structures in the temporal lobe and the inferior parietal cortex. Our findings also corroborate the modulatory role of the splenium in attentional orienting, but suggest the possibility of a more diffuse or separable network for social orienting in ASD. Future investigation should consider the use of whole brain analyses for a more robust assessment of white matter microstructure. PMID:25379451

Turbidity in the southern Irish Sea

NASA Astrophysics Data System (ADS)

Bowers, D. G.; Gaffney, S.; White, M.; Bowyer, P.

2002-10-01

This paper presents new in situ optical and associated measurements from 85 stations in the central and southern Irish Sea. There is a strong linear relationship between the irradiance reflectance RA in the orange-red part of the spectrum (580-680 nm) and the diffuse attenuation coefficient, K, for white light: K=0.05+0.26 R A, where K is in m -1 and RA has been corrected to just above-surface reflectance and expressed as a percentage. The significance of this result is that this particular reflectance can be measured by the advanced very high resolution radiometer on board the NOAA series of satellites. In principle, therefore, cloud cover permitting, the transparency of the Irish Sea to sunlight, can be mapped from space. This result is shown to be consistent with a simple optical model in which light scattering is principally by mineral suspended solids, and light absorption is by water, mineral suspended solids and chlorophyll. Best fit between model and observations is achieved with a specific scattering coefficient of 0.5 m 2 g -1. The measurements were made during four cruises, at different times of year and across the range of turbidity found in the Irish Sea. The geographical distribution of suspended sediments confirms the presence, previously inferred from satellite imagery, of two separate turbidity maxima, one off Wicklow Head, the other off Anglesey. These correspond to the areas of strongest tidal currents. Yellow substance was found in highest concentration in a band along the Irish coast. Chlorophyll concentrations were generally low during these cruises. A residual problem is that a direct comparison of in situ reflectance and satellite measured reflectance possible on one of the cruises shows a serious discrepancy, although on average there appears to be a good agreement between satellite and in situ reflectance.

Effect of field-aligned-beam in parallel diffusion of energetic particles in the Earth's foreshock

NASA Astrophysics Data System (ADS)

Matsukiyo, S.; Nakanishi, K.; Otsuka, F.; Kis, A.; Lemperger, I.; Hada, T.

2016-12-01

Diffusive shock acceleration (DSA) is one of the plausible acceleration mechanisms of cosmic rays. In the standard DSA model the partial density of the accelerated particles, diffused into upstream, exponentially decreases as the distance to the shock increases. Kis et al. (GRL, 31, L20801, 2004) examined the density gradients of energetic ions upstream of the bow shock with high accuracy by using Cluster data. They estimated the diffusion coefficients of energetic ions for the event in February 18, 2003 and showed that the obtained diffusion coefficients are significantly smaller than those estimated in the past statistical study. This implies that particle acceleration at the bow shock can be more efficient than considered before. Here, we focus on the effect of the field-aligned-beam (FAB) which is often observed in the foreshock, and examine how the FAB affects the efficiency of diffusion of the energetic ions by performing test particle simulations. The upstream turbulence is given by the superposition of parallel Alfven waves with power-law energy spectrum with random phase approximation. In the spectrum we further add a peak corresponding to the waves resonantly generated by the FAB. The dependence of the diffusion coefficient on the presence of the FAB as well as total energy of the turbulence, power-law index of the turbulence, and intensity of FAB oriented waves are discussed.

Infrared deflectometry for the inspection of diffusely specular surfaces

NASA Astrophysics Data System (ADS)

Höfer, Sebastian; Burke, Jan; Heizmann, Michael

2016-12-01

Deflectometry is a full-field gradient technique that lends itself very well to testing specular surfaces. It uses the geometry of specular reflection to determine the gradient of the surface under inspection. In consequence, a necessary precondition to apply deflectometry is the presence of at least partially specular reflection. Surfaces with larger roughness have increasingly diffuse reflection characteristics, making them inaccessible to usual deflectometry. However, many industrially relevant surfaces exist that change their reflection characteristic during production and processing. An example is metal sheets that are used as car body parts. Whereas the molded but otherwise raw metal sheets show a mostly diffuse reflection without sufficient specular reflection, the final car body panels have a high specular reflectance due to the lacquering. In consequence, it would be advantageous to apply the same inspection approach both for the raw material and for the final product. To solve this challenge, specular reflection from rough surfaces can be achieved using light with a larger wavelength, as the specular reflectivity of a surface depends on the ratio of the surface roughness and the wavelength of the light applied. Wavelengths in the thermal infrared range create enough specular reflection to apply deflectometry on many visually rough metal surfaces. This contribution presents the principles of thermal deflectometry, its special challenges, and illustrates its use with examples from the inspection of industrially produced surfaces.

A multigroup radiation diffusion test problem: Comparison of code results with analytic solution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shestakov, A I; Harte, J A; Bolstad, J H

2006-12-21

We consider a 1D, slab-symmetric test problem for the multigroup radiation diffusion and matter energy balance equations. The test simulates diffusion of energy from a hot central region. Opacities vary with the cube of the frequency and radiation emission is given by a Wien spectrum. We compare results from two LLNL codes, Raptor and Lasnex, with tabular data that define the analytic solution.

1/f noise: diffusive systems and music

DOE Office of Scientific and Technical Information (OSTI.GOV)

Voss, R.F.

1975-11-01

Measurements of the 1/f voltage noise in continuous metal films are reported. At room temperature, samples of pure metals and bismuth (with a carrier density smaller by 10/sup 5/) of similar volume had comparable noise. The results suggest that the noise arises from equilibrium temperature fluctuations modulating the resistance. Spatial correlation of the noise implied that the fluctuations obey a diffusion equation. The empirical inclusion of an explicit 1/f region and appropriate normalization lead to excellent agreement with the measured noise. If the fluctuations are assumed to be spatially correlated, the diffusion equation can yield an extended 1/f region inmore » the power spectrum. The temperature response of a sample to delta and step function power inputs is shown to have the same shape as the autocorrelation function for uncorrelated and correlated temperature fluctuations, respectively. The spectrum obtained from the cosine transform of the measured step function response is in excellent agreement with the measured 1/f voltage noise spectrum. Spatially correlated equilibrium temperature fluctuations are not the dominant source of 1/f noise in semiconductors and metal films. However, the agreement between the low-frequency spectrum of fluctuations in the mean-square Johnson noise voltage and the resistance fluctuation spectrum measured in the presence of a current demonstrates that in these systems the 1/f noise is also due to equilibrium resistance fluctuations. Loudness fluctuations in music and speech and pitch fluctuations in music also show the 1/f behavior. 1/f noise sources, consequently, are demonstrated to be the natural choice for stochastic composition. 26 figures, 1 table. (auth)« less

Polarized and non-polarized leaf reflectances of Coleus blumei

NASA Technical Reports Server (NTRS)

Grant, Lois; Daughtry, C. S. T.; Vanderbilt, V. C.

1987-01-01

A polarization photometer has been used to measure the reflectance of three variegated portions of Coleus blumei, Benth. in five wavelength bands of the visible and near-infrared spectrum. The polarized component of the reflectance factor was found to be independent of wavelength, indicating that the polarized reflectance arises from the leaf surface. It is suggested that differences in the polarized component result from variations in surface features. The nonpolarized component of the reflectance factor is shown to be related to the internal leaf structure. The variation of the degree of polarization with wavelength was found to be greatest in the regions of the spectrum where absorption occurs.

Optimized 2D array of thin silicon pillars for efficient antireflective coatings in the visible spectrum

PubMed Central

Proust, Julien; Fehrembach, Anne-Laure; Bedu, Frédéric; Ozerov, Igor; Bonod, Nicolas

2016-01-01

Light reflection occuring at the surface of silicon wafers is drastically diminished by etching square pillars of height 110 nm and width 140 nm separated by a 100 nm gap distance in a square lattice. The design of the nanostructure is optimized to widen the spectral tolerance of the antireflective coatings over the visible spectrum for both fundamental polarizations. Angle and polarized resolved optical measurements report a light reflection remaining under 5% when averaged in the visible spectrum for both polarizations in a wide angular range. Light reflection remains almost insensitive to the light polarization even in oblique incidence. PMID:27109643

Self-Referenced Method for Estimating Refractive Index and Absolute Absorption of Loose Semiconductor Powders

DOE PAGES

Huang, Huafeng; Colabello, Diane M.; Sklute, Elizabeth C.; ...

2017-04-23

The absolute absorption coefficient, α(E), is a critical design parameter for devices using semiconductors for light harvesting associated with renewable energy production, both for classic technologies such as photovoltaics and for emerging technologies such as direct solar fuel production. While α(E) is well-known for many classic simple semiconductors used in photovoltaic applications, the absolute values of α(E) are typically unknown for the complex semiconductors being explored for solar fuel production due to the absence of single crystals or crystalline epitaxial films that are needed for conventional methods of determining α(E). In this work, a simple self-referenced method for estimating bothmore » the refractive indices, n(E), and absolute absorption coefficients, α(E), for loose powder samples using diffuse reflectance data is demonstrated. In this method, the sample refractive index can be deduced by refining n to maximize the agreement between the relative absorption spectrum calculated from bidirectional reflectance data (calculated through a Hapke transform which depends on n) and integrating sphere diffuse reflectance data (calculated through a Kubleka–Munk transform which does not depend on n). This new method can be quickly used to screen the suitability of emerging semiconductor systems for light-harvesting applications. The effectiveness of this approach is tested using the simple classic semiconductors Ge and Fe 2O 3 as well as the complex semiconductors La 2MoO 5 and La 4Mo 2O 11. The method is shown to work well for powders with a narrow size distribution (exemplified by Fe 2O 3) and to be ineffective for semiconductors with a broad size distribution (exemplified by Ge). As such, it provides a means for rapidly estimating the absolute optical properties of complex solids which are only available as loose powders.« less

Physiological basis for noninvasive skin cancer diagnosis using diffuse reflectance spectroscopy

NASA Astrophysics Data System (ADS)

Zhang, Yao; Markey, Mia K.; Tunnell, James W.

2017-02-01

Diffuse reflectance spectroscopy offers a noninvasive, fast, and low-cost alternative to visual screening and biopsy for skin cancer diagnosis. We have previously acquired reflectance spectra from 137 lesions in 76 patients and determined the capability of spectral diagnosis using principal component analysis (PCA). However, it is not well elucidated why spectral analysis enables tissue classification. To provide the physiological basis, we used the Monte Carlo look-up table (MCLUT) model to extract physiological parameters from those clinical data. The MCLUT model results in the following physiological parameters: oxygen saturation, hemoglobin concentration, melanin concentration, vessel radius, and scattering parameters. Physiological parameters show that cancerous skin tissue has lower scattering and larger vessel radii, compared to normal tissue. These results demonstrate the potential of diffuse reflectance spectroscopy for detection of early precancerous changes in tissue. In the future, a diagnostic algorithm that combines these physiological parameters could be enable non-invasive diagnosis of skin cancer.

Reflectance spectroscopy for noninvasive evaluation of hair follicle stage

NASA Astrophysics Data System (ADS)

Liu, Caihua; Guan, Yue; Wang, Jianru; Zhong, Xiewei; Liu, Xiuli; Zhu, Dan

2015-05-01

Hair follicle offers an excellent model for systems biology and regenerative medicine. So far, the stages of hair follicle growth have been evaluated by histological examination. In this work, a noninvasive spectroscopy was proposed by measuring the diffuse reflectance of mouse skin and analyzing the melanin value. Results show that the skin diffuse reflectance was relatively high when hair follicles were at the telogen stage and at the beginning of the anagen stage, and decreased with the progression of the anagen stage. When the hair follicle entered into the catagen stage, the diffuse reflectance gradually increased. The changes in the melanin content of skin had contrary dynamics. Substages of the hair follicle cycle could be distinguished by comparing the changes in melanin value with the histological examination. This study provided a new method for noninvasive evaluation of the hair follicle stage, and should be valuable for basic and therapeutic investigations on hair regeneration.

Sound propagation in street canyons: comparison between diffusely and geometrically reflecting boundaries

PubMed

Kang

2000-03-01

This paper systematically compares the sound fields in street canyons with diffusely and geometrically reflecting boundaries. For diffuse boundaries, a radiosity-based theoretical/computer model has been developed. For geometrical boundaries, the image source method has been used. Computations using the models show that there are considerable differences between the sound fields resulting from the two kinds of boundaries. By replacing diffuse boundaries with geometrical boundaries, the sound attenuation along the length becomes significantly less; the RT30 is considerably longer; and the extra attenuation caused by air or vegetation absorption is reduced. There are also some similarities between the sound fields under the two boundary conditions. For example, in both cases the sound attenuation along the length with a given amount of absorption is the highest if the absorbers are arranged on one boundary and the lowest if they are evenly distributed on all boundaries. Overall, the results suggest that, from the viewpoint of urban noise reduction, it is better to design the street boundaries as diffusely reflective rather than acoustically smooth.

Spectral Characteristics of Hayabusa 2 Near-Earth Asteroid Targets 162173 1999 JU3 and 2001 QC34

NASA Astrophysics Data System (ADS)

Vilas, Faith

2008-04-01

Reflectance spectra of C-type near-Earth asteroid 162173 1999 JU3 were acquired on UT 2007 July 11, September 10 and 11. An absorption feature centered near 0.7 μm, and associated with the presence of iron-bearing phyllosilicates, is seen in the 2007 July 11 spectrum. The 2007 September spectrum shows a shallow absorption feature centered near 0.6 μm. In contrast, the reflectance spectrum of 162173 1999 JU3 obtained during its discovery apparition has no absorption feature, suggesting that the asteroid's surface covers the conjunction of two different geological units. The variation in the presence and absence of these features in reflectance spectra of the surface material of C-type asteroids is observed among main-belt asteroids. As the target for the planned Japanese mission Hayabusa 2, 162173 1999 JU3 could represent a sample of aqueously altered early solar system material. An alternative target for Hayabusa 2, 2001 QC34, was observed spectrally for the first time. Its reflectance spectrum has characteristics of a Q-class or O-class asteroid.

Relationships between diffuse reflectance and vegetation canopy variables based on the radiative transfer theory

NASA Technical Reports Server (NTRS)

Park, J. K.; Deering, D. W.

1981-01-01

Out of the lengthy original expression of the diffuse reflectance formula, simple working equations were derived by employing characteristic parameters, which are independent of the canopy coverage and identifiable by field observations. The typical asymptotic nature of reflectance data that is usually observed in biomass studies was clearly explained. The usefulness of the simplified equations was demonstrated by the exceptionally close fit of the theoretical curves to two separately acquired data sets for alfalfa and shortgrass prairie canopies.

Diffusely Reflecting Paints Containing TFE

NASA Technical Reports Server (NTRS)

Shai, M. C.; Schutt, J. B.

1985-01-01

Highly reflective, diffused coatings developed by incorporating polytetrafluoroethylene (TFE) pigment with alcohol-soluble binders. Alcohol and binder mixed together in blender before adding TFE. TFE preferably outgassed in mechanical-pump vacuum for typical interval of 4 hours before adding to liquid. Like wetting agent, vacuum treatment helps to prevent clumping of TFE and eases dispersion throughout mixture. Mixture blended for 3 to 5 minutes before used. Coatings useful on reflectance-standard surfaces for calibrating radiometric instruments in both laboratory and field. Paints washable and usable as optical reference surfaces.

Mercury: surface composition from the reflection spectrum.

PubMed

McCord, T B; Adams, J B

1972-11-17

The reflection spectrum for the integral disk of the planet Mercury was measured and was found to have a constant positive slope from 0.32 to 1.05 micrometers, except for absorption features in the infrared. The reflectivity curve matches closely the curve for the lunar upland and mare regions. Thus, the surface of Mercury is probably covered with a lunar-like soil rich in dark glasses of high iron and titanium content. Pyroxene is probably the dominant mafic mineral.

Quantification of Sheet Resistance in Boron-Diffused Silicon Using Micro-Photoluminescence Spectroscopy at Room Temperature

DOE PAGES

Nguyen, Hieu T.; Johnston, Steve; Paduthol, Appu; ...

2017-09-01

A micro-photoluminescence-based technique is presented, to quantify and map sheet resistances of boron-diffused layers in silicon solar cell precursors with micron-scale spatial resolution at room temperature. The technique utilizes bandgap narrowing effects in the heavily-doped layers, yielding a broader photoluminescence spectrum at the long-wavelength side compared to the spectrum emitted from lightly doped silicon. By choosing an appropriate spectral range as a metric to assess the doping density, the impacts of photon reabsorption on the analysis can be avoided; thus, an accurate characterization of the sheet resistance can be made. This metric is demonstrated to be better representative of themore » sheet resistance than the surface doping density or the total dopant concentration of the diffused layer. The technique is applied to quantify sheet resistances of 12-um-wide diffused fingers in interdigitated back-contact solar cell precursors and large diffused areas. The results are confirmed by both 4-point probe and time-of-flight secondary-ion mass spectrometry measurements. Lastly, the practical limitations associated with extending the proposed technique into an imaging mode are presented and explained.« less

Quantification of Sheet Resistance in Boron-Diffused Silicon Using Micro-Photoluminescence Spectroscopy at Room Temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nguyen, Hieu T.; Johnston, Steve; Paduthol, Appu

A micro-photoluminescence-based technique is presented, to quantify and map sheet resistances of boron-diffused layers in silicon solar cell precursors with micron-scale spatial resolution at room temperature. The technique utilizes bandgap narrowing effects in the heavily-doped layers, yielding a broader photoluminescence spectrum at the long-wavelength side compared to the spectrum emitted from lightly doped silicon. By choosing an appropriate spectral range as a metric to assess the doping density, the impacts of photon reabsorption on the analysis can be avoided; thus, an accurate characterization of the sheet resistance can be made. This metric is demonstrated to be better representative of themore » sheet resistance than the surface doping density or the total dopant concentration of the diffused layer. The technique is applied to quantify sheet resistances of 12-um-wide diffused fingers in interdigitated back-contact solar cell precursors and large diffused areas. The results are confirmed by both 4-point probe and time-of-flight secondary-ion mass spectrometry measurements. Lastly, the practical limitations associated with extending the proposed technique into an imaging mode are presented and explained.« less

Pinpointing the knee of cosmic rays with diffuse PeV γ-rays and neutrinos

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Y. Q.; Hu, H. B.; Yuan, Q.

2014-11-01

The origin of the knee in the cosmic ray spectrum remains to be an unsolved fundamental problem. There are various kinds of models that predict different break positions and the compositions of the knee. In this work, we suggest the use of diffuse γ-rays and neutrinos as probes to test these models. Based on several typical types of composition models, the diffuse γ-ray and neutrino spectra are calculated and show distinctive cutoff behaviors at energies from tens of TeV to multi-PeV. The expected flux will be observable by the newly upgraded Tibet-ASγ+MD (muon detector) experiment as well as more sensitivemore » future projects, such as LHAASO and HiSCORE. By comparing the neutrino spectrum with the recent observations by the IceCube experiment, we find that the diffuse neutrinos from interactions between the cosmic rays and the interstellar medium may not be responsible to the majority of the IceCube events. Future measurements of the neutrinos may be able to identify the Galactic diffuse component and shed further light on the problem of the knee of cosmic rays.« less

Noninvasive diagnostics of skin microphysical parameters based on spatially resolved diffuse reflectance spectroscopy

NASA Astrophysics Data System (ADS)

Lisenko, S. A.; Kugeiko, M. M.

2013-01-01

The ability to determine noninvasively microphysical parameters (MPPs) of skin characteristic of malignant melanoma was demonstrated. The MPPs were the melanin content in dermis, saturation of tissue with blood vessels, and concentration and effective size of tissue scatterers. The proposed method was based on spatially resolved spectral measurements of skin diffuse reflectance and multiple regressions between linearly independent measurement components and skin MPPs. The regressions were established by modeling radiation transfer in skin with a wide variation of its MPPs. Errors in the determination of skin MPPs were estimated using fiber-optic measurements of its diffuse reflectance at wavelengths of commercially available semiconductor diode lasers (578, 625, 660, 760, and 806 nm) at source-detector separations of 0.23-1.38 mm.

Landsat test of diffuse reflectance models for aquatic suspended solids measurement

NASA Technical Reports Server (NTRS)

Munday, J. C., Jr.; Alfoldi, T. T.

1979-01-01

Landsat radiance data were used to test mathematical models relating diffuse reflectance to aquatic suspended solids concentration. Digital CCT data for Landsat passes over the Bay of Fundy, Nova Scotia were analyzed on a General Electric Co. Image 100 multispectral analysis system. Three data sets were studied separately and together in all combinations with and without solar angle correction. Statistical analysis and chromaticity analysis show that a nonlinear relationship between Landsat radiance and suspended solids concentration is better at curve-fitting than a linear relationship. In particular, the quasi-single-scattering diffuse reflectance model developed by Gordon and coworkers is corroborated. The Gordon model applied to 33 points of MSS 5 data combined from three dates produced r = 0.98.

Microstructural Abnormalities of Short-Distance White Matter Tracts in Autism Spectrum Disorder

ERIC Educational Resources Information Center

Shukla, Dinesh K.; Keehn, Brandon; Smylie, Daren M.; Muller, Ralph-Axel

2011-01-01

Recent functional connectivity magnetic resonance imaging and diffusion tensor imaging (DTI) studies have suggested atypical functional connectivity and reduced integrity of long-distance white matter fibers in autism spectrum disorder (ASD). However, evidence for short-distance white matter fibers is still limited, despite some speculation of…

Cortexin diffusion in human eye sclera

DOE Office of Scientific and Technical Information (OSTI.GOV)

Genina, Elina A; Bashkatov, A N; Tuchin, Valerii V

2011-05-31

Investigation of the diffusion of cytamines, a typical representative of which is cortexin, is important for evaluating the drug dose, necessary to provide sufficient concentration of the preparation in the inner tissues of the eye. In the present paper, the cortexin diffusion rate in the eye sclera is measured using the methods of optical coherence tomography (OCT) and reflectance spectroscopy. The technique for determining the diffusion coefficient is based on the registration of temporal dependence of the eye sclera scattering parameters caused by partial replacement of interstitial fluid with the aqueous cortexin solution, which reduces the level of the OCTmore » signal and decreases the reflectance of the sclera. The values of the cortexin diffusion coefficient obtained using two independent optical methods are in good agreement. (optical technologies in biophysics and medicine)« less

Longitudinal Processing Speed Impairments in Males with Autism and the Effects of White Matter Microstructure

PubMed Central

Travers, Brittany G.; Bigler, Erin D.; Tromp, Do P. M.; Adluru, Nagesh; Froehlich, Alyson L.; Ennis, Chad; Lange, Nicholas; Nielsen, Jared A.; Prigge, Molly B. D.; Alexander, Andrew L.; Lainhart, Janet E.

