Laser-Induced Breakdown Spectroscopy: Capabilities and Applications

DTIC Science & Technology

2010-07-01

substances such as drugs, counterfeit goods, and laundered money . It may even be possible to pinpoint specific manufacturing facilities based on...point detection or standoff mode operation. LIBS used in conjunction with broadband detectors (ultraviolet [ UV ]-visible[VIS]-near-infrared[NIR] spectral...lines in the UV -VIS-NIR spectral range. Although most early LIBS applications involved metal targets, LIBS has recently been applied to a variety

Web-Resources for Astronomical Data in the Ultraviolet

NASA Astrophysics Data System (ADS)

Sachkov, M. E.; Malkov, O. Yu.

2017-12-01

In this paper we describe databases of space projects that are operating or have operated in the ultraviolet spectral region. We give brief descriptions and links to major sources for UV data on the web: archives, space mission sites, databases, catalogues. We pay special attention to the World Space Observatory—Ultraviolet mission that will be launched in 2021.

The MPI-Mainz UV/VIS Spectral Atlas of Gaseous Molecules of Atmospheric Interest

NASA Astrophysics Data System (ADS)

Keller-Rudek, H.; Moortgat, G. K.; Sander, R.; Sörensen, R.

2013-12-01

We present the MPI-Mainz UV/VIS Spectral Atlas of Gaseous Molecules, which is a large collection of absorption cross sections and quantum yields in the ultraviolet and visible (UV/VIS) wavelength region for gaseous molecules and radicals primarily of atmospheric interest. The data files contain results of individual measurements, covering research of almost a whole century. To compare and visualize the data sets, multicoloured graphical representations have been created. The MPI-Mainz UV/VIS Spectral Atlas is available on the Internet at http://www.uv-vis-spectral-atlas-mainz.org. It now appears with improved browse and search options, based on new database software. In addition to the Web pages, which are continuously updated, a frozen version of the data is available under the doi:10.5281/zenodo.6951.

The Space Weather and Ultraviolet Solar Variability (SWUSV) Microsatellite Mission

PubMed Central

Damé, Luc; Meftah, Mustapha; Hauchecorne, Alain; Keckhut, Philippe; Sarkissian, Alain; Marchand, Marion; Irbah, Abdenour; Quémerais, Éric; Bekki, Slimane; Foujols, Thomas; Kretzschmar, Matthieu; Cessateur, Gaël; Shapiro, Alexander; Schmutz, Werner; Kuzin, Sergey; Slemzin, Vladimir; Urnov, Alexander; Bogachev, Sergey; Merayo, José; Brauer, Peter; Tsinganos, Kanaris; Paschalis, Antonis; Mahrous, Ayman; Khaled, Safinaz; Ghitas, Ahmed; Marzouk, Besheir; Zaki, Amal; Hady, Ahmed A.; Kariyappa, Rangaiah

2013-01-01

We present the ambitions of the SWUSV (Space Weather and Ultraviolet Solar Variability) Microsatellite Mission that encompasses three major scientific objectives: (1) Space Weather including the prediction and detection of major eruptions and coronal mass ejections (Lyman-Alpha and Herzberg continuum imaging); (2) solar forcing on the climate through radiation and their interactions with the local stratosphere (UV spectral irradiance from 180 to 400 nm by bands of 20 nm, plus Lyman-Alpha and the CN bandhead); (3) simultaneous radiative budget of the Earth, UV to IR, with an accuracy better than 1% in differential. The paper briefly outlines the mission and describes the five proposed instruments of the model payload: SUAVE (Solar Ultraviolet Advanced Variability Experiment), an optimized telescope for FUV (Lyman-Alpha) and MUV (200–220 nm Herzberg continuum) imaging (sources of variability); UPR (Ultraviolet Passband Radiometers), with 64 UV filter radiometers; a vector magnetometer; thermal plasma measurements and Langmuir probes; and a total and spectral solar irradiance and Earth radiative budget ensemble (SERB, Solar irradiance & Earth Radiative Budget). SWUSV is proposed as a small mission to CNES and to ESA for a possible flight as early as 2017–2018. PMID:25685424

The Space Weather and Ultraviolet Solar Variability (SWUSV) Microsatellite Mission.

PubMed

Damé, Luc

2013-05-01

We present the ambitions of the SWUSV (Space Weather and Ultraviolet Solar Variability) Microsatellite Mission that encompasses three major scientific objectives: (1) Space Weather including the prediction and detection of major eruptions and coronal mass ejections (Lyman-Alpha and Herzberg continuum imaging); (2) solar forcing on the climate through radiation and their interactions with the local stratosphere (UV spectral irradiance from 180 to 400 nm by bands of 20 nm, plus Lyman-Alpha and the CN bandhead); (3) simultaneous radiative budget of the Earth, UV to IR, with an accuracy better than 1% in differential. The paper briefly outlines the mission and describes the five proposed instruments of the model payload: SUAVE (Solar Ultraviolet Advanced Variability Experiment), an optimized telescope for FUV (Lyman-Alpha) and MUV (200-220 nm Herzberg continuum) imaging (sources of variability); UPR (Ultraviolet Passband Radiometers), with 64 UV filter radiometers; a vector magnetometer; thermal plasma measurements and Langmuir probes; and a total and spectral solar irradiance and Earth radiative budget ensemble (SERB, Solar irradiance & Earth Radiative Budget). SWUSV is proposed as a small mission to CNES and to ESA for a possible flight as early as 2017-2018.

Revived STIS. II. Properties of Stars in the Next Generation Spectral Library

NASA Technical Reports Server (NTRS)

Heap, Sara R.; Lindler, D.

2010-01-01

Spectroscopic surveys of galaxies at high redshift will bring the rest-frame ultraviolet into view of large, ground-based telescopes. The UV-blue spectral region is rich in diagnostics, but these diagnostics have not yet been calibrated in terms of the properties of the responsible stellar population(s). Such calibrations are now possible with Hubble's Next Generation Spectral Library (NGSL). The NGSL contains UV-optical spectra (0.2 - 1.0 microns) of 374 stars having a wide range in temperature, luminosity, and metallicity. We will describe our work to derive basic stellar parameters from NGSL spectra using modern model spectra and to use these stellar parameters to develop UV-blue spectral diagnostics.

Characterizing ultraviolet and infrared observational properties for galaxies. II. Features of attenuation law

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

Mao, Ye-Wei; Kong, Xu; Lin, Lin, E-mail: ywmao@pmo.ac.cn, E-mail: xkong@ustc.edu.cn, E-mail: linlin@shao.ac.cn

Variations in the attenuation law have a significant impact on observed spectral energy distributions for galaxies. As one important observational property for galaxies at ultraviolet and infrared wavelength bands, the correlation between infrared-to-ultraviolet luminosity ratio and ultraviolet color index (or ultraviolet spectral slope), i.e., the IRX-UV relation (or IRX-β relation), offered a widely used formula for correcting dust attenuation in galaxies, but the usability appears to be in doubt now because of considerable dispersion in this relation found by many studies. In this paper, on the basis of spectral synthesis modeling and spatially resolved measurements of four nearby spiral galaxies,more » we provide an interpretation of the deviation in the IRX-UV relation with variations in the attenuation law. From both theoretical and observational viewpoints, two components in the attenuation curve, the linear background and the 2175 Å bump, are suggested to be the parameters in addition to the stellar population age (addressed in the first paper of this series) in the IRX-UV function; different features in the attenuation curve are diagnosed for the galaxies in our sample. Nevertheless, it is often difficult to ascertain the attenuation law for galaxies in actual observations. Possible reasons for preventing the successful detection of the parameters in the attenuation curve are also discussed in this paper, including the degeneracy of the linear background and the 2175 Å bump in observational channels, the requirement for young and dust-rich systems to study, and the difficulty in accurate estimates of dust attenuations at different wavelength bands.« less

Characterizing Ultraviolet and Infrared Observational Properties for Galaxies. II. Features of Attenuation Law

NASA Astrophysics Data System (ADS)

Mao, Ye-Wei; Kong, Xu; Lin, Lin

2014-07-01

Variations in the attenuation law have a significant impact on observed spectral energy distributions for galaxies. As one important observational property for galaxies at ultraviolet and infrared wavelength bands, the correlation between infrared-to-ultraviolet luminosity ratio and ultraviolet color index (or ultraviolet spectral slope), i.e., the IRX-UV relation (or IRX-β relation), offered a widely used formula for correcting dust attenuation in galaxies, but the usability appears to be in doubt now because of considerable dispersion in this relation found by many studies. In this paper, on the basis of spectral synthesis modeling and spatially resolved measurements of four nearby spiral galaxies, we provide an interpretation of the deviation in the IRX-UV relation with variations in the attenuation law. From both theoretical and observational viewpoints, two components in the attenuation curve, the linear background and the 2175 Å bump, are suggested to be the parameters in addition to the stellar population age (addressed in the first paper of this series) in the IRX-UV function; different features in the attenuation curve are diagnosed for the galaxies in our sample. Nevertheless, it is often difficult to ascertain the attenuation law for galaxies in actual observations. Possible reasons for preventing the successful detection of the parameters in the attenuation curve are also discussed in this paper, including the degeneracy of the linear background and the 2175 Å bump in observational channels, the requirement for young and dust-rich systems to study, and the difficulty in accurate estimates of dust attenuations at different wavelength bands.

Constraints on the temperature inhomogeneity in quasar accretion discs from the ultraviolet-optical spectral variability

NASA Astrophysics Data System (ADS)

Kokubo, Mitsuru

2015-05-01

The physical mechanisms of the quasar ultraviolet (UV)-optical variability are not well understood despite the long history of observations. Recently, Dexter & Agol presented a model of quasar UV-optical variability, which assumes large local temperature fluctuations in the quasar accretion discs. This inhomogeneous accretion disc model is claimed to describe not only the single-band variability amplitude, but also microlensing size constraints and the quasar composite spectral shape. In this work, we examine the validity of the inhomogeneous accretion disc model in the light of quasar UV-optical spectral variability by using five-band multi-epoch light curves for nearly 9 000 quasars in the Sloan Digital Sky Survey (SDSS) Stripe 82 region. By comparing the values of the intrinsic scatter σint of the two-band magnitude-magnitude plots for the SDSS quasar light curves and for the simulated light curves, we show that Dexter & Agol's inhomogeneous accretion disc model cannot explain the tight inter-band correlation often observed in the SDSS quasar light curves. This result leads us to conclude that the local temperature fluctuations in the accretion discs are not the main driver of the several years' UV-optical variability of quasars, and consequently, that the assumption that the quasar accretion discs have large localized temperature fluctuations is not preferred from the viewpoint of the UV-optical spectral variability.

The application of UV multispectral technology in extract trace evdidence

NASA Astrophysics Data System (ADS)

Guo, Jingjing; Xu, Xiaojing; Li, Zhihui; Xu, Lei; Xie, Lanchi

2015-11-01

Multispectral imaging is becoming more and more important in the field of examination of material evidence, especially the ultraviolet spectral imaging. Fingerprints development, questioned document detection, trace evidence examination-all can used of it. This paper introduce a UV multispectral equipment which was developed by BITU & IFSC, it can extract trace evidence-extract fingerprints. The result showed that this technology can develop latent sweat-sebum mixed fingerprint on photo and ID card blood fingerprint on steel hold. We used the UV spectrum data analysis system to make the UV spectral image clear to identify and analyse.

Cloud effects on ultraviolet photoclimatology

NASA Technical Reports Server (NTRS)

Green, A. E. S.; Spinhirne, J. D.

1978-01-01

The purpose of this study is to quantify for the needs of photobiology the influence of clouds upon the ultraviolet spectral irradiance reaching the ground. Towards this end, analytic formulas are developed which approximately characterize the influence of clouds upon total solar radiation. These may be used in conjunction with a solar pyranometer to assign an effective visual optical depth for the cloud cover. A formula is also developed which characterizes the influence of the optical depth of clouds upon the UV spectral irradiance in the 280-340 nm region. Thus total solar energy observations to assign cloud optical properties can be used to calculate the UV spectral irradiance at the ground in the presence of these clouds. As incidental by-products of this effort, convenient formulas are found for the direct and diffuse components of total solar energy.

The linear polarization of 3C 345 in the ultraviolet

NASA Technical Reports Server (NTRS)

Dolan, Joseph F.; Boyd, Patricia T.; Wolinski, Karen G.; Smith, Paul S.; Impey, C. D.; Bless, Robert C.; Nelson, M. J.; Percival, J. W.; Taylor, M. J.; Elliot, J. L.

1994-01-01

The linear polarization of 3C 345, a superluminal radio source and OVV quasar, was observed in two bandpasses in the ultraviolet (centered at 2160 A and 2770 A) in 1993 April using the High Speed Photometer on the Hubble Space Telescope. The quasar is significantly polarized in the UV (p greater than 5%). Ground-based polarimetry was obtained 11 days later, but a difference in the position angle between the observations in the visible and those in the UV indicate that the magnitude of the polarization of 3C 345 may have changed over that time. If the two observation sets represent the same state of spectral polarization, then the large UV flux implies that either the polarization of the synchrotron continuum must stop decreasing in the UV, or that there is an additional source of polarized flux in the ultraviolet. Only if the UV observations represent a spectral polarization state with the same position angle in the visible seen previously in 3C 345 can the polarized flux be represented by a single power law consistent with the three-component model of Smith et al. This model consists of a polarized synchrotron component, an unpolarized component from the broad-line region, and an unpolarized component attributed to thermal radiation from an optically thick accretion disk. Additional simultaneous polarimetry in the UV and visible will be required to further constrain models of the continuum emission processes in 3C 345 and determine if the UV polarized flux is synchrotron in origin.

Measuring spatially varying, multispectral, ultraviolet bidirectional reflectance distribution function with an imaging spectrometer

NASA Astrophysics Data System (ADS)

Li, Hongsong; Lyu, Hang; Liao, Ningfang; Wu, Wenmin

2016-12-01

The bidirectional reflectance distribution function (BRDF) data in the ultraviolet (UV) band are valuable for many applications including cultural heritage, material analysis, surface characterization, and trace detection. We present a BRDF measurement instrument working in the near- and middle-UV spectral range. The instrument includes a collimated UV light source, a rotation stage, a UV imaging spectrometer, and a control computer. The data captured by the proposed instrument describe spatial, spectral, and angular variations of the light scattering from a sample surface. Such a multidimensional dataset of an example sample is captured by the proposed instrument and analyzed by a k-mean clustering algorithm to separate surface regions with same material but different surface roughnesses. The clustering results show that the angular dimension of the dataset can be exploited for surface roughness characterization. The two clustered BRDFs are fitted to a theoretical BRDF model. The fitting results show good agreement between the measurement data and the theoretical model.

Hubble's Next Generation Spectral Library

NASA Astrophysics Data System (ADS)

Heap, Sara R.; Lindler, D.

2008-03-01

Spectroscopic surveys of galaxies at z 1 or more bring the rest-frame ultraviolet into view of large, ground-based telescopes. This spectral region is rich in diagnostics, but these diagnostics have not yet been calibrated in terms of the properties of the responsible stellar population(s). Such calibrations are now possible with Hubble's Next Generation Spectral Library (NGSL). This library contains UV-optical spectra (0.2-1.0 microns) of 378 stars having a wide range in temperature, luminosity, and metallicity. We have derived the basic stellar parameters from the optical spectral region (0.35 - 1.0 microns) and are using them to calibrate UV spectral diagnostic indices and colors.

Thin film optical coatings for the ultraviolet spectral region

NASA Astrophysics Data System (ADS)

Torchio, P.; Albrand, G.; Alvisi, M.; Amra, C.; Rauf, H.; Cousin, B.; Otrio, G.

2017-11-01

The applications and innovations related to the ultraviolet field are today in strong growth. To satisfy these developments which go from biomedical to the large equipment like the Storage Ring Free Electron Laser, it is crucial to control with an extreme precision the optical performances, in using the substrates and the thin film materials impossible to circumvent in this spectral range. In particular, the reduction of the losses by electromagnetic diffusion, Joule effect absorption, or the behavior under UV luminous flows of power, resistance to surrounding particulate flows... become top priority which concerns a broad European and international community. Our laboratory has the theoretical, experimental and technological tools to design and fabricate numerous multilayer coatings with desirable optical properties in the visible and infrared spectral ranges. We have extended our expertise to the ultraviolet. We present here some results on high reflectivity multidielectric mirrors towards 250 nm in wavelength, produced by Ion Plating Deposition. The latter technique allows us to obtain surface treatments with low absorption and high resistance. We give in this study the UV transparent materials and the manufacturing technology which have been the best suited to meet requirements. Single UV layers were deposited and characterized. HfO2/SiO2 mirrors with a reflectance higher than 99% at 300 nm were obtained. Optical and non-optical characterizations such as UV spectrophotometric measurements, X-Ray Diffraction spectra, Scanning Electron Microscope and Atomic Force Microscope images were performed

Measurement of the solar ultraviolet radiation at ground level in Bangi, Malaysia

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

Aljawi, Ohoud; Gopir, Geri; Duay, Abdul Basit

2015-04-24

Understanding the amount of ultraviolet (UV) radiation received by human, plant, and animal organisms near the earth’s surface is important to a wide range of fields such as cancer research, agriculture and forestry. The solar ultraviolet spectral irradiance at ground level was measured using the Avantes spectrometer for the period of January to March 2014 at Bangi (2°55´N, 101°46´E, 50 m above sea level) in Malaysia. These data were used to estimate the diurnal variation of UV irradiance (300 – 400 nm). The maximum irradiance of UV radiation was 45 W m{sup −2} on horizontal surface. The maximum irradiance ofmore » UV received in the local noon time, and the minimum values of UV irradiance was received in the local morning time. It is found a bigger value of UV radiation was observed on clear sky in January. The estimation of daily flux average of UV irradiance was (921± 91) kJ m{sup −2}.« less

Low-cost 3D printed 1  nm resolution smartphone sensor-based spectrometer: instrument design and application in ultraviolet spectroscopy.

PubMed

Wilkes, Thomas C; McGonigle, Andrew J S; Willmott, Jon R; Pering, Tom D; Cook, Joseph M

2017-11-01

We report on the development of a low-cost spectrometer, based on off-the-shelf optical components, a 3D printed housing, and a modified Raspberry Pi camera module. With a bandwidth and spectral resolution of ≈60  nm and 1 nm, respectively, this device was designed for ultraviolet (UV) remote sensing of atmospheric sulphur dioxide (SO 2 ), ≈310  nm. To the best of our knowledge, this is the first report of both a UV spectrometer and a nanometer resolution spectrometer based on smartphone sensor technology. The device performance was assessed and validated by measuring column amounts of SO 2 within quartz cells with a differential optical absorption spectroscopy processing routine. This system could easily be reconfigured to cover other UV-visible-near-infrared spectral regions, as well as alternate spectral ranges and/or linewidths. Hence, our intention is also to highlight how this framework could be applied to build bespoke, low-cost, spectrometers for a range of scientific applications.

Lunar UV-visible-IR mapping interferometric spectrometer

NASA Technical Reports Server (NTRS)

Smith, W. Hayden; Haskin, L.; Korotev, R.; Arvidson, R.; Mckinnon, W.; Hapke, B.; Larson, S.; Lucey, P.

1992-01-01

Ultraviolet-visible-infrared mapping digital array scanned interferometers for lunar compositional surveys was developed. The research has defined a no-moving-parts, low-weight and low-power, high-throughput, and electronically adaptable digital array scanned interferometer that achieves measurement objectives encompassing and improving upon all the requirements defined by the LEXSWIG for lunar mineralogical investigation. In addition, LUMIS provides a new, important, ultraviolet spectral mapping, high-spatial-resolution line scan camera, and multispectral camera capabilities. An instrument configuration optimized for spectral mapping and imaging of the lunar surface and provide spectral results in support of the instrument design are described.

The phylogenetic distribution of ultraviolet sensitivity in birds

PubMed Central

2013-01-01

Background Colour vision in birds can be categorized into two classes, the ultraviolet (UVS) and violet sensitive (VS). Their phylogenetic distributions have traditionally been regarded as highly conserved. However, the complicated nature of acquiring spectral sensitivities from cone photoreceptors meant that until recently, only a few species had actually been studied. Whether birds are UVS or VS can nowadays be inferred from a wide range of species via genomic sequencing of the UV/violet SWS1 cone opsin gene. Results We present genomic sequencing results of the SWS1 gene from 21 avian orders. Amino acid residues signifying UV sensitivity are found in the two most important spectral tuning sites 86 and 90 of Pteroclidiformes and Coraciiformes, in addition to the major clades, Palaeognathae, Charadriiformes, Trogoniformes, Psittaciformes and Passeriformes, where they where previously known to occur. We confirm that the presumed UVS-conferring amino acid combination F86, C90 and M93 is common to Palaeognathae and unique to this clade, despite available spectrometric evidence showing the ostrich retina to be VS. Conclusions By mapping our results together with data from previous studies on a molecular phylogeny we show that avian colour vision shifted between VS and UVS at least 14 times. Single nucleotide substitutions can explain all these shifts. The common ancestor of birds most likely had a VS phenotype. However, the ancestral state of the avian SWS1 opsin’s spectral tuning sites cannot be resolved, since the Palaeognathae are F86, C90 while the Neognathae are ancestrally S86, S90. The phylogenetic distribution of UVS and VS colour vision in birds is so complex that inferences of spectral sensitivities from closely related taxa should be used with caution. PMID:23394614

The MPI-Mainz UV/VIS Spectral Atlas of Gaseous Molecules of Atmospheric Interest

NASA Astrophysics Data System (ADS)

Sander, Rolf; Keller-Rudek, Hannelore; Moortgat, Geert; Sörensen, Rüdiger

2014-05-01

Measurements from satellites can be used to obtain global concentration maps of atmospheric trace constituents. Critical parameters needed in the analysis of the satellite data are the absorption cross sections of the observed molecules. Here, we present the MPI-Mainz UV/VIS Spectral Atlas, which is a large collection of more than 5000 absorption cross section and quantum yield data files in the ultraviolet and visible (UV/VIS) wavelength region for gaseous molecules and radicals primarily of atmospheric interest. The data files contain results of individual measurements, covering research of almost a whole century. To compare and visualize the data sets, multicoloured graphical representations have been created. The Spectral Atlas is available on the internet at http://www.uv-vis-spectral-atlas-mainz.org. It has been completely overhauled and now appears with improved browse and search options, based on PostgreSQL, Django and Python database software. The web pages are continuously updated.

The optical/ultraviolet excess of isolated neutron stars in the resonant cyclotron scattering model

NASA Astrophysics Data System (ADS)

Tong, Hao; Xu, Ren-Xin; Song, Li-Ming

2011-12-01

X-ray dim isolated neutron stars are peculiar pulsar-like objects, characterized by their Planck-like spectrum. In studying their spectral energy distributions, optical/ultraviolet (UV) excess is a long standing problem. Recently Kaplan et al. measured the optical/UV excess for all seven sources, which is understandable in the resonant cyclotron scattering (RCS) model previously addressed. The RCS model calculations show that the RCS process can account for the observed optical/UV excess for most sources. The flat spectrum of RX J2143.0+0654 may be due to contributions from the bremsstrahlung emission of the electron system in addition to the RCS process.

Galactic Astronomy in the Ultraviolet

NASA Astrophysics Data System (ADS)

Rastorguev, A. S.; Sachkov, M. E.; Zabolotskikh, M. V.

2017-12-01

We propose a number of prospective observational programs for the ultraviolet space observatory WSO-UV, which seem to be of great importance to modern galactic astronomy. The programs include the search for binary Cepheids; the search and detailed photometric study and the analysis of radial distribution of UV-bright stars in globular clusters ("blue stragglers", blue horizontal-branch stars, RR Lyrae variables, white dwarfs, and stars with UV excesses); the investigation of stellar content and kinematics of young open clusters and associations; the study of spectral energy distribution in hot stars, including calculation of the extinction curves in the UV, optical and NIR; and accurate definition of the relations between the UV-colors and effective temperature. The high angular resolution of the observatory allows accurate astrometric measurements of stellar proper motions and their kinematic analysis.

Neuronal Representation of Ultraviolet Visual Stimuli in Mouse Primary Visual Cortex

PubMed Central

Tan, Zhongchao; Sun, Wenzhi; Chen, Tsai-Wen; Kim, Douglas; Ji, Na

2015-01-01

The mouse has become an important model for understanding the neural basis of visual perception. Although it has long been known that mouse lens transmits ultraviolet (UV) light and mouse opsins have absorption in the UV band, little is known about how UV visual information is processed in the mouse brain. Using a custom UV stimulation system and in vivo calcium imaging, we characterized the feature selectivity of layer 2/3 neurons in mouse primary visual cortex (V1). In adult mice, a comparable percentage of the neuronal population responds to UV and visible stimuli, with similar pattern selectivity and receptive field properties. In young mice, the orientation selectivity for UV stimuli increased steadily during development, but not direction selectivity. Our results suggest that, by expanding the spectral window through which the mouse can acquire visual information, UV sensitivity provides an important component for mouse vision. PMID:26219604

First ultraviolet reflectance measurements of several Kuiper Belt objects, Kuiper Belt object satellites, and new ultraviolet measurements of A Centaur

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

Stern, S. A.; Schindhelm, E.; Cunningham, N. J., E-mail: astern@swri.edu

We observed the 2600-3200 Å (hereafter, mid-UV) reflectance of two Kuiper Belt Objects (KBOs), two KBO satellites, and a Centaur, using the Hubble Space Telescope (HST) Cosmic Origins Spectrograph (COS). Other than measurements of the Pluto system, these constitute the first UV measurements obtained of KBOs, and KBO satellites, and new HST UV measurements of the Centaur 2060 Chiron. We find significant differences among these objects, constrain the sizes and densities of Haumea's satellites, and report the detection of a possible spectral absorption band in Haumea's spectrum near 3050 Å. Comparisons of these objects to previously published UV reflectance measurementsmore » of Pluto and Charon are also made here.« less

The first UV spectrum of a Uranian satellite - IUE observations of Oberon from 2650-3200 A

NASA Technical Reports Server (NTRS)

Stern, S. A.; Festou, M. C.; Van Santvoort, J.; Buratti, B. J.

1990-01-01

Using the International Ultraviolet Explorer (IUE) observatory, the first vacuum UV spectrum of Oberon was obtained. The data contain useful information in the spectral range 2650-3200 A. Oberon's UV geometric albedo is found to be flat and essentially featureless with an average value of p(UV) = 0.19 + or - 0.025, and making it possible to extend Oberon's phase curve into the opposite region.

The Effects of Space Weathering at UV Wavelengths: S-Class Asteroids

NASA Technical Reports Server (NTRS)

Hendrix, Amanda R.; Vilas, Faith

2006-01-01

We present evidence that space weathering manifests itself at near-UV wavelengths as a bluing of the spectrum, in contrast with the spectral reddening that has been seen at visible-near-IR wavelengths. Furthermore, the effects of space weathering at UV wavelengths tend to appear with less weathering than do the longer wavelength effects, suggesting that the UV wavelength range is a more sensitive indicator of weathering, and thus age. We report results from analysis of existing near-UV (approx.220-350 nm) measurements of S-type asteroids from the International Ultraviolet Explorer and the Hubble Space Telescope and comparisons with laboratory measurements of meteorites to support this hypothesis. Composite spectra of S asteroids are produced by combining UV spacecraft data with ground-based longer wavelength data. At visible-near-IR wavelengths, S-type asteroids are generally spectrally redder (and darker) than ordinary chondrite meteorites, whereas the opposite is generally true at near-UV wavelengths. Similarly, laboratory measurements of lunar samples show that lunar soils (presumably more weathered) are spectrally redder at longer wavelengths, and spectrally bluer at near-UV wavelengths, than less weathered crushed lunar rocks. The UV spectral bluing may be a result of the addition of nanophase iron to the regolith through the weathering process. The UV bluing is most prominent in the 300-400 nm range, where the strong UV absorption edge is degraded with weathering.

Solar Irradiance from 165 to 400 nm in 2008 and UV Variations in Three Spectral Bands During Solar Cycle 24

NASA Astrophysics Data System (ADS)

Meftah, M.; Bolsée, D.; Damé, L.; Hauchecorne, A.; Pereira, N.; Irbah, A.; Bekki, S.; Cessateur, G.; Foujols, T.; Thiéblemont, R.

2016-12-01

Accurate measurements of the solar spectral irradiance (SSI) and its temporal variations are of primary interest to better understand solar mechanisms, and the links between solar variability and Earth's atmosphere and climate. The SOLar SPECtrum (SOLSPEC) instrument of the Solar Monitoring Observatory (SOLAR) payload onboard the International Space Station (ISS) has been built to carry out SSI measurements from 165 to 3088 nm. We focus here on the ultraviolet (UV) part of the measured solar spectrum (wavelengths less than 400 nm) because the UV part is potentially important for understanding the solar forcing of Earth's atmosphere and climate. We present here SOLAR/SOLSPEC UV data obtained since 2008, and their variations in three spectral bands during Solar Cycle 24. They are compared with previously reported UV measurements and model reconstructions, and differences are discussed.

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

NASA Astrophysics Data System (ADS)

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

2010-03-01

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

Development of ultraviolet- and visible-light one-shot spectral domain optical coherence tomography and in situ measurements of human skin

NASA Astrophysics Data System (ADS)

Hirayama, Heijiro; Nakamura, Sohichiro

2015-07-01

We have developed ultraviolet (UV)- and visible-light one-shot spectral domain (SD) optical coherence tomography (OCT) that enables in situ imaging of human skin with an arbitrary wavelength in the UV-visible-light region (370-800 nm). We alleviated the computational burden for each color OCT image by physically dispersing the irradiating light with a color filter. The system consists of SD-OCT with multicylindrical lenses; thus, mechanical scanning of the mirror or stage is unnecessary to obtain an OCT image. Therefore, only a few dozens of milliseconds are necessary to obtain single-image data. We acquired OCT images of one subject's skin in vivo and of a skin excision ex vivo for red (R, 650±20 nm), green (G, 550±20 nm), blue (B, 450±20 nm), and UV (397±5 nm) light. In the visible-light spectrum, R light penetrated the skin and was reflected at a lower depth than G or B light. On the skin excision, we demonstrated that UV light reached the dermal layer. We anticipated that basic knowledge about the spectral properties of human skin in the depth direction could be acquired with this system.

Development of ultraviolet- and visible-light one-shot spectral domain optical coherence tomography and in situ measurements of human skin.

PubMed

Hirayama, Heijiro; Nakamura, Sohichiro

2015-07-01

We have developed ultraviolet (UV)- and visible-light one-shot spectral domain (SD) optical coherence tomography (OCT) that enables in situ imaging of human skin with an arbitrary wavelength in the UV-visible-light region (370-800 nm). We alleviated the computational burden for each color OCT image by physically dispersing the irradiating light with a color filter. The system consists of SD-OCT with multicylindrical lenses; thus, mechanical scanning of the mirror or stage is unnecessary to obtain an OCT image. Therefore, only a few dozens of milliseconds are necessary to obtain single-image data. We acquired OCT images of one subject's skin in vivo and of a skin excision ex vivo for red (R, 650 ± 20 nm), green (G, 550 ± 20 nm), blue (B, 450 ± 20 nm), and UV (397 ± 5 nm) light. In the visible-light spectrum, R light penetrated the skin and was reflected at a lower depth than G or B light. On the skin excision, we demonstrated that UV light reached the dermal layer. We anticipated that basic knowledge about the spectral properties of human skin in the depth direction could be acquired with this system.

Autonomous portable solar ultraviolet spectroradiometer (APSUS) - a new CCD spectrometer system for localized, real-time solar ultraviolet (280-400 nm) radiation measurement.

PubMed

Hooke, Rebecca; Pearson, Andy; O'Hagan, John

2014-01-01

Terrestrial solar ultraviolet (UV) radiation has significant implications for human health and increasing levels are a key concern regarding the impact of climate change. Monitoring solar UV radiation at the earth's surface is therefore of increasing importance. A new prototype portable CCD (charge-coupled device) spectrometer-based system has been developed that monitors UV radiation (280-400 nm) levels at the earth's surface. It has the ability to deliver this information to the public in real time. Since the instrument can operate autonomously, it is called the Autonomous Portable Solar Ultraviolet Spectroradiometer (APSUS). This instrument incorporates an Ocean Optics QE65000 spectrometer which is contained within a robust environmental housing. The APSUS system can gather reliable solar UV spectral data from approximately April to October inclusive (depending on ambient temperature) in the UK. In this study the new APSUS unit and APSUS system are presented. Example solar UV spectra and diurnal UV Index values as measured by the APSUS system in London and Weymouth in the UK in summer 2012 are shown. © 2014 Crown copyright. Photochemistry and Photobiology © 2014 The American Society of Photobiology. This article is published with the permission of the Controller of HMSO and the Queen's Printer for Scotland and Public Health England.

Performance Assessment of a Plate Beam Splitter for Deep-Ultraviolet Raman Measurements with a Spatial Heterodyne Raman Spectrometer.

PubMed

Lamsal, Nirmal; Angel, S Michael

2017-06-01

In earlier works, we demonstrated a high-resolution spatial heterodyne Raman spectrometer (SHRS) for deep-ultraviolet (UV) Raman measurements, and showed its ability to measure UV light-sensitive compounds using a large laser spot size. We recently modified the SHRS by replacing the cube beam splitter (BS) with a custom plate beam splitter with higher light transmission, an optimized reflectance/transmission ratio, higher surface flatness, and better refractive index homogeneity than the cube beam splitter. Ultraviolet Raman measurements were performed using a SHRS modified to use the plate beam splitter and a matching compensator plate and compared to the previously described cube beam splitter setup. Raman spectra obtained using the modified SHRS exhibit much higher signals and signal-to-noise (S/N) ratio and show fewer spectral artifacts. In this paper, we discuss the plate beam splitter SHRS design features, the advantages over previous designs, and discuss some general SHRS issues such as spectral bandwidth, S/N ratio characteristics, and optical efficiency.

Icy Saturnian satellites: Disk-integrated UV-IR characteristics and links to exogenic processes

NASA Astrophysics Data System (ADS)

Hendrix, Amanda R.; Filacchione, Gianrico; Paranicas, Chris; Schenk, Paul; Scipioni, Francesca

2018-01-01

Combined Cassini observations obtained at similar observing geometries in the ultraviolet through infrared spectral range, along with additional ultraviolet (UV) data from Hubble Space Telescope where available, are used to study system-wide trends in spectral albedos of the inner icy Saturnian satellites (Mimas, Enceladus, Tethys, Dione, Rhea). We derive UV and visible geometric albedos and UV absorption strengths of the leading and trailing hemispheres and compare with E ring grain flux and charged particle intensities (electrons and ions of varying energies) to those hemispheres. We find that the UV absorption strength on the leading and trailing hemispheres is anti-correlated with E ring grain flux. On the trailing hemispheres, the UV absorption strength is correlated with intensity of electrons in the tens of keV range. We suggest that these relationships could imply links with the organic component of the E ring. Radiolytic processing of organics causes the products to become spectrally redder, increasing the UV absorption strength. Such processing occurs while organic-rich grains are in the E ring, and increases with exposure time in the E ring, such that grains interacting with Rhea are redder (more processed) than those impacting moons closer to Enceladus. Further processing (and associated darkening/reddening) occurs on the trailing hemispheres of the satellites, via radiolysis by electrons in the tens of keV range. Silicates and salts also redden with weathering; however because organics are present in the E ring in significantly greater abundance than salts or silicates, we suggest here that weathering of organics dominates the coloring of the inner Saturnian moons.

UV Spectroscopy of Lucy Mission Targets

NASA Astrophysics Data System (ADS)

Thomas, Cristina

2017-08-01

The Trojan asteroids are a significant population of primitive bodies trapped in Jupiter's stable L4 and L5 Lagrange regions. Their physical properties and existence in these particular orbits constrain the chemical and dynamical processes in our early Solar System. NASA's recently selected Lucy mission will perform the first reconnaissance of these asteroids and will answer many fundamental questions about the population. The compositions of the Trojans are not well understood. Spectroscopy and spectrophotometry in visible and near-infrared wavelengths show red slopes (spectra with reflectivity increasing towards the long wavelength end of the spectrum) and no diagnostic spectral absorption features. However, past spectral and photometric observations suggest there are unobserved features in ultraviolet wavelengths. We propose to obtain ultraviolet spectroscopy with WFC3 of four Trojan asteroids that are targets of the Lucy mission. Lucy will not have the capability to obtain ultraviolet spectra. The proposed observations can only be made using Hubble. We will determine if there are UV spectral features, as suggested by visible wavelength observations, and connect these features to candidate compositional components. These observations will enable connections between the compositions of Trojans and dynamical models of the early Solar System.

Airborne measurements of solar and planetary near ultraviolet radiation during the NASA/ESA CV-900 spacelab simulation

NASA Technical Reports Server (NTRS)

Sivjee, G. G.

1977-01-01

Results from a comparative study of the feasibility of employing experiment operators on the space shuttle to acquire scientifically worthwhile data are presented. The experiments performed during these tests included spectral observations of the Sun and Venus in the near ultraviolet region. The solar measurements were analyzed to determine ozone abundance in the terrestrial atmosphere. Using a detailed spectral matching technique to compare airborne solar UV measurements with synthetic spectral profiles of sunlight, it is deduced that in winter the total atmospheric ozone abundance is about 0.33 atm/cm at midlatitudes in the northern hemisphere.

SUITS/SWUSV: a small-size mission to address solar spectral variability, space weather and solar-climate relations

NASA Astrophysics Data System (ADS)

Damé, Luc; Keckhut, Philippe; Hauchecorne, Alain; Meftah, Mustapha; Bekki, Slimane

2016-07-01

We present the SUITS/SWUSV microsatellite mission investigation: "Solar Ultraviolet Influence on Troposphere/Stratosphere, a Space Weather & Ultraviolet Solar Variability" mission. SUITS/SWUSV was developed to determine the origins of the Sun's activity, understand the flaring process (high energy flare characterization) and onset of CMEs (forecasting). Another major objective is to determine the dynamics and coupling of Earth's atmosphere and its response to solar variability (in particular UV) and terrestrial inputs. It therefore includes the prediction and detection of major eruptions and coronal mass ejections (Lyman-Alpha and Herzberg continuum imaging) the solar forcing on the climate through radiation and their interactions with the local stratosphere (UV spectral irradiance measures from 170 to 400 nm). The mission is proposed on a sun-synchronous polar orbit 18h-6h (for almost constant observing) and proposes a 7 instruments model payload of 65 kg - 65 W with: SUAVE (Solar Ultraviolet Advanced Variability Experiment), an optimized telescope for FUV (Lyman-Alpha) and MUV (200-220 nm Herzberg continuum) imaging (sources of variability); SOLSIM (Solar Spectral Irradiance Monitor), a spectrometer with 0.65 nm spectral resolution from 170 to 340 nm; SUPR (Solar Ultraviolet Passband Radiometers), with UV filter radiometers at Lyman-Alpha, Herzberg, MgII index, CN bandhead and UV bands coverage up to 400 nm; HEBS (High Energy Burst Spectrometers), a large energy coverage (a few tens of keV to a few hundreds of MeV) instrument to characterize large flares; EPT-HET (Electron-Proton Telescope - High Energy Telescope), measuring electrons, protons, and heavy ions over a large energy range; ERBO (Earth Radiative Budget and Ozone) NADIR oriented; and a vector magnetometer. Complete accommodation of the payload has been performed on a PROBA type platform very nicely. Heritage is important both for instruments (SODISM and PREMOS on PICARD, LYRA on PROBA-2, SOLSPEC on ISS,...) and platform (PROBA-2, PROBA-V,...), leading to high TRL levels (>7). SUITS/SWUSV was initially designed in view of the ESA/CAS AO for a Small Mission; it is now envisaged for a joint CNES/NASA opportunity with Europeans and Americans partners for a possible flight in 2021.

Lighting considerations in controlled environments for nonphotosynthetic plant responses to blue and ultraviolet radiation

NASA Technical Reports Server (NTRS)

Caldwell, M. M.; Flint, S. D.

1994-01-01

This essay will consider both physical and photobiological aspects of controlled environment lighting in the spectral region beginning in the blue and taken to the normal limit of the solar spectrum in the ultraviolet. The primary emphasis is directed to questions of plant response to sunlight. Measurement and computations used in radiation dosimetry in this part of the spectrum are also briefly treated. Because of interest in the ozone depletion problem, there has been some activity in plant UV-B research and there are several recent reviews available. Some aspects of growth chamber lighting as it relates to UV-B research were covered earlier. Apart from work related to the blue/UV-A receptor, less attention has been given to UV-A responses.

Lighting considerations in controlled environments for nonphotosynthetic plant responses to blue and ultraviolet radiation

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

Caldwell, M.M.; Flint, S.D.

1994-12-31

This essay will consider both physical and photobiological aspects of controlled environment lighting in the spectral region beginning in the blue and taken to the normal limit of the solar spectrum in the ultraviolet. The primary emphasis is directed to questions of plant response to sunlight. Measurement and computations used in radiation dosimetry in this part of the spectrum are also briefly treated. Because of interest in the ozone depletion problem, there has been some activity in plant UV-B research and there are several recent reviews available. Some aspects of growth chamber lighting as it relates to UV-B research weremore » covered earlier. Apart from work related to the blue/UV-A receptor, less attention has been given to UV-A responses.« less

A dense plasma ultraviolet source

NASA Technical Reports Server (NTRS)

Lee, J. H.; Mcfarland, D. R.

1978-01-01

The intense ultraviolet emission from the NASA Hypocycloidal-Pinch (HCP) plasma is investigated. The HCP consists of three disk electrodes whose cross section has a configuration similar to the cross section of a Mather-type plasma focus. Plasma foci were produced in deuterium, helium, xenon, and krypton gases in order to compare their emission characteristics. Time-integrated spectra in the wavelength range from 200 nm to 350 nm and temporal variations of the uv emission were obtained with a uv spectrometer and a photomultiplier system. Modifications to enhance uv emission in the iodine-laser pump band (250 to 290 nm) and preliminary results produced by these modifications are presented. Finally, the advantages of the HCP as a uv over use of conventional xenon lamps with respect to power output limit, spectral range, and lifetime are discussed.

Horizontal and sun-normal spectral biologically effective ultraviolet irradiances.

PubMed

Parisi, A V; Kimlin, M G

1999-01-01

The dependence of the spectral biologically effective solar UV irradiance on the orientation of the receiver with respect to the sun has been determined for relatively cloud-free days at a sub-tropical Southern Hemisphere latitude for the solar zenith angle range 35-64 degrees. For the UV and biologically effective irradiances, the sun-normal to horizontal ratio for the total UV ranges from 1.18 +/- 0.05 to 1.27 +/- 0.06. The sun-normal to horizontal ratio for biologically effective irradiance is dependent on the relative effectiveness of the relevant action spectrum in the UV-A waveband. In contrast to the total UV, the diffuse UV and diffuse biologically effective irradiances are reduced in a sun-normal compared with a horizontal orientation by a factor ranging from 0.70 +/- 0.05 to 0.76 +/- 0.03.

Ultraviolet reflectance spectroscopy measurements of carbonaceous meteorites and planetary analog materials

NASA Astrophysics Data System (ADS)

Hibbitts, Charles A.; Stockstill-Cahill, Karen; Takir, Driss

2017-10-01

The compositions of airless solar system objects tell us about the origin and evolutionary processes that are responsible for the current state of our solar system and that shape our environment. Spectral reflectance measurements in the ultraviolet are being used more frequently for providing compositional information of airless solid surfaces. Most minerals absorb in the UV making studying surface composition both informative but also challenging [e.g. 1]. The UV region is sensitive to atomic and molecular electronic absorptions such as the ligand-metal charge transfer band that is present in oxides and silicates and the conduction band at vacuum UV wavelengths. At the JHU-APL, bidirectional UV reflectance measurements are obtained under vacuum using a McPherson monochrometer with a PMT detector to achieve measurements over the range from ~ 140 nm to ~ 570 nm. Sample temperature can also be controlled from ~ 100K to ~ 600K, which enables the exploring the interaction of water ice and other volatiles with refractory samples. We have measured the UV spectra of many carbonaceous chondrites, including Mokoia, Vigarano, Warrenton, Orgueil, SaU290, and Essebi. In addition to being dark, some also possess on OMCT band. We have also obtained IR measurement of these meteorites to explore possible correlations between their UV and IR spectral signatures. In addition, we have also measured the UV spectra of low water content lunar analog glasses and have found a correlation between the spectral nature of the OMCT band and the abundance of iron [3]. Also, the spectral signature of mineralic and adsorbed water in the UV has been investigated. While water-ice has a known strong absorption feature near 180 nm (e.g. 4], adsorbed molecular and disassociatively adsorbed OH appear to not be optically active in this spectral region [5]. References: [1] Wagner et al. (1987) Icarus, 69, 14-28.1987; [2] Cloutis et al. (2008) Icarus, 197, 321-347; [3] Greenspon et al. (2012), 43rd LPSC, 1659, 2490; [4] Hendrix, A. and C. J. Hansen (2008) Icarus, 193, 323-333; [5] Hibbitts, C.A. (2015) DPS #47, 215.05.

The development of a tunable, single-frequency ultraviolet laser source for UV filtered Rayleigh scattering

NASA Technical Reports Server (NTRS)

Finkelstein, N.; Gambogi, J.; Lempert, Walter R.; Miles, Richard B.; Rines, G. A.; Finch, A.; Schwarz, R. A.

1995-01-01

We present the development of a flexible, high power, narrow line width, tunable ultraviolet source for diagnostic application. By frequency tripling the output of a pulsed titanium-sapphire laser, we achieve broadly tunable (227-360 nm) ultraviolet light with high quality spatial and spectral resolution. We also present the characterization of a mercury vapor cell which provides a narrow band, sharp edge absorption filter at 253.7 nm. These two components form the basis for the extension of the Filtered Rayleigh Scattering technique into the ultraviolet. The UV-FRS system is comprised of four pieces: a single frequency, cw tunable Ti:Sapphire seeding source; a high-powered pulsed Ti:Sapphire oscillator; a third harmonic generator system; and an atomic mercury vapor filter. In this paper we discuss the development and characterization of each of these elements.

Light transmission and ultraviolet protection of contact lenses under artificial illumination.

PubMed

Artigas, José M; Navea, Amparo; García-Domene, M Carmen; Gené, Andrés; Artigas, Cristina

2016-04-01

To determine the spectral transmission of contact lenses (CLs), with and without an ultraviolet (UV) filter to evaluate their capacity for protection under UV radiation from artificial illumination (incandescent, fluorescent, xenon (Xe) lamps, or white LEDs (light-emitting diode)). The transmission curves of nine soft CLs were obtained by using a PerkinElmer Lambda 35 UV-vis spectrophotometer. A CIE standard was used for the emission spectra of incandescent and fluorescent lamps, and Xe lamps and white LEDs were measured by using an International Light Technologies ILT-950 spectroradiometer. Five of the nine soft CLs analysed state that they incorporate UV filters, but the other four do not specify anything in this regard. The spectral transmission of all the CLs studied is excellent in the visible region. The CLs with UV filters filter out this radiation more or less effectively. Xe lamps emit a part in the UV region. Incandescent, fluorescent and white LEDs do not emit at all in the UV. Incorporating UV filters is important when the illumination is from a Xe lamp since this light source emits in the UV region. This, however, does not occur with incandescent and fluorescent lamps or white LEDs. The CLs that do incorporate UV filters meet all the standard requirements that the U.S. FDA (Food and Drug Administration) has for UV-blocking CLs Class II (OcularScience, CooperVision and Neolens), and AcuvueMoist and HydronActifresh400 even comply with the stricter Class I. The CLs without UV filters let UVA, UVB and even some UVC through. Copyright © 2015. Published by Elsevier Ltd.

An All-reflective Integral Field Spectrograph for Far Ultraviolet Astrophysics

NASA Astrophysics Data System (ADS)

Kendrick, Stephen; Ebbets, D.; Hardesty, C.; Sembach, K.; Beasley, M.; Woodgate, B.

2010-01-01

This paper overviews the supporting optical technologies for an ultraviolet integral field spectrograph (IFS) that will be used for future space astrophysics missions. The new technology is an all-reflective image slicer that directs light to an array of imaging diffraction gratings. Previous UV instruments recorded the spectra of point sources or spatially resolved elements along a long slit. Our IFS has only one reflection more than the Cosmic Origins Spectrograph for Hubble Space Telescope, which is the most sensitive UV spectrograph yet built, but is limited to point sources. An efficient UV IFS enables simultaneous spectroscopy of many spatially resolved elements within a contiguous two dimensional field of view in diagnostically important ultraviolet lines. The output is thus a data cube having one spectral and two spatial coordinates. This is the astrophysical analog to hyperspectral imaging in Earth sciences. The scientific benefits of such an instrument were developed during Vision Missions, Origins Probes, and Astrophysics Strategic Mission Concept Studies between 2004 and 2009. Implementation can be scaled for a small payload such as a sounding rocket or Explorer-class mission, leading to a flight experiment within the next few years. Of particular interest would be the application of this technology for an instrument on a version of the Advanced Technology Large-Aperture Space Telescope (ATLAST) which will have an 8+-m aperture. We will focus on the spectral region near Lyman alpha, but the all-reflective approach is applicable to other spectral regions when matched with wavelength appropriate gratings and detectors. Our project is a collaboration between Ball Aerospace & Technologies Corp., the University of Colorado, NASA Goddard Space Flight Center and the Space Telescope Science Institute, all of which have extensive experience with the science and instrumentation for UV astrophysics.

Reference ultraviolet wavelengths of CrIII measured by Fourier transform spectrometry

NASA Astrophysics Data System (ADS)

Smillie, D. G.; Pickering, J. C.; Smith, P. L.

2008-10-01

We report CrIII ultraviolet (UV) transition wavelengths measured using a high-resolution Fourier transform spectrometer (FTS), for the first time, available for use as wavelength standards. The doubly ionized iron group element spectra dominate the observed opacity of hot B stars in the UV, and improved, accurate, wavelengths are required for the analysis of astronomical spectra. The spectrum was excited using a chromium-neon Penning discharge lamp and measured with the Imperial College vacuum ultraviolet FTS. 140 classified 3d34s-3d34p CrIII transition lines, in the spectral range 38000 to 49000 cm-1 (2632 to 2041 Å), the strongest having wavelength uncertainties less than one part in 107, are presented.

A Search for Rarely Seen Ultraviolet Coma Emissions and New Species Upper Limits at Comet 67P/Churyumov-Gerasimenko Using the Rosetta-Alice Ultraviolet Spectrograph

NASA Astrophysics Data System (ADS)

Noonan, J.; Stern, S. A.; Parker, J. W.; Keeney, B. A.; Weaver, H. A., Jr.; Feldman, P.; Steffl, A.; Feaga, L. M.; Bertaux, J. L.

2017-12-01

The Alice far/extreme-UV spectrograph aboard Rosetta is one of three US instruments provided by NASA; it is the first UV spectrograph to reach any comet. Numerous scientific results have been obtained regarding 67P/Churyumov-Gerasimenko by this instrument. Here we summarize two new sets of results from a search for rarely appearing atomic and molecular spectral emission features and a grand sum spectrum allowing us to place new atomic and molecular neutral and ionized species upper limits in the comet's coma.

Experimental evaluation of optimization method for developing ultraviolet barrier coatings

NASA Astrophysics Data System (ADS)

Gonome, Hiroki; Okajima, Junnosuke; Komiya, Atsuki; Maruyama, Shigenao

2014-01-01

Ultraviolet (UV) barrier coatings can be used to protect many industrial products from UV attack. This study introduces a method of optimizing UV barrier coatings using pigment particles. The radiative properties of the pigment particles were evaluated theoretically, and the optimum particle size was decided from the absorption efficiency and the back-scattering efficiency. UV barrier coatings were prepared with zinc oxide (ZnO) and titanium dioxide (TiO2). The transmittance of the UV barrier coating was calculated theoretically. The radiative transfer in the UV barrier coating was modeled using the radiation element method by ray emission model (REM2). In order to validate the calculated results, the transmittances of these coatings were measured by a spectrophotometer. A UV barrier coating with a low UV transmittance and high VIS transmittance could be achieved. The calculated transmittance showed a similar spectral tendency with the measured one. The use of appropriate particles with optimum size, coating thickness and volume fraction will result in effective UV barrier coatings. UV barrier coatings can be achieved by the application of optical engineering.

Spectral stability of supercontinuum generation in condensed mediums

NASA Astrophysics Data System (ADS)

Wang, Jier; Zhang, Yizhu; Shen, Huifeng; Jiang, Yuhai; Wang, Zhongyang

2017-07-01

The features of the supercontinuum generation (SCG) using intense femtosecond pulses are systematically investigated in condensed mediums [sapphire, BK7 glass, ultraviolet (UV)-fused silica, and fluoride crystals]. By optimizing the experimental conditions and choosing suitable mediums, the bandwidth of the SCG can be extended to the UV regime with good spectral stability. This study demonstrates that materials with high bandgap present high efficiency for SCG, particularly in the short wavelength region. The achievable short wavelength and low power-density threshold of the SCG exhibit complicated correlations with the bandgap of condensed mediums.

Ultraviolet Imaging with Low Cost Smartphone Sensors: Development and Application of a Raspberry Pi-Based UV Camera.

PubMed

Wilkes, Thomas C; McGonigle, Andrew J S; Pering, Tom D; Taggart, Angus J; White, Benjamin S; Bryant, Robert G; Willmott, Jon R

2016-10-06

Here, we report, for what we believe to be the first time, on the modification of a low cost sensor, designed for the smartphone camera market, to develop an ultraviolet (UV) camera system. This was achieved via adaptation of Raspberry Pi cameras, which are based on back-illuminated complementary metal-oxide semiconductor (CMOS) sensors, and we demonstrated the utility of these devices for applications at wavelengths as low as 310 nm, by remotely sensing power station smokestack emissions in this spectral region. Given the very low cost of these units, ≈ USD 25, they are suitable for widespread proliferation in a variety of UV imaging applications, e.g., in atmospheric science, volcanology, forensics and surface smoothness measurements.

The effect of stellar evolution uncertainties on the rest-frame ultraviolet stellar lines of C IV and He II in high-redshift Lyman-break galaxies

NASA Astrophysics Data System (ADS)

Eldridge, John J.; Stanway, Elizabeth R.

2012-01-01

Young, massive stars dominate the rest-frame ultraviolet (UV) spectra of star-forming galaxies. At high redshifts (z > 2), these rest-frame UV features are shifted into the observed-frame optical and a combination of gravitational lensing, deep spectroscopy and spectral stacking analysis allows the stellar population characteristics of these sources to be investigated. We use our stellar population synthesis code Binary Population and Spectral Synthesis (BPASS) to fit two strong rest-frame UV spectral features in published Lyman-break galaxy spectra, taking into account the effects of binary evolution on the stellar spectrum. In particular, we consider the effects of quasi-homogeneous evolution (arising from the rotational mixing of rapidly rotating stars), metallicity and the relative abundance of carbon and oxygen on the observed strengths of He IIλ1640 Å and C IVλ1548, 1551 Å spectral lines. We find that Lyman-break galaxy spectra at z ˜ 2-3 are best fitted with moderately sub-solar metallicities, and with a depleted carbon-to-oxygen ratio. We also find that the spectra of the lowest metallicity sources are best fitted with model spectra in which the He II emission line is boosted by the inclusion of the effect of massive stars being spun-up during binary mass transfer so these rapidly rotating stars experience quasi-homogeneous evolution.

Ultraviolet spectral reflectance of carbonaceous materials

NASA Astrophysics Data System (ADS)

Applin, Daniel M.; Izawa, Matthew R. M.; Cloutis, Edward A.; Gillis-Davis, Jeffrey J.; Pitman, Karly M.; Roush, Ted L.; Hendrix, Amanda R.; Lucey, Paul G.

2018-06-01

A number of planetary spacecraft missions have carried instruments with sensors covering the ultraviolet (UV) wavelength range. However, there exists a general lack of relevant UV reflectance laboratory data to compare against these planetary surface remote sensing observations in order to make confident material identifications. To address this need, we have systematically analyzed reflectance spectra of carbonaceous materials in the 200-500 nm spectral range, and found spectral-compositional-structural relationships that suggest this wavelength region could distinguish between otherwise difficult-to-identify carbon phases. In particular (and by analogy with the infrared spectral region), large changes over short wavelength intervals in the refractive indices associated with the trigonal sp2π-π* transition of carbon can lead to Fresnel peaks and Christiansen-like features in reflectance. Previous studies extending to shorter wavelengths also show that anomalous dispersion caused by the σ-σ* transition associated with both the trigonal sp2 and tetrahedral sp3 sites causes these features below λ = 200 nm. The peak wavelength positions and shapes of π-π* and σ-σ* features contain information on sp3/sp2, structure, crystallinity, and powder grain size. A brief comparison with existing observational data indicates that the carbon fraction of the surface of Mercury is likely amorphous and submicroscopic, as is that on the surface of the martian satellites Phobos and Deimos, and possibly comet 67P/Churyumov-Gerasimenko, while further coordinated observations and laboratory experiments should refine these feature assignments and compositional hypotheses. The new laboratory diffuse reflectance data reported here provide an important new resource for interpreting UV reflectance measurements from planetary surfaces throughout the solar system, and confirm that the UV can be rich in important spectral information.

Changes in ultraviolet-B and visible optical properties and absorbing pigment concentrations in pecan leaves during a growing season

Treesearch

Yadong Qi; Shuju Bai; Gordon M. Heisler

2003-01-01

UV-B (280-320 nm) and visible (400-760 nm) spectral reflectance, transmittance, and absorptance; chlorophyll content; UV-B absorbing compound concentration; and leaf thickness were measured for pecan (Carya illinoensis) leaves over a growing season (April-October). Leaf samples were collected monthly from a pecan plantation located on the Southern...

Action spectra affect variability of the climatology of biologically effective ultraviolet radiation on cloud-free days.

PubMed

Grifoni, D; Zipoli, G; Sabatini, F; Messeri, G; Bacci, L

2013-12-01

Action spectrum (AS) describes the relative effectiveness of ultraviolet (UV) radiation in producing biological effects and allows spectral UV irradiance to be weighted in order to compute biologically effective UV radiation (UVBE). The aim of this research was to study the seasonal and latitudinal distribution over Europe of daily UVBE doses responsible for various biological effects on humans and plants. Clear sky UV radiation spectra were computed at 30-min time intervals for the first day of each month of the year for Rome, Potsdam and Trondheim using a radiative transfer model fed with climatological data. Spectral data were weighted using AS for erythema, vitamin D synthesis, cataract and photokeratitis for humans, while the generalised plant damage and the plant damage AS were used for plants. The daily UVBE doses for the above-mentioned biological processes were computed and are analysed in this study. The patterns of variation due to season (for each location) and latitude (for each date) resulted as being specific for each adopted AS. The biological implications of these results are briefly discussed highlighting the importance of a specific UVBE climatology for each biological process.

Potential of far-ultraviolet absorption spectroscopy as a highly sensitive qualitative and quantitative analysis method for polymer films, part I: classification of commercial food wrap films.

PubMed

Sato, Harumi; Higashi, Noboru; Ikehata, Akifumi; Koide, Noriko; Ozaki, Yukihiro

2007-07-01

The aim of the present study is to propose a totally new technique for the utilization of far-ultraviolet (UV) spectroscopy in polymer thin film analysis. Far-UV spectra in the 120-300 nm region have been measured in situ for six kinds of commercial polymer wrap films by use of a novel type of far-UV spectrometer that does not need vacuum evaporation. These films can be straightforwardly classified into three groups, polyethylene (PE) films, polyvinyl chloride (PVC) films, and polyvinylidene chloride (PVDC) films, by using the raw spectra. The differences in the wavelength of the absorption band due to the sigma-sigma* transition of the C-C bond have been used for the classification of the six kinds of films. Using this method, it was easy to distinguish the three kinds of PE films and to separate the two kinds of PVDC films. Compared with other spectroscopic methods, the advantages of this technique include nondestructive analysis, easy spectral measurement, high sensitivity, and simple spectral analysis. The present study has demonstrated that far-UV spectroscopy is a very promising technique for polymer film analysis.

Spectral slopes of the absorption coefficient of colored dissolved and detrital material inverted from UV-visible remote sensing reflectance

PubMed Central

Wei, Jianwei; Lee, Zhongping; Ondrusek, Michael; Mannino, Antonio; Tzortziou, Maria; Armstrong, Roy

2017-01-01

The spectral slope of the absorption coefficient of colored dissolved and detrital material (CDM), Scdm (units: nm−1), is an important optical parameter for characterizing the absorption spectral shape of CDM. Although highly variable in natural waters, in most remote sensing algorithms, this slope is either kept as a constant or empirically modeled with multiband ocean color in the visible domain. In this study, we explore the potential of semianalytically retrieving Scdm with added ocean color information in the ultraviolet (UV) range between 360 and 400 nm. Unique features of hyperspectral remote sensing reflectance in the UV-visible wavelengths (360–500 nm) have been observed in various waters across a range of coastal and open ocean environments. Our data and analyses indicate that ocean color in the UV domain is particularly sensitive to the variation of the CDM spectral slope. Here, we used a synthesized data set to show that adding UV wavelengths to the ocean color measurements will improve the retrieval of Scdm from remote sensing reflectance considerably, while the spectral band settings of past and current satellite ocean color sensors cannot fully account for the spectral variation of remote sensing reflectance. Results of this effort support the concept to include UV wavelengths in the next generation of satellite ocean color sensors. PMID:29201583

Spectral slopes of the absorption coefficient of colored dissolved and detrital material inverted from UV-visible remote sensing reflectance.

PubMed

Wei, Jianwei; Lee, Zhongping; Ondrusek, Michael; Mannino, Antonio; Tzortziou, Maria; Armstrong, Roy

2016-03-01

The spectral slope of the absorption coefficient of colored dissolved and detrital material (CDM), S cdm (units: nm -1 ), is an important optical parameter for characterizing the absorption spectral shape of CDM. Although highly variable in natural waters, in most remote sensing algorithms, this slope is either kept as a constant or empirically modeled with multiband ocean color in the visible domain. In this study, we explore the potential of semianalytically retrieving S cdm with added ocean color information in the ultraviolet (UV) range between 360 and 400 nm. Unique features of hyperspectral remote sensing reflectance in the UV-visible wavelengths (360-500 nm) have been observed in various waters across a range of coastal and open ocean environments. Our data and analyses indicate that ocean color in the UV domain is particularly sensitive to the variation of the CDM spectral slope. Here, we used a synthesized data set to show that adding UV wavelengths to the ocean color measurements will improve the retrieval of S cdm from remote sensing reflectance considerably, while the spectral band settings of past and current satellite ocean color sensors cannot fully account for the spectral variation of remote sensing reflectance. Results of this effort support the concept to include UV wavelengths in the next generation of satellite ocean color sensors.

Effectiveness of eye drops protective against ultraviolet radiation.

PubMed

Daxer, A; Blumthaler, M; Schreder, J; Ettl, A

1998-01-01

To test the effectiveness of commercially available ultraviolet (UV)-protective eye drops (8-hydroxy-1-methylchinolinium methylsulphate) which are recommended for protection against both solar and artificial UV radiation. The spectral transmission in the wavelength range from 250 to 500 nm was investigated in 1-nm steps using a high-resolution double monochromator with holographic gratings of 2,400 lines/mm and a 1,000-watt halogen lamp as light source. The transmission spectrum was measured for different values of the layer thickness. The transmission of a liquid layer of about 10 microns, which corresponds to the thickness of the human tear film, shows a cut-off at 290 nm with a transmission of about 25-50% at shorter wavelengths. For wavelengths longer than 290 nm the transmission is higher than 90%. The threshold time ratio for keratitis formation with and without eye drops is above 0.93 considering solar radiation on the earth's surface and above 0.65 considering radiation from arc-welding, respectively. The transmission spectrum of the eye drops under realistic conditions does not show a protective effect against solar UV radiation. However, there exists reduction of UVC radiation in the spectral range typical of artificial UV sources such as arc-welding. We cannot recommend the application of these eye drops as an UV-protective aid against eye damage by solar UV radiation.

Reduction of short wavelength reflectance of multi-wall carbon nanotubes through ultraviolet laser irradiation

NASA Astrophysics Data System (ADS)

Stephens, Michelle S.; Simonds, Brian J.; Yung, Christopher S.; Conklin, Davis; Livigni, David J.; Oliva, Alberto Remesal; Lehman, John H.

2018-05-01

Multi-wall carbon nanotube coatings are used as broadband, low-reflectance absorbers for bolometric applications and for stray light control. They are also used as high emittance blackbody radiators. Irradiation of single wall carbon nanotubes with ultraviolet (UV) laser light has been shown to remove amorphous carbon debris, but there have been few investigations of the interaction of UV light with the more complex physics of multi-wall carbon nanotubes. We present measurements of reflectance and surface morphology before and after exposure of multi-wall carbon nanotube coatings to 248 nm UV laser light. We show that UV exposure reduces the reflectivity at wavelengths below 600 nm and present modeling of the thermal cycling the UV exposure causes at the surface of the carbon nanotubes. This effect can be used to flatten the spectral shape of the reflectivity curve of carbon nanotube absorber coatings used for broadband applications. Finally, we find that the effect of UV exposure depends on the nanotube growth process.

Vesta's UV Lightcurve: Hemispheric Variation in Brightness and Spectral Reversal

NASA Technical Reports Server (NTRS)

Hendrix, Amanda R.; Vilas, Faith; Festou, Michael

2003-01-01

Spectra of asteroid 4 Vesta obtained in October 1990 with the International Ultraviolet Explorer are reanalyzed and reinterpreted. A large portion of the eastern hemisphere (based on the prime meridian definition of Thomas et al., 1997a) is darker at UV Wavelengths than much of the western hemisphere. The UV lightcurve is in contrast with the visible lightcurve, which shows that the eastern hemisphere is brighter than the western. These IUE spectra of Vesta thus may be evidence for the "spectral reversal." first seen on the Moon by Apollo 17. where the visibly brighter lunar highlands are darker than the maria at far-UV wavelengths. This effect was linked to space weathering when it was noted (Wagner et al., 1987) that the spectral reversal appears in the laboratory spectra of lunar soils but not powdered lunar rocks. We investigate Vesta's UV lightcurve and spectral reversal, and its possible connection with space weathering. The addition to grain coatings of small amounts of submicroscopic iron (SMFe) through vapor deposition causes drastic spectral changes at UV-visible wavelengths (Hapke, 2001). while the longer wavelength spectrum remains largely unaffected. Other laboratory results (e.g., Hiroi and Pieters, 1998) indicate that the UV-visible wavelength range is affected by simulated weathering processes in a manner similar to what is seen on Vesta. It is likely that Vesta has experienced relatively minor amounts of space weathering, as indicated by the spectral reversal, along with the subtle visible-near infrared weathering effects (e.g., Binzel et al., 1997).

Calculating Solar Ultraviolet Irradiation Of The Human Cornea And Corresponding Required Sunglass Lens Transmittances

NASA Astrophysics Data System (ADS)

Hoover, Herbert L.; Marsaud, Serge G.

1986-05-01

Tinted ophthalmic lenses are used primarily for eye comfort in a brightly lit environment. An ancillary benefit is the attenuation of ultraviolet radiation. Some national product standards specify quantitative limits for ultraviolet transmittances. Such limits ought to be founded on quantitative estimates of solar irradiances of ocular tissues, with actinic effectiveness taken into account. We use the equations of Green and coworkers for direct and diffuse solar irradiance at the earth's surface to calculate average sky and ground spectral radiances. We use the geometric factors derived by us for the coupling of radiation from these sources to the human cornea. Actinically weighted corneal spectral irradiances integrated over wavelength and time yield peak irradiances and accumulated exposure doses that are compared with recommended exposure limits. This provides the maximal effective ultraviolet transmittances of tinted ophthalmic lenses such that these exposure limits will not be exceeded in the selected exposure environment. The influences on corneal irradiation of such exposure parameters as solar zenith angle, altitude of the exposure site, characteristics of atmospheric aerosols, and ground reflectances are illustrated. The relationships between the effective transmittance (which is a function of the environmental radiation and any actinicweighting function) and readily determined characteristics of the lens itself, viz., its mean transmittance, and a selected spectral transmittance, are derived for three lens transmittance curves. Limits of lens transmittance for the UV-B and UV-A wavelength regions are presented for several representative exposure sites in Europe and the U.S.A.

Rocket and spacecraft studies of ultraviolet emissions from astrophysical targets

NASA Technical Reports Server (NTRS)

Fastie, W. G.; Moos, H. W.; Feldman, P. D.; Henry, R. C.

1975-01-01

Rocket and spacecraft far-UV spectral measurements of several astrophysical targets are reviewed. These include observations of Ly-alpha emissions from Arcturus, Apollo-17 far-UV spectrometry of eta UMa and five other stars, Apollo-17 observations of the lunar atmosphere and the diffuse UV background, and far-UV spectral studies of Venus, Jupiter, and Comet Kohoutek. The Arcturus observations indicated a chromosphere with neutral atomic-hydrogen and atomic-oxygen emissions as well as a very weak atomic-carbon line. The planetary studies revealed O I and C I emissions in the Venusian spectrum as well as large Ly-alpha emissions and possible molecular-hydrogen emissions in that of Jupiter. The lunar observations demonstrated that solar protons do not produce an atomic-hydrogen atmosphere on the moon.

Reference Ultraviolet Wavelengths of Cr III Measured by Fourier Transform Spectrometry

NASA Technical Reports Server (NTRS)

Smillie, D.G.; Pickering, J.C.; Smith, P.L.

2008-01-01

We report Cr III ultraviolet (UV) transition wavelengths measured using a high-resolution Fourier transform spectrometer (FTS), for the first time, available for use as wavelength standards. The doubly ionized iron group element spectra dominate the observed opacity of hot B stars in the UV, and improved, accurate, wavelengths are required for the analysis of astronomical spectra. The spectrum was excited using a chromium-neon Penning discharge lamp and measured with the Imperial College vacuum ultraviolet FTS. 140 classified 3d(exp 3)4s- 3d(exp 3)4p Cr III transition lines, in the spectral range 38,000 to 49,000 cm(exp -1) (2632 to 2041 A), the strongest having wavelength uncertainties less than one part in 10(exp 7), are presented.

Spectral transmittance of UV-blocking soft contact lenses: a comparative study.

PubMed

Rahmani, Saeed; Mohammadi Nia, Mohadeseh; Akbarzadeh Baghban, Alireza; Nazari, Mohammad Reza; Ghassemi-Broumand, Mohammad

2014-12-01

Three major parts of sunlight consist of visible, ultraviolet and infrared radiation. Exposure to ultraviolet radiation (UVR) can result in a spectrum of skin and ocular diseases. UV-blocking contact lenses help provide protection against harmful UV radiation. We studied the ultraviolet and visible light rays transmission in some soft UV-blocking contact lenses. Four available tinted soft lenses (Acuvue Moist, Zeiss CONTACT Day 30 Air spheric, Pretty Eyes and Sauflon 56 UV) have been evaluated for UV and visible transmission. One-way ANOVA testing was performed to establish is there a statistically significant difference between the UV regions and visible spectra means for the contact lenses (α=0.05). Pretty Eyes, Zeiss CONTACT, Acuvue Moist and Sauflon 56 UV showed UV-B transmittance value of 0.65%, 10.69%, 1.22%, and 5.78%, respectively. Pretty Eyes and Acuvue Moist had UV-A transmittance values of 32% and 34%, Sauflon 56 UV and Zeiss CONTACT had transmittance values of 48% and 43%, respectively. All of the studied lenses transmitted at least 94.6% on the visible spectrum. The results of the one-way ANOVA statistical analysis show that a statistically significant difference exists within the group of contact lenses tested for the visible (p<0.001), UV-B (p<0.001) and UV-A (p<0.001) portions of the spectrum (α=0.05). Acuvue Moist has the best UV-blocking property and also visible transmission between other tested contact lenses in this study. Copyright © 2014 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

Determination of geographical origin of alcoholic beverages using ultraviolet, visible and infrared spectroscopy: A review

NASA Astrophysics Data System (ADS)

Uríčková, Veronika; Sádecká, Jana

2015-09-01

The identification of the geographical origin of beverages is one of the most important issues in food chemistry. Spectroscopic methods provide a relative rapid and low cost alternative to traditional chemical composition or sensory analyses. This paper reviews the current state of development of ultraviolet (UV), visible (Vis), near infrared (NIR) and mid infrared (MIR) spectroscopic techniques combined with pattern recognition methods for determining geographical origin of both wines and distilled drinks. UV, Vis, and NIR spectra contain broad band(s) with weak spectral features limiting their discrimination ability. Despite this expected shortcoming, each of the three spectroscopic ranges (NIR, Vis/NIR and UV/Vis/NIR) provides average correct classification higher than 82%. Although average correct classification is similar for NIR and MIR regions, in some instances MIR data processing improves prediction. Advantage of using MIR is that MIR peaks are better defined and more easily assigned than NIR bands. In general, success in a classification depends on both spectral range and pattern recognition methods. The main problem still remains the construction of databanks needed for all of these methods.

Growth of antarctic cyanobacteria under ultraviolet radiation: UVA counteracts UVB inhibition

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

Quesada, A.; Mouget, J.L.; Vincent, W.F.

A mat-forming cyanobacterium (Phormidium murayi West and West) isolated from an ice-shelf pond in Antarctica was grown under white light combined with a range of UVA and UVB irradiance. The 4-day growth rate decreased under increasing ultraviolet (UV) radiation, with a ninefold greater response to UVB relative to UVA. In vivo absorbance spectra showed that UVA and to a greater extent UVB caused a decrease in phycocyanin/chlorophyll a and an increase in carotenoids/chlorophyll a. The phycocyanin/chlorophyll a ratio was closely and positively correlated to the UVB-inhibited growth rate. Under fixed spectral gradients of UV radiation, the growth inhibition effect wasmore » dominated by UVB. However, at specific UVB irradiances the inhibition of growth depended on the ratio of UVB to UVA, and growth rates increased linearly with increasing UVA. These results are consistent with the view that UVB inhibition represents the balance between damage and repair processes that are each controlled by separate wavebands. They also underscore the need to consider UV spectral balance in laboratory and field assays of UVB toxicity. 49 refs., 6 figs.« less

40 CFR 796.1050 - Absorption in aqueous solution: Ultraviolet/visible spectra.

Code of Federal Regulations, 2011 CFR

2011-07-01

....50 λ in nm 235 257 313 350 (2) Fluoranthene (in methanol) from C.R.C. Atlas of Spectral Data...-nitrophenol (in methanol) from C.R.C. Atlas of Spectral Data, paragraph (d)(3) of this section: log ε 3.88 4... to obtain the UV-VIS spectrum of the test compound. Such an instrument should have a photometric...

Ultraviolet Studies of Jupiter's Hydrocarbons and Aerosols from Galileo

NASA Technical Reports Server (NTRS)

Gladstone, G. Randall

2001-01-01

This is the final report for this project. The purpose of this project was to support PI Wayne Pryor's effort to reduce and analyze Galileo UVS (Ultraviolet Spectrometer) data under the JSDAP program. The spectral observations made by the Galileo UVS were to be analyzed to determine mixing ratios for important hydrocarbon species (and aerosols) in Jupiter's stratosphere as a function of location on Jupiter. Much of this work is still ongoing. To date, we have concentrated on analyzing the variability of the auroral emissions rather than the absorption signatures of hydrocarbons, although we have done some work in this area with related HST-STIS data.

Self-service kiosk for testing sunglasses.

