Instrument Design of the Large Aperture Solar UV Visible and IR Observing Telescope (SUVIT) for the SOLAR-C Mission

NASA Astrophysics Data System (ADS)

Suematsu, Y.; Katsukawa, Y.; Shimizu, T.; Ichimoto, K.; Takeyama, N.

2012-12-01

We present an instrumental design of one major solar observation payload planned for the SOLAR-C mission: the Solar Ultra-violet Visible and near IR observing Telescope (SUVIT). The SUVIT is designed to provide high-angular-resolution investigation of the lower solar atmosphere, from the photosphere to the uppermost chromosphere, with enhanced spectroscopic and spectro-polarimetric capability in wide wavelength regions from 280 nm (Mg II h&k lines) to 1100 nm (He I 1083 nm line) with 1.5 m class aperture and filtergraphic and spectrographic instruments.

Complex damage distribution behaviour in cobalt implanted rutile TiO2 (1 1 0) lattice

NASA Astrophysics Data System (ADS)

Joshi, Shalik Ram; Padmanabhan, B.; Chanda, Anupama; Ojha, Sunil; Kanjilal, D.; Varma, Shikha

2017-11-01

The present work investigates the radiation damage, amorphization and structural modifications that are produced by ion-solid interactions in TiO2 crystals during 200 keV Cobalt ion implantation. RBS/C and GIXRD have been utilized to evaluate the damage in the host lattice as a function of ion fluence. Multiple scattering formalism has been applied to extract the depth dependent damage distributions in TiO2(1 1 0). The results have been compared with the MC simulations performed using SRIM-2013. RBS/C results delineate a buried amorphous layer at a low fluence. Surprisingly, ion induced dynamic activation produces a recovery in this damage at higher fluences. This improvement interestingly occurs only in deep regions (60-300 nm) where a systematic lowering in damage with fluence is observed. Formation of Co-Ti-O phases and generation of stress in TiO2 lattice can also be responsible for this improvement in deep regions. In contrast, surface region (0-60 nm) indicates a gradual increase in damage with fluence. Such a switch in the damage behavior creates a cross point in damage profiles at 60 nm. Surface region is a sink of vacancies whereas deep layers are interstitial rich. However, these regions are far separated from each other resulting in an intermediate (100-150 nm) region with a significant dip (valley) in damage which can be characterized by enhanced recombination of point defects. The damage profiles thus indicate a very complex behavior. MC simulations, however, present very different results. They depict a damage profile that extends to a depth of only 150 nm, which is only about half of the damage- width observed here via RBS/C. Moreover, MC simulations do not indicate presence of any valley like structure in the damage profile. The complex nature of damage distribution observed here via RBS/C may be related to the high ionic nature of the chemical bonds in the TiO2 lattice.

A silica optical fiber doped with yttrium aluminosilicate nanoparticles for supercontinuum generation

NASA Astrophysics Data System (ADS)

Cheng, Tonglei; Liao, Meisong; Xue, Xiaojie; Li, Jiang; Gao, Weiqing; Li, Xia; Chen, Danping; Zheng, Shupei; Pan, Yubai; Suzuki, Takenobu; Ohishi, Yasutake

2016-03-01

We design and fabricate a silica optical fiber doped with yttrium aluminosilicate (YAS, Y2O3-Al2O3-SiO2) nanoparticles in the core. The optical fiber is drawn directly from a silica tube with YAG (Y3Al5O12) ceramics and silica powders (the molar ratio 1:18) in the core at the temperature of ∼1950 °C. The YAS nanoparticles are formed during the optical fiber drawing process. Supercontinuum (SC) generation in the optical fiber is investigated at different pump wavelength. At the pump wavelength of ∼1750 nm which is in the deep anomalous dispersion region, SC spectrum evolution is mainly due to multiple solitons and dispersive waves (DWs), and three pairs of multiple optical solitons and DWs are observed. When the pump wavelength shifts to ∼1500 nm which is close to the zero-dispersion wavelength (ZDW), flattened SC spectrum with ±7 dB uniformity is obtained at the wavelength region of ∼990-1980 nm, and only one obvious soliton and DW are observed. At the pump wavelength of ∼1100 nm, a narrow SC spectrum from ∼1020 to 1180 nm is obtained in the normal dispersion region due to self-phase modulation (SPM) effect.