2014-01-01

The present study used an accelerated longitudinal design to examine group differences and age-related changes in processing speed in 81 individuals with Autism Spectrum Disorder (ASD) compared to 56 age-matched individuals with typical development (ages 6–39 years). Processing speed was assessed using the Wechsler Intelligence Scale for Children-3rd edition (WISC-III) and the Wechsler Adult Intelligence Scale-3rd edition (WAIS-III). Follow-up analyses examined processing speed subtest performance and relations between processing speed and white matter microstructure (as measured with diffusion tensor imaging [DTI] in a subset of these participants). After controlling for full scale IQ, the present results show that processing speed index standard scores were on average 12 points lower in the group with ASD compared to the group with typical development. There were, however, no significant group differences in standard score age-related changes within this age range. For subtest raw scores, the group with ASD demonstrated robustly slower processing speeds in the adult versions of the IQ test (i.e., WAIS-III) but not in the child versions (WISC-III), even though age-related changes were similar in both the ASD and typically developing groups. This pattern of results may reflect difficulties that become increasingly evident in ASD on more complex measures of processing speed. Finally, DTI measures of whole-brain white matter microstructure suggested that fractional anisotropy (but not mean diffusivity, radial diffusivity, or axial diffusivity) made significant but small-sized contributions to processing speed standard scores across our entire sample. Taken together, the present findings suggest that robust decreases in processing speed may be present in ASD, more pronounced in adulthood, and partially attributable to white matter microstructural integrity. PMID:24269298

Time-dependent models for blazar emission with the second-order Fermi acceleration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Asano, Katsuaki; Takahara, Fumio; Toma, Kenji

The second-order Fermi acceleration (Fermi-II) driven by turbulence may be responsible for the electron acceleration in blazar jets. We test this model with time-dependent simulations. The hard electron spectrum predicted by the Fermi-II process agrees with the hard photon spectrum of 1ES 1101–232. For other blazars that show softer spectra, the Fermi-II model requires radial evolution of the electron injection rate and/or diffusion coefficient in the outflow. Such evolutions can yield a curved electron spectrum, which can reproduce the synchrotron spectrum of Mrk 421 from the radio to the X-ray regime. The photon spectrum in the GeV energy range ofmore » Mrk 421 is hard to fit with a synchrotron self-Compton model. However, if we introduce an external radio photon field with a luminosity of 4.9 × 10{sup 38} erg s{sup –1}, GeV photons are successfully produced via inverse Compton scattering. The temporal variability of the diffusion coefficient or injection rate causes flare emission. The observed synchronicity of X-ray and TeV flares implies a decrease of the magnetic field in the flaring source region.« less

The role of cross-shock potential on pickup ion shock acceleration in the framework of focused transport theory

DOE PAGES

Zuo, Pingbing; Zhang, Ming; Rassoul, Hamid K.

2013-10-03

The focused transport theory is appropriate to describe the injection and acceleration of low-energy particles at shocks as an extension of diffusive shock acceleration (DSA). In this investigation, we aim to characterize the role of cross-shock potential (CSP) originated in the charge separation across the shock ramp on pickup ion (PUI) acceleration at various types of shocks with a focused transport model. The simulation results of energy spectrum and spatial density distribution for the cases with and without CSP added in the model are compared. With sufficient acceleration time, the focused transport acceleration finally falls into the DSA regime withmore » the power-law spectral index equal to the solution of the DSA theory. The CSP can affect the shape of the spectrum segment at lower energies, but it does not change the spectral index of the final power-law spectrum at high energies. It is found that the CSP controls the injection efficiency which is the fraction of PUIs reaching the DSA regime. A stronger CSP jump results in a dramatically improved injection efficiency. Our simulation results also show that the injection efficiency of PUIs is mass-dependent, which is lower for species with a higher mass. Additionally, the CSP is able to enhance the particle reflection upstream to produce a stronger intensity spike at the shock front. Lastly, we conclude that the CSP is a non-negligible factor that affects the dynamics of PUIs at shocks.« less

Light field and water clarity simulation of natural environments in laboratory conditions

NASA Astrophysics Data System (ADS)

Pe'eri, Shachak; Shwaery, Glenn

2012-06-01

Simulation of natural oceanic conditions in a laboratory setting is a challenging task, especially when that environment can be miles away. We present an attempt to replicate the solar radiation expected at different latitudes with varying water clarity conditions up to 30 m in depth using a 2.5 m deep engineering tank at the University of New Hampshire. The goals of the study were: 1) to configure an underwater light source that produced an irradiance spectrum similar to natural daylight with the sun at zenith and at 60° under clear atmospheric conditions, and 2) to monitor water clarity as a function of depth. Irradiance was measured using a spectra-radiometer with a cosine receiver to analyze the output spectrum of submersed lamps as a function of distance. In addition, an underwater reflection method was developed to measure the diffuse attenuation coefficient in real time. Two water clarity types were characterized, clear waters representing deep, open-ocean conditions, and murky waters representing littoral environments. Results showed good correlation between the irradiance measured at 400 nm to 600 nm and the natural daylight spectrum at 3 m from the light source. This can be considered the water surface conditions reference. Using these methodologies in a controlled laboratory setting, we are able to replicate illumination and water conditions to study the physical, chemical and biological processes on natural and man-made objects and/or systems in simulated, varied geographic locations and environments.

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

NASA Astrophysics Data System (ADS)

Chen, Yung-Sheng; Wang, Jeng-Yau

2015-09-01

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

Diffuse interstellar bands in reflection nebulae

NASA Technical Reports Server (NTRS)

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

1994-01-01

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

New Results from Fermi-LAT and Their Implications for the Nature of Dark Matter and the Origin of Cosmic Rays

NASA Technical Reports Server (NTRS)

Moiseev, Alexander

2009-01-01

The measured spectrum is compatible with a power law within our current systematic errors. The spectral index (-3.04) is harder than expected from previous experiments and simple theoretical considerations. "Pre-Fermi" diffusive model requires a harder electron injection spectrum (by 0.12) to fit the Fermi data, but inconsistent with positron excess reported by Pamela if it extends to higher energy. Additional component of electron flux from local source(s) may solve the problem; its origin, astrophysical or exotic, is still unclear. Valuable contribution to the calculation of IC component of diffuse gamma radiation.

MODIS Solar Diffuser Attenuation Screen Modeling Results

NASA Technical Reports Server (NTRS)

Waluschka, Eugene; Xuong, Xiaoxiong; Guenther, Bruce; Barnes, William

2004-01-01

On-orbit calibration of the reflected solar bands on the EOS Moderate Resolution Imaging Spectroradiometer (MODIS) is accomplished by have the instrument view a high reflectance diffuse surface illuminated by the sun. For some of the spectral bands this proves to be much too bright a signal that results in the saturation of detectors designed for measuring low reflectance (ocean) surfaces signals. A mechanical attenuation device in the form of a pin hole screen is used to reduce the signals to calibrate these bands. The sensor response to solar illumination of the SD with and without the attenuation screen in place will be presented. The MODIS detector response to the solar diffuser is smooth when the attenuation screen is absent, but has structures up to a few percent when the attenuation screen is present. This structure corresponds to non-uniform illumination from the solar diffuser. Each pin hole produces a pin-hole image of the sun on the solar diffuser, and there are very many pin hole images of the sun on the solar diffuser for each MODIS detector. Even though there are very many pin-hole images of the sun on the solar diffuser, it is no longer perfectly uniformly illuminated. This non-uniformly illuminated solar diffuser produces intensity variation on the focal planes. The results of a very detailed simulation will be discussed which show how the illumination of the focal plane changes as a result of the attenuation, and the impacts on the calibration will be discussed.

Diffusion-weighted imaging and demyelinating diseases: new aspects of an old advanced sequence.

PubMed

Rueda-Lopes, Fernanda C; Hygino da Cruz, Luiz C; Doring, Thomas M; Gasparetto, Emerson L

2014-01-01

The purpose of this article is to discuss classic applications in diffusion-weighted imaging (DWI) in demyelinating disease and progression of DWI in the near future. DWI is an advanced technique used in the follow-up of demyelinating disease patients, focusing on the diagnosis of a new lesion before contrast enhancement. With technical advances, diffusion-tensor imaging; new postprocessing techniques, such as tract-based spatial statistics; new ways of calculating diffusion, such as kurtosis; and new applications for DWI and its spectrum are about to arise.

The 2-79 keV X-ray Spectrum of the Circinus Galaxy with NuSTAR, XMM-Newton and Chandra: a Fully Compton-Thick Active Galactic Nucleus

DOE PAGES

Arevalo, P.; Bauer, F. E.; Puccetti, S.; ...

2014-07-30

Here, the Circinus galaxy is one of the closest obscured active galactic nuclei (AGNs), making it an ideal target for detailed study. Combining archival Chandra and XMM-Newton data with new NuSTAR observations, we model the 2-79 keV spectrum to constrain the primary AGN continuum and to derive physical parameters for the obscuring material. Chandra's high angular resolution allows a separation of nuclear and off-nuclear galactic emission. In the off-nuclear diffuse emission, we find signatures of strong cold reflection, including high equivalent-width neutral Fe lines. This Compton-scattered off-nuclear emission amounts to 18% of the nuclear flux in the Fe line region,more » but becomes comparable to the nuclear emission above 30 keV. The new analysis no longer supports a prominent transmitted AGN component in the observed band. We find that the nuclear spectrum is consistent with Compton scattering by an optically thick torus, where the intrinsic spectrum is a power law of photon index Γ = 2.2-2.4, the torus has an equatorial column density of N H = (6-10) × 10 24 cm –2, and the intrinsic AGN 2-10 keV luminosity is (2.3-5.1) × 10 42 erg s –1. These values place Circinus along the same relations as unobscured AGNs in accretion rate versus Γ and L X versus L IR phase space. NuSTAR's high sensitivity and low background allow us to study the short timescale variability of Circinus at X-ray energies above 10 keV for the first time. Here, the lack of detected variability favors a Compton-thick absorber, in line with the spectral fitting results.« less

Mechano-chemical synthesis K2MF6 (M = Mn, Ni) by cation-exchange reaction at room temperature

NASA Astrophysics Data System (ADS)

Rawat, Pooja; Nagarajan, Rajamani

2018-02-01

In order to establish the power of mechanochemistry to produce industrially important phosphors, synthesis of K2MnF6 has been attempted by the successive grinding reactions of manganese (II) acetate with ammonium fluoride and potassium fluoride. The progress of reaction was followed by ex-situ characterization after periodic intervals of time. Cubic symmetry of K2MnF6 was evident from its powder X-ray diffraction pattern which was refined successfully in cubic space group (Fm-3m) with a = 8.4658 (20) Å. Stretching and bending vibration modes of MnF62- octahedral units appeared at 740 and 482 cm-1 in the fourier transformed infrared spectrum. Bands at 405 and 652 cm-1 appeared in the Raman spectrum and they were finger-print positions of cubic K2MnF6. Other than the ligand to metal charge transfer transition at 242 nm, transitions from 4A2g to 4T1g, 4T2g and 2T2g of Mn4+-ion appeared at 352, 429, 474 and 569 nm in the UV-visible diffuse reflectance spectrum of the sample. Red emission due to Mn4+ was observed in the photoluminescence spectrum with a decay time of 0.22 ms. Following the success in forming cubic K2MnF6, this approach has been extended to synthesize cubic K2NiF6 at room temperature. All these results confirmed the susceptibility of acetate salts of transition metals belonging to first-row of the periodic table to facile fluorination at room temperature aided by mechanical forces.

Discrimination of various paper types using diffuse reflectance ultraviolet-visible near-infrared (UV-Vis-NIR) spectroscopy: forensic application to questioned documents.

PubMed

Kumar, Raj; Kumar, Vinay; Sharma, Vishal

2015-06-01

Diffuse reflectance ultraviolet-visible-near-infrared (UV-Vis-NIR) spectroscopy is applied as a means of differentiating various types of writing, office, and photocopy papers (collected from stationery shops in India) on the basis of reflectance and absorbance spectra that otherwise seem to be almost alike in different illumination conditions. In order to minimize bias, spectra from both sides of paper were obtained. In addition, three spectra from three different locations (from one side) were recorded covering the upper, middle, and bottom portions of the paper sample, and the mean average reflectivity of both the sides was calculated. A significant difference was observed in mean average reflectivity of Side A and Side B of the paper using Student's pair >t-test. Three different approaches were used for discrimination: (1) qualitative features of the whole set of samples, (2) principal component analysis, and (3) a combination of both approaches. On the basis of the first approach, i.e., qualitative features, 96.49% discriminating power (DP) was observed, which shows highly significant results with the UV-Vis-NIR technique. In the second approach the discriminating power is further enhanced by incorporating the principal component analysis (PCA) statistical method, where this method describes each UV-Vis spectrum in a group through numerical loading values connected to the first few principal components. All components described 100% variance of the samples, but only the first three PCs are good enough to explain the variance (PC1 = 51.64%, PC2 = 47.52%, and PC3 = 0.54%) of the samples; i.e., the first three PCs described 99.70% of the data, whereas in the third approach, the four samples, C, G, K, and N, out of a total 19 samples, which were not differentiated using qualitative features (approach no. 1), were therefore subjected to PCA. The first two PCs described 99.37% of the spectral features. The discrimination was achieved by using a loading plot between PC1 and PC2. It is therefore concluded that maximum discrimination of writing, office, and photocopy paper could be achieved on the basis of the second approach. Hence, the present inexpensive analytical method can be appropriate for application to routine questioned document examination work in forensic laboratories because it provides nondestructive, quantitative, reliable, and repeatable results.

Research on influence of different cover to the characteristic of FBG reflectance spectrum in vacuum thermal environment

NASA Astrophysics Data System (ADS)

Pei, Yifei; Zhang, Jingchuan; Zhang, Luosha; Liu, Yang; Zhang, Lina; Chen, Shiyu

2018-01-01

To satisfy the application of fiber grating sensor technology in high vacuum thermal environment, two different kinds of sleeve compactly single model fiber covered by acrylate and polyimide are researched. Influence of the cover to the characteristic of FBG reflectance spectrum in high vacuum thermal environment is analyzed and verified. First, transmission characteristic of single model fiber in high vacuum thermal environment is analyzed by solve the equation of heat conduction. Then, experimental program of influence on FBG reflection spectrum characteristics is designed and a hardware-in-the-loop detection platform is set up. Finally, the influence of temperature and vacuum on the reflection peak power of FBG in different coating single-mode transmission fiber under high vacuum thermal environment is studied and verified. Experimental results indicate that: when vacuum varied from normal pressure to 10-4Pa level and then return to normal pressure, temperature of two different coating single-mode transmission fiber dropped to -196 ° from room temperature and then returned to room temperature, after 224 hours, the peak power of the FBG reflectance spectrum did not change. It provided the theoretical and experimental basis for the application of optical fiber sensing technology in high vacuum (pressure about 10-4Pa level) and thermal environment (-196 ° 25 ° temperature cycle) .

Bidirectional reflectance distribution function effects in ladar-based reflection tomography.

PubMed

Jin, Xuemin; Levine, Robert Y

2009-07-20

Light reflection from a surface is described by the bidirectional reflectance distribution function (BRDF). In this paper, BRDF effects in reflection tomography are studied using modeled range-resolved reflection from well-characterized geometrical surfaces. It is demonstrated that BRDF effects can cause a darkening at the interior boundary of the reconstructed surface analogous to the well-known beam hardening artifact in x-ray transmission computed tomography (CT). This artifact arises from reduced reflection at glancing incidence angles to the surface. It is shown that a purely Lambertian surface without shadowed components is perfectly reconstructed from range-resolved measurements. This result is relevant to newly fabricated carbon nanotube materials. Shadowing is shown to cause crossed streak artifacts similar to limited-angle effects in CT reconstruction. In tomographic reconstruction, these effects can overwhelm highly diffuse components in proximity to specularly reflecting elements. Diffuse components can be recovered by specialized processing, such as reducing glints via thresholded measurements.

A portable system for noninvasive assessment of advanced glycation end-products using skin fluorescence and reflectance spectrum

NASA Astrophysics Data System (ADS)

Wang, Y. K.; Zhu, L.; Zhang, L.; Zhang, G.; Liu, Y.; Wang, A.

2012-07-01

An optical system has been developed for noninvasive assessment of skin advanced glycation end-products (AGEs). The system comprises mainly a high-power ultraviolet light emitting diode (LED) as an excitation source, an LED array for the reflectance measurement, a trifurcated fiber-optic probe for light transmitting and receiving, and a compact spectrometer for light detecting. Both skin fluorescence of a subject and the reflectance spectrum of the same site can be obtained in a single measurement with the system. Demonstrative measurements with the system have been conducted. Results indicate that the measured reflectance spectrum can be used to compensate for the distortion of AGEs fluorescence, which is caused by skin absorption and scattering. The system is noninvasive, portable, easy to operate, and has potential applications for clinical diagnosis of AGE-related diseases, especially diabetes mellitus.

High-Performance Dye-Sensitized Solar Cells Based on Morphology-Controllable Synthesis of ZnO–ZnS Heterostructure Nanocone Photoanodes

PubMed Central

Rouhi, Jalal; Mamat, Mohamad Hafiz; Ooi, C. H. Raymond; Mahmud, Shahrom; Mahmood, Mohamad Rusop

2015-01-01

High-density and well-aligned ZnO–ZnS core–shell nanocone arrays were synthesized on fluorine-doped tin oxide glass substrate using a facile and cost-effective two-step approach. In this synthetic process, the ZnO nanocones act as the template and provide Zn2+ ions for the ZnS shell formation. The photoluminescence spectrum indicates remarkably enhanced luminescence intensity and a small redshift in the UV region, which can be associated with the strain caused by the lattice mismatch between ZnO and ZnS. The obtained diffuse reflectance spectra show that the nanocone-based heterostructure reduces the light reflection in a broad spectral range and is much more effective than the bare ZnO nanocone and nanorod structures. Dye-sensitized solar cells based on the heterostructure ZnO–ZnS nanocones are assembled, and high conversion efficiency (η) of approximately 4.07% is obtained. The η improvement can be attributed primarily to the morphology effect of ZnO nanocones on light-trapping and effectively passivating the interface surface recombination sites of ZnO nanocones by coating with a ZnS shell layer. PMID:25875377

Numerical Modelling of the Sound Fields in Urban Streets with Diffusely Reflecting Boundaries

NASA Astrophysics Data System (ADS)

KANG, J.

2002-12-01

A radiosity-based theoretical/computer model has been developed to study the fundamental characteristics of the sound fields in urban streets resulting from diffusely reflecting boundaries, and to investigate the effectiveness of architectural changes and urban design options on noise reduction. Comparison between the theoretical prediction and the measurement in a scale model of an urban street shows very good agreement. Computations using the model in hypothetical rectangular streets demonstrate that though the boundaries are diffusely reflective, the sound attenuation along the length is significant, typically at 20-30 dB/100 m. The sound distribution in a cross-section is generally even unless the cross-section is very close to the source. In terms of the effectiveness of architectural changes and urban design options, it has been shown that over 2-4 dB extra attenuation can be obtained either by increasing boundary absorption evenly or by adding absorbent patches on the façades or the ground. Reducing building height has a similar effect. A gap between buildings can provide about 2-3 dB extra sound attenuation, especially in the vicinity of the gap. The effectiveness of air absorption on increasing sound attenuation along the length could be 3-9 dB at high frequencies. If a treatment is effective with a single source, it is also effective with multiple sources. In addition, it has been demonstrated that if the façades in a street are diffusely reflective, the sound field of the street does not change significantly whether the ground is diffusely or geometrically reflective.

MODIS Solar Diffuser On-orbit Performance

NASA Technical Reports Server (NTRS)

Xiong, Xiaoxiong; Chen, H.; Choi, T.; Sun, J.; Angal, A.

2008-01-01

MODIS is a key instrument for the NASA Earth Observing System (EOS), currently operated on both the Terra and Aqua missions. Each MODIS instrument has 20 reflective solar bands (RSBs) and 16 thermal emissive bands (TEBs). MODIS RSB on-orbit calibration is reflectance based using an on-board solar diffuser (SD). The SD bi-directional reflectance factors (BRFs) were characterized pre-launch using reference diffuser samples, which are traceable to NIST reflectance standards. The SD BRF on-orbit degradation (or change) is tracked by another onboard device, called the solar diffuser stability monitor (SDSM). The SDSM is operated during each scheduled SD calibration event, making alternate observations of direct sunlight and the diffusely reflected sunlight from the SD. The time series of the ratios of SDSM's SD view to its Sun view provide SD degradation information. This paper presents and compares the Terra and Aqua MODIS SD on-orbit performance. Results show that the SD on-orbit degradation depends on the amount of solar exposure of the SD plate. In addition, it is strongly wavelengthdependent, with a larger degradation rate at shorter wavelengths. For Terra MODIS, an SD door anomaly occurred in May 2003 that led to a decision to fix the door permanently at an "open" position. Since then, the SD degradation rate has significantly increased due to more frequent solar exposure. As expected, the SD on-orbit performance directly impacts the RSB calibration performance. The lessons learned from MODIS on-orbit calibration will provide useful insights into the development and operation of future SD calibration systems.

Analysis and correction of ground reflection effects in measured narrowband sound spectra using cepstral techniques

NASA Technical Reports Server (NTRS)

Miles, J. H.; Stevens, G. H.; Leininger, G. G.

1975-01-01

Ground reflections generate undesirable effects on acoustic measurements such as those conducted outdoors for jet noise research, aircraft certification, and motor vehicle regulation. Cepstral techniques developed in speech processing are adapted to identify echo delay time and to correct for ground reflection effects. A sample result is presented using an actual narrowband sound pressure level spectrum. The technique can readily be adapted to existing fast Fourier transform type spectrum measurement instrumentation to provide field measurements/of echo time delays.

The angular power spectrum measurement of the Galactic synchrotron emission using the TGSS survey

NASA Astrophysics Data System (ADS)

Choudhuri, Samir; Bharadwaj, Somnath; Ali, Sk. Saiyad; Roy, Nirupam; Intema, H. T.; Ghosh, Abhik

2018-05-01

Characterizing the diffuse Galactic synchrotron emission (DGSE) at arcminute angular scales is needed to remove this foregrounds in cosmological 21-cm measurements. Here, we present the angular power spectrum (Cl) measurement of the diffuse Galactic synchrotron emission using two fields observed by the TIFR GMRT Sky Survey (TGSS). We apply 2D Tapered Gridded Estimator (TGE) to estimate the Cl from the visibilities. We find that the residual data after subtracting the point sources is likely dominated by the diffuse Galactic synchrotron radiation across the angular multipole range 240 <= l <~ 500. We fit a power law to the measured Cl over this l range. We find that the slopes in both fields are consistent with earlier measurements. For the second field, however, we interpret the measured Cl as an upper limit for the DGSE as there is an indication of a significant residual point source contribution.

Comptonization of X-rays by low-temperature electrons. [photon wavelength redistribution in cosmic sources

NASA Technical Reports Server (NTRS)

Illarionov, A.; Kallman, T.; Mccray, R.; Ross, R.

1979-01-01

A method is described for calculating the spectrum that results from the Compton scattering of a monochromatic source of X-rays by low-temperature electrons, both for initial-value relaxation problems and for steady-state spatial diffusion problems. The method gives an exact solution of the inital-value problem for evolution of the spectrum in an infinite homogeneous medium if Klein-Nishina corrections to the Thomson cross section are neglected. This, together with approximate solutions for problems in which Klein-Nishina corrections are significant and/or spatial diffusion occurs, shows spectral structure near the original photon wavelength that may be used to infer physical conditions in cosmic X-ray sources. Explicit results, shown for examples of time relaxation in an infinite medium and spatial diffusion through a uniform sphere, are compared with results obtained by Monte Carlo calculations and by solving the appropriate Fokker-Planck equation.

Accelerated rescaling of single Monte Carlo simulation runs with the Graphics Processing Unit (GPU).

PubMed

Yang, Owen; Choi, Bernard

2013-01-01

To interpret fiber-based and camera-based measurements of remitted light from biological tissues, researchers typically use analytical models, such as the diffusion approximation to light transport theory, or stochastic models, such as Monte Carlo modeling. To achieve rapid (ideally real-time) measurement of tissue optical properties, especially in clinical situations, there is a critical need to accelerate Monte Carlo simulation runs. In this manuscript, we report on our approach using the Graphics Processing Unit (GPU) to accelerate rescaling of single Monte Carlo runs to calculate rapidly diffuse reflectance values for different sets of tissue optical properties. We selected MATLAB to enable non-specialists in C and CUDA-based programming to use the generated open-source code. We developed a software package with four abstraction layers. To calculate a set of diffuse reflectance values from a simulated tissue with homogeneous optical properties, our rescaling GPU-based approach achieves a reduction in computation time of several orders of magnitude as compared to other GPU-based approaches. Specifically, our GPU-based approach generated a diffuse reflectance value in 0.08ms. The transfer time from CPU to GPU memory currently is a limiting factor with GPU-based calculations. However, for calculation of multiple diffuse reflectance values, our GPU-based approach still can lead to processing that is ~3400 times faster than other GPU-based approaches.