PubMed

Mello, Marcio M; Lincoln, Victor A C; Ventura, Liliane

2014-04-25

Sunglasses users may only be assured on their ultraviolet protection by purchasing certified products, however they are not able to check if sunglasses are still ultraviolet (UV) protected as they age, unless they resort themselves to a professional who is qualified for using a spectrophotometer and is acknowledged on the standards for providing a report for the user. Current literature establishes safe limits on the exposure of the eyes relatively to the ultraviolet radiation exposure for the UVA and UVB ranges (280 nm - 400 nm). The UV protection is category dependent. Sunglasses are categorized from 0 to 4 and the categories are determined by the lenses transmission's percentage on the visible range (380 nm - 780 nm). In order to overcome inaccessibility of such measurements on sunglasses, a prototype for testing ultraviolet protection on sunglasses, according to Brazilian Standards, has been developed for amateur use. The system consists of assembling UVA and UVB light sources and two UV responsive photodiode sensors, with Erythema action response for measuring UV protection; for categories measurements, combination of white light and LEDs were used for the visible range, as well as a light sensor having spectral response similar to the human eye. Electronics has been developed for controlling the measurements and software has been implemented for providing the report as well as for the user's interface. All the system was embedded as a self-service touch screen kiosk and provides transmittance measurements that are within the deviation limit required by NBR15111, i.e., 0.25%. Measurements were performed in over 45 sunglasses and compared to CARY 5000 - VARIAN spectrophotometer and present a good correlation for the measurements of transmittance in the visible spectral range (r2 = 0.9999) and in the ultraviolet range (r2 = 0.9997). The prototype identifies the UV protection, for non-corrective sunglasses, according to category of the lens and is available for the public. In addition to educating the population about the importance of wearing protected sunglasses, the prototype has also allowed the public to have access to information about the quality of protection of their own sunglasses in an easy and free testing method.

DATA FROM A SOLAR ULTRAVIOLET MONITORING NETWORK

EPA Science Inventory

The U.S. Environmental Protection Agency, in conjunction with the National Park Service, operates a network of 21 spectrophotometers, measuring spectrally-resolved, surface UV radiation of wavelengths 290-363 nanometers. Fourteen of the measurement sites are in National Parks,...

Augmentation of the IUE Ultraviolet Spectral Atlas

NASA Astrophysics Data System (ADS)

Wu, Chi-Chao

Most likely IUE is the only and last satellite which will support a survey program to record the ultraviolet spectrum of a large number of bright normal stars. It is important to have a library of high quality Low dispersion spectra of sufficient number of stars that provide good coverage in spectral type and luminosity class. Such a library is invaluable for stellar population synthesis of galaxies, studying the nature of distant galaxies, establishing a UV spectral classification system, providing comparison stars for interstellar extinction studies and for peculiar objects or binary systems, studying the effects of temperature, gravity and metallicity on stellar UV spectra, and as a teaching aid. We propose to continue observations of normal stars in order to provide (1) a more complete coverage of the spectral type and luminosity class, and (2) more than one star per spectral typeluminosity class combination to guard against variability and peculiarity, and to allow a finite range of temperature, gravity, and metallicity in a given combination. Our primary goal is to collect the data and make them available to the community immediately (without claiming the 6-month proprietary right). The data will be published in the IUE Newsletter as soon as practical, and the data will be prepared for distribution by the IUE Observatory and the NSSDC.

Ultraviolet Imaging with Low Cost Smartphone Sensors: Development and Application of a Raspberry Pi-Based UV Camera

PubMed Central

Wilkes, Thomas C.; McGonigle, Andrew J. S.; Pering, Tom D.; Taggart, Angus J.; White, Benjamin S.; Bryant, Robert G.; Willmott, Jon R.

2016-01-01

Here, we report, for what we believe to be the first time, on the modification of a low cost sensor, designed for the smartphone camera market, to develop an ultraviolet (UV) camera system. This was achieved via adaptation of Raspberry Pi cameras, which are based on back-illuminated complementary metal-oxide semiconductor (CMOS) sensors, and we demonstrated the utility of these devices for applications at wavelengths as low as 310 nm, by remotely sensing power station smokestack emissions in this spectral region. Given the very low cost of these units, ≈ USD 25, they are suitable for widespread proliferation in a variety of UV imaging applications, e.g., in atmospheric science, volcanology, forensics and surface smoothness measurements. PMID:27782054

From ultraviolet to Prussian blue: a spectral response for the cyanotype process and a safe educational activity to explain UV exposure for all ages.

PubMed

Turner, J; Parisi, A V; Downs, N; Lynch, M

2014-12-01

Engaging students and the public in understanding UV radiation and its effects is achievable using the real time experiment that incorporates blueprint paper, an "educational toy" that is a safe and easy demonstration of the cyanotype chemical process. The cyanotype process works through the presence of UV radiation. The blueprint paper was investigated to be used as not only engagement in discussion for public outreach about UV radiation, but also as a practical way to introduce the exploration of measurement of UV radiation exposure and as a consequence, digital image analysis. Tests of print methods and experiments, dose response, spectral response and dark response were investigated. Two methods of image analysis for dose response calculation are provided using easy to access software and two methods of pixel count analysis were used to determine spectral response characteristics. Variation in manufacture of the blueprint paper product indicates some variance between measurements. Most importantly, as a result of this investigation, a preliminary spectral response range for the radiation required to produce the cyanotype reaction is presented here, which has until now been unknown.

First ultraviolet spectropolarimetry of Be stars from the Wisconsin Ultraviolet Photo-Polarimeter Experiment

NASA Technical Reports Server (NTRS)

Bjorkman, K. S.; Nordsieck, K. H.; Code, A. D.; Anderson, C. M.; Babler, B. L.; Clayton, G. C.; Magalhaes, A. M.; Meade, M. R.; Nook, M. A.; Schulte-Ladbeck, R. E.

1991-01-01

The first UV spectropolarimetric observations of Be stars are presented. They were obtained with the Wisconsin Ultraviolet Photo-Polarimeter Experiment (WUPPE) aboard the Astro-1 mission. WUPPE data on the Be stars Zeta Tau and Pi Aqr, along with near-simultaneous optical data obtained at the Pine Bluff Observatory (PBO). Combined WUPPE and PBO data give polarization as a function of wavelength across a very broad spectral region, from 1400 to 7600 A. Existing Be star models predicted increasing polarization toward shorter wavelengths in the UV, but this is not supported by the WUPPE observations. Instead, the observations show a constant or slightly declining continuum polarization shortward of the Balmer jump, and broad UV polarization dips around 1700 and 1900 A, which may be a result of Fe-line-attenuation effects on the polarized flux. Supporting evidence for this conclusion comes from the optical data, in which decreases in polarization across Fe II lines in Zeta Tau were discovered.

UV irradiance and albedo at Union Glacier Camp (Antarctica): a case study.

PubMed

Cordero, Raul R; Damiani, Alessandro; Ferrer, Jorge; Jorquera, Jose; Tobar, Mario; Labbe, Fernando; Carrasco, Jorge; Laroze, David

2014-01-01

We report on the first spectral measurements of ultraviolet (UV) irradiance and the albedo at a Camp located in the southern Ellsworth Mountains on the broad expanse of Union Glacier (700 m altitude, 79° 46' S; 82° 52'W); about 1,000 km from the South Pole. The measurements were carried out by using a double monochromator-based spectroradiometer during a campaign (in December 2012) meant to weight up the effect of the local albedo on the UV irradiance. We found that the albedo measured at noon was about 0.95 in the UV and the visible part of the spectrum. This high surface reflectivity led to enhancements in the UV index under cloudless conditions of about 50% in comparison with snow free surfaces. Spectral measurements carried out elsewhere as well as estimates retrieved from the Ozone Monitoring Instrument (OMI) were used for further comparisons.

UV Irradiance and Albedo at Union Glacier Camp (Antarctica): A Case Study

PubMed Central

Cordero, Raul R.; Damiani, Alessandro; Ferrer, Jorge; Jorquera, Jose; Tobar, Mario; Labbe, Fernando; Carrasco, Jorge; Laroze, David

2014-01-01

We report on the first spectral measurements of ultraviolet (UV) irradiance and the albedo at a Camp located in the southern Ellsworth Mountains on the broad expanse of Union Glacier (700 m altitude, 79° 46′ S; 82° 52′W); about 1,000 km from the South Pole. The measurements were carried out by using a double monochromator-based spectroradiometer during a campaign (in December 2012) meant to weight up the effect of the local albedo on the UV irradiance. We found that the albedo measured at noon was about 0.95 in the UV and the visible part of the spectrum. This high surface reflectivity led to enhancements in the UV index under cloudless conditions of about 50% in comparison with snow free surfaces. Spectral measurements carried out elsewhere as well as estimates retrieved from the Ozone Monitoring Instrument (OMI) were used for further comparisons. PMID:24598906

Photoprotection and photoreception of intraocular lenses under xenon and white LED illumination.

PubMed

Artigas, J M; Navea, A; García-Domene, M C; Artigas, C; Lanzagorta, A

2016-05-01

To analyze the photoprotection and phototransmission that various intraocular lenses (IOLs) provide under the illumination of a xenon (Xe) lamp and white LEDs (light emitting diode). The spectral transmission curves of six representative IOLs were measured using a Perkin-Elmer Lambda 35 UV/VIS spectrometer. Various filtering simulations were performed using a Xe lamp and white LEDs. The spectral emissions of these lamps were measured with an ILT-950 spectroradiometer. The IOLs analyzed primarily show transmission of nearly 100% in the visible spectrum. In the ultraviolet (UV) region, the filters incorporated in the various IOLs did not filter equally, and some of them let an appreciable amount of UV through. The Xe lamp presented a strong emission of ultraviolet A (UVA), and its emission under 300nm was not negligible. The white LED did not present an appreciable emission under 380nm. The cut-off wavelength of most filters is between 380 and 400nm (Physiol Hydriol60C(®), IOLTECH E4T(®), Alcon SA60AT(®), Alcon IQ SN60WF(®)), so that their UV protection is very effective. Nonetheless, the IOL OPHTEC Oculaid(®) contains a filter that, when a Xe lamp is used, lets through up to 20% for 350nm and up to 15% for 300nm, which at this point is ultraviolet B (UVB). The OPHTEC(®) Artisan IOL has a transmission peak below 300nm, which must be taken into account under Xe illumination. White LEDs do not emit energy below 380nm, so no special protection is required in the UV region. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

The 90-day report for SL4 experiment S019: UV stellar astronomy

NASA Technical Reports Server (NTRS)

1974-01-01

The use of Experiment S019 to obtain moderate dispersion stellar spectra extending down to 1300A with sufficient spectral resolution to permit the study of ultraviolet (UV) line spectra and of spectral energy distributions of early-type stars is studied. Data obtained from this experiment should be of sufficient accuracy to permit detailed physical analysis of individual stars and nebulae, but an even more basic consideration is the expectation of obtaining spectra of a sufficient number of stars so that a statistically meaningful survey may be made of the UV spectra of a wide variety of star types. These should include all luminosity classes of spectral types O, B and A, as well as peculiar stars such as Wolf-Rayet stars and Ap or Am stars. An attempt was also made to obtain, in the no-prism mode, low dispersion UV spectra in a number of Milky Way star fields and in nearby galaxies.

Attempts to probe the ozone layer and the ultraviolet-B levels of the past.

PubMed

Björn, Lars Olof; McKenzie, Richard L

2007-07-01

To get a proper perspective on the current status of atmospheric ozone, which protects the biosphere from ultraviolet-B (UV-B; 280-315 nm) radiation, it would be of value to know how ozone and UV-B radiation have varied in the past. The record of worldwide ozone monitoring goes back only a few decades, and the record of reliable UV-B measurements is even shorter. Here we review indirect methods to assess their status further back in time. These include variations in the Sun's emission and how these affect the atmosphere, changes in the Earth's orbit, geologic imprints of atmospheric ozone, effects of catastrophic events such as volcanic eruptions, biological proxies of UV-B radiation, the spectral signature of terrestrial ozone in old recordings of star spectra, and the modeling of UV-B irradiance from ozone data and meteorological recordings. Although reliable reconstructions do not yet extend far into the past, there is some hope for future progress.

Fast simulation tool for ultraviolet radiation at the earth's surface

NASA Astrophysics Data System (ADS)

Engelsen, Ola; Kylling, Arve

2005-04-01

FastRT is a fast, yet accurate, UV simulation tool that computes downward surface UV doses, UV indices, and irradiances in the spectral range 290 to 400 nm with a resolution as small as 0.05 nm. It computes a full UV spectrum within a few milliseconds on a standard PC, and enables the user to convolve the spectrum with user-defined and built-in spectral response functions including the International Commission on Illumination (CIE) erythemal response function used for UV index calculations. The program accounts for the main radiative input parameters, i.e., instrumental characteristics, solar zenith angle, ozone column, aerosol loading, clouds, surface albedo, and surface altitude. FastRT is based on look-up tables of carefully selected entries of atmospheric transmittances and spherical albedos, and exploits the smoothness of these quantities with respect to atmospheric, surface, geometrical, and spectral parameters. An interactive site, http://nadir.nilu.no/~olaeng/fastrt/fastrt.html, enables the public to run the FastRT program with most input options. This page also contains updated information about FastRT and links to freely downloadable source codes and binaries.

Ultraviolet vision in birds: the importance of transparent eye media

PubMed Central

Lind, Olle; Mitkus, Mindaugas; Olsson, Peter; Kelber, Almut

2014-01-01

Ultraviolet (UV)-sensitive visual pigments are widespread in the animal kingdom but many animals, for example primates, block UV light from reaching their retina by pigmented lenses. Birds have UV-sensitive (UVS) visual pigments with sensitivity maxima around 360–373 nm (UVS) or 402–426 nm (violet-sensitive, VS). We describe how these pigments are matched by the ocular media transmittance in 38 bird species. Birds with UVS pigments have ocular media that transmit more UV light (wavelength of 50% transmittance, λT0.5, 323 nm) than birds with VS pigments (λT0.5, 358 nm). Yet, visual models predict that colour discrimination in bright light is mostly dependent on the visual pigment (UVS or VS) and little on the ocular media. We hypothesize that the precise spectral tuning of the ocular media is mostly relevant for detecting weak UV signals, e.g. in dim hollow-nests of passerines and parrots. The correlation between eye size and UV transparency of the ocular media suggests little or no lens pigmentation. Therefore, only small birds gain the full advantage from shifting pigment sensitivity from VS to UVS. On the other hand, some birds with VS pigments have unexpectedly low UV transmission of the ocular media, probably because of UV blocking lens pigmentation. PMID:24258716

Ultraviolet vision in birds: the importance of transparent eye media.

PubMed

Lind, Olle; Mitkus, Mindaugas; Olsson, Peter; Kelber, Almut

2014-01-07

Ultraviolet (UV)-sensitive visual pigments are widespread in the animal kingdom but many animals, for example primates, block UV light from reaching their retina by pigmented lenses. Birds have UV-sensitive (UVS) visual pigments with sensitivity maxima around 360-373 nm (UVS) or 402-426 nm (violet-sensitive, VS). We describe how these pigments are matched by the ocular media transmittance in 38 bird species. Birds with UVS pigments have ocular media that transmit more UV light (wavelength of 50% transmittance, λ(T0.5), 323 nm) than birds with VS pigments (λ(T0.5), 358 nm). Yet, visual models predict that colour discrimination in bright light is mostly dependent on the visual pigment (UVS or VS) and little on the ocular media. We hypothesize that the precise spectral tuning of the ocular media is mostly relevant for detecting weak UV signals, e.g. in dim hollow-nests of passerines and parrots. The correlation between eye size and UV transparency of the ocular media suggests little or no lens pigmentation. Therefore, only small birds gain the full advantage from shifting pigment sensitivity from VS to UVS. On the other hand, some birds with VS pigments have unexpectedly low UV transmission of the ocular media, probably because of UV blocking lens pigmentation.

Everything you ever wanted to know about the ultraviolet spectra of star-forming galaxies but were afraid to ask

NASA Technical Reports Server (NTRS)

Kinney, A. L.; Bohlin, R.; Calzetti, D.; Panagia, N.; Wyse, R.

1993-01-01

We present ultraviolet spectra of 143 star-forming galaxies of different morphological types and activity classes including S0, Sa, Sb, Sc, Sd, irregular, starburst, blue compact, blue compact dwarf, Liner, and Seyfert 2 galaxies. These IUE spectra cover the wavelength range from 1200 to 3200 A and are taken in a large aperture (10 x 20 inch). The ultraviolet spectral energy distributions are shown for a subset of the galaxies, ordered by spectral index, and separated by type for normal galaxies, Liners, starburst galaxies, blue compact (BCG) and blue compact dwarf (BCDG) galaxies, and Seyfert 2 galaxies. The ultraviolet spectra of Liners are, for the most part, indistinguishable from the spectra of normal galaxies. Starburst galaxies have a large range of ultraviolet slope, from blue to red. The star-forming galaxies which are the bluest in the optical (BCG and BCDG), also have the 'bluest' average ultraviolet slope of beta = -1.75 +/- 0.63. Seyfert 2 galaxies are the only galaxies in the sample that consistently have detectable UV emission lines.

Spectral and Power Stability Tests of Deep UV LEDs for AC Charge Management

NASA Astrophysics Data System (ADS)

Sun, Ke-Xun; Higuchi, Sei; Goh, Allex; Allard, Brett; Gill, Dale; Buchman, Saps; Byer, Robert

2006-11-01

Deep ultraviolet (UV) LEDs have recently been used in AC charge management experiments to support gravitational reference sensors for future space missions. The UV LED based charge management system offers compact size, light weight, and low power consumption compared to plasma sources. The AC charge management technique, which is enabled by easy modulation of UV LED output, achieves higher dynamic range for charge control. Further, the high modulation frequency, which is out of the gravitational wave detection band, reduces disturbances to the proof mass. However, there is a need to test and possibly improve the lifetime of UV LEDs, which were developed only a year ago. We have initiated a series of spectral and power stability tests for UV LEDs and designed experiments according to the requirements of AC charge management. We operate UV LEDs with a modulated current drive and maintain the operating temperature at 22 °C,28 similar to the LISA spacecraft working condition. The testing procedures involve measuring the baseline spectral shape and output power level prior to the beginning of the tests and then re-measuring the same quantities periodically. As of the date of submission (August 28th, 2006), we have operated a UV LED for more than 2,700 hours.

Ultraviolet Observations of Three Dwarf Cepheids

NASA Astrophysics Data System (ADS)

Sturch, Conrad R.

Ultraviolet observations of three dwarf Cepheids (VZ Cnc, SX Phe, and AI Vel) have been obtained with the ANS. Analysis of these observations (Sturch and WU 1982) reveals that the flux distributions observed for each of these objects exhibit UV deficiencies which increase monotonically with decreasing wavelengths. The largest UV deficiencies are noted for SX Phe which has been identified with group of dwarf Cepheids with low metallicity and low luminosity, two attributes that are expected to have opposite effects on the UV flux distribution. It is proposed to obtain low dispersion IUE spectra of the three stars throughout each of their light cycles. Such observations will identify spectral features responsible for the flux deficiencies and will provide data necessary for a detailed comparison with model atmospheres. Knowledge of atmospheric parameters will lead to a better understanding of the evolutionary status of dwarf Cepheids.

Satellite estimation of surface spectral ultraviolet irradiance using OMI data in East Asia

NASA Astrophysics Data System (ADS)

Lee, H.; Kim, J.; Jeong, U.

2017-12-01

Due to a strong influence to the human health and ecosystem environment, continuous monitoring of the surface ultraviolet (UV) irradiance is important nowadays. The amount of UVA (320-400 nm) and UVB (290-320 nm) radiation at the Earth surface depends on the extent of Rayleigh scattering by atmospheric gas molecules, the radiative absorption by ozone, radiative scattering by clouds, and both absorption and scattering by airborne aerosols. Thus advanced consideration of these factors is the essential part to establish the process of UV irradiance estimation. Also UV index (UVI) is a simple parameter to show the strength of surface UV irradiance, therefore UVI has been widely utilized for the purpose of UV monitoring. In this study, we estimate surface UV irradiance at East Asia using realistic input based on OMI Total Ozone and reflectivity, and then validate this estimated comparing to UV irradiance from World Ozone and Ultraviolet Radiation Data Centre (WOUDC) data. In this work, we also try to develop our own retrieval algorithm for better estimation of surface irradiance. We use the Vector Linearized Discrete Ordinate Radiative Transfer (VLIDORT) model version 2.6 for our UV irradiance calculation. The input to the VLIDORT radiative transfer calculations are the total ozone column (TOMS V7 climatology), the surface albedo (Herman and Celarier, 1997) and the cloud optical depth. Based on these, the UV irradiance is calculated based on look-up table (LUT) approach. To correct absorbing aerosol, UV irradiance algorithm added climatological aerosol information (Arola et al., 2009). The further study, we analyze the comprehensive uncertainty analysis based on LUT and all input parameters.

UV protection for sunglasses: revisiting the standards

NASA Astrophysics Data System (ADS)

Masili, Mauro; Schiabel, Homero; Ventura, Liliane

2014-02-01

In a continuing work of establishing safe limits for UV protection on sunglasses, we have estimated the incident UV radiation for the 280 nm - 400 nm range for 5500 locations in Brazil. Current literature establishes safe limits regarding ultraviolet radiation exposure in the spectral region 180nm-400nm for weighted and unweighted UV radiant exposure. British Standard BSEN1836(2005) and American Standard ANZI Z80.3(2009) require the UV protection in the spectral range 280nm-380nm, and The Brazilian Standard for sunglasses protection, NBR15111(20013), currently requires protection for the 280nm - 400nm range as established by literature. However, none of them take into account the total (unweighted) UVA radiant exposure.Calculations of these limits have been made for 5500 Brazilian locations which included the geographic position of the city; altitude, inclination angle of the Earth; typical atmospheric data (ozone column; water vapor and others) as well as scattering from concrete, grass, sand, water, etc.. Furthermore, regarding UV safety for the ocular media, the resistance to irradiance test required on this standard of irradiating the lenses for 25 continuous hours with a 450W sunlight simulator leads to a correspondence of 26 hours and 10 minutes of continuous exposure to the Sun. Moreover, since the sun irradiance in Brazil is quite large, integrations made for the 280-400 nm range shows an average of 45% of greater ultraviolet radiant exposure than for the 280-380 nm range. Suggestions on the parameters of these tests are made in order to establish safe limits according to the UV irradiance in Brazil.

Effects of Regolith Properties on UV/VIS Spectra and Implications for Lunar Remote Sensing

NASA Astrophysics Data System (ADS)

Coman, Ecaterina Oana

Lunar regolith chemistry, mineralogy, various maturation factors, and grain size dominate the reflectance of the lunar surface at ultraviolet (UV) to visible (VIS) wavelengths. These regolith properties leave unique fingerprints on reflectance spectra in the form of varied spectral shapes, reflectance intensity values, and absorption bands. With the addition of returned lunar soils from the Apollo and Luna missions as ground truth, these spectral fingerprints can be used to derive maps of global lunar chemistry or mineralogy to analyze the range of basalt types on the Moon, their spatial distribution, and source regions for clues to lunar formation history and evolution. The Lunar Reconnaissance Orbiter Camera (LROC) Wide Angle Camera (WAC) is the first lunar imager to detect bands at UV wavelengths (321 and 360 nm) in addition to visible bands (415, 566, 604, 643, and 689 nm). This dissertation uses a combination of laboratory and remote sensing studies to examine the relation between TiO2 concentration and WAC UV/VIS spectral ratios and to test the effects of variations in lunar chemistry, mineralogy, and soil maturity on ultraviolet and visible wavelength reflectance. Chapter 1 presents an introduction to the dissertation that includes some background in lunar mineralogy and remote sensing. Chapter 2 covers coordinated analyses of returned lunar soils using UV-VIS spectroscopy, X-ray diffraction, and micro X-ray fluorescence. Chapter 3 contains comparisons of local and global remote sensing observations of the Moon using LROC WAC and Clementine UVVIS TiO2 detection algorithms and Lunar Prospector (LP) Gamma Ray Spectrometer (GRS)-derived FeO and TiO2 concentrations. While the data shows effects from maturity and FeO on the UV/VIS detection algorithm, a UV/VIS relationship remains a simple yet accurate method for TiO2 detection on the Moon.

Laser-Induced Breakdown Spectroscopy Infrared Emission From Inorganic and Organic Substances

DTIC Science & Technology

2006-11-01

using a liquid-nitrogen cooled indium antimonide (InSb) detector and the signal was recorded using a gated electronic circuit (boxcar averager). All...contaminants by analyzing the atomic spectral emission lines that result subsequent to plasmas generated by laser power. The ultraviolet-visible-near infrared...UV- Vis-NIR) spectral region exploited in conventional LIBS largely elucidates the elemental composition of the laser target by profiling these

Ultraviolet and visible radiation at Barrow, Alaska: Climatology and influencing factors on the basis of version 2 National Science Foundation network data

NASA Astrophysics Data System (ADS)

Bernhard, Germar; Booth, Charles R.; Ehramjian, James C.; Stone, Robert; Dutton, Ellsworth G.

2007-05-01

Spectral ultraviolet (UV) and visible irradiance has been measured near Barrow, Alaska (71°N, 157°W), between 1991 and 2005 with a SUV-100 spectroradiometer. The instrument is part of the U.S. National Science Foundation's UV Monitoring Network. Here we present results based on the recently produced "version 2" data release, which supersedes published "version 0" data. Cosine error and wavelength-shift corrections applied to the new version increased biologically effective UV dose rates by 0-10%. Corrected clear-sky measurements of different years are typically consistent to within ±3%. Measurements were complemented with radiative transfer model calculations to retrieve total ozone and surface albedo from measured spectra and for the separation of the different factors influencing UV and visible radiation. A climatology of UV and visible radiation was established, focusing on annual cycles, trends, and the effect of clouds. During several episodes in spring of abnormally low total ozone, the daily UV dose at 305 nm exceeded the climatological mean by up to a factor of 2.6. Typical noontime UV Indices during summer vary between 2 and 4; the highest UV Index measured was 5.0 and occurred when surface albedo was unusually high. Radiation levels in the UV-A and visible exhibit a strong spring-autumn asymmetry. Irradiance at 345 nm peaks on approximately 20 May, 1 month before the solstice. This asymmetry is caused by increased cloudiness in autumn and high albedo in spring, when the snow covered surface enhances downwelling UV irradiance by up to 57%. Clouds reduce UV radiation at 345 nm on average by 4% in March and by more than 40% in August. Aerosols reduce UV by typically 5%, but larger reductions were observed during Arctic haze events. Stratospheric aerosols from the Pinatubo eruption in 1991 enhanced spectral irradiance at 305 nm for large solar zenith angles. The year-to-year variations of spectral irradiance at 305 nm and of the UV Index are mostly caused by variations in total ozone and cloudiness. Changes in surface albedo that may occur in the future can have a marked impact on UV levels between May and July. No statistically significant trends in monthly mean noontime irradiance were found.

Detection of adulterated Ginkgo biloba supplements using chromatographic and spectral fingerprints

USDA-ARS?s Scientific Manuscript database

The fingerprints of 18 commercially available Ginkgo biloba supplements, 12 samples of raw Ginkgo biloba leaves, and 3 Ginkgo biloba Standard Reference Materials from the National Institute of Standards and Technology were acquired directly (no chromatography) by ultraviolet (UV) spectrophotometry a...

Space Weathering Trends (UV and NIR) at Lunar Magnetic Anomalies

NASA Astrophysics Data System (ADS)

Blewett, D. T.; Denevi, B. W.; Cahill, J. T.; Klima, R. L.

2017-12-01

Areas of magnetized crustal rocks on the Moon, known as magnetic anomalies, affect the flux of solar-wind ions that bombard the lunar surface. Hence, magnetically shielded areas could experience a space weathering regime different from the lunar norm. The unusual, high-albedo markings called lunar swirls are collocated with magnetic anomalies. The high albedo in the near-ultraviolet through near-infrared is consistent with the presence of material that is less weathered than that found in mature, non-shielded areas. We have undertaken an analysis of spectral trends associated with swirls in order to gain further insight into the nature and origin of these features. We examine swirls in the near-ultraviolet (Lunar Reconnaissance Orbiter LROC-WAC) and near-infrared (Chandrayaan Moon Mineralogy Mapper and Kaguya Spectral Profiler). We find that relative to the normal weathering trend, the swirls have a steeper NIR continuum slope (i.e., the continuum is redder than expected for their albedo) and steeper UV slope (i.e., greater UV drop-off than expected for their albedo). These trends can be understood in terms of differing relative abundances of microphase and nanophase metallic iron weathering products.

Tomographic separation of composite spectra. 2: The components of 29 UW Canis Majoris

NASA Technical Reports Server (NTRS)

Bagnuolo, William G., Jr.; Gies, Douglas R.; Hahula, Michael E.; Wiemker, Rafael; Wiggs, Michael S.

1994-01-01

We have analyzed the UV photospheric lines of 29 CMa, a 4.39 day period, double-lined O-type spectroscopic binary. Archival data from International Ultraviolet Explorer (IUE)(28 spectra well distributed in oribital phase) were analyzed with several techniques. We find that the mass ratio is q = 1.20 +/- 0.16 (secondary more massive) based on three independent arguments. A tomography algorithm was used to produce the separate spectra of the two stars in six UV spectral regions. The MK spectral classifications of the primary and secondary, O7.5-8 Iab and O9.7 Ib, respectively, were estimated through a comparison of UV line ratios with those in spectral standard stars. The flux ratio of the stars in the UV is 0.36 +/- 0.07 (primary brighter). The primary has a strong P Cygni NIV wavelength 1718 feature, indicating a strong stellar wind. We also present tomographic reconstructions of visual spectral data in the range 4300-4950 A, based on seven observations of differing orbital phases, which confirm the UV classifications, and show that the primary is an Of star. From the spectral classifications, we estimate the temperatures of the stars to be 33,750 K and 29,000 K for primary and secondary, respectively. We then fit visual and UV light curves and show that reasonably good fits can be obtained with these temperatures, a semicontact configuration, an inclination of 74 deg. +/- 2 deg., and an intensity ratio r is less than 0.5.

Analysis of the UV-B Regime and Potential Effects on Alfalfa

NASA Technical Reports Server (NTRS)

Seitz, Jeffery C.

1998-01-01

Life at the surface of the Earth, over the last 400 m.y., evolved under conditions of decreased short-wave radiation (i.e., ultraviolet) relative to solar output due to absorption and scattering by constituents (e.g., ozone, water vapor, aerosols) in the upper atmosphere. However, a significant amount of ultraviolet radiation in the range from 280-320 nm, known as ultraviolet-B radiation, reaches the Earth's surface and has sufficient energy to be damaging to biologic tissue. Natural fluctuations in atmospheric constituents (seasonal variation, volcanic eruptions, etc.), changes in the orbital attitude of the Earth (precession, axial tilt, orbital eccentricity), and long-term solar variability contribute to changes in the total amount of ultraviolet radiation reaching the surface of the Earth, and thus, the biosphere. More recently, the atmospheric release of commercial propellants and refrigerants, known as chlorofluorocarbons (CFCs), has contributed to a significant depletion in naturally occurring ozone in the stratosphere. Thus, decreased stratospheric ozone has resulted in an increased UV-B flux at the Earth's surface which may have profound effects on terrestrial and marine organisms. In this study, we are investigating the effects of differing solar UV-B fluxes on alfalfa (Medicago sativa L.), an important agricultural crop. A long-term goal of this research is to develop spectral signatures to detect plant response to increased UV-B radiation from remote sensor platforms.

The Ultraviolet Spectrograph on the Europa Mission (Europa-UVS)

NASA Astrophysics Data System (ADS)

Retherford, K. D.; Gladstone, R.; Greathouse, T. K.; Steffl, A.; Davis, M. W.; Feldman, P. D.; McGrath, M. A.; Roth, L.; Saur, J.; Spencer, J. R.; Stern, S. A.; Pope, S.; Freeman, M. A.; Persyn, S. C.; Araujo, M. F.; Cortinas, S. C.; Monreal, R. M.; Persson, K. B.; Trantham, B. J.; Versteeg, M. H.; Walther, B. C.

2015-12-01

NASA's Europa multi-flyby mission is designed to provide a diversity of measurements suited to enrich our understanding of the potential habitability of this intriguing ocean world. The Europa mission's Ultraviolet Spectrograph, Europa-UVS, is the sixth in a series of successful ultraviolet imaging spectrographs (Rosetta-Alice, New Horizons Pluto-Alice, LRO-LAMP) and, like JUICE-UVS (now under Phase B development), is largely based on the most recent of these to fly, Juno-UVS. Europa-UVS observes photons in the 55-210 nm wavelength range, at moderate spectral and spatial resolution along a 7.5° slit. Three distinct apertures send light to the off-axis telescope mirror feeding the long-slit spectrograph: i) a main entrance airglow port is used for most observations (e.g., airglow, aurora, surface mapping, and stellar occultations); ii) a high-spatial-resolution port consists of a small hole in an additional aperture door, and is used for detailed observations of bright targets; and iii) a separate solar port allows for solar occultations, viewing at a 60° offset from the nominal payload boresight. Photon event time-tagging (pixel list mode) and programmable spectral imaging (histogram mode) allow for observational flexibility and optimal science data management. As on Juno-UVS, the effects of penetrating electron radiation on electronic parts and data quality are mitigated through contiguous shielding, filtering of pulse height amplitudes, management of high-voltage settings, and careful use of radiation-hard parts. The science goals of Europa-UVS are to: 1) Determine the composition & chemistry, source & sinks, and structure & variability of Europa's atmosphere, from equator to pole; 2) Search for and characterize active plumes in terms of global distribution, structure, composition, and variability; 3) Explore the surface composition & microphysics and their relation to endogenic & exogenic processes; and 4) Investigate how energy and mass flow in the Europa atmosphere, neutral cloud & plasma torus, and footprint on Jupiter. Here we present the UVS investigation by describing the science we plan to address, the salient details of the instrument, and the basic concept of operations.

Far-UV Spectral Mapping of Lunar Composition, Porosity, and Space Weathering: LRO Lyman Alpha Mapping Project (LAMP)

NASA Astrophysics Data System (ADS)

Retherford, K. D.; Greathouse, T. K.; Mandt, K.; Gladstone, R.; Liu, Y.; Hendrix, A. R.; Hurley, D.; Cahill, J. T.; Stickle, A. M.; Egan, A.; Kaufmann, D. E.; Grava, C.; Pryor, W. R.

2016-12-01

Far ultraviolet reflectance measurements of the Moon, icy satellites, comets, and asteroids obtained within the last decade have ushered in a new era of scientific advancement for UV surface investigations. The Lunar Reconnaissance Orbiter (LRO) Lyman Alpha Mapping Project (LAMP) has demonstrated an innovative nightside observing technique, putting a new light on permanently shadowed regions (PSRs) and other features on the Moon. Dayside far-UV albedo maps complement the nightside data, and LRO's polar orbit and high data downlink capabilities enable searches for diurnal variations in spectral signals. We'll discuss the strengths of the far-UV reflectance imaging spectroscopy technique with respect to several new LAMP results. Detections of water frost and hydration signatures near 165 nm, for example, provide constraints on composition that complement infrared spectroscopy, visible imaging, neutron spectroscopy, radar, and other techniques. At far-UV wavelengths a relatively blue spectral slope is diagnostic of space weathering, which is opposite of the spectral reddening indicator of maturity at wavelengths longward of 180 nm. By utilizing natural diffuse illumination sources on the nightside the far-UV technique is able to identify relative increases in porosity within the PSRs, and provides an additional tool for determining relative surface ages. Prospects for future studies are further enabled by a new, more sensitive dayside operating mode enacted during the present LRO mission extension.

Why is it advantageous for animals to detect celestial polarization in the ultraviolet? Skylight polarization under clouds and canopies is strongest in the UV.

PubMed

Barta, András; Horváth, Gábor

2004-02-21

The perception of skylight polarization in the ultraviolet (UV) by many insect species for orientation purposes is rather surprising, because both the degree of linear polarization and the radiance of light from the clear sky are considerably lower in the UV than in the blue or green. In this work we call this the "UV-sky-pol paradox". Although in the past, several attempts have been made to resolve this paradox, none of them was convincing. We present here a possible quantitative resolution to the paradox. We show by a model calculation that if the air layer between a cloud and a ground-based observer is partly sunlit, the degree of linear polarization p of skylight originating from the cloudy region is highest in the UV, because in this spectral range the unpolarized UV-deficient cloudlight dilutes least the polarized light scattered in the air beneath the cloud. Similarly, if the air under foliage is partly sunlit, p of downwelling light from the canopied region is maximal in the UV, because in this part of spectrum the unpolarized UV-deficient green canopylight dilutes least the polarized light scattered in the air beneath the canopy. Therefore, the detection of polarization of downwelling light under clouds or canopies is most advantageous in the UV, in which spectral range the risk is the smallest that the degree of polarization p is lower than the threshold p(tr) of polarization sensitivity in animals. On the other hand, under clear skies there is no favoured wavelength for perception of celestial polarization, because p of skylight is high enough (p > p(tr)) at all wavelengths. We show that there is an analogy between the detection of UV skylight polarization and the polarotactic water detection in the UV. However, insects perceive skylight polarization by UV or blue or green receptors. The question, why they differ in the spectral channel used for the detection of celestial polarization cannot be answered at the present time, because data are insufficient. Nevertheless, we present here one possible atmospheric optical reason why certain visual systems involved in detecting celestial polarization, are specifically tuned to the UV part of the spectrum.

Distribution and nature of UV absorbers on Trition's surface

NASA Technical Reports Server (NTRS)

Stern, S. Alan

1995-01-01

Substantial evidence suggests that a UV (ultraviolet) Spectrally Absorbing Material (UV-SAM) exists on Triton's surface. This evidence is found in the positive slope in Triton's spectrum from the UV to the near-IR, and the increasing contrast in Triton's light curve in the blue and UV. Although it is now widely-thought that UV-SAM's exist on Triton, little is known about their distribution and spectral properties. The goal of this NDAP Project is to determine the spatial distribution and geological context of the UV-SAM material. We hope to determine if UV-SAM's on Triton are correlated with geologic wind streaks, craters, calderas, geomorphic/topographic units, regions containing (or lacking) volatile frosts, or some other process (e.g., magnetospheric interactions). Once the location and distribution of UV-SAM's has been determined, further constraints on their composition can be made by analyzing the spectrographic data set. To accomplish these goals, various data sets will be used, including Voyager 2 UV and visible images of Triton's surface, IUE and HST spectra of Triton, and a geologic map of the surface based on Voyager 2 and spectrophotometric data. The results of this research will be published in the planetary science literature.

Modelling a man-portable air-defence (MANPAD) system with a rosette scan two-colour infrared (IR) and ultraviolet (UV) seeker

NASA Astrophysics Data System (ADS)

Kumar, Devinder; Smith, Leon; Richardson, Mark A.; Ayling, Richard; Barlow, Nick

2014-10-01

The Ultraviolet (UV) band of the electromagnetic (EM) spectrum has the potential to be used as the host medium for the operation of guided weapons. Unlike in the Infrared (IR), a target propelled by an air breathing jet engine produces no detectable radiation in the UV band, and is opaque to the background UV produced by the Sun. Successful engineering of spectral airborne IR countermeasures (CM) against existing two colour IR seekers has encouraged missile counter-countermeasure (CCM) designers to utilise the silhouette signature of an aircraft in the UV as a means of distinguishing between a true target and a flare CM. In this paper we describe the modelling process of a dual band IR and UV rosette scan seeker using CounterSim, a missile engagement and countermeasure simulation software package developed by Chemring Countermeasures Ltd. Results are shown from various simulated engagements of the dual band MANPAD with a C-130 Hercules modelled by Chemring Countermeasures. These results have been used to estimate the aircrafts' vulnerability to this MANPAD threat. A discussion on possible future optical countermeasures against dual band IR-UV seekers is given in conclusion to the simulation results.

Further comparison of MODTRAN 5 to measured data in the UV band

NASA Astrophysics Data System (ADS)

Smith, Leon; Richardson, Mark; Ayling, Richard; Barlow, Nick

2014-10-01

The ability to accurately model background radiation from the sun is important in understanding the operation of missile systems with ultraviolet (UV) guard channels. In theory a missile system's UV channel detects a target's silhouette, caused by its `negative contrast' with respect to background UV radiation. The variation in background levels of UV will therefore have an effect on the operability of a missile system that utilises a UV channel. In this paper an update on the measurement and comparison of background UV-A radiation to data produced by Moderate Resolution Atmospheric Transmission 5 (MODTRAN®5) is given. In the past surface flux and radiance data calculated using MODTRAN®5 has been compared to data from the World Ozone and Ultraviolet Data Centre (WOUDC) archive, and measurements taken by the author at the Defence Academy of the UK. With the aid of spectral measurement equipment, new measurements have been made and compared with the radiance profiles produced by MODTRAN®5, including measurements made throughout both winter and summer months. Also discussed are the effects of scattering and absorption by different cloud types on the amount of radiation observed at the Earth's surface.

Self-service kiosk for testing sunglasses

PubMed Central

2014-01-01

Background Sunglasses users may only be assured on their ultraviolet protection by purchasing certified products, however they are not able to check if sunglasses are still ultraviolet (UV) protected as they age, unless they resort themselves to a professional who is qualified for using a spectrophotometer and is acknowledged on the standards for providing a report for the user. Current literature establishes safe limits on the exposure of the eyes relatively to the ultraviolet radiation exposure for the UVA and UVB ranges (280 nm – 400 nm). The UV protection is category dependent. Sunglasses are categorized from 0 to 4 and the categories are determined by the lenses transmission’s percentage on the visible range (380 nm – 780 nm). Methods In order to overcome inaccessibility of such measurements on sunglasses, a prototype for testing ultraviolet protection on sunglasses, according to Brazilian Standards, has been developed for amateur use. The system consists of assembling UVA and UVB light sources and two UV responsive photodiode sensors, with Erythema action response for measuring UV protection; for categories measurements, combination of white light and LEDs were used for the visible range, as well as a light sensor having spectral response similar to the human eye. Electronics has been developed for controlling the measurements and software has been implemented for providing the report as well as for the user’s interface. Results All the system was embedded as a self-service touch screen kiosk and provides transmittance measurements that are within the deviation limit required by NBR15111, i.e., 0.25%. Measurements were performed in over 45 sunglasses and compared to CARY 5000 – VARIAN spectrophotometer and present a good correlation for the measurements of transmittance in the visible spectral range (r2 = 0.9999) and in the ultraviolet range (r2 = 0.9997). Conclusions The prototype identifies the UV protection, for non-corrective sunglasses, according to category of the lens and is available for the public. In addition to educating the population about the importance of wearing protected sunglasses, the prototype has also allowed the public to have access to information about the quality of protection of their own sunglasses in an easy and free testing method. PMID:24761766

UV Signatures of Ices: Moons in the Solar System

NASA Astrophysics Data System (ADS)

Hendrix, A. R.; Hansen, C. J.; Retherford, K. D.; Vilas, F.

2017-12-01

Using Earth-orbiting telescopes such as the International Ultraviolet Explorer and the Hubble Space Telescope, significant advances have been made in the area of ultraviolet observations of solar system objects. More in-depth studies have been made using interplanetary probes such as Galileo, Cassini and Lunar Reconnaissance Orbiter (LRO). While the UV spectral range has traditionally been used to study atmospheric and auroral processes, there is much to be learned by examining solid surfaces in the UV, including surface composition, weathering processes and effects, and the generation of thin atmospheres. Here we focus on moons in the solar system, including Earth's moon and the Saturnian satellites. The diagnostic UV signature of H2O is used to study ice in the lunar polar regions as well as hydration at lower latitudes, in observations from LRO LAMP. The water ice signature is nearly ubiquitous in the Saturn system; Cassini UVIS datasets are used to study grain sizes, exogenic processes/effects and non-ice species.

Archival Study of Energetic Processes in the Upper Atmosphere of the Outer Planets

NASA Technical Reports Server (NTRS)

Ballester, Gilda E.; Harris, Walter M.

1998-01-01

We compare International Ultraviolet Explorer (IUE) spectral observations of Jupiter's UltraViolet (UV) aurora in H-Lyman alpha (H-Lya) and H2 emissions with images of the UV aurora with HST to make more realistic interpretations of the IUE dataset. Use the limited spatial information in the IUE line-by-line spectra of the bright H-Lya line emission in the form of pseudo-monochromatic images at the IUE 3.5 arcsec resolution (Lya pseudo-images), to derive information on the emissions. Analysing of H2 spectra of Saturn's UV aurora to infer atmospheric level of auroral excitation from the methane absorption (color ratios). Analysing of a Uranus IUE dataset to determine periodicity in the emissions attributable to auroral emission fixed in magnetic longitude. Reviewing of the results from IUE observations of the major planets, upper atmospheres and interactions with the planets magnetospheres. Analysing of IUE spectra of the UV emissions from Io to identify excitation processes and infer properties of the Io-torus-Jupiter system.

UV solar irradiance in observations and the NRLSSI and SATIRE-S models

NASA Astrophysics Data System (ADS)

Yeo, K. L.; Ball, W. T.; Krivova, N. A.; Solanki, S. K.; Unruh, Y. C.; Morrill, J.

2015-08-01

Total solar irradiance and UV spectral solar irradiance has been monitored since 1978 through a succession of space missions. This is accompanied by the development of models aimed at replicating solar irradiance by relating the variability to solar magnetic activity. The Naval Research Laboratory Solar Spectral Irradiance (NRLSSI) and Spectral And Total Irradiance REconstruction for the Satellite era (SATIRE-S) models provide the most comprehensive reconstructions of total and spectral solar irradiance over the period of satellite observation currently available. There is persistent controversy between the various measurements and models in terms of the wavelength dependence of the variation over the solar cycle, with repercussions on our understanding of the influence of UV solar irradiance variability on the stratosphere. We review the measurement and modeling of UV solar irradiance variability over the period of satellite observation. The SATIRE-S reconstruction is consistent with spectral solar irradiance observations where they are reliable. It is also supported by an independent, empirical reconstruction of UV spectral solar irradiance based on Upper Atmosphere Research Satellite/Solar Ultraviolet Spectral Irradiance Monitor measurements from an earlier study. The weaker solar cycle variability produced by NRLSSI between 300 and 400 nm is not evident in any available record. We show that although the method employed to construct NRLSSI is principally sound, reconstructed solar cycle variability is detrimentally affected by the uncertainty in the SSI observations it draws upon in the derivation. Based on our findings, we recommend, when choosing between the two models, the use of SATIRE-S for climate studies.

UV astronomy throughout the ages: a historical perspective

NASA Astrophysics Data System (ADS)

Linsky, Jeffrey L.

2018-05-01

Astronomers have long recognized the critical need for ultraviolet imaging, photometry and spectroscopy of stars, planets, and galaxies, but this need could not be satisfied without access to space and the development of efficient instrumentation. When UV measurements became feasible, first with rockets and then with satellites, major discoveries came rapidly. It is true in the UV spectral region as in all others, that significant increases in sensitivity, spectral resolution, and time domain coverage have led to significant new understanding of astrophysical phenomena. I will describe a selection of these discoveries made in each of three eras: (1) the early history of rocket instrumentation and Copernicus, the first UV satellite, (2) the discovery phase pioneered by the IUE, FUSE and EUVE satellites, and (3) the full flowering of UV astronomy with the successful operation of HST and its many instruments. I will also mention a few areas where future UV instrumentation could lead to new discoveries. This review concentrates on developments in stellar and interstellar UV spectroscopy; the major discoveries in galactic, extragalactic, and solar system research are beyond the scope of this review. The important topic of UV technologies and detectors, which enable the remarkable advances in UV astronomy are also not included in this review.

The influence of ambient ultraviolet light on sperm quality and sexual ornamentation in three-spined sticklebacks (Gasterosteus aculeatus).

PubMed

Rick, Ingolf P; Mehlis, Marion; Eßer, Elisabeth; Bakker, Theo C M

2014-02-01

Exposure to enhanced levels of ambient ultraviolet (UV) radiation (UVR) can have adverse effects on aquatic organisms including damage at the cellular and molecular level and impairment of development, fecundity and survival. Much research has been conducted on the role of the harmful UVB radiation. However, due to its greater penetration in water the more abundant UVA radiation can also act as an environmental stressor. Little is known about UVR effects on sperm characteristics although sperm cells should be especially prone to UV-induced oxidative stress. Moreover, UV-related changes in oxidative status may affect the phenotypic expression of energetically costly sexual ornaments. We investigated the effects of long-term exposure to ecologically relevant levels of simulated UVA radiation on sperm quality and sexual ornamentation in three-spined sticklebacks (Gasterosteus aculeatus). Males were assigned to three spectral exposure treatments differing in the UV spectral part so that they received either enhanced, moderate or no UVA radiation. The results reveal that exposure to enhanced ambient UVA levels had detrimental effects on both male breeding coloration and sperm velocity providing evidence that UVR affects traits targeted by pre- and post-copulatory sexual selection. By highlighting the role of UVA as a factor influencing fitness-relevant traits, our findings may contribute to a better understanding of the consequences of current and future levels of solar UVR for mating systems and life history.

Spectral shifts of mammalian ultraviolet-sensitive pigments (short wavelength-sensitive opsin 1) are associated with eye length and photic niche evolution.

PubMed

Emerling, Christopher A; Huynh, Hieu T; Nguyen, Minh A; Meredith, Robert W; Springer, Mark S

2015-11-22

Retinal opsin photopigments initiate mammalian vision when stimulated by light. Most mammals possess a short wavelength-sensitive opsin 1 (SWS1) pigment that is primarily sensitive to either ultraviolet or violet light, leading to variation in colour perception across species. Despite knowledge of both ultraviolet- and violet-sensitive SWS1 classes in mammals for 25 years, the adaptive significance of this variation has not been subjected to hypothesis testing, resulting in minimal understanding of the basis for mammalian SWS1 spectral tuning evolution. Here, we gathered data on SWS1 for 403 mammal species, including novel SWS1 sequences for 97 species. Ancestral sequence reconstructions suggest that the most recent common ancestor of Theria possessed an ultraviolet SWS1 pigment, and that violet-sensitive pigments evolved at least 12 times in mammalian history. We also observed that ultraviolet pigments, previously considered to be a rarity, are common in mammals. We then used phylogenetic comparative methods to test the hypotheses that the evolution of violet-sensitive SWS1 is associated with increased light exposure, extended longevity and longer eye length. We discovered that diurnal mammals and species with longer eyes are more likely to have violet-sensitive pigments and less likely to possess UV-sensitive pigments. We hypothesize that (i) as mammals evolved larger body sizes, they evolved longer eyes, which limited transmittance of ultraviolet light to the retina due to an increase in Rayleigh scattering, and (ii) as mammals began to invade diurnal temporal niches, they evolved lenses with low UV transmittance to reduce chromatic aberration and/or photo-oxidative damage. © 2015 The Author(s).

Spectral shifts of mammalian ultraviolet-sensitive pigments (short wavelength-sensitive opsin 1) are associated with eye length and photic niche evolution

PubMed Central

Emerling, Christopher A.; Huynh, Hieu T.; Nguyen, Minh A.; Meredith, Robert W.; Springer, Mark S.

2015-01-01

Retinal opsin photopigments initiate mammalian vision when stimulated by light. Most mammals possess a short wavelength-sensitive opsin 1 (SWS1) pigment that is primarily sensitive to either ultraviolet or violet light, leading to variation in colour perception across species. Despite knowledge of both ultraviolet- and violet-sensitive SWS1 classes in mammals for 25 years, the adaptive significance of this variation has not been subjected to hypothesis testing, resulting in minimal understanding of the basis for mammalian SWS1 spectral tuning evolution. Here, we gathered data on SWS1 for 403 mammal species, including novel SWS1 sequences for 97 species. Ancestral sequence reconstructions suggest that the most recent common ancestor of Theria possessed an ultraviolet SWS1 pigment, and that violet-sensitive pigments evolved at least 12 times in mammalian history. We also observed that ultraviolet pigments, previously considered to be a rarity, are common in mammals. We then used phylogenetic comparative methods to test the hypotheses that the evolution of violet-sensitive SWS1 is associated with increased light exposure, extended longevity and longer eye length. We discovered that diurnal mammals and species with longer eyes are more likely to have violet-sensitive pigments and less likely to possess UV-sensitive pigments. We hypothesize that (i) as mammals evolved larger body sizes, they evolved longer eyes, which limited transmittance of ultraviolet light to the retina due to an increase in Rayleigh scattering, and (ii) as mammals began to invade diurnal temporal niches, they evolved lenses with low UV transmittance to reduce chromatic aberration and/or photo-oxidative damage. PMID:26582021

Ultraviolet Spectroscopy of the Surfaces of the Inner Icy Saturnian Satellites

NASA Astrophysics Data System (ADS)

Hendrix, A. R.; Hansen, C. J.

2008-12-01

The Cassini mission has provided a unique opportunity to make high-resolution, multi-spectral measurements of Saturn's icy moons, to investigate their surface compositions, processes and evolution. Here we present results from the Ultraviolet Imaing Spectrograph (UVIS). This instrument allows for the first measurements of the icy satellites in the extreme ultraviolet (EUV) to far-ultraviolet (FUV) wavelength range. The icy satellites of the Saturn system exhibit a remarkable amount of variability: Dark, battered Phoebe orbiting at a distant 200 RS, black-and-white Iapetus, the wispy streaks of Dione, cratered Rhea and Mimas, bright Tethys and geologically active Enceladus. Phoebe, Iapetus and Hyperion all orbit largely outside Saturn's magnetosphere, while the inner icy satellites Mimas, Enceladus, Dione Tethys and Rhea all orbit within the magnetosphere. Furthermore, the inner icy satellites all orbit within the E-ring - so the extent of exogenic effects on these icy satellites is wide-ranging. We present an overview of UVIS results from Tethys, Dione, Mimas, Enceladus and Rhea, focusing on surface investigations. We expect that the UV signatures of these icy satellites are strongly influenced not only by their water ice composition, but by external effects and magnetospheric environments. We study the FUV reflectance spectra to learn about the surface composition, map out water ice grain size variations, investigate effects of coating by E-ring grains, examine disk-resolved and hemispheric compositional and brightness variations, and investigate the presence of radiation products. This is new work: FUV spectra of surfaces have not been well-studied in the past. Spectra of the inner icy moons have been used to better develop spectral models, to further understand existing lab data of water ice and to help with understanding instrument performance. Analysis is challenged by a lack of laboratory data in this wavelength region, but intriguing results are being found. We find that the FUV albedo is a critical tie- point to understand the composition of these moons -- important absorptions occur in the NUV-visible region. We present disk-integrated hemispherical reflectance spectra, and show that while Tethys and Dione exhibit strong UV leading-trailing differences, Mimas, Enceladus and Rhea do not. In the UV, Mimas is nearly as bright as Enceladus. Tethys is surprisingly dark in the UV. The visible-wavelength leading-trailing hemisphere albedo differences can be attributed to coating by E-ring grains; in the UV, a process appears to darken the trailing hemisphere of Tethys. We also investigate disk-resolved Enceladus spectra to understand spectral differences between the south polar tiger stripe region and elsewhere on the surface.

THE MUSCLES TREASURY SURVEY. II. INTRINSIC LY α AND EXTREME ULTRAVIOLET SPECTRA OF K AND M DWARFS WITH EXOPLANETS

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

Youngblood, Allison; France, Kevin; Loyd, R. O. Parke

2016-06-20

The ultraviolet (UV) spectral energy distributions (SEDs) of low-mass (K- and M-type) stars play a critical role in the heating and chemistry of exoplanet atmospheres, but are not observationally well-constrained. Direct observations of the intrinsic flux of the Ly α line (the dominant source of UV photons from low-mass stars) are challenging, as interstellar H i absorbs the entire line core for even the closest stars. To address the existing gap in empirical constraints on the UV flux of K and M dwarfs, the MUSCLES Hubble Space Telescope Treasury Survey has obtained UV observations of 11 nearby M and Kmore » dwarfs hosting exoplanets. This paper presents the Ly α and extreme-UV spectral reconstructions for the MUSCLES targets. Most targets are optically inactive, but all exhibit significant UV activity. We use a Markov Chain Monte Carlo technique to correct the observed Ly α profiles for interstellar absorption, and we employ empirical relations to compute the extreme-UV SED from the intrinsic Ly α flux in ∼100 Å bins from 100–1170 Å. The reconstructed Ly α profiles have 300 km s{sup −1} broad cores, while >1% of the total intrinsic Ly α flux is measured in extended wings between 300 and 1200 km s{sup −1}. The Ly α surface flux positively correlates with the Mg ii surface flux and negatively correlates with the stellar rotation period. Stars with larger Ly α surface flux also tend to have larger surface flux in ions formed at higher temperatures, but these correlations remain statistically insignificant in our sample of 11 stars. We also present H i column density measurements for 10 new sightlines through the local interstellar medium.« less

Space Weathering Effects at UV Wavelengths: Asteroids and the Moon

NASA Astrophysics Data System (ADS)

Hendrix, Amanda; Vilas, F.

2006-09-01

Space weathering, the bombardment of airless bodies by micrometeoroids and irradiation by solar wind particles, affects spectra of solar system bodies at visible/near IR (VNIR) wavelengths by darkening and reddening their surface materials, as well as degrading absorption features. We present new results detailing space weathering effects at ultraviolet wavelengths. We focus on new spectral modeling results, and also present spacecraft data of asteroids and the Moon, along with new UV measurements of asteroid families from HST, to demonstrate the effects of varying degrees of weathering and the outcome of weathering on surfaces of different compositions. Weathered surfaces are relatively bright and spectrally blue in the UV; these UV effects can be more obvious than the VNIR effects. The cause of these weathering effects is likely vapor deposition of submicroscopic iron (SMFe), through solar wind irradiation and micrometeoroid bombardment of the bodies' surfaces. In silicate minerals, the NUV region is dominated by a decrease in reflectance with wavelength - the "UV absorption edge.” In contrast to silicates, iron is opaque and relatively bright in the UV, so the addition of SMFe to a silicate grains has the effect of making the UV region brighter; this is in opposition to the situation at longer wavelengths, where the addition of SMFe decreases the albedo. Our spectral modeling results show that the addition of SMFe decreases the steepness of the UV dropoff, in effect making the UV spectrum bluer. This can explain the difference in UV spectral behavior seen between S-class asteroids and less-weathered ordinary chondrite meteorites, and between lunar rocks and more weathered lunar soils. This work is funded in part by Hubble Space Telescope Grant #10557.

Airborne remote sensing of ultraviolet-absorbing aerosols during the NASA ATom, SEAC4RS and DC3 campaigns

NASA Astrophysics Data System (ADS)

Hall, S. R.; Ullmann, K.; Commane, R.; Crounse, J. D.; Daube, B. C.; Diskin, G. S.; Dollner, M.; Froyd, K. D.; Katich, J. M.; Kim, M. J.; Madronich, S.; Murphy, D. M.; Podolske, J. R.; Schwarz, J. P.; Teng, A.; Weber, R. J.; Weinzierl, B.; Wennberg, P. O.; Sachse, G.; Wofsy, S.

2017-12-01

Spectrally resolved up and down-welling actinic flux was measured from the NASA DC-8 aircraft by the Charged-coupled device Actinic Flux Spectroradiometers (CAFS) during recent campaigns including ATom, DC3 and SEAC4RS. The primary purpose is retrieval of 40 photolysis frequencies to complement the in situ chemistry. However, the spectra also provide the opportunity to examine absorption trends in the UV where few other measurements exist. In particular, absorption by brown (BrC) and black (BC) carbon aerosols result in characteristic UV signatures. A new technique exploits the spectral changes to detect the presence of these aerosols for qualitative, real-time, remote sensing of biomass burning (BB). The data may prove useful for examination of the evolution of BrC, including chemical processing and hygroscopic growth. The induced UV changes also feed back to the photolysis frequencies affecting the chemistry. Further work will determine the robustness of the technique and if quantitative spectral absorption retrievals are possible.

The Ultraviolet Spectrograph (UVS) on ESA’s JUICE Mission

NASA Astrophysics Data System (ADS)

Gladstone, Randy; Retherford, K.; Steffl, A.; Eterno, J.; Davis, M.; Versteeg, M.; Greathouse, T.; Araujo, M.; Walther, B.; Persson, K.; Persyn, S.; Dirks, G.; McGrath, M.; Feldman, P.; Bagenal, F.; Spencer, J.; Schindhelm, E.; Fletcher, L.

2013-10-01

The Jupiter Icy Moons Explorer (JUICE) was selected in May 2012 as the first L-class mission of ESA’s Cosmic Vision Program. JUICE will launch in 2022 on a 7.6-year journey to the Jovian system, including a Venus and multiple Earth gravity assists, before entering Jupiter orbit in January 2030. JUICE will study the entire Jovian system for 3.5 years, concentrating on Europa, Ganymede, and Callisto, with the last 10 months spent in Ganymede orbit. The Ultraviolet Spectrograph (UVS) on JUICE was jointly selected by NASA and ESA as part of its ~130 kg payload of 11 scientific instruments. UVS is the fifth in a series of successful ultraviolet imaging spectrographs (Rosetta-Alice, New Horizons Pluto-Alice, LRO-LAMP) and is largely based on the most recent of these, Juno-UVS. It observes photons in the 55-210 nm wavelength range, at moderate spectral and spatial resolution along a 7.5-degree slit. A main entrance “airglow port” (AP) is used for most observations (e.g., airglow, aurora, surface mapping, and stellar occultations), while a separate “solar port” (SP) allows for solar occultations. Another aperture door, with a small hole through the centre, is used as a “high-spatial-resolution port” (HP) for detailed observations of bright targets. Time-tagging (pixel list mode) and programmable spectral imaging (histogram mode) allow for observational flexibility and optimal data management. As on Juno-UVS, the effects of penetrating electron radiation on electronic parts and data quality are substantially mitigated through contiguous shielding, filtering of pulse height amplitudes, management of high voltage settings, and careful use of radiation-hard, flight-tested parts. The science goals of UVS are to: 1) explore the atmospheres, plasma interactions, and surfaces of the Galilean satellites; 2) determine the dynamics, chemistry, and vertical structure of Jupiter’s upper atmosphere from equator to pole; and 3) investigate the Jupiter-Io connection by quantifying energy and mass flow in the Io atmosphere, neutral clouds, and torus. Here we present the salient features of the UVS instrument and describe the science we plan to address.

Spectral Types and Wind Velocities for Massive Stars in R136

NASA Astrophysics Data System (ADS)

Bostroem, K. A.; Maíz Apellániz, J.; Caballero-Nieves, S. M.; Walborn, N. R.; Crowther, P. A.

2014-01-01

We analyze spatially resolved, long-slit ultraviolet (UV) and optical stellar spectra of the compact starburst cluster R136 at the core of 30 Doradus. R136 is young and massive, making it an ideal place to study the upper end of the initial mass function. These spectra, taken with the Space Telescope Imaging Spectrograph on the Hubble Space Telescope, cover over 100 stars in the inner 4 arcseconds (1 parsec) of R136, a region which cannot be resolved with ground-based spectroscopy. In this poster we present both the UV and optical of over 20 of the brightest stars in R136, extracted with MULTISPEC, a tool written specifically for multiple objects in crowded fields. For each star we present an optical spectral type and a terminal wind velocity derived from the UV data

Satellite estimation of incident photosynthetically active radiation using ultraviolet reflectance

NASA Technical Reports Server (NTRS)

Eck, Thomas F.; Dye, Dennis G.

1991-01-01

A new satellite remote sensing method for estimating the amount of photosynthetically active radiation (PAR, 400-700 nm) incident at the earth's surface is described and tested. Potential incident PAR for clear sky conditions is computed from an existing spectral model. A major advantage of the UV approach over existing visible band approaches to estimating insolation is the improved ability to discriminate clouds from high-albedo background surfaces. UV spectral reflectance data from the Total Ozone Mapping Spectrometer (TOMS) were used to test the approach for three climatically distinct, midlatitude locations. Estimates of monthly total incident PAR from the satellite technique differed from values computed from ground-based pyranometer measurements by less than 6 percent. This UV remote sensing method can be applied to estimate PAR insolation over ocean and land surfaces which are free of ice and snow.

Pterin pigments amplify iridescent ultraviolet signal in males of the orange sulphur butterfly, Colias eurytheme

PubMed Central

Rutowski, R.L; Macedonia, J.M; Morehouse, N; Taylor-Taft, L

2005-01-01

Animal colouration is typically the product of nanostructures that reflect or scatter light and pigments that absorb it. The interplay between these colour-producing mechanisms may influence the efficacy and potential information content of colour signals, but this notion has received little empirical attention. Wing scales in the male orange sulphur butterfly (Colias eurytheme) possess ridges with lamellae that produce a brilliant iridescent ultraviolet (UV) reflectance via thin-film interference. Curiously, these same scales contain pterin pigments that strongly absorb wavelengths below 550 nm. Given that male UV reflectance functions as a sexual signal in C. eurytheme, it is paradoxical that pigments in the wing scales are highly UV absorbing. We present spectrophotometric analyses of the wings before and after pterin removal that show that pterins both depress the amplitude of UV iridescence and suppress a diffuse UV reflectance that emanates from the scales. This latter effect enhances the directionality and spectral purity of the iridescence, and increases the signal's chromaticity and potential signal content. Our findings also suggest that pterins amplify the contrast between iridescent UV reflectance and scale background colour as a male's wings move during flight. PMID:16191648

Pterin pigments amplify iridescent ultraviolet signal in males of the orange sulphur butterfly, Colias eurytheme.

PubMed

Rutowski, R L; Macedonia, J M; Morehouse, N; Taylor-Taft, L

2005-11-07

Animal colouration is typically the product of nanostructures that reflect or scatter light and pigments that absorb it. The interplay between these colour-producing mechanisms may influence the efficacy and potential information content of colour signals, but this notion has received little empirical attention. Wing scales in the male orange sulphur butterfly (Colias eurytheme) possess ridges with lamellae that produce a brilliant iridescent ultraviolet (UV) reflectance via thin-film interference. Curiously, these same scales contain pterin pigments that strongly absorb wavelengths below 550 nm. Given that male UV reflectance functions as a sexual signal in C. eurytheme, it is paradoxical that pigments in the wing scales are highly UV absorbing. We present spectrophotometric analyses of the wings before and after pterin removal that show that pterins both depress the amplitude of UV iridescence and suppress a diffuse UV reflectance that emanates from the scales. This latter effect enhances the directionality and spectral purity of the iridescence, and increases the signal's chromaticity and potential signal content. Our findings also suggest that pterins amplify the contrast between iridescent UV reflectance and scale background colour as a male's wings move during flight.

High-resolution UV-visible spectroscopy of lunar red spots

NASA Technical Reports Server (NTRS)

Bruno, B. C.; Lucey, P. G.; Hawke, B. R.

1991-01-01

A spectral reflectance study of selected lunar 'red spots', highland areas characterized by an absorption in the ultraviolet relative to the visible was conducted. Some red spots were suggested to be the sites of ancient highland volcanism. High-resolution spectral data of eight red spots on the western portion of the moon over the wavelength region 0.39-0.82 micron were obtained. Much spectral variation among these red spots in the magnitude as well as the wavelength position of the ultraviolet absorption were found. Spectral structure at visible and near-infrared wavelength were also identified. These spectral differences indicate that red spots do not have a single mineralogical composition, which in turn suggests that red spots may have multiple origins. Additional imaging spectroscopic observations were taken of the Herigonius red spot, a morphologically complex region northeast of Mare Humorum. These data reveal significant spectral differences among the various morphological units within the Herigonius red spot. Although some of these are likely due to the effects of the maturation process, others appear to reflect differences in mineral abundances and composition.

Ultraviolet corona detection sensor study

NASA Technical Reports Server (NTRS)

Schmitt, R. J.; MATHERN

1976-01-01

The feasibility of detecting electrical corona discharge phenomena in a space simulation chamber via emission of ultraviolet light was evaluated. A corona simulator, with a hemispherically capped point to plane electrode geometry, was used to generate corona glows over a wide range of pressure, voltage, current, electrode gap length and electrode point radius. Several ultraviolet detectors, including a copper cathode gas discharge tube and a UV enhanced silicon photodiode detector, were evaluated in the course of the spectral intensity measurements. The performance of both silicon target vidicons and silicon intensified target vidicons was evaluated analytically using the data generated by the spectroradiometer scans and the performance data supplied by the manufacturers.

Measurements of cavity ringdown spectroscopy of acetone in the ultraviolet and near-infrared spectral regions: potential for development of a breath analyzer.

PubMed

Wang, Chuji; Scherrer, Susan T; Hossain, Delwar

2004-07-01

We report a study on the cavity ringdown spectroscopy of acetone in both the ultraviolet (UV) and the near-infrared (NIR) spectral regions to explore the potential for development of a breath analyzer for disease diagnostics. The ringdown spectrum of acetone in the UV (282.4-285.0 nm) region is recorded and the spectrum is in good agreement with those obtained by other spectral techniques reported in the literature. The absorption cross-section of the C-H stretching overtone of acetone in the NIR (1632.7-1672.2 nm) is reported for the first time and the maximum absorption cross-section located at 1666.7 nm is 1.2 x 10(-21) cm(2). A novel, compact, atmospheric cavity with a cavity length of 10 cm has been constructed and implemented to investigate the technical feasibility of the potential instrument size, optical configuration, and detection sensitivity. The detection limit of such a mini cavity employing ringdown mirrors of reflectivity of 99.85% at 266 nm, where acetone has the strongest absorption, is approximately 1.5 ppmv based on the standard 3 criteria. No real breath gas samples are used in the present study. Discussions on the detection sensitivity and background spectral interferences for the instrument development are presented. This study demonstrates the potential of developing a portable, sensitive breath analyzer for medical applications using the cavity ringdown spectral technique.

Ultraviolet to optical spectral distributions of northern star-forming galaxies

NASA Technical Reports Server (NTRS)

Mcquade, Kerry; Calzetti, Daniela; Kinney, Anne L.

1995-01-01

We report spectral energy distribution from the UV to the optical for a sample of 31 northern star-forming galaxies. We also present measurements for emission-line fluxes, continuum levels, and equivalent widths of absorption features for each individual spectrum as well as averages for the eight galactic activity classes, including normal, starburst, Seyfert 2, blue compact dwarf, blue compact, Low-Inonization Nuclear Emission Regions (LINER), H II, and combination LINER-H II galaxies.

Augmentation of the IUE Ultraviolet Spectral Atlas

NASA Astrophysics Data System (ADS)

Wu, Chi-Chao

IUE is the only and last satellite which will support a survey program to record the ultraviolet spectrum of a large number of bright normal stars. It is important to have a library of high quality low dispersion spectra of sufficient number of stars that provide good coverage in spectral type and luminosity class. Such a library is invaluable for stellar population synthesis of galaxies, studying the nature of distant galaxies, establishing a UV spectral classification system, providing comparison stars for interstellar extinction studies and for peculiar objects or binary systems, studying the effects of temperature, gravity and metallicity on stellar UV spectra, and as a teaching aid. We propose to continue observations of normal stars in order to provide (1) a stellar library as complete as practical, which will be able to support astronomical research by the scientific community long into the future, and (2) a sufficient sample of stars to guard against variability and peculiarity, and to allow a finite range of temperature, gravity, and metallicity in a given spectral type-luminosity class combination. Our primary goal is to collect the data and make them available to the community immediately (without claiming the 6-month proprietary right). The data will be published in the IUE Newsletter as soon as practical, and the data will be prepared for distribution by the IUE Observatory and the NSSDC.

The MUSCLES Treasury Survey: Temporally- and Spectrally-Resolved Irradiance from Low-mass Exoplanet Host Stars

NASA Astrophysics Data System (ADS)

France, Kevin; Loyd, R. O. Parke; Youngblood, Allison; Linsky, Jeffrey; MUSCLES Treasury Survey Team

2016-01-01

The spectral and temporal behavior of exoplanet host stars is a critical input to models of the chemistry and evolution of planetary atmospheres. High-energy photons (X-ray to near-UV; 5 - 3200 Ang) from these stars regulate the atmospheric temperature profiles and photochemistry on orbiting planets, influencing the production of potential "biomarker" gases. It has been shown that the atmospheric signatures of potentially habitable planets around low-mass stars may be significantly different from planets orbiting Sun-like stars owing to the different UV spectral energy distribution. I will present results from a panchromatic survey (Hubble/Chandra/XMM/optical) of M and K dwarf exoplanet hosts, the MUSCLES Treasury Survey (Measurements of the Ultraviolet Spectral Characteristics of Low-mass Exoplanetary Systems). We reconstruct the Lyman-alpha and extreme-UV (100-900 Ang) radiation lost to interstellar attenuation and create 5 Angstrom to 5 micron stellar irradiance spectra; these data will be publically available as a High-Level Science Product on MAST. We find that all low-mass exoplanet host stars exhibit significant chromospheric/transition region/coronal emission -- no "UV inactive" M dwarfs are observed. The F(far-UV)/F(near-UV) flux ratio, a driver for possible abiotic production of the suggested biomarkers O2 and O3, increases by ~3 orders of magnitude as the habitable zone moves inward from 1 to 0.1 AU, while the incident far-UV (912 - 1700 Ang) and XUV (5 - 900 Ang) radiation field strengths decrease by factors of a few across this range. Far-UV flare activity is common in 'optically inactive' M dwarfs; statistics from the entire sample indicate that large UV flares (E(300 - 1700 Ang) >= 10^31 erg) occur several times per day on typical M dwarf exoplanet hosts.

Quality assessment of solar UV irradiance measured with array spectroradiometers

NASA Astrophysics Data System (ADS)

Egli, Luca; Gröbner, Julian; Hülsen, Gregor; Bachmann, Luciano; Blumthaler, Mario; Dubard, Jimmy; Khazova, Marina; Kift, Richard; Hoogendijk, Kees; Serrano, Antonio; Smedley, Andrew; Vilaplana, José-Manuel

2016-04-01

The reliable quantification of ultraviolet (UV) radiation at the earth's surface requires accurate measurements of spectral global solar UV irradiance in order to determine the UV exposure to human skin and to understand long-term trends in this parameter. Array spectroradiometers (ASRMs) are small, light, robust and cost-effective instruments, and are increasingly used for spectral irradiance measurements. Within the European EMRP ENV03 project "Solar UV", new devices, guidelines and characterization methods have been developed to improve solar UV measurements with ASRMs, and support to the end user community has been provided. In order to assess the quality of 14 end user ASRMs, a solar UV intercomparison was held on the measurement platform of the World Radiation Center (PMOD/WRC) in Davos, Switzerland, from 10 to 17 July 2014. The results of the blind intercomparison revealed that ASRMs, currently used for solar UV measurements, show a large variation in the quality of their solar UV measurements. Most of the instruments overestimate the erythema-weighted UV index - in particular at large solar zenith angles - due to stray light contribution in the UV-B range. The spectral analysis of global solar UV irradiance further supported the finding that the uncertainties in the UV-B range are very large due to stray light contribution in this wavelength range. In summary, the UV index may be detected by some commercially available ASRMs within 5 % compared to the world reference spectroradiometer, if well characterized and calibrated, but only for a limited range of solar zenith angles. Generally, the tested instruments are not yet suitable for solar UV measurements for the entire range between 290 and 400 nm under all atmospheric conditions.

Quality assessment of solar UV irradiance measured with array spectroradiometers

NASA Astrophysics Data System (ADS)

Egli, L.; Gröbner, J.; Hülsen, G.; Bachmann, L.; Blumthaler, M.; Dubard, J.; Khazova, M.; Kift, R.; Hoogendijk, K.; Serrano, A.; Smedley, A. R. D.; Vilaplana, J.-M.

2015-12-01

The reliable quantification of ultraviolet (UV) radiation at the Earth's surface requires accurate measurements of spectral global solar UV irradiance in order to determine the UV exposure to human skin and to understand long-term trends in this parameter. Array spectroradiometers are small, light, robust and cost effective instruments and are increasingly used for spectral irradiance measurements. Within the European EMRP-ENV03 project "Solar UV", new devices, guidelines, and characterization methods have been developed to improve solar UV measurements with array spectroradiometers and support to the end-user community has been provided. In order to assess the quality of 14 end-user array spectroradiometers, a solar UV intercomparison was held on the measurement platform of the World Radiation Center (PMOD/WRC) in Davos, Switzerland, from 10 to 17 July 2014. The results of the intercomparison revealed that array spectroradiometers, currently used for solar UV measurements, show a large variation in the quality of their solar UV measurements. Most of the instruments overestimate the erythema weighted UV index - in particular at low solar zenith angles - due to stray light contribution in the UV-B range. The spectral analysis of global solar UV irradiance further supported the finding that the uncertainties in the UV-B range are very large due to stray light contribution in this wavelength range. In summary, the UV index may be detected by some commercially available array spectroradiometer within 5 % compared to the world reference spectroradiometer, if well characterized and calibrated, but only for a limited range or solar zenith angle. Generally, the tested instruments are not yet suitable for solar UV measurements for the entire range between 290 to 400 nm under all atmospheric conditions.