Constraining Line-of-sight Confusion in the Corona Using Linearly Polarized Observations of the Infrared FeXIII 1075nm and SiX 1430nm Emission Lines

NASA Astrophysics Data System (ADS)

Dima, G. I.; Kuhn, J. R.; Berdyugina, S.

2017-12-01

Measurements of the coronal magnetic field are difficult because of the intrinsically faint emission of coronal plasma and the large spurious background due to the bright solar disk. This work addresses the problem of resolving the confusion of the line-of-sight (LOS) integration through the optically-thin corona being observed. Work on developing new measuring techniques based on single-point inversions using the Hanle effect has already been described (Dima et al. 2016). It is important to develop a technique to assess when the LOS confusion makes comparing models and observations problematic. Using forward integration of synthetic emission through magnetohydrodynamic (MHD) models together with simultaneous linearly polarized observations of the FeXIII 1075nm and SiX 1430nm emission lines allows us to assess LOS confusion. Since the lines are both in the Hanle saturated regime their polarization angles are expected to be aligned as long as the gas is sampling the same magnetic field. If significant contributions to the emission is taking place from different regions along the LOS due to the additive nature of the polarized brightness the measured linear polarization between the two lines will be offset. The size of the resolution element is important for this determination since observing larger coronal regions will confuse the variation along the LOS with that in the plane-of-sky. We also present comparisons between synthetic linearly polarized emission through a global MHD model and observations of the same regions obtained using the 0.5m Scatter-free Observatory for Limb Active Regions and Coronae (SOLARC) telescope located on Haleakala, Maui. This work is being done in preparation for the type of observations that will become possible when the next generation 4m DKIST telescope comes online in 2020.

Influence of quantum well inhomogeneities on absorption, spontaneous emission, photoluminescence decay time, and lasing in polar InGaN quantum wells emitting in the blue-green spectral region

NASA Astrophysics Data System (ADS)

Gladysiewicz, M.; Kudrawiec, R.; Syperek, M.; Misiewicz, J.; Siekacz, M.; Cywinski, G.; Khachapuridze, A.; Suski, T.; Skierbiszewski, C.

2014-06-01

It is shown that in polar InGaN QWs emitting in the blue-green spectral region a Stokes shift between spontaneous emission (SE) and optical transition observed in contactless electroreflectance (CER) spectrum (absorption-like technique) can be observed even at room temperature, despite the fact that the SE is not associated with localized states. Time resolved photoluminescence measurements clearly confirm that the SE is strongly localized at low temperatures whereas at room temperature the carrier localization disappears and the SE can be attributed to the fundamental transition in this QW. The Stokes shift is observed in this QW system because of the large built-in electric field, i.e., the CER transition is a superposition of all optical transitions with non-zero electron-hole overlap integrals and, therefore, the energy of this transition does not correspond to the fundamental transition of InGaN QW. Lasing from this QW has been observed at the wavelength of 475 nm, whereas the SE was observed at 500 nm. The 25 nm shift between the lasing and SE is observed because of a screening of the built-in electric field by photogenerated carriers. However, our analysis shows that the built-in electric field inside the InGaN QW region is not fully screened under the lasing conditions.

New Particle Formation and Growth in an Isoprene-Dominated Ozark Forest: From Sub-5 nm to CCN-Active Sizes

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

Yu, Huan; Ortega, John; Smith, James N.

