WorldWideScience
 
 
1

A New and Inexpensive Pyranometer for the Visible Spectral Range  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper presents the design, construction and testing of a new photodiode-based pyranometer for the visible spectral range (approx. 400 to 750 nm), whose principal characteristics are: accuracy, ease of connection, immunity to noise, remote programming and operation, interior temperature regulati...

Miguel A. Martínez; José M. Andújar; Juan M. Enrique

2

Progress in gaseous photomultipliers for the visible spectral range  

International Nuclear Information System (INIS)

Recent progress is described in gaseous photon detectors combining bialkali photocathodes and cascaded patterned gas-avalanche electron multipliers. Efficient avalanche-ion blocking permitted the development and feasibility demonstration of high-gain operation in continuous mode, of gaseous photomultipliers sensitive to single photons in the visible spectral range.

2010-11-01

3

A New and Inexpensive Pyranometer for the Visible Spectral Range  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents the design, construction and testing of a new photodiode-based pyranometer for the visible spectral range (approx. 400 to 750 nm), whose principal characteristics are: accuracy, ease of connection, immunity to noise, remote programming and operation, interior temperature regulation, cosine error minimisation and all this at a very low cost, tens of times lower than that of commercial thermopile-based devices. This new photodiode-based pyranometer overcomes traditional problems in this type of device and offers similar characteristics to those of thermopile-based pyranometers and, therefore, can be used in any installation where reliable measurement of solar irradiance is necessary, especially in those where cost is a deciding factor in the choice of a meter. This new pyranometer has been registered in the Spanish Patent and Trademark Office under the number P200703162.

Miguel A. Martínez; José M. Andújar; Juan M. Enrique

2009-01-01

4

A new and inexpensive pyranometer for the visible spectral range.  

Science.gov (United States)

This paper presents the design, construction and testing of a new photodiode-based pyranometer for the visible spectral range (approx. 400 to 750 nm), whose principal characteristics are: accuracy, ease of connection, immunity to noise, remote programming and operation, interior temperature regulation, cosine error minimisation and all this at a very low cost, tens of times lower than that of commercial thermopile-based devices. This new photodiode-based pyranometer overcomes traditional problems in this type of device and offers similar characteristics to those of thermopile-based pyranometers and, therefore, can be used in any installation where reliable measurement of solar irradiance is necessary, especially in those where cost is a deciding factor in the choice of a meter. This new pyranometer has been registered in the Spanish Patent and Trademark Office under the number P200703162. PMID:22408545

Martínez, Miguel A; Andújar, José M; Enrique, Juan M

2009-06-12

5

A new and inexpensive pyranometer for the visible spectral range.  

UK PubMed Central (United Kingdom)

This paper presents the design, construction and testing of a new photodiode-based pyranometer for the visible spectral range (approx. 400 to 750 nm), whose principal characteristics are: accuracy, ease of connection, immunity to noise, remote programming and operation, interior temperature regulation, cosine error minimisation and all this at a very low cost, tens of times lower than that of commercial thermopile-based devices. This new photodiode-based pyranometer overcomes traditional problems in this type of device and offers similar characteristics to those of thermopile-based pyranometers and, therefore, can be used in any installation where reliable measurement of solar irradiance is necessary, especially in those where cost is a deciding factor in the choice of a meter. This new pyranometer has been registered in the Spanish Patent and Trademark Office under the number P200703162.

Martínez MA; Andújar JM; Enrique JM

2009-01-01

6

High-gain DC-mode operated Gaseous Photomultipliers for the visible spectral range  

CERN Document Server

We shortly describe recent progress in photon detectors combining bi-alkali photocathodes and cascaded patterned gas-avalanche electron multipliers. It permitted the development and the first feasibility demonstration of high-gain gaseous photomultipliers sensitive in the visible spectral range, operated in DC mode with single-photon sensitivity.

Lyashenko, A; Chechik, R; Amaro, F D; Veloso, J; Santos, J M F Dos

2008-01-01

7

High-gain continuous-mode operated gaseous photomultipliers for the visible spectral range  

International Nuclear Information System (INIS)

We shortly describe recent progress in photon detectors combining bi-alkali photocathodes and cascaded patterned gas-avalanche electron multipliers. It permitted the development and the first feasibility demonstration of high-gain gaseous photomultipliers sensitive in the visible spectral range, operated in continuous-mode with single-photon sensitivity.

2009-10-21

8

Spectroscopy of fullerenes, fulleranes and PAHs in the UV, visible and near infrared spectral range  

CERN Document Server

The spectra of fullerenes C60 and C70, higher fullerenes C76, C78 and C84 and hydrogenated fullerenes (fulleranes) were studied in laboratory in the UV and in the visible spectral range and could be used for searching and recognizing these molecules in space. Furthermore, the radical cation spectra of all the mentioned fullerene series and also of a series of large and very large polycyclic aromatic hydrocarbons (PAHs) were generated in laboratory and studied in the near infrared spectral range.

Cataldo, F; Manchado, A; Iglesias-Groth, S

2013-01-01

9

Thermo-optical response of photonic crystal cavities operating in the visible spectral range.  

UK PubMed Central (United Kingdom)

In this paper we study thermo-optical effects in gallium phosphite photonic crystal cavities in the visible range. By measuring the shift of narrow resonances, we derive the temperature dependency of the local refractive index of gallium phosphide in an attoliter volume over a temperature range between 5 and 300 K at a wavelength of about 605 nm. Additionally, the potential of photonic crystal cavities for thermo-optical switching of visible light is investigated. As an example we demonstrate thermo-optical switching with 13 dB contrast.

Wolters J; Nikolay N; Schoengen M; Schell AW; Probst J; Löchel B; Benson O

2013-08-01

10

Investigation of silicon nitride based two-dimensional photonic crystals for the visible spectral range  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The main topics of this thesis included the fabrication and experimental investigation of silicon nitride based 2D photonic crystals in the visible range of the electromagnetic spectrum. For this purpose, a fabrication process capable of patterning silicon nitride with an ultimate resolution of 25 n...

Kouba, Josef

11

Development of high-gain gaseous photomultipliers for the visible spectral range  

CERN Document Server

We summarize the development of visible-sensitive gaseous photomultipliers, combining a semitransparent bi-alkali photocathode with a state-of-the-art cascaded electron multiplier. The latter has high photoelectron collection efficiency and a record ion blocking capability. We describe in details the system and methods of photocathode production and characterization, their coupling with the electron multiplier and the gaseous-photomultiplier operation and characterization in a continuous mode. We present results on the properties of laboratory-produced K$_2$CsSb, Cs$_3$Sb and Na$_2$KSb photocathodes and report on their stability and QE in gas; K$_2$CsSb photocathodes yielded QE values in Ar/CH$_4$(95/5) above 30% at wavelengths of 360-400 nm. The novel gaseous photomultiplier yielded stable operation at gains of 10$^5$, in continuous operation mode, in 700 Torr of this gas; its sensitivity to single photons was demonstrated. Other properties are described. The successful detection of visible light with this g...

Lyashenko, A V; Chechik, R; Santos, J M F Dos; Amaro, F D; Veloso, J F C A

2009-01-01

12

Optical Characterization of Organic Light-Emitting Thin Films in the Ultraviolet and Visible Spectral Ranges  

CERN Document Server

The spectrophotometric characterization of high efficiency, optically-active samples such as light-emitting organic bulks and thin films can be problematic because their broad-band luminescence is detected together with the monochromatic transmitted and reflected signals, hence perturbing measurements of optical transmittance and reflectance at wavelengths within the photoexcitation band. As a matter of fact, most commercial spectrophotometers apply spectral filtering before the light beam reaches the sample, not after it. In this Report, we introduce and discuss the method we have developed to correct photometric spectra that are perturbed by photoluminescence.

Montereali, R M; Nichelatti, E; Di Pompeo, F; Segreto, E; Canci, N; Cavanna, F

2012-01-01

13

Analysis of global water vapour trends from satellite measurements in the visible spectral range  

Directory of Open Access Journals (Sweden)

Full Text Available Global water vapour total column amounts have been retrieved from spectral data provided by the Global Ozone Monitoring Experiment (GOME) flying on ERS-2, which was launched in April 1995, and the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) onboard ENVISAT launched in March 2002. For this purpose the Air Mass Corrected Differential Optical Absorption Spectroscopy (AMC-DOAS) approach has been used. The combination of the data from both instruments provides us with a long-term global data set spanning more than 11 years with the potential of extension up to 2020 by GOME-2 data, on Metop. Using linear and non-linear methods from time series analysis and standard statistics the trends of H2O contents and their errors have been calculated. In this study, factors affecting the trend such as the length of the time series, the magnitude of the variability of the noise, and the autocorrelation of the noise are investigated. Special emphasis has been placed on the calculation of the statistical significance of the observed trends, which reveal significant local changes of water vapour columns distributed over the whole globe.

S. Mieruch; S. Noël; H. Bovensmann; J. P. Burrows

2007-01-01

14

Analysis of global water vapour trends from satellite measurements in the visible spectral range  

Directory of Open Access Journals (Sweden)

Full Text Available Global water vapour total column amounts have been retrieved from spectral data provided by the Global Ozone Monitoring Experiment (GOME) flying on ERS-2, which was launched in April 1995, and the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) onboard ENVISAT launched in March 2002. For this purpose the Air Mass Corrected Differential Optical Absorption Spectroscopy (AMC-DOAS) approach has been used. The combination of the data from both instruments provides us with a long-term global data set spanning more than 11 years with the potential of extension up to 2020 by GOME-2 data on MetOp. Using linear and non-linear methods from time series analysis and standard statistics the trends of H2O columns and their errors have been calculated. In this study, factors affecting the trend such as the length of the time series, the magnitude of the variability of the noise, and the autocorrelation of the noise are investigated. Special emphasis has been placed on the calculation of the statistical significance of the observed trends, which reveal significant local changes from ?5% per year to +5% per year. These significant trends are distributed over the whole globe. Increasing trends have been calculated for Greenland, East Europe, Siberia and Oceania, whereas decreasing trends have been observed for the northwest USA, Central America, Amazonia, Central Africa and the Arabian Peninsular.

S. Mieruch; S. Noël; H. Bovensmann; J. P. Burrows

2008-01-01

15

Radiative transfer model STORM for full Stokes vector calculations in the visible and near infrared spectral range  

Directory of Open Access Journals (Sweden)

Full Text Available Based on the Matrix-Operator Method the radiative transfer code STORM (STOkes vector Radiative transfer Model) is introduced, which was developed in a joint project of DLR and Institut f{ü}r Weltraumwissenschaften-Freie Universität Berlin. STORM calculates the Stokes parameters (I, Q, U, V) in a plane parallel, multi layered atmosphere in the visible and near infrared spectral range. The scattering characteristics of aerosols are determined by Mie theory. The surface represents a Lambertian reflector or a wind ruffled water surface described by Cox-Munk model. The results of one calculation are the upward and downward directed Stokes parameters for one wavelength at a desired number of sun incident and viewing angles at varying altitudes in the principal plane and other azimuth angles. STORM is applied for an analysis in view of designing downward looking Earth observing optical remote sensing systems and values of the degree of polarization are presented as generic basis for remote sensing system design and data processing.

U. Böttger; R. Preusker

2006-01-01

16

Absorption spectroscopy and multi-angle scattering measurements in the visible spectral range for the geographic classification of Italian exravirgin olive oils  

Science.gov (United States)

Absorption spectroscopy and multi-angle scattering measurements in the visible spectral range are innovately used to analyze samples of extra virgin olive oils coming from selected areas of Tuscany, a famous Italian region for the production of extra virgin olive oil. The measured spectra are processed by means of the Principal Component Analysis method, so as to create a 3D map capable of clustering the Tuscan oils within the wider area of Italian extra virgin olive oils.

Mignani, Anna G.; Ciaccheri, Leonardo; Cimato, Antonio; Sani, Graziano; Smith, Peter R.

2004-03-01

17

An Impurity Emission Survey in the near UV and Visible Spectral Ranges of Electron Cyclotron Heated (ECH) Plasma in the TJ-II Stellarator  

International Nuclear Information System (INIS)

[en] We report on a near-ultraviolet and visible spectroscopic survey (220-600 nm) of electron cyclotron resonance (ECR) heated plasmas created in the TJ-II stellarator, with central electron temperatures up to 2 keV and central electron densities up to 1.7 x 10 ''19 m''-3. Approximately 1200 lines from thirteen elements have been identified. The purpose of the work is to identify the principal impurities and spectral lines present in TJ-II plasmas, as well as their possible origin to search for transitions from highly ionised ions. This work will act as a base for identifying suitable transitions for following the evolution of impurities under different operating regimens and multiplet systems for line polarisation studies. It is intended to use the database creates as a spectral line reference for comparing spectra under different operating and plasma heating regimes. (Author)

2001-01-01

18

Tunable acousto-optic spectral imager for atmospheric composition measurements in the visible spectral domain.  

Science.gov (United States)

We describe a new spectral imaging instrument using a TeO(2) acousto-optical tunable filter (AOTF) operating in the visible domain (450-900 nm). It allows for fast (~1 second), monochromatic (FWHM ranges from 0.6 nm at 450 nm to 3.5 nm at 800 nm) picture acquisition with good spatial resolution. This instrument was designed as a breadboard of the visible channel of a new satellite-borne atmospheric limb spectral imager, named the Atmospheric Limb Tracker for the Investigation of the Upcoming Stratosphere (ALTIUS), that is currently being developed. We tested its remote sensing capabilities by observing the dense, turbulent plume exhausted by a waste incinerator stack at two wavelengths sensitive to NO(2). An average value of 6.0±0.4×10(17) molecules cm(-2) has been obtained for the NO(2) slant column density within the plume, close to the stack outlet. Although this result was obtained with a rather low accuracy, it demonstrates the potential of spectral imaging by using AOTFs in remote sensing. PMID:22945175

Dekemper, Emmanuel; Loodts, Nicolas; Van Opstal, Bert; Maes, Jeroen; Vanhellemont, Filip; Mateshvili, Nina; Franssens, Ghislain; Pieroux, Didier; Bingen, Christine; Robert, Charles; De Vos, Lieve; Aballea, Ludovic; Fussen, Didier

2012-09-01

19

Tunable acousto-optic spectral imager for atmospheric composition measurements in the visible spectral domain.  

UK PubMed Central (United Kingdom)

We describe a new spectral imaging instrument using a TeO(2) acousto-optical tunable filter (AOTF) operating in the visible domain (450-900 nm). It allows for fast (~1 second), monochromatic (FWHM ranges from 0.6 nm at 450 nm to 3.5 nm at 800 nm) picture acquisition with good spatial resolution. This instrument was designed as a breadboard of the visible channel of a new satellite-borne atmospheric limb spectral imager, named the Atmospheric Limb Tracker for the Investigation of the Upcoming Stratosphere (ALTIUS), that is currently being developed. We tested its remote sensing capabilities by observing the dense, turbulent plume exhausted by a waste incinerator stack at two wavelengths sensitive to NO(2). An average value of 6.0±0.4×10(17) molecules cm(-2) has been obtained for the NO(2) slant column density within the plume, close to the stack outlet. Although this result was obtained with a rather low accuracy, it demonstrates the potential of spectral imaging by using AOTFs in remote sensing.

Dekemper E; Loodts N; Van Opstal B; Maes J; Vanhellemont F; Mateshvili N; Franssens G; Pieroux D; Bingen C; Robert C; De Vos L; Aballea L; Fussen D

2012-09-01

20

Analysis of visible spectral lines in LHD helium discharge  

Energy Technology Data Exchange (ETDEWEB)

In this study, visible spectral lines in LHD helium discharges are analyzed and it was found that they could be well fitted with gaussian profile. The results reveal a simple mechanism of helium atom recycling. Ion temperatures were also derived from the fitting. A typical value of the ion temperature obtained was about 6 eV. (author)

Wan, B.N. [Institute of Plasma Physics, Chinese Academy of Science, Hefei (China); Goto, M.; Morita, S.

1999-06-01

 
 
 
 
21

Hyper-spectral imager of the visible band for lunar observations  

Science.gov (United States)

A prototype hyper-spectral imager in the visible spectral band was developed for the planned Korean lunar missions in the 2020s. The instrument is based on simple refractive optics that adopted a linear variable filter and an interline charge-coupled device. This prototype imager is capable of mapping the lunar surface at wavelengths ranging from 450 to 900 nm with a spectral resolution of ˜8 nm and selectable channels ranging from 5 to 252. The anticipated spatial resolution is 17.2 m from an altitude of 100 km with a swath width of 21 km

Lim, Y.-M.; Choi, Y.-J.; Jo, Y.-S.; Lim, T.-H.; Ham, J.; Min, K. W.; Choi, Y.-W.

2013-06-01

22

Spectral absorption studies of visible materials. Final report  

Energy Technology Data Exchange (ETDEWEB)

Results of studies of optical absorption in twelve thin-film optical coatings at 482 nm wavelength, surface and bulk absorption in sapphire throughout the visible and near IR, and initial measurements in KDP are described. Laser calorimetry was carried out at room temperature, using an unfocused laser beam at normal incidence. All thin-film absorption data yielded values of P/sub abs//P/sub inc/ in the range 3 x 10 U to 3 x 10 T at a wavelength of 482 nm. Sapphire absorption showed Urbach-tail behavior at 350 nm to 1300 nm. The range of absorption, being far lower than usual, extends the range of application of Urbach's rule. Finally, KDP measurements were attempted, but surface degradation due to the hydroscopic nature of the samples resulted in excessive light scatter.

Bass, M.; Swimm, R.T.

1986-01-01

23

Visible spectra in JT-60U divertor plasma. Wavelength range between 300 nm - 780 nm  

Energy Technology Data Exchange (ETDEWEB)

In JT-60U divertor plasma, spectra in a visible range (300 nm - 780 nm) were measured in order to study impurity behavior. In the spectra, spectral lines from D I, He I-II, B II, C II-IV and O I-III and spectral bands from CD and C{sub 2} molecules were identified. Most of spectral lines from light impurity ions were attributed to transitions without change in the principal quantum number ({Delta}n = 0). Transitions between levels with high azimuthal quantum number were observed in the case of {Delta}n {ne} 0. The spectral bands from C{sub 2} were identified as Swan bands. (author)

Nakano, Tomohide; Kubo, Hirotaka; Sugie, Tatsuo; Higashijima, Satoru; Suzuki, Shingo; Sakasai, Akira; Itami, Kiyoshi [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment

1999-01-01

24

Polarization of AGN in UV Spectral Range  

CERN Document Server

We present the review of some new problems in cosmology and physics of stars in connection with future launching of WSO. We discuss three problems. UV observations of distant z > 6 quasars allow to obtain information on the soft < 1 KeV X-ray radiation of the accretion disk around a supermassive black hole because of its cosmological redshift. Really the region of X-ray radiation is insufficiently investigated because of high galactic absorption. In a result one will get important information on the reionization zone of the Universe. Astronomers from ESO revealed the effect of alignment of electric vectors of polarized QSOs. One of the probable mechanism of such alignment is the conversion of QSO radiation into low mass pseudoscalar particles (axions) in the extragalactic magnetic field. These boson like particles have been predicted by new SUSY particle physics theory. Since the probability of such conversion is increasing namely in UV spectral range one can expect the strong correlation between UV spectr...

Gnedin, Yu N; Natsvlishvili, T M

2011-01-01

25

New fractal structures for frequencies close to the visible range  

DEFF Research Database (Denmark)

In this paper we present a new type of fractal resonator to be used in the red/NIR region of the spectra. The structure presents high-transmission band in 795-825nm range. The stop band is in the 683-731 nm range. Due to the huge difference in the spectra within such a short range, the structure can be used as an efficient sensor, both in transmission as well as in reflection. Thus, a variation of only 0.09 in the refraction index will for example change the structure’s behaviour from 90% reflection to 90% transmission. Such resonances lead to a sensitivity of 780 nm/RIU. Another advantage of this resonator is the independency of the incidence angle - in the spectral re-gion of interest; the incidence angle has very little influence over the response.

Malureanu, Radu; Sandru, A.

2011-01-01

26

The UV-A and visible solar irradiance spectrum: inter-comparison of absolutely calibrated, spectrally medium resolution solar irradiance spectra from balloon- and satellite-borne measurements  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Within the framework of the ENVISAT/-SCIAMACHY satellite validation, solar irradiance spectra are absolutely measured at moderate resolution in the UV/visible spectral range (in the UV from 316.7–418 nm and the visible from 400–652 nm at a full width half maximum resolution of 0.55 nm and 1.48 nm, r...

Gurlit, W.; Bösch, H.; Bovensmann, H.; Burrows, J. P.; Butz, A.; Camy-Peyret, C.; Dorf, M.; Gerilowski, K.; Lindner, A.

27

The UV-A and visible solar irradiance spectrum: inter-comparison of absolutely calibrated, spectrally medium resolution solar irradiance spectra from balloon- and satellite-borne measurements  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Within the framework of the ENVISAT/-SCIAMACHY satellite validation, solar irradiance spectra are absolutely measured at moderate resolution in the UV/visible spectral range (in the UV from 316.7-418 nm and the visible from 400-652 nm at a full width half maximum resolution of 0.55 nm and 1.48 nm, r...

Gurlit, W.; Bösch, H.; Bovensmann, H.; Burrows, J. P.; Butz, A.; Camy-Peyret, C.; Dorf, M.; Gerilowski, K.; Lindner, A.

28

The UV-A and visible solar irradiance spectrum: inter-comparison of absolutely calibrated, spectrally medium resolution solar irradiance spectra from balloon- and satellite-borne measurements  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Within the framework of the ENVISAT/-SCIAMACHY satellite validation, solar irradiance spectra are absolutely measured at moderate resolution in the UV/visible spectral range (in the UV from 316.7–418 nm and the visible from 400–652 nm at a full width half maximum resolution of 0.55 nm an...

W. Gurlit; H. Bösch; H. Bovensmann; J. P. Burrows; A. Butz; C. Camy-Peyret; M. Dorf; K. Gerilowski; A. Lindner; S. Noël

29

Understanding A-type supergiants. I. Ultraviolet and visible spectral atlas of A-type supergiants  

CERN Document Server

This paper is the first of a series whose aim is to perform a systematic study of A-type supergiant atmospheres and winds. Here we present a spectral atlas of 41 A-supergiants observed by us in high and medium resolution in the visible and ultraviolet. The atlas consists of profiles of the H alpha , H beta , H gamma , H delta , H epsilon , Ca II (H and K), Na I (D1 and D2), Mg II/sub 4481/, Mg II uv1 and Fe II uv1, uv2, uv3, uv62, uv63, uv161 lines for 41 stars with spectral types ranging from B9 to A9 and luminosity classes Ia, Iab and Ib, and provides the basic data for a thoughtful study of these stars. The overall characteristics of the sample as well as the data reduction procedures are described. We also present some examples of spectral variability. Figures 1-3 are only available in electronic form at http://www.edpsciences.com. (27 refs).

Verdugo, E; Gómez de Castro, A I

1999-01-01

30

Application of spectral derivative data in visible and near-infrared spectroscopy  

International Nuclear Information System (INIS)

The use of the spectral derivative method in visible and near-infrared optical spectroscopy is presented, whereby instead of using discrete measurements around several wavelengths, the difference between nearest neighbouring spectral measurements is utilized. The proposed technique is shown to be insensitive to the unknown tissue and fibre contact coupling coefficients providing substantially increased accuracy as compared to more conventional techniques. The self-calibrating nature of the spectral derivative techniques increases its robustness for both clinical and industrial applications, as is demonstrated based on simulated results as well as experimental data.

2010-06-21

31

Aurones: small molecule visible range fluorescent probes suitable for biomacromolecules.  

UK PubMed Central (United Kingdom)

Aurones, derivatives of 2-benylidenebenzofuran-3(2H)-one, are natural products that serve as plant pigments. There have been reports that some of these substances fluoresce, but little information about their optical properties is in the literature. In this report, series of aurone derivatives were synthesized as possible fluorescent probes that can be excited by visible light. We found that an amine substituent shifted the lowest energy absorption band from the near-UV to the visible region of the electromagnetic spectrum. Four amine-substituted aurone derivatives were synthesized to explore the effect of this substituent on the absorption and emission properties of the aurone chromophore. The emission maxima and intensities of the molecules are strongly dependent on the nature of the substituent and the solvent polarity. Overall, the emission intensity increases and the maximum wavelength decreases in less polar solvents; thus, the aurones may be useful probes for hydrophobic sites on biological molecules. A limited investigation with model protein, nucleic acid and fixed cells supports this idea. It is known that the sulfur analog of aurone can undergo photo-induced E/Z isomerization. This possibility was investigated for one of the aminoaurones, which was observed to reversible photoisomerize. The two isomers have similar absorption spectra, but the emission properties are distinct. We conclude that appropriately substituted aurones are potentially useful as biological probes and photoswitches.

Shanker N; Dilek O; Mukherjee K; McGee DW; Bane SL

2011-11-01

32

Titan's lower atmosphere haze and methane profile from visible and NIR HST spectral imaging  

Science.gov (United States)

We report high spatial resolution (320 km at the sub-Earth point) and spectral resolution (1 nm) visible/near-infrared observations of Titan taken at Ls=240 in November 2000. These data were obtained with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope through program GO-8580. We utilize 122 wavelengths that span Titan's 0.6 to 1 micron spectral range to address the tropospheric methane abundance, degree of methane supersaturation and haze concentration in Titan's lower stratosphere and troposphere. The contribution functions in the 0.6 to 1 micron range peak at altitudes from 100 km down to a few km above the surface. The 0.619 micron methane feature is of particular interest since it is highly sensitive to the amount of methane and haze, and previous investigators (Tomasko et al. 1997, ESA SP-1177, 345-358; Rannou et al. 2003, Plan. Space Sci. 51, 963-976) have had difficulty matching Titan's modeled and observed geometric albedo spectrum when they include this wavelength. To interpret these STIS data, we employ a 1D radiative transfer fractal particle model with a Bayesian parameter estimation algorithm that adjusts Titan's haze opacity below 100 km, the methane mole fraction below 34 km, the surface albedo, and the haze single scattering albedo. Retrieving the tropospheric methane and lower atmosphere haze profiles is crucial for understanding the interactions between the haze and methane in the atmosphere and on the surface. Results of this work may help to constrain Titan's haze opacity in dynamical models, and examine the spatially varying degree of methane supersaturation in conjunction with areas of known cloud formation. The correlation of our results with the Huygens Probe data showing reduced haze in the lower atmosphere will be discussed. Funding for this work was provided by the NASA Graduate Student Researchers Program and grant number AST-0335635 from the National Science Foundation.

Anderson, C. M.; Young, E. F.; Chanover, N. J.; McKay, C. P.

2005-08-01

33

Studies of the ECR plasma in the visible light range  

International Nuclear Information System (INIS)

High resolution visible light (VL) plasma photographs were taken at the ATOMKI-ECRIS by an 8 mega-pixel digital camera. Plasmas were generated from gases of He, methane, N, O, Ne, Ar, Kr, Xe and from their mixtures. The analysis of the photo series gave many qualitative and numerous valuable physical information on the nature of ECR plasmas. VL photos convey information mainly on the cold electron component of the plasma. Cold electrons are confined in the central part of the plasma. It is a further challenging task to understand the colors of this special type of plasmas. The colors can be determined by the VL electron transitions of the plasma atoms and ions combined with the human eye sensitivity. There is a good visual agreement between the calculated normalized color and the real color of the plasmas. Through the examples of He and Xe we analyze the physical processes which affect the characteristic colors of these plasmas. The paper is followed by the slides of the presentation. (authors)

2012-01-01

34

The Sun as a possible energy standard in spectral range of lambda<3000A  

International Nuclear Information System (INIS)

[en] Ultraviolet spectrum of the Sun as a star according to all available data of orbital observations is analysed. In the spectral range with lambda8-109 times. However, the solar radiation was used as a standard in a visible region during extra-atmospheric photometry of extended sources; 1012 times attenuation was reached. The second difficulty is the elimination of scattered light from the long-wave region of spectrum (radiation drop in the range from 1500-3000 A is approximately 4 orders). This requires a special device structure and efficiency of a light detector

1980-01-01

35

An Approach for Identifying of Fusarium Infected Maize Grains by Spectral Analysis in the Visible and Near Infrared Region, SIMCA Models, Parametric and Neural Classifiers  

Digital Repository Infrastructure Vision for European Research (DRIVER)

An approach for identifying of Fusarium infected single maize grains based on diffuse reflectance in visible and near infrared region is proposed in the paper. Spectral characteristics were collected in the range 400-2500 nm in steps of 2 nm. Soft independent modeling of class analogy (SIMCA) is use...

Tsvetelina Draganova; Plamen Daskalov; Rusin Tsonev

36

Evaluating potential spectral impacts of various artificial lights on melatonin suppression, photosynthesis, and star visibility.  

UK PubMed Central (United Kingdom)

Artificial light at night can be harmful to the environment, and interferes with fauna and flora, star visibility, and human health. To estimate the relative impact of a lighting device, its radiant power, angular photometry and detailed spectral power distribution have to be considered. In this paper we focus on the spectral power distribution. While specific spectral characteristics can be considered harmful during the night, they can be considered advantageous during the day. As an example, while blue-rich Metal Halide lamps can be problematic for human health, star visibility and vegetation photosynthesis during the night, they can be highly appropriate during the day for plant growth and light therapy. In this paper we propose three new indices to characterize lamp spectra. These indices have been designed to allow a quick estimation of the potential impact of a lamp spectrum on melatonin suppression, photosynthesis, and star visibility. We used these new indices to compare various lighting technologies objectively. We also considered the transformation of such indices according to the propagation of light into the atmosphere as a function of distance to the observer. Among other results, we found that low pressure sodium, phosphor-converted amber light emitting diodes (LED) and LED 2700 K lamps filtered with the new Ledtech's Equilib filter showed a lower or equivalent potential impact on melatonin suppression and star visibility in comparison to high pressure sodium lamps. Low pressure sodium, LED 5000 K-filtered and LED 2700 K-filtered lamps had a lower impact on photosynthesis than did high pressure sodium lamps. Finally, we propose these indices as new standards for the lighting industry to be used in characterizing their lighting technologies. We hope that their use will favor the design of new environmentally and health-friendly lighting technologies.

Aubé M; Roby J; Kocifaj M

2013-01-01

37

Magnetorefractive effect in manganites with a colossal magnetoresistance in the visible spectral region  

Energy Technology Data Exchange (ETDEWEB)

The magnetotransmission, magnetoreflection, and magnetoresistance of the La{sub 0.7}Ca{sub 0.3}MnO{sub 3} and La{sub 0.9}Ag{sub 0.1}MnO{sub 3} epitaxial films have been investigated. It has been found that the films exhibit a significant magnetorefractive effect in the case of reflection and transmission of light in the fundamental absorption region both in the vicinity of the Curie temperature and at low temperatures. It has been shown that the magnetorefractive effect in the infrared spectral region of the manganites is determined by a high-frequency response to magnetoresistance, whereas the magnetorefractive effect in the visible spectral region of these materials is associated with a change in the electronic structure in response to a magnetic field, which, in turn, leads to a change in the electron density of states, the probability of interband optical transitions, and the shift of light absorption bands. The obtained values of the magnetotransmittance and magnetoreflectance in the visible spectral region are less than those observed in the infrared region of the spectrum, but they are several times greater than the linear magneto-optical effects. As a result, the magnetorefractive effect, which is a nongyrotropic phenomenon, makes it possible to avoid the use of light analyzers and polarizers in optical circuits.

Sukhorukov, Yu. P., E-mail: suhorukov@imp.uran.ru; Telegin, A. V. [Russian Academy of Sciences, Institute of Metal Physics, Ural Branch (Russian Federation); Granovsky, A. B., E-mail: granov@magn.ru; Gan' shina, E. A. [Moscow State University, Faculty of Physics (Russian Federation); Zhukov, A.; Gonzalez, J. [Universidad del Pais Vasco (UPV)/Euskal Herriko Unibertsitatea (EHU), Departamento de Fisica de Materiales, Facultad de Quimica (Spain); Herranz, G. [Institut de Ciencia de Materials de Barcelona (ICMAB)-CSIC (Spain); Caicedo, J. M. [Universidad del Pais Vasco (UPV)/Euskal Herriko Unibertsitatea (EHU), Departamento de Fisica de Materiales, Facultad de Quimica (Spain); Yurasov, A. N. [Moscow State Institute of Radio-Engineering, Electronics, and Automation (Technical University) (Russian Federation); Bessonov, V. D. [Russian Academy of Sciences, Institute of Metal Physics, Ural Branch (Russian Federation); Kaul' , A. R.; Gorbenko, O. Yu.; Korsakov, I. E. [Moscow State University, Faculty of Physics (Russian Federation)

2012-01-15

38

Magnetorefractive effect in manganites with a colossal magnetoresistance in the visible spectral region  

International Nuclear Information System (INIS)

[en] The magnetotransmission, magnetoreflection, and magnetoresistance of the La0.7Ca0.3MnO3 and La0.9Ag0.1MnO3 epitaxial films have been investigated. It has been found that the films exhibit a significant magnetorefractive effect in the case of reflection and transmission of light in the fundamental absorption region both in the vicinity of the Curie temperature and at low temperatures. It has been shown that the magnetorefractive effect in the infrared spectral region of the manganites is determined by a high-frequency response to magnetoresistance, whereas the magnetorefractive effect in the visible spectral region of these materials is associated with a change in the electronic structure in response to a magnetic field, which, in turn, leads to a change in the electron density of states, the probability of interband optical transitions, and the shift of light absorption bands. The obtained values of the magnetotransmittance and magnetoreflectance in the visible spectral region are less than those observed in the infrared region of the spectrum, but they are several times greater than the linear magneto-optical effects. As a result, the magnetorefractive effect, which is a nongyrotropic phenomenon, makes it possible to avoid the use of light analyzers and polarizers in optical circuits.

2012-01-01

39

Research on visible and near infrared spectral-polarimetric properties of snow in different melting states  

Science.gov (United States)

During the course of reflecting light-wave, the surface of snow will cause polarimetric properties which are related to the nature of itself. Thus, detection of the polarimetric information for snow has become a new remote sensing monitoring method. In this paper, starting from the perspective of multi-angle polarimetric reflectance, the multi-angle spectral-polarimetric instrument was used to obtain the multi-angle visible and near infrared spectral-polarimetric characteristic data of snow in different melting states. And then, the change rule between polarimetric properties with different affecting factors, such as viewing zenith angle, incidence zenith angle of the light source, relative azimuth angle, waveband of the detector as well as different types of snowmelt were discussed. The visible and near infrared spectral-polarimetric properties of snow has not only important theoretical significance for the quantitative analysis of snowmelt properties, but also wide application prospect, and provides new ideas and methods for the quantitative research on snow using the remote sensing technology.

Shen, Hui-yan; Zhou, Pu-cheng

2013-09-01

40

Dependence of cloud properties derived from spectrally resolved visible satellite observations on surface temperature  

Directory of Open Access Journals (Sweden)

Full Text Available Cloud climate feedback constitutes the most important uncertainty in climate modelling, and currently even its sign is still unknown. In the recently published report of the intergovernmental panel on climate change (IPCC), 6 out of 20 climate models showed a positive and 14 a negative cloud radiative feedback in a doubled CO2 scenario. The radiative budget of clouds has also been investigated by experimental methods, especially by studying the relation of satellite observed broad band shortwave and longwave radiation to sea surface temperature. Here we present a new method for the investigation of the dependence of cloud properties on temperature changes, derived from spectrally resolved satellite observations in the visible spectral range. Our study differs from previous investigations in three important ways: first, we directly extract cloud properties (effective cloud fraction and effective cloud top height) and relate them to surface temperature. Second, we retrieve the cloud altitude from the atmospheric O2 absorption instead from thermal IR radiation. Third, our correlation analysis is performed using 7.5 years of global monthly anomalies (with respect to the average of the same month for all years). For most parts of the globe (except the tropics) we find a negative correlation of effective cloud fraction versus surface-near temperature. In contrast, for the effective cloud top height a positive correlation is found for almost the whole globe. Both findings might serve as an indicator for an overall positive cloud radiative feedback. Another peculiarity of our study is that the cloud-temperature relationships are determined for fixed locations (instead to spatial variations over selected areas) and are based on the "natural" variability over several years (instead the anomaly for a strong El-Nino event). From a detailed comparison to cloud properties from the International Satellite Cloud Climatology Project (ISCCP), in general good agreement is found. However, also systematic differences occurred indicating that our results provide independent and complementary information on cloud properties. Climate models should thus aim to reproduce our findings. Recommendations for the development of a "processor" to convert model results into the cloud sensitive quantities observed by the satellite are given.

T. Wagner; S. Beirle; T. Deutschmann; M. Grzegorski; U. Platt

2008-01-01

 
 
 
 
41

Radical Protection by Differently Composed Creams in the UV/VIS and IR Spectral Ranges.  

UK PubMed Central (United Kingdom)

Modern sunscreens are well suited to provide sufficient protection in the UV-range, because the filter substances absorb or scatter UV-radiation. Although up to 50% of radicals were formed in the visible and infrared spectral range during solar radiation protection strategies are not provided in this range. Previous investigations of commercially available products have shown that in addition to physical filters, antioxidants are necessary to provide protective effects in the infrared range by neutralizing already formed radicals. In this study the efficacy of filter substances and antioxidants to reduce radical formation in both spectral ranges was investigated after UV/VIS- or IR-irradiation. Optical properties and radical protection were determined for the investigated creams. It was found that organic UV-filters lower radical formation in the UV/VIS-range to 35% compared to untreated skin, independent of the presence of antioxidants. Further reduction to 14% was reached by addition of 2% physical filters, while physical filters alone were ineffective in the UV/VIS range due to the low concentration. In contrast, this filter type reduced radical formation in the IR-range significantly to 65%; similar effects were aroused after application of antioxidants. Sunscreens which contain organic UV-filters, physical filters and antioxidants ensure protection in the complete solar spectrum. This article is protected by copyright. All rights reserved.

Meinke MC; Syring F; Schanzer S; Haag SF; Graf R; Loch M; Gersonde I; Groth N; Pflücker F; Lademann J

2013-07-01

42

Spectral broadening in anatase titanium dioxide waveguides at telecommunication and near-visible wavelengths.  

UK PubMed Central (United Kingdom)

We observe spectral broadening of femtosecond pulses in single-mode anatase-titanium dioxide (TiO2) waveguides at telecommunication and near-visible wavelengths (1565 and 794 nm). By fitting our data to nonlinear pulse propagation simulations, we quantify nonlinear optical parameters around 1565 nm. Our fitting yields a nonlinear refractive index of 0.16 × 10-18 m2/W, no two-photon absorption, and stimulated Raman scattering from the 144 cm-1 Raman line of anatase with a gain coefficient of 6.6 × 10-12 m/W. Additionally, we report on asymmetric spectral broadening around 794 nm. The wide wavelength applicability and negligible two-photon absorption of TiO2 make it a promising material for integrated photonics.

Evans CC; Shtyrkova K; Bradley JD; Reshef O; Ippen E; Mazur E

2013-07-01

43

Method for detection and imaging over a broad spectral range  

Energy Technology Data Exchange (ETDEWEB)

A method of controlling the coordinate sensitivity in a superconducting microbolometer employs localized light, heating or magnetic field effects to form normal or mixed state regions on a superconducting film and to control the spatial location. Electron beam lithography and wet chemical etching were applied as pattern transfer processes in epitaxial Y--Ba--Cu--O films. Two different sensor designs were tested: (i) a 3 millimeter long and 40 micrometer wide stripe and (ii) a 1.25 millimeters long, and 50 micron wide meandering-like structure. Scanning the laser beam along the stripe leads to physical displacement of the sensitive area, and, therefore, may be used as a basis for imaging over a broad spectral range. Forming the superconducting film as a meandering structure provides the equivalent of a two-dimensional detector array. Advantages of this approach are simplicity of detector fabrication, and simplicity of the read-out process requiring only two electrical terminals.

Yefremenko, Volodymyr (Westmont, IL); Gordiyenko, Eduard (Westmont, IL); Pishko, legal representative, Olga (Kharkov, UA); Novosad, Valentyn (Chicago, IL); Pishko, deceased; Vitalii (Westmont, IL)

2007-09-25

44

Development of a reflectometer for the determination of the spectral emittance in the visible at high temperatures  

Energy Technology Data Exchange (ETDEWEB)

The design of a high temperature reflectometer is presented. The instrument allows measuring the directional-hemispherical spectral reflectance in the visible at temperatures up to 3000 K. For opaque samples the spectral emittance follows from the spectral reflectance. Limited by the current detection equipment the spectral reflectance between 510 nm and 860 nm can be measured simultaneously. An electrical resistance heater is used to reach temperatures up to 1200 K, for higher temperatures the samples are heated by a flash-lamp pumped dye laser. First measurements on stabilized ZrO{sub 2} and Mn{sub 2}O{sub 3} are presented. (author)

Eckhoff, S.; Alxneit, I.; Musella, M.; Tschudi, H.R.

2001-03-01

45

Visible and near-infrared spectral signatures for adulteration assessment of extra virgin olive oil  

Science.gov (United States)

Because of its high price, the extra virgin olive oil is frequently target for adulteration with lower quality oils. This paper presents an innovative optical technique capable of quantifying the adulteration of extra virgin olive oil caused by lowergrade olive oils. It relies on spectral fingerprinting the test liquid by means of diffuse-light absorption spectroscopy carried out by optical fiber technology in the wide 400-1700 nm spectral range. Then, a smart multivariate processing of spectroscopic data is applied for immediate prediction of adulterant concentration.

Mignani, A. G.; Ciaccheri, L.; Ottevaere, H.; Thienpont, H.; Conte, L.; Marega, M.; Cichelli, A.; Attilio, C.; Cimato, A.

2010-04-01

46

Rutile TiO(2) inverse opal with photonic bandgap in the UV-visible range.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Highly organized rutile Titania inverse opal-based photonic crystals that exhibit reflective properties in the UV-Visible range have been constructed. A self-assembly method was employed to infiltrate the interstitial space of a highly organized polymeric opal with a titania alkoxide precursor under...

Li, Yu; Piret, François; Léonard, Timothée; Su, Bao-Lian

47

From the infrared to the visible range: Spectroscopic studies of ytterbium doped oxyborates  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The spectroscopic study of yttrium oxyborates doped with trivalent ytterbium is conducted in the UV-Visible and infrared range. The multiplicity of the ytterbium environments in the studied compounds leads to complex emission spectra in the infrared and excitation spectra in the ultraviolet. Differe...

Jubera, Véronique; Sablayrolles, Jean; Guillen, François; Decourt, Rodolphe; Couzi, Michel; Garcia, Alain

48

Visible and NIR spectral band combination to produce high security ID tags for automatic identification  

Science.gov (United States)

Verification of a piece of information and/or authentication of a given object or person are common operations carried out by automatic security systems that can be applied, for instance, to control the entrance to restricted areas, access to public buildings, identification of cardholders, etc. Vulnerability of such security systems may depend on the ease of counterfeiting the information used as a piece of identification for verification and authentication. To protect data against tampering, the signature that identifies an object is usually encrypted to avoid an easy recognition at human sight and an easy reproduction using conventional devices for imaging or scanning. To make counterfeiting even more difficult, we propose to combine data from visible and near infrared (NIR) spectral bands. By doing this, neither the visible content nor the NIR data by theirselves are sufficient to allow the signature recognition and thus, the identification of a given object. Only the appropriate combination of both signals permits a satisfactory authentication. In addition, the resulting signature is encrypted following a fully-phase encryption technique and the obtained complex-amplitude distribution is encoded on an ID tag. Spatial multiplexing of the encrypted signature allows us to build a distortion-invariant ID tag, so that remote authentication can be achieved even if the tag is captured under rotation or at different distances. We also explore the possibility of using partial information of the encrypted signature to simplify the ID tag design.

Pérez-Cabré, Elisabet; Millán, María S.; Javidi, Bahram

2006-10-01

49

Design and fabrication of active spectral filter with metal-insulator-metal structure for visible light communication  

Science.gov (United States)

Visible light communication with LED is an important ICT for the ubiquitous network society. However visible light communication has the speed limit in the conventional blinking LED method. Therefore an active spectral filter would be useful in order to input information signals onto the LED spectrum. Plasmonic spectral filter based on a metalinsulator- metal (MIM) structure is one of the candidates of such active filter. We will explain our progress of fabrication of the MIM structures with the vacuum deposition technique and compare their absorption properties with the theoretical prediction.

Murai, Kensuke; Oshikane, Yasushi; Higashi, Takaya; Yamamoto, Fumihiko; Nakano, Motohiro; Inoue, Haruyuki

2013-02-01

50

Compact laser transmitter delivering a long-range infrared beam aligned with a monitoring visible beam.  

UK PubMed Central (United Kingdom)

A compact laser transmitter, which takes advantage of an optical subassembly module, was proposed and demonstrated, providing precisely aligned collinear IR and visible beams. The collimated IR beam acts as a long-range projectile for simulated combat, carrying an optical pulsed signal, whereas the visible beam plays the role of tracking the IR beam. The proposed laser transmitter utilizes IR (?(1)=905 nm) and visible (?(2)=660 nm) light sources, a fiber-optic collimator, and a beam combiner, which includes a wavelength division multiplexing (WDM) filter in conjunction with optical fiber. The device was built via the laser welding technique and then evaluated by investigating the characteristics of the generated light beams. The IR collimated beam produced had a Gaussian profile and a divergence angle of ~1.3 mrad, and the visible monitoring beam was appropriately collimated to be readily discernible in the vicinity of the transmitter. The two beams were highly aligned within an angle of 0.004 deg as anticipated. Finally, we performed a practical outdoor field test to assess the IR beam with the help of a receiver. An effective trajectory was observed ranging up to 660 m with an overall detectable beam width of ~60 cm.

Lee HS; Kim HI; Lee SS

2012-06-01

51

Compact laser transmitter delivering a long-range infrared beam aligned with a monitoring visible beam.  

Science.gov (United States)

A compact laser transmitter, which takes advantage of an optical subassembly module, was proposed and demonstrated, providing precisely aligned collinear IR and visible beams. The collimated IR beam acts as a long-range projectile for simulated combat, carrying an optical pulsed signal, whereas the visible beam plays the role of tracking the IR beam. The proposed laser transmitter utilizes IR (?(1)=905 nm) and visible (?(2)=660 nm) light sources, a fiber-optic collimator, and a beam combiner, which includes a wavelength division multiplexing (WDM) filter in conjunction with optical fiber. The device was built via the laser welding technique and then evaluated by investigating the characteristics of the generated light beams. The IR collimated beam produced had a Gaussian profile and a divergence angle of ~1.3 mrad, and the visible monitoring beam was appropriately collimated to be readily discernible in the vicinity of the transmitter. The two beams were highly aligned within an angle of 0.004 deg as anticipated. Finally, we performed a practical outdoor field test to assess the IR beam with the help of a receiver. An effective trajectory was observed ranging up to 660 m with an overall detectable beam width of ~60 cm. PMID:22695673

Lee, Hong-Shik; Kim, Haeng-In; Lee, Sang-Shin

2012-06-10

52

A feasibility study for the retrieval of the total column precipitable water vapor from satellite observations in the blue spectral range  

Science.gov (United States)

We present a new algorithm for satellite retrievals of the atmospheric water vapor column in the blue spectral range. The water vapor absorption cross section in the blue spectral range is much weaker than in the red spectral range. Thus the detection limit and the uncertainty of individual observations is systematically larger than for retrievals at longer wavelengths. Nevertheless, water vapor retrievals in the blue spectral range have also several advantages: since the surface albedo in the blue spectral range is similar over land and ocean, water vapor retrievals are more consistent than for longer wavelengths. Compared to retrievals at longer wavelengths, over ocean the sensitivity for atmospheric layers close to the surface is higher due to the (typically 2 to 3 times) higher ocean albedo in the blue. Water vapor retrievals in the blue spectral range are also possible for satellite sensors, which do not measure at longer wavelengths of the visible spectral range like the Ozone Monitoring instrument (OMI). We investigated details of the water vapor retrieval in the blue spectral range based on radiative transfer simulations and observations from the Global Ozone Monitoring Experiment 2 (GOME-2) and OMI. It is demonstrated that it is possible to retrieve the atmospheric water vapor column density in the blue spectral range over most parts of the globe. The findings of our study are of importance also for future satellite missions like e.g. Sentinel 4 and 5.

Wagner, T.; Beirle, S.; Sihler, H.; Mies, K.

2013-04-01

53

90% Extraordinary optical transmission in the visible range through annular aperture metallic arrays.  

UK PubMed Central (United Kingdom)

We demonstrate what we believe to be the first experimental extraordinary optical transmission (EOT) of up to 90%, thanks to a well-identified guided mode that propagates through annular apertures engraved into an optically thick silver layer. In spite of the metal losses, high transmission can be obtained by adjusting the geometrical parameters of the fabricated structure, as was already theoretically demonstrated. To our knowledge, this is the first study showing such a large transmission in the visible range.

Poujet Y; Salvi J; Baida FI

2007-10-01

54

A visibility matching tone reproduction operator for high dynamic range scenes  

Energy Technology Data Exchange (ETDEWEB)

The authors present a tone reproduction operator that preserves visibility in high dynamic range scenes. The method introduces a new histogram adjustment technique, based on the population of local adaptation luminances in a scene. To match subjective viewing experience, the method incorporates models for human contrast sensitivity, glare, spatial acuity and color sensitivity. They compare the results to previous work and present examples the techniques applied to lighting simulation and electronic photography.

Larson, G.W. [Lawrence Berkeley National Lab., CA (United States); Rushmeier, H. [International Business Machines Corp., Yorktown Heights, NY (United States). Thomas J. Watson Research Center; Piatko, C. [National Inst. of Standards and Technology, Gaithersburg, MD (United States)

1997-01-15

55

The UV-A and visible solar irradiance spectrum: inter-comparison of absolutely calibrated, spectrally medium resolution solar irradiance spectra from balloon- and satellite-borne measurements  

Directory of Open Access Journals (Sweden)

Full Text Available Within the framework of the ENVISAT/-SCIAMACHY satellite validation, solar irradiance spectra are absolutely measured at moderate resolution in the UV/visible spectral range (in the UV from 316.7–418 nm and the visible from 400–652 nm at a full width half maximum resolution of 0.55 nm and 1.48 nm, respectively) from aboard the azimuth-controlled LPMA/DOAS balloon gondola at around 32 km balloon float altitude. After accounting for the atmospheric extinction due to Rayleigh scattering and gaseous absorption (O3, and NO2), the measured solar spectra are compared with previous observations. Our solar irradiance is +1.6% larger than the re-calibrated Kurucz et al. (1984) solar spectrum (Fontenla et al., 1999, called MODTRAN 3.5) in the visible spectral range (435–650 nm), +1.5% larger in the (370–415 nm) wavelength interval, but ?4% smaller in the UV spectral range (316.7–370 nm), when the Kurucz spectrum is convolved to the spectral resolution of our instrument. The same comparison with the SOLSPEC solar spectrum (Thuillier et al., 1997, 1998a, b) confirms the somewhat larger solar irradiance (+1.7%) measured by the balloon instrument from 435–500 nm, but not from 500–650 nm, where the SOLSPEC is ?1.3% lower than MODTRAN 3.5. Comparison of the SCIAMACHY solar spectrum from channels 1 to 4 (– re-calibrated by the University of Bremen –) with MODTRAN 3.5 indicates an agreement of +0.2% in the visible spectral range (435–585 nm). With this calibration, the SCIAMACHY solar spectrum is congruent with the balloon observations (?1%) in the 316.7–370 nm wavelength range, but both are up to ?5%/?3% smaller than MODTRAN 3.5 and SOLSPEC, respectively. In agreement with findings of Skupin et al. (2002) our study emphasizes that the present ESA SCIAMACHY level 1 calibration is systematically +15% larger in the considered wavelength intervals when compared to all available other solar irradiance measurements.

W. Gurlit; H. Bösch; H. Bovensmann; J. P. Burrows; A. Butz; C. Camy-Peyret; M. Dorf; K. Gerilowski; A. Lindner; S. Noël; U. Platt; F. Weidner; K. Pfeilsticker

2004-01-01

56

Gravity-induced absorption changes in Phycomyces blakesleeanus during parabolic flights: first spectral approach in the visible.  

UK PubMed Central (United Kingdom)

Gravity-induced absorption changes as experienced during a series of parabolas on the Airbus 300 Zero-G have been measured previously pointwise on the basis of dual-wavelength spectroscopy. Only the two wavelengths of 460 and 665 nm as generated by light-emitting diodes have been utilised during our first two parabolic-flight campaigns. In order to gain complete spectral information throughout the wavelength range from 400 to 900 nm, a miniaturized rapid scan spectrophotometer was designed. The difference of spectra taken at 0 g and 1.8 g presents the first gravity-induced absorption change spectrum measured on wild-type Phycomyces blakesleeanus sporangiophores, exhibiting a broad positive hump in the visible range and negative values in the near infrared with an isosbestic point near 735 nm. The control experiment performed with the stiff mutant A909 of Phycomyces blakesleeanus does not show this structure. These results are in agreement with those obtained with an array spectrophotometer. In analogy to the more thoroughly understood so-called light-induced absorption changes, we assume that gravity-induced absorption changes reflect redox changes of electron transport components such as flavins and cytochromes localised within the plasma membrane.

