Clinical system model for monitoring the physiological status of jaundice by extracting bilirubin components from skin diffuse reflectance spectra

NASA Astrophysics Data System (ADS)

Kumar, Alla S.; Clark, Joseph; Beyette, Fred R., Jr.

2009-02-01

Neonatal jaundice is a medical condition which occurs in newborns as a result of an imbalance between the production and elimination of bilirubin. The excess bilirubin in the blood stream diffuses into the surrounding tissue leading to a yellowing of the skin. As the bilirubin levels rise in the blood stream, there is a continuous exchange between the extra vascular bilirubin and bilirubin in the blood stream. Exposure to phototherapy alters the concentration of bilirubin in the vascular and extra vascular regions by causing bilirubin in the skin layers to be broken down. Thus, the relative concentration of extra vascular bilirubin is reduced leading to a diffusion of bilirubin out of the vascular region. Diffuse reflectance spectra from human skin contains physiological and structural information of the skin and nearby tissue. A diffuse reflectance spectrum must be captured before and after blanching in order to isolate the intravascular and extra vascular bilirubin. A new mathematical model is proposed with extra vascular bilirubin concentration taken into consideration along with other optical parameters in defining the diffuse reflectance spectrum from human skin. A nonlinear optimization algorithm has been adopted to extract the optical properties (including bilirubin concentration) from the skin reflectance spectrum. The new system model and nonlinear algorithm have been combined to enable extraction of Bilirubin concentrations within an average error of 10%.

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

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

Diagnostics of breast cancer by analysis of spectra diffuse reflections

NASA Astrophysics Data System (ADS)

Kuzmina, Natalya V.; Plaksin, Fedor G.; Polovnikov, Eugeny S.

2001-05-01

The work is dedicated to problems of diagnostic oncologic diseases by a spectroscopic-optical method and is prolongation of long-term examinations held earlier by Vovk S.M, Naumov S.A. and Pushkarev S.V. The actual spectra of a diffuse reflection removed in vivo and in vitro are given, is angry- and good-quality neoplasms, healthy tissue and blood of breast and other organs. Problems of a clinical oncology are in a center of attention in medicine because the cases of disease malignant swellings increase, which is stipulated by an irregularity of present methods of diagnostic.

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

Diagnostic power of diffuse reflectance spectroscopy for targeted detection of breast lesions with microcalcifications

PubMed Central

Soares, Jaqueline S.; Barman, Ishan; Dingari, Narahara Chari; Volynskaya, Zoya; Liu, Wendy; Klein, Nina; Plecha, Donna; Dasari, Ramachandra R.; Fitzmaurice, Maryann

2013-01-01

Microcalcifications geographically target the location of abnormalities within the breast and are of critical importance in breast cancer diagnosis. However, despite stereotactic guidance, core needle biopsy fails to retrieve microcalcifications in up to 15% of patients. Here, we introduce an approach based on diffuse reflectance spectroscopy for detection of microcalcifications that focuses on variations in optical absorption stemming from the calcified clusters and the associated cross-linking molecules. In this study, diffuse reflectance spectra are acquired ex vivo from 203 sites in fresh biopsy tissue cores from 23 patients undergoing stereotactic breast needle biopsies. By correlating the spectra with the corresponding radiographic and histologic assessment, we have developed a support vector machine-derived decision algorithm, which shows high diagnostic power (positive predictive value and negative predictive value of 97% and 88%, respectively) for diagnosis of lesions with microcalcifications. We further show that these results are robust and not due to any spurious correlations. We attribute our findings to the presence of proteins (such as elastin), and desmosine and isodesmosine cross-linkers in the microcalcifications. It is important to note that the performance of the diffuse reflectance decision algorithm is comparable to one derived from the corresponding Raman spectra, and the considerably higher intensity of the reflectance signal enables the detection of the targeted lesions in a fraction of the spectral acquisition time. Our findings create a unique landscape for spectroscopic validation of breast core needle biopsy for detection of microcalcifications that can substantially improve the likelihood of an adequate, diagnostic biopsy in the first attempt. PMID:23267090

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...

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.

Pectin functionalised by fatty acids: Diffuse reflectance infrared Fourier transform (DRIFT) spectroscopic characterisation

NASA Astrophysics Data System (ADS)

Kamnev, Alexander A.; Calce, Enrica; Tarantilis, Petros A.; Tugarova, Anna V.; De Luca, Stefania

2015-01-01

Chemically modified pectin derivatives obtained by partial esterification of its hydroxyl moieties with fatty acids (FA; oleic, linoleic and palmitic acids), as well as the initial apple peel pectin were comparatively characterised using diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. Characteristic changes observed in DRIFT spectra in going from pectin to its FA esters are related to the corresponding chemical modifications. Comparing the DRIFT spectra with some reported data on FTIR spectra of the same materials measured in KBr or NaCl matrices has revealed noticeable shifts of several polar functional groups both in pectin and in its FA-esterified products induced by the halide salts. The results obtained have implications for careful structural analyses of biopolymers with hydrophilic functional groups by means of different FTIR spectroscopic methodologies.

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.

Reflectance spectroscopy of pigmented cutaneous benign and malignant lesions

NASA Astrophysics Data System (ADS)

Borisova, E.; Jeliazkova, Al.; Pavlova, E.; Troyanova, P.; Kundurdjiev, T.; Pavlova, P.; Avramov, L.

2014-10-01

For the DRS measurements of skin benign, dysplastic and malignant lesions in vivo we applied halogen lamp (LS-1, OceanOptics Inc, Dunedin, Fl, USA) as a continuous light source in the region of 400-900 nm, optical probe (6+1 fibers) for the delivery of illumination and diffuse reflected light from the skin investigated and microspectrometer USB4000 (OceanOptics Inc., Dunedin, Fl, USA) for a storage and display of the spectra detected. As a diffuse reflectance standard Spectralon® plate was used to calibrate the spectrometer. The reflectance spectra obtained from normal skin in identical anatomic sites of different patients have similar spectral shape features, slightly differ by the reflectance intensity at different wavelengths, depending on the particular patient' skin phototype. One could find diagnostically important spectral features, related to specific intensity changes for a given wavelength due to specific pigments appearance, slope changes by value and sign for the reflectance spectra curves in a specific spectral range, disappearance or manifestation of minima, related to hemoglobin absorption at 410-420 nm, 543, 575 nm. Based on the observed peculiarities multispectral analysis of the reflectance spectra of the different lesions was used and diagnostically specific features are found. Discrimination using the DRS data obtained between benign compound and dermal nevi (45 cases), dysplastic nevi (17 cases) and pigmented malignant melanoma (41 cases) lesions is achieved with a diagnostic accuracy of 96 % for the benign nevi vs. MM, and 90 % for the dysplastic nevi vs. MM.

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.

Diffuse reflectance spectra measured in vivo in human tissues during Photofrin-mediated pleural photodynamic therapy: updated results

NASA Astrophysics Data System (ADS)

Finlay, Jarod C.; Zhu, Timothy C.; Dimofte, Andreea; Friedberg, Joseph S.; Cengel, Keith A.; Hahn, Stephen M.

2009-02-01

We present the results of a series of spectroscopic measurements made in vivo in patients undergoing photodynamic therapy (PDT). The patients studied here were enrolled in Phase II clinical trials of Photofrin-mediated PDT for the treatment of non-small cell lung cancer and cancers with pleural effusion. Patients were given Photofrin at dose of 2 mg per kg body weight 24 hours prior to treatment. Each patient received surgical debulking of the tumor followed by intracavity PDT at 630nm to a dose of 60 J/cm2. Dose was monitored continuously using implanted isotropic fiber-based light detectors. We measured the diffuse reflectance spectra before and after PDT in various positions within the cavity, including tumor, diaphragm, pericardium, skin, and chest wall muscle in 10 patients. The measurements were acquired using a specially designed fiber optic-based probe consisting of one fluorescence excitation fiber, one white light delivery fiber, and 9 detection fibers spaced at distances from 0.36 to 7.8 mm from the source, all of which are imaged via a spectrograph onto a CCD, allowing measurement of radially-resolved diffuse reflectance and fluorescence spectra. The absorption spectra were analyzed using an analytical model of light propagation in diffuse media based on the P3 approximation to radiative transport, assuming a known basis set of absorbers including hemoglobin in its oxygenated and deoxygenated forms and Photofrin. We find significant variation in hemodynamics and sensitizer concentration among patients and within tissues in a single patient.

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.

Electroporation-assisted discrimination of normal, benign and cancerous human gastric tissues by OCT and diffuse reflectance spectra images

NASA Astrophysics Data System (ADS)

Li, Caiyun; Wei, Huajiang; Zhao, Yanping; Wu, Guoyong; Gu, Huaimin; Guo, Zhouyi; Yang, Hongqin; He, Yonghong; Xie, Shusen

2018-07-01

The purpose of this study is to illustrate experimentally the optical coherence tomography (OCT) signal slope and diffuse reflectance (DR) spectra of 30% and 80% glycerol combined with electroporation (EP) diffusion in normal, benign and cancerous human gastric tissues in vitro. The results of OCT showed that the permeability coefficients of 80% and 30% glycerol (both with and without EP) have the following trend: human cancerous gastric tissue  >  human benign gastric tissue  >  human normal gastric tissue under the same conditions. The permeability coefficient of the 30% glycerol group is larger than that of the 80% glycerol group under the same circumstances; the permeability coefficient of glycerol combined with the EP group is larger than that without the EP group under the same conditions. The permeability coefficient and the reduction of the DR spectra have perfect linear correlation (R2  =  0.9745). The research results suggest that OCT and the DR spectra combined with an optical clearing agent (glycerol) and the EP method can potentially become a powerful tool for the early diagnosis and monitoring of human gastric cancer.

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.

Stone/tissue differentiation during intracorporeal lithotripsy using diffuse white light reflectance spectroscopy: In vitro and clinical measurements.

PubMed

Lange, Birgit; Jocham, Dieter; Brinkmann, Ralf; Cordes, Jens

2014-10-01

Holmium laser lithotripsy is the 'gold standard' for intracorporeal fragmentation of stones. However, there is a risk of damaging and perforating the ureter wall when the laser is accidentally fired while the fiber is in contact with tissue. The aim of this study was to evaluate if white illumination light, diffusely reflected back into the treatment fiber and spectrally analyzed, can be used for differentiating between stone and tissue. Firstly, in vitro reflectance spectra (Xenon light source, wavelength range λ = 350-850 nm) of 38 human kidney stones, porcine renal calix and ureter tissue were collected. Secondly, in an in vivo study with 8 patients, 72 ureter and 49 stone reflectance signals were recorded during endourological interventions. The spectra were analyzed to discriminate between stone and tissue by the absence or presence of minima due to hemoglobin absorption at λ1  = 542nm and λ3  = 576nm. In vitro, all stone and tissue signals could correctly be identified by calculating the ratio R = I (λ1  = 542 nm)/I (λ2  = 475 nm): Because of the hemoglobin absorption at λ1 , R is smaller for tissue than for calculi. In vivo, only 75% tissue spots could correctly be identified utilizing this method. Using the more sophisticated evaluation of looking for minima in the diffuse reflectance spectra at λ1  = 542 nm and λ3  = 576 nm, 62 out of 64 tissue spots were correctly identified (sensitivity 96.9%). This was also the case for 39 out of 43 stone spots. Taking into account the number of measured spectra, a tissue detection probability of 91% and a stone detection probability of 77% was achieved (significance level 5%). White light diffusely reflected off the treatment zone into the fiber can be used to strongly improve the safety of Holmium laser lithotripsy by implementing an automatic feedback control algorithm that averts mispositioning the fiber. © 2014 Wiley Periodicals, Inc.

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

Effect of aluminum substitution on the reflectance spectra of hematite

NASA Technical Reports Server (NTRS)

Morris, R. V.; Lauer, H. V., Jr.; Mendell, W. W.

1982-01-01

Hematite and aluminous hematite were synthesized and the diffuse reflectance spectra were recorded for the region between 0.35 and 1.20 microns. Results show that the near-IR based minimum for the aluminous hematite is shifted longward by about 0.02 microns and is much more shallow. Also, the aluminous specimen is considerably more reflective shortward of approximately 0.55 microns where the ferritic specimen is strongly absorbing. This is noteworthy since the visible slope and the red shoulder are often used in the construction of false color and band ratio images.

Diffuse reflectance spectroscopy of liver tissue

NASA Astrophysics Data System (ADS)

Reistad, Nina; Nilsson, Jan; Vilhelmsson Timmermand, Oskar; Sturesson, Christian; Andersson-Engels, Stefan

2015-06-01

Diffuse reflectance spectroscopy (DRS) with a fiber-optic contact probe is a cost-effective, rapid, and non-invasive optical method used to extract diagnosis information of tissue. By combining commercially available VIS- and NIR-spectrometers with various fiber-optic contact-probes, we have access to the full wavelength range from around 400 to 1600 nm. Using this flexible and portable spectroscopy system, we have acquired ex-vivo DRS-spectra from murine, porcine, and human liver tissue. For extracting the tissue optical properties from the measured spectra, we have employed and compared predictions from two models for light propagation in tissue, diffusion theory model (DT) and Monte Carlo simulations (MC). The focus in this work is on the capacity of this DRS-technique in discriminating metastatic tumor tissue from normal liver tissue as well as in assessing and characterizing damage to non-malignant liver tissue induced by preoperative chemotherapy for colorectal liver metastases.

Diffuse Reflectance Spectroscopy of Hidden Objects, Part I: Interpretation of the Reflection-Absorption-Scattering Fractions in Near-Infrared (NIR) Spectra of Polyethylene Films.

PubMed

Pomerantsev, Alexey L; Rodionova, Oxana Ye; Skvortsov, Alexej N

2017-08-01

Investigation of a sample covered by an interfering layer is required in many fields, e.g., for process control, biochemical analysis, and many other applications. This study is based on the analysis of spectra collected by near-infrared (NIR) diffuse reflectance spectroscopy. Each spectrum is a composition of a useful, target spectrum and a spectrum of an interfering layer. To recover the target spectrum, we suggest using a new phenomenological approach, which employs the multivariate curve resolution (MCR) method. In general terms, the problem is very complex. We start with a specific problem of analyzing a system, which consists of several layers of polyethylene (PE) film and underlayer samples with known spectral properties. To separate information originating from PE layers and the target, we modify the system versus both the number of the PE layers as well as the reflectance properties of the target sample. We consider that the interfering spectrum of the layer can be modeled using three components, which can be tentatively called transmission, absorption, and scattering contributions. The novelty of our approach is that we do not remove the reflectance and scattering effects from the spectra, but study them in detail aiming to use this information to recover the target spectrum.

Influence of site and soil properties on the DRIFT spectra of northern cold-region soils

USDA-ARS?s Scientific Manuscript database

We investigated the influence of site characteristics and soil properties on the chemical composition of organic matter in soils collected from a latitudinal transect across Alaska through analysis of diffuse reflectance infrared Fourier transform mid infrared (MidIR) spectra of bulk soils. The stud...

Influence of low power CW laser irradiation on skin hemoglobin changes

NASA Astrophysics Data System (ADS)

Ferulova, Inesa; Lesins, Janis; Lihachev, Alexey; Jakovels, Dainis; Spigulis, Janis

2012-06-01

Influence of low power laser irradiance on healthy skin using diffuse reflectance spectroscopy and multispectral imaging was studied. Changes of diffuse reflectance spectra in spectral range from 500 to 600 nm were observed after 405 nm, 473 nm and 532 nm laser provocation, leading to conclusion that the content of skin hemoglobin has changed. Peaks in spectral absorbance (optical density) curves corresponded to well-known oxy-hemoglobin absorbance peaks at 542 and 577 nm.

Impact of one-layer assumption on diffuse reflectance spectroscopy of skin

NASA Astrophysics Data System (ADS)

Hennessy, Ricky; Markey, Mia K.; Tunnell, James W.

2015-02-01

Diffuse reflectance spectroscopy (DRS) can be used to noninvasively measure skin properties. To extract skin properties from DRS spectra, you need a model that relates the reflectance to the tissue properties. Most models are based on the assumption that skin is homogenous. In reality, skin is composed of multiple layers, and the homogeneity assumption can lead to errors. In this study, we analyze the errors caused by the homogeneity assumption. This is accomplished by creating realistic skin spectra using a computational model, then extracting properties from those spectra using a one-layer model. The extracted parameters are then compared to the parameters used to create the modeled spectra. We used a wavelength range of 400 to 750 nm and a source detector separation of 250 μm. Our results show that use of a one-layer skin model causes underestimation of hemoglobin concentration [Hb] and melanin concentration [mel]. Additionally, the magnitude of the error is dependent on epidermal thickness. The one-layer assumption also causes [Hb] and [mel] to be correlated. Oxygen saturation is overestimated when it is below 50% and underestimated when it is above 50%. We also found that the vessel radius factor used to account for pigment packaging is correlated with epidermal thickness.

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

The diffuse reflectance spectra of Hawaiian palagonite mixtures with an Fe-rich montmorillonite have prompted their present use as spectral analogs of the Martian surface. Like the Mars spectrum and unlike clays, the 2.2-micron reflectance spectrum absorption band is not present in the palagonite sample; neither is the 2.2-micron Al-OH clay lattice band seen in palagonite-montmorillonite mixtures, where the latter component remains below 15 wt pct. Fe-rich montmorillonite clay may therefore be present in Mars, in combination with palagonite, while remaining undetected in remotely sensed spectra.

In vivo optical characterization of pediatric epileptogenic lesions

NASA Astrophysics Data System (ADS)

Lin, W.-C.; Ragheb, J.; Bhatia, S.; Johnson, Mahlon D.; Sandberg, D.; Fernandez, A.; Morrison, G.; Duchowny, M.; Jayakar, P.

2007-02-01

Epileptogenic lesions and their margins are often difficult to define intraoperatively. We hypothesize that optical spectroscopy can detect unique pathophysiological features of epileptogenic lesions in children and hence differentiate them from normal brain. This hypothesis was tested by comparing the in vivo optical and fluorescence characteristics of epileptogenic brain lesions (non-neoplastic) with those of normal brain. Patients were recruited from those receiving epilepsy surgeries at Miami Children's Hospital. Using a portable spectroscopic system, optical characterization of brain was performed intraoperatively. Fluorescence spectra were measured at 337 nm excitation, and diffuse reflectance spectra were measured between 400 and 850 nm. To date, seven epilepsy patients have been enrolled in the study. A couple interesting trends have been observed in the recorded optical spectra. First, sites within the resection zone, as defined by the intracranial electroencephalogram data, often show higher diffuse reflectance signals than normal sites do. This is especially prominent around 500 nm and between 650 and 850 nm. Secondly, several investigated sites with abnormal electroencephalogram and/or pathology show a unique blue shift in their fluorescence spectra, which is not seen in other cases.

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.

On the possibility of spectroscopic cancer diagnostics

NASA Astrophysics Data System (ADS)

Khairullina, Alphiya Y.; Oleinik, Tatiana V.; Korolevich, Alexander N.; Sevkovsky, Yacob I.

1993-07-01

The diffuse reflection and transmission coefficients, other optical parameters of normal and cancer tissues have been investigated in visible and infrared spectra. The optimal spectral range for distinguishing the cancer is found. The spectral absorption coefficients and size of cells parameter determined using our approach are analyzed to be different for normal and pathological tissues. The method is proposed for calculating the diffuse reflectance and transmittance of multiple tissue layers. The investigations have shown that cancer may be distinguished under the layers of skin and normal tissue.

Influence of a fat layer on the near infrared spectra of human muscle: quantitative analysis based on two-layered Monte Carlo simulations and phantom experiments

NASA Technical Reports Server (NTRS)

Yang, Ye; Soyemi, Olusola O.; Landry, Michelle R.; Soller, Babs R.

2005-01-01

The influence of fat thickness on the diffuse reflectance spectra of muscle in the near infrared (NIR) region is studied by Monte Carlo simulations of a two-layer structure and with phantom experiments. A polynomial relationship was established between the fat thickness and the detected diffuse reflectance. The influence of a range of optical coefficients (absorption and reduced scattering) for fat and muscle over the known range of human physiological values was also investigated. Subject-to-subject variation in the fat optical coefficients and thickness can be ignored if the fat thickness is less than 5 mm. A method was proposed to correct the fat thickness influence. c2005 Optical Society of America.

Determination of optical band gap of powder-form nanomaterials with improved accuracy

NASA Astrophysics Data System (ADS)

Ahsan, Ragib; Khan, Md. Ziaur Rahman; Basith, Mohammed Abdul

2017-10-01

Accurate determination of a material's optical band gap lies in the precise measurement of its absorption coefficients, either from its absorbance via the Beer-Lambert law or diffuse reflectance spectrum via the Kubelka-Munk function. Absorption coefficients of powder-form nanomaterials calculated from absorbance spectrum do not match those calculated from diffuse reflectance spectrum, implying the inaccuracy of the traditional optical band gap measurement method for such samples. We have modified the Beer-Lambert law and the Kubelka-Munk function with proper approximations for powder-form nanomaterials. Applying the modified method for powder-form nanomaterial samples, both absorbance and diffuse reflectance spectra yield exactly the same absorption coefficients and therefore accurately determine the optical band gap.

NIR detection of pits and pit fragments in fresh cherries (abstract)

USDA-ARS?s Scientific Manuscript database

The feasibility of using near infrared (NIR) diffuse reflectance spectroscopy for the detection of pits and pit fragments in cherries was demonstrated. For detection of whole pits, 300 cherries were obtained locally and pits were removed from half. NIR reflectance spectra were obtained in triplicate...

Mapping the conduction band edge density of states of γ-In2Se3 by diffuse reflectance spectra

NASA Astrophysics Data System (ADS)

Kumar, Pradeep; Vedeshwar, Agnikumar G.

2018-03-01

It is demonstrated that the measured diffuse reflectance spectra of γ-In2Se3 can be used to map the conduction band edge density of states through Kubelka-Munk analysis. The Kubelka-Munk function derived from the measured spectra almost mimics the calculated density of states in the vicinity of conduction band edge. The calculation of density of states was carried out using first-principles approach yielding the structural, electronic, and optical properties. The calculations were carried out implementing various functionals and only modified Tran and Blaha (TB-MBJ) results tally closest with the experimental result of band gap. The electronic and optical properties were calculated using FP-LAPW + lo approach based on the Density Functional Theory formalism implementing only TB-mBJ functional. The electron and hole effective masses have been calculated as me * = 0.25 m 0 and mh * = 1.11 m 0 , respectively. The optical properties clearly indicate the anisotropic nature of γ-In2Se3.

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Wind profile recovery from intensity fluctuations of a laser beam reflected in a turbulent atmosphere

NASA Astrophysics Data System (ADS)

Banakh, V. A.; Marakasov, D. A.

2008-04-01

An algorithm for the wind profile recovery from spatiotemporal spectra of a laser beam reflected in a turbulent atmosphere is presented. The cases of a spherical wave incident on a diffuse reflector of finite size and a spatially limited beam reflected from an infinite random surface are considered.

The Diffuse Interstellar Bands: Contributed papers

NASA Technical Reports Server (NTRS)

Tielens, Alexander G. G. M. (Editor)

1994-01-01

Drawing a coherent picture of the observational characteristics of the Diffuse Interstellar Bands (DIB's) and the physical and chemical properties of its proposed carriers was the focus of this NASA sponsored conference. Information relating to absoption spectra, diffuse radiation carriers, carbon compounds, stellar composition, and interstellar extinction involving T-Tauri stars, Reflection Nebulae, Red Giants, and accretion discs are discussed from those papers presented at the conference, which are included in this analytic.

Reflectivity (visible and near IR), Moessbauer, static magnetic, and X ray diffraction properties of aluminum-substituted hematites

NASA Technical Reports Server (NTRS)

Morris, Richard V.; Schulze, Darrell G.; Lauer, Howard V., Jr.; Agresti, David G.; Shelfer, Tad D.

1992-01-01

The effect of substituting iron by aluminum in polymorphs of Fe2O3 and FeOOH on their reflectivity characteristics was investigated by comparing data on visible and NIR reflectivities and on static magnetic, XRD, and Moessbauer properties for a family of aluminum-substituted hematites alpha-(Fe,Al)2O3, with compositions where the values of the Al/(Al+Fe) ratio were up to 0.61. Samples were prepared by oxidation of magnetite, dehydroxylation of goethite, and direct precipitation. The analytical methods used for obtaining diffuse reflectivity spectra (350-2200 nm), Moessbauer spectra, and static magnetic data are those described by Morris et al. (1989).

Features of degradation and recovery of the optical properties of coatings based on ZnO powder modified with nanoparticles after irradiation

NASA Astrophysics Data System (ADS)

Mikhailov, M.; Neschimenko, V.; Sokolovskiy, A.

2018-04-01

The effect of electron irradiation with energy of 30 keV and fluence up to 7 × 1016 cm-2 on diffuse reflection spectra in situ of coatings based on ZnO powders unmodified and modified with zirconium dioxide and aluminum oxide nanopowders was investigated. The higher radiation stability of coatings based on modified pigments in comparison to unmodified pigments has been established. A significant recovery of the reflection spectra of irradiated coatings after exposure to residual vacuum and air was shown.

Examination of U valence states in the brannerite structure by near-infrared diffuse reflectance and X-ray photoelectron spectroscopies

NASA Astrophysics Data System (ADS)

Finnie, Kim S.; Zhang, Zhaoming; Vance, Eric R.; Carter, Melody L.

2003-04-01

The valence state of uranium doped into a f 0 thorium analog of brannerite (i.e., thorutite) has been examined using near-infrared (NIR) diffuse reflectance (DRS) and X-ray photoelectron (XPS) spectroscopies. NIR transitions of U 4+, which are not observed in spectra of brannerite, have been detected in the samples of U xTh 1- xTi 2O 6, and we propose that strong specular reflectance is responsible for the lack of U 4+ features in UTi 2O 6. Characteristic U 5+ bands have been identified in samples in which sufficient Ca 2+ has been added to nominally effect complete oxidation to U 5+. XPS results support the assignments of U 4+ and U 5+ by DRS. The presence of residual U 4+ bands in the spectra of the Ca-doped samples is consistent with segregation of Ca 2+ to the grain boundaries during high temperature sintering.

Spectrophotometric Method for Differentiation of Human Skin Melanoma. I. Optical Diffuse Reflection Coefficient

NASA Astrophysics Data System (ADS)

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

2016-03-01

We have designed an experimental setup, based on two integrating spheres, that lets us measure the optical diffuse reflectance spectra (diffuse reflection coefficient vs. wavelength) of human skin quickly under clinical conditions in vivo. For the wavelength interval 520-1100 nm, we give the values of the diffuse reflection coefficient for healthy tissue, skin with a benign nevus, and skin with a malignant melanoma for a large group of test subjects. We experimentally established a number of wavelengths in the red-near IR region of the spectrum which can be used for early differential diagnosis of nevi and melanoma in patient cancer screening. According to the Kramer-Welch test, the probability of the diffuse reflection coefficient for skin with melanoma and a nevus having different distributions is >0.94, and at many wavelengths it is >0.999. By solving the inverse problem, we estimated the changes in a number of structural and biophysical parameters of the tissue on going from healthy skin to nevus and melanoma. The results obtained can provide a basis for developing a clinical approach to identifying the risk of malignant transformation of the skin before surgery and histological analysis of the tissue.

Can a one-layer optical skin model including melanin and inhomogeneously distributed blood explain spatially resolved diffuse reflectance spectra?

NASA Astrophysics Data System (ADS)

Karlsson, Hanna; Pettersson, Anders; Larsson, Marcus; Strömberg, Tomas

2011-02-01

Model based analysis of calibrated diffuse reflectance spectroscopy can be used for determining oxygenation and concentration of skin chromophores. This study aimed at assessing the effect of including melanin in addition to hemoglobin (Hb) as chromophores and compensating for inhomogeneously distributed blood (vessel packaging), in a single-layer skin model. Spectra from four humans were collected during different provocations using a twochannel fiber optic probe with source-detector separations 0.4 and 1.2 mm. Absolute calibrated spectra using data from either a single distance or both distances were analyzed using inverse Monte Carlo for light transport and Levenberg-Marquardt for non-linear fitting. The model fitting was excellent using a single distance. However, the estimated model failed to explain spectra from the other distance. The two-distance model did not fit the data well at either distance. Model fitting was significantly improved including melanin and vessel packaging. The most prominent effect when fitting data from the larger separation compared to the smaller separation was a different light scattering decay with wavelength, while the tissue fraction of Hb and saturation were similar. For modeling spectra at both distances, we propose using either a multi-layer skin model or a more advanced model for the scattering phase function.

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.

Optical (diffuse reflectance) and Mossbauer spectroscopic study of nontronite and related Fe-bearing smectites

USGS Publications Warehouse

Sherman, David M.; Vergo, N.

1988-01-01

Near-ultraviolet to near-infrared optical (diffuse reflectance) spectra of several nontronites and related Fe-bearing smectites [(Fe2+,Fe3+)-bearing saponite and (Fe2+,Fe3+)-bearing montmorillonite] are presented and interpreted. Mossbauer spectra at 298 K are also presented to help interpret the optical spectra. The optical spectra of nontronites are dominated by the ligand field transitions of Fe3+ in octahedral coordination sites. In addition to the ligand field transitions of single Fe3+ cations, a broad absorption band centered near 22000 cm-1 is observed that may be due to the simultaneous excitation of two Fe3+ cations to the 4T1g (4G) state. Alternatively, this band may represent excitations to the 2A2g and 2T1g ligand field states. For most samples, the amount of tetrahedrally coordinated Fe3+ was below that detectable by Mossbauer spectroscopy (1-3% of total Fe). However, the optical spectra of all of the nontronites show an absorption band near 23000 cm-1. This band is assigned to the 6A1 ??? 4E,4A1 transition of tetrahedrally coordinated Fe3+. The optical spectra of mixed-valence Fe-bearing smectites show a broad absorption band at 14000-15000 cm-1 owing to Fe2+ ??? Fe3+ charge transfer. -from Authors

Nondestructive estimation of wood chemical composition of sections of radial wood strips by diffuse reflectance near infrared spectroscopy

Treesearch

P. David Jones; Laurence R. Schimleck; Gary F. Peter; Richard F. Daniels; Alexander Clark

2006-01-01

The use of calibrated near infrared (NIR) spectroscopy for predicting the chemical composition of Pirus taeda L. (loblolly pine) wood samples is investigated. Seventeen P. taeda radial strips, representing seven different sites were selected and NlR spectra were obtained from the radial longitudinal face of each strip. The spectra...

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.

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

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

A comparative study of mid-infrared diffuse reflection (DR) and attenuated total reflection (ATR) spectroscopy for the detection of fungal infection on RWA2-corn.

PubMed

Kos, Gregor; Krska, Rudolf; Lohninger, Hans; Griffiths, Peter R

2004-01-01

An investigation into the rapid detection of mycotoxin-producing fungi on corn by two mid-infrared spectroscopic techniques was undertaken. Corn samples from a single genotype (RWA2, blanks, and contaminated with Fusarium graminearum) were ground, sieved and, after appropriate sample preparation, subjected to mid-infrared spectroscopy using two different accessories (diffuse reflection and attenuated total reflection). The measured spectra were evaluated with principal component analysis (PCA) and the blank and contaminated samples were classified by cluster analysis. Reference data for fungal metabolites were obtained with conventional methods. After extraction and clean-up, each sample was analyzed for the toxin deoxynivalenol (DON) by gas chromatography with electron capture detection (GC-ECD) and ergosterol (a parameter for the total fungal biomass) by high-performance liquid chromatography with diode array detection (HPLC-DAD). The concentration ranges for contaminated samples were 880-3600 microg/kg for ergosterol and 300-2600 microg/kg for DON. Classification efficiency was 100% for ATR spectra. DR spectra did not show as obvious a clustering of contaminated and blank samples. Results and trends were also observed in single spectra plots. Quantification using a PLS1 regression algorithm showed good correlation with DON reference data, but a rather high standard error of prediction (SEP) with 600 microg/kg (DR) and 490 microg/kg (ATR), respectively, for ergosterol. Comparing measurement procedures and results showed advantages for the ATR technique, mainly owing to its ease of use and the easier interpretation of results that were better with respect to classification and quantification.

Infrared Spectroscopy of Explosives Residues: Measurement Techniques and Spectral Analysis

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

Phillips, Mark C.; Bernacki, Bruce E.

2015-03-11

Infrared laser spectroscopy of explosives is a promising technique for standoff and non-contact detection applications. However, the interpretation of spectra obtained in typical standoff measurement configurations presents numerous challenges. Understanding the variability in observed spectra from explosives residues and particles is crucial for design and implementation of detection algorithms with high detection confidence and low false alarm probability. We discuss a series of infrared spectroscopic techniques applied toward measuring and interpreting the reflectance spectra obtained from explosives particles and residues. These techniques utilize the high spectral radiance, broad tuning range, rapid wavelength tuning, high scan reproducibility, and low noise ofmore » an external cavity quantum cascade laser (ECQCL) system developed at Pacific Northwest National Laboratory. The ECQCL source permits measurements in configurations which would be either impractical or overly time-consuming with broadband, incoherent infrared sources, and enables a combination of rapid measurement speed and high detection sensitivity. The spectroscopic methods employed include standoff hyperspectral reflectance imaging, quantitative measurements of diffuse reflectance spectra, reflection-absorption infrared spectroscopy, microscopic imaging and spectroscopy, and nano-scale imaging and spectroscopy. Measurements of explosives particles and residues reveal important factors affecting observed reflectance spectra, including measurement geometry, substrate on which the explosives are deposited, and morphological effects such as particle shape, size, orientation, and crystal structure.« less

In vivo assessment of liver fibrosis using diffuse reflectance and fluorescence spectroscopy: a proof of concept.

PubMed

Fabila, Diego; de la Rosa, José Manuel; Stolik, Suren; Moreno, Edgard; Suárez-Álvarez, Karina; López-Navarrete, Giuliana; Guzmán, Carolina; Aguirre-García, Jesús; Acevedo-García, Christian; Kershenobich, David; Escobedo, Galileo

2012-12-01

A novel application of diffuse reflectance and fluorescence spectroscopy in the assessment of liver fibrosis is here reported. To induce different stages of liver fibrosis, a sufficient number of male Wistar rats were differentially exposed to chronic administration with carbon tetrachloride. Then, diffuse reflectance and fluorescence spectra were in vivo measured from the liver surface of each animal by a minimal invasive laparoscopic procedure. The liver fibrosis degree was conventionally determined by means of histological examination using the Mason's Trichrome stain, accompanied by hepatic expression of α-sma, and evaluation of the ALT/AST serum levels. The liver from rats exhibiting higher grades of fibrosis showed a significant increase in diffuse reflectance and fluorescence intensity when compared with control animals. At 365 nm, the diffuse reflectance spectrum exhibited an increase of 4 and 3-fold in mild and advanced fibrotic rats, respectively, when compared to the control group. Similarly, the fluorescence emission at 493 nm was 2-fold higher in fibrotic animals than in controls. By using fluorescence intensity, discrimination algorithms indicated 73% sensitivity and 94% specificity for recognition of hepatic fibrosis, while for diffuse reflectance, these values increased up to 85% and 100%, respectively. Taking into consideration there is a special need for developing new diagnostic approaches focused on detecting different stages of liver fibrosis with minimal invasiveness, these results suggest that diffuse reflectance and fluorescence spectroscopy could be worthy of further exploration in patients with liver disease. Copyright © 2012 Elsevier B.V. All rights reserved.

Monitoring Prepregs As They Cure

NASA Technical Reports Server (NTRS)

Young, P. R.; Gleason, J. R.; Chang, A. C.

1986-01-01

Quality IR spectra obtained in dynamic heating environment. New technique obtains quality infrared spectra on graphite-fiber-reinforced, polymeric-matrix-resin prepregs as they cure. Technique resulted from modification of diffuse reflectance/Fourier transform infrared (DR/FTIR) technique previously used to analyze environmentally exposed cured graphite composites. Technique contribute to better understanding of prepreg chemistry/temperature relationships and development of more efficient processing cycles for advanced materials.

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.

Optical absorption and scattering spectra of pathological stomach tissues

NASA Astrophysics Data System (ADS)

Giraev, K. M.; Ashurbekov, N. A.; Lakhina, M. A.

2011-03-01

Diffuse reflection spectra of biotissues in vivo and transmission and reflection coefficients for biotissues in vitro are measured over 300-800 nm. These data are used to determine the spectral absorption and scattering indices and the scattering anisotropy factor for stomach mucous membranes under normal and various pathological conditions (chronic atrophic and ulcerous defects, malignant neoplasms). The most importan tphysiological (hemodynamic and oxygenation levels) and structural-morphological (scatterer size and density) parameters are also determined. The results of a morphofunctional study correlate well with the optical properties and are consistent with data from a histomorphological analysis of the corresponding tissues.

On-line database of voltammetric data of immobilized particles for identifying pigments and minerals in archaeometry, conservation and restoration (ELCHER database).

PubMed

Doménech-Carbó, Antonio; Doménech-Carbó, María Teresa; Valle-Algarra, Francisco Manuel; Gimeno-Adelantado, José Vicente; Osete-Cortina, Laura; Bosch-Reig, Francisco

2016-07-13

A web-based database of voltammograms is presented for characterizing artists' pigments and corrosion products of ceramic, stone and metal objects by means of the voltammetry of immobilized particles methodology. Description of the website and the database is provided. Voltammograms are, in most cases, accompanied by scanning electron microphotographs, X-ray spectra, infrared spectra acquired in attenuated total reflectance Fourier transform infrared spectroscopy mode (ATR-FTIR) and diffuse reflectance spectra in the UV-Vis-region. For illustrating the usefulness of the database two case studies involving identification of pigments and a case study describing deterioration of an archaeological metallic object are presented. Copyright © 2016 Elsevier B.V. All rights reserved.

Transmission versus reflectance spectroscopy for quantitation

NASA Astrophysics Data System (ADS)

Gardner, Craig M.

2018-01-01

The objective of this work was to compare the accuracy of analyte concentration estimation when using transmission versus diffuse reflectance spectroscopy of a scattering medium. Monte Carlo ray tracing of light through the medium was used in conjunction with pure component absorption spectra and Beer-Lambert absorption along each ray's pathlength to generate matched sets of pseudoabsorbance spectra, containing water and six analytes present in skin. PLS regression models revealed an improvement in accuracy when using transmission compared to reflectance for a range of medium thicknesses and instrument noise levels. An analytical expression revealed the source of the accuracy degradation with reflectance was due both to the reduced collection efficiency for a fixed instrument etendue and to the broad pathlength distribution that detected light travels in the medium before exiting from the incident side.

The quality of geological information derivable from high resolution reflectance spectra - Results for mafic silicates

NASA Technical Reports Server (NTRS)

Cloutis, E. A.; Lambert, J.; Smith, D. G. W.; Gaffey, M. J.

1987-01-01

High-resolution visible and near-infrared diffuse reflectance spectra of mafic silicates can be deconvolved to yield quantitative information concerning mineral mixture properties, and the results can be directly applied to remotely sensed data. Spectral reflectance measurements of laboratory mixtures of olivine, orthophyroxene, and clinopyroxene with known chemistries, phase abundances, and particle size distributions have been utilized to develop correlations between spectral properties and the physicochemical parameters of the samples. A large number of mafic silicate spectra were measured and examined for systematic variations in spectral properties as a function of chemistry, phase abundance, and particle size. Three classes of spectral parameters (ratioed, absolute, and wavelength) were examined for any correlations. Each class is sensitive to particular mafic silicate properties. Spectral deconvolution techniques have been developed for quantifying, with varying degrees of accuracy, the assemblage properties (chemistry, phase abundance, and particle size).

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.

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.

[Achievement of the noninvasive measurement for human blood glucose with NIR diffusion reflectance spectrum method].

PubMed

Zhang, Hong-yan; Ding, Dong; Song, Li-qiang; Gu, Lin-na; Yang, Peng; Tang, Yu-guo

2005-06-01

The noninvasive measurement of human blood glucose was achieved with NIR diffusion reflectance spectrum method. The thumb fingertip NIR diffusion reflectance spectra of six different age healthy volunteers were collected using Nexus-870 and its NIR fiber port smart accessory. The test was implemented with changing the blood glucose concentration for the limosis and satiation of every volunteer. The calibration model was set up using PLS method with the smoothing, baseline correction and first derivatives pretreatment spectrum in the 7500-8500 cm(-1) region for single volunteer, the same age combination and that of different age. When the spectrum was obtained, the actual blood glucose value of every spectrun sample was demarcated using ultraviolet spectrophotometer. The correlation between the calibration value and true value for single volunteer is better than that for the combination of volunteers, the correlative coefficients are all over 0.90471, RMSECs are all less than 0.171.

Spectral characteristics of iron-bearing phyllosilicates: Comparison to Orgueil (CI1), Murchison and Murray (CM2)

USGS Publications Warehouse

Calvin, W.M.; King, T.V.V.

1997-01-01

Phyllosilicate alteration minerals are commonly found in low petrologic types of carbonaceous chondrites. Previous spectral studies have examined Mg-bearing phyllosilicates with limited success in matching the spectral properties of CM and CI chondrites. Transmission electron microscope and other analytical techniques suggest that Fe-bearing clays are more abundant in CI and CM chondrites than magnesian varieties. Here, we present the results of an examination of the reflectance spectra of Fe-phyllosilicates, including serpentines and berthierines, of which the latter were formerly known as septechlorites. We have measured the diffuse reflectance spectra of powdered samples from 0.3 to 25 ??m. We find that these minerals provide a better spectral match to many of the features seen in CI and CM chondrites, and simple linear combinations of the spectra of both Fe- and Mg-phyllosilicates closely approximate the spectra of CM and CI chondrites.

Mid-infrared reflectlance spectra (2.3-22 micions) of sulfur, gold, KBr, MgO, and halon

NASA Technical Reports Server (NTRS)

Nash, D. B.

1986-01-01

Biconical diffuse reflectance spectra in the mid-infrared are presented for powder and other solid forms of sulfur, gold, potassium bromide, magnesium oxide, and halon. Comparisons are made with previously published results of other investigators, and recommendations are made regarding the relative usefulnees of these materials as reflectance standards in the mid-IR. Sulfur has strong intrinsic bands at wavelengths greater than 7 microns that must be taken into account for its use as a reflectance standard. Some sulfur samples have hydrocarbon contaminants and in powder form may have adsorbed water, both of which produce bands in the 3-4-micron region. Potassium bromide has several weak intrinsic bands and is very sensitive to adsorbed water contamination; otherwise it is a good IR reference material. Magnesium oxide and halon have major bands structure and low reflectivity at wavelengths greater than 2.6 microns and thus are unsuitable as reference materials in the mid-IR. Vapor-deposited gold on fine sandpaper (600 grit) is very bright, spectrally flat, and fairly diffuse, so it is the superior material (of those examined) for reflectance reference material throughout the IR. Fine gold powder, on the other hand, is much less bright than evaporated gold, and its reflectivity at wavelengths greater than its particle size is highly sensitive to particle packing density.

Characterization of near infrared spectral variance in the authentication of skim and nonfat dry milk powder collection using ANOVA-PCA, Pooled-ANOVA, and partial least squares regression

USDA-ARS?s Scientific Manuscript database

Forty-one samples of skim milk powder (SMP) and non-fat dry milk (NFDM) from 8 suppliers, 13 production sites, and 3 processing temperatures were analyzed by NIR diffuse reflectance spectrometry over a period of three days. NIR reflectance spectra (1700-2500 nm) were converted to pseudo-absorbance ...

Transmission versus reflectance spectroscopy for quantitation.

PubMed

Gardner, Craig M

2018-01-01

The objective of this work was to compare the accuracy of analyte concentration estimation when using transmission versus diffuse reflectance spectroscopy of a scattering medium. Monte Carlo ray tracing of light through the medium was used in conjunction with pure component absorption spectra and Beer-Lambert absorption along each ray's pathlength to generate matched sets of pseudoabsorbance spectra, containing water and six analytes present in skin. PLS regression models revealed an improvement in accuracy when using transmission compared to reflectance for a range of medium thicknesses and instrument noise levels. An analytical expression revealed the source of the accuracy degradation with reflectance was due both to the reduced collection efficiency for a fixed instrument etendue and to the broad pathlength distribution that detected light travels in the medium before exiting from the incident side. (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

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.

Verification of reflectance models in turbid waters

NASA Technical Reports Server (NTRS)

Tanis, F. J.; Lyzenga, D. R.

1981-01-01

Inherent optical parameters of very turbid waters were used to evaluate existing water reflectance models. Measured upwelling radiance spectra and Monte Carlo simulations of the radiative transfer equations were compared with results from models based upon two flow, quasi-single scattering, augmented isotropic scattering, and power series approximation. Each model was evaluated for three separate components of upwelling radiance: (1) direct sunlight; (2) diffuse skylight; and (3) internally reflected light. Limitations of existing water reflectance models as applied to turbid waters and possible applications to the extraction of water constituent information are discussed.

A method for monitoring of oxygen saturation changes in brain tissue using diffuse reflectance spectroscopy.

PubMed

Rejmstad, Peter; Johansson, Johannes D; Haj-Hosseini, Neda; Wårdell, Karin

2017-03-01

Continuous measurement of local brain oxygen saturation (SO 2 ) can be used to monitor the status of brain trauma patients in the neurocritical care unit. Currently, micro-oxygen-electrodes are considered as the "gold standard" in measuring cerebral oxygen pressure (pO 2 ), which is closely related to SO 2 through the oxygen dissociation curve (ODC) of hemoglobin, but with the drawback of slow in response time. The present study suggests estimation of SO 2 in brain tissue using diffuse reflectance spectroscopy (DRS) for finding an analytical relation between measured spectra and the SO 2 for different blood concentrations. The P 3 diffusion approximation is used to generate a set of spectra simulating brain tissue for various levels of blood concentrations in order to estimate SO 2 . The algorithm is evaluated on optical phantoms mimicking white brain matter (blood volume of 0.5-2%) where pO 2 and temperature is controlled and on clinical data collected during brain surgery. The suggested method is capable of estimating the blood fraction and oxygen saturation changes from the spectroscopic signal and the hemoglobin absorption profile. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

Capabilities and limitations of handheld Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) for the analysis of colourants and binders in 20th-century reverse paintings on glass

NASA Astrophysics Data System (ADS)

Steger, Simon; Stege, Heike; Bretz, Simone; Hahn, Oliver

2018-04-01

A non-invasive method has been carried out to show the capabilities and limitations of Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) for identifying of colourants and binders in modern reverse glass paintings. For this purpose, the reverse glass paintings "Zwei Frauen am Tisch" (1920-22), "Bäume" (1946) (both by Heinrich Campendonk), "Lofoten" (1933) (Edith Campendonk-van Leckwyck) and "Ohne Titel" (1954) (Marianne Uhlenhuth), were measured. In contrast to other techniques (e.g. panel and mural painting), the paint layers are applied in reverse succession. In multi-layered paint systems, the front paint layer may no longer be accessible. The work points out the different spectral appearance of a given substance (gypsum, basic lead white) in reverse glass paintings. However, inverted bands, band overlapping and derivative-shaped spectral features can be interpreted by comparing the spectra from the paintings with spectra from pure powders and pigment/linseed oil mock-ups. Moreover, the work focuses on this method's capabilities in identifying synthetic organic pigments (SOP). Reference spectra of three common SOP (PG7, PY1, PR83) were obtained from powders and historical colour charts. We identified PR83 and PY1 in two reverse glass paintings, using the measured reference spectra. The recorded DRIFTS spectra of pure linseed oil, gum Arabic, mastic, polyvinyl acetate resin and bees wax can be used to classify the binding media of the measured paintings.

Enhancing the chroma of pigmented polymers using antireflective surface structures.

PubMed

Clausen, Jeppe S; Christiansen, Alexander B; Kristensen, Anders; Mortensen, N Asger

2013-11-10

In this paper we investigate how the color of a pigmented polymer is affected by reduction of the reflectance at the air-polymer interface. Both theoretical and experimental investigations show modified diffuse-direct reflectance spectra when the reflectance of the surface is lowered. Specifically it is found that the color change is manifested as an increase in chroma, leading to a clearer color experience. The experimental implementation is done using random tapered surface structures replicated in polymer from silicon masters using hot embossing.

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.

A hybrid sorption - Spectrometric method for determination of synthetic anionic dyes in foodstuffs.

PubMed

Tikhomirova, Tatyana I; Ramazanova, Gyulselem R; Apyari, Vladimir V

2017-04-15

A sorption-spectrometric method for determination of the anionic synthetic dyes based on their sorption on silica sorbent modified with hexadecyl groups (C16) followed by measuring the diffuse reflectance spectra on the surface of the sorbent has been proposed. Adsorption of sulfonated azo dyes Tartrazine (E102), Sunset Yellow FCF (E110), Ponceau 4R (E124) reaches maximum in acidic medium (1M HCl - pH 1). For the quinophthalone type dye Quinoline Yellow (E104), the adsorption is also maximal in an acidic medium (1M HCl - pH 2). The triphenylmethane dye Fast Green FCF (E143) is absorbed in the wider area of pH (1M HCl - pH 6). Increasing concentration of the dyes in a solution led to the increase in absorption band intensity in diffuse reflectance spectra of the adsorbent, which was used for their direct determination. The proposed method was applied to the determination of dyes in beverages and pharmaceuticals. Copyright © 2016 Elsevier Ltd. All rights reserved.

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.

Study on rapid valid acidity evaluation of apple by fiber optic diffuse reflectance technique

NASA Astrophysics Data System (ADS)

Liu, Yande; Ying, Yibin; Fu, Xiaping; Jiang, Xuesong

2004-03-01

Some issues related to nondestructive evaluation of valid acidity in intact apples by means of Fourier transform near infrared (FTNIR) (800-2631nm) method were addressed. A relationship was established between the diffuse reflectance spectra recorded with a bifurcated optic fiber and the valid acidity. The data were analyzed by multivariate calibration analysis such as partial least squares (PLS) analysis and principal component regression (PCR) technique. A total of 120 Fuji apples were tested and 80 of them were used to form a calibration data set. The influence of data preprocessing and different spectra treatments were also investigated. Models based on smoothing spectra were slightly worse than models based on derivative spectra and the best result was obtained when the segment length was 5 and the gap size was 10. Depending on data preprocessing and multivariate calibration technique, the best prediction model had a correlation efficient (0.871), a low RMSEP (0.0677), a low RMSEC (0.056) and a small difference between RMSEP and RMSEC by PLS analysis. The results point out the feasibility of FTNIR spectral analysis to predict the fruit valid acidity non-destructively. The ratio of data standard deviation to the root mean square error of prediction (SDR) is better to be less than 3 in calibration models, however, the results cannot meet the demand of actual application. Therefore, further study is required for better calibration and prediction.

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.

Brain tumor classification using the diffusion tensor image segmentation (D-SEG) technique.

PubMed

Jones, Timothy L; Byrnes, Tiernan J; Yang, Guang; Howe, Franklyn A; Bell, B Anthony; Barrick, Thomas R

2015-03-01

There is an increasing demand for noninvasive brain tumor biomarkers to guide surgery and subsequent oncotherapy. We present a novel whole-brain diffusion tensor imaging (DTI) segmentation (D-SEG) to delineate tumor volumes of interest (VOIs) for subsequent classification of tumor type. D-SEG uses isotropic (p) and anisotropic (q) components of the diffusion tensor to segment regions with similar diffusion characteristics. DTI scans were acquired from 95 patients with low- and high-grade glioma, metastases, and meningioma and from 29 healthy subjects. D-SEG uses k-means clustering of the 2D (p,q) space to generate segments with different isotropic and anisotropic diffusion characteristics. Our results are visualized using a novel RGB color scheme incorporating p, q and T2-weighted information within each segment. The volumetric contribution of each segment to gray matter, white matter, and cerebrospinal fluid spaces was used to generate healthy tissue D-SEG spectra. Tumor VOIs were extracted using a semiautomated flood-filling technique and D-SEG spectra were computed within the VOI. Classification of tumor type using D-SEG spectra was performed using support vector machines. D-SEG was computationally fast and stable and delineated regions of healthy tissue from tumor and edema. D-SEG spectra were consistent for each tumor type, with constituent diffusion characteristics potentially reflecting regional differences in tissue microstructure. Support vector machines classified tumor type with an overall accuracy of 94.7%, providing better classification than previously reported. D-SEG presents a user-friendly, semiautomated biomarker that may provide a valuable adjunct in noninvasive brain tumor diagnosis and treatment planning. © The Author(s) 2014. Published by Oxford University Press on behalf of the Society for Neuro-Oncology.

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.

Distortion correction and cross-talk compensation algorithm for use with an imaging spectrometer based spatially resolved diffuse reflectance system

NASA Astrophysics Data System (ADS)

Cappon, Derek J.; Farrell, Thomas J.; Fang, Qiyin; Hayward, Joseph E.

2016-12-01

Optical spectroscopy of human tissue has been widely applied within the field of biomedical optics to allow rapid, in vivo characterization and analysis of the tissue. When designing an instrument of this type, an imaging spectrometer is often employed to allow for simultaneous analysis of distinct signals. This is especially important when performing spatially resolved diffuse reflectance spectroscopy. In this article, an algorithm is presented that allows for the automated processing of 2-dimensional images acquired from an imaging spectrometer. The algorithm automatically defines distinct spectrometer tracks and adaptively compensates for distortion introduced by optical components in the imaging chain. Crosstalk resulting from the overlap of adjacent spectrometer tracks in the image is detected and subtracted from each signal. The algorithm's performance is demonstrated in the processing of spatially resolved diffuse reflectance spectra recovered from an Intralipid and ink liquid phantom and is shown to increase the range of wavelengths over which usable data can be recovered.

Optical spectroscopy for differentiation of liver tissue under distinct stages of fibrosis: an ex vivo study

NASA Astrophysics Data System (ADS)

Fabila, D. A.; Hernández, L. F.; de la Rosa, J.; Stolik, S.; Arroyo-Camarena, U. D.; López-Vancell, M. D.; Escobedo, G.

2013-11-01

Liver fibrosis is the decisive step towards the development of cirrhosis; its early detection affects crucially the diagnosis of liver disease, its prognosis and therapeutic decision making. Nowadays, several techniques are employed to this task. However, they have the limitation in estimating different stages of the pathology. In this paper we present a preliminary study to evaluate if optical spectroscopy can be employed as an auxiliary tool of diagnosis of biopsies of human liver tissue to differentiate the fibrosis stages. Ex vivo fluorescence and diffuse reflectance spectra were acquired from biopsies using a portable fiber-optic system. Empirical discrimination algorithms based on fluorescence intensity ratio at 500 nm and 680 nm as well as diffuse reflectance intensity at 650 nm were developed. Sensitivity and specificity of around 80% and 85% were respectively achieved. The obtained results show that combined use of fluorescence and diffuse reflectance spectroscopy could represent a novel and useful tool in the early evaluation of liver fibrosis.

Re-evaluation of model-based light-scattering spectroscopy for tissue spectroscopy

PubMed Central

Lau, Condon; Šćepanović, Obrad; Mirkovic, Jelena; McGee, Sasha; Yu, Chung-Chieh; Fulghum, Stephen; Wallace, Michael; Tunnell, James; Bechtel, Kate; Feld, Michael

2009-01-01

Model-based light scattering spectroscopy (LSS) seemed a promising technique for in-vivo diagnosis of dysplasia in multiple organs. In the studies, the residual spectrum, the difference between the observed and modeled diffuse reflectance spectra, was attributed to single elastic light scattering from epithelial nuclei, and diagnostic information due to nuclear changes was extracted from it. We show that this picture is incorrect. The actual single scattering signal arising from epithelial nuclei is much smaller than the previously computed residual spectrum, and does not have the wavelength dependence characteristic of Mie scattering. Rather, the residual spectrum largely arises from assuming a uniform hemoglobin distribution. In fact, hemoglobin is packaged in blood vessels, which alters the reflectance. When we include vessel packaging, which accounts for an inhomogeneous hemoglobin distribution, in the diffuse reflectance model, the reflectance is modeled more accurately, greatly reducing the amplitude of the residual spectrum. These findings are verified via numerical estimates based on light propagation and Mie theory, tissue phantom experiments, and analysis of published data measured from Barrett’s esophagus. In future studies, vessel packaging should be included in the model of diffuse reflectance and use of model-based LSS should be discontinued. PMID:19405760

On the Widths of Bands in the Infrared Spectra of Oxyanions.

PubMed

Griffiths, Peter R; Eastman Fries, Brandy; Weakley, Andrew T

2018-01-01

It is well known that the antisymmetric stretching (ν 3 ) band in the mid-infrared spectra of oxyanion salts is usually very broad, whereas all the other fundamental bands are narrow. In this paper, we propose that the underlying cause of the increased width is the effect of the very high absorption index of this band for samples prepared with a range of particle sizes. When oxyanion salts are ground, the diameter of the resulting particles usually varies from less than 100 nm to about 2 µm. While the peak absorbance of the ν 3 band of the smaller particles (diameter < 200 nm) is less than 1, that of the larger particles can be as high as 6. We show that the average transmittance of these particles leads to a significant band broadening, especially when there are small voids in the resulting sample. Although the effect is always seen in the spectra of alkali halide disks and mineral oil mulls, it is also seen in diffuse reflection and attenuated total reflection (ATR) spectra. Because the depth of penetration of infrared radiation below 1500 cm -1 is less than 1 µm for ATR spectra measured with a germanium internal reflection element (IRE), the width of the ν 3 band is lower than that of ATR spectra measured with an IRE of lower refractive index such as diamond on zinc selenide.

Capabilities and limitations of handheld Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) for the analysis of colourants and binders in 20th-century reverse paintings on glass.

PubMed

Steger, Simon; Stege, Heike; Bretz, Simone; Hahn, Oliver

2018-04-15

A non-invasive method has been carried out to show the capabilities and limitations of Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) for identifying of colourants and binders in modern reverse glass paintings. For this purpose, the reverse glass paintings "Zwei Frauen am Tisch" (1920-22), "Bäume" (1946) (both by Heinrich Campendonk), "Lofoten" (1933) (Edith Campendonk-van Leckwyck) and "Ohne Titel" (1954) (Marianne Uhlenhuth), were measured. In contrast to other techniques (e.g. panel and mural painting), the paint layers are applied in reverse succession. In multi-layered paint systems, the front paint layer may no longer be accessible. The work points out the different spectral appearance of a given substance (gypsum, basic lead white) in reverse glass paintings. However, inverted bands, band overlapping and derivative-shaped spectral features can be interpreted by comparing the spectra from the paintings with spectra from pure powders and pigment/linseed oil mock-ups. Moreover, the work focuses on this method's capabilities in identifying synthetic organic pigments (SOP). Reference spectra of three common SOP (PG7, PY1, PR83) were obtained from powders and historical colour charts. We identified PR83 and PY1 in two reverse glass paintings, using the measured reference spectra. The recorded DRIFTS spectra of pure linseed oil, gum Arabic, mastic, polyvinyl acetate resin and bees wax can be used to classify the binding media of the measured paintings. Copyright © 2018 Elsevier B.V. All rights reserved.