Particle Investigations at a Northern Ozarks Tower: NOx, Oxidant, Isoprene Research (PINOT-NOIR) were conducted in a Missouri forest dominated by isoprene emissions, from May to October 2012. This study presents results of new particle formation (NPF) and the growth of new particles to cloud condensation nuclei (CCN)-active sizes (~100 nm) observed from this field campaign. The measured sub-5 nm particles were up to ~20000 cm-3 during a typical NPF event. Nucleation rates J1 were relatively high (11.0±10.6 cm-3s-1), and one order of magnitude higher than formation rates of 5 nm particles (J5). Sub-5 nm particle events were observed on 64%more » of the measurement days, with a high preference in biogenic volatile organic compounds (BVOCs)- and SO2-poor northwesterly (90%) air masses than in BVOCs-rich southerly air masses (13%). About 80% of sub-5 nm particle events led to the further growth. While high temperatures and high aerosol loadings in the southerly air masses were not favorable for nucleation, high BVOCs in the southerly air masses facilitated the growth of new particles to CCN-active sizes. In overall, 0.4-9.4% of the sub-5 nm particles grew to CCN-active sizes within a NPF event. During a regional NPF event period that took place consecutively over several days, concentrations of CCN size particles increased by a factor of 5 in average. This enhanced production of CCN particles from new particles was commonly observed during all 13 regional NPF events observed during the campaign.« less

Solar Variability from 240 to 1750 nm in Terms of Faculae Brightening and Sunspot Darkening from SCIAMACHY

NASA Astrophysics Data System (ADS)

Pagaran, J.; Weber, M.; Burrows, J.

2009-08-01

The change of spectral decomposition of the total radiative output on various timescales of solar magnetic activity is of large interest to terrestrial and solar-stellar atmosphere studies. Starting in 2002, SCIAMACHY was the first satellite instrument to observe daily solar spectral irradiance (SSI) continuously from 230 nm (UV) to 1750 nm (near-infrared; near-IR). In order to address the question of how much UV, visible (vis), and IR spectral regions change on 27 day and 11 year timescales, we parameterize short-term SSI variations in terms of faculae brightening (Mg II index) and sunspot darkening (photometric sunspot index) proxies. Although spectral variations above 300 nm are below 1% and, therefore, well below the accuracy of absolute radiometric calibration, relative accuracy for short-term changes is shown to be in the per mill range. This enables us to derive short-term spectral irradiance variations from the UV to the near-IR. During Halloween solar storm in 2003 with a record high sunspot area, we observe a reduction of 0.3% in the near-IR to 0.5% in the vis and near-UV. This is consistent with a 0.4% reduction in total solar irradiance (TSI). Over an entire 11 year solar cycle, SSI variability covering simultaneously the UV, vis, and IR spectral regions have not been directly observed so far. Using variations of solar proxies over solar cycle 23, solar cycle spectral variations have been estimated using scaling factors that best matched short-term variations of SCIAMACHY. In the 300-400 nm region, which strongly contributes to TSI solar cycle change, a contribution of 34% is derived from SCIAMACHY observations, which is lower than the reported values from SUSIM satellite data and the empirical SATIRE model. The total UV contribution (below 400 nm) to TSI solar cycle variations is estimated to be 55%.

SOLAR VARIABILITY FROM 240 TO 1750 nm IN TERMS OF FACULAE BRIGHTENING AND SUNSPOT DARKENING FROM SCIAMACHY

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

Pagaran, J.; Weber, M.; Burrows, J.

2009-08-01

The change of spectral decomposition of the total radiative output on various timescales of solar magnetic activity is of large interest to terrestrial and solar-stellar atmosphere studies. Starting in 2002, SCIAMACHY was the first satellite instrument to observe daily solar spectral irradiance (SSI) continuously from 230 nm (UV) to 1750 nm (near-infrared; near-IR). In order to address the question of how much UV, visible (vis), and IR spectral regions change on 27 day and 11 year timescales, we parameterize short-term SSI variations in terms of faculae brightening (Mg II index) and sunspot darkening (photometric sunspot index) proxies. Although spectral variationsmore » above 300 nm are below 1% and, therefore, well below the accuracy of absolute radiometric calibration, relative accuracy for short-term changes is shown to be in the per mill range. This enables us to derive short-term spectral irradiance variations from the UV to the near-IR. During Halloween solar storm in 2003 with a record high sunspot area, we observe a reduction of 0.3% in the near-IR to 0.5% in the vis and near-UV. This is consistent with a 0.4% reduction in total solar irradiance (TSI). Over an entire 11 year solar cycle, SSI variability covering simultaneously the UV, vis, and IR spectral regions have not been directly observed so far. Using variations of solar proxies over solar cycle 23, solar cycle spectral variations have been estimated using scaling factors that best matched short-term variations of SCIAMACHY. In the 300-400 nm region, which strongly contributes to TSI solar cycle change, a contribution of 34% is derived from SCIAMACHY observations, which is lower than the reported values from SUSIM satellite data and the empirical SATIRE model. The total UV contribution (below 400 nm) to TSI solar cycle variations is estimated to be 55%.« less