Brief Report: Intuitive and Reflective Reasoning in Autism Spectrum Disorder

ERIC Educational Resources Information Center

Brosnan, Mark; Ashwin, Chris; Lewton, Marcus

2017-01-01

Dual Process Theory has recently been applied to Autism spectrum disorder (ASD) to suggest that reasoning by people with ASD and people with higher levels of ASD-like traits can be characterised by reduced intuitive and greater reflective processing. 26 adolescents and adults with ASD and 22 adolescent and adult controls completed an assessment of…

The physical basis for estimating wave-energy spectra with the radar ocean-wave spectrometer

NASA Technical Reports Server (NTRS)

Jackson, Frederick C.

1987-01-01

The derivation of the reflectivity modulation spectrum of the sea surface for near-nadir-viewing microwave radars using geometrical optics is described. The equations required for the derivation are presented. The derived reflectivity modulation spectrum provides data on the physical basis of the radar ocean-wave spectrometer measurements of ocean-wave directional spectra.

Realization of a near-perfect antireflection coating for silicon solar energy utilization.

PubMed

Kuo, Mei-Ling; Poxson, David J; Kim, Yong Sung; Mont, Frank W; Kim, Jong Kyu; Schubert, E Fred; Lin, Shawn-Yu

2008-11-01

To harness the full spectrum of solar energy, Fresnel reflection at the surface of a solar cell must be eliminated over the entire solar spectrum and at all angles. Here, we show that a multilayer nanostructure having a graded-index profile, as predicted by theory [J. Opt. Soc. Am. 66, 515 (1976); Appl. Opt. 46, 6533 (2007)], can accomplish a near-perfect transmission of all-color of sunlight. An ultralow total reflectance of 1%-6% has been achieved over a broad spectrum, lambda = 400 to 1600 nm, and a wide range of angles of incidence, theta = 0 degrees-60 degrees . The measured angle- and wavelength-averaged total reflectance of 3.79% is the smallest ever reported in the literature, to our knowledge.

Structural changes in the myocardium and serum lipid spectrum in experimental hypercholesterolemia and hypothyroidism.

PubMed

Nepomnyashchikh, L M; Lushnikova, E L; Polyakov, L P; Molodykh, O P; Klinnikova, M G; Russkikh, G S; Poteryaeva, O N; Nepomnyashchikh, R D; Pichigin, V I

2013-09-01

We studied the peculiarities of lipid spectrum of the blood and structural reorganization of the myocardium in experimental hypercholesterolemia with and without hypothyroidism. It was found that alimentary hypercholesterolemia accompanied by elevated total cholesterol, LDL, HDL, and triglyceride concentrations led to a decrease in body weight, heart weight, number of cardiomyocytes in the heart and induced pronounced lytic changes in cardiomyocytes, circulation disorders (sludge syndrome, echinocytosis of erythrocytes, lymphostasis), diffuse fibrosis of the stroma, and appearance of foam cells among diffuse mononuclear infiltrate cells. The combination of hypercholesterolemia with hypothyroid status caused more pronounced changes in the lipid spectrum and atherogenic index and more pronounced lytic and necrobiotic changes in cardiomyocytes. These findings suggest that elevated cholesterol concentrations in the blood, especially against the background of suppressed thyroid function, can directly induce considerable damage to cardiomyocytes, intramural vessels, and erythrocytes without the development of myocardial ischemia and in the absence of atherosclerotic plaques.

Graded bandgap perovskite solar cells.

PubMed

Ergen, Onur; Gilbert, S Matt; Pham, Thang; Turner, Sally J; Tan, Mark Tian Zhi; Worsley, Marcus A; Zettl, Alex

2017-05-01

Organic-inorganic halide perovskite materials have emerged as attractive alternatives to conventional solar cell building blocks. Their high light absorption coefficients and long diffusion lengths suggest high power conversion efficiencies, and indeed perovskite-based single bandgap and tandem solar cell designs have yielded impressive performances. One approach to further enhance solar spectrum utilization is the graded bandgap, but this has not been previously achieved for perovskites. In this study, we demonstrate graded bandgap perovskite solar cells with steady-state conversion efficiencies averaging 18.4%, with a best of 21.7%, all without reflective coatings. An analysis of the experimental data yields high fill factors of ∼75% and high short-circuit current densities up to 42.1 mA cm -2 . The cells are based on an architecture of two perovskite layers (CH 3 NH 3 SnI 3 and CH 3 NH 3 PbI 3-x Br x ), incorporating GaN, monolayer hexagonal boron nitride, and graphene aerogel.

A High Sensitivity Isopropanol Vapor Sensor Based on Cr₂O₃-SnO₂ Heterojunction Nanocomposites via Chemical Precipitation Route.

PubMed

Jawaher, K Rackesh; Indirajith, R; Krishnan, S; Robert, R; Pasha, S K Khadheer; Deshmukh, Kalim; Sastikumar, D; Das, S Jerome

2018-08-01

Cr2O3-SnO2 heterojunction nanocomposites were prepared via chemical precipitation method. The prepared samples were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), UV-Vis diffuse reflectance spectra and Field Emission Electron Microscopy (FESEM). The XRD spectrum confirms the presence of both tetragonal rutile SnO2 and rhombohedral corundum Cr2O3 structure. Further investigation into the gas sensing performances of the prepared Cr2O3-SnO2 nanocomposites exhibited an enhanced sensitivity towards VOPs such as isopropanol, acetone, ethanol and formaldehyde. Especially, isopropanol vapor sensor shows excellent sensitivity at an operating temperature of 100 °C. The highest sensitivity for Cr2O3-SnO2 heterojunction nanocomposites indicate that these materials can be a good candidate for the production of high-performance isopropanol sensors.

Resonance Raman and UV-visible spectroscopy of black dyes on textiles.

PubMed

Abbott, Laurence C; Batchelor, Stephen N; Smith, John R Lindsay; Moore, John N

2010-10-10

Resonance Raman and UV-visible diffuse reflectance spectra were recorded from samples of cotton, viscose, polyester, nylon, and acrylic textile swatches dyed black with one of seven single dyes, a mixture of two dyes, or one of seven mixtures of three dyes. The samples generally gave characteristic Raman spectra of the dyes, demonstrating that the technique is applicable for the forensic analysis of dyed black textiles. Survey studies of the widely used dye Reactive Black 5 show that essentially the same Raman spectrum is obtained on bulk sampling from the dye in solution, on viscose, on cotton at different uptakes, and on microscope sampling from the dye in cotton threads and single fibres. The effects of laser irradiation on the Raman bands and emission backgrounds from textile samples with and without dye are also reported. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

Increased photocatalytic activity of TiO 2 mesoporous microspheres from codoping with transition metals and nitrogen

DOE PAGES

Mathis, John E.; Lieffers, Justin J.; Mitra, Chandrima; ...

2015-11-06

The composition of anatase TiO 2 was modified by codoping using combinations of a transition metal and nitrogen in order to increase its photocatalytic activity and extend it performance in the visible region of the electromagnetic spectrum. The transition metals (Mn, Co, Ni, Cu) were added during the hydrothermal preparation of mesoporous TiO 2 particles, and the nitrogen was introduced by post-annealing in flowing ammonia gas at high temperature. The samples were analyzed by SEM, XRD, BET, inductively-coupled plasma spectroscopy, and diffuse reflectance UV-vis spectroscopy. The photocatalytic activity was assessed by observing the change in methylene blue concentrations under bothmore » UV-vis and visible-only light irradiation. As a result, the photocatalytic activity of the (Mn,N), (Co,N), (Cu,N), and Ni,N) codoped TiO 2 was significantly enhanced relative to (N) TiO 2.« less

Hyperspectral Fluorescence and Reflectance Imaging Instrument

NASA Technical Reports Server (NTRS)

Ryan, Robert E.; O'Neal, S. Duane; Lanoue, Mark; Russell, Jeffrey

2008-01-01

The system is a single hyperspectral imaging instrument that has the unique capability to acquire both fluorescence and reflectance high-spatial-resolution data that is inherently spatially and spectrally registered. Potential uses of this instrument include plant stress monitoring, counterfeit document detection, biomedical imaging, forensic imaging, and general materials identification. Until now, reflectance and fluorescence spectral imaging have been performed by separate instruments. Neither a reflectance spectral image nor a fluorescence spectral image alone yields as much information about a target surface as does a combination of the two modalities. Before this system was developed, to benefit from this combination, analysts needed to perform time-consuming post-processing efforts to co-register the reflective and fluorescence information. With this instrument, the inherent spatial and spectral registration of the reflectance and fluorescence images minimizes the need for this post-processing step. The main challenge for this technology is to detect the fluorescence signal in the presence of a much stronger reflectance signal. To meet this challenge, the instrument modulates artificial light sources from ultraviolet through the visible to the near-infrared part of the spectrum; in this way, both the reflective and fluorescence signals can be measured through differencing processes to optimize fluorescence and reflectance spectra as needed. The main functional components of the instrument are a hyperspectral imager, an illumination system, and an image-plane scanner. The hyperspectral imager is a one-dimensional (line) imaging spectrometer that includes a spectrally dispersive element and a two-dimensional focal plane detector array. The spectral range of the current imaging spectrometer is between 400 to 1,000 nm, and the wavelength resolution is approximately 3 nm. The illumination system consists of narrowband blue, ultraviolet, and other discrete wavelength light-emitting-diode (LED) sources and white-light LED sources designed to produce consistently spatially stable light. White LEDs provide illumination for the measurement of reflectance spectra, while narrowband blue and UV LEDs are used to excite fluorescence. Each spectral type of LED can be turned on or off depending on the specific remote-sensing process being performed. Uniformity of illumination is achieved by using an array of LEDs and/or an integrating sphere or other diffusing surface. The image plane scanner uses a fore optic with a field of view large enough to provide an entire scan line on the image plane. It builds up a two-dimensional image in pushbroom fashion as the target is scanned across the image plane either by moving the object or moving the fore optic. For fluorescence detection, spectral filtering of a narrowband light illumination source is sometimes necessary to minimize the interference of the source spectrum wings with the fluorescence signal. Spectral filtering is achieved with optical interference filters and absorption glasses. This dual spectral imaging capability will enable the optimization of reflective, fluorescence, and fused datasets as well as a cost-effective design for multispectral imaging solutions. This system has been used in plant stress detection studies and in currency analysis.

Reflectance spectroscopy can quantify cutaneous haemoglobin oxygenation by oxygen uptake from the atmosphere after epidermal barrier disruption.

PubMed

Heise, H M; Lampen, P; Stücker, M

2003-11-01

The supply of oxygen to the viable skin tissue within the upper layers is not only secured by the cutaneous blood vascular system, but to a significant part also by oxygen diffusion from the atmosphere through the horny layer. The aim of this study was to examine whether changes in haemoglobin oxygenation can be observed within the isolated perfused bovine udder skin used as a skin model by removing the upper horny layer by adhesive tape stripping. Diffuse reflectance spectroscopy in the visible spectral range was used for non-invasive characterisation of haemoglobin oxygenation in skin under in vitro conditions. Mid-infrared attenuated total reflectance spectroscopy was employed for analysing the surface layer of the stratum corneum with respect to keratin, water and lipid components. Skin barrier disruption was achieved by repeated stripping of superficial corneocyte layers by adhesive tape. Significant changes in skin haemoglobin oxygenation were observed for skin areas with reduced lipid concentration and a reduced stratum corneum layer, as determined from the quantitative evaluation of the diffuse reflectance skin spectra. The result can be interpreted as an increase of oxygen diffusion after the removal of the upper horny layer.

Technique for examining biological materials using diffuse reflectance spectroscopy and the kubelka-munk function

DOEpatents

Alfano, Robert R.; Yang, Yuanlong

2003-09-02

Method and apparatus for examining biological materials using diffuse reflectance spectroscopy and the Kubelka-Munk function. In one aspect, the method is used to determine whether a tissue sample is cancerous or not and comprises the steps of (a) measuring the diffuse reflectance from the tissue sample at a first wavelength and at a second wavelength, wherein the first wavelength is a wavelength selected from the group consisting of 255-265 nm and wherein the second wavelength is a wavelength selected from the group consisting of 275-285 nm; (b) using the Kubelka-Munk function to transform the diffuse reflectance measurement obtained at the first and second wavelengths; and (c) comparing a ratio or a difference of the transformed Kubelka-Munk measurements at the first and second wavelengths to appropriate standards determine whether or not the tissue sample is cancerous. One can use the spectral profile of KMF between 250 nm to 300 nm to determine whether or not the tissue sample is cancerous or precancerous. According to the value at the first and second wavelengths determine whether or not the malignant tissue is invasive or mixed invasive and in situ or carcinoma in situ.

Role of Multiple Atmospheric Reflections in Formation of Electron Distribution Function in the Diffuse Aurora Region. Chapter 9

NASA Technical Reports Server (NTRS)

Khazanov, George V.; Himwich, Elizabeth W.; Glocer, Alex; Sibeck, David G.

2015-01-01

The precipitation of high-energy magnetospheric electrons (E greater than 500-600 electronvolts) in the diffuse aurora contributes significant energy flux into Earth's ionosphere. In the diffuse aurora, precipitating electrons initially injected from the plasmasheet via wave-particle interaction processes degrade in the atmosphere toward lower energies and produce secondary electrons via impact ionization of the neutral atmosphere. These initially precipitating electrons of magnetospheric origin can be additionally reflected back into the magnetosphere by the two magnetically conjugated atmospheres, leading to a series of multiple reflections that can greatly influence the initially precipitating flux at the upper ionospheric boundary (700-800 kilometers) and the resultant population of secondary electrons and electrons cascading toward lower energies. We present the solution of the Boltzmann.Landau kinetic equation that uniformly describes the entire electron distribution function in the diffuse aurora, including the affiliated production of secondary electrons (E is less than or equal to 600 electronvolts) and their energy interplay in the magnetosphere and two conjugated ionospheres. This solution takes into account the role of multiple atmospheric reflections of the precipitated electrons that were initially moved into the loss cone via wave.particle interaction processes in Earth's plasmasheet.

Spatially resolved, diffuse reflectance imaging for subsurface pattern visualization toward development of a lensless imaging platform: phantom experiments

NASA Astrophysics Data System (ADS)

Schelkanova, Irina; Pandya, Aditya; Saiko, Guennadi; Nacy, Lidia; Babar, Hannan; Shah, Duoaud; Lilge, Lothar; Douplik, Alexandre

2016-01-01

A portable, spatially resolved, diffuse reflectance lensless imaging technique based on the charge-coupled device or complementary metal-oxide semiconductor sensor directly coupled to the fiber optic bundle is proposed for visualization of subsurface structures such as superficial microvasculature in the epithelium. We discuss an experimental method for emulating a lensless imaging setup via raster scanning a single fiber-optic cable over a microfluidic phantom containing periodic hemoglobin absorption contrast. To evaluate the ability of the technique to recover information about the subsurface linear structures, scattering layers formed of the Sylgard® 184 Silicone Elastomer and titanium dioxide were placed atop the microfluidic phantom. Thickness of the layers ranged from 0.2 to 0.7 mm, and the values of the reduced scattering coefficient (μs‧) were between 0.85 and 4.25 mm-1. The results demonstrate that fiber-optic, lensless platform can be used for two-dimensional imaging of absorbing inclusions in diffuse reflectance mode. In these experiments, it was shown that diffuse reflectance imaging can provide sufficient spatial sampling of the phantom for differentiation of 30 μm structural features of the embedded absorbing pattern inside the scattering media.

ANALYTICAL SOLUTIONS OF THE ATMOSPHERIC DIFFUSION EQUATION WITH MULTIPLE SOURCES AND HEIGHT-DEPENDENT WIND SPEED AND EDDY DIFFUSIVITIES. (R825689C072)

EPA Science Inventory

Abstract

Three-dimensional analytical solutions of the atmospheric diffusion equation with multiple sources and height-dependent wind speed and eddy diffusivities are derived in a systematic fashion. For homogeneous Neumann (total reflection), Dirichlet (total adsorpti...

ANALYTICAL SOLUTIONS OF THE ATMOSPHERIC DIFFUSION EQUATION WITH MULTIPLE SOURCES AND HEIGHT-DEPENDENT WIND SPEED AND EDDY DIFFUSIVITIES. (R825689C048)

EPA Science Inventory

Abstract

Three-dimensional analytical solutions of the atmospheric diffusion equation with multiple sources and height-dependent wind speed and eddy diffusivities are derived in a systematic fashion. For homogeneous Neumann (total reflection), Dirichlet (total adsorpti...

XMM-Newton Observations of Solar Wind Charge Exchange Emission

NASA Technical Reports Server (NTRS)

Snowden, S. L.; Collier, M. R.; Kuntz, K. D.

2004-01-01

We present an XMM-Newton spectrum of diffuse X-ray emission from within the solar system. The spectrum is dominated by O VII and O VIII lines at 0.57 keV and 0.65 keV, O VIII (and possibly Fe XVII) lines at approximately 0.8 keV, Ne IX lines at approximately 0.92 keV, and Mg XI lines at approximately 1.35 keV. This spectrum is consistent with what is expected from charge exchange emission between the highly ionized solar wind and either interstellar neutrals in the heliosphere or material from Earth's exosphere. The emission is clearly seen as a low-energy ( E less than 1.5 keV) spectral enhancement in one of a series of observations of the Hubble Deep Field North. The X-ray enhancement is concurrent with an enhancement in the solar wind measured by the ACE satellite. The solar wind enhancement reaches a flux level an order of magnitude more intense than typical fluxes at 1 AU, and has ion ratios with significantly enhanced higher ionization states. Whereas observations of the solar wind plasma made at a single point reflect only local conditions which may only be representative of solar wind properties with spatial scales ranging from less than half of an Earth radii (approximately 10 s) to 100 Earth radii, X-ray observations of solar wind charge exchange are remote sensing measurements which may provide observations which are significantly more global in character. Besides being of interest in its own right for studies of the solar system, this emission can have significant consequences for observations of more cosmological objects. It can provide emission lines at zero redshift which are of particular interest (e.g., O VII and O VIII) in studies of diffuse thermal emission, and which can therefore act as contamination in objects which cover the entire detector field of view. We propose the use of solar wind monitoring data, such as from the ACE and Wind spacecraft, as a diagnostic to screen for such possibilities.

Effective emissivities of isothermal blackbody cavities calculated by the Monte Carlo method using the three-component bidirectional reflectance distribution function model.

PubMed

Prokhorov, Alexander

2012-05-01

This paper proposes a three-component bidirectional reflectance distribution function (3C BRDF) model consisting of diffuse, quasi-specular, and glossy components for calculation of effective emissivities of blackbody cavities and then investigates the properties of the new reflection model. The particle swarm optimization method is applied for fitting a 3C BRDF model to measured BRDFs. The model is incorporated into the Monte Carlo ray-tracing algorithm for isothermal cavities. Finally, the paper compares the results obtained using the 3C model and the conventional specular-diffuse model of reflection.

Retrieval of optical properties of skin from measurement and modeling the diffuse reflectance

NASA Astrophysics Data System (ADS)

Douven, Lucien F. A.; Lucassen, Gerald W.

2000-06-01

We present results on the retrieval of skin optical properties obtained by fitting of measurements of the diffuse reflectance of human skin. Reflectance spectra are simulated using an analytical model based on the diffusion approximation. This model is implemented in a simplex fit routine. The skin optical model used consists of five layers representing epidermis, capillary blood plexus, dermis, deep blood plexus and hypodermis. The optical properties of each layer are assumed homogeneously distributed. The main optical absorbers included are melanin in epidermis and blood. The experimental setup consists of a HP photospectrometer equipped with a remote fiber head. Total reflectance spectra were measured in the 400 - 820 nm wavelength range on the volar underarm of 19 volunteers under various conditions influencing the blood content and oxygenation degree. Changes in the reflectance spectra were observed. Using the fit routine changes in blood content in the capillary blood plexus and in the deep blood plexus could be quantified. These showed different influences on the total reflectance. The method can be helpful to quantitatively assess changes in skin color appearance such as occurs in the treatment of port wine stains, blanching, skin irritation and tanning.

The soft X-ray diffuse background observed with the HEAO 1 low-energy detectors

NASA Technical Reports Server (NTRS)

Garmire, G. P.; Nousek, J. A.; Apparao, K. M. V.; Burrows, D. N.; Fink, R. L.; Kraft, R. P.

1992-01-01

Results of a study of the diffuse soft-X-ray background as observed by the low-energy detectors of the A-2 experiment aboard the HEAO 1 satellite are reported. The observed sky intensities are presented as maps of the diffuse X-ray background sky in several energy bands covering the energy range 0.15-2.8 keV. It is found that the soft X-ray diffuse background (SXDB) between 1.5 and 2.8 keV, assuming a power law form with photon number index 1.4, has a normalization constant of 10.5 +/- 1.0 photons/sq cm s sr keV. Below 1.5 keV the spectrum of the SXDB exceeds the extrapolation of this power law. The low-energy excess for the NEP can be fitted with emission from a two-temperature equilibrium plasma model with the temperatures given by log I1 = 6.16 and log T2 = 6.33. It is found that this model is able to account for the spectrum below 1 keV, but fails to yield the observed Galactic latitude variation.

Multi-year search for a diffuse flxu of muon neutrinos with AMANDA-II

DOE Office of Scientific and Technical Information (OSTI.GOV)

IceCube Collaboration; Klein, Spencer; Achterberg, A.

2008-04-13

A search for TeV-PeV muon neutrinos from unresolved sources was performed on AMANDA-II data collected between 2000 and 2003 with an equivalent livetime of 807 days. This diffuse analysis sought to find an extraterrestrial neutrino flux from sources with non-thermal components. The signal is expected to have a harder spectrum than the atmospheric muon and neutrino backgrounds. Since no excess of events was seen in the data over the expected background, an upper limit of E{sup 2}{Phi}{sub 90%C.L.} < 7.4 x 10{sup -8} GeV cm{sup -2} s{sup -1} sr{sup -1} is placed on the diffuse flux of muon neutrinos withmore » a {Phi} {proportional_to} E{sup -2} spectrum in the energy range 16 TeV to 2.5 PeV. This is currently the most sensitive {Phi} {proportional_to} E{sup -2} diffuse astrophysical neutrino limit. We also set upper limits for astrophysical and prompt neutrino models, all of which have spectra different than {Phi} {proportional_to} E{sup -2}.« less

Multiyear search for a diffuse flux of muon neutrinos with AMANDA-II

DOE Office of Scientific and Technical Information (OSTI.GOV)

Achterberg, A.; Duvoort, M. R.; Heise, J.