Schmidt W

2006-12-01

57

The UV-A and visible solar irradiance spectrum: inter-comparison of absolutely calibrated, spectrally medium resolution solar irradiance spectra from balloon- and satellite-borne measurements  

Directory of Open Access Journals (Sweden)

Full Text Available Within the framework of the ENVISAT/-SCIAMACHY satellite validation, solar irradiance spectra are absolutely measured at moderate resolution in the UV/visible spectral range (in the UV from 316.7-418 nm and the visible from 400-652 nm at a full width half maximum resolution of 0.55 nm and 1.48 nm, respectively) from aboard the azimuth-controlled LPMA/DOAS balloon gondola at around 32 km balloon float altitude. After accounting for the atmospheric extinction due to Rayleigh scattering and gaseous absorption (O3 and NO2), the measured solar spectra are compared with previous observations. Our solar irradiance spectrum perfectly agrees within +0.03% with the re-calibrated Kurucz et al. (1984) solar spectrum (Fontenla et al., 1999, called MODTRAN 3.7) in the visible spectral range (415-650 nm), but it is +2.1% larger in the (370-415 nm) wavelength interval, and -4% smaller in the UV-A spectral range (316.7-370 nm), when the Kurucz spectrum is convolved to the spectral resolution of our instrument. Similar comparisons of the SOLSPEC (Thuillier et al., 1997, 1998a, b) and SORCE/SIM (Harder et al., 2000) solar spectra with MODTRAN 3.7 confirms our findings with the values being -0.5%, +2%, and -1.4% for SOLSPEC -0.33%, -0.47%, and -6.2% for SORCE/SIM, respectively. Comparison of the SCIAMACHY solar spectrum from channels 1 to 4 (- re-calibrated by the University of Bremen -) with MODTRAN 3.7 indicates an agreement within -0.4% in the visible spectral range (415-585 nm), -1.6% within the 370-415 nm, and -5.7% within 325-370 nm wavelength interval, in agreement with the results of the other sensors. In agreement with findings of Skupin et al. (2002) our study emphasizes that the present ESA SCIAMACHY level 1 calibration is systematically +15% larger in the considered wavelength intervals when compared to all available other solar irradiance measurements.

W. Gurlit; H. Bösch; H. Bovensmann; J. P. Burrows; A. Butz; C. Camy-Peyret; M. Dorf; K. Gerilowski; A. Lindner; S. Noël; U. Platt; F. Weidner; K. Pfeilsticker

2005-01-01

58

Optical properties of palladium in the visible and near UV spectral regions.  

Science.gov (United States)

The dielectric function data, epsilon = epsilon(1) -/+ iepsilon(2), of palladium thin films prepared by dc magnetron sputtering are given for the spectral range 1.6-5.5 eV. A comparison is made between these results and those obtained for Pd films and bulk specimens over the past twenty years. While a number of measurements show good agreement in epsilon(1), there is a considerable variation in the epsilon(2) data among the different groups. Some of these differences can be explained either by the sample preparation, which affects the morphology of the films, or else by uncertainties related to film thickness. PMID:20563117

Sullivan, B T

1990-05-01

59

Observation of the fine structure for rovibronic spectral lines in visible part of emission spectra of $D_2$  

CERN Document Server

For the first time the fine structure of rovibronic spectral lines in visible part of emission spectra of $D_2$ molecule has been observed. Observed splitting in visible doublets is about 0.2 cm$^{-1}$ in good accordance with previous observations in the infrared part of the spectrum ($a^3\\Sigma_g^+ \\to c^3\\Pi_u$ electronic transition) by means of FTIR and laser spectroscopy. Relative intensities of the fine structure components are in agreement with our calculations of adiabatic line strengths for Hund's case "b" coupling scheme.

Lavrov, B P; Zhukov, A S

2011-01-01

60

Optical properties in the UV and visible spectral region of organic acids relevant to tropospheric aerosols  

Directory of Open Access Journals (Sweden)

Full Text Available Refractive and absorption indices in the UV and visible region of selected aqueous organic acids relevant to tropospheric aerosols are reported. The acids investigated are the aliphatic dicarboxylic acids oxalic, malonic, tartronic, succinic and glutaric acid. In addition we report data for pyruvic, pinonic, benzoic and phthalic acid. To cover a wide range of conditions we have investigated the aqueous organic acids at different concentrations spanning from highly diluted samples to concentrations close to saturation. The density of the investigated samples is reported and a parameterisation of the absorption and refractive index that allows the calculation of the optical constants of mixed aqueous organic acids at different concentrations is presented. The single scattering albedo is calculated for two size distributions using measured and a synthetic set of optical constants. The results show that tropospheric aerosols consisting of only these organic acids and water have a pure scattering effect.

C. E. Lund Myhre; C. J. Nielsen

2004-01-01

 
 
 
 
61

Generation of pulsed light in the visible spectral region based on non-linear cavity dumping  

DEFF Research Database (Denmark)

We propose a novel generic approach for generation of pulsed light in the visible spectrum based on sum-frequency generation between the high circulating intra-cavity power of a high finesse CW laser and a single-passed pulsed laser. For demonstration, we used a CW 1342 nm laser mixed with a passively Q-switched 1064 nm laser to generate pulsed light at 593 nm. Light sources in the yellow spectral region have several applications, e.g. dermatology, laser displays and flow cytometry. Traditionally, copper-vapor lasers at 578 nm and dye lasers are used in this spectral region. These are however bulky, inefficient and contain highly toxic gasses and liquids. Different approaches to replace these are: frequency-doubled semiconductor lasers1, sum-frequency generation between solid-state lasers in both in CW2 and Q-switched3 operation and Raman lasers4. An intra-cavity 1342 nm Nd:YVO4 laser acted as the CW light source, using a folded cavity to achieve tight focussing in the non-linear crystal which was a 11 mm long PPKTP. The pulsed light source was a Nd:YVO4 laser emitting at 1064 nm using Cr:YAG as a passive saturable absorber, resulting in a pulse length of 100 ns and a repetition frequency of 215 kHz. Both lasers were pumped with 808 nm laser diodes delivering 4 W of output power. The circulating power of the 1342 nm laser was 57 W and the peak power of the 1064 nm laser reaching the PPKTP crystal was 17 W. A peak power of approximately 4 W at 593 nm was measured. Accounting for the Fresnel losses for the outcoupling mirror, this would correspond to 5.3 W of generated 593 nm power. The pulsed yellow-orange light follows exactly the 1064 nm pulses in terms of repetition frequency and pulse width. By matching the pulse length of the passively Q-switched laser to the round-trip time of the CW intra-cavity laser, the circulating power could be more efficiently depleted. Calculations give that yellow peak powers in the order of 50 W could be reached.

Johansson, Sandra; Andersen, Martin

62

Self-Complementary Plasmonic Structures for High Efficiency Broadband Absorber in the Visible Range  

Science.gov (United States)

We demonstrate, by simulation, that a planar 3-layer structure on a metal substrate can highly absorb electromagnetic radiation in the entire visible range, which can become a potential platform for high-efficiency broadband absorber. Such a structure consists of an ultrathin semiconducting layer topped with a solid nanoscopically perforated metallic film and then a dielectric interference layer. It is shown that the perforated metallic film and the ultrathin absorber form an effective metamaterial film, which negatively refracts light in this broad frequency range. Our quantitative simulation confirms that the absorption bandwidth is maximized at the self-complementary pattern of the percolation threshold. If amorphous silicon (a-Si) is selected as the ultrathin semiconducting material, the absorbance of the structure with a checkerboard-patterned perforated metallic film is about 90% in the visible range (from 400 nm to 700 nm), where 80% goes into the a-Si layer and the other 10% being absorbed by other layers. Further simulation shows that for a single p-i-n a-Si junction, the energy conversion efficiency of an optimized structure can exceed 12%.

Sun, Tianyi; Wang, Yang; Ren, Zhifeng; Kempa, Krzysztof

2013-03-01

63

Polarization effects of the spectral thermal IR and visible emission from ferromagnets  

Science.gov (United States)

Magneto-optical effects are usually investigated by reflection or transmission measurements. An alternative is the experimental study of the spectral thermal emission from a heated magnetized sample. In this paper we report on experiments and theory of two magneto-optical effects related to the spectral thermal emission from ferromagnets.The first effect was discovered by Muller, Fuchs and Kneubuhl in 1977. They demonstrated that the spectral thermal emission of an axially magnetized Fe rod exhibits a partial circular polarization. We have measured this effect in the Spectral range from 0.25 to 2 eV for a set of FeCo alloys. The spectra show a maximum at low energies. With increasing photon energy the polarization decreases and changes its sign at 1.35, 1.50 and 1.65 eV for the alloys Fe79 Co21, Fe55 Co45 and Fe31 Co69, respectively. With a specific theoretical model we have succeeded in explaining the dependence of the effect on the wavelength and on the Co concentration.In relation to the above effect we have discovered that the thermal radiation emitted from a ferromagnetic sample magnetized parallel to its surface is partially linearly polarized. This effect is even with respect to the magnetization and of the order of 10-3 for saturated Fe. We have determined experimentally this linear polarization as a function of the wavelength, the temperature and the external field. In the spectral range of 0.25-1.25 eV minima have been observed at 0.3, 0.45 and 0.6 eV for Fe79 Co21, Fe55 Co45 and Fe31 Co69, respectively, and maxima at 0.5, 0.75, 1 and 1.15eV for Fe79 Co21, Fe55 Co45 and Fe31 Co69, respectively. These spectra show a shift to higher energies for increasing Co concentration in analogy to the spectra of the circular polarization effect. Furthermore, we have measured the dependence of the polarization on the temperature from 600 K up to the Curie temperature where the effect vanishes. The polarization decreases almost linearly with rising temperature for Fe and Fe31 Co69. However, for Fe79 Co21 and Fe55 Co45 the polarization shows a sharp drop at the Curie temperature, which can be associated with the phase transition from bcc to fcc. In addition, Fe55 Co45 shows a hysteresis of linear polarization for rising and falling temperature. The origin is the order-disorder transition at 1000 K.Our study demonstrates that the measurement of polarization effects of the spectral thermal emission is supplementary to the standard transmission and reflection measurements and, therefore, is a valuable tool for the investigation of magneto-optical effects.

Bronnimann, R.; Kneubuhl, F. K.

1986-05-01

64

Single-order operation of lamellar multilayer gratings in the soft x-ray spectral range  

Directory of Open Access Journals (Sweden)

Full Text Available We demonstrate single-order operation of Lamellar Multilayer Gratings in the soft x-ray spectral range. The spectral resolution was found to be 3.8 times higher than from an unpatterned multilayer mirror, while there were no significant spectral sideband structures adjacent to the main Bragg peak. The measured spectral bandwidths and peak reflectivities were in good agreement with our theoretical calculations.

Robert van der Meer; Igor Kozhevnikov; Balachander Krishnan; Jurriaan Huskens; Petra Hegeman; Christian Brons; Boris Vratzov; Bert Bastiaens; Klaus Boller; Fred Bijkerk

2013-01-01

65

An Approach for Identifying of Fusarium Infected Maize Grains by Spectral Analysis in the Visible and Near Infrared Region, SIMCA Models, Parametric and Neural Classifiers  

Directory of Open Access Journals (Sweden)

Full Text Available An approach for identifying of Fusarium infected single maize grains based on diffuse reflectance in visible and near infrared region is proposed in the paper. Spectral characteristics were collected in the range 400-2500 nm in steps of 2 nm. Soft independent modeling of class analogy (SIMCA) is used for data processing. Maize grains classification is based on SIMCA classifier and Probabilistic neural network (PNN). Recognition accuracy which is achieved for both classes of grains is respectively 99.89% for healthy, and 93.7% for infected.

Tsvetelina Draganova; Plamen Daskalov; Rusin Tsonev

2010-01-01

66

Response of diamond photoconductors to soft x-ray in the spectral range 125 {angstrom} to 240 {angstrom}  

Energy Technology Data Exchange (ETDEWEB)

Due to the large bandgap of diamond, it is transparent to the visible spectrum, making it an attractive material for soft x-ray detection. Response of diamond photoconductors fabricated using Polycrystalline chemical-vapor-deposited (CVD) diamond to soft x-rays has been measured using x-rays emitted from a laser-produced plasma source in the spectral range 125 {Angstrom} to 240 {Angstrom}. These photoconductors have interdigitated electrode structure in order to increase the active area as well as detector sensitivity. Contributions to the detector sensitivity by the photoelectrons is discussed.

Han, S.; Wagner, R.S. [Los Alamos National Lab., NM (United States); Gullikson, E. [Lawrence Berkeley Lab., CA (United States)

1995-12-01

67

Tunable femtosecond laser in the visible range with an intracavity frequency-doubled optical parametric oscillator  

Science.gov (United States)

We demonstrated experimentally a synchronously pumped intracavity frequency-doubled femtosecond optical parametric oscillator (OPO) using a periodically-poled lithium niobate (PPLN) as the nonlinear material in combination with a lithium triborate (LBO) as the doubling crystal. A Kerr-lens-mode-locked (KLM) Ti:sapphire oscillator at the wavelength of 790 nm was used as the pump source, which was capable of generating pulses with a duration as short as 117 fs. A tunable femtosecond laser covering the 624–672 nm range was realized by conveniently adjusting the OPO cavity length. A maximum average output power of 260 mW in the visible range was obtained at the pump power of 2.2 W, with a typical pulse duration of 205 fs assuming a sech2 pulse profile.

Zhu, Jiang-Feng; Xu, Liang; Lin, Qing-Feng; Zhong, Xin; Han, Hai-Nian; Wei, Zhi-Yi

2013-05-01

68

Solid state image sensors in visual spectral range. Kashiko kotai satsuzo soshi  

Energy Technology Data Exchange (ETDEWEB)

This paper describes configurations and operations of solid state image sensors in visible spectral range, and structure and characteristics of the charge coupled device (CCD), a representative solid state image sensor. It also mentions research trends in latest solid state image sensors. A solid state image sensor is a light sensor that utilizes a photoelectric effect of a semiconductor. It spreads unit cells called picture elements two-dimensionally to form an image sensor. The number of picture elements is about 300,000 elements in a standard television mode, and two million elements in the high definition television (HDTV) set under development. A high definition monochrome camera that uses the developed HDTVCCD shows such superior values as sensitivity of 400 Lux (F4) and S/N ratio of 56 dB. Development trends of solid state image sensors are represented by size reduction and improvement in resolution and sensitivity of the elements, and signal processing functions performed on chips. A multi-element CCD image sensor with 26.2 million picture elements has been reported. The picture element used mainly for astronomic observation has a picture element size of 12 [mu]m and a light receiving area of 6.1 cm square. 17 refs., 10 figs., 3 tabs.

Matsumoto, K. (Olympus Optical Co. Ltd., Tokyo (Japan))

1994-02-25

69

Photocatalysis in the visible range of sub-stoichiometric anatase films prepared by MOCVD  

International Nuclear Information System (INIS)

Anatase phase of titanium oxide is the most promising photocatalyst material for organic pollutant degradation. However, due to its large band gap energy (3.2 eV) it is not viable to use sunlight as an energy source for the photocatalysis activation, and so, ultraviolet (UV) radiation below the wavelength of 380 nm is required. This paper focuses on the experimental demonstration of the reduction of this large band gap energy by inducing defects in the anatase structure under the form of oxygen sub-stoichiometry. TiO2 thin films were prepared in a metal organic chemical vapour deposition (MOCVD) reactor. The samples stoichiometry was measured by the Rutherford backscattering spectrometry (RBS) technique. Optical characterisation was also performed and the photodegradation activity in the visible range was tested using nonylphenol, which is one of the most harmful pollutants present in waste waters.

2005-08-25

70

Tailoring Metallodielectric Structures for Super Resolution and Superguiding Applications in the Visible and Near IR Ranges  

CERN Multimedia

We discuss propagation effects in realistic, transparent, metallo-dielectric photonic band gap structures in the context of negative refraction and super-resolution in the visible and near infrared ranges. In the resonance tunneling regime, we find that for transverse-magnetic incident polarization, field localization effects contribute to a waveguiding phenomenon that makes it possible for the light to remain confined within a small fraction of a wavelength, without any transverse boundaries, due to the suppression of diffraction. This effect is related to negative refraction of the Poynting vector inside each metal layer, balanced by normal refraction inside the adjacent dielectric layer: The degree of field localization and material dispersion together determine the total momentum that resides within any given layer, and thus the direction of energy flow. We find that the transport of evanescent wave vectors is mediated by the excitation of quasi-stationary, low group velocity surface waves responsible for...

De Ceglia, D; Cappeddu, M G; Centini, M; Akozbek, N; DOrazio, A; Haus, J W; Bloemer, M J; Scalora, M

2008-01-01

71

Spectral irradiance measurement in the visible-ultraviolet region using synchrotron radiation  

International Nuclear Information System (INIS)

Spectral irradiances of a quartz-bromine lamp calibrated against the currently maintained ETL standard were compared with those of synchrotron radiation from TERAS in order to reconfirm the magnitude of standard unit, especially, in the ultraviolet region. The spectral irradiance unit at the wavelength of 500 nm was taken to be equal to each other. It was concluded that the magnitude of spectral irradiance unit currently used at ETL should be increased at the short wavelengths by maximum 7%. (author)

1991-01-01

72

Droplet-Turbulence Interactions Over a Wide Spectral Range.  

Science.gov (United States)

In the last year, the unsteady, three-dimensional, incompressible, viscous flow interactions between a single vortex tube advected by a uniform free stream and a spherical particle held fixed in space was investigated numerically for a range of particle R...

W. A. Sirignano S. E. Elghobashi I. Kim M. Masoudi

1994-01-01

73

[Spectral analysis of nitrofurantoin in the terahertz frequency range].  

UK PubMed Central (United Kingdom)

The present article measured the absorption coefficient spectra and refractive index spectra of nitrofurantoin original drug, which is one kind of nitrofuran drugs, in the terahertz frequency range from 0.2 to 1.8 THz using terahertz time-domain spectroscopy. The results showed that there exist a number of characteristic absorption peaks of nitrofurantoin with different intensity in the range and the absorption coefficient spectra can be used to identify nitrofurantoin. The article also simulated absorption coefficient spectra of nitrofurantoin molecule within 0.2 - 1.8 THz using density functional theory by Gaussian software, and vibrational modes of some peaks in the experimental absorption coefficient spectra were analyzed and identified. The results show that the experimental absorption peaks at 1.25 and 1.60 THz correspond with the theoretical peaks at 1.30 and 1.67 THz, and these experimental peaks were caused by intramolecular vibrational modes of nitrofurantoin.

Kang XS; Hou DB; Zhang GX; Chen XA; Yue FH; Huang PJ; Zhou ZK

2012-07-01

74

Spectral evolution of SN 1987A in the IUE long wavelength range  

International Nuclear Information System (INIS)

IUE low resolution spectra of SN 1987 A, in the long wavelength range, (1952 - 3348A), obtained in the period Feb 25, 1987 - Mar 17, 1988, have been analyzed to study its spectral evolution. We study the spectral variations by comparing spectra obtained at two consecutive observing dates.

1988-01-01

75

Physical base of the monitoring of water bodies from space using visible and near-infrared spectral bands  

Energy Technology Data Exchange (ETDEWEB)

The characteristics of spectral radiance in the visible and the NIR bands emitted from natural water bodies of different types (such as oceanic and lake waters of various colors and color intensities) are examined, taking into consideraton the varying optical parameters of water and the air above it. The contribution from different optically active components suspended or dissolved in various waters is estimated. Practical suggestions are offered for the use of multispectral images in the retrieval of various parameters of natural water bodies. 11 refs.

Kondrat' ev, K.IA.; Shumakov, F.T. (AN SSSR, Institut Ozerovedeniia, Leningrad (USSR) Vsesoiuznyi Nauchno-Issledovatel' skii Institut po Okhrane Vod, Moscow (USSR))

1990-12-01

76

Spectral measurements of ultraviolet and visible solar irradiance at the Weddell-Scotia Confluence during 1993 austral spring  

Energy Technology Data Exchange (ETDEWEB)

Spectral measurements were made of incident and undersea solar irradiance in the October and November 1993 austral spring, during transits of low ozone {open_quotes}hole{close_quotes} over the Weddell-Scotia Confluence. Several scanning radiometers were intercalibrated between research groups and used for measurements of ultraviolet (UV) and visible exposure for in situ processes and for on-deck and in-lab productivity, photoinhibition, and photochemistry experiments. The intercalibration of instruments also gave valuable information for comparison of data from various published and unpublished sources. 2 refs., 3 figs., 1 tab.

Sikorski, R.J. [Univ. of Miami, FL (United States); Sigleo, A.C. [Environmental Protection Agency, Newport, OR (United States); Neale, P.J. [Smithsonian Environmental Research Center, Edgewater, MD (United States)

1994-12-31

77

Spectrally tailored narrowband pulses for femtosecond stimulated Raman spectroscopy in the range 330-750 nm.  

UK PubMed Central (United Kingdom)

Spectral compression of femtosecond pulses by second harmonic generation in the presence of substantial group velocity dispersion provides a convenient source of narrowband Raman pump pulses for femtosecond stimulated Raman spectroscopy (FSRS). We discuss here a simple and efficient modification that dramatically increases the versatility of the second harmonic spectral compression technique. Adding a spectral filter following second harmonic generation produces narrowband pulses with a superior temporal profile. This simple modification i) increases the Raman gain for a given pulse energy, ii) improves the spectral resolution, iii) suppresses coherent oscillations associated with slowly dephasing vibrations, and iv) extends the useful tunable range to at least 330-750 nm.

Pontecorvo E; Ferrante C; Elles CG; Scopigno T

2013-03-01

78

External quantum efficiency of Pt/n-GaN Schottky diodes in the spectral range 5-500nm  

International Nuclear Information System (INIS)

The external quantum efficiency in the spectral wavelength range 5-500nm of a large active area Pt/n-type GaN Schottky photodiode that exhibits low reverse bias leakage current, is reported. The Schottky photodiodes were fabricated from n-/n+ epitaxial layers grown by low pressure metalorganic vapour phase epitaxy on single crystal c-plane sapphire. The current-voltage (I-V) characteristics of several 0.25cm2 devices are presented together with the capacitance-voltage (C-V) characteristics of one of these devices. A leakage current as low as 14 pA at 0.5V reverse bias is reported, for a 0.25cm2 diode. The ultraviolet quantum efficiency measurements show that the diodes can be used as radiation hard detectors for the 5-365nm spectral range without the use of visible blocking filters. A peak responsivity of 77.5mA/W at 320nm is reported for one of the fabricated devices, corresponding to a spectral detectivity, D*=1.5x1014cmHz1/2W-1. The average detectivity between 250 and 350nm, for the same device, is reported to be D-bar*=1.3x1014cmHz1/2W-1. The spatial responsivity uniformity variation was established, using H2 Lyman-? radiation, to be +/-3% across the surface of a typical 0.25cm2 diode.

2005-02-21

79

Demonstration of a spatial-spectral holographic LIDAR range-Doppler processor  

International Nuclear Information System (INIS)

We present a new approach to laser interferometric Doppler and ranging (LIDAR) processing using spatial-spectral holography (SSH). In this approach, broadband optical signals from a random noise or frequency-modulated laser are transmitted and reflected off remote targets. The return signals interfere spatially and spectrally with a local copy of the original transmit signal in an SSH medium, resulting in spectral gratings that have a spectral period inversely proportional to the LIDAR target's range and a position proportional to the target's Doppler (or velocity). These gratings are subsequently read out by a slowly chirped source onto a parallel detector array, and the velocity and range of the targets are inferred. We present the theoretical framework that describes the function of the LIDAR processor, as well as proof-of-concept experimental results.

2007-01-01

80

Time-resolved photoluminescence spectroscopy of semiconductors for optical applications beyond the visible spectral range  

Energy Technology Data Exchange (ETDEWEB)

The work discussed in this thesis is focused on the experimental studies regarding these three steps: (1) investigation of the fundamental effects, (2) characterization of new material systems, and (3) optimization of the semiconductor devices. In all three cases, the experimental technique of choice is photoluminescence (PL) spectroscopy. The thesis is organized as follows. Chapter 2 gives a summary of the PL properties of semiconductors relevant for this work. The first section deals with the intrinsic processes in an ideal direct band gap material, starting with a brief summary of the theoretical background followed by the overview of a typical PL scenario. In the second part of the chapter, the role of the lattice-vibrations, the internal electric fields as well as the influence of the band-structure and the dielectric environment are discussed. Finally, extrinsic PL properties are presented in the third section, focusing on defects and disorder in real materials. In chapter 3, the experimental realization of the spectroscopic studies is discussed. The time-resolved photoluminescence (TRPL) setup is presented, focusing on the applied excitation source, non-linear frequency mixing, and the operation of the streak camera used for the detection. In addition, linear spectroscopy setup for continous-wave (CW) PL and absorption measurements is illustrated. Chapter 4 aims at the study of the interactions between electrons and lattice-vibrations in semiconductor crystals relevant for the proper description of carrier dynamics as well as the heat-transfer processes. The presented discussion covers the experimental studies of many-body effects in phonon-assisted emission of semiconductors due to the carriercarrier Coulomb-interaction. The corresponding theoretical background is discussed in detail in chapter 2. The investigations are focused on the two main questions regarding electron-hole plasma contributions to the phonon-assisted light-matter interaction as well as the impact of Coulomb-correlations on the carrier-phonon scattering. The experiments presented in chapter 5 deal with the characterization of recently synthesizedmaterial systems: ZnO/(ZnMg)O heterostructures, GaN quantum wires (QWires), as well as (GaAs)Bi quantum wells (QWs). TRPL spectroscopy is applied to gain insight as well as a better understanding of the respective carrier relaxation and recombination processes crucial for the device operation. The aim of the studies is the systematic investigation of carrier dynamics influenced by disorder. The measurements are supported by kinetic Monte- Carlo simulations, providing a quantitative analysis of carrier localization effects. In chapter 6, optimization and characterization studies of semiconductor lasers, based on the well-studied (GaIn)As material system designed for NIR applications, are performed. The device under investigation is the so-called vertical-external-cavity surface emitting laser (VECSEL). The experiments focus on the study of the thermal properties of a high-power VECSEL. The distribution and removal of the excess heat as well as the optimization of the laser for increased performance are addressed applying different heat-spreading and heat-transfer approaches. Based on these investigations, the possibility for power-scaling is evaluated and the underlying restrictions are analyzed. The latter investigations are performed applying spatially-resolved PL spectroscopy. An experimental setup is designed for monitoring the spatial distribution of heat in the semiconductor structure during laser operation.

Chernikov, Alexey A.

2011-07-01

 
 
 
 
81

Stark Broadening of several Ar I Spectral Lines in the Visible Part of the Spectrum  

CERN Multimedia

In order to complete data on Stark broadening parameters for Ar I line in the visible spectrum, we determined Stark widths and shifts due to electron, proton, and ionized helium impacts, for nine lines (4191.0, 4259.4, 5912.1, 6043.2, 6045.0, 6752.9, 7503.9, 7514.6, 7724.2 {\\AA}), using jK coupling and semiclassical-perturbation theory. The obtained results will enter the STARK-B database, which is a part of Virtual Atomic and Molecular Data Center.

Dimitrijevic, Milan S; Simic, Zoran; Sahal-Brechot, Sylvie

2012-01-01

82

FTIR AND UV-VISIBLE SPECTRAL STUDY ON NORMAL BLOOD SAMPLES  

Directory of Open Access Journals (Sweden)

Full Text Available Spectroscopic techniques can be effectively employed as a diagnostic tool in clinical chemistry and it can be an alternate method in clinical analysis. The study of blood by spectroscopic techniques can be used not only for understanding the biological nature of the disease, but also for the diagnosis of the disease. In the present work, FTIR and UV-Vis spectroscopic technique is employed to study the spectral differences in the serum of normal blood samples.

Kanagathara N1*

2011-01-01

83

Preparation of photoelectrodes with spectral response in the visible without applied bias based on photochemically deposited copper oxide inside a porous titanium dioxide film  

Energy Technology Data Exchange (ETDEWEB)

A soft and simple photochemical technique is proposed for the incorporation of copper oxide to nanoporous TiO{sub 2} with the purpose of sensitizing the TiO{sub 2} to wavelengths in the visible range. An aqueous solution of copper formate is employed as precursor. The light intensity value needed for the process, as well as its spectral range, is readily attainable with solar light. Because of the importance of heterojunctions of porous semiconductors in solar energy application, like extremely thin absorber solar cells, experimental conditions have been studied in order to obtain a thin absorption layer of copper oxide covering the TiO{sub 2}. Selection of copper formate solution concentration, irradiation time and previous immersion time in the precursor solution has been studied using X-ray diffraction, scanning electron microscopy and optical spectral transmission. Direction and wavelength dependence of photocurrent show that photons are absorbed by the copper oxide and electrons injected to the TiO{sub 2}.

Vigil, Elena [Institute of Materials-Physics Faculty, University of Havana, Colina Universitaria, C. Habana 10 400 (Cuba); Gonzalez, Bernardo [Institute of Materials-Physics Faculty, University of Havana, Colina Universitaria, C. Habana 10 400 (Cuba); Zumeta, Inti [Institute of Materials-Physics Faculty, University of Havana, Colina Universitaria, C. Habana 10 400 (Cuba); Domingo, Concepcion [Institut de Ciencia de Materials de Barcelona (ICMAB), CSIC, 08290 Cerdanyola del Valles (Spain); Domenech, Xavier [Department of Chemistry, Universitat Autonoma de Barcelona, 08290 Cerdanyola del Valles (Spain); Ayllon, Jose A. [Department of Chemistry, Universitat Autonoma de Barcelona, 08290 Cerdanyola del Valles (Spain)]. E-mail: JoseAntonio.Ayllon@uab.es

2005-10-01

84

Measuring True Temperatures Via Polarized Radiation Fluxes in Visible Range of the Spectrum.  

Science.gov (United States)

A method for measuring the true temperature by the relative spectral density distribution of polarized radiation is proposed. One simple version of the technical realization of this method is measurement of the true temperature by the ratio of parallel co...

D. Y. Svet V. I. Sayapina

1970-01-01

85

Spectral LADAR: active range-resolved three-dimensional imaging spectroscopy.  

UK PubMed Central (United Kingdom)

We present the concept and experimental results for Spectral LADAR, an augmented LADAR imager combining three-dimensional (3D) time-of-flight ranging with active multispectral sensing in the shortwave infrared (1080-1620 nm). The demonstrated technique is based on a nanosecond regime pulsed supercontinuum transmitter and spectrally multiplexed receiver that computes a high-resolution range value for each of 25 spectral bands. A low frame-rate prototype unit is described. Results demonstrating 3D imaging and material type classification of objects, especially those obscured by camouflage, are shown at effective stand-off ranges exceeding 40 m. These capabilities and the highly eye safe wavelengths at which the system operates make it suitable for applications in military imaging and robotic perception.

Powers MA; Davis CC

2012-04-01

86

Flat lensing in the visible frequency range by woodpile photonic crystals.  

UK PubMed Central (United Kingdom)

We experimentally demonstrate full two-dimensional focalization of light beams at visible frequencies by a three-dimensional woodpile photonic crystal. The focalization (the flat lensing) with focal distances of the order of 50-70 ?m is experimentally demonstrated. Experimental results are compared with numerical calculations and interpreted by harmonic expansion studies.

Maigyte L; Purlys V; Trull J; Peckus M; Cojocaru C; Gailevi?ius D; Malinauskas M; Staliunas K

2013-07-01

87

Mode-locked ytterbium fiber laser tunable in the 980-1070-nm spectral range.  

UK PubMed Central (United Kingdom)

Spectral tuning of a mode-locked Yb-doped fiber laser over a 90-nm range is reported. Using semiconductor saturable absorber mirrors in a fiber laser cavity incorporating a grating-pair dispersive delay line, we obtain reliable self-starting mode locking over the whole tuning range. The wide tuning range is achieved by optimization of reflection characteristics and bandgap energy of the multiple-quantum-well semiconductor saturable absorber and by proper engineering of the laser cavity.

Okhotnikov OG; Gomes L; Xiang N; Jouhti T; Grudinin AB

2003-09-01

88

Mode-locked ytterbium fiber laser tunable in the 980-1070-nm spectral range.  

Science.gov (United States)

Spectral tuning of a mode-locked Yb-doped fiber laser over a 90-nm range is reported. Using semiconductor saturable absorber mirrors in a fiber laser cavity incorporating a grating-pair dispersive delay line, we obtain reliable self-starting mode locking over the whole tuning range. The wide tuning range is achieved by optimization of reflection characteristics and bandgap energy of the multiple-quantum-well semiconductor saturable absorber and by proper engineering of the laser cavity. PMID:12956366

Okhotnikov, O G; Gomes, L; Xiang, N; Jouhti, T; Grudinin, A B

2003-09-01

89

Free spectral range measurement of a fiberized Fabry-Perot etalon with sub-Hz accuracy.  

Science.gov (United States)

In this work a narrow linewidth (1 kHz) laser source is used to measure the free spectral range of a fiberized Fabry-Perot etalon with sub-Hz accuracy (10(-8)). A previously demonstrated technique based on the Pound-Drever-Hall error signal is improved in accuracy by the use of a narrow linewidth laser swept in frequency via an acousto-optic modulator, or single sideband generation. The sub-Hz (10(-8)) accuracy attained enables the characterization of both the long-term drift and the polarization dependence of the free spectral range of the fiberized etalon. PMID:20588986

Mandridis, Dimitrios; Ozdur, Ibrahim; Bagnell, Marcus; Delfyett, Peter J

2010-05-24

90

Measurement of transition probabilities in Kr II UV and visible spectral lines  

Energy Technology Data Exchange (ETDEWEB)

This work reports an extensive collection of 120 atomic transition probabilities of Kr II lines in the spectral region 350-720 nm, all of them measured in an emission experiment. For many of them, these are the first data up to the authors' knowledge. Relative intensity measurements have been obtained on a pulsed discharge lamp and the absolute A{sub ki}-values have been calculated by considering the available data from the literature as reference for the plasma temperature diagnosis. Excitation temperature (14 000-28 000 K) has been determined by using the Boltzmann-plot method. The plasma electron density (0.2-0.8 x 10{sup 23} m{sup -3}) has been determined by two-wavelength interferometry. This work extends a previous one already published by our laboratory [1, 2]. Comparisons have also been made with previous literature values.

Mar, S [Departamento de Fisica Teorica, Atomica y Optica, Universidad de Valladolid, 47071 Valladolid (Spain); Val, J A del [Departamento de Fisica Aplicada, Universidad de Salamanca, E. Politecnica Superior 05071 Avila (Spain); RodrIguez, F [Departamento de Fisica Teorica, Atomica y Optica, Universidad de Valladolid, 47071 Valladolid (Spain); Pelaez, R J [Departamento de Fisica Teorica, Atomica y Optica, Universidad de Valladolid, 47071 Valladolid (Spain); Gonzalez, V R [Departamento de Fisica Teorica, Atomica y Optica, Universidad de Valladolid, 47071 Valladolid (Spain); Gonzalo, A B [Departamento de Fisica Aplicada, Universidad de Salamanca, E. Politecnica Superior 05071 Avila (Spain); Castro, A de [Departamento de Fisica Teorica, Atomica y Optica, Universidad de Valladolid, 47071 Valladolid (Spain); Aparicio, J A [Departamento de Fisica Teorica, Atomica y Optica, Universidad de Valladolid, 47071 Valladolid (Spain)

2006-09-28

91

Method And Apparatus For Examining A Tissue Using The Spectral Wing Emission Therefrom Induced By Visible To Infrared Photoexcitation.  

Energy Technology Data Exchange (ETDEWEB)

Method and an apparatus for examining a tissue using the spectral wing emission therefrom induced by visible to infrared photoexcitation. In one aspect, the method is used to characterize the condition of a tissue sample and comprises the steps of (a) photoexciting the tissue sample with substantially monochromatic light having a wavelength of at least 600 nm; and (b) using the resultant far red and near infrared spectral wing emission (SW) emitted from the tissue sample to characterize the condition of the tissue sample. In one embodiment, the substantially monochromatic photoexciting light is a continuous beam of light, and the resultant steady-state far red and near infrared SW emission from the tissue sample is used to characterize the condition of the tissue sample. In another embodiment, the substantially monochromatic photoexciting light is a light pulse, and the resultant time-resolved far red and near infrared SW emission emitted from the tissue sample is used to characterize the condition of the tissue sample. In still another embodiment, the substantially monochromatic photoexciting light is a polarized light pulse, and the parallel and perpendicular components of the resultant polarized time-resolved SW emission emitted from the tissue sample are used to characterize the condition of the tissue sample.

Alfano, Robert R. (3777 Independence Ave., Bronx, NY 10463); Demos, Stavros G. (3550 Pacific Ave., Apt. 304, Livermore, CA 94550); Zhang, Gang (3 Rieder Rd., Edison, NJ 08817)

2003-12-16

92

Long-range 1H-15N heteronuclear shift correlation across wide F1 spectral windows.  

UK PubMed Central (United Kingdom)

Long-range (1)H-(15)N heteronuclear shift correlation experiments at natural abundance are becoming more routinely utilized in the characterization of unknown chemical structures from a diverse range of sources including natural products and pharmaceuticals. Apart from the inherent challenges of the low gyromagnetic ratio and natural abundance of (15)N, investigators are also occasionally hampered by having to deal with the wide spectral range inherent to various nitrogen functional groups, which can exceed 500 ppm. Earlier triple resonance cryoprobe designs typically provided 90° (15)N pulses in the range of 35-40 µs, which did not allow the uniform excitation of wide F(1) spectral ranges for (1)H-(15)N GHMBC spectra. We report the results obtained with a newly designed Bruker 600 MHz triple resonance TCI Micro CryoProbe™ using methyl orange as a model compound, in which the (15)N resonances are separated by >450 ppm.

Martin GE; Hilton BD; Moskau D; Freytag N; Kessler K; Colson K

2010-12-01

93

Long-range 1H-15N heteronuclear shift correlation across wide F1 spectral windows.  

Science.gov (United States)

Long-range (1)H-(15)N heteronuclear shift correlation experiments at natural abundance are becoming more routinely utilized in the characterization of unknown chemical structures from a diverse range of sources including natural products and pharmaceuticals. Apart from the inherent challenges of the low gyromagnetic ratio and natural abundance of (15)N, investigators are also occasionally hampered by having to deal with the wide spectral range inherent to various nitrogen functional groups, which can exceed 500 ppm. Earlier triple resonance cryoprobe designs typically provided 90° (15)N pulses in the range of 35-40 µs, which did not allow the uniform excitation of wide F(1) spectral ranges for (1)H-(15)N GHMBC spectra. We report the results obtained with a newly designed Bruker 600 MHz triple resonance TCI Micro CryoProbe™ using methyl orange as a model compound, in which the (15)N resonances are separated by >450 ppm. PMID:21072790

Martin, Gary E; Hilton, Bruce D; Moskau, Detlef; Freytag, Nicolas; Kessler, Klemens; Colson, Kim

2010-12-01

94

Negative refraction and sub-wavelength focusing in the visible range using transparent metallo-dielectric stacks.  

UK PubMed Central (United Kingdom)

We numerically demonstrate negative refraction of the Poynting vector and sub-wavelength focusing in the visible part of the spectrum using a transparent multilayer, metallo-dielectric photonic band gap structure. Our results reveal that in the wavelength regime of interest evanescent waves are not transmitted by the structure, and that the main underlying physical mechanisms for sub-wavelength focusing are resonance tunneling, field localization, and propagation effects. These structures offer several advantages: tunability and high transmittance (50% or better) across the visible and near IR ranges; large object-image distances, with image planes located beyond the range where the evanescent waves have decayed. From a practical point of view, our findings point to a simpler way to fabricate a material that exhibits negative refraction and maintains high transparency across a broad wavelength range. Transparent metallo-dielectric stacks also provide an opportunity to expand the exploration of wave propagation phenomena in metals, both in the linear and nonlinear regimes.

Scalora M; D'Aguanno G; Mattiucci N; Bloemer MJ; de Ceglia D; Centini M; Mandatori A; Sibilia C; Akozbek N; Cappeddu MG; Fowler M; Haus JW

2007-01-01

95

Spectral irradiance model for tungsten halogen lamps in 340-850 nm wavelength range  

International Nuclear Information System (INIS)

We have developed a physical model for the spectral irradiance of 1 kW tungsten halogen incandescent lamps for the wavelength range 340-850 nm. The model consists of the Planck's radiation law, published values for the emissivity of tungsten, and a residual spectral correction function taking into account unknown factors of the lamp. The correction function was determined by measuring the spectra of a 1000 W, quartz-halogen, tungsten coiled filament (FEL) lamp at different temperatures. The new model was tested with lamps of types FEL and 1000 W, 120 V quartz halogen (DXW). Comparisons with measurements of two national standards laboratories indicate that the model can account for the spectral irradiance values of lamps with an agreement better than 1% throughout the spectral region studied. We further demonstrate that the spectral irradiance of a lamp can be predicted with an expanded uncertainty of 2.6% if the color temperature and illuminance values for the lamp are known with expanded uncertainties of 20 K and 2%, respectively. In addition, it is suggested that the spectral irradiance may be derived from resistance measurements of the filament with lamp on and off.

2010-02-10

96

Spectral solar irradiance in the range 300-1100 nm measured at Valencia, Spain  

Energy Technology Data Exchange (ETDEWEB)

A programme of measurements aimed at originating a database of spectral solar irradiance which is representative of a wide range of optical masses and atmospheric conditions is described. A preliminary analysis of the measurements for clear-sky conditions is also presented. (Author)

Martinez-Lozano, J.A.; Utrillas, M.P.; Tena, F. [Valencia Univ. (Spain). Dept. de Termodinamica

1995-12-31

97

Evaluation of skin melanoma in spectral range 450-950 nm using principal component analysis  

Science.gov (United States)

Diagnostic potential of principal component analysis (PCA) of multi-spectral imaging data in the wavelength range 450- 950 nm for distant skin melanoma recognition is discussed. Processing of the measured clinical data by means of PCA resulted in clear separation between malignant melanomas and pigmented nevi.

Jakovels, D.; Lihacova, I.; Kuzmina, I.; Spigulis, J.

2013-06-01

98

A first glance into the Spectral Energy Distributions of Single Stellar Populations in the Infrared range  

Science.gov (United States)

The present work shows the Spectral Energy Distributions (SEDs) in the infrared using the IRTF stellar library, obtained using models based on Single Stellar population Models (SSP). We have focused on the K band in order to compare with observables of elliptical galaxies. We also present the comparisons of our models with velocity dispersions, ages and metallicities obtained with models in the optical range.

Meneses-Goytia, Sofia; Peletier, Reynier F.

2012-08-01

99

Wavelength conversion based spectral imaging  

DEFF Research Database (Denmark)

There has been a strong, application driven development of Si-based cameras and spectrometers for imaging and spectral analysis of light in the visible and near infrared spectral range. This has resulted in very efficient devices, with high quantum efficiency, good signal to noise ratio and high resolution for this spectral region. Today, an increasing number of applications exists outside the spectral region covered by Si-based devices, e.g. within cleantech, medical or food imaging. We present a technology based on wavelength conversion which will extend the spectral coverage of state of the art visible or near infrared cameras and spectrometers to include other spectral regions of interest.

Dam, Jeppe Seidelin

100

Minor planet spectrometry. 4 Vesta: spectral range 0.48-0.55?m  

International Nuclear Information System (INIS)

Two absorption bands at 0.51 and 0.54 ?m are found in the spectrum of 4 Vesta, obtained with the 20.48 A spectral resolution. These bands are due to spin-forbidden transitions of the d-electrons in Fe2+ ions in pyroxene. Analogous bands are present only in the basaltic achondritic spectra. A conclusion is drawn that detailed spectrophotometry of the S-, R-, U-asteroids in the spectral range 0.48-0.6 ?m can give information on the presence of the differentiated matter of the certain kind on their surface.

1986-01-01

 
 
 
 
101

Average spectral curves of extraterrestrial solar irradiance in the (180-400) nm wavelength range  

Energy Technology Data Exchange (ETDEWEB)

Twenty-three spectral curves of extraterrestrial solar irradiance in the (180-400) nm wavelength range, derived from measurements taken on rockets and airborne platforms by various research groups, were examined in order to determine the average spectral curves of extraterrestrial solar irradiance. Such curves can be more realibly used in computational programmes prepared for simulating the radiative-transfer processes occurring in the terrestrial atmosphere. For each spectral curve, a careful examination was performed of the errors due to instrumental characteristics, calibration procedures, atmospheric extinction, solar limb-darkening effects, as well as to the use of normalization procedures to zero-air-mass and the mean Earth-Sun distance. A further analysis was performed in order to evaluate the variability of the extraterrestrial solar irradiance as a function of solar activity, but indistinct and contradictory results were found, presumably because the experimental errors were greater than the periodical changes in the density flux of extraterrestrial solar radiation.

Tomasi, C.; Di Giuseppe, F.; Cappelli, L.; Vitale, L. [CNR, Bologna (Italy). Istituto Fisbat

1996-07-01

102

Optical properties of metallic (III,Mn)V ferromagnetic semiconductors in the infrared to visible range  

CERN Document Server

We report on a study of the ac conductivity and magneto-optical properties of metallic ferromagnetic (III,Mn)V semiconductors in the infrared to visible spectrum. Our analysis is based on the successful kinetic exchange model for (III,Mn)V ferromagnetic semiconductors. We perform the calculations within the Kubo formalism and treat the disorder effects pertubatively within the Born approximation, valid for the metallic regime. We consider an eight-band Kohn-Luttinger model (six valence bands plus two conduction bands) as well as a ten-band model with additional dispersionless bands simulating phenomenologically the upper-mid-gap states induced by antisite and interstitial impurities. These models qualitatively account for optical-absorption experiments and predict new features in the mid-infrared Kerr angle and magnetic-circular-dichroism properties as a function of Mn concentration and free carrier density.

Hankiewicz, E M; Dietl, T; Timm, C; Sinova, J; Sinova, Jairo

2004-01-01

103

Study on the Incidence of Opportunity Crime on Residential Streets Considering Traffic Volume and Visible Range  

Directory of Open Access Journals (Sweden)

Full Text Available As a basic step, in this study we propose a model to describe the snatchincident on residential streets. This model is based on one of themethodologies of social science and the Crime Prevention ThroughEnvironmental Design’s concept. The objective variable is the feasibility ofsnatch and explanatory variables are physical factors concerning roadnetwork design and traffic regulation, like traffic volume and visible rangeon streets.As the result of the application to actual situations, the model providedreasonable predictions for distribution of point of incidence in a streetsection. It is possible to examine the influence that road network design andtraffic regulation have on snatch by extending this model to road network.

Chiaki MATSUNAGA; Daiki OKUDA; Kenichi TERAMACHI; Tomonori SUMI

2011-01-01

104

The influence of thermal treatment of the porous glass plates on the character of their scattering in visible spectral region  

Directory of Open Access Journals (Sweden)

Full Text Available The pore structure and light transmission of the high-silica porous glasses in visible spectral region are investigated depending on a temperature of their thermal treatment and composition of the initial two-phase alkali borosilicate glasses. The character of light transmission in porous glasses is analyzed considering the features of their pore space structure and processes occurring in porous glass upon heating. It is shown that with an increase in temperature of thermal treatment of the porous glasses of different composition the pore size increases, and their specific surface decreases (at practically constant common porosity), which is due to the processes of pore overcondensation, that occur owing to the regrouping and change of packing density of the secondary silica particles. It is shown that introducting phosphate and fluoride ions in the basic alkali borosilicate glass results in an increase in the light attenuation factors of the porous glasses owing to an increase in the sizes of liquation areas of heterogeneity in initial two-phase glasses, formation of larger pores and presence of the nanostructured microcrystalline phases in the porous glasses.

Tatyana V. Antropova; Irina N. Anfimova

2010-01-01

105

Natural variability of bio-optical properties in Case 1 waters: attenuation and reflectance within the visible and near-UV spectral domains, as observed in South Pacific and Mediterranean waters  

Directory of Open Access Journals (Sweden)

Full Text Available The optical properties of Case 1 waters have been empirically related to the chlorophyll concentration, [Chl], historically used as an index of the trophic state and of the abundance of the biological materials. The well-known natural variability around the mean statistical relationships is here examined by comparing the apparent optical properties (spectral downward irradiance attenuation and reflectance) as a function of [Chl] in two Case 1 environments, the Pacific and Mediterranean waters. These oceanic zones apparently represent two extremes of the possible bio-optical variability range around the mean. The systematic deviations, in both directions with respect to the average laws, mainly result from the differing contents in non-algal detrital materials and dissolved colored substance for a given [Chl] level. These contents are higher than the average in the Mediterranean Sea, and lower in the Pacific Ocean, respectively. These divergences between the two water bodies, detectable in the visible spectral domain, are considerably accentuated in the UV domain. The bio-optical properties in this spectral domain (310–400 nm) are systematically explored. They are more varying for a given [Chl] than those in the visible domain. Their prediction based on the sole [Chl] index is thus problematic, although it is probably possible on a regional scale if reliable field data are available. It does not seem, however, that ubiquitous relationships exist for this spectral domain for all Case 1 waters at global scale.

A. Morel; H. Claustre; D. Antoine; B. Gentili

2007-01-01

106

New method for automatic optimization of glass combination in optical systems working in the visible range  

Science.gov (United States)

The algorithm presented in this paper proposes a way to find the optimum glasses that assure a better correction for optical apparatus with the human eye as a final receiver. The model (Ne, v1, v2), based on the Buchdahl formula, gives an approximation error for the refraction index less than 5(DOT)10-5 for visible domain. We introduced in the merit function used for optimizing the optical system an operand that describes the existence of an optical glass. This operand was defined so that the obtained value for Ne, v1 and v2 can be closed to some values for a real glass. A definition for this operand is obtained using the PNe, Pv1, Pv2, probabilities of existence for a glass with a certain parameter Ne, v1 or v2. Another possibility to define this operand is to describe the volume occupied by the optical glass in (Ne, v1, v2) space with some elliptical functions. The probabilities and the elliptical functions were found after an analysis for all optical glasses listed in the Schott catalogues was made.

Ralea, Daniel; Marginean, Raluca-Maria; Marzu, Marinica

1998-07-01

107

Spectral 6DOF registration of noisy 3D range data with partial overlap.  

Science.gov (United States)

We present Spectral Registration with Multilayer Resampling (SRMR) as a 6 Degrees Of Freedom (DOF) registration method for noisy 3D data with partial overlap. The algorithm is based on decoupling 3D rotation from 3D translation by a corresponding resampling process of the spectral magnitude of a 3D Fast Fourier Transform (FFT) calculation on discretized 3D range data. The registration of all 6DOF is then subsequently carried out with spectral registrations using Phase Only Matched Filtering (POMF). There are two main aspects for the fast and robust registration of Euler angles from spherical information in SRMR. First of all, there is the permanent use of phase matching. Second, based on the FFT on a discrete Cartesian grid, not only one spherical layer but also a complete stack of layers are processed in one step. Experiments are presented with challenging datasets with respect to interference and overlap. The results include the fast and robust registration of artificially transformed data for ground-truth comparison, scans from the Stanford Bunny dataset, high end 3D laser range finder (LRF) scans of a city center, and range data from a low-cost actuated LRF in a disaster response scenario. PMID:22868648

Bülow, Heiko; Birk, Andreas

2013-04-01

108

Spectral 6DOF registration of noisy 3D range data with partial overlap.  

UK PubMed Central (United Kingdom)

We present Spectral Registration with Multilayer Resampling (SRMR) as a 6 Degrees Of Freedom (DOF) registration method for noisy 3D data with partial overlap. The algorithm is based on decoupling 3D rotation from 3D translation by a corresponding resampling process of the spectral magnitude of a 3D Fast Fourier Transform (FFT) calculation on discretized 3D range data. The registration of all 6DOF is then subsequently carried out with spectral registrations using Phase Only Matched Filtering (POMF). There are two main aspects for the fast and robust registration of Euler angles from spherical information in SRMR. First of all, there is the permanent use of phase matching. Second, based on the FFT on a discrete Cartesian grid, not only one spherical layer but also a complete stack of layers are processed in one step. Experiments are presented with challenging datasets with respect to interference and overlap. The results include the fast and robust registration of artificially transformed data for ground-truth comparison, scans from the Stanford Bunny dataset, high end 3D laser range finder (LRF) scans of a city center, and range data from a low-cost actuated LRF in a disaster response scenario.

Bülow H; Birk A

2013-04-01

109

Inertial-range structure of Gross–Pitaevskii turbulence within a spectral closure approximation  

Science.gov (United States)

The inertial-range structure of turbulence obeying the Gross–Pitaevskii equation, the equation of motion for quantum fluids, is analyzed by means of a spectral closure approximation. It is revealed that, for the energy-transfer range, the spectrum of the order parameter field ? obeys k?2 law for k ? k* and k?1 law for k ? k*, where k* is the wavenumber where the characteristic timescales associated with linear and nonlinear terms are of the same order. It is also shown that, for the particle-number-transfer range, the spectrum obeys k?1 law for k ? k*, n and k?1/3 law for k ? k*, n, where k*, n is the wavenumber corresponding to k* in the particle-number-transfer range.

Yoshida, Kyo; Arimitsu, Toshihico

2013-08-01

110

Emission of an oxygen-iodine chemical laser in the visible range  

Energy Technology Data Exchange (ETDEWEB)

Luminescence spectra of the active medium of the oxygen-iodine chemical laser are presented in the range 600-700 nm for different iodine concentrations. It is suggested that the red luminescence observed for small ion concentrations is produced by the ICl molecule. A possible mechanism for the formation of excited ICl molecules is proposed.

Vagin, N.P.; Konoshenko, A.F.; Kriukov, P.G.; Frolov, M.P.; Iuryshev, N.N. (Fizicheskii Institut, Moscow (USSR))

1990-02-01

111

A Visibility Matching Tone Reproduction Operator for High Dynamic Range Scenes  

UK PubMed Central (United Kingdom)

We present a tone reproduction operator that preservesvisibility in high dynamic range scenes. Our methodintroduces a new histogram adjustment technique, based onthe population of local adaptation luminances in a scene.To match subjective viewing experience, the methodincorporates models for human contrast sensitivity, glare,spatial acuity and color sensitivity. We compare our resultsto previous work and present examples of our techniquesapplied to lighting simulation and electronic photography.Keywords: Shading, Image Manipulation.1 IntroductionThe real world exhibits a wide range of luminance values. The human visual system iscapable of perceiving scenes spanning 5 orders of magnitude, and adapting moregradually to over 9 orders of magnitude. Advanced techniques for producing syntheticimages, such as radiosity and Monte Carlo ray tracing, compute the map of luminancesthat would reach an observer of a real scene. The media used to display these results --either a vide...