Source region and sector contributions of atmospheric soot particle in a coalfield region of Dhanbad, eastern part of India

NASA Astrophysics Data System (ADS)

Singh, S.; Tiwari, S.; Dumka, U. C.; Kumar, R.; Singh, P. K.

2017-11-01

Black carbon (BC) aerosols affect the Earth's climate directly by interacting with the solar radiation and indirectly by modifying the lifetime and optical properties of clouds. However, our understanding of BC aerosols and their impacts on the climate are limited by lack of in situ measurements of BC, especially in the developing world. This study reports measurements of BC from Dhanbad, a coalfields area of eastern India, we analyze BC data at 370 and 880 nm during 2013 to gain insight into the emission sources affecting the study area. Our analysis indicates significantly higher absorption at the lower wavelength (ultraviolet). We estimate that 33% of BC at Dhanbad comes from biomass/biofuel combustion and the remaining 67% from the fossil fuel combustion. Higher concentrations of BC370 nm (> 12 μg m- 3) were observed when the air masses affecting Dhanbad originated far away in countries like Iran, Afghanistan, Pakistan, Oman, United Arab Emirates and passed over the Indo-Gangetic Plains (IGP) prior to arriving at the observation site. The source regions affecting BC880 nm were localized over the IGP but BC880 nm concentrations are 33% lower ( 8 μg m- 3) than BC370 nm. The cluster analysis showed that the largest fraction (35 and 29%) of the air masses arriving at Dhanbad passed through the boundary layer of the central IGP and north-west IGP region during the post-monsoon season. Average values of BC370 nm (16.0 and 20.0 μg m- 3) and BC880 nm (9.5 and 10.0 μg m- 3) in the IGP influenced air masses were significantly higher than those arriving from other source regions. The Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) model were applied to understand the relative importance of different sources affecting Dhanbad. The variability of observed BC mass concentrations was captured fairly well by WRF-Chem with minor deviations from the measured values. Model results indicate that anthropogenic emissions account for more than 75% of the surface BC at Dhanbad. Biomass burning contribution peaks in March-April and October-November but remains less than 25%. Long-range transport estimated in terms of inflow from domain boundaries does not affect BC concentrations at Dhanbad significantly.

An Erupting Active Region Filament: Three-Dimensional Trajectory and Hydrogen Column Density

NASA Astrophysics Data System (ADS)

Penn, M. J.

2000-12-01

From 15:33 through 16:02 UT on 13 June 1998, observations of an erupting filament as it crossed solar disk center were obtained with the NSO/KPVT and SOHO/CDS instruments as part of the SOHO Joint Observing Program 70. Context observations show that this event was the eruption of the north-east section of a small active region filament associated with NOAA 8237, that the photospheric magnetic field was changing in this active region between 12-14 June 1998, and that a coronal Moreton-wave disk event occurred, as well as a white-light CME off the south-west solar limb. The NSO/KPVT imaging spectroscopy data covered 512 × 512 arc sec of the disk center and were spectrally centered at the Hei 1083 nm line and captured +/-1.0 nm of surrounding solar spectrum. The Hei absorption line is seen blue-shifted to velocities of between 200 and 300 km s^-1. The true solar trajectory of the eruption is obtained by using the projected solar coordinates and by integrating the Doppler velocity. The filament travels with a total velocity of about 300 km s^-1 along a path inclined roughly 49 deg to the solar surface and rises to a height of just over 1.5 solar radii before it becomes too diffuse to follow. The filament also shows internal motions with multiple Doppler components shifted by +/-25 km s^-1. Finally, the KPVT data show no Stokes V profiles in the Doppler-shifted Hei 1083.03 nm absorption to a limit of roughly 3×10^-3 times the continuum intensity. The SOHO/CDS scanned the center of the KPVT FOV using seven EUV lines; Doppler-shifted filament emission is seen in lines from Hei 58.4 nm, Heii 30.4 nm, Oiv 55.5 nm, Ov 63.0 nm, Nevi 56.3 nm, and Mgx 61.0 nm representing temperatures from about 2×10^4K through 1×10^6K. Bound-free continuum absorption from Hi, without confusion from foreground emission and line emission, is seen as the filament obscures underlying chromospheric emission. A fit to the wavelength dependence of the absorption from five lines between 55.5 to 63.0 nm yields a column density ξ_H I =4.8+/-2.5×10^17 cm^-2. Spatial maps show that this filament absorption is more confined than the regions which show emission.