2007-08-15

A search for TeV-PeV muon neutrinos from unresolved sources was performed on AMANDA-II data collected between 2000 and 2003 with an equivalent live time of 807 days. This diffuse analysis sought to find an extraterrestrial neutrino flux from sources with nonthermal components. The signal is expected to have a harder spectrum than the atmospheric muon and neutrino backgrounds. Since no excess of events was seen in the data over the expected background, an upper limit of E{sup 2}{phi}{sub 90percentC.L.}<7.4x10{sup -8} GeV cm{sup -2} s{sup -1} sr{sup -1} is placed on the diffuse flux of muon neutrinos with a {phi}{proportional_to}E{sup -2}more » spectrum in the energy range 16 TeV to 2.5 PeV. This is currently the most sensitive {phi}{proportional_to}E{sup -2} diffuse astrophysical neutrino limit. We also set upper limits for astrophysical and prompt neutrino models, all of which have spectra different from {phi}{proportional_to}E{sup -2}.« less

Monitoring of caffeine consumption effect on skin blood properties by diffuse reflectance spectroscopy

NASA Astrophysics Data System (ADS)

Milanic, Matija; Marin, Ana; Stergar, Jost; Verdel, Nina; Majaron, Boris

2017-07-01

Caffeine is the most widely consumed psychoactive substance in the world. It affects many tissues and organs, in particular central nervous system, heart, and blood vessels. The effect of caffeine on vascular smooth muscle cells is an initial transient contraction followed by significant vasodilatation. In this study we investigate the use of diffuse reflectance spectroscopy (DRS) for monitoring of vascular changes in human skin induced by caffeine consumption. DRS spectra were recorded on volar sides of the forearms of ten healthy volunteers at time delays of 0, 30, 60, 120, and 180 minutes after consumption of caffeine, while one subject served as a negative control. Analytical diffusion approximation solutions for diffuse reflectance from three-layer structures were used to assess skin composition (e.g., dermal blood volume fraction and oxygen saturation) by fitting to experimental data. The results demonstrate that cutaneous vasodynamics induced by caffeine consumption can be monitored by DRS, while changes in the control subject not consuming caffeine were insignificant.

Photothermal Radiometry and Diffuse Reflectance Analysis of Thermally Treated Bones

NASA Astrophysics Data System (ADS)

Trujillo, S.; Martínez-Torres, P.; Quintana, P.; Alvarado-Gil, Juan Jose

2010-05-01

Different fields such as archaeology, biomedicine, forensic science, and pathology involve the analysis of burned bones. In this work, the effects of successive thermal treatments on pig long bones, measured by photothermal radiometry and diffuse reflectance are reported. Measurements were complemented by X-ray diffraction and infrared spectroscopy. Samples were thermally treated for 1 h within the range of 25 °C to 350 °C. The thermal diffusivity and reflectance increase in the low-temperature range, reaching a maximum around 125 °C and decaying at higher temperatures. These results are the consequence of complex modifications occurring in the inorganic and organic bone structure. For lower temperatures dehydration, dehydroxilation, and carbonate loss processes are dominant, followed by collagen denaturing and decompositions, which have an influence on the bone microstructure.

A Study of Brownian Motion Using Light Scattering

ERIC Educational Resources Information Center

Clark, Noel A.; And Others

1970-01-01

Presents an advanced laboratory experiment and lecture demonstration by which the intensity spectrum of light scattered by a suspension of particles in a fluid can be studied. From this spectrum, it is possible to obtain quantitative information about the motion of the particles, including an accurate determination of their diffusion constant.…

First evidence of diffuse ultra-steep-spectrum radio emission surrounding the cool core of a cluster

NASA Astrophysics Data System (ADS)

Savini, F.; Bonafede, A.; Brüggen, M.; van Weeren, R.; Brunetti, G.; Intema, H.; Botteon, A.; Shimwell, T.; Wilber, A.; Rafferty, D.; Giacintucci, S.; Cassano, R.; Cuciti, V.; de Gasperin, F.; Röttgering, H.; Hoeft, M.; White, G.

2018-05-01

Diffuse synchrotron radio emission from cosmic-ray electrons is observed at the center of a number of galaxy clusters. These sources can be classified either as giant radio halos, which occur in merging clusters, or as mini halos, which are found only in cool-core clusters. In this paper, we present the first discovery of a cool-core cluster with an associated mini halo that also shows ultra-steep-spectrum emission extending well beyond the core that resembles radio halo emission. The large-scale component is discovered thanks to LOFAR observations at 144 MHz. We also analyse GMRT observations at 610 MHz to characterise the spectrum of the radio emission. An X-ray analysis reveals that the cluster is slightly disturbed, and we suggest that the steep-spectrum radio emission outside the core could be produced by a minor merger that powers electron re-acceleration without disrupting the cool core. This discovery suggests that, under particular circumstances, both a mini and giant halo could co-exist in a single cluster, opening new perspectives for particle acceleration mechanisms in galaxy clusters.

Study of the oxidation of uranium by external and diffuse reflectance FTIR spectroscopy using remote-sensing and evacuable cell techniques

NASA Astrophysics Data System (ADS)

Powell, G. L.; Dobbins, A.; Cristy, S. S.; Cliff, T. L.; Meyer, H. M., III; Lucania, J.; Milosevic, Milan

1994-01-01

This report describes the application of reflectance FTIR spectroscopy to the measurement of the oxidation rate of uranium by environmental gases near room temperature. It also describes very efficient evacuable cells designed for 75 degree(s) external reflectance with polarized light and for diffuse reflectance using mid-infrared FTIR spectroscopy. These cells, along with functionally similar remote sensing accessories, have been applied to the study of the oxidation of uranium metal in air, oxygen, and water vapor by precisely measuring the 575 cm-1 band of UO2 and other properties of the corrosion film such as absorbed water and reflective losses caused by film degradation related to pitting or nucleation phenomena.

LD-cladding-pumped 50 pm linewidth Tm 3+ -doped silica fiber laser.

PubMed

Yunjun, Zhang; Baoquan, Yao; Youlun, Ju; Hui, Zhou; Yuezhu, Wang

2008-05-26

We report on a Tm(3+)-doped fiber laser source operating at 1936.4 nm with a very narrow linewidth (50 pm) laser output. Up to 2.4 W cw laser power was obtained from an 82 cm long Tm(3+)-doped multimode-core fiber cladding pumped by a 792 nm laser diode (LD). The fiber laser cavity included a high-reflective dichroic and a low-reflective FBG output coupler. The multimode fiber Bragg grating (FBG) transmission spectrum and output laser spectrum were measured. By adjusting the distance between the dichroic and the Tm(3+)-doped fiber end, the multipeak laser spectrum changed to a single-peak laser spectrum.

Single Molecule Fluorescence Measurements of Complex Systems

NASA Astrophysics Data System (ADS)

Sadegh, Sanaz

Single molecule methods are powerful tools for investigating the properties of complex systems that are generally concealed by ensemble measurements. Here we use single molecule fluorescent measurements to study two different complex systems: 1/ƒ noise in quantum dots and diffusion of the membrane proteins in live cells. The power spectrum of quantum dot (QD) fluorescence exhibits 1/ƒ beta noise, related to the intermittency of these nanosystems. As in other systems exhibiting 1/ƒ noise, this power spectrum is not integrable at low frequencies, which appears to imply infinite total power. We report measurements of individual QDs that address this long-standing paradox. We find that the level of 1/ƒbeta noise for QDs decays with the observation time. We show that the traditional description of the power spectrum with a single exponent is incomplete and three additional critical exponents characterize the dependence on experimental time. A broad range of membrane proteins display anomalous diffusion on the cell surface. Different methods provide evidence for obstructed subdiffusion and diffusion on a fractal space, but the underlying structure inducing anomalous diffusion has never been visualized due to experimental challenges. We addressed this problem by imaging the cortical actin at high resolution while simultaneously tracking individual membrane proteins in live mammalian cells. Our data show that actin introduces barriers leading to compartmentalization of the plasma membrane and that membrane proteins are transiently confined within actin fences. Furthermore, superresolution imaging shows that the cortical actin is organized into a self-similar fractal.

Thermal and non-thermal X-rays from the Galactic supernova remnant G348.5+0.1

NASA Astrophysics Data System (ADS)

Yamauchi, Shigeo; Minami, Sari; Ota, Naomi; Koyama, Katsuji

2014-02-01

We report on Suzaku results of the two distinct regions in the Galactic supernova remnant G348.5+0.1: extended thermal X-rays ("soft diffuse") at the north-east region and non-thermal X-rays (CXOU J171419.8-383023) at the north-west region. The X-ray spectrum of the soft diffuse X-rays can be fitted with neither an ionization equilibrium nor a non-equilibrium (ionizing) plasma model, leaving saw- tooth residuals in the 1.5-3 keV energy band. The residual structures can be produced when free electrons are recombined to the K-shells of highly ionized Mg and Si ions. In fact, the X-ray spectrum is nicely fitted with a recombination-dominant plasma model. We propose a scenario whereby the plasma in a nearly fully ionized state at high temperature quickly changed to a recombining phase due to selective cooling of electrons to a lower temperature of ˜ 0.5 keV. The spectrum of CXOU J171419.8-383023 is well explained by a simple power-law model with a photon index of 1.9, nearly equal to the typical value for pulsar wind nebulae. Since the distance is estimated to be the same as that of the soft diffuse radiation, we infer that both the soft diffuse X-rays and CXOU J171419.8-383023 are associated with the same object, SNR G348.5+0.1.

Fast Diffusion to Self-Similarity: Complete Spectrum, Long-Time Asymptotics, and Numerology

NASA Astrophysics Data System (ADS)

Denzler, Jochen; McCann, Robert J.

2005-03-01

The complete spectrum is determined for the operator on the Sobolev space W1,2ρ(Rn) formed by closing the smooth functions of compact support with respect to the norm Here the Barenblatt profile ρ is the stationary attractor of the rescaled diffusion equation in the fast, supercritical regime m the same diffusion dynamics represent the steepest descent down an entropy E(u) on probability measures with respect to the Wasserstein distance d2. Formally, the operator H=HessρE is the Hessian of this entropy at its minimum ρ, so the spectral gap H≧α:=2-n(1-m) found below suggests the sharp rate of asymptotic convergence: from any centered initial data 0≦u(0,x) ∈ L1(Rn) with second moments. This bound improves various results in the literature, and suggests the conjecture that the self-similar solution u(t,x)=R(t)-nρ(x/R(t)) is always slowest to converge. The higher eigenfunctions which are polynomials with hypergeometric radial parts and the presence of continuous spectrum yield additional insight into the relations between symmetries of Rn and the flow. Thus the rate of convergence can be improved if we are willing to replace the distance to ρ with the distance to its nearest mass-preserving dilation (or still better, affine image). The strange numerology of the spectrum is explained in terms of the number of moments of ρ.

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

NASA Technical Reports Server (NTRS)

Vanderbilt, V. C.; Grant, L.

1984-01-01

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

Ultraviolet stability and contamination analysis of Spectralon diffuse reflectance material

NASA Technical Reports Server (NTRS)

Stiegman, Albert E.; Bruegge, Carol J.; Springsteen, Arthur W.

1993-01-01

A detailed chemical analysis was carried out on Spectralon, a highly Lambertian, diffuse reflectance material. Results of this investigation unambiguously identified the presence of an organic (hydrocarbon) impurity intrinsic to the commercial material. This impurity could be removed by a vacuum bake-out procedure and was identified as the cause of optical changes (degradation) that occur in the material when exposed to UV light. It was found that when this impurity was removed, the Spectralon material was photochemically stable and maintained its reflectance properties even after extensive solar UV exposure.

Stochastic particle acceleration at shocks in the presence of braided magnetic fields.

NASA Astrophysics Data System (ADS)

Kirk, J. G.; Duffy, P.; Gallant, Y. A.

1996-10-01

The theory of diffusive acceleration of energetic particles at shock fronts assumes charged particles undergo spatial diffusion in a uniform magnetic field. If, however, the magnetic field is not uniform, but has a stochastic or braided structure, the transport of charged particles across the average direction of the field is more complicated. Assuming quasi-linear behaviour of the field lines, the particles undergo sub-diffusion on short time scales. We derive the propagator for such motion, which differs from the Gaussian form relevant for diffusion, and apply it to a configuration with a plane shock front whose normal is perpendicular to the average field direction. Expressions are given for the acceleration time as a function of the diffusion coefficient of the wandering magnetic field lines and the spatial diffusion coefficient of the charged particles parallel to the local field. In addition we calculate the spatial dependence of the particle density in both the upstream and downstream plasmas. In contrast to the diffusive case, the density of particles at the shock front is lower than it is far downstream. This is a consequence of the partial trapping of particles by structures in the magnetic field. As a result, the spectrum of accelerated particles is a power-law in momentum which is steeper than in the diffusive case. For a phase-space density f{prop.to}p^-s^, we find s=s_diff_[1+1/(2ρ_c_)], where ρ_c_ is the compression ratio of the shock front and s_diff_ is the standard result of diffusive acceleration: s_diff_=3ρ_c_/(ρ_c_-1). A strong shock in a monatomic ideal gas yields a spectrum of s=4.5. In the case of electrons, this corresponds to a radio synchrotron spectral index of α=0.75.

Radiative transfer simulations of the two-dimensional ocean glint reflectance and determination of the sea surface roughness.

PubMed

Lin, Zhenyi; Li, Wei; Gatebe, Charles; Poudyal, Rajesh; Stamnes, Knut

2016-02-20

An optimized discrete-ordinate radiative transfer model (DISORT3) with a pseudo-two-dimensional bidirectional reflectance distribution function (BRDF) is used to simulate and validate ocean glint reflectances at an infrared wavelength (1036 nm) by matching model results with a complete set of BRDF measurements obtained from the NASA cloud absorption radiometer (CAR) deployed on an aircraft. The surface roughness is then obtained through a retrieval algorithm and is used to extend the simulation into the visible spectral range where diffuse reflectance becomes important. In general, the simulated reflectances and surface roughness information are in good agreement with the measurements, and the diffuse reflectance in the visible, ignored in current glint algorithms, is shown to be important. The successful implementation of this new treatment of ocean glint reflectance and surface roughness in DISORT3 will help improve glint correction algorithms in current and future ocean color remote sensing applications.

Radiative Transfer Simulations of the Two-Dimensional Ocean Glint Reflectance and Determination of the Sea Surface Roughness

NASA Technical Reports Server (NTRS)

Lin, Zhenyi; Li, Wei; Gatebe, Charles; Poudyal, Rajesh; Stamnes, Knut

2016-01-01

An optimized discrete-ordinate radiative transfer model (DISORT3) with a pseudo-two-dimensional bidirectional reflectance distribution function (BRDF) is used to simulate and validate ocean glint reflectances at an infrared wavelength (1036 nm) by matching model results with a complete set of BRDF measurements obtained from the NASA cloud absorption radiometer (CAR) deployed on an aircraft. The surface roughness is then obtained through a retrieval algorithm and is used to extend the simulation into the visible spectral range where diffuse reflectance becomes important. In general, the simulated reflectances and surface roughness information are in good agreement with the measurements, and the diffuse reflectance in the visible, ignored in current glint algorithms, is shown to be important. The successful implementation of this new treatment of ocean glint reflectance and surface roughness in DISORT3 will help improve glint correction algorithms in current and future ocean color remote sensing applications.

Classification of road sign type using mobile stereo vision

NASA Astrophysics Data System (ADS)

McLoughlin, Simon D.; Deegan, Catherine; Fitzgerald, Conor; Markham, Charles

2005-06-01

This paper presents a portable mobile stereo vision system designed for the assessment of road signage and delineation (lines and reflective pavement markers or "cat's eyes"). This novel system allows both geometric and photometric measurements to be made on objects in a scene. Global Positioning System technology provides important location data for any measurements made. Using the system it has been shown that road signs can be classfied by nature of their reflectivity. This is achieved by examining the changes in the reflected light intensity with changes in range (facilitated by stereo vision). Signs assessed include those made from retro-reflective materials, those made from diffuse reflective materials and those made from diffuse reflective matrials with local illumination. Field-testing results demonstrate the systems ability to classify objects in the scene based on their reflective properties. The paper includes a discussion of a physical model that supports the experimental data.

[The research of UV-responsive sensitivity enhancement of fluorescent coating films by MgF2 layer].

PubMed

Lu, Zhong-Rong; Ni, Zheng-Ji; Tao, Chun-Xian; Hong, Rui-Jin; Zhang, Da-Wei; Huang, Yuan-Shen

2014-03-01

A low cost and less complicated expansion approach of wavelength responses with a Lumogen phosphor coating was adopted, as they increased the quantum efficiency of CCD and CMOS detectors in ultra-violet by absorbing UV light and then re emitting visible light. In this paper, the sensitivity enhancement of fluorescence coatings was studied by adding an anti-reflection film or barrier film to reduce the loss of the scattering and reflection on the incident interface. The Lumogen and MgF2/Lumogen film were deposited on quartz glasses by physical vacuum deposition. The surface morphology, transmittance spectrum, reflectance spectrum and fluorescence emission spectrum were obtained by atomic force microscope (AFM), spectrophotometer and fluorescence spectrometer, respectively. The results indicated that MgF2 film had obvious positive effect on reducing scattering and reflection loss in 500-700 nm, and enhancing the absorption of Lumogen coating in ultraviolet spectrum. Meanwhile, the fluorescent emission intensity had a substantial increase by smoothing the film surface and thus reducing the light scattering. At the same time, the MgF2 layer could protect Lumogen coating from damaging and contamination, which give a prolong lifetime of the UV-responsive CCD sensors with fluorescent coatings.

Spectroscopic limits to an extragalactic far-ultraviolet background.

PubMed

Martin, C; Hurwitz, M; Bowyer, S

1991-10-01

We use a spectrum of the lowest intensity diffuse far-ultraviolet background obtained from a series of observations in a number of celestial view directions to constrain the properties of the extragalactic FUV background. The mean continuum level, IEG = 280 +/- 35 photons cm-2 s-1 angstrom-1 sr-1, was obtained in a direction with very low H I column density, and this represents a firm upper limit to any extragalactic background in the 1400-1900 angstroms band. Previous work has demonstrated that the far-ultraviolet background includes (depending on a view direction) contributions from dust-scattered Galactic light, high-ionization emission lines, two-photon emission from H II, H2 fluorescence, and the integrated light of spiral galaxies. We find no evidence in the spectrum of line or continuum features that would signify additional extragalactic components. Motivated by the observation of steep BJ and U number count distributions, we have made a detailed comparison of galaxy evolution models to optical and UV data. We find that the observations are difficult to reconcile with a dominant contribution from unclustered, starburst galaxies at low redshifts. Our measurement rules out large ionizing fluxes at z = 0, but cannot strongly constrain the QSO background light, which is expected to be 0.5%-4% of IEG. We present improved limits on radiative lifetimes of massive neutrinos. We demonstrated with a simple model that IGM radiation is unlikely to make a significant contribution to IEG. Since dust scattering could produce a significant part of the continuum in this lowest intensity spectrum, we carried out a series of tests to evaluate this possibility. We find that the spectrum of a nearby target with higher NH I, when corrected for H2 fluorescence, is very similar to the spectrum obtained in the low H I view direction. This is evidence that the majority of the continuum observed at low NH I is also dust reflection, indicating either the existence of a hitherto unidentified dust component, or of a large enhancement in dust scattering efficiency in low-density gas. We also review the effects of an additional dust component on the far-infrared background and on extragalactic FUV observations. We conclude that dust reflection, combined with modest contributions from H II two-photon emission and from the integrated light of late-type galaxies, may account for virtually all of the FUV background in low H I column density directions.

Alternative Measurement Configurations for Extracting Bulk Optical Properties Using an Integrating Sphere Setup.

PubMed

Thennadil, Suresh N; Chen, Yi-Chieh

2017-02-01

The usual approach for estimating bulk optical properties using an integrating sphere measurement setup is by acquiring spectra from three measurement modes namely collimated transmittance (T c ), total transmittance (T d ), and total diffuse reflectance (R d ), followed by the inversion of these measurements using the adding-doubling method. At high scattering levels, accurate acquisition of T c becomes problematic due to the presence of significant amounts of forward-scattered light in this measurement which is supposed to contain only unscattered light. In this paper, we propose and investigate the effectiveness of using alternative sets of integrating sphere measurements that avoid the use of T c and could potentially increase the upper limit of concentrations of suspensions at which bulk optical property measurements can be obtained in the visible-near-infrared (Vis-NIR) region of the spectrum. We examine the possibility of replacing T c with one or more reflectance measurements at different sample thicknesses. We also examine the possibility of replacing both the collimated (T c ) and total transmittance (T d ) measurements with reflectance measurements taken from different sample thicknesses. The analysis presented here indicates that replacing T c with a reflectance measurement can reduce the errors in the bulk scattering properties when scattering levels are high. When only multiple reflectance measurements are used, good estimates of the bulk optical properties can be obtained when the absorption levels are low. In addition, we examine whether there is any advantage in using three measurements instead of two to obtain the reduced bulk scattering coefficient and the bulk absorption coefficient. This investigation is made in the context of chemical and biological suspensions which have a much larger range of optical properties compared to those encountered with tissue.

Analyses of Impact of Needle Surface Properties on Estimation of Needle Absorption Spectrum: Case Study with Coniferous Needle and Shoot Samples

PubMed Central

Yang, Bin; Knyazikhin, Yuri; Lin, Yi; Yan, Kai; Chen, Chi; Park, Taejin; Choi, Sungho; Mõttus, Matti; Rautiainen, Miina; Myneni, Ranga B.; Yan, Lei

2017-01-01

Leaf scattering spectrum is the key optical variable that conveys information about leaf absorbing constituents from remote sensing. It cannot be directly measured from space because the radiation scattered from leaves is affected by the 3D canopy structure. In addition, some radiation is specularly reflected at the surface of leaves. This portion of reflected radiation is partly polarized, does not interact with pigments inside the leaf and therefore contains no information about its interior. Very little empirical data are available on the spectral and angular scattering properties of leaf surfaces. Whereas canopy-structure effects are well understood, the impact of the leaf surface reflectance on estimation of leaf absorption spectra remains uncertain. This paper presents empirical and theoretical analyses of angular, spectral, and polarimetric measurements of light reflected by needles and shoots of Pinus koraiensis and Picea koraiensis species. Our results suggest that ignoring the leaf surface reflected radiation can result in an inaccurate estimation of the leaf absorption spectrum. Polarization measurements may be useful to account for leaf surface effects because radiation reflected from the leaf surface is partly polarized, whereas that from the leaf interior is not. PMID:28868160

Diffusely reflecting paints including polytetrafluoroethylene and method of manufacture

NASA Technical Reports Server (NTRS)

Schutt, J. B.; Shai, M. C. (Inventor)

1985-01-01

The invention pertains to a high diffuse, reflective paint comprising an alcohol soluble binder, polytetrafluoroethylene (TFE) and an alcohol for coating a substrate and forming an optical reference with a superior Lambertian characteristic. A method for making the paint by first mixing the biner and alcohol, and thereafter by mixing in outgassed TFE is described. A wetting agent may be employed to aid the mixing process.

Improvement of direct determination of trace nickel in environmental samples by diffuse reflection spectroscopy using chromaticity characteristics.

PubMed

Ershova, N I; Ivanov, V M

2000-05-01

Cellulose and chromaton-N-super as solid supports for direct determination of the immobilized nickel complexes with dimethylglyoxime and benzyldioxime by diffuse reflection spectroscopy were compared. The advantage of chromaton-N-super with use of benzyldioxime is shown. Detection limit is 0.02 microg/mL. The proposed method was applied for the analysis of soil.

Dynamic Structural Changes of SiO₂ Supported Pt-Ni Bimetallic Catalysts over Redox Treatments Revealed by NMR and EPR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Suochang; Walter, Eric D.; Zhao, Zhenchao

2015-08-18

SiO 2 supported Pt-Ni bimetallic catalysts with different nickel loadings were prepared and their structural changes after redox treatments were studied by XRD, NMR, and EPR. It is found that the paramagnetic Ni species are mainly located on the surface of silica lattice. The relaxation of detected 29Si nuclei in our samples is mainly governed by a spin-diffusion mechanism. The paramagnetic effects are reflected in the spin-lattice relaxation of Q 4 species, with the oxidized samples presenting faster relaxation rates than the corresponding reduced ones. Meanwhile the Q 3 species, which are in close contact with the paramagnetic nickel ions,more » are “spectrally invisible”. In reducing atmosphere Ni gradually diffuses into Pt NPs to form PtNi alloys. While under oxidization treatment, the alloyed Ni atoms migrate outward from the core of Pt NPs and are oxidized. The main EPR spectrum results from reduced nickel species, and the reduced samples show stronger EPR signal than the corresponding oxidized ones. However, in the reduced samples, the superparamagnetic or ferromagnetic metallic Ni particles were inside the PtNi NPs, making their influence on the 29Si relaxation in the SiO 2 support weaker than the oxidized samples.« less

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

PubMed Central

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

2014-01-01

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

Some new results on electron transport in the atmosphere. [Monte Carlo calculation of penetration, diffusion, and slowing down of electron beams in air

NASA Technical Reports Server (NTRS)

Berger, M. J.; Seltzer, S. M.; Maeda, K.