Photodegradation of hexythiazox in different solvent systems under the influence of ultraviolet light and sunlight in the presence of TiO2, H2O2, and KNO3 and identification of the photometabolites.

PubMed

Mandal, Sudeb; Joardar, Soumen; Das, Saktipada; Bhattacharyya, Anjan

2011-11-09

The photodegradation of the carboxamide acaricide hexythiazox in three different solvent systems (aqueous methanolic, aqueous isopropanolic, and aqueous acetonitrilic solutions) in the presence of H(2)O(2), KNO(3), and TiO(2) under ultraviolet (UV) light (λ(max) ≥ 250 nm) and sunlight (λ(max) ≥290 nm) has been assessed in this work. The kinetics of photodecomposition of hexythiazox and the identification of photoproducts were carried out using liquid chromatography-mass spectrometry. The rate of photodecomposition of hexythiazox in different solvents followed first-order kinetics in both UV radiation and natural sunlight, and the degradation rates were faster under UV light than under sunlight. Hexythiazox was found to be more efficiently photodegraded in the presence of TiO(2) than in the presence of H(2)O(2) and KNO(3). Two major photoproducts were separated in pure form using column chromatography and identified according to IR, (1)H NMR, and mass spectral information as cyclohexylamine and 5-(4-chlorophenyl)-4-methylthiazolidin-2-one. Another nine photoproducts were identified according to LC-MS/MS spectral information. The plausible photodegradation pathways of hexythiazox were proposed according to the structures of the photoproducts.

Ultraviolet reflectance spectroscopy measurements of planetary materials and their analogs

NASA Astrophysics Data System (ADS)

Hibbitts, C.; Stockstill-Cahill, K.

2017-12-01

The compositions of airless solar system objects tell us about the origin and evolutionary processes that are responsible for the current state of our solar system and that shape our environment. Spacecraft have obtained UV reflectance measurements of the surfaces of Mercury, the Moon, asteroids, comets, icy satellites, and Pluto from which composition is being inferred. Most minerals absorb in the UV making studying surface composition both informative but also challenging [e.g. 1]. The UV region is sensitive to atomic and molecular electronic absorptions such as the ligand-metal charge transfer band that is present in oxides and silicates and the conduction band at vacuum UV wavelengths. Unfortunately, limited laboratory reflectance measurements in the ultraviolet hampers the interpretation of some of these planetary UV reflectance datasets. However, several laboratory efforts have been developed [e.g. 2,3] to fill the need for laboratory UV measurements. These are difficult measurements to make, being complicated by the absorptive nature of the atmosphere, requiring measurements to be conducted under vacuum or over very short path lengths of a N2-purged system. Also, the lack of a widely accepted UV diffuse reflectance standard is problematic. At the JHU-APL, bidirectional UV reflectance measurements are obtained under vacuum from 140 nm to 570 nm. Sample temperature can be controlled from 100K to 600K, which enables the study of the interaction of water ice and other volatiles with the refractory samples. Results from our laboratory research include the development of a correlation between the spectral nature of the OMCT band and the abundance of iron in low water content lunar analog glasses [3]. Also, the spectral signature of water in the UV has been investigated. While water-ice has a known strong absorption feature near 180 nm [e.g. 4], adsorbed molecular and disassociatively adsorbed OH apparently are not optically active in this spectral region [5]. We have also measured the UV spectra of carbonaceous chondrites. References: [1] Wagner et al. (1987) Icarus, 69, 14-28.1987; [2] Cloutis et al. (2008) Icarus, 197, 321-347; [3] Greenspon et al. (2012), 43rd LPSC, 1659, 2490, [4] Hendrix, A. and C. J. Hansen (2008) Icarus, 193, 323-333; [5] Hibbitts, C.A. (2015) DPS #47, 215.05.

New UV-source catalogs, UV spectral database, UV variables and science tools from the GALEX surveys

NASA Astrophysics Data System (ADS)

Bianchi, Luciana; de la Vega, Alexander; Shiao, Bernard; Bohlin, Ralph

2018-03-01

We present a new, expanded and improved catalog of Ultraviolet (UV) sources from the GALEX All-Sky Imaging survey: GUVcat_AIS (Bianchi et al. in Astrophys. J. Suppl. Ser. 230:24, 2017). The catalog includes 83 million unique sources (duplicate measurements and rim artifacts are removed) measured in far-UV and near-UV. With respect to previous versions (Bianchi et al. in Mon. Not. R. Astron. Soc. 411:2770 2011a, Adv. Space Res. 53:900-991, 2014), GUVcat_AIS covers a slightly larger area, 24,790 square degrees, and includes critical corrections and improvements, as well as new tags, in particular to identify sources in the footprint of extended objects, where pipeline source detection may fail and custom-photometry may be necessary. The UV unique-source catalog facilitates studies of density of sources, and matching of the UV samples with databases at other wavelengths. We also present first results from two ongoing projects, addressing respectively UV variability searches on time scales from seconds to years by mining the GALEX photon archive, and the construction of a database of ˜120,000 GALEX UV spectra (range ˜1300-3000 Å), including quality and calibration assessment and classification of the grism, hence serendipitous, spectral sources.

UV filters for lighting of plants

NASA Astrophysics Data System (ADS)

Doehring, T.; Koefferlein, M.; Thiel, S.; Seidlitz, H. K.; Payer, H. D.

1994-03-01

The wavelength dependent interaction of biological systems with radiation is commonly described by appropriate action spectra. Particularly effective plant responses are obtained for ultraviolet (UV) radiation. Excess shortwave UV-B radiation will induce genetic defects and plant damage. Besides the ecological discussion of the deleterious effects of the excess UV radiation there is increasing interest in horticultural applications of this spectral region. Several metabolic pathways leading to valuable secondary plant products like colors, odors, taste, or resulting in mechanical strength and vitality are triggered by UV radiation. Thus, in ecologically as well as in economically oriented experiments the exact generation and knowledge of the spectral irradiance, particularly near the UV absorption edge, is essential. The ideal filter 'material' to control the UV absorption edge would be ozone itself. However, due to problems in controlling the toxic and chemically aggressive, instable gas, only rather 'small ozone filters' have been realized so far. In artificial plant lighting conventional solid filter materials such as glass sheets and plastic foils (celluloseacetate or cellulosetriacetate) which can be easily handled have been used to absorb the UV-C and the excess shortwave UV-B radiation of the lamp emissions. Different filter glasses are available which provide absorption properties suitable for gradual changes of the spectral UV-B illumination of artificial lighting. Using a distinct set of lamps and filter glasses an acceptable simulation of the UV-B part of natural global radiation can be achieved. The aging of these and other filter materials under the extreme UV radiation in the lamphouse of a solar simulator is presently unavoidable. This instability can be dealt with only by a precise spectral monitoring and by replacing the filters accordingly. For this reason attempts would be useful to develop real ozone filters which can replace glass filters. In any case chamber experiments require a careful selection of the filter material used and must be accompanied by a continuous UV-B monitoring.

UV filters for lighting of plants

NASA Technical Reports Server (NTRS)

Doehring, T.; Koefferlein, M.; Thiel, S.; Seidlitz, H. K.; Payer, H. D.

1994-01-01

The wavelength dependent interaction of biological systems with radiation is commonly described by appropriate action spectra. Particularly effective plant responses are obtained for ultraviolet (UV) radiation. Excess shortwave UV-B radiation will induce genetic defects and plant damage. Besides the ecological discussion of the deleterious effects of the excess UV radiation there is increasing interest in horticultural applications of this spectral region. Several metabolic pathways leading to valuable secondary plant products like colors, odors, taste, or resulting in mechanical strength and vitality are triggered by UV radiation. Thus, in ecologically as well as in economically oriented experiments the exact generation and knowledge of the spectral irradiance, particularly near the UV absorption edge, is essential. The ideal filter 'material' to control the UV absorption edge would be ozone itself. However, due to problems in controlling the toxic and chemically aggressive, instable gas, only rather 'small ozone filters' have been realized so far. In artificial plant lighting conventional solid filter materials such as glass sheets and plastic foils (celluloseacetate or cellulosetriacetate) which can be easily handled have been used to absorb the UV-C and the excess shortwave UV-B radiation of the lamp emissions. Different filter glasses are available which provide absorption properties suitable for gradual changes of the spectral UV-B illumination of artificial lighting. Using a distinct set of lamps and filter glasses an acceptable simulation of the UV-B part of natural global radiation can be achieved. The aging of these and other filter materials under the extreme UV radiation in the lamphouse of a solar simulator is presently unavoidable. This instability can be dealt with only by a precise spectral monitoring and by replacing the filters accordingly. For this reason attempts would be useful to develop real ozone filters which can replace glass filters. In any case chamber experiments require a careful selection of the filter material used and must be accompanied by a continuous UV-B monitoring.

Observations of Cygnus X-2 with IUE: Ultraviolet results from a multiwavelength campaign

NASA Technical Reports Server (NTRS)

Vrtilek, S. D.; Raymond, J. C.; Garcia, M. R.; Verbunt, F.; Hasinger, Guenther; Kuerster, M.

1989-01-01

The observations of the low-mass x ray binary, Cyg X-2, taken with the International Ultraviolet Explorer (IUE) in a campaign conducted in June and October of 1988 are reported. A direct relationship between the strength of the UV continuum and line emission and the placement of the x ray spectrum in one of three branches of the so-called Z-shaped curve is found by comparison with simultaneous x ray observations. All three previously known x ray spectral states are detected; the UV continuum and line emission increase monotonically along the Z with the least emission in the horizontal branch, and the most in the flaring branch. Emission lines due to HeII, CIV, NIII, NIV, NV, SiIV, and MgII are observed.

Hubble Space Telescope far-ultraviolet imaging of the jet in 3C273: a common emission component from optical to X-rays

NASA Astrophysics Data System (ADS)

Jester, Sebastian; Meisenheimer, Klaus; Martel, André R.; Perlman, Eric S.; Sparks, William B.

2007-09-01

We present far-ultraviolet (far-UV) observations at ~150 nm of the jet of quasar 3C273 obtained with the Advanced Camera for Surveys (ACS) Solar Blind Channel onboard the Hubble Space Telescope. While the jet morphology is very similar to that in the optical and near-UV, the spectral energy distributions of the jet's subregions show an upturn in νfν at 150nm compared to 300nm everywhere in the jet. Moreover, the 150-nm flux is compatible with extrapolating the X-ray power law down to the UV region. This constitutes strong support for a common origin of the jet's far-UV and X-ray emission. It implies that even a substantial fraction of the visible light in the X-ray brightest parts of the jet arises from the same spectral component as the X-rays, as had been suggested earlier based on Spitzer Space Telescope observations. We argue that the identification of this UV/X-ray component opens up the possibility to establish the synchrotron origin of the X-ray emission by optical polarimetry. Based on observations made with the NASA/ESA Hubble Space Telescope (HST), obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with HST programme GO-9814. This work was begun at the Particle Astrophysics Center, Fermilab, Batavia, IL 60510, USA. ‡ E-mail: jester@mpia.de

Solar-Iss a New Solar Reference Spectrum Covering the Far UV to the Infrared (165 to 3088 Nm) Based on Reanalyzed Solar/solspec Cycle 24 Observations

NASA Astrophysics Data System (ADS)

Damé, L.; Meftah, M.; Irbah, A.; Hauchecorne, A.; Bekki, S.; Bolsée, D.; Pereira, N.; Sluse, D.; Cessateur, G.

2017-12-01

Since April 5, 2008 and until February 15, 2017, the SOLSPEC (SOLar SPECtrometer) spectro-radiometer of the SOLAR facility on the International Space Station performed accurate measurements of Solar Spectral Irradiance (SSI) from the far ultraviolet to the infrared (165 nm to 3088 nm). These measurements, unique by their large spectral coverage and long time range, are of primary importance for a better understanding of solar physics and of the impact of solar variability on climate (via Earth's atmospheric photochemistry), noticeably through the "top-down" mechanism amplifying ultraviolet (UV) solar forcing effects on the climate (UV affects stratospheric dynamics and temperatures, altering interplanetary waves and weather patterns both poleward and downward to the lower stratosphere and troposphere regions). SOLAR/SOLSPEC, with almost 9 years of observations covering the essential of the unusual solar cycle 24 from minimum in 2008 to maximum, allowed to establish new reference solar spectra from UV to IR (165 to 3088 nm) at minimum (beginning of mission) and maximum of activity. The complete reanalysis was possible thanks to revised engineering corrections, improved calibrations and advanced procedures to account for thermal, aging and pointing corrections. The high quality and sensitivity of SOLSPEC data allow to follow temporal variability in UV but also in visible along the cycle. Uncertainties on these measurements are evaluated and results, absolute reference spectra and variability, are compared with other measurements (WHI, ATLAS-3, SCIAMACHY, SORCE/SOLSTICE, SORCE/SIM) and models (SATIRE-S, NRLSSI, NESSY)

The MUSCLES Treasury Survey. IV. Scaling Relations for Ultraviolet, Ca II K, and Energetic Particle Fluxes from M Dwarfs

NASA Astrophysics Data System (ADS)

Youngblood, Allison; France, Kevin; Loyd, R. O. Parke; Brown, Alexander; Mason, James P.; Schneider, P. Christian; Tilley, Matt A.; Berta-Thompson, Zachory K.; Buccino, Andrea; Froning, Cynthia S.; Hawley, Suzanne L.; Linsky, Jeffrey; Mauas, Pablo J. D.; Redfield, Seth; Kowalski, Adam; Miguel, Yamila; Newton, Elisabeth R.; Rugheimer, Sarah; Segura, Antígona; Roberge, Aki; Vieytes, Mariela

2017-07-01

Characterizing the UV spectral energy distribution (SED) of an exoplanet host star is critically important for assessing its planet’s potential habitability, particularly for M dwarfs, as they are prime targets for current and near-term exoplanet characterization efforts and atmospheric models predict that their UV radiation can produce photochemistry on habitable zone planets different from that on Earth. To derive ground-based proxies for UV emission for use when Hubble Space Telescope (HST) observations are unavailable, we have assembled a sample of 15 early to mid-M dwarfs observed by HST and compared their nonsimultaneous UV and optical spectra. We find that the equivalent width of the chromospheric Ca II K line at 3933 Å, when corrected for spectral type, can be used to estimate the stellar surface flux in ultraviolet emission lines, including H I Lyα. In addition, we address another potential driver of habitability: energetic particle fluxes associated with flares. We present a new technique for estimating soft X-ray and >10 MeV proton flux during far-UV emission line flares (Si IV and He II) by assuming solar-like energy partitions. We analyze several flares from the M4 dwarf GJ 876 observed with HST and Chandra as part of the MUSCLES Treasury Survey and find that habitable zone planets orbiting GJ 876 are impacted by large Carrington-like flares with peak soft X-ray fluxes ≥10-3 W m-2 and possible proton fluxes ˜102-103 pfu, approximately four orders of magnitude more frequently than modern-day Earth.

Evolution of ultraviolet vision in the largest avian radiation - the passerines.

PubMed

Ödeen, Anders; Håstad, Olle; Alström, Per

2011-10-24

Interspecific variation in avian colour vision falls into two discrete classes: violet sensitive (VS) and ultraviolet sensitive (UVS). They are characterised by the spectral sensitivity of the most shortwave sensitive of the four single cones, the SWS1, which is seemingly under direct control of as little as one amino acid substitution in the cone opsin protein. Changes in spectral sensitivity of the SWS1 are ecologically important, as they affect the abilities of birds to accurately assess potential mates, find food and minimise visibility of social signals to predators. Still, available data have indicated that shifts between classes are rare, with only four to five independent acquisitions of UV sensitivity in avian evolution. We have classified a large sample of passeriform species as VS or UVS from genomic DNA and mapped the evolution of this character on a passerine phylogeny inferred from published molecular sequence data. Sequencing a small gene fragment has allowed us to trace the trait changing from one stable state to another through the radiation of the passeriform birds. Their ancestor is hypothesised to be UVS. In the subsequent radiation, colour vision changed between UVS and VS at least eight times. The phylogenetic distribution of SWS1 cone opsin types in Passeriformes reveals a much higher degree of complexity in avian colour vision evolution than what was previously indicated from the limited data available. Clades with variation in the colour vision system are nested among clades with a seemingly stable VS or UVS state, providing a rare opportunity to understand how an ecologically important trait under simple genetic control may co-evolve with, and be stabilised by, associated traits in a character complex.

Direct comparison between the angular distributions of the erythemal and eye-damaging UV irradiances: a pilot study.

PubMed

Schouten, P; Parisi, A V

2011-02-07

Several broadband ultraviolet (UV) radiation angular distribution investigations have been previously presented. As the biologically damaging effectiveness of UV radiation is known to be wavelength dependent, it is necessary to expand this research into the distribution of the spectral UV. UV radiation is also susceptible to Rayleigh and Mie scattering processes, both of which are completely wavelength dependent. Additionally, the majority of previous measurements detailing the biologically damaging effect of spectral UV radiation have been oriented with respect to the horizontal plane or in a plane directed towards the sun (sun-normal), with the irradiance weighted against action spectra formulated specifically for human skin and tissue. However, the human body consists of very few horizontal or sun-normal surfaces. Extending the previous research by measuring the distribution of the spectral irradiance across the sky for the complete terrestrial solar UV waveband and weighting it against erythemal, photoconjunctivital and photokeratital action spectra allowed for the analysis of the differences between the biologically effective irradiance (UV(BE)) values intercepted at different orientations and the effect of scattering processes upon the homogeneity of these UV(BE) distributions. It was established that under the local atmospheric environment, the distribution profile of the UV(BE) for each biological response was anisotropic, with the highest intensities generally intercepted at inclination angles situated between the horizontal and vertical planes along orientations closely coinciding with the sun-normal. A finding from this was that the angular distributions of the erythemal UV(BE) and the photoconjunctivital UV(BE) were different, due to the differential scattering between the shorter and longer UV wavelengths within the atmosphere. Copyright © 2010 Elsevier B.V. All rights reserved.

The B3-VLA CSS sample. VIII. New optical identifications from the Sloan Digital Sky Survey The ultraviolet-optical spectral energy distribution of the young radio sources

NASA Astrophysics Data System (ADS)

Fanti, C.; Fanti, R.; Zanichelli, A.; Dallacasa, D.; Stanghellini, C.

2011-04-01

Context. Compact steep-spectrum radio sources and giga-hertz peaked spectrum radio sources (CSS/GPS) are generally considered to be mostly young radio sources. In recent years we studied at many wavelengths a sample of these objects selected from the B3-VLA catalog: the B3-VLA CSS sample. Only ≈60% of the sources were optically identified. Aims: We aim to increase the number of optical identifications and study the properties of the host galaxies of young radio sources. Methods: We cross-correlated the CSS B3-VLA sample with the Sloan Digital Sky Survey (SDSS), DR7, and complemented the SDSS photometry with available GALEX (DR 4/5 and 6) and near-IR data from UKIRT and 2MASS. Results: We obtained new identifications and photometric redshifts for eight faint galaxies and for one quasar and two quasar candidates. Overall we have 27 galaxies with SDSS photometry in five bands, for which we derived the ultraviolet-optical spectral energy distribution (UV-O-SED). We extended our investigation to additional CSS/GPS selected from the literature. Most of the galaxies show an excess of ultra-violet (UV) radiation compared with the UV-O-SED of local radio-quiet ellipticals. We found a strong dependence of the UV excess on redshift and analyzed it assuming that it is generated either from the nucleus (hidden quasar) or from a young stellar population (YSP). We also compare the UV-O-SEDs of our CSS/GPS sources with those of a selection of large size (LSO) powerful radio sources from the literature. Conclusions: If the major process of the UV excess is caused by a YSP, our conclusion is that it is the result of the merger process that also triggered the onset of the radio source with some time delay. We do not see evidence for a major contribution from a YSP triggered by the radio sources itself. Appendices A-G are only available in electronic form at http://www.aanda.org

Comparisons of spectral aerosol single scattering albedo in Seoul, South Korea

NASA Astrophysics Data System (ADS)

Mok, Jungbin; Krotkov, Nickolay A.; Torres, Omar; Jethva, Hiren; Li, Zhanqing; Kim, Jhoon; Koo, Ja-Ho; Go, Sujung; Irie, Hitoshi; Labow, Gordon; Eck, Thomas F.; Holben, Brent N.; Herman, Jay; Loughman, Robert P.; Spinei, Elena; Lee, Seoung Soo; Khatri, Pradeep; Campanelli, Monica

2018-04-01

Quantifying aerosol absorption at ultraviolet (UV) wavelengths is important for monitoring air pollution and aerosol amounts using current (e.g., Aura/OMI) and future (e.g., TROPOMI, TEMPO, GEMS, and Sentinel-4) satellite measurements. Measurements of column average atmospheric aerosol single scattering albedo (SSA) are performed on the ground by the NASA AERONET in the visible (VIS) and near-infrared (NIR) wavelengths and in the UV-VIS-NIR by the SKYNET networks. Previous comparison studies have focused on VIS and NIR wavelengths due to the lack of co-incident measurements of aerosol and gaseous absorption properties in the UV. This study compares the SKYNET-retrieved SSA in the UV with the SSA derived from a combination of AERONET, MFRSR, and Pandora (AMP) retrievals in Seoul, South Korea, in spring and summer 2016. The results show that the spectrally invariant surface albedo assumed in the SKYNET SSA retrievals leads to underestimated SSA compared to AMP values at near UV wavelengths. Re-processed SKYNET inversions using spectrally varying surface albedo, consistent with the AERONET retrieval improve agreement with AMP SSA. The combined AMP inversions allow for separating aerosol and gaseous (NO2 and O3) absorption and provide aerosol retrievals from the shortest UVB (305 nm) through VIS to NIR wavelengths (870 nm).

Impacts of Brown Carbon from Biomass Burning on Surface UV and Ozone Photochemistry in the Amazon Basin

NASA Technical Reports Server (NTRS)

Mok, Jungbin; Krotkov, Nickolay A.; Arola, Antti; Torres, Omar; Jethva, Hiren; Andrade, Marcos; Labow, Gordon; Eck, Thomas F.; Li, Zhangqing; Dickerson, Russell R.;

Impacts of brown carbon from biomass burning on surface UV and ozone photochemistry in the Amazon Basin.

PubMed

Mok, Jungbin; Krotkov, Nickolay A; Arola, Antti; Torres, Omar; Jethva, Hiren; Andrade, Marcos; Labow, Gordon; Eck, Thomas F; Li, Zhanqing; Dickerson, Russell R; Stenchikov, Georgiy L; Osipov, Sergey; Ren, Xinrong

2016-11-11

The spectral dependence of light absorption by atmospheric particulate matter has major implications for air quality and climate forcing, but remains uncertain especially in tropical areas with extensive biomass burning. In the September-October 2007 biomass-burning season in Santa Cruz, Bolivia, we studied light absorbing (chromophoric) organic or "brown" carbon (BrC) with surface and space-based remote sensing. We found that BrC has negligible absorption at visible wavelengths, but significant absorption and strong spectral dependence at UV wavelengths. Using the ground-based inversion of column effective imaginary refractive index in the range 305-368 nm, we quantified a strong spectral dependence of absorption by BrC in the UV and diminished ultraviolet B (UV-B) radiation reaching the surface. Reduced UV-B means less erythema, plant damage, and slower photolysis rates. We use a photochemical box model to show that relative to black carbon (BC) alone, the combined optical properties of BrC and BC slow the net rate of production of ozone by up to 18% and lead to reduced concentrations of radicals OH, HO 2 , and RO 2 by up to 17%, 15%, and 14%, respectively. The optical properties of BrC aerosol change in subtle ways the generally adverse effects of smoke from biomass burning.

EXPERIMENT - APOLLO 16 (UV)

NASA Image and Video Library

1972-06-06

S72-40820 (21 April 1972) --- A color enhancement of a photograph taken on ultra-violet light showing the spectrum of the upper atmosphere of Earth and geocorona. The bright horizontal line is far ultra-violet emission (1216 angstrom) of hydrogen extending 10 degrees (40,000 miles) either side of Earth. The knobby vertical line shows several ultra-violet emissions from Earth's sunlit atmosphere, each "lump" being produced by one type gas (oxygen, nitrogen, helium, etc.). The spectral dispersion is about 10 angstrom per millimeter on this enlargement. The UV camera/spectrograph was operated on the lunar surface by astronaut John W. Young, commander of the Apollo 16 lunar landing mission. It was designed and built at the Naval Research Laboratory, Washington, D.C. While astronauts Young and Charles M. Duke Jr., lunar module pilot, descended in the Lunar Module (LM) "Orion" to explore the Descartes highlands region of the moon, astronaut Thomas K. Mattingly II, command module pilot, remained with the Command and Service Modules (CSM) "Casper" in lunar orbit.

Enhanced Aluminum Reflecting and Solar-Blind Filter Coatings for the Far-Ultraviolet

NASA Technical Reports Server (NTRS)

Del Hoyo, Javier; Quijada, Manuel

2017-01-01

The advancement of far-ultraviolet (FUV) coatings is essential to meet the specified throughput requirements of the Large UV/Optical/IR (LUVOIR) Surveyor Observatory which will cover wavelengths down to the 100 nm range. The biggest constraint in the optical thin film coating design is attenuation in the Lyman-Alpha Ultraviolet range of 100-130 nm in which conventionally deposited thin film materials used in this spectral region (e.g. aluminum [Al] protected with Magnesium fluoride [MgF2]) often have high absorption and scatter properties degrading the throughput in an optical system. We investigate the use of optimally deposited aluminum and aluminum tri-fluoride (AlF3) materials for reflecting and solar blind band-pass filter coatings for use in the FUV. Optical characterization of the deposited designs has been performed using UV spectrometry. The optical thin film design and optimal deposition conditions to produce superior reflectance and transmittance using Al and AlF3 are presented.

Enhanced aluminum reflecting and solar-blind filter coatings for the far-ultraviolet

NASA Astrophysics Data System (ADS)

Del Hoyo, Javier; Quijada, Manuel

2017-09-01

The advancement of far-ultraviolet (FUV) coatings is essential to meet the specified throughput requirements of the Large UV/Optical/IR (LUVOIR) Surveyor Observatory which will cover wavelengths down to the 100 nm range. The biggest constraint in the optical thin film coating design is attenuation in the Lyman-Alpha Ultraviolet range of 100-130 nm in which conventionally deposited thin film materials used in this spectral region (e.g., aluminum [Al] protected with Magnesium fluoride [MgF2]) often have high absorption and scatter properties degrading the throughput in an optical system. We investigate the use of optimally deposited aluminum and aluminum tri-fluoride (AlF3) materials for reflecting and solar blind band-pass filter coatings for use in the FUV. Optical characterization of the deposited designs has been performed using UV spectrometry. The optical thin film design and optimal deposition conditions to produce superior reflectance and transmittance using Al and AlF3 are presented.

Simultaneous UV and optical study of O star winds and UV and optical covariability of O star winds

NASA Technical Reports Server (NTRS)

Nichols, Joy S.

1995-01-01

Simultaneous ultraviolet and optical observations of 10 bright O stars were organized in several observing campaigns lasting 3-6 days each. The observing campaigns included 12 observatories in the Northern hemisphere obtaining high resolution spectroscopy, photometry, and polarimetry, as well as 24-hour coverage with the IUE (International Ultraviolet Explorer) observatory. Over 600 high dispersion SWP spectra were acquired with IUE at both NASA and VILSPA for the completion of this work. The massive amount of data from these observing campaigns, both from IUE and the ground-based instruments, has been reduced and analyzed. The accompanying paper describes the data acquisition, analysis, and conclusions of the study performed. The most important results of this study are the strong confirmation of the ubiquitous variability of winds of O stars, and the critical correlation between rotation of the star and the wind variability as seen in the ultraviolet and optical spectral lines.

Spectral synthesis in the ultraviolet. II - Stellar populations and star formation in blue compact galaxies

NASA Technical Reports Server (NTRS)

Fanelli, Michael N.; O'Connell, Robert W.; Thuan, Trinh X.

1988-01-01

An initial attempt to apply optimizing spectral synthesis techniques to the far-UV spectra of blue compact galaxies (BCGs) is presented. The far-UV absorption-line spectra of the galaxies are clearly composite, with the signatures of the main-sequence types between O3 and mid-A. Most of the low-ionization absorption lines have a stellar origin. The Si IV and C IV features in several objects have P Cygni profiles. In Haro I the strength of Si IV indicates a significant blue supergiant population. The metal-poor blue compact dwarf Mrk 209 displays weak absorption lines, evidence that the stellar component has the same low metallicity as observed in the ionized gas. Good fits to the data are obtained the technique of optimizing population synthesis. The solutions yield stellar luminosity functions which display large discontinuities, indicative of discrete star formation episodes or bursts. The amount of UV extinction is low.

Newer views of the Moon: Comparing spectra from Clementine and the Moon Mineralogy Mapper

USGS Publications Warehouse

Kramer, G.Y.; Besse, S.; Nettles, J.; Combe, J.-P.; Clark, R.N.; Pieters, C.M.; Staid, M.; Malaret, E.; Boardman, J.; Green, R.O.; Head, J.W.; McCord, T.B.

2011-01-01

The Moon Mineralogy Mapper (M3) provided the first global hyperspectral data of the lunar surface in 85 bands from 460 to 2980 nm. The Clementine mission provided the first global multispectral maps the lunar surface in 11 spectral bands across the ultraviolet-visible (UV-VIS) and near-infrared (NIR). In an effort to understand how M3 improves our ability to analyze and interpret lunar data, we compare M3 spectra with those from Clementine's UV-VIS and NIR cameras. The Clementine mission provided the first global multispectral maps the lunar surface in 11 spectral bands across the UV-VIS and NIR. We have found that M3 reflectance values are lower across all wavelengths compared with albedos from both of Clementine's UV-VIS and NIR cameras. M3 spectra show the Moon to be redder, that is, have a steeper continuum slope, than indicated by Clementine. The 1 m absorption band depths may be comparable between the instruments, but Clementine data consistently exhibit shallower 2 m band depths than M 3. Absorption band minimums are difficult to compare due to the significantly different spectral resolutions. Copyright 2011 by the American Geophysical Union.

Newer views of the Moon: Comparing spectra from Clementineand the Moon Mineralogy Mapper

USGS Publications Warehouse

Georgiana Y. Kramer,; Sebastian Besse,; Nettles, Jeff; Jean-Philippe Combe,; Clark, Roger N.; Pieters, Carle M.; Matthew Staid,; Joseph Boardman,; Robert Green,; McCord, Thomas B.; Malaret, Erik; Head, James W.

2011-01-01

The Moon Mineralogy Mapper (M3) provided the first global hyperspectral data of the lunar surface in 85 bands from 460 to 2980 nm. The Clementine mission provided the first global multispectral maps the lunar surface in 11 spectral bands across the ultraviolet-visible (UV-VIS) and near-infrared (NIR). In an effort to understand how M3 improves our ability to analyze and interpret lunar data, we compare M3 spectra with those from Clementine's UV-VIS and NIR cameras. The Clementine mission provided the first global multispectral maps the lunar surface in 11 spectral bands across the UV-VIS and NIR. We have found that M3 reflectance values are lower across all wavelengths compared with albedos from both of Clementine's UV-VIS and NIR cameras. M3 spectra show the Moon to be redder, that is, have a steeper continuum slope, than indicated by Clementine. The 1 μm absorption band depths may be comparable between the instruments, but Clementine data consistently exhibit shallower 2 μm band depths than M3. Absorption band minimums are difficult to compare due to the significantly different spectral resolutions.

Assessment of UV biological spectral weighting functions for phenolic metabolites and growth responses in silver birch seedlings.

PubMed

Kotilainen, Titta; Venäläinen, Tuulia; Tegelberg, Riitta; Lindfors, Anders; Julkunen-Tiitto, Riitta; Sutinen, Sirkka; O'Hara, Robert B; Aphalo, Pedro J

2009-01-01

In research concerning stratospheric ozone depletion, action spectra are used as biological spectral weighting functions (BSWFs) for describing the effects of UV radiation on plant responses. Our aim was to evaluate the appropriateness of six frequently used BSWFs that differ in effectiveness with increasing wavelength. The evaluation of action spectra was based on calculating the effective UV radiation doses according to 1-2) two formulations of the generalized plant action spectrum, 3) a spectrum for ultraviolet induced erythema in human skin, 4) a spectrum for the accumulation of a flavonol in Mesembryanthemum crystallinum, 5) a spectrum for DNA damage in alfalfa seedlings and 6) the plant growth action spectrum. We monitored effects of UV radiation on the concentration of individual UV absorbing metabolites and chlorophyll concentrations in leaves and growth responses of silver birch (Betula pendula) seedlings. Experiments were conducted outdoors using plastic films attenuating different parts of the UV spectrum. Chlorophyll concentrations and growth were not affected by the UV treatments. The response to UV radiation varied between and within groups of phenolics. In general, the observed responses of phenolic groups and individual flavonoids were best predicted by action spectra extending into the UV-A region with moderate effectiveness.

International Ultraviolet Explorer (IUE) ultraviolet spectral atlas of selected astronomical objects

NASA Technical Reports Server (NTRS)

Wu, Chi-Chao; Reichert, Gail A.; Ake, Thomas B.; Boggess, Albert; Holm, Albert V.; Imhoff, Catherine L.; Kondo, Yoji; Mead, Jaylee M.; Shore, Steven N.

1992-01-01

The IUE Ultraviolet Spectral Atlas of Selected Astronomical Objects (or 'the Atlas'), is based on the data that were available in the IUE archive in 1986, and is intended to be a quick reference for the ultraviolet spectra of many categories of astronomical objects. It shows reflected sunlight from the Moon, planets, and asteroids, and also shows emission from comets. Comprehensive compilations of UV spectra for main sequence, subgiant, giant, bright giant, and supergiant stars are published elsewhere. This Atlas contains the spectra for objects occupying other areas of the Hertzsprung-Russell diagram: pre-main sequence stars, chemically peculiar stars, pulsating variables, subluminous stars, and Wolf-Rayet stars. This Atlas also presents phenomena such as the chromospheric and transition region emissions from late-type stars; composite spectra of stars, gas streams, accretion disks and gas envelopes of binary systems; the behavior of gas ejecta shortly after the outburst of novac and supernovac; and the H II regions, planetary nebulae, and supernova remnants. Population 2 stars, globular clusters, and luminous stars in the Magellanic Clouds, M31, and M33, are also included in this publication. Finally, the Atlas gives the ultraviolet spectra of galaxies of different Hubble types and of active galaxies.

FUV Emission from AGB Stars: Modeling Accretion Activity Associated with a Binary Companion

NASA Technical Reports Server (NTRS)

Stevens, Alyx Catherine; Sahai, Raghvendra

2012-01-01

It is widely believed that the late stages of evolution for Asymptotic Giant Branch (AGB) stars are influenced by the presence of binary companions. Unfortunately, there is a lack of direct observational evidence of binarity. However, more recently, strong indirect evidence comes from the discovery of UV emission in a subsample of these objects (fuvAGB stars). AGB stars are comparatively cool objects (< or =3000 K), thus their fluxes falls off drastically for wavelengths 3000 Angstroms and shorter. Therefore, ultraviolet observations offer an important, new technique for detecting the binary companions and/or associated accretion activity. We develop new models of UV emission from fuvAGB stars constrained by GALEX photometry and spectroscopy of these objects. We compare the GALEX UV grism spectra of the AGB M7 star EY Hya to predictions using the spectral synthesis code Cloudy, specifically investigating the ultraviolet wavelength range (1344-2831 Angstroms). We investigate models composed of contributions from a photoionized "hot spot" due to accretion activity around the companion, and "chromospheric" emission from collisionally ionized plasma, to fit the UV observations.

High-performance ultraviolet photodetectors based on solution-grown ZnS nanobelts sandwiched between graphene layers

PubMed Central

Kim, Yeonho; Kim, Sang Jin; Cho, Sung-Pyo; Hong, Byung Hee; Jang, Du-Jeon

2015-01-01

Ultraviolet (UV) light photodetectors constructed from solely inorganic semiconductors still remain unsatisfactory because of their low electrical performances. To overcome this limitation, the hybridization is one of the key approaches that have been recently adopted to enhance the photocurrent. High-performance UV photodetectors showing stable on-off switching and excellent spectral selectivity have been fabricated based on the hybrid structure of solution-grown ZnS nanobelts and CVD-grown graphene. Sandwiched structures and multilayer stacking strategies have been applied to expand effective junction between graphene and photoactive ZnS nanobelts. A multiply sandwich-structured photodetector of graphene/ZnS has shown a photocurrent of 0.115 mA under illumination of 1.2 mWcm−2 in air at a bias of 1.0 V, which is higher 107 times than literature values. The multiple-sandwich structure of UV-light sensors with graphene having high conductivity, flexibility, and impermeability is suggested to be beneficial for the facile fabrication of UV photodetectors with extremely efficient performances. PMID:26197784

Intrinsic Lyα Profile Reconstructions of the MUSCLES Low-Mass Exoplanet Host Stars

NASA Astrophysics Data System (ADS)

Youngblood, Allison A.; France, Kevin; Loyd, R. O. Parke

2015-12-01

UV stellar radiation can significantly impact planetary atmospheres through heating and photochemistry, even regulating production of potential biomarkers. Cool stars emit the majority of their UV radiation in the form of emission lines, and the incident UV radiation on close-in habitable-zone planets is significant. Lyα (1215.67 Å) dominates the 912 - 3200 Å spectrum of cool stars, but strong absorption from the interstellar medium (ISM) makes direct observations of the intrinsic Lyα emission of even nearby stars challenging. The MUSCLES Hubble Space Telescope Treasury Survey (Measurements of the Ultraviolet Spectral Characteristics of Low-mass Exoplanetary Systems) has completed observations of 7 M and 4 K stars hosting exoplanets (d < 22 pc). We have reconstructed the intrinsic Lyα profiles using an MCMC technique and used the results to estimate the extreme ultraviolet (100 - 911 Å) spectrum. We also present empirical relations between Lyα and chromospheric UV metal lines, e.g., Mg II, for use when ISM absorption prevents direct measurement of Lyα. The spectra presented here will be made publicly available through MAST to support exoplanet atmosphere modeling.

CR-39 (PADC) Reflection and Transmission of Light in the Ultraviolet-Near-Infrared (UV-NIR) Range.

PubMed

Traynor, Nathan B J; McLauchlin, Christopher; Dodge, Kenneth; McGarrah, James E; Padalino, Stephen J; McCluskey, Michelle; Sangster, T C; McLean, James G

2018-04-01

The spectral reflection (specular and diffuse) and transmission of Columbia Resin 39 (CR-39) were measured for incoherent light with wavelengths in the range of 200-2500 nm. These results will be of use for the optical characterization of CR-39, as well as in investigations of the chemical modifications of the polymer caused by ultraviolet (UV) exposure. A Varian Cary 5000 was used to perform spectroscopy on several different thicknesses of CR-39. With proper analysis for the interdependence of reflectance and transmittance, results are consistent across all samples. The reflectivity from each CR-39-air boundary reveals an increase in the index of refraction in the near-UV. Absorption observations are consistent with the Beer-Lambert law. Strong absorption of UV light of wavelength shorter than 350 nm suggests an optical band gap of 3.5 eV, although the standard analysis is not conclusive. Absorption features observed in the near infrared are assigned to molecular vibrations, including some that are new to the literature.

Wide-field ultraviolet imager for astronomical transient studies

NASA Astrophysics Data System (ADS)

Mathew, Joice; Ambily, S.; Prakash, Ajin; Sarpotdar, Mayuresh; Nirmal, K.; G. Sreejith, A.; Safonova, Margarita; Murthy, Jayant; Brosch, Noah

2018-04-01

Though the ultraviolet (UV) domain plays a vital role in the studies of astronomical transient events, the UV time-domain sky remains largely unexplored. We have designed a wide-field UV imager that can be flown on a range of available platforms, such as high-altitude balloons, CubeSats, and larger space missions. The major scientific goals are the variability of astronomical sources, detection of transients such as supernovae, novae, tidal disruption events, and characterizing active galactic nuclei variability. The instrument has a 80 mm aperture with a circular field of view of 10.8 degrees, an angular resolution of ˜22 arcsec, and a 240 - 390 nm spectral observation window. The detector for the instrument is a Microchannel Plate (MCP)-based image intensifier with both photon counting and integration capabilities. An FPGA-based detector readout mechanism and real time data processing have been implemented. The imager is designed in such a way that its lightweight and compact nature are well fitted for the CubeSat dimensions. Here we present various design and developmental aspects of this UV wide-field transient explorer.

Ultraviolet Spectroscopy of Asteroid(4) Vesta

NASA Technical Reports Server (NTRS)

Li, Jian-Yang; Bodewits, Dennis; Feaga, Lori M.; Landsman, Wayne; A'Hearn, Michael F.; Mutchler, Max J.; Russell, Christopher T.; McFadden, Lucy A.; Raymond, Carol A.

2011-01-01

We report a comprehensive review of the UV-visible spectrum and rotational lightcurve of Vesta combining new observations by Hubble Space Telescope and Swift with archival International Ultraviolet Explorer observations. The geometric albedos of Vesta from 220 nm to 953 nm arc derived by carefully comparing these observations from various instruments at different times and observing geometries. Vesta has a rotationally averaged geometric albedo of 0.09 at 250 nm, 0.14 at 300 nm, 0.26 at 373 nm, 0.38 at 673 nm, and 0.30 at 950 nm. The linear spectral slope in the ultraviolet displays a sharp minimum ncar sub-Earth longitude of 20deg, and maximum in the eastern hemisphere. This is completely consistent with the distribution of the spectral slope in the visible wavelength. The uncertainty of the measurement in the ultraviolet is approx.20%, and in the visible wavelengths better than 10%. The amplitude of Vesta's rotational lightcurves is approx.10% throughout the range of wavelengths we observed, but is smaller at 950 nm (approx.6%) ncar the 1-micron mafic band center. Contrary to earlier reports, we found no evidence for any difference between the phasing of the ultraviolet and visible/ncar-infrared lightcurves with respect to sub-Earth longitude. Vesta's average spectrum between 220 and 950 nm can well be described by measured reflectance spectra of fine particle howardite-like materials of basaltic achondrite meteorites. Combining this with the in-phase behavior of the ultraviolet, visible. and ncar-infrared lightcurves, and the spectral slopes with respect to the rotational phase, we conclude that there is no global ultraviolet/visible reversal on Vesta. Consequently, this implies lack of global space weathering on Vesta. Keyword,: Asteroid Vesta; Spectrophotometry; Spectroscopy; Ultraviolet observations; Hubble Space Telescope observations

AlN/GaN Digital Alloy for Mid- and Deep-Ultraviolet Optoelectronics.

PubMed

Sun, Wei; Tan, Chee-Keong; Tansu, Nelson

2017-09-19

The AlN/GaN digital alloy (DA) is a superlattice-like nanostructure formed by stacking ultra-thin ( ≤ 4 monolayers) AlN barriers and GaN wells periodically. Here we performed a comprehensive study on the electronics and optoelectronics properties of the AlN/GaN DA for mid- and deep-ultraviolet (UV) applications. Our numerical analysis indicates significant miniband engineering in the AlN/GaN DA by tuning the thicknesses of AlN barriers and GaN wells, so that the effective energy gap can be engineered from ~3.97 eV to ~5.24 eV. The band structure calculation also shows that the valence subbands of the AlN/GaN DA is properly rearranged leading to the heavy-hole (HH) miniband being the top valence subband, which results in the desired transverse-electric polarized emission. Furthermore, our study reveals that the electron-hole wavefunction overlaps in the AlN/GaN DA structure can be remarkably enhanced up to 97% showing the great potential of improving the internal quantum efficiency for mid- and deep-UV device application. In addition, the optical absorption properties of the AlN/GaN DA are analyzed with wide spectral coverage and spectral tunability in mid- and deep-UV regime. Our findings suggest the potential of implementing the AlN/GaN DA as a promising active region design for high efficiency mid- and deep-UV device applications.

Shock-layer-induced ultraviolet emissions measured by rocket payloads

NASA Astrophysics Data System (ADS)

Caveny, Leonard H.; Mann, David M.

1991-08-01

Hypervelocity missiles in the continuum and near-continuum atmosphere produce high temperature shocklayers (i.e., greater than 4000 K at 3.5 km/s and 9000 K at 5.5 km/s). Atmospheric oxygen and nitrogen react and the products are excited to produce nitrogen oxide gamma-band radiation. Analyses and shock tube experiments explored the reaction chemistry and the emissions. Two rocket experiments were conducted to obtain ultraviolet (UV) data under flight conditions using innovative onboard instruments. The first (Bow Shock 1) flew onboard a Terrier-Malemute in April 1990; the second (Bow Shock 2) flew aboard a Strypi XI (Castor 1/Antares IIa/Star 27) in February 1991. The principal instruments were: (1) scanning UV spectrometers, from 190 to 400 nm, (2) quartz fiber-optic coupled photometers to measure selected spectral features, and (3) atomic oxygen (130.4 nm) and hydrogen Lyman-alpha (121.6 nm) detectors. Bow Shock 1 acquired new data on the spectral intensity from UV emissions at 3.5 km/s between 40 and 70 km. For example, at 55 km, the observations included well-defined spectra of nitrogen oxide gamma-band UV emitters with signal strengths more than 10 times stronger than recent theory predicted. Significant signal strength persisted to 70 km, 20 km higher than anticipated. Bow Shock 2 extended the velocity to 5 km/s. An additional scanning spectrometer and 8 photometers observed the downstream shock structures and shock plume interactions. Initial data interpretations indicate that aerodynamic interactions significantly enhance plume emissions.

WUVS simulator: detectability of spectral lines with the WSO-UV spectrographs

NASA Astrophysics Data System (ADS)

Marcos-Arenal, Pablo; de Castro, Ana I. Gómez; Abarca, Belén Perea; Sachkov, Mikhail

2017-04-01

The World Space Observatory Ultraviolet telescope is equipped with high dispersion (55,000) spectrographs working in the 1150 to 3100 Å spectral range. To evaluate the impact of the design on the scientific objectives of the mission, a simulation software tool has been developed. This simulator builds on the development made for the PLATO space mission and it is designed to generate synthetic time-series of images by including models of all important noise sources. We describe its design and performance. Moreover, its application to the detectability of important spectral features for star formation and exoplanetary research is addressed.

Multi-spectral endogenous fluorescence imaging for bacterial differentiation

NASA Astrophysics Data System (ADS)

Chernomyrdin, Nikita V.; Babayants, Margarita V.; Korotkov, Oleg V.; Kudrin, Konstantin G.; Rimskaya, Elena N.; Shikunova, Irina A.; Kurlov, Vladimir N.; Cherkasova, Olga P.; Komandin, Gennady A.; Reshetov, Igor V.; Zaytsev, Kirill I.

2017-07-01

In this paper, the multi-spectral endogenous fluorescence imaging was implemented for bacterial differentiation. The fluorescence imaging was performed using a digital camera equipped with a set of visual bandpass filters. Narrowband 365 nm ultraviolet radiation passed through a beam homogenizer was used to excite the sample fluorescence. In order to increase a signal-to-noise ratio and suppress a non-fluorescence background in images, the intensity of the UV excitation was modulated using a mechanical chopper. The principal components were introduced for differentiating the samples of bacteria based on the multi-spectral endogenous fluorescence images.

Detection of melanomas by digital imaging of spectrally resolved UV light-induced autofluorescence of human skin

NASA Astrophysics Data System (ADS)

Chwirot, B. W.; Chwirot, S.; Jedrzejczyk, W.; Redzinski, J.; Raczynska, A. M.; Telega, K.

2001-07-01

We studied spectral and spatial distributions of the intensity of the ultraviolet light-excited fluorescence of human skin. Our studied performed in situ in 162 patients with malignant and non-malignant skin lesions resulted in a new method of detecting melanomas in situ using digital imaging of the spectrally resolved fluorescence. With our diagnostic algorithm we could successfully detect 88.5% of the cases of melanoma in the group of patients subject to examinations with the fluorescence method. A patent application for the method has been submitted to the Patent Office in Warsaw.

Ultraviolet resources over Northern Eurasia.

PubMed

Chubarova, Natalia; Zhdanova, Yekaterina

2013-10-05

We propose a new climatology of UV resources over Northern Eurasia, which includes the assessments of both detrimental (erythema) and positive (vitamin D synthesis) effects of ultraviolet radiation on human health. The UV resources are defined by using several classes and subclasses - UV deficiency, UV optimum, and UV excess - for 6 different skin types. To better quantifying the vitamin D irradiance threshold we accounted for an open body fraction S as a function of effective air temperature. The spatial and temporal distribution of UV resources was estimated by radiative transfer (RT) modeling (8 stream DISORT RT code) with 1×1° grid and monthly resolution. For this purpose special datasets of main input geophysical parameters (total ozone content, aerosol characteristics, surface UV albedo, UV cloud modification factor) have been created over the territory of Northern Eurasia. The new approaches were used to retrieve aerosol parameters and cloud modification factor in the UV spectral region. As a result, the UV resources were obtained for clear-sky and mean cloudy conditions for different skin types. We show that the distribution of UV deficiency, UV optimum and UV excess is regulated by various geophysical parameters (mainly, total ozone, cloudiness and open body fraction) and can significantly deviate from latitudinal dependence. We also show that the UV optimum conditions can be simultaneously observed for people with different skin types (for example, for 4-5 skin types at the same time in spring over Western Europe). These UV optimum conditions for different skin types occupy a much larger territory over Europe than that over Asia. Copyright © 2013 Elsevier B.V. All rights reserved.

Ultraviolet spectral distribution and erythema-weighted irradiance from indoor tanning devices compared with solar radiation exposures.

PubMed

Sola, Yolanda; Baeza, David; Gómez, Miguel; Lorente, Jerónimo

2016-08-01

Concern regarding the impact of indoor tanning devices on human health has led to different regulations and recommendations, which set limits on erythema-weighted irradiance. Here, we analyze spectral emissions from 52 tanning devices in Spanish facilities and compare them with surface solar irradiance for different solar zenith angles. Whereas most of the devices emitted less UV-B radiation than the midday summer sun, the unweighted UV-A irradiance was 2-6 times higher than solar radiation. Moreover, the spectral distributions of indoor devices were completely different from that of solar radiation, differing in one order of magnitude at some UV-A wavelengths, depending on the lamp characteristics. In 21% of the devices tested, the erythema-weighted irradiance exceeded 0.3Wm(-2): the limit fixed by the European standard and the Spanish regulation. Moreover, 29% of the devices fall within the UV type 4 classification, for which medical advice is required. The high variability in erythema-weighted irradiance results in a wide range of exposure times to reach 1 standard erythemal dose (SED: 100Jm(-2)), with 62% of devices requiring exposures of <10min to reach 1 SED. Nevertheless, the unweighted UV-A dose during this time period would be from 1.4 to 10.3 times more than the solar UV-A dose. Copyright © 2016 Elsevier B.V. All rights reserved.

The IRX-β dust attenuation relation in cosmological galaxy formation simulations

NASA Astrophysics Data System (ADS)

Narayanan, Desika; Davé, Romeel; Johnson, Benjamin D.; Thompson, Robert; Conroy, Charlie; Geach, James

2018-02-01

We utilize a series of galaxy formation simulations to investigate the relationship between the ultraviolet (UV) slope, β, and the infrared excess (IRX) in the spectral energy distributions (SEDs) of galaxies. Our main goals are to understand the origin of and scatter in the IRX-β relation; to assess the efficacy of simplified stellar population synthesis screen models in capturing the essential physics in the IRX-β relation; and to understand systematic deviations from the canonical local IRX-β relations in particular populations of high-redshift galaxies. Our main results follow. Young galaxies with relatively cospatial UV and IR emitting regions and a Milky Way-like extinction curve fall on or near the standard Meurer relation. This behaviour is well captured by simplified screen models. Scatter in the IRX-β relation is dominated by three major effects: (i) older stellar populations drive galaxies below the relations defined for local starbursts due to a reddening of their intrinsic UV SEDs; (ii) complex geometries in high-z heavily star-forming galaxies drive galaxies towards blue UV slopes owing to optically thin UV sightlines; (iii) shallow extinction curves drive galaxies downwards in the IRX-β plane due to lowered near-ultraviolet/far-ultraviolet extinction ratios. We use these features of the UV slopes of galaxies to derive a fitting relation that reasonably collapses the scatter back towards the canonical local relation. Finally, we use these results to develop an understanding for the location of two particularly enigmatic populations of galaxies in the IRX-β plane: z ˜ 2-4 dusty star-forming galaxies and z > 5 star-forming galaxies.

Plant response to solar ultraviolet radiation

NASA Technical Reports Server (NTRS)

Caldwell, M. M.

1981-01-01

Plant reactions and mechanisms of reaction to solar UV radiation are reviewed, along with characteristics of plants which enhance UV tolerance. Wavelength regions to which proteins are particularly sensitive are examined and the possibility of synergistic effects from photoreactions to multiple wavelengths is considered, along with available evidence of nonadditive plant spectral responses to UV radiation. Decreases in atmospheric ozone content are explored in terms of UV wavelengths which would increase with the ozone decreases, particularly for UV-B, which depresses photosynthesis and would increase 1% with a 16% reduction of stratospheric ozone. Higher elevations are projected to display effects of increased UV incident flux first, and global distributions of UV increases due to atmospheric inhomogeneity and water surface clarity are examined. Finally, the response of plant nucleic acids, DNA, chlorophyll to enhanced UV are described, along with repair, avoidance, and optical mechanisms which aid plant survival

A Comparison of Analytical and Data Preprocessing Methods for Spectral Fingerprinting

PubMed Central

LUTHRIA, DEVANAND L.; MUKHOPADHYAY, SUDARSAN; LIN, LONG-ZE; HARNLY, JAMES M.

2013-01-01

Spectral fingerprinting, as a method of discriminating between plant cultivars and growing treatments for a common set of broccoli samples, was compared for six analytical instruments. Spectra were acquired for finely powdered solid samples using Fourier transform infrared (FT-IR) and Fourier transform near-infrared (NIR) spectrometry. Spectra were also acquired for unfractionated aqueous methanol extracts of the powders using molecular absorption in the ultraviolet (UV) and visible (VIS) regions and mass spectrometry with negative (MS−) and positive (MS+) ionization. The spectra were analyzed using nested one-way analysis of variance (ANOVA) and principal component analysis (PCA) to statistically evaluate the quality of discrimination. All six methods showed statistically significant differences between the cultivars and treatments. The significance of the statistical tests was improved by the judicious selection of spectral regions (IR and NIR), masses (MS+ and MS−), and derivatives (IR, NIR, UV, and VIS). PMID:21352644

Ultraviolet-B phototoxicity and hypothetical photomelanomagenesis: intraocular and crystalline lens photoprotection.

PubMed

Mainster, Martin A; Turner, Patricia L

2010-04-01

Ultraviolet-B (UV-B) radiation can cause phototoxic macular injuries in young people who have been sunbathing but not sungazing and in welders. Welders have a reportedly increased risk of uveal melanoma. We analyze phakic and pseudophakic risks for solar and welding arc UV-B exposure. Optical radiation measurement, analysis, and perspective. Spectral transmittances were measured for UV-transmitting, UV-blocking, and blue-blocking intraocular lenses (IOLs). The photoprotective performances of crystalline and intraocular lenses were analyzed using relevant epidemiologic and laboratory data and action spectra for acute retinal phototoxicity and melanoma photocarcinogenesis. Crystalline lens UV-B retinal protection is deficient in children and young adults, increasing their potential susceptibility to acute retinal phototoxicity and hypothetical photomelanomagenesis. UV-B radiation has sufficient energy/photon to induce primary melanomagenic DNA lesions, unlike blue light or UV-A radiation. UV-blocking and blue-blocking IOLs have negligible UV-B transmittance. UV-transmitting IOL transmittance of UV-B radiation is equivalent to that of a 15-year-old crystalline lens. If optical radiation exposure is responsible for welders' increased risk of uveal melanoma, then UV-B radiation is the most probable causative agent and spectacle wear is a potential confounding factor in epidemiologic studies of ocular melanoma. Welders under 30 years of age are at greater risk for welding maculopathy than older welders. Children, adults under 30 years of age, and pseudophakic individuals with UV-transmitting IOLs should wear sunglasses in bright environments because of the UV-B window in their crystalline lenses or IOLs. Copyright 2010 Elsevier Inc. All rights reserved.

Spectral Properties of Gas-phase Condensed Fullerene-like Carbon Nanoparticles from Far-ultraviolet to Infrared Wavelengths

NASA Astrophysics Data System (ADS)

Jäger, C.; Mutschke, H.; Henning, Th.; Huisken, F.

2008-12-01

Carbon solids are ubiquitous material in interstellar space. However, the formation pathway of carbonaceous matter in astrophysical environments, as well as in terrestrial gas-phase condensation reactions, is not yet understood. Laser ablation of graphite in different quenching gas atmospheres, such as pure He, He/H2, and He/H2O at varying pressures, is used to synthesize very small, fullerene-like carbon nanoparticles. The particles are characterized by very small diameters between 1 and 4 nm and a disturbed onion-like structure. The soot particles extracted from the condensation zone obviously represent a very early stage of particle condensation. The spectral properties have been measured from the far-ultraviolet (FUV; λ = 120 nm) to the mid-infrared (MIR; λ = 15 μm). The seedlike soot particles show strong absorption bands in the 3.4 μm range. The profile and the intensity pattern of the 3.4 μm band of the diffuse interstellar medium can be well reproduced by the measured 3.4 μm profile of the condensed particles; however, all the carbon which is left to form solids is needed to fit the intensity of the interstellar bands. In contrast to the assumption that onion-like soot particles could be the carriers of the interstellar ultraviolet (UV) bump, our very small onion-like carbon nanoparticles do not show distinct UV bands due to (π-π*) transitions.

Skyglow effects in UV and visible spectra: Radiative fluxes

NASA Astrophysics Data System (ADS)

Kocifaj, Miroslav; Solano Lamphar, Hector Antonio

2013-09-01

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.

The MUSCLES Treasury Survey: Intrinsic Lyα Profile Reconstructions and UV, X-ray, and Optical Correlations of Low-mass Exoplanet Host Stars

NASA Astrophysics Data System (ADS)

Youngblood, Allison; France, Kevin; Loyd, R. O. Parke

2016-01-01

UV stellar radiation can significantly impact planetary atmospheres through heating and photochemistry, even regulating production of potential biomarkers. Cool stars emit the majority of their UV radiation in the form of emission lines, and the incident UV radiation on close-in habitable-zone planets is significant. Lyα (1215.67 Å) dominates the 912 - 3200 Å spectrum of cool stars, but strong absorption from the interstellar medium (ISM) makes direct observations of the intrinsic Lyα emission of even nearby stars challenging. The MUSCLES Hubble Space Telescope Treasury Survey (Measurements of the Ultraviolet Spectral Characteristics of Low-mass Exoplanetary Systems) has completed observations of 7 M and 4 K stars hosting exoplanets (d < 22 pc) with simultaneous X-ray and ground-based optical spectroscopy for many of the targets. We have reconstructed the intrinsic Lyα profiles using an MCMC technique and used the results to estimate the extreme ultraviolet (100 - 911 Å) spectrum. We also present empirical relations between chromospheric UV and optical lines, e.g., Lyα, Mg II, Ca II H & K, and Hα, for use when direct UV observations of low-mass exoplanet host stars are not possible. The spectra presented here will be made publicly available through MAST to support exoplanet atmosphere modeling.

Developing an Approach to Model UV Fluxes in Smoke Laden Conditions over Central Asia

NASA Astrophysics Data System (ADS)

Park, Y. H.; Sokolik, I. N.

2016-12-01

The UV characteristics of smoke aerosols are valuable inputs to the UV Index forecasts, air quality studies, and assessments of the impact of regional environmental changes. The wavelength dependence of light absorption by aerosol particles is pronounced throughout the UV spectral region. Also in assumption that smoke consists of BC, OC, and Sulfate, the mass fraction of smoke is different with fire types. The purpose of this study is to introduce an approach to calculate the UV fluxes in the aerosol laden conditions, and investigate the irradiance compared to measured irradiance in the UV spectrum. To compute the spectral optical properties (e.g., the effective single scattering albedo, asymmetry parameter, and aerosol optical thickness) for the selected scenarios, the representative size distribution and the refractive index are selected and used in the Mie code. Smoke aerosol information (e.g. emission injection height, mass concentration of smoke components) from WRF Chem is applied to run tropospheric ultraviolet and visible (TUV) model. Using the TUV model, we make the comparisons between model and measured irradiance in UV spectrum in smoke aerosol conditions. An advantage of this approach and the uncertainty of the evaluation are discussed. Overall, the results of this investigation show that this approach is valuable to estimate UV fluxes in smoke laden conditions.

Characterising and testing deep UV LEDs for use in space applications

NASA Astrophysics Data System (ADS)

Hollington, D.; Baird, J. T.; Sumner, T. J.; Wass, P. J.

2015-12-01

Deep ultraviolet (DUV) light sources are used to neutralise isolated test masses in highly sensitive space-based gravitational experiments. An example is the LISA Pathfinder charge management system, which uses low-pressure mercury lamps. A future gravitational-wave observatory such as eLISA will use UV light-emitting diodes (UV LEDs), which offer numerous advantages over traditional discharge lamps. Such devices have limited space heritage but are now available from a number of commercial suppliers. Here we report on a test campaign that was carried out to quantify the general properties of three types of commercially available UV LEDs and demonstrate their suitability for use in space. Testing included general electrical and UV output power measurements, spectral stability, pulsed performance and temperature dependence, as well as thermal vacuum, radiation and vibration survivability.

Nearly simultaneous optical, ultraviolet, and x ray observations of three PG quasars

NASA Technical Reports Server (NTRS)

Kriss, Gerard A.

1990-01-01

Nearly simultaneous optical, ultraviolet, and x ray observations of three low redshift quasars are presented. The EXOSAT x ray spectra span the range of observed spectral indices for quasars from the canonical 0.7 energy index typical of Seyfert galaxies for PG0923+129 (Mrk 705) to the steep spectral indices frequently seen in higher luminosity quasars with an index of 1.58 for PG0844+349 (Ton 951). None of the quasars exhibits any evidence for a soft x ray excess. This is consistent with accretion disk spectra fit to the IR through UV continua of the quasars -- the best fitting disk spectra peak at approximately 6 eV with black hole masses in the range 5 x 10(exp 7) to 1 x 10(exp 9) solar mass and mass accretion rates of approximately 0.1 times the Eddington-limited rate. These rather soft disk spectra are also compatible with the observed optical and ultraviolet line ratios.

Variation in the Humification Degree of Dissolved Organic Matter from Cattle Manure during Composting as Analyzed by Ultraviolet-Visible and Fluorescence Spectroscopy.

PubMed

Chen, Yukun; Jiang, Zhao; Zhang, Xiuyuan; Cao, Bo; Yang, Fan; Wang, Ziyi; Zhang, Ying

2017-11-01

This study investigated the degree of humification of dissolved organic matter (DOM) during different periods of cattle manure composting using ultraviolet-visible (UV-vis) and fluorescence spectroscopy (emission, synchronous scan, and excitation-emission matrix) and determined which method is more suitable for analysis of the humification degree of DOM. Two composting piles were prepared by mixing manure and corn straw. One pile (Pile A [PA]) contained inoculated exogenous composite agents at a ratio of 2% (v/v), and a pile without the addition of inoculants (PNA) served as the control treatment. The results showed that ultraviolet integrated absorption intensities in the range of 226 to 400 nm and 260 to 280 nm and specific ultraviolet absorbances at 254 and 280 nm of both PA and PNA gradually increased with composting time. Based on the fluorescence regional integration analysis and parallel factor analysis, the humic-like substances became the main components of the DOM after composting. Our study demonstrated that the humification degree of DOM was enhanced during composting and that the inoculation composite agent was beneficial for the humification of DOM at the mesophilic and thermophilic phases of the composting process. Moreover, the results of correlation analysis and principal component analysis demonstrated that the fluorescence spectral parameters evaluated the humification degree of DOM during the whole cattle manure composting process better than the UV-vis spectral parameters. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Characterization of potassium dichromate solutions for spectrophotometercalibration

NASA Astrophysics Data System (ADS)

Conceição, F. C.; Silva, E. M.; Gomes, J. F. S.; Borges, P. P.

2018-03-01

Spectrophotometric analysis in the ultraviolet (UV) region is used in the determination of several quantitative and qualitative parameters. For ensuring reliability of the analyses performed on the spectrophotometers, verification / calibration of the equipment must be performed periodically using certified reference materials (CRMs). This work presents the characterization stage needed for producing this CRM. The property value characterized was the absorbance for the wavelengths in the UV spectral regions. This CRM will contribute to guarantee the accuracy and linearity of the absorbance scale to the spectrophotometers, through which analytical measurement results will be provided with metrological traceability.

Flower colours through the lens: quantitative measurement with visible and ultraviolet digital photography.

PubMed

Garcia, Jair E; Greentree, Andrew D; Shrestha, Mani; Dorin, Alan; Dyer, Adrian G

2014-01-01

The study of the signal-receiver relationship between flowering plants and pollinators requires a capacity to accurately map both the spectral and spatial components of a signal in relation to the perceptual abilities of potential pollinators. Spectrophotometers can typically recover high resolution spectral data, but the spatial component is difficult to record simultaneously. A technique allowing for an accurate measurement of the spatial component in addition to the spectral factor of the signal is highly desirable. Consumer-level digital cameras potentially provide access to both colour and spatial information, but they are constrained by their non-linear response. We present a robust methodology for recovering linear values from two different camera models: one sensitive to ultraviolet (UV) radiation and another to visible wavelengths. We test responses by imaging eight different plant species varying in shape, size and in the amount of energy reflected across the UV and visible regions of the spectrum, and compare the recovery of spectral data to spectrophotometer measurements. There is often a good agreement of spectral data, although when the pattern on a flower surface is complex a spectrophotometer may underestimate the variability of the signal as would be viewed by an animal visual system. Digital imaging presents a significant new opportunity to reliably map flower colours to understand the complexity of these signals as perceived by potential pollinators. Compared to spectrophotometer measurements, digital images can better represent the spatio-chromatic signal variability that would likely be perceived by the visual system of an animal, and should expand the possibilities for data collection in complex, natural conditions. However, and in spite of its advantages, the accuracy of the spectral information recovered from camera responses is subject to variations in the uncertainty levels, with larger uncertainties associated with low radiance levels.

The importance of ultraviolet and near-infrared sensitivity for visual discrimination in two species of lacertid lizards.

PubMed

Martin, Mélissa; Le Galliard, Jean-François; Meylan, Sandrine; Loew, Ellis R

2015-02-01

Male and female Lacertid lizards often display conspicuous coloration that is involved in intraspecific communication. However, visual systems of Lacertidae have rarely been studied and the spectral sensitivity of their retinal photoreceptors remains unknown. Here, we characterise the spectral sensitivity of two Lacertid species from contrasting habitats: the wall lizard Podarcis muralis and the common lizard Zootoca vivipara. Both species possess a pure-cone retina with one spectral class of double cones and four spectral classes of single cones. The two species differ in the spectral sensitivity of the LWS cones, the relative abundance of UVS single cones (potentially more abundant in Z. vivipara) and the coloration of oil droplets. Wall lizards have pure vitamin A1-based photopigments, whereas common lizards possess mixed vitamin A1 and A2 photopigments, extending spectral sensitivity into the near infrared, which is a rare feature in terrestrial vertebrates. We found that spectral sensitivity in the UV and near infrared improves discrimination of small variations in throat coloration among Z. vivipara. Thus, retinal specialisations optimise chromatic resolution in common lizards, indicating that the visual system and visual signals might co-evolve. © 2015. Published by The Company of Biologists Ltd.

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

Shamirzaev, V. T., E-mail: tim@isp.nsc.ru; Gaisler, V. A.; Shamirzaev, T. S.

The spectrum of ultraviolet (UV) InGaN/GaN light-emitting diodes and its dependence on the current flowing through the structure are studied. The intensity of the UV contribution to the integrated diode luminescence increases steadily with increasing density of current flowing through the structure, despite a drop in the emission quantum efficiency. The electroluminescence excitation conditions that allow the fraction of UV emission to be increased to 97% are established. It is shown that the nonuniform generation of extended defects, which penetrate the active region of the light-emitting diodes as the structures degrade upon local current overheating, reduces the integrated emission intensitymore » but does not affect the relative intensity of diode emission in the UV (370 nm) and visible (550 nm) spectral ranges.« less

The MUSCLES Treasury Survey. IV. Scaling Relations for Ultraviolet, Ca ii K, and Energetic Particle Fluxes from M Dwarfs

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

Youngblood, Allison; France, Kevin; Loyd, R. O. Parke

Characterizing the UV spectral energy distribution (SED) of an exoplanet host star is critically important for assessing its planet’s potential habitability, particularly for M dwarfs, as they are prime targets for current and near-term exoplanet characterization efforts and atmospheric models predict that their UV radiation can produce photochemistry on habitable zone planets different from that on Earth. To derive ground-based proxies for UV emission for use when Hubble Space Telescope ( HST ) observations are unavailable, we have assembled a sample of 15 early to mid-M dwarfs observed by HST and compared their nonsimultaneous UV and optical spectra. We findmore » that the equivalent width of the chromospheric Ca ii K line at 3933 Å, when corrected for spectral type, can be used to estimate the stellar surface flux in ultraviolet emission lines, including H i Ly α . In addition, we address another potential driver of habitability: energetic particle fluxes associated with flares. We present a new technique for estimating soft X-ray and >10 MeV proton flux during far-UV emission line flares (Si iv and He ii) by assuming solar-like energy partitions. We analyze several flares from the M4 dwarf GJ 876 observed with HST and Chandra as part of the MUSCLES Treasury Survey and find that habitable zone planets orbiting GJ 876 are impacted by large Carrington-like flares with peak soft X-ray fluxes ≥10{sup −3} W m{sup −2} and possible proton fluxes ∼10{sup 2}–10{sup 3} pfu, approximately four orders of magnitude more frequently than modern-day Earth.« less

Tolerance of entomopathogenic fungi to ultraviolet radiation: a review on screening of strains and their formulation.

PubMed

Fernandes, Éverton K K; Rangel, Drauzio E N; Braga, Gilberto U L; Roberts, Donald W

2015-08-01

Ultraviolet radiation from sunlight is probably the most detrimental environmental factor affecting the viability of entomopathogenic fungi applied to solar-exposed sites (e.g., leaves) for pest control. Most entomopathogenic fungi are sensitive to UV radiation, but there is great inter- and intraspecies variability in susceptibility to UV. This variability may reflect natural adaptations of isolates to their different environmental conditions. Selecting strains with outstanding natural tolerance to UV is considered as an important step to identify promising biological control agents. However, reports on tolerance among the isolates used to date must be analyzed carefully due to considerable variations in the methods used to garner the data. The current review presents tables listing many studies in which different methods were applied to check natural and enhanced tolerance to UV stress of numerous entomopathogenic fungi, including several well-known isolates of these fungi. The assessment of UV tolerance is usually conducted with conidia using dose-response methods, wherein the UV dose is calculated simply by multiplying the total irradiance by the period (time) of exposure. Although irradiation from lamps seldom presents an environmentally realistic spectral distribution, laboratory tests circumvent the uncontrollable circumstances associated with field assays. Most attempts to increase field persistence of microbial agents have included formulating conidia with UV protectants; however, in many cases, field efficacy of formulated fungi is still not fully adequate for dependable pest control.

Daily light integral and day light quality: Potentials and pitfalls of nighttime UV treatments on cucumber powdery mildew.

PubMed

Suthaparan, Aruppillai; Solhaug, Knut Asbjørn; Stensvand, Arne; Gislerød, Hans Ragnar

2017-10-01

Nighttime ultraviolet (UV) radiation, if applied properly, has a significant potential for management of powdery mildews in many crop species. In this study, the role of growth light duration, irradiance, a combination of both (daily light integral) and light spectral quality (blue or red) on the efficacy of UV treatments against powdery mildew caused by Podosphaera xanthii and the growth performance of cucumber plants was studied in growth chambers. Increasing daily light integral provided by high-pressure sodium lamps (HPS) decreased efficacy of nighttime UV treatments against P. xanthii, but it increased plant growth. Furthermore, the efficacy of nighttime UV decreased when day length was increased from 16 to 20h at a constant daily light integral. The efficacy of nighttime UV increased if red light was applied after UV treatment, showing the possibility of day length extension without reducing the effect of UV. Increasing the dose of blue light during daytime reduced the efficacy of nighttime UV in controlling the disease, whereas blue deficient growth light (<6% of blue) caused UV mediated curling of young leaves. Furthermore, application of blue light after nighttime UV reduced its disease control efficacy. This showed the importance of maintaining a minimum of blue light in the growth light before nighttime UV treatment. Findings from this study showed that optimization of nighttime UV for management of powdery mildew is dependent on the spectral composition of the photosynthetically active radiation. Copyright © 2017 Elsevier B.V. All rights reserved.

The MUSCLES Treasury Survey. II. Intrinsic LYα and Extreme Ultraviolet Spectra of K and M Dwarfs with Exoplanets*

NASA Astrophysics Data System (ADS)

Youngblood, Allison; France, Kevin; Loyd, R. O. Parke; Linsky, Jeffrey L.; Redfield, Seth; Schneider, P. Christian; Wood, Brian E.; Brown, Alexander; Froning, Cynthia; Miguel, Yamila; Rugheimer, Sarah; Walkowicz, Lucianne

2016-06-01

The ultraviolet (UV) spectral energy distributions (SEDs) of low-mass (K- and M-type) stars play a critical role in the heating and chemistry of exoplanet atmospheres, but are not observationally well-constrained. Direct observations of the intrinsic flux of the Lyα line (the dominant source of UV photons from low-mass stars) are challenging, as interstellar H I absorbs the entire line core for even the closest stars. To address the existing gap in empirical constraints on the UV flux of K and M dwarfs, the MUSCLES Hubble Space Telescope Treasury Survey has obtained UV observations of 11 nearby M and K dwarfs hosting exoplanets. This paper presents the Lyα and extreme-UV spectral reconstructions for the MUSCLES targets. Most targets are optically inactive, but all exhibit significant UV activity. We use a Markov Chain Monte Carlo technique to correct the observed Lyα profiles for interstellar absorption, and we employ empirical relations to compute the extreme-UV SED from the intrinsic Lyα flux in ˜100 Å bins from 100-1170 Å. The reconstructed Lyα profiles have 300 km s-1 broad cores, while >1% of the total intrinsic Lyα flux is measured in extended wings between 300 and 1200 km s-1. The Lyα surface flux positively correlates with the Mg II surface flux and negatively correlates with the stellar rotation period. Stars with larger Lyα surface flux also tend to have larger surface flux in ions formed at higher temperatures, but these correlations remain statistically insignificant in our sample of 11 stars. We also present H I column density measurements for 10 new sightlines through the local interstellar medium. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555.

Which way is up? Asymmetric spectral input along the dorsal-ventral axis influences postural responses in an amphibious annelid.

PubMed

Jellies, John

2014-11-01

Medicinal leeches are predatory annelids that exhibit countershading and reside in aquatic environments where light levels might be variable. They also leave the water and must contend with terrestrial environments. Yet, leeches generally maintain a dorsal upward position despite lacking statocysts. Leeches respond visually to both green and near-ultraviolet (UV) light. I used LEDs to test the hypothesis that ventral, but not dorsal UV would evoke compensatory movements to orient the body. Untethered leeches were tested using LEDs emitting at red (632 nm), green (513 nm), blue (455 nm) and UV (372 nm). UV light evoked responses in 100 % of trials and the leeches often rotated the ventral surface away from it. Visible light evoked no or modest responses (12-15 % of trials) and no body rotation. Electrophysiological recordings showed that ventral sensilla responded best to UV, dorsal sensilla to green. Additionally, a higher order interneuron that is engaged in a variety of parallel networks responded vigorously to UV presented ventrally, and both the visible and UV responses exhibited pronounced light adaptation. These results strongly support the suggestion that a dorsal light reflex in the leech uses spectral comparisons across the dorsal-ventral axis rather than, or in addition to, luminance.