Relation between textured surface and diffuse reflectance of Cu films

NASA Astrophysics Data System (ADS)

Shukla, Gaurav; Angappane, S.

2018-04-01

Cu nanostructures namely chevron, slanted and vertical posts deposited on Si substrate by glancing angle deposition (GLAD) technique using DC magnetron sputtering are studied to understand the optical reflectance properties of various textures. The X-ray diffraction analysis confirmed the crystalline nature of the different structures of deposited Cu films. The FESEM images confirmed the formation of chevron, slanted and vertical posts. From the optical reflectance spectra, we found that the reflectance is more for chevron than vertical and slanted posts which have almost the same reflectance over the entire wavelength. The films with chevron texture would find various applications, like, light detector, light trapping, sensors etc.

Synthesis of Cu/CuO nanoparticles in mesoporous material by solid state reaction

NASA Astrophysics Data System (ADS)

Sohrabnezhad, Sh.; Valipour, A.

2013-10-01

The Mobil Composition of Matter No. 41 (MCM-41) containing 1.0 and 5.0 wt.% of Cu was synthesized under solid state reaction. The calcinations of samples were done at two different temperatures, 500 and 300 °C. X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM) were used for samples characterization. Powder X-ray diffraction showed that when Cu(CH3COO)2 content is about 1.0 wt.% in Cu/MCM-41, the guest CuO-NPs and copper ions is formed on the silica channel wall, and more exists in the crystalline state. When Cu(CH3COO)2 content exceeds this value (5.0 wt.%), CuO nanoparticles and Cu2+ ions can be observed in low crystalline state. From the diffuse reflectance spectra it was confirmed that 5 wt.% Cu/MCM-41 sample calcined at 500 °C show plasmon resonance band due to Cu nanoparticles in the range between 500 and 600 nm and small copper clusters Cun in 450 nm. It also shows that some of the Cu2+ ions are present octahedrally in extraframework position in all samples. Both fourier transform infrared and diffuse reflectance spectra indicate that some of Cu2+ ions are tetrahedrally within the framework position in 1 wt.% Cu/MCM-41 samples. TEM images indicated that nanoparticles size of CuO is in range of 30-40 nm.

Differentiating pediatric epileptic brain tissue from normal brain tissue by using time-dependent diffuse reflectance spectroscopy in vivo: comprehensive data analysis method in the time domain

NASA Astrophysics Data System (ADS)

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

2009-05-01

This research investigated the feasibility of using time-dependent diffuse reflectance spectroscopy to differentiate pediatric epileptic brain tissue from normal brain tissue. The optical spectroscopic technique monitored the dynamic optical properties of the cerebral cortex that are associated with its physiological, morphological, and compositional characteristics. Due to the transient irregular epileptic discharge activity within the epileptic brain tissue it was hypothesized that the lesion would express abnormal dynamic optical behavior that would alter normal dynamic behavior. Thirteen pediatric epilepsy patients and seven pediatric brain tumor patients (normal controls) were recruited for this clinical study. Dynamic optical properties were obtained from the cortical surface intraoperatively using a timedependent diffuse reflectance spectroscopy system. This system consisted of a fiber-optic probe, a tungsten-halogen light source, and a spectrophotometer. It acquired diffuse reflectance spectra with a spectral range of 204 nm to 932 nm at a rate of 33 spectra per second for approximately 12 seconds. Biopsy samples were taken from electrophysiologically abnormal cortex and evaluated by a neuropathologist, which served as a gold standard for lesion classification. For data analysis, spectral intensity changes of diffuse reflectance in the time domain at two different wavelengths from each investigated site were compared. Negative correlation segment, defined by the periods where the intensity changes at the two wavelengths were opposite in their slope polarity, were extracted. The total duration of negative correlation, referred to as the "negative correlation time index", was calculated by integrating the negative correlation segments. The negative correlation time indices from all investigated sites were sub-grouped according to the corresponding histological classifications. The difference between the mean indices of two subgroups was evaluated by standard t-test. These comparison and calculation procedures were carried out for all possible wavelength combinations between 400 nm and 800 nm with 2 nm increments. The positive group consisted of seven pathologically abnormal test sites, and the negative group consisted of 13 normal test sites from non-epileptic tumor patients. A standard t-test showed significant difference between negative correlation time indices from the two groups at the wavelength combinations of 700-760 nm versus 550-580 nm. An empirical discrimination algorithm based on the negative correlation time indices in this range produced 100% sensitivity and 85% specificity. Based on these results time-dependent diffuse reflectance spectroscopy with optimized data analysis methods differentiates epileptic brain tissue from normal brain tissue adequately, therefore can be utilized for surgical guidance, and may enhance the surgical outcome of pediatric epilepsy surgery.

Microcirculation assessment using an individualized model for diffuse reflectance spectroscopy and conventional laser Doppler flowmetry

NASA Astrophysics Data System (ADS)

Strömberg, Tomas; Karlsson, Hanna; Fredriksson, Ingemar; Nyström, Fredrik H.; Larsson, Marcus

2014-05-01

Microvascular assessment would benefit from co-registration of blood flow and hemoglobin oxygenation dynamics during stimulus response tests. We used a fiber-optic probe for simultaneous recording of white light diffuse reflectance (DRS; 475-850 nm) and laser Doppler flowmetry (LDF; 780 nm) spectra at two source-detector distances (0.4 and 1.2 mm). An inverse Monte Carlo algorithm, based on a multiparameter three-layer adaptive skin model, was used for analyzing DRS data. LDF spectra were conventionally processed for perfusion. The system was evaluated on volar forearm recordings of 33 healthy subjects during a 5-min systolic occlusion protocol. The calibration scheme and the optimal adaptive skin model fitted DRS spectra at both distances within 10%. During occlusion, perfusion decreased within 5 s while oxygenation decreased slowly (mean time constant 61 s dissociation of oxygen from hemoglobin). After occlusion release, perfusion and oxygenation increased within 3 s (inflow of oxygenized blood). The increased perfusion was due to increased blood tissue fraction and speed. The supranormal hemoglobin oxygenation indicates a blood flow in excess of metabolic demands. In conclusion, by integrating DRS and LDF in a fiber-optic probe, a powerful tool for assessment of blood flow and oxygenation in the same microvascular bed has been presented.

Microcirculation assessment using an individualized model for diffuse reflectance spectroscopy and conventional laser Doppler flowmetry.

PubMed

Strömberg, Tomas; Karlsson, Hanna; Fredriksson, Ingemar; Nyström, Fredrik H; Larsson, Marcus

2014-05-01

Microvascular assessment would benefit from co-registration of blood flow and hemoglobin oxygenation dynamics during stimulus response tests. We used a fiber-optic probe for simultaneous recording of white light diffuse reflectance (DRS; 475-850 nm) and laser Doppler flowmetry (LDF; 780 nm) spectra at two source-detector distances (0.4 and 1.2 mm). An inverse Monte Carlo algorithm, based on a multiparameter three-layer adaptive skin model, was used for analyzing DRS data. LDF spectra were conventionally processed for perfusion. The system was evaluated on volar forearm recordings of 33 healthy subjects during a 5-min systolic occlusion protocol. The calibration scheme and the optimal adaptive skin model fitted DRS spectra at both distances within 10%. During occlusion, perfusion decreased within 5 s while oxygenation decreased slowly (mean time constant 61 s; dissociation of oxygen from hemoglobin). After occlusion release, perfusion and oxygenation increased within 3 s (inflow of oxygenized blood). The increased perfusion was due to increased blood tissue fraction and speed. The supranormal hemoglobin oxygenation indicates a blood flow in excess of metabolic demands. In conclusion, by integrating DRS and LDF in a fiber-optic probe, a powerful tool for assessment of blood flow and oxygenation in the same microvascular bed has been presented.

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.

Determining Reflectance Spectra of Surfaces and Clouds on Exoplanets

NASA Astrophysics Data System (ADS)

Cowan, Nicolas B.; Strait, Talia E.

2013-03-01

Planned missions will spatially resolve temperate terrestrial planets from their host star. Although reflected light from such a planet encodes information about its surface, it has not been shown how to establish surface characteristics of a planet without assuming known surfaces to begin with. We present a reanalysis of disk-integrated, time-resolved, multiband photometry of Earth obtained by the Deep Impact spacecraft as part of the EPOXI Mission of Opportunity. We extract reflectance spectra of clouds, ocean, and land without a priori knowledge of the numbers or colors of these surfaces. We show that the inverse problem of extracting surface spectra from such data is a novel and extreme instance of spectral unmixing, a well-studied problem in remote sensing. Principal component analysis is used to determine an appropriate number of model surfaces with which to interpret the data. Shrink-wrapping a simplex to the color excursions of the planet yields a conservative estimate of the planet's endmember spectra. The resulting surface maps are unphysical, however, requiring negative or larger-than-unity surface coverage at certain locations. Our "rotational unmixing" supersedes the endmember analysis by simultaneously solving for the surface spectra and their geographical distributions on the planet, under the assumption of diffuse reflection and known viewing geometry. We use a Markov Chain Monte Carlo to determine best-fit parameters and their uncertainties. The resulting albedo spectra are similar to clouds, ocean, and land seen through a Rayleigh-scattering atmosphere. This study suggests that future direct-imaging efforts could identify and map unknown surfaces and clouds on exoplanets.

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.

Optical property analysis of thermally and photolytically aged Eucalyptus Camaldulensis chemithermomechanical pulp (CTMP)

Treesearch

Yao Chen; Yongming Fan; Mandla A. Tshabalala; Nicole M. Stark; Jianmin Gao

2012-01-01

To investigate the optical properties of chemithermomechanical pulp (CTMP) from Eucalyptus camaldulensis, one group of samples of CTMP was aged by heating, and another group was first subjected to bleaching with different bleaching agents, and then aging by exposure to sunlight. Chromophores were analyzed using diffuse reflectance UV-Vis spectra (...

A novel combined approach of diffuse reflectance UV-Vis-NIR spectroscopy and multivariate analysis for non-destructive examination of blue ballpoint pen inks in forensic application

NASA Astrophysics Data System (ADS)

Kumar, Raj; Sharma, Vishal

2017-03-01

The present research is focused on the analysis of writing inks using destructive UV-Vis spectroscopy (dissolution of ink by the solvent) and non-destructive diffuse reflectance UV-Vis-NIR spectroscopy along with Chemometrics. Fifty seven samples of blue ballpoint pen inks were analyzed under optimum conditions to determine the differences in spectral features of inks among same and different manufacturers. Normalization was performed on the spectroscopic data before chemometric analysis. Principal Component Analysis (PCA) and K-mean cluster analysis were used on the data to ascertain whether the blue ballpoint pen inks could be differentiated by their UV-Vis/UV-Vis NIR spectra. The discriminating power is calculated by qualitative analysis by the visual comparison of the spectra (absorbance peaks), produced by the destructive and non-destructive methods. In the latter two methods, the pairwise comparison is made by incorporating the clustering method. It is found that chemometric method provides better discriminating power (98.72% and 99.46%, in destructive and non-destructive, respectively) in comparison to the qualitative analysis (69.67%).

Controlled Synthesis and Photocatalytic Antifouling Properties of BiVO4 with Tunable Morphologies

NASA Astrophysics Data System (ADS)

Xiang, Zhenbo; Wang, Yi; Ju, Peng; Zhang, Dun

2017-02-01

Monoclinic BiVO4 with different nanostructures were prepared via a facile and rapid route by adding different surfactants. Ethylenediaminetetraacetic acid, polyvinylpyrrolidone, and sodium dodecyl sulfate surfactants were selected as morphology controlling agents. The crystal phase, morphology, and diffuse reflectance spectra of BiVO4 were characterized by x-ray diffraction, scanning electron microscopy, and UV-visible diffuse reflectance spectra techniques, respectively. The photocatalytic activities of BiVO4 were investigated by killing the typical marine fouling bacteria Pseudomonas aeruginosa ( P. aeruginosa) under visible light irradiation. BiVO4 with grape-like nanostructure exhibited the best photocatalytic bactericidal activity. The sterilization rate of P. aeruginosa could reach up to 99.9% in 120 min. The photocatalytic mechanism was studied by captive species trapping experiments. The result revealed that photogenerated hole (h+) is the main reactive specie for killing P. aeruginosa under visible light irradiation. In addition, after five recycles, BiVO4 does not exhibit significant loss of photocatalytic sterilization activity. The results confirm that the synthesized BiVO4 photocatalyst has long-time reusability and good photocatalytic stability.

Change of optical properties of the breast tissues under the influence of pharmacological agents

NASA Astrophysics Data System (ADS)

Naumov, Sergey A.; Vovk, Sergey M.; Pushkarev, Sergey V.; Volovodenko, Vitaly A.

2001-05-01

The influence of vasoactive pharmacological agents (VPhA) on the spectral characteristics of the breast tissues in vivo has been studied. The effect of adrenaline and its antagonist dibazole on the character of diffuse reflection spectra of the breast registered during puncture biopsy were investigated. Adrenaline and dibazole were injected both locally, i.e. to the examined breast tissue and subcutaneously to the shoulder. The choice of this or that VPhA was caused by the functional condition of an examinee. It has been shown that the main functional units of the stroma of parenchymatous organs and their tumors responsible for the state of spectral characteristics in vivo are considered to be the vessels. The cancerous tissue has a lesser pronounced response compared to the normal one that is indicative of the functional inferiority of the tumor vessels and it is confirmed by the results of morphological examinations including the ultrastructural level. Thus, using VPhA it is possible to have an influence on characteristics of diffuse reflection spectra of the examined tissues in vivo and make diagnostics more effectively.

Reflectance spectrometry of placental vessels in cases of twin-twin transfusion syndrome: experiments and modeling

NASA Astrophysics Data System (ADS)

Lines, Collin; Kim, Oleg; McMurdy, John; Luks, Francois; Alber, Mark; Crawford, Greg

2013-03-01

A stochastic photon transport model in multilayer skin tissue combined with reflectance spectroscopy measurements is used to study placental vessels in cases of twin-twin transfusion syndrome (TTTS). TTTS occurs in about 12% of monozygotic (identical) twin pregnancies wherein flow within placental vessels linking the twins together becomes unbalanced, leading to dual mortality. Endoscopic laser ablation can halt the syndrome by occluding the anastomoses connecting the two fetuses. The objective of this study is to develop a technique to determine hemoglobin (Hb) content through spectral analysis of diffuse reflectance spectra of placental vessels to aid in identification of the anastomoses. Previous work by researchers at Brown University has shown that the reflectance spectra of the donor twin and recipient twin are considerably different in the wavelengths for Hb absorbance. This presentation will give preliminary results for a Monte Carlo model adapted to fit the physiology of the placenta that can be used to quantitative determine the Hb levels. The reflectance spectra of the vessels are simulated for different values of Hb as well oxygenation and water concentration with the vessel and placental mass. The preliminary results will be shown to be in good approximation with the prior experimental data. The combination of modeling with spectroscopic measurement will provide a new tool for detailed prenatal study.

Fluorescence spectral properties of stomach tissues with pathology

NASA Astrophysics Data System (ADS)

Giraev, K. M.; Ashurbekov, N. A.; Lahina, M. A.

2012-05-01

Steady-state fluorescence and diffuse reflection spectra are measured for in vivo normal and pathological (chronic atrophic and ulcerating defects, malignant neoplasms) stomach mucous lining tissues. The degree of distortion of the fluorescence spectra is estimated taking light scattering and absorption into account. A combination of Gauss and Lorentz functions is used to decompose the fluorescence spectra. Potential groups of fluorophores are determined and indices are introduced to characterize the dynamics of their contributions to the resultant spectra as pathologies develop. Reabsorption is found to quench the fluorescence of structural proteins by as much as a factor of 3, while scattering of the light can increase the fluorescence intensity of flavin and prophyrin groups by as much as a factor of 2.

Microscopic video observation of capillary vessel systems using diffuse back lighting

NASA Astrophysics Data System (ADS)

Sakai, Minako; Arai, Hiroki; Iwai, Toshiaki

2017-04-01

We have been developing a simple and practical video microscopy system based on absorption spectra of biological substance to perform spectroscopic observation of living tissues. The diffuse backlighting effect is actively used in the developed system, which is generated by multiple light scattering in the tissue. It is demonstrated that the light specularly reflected from the skin surface can be completely suppressed in the microscopic observation and the biological activity of the capillary vessel systems distributed under the skin can be successfully observed. As a result, we can confirm the effectiveness of the video microscopy system using diffuse backlighting and the applicability of our developed system.

Autofluorescence and diffuse reflectance patterns in cervical spectroscopy

NASA Astrophysics Data System (ADS)

Marin, Nena Maribel

Fluorescence and diffuse reflectance spectroscopy are two new optical technologies, which have shown promise to aid in the real time, non-invasive identification of cancers and precancers. Spectral patterns carry a fingerprint of scattering, absorption and fluorescence properties in tissue. Scattering, absorption and fluorescence in tissue are directly affected by biological features that are diagnostically significant, such as nuclear size, micro-vessel density, volume fraction of collagen fibers, tissue oxygenation and cell metabolism. Thus, analysis of spectral patterns can unlock a wealth of information directly related with the onset and progression of disease. Data from a Phase II clinical trial to assess the technical efficacy of fluorescence and diffuse reflectance spectroscopy acquired from 850 women at three clinical locations with two research grade optical devices is calibrated and analyzed. Tools to process and standardize spectra so that data from multiple spectrometers can be combined and analyzed are presented. Methodologies for calibration and quality assurance of optical systems are established to simplify design issues and ensure validity of data for future clinical trials. Empirically based algorithms, using multivariate statistical approaches are applied to spectra and evaluated as a clinical diagnostic tool. Physically based algorithms, using mathematical models of light propagation in tissue are presented. The presented mathematical model combines a diffusion theory in P3 approximation reflectance model and a 2-layer fluorescence model using exponential attenuation and diffusion theory. The resulting adjoint fluorescence and reflectance model extracts twelve optical properties characterizing fluorescence efficiency of cervical epithelium and stroma fluorophores, stromal hemoglobin and collagen absorption, oxygen saturation, and stromal scattering strength and shape. Validations with Monte Carlo simulations show that adjoint model extracted optical properties of the epithelium and the stroma can be estimated accurately. Adjoint model is applied to 926 clinical measurements from 503 patients. Mean values of extracted optical properties have demonstrated to characterize the biological changes associated with dysplastic progression. Finally, penalized logistic regression algorithms are applied to discriminate dysplastic stages in tissue based on extracted optical features. This work provides understandable and interpretable information regarding predictive and generalization ability of optical spectroscopy in neoplastic changes using a minimum subset of optical measurements. Ultimately these methodologies would facilitate the transfer of these optical technologies into clinical practice.

An intercomparison of methods for solving the stochastic collection equation with a focus on cloud radar Doppler spectra in drizzling stratocumulus

NASA Astrophysics Data System (ADS)

Lee, H.; Fridlind, A. M.; Ackerman, A. S.; Kollias, P.

2017-12-01

Cloud radar Doppler spectra provide rich information for evaluating the fidelity of particle size distributions from cloud models. The intrinsic simplifications of bulk microphysics schemes generally preclude the generation of plausible Doppler spectra, unlike bin microphysics schemes, which develop particle size distributions more organically at substantial computational expense. However, bin microphysics schemes face the difficulty of numerical diffusion leading to overly rapid large drop formation, particularly while solving the stochastic collection equation (SCE). Because such numerical diffusion can cause an even greater overestimation of radar reflectivity, an accurate method for solving the SCE is essential for bin microphysics schemes to accurately simulate Doppler spectra. While several methods have been proposed to solve the SCE, here we examine those of Berry and Reinhardt (1974, BR74), Jacobson et al. (1994, J94), and Bott (2000, B00). Using a simple box model to simulate drop size distribution evolution during precipitation formation with a realistic kernel, it is shown that each method yields a converged solution as the resolution of the drop size grid increases. However, the BR74 and B00 methods yield nearly identical size distributions in time, whereas the J94 method produces consistently larger drops throughout the simulation. In contrast to an earlier study, the performance of the B00 method is found to be satisfactory; it converges at relatively low resolution and long time steps, and its computational efficiency is the best among the three methods considered here. Finally, a series of idealized stratocumulus large-eddy simulations are performed using the J94 and B00 methods. The reflectivity size distributions and Doppler spectra obtained from the different SCE solution methods are presented and compared with observations.

A study of muscular tissue of animal origin by reflection-spectroscopy methods

NASA Astrophysics Data System (ADS)

Plotnikova, L. V.; Nechiporenko, A. P.; Orekhova, S. M.; Plotnikov, P. P.; Ishevskii, A. L.

2017-06-01

A comparative analysis of the spectral characteristics of the surface of muscular tissue of animal origin (pork) and its main components has been performed by the methods of diffuse reflection electronic spectroscopy (DRES) and frustrated total internal reflection IR spectroscopy. The experiments have shown that the application of the DRES method makes it possible to detect more pronounced changes in the surface optical characteristics of muscular tissue and obtain electronic spectra containing information about the component composition of its main parts under successive extraction of sarcoplasmic materials, myofibrillar proteins of the actomyosin complex, and stroma mucopolysaccharides.

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.

[Study on brand traceability of vinegar based on near infrared spectroscopy technology].

PubMed

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

2014-09-01

In the present paper, 152 vinegar samples with four different brands were chosen as research targets, and their near infrared spectra were collected by diffusion reflection mode and transmission mode, respectively. Furthermore, the brand traceability models for edible vinegar were constructed. The effects of the collection mode and pretreatment methods of spectrum on the precision of traceability models were investigated intensively. The models constructed by PLS1-DA modeling method using spectrum data of 114 training samples were applied to predict 38 test samples, and R2, RMSEC and RMSEP of the model based on transmission mode data were 0.92, 0.113 and 0.127, respectively, with recognition rate of 76.32%, and those based on diffusion reflection mode data were 0.97, 0.102 and 0.119, with recognition rate of 86.84%. The results demonstrated that the near infrared spectrum combined with PLS1-DA can be used to establish the brand traceability models for edible vinegar, and diffuse reflection mode is more beneficial for predictive ability of the model.

Portable laser-induced breakdown spectroscopy/diffuse reflectance hybrid spectrometer for analysis of inorganic pigments

NASA Astrophysics Data System (ADS)

Siozos, Panagiotis; Philippidis, Aggelos; Anglos, Demetrios

2017-11-01

A novel, portable spectrometer, combining two analytical techniques, laser-induced breakdown spectroscopy (LIBS) and diffuse reflectance spectroscopy, was developed with the aim to provide an enhanced instrumental and methodological approach with regard to the analysis of pigments in objects of cultural heritage. Technical details about the hybrid spectrometer and its operation are presented and examples are given relevant to the analysis of paint materials. Both LIBS and diffuse reflectance spectra in the visible and part of the near infrared, corresponding to several neat mineral pigment samples, were recorded and the complementary information was used to effectively distinguish different types of pigments even if they had similar colour or elemental composition. The spectrometer was also employed in the analysis of different paints on the surface of an ancient pottery sherd demonstrating the capabilities of the proposed hybrid diagnostic approach. Despite its instrumental simplicity and compact size, the spectrometer is capable of supporting analytical campaigns relevant to archaeological, historical or art historical investigations, particularly when quick data acquisition is required in the context of surveys of large numbers of objects and samples.

[Research on NIR equivalent spectral measurement].

PubMed

Wang, Zhi-Hong; Liu, Jie; Sun, Yu-Yang; Teng, Fei; Lin, Jun

2013-04-01

When the spectra of the diffuse reflectance of low reflectivity samples or the transmittance of low transmisivity samples are measured by a portable near infrared (NIR) spectrometer, because there is the noise of the spectrometer, the smaller the reflectance or transmittance of the sample, the lower its SNR. Even if treated by denoise methods, the spectra can not meet the requirement of NIR analysis. So the equivalent spectrum measure method was researched. Based on the intensity of the reflected or transmitted signal by the sample under the traditional measure conditions, the light current of the spectrometer was enlarged, and then the signal of the measured sample increased; the reflected or transmitted light of the measure reference was reduced to avoid the signal of the measure reference over range. Moreover the equivalent spectrum of the sample was calculated in order to make it identical with the spectrum measured by traditional method. Thus the NIR spectral SNR was improved. The results of theory analysis and experiments show that if the light signal of the spectrometer was properly increased according to the reflected or transmitted signal of the low reflectivity or transmisivity sample, the equivalent spectrum was the same as the spectrum measured by traditional method and its SNR was improved.

Visible and infrared reflectance imaging spectroscopy of paintings: pigment mapping and improved infrared reflectography

NASA Astrophysics Data System (ADS)

Delaney, John K.; Zeibel, Jason G.; Thoury, Mathieu; Littleton, Roy; Morales, Kathryn M.; Palmer, Michael; de la Rie, E. René

2009-07-01

Reflectance imaging spectroscopy, the collection of images in narrow spectral bands, has been developed for remote sensing of the Earth. In this paper we present findings on the use of imaging spectroscopy to identify and map artist pigments as well as to improve the visualization of preparatory sketches. Two novel hyperspectral cameras, one operating from the visible to near-infrared (VNIR) and the other in the shortwave infrared (SWIR), have been used to collect diffuse reflectance spectral image cubes on a variety of paintings. The resulting image cubes (VNIR 417 to 973 nm, 240 bands, and SWIR 970 to 1650 nm, 85 bands) were calibrated to reflectance and the resulting spectra compared with results from a fiber optics reflectance spectrometer (350 to 2500 nm). The results show good agreement between the spectra acquired with the hyperspectral cameras and those from the fiber reflectance spectrometer. For example, the primary blue pigments and their distribution in Picasso's Harlequin Musician (1924) are identified from the reflectance spectra and agree with results from X-ray fluorescence data and dispersed sample analysis. False color infrared reflectograms, obtained from the SWIR hyperspectral images, of extensively reworked paintings such as Picasso's The Tragedy (1903) are found to give improved visualization of changes made by the artist. These results show that including the NIR and SWIR spectral regions along with the visible provides for a more robust identification and mapping of artist pigments than using visible imaging spectroscopy alone.

The effect of an external mechanical compression on in vivo optical properties of human skin

NASA Astrophysics Data System (ADS)

Nakhaeva, I. A.; Mohammed, M. R.; Zyuryukina, O. A.; Sinichkin, Yu. P.

2014-09-01

We have studied the influence of an external mechanical compression on diffuse reflection spectra of skin tissue under in vivo conditions. An analysis of these spectra based on the diffusion approximation of the radiation transfer theory has allowed us to find that the application of the external compression weakens absorbing and scattering properties of skin tissue. After the removal of the compression, the recovery time of the skin tissue (on the order of 1 h) considerably exceeds the stabilization time of its parameters after application of external mechanical compression (several minutes). In this case, at the initial moment of time after the removal of the compression, the fullness of blood vessels and the degree of oxygenation of blood hemoglobin in the skin tissue increase considerably compared to normal skin.

Effect of fusion mixture treatment on the surface of low grade natural ruby

NASA Astrophysics Data System (ADS)

Sakthivel, R.; Pradhan, K. C.; Nayak, B. B.; Dash, Tapan; Sahu, R. K.; Mishra, B. K.

2017-05-01

Improvement in aesthetic look of low grade natural ruby (gemstone) surface was clearly evident after fusion mixture treatment. Surface impurities of the gemstone were significantly reduced to give it a face lift. The processing consists of heat treatment (1000 °C) of the raw gemstone with fusion mixture (sodium and potassium carbonates), followed by hydrochloric acid digestion (90 °C) and ultrasonic cleaning.Both the untreated and the treated gemstone were characterized by X-ray diffraction, UV-vis spectroscopy (diffuse reflectance),photoluminescence and X-ray photoelectron spectroscopy. The paper consolidates the results of these studies and presents the effect of the typical chemical treatment (stated above) on the low grade natural ruby. While X-ray diffraction study identifies the occurrence of alumina phase in both the treated and the untreated gemstones, the UV-vis spectra exhibit strong characteristic absorption of Cr3+at 400 and 550 nm wavelength for the treated gemstone in contrast to weak absorption observed for the untreated gemstone at such wavelengths, thus showing the beneficial effect of fusion mixture treatment. Peaks observed for the gemstone (for both treated and untreated samples) in the excitation spectra of photoluminescence show a good correlation with observed UV-vis (diffuse reflectance) spectra. Photoluminescence emission spectra of the untreated gemstone show characteristic emission at 695 nm for Cr3+ ion (as in alumina matrix), but its emission intensity significantly reduces after fusion mixture treatment. It is found that the surface of the fusion mixture treated ruby gemstone looks much brighter than the corresponding untreated surface.

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

Design and fabrication of SiO2/TiO2 and MgO/TiO2 based high selective optical filters for diffuse reflectance and fluorescence signals extraction.

PubMed

Pimenta, S; Cardoso, S; Miranda, A; De Beule, P; Castanheira, E M S; Minas, G

2015-08-01

This paper presents the design, optimization and fabrication of 16 MgO/TiO2 and SiO2/TiO2 based high selective narrow bandpass optical filters. Their performance to extract diffuse reflectance and fluorescence signals from gastrointestinal tissue phantoms was successfully evaluated. The obtained results prove their feasibility to correctly extract those spectroscopic signals, through a Spearman's rank correlation test (Spearman's correlation coefficient higher than 0.981) performed between the original spectra and the ones obtained using those 16 fabricated optical filters. These results are an important step for the implementation of a miniaturized, low-cost and minimal invasive microsystem that could help in the detection of gastrointestinal dysplasia.

Spectral diffusion in poly(para-phenylene)-type polymers with different energetic disorder

NASA Astrophysics Data System (ADS)

Hoffmann, Sebastian T.; Bässler, Heinz; Koenen, Jan-Moritz; Forster, Michael; Scherf, Ullrich; Scheler, Esther; Strohriegl, Peter; Köhler, Anna

2010-03-01

We have employed quasicontinuous fluorescence and phosphorescence spectroscopy within a temperature range between 10 and 500 K to monitor the spectral diffusion of singlet and triplet excitons in a series of π -conjugated polymers. We investigated (i) how spectral diffusion is controlled by the degree of energetic disorder present in the amorphous film (that is reflected by the inhomogeneous broadening of the photoluminescence spectra) and (ii) how this process depends on the range of the electronic coupling (by comparing singlet exciton diffusion via long-range Förster transfer against triplet exciton diffusion by short-range Dexter transfer). For singlets, we find that the fluorescence spectra bear out a bathochromic shift upon cooling the sample down to a critical temperature below which the shift saturates. This bathochromic shift is a signature of spectral relaxation. Random-walk theory applied to excitation transport within a Gaussian density-of-states distribution is both necessary and sufficient to rationalize the experimental results in a quantitative fashion. The same behavior is observed for triplets in weakly disordered systems, such as in a polymer containing platinum in the main chain and a ladder-type polyphenylene. In contrast we observe a hypsochromic shift of the phosphorescence spectra below a characteristic temperature for triplets in systems with at least moderate energetic disorder. The hypsochromic shift proves that triplet exciton relaxation becomes frustrated because thermally activated exciton jumps that otherwise promote spectral diffusion become progressively frozen out. The frustration effect is controlled by the jump distance and thus it is specific for triplet excitations that migrate via short-range coupling among strongly localized states as compared to singlet excitons.

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.

Regional calibration models for predicting loblolly pine tracheid properties using near-infrared spectroscopy

Treesearch

Mohamad Nabavi; Joseph Dahlen; Laurence Schimleck; Thomas L. Eberhardt; Cristian Montes

2018-01-01

This study developed regional calibration models for the prediction of loblolly pine (Pinus taeda) tracheid properties using near-infrared (NIR) spectroscopy. A total of 1842 pith-to-bark radial strips, aged 19–31 years, were acquired from 268 trees from 109 stands across the southeastern USA. Diffuse reflectance NIR spectra were collected at 10-mm...

Diffuse reflectance spectroscopy as a tool for real-time tissue assessment during colorectal cancer surgery

NASA Astrophysics Data System (ADS)

Baltussen, Elisabeth J. M.; Snaebjornsson, Petur; de Koning, Susan G. Brouwer; Sterenborg, Henricus J. C. M.; Aalbers, Arend G. J.; Kok, Niels; Beets, Geerard L.; Hendriks, Benno H. W.; Kuhlmann, Koert F. D.; Ruers, Theo J. M.

2017-10-01

Colorectal surgery is the standard treatment for patients with colorectal cancer. To overcome two of the main challenges, the circumferential resection margin and postoperative complications, real-time tissue assessment could be of great benefit during surgery. In this ex vivo study, diffuse reflectance spectroscopy (DRS) was used to differentiate tumor tissue from healthy surrounding tissues in patients with colorectal neoplasia. DRS spectra were obtained from tumor tissue, healthy colon, or rectal wall and fat tissue, for every patient. Data were randomly divided into training (80%) and test (20%) sets. After spectral band selection, the spectra were classified using a quadratic classifier and a linear support vector machine. Of the 38 included patients, 36 had colorectal cancer and 2 had an adenoma. When the classifiers were applied to the test set, colorectal cancer could be discriminated from healthy tissue with an overall accuracy of 0.95 (±0.03). This study demonstrates the possibility to separate colorectal cancer from healthy surrounding tissue by applying DRS. High classification accuracies were obtained both in homogeneous and inhomogeneous tissues. This is a fundamental step toward the development of a tool for real-time in vivo tissue assessment during colorectal surgery.

Modeling and measuring extravascular hemoglobin: aging contusions

NASA Astrophysics Data System (ADS)

Lines, Collin; Kim, Oleg; Duffy, Susan; Alber, Mark; Crawford, Gregory P.

2011-07-01

Medical expertise is frequently elicited to aid in determining the age and the cause of the trauma or injury. Child protection and law enforcement frequently rely on the physical assessment of the trauma which involves delineating intentional from unintentional types of trauma. Recent studies have shown that current methods to assess the age of traumatic injuries are highly inaccurate and do not give reasonable predictions. Hemoglobin is one of the strongest chromophores in human tissues. Transport of hemoglobin and its breakdown products in tissue determines the spectrophotometric characteristics of the skin and its variations in time. Therefore, measurements of diffuse reflective spectra of the skin allow noninvasive screening. This paper reviews potential transmission and diffusive reflection spectroscopy based techniques and predictive and quantitative modeling methods assisting in efficient retrieval of the age of extravascular contusions. This paper then presents a novel Monte Carlo technique for 3D photon tracking and blood transport model. In future studies, clinically obtained spectra will be used to validate the model as well as fine-tune coefficients for absorption. It is the goal of this study to develop a model that would allow a non-invasive, accurate determination of the age of a bruise.

A novel combined approach of diffuse reflectance UV-Vis-NIR spectroscopy and multivariate analysis for non-destructive examination of blue ballpoint pen inks in forensic application.

PubMed

Kumar, Raj; Sharma, Vishal

2017-03-15

The present research is focused on the analysis of writing inks using destructive UV-Vis spectroscopy (dissolution of ink by the solvent) and non-destructive diffuse reflectance UV-Vis-NIR spectroscopy along with Chemometrics. Fifty seven samples of blue ballpoint pen inks were analyzed under optimum conditions to determine the differences in spectral features of inks among same and different manufacturers. Normalization was performed on the spectroscopic data before chemometric analysis. Principal Component Analysis (PCA) and K-mean cluster analysis were used on the data to ascertain whether the blue ballpoint pen inks could be differentiated by their UV-Vis/UV-Vis NIR spectra. The discriminating power is calculated by qualitative analysis by the visual comparison of the spectra (absorbance peaks), produced by the destructive and non-destructive methods. In the latter two methods, the pairwise comparison is made by incorporating the clustering method. It is found that chemometric method provides better discriminating power (98.72% and 99.46%, in destructive and non-destructive, respectively) in comparison to the qualitative analysis (69.67%). Copyright © 2016 Elsevier B.V. All rights reserved.

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.

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.

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

Multi-spectral imaging of oxygen saturation

NASA Astrophysics Data System (ADS)

Savelieva, Tatiana A.; Stratonnikov, Aleksander A.; Loschenov, Victor B.

2008-06-01

The system of multi-spectral imaging of oxygen saturation is an instrument that can record both spectral and spatial information about a sample. In this project, the spectral imaging technique is used for monitoring of oxygen saturation of hemoglobin in human tissues. This system can be used for monitoring spatial distribution of oxygen saturation in photodynamic therapy, surgery or sports medicine. Diffuse reflectance spectroscopy in the visible range is an effective and extensively used technique for the non-invasive study and characterization of various biological tissues. In this article, a short review of modeling techniques being currently in use for diffuse reflection from semi-infinite turbid media is presented. A simple and practical model for use with a real-time imaging system is proposed. This model is based on linear approximation of the dependence of the diffuse reflectance coefficient on relation between absorbance and reduced scattering coefficient. This dependence was obtained with the Monte Carlo simulation of photon propagation in turbid media. Spectra of the oxygenated and deoxygenated forms of hemoglobin differ mostly in the red area (520 - 600 nm) and have several characteristic points there. Thus four band-pass filters were used for multi-spectral imaging. After having measured the reflectance, the data obtained are used for fitting the concentration of oxygenated and free hemoglobin, and hemoglobin oxygen saturation.

Detection of cervical lesions by multivariate analysis of diffuse reflectance spectra: a clinical study.

PubMed

Prabitha, Vasumathi Gopala; Suchetha, Sambasivan; Jayanthi, Jayaraj Lalitha; Baiju, Kamalasanan Vijayakumary; Rema, Prabhakaran; Anuraj, Koyippurath; Mathews, Anita; Sebastian, Paul; Subhash, Narayanan

2016-01-01

Diffuse reflectance (DR) spectroscopy is a non-invasive, real-time, and cost-effective tool for early detection of malignant changes in squamous epithelial tissues. The present study aims to evaluate the diagnostic power of diffuse reflectance spectroscopy for non-invasive discrimination of cervical lesions in vivo. A clinical trial was carried out on 48 sites in 34 patients by recording DR spectra using a point-monitoring device with white light illumination. The acquired data were analyzed and classified using multivariate statistical analysis based on principal component analysis (PCA) and linear discriminant analysis (LDA). Diagnostic accuracies were validated using random number generators. The receiver operating characteristic (ROC) curves were plotted for evaluating the discriminating power of the proposed statistical technique. An algorithm was developed and used to classify non-diseased (normal) from diseased sites (abnormal) with a sensitivity of 72 % and specificity of 87 %. While low-grade squamous intraepithelial lesion (LSIL) could be discriminated from normal with a sensitivity of 56 % and specificity of 80 %, and high-grade squamous intraepithelial lesion (HSIL) from normal with a sensitivity of 89 % and specificity of 97 %, LSIL could be discriminated from HSIL with 100 % sensitivity and specificity. The areas under the ROC curves were 0.993 (95 % confidence interval (CI) 0.0 to 1) and 1 (95 % CI 1) for the discrimination of HSIL from normal and HSIL from LSIL, respectively. The results of the study show that DR spectroscopy could be used along with multivariate analytical techniques as a non-invasive technique to monitor cervical disease status in real time.

Noninvasive detection of skin cancers by measuring optical properties of tissues

NASA Astrophysics Data System (ADS)

Wang, Lihong V.; Jacques, Steven L.

1995-05-01

Skin cancer is the most frequently occurring cancer of all cancers. Each yea rover 500,000 new cases of skin cancer will be detected. A high percentage of skin cancers are diseases in which fatalities can be all but eliminated and morbidity reduced if detected early and treated properly. These skin lesions are distinguished generally by subjective visual inspection and their definitive diagnosis requires time-consuming expensive histopathological evaluation of excisional or incisional biopsies. In vivo experimental evidence published in the literature has shown that cancerous skin lesions have different total diffuse reflectance spectra than non- cancerous lesions or normal skin. Therefore, cancerous skin lesions may be differentiated from non-cancerous skin lesions by comparing the optical properties of the skin lesions with those of the surrounding normal skin sites, where the optical properties of the normal skin sites are used to account for different types of skin or different areas of skin. We have demonstrated that the effect of melanin concentration on the diffuse reflectance may be removed by extrapolating the reflectance at different wavelengths to an apparent pivot point. Because the concentration of melanin does not indicate malignancy, the removal of its effect is important to avoid false detection. The total diffuse reflectance depends on the albedo and anisotropy of tissues. Therefore, the total diffuse reflectance will remain the same as long as the anisotropy and the ratio between the absorption coefficient and the reduced scattering coefficient remain the same. Separating the absorption and scattering effects should enhance the detection sensitivity of skin cancers.

Spectral reflectance properties (0.4-2.5 um) of secondary Fe-oxide, Fe-hydroxide, and Fe-sulfate-hydrate minerals associated with sulfide-bearing mine waste

USGS Publications Warehouse

Crowley, J.K.; Williams, D.E.; Hammarstrom1, J.M.; Piatak, N.; Mars, J.C.; Chou, I-Ming

2006-01-01

Fifteen Fe-oxide, Fe-hydroxide, and Fe-sulphate-hydrate mineral species commonly associated with sulphide bearing mine wastes were characterized by using X-ray powder diffraction and scanning electron microscope methods. Diffuse reflectance spectra of the samples show diagnostic absorption features related to electronic processes involving ferric and/or ferrous iron, and to vibrational processes involving water and hydroxyl ions. Such spectral features enable field and remote sensing based studies of the mineral distributions. Because secondary minerals are sensitive indicators of pH, Eh, relative humidity, and other environmental conditions, spectral mapping of these minerals promises to have important applications to mine waste remediation studies. This report releases digital (ascii) spectra (spectral_data_files.zip) of the fifteen mineral samples to facilitate usage of the data with spectral libraries and spectral analysis software. The spectral data are provided in a two-column format listing wavelength (in micrometers) and reflectance, respectively.

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.

Portable, Fiber-Based, Diffuse Reflection Spectroscopy (DRS) Systems for Estimating Tissue Optical Properties.

PubMed

Vishwanath, Karthik; Chang, Kevin; Klein, Daniel; Deng, Yu Feng; Chang, Vivide; Phelps, Janelle E; Ramanujam, Nimmi

2011-02-01

Steady-state diffuse reflection spectroscopy is a well-studied optical technique that can provide a noninvasive and quantitative method for characterizing the absorption and scattering properties of biological tissues. Here, we compare three fiber-based diffuse reflection spectroscopy systems that were assembled to create a light-weight, portable, and robust optical spectrometer that could be easily translated for repeated and reliable use in mobile settings. The three systems were built using a broadband light source and a compact, commercially available spectrograph. We tested two different light sources and two spectrographs (manufactured by two different vendors). The assembled systems were characterized by their signal-to-noise ratios, the source-intensity drifts, and detector linearity. We quantified the performance of these instruments in extracting optical properties from diffuse reflectance spectra in tissue-mimicking liquid phantoms with well-controlled optical absorption and scattering coefficients. We show that all assembled systems were able to extract the optical absorption and scattering properties with errors less than 10%, while providing greater than ten-fold decrease in footprint and cost (relative to a previously well-characterized and widely used commercial system). Finally, we demonstrate the use of these small systems to measure optical biomarkers in vivo in a small-animal model cancer therapy study. We show that optical measurements from the simple portable system provide estimates of tumor oxygen saturation similar to those detected using the commercial system in murine tumor models of head and neck cancer.

Evaluation of apparent viscosity of Para rubber latex by diffuse reflection near-infrared spectroscopy.

PubMed

Sirisomboon, Panmanas; Chowbankrang, Rawiphan; Williams, Phil

2012-05-01

Near-infrared spectroscopy in diffuse reflection mode was used to evaluate the apparent viscosity of Para rubber field latex and concentrated latex over the wavelength range of 1100 to 2500 nm, using partial least square regression (PLSR). The model with ten principal components (PCs) developed using the raw spectra accurately predicted the apparent viscosity with correlation coefficient (r), standard error of prediction (SEP), and bias of 0.974, 8.6 cP, and -0.4 cP, respectively. The ratio of the SEP to the standard deviation (RPD) and the ratio of the SEP to the range (RER) for the prediction were 4.4 and 16.7, respectively. Therefore, the model can be used for measurement of the apparent viscosity of field latex and concentrated latex in quality assurance and process control in the factory.

Design and fabrication of SiO2/TiO2 and MgO/TiO2 based high selective optical filters for diffuse reflectance and fluorescence signals extraction

PubMed Central

Pimenta, S.; Cardoso, S.; Miranda, A.; De Beule, P.; Castanheira, E.M.S.; Minas, G.

2015-01-01

This paper presents the design, optimization and fabrication of 16 MgO/TiO2 and SiO2/TiO2 based high selective narrow bandpass optical filters. Their performance to extract diffuse reflectance and fluorescence signals from gastrointestinal tissue phantoms was successfully evaluated. The obtained results prove their feasibility to correctly extract those spectroscopic signals, through a Spearman’s rank correlation test (Spearman’s correlation coefficient higher than 0.981) performed between the original spectra and the ones obtained using those 16 fabricated optical filters. These results are an important step for the implementation of a miniaturized, low-cost and minimal invasive microsystem that could help in the detection of gastrointestinal dysplasia. PMID:26309769

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.

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.

Use of cloud radar Doppler spectra to evaluate stratocumulus drizzle size distributions in large-eddy simulations with size-resolved microphysics

DOE PAGES

Remillard, J.; Fridlind, Ann M.; Ackerman, A. S.; ...

2017-09-20

Here, a case study of persistent stratocumulus over the Azores is simulated using two independent large-eddy simulation (LES) models with bin microphysics, and forward-simulated cloud radar Doppler moments and spectra are compared with observations. Neither model is able to reproduce the monotonic increase of downward mean Doppler velocity with increasing reflectivity that is observed under a variety of conditions, but for differing reasons. To a varying degree, both models also exhibit a tendency to produce too many of the largest droplets, leading to excessive skewness in Doppler velocity distributions, especially below cloud base. Excessive skewness appears to be associated withmore » an insufficiently sharp reduction in droplet number concentration at diameters larger than ~200 μm, where a pronounced shoulder is found for in situ observations and a sharp reduction in reflectivity size distribution is associated with relatively narrow observed Doppler spectra. Effectively using LES with bin microphysics to study drizzle formation and evolution in cloud Doppler radar data evidently requires reducing numerical diffusivity in the treatment of the stochastic collection equation; if that is accomplished sufficiently to reproduce typical spectra, progress toward understanding drizzle processes is likely.« less

Use of cloud radar Doppler spectra to evaluate stratocumulus drizzle size distributions in large-eddy simulations with size-resolved microphysics

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

Remillard, J.; Fridlind, Ann M.; Ackerman, A. S.

Here, a case study of persistent stratocumulus over the Azores is simulated using two independent large-eddy simulation (LES) models with bin microphysics, and forward-simulated cloud radar Doppler moments and spectra are compared with observations. Neither model is able to reproduce the monotonic increase of downward mean Doppler velocity with increasing reflectivity that is observed under a variety of conditions, but for differing reasons. To a varying degree, both models also exhibit a tendency to produce too many of the largest droplets, leading to excessive skewness in Doppler velocity distributions, especially below cloud base. Excessive skewness appears to be associated withmore » an insufficiently sharp reduction in droplet number concentration at diameters larger than ~200 μm, where a pronounced shoulder is found for in situ observations and a sharp reduction in reflectivity size distribution is associated with relatively narrow observed Doppler spectra. Effectively using LES with bin microphysics to study drizzle formation and evolution in cloud Doppler radar data evidently requires reducing numerical diffusivity in the treatment of the stochastic collection equation; if that is accomplished sufficiently to reproduce typical spectra, progress toward understanding drizzle processes is likely.« less

The Shell Seeker: What Is the Quantity of Shell in the Lido di Venezia Sand? A Calibration DRIFTS Experiment

ERIC Educational Resources Information Center

Pezzolo, Alessandra De Lorenzi

2011-01-01

In this experiment, students are given a fanciful application of the standard addition method to evaluate the approximate quantity of the shell component in a sample of sand collected on the Lido di Venezia seashore. Several diffuse reflectance infrared Fourier transform (DRIFT) spectra are recorded from a sand sample before and after addition of…

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.

Optical properties of human colon tissues in the 350 – 2500 nm spectral range

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

Bashkatov, A N; Genina, E A; Kochubey, V I

2014-08-31

We present the optical characteristics of the mucosa and submucosa of human colon tissue. The experiments are performed in vitro using a LAMBDA 950 spectrophotometer in the 350 – 2500 nm spectral range. The absorption and scattering coefficients and the scattering anisotropy factor are calculated based on the measured diffuse reflectance and total and collimated transmittance spectra using the inverse Monte Carlo method. (laser biophotonics)

Inverse Monte Carlo method in a multilayered tissue model for diffuse reflectance spectroscopy

NASA Astrophysics Data System (ADS)

Fredriksson, Ingemar; Larsson, Marcus; Strömberg, Tomas

2012-04-01

Model based data analysis of diffuse reflectance spectroscopy data enables the estimation of optical and structural tissue parameters. The aim of this study was to present an inverse Monte Carlo method based on spectra from two source-detector distances (0.4 and 1.2 mm), using a multilayered tissue model. The tissue model variables include geometrical properties, light scattering properties, tissue chromophores such as melanin and hemoglobin, oxygen saturation and average vessel diameter. The method utilizes a small set of presimulated Monte Carlo data for combinations of different levels of epidermal thickness and tissue scattering. The path length distributions in the different layers are stored and the effect of the other parameters is added in the post-processing. The accuracy of the method was evaluated using Monte Carlo simulations of tissue-like models containing discrete blood vessels, evaluating blood tissue fraction and oxygenation. It was also compared to a homogeneous model. The multilayer model performed better than the homogeneous model and all tissue parameters significantly improved spectral fitting. Recorded in vivo spectra were fitted well at both distances, which we previously found was not possible with a homogeneous model. No absolute intensity calibration is needed and the algorithm is fast enough for real-time processing.

Infrared Spectroscopy of Hydrogen in Fullerite and MOF-5 Hosts

NASA Astrophysics Data System (ADS)

Fitzgerald, Stephen; Churchill, Hugh; Korngut, Phil; Simmons, Christie; Strangas, Yorgos

2006-03-01

We present a novel use of diffuse reflectance infrared spectroscopy to study the quantum dynamics of hydrogen molecules trapped within a host material. This technique is particularly useful for the study of hydrogen storage materials since it provides detailed information about the intermolecular potential at the binding site. Because H2 has no intrinsic infrared activity any observed features arise solely through interaction with the host material and as such are very sensitive to the symmetry of the binding site. The drawback is that the induced spectra are quite weak. However, a technique based on diffuse reflectance has been shown to produce a sufficiently large signal [1]. We have now constructed a cryogenic system that allows spectra to be obtained in this manner at pressures as high as 100 atm. and at temperatures as low as 10 K. Data will be presented for H2 in both C60 and MOF-5 showing a series of absorption features arising from the quantized vibrational, rotational, and translational motion of the trapped H2. At the lowest temperature these peaks become quite sharp, FWHM less than 1 cm-1, with a detailed fine structure arising from the H2 host interactions. 1. S. A. FitzGerald et al., Phys. Rev. B 65, 140302. (2002)

Inverse Monte Carlo in a multilayered tissue model: merging diffuse reflectance spectroscopy and laser Doppler flowmetry.

PubMed

Fredriksson, Ingemar; Burdakov, Oleg; Larsson, Marcus; Strömberg, Tomas

2013-12-01

The tissue fraction of red blood cells (RBCs) and their oxygenation and speed-resolved perfusion are estimated in absolute units by combining diffuse reflectance spectroscopy (DRS) and laser Doppler flowmetry (LDF). The DRS spectra (450 to 850 nm) are assessed at two source-detector separations (0.4 and 1.2 mm), allowing for a relative calibration routine, whereas LDF spectra are assessed at 1.2 mm in the same fiber-optic probe. Data are analyzed using nonlinear optimization in an inverse Monte Carlo technique by applying an adaptive multilayered tissue model based on geometrical, scattering, and absorbing properties, as well as RBC flow-speed information. Simulations of 250 tissue-like models including up to 2000 individual blood vessels were used to evaluate the method. The absolute root mean square (RMS) deviation between estimated and true oxygenation was 4.1 percentage units, whereas the relative RMS deviations for the RBC tissue fraction and perfusion were 19% and 23%, respectively. Examples of in vivo measurements on forearm and foot during common provocations are presented. The method offers several advantages such as simultaneous quantification of RBC tissue fraction and oxygenation and perfusion from the same, predictable, sampling volume. The perfusion estimate is speed resolved, absolute (% RBC×mm/s), and more accurate due to the combination with DRS.

Inverse Monte Carlo in a multilayered tissue model: merging diffuse reflectance spectroscopy and laser Doppler flowmetry

NASA Astrophysics Data System (ADS)

Fredriksson, Ingemar; Burdakov, Oleg; Larsson, Marcus; Strömberg, Tomas

2013-12-01

The tissue fraction of red blood cells (RBCs) and their oxygenation and speed-resolved perfusion are estimated in absolute units by combining diffuse reflectance spectroscopy (DRS) and laser Doppler flowmetry (LDF). The DRS spectra (450 to 850 nm) are assessed at two source-detector separations (0.4 and 1.2 mm), allowing for a relative calibration routine, whereas LDF spectra are assessed at 1.2 mm in the same fiber-optic probe. Data are analyzed using nonlinear optimization in an inverse Monte Carlo technique by applying an adaptive multilayered tissue model based on geometrical, scattering, and absorbing properties, as well as RBC flow-speed information. Simulations of 250 tissue-like models including up to 2000 individual blood vessels were used to evaluate the method. The absolute root mean square (RMS) deviation between estimated and true oxygenation was 4.1 percentage units, whereas the relative RMS deviations for the RBC tissue fraction and perfusion were 19% and 23%, respectively. Examples of in vivo measurements on forearm and foot during common provocations are presented. The method offers several advantages such as simultaneous quantification of RBC tissue fraction and oxygenation and perfusion from the same, predictable, sampling volume. The perfusion estimate is speed resolved, absolute (% RBC×mm/s), and more accurate due to the combination with DRS.

Calibration schemes of a field-compatible optical spectroscopic system to quantify neovascular changes in the dysplastic cervix

NASA Astrophysics Data System (ADS)

Chang, Vivide Tuan-Chyan; Merisier, Delson; Yu, Bing; Walmer, David K.; Ramanujam, Nirmala

2011-03-01

A significant challenge in detecting cervical pre-cancer in low-resource settings is the lack of effective screening facilities and trained personnel to detect the disease before it is advanced. Light based technologies, particularly quantitative optical spectroscopy, have the potential to provide an effective, low cost, and portable solution for cervical pre-cancer screening in these communities. We have developed and characterized a portable USB-powered optical spectroscopic system to quantify total hemoglobin content, hemoglobin saturation, and reduced scattering coefficient of cervical tissue in vivo. The system consists of a high-power LED as light source, a bifurcated fiber optic assembly, and two USB spectrometers for sample and calibration spectra acquisitions. The system was subsequently tested in Leogane, Haiti, where diffuse reflectance spectra from 33 colposcopically normal sites in 21 patients were acquired. Two different calibration methods, i.e., a post-study diffuse reflectance standard measurement and a real time self-calibration channel were studied. Our results suggest that a self-calibration channel enabled more accurate extraction of scattering contrast through simultaneous real-time correction of intensity drifts in the system. A self-calibration system also minimizes operator bias and required training. Hence, future contact spectroscopy or imaging systems should incorporate a selfcalibration channel to reliably extract scattering contrast.

Optical fiber spectroscopy measures perfusion of the brain in a murine Alzheimer's disease model

NASA Astrophysics Data System (ADS)

Ahn, Hyung Jin; Strickland, Sidney; Krueger, James; Gareau, Daniel

2014-02-01

Optical fiber spectroscopy is a versatile tool for measuring diffuse reflectance and extracting absorption information that can noninvasively quantify the presence of chromophores such as oxyhemoglobin and deoxy-hemoglobin in tissues. Cerebrovascular abnormalities were widely recognized in Alzheimer's disease (AD) patients. We analyzed blood volume fraction and level of oxygenated hemoglobin in Tg6799 mice, which are transgenic mice expressing five different familial Alzheimer disease-associated mutations in the human amyloid precursor protein and presenilin-1 genes. Diffuse reflectance spectra were iteratively fit as weighted sums of oxy- and deoxy-hemoglobin. Our observations showed slightly hypoxic conditions and significantly increased blood volume in the Alzheimer's mice versus wild type. These results suggest that hyperperfusion of our AD mice may be a compensating mechanism for impaired cerebral vascular function and somehow relevant with early stage of AD patients. Ongoing work focuses on developing a cannula fixture that allows measurement in awake, behaving animals.

Diffuse Reflectance Spectroscopy of Hidden Objects. Part II: Recovery of a Target Spectrum.

PubMed

Pomerantsev, Alexey L; Rodionova, Oxana Ye; Skvortsov, Alexej N

2017-08-01

In this study, we consider the reconstruction of a diffuse reflectance near-infrared spectrum of an object (target spectrum) in case the object is covered by an interfering absorbing and scattering layer. Recovery is performed using a new empirical method, which was developed in our previous study. We focus on a system, which consists of several layers of polyethylene (PE) film and underlayer objects with different spectral features. The spectral contribution of the interfering layer is modeled by a three-component two-parameter multivariate curve resolution (MCR) model, which was built and calibrated using spectrally flat objects. We show that this model is applicable to real objects with non-uniform spectra. Ultimately, the target spectrum can be reconstructed from a single spectrum of the covered target. With calculation methods, we are able to recover quite accurately the spectrum of a target even when the object is covered by 0.7 mm of PE.

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.

Effect of Annealing Temperature on Morphological and Optical Transition of Silver Nanoparticles on c-Plane Sapphire.

PubMed

Pandey, Puran; Kunwar, Sundar; Sui, Mao; Li, Ming-Yu; Zhang, Quanzhen; Lee, Jihoon

2018-05-01

As a promising candidate for the improved performance, silver nanoparticles (Ag NPs) have been successfully adapted in various applications such as photovoltaics, light emitting diodes (LEDs), sensors and catalysis by taking the advantage of their controllable plasmonic properties. In this paper, the control on the morphologies and optical properties of Ag NPs on c-plane sapphire (0001) is demonstrated by the systematic control of annealing temperature (between 200 and 950 °C) with 20 and 6 nm thick Ag films through the solid state dewetting. With the relatively thicker film of 20 nm, various configuration and size of Ag NPs are fabricated such as irregular, round dome-shaped and tiny Ag NPs depending on the annealing temperature. In a shrill contrast, the 6 nm Ag set exhibits a sharp distinction with the formation of densely packed small NPs and ultra-highly dense tiny Ag NPs due to the higher dewetting rate. While, the surface diffusion assumes the main driving force in the evolution process of Ag NP morphologies up to 550 °C, the sublimation of Ag atoms has played a significant role on top on the surface diffusion between 600 and 950 °C. The reflectance spectra of Ag NPs exhibit the quadrupolar resonance and dipolar resonance peaks, and the evolution of peaks, shift and average reflectance were discussed based on the Ag NPs size and surface coverage. In particular, the dipolar resonance peak in the reflectance spectra red shifts from ~475 to ~570 nm due to the size increment of Ag NPs (38.31 to 74.68 nm). The wide surface coverage of Ag NPs exhibits the highest average reflectance (~27%) and the lowest Raman intensity.