1972-01-01

The penetration, diffusion and slowing down of electrons in a semi-infinite air medium has been studied by the Monte Carlo method. The results are applicable to the atmosphere at altitudes up to 300 km. Most of the results pertain to monoenergetic electron beams injected into the atmosphere at a height of 300 km, either vertically downwards or with a pitch-angle distribution isotropic over the downward hemisphere. Some results were also obtained for various initial pitch angles between 0 deg and 90 deg. Information has been generated concerning the following topics: (1) the backscattering of electrons from the atmosphere, expressed in terms of backscattering coefficients, angular distributions and energy spectra of reflected electrons, for incident energies T(o) between 2 keV and 2 MeV; (2) energy deposition by electrons as a function of the altitude, down to 80 km, for T(o) between 2 keV and 2 MeV; (3) the corresponding energy depostion by electron-produced bremsstrahlung, down to 30 km; (4) the evolution of the electron flux spectrum as function of the atmospheric depth, for T(o) between 2 keV and 20 keV. Energy deposition results are given for incident electron beams with exponential and power-exponential spectra.

Fast determination of the current loss mechanisms in textured crystalline Si-based solar cells

NASA Astrophysics Data System (ADS)

Nakane, Akihiro; Fujimoto, Shohei; Fujiwara, Hiroyuki

2017-11-01

A quite general device analysis method that allows the direct evaluation of optical and recombination losses in crystalline silicon (c-Si)-based solar cells has been developed. By applying this technique, the current loss mechanisms of the state-of-the-art solar cells with ˜20% efficiencies have been revealed. In the established method, the optical and electrical losses are characterized from the analysis of an experimental external quantum efficiency (EQE) spectrum with very low computational cost. In particular, we have performed the EQE analyses of textured c-Si solar cells by employing the experimental reflectance spectra obtained directly from the actual devices while using flat optical models without any fitting parameters. We find that the developed method provides almost perfect fitting to EQE spectra reported for various textured c-Si solar cells, including c-Si heterojunction solar cells, a dopant-free c-Si solar cell with a MoOx layer, and an n-type passivated emitter with rear locally diffused solar cell. The modeling of the recombination loss further allows the extraction of the minority carrier diffusion length and surface recombination velocity from the EQE analysis. Based on the EQE analysis results, the current loss mechanisms in different types of c-Si solar cells are discussed.

The prediction of the optical contrast of air-borne targets against the night-sky background for Photopic and NVG sensors

NASA Astrophysics Data System (ADS)

Havemann, Stephan; Wong, Gerald

2016-10-01

The Havemann-Taylor Fast Radiative Transfer Code (HT-FRTC) represents transmittances, radiances and fluxes by principal components that cover the spectra at very high resolution, allowing fast highly-resolved pseudo line-by-line, hyperspectral and broadband simulations across the electromagnetic spectrum form the microwave to the ultraviolet for satellite-based, airborne and ground-based sensors. HT-FRTC models clear atmospheres and those containing clouds and aerosols, as well as any surface (land/sea/man-made). The HT-FRTC has been used operationally in the NEON Tactical Decision Aid (TDA) since 2008. The TDA combines the HT-FRTC with a thermal contrast model and an NWP model forecast data feed to predict the apparent thermal contrast between different surfaces and ground-based targets in the thermal and short-wave IR. The new objective here is to predict the optical contrast of air-borne targets under realistic night-time scenarios in the Photopic and NVG parts of the spectrum. This requires the inclusion of all the relevant radiation sources, which include twilight, moonlight, starlight, airglow and cultural light. A completely new exact scattering code has been developed which allows the straight-forward addition of any number of direct and diffuse sources anywhere in the atmosphere. The new code solves the radiative transfer equation iteratively and is faster than the previous solution. Simulations of scenarios with different light levels, from situations during a full moon to a moonless night with very low light levels and a situation with cultural light from a town are presented. The impact of surface reflectance and target reflectance is investigated.

Two years comparative studies on biological effects of environmental UV radiation

NASA Astrophysics Data System (ADS)

Grof, P.; Ronto, Gyorgyi; Gaspar, S.; Berces, A.; Szabo, Laszlo D.

1994-07-01

A method has been developed for determination of the biologically effective UV dose based on T7 phage as biosensor. In field experiments clockwork driven telescope has been used for determining doses from direct and global (direct plus diffuse) solar radiation. On fine summer days at mid-latitude this arrangement allowed the following comparisons: measured doses from direct and global radiation obtained at the same time and measuring site reflecting the biological importance of diffuse radiation; direct and global radiation obtained at the same time and measuring site reflecting the biological importance of diffuse radiation; direct and global doses obtained at the same time on different measuring sites (downtown, suburb, outside the town) reflecting the differences caused by air quality; direct and global doses obtained on the same measuring place, in summertime of two different years reflecting the importance of the long-term measurements for estimating the biological risk caused by increased UV-B radiation; measured data and model calculations.

[Crop geometry identification based on inversion of semiempirical BRDF models].

PubMed

Huang, Wen-jiang; Wang, Jin-di; Mu, Xi-han; Wang, Ji-hua; Liu, Liang-yun; Liu, Qiang; Niu, Zheng

2007-10-01

Investigations have been made on identification of erective and horizontal varieties by bidirectional canopy reflected spectrum and semi-empirical bidirectional reflectance distribution function (BRDF) models. The qualitative effect of leaf area index (LAI) and average leaf angle (ALA) on crop canopy reflected spectrum was studied. The structure parameter sensitive index (SPEI) based on the weight for the volumetric kernel (fvol), the weight for the geometric kernel (fgeo), and the weight for constant corresponding to isotropic reflectance (fiso), was defined in the present study for crop geometry identification. However, the weights associated with the kernels of semi-empirical BRDF model do not have a direct relationship with measurable biophysical parameters. Therefore, efforts have focused on trying to find the relation between these semi-empirical BRDF kernel weights and various vegetation structures. SPEI was proved to be more sensitive to identify crop geometry structures than structural scattering index (SSI) and normalized difference f-index (NDFI), SPEI could be used to distinguish erective and horizontal geometry varieties. So, it is feasible to identify horizontal and erective varieties of wheat by bidirectional canopy reflected spectrum.

Development and optimization of a noncontact optical device for online monitoring of jaundice in human subjects.

PubMed

Polley, Nabarun; Saha, Srimoyee; Singh, Soumendra; Adhikari, Aniruddha; Das, Sukhen; Choudhury, Bhaskar Roy; Pal, Samir Kumar

2015-06-01

Jaundice is one of the notable markers of liver malfunction in our body, revealing a significant rise in the concentration of an endogenous yellow pigment bilirubin. We have described a method for measuring the optical spectrum of our conjunctiva and derived pigment concentration by using diffused reflection measurement. The method uses no prior model and is expected to work across the races (skin color) encompassing a wide range of age groups. An optical fiber-based setup capable of measuring the conjunctival absorption spectrum from 400 to 800 nm is used to monitor the level of bilirubin and is calibrated with the value measured from blood serum of the same human subject. We have also developed software in the LabVIEW platform for use in online monitoring of bilirubin levels in human subjects by nonexperts. The results demonstrate that relative absorption at 460 and 600 nm has a distinct correlation with that of the bilirubin concentration measured from blood serum. Statistical analysis revealed that our proposed method is in agreement with the conventional biochemical method. The innovative noncontact, low-cost technique is expected to have importance in monitoring jaundice in developing/underdeveloped countries, where the inexpensive diagnosis of jaundice with minimally trained manpower is obligatory.

Development and optimization of a noncontact optical device for online monitoring of jaundice in human subjects

NASA Astrophysics Data System (ADS)

Polley, Nabarun; Saha, Srimoyee; Singh, Soumendra; Adhikari, Aniruddha; Das, Sukhen; Choudhury, Bhaskar Roy; Pal, Samir Kumar

2015-06-01

Jaundice is one of the notable markers of liver malfunction in our body, revealing a significant rise in the concentration of an endogenous yellow pigment bilirubin. We have described a method for measuring the optical spectrum of our conjunctiva and derived pigment concentration by using diffused reflection measurement. The method uses no prior model and is expected to work across the races (skin color) encompassing a wide range of age groups. An optical fiber-based setup capable of measuring the conjunctival absorption spectrum from 400 to 800 nm is used to monitor the level of bilirubin and is calibrated with the value measured from blood serum of the same human subject. We have also developed software in the LabVIEW platform for use in online monitoring of bilirubin levels in human subjects by nonexperts. The results demonstrate that relative absorption at 460 and 600 nm has a distinct correlation with that of the bilirubin concentration measured from blood serum. Statistical analysis revealed that our proposed method is in agreement with the conventional biochemical method. The innovative noncontact, low-cost technique is expected to have importance in monitoring jaundice in developing/underdeveloped countries, where the inexpensive diagnosis of jaundice with minimally trained manpower is obligatory.

Visual event-related potentials to biological motion stimuli in autism spectrum disorders

PubMed Central

Bletsch, Anke; Krick, Christoph; Siniatchkin, Michael; Jarczok, Tomasz A.; Freitag, Christine M.; Bender, Stephan

2014-01-01

Atypical visual processing of biological motion contributes to social impairments in autism spectrum disorders (ASD). However, the exact temporal sequence of deficits of cortical biological motion processing in ASD has not been studied to date. We used 64-channel electroencephalography to study event-related potentials associated with human motion perception in 17 children and adolescents with ASD and 21 typical controls. A spatio-temporal source analysis was performed to assess the brain structures involved in these processes. We expected altered activity already during early stimulus processing and reduced activity during subsequent biological motion specific processes in ASD. In response to both, random and biological motion, the P100 amplitude was decreased suggesting unspecific deficits in visual processing, and the occipito-temporal N200 showed atypical lateralization in ASD suggesting altered hemispheric specialization. A slow positive deflection after 400 ms, reflecting top-down processes, and human motion-specific dipole activation differed slightly between groups, with reduced and more diffuse activation in the ASD-group. The latter could be an indicator of a disrupted neuronal network for biological motion processing in ADS. Furthermore, early visual processing (P100) seems to be correlated to biological motion-specific activation. This emphasizes the relevance of early sensory processing for higher order processing deficits in ASD. PMID:23887808

A photoelectrochemical immunosensor for detection of α-fetoprotein based on Au-ZnO flower-rod heterostructures

NASA Astrophysics Data System (ADS)

Han, Zhizhong; Luo, Min; Chen, Li; Chen, Jinghua; Li, Chunyan

2017-04-01

In this work, a novel label free photoelectrochemical (PEC) immunosensor has been developed for the detection of α-fetoprotein (AFP). The immunosensor was based on Au-ZnO flower-rods (FRs) heterostructure, where Au nanoparticles (NPs) were firstly electrodeposited by cyclic voltammetry methods. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Mott-Schottky plot (MS), UV-vis diffuse reflectance spectrum and fluorescence emission spectrum were used for the characterizations of Au-ZnO FRs. The results demonstrated that Au NPs not only obviously enhanced the visible light absorption of ZnO FRs due to surface plasmon resonance (SPR) but also improved the separation of photo-generated electron-hole pairs. Therefore, the photocurrent of Au-ZnO FRs was increased under simulated sunlight. The photocurrent was reduced after the specific antibody-antigen immune reaction. And the photocurrent decrement was linear with the logarithm of AFP antigen concentration in the range from 0.005 ng mL-1 to 50 ng mL-1 with a low detection limit of 0.56 pg mL-1 (S/N = 3). The PEC immunosensor also exhibited high anti-interference property and acceptable stability. This work would provide a promising photoelectrochemical strategy for the detection of other proteins in clinical diagnosis.

Utilization of visible to NIR light energy by Yb+3, Er+3 and Tm+3 doped BiVO4 for the photocatalytic degradation of methylene blue

NASA Astrophysics Data System (ADS)

Regmi, Chhabilal; Kshetri, Yuwaraj K.; Ray, Schindra Kumar; Pandey, Ramesh Prasad; Lee, Soo Wohn

2017-01-01

Lanthanide-doped BiVO4 semiconductors with efficient photocatalytic activities over a broad range of the solar light spectrum have been synthesized by the microwave hydrothermal method using ethylenediaminetetraacetic acid (EDTA). The structural, morphological, and optical properties of the as-synthesized samples were evaluated by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray powder diffraction (XRD), Raman spectroscopy, FT-IR spectroscopy, UV-vis diffuse reflectance spectroscopy (DRS), and photoluminescence spectroscopy (PL). The chemical compositions were analyzed by X-ray photoelectron spectroscopy (XPS). The toxicity of the samples was measured using Mus musculus skin melanoma cells (B16-F10 (ATCC® CRL-6475™)) and were found to be nontoxic for human cells. The photocatalytic efficiency of the prepared samples was evaluated by methylene blue (MB) degradation. The best photocatalytic activity was shown by BiVO4 with 6:3:3 mol percentage of Yb+3:Er+3:Tm+3 in all solar light spectrum. The synthesized samples possess low band gap energy and a hollow structure suitable for the better photocatalytic activity. The observed NIR photoactivity supports that the upconversion mechanism is involved in the overall photocatalytic process. Therefore, this approach provides a better alternative upconversion material for integral solar light absorption.

Physical and photoelectrochemical properties of the spinel LiMn2O4 and its application in photocatalysis

NASA Astrophysics Data System (ADS)

Douafer, S.; Lahmar, H.; Benamira, M.; Rekhila, G.; Trari, M.

2018-07-01

Nanocrystalline lithium manganese oxide (LiMn2O4), synthesized by the sol-gel method, crystallizes in the spinel structure. The physical, electrical, and photoelectrochemical properties were studied for the photocatalytic degradation of methyl orange, a toxic compound, under solar irradiation. The diffuse reflectance spectrum allowed the direct band gap (1.99 eV) to be calculated. The Fourier transform IR spectrum contained all the characteristic peaks of the spinel LiMn2O4, which exhibited n-type behavior. The thermal evolution of the electrical conductivity exhibited an Arrhenius-type behavior with an activation energy of 0.27 eV. The Mott-Schottky curve allowed the determination of the flat band potential (-0.24 V vs. the saturated calomel electrode) as well as the carrier density (1.78 × 1021 cm-3). The detoxification of water containing methyl orange with LiMn2O4 as a photocatalyst was successfully completed. Total degradation for an initial concentration of 10-4 M methyl orange at pH ∼3 and 25 °C was obtained in less than 5 h under solar irradiation. No adsorption was obtained in the dark in the presence of LiMn2O4.

Brief Report: Intuitive and Reflective Reasoning in Autism Spectrum Disorder.

PubMed

Brosnan, Mark; Ashwin, Chris; Lewton, Marcus

2017-08-01

Dual Process Theory has recently been applied to Autism spectrum disorder (ASD) to suggest that reasoning by people with ASD and people with higher levels of ASD-like traits can be characterised by reduced intuitive and greater reflective processing. 26 adolescents and adults with ASD and 22 adolescent and adult controls completed an assessment of ASD-like traits, the cognitive reflections test (CRT) to measure intuitive and reflective reasoning and an index of general cognitive ability. The ASD group produced less intuitive responses, and the degree of ASD-like traits showed a negative correlation with intuitive responses and positive correlation with reflective responses on the CRT. Together, these results are consistent with ASD being associated with reduced intuitive reasoning and greater deductive reasoning.

System and technique for characterizing fluids using ultrasonic diffraction grating spectroscopy

DOEpatents

Greenwood, Margaret S [Richland, WA

2008-07-08

A system for determining property of multiphase fluids based on ultrasonic diffraction grating spectroscopy includes a diffraction grating on a solid in contact with the fluid. An interrogation device delivers ultrasound through the solid and a captures a reflection spectrum from the diffraction grating. The reflection spectrum exhibits peaks whose relative size depends on the properties of the various phases of the multiphase fluid. For example, for particles in a liquid, the peaks exhibit dependence on the particle size and the particle volume fraction. Where the exact relationship is know know a priori, data from different peaks of the same reflection spectrum or data from the peaks of different spectra obtained from different diffraction gratings can be used to resolve the size and volume fraction.

Radiative transfer in dusty nebulae. III - The effects of dust albedo

NASA Technical Reports Server (NTRS)

Petrosian, V.; Dana, R. A.

1980-01-01

The effects of an albedo of internal dust, such as ionization structure and temperature of dust grain, were studied by the quasi-diffusion method with an iterative technique for solving the radiative heat transfer equations. It was found that the generalized on-the-spot approximation solution is adequate for most astrophysical applications for a zero albedo; for a nonzero albedo, the Eddington approximation is more accurate. The albedo increases the average energy of the diffuse photons, increasing the ionization level of hydrogen and heavy elements if the Eddington approximation is applied; the dust thermal gradient is reduced so that the infrared spectrum approaches blackbody spectrum with an increasing albedo.

Plasma fluctuations as Markovian noise.

PubMed

Li, B; Hazeltine, R D; Gentle, K W

2007-12-01

Noise theory is used to study the correlations of stationary Markovian fluctuations that are homogeneous and isotropic in space. The relaxation of the fluctuations is modeled by the diffusion equation. The spatial correlations of random fluctuations are modeled by the exponential decay. Based on these models, the temporal correlations of random fluctuations, such as the correlation function and the power spectrum, are calculated. We find that the diffusion process can give rise to the decay of the correlation function and a broad frequency spectrum of random fluctuations. We also find that the transport coefficients may be estimated by the correlation length and the correlation time. The theoretical results are compared with the observed plasma density fluctuations from the tokamak and helimak experiments.

Polarimetric phenomenology in the reflective regime: a case study using polarized hyperspectral data

NASA Astrophysics Data System (ADS)

Gibney, Mark

2016-05-01

Understanding the phenomenology of polarimetric data is necessary if we want to obtain the maximum benefit when we exploit that data. To first order, polarimetric phenomenology is driven by two things; the target material type (specular or diffuse) and the illuminating source (point (sun) or extended (body emission)). Polarimetric phenomenology can then be broken into three basic categories; ([specular material/sun source], [diffuse/sun], [specular/body]) where we have assigned body emission to the IR passband where materials are generally specular. The task of interest determines the category of interest since the task determines the dominant target material and the illuminating source (eg detecting diffuse targets under trees in VNIR = [diffuse/sun] category). In this paper, a specific case study for the important [diffuse/sun] category will be presented. For the reflective regime (0.3 - 3.0um), the largest polarimetric signal is obtained when the sun illuminates a significant portion of the material BRDF lobe. This naturally points us to problems whose primary target materials are diffuse since the BRDF lobe for specular materials is tiny (low probability of acquiring on the BRDF lobe) and glinty (high probability of saturating the sensor when on lobe). In this case study, we investigated signatures of solar illuminated diffuse paints acquired by a polarimetric hyperspectral sensor. We will discuss the acquisition, reduction and exploitation of that data, and use it to illustrate the primary characteristics of reflective polarimetric phenomenology.

Preliminary results of BTDF calibration of transmissive solar diffusers for remote sensing

NASA Astrophysics Data System (ADS)

Georgiev, Georgi T.; Butler, James J.; Thome, Kurt; Cooksey, Catherine; Ding, Leibo

2016-09-01

Satellite instruments operating in the reflected solar wavelength region require accurate and precise determination of the optical properties of their diffusers used in pre-flight and post-flight calibrations. The majority of recent and current space instruments use reflective diffusers. As a result, numerous Bidirectional Reflectance Distribution Function (BRDF) calibration comparisons have been conducted between the National Institute of Standards and Technology (NIST) and other industry and university-based metrology laboratories. However, based on literature searches and communications with NIST and other laboratories, no Bidirectional Transmittance Distribution Function (BTDF) measurement comparisons have been conducted between National Measurement Laboratories (NMLs) and other metrology laboratories. On the other hand, there is a growing interest in the use of transmissive diffusers in the calibration of satellite, air-borne, and ground-based remote sensing instruments. Current remote sensing instruments employing transmissive diffusers include the Ozone Mapping and Profiler Suite instrument (OMPS) Limb instrument on the Suomi-National Polar-orbiting Partnership (S-NPP) platform,, the Geostationary Ocean Color Imager (GOCI) on the Korea Aerospace Research Institute's (KARI) Communication, Ocean, and Meteorological Satellite (COMS), the Ozone Monitoring Instrument (OMI) on NASA's Earth Observing System (EOS) Aura platform, the Tropospheric Emissions: Monitoring of Pollution (TEMPO) instrument and the Geostationary Environmental Monitoring Spectrometer (GEMS).. This ensemble of instruments requires validated BTDF measurements of their onboard transmissive diffusers from the ultraviolet through the near infrared. This paper presents the preliminary results of a BTDF comparison between the NASA Diffuser Calibration Laboratory (DCL) and NIST on quartz and thin Spectralon samples.

Carbon chain abundance in the diffuse interstellar medium

NASA Technical Reports Server (NTRS)

Allamandola, L. J.; Hudgins, D. M.; Bauschlicher, C. W. Jr; Langhoff, S. R.

1999-01-01

Thanks to the mid-IR sensitivities of the ISO and IRTS orbiting spectrometers it is now possible to search the diffuse interstellar medium for heretofore inaccessible molecular emission. In view of the recent strong case for the presence of C(7-) (Kirkwood et al. 1998, Tulej et al. 1998),and the fact that carbon chains possess prominent infrared active modes in a very clean portion of the interstellar spectrum, we have analyzed the IRTS spectrum of the diffuse interstellar medium for the infrared signatures of these species. Theoretical and experimental infrared band frequencies and absolute intensities of many different carbon chain species are presented. These include cyanopolyynes, neutral and anionic linear carbon molecules, and neutral and ionized, even-numbered, hydrogenated carbon chains. We show that--as a family--these species have abundances in the diffuse ISM on the order of 10(-10) with respect to hydrogen, values consistent with their abundances in dense molecular clouds. Assuming an average length of 10 C atoms per C-chain implies that roughly a millionth of the cosmically available carbon is in the form of carbon chains and that carbon chains can account for a few percent of the visible to near-IR diffuse interstellar band (DIB) total equivalent width (not DIB number).

Tunneling-thermally activated vacancy diffusion mechanism in quantum crystals

NASA Astrophysics Data System (ADS)

Natsik, V. D.; Smirnov, S. N.

2017-10-01

We consider a quasiparticle model of a vacancy in a quantum crystal, with metastable quantum states localized at the lattice sites in potential wells of the crystal field. It is assumed that the quantum dynamics of such vacancies can be described in the semi-classical approximation, where its spectrum consists of a broad band with several split-off levels. The diffusive movement of the vacancy in the crystal volume is reduced to a sequence of tunneling and thermally activated hops between the lattice cites. The temperature dependence of the vacancy diffusion coefficient shows a monotonic decrease during cooling with a sharp transition from an exponential dependence that is characteristic of a high-temperature thermally activated diffusion, to a non-thermal tunneling process in the region of extremely low temperatures. Similar trends have been recently observed in an experimental study of mass-transfer in the 4He and 3He crystals [V. A. Zhuchkov et al., Low Temp. Phys. 41, 169 (2015); Low Temp. Phys. 42, 1075 (2016)]. This mechanism of vacancy diffusion and its analysis complement the concept of a diffusional flow of a defection-quasiparticle quantum gas with a band energy spectrum proposed by Andreev and Lifshitz [JETP 29, 1107 (1969)] and Andreev [Sov. Phys. Usp. 19, 137 (1976)].