An experimental test of plant canopy reflectance models on cotton

NASA Technical Reports Server (NTRS)

Lemaster, E. W.

1974-01-01

Extensive data on the plant parameters necessary to evaluate any model are presented for a cotton crop. The variation of the bidirectional reflectance function with observer altitude, observer azimuth, and sun altitude angle is presented for a high density cotton crop having leaf index of 19. A comparison with the quantitative behavior obtained from the Suits model is accomplished in the wavelength region from 400 nm to 1050 nm.

Midnight latitude-altitude distribution of 630 nm airglow in the Asian sector measured with FORMOSAT-2/ISUAL

NASA Astrophysics Data System (ADS)

Adachi, Toru; Yamaoka, Masashi; Yamamoto, Mamoru; Otsuka, Yuichi; Liu, Huixin; Hsiao, Chun-Chieh; Chen, Alfred B.; Hsu, Rue-Ron

2010-09-01

The Imager for Sprites and Upper Atmospheric Lightning (ISUAL) payload on board the FORMOSAT-2 satellite carried out the first limb imaging observation of 630 nm airglow for the purpose of studying physical processes in the F region ionosphere. For a total of 14 nights in 2006-2008, ISUAL scanned the midnight latitude-altitude distribution of 630 nm airglow in the Asian sector. On two nights of relatively active conditions (ΣKp = 26, 30+) we found several bright airglow regions, which were highly variable each night in terms of luminosity and location. In relatively quiet conditions (ΣKp = 4-20) near May/June we found two bright regions which were stably located in the midlatitude region of 40°S-10°S (50°S-20°S magnetic latitude (MLAT)) and in the equatorial region of 0°-10°N (10°S-0° MLAT). On one of the quiet nights, FORMOSAT-3/COSMIC and CHAMP simultaneously measured the plasma density in the same region where ISUAL observed airglow. The plasma density data generally show good agreement, suggesting that plasma enhancements were the primary source of these two bright airglow regions. From detailed comparison with past studies we explain that the airglow in the equatorial region was due to the midnight brightness wave produced in association with the midnight temperature maximum, while that in the midlatitude region was due to the typical plasma distribution usually formed in the midnight sector. The fact that the equatorial airglow was much brighter than the midlatitude airglow and was observed on most nights during the campaign period strongly suggests the importance of further studies on the MTM/MBW phenomenology, which is not well reproduced in the current general circulation model.

Determination of polycyclic aromatic hydrocarbons and their nitro-, amino-derivatives absorbed on particulate matter 2.5 by multiphoton ionization mass spectrometry using far-, deep-, and near-ultraviolet femtosecond lasers.