Gregory Ward Larson; Holly Rushmeier; Christine Piatko

112

Broadband superresolving lens with high transparency for propagating and evanescent waves in the visible range  

CERN Multimedia

We present a theoretical analysis of a super-resolving lens based on 1-dimensional metallo-dielectric photonic crystals composed of Ag/GaP multilayers. The lens contains a total of 10 optical skin depths of Ag, yet maintains a normal incidence transmittance of ~50% for propagating waves over the super-resolving wavelength range of 500-650 nm. The individual Ag layers are 22 nm thick and can be readily fabricated in conventional deposition systems. The importance of anti-reflection coatings for the transmission of evanescent and propagating waves is illustrated by comparison to periodic and symmetric structures without the coatings. In addition, the reflection for propagating waves is reduced to ~5% across the super-resolving wavelength band diminishing the interference between the object and the lens.

Bloemer, M J; D'Aguanno, G; Mattiucci, N; Scalora, M; Aguanno, Giuseppe D'; Akozbek, Neset; Bloemer, Mark J.; Mattiucci, Nadia; Scalora, Michael

2006-01-01

113

Model-Independent Sum Rule Analysis Based on Limited-Range Spectral Data  

CERN Document Server

Partial sum rules are widely used in physics to separate low- and high-energy degrees of freedom of complex dynamical systems. Their application, though, is challenged in practice by the always finite spectrometer bandwidth and is often performed using risky model-dependent extrapolations. We show that, given spectra of the real and imaginary parts of any causal frequency-dependent response function (for example, optical conductivity, magnetic susceptibility, acoustical impedance etc.) in a limited range, the sum-rule integral from zero to a certain cutoff frequency inside this range can be safely derived using only the Kramers-Kronig dispersion relations without any extra model assumptions. This implies that experimental techniques providing both active and reactive response components independently, such as spectroscopic ellipsometry in optics, allow an extrapolation-independent determination of spectral weight 'hidden' below the lowest accessible frequency.

Kuzmenko, A B; Carbone, F; Marsiglio, F

2007-01-01

114

Cassini/CIRS Observations of Titan's Equatorial Region in the Submillimeter Spectral Range  

Science.gov (United States)

On July 2--3, 2004 UT, the Composite Infrared Spectrometer (CIRS) aboard Cassini recorded spectra of Titan's equatorial latitudes (13S--2N) with a spectral resolution of 0.26 cm-1 (unapodized). We present here the analysis of the average spectrum recorded by the far infrared spectrometer (FP1), covering 10 to 600 cm-1 and corresponding to a total integration time of 4.7 hours. This spectrum shows rotational lines from CO, HCN ,CH4, and possibly H2O. Mean stratospheric abundances of these species have been derived using temperature information from the collision--induced continuum in the FP1 and the 7.7--? m ? 4 band of methane recorded by the mid-infrared spectrometer in FP4. In particular, analyzing simultaneously the ? 4 band and the rotational lines, prominent in the 70--140 cm-1 range, allows us in principle to disentangle the methane mixing ratio and the temperature profile in the stratosphere, the two components affecting differently the emission observed in the two spectral regions.

Bézard, B.; Coustenis, A.; Fouchet, T.; Lellouch, E.; Conrath, B.; Achterberg, R.; Jennings, D.; Flasar, M.; CIRS Investigation

2004-11-01

115

Retrieval interval mapping, a tool to optimize the spectral retrieval range in differential optical absorption spectroscopy  

Directory of Open Access Journals (Sweden)

Full Text Available Remote sensing via differential optical absorption spectroscopy (DOAS) has become a standard technique to identify and quantify trace gases in the atmosphere. The technique is applied in a variety of configurations, commonly classified into active and passive instruments using artificial and natural light sources, respectively. Platforms range from ground based to satellite instruments and trace-gases are studied in all kinds of different environments. Due to the wide range of measurement conditions, atmospheric compositions and instruments used, a specific challenge of a DOAS retrieval is to optimize the parameters for each specific case and particular trace gas of interest. This becomes especially important when measuring close to the detection limit. A well chosen evaluation wavelength range is crucial to the DOAS technique. It should encompass strong absorption bands of the trace gas of interest in order to maximize the sensitivity of the retrieval, while at the same time minimizing absorption structures of other trace gases and thus potential interferences. Also, instrumental limitations and wavelength depending sources of errors (e.g. insufficient corrections for the Ring effect and cross correlations between trace gas cross sections) need to be taken into account. Most often, not all of these requirements can be fulfilled simultaneously and a compromise needs to be found depending on the conditions at hand. Although for many trace gases the overall dependence of common DOAS retrieval on the evaluation wavelength interval is known, a systematic approach to find the optimal retrieval wavelength range and qualitative assessment is missing. Here we present a novel tool to determine the optimal evaluation wavelength range. It is based on mapping retrieved values in the retrieval wavelength space and thus visualize the consequence of different choices of retrieval spectral ranges, e.g. caused by slightly erroneous absorption cross sections, cross correlations and instrumental features. The technique is demonstrated using the examples of a theoretical study of BrO retrievals for stratospheric BrO measurements and for BrO measurements in volcanic plumes. However, due to the general nature of the tool, it is applicable to any type (active or passive) of DOAS retrieval.

L. Vogel; H. Sihler; J. Lampel; T. Wagner; U. Platt

2012-01-01

116

Spectral and spatial characteristics of x-ray film detectors in the wavelength range 20--150 {angstrom}  

Energy Technology Data Exchange (ETDEWEB)

Investigations of spectral sensitivity, contrast coefficient, and spatial resolution of widely used x-ray films have been undertaken at the P.N. Lebedev Institute. A description of experimental methodologies and results are presented. These studies were carried out using synchrotron radiation in the range of 20--150 {angstrom}. Spectral sensitivity and contrast coefficient dependencies on wavelength for Kodak 10106, DEF, RAR2490, and TPF films and spatial resolution for Kodak 10106 and RAR2490 films are presented and discussed.

Fedin, D.A.; Fedorchuk, R.V.; Koshevoi, M.O.; Lukjantsev, I.V.; Rupasov, A.A.; Shikanov, A.S. [Russian Academy of Sciences, Moscow (Russian Federation). P.N. Lebedev Physics Inst.; Gullikson, E. [Lawrence Berkeley Lab., CA (United States)

1995-12-31

117

Full-range k-domain linearization in spectral-domain optical coherence tomography  

Science.gov (United States)

A full-bandwidth k-domain linearization method for spectral-domain optical coherence tomography (SD-OCT) is demonstrated. The method uses information of the wavenumber–pixel-position provided by a translating-slit-based wavelength filter. For calibration purposes, the filter is placed either after a broadband source or at the end of the sample path, and the filtered spectrum with a narrowed line width (~0.5 nm) is incident on a line-scan camera in the detection path. The wavelength-swept spectra are co-registered with the pixel positions according to their central wavelengths, which can be automatically measured with an optical spectrum analyzer. For imaging, the method does not require a filter or a software recalibration algorithm; it simply resamples the OCT signal from the detector array without employing rescaling or interpolation methods. The accuracy of k-linearization is maximized by increasing the k-linearization order, which is known to be a crucial parameter for maintaining a narrow point-spread function (PSF) width at increasing depths. The broadening effect is studied by changing the k-linearization order by undersampling to search for the optimal value. The system provides more position information, surpassing the optimum without compromising the imaging speed. The proposed full-range k-domain linearization method can be applied to SD-OCT systems to simplify their hardware/software, increase their speed, and improve the axial image resolution. The experimentally measured width of PSF in air has an FWHM of 8 ?m at the edge of the axial measurement range. At an imaging depth of 2.5 mm, the sensitivity of the full-range calibration case drops less than 10 dB compared with the uncompensated case.

Jeon, Mansik; Kim, Jeehyun; Jung, Unsang; Lee, Changho; Jung, Woonggyu; Boppart, Stephen A.

2011-01-01

118

Full-range k-domain linearization in spectral-domain optical coherence tomography.  

UK PubMed Central (United Kingdom)

A full-bandwidth k-domain linearization method for spectral-domain optical coherence tomography (SD-OCT) is demonstrated. The method uses information of the wavenumber-pixel-position provided by a translating-slit-based wavelength filter. For calibration purposes, the filter is placed either after a broadband source or at the end of the sample path, and the filtered spectrum with a narrowed line width (?0.5?nm) is incident on a line-scan camera in the detection path. The wavelength-swept spectra are co-registered with the pixel positions according to their central wavelengths, which can be automatically measured with an optical spectrum analyzer. For imaging, the method does not require a filter or a software recalibration algorithm; it simply resamples the OCT signal from the detector array without employing rescaling or interpolation methods. The accuracy of k-linearization is maximized by increasing the k-linearization order, which is known to be a crucial parameter for maintaining a narrow point-spread function (PSF) width at increasing depths. The broadening effect is studied by changing the k-linearization order by undersampling to search for the optimal value. The system provides more position information, surpassing the optimum without compromising the imaging speed. The proposed full-range k-domain linearization method can be applied to SD-OCT systems to simplify their hardware/software, increase their speed, and improve the axial image resolution. The experimentally measured width of PSF in air has an FWHM of 8??m at the edge of the axial measurement range. At an imaging depth of 2.5?mm, the sensitivity of the full-range calibration case drops less than 10?dB compared with the uncompensated case.

Jeon M; Kim J; Jung U; Lee C; Jung W; Boppart SA

2011-03-01

119

Spatial distribution of spectral parameters of high latitude geomagnetic disturbances in the Pc5/Pi3 frequency range  

Directory of Open Access Journals (Sweden)

Full Text Available We analyze spectral parameters of the geomagnetic disturbances within the 1–4 mHz (Pc5/Pi3) frequency range for 29 observatories from polar to auroral latitudes. The main object of this study is the broadband (noise) background under quiet and moderately disturbed conditions. To obtain a quantitative description of background high-latitude long period ULF activity the log-log dependence of the spectral power on frequency is expanded over Legendre polynomials, and the coefficients of this expansion (spectral moments) are used to describe the most common features of these spectra. Not only the spectral power, but also the spectral slope and higher spectral moments, averaged over relatively long time intervals, demonstrate a systematic dependence on corrected geomagnetic (CGM) latitude, ?, and magnetic local time, MLT. The 2-D distributions of the spectral moments in ?-MLT coordinates are characterized by existence of structures, narrow in latitude and extended in MLT, which can be attributed to the projections of different magnetospheric domains. Spatio-temporal distributions of spectral power of elliptically (P-component) and randomly (N-component) polarized signal are similar, but not identical. The N-component contribution to the total signal becomes non-negligible in regions with a high local activity, such as the auroral oval and dayside polar cusp. The spectral slope indicates a larger relative contribution of higher frequencies upon the latitude decrease, probably, as a result of the resonant effects in the ULF noise. The higher spectral moments are also controlled mostly by CGM latitude and MLT and are fundamentally different for the polarized and non-polarized components. This study is a step towards the construction of an empirical model of the ULF wave power in Earth's magnetosphere.

N. V. Yagova; V. A. Pilipenko; L. N. Baransky; M. J. Engebretson

2010-01-01

120

Spectral conditions for strong local nondeterminism and exact Hausdorff measure of ranges of Gaussian random fields  

CERN Document Server

Let $X= \\{X(t), t \\in \\R^N\\}$ be a Gaussian random field with values in $\\R^d$ defined by \\[ X(t) = \\big(X_1(t),..., X_d(t)\\big),\\qquad t \\in \\R^N, \\] where $X_1, ..., X_d$ are independent copies of a real-valued, centered, anisotropic Gaussian random field $X_0$ which has stationary increments and the property of strong local nondeterminism. In this paper we determine the exact Hausdorff measure function for the range $X([0, 1]^N)$. We also provide a sufficient condition for a Gaussian random field with stationary increments to be strongly locally nondeterministic. This condition is given in terms of the spectral measures of the Gaussian random fields which may contain either an absolutely continuous or discrete part. This result strengthens and extends significantly the related theorems of Berman (1973, 1988), Pitt (1978) and Xiao (2007, 2009), and will have wider applicability beyond the scope of the present paper.

Luan, Nana

2011-01-01

 
 
 
 
121

Excitation spectrum of the chemical reaction F2+O2 in the red spectral range  

International Nuclear Information System (INIS)

A search has been made for new, low-energy pathways of the reaction F2+O2?O2F+F or O2F2 through excitation of F2 or O2 in an oxygen matrix with red and near infrared photons. By monitoring the product yield as a function of laser irradiation frequency, a reaction excitation spectrum of O2+F2 was recorded which begins at 14 500 cm-1 and extends through the entire red spectral range. It revealed two discrete absorptions O2 1?+/sub g/, v' = 1reverse arrow3?-/sub g/, v'' = 0 and (O2)2(1?/sub g/,1?/sub g/)0,0 reverse arrow(3?-/sub g/, 3?-/sub g/)0,0, and a continuous, oxygen-enhanced absorption of F2 which is assigned to excitation to the repulsive part of the weakly bound 3Pi0+/sub u/ state. The F2 absorption detected in this experiment extends more than 200 nm to longer wavelengths than any electronic absorption of molecular fluorine reported so far.

1984-01-01

122

Relative calibration of photodiodes in the soft-X-ray spectral range  

International Nuclear Information System (INIS)

A method of obtaining a relative calibration of Si-photodiodes for the spectral range of soft X-rays (1-30 keV) is presented. A simple mathematical model of the pn-diode is adopted which allows the response to be described in terms of a small set of parameters. The diffusion length as well as the thickness of a dead layer below the front surface of the diodes are obtained from measurements of angular dependences of the photoinduced current. We show that a precise characterisation of the diode response and an accurate relative calibration can be obtained using this method. However, we find that the presence of a dead layer a few tenths of a ?m thick can pose severe restrictions on the use of planar diode arrays in X-ray tomography systems where uniformity of response is crucial. The method has been applied to the diode arrays equipping the X-ray tomography system built for the TCV tokamak, a magnetic fusion research device. (author) 13 figs., 10 refs

1995-01-01

123

Natural variability of bio-optical properties in Case 1 waters: attenuation and reflectance within the visible and near-UV spectral domains, as observed in South Pacific and Mediterranean waters  

Directory of Open Access Journals (Sweden)

Full Text Available The optical properties of Case 1 waters have been empirically related to the chlorophyll concentration, [Chl], historically used as an index of the trophic state and of the abundance of the biological materials. The natural variability around the mean statistical relationships is here examined by comparing the apparent optical properties (spectral downward irradiance attenuation and reflectance as a function of [Chl]) which were determined in two environments, the Pacific and Mediterranean waters. These oceanic zones apparently form two extremes of the bio-optical variability range. The systematic deviations, in both directions with respect to the average laws, mainly result from the differing contents in non-algal detrital materials and dissolved colored substance for a given [Chl] level. These contents are higher and lower than the average, in the Mediterranean Sea and Pacific Ocean, respectively. The divergences between the two water bodies, detected in the visible spectral domain, are considerably accentuated in the UV domain. The bio-optical properties in this spectral domain (310–400 nm) are systematically explored. Their prediction based on the sole [Chl] index is problematic; although it is probably possible on a regional scale, an ubiquitous relationship does not seem to exist for the global scale.

A. Morel; H. Claustre; D. Antoine; B. Gentili

2007-01-01

124

Spectral range optimization for the near-infrared quantitative analysis of petrochemical and petroleum products: naphtha and gasoline.  

UK PubMed Central (United Kingdom)

The proper selection of the spectral range in partial least squares (PLS) calibration is critical when highly overlapping spectra from compositionally complex samples are used, such as naphtha and gasoline. In particular, the relevant spectral information related to a given property is frequently localized in a narrow range, and the most selective region may be difficult to locate. We have presented the importance of range optimization in near-infrared (NIR) spectroscopy for the analyses of petrochemical and petroleum products that are generally highly complex in composition. For this purpose, the determination of a detailed compositional analysis (so called PIONA) and the distillation temperature of naphtha were evaluated. In the same fashion, the research octane number (RON) and Reid vapor pressure (RVP) were selected for gasoline. By optimizing the range using moving window (MW) PLS, the overall calibration performance was improved by finding the optimal spectral range for each property. In particular, for a detailed compositional analysis of naphtha, it was effective to search for localized spectral information in a relatively narrow range with fewer factors.

Lee Y; Chung H; Kim N

2006-08-01

125

Spectral range optimization for the near-infrared quantitative analysis of petrochemical and petroleum products: naphtha and gasoline.  

Science.gov (United States)

The proper selection of the spectral range in partial least squares (PLS) calibration is critical when highly overlapping spectra from compositionally complex samples are used, such as naphtha and gasoline. In particular, the relevant spectral information related to a given property is frequently localized in a narrow range, and the most selective region may be difficult to locate. We have presented the importance of range optimization in near-infrared (NIR) spectroscopy for the analyses of petrochemical and petroleum products that are generally highly complex in composition. For this purpose, the determination of a detailed compositional analysis (so called PIONA) and the distillation temperature of naphtha were evaluated. In the same fashion, the research octane number (RON) and Reid vapor pressure (RVP) were selected for gasoline. By optimizing the range using moving window (MW) PLS, the overall calibration performance was improved by finding the optimal spectral range for each property. In particular, for a detailed compositional analysis of naphtha, it was effective to search for localized spectral information in a relatively narrow range with fewer factors. PMID:16925925

Lee, Youngbok; Chung, Hoeil; Kim, Nakjoong

2006-08-01

126

Directional visible light scattering by silicon nanoparticles  

CERN Multimedia

Directional light scattering by spherical silicon nanoparticles in the visible spectral range is experimentally demonstrated for the first time. These unique scattering properties arise due to simultaneous excitation and mutual interference of magnetic and electric dipole resonances inside a single nanosphere. Directivity of the far-field radiation pattern can be controlled by changing light wavelength and the nanoparticle size. Forward-to-backward scattering ratio above 6 can be experimentally obtained at visible wavelengths. These unique properties of silicon nanoparticles make them promising for design of novel low-loss visible- and telecom-range nanoantenna devices.

Fu, Yuan Hsing; Miroshnichenko, Andrey E; Yu, Ye Feng; Lukiyanchuk, Boris

2012-01-01

127

A visible/near-ir spectral database for plutonium solutions of known nitric acid, fluoride, and oxalate composition  

Energy Technology Data Exchange (ETDEWEB)

Fluoride and oxalate are common components of plutonium process solutions. Unfortunately, these anions form highly stable complexes that interfere in many plutonium process operations. Knowledge of the fluoride and oxalate content of process solutions may allow appropriate corrective action to be taken to prevent such interference. On-line spectrophotometry, which is being developed to monitor process solutions at the Los Alamos Plutonium Facility, has the potential to detect and estimate the concentration of these two anions and other solution constituents when the spectral data are processed using chemometric techniques. Spectra of 126 solutions that contained known concentrations of plutonium, fluoride, oxalate, and nitric acid were acquired as a database for on-line spectrophotometry. These spectra and a discussion of their unique spectral features are presented. 4 refs., 34 figs.

Day, R.S.; Vigil, A.R.; Marsh, S.F.

1989-04-01

128

Increasing of frequency range of noise spectral density of silicon p-n-structures under gamma irradiation  

CERN Multimedia

One studied possibility of purpose-oriented shifting of high-frequency boundary of noise plateau-spectral density of silicon p-n-structures towards high frequency range under irradiation by gamma-quanta. One observed the maximum increase of frequency range working band up to 2-2.5 times. At further irradiation of the studied structures the plateau width was not increased and its boundary was eroded. One detected correlation between the variation of lifetime of charge secondary carriers and the width of low-frequency plateau of noise spectral density. One introduced a qualitative model to describe variation of noise spectral density with irradiation flow fro silicon p-n-structures governed by distances of p-n-transition

Baranovskij, O K; Kuchinskij, P V; Petrunin, A P; Savenok, E D

2001-01-01

129

Efficient noncollinear parametric amplification of weak femtosecond pulses in the visible and near-infrared spectral range.  

UK PubMed Central (United Kingdom)

We report measurement of efficient amplification of weak femtosecond supercontinuum seed pulses by use of a noncollinear optical parametric process in BBO crystal pumped with 150-fs pulses from a frequency-doubled regenerative-amplified Ti:sapphire laser at 390nm . The highest amplification factor, 10(8) , was achieved for 3x10(-16)J energy seed pulses at wavelength of 560nm.

Krylov V; Ollikainen O; Gallus J; Wild U; Rebane A; Kalintsev A

1998-01-01

130

Time-resolved spectroscopy on epitaxial graphene in the infrared spectral range: relaxation dynamics and saturation behavior.  

UK PubMed Central (United Kingdom)

We present the results of pump–probe experiments on multilayer graphene samples performed in a wide spectral range, namely from the near infrared (photon energy 1.5 eV) to the terahertz (photon energy 8 meV) spectral range. In the near infrared, exciting carriers and probing at higher photon energies provides direct evidence for a hot carrier distribution. Furthermore, spectroscopic signatures of the highly doped graphene layers at the interface to SiC are observed in the near-infrared range. In the mid-infrared range, the various relaxation mechanisms, in particular scattering via optical phonons and Auger-type processes, are identified by comparing the experimental results to microscopic modeling. Changes from induced transmission to induced absorption are attributed to probing above or below the Fermi edge of the graphene layers. This effect occurs for certain photon energies in the near-infrared range, where it is related to highly doped graphene layers at the interface to SiC, and in the far-infrared range for the quasi-intrinsic graphene layers. In addition to the relaxation dynamics, the saturation of pump-induced bleaching of graphene is studied. Here a quadratic dependence of the saturation fluence on the pump photon energy in the infrared spectral range is revealed.

Winnerl S; Göttfert F; Mittendorff M; Schneider H; Helm M; Winzer T; Malic E; Knorr A; Orlita M; Potemski M; Sprinkle M; Berger C; de Heer WA

2013-02-01

131

Design and development of an injection-molded demultiplexer for optical communication systems in the visible range.  

UK PubMed Central (United Kingdom)

Optical simulation software based on the ray-tracing method offers easy and fast results in imaging optics. This method can also be applied in other fields of light propagation. For short distance communications, polymer optical fibers (POFs) are gradually gaining importance. This kind of fiber offers a larger core diameter, e.g., the step index POF features a core diameter of 980 ?m. Consequently, POFs have a large number of modes (>3 million modes) in the visible range, and ray tracing could be used to simulate the propagation of light. This simulation method is applicable not only for the fiber itself but also for the key components of a complete POF network, e.g., couplers or other key elements of the transmission line. In this paper a demultiplexer designed and developed by means of ray tracing is presented. Compared to the classical optical design, requirements for optimal design differ particularly with regard to minimizing the insertion loss (IL). The basis of the presented key element is a WDM device using a Rowland spectrometer setup. In this approach the input fiber carries multiple wavelengths, which will be divided into multiple output fibers that transmit only one wavelength. To adapt the basic setup to POF, the guidance of light in this element has to be changed fundamentally. Here, a monolithic approach is presented with a blazed grating using an aspheric mirror to minimize most of the aberrations. In the simulations the POF is represented by an area light source, while the grating is analyzed for different orders and the highest possible efficiency. In general, the element should be designed in a way that it can be produced with a mass production technology like injection molding in order to offer a reasonable price. However, designing the elements with regard to injection molding leads to some inherent challenges. The microstructure of an optical grating and the thick-walled 3D molded parts both result in high demands on the injection molding process. This also requires complex machining of the molding tool. Therefore, different experiments are done to optimize the process parameter, find the best molding material, and find a suitable machining method for the molding tool. The paper will describe the development of the demultiplexer by means of ray-tracing simulations step by step. Also, the process steps and the realized solutions for the injection molding are described.

Höll S; Haupt M; Fischer UH

2013-06-01

132

Design and development of an injection-molded demultiplexer for optical communication systems in the visible range.  

Science.gov (United States)

Optical simulation software based on the ray-tracing method offers easy and fast results in imaging optics. This method can also be applied in other fields of light propagation. For short distance communications, polymer optical fibers (POFs) are gradually gaining importance. This kind of fiber offers a larger core diameter, e.g., the step index POF features a core diameter of 980 ?m. Consequently, POFs have a large number of modes (>3 million modes) in the visible range, and ray tracing could be used to simulate the propagation of light. This simulation method is applicable not only for the fiber itself but also for the key components of a complete POF network, e.g., couplers or other key elements of the transmission line. In this paper a demultiplexer designed and developed by means of ray tracing is presented. Compared to the classical optical design, requirements for optimal design differ particularly with regard to minimizing the insertion loss (IL). The basis of the presented key element is a WDM device using a Rowland spectrometer setup. In this approach the input fiber carries multiple wavelengths, which will be divided into multiple output fibers that transmit only one wavelength. To adapt the basic setup to POF, the guidance of light in this element has to be changed fundamentally. Here, a monolithic approach is presented with a blazed grating using an aspheric mirror to minimize most of the aberrations. In the simulations the POF is represented by an area light source, while the grating is analyzed for different orders and the highest possible efficiency. In general, the element should be designed in a way that it can be produced with a mass production technology like injection molding in order to offer a reasonable price. However, designing the elements with regard to injection molding leads to some inherent challenges. The microstructure of an optical grating and the thick-walled 3D molded parts both result in high demands on the injection molding process. This also requires complex machining of the molding tool. Therefore, different experiments are done to optimize the process parameter, find the best molding material, and find a suitable machining method for the molding tool. The paper will describe the development of the demultiplexer by means of ray-tracing simulations step by step. Also, the process steps and the realized solutions for the injection molding are described. PMID:23842150

Höll, S; Haupt, M; Fischer, U H P

2013-06-20

133

Very efficient visible light energy harvesting and conversion by spectral sensitization of high surface area polycrystalline titanium dioxide films  

Energy Technology Data Exchange (ETDEWEB)

By using high surface area (roughness factor ca. 200) polycrystalline anatase films together with tris(2,2'-bipyridyl-4,4'-dicarboxylate)ruthenium(II), RuL/sub 3//sup 4 -/, as a sensitizer, the authors have achieved unprecedentedly high visible light to electric current conversion efficiencies in regenerative photoeletrochemical cells. Incident photon to current conversion efficiencies of 73% have been obtained at the wavelength of maximum absorption of the dye in the presence of iodide as an electron donor. Bromide is oxidized under the same conditions with an efficiency of 56%. A regenerative cell based on the Br/sub 2//By/sup -/ redox system gives a monochromatic light to power conversion efficiency of 12% with a fill factor of 74%. Preliminary results with polychromatic illumination are also presented.

Vlachopoulos, N.; Liska, P.; Augustynski, J.; Graetzel, M.

1988-02-17

134

Single-step method for fiber-optic probe-based full-range spectral domain optical coherence tomography.  

UK PubMed Central (United Kingdom)

We propose a single-step method appropriated for a fiber-optic probe-based full-range spectral domain optical coherence tomography (OCT). The fiber-optic probe was scanned over a sample with a magnetically driven actuator. In the reference arm, a phase shift of ?/2 was applied during two neighbor axial scanning, from which the complex spectral interferogram was directly reconstructed. Since the complex-conjugate-free OCT image is obtained by doing just one Fourier transform on the complex interferogram, obtaining the full-range image is simple in algorithm and effective in computation time. Some full-range images of biological samples created with the proposed method are presented and the processing time is analyzed.

Min EJ; Shin JG; Lee JH; Yasuno Y; Lee BH

2013-07-01

135

Extended in vivo anterior eye-segment imaging with full-range complex spectral domain optical coherence tomography  

Science.gov (United States)

We demonstrate the capability of full-range complex (FRC) spectral domain optical coherence tomography (SD-OCT) to image the anterior eye segment from the cornea to the posterior surface of the lens. With an adapted spectrometer design, we developed a SD-OCT system with an extended normal (single half-space) depth range of 7mm (in air). This OCT-intrinsic depth range was doubled with a FRC technique. We demonstrate the performance of our OCT system by imaging the whole anterior segment of a healthy human eye in vivo.

Jungwirth, Johannes; Baumann, Bernhard; Pircher, Michael; Gotzinger, Erich; Hitzenberger, Christoph K.

2010-01-01

136

A fast radiative transfer model for visible through shortwave infrared spectral reflectances in clear and cloudy atmospheres  

Science.gov (United States)

A computationally efficient radiative transfer model (RTM) for calculating visible (VIS) through shortwave infrared (SWIR) reflectances is developed for use in satellite and airborne cloud property retrievals. The full radiative transfer equation (RTE) for combinations of cloud, aerosol, and molecular layers is solved approximately by using six independent RTEs that assume the plane-parallel approximation along with a single-scattering approximation for Rayleigh scattering. Each of the six RTEs can be solved analytically if the bidirectional reflectance/transmittance distribution functions (BRDF/BTDF) of the cloud/aerosol layers are known. The adding/doubling (AD) algorithm is employed to account for overlapped cloud/aerosol layers and non-Lambertian surfaces. Two approaches are used to mitigate the significant computational burden of the AD algorithm. First, the BRDF and BTDF of single cloud/aerosol layers are pre-computed using the discrete ordinates radiative transfer program (DISORT) implemented with 128 streams, and second, the required integral in the AD algorithm is numerically implemented on a twisted icosahedral mesh. A concise surface BRDF simulator associated with the MODIS land surface product (MCD43) is merged into a fast RTM to accurately account for non-isotropic surface reflectance. The resulting fast RTM is evaluated with respect to its computational accuracy and efficiency. The simulation bias between DISORT and the fast RTM is large (e.g., relative error >5%) only when both the solar zenith angle (SZA) and the viewing zenith angle (VZA) are large (i.e., SZA>45° and VZA>70°). For general situations, i.e., cloud/aerosol layers above a non-Lambertian surface, the fast RTM calculation rate is faster than that of the 128-stream DISORT by approximately two orders of magnitude.

Wang, Chenxi; Yang, Ping; Nasiri, Shaima L.; Platnick, Steven; Baum, Bryan A.; Heidinger, Andrew K.; Liu, Xu

2013-02-01

137

INFRARED SPECTROSCOPY OF GAS-PHASE POLYCYCLIC AROMATIC HYDROCARBON CATIONS IN THE 10–50 ?m SPECTRAL RANGE  

International Nuclear Information System (INIS)

The gas-phase infrared spectra of four polycyclic aromatic hydrocarbon (PAH) cations have been recorded in the 10-50 ?m (or 1000-200 cm–1) spectral range via IR multiple photon dissociation (IRMPD) spectroscopy. Ionized PAHs are formed by UV laser ionization in an effusive beam and subsequently irradiated with a single pulse of narrowband tunable infrared light produced by the Free-Electron Laser for IntraCavity Experiments FELICE. The ion population is then analyzed in a time-of-flight mass spectrometer. Upon resonance, dissociation is induced so that IR spectra can be recorded by monitoring either the depleted parent ion intensity or the appearance of fragment ions as a function of the wavelength. The intracavity IR fluence enables the recording of IRMPD spectra of strongly bound PAH cations in the hitherto inaccessible far-IR spectral range. Experimental spectra are presented for the radical cations of anthracene, tetracene, pentacene, and coronene. Spectra calculated with density functional theory at the B3LYP/6-311g(2df,2pd) level reproduce IR frequencies reasonably accurately in this spectral range when a uniform scaling factor of 0.94 over the complete 10-50 ?m spectral range is employed. We show that even vibrational modes with a calculated IR intensity lower than 1 km mol–1 can be observed. For the catacondensed PAH cations we find CH out-of-plane bending vibrations involving four adjacent CH groups within a few wavenumbers of 733 cm–1, closely matching the 13.6 ?m UIR band. For the larger systems, pentacene and coronene, we observe a continuous structureless background absorption above 400 cm–1 which is attributed to the high density of IR dipole allowed combination modes for these systems.

2011-11-10

138

Wideband range-Doppler processing and beamforming using electro-optic arrays and spectral hole burning materials.  

UK PubMed Central (United Kingdom)

Ubiquitous radar systems look everywhere at all times and require both parallel radar processors and parallel beamformers. Current systems operate with subgigahertz bandwidths and produce a handful of angle-of-arrival (AOA) beams. We present an electro-optic radar processor that combines the multigigahertz wideband capabilities of a spectral hole burning correlator with wideband Doppler processing and the thousands of parallel channels available from an electro-optical beamformer. Preliminary experiments demonstrate 150 MHz bandwidth range correlations across 20 AOA beams.

Braker B; Wagner K

2010-07-01

139

Velocity Dealiased Spectral Estimators of Range Migrating Targets using a Single Low-PRF Wideband Waveform  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Wideband radars are promising systems that may provide numerous advantages, like simultaneous detection of slow and fast moving targets, high range-velocity resolution classification, and electronic countermeasures. Unfortunately, classical processing algorithms are challenged by the range-migration...

Deudon, Francois; Bidon, Stéphanie; Besson, Olivier; Tourneret, Jean-Yves

140

Improving prediction selectivity for on-line near-infrared monitoring of components in etchant solution by spectral range optimization  

Energy Technology Data Exchange (ETDEWEB)

The components (H{sub 3}PO{sub 4}, HNO{sub 3}, CH{sub 3}COOH and water) in an etchant solution have been accurately measured in an on-line manner using near-infrared (NIR) spectroscopy by directly illuminating NIR radiation through a Teflon line. In particular, the spectral features according to the change of H{sub 3}PO{sub 4} or HNO{sub 3} concentrations were not mainly from NIR absorption themselves, but from the perturbation (or displacement) of water bands; therefore, the resulting spectral variations were quite similar to each other. Consequently partial least squares (PLS) prediction selectivity among the components should be the most critical issue for continuous on-line compositional monitoring by NIR spectroscopy. To improve selectivity of the calibration model, we have optimized the calibration models by finding selective spectral ranges with the use of moving window PLS. Using the optimized PLS models for each component, the resulting prediction accuracies were substantially improved. Furthermore, on-line prediction selectivity was evaluated by spiking individual pure components step by step and examining the resulting prediction trends. When optimized PLS models were used, each concentration was selectively and sensitively varied at each spike; meanwhile, when whole or non-optimized ranges were used for PLS, the prediction selectivity was greatly degraded. This study verifies that the selection of an optimal spectral range for PLS is the most important factor to make Teflon-based NIR measurements successful for on-line and real-time monitoring of etching solutions.

Namkung, Hankyu; Lee, Youngbok [Department of Chemistry, College of Natural Sciences, Hanyang University, Haengdang-Dong, Seongdong-Gu, Seoul 133-791 (Korea, Republic of); Chung, Hoeil [Department of Chemistry, College of Natural Sciences, Hanyang University, Haengdang-Dong, Seongdong-Gu, Seoul 133-791 (Korea, Republic of)], E-mail: hoeil@hanyang.ac.kr

2008-01-07

 
 
 
 
141

Cascaded Nondegenerate Four-Wave Mixing Technique for High-Power Single-Cycle Pulse Synthesis in the Visible and Ultraviolet Ranges  

CERN Document Server

We present a new technique to synthesize high-power single-cycle pulses in the visible and ultraviolet ranges by coherent superposition of a multiband octave-spanning spectrum obtained by highly-nondegenerate cascaded four-wave mixing of femtosecond pulses in bulk isotropic nonresonant media. The generation of coherent spectra spanning over two octaves in bandwidth is experimentally demonstrated using a thin fused silica slide. Full characterization of the intervening multicolored fields using frequency-resolved optical gating, where multiple cascaded orders have been measured simultaneously for the first time, supports the possibility of direct synthesis of near-single-cycle 2.2 fs visible-UV pulses without recurring to complex amplitude or phase control, which should enable many applications in science and technology.

Weigand, Rosa; Crespo, Helder M

2009-01-01

142

Thiol-stabilized PbS quantum dots with stable luminescence in the infrared spectral range  

Science.gov (United States)

Using thiol-stabilizing aqueous solution method, we have synthesized PbS quantum dots (QDs) that emit stable and spectrally tunable photoluminescence in the optical telecommunication band at around 1300nm. The emission wavelength of the QDs was varied from 1295 to 1330nm by increasing the synthesis time or Pb2+/TGA molar ratio. PbS nanocrystals (NCs) were directly imaged using high-resolution transmission electron microscopy, which gave an evaluation of the averaged sizes and the symmetry indexes of NCs. The symmetry index of NCs synthesized for 96h was improved to 0.92 from 0.85, compared with that synthesized for 24h. It has been found that chemically synthesized water-soluble PbS QDs are a potential source of entangled photon pairs in the near future.

Nakashima, Seisuke; Hoshino, Ai; Cai, Junjiang; Mukai, Kohki

2013-09-01

143

Effect of index contrasts in the wide spectral-range control of slot waveguide dispersion.  

Science.gov (United States)

Here we examine the waveguide dispersion property of slot waveguides, approaching/analyzing the given problem with respect to the normalized index contrast, ?nslot-core/ncore and ?ncore-clad/ncore between adjacent layers . For two index contrasts of concern, it is found that their contributions to slot waveguide dispersions are substantially different, with ?nslot-core and ?ncore-clad each acting preferentially on short- and long-wavelength regions. Additional degrees of freedom in the waveguide design, such as the effect of absolute refractive index and waveguide geometry are also investigated to enable flexible tuning of the waveguide dispersion. Focusing on the unexplored regime of slot waveguides design in short wavelength (Ta2O5/TiO2/silica slot, either of two-octave spectral width (0.467–1.581 ?m), or of one-octave, near unity coherence |g12(1)| = 1. PMID:22714346

Ryu, Hyungsuk; Kim, Jaehun; Jhon, Young Min; Lee, Seok; Park, Namkyoo

2012-06-01

144

Scanning Fabry-Perot interferometer with largely tuneable free spectral range for high resolution spectroscopy of single quantum dots.  

UK PubMed Central (United Kingdom)

We report on the implementation of a scanning Fabry-Pérot interferometer for photoluminescence spectroscopy investigation. We choose a conveniently small reflectivity of the two planar semitransparent mirrors which, in spite of a moderate cavity finesse, ensures a good mechanical stability over a long time. We also exploit the large tuneability of the cavity length (i.e., of the free spectral range) for changing the spectral resolution over two order of magnitude (from ~300 ?eV to ~4 ?eV in full width at half maximum). Such a characteristic easily allows to scan both sharp and broad luminescence bands. We test our Fabry-Pérot interferometer on sharp photoluminescence lines resulting from excitonic recombination in self-assembled GaAs quantum dots. We demonstrate the ability of our system to resolve linewidth as small as 4 ?eV.

Abbarchi M; Kuroda T; Duval R; Mano T; Sakoda K

2011-07-01

145

Spectral Broadening and Suppression of Excitation Induced by Ultralong-Range Interactions in a Cold Gas of Rydberg Atoms  

CERN Multimedia

We report on the observation of ultra long-range interactions in a gas of cold Rubidium Rydberg atoms. The van-der-Waals interaction between a pair of Rydberg atoms separated as far as 100,000 Bohr radii features two important effects: Spectral broadening of the resonance lines and suppression of excitation with increasing density. The density dependence of these effects is investigated in detail for S-, P- and D-Rydberg states with main quantum numbers n~60 and n~80 excited by narrow-band continuous-wave laser light. The spectral broadening of the P-states is compared to ab initio interaction potentials. The density-dependent suppression of excitation can be interpreted as the onset of an interaction-induced local blockade.

Singer, K; Amthor, T; Marcassa, L G; Weidemüller, M; Singer, Kilian; Reetz-Lamour, Markus; Amthor, Thomas; Marcassa, Luis Gustavo; Weidem\\"uller, Matthias

2004-01-01

146

Vesta and the HED Meteorites: Comparison of Spectral Properties  

Science.gov (United States)

We present the main results obtained comparing spectral data in the visible-near infrared range of Vesta’s surface acquired by the Dawn spacecraft with those for howardite, eucrite, diogenite (HED) meteorites.

Ammannito, E.; De Sanctis, M. C.; Fonte, S.; Magni, G.; Capaccioni, F.; Carraro, F.; Capria, M. T.; Farina, M.; Frigeri, A.; Marchi, S.; Palomba, E.; Tosi, F.; Zambon, F.; Blewett, D.; Combe, J. P.; McCord, T. B.; Mittlefehldt, D. W.; McSween, H. Y.; Pieters, C. M.; Sunshine, J. M.; Titus, T. N.; Toplis, M.; Joy, S. P.; Polanskey, C. A.; Raymond, C. A.; Russell, C. T.

2012-05-01

147

Spectral optical properties of long-range transport Asian dust and pollution aerosols over Northeast Asia in 2007 and 2008  

Directory of Open Access Journals (Sweden)

Full Text Available As a part of the IGAC (International Global Atmospheric Chemistry) Mega-cities program, aerosol physical and optical properties were continuously measured from March 2007 to March 2008 at an urban site (37.57° N, 126.94° E) in Seoul, Korea. Spectral optical properties of long-range transported Asian dust and pollution aerosols have been investigated based on the year long measurement data. Optically measured black carbon/thermally measured elemental carbon (BC/EC) ratio showed clear monthly variation with high values in summer and low values in winter mainly due to the enhancement of light attenuation by the internal mixing of EC. Novel approach has been suggested to retrieve the spectral light absorption coefficient (babs) from Aethalometer raw data by using BC/EC ratio. Mass absorption efficiency, ?abs (=babs/EC) at 550 nm was determined to be 9.0±1.3, 8.9±1.5, 9.5±2.0, and 10.3±1.7 m2 g?1 in spring, summer, fall, and winter, respectively with an annual mean of 9.4±1.8 m2 g?1. Threshold values to classify severe haze events were suggested in this study. Increasing trend of aerosol single scattering albedo (SSA) with wavelength was observed during Asian dust events while little spectral dependence of SSA was observed during long-range transport pollution (LTP) events. Satellite aerosol optical thickness (AOT) and Hysplit air mass backward trajectory analyses as well as chemical analysis were performed to characterize the dependence of spectral optical properties on aerosol type. Results from this study can provide useful information for studies on regional air quality and aerosol's effects on climate change.

J. Jung; Y. J. Kim; K. Y. Lee; M. G. -Cayetano; T. Batmunkh; J.-H. Koo; J. Kim

2010-01-01

148

Spectral optical properties of long-range transport Asian dust and pollution aerosols over Northeast Asia in 2007 and 2008  

Directory of Open Access Journals (Sweden)

Full Text Available As a part of the IGAC (International Global Atmospheric Chemistry) Mega-cities program, aerosol physical and optical properties were continuously measured from March 2007 to March 2008 at an urban site (37.57° N, 126.94° E) in Seoul, Korea. Spectral optical properties of long-range transported Asian dust and pollution aerosols have been investigated based on the year long measurement data. Optically measured black carbon/thermally measured elemental carbon (BC/EC) ratio showed clear monthly variation with high values in summer and low values in winter mainly due to the enhancement of light attenuation by the internal mixing of EC. Novel approach has been suggested to retrieve the spectral light absorption coefficient (babs) from Aethalometer raw data by using BC/EC ratio. Mass absorption efficiency, ?abs(=babs/EC) at 550 nm at the measurement site was determined to be 9.0±1.3, 8.9±1.5, 9.5±2.0, and 10.3±1.7 m2 g?1 in spring, summer, fall, and winter, respectively with an annual mean of 9.4±1.8 m2 g?1. Threshold values to classify severe haze events were suggested in this study. Increasing trend of aerosol single scattering albedo (SSA) with wavelength was observed during Asian dust events while little spectral dependence of SSA was observed during long-range transport pollution (LTP) events. Satellite aerosol optical thickness (AOT) and Hysplit air mass backward trajectory analyses as well as chemical analysis were performed to characterize the dependence of spectral optical properties on aerosol type. Results from this study can provide useful information for studies on regional air quality and aerosol's effects on climate change.

J. Jung; Y. J. Kim; K. Y. Lee; M. G. -Cayetano; T. Batmunkh; J.-H. Koo; J. Kim

2010-01-01

149

Effect of the volcanic ash type uncertainties on ash and SO2 retrievals from satellite multi-spectral measurements in the TIR spectral range  

Science.gov (United States)

After the Eyjafjallajokull 2010 eruption the quantitative determination of the volcanic ash present in ash clouds has become more important because of the policy change from the previous zero tolerance to the new ash threshold based approach in the aviation hazard management. Volcanic SO2 has an impact on the environment and when injected at high altitudes can be oxidized to form sulphates capable of reflecting solar radiation then causing surface cooling. Observations of the volcanic degassing also yield insights into the magmatic processes which control volcanic activity during both quiescent and eruptive phases. During volcanic eruptions ash and gases are often emitted simultaneously. The plume ash particles reduce the top of atmosphere radiance in the entire thermal infrared (TIR) spectral range causing a significant SO2 columnar abundance overestimation. The ash optical properties are among the most critical parameters to set, their uncertainties cause meaningful errors on both ash and SO2 retrievals. In this work the effect effect of the volcanic ash type uncertainties on ash and SO2 retrievals from MODIS measurements in the TIR spectral range have been quantified. As test case some events of the 2010 Eyjafjallajokull (Iceland) eruption has been considered. The ash optical properties derive from the ARIA database of the Oxford University, while the MODIS SO2 and ash retrievals strategies are based on the BTD and minimization approaches using the channels centered at 8.7, 11 and 12 micron. The radiative transfer model simulations, needed for the retrievals schemes, are carried out by using MODTRAN [Corradini et al., 2009]. The MODIS SO2 retrievals have been also compared with the retrievals obtained by using IASI hyper-spectral and ASTER high spatial resolution data. The two procedures are considered less sensitive to the ash type: the ASTER retrieval scheme [Campion et al. 2010] consists of adjusting the SO2 column amount until the ratios of radiance simulated on several ASTER bands match the observations, while the IASI retrieval [Carboni et al. 2012] is an optimal estimation scheme that exploit the high resolution spectrometer measurements of the two SO2 absorption bands around 7.3 and 8.7 micron.

Corradini, Stefano; Merucci, Luca; Campion, Robin; Carboni, Elisa

2013-04-01

150

[IR spectral-analysis-based range estimation for an object with small temperature difference from background].  

UK PubMed Central (United Kingdom)

It is a typical passive ranging technology that estimation of distance of an object is based on transmission characteristic of infrared radiation, it is also a hotspot in electro-optic countermeasures. Because of avoiding transmitting energy in the detection, this ranging technology will significantly enhance the penetration capability and infrared conceal capability of the missiles or unmanned aerial vehicles. With the current situation in existing passive ranging system, for overcoming the shortage in ranging an oncoming target object with small temperature difference from background, an improved distance estimation scheme was proposed. This article begins with introducing the concept of signal transfer function, makes clear the working curve of current algorithm, and points out that the estimated distance is not unique due to inherent nonlinearity of the working curve. A new distance calculation algorithm was obtained through nonlinear correction technique. It is a ranging formula by using sensing information at 3-5 and 8-12 microm combined with background temperature and field meteorological conditions. The authors' study has shown that the ranging error could be mainly kept around the level of 10% under the condition of the target and background apparent temperature difference equal to +/- 5 K, and the error in estimating background temperature is no more than +/- 15 K.

Fu XN; Wang J; Yang L

2013-01-01

151

Spectral detectability of Ca- and Mg-sulfates in Martian bright soils in the 4 5 ?m wavelength range  

Science.gov (United States)

Chemical analyses of soil samples performed at different landing sites on Mars suggest the presence of sulfate minerals. These minerals are also thought to be present in the globally mixed Martian bright soils covering large areas of the planet. However, remote soil spectra have so far provided only tentative identification of sulfates regarding mineral types and abundances. This paper concentrates on the detectability of four Ca- and Mg-sulfates (anhydrite, gypsum, kieserite, hexahydrite) in the 4-5 ?m range of Martian remote soil spectra. This spectral range is important for sulfate detection as most fine-grained sulfates exhibit significant absorption bands between 4 and 5 ?m, independent of the texture of the host soils (e.g., loose powdered or cemented soils). Furthermore, this is the spectral range for which the Planetary Fourier Spectrometer (PFS) and Observatoire pour la Minéralogie, l'Eau, les Glaces, et l'Activité (OMEGA) instruments onboard ESA/Mars Express mission provide high spectral and spatial resolution data. Laboratory near- and mid-IR reflectance spectra of the pure sulfates and their mixtures with a terrestrial Martian soil analog were acquired. The results show that even the smallest amount of admixed sulfate (˜5 wt%) generates significant absorption features in the portion of the 4-5 ?m range not covered by the saturated Martian atmospheric CO 2 absorption band between 4.2 and 4.4 ?m. Model calculations of the influence of emitted surface radiation on the detectability of sulfate features show that the depth of the features decreases strongly with increasing surface temperature of an observed area resulting in the fact that all sulfates are spectrally hidden at surface temperatures around 270 K even at ˜14 or ˜25 wt% sulfate content in the soils. Sulfates become increasingly detectable depending on the sulfate content if the surface temperature is below 260 K. The outcome of this work helps to constrain the conditions needed for remote detection of sulfates within Martian bright soils in the 4-5 ?m range.

Witzke, A.; Arnold, G.; Stöffler, D.

2007-03-01

152

Phototransformation of 2,4,6-trinitrotoluene: Sensitized by riboflavin under different irradiation spectral range  

International Nuclear Information System (INIS)

Riboflavin-sensitized phototransformation of 2,4,6-trinitrotoluene (TNT) under natural sunlight was investigated with reverse-phase high performance liquid chromatography/mass spectrometry (HPLC/MS) and gas chromatography/mass spectrometry (GC/MS). The effect of different spectral region of sunlight on TNT phototransformation in the absence or presence of riboflavin was also investigated by using optical filters with cut-off at 400 or 455 nm. The concentration of riboflavin in the phototransformation of TNT was optimized. Concentration of riboflavin and TNT was 1.0 and 50 ?M, respectively. The rates of phototransformation of TNT under natural sunlight in the presence or absence of riboflavin were conformed to initial pseudo-first-order rate equation. The photolysis half life of TNT in the presence of riboflavin was 21.87 min, compared to 39 min in the absence of riboflavin under natural sunlight. Two major phototransformation products of TNT, 3,5-dinitroaniline (3,5-DNA) and 1,3,5-trinitrobenzene (1,3,5-TNB), were detected in the samples in the presence of riboflavin receiving irradiation at full wavelength or wavelength >400 nm. The results indicate that riboflavin mediates TNT sensitized-phototransfomation under natural sunlight or near-UV-vis light

2007-05-08

153

Effect of index contrasts in the wide spectral-range control of slot waveguide dispersion.  

UK PubMed Central (United Kingdom)

Here we examine the waveguide dispersion property of slot waveguides, approaching/analyzing the given problem with respect to the normalized index contrast, ?nslot-core/ncore and ?ncore-clad/ncore between adjacent layers . For two index contrasts of concern, it is found that their contributions to slot waveguide dispersions are substantially different, with ?nslot-core and ?ncore-clad each acting preferentially on short- and long-wavelength regions. Additional degrees of freedom in the waveguide design, such as the effect of absolute refractive index and waveguide geometry are also investigated to enable flexible tuning of the waveguide dispersion. Focusing on the unexplored regime of slot waveguides design in short wavelength (<1 ?m), we also study the feasibility of low-threshold super-continuum sources using a Ta2O5/TiO2/silica slot, either of two-octave spectral width (0.467–1.581 ?m), or of one-octave, near unity coherence |g12(1)| = 1.

Ryu H; Kim J; Jhon YM; Lee S; Park N

2012-06-01

154

A new undulator for the extension of the spectral range of the CLIO FEL  

Energy Technology Data Exchange (ETDEWEB)

We built a new undulator in order to extend the lasing range of the CLIO infrared FEL. Presently, CLIO operates in the wavelength range 2 - 17 {mu}m. Beyond 14 {mu}m, the power decreases rapidly, because of the diffraction losses of the vacuum chamber (7 mm height and 2 m long). Thus, lasing at higher wavelengths implies installing a chamber with a height approximately twice. Then the minimum gap is increased and the maximum deflection parameter, K, is reduced from 2 to 1 : the laser tunability is greatly reduced. This is why a new undulator has been built.

Marcouille, O.; Berset, J.M.; Glotin, F. [LURE, Orsay (France)] [and others

1995-12-31

155

Photometric calibration of soft x-ray and p-terphenyl coated visible photodiodes in the 180--1500 eV range for fusion plasma spectroscopy  

International Nuclear Information System (INIS)

The efficiencies of x-ray ultraviolet silicon, and p-terphenyl coated visible photodiodes have been measured in the 180--1500 eV range using a K radiation-Manson source. It is found that the quantum efficiency (electrons/photon) of the silicon diode varies between 25 and 400 in the above-mentioned range; the p-terphenyl coated diode is by two orders of magnitude less performing at the high-energy end of the range considered, but approaches the efficiency of the silicon diode at 100 A. Such diodes with built-in amplifiers, coated with scintillator and thin layers of metal films, can be efficiently used in spectroscopic diagnostics of magnetically confined plasmas.

1991-01-01

156

Photometric calibration of soft x-ray and p -terphenyl coated visible photodiodes in the 180--1500 eV range for fusion plasma spectroscopy  

Energy Technology Data Exchange (ETDEWEB)

The efficiencies of x-ray ultraviolet silicon, and {ital p}-terphenyl coated visible photodiodes have been measured in the 180--1500 eV range using a {ital K} radiation-Manson source. It is found that the quantum efficiency (electrons/photon) of the silicon diode varies between 25 and 400 in the above-mentioned range; the {ital p}-terphenyl coated diode is by two orders of magnitude less performing at the high-energy end of the range considered, but approaches the efficiency of the silicon diode at 100 A. Such diodes with built-in amplifiers, coated with scintillator and thin layers of metal films, can be efficiently used in spectroscopic diagnostics of magnetically confined plasmas.

Stutman, D.; Kovnovich, S.; Finkenthal, M. (Racah Institute of Physics, The Hebrew University, Jerusalem (Israel)); Zwicker, A.; Moos, H.W. (Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland (USA))

1991-11-01

157

Retrieval interval mapping: a tool to visualize the impact of the spectral retrieval range on differential optical absorption spectroscopy evaluations  

Directory of Open Access Journals (Sweden)

Full Text Available Remote sensing via differential optical absorption spectroscopy (DOAS) has become a standard technique to identify and quantify trace gases in the atmosphere. Due to the wide range of measurement conditions, atmospheric compositions and instruments used, a specific challenge of a DOAS retrieval is to optimize the retrieval parameters for each specific case and particular trace gas of interest. Of these parameters, the retrieval wavelength range is one of the most important ones. Although for many trace gases the overall dependence of common DOAS retrieval on the evaluation wavelength interval is known, a systematic approach for finding the optimal retrieval wavelength range and quantitative assessment is missing. Here we present a novel tool to visualize the effect of different evaluation wavelength ranges. It is based on mapping retrieved column densities in the retrieval wavelength space and thus visualizing the consequences of different choices of spectral retrieval ranges caused by slightly erroneous absorption cross sections, cross correlations and instrumental features. Based on the information gathered, an optimal retrieval wavelength range may be determined systematically. The technique is demonstrated using examples of a theoretical study of BrO retrievals for stratospheric BrO and BrO measurements in volcanic plumes. However, due to the general nature of the tool, it is applicable to any type of DOAS retrieval (active or passive).