Discovery of the linear region of Near Infrared Diffuse Reflectance spectra using the Kubelka-Munk theory

NASA Astrophysics Data System (ADS)

Dai, Shengyun; Pan, Xiaoning; Ma, Lijuan; Huang, Xingguo; Du, Chenzhao; Qiao, Yanjiang; Wu, Zhisheng

2018-05-01

Particle size is of great importance for the quantitative model of the NIR diffuse reflectance. In this paper, the effect of sample particle size on the measurement of harpagoside in Radix Scrophulariae powder by near infrared diffuse (NIR) reflectance spectroscopy was explored. High-performance liquid chromatography (HPLC) was employed as a reference method to construct the quantitative particle size model. Several spectral preprocessing methods were compared, and particle size models obtained by different preprocessing methods for establishing the partial least-squares (PLS) models of harpagoside. Data showed that the particle size distribution of 125-150 μm for Radix Scrophulariae exhibited the best prediction ability with R2pre=0.9513, RMSEP=0.1029 mg·g-1, and RPD = 4.78. For the hybrid granularity calibration model, the particle size distribution of 90-180 μm exhibited the best prediction ability with R2pre=0.8919, RMSEP=0.1632 mg·g-1, and RPD = 3.09. Furthermore, the Kubelka-Munk theory was used to relate the absorption coefficient k (concentration-dependent) and scatter coefficient s (particle size-dependent). The scatter coefficient s was calculated based on the Kubelka-Munk theory to study the changes of s after being mathematically preprocessed. A linear relationship was observed between k/s and absorption A within a certain range and the value for k/s was greater than 4. According to this relationship, the model was more accurately constructed with the particle size distribution of 90-180 μm when s was kept constant or in a small linear region. This region provided a good reference for the linear modeling of diffuse reflectance spectroscopy. To establish a diffuse reflectance NIR model, further accurate assessment should be obtained in advance for a precise linear model.

Design and characteristics of refractive index sensor based on thinned and microstructure fiber Bragg grating.

PubMed

Huang, Xue-Feng; Chen, Zhe-Min; Shao, Li-Yang; Cen, Ke-Fa; Sheng, De-Ren; Chen, Jun; Zhou, Hao

2008-02-01

A refractive index sensor based on the thinned and microstructure fiber Bragg grating (ThMs-FBG) was proposed and realized as a chemical sensing. The numerical simulation for the reflectance spectrum of the ThMs-FBG was calculated and the phase shift down-peak could be observed from the reflectance spectrum. Many factors influencing the reflectance spectrum were considered in detail for simulation, including the etched depth, length, and position. The sandwich-solution etching method was utilized to realize the microstructure of the ThMs-FBG, and the photographs of the microstructure were obtained. Experimental results demonstrated that the reflectance spectrum, phase shift down-peak wavelength, and reflected optical intensity of the ThMs-FBG all depended on the surrounding refractive index. However, only the down-peak wavelength of the ThMs-FBG changed with the surrounding temperature. Under the condition that the length and cladding diameter of the ThMs-FBG microstructure were 800 and 14 mum, respectively, and the position of the microstructure of the ThMs-FBG is in the middle of grating region, the refractive index sensitivity of the ThMs-FBG was 0.79 nm/refractive index unit with the wide range of 1.33-1.457 and a high resolution of 1.2 x 10(-3). The temperature sensitivity was 0.0103 nm/ degrees C, which was approximately equal to that of common FBG.

Spectrum of spin waves in cold polarized gases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andreeva, T. L., E-mail: phdocandreeva@yandex.ru

2017-02-15

The spin dynamics of cold polarized gases are investigated using the Boltzmann equation. The dispersion relation for spin waves (transverse component of the magnetic moment) and the spin diffusion coefficient of the longitudinal component of the magnetic moment are calculated without using fitting parameters. The spin wave frequency and the diffusion coefficient for rubidium atoms are estimated numerically.

[Brunners gland hiperplasia. Report of two cases].

PubMed

Padilla Ruiz, Maykel

2014-04-01

Brunner's gland hyperplasia is an infrequent benign injury located on the first or second portion of the duodenum. The disease spectrum includes diffuse nodular hyperplasia, circumscribed nodular hyperplasia, and Brunner's gland adenoma. We report two cases, one with an adenoma of Brunner's glands as a duodenal polyp and the other as a diffuse nodular hyperplasia of the duodenal bulb.

Spectral distribution of UV range diffuse reflectivity for Si+ ion implanted polymers

NASA Astrophysics Data System (ADS)

Balabanov, S.; Tsvetkova, T.; Borisova, E.; Avramov, L.; Bischoff, L.

2008-05-01

The analysis of the UV range spectral characteristics can supply additional information on the formed sub-surface buried layer with implanted dopants. The near-surface layer (50÷150 nm) of bulk polymer samples have been implanted with silicon (Si+) ions at low energies (E = 30 keV) and a wide range of ion doses (D = 1.1013 ÷ 1, 2.1017 cm-2). The studied polymer materials were: ultra-high-molecular-weight polyethylene (UHMWPE), poly-methyl-metacrylate (PMMA) and poly-tetra-fluor-ethylene (PTFE). The diffuse optical reflectivity spectra Rd = f(λ) of the ion implanted samples have been measured in the UV range (λ = 220÷350 nm). In this paper the dose dependences of the size and sign of the diffuse optical reflectivity changes λRd = f(D) have been analysed.

Prepreg cure monitoring using diffuse reflectance-FTIR. [Fourier Transform Infrared Technique

NASA Technical Reports Server (NTRS)

Young, P. R.; Chang, A. C.

1984-01-01

An in situ diffuse reflectance-Fourier transform infrared technique was developed to determine infrared spectra of graphite fiber prepregs as they were being cured. A bismaleimide, an epoxy, and addition polyimide matrix resin prepregs were studied. An experimental polyimide adhesive was also examined. Samples were positioned on a small heater at the focal point of diffuse reflectance optics and programmed at 15 F/min while FTIR spectra were being scanned, averaged, and stored. An analysis of the resulting spectra provided basic insights into changes in matrix resin molecular structure which accompanied reactions such as imidization and crosslinking. An endo-exothermal isomerization involving reactive end-caps was confirmed for the addition polyimide prepregs. The results of this study contribute to a fundamental understanding of the processing of composites and adhesives. Such understanding will promote the development of more efficient cure cycles.

Widespread White Matter Differences in Children and Adolescents with Autism Spectrum Disorder

ERIC Educational Resources Information Center

Vogan, V. M.; Morgan, B. R.; Leung, R. C.; Anagnostou, E.; Doyle-Thomas, K.; Taylor, M. J.

2016-01-01

Diffusion tensor imaging studies show white matter (WM) abnormalities in children with autism spectrum disorder (ASD). However, investigations are often limited by small samples, particularly problematic given the heterogeneity of ASD. We explored WM using DTI in a large sample of 130 children and adolescents (7-15 years) with and without ASD,…

Language Laterality in Autism Spectrum Disorder and Typical Controls: A Functional, Volumetric, and Diffusion Tensor MRI Study

ERIC Educational Resources Information Center

Knaus, Tracey A.; Silver, Andrew M.; Kennedy, Meaghan; Lindgren, Kristen A.; Dominick, Kelli C.; Siegel, Jeremy; Tager-Flusberg, Helen

2010-01-01

Language and communication deficits are among the core features of autism spectrum disorder (ASD). Reduced or reversed asymmetry of language has been found in a number of disorders, including ASD. Studies of healthy adults have found an association between language laterality and anatomical measures but this has not been systematically…

White Matter and Development in Children with an Autism Spectrum Disorder

ERIC Educational Resources Information Center

Mak-Fan, Kathleen M.; Morris, Drew; Vidal, Julie; Anagnostou, Evdokia; Roberts, Wendy; Taylor, Margot J.

2013-01-01

Recent research suggests that brain development follows an abnormal trajectory in children with autism spectrum disorders (ASD). The current study examined changes in diffusivity with age within defined white matter tracts in a group of typically developing children and a group of children with an ASD, aged 6 to 14 years. Age by group interactions…

Scientific Accomplishments for ARL Brain Structure-Function Couplings Research on Large-Scale Brain Networks from FY11-FY13 (DSI Final Report)

DTIC Science & Technology

2014-03-01

streamlines) from two types of diffusion weighted imaging scans, diffusion tensor imaging ( DTI ) and diffusion spectrum imaging (DSI). We examined...individuals. Importantly, the results also showed that this effect was greater for the DTI method than the DSI method. This suggested that DTI can better...compared to level surface walking. This project combines experimental EEG data and electromyography (EMG) data recorded from seven muscles of the leg

Diffuse cosmic gamma rays: Present status of theory and observation

NASA Technical Reports Server (NTRS)

Stecker, F. W.

1972-01-01

Positive diffuse gamma ray flux measurements now exist for energies up to the 100 MeV range. The totality of the observations in the 0.001 to 100 MeV range follow an E to the minus 2nd power trend in the differential isotropic photon spectrum but significant features appear. Possible theoretical interpretations of these features are discussed. New results on the diffuse flux from the galaxy substantiate the pion-decay origin hypothesis for gamma radiation above 100 MeV.

Developments in the realization of diffuse reflectance scales at NPL

NASA Astrophysics Data System (ADS)

Chunnilall, Christopher J.; Clarke, Frank J. J.; Shaw, Michael J.

2005-08-01

The United Kingdom scales for diffuse reflectance are realized using two primary instruments. In the 360 nm to 2.5 μm spectral region the National Reference Reflectometer (NRR) realizes absolute measurement of reflectance and radiance factor by goniometric measurements. Hemispherical reflectance scales are obtained through the spatial integration of these goniometric measurements. In the mid-infrared region (2.5 μm - 55 μm) the hemispherical reflectance scale is realized by the Absolute Hemispherical Reflectometer (AHR). This paper describes some of the uncertainties resulting from errors in aligning the NRR and non-ideality in sample topography, together with its use to carry out measurements in the 1 - 1.6 μm region. The AHR has previously been used with grating spectrometers, and has now been coupled to a Fourier transform spectrometer.

Off-axis holographic lens spectrum-splitting photovoltaic system for direct and diffuse solar energy conversion.

PubMed

Vorndran, Shelby D; Chrysler, Benjamin; Wheelwright, Brian; Angel, Roger; Holman, Zachary; Kostuk, Raymond

2016-09-20

This paper describes a high-efficiency, spectrum-splitting photovoltaic module that uses an off-axis volume holographic lens to focus and disperse incident solar illumination to a rectangular shaped high-bandgap indium gallium phosphide cell surrounded by strips of silicon cells. The holographic lens design allows efficient collection of both direct and diffuse illumination to maximize energy yield. We modeled the volume diffraction characteristics using rigorous coupled-wave analysis, and simulated system performance using nonsequential ray tracing and PV cell data from the literature. Under AM 1.5 illumination conditions the simulated module obtained a 30.6% conversion efficiency. This efficiency is a 19.7% relative improvement compared to the more efficient cell in the system (silicon). The module was also simulated under a typical meteorological year of direct and diffuse irradiance in Tucson, Arizona, and Seattle, Washington. Compared to a flat panel silicon module, the holographic spectrum splitting module obtained a relative improvement in energy yield of 17.1% in Tucson and 14.0% in Seattle. An experimental proof-of-concept volume holographic lens was also fabricated in dichromated gelatin to verify the main characteristics of the system. The lens obtained an average first-order diffraction efficiency of 85.4% across the aperture at 532 nm.

Effect of Upstream ULF Waves on the Energetic Ion Diffusion at the Earth's Foreshock. I. Theory and Simulation

NASA Astrophysics Data System (ADS)

Otsuka, Fumiko; Matsukiyo, Shuichi; Kis, Arpad; Nakanishi, Kento; Hada, Tohru

2018-02-01

Field-aligned diffusion of energetic ions in the Earth’s foreshock is investigated by using the quasi-linear theory (QLT) and test particle simulation. Non-propagating MHD turbulence in the solar wind rest frame is assumed to be purely transverse with respect to the background field. We use a turbulence model based on a multi-power-law spectrum including an intense peak that corresponds to upstream ULF waves resonantly generated by the field-aligned beam (FAB). The presence of the ULF peak produces a concave shape of the diffusion coefficient when it is plotted versus the ion energy. The QLT including the effect of the ULF wave explains the simulation result well, when the energy density of the turbulent magnetic field is 1% of that of the background magnetic field and the power-law index of the wave spectrum is less than 2. The numerically obtained e-folding distances from 10 to 32 keV ions match with the observational values in the event discussed in the companion paper, which contains an intense ULF peak in the spectra generated by the FAB. Evolution of the power spectrum of the ULF waves when approaching the shock significantly affects the energy dependence of the e-folding distance.

Method for determining shear direction using liquid crystal coatings

NASA Technical Reports Server (NTRS)

Reda, Daniel C.

1995-01-01

A method is provided for determining shear direction wherein a beam of white light is directed onto the surface of a liquid crystal coating to cause the white light to be dispersed (reflected) from the surface in a spectrum having bands of different colors in a fixed spatial 2 (angular) sequence. The system is calibrated by locating an observer, e.g., a video and movie camera, such that a particular color band (preferably at or near the center of the reflected spectrum) is observed to thereby provide a reference color band. Because the application of shear causes either clockwise or counterclockwise rotation of the reflected spectrum dependent on the direction of the shear, a determination is then made of the reflected color band observed by the observer when the surface of the liquid crystal is subjected to shear to thereby determine the direction of the shear based on the directional (rotation) relation of the observed color band with respect to the reference color band in the spatial sequence of color bands.

Diffuse reflectance spectroscopy for optical nerve identification. Preliminary ex vivo results for feedback controlled oral and maxillofacial laser surgery

NASA Astrophysics Data System (ADS)

Stelzle, Florian; Zam, Azhar; Adler, Werner; Douplik, Alexandre; Tangermann-Gerk, Katja; Nkenke, Emeka; Neukam, Friedrich Wilhelm; Schmidt, Michael

Objective: Laser surgery has many advantages. However, due to a lack of haptic feedback it is accompanied by the risk of iatrogenic nerve damage. The aim of this study was to evaluate the possibilities of optical nerve identification by diffuse reflectance spectroscopy to set the base for a feedback control system to enhance nerve preservation in oral and maxillofacial laser surgery. Materials and Methods: Diffuse reflectance spectra of nerve tissue, skin, mucosa, fat tissue, muscle, cartilage and bone (15120 spectra) of ex vivo pig heads were acquired in the wavelength range of 350-650 nm. Tissue differentiation was performed by principal components analysis (PCA) followed by linear discriminant analysis (LDA). Specificity and sensitivity were calculated by receiver operating characteristic (ROC) analysis and the area under curve (AUC). Results: Nerve tissue could correctly be identified and differed from skin, mucosa, fat tissue, muscle, cartilage and bone in more than 90% of the cases (AUC results) with a specificity of over 78% and a sensitivity of more than 86%. Conclusion: Nerve tissue can be identified by diffuse reflectance spectroscopy with high precision and reliability. The results may set the base for a feedback system to prevent iatrogenic nerve damage performing oral and maxillofacial laser surgery.

Probe pressure effects on human skin diffuse reflectance and fluorescence spectroscopy measurements

PubMed Central

Lim, Liang; Nichols, Brandon; Rajaram, Narasimhan; Tunnell, James W.

2011-01-01

Diffuse reflectance and fluorescence spectroscopy are popular research techniques for noninvasive disease diagnostics. Most systems include an optical fiber probe that transmits and collects optical spectra in contact with the suspected lesion. The purpose of this study is to investigate probe pressure effects on human skin spectroscopic measurements. We conduct an in-vivo experiment on human skin tissue to study the short-term (<2 s) and long-term (>30 s) effects of probe pressure on diffuse reflectance and fluorescence measurements. Short-term light probe pressure (P0 < 9 mN∕mm2) effects are within 0 ± 10% on all physiological properties extracted from diffuse reflectance and fluorescence measurements, and less than 0 ± 5% for diagnostically significant physiological properties. Absorption decreases with site-specific variations due to blood being compressed out of the sampled volume. Reduced scattering coefficient variation is site specific. Intrinsic fluorescence shows a large standard error, although no specific pressure-related trend is observed. Differences in tissue structure and morphology contribute to site-specific probe pressure effects. Therefore, the effects of pressure can be minimized when the pressure is small and applied for a short amount of time; however, long-term and large pressures induce significant distortions in measured spectra. PMID:21280899

On the renormalisation of the diffusion asymptotics in the problem of reflection of a narrow optical beam from a biological medium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Appanov, A Yu; Barabanenkov, Yu N

2005-12-31

An analytic hybrid method is considered for solving the stationary radiation transfer equation in the problem on reflection of a narrow laser beam from biological media such as the 2% aqueous solution of intralipid and erythrocyte suspension with the volume concentration (hematocrit) H=0.41. The method is based on the reciprocity of the Green function in the radiation transfer theory and on the iteration solution of the integral equation for this function. As a result, the ray intensity is represented as a sum of two terms. The first of them describes the contribution of finite-order scattering to the intensity of amore » beam diffusely reflected from the medium. The second term contains the explicit analytic expression for a spatially distributed effective source of diffuse radiation emerging from the deep layers of the medium to the surface. This approach substantially improves the diffusion approximation for the problem under study and allows one to obtain the uniform asymptotics of the reflection coefficient at the specified interval of distances between the radiation source and detector on the medium surface with the relative error within {+-}6% for the 2% intralipid emulsion and erythrocyte suspension (H=0.41). (radiation scattering)« less

Optical Reflectance Measurements for Commonly Used Reflectors

NASA Astrophysics Data System (ADS)

Janecek, Martin; Moses, William W.

2008-08-01

When simulating light collection in scintillators, modeling the angular distribution of optical light reflectance from surfaces is very important. Since light reflectance is poorly understood, either purely specular or purely diffuse reflectance is generally assumed. In this paper we measure the optical reflectance distribution for eleven commonly used reflectors. A 440 nm, output power stabilized, un-polarized laser is shone onto a reflector at a fixed angle of incidence. The reflected light's angular distribution is measured by an array of silicon photodiodes. The photodiodes are movable to cover 2pi of solid angle. The light-induced current is, through a multiplexer, read out with a digital multimeter. A LabVIEW program controls the motion of the laser and the photodiode array, the multiplexer, and the data collection. The laser can be positioned at any angle with a position accuracy of 10 arc minutes. Each photodiode subtends 6.3deg, and the photodiode array can be positioned at any angle with up to 10 arc minute angular resolution. The dynamic range for the current measurements is 10 5:1. The measured light reflectance distribution was measured to be specular for several ESR films as well as for aluminum foil, mostly diffuse for polytetrafluoroethylene (PTFE) tape and titanium dioxide paint, and neither specular nor diffuse for Lumirrorreg, Melinexreg and Tyvekreg. Instead, a more complicated light distribution was measured for these three materials.

Specular, diffuse and polarized imagery of an oat canopy

NASA Technical Reports Server (NTRS)

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

1988-01-01

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

Diffusion-weighted imaging in cancer: Physical foundations and applications of Restriction Spectrum Imaging

PubMed Central

White, Nathan S.; McDonald, Carrie; Farid, Niky; Kuperman, Josh; Karow, David; Schenker-Ahmed, Natalie M.; Bartsch, Hauke; Rakow-Penner, Rebecca; Holland, Dominic; Shabaik, Ahmed; Bjørnerud, Atle; Hope, Tuva; Hattangadi-Gluth, Jona; Liss, Michael; Parsons, J. Kellogg; Chen, Clark C.; Raman, Steve; Margolis, Daniel; Reiter, Robert E.; Marks, Leonard; Kesari, Santosh; Mundt, Arno J.; Kane, Chris J.; Carter, Bob S.; Bradley, William G.; Dale, Anders M.

2014-01-01

Diffusion weighted imaging (DWI) has been at the forefront of cancer imaging since the early 2000’s. Prior to its application in clinical oncology, this powerful technique had already achieved widespread recognition due to its utility in the diagnosis of cerebral infarction. Following this initial success, the ability of DWI to detect inherent tissue contrast began to be exploited in the field of oncology. Although the initial oncologic applications for tumor detection and characterization, assessing treatment response, and predicting survival were primarily in the field of neuro-oncology, the scope of DWI has since broadened to include oncologic imaging of the prostate gland, breast, and liver. Despite its growing success and application, misconceptions as to the underlying physical basis of the DWI signal exist among researchers and clinicians alike. In this review, we provide a detailed explanation of the biophysical basis of diffusion contrast, emphasizing the difference between hindered and restricted diffusion, and elucidating how diffusion parameters in tissue are derived from the measurements via the diffusion model. We describe one advanced DWI modeling technique, called Restriction Spectrum Imaging (RSI). This technique offers a more direct in vivo measure of tumor cells, due to its ability to distinguish separable pools of water within tissue based on their intrinsic diffusion characteristics. Using RSI as an example, we then highlight the ability of advanced DWI techniques to address key clinical challenges in neuro-oncology, including improved tumor conspicuity, distinguishing actual response to therapy from pseudoresponse, and delineation of white matter tracts in regions of peritumoral edema. We also discuss how RSI, combined with new methods for correction of spatial distortions inherent diffusion MRI scans, may enable more precise spatial targeting of lesions, with implications for radiation oncology, and surgical planning. PMID:25183788

Neutron Reflectivity Measurement for Polymer Dynamics near Graphene Oxide Monolayers

NASA Astrophysics Data System (ADS)

Koo, Jaseung

We investigated the diffusion dynamics of polymer chains confined between graphene oxide layers using neutron reflectivity (NR). The bilayers of polymethylmetacrylate (PMMA)/ deuterated PMMA (d-PMMA) films and polystyrene (PS)/d-PS films with various film thickness sandwiched between Langmuir-Blodgett (LB) monolayers of graphene oxide (GO) were prepared. From the NR results, we found that PMMA diffusion dynamics was reduced near the GO surface while the PS diffusion was not significantly changed. This is due to the different strength of GO-polymer interaction. In this talk, these diffusion results will be compared with dewetting dynamics of polymer thin films on the GO monolayers. This has given us the basis for development of graphene-based nanoelectronics with high efficiency, such as heterojunction devices for polymer photovoltaic (OPV) applications.

Exploring the effect of diffuse reflection on indoor localization systems based on RSSI-VLC.

PubMed

Mohammed, Nazmi A; Elkarim, Mohammed Abd

2015-08-10

This work explores and evaluates the effect of diffuse light reflection on the accuracy of indoor localization systems based on visible light communication (VLC) in a high reflectivity environment using a received signal strength indication (RSSI) technique. The effect of the essential receiver (Rx) and transmitter (Tx) parameters on the localization error with different transmitted LED power and wall reflectivity factors is investigated at the worst Rx coordinates for a directed/overall link. Since this work assumes harsh operating conditions (i.e., a multipath model, high reflectivity surfaces, worst Rx position), an error of ≥ 1.46 m is found. To achieve a localization error in the range of 30 cm under these conditions with moderate LED power (i.e., P = 0.45 W), low reflectivity walls (i.e., ρ = 0.1) should be used, which would enable a localization error of approximately 7 mm at the room's center.

The Spectrum of Isotropic Diffuse Gamma-Ray Emission Between 100 Mev and 820 Gev

NASA Technical Reports Server (NTRS)

Ackermann, M.; Ajello, M.; Albert, A.; Atwood, W. B.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Brandt, T. J.; Hays, E.;

Specular Reflection and Diffuse Reflectance Spectroscopy of Soils

USDA-ARS?s Scientific Manuscript database

Studies on the occurrence and effects of specular reflection in mid-infrared spectra of soils have shown that distortions due to specular reflection occur for both organic (humic acid) and non-organic fractions (carbonates, silica, ashed fraction of soil). The results demonstrated explain why the s...