The Ultraviolet Spectrograph (UVS) on Juno

NASA Astrophysics Data System (ADS)

Gladstone, G. R.; Persyn, S.; Eterno, J.; Slater, D. C.; Davis, M. W.; Versteeg, M. H.; Persson, K. B.; Siegmund, O. H.; Marquet, B.; Gerard, J.; Grodent, D. C.

2008-12-01

Juno, a NASA New Frontiers mission, plans for launch in August 2011, a 5-year cruise (including a flyby of Earth in October 2013 for a gravity boost), and 14 months around Jupiter after arriving in August 2016. The spinning (2 RPM), solar-powered Juno will study Jupiter from a highly elliptical orbit, in which the spacecraft (for about 6 hours once every 11 days) dives down over the north pole, skims the outermost atmosphere, and rises back up over the south pole. This orbit allows Juno avoid most of the intense particle radiation surrounding the planet and provides an excellent platform for investigating Jupiter's polar magnetosphere. Part of the exploration of Jupiter's polar magnetosphere will involve remote sensing of the far-ultraviolet H and H2 auroral emissions, plus gases such as methane and acetylene which add their absorption signature to the H2 emissions. This hydrocarbon absorption can be used to estimate the energy of the precipitating electrons; since more energetic electrons penetrate deeper into the atmosphere and the UV emissions they produce will show more absorption. Juno will carry an Ultraviolet Spectrograph (UVS) to make spectral images of Jupiter's aurora. UVS is a UV imaging spectrograph sensitive to both extreme and far ultraviolet emissions in the 70-205~nm range that will characterize the morphology and spectral nature of Jupiter's auroral emissions. Juno UVS consists of two separate sections: a dedicated telescope/spectrograph assembly and a vault electronics box. The telescope/spectrograph assembly contains a telescope which feeds a 0.15-m Rowland circle spectrograph. The telescope has an input aperture 40×40~mm2 and uses an off-axis parabolic primary mirror. A flat scan mirror situated at the front end of the telescope (used to target specific auroral features at up to ±30° perpendicular to the Juno spin plane) directs incoming light to the primary. The light is then focused onto the spectrograph entrance slit, which has a 'dog- bone' shape 6° long, in three 2° sections of 0.2°, 0.05°, and 0.2° width (projected onto the sky). Light entering the slit is dispersed by a toroidal grating which focuses the UV bandpass onto a curved microchannel plate (MCP) cross delay line (XDL) detector with a solar blind UV- sensitive CsI photocathode, which makes up the instrument's focal plane. Tantalum shielding surrounds the detector assembly to protect the detector and the adjacent detector electronics from high-energy electrons. The main electronics box is located in the Juno vault. Inside are two redundant high-voltage power supplies (HVPS), two redundant low-voltage power supplies, the command and data handling (C&DH) electronics, heater/actuator activation electronics, scan mirror electronics, and event processing electronics. An overview of the UVS design and scientific performance will be presented.

Solar UV Variations During the Decline of Cycle 23

NASA Technical Reports Server (NTRS)

DeLand, Matthew, T.; Cebula, Richard P.

2011-01-01

Characterization of temporal and spectral variations in solar ultraviolet irradiance over a solar cycle is essential for understanding the forcing of Earth's atmosphere and climate. Satellite measurements of solar UV variability for solar cycles 21, 22, and 23 show consistent solar cycle irradiance changes at key wavelengths (e.g. 205 nm, 250 nm) within instrumental uncertainties. All historical data sets also show the same relative spectral dependence for both short-term (rotational) and long-term (solar cycle) variations. Empirical solar irradiance models also produce long-term solar UV variations that agree well with observational data. Recent UV irradiance data from the Solar Radiation and Climate Experiment (SORCE) Spectral Irradiance Monitor (SIM) and Solar Stellar Irradiance Comparison Experiment (SOLSTICE) instruments covering the declining phase of Cycle 23 present a different picture oflong-term solar variations from previous results. Time series of SIM and SOLSTICE spectral irradiance data between 2003 and 2007 show solar variations that greatly exceed both previous measurements and predicted irradiance changes over this period, and the spectral dependence of the SIM and SOLSTICE variations during these years do not show features expected from solar physics theory. The use of SORCE irradiance variations in atmospheric models yields substantially different middle atmosphere ozone responses in both magnitude and vertical structure. However, short-term solar variability derived from SIM and SOLSTICE UV irradiance data is consistent with concurrent solar UV measurements from other instruments, as well as previous results, suggesting no change in solar physics. Our analysis of short-term solar variability is much less sensitive to residual instrument response changes than the observations of long-term variations. The SORCE long-term UV results can be explained by under-correction of instrument response changes during the first few years of measurements, rather than requiring an unexpected change in the physical behavior of the Sun.

Impacts of brown carbon from biomass burning on surface UV and ozone photochemistry in the Amazon Basin

PubMed Central

Mok, Jungbin; Krotkov, Nickolay A.; Arola, Antti; Torres, Omar; Jethva, Hiren; Andrade, Marcos; Labow, Gordon; Eck, Thomas F.; Li, Zhanqing; Dickerson, Russell R.; Stenchikov, Georgiy L.; Osipov, Sergey; Ren, Xinrong

2016-01-01

The spectral dependence of light absorption by atmospheric particulate matter has major implications for air quality and climate forcing, but remains uncertain especially in tropical areas with extensive biomass burning. In the September-October 2007 biomass-burning season in Santa Cruz, Bolivia, we studied light absorbing (chromophoric) organic or “brown” carbon (BrC) with surface and space-based remote sensing. We found that BrC has negligible absorption at visible wavelengths, but significant absorption and strong spectral dependence at UV wavelengths. Using the ground-based inversion of column effective imaginary refractive index in the range 305–368 nm, we quantified a strong spectral dependence of absorption by BrC in the UV and diminished ultraviolet B (UV-B) radiation reaching the surface. Reduced UV-B means less erythema, plant damage, and slower photolysis rates. We use a photochemical box model to show that relative to black carbon (BC) alone, the combined optical properties of BrC and BC slow the net rate of production of ozone by up to 18% and lead to reduced concentrations of radicals OH, HO2, and RO2 by up to 17%, 15%, and 14%, respectively. The optical properties of BrC aerosol change in subtle ways the generally adverse effects of smoke from biomass burning. PMID:27833145

Emission spectra of photoionized plasmas induced by intense EUV pulses: Experimental and theoretical investigations

NASA Astrophysics Data System (ADS)

Saber, Ismail; Bartnik, Andrzej; Skrzeczanowski, Wojciech; Wachulak, Przemysław; Jarocki, Roman; Fiedorowicz, Henryk

2017-03-01

Experimental measurements and numerical modeling of emission spectra in photoionized plasma in the ultraviolet and visible light (UV/Vis) range for noble gases have been investigated. The photoionized plasmas were created using laser-produced plasma (LPP) extreme ultraviolet (EUV) source. The source was based on a gas puff target; irradiated with 10ns/10J/10Hz Nd:YAG laser. The EUV radiation pulses were collected and focused using grazing incidence multifoil EUV collector. The laser pulses were focused on a gas stream, injected into a vacuum chamber synchronously with the EUV pulses. Irradiation of gases resulted in a formation of low temperature photoionized plasmas emitting radiation in the UV/Vis spectral range. Atomic photoionized plasmas produced this way consisted of atomic and ionic with various ionization states. The most dominated observed spectral lines originated from radiative transitions in singly charged ions. To assist in a theoretical interpretation of the measured spectra, an atomic code based on Cowan's programs and a collisional-radiative PrismSPECT code have been used to calculate the theoretical spectra. A comparison of the calculated spectral lines with experimentally obtained results is presented. Electron temperature in plasma is estimated using the Boltzmann plot method, by an assumption that a local thermodynamic equilibrium (LTE) condition in the plasma is validated in the first few ionization states. A brief discussion for the measured and computed spectra is given.

Reversible photoinduced spectral change in Eu2O3 at room temperature

NASA Astrophysics Data System (ADS)

Mochizuki, Shosuke; Nakanishi, Tauto; Suzuki, Yuya; Ishi, Kimihiro

2001-12-01

When Eu2O3 powder compact and film are irradiated with ultraviolet (UV) laser light in a vacuum, their photoluminescence (PL) spectra change from a red sharp-line structure to a white broad band, which can be clearly seen with the naked eye. After removing the UV laser light, the white PL continues for more than several months at room temperature under room light, in spite of any changes of atmosphere. By irradiating with the same UV laser light at room temperature under O2 gas atmosphere, the original red PL state reappears. Such a reversible phenomenon may well yield materials for white-light-emitting devices and erasable optical storage.

UV Spectroradiometric Output Of An F404 Turbojet Aircraft Engine

NASA Astrophysics Data System (ADS)

Schneider, William E.; Spaberg, Gordon H.

1989-09-01

Spectroradiometric measurements of the ultraviolet output of a GE F404 aircraft engine were made over the wavelength range of 200 to 320 nm. The tests were conducted at the GE Lynn, Mass. Riverworks facility in the F404 ram cell. The severe environmental conditions associated with the test cell required a special acoustical noise-proof and mechanical shock-proof enclosure for the double monochromator and UV detectors along with special long cabling to the externally located radiometer and automatic data reduction system. The tests successfully provided spectral irradiance measurements of the afterburner over the 225-320 nm wavelength range with a UV-enhanced silicon detector and over the 200-260 nm range with a PMT detector.

Determining the refractive index of human hemoglobin solutions by Kramers-Kronig relations with an improved absorption model.

PubMed

Gienger, Jonas; Groß, Hermann; Neukammer, Jörg; Bär, Markus

2016-11-01

The real part of the refractive index of aqueous solutions of human hemoglobin is computed from their absorption spectra in the wavelength range 250-1100 nm using the Kramers-Kronig (KK) relations, and the corresponding uncertainty analysis is provided. The strong ultraviolet (UV) and infrared absorbance of the water outside this spectral range were taken into account in a previous study employing KK relations. We improve these results by including the concentration dependence of the water absorbance as well as by modeling the deep UV absorbance of hemoglobin's peptide backbone. The two free parameters of the model for the deep UV absorbance are fixed by a global fit.

Quasi-simultaneous observations of the BL Lac object MK 501 in X-ray, UV, visible, IR and radio frequencies

NASA Technical Reports Server (NTRS)

Kondo, D. M.; Worrall, D. M.; Mushotzky, R. F.; Hackney, R. L.; Hackney, K. H.; Oke, J. B.; Yee, H.; Neugebauer, G.; Matthews, K.; Feldman, P. A.

1980-01-01

Quasi-simultaneous observations of the BL Lacertae (Lac) objects MK 501 were performed for the first time at X-ray, ultraviolet, visible, infrared, and radio frequencies. The observed spectral slope from the X-ray to UV regions is positive and continuous, but that from the mid UV to visible light region becomes gradually flat and possibly turns down toward lower frequencies; the optical radio emission can not be accounted for by a single power law. Several theoretical models were considered for the emission mechanism. A quantitative comparison was performed with the synchrotron-self-Compton model; the total spectrum is found consistent with this model. The spectrum from visible light to X-ray is consistent with synchrotron radiation or with inverse-Compton scattering by a hot thermal cloud of electrons. The continuity of the spectral slope from X-ray to UV implied by the current data suggests that the previous estimates of the total luminosity of this BL Lac object is underestimated by a factor of about three or four.

An AlGaN Core-Shell Tunnel Junction Nanowire Light-Emitting Diode Operating in the Ultraviolet-C Band.

PubMed

Sadaf, S M; Zhao, S; Wu, Y; Ra, Y-H; Liu, X; Vanka, S; Mi, Z

2017-02-08

To date, semiconductor light emitting diodes (LEDs) operating in the deep ultraviolet (UV) spectral range exhibit very low efficiency due to the presence of large densities of defects and extremely inefficient p-type conduction of conventional AlGaN quantum well heterostructures. We have demonstrated that such critical issues can be potentially addressed by using nearly defect-free AlGaN tunnel junction core-shell nanowire heterostructures. The core-shell nanowire arrays exhibit high photoluminescence efficiency (∼80%) in the UV-C band at room temperature. With the incorporation of an epitaxial Al tunnel junction, the p-(Al)GaN contact-free nanowire deep UV LEDs showed nearly one order of magnitude reduction in the device resistance, compared to the conventional nanowire p-i-n device. The unpackaged Al tunnel junction deep UV LEDs exhibit an output power >8 mW and a peak external quantum efficiency ∼0.4%, which are nearly one to two orders of magnitude higher than previously reported AlGaN nanowire devices. Detailed studies further suggest that the maximum achievable efficiency is limited by electron overflow and poor light extraction efficiency due to the TM polarized emission.

[Experimental research of turbidity influence on water quality monitoring of COD in UV-visible spectroscopy].

PubMed

Tang, Bin; Wei, Biao; Wu, De-Cao; Mi, De-Ling; Zhao, Jing-Xiao; Feng, Peng; Jiang, Shang-Hai; Mao, Ben-Jiang

2014-11-01

Eliminating turbidity is a direct effect spectroscopy detection of COD key technical problems. This stems from the UV-visible spectroscopy detected key quality parameters depend on an accurate and effective analysis of water quality parameters analytical model, and turbidity is an important parameter that affects the modeling. In this paper, we selected formazine turbidity solution and standard solution of potassium hydrogen phthalate to study the turbidity affect of UV--visible absorption spectroscopy detection of COD, at the characteristics wavelength of 245, 300, 360 and 560 nm wavelength point several characteristics with the turbidity change in absorbance method of least squares curve fitting, thus analyzes the variation of absorbance with turbidity. The results show, In the ultraviolet range of 240 to 380 nm, as the turbidity caused by particle produces compounds to the organics, it is relatively complicated to test the turbidity affections on the water Ultraviolet spectra; in the visible region of 380 to 780 nm, the turbidity of the spectrum weakens with wavelength increases. Based on this, this paper we study the multiplicative scatter correction method affected by the turbidity of the water sample spectra calibration test, this method can correct water samples spectral affected by turbidity. After treatment, by comparing the spectra before, the results showed that the turbidity caused by wavelength baseline shift points have been effectively corrected, and features in the ultraviolet region has not diminished. Then we make multiplicative scatter correction for the three selected UV liquid-visible absorption spectroscopy, experimental results shows that on the premise of saving the characteristic of the Ultraviolet-Visible absorption spectrum of water samples, which not only improve the quality of COD spectroscopy detection SNR, but also for providing an efficient data conditioning regimen for establishing an accurate of the chemical measurement methods.

Two novel nonlinear optical carbonates in the deep-ultraviolet region: KBeCO3F and RbAlCO3F2

PubMed Central

Kang, Lei; Lin, Zheshuai; Qin, Jingui; Chen, Chuangtian

2013-01-01

With the rapid developments of the all-solid-state deep-ultraviolet (deep-UV) lasers, the good nonlinear optical (NLO) crystal applied in this spectral region is currently lacking. Here, we design two novel NLO carbonates KBeCO3F and RbAlCO3F2 from the first-principles theory implemented in the molecular engineering expert system especially for NLO crystals. Both structurally stable crystals possess very large energy band gaps and optical anisotropy, so they would become the very promising deep-UV NLO crystals alternative to KBBF. Recent experimental results on MNCO3F (M = K, Rb, Cs; N = Ca, Sr, Ba) not only confirm our calculations, but also suggest that the synthesis of the KBeCO3F and RbAlCO3F2 crystals is feasible. PMID:23455618

Quantum chemical investigations on the molecular structure, FTIR, UV-Vis and HOMO-LUMO analysis of 15-16-epoxy-7b, 9a dihydroxylabdane 13(16), 14-dien-6-one

NASA Astrophysics Data System (ADS)

Uppal, Anshul; Pathania, Kamni; Khajuria, Yugal

2018-05-01

The structural, spectroscopic (Fourier Transform Infrared (FT-IR), Ultra-Violet Visible (UV-VIS)) and thermodynamic properties of 15, 16-epoxy-7b, 9a dihydroxylabdane-13(16), 14-dien-6-one were studied by using both experimental techniques and theoretical methods. The FTIR spectrum of the title compound was recorded in the spectral range 4000-400 cm-1. The UV-VIS spectrum was measured in the spectral range 190-800 nm. The quantum chemistry calculations have been performed to compute optimized geometry, molecular parameters, vibrational frequencies along with intensities using Hartree Fock (HF) theory and Density Functional Theory (DFT) with 6-31G basis set. The calculated HOMO-LUMO energies show that the charge transfer occurs within the molecule. The temperature dependence of the thermodynamic properties like heat capacity, entropy and enthalpy of the optimized structure were obtained. Finally, a comparison between the experimental data and the calculated results presented a good agreement.

The 1997 North American Interagency Intercomparison of Ultraviolet Spectroradiometers Including Narrowband Filter Radiometers

PubMed Central

Lantz, Kathleen; Disterhoft, Patrick; Early, Edward; Thompson, Ambler; DeLuisi, John; Berndt, Jerry; Harrison, Lee; Kiedron, Peter; Ehramjian, James; Bernhard, Germar; Cabasug, Lauriana; Robertson, James; Mou, Wanfeng; Taylor, Thomas; Slusser, James; Bigelow, David; Durham, Bill; Janson, George; Hayes, Douglass; Beaubien, Mark; Beaubien, Arthur

2002-01-01

The fourth North American Intercomparison of Ultraviolet Monitoring Spectroradiometers was held September 15 to 25, 1997 at Table Mountain outside of Boulder, Colorado, USA. Concern over stratospheric ozone depletion has prompted several government agencies in North America to establish networks of spectroradiometers for monitoring solar ultraviolet irradiance at the surface of the Earth. The main purpose of the Intercomparison was to assess the ability of spectroradiometers to accurately measure solar ultraviolet irradiance, and to compare the results between instruments of different monitoring networks. This Intercomparison was coordinated by NIST and NOAA, and included participants from the ASRC, EPA, NIST, NSF, SERC, USDA, and YES. The UV measuring instruments included scanning spectroradiometers, spectrographs, narrow band multi-filter radiometers, and broadband radiometers. Instruments were characterized for wavelength accuracy, bandwidth, stray-light rejection, and spectral irradiance responsivity. The spectral irradiance responsivity was determined two to three times outdoors to assess temporal stability. Synchronized spectral scans of the solar irradiance were performed over several days. Using the spectral irradiance responsivities determined with the NIST traceable standard lamp, and a simple convolution technique with a Gaussian slit-scattering function to account for the different bandwidths of the instruments, the measured solar irradiance from the spectroradiometers excluding the filter radiometers at 16.5 h UTC had a relative standard deviation of ±4 % for wavelengths greater than 305 nm. The relative standard deviation for the solar irradiance at 16.5 h UTC including the filter radiometer was ±4 % for filter functions above 300 nm. PMID:27446717

Monitoring ultraviolet (UV) radiation inactivation of Cronobacter sakazakii in dry infant formula using Fourier transform infrared spectroscopy.

PubMed

Liu, Qian; Lu, Xiaonan; Swanson, Barry G; Rasco, Barbara A; Kang, Dong-Hyun

2012-01-01

Cronobacter sakazakii is an opportunistic pathogen associated with dry infant formula presenting a high risk to low birth weight neonates. The inactivation of C. sakazakii in dry infant formula by ultraviolet (UV) radiation alone and combined with hot water treatment at temperatures of 55, 60, and 65 °C were applied in this study. UV radiation with doses in a range from 12.1 ± 0.30 kJ/m² to 72.8 ± 1.83 kJ/m² at room temperature demonstrated significant inactivation of C. sakazakii in dry infant formula (P < 0.05). UV radiation combining 60 °C hot water treatment increased inactivation of C. sakazakii cells significantly (P < 0.05) in reconstituted infant formula. Significant effects of UV radiation on C. sakazakii inactivation kinetics (D value) were not observed in infant formula reconstituted in 55 and 65 °C water (P > 0.05). The inactivation mechanism was investigated using vibrational spectroscopy. Infrared spectroscopy detected significant stretching mode changes of macromolecules on the basis of spectral features, such as DNA, proteins, and lipids. Minor changes on cell membrane composition of C. sakazakii under UV radiation could be accurately and correctly monitored by infrared spectroscopy coupled with 2nd derivative transformation and principal component analysis. © 2011 Institute of Food Technologists®

Accuracy of Td-DFT in the Ultraviolet and Circular Dichroism Spectra of Deoxyguanosine and Uridine.

PubMed

Miyahara, Tomoo; Nakatsuji, Hiroshi

2018-01-11

Accuracy of the time-dependent density functional theory (Td-DFT) was examined for the ultraviolet (UV) and circular dichroism (CD) spectra of deoxyguanosine (dG) and uridine, using 11 different DFT functionals and two different basis sets. The Td-DFT results of the UV and CD spectra were strongly dependent on the functionals used. The basis-set dependence was observed only for the CD spectral calculations. For the UV spectra, the B3LYP and PBE0 functionals gave relatively good results. For the CD spectra, the B3LYP and PBE0 with 6-311G(d,p) basis gave relatively permissible result only for dG. The results of other functionals were difficult to be used for the studies of the UV and CD spectra, though the symmetry adapted cluster-configuration interaction (SAC-CI) method reproduced well the experimental spectra of these molecules. To obtain valuable information from the theoretical calculations of the UV and CD spectra, the theoretical tool must be able to reproduce correctly both of the intensities and peak positions of the UV and CD spectra. Then, we can analyze the reasons of the changes of the intensity and/or the peak position to clarify the chemistry involved. It is difficult to recommend Td-DFT as such tools of science, at least from the examinations using dG and uridine.

GAMA/H-ATLAS: the ultraviolet spectral slope and obscuration in galaxies

NASA Astrophysics Data System (ADS)

Wijesinghe, D. B.; da Cunha, E.; Hopkins, A. M.; Dunne, L.; Sharp, R.; Gunawardhana, M.; Brough, S.; Sadler, E. M.; Driver, S.; Baldry, I.; Bamford, S.; Liske, J.; Loveday, J.; Norberg, P.; Peacock, J.; Popescu, C. C.; Tuffs, R.; Andrae, E.; Auld, R.; Baes, M.; Bland-Hawthorn, J.; Buttiglione, S.; Cava, A.; Cameron, E.; Conselice, C. J.; Cooray, A.; Croom, S.; Dariush, A.; Dezotti, G.; Dye, S.; Eales, S.; Frenk, C.; Fritz, J.; Hill, D.; Hopwood, R.; Ibar, E.; Ivison, R.; Jarvis, M.; Jones, D. H.; van Kampen, E.; Kelvin, L.; Kuijken, K.; Maddox, S. J.; Madore, B.; Michałowski, M. J.; Nichol, B.; Parkinson, H.; Pascale, E.; Pimbblet, K. A.; Pohlen, M.; Prescott, M.; Rhodighiero, G.; Robotham, A. S. G.; Rigby, E. E.; Seibert, M.; Sergeant, S.; Smith, D. J. B.; Temi, P.; Sutherland, W.; Taylor, E.; Thomas, D.; van der Werf, P.

2011-08-01

We use multiwavelength data from the Galaxy And Mass Assembly (GAMA) and Herschel-ATLAS (H-ATLAS) surveys to compare the relationship between various dust obscuration measures in galaxies. We explore the connections between the ultraviolet (UV) spectral slope, β, the Balmer decrement and the far-infrared (FIR) to 150 nm far-ultraviolet (FUV) luminosity ratio. We explore trends with galaxy mass, star formation rate (SFR) and redshift in order to identify possible systematics in these various measures. We reiterate the finding of other authors that there is a large scatter between the Balmer decrement and the β parameter, and that β may be poorly constrained when derived from only two broad passbands in the UV. We also emphasize that FUV-derived SFRs, corrected for dust obscuration using β, will be overestimated unless a modified relation between β and the attenuation factor is used. Even in the optimum case, the resulting SFRs have a significant scatter, well over an order of magnitude. While there is a stronger correlation between the IR-to-FUV luminosity ratio and β parameter than with the Balmer decrement, neither of these correlations are particularly tight, and dust corrections based on β for high-redshift galaxy SFRs must be treated with caution. We conclude with a description of the extent to which the different obscuration measures are consistent with each other as well as the effects of including other galactic properties on these correlations.

Spectral downshifting in MBO3:Nd3+ (M=Y, La) phosphor

NASA Astrophysics Data System (ADS)

Omanwar, S. K.; Sawala, N. S.

2017-11-01

The spectral downshifting (DS) from ultra-violet (UV)/visible (VIS) light to near infra-red (NIR) radiation in Nd3+ doped YBO3 and LaBO3 phosphors is reported. The prepared materials were characterized by X-ray powder diffraction (XRD) and photoluminescence (PL) properties along with time-decay curves were studied which confirmed the spectral DS from VIS to NIR radiation. This can be employed to overcome the spectral mismatch of crystalline silicon (c-Si) solar cell with solar spectrum. The prepared Nd3+ doped as prepared phosphors provide NIR emission (1052 nm) at excitation of 586 nm where response of c-Si solar cell was optimum. Thus spectral modification by mentioned phosphor can be utilized to improve solar cells performance. Hence these phosphors have potential application for photovoltaic (PV) technology.

Inhibition by ultraviolet and photosynthetically available radiation lowers model estimates of depth-integrated picophytoplankton photosynthesis: global predictions for Prochlorococcus and Synechococcus.

PubMed

Neale, Patrick J; Thomas, Brian C

2017-01-01

Phytoplankton photosynthesis is often inhibited by ultraviolet (UV) and intense photosynthetically available radiation (PAR), but the effects on ocean productivity have received little consideration aside from polar areas subject to periodic enhanced UV-B due to depletion of stratospheric ozone. A more comprehensive assessment is important for understanding the contribution of phytoplankton production to the global carbon budget, present and future. Here, we consider responses in the temperate and tropical mid-ocean regions typically dominated by picophytoplankton including the prokaryotic lineages, Prochlorococcus and Synechococcus. Spectral models of photosynthetic response for each lineage were constructed using model strains cultured at different growth irradiances and temperatures. In the model, inhibition becomes more severe once exposure exceeds a threshold (E max ) related to repair capacity. Model parameters are presented for Prochlorococcus adding to those previously presented for Synechococcus. The models were applied to estimate midday, water column photosynthesis based on an atmospheric model of spectral radiation, satellite-derived spectral water transparency and temperature. Based on a global survey of inhibitory exposure severity, a full-latitude section of the mid-Pacific and near-equatorial region of the east Pacific were identified as representative regions for prediction of responses over the entire water column. Comparing predictions integrated over the water column including versus excluding inhibition, production was 7-28% lower due to inhibition depending on strain and site conditions. Inhibition was consistently greater for Prochlorococcus compared to two strains of Synechococcus. Considering only the surface mixed layer, production was inhibited 7-73%. On average, including inhibition lowered estimates of midday productivity around 20% for the modeled region of the Pacific with UV accounting for two-thirds of the reduction. In contrast, most other productivity models either ignore inhibition or only include PAR inhibition. Incorporation of E max model responses into an existing spectral model of depth-integrated, daily production will enable efficient global predictions of picophytoplankton productivity including inhibition. © 2016 John Wiley & Sons Ltd.

Emission characteristics of plasma based on xenon-rubidium bromide mixture

NASA Astrophysics Data System (ADS)

Heneral, A. A.; Avtaeva, S. V.

2017-10-01

Luminescence spectra of a longitudinal pulse-periodic discharge in xenon mixture with rubidium bromide vapors (Xe-RbBr) are studied experimentally at low pressures. The conditions leading to the appearance of intense bands of ultraviolet radiation of exciplex XeBr* molecules in the spectral interval between 200 and 400 nm are found. The highest yield of UV radiation of XeBr* molecules is achieved when the temperature of discharge-tube walls is equal to 750°C. A maximum power of UV radiation from the entire plasma volume as high as 4.8 W is obtained.

UV chromospheric and circumstellar diagnostic features among F supergiant stars

NASA Technical Reports Server (NTRS)

Stencel, R. E.; Worden, S. P.; Giampapa, M. S.

1981-01-01

A survey of F supergiant stars to evaluate the extension of chromospheric and circumstellar characteristics commonly observed in the slightly cooler G, K, and M supergiant is discussed. An ultraviolet survey was elected since UV features of Mg II and Fe II might persist in revealing outer atmosphere phenomena even among F supergiants. The encompassed spectral types F0 to G0, and luminosity classes Ib, Ia, and Ia-0. In addition, the usefulness of the emission line width-to-luminosity correlation for the G-M stars in both the Ca II and Mg II lines is examined.

UV SEDs of early-type cluster galaxies: a new look at the UV upturn

NASA Astrophysics Data System (ADS)

Ali, S. S.; Bremer, M. N.; Phillipps, S.; De Propris, R.

2018-05-01

Using GALEX, Ultraviolet Optical Telescope (UVOT), and optical photometry, we explore the prevalence and strength of the Ultraviolet (UV) upturn in the spectra of quiescent early-type galaxies in several nearby clusters. Even for galaxies with completely passive optical colours, there is a large spread in vacuum UV colour consistent with almost all having some UV upturn component. Combining GALEX and UVOT data below 3000 Å, we generate for the first time comparatively detailed UV spectral energy distributions for Coma cluster galaxies. Fitting the UV upturn component with a blackbody, 26 of these show a range of characteristic temperatures (10 000-21 000K) for the UV upturn population. Assuming a single temperature to explain GALEX-optical colours could underestimate the fraction of galaxies with UV upturns and mis-classify some as systems with residual star formation. The UV upturn phenomenon is not an exclusive feature found only in giant galaxies; we identify galaxies with similar (or even bluer) FUV - V colours to the giants with upturns over a range of fainter luminosities. The temperature and strength of the UV upturn are correlated with galaxy mass. Under the plausible hypothesis that the sources of the UV upturn are blue horizontal branch stars, the most likely mechanism for this is the presence of a substantial (between 4 per cent and 20 per cent) Helium-rich (Y > 0.3) population of stars in these galaxies, potentially formed at z ˜ 4 and certainly at z > 2; this plausibly sets a lower limit of {˜ } {0.3- 0.8} × 10^{10} M⊙ to the in situ stellar mass of ˜L* galaxies at this redshift.

Fusion of Ultraviolet-Visible and Infrared Transient Absorption Spectroscopy Data to Model Ultrafast Photoisomerization.

PubMed

Debus, Bruno; Orio, Maylis; Rehault, Julien; Burdzinski, Gotard; Ruckebusch, Cyril; Sliwa, Michel

2017-08-03

Ultrafast photoisomerization reactions generally start at a higher excited state with excess of internal vibrational energy and occur via conical intersections. This leads to ultrafast dynamics which are difficult to investigate with a single transient absorption spectroscopy technique, be it in the ultraviolet-visible (UV-vis) or infrared (IR) domain. On one hand, the information available in the UV-vis domain is limited as only slight spectral changes are observed for different isomers. On the other hand, the interpretation of vibrational spectra is strongly hindered by intramolecular relaxation and vibrational cooling. These limitations can be circumvented by fusing UV-vis and IR transient absorption spectroscopy data in a multiset multivariate curve resolution analysis. We apply this approach to describe the spectrodynamics of the ultrafast cis-trans photoisomerization around the C-N double bond observed for aromatic Schiff bases. Twisted intermediate states could be elucidated, and isomerization was shown to occur through a continuous complete rotation. More broadly, data fusion can be used to rationalize a vast range of ultrafast photoisomerization processes of interest in photochemistry.

In-Field Diffuse Ultraviolet Spectroscopy and Imaging of the Stardust Sample Return Capsule

NASA Technical Reports Server (NTRS)

Pugel, D. Elizabeth; Stackpoole, Mairead; McNamara, Karen; Schwartz, C.; Warren, J.; Kontinos, Dean

2008-01-01

In-field diffuse Ultraviolet (UV) spectroscopy and imaging systems were developed for the purposes of evaluating the surface chemical composition of spacecraft thermal control coatings and materials. The investigation of these systems and the compilation of an associated UV reflectance and luminescence database were conducted using the Stardust Sample Return Capsule (SRC), located at the Johnson Space Center. Spectral responses of the surfaces of the Stardust forebody and aftbody in both reflectance and fluorescence modes were examined post-flight. In this paper, we report on two primary findings of in-field diffuse UV spectroscopy and imaging: (1) deduction of the thermal history of thermal control coatings of the forebody and (2) bond line variations in the aftbody. In the forebody, the thermal history of thermal control coatings may be deduced from the presence of particular semiconducting defect states associated with ZnO, a common emissivity constituent in thermal control coatings. A spatial dependence of this history was mapped for these regions. In the aftbody, luminescing defect states, associated with Si and SiO2 color centers were found along regions of bond variability.

Multi-Satellite Attitude Prediction program/Orbiting Solar Observatory-8 (MSAP/OSO-8) operating guide

NASA Technical Reports Server (NTRS)

Tate, V. H.; Wyckoff, D. C.; Decicco, J. M.

1976-01-01

The sun's lower corona and chromosphere and their interaction in the X-ray and ultraviolet (UV) spectral regions were investigated to better understand the transport of energy from the photosphere to the corona. The interaction between the solar electromagnetic and particle radiation and the earth's environment was studied and the background component of cosmic X-rays was discussed.

An operational retrieval algorithm for determining aerosol optical properties in the ultraviolet

NASA Astrophysics Data System (ADS)

Taylor, Thomas E.; L'Ecuyer, Tristan S.; Slusser, James R.; Stephens, Graeme L.; Goering, Christian D.

2008-02-01

This paper describes a number of practical considerations concerning the optimization and operational implementation of an algorithm used to characterize the optical properties of aerosols across part of the ultraviolet (UV) spectrum. The algorithm estimates values of aerosol optical depth (AOD) and aerosol single scattering albedo (SSA) at seven wavelengths in the UV, as well as total column ozone (TOC) and wavelength-independent asymmetry factor (g) using direct and diffuse irradiances measured with a UV multifilter rotating shadowband radiometer (UV-MFRSR). A novel method for cloud screening the irradiance data set is introduced, as well as several improvements and optimizations to the retrieval scheme which yield a more realistic physical model for the inversion and increase the efficiency of the algorithm. Introduction of a wavelength-dependent retrieval error budget generated from rigorous forward model analysis as well as broadened covariances on the a priori values of AOD, SSA and g and tightened covariances of TOC allows sufficient retrieval sensitivity and resolution to obtain unique solutions of aerosol optical properties as demonstrated by synthetic retrievals. Analysis of a cloud screened data set (May 2003) from Panther Junction, Texas, demonstrates that the algorithm produces realistic values of the optical properties that compare favorably with pseudo-independent methods for AOD, TOC and calculated Ångstrom exponents. Retrieval errors of all parameters (except TOC) are shown to be negatively correlated to AOD, while the Shannon information content is positively correlated, indicating that retrieval skill improves with increasing atmospheric turbidity. When implemented operationally on more than thirty instruments in the Ultraviolet Monitoring and Research Program's (UVMRP) network, this retrieval algorithm will provide a comprehensive and internally consistent climatology of ground-based aerosol properties in the UV spectral range that can be used for both validation of satellite measurements as well as regional aerosol and ultraviolet transmission studies.

Evidence for sulphur implantation in Europa's UV absorption band

NASA Technical Reports Server (NTRS)

Lane, A. L.; Nelson, R. M.; Matson, D. L.

1981-01-01

The UV spectral characteristics of the Galilean satellites are investigated (using data from the International Ultraviolet Explorer (IUE) spacecraft) as a function of the orbital position, large-scale areal variability, and temporal dynamics. The discovery of an absorption feature at 280 nm in Europa's reflection spectrum is reported and observations show that the absorption is strongest on the trailing hemisphere (central longitude 270 degrees). The feature resembles SO2 and seems to result from S-O bond formation between deeply implanted sulphur atoms and the adjacent damaged water-ice-lattice. The sulphur supposedly comes from energetic (hundreds of keV) sulphur ions that are present in the Jovian magnetosphere. An appropriate equilibrium condition can be found to match the observed spectral data if sputtering erosion occurs at no greater than approximately 20 meters per one billion years.

Ultraviolet-B and photosynthetically active radiation interactively affect yield and pattern of monoterpenes in leaves of peppermint (Mentha x piperita L.).

PubMed

Behn, Helen; Albert, Andreas; Marx, Friedhelm; Noga, Georg; Ulbrich, Andreas

2010-06-23

Solar radiation is a key environmental signal in regulation of plant secondary metabolism. Since metabolic responses to light and ultraviolet (UV) radiation exposure are known to depend on the ratio of spectral ranges (e.g., UV-B/PAR), we examined effects of different UV-B radiation (280-315 nm) and photosynthetically active radiation (PAR, 400-700 nm) levels and ratios on yield and pattern of monoterpenoid essential oil of peppermint. Experiments were performed in exposure chambers, technically equipped for realistic simulation of natural climate and radiation. The experimental design comprised four irradiation regimes created by the combination of two PAR levels including or excluding UV-B radiation. During flowering, the highest essential oil yield was achieved at high PAR (1150 micromol m(-2) s(-1)) and approximate ambient UV-B radiation (0.6 W m(-2)). Regarding the monoterpene pattern, low PAR (550 micromol m(-2) s(-1)) and the absence of UV-B radiation led to reduced menthol and increased menthone contents and thereby to a substantial decrease in oil quality. Essential oil yield could not be correlated with density or diameter of peltate glandular trichomes, the epidermal structures specialized on biosynthesis, and the accumulation of monoterpenes. The present results lead to the conclusion that production of high quality oils (fulfilling the requirements of the Pharmacopoeia Europaea) requires high levels of natural sunlight. In protected cultivation, the use of UV-B transmitting covering materials is therefore highly recommended.

Ultraviolet vision in lacertid lizards: evidence from retinal structure, eye transmittance, SWS1 visual pigment genes and behaviour.

PubMed

Pérez i de Lanuza, Guillem; Font, Enrique

2014-08-15

Ultraviolet (UV) vision and UV colour patches have been reported in a wide range of taxa and are increasingly appreciated as an integral part of vertebrate visual perception and communication systems. Previous studies with Lacertidae, a lizard family with diverse and complex coloration, have revealed the existence of UV-reflecting patches that may function as social signals. However, confirmation of the signalling role of UV coloration requires demonstrating that the lizards are capable of vision in the UV waveband. Here we use a multidisciplinary approach to characterize the visual sensitivity of a diverse sample of lacertid species. Spectral transmission measurements of the ocular media show that wavelengths down to 300 nm are transmitted in all the species sampled. Four retinal oil droplet types can be identified in the lacertid retina. Two types are pigmented and two are colourless. Fluorescence microscopy reveals that a type of colourless droplet is UV-transmitting and may thus be associated with UV-sensitive cones. DNA sequencing shows that lacertids have a functional SWS1 opsin, very similar at 13 critical sites to that in the presumed ancestral vertebrate (which was UV sensitive) and other UV-sensitive lizards. Finally, males of Podarcis muralis are capable of discriminating between two views of the same stimulus that differ only in the presence/absence of UV radiance. Taken together, these results provide convergent evidence of UV vision in lacertids, very likely by means of an independent photopigment. Moreover, the presence of four oil droplet types suggests that lacertids have a four-cone colour vision system. © 2014. Published by The Company of Biologists Ltd.

The spectral energy distribution of Zeta Puppis and HD 50896

NASA Technical Reports Server (NTRS)

Holm, A. V.; Cassinelli, J. P.

1977-01-01

The ultraviolet spectral energy distribution of the O5f star Zeta Pup and the WN5 star HD 50896 are derived from OAO-2 observations with the calibration of Bless, Code, and Fairchild (1976). An estimate of the interstellar reddening (0.12 magnitude) of the Wolf-Rayet star is determined from the size of the characteristic interstellar extinction bump at 4.6 inverse microns. After correction for extinction, both stars show a flat energy distribution in the ultraviolet. The distribution of HD 50896 from 1100 A to 2 microns is in good agreement with results of extended model atmospheres, but some uncertainty remains because of the interstellar-extinction correction. The absolute energy distribution of Zeta Pup is fitted by a 42,000-K plane-parallel model if the model's flux is adjusted for the effects of electron scattering in the stellar wind and for UV line blanketing that was determined empirically from high-resolution Copernicus satellite observations. To achieve this fit, it is necessary to push both the spectroscopically determined temperature and the ultraviolet calibration to the limits of their probable errors.

Development of a safe ultraviolet camera system to enhance awareness by showing effects of UV radiation and UV protection of the skin (Conference Presentation)

NASA Astrophysics Data System (ADS)

Verdaasdonk, Rudolf M.; Wedzinga, Rosaline; van Montfrans, Bibi; Stok, Mirte; Klaessens, John; van der Veen, Albert

2016-03-01

The significant increase of skin cancer occurring in the western world is attributed to longer sun expose during leisure time. For prevention, people should become aware of the risks of UV light exposure by showing skin damage and the protective effect of sunscreen with an UV camera. An UV awareness imaging system optimized for 365 nm (UV-A) was develop using consumer components being interactive, safe and mobile. A Sony NEX5t camera was adapted to full spectral range. In addition, UV transparent lenses and filters were selected based on spectral characteristics measured (Schott S8612 and Hoya U-340 filters) to obtain the highest contrast for e.g. melanin spots and wrinkles on the skin. For uniform UV illumination, 2 facial tanner units were adapted with UV 365 nm black light fluorescent tubes. Safety of the UV illumination was determined relative to the sun and with absolute irradiance measurements at the working distance. A maximum exposure time over 15 minutes was calculate according the international safety standards. The UV camera was successfully demonstrated during the Dutch National Skin Cancer day and was well received by dermatologists and participating public. Especially, the 'black paint' effect putting sun screen on the face was dramatic and contributed to the awareness of regions on the face what are likely to be missed applying sunscreen. The UV imaging system shows to be promising for diagnostics and clinical studies in dermatology and potentially in other areas (dentistry and ophthalmology)

Long-term variability and impact on human health of biologically active UV radiation in Moscow

NASA Astrophysics Data System (ADS)

Zhdanova, Ekaterina; Chubarova, Natalia

2014-05-01

Measurements of erythemally weighted UV irradiance (Qer) have been performed at the Meteorological Observatory of Moscow State University since 1999 with the UVB-1 YES pyranometers. These types of devices are broadband with a spectral sensitivity curve close to the action spectrum of erythema. Main uncertainties of UVB-1 YES measurements include the difference in spectral curves of the instrument and the action spectrum of erythema, as well as the deviation from the cosine law. These uncertainties were taken into account in the database of Qer measurements (Chubarova, 2008. Additional corrections of UVB-1 measurements at low ambient temperatures have been made. We analyze interannual, seasonal and diurnal Qer changes over the time period 1999-2012. In addition, the comparisons with the results of UV reconstruction model (Chubarova, 2008) are made. This model allows us to evaluate relative changes in Qer due to variations in total ozone, effective cloud amount transmission, aerosol and cloud optical thickness since 1968. It is important to note that the main reason for UV irradiance monitoring development is the strong influence of UV irradiance on the biosphere and especially on human health mainly on human skin (CIE, 1993, CIE, 2006) and eyes (Oriowo, M. et al., 2001). Based on the detailed studies we have shown the possibility of utilizing UVB-1 pyranometers for measuring the eye-damage UV radiation. Parallel measurements by the Bentham DTM-300 spectrometer and the UVB-1 YES pyranometer at the Innsbruck Medical University (Austria) have provided us the calibration factor in eye-damage units for this broadband instrument. Influence of main geophysical factors on different types of UV irradiance is estimated by means the RAF ideology (Booth, Madronich, 1994). We discuss the responses of different types of biologically active UV radiation to the impact of various atmospheric factors. The UV conditions (deficiency, optimum, excess for human) are analyzed according to the developed classification for Moscow. Booth, C.R. and S. Madronich, 1994: Radiation amplification factors: improved formulation accounts for large increases in ultraviolet radiation associated with Antarctic ozone depletion. In: Ultraviolet Radiation in Antarctica: Measurements and Biological Research [Weiler, C.S. and P.A. Penhale (eds.)]. AGU Antarctic Research Series, 62, Washington, DC, USA, 39-42. Chubarova N.Y., 2008: UV variability in Moscow according to long-term UV measurements and reconstruction model. Atmos.Chem.Phys., 8, 3025-3031 Oriowo, M. et al., 2001:, Action spectrum for in vitro UV-induced cataract using whole lenses. Invest.Ophthalmol.&Vis.Sci, 42, 2596-2602. CIE, 1993: Reference Action Spectra for Ultraviolet Induced Erythema and Pigmentation of Different Human skin Types. CIE Research Note, CIE Technical Collection., N.3 CIE, 2006: Action spectrum for the production of previtamin D3 in human skin, Technical report 174, International commission on illumination

LED-based UV source for monitoring spectroradiometer properties

NASA Astrophysics Data System (ADS)

Sildoja, Meelis-Mait; Nevas, Saulius; Kouremeti, Natalia; Gröbner, Julian; Pape, Sven; Pendsa, Stefan; Sperfeld, Peter; Kemus, Fabian

2018-06-01

A compact and stable UV monitoring source based on state-of-the-art commercially available ultraviolet light emitting diodes (UV-LEDs) has been developed. It is designed to trace the radiometric stability—both responsivity and wavelength scale—of array spectroradiometers measuring direct solar irradiance in the wavelength range between 300 nm and 400 nm. The spectral irradiance stability of the UV-LED-based light source observed in the laboratory after seasoning (burning-in) the individual LEDs was better than 0.3% over a 12 h period of continuous operation. The integral irradiance measurements of the source over a period of several months, where the UV-LED source was not operated continuously between the measurements, showed stability within 0.3%. In-field measurements of the source with an array spectroradiometer indicated the stability of the source to be within the standard uncertainty of the spectroradiometer calibration, which was within 1% to 2%.

Solution and solid trinitrotoluene (TNT) photochemistry: persistence of TNT-like ultraviolet (UV) resonance Raman bands.

PubMed

Gares, Katie L; Bykov, Sergei V; Godugu, Bhaskar; Asher, Sanford A

2014-01-01

We examined the 229 nm deep-ultraviolet resonance Raman (DUVRR) spectra of solution and solid-state trinitrotoluene (TNT) and its solution and solid-state photochemistry. Although TNT photodegrades with a solution quantum yield of ϕ ∼ 0.015, the initial photoproducts show DUVRR spectra extraordinarily similar to pure TNT, due to the similar photoproduct enhancement of the -NO2 stretching vibrations. This results in TNT-like DUVRR spectra even after complete TNT photolysis. These ultraviolet resonance Raman spectral bands enable DUVRR of trace as well as DUVRR standoff TNT detection. We determined the structure of various initial TNT photoproducts by using liquid chromatography-mass spectrometry and tandem mass spectrometry. Similar TNT DUVRR spectra and photoproducts are observed in the solution and solid states.

GEMINI-TITAN (GT)-11 - MISC. EXPERIMENTS - MSC

NASA Image and Video Library

1966-03-22

S66-02611 (22 March 1966) --- Gemini-11 Experiment S-13 Ultraviolet Astronomical Camera. It will be used to test the techniques of ultraviolet photography under vacuum conditions and obtain ultraviolet radiation observations of stars in wave length region of 2,000 to 4,000 Angstroms by spectral means. Equipment is the Maurer 70mm camera with UV lens (f3.3) and magazine, objective grating and objective prism, extended shuttle actuator, and mounting bracket. For the experiment, the camera is mounted on the centerline torque box to point through the opened right-hand hatch. Propellant expenditure is estimated at 4.5 pounds per night pass. Two night passes will be used to photograph probably six star fields. Sponsors are NASA's Office of Space Science and Applications and Northwestern University. Photo credit: NASA

Design of p-type cladding layers for tunnel-injected UV-A light emitting diodes

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

Zhang, Yuewei; Krishnamoorthy, Sriram; Akyol, Fatih

Here, we discuss the engineering of p-AlGaN cladding layers for achieving efficient tunnel-injected III-Nitride ultraviolet light emitting diodes (UV LEDs) in the UV-A spectral range. We show that the capacitance-voltage measurements can be used to estimate the compensation and doping in the p-AlGaN layers located between the multi-quantum well region and the tunnel junction layer. By increasing the p-type doping concentration to overcome the background compensation, on-wafer external quantum efficiency and wall-plug efficiency of 3.37% and 1.62%, respectively, were achieved for the tunnel-injected UV LEDs emitting at 325 nm. We also show that interband tunneling hole injection can be usedmore » to realize UV LEDs without any acceptor doping. The work discussed here provides new understanding of hole doping and transport in AlGaN-based UV LEDs and demonstrates the excellent performance of tunnel-injected LEDs for the UV-A wavelength range.« less

Design of p-type cladding layers for tunnel-injected UV-A light emitting diodes

DOE PAGES

Zhang, Yuewei; Krishnamoorthy, Sriram; Akyol, Fatih; ...

2016-11-09

Here, we discuss the engineering of p-AlGaN cladding layers for achieving efficient tunnel-injected III-Nitride ultraviolet light emitting diodes (UV LEDs) in the UV-A spectral range. We show that the capacitance-voltage measurements can be used to estimate the compensation and doping in the p-AlGaN layers located between the multi-quantum well region and the tunnel junction layer. By increasing the p-type doping concentration to overcome the background compensation, on-wafer external quantum efficiency and wall-plug efficiency of 3.37% and 1.62%, respectively, were achieved for the tunnel-injected UV LEDs emitting at 325 nm. We also show that interband tunneling hole injection can be usedmore » to realize UV LEDs without any acceptor doping. The work discussed here provides new understanding of hole doping and transport in AlGaN-based UV LEDs and demonstrates the excellent performance of tunnel-injected LEDs for the UV-A wavelength range.« less

Stray light correction of array spectroradiometer measurement in ultraviolet

NASA Astrophysics Data System (ADS)

Wu, Zhifeng; Dai, Caihong; Wang, Yanfei; Li, Ling

2018-02-01

For most of the array spectroradiometer, stray light is significant in UV band. Stray light correction of a UV array spectroradiometer is investigated using optical filters. If a group of filters with continuous bandpass are chosen, stray light contribution due to all the bands can be obtained using a numerical algorithm. The array spectroradiometer with the stray light corrected is used to measure the spectral irradiance of several UV lamps. The measurement results are compared to a double monochromator spectroradiometer. When xenon lamp is the array spectroradiometer calibration lamp, after stray light correction, the difference can be improved from nearly 10% to 2.0% in UVC band. When tungsten lamp is the calibration lamp, the difference can be improved from around 90% to less than 20%.

Ocean Raman Scattering in Satellite Backscatter UV Measurements

NASA Technical Reports Server (NTRS)

Vasilkov, Alexander P.; Joiner, Joanna; Gleason, James; Bhartia, Pawan; Bhartia, P. K. (Technical Monitor)

2002-01-01

Ocean Raman scattering significantly contributes to the filling-in of solar Fraunhofer lines measured by satellite backscatter ultraviolet (buy) instruments in the cloudless atmosphere over clear ocean waters. A model accounting for this effect in buy measurements is developed and compared with observations from the Global Ozone Monitoring Experiment (GONE). The model extends existing models for ocean Raman scattering to the UV spectral range. Ocean Raman scattering radiance is propagated through the atmosphere using a concept of the Lambert equivalent reflectively and an accurate radiative transfer model for Rayleigh scattering. The model and observations can be used to evaluate laboratory measurements of pure water absorption in the UV. The good agreement between model and observations suggests that buy instruments may be useful for estimating chlorophyll content.

Comparisons of Spectral Aerosol Single Scattering Albedo in Seoul, South Korea

NASA Technical Reports Server (NTRS)

Mok, Jungbin; Krotkov, Nickolay A.; Torres, Omar; Jethva, Hiren; Loughman, Robert P.; Spinei, Elena; Campanelli, Monica; Li, Zhanqing; Go, Sujung; Labow, Gordon;

Solar UV exposure among outdoor workers in Denmark measured with personal UV-B dosimeters: technical and practical feasibility.

PubMed

Grandahl, Kasper; Mortensen, Ole Steen; Sherman, David Zim; Køster, Brian; Lund, Paul-Anker; Ibler, Kristina Sophie; Eriksen, Paul

2017-10-10

Exposure to solar ultraviolet radiation is a well-known cause of skin cancer. This is problematic for outdoor workers. In Denmark alone, occupational skin cancer poses a significant health and safety risk for around 400,000 outdoor workers. Objective measures of solar ultraviolet radiation exposure are needed to help resolve this problem. This can be done using personal ultraviolet radiation dosimeters. We consider technical and practical feasibility of measuring individual solar ultraviolet exposure at work and leisure in professions with different á priori temporal high-level outdoor worktime, using aluminium gallium nitride (AlGaN) photodiode detector based personal UV-B dosimeters. Essential technical specifications including the spectral and angular responsivity of the dosimeters are described and pre-campaign dosimeter calibration applicability is verified. The scale and conduct of dosimeter deployment and campaign in-field measurements including failures and shortcomings affecting overall data collection are presented. Nationwide measurements for more than three hundred and fifty workers from several different professions were collected in the summer of 2016. On average, each worker's exposure was measured for a 2-week period, which included both work and leisure. Data samples of exposure at work during a Midsummer day show differences across professions. A construction worker received high-level occupational UV exposure most of the working day, except during lunch hour, accumulating to 5.1 SED. A postal service worker was exposed intermittently around noon and in the afternoon, preceded by no exposure forenoon when packing mail, accumulating to 1.6 SED. A crane fitter was exposed only during lunch hour, accumulating to 0.7 SED. These findings are in line with our specialist knowledge as occupational physicians. Large-scale use of personal UV-B dosimeters for measurement of solar ultraviolet radiation exposure at work and leisure in Denmark is indeed feasible from a technical and practical viewpoint. Samples of exposure data shown support the presumption that the Danish campaign UV-B dosimeter measurement dataset can be used to sum and compare exposure between groups of professions with reliable results to be used in future analysis with clinical as well as epidemiological/questionnaire data. This was despite some dosimeter failures and shortcomings.

LRO Lyman Alpha Mapping Project (LAMP) Far-UV Investigations of Lunar Composition, Porosity, and Space Weathering

NASA Astrophysics Data System (ADS)

Retherford, K. D.; Greathouse, T. K.; Mandt, K. E.; Gladstone, R.; Hendrix, A.; Cahill, J. T.; Liu, Y.; Grava, C.; Hurley, D.; Egan, A.; Kaufmann, D. E.; Raut, U.; Byron, B. D.; Magana, L. O.; Stickle, A. M.; Wyrick, D. Y.; Pryor, W. R.

2017-12-01

Far ultraviolet reflectance measurements of the Moon, icy satellites, comets, and asteroids have proven surprisingly useful for advancing our understanding of planetary surfaces. This new appreciation for planetary far-UV imaging spectroscopy is provided in large part thanks to nearly a decade of investigations with the Lunar Reconnaissance Orbiter (LRO) Lyman Alpha Mapping Project (LAMP). LAMP has demonstrated an innovative nightside observing technique, putting a new light on permanently shadowed regions (PSRs) and other features on the Moon. Dayside far-UV albedo maps complement the nightside data, enabling comparisons of direct and hemispheric (diffuse) illumination derived albedos. We'll discuss the strengths of the far-UV reflectance imaging spectroscopy technique with respect to several new LAMP results. Detections of water frost and hydration signatures near 165 nm, for example, provide constraints on composition that complement infrared spectroscopy, visible imaging, neutron spectroscopy, radar, and other techniques. LRO's polar orbit and high data downlink capabilities enable searches for diurnal variations in spectral signals. At far-UV wavelengths a relatively blue spectral slope is diagnostic of space weathering, which is opposite of the spectral reddening indicator of maturity at wavelengths longward of 180 nm. By utilizing natural diffuse illumination sources on the nightside the far-UV technique is able to identify relative increases in porosity within the PSRs, and provides an additional tool for determining relative surface ages. On October 6, 2016 LAMP enacted a new, more sensitive dayside operating mode that expands its ability to search for diurnally varying hydration signals associated with different regions and features.

Multiple UV reflectance peaks in the iridescent neck feathers of pigeons

NASA Astrophysics Data System (ADS)

McGraw, Kevin J.

Recent studies of colorful plumage signals in birds have been aided by the finding that birds can see ultraviolet (UV) light and thus may communicate using colors invisible to humans. Some of the pioneering and more pivotal work on avian color vision was performed with domestic pigeons (Columba livia), yet surprisingly there have been few detailed reports of the UV-reflecting properties of pigeon feathers. Here, I use UV-VIS fiber-optic spectrometry to document the full-spectrum reflectance characteristics of iridescent purple and green neck plumage in pigeons. Neck feathers that appear purple to the human eye exhibit four reflectance peaks-two in the UV and one in the blue and red regions-and thus exhibit a UV-purple hue. Neck feathers that appear green to the human eye are characterized by five spectral peaks: two in the UV (UVA and UVB), a predominant green peak, and secondary violet and red peaks, conferring a UV-purple-green color. Such elaborate UV coloration suggests that birds may use an even more complex and `hidden' UV signaling system than previously thought.

Adverse Effects of UV-B Radiation on Plants Growing at Schirmacher Oasis, East Antarctica.

PubMed

Singh, Jaswant; Singh, Rudra P

2014-01-01

This study aimed to assess the impacts of ultraviolet-B (UV-B) radiation over a 28-day period on the levels of pigments of Umbilicaria aprina and Bryum argenteum growing in field. The depletion of stratospheric ozone is most prominent over Antarctica, which receives more UV-B radiation than most other parts of the planet. Although UV-B radiation adversely affects all flora, Antarctic plants are better equipped to survive the damaging effects of UV-B owing to defenses provided by UV-B absorbing compounds and other screening pigments. The UV-B radiations and daily average ozone values were measured by sun photometer and the photosynthetic pigments were analyzed by the standard spectrophotometric methods of exposed and unexposed selected plants. The daily average atmospheric ozone values were recorded from 5 January to 2 February 2008. The maximum daily average for ozone (310.7 Dobson Units (DU)) was recorded on 10 January 2008. On that day, average UV-B spectral irradiances were 0.016, 0.071, and 0.186 W m(-2) at wavelengths of 305, 312, and 320 nm, respectively. The minimum daily average ozone value (278.6 DU) was recorded on 31 January 2008. On that day, average UV-B spectral irradiances were 0.018, 0.085, and 0.210 W m(-2) at wavelengths of 305, 312, and 320 nm, respectively. Our results concludes that following prolonged UV-B exposure, total chlorophyll levels decreased gradually in both species, whereas levels of UV-B absorbing compounds, phenolics, and carotenoids gradually increased.

Adverse Effects of UV-B Radiation on Plants Growing at Schirmacher Oasis, East Antarctica

PubMed Central

Singh, Jaswant; Singh, Rudra P.

2014-01-01

This study aimed to assess the impacts of ultraviolet-B (UV-B) radiation over a 28-day period on the levels of pigments of Umbilicaria aprina and Bryum argenteum growing in field. The depletion of stratospheric ozone is most prominent over Antarctica, which receives more UV-B radiation than most other parts of the planet. Although UV-B radiation adversely affects all flora, Antarctic plants are better equipped to survive the damaging effects of UV-B owing to defenses provided by UV-B absorbing compounds and other screening pigments. The UV-B radiations and daily average ozone values were measured by sun photometer and the photosynthetic pigments were analyzed by the standard spectrophotometric methods of exposed and unexposed selected plants. The daily average atmospheric ozone values were recorded from 5 January to 2 February 2008. The maximum daily average for ozone (310.7 Dobson Units (DU)) was recorded on 10 January 2008. On that day, average UV-B spectral irradiances were 0.016, 0.071, and 0.186 W m-2 at wavelengths of 305, 312, and 320 nm, respectively. The minimum daily average ozone value (278.6 DU) was recorded on 31 January 2008. On that day, average UV-B spectral irradiances were 0.018, 0.085, and 0.210 W m-2 at wavelengths of 305, 312, and 320 nm, respectively. Our results concludes that following prolonged UV-B exposure, total chlorophyll levels decreased gradually in both species, whereas levels of UV-B absorbing compounds, phenolics, and carotenoids gradually increased. PMID:24748743

Spectral dependence on the correction factor of erythemal UV for cloud, aerosol, total ozone, and surface properties: A modeling study

NASA Astrophysics Data System (ADS)

Park, Sang Seo; Jung, Yeonjin; Lee, Yun Gon

2016-07-01

Radiative transfer model simulations were used to investigate the erythemal ultraviolet (EUV) correction factors by separating the UV-A and UV-B spectral ranges. The correction factor was defined as the ratio of EUV caused by changing the amounts and characteristics of the extinction and scattering materials. The EUV correction factors (CFEUV) for UV-A [CFEUV(A)] and UV-B [CFEUV(B)] were affected by changes in the total ozone, optical depths of aerosol and cloud, and the solar zenith angle. The differences between CFEUV(A) and CFEUV(B) were also estimated as a function of solar zenith angle, the optical depths of aerosol and cloud, and total ozone. The differences between CFEUV(A) and CFEUV(B) ranged from -5.0% to 25.0% for aerosols, and from -9.5% to 2.0% for clouds in all simulations for different solar zenith angles and optical depths of aerosol and cloud. The rate of decline of CFEUV per unit optical depth between UV-A and UV-B differed by up to 20% for the same aerosol and cloud conditions. For total ozone, the variation in CFEUV(A) was negligible compared with that in CFEUV(B) because of the effective spectral range of the ozone absorption band. In addition, the sensitivity of the CFEUVs due to changes in surface conditions (i.e., surface albedo and surface altitude) was also estimated by using the model in this study. For changes in surface albedo, the sensitivity of the CFEUVs was 2.9%-4.1% per 0.1 albedo change, depending on the amount of aerosols or clouds. For changes in surface altitude, the sensitivity of CFEUV(B) was twice that of CFEUV(A), because the Rayleigh optical depth increased significantly at shorter wavelengths.

Spectral transmittance of intraocular lenses under natural and artificial illumination: criteria analysis for choosing a suitable filter.

PubMed

Artigas, Jose M; Felipe, Adelina; Navea, Amparo; Artigas, Cristina; García-Domene, Maria C

2011-01-01

To compare the spectral transmission of different intraocular lenses (IOLs) with either ultraviolet (UV) or blue-light filters, and to analyze the performance of these filters with artificial light sources as well as sunlight. Experimental study. The spectral transmission curve of 10 IOLs was measured using a PerkinElmer Lambda 800 UV/VIS spectrometer (Waltham, MA). Different filtering simulations were performed using the D65 standard illuminant as daylight and standard incandescent lamp and fluorescent bulb illuminants. Spectral transmittance of the IOLs. All the IOLs studied provide good UVC (200-280 nm) and UVB (280-315 nm) protection, except for one that presented an appreciable window at 270 nm. Nevertheless, both natural and artificial sources have practically no emission under 300 nm. In the UVA (315-380 nm) range the curves of the different IOLs manifested different degrees of absorption. Not all the UV filters incorporated in different IOLs protect equally. The filters that provide greater photoprotection against UV radiation, even blue light, are yellow and orange. Then, yellow and orange IOL filters may be best suited for cases requiring special retinal protection. The filters that favor better photoreception of visible light (380-780 nm) are those that transmit this radiation close to 100%. Artificial illumination practically does not emit in the UV range, but its levels of illumination are very low when compared with solar light. A possible balance between photoprotection and photoreception could be a sharp cutoff filter with the cutoff wavelength near 400 nm and a maximum transmittance around 100%. Copyright © 2011 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

GOME-2A retrievals of tropospheric NO2 in different spectral ranges - influence of penetration depth

NASA Astrophysics Data System (ADS)

Behrens, Lisa K.; Hilboll, Andreas; Richter, Andreas; Peters, Enno; Eskes, Henk; Burrows, John P.

2018-05-01

In this study, we present a novel nitrogen dioxide (NO2) differential optical absorption spectroscopy (DOAS) retrieval in the ultraviolet (UV) spectral range for observations from the Global Ozone Monitoring Instrument 2 on board EUMETSAT's MetOp-A (GOME-2A) satellite. We compare the results to those from an established NO2 retrieval in the visible (vis) spectral range from the same instrument and investigate how differences between the two are linked to the NO2 vertical profile shape in the troposphere. As expected, radiative transfer calculations for satellite geometries show that the sensitivity close to the ground is higher in the vis than in the UV spectral range. Consequently, NO2 slant column densities (SCDs) in the vis are usually higher than in the UV if the NO2 is close to the surface. Therefore, these differences in NO2 SCDs between the two spectral ranges contain information on the vertical distribution of NO2 in the troposphere. We combine these results with radiative transfer calculations and simulated NO2 fields from the TM5-MP chemistry transport model to evaluate the simulated NO2 vertical distribution. We investigate regions representative of both anthropogenic and biomass burning NO2 pollution. Anthropogenic air pollution is mostly located in the boundary layer close to the surface, which is reflected by large differences between UV and vis SCDs of ˜ 60 %. Biomass burning NO2 in contrast is often uplifted into elevated layers above the boundary layer. This is best seen in tropical Africa south of the Equator, where the biomass burning NO2 is well observed in the UV, and the SCD difference between the two spectral ranges is only ˜ 36 %. In tropical Africa north of the Equator, however, the biomass burning NO2 is located closer to the ground, reducing its visibility in the UV. While not enabling a full retrieval of the vertical NO2 profile shape in the troposphere, our results can help to constrain the vertical profile of NO2 in the lower troposphere and, when analysed together with simulated NO2 fields, can help to better interpret the model output.

Photosynthetic carbon reduction by seagrasses exposed to ultraviolet A radiation

NASA Technical Reports Server (NTRS)

1979-01-01

The seagrasses Halophila engelmannii, Halodule wrightii, and Syringodium filiforme were examined for their intrinsic sensitivity to ultraviolet-A-UV-A and ultraviolet-B-UV-B radiation. The effect of UV-A on photosynthetically active radiation (PAR) was also determined. Ultraviolet-A and ultraviolet-B were studied with emphasis on the greater respective environmental consequence in terms of seagrass distribution and abundance. Results indicate that an intrinsic sensitivity to UV-A alone is apparent only in Halophila, while net photosynthesis in Halodule and Syringodium seems unaffected by the level of UV-A provided. The sensitivity of Halophila to UV-A in the absense of (PAR) indicates that the photosynthetic reaction does not need to be in operation for damage to occur. Other significant results are reported.

Uranium plasma emission coefficient in the visible and near UV.

NASA Technical Reports Server (NTRS)

Mack, J. M., Jr.; Usher, J. L.; Schneider, R. T.; Campbell, H. D.

1971-01-01

Measurements of the specific emission coefficient in the near ultra-violet and visible region of a uranium arc plasma are reported. Spatial unfolding of the intensity profile is used to determine the emission coefficient in the spectral range of 2000 A to 6000 A. The uranium partial pressure is estimated to range between .001 and .01 atmosphere, and the corresponding temperature range is 5000 - 10,000 K.

Flower Colours through the Lens: Quantitative Measurement with Visible and Ultraviolet Digital Photography

PubMed Central

Garcia, Jair E.; Greentree, Andrew D.; Shrestha, Mani; Dorin, Alan; Dyer, Adrian G.

2014-01-01

Background The study of the signal-receiver relationship between flowering plants and pollinators requires a capacity to accurately map both the spectral and spatial components of a signal in relation to the perceptual abilities of potential pollinators. Spectrophotometers can typically recover high resolution spectral data, but the spatial component is difficult to record simultaneously. A technique allowing for an accurate measurement of the spatial component in addition to the spectral factor of the signal is highly desirable. Methodology/Principal findings Consumer-level digital cameras potentially provide access to both colour and spatial information, but they are constrained by their non-linear response. We present a robust methodology for recovering linear values from two different camera models: one sensitive to ultraviolet (UV) radiation and another to visible wavelengths. We test responses by imaging eight different plant species varying in shape, size and in the amount of energy reflected across the UV and visible regions of the spectrum, and compare the recovery of spectral data to spectrophotometer measurements. There is often a good agreement of spectral data, although when the pattern on a flower surface is complex a spectrophotometer may underestimate the variability of the signal as would be viewed by an animal visual system. Conclusion Digital imaging presents a significant new opportunity to reliably map flower colours to understand the complexity of these signals as perceived by potential pollinators. Compared to spectrophotometer measurements, digital images can better represent the spatio-chromatic signal variability that would likely be perceived by the visual system of an animal, and should expand the possibilities for data collection in complex, natural conditions. However, and in spite of its advantages, the accuracy of the spectral information recovered from camera responses is subject to variations in the uncertainty levels, with larger uncertainties associated with low radiance levels. PMID:24827828

UV-B radiation amplification factor determined based on the simultaneous observation of total ozone and global spectral irradiance

NASA Technical Reports Server (NTRS)

Ito, T.; Sakoda, Y.; Matsubara, K.; Kajihara, R.; Uekubo, T.; Kobayashi, M.; Shitamichi, M.; Ueno, T.; Ito, M.

1994-01-01

The Japan Meteorological Agency started the spectral observation of solar ultraviolet (UV) irradiance on 1 January 1990 at Tateno, Aerological Observatory in Tsukuba (35 deg N, 140 deg E). The observation has been carried out using the Brewer spectrophotometer for the wavelengths from 290 to 325 nm with a 0.5 nm interval every hour from 30 minutes before sunrise to 30 minutes after sunset throughout a year. Because of remarkable similarity within observed spectra, an observed spectrum can be expressed by a simple combination of a reference spectrum and two parameters expressing the deformation of the observed spectrum from the reference. By use of the relation between one of the deformation parameters and the total ozone simultaneously observed with the Dobson spectrophotometer, the possible increase of UV irradiance due to ozone depletion is estimated. For damaging UV, the irradiance possibly increases about 19 percent with the ozone depletion of 10 percent at noon throughout the year in the northern midlatitudes. DUV at noon on the summer solstice possibly increases about 5.6 percent with the ozone depletion of 10 m atm-cm for all latitudes in the Northern Hemisphere.

Assessment of 10 Year Record of Aerosol Optical Depth from OMI UV Observations

NASA Technical Reports Server (NTRS)

Ahn, Changwoo; Torres, Omar; Jethva, Hiren

2014-01-01

The Ozone Monitoring Instrument (OMI) onboard the EOS-Aura satellite provides information on aerosol optical properties by making use of the large sensitivity to aerosol absorption in the near-ultraviolet (UV) spectral region. Another important advantage of using near UV observations for aerosol characterization is the low surface albedo of all terrestrial surfaces in this spectral region that reduces retrieval errors associated with land surface reflectance characterization. In spite of the 13 × 24 square kilometers coarse sensor footprint, the OMI near UV aerosol algorithm (OMAERUV) retrieves aerosol optical depth (AOD) and single-scattering albedo under cloud-free conditions from radiance measurements at 354 and 388 nanometers. We present validation results of OMI AOD against space and time collocated Aerosol Robotic Network measured AOD values over multiple stations representing major aerosol episodes and regimes. OMAERUV's performance is also evaluated with respect to those of the Aqua-MODIS Deep Blue and Terra-MISR AOD algorithms over arid and semi-arid regions in Northern Africa. The outcome of the evaluation analysis indicates that in spite of the "row anomaly" problem, affecting the sensor since mid-2007, the long-term aerosol record shows remarkable sensor stability.

Extending Supernova Spectral Templates for Next Generation Space Telescope Observations

NASA Astrophysics Data System (ADS)

Roberts-Pierel, Justin; Rodney, Steven A.; Steven Rodney

2018-01-01

Widely used empirical supernova (SN) Spectral Energy Distributions (SEDs) have not historically extended meaningfully into the ultraviolet (UV), or the infrared (IR). However, both are critical for current and future aspects of SN research including UV spectra as probes of poorly understood SN Ia physical properties, and expanding our view of the universe with high-redshift James Webb Space Telescope (JWST) IR observations. We therefore present a comprehensive set of SN SED templates that have been extended into the UV and IR, as well as an open-source software package written in Python that enables a user to generate their own extrapolated SEDs. We have taken a sampling of core-collapse (CC) and Type Ia SNe to get a time-dependent distribution of UV and IR colors (U-B,r’-[JHK]), and then generated color curves are used to extrapolate SEDs into the UV and IR. The SED extrapolation process is now easily duplicated using a user’s own data and parameters via our open-source Python package: SNSEDextend. This work develops the tools necessary to explore the JWST’s ability to discriminate between CC and Type Ia SNe, as well as provides a repository of SN SEDs that will be invaluable to future JWST and WFIRST SN studies.

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

Waszczak, Adam; Kulkarni, Shrinivas R.; Ofek, Eran O., E-mail: waszczak@caltech.edu

We present ultraviolet (UV) photometry (near-UV (NUV) band, 180–280 nm) of 405 asteroids observed serendipitously by GALEX from 2003 to 2012. All asteroids in this sample were detected by GALEX at least twice. Unambiguous visible-color-based taxonomic labels (C type versus S type) exist for 315 of these asteroids; of these, thermal-infrared-based diameters are available for 245. We derive NUV − V color using two independent models to predict the visual magnitude V at each NUV-detection epoch. Both V models produce NUV − V distributions in which the S types are redder than C types with more than 8σ confidence. Thismore » confirms that the S types’ redder spectral slopes in the visible remain redder than the C types’ into the NUV, this redness being consistent with absorption by silica-containing rocks. The GALEX asteroid data confirm earlier results from the International Ultraviolet Explorer, which two decades ago produced the only other sizeable set of UV asteroid photometry. The GALEX-derived NUV − V data also agree with previously published Hubble Space Telescope (HST) UV observations of asteroids 21 Lutetia and 1 Ceres. Both the HST and GALEX data indicate that NUV band is less useful than u band for distinguishing subgroups within the greater population of visible-color-defined C types (notably, M types and G types)« less

Evidence for Type Ia Supernova Diversity from Ultraviolet Observations with the Hubble Space Telescope

NASA Technical Reports Server (NTRS)

Wang, Xiaofeng; Wang, Lifan; Filippenko, Alexei; Baron, Eddie; Kromer, Markus; Jack, Dennis; Zhang, Tianmeng; Aldering, Greg; Antilogus, Pierre; Arnett, W. David;

Photochromic properties of the N-Salicylideneaniline in Polyvinyl Butyral matrix: Experimental and theoretical investigations

NASA Astrophysics Data System (ADS)

Shahab, Siyamak; Filippovich, Liudmila; Aharodnikova, M.; Almodarresiyeh, Hora A.; Hajikolaee, Fatemeh Haji; Kumar, Rakesh; Mashayekhi, Mahsa

2017-04-01

In the present work, isomerization, photophysical properties, thermal conductivity (λ) and spectral study of the N-Salicylideneaniline: 2-[(E)-(phenylimino)methyl]phenol (SA) under the action of UV radiation in the Polyvinyl Butyral (PVB) matrix were studied using the Indicator method and Density Functional Theory (DFT). The electronic absorption spectra of SA and its isomers (SA1 and SA2) in dimethylformamide (DMF) solutions were also calculated. The nature of absorption bands of SA, SA1 and SA2 in the visible and near ultraviolet spectral regions was interpreted. The excitation energies, electronic transitions and oscillator strengths for SA, SA1 and SA2 have also been calculated. Thermal Conductivity of PVB-films containing SA before and after UV radiation was also measured. A Photochromic PVB - film on the basis of SA for application in optical devices and display technologies was made.

High performance small molecule photodetector with broad spectral response range from 200 to 900 nm

NASA Astrophysics Data System (ADS)

Wu, Shuang-hong; Li, Wen-lian; Chu, Bei; Su, Zi-sheng; Zhang, Feng; Lee, C. S.

2011-07-01

We demonstrate a photodetector (PD) with broad spectral response by taking the advantages of more flexible device design in using small molecule materials. The optimized device shows an external quantum efficiency of over 20% from 200 to 900 nm. The high performance is achieved by jointing two donor (D)/acceptor (A) hetero-junctions [m-MTDATA(D)/TiOPc(A) and TiOPc(D)/F16CuPc: PTCDI-C8(A)] such that photoresponses over the deep-ultraviolet (UV) and visible-near infrared regions can be independently optimized. By choosing D- and A-materials with matched energy level alignment, high carrier mobility, and balanced carrier transporting properties, the present PD shows a fast response of 56 ns. The high speed and deep-UV sensitivity might lead to potential military applications such as missile tracking in addition to optical communications, chemical/biological sensing etc.