L. Vogel; H. Sihler; J. Lampel; T. Wagner; U. Platt

2013-01-01

158

Spectral Content of the NLC Bunch Train due to Long Range Wakefields(LCC-0015)  

International Nuclear Information System (INIS)

The functional specifications of the sub-train position feedback for the NLC Main Linac are determined by the expected amplitude and spectrum of distortions to the bunch train, which in turn arise from the long-range wakefields of the RF structures. We describe a method for estimating the amplitude and spectrum of the distortions due to assorted structure misalignments, and apply the method to both tilted structures and structures with a cell-to-cell misalignment determined by a random-walk model. Some implications for the sub-train feedback, such as the required system bandwidth, are considered.

2004-01-01

159

Chlorine detection in cement with laser-induced breakdown spectroscopy in the infrared and ultraviolet spectral range  

International Nuclear Information System (INIS)

A significant parameter to monitor the status of concrete buildings like bridges or parking garages is the determination of the depth profile of the chlorine concentration below the exposed concrete surface. This information is required to define the needed volume of restoration for a construction. Conventional methods like wet chemical analysis are time- and cost-intensive so an alternative method is developed using laser-induced breakdown spectroscopy (LIBS). The idea is to deploy LIBS to analyze drill cores by scanning the sample surface with laser pulses. Chlorine spectral lines in the infrared (IR) and ultraviolet (UV)-range were studied for chlorine detection in hydrated cement samples. The excitation energies of these spectral lines are above 9.2 eV. Hence high plasma temperatures and pulse energies in the range of some hundred millijoules are needed to induce sufficient line intensity levels at the required working distance. To further increase the line intensity and to lower the detection limit (LOD) of chlorine a measuring chamber is used where different ambient pressures and gases can be chosen for the measurements. The influences on the line intensity for pressures between 5 mbar and 400 mbar using helium as process gas and the influence of different laser burst modi like single and collinear double pulses are investigated. For the first time a LOD according to DIN 32 645 of 0.1 mass% was achieved for chlorine in hydrated cement using the UV line 134.72 nm.

2009-01-01

160

Chlorine detection in cement with laser-induced breakdown spectroscopy in the infrared and ultraviolet spectral range  

Energy Technology Data Exchange (ETDEWEB)

A significant parameter to monitor the status of concrete buildings like bridges or parking garages is the determination of the depth profile of the chlorine concentration below the exposed concrete surface. This information is required to define the needed volume of restoration for a construction. Conventional methods like wet chemical analysis are time- and cost-intensive so an alternative method is developed using laser-induced breakdown spectroscopy (LIBS). The idea is to deploy LIBS to analyze drill cores by scanning the sample surface with laser pulses. Chlorine spectral lines in the infrared (IR) and ultraviolet (UV)-range were studied for chlorine detection in hydrated cement samples. The excitation energies of these spectral lines are above 9.2 eV. Hence high plasma temperatures and pulse energies in the range of some hundred millijoules are needed to induce sufficient line intensity levels at the required working distance. To further increase the line intensity and to lower the detection limit (LOD) of chlorine a measuring chamber is used where different ambient pressures and gases can be chosen for the measurements. The influences on the line intensity for pressures between 5 mbar and 400 mbar using helium as process gas and the influence of different laser burst modi like single and collinear double pulses are investigated. For the first time a LOD according to DIN 32 645 of 0.1 mass% was achieved for chlorine in hydrated cement using the UV line 134.72 nm.

Gehlen, Christoph Dominic, E-mail: christoph.gehlen@lsa-systems.d [RWTH Aachen University, Lehrstuhl fuer Lasertechnik (LLT), Steinbachstr. 15, 52074 Aachen (Germany); Wiens, Eugen; Noll, Reinhard [Fraunhofer-Institut fuer Lasertechnik (ILT), Steinbachstr. 15, 52074 Aachen (Germany); Wilsch, Gerd [Bundesanstalt fuer Materialforschung und -pruefung (BAM), Unter den Eichen 87, 12205 Berlin (Germany); Reichling, Kenji [RWTH Aachen University, Institut fuer Bauforschung (IBAC), Schinkelstr. 3, 52062 Aachen (Germany)

2009-10-15

 
 
 
 
161

Microcirculation imaging based on full-range high-speed spectral domain correlation mapping optical coherence tomography.  

UK PubMed Central (United Kingdom)

Microcirculation imaging is a key parameter for studying the pathophysiological processes of various disease conditions, in both clinical and fundamental research. A full-range spectral-domain correlation mapping optical coherence tomography (cm-OCT) method to obtain a complex-conjugate-free, full-range depth-resolved microcirculation map is presented. The proposed system is based on a high-speed spectrometer at 91 kHz with a modified scanning protocol to achieve higher acquisition speed to render cm-OCT images with high-speed and wide scan range. The mirror image elimination is based on linear phase modulation of B-frames by introducing a slight off-set of the probe beam with respect to the lateral scanning fast mirror's pivot axis. An algorithm that exploits the Hilbert transform to obtain a complex-conjugate-free image in conjunction with the cm-OCT algorithm is used to obtain full-range imaging of microcirculation within tissue beds in vivo. The estimated sensitivity of the system was around 105 dB near the zero-delay line with ?20??dB roll-off from ±0.5 to ±3??mm imaging-depth position. The estimated axial and lateral resolutions are ?12 and ?30????m, respectively. A direct consequence of this complex conjugate artifact elimination is the enhanced flow imaging sensitivity for deep tissue imaging application by imaging through the most sensitive zero-delay line and doubling the imaging range.

Subhash HM; Leahy MJ

2014-02-01

162

Microcirculation imaging based on full-range high-speed spectral domain correlation mapping optical coherence tomography.  

Science.gov (United States)

Microcirculation imaging is a key parameter for studying the pathophysiological processes of various disease conditions, in both clinical and fundamental research. A full-range spectral-domain correlation mapping optical coherence tomography (cm-OCT) method to obtain a complex-conjugate-free, full-range depth-resolved microcirculation map is presented. The proposed system is based on a high-speed spectrometer at 91 kHz with a modified scanning protocol to achieve higher acquisition speed to render cm-OCT images with high-speed and wide scan range. The mirror image elimination is based on linear phase modulation of B-frames by introducing a slight off-set of the probe beam with respect to the lateral scanning fast mirror's pivot axis. An algorithm that exploits the Hilbert transform to obtain a complex-conjugate-free image in conjunction with the cm-OCT algorithm is used to obtain full-range imaging of microcirculation within tissue beds in vivo. The estimated sensitivity of the system was around 105 dB near the zero-delay line with ?20??dB roll-off from ±0.5 to ±3??mm imaging-depth position. The estimated axial and lateral resolutions are ?12 and ?30????m, respectively. A direct consequence of this complex conjugate artifact elimination is the enhanced flow imaging sensitivity for deep tissue imaging application by imaging through the most sensitive zero-delay line and doubling the imaging range. PMID:23807553

Subhash, Hrebesh M; Leahy, Martin J

2014-02-01

163

RF magnetron sputtered (BiDy)3(FeGa)5O12:Bi2O3 composite garnet-oxide materials possessing record magneto-optic quality in the visible spectral region.  

Science.gov (United States)

Bismuth-substituted iron garnets are considered to be the most promising magneto-optical materials because of their excellent optical transparency and very high magneto-optical figures of merit in the near-infrared spectral region. However, the practical application of garnets in the visible and short-wavelength infrared parts of spectrum is currently limited, due to their very high optical absorption (especially in sputtered films) in these spectral regions. In this paper, we identify the likely source of excess absorption observed in sputtered garnet films in comparison with epitaxial layers and demonstrate (Bi,Dy)(3)(Fe,Ga)(5)O(12): Bi(2)O(3) composites possessing record MO quality in the visible region. PMID:19997172

Vasiliev, Mikhail; Alam, Mohammad Nur-E; Kotov, Viacheslav A; Alameh, Kamal; Belotelov, Vladimir I; Burkov, Vladimir I; Zvezdin, Anatoly K

2009-10-26

164

RF magnetron sputtered (BiDy)3(FeGa)5O12:Bi2O3 composite garnet-oxide materials possessing record magneto-optic quality in the visible spectral region.  

UK PubMed Central (United Kingdom)

Bismuth-substituted iron garnets are considered to be the most promising magneto-optical materials because of their excellent optical transparency and very high magneto-optical figures of merit in the near-infrared spectral region. However, the practical application of garnets in the visible and short-wavelength infrared parts of spectrum is currently limited, due to their very high optical absorption (especially in sputtered films) in these spectral regions. In this paper, we identify the likely source of excess absorption observed in sputtered garnet films in comparison with epitaxial layers and demonstrate (Bi,Dy)(3)(Fe,Ga)(5)O(12): Bi(2)O(3) composites possessing record MO quality in the visible region.

Vasiliev M; Alam MN; Kotov VA; Alameh K; Belotelov VI; Burkov VI; Zvezdin AK

2009-10-01

165

Novel SO2 spectral evaluation scheme using the 360–390 nm wavelength range  

Directory of Open Access Journals (Sweden)

Full Text Available Differential Optical Absorption Spectroscopy (DOAS) is a well established spectroscopic method to determine trace gases in the atmosphere. During the last decade, passive DOAS, which uses solar radiation scattered in the atmosphere as a light source, has become a standard tool to determine SO2 column densities and emission fluxes from volcanoes and other large sources by ground based as well as satellite measurements. For the determination of SO2 column densities, the structured absorption of the molecule in the 300–330 nm region (due to the A1B1 ? X1A1 transition) is used. However, there are several problems limiting the accuracy of the technique in this particular application. Here we propose to use an alternative wavelength region (360–390 nm) due to the spin-forbidden a3B2 ? X1A1 transition for the DOAS evaluation of SO2 in conditions where high SO2 column densities prevail. We show this range to have considerable advantages in such cases, in particular when the particle content of the plume is high and when measurements are performed at large distances from the area of interest.

N. Bobrowski; C. Kern; U. Platt; C. Hörmann; T. Wagner

2010-01-01

166

Novel SO2 spectral evaluation scheme using the 360–390 nm wavelength range  

Directory of Open Access Journals (Sweden)

Full Text Available Differential Optical Absorption Spectroscopy (DOAS) is a well established spectroscopic method to determine trace gases in the atmosphere. During the last decade, passive DOAS, which uses solar radiation scattered in the atmosphere as a light source, has become a standard tool to determine SO2 column densities and emission fluxes from volcanoes and other large sources by ground based as well as satellite measurements. For the determination of SO2 column densities, the structured absorption of the molecule in the 300–330 nm region (due to the A1B1?X1A1 transition) is used. However, there are several problems limiting the accuracy of the technique in this particular application. Here we propose to use an alternative wavelength region (360–390 nm) due to the spin-forbidden a3B2?X1A1 transition for the DOAS evaluation of SO2 in conditions where high SO2 column densities prevail. We show this range to have considerable advantages in such cases, in particular when the particle content of the plume is high and when measurements are performed at large distances from the area of interest.

N. Bobrowski; C. Kern; U. Platt; C. Hörmann; T. Wagner

2010-01-01

167

Development and testing of a fast Fourier transform high dynamic-range spectral diagnostics for millimeter wave characterization  

Science.gov (United States)

A fast Fourier transform (FFT) based wide range millimeter wave diagnostics for spectral characterization of scattered millimeter waves in plasmas has been successfully brought into operation. The scattered millimeter waves are heterodyne downconverted and directly digitized using a fast analog-digital converter and a compact peripheral component interconnect computer. Frequency spectra are obtained by FFT in the time domain of the intermediate frequency signal. The scattered millimeter waves are generated during high power electron cyclotron resonance heating experiments on the TEXTOR tokamak and demonstrate the performance of the diagnostics and, in particular, the usability of direct digitizing and Fourier transformation of millimeter wave signals. The diagnostics is able to acquire 4 GHz wide spectra of signals in the range of 136-140 GHz. The rate of spectra is tunable and has been tested between 200 000 spectra/s with a frequency resolution of 100 MHz and 120 spectra/s with a frequency resolution of 25 kHz. The respective dynamic ranges are 52 and 88 dB. Major benefits of the new diagnostics are a tunable time and frequency resolution due to postdetection, near-real time processing of the acquired data. This diagnostics has a wider application in astrophysics, earth observation, plasma physics, and molecular spectroscopy for the detection and analysis of millimeter wave radiation, providing high-resolution spectra at high temporal resolution and large dynamic range.

Thoen, D. J.; Bongers, W. A.; Westerhof, E.; Oosterbeek, J. W.; de Baar, M. R.; van den Berg, M. A.; van Beveren, V.; Bürger, A.; Goede, A. P. H.; Graswinckel, M. F.; Hennen, B. A.; Schüller, F. C.

2009-10-01

168

Development and testing of a fast Fourier transform high dynamic-range spectral diagnostics for millimeter wave characterization  

International Nuclear Information System (INIS)

A fast Fourier transform (FFT) based wide range millimeter wave diagnostics for spectral characterization of scattered millimeter waves in plasmas has been successfully brought into operation. The scattered millimeter waves are heterodyne downconverted and directly digitized using a fast analog-digital converter and a compact peripheral component interconnect computer. Frequency spectra are obtained by FFT in the time domain of the intermediate frequency signal. The scattered millimeter waves are generated during high power electron cyclotron resonance heating experiments on the TEXTOR tokamak and demonstrate the performance of the diagnostics and, in particular, the usability of direct digitizing and Fourier transformation of millimeter wave signals. The diagnostics is able to acquire 4 GHz wide spectra of signals in the range of 136-140 GHz. The rate of spectra is tunable and has been tested between 200 000 spectra/s with a frequency resolution of 100 MHz and 120 spectra/s with a frequency resolution of 25 kHz. The respective dynamic ranges are 52 and 88 dB. Major benefits of the new diagnostics are a tunable time and frequency resolution due to postdetection, near-real time processing of the acquired data. This diagnostics has a wider application in astrophysics, earth observation, plasma physics, and molecular spectroscopy for the detection and analysis of millimeter wave radiation, providing high-resolution spectra at high temporal resolution and large dynamic range.

2009-01-01

169

A High-resolution, Multi-epoch Spectral Atlas of Peculiar Stars Including RAVE, GAIA , and HERMES Wavelength Ranges  

Science.gov (United States)

We present an Echelle+CCD, high signal-to-noise ratio, high-resolution (R = 20,000) spectroscopic atlas of 108 well-known objects representative of the most common types of peculiar and variable stars. The wavelength interval extends from 4600 to 9400 Å and includes the RAVE, Gaia, and HERMES wavelength ranges. Multi-epoch spectra are provided for the majority of the observed stars. A total of 425 spectra of peculiar stars, which were collected during 56 observing nights between 1998 November and 2002 August, are presented. The spectra are given in FITS format and heliocentric wavelengths, with accurate subtraction of both the sky background and the scattered light. Auxiliary material useful for custom applications (telluric dividers, spectrophotometric stars, flat-field tracings) is also provided. The atlas aims to provide a homogeneous database of the spectral appearance of stellar peculiarities, a tool useful both for classification purposes and inter-comparison studies. It could also serve in the planning and development of automated classification algorithms designed for RAVE, Gaia, HERMES, and other large-scale spectral surveys. The spectrum of XX Oph is discussed in some detail as an example of the content of the present atlas.

Tomasella, Lina; Munari, Ulisse; Zwitter, Tomaž

2010-12-01

170

A HIGH-RESOLUTION, MULTI-EPOCH SPECTRAL ATLAS OF PECULIAR STARS INCLUDING RAVE, GAIA , AND HERMES WAVELENGTH RANGES  

International Nuclear Information System (INIS)

[en] We present an Echelle+CCD, high signal-to-noise ratio, high-resolution (R = 20,000) spectroscopic atlas of 108 well-known objects representative of the most common types of peculiar and variable stars. The wavelength interval extends from 4600 to 9400 A and includes the RAVE, Gaia, and HERMES wavelength ranges. Multi-epoch spectra are provided for the majority of the observed stars. A total of 425 spectra of peculiar stars, which were collected during 56 observing nights between 1998 November and 2002 August, are presented. The spectra are given in FITS format and heliocentric wavelengths, with accurate subtraction of both the sky background and the scattered light. Auxiliary material useful for custom applications (telluric dividers, spectrophotometric stars, flat-field tracings) is also provided. The atlas aims to provide a homogeneous database of the spectral appearance of stellar peculiarities, a tool useful both for classification purposes and inter-comparison studies. It could also serve in the planning and development of automated classification algorithms designed for RAVE, Gaia, HERMES, and other large-scale spectral surveys. The spectrum of XX Oph is discussed in some detail as an example of the content of the present atlas.

2010-01-01

171

Visible-range hybrid femtosecond systems based on a XeF(C–A) amplifier: state of the art and prospects  

International Nuclear Information System (INIS)

[en] Results of experimental and theoretical investigations of the hybrid (solid state/gas) visible-range femtosecond systems THL-100 (IHCE SB RAS) and THL-30 (P.N. Lebedev Physics Institute) based on a Ti : sapphire front end and a photochemical XeF(C–A) amplifier are reported. The front end generates 50-fs optical pulses with the second-harmonic (475 nm) energy of up to 5 mJ. The active medium of the amplifier is produced in a mixture XeF2 – N2 subjected to VUV radiation of xenon excited by an electron beam. The computer model is developed for calculating parameters of the XeF(C – A) amplifier, which is in a good agreement with experiments. In the THL-100 system with the 25-cm output aperture of the XeF(C–A) amplifier, a record visible-range femtosecond radiation peak power of 14 GW was obtained in a 50-fs pulse with the time contrast of above 108. The measured power of an amplified spontaneous emission of the XeF(C–A) amplifier in the angle of 0.2 mrad was 32 W. The result obtained testifies that the hybrid approach to the development of ultrahigh-power systems provides a high time contrast of radiation (greater than 1012 for the projected peak power of 100 TW). In the THL-30 system, prospects for shortening an amplified femtosecond pulse are studied and it is experimentally shown that by compensating a third-order dispersion in a hybrid system one can obtain pulses with duration of at least 27 fs with a recompression of amplified pulses in bulk glass. Also, a new phenomenon was observed of spectrum broadening and self-compression of negatively chirped femtosecond pulses in the visible range under a nonlinear interaction of wide-aperture beams with fused silica. This result opens prospects for development of the new methods of selfcompression for femtosecond pulses that are lacking physical limitations on pulse energy and realisation of self-compression of amplified pulses in the output window of the XeF(C–A) amplifier. (extreme light fields and their applications)

2013-03-31

172

Visible-range hybrid femtosecond systems based on a XeF(C-A) amplifier: state of the art and prospects  

Science.gov (United States)

Results of experimental and theoretical investigations of the hybrid (solid state/gas) visible-range femtosecond systems THL-100 (IHCE SB RAS) and THL-30 (P.N. Lebedev Physics Institute) based on a Ti : sapphire front end and a photochemical XeF(C-A) amplifier are reported. The front end generates 50-fs optical pulses with the second-harmonic (475 nm) energy of up to 5 mJ. The active medium of the amplifier is produced in a mixture XeF2 - N2 subjected to VUV radiation of xenon excited by an electron beam. The computer model is developed for calculating parameters of the XeF(C - A) amplifier, which is in a good agreement with experiments. In the THL-100 system with the 25-cm output aperture of the XeF(C-A) amplifier, a record visible-range femtosecond radiation peak power of 14 GW was obtained in a 50-fs pulse with the time contrast of above 108. The measured power of an amplified spontaneous emission of the XeF(C-A) amplifier in the angle of 0.2 mrad was 32 W. The result obtained testifies that the hybrid approach to the development of ultrahigh-power systems provides a high time contrast of radiation (greater than 1012 for the projected peak power of 100 TW). In the THL-30 system, prospects for shortening an amplified femtosecond pulse are studied and it is experimentally shown that by compensating a third-order dispersion in a hybrid system one can obtain pulses with duration of at least 27 fs with a recompression of amplified pulses in bulk glass. Also, a new phenomenon was observed of spectrum broadening and self-compression of negatively chirped femtosecond pulses in the visible range under a nonlinear interaction of wide-aperture beams with fused silica. This result opens prospects for development of the new methods of selfcompression for femtosecond pulses that are lacking physical limitations on pulse energy and realisation of self-compression of amplified pulses in the output window of the XeF(C-A) amplifier.

Alekseev, S. V.; Aristov, A. I.; Grudtsyn, Ya V.; Ivanov, N. G.; Koval'chuk, B. M.; Losev, B. F.; Mamaev, S. B.; Mesyats, Gennadii A.; Mikheev, L. D.; Panchenko, Yu N.; Polivin, A. V.; Stepanov, S. G.; Ratakhin, N. A.; Yalovoi, V. I.; Yastremskii, Arkadii G.

2013-03-01

173

Quantum efficiency of cesium iodide photocathodes in the 120-220 nm spectral range traceable to a primary detector standard  

CERN Multimedia

Differently prepared CsI samples have been investigated in the 120-220 nm spectral range for their quantum efficiency, spatial uniformity and the effect of radiation aging. The experiments were performed at the PTB radiometry laboratory at the Berlin synchrotron radiation facility BESSY. A calibrated GaAsP Schottky photodiode was used as transfer detector standard to establish traceability to the primary detector standard, because this type of photodiode - unlike silicon p-on-n photodiodes - proved to be of sufficiently stable response when exposed to vacuum ultraviolet radiation. The paper reviews the experimental procedures that were employed to characterize and calibrate the GaAsP photodiode and reports the results that were obtained on the investigated CsI photocathodes.

Rabus, H; Richter, M; Ulm, G; Friese, J; Gernhäuser, R; Kastenmüller, A; Maier-Komor, P; Zeitelhack, K

1999-01-01

174

Effects of external intermittency and mean shear on the spectral inertial-range exponent in a turbulent square jet  

Science.gov (United States)

This study investigates by experiment the dependence of the inertial-range exponent m of the streamwise velocity spectrum on the external intermittency factor ? (? the fraction of time the flow is fully turbulent) and the mean shear S in a turbulent square jet. Velocity measurements were made using hot-wire anemometry in the jet at 15 Zoran Zariç Memorial Conference, edited by S. J. Kline and N. H. Afgan (Hemisphere Publishing Corp., Washington, DC, 1990), pp. 911–931] is discussed and applied to estimate the intermittency factor from velocity signals. It is shown that m depends strongly on ? but negligibly on S. More specifically, m varies with ? following m=mt+(ln??0.0173)1/2, where mt denotes the spectral exponent found in fully turbulent regions.

Zhang, J.; Xu, M.; Pollard, A.; Mi, J.

2013-05-01

175

Spectral counting assessment of protein dynamic range in cerebrospinal fluid following depletion with plasma-designed immunoaffinity columns  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background In cerebrospinal fluid (CSF), which is a rich source of biomarkers for neurological diseases, identification of biomarkers requires methods that allow reproducible detection of low abundance proteins. It is therefore crucial to decrease dynamic range and improve assessment of protein abundance. Results We applied LC-MS/MS to compare the performance of two CSF enrichment techniques that immunodeplete either albumin alone (IgYHSA) or 14 high-abundance proteins (IgY14). In order to estimate dynamic range of proteins identified, we measured protein abundance with APEX spectral counting method. Both immunodepletion methods improved the number of low-abundance proteins detected (3-fold for IgYHSA, 4-fold for IgY14). The 10 most abundant proteins following immunodepletion accounted for 41% (IgY14) and 46% (IgYHSA) of CSF protein content, whereas they accounted for 64% in non-depleted samples, thus demonstrating significant enrichment of low-abundance proteins. Defined proteomics experiment metrics showed overall good reproducibility of the two immunodepletion methods and MS analysis. Moreover, offline peptide fractionation in IgYHSA sample allowed a 4-fold increase of proteins identified (520 vs. 131 without fractionation), without hindering reproducibility. Conclusions The novelty of this study was to show the advantages and drawbacks of these methods side-to-side. Taking into account the improved detection and potential loss of non-target proteins following extensive immunodepletion, it is concluded that both depletion methods combined with spectral counting may be of interest before further fractionation, when searching for CSF biomarkers. According to the reliable identification and quantitation obtained with APEX algorithm, it may be considered as a cheap and quick alternative to study sample proteomic content.

Borg Jacques; Campos Alex; Diema Claudio; Omeñaca Núria; de Oliveira Eliandre; Guinovart Joan; Vilaseca Marta

2011-01-01

176

Valid ranges for using the cross-power spectral density phase angle for moderator temperature coefficient sign determination  

International Nuclear Information System (INIS)

The value of the moderator temperature coefficient (MTC) of reactivity is contained in correlations between fluctuations of the neutron flux and core-exit coolant temperature. The absolute magnitude of the MTC is obtained from noise analysis by using the root-mean-square method and the frequency response function technique. Both approaches are used in conjunction with the phase angle method, which determines the MTC sign, to obtain complete information about the MTC. Analytical expressions that are derived show that a limitation exists on the range of MTC values for which the cross-power spectral density phase angle can be used to establish the MTC sign. This research shows that small positive values of the MTC (an unstable condition) can result in a -180-deg phase angle shift, contrary to earlier studies that indicated a stable reactor. The range of sign determinate MTC values is dependent on the driving noise source. Simulated noise data are generated for different MTC values and analyzed to verify the theoretical work. A comparison of the indeterminate regions to allowable MTC values for an operating pressurized water reactor is also presented

1995-01-01

177

Valid ranges for using the cross-power spectral density phase angle for moderator temperature coefficient sign determination  

Energy Technology Data Exchange (ETDEWEB)

The value of the moderator temperature coefficient (MTC) of reactivity is contained in correlations between fluctuations of the neutron flux and core-exit coolant temperature. The absolute magnitude of the MTC is obtained from noise analysis by using the root-mean-square method and the frequency response function technique. Both approaches are used in conjunction with the phase angle method, which determines the MTC sign, to obtain complete information about the MTC. Analytical expressions that are derived show that a limitation exists on the range of MTC values for which the cross-power spectral density phase angle can be used to establish the MTC sign. This research shows that small positive values of the MTC (an unstable condition) can result in a {minus}180-deg phase angle shift, contrary to earlier studies that indicated a stable reactor. The range of sign determinate MTC values is dependent on the driving noise source. Simulated noise data are generated for different MTC values and analyzed to verify the theoretical work. A comparison of the indeterminate regions to allowable MTC values for an operating pressurized water reactor is also presented.

Holbert, K.E.; Venkatesh, N. [Arizona State Univ., Tempe, AZ (United States)

1995-03-01

178

Observing ice clouds in the submillimeter spectral range: the CloudIce mission proposal for ESA's Earth Explorer 8  

Directory of Open Access Journals (Sweden)

Full Text Available Passive submillimeter-wave sensors are a way to obtain urgently needed global data on ice clouds, particularly on the so far poorly characterized "essential climate variable" ice water path (IWP) and on ice particle size. CloudIce was a mission proposal to the European Space Agency ESA in response to the call for Earth Explorer 8 (EE8), which ran in 2009/2010. It proposed a passive submillimeter-wave sensor with channels ranging from 183 GHz to 664 GHz. The article describes the CloudIce mission proposal, with particular emphasis on describing the algorithms for the data-analysis of submillimeter-wave cloud ice data (retrieval algorithms) and demonstrating their maturity. It is shown that we have a robust understanding of the radiative properties of cloud ice in the millimeter/submillimeter spectral range, and that we have a proven toolbox of retrieval algorithms to work with these data. Although the mission was not selected for EE8, the concept will be useful as a reference for other future mission proposals.

S. A. Buehler; E. Defer; F. Evans; S. Eliasson; J. Mendrok; P. Eriksson; C. Lee; C. Jiménez; C. Prigent; S. Crewell; Y. Kasai; R. Bennartz; A. J. Gasiewski

2012-01-01

179

An improved algorithm for the determination of aerosol optical depth in the ultraviolet spectral range from Brewer spectrophotometer observations  

Science.gov (United States)

Methods to derive aerosol optical depth in the UV spectral range from ground-based remote-sensing stations equipped with Brewer spectrophotometers have been recently developed. In this study a modified Langley plot method has been implemented to retrieve aerosol optical depth from direct sun Brewer measurements. The method uses measurements over an extended range of atmospheric airmasses obtained with two different neutral density filters, and accounts for short-term variations of total ozone, derived from the same direct sun observations. The improved algorithm has been applied to data collected with a Brewer mark IV, operational in Rome, Italy, and with a Brewer mark III, operational in Lampedusa, Italy, in the Mediterranean. The efficiency of the improved algorithm has been tested comparing the number of determinations of the extraterrestrial constant against those obtained with a standard Langley plot procedure. The improved method produces a larger number of reliable Langley plots, allowing for a better statistical characterization of the extraterrestrial constant and a better study of its temporal variability. The values of aerosol optical depth calculated in Rome and Lampedusa compare well with simultaneous determinations in the 416-440 nm interval derived from MFRSR and CIMEL measurements.

Sellitto, P.; di Sarra, A.; Siani, A. M.

2006-10-01

180

X-ray grating spectrometer for opacity measurements in the 50 eV to 250 eV spectral range at the LULI 2000 laser facility  

Energy Technology Data Exchange (ETDEWEB)

An x-ray grating spectrometer was built in order to measure opacities in the 50 eV to 250 eV spectral range with an average spectral resolution {approx} 50. It has been used at the LULI-2000 laser facility at Ecole Polytechnique (France) to measure the {Delta}n = 0, n = 3 transitions of several elements with neighboring atomic number: Cr, Fe, Ni, and Cu in the same experimental conditions. Hence a spectrometer with a wide spectral range is required. This spectrometer features one line of sight looking through a heated sample at backlighter emission. It is outfitted with one toroidal condensing mirror and several flat mirrors cutting off higher energy photons. The spectral dispersion is obtained with a flatfield grating. Detection consists of a streak camera sensitive to soft x-ray radiation. Some experimental results showing the performance of this spectrometer are presented.

Reverdin, Charles; Caillaud, T.; Gilleron, F.; Pain, J. C.; Silvert, V.; Soullie, G.; Villette, B. [CEA, DAM, DIF, 91297 Arpajon (France); Thais, Frederic; Loisel, Guillaume; Blenski, T.; Poirier, M. [CEA, DSM, IRAMIS, Service Photons, Atomes et Molecules, 91191 Gif-sur-Yvette (France); Busquet, M. [ARTEP Inc, Ellicott City, Maryland 21042 (United States); Bastiani-Ceccotti, S.; Serres, F. [LULI, Ecole Polytechnique, CNRS, CEA, UPMC, route de Saclay, 91128 Palaiseau (France); Ducret, J. E. [CELIA, UMR5107, CEA, CNRS, Universite de Bordeaux, 33400 Talence (France); Foelsner, W. [Max Planck Instituet fuer Quantum Optik, 85748 Garching (Germany); Gilles, D.; Turck-Chieze, S. [CEA, DSM, IRFU, Service d' astrophysique, 91191 Gif-sur-Yvette (France)

2012-10-15

 
 
 
 
181

X-ray grating spectrometer for opacity measurements in the 50 eV to 250 eV spectral range at the LULI 2000 laser facility  

International Nuclear Information System (INIS)

[en] An x-ray grating spectrometer was built in order to measure opacities in the 50 eV to 250 eV spectral range with an average spectral resolution ? 50. It has been used at the LULI-2000 laser facility at École Polytechnique (France) to measure the ?n = 0, n = 3 transitions of several elements with neighboring atomic number: Cr, Fe, Ni, and Cu in the same experimental conditions. Hence a spectrometer with a wide spectral range is required. This spectrometer features one line of sight looking through a heated sample at backlighter emission. It is outfitted with one toroidal condensing mirror and several flat mirrors cutting off higher energy photons. The spectral dispersion is obtained with a flatfield grating. Detection consists of a streak camera sensitive to soft x-ray radiation. Some experimental results showing the performance of this spectrometer are presented.

2012-01-01

182

Multiple fiber Bragg grating sensor network with a rapid response and wide spectral dynamic range using code division multiple access  

Science.gov (United States)

Fiber Bragg grating (FBG) sensor networks have been intensively researched in optical sensor area and it developed in wavelength division multiplexing (WDM) and time division multiplexing (TDM) technologies which was adopted for its interrogating many optical sensors. In particular, WDM technology can be easily employed to interrogate FBG sensor however, the number of FBG sensors is limited. On the other hand, the TDM technique can extremely expand the number of sensor because the FBG sensors have same center wavelength. However, it suffers from a reduced sensor output power due to low reflectivity of FBG sensor. In this paper, we proposed and demonstrated the FBG sensor network based on code division multiple access (CDMA) with a rapid response and wide spectral dynamic range. The reflected semiconductor optical amplifier (RSOA) as a light source was directly modulated by the generated pseudorandom binary sequence (PRBS) code and the modulated signal is amplified and goes through FBG sensors via circulator. When the modulated optical signal experienced FBG sensor array, the optical signal which was consistent with center wavelength of FBGs is reflected and added from each sensors. The added signal goes into dispersion compensating fiber (DCF) as a dispersion medium. After through the DCF, the optical signal is converted into electrical signal by using photodetector (PD). For separate individual reflected sensor signal, the sliding correlation method was used. The proposed method improves the code interference and it also has advantages such as a large number of sensors, continuously measuring individual sensors, and decreasing the complexity of the sensor network.

Kim, Youngbok; Jeon, Sie-Wook; Park, Chang-Soo

2011-05-01

183

A high resolution, multi-epoch spectral atlas of peculiar stars including RAVE, GAIA and HERMES wavelength ranges  

CERN Document Server

We present an Echelle+CCD, high S/N, high resolution (R = 20\\,000) spectroscopic atlas of 108 well-known objects representative of the most common types of peculiar and variable stars. The wavelength interval extends from 4600 to 9400 Ang, and includes the RAVE, Gaia and HERMES wavelength ranges. Multi-epoch spectra are provided for the majority of observed stars. A total of 425 spectra of peculiar stars are presented, which have been collected during 56 observing nights between November 1998 and August 2002. The spectra are given in FITS format and heliocentric wavelengths, with accurate subtraction of both the sky background and the scattered light. Auxiliary material useful for custom applications (telluric dividers, spectro-photometric stars, flat-field tracings) is also provided. The atlas aims to provide a homogeneous database of the spectral appearance of stellar peculiarities, a tool useful both for classification purposes and inter-comparison studies. It could also serve the planning for and training...

Tomasella, L; Zwitter, T

2010-01-01

184

Effects of external intermittency and mean shear on the spectral inertial-range exponent in a turbulent square jet.  

UK PubMed Central (United Kingdom)

This study investigates by experiment the dependence of the inertial-range exponent m of the streamwise velocity spectrum on the external intermittency factor ? (??the fraction of time the flow is fully turbulent) and the mean shear S in a turbulent square jet. Velocity measurements were made using hot-wire anemometry in the jet at 15 < x/D(e) < 40, where D(e) denotes the exit equivalent diameter, and for an exit Reynolds number of Re = 50,000. The Taylor microscale Reynolds number R(?) varies from about 70 to 450 in the present study. The TERA (turbulent energy recognition algorithm) method proposed by Falco and Gendrich [in Near-Wall Turbulence: 1988 Zoran Zariç Memorial Conference, edited by S. J. Kline and N. H. Afgan (Hemisphere Publishing Corp., Washington, DC, 1990), pp. 911-931] is discussed and applied to estimate the intermittency factor from velocity signals. It is shown that m depends strongly on ? but negligibly on S. More specifically, m varies with ? following m=m(t)+(ln?(-0.0173))(1/2), where m(t) denotes the spectral exponent found in fully turbulent regions.

Zhang J; Xu M; Pollard A; Mi J

2013-05-01

185

Effects of external intermittency and mean shear on the spectral inertial-range exponent in a turbulent square jet.  

Science.gov (United States)

This study investigates by experiment the dependence of the inertial-range exponent m of the streamwise velocity spectrum on the external intermittency factor ? (??the fraction of time the flow is fully turbulent) and the mean shear S in a turbulent square jet. Velocity measurements were made using hot-wire anemometry in the jet at 15 Reynolds number of Re = 50,000. The Taylor microscale Reynolds number R(?) varies from about 70 to 450 in the present study. The TERA (turbulent energy recognition algorithm) method proposed by Falco and Gendrich [in Near-Wall Turbulence: 1988 Zoran Zariç Memorial Conference, edited by S. J. Kline and N. H. Afgan (Hemisphere Publishing Corp., Washington, DC, 1990), pp. 911-931] is discussed and applied to estimate the intermittency factor from velocity signals. It is shown that m depends strongly on ? but negligibly on S. More specifically, m varies with ? following m=m(t)+(ln?(-0.0173))(1/2), where m(t) denotes the spectral exponent found in fully turbulent regions. PMID:23767622

Zhang, J; Xu, M; Pollard, A; Mi, J

2013-05-14

186

Optimal spectral inversion of atmospheric radiometric measurements in the near-UV to near-IR range: A case study  

Science.gov (United States)

WWe present a general analysis of the error budget in the spectral inversion of atmospheric radiometric measurements. By focussing on the case of an occultation experiment, we simplify the problem through a reduced number of absorbers in a linearized formalism. However, our analysis is quite general and applies to many other situations. For a spectrometer having an infinite spectral resolution, we discuss the origin of systematic and random errors. In particular, the difficult case of aerosols is investigated and several inversion techniques are compared. We underline the importance of carefully simulating the spectral inversion as a function of the target constituent to be retrieved, and the required accuracy level.

Fussen, Didier; Vanhellemont, Filip; Bingen, Christine

2002-01-01

187

Optimal spectral inversion of atmospheric radiometric measurements in the near-UV to near-IR range: A case study.  

UK PubMed Central (United Kingdom)

WWe present a general analysis of the error budget in the spectral inversion of atmospheric radiometric measurements. By focussing on the case of an occultation experiment, we simplify the problem through a reduced number of absorbers in a linearized formalism. However, our analysis is quite general and applies to many other situations. For a spectrometer having an infinite spectral resolution, we discuss the origin of systematic and random errors. In particular, the difficult case of aerosols is investigated and several inversion techniques are compared. We underline the importance of carefully simulating the spectral inversion as a function of the target constituent to be retrieved, and the required accuracy level.

Fussen D; Vanhellemont F; Bingen C

2002-01-01

188

Effect of particle size and spectral sub-range within the UV-VIS-NIR range using diffuse reflectance spectra on multivariate models in evaluating the severity of fusariosis in ground wheat.  

UK PubMed Central (United Kingdom)

Control (crops grown in natural conditions) and Fusarium head blight (FHB) damaged (crops inoculated with Fusarium culmorum conidia) grain of four wheat cultivars was ground and sieved into three fractions of different particle size. A series of blended samples differing in content of damaged material were prepared within fractions and cultivars, and diffuse reflectance spectra recorded within the 200-2500 nm wavelength range. Partial least-squares (PLS) models for the percentage of damaged material in blended samples were built for each of twelve series within different spectral ranges, and the root-mean-squared error of cross-validation (RMSECV) was used for the assessment of model performance. Errors using the models were lowest for the finest fraction independent of spectral range; however, their values depended on the cultivar. RMSECV for the finest fraction averaged over cultivars ranged from a little below 3.0 (when the ultraviolet light sub-range was used or participated with another one) to 8.1% (when only the near infrared (NIR) sub-range was used). For the medium and coarse fractions, averaged errors showed the same tendency of dependence on the sub-range(s); however, with higher values that increased with an increase in particle size. In conclusion, within the different fractions of particle size and spectral ranges, the most sensitive to the presence of damaged material were models developed for the finest fraction and when the ultraviolet light sub-range was used in modelling.

Balcerowska G; Siuda R; Skrzypczak J; ?ukanowski A; Sadowski C

2009-05-01

189

Directional visible light scattering by silicon nanoparticles.  

UK PubMed Central (United Kingdom)

Directional light scattering by spherical silicon nanoparticles in the visible spectral range is experimentally demonstrated for the first time. These unique optical properties arise because of simultaneous excitation and mutual interference of magnetic and electric dipole resonances inside a single nanosphere. Such behaviour is similar to Kerker's-type scattering by hypothetic magneto-dielectric particles predicted theoretically three decades ago. Here we show that directivity of the far-field radiation pattern of single silicon spheres can be strongly dependent on the light wavelength and the nanoparticle size. For nanoparticles with sizes ranging from 100 to 200 nm, forward-to-backward scattering ratio above six can be experimentally obtained, making them similar to 'Huygens' sources. Unique optical properties of silicon nanoparticles make them promising for design of novel low-loss visible- and telecom-range metamaterials and nanoantenna devices.

Fu YH; Kuznetsov AI; Miroshnichenko AE; Yu YF; Luk'yanchuk B

2013-01-01

190

Self-association of acetic acid in dilute deuterated chloroform. Wide-range spectral reconstructions and analysis using FTIR spectroscopy, BTEM, and DFT.  

Science.gov (United States)

The binary solution of acetic acid in CDCl(3) was studied at room pressure on the interval T = 293-313 K with a series of acetic acid concentrations up to 0.16 M. In-situ Fourier transform infrared (FTIR) spectroscopy measurements on the interval of 400-3800 cm(-1) were utilized as the analytical method to monitor the spectral changes due to self-association of acetic acid. The band-target entropy minimization (BTEM) algorithm was employed to reconstruct the underlying pure component spectra. Analysis successfully provided two major spectral estimates of acetic acid, namely, the monomer (primarily in the form of monomer-CDCl(3) complex) and the centrosymmetric cyclic dimer. In addition, analysis provided one minor spectral estimate containing signals from both noncyclic dimers and higher aggregates. Also, spectral estimates were obtained for phosgene and water which were present at trace levels even though considerable precaution was taken to conduct the experiments under anhydrous and anaerobic conditions. Density functional theory (DFT) calculation was performed to assign the acetic acid structures corresponding to the BTEM spectral estimates. Since the structure of dilute acetic acid has been the subject of numerous studies, the present investigation helps to resolve some issues concerning the speciation of acetic acid at low concentrations in low polarity solvents. In particular, the present study provides for the first time, wide-range spectral reconstructions of the species present. PMID:21043480

Tjahjono, Martin; Cheng, Shuying; Li, Chuanzhao; Garland, Marc

2010-11-02

191

Self-association of acetic acid in dilute deuterated chloroform. Wide-range spectral reconstructions and analysis using FTIR spectroscopy, BTEM, and DFT.  

UK PubMed Central (United Kingdom)

The binary solution of acetic acid in CDCl(3) was studied at room pressure on the interval T = 293-313 K with a series of acetic acid concentrations up to 0.16 M. In-situ Fourier transform infrared (FTIR) spectroscopy measurements on the interval of 400-3800 cm(-1) were utilized as the analytical method to monitor the spectral changes due to self-association of acetic acid. The band-target entropy minimization (BTEM) algorithm was employed to reconstruct the underlying pure component spectra. Analysis successfully provided two major spectral estimates of acetic acid, namely, the monomer (primarily in the form of monomer-CDCl(3) complex) and the centrosymmetric cyclic dimer. In addition, analysis provided one minor spectral estimate containing signals from both noncyclic dimers and higher aggregates. Also, spectral estimates were obtained for phosgene and water which were present at trace levels even though considerable precaution was taken to conduct the experiments under anhydrous and anaerobic conditions. Density functional theory (DFT) calculation was performed to assign the acetic acid structures corresponding to the BTEM spectral estimates. Since the structure of dilute acetic acid has been the subject of numerous studies, the present investigation helps to resolve some issues concerning the speciation of acetic acid at low concentrations in low polarity solvents. In particular, the present study provides for the first time, wide-range spectral reconstructions of the species present.

Tjahjono M; Cheng S; Li C; Garland M

2010-11-01

192

Design of a sun tracker for the automatic measurement of spectral irradiance and construction of an irradiance database in the 330-1100 nm range  

Energy Technology Data Exchange (ETDEWEB)

An automatic global and direct solar spectral irradiance system has been designed based on two LICOR spectro radiometers equipped with fibre optics and remote cosine sensors. To measure direct irradiance a sun tracker based on step motors has been developed. The whole system is autonomous and works continuously. From the measurements provided by this system a spectral irradiance database in the 330-1100 nm range has been created. This database contains normal direct and global horizontal irradiances as well as diffuse irradiance on a horizontal plane, together with total atmospheric optical thickness and aerosol optical depth. (author)

Canada, J.; Maj, A. [Departamento de Termodinamica Aplicada, Universidad Politecnica de Valencia, Camino de Vera, s/n. 46022 Valencia (Spain); Utrillas, M.P.; Martinez-Lozano, J.A.; Pedros, R.; Gomez-Amo, J.L. [Departamento de Fisica de la Tierra y Termodinamica, Facultat de Fisica, Universitat de Valencia, 46100 Burjassot (Valencia) (Spain)

2007-10-15

193

Efficiency comparison of spatial and spectral diversity techniques for fading mitigation in free-space optical communications over tactical-range distances  

Science.gov (United States)

In long-range situations, the performance of free-space optical (FSO) communication links is strongly impacted by atmospheric turbulence. In this paper we compare efficiency of turbulence effects mitigation in FSO communication links using spectral (wavelength) and spatial diversity techniques. Numerical analysis of both techniques is performed considering FSO communication setting with single-mode fiber-collimator transceivers. In the case of spectral diversity setting, the fiber-collimators are based on the use of photonic crystal fibers that provide single-mode operation for three distinct wavelengths (532, 1064 and 1550nm). In the spatial diversity communication setting, analysis is performed using multiple-transceiver configurations. Analysis includes both received signal's statistical and temporal spectral characteristics.

Minet, Jean; Vorontsov, Mikhail A.; Wu, G.; Dolfi, Daniel

2013-03-01

194

Visible emission of hydrogen flames  

Energy Technology Data Exchange (ETDEWEB)

The common misconception that hydrogen flames are not visible is examined. Examples are presented of clearly visible emissions from typical hydrogen flames. It is shown that while visible emissions from these flames are considerably weaker than those from comparable hydrocarbon flames, they are indeed visible, albeit at reduced light levels in most cases. Detailed flame spectra are presented to characterize flame emission bands in the ultraviolet, visible and infrared regions of the spectrum that result in a visible hydrogen flame. The visible blue emission is emphasized, and recorded spectra indicate that fine spectral structure is superimposed on a broadband continuum extending from the ultraviolet into the visible region. Tests were performed to show that this emission does not arise from carbon or nitrogen chemistry resulting from carbon-containing impurities (hydrocarbons) in the hydrogen fuel or from CO{sub 2} or N{sub 2} entrainment from the surrounding air. The spectral structure, however, is also observed in methane flames. The magnitude of the broadband emission increases with flame temperature in a highly nonlinear manner while the finer spectral structure is insensitive to temperature. A comparison of diffusion and premixed H{sub 2} flames shows that the fine scale structure is comparable in both flames. (author)

Schefer, R.W.; Kulatilaka, W.D.; Patterson, B.D.; Settersten, T.B. [Combustion Research Facility, Sandia National Laboratories, Livermore, CA 94551-0969 (United States)

2009-06-15

195

InAs1-xSbx photodiodes for the spectral range of 3-5 ?m  

International Nuclear Information System (INIS)

[en] High-performance InAs1-xSbx photodiode structures (x=0.12-0.14) have been grown near lattice-matched on InAs (111) substrats by liquid phase epitaxy. Spectral response, current-voltage characteristics, differential resistance, R0 and detectivity, D*, were studied. Detector noises were calculated and compared with the experimental data. It was found that generation-recombination noises dominated at T=77-200 K

1996-01-01

196

High-Purcell-factor dipolelike modes at visible wavelengths in H1 photonic crystal cavity.  

UK PubMed Central (United Kingdom)

The optimization of H1 photonic crystal cavities for applications in the visible spectral range is reported, with the goal to obtain a versatile photonic platform to explore strongly and weakly coupled systems. The resonators have been realized in silicon nitride and weakly coupled to both organic (fluorophores) and inorganic (colloidal nanocrystals) nanoparticles emitting in the visible spectral range. The theoretical Purcell factor of the two dipolelike modes in the defect has been increased up to approximately 90, and the experimental quality factor was measured to be approximately 750.

Pisanello F; Qualtieri A; Stomeo T; Martiradonna L; Cingolani R; Bramati A; De Vittorio M

2010-05-01

197

Investigations of the March 2006 African dust storm using ground-based column-integrated high spectral resolution infrared (8-13 ?m) and visible aerosol optical thickness measurements: 1. Measurement procedures and results  

Science.gov (United States)

The infrared (IR) aerosol optical thickness (AOT) spectra of Saharan dust measured during the Portable Infrared Aerosol Transmission Experiment (PIRATE) are reported. Saharan dust optical thickness (extinction) spectra from 8 to 13 ?m were obtained using column-integrated solar transmission measurements in Puerto Rico in July 2005 and Senegal in January and March 2006 (during a dust plume) using a Fourier transform infrared (FTIR) spectrometer. The FTIR measured the solar spectral irradiance in the IR in the presence of Saharan dust, and the AOT was determined by comparing the measured spectra to modeled downwelling spectra without dust for the same atmospheric temperature profile, solar zenith angle, water vapor, and ozone concentrations. The modeled dust-free spectra are generated using the Santa Barbara Disort Atmospheric Radiative Transfer (SBDART) program. The measured dust AOT is compared with modeled AOT spectra obtained using Mie theory with dust indices of refraction from Volz and Fouquart with assumed lognormal size distributions. When the visible AOT values from nearby Aerosol Robotic Network (AERONET) sensors are compared to the IR AOT values, results from various dust loadings show that the IR dust AOT at 9.5 ?m is typically only one third that of the visible (670 nm) dust AOT, but there is some evidence that this ratio could increase for larger dust size distributions. The surface IR dust forcing is determined to be about -0.4 W/m2 by summing the dusty and clear irradiance differences.

Thomas, M.; Gautier, C.; Ricchiazzi, P.

2009-06-01

198

Fabrication of an efficient BaTaO2N photoanode harvesting a wide range of visible light for water splitting.  

UK PubMed Central (United Kingdom)

Photoanodes made from BaTaO2N that can harvest visible light up to 660 nm wavelength were fabricated on Ti substrates for achieving efficient water splitting. Both pre-treatment of BaTaO2N particles with an H2 stream and post-necking treatment with TaCl5 effectively increased the photocurrent due to the decreased electrical resistance in the porous BaTaO2N photoanode. A combination of pre-loading of CoO(x) on the BaTaO2N particles and post-loading of RhO(x) significantly improved both the photocurrent and stability under visible light irradiation, along with an obvious negative shift (ca. 300 mV) of the onset potential for water oxidation, while sole loading resulted in a lower photocurrent or insufficient stability. The IPCE value was estimated to be ca. 10% at 1.2 V vs RHE under 600 nm, which is the highest among photoanode materials that can harvest light beyond 600 nm for water oxidation. Photoelectrochemical water splitting into H2 and O2 under visible light was demonstrated using RhO(x)/CoO(x)/BaTaO2N/Ti photoanodes under an externally applied bias larger than 0.7 V to a Pt counter electrode.

Higashi M; Domen K; Abe R

2013-07-01

199

Fabrication of an efficient BaTaO2N photoanode harvesting a wide range of visible light for water splitting.  

Science.gov (United States)

Photoanodes made from BaTaO2N that can harvest visible light up to 660 nm wavelength were fabricated on Ti substrates for achieving efficient water splitting. Both pre-treatment of BaTaO2N particles with an H2 stream and post-necking treatment with TaCl5 effectively increased the photocurrent due to the decreased electrical resistance in the porous BaTaO2N photoanode. A combination of pre-loading of CoO(x) on the BaTaO2N particles and post-loading of RhO(x) significantly improved both the photocurrent and stability under visible light irradiation, along with an obvious negative shift (ca. 300 mV) of the onset potential for water oxidation, while sole loading resulted in a lower photocurrent or insufficient stability. The IPCE value was estimated to be ca. 10% at 1.2 V vs RHE under 600 nm, which is the highest among photoanode materials that can harvest light beyond 600 nm for water oxidation. Photoelectrochemical water splitting into H2 and O2 under visible light was demonstrated using RhO(x)/CoO(x)/BaTaO2N/Ti photoanodes under an externally applied bias larger than 0.7 V to a Pt counter electrode. PMID:23808352

Higashi, Masanobu; Domen, Kazunari; Abe, Ryu

2013-07-03

200

Third-harmonic generation in silicon and photonic crystals of macroporous silicon in the spectral intermediate-IR range; Erzeugung der Dritten Harmonischen in Silizium und Photonischen Kristallen aus makroporoesem Silizium im spektralen mittleren IR-Bereich  

Energy Technology Data Exchange (ETDEWEB)

Nonlinear optical spectroscopy is a powerful method to study surface or bulk properties of condensed matter. In centrosymmetric materials like silicon even order nonlinear optical processes are forbidden. Besides self-focussing or self phase modulation third-harmonic-generation (THG) is the simplest process that can be studied. This work demonstrates that THG is a adapted non-contact and non-invasive optical method to get information about bulk structures of silicon and Photonic crystals (PC), consisting of silicon. Until now most studies are done in the visible spectral range being limited by the linear absorption losses. So the extension of THG to the IR spectral range is extremely useful. This will allow the investigation of Photonic Crystals, where frequencies near a photonic bandgap are of special interest. 2D- photonic structures under investigation were fabricated via photoelectrochemical etching of the Si (100) wafer (thickness 500 {mu}m) receiving square and hexagonal arranged pores. The typical periodicity of the structures used is 2 {mu}m and the length of the pores reached to 400 {mu}m. Because of stability the photonic structures were superimposed on silicon substrate. The experimental set-up used for the THG experiments generates tuneable picosecond IR pulses (tuning range 1500-4000 cm{sup -1}). The IR-pulse hit the sample either perpendicular to the sample surface or under an angle {theta}. The sample can be rotated (f) around the surface normal. The generated third harmonic is analysed by a polarizer, spectrally filtered by a polychromator and registered by a CCD camera. The setup can be used either in transmission or in reflection mode. Optical transmission and reflection spectra of the Si bulk correspond well with the theoretical description, a 4-fold and a 8-fold dependencies of the azimuth angle resulting in the structure of the x{sup (3)}-tensor of (100)-Si. The situation changes dramatically if the PC with hexagonal structure is investigated. In reflection mode a six fold symmetry is observed. This can only be explained by the symmetry of the Photonic Crystal. Changing the transmission mode the result depends on the mount of the PC - fundamental entering from the structure side or fundamental entering from the bulk side. Common to both results are there six maxima. To explain the difference between the transmission and reflection results one has to recognise, that the effective interaction length is limited: so in the reflection geometry of generated TH is from the structured region, whereas in the transmission cases a combination of the structure and the bulk has to be taken into account. This work gives a first theoretical description of this effects. (orig.)