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.

Antibacterial studies of novel Cu2WS4 ternary chalcogenide synthesized by hydrothermal process

NASA Astrophysics Data System (ADS)

Kannan, Selvaraj; Vinitha, Perumal; Mohanraj, Kannusamy; Sivakumar, Ganesan

2018-02-01

This is the first report for the synthesis of L-cysteine mediated Cu2WS4 nanoparticles for different temperatures by an inexpensive and less pollutive hydrothermal method. The as-synthesized particles were characterized by XRD, FTIR, FESEM, UV-vis diffuse reflectance and PL spectra technique respectively. The phase purity and structural confirmation were studied by X-ray powder diffraction technique. It is observed that the synthesis temperature affecting the crystalline size. The optical analysis of the Cu2WS4 nanoparticles showed direct band gap in the range of 2.1-2.3 eV. The intensity of the PL emission spectra decreases with increase of reaction temperature. The antibacterial performance of Cu2WS4 nanoparticles were investigated by agar well diffusion method and the results confirm that the antibacterial activity of Cu2WS4 against Gram-positive (B. subtilis, M. luteus) and Gram-negative (E. coli, P. aeruginosa and K. pneumoniae) bacteria.

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.

Measuring joint cartilage thickness using reflectance spectroscopy non-invasively and in real-time

NASA Astrophysics Data System (ADS)

Canpolat, Murat; Denkceken, Tuba; Karagol, Cosar; Aydin, Ahmet T.

2011-03-01

Joint cartilage thickness has been estimated using spatially resolved steady-state reflectance spectroscopy noninvasively and in-real time. The system consists of a miniature UV-VIS spectrometer, a halogen tungsten light source, and an optical fiber probe with six 400 um diameter fibers. The first fiber was used to deliver the light to the cartilage and the other five were used to detect back-reflected diffused light. Distances from the detector fibers to the source fiber were 0.8 mm, 1.6 mm, 2.4 mm, 3.2 mm and 4 mm. Spectra of back-reflected diffused light were taken on 40 bovine patella cartilages. The samples were grouped into four; the first group was the control group with undamaged cartilages, in the 2nd, 3rd and 4th groups cartilage thickness was reduced approximately 25%, 50% and 100%, respectively. A correlation between cartilage thicknesses and hemoglobin absorption of light in the wavelength range of 500 nm- 600 nm for source-detector pairs was found. The proposed system with an optical fiber probe less than 4 mm in diameter has the potential for cartilage thickness assessment through an arthroscopy channel in real-time without damaging the cartilage.

Breaking through the glass ceiling: The correlation between the self-diffusivity in and krypton permeation through deeply supercooled liquid nanoscale methanol films

NASA Astrophysics Data System (ADS)

Smith, R. Scott; Matthiesen, Jesper; Kay, Bruce D.

2010-03-01

Molecular beam techniques, temperature-programmed desorption (TPD), and reflection absorption infrared spectroscopy (RAIRS) are used to explore the relationship between krypton permeation through and the self-diffusivity of supercooled liquid methanol at temperatures (100-115 K) near the glass transition temperature, Tg (103 K). Layered films, consisting of CH3OH and CD3OH, are deposited on top of a monolayer of Kr on a graphene covered Pt(111) substrate at 25 K. Concurrent Kr TPD and RAIRS spectra are acquired during the heating of the composite film to temperatures above Tg. The CO vibrational stretch is sensitive to the local molecular environment and is used to determine the supercooled liquid diffusivity from the intermixing of the isotopic layers. We find that the Kr permeation and the diffusivity of the supercooled liquid are directly and quantitatively correlated. These results validate the rare-gas permeation technique as a tool for probing the diffusivity of supercooled liquids.

Breaking through the glass ceiling: the correlation between the self-diffusivity in and krypton permeation through deeply supercooled liquid nanoscale methanol films.

PubMed

Smith, R Scott; Matthiesen, Jesper; Kay, Bruce D

2010-03-28

Molecular beam techniques, temperature-programmed desorption (TPD), and reflection absorption infrared spectroscopy (RAIRS) are used to explore the relationship between krypton permeation through and the self-diffusivity of supercooled liquid methanol at temperatures (100-115 K) near the glass transition temperature, T(g) (103 K). Layered films, consisting of CH(3)OH and CD(3)OH, are deposited on top of a monolayer of Kr on a graphene covered Pt(111) substrate at 25 K. Concurrent Kr TPD and RAIRS spectra are acquired during the heating of the composite film to temperatures above T(g). The CO vibrational stretch is sensitive to the local molecular environment and is used to determine the supercooled liquid diffusivity from the intermixing of the isotopic layers. We find that the Kr permeation and the diffusivity of the supercooled liquid are directly and quantitatively correlated. These results validate the rare-gas permeation technique as a tool for probing the diffusivity of supercooled liquids.

Comparison of Pinus taeda L. whole-tree wood property calibrations using diffuse reflectance near infrared spectra obtained using a variety of sampling options

Treesearch

P. David Jones; Laurence R. Schimleck; Richard F. Daniels; Alexander Clark; Robert C. Purnell

2008-01-01

A necessary objective for tree-breeding programs, with a focus on wood quality, is the measurement of wood properties on a whole-tree basis, however, the time and cost involved limits the numbers of trees sampled. Near infrared (NIR) spectroscopy provides an alternative and recently, it has been demonstrated that calibrations based on milled increment cores and whole-...

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.

Unpredictable adsorption and visible light induced decolorization of nano rutile for the treatment of crystal violet

NASA Astrophysics Data System (ADS)

Dong, Yanling; Liu, Yang; Lu, Dingze; Zheng, Feng; Fang, Pengfei; Zhang, Haining

2017-04-01

Photocatalysts containing different ratios of anatase and rutile are prepared via heat treatment of Degussa P-25 titania. X-ray diffraction (XRD), Bruuauer-Emmett-Teller (BET), ultraviolet-visible light diffuse reflectance spectra (DRS), Raman spectra (Raman), positron annihilation lifetime spectra (PAL) and temperature-programmed desorption (TPD) are applied to investigate the phase composition of the synthesized catalysts. Using crystal violet (CV) as the target pollutant, the unexpected visible light decolorization of rutile is observed. Despite the decreased specific surface area, the as-synthesized rutile samples exhibit much higher adsorption capability of CV than P-25 does, which in turn leads to improved photoreaction efficiency. Since the rutile samples can't absorb the visible light, the degradation under visible light irradiation is attributed to self-sensitization of CV on the surface of rutile.

Detection of cancer in cervical tissue biopsies using mobile lipid resonances measured with diffusion-weighted (1)H magnetic resonance spectroscopy.

PubMed

Zietkowski, D; Davidson, R L; Eykyn, T R; De Silva, S S; Desouza, N M; Payne, G S

2010-05-01

The purpose of this study was to implement a diffusion-weighted sequence for visualisation of mobile lipid resonances (MLR) using high resolution magic angle spinning (HR-MAS) (1)H MRS and to evaluate its use in establishing differences between tissues from patients with cervical carcinoma that contain cancer from those that do not. A stimulated echo sequence with bipolar gradients was modified to allow T(1) and T(2) measurements and optimised by recording signal loss in HR-MAS spectra as a function of gradient strength in model lipids and tissues. Diffusion coefficients, T(1) and apparent T(2) relaxation times were measured in model lipid systems. MLR profiles were characterised in relation to T(1) and apparent T(2) relaxation in human cervical cancer tissue samples. Diffusion-weighted (DW) spectra of cervical biopsies were quantified and peak areas analysed using linear discriminant analysis (LDA). The optimised sequence reduced spectral overlap by suppressing signals originating from low molecular weight metabolites and non-lipid contributions. Significantly improved MLR visualisation allowed visualisation of peaks at 0.9, 1.3, 1.6, 2.0, 2.3, 2.8, 4.3 and 5.3 ppm. MLR analysis of DW spectra showed at least six peaks arising from saturated and unsaturated lipids and those arising from triglycerides. Significant differences in samples containing histologically confirmed cancer were seen for peaks at 0.9 (p < 0.006), 1.3 (p < 0.04), 2.0 (p < 0.03), 2.8 (p < 0.003) and 4.3 ppm (p < 0.0002). LDA analysis of MLR peaks from DW spectra almost completely separated two clusters of cervical biopsies (cancer, 'no-cancer'), reflecting underlying differences in MLR composition. Generated Receiver Operating Characteristic (ROC) curves and calculated area under the curve (0.962) validated high sensitivity and specificity of the technique. Diffusion-weighting of HR-MAS spectroscopic sequences is a useful method for characterising MLR in cancer tissues and displays an accumulation of lipids arising during tumourigenesis and an increase in the unsaturated lipid and triglyceride peaks with respect to saturated MLR. Copyright © 2009 John Wiley & Sons, Ltd.

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.

Photocatalytic oxidation of propylene on La and N codoped TiO2 nanoparticles

NASA Astrophysics Data System (ADS)

Liu, Jinfeng; Li, Haiyan; Zong, Lanlan; Li, Qiuye; Wang, Xiaodong; Zhang, Min; Yang, Jianjun

2015-02-01

Lanthanum- and nitrogen-codoped TiO2 photocatalysts was synthesized using orthorhombic nanotubes titanic acid as the precursor by a simple impregnation and subsequent calcination method. The morphology, phase structure, and properties of La- and N-codoped TiO2 were well characterized by transmission electron microscopy, X-ray diffraction, Raman spectra, X-ray photoelectron spectroscopy, and UV-Vis diffuse reflectance spectra. The La-/N-codoped TiO2 showed excellent photoactivity of propylene oxidation compared with the single-doped TiO2 and La-/N-codoped P25 TiO2 nanoparticles under visible light irradiation. The origin of the enhancement of the visible light-responsive photocatalytic activity was discussed in detail.

Inorganic photochromic and cathodochromic recording materials.

NASA Technical Reports Server (NTRS)

Duncan, R. C., Jr.; Faughnan, B. W.; Phillips, W.

1971-01-01

Discussion of studies at RCA Laboratories of the properties of rare-earth-doped CaF2, transition-metal-doped SrTiO3 and iron- or sulfur-doped sodalite as photochromic materials which change color during light or electron beam exposures. Particular attention is given to their photochromic characteristics in single-crystal and powder forms and to their cathodochromic properties in powder form. Details are given on the photochromic mechanisms, spectra, optical density, thermal decay rates, and coloring and bleaching efficiency of their single crystals and on the diffuse reflectance spectra, saturated photochromic contrast ratio, switching and erase sensitivities, and cathodochromic excitation of their photochromic powders. The many attractive characteristics of these materials when used in display storage systems are indicated.

Visualization of hemodynamics and light scattering in exposed brain of rat using multispectral image reconstruction based on Wiener estimation method

NASA Astrophysics Data System (ADS)

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

2015-07-01

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. We performed simultaneous recordings of spectral diffuse reflectance images and of the electrophysiological signals for in vivo exposed rat brain during the cortical spreading depression evoked by the topical application of KCl. Changes in the total hemoglobin concentration and the tissue oxygen saturation imply the temporary change in cerebral blood flow during CSD. Change in the reduced scattering coefficient was observed before the profound increase in the total hemoglobin concentration, and its occurrence was synchronized with the negative dc shift of the local field potential.

Bio-Optical Properties of the Arabian Sea as Determined by In Situ and Sea WiFS Data

NASA Technical Reports Server (NTRS)

Trees, Charles C.

1997-01-01

The overall objective of this work was to characterize optical and fluorescence properties in the euphotic zone during two British Ocean Flux Study (BOFS) Arabian Sea cruises. This was later expanded in 1995 to include three U.S. JGOFS Arabian Sea Cruises. The region was to be divided into one or more "bio-optical provinces," within each of which a single set of regression models was to be developed to relate the vertical distribution of irradiance attenuation and normalized fluorescence (SF and NF) to remote sensing reflectance and diffuse attenuation coefficient. The working hypothesis was that over relatively large spatial and temporal scales, the vertical profiles of bio-optical properties were predictable. The specific technical objectives were: (1) To characterize the vertical distribution of the inherent and apparent optical properties by measuring downwelling and upwelling irradiances, upwelling radiances, scalar irradiance of PAR, and beam transmissions at each station - from these data, spectral diffuse attenuation coefficients, irradiance reflectances, remote sensing reflectances, surface-leaving radiances and beam attenuation coefficients were determined; (2) To characterize the spectral absorption of total particulate, detrital, and dissolved organic material at each station from discrete water samples; (3) To describe the vertical distribution of photoadaptive properties in the water column by measuring profiles of stimulated (SF) and natural (NF) fluorescence and examining relationships between SF and NF as a function of diffuse optical depth, pigment biomass and primary productivity; and (4) To establish locally derived, in-water algorithms relating remote sensing reflectance spectra to diffuse attenuation coefficients, phytoplankton pigment concentrations and primary productivity, through intercomparisons with in situ measurements, for application to SeaWiFS data.

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.

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

Cowan, Nicolas B.; Strait, Talia E., E-mail: n-cowan@northwestern.edu

Planned missions will spatially resolve temperate terrestrial planets from their host star. Although reflected light from such a planet encodes information about its surface, it has not been shown how to establish surface characteristics of a planet without assuming known surfaces to begin with. We present a reanalysis of disk-integrated, time-resolved, multiband photometry of Earth obtained by the Deep Impact spacecraft as part of the EPOXI Mission of Opportunity. We extract reflectance spectra of clouds, ocean, and land without a priori knowledge of the numbers or colors of these surfaces. We show that the inverse problem of extracting surface spectramore » from such data is a novel and extreme instance of spectral unmixing, a well-studied problem in remote sensing. Principal component analysis is used to determine an appropriate number of model surfaces with which to interpret the data. Shrink-wrapping a simplex to the color excursions of the planet yields a conservative estimate of the planet's endmember spectra. The resulting surface maps are unphysical, however, requiring negative or larger-than-unity surface coverage at certain locations. Our ''rotational unmixing'' supersedes the endmember analysis by simultaneously solving for the surface spectra and their geographical distributions on the planet, under the assumption of diffuse reflection and known viewing geometry. We use a Markov Chain Monte Carlo to determine best-fit parameters and their uncertainties. The resulting albedo spectra are similar to clouds, ocean, and land seen through a Rayleigh-scattering atmosphere. This study suggests that future direct-imaging efforts could identify and map unknown surfaces and clouds on exoplanets.« less

Influence of Li+ charge compensator ion on the energy transfer from Pr3 + to Gd3 + ions in Ca9Mg(PO4)6F2:Gd3 +, Pr3 +, Li+ phosphor

NASA Astrophysics Data System (ADS)

Tamboli, Sumedha; Dhoble, S. J.

2017-09-01

Phototherapy is a renowned treatment for curing skin diseases since ancient times. Phototherapeutic treatment for psoriasis and many other diseases require narrow band ultra violet-B (NB-UVB) light with peak intensity at 313 nm to be exposed to the affected part of body. In this paper, we report combustion synthesis of NB-UVB - 313 nm emitting Ca9Mg(PO4)6F2 phosphors doped with Gd3 +, Pr3 + and Li+ ions. The phase formation was confirmed by obtaining X-ray diffraction (XRD) pattern and morphology was studied with the Scanning electron microscopy (SEM) images. Photoluminescence (PL) emission spectra show intense narrow band emission at 313 nm under 274 nm excitation wavelengths. Emission intensity was enhanced when Ca9Mg(PO4)6F2 compound is co-doped with Pr3 + ions. Excitation spectra of Ca9Mg(PO4)6F2:Gd3 +, Pr3 + doped samples shows broad excitation in ultra violet C (UVC) region. Diffuse reflectance spectra (DRS), obtained by UV-visible spectrophotometer, measures the absorption properties of the material. By applying Kubelka Munk function on the diffuse reflectance spectra, band gap of the material is determined. PL decay curves were examined which indicates efficient energy transfer between Pr3 + and Gd3 + ions. Charge compensation effect was also studied by co-doping Li+ ion in host. Emission intensity was found to increase with the addition of charge compensator. The prepared phosphor has potential to convert UVC light into NB-UVB. The luminescence intensity of Gd3 + shows remarkable increase when it is sensitized with Pr3 +, and an addition of charge compensator in the form of Li+, show even better results. This phosphor surely has the potential to be used as phototherapy lamp phosphor.

Optical and electrical properties of composites based on functional components of an electroluminescent layer

NASA Astrophysics Data System (ADS)

Avanesyan, V. T.; Rakina, A. V.; Sychov, M. M.; Vasina, E. S.

2016-07-01

Optical and electrical properties of cyanoethyl ether of polyvinyl alcohol with filling of barium titanate BaTiO3 modified by shungite carbon nanoparticles are studied. It is found that the modification affects the diffuse reflectance spectra and dispersion characteristics of the impedance components due to a change in the nature of interfacial interactions in the system. The values of the forbidden band width for various modifier and filler concentrations are determined.

Acceleration of Particles Near Earth's Bow Shock

NASA Astrophysics Data System (ADS)

Sandroos, A.

2012-12-01

Collisionless shock waves, for example, near planetary bodies or driven by coronal mass ejections, are a key source of energetic particles in the heliosphere. When the solar wind hits Earth's bow shock, some of the incident particles get reflected back towards the Sun and are accelerated in the process. Reflected ions are responsible for the creation of a turbulent foreshock in quasi-parallel regions of Earth's bow shock. We present first results of foreshock macroscopic structure and of particle distributions upstream of Earth's bow shock, obtained with a new 2.5-dimensional self-consistent diffusive shock acceleration model. In the model particles' pitch angle scattering rates are calculated from Alfvén wave power spectra using quasilinear theory. Wave power spectra in turn are modified by particles' energy changes due to the scatterings. The new model has been implemented on massively parallel simulation platform Corsair. We have used an earlier version of the model to study ion acceleration in a shock-shock interaction event (Hietala, Sandroos, and Vainio, 2012).

Synthesis of a ternary Ag/RGO/ZnO nanocomposite via microwave irradiation and its application for the degradation of Rhodamine B under visible light.

PubMed

Surendran, Divya Kollikkara; Xavier, Marilyn Mary; Viswanathan, Vandana Parakkal; Mathew, Suresh

2017-06-01

Reduced graphene oxide supporting plasmonic photocatalyst (Ag) on ZnO has been synthesized via a facile two-step microwave synthesis using RGO/ZnO and AgNO 3 . First step involves fabrication of RGO/ZnO via microwave irradiation. The nanocomposites were characterized by X-ray diffraction analysis, transmission electron microscopy, Fourier transform infrared spectroscopy, and Raman spectroscopy. Ag/RGO/ZnO shows enhanced photoactivity under visible light for the degradation of Rhodamine B. Enhanced charge separation and migration have been assigned using UV-vis diffuse reflectance spectra, photoluminescence spectra, electrochemical impedance spectra, and TCSPC analysis. The improved photoactivity of Ag/RGO/ZnO can be ascribed to the prolonged lifetime of photogenerated electron-hole pairs and effective interfacial hybridization between RGO and Ag with ZnO nanoparticles. Ag nanoparticles can absorb visible light via surface plasmon resonance to enhance photocatalytic activity.

Diffuse reflectance imaging: a tool for guided biopsy

NASA Astrophysics Data System (ADS)

Jayanthi, Jayaraj L.; Subhash, Narayanan; Manju, Stephen; Nisha, Unni G.; Beena, Valappil T.

2012-01-01

Accurate diagnosis of premalignant or malignant oral lesions depends on the quality of the biopsy, adequate clinical information and correct interpretation of the biopsy results. The major clinical challenge is to precisely locate the biopsy site in a clinically suspicious lesion. Dips due to oxygenated hemoglobin absorption have been noticed at 545 and 575 nm in the diffusely reflected white light spectra of oral mucosa and the intensity ratio R545/R575 has been found suited for early detection of oral pre-cancers. A multi-spectral diffuse reflectance (DR) imaging system has been developed consisting of an electron multiplying charge coupled device (EMCCD) camera and a liquid crystal tunable filter for guiding the clinician to an optimal biopsy site. Towards this DR images were recorded from 27 patients with potentially malignant lesions on their tongue (dorsal, lateral and ventral sides) and from 44 healthy controls at 545 and 575 nm with the DR imaging system. False colored ratio image R545/R575 of the lesion provides a visual discerning capability that helps in locating the most malignant site for biopsy. Histopathological report of guided biopsy showed that out of the 27 patients 16 were cancers, 9 pre-cancers and 2 lichen planus. In this clinical trial DR imaging has correctly guided 25 biopsy sites, yielding a sensitivity of 93% and a specificity of 98%, thereby establishing the potential of DR imaging as a tool for guided biopsy.

Light-induced autofluorescence and diffuse reflectance spectroscopy in clinical diagnosis of skin cancer

NASA Astrophysics Data System (ADS)

Borisova, E.; Pavlova, E.; Kundurjiev, T.; Troyanova, P.; Genova, Ts.; Avramov, L.

2014-05-01

We investigated more than 500 clinical cases to receive the spectral properties of basal cell (136 patients) and squamous cell carcinoma (28), malignant melanoma (41) and different cutaneous dysplastic and benign cutaneous lesions. Excitation at 365, 385 and 405 nm using LEDs sources is applied to obtain autofluorescence spectra, and broad-band illumination in the region of 400-900 nm is used to detect diffuse reflectance spectra of all pathologies investigated. USB4000 microspectrometer (Ocean Optics Inc, USA) is applied as a detector and fiber-optic probe is used for delivery of the light. In the case of in vivo tumor measurements spectral shape and intensity changes are observed that are specific for a given type of lesion. Autofluorescence origins of the signals coming from skin tissues are mainly due to proteins, such as collagen, elastin, keratin, their cross-links, co-enzimes - NADH and flavins and endogenous porphyrins. Spectral features significant into diffuse spectroscopy diagnosis are related to the effects of re-absorption of hemoglobin and its forms, as well as melanin and its concentration in different pathologies. We developed significant database and revealed specific features for a large class of cutaneous neoplasia, using about 30 different spectral peculiarities to differentiate cutaneous tumors. Sensitivity and specificity obtained exceed 90%, which make optical biopsy very useful tool for clinical practice. These results are obtained in the frames of clinical investigations for development of significant "spectral features" database for the most common cutaneous malignant, dysplastic and benign lesions. In the forthcoming plans, our group tries to optimize the existing experimental system for optical biopsy of skin, and to introduce it and the diagnostic algorithms developed into clinical practice, based on the high diagnostic accuracy achieved.

Investigation on the morphological and optical evolution of bimetallic Pd-Ag nanoparticles on sapphire (0001) by the systematic control of composition, annealing temperature and time.

PubMed

Pandey, Puran; Kunwar, Sundar; Sui, Mao; Bastola, Sushil; Lee, Jihoon

2017-01-01

Multi-metallic alloy nanoparticles (NPs) can offer additional opportunities for modifying the electronic, optical and catalytic properties by the control of composition, configuration and size of individual nanostructures that are consisted of more than single element. In this paper, the fabrication of bimetallic Pd-Ag NPs is systematically demonstrated via the solid state dewetting of bilayer thin films on c-plane sapphire by governing the temperature, time as well as composition. The composition of Pd-Ag bilayer remarkably affects the morphology of alloy nanostructures, in which the higher Ag composition, i.e. Pd0.25Ag0.75, leads to the enhanced dewetting of bilayers whereas the higher Pd composition (Pd0.75Ag0.25) hinders the dewetting. Depending on the annealing temperature, Pd-Ag alloy nanostructures evolve with a series of configurations, i.e. nucleation of voids, porous network, elongated nanoclusters and round alloy NPs. In addition, with the annealing time set, the gradual configuration transformation from the elongated to round alloy NPs as well as size reduction is demonstrated due to the enhanced diffusion and sublimation of Ag atoms. The evolution of various morphology of Pd-Ag nanostructures is described based on the surface diffusion and inter-diffusion of Pd and Ag adatoms along with the Ag sublimation, Rayleigh instability and energy minimization mechanism. The reflectance spectra of bimetallic Pd-Ag nanostructures exhibit various quadrupolar and dipolar resonance peaks, peak shifts and absorption dips owing to the surface plasmon resonance of nanostructures depending on the surface morphology. The intensity of reflectance spectra is gradually decreased along with the surface coverage and NP size evolution. The absorption dips are red-shifted towards the longer wavelength for the larger alloy NPs and vice-versa.

Measurement of drug and macromolecule diffusion across atherosclerotic rabbit aorta ex vivo by attenuated total reflection-Fourier transform infrared imaging

NASA Astrophysics Data System (ADS)

Palombo, Francesca; Danoux, Charlène B.; Weinberg, Peter D.; Kazarian, Sergei G.

2009-07-01

Diffusion of two model drugs-benzyl nicotinate and ibuprofen-and the plasma macromolecule albumin across atherosclerotic rabbit aorta was studied ex vivo by attenuated total reflection-Fourier transform infrared (ATR-FTIR) imaging. Solutions of these molecules were applied to the endothelial surface of histological sections of the aortic wall that were sandwiched between two impermeable surfaces. An array of spectra, each corresponding to a specific location in the section, was obtained at various times during solute diffusion into the wall and revealed the distribution of the solutes within the tissue. Benzyl nicotinate in Ringer's solution showed higher affinity for atherosclerotic plaque than for apparently healthy tissue. Transmural concentration profiles for albumin demonstrated its permeation across the section and were consistent with a relatively low distribution volume for the macromolecule in the middle of the wall. The ability of albumin to act as a drug carrier for ibuprofen, otherwise undetected within the tissue, was demonstrated by multivariate subtraction image analysis. In conclusion, ATR-FTIR imaging can be used to study transport processes in tissue samples with high spatial and temporal resolution and without the need to label the solutes under study.

Noncontact discrimination of animal and human blood with vacuum blood vessel and factors affect the discrimination

NASA Astrophysics Data System (ADS)

Zhang, Linna; Zhang, Shengzhao; Sun, Meixiu; Li, Hongxiao; Li, Yingxin; Fu, Zhigang; Guan, Yang; Li, Gang; Lin, Ling

2017-03-01

Discrimination of human and nonhuman blood is crucial for import-export ports and inspection and quarantine departments. Current methods are usually destructive, complicated and time-consuming. We had previously demonstrated that visible diffuse reflectance spectroscopy combining PLS-DA method can successfully realize human blood discrimination. In that research, the spectra were measured with the fiber probe under the surface of blood samples. However, open sampling may pollute the blood samples. Virulence factors in blood samples can also endanger inspectors. In this paper, we explored the classification effect with the blood samples measured in the original containers-vacuum blood vessel. Furthermore, we studied the impact of different conditions of blood samples, such as coagulation and hemolysis, on the prediction ability of the discrimination model. The calibration model built with blood samples in different conditions displayed a satisfactory prediction result. This research demonstrated that visible and near-infrared diffuse reflectance spectroscopy method was potential for noncontact discrimination of human blood.

A Complex Approach to Noninvasive Estimation of Microcirculatory Tissue Impairments in Feet of Patients with Diabetes Mellitus using Spectroscopy

NASA Astrophysics Data System (ADS)

Potapova, E. V.; Dremin, V. V.; Zherebtsov, E. A.; Makovik, I. N.; Zharkikh, E. V.; Dunaev, A. V.; Pilipenko, O. V.; Sidorov, V. V.; Krupatkin, A. I.

2017-12-01

The possibility of a complex approach for studying changes in the system of blood microcirculation and metabolic processes in the biotissue of lower extremities using optical noninvasive methods of laser doppler flowmetry (LDF), fluorescence spectroscopy, and diffuse reflectance spectroscopy in combination with different modes of heating tests has been assessed. Seventy-six patients with type 2 diabetes mellitus, with 14 patients having visible trophic foot impairments, and 48 healthy volunteers have been examined. The parameters of LDF signals and spectra of fluorescence intensity and diffuse reflectance for foot skin have been analyzed. Statistically significant differences in the recorded parameters between the groups under study have been found. It has been concluded that combined application of noninvasive methods of spectroscopy could be used for diagnostics of complications both upon the occurrence of preliminary symptoms of diabetes, when pathological changes are still reversible, and in the presence of impairments to prevent aggravation of the disease and select an adequate correction of the treatment.

Quantitative evaluation of multiple adulterants in roasted coffee by Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) and chemometrics.

PubMed

Reis, Nádia; Franca, Adriana S; Oliveira, Leandro S

2013-10-15

The current study presents an application of Diffuse Reflectance Infrared Fourier Transform Spectroscopy for detection and quantification of fraudulent addition of commonly employed adulterants (spent coffee grounds, coffee husks, roasted corn and roasted barley) to roasted and ground coffee. Roasted coffee samples were intentionally blended with the adulterants (pure and mixed), with total adulteration levels ranging from 1% to 66% w/w. Partial Least Squares Regression (PLS) was used to relate the processed spectra to the mass fraction of adulterants and the model obtained provided reliable predictions of adulterations at levels as low as 1% w/w. A robust methodology was implemented that included the detection of outliers. High correlation coefficients (0.99 for calibration; 0.98 for validation) coupled with low degrees of error (1.23% for calibration; 2.67% for validation) confirmed that DRIFTS can be a valuable analytical tool for detection and quantification of adulteration in ground, roasted coffee. Copyright © 2013 Elsevier B.V. All rights reserved.

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.

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.

Synthesis, crystal structure and spectroscopy properties of Na 3AZr(PO 4) 3 ( A=Mg, Ni) and Li 2.6Na 0.4NiZr(PO 4) 3 phosphates

NASA Astrophysics Data System (ADS)

Chakir, M.; El Jazouli, A.; de Waal, D.

2006-06-01

Na 3AZr(PO 4) 3 ( A=Mg, Ni) phosphates were prepared at 750 °C by coprecipitation route. Their crystal structures have been refined at room temperature from X-ray powder diffraction data using Rietveld method. Li 2.6Na 0.4NiZr(PO 4) 3 was synthesized through ion exchange from the sodium analog. These materials belong to the Nasicon-type structure. Raman spectra of Na 3AZr(PO 4) 3 ( A=Mg, Ni) phosphates present broad peaks in favor of the statistical distribution in the sites around PO 4 tetrahedra. Diffuse reflectance spectra indicate the presence of octahedrally coordinated Ni 2+ ions.

Investigation of Chemical and Physical Changes to Bioapatite During Fossilization Using Trace Element Geochemistry, Infrared Spectroscopy and Stable Isotopes

NASA Astrophysics Data System (ADS)

Suarez, C. A.; Kohn, M. J.

2013-12-01

Bioapatite in the form of vertebrate bone can be used for a wide variety of paleo-proxies, from determination of ancient diet to the isotopic composition of meteoric water. Bioapatite alteration during diagenesis is a constant barrier to the use of fossil bone as a paleo-proxy. To elucidate the physical and chemical alteration of bone apatite during fossilization, we analyzed an assortment of fossil bones of different ages for trace elements, using LA-ICP-MS, stable isotopes, and reflected IR spectroscopy. One set of fossil bones from the Pleistocene of Idaho show a diffusion recrystallization profile, however, rare earth element (REE) profiles indicate diffusion adsorption. This suggests that REE diffusion is controlled by changing (namely decreasing) boundary conditions (i.e. decreasing concentration of REE in surrounding pore fluids). Reflected IR analysis along this concentration profile reveal that areas high in U have lost type A carbonate from the crystal structure in addition to water and organics. Stable isotopic analysis of carbon and oxygen will determine what, if any, change in the isotopic composition of the carbonate component of apatite has occurred do to the diffusion and recrystallization process. Analysis of much older bone from the Cretaceous of China reveal shallow REE and U concentration profiles and very uniform reflected IR spectra with a significant loss of type A carbonate throughout the entire bone cortex. Analysis of stable isotopes through the bone cortex will be compared to the stable isotopes collected from the Pleistocene of Idaho.

Characterization of Tissue Structure at Varying Length Scales Using Temporal Diffusion Spectroscopy

PubMed Central

Gore, John C.; Xu, Junzhong; Colvin, Daniel C.; Yankeelov, Thomas E.; Parsons, Edward C.; Does, Mark D.

2011-01-01

The concepts, theoretical behavior and experimental applications of temporal diffusion spectroscopy are reviewed and illustrated. Temporal diffusion spectra are obtained by using oscillating gradient waveforms in diffusion-weighted measurements, and represent the manner in which various spectral components of molecular velocity correlations vary in different geometrical structures that restrict or hinder free movements. Measurements made at different gradient frequencies reveal information on the scale of restrictions or hindrances to free diffusion, and the shape of a spectrum reveals the relative contributions of spatial restrictions at different distance scales. Such spectra differ from other so-called diffusion spectra which depict spatial frequencies and are defined at a fixed diffusion time. Experimentally, oscillating gradients at moderate frequency are more feasible for exploring restrictions at very short distances, which in tissues correspond to structures smaller than cells. We describe the underlying concepts of temporal diffusion spectra and provide analytical expressions for the behavior of the diffusion coefficient as a function of gradient frequency in simple geometries with different dimensions. Diffusion in more complex model media that mimic tissues has been simulated using numerical methods. Experimental measurements of diffusion spectra have been obtained in suspensions of particles and cells, as well as in vivo in intact animals. An observation of particular interest is the increased contrast and heterogeneity observed in tumors using oscillating gradients at moderate frequency compared to conventional pulse gradient methods, and the potential for detecting changes in tumors early in their response to treatment. Computer simulations suggest that diffusion spectral measurements may be sensitive to intracellular structures such as nuclear size, and that changes in tissue diffusion properties may be measured before there are changes in cell density. PMID:20677208

Scanning tunneling spectroscopy study of the proximity effect in a disordered two-dimensional metal.

PubMed

Serrier-Garcia, L; Cuevas, J C; Cren, T; Brun, C; Cherkez, V; Debontridder, F; Fokin, D; Bergeret, F S; Roditchev, D

2013-04-12

The proximity effect between a superconductor and a highly diffusive two-dimensional metal is revealed in a scanning tunneling spectroscopy experiment. The in situ elaborated samples consist of superconducting single crystalline Pb islands interconnected by a nonsuperconducting atomically thin disordered Pb wetting layer. In the vicinity of each superconducting island the wetting layer acquires specific tunneling characteristics which reflect the interplay between the proximity-induced superconductivity and the inherent electron correlations of this ultimate diffusive two-dimensional metal. The observed spatial evolution of the tunneling spectra is accounted for theoretically by combining the Usadel equations with the theory of dynamical Coulomb blockade; the relevant length and energy scales are extracted and found in agreement with available experimental data.

Comparing classification methods for diffuse reflectance spectra to improve tissue specific laser surgery.

PubMed

Engelhardt, Alexander; Kanawade, Rajesh; Knipfer, Christian; Schmid, Matthias; Stelzle, Florian; Adler, Werner

2014-07-16

In the field of oral and maxillofacial surgery, newly developed laser scalpels have multiple advantages over traditional metal scalpels. However, they lack haptic feedback. This is dangerous near e.g. nerve tissue, which has to be preserved during surgery. One solution to this problem is to train an algorithm that analyzes the reflected light spectra during surgery and can classify these spectra into different tissue types, in order to ultimately send a warning or temporarily switch off the laser when critical tissue is about to be ablated. Various machine learning algorithms are available for this task, but a detailed analysis is needed to assess the most appropriate algorithm. In this study, a small data set is used to simulate many larger data sets according to a multivariate Gaussian distribution. Various machine learning algorithms are then trained and evaluated on these data sets. The algorithms' performance is subsequently evaluated and compared by averaged confusion matrices and ultimately by boxplots of misclassification rates. The results are validated on the smaller, experimental data set. Most classifiers have a median misclassification rate below 0.25 in the simulated data. The most notable performance was observed for the Penalized Discriminant Analysis, with a misclassifiaction rate of 0.00 in the simulated data, and an average misclassification rate of 0.02 in a 10-fold cross validation on the original data. The results suggest a Penalized Discriminant Analysis is the most promising approach, most probably because it considers the functional, correlated nature of the reflectance spectra.The results of this study improve the accuracy of real-time tissue discrimination and are an essential step towards improving the safety of oral laser surgery.

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.

Determining moisture content in pasta by vibrational spectroscopy.

PubMed

Czaja, Tomasz; Kuzawińska, Ewelina; Sobota, Aldona; Szostak, Roman

2018-02-01

Pasta aside from bread is the most consumed cereal-based product in the world. Its taste and cooking ease makes it the basis of many cuisines. The pasta dough formed by mixing flour and water is extruded through an extrusion die to mould the appropriate pasta form and is dried to obtain a stable product. The concentration of moisture in the pasta dough is a one of key parameters determining the final quality of the product. Monitoring the moisture content of pasta after extrusion is also critically important. It enables a selection of suitable drying conditions that ensure the appropriate parameters of pasta, such as texture, color and taste, are met. A method for the quantitative determination of moisture content in pasta dough and in pasta based on the partial least squares treatment of infrared spectra registered using a single-reflection attenuated total reflectance diamond accessory is described. Results of a similar quality were found using models derived from near infrared spectra obtained in a diffuse reflectance mode and slightly worse based on Raman spectra. Relative standard errors of prediction calculated for moisture quantification by ATR/NIR/Raman techniques amounted to 2.54/3.16/5.56% and 2.15/3.32/5.67%, for calibration and validation sets, respectively. The proposed procedures can be used for fast and efficient pasta moisture quantification and may replace the current, more laborious methods used. Copyright © 2017 Elsevier B.V. All rights reserved.

A Fast Smoothing Algorithm for Post-Processing of Surface Reflectance Spectra Retrieved from Airborne Imaging Spectrometer Data

PubMed Central

Gao, Bo-Cai; Liu, Ming

2013-01-01

Surface reflectance spectra retrieved from remotely sensed hyperspectral imaging data using radiative transfer models often contain residual atmospheric absorption and scattering effects. The reflectance spectra may also contain minor artifacts due to errors in radiometric and spectral calibrations. We have developed a fast smoothing technique for post-processing of retrieved surface reflectance spectra. In the present spectral smoothing technique, model-derived reflectance spectra are first fit using moving filters derived with a cubic spline smoothing algorithm. A common gain curve, which contains minor artifacts in the model-derived reflectance spectra, is then derived. This gain curve is finally applied to all of the reflectance spectra in a scene to obtain the spectrally smoothed surface reflectance spectra. Results from analysis of hyperspectral imaging data collected with the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data are given. Comparisons between the smoothed spectra and those derived with the empirical line method are also presented. PMID:24129022

Non-invasive detection of periodontal disease using diffuse reflectance spectroscopy: a clinical study

NASA Astrophysics Data System (ADS)

Prasanth, Chandra Sekhar; Betsy, Joseph; Subhash, Narayanan; Jayanthi, Jayaraj L.; Prasanthila, Janam

2012-03-01

In clinical diagnostic procedures, gingival inflammation is considered as the initial stage of periodontal breakdown. This is often detected clinically by bleeding on probing as it is an objective measure of inflammation. Since conventional diagnostic procedures have several inherent drawbacks, development of novel non-invasive diagnostic techniques assumes significance. This clinical study was carried out in 15 healthy volunteers and 25 patients to demonstrate the applicability of diffuse reflectance (DR) spectroscopy for quantification and discrimination of various stages of inflammatory conditions in periodontal disease. The DR spectra of diseased lesions recorded using a point monitoring system consisting of a tungsten halogen lamp and a fiber-optic spectrometer showed oxygenated hemoglobin absorption dips at 545 and 575 nm. Mean DR spectra on normalization shows marked differences between healthy and different stages of gingival inflammation. Among the various DR intensity ratios investigated, involving oxy Hb absorption peaks, the R620/R575 ratio was found to be a good parameter of gingival inflammation. In order to screen the entire diseased area and its surroundings instantaneously, DR images were recorded with an EMCCD camera at 620 and 575 nm. We have observed that using the DR image intensity ratio R620/R575 mild inflammatory tissues could be discriminated from healthy with a sensitivity of 92% and specificity of 93%, and from moderate with a sensitivity of 83% and specificity of 96%. The sensitivity and specificity obtained between moderate and severe inflammation are 82% and 76% respectively.

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.

Oxygenated hemoglobin diffuse reflectance ratio for in vitro detection of human gastric pre-cancer

NASA Astrophysics Data System (ADS)

Li, L. Q.; Wei, H. J.; Guo, Z. Y.; Yang, H. Q.; Wu, G. Y.; Xie, S. S.; Zhong, H. Q.; Li, X. Y.; Zhao, Q. L.; Guo, X.

2010-07-01

Oxygenated hemoglobin diffuse reflectance (DR) ratio (R540/R575) method based on DR spectral signatures is used for early diagnosis of malignant lesions of human gastric epithelial tissues in vitro. The DR spectra for four different kinds of gastric epithelial tissues were measured using a spectrometer with an integrating sphere detector in the spectral range from 400 to 650 nm. The results of measurement showed that the average DR spectral intensity for the epithelial tissues of normal stomach is higher than that for the epithelial tissues of chronic and malignant stomach and that for the epithelial tissues of chronic gastric ulcer is higher than that for the epithelial tissues of malignant stomach. The average DR spectra for four different kinds of gastric epithelial tissues show dips at 542 and 577 nm owing to absorption from oxygenated Hemoglobin (HbO2). The differences in the mean R540/R575 ratios of HbO2 bands are 6.84% between the epithelial tissues of normal stomach and chronic gastric ulcer, 14.7% between the epithelial tissues of normal stomach and poorly differentiated gastric adenocarcinoma and 22.6% between the epithelial tissues of normal stomach and undifferentiated gastric adenocarcinoma. It is evident from results that there were significant differences in the mean R540/R575 ratios of HbO2 bands for four different kinds of gastric epithelial tissues in vitro ( P < 0.01).

Continuous Diffusion Model for Concentration Dependence of Nitroxide EPR Parameters in Normal and Supercooled Water.

PubMed

Merunka, Dalibor; Peric, Miroslav

2017-05-25

Electron paramagnetic resonance (EPR) spectra of radicals in solution depend on their relative motion, which modulates the Heisenberg spin exchange and dipole-dipole interactions between them. To gain information on radical diffusion from EPR spectra demands both reliable spectral fitting to find the concentration coefficients of EPR parameters and valid expressions between the concentration and diffusion coefficients. Here, we measured EPR spectra of the 14 N- and 15 N-labeled perdeuterated TEMPONE radicals in normal and supercooled water at various concentrations. By fitting the EPR spectra to the functions based on the modified Bloch equations, we obtained the concentration coefficients for the spin dephasing, coherence transfer, and hyperfine splitting parameters. Assuming the continuous diffusion model for radical motion, the diffusion coefficients of radicals were calculated from the concentration coefficients using the standard relations and the relations derived from the kinetic equations for the spin evolution of a radical pair. The latter relations give better agreement between the diffusion coefficients calculated from different concentration coefficients. The diffusion coefficients are similar for both radicals, which supports the presented method. They decrease with lowering temperature slower than is predicted by the Stokes-Einstein relation and slower than the rotational diffusion coefficients, which is similar to the diffusion of water molecules in supercooled water.

Construction of Models for Nondestructive Prediction of Ingredient Contents in Blueberries by Near-infrared Spectroscopy Based on HPLC Measurements.

PubMed

Bai, Wenming; Yoshimura, Norio; Takayanagi, Masao; Che, Jingai; Horiuchi, Naomi; Ogiwara, Isao

2016-06-28

Nondestructive prediction of ingredient contents of farm products is useful to ship and sell the products with guaranteed qualities. Here, near-infrared spectroscopy is used to predict nondestructively total sugar, total organic acid, and total anthocyanin content in each blueberry. The technique is expected to enable the selection of only delicious blueberries from all harvested ones. The near-infrared absorption spectra of blueberries are measured with the diffuse reflectance mode at the positions not on the calyx. The ingredient contents of a blueberry determined by high-performance liquid chromatography are used to construct models to predict the ingredient contents from observed spectra. Partial least squares regression is used for the construction of the models. It is necessary to properly select the pretreatments for the observed spectra and the wavelength regions of the spectra used for analyses. Validations are necessary for the constructed models to confirm that the ingredient contents are predicted with practical accuracies. Here we present a protocol to construct and validate the models for nondestructive prediction of ingredient contents in blueberries by near-infrared spectroscopy.

Depositing of CuS nanocrystals upon the graphene scaffold and their photocatalytic activities

NASA Astrophysics Data System (ADS)

Wang, Yongbin; Zhang, Lixin; Jiu, Hongfang; Li, Na; Sun, Yixin

2014-06-01

A series of copper sulfide nanocrystals/graphene nanocomposites (CuS/GR) with different weight ratios of GR were fabricated via a one-step hydrothermal approach by using dimethylsulfoxide (DMSO) as the source of sulfur and solvent. The as-prepared samples were studied by X-ray diffraction (XRD), UV-vis diffuse reflectance spectra (DRS), transmission scanning electron microscopy (TEM) and photoluminescence spectra (PL) are employed to determine the properties of the samples. The results show that the CuS nanocrystals with an average size of 16 nm almost overspread on the GR graphene scaffold. The samples exhibit excellent photocatalytic activities in degrading the methylene blue (MB) compared with pure CuS. This work shows that CuS/GR nanocomposites would be promising in dye wastewater treatment as Fenton-like reagents.

Mirrorlike pulsed laser deposited tungsten thin film.

PubMed

Mostako, A T T; Rao, C V S; Khare, Alika

2011-01-01

Mirrorlike tungsten thin films on stainless steel substrate deposited via pulsed laser deposition technique in vacuum (10(-5) Torr) is reported, which may find direct application as first mirror in fusion devices. The crystal structure of tungsten film is analyzed using x-ray diffraction pattern, surface morphology of the tungsten films is studied with scanning electron microscope and atomic force microscope. The film composition is identified using energy dispersive x-ray. The specular and diffuse reflectivities with respect to stainless steel substrate of the tungsten films are recorded with FTIR spectra. The thickness and the optical quality of pulsed laser deposition deposited films are tested via interferometric technique. The reflectivity is approaching about that of the bulk for the tungsten film of thickness ∼782 nm.

Sub-diffusive scattering parameter maps recovered using wide-field high-frequency structured light imaging.

PubMed

Kanick, Stephen Chad; McClatchy, David M; Krishnaswamy, Venkataramanan; Elliott, Jonathan T; Paulsen, Keith D; Pogue, Brian W

2014-10-01

This study investigates the hypothesis that structured light reflectance imaging with high spatial frequency patterns [Formula: see text] can be used to quantitatively map the anisotropic scattering phase function distribution [Formula: see text] in turbid media. Monte Carlo simulations were used in part to establish a semi-empirical model of demodulated reflectance ([Formula: see text]) in terms of dimensionless scattering [Formula: see text] and [Formula: see text], a metric of the first two moments of the [Formula: see text] distribution. Experiments completed in tissue-simulating phantoms showed that simultaneous analysis of [Formula: see text] spectra sampled at multiple [Formula: see text] in the frequency range [0.05-0.5] [Formula: see text] allowed accurate estimation of both [Formula: see text] in the relevant tissue range [0.4-1.8] [Formula: see text], and [Formula: see text] in the range [1.4-1.75]. Pilot measurements of a healthy volunteer exhibited [Formula: see text]-based contrast between scar tissue and surrounding normal skin, which was not as apparent in wide field diffuse imaging. These results represent the first wide-field maps to quantify sub-diffuse scattering parameters, which are sensitive to sub-microscopic tissue structures and composition, and therefore, offer potential for fast diagnostic imaging of ultrastructure on a size scale that is relevant to surgical applications.

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.

Multispectral detection of cutaneous lesions using spectroscopy and microscopy approaches

NASA Astrophysics Data System (ADS)

Borisova, E.; Genova-Hristova, Ts.; Troyanova, P.; Pavlova, E.; Terziev, I.; Semyachkina-Glushkovskaya, O.; Lomova, M.; Genina, E.; Stanciu, G.; Tranca, D.; Avramov, L.

2018-02-01

Autofluorescence, diffuse-reflectance and transmission spectral, and microscopic measurements were made on different cutaneous neoplastic lesions, namely basal cell carcinoma, squamous cell carcinoma, malignant melanoma, and dysplastic and benign lesions related. Spectroscopic measurements were made on ex vivo tissue samples, and confocal microscopy investigations were made on thin tissue slices. Fluorescence spectra obtained reveal statistically significant differences between the different benign, dysplastic and malignant lesions by the level of emission intensity, as well by spectral shape, which are fingerprints applicable for differentiation algorithms. In reflectance mode the most significant differences are related to the influence of skin pigments - melanin and hemoglobin. Transmission spectroscopy mode gave complementary optical properties information about the tissue samples investigated to that one of reflectance and absorption spectroscopy. Using autofluorescence detection of skin lesions we obtain very good diagnostic performance for distinguishing of nonmelanoma lesions. Using diffuse reflectance and transmission spectroscopy we obtain significant tool for pigmented pathologies differentiation, but it is a tool with moderate sensitivity for non-melanoma lesions detection. One could rapidly increase the diagnostic accuracy of the received combined "optical biopsy" method when several spectral detection techniques are applied in common algorithm for lesions' differentiation. Specific spectral features observed in each type of lesion investigated on micro and macro level would be presented and discussed. Correlation between the spectral data received and the microscopic features observed would be discussed in the report.

Structural characterization of humic-like substances with conventional and surface-enhanced spectroscopic techniques

NASA Astrophysics Data System (ADS)

Carletti, Paolo; Roldán, Maria Lorena; Francioso, Ornella; Nardi, Serenella; Sanchez-Cortes, Santiago

2010-10-01

Emission-excitation, synchronous fluorescence spectroscopy and surface-enhanced Raman scattering (SERS) combined with surface-enhanced fluorescence (SEF) were applied to aqueous solutions of a humic-like substance (HLS) extracted from earthworm faeces. All measurements were acquired in a wide range of pH (4-12) and analysed by the linear regression analysis. Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectra were also acquired to assist in the structural characterization of this HLS. The emission and excitation spectra allowed the identification of two main fluorophores in the analysed sample. Moreover, a close correlation between fluorescence intensities of each fluorophore with pH variation was observed. SERS and SEF, in agreement with the fluorescence spectroscopy, showed that the HLS at low pH values exists in an aggregated and coiled molecular structure while it is dispersed and uncoiled at alkaline conditions. The obtained spectra also evidenced that different conditions modify the functional groups exposed to the surrounding aqueous environment.

[Identification of special quality eggs with NIR spectroscopy technology based on symbol entropy feature extraction method].

PubMed

Zhao, Yong; Hong, Wen-Xue

2011-11-01

Fast, nondestructive and accurate identification of special quality eggs is an urgent problem. The present paper proposed a new feature extraction method based on symbol entropy to identify near infrared spectroscopy of special quality eggs. The authors selected normal eggs, free range eggs, selenium-enriched eggs and zinc-enriched eggs as research objects and measured the near-infrared diffuse reflectance spectra in the range of 12 000-4 000 cm(-1). Raw spectra were symbolically represented with aggregation approximation algorithm and symbolic entropy was extracted as feature vector. An error-correcting output codes multiclass support vector machine classifier was designed to identify the spectrum. Symbolic entropy feature is robust when parameter changed and the highest recognition rate reaches up to 100%. The results show that the identification method of special quality eggs using near-infrared is feasible and the symbol entropy can be used as a new feature extraction method of near-infrared spectra.

Hydrothermal synthesis of tungsten doped tin dioxide nanocrystals

NASA Astrophysics Data System (ADS)

Zhou, Cailong; Li, Yufeng; Chen, Yiwen; Lin, Jing

2018-01-01

Tungsten doped tin dioxide (WTO) nanocrystals were synthesized through a one-step hydrothermal method. The structure, composition and morphology of WTO nanocrystals were characterized by x-ray diffraction, x-ray photoelectron spectroscopy, energy dispersive x-ray spectroscopy, UV-vis diffuse reflectance spectra, zeta potential analysis and high-resolution transmission electron microscopy. Results show that the as-prepared WTO nanocrystals were rutile-type structure with the size near 13 nm. Compared with the undoped tin dioxide nanocrystals, the WTO nanocrystals possessed better dispersity in ethanol phase and formed transparent sol.

Photoactive lead oxide thin films by spray pyrolysis

NASA Astrophysics Data System (ADS)

Bhagat, Dharini; Waldiya, Manmohansingh; Mukhopadhyay, Indrajit

2018-05-01

We report the synthesis of photoactive lead monoxide thin films on fluorine doped tin oxide substrate by cost effective spray pyrolysis technique using aqueous solution of lead acetate trihydrate. Influence of substrate temperature on the structural and optical properties of thin films was studied. Polymorph of lead monoxide, litharge (α-PbO), was obtained when the substrate temperature was kept constant at 360 °C. XRD analysis revealed that the deposits were tetragonal structured with preferred orientation along 002 plane. Band gap value was found to be 1.93ev from diffuse reflectance spectra.

Cation–hydroxide–water coadsorption inhibits the alkaline hydrogen oxidation reaction

DOE PAGES

Chung, Hoon Taek; Martinez, Ulises; Matanovic, Ivana; ...

2016-10-24

Rotating disk electrode voltammograms and infrared reflection absorption spectra indicate that the hydrogen oxidation reaction of platinum in 0.1 M tetramethylammonium hydroxide solution is adversely impacted by time-dependent and potential-driven cation–hydroxide–water coadsorption. Impedance analysis suggests that the hydrogen oxidation reaction inhibition is mainly caused by the hydrogen diffusion barrier of the coadsorbed trilayer rather than intuitive catalyst site blocking by the adsorbed cation species. Finally, these results give useful insights on how to design ionomeric binders for advanced alkaline membrane fuel cells.

The properties of LaSrМnO3 powders synthesized at various regimes

NASA Astrophysics Data System (ADS)

Mikhailov, M.; Sokolovskiy, A.; Vlasov, V.; Smolin, A.

2017-09-01

For the first time the concentration of ferromagnetic and paramagnetic phases in LaSrMnO3 compounds has been defined using diffuse reflection and absorption spectra in the visible and near-infrared regions. The compounds as powders were synthesized by heating La2O3/SrCO3/МnСO3 mixtures at 1200 °C which is less than their sintering temperature. The possibility to obtain LaSrMnO3 powders by solid state synthesis for smart coatings was shown.

Collection and corrections of oblique multiangle hyperspectral bidirectional reflectance imagery of the water surface

NASA Astrophysics Data System (ADS)

Bostater, Charles R.; Oney, Taylor S.

2017-10-01

Hyperspectral images of coastal waters in urbanized regions were collected from fixed platform locations. Surf zone imagery, images of shallow bays, lagoons and coastal waters are processed to produce bidirectional reflectance factor (BRF) signatures corrected for changing viewing angles. Angular changes as a function of pixel location within a scene are used to estimate changes in pixel size and ground sampling areas. Diffuse calibration targets collected simultaneously from within the image scene provides the necessary information for calculating BRF signatures of the water surface and shorelines. Automated scanning using a pushbroom hyperspectral sensor allows imagery to be collected on the order of one minute or less for different regions of interest. Imagery is then rectified and georeferenced using ground control points within nadir viewing multispectral imagery via image to image registration techniques. This paper demonstrates the above as well as presenting how spectra can be extracted along different directions in the imagery. The extraction of BRF spectra along track lines allows the application of derivative reflectance spectroscopy for estimating chlorophyll-a, dissolved organic matter and suspended matter concentrations at or near the water surface. Imagery is presented demonstrating the techniques to identify subsurface features and targets within the littoral and surf zones.

Monitoring of tissue optical properties during thermal coagulation of ex vivo tissues.

PubMed

Nagarajan, Vivek Krishna; Yu, Bing

2016-09-01

Real-time monitoring of tissue status during thermal ablation of tumors is critical to ensure complete destruction of tumor mass, while avoiding tissue charring and excessive damage to normal tissues. Currently, magnetic resonance thermometry (MRT), along with magnetic resonance imaging (MRI), is the most commonly used technique for monitoring and assessing thermal ablation process in soft tissues. MRT/MRI is very expensive, bulky, and often subject to motion artifacts. On the other hand, light propagation within tissue is sensitive to changes in tissue microstructure and physiology which could be used to directly quantify the extent of tissue damage. Furthermore, optical monitoring can be a portable, and cost-effective alternative for monitoring a thermal ablation process. The main objective of this study, is to establish a correlation between changes in tissue optical properties and the status of tissue coagulation/damage during heating of ex vivo tissues. A portable diffuse reflectance spectroscopy system and a side-firing fiber-optic probe were developed to study the absorption (μa (λ)), and reduced scattering coefficients (μ's (λ)) of native and coagulated ex vivo porcine, and chicken breast tissues. In the first experiment, both porcine and chicken breast tissues were heated at discrete temperature points between 24 and 140°C for 2 minutes. Diffuse reflectance spectra (430-630 nm) of native and coagulated tissues were recorded prior to, and post heating. In a second experiment, porcine tissue samples were heated at 70°C and diffuse reflectance spectra were recorded continuously during heating. The μa (λ) and μ's (λ) of the tissues were extracted from the measured diffuse reflectance spectra using an inverse Monte-Carlo model of diffuse reflectance. Tissue heating was stopped when the wavelength-averaged scattering plateaued. The wavelength-averaged optical properties, <μ's (λ)> and <μa (λ)>, for native porcine tissues (n = 66) at room temperature, were 5.4 ± 0.3 cm(-1) and 0.780 ± 0.008 cm(-1) (SD), respectively. The <μ's (λ)> and <μa (λ)> for native chicken breast tissues (n = 66) at room temperature, were 2.69 ± 0.08 cm(-1) and 0.29 ± 0.01 cm(-1) (SD), respectively. In the first experiment, the <μ's (λ)> of coagulated porcine and chicken breast tissue rose to 56.4 ± 3.6 cm(-1) at 68.7 ± 1.7°C (SD), and 52.8 ± 1 cm(-1) at 57.1 ± 1.5°C (SD), respectively. Correspondingly, the <μa (λ)> of coagulated porcine (140.6°C), and chicken breast tissues (130°C) were 0.75 ± 0.05 cm(-1) and 0.263 ± 0.004 cm(-1) (SD). For both tissues, charring was observed at temperatures above 80°C. During continuous monitoring of porcine tissue (with connective tissues) heating, the <μ's (λ)> started to rise rapidly from 13.7 ± 1.5 minutes and plateaued at 19 ± 2.5 (SD) minutes. The <μ's (λ)> plateaued at 11.7 ± 3 (SD) minutes for porcine tissue devoid of connective tissue between probe and tissue surface. No charring was observed during continuous monitoring of thermal ablation process. The changes in optical absorption and scattering properties can be continuously quantified, which could be used as a diagnostic biomarker for assessing tissue coagulation/damage during thermal ablation. Lasers Surg. Med. 48:686-694, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

In vivo inflammation mapping of periodontal disease based on diffuse reflectance spectral imaging: a clinical study

NASA Astrophysics Data System (ADS)

Prasanth, Chandra Sekhar; Betsy, Joseph; Jayanthi, Jayaraj L.; Nisha, Unni G.; Prasantila, Janam; Subhash, Narayanan

2013-02-01

Since conventional techniques using periodontal probes have inherent drawbacks in the diagnosis of different grades of gingival inflammation, development of noninvasive screening devices becomes significant. Diffuse reflectance (DR) spectra recorded with white light illumination is utilized to detect periodontal inflammation from the oxygenated hemoglobin absorption ratio R620/R575. A multispectral imaging system is utilized to record narrow-band DR images at 575 and 620 nm from the anterior sextant of the gingivia of 15 healthy volunteers and 25 patients (N=40). An experienced periodontist assesses the level of gingival inflammation at each site through periodontal probing and assigns diagnosis as healthy, mild, moderate, or severe inflammation. The DR image ratio R620/R575 computed for each pixel (8-μm resolution) from the monochrome images is pseudo-color-mapped to identify gingival inflammation sites. The DR image ratio values at each site are compared with clinical diagnosis to estimate the specificity and sensitivity of the DR imaging technique in inflammation mapping. The high diagnostic accuracy is utilized to detect underlying inflammation in six patients with a previous history of periodontitis.