Activation and evaluation of GaN photocathodes

NASA Astrophysics Data System (ADS)

Qian, Yunsheng; Chang, Benkang; Qiao, Jiangliang; Zhang, Yijun; Fu, Rongguo; Qiu, Yafeng

2009-09-01

Gallium Nitride (GaN) photocathodes are potentially attractive as UV detective materials and electron sources. Based on the activation and evaluation system for GaAs photocathode, which consists of ultra-high vacuum (UHV) activation chamber, multi-information measurement system, X-ray photoelectron spectroscopy (XPS), and ultraviolet ray photoelectron spectroscopy (UPS), the control and measurement system for the activation of UV photocathodes was developed. The developed system, which consists of Xenon lamp, monochromator with scanner, signal-processing module, power control unit of Cs and O source, A/D adapter, digital I/O card, computer and software, can control the activation of GaN photocathodes and measure on-line the spectral response curves of GaN photocathodes. GaN materials on sapphire substrate were grown by Metal-Organic Chemical Vapor Deposition (MOCVD) with p-type Mg doping. The GaN materials were activated by Cs-O. The spectral response and quantum efficiency (QE) were measured and calculated. The experiment results are discussed.

Optical-fiber-based laser-induced breakdown spectroscopy for detection of early caries

NASA Astrophysics Data System (ADS)

Sasazawa, Shuhei; Kakino, Satoko; Matsuura, Yuji

2015-06-01

A laser-induced breakdown spectroscopy (LIBS) system targeting for the in vivo analysis of tooth enamel is described. The system is planned to enable real-time analysis of teeth during laser dental treatment by utilizing a hollow optical fiber that transmits both Q-switched Nd:YAG laser light for LIBS and infrared Er:YAG laser light for tooth ablation. The sensitivity of caries detection was substantially improved by expanding the spectral region under analysis to ultraviolet (UV) light and by focusing on emission peaks of Zn in the UV region. Subsequently, early caries were distinguished from healthy teeth with accuracy rates above 80% in vitro.

Experimental determination of the reference plane of shaped diffusers by solar ultraviolet measurements.

PubMed

Gröbner, Julian; Blumthaler, Mario

2007-01-01

The optical reference plane of a J1002 shaped dome diffuser from CMS-Schreder was determined using direct normal spectral solar UV irradiance measurements relative to a flat Teflon diffuser. The spectroradiometers were calibrated relative to the same irradiance standard. The optical reference plane of the shaped J1002 diffuser is 5.3 mm behind the top of the dome with an uncertainty of 1.0 mm. Solar UV irradiance measurements based on a lamp calibration using the top of the dome as the reference will overestimate the global solar irradiance by 2.1% for the usual calibration distance of 500 mm.

Influence of the absorption behavior of sunscreens in the short-wavelength UV range (UVB) and the long-wavelength UV range (UVA) on the relation of the UVB absorption to sun protection factor

NASA Astrophysics Data System (ADS)

Weigmann, Hans-Juergen; Schanzer, Sabine; Antoniou, Christina; Sterry, Wolfram; Lademann, Juergen

2010-09-01

The absorption of filter substances in sunscreens, reducing the incident ultraviolet (UV) radiation, is the basis for the protecting ability of such formulations. The erythema-correlated sun protection factor (SPF), depending mainly on the intensity of the UVB radiation, is the common value to quantify the efficacy of the formulations avoiding sunburn. An ex vivo method combining tape stripping and optical spectroscopy is applied to measure the absorption of sunscreens in the entire UV spectral range. The obtained relations between the short-wavelength UV (UVB) absorption and the SPF confirm a clear influence of the long-wavelength UV (UVA) absorption on the SPF values. The data reflect the historical development of the relation of the concentration of UVB and UVA filters in sunscreens and points to the influence of additional ingredients, e.g., antioxidants and cell-protecting agents on the efficacy of the products.

Estimated ultraviolet radiation doses in wetlands in six national parks

USGS Publications Warehouse

Diamond, S.A.; Trenham, P.C.; Adams, Michael J.; Hossack, B.R.; Knapp, R.A.; Stark, L.; Bradford, D.; Corn, P.S.; Czarnowski, K.; Brooks, P.D.; Fagre, D.B.; Breen, B.; Dentenbeck, N.E.; Tonnessen, K.

2005-01-01

Ultraviolet-B radiation (UV-B, 280–320-nm wavelengths) doses were estimated for 1024 wetlands in six national parks: Acadia (Acadia), Glacier (Glacier), Great Smoky Mountains (Smoky), Olympic (Olympic), Rocky Mountain (Rocky), and Sequoia/Kings Canyon (Sequoia). Estimates were made using ground-based UV-B data (Brewer spectrophotometers), solar radiation models, GIS tools, field characterization of vegetative features, and quantification of DOC concentration and spectral absorbance. UV-B dose estimates were made for the summer solstice, at a depth of 1 cm in each wetland. The mean dose across all wetlands and parks was 19.3 W-h m−2 (range of 3.4–32.1 W-h m−2). The mean dose was lowest in Acadia (13.7 W-h m−2) and highest in Rocky (24.4 W-h m−2). Doses were significantly different among all parks. These wetland doses correspond to UV-B flux of 125.0 μW cm−2 (range 21.4–194.7 μW cm−2) based on a day length, averaged among all parks, of 15.5 h. Dissolved organic carbon (DOC), a key determinant of water-column UV-B flux, ranged from 0.6 (analytical detection limit) to 36.7 mg C L−1 over all wetlands and parks, and reduced potential maximal UV-B doses at 1-cm depth by 1%–87 %. DOC concentration, as well as its effect on dose, was lowest in Sequoia and highest in Acadia (DOC was equivalent in Acadia, Glacier, and Rocky). Landscape reduction of potential maximal UV-B doses ranged from zero to 77% and was lowest in Sequoia. These regional differences in UV-B wetland dose illustrate the importance of considering all aspects of exposure in evaluating the potential impact of UV-B on aquatic organisms.

LADEE UVS (UltraViolet Visible Spectrometer) and the Search for Lunar Exospheric Dust: A Detailed Spectral Analysis

NASA Technical Reports Server (NTRS)

Wooden, Diane H.; Cook, Amanda; Colaprete, Anthony; Shirley, Mark; Vargo, Kara; Elphic, Richard C.; Hermalyn, Brendan; Stubbs, Timothy John; Glenar, David A.

2014-01-01

The Lunar Atmosphere and Dust Environment Explorer (LADEE) executed science observations in lunar orbit spanning 2013-Oct-16- 2014-04-18 UT. LADEE's Ultraviolet/Visible Spectrometer (UVS) studies the composition and temporal variations of the tenuous lunar exosphere and dust environment, utilizing two sets of optics: a limb-viewing telescope, and a solar-viewer. The limb-viewing telescope observes illuminated dust and emitting gas species while the Sun is just behind the lunar limb. The solar viewer, with its diffuser, allows UVS to also stare directly at the solar disk as it approaches the limb, sampling progressively lower exosphere altitudes. Solar viewer "Occultation" activities occur at the lunar sunrise limb, as the LADEE spacecraft passes into the lunar night side, facing the Sun (the spacecraft orbit is near-equatorial retrograde). A loss of transmission of sunlight occurs by the occultation of dust grains along the line-of-sight. So-called "Inertial Limb" activities have the limb-viewing telescope pointed at the lit exosphere just after the Sun has set. Inertial Limb activities follow a similar progression of diminishing sampling altitudes but hold the solar elongation angle constant so the zodiacal light contribution remains constant while seeking to observe the weak lunar horizon glow. On the dark side of the moon, "Sodium Tail" activities pointed the limb-viewing telescope in the direction of the Moon's sodium tail (similar to anti-sunward), during different lunar phases. Of the UVS data sets, these show the largest excess of scattered blue light, indicative of the presence of small (approximately 100 nm) dust grains in the tail. Correlations are sought between dust in the sodium tail and meteor streams and magnetotail crossings to investigate impact- versus electrostatic-lofting. Once lofted, nanoparticles can become charged and picked up by the solar wind. The LADEE UVS Occultation, Inertial Limb, and Sodium Tail spectral datasets provide evidence of a lunar dust exosphere.

A Long-term Record of Saharan Dust Aerosol Properties from TOMS Observations: Optical Depth and Single Scattering Albedo

NASA Technical Reports Server (NTRS)

Torres, Omar; Bhartia, P. K.; Herman, J. R.; Einaudi, Franco (Technical Monitor)

2000-01-01

The interaction between the strong Rayleigh scattering in the near UV spectral region (330-380 nm) and the processes of aerosol absorption and scattering, produce a clear spectral signal in the upwelling radiance at the top of the atmosphere. This interaction is the basis of the TOMS (Total Ozone Mapping Spectrometer) aerosol retrieval technique that can be used for their characterization and to differentiate non-absorbing sulfates from strongly UV-absorbing aerosols such as mineral dust. For absorbing aerosols, the characterization is in terms of the optical depth and single scattering albedo with assumptions about the aerosol plume height. The results for non-absorbing aerosols are not dependent on plume height. Although iron compounds represent only between 5% to 8% of desert dust aerosol mass, hematite (Fe2O3) accounts for most of the near UV absorption. Because of the large ultraviolet absorption characteristic of hematite, the near UV method of aerosol sensing is especially suited for the detection and characterization of desert dust aerosols. Using the combined record of near UV measurements by the Nimbus7 (1978-1992) and Earth Probe (1996-present) TOMS instruments, a global longterm climatology of near UV optical depth and single scattering albedo has been produced. The multi-year long record of mineral aerosol properties over the area of influence of the Saharan desert, will be discussed.

Ultraviolet spectrophotometer for measuring columnar atmospheric ozone from aircraft

NASA Technical Reports Server (NTRS)

Hanser, F. A.; Sellers, B.; Briehl, D. C.

1978-01-01

An ultraviolet spectrophotometer (UVS) to measure downward solar fluxes from an aircraft or other high altitude platform is described. The UVS uses an ultraviolet diffuser to obtain large angular response with no aiming requirement, a twelve-position filter wheel with narrow (2-nm) and broad (20-nm) bandpass filters, and an ultraviolet photodiode. The columnar atmospheric ozone above the UVS (aircraft) is calculated from the ratios of the measured ultraviolet fluxes. Comparison with some Dobson station measurements gives agreement to 2%. Some UVS measured ozone profiles over the Pacific Ocean for November 1976 are shown to illustrate the instrument's performance.

Dynamics of defects in Ce³⁺ doped silica affecting its performance as protective filter in ultraviolet high-power lasers.

PubMed

Demos, Stavros G; Ehrmann, Paul R; Qiu, S Roger; Schaffers, Kathleen I; Suratwala, Tayyab I

2014-11-17

We investigate defects forming in Ce³⁺-doped fused silica samples following exposure to nanosecond ultraviolet laser pulses and their relaxation as a function of time and exposure to low intensity light at different wavelengths. A subset of these defects are responsible for inducing absorption in the visible and near infrared spectral range, which is of critical importance for the use of this material as ultraviolet light absorbing filter in high power laser systems. The dependence of the induced absorption as a function of laser fluence and methods to most efficiently mitigate this effect are presented. Experiments simulating the operation of the material as a UV protection filter for high power laser systems were performed in order to determine limitations and practical operational conditions.

Study of energy transfer and spectral downshifting in Ce, RE (RE = Nd and Yb) co-doped lanthanum phosphate

NASA Astrophysics Data System (ADS)

Sawala, N. S.; Omanwar, S. K.

2017-03-01

The phosphors LaPO4 (Lanthanum phosphate) doped with Ce(III)/Ce3+ and co-doped with Ce3+-Nd3+ and Ce3+-Yb3+ were effectively synthesized by conventional solid state reaction method. The prepared samples were characterized by powder X-ray diffraction (XRD) and surface morphology was studied by scanning electronic microscope (SEM). The photoluminescence (PL) properties were studied by spectrophotometers in near infrared (NIR) and ultraviolet visible (UV-VIS) region. Additionally the luminescence time decay curves of samples were investigated to confirm energy transfer (ET) process. The Ce3+-Nd3+ ion co-doped LaPO4 phosphors can convert a photon of UV region (278 nm) into photons of NIR region (1058 nm). While Ce3+-Yb3+ ion doped LaPO4 phosphors convert photons of UV region (278 nm) into photons of NIR region (979 nm). The Ce3+ ion acts like sensitizer and Nd3+/Yb3+ ions act as activators. Both kinds of emissions are suitable for improving spectral response of solar cells.

Building galaxies, stars, planets and the ingredients for life between the stars. The science behind the European Ultraviolet-Visible Observatory

NASA Astrophysics Data System (ADS)

Gómez de Castro, Ana I.; Appourchaux, Thierry; Barstow, Martin A.; Barthelemy, Mathieu; Baudin, Frederic; Benetti, Stefano; Blay, Pere; Brosch, Noah; Bunce, Emma; de Martino, Domitilla; Deharveng, Jean-Michel; Ferlet, Roger; France, Kevin; García, Miriam; Gänsicke, Boris; Gry, Cecile; Hillenbrand, Lynne; Josselin, Eric; Kehrig, Carolina; Lamy, Laurent; Lapington, Jon; Lecavelier des Etangs, Alain; LePetit, Frank; López-Santiago, Javier; Milliard, Bruno; Monier, Richard; Naletto, Giampiero; Nazé, Yael; Neiner, Coralie; Nichols, Jonathan; Orio, Marina; Pagano, Isabella; Peroux, Céline; Rauw, Gregor; Shore, Steven; Spaans, Marco; Tovmassian, Gagik; ud-Doula, Asif; Vilchez, José

2014-11-01

This contribution gathers the contents of the white paper submitted by the UV community to the Call issued by the European Space Agency in March 2013, for the definition of the L2 and L3 missions in the ESA science program. We outlined the key science that a large UV facility would make possible and the instrumentation to be implemented. The growth of luminous structures and the building blocks of life in the Universe began as primordial gas was processed in stars and mixed at galactic scales. The mechanisms responsible for this development are not well-understood and have changed over the intervening 13 billion years. To follow the evolution of matter over cosmic time, it is necessary to study the strongest (resonance) transitions of the most abundant species in the Universe. Most of them are in the ultraviolet (UV; 950 Å-3000 Å) spectral range that is unobservable from the ground. A versatile space observatory with UV sensitivity a factor of 50-100 greater than existing facilities will revolutionize our understanding of the Universe. Habitable planets grow in protostellar discs under ultraviolet irradiation, a by-product of the star-disk interaction that drives the physical and chemical evolution of discs and young planetary systems. The electronic transitions of the most abundant molecules are pumped by this UV field, providing unique diagnostics of the planet-forming environment that cannot be accessed from the ground. Earth's atmosphere is in constant interaction with the interplanetary medium and the solar UV radiation field. A 50-100 times improvement in sensitivity would enable the observation of the key atmospheric ingredients of Earth-like exoplanets (carbon, oxygen, ozone), provide crucial input for models of biologically active worlds outside the solar system, and provide the phenomenological baseline to understand the Earth atmosphere in context.

Spectral solar UV irradiance data for cycle 21

NASA Astrophysics Data System (ADS)

DeLand, Matthew T.; Cebula, Richard P.

2001-10-01

The Nimbus 7 Solar Backscatter Ultraviolet (SBUV) instrument, which began taking data in November 1978, was the first instrument to make solar UV irradiance measurements covering both the minimum and maximum activity levels of a solar cycle. The currently archived irradiance data set was processed with an instrument characterization which fails to completely account for sensor degradation in the later part of the data record, thus limiting the accuracy of estimated long-term solar activity variations and the scientific value of the data. In this paper, we describe an improved Nimbus 7 SBUV spectral irradiance data set, which utilizes a more accurate model for instrument sensitivity and treats other time-dependent problems in the archived data. Estimated long-term irradiance changes during solar cycle 21 are 8.3(+/-2.6%) at 205 nm, and 4.9(+/-1.8)% at 240 nm. The revised Nimbus 7 SBUV irradiance data are in good agreement with predictions of solar cycle variations from the Mg II index proxy model. These solar irradiance changes are also consistent with overlapping irradiance data from the declining phase of solar cycle 21 measured by the Solar Mesosphere Explorer (SME). The Nimbus 7 SBUV irradiance data represent the earliest component of a 20+ year continuous record of solar spectral UV activity.

UV Timing and Spectroscopy of the Crab Nebula Pulsar

NASA Technical Reports Server (NTRS)

Gull, Theodore R.; Lunqvist, Peter; Sollerman, Jesper; Lindler, Don; Fisher, Richard R. (Technical Monitor)

2001-01-01

We have used the Hubble Space Telescope and Space Telescope Imaging Spectrograph to obtain Near Ultraviolet (NUV) (1600-3200 Angstroms) and Far Ultraviolet (FUV) (1140-1720 Angstroms) spectra and pulse profiles of the Crab Nebula's pulsar. The pulse period agrees well with the radio predictions. The NUV and FUV pulse profiles are little changed from the visible wavelength profile. Spectra obtained with the Nordic Optical Telescope were combined with the UV spectra for full coverage from 1140-9250Angstoms. Dereddening the spectrum with a standard extinction curve achieves a flat spectrum for E(B-V)=0.52, R=3.1. Lyman alpha absorption indicates a column density of 3.0=/-0.5 x 10(exp 21) cm -2, consistent with the E(B-V) of 0.52. The dereddened spectrum can be fitted by a power law with spectral index alpha=0.11+/-0.04. A broad, blueshifted absorption is seen in CIV (1550Angstroms), reaching a velocity of about 2500 kilometer per second.

30 Doradus - Ultraviolet and optical stellar photometry

NASA Technical Reports Server (NTRS)

Hill, Jesse K.; Bohlin, Ralph C.; Cheng, Kwang-Ping; Fanelli, Michael N.; Hintzen, Paul; O'Connell, Robert W.; Roberts, Morton S.; Smith, Andrew M.; Smith, Eric P.; Stecher, Theodore P.

1993-01-01

Ultraviolet Imaging Telescope (UIT) UV magnitudes in four bands, together with optical B magnitudes, are presented for up to 314 early-type stars located in a 9.7 x 9.7 arcmin field centered on R136. The magnitudes have an rms uncertainty estimated at 0.10 mag from a comparison between the UIT magnitudes and the IUE spectra. Spectral types and E(B-V) color excesses are estimated. The mean color excesses following the two extinction curves agree well with the predictions of the two-component extinction model of Fitzpatrick and Savage (1984). However, the degree of nebular extinction is found to vary systematically by large amounts over the 30 Dor field. The minimum of nebular extinction in the central parts of the nebula suggests that dust has been expelled from this region by stellar winds. It is suggested that the form of the UV extinction curve can be understood as a consequence of the evolutionary state of the stellar population responsible for making the dust grains.

The UV Spectrum of Phobos as measured by MAVEN/IUVS

NASA Astrophysics Data System (ADS)

Chaffin, M.; Deighan, J.; Schneider, N. M.; Thiemann, E.; Stewart, I. F.; Jain, S.; Lo, D.; Crismani, M. M. J.; Stiepen, A.; Clarke, J. T.; Mayyasi, M.; Montmessin, F.; Holsclaw, G.; McClintock, B.; Epavier, F.; Jakosky, B. M.

2017-12-01

In late 2015, the Mars Atmosphere and Volatile Evolution (MAVEN) mission apoapsis was near the orbit of Phobos and the spacecraft had several close encounters with the moon. Using a specially designed imaging sequence, MAVEN's Imaging Ultraviolet Spectrograph (IUVS) was able to gather the first spectral images of the moon in the mid-ultraviolet. IUVS observed the trailing hemisphere of the moon, producing spectra useful for comparison with the leading hemisphere measurements of the Mariner 9 UV spectrometer and Mars Express SPICAM observations. IUVS shows the trailing side to be bluer than the leading side, potentially revealing differences in the space weathering history of the hemispheres. In addition, there is marginal evidence for an absorption feature longward of 300 nm, potentially produced by organic compounds. Due to short integration times, the FUV spectrum of the moon is limited to some reflectance signal at Lyman alpha, constraining the albedo at this wavelength and placing an upper limit on it elsewhere.

Ultraviolet observations of four symbiotic stars

NASA Technical Reports Server (NTRS)

Michalitsianos, A. G.; Feibelman, W. A.; Hobbs, R. W.; Kafatos, M.

1982-01-01

Observations were obtained with the International Ultraviolet Explorer (IUE) of four symbiotic stars. The UV spectra of YY Her, SY Mus, CL Sco, and BX Mon are characterized by varying degrees of thermal excitation. These low resolution spectra have been analyzed in terms of line-blanketed model atmospheres of early A, B, and F type stars in order to identify the nature of the hot companion in these systems. The expected emission from early main sequence stars does not fully explain the observed distribution of UV continuum energy over the entire IUE spectral range (1200-3200 A). More likely the observed continuum may be originating from an accretion disk and/or hot subdwarf that photoionizes circumstellar material, and gives rise to the high excitation lines that have been detected. The Bowen fluorescent excited lines of O III in SY Mus exhibit slightly broadened profiles that suggest possible turbulent motions in an extended circumstellar cloud with characteristic velocities of approximately 300 km/s.

Rapid measurement of methyl cellulose precipitable tannins using ultraviolet spectroscopy with chemometrics: application to red wine and inter-laboratory calibration transfer.

PubMed

Dambergs, Robert G; Mercurio, Meagan D; Kassara, Stella; Cozzolino, Daniel; Smith, Paul A

2012-06-01

Information relating to tannin concentration in grapes and wine is not currently available simply and rapidly enough to inform decision-making by grape growers, winemakers, and wine researchers. Spectroscopy and chemometrics have been implemented for the analysis of critical grape and wine parameters and offer a possible solution for rapid tannin analysis. We report here the development and validation of an ultraviolet (UV) spectral calibration for the prediction of tannin concentration in red wines. Such spectral calibrations reduce the time and resource requirements involved in measuring tannins. A diverse calibration set (n = 204) was prepared with samples of Australian wines of five varieties (Cabernet Sauvignon, Shiraz, Merlot, Pinot Noir, and Durif), from regions spanning the wine grape growing areas of Australia, with varying climate and soils, and with vintages ranging from 1991 to 2007. The relationship between tannin measured by the methyl cellulose precipitation (MCP) reference method at 280 nm and tannin predicted with a multiple linear regression (MLR) calibration, using ultraviolet (UV) absorbance at 250, 270, 280, 290, and 315 nm, was strong (r(2)val = 0.92; SECV = 0.20 g/L). An independent validation set (n = 85) was predicted using the MLR algorithm developed with the calibration set and gave confidence in the ability to predict new samples, independent of the samples used to prepare the calibration (r(2)val = 0.94; SEP = 0.18 g/L). The MLR algorithm could also predict tannin in fermenting wines (r(2)val = 0.76; SEP = 0.18 g/L), but worked best from the second day of ferment on. This study also explored instrument-to-instrument transfer of a spectral calibration for MCP tannin. After slope and bias adjustments of the calibration, efficient calibration transfer to other laboratories was clearly demonstrated, with all instruments in the study effectively giving identical results on a transfer set.

Inverted Al0.25Ga0.75N/GaN ultraviolet p-i-n photodiodes formed on p-GaN template layer grown by metalorganic vapor phase epitaxy

NASA Astrophysics Data System (ADS)

Chang, Kuo-Hua; Sheu, Jinn-Kong; Lee, Ming-Lun; Tu, Shang-Ju; Yang, Chih-Ciao; Kuo, Huan-Shao; Yang, J. H.; Lai, Wei-Chih

2010-07-01

Inverted Al0.25Ga0.75N/GaN ultraviolet (UV) p-i-n photodiodes (PDs) were grown by selective-area regrowth on p-GaN template. The inverted devices with low-resistivity n-type AlGaN top-contact layers exhibited a typical zero-bias peak responsivity of 66.7 mA/W at 310 nm corresponding to the external quantum efficiency of 26.6%. The typical UV-to-visible (310/400 nm) spectral rejection ratio at zero-bias was over three orders of magnitude. The differential resistance and detectivity were obtained at approximately 6.2×1012 Ω and 3.4×1013 cm Hz1/2 W-1, respectively. Compared with conventional AlGaN/GaN-based UV p-i-n PDs, the proposed device structure can potentially achieve solar-blind AlGaN/GaN-based p-i-n PDs with low-aluminum content or aluminum-free p-contact layer and reduce excessive tensile strain due to the lattice mismatch between AlGaN and GaN layers.

Synthesis and Characterization of YVO4-Based Phosphor Doped with Eu3+ Ions for Display Devices

NASA Astrophysics Data System (ADS)

Thakur, Shashi; Gathania, Arvind K.

2015-10-01

YVO4:Eu nanophosphor has been synthesized by the sol-gel method. Samples were characterized by x-ray diffraction (XRD), energy-dispersive x-ray spectroscopy, Fourier-transform infrared spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy, photoluminescence, and Raman spectroscopy. The XRD profile confirms the tetragonal phase of the Eu3+-doped YVO4 nanophosphor. The efficiency of the prepared phosphor was analyzed by means of its emission spectral profile. We also observed rich red emission from the prepared phosphor on excitation by an ultraviolet source. The calculated Commission International de l'Éclairage coordinates reveal excellent color purity efficiency. Such luminescent powder is useful as red phosphor in display device applications.

Ultraviolet photosensitivity of sulfur-doped micro- and nano-crystalline diamond

DOE PAGES

Mendoza, Frank; Makarov, Vladimir; Hidalgo, Arturo; ...

2011-06-06

The room-temperature photosensitivity of sulfur-doped micro- (MCD), submicro- (SMCD) and nano- (NCD) crystalline diamond films synthesized by hot-filament chemical vapor deposition was studied. The structure and composition of these diamond materials were characterized by Raman spectroscopy, scanning electron microscopy and X-ray diffraction. The UV sensitivity and response time were studied for the three types of diamond materials using a steady state broad UV excitation source and two pulsed UV laser radiations. It was found that they have high sensitivity in the UV region, as high as 10 9 sec -1mV -1 range, linear response in a broad spectral range belowmore » 320 nm, photocurrents around ~10 -5 A, and short response time better than 100 ns, which is independent of fluency intensity. A phenomenological model was applied to help understand the role of defects and dopant concentration on the materials’ photosensitivity.« less

Direct Retrieval of Sulfur Dioxide Amount and Altitude from Spaceborne Hyperspectral UV Measurements: Theory and Application

NASA Technical Reports Server (NTRS)

Yang, Kau; Liu, Xiong; Bhartia, Pawan K.; Krotkov, Nickolay A.; Carn, Simon A.; Hughes, Eric J.; Krueger, Arlin J.; Spurr, Robert D.; Trahan, Samuel G.

2010-01-01

We describe the physical processes by which a vertically localized absorber perturbs the top-of-atmosphere solar backscattered ultraviolet (UV) radiance. The distinct spectral responses to perturbations of an absorber in its column amount and layer altitude provide the basis for a practical satellite retrieval technique, the Extended Iterative Spectral Fitting (EISF) algorithm, for the simultaneous retrieval of these quantities of a SO2 plume. In addition, the EISF retrieval provides an improved UV aerosol index for quantifying the spectral contrast of apparent scene reflectance at the bottom of atmosphere bounded by the surface and/or cloud; hence it can be used for detection of the presence or absence of UV absorbing aerosols. We study the performance and characterize the uncertainties of the EISF algorithm using synthetic backscattered UV radiances, retrievals from which can be compared with those used in the simulation. Our findings indicate that the presence of aerosols (both absorbing and nonabsorbing) does not cause large errors in EISF retrievals under most observing conditions when they are located below the SO2 plume. The EISF retrievals assuming a homogeneous field of view can provide accurate column amounts for inhomogeneous scenes, but they always underestimate the plume altitudes. The EISF algorithm reduces systematic errors present in existing linear retrieval algorithms that use prescribed SO2 plume heights. Applying the EISF algorithm to Ozone Monitoring Instrument satellite observations of the recent Kasatochi volcanic eruption, we demonstrate the successful retrieval of effective plume altitude of volcanic SO2, and we also show the improvement in accuracy in the corresponding SO2 columns.

Modelling Stellar Optical and Mid-Ultraviolet Spectra from First Principles

NASA Astrophysics Data System (ADS)

Peterson, R. C.; Carney, B. W.; Dorman, B.; Green, E. M.; Landsman, W.; Liebert, J.; O'Connell, R. W.; Rood, R. T.; Schiavon, R. P.

2004-05-01

We present comparisons of theoretical and observational high-resolution spectra for a half-dozen stars of a wide range of temperature and abundance, from A star to K giant. These show the fits achieved to date by our ab initio spectral calculations. These comparisons form the first phase of our three-year Hubble Treasury program GO-9455/9974, aimed at providing mid-ultraviolet spectral templates to improve the determination of the age and metallicity of old stellar systems. From matches such as these, we have modified the input atomic-line parameters and guessed the identifications of spectral lines missing from the calculations, as described by Peterson, Dorman, & Rood (2001, ApJ, 559, 372). With this new line list, we now match well the optical spectra of stars of all line strengths. We have begun to calculate a grid of optical indices from the theoretical spectra. In the mid-UV, while the fits at solar abundance are much improved, we are still missing very weak absorption lines near 2650Å and 2900Å. This will be addressed as additional mid-ultraviolet spectra are taken for a larger range of stellar targets during Cycle 13. Support for this work includes grants GO-9455 and GO-9974 from the Hubble Space Telescope Science Institute, and an award from the NASA-OSS Long Term Space Astrophysics program.

HAZMAT. II. Ultraviolet Variability of Low-mass Stars in the GALEX Archive

NASA Astrophysics Data System (ADS)

Miles, Brittany E.; Shkolnik, Evgenya L.

2017-08-01

The ultraviolet (UV) light from a host star influences a planet’s atmospheric photochemistry and will affect interpretations of exoplanetary spectra from future missions like the James Webb Space Telescope. These effects will be particularly critical in the study of planetary atmospheres around M dwarfs, including Earth-sized planets in the habitable zone. Given the higher activity levels of M dwarfs compared to Sun-like stars, time-resolved UV data are needed for more accurate input conditions for exoplanet atmospheric modeling. The Galaxy Evolution Explorer (GALEX) provides multi-epoch photometric observations in two UV bands: near-ultraviolet (NUV; 1771-2831 Å) and far-ultraviolet (FUV; 1344-1786 Å). Within 30 pc of Earth, there are 357 and 303 M dwarfs in the NUV and FUV bands, respectively, with multiple GALEX observations. Simultaneous NUV and FUV detections exist for 145 stars in both GALEX bands. Our analyses of these data show that low-mass stars are typically more variable in the FUV than the NUV. Median variability increases with later spectral types in the NUV with no clear trend in the FUV. We find evidence that flares increase the FUV flux density far more than the NUV flux density, leading to variable FUV to NUV flux density ratios in the GALEX bandpasses.The ratio of FUV to NUV flux is important for interpreting the presence of atmospheric molecules in planetary atmospheres such as oxygen and methane as a high FUV to NUV ratio may cause false-positive biosignature detections. This ratio of flux density in the GALEX bands spans three orders of magnitude in our sample, from 0.008 to 4.6, and is 1 to 2 orders of magnitude higher than for G dwarfs like the Sun. These results characterize the UV behavior for the largest set of low-mass stars to date.

HAZMAT. II. Ultraviolet Variability of Low-mass Stars in the GALEX Archive

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

Miles, Brittany E.; Shkolnik, Evgenya L., E-mail: bmiles@ucsc.edu

The ultraviolet (UV) light from a host star influences a planet’s atmospheric photochemistry and will affect interpretations of exoplanetary spectra from future missions like the James Webb Space Telescope . These effects will be particularly critical in the study of planetary atmospheres around M dwarfs, including Earth-sized planets in the habitable zone. Given the higher activity levels of M dwarfs compared to Sun-like stars, time-resolved UV data are needed for more accurate input conditions for exoplanet atmospheric modeling. The Galaxy Evolution Explorer ( GALEX ) provides multi-epoch photometric observations in two UV bands: near-ultraviolet (NUV; 1771–2831 Å) and far-ultraviolet (FUV;more » 1344–1786 Å). Within 30 pc of Earth, there are 357 and 303 M dwarfs in the NUV and FUV bands, respectively, with multiple GALEX observations. Simultaneous NUV and FUV detections exist for 145 stars in both GALEX bands. Our analyses of these data show that low-mass stars are typically more variable in the FUV than the NUV. Median variability increases with later spectral types in the NUV with no clear trend in the FUV. We find evidence that flares increase the FUV flux density far more than the NUV flux density, leading to variable FUV to NUV flux density ratios in the GALEX bandpasses.The ratio of FUV to NUV flux is important for interpreting the presence of atmospheric molecules in planetary atmospheres such as oxygen and methane as a high FUV to NUV ratio may cause false-positive biosignature detections. This ratio of flux density in the GALEX bands spans three orders of magnitude in our sample, from 0.008 to 4.6, and is 1 to 2 orders of magnitude higher than for G dwarfs like the Sun. These results characterize the UV behavior for the largest set of low-mass stars to date.« less

The Far-UV Albedo of the Moon Determined from Dayside LAMP Observations

NASA Astrophysics Data System (ADS)

Bullock, Mark A.; Retherford, K. D.; Gladstone, R.; Greathouse, T. K.; Mandt, K. E.; Hendrix, A. R.; Feldman, P. D.; Miles, P. F.; Egan, A. F.

2013-10-01

The Lyman Alpha Mapping Project (LAMP) onboard the Lunar Reconnaissance Orbiter (LRO) has been recording far-UV photons reflected from the lunar surface almost continuously since December 2009 (Gladstone et al., 2010). One photon at a time, LAMP builds up spectra from 575 to 1965 Å with a resolution of 26 Å. We will present 3 years of accumulated LAMP lunar dayside spectral maps and derive the lunar geometric albedo spectrum for a range of phase angles. These LAMP observations can thus be used to reconstruct the lunar far-UV photometric function and refine photometric models of the lunar surface (Hapke, 1963; Lucke et al., 1976). We will also compare LAMP lunar dayside albedo with the albedo from 820-1840 Å obtained by the Hopkins Ultraviolet Telescope (HUT) on the March 1995 Astro-2 Space Shuttle mission (Henry et al., 1995). The improved lunar photometric functions from our analysis of LAMP albedo spectra will enable a better quantitative assessment of how phase angle and composition affect the Moon’s reflectance in the far-UV. Gladstone, G. R., Stern, S. A., Retherford, K. D., Black, R. K., Slater, D. C., Davis, M. W., Versteeg, M. H., Persson, K. B., Parker, J. W., Kaufmann, D. E., Egan, A. F., Greathouse, T. K., Feldman, P. D., Hurley, D., Pryor, W. R., Hendrix, A. R., 2010. LAMP: The lyman alpha mapping project on NASA's lunar reconnaissance orbiter mission. Space Science Reviews. 150, 161-181. Hapke, B. W., 1963. A theoretical photometric function for the lunar surface. Journal of Geophysical Research. 68, 4571-4586. Henry, R. C., Feldman, P. D., Kruk, J. W., Davidsen, A. F., Durrance, S. T., 1995. Ultraviolet Albedo of the Moon with the Hopkins Ultraviolet Telescope. The Astrophysical Journal Letters. 454, L69. Lucke, R. L., Henry, R. C., Fastie, W. G., 1976. Far-ultraviolet albedo of the moon. The Astronomical Journal. 81, 1162-1169.

GESE: a small UV space telescope to conduct a large spectroscopic survey of z˜1 Galaxies

NASA Astrophysics Data System (ADS)

Heap, Sara R.; Gong, Qian; Hull, Tony; Kruk, Jeffrey; Purves, Lloyd

2014-11-01

One of the key goals of NASA's astrophysics program is to answer the question: How did galaxies evolve into the spirals and elliptical galaxies that we see today? We describe a space mission concept called Galaxy Evolution Spectroscopic Explorer (GESE) to address this question by making a large spectroscopic survey of galaxies at a redshift, z˜1 (look-back time of ˜8 billion years). GESE is a 1.5-m space telescope with an ultraviolet (UV) multi-object slit spectrograph that can obtain spectra of hundreds of galaxies per exposure. The spectrograph covers the spectral range, 0.2-0.4 μm at a spectral resolving power, R˜500. This observed spectral range corresponds to 0.1-0.2 μm as emitted by a galaxy at a redshift, z=1. The mission concept takes advantage of two new technological advances: (1) light-weighted, wide-field telescope mirrors, and (2) the Next-Generation MicroShutter Array (NG-MSA) to be used as a slit generator in the multi-object slit spectrograph.

GESE: A Small UV Space Telescope to Conduct a Large Spectroscopic Survey of Z-1 Galaxies

NASA Technical Reports Server (NTRS)

Heap, Sara R.; Gong, Qian; Hull, Tony; Kruk, Jeffrey; Purves, Lloyd

2013-01-01

One of the key goals of NASA's astrophysics program is to answer the question: How did galaxies evolve into the spirals and elliptical galaxies that we see today? We describe a space mission concept called Galaxy Evolution Spectroscopic Explorer (GESE) to address this question by making a large spectroscopic survey of galaxies at a redshift, z is approximately 1 (look-back time of approximately 8 billion years). GESE is a 1.5-meter space telescope with an ultraviolet (UV) multi-object slit spectrograph that can obtain spectra of hundreds of galaxies per exposure. The spectrograph covers the spectral range, 0.2-0.4 micrometers at a spectral resolving power, R approximately 500. This observed spectral range corresponds to 0.1-0.2 micrometers as emitted by a galaxy at a redshift, z=1. The mission concept takes advantage of two new technological advances: (1) light-weighted, wide-field telescope mirrors, and (2) the Next- Generation MicroShutter Array (NG-MSA) to be used as a slit generator in the multi-object slit spectrograph.

Detection of latent fingerprints by ultraviolet spectral imaging

NASA Astrophysics Data System (ADS)

Huang, Wei; Xu, Xiaojing; Wang, Guiqiang

2013-12-01

Spectral imaging technology research is becoming more popular in the field of forensic science. Ultraviolet spectral imaging technology is an especial part of the full spectrum of imaging technology. This paper finished the experiment contents of the ultraviolet spectrum imaging method and image acquisition system based on ultraviolet spectral imaging technology. Ultraviolet spectral imaging experiments explores a wide variety of ultraviolet reflectance spectra of the object material curve and its ultraviolet spectrum of imaging modalities, can not only gives a reference for choosing ultraviolet wavelength to show the object surface potential traces of substances, but also gives important data for the ultraviolet spectrum of imaging technology development.

On the change in the spectral composition of solar ultraviolet emission preceding proton flares, and its connection with the preflare fluctuations in the horizontal component of the geomagnetic field

NASA Astrophysics Data System (ADS)

Sheiner, Olga; Snegirev, Sergei; Smirnova, Anna

The importance problem of Solar-terrestrial physics is regular forecasting of solar activity phenomena, which negatively influence the human’s health, operating safety, communication, radar sets and others. We previously reported the existence of long-period pulsations of H component of the geomagnetic field recorded at stations tested 2-3 days before the proton solar flares. There are the increasing of pulsation amplitude of the horizontal component of the magnetic field with periods of 30-60 minutes. The spectrum of the flux of ultraviolet solar radiation on the eve of proton flares was conducted to determine the presence of oscillations - precursors of flares, as one of the possible agents causing amplification of large periods pulsations of H component of the geomagnetic field. Used data on ultraviolet radiation of the sun with a wavelength of 115-127 nm are obtained from a geostationary satellite GOES 15, the method of wavelet analysis is used. It is found the congruence in the behavior of spectral components with periods of 30-60 minutes in the ground-based measurements and in UV emission for 3-1 days before the proton flare.

UV EFFECTS IN TOOTH ENAMEL AND THEIR POSSIBLE APPLICATION IN EPR DOSIMETRY WITH FRONT TEETH

PubMed Central

Sholom, S.; Desrosiers, M.; Chumak, V.; Luckyanov, N.; Simon, S.L.; Bouville, A.

2009-01-01

The effects of ultraviolet (UV) radiation on ionizing radiation biodosimetry were studied in human tooth enamel samples using the technique of electron paramagnetic resonance (EPR) in X-band. For samples in the form of grains, UV-specific EPR spectra were spectrally distinct from that produced by exposure to gamma radiation. From larger enamel samples, the UV penetration depth was determined to be in the 60–120 μm range. The difference in EPR spectra from UV exposure and from exposure to gamma radiation samples was found to be a useful marker of UV equivalent dose (defined as the apparent contribution to the gamma dose in mGy that results from UV radiation absorption) in tooth enamel. This concept was preliminarily tested on front teeth from inhabitants of the region of the Semipalatinsk Nuclear Test Site (Kazakhstan) who might have received some exposure to gamma radiation from the nuclear tests conducted there as well as from normal UV radiation in sunlight. The technique developed here to quantify and subtract the UV contribution to the measured tooth is currently limited to cumulative dose measurements with a component of UV equivalent dose equal to or greater than 300 mGy. PMID:20065706

Calibration and characterization of UV sensors for water disinfection

NASA Astrophysics Data System (ADS)

Larason, T.; Ohno, Y.

2006-04-01

The National Institute of Standards and Technology (NIST), USA is participating in a project with the American Water Works Association Research Foundation (AwwaRF) to develop new guidelines for ultraviolet (UV) sensor characteristics to monitor the performance of UV water disinfection plants. The current UV water disinfection standards, ÖNORM M5873-1 and M5873-2 (Austria) and DVGW W294 3 (Germany), on the requirements for UV sensors for low-pressure mercury (LPM) and medium-pressure mercury (MPM) lamp systems have been studied. Additionally, the characteristics of various types of UV sensors from several different commercial vendors have been measured and analysed. This information will aid in the development of new guidelines to address issues such as sensor requirements, calibration methods, uncertainty and traceability. Practical problems were found in the calibration methods and evaluation of spectral responsivity requirements for sensors designed for MPM lamp systems. To solve the problems, NIST is proposing an alternative sensor calibration method for MPM lamp systems. A future calibration service is described for UV sensors intended for low- and medium-pressure mercury lamp systems used in water disinfection applications.

Preliminary investigation of intrinsic UV fluorescence spectroscopic changes associated with proteolytic digestion of bovine articular cartilage

NASA Astrophysics Data System (ADS)

Lewis, William; Padilla-Martinez, Juan-Pablo; Ortega-Martinez, Antonio; Franco, Walfre

2016-03-01

Degradation and destruction of articular cartilage is the etiology of osteoarthritis (OA), an entity second only to cardiovascular disease as a cause of disability in the United States. Joint mechanics and cartilage biochemistry are believed to play a role in OA; an optical tool to detect structural and chemical changes in articular cartilage might offer benefit for its early detection and treatment. The objective of the present study was to identify the spectral changes in intrinsic ultraviolet (UV) fluorescence of cartilage that occur after proteolytic digestion of cartilage. Bovine articular cartilage samples were incubated in varying concentrations of collagenase ranging from 10ug/mL up to 5mg/mL for 18 hours at 37°C, a model of OA. Pre- and post-incubation measurements were taken of the UV excitation-emission spectrum of each cartilage sample. Mechanical tests were performed to determine the pre- and post-digestion force/displacement ratio associated with indentation of each sample. Spectral changes in intrinsic cartilage fluorescence and stiffness of the cartilage were associated with proteolytic digestion. In particular, changes in the relative intensity of fluorescence peaks associated with pentosidine crosslinks (330 nm excitation, 390 nm emission) and tryptophan (290 nm excitation, 340 nm emission) were found to correlate with different degrees of cartilage digestion and cartilage stiffness. In principle, it may be possible to use UV fluorescence spectral data for early detection of damage to articular cartilage, and as a surrogate measure for cartilage stiffness.

ULTRAVIOLET PROTECTIVE PIGMENTS AND DNA DIMER INDUCTION AS RESPONSES TO ULTRAVIOLET RADIATION

EPA Science Inventory

Life on Earth has evolved adaptations to many environmental stresses over the epochs. One consistent stress has been exposure to ultraviolet (UV) radiation. The most basic effect of UV radiation on biological systems is damage to DNA. In response to UV radiation organisms have ad...

Reddened, Redshifted, or Intrinsically Red? Understanding Near-ultraviolet Colors of Type Ia Supernovae

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

Brown, Peter J.; Landez, Nancy J.; Milne, Peter A.

The intrinsic colors of Type Ia supernovae (SNe Ia) are important to understanding their use as cosmological standard candles. Understanding the effects of reddening and redshift on the observed colors are complicated and dependent on the intrinsic spectrum, the filter curves, and the wavelength dependence of reddening. We present ultraviolet and optical data of a growing sample of SNe Ia observed with the Ultraviolet/Optical Telescope on the Swift spacecraft and use this sample to re-examine the near-UV (NUV) colors of SNe Ia. We find that a small amount of reddening ( E ( B − V ) = 0.2 mag)more » could account for the difference between groups designated as NUV-blue and NUV-red, and a moderate amount of reddening ( E ( B − V ) = 0.5 mag) could account for the whole NUV-optical differences. The reddening scenario, however, is inconsistent with the mid-UV colors and color evolution. The effect of redshift alone only accounts for part of the variation. Using a spectral template of SN2011fe, we can forward model the effects of redshift and reddening and directly compare those with the observed colors. We find that some SNe are consistent with reddened versions of SN2011fe, but most SNe Ia are much redder in the uvw 1 − v color than SN2011fe reddened to the same b − v color. The absolute magnitudes show that two out of five NUV-blue SNe Ia are blue because their near-UV luminosity is high, and the other three are optically fainter. We also show that SN 2011fe is not a “normal” SN Ia in the UV, but has colors placing it at the blue extreme of our sample.« less

Light absorption of organic aerosol from pyrolysis of corn stalk

NASA Astrophysics Data System (ADS)

Li, Xinghua; Chen, Yanju; Bond, Tami C.

2016-11-01

Organic aerosol (OA) can absorb solar radiation in the low-visible and ultra-violet wavelengths thereby modifying radiative forcing. Agricultural waste burning emits a large quantity of organic carbon in many developing countries. In this work, we improved the extraction and analysis method developed by Chen and Bond, and extended the spectral range of OC absorption. We examined light absorbing properties of primary OA from pyrolysis of corn stalk, which is a major type of agricultural wastes. Light absorption of bulk liquid extracts of OA was measured using a UV-vis recording spectrophotometer. OA can be extracted by methanol at 95%, close to full extent, and shows polar character. Light absorption of organic aerosol has strong spectral dependence (Absorption Ångström exponent = 7.7) and is not negligible at ultra-violet and low-visible regions. Higher pyrolysis temperature produced OA with higher absorption. Imaginary refractive index of organic aerosol (kOA) is 0.041 at 400 nm wavelength and 0.005 at 550 nm wavelength, respectively.

Ultraviolet safety assessments of insect light traps.

PubMed

Sliney, David H; Gilbert, David W; Lyon, Terry

2016-01-01

Near-ultraviolet (UV-A: 315-400 nm), "black-light," electric lamps were invented in 1935 and ultraviolet insect light traps (ILTs) were introduced for use in agriculture around that time. Today ILTs are used indoors in several industries and in food-service as well as in outdoor settings. With recent interest in photobiological lamp safety, safety standards are being developed to test for potentially hazardous ultraviolet emissions. A variety of UV "Black-light" ILTs were measured at a range of distances to assess potential exposures. Realistic time-weighted human exposures are shown to be well below current guidelines for human exposure to ultraviolet radiation. These UV-A exposures would be far less than the typical UV-A exposure in the outdoor environment. Proposals are made for realistic ultraviolet safety standards for ILT products.

Solar UV Radiation and the Origin of Life On Earth

NASA Technical Reports Server (NTRS)

Heap, S. R.; Lanz, T.; Hubeny, I.; Gaidos, E.; Oegerle, William R. (Technical Monitor)

2002-01-01

We have embarked on a program aimed at understanding the atmosphere of the early Earth, because of its importance as a greenhouse, radiation shield and energy source for life. Here, we give a progress report on the first phase of this program to establish the UV radiation from the early Sun. We have obtained ultraviolet spectra (STIS, FUSE, EUVE) of carefully selected nearby, young solar-type stars, which act as surrogates for the early Sun We are making detailed non-LTE analyses of the spectra and constructing models of their photospheres + chromospheres. Once validated, these models will allow us to extrapolate our theoretical spectra to other metallicities and to unobserved spectral regions.

A general study of techniques for ultraviolet astrophysical studies on space vehicles

NASA Technical Reports Server (NTRS)

Moos, H. W.; Fastie, W. G.; Davidsen, A. F.

1977-01-01

Recent accomplishments in three areas of UV instrumentation for space astronomy are discussed. These areas include reliable UV photometry, sensitive photon-detection techniques, and precise telescope pointing. Calibration facilities for spectrometers designed to operate in the spectral regions above 1200 A and down to 400 A are described which employ a series of diodes calibrated against electron synchrotron radiation as well as other radiometric standards. Improvements in photon-detection sensitivity achieved with the aid of pulse-counting electronics and multispectral detectors are reported, and the technique of precise subarcsecond telescope pointing is briefly noted. Some observational results are presented which demonstrate the advantages and precision of the instruments and techniques considered.

Microchannel plate life testing for UV spectroscopy instruments

NASA Astrophysics Data System (ADS)

Darling, N. T.; Siegmund, O. H. W.; Curtis, T.; McPhate, J.; Tedesco, J.; Courtade, S.; Holsclaw, G.; Hoskins, A.; Al Dhafri, S.

2017-08-01

The Emirates Mars Mission (EMM) UV Spectrograph (EMUS) is a far ultraviolet (102 nm to 170 nm) imaging spectrograph for characterization of the Martian exosphere and thermosphere. Imaging is accomplished by a photon counting open-face microchannel plate (MCP) detector using a cross delay line (XDL) readout. An MCP gain stabilization ("scrub") followed by lifetime spectral line burn-in simulation has been completed on a bare MCP detector at SSL. Gain and sensitivity stability of better than 7% has been demonstrated for total dose of 2.5 × 1012 photons cm-2 (2 C · cm-2 ) at 5.5 kHz mm-2 counting rates, validating the efficacy of an initial low gain full-field scrub.

Jupiter Systems Data Analysis Program Galileo Multi-Spectral Analysis of the Galilean Satellites

NASA Technical Reports Server (NTRS)

Hendrix, Amanda; Carlson, Robert; Smythe, William

2002-01-01

Progress was made on this project at the University of Colorado, particularly concerning analysis of data of the galilean moons Io and Europa. The goal of the Io portion of this study is to incorporate Near Infrared Mapping Spectrometer (NIMS) measured sulfur dioxide (SO2) frost amounts into models used with Ultraviolet spectrometer (UVS) spectra, in order to better constrain SO2 gas amounts determined by the UVS. The overall goal of this portion of the study is to better understand the thickness and distribution of Io's SO2 atmosphere. The goal of the analysis of the Europa data is to better understand the source of the UV absorption feature centered near 280 rim which has been noted in disk-integrated spectra primarily on the trailing hemisphere. The NIMS data indicate asymmetric water ice bands on Europa, particularly over the trailing hemisphere, and especially concentrated in the visibly dark regions associated with chaotic terrain and lines. The UPS data, the first-ever disk-resolved UV spectra of Europa, shown that the UV absorber is likely concentrated in regions where the NIMS data show asymmetric water ice bands. The material that produces both spectral features is likely the same, and we use data from both wavelength regions to better understand this material, and whether it is endogenically or exogenically produced. This work is still in progress at JPL.

Kr photoionized plasma induced by intense extreme ultraviolet pulses

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

Bartnik, A., E-mail: andrzej.bartnik@wat.edu.pl; Wachulak, P.; Fiedorowicz, H.

Irradiation of any gas with an intense EUV (extreme ultraviolet) radiation beam can result in creation of photoionized plasmas. The parameters of such plasmas can be significantly different when compared with those of the laser produced plasmas (LPP) or discharge plasmas. In this work, the photoionized plasmas were created in a krypton gas irradiated using an LPP EUV source operating at a 10 Hz repetition rate. The Kr gas was injected into the vacuum chamber synchronously with the EUV radiation pulses. The EUV beam was focused onto a Kr gas stream using an axisymmetrical ellipsoidal collector. The resulting low temperature Krmore » plasmas emitted electromagnetic radiation in the wide spectral range. The emission spectra were measured either in the EUV or an optical range. The EUV spectrum was dominated by emission lines originating from Kr III and Kr IV ions, and the UV/VIS spectra were composed from Kr II and Kr I lines. The spectral lines recorded in EUV, UV, and VIS ranges were used for the construction of Boltzmann plots to be used for the estimation of the electron temperature. It was shown that for the lowest Kr III and Kr IV levels, the local thermodynamic equilibrium (LTE) conditions were not fulfilled. The electron temperature was thus estimated based on Kr II and Kr I species where the partial LTE conditions could be expected.« less

Kr photoionized plasma induced by intense extreme ultraviolet pulses

NASA Astrophysics Data System (ADS)

Bartnik, A.; Wachulak, P.; Fiedorowicz, H.; Skrzeczanowski, W.

2016-04-01

Irradiation of any gas with an intense EUV (extreme ultraviolet) radiation beam can result in creation of photoionized plasmas. The parameters of such plasmas can be significantly different when compared with those of the laser produced plasmas (LPP) or discharge plasmas. In this work, the photoionized plasmas were created in a krypton gas irradiated using an LPP EUV source operating at a 10 Hz repetition rate. The Kr gas was injected into the vacuum chamber synchronously with the EUV radiation pulses. The EUV beam was focused onto a Kr gas stream using an axisymmetrical ellipsoidal collector. The resulting low temperature Kr plasmas emitted electromagnetic radiation in the wide spectral range. The emission spectra were measured either in the EUV or an optical range. The EUV spectrum was dominated by emission lines originating from Kr III and Kr IV ions, and the UV/VIS spectra were composed from Kr II and Kr I lines. The spectral lines recorded in EUV, UV, and VIS ranges were used for the construction of Boltzmann plots to be used for the estimation of the electron temperature. It was shown that for the lowest Kr III and Kr IV levels, the local thermodynamic equilibrium (LTE) conditions were not fulfilled. The electron temperature was thus estimated based on Kr II and Kr I species where the partial LTE conditions could be expected.

Surface/Interface Carrier-Transport Modulation for Constructing Photon-Alternative Ultraviolet Detectors Based on Self-Bending-Assembled ZnO Nanowires.

PubMed

Guo, Zhen; Zhou, Lianqun; Tang, Yuguo; Li, Lin; Zhang, Zhiqi; Yang, Hongbo; Ma, Hanbin; Nathan, Arokia; Zhao, Dongxu

2017-09-13

Surface/interface charge-carrier generation, diffusion, and recombination/transport modulation are especially important in the construction of photodetectors with high efficiency in the field of nanoscience. In the paper, a kind of ultraviolet (UV) detector is designed based on ZnO nanostructures considering photon-trapping, surface plasmonic resonance (SPR), piezophototronic effects, interface carrier-trapping/transport control, and collection. Through carefully optimized surface/interface carrier-transport modulation, a designed device with detectivity as high as 1.69 × 10 16 /1.71 × 10 16 cm·Hz 1/2 /W irradiating with 380 nm photons under ultralow bias of 0.2 V is realized by alternating nanoparticle/nanowire active layers, respectively, and the designed UV photodetectors show fast and slow recovery processes of 0.27 and 4.52 ms, respectively, which well-satisfy practical needs. Further, it is observed that UV photodetection could be performed within an alternative response by varying correlated key parameters, through efficient surface/interface carrier-transport modulation, spectrally resolved photoresponse of the detector revealing controlled detection in the UV region based on the ZnO nanomaterial, photodetection allowed or limited by varying the active layers, irradiation distance from one of the electrodes, standing states, or electric field. The detailed carrier generation, diffusion, and recombination/transport processes are well illustrated to explain charge-carrier dynamics contributing to the photoresponse behavior.

Retrieval of the ultraviolet aerosol optical depth during a spring campaign in the Bavarian Alps.

PubMed

Lenoble, Jacqueline; Martin, Timothy; Blumthaler, Mario; Philipona, Rolf; Albold, Astrid; Cabot, Thierry; de La Casinière, Alain; Gröbner, Julian; Masserot, Dominique; Müller, Martin; Pichler, Thomas; Seckmeyer, Günther; Schmucki, Daniel; Touré, Mamadou Lamine; Yvon, Alexis

2002-03-20

A measurement campaign was organized in March 1999 in the Bavarian Alps as part of the European project, Characteristics of the UV Radiation Field in the Alps (CUVRA), to analyze the effect of altitude, aerosols, and snow cover on ground-level UV spectral irradiance. We present the results of simultaneous measurements of aerosol optical depth (AOD) made at various sites on two cloudless days in March 1999. The two days exhibited different aerosol conditions. Results derived from spectral measurements of UV irradiance are compared with data from filter radiometer measurements made at discrete wavelengths extending from the UV to the near IR. The different methods generated values for the AOD that were in good agreement. This result confirms that one can use either method to retrieve the AOD with an uncertainty of approximately 0.03-0.05. On 18 March, high turbidity was observed at low altitude (400-nm AOD approximately 0.5 at 700 m above sea level), and the AOD decreased regularly with altitude; on 24 March, the turbidity was much less (0.11 at 700 m above sea level). On both days very low AODs (0.05-0.09) were measured at 3000 m above sea level. The spectral dependence of the AOD is often parameterized by the angstrom relationship; the alpha parameter is generally difficult or impossible to retrieve from spectral measurements because of the relatively narrow wavelength range (320-400 nm), and only one of the spectro-radiometers used during the campaign permits this retrieval. In most cases, during this field campaign, alpha was found by filter sunphotometers to be 1.1-1.5.

Modifying the Standard Disk Model for the Ultraviolet Spectral Analysis of Disk-dominated Cataclysmic Variables. I. The Novalikes MV Lyrae, BZ Camelopardalis, and V592 Cassiopeiae.

PubMed

Godon, Patrick; Sion, Edward M; Balman, Şölen; Blair, William P

2017-09-01

The standard disk is often inadequate to model disk-dominated cataclysmic variables (CVs) and generates a spectrum that is bluer than the observed UV spectra. X-ray observations of these systems reveal an optically thin boundary layer (BL) expected to appear as an inner hole in the disk. Consequently, we truncate the inner disk. However, instead of removing the inner disk, we impose the no-shear boundary condition at the truncation radius, thereby lowering the disk temperature and generating a spectrum that better fits the UV data. With our modified disk, we analyze the archival UV spectra of three novalikes that cannot be fitted with standard disks. For the VY Scl systems MV Lyr and BZ Cam, we fit a hot inflated white dwarf (WD) with a cold modified disk ( [Formula: see text] ~ a few 10 -9 M ⊙ yr -1 ). For V592 Cas, the slightly modified disk ( [Formula: see text] ~ 6 × 10 -9 M ⊙ yr -1 ) completely dominates the UV. These results are consistent with Swift X-ray observations of these systems, revealing BLs merged with ADAF-like flows and/or hot coronae, where the advection of energy is likely launching an outflow and heating the WD, thereby explaining the high WD temperature in VY Scl systems. This is further supported by the fact that the X-ray hardness ratio increases with the shallowness of the UV slope in a small CV sample we examine. Furthermore, for 105 disk-dominated systems, the International Ultraviolet Explorer spectra UV slope decreases in the same order as the ratio of the X-ray flux to optical/UV flux: from SU UMa's, to U Gem's, Z Cam's, UX UMa's, and VY Scl's.

Thermal Pressure in Diffuse H2 Gas Measured by Herschel [C II] Emission and FUSE UV H2 Absorption

NASA Astrophysics Data System (ADS)

Velusamy, T.; Langer, W. D.; Goldsmith, P. F.; Pineda, J. L.

2017-04-01

UV absorption studies with the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite have made important observations of H2 molecular gas in Galactic interstellar translucent and diffuse clouds. Observations of the 158 μm [C II] fine-structure line with Herschel trace the same H2 molecular gas in emission. We present [C II] observations along 27 lines of sight (LOSs) toward target stars of which 25 have FUSE H2 UV absorption. Two stars have only HST STIS C II λ2325 absorption data. We detect [C II] 158 μm emission features in all but one target LOS. For three target LOSs that are close to the Galactic plane, | {\\text{}}b| < 1°, we also present position-velocity maps of [C II] emission observed by Herschel Heterodyne Instrument in the Far Infrared (HIFI) in on-the-fly spectral-line mapping. We use the velocity-resolved [C II] spectra observed by the HIFI instrument toward the target LOSs observed by FUSE to identify [C II] velocity components associated with the H2 clouds. We analyze the observed velocity integrated [C II] spectral-line intensities in terms of the densities and thermal pressures in the H2 gas using the H2 column densities and temperatures measured by the UV absorption data. We present the H2 gas densities and thermal pressures for 26 target LOSs and from the [C II] intensities derive a mean thermal pressure in the range of ˜6100-7700 K cm-3 in diffuse H2 clouds. We discuss the thermal pressures and densities toward 14 targets, comparing them to results obtained using the UV absorption data for two other tracers C I and CO. Our results demonstrate the richness of the far-IR [C II] spectral data which is a valuable complement to the UV H2 absorption data for studying diffuse H2 molecular clouds. While the UV absorption is restricted to the directions of the target star, far-IR [C II] line emission offers an opportunity to employ velocity-resolved spectral-line mapping capability to study in detail the clouds’ spatial and velocity structures.

An atlas of ultraviolet spectra of star-forming galaxies

NASA Technical Reports Server (NTRS)

Kinney, A. L.; Bohlin, R. C.; Calzetti, D.; Panagia, N.; Wyse, Rosemary F. G.

1993-01-01

A systematic study is presented of the UV spectra of star-forming galaxies of different morphological type and activity class using a sample drawn from a uniformly reduced IUE data set. The spectra for a wide variety of galaxies, including normal spiral, LINER, starburst, blue compact, blue compact dwarf, and Seyfert 2 galaxies, are presented in the form of spectral energy distributions to demonstrate the overall characteristics according to morphology and activity class and in the form of absolute flux distributions to better show the absorption and emission features of individual objects. The data support the picture based on UV spectra of the Orbiting Astronomical Observatory and of the Astronautical Netherlands Satellite that spiral galaxies of later Hubble class have more flux at the shortest UV wavelengths than do spiral galaxies of earlier Hubble class.

Spectral lines and characteristic of temporal variations in photoionized plasmas induced with laser-produced plasma extreme ultraviolet source

NASA Astrophysics Data System (ADS)

Saber, I.; Bartnik, A.; Wachulak, P.; Skrzeczanowski, W.; Jarocki, R.; Fiedorowicz, H.

2017-11-01

Spectral lines for Kr/Ne/H2 photoionized plasma in the ultraviolet and visible (UV/Vis) wavelength ranges have been created using a laser-produced plasma (LPP) EUV source. The source is based on a double-stream gas puff target irradiated with a commercial Nd:YAG laser. The laser pulses were focused onto a gas stream, injected into a vacuum chamber synchronously with the EUV pulses. Spectral lines from photoionization in neutral Kr/Ne/H2 and up to few charged states were observed. The intense emission lines were associated with the Kr transition lines. Experimental and theoretical investigations on intensity variations for some ionic lines are presented. A decrease in the intensity with the delay time between the laser pulse and the spectrum acquisition was revealed. Electron temperature and electron density in the photoionized plasma have been estimated from the characteristic emission lines. Temperature was obtained using Boltzmann plot method, assuming that the population density of atoms and ions are considered in a local thermodynamic equilibrium (LTE). Electron density was calculated from the Stark broadening profile. The temporal evaluation of the plasma and the way of optimizing the radiation intensity of LPP EUV sources is discussed.

Solar Imaging UV/EUV Spectrometers Using TVLS Gratings

NASA Technical Reports Server (NTRS)

Thomas, Roger J.

2003-01-01

It is a particular challenge to develop a stigmatic spectrograph for UV, EUV wavelengths since the very low normal-incidence reflectance of standard materials most often requires that the design be restricted to a single optical element which must simultaneously provide both reimaging and spectral dispersion. This problem has been solved in the past by the use of toroidal gratings with uniform line-spaced rulings (TULS). A number of solar extreme ultraviolet (EUV) spectrometers have been based on such designs, including SOHO/CDS, Solar-B/EIS, and the sounding rockets Solar Extreme ultraviolet Research Telescope and Spectrograph (SERTS) and Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS). More recently, Kita, Harada, and collaborators have developed the theory of spherical gratings with varied line-space rulings (SVLS) operated at unity magnification, which have been flown on several astronomical satellite missions. We now combine these ideas into a spectrometer concept that puts varied-line space rulings onto toroidal gratings. Such TVLS designs are found to provide excellent imaging even at very large spectrograph magnifications and beam-speeds, permitting extremely high-quality performance in remarkably compact instrument packages. Optical characteristics of three new solar spectrometers based on this concept are described: SUMI and RAISE, two sounding rocket payloads, and NEXUS, currently being proposed as a Small-Explorer (SMEX) mission.

Ultraviolet safety assessments of insect light traps

PubMed Central

Sliney, David H.; Gilbert, David W.; Lyon, Terry

2016-01-01

ABSTRACT Near-ultraviolet (UV-A: 315–400 nm), “black-light,” electric lamps were invented in 1935 and ultraviolet insect light traps (ILTs) were introduced for use in agriculture around that time. Today ILTs are used indoors in several industries and in food-service as well as in outdoor settings. With recent interest in photobiological lamp safety, safety standards are being developed to test for potentially hazardous ultraviolet emissions. A variety of UV “Black-light” ILTs were measured at a range of distances to assess potential exposures. Realistic time-weighted human exposures are shown to be well below current guidelines for human exposure to ultraviolet radiation. These UV-A exposures would be far less than the typical UV-A exposure in the outdoor environment. Proposals are made for realistic ultraviolet safety standards for ILT products. PMID:27043058

Variability of pre-vitamin D3 effectiveness of UV appliances for skin tanning.

PubMed

Sayre, Robert M; Dowdy, John C; Shepherd, James G

2010-07-01

While there is limited documentation that certain indoor tanning lamps effectively produce vitamin D, the diversity of such devices has not been extensively surveyed. This study compares the spectral effectiveness of a variety of tanning units, and solar spectra, for ultraviolet (UV) photosynthesis of pre-vitamin D3 (preD3) and UV induced erythema. Well-established techniques exist for the calculation of spectral effectiveness for photobiological responses that have defined action spectra. Using spectroradiometric data from sunlamp measurements, and standard solar reference spectra, we computed effective irradiances using the CIE action spectrum for the production of preD3 in human skin and the ISO/CIE human erythema reference action spectrum. We found, as with sunlight at different times or latitude, the preD3 and erythemal effectiveness of sunlamps varied as a function of the UV-B proportion of the spectrum. Ratios of sunlamp preD3 to erythemal effectiveness ranged from approximately 0.5 to nearly 2.0, similar to ratios for sunlight. Optimal risk to benefit conditions for preD3 from solar UV exposure occurs under high solar altitude, low zenith angle, midday midsummer sunlight. Analogous optimal preD3 exposure conditions are provided by low to intermediate pressure sunlamps with greater UV-B spectral overlap with the preD3 action spectrum. Similar to low altitude or high latitude sunlight, high pressure tanning units, filtered for negligible UV-B emissions, have insignificant vitamin D benefit. We conclude that while vitamin D can be made by both UVB exposure from indoor tanning units and by exposure UVB from sunlight, the effect is also comparably variable. Unlike sunlight, indoor tanning offers privacy and environmental conditions for practical full body exposure, lowering the requisite exposure per skin surface area, and device timers limit the potential of overexposure. Guidance for optimal use of tanning sources for vitamin D benefit is needed. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

HST-COS Observations of AGNs. III. Spectral Constraints in the Lyman Continuum from Composite COS/G140L Data

NASA Astrophysics Data System (ADS)

Tilton, Evan M.; Stevans, Matthew L.; Shull, J. Michael; Danforth, Charles W.

2016-01-01

The rest-frame ultraviolet (UV) spectra of active galactic nuclei (AGNs) are important diagnostics of both accretion disk physics and their contribution to the metagalactic ionizing UV background. Though the mean AGN spectrum is well characterized with composite spectra at wavelengths greater than 912 Å, the shorter-wavelength extreme-UV (EUV) remains poorly studied. In this third paper in a series on the spectra of AGNs, we combine 11 new spectra taken with the Cosmic Origins Spectrograph on the Hubble Space Telescope with archival spectra to characterize the typical EUV spectral slope of AGNs from λrest ˜ 850 Å down to λrest ˜ 425 Å. Parameterizing this slope as a power law, we obtain Fν ∝ ν-0.72±0.26, but we also discuss the limitations and systematic uncertainties of this model. We identify broad emission features in this spectral region, including emission due to ions of O, Ne, Mg, and other species, and we limit the intrinsic He I 504 Å photoelectric absorption edge opacity to τHe I < 0.047. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

Spectrally-selective all-inorganic scattering luminophores for solar energy-harvesting clear glass windows.

PubMed

Alghamedi, Ramzy; Vasiliev, Mikhail; Nur-E-Alam, Mohammad; Alameh, Kamal

2014-10-16

All-inorganic visibly-transparent energy-harvesting clear laminated glass windows are the most practical solution to boosting building-integrated photovoltaics (BIPV) energy outputs significantly while reducing cooling- and heating-related energy consumption in buildings. By incorporating luminophore materials into lamination interlayers and using spectrally-selective thin-film coatings in conjunction with CuInSe2 solar cells, most of the visible solar radiation can be transmitted through the glass window with minimum attenuation while ultraviolet (UV) radiation is down-converted and routed together with a significant part of infrared radiation to the edges for collection by solar cells. Experimental results demonstrate a 10 cm × 10 cm vertically-placed energy-harvesting clear glass panel of transparency exceeding 60%, invisible solar energy attenuation greater than 90% and electrical power output near 30 Wp/m(2) mainly generated by infrared (IR) and UV radiations. These results open the way for the realization of large-area visibly-transparent energy-harvesting clear glass windows for BIPV systems.

Spectrally-selective all-inorganic scattering luminophores for solar energy-harvesting clear glass windows

PubMed Central

Alghamedi, Ramzy; Vasiliev, Mikhail; Nur-E-Alam, Mohammad; Alameh, Kamal

2014-01-01

All-inorganic visibly-transparent energy-harvesting clear laminated glass windows are the most practical solution to boosting building-integrated photovoltaics (BIPV) energy outputs significantly while reducing cooling- and heating-related energy consumption in buildings. By incorporating luminophore materials into lamination interlayers and using spectrally-selective thin-film coatings in conjunction with CuInSe2 solar cells, most of the visible solar radiation can be transmitted through the glass window with minimum attenuation while ultraviolet (UV) radiation is down-converted and routed together with a significant part of infrared radiation to the edges for collection by solar cells. Experimental results demonstrate a 10 cm × 10 cm vertically-placed energy-harvesting clear glass panel of transparency exceeding 60%, invisible solar energy attenuation greater than 90% and electrical power output near 30 Wp/m2 mainly generated by infrared (IR) and UV radiations. These results open the way for the realization of large-area visibly-transparent energy-harvesting clear glass windows for BIPV systems. PMID:25321890

Screening spectroscopy of prostate cancer

NASA Astrophysics Data System (ADS)

Yermolenko, S. B.; Voloshynskyy, D. I.; Fedoruk, O. S.

2015-11-01

The aim of the study was to establish objective parameters of the field of laser and incoherent radiation of different spectral ranges (UV, visible, IR) as a non-invasive optical method of interaction with different samples of biological tissues and fluids of patients to determine the state of prostate cancer and choosing the best personal treatment. The objects of study were selected venous blood plasma of patient with prostate cancer, histological sections of rat prostate gland in the postoperative period. As diagnostic methods have been used ultraviolet spectrometry samples of blood plasma in the liquid state, infrared spectroscopy middle range (2,5-25 microns) dry residue of plasma by spectral diagnostic technique of thin histological sections of biological tissues.

Ultraviolet radiation properties as applied to photoclimatherapy at the Dead Sea.

PubMed

Kudish, A I; Abels, D; Harari, M

2003-05-01

The Dead Sea basin, the lowest terrestrial point on earth, is recognized as a natural treatment center for patients with various cutaneous and rheumatic diseases. Psoriasis is the major skin disease treated at the Dead Sea with excellent improvement to complete clearance exceeding 85% after 4 weeks of treatment. These results were postulated to be associated with a unique spectrum of ultraviolet radiation present in the Dead Sea area. The UVB and UVA radiation at two sites is measured continuously by identical sets of broad-band Solar Light Co. Inc. meters (Philadelphia, PA). The spectral selectivity within the UVB and UVA spectrum was determined using a narrow-band spectroradiometer, UV-Optronics 742 (Orlando, FL). The optimum exposure time intervals for photoclimatherapy, defined as the minimum ratio of erythema to therapeutic radiation intensities, were also determined using a Solar Light Co. Inc. Microtops II, Ozone Monitor-Sunphotometer. The ultraviolet radiation at the Dead Sea is attenuated relative to Beer Sheva as a result of the increased optical path length and consequent enhanced scattering. The UVB radiation is attenuated to a greater extent than UVA and the shorter erythema UVB spectral range decreased significantly compared with the longer therapeutic UVB wavelengths. It was demonstrated that the relative attenuation within the UVB spectral range is greatest for the shorter erythema rays and less for the longer therapeutic UVB wavelengths, thus producing a greater proportion of the longer therapeutic UVB wavelengths in the ultraviolet spectrum. These measurements can be utilized to minimize the exposure to solar radiation by correlating the cumulative UVB radiation dose to treatment efficacy and by formulating a patient sun exposure treatment protocol for Dead Sea photoclimatherapy.

Reconstruction of solar UV irradiance since 1974

NASA Astrophysics Data System (ADS)

Krivova, N. A.; Solanki, S. K.; Wenzler, T.; Podlipnik, B.

2009-09-01

Variations of the solar UV irradiance are an important driver of chemical and physical processes in the Earth's upper atmosphere and may also influence global climate. Here we reconstruct solar UV irradiance in the range 115-400 nm over the period 1974-2007 by making use of the recently developed empirical extension of the Spectral And Total Irradiance Reconstruction (SATIRE) models employing Solar Ultraviolet Spectral Irradiance Monitor (SUSIM) data. The evolution of the solar photospheric magnetic flux, which is a central input to the model, is described by the magnetograms and continuum images recorded at the Kitt Peak National Solar Observatory between 1974 and 2003 and by the Michelson Doppler Imager instrument on SOHO since 1996. The reconstruction extends the available observational record by 1.5 solar cycles. The reconstructed Ly-α irradiance agrees well with the composite time series by Woods et al. (2000). The amplitude of the irradiance variations grows with decreasing wavelength and in the wavelength regions of special interest for studies of the Earth's climate (Ly-α and oxygen absorption continuum and bands between 130 and 350 nm) is 1-2 orders of magnitude stronger than in the visible or if integrated over all wavelengths (total solar irradiance).

High-resolution setup for measuring wavelength sensitivity of photoyellowing of translucent materials

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

Vaskuri, Anna, E-mail: anna.vaskuri@aalto.fi; Kärhä, Petri; Heikkilä, Anu

2015-10-15

Polystyrene and many other materials turn yellow when exposed to ultraviolet (UV) radiation. All photodegradation mechanisms including photoyellowing are functions of the exposure wavelength, which can be described with an action spectrum. In this work, a new high-resolution transmittance measurement setup based on lasers has been developed for measuring color changes, such as the photoyellowing of translucent materials aged with a spectrograph. The measurement setup includes 14 power-stabilized laser lines between 325 nm and 933 nm wavelengths, of which one at a time is directed on to the aged sample. The power transmitted through the sample is measured with amore » silicon detector utilizing an integrating sphere. The sample is mounted on a high-resolution XY translation stage. Measurement at various locations aged with different wavelengths of exposure radiation gives the transmittance data required for acquiring the action spectrum. The combination of a UV spectrograph and the new high-resolution transmittance measurement setup enables a novel method for studying the UV-induced ageing of translucent materials with a spectral resolution of 3–8 nm, limited by the adjustable spectral bandwidth range of the spectrograph. These achievements form a significant improvement over earlier methods.« less

VizieR Online Data Catalog: Spectra of a Holmium in the near-UV. I. Ho I. (Al-Labady+, 2017)

NASA Astrophysics Data System (ADS)

Al-Labady, N.; Ozdalgic, B.; Er, A.; Guzelcimen, F.; Ozturk, I. K.; Kroger, S.; Kruzins, A.; Tamanis, M.; Ferber, R.; Basar, G.