Acoustic radiosity for computation of sound fields in diffuse environments

NASA Astrophysics Data System (ADS)

Muehleisen, Ralph T.; Beamer, C. Walter

2002-05-01

The use of image and ray tracing methods (and variations thereof) for the computation of sound fields in rooms is relatively well developed. In their regime of validity, both methods work well for prediction in rooms with small amounts of diffraction and mostly specular reflection at the walls. While extensions to the method to include diffuse reflections and diffraction have been made, they are limited at best. In the fields of illumination and computer graphics the ray tracing and image methods are joined by another method called luminous radiative transfer or radiosity. In radiosity, an energy balance between surfaces is computed assuming diffuse reflection at the reflective surfaces. Because the interaction between surfaces is constant, much of the computation required for sound field prediction with multiple or moving source and receiver positions can be reduced. In acoustics the radiosity method has had little attention because of the problems of diffraction and specular reflection. The utility of radiosity in acoustics and an approach to a useful development of the method for acoustics will be presented. The method looks especially useful for sound level prediction in industrial and office environments. [Work supported by NSF.

Earth's transmission spectrum from lunar eclipse observations.

PubMed

Pallé, Enric; Osorio, María Rosa Zapatero; Barrena, Rafael; Montañés-Rodríguez, Pilar; Martín, Eduardo L

2009-06-11

Of the 342 planets so far discovered orbiting other stars, 58 'transit' the stellar disk, meaning that they can be detected through a periodic decrease in the flux of starlight. The light from the star passes through the atmosphere of the planet, and in a few cases the basic atmospheric composition of the planet can be estimated. As we get closer to finding analogues of Earth, an important consideration for the characterization of extrasolar planetary atmospheres is what the transmission spectrum of our planet looks like. Here we report the optical and near-infrared transmission spectrum of the Earth, obtained during a lunar eclipse. Some biologically relevant atmospheric features that are weak in the reflection spectrum (such as ozone, molecular oxygen, water, carbon dioxide and methane) are much stronger in the transmission spectrum, and indeed stronger than predicted by modelling. We also find the 'fingerprints' of the Earth's ionosphere and of the major atmospheric constituent, molecular nitrogen (N(2)), which are missing in the reflection spectrum.

Characterization of MODIS and SeaWiFS Solar Diffuser On-Orbit Degradation

NASA Technical Reports Server (NTRS)

Xiong, X.; Eplee, R. E., Jr.; Sun, J.; Patt, F. S.; Angal, A.; McClain, C. R.

2009-01-01

MODIS has 20 reflective solar bands (RSB), covering the VIS, NIR, and SWIR spectral regions. They are calibrated on-orbit using a solar diffuser (SD) panel, made of space-grade Spectralon. The SD bi-directional reflectance factor (BRF) was characterized pre-launch by the instrument vendor reference to the NIST reflectance standard. Its on-orbit degradation is tracked by an on-board solar diffuser stability monitor (SDSM). The SeaWifS on-orbit calibration strategy uses monthly lunar observations to monitor the long-term radiometric stability of the instrument and applies daily observations of its solar diffuser (an aluminum plate coated with YB71 paint) to track the short-term changes in the instrument response. This paper provides an overview of MODIS and SeaWiFS SD observations, applications, and approaches used to track their on-orbit degradations. Results from sensors are presented with emphasis on the spectral dependence and temporal trends of the SD degradation. Lessons and challenges from the use of SD for sensor on-orbit calibration are also discussed.

Influence of earlobe thickness on near infrared spectroscopy

NASA Astrophysics Data System (ADS)

Jiang, Jingying; Wang, Tianpei; Li, Si; Li, Lin; Liu, Jiajia; Xu, Kexin

2017-03-01

Near-infrared spectroscopy has been recognized as a potential technology for noninvasive blood glucose sensing. However, the detected spectral signal is unstable mainly because of (1) the weak light absorption of glucose itself within NIR range, (2) the influence of temperature and individual differences of biotissue. Our previous results demonstrated that the synergistic effect of both transmittance and reflectance could enhance the strength of the detection signal. In this talk, we design a set of experiments to analyze the effect of earlobe thickness on Near Infrared spectroscopic measurement by using home-made optical fiber probe within the wavelength of 1000-1600nm. Firstly, we made a MC simulation of single-layer skin model and five-layer skin model to get the diffused transmittance spectra and diffused reflectance spectra under different optaical path lengths. And then we obtain the spectra of the earlobes from different volunteers by the same way. The experimental results showed that with the increase of the thickness,the light intensity of diffused transmittance decreases, and the light intensity of diffused reflectance remaines substantially unchanged.

SeaWiFS Postlaunch Technical Report Series. Volume 5; The SeaWiFS Solar Radiation-Based Calibration and the Transfer-to-Orbit Experiment

NASA Technical Reports Server (NTRS)

Hooker, Stanford B. (Editor); Firestone, Elaine R. (Editor); Barnes, Robert A.; Eplee, Robert E., Jr.; Biggar, Stuart F.; Thome, Kurtis J.; Zalewski, Edward F.; Slater, Philip N.; Holmes, Alan W.

1999-01-01

The solar radiation-based calibration (SRBC) of the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) was performed on 1 November 1993. Measurements were made outdoors in the courtyard of the instrument manufacturer. SeaWiFS viewed the solar irradiance reflected from the sensor's diffuser in the same manner as viewed on orbit. The calibration included measurements using a solar radiometer designed to determine the transmittances of principal atmospheric constituents. The primary uncertainties in the outdoor measurements are the transmission of the atmosphere and the reflectance of the diffuser. Their combined uncertainty is about 5 or 6%. The SRBC also requires knowledge of the extraterrestrial solar spectrum. Four solar models are used. When averaged over the responses of the SeaWiFS bands, the irradiance models agree at the 3.6% level, with the greatest difference for SeaWiFS band 8. The calibration coefficients from the SRBC are lower than those from the laboratory calibration of the instrument in 1997. For a representative solar model, the ratios of the SRBC coefficients to laboratory values average 0.962 with a standard deviation of 0.012. The greatest relative difference is 0.946 for band 8. These values are within the estimated uncertainties of the calibration measurements. For the transfer-to-orbit experiment, the measurements in the manufacturer's courtyard are used to predict the digital counts from the instrument on its first day on orbit (August 1, 1997). This experiment requires an estimate of the relative change in the diffuser response for the period between the launch of the instrument and its first solar measurements on orbit (September 9, 1997). In relative terms, the counts from the instrument on its first day on orbit averaged 1.3% higher than predicted, with a standard deviation of 1.2% and a greatest difference of 2.4% or band 7. The estimated uncertainty for the transfer-to-orbit experiment is about 3 or 4%.

Neural Correlates of Reflection on Present and Past Selves in Autism Spectrum Disorder.

PubMed

Cygan, Hanna B; Marchewka, Artur; Kotlewska, Ilona; Nowicka, Anna

2018-06-05

Previous studies indicate that autobiographical memory is impaired in individuals with autism spectrum disorder (ASD). Successful recollection of information referring to one's own person requires the intact ability to re-activate representation of the past self. In the current fMRI study we investigated process of conscious reflection on the present self, the past self, and a close-other in the ASD and typically developing groups. Significant inter-group differences were found in the Past-Self condition. In individuals with ASD, reflection on the past self was associated with additional engagement of the posterior cingulate and posterior temporal structures. We hypothesize that this enhanced activation of widely distributed neural network reflects substantial difficulties in processes of reflection on one's own person in the past.

Compilation of load spectrum of loader drive axle

NASA Astrophysics Data System (ADS)

Wei, Yongxiang; Zhu, Haoyue; Tang, Heng; Yuan, Qunwei

2018-03-01

In order to study the preparation method of gear fatigue load spectrum for loaders, the load signal of four typical working conditions of loader is collected. The signal that reflects the law of load change is obtained by preprocessing the original signal. The torque of the drive axle is calculated by using the rain flow counting method. According to the operating time ratio of each working condition, the two dimensional load spectrum based on the real working conditions of the drive axle of loader is established by the cycle extrapolation and synthesis method. The two-dimensional load spectrum is converted into one-dimensional load spectrum by means of the mean of torque equal damage method. Torque amplification includes the maximum load torque of the main reduction gear. Based on the theory of equal damage, the accelerated cycles are calculated. In this way, the load spectrum of the loading condition of the drive axle is prepared to reflect loading condition of the loader. The load spectrum can provide reference for fatigue life test and life prediction of loader drive axle.

A Simple Experiment for Visualizing Diffusion

ERIC Educational Resources Information Center

Helseth, L. E.

2011-01-01

We propose a simple and fascinating experiment for studying diffusion in gels using a pH-sensitive dye. By doping agar with methyl red, we obtain a gel which rapidly reacts to changes in pH by changing its absorption spectrum. The pH gradients can be followed using a digital camera, and we demonstrate here that the pH-sensitive colour changes can…

Self-averaging and weak ergodicity breaking of diffusion in heterogeneous media

NASA Astrophysics Data System (ADS)

Russian, Anna; Dentz, Marco; Gouze, Philippe

2017-08-01

Diffusion in natural and engineered media is quantified in terms of stochastic models for the heterogeneity-induced fluctuations of particle motion. However, fundamental properties such as ergodicity and self-averaging and their dependence on the disorder distribution are often not known. Here, we investigate these questions for diffusion in quenched disordered media characterized by spatially varying retardation properties, which account for particle retention due to physical or chemical interactions with the medium. We link self-averaging and ergodicity to the disorder sampling efficiency Rn, which quantifies the number of disorder realizations a noise ensemble may sample in a single disorder realization. Diffusion for disorder scenarios characterized by a finite mean transition time is ergodic and self-averaging for any dimension. The strength of the sample to sample fluctuations decreases with increasing spatial dimension. For an infinite mean transition time, particle motion is weakly ergodicity breaking in any dimension because single particles cannot sample the heterogeneity spectrum in finite time. However, even though the noise ensemble is not representative of the single-particle time statistics, subdiffusive motion in q ≥2 dimensions is self-averaging, which means that the noise ensemble in a single realization samples a representative part of the heterogeneity spectrum.

Monte Carlo Simulations of the Photospheric Emission in Gamma-Ray Bursts

NASA Astrophysics Data System (ADS)

Bégué, D.; Siutsou, I. A.; Vereshchagin, G. V.

2013-04-01

We studied the decoupling of photons from ultra-relativistic spherically symmetric outflows expanding with constant velocity by means of Monte Carlo simulations. For outflows with finite widths we confirm the existence of two regimes: photon-thick and photon-thin, introduced recently by Ruffini et al. (RSV). The probability density function of the last scattering of photons is shown to be very different in these two cases. We also obtained spectra as well as light curves. In the photon-thick case, the time-integrated spectrum is much broader than the Planck function and its shape is well described by the fuzzy photosphere approximation introduced by RSV. In the photon-thin case, we confirm the crucial role of photon diffusion, hence the probability density of decoupling has a maximum near the diffusion radius well below the photosphere. The time-integrated spectrum of the photon-thin case has a Band shape that is produced when the outflow is optically thick and its peak is formed at the diffusion radius.

MONTE CARLO SIMULATIONS OF THE PHOTOSPHERIC EMISSION IN GAMMA-RAY BURSTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Begue, D.; Siutsou, I. A.; Vereshchagin, G. V.

2013-04-20

We studied the decoupling of photons from ultra-relativistic spherically symmetric outflows expanding with constant velocity by means of Monte Carlo simulations. For outflows with finite widths we confirm the existence of two regimes: photon-thick and photon-thin, introduced recently by Ruffini et al. (RSV). The probability density function of the last scattering of photons is shown to be very different in these two cases. We also obtained spectra as well as light curves. In the photon-thick case, the time-integrated spectrum is much broader than the Planck function and its shape is well described by the fuzzy photosphere approximation introduced by RSV.more » In the photon-thin case, we confirm the crucial role of photon diffusion, hence the probability density of decoupling has a maximum near the diffusion radius well below the photosphere. The time-integrated spectrum of the photon-thin case has a Band shape that is produced when the outflow is optically thick and its peak is formed at the diffusion radius.« less

On the origin of the soft X-ray background. [in cosmological observations

NASA Technical Reports Server (NTRS)

Wang, Q. D.; Mccray, Richard

1993-01-01

The angular autocorrelation function and spectrum of the soft X-ray background is studied below a discrete source detection limit, using two deep images from the Rosat X-ray satellite. The average spectral shape of pointlike sources, which account for 40 to 60 percent of the background intensity, is determined by using the autocorrelation function. The background spectrum, in the 0.5-0.9 keV band (M band), is decomposed into a pointlike source component characterized by a power law and a diffuse component represented by a two-temperature plasma. These pointlike sources cannot contribute more than 60 percent of the X-ray background intensity in the M band without exceeding the total observed flux in the R7 band. Spectral analysis has shown that the local soft diffuse component, although dominating the background intensity at energies not greater than 0.3 keV, contributes only a small fraction of the M band background intensity. The diffuse component may represent an important constituent of the interstellar or intergalactic medium.

Dynamics of controllably induced bruises assessed by diffuse reflectance spectroscopy and pulsed photothermal radiometry

NASA Astrophysics Data System (ADS)

Marin, Ana; Milanič, Matija; Verdel, Nina; Vidovič, Luka; Majaron, Boris

2018-02-01

Combination of diffuse reflectance spectroscopy (DRS) and pulsed photothermal radiometry (PPTR) was recently successfully used to study evolution of accidental traumatic bruises. Yet, accidental bruises introduce many unknowns into the evolution analysis and thus a more controllable and repeatable approach for bruising is desired. In this study, evolution of bruises induced by aluminum projectiles of known mass and velocity were studied by DRS and PPTR. Bruises were induced on volar forearm skin of two healthy volunteers. Inverse Monte Carlo including four-layer skin model, was used to analyze the DRS and PPTR data to determine skin chromophores, their concentrations and depths. For bruise analysis, a bruise model was constructed and evolved according to hemoglobin diffusion kinetics. Bruise analysis of PPTR signals yielded bruise evolution parameters, most importantly hemoglobin diffusion constant, hemoglobin decomposition time and blood pool depth. The study results show that chronological tracking of hemoglobin decomposition can be assessed by the combined DRS and PPTR technique on induced bruise. Parameters of individual bruises were compared and two trends in chronological behavior of hemoglobin decomposition time discerned. Changes in bruise diffuse reflectance spectra were noted. Induced bruise parameters, however, still showed some scatter and thus further research is needed to reduce bruise variability.

How I Attend--Not How Well Do I Attend: Rethinking Developmental Frameworks of Attention and Cognition in Autism Spectrum Disorder and Typical Development

ERIC Educational Resources Information Center

Burack, Jacob A.; Russo, Natalie; Kovshoff, Hannah; Palma Fernandes, Tania; Ringo, Jason; Landry, Oriane; Iarocci, Grace

2016-01-01

Evidence from the study of attention among persons with autism spectrum disorder (ASD) and typically developing (TD) children suggests a rethinking of the notion that performance inherently reflects disability, ability, or capacity in favor of a more nuanced story that involves an emphasis on styles and biases that reflect real-world attending. We…

Diffuse gamma radiation

NASA Technical Reports Server (NTRS)

Fichtel, C. E.; Simpson, G. A.; Thompson, D. J.

1977-01-01

An examination of the intensity, energy spectrum, and spatial distribution of the diffuse gamma-radiation observed by SAS-2 satellite away from the galactic plane in the energy range above 35 MeV has shown that it consists of two components. One component is generally correlated with galactic latitudes, the atomic hydrogen column density was deduced from 21 cm measurements, and the continuum radio emission, believed to be synchrotron emission. It has an energy spectrum similar to that in the plane and joins smoothly to the intense radiation from the plane. It is therefore presumed to be of galactic origin. The other component is apparently isotropic, at least on a coarse scale, and has a steep energy spectrum. No evidence is found for a cosmic ray halo surrounding the galaxy in the shape of a sphere or oblate spheroid with galactic dimensions. Constraints for a halo model with significantly larger dimensions are set on the basis of an upper limit to the gamma-ray anisotropy.

Spectrum of the Nuclear Environment for GaAs Spin Qubits.

PubMed

Malinowski, Filip K; Martins, Frederico; Cywiński, Łukasz; Rudner, Mark S; Nissen, Peter D; Fallahi, Saeed; Gardner, Geoffrey C; Manfra, Michael J; Marcus, Charles M; Kuemmeth, Ferdinand

2017-04-28

Using a singlet-triplet spin qubit as a sensitive spectrometer of the GaAs nuclear spin bath, we demonstrate that the spectrum of Overhauser noise agrees with a classical spin diffusion model over 6 orders of magnitude in frequency, from 1 mHz to 1 kHz, is flat below 10 mHz, and falls as 1/f^{2} for frequency f≳1  Hz. Increasing the applied magnetic field from 0.1 to 0.75 T suppresses electron-mediated spin diffusion, which decreases the spectral content in the 1/f^{2} region and lowers the saturation frequency, each by an order of magnitude, consistent with a numerical model. Spectral content at megahertz frequencies is accessed using dynamical decoupling, which shows a crossover from the few-pulse regime (≲16π pulses), where transverse Overhauser fluctuations dominate dephasing, to the many-pulse regime (≳32 π pulses), where longitudinal Overhauser fluctuations with a 1/f spectrum dominate.

Non-destructive Techniques for Classifying Aircraft Coating Degradation

DTIC Science & Technology

2015-03-26

model is bidirectional reflectance distribution func- tions ( BRDF ) which describes how much radiation is reflected for each solid angle and each...incident angle. An intermediate model between ideal reflectors and BRDF is to assume all reflectance is a combination of diffuse and specular reflectance...19 K-Fold Cross Validation

PRELIMINARY RESULTS OF BTDF CALIBRATION OF TRANSMISSIVE SOLAR DIFFUSERS FOR REMOTE SENSING.

PubMed

Georgiev, Georgi T; Butler, James J; Thome, Kurt; Cooksey, Catherine; Ding, Leibo

2016-01-01

Satellite instruments operating in the reflected solar wavelength region require accurate and precise determination of the optical properties of their diffusers used in pre-flight and post-flight calibrations. The majority of recent and current space instruments use reflective diffusers. As a result, numerous Bidirectional Reflectance Distribution Function (BRDF) calibration comparisons have been conducted between the National Institute of Standards and Technology (NIST) and other industry and university-based metrology laboratories. However, based on literature searches and communications with NIST and other laboratories, no Bidirectional Transmittance Distribution Function (BTDF) measurement comparisons have been conducted between National Measurement Laboratories (NMLs) and other metrology laboratories. On the other hand, there is a growing interest in the use of transmissive diffusers in the calibration of satellite, air-borne, and ground-based remote sensing instruments. Current remote sensing instruments employing transmissive diffusers include the Ozone Mapping and Profiler Suite instrument (OMPS) Limb instrument on the Suomi-National Polar-orbiting Partnership (S-NPP) platform,, the Geostationary Ocean Color Imager (GOCI) on the Korea Aerospace Research Institute's (KARI) Communication, Ocean, and Meteorological Satellite (COMS), the Ozone Monitoring Instrument (OMI) on NASA's Earth Observing System (EOS) Aura platform, the Tropospheric Emissions: Monitoring of Pollution (TEMPO) instrument and the Geostationary Environmental Monitoring Spectrometer (GEMS).. This ensemble of instruments requires validated BTDF measurements of their on-board transmissive diffusers from the ultraviolet through the near infrared. This paper presents the preliminary results of a BTDF comparison between the NASA Diffuser Calibration Laboratory (DCL) and NIST on quartz and thin Spectralon samples.

Preliminary Results of BTDF Calibration of Transmissive Solar Diffusers for Remote Sensing

NASA Technical Reports Server (NTRS)

Georgiev, Georgi T.; Butler, James J.; Thome, Kurt; Cooksey, Catherine; Ding, Leibo

2016-01-01

Satellite instruments operating in the reflected solar wavelength region require accurate and precise determination of the optical properties of their diffusers used in pre-flight and post-flight calibrations. The majority of recent and current space instruments use reflective diffusers. As a result, numerous Bidirectional Reflectance Distribution Function (BRDF) calibration comparisons have been conducted between the National Institute of Standards and Technology (NIST) and other industry and university-based metrology laboratories. However, based on literature searches and communications with NIST and other laboratories, no Bidirectional Transmittance Distribution Function (BTDF) measurement comparisons have been conducted between National Measurement Laboratories (NMLs) and other metrology laboratories. On the other hand, there is a growing interest in the use of transmissive diffusers in the calibration of satellite, air-borne, and ground-based remote sensing instruments. Current remote sensing instruments employing transmissive diffusers include the Ozone Mapping and Profiler Suite instrument (OMPS) Limb instrument on the Suomi-National Polar-orbiting Partnership (S-NPP) platform,, the Geostationary Ocean Color Imager (GOCI) on the Korea Aerospace Research Institute's (KARI) Communication, Ocean, and Meteorological Satellite (COMS), the Ozone Monitoring Instrument (OMI) on NASA's Earth Observing System (EOS) Aura platform, the Tropospheric Emissions: Monitoring of Pollution (TEMPO) instrument and the Geostationary Environmental Monitoring Spectrometer (GEMS).. This ensemble of instruments requires validated BTDF measurements of their on-board transmissive diffusers from the ultraviolet through the near infrared. This paper presents the preliminary results of a BTDF comparison between the NASA Diffuser Calibration Laboratory (DCL) and NIST on quartz and thin Spectralon samples.

PRELIMINARY RESULTS OF BTDF CALIBRATION OF TRANSMISSIVE SOLAR DIFFUSERS FOR REMOTE SENSING

PubMed Central

Georgiev, Georgi T.; Butler, James J.; Thome, Kurt; Cooksey, Catherine; Ding, Leibo

2016-01-01

Satellite instruments operating in the reflected solar wavelength region require accurate and precise determination of the optical properties of their diffusers used in pre-flight and post-flight calibrations. The majority of recent and current space instruments use reflective diffusers. As a result, numerous Bidirectional Reflectance Distribution Function (BRDF) calibration comparisons have been conducted between the National Institute of Standards and Technology (NIST) and other industry and university-based metrology laboratories. However, based on literature searches and communications with NIST and other laboratories, no Bidirectional Transmittance Distribution Function (BTDF) measurement comparisons have been conducted between National Measurement Laboratories (NMLs) and other metrology laboratories. On the other hand, there is a growing interest in the use of transmissive diffusers in the calibration of satellite, air-borne, and ground-based remote sensing instruments. Current remote sensing instruments employing transmissive diffusers include the Ozone Mapping and Profiler Suite instrument (OMPS) Limb instrument on the Suomi-National Polar-orbiting Partnership (S-NPP) platform,, the Geostationary Ocean Color Imager (GOCI) on the Korea Aerospace Research Institute’s (KARI) Communication, Ocean, and Meteorological Satellite (COMS), the Ozone Monitoring Instrument (OMI) on NASA’s Earth Observing System (EOS) Aura platform, the Tropospheric Emissions: Monitoring of Pollution (TEMPO) instrument and the Geostationary Environmental Monitoring Spectrometer (GEMS).. This ensemble of instruments requires validated BTDF measurements of their on-board transmissive diffusers from the ultraviolet through the near infrared. This paper presents the preliminary results of a BTDF comparison between the NASA Diffuser Calibration Laboratory (DCL) and NIST on quartz and thin Spectralon samples. PMID:28003712

Comparison of holographic lens and filter systems for lateral spectrum splitting

NASA Astrophysics Data System (ADS)

Vorndran, Shelby; Chrysler, Benjamin; Kostuk, Raymond K.