Non-contact assessment of COD and turbidity concentrations in water using diffuse reflectance UV-Vis spectroscopy.

PubMed

Agustsson, Jon; Akermann, Oliver; Barry, D Andrew; Rossi, Luca

2014-08-01

Water contamination is an important environmental concern underlining the need for reliable real-time information on contaminant concentrations in natural waters. Here, a new non-contact UV-Vis spectroscopic approach for monitoring contaminants in water, and especially wastewater, is proposed. Diffuse reflectance UV-Vis spectroscopy was applied to measure simultaneously the chemical oxygen demand (COD) and turbidity (TUR) concentrations in water. The measurements were carried out in the wavelength range from 200-1100 nm. The measured spectra were analysed using partial-least-squares (PLS) regression. The correlation coefficient between the measured and the reference concentrations of COD and TUR in the water samples were R(2) = 0.85 and 0.96, respectively. These results highlight the potential of non-contact UV-Vis spectroscopy for the assessment of water contamination. A system built on the concept would be able to monitor wastewater pollution continuously, without the need for laborious sample collection and subsequent laboratory analysis. Furthermore, since no parts of the system are in contact with the wastewater stream the need for maintenance is minimised.

Reflectivity Spectra for Commonly Used Reflectors

NASA Astrophysics Data System (ADS)

Janecek, Martin

2012-06-01

Monte Carlo simulations play an important role in developing and evaluating the performance of radiation detection systems. To accurately model a reflector in an optical Monte Carlo simulation, the reflector's spectral response has to be known. We have measured the reflection coefficient for many commonly used reflectors for wavelengths from 250 nm to 800 nm. The reflectors were also screened for fluorescence and angular distribution changes with wavelength. The reflectors examined in this work include several polytetrafluoroethylene (PTFE) reflectors, Spectralon, GORE diffuse reflector, titanium dioxide paint, magnesium oxide, nitrocellulose filter paper, Tyvek paper, Lumirror, Melinex, ESR films, and aluminum foil. All PTFE films exhibited decreasing reflectivity with longer wavelengths due to transmission. To achieve >;0.95 reflectivity in the 380 to 500 nm range, the PTFE films have to be at least 0.5 mm thick-nitrocellulose is a good alternative if a thin diffuse reflector is needed. Several of the reflectors have sharp declines in reflectivity below a cut-off wavelength, including TiO2 (420 nm), ESR film (395 nm), nitrocellulose (330 nm), Lumirror (325 nm), and Melinex (325 nm). PTFE-like reflectors were the only examined reflectors that had reflectivity above 0.90 for wavelengths below 300 nm. Lumirror, Melinex, and ESR film exhibited fluorescence. Lumirror and Melinex are excited by wavelengths between 320 and 420 nm and have their emission peaks located at 440 nm, while ESR film is excited by wavelengths below 400 nm and the emission peak is located at 430 nm. Lumirror and Melinex also exhibited changing angular distributions with wavelength.

Self-assembly of bimetallic AuxPd1-x alloy nanoparticles via dewetting of bilayers through the systematic control of temperature, thickness, composition and stacking sequence

NASA Astrophysics Data System (ADS)

Kunwar, Sundar; Pandey, Puran; Sui, Mao; Bastola, Sushil; Lee, Jihoon

2018-03-01

Bimetallic alloy nanoparticles (NPs) are attractive materials for various applications with their morphology and elemental composition dependent optical, electronic, magnetic and catalytic properties. This work demonstrates the evolution of AuxPd1-x alloy nanostructures by the solid-state dewetting of sequentially deposited bilayers of Au and Pd on sapphire (0001). Various shape, size and configuration of AuxPd1‑x alloy NPs are fabricated by the systematic control of annealing temperature, deposition thickness, composition as well as stacking sequence. The evolution of alloy nanostructures is attributed to the surface diffusion, interface diffusion between bilayers, surface and interface energy minimization, Volmer-Weber growth model and equilibrium configuration. Depending upon the temperature, the surface morphologies evolve with the formation of pits, grains and voids and gradually develop into isolated semi-spherical alloy NPs by the expansion of voids and agglomeration of Au and Pd adatoms. On the other hand, small isolated to enlarged elongated and over-grown layer-like alloy nanostructures are fabricated due to the coalescence, partial diffusion and inter-diffusion with the increased bilayer thickness. In addition, the composition and stacking sequence of bilayers remarkably affect the final geometry of AuxPd1‑x nanostructures due to the variation in the dewetting process. The optical analysis based on the UV–vis-NIR reflectance spectra reveals the surface morphology dependent plasmonic resonance, scattering, reflection and absorption properties of AuxPd1‑x alloy nanostructures.

Non-invasive tissue temperature measurements based on quantitative diffuse optical spectroscopy (DOS) of water.

PubMed

Chung, S H; Cerussi, A E; Merritt, S I; Ruth, J; Tromberg, B J

2010-07-07

We describe the development of a non-invasive method for quantitative tissue temperature measurements using Broadband diffuse optical spectroscopy (DOS). Our approach is based on well-characterized opposing shifts in near-infrared (NIR) water absorption spectra that appear with temperature and macromolecular binding state. Unlike conventional reflectance methods, DOS is used to generate scattering-corrected tissue water absorption spectra. This allows us to separate the macromolecular bound water contribution from the thermally induced spectral shift using the temperature isosbestic point at 996 nm. The method was validated in intralipid tissue phantoms by correlating DOS with thermistor measurements (R=0.96) with a difference of 1.1+/-0.91 degrees C over a range of 28-48 degrees C. Once validated, thermal and hemodynamic (i.e. oxy- and deoxy-hemoglobin concentration) changes were measured simultaneously and continuously in human subjects (forearm) during mild cold stress. DOS-measured arm temperatures were consistent with previously reported invasive deep tissue temperature studies. These results suggest that DOS can be used for non-invasive, co-registered measurements of absolute temperature and hemoglobin parameters in thick tissues, a potentially important approach for optimizing thermal diagnostics and therapeutics.

Hybrid method to estimate two-layered superficial tissue optical properties from simulated data of diffuse reflectance spectroscopy.

PubMed

Hsieh, Hong-Po; Ko, Fan-Hua; Sung, Kung-Bin

2018-04-20

An iterative curve fitting method has been applied in both simulation [J. Biomed. Opt.17, 107003 (2012)JBOPFO1083-366810.1117/1.JBO.17.10.107003] and phantom [J. Biomed. Opt.19, 077002 (2014)JBOPFO1083-366810.1117/1.JBO.19.7.077002] studies to accurately extract optical properties and the top layer thickness of a two-layered superficial tissue model from diffuse reflectance spectroscopy (DRS) data. This paper describes a hybrid two-step parameter estimation procedure to address two main issues of the previous method, including (1) high computational intensity and (2) converging to local minima. The parameter estimation procedure contained a novel initial estimation step to obtain an initial guess, which was used by a subsequent iterative fitting step to optimize the parameter estimation. A lookup table was used in both steps to quickly obtain reflectance spectra and reduce computational intensity. On simulated DRS data, the proposed parameter estimation procedure achieved high estimation accuracy and a 95% reduction of computational time compared to previous studies. Furthermore, the proposed initial estimation step led to better convergence of the following fitting step. Strategies used in the proposed procedure could benefit both the modeling and experimental data processing of not only DRS but also related approaches such as near-infrared spectroscopy.

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.

Aqueous Reversed-Phase HPLC/FT-IR Using Diffuse Reflectance Detections

NASA Astrophysics Data System (ADS)

Kalasinsky, Victor F.; Pai, T. H.; Kenton, R. C.; Kalasinsky, Kathryn S.

1989-12-01

Solvent-elimination HPLC/FT-IR has become a viable combination of two important techniques, and we have been developing a system which is adaptable to both normal and reversed-phase liquid chromatography. The interface involves the deposition of HPLC eluites onto a KCI-laden train with subsequent analysis via diffuse reflectance spectroscopy, and with minor modifications, the system can be used with microbore and analytical columns. With aqueous solvents, the water is converted to methanol and acetone in a post-column reaction with 2,2-dimethoxypropane before the eluites are deposited. A number of different samples have been used to demonstrate the interface and its flexibility. Steroids, analgesics, and other pharmaceutical preparations have been separated with reverse-phase solvents and identified by their infrared spectra. For some of the compounds studied, different infrared spectra of a given compound have been found to exhibit intensity variations, which arise from different crystalline states. The differences can be concentration dependent and may be useful in obtaining semi-quantitative information from the infrared spectra. Applications involving both gradient elution and isocratic separations have been successful. The former provides the same advantages for HPLC/FT-IR as one finds in conventional HPLC. More recent work has been applied to the use of buffers such as those frequently used in bioanalytical separations. In trying to simplify the post-column reaction with water, we have immobilized dehydration reagents onto silica particles and packed these materials into a column which is inserted in-line after the analytical column. Of the reagents utilized to date, 3,3-dimethoxypropyltrimethoxysilane has been found to perform most efficiently. It has advantages over the simpler reagents because it can be regenerated in the reaction column. Results and the efficiency of the dehydration process and its relation to the type of reagent and its coverage will be discussed.

Preparation and spectral properties of europium hydrogen squarate microcrystals

NASA Astrophysics Data System (ADS)

Kolev, T.; Danchova, N.; Shandurkov, D.; Gutzov, S.

2018-04-01

A simple scheme for preparation of europium hydrogen squarate octahydrate microcrystals, Eu(HSq)3·8H2O is demonstrated. The microcrystalline powders obtained have a potential application as non-centrosymmetric and UV radiation - protective hybrid optical material. The site-symmetry of the Eu - ion is C2V or lower, obtained from diffuse reflectance spectra. The formation of europium hydrogen squarate is supported by IR - spectroscopy, UV-vis spectroscopy, chemical analysis and X-ray diffraction. A detailed analysis of the UV-vis and IR spectra of the micropowders prepared is presented. The reaction between europium oxide and squaric acid leads to formation of microcrystalline plate-like crystals of europium hydrogen squarate Eu(HSq)3·8H2O, a non-centrosymmetric hybrid optical material with a potential application as UV radiation - protective coatings.

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.

Further characterization of spectral features attributable to titanium on the moon

NASA Technical Reports Server (NTRS)

Burns, R. G.; Parkin, K. M.; Loeffler, B. M.; Leung, I. S.; Abu-Eid, R. M.

1976-01-01

The following transitions are observed in the electronic absorption spectra of lunar titanaugites: Fe(2+) spin-allowed and spin-forbidden crystal field; Ti(3+) spin allowed and Jahn-Teller split crystal field; Ti(3+)-Ti(4+) CT; Fe(2+)-Ti(4+) CT; and O(2-)-Fe(2+), Ti(3+), Ti(4+) CT. Of these, the transitions involving Ti(3+) are unique to lunar or nonferric-bearing titanaugites. All titanaugites have the Fe(2+) crystal field and Fe(2+)-Ti(4+) CT transitions in common. These features in the diffuse reflectance spectra of lunar materials give rise to the '1.0 band' and to the observed absorption around 0.5-0.6 micron, respectively. Since regolith contains a variety of phases with coexisting Fe(2+), Ti(3+), and Ti(4+) ions, several metal-metal charge transfer processes are possible.

Diffuse emission and pathological Seyfert spectra

NASA Technical Reports Server (NTRS)

Halpern, Jules P.

1995-01-01

In this annual ROSAT status report, the diffuse emission and spectra from Seyfert galaxies are examined. Three papers are presented and their contents include the soft x-ray properties and spectra of a binary millisecond pulsar, the PSPC and HRI observations of a Starburst/Seyfert 2 Galaxy, and an analysis of the possibility of x-ray luminous starbursts in the Einstein Medium Sensitivity Survey.

Investigation on the morphological and optical evolution of bimetallic Pd-Ag nanoparticles on sapphire (0001) by the systematic control of composition, annealing temperature and time

PubMed Central

Pandey, Puran; Kunwar, Sundar; Sui, Mao; Bastola, Sushil

2017-01-01

Multi-metallic alloy nanoparticles (NPs) can offer additional opportunities for modifying the electronic, optical and catalytic properties by the control of composition, configuration and size of individual nanostructures that are consisted of more than single element. In this paper, the fabrication of bimetallic Pd-Ag NPs is systematically demonstrated via the solid state dewetting of bilayer thin films on c-plane sapphire by governing the temperature, time as well as composition. The composition of Pd-Ag bilayer remarkably affects the morphology of alloy nanostructures, in which the higher Ag composition, i.e. Pd0.25Ag0.75, leads to the enhanced dewetting of bilayers whereas the higher Pd composition (Pd0.75Ag0.25) hinders the dewetting. Depending on the annealing temperature, Pd-Ag alloy nanostructures evolve with a series of configurations, i.e. nucleation of voids, porous network, elongated nanoclusters and round alloy NPs. In addition, with the annealing time set, the gradual configuration transformation from the elongated to round alloy NPs as well as size reduction is demonstrated due to the enhanced diffusion and sublimation of Ag atoms. The evolution of various morphology of Pd-Ag nanostructures is described based on the surface diffusion and inter-diffusion of Pd and Ag adatoms along with the Ag sublimation, Rayleigh instability and energy minimization mechanism. The reflectance spectra of bimetallic Pd-Ag nanostructures exhibit various quadrupolar and dipolar resonance peaks, peak shifts and absorption dips owing to the surface plasmon resonance of nanostructures depending on the surface morphology. The intensity of reflectance spectra is gradually decreased along with the surface coverage and NP size evolution. The absorption dips are red-shifted towards the longer wavelength for the larger alloy NPs and vice-versa. PMID:29253017

Diffuse Reflectance Spectroscopy (DRS) of radiation-induced re-oxygenation in sensitive and resistant head and neck tumor xenografts

NASA Astrophysics Data System (ADS)

Dadgar, Sina; Rodríguez Troncoso, Joel; Rajaram, Narasimhan

2018-02-01

Currently, anatomical assessment of tumor volume performed several weeks after completion of treatment is the clinical standard to determine whether a cancer patient has responded to a treatment. However, functional changes within the tumor could potentially provide information regarding treatment resistance or response much earlier than anatomical changes. We have used diffuse reflectance spectroscopy to assess the short and long-term re-oxygenation kinetics of a human head and neck squamous cell carcinoma xenografts in response to radiation therapy. First, we injected UM-SCC-22B cell line into the flank of 50 mice to grow xenografts. Once the tumor volume reached 200 mm3 (designated as Day 1), the mice were distributed into radiation and control groups. Members of radiation group underwent a clinical dose of radiation of 2 Gy/day on Days 1, 4, 7, and 10 for a cumulative dose of 8 Gy. DRS spectra of these tumors were collected for 14 days during and after therapy, and the collected spectra of each tumor were converted to its optical properties using a lookup table-base inverse model. We found statistically significant differences in tumor growth rate between two groups which is in indication of the sensitivity of this cell line to radiation. We further acquired significantly different contents of hemoglobin and scattering magnitude and size in two groups. The scattering has previously been associated with necrosis. We furthermore found significantly different time-dependent changes in vascular oxygenation and tumor hemoglobin concentration in post-radiation days.

Integrated Mueller-matrix near-infrared imaging and point-wise spectroscopy improves colonic cancer detection

PubMed Central

Wang, Jianfeng; Zheng, Wei; Lin, Kan; Huang, Zhiwei

2016-01-01

We report the development and implementation of a unique integrated Mueller-matrix (MM) near-infrared (NIR) imaging and Mueller-matrix point-wise diffuse reflectance (DR) spectroscopy technique for improving colonic cancer detection and diagnosis. Point-wise MM DR spectra can be acquired from any suspicious tissue areas indicated by MM imaging. A total of 30 paired colonic tissue specimens (normal vs. cancer) were measured using the integrated MM imaging and point-wise MM DR spectroscopy system. Polar decomposition algorithms are employed on the acquired images and spectra to derive three polarization metrics including depolarization, diattentuation and retardance for colonic tissue characterization. The decomposition results show that tissue depolarization and retardance are significantly decreased (p<0.001, paired 2-sided Student’s t-test, n = 30); while the tissue diattentuation is significantly increased (p<0.001, paired 2-sided Student’s t-test, n = 30) associated with colonic cancer. Further partial least squares discriminant analysis (PLS-DA) and leave-one tissue site-out, cross validation (LOSCV) show that the combination of the three polarization metrics provide the best diagnostic accuracy of 95.0% (sensitivity: 93.3%, and specificity: 96.7%) compared to either of the three polarization metrics (sensitivities of 93.3%, 83.3%, and 80.0%; and specificities of 90.0%, 96.7%, and 80.0%, respectively, for the depolarization, diattentuation and retardance metrics) for colonic cancer detection. This work suggests that the integrated MM NIR imaging and point-wise MM NIR diffuse reflectance spectroscopy has the potential to improve the early detection and diagnosis of malignant lesions in the colon. PMID:27446640

Berlin Reflectance Spectral Library (BRSL)

NASA Astrophysics Data System (ADS)

Henckel, D.; Arnold, G.; Kappel, D.; Moroz, L. V.; Markus, K.

2017-09-01

The Berlin Reflectance Spectral Library (BRSL) provides a collection of reflectance spectra between 0.3 and 17 µm. It was originally dedicated to support space missions to small solar system bodies. Meanwhile the library includes selections of biconical reflectance spectra for spectral data analysis of other planetary bodies as well. The library provides reference spectra of well-characterized terrestrial analogue materials and meteorites for interpretation of remote sensing reflectance spectra of planetary surfaces. We introduce the BRSL, summarize the data available, and access to use them for further relevant applications.

Estimating the leaf nitrogen content of paddy rice by using the combined reflectance and laser-induced fluorescence spectra.

PubMed

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

2016-08-22

Paddy rice is one of the most important crops in China, and leaf nitrogen content (LNC) serves as a significant indictor for monitoring crop status. A reliable method is needed for precise and fast quantification of LNC. Laser-induced fluorescence (LIF) technology and reflectance spectra of crops are widely used to monitor leaf biochemical content. However, comparison between the fluorescence and reflectance spectra has been rarely investigated in the monitoring of LNC. In this study, the performance of the fluorescence and reflectance spectra for LNC estimation was discussed based on principal component analysis (PCA) and back-propagation neural network (BPNN). The combination of fluorescence and reflectance spectra was also proposed to monitor paddy rice LNC. The fluorescence and reflectance spectra exhibited a high degree of multi-collinearity. About 95.38%, and 97.76% of the total variance included in the spectra were efficiently extracted by using the first three PCs in PCA. The BPNN was implemented for LNC prediction based on new variables calculated using PCA. The experimental results demonstrated that the fluorescence spectra (R² = 0.810, 0.804 for 2014 and 2015, respectively) are superior to the reflectance spectra (R² = 0.721, 0.671 for 2014 and 2015, respectively) for estimating LNC based on the PCA-BPNN model. The proposed combination of fluorescence and reflectance spectra can greatly improve the accuracy of LNC estimation (R² = 0.912, 0.890 for 2014 and 2015, respectively).

TRES Survey of Variable Diffuse Interstellar Bands

NASA Astrophysics Data System (ADS)

Law, Charles; Milisavljevic, Dan; Crabtree, Kyle; Johansen, Sommer; Patnaude, Daniel

2017-01-01

Diffuse interstellar bands (DIBs) are absorption features commonly observed in optical/near-infrared spectra of stars and thought to be associated with polyatomic molecules that comprise a significant reservoir of organic material in the universe. However, because the central wavelengths of DIBs do not correspond with electronic transitions of known atomic or molecular species, the specific physical nature of their carriers remains inconclusive despite decades of observational, theoretical, and experimental research. It is well established that DIB carriers must be located in the interstellar medium, but the recent discovery of time-varying DIBs in the spectra of the extragalactic supernova SN 2012ap suggests that some may be created in massive star environments. We report evidence of short time-scale (˜1-60 days) variations in DIB absorption line substructure toward 3 of 17 massive stars observed as part of a pathfinder survey of variable DIBs. The detections are made in high-resolution optical spectra (R ˜ 44000) from the Tillinghast Reflection Echelle Spectrograph on the 1.5m Tillinghast telescope at the Smithsonian Astrophysical Observatory's Fred L. Whipple Observatory on Mt. Hopkins in Arizona. Our detections have signal-to-noise ratios of 5-15 around the features of interest, and are thus considered significant but requiring further investigation. We find that these changes are potentially consistent with interactions between stellar winds and DIB carriers in close proximity. Our findings motivate a larger survey to further characterize these variations and may establish a powerful new method for probing the poorly understood physical characteristics of DIB carriers.

Spatial Variation of Diapycnal Diffusivity Estimated From Seismic Imaging of Internal Wave Field, Gulf of Mexico

NASA Astrophysics Data System (ADS)

Dickinson, Alex; White, N. J.; Caulfield, C. P.

2017-12-01

Bright reflections are observed within the upper 1,000 m of the water column along a seismic reflection profile that traverses the northern margin of the Gulf of Mexico. Independent hydrographic calibration demonstrates that these reflections are primarily caused by temperature changes associated with different water masses that are entrained into the Gulf along the Loop Current. The internal wave field is analyzed by automatically tracking 1,171 reflections, each of which is greater than 2 km in length. Power spectra of the horizontal gradient of isopycnal displacement, ϕξx, are calculated from these tracked reflections. At low horizontal wave numbers (kx<10-2 cpm), ϕξx∝kx-0.2±0.6, in agreement with hydrographic observations of the internal wave field. The turbulent spectral subrange is rarely observed. Diapycnal diffusivity, K, is estimated from the observed internal wave spectral subrange of each tracked reflection using a fine-scale parametrization of turbulent mixing. Calculated values of K vary between 10-8 and 10-4 m2 s-1 with a mean value of K˜4×10-6 m2 s-1. The spatial distribution of turbulent mixing shows that K˜10-7 m2 s-1 away from the shelf edge in the upper 300 m where stratification is strong. Mixing is enhanced by up to 4 orders of magnitude adjacent to the shoaling bathymetry of the continental slope. This overall pattern matches that determined by analyzing nearby suites of CTD casts. However, the range of values recovered by spectral analysis of the seismic image is greater as a consequence of significantly better horizontal resolution.

Infrared reflectance spectra (4-12 micron) of lunar samples

NASA Technical Reports Server (NTRS)

Nash, Douglas B.

1991-01-01

Presented here are infrared reflectance spectra of a typical set of Apollo samples to illustrate spectral character in the mid-infrared (4 to 12 microns) of lunar materials and how the spectra varies among three main forms: soil, breccia, and igneous rocks. Reflectance data, to a close approximation, are the inverse of emission spectra; thus, for a given material the spectral reflectance (R) at any given wavelength is related to emission (E) by 1 - R equals E. Therefore, one can use reflectance spectra of lunar samples to predict how emission spectra of material on the lunar surface will appear to spectrometers on orbiting spacecraft or earthbound telescopes. Spectra were measured in the lab in dry air using a Fourier Transform Infrared spectrometer. Shown here is only the key portion (4 to 12 microns) of each spectrum relating to the principal spectral emission region for sunlit lunar materials and to where the most diagnostic spectral features occur.

The use of UV-visible reflectance spectroscopy as an objective tool to evaluate pearl quality.

PubMed

Agatonovic-Kustrin, Snezana; Morton, David W

2012-07-01

Assessing the quality of pearls involves the use of various tools and methods, which are mainly visual and often quite subjective. Pearls are normally classified by origin and are then graded by luster, nacre thickness, surface quality, size, color and shape. The aim of this study was to investigate the capacity of Artificial Neural Networks (ANNs) to classify and estimate the quality of 27 different pearls from their UV-Visible spectra. Due to the opaque nature of pearls, spectroscopy measurements were performed using the Diffuse Reflectance UV-Visible spectroscopy technique. The spectra were acquired at two different locations on each pearl sample in order to assess surface homogeneity. The spectral data (inputs) were smoothed to reduce the noise, fed into ANNs and correlated to the pearl's quality/grading criteria (outputs). The developed ANNs were successful in predicting pearl type, mollusk growing species, possible luster and color enhancing, donor condition/type, recipient/host color, donor color, pearl luster, pearl color, origin. The results of this study shows that the developed UV-Vis spectroscopy-ANN method could be used as a more objective method of assessing pearl quality (grading) and may become a valuable tool for the pearl grading industry.

HIREGS observations of the Galactic center and Galactic plane: Separation of the diffuse Galactic hard X-ray continuum from the point source spectra

NASA Technical Reports Server (NTRS)

Boggs, S. E.; Lin, R. P.; Coburn, W.; Feffer, P.; Pelling, R. M.; Schroeder, P.; Slassi-Sennou, S.

1997-01-01

The balloon-borne high resolution gamma ray and X-ray germanium spectrometer (HIREGS) was used to observe the Galactic center and two positions along the Galactic plane from Antarctica in January 1995. For its flight, the collimators were configured to measure the Galactic diffuse hard X-ray continuum between 20 and 200 keV by directly measuring the point source contributions to the wide field of view flux for subtraction. The hard X-ray spectra of GX 1+4 and GRO J1655-40 were measured with the diffuse continuum subtracted off. The analysis technique for source separation is discussed and the preliminary separated spectra for these point sources and the Galactic diffuse emission are presented.

A large-area diffuse air discharge plasma excited by nanosecond pulse under a double hexagon needle-array electrode.

PubMed

Liu, Zhi-Jie; Wang, Wen-Chun; Yang, De-Zheng; Wang, Sen; Zhang, Shuai; Tang, Kai; Jiang, Peng-Chao

2014-01-01

A large-area diffuse air discharge plasma excited by bipolar nanosecond pulse is generated under a double hexagon needle-array electrode at atmospheric pressure. The images of the diffuse discharge, electric characteristics, and the optical emission spectra emitted from the diffuse air discharge plasma are obtained. Based on the waveforms of pulse voltage and current, the power consumption, and the power density of the diffuse air discharge plasma are investigated under different pulse peak voltages. The electron density and the electron temperature of the diffuse plasma are estimated to be approximately 1.42×10(11) cm(-3) and 4.4 eV, respectively. The optical emission spectra are arranged to determine the rotational and vibrational temperatures by comparing experimental with simulated spectra. Meanwhile, the rotational and vibrational temperatures of the diffuse discharge plasma are also discussed under different pulse peak voltages and pulse repetition rates, respectively. In addition, the diffuse air discharge plasma can form an area of about 70×50 mm(2) on the surface of dielectric layer and can be scaled up to the required size. Crown Copyright © 2013. Published by Elsevier B.V. All rights reserved.

In vivo measurements of optical properties of human muscles with visible and near infrared reflectance spectroscopy

NASA Astrophysics Data System (ADS)

Wang, Chiao Yi; Yu, Ting Wen; Sung, Kung Bin

2018-02-01

Estimating optical properties of tissues is a crucial step to model photon migration in tissue, facilitate the design of the probe geometry, better interpret data measured from tissue and predict photon energy distributions in tissue for various diagnostic and therapeutic applications. Diffuse reflectance spectroscopy (DRS) using visible and near-infrared light is a well-known method for estimating optical properties of tissues. For estimating optical properties of muscles, most existing researches have used integrating spheres for ex-vivo measurements. However, due to inter-subject variability and sitespecific conditions, an in-vivo approach can provide more accurate estimations of muscle absorption and scattering coefficients, which is important for the tomographic reconstruction of changes in the absorption or fluorescence in tissue. In this study, we used DRS with wavelengths between 600 nm and 800 nm and a fiber bundle with source-to-detector separations in the range of 0.18-0.35 cm to quantify wavelength-dependent scattering and absorption coefficients of human muscles in vivo with an inverse Monte Carlo model. Reflectance spectra were measured on the neck and the upper arm of one volunteer. After calibrating spectra with tissue phantoms made of Intralipid and India ink, we estimated scattering and absorption coefficients of muscles. The results are compared to those measured ex vivo in the literature.

AFM investigation and optical band gap study of chemically deposited PbS thin films

NASA Astrophysics Data System (ADS)

Zaman, S.; Mansoor, M.; Abubakar; Asim, M. M.

2016-08-01

The interest into deposition of nanocrystalline PbS thin films, the potential of designing and tailoring both the topographical features and the band gap energy (Eg) by controlling growth parameters, has significant technological importance. Nanocrystalline thin films of lead sulfide were grown onto glass substrates by chemical bath deposition (CBD) method. The experiments were carried out by varying deposition temperature. We report on the modification of structural and optical properties as a function of deposition temperature. The morphological changes of the films were analyzed by using SEM and AFM. AFM was also used to calculate average roughness of the films. XRD spectra indicated preferred growth of cubic phase of PbS films in (200) direction with increasing deposition time. Optical properties have been studied by UV-Spectrophotometer. From the diffused reflectance spectra we have calculated the optical Eg shift from 0.649-0.636 eV with increasing deposition time.

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.

Subcarbonyl species of molybdenum hexacarbonyl supported on silica: A DRIFT study

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

Kurhinen, M.; Venaelaeinen, T.; Pakkanen, T.A.

1994-10-06

Subspecies of partially decarbonylated molybdenum hexacarbonyl supported on silica were studied by diffuse reflectance IR spectroscopy. Mo(CO)[sub 6]/SiO[sub 2] was prepared in a fluidized bed reactor by vapor-phase adsorption of molybdenum hexacarbonyl under nitrogen flow. Decarbonylation begins when Mo(CO)[sub 6] has adsorbed onto the silica. Dehydroxylation of the support during calcination facilitates the formation of subspecies of Mo(CO)[sub 6]. The activation energy needed for bond formation between a transition metal and silica and for decarbonylation is lower than the desorption energy of physisorbed Mo(CO)[sub 6], and this was seen in the IR spectra as a disappearance of bands due tomore » subspecies. When the supported Mo(CO)[sub 6] was reheated the physisorption bands were the last to disappear from the IR spectra. 37 refs., 6 figs., 2 tabs.« less

Astronomy Meets Biology: EFOSC2 and the Chirality of Life

NASA Astrophysics Data System (ADS)

Sterzik, M.; Bagnulo, S.; Azua, A.; Salinas, F.; Alfaro, J.; Vicuna, R.

2010-12-01

Homochirality, i.e., the exclusive use of L-amino acids and D-sugar in biological material, induces circular polarisation in the diffuse reflectance spectra of biotic material. Polarimetry may therefore become an interesting remote sensing technique in the future search for extraterrestrial life. We have explored this technique and performed a laboratory experiment making an exotic use of an astronomical instrument. During a period when EFOSC2 was detached from the Nasmyth focus to host a visitor instrument at the NTT, we have observed various samples of biotic and abiotic material and measured their linear and circular polarisation spectra. Among the various targets, we have included samples of the hypolithic cyanobacteria species Chroococcidiopsis isolated from the Coastal Range of the Atacama Desert. To our knowledge, these are the first and highest precision measurements of circular polarisation using living material and obtained with an astronomical instrument.

Spherical V-Fe-MCM-48: The Synthesis, Characterization and Hydrothermal Stability.

PubMed

Qian, Wang; Wang, Haiqing; Chen, Jin; Kong, Yan

2015-04-14

Spherical MCM-48 mesoporous sieve co-doped with vanadium and iron was successfully synthesized via one-step hydrothermal method. The material was characterized by X-ray diffraction (XRD), nitrogen adsorption-desorption isotherms, inductively coupled plasma (ICP), scanning electron microscopy (SEM), transmission electron microscopy (TEM), diffuse reflectance UV-vis spectra, and X-ray photoelectron spectra (XPS) techniques. Results indicated that the V-Fe-MCM-48 showed an ordered 3D cubic mesostructure with spherical morphology, narrow pore size distribution and high specific surface area. Most of vanadium and iron atoms existing as tetrahedral V 4+ and Fe 3+ species were co-doped into the silicate framework. The particle sizes of V-Fe-MCM-48 were smaller and the specific area was much higher than those of of V-MCM-48. Additionally, the synthesized V-Fe-MCM-48 exhibited improved hydrothermal stability compared with the pure MCM-48.

Spherical V-Fe-MCM-48: The Synthesis, Characterization and Hydrothermal Stability

PubMed Central

Qian, Wang; Wang, Haiqing; Chen, Jin; Kong, Yan

2015-01-01

Spherical MCM-48 mesoporous sieve co-doped with vanadium and iron was successfully synthesized via one-step hydrothermal method. The material was characterized by X-ray diffraction (XRD), nitrogen adsorption-desorption isotherms, inductively coupled plasma (ICP), scanning electron microscopy (SEM), transmission electron microscopy (TEM), diffuse reflectance UV-vis spectra, and X-ray photoelectron spectra (XPS) techniques. Results indicated that the V-Fe-MCM-48 showed an ordered 3D cubic mesostructure with spherical morphology, narrow pore size distribution and high specific surface area. Most of vanadium and iron atoms existing as tetrahedral V4+ and Fe3+ species were co-doped into the silicate framework. The particle sizes of V-Fe-MCM-48 were smaller and the specific area was much higher than those of of V-MCM-48. Additionally, the synthesized V-Fe-MCM-48 exhibited improved hydrothermal stability compared with the pure MCM-48. PMID:28788030

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

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.

Enhanced photocatalytic performance of RGO/Ag nanocomposites produced via a facile microwave irradiation for the degradation of Rhodamine B in aqueous solution

NASA Astrophysics Data System (ADS)

Divya, K. S.; Chandran, Akash; Reethu, V. N.; Mathew, Suresh

2018-06-01

A series of RGO/Ag nanocomposites with different weight addition ratios of graphene oxide (GO) have been successfully prepared in situ through the simultaneous reduction of GO and AgNO3 via a facile microwave irradiation. X-ray diffraction analysis, Fourier Transform Infrared Spectroscopy, UV-vis diffuse reflectance spectra, Scanning electron microscopy, Photoluminescence spectra, Raman spectra, Atomic Force Microscopy, X-ray photoelectron spectroscopy (XPS) and Transmission electron microscopy are employed to determine the properties of the samples. It is found that RGO/Ag nanocomposites with a proper weight addition ratios of GO exhibit higher photocatalytic activity toward liquid phase photodegradation of Rhodamine B under visible light irradiation. The improved photoactivity of RGO/Ag nanocomposites can be ascribed to the integrative synergestic effect of enhanced adsorption capacity, the prolonged lifetime of photogenerated electron-hole pairs and effective interfacial hybridization between RGO and Ag nanoparticles. This study also shows that graphene sheets act as electronic conductive channels to efficiently separate charge carriers from Ag nanoparticles.

Diffuse Reflectance Spectroscopy for Surface Measurement of Liver Pathology.

PubMed

Nilsson, Jan H; Reistad, Nina; Brange, Hannes; Öberg, Carl-Fredrik; Sturesson, Christian

2017-01-01

Liver parenchymal injuries such as steatosis, steatohepatitis, fibrosis, and sinusoidal obstruction syndrome can lead to increased morbidity and liver failure after liver resection. Diffuse reflectance spectroscopy (DRS) is an optical measuring method that is fast, convenient, and established. DRS has previously been used on the liver with an invasive technique consisting of a needle that is inserted into the parenchyma. We developed a DRS system with a hand-held probe that is applied to the liver surface. In this study, we investigated the impact of the liver capsule on DRS measurements and whether liver surface measurements are representative of the whole liver. We also wanted to confirm that we could discriminate between tumor and liver parenchyma by DRS. The instrumentation setup consisted of a light source, a fiber-optic contact probe, and two spectrometers connected to a computer. Patients scheduled for liver resection due to hepatic malignancy were included, and DRS measurements were performed on the excised liver part with and without the liver capsule and alongside a newly cut surface. To estimate the scattering parameters and tissue chromophore volume fractions, including blood, bile, and fat, the measured diffuse reflectance spectra were applied to an analytical model. In total, 960 DRS spectra from the excised liver tissue of 18 patients were analyzed. All factors analyzed regarding tumor versus liver tissue were significantly different. When measuring through the capsule, the blood volume fraction was found to be 8.4 ± 3.5%, the lipid volume fraction was 9.9 ± 4.7%, and the bile volume fraction was 8.2 ± 4.6%. No differences could be found between surface measurements and cross-sectional measurements. In measurements with/without the liver capsule, the differences in volume fraction were 1.63% (0.75-2.77), -0.54% (-2.97 to 0.32), and -0.15% (-1.06 to 1.24) for blood, lipid, and bile, respectively. This study shows that it is possible to manage DRS measurements through the liver capsule and that surface DRS measurements are representative of the whole liver. The results are consistent with data published earlier on the combination of liver chromophores. The results encourage us to proceed with in vivo measurements for further quantification of the liver's composition and assessment of parenchymal damage such as steatosis and fibrosis grade. © 2016 S. Karger AG, Basel.

New insight into the promoting role of process on the CeO₂-WO₃/TiO₂ catalyst for NO reduction with NH₃ at low-temperature.

PubMed

Zhang, Shule; Zhong, Qin; Shen, Yuge; Zhu, Li; Ding, Jie

2015-06-15

This study aimed at investigating the reason of high catalytic activity for CeO2-WO3/TiO2 catalyst from the aspects of WO3 interaction with other species and the NO oxidation process. Analysis by X-ray diffractometry, photoluminescence spectra, diffuse reflectance UV-visible, X-ray photoelectron spectroscopy, density functional theory calculations, electron paramagnetic resonance spectroscopy, temperature-programmed-desorption of NO and in situ diffuse reflectance infrared transform spectroscopy showed that WO3 could interact with CeO2 to improve the electron gaining capability of CeO2 species. In addition, WO3 species acted as electron donating groups to transfer the electrons to CeO2 species. The two aspects enhanced the formation of reduced CeO2 species to improve the formation of superoxide ions. Furthermore, the Ce species were the active sites for the NO adsorption and the superoxide ions over the catalyst needed oxidizing the adsorbed NO to improve the NO oxidation. This process was responsible for the high catalytic activity of CeO2-WO3/TiO2 catalyst. Copyright © 2015 Elsevier Inc. All rights reserved.

Synthesis and photocatalytic activity of ytterbium-doped titania/diatomite composite photocatalysts

NASA Astrophysics Data System (ADS)

Tang, Wenjian; Qiu, Kehui; Zhang, Peicong; Yuan, Xiqiang

2016-01-01

Ytterbium-doped titanium dioxide (Yb-TiO2)/diatomite composite materials with different Yb concentrations were prepared by sol-gel method. The phase structure, morphology, and chemical composition of the as-prepared composites were well characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM), and ultraviolet-visible (UV-vis) diffuse reflection spectroscopy. The XRD and Raman spectroscopy analysis indicated that the TiO2 existed in the form of pure anatase in the composites. The SEM images exhibited the well deposition and dispersion of TiO2 nanoparticles with little agglomeration on the surfaces of diatoms. The UV-vis diffuse reflection spectra showed that the band gap of TiO2 could be narrowed by the introduction of Yb species, which was further affected by doping concentration of Yb. The photocatalytic activity of synthesized samples was investigated by the degradation of methylene blue (MB) under UV light irradiation. It was observed that the photocatalytic degradation followed a pseudo-first-order kinetics according to the Langmuir-Hinshelwood model. Compared to TiO2 and TiO2/diatomite, the Yb-TiO2/diatomite composites exhibited higher photocatalytic activity toward degradation of MB using UV light irradiation.

Structural, Morphological, Optical and Photocatalytic Properties of Y, N-Doped and Codoped TiO2 Thin Films

PubMed Central

Hamden, Zeineb; Conceição, David; Boufi, Sami; Vieira Ferreira, Luís Filipe; Bouattour, Soraa

2017-01-01

Pure TiO2, Y-N single-doped and codoped TiO2 powders and thin films deposited on glass beads were successfully prepared using dip-coating and sol-gel methods. The samples were analyzed using grazing angle X-ray diffraction (GXRD), Raman spectroscopy, time resolved luminescence, ground state diffuse reflectance absorption and scanning electron microscopy (SEM). According to the GXRD patterns and micro-Raman spectra, only the anatase form of TiO2 was made evident. Ground state diffuse reflectance absorption studies showed that doping with N or codoping with N and Y led to an increase of the band gap. Laser induced luminescence analysis revealed a decrease in the recombination rate of the photogenerated holes and electrons. The photocatalytic activity of supported catalysts, toward the degradation of toluidine, revealed a meaningful enhancement upon codoping samples at a level of 2% (atomic ratio). The photocatalytic activity of the material and its reactivity can be attributed to a reduced, but significant, direct photoexcitation of the semiconductor by the halogen lamp, together with a charge-transfer-complex mechanism, or with the formation of surface oxygen vacancies by the N dopant atoms. PMID:28772962

Structural, Morphological, Optical and Photocatalytic Properties of Y, N-Doped and Codoped TiO₂ Thin Films.

PubMed

Hamden, Zeineb; Conceição, David; Boufi, Sami; Vieira Ferreira, Luís Filipe; Bouattour, Soraa

2017-05-31

Pure TiO₂, Y-N single-doped and codoped TiO₂ powders and thin films deposited on glass beads were successfully prepared using dip-coating and sol-gel methods. The samples were analyzed using grazing angle X-ray diffraction (GXRD), Raman spectroscopy, time resolved luminescence, ground state diffuse reflectance absorption and scanning electron microscopy (SEM). According to the GXRD patterns and micro-Raman spectra, only the anatase form of TiO₂ was made evident. Ground state diffuse reflectance absorption studies showed that doping with N or codoping with N and Y led to an increase of the band gap. Laser induced luminescence analysis revealed a decrease in the recombination rate of the photogenerated holes and electrons. The photocatalytic activity of supported catalysts, toward the degradation of toluidine, revealed a meaningful enhancement upon codoping samples at a level of 2% (atomic ratio). The photocatalytic activity of the material and its reactivity can be attributed to a reduced, but significant, direct photoexcitation of the semiconductor by the halogen lamp, together with a charge-transfer-complex mechanism, or with the formation of surface oxygen vacancies by the N dopant atoms.

Fabrication of Ternary AgPdAu Alloy Nanoparticles on c-Plane Sapphire by the Systematical Control of Film Thickness and Deposition Sequence

NASA Astrophysics Data System (ADS)

Kunwar, Sundar; Pandey, Puran; Sui, Mao; Bastola, Sushil; Lee, Jihoon

2018-06-01

In this work, a systematic study on the fabrication of ternary AgPdAu alloy nanoparticles (NPs) on c-plane sapphire (0001) is presented and the corresponding structural and optical characteristics are demonstrated. The metallic trilayers of various thicknesses and deposition orders are annealed in a controlled manner (400 °C to 900 °C) to induce the solid-state dewetting that yields the various structural configurations of AgPdAu alloy NPs. The dewetting of relatively thicker trilayers (15 nm) is gradually progressed with void nucleation, growth, and coalescence, isolated NP formation, and shape transformation, along with the temperature control. For 6 nm thickness, owing to the sufficient dewetting of trilayers along with enhanced diffusion, dense and small spherical alloy NPs are fabricated. Depending on the specific growth condition, the surface diffusion and interdiffusion of metal atoms, surface and interface energy minimization, Rayleigh instability, and equilibrium configuration are correlated to describe the fabrication of ternary alloy NPs. Ternary alloy NPs exhibit morphology-dependent ultraviolet-visible-near infrared (UV-VIS-NIR) reflectance properties such as the inverse relationship of average reflectance with the surface coverage, absorption enhancement in specific regions, and reflectance maxima in UV and NIR regions. In addition, Raman spectra depict the six active phonon modes of sapphires and their intensity and position modulation by the alloy NPs.

Detection of plum pox virus infection in selection plum trees using spectral imaging

NASA Astrophysics Data System (ADS)

Angelova, Liliya; Stoev, Antoniy; Borisova, Ekaterina; Avramov, Latchezar

2016-01-01

Plum pox virus (PPV) is among the most studied viral diseases in the world in plants. It is considered to be one of the most devastating diseases of stone fruits in terms of agronomic impact and economic importance. Noninvasive, fast and reliable techniques are required for evaluation of the pathology in selection trees with economic impact. Such advanced tools for PPV detection could be optical techniques as light-induced fluorescence and diffuse reflectance spectroscopies. Specific regions in the electromagnetic spectra have been found to provide information about the physiological stress in plants, and consequently, diseased plants usually exhibit different spectral signature than non-stressed healthy plants in those specific ranges. In this study spectral reflectance and chlorophyll fluorescence were used for the identification of biotic stress caused by the pox virus on plum trees. The spectral responses of healthy and infected leaves from cultivars, which are widespread in Bulgaria were investigated. The two applied techniques revealed statistically significant differences between the spectral data of healthy plum leaves and those infected by PPV in the visible and near-infrared spectral ranges. Their application for biotic stress detection helps in monitoring diseases in plants using the different plant spectral properties in these spectral ranges. The strong relationship between the results indicates the applicability of diffuse reflectance and fluorescence techniques for conducting health condition assessments of vegetation and their importance for plant protection practices.

Spectral reflectance properties (0.4-2.5 μm) of secondary Fe-oxide, Fe-hydroxide, and Fe-sulphate-hydrate minerals associated with sulphide-bearing mine wastes

USGS Publications Warehouse

Crowley, J.K.; Williams, D.E.; Hammarstrom, J.M.; Piatak, N.; Chou, I.-Ming; Mars, J.C.

2003-01-01

Diffuse reflectance spectra of 15 mineral species commonly associated with sulphide-bearing mine wastes show diagnostic absorption bands related to electronic processes involving ferric and/or ferrous iron, and to vibrational processes involving water and hydroxyl. Many of these absorption bands are relatively broad and overlapping; however, spectral analysis methods, including continuum removal and derivative analysis, permit most of the minerals to be distinguished. Key spectral differences between the minerals are illustrated in a series of plots showing major absorption band centres and other spectral feature positions. Because secondary iron minerals are sensitive indicators of pH, Eh, relative humidity, and other environmental conditions, spectral mapping of mineral distributions promises to have important application to mine waste remediation studies.

Simulations of Effects of Nanophase Iron Space Weather Products on Lunar Regolith Reflectance Spectra

NASA Astrophysics Data System (ADS)

Escobar-Cerezo, J.; Penttilä, A.; Kohout, T.; Muñoz, O.; Moreno, F.; Muinonen, K.

2018-01-01

Lunar soil spectra differ from pulverized lunar rocks spectra by reddening and darkening effects, and shallower absorption bands. These effects have been described in the past as a consequence of space weathering. In this work, we focus on the effects of nanophase iron (npFe0) inclusions on the experimental reflectance spectra of lunar regolith particles. The reflectance spectra are computed using SIRIS3, a code that combines ray optics with radiative-transfer modeling to simulate light scattering by different types of scatterers. The imaginary part of the refractive index as a function of wavelength of immature lunar soil is derived by comparison with the measured spectra of the corresponding material. Furthermore, the effect of adding nanophase iron inclusions on the reflectance spectra is studied. The computed spectra qualitatively reproduce the observed effects of space weathered lunar regolith.

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.

Facile solvothermal synthesis of cube-like Ag@AgCl: a highly efficient visible light photocatalyst

NASA Astrophysics Data System (ADS)

Han, Lei; Wang, Ping; Zhu, Chengzhou; Zhai, Yueming; Dong, Shaojun

2011-07-01

In this paper, a stable and highly efficient plasmonic photocatalyst, Ag@AgCl, with cube-like morphology, has been successfully prepared via a simple hydrothermal method. Using methylene dichloride as chlorine source in the synthesis can efficiently control the morphology of Ag@AgCl, due to the low release rate of chloride ions. Scanning electron microscopy (SEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV-vis diffuse reflectance spectra were used to characterize the obtained product. The photocatalytic activity of the obtained product was evaluated by the photodegradation of methyl orange (MO) under visible light irradiation, and it was found, interestingly, that Ag@AgCl exhibits high visible light photocatalytic activity and good stability.In this paper, a stable and highly efficient plasmonic photocatalyst, Ag@AgCl, with cube-like morphology, has been successfully prepared via a simple hydrothermal method. Using methylene dichloride as chlorine source in the synthesis can efficiently control the morphology of Ag@AgCl, due to the low release rate of chloride ions. Scanning electron microscopy (SEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV-vis diffuse reflectance spectra were used to characterize the obtained product. The photocatalytic activity of the obtained product was evaluated by the photodegradation of methyl orange (MO) under visible light irradiation, and it was found, interestingly, that Ag@AgCl exhibits high visible light photocatalytic activity and good stability. Electronic supplementary information (ESI) available: SEM images of the AgCl samples synthesized by changing the addition amount of PVP and AgNO3. See DOI: 10.1039/c1nr10247h

Modification of kaolinite surfaces through mechanochemical activation with quartz: A diffuse reflectance infrared fourier transform and chemometrics study.

PubMed

Carmody, Onuma; Frost, Ray L; Kristóf, János; Kokot, Serge; Kloprogge, J Theo; Makó, Eva

2006-12-01

Studies of kaolinite surfaces are of industrial importance. One useful method for studying the changes in kaolinite surface properties is to apply chemometric analyses to the kaolinite surface infrared spectra. A comparison is made between the mechanochemical activation of Kiralyhegy kaolinites with significant amounts of natural quartz and the mechanochemical activation of Zettlitz kaolinite with added quartz. Diffuse reflectance infrared Fourier transform (DRIFT) spectra were analyzed using principal component analysis (PCA) and multi-criteria decision making (MCDM) methods, the preference ranking organization method for enrichment evaluations (PROMETHEE) and geometrical analysis for interactive assistance (GAIA). The clear discrimination of the Kiralyhegy spectral objects on the two PC scores plots (400-800 and 800-2030 cm(-1)) indicated the dominance of quartz. Importantly, no ordering of any spectral objects appeared to be related to grinding time in the PC plots of these spectral regions. Thus, neither the kaolinite nor the quartz are systematically responsive to grinding time according to the spectral criteria investigated. The third spectral region (2600-3800 cm(-1), OH vibrations), showed apparent systematic ordering of the Kiralyhegy and, to a lesser extent, Zettlitz spectral objects with grinding time. This was attributed to the effect of the natural quartz on the delamination of kaolinite and the accompanying phenomena (i.e., formation of kaolinite spheres and water). The mechanochemical activation of kaolinite and quartz, through dry grinding, results in changes to the surface structure. Different grinding times were adopted to study the rate of destruction of the kaolinite and quartz structures. This relationship (i.e., grinding time) was classified using PROMETHEE and GAIA methodology.

Using visible and near-infrared diffuse reflectance spectroscopy for predicting soil properties based on regression with peaks parameters as derived from continuum-removed spectra

NASA Astrophysics Data System (ADS)

Vasat, Radim; Klement, Ales; Jaksik, Ondrej; Kodesova, Radka; Drabek, Ondrej; Boruvka, Lubos

2014-05-01

Visible and near-infrared diffuse reflectance spectroscopy (VNIR-DRS) provides a rapid and inexpensive tool for simultaneous prediction of a variety of soil properties. Usually, some sophisticated multivariate mathematical or statistical methods are employed in order to extract the required information from the raw spectra measurement. For this purpose especially the Partial least squares regression (PLSR) and Support vector machines (SVM) are the most frequently used. These methods generally benefit from the complexity with which the soil spectra are treated. But it is interesting that also techniques that focus only on a single spectral feature, such as a simple linear regression with selected continuum-removed spectra (CRS) characteristic (e.g. peak depth), can often provide competitive results. Therefore, we decided to enhance the potential of CRS taking into account all possible CRS peak parameters (area, width and depth) and develop a comprehensive methodology based on multiple linear regression approach. The eight considered soil properties were oxidizable carbon content (Cox), exchangeable (pHex) and active soil pH (pHa), particle and bulk density, CaCO3 content, crystalline and amorphous (Fed) and amorphous Fe (Feox) forms. In four cases (pHa, bulk density, Fed and Feox), of which two (Fed and Feox) were predicted reliably accurately (0.50 < R2cv < 0.80) and the other two (pHa and bulk density) only poorly (R2cv < 0.50), we obtained slightly better results than with PLSR and SVM. In one case (pHex) we achieved a significantly higher, although just reliable, accuracy (R2cv = 0.601) than with PLSR and SVM (R2cv = 0.448 and 0.442, resp.). But most interestingly, in the case of particle density, the presented approach outperformed the PLSR and SVM dramatically offering a fairly accurate prediction (R2cv = 0.827) against two failures (R2cv = 0.034 and 0.121 for PLSR and SVM, resp.). In last two cases (Cox and CaCO3) a slightly worse results were achieved then with PLSR and SVM with overall fairly accurate prediction (R2cv > 0.80). Acknowledgment: Authors acknowledge the financial support of the Ministry of Agriculture of the Czech Republic (grant No. QJ1230319).

A portable device for detecting fruit quality by diffuse reflectance Vis/NIR spectroscopy

NASA Astrophysics Data System (ADS)

Sun, Hongwei; Peng, Yankun; Li, Peng; Wang, Wenxiu

2017-05-01

Soluble solid content (SSC) is a major quality parameter to fruit, which has influence on its flavor or texture. Some researches on the on-line non-invasion detection of fruit quality were published. However, consumers desire portable devices currently. This study aimed to develop a portable device for accurate, real-time and nondestructive determination of quality factors of fruit based on diffuse reflectance Vis/NIR spectroscopy (520-950 nm). The hardware of the device consisted of four units: light source unit, spectral acquisition unit, central processing unit, display unit. Halogen lamp was chosen as light source. When working, its hand-held probe was in contact with the surface of fruit samples thus forming dark environment to shield the interferential light outside. Diffuse reflectance light was collected and measured by spectrometer (USB4000). ARM (Advanced RISC Machines), as central processing unit, controlled all parts in device and analyzed spectral data. Liquid Crystal Display (LCD) touch screen was used to interface with users. To validate its reliability and stability, 63 apples were tested in experiment, 47 of which were chosen as calibration set, while others as prediction set. Their SSC reference values were measured by refractometer. At the same time, samples' spectral data acquired by portable device were processed by standard normalized variables (SNV) and Savitzky-Golay filter (S-G) to eliminate the spectra noise. Then partial least squares regression (PLSR) was applied to build prediction models, and the best predictions results was achieved with correlation coefficient (r) of 0.855 and standard error of 0.6033° Brix. The results demonstrated that this device was feasible to quantitatively analyze soluble solid content of apple.

Rapid and quantitative detection of the microbial spoilage in chicken meat by diffuse reflectance spectroscopy (600-1100 nm).

PubMed

Lin, M; Al-Holy, M; Mousavi-Hesary, M; Al-Qadiri, H; Cavinato, A G; Rasco, B A

2004-01-01

To evaluate the feasibility of visible and short-wavelength near-infrared (SW-NIR) diffuse reflectance spectroscopy (600-1100 nm) to quantify the microbial loads in chicken meat and to develop a rapid methodology for monitoring the onset of spoilage. Twenty-four prepackaged fresh chicken breast muscle samples were prepared and stored at 21 degrees C for 24 h. Visible and SW-NIR was used to detect and quantify the microbial loads in chicken breast muscle at time intervals of 0, 2, 4, 6, 8, 10, 12 and 24 h. Spectra were collected in the diffuse reflectance mode (600-1100 nm). Total aerobic plate count (APC) of each sample was determined by the spread plate method at 32 degrees C for 48 h. Principal component analysis (PCA) and partial least squares (PLS) based prediction models were developed. PCA analysis showed clear segregation of samples held 8 h or longer compared with 0-h control. An optimum PLS model required eight latent variables for chicken muscle (R = 0.91, SEP = 0.48 log CFU g(-1)). Visible and SW-NIR combined with PCA is capable of perceiving the change of the microbial loads in chicken muscle once the APC increases slightly above 1 log cycle. Accurate quantification of the bacterial loads in chicken muscle can be calculated from the PLS-based prediction method. Visible and SW-NIR spectroscopy is a technique with a considerable potential for monitoring food safety and food spoilage. Visible and SW-NIR can acquire a metabolic snapshot and quantify the microbial loads of food samples rapidly, accurately, and noninvasively. This method would allow for more expeditious applications of quality control in food industries.

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.

Monitoring longitudinal changes in irradiated head and neck cancer xenografts using diffuse reflectance spectroscopy

NASA Astrophysics Data System (ADS)

Vishwanath, Karthik; Jiang, Shudong; Gunn, Jason R.; Marra, Kayla; Andreozzi, Jacqueline M.; Pogue, Brian W.

2016-02-01

Radiation therapy is often used as the preferred clinical treatment for control of localized head and neck cancer. However, during the course of treatment (6-8 weeks), feedback about functional and/or physiological changes within impacted tissue are not obtained, given the onerous financial and/or logistical burdens of scheduling MRI, PET or CT scans. Diffuse optical sensing is well suited to address this problem since the instrumentation can be made low-cost and portable while still being able to non-invasively provide information about vascular oxygenation in vivo. Here we report results from studies that employed an optical fiber-based portable diffuse reflectance spectroscopy (DRS) system to longitudinally monitor changes in tumor vasculature within two head and neck cancer cell lines (SCC-15 and FaDu) xenografted in the flanks of nude mice, in two separate experiments. Once the tumor volumes were 100mm3, 67% of animals received localized (electron beam) radiation therapy in five fractions (8Gy/day, for 5 days) while 33% of the animals served as controls. DRS measurements were obtained from each animal on each day of treatment and then for two weeks post-treatment. Reflectance spectra were parametrized to extract total hemoglobin concentration and blood oxygen-saturation and the resulting time-trends of optical parameters appear to be dissimilar for the two cell-lines. These findings are also compared to previous animal experiments (using the FaDu line) that were irradiated using a photon beam radiotherapy protocol. These results and implications for the use of fiber-based DRS measurements made at local (irradiated) tumor site as a basis for identifying early radiotherapy-response are presented and discussed.