2017-04-01

The high-resolution spectra of Holmium (Ho) were recorded with a Fourier Transform spectrometer IFS125 HR at the Laser Centre of the University of Latvia in Riga. Two Ho spectra were recorded, one with argon (Ar) as a buffer gas and one with neon (Ne). The spectra cover the ultraviolet spectral range from 25000 up to 31530cm-1, or 317 to 400nm, respectively. (1 data file).

Potential Jupiter astmospheric constituents: candidates for the mass spectrometer in the Galileo atmospheric probe

NASA Technical Reports Server (NTRS)

Keane, T. C.; Yuan, F.; Ferris, J. P.

1996-01-01

An array of carbon-hydrogen-nitrogen (CHN) compounds are formed when mixtures of ammonia and acetylene are photolyzed with ultraviolet (UV) light. Some of these compounds, formed in our investigation of pathways for HCN synthesis on Jupiter, have not been encountered previously in observational, theoretical or laboratory photochemical studies. Knowledge of these structures may facilitate the interpretation of the mass spectral data obtained by the Galileo probe as it passed through the atmosphere of Jupiter.

Epidermal UV-A absorbance and whole-leaf flavonoid composition in pea respond more to solar blue light than to solar UV radiation.

PubMed

Siipola, Sari M; Kotilainen, Titta; Sipari, Nina; Morales, Luis O; Lindfors, Anders V; Robson, T Matthew; Aphalo, Pedro J

2015-05-01

Plants synthesize phenolic compounds in response to certain environmental signals or stresses. One large group of phenolics, flavonoids, is considered particularly responsive to ultraviolet (UV) radiation. However, here we demonstrate that solar blue light stimulates flavonoid biosynthesis in the absence of UV-A and UV-B radiation. We grew pea plants (Pisum sativum cv. Meteor) outdoors, in Finland during the summer, under five types of filters differing in their spectral transmittance. These filters were used to (1) attenuate UV-B; (2) attenuate UV-B and UV-A < 370 nm; (3) attenuate UV-B and UV-A; (4) attenuate UV-B, UV-A and blue light; and (5) as a control not attenuating these wavebands. Attenuation of blue light significantly reduced the flavonoid content in leaf adaxial epidermis and reduced the whole-leaf concentrations of quercetin derivatives relative to kaempferol derivatives. In contrast, UV-B responses were not significant. These results show that pea plants regulate epidermal UV-A absorbance and accumulation of individual flavonoids by perceiving complex radiation signals that extend into the visible region of the solar spectrum. Furthermore, solar blue light instead of solar UV-B radiation can be the main regulator of phenolic compound accumulation in plants that germinate and develop outdoors. © 2014 John Wiley & Sons Ltd.

Ultraviolet Communication for Medical Applications

DTIC Science & Technology

2015-06-01

DEI procured several UVC phosphors and tested them with vacuum UV (VUV) excitation. Available emission peaks include: 226 nm, 230 nm, 234 nm, 242...SUPPLEMENTARY NOTES Report contains color. 14. ABSTRACT Under this Phase II SBIR effort, Directed Energy Inc.’s (DEI) proprietary ultraviolet ( UV ...15. SUBJECT TERMS Non-line-of-sight (NLOS), networking, optical communication, plasma-shells, short range, ultraviolet ( UV ) light 16. SECURITY

Ultraviolet radiation, human health, and the urban forest

Treesearch

Gordon M. Heisler; Richard H. Grant

2000-01-01

Excess exposure to ultraviolet (UV) radiation from the sun, particularly the ultraviolet B (UVB) portion, has been linked with adverse effects on human health ranging from skin cancers to eye diseases such as cataracts. Trees may prevent even greater disease rates in humans by reducing UV exposure. Tree shade greatly reduces UV irradiance when both the sun and sky are...

Prediction of the Ultraviolet-Visible Absorption Spectra of Polycyclic Aromatic Hydrocarbons (Dibenzo and Naphtho) Derivatives of Fluoranthene.

PubMed

Oña-Ruales, Jorge O; Ruiz-Morales, Yosadara

2017-06-01

The annellation theory method has been used to predict the locations of maximum absorbance (LMA) of the ultraviolet-visible (UV-Vis) spectral bands in the group of polycyclic aromatic hydrocarbons (PAHs) C 24 H 14 (dibenzo and naphtho) derivatives of fluoranthene (DBNFl). In this group of 21 PAHs, ten PAHs present a sextet migration pattern with four or more benzenoid rings that is potentially related to a high molecular reactivity and high mutagenic conduct. This is the first time that the locations of maximum absorbance in the UV-Vis spectra of naphth[1,2- a]aceanthrylene, dibenz[ a,l]aceanthrylene, indeno[1,2,3- de]naphthacene, naphtho[1,2- j]fluoranthene, naphth[2,1- e]acephenanthrylene, naphth[2,1- a]aceanthrylene, dibenz[ a,j]aceanthrylene, naphth[1,2- e]acephenanthrylene, and naphtho[2,1- j]fluoranthene have been predicted. Also, this represents the first report about the application of the annellation theory for the calculation of the locations of maximum absorbance in the UV-Vis spectra of PAHs with five-membered rings. Furthermore, this study constitutes the premier investigation beyond the pure benzenoid classical approach toward the establishment of a generalized annellation theory that will encompass not only homocyclic benzenoid and non-benzenoid PAHs, but also heterocyclic compounds.

Calibration and Limitations of the Mg II Line-based Black Hole Masses

NASA Astrophysics Data System (ADS)

Woo, Jong-Hak; Le, Huynh Anh N.; Karouzos, Marios; Park, Dawoo; Park, Daeseong; Malkan, Matthew A.; Treu, Tommaso; Bennert, Vardha N.

2018-06-01

We present single-epoch black hole mass ({M}BH}) calibrations based on the rest-frame ultraviolet (UV) and optical measurements of Mg II 2798 Å and Hβ 4861 Å lines and the active galactic nucleus (AGN) continuum, using a sample of 52 moderate-luminosity AGNs at z ∼ 0.4 and z ∼ 0.6 with high-quality Keck spectra. We combine this sample with a large number of luminous AGNs from the Sloan Digital Sky Survey to increase the dynamic range for a better comparison of UV and optical velocity and luminosity measurements. With respect to the reference {M}BH} based on the line dispersion of Hβ and continuum luminosity at 5100 Å, we calibrate the UV and optical mass estimators by determining the best-fit values of the coefficients in the mass equation. By investigating whether the UV estimators show a systematic trend with Eddington ratio, FWHM of Hβ, Fe II strength, or UV/optical slope, we find no significant bias except for the slope. By fitting the systematic difference of Mg II-based and Hβ-based masses with the L 3000/L 5100 ratio, we provide a correction term as a function of the spectral index as ΔC = 0.24 (1 + α λ ) + 0.17, which can be added to the Mg II-based mass estimators if the spectral slope can be well determined. The derived UV mass estimators typically show >∼0.2 dex intrinsic scatter with respect to the Hβ-based {M}BH}, suggesting that the UV-based mass has an additional uncertainty of ∼0.2 dex, even if high-quality rest-frame UV spectra are available.

Global Mapping of Underwater UV Irradiances and DNA-Weighted Exposures using TOMS and SeaWiFS Data Products

NASA Technical Reports Server (NTRS)

Vasilkov, Alexander; Krotkov, Nickolay; Herman, Jay; McClain, Charles; Arrigo, Kevin; Robinson, Wayne

1999-01-01

The global stratospheric ozone-layer depletion results In an increase in biologically harmful ultraviolet (UV) radiation reaching the surface and penetrating to ecologically significant depths in natural waters. Such an increase can be estimated on a global scale by combining satellite estimates of UV irradiance at the ocean surface from the Total Ozone Mapping Spectrometer (TOMS) satellite instrument with the SeaWIFS satellite ocean-color measurements in the visible spectral region. In this paper we propose a model of seawater optical properties in the UV spectral region based on the Case I water model in the visible range. The inputs to the model are standard monthly SeaWiFS products: chlorophyll concentration and the diffuse attenuation coefficient at 490nm. Penetration of solar UV radiation to different depths in open ocean waters is calculated using the RT (radiative transfer) quasi-single scattering approximation (QSSA). The accuracy of the QSSA approximation in the water is tested using more accurate codes. The sensitivity study of the underwater UV irradiance to atmospheric and oceanic optical properties have shown that the main environmental parameters controlling the absolute levels of the UVB (280-320nm) and DNA-weighted irradiance underwater are: solar-zenith angle, cloud transmittance, water optical properties, and total ozone. Weekly maps of underwater UV irradiance and DNA-weighted exposure are calculated using monthly-mean SeaWiFS chlorophyll and diffuse attenuation coefficient products, daily SeaWiFS cloud fraction data, and the TOMS-derived surface UV irradiance daily maps. The final products include global maps of weekly-average UVB irradiance and DNA-weighted daily exposures at 3m and 10m, and depths where the UVB irradiance and DNA-weighted dose rate at local noon are equal to 10% of their surface values.

Constraining the Accretion Mode in LINER 1.9s

NASA Astrophysics Data System (ADS)

Sabra, Bassem; Der Sahaguian, Elias; Badr, Elie

2016-01-01

The accretion mode and the dominant power source in low-ionization nuclear emission-line regions (LINERs), a class of active galactic nuclei (AGN), are still elusive. We focus on a sample of 22 LINER 1.9s (Ho et al. 1997), a subclass of LINERs that show broad Halpha lines, a signature of blackhole-powered accretion, to test the hypothesis that the ionizing continuum emitted by a radiatively inefficient accretion flow (RIAF) could lead to the LINER ultraviolet (UV) emission-line ratios. Optical line-ratio diagrams are a weak diagnostic tool in distinguishing between possible power sources (Sabra et al. 2003). We search the Mikulski Archive for Space Telescopes (MAST) for UV spectra of the objects in the above sample and also perform photoionization simulations using CLOUDY (Ferland et al. 2013). Unfortunately, only one object (NGC 1052; Gabel et al. 2000) of the 22 LINER 1.9s has UV spectra that cover many emission lines; the rest of the objects either do not have any UV spectra, the spectral coverage is in-adequate, or the spectra have very low signal-to-noise ratios. Our photoionization simulations set up two identical grids of clouds with a range of densities and ionization parameters. We illuminate one grid with radiation emitted by a thin accretion disk (AD) and we illuminate the other grid with radiation from a RIAF. We overplot the UV emission-line ratio predictions for AD and RIAF illumination, together with the available line ratios for NGC 1052. Initial results show that UV lines could be used as diagnostics for the accretion mode in AGN. More UV spectral coverage of LINER 1.9s is needed in order to more fully utilize the diagnostic powers of UV emission line ratios.

Solar UV light regulates flavonoid metabolism in apple (Malus x domestica).

PubMed

Henry-Kirk, Rebecca A; Plunkett, Blue; Hall, Miriam; McGhie, Tony; Allan, Andrew C; Wargent, Jason J; Espley, Richard V

2018-03-01

Ultraviolet-B light (UV-B) is one environmental signal perceived by plants that affects the flavonoid pathway and influences the levels of anthocyanins, flavonols, and proanthocyanidins. To understand the mechanisms underlying UV exposure, apple trees were grown under spectral filters that altered transmission of solar UV light. Fruit analysis showed that UV induced changes in physiology, metabolism, and gene expression levels during development over a season. These changes were sustained after storage. Under low UV, ripening was delayed, fruit size decreased, and anthocyanin and flavonols were reduced. Expression analysis showed changes in response to UV light levels for genes in the regulation and biosynthesis of anthocyanin and flavonols. Transcription of flavonol synthase (FLS), ELONGATED HYPOCOTYL 5 (HY5), MYB10, and MYB22 were down-regulated throughout fruit development under reduced UV. Functional testing showed that the FLS promoter was activated by HY5, and this response was enhanced by the presence of MYB22. The MYB22 promoter can also be activated by the anthocyanin regulator, MYB10. As ambient levels of UV light vary around the globe, this study has implications for future crop production, the quality of which can be determined by the response to UV. © 2018 John Wiley & Sons Ltd.

Optical characteristics of natural waters protect amphibians from UV-B in the U.S. Pacific Northwest

USGS Publications Warehouse

Palen, Wendy J.; Schindler, David E.; Adams, Michael J.; Pearl, Christopher A.; Bury, R. Bruce; Diamond, S.A.

2002-01-01

Increased exposure to ultraviolet-B (UV-B) radiation has been proposed as a major environmental stressor leading to global amphibian declines. Prior experimental evidence from the U.S. Pacific Northwest (PNW) indicating the acute embryonic sensitivity of at least four amphibian species to UV-B has been central to the literature about amphibian decline. However, these results have not been expanded to address population-scale effects and natural landscape variation in UV-B transparency of water at amphibian breeding sites: both necessary links to assess the importance of UV-B for amphibian declines. We quantified the UV-B transparency of 136 potential amphibian breeding sites to establish the pattern of UV-B exposure across two montane regions in the PNW. Our data suggest that 85% of sites are naturally protected by dissolved organic matter in pond water, and that only a fraction of breeding sites are expected to experience UV-B intensities exceeding levels associated with elevated egg mortality. Thus, the spectral characteristics of natural waters likely mediate the physiological effects of UV-B on amphibian eggs in all but the clearest waters. These data imply that UV-B is unlikely to cause broad amphibian declines across the landscape of the American Northwest.

Free radicals induced by sunlight in different spectral regions - in vivo versus ex vivo study.

PubMed

Lohan, Silke B; Müller, Robert; Albrecht, Stephanie; Mink, Kathrin; Tscherch, Kathrin; Ismaeel, Fakher; Lademann, Jürgen; Rohn, Sascha; Meinke, Martina C

2016-05-01

Sunlight represents an exogenous factor stimulating formation of free radicals which can induce cell damage. To assess the effect of the different spectral solar regions on the development of free radicals in skin, in vivo electron paramagnetic resonance (EPR) investigations with human volunteers and ex vivo studies on excised human and porcine skin were carried out. For all skin probes, the ultraviolet (UV) spectral region stimulates the most intensive radical formation, followed by the visible (VIS) and the near infrared (NIR) regions. A comparison between the different skin models shows that for UV light, the fastest and highest production of free radicals could be detected in vivo, followed by excised porcine and human skin. The same distribution pattern was found for the VIS/NIR spectral regions, whereby the differences in radical formation between in vivo and ex vivo were less pronounced. An analysis of lipid composition in vivo before and after exposure to UV light clearly showed modifications in several skin lipid components; a decrease of ceramide subclass [AP2] and an increase of ceramide subclass [NP2], sodium cholesterol sulphate and squalene (SQ) were detectable. In contrast, VIS/NIR irradiation led to an increase of ceramides [AP2] and SCS, and a decrease of SQ. These results, which are largely comparable for the different skin models investigated in vivo and ex vivo, indicate that radiation exposure in different spectral regions strongly influences radical production in skin and also results in changes in skin lipid composition, which is essential for barrier function. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Ultraviolet, visible, and infrared laser delivery using laser-to-fiber coupling via a grazing-incidence-based hollow taper

NASA Astrophysics Data System (ADS)

Ilev, Ilko K.; Waynant, Ronald W.

2001-01-01

We present a novel all-optical-waveguide method for ultraviolet (UV), visible (VIS) and infrared (IR) laser delivery including a lens-free method of laser-to-fiber coupling using a simple uncoated glass hollow taper. Based on the grazing incidence effect, the hollow taper provides a way of direct launching, without any intermediate focusing elements, high power laser radiation into delivery fibers. Because of the mutual action of the nearly parallel laser excitation, the mode coupling process, and mode filtering effect, the hollow taper serves as a mode converter that transforms the highly multimode profile of the input laser emission into a high-quality Gaussian-shaped profile at the taper output. When the grazing incidence effect of the taper is applied to laser delivery, the maintenance of high reflectance coefficients in a wide spectral region allows to utilize the same uncoated hollow taper for laser radiation in the UV, VIS and IR ranges. Applying the experimental hollow-taper based delivery systems, we obtain high laser- to-taper and taper-to-fiber coupling efficiencies.

[Effect of long-wave ultraviolet light (UV-A) and medium-wave ultraviolet rays (UV-B) on human skin. Critical comparison].

PubMed

Raab, W

1980-04-15

When discussing the effects of ultraviolet radiation on human skin, one should carefully distinguish between the long wave ultraviolet light (UV-A) and the short wave radiations (UV-B and UV-C). Ultraviolet A induces immediate pigmentation but, if high energies are applied, a permanent pigmentation is elicited. This type of ultraviolet A-induced pigmentation has been called "spontaneous" pigmentation as no erythematous reaction is necessary to induce or accelerate melanine formation. Ultraviolet B provokes erythema and consecutive pigmentation. Upon chronic exposure, ultraviolet B causes the wellknown actinic damage of the skin and even provokes carcinoma. With exposures to the sunlight (global radiation), one should be most careful. The public must be informed extensively about the dangers of excessive sunbaths. The use of artificial "suns" with spectra between 260 and 400 nm is limited as it may cause the same type of damage as the global radiation. An exact schedule for use of artificial lamps is strongly recommended. After one cycle of exposures, an interruption is necessary until the next cycle of irradiations may start. Upon continual use for tanning of the skin, artificial lamps may provoke irreversible damage of the skin. Radiation sources with emission spectra of wavelengths between 315 and 400 nm exclusively are well suited for the induction of skin pigmentation (cosmetic use). Potent radiation such as UVASUN systems provoke a "pleasant" permanent pigmentation after exposures for less than one hour. The use of ultraviolet A (UV-A) does not carry any risk for the human skin.

Berkeley extreme-ultraviolet airglow rocket spectrometer: BEARS.

PubMed

Cotton, D M; Chakrabarti, S

1992-09-20

We describe the Berkeley extreme-UV airglow rocket spectrometer, which is a payload designed to test several thermospheric remote-sensing concepts by measuring the terrestrial O I far-UV and extreme-UV dayglow and the solar extreme-UV spectrum simultaneously. The instrument consisted of two near-normal Rowland mount spectrometers and a Lyman-alpha photometer. The dayglow spectrometer covered two spectral regions from 980 to 1040 A and from 1300 to 1360 A with 1.5-A resolution. The solar spectrometer had a bandpass of 250-1150 A with an ~ 10-A resolution. All three spectra were accumulated by using a icrochannel-plate-intensified, two-dimensional imaging detector with three separate wedge-and strip anode readouts. The hydrogen Lyman-alpha photometer was included to monitor the solar Lyman-alpha irradiance and geocoronal Lyman-alpha emissions. The instrument was designed, fabricated, and calibrated at the University of California, Berkeley and was successfully launched on 30 September 1988 aboard the first test flight of a four-stage sounding rocket, Black Brant XII.

ZnO nanoneedle/H2O solid-liquid heterojunction-based self-powered ultraviolet detector

PubMed Central

2013-01-01

ZnO nanoneedle arrays were grown vertically on a fluorine-doped tin oxide-coated glass by hydrothermal method at a relatively low temperature. A self-powered photoelectrochemical cell-type UV detector was fabricated using the ZnO nanoneedles as the active photoanode and H2O as the electrolyte. This solid-liquid heterojunction offers an enlarged ZnO/water contact area and a direct pathway for electron transport simultaneously. By connecting this UV photodetector to an ammeter, the intensity of UV light can be quantified using the output short-circuit photocurrent without a power source. High photosensitivity, excellent spectral selectivity, and fast photoresponse at zero bias are observed in this UV detector. The self-powered behavior can be well explained by the formation of a space charge layer near the interface of the solid-liquid heterojunction, which results in a built-in potential and makes the solid-liquid heterojunction work in photovoltaic mode. PMID:24103153

Ultraviolet emission in Tm3+-doped fluoride fiber pumped with two infrared wavelengths

NASA Astrophysics Data System (ADS)

Mejía, E. B.

2006-12-01

An infrared, two-wavelength pumping scheme for generating UV in Tm3+-doped fibers is investigated and proposed as an alternative because the pump wavelengths are accessible from laser diodes. Spectral characterizations of fiber samples with different concentrations revealed that moderate concentrations are best suitable to produce UV (348-362nm) emission when single—or double-line pumping with 1117 and 725nm. Detailed spectroscopic measurements realized to the fiber with the best performance, the 2000ppmwt, allowed to obtain the copumping wavelengths (in the ˜725nm region) that enhanced the UV emission. For example, when applying tens of milliwatts at 725nm, which represented a 28% increase of total pump power, the UV emission increased in an avalanchelike fashion up to three orders of magnitude. Then, a high-power 1117nm source that currently exists in the market and a moderate power 725nm source under development are possible to be used as pumps for this scheme.

Low temperature plasmas induced in SF6 by extreme ultraviolet (EUV) pulses

NASA Astrophysics Data System (ADS)

Bartnik, A.; Skrzeczanowski, W.; Czwartos, J.; Kostecki, J.; Fiedorowicz, H.; Wachulak, P.; Fok, T.

2018-06-01

In this work, a comparative study of extreme ultraviolet (EUV) induced low temperature SF6-based plasmas, created using two different irradiation systems, was performed. Both systems utilized laser-produced plasma (LPP) EUV sources. The essential difference between the systems concerned the formation of the driving EUV beam. The first one contained an efficient ellipsoidal EUV collector allowing for focusing of the EUV radiation at a large distance from the LPP source. The spectrum of focused radiation was limited to the long-wavelength part of the total LPP emission, λ > 8 nm, due to the reflective properties of the collector. The second system did not contain any EUV collector. The gas to be ionized was injected in the vicinity of the LPP, at a distance of the order of 10 mm. In both systems, energies of the driving photons were high enough for dissociative ionization of the SF6 molecules and ionization of atoms or even singly charged ions. Plasmas, created due to these processes, were investigated by spectral measurements in the EUV, ultraviolet (UV), and visible (VIS) spectral ranges. These low temperature plasmas were employed for preliminary experiments concerning surface treatment. The formation of pronounced nanostructures on the silicon surface after plasma treatment was demonstrated.

Blood characterization using UV/vis spectroscopy

NASA Astrophysics Data System (ADS)

Mattley, Yvette D.; Mitrani-Gold, F.; Orton, S.; Bacon, Christina P.; Leparc, German F.; Bayona, M.; Potter, Robert L.; Garcia-Rubio, Luis H.

1995-05-01

The current methods used for typing blood involve an agglutination reaction which results from the association of specific antibodies with antigens present on the erythrocyte cell surface. While this method is effective, it requires involved laboratory procedures to detect the cell surface antigens. As an alternative technique, uv/vis spectroscopy has been investigated as a novel way to characterize and differentiate the blood types. Typing with this technique is based on spectral differences which appear throughout portions of both the ultraviolet and visible range. The origin of these spectral differences is unknown and presently under investigation. They may be due to intrinsic absorption differences at the molecular level, and/or they may be due to scattering differences brought about by either subtle variation in cell surface characteristics, cell shape or state of aggregation. As the background optical density in these samples is identified and accounted for, the spectral differences become more defined. This work and the continuation of this project will be included in a general database encompassing a wide range of blood samples. In addition, long term goals involve the investigation of diseased blood with the potential of providing a more rapid diagnosis for blood borne pathogens.

8 years of Solar Spectral Irradiance Observations from the ISS with the SOLAR/SOLSPEC Instrument

NASA Astrophysics Data System (ADS)

Damé, L.; Bolsée, D.; Meftah, M.; Irbah, A.; Hauchecorne, A.; Bekki, S.; Pereira, N.; Cessateur, G.; Marchand, M.; Thiéblemont, R.; Foujols, T.

2016-12-01

Accurate measurements of Solar Spectral Irradiance (SSI) are of primary importance for a better understanding of solar physics and of the impact of solar variability on climate (via Earth's atmospheric photochemistry). The acquisition of a top of atmosphere reference solar spectrum and of its temporal and spectral variability during the unusual solar cycle 24 is of prime interest for these studies. These measurements are performed since April 2008 with the SOLSPEC spectro-radiometer from the far ultraviolet to the infrared (166 nm to 3088 nm). This instrument, developed under a fruitful LATMOS/BIRA-IASB collaboration, is part of the Solar Monitoring Observatory (SOLAR) payload, externally mounted on the Columbus module of the International Space Station (ISS). The SOLAR mission, with its actual 8 years duration, will cover almost the entire solar cycle 24. We present here the in-flight operations and performances of the SOLSPEC instrument, including the engineering corrections, calibrations and improved know-how procedure for aging corrections. Accordingly, a SSI reference spectrum from the UV to the NIR will be presented, together with its UV variability, as measured by SOLAR/SOLSPEC. Uncertainties on these measurements and comparisons with other instruments will be briefly discussed.

Spectral Skyline Separation: Extended Landmark Databases and Panoramic Imaging

PubMed Central

Differt, Dario; Möller, Ralf

2016-01-01

Evidence from behavioral experiments suggests that insects use the skyline as a cue for visual navigation. However, changes of lighting conditions, over hours, days or possibly seasons, significantly affect the appearance of the sky and ground objects. One possible solution to this problem is to extract the “skyline” by an illumination-invariant classification of the environment into two classes, ground objects and sky. In a previous study (Insect models of illumination-invariant skyline extraction from UV (ultraviolet) and green channels), we examined the idea of using two different color channels available for many insects (UV and green) to perform this segmentation. We found out that for suburban scenes in temperate zones, where the skyline is dominated by trees and artificial objects like houses, a “local” UV segmentation with adaptive thresholds applied to individual images leads to the most reliable classification. Furthermore, a “global” segmentation with fixed thresholds (trained on an image dataset recorded over several days) using UV-only information is only slightly worse compared to using both the UV and green channel. In this study, we address three issues: First, to enhance the limited range of environments covered by the dataset collected in the previous study, we gathered additional data samples of skylines consisting of minerals (stones, sand, earth) as ground objects. We could show that also for mineral-rich environments, UV-only segmentation achieves a quality comparable to multi-spectral (UV and green) segmentation. Second, we collected a wide variety of ground objects to examine their spectral characteristics under different lighting conditions. On the one hand, we found that the special case of diffusely-illuminated minerals increases the difficulty to reliably separate ground objects from the sky. On the other hand, the spectral characteristics of this collection of ground objects covers well with the data collected in the skyline databases, increasing, due to the increased variety of ground objects, the validity of our findings for novel environments. Third, we collected omnidirectional images, as often used for visual navigation tasks, of skylines using an UV-reflective hyperbolic mirror. We could show that “local” separation techniques can be adapted to the use of panoramic images by splitting the image into segments and finding individual thresholds for each segment. Contrarily, this is not possible for ‘global’ separation techniques. PMID:27690053

Improving the accuracy of S02 column densities and emission rates obtained from upward-looking UV-spectroscopic measurements of volcanic plumes by taking realistic radiative transfer into account

USGS Publications Warehouse

Kern, Christoph; Deutschmann, Tim; Werner, Cynthia; Sutton, A. Jeff; Elias, Tamar; Kelly, Peter J.

2012-01-01

Sulfur dioxide (SO2) is monitored using ultraviolet (UV) absorption spectroscopy at numerous volcanoes around the world due to its importance as a measure of volcanic activity and a tracer for other gaseous species. Recent studies have shown that failure to take realistic radiative transfer into account during the spectral retrieval of the collected data often leads to large errors in the calculated emission rates. Here, the framework for a new evaluation method which couples a radiative transfer model to the spectral retrieval is described. In it, absorption spectra are simulated, and atmospheric parameters are iteratively updated in the model until a best match to the measurement data is achieved. The evaluation algorithm is applied to two example Differential Optical Absorption Spectroscopy (DOAS) measurements conducted at Kilauea volcano (Hawaii). The resulting emission rates were 20 and 90% higher than those obtained with a conventional DOAS retrieval performed between 305 and 315 nm, respectively, depending on the different SO2 and aerosol loads present in the volcanic plume. The internal consistency of the method was validated by measuring and modeling SO2 absorption features in a separate wavelength region around 375 nm and comparing the results. Although additional information about the measurement geometry and atmospheric conditions is needed in addition to the acquired spectral data, this method for the first time provides a means of taking realistic three-dimensional radiative transfer into account when analyzing UV-spectral absorption measurements of volcanic SO2 plumes.

Application of principal component regression and partial least squares regression in ultraviolet spectrum water quality detection

NASA Astrophysics Data System (ADS)

Li, Jiangtong; Luo, Yongdao; Dai, Honglin

2018-01-01

Water is the source of life and the essential foundation of all life. With the development of industrialization, the phenomenon of water pollution is becoming more and more frequent, which directly affects the survival and development of human. Water quality detection is one of the necessary measures to protect water resources. Ultraviolet (UV) spectral analysis is an important research method in the field of water quality detection, which partial least squares regression (PLSR) analysis method is becoming predominant technology, however, in some special cases, PLSR's analysis produce considerable errors. In order to solve this problem, the traditional principal component regression (PCR) analysis method was improved by using the principle of PLSR in this paper. The experimental results show that for some special experimental data set, improved PCR analysis method performance is better than PLSR. The PCR and PLSR is the focus of this paper. Firstly, the principal component analysis (PCA) is performed by MATLAB to reduce the dimensionality of the spectral data; on the basis of a large number of experiments, the optimized principal component is extracted by using the principle of PLSR, which carries most of the original data information. Secondly, the linear regression analysis of the principal component is carried out with statistic package for social science (SPSS), which the coefficients and relations of principal components can be obtained. Finally, calculating a same water spectral data set by PLSR and improved PCR, analyzing and comparing two results, improved PCR and PLSR is similar for most data, but improved PCR is better than PLSR for data near the detection limit. Both PLSR and improved PCR can be used in Ultraviolet spectral analysis of water, but for data near the detection limit, improved PCR's result better than PLSR.

Space Weathering on Icy Satellites in the Outer Solar System

NASA Technical Reports Server (NTRS)

Clark, R. N.; Perlman, Z.; Pearson, N.; Cruikshank, D. P.

2014-01-01

Space weathering produces well-known optical effects in silicate minerals in the inner Solar System, for example, on the Moon. Space weathering from solar wind and UV (ultraviolet radiation) is expected to be significantly weaker in the outer Solar System simply because intensities are low. However, cosmic rays and micrometeoroid bombardment would be similar to first order. That, combined with the much higher volatility of icy surfaces means there is the potential for space weathering on icy outer Solar System surfaces to show optical effects. The Cassini spacecraft orbiting Saturn is providing evidence for space weathering on icy bodies. The Cassini Visible and Infrared Mapping Spectrometer (VIMS) instrument has spatially mapped satellite surfaces and the rings from 0.35-5 microns and the Ultraviolet Imaging Spectrograph (UVIS) instrument from 0.1 to 0.2 microns. These data have sampled a complex mixing space between H2O ice and non-ice components and they show some common spectral properties. Similarly, spectra of the icy Galilean satellites and satellites in the Uranian system have some commonality in spectral properties with those in the Saturn system. The UV absorber is spectrally similar on many surfaces. VIMS has identified CO2, H2 and trace organics in varying abundances on Saturn's satellites. We postulate that through the spatial relationships of some of these compounds that they are created and destroyed through space weathering effects. For example, the trapped H2 and CO2 observed by VIMS in regions with high concentrations of dark material may in part be space weathering products from the destruction of H2O and organic molecules. The dark material, particularly on Iapetus which has the highest concentration in the Saturn system, is well matched by space-weathered silicates in the .4 to 2.6 micron range, and the spectral shapes closely match those of the most mature lunar soils, another indicator of space weathered material.

Ultraviolet radiation-blocking characteristics of contact lenses: relevance to eye protection for psoralen-sensitised patients.

PubMed

Anstey, A; Taylor, D; Chalmers, I; Ansari, E

1999-10-01

Nine brands of contact lens marketed as "UV protective" were tested for ultraviolet (UV) transmission in order to assess potential suitability for psoralen-sensitised patients. UV-transmission characteristics of hydrated lenses was tested with a Bentham monochromator spectro-radiometer system. All lenses showed minimal transmission loss in the visible band. The performance of the nine lenses was uniform for ultraviolet B radiation with negligible transmission, but showed variation in transmission for ultraviolet A radiation. None of the lenses complied with UV-transmission criteria used previously to assess UV-blocking spectacles. Only two lenses had UV-blocking characteristics which came close to the arbitrary criteria used. The performance of ordinary soft and hard lenses was very similar, with negligible blocking of UV radiation. None of the nine contact lenses marketed as "UV protective" excluded sufficient UVA to comply with criteria in current use to assess UV protection in spectacles for psoralen-sensitised patients. However, the improved UV-blocking characteristics of contact lenses identified in this paper compared to previous studies suggests that such a contact lens will soon become available. Meanwhile, contact lens-wearing systemically sensitised PUVA patients should continue to wear approved spectacles for eye protection whilst photosensitised with psoralen.

Occupational Skin Hazards From Ultraviolet (UV) Exposures

NASA Astrophysics Data System (ADS)

Urbach, F.; Wolbarsht, M. L.

1980-10-01

The various types of UV effects on the skin are classified according to the part of the spectrum and their beneficial or deleterious nature. Some hazardous ultraviolet sources used in industrial processes are described, and examples of photoallergy, phototoxicity, and photosensitization resulting from UV exposures are given. The incidence of skin cancer as a function of geographical location and exposure to sunlight is discussed in relation to natural and artificial exposures to long and short wavelength UV, especially in connection with tanning booths. The conclusion is reached that there is enough ultraviolet in a normal environment to propose a hazard, and additional ultraviolet exposure from industrial or consumer sources is not necessary, and should be eliminated wherever possible.

Occupational Skin Hazards From Ultraviolet (UV) Exposures

NASA Astrophysics Data System (ADS)

Urbach, F.; Wolbarsht, M. L.

1981-11-01

The various types of UV effects on the skin are classified according to the part of the spectrum and their beneficial or deleterious nature. Some hazardous ultraviolet sources used in industrial processes are described, and examples of photoallergy, phototoxicity, and photosensitization resulting from UV exposures are given. The incidence of skin cancer as a function of geographical location and exposure to sunlight is discussed in relation to natural and artificial exposures to long and short wavelength UV, especially in connection with tanning booths. The conclusion is reached that there is enough ultraviolet in a normal environment to propose a hazard, and additional ultraviolet exposure from industrial or consumer sources is not necessary, and should be eliminated wherever possible.

Can we use the ozone response in a CCM to say which solar spectral irradiance is most likely correct?

NASA Astrophysics Data System (ADS)

Ball, William; Rozanov, Eugene; Shapiro, Anna

2015-04-01

Ozone plays a key role in the temperature structure of the Earth's atmosphere and absorbs damaging ultraviolet (UV) solar radiation. Evidence suggests that variations in stratospheric ozone resulting from changes in solar UV output may have an important role to play in weather over the North Atlantic and Europe on decadal timescales through a "top-down" coupling with the troposphere. However, the magnitude of the stratospheric response to the Sun over the 11-year solar cycle (SC) depends primarily on how much the UV changes. SC UV changes differ significantly between different observational instruments and the observations and models. The substantial disagreements between existing SSI datasets lead to different atmospheric responses when they are used in climate models and, therefore, we still cannot fully understand and simulate the ozone variability. We use the SOCOL chemistry-climate model, in specified dynamics mode, to calculate the atmospheric response from using different spectral irradiance from the SATIRE-S and NRLSSI models and with SORCE observations and a constant Sun. We compare the ozone and hydroxl results from these runs with observations to try to determine which SSI dataset is most likely to be correct. This is important to get a better understanding of which SSI dataset should be used in climate modelling and what magnitude of UV variability the Sun has. This will lead to a better understanding of the Sun's influence upon our climate and weather.

UV-Vis, infrared, and mass spectroscopy of electron irradiated frozen oxygen and carbon dioxide mixtures with water

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

Jones, Brant M.; Kaiser, Ralf I.; Strazzulla, Giovanni

2014-02-01

Ozone has been detected on the surface of Ganymede via observation of the Hartley band through the use of ultraviolet spectroscopy and is largely agreed upon to be formed by radiolytic processing via interaction of magnetospheric energetic ions and/or electrons with oxygen-bearing ices on Ganymede's surface. Interestingly, a clearly distinct band near 300 nm within the shoulder of the UV-Vis spectrum of Ganymede was also observed, but currently lacks an acceptable physical or chemical explanation. Consequently, the primary motivation behind this work was the collection of UV-Vis absorption spectroscopy of ozone formation by energetic electron bombardment of a variety ofmore » oxygen-bearing ices (oxygen, carbon dioxide, water) relevant to this moon as well as other solar system. Ozone was indeed synthesized in pure ices of molecular oxygen, carbon dioxide and a mixture of water and oxygen, in agreement with previous studies. The Hartley band of the ozone synthesized in these ice mixtures was observed in the UV-Vis spectra and compared with the spectrum of Ganymede. In addition, a solid state ozone absorption cross section of 6.0 ± 0.6 × 10{sup –17} cm{sup 2} molecule{sup –1} was obtained from the UV-Vis spectral data. Ozone was not produced in the irradiated carbon dioxide-water mixtures; however, a spectrally 'red' UV continuum is observed and appears to reproduce well what is observed in a large number of icy moons such as Europa.« less

A Falling Corona Model for the Anomalous Behavior of the Broad Emission Lines in NGC 5548

NASA Astrophysics Data System (ADS)

Sun, Mouyuan; Xue, Yongquan; Cai, Zhenyi; Guo, Hengxiao

2018-04-01

NGC 5548 has been intensively monitored by the AGN Space Telescope and Optical Reverberation Mapping collaboration. Approximately after half of the light curves, the correlation between the broad emission lines and the lag-corrected ultraviolet (UV) continua becomes weak. This anomalous behavior is accompanied by an increase of soft X-ray emission. We propose a simple model to understand this anomalous behavior, i.e., the corona might fall down, thereby increasing the covering fraction of the inner disk. Therefore, X-ray and extreme-UV emission suffer from spectral variations. The UV continua variations are driven by both X-ray and extreme-UV variations. Consequently, the spectral variability induced by the falling corona would dilute the correlation between the broad emission lines and the UV continua. Our model can explain many additional observational facts, including the dependence of the anomalous behavior on velocity and ionization energy. We also show that the time lag and correlation between the X-ray and the UV variations change as NGC 5548 displays the anomalous behavior. The time lag is dramatically longer than the expectation from disk reprocessing if the anomalous behavior is properly excluded. During the anomalous state, the time lag approaches the light-travel timescale of disk reprocessing albeit with a much weaker correlation. We speculate that the time lag in the normal state is caused by reprocessing of the broad line region gas. As NGC 5548 enters the abnormal state, the contribution of the broad line region gas is smaller; the time lag reflects disk reprocessing. We also discuss alternative scenarios.

Highlights from 40 Years of Satellite UV Measurements

NASA Technical Reports Server (NTRS)

Bhartia, Pawan K.

2010-01-01

This year we are celebrating the 40th anniversary of the launch of the Backscatter Ultraviolet (BUV) instrument on NASA's Nimbus-4 satellite. The purpose of this instrument was to demonstrate the capability to measure total column ozone and its vertical distribution from space. The success of this instrument led to about a dozen instruments of this type on various NASA and NOAA satellites. These instruments used a single photomultiplier tube (PMT) that restricted the measurements to 6-12 discrete wavelengths in the 250-380 nm range. With the availability of solid-state detector arrays in the past decade it has been possible to make similar measurements but with hyperspectral (contiguous in wavelength) sampling and enhanced spectral resolution. This has allowed global mapping of several weakly-absorbing trace gases including S0 2, NO2, BrO, HCHO, and CIIOCHO. Since these measurements are affected by clouds and aerosols, a great deal of effort has gone into understanding their effect on ultraviolet radiation- both upwelling and downwelling. The downwelling UV radiation is chemically and biologically active and has both negative (genetic damage, air pollution) and positive (production of vitamin D and OH radical) environmental effects. I will discuss how the interaction of Rayleigh-scattered UV radiation with clouds and aerosols produce a variety of interesting effects that are leading to new methods of remote sensing of their properties. The UV measurements can greatly enhance the information that one derives from more traditional methods that use infrared and visible part of the solar spectrum.

Ultraviolet radiation from the pulsed corona discharge in water

NASA Astrophysics Data System (ADS)

Lukes, Petr; Clupek, Martin; Babicky, Vaclav; Sunka, Pavel

2008-05-01

Quantitative analysis of ultraviolet radiation from the pulsed corona discharge in water with needle-plate electrode geometry (~1-3 J pulse-1) was performed using the potassium ferrioxalate actinometry. Photon flux J190-280 and radiant energy Q190-280 of the UV light emitted from the discharge at spectral region 190-280 nm was determined in dependence on the applied voltage (17-29 kV, positive polarity) and the solution conductivity (100-500 µS cm-1). The intensity of the UV radiation strongly increased with increasing water conductivity and applied voltage. Depending on the applied voltage the determined photon flux varied by more than two orders of magnitude within the range of solution conductivities 100-500 µS cm-1. It was found that photon flux from the discharge may be directly related to the discharge pulse mean power Pp as J190-280 = 44.33 P_p^{2.11} (quanta pulse-1). A significant role of UV radiation in the production of hydrogen peroxide and bacterial inactivation by the corona discharge in water has been identified. As the solution conductivity increased the yield of H2O2 produced by the discharge decreased due to increasing photolysis of H2O2 accounting for up to 14% of the total decomposition rate of H2O2. As regards bactericidal effects, it was estimated that the UV radiation contributes about 30% to the overall inactivation of Escherichia coli.

The influence of urban area opacity on biologically active UV-B irradiance

NASA Astrophysics Data System (ADS)

Chubarova, Nataly; Rozental', Victor

2013-04-01

The study of UV irradiance changes in urban area is an essential problem due to the significant effect of UV irradiance on human health which can be positive (vitamin D synthesis) and negative (erythema, skin cancer, eye damage). According to the results of several experiments within the Moscow megacity we studied the effects of urban area opacity on the different types of biologically active UV-B irradiance on the base of a specially developed mobile photometric complex snd additional measurements of the urban opacity by Nikon Fisheye Converter FC-E8. We analyzed both the level of erythemally-active irradiance and the UV eye damaging radiation using the broadband UVB-1 YES pyranometer calibrated against ultraviolet spectroradiometer Bentham DTM-300 of the Medical University of Innsbruck (courtesy of Dr. M.Blumthaler). In order to estimate the effects of the urban opacity the measurements were normalized on similar measurements at the Meteorological Observatory of Moscow State University with zero opacity. This ratio is defined as an urban radiative transmittance (URT). Different atmospheric conditions were considered. In cloudy conditions the effect of opacity on URT is much less than that in conditions when the sun disk is open from clouds. We revealed some spectral features in transmittance of biologically active UV-B irradiance which is characterized by higher URT variations in overcast cloudy conditions due to more intensive scattering and smaller direct solar radiation component. In the absence of cloudiness the effect of opacity was studied for open and screening solar disk conditions. We obtained much higher URT in UVB spectral region compared with that for total solar irradiance for screening solar disk conditions with a significant URT dependence on the opacity only in UVB spectral region. No URT dependence was obtained for total solar irradiance in these conditions. Some model calculations were fulfilled to match the experimental results.

Absorption line indices in the UV. I. Empirical and theoretical stellar population models

NASA Astrophysics Data System (ADS)

Maraston, C.; Nieves Colmenárez, L.; Bender, R.; Thomas, D.

2009-01-01

Aims: Stellar absorption lines in the optical (e.g. the Lick system) have been extensively studied and constitute an important stellar population diagnostic for galaxies in the local universe and up to moderate redshifts. Proceeding towards higher look-back times, galaxies are younger and the ultraviolet becomes the relevant spectral region where the dominant stellar populations shine. A comprehensive study of ultraviolet absorption lines of stellar population models is however still lacking. With this in mind, we study absorption line indices in the far and mid-ultraviolet in order to determine age and metallicity indicators for UV-bright stellar populations in the local universe as well as at high redshift. Methods: We explore empirical and theoretical spectral libraries and use evolutionary population synthesis to compute synthetic line indices of stellar population models. From the empirical side, we exploit the IUE-low resolution library of stellar spectra and system of absorption lines, from which we derive analytical functions (fitting functions) describing the strength of stellar line indices as a function of gravity, temperature and metallicity. The fitting functions are entered into an evolutionary population synthesis code in order to compute the integrated line indices of stellar populations models. The same line indices are also directly evaluated on theoretical spectral energy distributions of stellar population models based on Kurucz high-resolution synthetic spectra, In order to select indices that can be used as age and/or metallicity indicators for distant galaxies and globular clusters, we compare the models to data of template globular clusters from the Magellanic Clouds with independently known ages and metallicities. Results: We provide synthetic line indices in the wavelength range ~1200 Å to ~3000 Å for stellar populations of various ages and metallicities.This adds several new indices to the already well-studied CIV and SiIV absorptions. Based on the comparison with globular cluster data, we select a set of 11 indices blueward of the 2000 Å rest-frame that allows us to recover well the ages and the metallicities of the clusters. These indices are ideal to study ages and metallicities of young galaxies at high redshift. We also provide the synthetic high-resolution stellar population SEDs.

ULTRAVIOLET DISINFECTION STUDIES WITH CCL LISTED MICROORGANISMS

EPA Science Inventory

Resistance to ultraviolet (UV) disinfection is an essential aspect regarding all microbial groups listed on the CCL. The U.S. drinking water industry is interested in including UV light treatment as an amendment to conventional treatment for disinfecting water supplies. UV disi...

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

NASA Astrophysics Data System (ADS)

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

2018-02-01

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

Isolation and characterization of ultraviolet light-sensitive mutants of the blue-green alga Anacystis nidulans.

NASA Technical Reports Server (NTRS)

Asato, Y.

1972-01-01

Three independently isolated ultraviolet light sensitive (uvs) mutants of Anacystis nidulans were characterized. Strain uvs-1 showed the highest sensitivity to UV by its greatly reduced photoreactivation capacity following irradiation. Pretreatment with caffeine suppressed the dark-survival curve of strain uvs-1, thus indicating the presence of excision enzymes involved in dark repair. Under 'black' and 'white' illumination, strain uvs-1 shows photorecovery properties comparable with wild-type cultures. Results indicate that strains uvs-1, uvs-35, and uvs-88 are probably genetically distinct UV-sensitive mutants.

An Ultraviolet Excess in the Superluminous Supernova Gaia16apd Reveals a Powerful Central Engine

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

Nicholl, M.; Berger, E.; Blanchard, P. K.

Since the discovery of superluminous supernovae (SLSNe) in the last decade, it has been known that these events exhibit bluer spectral energy distributions than other supernova subtypes, with significant output in the ultraviolet. However, the event Gaia16apd seems to outshine even the other SLSNe at rest-frame wavelengths below ∼3000 Å. Yan et al. have recently presented HST UV spectra and attributed the UV flux to low iron-group abundance in the outer ejecta, and hence reduced line blanketing. Here, we present UV and optical light curves over a longer baseline in time, revealing a rapid decline at UV wavelengths despite amore » typical optical evolution. Combining the published UV spectra with our own optical data, we demonstrate that Gaia16apd has a much hotter continuum than virtually any SLSN at maximum light, but it cools rapidly thereafter and is indistinguishable from the others by ∼10–15 days after peak. Comparing the equivalent widths of UV absorption lines with those of other events, we show that the excess UV continuum is a result of a more powerful central power source, rather than a lack of UV absorption relative to other SLSNe or an additional component from interaction with the surrounding medium. These findings strongly support the central-engine hypothesis for hydrogen-poor SLSNe. An explosion ejecting M {sub ej} = 4.8(0.2/ κ ) M {sub ⊙}, where κ is the opacity in cm{sup 2} g{sup −1}, and forming a magnetar with spin period P = 2 ms, and B = 2 × 10{sup 14} G (lower than other SLSNe with comparable rise times) can consistently explain the light curve evolution and high temperature at peak. The host metallicity, Z = 0.18 Z {sub ⊙}, is comparable to other SLSNe.« less

Long-term monitoring of Ark 120 with Swift

NASA Astrophysics Data System (ADS)

Gliozzi, M.; Papadakis, I. E.; Grupe, D.; Brinkmann, W. P.; Räth, C.

2017-02-01

We report the results of a six-month Swift monitoring campaign of Ark 120, a prototypical `bare' Seyfert 1 galaxy. The lack of intrinsic absorption combined with the nearly contemporaneous coverage of the ultraviolet (UV) and X-ray bands makes it possible to investigate the link between the accretion disc and the putative Comptonization corona. Our observations confirm the presence of substantial temporal variability, with the X-ray characterized by large-amplitude flux changes on time-scales of few days, while the variations in the UV bands are smoother and occur on time-scales of several weeks. The source also shows spectral variability with the X-ray spectrum steepening when the source is brighter. We do not detect any correlation between the UV flux and the X-ray spectral slope. A cross-correlation analysis suggests positive delays between X-rays and the UV emission, favouring a scenario of disc reprocessing. Although the strength of the correlation is moderate with a delay which is not well constrained (7.5 ± 7 d), it is nevertheless indicative of a very large disc reprocessing region, with a separation between the X-ray and the UV-emitting regions, which could be as large as 1000 rG. The Ark 120 correlation results are in agreement with those obtained in similar multiwavelength monitoring studies of active galactic nuclei (AGN). When combined together, the observations so far can be well described by a linear relation between the X-ray/UV delays and the mass of the central black hole. Within the context of the simplest scenario, where these delays correspond to light-travel times, the implied distance between the X-ray source and the optical/UV disc reprocessing region in these AGN should be of the order of many hundreds of gravitational radii.

Surface abundance and the hunt for stratification in chemically peculiar hot subdwarfs: PG 0909+276 and UVO 0512-08

NASA Astrophysics Data System (ADS)

Wild, J. F.; Jeffery, C. S.

2018-01-01

Edelmann identified two chemically peculiar hot subdwarfs, PG 0909+276 and UVO 0512-08, as having very high overabundances of iron-group elements. We obtained high-resolution ultraviolet spectroscopy in order to measure abundances of species not observable in the optical, and to seek evidence for chemical stratification in the photosphere. Abundances were measured in three wavelength regions; the optical 3900-6900 Å range was re-analysed to confirm consistency with that analysed by Edelmann. Ultraviolet spectra were obtained with the Space Telescope Imaging Spectrograph on the Hubble Space Telescope, covering the far-UV (1140-1740 Å) and the near-UV (1740-2500 Å). We computed a grid of theoretical local thermodynamic equilibrium spectra to find basic parameters (effective temperatures, surface gravity, surface hydrogen and helium fractions). We measured abundances using a spectral-synthesis approach in each wavelength range. We confirm that several iron-group metals are highly enriched, including cobalt, copper and zinc, relative to typical sdB stars. We detect gallium, germanium, tin and lead, similar to analysis of ultraviolet spectra of some other sdB stars. Our results confirm that PG 0909+276 and UVO 0512-08 exhibit peculiarities which make them distinct from both the normal H-rich sdB and intermediate He-rich sdB stars. The process which leads to this particular composition has still to be identified.

Effect of UV-B Radiation and Desiccation Stress on Photoprotective Compounds Accumulation in Marine Leptolyngbya sp.

PubMed

Joshi, Devika; Mohandass, C; Dhale, Mohan

2018-01-01

Increased awareness regarding the harmful effects of ultraviolet (UV)-B radiation has led to the search for new sources of natural UV-B protecting compounds. Mycosporine-like amino acids are one of such promising compounds found in several organisms. Cyanobacteria are ideal organisms for isolation of these compounds due to their compatibility and adaptability to thrive under harsh environmental conditions. In the following investigation, we report the production of shinorine in Leptolyngbya sp. isolated from the intertidal region. Based on the spectral characteristics and liquid chromatography-mass spectrometry analysis, the UV-absorbing compound was identified as shinorine. To the best of our knowledge, this is the first report on the occurrence of shinorine in Leptolyngbya sp. We also investigated the effect of artificial UV-B radiation and periodic desiccation on chlorophyll-a, total carotenoids, and mycosporine-like amino acids (MAAs) production. The UV-B radiation had a negative effect on growth and chlorophyll concentration, whereas it showed an inductive effect on the production of total carotenoids and MAAs. Desiccation along with UV-B radiation led to an increase in the concentration of photoprotective compounds. These results indicate that carotenoids and MAAs thus facilitate cyanobacteria to avoid and protect themselves from the deleterious effects of UV-B and desiccation.

High-Power 365 nm UV LED Mercury Arc Lamp Replacement for Photochemistry and Chemical Photolithography

PubMed Central

2016-01-01

Ultraviolet light emitting diodes (UV LEDs) have become widespread in chemical research as highly efficient light sources for photochemistry and photopolymerization. However, in more complex experimental setups requiring highly concentrated light and highly spatially resolved patterning of the light, high-pressure mercury arc lamps are still widely used because they emit intense UV light from a compact arc volume that can be efficiently coupled into optical systems. Advances in the deposition and p-type doping of gallium nitride have recently permitted the manufacture of UV LEDs capable of replacing mercury arc lamps also in these applications. These UV LEDs exceed the spectral radiance of mercury lamps even at the intense I-line at 365 nm. Here we present the successful exchange of a high-pressure mercury arc lamp for a new generation UV LED as a light source in photolithographic chemistry and its use in the fabrication of high-density DNA microarrays. We show that the improved light radiance and efficiency of these LEDs offer substantial practical, economic and ecological advantages, including faster synthesis, lower hardware costs, very long lifetime, an >85-fold reduction in electricity consumption and the elimination of mercury waste and contamination. PMID:28066690

High-Power 365 nm UV LED Mercury Arc Lamp Replacement for Photochemistry and Chemical Photolithography.

PubMed

Hölz, K; Lietard, J; Somoza, M M

2017-01-03

Ultraviolet light emitting diodes (UV LEDs) have become widespread in chemical research as highly efficient light sources for photochemistry and photopolymerization. However, in more complex experimental setups requiring highly concentrated light and highly spatially resolved patterning of the light, high-pressure mercury arc lamps are still widely used because they emit intense UV light from a compact arc volume that can be efficiently coupled into optical systems. Advances in the deposition and p -type doping of gallium nitride have recently permitted the manufacture of UV LEDs capable of replacing mercury arc lamps also in these applications. These UV LEDs exceed the spectral radiance of mercury lamps even at the intense I-line at 365 nm. Here we present the successful exchange of a high-pressure mercury arc lamp for a new generation UV LED as a light source in photolithographic chemistry and its use in the fabrication of high-density DNA microarrays. We show that the improved light radiance and efficiency of these LEDs offer substantial practical, economic and ecological advantages, including faster synthesis, lower hardware costs, very long lifetime, an >85-fold reduction in electricity consumption and the elimination of mercury waste and contamination.

Accelerated Solar-UV Test Chamber

NASA Technical Reports Server (NTRS)

Gupta, A.; Laue, E. G.

1984-01-01

Medium-pressure mercury-vapor lamps provide high ratio of ultraviolet to total power. Chamber for evaluating solar-ultraviolet (UV) radiation damage permits accelerated testing without overheating test specimens.

Development and future of ultraviolet light-emitting diodes: UV-LED will replace the UV lamp

NASA Astrophysics Data System (ADS)

Muramoto, Yoshihiko; Kimura, Masahiro; Nouda, Suguru

2014-06-01

Ultraviolet light-emitting diodes (UV-LEDs) have started replacing UV lamps. The power per LED of high-power LED products has reached 12 W (14 A), which is 100 times the values observed ten years ago. In addition, the cost of these high-power LEDs has been decreasing. In this study, we attempt to understand the technologies and potential of UV-LEDs.

Prospects for Near Ultraviolet Astronomical Observations from the Lunar Surface — LUCI

NASA Astrophysics Data System (ADS)

Mathew, J.; Kumar, B.; Sarpotdar, M.; Suresh, A.; Nirmal, K.; Sreejith, A. G.; Safonova, M.; Murthy, J.; Brosch, N.

2018-04-01

We have explored the prospects for UV observations from the lunar surface and developed a UV telescope (LUCI-Lunar Ultraviolet Cosmic Imager) to put on the Moon, with the aim to detect bright UV transients such as SNe, novae, TDE, etc.

Ultraviolet Spectra of Two Magnetic White Dwarfs and Ultraviolet Spectra of Subluminous Objects Found in the Kiso Schmidt Survey and Ultraviolet Absorptions in the Spectra of DA White Dwarfds

NASA Technical Reports Server (NTRS)

Wegner, Gary A.

1988-01-01

Research under NASA Grant NAG5-287 has carried out a number of projects in conjunction with the International Ultraviolet Explorer (IUE) satellite. These include: (1) studies of the UV spectra of DA white dwarfs which show quasi-molecular bands of H2 and H2(+); (2) the peculiar star HR6560; (3) the UV spectra of two magnetic white dwarfs that also show the quasi-molecular features; (4) investigations of the UV spectra of subluminous stars, primarily identified from visual wavelength spectroscopy in the Kiso survey of UV excess stars, some of which show interesting metal lines in their UV spectra; and (5) completion of studies of UV spectra of DB stars. The main result of this research has been to further knowledge of the structure and compositions of subluminous stars which helps cast light on their formation and evolution.

Nonthermal combined ultraviolet and vacuum-ultraviolet curing process for organosilicate dielectrics

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

Zheng, H.; Guo, X.; Pei, D.

2016-06-13

Porous SiCOH films are of great interest in semiconductor fabrication due to their low-dielectric constant properties. Post-deposition treatments using ultraviolet (UV) light on organosilicate thin films are required to decompose labile pore generators (porogens) and to ensure optimum network formation to improve the electrical and mechanical properties of low-k dielectrics. The goal of this work is to choose the best vacuum-ultraviolet photon energy in conjunction with vacuum ultraviolet (VUV) photons without the need for heating the dielectric to identify those wavelengths that will have the most beneficial effect on improving the dielectric properties and minimizing damage. VUV irradiation between 8.3more » and 8.9 eV was found to increase the hardness and elastic modulus of low-k dielectrics at room temperature. Combined with UV exposures of 6.2 eV, it was found that this “UV/VUV curing” process is improved compared with current UV curing. We show that UV/VUV curing can overcome drawbacks of UV curing and improve the properties of dielectrics more efficiently without the need for high-temperature heating of the dielectric.« less

The modification of spectral characteristics of cytostatics by optical beams

NASA Astrophysics Data System (ADS)

Pascu, Mihail Lucian; Brezeanu, Mihail; Carstocea, Benone D.; Voicu, Letitia; Gazdaru, Doina M.; Smarandache, Adriana A.

2004-10-01

Besides the biochemical action of methotrexate (MTX) and 5-fluorouracil (FU) their effect in destroying cancer tumours could be enhanced by exposure to light at different doses. Absorption, excitation and emission spectra of 10-4M - 10-5M MTX solutions in natural saline and sodium hydroxide at pH = 8.4 were measured, while their exposure to coherent and uncoherent light in the visible and near ultraviolet (UV) spectral ranges was made (Hg lamps and Nitrogen pulsed laser radiation were used). Absorption spectra exhibit spectral bands in the range 200 nm - 450 nm. The 200 - 450 nm excitation spectra were measured with emission centered on 470 nm; MTX fluorescence excitation was measured at 390 nm and the emission was detected between 400 nm and 600 nm showing a maximum at 470 nm. Spectra modifications, nonlinearly depending on exposure time (varying from 1 min to 20 min), evidenced MTX photo-dissociation to the fluorescent compound 2,4 diamino-formylpteridine. In the 5-FU case the absorption spectra exhibit bands between 200 nm and 450 nm. The emission fluorescence spectra were measured between 400 nm and 600 nm, with λex = 350 nm for UV Hg lamp and with λex = 360 nm for laser irradiated samples; at irradiation with N2 laser emitted radiation the excitation spectra were measured in the range of 200 nm - 400 nm, with λem = 440 nm. New vascularity rapid destruction was observed for conjunctive impregnated with 5-FU solution whilst exposed to incoherent UV and visible light.

The role of a generalized ultraviolet cue for blackbird food selection.

PubMed

Werner, Scott J; Tupper, Shelagh K; Carlson, James C; Pettit, Susan E; Ellis, Jeremy W; Linz, George M

2012-07-16

Birds utilize ultraviolet (UV) wavelengths for plumage signaling and sexual selection. Ultraviolet cues may also be used for the process of avian food selection. The aim of our study was to investigate whether a UV cue and a postingestive repellent can be used to condition food avoidance in red-winged blackbirds (Agelaius phoeniceus). We found that birds conditioned with an UV-absorbent, postingestive repellent subsequently avoided UV-absorbent food. Thus, the UV-absorbent cue (coupled with 0-20% of the conditioned repellent concentration) was used to maintain avoidance for up to 18 days post-conditioning. Similarly, birds conditioned with the UV-absorbent, postingestive repellent subsequently avoided UV-reflective food. Thus, conditioned avoidance of an UV-absorbent cue can be generalized to an unconditioned, UV-reflective cue for nutrient selection and toxin avoidance. These findings support the hypothesized function of UV vision for avian food selection, the implications of which remain to be explored for the sensory and behavioral ecology within agronomic and natural environments. Published by Elsevier Inc.

Far-UV spectroscopy of two extremely hot, helium-rich white dwarfs

NASA Astrophysics Data System (ADS)

Werner, K.; Rauch, T.; Kruk, J. W.

2017-05-01

A large proportion of hot post-asymptotic giant branch stars and white dwarfs (WDs) are hydrogen-deficient. Two distinct evolutionary sequences have been identified. One of them comprises stars of spectral type [WC] and PG1159, and it originates from a late helium-shell flash, creating helium-rich stellar atmospheres with significant admixtures of carbon (up to about 50%, mass fraction). The other sequence comprises stars of spectral type O(He) and luminous subdwarf O stars which possibly are descendants of RCrB stars and extreme helium stars. Their carbon abundances are significantly lower (of the order of 1% or less) and it is thought that they originate from binary-star evolution (through merger or common-envelope evolution). Here we investigate two of the three hottest known helium-rich (DO) WDs (PG 1034+001 and PG 0038+199). They are the only ones for which spectra were recorded with the Far Ultraviolet Spectroscopic Explorer and the Hubble Space Telescope, allowing a comprehensive ultraviolet spectral analysis. We find effective temperatures of Teff = 115 000 ± 5000 K and 125 000 ± 5000 K, respectively, and a surface gravity of log g= 7 ± 0.5. In both stars, nitrogen is strongly oversolar while C and O are significantly subsolar. For all other assessed metals (Ne, Si, P, S, Ar, Fe, and Ni) we find abundances close to solar. We conclude that these WDs are immediate descendants of O(He) stars and, hence, result from close-binary evolution. Based on observations made with the NASA-CNES-CSA Far Ultraviolet Spectroscopic Explorer.

Simultaneous Ultraviolet and X-Ray Spectroscopy of the Seyfert 1 Galaxy NGC 5548. I. Physical Conditions in the Ultraviolet Absorbers

NASA Astrophysics Data System (ADS)

Crenshaw, D. M.; Kraemer, S. B.; Gabel, J. R.; Kaastra, J. S.; Steenbrugge, K. C.; Brinkman, A. C.; Dunn, J. P.; George, I. M.; Liedahl, D. A.; Paerels, F. B. S.; Turner, T. J.; Yaqoob, T.

2003-09-01

We present new UV spectra of the nucleus of the Seyfert 1 galaxy NGC 5548, which we obtained with the Space Telescope Imaging Spectrograph at high spectral resolution, in conjunction with simultaneous Chandra X-Ray Observatory spectra. Taking advantage of the low UV continuum and broad emission-line fluxes, we have determined that the deepest UV absorption component covers at least a portion of the inner, high-ionization narrow-line region (NLR). We find nonunity covering factors in the cores of several kinematic components, which increase the column density measurements of N V and C IV by factors of 1.2-1.9 over the full-covering case; however, the revised columns have only a minor effect on the parameters derived from our photoionization models. For the first time, we have simultaneous N V and C IV columns for component 1 (at -1040 km s-1) and find that this component cannot be an X-ray warm absorber, contrary to our previous claim based on nonsimultaneous observations. We find that models of the absorbers based on solar abundances severely overpredict the O VI columns previously obtained with the Far Ultraviolet Spectroscopic Explorer and present arguments that this is not likely due to variability. However, models that include either enhanced nitrogen (twice solar) or dust, with strong depletion of carbon in either case, are successful in matching all of the observed ionic columns. These models result in substantially lower ionization parameters and total column densities compared to dust-free solar-abundance models and produce little O VII or O VIII, indicating that none of the UV absorbers are X-ray warm absorbers. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. These observations are associated with proposal 9279.

X-Ray Emission from the MUSCLES Exoplanet Host Stars

NASA Astrophysics Data System (ADS)

Brown, Alexander; Schneider, P. Christian; France, Kevin; Loyd, Parke; MUSCLES Team

2016-07-01

The MUSCLES (Measurements of the Ultraviolet Spectral Characteristics of Low-mass Exoplanetary Systems) project is a multi-spectral-region investigation of the high-energy (UV/X-ray) radiation fields of K dwarf / M dwarf exoplanet host stars and how this radiation will influence the evolution of the exoplanet atmospheres. As part of this project we have used Chandra and XMM-Newton to study the X-ray emission from ten (7 M dwarf and 3 K dwarf), nearby (within 15 pc), low mass exoplanet hosts. Typically, we have coordinated the X-ray observations with HST-COS FUV and ground-based optical spectroscopy of the same targets. Even though these stars are generally considered to be inactive we find evidence for significant X-ray variability for many of the M dwarfs observed. In this poster we illustrate the coronal properties of the stars using example light-curves and spectral analyses. The UV and X-ray data are crucial input to the modeling the complete spectral energy distributions for exoplanet studies.This work was supported by Chandra grants GO4-15041X and GO5-16155X and NASA XMM grant NNX16AC09G to the University of Colorado at Boulder. The overall MUSCLES project was undertaken by HST GO programs 12464 and 13650 and supported by STScI grants HST-GO-12464.01 and HST-GO-13650.01 . P.C.S. is supported by an ESA Research Fellowship.

Can we match ultraviolet face images against their visible counterparts?

NASA Astrophysics Data System (ADS)

Narang, Neeru; Bourlai, Thirimachos; Hornak, Lawrence A.

2015-05-01

In law enforcement and security applications, the acquisition of face images is critical in producing key trace evidence for the successful identification of potential threats. However, face recognition (FR) for face images captured using different camera sensors, and under variable illumination conditions, and expressions is very challenging. In this paper, we investigate the advantages and limitations of the heterogeneous problem of matching ultra violet (from 100 nm to 400 nm in wavelength) or UV, face images against their visible (VIS) counterparts, when all face images are captured under controlled conditions. The contributions of our work are three-fold; (i) We used a camera sensor designed with the capability to acquire UV images at short-ranges, and generated a dual-band (VIS and UV) database that is composed of multiple, full frontal, face images of 50 subjects. Two sessions were collected that span over the period of 2 months. (ii) For each dataset, we determined which set of face image pre-processing algorithms are more suitable for face matching, and, finally, (iii) we determined which FR algorithm better matches cross-band face images, resulting in high rank-1 identification rates. Experimental results show that our cross spectral matching (the heterogeneous problem, where gallery and probe sets consist of face images acquired in different spectral bands) algorithms achieve sufficient identification performance. However, we also conclude that the problem under study, is very challenging, and it requires further investigation to address real-world law enforcement or military applications. To the best of our knowledge, this is first time in the open literature the problem of cross-spectral matching of UV against VIS band face images is being investigated.

Electron-bombarded CCD detectors for ultraviolet atmospheric remote sensing

NASA Technical Reports Server (NTRS)

Carruthers, G. R.; Opal, C. B.

1983-01-01

Electronic image sensors based on charge coupled devices operated in electron-bombarded mode, yielding real-time, remote-readout, photon-limited UV imaging capability are being developed. The sensors also incorporate fast-focal-ratio Schmidt optics and opaque photocathodes, giving nearly the ultimate possible diffuse-source sensitivity. They can be used for direct imagery of atmospheric emission phenomena, and for imaging spectrography with moderate spatial and spectral resolution. The current state of instrument development, laboratory results, planned future developments and proposed applications of the sensors in space flight instrumentation is described.

The ultraviolet spectrum of the eclipsing binary IM Aurigae

NASA Technical Reports Server (NTRS)

Bruhweiler, F. C.; Feibelman, W. A.; Kondo, Y.

1986-01-01

Low dispersion IUE spectra have been obtained at primary and secondary minima, together with a high dispersion spectrum near maximum, for the eclipsing Algol-type IM Aurigae system. The weak, sharp absorption features noted at two distinct velocities in the high dispersion data are attributed to circumbinary gaseous shells and/or gas streams between the stellar components. The implications of these results for the recently observed increase in O-C values of the primary minimum, which prompted this UV spectral search for evidence of a recent mass-loss event, are discussed.

Nonlinear optics in the LP(02) higher-order mode of a fiber.

PubMed

Chen, Y; Chen, Z; Wadsworth, W J; Birks, T A

2013-07-29

The distinct disperion properties of higher-order modes in optical fibers permit the nonlinear generation of radiation deeper into the ultraviolet than is possible with the fundamental mode. This is exploited using adiabatic, broadband mode convertors to couple light efficiently from an input fundamental mode and also to return the generated light to an output fundamental mode over a broad spectral range. For example, we generate visible and UV supercontinuum light in the LP(02) mode of a photonic crystal fiber from sub-ns pulses with a wavelength of 532 nm.

VizieR Online Data Catalog: CIII] emission in near & far star-forming galaxies (Rigby+, 2015)

NASA Astrophysics Data System (ADS)

Rigby, J. R.; Bayliss, M. B.; Gladders, M. D.; Sharon, K.; Wuyts, E.; Dahle, H.; Johnson, T.; Pena-Guerrero, M.

2016-03-01

We measure the equivalent widths of Lyα and the C III] doublet in the rest-frame UV spectra of 11 gravitationally lensed galaxies at 1.6

NIST High Accuracy Reference Reflectometer-Spectrophotometer

PubMed Central

Proctor, James E.; Yvonne Barnes, P.

1996-01-01

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

Spectral analysis of the He-enriched sdO-star HD 127493

NASA Astrophysics Data System (ADS)

Dorsch, Matti; Latour, Marilyn; Heber, Ulrich

2018-02-01

The bright sdO star HD127493 is known to be of mixed H/He composition and excellent archival spectra covering both optical and ultraviolet ranges are available. UV spectra play a key role as they give access to many chemical species that do not show spectral lines in the optical, such as iron and nickel. This encouraged the quantitative spectral analysis of this prototypical mixed H/He composition sdO star. We determined atmospheric parameters for HD127493 in addition to the abundance of C, N, O, Si, S, Fe, and Ni in the atmosphere using non-LTE model atmospheres calculated with TLUSTY/SYNSPEC. A comparison between the parallax distance measured by Hipparcos and the derived spectroscopic distance indicate that the derived atmospheric parameters are realistic. From our metal abundance analysis, we find a strong CNO signature and enrichment in iron and nickel.

On the Failure of Standard Emission Measure Analysis for Solar Extreme-Ultraviolet and Ultraviolet Irradiance Spectra

NASA Astrophysics Data System (ADS)

Judge, P. G.; Woods, T. N.; Brekke, P.; Rottman, G. J.

1995-12-01

We perform emission measure analysis of new and accurate UV ( lambda > 1200 A) and extreme-ultraviolet (EUV) ( lambda <= 1200 A) irradiance ("Sun-as-a-star") emission-line spectra of the Sun. Our data consist of (1) daily averaged UV irradiances from the SOLSTICE on the UARS spacecraft and (2) EUV irradiances obtained on the same date from a \\frac {1}{4} m spectrograph flown on a sounding rocket. Both instruments have a spectral resolution of roughly 1 A. The absolute uncertainties in these data are at most +/-15% (+/-2 sigma ), one of the highest photometric accuracies yet achieved. We find large, highly significant and systematic discrepancies in the emission measure analysis of transition region lines which can only be accounted for by a breakdown of one or more standard assumptions. All strong lines above 1000 A, which are from the Li and Na isoelectronic sequences, are too strong by factors of between 2.5 and 7 compared with their counterparts in the EUV region. Previous studies were tantalizingly close to finding these discrepancies, but those data lacked the wavelength coverage and relative photometric precision necessary for definitive conclusions. We argue that either dynamical effects, inaccurate treatments of atomic processes, and/or Lyman continuum absorption are the culprits. However, we favor the former explanation. In any event, this study should have implications for models of the solar transition region, for observing programs with the CDS and SUMER instruments on SOHO, and for analysis of UV spectra for stars across the cool half of the H-R diagram. Finally, the discrepancy is not seen for the "coronal" Li-like ions.

Solar UV Radiation and the Origin of Life on Earth

NASA Technical Reports Server (NTRS)

Heap, S. R.; Gaidos, E.; Hubeny, I.; Lanz, T. M.; Fisher, Richard R. (Technical Monitor)

2001-01-01

We have embarked on a program aimed at understanding the atmosphere of the early Earth, because of its importance as a greenhouse, radiation shield, and energy source for life. Here, we give a progress report on the first phase of this program: to establish the UV radiation from the early Sun. We are presently obtaining ultraviolet spectra (STIS, FUSE, EUVE) of carefully selected nearby, young solar-type stars, which act as surrogates for the early Sun. We are currently making detailed non-LTE analyses of the spectra and constructing models of their photospheres + chromospheres. once validated, these models will allow us to extrapolate our theoretical spectra to unobserved spectral regions, and to proceed to the next step: to develop photochemical models of the pre-biotic and Archean atmosphere of the Earth.

Investigation of magnesium fluoride crystals for imaging acousto-optic tunable filter applications.

PubMed

Voloshinov, Vitaly B; Gupta, Neelam

2006-05-01

Results of an investigation of acousto-optic (AO) cells using single crystals of magnesium fluoride (MgF2) are presented. Two acousto-optic tunable filter (AOTF) cells for imaging application have been designed and tested in the visible and ultraviolet (UV) regions of the spectrum from 190 to 490 nm. The two imaging filters were developed by using the wide-angle AO interaction geometry in the (010) and (11 0) planes of the crystal. These filters were used to obtain spectral images at the shortest wavelengths achieved so far. Advantages and drawbacks of this crystal are discussed and photoelastic, acoustic, and AO properties of MgF2 are examined. The investigation confirmed that MgF2-based AOTF cells can be used in the deep UV region up to 110 nm.

Visual outdoor response of multiple wild bee species: highly selective stimulation of a single photoreceptor type by sunlight-induced fluorescence.

PubMed

Rao, Sujaya; Ostroverkhova, Oksana

2015-07-01

Bees have ultraviolet (UV), blue and green photoreceptor types in their compound eyes with which they locate food sources in landscapes that change continuously in cues emanating from plants and backgrounds against which they are perceived. The complexity of bee vision has been elucidated through studies examining individual species under laboratory conditions. Here, we used a bee-attractive fluorescent blue trap as a model for analyzing visual signals in operation outdoors, and across bee species. We manipulated trap color (appearance to humans under light with weak UV component) and UV-induced fluorescence emission, and aligned field capture results with bee vision models. Our studies show that the bees were attracted to traps that under solar illumination exhibited strong fluorescence emission exclusively in the blue spectral region. Through quantitative analysis, we established that strong spectral overlap of trap emittance with the photosensitivity characteristic of the blue receptor type and minimal overlap with those of the other two receptor types is the most critical property of attractive traps. A parameter has been identified which predicts the degree of attractiveness of the traps and which captures trends in the field data across wild bee species and for a diversity of backgrounds.

Gas-phase mercury reduction to measure total mercury in the flue gas of a coal-fired boiler.