Mitzschke, Kerstin

2007-11-01

 
 
 
 
201

Thermodynamic properties of a classical d-dimensional spin-S Heisenberg ferromagnet with long-range interactions via the spectral density method  

CERN Multimedia

The thermodynamic properties of a classical d-dimensional spin-S Heisenberg ferromagnet, with long-range interactions decaying as $r^{-p}$ and in the presence of an external magnetic field, is investigated by means of the spectral density method in the framework of classical statistical mechanics. We find that long-range order exists at finite temperature for $dd$ with $d>2$, consistently with known theorems. Besides, the related critical temperature is determined and a study of the critical properties is performed.

Cavallo, A; De Cesare, L

2003-01-01

202

Construction of TSL lector equipment with spectral resolution for the determination of thermally stimulated luminescence (TSL) properties of NaCl: Tl+ induced by UV-visible radiation  

International Nuclear Information System (INIS)

A revision of physical models of thermally stimulated luminescence (TSL) in crystals induced by both ionizing and non-ionizing radiation is presented. Particular emphasis is given to the connection of TSL with other thermally stimulated processes and physico-chemical phenomena because basic information on physical mechanics for TSL can be obtained through them. Glow curves of TSL induced by UV-visible radiation in NaCl: Tl+ were measured. Additionally, the following spectrums were obtained for the same samples: optical absorption, excitation, fluorescent emission, and TSL emission. An optical absorption peak was correlated with the Thallium ion concentration. With respect to the TSL emission spectrums, some peaks associated to Thallium dimmers were at 298 and at 480 nm; others which were attributed to NaCl intrinsic properties were at 365, 430, 450 and 525 nm. Also TSL glow curves were studied as a function of the Thallium ion concentration (0.8 ppm to 14.8 ppm). They were de convoluted so as to calculate the activation energy, the frequency factor and the kinetic order for each separate TSL peak. Anomalous values were observed for some frequency factors. A method and TSL lector equipment to obtain TSL emission spectra were developed. (Author).

1993-01-01

203

Spectrally resolved chromatic confocal interferometry for one-shot nano-scale surface profilometry with several tens of micrometric depth range  

Science.gov (United States)

In this research, new nano-scale measurement methodology based on spectrally-resolved chromatic confocal interferometry (SRCCI) was successfully developed by employing integration of chromatic confocal sectioning and spectrally-resolve white light interferometry (SRWLI) for microscopic three dimensional surface profilometry. The proposed chromatic confocal method (CCM) using a broad band while light in combination with a specially designed chromatic dispersion objective is capable of simultaneously acquiring multiple images at a large range of object depths to perform surface 3-D reconstruction by single image shot without vertical scanning and correspondingly achieving a high measurement depth range up to hundreds of micrometers. A Linnik-type interferometric configuration based on spectrally resolved white light interferometry is developed and integrated with the CCM to simultaneously achieve nanoscale axis resolution for the detection point. The white-light interferograms acquired at the exit plane of the spectrometer possess a continuous variation of wavelength along the chromaticity axis, in which the light intensity reaches to its peak when the optical path difference equals to zero between two optical arms. To examine the measurement accuracy of the developed system, a pre-calibrated accurate step height target with a total step height of 10.10 ?m was measured. The experimental result shows that the maximum measurement error was verified to be less than 0.3% of the overall measuring height.

Chen, Liang-Chia; Chen, Yi-Shiuan; Chang, Yi-Wei; Lin, Shyh-Tsong; Yeh, Sheng Lih

2013-01-01

204

Efficient frequency downconversion at the single photon level from the red spectral range to the telecommunications C-band.  

Science.gov (United States)

We report on single photon frequency downconversion from the red part of the spectrum (738 nm) to the telecommunications C-band. By mixing attenuated laser pulses with an average photon number per pulse < 1 with a strong continuous light field at 1403 nm in a periodically poled Zn:LiNbO3 ridge waveguide an internal conversion efficiency of ? 73% is achieved. We further investigate the noise properties of the process by measuring the output spectrum. Our results indicate that by narrow spectral filtering a quantum interface should be feasible which bridges the wavelength gap between quantum emitters like color centers in diamond emitting in the red part of the spectrum and low-loss fiber-optic telecommunications wavelengths. PMID:21716525

Zaske, Sebastian; Lenhard, Andreas; Becher, Christoph

2011-06-20

205

Directional emission, increased free spectral range and mode Q-factors in 2-D wavelength-scale optical microcavity structures  

CERN Document Server

Achieving single-mode operation and highly directional (preferably unidirectional) in-plane light output from whispering-gallery (WG) mode semiconductor microdisk resonators without seriously degrading the mode Q-factor challenges designers of low-threshold microlasers. To address this problem, basic design rules to tune the spectral and emission characteristics of micro-scale optical cavity structures with nanoscale features by tailoring their geometry are formulated and discussed in this paper. The validity and usefulness of these rules is demonstrated by reviewing a number of previously studied cavity shapes with global and local deformations. The rules provide leads to novel improved WG-mode cavity designs, two of which are presented: a cross-shaped photonic molecule with introduced asymmetry and a photonic-crystal-assisted microdisk resonator. Both these designs yield degenerate mode splitting, as well as Q-factor enhancement and directional light output of one of the split modes.

Boriskina, S V; Nosich, A I; Sewell, P; Benson, Trevor M.; Boriskina, Svetlana V.; Nosich, Alexander I.; Sewell, Phillip

2006-01-01

206

Evidence for Alteration in Chemical and Physical Properties of Water and Modulation of its Biological Functions by Sunlight Transmitted through Color Ranges of the Visible Spectrum-A Novel Study  

Directory of Open Access Journals (Sweden)

Full Text Available We investigated the changes in the properties of water when exposed to sunlight for 40 days. We hypothesize and prove that solar irradiation to water entraps electromagnetic radiation as potential energy, which becomes kinetic energy in various systems. It is postulated that photochemically-induced energy transfers, associated with individual spectral emission of visible spectrum of solar light, exert diverse influences on biological systems. Bottles of distilled water, individually wrapped in spectral-colored cellophane were exposed to sunlight and compared to an unwrapped bottle to determine chemical and physical changes as well as modifications of biological properties. Each bottle of water was named according to the color of cellophane paper with letter E (stands for exposed) as a prefix with (E-violet, E-indigo, E-blue, E-green, E-yellow, E-orange, and Ered). E-control (without wrap) was exposed to polychromatic sunlight. This study addresses two main issues viz., the chemical and physical changes in E-water and its effect on biological activities. Chemical and physical composition analysis using inductively coupled plasma atomic emission spectrometry; physical conductance by a Wheatstone Bridge type conductivity meter; osmolarity by a vapor pressure osmometer; and, salt solubility profile of 10% sodium bicarbonate were determined. Furthermore, testing the effect of E-waters on human lymphocyte proliferation, mosquito larvae hatching and seed germination determined the functional role of solar radiation through specific spectrum/s of visible light on various biological processes. We found that water exposed to visible spectral emissions of sunlight had an altered elemental composition, electrical conductance, osmolarity and salt-solubility, as well as differences in bio-modulatory effects. A gradual increase in leaching of Boron from Eviolet to E-red was noted. E-indigo showed maximal increase in electrical conductance and maximal salt solubility of sodium bicarbonate. E-blue inhibited phyto-hemagglutinin-induced immune cell proliferation and mosquito larvae hatching. E-orange stimulated root elongation in seed germination. We conclude that 40-day exposure of water to specific solar spectrum changes chemical and physical properties and influences on biological activity.

Hari H. P. Cohly; Asit Panja; William L. Reno; Don Obenhuber; Margot S. Koelle; Suman K. Das; Michael F. Angel; M. Rajeswara Rao

2005-01-01

207

Excited-state absorption spectroscopy of Nd3+:SrF2 crystals in the 1280 - 1320 nm spectral wavelength range  

International Nuclear Information System (INIS)

The excited-state absorption (ESA) in Nd3+:SrF2 crystals was investigated in the 1280 - 1320 nm spectral wavelength range by selective laser excitation. It was found that, on excitation at wavelengths of 743 and 800.5 nm, there is no ESA in the ranges 1304 - 1309 and 1295 - 1297 nm. Weak ESA bands are observed in the 1297 - 1304 and 1309 - 1320 nm ranges and the differential ESA cross section does not exceed 0.3 x 10-21 cm2 . The results indicate that the ESA does not preclude the use of an Nd3+:SrF2 crystal as the amplifying medium in the wavelength range 1280 - 1320 nm. (active media)

1999-02-28

208

Experimental verification of n = 0 structures for visible light.  

UK PubMed Central (United Kingdom)

We fabricate and characterize a metal-dielectric nanostructure with an effective refractive index n = 0 in the visible spectral range. Light is excited in the material at deep subwavelength resolution by a 30-keV electron beam. From the measured spatially and angle-resolved emission patterns, a vanishing phase advance, corresponding to an effective [Symbol: see text] = 0 and n = 0, is directly observed at the cutoff frequency. The wavelength at which this condition is observed can be tuned over the entire visible or near-infrared spectral range by varying the waveguide width. This n = 0 plasmonic nanostructure may serve as a new building block in nanoscale optical integrated circuits and to control spontaneous emission as experimentally demonstrated by the strongly enhanced radiative optical density of states over the entire n = 0 structure.

Vesseur EJ; Coenen T; Caglayan H; Engheta N; Polman A

2013-01-01

209

(Oxy)nitrides with d0-electronic configuration as photocatalysts and photoanodes that operate under a wide range of visible light for overall water splitting.  

UK PubMed Central (United Kingdom)

Water splitting to form H2 and O2 using semiconductor photocatalysts under sunlight is a possible means of clean energy production from renewable resources. (Oxy)nitrides are regarded as suitable candidates for the application, because of their suitable band edge positions, small band gaps (<3 eV), and stability under irradiation. Since early reports published in 2002 by Domen et al., it has been demonstrated that several (oxy)nitrides are active photocatalysts capable of reducing and oxidizing water in the presence of suitable electron donors and acceptors, respectively, under visible light (? > 400 nm). Some have achieved direct water splitting into H2 and O2 with good reproducibility. (Oxy)nitrides are also attractive as water-splitting photoelectrodes, and highly efficient photoelectrochemical water splitting has been accomplished using tantalum-based (oxy)nitrides under visible light with good stability. However, there still remain a lot of challenges that have to be addressed in this research field. This perspective highlights recent progress in the development of (oxy)nitride materials for application in photocatalytic and photoelectrochemical water splitting made by the author and his colleagues, especially in the last 5 years.

Maeda K

2013-07-01

210

Efficient ion blocking in gaseous detectors and its application to gas-avalanche photomultipliers sensitive in the visible-light range  

International Nuclear Information System (INIS)

A novel concept for ion blocking in gas-avalanche detectors was developed, comprising cascaded micro-hole electron multipliers with patterned electrodes for ion defocusing. This leads to ion blocking at the 10-4 level, in DC mode, in operation conditions adequate for TPCs and for gaseous photomultipliers. The concept was validated in a cascaded visible-sensitive gas-avalanche photomultiplier operating at atmospheric pressure of Ar/CH4 (95/5) with a bi-alkali photocathode. While in previous works high gain, in excess of 105, was reached only in a pulse-gated cascaded-GEM gaseous photomultiplier, the present device yielded, for the first time, similar gain in DC mode. We describe shortly the physical processes involved in the charge transport within gaseous photomultipliers and the ion blocking method. We present results of ion back-flow fraction and of electron multiplication in cascaded patterned-electrode gaseous photomultiplier with K-Cs-Sb, Na-K-Sb and Cs-Sb visible-sensitive photocathodes, operated in DC mode.

2009-01-01

211

Ultraviolet-visible light spectral transmittance of rabbit corneas after riboflavin/ultraviolet-A (365 nm) corneal collagen cross-linking.  

UK PubMed Central (United Kingdom)

PURPOSE: To determine the effect of riboflavin/ultraviolet-A (365 nm) corneal collagen cross-linking on the transmission of the ultraviolet-visible (UV-VIS) light spectrum through the cornea. METHODS: Twelve New Zealand white male rabbits were used in this research. Cross-linking was performed unilaterally on the right eyes of the animals while only the epithelium was removed on the left eyes as the control. Seven weeks after cross-linking, the animals were euthanized, and the enucleated eyes were processed for transmission spectroscopy. To confirm that the cross-linking procedures was done successfully on the right corneas, the tensile force-extension relationship was measured using six corneas from three of the rabbits after the transmission spectrum was determined. RESULTS: Seven weeks after cross-linking, ten of the 12 rabbits had clear corneas in the cross-linked and control eyes. The two rabbits with neovascularization and granular opacities in the right corneas were not included in subsequent measurements. In the cross-linked corneas, transmittance was 87.57% at 650 nm, and decreased continuously as the wavelength shortened. From 315 nm, the transmittance rapidly decreased and was 35.52% at 300 nm. In the control corneas, transmittance was 95.95% at 650 nm and decreased continuously as the wavelength shortened. Below 315 nm, the transmittance rapidly decreased, to 40.29% at 300 nm. The transmittance of the cross-linking corneas was 10%-20% lower than that of the control corneas. The difference was 8.38% at 650 nm and increased as the wavelength shortened, reaching a maximum of 20.59% at 320 nm, and decreased rapidly to 4.77% at 300 nm. The tensile force-extension relationship showed that a greater force was necessary to extend the cross-linking corneas over 500 µm than that of the control corneas. CONCLUSIONS: The transmittance of the cross-linked corneas was 10%-20% lower than that of the control corneas. The difference increased as the wavelength decrease, reaching a maximum at 320 nm and then decreasing rapidly. Ultraviolet collagen cross-linking exhibited a protective effect against ultraviolet penetration.

Hwang HS; Kim MS

2013-01-01

212

Extending the known range of glycerol ether lipids in the environment: structural assignments based on tandem mass spectral fragmentation patterns.  

UK PubMed Central (United Kingdom)

RATIONALE: Glycerol-based alkyl ether lipids are ubiquitous components in marine sediments. In order to explore their structural diversity and biological sources, marine sediment samples from diverse environments were analyzed and the mass spectra of widely distributed, novel glycerol di- and tetraethers were examined systematically. METHODS: Lipid extracts of twelve globally distributed marine subsurface sediments were analyzed by atmospheric pressure chemical ionization mass spectrometry (APCI-MS). Tandem mass (MS/MS) spectra of compounds were obtained with a quadrupole time-of-flight (qTOF) mass spectrometer. RESULTS: In addition to the well-established isoprenoidal glycerol dialkyl glycerol tetraether (isoprenoidal GDGT) and branched GDGT, suites of novel lipids were detected in all studied samples. These lipids include the following classes of tentatively identified compounds: isoprenoidal glycerol dialkanol diether (isoprenoidal GDD), hydroxylated isoprenoidal GDGT (OH-GDGT), hybrid isoprenoidal/branched GDGT (IB-GDGT), hydroxylated isoprenoidal GDD (OH-GDD), overly branched GDGT (OB-GDGT), sparsely branched GDGT (SB-GDGT) and an abundant H-shaped GDGT with the [M+H](+) ion of m/z 1020 (H-1020). CONCLUSIONS: Characteristic MS/MS fragmentation patterns provided mass spectral 'fingerprints' for the recognition of diverse and prominent glycerol ether lipids. The ubiquitous distribution and substantial abundance of these glycerol ethers, as well as their structural variability, suggest a significant ecological role of their source organisms in various marine environments.

Liu XL; Summons RE; Hinrichs KU

2012-10-01

213

Method to analyze remotely sensed spectral data  

Energy Technology Data Exchange (ETDEWEB)

A fast and rigorous multivariate curve resolution (MCR) algorithm is applied to remotely sensed spectral data. The algorithm is applicable in the solar-reflective spectral region, comprising the visible to the shortwave infrared (ranging from approximately 0.4 to 2.5 .mu.m), midwave infrared, and thermal emission spectral region, comprising the thermal infrared (ranging from approximately 8 to 15 .mu.m). For example, employing minimal a priori knowledge, notably non-negativity constraints on the extracted endmember profiles and a constant abundance constraint for the atmospheric upwelling component, MCR can be used to successfully compensate thermal infrared hyperspectral images for atmospheric upwelling and, thereby, transmittance effects. Further, MCR can accurately estimate the relative spectral absorption coefficients and thermal contrast distribution of a gas plume component near the minimum detectable quantity.

Stork, Christopher L. (Albuquerque, NM); Van Benthem, Mark H. (Middletown, DE)

2009-02-17

214

Study of wave chaos in a randomly-inhomogeneous oceanic acoustic waveguide: spectral analysis of the finite-range evolution operator  

CERN Document Server

The proplem of sound propagation in an oceanic waveguide is considered. Scattering on random inhomogeneity of the waveguide leads to wave chaos. Chaos reveals itself in spectral properties of the finite-range evolution operator (FREO). FREO describes transformation of a wavefield in course of propagation along a finite segment of a waveguide. We study transition to chaos by tracking variations in spectral statistics with increasing length of the segment. Analysis of the FREO is accompanied with ray calculations using the one-step Poincar\\'e map which is the classical counterpart of the FREO. Underwater sound channel in the Sea of Japan is taken for an example. Several methods of spectral analysis are utilized. In particular, we approximate level spacing statistics by means of the Berry-Robnik and Brody distributions, explore the spectrum using the procedure elaborated by A. Relano with coworkers (Relano et al, Phys. Rev. Lett., 2002; Relano, Phys. Rev. Lett., 2008), and analyze modal expansions of the eigenfu...

Makarov, D V; Uleysky, M Yu; Petrov, P S

2012-01-01

215

Single-shot high-dynamic range laser pulse contrast measurement using Fourth-Order-Crosscorrelation via Self-Referenced-Spectral-Interferometry (FOX-SRSI)  

CERN Multimedia

High-dynamic range isolation of the interference term and the non-interference term in the inverse Fourier-transformed spectral interferogram as required in Self-Referenced-Spectral-Interferometry (SRSI) for single-shot high-dynamic range laser pulse characterization is not always practically possible due to presence of the non-interference term over the entire temporal widow. Alternatively, we propose and demonstrate that one could directly obtain the single-shot Fourth-Order-Crosscorrelation (FOX) of the laser pulse to be characterized via SRSI (FOX-SRSI) from the interference term as the high-dynamic range laser contrast measurement, avoiding the need to isolate the interference and non-interference terms. As a consequence, the undesired contribution from the non-interference term limits the valid temporal window of the measurement. The single-shot FOX-SRSI result is consistent with the laser contrast measured independently using a multi-shot scanning third-order autocorrelator.

Palaniyappan, Sasi; Shimada, T; Shah, R C; Jung, D; Gautier, D C; Hegelich, B M; Fernandez, J C

2012-01-01

216

Adjustment of a goniometer for X-rays optics calibration in the spectral range 1.5-20 KeV  

International Nuclear Information System (INIS)

[en] The aim of this memoir is the adjustment of a (?, 2?) goniometer coupled to X-rays source to calibrate mirrors (single layers like C, Ni, Au, etc... and multilayers like C/W, Si/W, etc...) in the spectral range 1.5 - 20 keV. For each kind of tested optics the adjustment of the goniometer include the procedure alignment of the different components (X-ray source, collimation slits, optics, detectors) and the first reflectivity measurements. Those measurements are compared those realized at LURE, using synchrotron radiation provided by SUPER ACO storage ring, and to a theoretical simulation

1992-01-01

217

Spectral Survey of the Star-Forming Region W51 e1/e2 in the 3-mm Wavelength Range  

Science.gov (United States)

One hundred and five molecules and their isotopic species have been detected as a result of a spectral survey of the W51 e1/e2 star-forming region at 84 - 115 GHz, beginning from simple diatomic or triatomic molecules, such as CO, CS, HCN, up to complex organic compounds, such as CH3OCH3, CH3COCH3, and C2H5OOCH. Ninety-three lines that were absent from the Lovas list of molecular lines, already observed in space, were detected and approximately half of them were identified. A significant part of the detected molecules are those that are typical for hot cores. Among them are neutral molecules CH3OCHO, C2H5OH, CH3COCH3 etc, which, according to current views exist in the gas phase only in hot cores and in shock-heated gas. In addition, vibrationally excited SiO, C4H, HCN, l-C3H, HCCCN, CH3CN, CH3OH, H2O, and SO2 lines with upper-level temperatures of several hundred Kelvins were found. Such lines can arise only in hot gas with temperature of the order of 100 K or higher. Apart from neutral molecules, various molecular ions were detected. Som of them (N2H+, HCO+, HCS+) usually exist in molecular clouds with high visual extinction Av. At the same time, the CF+ ion should be observed in Photon Dominated Regions with Av about unity or lower. An interesting result is the tentative detection of two molecules, MgCN and NaCN, which have thus far been observed only in the atmospheres of late-type giant stars. One can assume that the conditions in the hottest W51 regions (probably, in the vicinities of protostars) are close to those in the atmospheres of giant stars. It is desirable to search for other lines of these molecules in order to either confirm or rule out their detection.

Kalenskii, S.; Johansson, L. E. B.

2011-05-01

218

High resolution spectral survey of symbiotic stars in the near-IR over the GAIA wavelength range  

CERN Multimedia

High resolution (R~20,000), high signal-to-noise (S/N~100) spectra were collected for ~40 symbiotic stars with the Asiago echelle spectrograph over the same 8480-8740 Ang wavelength range covered by the ESA Cornerstone mission GAIA, centered on the near-IR CaII triplet and the head of the Paschen series. A large number (~140) of cool MKK giant and supergiant templates were observed with the same instrumentation to serve as a reference and classification grid. The spectra offer bright prospects in classifying and addressing the nature of the cool component of symbiotic stars (deriving T(eff), log g, [Fe/H], [alpha/Fe], V(rot)sin i both via MDM-like methods and syntetic atmosphere modeling) and mapping the physical condition and kinematics of the gas regions responsible for the emission lines.

Marrese, P M; Munari, U; Marrese, Paola M.; Sordo, Rosanna; Munari, Ulisse

2002-01-01

219

The Herschel/HIFI spectral survey of OMC-2 FIR 4 (CHESS): An overview of the 480 to 1902 GHz range  

CERN Multimedia

Broadband spectral surveys of protostars offer a rich view of the physical, chemical and dynamical structure and evolution of star-forming regions. The Herschel Space Observatory opened up the terahertz regime to such surveys, giving access to the fundamental transitions of many hydrides and to the high-energy transitions of many other species. A comparative analysis of the chemical inventories and physical processes and properties of protostars of various masses and evolutionary states is the goal of the Herschel CHEmical Surveys of Star forming regions (CHESS) key program. This paper focusses on the intermediate-mass protostar, OMC-2 FIR 4. We obtained a spectrum of OMC-2 FIR 4 in the 480 to 1902 GHz range with the HIFI spectrometer onboard Herschel and carried out the reduction, line identification, and a broad analysis of the line profile components, excitation, and cooling. We detect 719 spectral lines from 40 species and isotopologs. The line flux is dominated by CO, H2O, and CH3OH. The line profiles ar...

Kama, M; Dominik, C; Ceccarelli, C; Fuente, A; Caux, E; Higgins, R; Tielens, A G G M; Alonso-Albi, T

2013-01-01

220

A highly compact third-order silicon microring add-drop filter with a very large free spectral range, a flat passband and a low delay dispersion.  

UK PubMed Central (United Kingdom)

We demonstrate highly compact third-order silicon microring add-drop filters. The microring resonator has a small radius of 2.5 mum and a very large free spectral range of 32 nm at 1.55 mum. Experimental results show a low add-drop crosstalk of around -20 dB. Box-like channel dropping response is demonstrated, and it has a passband of ~ 1 nm (125 GHz), fast rolling-off (slope ~ 0.2 dB/GHz), high out-of-band signal rejection of around 40 dB and a low drop loss. Simulation agrees well with experiments in power transmission, and the group delay is also simulated and the variation is less than 1 ps within the passband. The propagation loss in microring resonators is optimized.

Xiao S; Khan MH; Shen H; Qi M

2007-10-01

 
 
 
 
221

The spectral characteristics of Gd sub 2 SiO sub 5 :Eu sup 3 sup + in VUV-UV range  

CERN Multimedia

Synchrotron radiation source was used to investigated the spectral characteristics of Gd sub 2 SiO sub 5 :Eu sup 3 sup + in VUV-UV range. The various energy transfers at room temperature and 10 K, including from host or Gd sup 3 sup + ions to Eu sup 3 sup + ions and transfer between Eu sup 3 sup + ions at two different lattice sites, were discussed. In addition the emission spectra under 186 nm and 276 nm excitation were compared from the view of quantum cutting. The results indicate that Gd sub 2 SiO sub 5 :Eu sup 3 sup + is a kind of material with potential high efficiency quantum cutting

Chen Yong; Wei Ya Guang; Tao Ye

2002-01-01

222

Influence of different spectral ranges of light and Ca2+ -channel blockers on Ca2+ and K+ levels in Phaseolus coccineus L. pulvini  

Directory of Open Access Journals (Sweden)

Full Text Available The effect of different spectral ranges of light on the modification of transport processes in isolated parts of Phaseolus coccineus pulvini was analysed in a bath medium by determining the Ca2+ and K+ contents. After 1 h incubation of separated fragments of the extensor and flexor in solutions containing deionized water, medium, or medium with verapamil or nifedipine, the investigated material was irradiated with monochromatic light of different wavelengths. The concentration of Ca2+, K+ and the pH value were determined in the medium. The obtained results suggest the occurrence of a specific coupling between the concentration of Ca2+ and K+ dependend on the wavelength of the applied light and part of the pulvinus. Certain spectral ranges of light brought about opposite effects on ion transport in opposite parts of the pulvinus. Changes in the pH of mediums containing isolated parts of the pulvini part to different effects of blue, red, and far-red light on the activity of H+-pumps located in the motor cells. The use of verapamil and nifedipine, specific Ca2+-channel blockers, made it possible to demonstrate the significant effect of Ca2+ on the activity and functioning of K+ -channels. The two types of inhibitors decreased the influx of Ca2+ and K+ to motor cells of the pulvini, however they did not limit the efflux of ions to the medium. The obtained results suggest that Ca2+ ions take part in transduction of the light signal. It seems probable that the action of blue light is also mediated by part of the Ca2+ ions.

Jan Bia?czyk; Zbigniew Lechowski

1992-01-01

223

Spectral measurements of aerosol particle extinction in the 0.4-3.7 {mu}m wavelength range, performed at Sagres with the IR-RAD sun-radiometer[Special issue with manuscripts related to the second Aerosol Characterization Experiment (ACE-2), 16 June-25 July 1997  

Energy Technology Data Exchange (ETDEWEB)

During the CLEARCOLUMN campaign which took place at Sagres (Portugal) from 16 June to 25 July 1997, more than 2000 spectral measurements of direct solar irradiance were performed at thirteen window-wavelengths in the 0.4-3.7 {mu}m range, on 27 days. The measurements were performed using the IR-RAD sun-radiometer designed and manufactured at the Institute ISAO (FISBAT), Bologna (Italy), and carefully calibrated by applying the Langley plot method to the measurements performed on 24 October 1996, at the Schneefernerhaus Observatory on the Zugspitze (Germany). From these measurements, the values of the total atmospheric optical depth were obtained at the various wavelengths, from which the corresponding spectral values of aerosol optical depth were determined through accurate corrections for Rayleigh scattering and gaseous absorption. Such values were found to be mostly smaller than 0.1 during June and early July, presenting almost neutral spectral dependence characteristics, closely related to the prevailing oceanic origins of particulate matter. Higher values of aerosol optical thickness, mainly ranging between 0.1 and 0.5 at visible wavelengths and sharply decreasing with wavelength, were found during the rest of July in the presence of predominant contents of continental and anthropogenic aerosol particles arriving from polluted European regions. The King inversion method was applied to the spectral series of aerosol optical depth to determine the particle size-distribution curves in the 0.2-20 {mu}m diameter range. For 2 of these cases (one chosen for a low atmospheric loading of marine aerosols and the other for a mean content of continental/anthropogenic aerosols), the changes in the outgoing solar radiation flux produced by aerosol particles were calculated, considering different surface albedo conditions. The results obtained in the second case show that changes of opposite sign can be caused by the same atmospheric aerosol loading when passing from oceanic to continental areas.

Vitale, Vito; Tomasi, Claudio; Bonafe, Ubaldo; Marani, Stefano; Lupi, Angelo; Cacciari, Alessandra; Ruggeri, Pietro [Istituto ISAO (FISBAT)-CNR, Bologna (Italy); Hoyningen-Huene, W. von [Bremen Univ. (Germany). Inst. fuer Umweltphysik

2000-04-01

224

A new method to extract gas concentrations in the ultraviolet and visible wavelength ranges, based on differential optical absorption technique and Fourier transform  

International Nuclear Information System (INIS)

By combining differential optical absorption technique with Fourier transformation we obtain a measuring method exhibiting high sensitivity, good accuracy and good robustness against wavelength displacements in the spectrum obtained. The method also separates different gases in the absorption spectrum from each other in an effective way. The above mentioned features make this method attractive. The ability to separate gases is especially rewarding; it means that we need not know which gases are present when we start to measure. The only prerequisite is that the gases involved absorb in the wavelength range that is to be measured. The method appears to be well suited for the detection of atmospheric pollutions.

1994-01-01

225

Comparison between visible and near-IR flame spectra from natural gas-fired furnace for blackbody temperature measurements  

Energy Technology Data Exchange (ETDEWEB)

This paper reports the results from investigating the feasibility of calculating flame temperature from a natural gas-fired furnace based on blackbody radiation in the visible spectral range. If successful, the visible spectral range would provide data for multi-task applications such as emission line analysis and temperature calculation simultaneously. A probe containing a lens connected to the fiber-optic cables is inserted into the furnace and pointed towards the flame. Spectral intensity data are fed back to a spectrometer and then to a monitoring computer. The approach is first applied to various furnace types using the visible range to establish a baseline for the technique. The results for temperature calculations in the visible range are then compared with those taken in the near-IR (NIR) range under the same conditions. This comparison indicates that temperatures calculated from visible region could be as accurate as the one obtained from NIR region. Challenges associated with this technique are also discussed. 17 refs., 5 figs., 1 tab.

Shahla Keyvan; Rodney Rossow; Carlos Romero; Xianchang Li [University of Missouri, Columbia, MO (United States). Department of Mechanical and Aerospace Engineering

2004-06-01

226

Regularities of color and brightness variations of R Coronae Borealis-type variable stars during the active state according to observational data in the visible range  

International Nuclear Information System (INIS)

[en] Color and brightness variations of RCrB star during three brightness minima with different depth, that is: 1982, 1983-1984 and 1985 - are considered. Variations of color indices are shown to depend on minimum depth: color indices decreases in minimal brightness phase during deep minimum, while in 1982 minimum they increase as compared to brightness maximum of variable. Occurrence of additional radiation during brightness decrease the intensity of which is maximal one in shortwave range represents common feature for three minima of RCrB star. It is stressed, that high amplitude brightness pulsations at reduced brightness of these stars may be considered as brightness secondary minima. On the basis of photoelectric observations it is assumed, that distortions of brightness monotonous variation for RCrB type stars in weakened state (flanges, abrupt variations of brightness reduction velocity) results from overlap of brightness secondary weakenings on brightness curves during minima

1990-01-01

227

Wavelength-resolved optical extinction measurements of aerosols using broad-band cavity-enhanced absorption spectroscopy over the spectral range of 445-480 nm.  

UK PubMed Central (United Kingdom)

Despite the significant progress in the measurements of aerosol extinction and absorption using spectroscopy approaches such as cavity ring-down spectroscopy (CRDS) and photoacoustic spectroscopy (PAS), the widely used single-wavelength instruments may suffer from the interferences of gases absorption present in the real environment. A second instrument for simultaneous measurement of absorbing gases is required to characterize the effect of light extinction resulted from gases absorption. We present in this paper the development of a blue light-emitting diode (LED)-based incoherent broad-band cavity-enhanced spectroscopy (IBBCEAS) approach for broad-band measurements of wavelength-resolved aerosol extinction over the spectral range of 445-480 nm. This method also allows for simultaneous measurement of trace gases absorption present in the air sample using the same instrument. On the basis of the measured wavelength-dependent aerosol extinction cross section, the real part of the refractive index (RI) can be directly retrieved in a case where the RI does not vary strongly with the wavelength over the relevant spectral region. Laboratory-generated monodispersed aerosols, polystyrene latex spheres (PSL) and ammonium sulfate (AS), were employed for validation of the RI determination by IBBCEAS measurements. On the basis of a Mie scattering model, the real parts of the aerosol RI were retrieved from the measured wavelength-resolved extinction cross sections for both aerosol samples, which are in good agreement with the reported values. The developed IBBCEAS instrument was deployed for simultaneous measurements of aerosol extinction coefficient and NO(2) concentration in ambient air in a suburban site during two representative days.

Zhao W; Dong M; Chen W; Gu X; Hu C; Gao X; Huang W; Zhang W

2013-02-01

228

A simple analysis method for measuring in real-time power spectral densities and coherence functions in a large frequency range  

International Nuclear Information System (INIS)

[en] This paper describes a real-time method which allows the measurement of auto and cross power spectral densities in a large frequency range with almost constant relative frequency resolution. Based on a normal digital frequency analysis the resolution at low frequencies can be increased to any extend without additional electronic equipment. The long time signals needed for the low frequencies are won from the high frequency data by a digital low pass filter. Due to this decimation of the time series only moderate storage region is needed allowing the use of a small digital computer for on-line application. The method is suitable to monitor the spectra in a wide frequency range without time delay. (orig.)[de] In diesem Bericht wird ein einfaches Echtzeitverfahren vorgestellt, das die Messung spektraler Leistungsdichten in einem grossen Frequenzbereich erlaubt, wobei eine fast konstante relative Frequenzaufloesung erreicht wird. Ausgehend von einer normalen digitalen Frequenzanalyse kann die Aufloesung fuer kleine Frequenzen praktisch beliebig verbessert werden. Die fuer die kleinen Frequenzen benoetigten langen Zeitsignale werden durch digitales Filtern erzeugt, das eine Reduktion der Daten und damit des Speicherplatzes erlaubt. Dadurch ist die Verwendung eines Kleinrechners im on-line Einsatz moeglich. Die Methode ist geeignet, Spektren in einem grossen Frequenzbereich ohne Verzoegerung zu ueberwachen. (orig.)

1976-05-11

229

Spectral sensitivity of the blood-retinal barrier at the pigment epithelium for blue light in the 400-500 nm range.  

UK PubMed Central (United Kingdom)

To specify the spectral sensitivity of the retinal pigment epithelium (RPE) for blue light damage, pigmented rabbits were exposed to light of 408, 418, 439, 455, 485, and 500 nm (half-peak bandwidth approximately 12 nm). The range of radiant exposure was 15-275 J cm-2 (1.7-19 mW cm-2 for 0.5-5 h). Vitreous fluorophotometry was used to functionally evaluate the blood-retinal barrier at the RPE in vivo, and electron microscopy to visualize RPE ultrastructure in vitro. A significant increase in permeability of the blood-retinal barrier was seen only after exposure to light of 418 nm. Radiant exposure at threshold for permeability increase was 18 J cm-2. Electron microscopy of the RPE demonstrated dispersion and clumping of melanin granules. The results suggest that the RPE is most sensitive to light in the range 412-425 nm, possibly due to damage-mediating chromophores such as cytochrome c oxidase and lipofuscin.

Putting BJ; van Best JA; Zweypfenning RC; Vrensen GF; Oosterhuis JA

1993-10-01

230

Machine Vision Beyond Visible Spectrum  

CERN Multimedia

The material of this book encompasses many disciplines, including visible, infrared, far infrared, millimeter wave, microwave, radar, synthetic aperture radar, and electro-optical sensors as well as the very dynamic topics of image processing, computer vision and pattern recognition. This book is composed of six parts: advanced background modeling for surveillance; advances in Tracking in Infrared imagery; methods for Pose estimation in Ultrasound and LWIR imagery; recognition in multi-spectral and synthetic aperture radar; fusion of disparate sensors; and smart Sensors.

Hammoud, Riad I; McMillan, Robert W; Ikeuchi, Katsushi

2011-01-01

231

Annual Variation of Local Photon Emissions’ Spectral Power within the mHz Range Overlaps with Seismic-Atmospheric Acoustic Oscillations  

Directory of Open Access Journals (Sweden)

Full Text Available Spheroidal modes of seismic and acoustic oscillations in the atmosphere occur within the 2 to 7 mHz range with peak-to-peak variations in the order of 10–12 to 10–11 m·s–2. Previous research indicated the amplitudes for 230 s and 270 s periods peak during the summer months. In the present study the amplitudes of a reliably apparent 3 mHz increment from spectral analyses of minute-to-minute measurements of background photon emissions by a photomultiplier tube housed in a dark room were sampled for a one year period. The peak increase in the power of this increment was maximal during the summer months and overlapped conspicuously with the annual variation in fundamental spheroidal modes of seismic free oscillations. Quantitative estimates indicate that relative shifts in the order of 10–11 W/m2 for photon emissions may reflect the annual variation in coupled oscillations between the earth and atmosphere.

Michael A. Persinger

2012-01-01

232

Wavelength-tunable spasing in the visible.  

UK PubMed Central (United Kingdom)

A SPASER, short for surface plasmon amplification by stimulated emission of radiation, is key to accessing coherent optical fields at the nanoscale. Nevertheless, the realization of a SPASER in the visible range still remains a great challenge because of strong dissipative losses. Here, we demonstrate that room-temperature SPASER emission can be achieved by amplifying longitudinal surface plasmon modes supported in gold nanorods as plasmon nanocavities and utilizing laser dyes to supply optical gain for compensation of plasmon losses. By choosing a particular organic dye and adjusting the doping level, the resonant wavelength of the SPASER emission can be tuned from 562 to 627 nm with a spectral line width narrowed down to 5-11 nm. This work provides a versatile route toward SPASERs at extended wavelength regimes.

Meng X; Kildishev AV; Fujita K; Tanaka K; Shalaev VM

2013-09-01

233

Visible spectroscopy at the Extrap-T1 pinch experiment  

International Nuclear Information System (INIS)

A wide range UV to visible spectrum from 2450 to 8050 Angstrom has been acquired and analysed for the EXTRAP-T1 plasma. The impurity lines in the spectrum are mainly from carbon and oxygen species up to four times ionized, but also nitrogen lines are present. No traces of metal impurity are observed. We have identified most of the spectral lines and compare intensities from several multiplets with predicted values. A spectral range free from line emission is found which is suitable for continuum measurements. Furthermore, line strictures are identified as originating from the CH molecule and are observed both using a center chord line of sight and an edge chord line-of-sight through the plasma. (au)

1991-01-01

234

Incremental Visualizer for Visible Objects  

DEFF Research Database (Denmark)

This paper discusses the integration of database back-end and visualizer front-end into a one tightly coupled system. The main aim which we achieve is to reduce the data pipeline from database to visualization by using incremental data extraction of visible objects in a fly-through scenarios. We also argue that passing only relevant data from the database will substantially reduce the overall load of the visualization system. We propose the system Incremental Visualizer for Visible Objects (IVVO) which considers visible objects and enables incremental visualization along the observer movement path. IVVO is the novel solution which allows data to be visualized and loaded on the fly from the database and which regards visibilities of objects. We run a set of experiments to convince that IVVO is feasible in terms of I/O operations and CPU load. We consider the example of data which uses visibility ranges and show that considering visibility ranges is crucial when considering incremental visible object extraction.

Bukauskas, Linas; BØhlen, Michael Hanspeter

2004-01-01

235

Fabrication and characterization of brookite-rich, visible light-active TiO2 films for water splitting  

Energy Technology Data Exchange (ETDEWEB)

We report that mild oxidation of Ti foils in air results in brookite-rich titanium oxide (TiO2) films with similar spectral response to that of dye-sensitized TiO2. X-ray powder diffraction and Raman spectroscopy show that the onset of brookite formation occurs at 500 8C, and the material is characterized by a strong absorption band in the visible spectral range. The first-principle calculations show that enhanced visible light absorption correlates with the presence of Ti interstitials. Photocurrent density measurements of water splitting reveal that the brookite-rich TiO2 exhibits the highest photocatalytic performance among the different forms of TiO2 produced by oxidation of Ti foils. With increasing oxidation temperature transformation to the rutile phase accompanied by declining visible range photoactivity is observed.

Pan, Hui [ORNL; Qiu, Xiaofeng [ORNL; Ivanov, Ilia N [ORNL; Meyer III, Harry M [ORNL; Wang, Wei [ORNL; Zhu, Wenguang [ORNL; Paranthaman, Mariappan Parans [ORNL; Zhang, Zhenyu [ORNL; Eres, Gyula [ORNL; Gu, Baohua [ORNL

2009-01-01

236

Visible Human Project  

Science.gov (United States)

... Tools Media Productions Related Projects The Visible Human Project ® Overview The Visible Human Project ® is an outgrowth of the NLM's 1986 Long- ... The long-term goal of the Visible Human Project ® is to produce a system of knowledge structures ...

237

Flexible metamaterials at visible wavelengths  

Energy Technology Data Exchange (ETDEWEB)

We report on the fabrication and characterization of plasmonic structures on flexible substrates (Metaflex) and demonstrate the optical properties of a single layer of Metaflex. The layer exhibits a plasmonic resonance in the visible region around 620 nm. We show experimental and numerical results for both nano-antennas and fishnet geometries. We anticipate the use of Metaflex as a building block for flexible metamaterials in the visible range.

Di Falco, Andrea; Ploschner, Martin; Krauss, Thomas F, E-mail: adf10@st-andrews.ac.u [School of Physics and Astronomy, University of St Andrews, North Haugh, KY16 9SS, Fife (United Kingdom)

2010-11-15

238

Morphology of the spectral resonance structure of the electromagnetic background noise in the range of 0.1–4 Hz at L = 5.2  

Directory of Open Access Journals (Sweden)

Full Text Available Continuous observations of fluctuations of the geomagnetic field at Sodankylä Geophysical Observatory (L = 5.2) were used for a comprehensive morphological study of the spectral resonance structure (SRS) seen in the background electromagnetic noise in the frequency range of 0.1–4.0 Hz. It is shown that the occurrence rate of SRS is higher in the nighttime than in the daytime. The occurrence rate is higher in winter than in summer. The SRS frequencies and the difference between neighbouring eigenfrequencies (the frequency scale) increase towards nighttime and decrease towards daytime. Both frequency scale and occurrence rate exhibit a clear tendency to decrease from minimum to maximum of the solar activity cycle. It is found that the occurrence rate of SRS decreases when geomagnetic activity increases. The SRS is believed to be a consequence of a resonator for Alfvén waves, which is suggested to exist in the upper ionosphere. According to the theory of the ionospheric Alfvén resonator (IAR), characteristics of SRS crucially depend on electron density in the F-layer maximum, as well as on the altitudinal scale of the density decay above the maximum.We compared the SRS morphological properties with predictions of the IAR theory. The ionospheric parameters needed for calculation were obtained from the ionosphere model (IRI-95), as well as from measurements made with the ionosonde in Sodankylä. We conclude that, indeed, the main morphological properties of SRS are explained on the basis of the IAR theory. The measured parameters of SRS can be used for improving the ionospheric models.Key words. Ionosphere (auroral ionosphere; wave propagation) – Radio Science (electromagnetic noise and interference)

A. G. Yahnin; N. V. Semenova; A. A. Ostapenko; J. Kangas; J. Manninen; T. Turunen

0000-01-01

239

Ultraviolet-visible-near infrared spectra of 50 samples  

Energy Technology Data Exchange (ETDEWEB)

Under the subject contract, Unidynamics/Phoenix recorded the ultraviolet-visible-near infrared spectra of 50 samples supplied by LANL. A Varian Cary 2300 series spectrophotometer produced the spectral data. The spectrophotometer was interfaced to a Varian D5-15 Data Station, and hard copies of data were made. Baseline corrections throughout the wavelength range were established using Halon as a reference material. Corrected measurements were automatically made by the system on every sample. Two types of sample holders were tried. Before collecting data on the LANL samples, identical samples of PETN were examined using both holders.

Taylor, B. [Crane Unidynamics Phoenix, AZ (United States)

1988-08-30

240

Demonstration of Magnetic Dipole Resonances of Dielectric Nanospheres in the Visible Region  

DEFF Research Database (Denmark)

Strong resonant light scattering by individual spherical Si nanoparticles is experimentally demonstrated, revealing pronounced resonances associated with the excitation of magnetic and electric modes in these nanoparticles. It is shown that the low-frequency resonance corresponds to the magnetic dipole excitation. Due to high permittivity, the magnetic dipole resonance is observed in the visible spectral range for Si nanoparticles with diameters of similar to 200 nm, thereby opening a way to the realization of isotropic optical metamaterials with strong magnetic responses in the visible region.

Evlyukhin, A. B.; Novikov, S. M.

2012-01-01

 
 
 
 
241

The benefits of visibility  

International Nuclear Information System (INIS)

[en] The benefits of visibility improvement (or the damages with additional degradation) refer to increases (or decreases) in utility obtained in three different dimensions. The first of these is associated with the nature of the visibility change. Visual range may be improved so that features of an area become more distinct or the sky becomes clearer. Alternatively, normal features of an area may be marred, say by the site of a power plant or its plume (called plume blight). The second dimension is the location of the change: in an urban area, in a rural setting, or in a recreational area or area of particular beauty, such as the Grand Canyon. The third dimension is the type of value: use or non-use. Thus, a person who visits the Grand Canyon (or may visit it in the future) may hold use values for improving his view of the Canyon or its surroundings and may also old non-use values for improved visibility (whether for altruistic or other reasons) irrespective of present or planned visits. In all, therefore, there are 12 possible combinations of the elements in these three dimension, each of which is logically distinct from the others and which demands attention in the literature to derive willingness to pay (WTP)

1994-01-01

242

Absolyutnaya spektral'naya chuvstvitel'nost' fotodiodnykh lineek v rentgenovskom diapazone 7-20 kehV. (Absolute spectral sensitivity of photodiode arrays in the X-ray energy range 7-20 keV).  

Science.gov (United States)

The results of the investigation of absolute spectral sensitivity of linear photodiode arrays (the kind LF1024-25/2) as X-ray one-coordinate detectors in the energy range from 7 to 20 keV are presented. The measurements have been carried out with the use ...

I. P. Dolbnya S. G. Kurylo

1991-01-01

243

Visible, vacuum ultraviolet and x-ray spectroscopy using back-illuminated CCD detector  

International Nuclear Information System (INIS)

[en] Back-illuminated CCD detectors have been used for visible, VUV and x-ray spectroscopy. The results are compared with those generated by conventional detection systems such as the photodiode array with image intensifier or micro-channel plate. The use of the back-illuminated CCD demonstrated excellent qualities including low noise, a high level of spectral resolution and a greatly extended output dynamic range. Detailed results of the comparison are also discussed. (author)

2000-01-01

244

Total bremsstrahlung spectral photon distributions in metallic targets in the photon energy range of 5-10 keV by 204Tl beta particles  

International Nuclear Information System (INIS)

Total bremsstrahlung spectral photon distributions produced by beta particles of the 204Tl beta emitter in thick targets of Al, Ti, Sn and Pb targets were evaluated at photon energies from 5 keV to 10 keV. Experimental measurements were compared with the theoretical total bremsstrahlung spectral photon distributions obtained from Elwert corrected (non-relativistic) Bethe-Heitler theory and modified Elwert factor (relativistic) Bethe-Heitler theories for ordinary bremsstrahlung, and the modified Elwert factor (relativistic) Bethe-Heitler theory which includes polarization bremsstrahlung in the stripped atom approximation. The experimental results show better agreement with the modified Elwert factor (relativistic) Bethe-Heitler theory which includes the contribution of polarization bremsstrahlung. The contributions of polarization bremsstrahlung decrease with increased photon energy, particularly for medium and high Z elements. Hence its contribution cannot be neglected while studying the total bremsstrahlung spectral photon distributions in thick targets, produced by continuous beta particles in the studied energy region.

2009-01-01

245

Tailorable, Visible Light Emission From Silicon Nanocrystals  

Energy Technology Data Exchange (ETDEWEB)

J. P. Wilcoxon and G. A. Samara Crystalline, size-selected Si nanocrystals in the size range 1.8-10 nm grown in inverse micellar cages exhibit highly structured optical absorption and photoluminescence (PL) across the visible range of the spectrum. The most intense PL for the smallest nanocrystals produced This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, make any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. to induce a useful level of visible photoluminescence (PL) from silicon (Si). The approaches understood. Visible PL has been observed from Si nanocrystals, or quantum dots, produced by a variety of techniques including aerosols,2 colloids,3 and ion implantation.4 However, all of The optical absorption spectra of our nanocrystals are much richer in spectral features spectrum of bulk Si where the spectral features reflect the details of the band structure shown in nanocrystals estimated to have a Si core diameter of 1-2 nm. These measured quantum those in the spectrum of bulk Si in Fig. 1 are striking indicating that nanocrystals of this size 8-Room temperature PL results on an HPLC size-selected, purified 2 nm nanocrystals but blue shifted by -0.4 eV due to quantum confinement. Excitation at 245 nm yields the PL shows the PL spectrum for a similar sample excited at 490 nm (2.53 eV) trapped excitons at the surface of Si nanocrystals. The excitons are obtained for dimer bonds 1.8- 10 nm. These nanocrystals retain bulk-like optical absorption and an indirect bandgap Figure 1. The absorption spectrum of d = 2 nm Si nanocrystals compared to that of bulk7 Si. Figure 2. The extinction and PL (excitation at 490 nm) spectra ford= 8-10 nm Si nanocrystals.

Samara, G.A.; Wilcoxon, J.P.

1999-07-20

246

Glasses for seeing beyond visible.  

UK PubMed Central (United Kingdom)

Conventional glasses based on oxides have a transparency limited by phonon absorption in the near IR region and have a limited interest for analyzing information located far beyond the visible. The IR spectral domain is nevertheless of prime interest, since it covers fundamental wavelength ranges used for thermal imaging as well as molecular vibrational signatures. Besides spectacular advances in the field of IR detectors, the main significant progresses are related to the development of IR glass optics, such as lenses or IR optical fibres. The field of IR glasses is almost totally dominated by glasses formed from heavy atoms such as the chalcogens S, Se and Te. Their transparency extends up to 12, 16 and 28 microm for sulfide-, selenide- and the new generation of telluride-based glasses, respectively. They cover the atmospheric transparency domains, 3-5 and 8-13 microm, respectively, at which the IR radiation can propagate allowing thermal imaging and night-vision operations through thick layers of atmosphere. The development of new glass compositions will be discussed on the basis of structural consideration with the objective of moulding low-cost lenses for IR cameras used, for instance, in car-driving assistance. Additionally, multimode, single-index, optical fibres operating in the 3 to 12 microm window developed for in situ remote evanescent-wave IR spectroscopy will also be mentioned. The detection of molecular IR signatures is applied to environmental monitoring for investigating the pollution of underground water with toxic molecules. The extension of this technique to the investigation of biomolecules in three different studies devoted to liver tissues analysis, bio-film formation, and cell metabolism will also be discussed. Finally we will mention the developments in the field of single-mode fibres operating around 10 mum for the Darwin space mission, which is aiming at discovering, signs of biological life in telluric earth-like exoplanets throughout the universe.

Zhang X; Bureau B; Lucas P; Boussard-Pledel C; Lucas J

2008-01-01

247

Automated multifunction apparatus for spectral and polarization measurements  

International Nuclear Information System (INIS)

An automated spectral apparatus is described that is based on an SDL-2 spectrometer for spectral and polarization measurements with small specimens (0.15 x 0.15 mm) by the Fourier-coefficient method in the visible and ultraviolet regions over a wide range of temperatures. The absorption, dichroism, birefringence, and polarization orientation of natural waves are determined simultaneously in a single measurement cycle. Polarization-luminescence spectra can also be recorded from one region of the specimen without its adjustment. 3 refs., 3 figs.

1992-01-01

248

Reflectance spectra of selected lunar areas within the 300 - 800 nm spectral range observed by means of the SVET instrument and their interpretation.  

Science.gov (United States)

The SVET instrument has been designed and built for use of Mars mineralogy mapping. Placed at the 2-m telescope at the high altitude Pic-du-Midi observatory and observing the Moon. The observations provide two kinds of results. Firstly, the validity of the design was proved, secondly - some interesting results on spectral characteristics and content of lunar regolith were obtained.

Ksanfomaliti, L. V.; Petrova, E. V.; Chesalin, L. S.; Busarev, V. V.; Shevchenko, V. V.; Pinet, P.; Chevrel, S.