A comparison of two laboratories for the measurement of wood dust using button sampler and diffuse reflection infrared Fourier-transform spectroscopy (DRIFTS).

PubMed

Chirila, Madalina M; Sarkisian, Khachatur; Andrew, Michael E; Kwon, Cheol-Woong; Rando, Roy J; Harper, Martin

2015-04-01

The current measurement method for occupational exposure to wood dust is by gravimetric analysis and is thus non-specific. In this work, diffuse reflection infrared Fourier transform spectroscopy (DRIFTS) for the analysis of only the wood component of dust was further evaluated by analysis of the same samples between two laboratories. Field samples were collected from six wood product factories using 25-mm glass fiber filters with the Button aerosol sampler. Gravimetric mass was determined in one laboratory by weighing the filters before and after aerosol collection. Diffuse reflection mid-infrared spectra were obtained from the wood dust on the filter which is placed on a motorized stage inside the spectrometer. The metric used for the DRIFTS analysis was the intensity of the carbonyl band in cellulose and hemicellulose at ~1735 cm(-1). Calibration curves were constructed separately in both laboratories using the same sets of prepared filters from the inhalable sampling fraction of red oak, southern yellow pine, and western red cedar in the range of 0.125-4 mg of wood dust. Using the same procedure in both laboratories to build the calibration curve and analyze the field samples, 62.3% of the samples measured within 25% of the average result with a mean difference between the laboratories of 18.5%. Some observations are included as to how the calibration and analysis can be improved. In particular, determining the wood type on each sample to allow matching to the most appropriate calibration increases the apparent proportion of wood dust in the sample and this likely provides more realistic DRIFTS results. Published by Oxford University Press on behalf of the British Occupational Hygiene Society 2014.

Emission and reflection spectra from AlxGa1-xN/GaN single heterostructures

NASA Astrophysics Data System (ADS)

Reynolds, D. C.; Hoelscher, J.; Litton, C. W.; Collins, T. C.; Fitch, R.; Via, G. D.; Gillespie, J.; Crespo, A.; Jenkins, T. J.; Saxler, A.

2003-10-01

Emission and reflection spectra from AlGaN/GaN single heterostructures grown on SiC substrates were investigated. Two-dimensional electron gas (2DEG) transitions were observed in both emission and reflection. The transitions are sharp, associated with the excited state of the 2DEG, reflect the conservation of the K-selection rule, and are excitonlike. The transitions are also associated with both the A- and B-valence bands. To verify the origin of the reflection and emission spectra, the top AlGaN layer was removed by reactive ion etching. After etching, only the excitonic reflection and emission spectra associated with GaN were observed.

Fourier transform-infrared spectroscopic methods for microbial ecology: analysis of bacteria, bacteria-polymer mixtures and biofilms

NASA Technical Reports Server (NTRS)

Nichols, P. D.; Henson, J. M.; Guckert, J. B.; Nivens, D. E.; White, D. C.

1985-01-01

Fourier transform-infrared (FT-IR) spectroscopy has been used to rapidly and nondestructively analyze bacteria, bacteria-polymer mixtures, digester samples and microbial biofilms. Diffuse reflectance FT-IR (DRIFT) analysis of freeze-dried, powdered samples offered a means of obtaining structural information. The bacteria examined were divided into two groups. The first group was characterized by a dominant amide I band and the second group of organisms displayed an additional strong carbonyl stretch at approximately 1740 cm-1. The differences illustrated by the subtraction spectra obtained for microbes of the two groups suggest that FT-IR spectroscopy can be utilized to recognize differences in microbial community structure. Calculation of specific band ratios has enabled the composition of bacteria and extracellular or intracellular storage product polymer mixtures to be determined for bacteria-gum arabic (amide I/carbohydrate C-O approximately 1150 cm-1) and bacteria-poly-beta-hydroxybutyrate (amide I/carbonyl approximately 1740 cm-1). The key band ratios correlate with the compositions of the material and provide useful information for the application of FT-IR spectroscopy to environmental biofilm samples and for distinguishing bacteria grown under differing nutrient conditions. DRIFT spectra have been obtained for biofilms produced by Vibrio natriegens on stainless steel disks. Between 48 and 144 h, an increase in bands at approximately 1440 and 1090 cm-1 was seen in FT-IR spectra of the V. natriegens biofilm. DRIFT spectra of mixed culture effluents of anaerobic digesters show differences induced by shifts in input feedstocks. The use of flow-through attenuated total reflectance has permitted in situ real-time changes in biofilm formation to be monitored and provides a powerful tool for understanding the interactions within adherent microbial consortia.

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.

Investigation of effects of background water on upwelled reflectance spectra and techniques for analysis of dilute primary-treated sewage sludge

NASA Technical Reports Server (NTRS)

Whitlock, C. H.; Usry, J. W.; Witte, W. G.; Farmer, F. H.; Gurganus, E. A.

1979-01-01

In an effort to improve understanding of the effects of variations in background water on reflectance spectra, laboratory tests were conducted with various concentrations of sewage sludge diluted with several types of background water. The results from these tests indicate that reflectance spectra for sewage-sludge mixtures are dependent upon the reflectance of the background water. Both the ratio of sewage-sludge reflectance to background-water reflectance and the ratio of the difference in reflectance to background-water reflectance show spectral variations for different turbid background waters. The difference in reflectance is the only parameter considered.

Effects of Sample Preparation on the Infrared Reflectance Spectra of Powders

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

Brauer, Carolyn S.; Johnson, Timothy J.; Myers, Tanya L.

2015-05-22

While reflectance spectroscopy is a useful tool in identifying molecular compounds, laboratory measurement of solid (particularly powder) samples often is confounded by sample preparation methods. For example, both the packing density and surface roughness can have an effect on the quantitative reflectance spectra of powdered samples. Recent efforts in our group have focused on developing standard methods for measuring reflectance spectra that accounts for sample preparation, as well as other factors such as particle size and provenance. In this work, the effect of preparation method on sample reflectivity was investigated by measuring the directional-hemispherical spectra of samples that were hand-packedmore » as well as pressed into pellets using an integrating sphere attached to a Fourier transform infrared spectrometer. The results show that the methods used to prepare the sample have a substantial effect on the measured reflectance spectra, as do other factors such as particle size.« less

Effects of sample preparation on the infrared reflectance spectra of powders

NASA Astrophysics Data System (ADS)

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

2015-05-01

While reflectance spectroscopy is a useful tool for identifying molecular compounds, laboratory measurement of solid (particularly powder) samples often is confounded by sample preparation methods. For example, both the packing density and surface roughness can have an effect on the quantitative reflectance spectra of powdered samples. Recent efforts in our group have focused on developing standard methods for measuring reflectance spectra that accounts for sample preparation, as well as other factors such as particle size and provenance. In this work, the effect of preparation method on sample reflectivity was investigated by measuring the directional-hemispherical spectra of samples that were hand-loaded as well as pressed into pellets using an integrating sphere attached to a Fourier transform infrared spectrometer. The results show that the methods used to prepare the sample can have a substantial effect on the measured reflectance spectra, as do other factors such as particle size.

Evaluation of light scattering and absorption properties ofin vivorat liver using a single-reflectance fiber probe during preischemia, ischemia-reperfusion, and postmortem

NASA Astrophysics Data System (ADS)

Akter, Sharmin; Maejima, Satoshi; Kawauchi, Satoko; Sato, Shunichi; Hinoki, Akinari; Aosasa, Suefumi; Yamamoto, Junji; Nishidate, Izumi

2015-07-01

Diffuse reflectance spectroscopy (DRS) has been extensively used for characterization of biological tissues as a noninvasive optical technique to evaluate the optical properties of tissue. We investigated a method for evaluating the reduced scattering coefficient , the absorption coefficient μa, the tissue oxygen saturation StO2, and the reduction of heme aa3 in cytochrome c oxidase CcO of in vivo liver tissue using a single-reflectance fiber probe with two source-collector geometries. We performed in vivo recordings of diffuse reflectance spectra for exposed rat liver during the ischemia-reperfusion induced by the hepatic portal (hepatic artery, portal vein, and bile duct) occlusion. The time courses of μa at 500, 530, 570, and 584 nm indicated the hemodynamic change in liver tissue as well as StO2. Significant increase in μa(605)/μa(620) during ischemia and after euthanasia induced by nitrogen breathing was observed, which indicates the reduction of heme aa3, representing a sign of mitochondrial energy failure. The time courses of at 500, 530, 570, and 584 nm were well correlated with those of μa, which also reflect the scattering by red blood cells. On the other hand, at 700 and 800 nm, a temporary increase in and an irreversible decrease in were observed during ischemia-reperfusion and after euthanasia induced by nitrogen breathing, respectively. The change in in the near-infrared wavelength region during ischemia is indicative of the morphological changes in the cellular and subcellular structures induced by the ischemia, whereas that after euthanasia implies the hepatocyte vacuolation. The results of the present study indicate the potential application of the current DRS system for evaluating the pathophysiological conditions of in vivo liver tissue.

Anomalous Galactic Cosmic Rays in the Framework of AMS-02

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

Khiali, Behrouz; Haino, Sadakazu; Feng, Jie, E-mail: behrouz.khiali@cern.ch

2017-02-01

The cosmic-ray (CR) energy spectra of protons and helium nuclei, which are the most abundant components of cosmic radiation, exhibit a remarkable hardening at energies above 100 GeV/nucleon. Recent data from AMS-02 confirm this feature with a higher significance. These data challenge the current models of CR acceleration in Galactic sources and propagation in the Galaxy. Here, we explain the observed break in the spectra of protons and helium nuclei in light of recent advances in CR diffusion theories in turbulent astrophysical sources as being a result of a transition between different CR diffusion regimes. We reconstruct the observed CRmore » spectra using the fact that a transition from normal diffusion to superdiffusion changes the efficiency of particle acceleration and causes the change in the spectral index. We find that calculated proton and helium spectra match the data very well.« less

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.

Infrared reflectometry of skin: Analysis of backscattered light from different skin layers

NASA Astrophysics Data System (ADS)

Pleitez, Miguel A.; Hertzberg, Otto; Bauer, Alexander; Lieblein, Tobias; Glasmacher, Mathias; Tholl, Hans; Mäntele, Werner

2017-09-01

We have recently reported infrared spectroscopy of human skin in vivo using quantum cascade laser excitation and photoacoustic or photothermal detection for non-invasive glucose measurement . Here, we analyze the IR light diffusely reflected from skin layers for spectral contributions of glucose. Excitation of human skin by an external cavity tunable quantum cascade laser in the spectral region from 1000 to 1245 cm- 1, where glucose exhibits a fingerprint absorption, yields reflectance spectra with some contributions from glucose molecules. A simple three-layer model of skin was used to calculate the scattering intensities from the surface and from shallow and deeper layers using the Boltzmann radiation transfer equation. Backscattering of light at wavelengths around 10 μm from the living skin occurs mostly from the Stratum corneum top layers and the shallow layers of the living epidermis. The analysis of the polarization of the backscattered light confirms this calculation. Polarization is essentially unchanged; only a very small fraction (< 3%) is depolarized at 90° with respect to the laser polarization set at 0°. Based on these findings, we propose that the predominant part of the backscattered light is due to specular reflectance and to scattering from layers close to the surface. Diffusely reflected light from deeper layers undergoing one or more scattering processes would appear with significantly altered polarization. We thus conclude that a non-invasive glucose measurement based on backscattering of IR light from skin would have the drawback that only shallow layers containing some glucose at concentrations only weakly related to blood glucose are monitored.

Acquiring Sediment and Element Compositional Changes Based on a Diffuse Reflectance Spectrophotometry Technology from Cores Offshore Southwestern Taiwan

NASA Astrophysics Data System (ADS)

Pan, H. J.; Chen, M. T.

2014-12-01

Heavy summer monsoon rainfall along with typhoon-induced extreme precipitation cause frequent geological hazards that often threaten the human's safety and property in Taiwan. These geological hazards can be triggered by both natural factors, and/or have become deteriorated by perturbations from more and more human activities ever since few thousand years ago. However, due to the limit of instrumental records for observing long-term environmental changes in Taiwan, few evidence exist for distinguishing the human-induced impacts from natural climate change. Here we report a study on a high quality marine sediment core (MD103264) which were retrieved from the high sedimentation rate area from offshore southwestern Taiwan and present evidence for the long-term climate and possibly human-induced environmental changes since the last glacial. We are using the VIS-NIR Diffuse Reflectance Spectrophotometry (DRS) methods to study the cores. Interpreting the VIS-NIR reflectance spectra through the VARIMAX-rotation, principle component analysis (VPCA) helps conducting rapid and inexpensive measurements for acquiring high-resolution biogenic component, clay, and iron oxide mineral compositional data from the cores. We are also using X-Ray Fluorescence (XRF) analysis, which is also useful in determining the element compositional changes in the core. Our studies aim toward understanding the sediment and element compositional changes that reflect the patterns of changes in precipitation and soil erosion on land since the last glacial to the Holocene, during which the human activities (deforestation, agriculture, and land uses change) may have increased drastically. We will report and interpret the preliminary results of the optical analyses of the core.

Anisotropic rotational diffusion studied by passage saturation transfer electron paramagnetic resonance

NASA Astrophysics Data System (ADS)

Robinson, Bruce H.; Dalton, Larry R.

1980-01-01

The stochastic Liouville equation for the spin density matrix is modified to consider the effects of Brownian anisotropic rotational diffusion upon electron paramagnetic resonance (EPR) and saturation transfer electron paramagnetic resonance (ST-EPR) spectra. Spectral shapes and the ST-EPR parameters L″/L, C'/C, and H″/H defined by Thomas, Dalton, and Hyde at X-band microwave frequencies [J. Chem. Phys. 65, 3006 (1976)] are examined and discussed in terms of the rotational times τ∥ and τ⊥ and in terms of other defined correlation times for systems characterized by magnetic tensors of axial symmetry and for systems characterized by nonaxially symmetric magnetic tensors. For nearly axially symmetric magnetic tensors, such as nitroxide spin labels studied employing 1-3 GHz microwaves, ST-EPR spectra for systems undergoing anisotropic rotational diffusion are virtually indistinguishable from spectra for systems characterized by isotropic diffusion. For nonaxially symmetric magnetic tensors, such as nitroxide spin labels studied employing 8-35 GHz microwaves, the high field region of the ST-EPR spectra, and hence the H″/H parameter, will be virtually indistinguishable from spectra, and parameter values, obtained for isotropic diffusion. On the other hand, the central spectral region at x-band microwave frequencies, and hence the C'/C parameter, is sensitive to the anisotropic diffusion model provided that a unique and static relationship exists between the magnetic and diffusion tensors. Random labeling or motion of the spin label relative to the biomolecule whose hydrodynamic properties are to be investigated will destroy spectral sensitivity to anisotropic motion. The sensitivity to anisotropic motion is enhanced in proceeding to 35 GHz with the increased sensitivity evident in the low field half of the EPR and ST-EPR spectra. The L″/L parameter is thus a meaningful indicator of anisotropic motion when compared with H″/H parameter analysis. However, consideration of spectral shapes suggests that the C'/C parameter definition is not meaningfully extended from 9.5 to 35 GHz. Alternative definitions of the L″/L and C'/C parameters are proposed for those microwave frequencies for which the electron Zeeman anisotropy is comparable to or greater than the electron-nitrogen nuclear hyperfine anisotropy.

Detecting jaundice by using digital image processing

NASA Astrophysics Data System (ADS)

Castro-Ramos, J.; Toxqui-Quitl, C.; Villa Manriquez, F.; Orozco-Guillen, E.; Padilla-Vivanco, A.; Sánchez-Escobar, JJ.

2014-03-01

When strong Jaundice is presented, babies or adults should be subject to clinical exam like "serum bilirubin" which can cause traumas in patients. Often jaundice is presented in liver disease such as hepatitis or liver cancer. In order to avoid additional traumas we propose to detect jaundice (icterus) in newborns or adults by using a not pain method. By acquiring digital images in color, in palm, soles and forehead, we analyze RGB attributes and diffuse reflectance spectra as the parameter to characterize patients with either jaundice or not, and we correlate that parameters with the level of bilirubin. By applying support vector machine we distinguish between healthy and sick patients.

Label-free hyperspectral dark-field microscopy for quantitative scatter imaging

NASA Astrophysics Data System (ADS)

Cheney, Philip; McClatchy, David; Kanick, Stephen; Lemaillet, Paul; Allen, David; Samarov, Daniel; Pogue, Brian; Hwang, Jeeseong

2017-03-01

A hyperspectral dark-field microscope has been developed for imaging spatially distributed diffuse reflectance spectra from light-scattering samples. In this report, quantitative scatter spectroscopy is demonstrated with a uniform scattering phantom, namely a solution of polystyrene microspheres. A Monte Carlo-based inverse model was used to calculate the reduced scattering coefficients of samples of different microsphere concentrations from wavelength-dependent backscattered signal measured by the dark-field microscope. The results are compared to the measurement results from a NIST double-integrating sphere system for validation. Ongoing efforts involve quantitative mapping of scattering and absorption coefficients in samples with spatially heterogeneous optical properties.

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.

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.

Monte Carlo simulation of reflection spectra of random multilayer media strongly scattering and absorbing light

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

Meglinskii, I V

2001-12-31

The reflection spectra of a multilayer random medium - the human skin - strongly scattering and absorbing light are numerically simulated. The propagation of light in the medium and the absorption spectra are simulated by the stochastic Monte Carlo method, which combines schemes for calculations of real photon trajectories and the statistical weight method. The model takes into account the inhomogeneous spatial distribution of blood vessels, water, and melanin, the degree of blood oxygenation, and the hematocrit index. The attenuation of the incident radiation caused by reflection and refraction at Fresnel boundaries of layers inside the medium is also considered.more » The simulated reflection spectra are compared with the experimental reflection spectra of the human skin. It is shown that a set of parameters that was used to describe the optical properties of skin layers and their possible variations, despite being far from complete, is nevertheless sufficient for the simulation of the reflection spectra of the human skin and their quantitative analysis. (laser applications and other topics in quantum electronics)« less

The True Color of Yogi: An Accurate Method for Removing Diffuse Illumination from Multispectral Images of Mars

NASA Technical Reports Server (NTRS)

Stoker, Carol R.; Rages, Kathy

2002-01-01

We correct spectra of Yogi to remove diffuse illumination and show that the part of Yogi facing the wind is less red than other faces of the rock. Our method eliminates ambiguity in interpreting spectra obtained under Mars illumination conditions. Additional information is contained in the original extended abstract.

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.

Far-infrared reflectance spectra of optical black coatings

NASA Technical Reports Server (NTRS)

Smith, S. M.

1983-01-01

Far-infrared specular reflectance spectra of six optically black coatings near normal incidence are presented. The spectra were obtained using nine bandpass transmission filters in the wavelength range between 12 and 300 microns. Data on the construction, thickness, and rms surface roughness of the coatings are also presented. The chemical composition of two coatings can be distinguished from that of the others by a strong absorption feature between 20 and 40 microns which is attributed to amorphous silicate material. Inverse relationships between these spectra and coating roughness and thickness are noted and lead to development of a reflecting-layer model for the measured reflectance. The model is applied to the spectra of several coatings whose construction falls within its constraints.

The Use of UV-Visible Reflectance Spectroscopy as an Objective Tool to Evaluate Pearl Quality

PubMed Central

Agatonovic-Kustrin, Snezana; Morton, David W.

2012-01-01

Assessing the quality of pearls involves the use of various tools and methods, which are mainly visual and often quite subjective. Pearls are normally classified by origin and are then graded by luster, nacre thickness, surface quality, size, color and shape. The aim of this study was to investigate the capacity of Artificial Neural Networks (ANNs) to classify and estimate the quality of 27 different pearls from their UV-Visible spectra. Due to the opaque nature of pearls, spectroscopy measurements were performed using the Diffuse Reflectance UV-Visible spectroscopy technique. The spectra were acquired at two different locations on each pearl sample in order to assess surface homogeneity. The spectral data (inputs) were smoothed to reduce the noise, fed into ANNs and correlated to the pearl’s quality/grading criteria (outputs). The developed ANNs were successful in predicting pearl type, mollusk growing species, possible luster and color enhancing, donor condition/type, recipient/host color, donor color, pearl luster, pearl color, origin. The results of this study shows that the developed UV-Vis spectroscopy-ANN method could be used as a more objective method of assessing pearl quality (grading) and may become a valuable tool for the pearl grading industry. PMID:22851919

An assessment of optical and biogeochemical multi-decadal trends in the Sargasso Sea

NASA Astrophysics Data System (ADS)

Allen, J. G.; Siegel, D.; Nelson, N. B.

2016-02-01

Observations of optical and biogeochemical data, made as part of the Bermuda Bio-Optics Project (BBOP) at the Bermuda Atlantic Time-series Study (BATS) site in the Sargasso Sea, allow for the examination of temporal trends in vertical light attenuation and their potential controls. Trends in both the magnitude and spectral slope of the diffuse attenuation coefficient should reflect changes in chlorophyll and chromophoric dissolved organic matter (CDOM) concentrations in the Sargasso Sea. The length and methodological consistency of this time series provides an excellent opportunity to extend analyses of seasonal cycles of apparent optical properties to interannual and multi-year time scales. Here, we characterize changes in the size and shape of diffuse attenuation coefficient spectra and compare them to temperature, chlorophyll a concentration, and to discrete measurements of phytoplankton and CDOM absorption. The time series analyses reveal up to a 1.2% annual increase of the magnitude of the diffuse attenuation coefficient over the upper 70 m of the water column while showing no significant change in the spectral slope of diffuse attenuation over the course of the study. These observations indicate that increases in phytoplankton pigment concentration rather than changes in CDOM are the primary driver for the attenuation trends on multi-year timescales for this region.

Explaining Space-Weathering Effects on UV-Vis-NIR Spectra with Light-Scattering Methods

NASA Astrophysics Data System (ADS)

Penttilä, Antti; Väisänen, Timo; Martikainen, Julia; Kohout, Tomas; Muinonen, Karri

2015-11-01

Space-weathering (SW) introduces changes to the asteroid reflectance spectra. In silicate minerals, SW is known to darken the spectra and reduce the silicate absorption band depths. In olivine, the neutral slope in Vis and NIR wavelengths is becoming positive [1]. In pyroxene, the positive slope over the 1 µm absorption band is decreasing, and the negative slope over the 2 µm band is increasing towards positive values with increasing SW [2].The SW process generates small nanophase iron (npFe0) inclusions in the surface layers of mineral grains. The inclusions are some tens of nm in size. This mechanism has been linked to the Moon and to a certain extent also to the silicate-rich S-complex asteroids.We offer two simple explanations from light-scattering theory to explain the SW effects on the spectral slope. First, the npFe0 will introduce a posititive general slope (reddening) to the spectra. The npFe0 inclusions (~10 nm) are in the Rayleigh domain with the wavelength λ in the UV-Vis-NIR range. Their absorption cross-section follows approximately the 1/λ-relation from the Rayleigh theory. Absorption is more efficient in the UV than in the NIR wavelengths, therefore the spectra are reddening.Second, the effect of npFe0 absorption is more efficient for originally brighter reflectance values. Explanation combines the effective medium theory and the exponential attenuation in the medium. When adding a small amount of highly absorbing npFe0, the effective absorption coefficient k will increase approximately the same Δk for the typical values of silicates. This change will increase more effectively the exponential attenuation if the original k was very small, and thus the reflectance high. Therefore, both positive and negative spectral slopes will approach zero with SW.We conclude that the SW will introduce a general reddening, and neutralize local slopes. This is verified using the SIRIS code [3], which combines geometric optics with small internal diffuse scatterers in the radiative transfer domain.[1] Kohout T. et al. (2014), Icarus 237(15), 75-83.[2] Kohout T. et al. (2015), Workshop on Space Weathering of Airless Bodies, Abstract.[3] Muinonen K. et al. (2009), JQSRT 110, 1628-1639.

Near infrared diffuse reflection and laser-induced fluorescence spectroscopy for myocardial tissue characterisation

NASA Astrophysics Data System (ADS)

Nilsson, A. M. K.; Heinrich, D.; Olajos, J.; Andersson-Engels, S.

1997-10-01

In order to evaluate the potential of cardiovascular tissue characterisation using near-infrared (NIR) spectroscopy, spectra in a previously unexplored wavelength region 0.8-2.3 μm were recorded from various pig heart tissue samples in vitro: normal myocardium (with and without endo/epicardium), aorta, fatty and fibrous heart tissue. The spectra were analysed with principal component analysis (PCA), revealing several spectroscopically characteristic features enabling tissue classification. Several of the identified spectral features could be attributed to specific tissue constituents by comparing the tissue signals with spectra obtained from water, elastin, collagen and cholesterol as well as with published data. The results obtained with the NIR spectroscopy technique in terms of its potential to classify different tissue types were compared with those from laser-induced fluorescence (LIF) using 337 nm excitation. LIF and NIR spectroscopy can in combination with PCA be used to discriminate between all previously mentioned tissue groups, apart from fatty versus fibrous tissue (LIF) and aorta versus fibrous tissue (NIR), respectively. The NIR analysis was improved by focusing the PCA to the wavelength segment 2.0-2.3 μm, resulting in successful spectral characterisation of all cardiovascular tissue groups.

Preparation and characterization of Bi-doped TiO{sub 2} and its solar photocatalytic activity for the degradation of isoproturon herbicide

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

Reddy, Police Anil Kumar; Srinivas, Basavaraju; Kala, Pruthu

Highlights: {yields} Visible active Bi-TiO{sub 2} photocatalyst preparation and thorough charaterization. {yields} Bi-TiO{sub 2} shows high activity for isoproturon degradation under solar light irradiation. {yields} The spectral response of TiO{sub 2} shifts from UV to visible light region by Bi doping. {yields} Bi{sup 3+{delta}+} species are playing a vital role in minimizing e{sup -}/h{sup +} recombination. -- Abstract: Bi-doped TiO{sub 2} catalyst was prepared by sol-gel method and was characterized by thermo gravimetric analysis (TGA), X-ray diffraction spectra (XRD), X-ray photo electronic spectroscopy (XPS), UV-Vis diffused reflectance spectra (DRS), photoluminescence spectra (PLS), transmission electron microscopy (TEM), energy dispersive analysis ofmore » X-rays (EDAX) and BET surface area. The photocatalytic activity of the catalysts were evaluated for the degradation of isoproturon herbicide under solar light irradiation. The UV-Visible DRS of Bi-doped TiO{sub 2} showed red shift in optical absorption. The presence of Bi{sup 3+{delta}+} species are playing a vital role in minimizing the electron hole recombination resulting higher activity compared to bare TiO{sub 2}.« less

Analysis of petroleum contaminated soils by spectral modeling and pure response profile recovery of n-hexane.

PubMed

Chakraborty, Somsubhra; Weindorf, David C; Li, Bin; Ali, Md Nasim; Majumdar, K; Ray, D P

2014-07-01

This pilot study compared penalized spline regression (PSR) and random forest (RF) regression using visible and near-infrared diffuse reflectance spectroscopy (VisNIR DRS) derived spectra of 164 petroleum contaminated soils after two different spectral pretreatments [first derivative (FD) and standard normal variate (SNV) followed by detrending] for rapid quantification of soil petroleum contamination. Additionally, a new analytical approach was proposed for the recovery of the pure spectral and concentration profiles of n-hexane present in the unresolved mixture of petroleum contaminated soils using multivariate curve resolution alternating least squares (MCR-ALS). The PSR model using FD spectra (r(2) = 0.87, RMSE = 0.580 log10 mg kg(-1), and residual prediction deviation = 2.78) outperformed all other models tested. Quantitative results obtained by MCR-ALS for n-hexane in presence of interferences (r(2) = 0.65 and RMSE 0.261 log10 mg kg(-1)) were comparable to those obtained using FD (PSR) model. Furthermore, MCR ALS was able to recover pure spectra of n-hexane. Copyright © 2014 Elsevier Ltd. All rights reserved.

Time-resolved spectroscopic measurements behind incident and reflected shock waves in air and xenon

NASA Technical Reports Server (NTRS)

Yoshinaga, T.

1973-01-01

Time-resolved spectra have been obtained behind incident and reflected shock waves in air and xenon at initial pressures of 0.1 and 1.0 torr using a rotating drum spectrograph and the OSU (The Ohio State University) arc-driven shock tube. These spectra were used to determine the qualitative nature of the flow as well as for making estimates of the available test time. The (n+1,n) and (n,n) band spectra of N2(+) (1st negative) were observed in the test gas behind incident shock waves in air at p1=1.0 torr and Us=9-10 km/sec. Behind reflected shock waves in air, the continuum of spectra appeared to cover almost the entire wavelength of 2,500-7,000 A for the shock-heated test gas. For xenon, the spectra for the incident shock wave cases for p1=0.1 torr show an interesting structure in which two intensely bright regions are witnessed in the time direction. The spectra obtained behind reflected shock waves in xenon were also dominated by continuum radiation but included strong absorption spectra due to FeI and FeII from the moment the reflected shock passed and on.

Magnetic, Mössbauer and optical spectroscopic properties of the AFe3O(PO4)3 (A = Ca, Sr, Pb) series of powder compounds

NASA Astrophysics Data System (ADS)

El Hafid, Hassan; Velázquez, Matias; El Jazouli, Abdelaziz; Wattiaux, Alain; Carlier, Dany; Decourt, Rodolphe; Couzi, Michel; Goldner, Philippe; Delmas, Claude

2014-10-01

AFe3O(PO4)3 (A = Ca, Sr and Pb) powder compounds were studied by means of X-ray diffraction (XRD), electron-probe microanalysis (EPMA) coupled with wavelength dispersion spectroscopy (WDS), Raman and diffuse reflectance spectroscopies, specific heat and magnetic properties measurements. Magnetization, magnetic susceptibility and specific heat measurements carried out on AFe3O(PO4)3 (A = Sr, Ca and Pb) powders firmly establish a series of three ferromagnetic (FM)-like second order phase transitions spanned over the 32-8 K temperature range. Room temperature Mössbauer spectroscopy and associated DFT calculations confirm the existence of three crystallographically non equivalent Fe3+ sites in the three compounds. Mössbauer spectra recorded as a function of temperature in the PbFe3O(PO4)3 compound also establishes the occurrence of two purely magnetic and reversible phase transitions at 32 and 10 K. Diffuse reflectance measurements reveal two broad absorption bands at 1047 and 837 nm, in both PbFe3O(PO4)3 and SrFe3O(PO4)3 powders, with peak cross sections ∼10-20 cm2 typical of spin-forbidden and forced electric dipole intraconfigurational transitions.

In vivo characterization of colorectal metastases in human liver using diffuse reflectance spectroscopy: toward guidance in oncological procedures

NASA Astrophysics Data System (ADS)

Spliethoff, Jarich W.; de Boer, Lisanne L.; Meier, Mark A. J.; Prevoo, Warner; de Jong, Jeroen; Kuhlmann, Koert; Bydlon, Torre M.; Sterenborg, Henricus J. C. M.; Hendriks, Benno H. W.; Ruers, Theo J. M.

2016-09-01

There is a strong need to develop clinical instruments that can perform rapid tissue assessment at the tip of smart clinical instruments for a variety of oncological applications. This study presents the first in vivo real-time tissue characterization during 24 liver biopsy procedures using diffuse reflectance (DR) spectroscopy at the tip of a core biopsy needle with integrated optical fibers. DR measurements were performed along each needle path, followed by biopsy of the target lesion using the same needle. Interventional imaging was coregistered with the DR spectra. Pathology results were compared with the DR spectroscopy data at the final measurement position. Bile was the primary discriminator between normal liver tissue and tumor tissue. Relative differences in bile content matched with the tissue diagnosis based on histopathological analysis in all 24 clinical cases. Continuous DR measurements during needle insertion in three patients showed that the method can also be applied for biopsy guidance or tumor recognition during surgery. This study provides an important validation step for DR spectroscopy-based tissue characterization in the liver. Given the feasibility of the outlined approach, it is also conceivable to make integrated fiber-optic tools for other clinical procedures that rely on accurate instrument positioning.

Photochemical and photocatalytic evaluation of 1D titanate/TiO2 based nanomaterials

NASA Astrophysics Data System (ADS)

Conceição, D. S.; Ferreira, D. P.; Graça, C. A. L.; Júlio, M. F.; Ilharco, L. M.; Velosa, A. C.; Santos, P. F.; Vieira Ferreira, L. F.

2017-01-01

One-dimensional (1D) titanate based nanomaterials were synthesized following an alkaline hydrothermal approach of commercial TiO2 nanopowder. The morphological features of all materials were monitored by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and also Brunauer-Emmett-Teller (BET) technique. In addition the photochemical behaviour of these nanostructured materials were evaluated with the use of laser induced luminescence (LIL), ground-state diffuse reflectance (GSDR), and laser-flash photolysis in diffuse reflectance mode (DRLFP). The mixed titanate/TiO2 nanowires presented the least intense fluorescence spectra, suggesting the presence of surficial defects that can extend the lifetime of the excited charge carriers. A fluorescent 'rhodamine-like' dye was adsorbed onto different materials and examined via photoexcitation in the visible range to study the self-photosensitization mechanism. The presence of the radical cation of the dye and the degradation kinetics, when compared with a neutral substrate-cellulose, provided significant evidences regarding the photoactivity of the different materials. Regarding all the materials under study, the nanowires exhibited a strong photocatalytic efficiency, for the adsorbed fluorescent probe. The photocatalytic mechanism was also considered by studying the photodegradation capability of the titanate based materials in the presence of an herbicide, Amicarbazone, after ultraviolet (UVA) photoexcitation.

Determination of band gap in epitaxial delafossite Cu oxide using optical techniques

NASA Astrophysics Data System (ADS)

Cabrera, Alejandro; Wheatley, R.; Seifert, B.; Wallentowitz, S.; Joshi, T.; Lederman, D.

Highly epitaxial delafossite CuFeO2 and CuFe1-xGaxO2 films were grown using Pulsed Laser Deposition techniques. The sample thicknesses were estimated to be 21 nm, 75 nm.The estimated gallium fraction of substituted ferric atoms was x =0.25 for the composite sample. We present the study of the fundamental band gap(s) for each sample via observation of their respective optical absorption properties in the NIR-VIS region using transmittance and diffuse reflection spectroscopy. Predominant absorption edges measured were between 1.1eV and 3.1eV from transmittance spectra. The sample of CuFe1-xGaxO2 showed measurable absorption features located at 2.4eV and 2.8eV. This study also found evidence of changes between apparent absorption edges between transmittance and diffuse reflectance spectroscopies of each sample and it may be resultant from absorption channels via surface states. Future photoluminescence experiments are planned to determine the photo-induced semiconductor behavior of these materials. ACNOWLEDGEMENTS: This work was supported by FONDECyT 1130372 and Proyecto Anillo ACT1409 at PUC and supported in part by the WV Higher Education Policy Commission (Grant HEPC.dsr.12.29) and by FAME sponsored by MARCO and DARPA (contract # 2013-MA-2382).

Ecological risk assessment on heavy metals in soils: Use of soil diffuse reflectance mid-infrared Fourier-transform spectroscopy

PubMed Central

Wang, Cheng; Li, Wei; Guo, Mingxing; Ji, Junfeng

2017-01-01

The bioavailability of heavy metals in soil is controlled by their concentrations and soil properties. Diffuse reflectance mid-infrared Fourier-transform spectroscopy (DRIFTS) is capable of detecting specific organic and inorganic bonds in metal complexes and minerals and therefore, has been employed to predict soil composition and heavy metal contents. The present study explored the potential of DRIFTS for estimating soil heavy metal bioavailability. Soil and corresponding wheat grain samples from the Yangtze River Delta region were analyzed by DRIFTS and chemical methods. Statistical regression analyses were conducted to correlate the soil spectral information to the concentrations of Cd, Cr, Cu, Zn, Pb, Ni, Hg and Fe in wheat grains. The principal components in the spectra influencing soil heavy metal bioavailability were identified and used in prediction model construction. The established soil DRIFTS-based prediction models were applied to estimate the heavy metal concentrations in wheat grains in the mid-Yangtze River Delta area. The predicted heavy metal concentrations of wheat grain were highly consistent with the measured levels by chemical analysis, showing a significant correlation (r2 > 0.72) with acceptable root mean square error RMSE. In conclusion, DRIFTS is a promising technique for assessing the bioavailability of soil heavy metals and related ecological risk. PMID:28198802

Canopy reflectance related to marsh dieback onset and progression in Coastal Louisiana

USGS Publications Warehouse

Ramsey, Elijah W.; Rangoonwala, A.

2006-01-01

In this study, we extended previous work linking leaf spectral changes, dieback onset, and progression of Spartina alterniflora marshes to changes in site-specific canopy reflectance spectra. First, we obtained canopy reflectance spectra (approximately 20 m ground resolution) from the marsh sites occupied during the leaf spectral analyses and from additional sites exhibiting visual signs of dieback. Subsequently, the canopy spectra were analyzed at two spectral scales: the first scale corresponded to whole-spectra sensors, such as the NASA Earth Observing-1 (EO-1) Hyperion, and the second scale corresponded to broadband spectral sensors, such as the EO-1 Advanced Land Imager and the Landsat Enhanced Thematic Mapper. In the whole-spectra analysis, spectral indicators were generated from the whole canopy spectra (about 400 nm to 1,000 nm) by extracting typical dead and healthy marsh spectra, and subsequently using them to determine the percent composition of all canopy reflectance spectra. Percent compositions were then used to classify canopy spectra at each field site into groups exhibiting similar levels of dieback progression ranging from relatively healthy to completely dead. In the broadband reflectance analysis, blue, green, red, red-edge, and near infrared (NIR) spectral bands and NIR/green and NIR/red transforms were extracted from the canopy spectra. Spectral band and band transform indicators of marsh dieback and progression were generated by relating them to marsh status indicators derived from classifications of the 35 mm slides collected at the same time as the canopy reflectance recordings. The whole spectra and broadband spectral indicators were both able to distinguish (a) healthy marsh, (b) live marsh impacted by dieback, and (c) dead marsh, and they both provided some discrimination of dieback progression. Whole-spectra resolution sensors like the EO-1 Hyperion, however, offered an enhanced ability to categorize dieback progression. ?? 2006 American Society for Photogrammetry and Remote Sensing.

LO-TO splittings, effective charges and interactions in electro-optic meta-nitroaniline crystal as studied by polarized IR reflection and transmission spectra

NASA Astrophysics Data System (ADS)

Szostak, M. M.; Le Calvé, N.; Romain, F.; Pasquier, B.

1994-10-01

The polarized IR reflection spectra of the meta-nitroaniline ( m-NA) single crystal along the a, b and c crystallographic axes as well as the b and c polarized transmission spectra have been measured in the 100-400 cm -1 region. The LO-TO splitting values have been calculated from the reflection spectra by fitting them with the four parameter dielectric function. The dipole moment derivatives, relevant to dynamic effective charges, of the vibrations have also been calculated and used to check the applicability of the oriented gas model (OGM) to reflection spectra. The discrepancies from the OGM have been discussed in terms of vibronic couplings, weak hydrogen bondings (HB) and intramolecular charge transfer.

A new diffusion matrix for whistler mode chorus waves

NASA Astrophysics Data System (ADS)

Horne, Richard B.; Kersten, Tobias; Glauert, Sarah A.; Meredith, Nigel P.; Boscher, Daniel; Sicard-Piet, Angelica; Thorne, Richard M.; Li, Wen

2013-10-01

Global models of the Van Allen radiation belts usually include resonant wave-particle interactions as a diffusion process, but there is a large uncertainty over the diffusion rates. Here we present a new diffusion matrix for whistler mode chorus waves that can be used in such models. Data from seven satellites are used to construct 3536 power spectra for upper and lower band chorus for 1.5≤L∗≤10 MLT, magnetic latitude 0°≤|λm|≤60° and five levels of Kp. Five density models are also constructed from the data. Gaussian functions are fitted to the spectra and capture typically 90% of the wave power. The frequency maxima of the power spectra vary with L∗ and are typically lower than that used previously. Lower band chorus diffusion increases with geomagnetic activity and is largest between 21:00 and 12:00 MLT. Energy diffusion extends to a few megaelectron volts at large pitch angles >60° and at high energies exceeds pitch angle diffusion at the loss cone. Most electron diffusion occurs close to the geomagnetic equator (<12°). Pitch angle diffusion rates for lower band chorus increase with L∗ and are significant at L∗=8 even for low levels of geomagnetic activity, while upper band chorus is restricted to mainly L∗<6. The combined drift and bounce averaged diffusion rates for upper and lower band chorus extend from a few kiloelectron volts near the loss cone up to several megaelectron volts at large pitch angles indicating loss at low energies and net acceleration at high energies.

Classification of specialty seed meals from NIR reflectance spectra

USDA-ARS?s Scientific Manuscript database

Near infrared reflectance spectroscopy was used to identify alternative seed meals proposed for food and feed formulations. Spectra were collected from cold pressed Camelina (Camelina sativa), Coriander (Coriandrum sativum), and Pennycress (Thlaspi arvense) meals. Additional spectra were collected ...

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.

Biophotonics of skin: method for correction of deep Raman spectra distorted by elastic scattering

NASA Astrophysics Data System (ADS)

Roig, Blandine; Koenig, Anne; Perraut, François; Piot, Olivier; Gobinet, Cyril; Manfait, Michel; Dinten, Jean-Marc

2015-03-01

Confocal Raman microspectroscopy allows in-depth molecular and conformational characterization of biological tissues non-invasively. Unfortunately, spectral distortions occur due to elastic scattering. Our objective is to correct the attenuation of in-depth Raman peaks intensity by considering this phenomenon, enabling thus quantitative diagnosis. In this purpose, we developed PDMS phantoms mimicking skin optical properties used as tools for instrument calibration and data processing method validation. An optical system based on a fibers bundle has been previously developed for in vivo skin characterization with Diffuse Reflectance Spectroscopy (DRS). Used on our phantoms, this technique allows checking their optical properties: the targeted ones were retrieved. Raman microspectroscopy was performed using a commercial confocal microscope. Depth profiles were constructed from integrated intensity of some specific PDMS Raman vibrations. Acquired on monolayer phantoms, they display a decline which is increasing with the scattering coefficient. Furthermore, when acquiring Raman spectra on multilayered phantoms, the signal attenuation through each single layer is directly dependent on its own scattering property. Therefore, determining the optical properties of any biological sample, obtained with DRS for example, is crucial to correct properly Raman depth profiles. A model, inspired from S.L. Jacques's expression for Confocal Reflectance Microscopy and modified at some points, is proposed and tested to fit the depth profiles obtained on the phantoms as function of the reduced scattering coefficient. Consequently, once the optical properties of a biological sample are known, the intensity of deep Raman spectra distorted by elastic scattering can be corrected with our reliable model, permitting thus to consider quantitative studies for purposes of characterization or diagnosis.

The ESO Diffuse Interstellar Band Large Exploration Survey (EDIBLES)

NASA Astrophysics Data System (ADS)

Cami, J.; Cox, N. L.; Farhang, A.; Smoker, J.; Elyajouri, M.; Lallement, R.; Bacalla, X.; Bhatt, N. H.; Bron, E.; Cordiner, M. A.; de Koter, A..; Ehrenfreund, P.; Evans, C.; Foing, B. H.; Javadi, A.; Joblin, C.; Kaper, L.; Khosroshahi, H. G.; Laverick, M.; Le Petit, F..; Linnartz, H.; Marshall, C. C.; Monreal-Ibero, A.; Mulas, G.; Roueff, E.; Royer, P.; Salama, F.; Sarre, P. J.; Smith, K. T.; Spaans, M.; van Loon, J. T..; Wade, G.

2018-03-01

The ESO Diffuse Interstellar Band Large Exploration Survey (EDIBLES) is a Large Programme that is collecting high-signal-to-noise (S/N) spectra with UVES of a large sample of O and B-type stars covering a large spectral range. The goal of the programme is to extract a unique sample of high-quality interstellar spectra from these data, representing different physical and chemical environments, and to characterise these environments in great detail. An important component of interstellar spectra is the diffuse interstellar bands (DIBs), a set of hundreds of unidentified interstellar absorption lines. With the detailed line-of-sight information and the high-quality spectra, EDIBLES will derive strong constraints on the potential DIB carrier molecules. EDIBLES will thus guide the laboratory experiments necessary to identify these interstellar “mystery molecules”, and turn DIBs into powerful diagnostics of their environments in our Milky Way Galaxy and beyond. We present some preliminary results showing the unique capabilities of the EDIBLES programme.

Spectral investigations and DFT studies of 3,7-dihydro-1,3,7-trimethyl-1H-purine-2,6-dione (caffeine) interaction and recognition by single amino acid derived self-assembled nanostructures

NASA Astrophysics Data System (ADS)

Govindhan, R.; Karthikeyan, B.

2018-03-01

Recognition of xanthine alkaloid caffeine with 3,5-bis(trifluoromethyl)benzylamine derived peptide nanotubes (BTTPNTs) through chemical interaction have been achieved through the host-guest like interaction. DFT simulation is carried out for caffeine interacted with BTTPNTs system and also experimentally characterized by ultraviolet-visible (UV-vis) absorbance, confocal Raman spectra (CRS) with microscopic imaging (CRM), FT-Raman, surface enhanced Raman scattering (SERS), UV-diffuse reflectance spectra (UV-DRS), high resolution transmission electron microscopy (HR-TEM) and cyclic voltammetry (CV) studies. The results are used to examine the morphologies, size of the nanostructure and study of its interaction with the caffeine molecule. The results show that BTTPNTs is having potential for sensing the caffeine molecules through the binding occurred from the NH2 of tyrosine moiety of the BTTPNTs. This intermolecular association through face-to-face stacking of BTTPNTs is explained by detailed DFT calculations.

Structural and plasmonic properties of noble metal doped ZnO nanomaterials

NASA Astrophysics Data System (ADS)

Pathak, Trilok K.; Swart, H. C.; Kroon, R. E.

2018-04-01

Noble metal doped ZnO has been synthesized by the combustion method and the effect of different metals (Ag, Au, Pd) on the structural, morphological, optical, photoluminescence and localized surface plasmon resonance (LSPR) properties has been investigated. X-ray diffraction analysis revealed that the ZnO had a hexagonal wurtzite structure and the crystallite sizes were affected by the doping. The formation of noble metal nanoparticles (NPs) was investigated using transmission electron microscopy and diffuse reflectance spectra. The LSPR of the metallic NPs was predicted using Mie theory calculations. The absorption spectra were calculated using the Kubelka-Munk function and the optical bandgap varied from 3.06 to 3.18 eV for the different doping materials. The experimental results suggest that the origin of enhanced emission was due to direct interaction between the laser photons and the noble material NPs which in turn leads to photoemission transfer of electrons from the noble metals NPs to the conduction band of ZnO.

Ultrathin nanosheets of graphitic carbon nitride heterojunction with flower like Bi2O3 for photodegradation of organic pollutants

NASA Astrophysics Data System (ADS)

Bano, Zahira; Muhmood, Tahir; Xia, Mingzhu; Lei, Wu; Wang, Fengyun

2018-05-01

The flower like microrods (MR) of α-Bi2O3 defined as (MR-Bi2O3) and ultrathin g-C3N4(UT-C3N4) p-n junction was successfully prepared by loading different concentrations of UT-C3N4 over MR-Bi2O3. Their morphology and structure were thoroughly studied by XRD, SEM, XPS, TEM, UV–vis diffuse reflectance spectra, FT-IR and PL spectra. The results showed that the UT-C3N4 has been wrapped in the flower like MR-Bi2O3. The designing of the p-n junction of UT- C3N4 and MR-Bi2O3 can enhance the separation efficiency of the electron-hole pairs. The photocatalytic degradation of RhB was drastically increased by designing of the p-n junction that is due to the photogenerated electron–hole pair’s separation efficiency.

Vacancy-Rich Monolayer BiO 2-x as a Highly Efficient UV, Visible, and Near-Infrared Responsive Photocatalyst

DOE PAGES

Li, Jun; Wu, Xiaoyong; Pan, Wenfeng; ...

2017-09-08

Here in this paper, a full-spectrum responsive vacancy-rich monolayer BiO 2-x has been synthesized. The increased density of states at the conduction band (CB) minimum in the monolayer BiO 2-x is responsible for the enhanced photon response and photo-absorption, which were confirmed by UV/Vis-NIR diffuse reflectance spectra (DRS) and photocurrent measurements. Compared to bulk BiO 2-x, monolayer BiO 2-x has exhibited enhanced photocatalytic performance for rhodamine B and phenol removal under UV, visible, and near-infrared light (NIR) irradiation, which can be attributed to the vacancy VBi-O"' as confirmed by the positron annihilation spectra. The presence of V Bi-O"' defects inmore » monolayer BiO 2-x promoted the separation of electrons and holes. This finding provides an atomic level understanding for developing highly efficient UV, visible, and NIR light responsive photocatalysts.« less

Vacancy-Rich Monolayer BiO 2-x as a Highly Efficient UV, Visible, and Near-Infrared Responsive Photocatalyst

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

Li, Jun; Wu, Xiaoyong; Pan, Wenfeng

Here in this paper, a full-spectrum responsive vacancy-rich monolayer BiO 2-x has been synthesized. The increased density of states at the conduction band (CB) minimum in the monolayer BiO 2-x is responsible for the enhanced photon response and photo-absorption, which were confirmed by UV/Vis-NIR diffuse reflectance spectra (DRS) and photocurrent measurements. Compared to bulk BiO 2-x, monolayer BiO 2-x has exhibited enhanced photocatalytic performance for rhodamine B and phenol removal under UV, visible, and near-infrared light (NIR) irradiation, which can be attributed to the vacancy VBi-O"' as confirmed by the positron annihilation spectra. The presence of V Bi-O"' defects inmore » monolayer BiO 2-x promoted the separation of electrons and holes. This finding provides an atomic level understanding for developing highly efficient UV, visible, and NIR light responsive photocatalysts.« less

Three coordination polymers based on a star-like geometry 4, 4', 4'' -nitrilotribenzoic acid ligand and their framework dependent luminescent properties

NASA Astrophysics Data System (ADS)

Hu, Zhiyong; Zhao, Meng; Su, Jian; Xu, Shasha; Hu, Lei; Liu, Hui; Zhang, Qiong; Zhang, Jun; Wu, Jieying; Tian, Yupeng

2018-02-01

Three novel coordination polymers, [Zn(μ2-HTCA)(Phen)]n (1), {[Cd(μ3-HTCA)(Phen)]·2H2O}n (2), [Mn(μ2-HTCA)(Phen)(H2O)]n (3) were prepared by hydrothermal synthesis from the 4, 4', 4''-nitrilotribenzoicacid (H3TCA) and 1, 10-phenanthroline monohydrate (Phen) with different transition metal salts, which were characterized by elemental analysis, IR spectra, powder and single-crystal X-ray diffraction and thermogravimetric analysis. The photophysical properties of the complexes were investigated by solid-state diffuse reflectance spectra, photoluminescent properties, lifetime and quantum yield. For these complexes, it was found that the band gaps follow the order: 3 ＜ 2 ＜ 1 ＜ 2.80 eV, fluorescence intensity order: 1 ＞ H3TCA ＞ 2 ＞ 3; quantum yield order: H3TCA ＞ 1 ＞ 2 ＞ 3; while the lifetime order: 1 ＞ 2 ＞ H3TCA ＞ 3.

Eco-friendly and green synthesis of BiVO4 nanoparticle using microwave irradiation as photocatalayst for the degradation of Alizarin Red S

NASA Astrophysics Data System (ADS)

Abraham, S. Daniel; David, S. Theodore; Bennie, R. Biju; Joel, C.; Kumar, D. Sanjay

2016-06-01

Bismuth vanadate (BiVO4) nanocrystals have been successfully synthesised using microwave-assisted combustion synthesis (MCS), and characterised using Fourier transform infrared (FT-IR) and Raman spectra, surface area analysis (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy Dispersive X-ray analysis (EDX), diffused reflectance spectroscopy (DRS) and Photoluminescence (PL) spectroscopy. The XRD results confirmed the formation of monoclinic bismuth vanadate. The formations of BiO & VO43-vibrations were ascertained from FT-IR data. The morphology of hallow internal structural micro entities were confirmed by SEM. The optical properties were determined by DRS and PL spectra. Hence, the influence of the preparation methods on the structure, morphology and optical activities of bismuth vanadate was investigated systematically. Photocatalytic degradation (PCD) of Alizarin Red S (ARS), an effective disrupting chemical in aqueous medium was investigated using BiVO4 nanoparticles. The kinetics of PCD was found to follow pseudo first-order.

Quick analysis of optical spectra to quantify epidermal melanin and papillary dermal blood content of skin.

PubMed

Jacques, Steven L

2015-04-01

This paper presents a practical approach for assessing the melanin and blood content of the skin from total diffuse reflectance spectra, R(λ), where λ is wavelength. A quick spectral analysis using just three wavelengths (585 nm, 700 nm and 800 nm) is presented, based on the 1985 work of Kollias and Baquer who documented epidermal melanin of skin using the slope of optical density (OD) between 620 nm and 720 nm. The paper describes the non-rectilinear character of such a quick analysis, and shows that almost any choice of two wavelengths in the 600-900 range can achieve the characterization of melanin. The extrapolation of the melanin slope to 585 nm serves as a baseline for subtraction from the OD (585 nm) to yield a blood perfusion score. Monte Carlo simulations created spectral data for a skin model with epidermis, papillary dermis and reticular dermis to illustrate the analysis. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis and characterization of heterometallic uranyl pyridinedicarboxylate compounds

NASA Astrophysics Data System (ADS)

Jayasinghe, Ashini S.; Payne, Maurice K.; Forbes, Tori Z.

2017-10-01

The incorporation of transition metals into hybrid uranyl materials can result in more diverse structural topologies and variations in physical and chemical properties. To explore the impact of transition metals on the uranyl cation, five uranium containing bimetallic chain compounds, [(UO2)M(PDC)2(H2O)4]·4(H2O) (PDC = 2,6 pyridinedicarboxylate; M = Ni2+, Co2+, Fe2+, Zn2+, and Cu2+) were synthesized by evaporation of aqueous solutions at room temperature. The uranyl cation is complex by two PDC ligands and the transition metal cations bond to the complex to form a one-dimensional chain topology. The presence of the transition metal leads to the presence of a stronger uranyl oxo bonds as shown by the single-crystal X-ray diffraction data and the Raman spectra. Solid state diffuse reflectance UV/Visible spectra confirmed the presence of the transition metals in the structure by the broad bands that appeared at relevant wavelengths.

Reflection spectra, 2.5-7 microns, of some solids of planetary interest

NASA Technical Reports Server (NTRS)

Fink, U.; Burk, S. D.

1973-01-01

Reflection spectra of 42 compounds of possible planetary interest were run from 2.5 to 7 microns. They were supplemented by some transmission spectra extending the wavelength coverage to 15 microns. The spectra were organized according to their constituent radicals and an attempt was made at the identification of the absorption features.

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.

Specular reflectance of optical-black coatings in the far infrared

NASA Technical Reports Server (NTRS)

Smith, S. M.

1984-01-01

Far-infrared specular reflectance spectra of seven optically black coatings near normal incidence are presented. Seven photometric spectra were obtained using eleven bandpass transmission filters in the wavelength range between 12 and 500 microns, and three interferometric spectra were obtained for corroboration. Data on the construction, thickness, and rms surface roughness of the coatings are also presented. The chemical composition of three coatings can be distinguished from that of the others by a strong absorption feature between 20 and 40 microns, which can be largely attributed to amorphous silicate material. At 100 microns, the most and least reflective coatings differ by nearly 3 orders of magnitude. Inverse relationships observed between the spectra and the roughness and thickness of the coatings led to development of a reflecting-layer model for the measured reflectance. The model successfully describes the spectra at wavelengths outside the silicate absorption, and optical constants are deduced from a nonlinear least squares fit to the data. Parametric errors are estimated by chi-square analysis, and sensitivity tests are performed to determine which parameters control reflectance in different spectral regions.

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.

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

Actinic Flux Calculations: A Model Sensitivity Study

NASA Technical Reports Server (NTRS)

Krotkov, Nickolay A.; Flittner, D.; Ahmad, Z.; Herman, J. R.; Einaudi, Franco (Technical Monitor)

2000-01-01

calculate direct and diffuse surface irradiance and actinic flux (downwelling (2p) and total (4p)) for the reference model. Sensitivity analysis has shown that the accuracy of the radiative transfer flux calculations for a unit ETS (i.e. atmospheric transmittance) together with a numerical interpolation technique for the constituents' vertical profiles is better than 1% for SZA less than 70(sub o) and wavelengths longer than 310 nm. The differences increase for shorter wavelengths and larger SZA, due to the differences in pseudo-spherical correction techniques and vertical discretetization among the codes. Our sensitivity study includes variation of ozone cross-sections, ETS spectra and the effects of wavelength shifts between vacuum and air scales. We also investigate the effects of aerosols on the spectral flux components in the UV and visible spectral regions. The "aerosol correction factors" (ACFs) were calculated at discrete wavelengths and different SZAs for each flux component (direct, diffuse, reflected) and prescribed IPMMI aerosol parameters. Finally, the sensitivity study was extended to calculation of selected photolysis rates coefficients.

Reflectance Spectra of Peacock Feathers and the Turning Angles of Melanin Rods in Barbules.

PubMed

Okazaki, Toshio

2018-02-01

I analyzed the association between the reflectance spectra and melanin rod arrangement in barbules of the eyespot of peacock feathers. The reflectance spectra from the yellow-green feather of the eyespot indicated double peaks of 430 and 540 nm. The maximum reflectance spectrum of the blue feather was 480 nm, and that of the dark blue feather was 420 nm. The reflectance spectra from brown feathers indicated double peaks of 490 and 610 nm. Transmission electron microscopic analysis confirmed that melanin rods were arranged fanwise in the outer layer toward the barbule tips. In addition, using polarized light microscope, I attempted to determine whether the turning angles of melanin rods in the barbules reflected different colors. The turning angle of the polarizing axis of the barbules was supported by that of the melanin rods, observed using transmission electron microscopic images. To compare the turning angle of melanin rods in the respective barbules, I calculated the opening width of the fanwise melanin rods by dividing the width of the barbules by the turning angle of the polarizing axis of barbules and obtained a positive correlation between the reflectance spectra and opening width of the fanwise melanin rods. Moreover, the widely spreading reflection from the barbules may occur because of the fanwise melanin rod arrangement.

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.

FluorMODgui V3.0: A graphic user interface for the spectral simulation of leaf and canopy chlorophyll fluorescence

NASA Astrophysics Data System (ADS)

Zarco-Tejada, P. J.; Miller, J. R.; Pedrós, R.; Verhoef, W.; Berger, M.