PubMed

Meischen, Sandra J; Van Pelt, Vincent J; Zarate, Eugene A; Stephens, Edward A

2004-01-01

Gaseous elemental and total (elemental + oxidized) mercury (Hg) in the flue gas from a coal-fired boiler was measured by a modified ultraviolet (UV) spectrometer. Challenges to Hg measurement were the spectral interferences from other flue gas components and that UV measures only elemental Hg. To eliminate interference from flue gas components, a cartridge filled with gold-coated sand removed elemental Hg from a flue gas sample. The Hg-free flue gas was the reference gas, eliminating the spectral interferences. To measure total Hg by UV, oxidized Hg underwent a gas-phase, thermal-reduction in a quartz cell heated to 750 degrees C. Simultaneously, hydrogen was added to flash react with the oxygen present forming water vapor and preventing Hg re-oxidation as it exits the cell. Hg concentration results are in parts per billion by volume Hg at the flue gas oxygen concentration. The modified Hg analyzer and the Ontario Hydro method concurrently measured Hg at a field test site. Measurements were made at a 700-MW steam turbine plant with scrubber units and selective catalytic reduction. The flue gas sampled downstream of the selective catalytic reduction contained 2100 ppm SO2 and 75 ppm NOx. Total Hg measured by the Hg analyzer was within 20% of the Ontario Hydro results.

Proteolytically-induced changes of secondary structural protein conformation of bovine serum albumin monitored by Fourier transform infrared (FT-IR) and UV-circular dichroism spectroscopy

NASA Astrophysics Data System (ADS)

Güler, Günnur; Vorob'ev, Mikhail M.; Vogel, Vitali; Mäntele, Werner

2016-05-01

Enzymatically-induced degradation of bovine serum albumin (BSA) by serine proteases (trypsin and α-chymotrypsin) in various concentrations was monitored by means of Fourier transform infrared (FT-IR) and ultraviolet circular dichroism (UV-CD) spectroscopy. In this study, the applicability of both spectroscopies to monitor the proteolysis process in real time has been proven, by tracking the spectral changes together with secondary structure analysis of BSA as proteolysis proceeds. On the basis of the FTIR spectra and the changes in the amide I band region, we suggest the progression of proteolysis process via conversion of α-helices (1654 cm- 1) into unordered structures and an increase in the concentration of free carboxylates (absorption of 1593 and 1402 cm- 1). For the first time, the correlation between the degree of hydrolysis and the concentration of carboxylic groups measured by FTIR spectroscopy was revealed as well. The far UV-CD spectra together with their secondary structure analysis suggest that the α-helical content decreases concomitant with an increase in the unordered structure. Both spectroscopic techniques also demonstrate that there are similar but less spectral changes of BSA for the trypsin attack than for α-chymotrypsin although the substrate/enzyme ratio is taken the same.

Overview of SPICAV occultation results for the UV channel

NASA Astrophysics Data System (ADS)

Montmessin, Franck; Bertaux, Jean-Loup; Belyaev, Denis; Marcq, Emmanuel; Korablev, Oleg; Vandaele, Ann-Carine; Fedorova, Anna

The SPICAV instrument onboard the Venus Express spacecraft is a multi-channel suite cov-ering the far ultraviolet to the mid-infrared. In this presentation, we will focus on the results obtained by the UV channel during stellar occultations observations. Stellar occultation tech-nique possesses well-known advantages: self-calibration, low sensitivity to instrument aging, simple laws of radiative transfer. In addition, occultation with stars permit to cover a broad range of latitudes at any given season and they provide optimal geometrical registration. Since Venus Express orbit insertion, several hundreds of occultations have been performed by SPI-CAV, yielding profiles of atmospheric constituents between 80 and 140 km. In the SPICAV UV range, CO2 possesses a broad signature shortward of 200 nm which allows one to retrieve CO2 concentration and subsequently to deduce atmospheric pressure and temperature profiles in the upper mesosphere and in the thermosphere. The Venusian thermosphere shows excessive variability, with the equivalent of more than three scale heights change in density in less than a few days. No other spectral signature besides that of CO2 and haze particles was expected to appear in SPICAV ultraviolet spectra at this altitude range but a consistent search was undertaken, revealing the presence of aan ozone at 100 km (¡108 cm-3) and of sulfur dioxide above 90 km at a concentration of 0.1 to 1 ppm.

Ultraviolet spectra of extreme nearby star-forming regions - approaching a local reference sample for JWST

NASA Astrophysics Data System (ADS)

Senchyna, Peter; Stark, Daniel P.; Vidal-García, Alba; Chevallard, Jacopo; Charlot, Stéphane; Mainali, Ramesh; Jones, Tucker; Wofford, Aida; Feltre, Anna; Gutkin, Julia

2017-12-01

Nearby dwarf galaxies provide a unique laboratory in which to test stellar population models below Z⊙/2. Such tests are particularly important for interpreting the surprising high-ionization ultraviolet (UV) line emission detected at z > 6 in recent years. We present HST/COS UV spectra of 10 nearby metal-poor star-forming galaxies selected to show He II emission in SDSS optical spectra. The targets span nearly a dex in gas-phase oxygen abundance (7.8 < 12 + log O/H < 8.5) and present uniformly large specific star formation rates (sSFR ∼102 Gyr-1). The UV spectra confirm that metal-poor stellar populations can power extreme nebular emission in high-ionization UV lines, reaching C III] equivalent widths comparable to those seen in systems at z ∼ 6-7. Our data reveal a marked transition in UV spectral properties with decreasing metallicity, with systems below 12 + log O/H ≲ 8.0 (Z/Z⊙ ≲ 1/5) presenting minimal stellar wind features and prominent nebular emission in He II and C IV. This is consistent with nearly an order of magnitude increase in ionizing photon production beyond the He+-ionizing edge relative to H-ionizing flux as metallicity decreases below a fifth solar, well in excess of standard stellar population synthesis predictions. Our results suggest that often-neglected sources of energetic radiation such as stripped binary products and very massive O-stars produce a sharper change in the ionizing spectrum with decreasing metallicity than expected. Consequently, nebular emission in C IV and He II powered by these stars may provide useful metallicity constraints in the reionization era.

Modifying the Standard Disk Model for the Ultraviolet Spectral Analysis of Disk-dominated Cataclysmic Variables. I. The Novalikes MV Lyrae, BZ Camelopardalis, and V592 Cassiopeiae

NASA Astrophysics Data System (ADS)

Godon, Patrick; Sion, Edward M.; Balman, Şölen; Blair, William P.

2017-09-01

The standard disk is often inadequate to model disk-dominated cataclysmic variables (CVs) and generates a spectrum that is bluer than the observed UV spectra. X-ray observations of these systems reveal an optically thin boundary layer (BL) expected to appear as an inner hole in the disk. Consequently, we truncate the inner disk. However, instead of removing the inner disk, we impose the no-shear boundary condition at the truncation radius, thereby lowering the disk temperature and generating a spectrum that better fits the UV data. With our modified disk, we analyze the archival UV spectra of three novalikes that cannot be fitted with standard disks. For the VY Scl systems MV Lyr and BZ Cam, we fit a hot inflated white dwarf (WD) with a cold modified disk (\\dot{M} ˜ a few 10-9 M ⊙ yr-1). For V592 Cas, the slightly modified disk (\\dot{M}˜ 6× {10}-9 {M}⊙ {{yr}}-1) completely dominates the UV. These results are consistent with Swift X-ray observations of these systems, revealing BLs merged with ADAF-like flows and/or hot coronae, where the advection of energy is likely launching an outflow and heating the WD, thereby explaining the high WD temperature in VY Scl systems. This is further supported by the fact that the X-ray hardness ratio increases with the shallowness of the UV slope in a small CV sample we examine. Furthermore, for 105 disk-dominated systems, the International Ultraviolet Explorer spectra UV slope decreases in the same order as the ratio of the X-ray flux to optical/UV flux: from SU UMa’s, to U Gem’s, Z Cam’s, UX UMa’s, and VY Scl’s.

ULTRAVIOLET DISINFECTION OF A SECONDARY EFFLUENT: MEASUREMENT OF DOSE AND EFFECTS OF FILTRATION

EPA Science Inventory

Ultraviolet (UV) disinfection of wastewater secondary effluent was investigated in a two-phase study to develop methods for measuring UV dose and to determine the effects of filtration on UV disinfection. The first phase of this study involved a pilot plant study comparing filtra...

Some Thoughts on Teaching about Ultraviolet Radiation

ERIC Educational Resources Information Center

Thumm, Walter

1975-01-01

Describes the major obstacles in the study of ultraviolet radiation (UV). Presents the beneficial aspects of UV such as vitamin O production, sterilization, clinical treatment of diseases and wounds, and the marking of patients for radiotherapy. Warns of the dangers of UV exposure such as skin cancer and early aging. (GS)

The UV and X-ray activity of the M dwarfs within 10 pc of the Sun

NASA Astrophysics Data System (ADS)

Stelzer, B.; Marino, A.; Micela, G.; López-Santiago, J.; Liefke, C.

2013-05-01

M dwarfs are the most numerous stars in the Galaxy. They are characterized by strong magnetic activity. The ensuing high-energy emission is crucial for the evolution of their planets and the eventual presence of life on them. We systematically study the X-ray and ultraviolet emission of a subsample of M dwarfs from a recent proper-motion survey, selecting all M dwarfs within 10 pc to obtain a nearly volume-limited sample (˜90 per cent completeness). Archival ROSAT, XMM-Newton and GALEX data are combined with published spectroscopic studies of Hα emission and rotation to obtain a broad picture of stellar activity on M dwarfs. We make use of synthetic model spectra to determine the relative contributions of photospheric and chromospheric emission to the ultraviolet flux. We also analyse the same diagnostics for a comparison sample of young M dwarfs in the TW Hya association (˜10 Myr). We find that generally the emission in the GALEX bands is dominated by the chromosphere but the photospheric component is not negligible in early-M field dwarfs. The surface fluxes for the Hα, near-ultraviolet, far-ultraviolet and X-ray emission are connected via a power-law dependence. We present here for the first time such flux-flux relations involving broad-band ultraviolet emission for M dwarfs. Activity indices are defined as flux ratio between the activity diagnostic and the bolometric flux of the star in analogy to the Ca IIR'HK index. For given spectral type, these indices display a spread of 2-3 dex which is largest for M4 stars. Strikingly, at mid-M spectral types, the spread of rotation rates is also at its highest level. The mean activity index for fast rotators, likely representing the saturation level, decreases from X-rays over the FUV to the NUV band and Hα, i.e. the fractional radiation output increases with atmospheric height. The comparison to the ultraviolet and X-ray properties of TW Hya members shows a drop of nearly three orders of magnitude for the luminosity in these bands between ˜10 Myr and few Gyr age. A few young field dwarfs (<1 Gyr) in the 10-pc sample bridge the gap indicating that the drop in magnetic activity with age is a continuous process. The slope of the age decay is steeper for the X-ray than for the UV luminosity.

Time scale variation of MgII resonance lines of HD 41335 in UV region

NASA Astrophysics Data System (ADS)

Nikolaou, I.

2012-01-01

It is known that hot emission stars (Be and Oe) present peculiar and very complex spectral line profiles. Due to these perplexed lines that appear, it is difficult to actually fit a classical distribution to those physical profiles. Therefore many physical parameters of the regions, where these lines are created, can not be determined. In this paper, we study the Ultraviolet (UV) MgII (?? 2795.523, 2802.698 A) resonance lines of the HD 41335 star, at three different periods. Considering that these profiles consist of a number of independent Discrete or Satellite Absorption Components (DACs, SACs), we use the Gauss-Rotation model (GR-model). From this analysis we can estimate the values of a group of physical parameters, such as the apparent rotational and radial velocities, the random velocities of the thermal motions of the ions, as well as the Full Width at Half Maximum (FWHM), the column density and the absorbed energy of the independent regions of matter, which produce the main and the satellite components of the studied spectral lines. Eventually, we calculate the time scale variations of the above physical parameters.

NIMBUS-7 SBUV (Solar Backscatter Ultraviolet) observations of solar UV spectral irradiance variations caused by solar rotation and active-region evolution for the period November 7, 1978 - November 1, 1980

NASA Technical Reports Server (NTRS)

Heath, D. F.; Repoff, T. P.; Donnelly, R. F.

1984-01-01

Observations of temporal variations of the solar UV spectral irradiance over several days to a few weeks in the 160-400 nm wavelength range are presented. Larger 28-day variations and a second episode of 13-day variations occurred during the second year of measurements. The thirteen day periodicity is not a harmonic of the 28-day periodicity. The 13-day periodicity dominates certain episodes of solar activity while others are dominated by 28-day periods accompanied by a week 14-day harmonic. Techniques for removing noise and long-term trends are described. Time series analysis results are presented for the Si II lines near 182 nm, the Al I continuum in the 190 nm to 205 nm range, the Mg I continuum in the 210 nm to 250 nm range, the MgII H & K lines at 280 nm, the Mg I line at 285 nm, and the Ca II K & H lines at 393 and 397 nm.

Probing the Martian atmosphere in the ultraviolet

NASA Technical Reports Server (NTRS)

Lindner, Bernhard Lee

1994-01-01

Ozone is a key to understanding atmospheric chemistry on Mars. The O3 abundance has been inferred from UV spectra by several spacecraft, with the most complete coverage provided by Mariner 9. The Mariner 9 UV spectrometer scanned from 2100 to 3500 Angstroms in one of its two spectral channels every 3 seconds with a spectral resolution of 15 Angstroms and an effective field-of-view of approximately 300 sq km. The only atmospheric absorption in the 2000 to 3000 Angstrom region was assumed to come from the Hardey band system of ozone, which has an opacity of order unity. Therefore, the amount of ozone was inferred by fitting this absorption feature with laboratory data of ozone absorption, as shown in Fig 1. Mars O3 shows strong seasonal and latitudinal variation, with column abundances ranging from 0.2 micron-atm at equatorial latitudes to 60 micron-atm over the northern winter polar latitudes (1 micron-atm is a column abundance of 2.689 x 10(exp 15) molecules cm(exp -2). However, the O3 abundance is never great enough to significantly affect atmospheric temperatures or surface temperatures and frost budgets.

Fitting the spectral energy distributions of galaxies with CIGALE : Code Investigating GALaxy Emission

NASA Astrophysics Data System (ADS)

Giovannoli, E.; Buat, V.

2013-03-01

We use the code CIGALE (Code Investigating Galaxies Emission: Burgarella et al. 2005; Noll et al. 2009) which provides physical information about galaxies by fitting their UV (ultraviolet)-to-IR (infrared) spectral energy distribuition (SED). CIGALE is based on the use of a UV-optical stellar SED plus a dust IR-emitting component. We study a sample of 136 Luminous Infrared Galaxies (LIRGs) at z˜0.7 in the ECDF-S previously studied in Giovannoli et al. (2011). We focus on the way the empirical Dale & Helou (2002) templates reproduce the observed SEDs of the LIRGs. Fig. 1 shows the total infrared luminosity (L IR ) provided by CIGALE using the 64 templates (x axis) and using 2 templates (y axis) representative of the whole sample. Despite the larger dispersion when only 1 or 2 Herschel data are available, the agreement between both values is good with Δ log L IR = 0.0013 ± 0.045 dex. We conclude that 2 IR SEDs can be used alone to determine the L IR of LIRGs at z˜0.7 in an SED-fitting procedure.

New facilities for Al+MgF2 coating for 2-m class mirrors for UV

NASA Astrophysics Data System (ADS)

Zhupanov, Valery; Vlasenko, Oleg; Sachkov, Mikhail; Fedoseev, Viktor

2014-07-01

The World Space Observatory--Ultraviolet (WSO--UV) project is a Russian-Spanish space mission for spectroscopic and imaging observations in the UV domain (115-320 nm) where some of the most important astrophysical processes can be efficiently studied with unprecedented capability. In the horizon of the next decade, WSO--UV will be the only mission with the large primary mirror fully devoted for UV studies. The observatory includes a 170 cm aperture telescope capable of high-resolution spectroscopy, long slit low-resolution spectroscopy, and deep UV imaging. The telescope T-170M is a Ritchey-Chrétien with a F/10 focal ratio and a corrected field of view of 0.5 degrees. Specific data on the WSO-UV project (telescope, satellite, orbit, launcher, ground segment, etc.) are given in [1-6]. The current status of the WSO-UV focal plane instruments, their status of implementation, and the expected performances are presented in [7]. The science drivers of the WSO-UV mission are described in [8, 9]. The main WSO-UV instruments, spectrographs (WUVS instrument) and imagers (ISSIS instrument) are described in [10-13] and [14-15] correspondingly. The prospects of stellar studies with WSO-UV are presented in papers [16-17]. A paper [18] describes our experience of using the DP-190 glue for adhesive attachment of a large space mirror and its rim. In the instrument compartment, see Figure 1, the optical bench (OB) - used as reference plane for all the onboard instrumentation - is aligned and maintained in the correct position with respect to the primary mirror (PM) using a three rods system. An imaging instrument ISSIS is mounted on the upper basis of the optical bench, in the space available between the PM and the OB itself, while spectrographs (WUVS instrument) are mounted to the OB bottom basis. One of the primary tasks in creating telescope's PM is to apply coating with required reflective and protective properties. Aluminum is a well known reflecting coating for wavelength above 120 nm [19] with reflectivity more than 90% at wavelength longer than 200 nm, but the spectral range from 700 to 900 nm, where it's lowest value of reflectivity is 86% at 850 nm. That makes aluminum one of the best coating materials in the creating a mirror for operations in vacuum ultraviolet. However, the aluminum membrane is prone to oxidization, so applying the protecting coating is essential. Magnesium fluoride is one of the few materials transparent in the UV range [20]. In this contribution, capacities of new facilities in LUCH company that are created for World Space Observatory - Ultraviolet (WSO-UV) project are described in Section 2, the process of applying Al + MgF2 coating workout is presented in Section 3, results of applying Al+MgF2 coating for WSO-UV primary mirror are presented in Section 4 and a brief summary are provided in the concluding Section 5.

Spectroscopic Chemical Analysis Methods and Apparatus

NASA Technical Reports Server (NTRS)

Hug, William F.; Reid, Ray D.

2012-01-01

This invention relates to non-contact spectroscopic methods and apparatus for performing chemical analysis and the ideal wavelengths and sources needed for this analysis. It employs deep ultraviolet (200- to 300-nm spectral range) electron-beam-pumped wide bandgap semiconductor lasers, incoherent wide bandgap semiconductor lightemitting devices, and hollow cathode metal ion lasers. Three achieved goals for this innovation are to reduce the size (under 20 L), reduce the weight [under 100 lb (.45 kg)], and reduce the power consumption (under 100 W). This method can be used in microscope or macroscope to provide measurement of Raman and/or native fluorescence emission spectra either by point-by-point measurement, or by global imaging of emissions within specific ultraviolet spectral bands. In other embodiments, the method can be used in analytical instruments such as capillary electrophoresis, capillary electro-chromatography, high-performance liquid chromatography, flow cytometry, and related instruments for detection and identification of unknown analytes using a combination of native fluorescence and/or Raman spectroscopic methods. This design provides an electron-beampumped semiconductor radiation-producing method, or source, that can emit at a wavelength (or wavelengths) below 300 nm, e.g. in the deep ultraviolet between about 200 and 300 nm, and more preferably less than 260 nm. In some variations, the method is to produce incoherent radiation, while in other implementations it produces laser radiation. In some variations, this object is achieved by using an AlGaN emission medium, while in other implementations a diamond emission medium may be used. This instrument irradiates a sample with deep UV radiation, and then uses an improved filter for separating wavelengths to be detected. This provides a multi-stage analysis of the sample. To avoid the difficulties related to producing deep UV semiconductor sources, a pumping approach has been developed that uses ballistic electron beam injection directly into the active region of a wide bandgap semiconductor material.

Analysis of direct solar ultraviolet irradiance measurements in the French Alps. Retrieval of turbidity and ozone column amount.

PubMed

Lenoble, Jacqueline; de la Casinière, Alain; Cabot, Thierry

2004-05-20

Direct ultraviolet spectral solar irradiance is regularly obtained by the difference between global and diffuse irradiances at the French Alpine station of Briançon; the data of years 2001 and 2002 are analyzed in this paper. Comparison with modeled values is used for cloud screening, and an average UV-A aerosol optical depth is used as an index of turbidity; it is found to be around 0.05 for the clear winter days and around 0.2 in summer. Langley plots are used to verify the instrument calibration; they confirm the expected uncertainty smaller than 5%. The ozone total column amount is estimated with an uncertainty between -3 and Dobson units; comparisons with TOMS (Total Ozone Mapping Spectrometer) overpass values shows agreement within the expected uncertainties of both instruments.

Improved sensing using simultaneous deep-UV Raman and fluorescence detection-II

NASA Astrophysics Data System (ADS)

Hug, W. F.; Bhartia, R.; Sijapati, K.; Beegle, L. W.; Reid, R. D.

2014-05-01

Photon Systems in collaboration with JPL is continuing development of a new technology robot-mounted or hand-held sensor for reagentless, short-range, standoff detection and identification of trace levels chemical, biological, and explosive (CBE) materials on surfaces. This deep ultraviolet CBE sensor is the result of Army STTR and DTRA programs. The evolving 10 to 15 lb, 20 W, sensor can discriminate CBE from background clutter materials using a fusion of deep UV excited resonance Raman (RR) and laser induced native fluorescence (LINF) emissions collected is less than 1 ms. RR is a method that provides information about molecular bonds, while LINF spectroscopy is a much more sensitive method that provides information regarding the electronic configuration of target molecules. Standoff excitation of suspicious packages, vehicles, persons, and other objects that may contain hazardous materials is accomplished using excitation in the deep UV where there are four main advantages compared to near-UV, visible or near-IR counterparts. 1) Excited between 220 and 250 nm, Raman emission occur within a fluorescence-free region of the spectrum, eliminating obscuration of weak Raman signals by fluorescence from target or surrounding materials. 2) Because Raman and fluorescence occupy separate spectral regions, detection can be done simultaneously, providing an orthogonal set of information to improve both sensitivity and lower false alarm rates. 3) Rayleigh law and resonance effects increase Raman signal strength and sensitivity of detection. 4) Penetration depth into target in the deep UV is short, providing spatial/spectral separation of a target material from its background or substrate. 5) Detection in the deep UV eliminates ambient light background and enable daylight detection.

M dwarf energetic proton flux on exoplanets during flares: estimates using solar UV-proton relations

NASA Astrophysics Data System (ADS)

Youngblood, Allison, France; Kevin; Mason, James P.

2016-10-01

UV and X-ray stellar radiation impacts planetary atmospheres through heating and photochemistry, even regulating production of potential biomarkers. The surface conditions on M dwarf planets are not greatly affected by flares in the emission line-dominated far-UV spectra of M dwarfs (M < 0.5 Msun), however, theoretical investigations have largely ignored the additional influence of stellar energetic particles (SEPs) released during flares. Magnetospheric compression and atmospheric stripping by SEPs could allow life-damaging (or catalyzing) radiation to reach the planetary surface and cause atmospheric heating closer to the surface. For the sun, a relationship between >10 MeV proton flux and 1-8 Å irradiance has been established with data from the GOES satellites (Belov et al. 2005), however, only a few X-ray observations of M-dwarf flares covering the complete 1-8 Å bandpass exist. Current M dwarf SEP estimates (Segura et al. 2010) employ the Neupert effect to first estimate the average X-ray flux over a broad band (1-62 Å) from the observed near- and far-UV flare flux (Mitra-Kraev et al. 2005). To improve the quality of proton flux estimates, we have analyzed the GOES >10 MeV observed proton flux and SDO EVE's solar spectral irradiance measurements to define relationships between SEPs and extreme-UV emission lines with formation temperatures similar to far-UV lines directly accessible by the Hubble Space Telescope (HST). Under the necessary assumption that an M dwarf's SEP production mechanism is similar to the sun's, we estimate SEP fluxes during M-dwarf flares observed with HST as part of the MUSCLES (Measurements of the Ultraviolet Spectral Characteristics of Low-mass Exoplanetary Systems) Treasury Survey.

Are High-redshift Galaxies Hot? Temperature of z > 5 Galaxies and Implications for Their Dust Properties

NASA Astrophysics Data System (ADS)

Faisst, Andreas L.; Capak, Peter L.; Yan, Lin; Pavesi, Riccardo; Riechers, Dominik A.; Barišić, Ivana; Cooke, Kevin C.; Kartaltepe, Jeyhan S.; Masters, Daniel C.

2017-09-01

Recent studies have found a significant evolution and scatter in the relationship between the UV spectral slope (β UV) and the infrared excess (IRX; L IR/L UV) at z > 4, suggesting different dust properties of these galaxies. The total far-infrared (FIR) luminosity is key for this analysis, but it is poorly constrained in normal (main-sequence) star-forming z > 5 galaxies, where often only one single FIR point is available. To better inform estimates of the FIR luminosity, we construct a sample of local galaxies and three low-redshift analogues of z > 5 systems. The trends in this sample suggest that normal high-redshift galaxies have a warmer infrared (IR) spectral energy distribution (SED) compared to average z < 4 galaxies that are used as priors in these studies. The blueshifted peak and mid-IR excess emission could be explained by a combination of a larger fraction of metal-poor interstellar medium being optically thin to ultraviolet (UV) light and a stronger UV radiation field due to high star formation densities. Assuming a maximally warm IR SED suggests a 0.6 dex increase in total FIR luminosities, which removes some tension between the dust attenuation models and observations of the IRX-β relation at z > 5. Despite this, some galaxies still fall below the minimum IRX-β relation derived with standard dust cloud models. We propose that radiation pressure in these highly star-forming galaxies causes a spatial offset between dust clouds and young star-forming regions within the lifetime of O/B stars. These offsets change the radiation balance and create viewing-angle effects that can change UV colors at fixed IRX. We provide a modified model that can explain the location of these galaxies on the IRX-β diagram.

GOME-2 Tropospheric Ozone Profile Retrievals from Joint UV/Visible Measurement

NASA Astrophysics Data System (ADS)

Liu, X.; Zoogman, P.; Chance, K.; Cai, Z.; Nowlan, C. R.; Huang, G.; Gonzalez Abad, G.

2016-12-01

It has been shown from sensitivity studies that adding visible measurements in the Chappuis ozone band to UV measurements in the Hartley/Huggins ozone bands can significantly enhance retrieval sensitivity to lower tropospheric ozone from backscattered solar radiances due to deeper photon penetration in the visible to the surface than in the ultraviolet. The first NASA EVI (Earth Venture Instrument) TEMPO (Tropospheric Emissions: Monitoring of Pollution) instrument is being developed to measure backscattered solar radiation in two channels ( 290-490 and 540-740 nm) and make atmospheric pollution measurements over North America from the Geostationary orbit. However, this retrieval enhancement has yet to be demonstrated from existing measurements due to the weak ozone absorption in the visible and strong interferences from surface reflectance and aerosols and the requirement of accurate radiometric calibration across different spectral channels. We present GOME-2 retrievals from joint UV/visible measurements using the SAO ozone profile retrieval algorithm, to directly explore the retrieval improvement in lower tropospheric ozone from additional visible measurements. To reduce the retrieval interference from surface reflectance, we add characterization of surface spectral reflectance in the visible based on combining EOFs (Empirical Orthogonal Functions) derived from ASTER and other surface reflectance spectra with MODIS BRDF climatology into the ozone profile algorithm. The impacts of various types of aerosols and surface BRDF on the retrievals will be investigated. In addition, we will also perform empirical radiometric calibration of the GOME-2 data based on radiative transfer simulations. We will evaluate the retrieval improvement of joint UV/visible retrieval over the UV retrieval based on fitting quality and validation against ozonesonde observations.

8 years of Solar Spectral Irradiance Variability Observed from the ISS with the SOLAR/SOLSPEC Instrument

NASA Astrophysics Data System (ADS)

Damé, Luc; Bolsée, David; Meftah, Mustapha; Irbah, Abdenour; Hauchecorne, Alain; Bekki, Slimane; Pereira, Nuno; Cessateur, Marchand; Gäel; , Marion; et al.

2016-10-01

Accurate measurements of Solar Spectral Irradiance (SSI) are of primary importance for a better understanding of solar physics and of the impact of solar variability on climate (via Earth's atmospheric photochemistry). The acquisition of a top of atmosphere reference solar spectrum and of its temporal and spectral variability during the unusual solar cycle 24 is of prime interest for these studies. These measurements are performed since April 2008 with the SOLSPEC spectro-radiometer from the far ultraviolet to the infrared (166 nm to 3088 nm). This instrument, developed under a fruitful LATMOS/BIRA-IASB collaboration, is part of the Solar Monitoring Observatory (SOLAR) payload, externally mounted on the Columbus module of the International Space Station (ISS). The SOLAR mission, with its actual 8 years duration, will cover almost the entire solar cycle 24. We present here the in-flight operations and performances of the SOLSPEC instrument, including the engineering corrections, calibrations and improved know-how procedure for aging corrections. Accordingly, a SSI reference spectrum from the UV to the NIR will be presented, together with its variability in the UV, as measured by SOLAR/SOLSPEC for 8 years. Uncertainties on these measurements and comparisons with other instruments will be briefly discussed.

Deep UV Narrow-Band Photodetector Based on Ion Beam Synthesized Indium Oxide Quantum Dots in Al2O3 Matrix.

PubMed

Rajamani, Saravanan; Arora, Kanika; Konakov, Anton; Belov, Alexey; Korolev, Dmitry; Nikolskaya, Alyona; Mikhaylov, Alexey N; Surodin, Sergey; Kryukov, Ruslan; Nikolichev, Dmitri; Sushkov, Artem; Pavlov, Dmitry; Tetelbaum, David; Kumar, Mukesh; Kumar, Mahesh

2018-04-20

Semiconductor quantum dots (QDs) have attracted tremendous attention owing to their novel electrical and optical properties due to the size dependent quantum confinement effects. This provides an advantage of tunable wavelength detection, which is essential to realize spectrally selective photodetectors. We report the fabrication and characterization of high performance narrow band ultraviolet photodetector (UV-B) based on In2O3 nanocrystals embedded in Al2O3 matrices. The In2O3 nanocrystals are synthesized in Al2O3 matrix by sequential implantation of In+ and N2+ ions and post-implantation annealing. The photodetector exhibits excellent optoelectronic performances with high spectral responsivity and external quantum efficiency. The spectral response showed a band-selective nature with a full width half maximum of ∼ 60 nm, and the responsivity reaches up to 70 A/W under 290 nm at 5 V bias. The corresponding rejection ratio to visible region was as high as 8400. The high performance of this photodetector makes it highly suitable for practical applications such as narrow-band spectrum-selective photodetectors. The device design based on ion-synthesized nanocrystals would provide a new approach for realizing a visible-blind photodetector. © 2018 IOP Publishing Ltd.

Tunable UV-visible absorption of SnS2 layered quantum dots produced by liquid phase exfoliation.

PubMed

Fu, Xiao; Ilanchezhiyan, P; Mohan Kumar, G; Cho, Hak Dong; Zhang, Lei; Chan, A Sattar; Lee, Dong J; Panin, Gennady N; Kang, Tae Won

2017-02-02

4H-SnS 2 layered crystals synthesized by a hydrothermal method were used to obtain via liquid phase exfoliation quantum dots (QDs), consisting of a single layer (SLQDs) or multiple layers (MLQDs). Systematic downshift of the peaks in the Raman spectra of crystals with a decrease in size was observed. The bandgap of layered QDs, estimated by UV-visible absorption spectroscopy and the tunneling current measurements using graphene probes, increases from 2.25 eV to 3.50 eV with decreasing size. 2-4 nm SLQDs, which are transparent in the visible region, show selective absorption and photosensitivity at wavelengths in the ultraviolet region of the spectrum while larger MLQDs (5-90 nm) exhibit a broad band absorption in the visible spectral region and the photoresponse under white light. The results show that the layered quantum dots obtained by liquid phase exfoliation exhibit well-controlled and regulated bandgap absorption in a wide tunable wavelength range. These novel layered quantum dots prepared using an inexpensive method of exfoliation and deposition from solution onto various substrates at room temperature can be used to create highly efficient visible-blind ultraviolet photodetectors and multiple bandgap solar cells.

Daily, seasonal, and latitudinal variations in solar ultraviolet A and B radiation in relation to vitamin D production and risk for skin cancer.

PubMed

Grigalavicius, Mantas; Moan, Johan; Dahlback, Arne; Juzeniene, Asta

2016-01-01

Solar ultraviolet (UV) radiation varies with latitude, time of day, and season. Both spectral UV composition and ambient UV dose lead to different health outcomes at different latitudes. Finding the optimal time for sun exposure, whereby the positive effects of UV exposure (vitamin D) are facilitated and the negative effects (skin cancer, photoimmunosuppression) avoided are the most important consideration in modern skin cancer prevention programs. This paper focuses on the latitude dependency of UVB, UVA, vitamin D production, and skin cancer risk in Caucasians. Biologically effective UVB (280-315 nm) and UVA (315-400 nm) doses were calculated using radiative transfer models with appropriate climatologic data for selected locations. Incidences of squamous cell carcinoma (SCC) and cutaneous melanoma (CM) were retrieved from cancer registries and published articles. Annual doses of UVA radiation decrease much less with increasing latitude than annual doses of UVB. Incidences of CM also decrease less steeply with increasing latitude than incidences of SCC. As SCC is caused mainly by UVB, these observations support the assumption that UVA plays an important role in the development of CM. The variations in UVA (relevant to CM) and UVB (relevant to vitamin D production) over 1 day differ: the UVB : UVA ratio is maximal at noon. The best way to obtain a given dose of vitamin D with minimal carcinogenic risk is through a non-burning exposure in the middle of the day, rather than in the afternoon or morning. © 2015 The International Society of Dermatology.

Characterization and error analysis of an operational retrieval algorithm for estimating column ozone and aerosol properties from ground-based ultra-violet irradiance measurements

NASA Astrophysics Data System (ADS)

Taylor, Thomas E.; L'Ecuyer, Tristan; Slusser, James; Stephens, Graeme; Krotkov, Nick; Davis, John; Goering, Christian

2005-08-01

Extensive sensitivity and error characteristics of a recently developed optimal estimation retrieval algorithm which simultaneously determines aerosol optical depth (AOD), aerosol single scatter albedo (SSA) and total ozone column (TOC) from ultra-violet irradiances are described. The algorithm inverts measured diffuse and direct irradiances at 7 channels in the UV spectral range obtained from the United States Department of Agriculture's (USDA) UV-B Monitoring and Research Program's (UVMRP) network of 33 ground-based UV-MFRSR instruments to produce aerosol optical properties and TOC at all seven wavelengths. Sensitivity studies of the Tropospheric Ultra-violet/Visible (TUV) radiative transfer model performed for various operating modes (Delta-Eddington versus n-stream Discrete Ordinate) over domains of AOD, SSA, TOC, asymmetry parameter and surface albedo show that the solutions are well constrained. Realistic input error budgets and diagnostic and error outputs from the retrieval are analyzed to demonstrate the atmospheric conditions under which the retrieval provides useful and significant results. After optimizing the algorithm for the USDA site in Panther Junction, Texas the retrieval algorithm was run on a cloud screened set of irradiance measurements for the month of May 2003. Comparisons to independently derived AOD's are favorable with root mean square (RMS) differences of about 3% to 7% at 300nm and less than 1% at 368nm, on May 12 and 22, 2003. This retrieval method will be used to build an aerosol climatology and provide ground-truthing of satellite measurements by running it operationally on the USDA UV network database.

Theoretical and experimental luminous characteristics of white LEDs composed of multiphosphors and near-UV LED for lighting

NASA Astrophysics Data System (ADS)

Uchida, Yuji; Taguchi, Tsunemasa

2003-07-01

We have performed theoretical studies on the luminous characeristics of white LED light source which composed of multi phosphors and near ultraviolet (UV) LED for general lighting. White LED source for general lighting applications requires the conditions that have high-flux, high luminous efficacy of radiation (> 100 lm/W) in addition to high color rendering index (Ra > 90) and variable color temperatures. Recently, we have proposed a novel type white LED based on multi phosphors and near UV LED system in order to high-Ra (>93). We will describe the excellent luminescence properties of white LED consisting of orange (O), yellow (Y), green (G) and blue (B) phosphor materials, and near UV LED. The color spectral contributions of individual phosphor-coated LED are theoretically analyzed using our multi LED lighting theory calculated the maximum luminous efficacy can be estimated to be approximately 300 lm/W having a high Ra of about 90 taking into account individual radiation spectrum. Illuminance distribution of white LED is in fairly good agreement with the experimental data.

Light Scattering by Lunar Exospheric Dust: What could be Learned from LRO LAMP and LADEE UVS?

NASA Astrophysics Data System (ADS)

Glenar, D. A.; Stubbs, T. J.; Richard, D. T.; Stern, S. A.; Retherford, K. D.; Gladstone, R.; Feldman, P. D.; Colaprete, A.; Delory, G. T.

2011-12-01

Two complementary spectrometers, namely the Lunar Reconnaissance Orbiter, Lyman Alpha Mapping Project (LAMP) and the planned Lunar Atmosphere and Dust Environment Explorer (LADEE) Ultraviolet Explorer (UVS) will carry out sensitive searches for high altitude exospheric dust, via detection of scattered sunlight. The combined spectral coverage of these instruments extends from far-UV to near-IR wavelengths. Over this wavelength range, grain size parameter (X=2πr/λ, with r the grain radius and λ the wavelength) changes dramatically, which makes broad wavelength coverage a good diagnostic of grain size. Utilizing different pointing geometries, both LAMP and UVS are able to observe dust over a range of scattering angles, as well as measure the dust vertical profile via limb measurements at multiple tangent heights. We summarize several categories of information that can be inferred from the data sets, using broadband simulations of horizon glow as observed at the limb. Grain scattering properties used in these simulations were computed for multiple grain shapes using Discrete-Dipole theory. Some cautionary remarks are included regarding the use of Mie theory to interpret scattering measurements.

Ultraviolet radiation and bio-optics in Crater Lake, Oregon

USGS Publications Warehouse

Hargreaves, B.R.; Girdner, S.F.; Buktenica, M.W.; Collier, R.W.; Urbach, E.; Larson, G.L.

2007-01-01

Crater Lake, Oregon, is a mid-latitude caldera lake famous for its depth (594 m) and blue color. Recent underwater spectral measurements of solar radiation (300-800 nm) support earlier observations of unusual transparency and extend these to UV-B wavelengths. New data suggest that penetration of solar UVR into Crater Lake has a significant ecological impact. Evidence includes a correlation between water column chlorophyll-a and stratospheric ozone since 1984, the scarcity of organisms in the upper water column, and apparent UV screening pigments in phytoplankton that vary with depth. The lowest UV-B diffuse attenuation coefficients (K d,320) were similar to those reported for the clearest natural waters elsewhere, and were lower than estimates for pure water published in 1981. Optical proxies for UVR attenuation were correlated with chlorophyll-a concentration (0-30 m) during typical dry summer months from 1984 to 2002. Using all proxies and measurements of UV transparency, decadal and longer cycles were apparent but no long-term trend since the first optical measurement in 1896. ?? 2007 Springer Science+Business Media B.V.

BD-22deg3467, a DAO-type Star Exciting the Nebula Abell 35

NASA Technical Reports Server (NTRS)

Ziegler, M.; Rauch, T.; Werner, K.; Koppen, J.; Kruk, J. W.

2013-01-01

Spectral analyses of hot, compact stars with non-local thermodynamical equilibrium (NLTE) model-atmosphere techniques allow the precise determination of photospheric parameters such as the effective temperature (T(sub eff)), the surface gravity (log g), and the chemical composition. The derived photospheric metal abundances are crucial constraints for stellar evolutionary theory. Aims. Previous spectral analyses of the exciting star of the nebula A35, BD-22deg3467, were based on He+C+N+O+Si+Fe models only. For our analysis, we use state-of-the-art fully metal-line blanketed NLTE model atmospheres that consider opacities of 23 elements from hydrogen to nickel. We aim to identify all observed lines in the ultraviolet (UV) spectrum of BD-22deg3467 and to determine the abundances of the respective species precisely. Methods. For the analysis of high-resolution and high signal-to-noise ratio (S/N) far-ultraviolet (FUSE) and UV (HST/STIS) observations, we combined stellar-atmosphere models and interstellar line-absorption models to fully reproduce the entire observed UV spectrum. Results. The best agreement with the UV observation of BD-22deg3467 is achieved at T(sub eff) = 80 +/- 10 kK and log g = 7.2 +/- 0.3. While T(sub eff) of previous analyses is verified, log g is significantly lower. We re-analyzed lines of silicon and iron (1/100 and about solar abundances, respectively) and for the first time in this star identified argon, chromium, manganese, cobalt, and nickel and determined abundances of 12, 70, 35, 150, and 5 times solar, respectively. Our results partially agree with predictions of diffusion models for DA-type white dwarfs. A combination of photospheric and interstellar line-absorption models reproduces more than 90% of the observed absorption features. The stellar mass is M approx. 0.48 Solar Mass. Conclusions. BD.22.3467 may not have been massive enough to ascend the asymptotic giant branch and may have evolved directly from the extended horizontal branch to the white dwarf state. This would explain why it is not surrounded by a planetary nebula. However, the star, ionizes the ambient interstellar matter, mimicking a planetary nebula.

Spatiotemporal exposure modeling of ambient erythemal ultraviolet radiation.

PubMed

VoPham, Trang; Hart, Jaime E; Bertrand, Kimberly A; Sun, Zhibin; Tamimi, Rulla M; Laden, Francine

2016-11-24

Ultraviolet B (UV-B) radiation plays a multifaceted role in human health, inducing DNA damage and representing the primary source of vitamin D for most humans; however, current U.S. UV exposure models are limited in spatial, temporal, and/or spectral resolution. Area-to-point (ATP) residual kriging is a geostatistical method that can be used to create a spatiotemporal exposure model by downscaling from an area- to point-level spatial resolution using fine-scale ancillary data. A stratified ATP residual kriging approach was used to predict average July noon-time erythemal UV (UV Ery ) (mW/m 2 ) biennially from 1998 to 2012 by downscaling National Aeronautics and Space Administration (NASA) Total Ozone Mapping Spectrometer (TOMS) and Ozone Monitoring Instrument (OMI) gridded remote sensing images to a 1 km spatial resolution. Ancillary data were incorporated in random intercept linear mixed-effects regression models. Modeling was performed separately within nine U.S. regions to satisfy stationarity and account for locally varying associations between UV Ery and predictors. Cross-validation was used to compare ATP residual kriging models and NASA grids to UV-B Monitoring and Research Program (UVMRP) measurements (gold standard). Predictors included in the final regional models included surface albedo, aerosol optical depth (AOD), cloud cover, dew point, elevation, latitude, ozone, surface incoming shortwave flux, sulfur dioxide (SO 2 ), year, and interactions between year and surface albedo, AOD, cloud cover, dew point, elevation, latitude, and SO 2 . ATP residual kriging models more accurately estimated UV Ery at UVMRP monitoring stations on average compared to NASA grids across the contiguous U.S. (average mean absolute error [MAE] for ATP, NASA: 15.8, 20.3; average root mean square error [RMSE]: 21.3, 25.5). ATP residual kriging was associated with positive percent relative improvements in MAE (0.6-31.5%) and RMSE (3.6-29.4%) across all regions compared to NASA grids. ATP residual kriging incorporating fine-scale spatial predictors can provide more accurate, high-resolution UV Ery estimates compared to using NASA grids and can be used in epidemiologic studies examining the health effects of ambient UV.

Protective mechanisms and acclimation to solar ultraviolet-B radiation in Oenothera stricta

NASA Technical Reports Server (NTRS)

Robberecht, R.; Caldwell, M. M.

1981-01-01

Plant adaptations ameliorating or repairing the damaging effects of ultraviolet-B (UV-B) radiation on plant tissue were investigated. The degree of phenotype plasticity in UV protective mechanisms and acclimation in relation to the natural solar UV-B radiation flux and in an enhanced UV-B irradiance environment was also examined. Mechanisms by which plants avoid radiation, adaptations altering the path of radiation incident on the leaf, and repair processes were considered. Attenuation of UV-B by tissues, UV-B irradiation into the leaf, and the effects of UV-B on photosynthesis were investigated.

Comets in UV

NASA Astrophysics Data System (ADS)

Shustov, B.; Sachkov, M.; Gómez de Castro, A. I.; Vallejo, J. C.; Kanev, E.; Dorofeeva, V.

2018-04-01

Comets are important "eyewitnesses" of Solar System formation and evolution. Important tests to determine the chemical composition and to study the physical processes in cometary nuclei and coma need data in the UV range of the electromagnetic spectrum. Comprehensive and complete studies require additional ground-based observations and in situ experiments. We briefly review observations of comets in the ultraviolet (UV) and discuss the prospects of UV observations of comets and exocomets with space-borne instruments. A special reference is made to the World Space Observatory-Ultraviolet (WSO-UV) project.

A Complete UV Atlas of Standard Stars

NASA Technical Reports Server (NTRS)

Wu, Chi-Chao

2000-01-01

The general objective of this project is to provide a comprehensive ultraviolet spectral atlas of stars based on the data in the IUE Final Archive. The data have been uniformly processed by the IUE NEWSIPS pipeline system. The NEWSIPS gives an improved signal to noise ratio for the data that will be especially beneficial to low signal portions of the spectra; and it also gives more accurate fluxes for stars by adopting the latest absolute calibration and measured instrument parameters. Our new atlas, therefore, provides more uniform and accurate data than the version previously published. In addition, considerable efforts were devoted to obtain reliable spectral types, V,B-V, and E(B-V). Our goal is to provide the information which can be used with reasonable confidence by scientists.

Polynomial coefficients for calculating O2 Schumann-Runge cross sections at 0.5/cm resolution

NASA Technical Reports Server (NTRS)

Minschwaner, K.; Anderson, G. P.; Hall, L. A.; Yoshino, K.

1992-01-01

O2 cross sections from 49,000 to 57,000/cm have been fitted with temperature dependent polynomial expressions, providing an accurate and efficient means of determining Schumann-Runge band cross sections for temperatures between 130 and 500 K. The least squares fits were carried out on a 0.5/cm spectral grid, using cross sections obtained from a Schumann-Runge line-by-line model that incorporates the most recent spectroscopic data. The O2 cross sections do not include the underlying Herzberg continuum, but they do contain contributions from the temperature dependent Schumann-Runge continuum. The cross sections are suitable for use in UV transmission calculations at high spectral resolution. They should also prove useful for updating existing parameterizations of ultraviolet transmission and O2 photolysis.

Low Dark-Current, High Current-Gain of PVK/ZnO Nanoparticles Composite-Based UV Photodetector by PN-Heterojunction Control.

PubMed

Lee, Sang-Won; Cha, Seung-Hwan; Choi, Kyung-Jae; Kang, Byoung-Ho; Lee, Jae-Sung; Kim, Sae-Wan; Kim, Ju-Seong; Jeong, Hyun-Min; Gopalan, Sai-Anand; Kwon, Dae-Hyuk; Kang, Shin-Won

2016-01-07

We propose a solution-processable ultraviolet (UV) photodetector with a pn-heterojunction hybrid photoactive layer (HPL) that is composed of poly-n-vinylcarbazole (PVK) as a p-type polymer and ZnO nanoparticles (NPs) as an n-type metal oxide. To observe the effective photo-inducing ability of the UV photodetector, we analyzed the optical and electrical properties of HPL which is controlled by the doping concentration of n-type ZnO NPs in PVK matrix. Additionally, we confirmed that the optical properties of HPL dominantly depend on the ZnO NPs from the UV-vis absorption and the photoluminescence (PL) spectral measurements. This HPL can induce efficient charge transfer in the localized narrow pn-heterojunction domain and increases the photocurrent gain. It is essential that proper doping concentration of n-type ZnO NPs in polymer matrix is obtained to improve the performance of the UV photodetector. When the ZnO NPs are doped with the optimized concentration of 3.4 wt.%, the electrical properties of the photocurrent are significantly increased. The ratio of the photocurrent was approximately 10³ higher than that of the dark current.

Low Dark-Current, High Current-Gain of PVK/ZnO Nanoparticles Composite-Based UV Photodetector by PN-Heterojunction Control

PubMed Central

Lee, Sang-Won; Cha, Seung-Hwan; Choi, Kyung-Jae; Kang, Byoung-Ho; Lee, Jae-Sung; Kim, Sae-Wan; Kim, Ju-Seong; Jeong, Hyun-Min; Gopalan, Sai-Anand; Kwon, Dae-Hyuk; Kang, Shin-Won

2016-01-01

We propose a solution-processable ultraviolet (UV) photodetector with a pn-heterojunction hybrid photoactive layer (HPL) that is composed of poly-n-vinylcarbazole (PVK) as a p-type polymer and ZnO nanoparticles (NPs) as an n-type metal oxide. To observe the effective photo-inducing ability of the UV photodetector, we analyzed the optical and electrical properties of HPL which is controlled by the doping concentration of n-type ZnO NPs in PVK matrix. Additionally, we confirmed that the optical properties of HPL dominantly depend on the ZnO NPs from the UV-vis absorption and the photoluminescence (PL) spectral measurements. This HPL can induce efficient charge transfer in the localized narrow pn-heterojunction domain and increases the photocurrent gain. It is essential that proper doping concentration of n-type ZnO NPs in polymer matrix is obtained to improve the performance of the UV photodetector. When the ZnO NPs are doped with the optimized concentration of 3.4 wt.%, the electrical properties of the photocurrent are significantly increased. The ratio of the photocurrent was approximately 103 higher than that of the dark current. PMID:26751453

Properties of the Visible Light Phototaxis and UV Avoidance Behaviors in the Larval Zebrafish.

PubMed

Guggiana-Nilo, Drago A; Engert, Florian

2016-01-01

For many organisms, color is an essential source of information from visual scenes. The larval zebrafish has the potential to be a model for the study of this topic, given its tetrachromatic retina and high dependence on vision. In this study we took a step toward understanding how the larval zebrafish might use color sensing. To this end, we used a projector-based paradigm to force a choice of a color stimulus at every turn of the larva. The stimuli used spanned most of the larval spectral range, including activation of its Ultraviolet (UV) cone, which has not been described behaviorally before. We found that zebrafish larvae swim toward visible wavelengths (>400 nm) when choosing between them and darkness, as has been reported with white light. However, when presented with UV light and darkness zebrafish show an intensity dependent avoidance behavior. This UV avoidance does not interact cooperatively with phototaxis toward longer wavelengths, but can compete against it in an intensity dependent manner. Finally, we show that the avoidance behavior depends on the presence of eyes with functional UV cones. These findings open future avenues for studying the neural circuits that underlie color sensing in the larval zebrafish.

Properties of the Visible Light Phototaxis and UV Avoidance Behaviors in the Larval Zebrafish

PubMed Central

Guggiana-Nilo, Drago A.; Engert, Florian

2016-01-01

For many organisms, color is an essential source of information from visual scenes. The larval zebrafish has the potential to be a model for the study of this topic, given its tetrachromatic retina and high dependence on vision. In this study we took a step toward understanding how the larval zebrafish might use color sensing. To this end, we used a projector-based paradigm to force a choice of a color stimulus at every turn of the larva. The stimuli used spanned most of the larval spectral range, including activation of its Ultraviolet (UV) cone, which has not been described behaviorally before. We found that zebrafish larvae swim toward visible wavelengths (>400 nm) when choosing between them and darkness, as has been reported with white light. However, when presented with UV light and darkness zebrafish show an intensity dependent avoidance behavior. This UV avoidance does not interact cooperatively with phototaxis toward longer wavelengths, but can compete against it in an intensity dependent manner. Finally, we show that the avoidance behavior depends on the presence of eyes with functional UV cones. These findings open future avenues for studying the neural circuits that underlie color sensing in the larval zebrafish. PMID:27594828

UV-visible-DAD and 1H-NMR spectroscopy data fusion for studying the photodegradation process of azo-dyes using MCR-ALS.

PubMed

Fernández, Cristina; Pilar Callao, M; Larrechi, M Soledad

2013-12-15

The photodegradation process of three azo-dyes - Acid Orange 61, Acid Red 97 and Acid Brown 425 - was monitored simultaneously by ultraviolet-visible spectroscopy with diode array detector (UV-vis-DAD) and (1)H-nuclear magnetic resonance ((1)H-NMR). Multivariate curve resolution-alternating least squares (MCR-ALS) was applied to obtain the concentration and spectral profile of the chemical compounds involved in the process. The analysis of the H-NMR data suggests there are more intermediate compounds than those obtained with the UV-vis-DAD data. The fusion of UV-vis-DAD and the (1)H-NMR signal before the multivariate analysis provides better results than when only one of the two detector signals was used. It was concluded that three degradation products were present in the medium when the three azo-dyes had practically degraded. This study is the first application of UV-vis-DAD and (1)H-NMR spectroscopy data fusion in this field and illustrates its potential as a quick method for evaluating the evolution of the azo-dye photodegradation process. © 2013 Elsevier B.V. All rights reserved.

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

NASA Astrophysics Data System (ADS)

Govindhan, R.; Karthikeyan, B.

2018-03-01

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

Design and UV-curable behaviour of boron based reactive diluent for epoxy acrylate oligomer used for flame retardant wood coating

PubMed Central

Chambhare, Sachin U.; Lokhande, Gunawant P.; Jagtap, Ramanand N.

2017-01-01

Abstract Difunctional boron-containing reactive flame retardant for UV-curable epoxy acrylate oligomer was synthesized from phenyl boronic acid and glycidyl methacrylate. The synthesized reactive diluent was utilized to formulate ultraviolet (UV)-curable wood coatings. The weight fractions of reactive diluent in coatings formulation was varied from 5 to 25 wt % with constant photoinitiator concentration. The molecular structure of reactive flame retardant was confirmed by Fourier-transform infrared, Nuclear magnetic resonance (NMR) and 11B NMR spectral analysis. Further, the efficacy of flame retardant behaviour of coatings was evaluated using limiting oxygen index and UL-94 vertical burning test. Thermal stability of cured coatings films were estimated from thermogravimetric and differential scanning calorimetry analysis. The effects of varying concentration of reactive diluent on the viscosity of coatings formulation along with optical, mechanical and chemical resistance properties of coatings were also evaluated. The coatings gel content, water absorption behaviour, contact angle analysis and stain resistance were also studied. PMID:29491786

Ultraviolet radiation changes

NASA Technical Reports Server (NTRS)

Mckenzie, Richard L.; Frederick, John E.; Ilyas, Mohammad; Filyushkin, V.; Wahner, Andreas; Stamnes, K.; Muthusubramanian, P.; Blumthaler, M.; Roy, Colin E.; Madronich, Sasha

1991-01-01

A major consequence of ozone depletion is an increase in solar ultraviolet (UV) radiation received at the Earth's surface. This chapter discusses advances that were made since the previous assessment (World Meteorological Organization (WMO)) to our understanding of UV radiation. The impacts of these changes in UV on the biosphere are not included, because they are discussed in the effects assessment.

Ultraviolet emissions from the upper atmospheres of the planets

NASA Technical Reports Server (NTRS)

Moos, H. W.

1981-01-01

Some recent results on planetary upper atmospheres obtained by means of orbiting ultraviolet observatories are reviewed with emphasis on Jupiter and Io torus. Consideration is given to long-term variation in Jovian Ly alpha emission, UV polar auroras on Jupiter, and UV emission from the Io torus. Requirements for UV planetary astronomy are briefly discussed.

Solar UV dose patterns in Italy.

PubMed

Meloni, D; Casale, G R; Siani, A M; Palmieri, S; Cappellani, F

2000-06-01

Since 1992 solar ultraviolet (UV) spectral irradiance (290-325 nm) has been measured at two Italian stations of Rome (urban site) and Ispra (semirural site) using Brewer spectrophotometry. The data collected under all sky conditions, are compared with the output of a sophisticated radiative transfer model (System for Transfer of Atmospheric Radiation--STAR model). The STAR multiple scattering scheme is able to cope with all physical processes relevant to the UV transfer through the atmosphere. The experience so far acquired indicates that, in spite of the unavoidable uncertainties in the input parameters (ozone, aerosol, surface albedo, pressure, temperature, relative humidity, cloud cover), measured and computed clear sky iradiances are in reasonable agreement. The STAR model is applied to build up the solar UV geographic patterns in Italy: the daily dose in the range 290-325 nm is computed at about 70 sites where a thorough and homogeneous climatology is available. For each month the concept of an idealized "standard day" is introduced and the surface distribution of solar UV field determined. The map of solar UV patterns for Italy, available for the first time, meets the study requirements in the field of skin and eye epidemiology, as well as in other investigations dealing with the impact of UV on the biosphere. The results are interpreted in terms of atmospheric and meteorological parameters modulating UV radiation reaching the ground.

UV-POSIT: Web-Based Tools for Rapid and Facile Structural Interpretation of Ultraviolet Photodissociation (UVPD) Mass Spectra

NASA Astrophysics Data System (ADS)

Rosenberg, Jake; Parker, W. Ryan; Cammarata, Michael B.; Brodbelt, Jennifer S.

2018-04-01

UV-POSIT (Ultraviolet Photodissociation Online Structure Interrogation Tools) is a suite of web-based tools designed to facilitate the rapid interpretation of data from native mass spectrometry experiments making use of 193 nm ultraviolet photodissociation (UVPD). The suite includes four separate utilities which assist in the calculation of fragment ion abundances as a function of backbone cleavage sites and sequence position; the localization of charge sites in intact proteins; the calculation of hydrogen elimination propensity for a-type fragment ions; and mass-offset searching of UVPD spectra to identify unknown modifications and assess false positive fragment identifications. UV-POSIT is implemented as a Python/Flask web application hosted at http://uv-posit.cm.utexas.edu. UV-POSIT is available under the MIT license, and the source code is available at https://github.com/jarosenb/UV_POSIT. [Figure not available: see fulltext.

UV-POSIT: Web-Based Tools for Rapid and Facile Structural Interpretation of Ultraviolet Photodissociation (UVPD) Mass Spectra.

PubMed

Rosenberg, Jake; Parker, W Ryan; Cammarata, Michael B; Brodbelt, Jennifer S

2018-06-01

UV-POSIT (Ultraviolet Photodissociation Online Structure Interrogation Tools) is a suite of web-based tools designed to facilitate the rapid interpretation of data from native mass spectrometry experiments making use of 193 nm ultraviolet photodissociation (UVPD). The suite includes four separate utilities which assist in the calculation of fragment ion abundances as a function of backbone cleavage sites and sequence position; the localization of charge sites in intact proteins; the calculation of hydrogen elimination propensity for a-type fragment ions; and mass-offset searching of UVPD spectra to identify unknown modifications and assess false positive fragment identifications. UV-POSIT is implemented as a Python/Flask web application hosted at http://uv-posit.cm.utexas.edu . UV-POSIT is available under the MIT license, and the source code is available at https://github.com/jarosenb/UV_POSIT . Graphical Abstract.

A Hot Companion to a Blue Straggler in NGC 188 as Revealed by the Ultra-Violet Imaging Telescope (UVIT) on ASTROSAT

NASA Astrophysics Data System (ADS)

Subramaniam, Annapurni; Sindhu, N.; Tandon, S. N.; Kameswara Rao, N.; Postma, J.; Côté, Patrick; Hutchings, J. B.; Ghosh, S. K.; George, K.; Girish, V.; Mohan, R.; Murthy, J.; Sankarasubramanian, K.; Stalin, C. S.; Sutaria, F.; Mondal, C.; Sahu, S.

2016-12-01

We present early results from the Ultra-Violet Imaging Telescope (UVIT) on board the ASTROSAT observatory. We report the discovery of a hot companion associated with one of the blue straggler stars (BSSs) in the old open cluster, NGC 188. Using fluxes measured in four filters in UVIT’s far-UV (FUV) channel, and two filters in the near-UV (NUV) channel, we have constructed the spectral energy distribution (SED) of the star WOCS-5885, after combining with flux measurements from GALEX, Ultraviolet Imaging Telescope, Ultraviolet Optical Telescope, SPITZER, WISE, and several ground-based facilities. The resulting SED spans a wavelength range of 0.15 μm to 7.8 μm. This object is found to be one of the brightest FUV sources in the cluster. An analysis of the SED reveals the presence of two components. The cooler component is found to have a temperature of 6000 ± 150 K, confirming that it is a BSS. Assuming it to be a main-sequence star, we estimate its mass to be ˜1.1-1.2 M ⊙. The hotter component, with an estimated temperature of 17,000 ± 500 K, has a radius of ˜ 0.6 R ⊙ and L ˜30 L ⊙. Bigger and more luminous than a white dwarf, yet cooler than a sub-dwarf, we speculate that it is a post-AGB/HB star that has recently transferred its mass to the BSS, which is known to be a rapid rotator. This binary system, which is the first BSS with a post-AGB/HB companion identified in an open cluster, is an ideal laboratory to study the process of BSS formation via mass transfer.

Structural, energetic, and UV-Vis spectral analysis of UVA filter 4-tert-butyl-4'-methoxydibenzoylmethane.

PubMed

Pinto da Silva, Luís; Ferreira, Paulo J O; Duarte, Darío J R; Miranda, Margarida S; Esteves da Silva, Joaquim C G

2014-02-27

The growing awareness of the harmful effects of ultraviolet (UV) solar radiation has increased the production and consumption of sunscreen products, which contain organic and inorganic molecules named UV filters that absorb, reflect, or scatter UV radiation, thus minimizing negative human health effects. 4-tert-Butyl-4'-methoxydibenzoylmethane (BMDBM) is one of the few organic UVA filters and the most commonly used. BMDBM exists in sunscreens in the enol form which absorbs strongly in the UVA range. However, under sunlight irradiation tautomerization occurs to the keto form, resulting in the loss of UV protection. In this study we have performed quantum chemical calculations to study the excited-state molecular structure and excitation spectra of the enol and keto tautomers of BMDBM. This knowledge is of the utmost importance as the starting point for studies aiming at the understanding of its activity when applied on human skin and also its fate once released into the aquatic environment. The efficiency of excitation transitions was rationalized based on the concept of molecular orbital superposition. The loss of UV protection was attributed to the enol → keto phototautomerism and subsequent photodegradation. Although this process is not energetically favorable in the singlet bright state, photodegradation is possible because of intersystem crossing to the first two triplet states.

Exposure to Non-Extreme Solar UV Daylight: Spectral Characterization, Effects on Skin and Photoprotection

PubMed Central

Marionnet, Claire; Tricaud, Caroline; Bernerd, Françoise

2014-01-01

The link between chronic sun exposure of human skin and harmful clinical consequences such as photo-aging and skin cancers is now indisputable. These effects are mostly due to ultraviolet (UV) rays (UVA, 320–400 nm and UVB, 280–320 nm). The UVA/UVB ratio can vary with latitude, season, hour, meteorology and ozone layer, leading to different exposure conditions. Zenithal sun exposure (for example on a beach around noon under a clear sky) can rapidly induce visible and well-characterized clinical consequences such as sunburn, predominantly induced by UVB. However, a limited part of the global population is exposed daily to such intense irradiance and until recently little attention has been paid to solar exposure that does not induce any short term clinical impact. This paper will review different studies on non-extreme daily UV exposures with: (1) the characterization and the definition of the standard UV daylight and its simulation in the laboratory; (2) description of the biological and clinical effects of such UV exposure in an in vitro reconstructed human skin model and in human skin in vivo, emphasizing the contribution of UVA rays and (3) analysis of photoprotection approaches dedicated to prevent the harmful impact of such UV exposure. PMID:25546388

Exposure to non-extreme solar UV daylight: spectral characterization, effects on skin and photoprotection.

PubMed

Marionnet, Claire; Tricaud, Caroline; Bernerd, Françoise

2014-12-23

The link between chronic sun exposure of human skin and harmful clinical consequences such as photo-aging and skin cancers is now indisputable. These effects are mostly due to ultraviolet (UV) rays (UVA, 320-400 nm and UVB, 280-320 nm). The UVA/UVB ratio can vary with latitude, season, hour, meteorology and ozone layer, leading to different exposure conditions. Zenithal sun exposure (for example on a beach around noon under a clear sky) can rapidly induce visible and well-characterized clinical consequences such as sunburn, predominantly induced by UVB. However, a limited part of the global population is exposed daily to such intense irradiance and until recently little attention has been paid to solar exposure that does not induce any short term clinical impact. This paper will review different studies on non-extreme daily UV exposures with: (1) the characterization and the definition of the standard UV daylight and its simulation in the laboratory; (2) description of the biological and clinical effects of such UV exposure in an in vitro reconstructed human skin model and in human skin in vivo, emphasizing the contribution of UVA rays and (3) analysis of photoprotection approaches dedicated to prevent the harmful impact of such UV exposure.

High sensitivity to short wavelengths in a lizard and implications for understanding the evolution of visual systems in lizards

PubMed Central

Fleishman, Leo J.; Loew, Ellis R.; Whiting, Martin J.

2011-01-01

Progress in developing animal communication theory is frequently constrained by a poor understanding of sensory systems. For example, while lizards have been the focus of numerous studies in visual signalling, we only have data on the spectral sensitivities of a few species clustered in two major clades (Iguania and Gekkota). Using electroretinography and microspectrophotometry, we studied the visual system of the cordylid lizard Platysaurus broadleyi because it represents an unstudied clade (Scinciformata) with respect to visual systems and because UV signals feature prominently in its social behaviour. The retina possessed four classes of single and one class of double cones. Sensitivity in the ultraviolet region (UV) was approximately three times higher than previously reported for other lizards. We found more colourless oil droplets (associated with UV-sensitive (UVS) and short wavelength-sensitive (SWS) photoreceptors), suggesting that the increased sensitivity was owing to the presence of more UVS photoreceptors. Using the Vorobyev–Osorio colour discrimination model, we demonstrated that an increase in the number of UVS photoreceptors significantly enhances a lizard's ability to discriminate conspecific male throat colours. Visual systems in diurnal lizards appear to be broadly conserved, but data from additional clades are needed to confirm this. PMID:21389031

Observations of Solar Spectral Irradiance Change During Cycle 22 from NOAA-9 SBUV/2

NASA Technical Reports Server (NTRS)

DeLand, Matthew T.; Cebula, Richard P.; Hilsenrath, Ernest

2003-01-01

The NOM-9 Solar Backscatter Ultraviolet, model 2 (SBUV/2) instrument is one of a series of instruments providing daily solar spectral irradiance measurements in the middle and near ultraviolet since 1978. The SBUV/2 instruments are primarily designed to measure stratospheric profile and total column ozone, using the directional albedo as the input to the ozone processing algorithm. As a result, the SBUV/2 instrument does not have onboard monitoring of all time-dependent response changes. We have applied internal comparisons and vicarious (external) comparisons to determine the long-term instrument characterization for NOAA-9 SBUV/2 to derive accurate solar spectral irradiances from March 1985 to May 1997 spanning two solar cycle minima with a single instrument. The NOAA-9 data show an amplitude of 9.3(+/- 2.3)% (81-day averaged) at 200-205 nm for solar cycle 22. This is consistent with the result of (Delta)F(sub 200-205) = 8.3(+/- 2.6)% for cycle 21 from Nimbus-7 SBUV and (Delta)F(sub 200-205) = 10(+/- 2)% (daily values) for cycle 23 from UARS SUSIM. NOAA-9 data at 245-250 nm show a solar cycle amplitude of (Delta)F(sub 245-250) = 5.7(+/- 1.8)%. NOAA-9 SBUV/2 data can be combined with other instruments to create a 25-year record of solar UV irradiance.

The Colorado Ultraviolet Transit Experiment (CUTE): a dedicated cubesat mission for the study of exoplanetary mass loss and magnetic fields

NASA Astrophysics Data System (ADS)

Fleming, Brian T.; France, Kevin; Nell, Nicholas; Kohnert, Richard; Pool, Kelsey; Egan, Arika; Fossati, Luca; Koskinen, Tommi; Vidotto, Aline A.; Hoadley, Keri; Desert, Jean-Michel; Beasley, Matthew; Petit, Pascal

2017-08-01

The Colorado Ultraviolet Transit Experiment (CUTE) is a near-UV (2550 - 3300 Å) 6U cubesat mission designed to monitor transiting hot Jupiters to quantify their atmospheric mass loss and magnetic fields. CUTE will probe both atomic (Mg and Fe) and molecular (OH) lines for evidence of enhanced transit absorption, and to search for evidence of early ingress due to bow shocks ahead of the planet's orbital motion. As a dedicated mission, CUTE will observe > 60 spectroscopic transits of hot Jupiters over a nominal seven month mission. This represents the equivalent of > 700 orbits of the only other instrument capable of these measurements, the Hubble Space Telescope. CUTE efficiently utilizes the available cubesat volume by means of an innovative optical design to achieve a projected effective area of ˜ 22 cm2 , low instrumental background, and a spectral resolving power of R ˜ 3000 over the entire science bandpass. These performance characteristics enable CUTE to discern a transit depth of < 1% in individual spectral absorption lines. We present the CUTE optical and mechanical design, a summary of the science motivation and expected results, and an overview of the projected fabrication, calibration and launch timeline.

Sexual dimorphism in the compound eye of Heliconius erato: a nymphalid butterfly with at least five spectral classes of photoreceptor.

PubMed

McCulloch, Kyle J; Osorio, Daniel; Briscoe, Adriana D

2016-08-01

Most butterfly families expand the number of spectrally distinct photoreceptors in their compound eye by opsin gene duplications together with lateral filter pigments; however, most nymphalid genera have limited diversity, with only three or four spectral types of photoreceptor. Here, we examined the spatial pattern of opsin expression and photoreceptor spectral sensitivities in Heliconius erato, a nymphalid with duplicate ultraviolet opsin genes, UVRh1 and UVRh2 We found that the H. erato compound eye is sexually dimorphic. Females express the two UV opsin proteins in separate photoreceptors, but males do not express UVRh1. Intracellular recordings confirmed that females have three short wavelength-sensitive photoreceptors (λmax=356, ∼390 and 470 nm), while males have two (λmax=390 and ∼470 nm). We also found two long wavelength-sensitive photoreceptors (green, λmax∼555 nm, and red, λmax∼600 nm), which express the same LW opsin. The red cell's shifted sensitivity is probably due to perirhabdomal filtering pigments. Sexual dimorphism of the UV-absorbing rhodopsins may reflect the females' need to discriminate conspecifics from co-mimics. Red-green color vision may be used to detect differences in red coloration on Heliconius wings, or for host-plant identification. Among nymphalids so far investigated, only H. erato is known to possess five spectral classes of photoreceptor; sexual dimorphism of the eye via suppression of one class of opsin (here UVRh1 in males) has not - to our knowledge - been reported in any animal. © 2016. Published by The Company of Biologists Ltd.

Standardization of UV LED measurements

NASA Astrophysics Data System (ADS)

Eppeldauer, G. P.; Larason, T. C.; Yoon, H. W.

2015-09-01

Traditionally used source spectral-distribution or detector spectral-response based standards cannot be applied for accurate UV LED measurements. Since the CIE standardized rectangular-shape spectral response function for UV measurements cannot be realized with small spectral mismatch when using filtered detectors, the UV measurement errors can be several times ten percent or larger. The UV LEDs produce broadband radiation and both their peaks or spectral bandwidths can change significantly. The detectors used for the measurement of these LEDs also have different spectral bandwidths. In the discussed example, where LEDs with 365 nm peak are applied for fluorescent crack-recognition using liquid penetrant (non-destructive) inspection, the broadband radiometric LED (signal) measurement procedure is standardized. A UV LED irradiance-source was calibrated against an FEL lamp standard to determine its spectral irradiance. The spectral irradiance responsivity of a reference UV meter was also calibrated. The output signal of the reference UV meter was calculated from the spectral irradiance of the UV source and the spectral irradiance responsivity of the reference UV meter. From the output signal, both the integrated irradiance (in the reference plane of the reference meter) and the integrated responsivity of the reference meter were determined. Test UV meters calibrated for integrated responsivity against the reference UV meter, can be used to determine the integrated irradiance from a field UV source. The obtained 5 % (k=2) measurement uncertainty can be decreased when meters with spectral response close to a constant value are selected.

Micro-optics for simultaneous multi-spectral imaging applied to chemical/biological and IED detection

NASA Astrophysics Data System (ADS)

Hinnrichs, Michele

2012-06-01

Using diffractive micro-lenses configured in an array and placed in close proximity to the focal plane array will enable a small compact simultaneous multispectral imaging camera. This approach can be applied to spectral regions from the ultraviolet (UV) to the long-wave infrared (LWIR). The number of simultaneously imaged spectral bands is determined by the number of individually configured diffractive optical micro-lenses (lenslet) in the array. Each lenslet images at a different wavelength determined by the blaze and set at the time of manufacturing based on application. In addition, modulation of the focal length of the lenslet array with piezoelectric or electro-static actuation will enable spectral band fill-in allowing hyperspectral imaging. Using the lenslet array with dual-band detectors will increase the number of simultaneous spectral images by a factor of two when utilizing multiple diffraction orders. Configurations and concept designs will be presented for detection application for biological/chemical agents, buried IED's and reconnaissance. The simultaneous detection of multiple spectral images in a single frame of data enhances the image processing capability by eliminating temporal differences between colors and enabling a handheld instrument that is insensitive to motion.

Estimating solar ultraviolet irradiance (290-385 nm) by means of the spectral parametric models: SPCTRAL2 and SMARTS2

NASA Astrophysics Data System (ADS)

Foyo-Moreno, I.; Vida, J.; Olmo, F. J.; Alados-Arboledas, L.

2000-11-01

Since the discovery of the ozone depletion in Antarctic and the globally declining trend of stratospheric ozone concentration, public and scientific concern has been raised in the last decades. A very important consequence of this fact is the increased broadband and spectral UV radiation in the environment and the biological effects and heath risks that may take place in the near future. The absence of widespread measurements of this radiometric flux has lead to the development and use of alternative estimation procedures such as the parametric approaches. Parametric models compute the radiant energy using available atmospheric parameters. Some parametric models compute the global solar irradiance at surface level by addition of its direct beam and diffuse components. In the present work, we have developed a comparison between two cloudless sky parametrization schemes. Both methods provide an estimation of the solar spectral irradiance that can be integrated spectrally within the limits of interest. For this test we have used data recorded in a radiometric station located at Granada (37.180°N, 3.580°W, 660 m a.m.s.l.), an inland location. The database includes hourly values of the relevant variables covering the years 1994-95. The performance of the models has been tested in relation to their predictive capability of global solar irradiance in the UV range (290-385 nm). After our study, it appears that information concerning the aerosol radiative effects is fundamental in order to obtain a good estimation. The original version of SPCTRAL2 provides estimates of the experimental values with negligible mean bias deviation. This suggests not only the appropriateness of the model but also the convenience of the aerosol features fixed in it to Granada conditions. SMARTS2 model offers increased flexibility concerning the selection of different aerosol models included in the code and provides the best results when the selected models are those considered as urban. Although SMARTS2 provide slightly worse results, both models give estimates of solar ultraviolet irradiance with mean bias deviation below 5%, and root mean square deviation close to experimental errors.

Dynamics of blood plasma by spectropolarimetry and biochemical techniques

NASA Astrophysics Data System (ADS)

Voloshynska, Katerina; Ilashchuka, Tetjana; Prydij, Olexander; Gruia, Maria

2014-08-01

The aim of the study was to establish objective parameters of the field of laser and incoherent radiation of different spectral ranges (UV, visible, IR) as a non-invasive optical method of interaction with different samples of biological tissues and fluids of patients to determine the dynamics of metabolic syndrome and choosing the best personal treatment. As diagnostic methods have been used ultraviolet spectrometry samples of blood plasma in the liquid state, infrared spectroscopy middle range (2,5 - 25 microns) dry residue of plasma polarization and laser diagnostic technique of thin histological sections of biological tissues.

Spectropolarimetry of blood plasma in optimal molecular targeted therapy

NASA Astrophysics Data System (ADS)

Voloshynska, Katerina; Ilashchuk, Tetjana; Yermolenko, Sergey

2015-02-01

The aim of the study was to establish objective parameters of the field of laser and incoherent radiation of different spectral ranges (UV, visible, IR) as a non-invasive optical method of interaction with different samples of biological tissues and fluids of patients to determine the dynamics of metabolic syndrome and choosing the best personal treatment. As diagnostic methods have been used ultraviolet spectrometry samples of blood plasma in the liquid state, infrared spectroscopy middle range (2,5 - 25 microns) dry residue of plasma polarization and laser diagnostic technique of thin histological sections of biological tissues.