1994-12-01

249

Caracterización espectral y mineralógica de los suelos del valle del río Cauca por espectroscopía visible e infrarroja (400 - 2.500 nm)/ Soil spectral characterization and mineralogy of the Cauca River Valley by visible and infrared (400 - 2,500 nm) spectroscopy  

Scientific Electronic Library Online (English)

Full Text Available Abstract in spanish Las librerías espectrales se utilizan para identificar diferentes tipos de suelo a partir de análisis espectrales que caracterizan su composición mineralógica y química. Los objetivos del presente trabajo consistieron en determinar si existen diferencias en el perfil espectral de los suelos del valle geográfico del río Cauca a nivel de subgrupo taxonómico; y cuantificar en sus perfiles espectrales la abundancia de minerales arcillosos. Por medio de un análisis de (more) conglomerados se seleccionaron las muestras más homogéneas de cada subgrupo taxonómico para construir el perfil espectral de cada uno de ellos. El modelo linear spectral unmixing se utilizó para determinar las concentraciones de minerales arcillosos. A nivel de subgrupo taxonómico se observaron diferencias en la magnitud de los perfiles espectrales, así como en sus longitudes de onda a los 1.400, 1.900 y 2.200 nm. El modelo utilizado permite caracterizar de manera objetiva las concentraciones de minerales arcillosos de cada suelo a partir de su perfil espectral. Abstract in english Spectral libraries are used to identify different soil types based on spectral analyses which feature their mineralogical and chemical composition. On these grounds, the objective of the present work consisted in determining whether there are any differences in the spectral profile of the soils of the geographical Cauca Valley at the taxonomic subgroup level; and to assess their spectral profiles in terms of the abundance of clay minerals. By means of cluster analysis we (more) selected the most homogeneous samples of each taxonomic sub group to elaborate its spectral profile. Clay mineral concentrations were determined by means of a linear spectral unmixing model. Differences among taxonomic subgroups were found in both the magnitude of the spectral profiles and their wavelengths (1.400, 1.900 and 2.200 nm). Based on soil spectral profiles, the applied model can be used to objectively characterize clay mineral concentrations.

Bastidas-Obando, Ernesto; Carbonell, Javier A.

2010-08-01

250

Visibility in California  

Energy Technology Data Exchange (ETDEWEB)

A comprehensive study is conducted of visibility in California using prevailing visibility measurements at 67 weather stations in conjunction with data on particulate concentrations and meteorology. The weather station visibility data, when handled with special techniques that account for the nature of visibility reporting practices, prove to be of very good quality for the purposes of most of the analyses that are attempted. It is found that the most important meteorological parameters with respect to visibility are relative humidity, temperature, and special weather events (especially fog). A detailed isopleth map of visibility within California, when compared with earlier work on nationwide visibility, reveals that California experiences far more severe and complex spatial gradients in visibility than those observed anywhere else in the U.S. Two major pockets of heavy man-made visibility impact in California are the Los Angeles basin and the San Joaquin Valley. The spatial, seasonal, and diurnal patterns of visibility are found to be readily explainable in terms of corresponding patterns in emissions, air quality, and meteorology. Regression analyses relating visibility to relative humidity and aerosol concentrations produce high levels of correlation and physically reasonable regression coefficients; these analyses indicate that secondary aerosols are major contributors to visibility reduction in California. An analysis of long-term visibility trends from 1949 to 1976 reveals several interesting features in historical visibility changes for California.

Trijonis, J.

1982-02-01

251

Validation of line and continuum spectroscopic parameters with measurements of atmospheric emitted spectral radiance from far to mid infrared wave number range  

International Nuclear Information System (INIS)

[en] The latest release of a high-resolution transmission molecular absorption database along with two improved models of water vapor continuum absorption are used to check their impact on the improvement of state-of-art radiative transfer. Radiative transfer performance has been assessed using high mountains atmospheric emitted spectral downwelling radiance observations in the 360-1200 cm-1 spectral regions. These high mountains observations are particularly suited to check the behavior and performance in the water vapor rotation band. In addition, they also have allowed us to gain insight into understanding the quality of recent new compilation of lines and related treatment for the ?2 CO2 band and the O3 band at 9.6?m. Comparisons are made between forward calculations of atmospheric transmission spectra and spectral radiances measured using two ground-based Fourier transform instruments. The results demonstrate that water vapor absorption largely benefits from the recent improvement in the related continuum (both self and foreign). In addition, ozone absorption is very accurately reproduced and, although to a less extent, this is also the case of CO2 absorption in the long wave ?2 band.

2012-01-01

252

No Visible Scar Colectomy  

Medline Plus

Full Text Available No Visible Scar Colectomy Ethicon Endo-Surgery Orange County, California January 28, 2010 This program is presented ... to this OR-Live webcast presentation featuring a no visible scar colectomy. During the program, viewers are ...

253

Silicon for visible-to-VLWIR photon detection  

Science.gov (United States)

Photon detectors and focal plane arrays (FPAs) are fabricated from silicon in many varieties. With appropriate choices for detector architecture, dopants, and operating temperature, silicon can cover the spectral range from ultraviolet to the very-long-wavelength infrared (VLWIR), exhibit high internal gain to allow photon counting over this broad spectral range, and can be made in large array formats for imaging. DRS makes silicon detectors and FPAs with unique architectures for a variety of applications. Large-format, VLWIR FPAs based on doped-silicon Blocked-Impurity-Band (BIB) detectors have been developed. These FPAs comprise an array of BIB detectors interfaced via indium column interconnects to a matching read-out integrated circuit (ROIC). Arsenic-doped silicon (Si:As) BIB detector arrays with useful photon response out to about 28 ?m are the most fully developed embodiment of this technology. FPAs with Si:As BIB arrays have been made in a variety of pixel formats (to 10242) and have been optimized for low, moderate, and high infrared backgrounds. Antimony-doped silicon (Si:Sb) BIB arrays having response to wavelengths > 40 ?m have also been demonstrated. Avalanche processes in Si:As at low temperatures (~ 8 K) have led to two unique solid-state photon-counting detectors adapted to infrared and visible wavelengths. The infrared device is the solid-state photomultiplier (SSPM). To our knowledge, it is the only detector capable of counting VLWIR photons (? <= 28 ?m) with high quantum efficiency. A related device optimized for the visible spectral region is the visible-light photon counter (VLPC). The VLPC is a nearly ideal device for detection of small bunches of photons with excellent time resolution. VLPCs coupled to scintillating fibers have demonstrated new capabilities for energetic charged particle tracking in high-energy physics. A fiber tracking system that utilizes VLPCs is currently in operation in the D0 detector at Fermilab"s Tevatron. VLPCs may also be useful for quantum cryptography and quantum computation. Finally, DRS makes imaging arrays of pin-diodes utilizing the intrinsic silicon photoresponse to provide high performance over the 0.4 1.0 ?m spectral range operating near room temperature. pin-diode arrays are particularly attractive as an alternative to charge-coupled devices (CCDs) for space applications where radiation hardening is needed.

Stapelbroek, Maryn G.; Hogue, Henry H.; Atkins, Ernest W.; Reynolds, David B.; D'Souza, Arvind I.

2003-09-01

254

COLLI - a Monte Carlo program for calculating neutron spectral fluences in the energy range 10 keV to 20 MeV - description and application  

International Nuclear Information System (INIS)

[en] The program described can be applied to calculating the transport of neutrons through an arrangement of bodies that can be extensively varied in geometry and materials. The information obtainable by this program includes data on the spectral fluence of scattered neutrons for a set of up to 10 random measuring points. Fortran IV is the programming language. For the calculation of neutron interactions, point cross sections of the ENDF data library are used, either in the original version or in a condensed form. The data are processed for the following elements: Hydrogen, carbon, nitrogen, oxygen, aluminum, silicon, calcium, iron, copper, tungsten, and lead. (orig./HP)

1985-01-01

255

The ultrafast nonlinear optical response and multi-photon absorption of a new metal complex in the near-infrared spectral range  

Science.gov (United States)

A new coordination compound, chloro(1,10-phenanthroline-N, N')(triphenylphosphine)copper(I) dichloromethane, incorporated in poly(methyl methacrylate) exhibits superior nonlinear optical properties in the near-infrared spectral region. Its nonlinear response time and third-order nonlinear optical susceptibility at 800 nm are <= 90 fs and 1.8 × 10 - 10 esu, respectively. Considerable nonlinear absorption is observed with this sample, near 800 and 1250 nm. The contribution of the excited states to the total nonlinear absorption process is discussed. The results reveal the potential of this newly designed compound for multi-photon absorption-based photonic applications.

Kiran, A. J.; Lee, H. W.; Sampath Kumar, H. C.; Rudresha, B. J.; Bhat, B. R.; Yeom, D.-I.; Kim, K.; Rotermund, F.

2010-03-01

256

Visible and near infrared detector for BepiColombos spectrometer VIHI  

Science.gov (United States)

VIHI: the Visible and Infrared Hyperspectral Imager is one of the three channels of the Simbio-Sys instrument for the BepiColombo mission to Mercury. Its scientific objective is to study the hermean surfaces composition by sensing the photon flux reflected off the planet. VIHI works in the range of 400 to 2000 nm with a spectral resolution around a few hundreds. The particularity of this channel is the use of a single detector matrix (264 × 264) for both visible and infrared wavelengths. Getting the visible part of the detector responsivity is achieved by thinning an infrared HgCdTe matrix because visible light is completely absorbed inside the substrate. The thinning process is well controlled since a long time and was used to increase number of thermal cycle of the hybrid devices. Recently, this process is able to remove completely the substrate and, thus, open the detector to the visible range. The detector is a custom design made by Raytheon Vision System in Goleta (USA). In this paper, we will describe the expected performances of the detector which is designed to work in the very harsh radiation environment of Mercury.

Hello, Y.; Roig, J. F.; Doressoundiram, A.; Capaccioni, F.; Cosi, M.; Tommasi, L.; Beuville, E.; Corrales, E.; Peralta, R.; Rabkin, C.

257

Microfluidics integration of aperiodic plasmonic arrays for spatial-spectral optical detection.  

UK PubMed Central (United Kingdom)

We demonstrate successful integration of aperiodic arrays of metal nanoparticles with microfluidics technology for optical sensing using the spectral-colorimetric responses of nanostructured arrays to refractive index variations. Different aperiodic arrays of gold (Au) nanoparticles with varying interparticle separations and Fourier spectral properties are fabricated using Electron Beam Lithography (EBL) and integrated with polydimethylsiloxane (PDMS) microfluidics structures by soft-lithographic micro-imprint techniques. The spectral shifts of scattering spectra and the distinctive modifications of structural color patterns induced by refractive index variations were simultaneously measured inside microfluidic flow cells by dark-field spectroscopy and image correlation analysis in the visible spectral range. The integration of engineered aperiodic arrays of Au nanoparticles with microfluidics devices provides a novel sensing platform with multiplexed spatial-spectral responses for opto-fluidics applications and lab-on-a-chip optical biosensing.

Lee SY; Walsh GF; Dal Negro L

2013-02-01

258

Microfluidics integration of aperiodic plasmonic arrays for spatial-spectral optical detection.  

Science.gov (United States)

We demonstrate successful integration of aperiodic arrays of metal nanoparticles with microfluidics technology for optical sensing using the spectral-colorimetric responses of nanostructured arrays to refractive index variations. Different aperiodic arrays of gold (Au) nanoparticles with varying interparticle separations and Fourier spectral properties are fabricated using Electron Beam Lithography (EBL) and integrated with polydimethylsiloxane (PDMS) microfluidics structures by soft-lithographic micro-imprint techniques. The spectral shifts of scattering spectra and the distinctive modifications of structural color patterns induced by refractive index variations were simultaneously measured inside microfluidic flow cells by dark-field spectroscopy and image correlation analysis in the visible spectral range. The integration of engineered aperiodic arrays of Au nanoparticles with microfluidics devices provides a novel sensing platform with multiplexed spatial-spectral responses for opto-fluidics applications and lab-on-a-chip optical biosensing. PMID:23482027

Lee, Sylvanus Y; Walsh, Gary F; Dal Negro, Luca

2013-02-25

259

Air fluorescence measurements in the spectral range 300-420 nm using a 28.5 GeV electron beam  

CERN Multimedia

Measurements are reported of the yield and spectrum of fluorescence, excited by a 28.5 GeV electron beam, in air at a range of pressures of interest to ultra-high energy cosmic ray detectors. The wavelength range was 300 - 420 nm. System calibration has been performed using Rayleigh scattering of a nitrogen laser beam. In atmospheric pressure dry air at 304 K the yield is 20.8 +/- 1.6 photons per MeV.

Abbasi, R; Belov, K; Belz, J; Cao, Z; Dalton, M; Fedorova, Y; Huentemeyer, P; Jones, B F; Jui, C C H; Loh, E C; Manago, N; Martens, K; Matthews, J N; Maestas, M; Smith, J; Sokolsky, P; Springer, R W; Thomas, J; Thomas, S; Chen, P; Field, C; Hast, C; Iverson, R; Ng, J S T; Odian, A; Reil, K; Walz, D; Bergman, D R; Thomson, G; Zech, A; Chang, F-Y; Chen, C-C; Chen, C-W; Huang, M A; Hwang, W-Y P; Lin, G-L

2007-01-01

260

Noncovalent functionalization of disentangled boron nitride nanotubes with flavin mononucleotides for strong and stable visible-light emission in aqueous solution.  

UK PubMed Central (United Kingdom)

Strong and stable visible-light-emitting boron nitride nanotube (BNNT)/biomolecule nanohybrids were successfully fabricated via noncovalent functionalization of BNNTs with flavin mononucleotides (FMN). Atomic force microscopy showed excellent dispersion of the nanohybrids in aqueous solution. Infrared absorption spectroscopy revealed strong ?-? stacking interactions between FMN and BNNT sidewalls. Importantly, the fluorescence spectra revealed that the nanohybrids were highly fluorescent in the visible-light spectral range. Moreover, this fluorescence had unique pH-dependent and thermally stable properties. These nanohybrids might be used to construct novel fluorescence imaging probes that function over a wide pH and temperature range.

Gao Z; Zhi C; Bando Y; Golberg D; Serizawa T

2011-03-01

 
 
 
 
261

Photovoltaic Detector Based on Type II Heterostructure with Deep AlSb/InAsSb/AlSb Quantum Well in the Active Region for the Mid-Infrared Spectral Range  

Science.gov (United States)

Photodetectors for the spectral range 2-4 ?m, based on an asymmetric type-II heterostructure p-InAs/AlSb/InAsSb/AlSb/(p, n)-GaSb with a single deep quantum well (QW) or three deep QWs at the heterointerface, have been grown by metal-organic vapor phase epitaxy and analysed. The transport, luminescent, photoelectric, current-voltage, and capacitance-voltage characteristics of these structures have been examined. A high-intensity positive and negative luminescence was observed in the spectral range 3-4 ?m at high temperatures (300–400 K). The photosensitivity spectra were in the range 1.2–3.6 ?m (T = 77 K). Large values of quantum efficiency (? = 0.6–0.7), responsivity (S? = 0.9–1.4 A·W1), and detectivity D*? 3.5·1011 to 1010 cm·Hz1/2·W?1) were obtained at T = 77–200 K. The small capacitance of the structures (C = 1.5 pF at V = ?1 V and T = 300 K) enabled an estimate of the response time of the photodetector at ? = 75 ps, which corresponds to a bandwidth of about 6 GHz. Photodetectors of this kind are promising for heterodyne detection of the emission of quantum-cascade lasers and IR spectroscopy.

Konovalov, G. G.; Mikhailova, M. P.; Andreev, I. A.; Moiseev, K. D.; Ivanov, E. V.; Mikhailov, M. Yu; Yakovlev, Yu P.

2013-08-01

262

Thermal coagulation-induced changes of the optical properties of normal and adenomatous human colon tissues in vitro in the spectral range 400-1100 nm  

International Nuclear Information System (INIS)

The absorption coefficients, the reduced scattering coefficients and the optical penetration depths for native and coagulated human normal and adenomatous colon tissues in vitro were determined over the range of 400-1100 nm using a spectrophotometer with an internal integrating sphere system, and the inverse adding-doubling method was applied to calculate the tissue optical properties from diffuse reflectance and total transmittance measurements. The experimental results showed that in the range of 400-1100 nm there were larger absorption coefficients (P

2008-04-21

263

Spectral reflectance properties of carbonaceous chondrites: 2. CM chondrites  

Science.gov (United States)

We have examined the spectral reflectance properties and available modal mineralogies of 39 CM carbonaceous chondrites to determine their range of spectral variability and to diagnose their spectral features. We have also reviewed the published literature on CM mineralogy and subclassification, surveyed the published spectral literature and added new measurements of CM chondrites and relevant end members and mineral mixtures, and measured 11 parameters and searched pair-wise for correlations between all quantities. CM spectra are characterized by overall slopes that can range from modestly blue-sloped to red-sloped, with brighter spectra being generally more red-sloped. Spectral slopes, as measured by the 2.4:0.56 ?m and 2.4 ?m:visible region peak reflectance ratios, range from 0.90 to 2.32, and 0.81 to 2.24, respectively, with values saponite-group phyllosilicate absorption band. Spectra of different subsamples of a single CM can show large variations in absolute reflectance and overall slope. This is probably due to petrologic variations that likely exist within a single CM chondrite, as duplicate spectra for a single subsample show much less spectral variability. When the full suite of available CM spectra is considered, few clear spectral-compositional trends emerge. This indicates that multiple compositional and physical factors affect absolute reflectance, absorption band depths, and absorption band wavelength positions. Asteroids with reflectance spectra that exhibit absorption features consistent with CM spectra (i.e., absorption bands near 0.7 and 0.9 ?m) include members from multiple taxonomic groups. This suggests that on CM parent bodies, aqueous alteration resulted in the consistent production of serpentine-group phyllosilicates, however resulting absolute reflectances and spectral shapes seen in CM reflectance spectra are highly variable, accounting for the presence of phyllosilicate features in reflectance spectra of asteroids across diverse taxonomic groups.

Cloutis, E. A.; Hudon, P.; Hiroi, T.; Gaffey, M. J.; Mann, P.

2011-11-01

264

Investigations of the March 2006 African dust storm using ground-based column-integrated high spectral resolution infrared (8-13 ?m) and visible aerosol optical thickness measurements: 2. Mineral aerosol mixture analyses  

Science.gov (United States)

The mineral aerosol mixture composition for the March 2006 Saharan dust storm is assessed in this paper on the basis of the analysis of visible to near-infrared (VIS-NIR) and infrared (IR) aerosol optical thickness (AOT) spectra obtained during the Portable Infrared Aerosol Transmission Experiment (PIRATE). The AOT spectra from 8 to 13 ?m were determined using column-integrated solar transmission measurements using a Fourier transform infrared spectrometer. To determine the mineralogy and mixture composition of the dust, we determined the expected mineralogy of dust from the Algerian source region in a dust storm environment. Then we computed the modeled VIS-IR AOT spectra using Mie theory for external and internal mixtures. We compared the modeled VIS-NIR AOT spectra and derived index of refraction and single-scattering albedo with the measured values from AERONET and compared the modeled IR AOT spectra with the values from our IR measurements. The fit between the measured and modeled values was best when we used an extinction resonance correction to the Mie theory results to better account for the exact wavelengths and shapes of some of the AOT peaks for mineral particles. The mineralogy and mixture composition of the best dust model includes external mixtures, internal mixtures, and mineralogy dominated by quartz, illite, and calcite. The modeled mean radius was determined, and several modes were computed in agreement with AERONET results.

Thomas, M.; Gautier, C.

2009-07-01

265

Visible and near-infrared spectroscopy for distinguishing malignant tumor tissue from benign tumor and normal breast tissues in vitro.  

Science.gov (United States)

The high incidence and mortality of breast cancer requires an effective, rapid, and cost-effective method for its diagnosis. Here, visible and near-infrared spectroscopy in the wavelength range of 400 to 2200 nm is utilized for distinguishing the malignant tumor tissue from benign tumor and normal breast tissues. Based on the absorption and scattering spectra of fixed samples, three spectral analysis methods are proposed which include an absorption spectral analysis, a scattering spectral analysis, and a combined spectral analysis of the two. By comparison with the histopathological examination, the sensitivity, specificity, and accuracy of the three analysis methods are calculated. The results showed that the combined spectral analysis method can significantly enhance the effectiveness when compared with the sole absorption or scattering spectral analysis method. The sensitivity, specificity, and accuracy of the combined spectral analysis method are 100%, 87.82%, and 87.50% for the benign tumor tissue and 81.82%, 100%, and 87.5% for malignant tumor tissue, respectively. All of the three values are 100% for normal breast tissue. This study demonstrates that the combined spectral analysis method has better potential for in vitro optical diagnosis for breast lesions. PMID:23839487

Zhang, Yang; Chen, Yongjun; Yu, Yuan; Xue, Xingbo; Tuchin, Valery V; Zhu, Dan

2013-07-01

266

Visible and near-infrared spectroscopy for distinguishing malignant tumor tissue from benign tumor and normal breast tissues in vitro.  

UK PubMed Central (United Kingdom)

The high incidence and mortality of breast cancer requires an effective, rapid, and cost-effective method for its diagnosis. Here, visible and near-infrared spectroscopy in the wavelength range of 400 to 2200 nm is utilized for distinguishing the malignant tumor tissue from benign tumor and normal breast tissues. Based on the absorption and scattering spectra of fixed samples, three spectral analysis methods are proposed which include an absorption spectral analysis, a scattering spectral analysis, and a combined spectral analysis of the two. By comparison with the histopathological examination, the sensitivity, specificity, and accuracy of the three analysis methods are calculated. The results showed that the combined spectral analysis method can significantly enhance the effectiveness when compared with the sole absorption or scattering spectral analysis method. The sensitivity, specificity, and accuracy of the combined spectral analysis method are 100%, 87.82%, and 87.50% for the benign tumor tissue and 81.82%, 100%, and 87.5% for malignant tumor tissue, respectively. All of the three values are 100% for normal breast tissue. This study demonstrates that the combined spectral analysis method has better potential for in vitro optical diagnosis for breast lesions.

Zhang Y; Chen Y; Yu Y; Xue X; Tuchin VV; Zhu D

2013-07-01

267

CHARACTERIZATION OF SOIL HUMIC SUBSTANCES BY ULTRAVIOLET-VISIBLE AND SYNCHRONOUS FLUORESCENCE SPECTROSCOPY  

Directory of Open Access Journals (Sweden)

Full Text Available We focused our study on ultraviolet-visible and synchronous fluorescence spectra and indexes of humic subctances isolated from five Czech soil samples: Haplic Chernozem, Luvic Chernozem, Gleyic Luvisol, Haplic Cambisol and Leptic Cambisol. Results indicated the following HS quality: Haplic Chernozem > Luvic Chernozem > Gleyic Luvisol > Haplic Cambisol > Leptic Cambisol. Humic acids and fulvic acids ratios (HA/FA) were increasing together with decreasing values of Q4/6 measured in visible spectral range. Highest absorbance in visible spectral range was detected in Haplic Chernozem and Luvic Chernozem. Maximum relative fluorescence was found in Haplic Chernozem. SFS spectra (in emission mode) at ??=20 nm showed five main fluorophore peaks at: 360, 470, 488, 502 and 512 nm. Fluorescence behaviour of studied samples was compared with Elliot soil humic acid standard (IHSS). Correlation between fluorescence indexes (F) and humification degree (HD) R2= 0.88 and between calculated humification degree (HD*) and humic acids content (HA sum) R2=0.84 and between fluorescence indexes F and HA/FA ratios (R2=0.88) were found.

NAD?ŽDA FASUROVÁ; LUBICA POSP͊ILOVÁ

2011-01-01

268

Visible and UV emission spectroscopy  

International Nuclear Information System (INIS)

Visible and ultra-violet emission spectroscopy is a well established plasma diagnostic technique extensively used in contemporary fusion experiments. Theoretical plasma models are required to derive the relevant physical parameters. These models are reviewed in the first part of this paper. They allow spectral line intensities and radiative power losses to be calculated from the knowledge of the detailed atomic physics processes occurring in the plasma. In tokamak plasma experiments, impurity contamination and transport are important concerns. Basic spectroscopic methods used in their understanding are described. They include the determination of impurity concentrations either by line emission modelling (through the use of an impurity transport code), or by direct charge-exchange recombination measurement. They also include the evaluation of neutral particle fluxes at the plasma periphery. Finally, the experimental techniques used in the derivation of impurity transport coefficients are reported

1991-09-06

269

Analyzing Visibility Configurations.  

Science.gov (United States)

Many algorithms, such as level of detail rendering and occlusion culling methods, make decisions based on the degree of visibility of an object, but do not analyze the distribution, or structure, of the visible and occluded regions across surfaces. We present an efficient method to classify different \\emph{visibility configurations} and show how this can be used on top of existing methods based on visibility determination. We adapt co-occurrence matrices for visibility analysis and generalize them to operate on clusters of triangular surfaces instead of pixels. We employ machine learning techniques to reliably classify the thus extracted feature vectors. Our method allows perceptually-motivated level of detail methods for real-time rendering applications by detecting configurations with expected visual masking. We exemplify the versatility of our method with an analysis of area-light visibility configurations in ray tracing and an area-to-area visibility analysis suitable for hierarchical radiosity refinement. Initial results demonstrate the robustness, simplicity, and performance of our method in synthetic scenes, as well as real applications. PMID:20498504

Dachsbacher, Carsten

2010-05-20

270

Analyzing Visibility Configurations.  

UK PubMed Central (United Kingdom)

Many algorithms, such as level of detail rendering and occlusion culling methods, make decisions based on the degree of visibility of an object, but do not analyze the distribution, or structure, of the visible and occluded regions across surfaces. We present an efficient method to classify different \\emph{visibility configurations} and show how this can be used on top of existing methods based on visibility determination. We adapt co-occurrence matrices for visibility analysis and generalize them to operate on clusters of triangular surfaces instead of pixels. We employ machine learning techniques to reliably classify the thus extracted feature vectors. Our method allows perceptually-motivated level of detail methods for real-time rendering applications by detecting configurations with expected visual masking. We exemplify the versatility of our method with an analysis of area-light visibility configurations in ray tracing and an area-to-area visibility analysis suitable for hierarchical radiosity refinement. Initial results demonstrate the robustness, simplicity, and performance of our method in synthetic scenes, as well as real applications.

Dachsbacher C

2010-05-01

271

All-fiber femtosecond Cherenkov laser at visible wavelengths  

DEFF Research Database (Denmark)

Fiber-optic Cherenkov radiation (CR), also known as dispersive wave generation or non-solitonic radiation, is produced in small-core photonic crystal fibers (PCF) when a soliton perturbed by fiber higher-order dispersion co-propagates with a dispersive wave fulfilling a certain phase-matching condition [1]. The resonant ultrafast wave conversion via the fiber-optic CR mechanism is instrumental for applications in biophotonics such as bio-imaging and microscopy [2]. In this work, we demonstrate a highly-stable all-fiber, fully monolithic CR system based on an Yb-fiber femtosecond laser, producing electrically tunable femtosecond CR output in the visible (VIS) spectral range of 580-630 nm, with the 3 dB spectral bandwidth not exceeding 36 nm, with average power in the milliwatt range. Relative intensity noise (RIN) of this laser, affecting the sensitivity of bio-imaging and microscopy systems, is found to be as low as -103 dBc/Hz. This is 2 orders of magnitudes lower noise as compared to spectrally-sliced supercontinuum, which is the current standard of ultrafast fiber-optic generation at visible wavelength. The layout of the laser system is shown in Fig. 1(a). The system consists of two parts: an all-fiber selfstabilized Yb-doped femtosecond laser [3,4] operating at 1035 nm central wavelength and 26.7 MHz repetition rate used as the pump source; and a spliced-on small-core nonlinear PCF NL-3.0-850 (NKT Photonics A/S) with zero-dispersion wavelength around 850 nm, used for Cherenkov wave conversion [5]. Bridge fibers are used in the CR link to enhance the conversion efficiency. Fig. 1(b) shows the far-field saturated visible images of the CR emitted from the laser system, generated as the pump power increases in the range 150 mW - 300 mW. The emitted CR spectra corresponding to different average output powers are shown in Fig. 1(c). When the average emitted CR power is increasing from 0.46 mW to 4.2 mW, the central wavelength is shifting from 630 nm to 580 nm, and the 3 dB bandwidth of the spectrum increases from14 nm to 36 nm. The physical mechanism of wavelength tunability with changing the pump power is related to different linear and nonlinear compression conditions for weaker and stronger pump laser pulses in the hollow-core pulse compressor and CR stages of the laser (Fig. 1(a)). Fig. 1 (d) shows the autocorrelation (AC) of the CR with the output power of 1.7 mW. The FWHM of the AC trace for the generated CR pulse is 160 fs. The FWHM of the AC of the input pump pulse at 1035 nm is 832 fs. The CR pulse is more than 5 times shorter than the pump pulse, as a result of the nonlinear pump pulse compression in the CR fiber link. We are currently working on achieving an even broader electrical tunability of the CR output, ideally covering the significant part of the visible spectral range.

Liu, Xiaomin; Lægsgaard, Jesper

2013-01-01

272

On the spectral domain approach to long-range propagation of high-frequency waves along a strip conductor above a PEC surface  

CERN Document Server

A generic problem of high frequency wave propagation along a metallic strip in parallel above a PEC ground plane is considered. The wave is excited by an elemental electric dipole at an arbitrary location above the PEC plane. The full wave problem, for arbitrary widths of the strip, is solved by means of a mode matching approach and expansion of the strip surface current into Chebyshev polynomials. For narrow strips, an approximate method using only longitudinal currents is derived, and compared numerically with the full wave method. Utilizing the concept of equivalent radius, the approximate method for narrow strips is evaluated numerically against results for thin circular wires. It is concluded that the approximate method is suitable for handling multiple wires in layered structures, wherefore the method has potential usefulness for estimating long range propagation of high frequency waves in wire structures like power lines and railway feeding systems, containing over-head wires and wires submerged into g...

Norgren, Martin

2012-01-01

273

Optical constants determination of samarium, holmium, and erbium in the 1.5-850 eV spectral range using a transmittance method  

International Nuclear Information System (INIS)

The optical constants ? and ? of the complex refractive index n?=1-?+i? of Sm, Ho, and Er were obtained in the 1.5-850eV energy range using a transmittance method. Thin films of Sm, Ho, and Er were deposited by magnetron sputtering, and transmittance was measured using synchrotron radiation under a high vacuum condition. All films were directly coated on Si photodiodes, which were used as coating substrates, as well as photon detectors. Si was used as capping layer while a thin W layer was used as barrier against interface diffusion between Si and the highly reactive rare earth elements. The constants ? were extracted from transmittance results, and the constants ? were calculated based on measured ? values using the Kramers-Kronig formalism. Small deficiencies determined from the present data using the partial sum rules were partly attributed to the sputtered film densities that could be slightly lower than the bulk values.

2010-11-01

274

No Visible Scar Colectomy  

Medline Plus

Full Text Available ... this an exciting and educational program, highlighting the evolution to the no visible scar colectomy, and we’ ... was the process of what you call the evolution? Really, the evolution has taken place over the ...

275

No Visible Scar Colectomy  

Medline Plus

Full Text Available ... visible scar colectomy and really how did we get here? What was the process of what you ... quadrant nature of the operation, and trying to get to two- or even three-quadrants through a ...

276

No Visible Scar Colectomy  

Medline Plus

Full Text Available ... those questions throughout the program. Well, why don’t we begin now. Talking about the no visible ... go outside the umbilical ring and actually don’t look s o great. And finally we have a ...

277

No Visible Scar Colectomy  

Medline Plus

Full Text Available ... presented by Ethicon Endo-Surgery. Welcome to this OR-Live webcast presentation featuring a no visible scar ... a lot about NOTES, single port trans -oral or trans-visceral surgery. How are NOTES and single ...

278

No Visible Scar Colectomy  

Medline Plus

Full Text Available ... Visible Scar Colectomy Ethicon Endo-Surgery Orange County, California January 28, 2010 This program is presented by ... re coming to you live from Orange County, California. My name is James Fleshman, and I am ...

279

HIGH VISIBILITY PROTECTIVE FABRIC  

UK PubMed Central (United Kingdom)

A fabric which meets the high visibility standards of ANSI/ISEA 107 2004 or CSA Z- 96 is disclosed. Yarn used in the fabric includes Aramid-based fibers and fibers that are capable of being dyed to meet the high visibility standards. The fibers may be selected and/or positioned so that the standards of ASTM D4108-87 and/or ASTM F 1506 are met. The fabric may be used for safety garments.

MIKHAIL RAOUF; LANGBURT HARRY; LANGBURT ZEEV

280

Spectral-domain spectrally-encoded endoscopy  

Science.gov (United States)

Spectrally-encoded miniature endoscopy uses a single optical fiber and wavelength division multiplexing to obtain macroscopic images through miniature, flexible probes. In turn, it has the potential to enable two- and three-dimensional imaging within the body at locations that are currently difficult to access with conventional endoscopes. Here we present a novel detection scheme for spectrally-encoded endoscopy using spectral-domain interferometry. Compared to previous time-domain configurations, this new detection method results in greater than 1000-fold increase in sensitivity (77 dB), a 6-fold increase in imaging speed (30 volumes per second), and a 2-fold increase in depth range (2.8 mm). We demonstrate spectrally-encoded, spectral-domain detection by conducting video-rate, three-dimensional imaging in a variety of specimens, including the paws of a mouse embryo and excised human ear bones. Our results show that this new technology enables video rate spectrally-encoded endoscopy and will therefore be useful for a variety of minimally invasive medical applications.

Yelin, Dvir; White, W. M.; Motz, Jason T.; Yun, Seok H.; Bouma, Brett E.; Tearney, Guillermo J.

2007-03-01

 
 
 
 
281

Miniaturized spectral imager for Aalto-1 nanosatellite  

Science.gov (United States)

The Aalto-1 is a 3U-cubesat project coordinated by Aalto University. The satellite, Aalto-1, will be mainly built by students as project assignments and thesis works. VTT Technical Research Centre of Finland will develop the main Earth observation payload, a miniaturized spectral imager, for the satellite. It is a novel highly miniaturized tunable filter type spectral imager. Mass of the spectral imager will be less than 400 grams, and dimensions will be approximately 80 mm x 80 mm x 45 mm. The spectral imager is based on a tunable Fabry-Pérot interferometer (FPI) accompanied by an RGB CMOS image sensor. The FPI consists of two highly reflective surfaces separated by a tunable air gap and it is based either on a microelectromechanical (MEMS) or piezo-actuated structure. The MEMS FPI is a monolithic device, i.e. it is made entirely on one substrate in a batch process, without assembling separate pieces together. The gap is adjusted by moving the upper mirror with electrostatic force. Benefits of the MEMS FPI are low mass and small size. However, large aperture (2-10 mm) MEMS FPIs are currently under development, thus it is not yet known if their performance is adequate. The piezo-actuated FPI uses three piezo-actuators and is controlled in a closed capacitive feedback loop. The drawback of the piezo-actuated FPI is its higher mass. However, it has a large aperture which enables a shorter exposure times. Selection of the FPI type will be done after thorough evaluation. Depending on the selected FPI type, the spectral resolution of the imager will be 5 - 10 nm at full width at half maximum and it will operate in the visible and/or near infrared range.

Mannila, Rami; Näsilä, Antti; Praks, Jaan; Saari, Heikki; Antila, Jarkko

2011-10-01

282

Observation of carbon-containing nanostructured mixed titania phases for visible-light photocatalysts  

International Nuclear Information System (INIS)

This research analyzed a visible-light-responsive carbon-containing titania photocatalysts prepared by sol-gel method using confocal Raman spectral mapping, transmission electron microscopy, and UV/visible spectroscopy. The incorporation of carbons in the initial titania powder of anatase and amorphous phases was found to facilitate the formation of rutile or brookite phases from the amorphous phase in the 150-250 deg. C temperature range, resulting in nanostructured mixed titania phases which create interface states and effectively shift the band gap to ?2.7 eV. The further shift in the absorption tails up to 800 nm was attributed to carbon species-covered and/or defected titania powders.

2006-09-25

283

Visible-blind photodetector based on p-i-n junction GaN nanowire ensembles  

International Nuclear Information System (INIS)

We report the synthesis, fabrication and extensive characterization of a visible-blind photodetector based on p-i-n junction GaN nanowire ensembles. The nanowires were grown by plasma-assisted molecular beam epitaxy on an n-doped Si(111) substrate, encapsulated into a spin-on-glass and processed using dry etching and metallization techniques. The detector presents a high peak responsivity of 0.47 A W-1 at - 1 V. The spectral response of the detector is restricted to the UV range with a UV-to-visible rejection ratio of 2 x 102. The dependence on the incident power and the operation speed of the photodetector are discussed.

2010-08-06

284

Effects of visible light on the skin.  

UK PubMed Central (United Kingdom)

Electromagnetic radiation has vast and diverse effects on human skin. Although photobiologic studies of sunlight date back to Sir Isaac Newton in 1671, most available studies focus on the UV radiation part of the spectrum. The effects of visible light and infrared radiation have not been, until recently, clearly elucidated. The goal of this review is to highlight the effects of visible light on the skin. As a result of advances in the understanding of skin optics, and comprehensive studies regarding the absorption spectrum of endogenous and exogenous skin chromophores, various biologic effects have been shown to be exerted by visible light radiation including erythema, pigmentation, thermal damage and free radical production. It has also been shown that visible light can induce indirect DNA damage through the generation of reactive oxygen species. Furthermore, a number of photodermatoses have an action spectrum in the visible light range, even though most of the currently available sunscreens offer, if any, weak protection against visible light. Conversely, because of its cutaneous biologic effects, visible light is used for the treatment of a variety of skin diseases and esthetic conditions in the form of lasers, intense pulsed light and photodynamic therapy.

Mahmoud BH; Hexsel CL; Hamzavi IH; Lim HW

2008-03-01

285

Incremental terrain visibility analysis  

Science.gov (United States)

Visibility analysis is an important aspect in terrain analysis. Terrain visibility calculation is a time-consuming process, and visibility algorithms are dedicated to reduce the algorithm complexity to enhance calculation speed. We use digital elevation model to represent terrain. This equal-distance discrete data structure can be processed by geometric algorithm. The paper judges line of sight (LOS) visibility through geometric vector cross product, then delivers an incremental method to calculate terrain visibility with comparison of elevation difference using increments base on grid size. We analyze the algorithm performance in two aspects: horizontal and vertical comparisons. Through vertical analysis, the run-time of the algorithms has been measured for different terrain configurations and different heights of the viewpoint in terrain region. The method is more simple, lower complexity and easier to realize. We give out many computational results of viewshed with different location, and analyze the their distribution characteristics. We conclude that this method have high efficiency in undulant terrain with long line of sight or deep valleys. Also we compare this method with ARCGIS viewshed function horizontally through many tests and find that incremental method is faster and finer than ARCGIS model.

Ying, Shen; Li, Lin; Mei, Yang; Peng, Xiaoyan

2006-10-01

286

Peripheral absolute threshold spectral sensitivity in retinitis pigmentosa.  

UK PubMed Central (United Kingdom)

Dark-adapted spectral sensitivities were measured in the peripheral retinas of 38 patients diagnosed as having typical retinitis pigmentosa (RP) and in 3 normal volunteers. The patients included those having autosomal dominant and autosomal recessive inheritance patterns. Results were analysed by comparisons with the CIE standard scotopic spectral visibility function and with Judd's modification of the photopic spectral visibility function, with consideration of contributions from changes in spectral transmission of preretinal media. The data show 3 general patterns. One group of patients had absolute threshold spectral sensitivities that were fit by Judd's photopic visibility curve. Absolute threshold spectral sensitivities for a second group of patients were fit by a normal scotopic spectral visibility curve. The third group of patients had absolute threshold spectral sensitivities that were fit by a combination of scotopic and photopic spectral visibility curves. The autosomal dominant and autosomal recessive modes of inheritance were represented in each group of patients. These data indicate that RP patients have normal rod and/or cone spectral sensitivities, and support the subclassification of patients described previously by Massof and Finkelstein.

Massof RW; Johnson MA; Finkelstein D

1981-02-01

287

Measuring and predicting eyelid spectral transmittance.  

UK PubMed Central (United Kingdom)

The purpose of the present study was to objectively quantify the spectral transmittance of the eyelid. Reported here are data acquired using a technique that was developed to provide practical and accurate measurements of eyelid transmittance across the visible portion of the electromagnetic spectrum. The empirical data were analyzed in terms of the absorption and scattering characteristics of the constituents of skin to develop a method for predicting eyelid transmission. Results showed that the eyelid has a much higher optical density at short wavelengths than previously published. The mean ± standard deviation (s.d.) optical density of the eyelid from 450 to 650 nm was 2.1 ± 0.3 with an optical density range among subjects of approximately 1.0. The study results indicate that skin pigmentation is poorly correlated with eyelid transmission; eyelid transmission is most affected by wavelength-independent macromolecules in the eyelid as well as its overall thickness.

Bierman A; Figueiro MG; Rea MS

2011-06-01

288

Visibility of plasmonic particles embedded in transparent materials  

Science.gov (United States)

Recently, several experiments have shown that it is possible to visualize the optical near-field generated around individual plasmonic particles through the photo-induced structuration of polymer films. In this communication, we show that the particle visibility can be controlled at will down to the quasi-invisibility by tuning the incident wavelength around the plasmon frequency. This phenomenon occurs when the real part of the particle polarizability displays a sign change. This simple spectrally controlled visibility is an alternative to the more classical spatially controlled visibility approach.

Teulle, A.; Marty, R.; Girard, C.; Arbouet, A.; Dujardin, E.

2013-03-01

289

Role of enhanced visibility in evaluating polyposis syndromes using a newly developed contrast image capsule endoscope.  

UK PubMed Central (United Kingdom)

BACKGROUND/AIMS: A flexible spectral imaging color enhancement system was installed in new capsule software for video capsule endoscopy. Contrast image capsule endoscopy (CICE) is a novel technology using light-emitting diodes selected for the main absorption range of hemoglobin. We assessed the feasibility and diagnostic effi cacy for small bowel surveillance in patients with polyposis syndromes. METHODS: Six patients with polyposis syndromes, four with familial adenomatous polyposis and one each with Cowden syndrome (CS) and Cronkhite-Canada syndrome (CCS) were examined using CICE. We conducted three evaluations to assess the effect on the numbers of the detected polyps; compare polyp diagnostic rates between adenoma and hamartoma; and assess polyp visibility. RESULTS: The numbers of detected polyps and diagnostic accuracy did not differ signifi cantly between pre-contrast and contrast images. However, 50% of the adenomatous polyps displayed enhanced visibility on contrast images. CICE contrast images exhibited clearly demarcated lesions and improved the visibility of minute structures of adenomatous polyps. Hamartomatous polyp micro-structures in patients with CS and CCS were more clearly visualized on contrast than pre-contrast images. CONCLUSIONS: CICE is an effective tool for enhancing the visibility of polyps in patients with polyposis syndrome.

Hatogai K; Hosoe N; Imaeda H; Rey JF; Okada S; Ishibashi Y; Kimura K; Yoneno K; Usui S; Ida Y; Tsukada N; Kanai T; Hibi T; Ogata H

2012-04-01

290

Assessment and mapping of soil nitrogen using Visible-Near-Infrared (Vis-NIR) spectra  

Science.gov (United States)

Visible and near infrared (Vis-NIR) reflectance spectroscopy technology, which is rapid, cost-effective, in-situ and non-destructive, is getting more and more widely used in improving the prediction and digital mapping for soil properties. Soil available nitrogen (AN) is closely related to soil fertility and quality, assessing its content and mapping the spatial variability greatly satisfies precision agriculture. In this study, the Vis-NIR diffuse reflectance spectra collected by ASD FieldSpec Pro FR spectrometer with a performance of spectral range from 350 nm to 2500 nm, 1 nm resampling intervals, was used to model and characterize the spatial variability of available nitrogen. Firstly, the raw soil spectra was pre-processing by reducing to 400 nm - 2450 nm with transformation into apparent absorbance spectral using Log(1/R) and Savitzky-Golay smoothing. Secondly, spectral indices (normalized spectral index-NDI; difference index-DI; ratio index-RI) were convinced for seeking further relationship between AN. Afterwards, Partial Least Squares Regression (PLSR) method was employed to predict AN. The results indicated good predictions with RPD more than 1.4. Finally, the spatial variability of AN was mapped by (co)kriging method, digital mapping of the measured and predicted AN showed similar patterns and value ranges, though there are some minor differences. The resultant prediction and mapping demonstrated a promotion of assessing and mapping of soil properties by a rapid and reliable approach from lab to field in-situ.

Liu, Xiang; Guo, Yan; Wang, Qian-long; Zhang, Jian; Shi, Zhou

2013-08-01

291

NASA Visible Earth: Runoff  

Science.gov (United States)

The NASA Visible Earth site is a searchable collection of images of the Earth taken by orbiting satellites. This section features a variety of images specifically illustrating effects of runoff. Each image is available in one or more graphic formats and sizes, and is accompanied by a description, as well as detailed metadata about how the image was obtained.

292

No Visible Scar Colectomy  

Medline Plus

Full Text Available ... we’ve tried to make it a very standard approach, very similar to our standard laparoscopic colectomy. It’s app licable to right and left sigmoid colons. The only difference between standard laparoscopic colectomy and LESS colectomy or No Visible ...

293

No Visible Scar Colectomy  

Medline Plus

Full Text Available ... couple of things. We will look at the CT scan and see if the tumor is visible on a CT scan, which it often is. Even if the ... if at all possible. So you do a CT scan pre-op. Do you do ultrasound intra- ...

294

Spectral discomfort glare sensitivity investigations.  

UK PubMed Central (United Kingdom)

The main concern of car headlamp manufacturers is to provide better visibility. Unfortunately, by increasing the luminous intensity of the headlamp, the risk of increasing discomfort glare for the other road users increases. One possibility to increase visibility and decrease glare could be the selection of a spectral power distribution for the headlamp such that it emits in wavelength regions (if such wavelengths exist) where luminous sensitivity is high, and glare sensitivity is low. For this the spectral discomfort glare sensitivity of humans under low photopic conditions has to be determined. Spectral discomfort glare sensitivity was determined using ten young observers, requesting the observers to select medium glare settings of monochromatic radiations based on the de Boer glare rating scale, both at near-foveal and 10 degrees extra-foveal directions of the 2 degrees diameter glare source. It was found that the spectral discomfort glare sensitivity function could not be described by a simple addition of the photopic spectral luminous efficiency function and the short wavelength cone fundamental, but that the contribution of the chromatic channels of human vision may also have to be considered.

Fekete J; Sik-Lányi C; Schanda J

2010-03-01

295

Spectral discomfort glare sensitivity investigations.  

Science.gov (United States)

The main concern of car headlamp manufacturers is to provide better visibility. Unfortunately, by increasing the luminous intensity of the headlamp, the risk of increasing discomfort glare for the other road users increases. One possibility to increase visibility and decrease glare could be the selection of a spectral power distribution for the headlamp such that it emits in wavelength regions (if such wavelengths exist) where luminous sensitivity is high, and glare sensitivity is low. For this the spectral discomfort glare sensitivity of humans under low photopic conditions has to be determined. Spectral discomfort glare sensitivity was determined using ten young observers, requesting the observers to select medium glare settings of monochromatic radiations based on the de Boer glare rating scale, both at near-foveal and 10 degrees extra-foveal directions of the 2 degrees diameter glare source. It was found that the spectral discomfort glare sensitivity function could not be described by a simple addition of the photopic spectral luminous efficiency function and the short wavelength cone fundamental, but that the contribution of the chromatic channels of human vision may also have to be considered. PMID:20444123

Fekete, Judit; Sik-Lányi, Cecilia; Schanda, János

2009-12-09

296

Data on total and spectral solar irradiance  

Energy Technology Data Exchange (ETDEWEB)

This paper presents a brief survey of the data available on solar constant and extraterrestrial solar spectral irradiance. The spectral distribution of solar radiation at ground surface, computed from extraterrestrial solar spectral irradiance for several air mass values and for four levels of atmospheric pollution, is also presented. The total irradiance at ground level is obtained by integration of the area under the spectral irradiance curves. It is significant that, as air mass increases or as turbidity increases, the amount of energy in the infrared relative to the total increases and that the energy in the UV and visible decreases.

Mecherikunnel, A.T.; Gatlin, J.A.; Richmond, J.C.

1983-05-01

297

Spectral CT of carotid atherosclerotic plaque: comparison with histology.  

UK PubMed Central (United Kingdom)

OBJECTIVE: To distinguish components of vulnerable atherosclerotic plaque by imaging their energy response using spectral CT and comparing images with histology. METHODS: After spectroscopic calibration using phantoms of plaque surrogates, excised human carotid atherosclerotic plaques were imaged using MARS CT using a photon-processing detector with a silicon sensor layer and microfocus X-ray tube (50 kVp, 0.5 mA) at 38-?m voxel size. The plaques were imaged, sectioned and re-imaged using four threshold energies: 10, 16, 22 and 28 keV; then sequentially stained with modified Von Kossa, Perl's Prussian blue and Oil-Red O, and photographed. Relative Hounsfield units across the energies were entered into a linear algebraic material decomposition model to identify the unknown plaque components. RESULTS: Lipid, calcium, iron and water-like components of plaque have distinguishable energy responses to X-ray, visible on spectral CT images. CT images of the plaque surface correlated very well with histological photographs. Calcium deposits (>1,000 ?m) in plaque are larger than iron deposits (<100 ?m), but could not be distinguished from each other within the same voxel using the energy range available. CONCLUSIONS: Spectral CT displays energy information in image form at high spatial resolution, enhancing the intrinsic contrast of lipid, calcium and iron within atheroma. KEY POINTS: Spectral computed tomography offers new insights into tissue characterisation. Components of vulnerable atherosclerotic plaque are spectrally distinct with intrinsic contrast. Spectral CT of excised atherosclerotic plaques can display iron, calcium and lipid. Calcium deposits are larger than iron deposits in atheroma. Spectral CT may help in the non-invasive detection of vulnerable plaques.

Zainon R; Ronaldson JP; Janmale T; Scott NJ; Buckenham TM; Butler AP; Butler PH; Doesburg RM; Gieseg SP; Roake JA; Anderson NG

2012-12-01

298

Quantitative analysis and classification of tongue inspection based on the visible reflection spectrum  

Directory of Open Access Journals (Sweden)

Full Text Available Objective: In this study, optical data on color of tongue tips were collected by using a visible reflection spectrum system. Quantitative method of tongue inspection and classification of tongue states including pale, pale red, red and crimson manifestations were investigated. Methods: Chromaticity coordinates of the tongue tips from 98 subjects were calculated on the basis of the visible reflection spectrum. The tongue color was quantified and classified by the visible reflection spectrum in the range from 590 nm to 780 nm, based on the higher red-band energy distribution on the tongue tip color. Results: It was found that comparison and analysis of tongue tip color from different samples would be well-suited after spectrum vector normalization, and the difference of tongue tip color between different samples could be observed easily when the tongue tip optical data were sited in CIE 1931 chromaticity diagram. The tongue tip colors were analyzed quantitatively and classified by the spectral energy intensity at the wavelength of 670 nm and (or) spectral energy ratio of red bank from 590 nm to 780 nm. The results of classification showed that there was sound corresponding accuracy with the clinical diagnosis of pale tongue, pale red tongue, red tongue and crimson tongue.Conclusion: In this study, based on the collection of the information data on tongue tip characteristics with the visible spectrum from 380 nm to 780 nm, the quantitative analysis of tongue inspection for pale tongue, pale red tongue, red tongue and crimson tongue was established. The quantitative value for tongue tip color is an effective method for classification of the condition of the tongue tip, which provides a useful tool for the modernization of tongue inspection in traditional Chinese medicine.

Meng Kong; Chang-chun Zeng

2011-01-01

299

Visible Hyperspectral Imaging for Standoff Detection of Explosives on Surfaces  

Energy Technology Data Exchange (ETDEWEB)

There is an ever-increasing need to be able to detect the presence of explosives, preferably from standoff distances. This paper presents an application of visible hyperspectral imaging using anomaly, polarization and spectral identification approaches for the standoff detection (13 meters) of nitroaromatic explosives on realistic painted surfaces based upon the colorimetric differences between tetryl and TNT which are enhanced by solar irradiation.

Bernacki, Bruce E.; Blake, Thomas A.; Mendoza, Albert; Johnson, Timothy J.

2010-11-01

300

Dynamic range compression and contrast enhancement in IR imaging systems  

Science.gov (United States)

The visualization of IR images on traditional display devices is often complicated by their high dynamic range. Classical dynamic range compression techniques based on simple linear mapping, reduce the perceptibility of small objects and often prevent the human observer from understanding some of the important details. Thus, more sophisticated techniques are required to adapt the recorded signal to the monitor maintaining, and possibly improving, object visibility and image contrast. The problem has already been studied with regard to images acquired in the visible spectral domain, but it has been scarcely investigated in the IR domain. In this work, we address this latter subject and propose a new method for IR dynamic range compression which stems from the lesson learnt from existing techniques. First, we review the techniques proposed in the literature for contrast enhancement and dynamic range compression of images acquired in the visible domain. Then, we present the new algorithm which accounts for the specific characteristics of IR images. The performance of the proposed method are studied on experimental IR data and compared with those yielded by two well established algorithms.

Branchitta, Francesco; Diani, Marco; Corsini, Giovanni; Porta, Antonio; Romagnoli, Marco

2007-11-01

 
 
 
 
301

Visible Spectrum Incandescent Selective Emitter  

Energy Technology Data Exchange (ETDEWEB)

The purpose of the work performed was to demonstrate the feasibility of a novel bi-layer selective emitter. Selective emitters are incandescent radiant bodies with emissivities that are substantially larger in a selected part of the radiation spectrum, thereby significantly shifting their radiated spectral distribution from that of a blackbody radiating at the same temperature. The major research objectives involved answering the following questions: (1) What maximum VIS/NIR radiant power and emissivity ratios can be attained at 2650 K? (2) What is the observed emitter body life and how does its performance vary with time? (3) What are the design tradeoffs for a dual heating approach in which both an internally mounted heating coil and electrical resistance self-heating are used? (4) What are the quantitative improvements to be had from utilizing a bi-layer emitter body with a low emissivity inner layer and a partially transmissive outer layer? Two approaches to obtaining selective emissivity were investigated. The first was to utilize large optical scattering within an emitter material with a spectral optical absorption that is much greater within the visible spectrum than that within the NIR. With this approach, an optically thick emitter can radiate almost as if optically thin because essentially, scattering limits the distance below the surface from which significant amounts of internally generated radiation can emerge. The performance of thin emitters was also investigated (for optically thin emitters, spectral emissivity is proportional to spectral absorptivity). These emitters were fabricated from thin mono-layer emitter rods as well as from bi-layer rods with a thin emitter layer mounted on a substrate core. With an initially estimated energy efficiency of almost three times that of standard incandescent bulbs, a number of energy, economic and environmental benefits such as less energy use and cost, reduced CO{sub 2} emissions, and no mercury contamination was initially projected. The work performed provided answers to a number of important questions. The first is that, with the investigated approaches, the maximum sustained emitter efficiencies are about 1.5 times that of a standard incandescent bulb. This was seen to be the case for both thick and thin emitters, and for both mono-layer and bi-layer designs. While observed VIS/NIR ratios represent improvements over standard incandescent bulbs, it does not appear sufficient to overcome higher cost (i.e. up to five times that of the standard bulb) and ensure commercial success. Another result is that high temperatures (i.e. 2650 K) are routinely attainable without platinum electrodes. This is significant for reducing material costs. A novel dual heating arrangement and insulated electrodes were used to attain these temperatures. Another observed characteristic of the emitter was significant grain growth soon after attaining operating temperatures. This is an undesirable characteristic that results in substantially less optical scattering and spectral selectivity, and which significantly limits emitter efficiencies to the values reported. Further work is required to address this problem.