2006-06-01

The FluorMODgui Graphic User Interface (GUI) software package developed within the frame of the FluorMOD project Development of a Vegetation Fluorescence Canopy Model is presented in this manuscript. The FluorMOD project was launched in 2002 by the European Space Agency (ESA) to advance the science of vegetation fluorescence simulation through the development and integration of leaf and canopy fluorescence models based on physical methods. The design of airborne or space missions dedicated to the measurement of solar-induced chlorophyll fluorescence using remote-sensing instruments require physical methods for quantitative feasibility analysis and sensor specification studies. The FluorMODgui model developed as part of this project is designed to simulate the effects of chlorophyll fluorescence at leaf and canopy levels using atmospheric inputs, running the leaf model, FluorMODleaf, and the canopy model, FluorSAIL, independently, through a coupling scheme, and by a multiple iteration protocol to simulate changes in the viewing geometry and atmospheric characteristics. Inputs for the FluorMODleaf model are the number of leaf layers, chlorophyll a+ b content, water equivalent thickness, dry matter content, fluorescence quantum efficiency, temperature, species type, and stoichiometry. Inputs for the FluorSAIL canopy model are a MODTRAN-4 6-parameter spectra or measured direct horizontal irradiance and diffuse irradiance spectra, a soil reflectance spectrum, leaf reflectance & transmittance spectra and a excitation-fluorescence response matrix in upward and downward directions (all from FluorMODleaf), 2 PAR-dependent coefficients for the fluorescence response to light level, relative azimuth angle and viewing zenith angle, canopy leaf area index, leaf inclination distribution function, and a hot spot parameter. Outputs available in the 400-1000 nm spectral range from the graphical user interface, FluorMODgui, are the leaf spectral reflectance and transmittance, and the canopy reflectance, with and without fluorescence effects. In addition, solar and sky irradiance on the ground, radiance with and without fluorescence on the ground, and top-of-atmosphere (TOA) radiances for bare soil and surroundings same as target are also produced. The models and documentation regarding the FluorMOD project can be downloaded at http://www.ias.csic.es/fluormod.

Visible and near-infrared (0.4-2.5 μm) reflectance spectra of playa evaporite minerals

USGS Publications Warehouse

Crowley, James K.

1991-01-01

Visible and near-infrared (VNIR; 0.4–2.4 μm) reflectance spectra were recorded for 35 saline minerals that represent the wide range of mineral and brine chemical compositions found in playa evaporite settings. The spectra show that many of the saline minerals exhibit diagnostic near-infrared absorption bands, chiefly attributable to vibrations of hydrogen-bonded structural water molecules. VNIR reflectance spectra can be used to detect minor hydrate phases present in mixtures dominated by anhydrous halite or thenardite, and therefore will be useful in combination with X ray diffraction data for characterizing natural saline mineral assemblages. In addition, VNIR reflectance spectra are sensitive to differences in sample hydration state and should facilitate in situ studies of minerals that occur as fragile, transitory dehydration products in natural salt crusts. The use of spectral reflectance measurements in playa studies should aid in mapping evaporite mineral distributions and may provide insight into the geochemical and hydrological controls on playa mineral and brine development.

Variable Temperature Infrared Spectroscopy Investigations of Benzoic Acid Desorption from Sodium and Calcium Montmorillonite Clays.

PubMed

Nickels, Tara M; Ingram, Audrey L; Maraoulaite, Dalia K; White, Robert L

2015-12-01

Processes involved in thermal desorption of benzoic acid from sodium and calcium montmorillonite clays are investigated by using variable temperature diffuse reflection Fourier transform infrared spectroscopy (DRIFTS). By monitoring the temperature dependence of infrared absorbance bands while heating samples, subtle changes in molecular vibrations are detected and employed to characterize specific benzoic acid adsorption sites. Abrupt changes in benzoic acid adsorption site properties occur for both clay samples at about 125 °C. Difference spectra absorbance band frequency variations indicate that adsorbed benzoic acid interacts with interlayer cations through water bridges and that these interactions can be disrupted by the presence of organic anions, in particular, benzoate.

Variable Temperature Infrared Spectroscopy Investigation of Benzoic Acid Interactions with Montmorillonite Clay Interlayer Water.

PubMed

Nickels, Tara M; Ingram, Audrey L; Maraoulaite, Dalia K; White, Robert L

2015-07-01

Molecular interactions between benzoic acid and cations and water contained in montmorillonite clay interlayer spaces are characterized by using variable temperature diffuse reflection infrared Fourier transform spectroscopy (VT-DRIFTS). Using sample perturbation and difference spectroscopy, infrared spectral changes resulting from removal of interlayer water and associated changes in local benzoic acid environments are identified. Difference spectra features can be correlated with changes in specific molecular vibrations that are characteristic of benzoic acid molecular orientation. Results suggest that the carboxylic acid functionality of benzoic acid interacts with interlayer cations through a bridging water molecule and that this interaction is affected by the nature of the cation present in the clay interlayer space.

Synthesis and photocatalytic activity of N-doped TiO2 produced in a solid phase reaction

NASA Astrophysics Data System (ADS)

Xin, Gang; Pan, Hongfei; Chen, Dan; Zhang, Zhihua; Wen, Bin

2013-02-01

N-doped TiO2 was synthesized by calcining a mixture of titanic acid and graphitic carbon nitride (g-C3N4) at temperatures above 500 °C. The final samples were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS), and UV-vis diffuse reflectance spectra. The photocatalytic activity of N-doped TiO2 was studied by assessing the degradation of methylene blue in an aqueous solution, under visible light and UV light irradiation. It was found that the N-doped TiO2 displayed higher photocatalytic activity than pure TiO2, under both visible and UV light.

Optical study of plasma sprayed hydroxyapatite coatings deposited at different spray distance

NASA Astrophysics Data System (ADS)

Belka, R.; Kowalski, S.; Żórawski, W.

2017-08-01

Series of hydroxyapatite (HA) coatings deposited on titanium substrate at different spray (plasma gun to workpiece) distance were investigated. The optical methods as dark field confocal microscopy, Raman/PL and UV-VIS spectroscopy were used for study the influence of deposition process on structural degradation of HA precursor. The hydroxyl group concentration was investigated by study the OH mode intensity in the Raman spectra. Optical absorption coefficients at near UV region were analyzed by Diffuse Reflectance Spectroscopy. PL intensity observed during Raman measurement was also considered as relation to defects concentration and degradation level. It was confirmed the different gunsubstrate distance has a great impact on structure of deposited HA ceramics.

Facile preparation of highly-dispersed cobalt-silicon mixed oxide nanosphere and its catalytic application in cyclohexane selective oxidation

PubMed Central

2011-01-01

Highly dispersed cobalt-silicon mixed oxide [Co-SiO2] nanosphere was successfully prepared with a modified reverse-phase microemulsion method. This material was characterized in detail by X-ray diffraction, transmission electron microscopy, Fourier transform infrared, ultraviolet-visible diffuse reflectance spectra, X-ray absorption spectroscopy near-edge structure, and N2 adsorption-desorption measurements. High valence state cobalt could be easily obtained without calcination, which is fascinating for the catalytic application for its strong oxidation ability. In the selective oxidation of cyclohexane, Co-SiO2 acted as an efficient catalyst, and good activity could be obtained under mild conditions. PMID:22067075

Application of fuzzy logic in multicomponent analysis by optodes.

PubMed

Wollenweber, M; Polster, J; Becker, T; Schmidt, H L

1997-01-01

Fuzzy logic can be a useful tool for the determination of substrate concentrations applying optode arrays in combination with flow injection analysis, UV-VIS spectroscopy and kinetics. The transient diffuse reflectance spectra in the visible wavelength region from four optodes were evaluated to carry out the simultaneous determination of artificial mixtures of ampicillin and penicillin. The discrimination of the samples was achieved by changing the composition of the receptor gel and working pH. Different algorithms of pre-processing were applied on the data to reduce the spectral information to a few analytic-specific variables. These variables were used to develop the fuzzy model. After calibration the model was validated by an independent test data set.

Analysis of aircraft spectrometer data with logarithmic residuals

NASA Technical Reports Server (NTRS)

Green, A. A.; Craig, M. D.

1985-01-01

Spectra from airborne systems must be analyzed in terms of their mineral-related absorption features. Methods for removing backgrounds and extracting these features one at a time from reflectance spectra are discussed. Methods for converting radiance spectra into a form similar to reflectance spectra so that the feature extraction procedures can be implemented on aircraft spectrometer data are also discussed.

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.

Polar phonons in β-Ga2O3 studied by IR reflectance spectroscopy and first-principle calculations

NASA Astrophysics Data System (ADS)

Azuhata, Takashi; Shimada, Kazuhiro

2017-08-01

IR reflectance spectra of β-Ga2O3 are measured in the range from 400 to 1100 cm-1 using the (\\bar{2}01) and (010) planes for pure transverse Au- and Bu-mode phonons, respectively. The spectra measured using the (010) plane depend remarkably on the polarization direction of the incident light because of the monoclinic symmetry. Reflectance spectra simulated using parameters obtained from first-principle calculations are in good agreement with the experimental spectra. By adjusting the calculated phonon parameters so as to reproduce the experimental spectra, the polar phonon parameters were determined for six modes above 400 cm-1.

Reflection spectra of etched FBGs under the influence of axial contraction and stress-induced index change.

PubMed

Yang, Hang-Zhou; Lim, Kok-Sing; Qiao, Xue-Guang; Chong, Wu-Yi; Cheong, Yew-Ken; Lim, Weng-Hong; Lim, Wei-Sin; Ahmad, Harith

2013-06-17

We present a new theoretical model for the broadband reflection spectra of etched FBGs which includes the effects of axial contraction and stress-induced index change. The reflection spectra of the etched FBGs with several different taper profiles are simulated based on the proposed model. In our observation, decaying exponential profile produces a broadband reflection spectrum with good uniformity over the range of 1540-1560 nm. An etched FBG with similar taper profile is fabricated and the experimental result shows good agreement with the theoretical model.

VizieR Online Data Catalog: Reflectance spectra of 12 Trojans and Hildas (Marsset+, 2014)

NASA Astrophysics Data System (ADS)

Marsset, M.; Vernazza, P.; Gourgeot, F.; Dumas, C.; Birlan, M.; Lamy, P.; Binzel, R. P.

2014-07-01

We present 17 reflectance spectra of 12 high albedo (pv>0.14) Trojans (8 objects) and Hildas (4 objects) obtained with the ESO/VLT Echelle spectrograph X-SHOOTER in the 0.3-2.2um spectral range (14 spectra) and with the NASA/IRTF spectrograph SpeX in the 0.8-2.5um spectral range (3 spectra). X-SHOOTER spectra were normalized to unity at 0.55um and SpeX spectra were normalized to unity at 2.2um . The spectra presented in this work were collected between April and December 2013. (18 data files).

Holographically Fabricated Photonic Crystals with Large Reflectance

DTIC Science & Technology

2008-07-16

CLASSIFICATION OF: We report reflection and transmission spectra from three-dimensional polymer photonic crystals fabricated by holographic...transmission spectra from three-dimensional polymer photonic crystals fabricated by holographic lithography. The measured peak reflectance matches that... polymer photonic crystals fabricated by holographic lithography. The measured peak reflectance matches that predicted by both a finite-difference time

Catheter based mid-infrared reflectance and reflectance generated absorption spectroscopy

DOEpatents

Holman, Hoi-Ying N

2013-10-29

A method of characterizing conditions in a tissue, by (a) providing a catheter that has a light source that emits light in selected wavenumbers within the range of mid-IR spectrum; (b) directing the light from the catheter to an area of tissue at a location inside a blood vessel of a subject; (c) collecting light reflected from the location and generating a reflectance spectra; and (d) comparing the reflectance spectra to a reference spectra of normal tissue, whereby a location having an increased number of absorbance peaks at said selected wavenumbers indicates a tissue inside the blood vessel containing a physiological marker for atherosclerosis.

The impacts of environmental variables on water reflectance measured using a lightweight unmanned aerial vehicle (UAV)-based spectrometer system

NASA Astrophysics Data System (ADS)

Zeng, Chuiqing; Richardson, Murray; King, Douglas J.

2017-08-01

Remote sensing methods to study spatial and temporal changes in water quality using satellite or aerial imagery are limited by the inherently low reflectance signal of water across the visible and near infrared spectrum, as well as environmental variables such as surface scattering effects (sun glint), substrate and aquatic vegetation reflectance, and atmospheric effects. This study exploits the low altitude, high-resolution remote sensing capabilities of unmanned aerial vehicle (UAV) platforms to examine the major environmental variables that affect water reflectance acquisition, without the confounding influence of atmospheric effects typical of higher-altitude platforms. After observation and analysis, we found: (1) multiple water spectra measured at the same location had a standard deviation of 10.4%; (2) water spectra changes associated with increasing altitude from 20 m to 100 m were negligible; (3) the difference between mean reflectance at three off-shore locations in an urban water body reached 29.9%; (4) water bottom visibility increased water reflectance by 20.1% in near shore areas compared to deep water spectra in a clear water lake; (5) emergent plants caused the water spectra to shift towards a shape that is characteristic of vegetation, whereas submerged vegetation showed limited effect on water spectra in the studied lake; (6) cloud and sun glint had major effects and caused water spectra to change abruptly; while glint and shadow effects on spectra may balance each other under certain conditions, the water reflectance can also be unpredictable at times due to wave effects and their effects on lines-of-site to calm water; (7) water spectra collected under a variety of different conditions (e.g. multiple locations, waves) resulted in weaker regression models compared to spectra collected under ideal conditions (e.g. single location, no wave), although the resulting model coefficients were relatively stable. The methods and results from this study contribute to better understanding of water reflectance acquisition using remote sensing, and can be applied in UAV-based water quality assessment or to aid in validation of higher altitude imagery.

Comparison of sub-Doppler-width resonances in transmission and reflection spectra of micrometer-thick Cs vapor layers

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

Krasteva, A., E-mail: anna0kr0stz@gmail.com; Cartaleva, S., E-mail: stefka-c@ie.bas.bg; Vartanyan, T., E-mail: tigran@vartanyan.com

2016-03-25

We report experimental study of resonance sign reversal at the hyperfine F{sub g} = 4 → F{sub e} = 5 transition on D{sub 2} line of {sup 133}Cs. Alkali vapors are confined in an optical cell with micrometric thickness. For circular polarization of the irradiating light, transmission and reflection spectra, recorded at different laser intensities and different temperature of alkali vapor, are studied and compared. At low laser intensity, in the transmission spectra we observe a narrow resonance of increased absorption (bright resonance) at the F{sub g} = 4 → F{sub e} = 5 transition, however in reflection spectra, recordedmore » at the same experimental conditions, this bright resonance transforms into a dark resonance of reduced absorption. A simple explanation is proposed in order to explain the observed difference between the transmission and reflection spectra.« less

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.

Deriving Polarization Properties of Desert-Reflected Solar Spectra with PARASOL Data

NASA Technical Reports Server (NTRS)

Sun, Wenbo; Baize, Rosemary R.; Lukashin, Constantine

2015-01-01

Reflected solar radiation from desert is strongly polarized by sand particles. To date, there is no reliable desert surface reflection model to calculate desert reflection matrix. In this study, the PARASOL data are used to retrieve physical properties of desert. These physical properties are then used in the ADRTM to calculate polarization of desert-reflected light for the whole solar spectra.

Impact of pentacene film thickness on the photoresponse spectra: Determination of the photocarrier generation mechanism

NASA Astrophysics Data System (ADS)

Gorgolis, S.; Giannopoulou, A.; Anastassopoulos, D.; Kounavis, P.

2012-07-01

Photocurrent response, optical absorption, and x-ray diffraction (XRD) measurements in pentacene films grown on glass substrates are performed in order to obtain an insight into the mobile photocarriers generation mechanism. For film thickness of the order of 50 nm and lower, the photocurrent response spectra are found to follow the optical absorption spectra demonstrating the so-called symbatic response. Upon increasing the film thickness, the photoresponse demonstrates a transition to the so-called antibatic response, which is characterized by a maximum and minimum photocurrent for photon energies of minimum and maximum optical absorption, respectively. The experimental results are not in accordance with the model of important surface recombination rate. By taking into account the XRD patterns, the experimental photoresponse spectra can be reproduced by model simulations assuming efficient exciton dissociation at a narrow layer of the order of 20 nm near the pentacene-substrate interface. The simulated spectra are found sensitive to the film thickness, the absolute optical absorption coefficient, and the diffusion exciton length. By comparing the experimental with the simulated spectra, it is deduced that the excitons, which are created by optical excitation in the spectral region of 1.7-2.2 eV, diffuse with a diffusion length of the order of 10-80 nm to the pentacene-substrate interface where efficiently dissociate into mobile charge carriers.

CLARREO shortwave observing system simulation experiments of the twenty-first century: Simulator design and implementation

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

Feldman, D.R.; Algieri, C.A.; Ong, J.R.

2011-04-01

Projected changes in the Earth system will likely be manifested in changes in reflected solar radiation. This paper introduces an operational Observational System Simulation Experiment (OSSE) to calculate the signals of future climate forcings and feedbacks in top-of-atmosphere reflectance spectra. The OSSE combines simulations from the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report for the NCAR Community Climate System Model (CCSM) with the MODTRAN radiative transfer code to calculate reflectance spectra for simulations of current and future climatic conditions over the 21st century. The OSSE produces narrowband reflectances and broadband fluxes, the latter of which have been extensivelymore » validated against archived CCSM results. The shortwave reflectance spectra contain atmospheric features including signals from water vapor, liquid and ice clouds, and aerosols. The spectra are also strongly influenced by the surface bidirectional reflectance properties of predicted snow and sea ice and the climatological seasonal cycles of vegetation. By comparing and contrasting simulated reflectance spectra based on emissions scenarios with increasing projected and fixed present-day greenhouse gas and aerosol concentrations, we find that prescribed forcings from increases in anthropogenic sulfate and carbonaceous aerosols are detectable and are spatially confined to lower latitudes. Also, changes in the intertropical convergence zone and poleward shifts in the subsidence zones and the storm tracks are all detectable along with large changes in snow cover and sea ice fraction. These findings suggest that the proposed NASA Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission to measure shortwave reflectance spectra may help elucidate climate forcings, responses, and feedbacks.« less

Similarity analysis of spectra obtained via reflectance spectrometry in legal medicine.

PubMed

Belenki, Liudmila; Sterzik, Vera; Bohnert, Michael

2014-02-01

In the present study, a series of reflectance spectra of postmortem lividity, pallor, and putrefaction-affected skin for 195 investigated cases in the course of cooling down the corpse has been collected. The reflectance spectrometric measurements were stored together with their respective metadata in a MySQL database. The latter has been managed via a scientific information repository. We propose similarity measures and a criterion of similarity that capture similar spectra recorded at corpse skin. We systematically clustered reflectance spectra from the database as well as their metadata, such as case number, age, sex, skin temperature, duration of cooling, and postmortem time, with respect to the given criterion of similarity. Altogether, more than 500 reflectance spectra have been pairwisely compared. The measures that have been used to compare a pair of reflectance curve samples include the Euclidean distance between curves and the Euclidean distance between derivatives of the functions represented by the reflectance curves at the same wavelengths in the spectral range of visible light between 380 and 750 nm. For each case, using the recorded reflectance curves and the similarity criterion, the postmortem time interval during which a characteristic change in the shape of reflectance spectrum takes place is estimated. The latter is carried out via a software package composed of Java, Python, and MatLab scripts that query the MySQL database. We show that in legal medicine, matching and clustering of reflectance curves obtained by means of reflectance spectrometry with respect to a given criterion of similarity can be used to estimate the postmortem interval.

Remote compositional analysis of lunar olivine-rich lithologies with Moon Mineralogy Mapper (M3) spectra

USGS Publications Warehouse

Isaacson, P.J.; Pieters, C.M.; Besse, S.; Clark, R.N.; Head, J.W.; Klima, R.L.; Mustard, J.F.; Petro, N.E.; Staid, M.I.; Sunshine, J.M.; Taylor, L.A.; Thaisen, K.G.; Tompkins, S.

2011-01-01

A systematic approach for deconvolving remotely sensed lunar olivine-rich visible to near-infrared (VNIR) reflectance spectra with the Modified Gaussian Model (MGM) is evaluated with Chandrayaan-1 Moon Mineralogy Mapper (M 3) spectra. Whereas earlier studies of laboratory reflectance spectra focused only on complications due to chromite inclusions in lunar olivines, we develop a systematic approach for addressing (through continuum removal) the prominent continuum slopes common to remotely sensed reflectance spectra of planetary surfaces. We have validated our continuum removal on a suite of laboratory reflectance spectra. Suites of olivine-dominated reflectance spectra from a small crater near Mare Moscoviense, the Copernicus central peak, Aristarchus, and the crater Marius in the Marius Hills were analyzed. Spectral diversity was detected in visual evaluation of the spectra and was quantified using the MGM. The MGM-derived band positions are used to estimate the olivine's composition in a relative sense. Spectra of olivines from Moscoviense exhibit diversity in their absorption features, and this diversity suggests some variation in olivine Fe/Mg content. Olivines from Copernicus are observed to be spectrally homogeneous and thus are predicted to be more compositionally homogeneous than those at Moscoviense but are of broadly similar composition to the Moscoviense olivines. Olivines from Aristarchus and Marius exhibit clear spectral differences from those at Moscoviense and Copernicus but also exhibit features that suggest contributions from other phases. If the various precautions discussed here are weighed carefully, the methods presented here can be used to make general predictions of absolute olivine composition (Fe/Mg content). Copyright ?? 2011 by the American Geophysical Union.

Diffuse near-infrared reflectance spectroscopy during heatstroke in a mouse model: pilot study.

PubMed

Abookasis, David; Zafrir, Elad; Nesher, Elimelech; Pinhasov, Albert; Sternklar, Shmuel; Mathews, Marlon S

2012-10-01

Heatstroke, a form of hyperthermia, is a life-threatening condition characterized by an elevated core body temperature that rises above 40°C (104°F) and central nervous system dysfunction that results in delirium, convulsions, or coma. Without emergency treatment, the victim lapses into a coma and death soon follows. The study presented was conducted with a diffuse reflectance spectroscopy (DRS) setup to assess the effects of brain dysfunction that occurred during heatstroke in mice model (n=6). It was hypothesized that DRS can be utilized in small animal studies to monitor change in internal brain tissue temperature during heatstroke injury since it induces a sequence of pathologic changes that change the tissue composition and structure. Heatstroke was induced by exposure of the mice body under general anesthesia, to a high ambient temperature. A type of DRS in which the brain tissue was illuminated through the intact scalp with a broadband light source and diffuse reflected spectra was employed, taking in the spectral region between 650 and 1000 nm and acquired at an angle of 90 deg at a position on the scalp ∼12  mm from the illumination site. The temperature at the onset of the experiment was ∼34°C (rectal temperature) with increasing intervals of 1°C until mouse death. The increase in temperature caused optical scattering signal changes consistent with a structural alteration of brain tissue, ultimately resulting in death. We have found that the peak absorbance intensity and its second derivative at specific wavelengths correlate well with temperature with an exponential dependence. Based on these findings, in order to estimate the influence of temperature on the internal brain tissue a reflectance-temperature index was established and was seen to correlate as well with measured temperature. Overall, results indicate variations in neural tissue properties during heatstroke and the feasibility to monitor and assess internal temperature variations using DRS. Although several approaches have described the rise in temperature and its impact on tissue, to the best of our knowledge no information is available describing the ability to monitor temperature during heatstroke with DRS. The motivation of this study was to successfully describe this ability.

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.

Transport of oxygen ions in Er doped La2Mo2O9 oxide ion conductors: Correlation with microscopic length scales

NASA Astrophysics Data System (ADS)

Paul, T.; Ghosh, A.

2018-01-01

We report oxygen ion transport in La2-xErxMo2O9 (0.05 ≤ x ≤ 0.25) oxide ion conductors. We have measured conductivity and dielectric spectra at different temperatures in a wide frequency range. The mean square displacement and spatial extent of non-random sub-diffusive regions are estimated from the conductivity spectra and dielectric spectra, respectively, using linear response theory. The composition dependence of the conductivity is observed to be similar to that of the spatial extent of non-random sub-diffusive regions. The behavior of the composition dependence of the mean square displacement of oxygen ions is opposite to that of the conductivity. The attempt frequency estimated from the analysis of the electric modulus agrees well with that obtained from the Raman spectra analysis. The full Rietveld refinement of X-ray diffraction data of the samples is performed to estimate the distance between different oxygen lattice sites. The results obtained from such analysis confirm the ion hopping within the spatial extent of non-random sub-diffusive regions.

Flower-like nanostructure MNb{sub 2}O{sub 6} (M = Mn, Zn) with high surface area: Hydrothermal synthesis and enhanced photocatalytic performance

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

Huang, Xue; Jing, Yan; Yang, Jia

Graphical abstract: - Highlights: • MNb{sub 2}O{sub 6} was prepared by a mild two-step hydrothermal method. • Their flower-like nanostructure morphology was studied by SEM and TEM. • High BET surface areas for MnNb{sub 2}O{sub 6} (∼50 m{sup 2}/g) and ZnNb{sub 2}O{sub 6} (∼100 m{sup 2}/g). • Band gap energies were estimated by UV–vis diffuse reflectance spectra. • Photocatalytic activities were evaluated under UV-light irradiation. - Abstract: Nano-scaled MNb{sub 2}O{sub 6} (M = Mn, Zn) was successfully synthesized via a two-step hydrothermal method. It is important to control the exact pH of the reaction solution in order to obtain puremore » products. The as-prepared samples both crystallize in the columbite structure. Interestingly, the products possess a flower-like morphology in a pseudo-six-fold symmetry, which is in fact arrayed by two-dimensional nanosheets. Their surface areas (51 m{sup 2}/g for MnNb{sub 2}O{sub 6} and 103 m{sup 2}/g for ZnNb{sub 2}O{sub 6}) are about 25–50 times of those prepared by solid state reaction. UV–vis diffuse reflectance spectra show the nano-scaled sample has a stronger absorption and a narrower band gap than its bulk form. The estimated band gap energies are 2.70 eV (MnNb{sub 2}O{sub 6}) and 3.77 eV (ZnNb{sub 2}O{sub 6}), respectively. The nano-scaled ZnNb{sub 2}O{sub 6} exhibits a double enhancement of photocatalytic activity in the decolorization of methylene blue than bulk ZnNb{sub 2}O{sub 6}.« less

Effects of Americium-241 and humic substances on Photobacterium phosphoreum: bioluminescence and diffuse reflectance FTIR spectroscopic studies.

PubMed

Kamnev, Alexander A; Tugarova, Anna V; Selivanova, Maria A; Tarantilis, Petros A; Polissiou, Moschos G; Kudryasheva, Nadezhda S

2013-01-01

The integral bioluminescence (BL) intensity of live Photobacterium phosphoreum cells (strain 1883 IBSO), sampled at the stationary growth stage (20 h), was monitored for further 300 h in the absence (control) and presence of (241)Am (an α-emitting radionuclide of a high specific activity) in the growth medium. The activity concentration of (241)Am was 2 kBq l(-1); [(241)Am]=6.5×10(-11) M. Parallel experiments were also performed with water-soluble humic substances (HS, 2.5 mg l(-1); containing over 70% potassium humate) added to the culture medium as a possible detoxifying agent. The BL spectra of all the bacterial samples were very similar (λ(max)=481±3 nm; FWHM=83±3 nm) showing that (241)Am (also with HS) influenced the bacterial BL system at stages prior to the formation of electronically excited states. The HS added per se virtually did not influence the integral BL intensity. In the presence of (241)Am, BL was initially activated but inhibited after 180 h, while the system (241)Am+HS showed an effective activation of BL up to 300 h which slowly decreased with time. Diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, applied to dry cell biomass sampled at the stationary growth phase, was used to control possible metabolic responses of the bacteria to the α-radioactivity stress (observed earlier for other bacteria under other stresses). The DRIFT spectra were all very similar showing a low content of intracellular poly-3-hydroxybutyrate (at the level of a few percent of dry biomass) and no or negligible spectroscopic changes in the presence of (241)Am and/or HS. This assumes the α-radioactivity effect to be transmitted by live cells mainly to the bacterial BL enzyme system, with negligible structural or compositional changes in cellular macrocomponents at the stationary growth phase. Copyright © 2012 Elsevier B.V. All rights reserved.

Effects of americium-241 and humic substances on Photobacterium phosphoreum: Bioluminescence and diffuse reflectance FTIR spectroscopic studies

NASA Astrophysics Data System (ADS)

Kamnev, Alexander A.; Tugarova, Anna V.; Selivanova, Maria A.; Tarantilis, Petros A.; Polissiou, Moschos G.; Kudryasheva, Nadezhda S.

The integral bioluminescence (BL) intensity of live Photobacterium phosphoreum cells (strain 1883 IBSO), sampled at the stationary growth stage (20 h), was monitored for further 300 h in the absence (control) and presence of 241Am (an α-emitting radionuclide of a high specific activity) in the growth medium. The activity concentration of 241Am was 2 kBq l-1; [241Am] = 6.5 × 10-11 M. Parallel experiments were also performed with water-soluble humic substances (HS, 2.5 mg l-1; containing over 70% potassium humate) added to the culture medium as a possible detoxifying agent. The BL spectra of all the bacterial samples were very similar (λmax = 481 ± 3 nm; FWHM = 83 ± 3 nm) showing that 241Am (also with HS) influenced the bacterial BL system at stages prior to the formation of electronically excited states. The HS added per se virtually did not influence the integral BL intensity. In the presence of 241Am, BL was initially activated but inhibited after 180 h, while the system 241Am + HS showed an effective activation of BL up to 300 h which slowly decreased with time. Diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, applied to dry cell biomass sampled at the stationary growth phase, was used to control possible metabolic responses of the bacteria to the α-radioactivity stress (observed earlier for other bacteria under other stresses). The DRIFT spectra were all very similar showing a low content of intracellular poly-3-hydroxybutyrate (at the level of a few percent of dry biomass) and no or negligible spectroscopic changes in the presence of 241Am and/or HS. This assumes the α-radioactivity effect to be transmitted by live cells mainly to the bacterial BL enzyme system, with negligible structural or compositional changes in cellular macrocomponents at the stationary growth phase.

Laboratory measurements of radiance and reflectance spectra of a dilute biosolid industrial waste product

NASA Technical Reports Server (NTRS)

Usry, J. W.; Witte, W. G.; Whitlock, C. H.; Gurganus, E. A.

1979-01-01

Experimental measurements were made of upwelled spectral signatures of various concentrations of industrial waste products mixed with water in a large water tank. Radiance and reflectance spectra for a biosolid waste product (sludge) mixed with conditioned tap water and natural river water are reported. Results of these experiments indicate that reflectance increases with increasing concentration of the sludge at practically all wavelengths for concentration of total suspended solids up to 117 ppm in conditioned tap water and 171 ppm in natural river water. Significant variations in the spectra were observed and may be useful in defining spectral characteristics for this waste product. No significant spectral differences were apparent in the reflectance spectra of the two experiments, especially for wavelengths greater than 540 nm. Reflectance values, however, were generally greater in natural river water for wavelengths greater than 540 nm. Reflectance may be considered to increase linearly with concentration of total suspended solids from 5 to 171 ppm at all wavelengths without introducing errors larger than 10 percent.

Effects of Space Weathering on Reflectance Spectra of Ureilites: First Studies

NASA Technical Reports Server (NTRS)

Goodrich, C. A.; Gillis-Davis, J.; Cloutis, E.; Applin, D.; Takir, D.; Hibbitts, C.; Christoffersen, R.; Fries, M.; Klima, R.; Decker, S.

2018-01-01

Ureilites are differentiated meteorites (ultramafic rocks interpreted to be mantle residues) that contain as much carbon as the most carbon-rich carbonaceous chondrites (CCs). Reflectance spectra of ureilites are similar to those of some CCs. Hence, ureilitic asteroids may accidentally be categorized as primitive because their spectra could resemble those of C-complex asteroids, which are thought to be CC-like. We began spectral studies of progressively laser-weathered ureilites with the goals of predicting UV-VIS-IR spectra of ureilitic asteroids, and identifying features that could distinguish differentiated from primitive dark asteroids. Space weathering has not previously been studied for ureilites, and, based on space weathering studies of CCs and other C-rich materials, it could significantly alter their reflectance spectra.

Measuring tissue oxygenation

NASA Technical Reports Server (NTRS)

Soyemi, Olusola O. (Inventor); Soller, Babs R. (Inventor); Yang, Ye (Inventor)

2009-01-01

Methods and systems for calculating tissue oxygenation, e.g., oxygen saturation, in a target tissue are disclosed. In some embodiments, the methods include: (a) directing incident radiation to a target tissue and determining reflectance spectra of the target tissue by measuring intensities of reflected radiation from the target tissue at a plurality of radiation wavelengths; (b) correcting the measured intensities of the reflectance spectra to reduce contributions thereto from skin and fat layers through which the incident radiation propagates; (c) determining oxygen saturation in the target tissue based on the corrected reflectance spectra; and (d) outputting the determined value of oxygen saturation.

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.

Mechanism of conductivity relaxation in liquid and polymeric electrolytes: Direct link between conductivity and diffusivity

DOE PAGES

Gainaru, Catalin P.; Technische Univ. Dortmund, Dortmund; Stacy, Eric W.; ...

2016-09-28

Combining broadband impedance spectroscopy, differential scanning calorimetry, and nuclear magnetic resonance we analyzed charge and mass transport in two polymerized ionic liquids and one of their monomeric precursors. In order to establish a general procedure for extracting single-particle diffusivity from their conductivity spectra, we critically assessed several approaches previously employed to describe the onset of diffusive charge dynamics and of the electrode polarization in ion conducting materials. Based on the analysis of the permittivity spectra, we demonstrate that the conductivity relaxation process provides information on ion diffusion and the magnitude of cross-correlation effects between ionic motions. A new approach ismore » introduced which is able to estimate ionic diffusivities from the characteristic times of conductivity relaxation and ion concentration without any adjustable parameters. Furthermore, this opens the venue for a deeper understanding of charge transport in concentrated and diluted electrolyte solutions.« less

The Effect of He3 Diffusion on the Pulsational Spectra of DBV Models

NASA Astrophysics Data System (ADS)

Montgomery, M. H.; Winget, D. E.

Isotopic separation is inevitable in white dwarf stars if our understanding of diffusion is correct. This can have many important, and largely unexplored, astrophysical consequences. Asteroseismology gives an opportunity to investigate this possibility. We first examine the relevant timescales for diffusion in these objects, and compare them to the evolutionary timescales in the context of the DBV white dwarfs. We then explore the consequences which He3 separation has on the pulsational spectra of DBV models. Since GD 358 is the best-studied member of this class of variables, we pay particular attention to the way this could affect previous fits.

Overview of ACE-Asia Spring 2001 Investigations On Aerosol-Radiation Interactions

NASA Technical Reports Server (NTRS)

Russell, P. B.; Flatau, P. J.; Valero, F. P. J.; Nakajima, T.; Holben, B.; Pilewskie, P.; Bergin, M.; Schmid, B.; Bergstrom, R. W.; Vogelmann, A.;

Spectral characterisation of aperiodic normal-incidence Sb/B4C multilayer mirrors for the λ < 124 Å range

NASA Astrophysics Data System (ADS)

Vishnyakov, E. A.; Kopylets, I. A.; Kondratenko, V. V.; Kolesnikov, A. O.; Pirozhkov, A. S.; Ragozin, E. N.; Shatokhin, A. N.

2018-03-01

Three broadband aperiodic Sb/B4C multilayer mirrors were synthesised for the purposes of soft X-ray optics and spectroscopy in the wavelength range beyond the L-edge of Si (λ < 124 Å), and their reflection spectra were measured. The multilayer structures were optimised for maximum uniform reflectivity in the ranges 100–120 Å, 95–105 Å and 90–100 Å. The reflection spectra were recorded using a laboratory laser-plasma radiation source and an electronic detector with a 2D spatial resolution (a CCD matrix with 13 × 13 μm sized pixels). The experimental spectra are compared with theoretical calculations. The effect of lower antimony and B4C layer densities on the reflection spectra is discussed.

A quantitative model for transforming reflectance spectra into the Munsell color space using cone sensitivity functions and opponent process weights.

PubMed

D'Andrade, Roy G; Romney, A Kimball

2003-05-13

This article presents a computational model of the process through which the human visual system transforms reflectance spectra into perceptions of color. Using physical reflectance spectra data and standard human cone sensitivity functions we describe the transformations necessary for predicting the location of colors in the Munsell color space. These transformations include quantitative estimates of the opponent process weights needed to transform cone activations into Munsell color space coordinates. Using these opponent process weights, the Munsell position of specific colors can be predicted from their physical spectra with a mean correlation of 0.989.

Spectra Transfer Between a Fourier Transform Near-Infrared Laboratory and a Miniaturized Handheld Near-Infrared Spectrometer.

PubMed

Hoffmann, Uwe; Pfeifer, Frank; Hsuing, Chang; Siesler, Heinz W

2016-05-01

The aim of this contribution is to demonstrate the transfer of spectra that have been measured on two different laboratory Fourier transform near-infrared (FT-NIR) spectrometers to the format of a handheld instrument by measuring only a few samples with both spectrometer types. Thus, despite the extreme differences in spectral range and resolution, spectral data sets that have been collected and quantitative as well as qualitative calibrations that have been developed thereof, respectively, over a long period on a laboratory instrument can be conveniently transferred to the handheld system. Thus, the necessity to prepare completely new calibration samples and the effort required to develop calibration models when changing hardware platforms is minimized. The enabling procedure is based on piecewise direct standardization (PDS) and will be described for the data sets of a quantitative and a qualitative application case study. For this purpose the spectra measured on the FT-NIR laboratory spectrometers were used as "master" data and transferred to the "target" format of the handheld instrument. The quantitative test study refers to transmission spectra of three-component liquid solvent mixtures whereas the qualitative application example encompasses diffuse reflection spectra of six different current polymers. To prove the performance of the transfer procedure for quantitative applications, partial least squares (PLS-1) calibrations were developed for the individual components of the solvent mixtures with spectra transferred from the master to the target instrument and the cross-validation parameters were compared with the corresponding parameters obtained for spectra measured on the master and target instruments, respectively. To test the retention of the discrimination ability of the transferred polymer spectra sets principal component analyses (PCAs) were applied exemplarily for three of the six investigated polymers and their identification was demonstrated by Mahalanobis distance plots for all polymers. © The Author(s) 2016.

Simple algorithms for remote determination of mineral abundances and particle sizes from reflectance spectra

NASA Technical Reports Server (NTRS)

Johnson, Paul E.; Smith, Milton O.; Adams, John B.

1992-01-01

Algorithms were developed, based on Hapke's (1981) equations, for remote determinations of mineral abundances and particle sizes from reflectance spectra. In this method, spectra are modeled as a function of end-member abundances and illumination/viewing geometry. The method was tested on a laboratory data set. It is emphasized that, although there exist more sophisticated models, the present algorithms are particularly suited for remotely sensed data, where little opportunity exists to independently measure reflectance versus article size and phase function.

Characterization and activity of Pd-modified TiO2 catalysts for photocatalytic oxidation of NO in gas phase.

PubMed

Wu, Zhongbiao; Sheng, Zhongyi; Liu, Yue; Wang, Haiqiang; Tang, Nian; Wang, Jie

2009-05-30

Pd-modified TiO(2) prepared by thermal impregnation method was used in this study for photocatalytic oxidation of NO in gas phase. The physico-chemical properties of Pd/TiO(2) catalysts were characterized by X-ray diffraction analysis (XRD), Brunauer-Emmett-Teller measurements (BET), X-ray photoelectron spectrum analysis (XPS), transmission electron microscopy (TEM), high resolution-transmission electron microscopy (HR-TEM), UV-vis diffuse reflectance spectra (UV-vis DRS) and photoluminescence spectra (PL). It was found that Pd dopant existed as PdO particles in as-prepared photocatalysts. The results of PL spectra indicated that the photogenerated electrons and holes were efficiently separated after Pd doping. During in situ XPS study, it was found that the content of hydroxyl groups on the surface of Pd/TiO(2) increased when the catalyst was irradiated by UV light, which could result in the improvement of photocatalytic activity. The activity test showed that the optimum Pd dopant content was 0.05 wt.%. And the maximum conversion of NO was about 72% higher than that of P25 when the initial concentration of NO was 200 ppm, which showed that Pd/TiO(2) photocatalysts could be potentially applied to oxidize higher concentration of NO.

Preparation of an anionic azo pigment-pillared layered double hydroxide and the thermo- and photostability of the resulting intercalated material

NASA Astrophysics Data System (ADS)

Guo, Shengchang; Li, Dianqing; Zhang, Weifeng; Pu, Min; Evans, David G.; Duan, Xue

2004-12-01

A large anionic pigment has been intercalated into a layered double hydroxide (LDH) host by ion-exchange of an Mg/Al LDH-nitrate precursor with a solution of C.I. Pigment Red 48:2 (the calcium salt of 4-((5-chloro-4-methyl-2-sulfophenyl)azo)-3-hydroxy-2-naphthalene-carboxylic acid), in ethane-1,2-diol. After intercalation of the pigment, the interlayer distance in the LDH increases from 0.86 to 1.72 nm. Infrared spectra and TG-DTA curves reveal the presence of a complex system of supramolecular host-guest interactions. The UV-visible diffuse reflectance spectra of C.I. Pigment Red 48:2 show marked changes after heating at 200 °C and above, whereas there are no significant changes in the spectra of the intercalated pigment after heating at temperatures up to 300 °C, showing that the thermostability is markedly enhanced by intercalation in the LDH host. The pigment-intercalated LDHs exhibits much higher photostability to UV light than the pristine pigment, in the case of both the pure solids and their composites with polypropylene, as shown by measurement of CIE 1976 L*a*b* color difference ( ΔE) values.

Comparative Photoluminescence Properties and Judd-Ofelt Analysis of Eu3+ Ion-Activated Metal Molybdate Phosphors A2MoO6:Eu3+ (A = La, Y, Gd and Bi)

NASA Astrophysics Data System (ADS)

Han, Bing; Liu, Bingkun; Zhang, Jie; Li, Pengju; Shi, Hengzhen

2017-07-01

A class of red-emitting Eu3+ ion-activated metal molybdate A2MoO6:Eu3+ (A = La, Y, Gd and Bi) phosphors were synthesized by a conventional high-temperature solid-state reaction method. The x-ray diffraction patterns, scanning electron microscope images, Fourier transform infrared spectra, ultraviolet-visible diffuse reflection spectra as well as photoluminescence properties were measured to characterize the as-prepared samples. The photoluminescence properties including excitation/emission spectra, decay curves, Commission Internationale de L'Eclairage chromaticity coordinates and quantum efficiency were comparatively investigated in detail. The Judd-Ofelt theory was also applied to understand the radiative properties of f-f transitions of Eu3+ ions in this system for the first time. The as-prepared phosphors can be effectively excited with near-ultraviolet and/or blue light, and exhibit red emission belonging to the prevailing 5D0 → 7F2 transitions of Eu3+ with short decay time (millisecond level). The results demonstrated that A2MoO6:Eu3+ (A = La, Y, Gd and Bi) phosphors could have potential application as red-emitting phosphors in white light-emitting diodes based on near-ultraviolet and/or blue light-emitting diode chips.

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.

Non-destructive prediction of 'Hass' avocado dry matter via FT-NIR spectroscopy.

PubMed

Wedding, Brett B; White, Ronald D; Grauf, Steve; Wright, Carole; Tilse, Bonnie; Hofman, Peter; Gadek, Paul A

2011-01-30

The inability to consistently guarantee internal quality of horticulture produce is of major importance to the primary producer, marketers and ultimately the consumer. Currently, commercial avocado maturity estimation is based on the destructive assessment of percentage dry matter (%DM), and sometimes percentage oil, both of which are highly correlated with maturity. In this study the utility of Fourier transform (FT) near-infrared spectroscopy (NIRS) was investigated for the first time as a non-invasive technique for estimating %DM of whole intact 'Hass' avocado fruit. Partial least squares regression models were developed from the diffuse reflectance spectra to predict %DM, taking into account effects of intra-seasonal variation and orchard conditions. It was found that combining three harvests (early, mid and late) from a single farm in the major production district of central Queensland yielded a predictive model for %DM with a coefficient of determination for the validation set of 0.76 and a root mean square error of prediction of 1.53% for DM in the range 19.4-34.2%. The results of the study indicate the potential of FT-NIRS in diffuse reflectance mode to non-invasively predict %DM of whole 'Hass' avocado fruit. When the FT-NIRS system was assessed on whole avocados, the results compared favourably against data from other NIRS systems identified in the literature that have been used in research applications on avocados. 2010 Society of Chemical Industry.

The green synthesis of Ag/ZnO in montmorillonite with enhanced photocatalytic activity

NASA Astrophysics Data System (ADS)

Sohrabnezhad, Sh.; Seifi, A.

2016-11-01

The Ag/ZnO-MMT nanocomposite was prepared using urtica dioica leaf extract. To improve the photocatalytic properties of ZnO-MMT nanocomposite, silver metal nanoparticles was deposited over nanocomposite. Zn(CH3COO)2, AgNO3 and Urtica dioica leaf extract were used as a zinc, silver precursor and reducing agent, respectively. The nanocomposite was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and ultraviolet-visible diffuse reflectance spectroscopy (DRS). The powder X-ray diffraction showed that Ag/ZnO nanoparticles located on the surface MMT layers. The diffuse reflectance spectra of nanocomposite indicated a strong surface plasmon resonance (SPR) absorption band in the visible region, resulting from metallic Ag nanoparticles. TEM image demonstrated the presence of silver nanoparticles with an average size of 2-4 nm over both MMT and flower-shape ZnO. The photocatalytic activity of nanocomposite was studied for destructive reaction methylene blue dye under visible light. In addition, the effects of different parameters such as amount of nanocomposite, concentration of the dye and pH of the solution were studied. The results showed that modiffication of ZnO-MMT nanocomposite with silver nanoparticles increased the percentage of discoloration methylene blue (MB) from 38.95 to 91.95. MMT matrix showed an important role in the reduction of recombination of electron-hole in nanocomposite.

Sensitive determination of trace mercury by UV-visible diffuse reflectance spectroscopy after complexation and membrane filtration-enrichment.

PubMed

Yin, Changhai; Iqbal, Jibran; Hu, Huilian; Liu, Bingxiang; Zhang, Lei; Zhu, Bilin; Du, Yiping

2012-09-30

A simple, sensitive and selective solid phase reflectometry method is proposed for the determination of trace mercury in aqueous samples. The complexation reagent dithizone was firstly injected into the properly buffered solution with vigorous stirring, which started a simultaneous formation of nanoparticles suspension of dithizone and its complexation reaction with the mercury(II) ions to make Hg-dithizone nanoparticles. After a definite time, the mixture was filtered with membrane, and then quantified directly on the surface of the membrane by using integrating sphere accessory of the UV-visible spectrophotometer. The quantitative analysis was carried out at a wavelength of 485 nm since it yielded the largest difference in diffuse reflectance spectra before and after reaction with mercury(II).A good linear correlation in the range of 0.2-4.0 μg/L with a squared correlation coefficient (R(2)) of 0.9944 and a detection limit of 0.12 μg/L were obtained. The accuracy of the method was evaluated by the analysis of spiked mercury(II) concentrations determined using this method along with those determined by the atomic fluorescence mercury vapourmeter and the results obtained were in good agreement. The proposed method was applied to the determination of mercury in tap water and river water samples with the recovery in an acceptable range (95.7-105.3%). Copyright © 2012 Elsevier B.V. All rights reserved.

Multifunctional silver nanoparticle-doped silica for solid-phase extraction and surface-enhanced Raman scattering detection

NASA Astrophysics Data System (ADS)

Markina, Natalia E.; Markin, Alexey V.; Zakharevich, Andrey M.; Gorin, Dmitry A.; Rusanova, Tatiana Yu.; Goryacheva, Irina Yu.

2016-12-01

Multifunctional silica gel with embedded silver nanoparticles (SiO2-AgNP) is proposed for application as sorbent for solid-phase extraction (SPE) and simultaneously as substrate for surface-enhanced Raman spectroscopy (SERS) due to their high sorption properties and ability to enhance Raman signal (SERS-active sorbents). SiO2-AgNP was synthesized via alkaline hydrolysis of tetraethyl orthosilicate with simultaneous reduction of silver ions to silver nanoparticles (AgNP) within the SiO2 bulk. Synthesis of AgNP directly to the SiO2 matrix enables to exclude any additional stabilizers for the nanoparticles that educes signal-to-noise ratio during SERS measurement. Apart from Raman spectroscopy, obtained sorbents were also characterized by scanning electron microscopy and UV-visible diffuse reflectance spectroscopy. The influence of AgNO3 concentration used during the SiO2-AgNP synthesis on its gelling time, color, diffuse reflectance spectra, and enhancement of Raman signal was investigated. A Raman enhancement factor of SiO2-AgNP with optimal composition was around 105. Finally, the sorbents were applied for SPE and subsequent SERS detection of model compounds (rhodamine 6G and folic acid). It was found that SPE enables to decrease detectable concentrations by two orders. Therefore, SPE combined with SERS has high potential for further analytical investigations.

Spectroscopic method for determination of the absorption coefficient in brain tissue

NASA Astrophysics Data System (ADS)

Johansson, Johannes D.

2010-09-01

I use Monte Carlo simulations and phantom measurements to characterize a probe with adjacent optical fibres for diffuse reflectance spectroscopy during stereotactic surgery in the brain. Simulations and measurements have been fitted to a modified Beer-Lambert model for light transport in order to be able to quantify chromophore content based on clinically measured spectra in brain tissue. It was found that it is important to take the impact of the light absorption into account when calculating the apparent optical path length, lp, for the photons in order to get good estimates of the absorption coefficient, μa. The optical path length was found to be well fitted to the equation lp=a+b ln(Is)+c ln(μa)+d ln(Is)ln(μa), where Is is the reflected light intensity for scattering alone (i.e., zero absorption). Although coefficients a-d calculated in this study are specific to the probe used here, the general form of the equation should be applicable to similar probes.

High-speed mid-infrared hyperspectral imaging using quantum cascade lasers

NASA Astrophysics Data System (ADS)

Kelley, David B.; Goyal, Anish K.; Zhu, Ninghui; Wood, Derek A.; Myers, Travis R.; Kotidis, Petros; Murphy, Cara; Georgan, Chelsea; Raz, Gil; Maulini, Richard; Müller, Antoine

2017-05-01

We report on a standoff chemical detection system using widely tunable external-cavity quantum cascade lasers (ECQCLs) to illuminate target surfaces in the mid infrared (λ = 7.4 - 10.5 μm). Hyperspectral images (hypercubes) are acquired by synchronously operating the EC-QCLs with a LN2-cooled HgCdTe camera. The use of rapidly tunable lasers and a high-frame-rate camera enables the capture of hypercubes with 128 x 128 pixels and >100 wavelengths in <0.1 s. Furthermore, raster scanning of the laser illumination allowed imaging of a 100-cm2 area at 5-m standoff. Raw hypercubes are post-processed to generate a hypercube that represents the surface reflectance relative to that of a diffuse reflectance standard. Results will be shown for liquids (e.g., silicone oil) and solid particles (e.g., caffeine, acetaminophen) on a variety of surfaces (e.g., aluminum, plastic, glass). Signature spectra are obtained for particulate loadings of RDX on glass of <1 μg/cm2.

Chemical fingerprinting of Arabidopsis using Fourier transform infrared (FT-IR) spectroscopic approaches.

PubMed

Gorzsás, András; Sundberg, Björn

2014-01-01

Fourier transform infrared (FT-IR) spectroscopy is a fast, sensitive, inexpensive, and nondestructive technique for chemical profiling of plant materials. In this chapter we discuss the instrumental setup, the basic principles of analysis, and the possibilities for and limitations of obtaining qualitative and semiquantitative information by FT-IR spectroscopy. We provide detailed protocols for four fully customizable techniques: (1) Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS): a sensitive and high-throughput technique for powders; (2) attenuated total reflectance (ATR) spectroscopy: a technique that requires no sample preparation and can be used for solid samples as well as for cell cultures; (3) microspectroscopy using a single element (SE) detector: a technique used for analyzing sections at low spatial resolution; and (4) microspectroscopy using a focal plane array (FPA) detector: a technique for rapid chemical profiling of plant sections at cellular resolution. Sample preparation, measurement, and data analysis steps are listed for each of the techniques to help the user collect the best quality spectra and prepare them for subsequent multivariate analysis.

A broadband LED source in visible to short-wave-infrared wavelengths for spectral tumor diagnostics

NASA Astrophysics Data System (ADS)

Hayashi, Daiyu; van Dongen, Anne Marie; Boerekamp, Jack; Spoor, Sandra; Lucassen, Gerald; Schleipen, Jean

2017-06-01

Various tumor types exhibit the spectral fingerprints in the absorption and reflection spectra in visible and especially in near- to short-wave-infrared wavelength ranges. For the purpose of spectral tumor diagnostics by means of diffuse reflectance spectroscopy, we developed a broadband light emitting diode (LED) source consisting of a blue LED for optical excitation, Lu3Al5O12:Ce3+,Cr3+ luminescent garnet for visible to near infrared emissions, and Bismuth doped GeO2 luminescent glass for near-infrared to short-wave infrared emissions. It emits broad-band light emissions continuously in 470-1600 nm with a spectral gap at 900-1000 nm. In comparison to the currently available broadband light sources like halogen lamps, high-pressure discharge lamps and super continuum lasers, the light sources of this paper has significant advantages for spectral tissue diagnostics in high-spectral stability, improved light coupling to optical fibers, potential in low light source cost and enabling battery-drive.

Multivariate Curve Resolution Applied to Infrared Reflection Measurements of Soil Contaminated with an Organophosphorus Analyte

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

Gallagher, Neal B.; Blake, Thomas A.; Gassman, Paul L.

2006-07-01

Multivariate curve resolution (MCR) is a powerful technique for extracting chemical information from measured spectra on complex mixtures. The difficulty with applying MCR to soil reflectance measurements is that light scattering artifacts can contribute much more variance to the measurements than the analyte(s) of interest. Two methods were integrated into a MCR decomposition to account for light scattering effects. Firstly, an extended mixture model using pure analyte spectra augmented with scattering ‘spectra’ was used for the measured spectra. And secondly, second derivative preprocessed spectra, which have higher selectivity than the unprocessed spectra, were included in a second block as amore » part of the decomposition. The conventional alternating least squares (ALS) algorithm was modified to simultaneously decompose the measured and second derivative spectra in a two-block decomposition. Equality constraints were also included to incorporate information about sampling conditions. The result was an MCR decomposition that provided interpretable spectra from soil reflectance measurements.« less

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

Data on energy-band-gap characteristics of composite nanoparticles obtained by modification of the amorphous potassium polytitanate in aqueous solutions of transition metal salts

PubMed Central

Zimnyakov, D.A.; Sevrugin, A.V.; Yuvchenko, S.A.; Fedorov, F.S.; Tretyachenko, E.V.; Vikulova, M.A.; Kovaleva, D.S.; Krugova, E.Y.; Gorokhovsky, A.V.

2016-01-01

Here we present the data on the energy-band-gap characteristics of composite nanoparticles produced by modification of the amorphous potassium polytitanate in aqueous solutions of different transition metal salts. Band gap characteristics are investigated using diffuse reflection spectra of the obtained powders. Calculated logarithmic derivative quantity of the Kubelka–Munk function reveals a presence of local maxima in the regions 0.5–1.5 eV and 1.6–3.0 eV which correspond to band gap values of the investigated materials. The values might be related to the constituents of the composite nanoparticles and intermediate products of their chemical interaction. PMID:27158654

Effect of sulfate ions on the crystallization and photocatalytic activity of TiO2/diatomite composite photocatalyst

NASA Astrophysics Data System (ADS)

Zhang, Jinjun; Wang, Xiaoyan; Wang, Jimei; Wang, Jing; Ji, Zhijiang

2016-01-01

TiO2 nanoparticles were immobilized on diatomite by hydrolysis-deposition method using titanium tetrachloride as precursor. The effect of sulfate ions on the crystallization and photocatalytic activity of TiO2/diatomite composite photocatalyst was characterized by TG-DSC, XRD, BET surface area, SEM, FT-IR spectroscopy, XPS and UV-vis diffuse reflectance spectra. The results indicate that addition of a small amount of sulfate ions promotes the formation of anatase phase and inhibits the transformation from anatase to rutile. On the other hand, sulfate ions immobilized on the surface of TiO2/diatomite have strong affinity for electrons, capturing the photo-generated electrons, which hinders the recombination of electrons and holes.

Infrared spectroscopy of Mercury analogue materials under simulated Mercury surface temperature conditions

NASA Astrophysics Data System (ADS)

Reitze, Maximilian; Morlok, Andreas; Hiesinger, Harald; Weber, Iris; Stojic, Aleksandra

2017-04-01

Infrared spectroscopy is a powerful technique for the exploration of planetary surfaces with remote sensing observations [e.g., 1]. The MERTIS (Mercury Radiometer and Thermal Infrared Spectrometer) instrument onboard the BepiColombo spacecraft is designed to explore the surface mineralogy of Mercury in the wavelength region from 7 μ m to 14 μ m [2]. Mercury's surface reaches dayside temperatures of about 700 K [3]. It is well known that bondings between atoms change with temperature, resulting in infrared spectra changes with temperature [4]. In particular, rock-forming minerals like silicates show distinct absorption bands in the infrared due to molecular vibrations, for example, of Si-O bondings [4]. To accurately understand and correctly interpret returned MERTIS data, it is necessary to collect laboratory data of analogue materials under condition similar to Mercury [5]. It is known from previous investigations [5] that the Reststrahlenbands of olivine shift with temperature. In this work we report on temperature effects on Mercury analogue materials in ambient air. At the IRIS (Infrared & Raman for Interplanetary Spectroscopy) laboratory in Münster we used a Bruker VERTEX 70v IR spectrometer together with a Harrick heating stage in a Praying Mantis Diffuse Reflectance Accessory to measure mid-infrared reflectance of mineral powder samples with different grain sizes at increasing temperatures. We report on our spectral results for a natural olivine with Fo91 with a grain size range between 63 μ m and 125 μ m as well as a natural labradorite with a grain size range between 90 μ m and 125 μ m. Spectra were collected at 26, 75, 150, 200, 250, 300, and 350 degrees Celsius with a liquid nitrogen cooled MCT detector under normal ambient pressure. To ensure complete thermal equilibrium of our measured samples, we heated them to higher temperatures and subsequently cooled them to the temperatures at which the spectra were taken. For background calibration, we used a commercial diffuse reflectance gold standard (INFRAGOLD). Our results confirm the temperature-dependent shift of the strongest silicate feature in olivine spectra observed by [5]. For the shift of the peak position of this feature we calculated a shift function depending on the temperature in the form of Rmax[μ m]=0.00027μ m/K\\cdot x[K]+10.454μ m (R^2=0.92). Differences in the intensity of the spectra between [5] and our work are most likely due to smaller grain sizes of our samples. We are also planning on presenting results obtained from evacuated samples (down to 10-6 mbar), which are close to pressures existing on Mercury. References} [1] A. Maturilli, J. Helbert, A. Witzke, and L. Moroz, Planet. Space Sci., 54:1057-1064, 2006. [2] H. Hiesinger, J. Helbert, and MERTIS Co-I Team, Planet. Space Sci., 58:144-165, 2010. [3] M. A. Slade, B. J. Butler, and D. O. Muhleman, Science, 258:635-640, 1992. [4] C. M. Pieters and P. A. J. Englert, editors. Topics in Remote Sensing 4. Remote Geo-chemical Analysis: Elemental and Mineralogical Composition. Cambridge University Press, 1993. [5] J. Helbert, F. Nestola, S. Ferrari, A. Maturilli, M. Massironi, G. J. Redhammer, M. T. Capria, F. Capaccioni, and M. Bruno, EPSL, 371-372:252-257, 2013.