2016-09-01

Spectrum splitting is an approach to increasing the conversion efficiency of a photovoltaic (PV) system. Several methods can be used to perform this function which requires efficient spatial separation of different spectral bands of the incident solar radiation. In this paper several of holographic methods for implementing spectrum splitting are reviewed along with the benefits and disadvantages associated with each approach. The review indicates that a volume holographic lens has many advantages for spectrum splitting in terms of both power conversion efficiency and energy yield. A specific design for a volume holographic spectrum splitting lens is discussed for use with high bandgap InGaP and low bandgap silicon PV cells. The holographic lenses are modeled using rigorous coupled wave analysis, and the optical efficiency is evaluated using non-sequential raytracing. A proof-of-concept off-axis holographic lens is also recorded in dichromated gelatin film and the spectral diffraction efficiency of the hologram is measured with multiple laser sources across the diffracted spectral band. The experimental volume holographic lens (VHL) characteristics are compared to an ideal spectrum splitting filter in terms of power conversion efficiency and energy yield in environments with high direct normal incidence (DNI) illumination and high levels of diffuse illumination. The results show that the experimental VHL can achieve 62.5% of the ideal filter power conversion efficiency, 64.8% of the ideal filter DNI environment energy yield, and 57.7% of the ideal diffuse environment energy yield performance.

[Baseline correction of spectrum for the inversion of chlorophyll-a concentration in the turbidity water].

PubMed

Wei, Yu-Chun; Wang, Guo-Xiang; Cheng, Chun-Mei; Zhang, Jing; Sun, Xiao-Peng

2012-09-01

Suspended particle material is the main factor affecting remote sensing inversion of chlorophyll-a concentration (Chla) in turbidity water. According to the optical property of suspended material in water, the present paper proposed a linear baseline correction method to weaken the suspended particle contribution in the spectrum above turbidity water surface. The linear baseline was defined as the connecting line of reflectance from 450 to 750 nm, and baseline correction is that spectrum reflectance subtracts the baseline. Analysis result of field data in situ of Meiliangwan, Taihu Lake in April, 2011 and March, 2010 shows that spectrum linear baseline correction can improve the inversion precision of Chl a and produce the better model diagnoses. As the data in March, 2010, RMSE of band ratio model built by original spectrum is 4.11 mg x m(-3), and that built by spectrum baseline correction is 3.58 mg x m(-3). Meanwhile, residual distribution and homoscedasticity in the model built by baseline correction spectrum is improved obviously. The model RMSE of April, 2011 shows the similar result. The authors suggest that using linear baseline correction as the spectrum processing method to improve Chla inversion accuracy in turbidity water without algae bloom.

Highly reflective Ag-Cu alloy-based ohmic contact on p-type GaN using Ru overlayer.

PubMed

Son, Jun Ho; Jung, Gwan Ho; Lee, Jong-Lam

2008-12-15

We report on a metallization scheme of high reflectance, low resistance, and smooth surface morphology ohmic contact on p-type GaN. Ag-Cu alloy/Ru contact showed low contact resistivity as low as 6.2 x 10(-6) Ohms cm(2) and high reflectance of 91% at 460 nm after annealing at 400 degrees C in air ambient. The oxidation annealing promoted the out-diffusion of Ga atoms to dissolve in an Ag-Cu layer with the formation of an Ag-Ga solid solution, lowering the contact resistivity. The Ru overlayer acts as a diffusion barrier for excessive oxygen incorporation during oxidation annealing, resulting in high reflectance, good thermal stability, and smooth surface quality of the contact.

On the Symmetry of Molecular Flows Through the Pipe of an Arbitrary Shape (I) Diffusive Reflection

NASA Astrophysics Data System (ADS)

Kusumoto, Yoshiro

Molecular gas flows through the pipe of an arbitrary shape is mathematically considered based on a diffusive reflection model. To avoid a perpetual motion, the magnitude of the molecular flow rate must remain invariant under the exchange of inlet and outlet pressures. For this flow symmetry, the cosine law reflection at the pipe wall was found to be sufficient and necessary, on the assumption that the molecular flux is conserved in a collision with the wall. It was also shown that a spontaneous flow occurs in a hemispherical apparatus, if the reflection obeys the n-th power of cosine law with n other than unity. This apparatus could work as a molecular pump with no moving parts.

Autism spectrum disorder: does neuroimaging support the DSM-5 proposal for a symptom dyad? A systematic review of functional magnetic resonance imaging and diffusion tensor imaging studies.

PubMed

Pina-Camacho, Laura; Villero, Sonia; Fraguas, David; Boada, Leticia; Janssen, Joost; Navas-Sánchez, Francisco J; Mayoral, Maria; Llorente, Cloe; Arango, Celso; Parellada, Mara

2012-07-01

A systematic review of 208 studies comprising functional magnetic resonance imaging and diffusion tensor imaging data in patients with 'autism spectrum disorder' (ASD) was conducted, in order to determine whether these data support the forthcoming DSM-5 proposal of a social communication and behavioral symptom dyad. Studies consistently reported abnormal function and structure of fronto-temporal and limbic networks with social and pragmatic language deficits, of temporo-parieto-occipital networks with syntactic-semantic language deficits, and of fronto-striato-cerebellar networks with repetitive behaviors and restricted interests in ASD patients. Therefore, this review partially supports the DSM-5 proposal for the ASD dyad.

Discrete ordinates solutions of nongray radiative transfer with diffusely reflecting walls

NASA Technical Reports Server (NTRS)

Menart, J. A.; Lee, Haeok S.; Kim, Tae-Kuk

1993-01-01

Nongray gas radiation in a plane parallel slab bounded by gray, diffusely reflecting walls is studied using the discrete ordinates method. The spectral equation of transfer is averaged over a narrow wavenumber interval preserving the spectral correlation effect. The governing equations are derived by considering the history of multiple reflections between two reflecting wails. A closure approximation is applied so that only a finite number of reflections have to be explicitly included. The closure solutions express the physics of the problem to a very high degree and show relatively little error. Numerical solutions are obtained by applying a statistical narrow-band model for gas properties and a discrete ordinates code. The net radiative wail heat fluxes and the radiative source distributions are obtained for different temperature profiles. A zeroth-degree formulation, where no wall reflection is handled explicitly, is sufficient to predict the radiative transfer accurately for most cases considered, when compared with increasingly accurate solutions based on explicitly tracing a larger number of wail reflections without any closure approximation applied.

Simultaneous measurements of radar reflectivity and refractive index spectra in clear air convection.

NASA Technical Reports Server (NTRS)

Konrad, T. G.; Robison, F. L.

1972-01-01

Simultaneous measurements of radar reflectivity and radio refractive index at several altitudes in clear air convection have been made. The experimental data were compared with the theoretical relationship which relates the reflectivity to the refractivity spectrum. The agreement between the measurements and the theory is excellent and shows that the radar returns in clear air are the result of, and can be quantitatively described as being from, fine-scale refractivity fluctuations due to turbulent mixing. Further, the data give strong support to the -5/3 spectral decay of the refractivity spectrum in the inertial subrange.

Spectrophotometry of Pluto-Charon mutual events - Individual spectra of Pluto and Charon

NASA Technical Reports Server (NTRS)

Sawyer, S. R.; Barker, E. S.; Cochran, A. L.; Cochran, W. D.

1987-01-01

Time-resolved spectra of the March 3 and April 4, 1987 mutual events of Pluto and Charon, obtained with spectral coverage from 5500 to 10,000 A with 25-A spectral resolution, are discussed. Charon has a featureless reflectance spectrum, with no evidence of methane absorption. Charon's reflectance appears neutral in color and corresponds to a geometric albedo of about 0.37 at 6000 A. The Pluto reflectance spectrum displays methane absorption bands at 7300, 7900, 8400, 8600, and 8900 A and is red in color, with a geometric albedo of about 0.56 at 6000 A.

Film sensor based on cascaded tilted long-period and tilted fiber Bragg grating

NASA Astrophysics Data System (ADS)

Sang, Jiangang; Gu, Zhengtian; Ling, Qiang; Feng, Wenbin

2018-06-01

A film sensor based on a tilted long-period fiber grating (TLPFG) inserted before a tilted fiber Bragg grating (TFBG) is proposed. The sensor is described theoretically using the transfer matrix method. This structure has two reflected peaks in the reflection spectrum. One peak is for the selected recoupled cladding mode of azimuthal order l = 2 and the other one is for the coupled core mode. The tilt angles of the TLPFG and TFBG and the mode order of the l = 2 cladding mode mainly determine the reflected power of the recoupled-(l = 2) cladding-mode peak in the reflection spectrum. By analyzing the relation between the film parameters (film refractive index and film thickness) and reflection spectrum, the characteristics of the film sensor are studied. The results show that this film sensor has a high sensitivity to the film parameters and increases the sensitivity of the film refractive index by two orders of magnitude in comparison with the normal cascaded long-period fiber grating (LPFG) and the fiber Bragg grating (FBG). The resolutions of the refractive index and the thickness of the sensing film are predicted to be 10‑6 and 10‑3 nm.

Comparison of reflectance spectra of sound and carious enamel

NASA Astrophysics Data System (ADS)

Analoui, Mostafa; Ando, Masatoshi; Stookey, George K.

2000-03-01

Development of dental caries is associated with the loss of minerals and change in the enamel structure. In this study, we have measured and compared reflectance spectra of sound and carious enamel, to investigate its utility in detection and analysis of dental caries. One hundred twenty, 3-mm diameter human enamel cores, with no sign of fluorosis, tetracycline stain, hypoplasia, fracture and restorations, were prepared. The enamel surfaces then were ground and polished. Specimens were placed on a fitted holder with either black or white color for background, with no fluorescence. The baseline spectra were measured using a spectrophotometer with enclosed diffused illumination. Spectra measured from 380 to 780 nm at 5 nm intervals. All measurements were corrected to compensate for the spectrum of illumination. The specimens were divided into two groups and exposed to a demineralizing solution, for 48 and 96 hours, respectively. Reflectance spectra of specimens were measured following lesion induction. All specimens were sectioned and analyzed by transverse microradiography (TMR), where lesion depth and mineral loss ((Delta) Z) were measured. Dimensionality of multi-spectral data was reduced through its conversion to L*a*b* color coordinates and principal component analysis (PCA). Multiple linear regression analysis showed low correlation between L*a*b* and lesion depth and mineral loss. PCA analysis showed higher correlation coefficient, compared to L*a*b*. Preliminary results of this study suggest that multi-spectral measurement and analysis of the tooth surface could be useful in predicting the depth and severity of an early carious lesion.

Temperature dependence of Fe/++/ crystal field spectra - Implications to mineralogical mapping of planetary surfaces

NASA Technical Reports Server (NTRS)

Sung, C.-M.; Singer, R. B.; Parkin, K. M.; Burns, R. G.; Osborne, M.

1977-01-01

Results are reported of Fe(++) crystal field spectral measurements for olivines and pyroxenes up to 400 C. The results are correlated with crystal structure data at elevated temperatures, and the validity of remote-sensed identifications of minerals on hot surfaces of the moon and Mercury is assessed. Two techniques were used to obtain spectra of minerals at elevated temperatures using a spectrophotometer. One employed a diamond cell assembly or a specially designed sample holder to measure polarized absorption spectra of heated single crystals. For the other technique, a sample holder was designed to attach to a diffuse reflectance accessory to produce reflectance spectra of heated powdered samples. Polarized absorption spectra of forsterite at 20-400 C are shown in a graph. Other graphs show the temperature dependence of Fe(++) crystal field bands in olivines, the diffuse reflectance spectra of olivine at 40-400 C, the polarization absorption spectra of orthopyroxene at 30-400 C, the diffuse reflectance spectra of pigeonite at 40-400 C, and unpolarized absorption spectra of lunar pyroxene from Apollo 15 rock 15058.

Diffuse reflectance spectroscopy for monitoring diabetic foot ulcer - A pilot study

NASA Astrophysics Data System (ADS)

Anand, Suresh; Sujatha, N.; Narayanamurthy, V. B.; Seshadri, V.; Poddar, Richa

2014-02-01

Foot ulceration due to diabetes mellitus is a major problem affecting 12-25% of diabetic subjects in their lifetime. An untreated ulcer further gets infected which causes necrosis leading to amputation of lower extremities. Early identification of risk factors and treatment for these chronic wounds would reduce health care costs and improve the quality of life for people with diabetes. Recent clinical investigations have shown that a series of factors including reduced oxygen delivery and disturbed metabolism have been observed on patients with foot ulceration due to diabetes. Also, these factors can impair the wound healing process. Optical techniques based on diffuse reflectance spectroscopy provide characteristic spectral finger prints shed light on tissue oxygenation levels and morphological composition of a tissue. This study deals with the application of diffuse reflectance intensity ratios based on oxyhemoglobin bands (R542/R580), ratios of oxy- and deoxy-hemoglobin bands (R580/R555), total hemoglobin concentration and hemoglobin oxygen saturation between normal and diabetic foot ulcer sites. Preliminary results obtained are found to be promising indicating the application of reflectance spectroscopy in the assessment of foot ulcer healing.

High reflected cubic cavity as long path absorption cell for infrared gas sensing

NASA Astrophysics Data System (ADS)

Yu, Jia; Gao, Qiang; Zhang, Zhiguo

2014-10-01

One direct and efficient method to improve the sensitivity of infrared gas sensors is to increase the optical path length of gas cells according to Beer-Lambert Law. In this paper, cubic shaped cavities with high reflected inner coating as novel long path absorption cells for infrared gas sensing were developed. The effective optical path length (EOPL) for a single cubic cavity and tandem cubic cavities were investigated based on Tunable Diode Laser Absorption Spectroscopy (TDLAS) measuring oxygen P11 line at 763 nm. The law of EOPL of a diffuse cubic cavity in relation with the reflectivity of the coating, the port fraction and side length of the cavity was obtained. Experimental results manifested an increase of EOPL for tandem diffuse cubic cavities as the decrease of port fraction of the connecting aperture f', and the EOPL equaled to the sum of that of two single cubic cavities at f'<0.01. The EOPL spectra at infrared wavelength range for different inner coatings including high diffuse coatings and high reflected metallic thin film coatings were deduced.

Communication: Probing anomalous diffusion in frequency space

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stachura, Sławomir; Synchrotron Soleil, L’Orme de Merisiers, 91192 Gif-sur-Yvette; Kneller, Gerald R., E-mail: gerald.kneller@cnrs-orleans.fr

Anomalous diffusion processes are usually detected by analyzing the time-dependent mean square displacement of the diffusing particles. The latter evolves asymptotically as W(t) ∼ 2D{sub α}t{sup α}, where D{sub α} is the fractional diffusion constant and 0 < α < 2. In this article we show that both D{sub α} and α can also be extracted from the low-frequency Fourier spectrum of the corresponding velocity autocorrelation function. This offers a simple method for the interpretation of quasielastic neutron scattering spectra from complex (bio)molecular systems, in which subdiffusive transport is frequently encountered. The approach is illustrated and validated by analyzing molecularmore » dynamics simulations of molecular diffusion in a lipid POPC bilayer.« less

Diffuse Gamma Rays Galactic and Extragalactic Diffuse Emission

NASA Technical Reports Server (NTRS)

Moskalenko, Igor V.; Strong, Andrew W.; Reimer, Olaf

2004-01-01

Diffuse gamma rays consist of several components: truly diffuse emission from the interstellar medium, the extragalactic background, whose origin is not firmly established yet, and the contribution from unresolved and faint Galactic point sources. One approach to unravel these components is to study the diffuse emission from the interstellar medium, which traces the interactions of high energy particles with interstellar gas and radiation fields. Because of its origin such emission is potentially able to reveal much about the sources and propagation of cosmic rays. The extragalactic background, if reliably determined, can be used in cosmological and blazar studies. Studying the derived average spectrum of faint Galactic sources may be able to give a clue to the nature of the emitting objects.

Beer-Lambert-Law Parametric Model of Reflectance Spectra for Dyed Fabrics

DTIC Science & Technology

2016-06-06

optical constants), phenomenological quantities and combinations of both [27,28,29]. For reflection from a dyed fabric of finite and nonuniform ...fabrics are characterized, inherently, by rough surfaces (thus diffuse reflectance), heterogeneous compositions, and nonuniform thicknesses. It follows

Optical materials and films applied in industrial lasers

NASA Astrophysics Data System (ADS)

Zhang, Peng; Liu, Shengyong

1999-09-01

Optical materials and films are often used in industrial lasers. Most of industrial lasers work at visible spectrum and near-infrared spectrum. Only CO2 laser works at far- infrared region (10.6 micrometers ). The optical materials and films are categorized in this article, and the properties of the materials and films are related. From visible to infrared spectrum, many optical materials can be used: K9 glass, fused silica, germanium, gallium arsenide, zinc selenide, silicon, copper, and so on. Optical films for lasers include reflection coating, antireflection coating, edge filter, VRM (variable reflectance mirror) coating and polarizer. The characteristic and application of them will be introduced.

Copper Gas Diffusers For Purging Line-Focus Laser Welds

NASA Technical Reports Server (NTRS)

Fonteyne, Steve L.; Hosking, Timothy J.; Shelley, D. Mark

1996-01-01

Modified flow diffusers built for inert-gas purging of welds made with 5-kW CO(2) lasers operating with line-focus optics in conduction mode instead of with point-focus optics in customary keyhole mode. Diffusers made of copper components brazed together, robust enough to withstand strong reflections of line-focused laser energy.

Cross-frequency and band-averaged response variance prediction in the hybrid deterministic-statistical energy analysis method

NASA Astrophysics Data System (ADS)

Reynders, Edwin P. B.; Langley, Robin S.

2018-08-01

The hybrid deterministic-statistical energy analysis method has proven to be a versatile framework for modeling built-up vibro-acoustic systems. The stiff system components are modeled deterministically, e.g., using the finite element method, while the wave fields in the flexible components are modeled as diffuse. In the present paper, the hybrid method is extended such that not only the ensemble mean and variance of the harmonic system response can be computed, but also of the band-averaged system response. This variance represents the uncertainty that is due to the assumption of a diffuse field in the flexible components of the hybrid system. The developments start with a cross-frequency generalization of the reciprocity relationship between the total energy in a diffuse field and the cross spectrum of the blocked reverberant loading at the boundaries of that field. By making extensive use of this generalization in a first-order perturbation analysis, explicit expressions are derived for the cross-frequency and band-averaged variance of the vibrational energies in the diffuse components and for the cross-frequency and band-averaged variance of the cross spectrum of the vibro-acoustic field response of the deterministic components. These expressions are extensively validated against detailed Monte Carlo analyses of coupled plate systems in which diffuse fields are simulated by randomly distributing small point masses across the flexible components, and good agreement is found.

Baseline Correction of Diffuse Reflection Near-Infrared Spectra Using Searching Region Standard Normal Variate (SRSNV).

PubMed

Genkawa, Takuma; Shinzawa, Hideyuki; Kato, Hideaki; Ishikawa, Daitaro; Murayama, Kodai; Komiyama, Makoto; Ozaki, Yukihiro

2015-12-01

An alternative baseline correction method for diffuse reflection near-infrared (NIR) spectra, searching region standard normal variate (SRSNV), was proposed. Standard normal variate (SNV) is an effective pretreatment method for baseline correction of diffuse reflection NIR spectra of powder and granular samples; however, its baseline correction performance depends on the NIR region used for SNV calculation. To search for an optimal NIR region for baseline correction using SNV, SRSNV employs moving window partial least squares regression (MWPLSR), and an optimal NIR region is identified based on the root mean square error (RMSE) of cross-validation of the partial least squares regression (PLSR) models with the first latent variable (LV). The performance of SRSNV was evaluated using diffuse reflection NIR spectra of mixture samples consisting of wheat flour and granular glucose (0-100% glucose at 5% intervals). From the obtained NIR spectra of the mixture in the 10 000-4000 cm(-1) region at 4 cm intervals (1501 spectral channels), a series of spectral windows consisting of 80 spectral channels was constructed, and then SNV spectra were calculated for each spectral window. Using these SNV spectra, a series of PLSR models with the first LV for glucose concentration was built. A plot of RMSE versus the spectral window position obtained using the PLSR models revealed that the 8680–8364 cm(-1) region was optimal for baseline correction using SNV. In the SNV spectra calculated using the 8680–8364 cm(-1) region (SRSNV spectra), a remarkable relative intensity change between a band due to wheat flour at 8500 cm(-1) and that due to glucose at 8364 cm(-1) was observed owing to successful baseline correction using SNV. A PLSR model with the first LV based on the SRSNV spectra yielded a determination coefficient (R2) of 0.999 and an RMSE of 0.70%, while a PLSR model with three LVs based on SNV spectra calculated in the full spectral region gave an R2 of 0.995 and an RMSE of 2.29%. Additional evaluation of SRSNV was carried out using diffuse reflection NIR spectra of marzipan and corn samples, and PLSR models based on SRSNV spectra showed good prediction results. These evaluation results indicate that SRSNV is effective in baseline correction of diffuse reflection NIR spectra and provides regression models with good prediction accuracy.

Polymer-cholesteric liquid-crystalline composites with a broad light reflection band

NASA Astrophysics Data System (ADS)

Mitov, Michel

2016-05-01

Cholesteric liquid crystals selectively reflect the light. The reflection bandgap is typically limited to 100 nm in the visible spectrum and, at the best, 50% of the unpolarized incident light is reflected. Solutions are found in biopolymers and polymer-liquid crystal composite materials to go beyond these limits.

A laboratory study of magnesium-tetrabenz-porphyrin - Lack of agreement with diffuse interstellar bands

NASA Technical Reports Server (NTRS)

Donn, B.; Khanna, R. K.

1980-01-01

The visible and infrared spectra and thermal behavior of the bis-pyridal-magnesium-tetrabenz-porphyrin molecule proposed as the carrier of the diffuse interstellar bands were measured. Of the six band coincidences reported by Johnson (1977), only one, 4430 A, occurs in these experiments. This coincidence requires a special environment, not likely to occur in interstellar space but the infrared spectrum does not support Johnson's vibrational scheme. These spectroscopic and thermal measurements contradict the hypothesis that this molecule causes the diffuse bands.

Volume holographic lens spectrum-splitting photovoltaic system for high energy yield with direct and diffuse solar illumination

NASA Astrophysics Data System (ADS)

Chrysler, Benjamin D.; Wu, Yuechen; Yu, Zhengshan; Kostuk, Raymond K.

2017-08-01

In this paper a prototype spectrum-splitting photovoltaic system based on volume holographic lenses (VHL) is designed, fabricated and tested. In spectrum-splitting systems, incident sunlight is divided in spectral bands for optimal conversion by a set of single-junction PV cells that are laterally separated. The VHL spectrumsplitting system in this paper has a form factor similar to conventional silicon PV modules but with higher efficiencies (>30%). Unlike many other spectrum-splitting systems that have been proposed in the past, the system in this work converts both direct and diffuse sunlight while using inexpensive 1-axis tracking systems. The VHL system uses holographic lenses that focus light at a transition wavelength to the boundary between two PV cells. Longer wavelength light is dispersed to the narrow bandgap cell and shorter wavelength light to the wide bandgap cell. A prototype system is designed with silicon and GaAs PV cells. The holographic lenses are fabricated in Covestro Bayfol HX photopolymer by `stitching' together lens segments through sequential masked exposures. The PV cells and holographic lenses were characterized and the data was used in a raytrace simulation and predicts an improvement in total power output of 15.2% compared to a non-spectrum-splitting reference. A laboratory measurement yielded an improvement in power output of 8.5%.

Bidirectional reflectance measurement of zinc oxide in 0.25 to 2.5 microns spectrum

NASA Technical Reports Server (NTRS)

Scott, R. L., Jr.

1974-01-01

An experimental apparatus was designed and used to measure the bidirectional reflectance of zinc oxide in the spectrum 0.25 to 2.5 microns. The nonspecular reflectance is essentially Lambert for wavelengths above 0.40 microns with the most deviation occuring for large source zenith angles. Below 0.400 microns the nonspecular reflectance is greater than Lambert in all directions and is greatest in the forward and backscatter directions. The ratio of the specular component to the nonspecular component at a zenith of 0 degrees was found to increase with source zenith and wavelength for wavelengths above 0.400 microns. Below 0.400 microns this ratio increases as wavelengths decrease. The variation of bidirectional reflectance with wavelength was found to have the characteristics absorption for Zn0 for wavelength below 0.400 microns.