Sonsight Inc.

2004-04-30

302

Visible Genotype Sensor Array  

Directory of Open Access Journals (Sweden)

Full Text Available A visible sensor array system for simultaneous multiple SNP genotyping has been developed using a new plastic base with specific surface chemistry. Discrimination of SNP alleles is carried out by an allele-specific extension reaction using immobilized oligonucleotide primers. The 3’-ends of oligonucleotide primers are modified with a locked nucleic acid to enhance their efficiency in allelic discrimination. Biotin-dUTPs included in the reaction mixture are selectively incorporated into extending primer sequences and are utilized as tags for alkaline phosphatase-mediated precipitation of colored chemical substrates onto the surface of the plastic base. The visible precipitates allow immediate inspection of typing results by the naked eye and easy recording by a digital camera equipped on a commercial mobile phone. Up to four individuals can be analyzed on a single sensor array and multiple sensor arrays can be handled in a single operation. All of the reactions can be performed within one hour using conventional laboratory instruments. This visible genotype sensor array is suitable for “focused genomics” that follows “comprehensive genomics”.

Yuichi Michikawa; Tomo Suga; Yoshimi Ohtsuka; Izumi Matsumoto; Atsuko Ishikawa; Kenichi Ishikawa; Mayumi Iwakawa; Takashi Imai

2008-01-01

303

Linear optical properties of (Cu2O)x (Al2O3)0.05-x (B2O3)0.20 (PbO)0.75 glasses in the spectral range 200-3300 nm  

Science.gov (United States)

Glasses of composition (Cu2O)x (Al2O3)0.05-x (B2O3)0.20 (PbO)0.75, where x = 0.0, 0.005, 0.0075, 0.01, 0.02, 0.035, and 0.05, are prepared using the normal melt quench technique. Reflectance and transmittance at normal incidence are measured by a spectrophotometer in the spectral range of 200-3300 nm. Analytical relations are used to deduce the real and imaginary refractive indices, at each scanned wavelength, from the measured reflectance and transmittance. Dispersive parameters of Wemple-DiDomenico dispersion's relation, molar refraction and molar polarizability are deduced. Direct and indirect allowed transitions optical energy gaps are calculated from the absorption coefficients. Effects of substituting Al2O3 by Cu2O, on these linear optical properties of the prepared glasses are studied. The prepared glasses can be used as near IR filters with 70% transmittance.

El-Naggar, A. M.; El-Zaiat, S. Y.; Youssif, M. I.; Alsaud, F. A.

2013-10-01

304

Efficient generation of 3.9 W of diffraction-limited green light with spectrally combined tapered diode lasers  

DEFF Research Database (Denmark)

We propose an efficient concept increasing the power of diode laser systems in the visible spectral range. In comparison with second harmonic generation of single emitters, spectral beam combining with subsequent sum-frequency generation enhances the available power significantly. Combining two 1060 nm tapered diode lasers, we achieve a 2.5-3.2 fold increase of green light with a maximum power of 3.9 Watts in a diffraction-limited beam. At this level, diode lasers have a high application potential, for example, within the biomedical field. In order to enhance the power even further, our concept can be expanded combining multiple diode lasers.

Müller, André; Jensen, Ole Bjarlin

305

MSI: a visible multispectral imager for 1.6-m telescope of Hokkaido University  

Science.gov (United States)

We have built a visible multi-spectral imager (MSI) for the 1.6-m Pirka telescope of the Hokkaido University in Hokkaido, Japan. The instrument is equipped with two liquid crystal tunable filters and a 512 × 512 pixel EMCCD camera. One of the major purposes of this instrument is to obtain multi-spectral images (series of narrow-band images at many different wavelengths) of the solar planets rapidly. These tunable filters are a Lyot filter with liquid crystal variable retarders and thus can tune the transmitting wavelength rapidly without moving parts. Their spectral ranges are 400-720 nm and 650-1100 nm and the bandwidth is typically 10 nm on both filters. The EMCCD camera can obtain images at a frame rate of about 32 Hz, which also enables us to improve the spatial resolution with the shift-and-add or the Lucky imaging techniques. The field of view is 3.3 × 3.3 arcmin with a pixel scale of 0.39 arcsec pixel-1. The instrument also has UBV RI-band broad-band filters and several narrow-band filters. MSI is mounted at the f/12 Cassegrain focus of the telescope. It had the first light on February 2011, and then have been used for several astronomical and planetary science programs as a major facility instrument at this telescope. We describe the design, construction, integration, and performance of this multi-spectral imager.

Watanabe, Makoto; Takahashi, Yukihiro; Sato, Mitsuteru; Watanabe, Shigeto; Fukuhara, Tetsuya; Hamamoto, Ko; Ozaki, Akihito

2012-09-01

306

Spectral Ranking  

CERN Multimedia

This note tries to attempt a sketch of the history of spectral ranking, a general umbrella name for techniques that apply the theory of linear maps (in particular, eigenvalues and eigenvectors) to matrices that do not represent geometric transformations, but rather some kind of relationship between entities. Albeit recently made famous by the ample press coverage of Google's PageRank algorithm, spectral ranking was devised more than fifty years ago, almost exactly in the same terms, and has been studied in psychology and social sciences. I will try to describe it in precise and modern mathematical terms, highlighting along the way the contributions given by previous scholars.

Vigna, Sebastiano

2009-01-01

307

Solar irradiance forecasts for energy applications. The influence of aerosols on the visible range; Solare Strahlungsvorhersagen fuer energiewirtschaftliche Anwendungen. Der Einfluss von Aerosolen auf das solare Strahlungsangebot in Europa  

Energy Technology Data Exchange (ETDEWEB)

Due to the limitation of fossil fuel resources and their impact on climate change, the future energy system will increasingly depend on growing shares of renewable energy sources. This study deals with solar irradiance forecasts of the next few days and hours with respect to their application in solar energy industries. The main atmospheric parameter responsible for the extinction of solar irradiance is clouds. However, a main focus and economic potential of the solar energy industry is situated in regions arid time periods with minimal cloud cover. During these 'clear sky cases' it is mainly aerosols, solid and liquid particles in the atmosphere, that influence the direct and diffuse irradiance at ground level. Aerosols are highly variable in space and time, which leads to difficulties in calculating and forecasting their spatio-temporal patterns and thus their influence on irradiance. Using these aerosol forecasts and other remote sensing data (ground albedo, ozone) as well as numerical weather prediction parameters (water vapor, clouds), a prototype for an irradiance forecasting system is set up: the AFSOL system (Aerosol-based Forecasts of Solar Irradiance for Energy Applications). Based on the five month dataset its results are compared to forecasts of the European Centre for Medium-Range Weather Forecasts (ECMWF), satellite based irradiance data from Meteosat-7 and ground measurements. It is demonstrated that for clear sky situations the AFSOL system significantly improves direct irradiance forecasts compared to ECMWF forecasts, with a reduction of relative bias from -26% to +11% and a reduction of relative RMSE from 31% to 19%. This can be attributed to the increased accuracy of atmospheric aerosol description compared to the climatological values used by the ECMWF, regardless if there are still deficiencies especially for desert dust situations. Finally, a case study on the use of the AFSOL irradiance forecasts for optimizing operation strategies of a solar thermal power plant in Spain is presented.

Breitkreuz, Hanne

2008-05-15

308

Non-Euclidean visibility problems  

CERN Document Server

We consider the analog of visibility problems in hyperbolic plane (represented by Poincar\\'{e} half-plane model H), replacing the standard lattice $Z\\times Z$ by the orbit $z=i$ under the full modular group $z$. We prove a visibility criterion and study orchard problem and the cardinality of visible points in large circles

Chamizo, F

2006-01-01

309

A novel automated object identification approach using key spectral components  

Science.gov (United States)

Spectral remote sensing provides solutions to a wide range of commercial, civil, agricultural, atmospheric, security, and defense problems. Technological advances have expanded multispectral (MSI) and hyperspectral (HSI) sensing capabilities from air and space borne sensors. The greater spectral and spatial sensitivity have vastly increased the available content for analysis. The amount of information in the data cubes obtained from today's sensors enable material identification via complex processing techniques. With sufficient sensor resolution, multiple pixels on target are obtained and by exploiting the key spectral features of a material signature among a group of target pixels and associating the features with neighboring pixels, object identification is possible. The authors propose a novel automated approach to object classification with HSI data by focusing on the key components of an HSI signature and the relevant areas of the spectrum (bands) of surrounding pixels to identify an object. The proposed technique may be applied to spectral data from any region of the spectrum to provide object identification. The effort will focus on HSI data from the visible, near-infrared and short-wave infrared to prove the algorithm concept.

Kahler, Bart; Noble, Todd

2013-06-01

310

Huanglongbing (Citrus Greening) Detection Using Visible, Near Infrared and Thermal Imaging Techniques  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This study demonstrates the applicability of visible-near infrared and thermal imaging for detection of Huanglongbing (HLB) disease in citrus trees. Visible-near infrared (440–900 nm) and thermal infrared spectral reflectance data were collected from individual healthy and HLB-infected trees. Data a...

Sindhuja Sankaran; Joe Mari Maja; Sherrie Buchanon; Reza Ehsani

311

LEAD INSERTION VISIBILITY  

UK PubMed Central (United Kingdom)

An implantable medical device system that includes a housing containing an electrical circuit and a connector header mounted on the housing. A first inner surface of the connector header forms a connector bore adapted for receiving a lead connector assembly for electrically coupling a medical lead to the circuitry contained in the housing, and one of the connector header and the lead connector includes a visibly modified surface for facilitating visual verification of full insertion of the medical lead connector assembly in the connector bore.

MAJEWSKI THOMAS; SCOTT DAVID W; KLARDIE MIKE R; KESSLER AMY K; HECTOR WAYNE M; SCHAENZER DAVID G

312

High performance broadband absorber in the visible band by engineered dispersion and geometry of a metal-dielectric-metal stack  

Science.gov (United States)

We propose a nanostructured broadband absorber in the visible regime through designing the dispersion and geometry of a Cu/Si3N4/Cu stack. Two examples with nearly perfect absorption at different spectral ranges are designed based on the special dispersion relationship and fabricated using nanoimprint lithography. Experiments confirm an ultra flat average absorption greater than 80% from 400 nm to 700 nm. The robustness of the design with angle insensitive absorption characteristic is desirable for the applications in thin-film thermal emitters and photovoltaic cells.

Zhu, Peng; Jay Guo, L.

2012-12-01

313

On spectropolarimetric measurements with visible lines  

CERN Document Server

The ability of new instruments for providing accurate inferences of vector magnetic fields and line-of-sight velocities of the solar plasma depends a great deal on the sensitivity to these physical quantities of the spectral lines chosen to be measured. Recently, doubts have been raised about visible Stokes profiles to provide a clear distinction between weak fields and strong ones filling a small fraction of the observed area. The goal of this paper is to give qualitative and quantitative arguments that help in settling the debate since several instruments that employ visible lines are either operating or planned for the near future. The sensitivity of the Stokes profiles is calculated through the response functions (e.g. Ruiz Cobo & Del Toro Iniesta, 1994). Both theoretical and empirical evidences are gathered in favor of the reliability of visible Stokes profiles. The response functions are used as well for estimating the uncertainties in the physical quantities due to noise in the observations. A usef...

Iniesta, J C del Toro; Rubio, L R Bellot

2010-01-01

314

Spectral Predictors  

Energy Technology Data Exchange (ETDEWEB)

Many scientific, imaging, and geospatial applications produce large high-precision scalar fields sampled on a regular grid. Lossless compression of such data is commonly done using predictive coding, in which weighted combinations of previously coded samples known to both encoder and decoder are used to predict subsequent nearby samples. In hierarchical, incremental, or selective transmission, the spatial pattern of the known neighbors is often irregular and varies from one sample to the next, which precludes prediction based on a single stencil and fixed set of weights. To handle such situations and make the best use of available neighboring samples, we propose a local spectral predictor that offers optimal prediction by tailoring the weights to each configuration of known nearby samples. These weights may be precomputed and stored in a small lookup table. We show that predictive coding using our spectral predictor improves compression for various sources of high-precision data.

Ibarria, L; Lindstrom, P; Rossignac, J

2006-11-17

315

Spectral branes  

International Nuclear Information System (INIS)

[en] We study the objects (called spectral branes or S-branes) which are obtained by imposing non-local spectral boundary conditions at the boundary of the world sheet of the bosonic string. They possess many nice properties which make them an ideal test ground for the string theory methods. Depending on a particular choice of the boundary operator S-branes may be commutative or non-commutative. We demonstrate that projection of the B-field on the brane directions (i.e. on the components which actually influence the boundary conditions) is done with the help of the chirality operator. We show that the T-duality transformation maps an S-brane to another S-brane. At the expense of introducing non-local interactions in the bulk we construct also a duality transformation between S-branes and D-branes or open strings. (author)

2001-01-01

316

Spectral Pollution  

CERN Multimedia

We discuss the problems arising when computing eigenvalues of self-adjoint operators which lie in a gap between two parts of the essential spectrum. Spectral pollution, i.e. the apparent existence of eigenvalues in numerical computations, when no such eigenvalues actually exist, is commonplace in problems arising in applied mathematics. We describe a geometrically inspired method which avoids this difficulty, and show that it yields the same results as an algorithm of Zimmermann and Mertins.

Davies, E B

2003-01-01

317

Inactivation of viruses by coherent excitations with a low power visible femtosecond laser  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Resonant microwave absorption has been proposed in the literature to excite the vibrational states of microorganisms in an attempt to destroy them. But it is extremely difficult to transfer microwave excitation energy to the vibrational energy of microorganisms due to severe absorption of water in this spectral range. We demonstrate for the first time that, by using a visible femtosecond laser, it is effective to inactivate viruses such as bacteriophage M13 through impulsive stimulated Raman scattering. Results and discussion By using a very low power (as low as 0.5 nj/pulse) visible femtosecond laser having a wavelength of 425 nm and a pulse width of 100 fs, we show that M13 phages were inactivated when the laser power density was greater than or equal to 50 MW/cm2. The inactivation of M13 phages was determined by plaque counts and had been found to depend on the pulse width as well as power density of the excitation laser. Conclusion Our experimental findings lay down the foundation for an innovative new strategy of using a very low power visible femtosecond laser to selectively inactivate viruses and other microorganisms while leaving sensitive materials unharmed by manipulating and controlling with the femtosecond laser system.

Tsen KT; Tsen Shaw-Wei D; Chang Chih-Long; Hung Chien-Fu; Wu T-C; Kiang Juliann G

2007-01-01

318

Effects of Dopant Concentrations on Thin Films with Coherent Formulation at Visible Wavelengths  

Directory of Open Access Journals (Sweden)

Full Text Available Semiconductor materials with coatings have a wide range of applications in MEMS and NEMS. This work uses transfer-matrix method for calculating the radiative properties. Dopped silicon is used and the coherent formulation is applied. The Drude model for the optical constants of doped silicon is employed. Results showed that for the visible wavelengths, more emittance occurs in high concentrations and the reflectance decreases as the concentration increases. In these wavelengths, transmittance is negligible. Donars and acceptors act similar in visible wavelengths. The effect of wave interference can be understood by plotting the spectral properties such as reflectance or transmittance of a thin dielectric film versus the film thickness and analyzing the oscillations of properties due to constructive and destructive interferences. But this effect has not been shown at visible wavelengths. At room temperature, the scattering process is dominated by lattice scattering for lightly doped silicon, and the impurity scattering becomes important for heavily doped silicon when the dopant concentration exceeds 1018cm-3.

M. Omidpanah; S.A.A. Oloomi

2012-01-01

319

Single nanowire photodetector array for spectral discrimination  

Science.gov (United States)

Recently, nanowire (NW) photodetectors with broad spectral response from ultraviolet (UV)-visible to near-infrared (NIR) have been suggested for many applications, such as communications and remote control. In this connection, the development of the NW photodetectors that enable to discriminate UV and Visible lights has been requested. In this study, we report on the fabrication of single NW photodetectors that are capable of discriminating UV and Visible lights. Specifically, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/ZnO nanoparticles hybrid NWs were directly grown on Au electrode by the meniscus-guided method. In fact, the single NW photodetector showed spectral discrimination behavior by a negative photocurrent under UV but by a positive under Visible light. The different photocurrent behaviors were attributed to charge transfer between PEDOT:PSS and ZnO nanoparticles. We also demonstrated single NW photodetector array with selectively positioned photodetectors on Au electrodes. Each single photodetector of the array showed its own spectral discrimination behavior. We believe that our NW photodetectors with the characteristics of spectral discrimination would contribute to advanced photosensing and remote control in nanophotonic devices.

Yoo, Jewon; Pyo, Jaeyeon; Je, Jung Ho

2013-03-01

320

ON SPECTROPOLARIMETRIC MEASUREMENTS WITH VISIBLE LINES  

International Nuclear Information System (INIS)

[en] The ability of new instruments for providing accurate inferences of vector magnetic fields and line-of-sight velocities of the solar plasma depends a great deal on the sensitivity to these physical quantities of the spectral lines chosen to be measured. Recently, doubts have been raised about visible Stokes profiles to provide a clear distinction between weak fields and strong ones filling a small fraction of the observed area. The goal of this paper is to give qualitative and quantitative arguments that help in settling the debate since several instruments that employ visible lines are either operating or planned for the near future. The sensitivity of the Stokes profiles is calculated through the response functions (RFs), for e.g., by Ruiz Cobo and Del Toro Iniesta. Both theoretical and empirical evidences are gathered in favor of the reliability of visible Stokes profiles. The RFs are also used for estimating the uncertainties in the physical quantities due to noise in observations. A useful formula has been derived that takes into account the measurement technique (number of polarization measurements, polarimetric efficiencies, and number of wavelength samples), the model assumptions (number of free parameters and the filling factor), and the radiative transfer (RFs). We conclude that a scenario with a weak magnetic field can reasonably be distinguished with visible lines from another with a strong field but a similar Stokes V amplitude, provided that the Milne-Eddington approximation is good enough to describe the solar atmosphere and the polarization signal is at least 3 or 4 times larger than the typical rms noise of 10-3 Ic reached in the observations.

2010-03-01

 
 
 
 
321

Cloud Computing Infusion for Generating ESDRs of Visible Spectra Radiances  

Science.gov (United States)

The AIRS and AVHRR instruments have been collecting radiances of the Earth in the visible spectrum for over 25 years. These measurements have been used to develop such useful products as NDVI, Snow cover and depth, Outgoing long wave radiation and other products. Yet, no long-term data record of the level 1b visible spectra is available in a grid form to researchers for various climate studies. We present here an Earth System Data Record observed in the visible spectrum as gridded radiance fields of 8kmx10km grid resolution for the six years in the case of AIRS and from 1981 to the present for AVHRR. The AIRS data has four visible channels from 0.41?m to 0.94?m with an IFOV of 1 km and AVHRR has two visible channels in the 0.58?m to 1.00?m range also at 1 km. In order to process such large amounts of data on demand, two components need to be implemented,(i) a processing system capable of gridding TBs of data in a reasonable amount of time and (ii) a download mechanism to access and deliver the data to the processing system. We implemented a cloud computing approach to be able to process such large amounts of data. We use Hadoop, a distributed computation system developed by the Apache Software Foundation. With Hadoop, we are able to store the data in a distributed fashion, taking advantage of Hadoop's distributed file system (dfs). We also take advantage of Hadoop's MapReduce functionality to perform as much computations as is possible on available nodes of the UMBC bluegrit Cell cluster system that contain the data. We make use of the SOAR system developed under the ACCESS program to acquire and process the AIRS and AVHRR observations. Comparisons of the AIRS data witth selected periods of MODIS visible spectral channels on the same sattelite indicate the two instruments have maintained calibration consistency and continuity of their measurements over the six year period. Our download mechanism transfers the data from these instruments into hadoop's dfs. Our MapReduce implementation grids the data in a distributed fashion by returning each radiance as a key/value pair with the value being the radiance measurement and the key being a unique ID that corresponds to a particular grid box. The reducing function then performs averaging for each of the grid boxes, returning the final average radiance for each grid box. We implemented a generalized downloading mechanism in the SOAR system that is capable of intelligently streaming of data for these three instruments with a single interface. The downloader is capable of error checking and user defined operations when downloading data. The download mechanism takes advantage of multithreading to download the next dataset, while currently downloaded datasets are being processed. Additionally, the download mechanism allows for easy expansion to enable datasets for other instruments to be downloaded.

Golpayegani, N.; Halem, M.; Nguyen, P.

2008-12-01

322

Vibrational sum frequency generation spectroscopy using inverted visible pulses.  

UK PubMed Central (United Kingdom)

We present a broadband vibrational sum frequency generation (BB-VSFG) scheme using a novel ps visible pulse shape. We generate the fs IR pulse via standard procedures and simultaneously generate an 'inverted' time-asymmetric narrowband ps visible pulse via second harmonic generation in the pump depletion regime using a very long nonlinear crystal which has high group velocity mismatch (LiNbO3). The 'inverted' ps pulse shape minimally samples the instantaneous nonresonant response but maximally samples the resonant response, maintaining high spectral resolution. We experimentally demonstrate this scheme, presenting SFG spectra of canonical organic monolayer systems in the C-H stretch region (2800-3000 cm(-1)).

Weeraman C; Mitchell SA; Lausten R; Johnston LJ; Stolow A

2010-05-01

323

Near-infrared spectral imaging of the female breast for quantitative oximetry in optical mammography.  

UK PubMed Central (United Kingdom)

We present a hybrid continuous-wave, frequency-domain instrument for near-infrared spectral imaging of the female breast based on a tandem, planar scanning of one illumination optical fiber and one collection optical fiber configured in a transmission geometry. The spatial sampling rate of 25 points/cm(2) is increased to 400 points/cm(2) by postprocessing the data with a 2D cubic spline interpolation. We then apply a previously developed spatial second-derivative algorithm to an edge-corrected intensity image (N-image) to enhance the visibility and resolution of optical inhomogeneities in breast tissue such as blood vessels and tumors. The spectral data at each image pixel consist of 515-point spectra over the 650-900 nm wavelength range, thus featuring a spectral density of two data points per nanometer. We process the measured spectra with a paired-wavelength spectral analysis method to quantify the oxygen saturation of detected optical inhomogeneities, under the assumption that they feature a locally higher hemoglobin concentration. Our initial measurements on two healthy human subjects have generated high-resolution optical mammograms displaying a network of blood vessels with values of hemoglobin saturation typically falling within the 60%-95% range, which is physiologically reasonable. This approach to spectral imaging and oximetry of the breast has the potential to efficiently exploit the high intrinsic contrast provided by hemoglobin in breast tissue and to contribute a useful tool in the detection, diagnosis, and monitoring of breast pathologies.

Yu Y; Liu N; Sassaroli A; Fantini S

2009-04-01

324

Correlation of Spectral Solar Irradiance with solar activity as measured by VIRGO  

CERN Document Server

Context. The variability of Solar Spectral Irradiance over the rotational period and its trend over the solar activity cycle are important for understanding the Sun-Earth connection as well as for observational constraints for solar models. Recently the SIM experiment on SORCE has published an unexpected negative correlation with Total Solar Irradiance of the visible spectral range. It is compensated by a strong and positive variability of the near UV range. Aims. We aim to verify whether the anti-correlated SIM/SORCE-trend in the visible can be confirmed by independent observations of the VIRGO experiment on SOHO. The challenge of all space experiments measuring solar irradiance are sensitivity changes of their sensors due to exposure to intense UV radiation, which are difficult to assess in orbit. Methods. We analyze a 10-year time series of VIRGO sun photometer data between 2002 and 2012. The variability of Spectral Solar Irradiance is correlated with the variability of the Total Solar Irradiance, which is...

Wehrli, C; Shapiro, A I

2013-01-01

325

Stark broadening and shift measurements of visible Si II lines  

International Nuclear Information System (INIS)

A set of experimental Stark width and shift parameters of visible singly ionized silicon spectral lines is reported in this paper. Measurements have been made on a pulsed plasma generated in a linear discharge lamp filled with a mixture of silane and helium. Electron density and temperature in this plasma range from 0.2 to 0.9x1023 m-3 and from 16 000 to 20 000 K respectively. Electron density has been simultaneously determined by two-wavelength interferometry and from Stark broadening of He I 501.6 nm, He I 728.1 nm and H? lines. Temperature has been simultaneously determined from a Boltzmann plot of He I lines, from absolute emission of He I lines and from a Boltzmann plot of Si II lines. Dependences of measured Stark parameters on electron density and temperature have been investigated and the final results have been compared with most of the previous experimental data as well as with some theoretical models. (author)

2002-08-28

326

Visible spatial frequency domain imaging with a digital light microprojector.  

UK PubMed Central (United Kingdom)

ABSTRACT. There is a need for cost effective, quantitative tissue spectroscopy and imaging systems in clinical diagnostics and pre-clinical biomedical research. A platform that utilizes a commercially available light-emitting diode (LED) based projector, cameras, and scaled Monte Carlo model for calculating tissue optical properties is presented. These components are put together to perform spatial frequency domain imaging (SFDI), a model-based reflectance technique that measures and maps absorption coefficients (?a) and reduced scattering coefficients (?s') in thick tissue such as skin or brain. We validate the performance of the flexible LED and modulation element (FLaME) system at 460, 530, and 632 nm across a range of physiologically relevant ?a values (0.07 to 1.5??mm-1) in tissue-simulating intralipid phantoms, showing an overall accuracy within 11% of spectrophotometer values for ?a and 3% for ?s'. Comparison of oxy- and total hemoglobin fits between the FLaME system and a spectrophotometer (450 to 1000 nm) is differed by 3%. Finally, we acquire optical property maps of a mouse brain in vivo with and without an overlying saline well. These results demonstrate the potential of FLaME to perform tissue optical property mapping in visible spectral regions and highlight how the optical clearing effect of saline is correlated to a decrease in ?s' of the skull.

Lin AJ; Ponticorvo A; Konecky SD; Cui H; Rice TB; Choi B; Durkin AJ; Tromberg BJ

2013-09-01

327

Visible spatial frequency domain imaging with a digital light microprojector.  

Science.gov (United States)

ABSTRACT. There is a need for cost effective, quantitative tissue spectroscopy and imaging systems in clinical diagnostics and pre-clinical biomedical research. A platform that utilizes a commercially available light-emitting diode (LED) based projector, cameras, and scaled Monte Carlo model for calculating tissue optical properties is presented. These components are put together to perform spatial frequency domain imaging (SFDI), a model-based reflectance technique that measures and maps absorption coefficients (?a) and reduced scattering coefficients (?s') in thick tissue such as skin or brain. We validate the performance of the flexible LED and modulation element (FLaME) system at 460, 530, and 632 nm across a range of physiologically relevant ?a values (0.07 to 1.5??mm-1) in tissue-simulating intralipid phantoms, showing an overall accuracy within 11% of spectrophotometer values for ?a and 3% for ?s'. Comparison of oxy- and total hemoglobin fits between the FLaME system and a spectrophotometer (450 to 1000 nm) is differed by 3%. Finally, we acquire optical property maps of a mouse brain in vivo with and without an overlying saline well. These results demonstrate the potential of FLaME to perform tissue optical property mapping in visible spectral regions and highlight how the optical clearing effect of saline is correlated to a decrease in ?s' of the skull. PMID:24005154

Lin, Alexander J; Ponticorvo, Adrien; Konecky, Soren D; Cui, Haotian; Rice, Tyler B; Choi, Bernard; Durkin, Anthony J; Tromberg, Bruce J

2013-09-01

328

Air Pollution: Visible and Invisible  

Science.gov (United States)

In this lesson, students test for visible and invisible pollutants in the air and keep a journal of experimental results, procedures, and conclusions. Using simple materials, they will form groups to set up experiments around the school, keep records, research the history of acid rain, make a mural showing the acid rain cycle, and post a chart displaying the sources of visible pollutants.

329

Visibility of dichalcogenide nanolayers  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Dichalcogenides with the common formula MX2 are layered materials with electrical properties that range from semiconducting to superconducting. Here, we describe optimal imaging conditions for the optical detection of ultrathin, two-dimensional dichalcogenide nanocrystals containing single, double a...

Benameur, M. M.; Radisavljevic, B.; Héron, J. S.; Sahoo, S.; Berger, H.; Kis, A.

330

Signature spectrale des grains interstellaires.  

Science.gov (United States)

Notre connaissance de la nature des grains interstellaires reposait sur un nombre très restreint de signatures spectrales dans la courbe d'extinction du milieu interstellaire. Une information considérable est contenue dans les 40 bandes interstellaires diffuses dans le visible, mais reste inexploitée. L'interprétation récente des cinq bandes IR en émission, en terme de molécules d'hydrocarbures aromatiques polycycliques, est développée. Elle permet l'utilisation d'une information spectroscopique comparable, à elle seule, à ce sur quoi était basée jusqu'alors notre connaissance de la matière interstellaire condensée. Différentes implications de cette mise en évidence sont proposées.

Léger, A.

331

Visible spectroscopy in the DIII-D divertor  

International Nuclear Information System (INIS)

Spectroscopy measurements in the DIII-D divertor have been carried out with a survey spectrometer which provides simultaneous registration of the visible spectrum over the region 400--900 nm with a resolution of 0.2 nm. Broad spectral coverage is achieved through use of a fiberoptic transformer assembly to map the curved focal plane of a fast (f/3) Rowland spectrograph into a rastered format on the rectangular sensor area of a two-dimensional CCD camera. Vertical grouping of pixels during CCD readout integrates the signal intensity over the height of each spectral segment in the rastered image, minimizing readout time. For the full visible spectrum, readout time is 50 ms. Faster response time (

1996-01-01

332

Spectral CT of carotid atherosclerotic plaque: comparison with histology  

Energy Technology Data Exchange (ETDEWEB)

To distinguish components of vulnerable atherosclerotic plaque by imaging their energy response using spectral CT and comparing images with histology. After spectroscopic calibration using phantoms of plaque surrogates, excised human carotid atherosclerotic plaques were imaged using MARS CT using a photon-processing detector with a silicon sensor layer and microfocus X-ray tube (50 kVp, 0.5 mA) at 38-{mu}m voxel size. The plaques were imaged, sectioned and re-imaged using four threshold energies: 10, 16, 22 and 28 keV; then sequentially stained with modified Von Kossa, Perl's Prussian blue and Oil-Red O, and photographed. Relative Hounsfield units across the energies were entered into a linear algebraic material decomposition model to identify the unknown plaque components. Lipid, calcium, iron and water-like components of plaque have distinguishable energy responses to X-ray, visible on spectral CT images. CT images of the plaque surface correlated very well with histological photographs. Calcium deposits (>1,000 {mu}m) in plaque are larger than iron deposits (<100 {mu}m), but could not be distinguished from each other within the same voxel using the energy range available. Spectral CT displays energy information in image form at high spatial resolution, enhancing the intrinsic contrast of lipid, calcium and iron within atheroma. (orig.)

Zainon, R.; Doesburg, R.M. [University of Canterbury, Department of Physics and Astronomy, Christchurch (New Zealand); Ronaldson, J.P.; Gieseg, S.P. [University of Otago, Centre for Bioengineering, Christchurch (New Zealand); Janmale, T. [University of Canterbury, Free Radical Biochemistry Laboratory, School of Biological Sciences, Christchurch (New Zealand); Scott, N.J. [University of Otago, Department of Medicine, Christchurch (New Zealand); Buckenham, T.M. [University of Otago, Department of Academic Radiology, Christchurch (New Zealand); Butler, A.P.H. [University of Otago, Centre for Bioengineering, Christchurch (New Zealand); University of Otago, Department of Academic Radiology, Christchurch (New Zealand); University of Canterbury, Department of Electrical and Computer Engineering, Christchurch (New Zealand); European Organisation for Nuclear Research (CERN), Geneva (Switzerland); Butler, P.H. [University of Canterbury, Department of Physics and Astronomy, Christchurch (New Zealand); European Organisation for Nuclear Research (CERN), Geneva (Switzerland); Roake, J.A. [Christchurch Hospital, Department of Vascular, Endovascular and Transplant Surgery, Christchurch (New Zealand); Anderson, N.G. [University of Otago, Centre for Bioengineering, Christchurch (New Zealand); University of Otago, Department of Academic Radiology, Christchurch (New Zealand); University of Otago, Christchurch, Department of Radiology, PO Box 4345, Christchurch (New Zealand)

2012-12-15

333

Visible light emission from silicon  

International Nuclear Information System (INIS)

Although crystalline silicon is not expected to emit light in the visible range, bright red emission has been reported for high porosity porous silicon films. This recent discovery which opens the door to silicon-based optoelectronics has raised up a great interest in the scientific community, and the paper presents the state of art of the question after a year of investigations. After a short presentation of the main features of porous silicon, the different characteristics of the photoluminescence phenomena are described in some detail. In this paper, the evolution of the emission spectra with the properties of the material which can be varied by chemical or electrochemical methods are presented. Results confirm that quantum size effects within the crystalline material can be responsible for the light emission far above the band gap of silicon. Bright electroluminescence has also been evidenced during anodic oxidation of the material. The dependence of this emission with the material properties and the characteristics of the oxidation process will be discussed and compared t the photoluminescence features

1992-01-01

334

Visible Imaging Fourier Transform Spectrometer: Design and Calibration  

Energy Technology Data Exchange (ETDEWEB)

We present details of the design, operation and calibration of an astronomical visible-band imaging Fourier transform spectrometer (IFTS). This type of instrument produces a spectrum for every pixel in the field of view where the spectral resolution is flexible. The instrument is a dual-input/dual-output Michelson interferometer coupled to the 3.5 meter telescope at the Apache Point Observatory. Imaging performance and interferograms and spectra from calibration sources and standard stars are discussed.

Wishnow, E H; Wurtz, R; Blais-Ouellette, S; Cook, K H; Carr, D; Lewis, I; Grandmont, F; Stubbs, C W

2002-09-19

335

Skyglow effects in UV and visible spectra: radiative fluxes.  

UK PubMed Central (United Kingdom)

Several studies have tried to understand the mechanisms and effects of radiative transfer under different night-sky conditions. However, most of these studies are limited to the various effects of visible spectra. Nevertheless, the invisible parts of the electromagnetic spectrum can pose a more profound threat to nature. One visible threat is from what is popularly termed skyglow. Such skyglow is caused by injudiciously situated or designed artificial night lighting systems which degrade desired sky viewing. Therefore, since lamp emissions are not limited to visible electromagnetic spectra, it is necessary to consider the complete spectrum of such lamps in order to understand the physical behaviour of diffuse radiation at terrain level. In this paper, the downward diffuse radiative flux is computed in a two-stream approximation and obtained ultraviolet spectral radiative fluxes are inter-related with luminous fluxes. Such a method then permits an estimate of ultraviolet radiation if the traditionally measured illuminance on a horizontal plane is available. The utility of such a comparison of two spectral bands is shown, using the different lamp types employed in street lighting. The data demonstrate that it is insufficient to specify lamp type and its visible flux production independently of each other. Also the UV emissions have to be treated by modellers and environmental scientists because some light sources can be fairly important pollutants in the near ultraviolet. Such light sources can affect both the living organisms and ambient environment.

Kocifaj M; Solano Lamphar HA

2013-09-01

336

Skyglow effects in UV and visible spectra: Radiative fluxes.  

Science.gov (United States)

Several studies have tried to understand the mechanisms and effects of radiative transfer under different night-sky conditions. However, most of these studies are limited to the various effects of visible spectra. Nevertheless, the invisible parts of the electromagnetic spectrum can pose a more profound threat to nature. One visible threat is from what is popularly termed skyglow. Such skyglow is caused by injudiciously situated or designed artificial night lighting systems which degrade desired sky viewing. Therefore, since lamp emissions are not limited to visible electromagnetic spectra, it is necessary to consider the complete spectrum of such lamps in order to understand the physical behaviour of diffuse radiation at terrain level. In this paper, the downward diffuse radiative flux is computed in a two-stream approximation and obtained ultraviolet spectral radiative fluxes are inter-related with luminous fluxes. Such a method then permits an estimate of ultraviolet radiation if the traditionally measured illuminance on a horizontal plane is available. The utility of such a comparison of two spectral bands is shown, using the different lamp types employed in street lighting. The data demonstrate that it is insufficient to specify lamp type and its visible flux production independently of each other. Also the UV emissions have to be treated by modellers and environmental scientists because some light sources can be fairly important pollutants in the near ultraviolet. Such light sources can affect both the living organisms and ambient environment. PMID:23792881

Kocifaj, Miroslav; Solano Lamphar, H A

2013-06-21

337

Electric dipole-free interaction of visible light with silver metadimers  

CERN Multimedia

In subwavelength-sized particles, light-induced multipole moments of orders higher than the electric dipole are usually negligibly small, which allows for the light-matter interaction to be accurately treated within the electric dipole approximation. In this work we show that in a specially designed meta-atom, a disc metadimer, the electric quadrupole and magnetic dipole can be the only excitable multipoles. This condition is achieved in a narrow but tunable spectral range of visible light both for individual metadimers and for a periodic array of such particles. The electromagnetic fields scattered by the metadimers fundamentally differ from those created by electric dipoles. A metamaterial composed of such metadimers will therefore exhibit unusual optical properties.

Grahn, P; Kaivola, M

2012-01-01

338

Visible spectroscopy of the new ESO Large Program on trans-Neptunian objects and Centaurs: final results  

CERN Multimedia

A second large programme (LP) for the physical studies of TNOs and Centaurs, started at ESO Cerro Paranal on October 2006 to obtain high-quality data, has recently been concluded. In this paper we present the spectra of these pristine bodies obtained in the visible range during the last two semesters of the LP. We investigate the spectral behaviour of the TNOs and Centaurs observed, and we analyse the spectral slopes distribution of the full data set coming from this LP and from the literature. We computed the spectral slope for each observed object, and searched for possible weak absorption features. A statistical analysis was performed on a total sample of 73 TNOs and Centaurs to look for possible correlations between dynamical classes, orbital parameters, and spectral gradient. We obtained new spectra for 28 bodies, 15 of which were observed for the first time. All the new presented spectra are featureless, including 2003 AZ84, for which a faint and broad absorption band possibly attributed to hydrated sil...

Fornasier, S; de Bergh, C; Alvarez-Candal, A; DeMeo, F; Merlin, F; Perna, D; Guilbert, A; Delsanti, A; Dotto, E; Doressoundiram, A

2009-01-01

339

Spectral selectivity of electrochromic windows with color state for all-sky conditions  

Energy Technology Data Exchange (ETDEWEB)

The optical performance of an electrochromic window is studied for the visible, ultraviolet, and near infrared spectral regions. The performance is found to deviate strongly with window color state and for clear or cloudy skies. A new spectral cloud model is applied to an electrochromic window recently developed at NREL. A spectral comparison is made between the electrochromic window and spectrally selective standard windows. Two series of double-glazed window sections, including the electrochromic window with color state and a series of low-E windows, were measured for transmittance and reflectance (300-2500nm), With these spectral data, a new near-infrared blocking (reflection + absorption) factor is developed for window application in warm climates for cooling load reduction. A chromaticity analysis is presented for both the daylight spectra and the transmitted electrochromic window spectra with color state, Computed daylight correlated color temperatures show a wide range, with values of 5660K for clear global irradiation, 6210K for clouds, and 13,250K for a zenith blue sky. Chromatic trajectories with color state for transmitted radiation extend further toward the blue to 8180K for the global and 28,990K for zenith sky irradiation.

Soule, D.E. [Western Illinois Univ., Macomb, IL (United States); Zhang, J.G.; Benson, D.K. [National Renewable Energy Lab., Golden, CO (United States)

1995-07-01

340

Design, testing and characterization of innovative TiN–TiO2 surfaces inactivating bacteria under low intensity visible light  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Ti was sputtered in a plasma chamber under a N2 atmosphere, depositing TiN films on polyester fibers. These films show a significant adsorption in the visible spectral region. A TiN layer 50 nm thick sputtered for 3 min under low intensity/actinic visible light led to the fastest bacterial inactivat...

Rtimi, S.; Baghriche, O.; Pulgarin, C.; Sanjines, R.; Kiwi, J.

 
 
 
 
341

No-visible-scar cholecystectomy  

Directory of Open Access Journals (Sweden)

Full Text Available Introduction: Single incision laparoscopic surgery (SILS) is a laparoscopic method providing a good cosmetic effect,but requiring the application of special ports and instruments enabling the surgeon to perform the procedure.We report three-ports cholecystectomy through umbilical and suprapubic incisions performed with typical laparos -copic instruments which calls no-visible-scar cholecystectomy (NVSC).Material and methods: Twenty patients with symptomatic cholelithiasis were qualified for NVSC. Typical CO2 pneumoperitoneumwas done after umbilical skin incision. Two ports of 5 mm were inserted in the maximum externaledges of this incision. After cystic duct and cystic artery dissection the right one was exchanged for a port of 11 mm.The second incision for the 11-mm trocar for the laparoscope was done in the suprapubic median line within the hairarea.Results: Cholecystectomies were performed without any conversion to classical laparoscopic cholecystectomy (LCH)or open surgery. They were not technically identical due to the gradual improvement in the access and manipulationof instruments. The time of the intervention ranged from 2 hours during the introduction of the new method to 50 minfor the last procedures. No postoperative complications were observed and all patients were discharged not later thanafter conventional LCH.Conclusions: NVSC is a three-port laparoscopic intervention performed with typical laparoscopic instruments. It ismore convenient for the surgeon than single incision LCH, because the placement of the optic in the suprapubic regiongives more space for the instruments. It also provides a very good cosmetic effect of the intervention. The describedprocedure is easy to learn and in case of technical problems additional ports can be applied (as in typical LCH).

Tadeusz M. Wróblewski; Sebastian Piotrowicz; Marcin Kotulski; Piotr Gierej; Bogna Ziarkiewicz-Wróblewska

2010-01-01

342

Recent variability of the solar spectral irradiance and its impact on climate modelling  

CERN Document Server

The lack of long and reliable time series of solar spectral irradiance (SSI) measurements makes an accurate quantification of solar contributions to recent climate change difficult. Whereas earlier SSI observations and models provided a qualitatively consistent picture of the SSI variability, recent measurements by the SORCE satellite suggest a significantly stronger variability in the ultraviolet (UV) spectral range and changes in the visible and near-infrared (NIR) bands in anti-phase with the solar cycle. A number of recent chemistry-climate model (CCM) simulations have shown that this might have significant implications on the Earth's atmosphere. Motivated by these results, we summarize here our current knowledge of SSI variability and its impact on Earth's climate. We present a detailed overview of existing SSI measurements and provide thorough comparison of models available to date. SSI changes influence the Earth's atmosphere, both directly, through changes in shortwave (SW) heating and therefore, temp...

Ermolli, I; de Wit, T Dudok; Krivova, N A; Tourpali, K; Weber, M; Unruh, Y C; Gray, L; Langematz, U; Pilewskie, P; Rozanov, E; Schmutz, W; Shapiro, A; Solanki, S K; Woods, T N

2013-01-01

343

Methods for measuring the spectral reflectivity of advanced materials at high temperature  

International Nuclear Information System (INIS)

For investigation in the domain of advanced materials as well as for new technologies there is an urgent need for knowledge of the spectral reflectivity of the materials specially at high temperatures. However the methods available are mostly intended for measuring the model materials with specular or diffuse reflection surface. This is not quite correct since advanced materials have mixed specular diffuse reflection surfaces. New methods for reflectivity measurements of materials in the visible, near and middle infrared range at high temperature, regardless of surface texture, have been developed. The advantages of the methods proposed are as flows: (a) the facility of performing the reflectivity measurements for materials with mixed specular diffuse reflectance; (b) wide spectral range 0,38-8 micro m; (c) wide temperature range 300-3000 K; (d) high accuracy and rapid measurements. The methods are based on the following principals (i) Diffuse irradiation of the sample surface and the use of Helkholtz reciprocity principle to determine the directional hemispherical reflectivity ii) Pulse polychromatic probing of the sample by additional light source. The first principle excludes the influence of the angular reflection distribution of sample surface on data obtained. The second principle gives the possibility of simultaneous measurements of the reflectivity. The second principle gives the possibility of simultaneous measurements of the reflectivity in wide spectral range. On the basis of these principles for high temperature reflectometers have been developed and discussed here. (author)

1993-01-01

344

Visible light scatter as quantitative information source on milk constituents  

DEFF Research Database (Denmark)

VISIBLE LIGHT SCATTER AS A QUANTITATIVE INFORMATION SOURCE ON MILK CONSTITUENTS A. Melenteva 1, S. Kucheryavski 2, A. Bogomolov 1,31Samara State Technical University, Molodogvardeyskaya Street 244, 443100 Samara, Russia. 2Aalborg University, campus Esbjerg, Niels Bohrs vej 8, 6700 Esbjerg, Denmark. 3J&M Analytik AG, Willy-Messerschmitt-Strasse 8, 73457 Essingen, Germany. bogomolov@j-m.de Fat and protein are two major milk nutrients that are routinely analyzed in the dairy industry. Growing food quality requirements promote the dissemination of spectroscopic analysis, enabling real-time monitoring of processes and products. Optical analysis is generally performed in near and middle infrared (NIR and MIR) regions and relies on the component absorbance and Beer’s Law. The light scatter effect is therefore considered as a disturbance to be avoided during the measurement or eliminated at the data analysis stage. The region of visible (Vis) light (400-800 nm) is economically attractive, because it offers a range of inexpensive light sources, optics and detectors. At present, however, it is commonly considered useless, because of the light scatter by fat globules (1-10 ?m) and protein micelles (80-200 ?m) that strongly dominates; therefore, making the classical absorbance analysis hardly applicable. At the same time, diffused light by itself delivers information on the milk composition, specifically, fat content as illustrated in Fig. 1, and can potentially be used for the quantitative analysis. The main task here is to extract individual quantitative information on milk fat and total protein content from spectral data. This is particularly challenging problem in the case of raw natural milk, where the fat globule sizes may essentially differ depending on source. Fig. 1. Spots of light transmitted through homogenized milk samples with different fat content. The preceding research [1] has shown that individual scatter patterns of fat and protein in non-homogenized milk can be distinguished, thus, enabling their quantitative multivariate analysis. In the present study, a representative designed set of raw milk samples with simultaneously varying fat, total protein and particle size distribution has been analyzed in the Vis spectral region. The feasibility of raw milk analysis by PLS regression on spectral data has been proved. The root mean-square errors below 0.10% and 0.04% for fat and protein, respectively, have been obtained. PLS components were interpreted in terms of captured information. The results obtained provide a basis for the replacement of traditional spectroscopy by custom optical analyzers, optimized for the purpose of milk analysis. Preliminary achievements in this new research area are presented and discussed. References: [1] A. Bogomolov, S. Dietrich, B. Boldrini, R.W. Kessler, Food Chemistry (2012), doi:10.1016/j.foodchem.2012.02.077.

Melentieva, Anastasiya; Kucheryavskiy, Sergey

2012-01-01

345

Visible Spectrum Circular Dichroism in Extrinsic Chirality Metamaterials  

CERN Multimedia

We present the new planar extrinsic chirality metamaterial (ECM) design that manifests giant circular dichroism (CD) in the visible spectrum range rather than usual near-infrared and terahertz range. Effects of incident beam angles and meta-molecules unit sizes on the CD spectrums were theoretically analyzed; Physical mechanism was illustrated in new figures of asymmetrical current excitation in neighboring unit cells.

Lee, Seoungjun; Feng, Cheng; Jiao, Jiao; Khan, Ashfaq; Li, Lin

2012-01-01

346

Visibility of dichalcogenide nanolayers  

International Nuclear Information System (INIS)

[en] Dichalcogenides with the common formula MX2 are layered materials with electrical properties that range from semiconducting to superconducting. Here, we describe optimal imaging conditions for the optical detection of ultrathin, two-dimensional dichalcogenide nanocrystals containing single, double and triple layers of MoS2, WSe2 and NbSe2. A simple optical model is used to calculate the contrast for nanolayers deposited on wafers with varying thicknesses of SiO2. The model is extended for imaging using the green channel of a video camera. Using AFM and optical imaging we confirm that single layers of MoS2 and WSe2 can be detected on 90 and 270 nm SiO2 using optical means. By measuring contrast under broadband green illumination we are also able to distinguish between nanostructures containing single, double and triple layers of MoS2 and WSe2. We observe and discuss discrepancies in the case of NbSe2.

2011-03-25

347

Visibility of dichalcogenide nanolayers  

Science.gov (United States)

Dichalcogenides with the common formula MX2 are layered materials with electrical properties that range from semiconducting to superconducting. Here, we describe optimal imaging conditions for the optical detection of ultrathin, two-dimensional dichalcogenide nanocrystals containing single, double and triple layers of MoS2, WSe2 and NbSe2. A simple optical model is used to calculate the contrast for nanolayers deposited on wafers with varying thicknesses of SiO2. The model is extended for imaging using the green channel of a video camera. Using AFM and optical imaging we confirm that single layers of MoS2 and WSe2 can be detected on 90 and 270 nm SiO2 using optical means. By measuring contrast under broadband green illumination we are also able to distinguish between nanostructures containing single, double and triple layers of MoS2 and WSe2. We observe and discuss discrepancies in the case of NbSe2.

Benameur, M. M.; Radisavljevic, B.; Héron, J. S.; Sahoo, S.; Berger, H.; Kis, A.

2011-03-01

348

A review of the latest developments of MCT infrared technology from visible to VLWIR for space applications at Sofradir  

Science.gov (United States)

Based on a large experience, SOFRADIR is conducting major space programs covering all the wavelength range from visible to VLWIR as Sentinel projects in the frame of the GMES program or MTG detectors development and manufacturing for the future European meteorological satellites of third generation. In particular, new developments of MCT infrared detectors are currently made: • A new generation of SWIR hyperspectral detectors with a format of 1024x1024 / 15 µm pitch • Optimization of MCT performances for VLWIR spectral range aiming at new sounding missions • Developments of new infrared detectors for MTG program In this paper, a review of the main space programs conducted by SOFRADIR is presented with a particular emphasis on the last developments.

Pidancier, Patricia; Jamin, Nicolas; Fièque, Bruno; Leroy, Cédric; Chorier, Philippe

2013-06-01

349

Novel non-invasive distribution measurement of texture profile analysis (TPA) in salmon fillet by using visible and near infrared hyperspectral imaging.  

UK PubMed Central (United Kingdom)

This study developed a pushbroom visible and near-infrared hyperspectral imaging system in the wavelength range of 400-1758nm to determine the spatial distribution of texture profile analysis (TPA) parameters of salmon fillets. Six TPA parameters (hardness, adhesiveness, chewiness, springiness, cohesiveness, and gumminess) were analysed. Five spectral features (mean, standard deviation, skew, energy, and entropy) and 22 image texture features obtained from graylevel co-occurrence matrix (GLCM) were extracted from hyperspectral images. Quantitative models were established with the extracted spectral and image texture signatures of samples based on partial least squares regression (PLSR). The results indicated that spectral features had better ability to predict TPA parameters of salmon samples than image texture features, and Spectral Set I (400-1000nm) performed better than Spectral II (967-1634nm). On the basis of the wavelengths selected by regression coefficients of PLSR models, instrumental optimal wavelengths (IOW) and predictive optimal wavelengths (POW) were further chosen to reduce the high dimensionality of the hyperspectral image data. Our results show that hyperspectral imaging holds promise as a reliable and rapid alternative to traditional universal testing machines for measuring the spatial distribution of TPA parameters.

Wu D; Sun DW; He Y

2014-02-01

350

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

UK PubMed Central (United Kingdom)

The field spectroradiometer was used to measure spectra of different snow and snow-covered land surface objects in Beijing area. The result showed that for a pure snow spectrum, the snow reflectance peaks appeared from visible to 800 nm band locations; there was an obvious absorption valley of snow spectrum near 1 030 nm wavelength. Compared with fresh snow, the reflection peaks of the old snow and melting snow showed different degrees of decline in the ranges of 300-1 300, 1 700-1 800 and 2 200-2 300 nm, the lowest was from the compacted snow and frozen ice. For the vegetation and snow mixed spectral characteristics, it was indicated that the spectral reflectance increased for the snow-covered land types (including pine leaf with snow and pine leaf on snow background), due to the influence of snow background in the range of 350-1 300 nm. However, the spectrum reflectance of mixed pixel remained a vegetation spectral characteristic. In the end, based on the spectrum analysis of snow, vegetation, and mixed snow/vegetation pixels, the mixed spectral fitting equations were established, and the results showed that there was good correlation between spectral curves by simulation fitting and observed ones (correlation coefficient R2 = 0.950 9).

Zhang JH; Zhou ZM; Wang PJ; Yao FM; Liming Y

2011-09-01

351

Multispectral antireflection coating simultaneously effective in visible, diode laser, Nd-YAG and eye safe laser wavelength  

International Nuclear Information System (INIS)

Multi-spectral antireflection coating effective in visible region for sighting system, Nd-YAG laser wavelength for designator/seeker system, both diode laser and eye safe laser wavelength for ranging purpose can use common objective/receiver optics highly useful for state of art laser instrumentation. In this paper, design and fabrication of antireflection coating simultaneously effective in visible region (500 to 650nm), diode laser at 904±25nm and Nd-YAG laser at 1064±25nm, and erbium-glass laser wavelength at 1540±25nm has been reported. Inhomogeneous refractive index profile as suggested by Southwell was used to design this coating. The inhomogeneous profile was then approximated with eleven steps from substrate to air medium in order to obtain desirable antireflection property in the visible and laser wavelengths. These steps were then converted into the available coating materials (titanium-di-oxide and magnesium fluoride) of twenty-two layer stack. The multilayer stack was fabricated by using electron beam gun evaporation system in Balzers BAK-600 vacuum coating unit. The result achieved were less than 2% average reflection (98% average transmission) from 500 to 650nm, 1.5% reflection (98.5% average transmission) at 904nm, 1064nm and 1540nm. The coated samples successfully passed the specifications of MIL-C-14806 tests.