Modeling the influence of the BRDF characteristics of vegetation on the retrieval of solar-induced chlorophyll fluorescence under different illumination conditions

NASA Astrophysics Data System (ADS)

Liu, Xinjie; Liu, Liangyun

2017-04-01

The Fraunhofer Line Discrimination (FLD) principle is the main approach used for the retrieval of solar-induced chlorophyll fluorescence (SIF). The basic assumption of the FLD principle is that the apparent reflectance spectra without SIF in-filling are smooth in the region of the absorption bands. However, in fact, this assumption is not valid due to the so-called "direct radiation in-filling" effect caused by the non-linear contribution of direct and diffuse radiation at the oxygen absorption bands, which are widely used for ground-based SIF retrieval. In this study, we first analyzed the physical mechanism of the direct radiation in-filling effect on the oxygen absorption bands and found that the bias in the SIF retrieval caused by the direct radiation in-filling effect at the O2-A band was less than 20% based on the use of a simulated dataset. Secondly, we established a simple correction model of the direct radiation in-filling effect. We found that the direct radiation in-filling effect at the O2-A band was directly proportional to the difference between the reflectance of the direct and diffuse radiation, and that the coefficient of proportionality was well correlated with the diffuse-to-global radiation ratio in the form of a quadratic function. The coefficient of determination (R-squared) for this correlation was 0.97. Finally, the model was validated using both simulated and field datasets. The validation results show that the bias in the SIF retrieval caused by the direct radiation in-filling effect can be efficiently corrected using the model proposed in this paper. This study thus provides a possible approach to estimating and correcting for the direct radiation-infilling effect using prior knowledge of the BRDF characteristics of direct and diffuse radiation for specific targets.

Experimental Effects on IR Reflectance Spectra: Particle Size and Morphology

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

Beiswenger, Toya N.; Myers, Tanya L.; Brauer, Carolyn S.

For geologic and extraterrestrial samples it is known that both particle size and morphology can have strong effects on the species’ infrared reflectance spectra. Due to such effects, the reflectance spectra cannot be predicted from the absorption coefficients alone. This is because reflectance is both a surface as well as a bulk phenomenon, incorporating both dispersion as well as absorption effects. The same spectral features can even be observed as either a maximum or minimum. The complex effects depend on particle size and preparation, as well as the relative amplitudes of the optical constants n and k, i.e. the realmore » and imaginary components of the complex refractive index. While somewhat oversimplified, upward-going amplitude in the reflectance spectrum usually result from surface scattering, i.e. rays that have been reflected from the surface without 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. While the effects are well known, we report seminal measurements of reflectance along with quantified particle size of the samples, the sizing obtained from optical microscopy measurements. The size measurements are correlated with 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 understand the effects on the spectral features as a function of the mean grain size of the sample. We report results for both sodium sulfate Na2SO4 as well as ammonium sulfate (NH4)2SO4; the optical constants have been measured for (NH4)2SO4. To go a step further from the field to the laboratory we explore our understanding of particle size effects on reflectance spectra in the field using standoff detection. This has helped identify weaknesses and strengths in detection using standoff distances of up 160 meters away from the Target. The studies have shown that particle size has an enormous influence on the measured reflectance spectra of such materials; successful identification requires sufficient, representative reflectance data to include the particle sizes of interest.« less

Assessing pearl quality using reflectance UV-Vis spectroscopy: does the same donor produce consistent pearl quality?

PubMed

Mamangkey, Noldy Gustaf F; Agatonovic, Snezana; Southgate, Paul C

2010-09-20

Two groups of commercial quality ("acceptable") pearls produced using two donors, and a group of "acceptable" pearls from other donors were analyzed using reflectance UV-Vis spectrophotometry. Three pearls with different colors produced by the same donor showed different absorption spectra. Cream and gold colored pearls showed a wide absorption from 320 to about 460 nm, while there was just slight reflectance around 400 nm by the white pearl with a pink overtone. Cream and gold pearls reached a reflectance peak at 560 to 590 nm, while the white pearl with pink overtone showed slightly wider absorption in this region. Both cream and gold pearls showed an absorption peak after the reflectance peak, at about 700 nm for the cream pearl and 750 nm for the gold pearl. Two other pearls produced by the same donor (white with cream overtone and cream with various overtones) showed similar spectra, which differed in their intensity. One of these pearls had very high lustre and its spectrum showed a much higher percentage reflectance than the second pearl with inferior lustre. This result may indicate that reflectance is a useful quantitative indicator of pearl lustre. The spectra of two white pearls resulting from different donors with the same color nacre (silver) showed a reflectance at 260 nm, followed by absorption at 280 nm and another reflectance peak at 340 nm. After this peak the spectra for these pearls remained flat until a slight absorption peak around 700 nm. Throughout the visible region, all white pearls used in this study showed similar reflectance spectra although there were differences in reflectance intensity. Unlike the spectral results from white pearls, the results from yellow and gold pearls varied according to color saturation of the pearl. The results of this study show that similarities between absorption and reflectance spectra of cultured pearls resulting from the same saibo donor are negligible and could not be detected with UV-Vis spectrophotometry. Nevertheless, this technique could have a role to play in developing less subjective methods of assessing pearl quality and in further studies of the relationships between pearl quality and that of the donor and recipient oysters.

Use of field reflectance data for crop mapping using airborne hyperspectral image

NASA Astrophysics Data System (ADS)

Nidamanuri, Rama Rao; Zbell, Bernd

2011-09-01

Recent developments in hyperspectral remote sensing technologies enable acquisition of image with high spectral resolution, which is typical to the laboratory or in situ reflectance measurements. There has been an increasing interest in the utilization of in situ reference reflectance spectra for rapid and repeated mapping of various surface features. Here we examined the prospect of classifying airborne hyperspectral image using field reflectance spectra as the training data for crop mapping. Canopy level field reflectance measurements of some important agricultural crops, i.e. alfalfa, winter barley, winter rape, winter rye, and winter wheat collected during four consecutive growing seasons are used for the classification of a HyMAP image acquired for a separate location by (1) mixture tuned matched filtering (MTMF), (2) spectral feature fitting (SFF), and (3) spectral angle mapper (SAM) methods. In order to answer a general research question "what is the prospect of using independent reference reflectance spectra for image classification", while focussing on the crop classification, the results indicate distinct aspects. On the one hand, field reflectance spectra of winter rape and alfalfa demonstrate excellent crop discrimination and spectral matching with the image across the growing seasons. On the other hand, significant spectral confusion detected among the winter barley, winter rye, and winter wheat rule out the possibility of existence of a meaningful spectral matching between field reflectance spectra and image. While supporting the current notion of "non-existence of characteristic reflectance spectral signatures for vegetation", results indicate that there exist some crops whose spectral signatures are similar to characteristic spectral signatures with possibility of using them in image classification.

Nuclear resonance reflectivity from a [57Fe/Cr]30 multilayer with the Synchrotron Mössbauer Source.

PubMed

Andreeva, Marina A; Baulin, Roman A; Chumakov, Aleksandr I; Rüffer, Rudolf; Smirnov, Gennadii V; Babanov, Yurii A; Devyaterikov, Denis I; Milyaev, Mikhail A; Ponomarev, Dmitrii A; Romashev, Lazar N; Ustinov, Vladimir V

2018-03-01

Mössbauer reflectivity spectra and nuclear resonance reflectivity (NRR) curves have been measured using the Synchrotron Mössbauer Source (SMS) for a [ 57 Fe/Cr] 30 periodic multilayer, characterized by the antiferromagnetic interlayer coupling between adjacent 57 Fe layers. Specific features of the Mössbauer reflectivity spectra measured with π-polarized radiation of the SMS near the critical angle and at the `magnetic' maximum on the NRR curve are analyzed. The variation of the ratio of lines in the Mössbauer reflectivity spectra and the change of the intensity of the `magnetic' maximum under an applied external field has been used to reveal the transformation of the magnetic alignment in the investigated multilayer.

Optical spectroscopic studies of animal skin used in modeling of human cutaneous tissue

NASA Astrophysics Data System (ADS)

Drakaki, E.; Makropoulou, M.; Serafetinides, A. A.; Borisova, E.; Avramov, L.; Sianoudis, J. A.

2007-03-01

Optical spectroscopy and in particular laser-induced autofluorescence spectroscopy (LIAFS) and diffuse reflectance spectroscopy (DRS), provide excellent possibilities for real-time, noninvasive diagnosis of different skin tissue pathologies. However, the introduction of optical spectroscopy in routine medical practice demands a statistically important data collection, independent from the laser sources and detectors used. The scientists collect databases either from patients, in vivo, or they study different animal models to obtain objective information for the optical properties of various types of normal and diseased tissue. In the present work, the optical properties (fluorescence and reflectance) of two animal skin models are investigated. The aim of using animal models in optical spectroscopy investigations is to examine the statistics of the light induced effects firstly on animals, before any extrapolation effort to humans. A nitrogen laser (λ=337.1 nm) was used as an excitation source for the autofluorescence measurements, while a tungsten-halogen lamp was used for the reflectance measurements. Samples of chicken and pig skin were measured in vitro and were compared with results obtained from measurements of normal human skin in vivo. The specific features of the measured reflectance and fluorescence spectra are discussed, while the limits of data extrapolation for each skin type are also depicted.

Spectral characteristics of the bentonite loaded with benzyldimethyloctadecylammonium chloride, hexadecyltrimethylammonium bromide and dimethyldioctadecylammonium bromide

NASA Astrophysics Data System (ADS)

Majdan, Marek; Maryuk, Oksana; Gładysz-Płaska, Agnieszka; Pikus, Stanisław; Kwiatkowski, Ryszard

2008-02-01

The spectral characterization, including the FTIR, DRIFT (diffusive reflectance), SWAXS (small and wide angle X-ray scattering) spectra comparison of the sodium bentonite modified by BDMODA-Cl (benzyldimethyloctadecylammonium chloride), HDTMA-Br (hexadecyltrimethylammonium bromide), DDA-Br (dimethyldioctadecylammonium bromide) is presented in the paper. The FTIR spectra show the shift of C-H stretching vibrations: νsym(CH2), νasym(CH2) of surfactants methylene chains toward lower frequencies (from 2855 to 2851 cm -1 for νsym(CH2) and from 2927 to 2918 cm -1 for νansym(CH2) with the surfactant concentration in bentonite phase. The bending vibrations δH-O-H in water molecules change their positions in the direction of higher frequencies (from 1634 to 1647 cm -1) with the surfactant concentration for bentonite-BDMODA and bentonite-DDA contrary to bentonite-HDTMA, where the constant position δH-O-H is explained as the consequence of the lower concentration of the hydrogen bonded water in bentonite-HDTMA phase when compared with the remaining forms of bentonite. The DRIFT spectra reveal dramatic shift of the νSi-O stretching vibration toward higher frequencies upon intercalation of the sodium bentonite with the surfactant cations. The SWAXS spectra and SEM images of the bentonite are the evidence of somewhat different sorption mechanism of DDA-Br when compared with the BDMODA-Cl and HDTMA-Br, including remarkable external surface sorption contribution in the overall sorption.

ChemCam passive reflectance spectroscopy of surface materials at the Curiosity landing site, Mars

NASA Astrophysics Data System (ADS)

Johnson, Jeffrey R.; Bell, J. F.; Bender, S.; Blaney, D.; Cloutis, E.; DeFlores, L.; Ehlmann, B.; Gasnault, O.; Gondet, B.; Kinch, K.; Lemmon, M.; Le Mouélic, S.; Maurice, S.; Rice, M.; Wiens, R. C.

2015-03-01

The spectrometers on the Mars Science Laboratory (MSL) ChemCam instrument were used in passive mode to record visible/near-infrared (400-840 nm) radiance from the martian surface. Using the onboard ChemCam calibration targets' housing as a reflectance standard, we developed methods to collect, calibrate, and reduce radiance observations to relative reflectance. Such measurements accurately reproduce the known reflectance spectra of other calibration targets on the rover, and represent the highest spatial resolution (0.65 mrad) and spectral sampling (<1 nm) visible/near-infrared reflectance spectra from a landed platform on Mars. Relative reflectance spectra of surface rocks and soils match those from orbital observations and multispectral data from the MSL Mastcam camera. Preliminary analyses of the band depths, spectral slopes, and reflectance ratios of the more than 2000 spectra taken during the first year of MSL operations demonstrate at least six spectral classes of materials distinguished by variations in ferrous and ferric components. Initial comparisons of ChemCam spectra to laboratory spectra of minerals and Mars analog materials demonstrate similarities with palagonitic soils and indications of orthopyroxene in some dark rocks. Magnesium-rich "raised ridges" tend to exhibit distinct near-infrared slopes. The ferric absorption downturn typically found for martian materials at <600 nm is greatly subdued in brushed rocks and drill tailings, consistent with their more ferrous nature. Calcium-sulfate veins exhibit the highest relative reflectances observed, but are still relatively red owing to the effects of residual dust. Such dust is overall less prominent on rocks sampled within the "blast zone" immediately surrounding the landing site. These samples were likely affected by the landing thrusters, which partially removed the ubiquitous dust coatings. Increased dust coatings on the calibration targets during the first year of the mission were documented by the ChemCam passive measurements as well. Ongoing efforts to model and correct for this dust component should improve calibration of the relative reflectance spectra. This will be useful as additional measurements are acquired during the rover's future examinations of hematite-, sulfate-, and phyllosilicate-bearing materials near the base of Mt. Sharp that are spectrally active in the 400-840 nm region.

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.

Spectral reflectance "deconstruction" of the Murchison CM2 carbonaceous chondrite and implications for spectroscopic investigations of dark asteroids

NASA Astrophysics Data System (ADS)

Cloutis, Edward A.; Pietrasz, Valerie B.; Kiddell, Cain; Izawa, Matthew R. M.; Vernazza, Pierre; Burbine, Thomas H.; DeMeo, Francesca; Tait, Kimberly T.; Bell, James F.; Mann, Paul; Applin, Daniel M.; Reddy, Vishnu

2018-05-01

Carbonaceous chondrites (CCs) are important materials for understanding the early evolution of the solar system and delivery of volatiles and organic material to the early Earth. Presumed CC-like asteroids are also the targets of two current sample return missions: OSIRIS-REx to asteroid Bennu and Hayabusa-2 to asteroid Ryugu, and the Dawn orbital mission at asteroid Ceres. To improve our ability to identify and characterize CM2 CC-type parent bodies, we have examined how factors such as particle size, particle packing, and viewing geometry affect reflectance spectra of the Murchison CM2 CC. The derived relationships have implications for disc-resolved examinations of dark asteroids and sampleability. It has been found that reflectance spectra of slabs are more blue-sloped (reflectance decreasing toward longer wavelengths as measured by the 1.8/0.6 μm reflectance ratio), and generally darker, than powdered sample spectra. Decreasing the maximum grain size of a powdered sample results in progressively brighter and more red-sloped spectra. Decreasing the average grain size of a powdered sample results in a decrease in diagnostic absorption band depths, and redder and brighter spectra. Decreasing porosity of powders and variations in surface texture result in spectral changes that may be different as a function of viewing geometry. Increasing thickness of loose dust on a denser powdered substrate leads to a decrease in absorption band depths. Changes in viewing geometry lead to different changes in spectral metrics depending on whether the spectra are acquired in backscatter or forward-scatter geometries. In backscattered geometry, increasing phase angle leads to an initial increase and then decrease in spectral slope, and a general decrease in visible region reflectance and absorption band depths, and frequent decreases in absorption band minima positions. In forward scattering geometry, increasing phase angle leads to small non-systematic changes in spectral slope, and general decreases in visible region reflectance, and absorption band depths. The highest albedos and larger band depths are generally seen in the lowest phase angle backscattering geometry spectra. The reddest spectra are generally seen in the lowest phase angle backscatter geometry spectra. For the same phase angle, spectra acquired in forward scatter geometry are generally redder and darker and have shallower absorption bands than those acquired in backscatter geometry. Overall, backscatter geometry-acquired spectra are flatter, brighter, and have deeper 0.7 μm region absorption band depths than forward scatter geometry-acquired spectra. It was also found that the 0.7, 0.9, and 1.1 μm absorption bands in Murchison spectra, which are attributable to various Fe electronic processes, are ubiquitous and can be used to recognize CM2 chondrites regardless of the physical properties of the meteorite and viewing geometry.

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.

Evaluation of chemical conversion material (protective coating) exposed to space environmental conditions

NASA Technical Reports Server (NTRS)

Edwards, D. L.

1993-01-01

This report focuses on the development of an operational Rutherford backscattering spectrometry (RBS) system and shows the application of such a system on a space environmental test. Thin films of aluminum and tantalum were deposited on diamond substrates. These films were anodized and preexposure characterization spectra obtained using RBS and total hemispherical reflectance. The samples were exposed to energetic protons then postexposure characterization spectra was obtained using the same techniques. Conclusions based on the comparison of preexposure and postexposure spectra are presented. RBS comparison spectra show no change in the metal/metal oxide interface, while the comparison reflectance data indicate change. Explanations for this reflectance change are presented in this report.

Data bank of optical properties of biological tissue and blood in the visible and near infrared spectral region

NASA Astrophysics Data System (ADS)

Khairullina, Alphiya Y.; Bui, Lilia; Oleinik, Tatiana V.; Artishevsky, Nelli; Prigoun, Natalia; Sevkovsky, Jakov; Mokhort, Tatiana

1996-12-01

The data bank contains optical, ordinary biochemical and biophysical information on 120 venous blood samples of donors, healthy persons, patients with high pathology, 60 tissue samples. The optical parameters include diffuse reflection R((lambda) ) and transmission T((lambda) ) coefficients for optically thick layers, the absorption K((lambda) ) and extinction (epsilon) ((lambda) ) spectra, oxygenation degree CO2, parameter p determined by sizes and shapes of cells and their aggregates, refractive index of a disperse phase relative to surrounding media, and cooperative effects at high relative concentration. The peculiarities in absorption K((lambda) spectra are connected with different pathologies. It is shown from K((lambda) ) that the grade of pathology connected with the concentration of hemoglobin and mithohondrion together with oxygenation degree of blood and tissues, with the pathological hemoglobin's forms and its decomposition products of different levels. Parameter p is an important diagnostic parameter. We consider that it is necessary to include the oxygenation degree and erythrocyte's aggregation parameter to extend the range of common diagnostic parameters of blood by the first rota.

High efficient photocatalytic selective oxidation of benzyl alcohol to benzaldehyde by solvothermal-synthesized ZnIn2S4 microspheres under visible light irradiation

NASA Astrophysics Data System (ADS)

Chen, Zhixin; Xu, Jingjing; Ren, Zhuyun; He, Yunhui; Xiao, Guangcan

2013-09-01

Hexagonal ZnIn2S4 samples have been synthesized by a solvothermal method. Their properties have been determined by X-ray diffraction, ultraviolet-visible-light diffuse reflectance spectra, field emission scanning electron microscopy, nitrogen adsorption-desorption and X-ray photoelectron spectra. These results demonstrate that ethanol solvent has significant influence on the morphology, optical and electronic nature for such marigold-like ZnIn2S4 microspheres. The visible light photocatalytic activities of the ZnIn2S4 have been evaluated by selective oxidation of benzyl alcohol to benzaldehyde using molecular oxygen as oxidant. The results show that 100% conversion along with >99% selectivity are reached over ZnIn2S4 prepared in ethanol solvent under visible light irradiation (λ>420 nm) of 2 h, but only 58% conversion and 57% yield are reached over ZnIn2S4 prepared in aqueous solvent. A possible mechanism of the high photocatalytic activity for selective oxidation of benzyl alcohol over ZnIn2S4 is proposed and discussed.

Synthesis and characterization of Ce, Cu co-doped ZnS nanoparticles

NASA Astrophysics Data System (ADS)

Harish, G. S.; Sreedhara Reddy, P.

2015-09-01

Ce, Cu co-doped ZnS nanoparticles were prepared at room temperature using a chemical co-precipitation method. The prepared nanoparticles were characterized by X- ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive analysis of X-rays (EDAX), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) and high resolution Raman spectroscopic techniques. Transmission electron microscopy (TEM) and X-ray diffraction studies showed that the diameter of the particles was around 2-3 nm. Broadened XRD peaks revealed the formation of nanoparticles with a face centered cubic (fcc) structure. DRS studies confirmed that the band gap increased with an increase in the dopant concentration. The Raman spectra of undoped and Ce, Cu ions co-doped ZnS nanoparticles showed longitudinal optical mode and transverse optical mode. Compared with the Raman modes (276 and 351 cm-1) of undoped ZnS nanoparticles, the Raman modes of Ce, Cu co- doped ZnS nanoparticles were slightly shifted towards lower frequency. PL spectra of the samples showed remarkable enhancement in the intensity upon doping.

TiO2 nanosheets decorated with B4C nanoparticles as photocatalysts for solar fuel production under visible light irradiation

NASA Astrophysics Data System (ADS)

Zhang, Xiaojie; Yang, Jipeng; Cai, Tiancong; Zuo, Guoqiang; Tang, Changqing

2018-06-01

Boron carbide (B4C) nanoparticles-decorated anatase titanium dioxide (TiO2) nanosheets photocatalysts were synthesized by a hydrothermal method in the presence of hydrofluoric acid and characterized by field emission scanning electron microscope, high-resolution transmission electron microscope, UV-vis diffuse reflectance spectra, photoluminescence spectra, etc. With metallic Pt nanoparticles as a co-catalyst, the as-synthesized B4C/TiO2 composites were evaluated using photocatalytic CO2 or H2O reduction to solar fuels such as methane and hydrogen. Under either simulated sunlight or visible light irradiation, coupling p-type B4C with n-type anatase TiO2 significantly improved the photocatalytic performance. Both photoluminescence and transient photocurrent measurements indicated that the interfacial coupling effect between B4C and anatase TiO2 could significantly promote photo-excited charges separations. On the basis of measurements and literatures, a possible mechanism of excited charges transfer at the B4C-anatase TiO2 heterojunction interface during irradiation was deduced.

Studies on graphene zinc-oxide nanocomposites photoanodes for high-efficient dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Effendi, N. A. S.; Samsi, N. S.; Zawawi, S. A.; Hassan, O. H.; Zakaria, R.; Yahya, M. Z. A.; Ali, A. M. M.

2017-09-01

A dye-sensitized solar cells (DSSCs) using a nanocomposite (NC) semiconductor film, consisting of graphene layer and ZnO nanosheets (Gr-ZnO) is fabricated by electrodeposition process. The DSSCs based on Gr-ZnO NC were determined via electrochemical impedance spectra (EIS), UV-Visible diffused reflectance spectroscopy (UV-Vis), and photovoltaic performances J-V curves to substantiate the explanations. Impedance spectra shows that a smaller charge transport time constant occurs in DSSCs based on Gr-ZnO NC comparing to ZnO. This improved the electron collecting efficiency significantly, resulting in high open circuit voltage. Moreover, Gr-ZnO NC shows an efficient photoinduced charge separation and transportation can be achieved at the interface thus exhibit excellent potential for photocurrent generation compared with sole ZnO. Gr-ZnO NC obtained a maximum photocurrent response for an open-circuit voltage and a power conversion efficiency of 0.96 V and 7.01% respectively, which is doubled from sole ZnO. The fabricated Gr-ZnO NC cells show better performances compared to conventional ZnO structure reference cell.

Preparation and Characterization of Nano Gold Supported over Montmorillonite Clays

NASA Astrophysics Data System (ADS)

Suraja, P. V.; Binitha, N. N.; Yaakob, Z.; Silija, P. P.

2011-02-01

The use of montmorillonite clays as a matrix, or as a host, for obtaining intercalated/supported metal particles has potential applications in catalysis and other areas. The gold nanoparticles were obtained from the most common anionic gold precursor HAuCl4·3H2O by deposition-precipitation (DP) methods. However, it is difficult to prepare nanoscale gold catalysts supported on silica surfaces with lower isoelectric point (IEP). Homogeneous precipitation method using urea also fails on silica surfaces. Reasons for the inefficiency of these methods are the negative charge of the metal precursor as well as the support surface and the high pH required for depositing gold nanoparticles. In the present work, we use glucose as the reductant in the presence of stabilizer for preparation of nano gold supported on montmorillonite clay. There is no need of increasing the pH of the solution to reduce the Au3+ ions. The prepared systems are characterized using various techniques such as using X-ray fluorescence (XRF), UV-VIS Diffuse reflectance spectra (DRS) and Fourier Transform infra red spectra (FTIR) to prove the efficiency of the present method.

Development of a hybrid proximal sensing method for rapid identification of petroleum contaminated soils.

PubMed

Chakraborty, Somsubhra; Weindorf, David C; Li, Bin; Ali Aldabaa, Abdalsamad Abdalsatar; Ghosh, Rakesh Kumar; Paul, Sathi; Nasim Ali, Md

2015-05-01

Using 108 petroleum contaminated soil samples, this pilot study proposed a new analytical approach of combining visible near-infrared diffuse reflectance spectroscopy (VisNIR DRS) and portable X-ray fluorescence spectrometry (PXRF) for rapid and improved quantification of soil petroleum contamination. Results indicated that an advanced fused model where VisNIR DRS spectra-based penalized spline regression (PSR) was used to predict total petroleum hydrocarbon followed by PXRF elemental data-based random forest regression was used to model the PSR residuals, it outperformed (R(2)=0.78, residual prediction deviation (RPD)=2.19) all other models tested, even producing better generalization than using VisNIR DRS alone (RPD's of 1.64, 1.86, and 1.96 for random forest, penalized spline regression, and partial least squares regression, respectively). Additionally, unsupervised principal component analysis using the PXRF+VisNIR DRS system qualitatively separated contaminated soils from control samples. Fusion of PXRF elemental data and VisNIR derivative spectra produced an optimized model for total petroleum hydrocarbon quantification in soils. Copyright © 2015 Elsevier B.V. All rights reserved.

Synthesis of Ni nanoparticles decorated SiO2/TiO2 magnetic spheres for enhanced photocatalytic activity towards the degradation of azo dye

NASA Astrophysics Data System (ADS)

Mahesh, K. P. O.; Kuo, Dong-Hau

2015-12-01

Highly photocatalytic active Ni magnetic nanoparticles-decorated SiO2 core/TiO2 shell (Ni-SiO2/TiO2) particles have been prepared by the simultaneous hydrolysis and condensation of titanium tetra-isopropoxide on SiO2 sphere of ∼300 nm in size followed by the reduction of nickel chloride using hydrazine hydrate as a reducing agent. The crystalline nature, surface morphology, electrochemical impedance spectra and UV-vis diffuse reflectance spectra of the Ni-SiO2/TiO2 magnetic spheres were characterized by PXRD, FE-SEM, TEM, EIS and UV-vis DRS. The Ni-SiO2/TiO2 magnetic photocatalyst was used for the degradation of Acid Black 1 (AB 1) dye under UV irradiation. The effects of different concentrations of the Ni nanoparticles deposited on the SiO2/TiO2 composite spheres for the photo-mineralization of AB 1 dye were analyzed. The results showed the Ni-SiO2/TiO2 magnetic photocatalyst to be efficient and reusable.

New method to synthesize mesoporous titania by photodegradation of surfactant template

NASA Astrophysics Data System (ADS)

Zi, Shamsuddin Chik; Chandren, Sheela; Yuan, Lai Sin; Razali, Rasidah; Ho, Chin Siong; Hartanto, Djoko; Indra Mahlia, Teuku Meurah; Nur, Hadi

2016-02-01

Mesoporous titania has been successfully synthesized by photodegradation removal of cetyltrimethylammonium bromide as the surfactant, after slow hydrolyzation of titanium(IV) isopropoxide. Fourier transform infrared spectra proved that photodegradation has successfully decreased the peak areas of the alkyl groups from the template. The nitrogen adsorption analysis showed that the pore size and the specific surface area of the mesoporous titania were 3.7 nm and 203 m2 g-1, respectively, proving the mesoporosity of the titania obtained with the existence of the interparticle mesoporosity which was confirmed by transmission electron microscopy. Based on X-ray diffraction results, the mesoporous titania obtained was in the form of crystalline anatase phase. Furthermore, results from the diffuse reflectance ultra violet-visible spectra showed that the composition of tetrahedral titanium(IV) was more than the octahedral titanium(IV). When the mesoporous titania obtained was used as a catalyst in the oxidation of styrene, an improvement in the conversion of styrene (38%) was observed when compared to those obtained using Degussa P25 TiO2 (14%) as the catalyst.

The size effect to O2- -Ce4+ charge transfer emission and band gap structure of Sr2 CeO4.

PubMed

Wang, Wenjun; Pan, Yu; Zhang, Wenying; Liu, Xiaoguang; Li, Ling

2018-04-24

Sr 2 CeO 4 phosphors with different crystalline sizes were synthesized by the sol-gel method or the solid-state reaction. Their crystalline size, luminescence intensity of O 2- -Ce 4+ charge transfer and energy gaps were obtained through the characterization by X-ray diffraction, photoluminescence spectra, as well as UV-visible diffuse reflectance measurements. An inverse relationship between photoluminescence (PL) spectra and crystalline size was observed when the heating temperature was from 1000°C to 1300°C. In addition, band energy calculated for all samples showed that a reaction temperature of 1200°C for the solid-state method and 1100°C for sol-gel method gave the largest values, which corresponded with the smallest crystalline size. Correlation between PL intensity and crystalline size showed an inverse relationship. Band structure, density of states and partial density of states of the crystal were calculated to analyze the mechanism using the cambrige sequential total energy package (CASTEP) module integrated with Materials Studio software. Copyright © 2018 John Wiley & Sons, Ltd.

Vacancy-Rich Monolayer BiO2-x as a Highly Efficient UV, Visible, and Near-Infrared Responsive Photocatalyst.

PubMed

Li, Jun; Wu, Xiaoyong; Pan, Wenfeng; Zhang, Gaoke; Chen, Hong

2018-01-08

Vacancy-rich layered materials with good electron-transfer property are of great interest. Herein, a full-spectrum responsive vacancy-rich monolayer BiO 2-x has been synthesized. The increased density of states at the conduction band (CB) minimum in the monolayer BiO 2-x is responsible for the enhanced photon response and photo-absorption, which were confirmed by UV/Vis-NIR diffuse reflectance spectra (DRS) and photocurrent measurements. Compared to bulk BiO 2-x , monolayer BiO 2-x has exhibited enhanced photocatalytic performance for rhodamine B and phenol removal under UV, visible, and near-infrared light (NIR) irradiation, which can be attributed to the vacancy V Bi-O ''' as confirmed by the positron annihilation spectra. The presence of V Bi-O ''' defects in monolayer BiO 2-x promoted the separation of electrons and holes. This finding provides an atomic level understanding for developing highly efficient UV, visible, and NIR light responsive photocatalysts. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Solar photocatalytic degradation of isoproturon over TiO2/H-MOR composite systems.

PubMed

Sharma, Mangalampalli V Phanikrishna; Durgakumari, Valluri; Subrahmanyam, Machiraju

2008-12-30

The photocatalytic degradation and mineralization of isoproturon herbicide was investigated in aqueous solution containing TiO2 over H-mordenite (H-MOR) photocatalysts under solar light. The catalysts are characterized by X-ray diffraction (XRD), UV-Vis diffused reflectance spectra (UV-Vis DRS), Fourier transform-infra red spectra (FT-IR) and scanning electron microscopy (SEM) techniques. The effect of TiO2, H-MOR support and different wt% of TiO2 over the support on the photocatalytic degradation and influence of parameters such as TiO2 loading, catalyst amount, pH and initial concentration of isoproturon on degradation are evaluated. 15wt% TiO2/H-MOR composite is found to be optimum. The degradation reaction follows pseudo-first order kinetics and is discussed in terms of Langmuir-Hinshelwood (L-H) kinetic model. The extent of isoproturon mineralization studied with chemical oxygen demand (COD) and total organic carbon (TOC) measurements and approximately 80% mineralization occurred in 5h. A plausible mechanism is proposed based on the intermediates identified by liquid chromatography-mass spectroscopy (LC-MS).

Visible-light-assisted photocatalytic activity of bismuth-TiO2 nanotube composites for chromium reduction and dye degradation.

PubMed

Ali, Imran; Kim, Jong-Oh

2018-09-01

TiO 2 nanotubes (TNTs) were synthesized on a Ti sheet using the electrochemical anodization method. Bismuth (Bi) was coupled on the anodized TNTs via hydrothermal process. We verified the effect of different Bi concentrations on the photocatalytic properties of Bi-TNT composites. The obtained samples were characterized using field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, UV-Vis diffuse reflectance spectra, and photoluminescence spectra. The Bi-TNT photocatalysts exhibited higher activities by factors of 6.6 and 3.6 toward chromium reduction and methylene blue degradation, respectively, under visible light than the pure TNTs. The Bi-TNT material was recycled to examine the stability of the catalyst. The quantum efficiency of the photocatalytic system was calculated, and the synergistic effects of bismuth modification were discussed. The Bi-TNT composites were observed to be promising for separation of photoinduced e - and h + by decreasing charge recombination, and helped the formation of the hydroxyl radicals, h + , and superoxides used in the photocatalytic process. Copyright © 2018 Elsevier Ltd. All rights reserved.

Soil emissivity and reflectance spectra measurements

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

Sobrino, Jose A.; Mattar, Cristian; Pardo, Pablo

We present an analysis of the laboratory reflectance and emissivity spectra of 11 soil samples collected on different field campaigns carried out over a diverse suite of test sites in Europe, North Africa, and South America from 2002 to 2008. Hemispherical reflectance spectra were measured from 2.0 to 14 {mu}m with a Fourier transform infrared spectrometer, and x-ray diffraction analysis (XRD) was used to determine the mineralogical phases of the soil samples. Emissivity spectra were obtained from the hemispherical reflectance measurements using Kirchhoff's law and compared with in situ radiance measurements obtained with a CIMEL Electronique CE312-2 thermal radiometer andmore » converted to emissivity using the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) temperature and emissivity separation algorithm. The CIMEL has five narrow bands at approximately the same positions as the ASTER. Results show a root mean square error typically below 0.015 between laboratory emissivity measurements and emissivity measurements derived from the field radiometer.« less

Kosmos 856 and Kosmos 914 measurements of high-energy diffuse gamma rays

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

Kalinkin, L.F.; Nagornykh, Y.I.

1982-09-01

The measurements by the Kosmos 856 and Kosmos 914 satellites of diffuse cosmic ..gamma.. rays with photon energies above 100 MeV are discussed. Integrated energy spectra for the 100--4000 MeV energy range are given for galactic lattitudes Vertical BarbVertical Bar< or =30/sup 0/ and Vertical BarbVertical Bar>30/sup 0/. The form of the spectra suggests that at high lattitudes there may still be some contribution from the galactic component.

Single-Molecule Spectroscopy Unmasks the Lowest Exciton State of the B850 Assembly in LH2 from Rps. acidophila

PubMed Central

Kunz, Ralf; Timpmann, Kõu; Southall, June; Cogdell, Richard J.; Freiberg, Arvi; Köhler, Jürgen

2014-01-01

We have recorded fluorescence-excitation and emission spectra from single LH2 complexes from Rhodopseudomonas (Rps.) acidophila. Both types of spectra show strong temporal spectral fluctuations that can be visualized as spectral diffusion plots. Comparison of the excitation and emission spectra reveals that for most of the complexes the lowest exciton transition is not observable in the excitation spectra due to the cutoff of the detection filter characteristics. However, from the spectral diffusion plots we have the full spectral and temporal information at hand and can select those complexes for which the excitation spectra are complete. Correlating the red most spectral feature of the excitation spectrum with the blue most spectral feature of the emission spectrum allows an unambiguous assignment of the lowest exciton state. Hence, application of fluorescence-excitation and emission spectroscopy on the same individual LH2 complex allows us to decipher spectral subtleties that are usually hidden in traditional ensemble spectroscopy. PMID:24806933

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.

THE EFFECT OF DIFFUSION ON THE PARTICLE SPECTRA IN PULSAR WIND NEBULAE

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

Vorster, M. J.; Moraal, H., E-mail: 12792322@nwu.ac.za

2013-03-01

A possible way to calculate particle spectra as a function of position in pulsar wind nebulae is to solve a Fokker-Planck transport equation. This paper presents numerical solutions to the transport equation with the processes of convection, diffusion, adiabatic losses, and synchrotron radiation included. In the first part of the paper, the steady-state version of the transport equation is solved as a function of position and energy. This is done to distinguish the various effects of the aforementioned processes on the solutions to the transport equation. The second part of the paper deals with a time-dependent solution to the transportmore » equation, specifically taking into account the effect of a moving outer boundary. The paper highlights the fact that diffusion can play a significant role in reducing the amount of synchrotron losses, leading to a modification in the expected particle spectra. These modified spectra can explain the change in the photon index of the synchrotron emission as a function of position. The solutions presented in this paper are not limited to pulsar wind nebulae, but can be applied to any similar central source system, e.g., globular clusters.« less

Accelerated ions and self-excited Alfvén waves at the Earth's bow shock

NASA Astrophysics Data System (ADS)

Berezhko, E. G.; Taneev, S. N.; Trattner, K. J.

2011-07-01

The diffuse energetic ion event and related Alfvén waves upstream of the Earth's bow shock, measured by AMPTE/IRM satellite on 29 September 1984, 06:42-07:22 UT, was studied using a self-consistent quasi-linear theory of ion diffusive shock acceleration and associated Alfvén wave generation. The wave energy density satisfies a wave kinetic equation, and the ion distribution function satisfies the diffusive transport equation. These coupled equations are solved numerically, and calculated ion and wave spectra are compared with observations. It is shown that calculated steady state ion and Alfvén wave spectra are established during the time period of about 1000 s. Alfvén waves excited by accelerated ions are confined within the frequency range (10-2 to 1) Hz, and their spectral peak with the wave amplitude δB ≈ B comparable to the interplanetary magnetic field value B corresponds to the frequency 2 × 10-2 Hz. The high-frequency part of the wave spectrum undergoes absorption by thermal protons. It is shown that the observed ion spectra and the associated Alfvén wave spectra are consistent with the theoretical prediction.

Maturation of EEG Power Spectra in Early Adolescence: A Longitudinal Study

ERIC Educational Resources Information Center

Cragg, Lucy; Kovacevic, Natasa; McIntosh, Anthony Randal; Poulsen, Catherine; Martinu, Kristina; Leonard, Gabriel; Paus, Tomas

2011-01-01

This study investigated the fine-grained development of the EEG power spectra in early adolescence, and the extent to which it is reflected in changes in peak frequency. It also sought to determine whether sex differences in the EEG power spectra reflect differential patterns of maturation. A group of 56 adolescents were tested at age 10 years and…

[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.

CCD reflectance spectra of selected asteroids. I - Presentation and data analysis considerations

NASA Technical Reports Server (NTRS)

Vilas, Faith; Mcfadden, Lucy A.

1992-01-01

Narrowband reflectance spectra have been acquired which contribute to the library of asteroid data in the visible and near-IR spectral regions. The spectra support the existence of aqueous alteration products on asteroids located in the outer part of the main asteroid belt out to at least 4 AU. No evidence for features similar to the spectral features of ordinary chondrite meteorites was found in the spectra of asteroids located near the 3:1 Kirkwood Gap chaotic zone.

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.

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.

Modeling Suomi-NPP VIIRS Solar Diffuser Degradation due to Space Radiation

NASA Astrophysics Data System (ADS)

Shao, X.; Cao, C.

2014-12-01

The Visible Infrared Imaging Radiometer Suite (VIIRS) onboard Suomi-NPP uses a solar diffuser (SD) as on-board radiometric calibrator for the reflective solar band (RSB) calibration. Solar diffuser is made of Spectralon (one type of fluoropolymer) and was chosen because of its controlled reflectance in the VIS-NIR-SWIR region and its near-Lambertian reflectance profile. Spectralon is known to degrade in reflectance at the blue end of the spectrum due to exposure to space radiations such as solar UV radiation and energetic protons. These space radiations can modify the Spectralon surface through breaking C-C and C-F bonds and scissioning or cross linking the polymer, which causes the surface roughness and degrades its reflectance. VIIRS uses a SDSM (Solar Diffuser Stability Monitor) to monitor the change in the Solar Diffuser reflectance in the 0.4 - 0.94 um wavelength range and provide a correction to the calibration constants. The H factor derived from SDSM reveals that reflectance of 0.4 to 0.6um channels of VIIRS degrades faster than the reflectance of longer wavelength RSB channels. A model is developed to derive characteristic parameters such as mean SD surface roughness height and autocovariance length of SD surface roughness from the long term spectral degradation of SD reflectance as monitored by SDSM. These two parameters are trended to assess development of surface roughness of the SD over the operation period of VIIRS.

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.

Development of Infrared Library Search Prefilters for Automotive Clear Coats from Simulated Attenuated Total Reflection (ATR) Spectra.

PubMed

Perera, Undugodage Don Nuwan; Nishikida, Koichi; Lavine, Barry K

2018-06-01

A previously published study featuring an attenuated total reflection (ATR) simulation algorithm that mitigated distortions in ATR spectra was further investigated to evaluate its efficacy to enhance searching of infrared (IR) transmission libraries. In the present study, search prefilters were developed from transformed ATR spectra to identify the assembly plant of a vehicle from ATR spectra of the clear coat layer. A total of 456 IR transmission spectra from the Paint Data Query (PDQ) database that spanned 22 General Motors assembly plants and served as a training set cohort were transformed into ATR spectra by the simulation algorithm. These search prefilters were formulated using the fingerprint region (1500 cm -1 to 500 cm -1 ). Both the transformed ATR spectra (training set) and the experimental ATR spectra (validation set) were preprocessed for pattern recognition analysis using the discrete wavelet transform, which increased the signal-to-noise of the ATR spectra by concentrating the signal in specific wavelet coefficients. Attenuated total reflection spectra of 14 clear coat samples (validation set) measured with a Nicolet iS50 Fourier transform IR spectrometer were correctly classified as to assembly plant(s) of the automotive vehicle from which the paint sample originated using search prefilters developed from 456 simulated ATR spectra. The ATR simulation (transformation) algorithm successfully facilitated spectral library matching of ATR spectra against IR transmission spectra of automotive clear coats in the PDQ database.

Thermo-Reflectance Spectra of Eros: Unambiguous Detection of Olivine

NASA Technical Reports Server (NTRS)

Lucey, P. G.; Hinrichs, J. L.; Urquhart-Kelly, M.; Wellnitz, D.; Bell, J. F., III; Clark, B. E.

2001-01-01

Olivine is readily detected on 433 Eros using the new thermo-reflectance spectral technique applied to near-IR spectra obtained at Eros by the NEAR spacecraft. Additional information is contained in the original extended abstract.

Excitonic spectra and energy band structure of ZnAl2Se4 crystals

NASA Astrophysics Data System (ADS)

Syrbu, N. N.; Zalamai, V. V.; Tiron, A. V.; Tiginyanu, I. M.

2015-11-01

Absorption, reflection and wavelength modulated reflection spectra were investigated in ZnAl2Se4 crystals. The energy positions of ground and excited states for three excitonic series (А, В and С) were determined. The main parameters of excitons and more precise values of energy intervals V1(Γ7)-C1(Γ6), V2(Γ6)-C1(Γ6), and V3(Γ7)-C1(Γ6) were estimated. Values of splitting due to crystal field and spin-orbital interaction were calculated. Effective masses of electrons (mC1∗) and holes (mV1∗, mV2∗, mV3∗) were estimated. Reflection spectra contours in excitonic region were calculated using dispersion equations. Optical functions for E > Eg from measured reflection spectra were assigned on the base of Kramers-Kronig relations.

Perspective: C60+ and laboratory spectroscopy related to diffuse interstellar bands

NASA Astrophysics Data System (ADS)

Campbell, E. K.; Maier, J. P.

2017-04-01

In the last 30 years, our research has focused on laboratory measurements of the electronic spectra of organic radicals and ions. Many of the species investigated were selected based on their potential astrophysical relevance, particularly in connection with the identification of appealing candidate molecules for the diffuse interstellar absorptions. Notably, carbon chains and derivatives containing hydrogen and nitrogen atoms in their neutral and ionic forms were studied. These data could be obtained after developing appropriate techniques to record spectra at low temperatures relevant to the interstellar medium. The measurement of gas phase laboratory spectra has enabled direct comparisons with astronomical data to be made and though many species were found to have electronic transitions in the visible where the majority of diffuse bands are observed, none of the absorptions matched the prominent interstellar features. In 2015, however, the first carrier molecule was identified: C60 + . This was achieved after the measurement of the electronic spectrum of C60 + -He at 6K in a radiofrequency ion trap.

Effect of radiance-to-reflectance transformation and atmosphere removal on maximum likelihood classification accuracy of high-dimensional remote sensing data

NASA Technical Reports Server (NTRS)

Hoffbeck, Joseph P.; Landgrebe, David A.

1994-01-01

Many analysis algorithms for high-dimensional remote sensing data require that the remotely sensed radiance spectra be transformed to approximate reflectance to allow comparison with a library of laboratory reflectance spectra. In maximum likelihood classification, however, the remotely sensed spectra are compared to training samples, thus a transformation to reflectance may or may not be helpful. The effect of several radiance-to-reflectance transformations on maximum likelihood classification accuracy is investigated in this paper. We show that the empirical line approach, LOWTRAN7, flat-field correction, single spectrum method, and internal average reflectance are all non-singular affine transformations, and that non-singular affine transformations have no effect on discriminant analysis feature extraction and maximum likelihood classification accuracy. (An affine transformation is a linear transformation with an optional offset.) Since the Atmosphere Removal Program (ATREM) and the log residue method are not affine transformations, experiments with Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data were conducted to determine the effect of these transformations on maximum likelihood classification accuracy. The average classification accuracy of the data transformed by ATREM and the log residue method was slightly less than the accuracy of the original radiance data. Since the radiance-to-reflectance transformations allow direct comparison of remotely sensed spectra with laboratory reflectance spectra, they can be quite useful in labeling the training samples required by maximum likelihood classification, but these transformations have only a slight effect or no effect at all on discriminant analysis and maximum likelihood classification accuracy.

Laboratory measurements of radiance and reflectance spectra of dilute primary-treated sewage sludge

NASA Technical Reports Server (NTRS)

Usry, J. W.; Witte, W. G.; Whitlock, C. H.; Gurganus, E. A.

1977-01-01

The feasibility of remotely monitoring ocean dumping of waste products such as acid and sewage sludge is evaluated. The laboratory arrangement, solar simulator, and test results from three experiments conducted in the laboratory are described. Radiance and reflectance spectra are presented for primary-treated sewage sludge mixed with two types of base water. Results indicate that upwelled reflectance varies in a near-linear manner with concentration and that the sludge has a practically flat signal response between 420 and 970 nm. Well-defined upwelled reflectance spectra were obtained for the sewage-sludge mixtures at all wavelengths and concentrations. The spectral-reflectance values appeared to be influenced by the type of base water, but this influence was small, especially for the mixtures with low concentrations of sewage sludge.

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%.

PRISM: Processing routines in IDL for spectroscopic measurements (installation manual and user's guide, version 1.0)

USGS Publications Warehouse

Kokaly, Raymond F.

2011-01-01

This report describes procedures for installing and using the U.S. Geological Survey Processing Routines in IDL for Spectroscopic Measurements (PRISM) software. PRISM provides a framework to conduct spectroscopic analysis of measurements made using laboratory, field, airborne, and space-based spectrometers. Using PRISM functions, the user can compare the spectra of materials of unknown composition with reference spectra of known materials. This spectroscopic analysis allows the composition of the material to be identified and characterized. Among its other functions, PRISM contains routines for the storage of spectra in database files, import/export of ENVI spectral libraries, importation of field spectra, correction of spectra to absolute reflectance, arithmetic operations on spectra, interactive continuum removal and comparison of spectral features, correction of imaging spectrometer data to ground-calibrated reflectance, and identification and mapping of materials using spectral feature-based analysis of reflectance data. This report provides step-by-step instructions for installing the PRISM software and running its functions.

Fermi Large Area Telescope Measurements of the Diffuse Gamma-Ray Emission at Intermediate Galactic Latitudes

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

Abdo, A.A.; /Naval Research Lab, Wash., D.C.; Ackermann, M.

The diffuse galactic {gamma}-ray emission is produced by cosmic rays (CRs) interacting with the interstellar gas and radiation field. Measurements by the Energetic Gamma-Ray Experiment Telescope (EGRET) instrument on the Compton Gamma-Ray Observatory indicated excess {gamma}-ray emission {ge}1 GeV relative to diffuse galactic {gamma}-ray emission models consistent with directly measured CR spectra (the so-called 'EGRET GeV excess'). The Large Area Telescope (LAT) instrument on the Fermi Gamma-Ray Space Telescope has measured the diffuse {gamma}-ray emission with improved sensitivity and resolution compared to EGRET. We report on LAT measurements for energies 100 MeV to 10 GeV and galactic latitudes 10{sup o}more » {le} |b| {le} 20{sup o}. The LAT spectrum for this region of the sky is well reproduced by a diffuse galactic {gamma}-ray emission model that is consistent with local CR spectra and inconsistent with the EGRET GeV excess.« less

Fermi Large Area Telescope Measurements of the Diffuse Gamma-Ray Emission at Intermediate Galactic Latitudes

DOE PAGES

Abdo, A. A.; Ackermann, M.; Ajello, M.; ...

2009-12-16

We report that the diffuse galactic γ-ray emission is produced by cosmic rays (CRs) interacting with the interstellar gas and radiation field. Measurements by the Energetic Gamma-Ray Experiment Telescope (EGRET) instrument on the Compton Gamma-Ray Observatory indicated excess γ-ray emission ≳1 GeV relative to diffuse galactic γ-ray emission models consistent with directly measured CR spectra (the so-called “EGRET GeV excess”). The Large Area Telescope (LAT) instrument on the Fermi Gamma-Ray Space Telescope has measured the diffuse γ -ray emission with improved sensitivity and resolution compared to EGRET. We report on LAT measurements for energies 100 MeV to 10 GeV andmore » galactic latitudes 10° ≤ | b | ≤ 20°. Finally, the LAT spectrum for this region of the sky is well reproduced by a diffuse galactic γ-ray emission model that is consistent with local CR spectra and inconsistent with the EGRET GeV excess.« less

Fermi large area telescope measurements of the diffuse gamma-ray emission at intermediate galactic latitudes.

PubMed

Abdo, A A; Ackermann, M; Ajello, M; Anderson, B; Atwood, W B; Axelsson, M; 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; Caliandro, G A; Cameron, R A; Caraveo, P A; Casandjian, J M; Cecchi, C; Charles, E; Chekhtman, A; Cheung, C C; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Conrad, J; Dereli, H; Dermer, C D; de Angelis, A; de Palma, F; Digel, S W; Di Bernardo, G; Dormody, M; do Couto e Silva, E; Drell, P S; Dubois, R; Dumora, D; Edmonds, Y; Farnier, C; Favuzzi, C; Fegan, S J; Focke, W B; Frailis, M; Fukazawa, Y; Funk, S; Fusco, P; Gaggero, D; Gargano, F; Gehrels, N; Germani, S; Giebels, B; Giglietto, N; Giordano, F; Glanzman, T; Godfrey, G; Grenier, I A; Grondin, M-H; Grove, J E; Guillemot, L; Guiriec, S; Hanabata, Y; Harding, A K; Hayashida, M; Hays, E; Hughes, R E; 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; 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; Nuss, E; Ohsugi, T; Okumura, A; 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; 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; Smith, D A; Smith, P D; Spandre, G; Spinelli, P; Starck, J-L; Stecker, F W; Striani, E; Strickman, M S; Strong, A W; Suson, D J; Tajima, H; Takahashi, H; 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

2009-12-18

The diffuse galactic gamma-ray emission is produced by cosmic rays (CRs) interacting with the interstellar gas and radiation field. Measurements by the Energetic Gamma-Ray Experiment Telescope (EGRET) instrument on the Compton Gamma-Ray Observatory indicated excess gamma-ray emission greater, > or approximately equal to 1 GeV relative to diffuse galactic gamma-ray emission models consistent with directly measured CR spectra (the so-called "EGRET GeV excess"). The Large Area Telescope (LAT) instrument on the Fermi Gamma-Ray Space Telescope has measured the diffuse gamma-ray emission with improved sensitivity and resolution compared to EGRET. We report on LAT measurements for energies 100 MeV to 10 GeV and galactic latitudes 10 degrees < or = |b| < or = 20 degrees. The LAT spectrum for this region of the sky is well reproduced by a diffuse galactic gamma-ray emission model that is consistent with local CR spectra and inconsistent with the EGRET GeV excess.

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.

Acquisition of reproducible transmission near-infrared (NIR) spectra of solid samples with inconsistent shapes by irradiation with isotropically diffused radiation using polytetrafluoroethylene (PTFE) beads.

PubMed

Lee, Jinah; Duy, Pham Khac; Yoon, Jihye; Chung, Hoeil

2014-06-21

A bead-incorporated transmission scheme (BITS) has been demonstrated for collecting reproducible transmission near-infrared (NIR) spectra of samples with inconsistent shapes. Isotropically diffused NIR radiation was applied around a sample and the surrounding radiation was allowed to interact homogeneously with the sample for transmission measurement. Samples were packed in 1.40 mm polytetrafluoroethylene (PTFE) beads, ideal diffusers without NIR absorption, and then transmission spectra were collected by illuminating the sample-containing beads using NIR radiation. When collimated radiation was directly applied, a small portion of the non-fully diffused radiation (NFDR) propagated through the void space of the packing and eventually degraded the reproducibility. Pre-diffused radiation was introduced by placing an additional PTFE disk in front of the packing to diminish NFDR, which produced more reproducible spectral features. The proposed scheme was evaluated by analyzing two different solid samples: density determination for individual polyethylene (PE) pellets and identification of mining locality for tourmalines. Because spectral collection was reproducible, the use of the spectrum acquired from one PE pellet was sufficient to accurately determine the density of nine other pellets with different shapes. The differentiation of tourmalines, which are even more dissimilar in appearance, according to their mining locality was also feasible with the help of the scheme.

HD 62542: Probing the Bare, Dense Core of an Interstellar Cloud

NASA Astrophysics Data System (ADS)

Welty, Daniel; Sonnentrucker, Paule G.; Rachford, Brian; Snow, Theodore; York, Donald G.

2018-01-01

We discuss the interstellar absorption from many atomic and molecular species seen in high-resolution HST/STIS UV spectra of the moderately reddened B3-5 V star HD 62542 [E(B-V) ~ 0.35; AV ~ 1.2]. This remarkable sight line exhibits both very steep far-UV extinction and a high fraction of hydrogen in molecular form -- with strong absorption from CH, C2, CN, and CO but weak absorption from CH+ and most of the commonly observed diffuse interstellar bands. Most of the material appears to reside in a single narrow velocity component -- thus offering a rare opportunity to probe the relatively dense, primarily molecular core of a single interstellar cloud, with little associated diffuse atomic gas.Detailed analyses of the absorption-line profiles seen in the UV spectra reveal a number of properties of the main diffuse molecular cloud toward HD 62542:1) The depletions of Mg, Si, and Fe are more severe than those seen in any other sight line, but the depletions of Cl and Kr are very mild; the overall pattern of depletions differs somewhat from those derived from larger samples of Galactic sight lines.2) The rotational excitation of H2 and C2 indicates that the gas is fairly cold (Tk = 40-45 K) and moderately dense (nH > 420 cm-3) somewhat higher densities are suggested by the fine-structure excitation of neutral carbon.3) The excitation temperatures characterizing the rotational populations of both 12CO (11.7 K) and 13CO (7.7 K) are higher than those typically found for Galactic diffuse molecular clouds.4) Carbon is primarily singly ionized -- N(C+) > N(CO) > N(C).5) The relative abundances of various trace neutral atomic species reflect the effects of both the steep far-UV extinction and the severe depletions of some elements.6) Differences in line widths for the various atomic and molecular species are suggestive of differences in spatial distribution within the main cloud.Support for this study was provided by NASA, via STScI grant GO-12277.008-A.

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.

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.

Chemoinformetrical evaluation of dissolution property of indomethacin tablets by near-infrared spectroscopy.

PubMed

Otsuka, Makoto; Tanabe, Hideaki; Osaki, Kazuo; Otsuka, Kuniko; Ozaki, Yukihiro

2007-04-01

The purpose of this study was to use near-infrared spectrometry (NIR) with chemoinformetrics to predict the change of dissolution properties in indomethacin (IMC) tablets during the manufacturing process. A comparative evaluation of the dissolution properties of the tablets was performed by the diffused reflectance (DRNIR) and transmittance (TNIR) NIR spectroscopic methods. Various kinds of IMC tablets (200 mg) were obtained from a powder (20 mg of IMC, 18 mg of microcrystalline cellulose, 160 mg of lactose, and 2 mg of magnesium stearate) under various compression pressures (60-398 MPa). Dissolution tests were performed in phosphate buffer, and the time required for 75% dissolution (T75) and mean dissolution time (MDT) were calculated. DRNIR and TNIR spectra were recorded, and the both NIR spectra used to establish a calibration model for predicting the dissolution properties by principal component regression analysis (PCR). The T75 and MDT increased as the compression pressure increased, since tablet porosity decreased with increasing pressure. Intensity of the DRNIR spectra of the compressed tablets decreased as the compression pressure increased. However, the intensity of TNIR spectra increased along with the pressure. The calibration models used to evaluate the dissolution properties of tablets were established by using PCR based on both DRNIR and TNIR spectra of the tablets. The multiple correlation coefficients of the relationship between the actual and predictive T75 by the DRNIR and TNIR methods were 0.831 and 0.962, respectively. It is possible to predict the dissolution properties of pharmaceutical preparations using both DRNIR and TNIR chemoinformetric methods. The TNIR method was more accurate for predictions of the dissolution behavior of tablets than the DRNIR method. (c) 2007 Wiley-Liss, Inc.