Does UV CETI Suffer from the Mad Syndrome?

NASA Technical Reports Server (NTRS)

Drake, Jeremy

1999-01-01

Photometric data have been analyzed and searched for events of flaring and other variability. Some flaring has been detected, though probably not at a level that will hinder our continuing spectral analysis. X-ray diagnostics for the very hot coronal emission measure are under investigation in order to determine whether or not the very hot coronal plasma contributes significantly to the observed X-ray flux in the (EUV) Extreme Ultraviolet Radiation. The key test of the MAD syndrome lies in whether or not the coronal lines indicate a depletion in metals in the corona relative to the underlying photosphere.

Durable silver mirror with ultra-violet thru far infra-red reflection

DOEpatents

Wolfe, Jesse D.

2010-11-23

A durable highly reflective silver mirror characterized by high reflectance in a broad spectral range of about 300 nm in the UV to the far infrared (.about.10000 nm), as well as exceptional environmental durability. A high absorptivity metal underlayer is used which prevents the formation of a galvanic cell with a silver layer while increasing the reflectance of the silver layer. Environmentally durable overcoat layers are provided to enhance mechanical and chemical durability and protect the silver layer from corrosion and tarnishing, for use in a wide variety of surroundings or climates, including harsh or extreme environments.

Ingress observations of the 1980 eclipse of the symbiotic star CI Cyngni

NASA Technical Reports Server (NTRS)

Stencel, R. E.; Michalitsianos, A. G.; Kafatos, M.; Boyarchuk, A. A.

1981-01-01

One of the major results from the IUE may prove to be the knowledge gained by studies of the ultraviolet spectra of symbiotic stars. Symbiotics combine spectral features of a cool M giant like photosphere with strong high excitation emission lines of nebular origin, superposed. The UV spectra are dominated by intense permitted and semiforbidden emission lines and weak continua indicative of hot compact objects and accretion disks. Two symbiotics, AR Pav and CI Cyg are thought to be eclipsing binaries and IUE observations during the 1980 eclipse of CI Cygni are discussed.

Temperature Effects of Ultraviolet Irradiation on Material Degradation

NASA Astrophysics Data System (ADS)

Mori, Kazuyuki; Ishizawa, Junichiro

Ultraviolet rays (UV) cause organic materials to deteriorate. UV irradiation ground testing is therefore important to understand the “adequate lifetime assessment” and the “end-of-life (EOL) characteristic” of materials used in space. In previous experiments, high temperatures were found to accelerate the UV degradation of cross-linked ethylene tetrafluoroethylene (X-ETFE). This causes concern of potentially similar effects in other materials. In this study, we evaluated UV degradation at high temperatures and subsequently determined materials usable in space that had shown accelerated degradation due to UV irradiation at high temperatures.

Fiscal Year 2011 Director’s Strategic Initiative Final Report Heterogeneous Device Architectures Incorporating Nitride Semiconductors for Enhanced Functionality of Optoelectronic Devices

DTIC Science & Technology

2014-03-01

electromagnetic radiation across the spectrum from the ultraviolet ( UV ) to terahertz, heterogeneous integration of these materials with others having different...weak absorption that limit the QE of homogenous SiC-based photodetectors in the deep UV and near UV regions, respectively. Furthermore, we have...Polarization-Enhanced III-Nitride-SiC Avalanche Photodiodes Semiconductor-based ultraviolet ( UV ) avalanche photodetectors (APDs) have significant promise

PAR modulation of the UV-dependent levels of flavonoid metabolites in Arabidopsis thaliana (L.) Heynh. leaf rosettes: cumulative effects after a whole vegetative growth period.

PubMed

Götz, Michael; Albert, Andreas; Stich, Susanne; Heller, Werner; Scherb, Hagen; Krins, Andreas; Langebartels, Christian; Seidlitz, Harald K; Ernst, Dieter

2010-07-01

Long-term effects of ultraviolet (UV) radiation on flavonoid biosynthesis were investigated in Arabidopsis thaliana using the sun simulators of the Helmholtz Zentrum München. The plants, which are widely used as a model system, were grown (1) at high photosynthetically active radiation (PAR; 1,310 micromol m(-2) s(-1)) and high biologically effective UV irradiation (UV-B(BE) 180 mW m(-2)) during a whole vegetative growth period. Under this irradiation regime, the levels of quercetin products were distinctively elevated with increasing UV-B irradiance. (2) Cultivation at high PAR (1,270 micromol m(-2) s(-1)) and low UV-B (UV-B(BE) 25 mW m(-2)) resulted in somewhat lower levels of quercetin products compared to the high-UV-B(BE) conditions, and only a slight increase with increasing UV-B irradiance was observed. On the other hand, when the plants were grown (3) at low PAR (540 micromol m(-2) s(-1)) and high UV-B (UV-B(BE) 180 mW m(-2)), the accumulation of quercetin products strongly increased from very low levels with increasing amounts of UV-B but the accumulation of kaempferol derivatives and sinapoyl glucose was less pronounced. We conclude (4) that the accumulation of quercetin products triggered by PAR leads to a basic UV protection that is further increased by UV-B radiation. Based on our data, (5) a combined effect of PAR and different spectral sections of UV radiation is satisfactorily described by a biological weighting function, which again emphasizes the additional role of UV-A (315-400 nm) in UV action on A. thaliana.

Measurement of free radical kinetics in pulsed plasmas by UV and VUV absorption spectroscopy and by modulated beam mass spectrometry

NASA Astrophysics Data System (ADS)

Cunge, G.; Bodart, P.; Brihoum, M.; Boulard, F.; Chevolleau, T.; Sadeghi, N.

2012-04-01

This paper reviews recent progress in the development of time-resolved diagnostics to probe high-density pulsed plasma sources. We focus on time-resolved measurements of radicals' densities in the afterglow of pulsed discharges to provide useful information on production and loss mechanisms of free radicals. We show that broad-band absorption spectroscopy in the ultraviolet and vacuum ultraviolet spectral domain and threshold ionization modulated beam mass spectrometry are powerful techniques for the determination of the time variation of the radicals' densities in pulsed plasmas. The combination of these complementary techniques allows detection of most of the reactive species present in industrial etching plasmas, giving insights into the physico-chemistry reactions involving these species. As an example, we discuss briefly the radicals' kinetics in the afterglow of a SiCl4/Cl2/Ar discharge.

Experimental realization of a polarization-independent ultraviolet/visible coaxial plasmonic metamaterial.

PubMed

van de Haar, M A; Maas, R; Schokker, H; Polman, A

2014-11-12

We report the experimental realization of an optical metamaterial composed of a hexagonal array of coaxial plasmonic metal/insulator/metal waveguides that shows strong polarization-independent optical mode index dispersion in the ultraviolet/blue. The metamaterial is composed of silicon coaxes with a well-defined diameter in the range of 150-168 nm with extremely thin sidewalls (13-15 nm), embedded in a silver film, fabricated using a combination of electron beam lithography, physical vapor deposition, reactive ion etching, and focused ion beam polishing. Using a Mach-Zehnder interferometer the phase advance is measured on several metamaterial samples with different dimensions in the UV/visible part of the spectrum. For all geometries the spectral features as well as the geometry dependence of the data correspond well with numerical finite-difference time domain simulations and the calculated waveguide dispersion diagram, showing a negative mode index between 440 and 500 nm.

Assessment of Transition Element Speciation in Glasses Using a Portable Transmission Ultraviolet-Visible-Near-Infrared (UV-Vis-NIR) Spectrometer.

PubMed

Hunault, Myrtille; Lelong, Gérald; Gauthier, Michel; Gélébart, Frédéric; Ismael, Saindou; Galoisy, Laurence; Bauchau, Fanny; Loisel, Claudine; Calas, Georges

2016-05-01

A new low-cost experimental setup based on two compact dispersive optical spectrometers has been developed to measure optical absorption transmission spectra over the 350-2500 nm energy range. We demonstrate how near-infrared (NIR) data are essential to identify the coloring species in addition to ultraviolet visible data. After calibration with reference glasses, the use of an original sample stage that maintains the window panel in the vertical position enables the comparison of ancient and modern glasses embedded in a panel from the Sainte-Chapelle of Paris, without any sampling. The spectral resolution enables to observe fine resonances arising in the absorption bands of Cr(3+), and the complementary information obtained in the NIR enables to determine the contribution of Fe(2+), a key indicator of glassmaking conditions. © The Author(s) 2016.

The World Space Observatory Ultraviolet (WSO-UV), as a bridge to future UV astronomy

NASA Astrophysics Data System (ADS)

Shustov, B.; Gómez de Castro, A. I.; Sachkov, M.; Vallejo, J. C.; Marcos-Arenal, P.; Kanev, E.; Savanov, I.; Shugarov, A.; Sichevskii, S.

2018-04-01

Ultraviolet (UV) astronomy is a vital branch of space astronomy. Many dozens of short-term UV-experiments in space, as well as long-term observatories, have brought a very important knowledge on the physics and chemistry of the Universe during the last decades. Unfortunately, no large UV-observatories are planned to be launched by most of space agencies in the coming 10-15 years. Conversely, the large UVOIR observatories of the future will appear not earlier than in 2030s. This paper briefly describes the projects that have been proposed by various groups. We conclude that the World Space Observatory-Ultraviolet (WSO-UV) will be the only 2-m class UV telescope with capabilities similar to those of the HST for the next decade. The WSO-UV has been described in detail in previous publications, and this paper updates the main characteristics of its instruments and the current state of the whole project. It also addresses the major science topics that have been included in the core program of the WSO-UV, making this core program very relevant to the current state of the UV-astronomy. Finally, we also present here the ground segment architecture that will implement this program.

Standardization of Broadband UV Measurements for 365 nm LED Sources

PubMed Central

Eppeldauer, George P.

2012-01-01

Broadband UV measurements are evaluated when UV-A irradiance meters measure optical radiation from 365 nm UV sources. The CIE standardized rectangular-shape UV-A function can be realized only with large spectral mismatch errors. The spectral power-distribution of the 365 nm excitation source is not standardized. Accordingly, the readings made with different types of UV meters, even if they measure the same UV source, can be very different. Available UV detectors and UV meters were measured and evaluated for spectral responsivity. The spectral product of the source-distribution and the meter’s spectral-responsivity were calculated for different combinations to estimate broad-band signal-measurement errors. Standardization of both the UV source-distribution and the meter spectral-responsivity is recommended here to perform uniform broad-band measurements with low uncertainty. It is shown what spectral responsivity function(s) is needed for new and existing UV irradiance meters to perform low-uncertainty broadband 365 nm measurements. PMID:26900516

The Ultraviolet Radiation Environment around M Dwarf Exoplanet Host Stars

NASA Technical Reports Server (NTRS)

France, Kevin; Froning, Cynthia S.; Linsky, Jeffrey L.; Roberge, Aki; Stocke, John T.; Tian, Feng; Bushinsky, Rachel; Desert, Jean-Michel; Mauas, Pablo; Mauas, Pablo;

General Astrophysics Science Enabled by the HabEx Ultraviolet Spectrograph (UVS)

NASA Astrophysics Data System (ADS)

Scowen, Paul; Clarke, John; Gaudi, B. Scott; Kiessling, Alina; Martin, Stefan; Somerville, Rachel; Stern, Daniel; HabEx Science and Technology Definition Team

2018-01-01

The Habitable Exoplanet Imaging Mission (HabEx) is one of the four large mission concepts being studied by NASA as input to the upcoming 2020 Decadal Survey. The mission implements two world-class General Astrophysics instruments as part of its complement of instrumentation to enable compelling science using the 4m aperture. The Ultraviolet Spectrograph has been designed to address cutting edge far ultraviolet (FUV) science that has not been possible with the Hubble Space Telescope, and to open up a wide range of capabilities that will advance astrophysics as we look into the 2030s. Our poster discusses some of those science drivers and possible applications, which range from Solar System science, to nearby and more distant studies of star formation, to studies of the circumgalactic and intergalactic mediums where the ecology of mass and energy transfer are vital to understanding stellar and galactic evolution. We discuss the performance features of the instrument that include a large 3’x3’ field of view for multi-object spectroscopy, and some 20 grating modes for a variety of spectral resolution and coverage.

Extreme ultraviolet explorer satellite observation of Jupiter's Io plasma torus

NASA Technical Reports Server (NTRS)

Hall, D. T; Gladstone, G. R.; Moos, H. W.; Bagenal, F.; Clarke, J. T.; Feldman, P. D.; Mcgrath, M. A.; Schneider, N. M.; Shemansky, D. E.; Strobel, D. F.

1994-01-01

We present the first Extreme Ultraviolet Explorer (EUVE) satellite observation of the Jupiter system, obtained during the 2 day period 1993 March 30 through April 1, which shows a rich emission-line spectrum from the Io plasma torus spanning wavelengths 370 to 735 A. The emission features correspond primarily to known multiplets of oxygen and sulfur ions, but a blended feature near 372 A is a plausible Na II transition. The summed detected energy flux of (7.2 +/- 0.2) x 10(exp -11) ergs/sq cm(s) corresponds to a radiated power of approximately equal to 4 x 10(exp 11) W in this spectral range. All ansa emissions show a distinct dawn-dusk brightness asymmetry and the measured dusk/dawn ratio of the bright S III lambda-680 feature is 2.3 +/- 0.3, significantly larger than the ratio measured by the Voyager spacecraft ultraviolet (UV) instruments. A preliminary estimate of ion partitioning indicates that the oxygen/sulfur ion ratio is approximately equal to 2, compared to the value approximately equal to 1.3 measured by Voyager, and that (Na(+))/(e) greater than 0.01.

Impact of shortwave ultraviolet (UV-C) radiation on the antioxidant activity of thyme (Thymus vulgaris L.).

PubMed

Dogu-Baykut, Esra; Gunes, Gurbuz; Decker, Eric Andrew

2014-08-15

Thyme is a good source of antioxidant compounds but it can be contaminated by microorganisms. An experimental fluid bed ultraviolet (UV) reactor was designed for microbial decontamination of thyme samples and the effect of shortwave ultraviolet light (UV-C) radiation on antioxidant properties of thyme was studied. Samples were exposed to UV-C radiation for 16 or 64 min. UV-C treatment led to 1.04 and 1.38 log CFU/g reduction of total aerobic mesophilic bacteria (TAMB) counts. Hunter a(∗) value was the most sensitive colour parameter during UV-C treatment. 2,2-Diphenyl-1-picrylhydrazyl (DPPH) scavenging activity of extracts was not significantly affected by UV-C. Addition of thyme extracts at 0.15 and 0.3 μmol GAE/ml emulsion delayed the formation of lipid hydroperoxides and headspace hexanal in the 5.0%(wt) corn oil-in-water emulsion from 4 to 9 and 14 days, respectively. No significant changes in oxidation rates were observed between UV-C treated and untreated samples at same concentrations. Copyright © 2014 Elsevier Ltd. All rights reserved.

DEMONSTRATION BULLETIN - ULTROX INTERNATIONAL, INC. ULTRAVIOLET RADIATION AND OXIDATION

EPA Science Inventory

The ultraviolet (UV) radiation/oxidation treatment technology developed by Ultrox International uses a combination of UV radiation, ozone, and hydrogen peroxide to oxidize organic compounds in water. Various operating parameters can be adjusted in the Ultrox® system to enhan...

UV exposure in cars.

PubMed

Moehrle, Matthias; Soballa, Martin; Korn, Manfred

2003-08-01

There is increasing knowledge about the hazards of solar and ultraviolet (UV) radiation to humans. Although people spend a significant time in cars, data on UV exposure during traveling are lacking. The aim of this study was to obtain basic information on personal UV exposure in cars. UV transmission of car glass samples, windscreen, side and back windows and sunroof, was determined. UV exposure of passengers was evaluated in seven German middle-class cars, fitted with three different types of car windows. UV doses were measured with open or closed windows/sunroof of Mercedes-Benz E 220 T, E 320, and S 500, and in an open convertible car (Mercedes-Benz CLK). Bacillus subtilis spore film dosimeters (Viospor) were attached to the front, vertex, cheeks, upper arms, forearms and thighs of 'adult' and 'child' dummies. UV wavelengths longer than >335 nm were transmitted through car windows, and UV irradiation >380 nm was transmitted through compound glass windscreens. There was some variation in the spectral transmission of side windows according to the type of glass. On the arms, UV exposure was 3-4% of ambient radiation when the car windows were shut, and 25-31% of ambient radiation when the windows were open. In the open convertible car, the relative personal doses reached 62% of ambient radiation. The car glass types examined offer substantial protection against short-wave UV radiation. Professional drivers should keep car windows closed on sunny days to reduce occupational UV exposure. In individuals with polymorphic light eruption, produced by long-wave UVA, additional protection by plastic films, clothes or sunscreens appears necessary.

Foraging performance of two fishes, the threespine stickleback and the Cumaná guppy, under different light backgrounds.

PubMed

Zukoshi, Reo; Savelli, Ilaria; Novales Flamarique, Iñigo

2018-04-01

Many vertebrates have cone photoreceptors that are most sensitive to ultraviolet (UV) light termed UV cones. The ecological functions that these cones contribute to are seldom known though they are suspected of improving foraging and communication in a variety of fishes. In this study, we used several spectral backgrounds to assess the contribution of UV and violet cones, or long wavelength (L) cones, in the foraging performance of juvenile Cumaná guppy, Poecilia reticulata, or marine stickleback, Gasterosteus aculeatus. Regardless of whether the light spectrum contained or not wavelengths below 450 nm (the limiting wavelength for UV cone stimulation), the foraging performance of both species was statistically the same, as judged by the mean distance and angle associated with attacks on prey (Daphnia magna). Our experiments also showed that the foraging performance of sticklebacks when only the double cones (and, almost exclusively, the L cones) were active was similar to that when all cones were functional, demonstrating that the double cone was sufficient for prey detection. This result indicates that foraging potentially relied on an achromatic channel serving prey motion detection, as the two spectral cone types that make up the double cone [maximally sensitive to middle (M) and long (L) wavelengths, respectively] form the input to the achromatic channel in cyprinid fishes and double cones are widely associated with achromatic tasks in other vertebrates including reptiles and birds. Stickleback performance was also substantially better when foraging under a 100% linearly polarized light field than when under an unpolarized light field. Together, our results suggest that in some teleost species UV cones exert visually-mediated ecological functions different from foraging, and furthermore that polarization sensitivity could improve the foraging performance of sticklebacks. Copyright © 2018 Elsevier Ltd. All rights reserved.

UV/PAR radiation and DOM properties in surface coastal waters of the Canadian shelf of the Beaufort Sea during summer 2009

NASA Astrophysics Data System (ADS)

Para, J.; Charrière, B.; Matsuoka, A.; Miller, W. L.; Rontani, J. F.; Sempéré, R.

2013-04-01

Surface waters from the Beaufort Sea in the Arctic Ocean were evaluated for dissolved organic carbon (DOC), and optical characteristics including UV (ultraviolet) radiation and PAR (photosynthetically active radiation) diffuse attenuation (Kd), and chromophoric and fluorescent dissolved organic matter (CDOM and FDOM) as part of the MALINA field campaign (30 July to 27 August). Spectral absorption coefficients (aCDOM (350 nm) (m-1)) were significantly correlated to both diffuse attenuation coefficients (Kd) in the UV-A and UV-B and to DOC concentrations. This indicates CDOM as the dominant attenuator of both UV and PAR solar radiation and suggests its use as an optical proxy for DOC concentrations in this region. While the Mackenzie input is the main driver of CDOM dynamics in low salinity waters, locally, primary production can create significant increases in CDOM. Extrapolating CDOM to DOC relationships, we estimate that ∼16% of the DOC in the Mackenzie River does not absorb radiation at 350 nm. The discharges of DOC and its chromophoric subset (CDOM) by the Mackenzie River during the MALINA cruise are estimated as ∼0.22 TgC and 0.18 TgC, respectively. Three dissolved fluorescent components (C1-C3) were identified by fluorescence excitation/emission matrix spectroscopy (EEMS) and parallel factor (PARAFAC) analysis. Our results showed an aquatic dissolved organic matter (DOM) component (C1), probably produced in the numerous lakes of the watershed, that co-dominated with a terrestrial humic-like component (C2) in the Mackenzie Delta Sector. This aquatic DOM could partially explain the high CDOM spectral slopes observed in the Beaufort Sea.

Spatially resolved star formation and dust attenuation in Mrk 848: Comparison of the integral field spectra and the UV-to-IR SED

NASA Astrophysics Data System (ADS)

Yuan, Fang-Ting; Argudo-Fernández, María; Shen, Shiyin; Hao, Lei; Jiang, Chunyan; Yin, Jun; Boquien, Médéric; Lin, Lihwai

2018-05-01

We investigate the star formation history and the dust attenuation in the galaxy merger Mrk 848. Thanks to the multiwavelength photometry from the ultraviolet (UV) to the infrared (IR), and MaNGA's integral field spectroscopy, we are able to study this merger in a detailed way. We divide the whole merger into the core and tail regions, and fit both the optical spectrum and the multi-band spectral energy distribution (SED) to models to obtain the star formation properties for each region respectively. We find that the color excess of stars in the galaxy E(B-V)sSED measured with the multi-band SED fitting is consistent with that estimated both from the infrared excess (the ratio of IR to UV flux) and from the slope of the UV continuum. Furthermore, the reliability of the E(B-V)sSED is examined with a set of mock SEDs, showing that the dust attenuation of the stars can be well constrained by the UV-to-IR broadband SED fitting. The dust attenuation obtained from optical continuum E(B-V)sspec is only about half of E(B-V)sSED. The ratio of the E(B-V)sspec to the E(B-V)g obtained from the Balmer decrement is consistent with the local value (around 0.5). The difference between the results from the UV-to-IR data and the optical data is consistent with the picture that younger stellar populations are attenuated by an extra dust component from the birth clouds compared to older stellar populations which are only attenuated by the diffuse dust. Both with the UV-to-IR SED fitting and the spectral fitting, we find that there is a starburst younger than 100 Myr in one of the two core regions, consistent with the scenario that the interaction-induced gas inflow can enhance the star formation in the center of galaxies.

DirtyGrid I: 3D Dust Radiative Transfer Modeling of Spectral Energy Distributions of Dusty Stellar Populations

NASA Astrophysics Data System (ADS)

Law, Ka-Hei; Gordon, Karl D.; Misselt, Karl A.

2018-06-01

Understanding the properties of stellar populations and interstellar dust has important implications for galaxy evolution. In normal star-forming galaxies, stars and the interstellar medium dominate the radiation from ultraviolet (UV) to infrared (IR). In particular, interstellar dust absorbs and scatters UV and optical light, re-emitting the absorbed energy in the IR. This is a strongly nonlinear process that makes independent studies of the UV-optical and IR susceptible to large uncertainties and degeneracies. Over the years, UV to IR spectral energy distribution (SED) fitting utilizing varying approximations has revealed important results on the stellar and dust properties of galaxies. Yet the approximations limit the fidelity of the derived properties. There is sufficient computer power now available that it is now possible to remove these approximations and map out of landscape of galaxy SEDs using full dust radiative transfer. This improves upon previous work by directly connecting the UV, optical, and IR through dust grain physics. We present the DIRTYGrid, a grid of radiative transfer models of SEDs of dusty stellar populations in galactic environments designed to span the full range of physical parameters of galaxies. Using the stellar and gas radiation input from the stellar population synthesis model PEGASE, our radiative transfer model DIRTY self-consistently computes the UV to far-IR/sub-mm SEDs for each set of parameters in our grid. DIRTY computes the dust absorption, scattering, and emission from the local radiation field and a dust grain model, thereby physically connecting the UV-optical to the IR. We describe the computational method and explain the choices of parameters in DIRTYGrid. The computation took millions of CPU hours on supercomputers, and the SEDs produced are an invaluable tool for fitting multi-wavelength data sets. We provide the complete set of SEDs in an online table.

Visible-Blind UV Photodetector Based on Single-Walled Carbon Nanotube Thin Film/ZnO Vertical Heterostructures.

PubMed

Li, Guanghui; Suja, Mohammad; Chen, Mingguang; Bekyarova, Elena; Haddon, Robert C; Liu, Jianlin; Itkis, Mikhail E

2017-10-25

Ultraviolet (UV) photodetectors based on heterojunctions of conventional (Ge, Si, and GaAs) and wide bandgap semiconductors have been recently demonstrated, but achieving high UV sensitivity and visible-blind photodetection still remains a challenge. Here, we utilized a semitransparent film of p-type semiconducting single-walled carbon nanotubes (SC-SWNTs) with an energy gap of 0.68 ± 0.07 eV in combination with a molecular beam epitaxy grown n-ZnO layer to build a vertical p-SC-SWNT/n-ZnO heterojunction-based UV photodetector. The resulting device shows a current rectification ratio of 10 3 , a current photoresponsivity up to 400 A/W in the UV spectral range from 370 to 230 nm, and a low dark current. The detector is practically visible-blind with the UV-to-visible photoresponsivity ratio of 10 5 due to extremely short photocarrier lifetimes in the one-dimensional SWNTs because of strong electron-phonon interactions leading to exciton formation. In this vertical configuration, UV radiation penetrates the top semitransparent SC-SWNT layer with low losses (10-20%) and excites photocarriers within the n-ZnO layer in close proximity to the p-SC-SWNT/n-ZnO interface, where electron-hole pairs are efficiently separated by a high built-in electric field associated with the heterojunction.

The endogenous hormones in soybean seedlings under the joint actions of rare earth element La(III) and ultraviolet-B stress.

PubMed

Peng, Qi; Zhou, Qing

2009-12-01

The dynamic state of endogenous hormone content in soybean seedlings was investigated for a further demonstration of alleviating the damage of the ultraviolet ultraviolet-B (UV-B) radiation in the La(III)-treated soybean seedlings under UV-B stress. Using hydroponics culture, the effects of lanthanum(III) on the contents of endogenous hormone under elevated ultraviolet-B radiation (280–320 nm) was studied. The results showed that the content of indole-3-acetic acid (IAA) in soybean seedlings decreased initially and then increased when the seedlings underwent UV-B treatment during the stress and convalescent period; this was compared with a control; acetic acid oxidase (IAAO) activity increased at first (first to fifth day) and then decreased (sixth to 11th day). A similar change of abscisic acid content and IAAO content in soybean seedlings occurred; gibberellic acid (GA) content decreased during the experiment compared with control. The content of IAA and GA in soybean seedlings with La(III) + UV-B treatment was higher than those of UV-B treatment; IAAO activity and GA content in soybean seedlings with La (III) + UV-B treatment were lower than those of UV-B treatment. It suggested that the regulative effect of La(III) at the optimum concentration on endogenous hormone improved the ability of plant stress resistance, and its protective effect against low UV-B radiation was superior to high UV-B radiation. The defensive effect of La(III) on soybean seedlings under UV-B stress was carried out on the layer of defense system.

Drinking water treatment with ultraviolet light for travelers -- Evaluation of a mobile lightweight system.

PubMed

Timmermann, Lisa F; Ritter, Klaus; Hillebrandt, David; Küpper, Thomas

2015-01-01

The SteriPEN(®) is a handheld device for disinfecting water with ultraviolet (UV) radiation. The manufacturer claims a reduction of at least 99.9% of bacteria, viruses, and protozoa. The present study intends to verify the general effectiveness of the device. Furthermore, the influence of bottle geometry and water movement is examined and the issue of user safety with regard to UV-C radiation is addressed. The device was applied on water containing a known number of microorganisms (Escherichia coli, Staphylococcus aureus, and the spore of Geobacillusstearothermophilus) and the survival rate was examined. Three different types of bottles commonly used among travelers served as test containers. All tests were conducted with and without agitating the water during irradiation. Furthermore, a spectral analysis was performed on the light of the device. The SteriPEN(®) reached a mean reduction of more than 99.99% of bacteria and 99.57% of the spores when applied correctly. However, the results of the trials without agitating the water only yielded a 94.98% germ reduction. The device's maximal radiation intensity lies at 254 nm which is the wavelength most efficient in inactivating bacteria. The UV-C fraction is filtered out completely by common bottle materials. However, when applied in larger containers a portion of the UV-C rays exits the water surface. If applied according to the instructions the device manages a satisfactory inactivation of bacteria. However, it bears the danger of user errors relevant to health. Therefore, education on the risks of incorrect application should be included in the travel medical consultation. Also there are still aspects that need to be subject to further independent research. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

Ultraviolet Testing of Space Suit Materials for Mars

NASA Technical Reports Server (NTRS)

Larson, Kristine; Fries, Marc

2017-01-01

Human missions to Mars may require radical changes in the approach to extra-vehicular (EVA) suit design. A major challenge is the balance of building a suit robust enough to complete multiple EVAs under intense ultraviolet (UV) light exposure without losing mechanical strength or compromising the suit's mobility. To study how the materials degrade on Mars in-situ, the Jet Propulsion Laboratory (JPL) invited the Advanced Space Suit team at NASA's Johnson Space Center (JSC) to place space suit materials on the Scanning Habitable Environments with Raman & Luminescence for Organics and Chemicals (SHERLOC) instrument's calibration target of the Mars 2020 rover. In order to select materials for the rover and understand the effects from Mars equivalent UV exposure, JSC conducted ground testing on both current and new space suit materials when exposed to 2500 hours of Mars mission equivalent UV. To complete this testing, JSC partnered with NASA's Marshall Space Flight Center to utilize their UV vacuum chambers. Materials tested were Orthofabric, polycarbonate, Teflon, Dacron, Vectran, spectra, bladder, nGimat coated Teflon, and nGimat coated Orthofabric. All samples were measured for mass, tensile strength, and chemical composition before and after radiation. Mass loss was insignificant (less than 0.5%) among the materials. Most materials loss tensile strength after radiation and became more brittle with a loss of elongation. Changes in chemical composition were seen in all radiated materials through Spectral Analysis. Results from this testing helped select the materials that will fly on the Mars 2020 rover. In addition, JSC can use this data to create a correlation to the chemical changes after radiation-which is what the rover will send back while on Mars-to the mechanical changes, such as tensile strength.

Astrophysics Meets Atomic Physics: Fe I Line Identifications and Templates for Old Stellar Populations from Warm and Hot Stellar UV Spectra

NASA Astrophysics Data System (ADS)

Peterson, Ruth

2017-08-01

Imaging surveys from the ultraviolet to the infrared are recording ever more distant astronomical sources. Needed to interpret them are high-resolution ultraviolet spectral templates at all metallicities for both old and intermediate-age stars, and the atomic physics data essential to model their spectra. To this end we are proposing new UV spectra of four warm and hot stars spanning a wide range of metallicity. These will provide observational templates of old and young metal-poor turnoff stars, and the laboratory source for the identification of thousands of lines of neutral iron that appear in stellar spectra but are not identified in laboratory spectra. By matching existing and new stellar spectra to calculations of energy levels, line wavelengths, and gf-values, Peterson & Kurucz (2015) and Peterson, Kurucz, & Ayres (2017) identified 124 Fe I levels with energies up to 8.4eV. These provided 3000 detectable Fe I lines from 1600A to 5.4mu, and yielded empirical gf-values for 640 of these. Here we propose high-resolution UV spectra reaching 1780A for the first time at the turnoff, to detect and identify the strongest Fe I lines at 1800 - 1850A. This should add 250 new Fe I levels. These spectra, plus one at lower resolution reaching 1620A, will also provide empirical UV templates for turnoff stars at high redshifts as well as low. This is essential to deriving age and metallicity independently for globular clusters and old galaxies out to z 3. It will also improve abundances of trace elements in metal-poor stars, constraining nucleosynthesis at early epochs and aiding the reconstruction of the populations of the Milky Way halo and of nearby globular clusters.

CHALLENGES OF COMBINED SEWER OVERFLOW DISINFECTION BY ULTRAVIOLET LIGHT IRRADIATION

EPA Science Inventory

This article examines the performance and effectiveness of ultraviolet (UV) light irradiation for disinfection of combined sewer overflow (CSO). Due to the negative impact of conventional water disinfectants on aquatic life, new agents (e.g., UV light) are being investigated for ...

ULTRAVIOLET RADIATION AND ARSENIC INTERACTIONS: EFFECTS ON CLADOCERANS

EPA Science Inventory

The effects of arsenic and ultraviolet radiation (UV) on cladocerans have been examined separately, however the interaction of these two stresses has not been explored. Potential synergism between these two stresses is possible as arsenic is known to inhibit repair of UV induced ...

Bias Selectable Dual Band AlGaN Ultra-violet Detectors

NASA Technical Reports Server (NTRS)

Yan, Feng; Miko, Laddawan; Franz, David; Guan, Bing; Stahle, Carl M.

2007-01-01

Bias selectable dual band AlGaN ultra-violet (UV) detectors, which can separate UV-A and UV-B using one detector in the same pixel by bias switching, have been designed, fabricated and characterized. A two-terminal n-p-n photo-transistor-like structure was used. When a forward bias is applied between the top electrode and the bottom electrode, the detectors can successfully detect W-A and reject UV-B. Under reverse bias, they can detect UV-B and reject UV-A. The proof of concept design shows that it is feasible to fabricate high performance dual-band UV detectors based on the current AlGaN material growth and fabrication technologies.

Development of a method for the characterization and operation of UV-LED for water treatment.

PubMed

Kheyrandish, Ataollah; Mohseni, Madjid; Taghipour, Fariborz

2017-10-01

Tremendous improvements in semiconductor technology have made ultraviolet light-emitting diodes (UV-LEDs) a viable alternative to conventional UV sources for water treatment. A robust and validated experimental protocol for studying the kinetics of microorganism inactivation is key to the further development of UV-LEDs for water treatment. This study proposes a protocol to operate UV-LEDs and control their output as a polychromatic radiation source. In order to systematically develop this protocol, the results of spectral power distribution, radiation profile, and radiant power measurements of a variety of UV-LEDs are presented. A wide range of UV-LEDs was selected for this study, covering various UVA, UVB, and UVC wavelengths, viewing angles from 3.5° to 135°, and a variety of output powers. The effects of operational conditions and measurement techniques were investigated on these UV-LEDs using a specially designed and fabricated setup. Operating conditions, such as the UV-LED electrical current and solder temperature, were found to significantly affect the power and peak wavelength output. The measurement techniques and equipment, including the detector size, detector distance from the UV-LED, and potential reflection from the environment, were shown to influence the results for many of the UV-LEDs. The results obtained from these studies were analyzed and applied to the development of a protocol for UV-LED characterization. This protocol is presented as a guideline that allows the operation and control of UV-LEDs in any structure, as well as accurately measuring the UV-LED output. Such information is essential for performing a reliable UV-LED assessment for the inactivation of microorganisms and for obtaining precise kinetic data. Copyright © 2017 Elsevier Ltd. All rights reserved.

Measurements of OH(X2pi) in the stratosphere by high resolution UV spectroscopy

NASA Technical Reports Server (NTRS)

Torr, D. G.; Swift, W.; Fennelly, J.; Liu, G.; Torr, M. R.

1987-01-01

This paper reports the first results obtained using high spectral resolution imaging ultraviolet spectroscopy to observe multiple rotational lines of OH A2 Sigma-X2pi (0-0) band. A 9.2 A spectral segment from 3075.8 A to 3085.0 A is imaged at 0.08 A FWHM spectral resolution, allowing the simultaneous acquisition of six of the brightest OH resonance fluorescence emission lines. The high spectral resolution and low scattered light design of the instrument allows these lines to be detected above the Rayleigh scattered sunlight background. The technique permits remote sensing of stratospheric OH from a high altitude instrument. The instrument was flown to an altitude of 40 km on Aug. 25, 1983, and again on June 12, 1986, on scientific balloons from Palestine, TX. The OH profiles inverted from the limb scans made during these flights are reported here. These profiles represent the first measurements of the temporal variation of OH over an extended height range. The results demonstrate that the technique can be used to monitor OH from orbit.

Some remarks on relativistic diffusion and the spectral dimension criterion

NASA Astrophysics Data System (ADS)

Muniz, C. R.; Cunha, M. S.; Filho, R. N. Costa; Bezerra, V. B.

2015-01-01

The spectral dimension ds for high energies is calculated using the Relativistic Schrödinger Equation Analytically Continued (RSEAC) instead of the so-called Telegraph's equation (TE), in both ultraviolet (UV) and infrared (IR) regimens. Regarding the TE, the recent literature presents difficulties related to its stochastic derivation and interpretation, advocating the use of the RSEAC to properly describe the relativistic diffusion phenomena. Taking into account that the Lorentz symmetry is broken in UV regime at Lifshitz point, we show that there exists a degeneracy in very high energies, meaning that both the RSEAC and TE correctly describe the diffusion processes at these energy scales, at least under the spectral dimension criterion. In fact, both the equations yield the same result, namely, ds=2 , a dimensional reduction that is compatible with several theories of quantum gravity. This result is reached even when one takes into account a cosmological model, as for example, the de Sitter universe. On the other hand, in the IR regimen, such degeneracy is lifted in favor of the approach via TE, due to the fact that only this equation provides the correct value for ds, which is equal to the actual number of spacetime dimensions, i.e., ds=4 , while RSEAC yields ds=3 , so that a diffusing particle described by this method experiences a three-dimensional spacetime.

The absorption budget of fresh biomass burning aerosol from realistic laboratory fires

NASA Astrophysics Data System (ADS)

Wagner, N. L.; Adler, G. A.; Franchin, A.; Lamb, K.; Manfred, K.; Middlebrook, A. M.; Selimovic, V.; Schwarz, J. P.; Washenfelder, R. A.; Womack, C.; Yokelson, R. J.

2017-12-01

Wildfires are expected to increase globally due to climate change. The smoke from these wildfires has a highly uncertain radiative effect, largely due to the lack of detailed understanding of its optical properties. As part of the NOAA FIREX project, we have measured the optical properties of smoke primarily from laboratory burning of North American fuels at the Missoula Fire Sciences Laboratory. Here, we present a budget of the aerosol absorption from a portion of the laboratory fires. The total aerosol absorption was measured with photoacoustic spectrometers (PAS) at four wavelengths (405 nm, 532 nm, 660 nm, 870 nm) spanning the visible spectral region. The aerosol absorption is attributed to black carbon which absorbs broadly across the visible and ultraviolet (UV) spectral region and brown carbon (BrC) which absorbs in the blue and UV spectral regions. Then aerosol absorption measurements are compared with measurements of refractory black carbon (rBC) concentration by laser induced incandescence (SP2) and measurements of BrC concentration from a particle-into-liquid sampler coupled to a liquid absorption cell (BrC-PILS). Periodically, a thermodenuder was inserted upstream of all of the instruments to constrain the relationship between aerosol volatility and absorption. We synthesize these measurements to constrain the various contributors to total absorption including effects of lensing on rBC absorption, and of BrC that is not volatilized in the thermodenuder.

ULTRAVIOLET HALOS AROUND SPIRAL GALAXIES. I. MORPHOLOGY

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

Hodges-Kluck, Edmund; Cafmeyer, Julian; Bregman, Joel N., E-mail: hodgeskl@umich.edu

2016-12-10

We examine ultraviolet halos around a sample of highly inclined galaxies within 25 Mpc to measure their morphology and luminosity. Despite contamination from galactic light scattered into the wings of the point-spread function, we find that ultraviolet (UV) halos occur around each galaxy in our sample. Around most galaxies the halos form a thick, diffuse disk-like structure, but starburst galaxies with galactic superwinds have qualitatively different halos that are more extensive and have filamentary structure. The spatial coincidence of the UV halos above star-forming regions, the lack of consistent association with outflows or extraplanar ionized gas, and the strong correlationmore » between the halo and galaxy UV luminosity suggest that the UV light is an extragalactic reflection nebula. UV halos may thus represent 10{sup 6}–10{sup 7} M {sub ⊙} of dust within 2–10 kpc of the disk, whose properties may change with height in starburst galaxies.« less

Photoenhanced toxicity of a carbamate insecticide to early life stage anuran amphibians

USGS Publications Warehouse

Zaga, A.; Little, E.E.; Rabeni, C.F.; Ellersieck, Mark R.

1998-01-01

Aican clawed frog (Xenopus laevis) and gray tree frog (Hyla versicolor) embryos and tadpoles were exposed to sublethal levels of carbaryl, a broad-spectrum insecticide, and ultraviolet radiation to determine interactive and sublethal effects. Ultraviolet intensity (UV-B [285–320 nm] plus UV-A [321–400 nm]) was controlled with various types of plastic filters and quantified with a scanning spectroradiometer. Significant differences in swimming activity and mortality of both species were evident during the 96-h experiments. Ultraviolet-B radiation alone and carbaryl in the presence of UV-B significantly decreased swimming activity of both species. As little as 1.5% intensity of ambient solar UV-B radiation photoactivated carbaryl. Toxicity of 7.5 mg/L carbaryl increased by 10-fold in the presence of UV-B in all species and life stages tested. Our results indicate that photoenhancement by solar UV-B radiation should be considered when evaluating the toxicity of contaminants to amphibians and other organisms.

Next step in Studying the Ultraviolet Universe: WSO-UV

NASA Astrophysics Data System (ADS)

Shustov, Boris M.; Sachkov, Mikhail; Gomez De Castro, Ana

The World Space Observatory-Ultraviolet (WSO-UV) is an international space mission born as a response to the growing up demand for UV facilities by the astronomical community. In the horizon of the next 10 years, the WSO-UV will be the only 2-meters class mission in the after-HST epoch that will guarantee access to UV wavelength domain. The project is managed by an international consortium led by the Federal Space Agency (ROSCOSMOS, Russia). Here we describe the WSO-UV project with its general objectives and main features, the details and status of instrumentation that includes WUVS (spectrographs) and the ISSIS instrument (Field Camera Unit), WSO-UV ground segment, science management plan, the WSO-UV key science issues and prospects of high resolution spectroscopic studies with WSO-UV.

The dynamics of color signals in male threespine sticklebacks Gasterosteus aculeatus

PubMed Central

Hiermes, Meike

2016-01-01

Abstract Body coloration and color patterns are ubiquitous throughout the animal kingdom and vary between and within species. Recent studies have dealt with individual dynamics of various aspects of coloration, as it is in many cases a flexible trait and changes in color expression may be context-dependent. During the reproductive phase, temporal changes of coloration in the visible spectral range (400–700 nm) have been shown for many animals but corresponding changes in the ultraviolet (UV) waveband (300–400 nm) have rarely been studied. Threespine stickleback Gasterosteus aculeatus males develop conspicuous orange–red breeding coloration combined with UV reflectance in the cheek region. We investigated dynamics of color patterns including UV throughout a male breeding cycle, as well as short-term changes in coloration in response to a computer-animated rival using reflectance spectrophotometry and visual modeling, to estimate how colors would be perceived by conspecifics. We found the orange–red component of coloration to vary during the breeding cycle with respect to hue (theta/R50) and intensity (achieved chroma/red chroma). Furthermore, color intensity in the orange–red spectral part (achieved chroma) tended to be increased after the presentation of an artificial rival. Dynamic changes in specific measures of hue and intensity in the UV waveband were not found. In general, the orange–red component of the signal seems to be dynamic with respect to color intensity and hue. This accounts in particular for color changes during the breeding cycle, presumably to signal reproductive status, and with limitations as well in the intrasexual context, most likely to signal dominance or inferiority. PMID:29491887

The dynamics of color signals in male threespine sticklebacks Gasterosteus aculeatus.

PubMed

Hiermes, Meike; Rick, Ingolf P; Mehlis, Marion; Bakker, Theo C M

2016-02-01

Body coloration and color patterns are ubiquitous throughout the animal kingdom and vary between and within species. Recent studies have dealt with individual dynamics of various aspects of coloration, as it is in many cases a flexible trait and changes in color expression may be context-dependent. During the reproductive phase, temporal changes of coloration in the visible spectral range (400-700 nm) have been shown for many animals but corresponding changes in the ultraviolet (UV) waveband (300-400 nm) have rarely been studied. Threespine stickleback Gasterosteus aculeatus males develop conspicuous orange-red breeding coloration combined with UV reflectance in the cheek region. We investigated dynamics of color patterns including UV throughout a male breeding cycle, as well as short-term changes in coloration in response to a computer-animated rival using reflectance spectrophotometry and visual modeling, to estimate how colors would be perceived by conspecifics. We found the orange-red component of coloration to vary during the breeding cycle with respect to hue ( theta /R50) and intensity (achieved chroma/red chroma). Furthermore, color intensity in the orange-red spectral part (achieved chroma) tended to be increased after the presentation of an artificial rival. Dynamic changes in specific measures of hue and intensity in the UV waveband were not found. In general, the orange-red component of the signal seems to be dynamic with respect to color intensity and hue. This accounts in particular for color changes during the breeding cycle, presumably to signal reproductive status, and with limitations as well in the intrasexual context, most likely to signal dominance or inferiority.

Enhancement of pectinase production by ultraviolet irradiation and diethyl sulfate mutagenesis of a Fusarium oxysporum isolate.

PubMed

Yin, L B; Zhang, C F; Xia, Q L; Yang, Y; Xiao, K; Zhao, L Z

2016-09-23

Fusarium oxysporum strain BM-201 was treated with ultraviolet (UV) radiation to obtain a high pectinase-producing strain. Mutant UV-10-41 was obtained and then treated by diethyl sulfate. Next, the mutant UV-diethyl sulfate-43 derived from UV-10-41 was selected as high pectinase-producing strain. Mutant UV-diethyl sulfate-43 was incubated on slant for 10 generations, demonstrating that the pectinase-producing genes were stable. Pectinase activity reached 391.2 U/mL, which is 73.6% higher than that of the original strain.

Near-ultraviolet Excess in Slowly Accreting T Tauri Stars: Limits Imposed by Chromospheric Emission

NASA Astrophysics Data System (ADS)

Ingleby, Laura; Calvet, Nuria; Bergin, Edwin; Herczeg, Gregory; Brown, Alexander; Alexander, Richard; Edwards, Suzan; Espaillat, Catherine; France, Kevin; Gregory, Scott G.; Hillenbrand, Lynne; Roueff, Evelyne; Valenti, Jeff; Walter, Frederick; Johns-Krull, Christopher; Brown, Joanna; Linsky, Jeffrey; McClure, Melissa; Ardila, David; Abgrall, Hervé; Bethell, Thomas; Hussain, Gaitee; Yang, Hao

2011-12-01

Young stars surrounded by disks with very low mass accretion rates are likely in the final stages of inner disk evolution and therefore particularly interesting to study. We present ultraviolet (UV) observations of the ~5-9 Myr old stars RECX-1 and RECX-11, obtained with the Cosmic Origins Spectrograph and Space Telescope Imaging Spectrograph on the Hubble Space Telescope, as well as optical and near-infrared spectroscopic observations. The two stars have similar levels of near-UV emission, although spectroscopic evidence indicates that RECX-11 is accreting and RECX-1 is not. The line profiles of Hα and He I λ10830 in RECX-11 show both broad and narrow redshifted absorption components that vary with time, revealing the complexity of the accretion flows. We show that accretion indicators commonly used to measure mass accretion rates, e.g., U-band excess luminosity or the Ca II triplet line luminosity, are unreliable for low accretors, at least in the middle K spectral range. Using RECX-1 as a template for the intrinsic level of photospheric and chromospheric emission, we determine an upper limit of 3 × 10-10 M ⊙ yr-1 for RECX-11. At this low accretion rate, recent photoevaporation models predict that an inner hole should have developed in the disk. However, the spectral energy distribution of RECX-11 shows fluxes comparable to the median of Taurus in the near-infrared, indicating that substantial dust remains. Fluorescent H2 emission lines formed in the innermost disk are observed in RECX-11, showing that gas is present in the inner disk, along with the dust. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

Origins, Structure, and Evolution of Magnetic Activity in the Cool Half of the H--R Diagram: an HST STIS Survey

NASA Astrophysics Data System (ADS)

Ayres, T. R.; Brown, A.; Drake, S. A.; Dupree, A. K.; Guedel, M.; Guinan, E.; Harper, G. M.; Jordan, C.; Linsky, J. L.; Reimers, D.; Schmitt, J. H. M. M.; Simon, T.

1999-12-01

In HST's cycle 8, we are carrying out a major ultraviolet spectral survey of late-type stars using the powerful capabilities of the Space Telescope Imaging Spectrograph (STIS). The origin of the hot UV emissions of otherwise cool stars is a fundamental puzzle in astrophysics. Magnetic phenomena---at the heart of chromospheric and coronal activity, and perhaps wind driving as well---play a central role in many cosmic settings. Our objective is to obtain high-quality ultraviolet spectra of a diverse collection of F--K stars, of all luminosity classes. Such a major project was unthinkable before STIS, but now is practical given the high resolution, broad spectral coverage, and sensitivity of the second generation spectrograph. Here, we discuss our choice of the thirteen targets; the observing strategy (which captures the entire UV spectrum between 1150--3000 Angstroms at resolutions λ /δ λ 30--100*E3 with good S/N); and preliminary results for the several targets observed to date (ζ Dor, F7 V, 1 May 1999, 2 CVZ orbits; V711 Tau, K1 IV+G5 IV, 15 September 1999, 5 orbits; β Cam, G0 I, 19 September 1999, 4 CVZ orbits). The observation of V711 Tau (HR 1099) was carried out during a long transmission grating pointing by the Chandra X-ray Observatory, in support of its ``Emission Line Project.'' This work was supported by grant GO-08280.01-97A from STScI. Observations were from the NASA/ESA HST, collected at the STScI, operated by AURA, under contract NAS5-26555.

ULTRAVIOLET LIGHT DISINFECTION OF COMBINED SEWER OVERFLOW (NEW ORLEANS)

EPA Science Inventory

The objective of this state-of-the-art review is to examine the performance and effectiveness of ultraviolet (UV) light disinfection for combined sewer overflow (CSO) applications. Topics presented include the use of UV light as a disinfecting agent, its practical applications, d...

LOW PRESSURE ULTRAVIOLET STUDIES FOR INACTIVATION OF GIARDIA MURIS CYSTS

EPA Science Inventory

This research was initiated to confirm and expand the current database for the inactivation of Giardia spp. using ultraviolet (UV) radiation. Initially, previous research that used in vitro excystation as the indicator for UV effectiveness was confirmed. Later, the in vitro excys...

Integrated oxide graphene based device for laser inactivation of pathogenic microorganisms

NASA Astrophysics Data System (ADS)

Grishkanich, Alexsandr; Ruzankina, Julia; Afanasyev, Mikhail; Paklinov, Nikita; Hafizov, Nail

2018-02-01

We develop device for virus disinfection of pathogenic microorganisms. Viral decontamination can be carried out due to hard ultraviolet irradiation and singlet oxygen destroying the genetic material of a virus capsid. UV rays can destroy DNA, leading to the formation of dimers of nucleic acids. This practically does not occur in tissues, tk. UV rays penetrate badly through them, however, the viral particles are small and UV can destroy their genetic material, RNA / DNA and the virus can not replicate. It is with the construction of the ultraviolet laser water disinfection system (UFLOV) based on the continuous and periodic pulsed ultraviolet laser sources (pump) binds to solve sterility and depyrogenation of water. It has been established that small doses of UV irradiation stimulate reproduction, and large doses cause the death of pathogenic microorganisms. The effect of a dose of ultraviolet is the result of photochemical action on the substance of a living bacterial cell or virion. Also complex photodynamic laser inactivation on graphene oxide is realized.

Microwave assisted scalable synthesis of titanium ferrite nanomaterials

NASA Astrophysics Data System (ADS)

Shukla, Abhishek; Bhardwaj, Abhishek K.; Singh, S. C.; Uttam, K. N.; Gautam, Nisha; Himanshu, A. K.; Shah, Jyoti; Kotnala, R. K.; Gopal, R.

2018-04-01

Titanium ferrite magnetic nanomaterials are synthesized by one-step, one pot, and scalable method assisted by microwave radiation. Effects of titanium content and microwave exposure time on size, shape, morphology, yield, bonding nature, crystalline structure, and magnetic properties of titanium ferrite nanomaterials are studied. As-synthesized nanomaterials are characterized by X-ray diffraction (XRD), ultraviolet-visible absorption spectroscopy (UV-Vis), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), Raman spectroscopy, transmission electron microscopy (TEM), and vibrating sample magnetometer measurements. XRD measurements depict the presence of two phases of titanium ferrite into the same sample, where crystallite size increases from ˜33 nm to 37 nm with the increase in titanium concentration. UV-Vis measurement showed broad spectrum in the spectral range of 250-600 nm which reveals that its characteristic peaks lie between ultraviolet and visible region; ATR-FTIR and Raman measurements predict iron-titanium oxide structures that are consistent with XRD results. The micrographs of TEM and selected area electron diffraction patterns show formation of hexagonal shaped particles with a high degree of crystallinity and presence of multi-phase. Energy dispersive spectroscopy measurements confirm that Ti:Fe compositional mass ratio can be controlled by tuning synthesis conditions. Increase of Ti defects into titanium ferrite lattice, either by increasing titanium precursor or by increasing exposure time, enhances its magnetic properties.

New Fe i Level Energies and Line Identifications from Stellar Spectra. II. Initial Results from New Ultraviolet Spectra of Metal-poor Stars

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

Peterson, Ruth C.; Kurucz, Robert L.; Ayres, Thomas R., E-mail: peterson@ucolick.org

2017-04-01

The Fe i spectrum is critical to many areas of astrophysics, yet many of the high-lying levels remain uncharacterized. To remedy this deficiency, Peterson and Kurucz identified Fe i lines in archival ultraviolet and optical spectra of metal-poor stars, whose warm temperatures favor moderate Fe i excitation. Sixty-five new levels were recovered, with 1500 detectable lines, including several bound levels in the ionization continuum of Fe i. Here, we extend the previous work by identifying 59 additional levels, with 1400 detectable lines, by incorporating new high-resolution UV spectra of warm metal-poor stars recently obtained by the Hubble Space Telescope Imagingmore » Spectrograph. We provide gf values for these transitions, both computed as well as adjusted to fit the stellar spectra. We also expand our spectral calculations to the infrared, confirming three levels by matching high-quality spectra of the Sun and two cool stars in the H -band. The predicted gf values suggest that an additional 3700 Fe i lines should be detectable in existing solar infrared spectra. Extending the empirical line identification work to the infrared would help confirm additional Fe i levels, as would new high-resolution UV spectra of metal-poor turnoff stars below 1900 Å.« less

Biochemical Detection and Identification False Alarm Rate Dependence on Wavelength Using Laser Induced Fluorescence

NASA Technical Reports Server (NTRS)

Bhartia, R.; Hug, W. F.; Sala, E. C.; Sijapati, K.; Lane, A. L.; Reid, R. D.; Conrad, P. G.

2006-01-01

Most organic and many inorganic materials absorb strongly in specific wavelength ranges in the deep UV between about 220nm and 300nm. Excitation within these absorption bands results in native fluorescence emission. Each compound or composite material, such as a bacterial spore, has a unique excitation-emission fingerprint that can be used to provide information about the material. The sensitivity and specificity with which these materials can be detected and identified depends on the excitation wavelength and the number and location of observation wavelengths.We will present data on our deep ultraviolet Targeted Ultraviolet Chemical Sensors that demonstrate the sensitivity and specificity of the sensors. In particular, we will demonstrate the ability to quantitatively differentiate a wide range of biochemical agent targets against a wide range of background materials. We will describe the relationship between spectral resolution and specificity in target identification, as well as simple, fast, algorithms to identify materials.Hand-held, battery operated instruments using a deep UV laser and multi-band detection have been developed and deployed on missions to the Antarctic, the Arctic, and the deep ocean with the capability of detecting a single bacterial spore and to differentiate a wide range of organic and biological compounds.

CITIUS: An infrared-extreme ultraviolet light source for fundamental and applied ultrafast science

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

Grazioli, C.; Gauthier, D.; Ivanov, R.

2014-02-15

We present the main features of CITIUS, a new light source for ultrafast science, generating tunable, intense, femtosecond pulses in the spectral range from infrared to extreme ultraviolet (XUV). The XUV pulses (about 10{sup 5}-10{sup 8} photons/pulse in the range 14-80 eV) are produced by laser-induced high-order harmonic generation in gas. This radiation is monochromatized by a time-preserving monochromator, also allowing one to work with high-resolution bandwidth selection. The tunable IR-UV pulses (10{sup 12}-10{sup 15} photons/pulse in the range 0.4-5.6 eV) are generated by an optical parametric amplifier, which is driven by a fraction of the same laser pulse thatmore » generates high order harmonics. The IR-UV and XUV pulses follow different optical paths and are eventually recombined on the sample for pump-probe experiments. We also present the results of two pump-probe experiments: with the first one, we fully characterized the temporal duration of harmonic pulses in the time-preserving configuration; with the second one, we demonstrated the possibility of using CITIUS for selective investigation of the ultra-fast dynamics of different elements in a magnetic compound.« less

First results of an Investigation of Sulfur Dioxide in the Ultraviolet from Pioneer Venus through Venus Express

NASA Astrophysics Data System (ADS)

McGouldrick, Kevin; Molaverdikhani, K.; Esposito, L. W.; Pankratz, C. K.

2010-10-01

The Laboratory for Atmospheric and Space Physics is carrying on a project to restore and preserve data products from several past missions for archival and use by the scientific community. This project includes the restoration of data from Mariner 6/7, Pioneer Venus, Voyager 1/2, and Galileo. Here, we present initial results of this project that involve Pioneer Venus Orbiter Ultraviolet Spectrometer (PVO UVS) data. Using the Discrete Ordinate Method for Radiative Transfer (DISORT), we generate a suite of models for the three free parameters in the upper atmosphere of Venus in which we are interested: sulfur dioxide abundance at 40mb, scale height of sulfur dioxide, and the typical radius of the upper haze particles (assumed to be composed of 84.5% sulfuric acid). We calculate best fits to our radiative transfer model results for multi-spectral images taken with PVO UVS, as well as the 'visible' channel (includes wavelengths from 290nm to about 1000nm) of the mapping mode of the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS-M-Vis) on the Venus Express spacecraft, currently orbiting Venus. This work is funded though the NASA Planetary Mission Data Analysis Program, NNH08ZDA001N.

Detection of global phenomena of technogenic ultraviolet and infrared nightglows onboard the Vernov satellite

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

Garipov, G. K., E-mail: ggkmsu@yandex.ru; Panasyuk, M. I.; Svertilov, S. I.

2016-09-15

The generation of transients in the Earth’s upper atmosphere under the action of electron fluxes and high- and low-frequency electromagnetic waves has been studied onboard the small Vernov spacecraft (solar synchronous orbit, 98° inclination, height 640–830 km). The studies were carried out with ultraviolet (UV, 240–380 nm), red–infrared (IR, 610–800 nm), gamma-ray (0.01–3 MeV), and electron (0.2–15 MeV) detectors as well as with high-frequency (0.05–15 MHz) and low-frequency (0.1 Hz–40 kHz) radio receivers. Artificial optical signals distributed along the meridian in an extended region of latitudes in the Earth’s Northern and Southern Hemispheres modulated by a low frequency were recordedmore » during the nadir observations at nighttime. Examples of the oscillograms of such signals in the UV and IR spectral ranges and their global distribution are presented. The emission generation altitude and the atmospheric components that can be the sources of this emission are discussed. Particular attention is given to the technogenic causes of this glow in the ionosphere under the action of powerful low- and high-frequency radio stations on the ionosphere.« less

New Fe I Level Energies and Line Identifications from Stellar Spectra. II. Initial Results from New Ultraviolet Spectra of Metal-poor Stars

NASA Astrophysics Data System (ADS)

Peterson, Ruth C.; Kurucz, Robert L.; Ayres, Thomas R.

2017-04-01

The Fe I spectrum is critical to many areas of astrophysics, yet many of the high-lying levels remain uncharacterized. To remedy this deficiency, Peterson & Kurucz identified Fe I lines in archival ultraviolet and optical spectra of metal-poor stars, whose warm temperatures favor moderate Fe I excitation. Sixty-five new levels were recovered, with 1500 detectable lines, including several bound levels in the ionization continuum of Fe I. Here, we extend the previous work by identifying 59 additional levels, with 1400 detectable lines, by incorporating new high-resolution UV spectra of warm metal-poor stars recently obtained by the Hubble Space Telescope Imaging Spectrograph. We provide gf values for these transitions, both computed as well as adjusted to fit the stellar spectra. We also expand our spectral calculations to the infrared, confirming three levels by matching high-quality spectra of the Sun and two cool stars in the H-band. The predicted gf values suggest that an additional 3700 Fe I lines should be detectable in existing solar infrared spectra. Extending the empirical line identification work to the infrared would help confirm additional Fe I levels, as would new high-resolution UV spectra of metal-poor turnoff stars below 1900 Å.

Preparation and characterization of functional poly(vinylidene fluoride) (PVDF) membranes with ultraviolet-absorbing property

NASA Astrophysics Data System (ADS)

Dong, Li; Liu, Xiangdong; Xiong, Zhengrong; Sheng, Dekun; Lin, Changhong; Zhou, Yan; Yang, Yuming

2018-06-01

We first reported a strategy to prepare functional poly(vinylidene fluoride) (PVDF) membranes with excellent ultraviolet-absorbing property through chemically induced grafting. Herein, the polymerizable ultraviolet (UV) absorber 2-hydroxy-4-(3-methacryloxy-2-hydroxylpropoxy) benzophenone (BPMA) made by ourselves was grafted onto the PVDF chains that have been pretreated with tetraethylammonium hydroxide (TEAH) alkaline solution. Moreover, the effect of experiment conditions such as the alkali and monomer concentrations, alkali treatment time on the UV-absorbing property of the obtained PVDF-g-PBPMA membranes were studied in detail. The chemical structure of the modified membranes was confirmed by 1H NMR, FT-IR and XPS measurements. Meanwhile, the thermal and UV-absorbing properties were characterized by TGA, DSC and UV-Vis spectrophotometer, respectively. The results indicated that BPMA side chains were successfully introduced onto PVDF backbones. Most importantly, the obtained PVDF-g-PBPMA membranes exhibited excellent UV-absorbing property. The transmittance of UV light at 300 nm decreased to as low as 0.02% and the UV light below 388 nm could be completely absorbed by the PVDF-g-PBPMA membrane made under optimal condition.

Photocatalytic antibacterial effects on TiO2-anatase upon UV-A and UV-A/VIS threshold irradiation.

PubMed

Wu, Yanyun; Geis-Gerstorfer, Jürgen; Scheideler, Lutz; Rupp, Frank

2016-01-01

Photocatalysis mediated by the anatase modification of titanium dioxide (TiO2) has shown antibacterial effects in medical applications. The aim of this study was to investigate the possibility of expanding the excitation wavelengths for photocatalytic antibacterial effects from ultraviolet (UV) into the visible light range. After deposition of salivary pellicle and adhesion of Streptococcus gordonii on anatase, different irradiation protocols were applied to induce photocatalysis: ultraviolet A (UV-A) > 320 nm; ultraviolet/visible (UV-A/VIS) light > 380 nm and > 390 nm; and VIS light 400-410 nm. A quartz crystal microbalance with dissipation (QCM-D) tests and microscopic examination were used to observe the photoinduced antibacterial effects. Salivary pellicle could be photocatalytically decomposed under all irradiation protocols. In contrast, effective photocatalytic attack of bacteria could be observed by UV-A as well as by UV-A/VIS at 380 nm < λ < 390 nm only. Wavelengths above 380 nm show promise for in situ therapeutic antifouling applications.

Two ultraviolet radiation datasets that cover China

NASA Astrophysics Data System (ADS)

Liu, Hui; Hu, Bo; Wang, Yuesi; Liu, Guangren; Tang, Liqin; Ji, Dongsheng; Bai, Yongfei; Bao, Weikai; Chen, Xin; Chen, Yunming; Ding, Weixin; Han, Xiaozeng; He, Fei; Huang, Hui; Huang, Zhenying; Li, Xinrong; Li, Yan; Liu, Wenzhao; Lin, Luxiang; Ouyang, Zhu; Qin, Boqiang; Shen, Weijun; Shen, Yanjun; Su, Hongxin; Song, Changchun; Sun, Bo; Sun, Song; Wang, Anzhi; Wang, Genxu; Wang, Huimin; Wang, Silong; Wang, Youshao; Wei, Wenxue; Xie, Ping; Xie, Zongqiang; Yan, Xiaoyuan; Zeng, Fanjiang; Zhang, Fawei; Zhang, Yangjian; Zhang, Yiping; Zhao, Chengyi; Zhao, Wenzhi; Zhao, Xueyong; Zhou, Guoyi; Zhu, Bo

2017-07-01

Ultraviolet (UV) radiation has significant effects on ecosystems, environments, and human health, as well as atmospheric processes and climate change. Two ultraviolet radiation datasets are described in this paper. One contains hourly observations of UV radiation measured at 40 Chinese Ecosystem Research Network stations from 2005 to 2015. CUV3 broadband radiometers were used to observe the UV radiation, with an accuracy of 5%, which meets the World Meteorology Organization's measurement standards. The extremum method was used to control the quality of the measured datasets. The other dataset contains daily cumulative UV radiation estimates that were calculated using an all-sky estimation model combined with a hybrid model. The reconstructed daily UV radiation data span from 1961 to 2014. The mean absolute bias error and root-mean-square error are smaller than 30% at most stations, and most of the mean bias error values are negative, which indicates underestimation of the UV radiation intensity. These datasets can improve our basic knowledge of the spatial and temporal variations in UV radiation. Additionally, these datasets can be used in studies of potential ozone formation and atmospheric oxidation, as well as simulations of ecological processes.

Eclipsing and density effects on the spectral behavior of Beta Lyrae binary system in the UV

NASA Astrophysics Data System (ADS)

Sanad, M. R.

2010-01-01

We analyze both long and short high resolution ultraviolet spectrum of Beta Lyrae eclipsing binary system observed with the International Ultraviolet Explorer (IUE) between 1980 and 1989. The main spectral features are P Cygni profiles originating from different environments of Beta Lyrae. A set of 23 Mg II k&h spectral lines at 2800 Å, originating from the extended envelope [Hack, M., 1980. IAUS, 88, 271H], have been identified and measured to determine their fluxes and widths. We found that there is spectral variability for these physical parameters with phase, similar to that found for the light curve [Kondo, Y., McCluskey, G.E., Jeffery, M.M.S., Ronald, S.P., Carolina, P.S. McCluskey, Joel, A.E., 1994. ApJ, 421, 787], which we attribute to the eclipse effects [Ak, H., Chadima, P., Harmanec, P., Demircan, O., Yang, S., Koubský, P., Škoda, P., Šlechta, M., Wolf, M., Božić, H., 2007. A&A, 463, 233], in addition to the changes of density and temperature of the region from which these lines are coming, as a result of the variability of mass loss from the primary star to the secondary [Hoffman, J.L., Nordsieck, K.H., Fox, G.K., 1998. AJ, 115, 1576; Linnell, A.P., Hubeny, I., Harmanec, P., 1998. ApJ, 509, 379]. Also we present a study of Fe II spectral line at 2600 Å, originating from the atmosphere of the primary star [Hack, M., 1980. IAUS, 88, 271H]. We found spectral variability of line fluxes and line widths with phase similar to that found for Mg II k&h lines. Finally we present a study of Si IV spectral line at 1394 Å, originating from the extended envelope [Hack, M., 1980. IAUS, 88, 271H]. A set of 52 Si IV spectral line at 1394 Å have been identified and measured to determine their fluxes and widths. Also we found spectral variability of these physical parameters with phase similar to that found for Mg II k&h and Fe II spectral lines.

HerMES: dust attenuation and star formation activity in ultraviolet-selected samples from z˜ 4 to ˜ 1.5

NASA Astrophysics Data System (ADS)

Heinis, S.; Buat, V.; Béthermin, M.; Bock, J.; Burgarella, D.; Conley, A.; Cooray, A.; Farrah, D.; Ilbert, O.; Magdis, G.; Marsden, G.; Oliver, S. J.; Rigopoulou, D.; Roehlly, Y.; Schulz, B.; Symeonidis, M.; Viero, M.; Xu, C. K.; Zemcov, M.

2014-01-01

We study the link between observed ultraviolet (UV) luminosity, stellar mass and dust attenuation within rest-frame UV-selected samples at z ˜ 4, ˜ 3 and ˜1.5. We measure by stacking at 250, 350 and 500 μm in the Herschel/Spectral and Photometric Imaging Receiver images from the Herschel Multi-Tiered Extragalactic Survey (HerMES) program the average infrared luminosity as a function of stellar mass and UV luminosity. We find that dust attenuation is mostly correlated with stellar mass. There is also a secondary dependence with UV luminosity: at a given UV luminosity, dust attenuation increases with stellar mass, while at a given stellar mass it decreases with UV luminosity. We provide new empirical recipes to correct for dust attenuation given the observed UV luminosity and the stellar mass. Our results also enable us to put new constraints on the average relation between star formation rate (SFR) and stellar mass at z ˜ 4, ˜3 and ˜1.5. The SFR-stellar mass relations are well described by power laws (SFR∝ M_*^{0.7}), with the amplitudes being similar at z ˜ 4 and ˜3, and decreasing by a factor of 4 at z ˜ 1.5 at a given stellar mass. We further investigate the evolution with redshift of the specific SFR. Our results are in the upper range of previous measurements, in particular at z ˜ 3, and are consistent with a plateau at 3 < z < 4. Current model predictions (either analytic, semi-analytic or hydrodynamic) are inconsistent with these values, as they yield lower predictions than the observations in the redshift range we explore. We use these results to discuss the star formation histories of galaxies in the framework of the main sequence of star-forming galaxies. Our results suggest that galaxies at high redshift (2.5 < z < 4) stay around 1 Gyr on the main sequence. With decreasing redshift, this time increases such that z = 1 main-sequence galaxies with 108

Ultraviolet spectrophotometry of three LINERs

NASA Technical Reports Server (NTRS)

Goodrich, R. W.; Keel, W. C.

1986-01-01

Three galaxies known to be LINERs were observed spectroscopically in the ultraviolet in an attempt to detect the presumed nonthermal continuum source thought to be the source of photoionization in the nuclei. NGC 4501 was found to be too faint for study with the IUE spectrographs, while NGC 5005 had an extended ultraviolet light profile. Comparison with the optical light profile of NGC 5005 indicates that the ultraviolet source is distributed spatially in the same manner as the optical starlight, probably indicating that the ultraviolet excess is due to a component of hot stars in the nucleus. These stars contribute detectable absorption features longward of 2500 A; together with optical data, the IUE spectra suggest a burst of star formation about 1 billion yr ago, with a lower rate continuing to produce a few OB stars. In NGC 4579, a point source contributing most of the ultraviolet excess is found that is much different than the optical light distribution. Furthermore, the ultraviolet to X-ray spectral index in NGC 4579 is 1.4, compatible with the UV to X-ray indices found for samples of Seyfert galaxies. This provides compelling evidence for the detection of the photoionizing continuum in NGC 4579 and draws the research fields of normal galaxies and active galactic nuclei closer together. The emission-line spectrum of NGC 4579 is compared with calculations from a photoionization code, CLOUDY, and several shock models. The photoionization code is found to give superior results, adding to the increasing weight of evidence that the LINER phenomenon is essentially a scaled-down version of the Seyfert phenomenon.

Polarized vacuum ultraviolet and X-radiation

NASA Technical Reports Server (NTRS)

Samson, J. A. R.

1978-01-01

The most intense source of polarized vacuum UV and X radiation is synchrotron radiation, which exhibits a degree of partially polarized light between about 80-100%. However, the radiation transmitted by vacuum UV monochromators can also be highly polarized. The Seya-Namioka type of monochromator can produce partially polarized radiation between 50-80%. For certain experiments it is necessary to know the degree of polarization of the radiation being used. Also, when synchrotron radiation and a monochromator are combined the polarization characteristic of both should be known in order to make full use of these polarization properties. The polarizing effect of monochromators (i.e., diffraction gratings) have been measured at the Seya angle and at grazing angles for various spectral orders. Experimental evidence is presented which shows that the reciprocity law holds for polarization by reflection where the angle of incidence and diffraction are unequal. These results are reviewed along with the techniques for measuring the degree of polarization.

Photoluminescence in Sm3+ doped Ba2P2O7 phosphor prepared by solution combustion method

NASA Astrophysics Data System (ADS)

Ghawade, Sonal P.; Deshmukh, Kavita A.; Dhoble, S. J.; Deshmukh, Abhay D.

2018-05-01

In this paper, Sm3+ doped Ba2P2O7 phosphors were synthesized via a Solution combustion method. The crystal structure of the phosphor was characterized by XRD. Orange-red emission was observed from these phosphors under near-ultraviolet (UV) excitation at 404 nm. The luminescence properties of the obtained phosphors were characterized by different techniques. The Ba2P2O7:Sm3+ phosphor can be efficiently excited by near-UV and blue light, and their emission spectrum consists of three emission peaks, at 564, 602, and 646 nm, respectively. Based on the results, the as prepared Ba2P2O7:Sm3+ phosphors are promising orange-red-emitting phosphors exhibit great potential may be applicable as a spectral convertor in c-Si solar cell to enhance the efficiency of solar cell in future.

Luminescent carbon quantum dots with high quantum yield as a single white converter for white light emitting diodes

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

Feng, X. T.; Zhang, Y.; Liu, X. G., E-mail: liuxuguang@tyut.edu.cn

Carbon quantum dots (CQDs) with high quantum yield (51.4%) were synthesized by a one-step hydrothermal method using thiosalicylic acid and ethylenediamine as precursor. The CQDs have the average diameter of 2.3 nm and possess excitation-independent emission wavelength in the range from 320 to 440 nm excitation. Under an ultraviolet (UV) excitation, the CQDs aqueous solutions emit bright blue fluorescence directly and exhibit broad emission with a high spectral component ratio of 67.4% (blue to red intensity to total intensity). We applied the CQDs as a single white-light converter for white light emitting diodes (WLEDs) using a UV-LED chip as the excitation lightmore » source. The resulted WLED shows superior performance with corresponding color temperature of 5227 K and the color coordinates of (0.34, 0.38) belonging to the white gamut.« less

VizieR Online Data Catalog: ANS UV Catalogue of Point Sources (Wesselius+ 1982)

NASA Astrophysics Data System (ADS)

Wesselius, P. R.; van Duinen, R. J.; de Jonge, A. R. W.; Aalders, J. W. G.; Luinge, W.; Wildeman, K. J.

2001-08-01

This catalog is a result of the observations made with the Astronomical Netherlands Satellite (ANS) which operated between October 1974 and April 1976. The ANS satellite observed in five UV channels centered around 150, 180, 220, 250 and 330nm. The photometric bands are: ------------------------------------------------------------------------- - Band designation 15N 15W 18 22 25 33 ------------------------------------------------------------------------- - Central wavelength (nm) 154.5 154.9 179.9 220.0 249.3 329.4 Bandwidth (nm) 5.0 14.9 14.9 20.0 15.0 10.1 ------------------------------------------------------------------------- - The reported magnitudes were obtained from mean count rates converted to fluxes using the ANS absolute calibration of Wesselius et al. (1980A&A....85..221W). In addition to the ultraviolet magnitudes, the catalog contains positions taken from the satellite pointing, spectral types, and UBV data from other sources as well as comments on duplicity, variability, and miscellaneous notes concerning individual objects. (1 data file).

Broad-band properties of the CfA Seyfert galaxies. III - Ultraviolet variability

NASA Technical Reports Server (NTRS)

Edelson, R. A.; Pike, G. F.; Krolik, J. H.

1990-01-01

A total of 657 archived IUE spectra are used to study the UV variability properties of six members of the CfA Seyfert I galaxy sample. All show strong evidence for continuum and line variations and a tendency for less luminous objects to be more strongly variable. Most objects show a clear correlation at zero lag between UV spectral index and luminosity, evidence that the variable component is an accretion disk around a black hole which is systematically smaller in less luminous sources. No correlation is seen between the continuum luminosity and equivalent width of the C IV, Mg II, and semiforbidden C III emission lines when the entire sample is examined, but a clear anticorrelation is present when only repeated observations of individual objects are considered. This is due to a combination of light-travel time effects in the broad-line region and the nonlinear responses of lines to continuum fluctuations.