2008-05-01

352

Multispectral antireflection coating simultaneously effective in visible, diode laser, Nd-YAG and eye safe laser wavelength  

Energy Technology Data Exchange (ETDEWEB)

Multi-spectral antireflection coating effective in visible region for sighting system, Nd-YAG laser wavelength for designator/seeker system, both diode laser and eye safe laser wavelength for ranging purpose can use common objective/receiver optics highly useful for state of art laser instrumentation. In this paper, design and fabrication of antireflection coating simultaneously effective in visible region (500 to 650nm), diode laser at 904{+-}25nm and Nd-YAG laser at 1064{+-}25nm, and erbium-glass laser wavelength at 1540{+-}25nm has been reported. Inhomogeneous refractive index profile as suggested by Southwell was used to design this coating. The inhomogeneous profile was then approximated with eleven steps from substrate to air medium in order to obtain desirable antireflection property in the visible and laser wavelengths. These steps were then converted into the available coating materials (titanium-di-oxide and magnesium fluoride) of twenty-two layer stack. The multilayer stack was fabricated by using electron beam gun evaporation system in Balzers BAK-600 vacuum coating unit. The result achieved were less than 2% average reflection (98% average transmission) from 500 to 650nm, 1.5% reflection (98.5% average transmission) at 904nm, 1064nm and 1540nm. The coated samples successfully passed the specifications of MIL-C-14806 tests.

Bandyopadhyay, P K [Instruments Research and Development Establishment, Dehra Dun-248008 (India)], E-mail: pkbandyo@irde.res.in

2008-05-01

353

High-power visible semiconductor lasers  

Energy Technology Data Exchange (ETDEWEB)

High power visible semiconductor laser diodes are reported at wavelengths ranging from 620 nm to 690 nm. Broad area laser diodes exhibit peak cw output powers of 3.8 W from a 250 {mu}m aperture at 688 nm and >1 W cw at 636 nm from a 100 gm aperture. Monolithic 1 cm arrays with a 24% filling factor provide output powers of 30 W cw at 687 nm. Single mode lasers in the 620 nm wavelength band emit >50 mW and operate at temperatures up to 80 C.

Geels, R.S.; Welch, D.F. [SDL, Inc., San Jose, CA (United States); Bour, D.P.; Treat, D.W.; Bringans, R.D. [Xerox PARC, Palo Alto, CA (United States)

1994-12-31

354

Light distribution system comprising spectral conversion means  

DEFF Research Database (Denmark)

System (200, 300) for the distribution of white light, having a supply side (201, 301, 401) and a delivery side (202, 302, 402), the system being configured for guiding light with a multitude of visible wavelengths in a propagation direction P from the supply side to the distribution side, the system comprising a transport fibre (210, 310, 330, 410, 410a-d) and a spectral conversion fibre (220, 320, 420ad, 500, 600, 700), the transport fibre having a length extending from a first end (211, 311, 331) to a second end (212, 312, 332), and a spectral transmission characteristics,the transport fibre being operationally connected to the spectral conversion fibre having a length extending from an input end (221, 321)to an output end (222, 322), the spectral conversion fibre comprising a photoluminescent agent (511, 611, 711) for converting light of a first wavelength to light of a second, longer wavelength,a spectral conversion characteristics of the spectral conversion fibre being essentially determined by the spectral absorption and emission properties of the photoluminescent agent, the amount of photo- luminescent agent,and the distribution of the photoluminescent agent in the spectral conversion fibre, wherein the first and second wavelengths are selected according to the spectral transmission characteristics of the transport fibre such that transmission loss in the transport fibre at the first wavelength is less than at the second wavelength. According to further aspects, a method of providing a light distribution system and a method of correcting the spectral transmission characteristics of a light distribution system are disclosed.

Bjarklev, Anders Overgaard Technical University of Denmark,

355

Spectral discomfort glare sensitivity under low photopic conditions.  

Science.gov (United States)

Car headlamp manufacturers have to optimise the headlamp spectrum to produce maximum visibility and minimal glare. There are very few investigations on the best spectrum for mesopic visibility and even less data on the spectrum of discomfort glare. We have performed pilot measurements to determine the spectral discomfort glare sensitivity under situations similar to night-driving conditions and conclude that it is not a simple additivity of the V(lambda) and the V' (lambda) functions. PMID:16684157

Fekete, J; Sik-Lányi, C; Schanda, J

2006-05-01

356

Spectral discomfort glare sensitivity under low photopic conditions.  

UK PubMed Central (United Kingdom)

Car headlamp manufacturers have to optimise the headlamp spectrum to produce maximum visibility and minimal glare. There are very few investigations on the best spectrum for mesopic visibility and even less data on the spectrum of discomfort glare. We have performed pilot measurements to determine the spectral discomfort glare sensitivity under situations similar to night-driving conditions and conclude that it is not a simple additivity of the V(lambda) and the V' (lambda) functions.

Fekete J; Sik-Lányi C; Schanda J

2006-05-01

357

Visible light switching of a BF2-coordinated azo compound.  

UK PubMed Central (United Kingdom)

Here we report the synthesis and characterization of a BF(2)-azo complex that can be induced to isomerize without the need of deleterious UV light. The complexation of the azo group with BF(2), coupled with the extended conjugation of the N?N ?-electrons, increases the energy of the n-?* transitions and introduces new ?-nonbonding (?(nb)) to ?* transitions that dominate the visible region. The well separated ?(nb)-?* transitions of the trans and cis isomers enable the efficient switching of the system by using only visible light. The complexation also leads to a slow cis ? trans thermal relaxation rate (t(1/2) = 12.5 h). Theoretical calculations indicate that the absorption bands in the visible range can be tuned using different Lewis acids, opening the way to a conceptually new strategy for the manipulation of azo compounds using only visible light.

Yang Y; Hughes RP; Aprahamian I

2012-09-01

358

General approach to high power, coherent visible and ultraviolet light sources  

DEFF Research Database (Denmark)

The main goal of this project is to develop a generic approach to synthesise any wavelength in the visible and UV spectral region based on sum frequency generation. The approach is based on a hybrid system combining solid state and semiconductor technology. The generation of light in the UV spectral region require nonlinear materials with a transparency range extending into the ultraviolet, the ability to sustain high photon energies and with the ability to obtain phasematching for the desired nonlinear conversion process. In this project experiments are conducted using three differently co-doped GdCOB crystals. The crystals are optimized for noncritical phasematching in the blue-UV spectral region through co-doping with Lu and Sc, a nonlinear coefficient for these crystals of 0.78, 0.81 and 0.89 pm/V are measured, which is comparable to LBO. The ability to adjust the noncritical phasematching by co-doping of these crystals makes them promising candidates for generation of light in the blue-UV region. A novelmethod for cavity dumping based on nonlinear frequency conversion is investigated. A high finesse laser is constructed with an intracavity nonlinear material inserted in a beam waist. The nonlinear material is phasematched to support sum frequency generation between the 1342nm circulating field in the cavity and a single pass passively Q-Switched 1064nm laser, effectively converting the circulating power whenever a single pass pulse is present. Furthermore the Q-Switched laser can easily be frequency doubled in a single pass configuration, therefore the nonlinear cavity dumping approach is suggested for the generation of 340nm UV light, using 532nm pulses to cavity dump a 946nm Nd:YAG laser. Furthermore experiments are conducted tripling a Q-switched 1064nm laser to 355nm by cascaded second harmonic and sum frequency generation using periodically poled KTP and BBO for the SHG and SFG process, respectively. The 355nm light is used to promote different photo induced reactions. The main limitation of reaching any desired wavelength in the visible spectrum using sum frequency generation is the limited laser lines available from efficient solid state lasers. One fundamental way to overcome this limitation is to use semiconductor lasers to provide one of the fundamental fields. The problem of using semiconductor lasers for nonlinear frequency conversion has previously been the lag of coherence of these devices. This problem can, however, to a large extent be solved using external cavity tapered diode lasers, which allows for the generation of coherent radiation at the watt power level. Using differently doped semiconductor materials these devices can potentially cover the wavelength range from the red and into the infrared spectral range. These devices are very efficient, however, the available devices in the visible region are still very inefficient, therefore a generic approach using high finesse solid state lasers with intracavity nonlinear materials and single pass tapered diode was sought to cover the shorter wavelength range. In this project more then 300mW of 488nm power is generated by direct sum frequency mixing of a solid state laser and a single pass external cavity tapered diode laser. The performance of the device is compared to systems where the output of the tapered diode laser is spatially filtered and to an all solid state laser system based on mixing with a single frequency Ti:Sapphire laser. Finally experiments with a semiconductor disk laser used as the high finesse cavity laser and sum frequency mixing with a single pass solid state laser is coniv ducted. These experiments show that it is possible to design systems exploiting the benefits of semiconductor based lasers and nonlinear sum frequency generation to cover large parts of the optical spectrum, which has previously been difficult to access due to the lag of efficient, coherent light sources

Andersen, Martin Thalbitzer

2009-01-01

359

Testing of infrared image enhancing algorithm in different spectral bands  

Science.gov (United States)

The paper presents results of testing the infrared image quality enhancing algorithm based on histogram processing. Testing were performed on real images registered in NIR, MWIR, and LWIR spectral bands. Infrared images are a very specific type of information. The perception and interpretation of such image depends not only on radiative properties of observed objects and surrounding scenery. Probably still most important are skills and experience of an observer itself. In practice, the optimal settings of the camera as well as automatic temperature range or contrast control do not guarantee the displayed images are optimal from observer's point of view. The solution to this are algorithms of image quality enhancing based on digital image processing methods. Such algorithms can be implemented inside the camera or applied later, after image registration. They must improve the visibility of low-contrast objects. They should also provide effective dynamic contrast control not only across entire image but also selectively to specific areas in order to maintain optimal visualization of observed scenery. In the paper one histogram equalization algorithm was tested. Adaptive nature of the algorithm should assure significant improvement of the image quality and the same effectiveness of object detection. Another requirement and difficulty is that it should also be effective for any given thermal image and it should not cause a visible image degradation in unpredictable situations. The application of tested algorithm is a promising alternative to a very effective but complex algorithms due to its low complexity and real time operation.

Dulski, R.; Sosnowski, T.; Kastek, M.; Trzaskawka, P.

2012-05-01

360

Visible and near infrared spectroscopic investigation of E-type asteroids, including 2867 Steins, a target of the Rosetta mission  

Science.gov (United States)

We present the results of a visible spectroscopic survey of igneous asteroids belonging to the small and intriguing E-class, including 2867 Steins, a target of the Rosetta mission. The survey was carried out at the 3.5 m Telescopio Nazionale Galileo (TNG), and at the 3.5 m New Technology Telescope (NTT) of the European Southern Observatory. We obtained new visible spectra for eighteen E-type asteroids, and near infrared spectra for eight of them. We confirm the presence of three different mineralogies in the small E-type populations. We classify each object in the E[I], E[II] or E[III] subgroups [Gaffey, M.J., Kelley, M.S., 2004. Lunar Planet. Sci. XXXV. Abstract 1812] on the basis of the spectral behavior and of the eventual presence of absorption features attributed to sulfides (such the 0.49 ?m band, on E[II]), or to iron bearing silicates (0.9 ?m band, on E[III]). We suggest that some asteroids (i.e. 64 Angelina, 317 Roxane, and 434 Hungaria), which show different spectral behavior comparing our data with those available in literature, have an inhomogeneous surface composition. 2867 Steins, a target of the Rosetta mission, shows a spectral behavior typical of the E[II] subgroup, as already suggested by Barucci et al. [Barucci, M.A., Fulchignoni, M., Fornasier, S., Dotto, E., Vernazza, P., Birlan, M., Binzel, R.P., Carvano, J., Merlin, F., Barbieri, C., Belskaya, I., 2005. Astron. Astrophys. 430, 313-317] and Fornasier et al. [Fornasier, S., Marzari, F., Dotto, E., Barucci, M.A., Migliorini, A., 2007. Astron. Astrophys. 474, 29-32]. Litva and 1990 TN1, initially classified as E-types, show a visible and near infrared behavior consistent with the olivine rich A-class asteroids, while 5806 Archieroy, also supposed to belong to the E-class, has a spectral behavior consistent with the S(V) classification following the Gaffey et al. [Gaffey, M.J., Burbine, T.H., Piatek, J.L., Reed, K.L., Chaky, D.A., Bell, J.F., Brown, R.H., 1993. Icarus 106, 573-602] classification scheme. To fully investigate the E-type population, we enlarged our sample including 6 E-type asteroids spectra available in literature, resulting in a total sample of 21 objects. The analysis of the spectral slope for the 3 different E-type subgroups versus the orbital elements show that E[III] members have the lowest mean spectral slope value inside the whole sample, and that they are located between 2.2-2.7 AU in low inclination orbits. E[II] members has the highest spectral slope inside the sample, half of them are located in the Hungaria region, 2 are NEA and 2 (64 Angelina and 2867 Steins), are in the main belt. A similar distribution is found for the 5 featureless E[I] members, located mainly in the Hungaria region (3 members), one in the middle main belt while one is a NEA (2004 VD17). Finally, for the five E-type asteroids observed both in the visible and near infrared range, plus 2867 Steins, we attempt to model their surface composition using linear geographical mixtures of no more than 3 components, selected from aubrite meteorites and correlated minerals. In particular we suggest that the aubrite Peña Blanca might have the E[III] Asteroid 317 Roxane as parent body, and that the aubrite ALH78113 might be related to the E[II] subgroup asteroids.

Fornasier, S.; Migliorini, A.; Dotto, E.; Barucci, M. A.

2008-07-01

 
 
 
 
361

NITRATE DETERMINATION IN CHILEAN CALICHE SAMPLES BY UV-VISIBLE ABSORBANCE MEASUREMENTS AND MULTIVARIATE CALIBRARON  

Directory of Open Access Journals (Sweden)

Full Text Available Multivariate calibration of UV-visible spectral data using partial least-squares (PLS) has been applied to the determination of the nitrate content in Chilean Caliche samples, in the concentration range from 1 to 20% NaNO3 The multivariate approach is required since the samples do also contain unknown interferences which are spectrally active in the useful wavelength region for nitrate quantitation (near 301 nm). A set of fifteen calibration samples was employed to build the multivariate model, selected using the Kennard-Stone methodology, starting from real Caliche samples whose nitrate content was previously determined using the reference Devarda method. The figures of merit of the multivariate model were satisfactory (the limit of detection and quantitation reached 0.04% and 0.12 % of NaNO3, respectively, with an average error of prediction of 0.3 % of NaNO3). Then, the PLS model was then applied to a set of independent Caliche samples. The results were compared with a univariate UV approach, and with the nitrate content determined by the reference method, using the linear regression of predicted vs. reference concentration values, together with the elliptical joint confidence region test for the slope and intercept of the latter regression. The results indícate that the univariate method is unsuitable for analyzing the presently studied samples, unlike the multivariate model. Finally, the analytical methodology proposed appears as reliable and cheap alternative for routine analysis of a large number of caliche samples.

MANUEL BRAVO; ALEJANDRO C OLWIERT; BEATRIZ OELCKERS

2009-01-01

362

Visible persistence in paranoid schizophrenics.  

UK PubMed Central (United Kingdom)

A visual temporal integration (i.e., visible persistence) task was performed by normal controls and paranoid schizophrenics. The task evaluated the critical duration (CD), which approximates the duration of peripheral persistence duration and post-CD persistence, which is possibly more associated with central processes. Subjects were required to report when temporally modulated spatial frequency patterns, which are known to have characteristic temporal processing rates, were pulsing "on-off" with a distinct "off" period. The dependent measure was the duration of visible persistence. An analysis of groups X spatial frequency duration (50, 75, 150, 300 msec) X spatial frequency (high, medium, low), with repeated measures on the last two variables, revealed that the second-order interaction was significant (p less than 0.05). Schizophrenics had shorter visible persistence only for the 300-msec presentation for the high spatial frequency pattern. Also, the CD of schizophrenics did not conform to the duration of normals on the high spatial frequency. The results are discussed in terms of the role high spatial frequencies plays in visual information processing and how shorter visible persistence by paranoid schizophrenics may reflect a premature termination of information necessary for synthesis into accurate percepts.

Schwartz BD; Winstead DK

1988-01-01

363

Titanium nitride as a plasmonic material for visible wavelengths  

CERN Multimedia

The search for alternative plasmonic materials with improved optical properties over the traditional materials like silver and gold could ultimately lead to the long-awaited, real-life applications of plasmonic devices and metamaterials. In this work, we show that titanium nitride could perform as an alternative plasmonic material in the visible wavelength range. We evaluate the performances of various plasmonic and metamaterial structures with titanium nitride as a plasmonic component and show that transformation-optics devices and an important class of metamaterials with hyperbolic dispersion based on TiN could significantly outperform similar devices based on conventional metals in the visible wavelengths range.

Naik, Gururaj V; Sands, Timothy D; Boltasseva, Alexandra

2010-01-01

364

SOURCE DETECTION IN INTERFEROMETRIC VISIBILITY DATA. I. FUNDAMENTAL ESTIMATION LIMITS  

International Nuclear Information System (INIS)

Transient radio signals of astrophysical origin present an avenue for studying the dynamic universe. With the next generation of radio interferometers being planned and built, there is great potential for detecting and studying large samples of radio transients. Currently used image-based techniques for detecting radio sources have not been demonstrated to be optimal, and there is a need for development of more sophisticated algorithms and methodology for comparing different detection techniques. A visibility-space detector benefits from our good understanding of visibility-space noise properties and does not suffer from the image artifacts and need for deconvolution in image-space detectors. In this paper, we propose a method for designing optimal source detectors using visibility data, building on statistical decision theory. The approach is substantially different to conventional radio astronomy source detection. Optimal detection requires an accurate model for the data, and we present a realistic model for the likelihood function of radio interferometric data, including the effects of calibration, signal confusion, and atmospheric phase fluctuations. As part of this process, we derive fundamental limits on the calibration of an interferometric array, including the case where many relatively weak 'in-beam' calibrators are used. These limits are then applied, along with a model for atmospheric phase fluctuations, to determine the limits on measuring source position, flux density, and spectral index, in the general case. We then present an optimal visibility-space detector using realistic models for an interferometer.

2011-04-20

365

Visible light emission and control by infrared-responsive materials  

Science.gov (United States)

Upconversion characteristics of rare-earth cations were utilized for emitting or controlling visible light with infrared light. A fluorescent glass rod was fabricated by using durable AlF3-based glass that contained high-concentration Er3+ cations. This glass rod acted as a two-way wavelength converter; i.e., visible light (~500 nm) was converted to infrared light (~800 nm) as it passed through the glass, and infrared light that propagated in the opposite direction was converted to visible light. An infrared-responsive photochromic compound was fabricated by dispersing spirobenzopyran and upconversion powder (Gd2O2S:Yb3+Er 3+) in photocurable acrylate. When this compound was exposed to ultraviolet light (~370 nm), a strong absorption band appeared in the visible spectral region due to photochromic isomerization of spirobenzopyran. This absorption band disappeared by irradiation of a 940-nm laser beam, since the upconversion powder emitted green light that caused bleaching of colored spirobenzopyran.

Saito, Mitsunori; Takahashi, Yoshinori; Matsuda, Kei; Yamazaki, Masaaki; Sawanobori, Naruhito

2008-11-01

366

New observation strategies for the solar UV spectral irradiance  

Directory of Open Access Journals (Sweden)

Full Text Available Many applications in space weather and in space situational awareness require continuous solar spectral irradiance measurements in the UV, and to a lesser degree in the visible band. Most space-borne solar radiometers are made out of two different parts: (i) a front filter that selects the passband and (ii) a detector that is usually based on silicon technology. Both are prone to degradation, which may be caused either by the degradation of the filter coating due to local deposition or to structural changes, or by the degradation of the silicon detector by solar radiative and energetic particle fluxes. In this study, we provide a theoretical analysis of the filter degradation that is caused by structural changes such as pinholes; contamination-induced degradation will not be considered. We then propose a new instrumental concept, which is expected to overcome, at least partially, these problems. We show how most of the solar UV spectrum can be reconstructed from the measurement of only five spectral bands. This instrumental concept outperforms present spectrometers in terms of degradation. This new concept in addition overcomes the need for silicon-based detectors, which are replaced by wide band gap material detectors. Front filters, which can contribute to in-flight degradation, therefore are not required, except for the extreme-UV (EUV) range. With a small weight and a low telemetry, this concept may also have applications in solar physics, in astrophysics and in planetology.

Cessateur Gaël; Lilensten Jean; Dudok de Wit Thierry; BenMoussa Ali; Kretzschmar Matthieu

2012-01-01

367

Visibility graph approach to the analysis of ocean tidal records  

International Nuclear Information System (INIS)

[en] By using the recent method of the visibility graph, three time series of oceanic tide level in central Argentina were investigated. The degree distributions show a rich structure; in particular the maximum is due to the main periodic oscillations at 24 hours and 12 hours and higher harmonics. The degree distributions of the residuals (obtained removing from the original signals the cyclic components) suggest that the local effects, linked with the particular coastal conditions of the sites, are discernible for the degree k 100. Although a relationship between the spectral exponent ? and the exponent of the degree distribution ? of tidal signals can be recognized, this cannot be simply stated due to the very rich and complex structure of time dynamics of tides. The present study, even if still preliminary, show the importance of the visibility graph method in investigating the complex time dynamics of observational and experimental signals.

2012-01-01

368

Huanglongbing (citrus greening) detection using visible, near infrared and thermal imaging techniques.  

UK PubMed Central (United Kingdom)

This study demonstrates the applicability of visible-near infrared and thermal imaging for detection of Huanglongbing (HLB) disease in citrus trees. Visible-near infrared (440-900 nm) and thermal infrared spectral reflectance data were collected from individual healthy and HLB-infected trees. Data analysis revealed that the average reflectance values of the healthy trees in the visible region were lower than those in the near infrared region, while the opposite was the case for HLB-infected trees. Moreover, 560 nm, 710 nm, and thermal band showed maximum class separability between healthy and HLB-infected groups among the evaluated visible-infrared bands. Similarly, analysis of several vegetation indices indicated that the normalized difference vegetation index (NDVI), Vogelmann red-edge index (VOG) and modified red-edge simple ratio (mSR) demonstrated good class separability between the two groups. Classification studies using average spectral reflectance values from the visible, near infrared, and thermal bands (13 spectral features) as input features indicated that an average overall classification accuracy of about 87%, with 89% specificity and 85% sensitivity could be achieved with classification models such as support vector machine for trees with symptomatic leaves.

Sankaran S; Maja JM; Buchanon S; Ehsani R

2013-01-01

369

Huanglongbing (Citrus Greening) Detection Using Visible, Near Infrared and Thermal Imaging Techniques  

Directory of Open Access Journals (Sweden)

Full Text Available This study demonstrates the applicability of visible-near infrared and thermal imaging for detection of Huanglongbing (HLB) disease in citrus trees. Visible-near infrared (440–900 nm) and thermal infrared spectral reflectance data were collected from individual healthy and HLB-infected trees. Data analysis revealed that the average reflectance values of the healthy trees in the visible region were lower than those in the near infrared region, while the opposite was the case for HLB-infected trees. Moreover, 560 nm, 710 nm, and thermal band showed maximum class separability between healthy and HLB-infected groups among the evaluated visible-infrared bands. Similarly, analysis of several vegetation indices indicated that the normalized difference vegetation index (NDVI), Vogelmann red-edge index (VOG) and modified red-edge simple ratio (mSR) demonstrated good class separability between the two groups. Classification studies using average spectral reflectance values from the visible, near infrared, and thermal bands (13 spectral features) as input features indicated that an average overall classification accuracy of about 87%, with 89% specificity and 85% sensitivity could be achieved with classification models such as support vector machine for trees with symptomatic leaves.

Sindhuja Sankaran; Joe Mari Maja; Sherrie Buchanon; Reza Ehsani

2013-01-01

370

Huanglongbing (citrus greening) detection using visible, near infrared and thermal imaging techniques.  

Science.gov (United States)

This study demonstrates the applicability of visible-near infrared and thermal imaging for detection of Huanglongbing (HLB) disease in citrus trees. Visible-near infrared (440-900 nm) and thermal infrared spectral reflectance data were collected from individual healthy and HLB-infected trees. Data analysis revealed that the average reflectance values of the healthy trees in the visible region were lower than those in the near infrared region, while the opposite was the case for HLB-infected trees. Moreover, 560 nm, 710 nm, and thermal band showed maximum class separability between healthy and HLB-infected groups among the evaluated visible-infrared bands. Similarly, analysis of several vegetation indices indicated that the normalized difference vegetation index (NDVI), Vogelmann red-edge index (VOG) and modified red-edge simple ratio (mSR) demonstrated good class separability between the two groups. Classification studies using average spectral reflectance values from the visible, near infrared, and thermal bands (13 spectral features) as input features indicated that an average overall classification accuracy of about 87%, with 89% specificity and 85% sensitivity could be achieved with classification models such as support vector machine for trees with symptomatic leaves. PMID:23389343

Sankaran, Sindhuja; Maja, Joe Mari; Buchanon, Sherrie; Ehsani, Reza

2013-02-06

371

Visible Earth: Volcanoes and Lava  

Science.gov (United States)

This webpage is part of NASA's Visible Earth, a searchable directory of images, visualizations, and animations of Earth. It features remotely sensed imagery of volcanic eruptions that display smoke plumes, lava flows, fires, and other eruptive features. Each image is accompanied by a caption describing the subject being illustrated and the satellite or instrument which captured the image. Files are in either TIFF, GIF, or JPEG formats.

372

Ultraviolet-visible absorptive features of water extractable and humic fractions of animal manure and compost  

Science.gov (United States)

UV-vis spectroscopy is a useful tool for characterizing water extractable or humic fractions of natural organic matter (WEOM). Whereas the whole UV-visible spectra of these fractions are more or less featureless, the specific UV absorptivity at 254 and 280 nm as well as spectral E2/E3 and E4/E6 rat...

373

Structural, vibrational, electronic and NMR spectral analysis of 3-chloro-6-methoxypyridazine by DFT calculations.  

UK PubMed Central (United Kingdom)

In this work, the FT-Raman and FT-Infrared spectra of 3-chloro-6-methoxypyridazine sample were measured to elucidate the spectroscopic properties of title molecule in the spectral range of 3500-50 cm(-1) and 4000-400 cm(-1), respectively. The molecular geometry and vibrational frequencies of 3-chloro-6-methoxypyridazine in the ground state were calculated using the DFT/B3LYP/6-31G(d),6-311G(d,p) level. The recorded FT-IR and FT-Raman spectral measurements favor the calculated structural parameters which are further supported by spectral simulation. The difference between the observed and scaled wavenumber values of most of the fundamentals is very small. The UV-Visible absorption spectrum of the compound that dissolved in methanol was recorded in the range of 800-200 nm. The formation of hydrogen bond and the most possible interaction are explained using natural bond orbital (NBO) analysis. The isotropic chemical shift computed by (13)C and (1)H NMR analysis also shows good agreement with experimental observations. In addition, the molecular electrostatic potential (MEP) and frontier molecular orbitals (FMOs) analysis of the title compound were investigated using theoretical calculations.

Vijaya Chamundeeswari SP; James Jebaseelan Samuel E; Sundaraganesan N

2013-06-01

374

Results of first experiments with using of a visible-near IR endoscope on the T-10 tokamak  

International Nuclear Information System (INIS)

[en] The work is devoted to the design and parameters of a visible - near IR endoscope, that has been recently installed on the T-10 tokamak. The arrangement of the instrument enables tangential observation of the cross-section, where the carbon limiters of the machine are situated. With use of the endoscope the following measurements of the space distribution of radiation intensity at different spectral regions are carried out: at the H?, H?, and CVI (529 nm) lines, at the Bremsstrahlung window 523,0 to 524,2 nm, at the range of 700 ± 5 nm (hydrogen molecular lines), and at the near IR region[ru] ????????? ???????? ??????????? ? ????????? ????????? ??? ??????? ? ??????? ?? ???????? ???????, ?????????????? ??????? ?? ???????? ?-10. ???????? ???????????? ?????????????? ?????????? ???????, ? ??????? ??????????? ?????????? ???????? ?????????. ??? ?????? ????????? ????????? ????????? ????????????????? ????????????? ????????? ??? ????????? ???????? ???????, ? ??????: ?? ?????? ??, ??, CVI (529 ??), ? ???? ?????????? ?????????? (523,0 - 524,2 ??), ? ????????? 700 ± 5 ??, ??? ???????????? ??????? ?????????? ????? ????????????? ????????, ? ????? ? ??????? ??-?????????

2007-01-01

375

Visible light photocatalytic activity in nitrogen-doped TiO2 nanobelts  

International Nuclear Information System (INIS)

We present a comprehensive experimental and theoretical study of the electronic properties and photocatalytic activity of nitrogen-doped anatase TiO2 nanobelts. UV-visible spectra show enhanced absorption in the visible light range for nitrogen-doped nanobelts compared to the pristine sample. The nitrogen-doped nanobelts exhibit improved photocatalytic activity compared to the pristine sample upon visible light irradiation. Furthermore, the incorporation of nitrogen introduces localized states in the band gap.

2009-03-02

376

The Spectral Shift Operator  

CERN Multimedia

We introduce the concept of a spectral shift operator and use it to derive Krein's spectral shift function for pairs of self-adjoint operators. Our principal tools are operator-valued Herglotz functions and their logarithms. Applications to Krein's trace formula and to the Birman-Solomyak spectral averaging formula are discussed.

Gesztesy, F; Naboko, S N; Gesztesy, Fritz; Makarov, Konstantin A.; Naboko, Serguei N.

1999-01-01

377

On spectral Cantor measures  

CERN Document Server

A probability measure in R^d is called a spectral measure if it has an orthonormal basis consisting of exponentials. In this paper we study spectral Cantor measures. We establish a large class of such measures and give a necessary and sufficient condition on the spectrum of a spectral Cantor measure. This extends the earlier results of Jorgensen-Pedersen and Strichartz.

Laba, I; Laba, Izabella; Wang, Yang

2001-01-01

378

New observation strategies for the solar UV spectral irradiance  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Many applications in space weather and in space situational awareness require continuous solar spectral irradiance measurements in the UV, and to a lesser degree in the visible band. Most space-borne solar radiometers are made out of two different parts: (i) a front filter that selects the passband...

Cessateur Gaël; Lilensten Jean; Dudok de Wit Thierry; BenMoussa Ali; Kretzschmar Matthieu

379

Spectral properties of nine M-type asteroids  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Aims. We present spectroscopic results for nine M-type asteroids (325 Heidelberga, 497 Iva, 558 Carmen, 687 Tinette, 766 Moguntia, 860 Ursina, 909 Ulla, 1280 Baillauda, and 1564 Srbija) in the 0.8?2.5 ?m spectral region. One visible spectrum is also presented for the asteroid 497 Iva. These asteroid...

Birlan, Mirel; Vernazza, Pierre; Nedelcu, Dan Alin

380

A samplin approach for predicting the eating quality of apples using visible - near infrared spectroscopy  

DEFF Research Database (Denmark)

BACKGROUND Visible–near infrared spectroscopy remains a method of increasing interest as a fast alternative for the evaluation of fruit quality. The success of the method is assumed to be achieved by using large sets of samples to produce robust calibration models. In this study we used representative samples of an early and a late season apple cultivar to evaluate model robustness (in terms of prediction ability and error) on the soluble solids content (SSC) and acidity prediction, in the wavelength range 400–1100?nm. RESULTS A total of 196 middle–early season and 219 late season apples (Malus domestica Borkh.) cvs ‘Aroma’ and ‘Holsteiner Cox’ samples were used to construct spectral models for SSC and acidity. Partial least squares (PLS), ridge regression (RR) and elastic net (EN) models were used to build prediction models. Furthermore, we compared three sub-sample arrangements for forming training and test sets (‘smooth fractionator’, by date of measurement after harvest and random). Using the ‘smooth fractionator’ sampling method, fewer spectral bands (26) and elastic net resulted in improved performance for SSC models of ‘Aroma’ apples, with a coefficient of variation CVSSC = 13%. The model showed consistently low errors and bias (PLS/EN: R2cal?=?0.60/0.60; SEC = 0.88/0.88°Brix; Biascal?=?0.00/0.00; R2val?=?0.33/0.44; SEP = 1.14/1.03; Biasval?=?0.04/0.03). However, the prediction acidity and for SSC (CV = 5%) of the late cultivar ‘Holsteiner Cox’ produced inferior results as compared with ‘Aroma’. CONCLUSION It was possible to construct local SSC and acidity calibration models for early season apple cultivars with CVs of SSC and acidity around 10%. The overall model performance of these data sets also depend on the proper selection of training and test sets. The ‘smooth fractionator’ protocol provided an objective method for obtaining training and test sets that capture the existing variability of the fruit samples for construction of visible–NIR prediction models. The implication is that by using such ‘efficient’ sampling methods for obtaining an initial sample of fruit that represents the variability of the population and for sub-sampling to form training and test sets it should be possible to use relatively small sample sizes to develop spectral predictions of fruit quality. Using feature selection and elastic net appears to improve the SSC model performance in terms of R2, RMSECV and RMSEP for ‘Aroma’ apples. © 2013 Society of Chemical Industry

Martinez Vega, Mabel Virginia; Sharifzadeh, Sara

2013-01-01

 
 
 
 
381

A sampling approach for predicting the eating quality of apples using visible - near infrared spectroscopy  

DEFF Research Database (Denmark)

BACKGROUND Visible–near infrared spectroscopy remains a method of increasing interest as a fast alternative for the evaluation of fruit quality. The success of the method is assumed to be achieved by using large sets of samples to produce robust calibration models. In this study we used representative samples of an early and a late season apple cultivar to evaluate model robustness (in terms of prediction ability and error) on the soluble solids content (SSC) and acidity prediction, in the wavelength range 400–1100?nm. RESULTS A total of 196 middle–early season and 219 late season apples (Malus domestica Borkh.) cvs ‘Aroma’ and ‘Holsteiner Cox’ samples were used to construct spectral models for SSC and acidity. Partial least squares (PLS), ridge regression (RR) and elastic net (EN) models were used to build prediction models. Furthermore, we compared three sub-sample arrangements for forming training and test sets (‘smooth fractionator’, by date of measurement after harvest and random). Using the ‘smooth fractionator’ sampling method, fewer spectral bands (26) and elastic net resulted in improved performance for SSC models of ‘Aroma’ apples, with a coefficient of variation CVSSC = 13%. The model showed consistently low errors and bias (PLS/EN: R2cal?=?0.60/0.60; SEC = 0.88/0.88°Brix; Biascal?=?0.00/0.00; R2val?=?0.33/0.44; SEP = 1.14/1.03; Biasval?=?0.04/0.03). However, the prediction acidity and for SSC (CV = 5%) of the late cultivar ‘Holsteiner Cox’ produced inferior results as compared with ‘Aroma’. CONCLUSION It was possible to construct local SSC and acidity calibration models for early season apple cultivars with CVs of SSC and acidity around 10%. The overall model performance of these data sets also depend on the proper selection of training and test sets. The ‘smooth fractionator’ protocol provided an objective method for obtaining training and test sets that capture the existing variability of the fruit samples for construction of visible–NIR prediction models. The implication is that by using such ‘efficient’ sampling methods for obtaining an initial sample of fruit that represents the variability of the population and for sub-sampling to form training and test sets it should be possible to use relatively small sample sizes to develop spectral predictions of fruit quality. Using feature selection and elastic net appears to improve the SSC model performance in terms of R2, RMSECV and RMSEP for ‘Aroma’ apples. © 2013 Society of Chemical Industry

Martinez Vega, Mabel Virginia; Sharifzadeh, Sara

2013-01-01

382

Evaluations of particulate mass loading from visibility observations and atmospheric turbidity measurements: Pt. 1  

International Nuclear Information System (INIS)

Two extinction models for continental and rural particles were defined by using a very accurate computer programme based on Mie extinction theory for spherical particles. The first extinction model gives several sets of volume extinction coefficients at seven visible and near-infra-red wave-lengths, calculated for twenty-seven Junge-type size distribution curves (with Junge parameter ranging from 1.8 to 4.4) and for eight relative-humidity values of the air. This model also gives the corresponding values of Aangstroem's exponent ? and mean particle mass. The second extinction model gives similar sets of data, calculated for two log-normal size distribution curves of tropospheric and large rural particles at five relative-humidity values of the air. These monomodal models can be used to determine bimodal extinction models consisting of variable number fractions of tropospherics and rural particles. Evaluations of the particulate mass loading can be obtained from measurements of visual range and atmospheric turbidity, choosing the most appropriate extinction model on the basis of the spectral features characterizing atmospheric attenuation. Measurements of visibility and atmospheric turbidity in two rural localities of the Po valley were examined by employing both the present extinction models and other extinction models commonly used. The comparison of the results shows that the Junge-type extinction model can be reliably used in cases in which the exponent Junge-type extinction model and bimodal model were found to give realistic evaluations of the lower and upper limits of particulate mass loading.

1984-01-01

383

The Deep SPIRE HerMES Survey: Spectral Energy Distributions and their Astrophysical Indications at High Redshift  

CERN Document Server

The Spectral and Photometric Imaging Receiver (SPIRE) on Herschel has been carrying out deep extragalactic surveys, one of whose aims is to establish spectral energy distributions (SED)s of individual galaxies spanning the infrared/submillimeter (IR/SMM) wavelength region. We report observations of the (IR/SMM) emission from the Lockman North field (LN) and Great Observatories Origins Deep Survey field North (GOODS-N). Because galaxy images in the wavelength range covered by Herschel generally represent a blend with contributions from neighboring galaxies, we present sets of galaxies in each field especially free of blending at 250, 350, and 500 microns. We identify the cumulative emission of these galaxies and the fraction of the far infrared cosmic background radiation they contribute. Our surveys reveal a number of highly luminous galaxies at redshift z �< 3 and a novel relationship between infrared and visible emission that shows a dependence on luminosity and redshift.

Brisbin, D; Altieri, B; Amblard, A; Arumugam, V; Aussel, H; Babbedge, T; Blain, A; Bock, J; Boselli, A; Buat, V; Castro-Rodríguez, N; Cava, A; Chanial, P; Clements, D L; Conley, A; Conversi, L; Cooray, A; Dowell, C D; Dwek, E; Eales, S; Elbaz, D; Fox, M; Franceschini, A; Gear, W; Glenn, J; Griffin, M; Halpern, M; Hatziminaoglou, E; Ibar, E; Isaak, K; Ivison, R J; Lagache, G; Levenson, L; Lonsdale, Carol J; Lu, N; Madden, S; Maï¬?ei, B; Mainetti, G; Marchetti, L; Morrison, G E; Nguyen, H T; Oâ??Halloran, B; Oliver, S J; Omont, A; Owen, F N; Pannella, M; Panuzzo, P; Papageorgiou, A; Pearson, C P; Pérez-Fournon, I; Pohlen, M; Rizzo, D; Roseboom, I G; Rowan-Robinson, M; Portal, M Sánchez; Schulz, B; Seymour, N; Shupe, D L; Smith, A J; Stevens, J A; Strazzullo, V; Symeonidis, M; Trichas, M; Tugwell, K E; Vaccari, M; Valtchanov, I; Vigroux, L; Wang, L; Ward, R; Wright, G; Xu, C K; Zemcov, M

2010-01-01

384

Stand for power calibration of radiometers at the wavelength range of 0.35-2.5 microns  

International Nuclear Information System (INIS)

[en] The stand for power calibration of radiometers for remote sounding in the wavelength range of 0.35-2.5 ?m with model means of measurement of power brightness spectral density is described. Main principles of such stand where the diffusely scattering extensive source brightness is determined by the method of comparison with model measurement means are given. Errors of matching the output parameters of calibration stand radiation to radiative scale does not exceed 4% in visible and near infrared radiation spectrum attaining 7% at the 0.35 ?m wavelength

1980-01-01

385

Multidimensional spectral load balancing  

Energy Technology Data Exchange (ETDEWEB)

We describe an algorithm for the static load balancing of scientific computations that generalizes and improves upon spectral bisection. Through a novel use of multiple eigenvectors, our new spectral algorithm can divide a computation into 4 or 8 pieces at once. These multidimensional spectral partitioning algorithms generate balanced partitions that have lower communication overhead and are less expensive to compute than those produced by spectral bisection. In addition, they automatically work to minimize message contention on a hypercube or mesh architecture. These spectral partitions are further improved by a multidimensional generalization of the Kernighan-Lin graph partitioning algorithm. Results on several computational grids are given and compared with other popular methods.

Hendrickson, B.; Leland, R.

1993-01-01

386

Spectral reflectance measurements in the genus Sphagnum  

Energy Technology Data Exchange (ETDEWEB)

High-spectral resolution reflectance data were acquired in the laboratory for four species of Sphagnum (peat moss): S. cuspidatum, S. papillosum, S. fallax, and S. capillifolium. All four species had different spectral reflectance properties. Species differences were noted especially in the visible portion of the spectrum from 0.45 [mu]m to 0.70 [mu]m; some major spectral differences were also noted in the near infrared. Samples analyzed had much lower reflectance than typical green vegetation in the midinfrared region of the spectrum from 1.30 [mu]m to 2.40 [mu]m. In addition, Sphagnum had very pronounced water-related absorption features at about 1.00m [mu] and 1.20 [mu]m, unlike typical green vegetation. Spectral data acquired as samples were dried indicated large spectral increases with increasing dryness, especially in the midinfrared. Simulated Landsat Thematic Mapper 5/4 band ratio data were linearly related to the log of wet weight/dry weight. Reflectance from vegetation in the midinfrared region of the electromagnetic spectrum is strongly modified by water content. Peatlands are major sources of global methane and it has been found that methane evolution within these peatlands is related to water status within these peatlands is related to water status within the wetland. It may be possible to indirectly estimate methane flux using remote sensing data.

Vogelmann, J.E.; Moss, D.M. (Univ. of New Hampshire, Durham, NH (United States). Complex Systems/Institute for the Study of Earth Oceans and Space)

1993-09-01

387

Macroscopic invisibility cloak for visible light.  

UK PubMed Central (United Kingdom)

Invisibility cloaks, a subject that usually occurs in science fiction and myths, have attracted wide interest recently because of their possible realization. The biggest challenge to true invisibility is known to be the cloaking of a macroscopic object in the broad range of wavelengths visible to the human eye. Here we experimentally solve this problem by incorporating the principle of transformation optics into a conventional optical lens fabrication with low-cost materials and simple manufacturing techniques. A transparent cloak made of two pieces of calcite is created. This cloak is able to conceal a macroscopic object with a maximum height of 2 mm, larger than 3500 free-space-wavelength, inside a transparent liquid environment. Its working bandwidth encompassing red, green, and blue light is also demonstrated.

Zhang B; Luo Y; Liu X; Barbastathis G

2011-01-01

388

Macroscopic Invisible Cloak for Visible Light  

CERN Multimedia

Invisibility cloaks, a subject that usually occurs in science fiction and myths, have attracted wide interest recently because of their possible realization. The biggest challenge to true invisibility is known to be the cloaking of a macroscopic object in the broad range of wavelengths visible to the human eye. Here we experimentally solve this problem by incorporating the principle of transformation optics into a conventional optical lens fabrication with low-cost materials and simple manufacturing techniques. A transparent cloak made of two pieces of calcite is created. This cloak is able to conceal a macroscopic object with a maximum height of 2 mm, larger than 3500 free-space-wavelength, inside a transparent liquid environment. Its working bandwidth encompassing red, green and blue light is also demonstrated.

Zhang, Baile; Liu, Xiaogang; Barbastathis, George

2011-01-01

389

Nanoantennas for visible and infrared radiation  

CERN Document Server

Nanoantennas for visible and infrared radiation can strongly enhance the interaction of light with nanoscale matter by their ability to efficiently link propagating and spatially localized optical fields. This ability unlocks an enormous potential for applications ranging from nanoscale optical microscopy and spectroscopy over solar energy conversion, integrated optical nanocircuitry, opto-electronics and density-ofstates engineering to ultra-sensing as well as enhancement of optical nonlinearities. Here we review the current understanding of optical antennas based on the background of both well-developed radiowave antenna engineering and the emerging field of plasmonics. In particular, we address the plasmonic behavior that emerges due to the very high optical frequencies involved and the limitations in the choice of antenna materials and geometrical parameters imposed by nanofabrication. Finally, we give a brief account of the current status of the field and the major established and emerging lines of inves...

Biagioni, Paolo; Hecht, Bert

2011-01-01

390

Near-infrared interferometry of ? Carinae with spectral resolutions of 1 500 and 12 000 using AMBER/VLTI  

Science.gov (United States)

Aims: We present the first NIR spectro-interferometry of the LBV ? Carinae. The observations were performed with the AMBER instrument of the ESO Very Large Telescope Interferometer (VLTI) using baselines from 42 to 89 m. The aim of this work is to study the wavelength dependence of ? Car's optically thick wind region with a high spatial resolution of 5 mas (11 AU) and high spectral resolution. Methods: The observations were carried out with three 8.2 m Unit Telescopes in the K-band. The raw data are spectrally dispersed interferograms obtained with spectral resolutions of 1500 (MR-K mode) and 12 000 (HR-K mode). The MR-K observations were performed in the wavelength range around both the He I 2.059 ?m and the Br? 2.166 ?m emission lines, the HR-K observations only in the Br? line region. Results: The spectrally dispersed AMBER interferograms allow the investigation of the wavelength dependence of the visibility, differential phase, and closure phase of ? Car. In the K-band continuum, a diameter of 4.0±0.2 mas (Gaussian FWHM, fit range 28-89 m baseline length) was measured for ? Car's optically thick wind region. If we fit Hillier et al. (2001, ApJ, 553, 837) model visibilities to the observed AMBER visibilities, we obtain 50% encircled-energy diameters of 4.2, 6.5 and 9.6 mas in the 2.17 ?m continuum, the He I, and the Br? emission lines, respectively. In the continuum near the Br? line, an elongation along a position angle of 120°±15° was found, consistent with previous VINCI/VLTI measurements by van Boekel et al. (2003, A&A, 410, L37). We compare the measured visibilities with predictions of the radiative transfer model of Hillier et al. (2001), finding good agreement. Furthermore, we discuss the detectability of the hypothetical hot binary companion. For the interpretation of the non-zero differential and closure phases measured within the Br? line, we present a simple geometric model of an inclined, latitude-dependent wind zone. Our observations support theoretical models of anisotropic winds from fast-rotating, luminous hot stars with enhanced high-velocity mass loss near the polar regions. Based on observations collected at the European Southern Observatory, Paranal, Chile, within the AMBER guaranteed time programme 074.A-9025 and the VLTI science demonstration programme 074.A-9024.

Weigelt, G.; Kraus, S.; Driebe, T.; Petrov, R. G.; Hofmann, K.-H.; Millour, F.; Chesneau, O.; Schertl, D.; Malbet, F.; Hillier, J. D.; Gull, T.; Davidson, K.; Domiciano de Souza, A.; Antonelli, P.; Beckmann, U.; Bresson, Y.; Chelli, A.; Dugué, M.; Duvert, G.; Gennari, S.; Glück, L.; Kern, P.; Lagarde, S.; Le Coarer, E.; Lisi, F.; Perraut, K.; Puget, P.; Rantakyrö, F.; Robbe-Dubois, S.; Roussel, A.; Tatulli, E.; Zins, G.; Accardo, M.; Acke, B.; Agabi, K.; Altariba, E.; Arezki, B.; Aristidi, E.; Baffa, C.; Behrend, J.; Blöcker, T.; Bonhomme, S.; Busoni, S.; Cassaing, F.; Clausse, J.-M.; Colin, J.; Connot, C.; Delboulbé, A.; Feautrier, P.; Ferruzzi, D.; Forveille, T.; Fossat, E.; Foy, R.; Fraix-Burnet, D.; Gallardo, A.; Giani, E.; Gil, C.; Glentzlin, A.; Heiden, M.; Heininger, M.; Hernandez Utrera, O.; Kamm, D.; Kiekebusch, M.; Le Contel, D.; Le Contel, J.-M.; Lesourd, T.; Lopez, B.; Lopez, M.; Magnard, Y.; Marconi, A.; Mars, G.; Martinot-Lagarde, G.; Mathias, P.; Mège, P.; Monin, J.-L.; Mouillet, D.; Mourard, D.; Nussbaum, E.; Ohnaka, K.; Pacheco, J.; Perrier, C.; Rabbia, Y.; Rebattu, S.; Reynaud, F.; Richichi, A.; Robini, A.; Sacchettini, M.; Schöller, M.; Solscheid, W.; Spang, A.; Stee, P.; Stefanini, P.; Tallon, M.; Tallon-Bosc, I.; Tasso, D.; Testi, L.; Vakili, F.; von der Lühe, O.; Valtier, J.-C.; Vannier, M.; Ventura, N.; Weis, K.; Wittkowski, M.

2007-03-01

391

Enhancing optical absorption of metal-organic frameworks for improved visible light photocatalysis.  

UK PubMed Central (United Kingdom)

NH2-MIL-125(Ti) has been post-synthetically functionalized with dye-like molecular fragments. The new material (methyl red-MIL-125(Ti)) exhibits improved light absorption over a wide range of the visible spectrum, and shows enhanced photocatalytic oxidation activity under visible light illumination. The consequences of functionalization and the bottlenecks in MOF photochemistry are studied in detail.

Nasalevich MA; Goesten MG; Savenije TJ; Kapteijn F; Gascon J

2013-10-01

392

Spectral analysis of signals the missing data case  

CERN Multimedia

Spectral estimation is important in many fields including astronomy, meteorology, seismology, communications, economics, speech analysis, medical imaging, radar, sonar, and underwater acoustics. Most existing spectral estimation algorithms are devised for uniformly sampled complete-data sequences. However, the spectral estimation for data sequences with missing samples is also important in many applications ranging from astronomical time series analysis to synthetic aperture radar imaging with angular diversity. For spectral estimation in the missing-data case, the challenge is how to extend t

Wang, Yanwei

2006-01-01

393

Study on the visibility of an electroluminescent display for automobiles; Jidoshayo EL display no shininsei  

Energy Technology Data Exchange (ETDEWEB)

This report explores the visibility of an Electroluminescent (EL) display for automotive use. Displays for automobiles are exposed to the direct rays of the sun and forced to operate in wide temperature range. Therefore, luminous flux density by the lighting on EL display panel and operating environment temperature must be considered for the visibility evaluation. Sensory evaluation on the visibility and physical measurements such as contrast, chromaticity difference in accordance with the viewing angle change indicate that the visibility of the EL display for automobiles is advantageous over other displays. 6 refs., 11 figs., 1 tab.

Matsumoto, N.; Harada, M.; Idogaki, T. [Denso Corp., Aichi (Japan)

1997-10-01

394

Retrieval of spectral aerosol optical thickness over land using ocean color sensors MERIS and SeaWiFS  

Directory of Open Access Journals (Sweden)

Full Text Available For the determination of aerosol optical thickness (AOT) Bremen AErosol Retrieval (BAER) has been developed. Method and main features on the aerosol retrieval are described together with validation and results. The retrieval separates the spectral aerosol reflectance from surface and Rayleigh path reflectance for the shortwave range of the measured spectrum of top-of-atmosphere reflectance for wavelength less than 0.670 ?m. The advantage of MERIS (Medium Resolution Imaging Spectrometer on the Environmental Satellite – ENVISAT – of the European Space Agency – ESA) and SeaWiFS (Sea viewing Wide Field Sensor on OrbView-2 spacecraft) observations is the availability of several spectral channels in the blue and visible range enabling the spectral determination of AOT in 7 (or 6) channels (0.412–0.670 ?m) and additionally channels in the NIR, which can be used to characterize the surface properties. A dynamical spectral surface reflectance model for different surface types is used to obtain the spectral surface reflectance for this separation. The normalized differential vegetation index (NDVI), taken from the satellite observations, is the model input. Further surface bi-directional reflectance distribution function (BRDF) is considered by the Raman-Pinty-Verstraete (RPV) model. Spectral AOT is obtained from aerosol reflectance using look-up-tables, obtained from radiative transfer calculations with given aerosol phase functions and single scattering albedos either from aerosol models, given by model package "optical properties of aerosol components" (OPAC) or from experimental campaigns. Validations of the obtained AOT retrieval results with data of Aerosol Robotic Network (AERONET) over Europe gave a preference for experimental phase functions derived from almucantar measurements. Finally long-term observations of SeaWiFS have been investigated for 11 year trends in AOT. Western European regions have negative trends with decreasing AOT with time. For the investigated Asian region increasing AOT have been found.

W. von Hoyningen-Huene; J. Yoon; M. Vountas; L. G. Istomina; G. Rohen; T. Dinter; A. A. Kokhanovsky; J. P. Burrows

2011-01-01

395

Long-lived visible luminescence of UV LEDs and impact on LED excited time-resolved fluorescence applications  

Energy Technology Data Exchange (ETDEWEB)

We report the results of a detailed study of the spectral and temporal properties of visible emission from three different GaN-based ultraviolet (UV) light emitting diodes (UV LEDs). The primary UV emission in the 360-380 nm band decays rapidly (less than 1 {mu}s) following switch-off; however, visible luminescence (470-750 nm) with a decay lifetime of tens of microseconds was observed at approximately 10{sup -4} of the UV intensity. For applications of UV LEDs in time-resolved fluorescence (TRF) employing lanthanide chelates, the visible luminescence from the LEDs competes with the target Eu{sup 3+} or Tb{sup 3+} fluorescence in both spectral and temporal domains. A UV band-pass filter (Schott UG11 glass) was therefore used to reduce the visible luminescence of the UV LEDs by three orders of magnitude relative to UV output to yield a practical excitation source for TRF.

Jin, D; Connally, R; Piper, J [Centre for Lasers and Applications, Division of Information and Communication Sciences, Macquarie University, Sydney NSW 2109 (Australia)

2006-02-07

396