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].

Monte Carlo simulations of particle acceleration at oblique shocks: Including cross-field diffusion

NASA Technical Reports Server (NTRS)

Baring, M. G.; Ellison, D. C.; Jones, F. C.

1995-01-01

The Monte Carlo technique of simulating diffusive particle acceleration at shocks has made spectral predictions that compare extremely well with particle distributions observed at the quasi-parallel region of the earth's bow shock. The current extension of this work to compare simulation predictions with particle spectra at oblique interplanetary shocks has required the inclusion of significant cross-field diffusion (strong scattering) in the simulation technique, since oblique shocks are intrinsically inefficient in the limit of weak scattering. In this paper, we present results from the method we have developed for the inclusion of cross-field diffusion in our simulations, namely model predictions of particle spectra downstream of oblique subluminal shocks. While the high-energy spectral index is independent of the shock obliquity and the strength of the scattering, the latter is observed to profoundly influence the efficiency of injection of cosmic rays into the acceleration process.

Optical and electrical properties of organic dye crystals

NASA Astrophysics Data System (ADS)

Eckhardt, C. J.

1984-02-01

Crystal spectra of three dyes were studied. The dyes are: 3,3'-diethylthiacyanine bromide, pseudoisocyanine and the squarylium dye, 2,4-bis (2-hydroxy-4-diethylaminophenyl)-1, 3-cyclobutadienediylium-1, 3-diolate (HBAPS). Polymorphs were discovered for the latter two dyes and their spectra were investigated. HBAPS showed markedly different spectra for its monoclinic and triclinic forms. The specular reflection spectra of the two crystal forms were successfully fit using molecular exciton-polariton theory employing lattice sums based on a point-charge appproximation. A three-oscillator model for a Gaussian frequency-dependent damping was successful in fitting the spectra. The thiacyanine and pseudoisocyanine dye crystals showed normal quasi-metallic reflection spectra. That of the thiacyanine was found to closely resemble the H-band (dimer) spectra of the dye aggregate in solution.

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.

Dust deposition on the Mars Exploration Rover Panoramic Camera (Pancam) calibration targets

USGS Publications Warehouse

Kinch, K.M.; Sohl-Dickstein, J.; Bell, J.F.; Johnson, J. R.; Goetz, W.; Landis, G.A.

2007-01-01

The Panoramic Camera (Pancam) on the Mars Exploration Rover mission has acquired in excess of 20,000 images of the Pancam calibration targets on the rovers. Analysis of this data set allows estimates of the rate of deposition and removal of aeolian dust on both rovers. During the first 150-170 sols there was gradual dust accumulation on the rovers but no evidence for dust removal. After that time there is ample evidence for both dust removal and dust deposition on both rover decks. We analyze data from early in both rover missions using a diffusive reflectance mixing model. Assuming a dust settling rate proportional to the atmospheric optical depth, we derive spectra of optically thick layers of airfall dust that are consistent with spectra from dusty regions on the Martian surface. Airfall dust reflectance at the Opportunity site appears greater than at the Spirit site, consistent with other observations. We estimate the optical depth of dust deposited on the Spirit calibration target by sol 150 to be 0.44 ?? 0.13. For Opportunity the value was 0.39 ?? 0.12. Assuming 80% pore space, we estimate that the dust layer grew at a rate of one grain diameter per ???100 sols on the Spirit calibration target. On Opportunity the rate was one grain diameter per ???125 sols. These numbers are consistent with dust deposition rates observed by Mars Pathfinder taking into account the lower atmospheric dust optical depth during the Mars Pathfinder mission. Copyright 2007 by the American Geophysical Union.

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.

Assessing Pearl Quality Using Reflectance UV-Vis Spectroscopy: Does the Same Donor Produce Consistent Pearl Quality?

PubMed Central

Mamangkey, Noldy Gustaf F.; Agatonovic, Snezana; Southgate, Paul C.

2010-01-01

Two groups of commercial quality (“acceptable”) pearls produced using two donors, and a group of “acceptable” pearls from other donors were analyzed using reflectance UV-Vis spectrophotometry. Three pearls with different colors produced by the same donor showed different absorption spectra. Cream and gold colored pearls showed a wide absorption from 320 to about 460 nm, while there was just slight reflectance around 400 nm by the white pearl with a pink overtone. Cream and gold pearls reached a reflectance peak at 560 to 590 nm, while the white pearl with pink overtone showed slightly wider absorption in this region. Both cream and gold pearls showed an absorption peak after the reflectance peak, at about 700 nm for the cream pearl and 750 nm for the gold pearl. Two other pearls produced by the same donor (white with cream overtone and cream with various overtones) showed similar spectra, which differed in their intensity. One of these pearls had very high lustre and its spectrum showed a much higher percentage reflectance than the second pearl with inferior lustre. This result may indicate that reflectance is a useful quantitative indicator of pearl lustre. The spectra of two white pearls resulting from different donors with the same color nacre (silver) showed a reflectance at 260 nm, followed by absorption at 280 nm and another reflectance peak at 340 nm. After this peak the spectra for these pearls remained flat until a slight absorption peak around 700 nm. Throughout the visible region, all white pearls used in this study showed similar reflectance spectra although there were differences in reflectance intensity. Unlike the spectral results from white pearls, the results from yellow and gold pearls varied according to color saturation of the pearl. The results of this study show that similarities between absorption and reflectance spectra of cultured pearls resulting from the same saibo donor are negligible and could not be detected with UV-Vis spectrophotometry. Nevertheless, this technique could have a role to play in developing less subjective methods of assessing pearl quality and in further studies of the relationships between pearl quality and that of the donor and recipient oysters. PMID:20948903

Improved Scheme of Modified Gaussian Deconvolution for Reflectance Spectra of Lunar Soils

NASA Technical Reports Server (NTRS)

Hiroi, T.; Pieters, C. M.; Noble, S. K.

2000-01-01

In our continuing effort for deconvolving reflectance spectra of lunar soils using the modified Gaussian model, a new scheme has been developed, including a new form of continuum. All the parameters are optimized with certain constraints.

Excitonic and band-band transitions of Cu2ZnSiS4 determined from reflectivity spectra

NASA Astrophysics Data System (ADS)

Guc, M.; Levcenko, S.; Dermenji, L.; Gurieva, G.; Schorr, S.; Syrbu, N. N.; Arushanov, E.

2014-07-01

Exciton spectra of Cu2ZnSiS4 single crystals are investigated by reflection spectroscopy at 10 and 300 K for light polarized perpendicular (E⊥c) and parallel (E∥c) to the optical axis. The parameters of the excitons and dielectric constant are determined. The free carriers effective masses have been estimated. The room temperature reflectivity spectra at photon energies higher than the fundamental band gap in the polarization Е⊥с and E∥с were measured and related to the electronic band structure of Cu2ZnSiS4.

The low-iron, reduced surface of Mercury as seen in spectral reflectance by MESSENGER

NASA Astrophysics Data System (ADS)

Izenberg, Noam R.; Klima, Rachel L.; Murchie, Scott L.; Blewett, David T.; Holsclaw, Gregory M.; McClintock, William E.; Malaret, Erick; Mauceri, Calogero; Vilas, Faith; Sprague, Ann L.; Helbert, Jörn; Domingue, Deborah L.; Head, James W.; Goudge, Timothy A.; Solomon, Sean C.; Hibbitts, Charles A.; Dyar, M. Darby

2014-01-01

The MESSENGER spacecraft's Mercury Atmospheric and Surface Composition Spectrometer (MASCS) obtained more than 1.6 million reflectance spectra of Mercury's surface from near-ultraviolet to near-infrared wavelengths during the first year of orbital operations. A global analysis of spectra in the wavelength range 300-1450 nm shows little regional variation in absolute reflectance or spectral slopes and a lack of mineralogically diagnostic absorptions. In particular, reflectance spectra show no clear evidence for an absorption band centered near 1 μm that would be associated with the presence of ferrous iron in silicates. There is, however, evidence for an ultraviolet absorption possibly consistent with a very low iron content (2-3 wt% FeO or less) in surface silicates and for the presence of small amounts of metallic iron or other opaque minerals in the form of nano- or micrometer-sized particles. These findings are consistent with MESSENGER X-ray and gamma-ray measurements of Mercury's surface iron abundance. Although X-ray and gamma-ray observations indicate higher than expected quantities of sulfur on the surface, reflectance spectra show no absorption bands diagnostic of sulfide minerals. Whereas there is strong evidence of water ice in permanently shadowed craters near Mercury's poles, MASCS spectra provide no evidence for hydroxylated materials near permanently shadowed craters.

Broadband diffuse terahertz wave scattering by flexible metasurface with randomized phase distribution

PubMed Central

Zhang, Yin; Liang, Lanju; Yang, Jing; Feng, Yijun; Zhu, Bo; Zhao, Junming; Jiang, Tian; Jin, Biaobing; Liu, Weiwei

2016-01-01

Suppressing specular electromagnetic wave reflection or backward radar cross section is important and of broad interests in practical electromagnetic engineering. Here, we present a scheme to achieve broadband backward scattering reduction through diffuse terahertz wave reflection by a flexible metasurface. The diffuse scattering of terahertz wave is caused by the randomized reflection phase distribution on the metasurface, which consists of meta-particles of differently sized metallic patches arranged on top of a grounded polyimide substrate simply through a certain computer generated pseudorandom sequence. Both numerical simulations and experimental results demonstrate the ultralow specular reflection over a broad frequency band and wide angle of incidence due to the re-distribution of the incident energy into various directions. The diffuse scattering property is also polarization insensitive and can be well preserved when the flexible metasurface is conformably wrapped on a curved reflective object. The proposed design opens up a new route for specular reflection suppression, and may be applicable in stealth and other technology in the terahertz spectrum. PMID:27225031

Broadband diffuse terahertz wave scattering by flexible metasurface with randomized phase distribution.

PubMed

Zhang, Yin; Liang, Lanju; Yang, Jing; Feng, Yijun; Zhu, Bo; Zhao, Junming; Jiang, Tian; Jin, Biaobing; Liu, Weiwei

2016-05-26

Suppressing specular electromagnetic wave reflection or backward radar cross section is important and of broad interests in practical electromagnetic engineering. Here, we present a scheme to achieve broadband backward scattering reduction through diffuse terahertz wave reflection by a flexible metasurface. The diffuse scattering of terahertz wave is caused by the randomized reflection phase distribution on the metasurface, which consists of meta-particles of differently sized metallic patches arranged on top of a grounded polyimide substrate simply through a certain computer generated pseudorandom sequence. Both numerical simulations and experimental results demonstrate the ultralow specular reflection over a broad frequency band and wide angle of incidence due to the re-distribution of the incident energy into various directions. The diffuse scattering property is also polarization insensitive and can be well preserved when the flexible metasurface is conformably wrapped on a curved reflective object. The proposed design opens up a new route for specular reflection suppression, and may be applicable in stealth and other technology in the terahertz spectrum.

Spectral characterization of Martian soil analogues

NASA Technical Reports Server (NTRS)

Agresti, David G.

1987-01-01

As previously reported, reflectance spectra of iron oxide precipitated as ultrafine particles, unlike ordinary fine grained hematite, have significant similarities to reflectance spectra from the bright regions of Mars. These particles were characterized according to composition, magnetic properties, and particle size distribution. Mossbauer, magnetic susceptibility, and optical data were obtained for samples with a range of concentrations of iron oxide in silica gel of varying pore diameters. To analyze the Mossbauer spectra, a versatile fitting program was enhanced to provide user friendly screen input and theoretical models appropriate for the superparamagnetic spectra obtained.

Prediction of iron oxide contents using diffuse reflectance spectroscopy

NASA Astrophysics Data System (ADS)

Marques, José, Jr.; Arantes Camargo, Livia

2015-04-01

Determining soil iron oxides using conventional analysis is relatively unfeasible when large areas are mapped, with the aim of characterizing spatial variability. Diffuse reflectance spectroscopy (DRS) is rapid, less expensive, non-destructive and sometimes more accurate than conventional analysis. Furthermore, this technique allows the simultaneous characterization of many soil attributes with agronomic and environmental relevance. This study aims to assess the DRS capability to predict iron oxides content -hematite and goethite - , characterizing their spatial variability in soils of Brazil. Soil samples collected from an 800-hectare area were scanned in the visible and near-infrared spectral range. Moreover, chemometric calibration was obtained through partial least-squares regression (PLSR). Then, spatial distribution maps of the attributes were constructed using predicted values from calibrated models through geostatistical methods. The studied area presented soils with varied contents of iron oxides as examples for the Oxisols and Entisols. In the spectra of each soil is observed that the reflectance decreases with the content of iron oxides present in the soil. In soils with a high content of iron oxides can be observed more pronounced concavities between 380 and 1100 nm which are characteristic of the presence of these oxides. In soils with higher reflectance it were observed concavity characteristics due to the presence of kaolinite, in agreement with the low iron contents of those soils. The best accuracy of prediction models [residual prediction deviation (RPD) = 1.7] was obtained for goethite within the visible region (380-800 nm), and for hematite (RPD = 2.0) within the visible near infrared (380-2300 nm). The maps of goethite and hematite predicted showed the spatial distribution pattern similar to the maps of clay and iron extracted by dithionite-citrate-bicarbonate, being consistent with the iron oxide contents of soils present in the study area. These results confirm the value of DRS in the mapping of iron oxides in large areas at detailed scale.

Ultraviolet Survey of CO and H2 in Diffuse Molecular Clouds: The Reflection of Two Photochemistry Regimes in Abundance Relationships

NASA Astrophysics Data System (ADS)

Sheffer, Y.; Rogers, M.; Federman, S. R.; Abel, N. P.; Gredel, R.; Lambert, D. L.; Shaw, G.

2008-11-01

We carried out a comprehensive far-UV survey of 12CO and H2 column densities along diffuse molecular Galactic sight lines. This sample includes new measurements of CO from HST spectra along 62 sight lines and new measurements of H2 from FUSE data along 58 sight lines. In addition, high-resolution optical data were obtained at the McDonald and European Southern Observatories, yielding new abundances for CH, CH+, and CN along 42 sight lines to aid in interpreting the CO results. These new sight lines were selected according to detectable amounts of CO in their spectra and provide information on both lower density (<=100 cm-3) and higher density diffuse clouds. A plot of log N(CO) versus log N(H2) shows that two power-law relationships are needed for a good fit of the entire sample, with a break located at log N(CO , cm -2) = 14.1 and log N(H2) = 20.4, corresponding to a change in production route for CO in higher density gas. Similar logarithmic plots among all five diatomic molecules reveal additional examples of dual slopes in the cases of CO versus CH (break at log N = 14.1, 13.0), CH+ versus H2 (13.1, 20.3), and CH+ versus CO (13.2, 14.1). We employ both analytical and numerical chemical schemes in order to derive details of the molecular environments. In the denser gas, where C2 and CN molecules also reside, reactions involving C+ and OH are the dominant factor leading to CO formation via equilibrium chemistry. In the low-density gas, where equilibrium chemistry studies have failed to reproduce the abundance of CH+, our numerical analysis shows that nonequilibrium chemistry must be employed for correctly predicting the abundances of both CH+ and CO.

Application of a Snow Growth Model to Radar Remote Sensing

NASA Astrophysics Data System (ADS)

Erfani, E.; Mitchell, D. L.

2014-12-01

Microphysical growth processes of diffusion, aggregation and riming are incorporated analytically in a steady-state snow growth model (SGM) to solve the zeroth- and second- moment conservation equations with respect to mass. The SGM is initiated by radar reflectivity (Zw), supersaturation, temperature, and a vertical profile of the liquid water content (LWC), and it uses a gamma size distribution (SD) to predict the vertical evolution of size spectra. Aggregation seems to play an important role in the evolution of snowfall rates and the snowfall rates produced by aggregation, diffusion and riming are considerably greater than those produced by diffusion and riming alone, demonstrating the strong interaction between aggregation and riming. The impact of ice particle shape on particle growth rates and fall speeds is represented in the SGM in terms of ice particle mass-dimension (m-D) power laws (m = αDβ). These growth rates are qualitatively consistent with empirical growth rates, with slower (faster) growth rates predicted for higher (lower) β values. In most models, β is treated constant for a given ice particle habit, but it is well known that β is larger for the smaller crystals. Our recent work quantitatively calculates β and α for cirrus clouds as a function of D where the m-D expression is a second-order polynomial in log-log space. By adapting this method to the SGM, the ice particle growth rates and fall speeds are predicted more accurately. Moreover, the size spectra predicted by the SGM are in good agreement with those from aircraft measurements during Lagrangian spiral descents through frontal clouds, indicating the successful modeling of microphysical processes. Since the lowest Zw over complex topography is often significantly above cloud base, the precipitation is often underestimated by radar quantitative precipitation estimates (QPE). Our SGM is capable of being initialized with Zw at the lowest reliable radar echo and consequently improves QPE at ground level.

Atlas of reflectance spectra of terrestrial, lunar and meteoritic powders and frosts from 92 to 1800 nm

NASA Technical Reports Server (NTRS)

Wagner, Jeffrey; Hapke, Bruce; Wells, Eddie

1987-01-01

The reflectance spectra of powdered samples of selected minerals, meteorites, lunar materials and frosts are presented as an aid in the interpretation of present and future remote sensing data of solar system objects. Spectra obtained in separate wavelength regions have been combined and normalized, yielding coverage from 92 to 1800 nm. Spectral features include reflectance maxima in the far UV region produced by valence-conduction interband transitions, and reflectance minima in the near UV, visible and near IR regions, produced by charge transfer and crystal field transitions. Specific maxima and minima are diagnostic of mineral type and composition; additionally, the minerals present in mixtures such as meteorites and lunar samples can be determined.

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.

Leaf and canopy reflectance spectrometry applied to the estimation of angular leaf spot disease severity of common bean crops

PubMed Central

Martínez-Martínez, Víctor; Machado, Marley L.; Pinto, Francisco A. C.

2018-01-01

This study is aimed at (i) estimating the angular leaf spot (ALS) disease severity in common beans crops in Brazil, caused by the fungus Pseudocercospora griseola, employing leaf and canopy spectral reflectance data, (ii) evaluating the informative spectral regions in the detection, and (iii) comparing the estimation accuracy when the reflectance or the first derivative reflectance (FDR) is employed. Three data sets of useful spectral reflectance measurements in the 440 to 850 nm range were employed; measurements were taken over the leaves and canopy of bean crops with different levels of disease. A system based in Principal Component Analysis (PCA) and Artificial Neural Networks (ANN) was developed to estimate the disease severity from leaf and canopy hyperspectral reflectance spectra. Levels of disease to be taken as true reference were determined from the proportion of the total leaf surface covered by necrotic lesions on RGB images. When estimating ALS disease severity in bean crops by using hyperspectral reflectance spectrometry, this study suggests that (i) successful estimations with coefficients of determination up to 0.87 can be achieved if the spectra is acquired by the spectroradiometer in contact with the leaves, (ii) unsuccessful estimations are obtained when the spectra are acquired by the spectroradiometer from one or more meters above the crop, (iii) the red to near-infrared spectral region (630–850 nm) offers the same precision in the estimation as the blue to near-infrared spectral region (440–850), and (iv) neither significant improvements nor significant detriments are achieved when the input data to the estimation processing system are the FDR spectra, instead of the reflectance spectra. PMID:29698420

Near-infrared diffuse reflection systems for chlorophyll content of tomato leaves measurement

NASA Astrophysics Data System (ADS)

Jiang, Huanyu; Ying, Yibin; Lu, Huishan

2006-10-01

In this study, two measuring systems for chlorophyll content of tomato leaves were developed based on near-infrared spectral techniques. The systems mainly consists of a FT-IR spectrum analyzer, optic fiber diffuses reflection accessories and data card. Diffuse reflectance of intact tomato leaves was measured by an optics fiber optic fiber diffuses reflection accessory and a smart diffuses reflection accessory. Calibration models were developed from spectral and constituent measurements. 90 samples served as the calibration sets and 30 samples served as the validation sets. Partial least squares (PLS) and principal component regression (PCR) technique were used to develop the prediction models by different data preprocessing. The best model for chlorophyll content had a high correlation efficient of 0.9348 and a low standard error of prediction RMSEP of 4.79 when we select full range (12500-4000 cm -1), MSC path length correction method by the log(1/R). The results of this study suggest that FT-NIR method can be feasible to detect chlorophyll content of tomato leaves rapidly and nondestructively.

Synthesis and photocatalytic properties of TiO{sub 2} nanostructures

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

Xia, X.H.; Liang, Y.; Wang, Z.

2008-08-04

TiO{sub 2} particles, rods, flowers and sheets were prepared by hydrothermal method via adjusting the temperature, the pressure and the concentration of TiCl{sub 4}. The as-prepared TiO{sub 2} powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectra and N{sub 2} adsorption-desorption measurements. It was found that pressure is the most important factor influencing the morphology of TiO{sub 2}. The photocatalytic activity of the products was evaluated by the photodegradation of aqueous brilliant red X-3B solution under UV light. Among the as-prepared nanostructures, the flower-like TiO{sub 2}more » exhibited the highest photocatalytic activity.« less

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.

Improving enzymatic hydrolysis of industrial hemp ( Cannabis sativa L.) by electron beam irradiation

NASA Astrophysics Data System (ADS)

Shin, Soo-Jeong; Sung, Yong Joo

2008-09-01

The electron beam irradiation was applied as a pretreatment of the enzymatic hydrolysis of hemp biomass with doses of 150, 300 and 450 kGy. The higher irradiation dose resulted in the more extraction with hot-water extraction or 1% sodium hydroxide solution extraction. The higher solubility of the treated sample was originated from the chains scission during irradiation, which was indirectly demonstrated by the increase of carbonyl groups as shown in diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) spectra. The changes in the micro-structure of hemp resulted in the better response to enzymatic hydrolysis with commercial cellulases (Celluclast 1.5L and Novozym 342). The improvement in enzymatic hydrolysis by the irradiation was more evident in the hydrolysis of the xylan than in that of the cellulose.

Visible-light photocatalytic activity of graphene oxide-wrapped Bi2WO6 hierarchical microspheres

NASA Astrophysics Data System (ADS)

Zhai, Jiali; Yu, Hongwen; Li, Haiyan; Sun, Lei; Zhang, Kexin; Yang, Hongjun

2015-07-01

A facile approach of fabricating homogeneous graphene oxide (GO)-wrapped Bi2WO6 microspheres (GO/Bi2WO6) is developed. The transmission electron microscopy (TEM) results show that a heterojunction interface between GO and Bi2WO6. The UV-vis diffuse reflection spectra (DRS) reveal that the as-prepared GO/Bi2WO6 composites own more intensive absorption in the visible light range compared with pure Bi2WO6. These characteristic structural and optical properties endow GO/Bi2WO6 composites with enhanced photocatalytic activity. The enhanced photocatalytic activity of the GO/Bi2WO6 is attributed predominantly to the synergetic effect between GO and Bi2WO6, causing rapid generation and separation of photo-generated charge carriers.

Sol-gel synthesis of nanosized titanium dioxide at various pH of the initial solution

NASA Astrophysics Data System (ADS)

Dorosheva, I. B.; Valeeva, A. A.; Rempel, A. A.

2017-09-01

Titanium dioxide (TiO2) was synthesized by sol-gel method at different values of pH = 3, 7, 8, 9, or 10. X-ray phase analysis has shown that in an acid rout an anatase phase was crystallized, and in an alkaline rout an amorphous phase of TiO2 was achieved. After annealing for 4 hours at 350 °C, all samples was transformed in the anatase phase. The particle size in the different samples varies from 7 to 49 nm depending on the pH. The diffuse reflection spectra revealed a high value of the band gap in the range from 3.2 to 3.7 eV and its narrowing after annealing to the range from 3.2 to 3.5 eV.

Enhanced photobactericidal activity of ZnO nanorods modified by meso-tetrakis(4-sulfonatophenyl)porphyrin under visible LED lamp irradiation.

PubMed

Rahimi, Rahmatollah; Shokraiyan, Javad; Rabbani, Mahboubeh; Fayyaz, Fatemeh

2015-01-01

In this study, zinc oxide (ZnO) nanorods have been synthesized using a simple template-free precipitation technique and deposited on glass substrate. The meso-tetrakis(4-sulfonatophenyl)porphyrin (TPPS) has been synthesized and then immobilized on the surface of ZnO nanorods to prepare an organic/inorganic composite. The samples were characterized by various techniques such as X-ray diffraction, diffuse reflectance spectra, Fourier transform-infrared spectroscopy and scanning electron microscopy. In addition, the photobactericidal activity of TPPS/ZnO composite, TPPS and ZnO nanorods was tested against the pathogenic bacterium of Escherichia coli under visible LED lamp irradiation. The results indicate that the photobactericidal activity of TPPS-loaded ZnO nanorods was better than TPPS or ZnO nanorods, separately.

Reflectance Hyperspectral Imaging for Investigation of Works of Art: Old Master Paintings and Illuminated Manuscripts.

PubMed

Cucci, Costanza; Delaney, John K; Picollo, Marcello

2016-10-18

Diffuse reflectance hyperspectral imaging, or reflectance imaging spectroscopy, is a sophisticated technique that enables the capture of hundreds of images in contiguous narrow spectral bands (bandwidth < 10 nm), typically in the visible (Vis, 400-750 nm) and the near-infrared (NIR, 750-2500 nm) regions. This sequence of images provides a data set that is called an image-cube or file-cube. Two dimensions of the image-cube are the spatial dimensions of the scene, and the third dimension is the wavelength. In this way, each spatial pixel in the image has an associated reflectance spectrum. This "big data" image-cube allows for the mining of artists' materials and mapping their distribution across the surface of a work of art. Reflectance hyperspectral imaging, introduced in the 1980s by Goetz and co-workers, led to a revolution in the field of remote sensing of the earth and near planets ( Goetz, F. H.; Vane, G.; Solomon, B. N.; Rock, N. Imaging Spectrometry for Earth Remote Sensing . Science , 1985 , 228 , 1147 - 1152 ). In the subsequent decades, thanks to rapid advances in solid-state sensor technology, reflectance hyperspectral imaging, once only available to large government laboratories, was extended to new fields of application, such as monitoring agri-foods, pharmaceutical products, the environment, and cultural heritage. In the 2000s, the potential of this noninvasive technology for the study of artworks became evident and, consequently, the methodology is becoming more widely used in the art conservation science field. Typically hyperspectral reflectance image-cubes contain millions of spectra. Many of these spectra are similar, making the reduction of the data set size an important first step. Thus, image-processing tools based on multivariate techniques, such as principal component analysis (PCA), automated classification methods, or expert knowledge systems, that search for known spectral features are often applied. These algorithms seek to reduce the large number of high-quality spectra to a common subset, which allow identifying and mapping artists' materials and alteration products. Hence, reflectance hyperspectral imaging is finding its place as the starting point to find sites on polychrome surfaces for spot analytical techniques, such as X-ray fluorescence, Raman spectroscopy, and Fourier transform infrared spectroscopy. Reflectance hyperspectral imaging can also provide image products that are a mainstay in the art conservation field, such as color-accurate images, broadband near-infrared images, and false-color products. This Account reports on the research activity carried out by two research groups, one at the "Nello Carrara" Institute of Applied Physics of the Italian National Research Council (IFAC-CNR) in Florence and the other at the National Gallery of Art (NGA) in Washington, D.C. Both groups have conducted parallel research, with frequent interchanges, to develop multispectral and hyperspectral imaging systems to study works of art. In the past decade, they have designed and experimented with some of the earliest spectral imaging prototypes for museum applications. In this Account, a brief presentation of the hyperspectral sensor systems is given with case studies showing how reflectance hyperspectral imaging is answering key questions in cultural heritage.

Visible/near-infrared spectra of experimentally shocked plagioclase feldspars

USGS Publications Warehouse

Johnson, J. R.; Horz, F.

2003-01-01

High shock pressures cause structural changes in plagioclase feldspars such as mechanical fracturing and disaggregation of the crystal lattice at submicron scales, the formation of diaplectic glass (maskelynite), and genuine melting. Past studies of visible/ near-infrared spectra of shocked feldspars demonstrated few spectral variations with pressure except for a decrease in the depth of the absorption feature near 1250-1300 nm and an overall decrease in reflectance. New visible/near-infrared spectra (400-2500 nm) of experimentally shocked (17-56 GPa) albite- and anorthite-rich rock powders demonstrate similar trends, including the loss of minor hydrated mineral bands near 1410, 1930, 2250, and 2350 nm. However, the most interesting new observations are increases in reflectance at intermediate pressures, followed by subsequent decreases in reflectance at higher pressures. The amount of internal scattering and overall sample reflectance is controlled by the relative proportions of micro-fractures, submicron grains, diaplectic glass, and melts formed during shock metamorphism. We interpret the observed reflectance increases at intermediate pressures to result from progressively larger proportions of submicron feldspar grains and diaplectic glass. The ensuing decreases in reflectance occur after diaplectic glass formation is complete and the proportion of genuine melt inclusions increases. The pressure regimes over which these reflectance variations occur differ between albite and anorthite, consistent with thermal infrared spectra of these samples and previous studies of shocked feldspars. These types of spectral variations associated with different peak shock pressures should be considered during interpretation and modeling of visible/near-infrared remotely sensed spectra of planetary and asteroidal surfaces.

Automatic classification of fluorescence and optical diffusion spectroscopy data in neuro-oncology

NASA Astrophysics Data System (ADS)

Savelieva, T. A.; Loshchenov, V. B.; Goryajnov, S. A.; Potapov, A. A.

2018-04-01

The complexity of the biological tissue spectroscopic analysis due to the overlap of biological molecules' absorption spectra, multiple scattering effect, as well as measurement geometry in vivo has caused the relevance of this work. In the neurooncology the problem of tumor boundaries delineation is especially acute and requires the development of new methods of intraoperative diagnosis. Methods of optical spectroscopy allow detecting various diagnostically significant parameters non-invasively. 5-ALA induced protoporphyrin IX is frequently used as fluorescent tumor marker in neurooncology. At the same time analysis of the concentration and the oxygenation level of haemoglobin and significant changes of light scattering in tumor tissues have a high diagnostic value. This paper presents an original method for the simultaneous registration of backward diffuse reflectance and fluorescence spectra, which allows defining all the parameters listed above simultaneously. The clinical studies involving 47 patients with intracranial glial tumors of II-IV Grades were carried out in N.N. Burdenko National Medical Research Center of Neurosurgery. To register the spectral dependences the spectroscopic system LESA- 01-BIOSPEC was used with specially developed w-shaped diagnostic fiber optic probe. The original algorithm of combined spectroscopic signal processing was developed. We have created a software and hardware, which allowed (as compared with the methods currently used in neurosurgical practice) to increase the sensitivity of intraoperative demarcation of intracranial tumors from 78% to 96%, specificity of 60% to 82%. The result of analysis of different techniques of automatic classification shows that in our case the most appropriate is the k Nearest Neighbors algorithm with cubic metrics.

Reflection spectra and magnetochemistry of iron oxides and natural surfaces

NASA Technical Reports Server (NTRS)

Wasilewski, P.

1978-01-01

The magnetic properties and spectral characteristics of iron oxides are distinctive. Diagnostic features in reflectance spectra (0.5 to 2.4 micron) for alpha Fe2O3, gamma Fe2O3, and FeOOH include location of Fe3(+) absorption features, intensity ratios at various wavelengths, and the curve shape between 1.2 micron and 2.4 micron. The reflection spectrum of natural rock surfaces are seldom those of the bulk rock because of weathering effects. Coatings are found to be dominated by iron oxides and clay. A simple macroscopic model of rock spectra (based on concepts of stains and coatings) is considered adequate for interpretation of LANDSAT data. The magnetic properties of materials associated with specific spectral types and systematic changes in both spectra and magnetic properties are considered.

Bimodal spectroscopic evaluation of ultra violet-irradiated mouse skin inflammatory and precancerous stages: instrumentation, spectral feature extraction/selection and classification (k-NN, LDA and SVM)

NASA Astrophysics Data System (ADS)

Díaz-Ayil, G.; Amouroux, M.; Blondel, W. C. P. M.; Bourg-Heckly, G.; Leroux, A.; Guillemin, F.; Granjon, Y.

2009-07-01

This paper deals with the development and application of in vivo spatially-resolved bimodal spectroscopy (AutoFluorescence AF and Diffuse Reflectance DR), to discriminate various stages of skin precancer in a preclinical model (UV-irradiated mouse): Compensatory Hyperplasia CH, Atypical Hyperplasia AH and Dysplasia D. A programmable instrumentation was developed for acquiring AF emission spectra using 7 excitation wavelengths: 360, 368, 390, 400, 410, 420 and 430 nm, and DR spectra in the 390-720 nm wavelength range. After various steps of intensity spectra preprocessing (filtering, spectral correction and intensity normalization), several sets of spectral characteristics were extracted and selected based on their discrimination power statistically tested for every pair-wise comparison of histological classes. Data reduction with Principal Components Analysis (PCA) was performed and 3 classification methods were implemented (k-NN, LDA and SVM), in order to compare diagnostic performance of each method. Diagnostic performance was studied and assessed in terms of sensitivity (Se) and specificity (Sp) as a function of the selected features, of the combinations of 3 different inter-fibers distances and of the numbers of principal components, such that: Se and Sp ≈ 100% when discriminating CH vs. others; Sp ≈ 100% and Se > 95% when discriminating Healthy vs. AH or D; Sp ≈ 74% and Se ≈ 63%for AH vs. D.

Synthesis and photoluminescence properties of multicolor tunable GdNbO4: Tb3+, Eu3+ phosphors based on energy transfer

NASA Astrophysics Data System (ADS)

Zhang, Lu; Yi, Shuangping; Hu, Xiaoxue; Liang, Boxin; Zhao, Weiren; Wang, Yinhai

2017-03-01

A color-tunable phosphor based on Tb3+/Eu3+ co-doped GdNbO4 were synthesized by a traditional solid-state reaction method. X-ray powder diffraction (XRD), diffuse reflectance spectra, photoluminescence spectra and decay curves were utilized to characterize the as-prepared phosphors. XRD result indicated that various concentrations Tb3+/Eu3+ single-doped and co-doped phosphors were well indexed to the pure GdNbO4 phase. The GdNbO4 host was proved to be a self-activated phosphor with broad absorption range from 200 nm to 325 nm. When Tb3+ ions were added into the host lattice, the energy transferring from host to Tb3+ was identified. And the broad absorption in the UV region was changed and enhanced. Therefore, we selected Tb3+ as the sensitizer ion, and adjusted red component from Eu3+ to control the emission color. The energy transfer from Tb3+ to Eu3+ was confirmed based on the luminescence spectra and decay curves. Furthermore, the energy transmission mechanism was deduced to be the dipole-quadrupole interaction. On the whole, the obtained GdNbO4, GdNbO4:Tb3+, and GdNbO4:Tb3+, Eu3+ phosphors may have potential application in the UV white-light-emitting diodes (w-LEDs) and display devices.

NADH-fluorescence scattering correction for absolute concentration determination in a liquid tissue phantom using a novel multispectral magnetic-resonance-imaging-compatible needle probe

NASA Astrophysics Data System (ADS)

Braun, Frank; Schalk, Robert; Heintz, Annabell; Feike, Patrick; Firmowski, Sebastian; Beuermann, Thomas; Methner, Frank-Jürgen; Kränzlin, Bettina; Gretz, Norbert; Rädle, Matthias

2017-07-01

In this report, a quantitative nicotinamide adenine dinucleotide hydrate (NADH) fluorescence measurement algorithm in a liquid tissue phantom using a fiber-optic needle probe is presented. To determine the absolute concentrations of NADH in this phantom, the fluorescence emission spectra at 465 nm were corrected using diffuse reflectance spectroscopy between 600 nm and 940 nm. The patented autoclavable Nitinol needle probe enables the acquisition of multispectral backscattering measurements of ultraviolet, visible, near-infrared and fluorescence spectra. As a phantom, a suspension of calcium carbonate (Calcilit) and water with physiological NADH concentrations between 0 mmol l-1 and 2.0 mmol l-1 were used to mimic human tissue. The light scattering characteristics were adjusted to match the backscattering attributes of human skin by modifying the concentration of Calcilit. To correct the scattering effects caused by the matrices of the samples, an algorithm based on the backscattered remission spectrum was employed to compensate the influence of multiscattering on the optical pathway through the dispersed phase. The monitored backscattered visible light was used to correct the fluorescence spectra and thereby to determine the true NADH concentrations at unknown Calcilit concentrations. Despite the simplicity of the presented algorithm, the root-mean-square error of prediction (RMSEP) was 0.093 mmol l-1.

Effect of Systematic Control of Pd Thickness and Annealing Temperature on the Fabrication and Evolution of Palladium Nanostructures on Si (111) via the Solid State Dewetting.

PubMed

Kunwar, Sundar; Pandey, Puran; Sui, Mao; Zhang, Quanzhen; Li, Ming-Yu; Lee, Jihoon

2017-12-01

Si-based optoelectronic devices embedded with metallic nanoparticles (NPs) have demonstrated the NP shape, size, spacing, and crystallinity dependent on light absorption and emission induced by the localized surface plasmon resonance. In this work, we demonstrate various sizes and configurations of palladium (Pd) nanostructures on Si (111) by the systematic thermal annealing with the variation of Pd thickness and annealing temperature. The evolution of Pd nanostructures are systematically controlled by the dewetting of thin film by means of the surface diffusion in conjunction with the surface and interface energy minimization and Volmer-Weber growth model. Depending on the control of deposition amount ranging between 0.5 and 100 nm at various annealing temperatures, four distinctive regimes of Pd nanostructures are demonstrated: (i) small pits and grain formation, (ii) nucleation and growth of NPs, (iii) lateral evolution of NPs, and (iv) merged nanostructures. In addition, by the control of annealing between 300 and 800 °C, the Pd nanostructures show the evolution of small pits and grains, isolated NPs, and finally, Pd NP-assisted nanohole formation along with the Si decomposition and Pd-Si inter-diffusion. The Raman analysis showed the discrepancies on phonon modes of Si (111) such that the decreased peak intensity with left shift after the fabrication of Pd nanostructures. Furthermore, the UV-VIS-NIR reflectance spectra revealed the existence of surface morphology dependent on absorption, scattering, and reflectance properties.

Effect of Systematic Control of Pd Thickness and Annealing Temperature on the Fabrication and Evolution of Palladium Nanostructures on Si (111) via the Solid State Dewetting

NASA Astrophysics Data System (ADS)

Kunwar, Sundar; Pandey, Puran; Sui, Mao; Zhang, Quanzhen; Li, Ming-Yu; Lee, Jihoon

2017-05-01

Si-based optoelectronic devices embedded with metallic nanoparticles (NPs) have demonstrated the NP shape, size, spacing, and crystallinity dependent on light absorption and emission induced by the localized surface plasmon resonance. In this work, we demonstrate various sizes and configurations of palladium (Pd) nanostructures on Si (111) by the systematic thermal annealing with the variation of Pd thickness and annealing temperature. The evolution of Pd nanostructures are systematically controlled by the dewetting of thin film by means of the surface diffusion in conjunction with the surface and interface energy minimization and Volmer-Weber growth model. Depending on the control of deposition amount ranging between 0.5 and 100 nm at various annealing temperatures, four distinctive regimes of Pd nanostructures are demonstrated: (i) small pits and grain formation, (ii) nucleation and growth of NPs, (iii) lateral evolution of NPs, and (iv) merged nanostructures. In addition, by the control of annealing between 300 and 800 °C, the Pd nanostructures show the evolution of small pits and grains, isolated NPs, and finally, Pd NP-assisted nanohole formation along with the Si decomposition and Pd-Si inter-diffusion. The Raman analysis showed the discrepancies on phonon modes of Si (111) such that the decreased peak intensity with left shift after the fabrication of Pd nanostructures. Furthermore, the UV-VIS-NIR reflectance spectra revealed the existence of surface morphology dependent on absorption, scattering, and reflectance properties.

Direct and simultaneous quantification of tannin mean degree of polymerization and percentage of galloylation in grape seeds using diffuse reflectance fourier transform-infrared spectroscopy.

PubMed

Pappas, Christos; Kyraleou, Maria; Voskidi, Eleni; Kotseridis, Yorgos; Taranilis, Petros A; Kallithraka, Stamatina

2015-02-01

The direct and simultaneous quantitative determination of the mean degree of polymerization (mDP) and the degree of galloylation (%G) in grape seeds were quantified using diffuse reflectance infrared Fourier transform spectroscopy and partial least squares (PLS). The results were compared with those obtained using the conventional analysis employing phloroglucinolysis as pretreatment followed by high performance liquid chromatography-UV and mass spectrometry detection. Infrared spectra were recorded in solid state samples after freeze drying. The 2nd derivative of the 1832 to 1416 and 918 to 739 cm(-1) spectral regions for the quantification of mDP, the 2nd derivative of the 1813 to 607 cm(-1) spectral region for the degree of %G determination and PLS regression were used. The determination coefficients (R(2) ) of mDP and %G were 0.99 and 0.98, respectively. The corresponding values of the root-mean-square error of calibration were found 0.506 and 0.692, the root-mean-square error of cross validation 0.811 and 0.921, and the root-mean-square error of prediction 0.612 and 0.801. The proposed method in comparison with the conventional method is simpler, less time consuming, more economical, and requires reduced quantities of chemical reagents and fewer sample pretreatment steps. It could be a starting point for the design of more specific models according to the requirements of the wineries. © 2015 Institute of Food Technologists®

Rapid identification of oil-contaminated soils using visible near-infrared diffuse reflectance spectroscopy.

PubMed

Chakraborty, Somsubhra; Weindorf, David C; Morgan, Cristine L S; Ge, Yufeng; Galbraith, John M; Li, Bin; Kahlon, Charanjit S

2010-01-01

In the United States, petroleum extraction, refinement, and transportation present countless opportunities for spillage mishaps. A method for rapid field appraisal and mapping of petroleum hydrocarbon-contaminated soils for environmental cleanup purposes would be useful. Visible near-infrared (VisNIR, 350-2500 nm) diffuse reflectance spectroscopy (DRS) is a rapid, nondestructive, proximal-sensing technique that has proven adept at quantifying soil properties in situ. The objective of this study was to determine the prediction accuracy of VisNIR DRS in quantifying petroleum hydrocarbons in contaminated soils. Forty-six soil samples (including both contaminated and reference samples) were collected from six different parishes in Louisiana. Each soil sample was scanned using VisNIR DRS at three combinations of moisture content and pretreatment: (i) field-moist intact aggregates, (ii) air-dried intact aggregates, (iii) and air-dried ground soil (sieved through a 2-mm sieve). The VisNIR spectra of soil samples were used to predict total petroleum hydrocarbon (TPH) content in the soil using partial least squares (PLS) regression and boosted regression tree (BRT) models. Each model was validated with 30% of the samples that were randomly selected and not used in the calibration model. The field-moist intact scan proved best for predicting TPH content with a validation r2 of 0.64 and relative percent difference (RPD) of 1.70. Because VisNIR DRS was promising for rapidly predicting soil petroleum hydrocarbon content, future research is warranted to evaluate the methodology for identifying petroleum contaminated soils.

Single-molecule spectroscopy unmasks the lowest exciton state of the B850 assembly in LH2 from Rps. acidophila.

PubMed

Kunz, Ralf; Timpmann, Kõu; Southall, June; Cogdell, Richard J; Freiberg, Arvi; Köhler, Jürgen

2014-05-06

We have recorded fluorescence-excitation and emission spectra from single LH2 complexes from Rhodopseudomonas (Rps.) acidophila. Both types of spectra show strong temporal spectral fluctuations that can be visualized as spectral diffusion plots. Comparison of the excitation and emission spectra reveals that for most of the complexes the lowest exciton transition is not observable in the excitation spectra due to the cutoff of the detection filter characteristics. However, from the spectral diffusion plots we have the full spectral and temporal information at hand and can select those complexes for which the excitation spectra are complete. Correlating the red most spectral feature of the excitation spectrum with the blue most spectral feature of the emission spectrum allows an unambiguous assignment of the lowest exciton state. Hence, application of fluorescence-excitation and emission spectroscopy on the same individual LH2 complex allows us to decipher spectral subtleties that are usually hidden in traditional ensemble spectroscopy. Copyright © 2014 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Numerical models for the diffuse ionized gas in galaxies. I. Synthetic spectra of thermally excited gas with turbulent magnetic reconnection as energy source

NASA Astrophysics Data System (ADS)

Hoffmann, T. L.; Lieb, S.; Pauldrach, A. W. A.; Lesch, H.; Hultzsch, P. J. N.; Birk, G. T.

2012-08-01

Aims: The aim of this work is to verify whether turbulent magnetic reconnection can provide the additional energy input required to explain the up to now only poorly understood ionization mechanism of the diffuse ionized gas (DIG) in galaxies and its observed emission line spectra. Methods: We use a detailed non-LTE radiative transfer code that does not make use of the usual restrictive gaseous nebula approximations to compute synthetic spectra for gas at low densities. Excitation of the gas is via an additional heating term in the energy balance as well as by photoionization. Numerical values for this heating term are derived from three-dimensional resistive magnetohydrodynamic two-fluid plasma-neutral-gas simulations to compute energy dissipation rates for the DIG under typical conditions. Results: Our simulations show that magnetic reconnection can liberate enough energy to by itself fully or partially ionize the gas. However, synthetic spectra from purely thermally excited gas are incompatible with the observed spectra; a photoionization source must additionally be present to establish the correct (observed) ionization balance in the gas.

Theoretical Study of the Electronic Spectra of a Polycyclic Aromatic Hydrocarbon, Naphthalene, and its Derivatives

NASA Technical Reports Server (NTRS)

Du, Ping; Salama, Farid; Loew, Gilda H.

1993-01-01

In order to preselect possible candidates for the origin of diffuse interstellar bands observed, semiempirical quantum mechanical method INDO/S was applied to the optical spectra of neutral, cationic, and anionic states of naphthalene and its hydrogen abstraction and addition derivatives. Comparison with experiment shows that the spectra of naphthalene and its ions were reliably predicted. The configuration interaction calculations with single-electron excitations provided reasonable excited state wavefunctions compared to ab initio calculations that included higher excitations. The degree of similarity of the predicted spectra of the hydrogen abstraction and derivatives to those of naphthalene and ions depends largely on the similarity of the it electron configurations. For the hydrogen addition derivatives, very little resemblance of the predicted spectra to naphthalene was found because of the disruption of the aromatic conjugation system. The relevance of these calculations to astrophysical issues is discussed within the context of these polycyclic aromatic hydrocarbon models. Comparing the calculated electronic energies to the Diffuse Interstellar Bands (DIBs), a list of possible candidates of naphthalene derivatives is established which provides selected candidates for a definitive test through laboratory studies.

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 ...

Online spectral fit tool (OSFT) for analyzing reflectance spectra

NASA Astrophysics Data System (ADS)

Penttilä, A.; Kohout, T.; Muinonen, K.

2015-10-01

We present an algorithm and its implementation for fitting continuum and absorption bands to UV/VIS/NIR reflectance spectra. The implementation is done completely in JavaScript and HTML, and will run in any modern web browser without requiring external libraries to be installed.

Remote sensing reflectance simulation of coastal optical complex water in the East China Sea

NASA Astrophysics Data System (ADS)

He, Shuo; Lou, Xiulin; Zhang, Huaguo; Zheng, Gang

2018-02-01

In this work, remote sensing reflectance (Rrs) spectra of the Zhejiang coastal water in the East China Sea (ECS) were simulated by using the Hydrolight software with field data as input parameters. The seawater along the Zhejiang coast is typical Case II water with complex optical properties. A field observation was conducted in the Zhejiang coastal region in late May of 2016, and the concentration of ocean color constituents (pigment, SPM and CDOM), IOPs (absorption and backscattering coefficients) and Rrs were measured at 24 stations of 3 sections covering the turbid to clear inshore coastal waters. Referring to these ocean color field data, an ocean color model suitable for the Zhejiang coastal water was setup and applied in the Hydrolight. A set of 11 remote sensing reflectance spectra above water surface were modeled and calculated. Then, the simulated spectra were compared with the filed measurements. Finally, the spectral shape and characteristics of the remote sensing reflectance spectra were analyzed and discussed.

Far-UV, visible, and near-IR reflectance spectra of frosts of H2O, CO2, NH3 and SO2

NASA Technical Reports Server (NTRS)

Hapke, B.; Wells, E.; Wagner, J.; Partlow, W.

1981-01-01

Measurements in the 0.1-2.5 micron range are presented for the reflectance spectra of the frosts of several volatiles pertinent to the study of comet nuclei. The frost spectra have distinctive features permitting their identification by spectroscopic reflectance remote sensing, notably in the far UV. It is found that: (1) H2O has a minimum at 0.16 microns and a maximum at 0.13 microns; (2) CO2 has minima near 0.21, 0.18 and 0.125 microns, with maxima at 0.19, 0.135 and 0.120 microns; (3) NH3 is bright at wavelengths longer than 0.21 microns, where reflectance drops to a value of only a few per cent at shorter wavelengths; (4) SO2 has a sharp drop at 0.32 microns, with a minimum at 0.18 microns and a maximum at 0.13 microns. The features in the frost spectra largely correspond to absorption line bands in the gas phase.

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.

Non-Markovian Quantum State Diffusion for temperature-dependent linear spectra of light harvesting aggregates

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

Ritschel, Gerhard; Möbius, Sebastian; Eisfeld, Alexander, E-mail: eisfeld@mpipks-dresden.mpg.de

2015-01-21

Non-Markovian Quantum State Diffusion (NMQSD) has turned out to be an efficient method to calculate excitonic properties of aggregates composed of organic chromophores, taking into account the coupling of electronic transitions to vibrational modes of the chromophores. NMQSD is an open quantum system approach that incorporates environmental degrees of freedom (the vibrations in our case) in a stochastic way. We show in this paper that for linear optical spectra (absorption, circular dichroism), no stochastics is needed, even for finite temperatures. Thus, the spectra can be obtained by propagating a single trajectory. To this end, we map a finite temperature environmentmore » to the zero temperature case using the so-called thermofield method. The resulting equations can then be solved efficiently by standard integrators.« less

Laboratory upwelled radiance and reflectance spectra of Kerr reservoir sediment waters

NASA Technical Reports Server (NTRS)

Witte, W. G.; Whitlock, C. H.; Morris, W. D.; Gurganus, E. A.

1982-01-01

Reflectance, chromaticity, and several other physical and chemical properties were measured for various water mixtures of bottom sediments taken from two sites at Kerr Reservoir, Virginia. Mixture concentrations ranged from 5 to 1000 ppm by weight of total suspended solids (TSS) in filtered deionized tap water. The two sets of radiance and reflectance spectra obtained were similar in shape and magnitude for comparable values of TSS. Upwelled reflectance was observed to be a nonlinear function of TSS with the degree of curvature a function of wavelength. Sediment from the downstream site contained a greater amount of particulate organic carbon than from the upstream site. No strong conclusions can be made regarding the effects of this difference on the radiance and reflectance spectra. Near-infrared wavelengths appear useful for measuring highly turbid water with concentrations up to 1000 ppm or more. Chromaticity characteristics do not appear useful for monitoring sediment loads above 150 ppm.

Hyperspectral optical imaging of two different species of lepidoptera

PubMed Central

2011-01-01

In this article, we report a hyperspectral optical imaging application for measurement of the reflectance spectra of photonic structures that produce structural colors with high spatial resolution. The measurement of the spectral reflectance function is exemplified in the butterfly wings of two different species of Lepidoptera: the blue iridescence reflected by the nymphalid Morpho didius and the green iridescence of the papilionid Papilio palinurus. Color coordinates from reflectance spectra were calculated taking into account human spectral sensitivity. For each butterfly wing, the observed color is described by a characteristic color map in the chromaticity diagram and spreads over a limited volume in the color space. The results suggest that variability in the reflectance spectra is correlated with different random arrangements in the spatial distribution of the scales that cover the wing membranes. Hyperspectral optical imaging opens new ways for the non-invasive study and classification of different forms of irregularity in structural colors. PMID:21711872

Multicolor observations of phobos with the viking lander cameras: evidence for a carbonaceous chondritic composition.

PubMed

Pollack, J B; Veverka, J; Pang, K; Colburn, D; Lane, A L; Ajello, J M

1978-01-06

The reflectivity of Phobos has been determined in the spectral region from 0.4 to 1.1 micrometers from images taken with a Viking lander camera. The reflectivity curve is flat in this spectral interval and the geometric albedo equals 0.05 +/- 0.01. These results, together with Phobos's reflectivity spectrum in the ultraviolet, are compared with laboratory spectra of carbonaceous chondrites and basalts. The spectra of carbonaceous chondrites are consistent with the observations, whereas the basalt spectra are not. These findings raise the possibility that Phobos may be a captured object rather than a natural satellite of Mars.

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.

Comparison of visible and near-infrared reflectance spectra of CM2 carbonaceous chondrites and primitive asteroids

NASA Technical Reports Server (NTRS)

Vilas, F.; Hiroi, T.; Zolensky, M. E.

1993-01-01

Spectra of primitive asteroids (defined as C, P, and D classes and associated subclasses) were compared to the limited number of spectra of CM2 carbonaceous chondrites. An absorption feature located at 0.7 microns attributed to an Fe(+2) - Fe(+3) charge transfer absorption in iron oxides in phyllosilicates is apparent in some of the CM2 carbonaceous chondrite spectra and many of the asteroid spectra. Sawyer found a correlation between the area of the 0.7 micron feature and the mean semimajor axis of the asteroids. Spectra of a larger sample of carbonaceous chondrites, including 7 CM2 chondrites, covering a spectral interval of 0.30-2.5 microns were recently obtained using the Relab instrument at Brown University. These spectra were compared with spectrophotometric asteroid observations in a separate abstract. Those spectra of CM2 chondrites were isolated into the UV, visible and near-infrared spectral regions in order to compare them with high-quality narrowband reflectance spectra.

Leaf color is fine-tuned on the solar spectra to avoid strand direct solar radiation.

PubMed

Kume, Atsushi; Akitsu, Tomoko; Nasahara, Kenlo Nishida

2016-07-01

The spectral distributions of light absorption rates by intact leaves are notably different from the incident solar radiation spectra, for reasons that remain elusive. Incident global radiation comprises two main components; direct radiation from the direction of the sun, and diffuse radiation, which is sunlight scattered by molecules, aerosols and clouds. Both irradiance and photon flux density spectra differ between direct and diffuse radiation in their magnitude and profile. However, most research has assumed that the spectra of photosynthetically active radiation (PAR) can be averaged, without considering the radiation classes. We used paired spectroradiometers to sample direct and diffuse solar radiation, and obtained relationships between the PAR spectra and the absorption spectra of photosynthetic pigments and organs. As monomers in solvent, the spectral absorbance of Chl a decreased with the increased spectral irradiance (W m(-2) nm(-1)) of global PAR at noon (R(2) = 0.76), and was suitable to avoid strong spectral irradiance (λmax = 480 nm) rather than absorb photon flux density (μmol m(-2) s(-1) nm(-1)) efficiently. The spectral absorption of photosystems and the intact thallus and leaves decreased linearly with the increased spectral irradiance of direct PAR at noon (I dir-max), where the wavelength was within the 450-650 nm range (R(2) = 0.81). The higher-order structure of photosystems systematically avoided the strong spectral irradiance of I dir-max. However, when whole leaves were considered, leaf anatomical structure and light scattering in leaf tissues made the leaves grey bodies for PAR and enabled high PAR use efficiency. Terrestrial green plants are fine-tuned to spectral dynamics of incident solar radiation and PAR absorption is increased in various structural hierarchies.

Millimeter and submillimeter spectra of hot cores and diffuse clouds: comparing IRAM and Herschel spectra with CASSIS simulations.

NASA Astrophysics Data System (ADS)

de Luca, Massimo

The primary goal of the PRISMAS Herschel key program is the spectroscopic study of key molecular lines towards bright Galactic star-forming regions and the diffuse interstellar clouds distributed along the lines of sight. Models of the source emission and absorption spectra have been constructed with CASSIS, based on 1) observational evidence in comparable environments, 2) warm-up chemical models with gas-grain networks, and 3) ground-based spectra of various molecules in the target sources obtained at the IRAM 30m telescope. These models include contributions from the hot core, its parental molecular cloud and the foreground diffuse inter-stellar matter. The considerable complexity of the hot core chemistry, together with the huge amount of information buried in the spectra, often prevents a straightforward interpretation of the data without the help simulations. This is particularly true for the largely unexplored wavelength range of HIFI. In this contribution, we compare HIFI and IRAM observations to our models, in order to either consolidate present day assumptions and knowledge of these environments, or to highlight the model limitations, poorly understood physical and chemical conditions or unexpected abundances. We pay particular attention to the ground state tran-sitions of the most important hydrides, which the PRISMAS program has been designed for, though the HIFI spectra are expected to be rich in other molecules as well. List of Authors De Luca, M., Observatoire de Paris, Ecole Normale Supérieure and CNRS, FRANCE; Bell, T., CalTech, UNITED STATES; Coutens, A., CESR, FRANCE; Godard, B., IAS, FRANCE; Gupta, H., JPL, UNITED STATES; Mook-erjea, B., Tata Institute for Fundamental Research, INDIA; and the PRISMAS consortium, PRISMAS, FRANCE

Analysis of bacteria on steel surfaces using reflectance micro-Fourier transform infrared spectroscopy.

PubMed

Ojeda, Jesús J; Romero-González, María E; Banwart, Steven A

2009-08-01

Reflectance micro-Fourier transform infrared (FT-IR) analysis has been applied to characterize biofilm formation of Aquabacterium commune, a common microorganism present on drinking water distribution systems, onto the increasingly popular pipe material stainless steel EN1.4307. The applicability of the reflectance micro-FT-IR technique for analyzing the bacterial functional groups is discussed, and the results are compared to spectra obtained using more conventional FT-IR techniques: transmission micro-FT-IR, attenuated transmitted reflectance (ATR), and KBr pellets. The differences between the infrared spectra of wet and dried bacteria, as well as free versus attached bacteria, are also discussed. The spectra obtained using reflectance micro-FT-IR spectroscopy were comparable to those obtained using other FT-IR techniques. The absence of sample preparation, the potential to analyze intact samples, and the ability to characterize opaque and thick samples without the need to transfer the bacterial samples to an infrared transparent medium or produce a pure culture were the main advantages of reflectance micro-FT-IR spectroscopy.

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