PubMed

Tang, Yuanyuan; Imasaka, Tomoko; Yamamoto, Shigekazu; Imasaka, Totaro

2016-06-01

Multiphoton ionization processes of parent-polycyclic aromatic hydrocarbons (PPAHs), nitro-PAHs (NPAHs), and amino-PAHs (APAHs) were examined by gas chromatography combined with time-of-flight mass spectrometry using a femtosecond Ti:sapphire laser as the ionization source. The efficiency of multiphoton ionization was examined using lasers emitting in the far-ultraviolet (200 nm), deep-ultraviolet (267 nm), and near-ultraviolet (345 nm) regions. The largest signal intensities were obtained when the far-ultraviolet laser was employed. This favorable result can be attributed to the fact that these compounds have the largest molar absorptivities in the far-ultraviolet region. On the other hand, APAHs were ionized more efficiently than NPAHs in the near-ultraviolet region because of their low ionization energies. A sample extracted from a real particulate matter 2.5 (PM2.5) sample was measured, and numerous signal peaks arising from PAH and its analogs were observed at 200 nm. On the other hand, only a limited number of signed peaks were observed at 345 nm, some of which were signed to PPAHs, NPAHs, and APAHs. Thus, multiphoton ionization mass spectrometry has potential for the use in comprehensive analysis of toxic environmental pollutants. Copyright © 2016 Elsevier Ltd. All rights reserved.

VizieR Online Data Catalog: Halpha measurements in Abell 2465 (Wegner+, 2015)

NASA Astrophysics Data System (ADS)

Wegner, G. A.; Chu, D. S.; Hwang, H. S.

2015-07-01

The wavelength of the Hα line at the redshift of Abell 2465 is near 817nm in a clear spectral region between the many telluric emission lines. A custom narrow-band filter for observing Hα was obtained from the Andover Corp. It has a peak transmission at 817.7nm (m817) and a full width at half-maximum (FWHM) of 8.77nm. The wide filter was a Gunn i (ig) filter with nearly the same central wavelength of 820nm and a FWHM of 185nm, and was manufactured by Custom Scientific. Hα observations of Abell 2465 were obtained 2012 September 19-23 using the 2.4m Hiltner telescope at the MDM Observatory on Kitt Peak. The 'Nellie' CCD was used. (1 data file).

Enhanced frequency upconversion study in Er3+/Yb3+ doped/codoped TWTi glasses

NASA Astrophysics Data System (ADS)

Azam, Mohd; Rai, Vineet Kumar

2018-04-01

Er3+/Yb3+ doped/codoped TeO2-WO3-TiO2 (TWTi) glasses have been prepared by using the melt-quenching technique. The upconversion (UC) emission spectra of the developed glasses have been recorded upon 980 nm laser excitation. Three intense UC emission bands have been observed within the green and red region centered at ˜532 nm, ˜553 nm and ˜669 nm corresponding to the 2H11/2→4I15/2, 4S3/2→4I15/2 and 4F9/2→4I15/2 transitions respectively in the singly Er3+ doped glass. On introducing Yb3+ ions in the singly Er3+ doped glass, an enhancement of about ˜ 12 times and ˜50 times in the green and red bands respectively have been observed even at low pump power ˜ 364 mW followed by two photon absorption process. Colour tunability from yellowish green to pure green colour region has been observed on varying the pump power. The prepared glass can be used to produce NIR to green upconverter and colour tunable display devices.

Broadband two-photon absorption cross sections of benzothiazole derivatives and benzobisthiazolium salts

NASA Astrophysics Data System (ADS)

Noskovičova, Eva; Lorenc, Dušan; Magdolen, Peter; Sigmundová, Ivica; Zahradník, Pavol; Velič, Dušan

2018-05-01

Two-photon absorption (TPA) cross sections of conjugated donor-π-acceptor dipolar structures containing benzothiazole or benzobisthiazolium moieties are determined in a broad spectral range from 700 nm to 1000 nm using two-photon induced fluorescence technique. The TPA cross section values range from 150 GM to 4600 GM. The largest values are observed in near-infrared region. The dipolar derivative of benzothiazole has the largest TPA cross section of 4600 GM at wavelength of 890 nm. A combination of the large TPA in the near-infrared region and the high emission quantum yield makes these compounds excellent candidates for two-photon fluorescence microscopy.

Comparison of the Changes in the Visible and Infrared Irradiance Observed by the SunPhotometers on EURECA to the UARS Total Solar and UV Irradiances

NASA Technical Reports Server (NTRS)

Pap, Judit

1995-01-01

Solar irradiance in the near-UV (335 nm), visible (500 nm) and infrared (778 nm) spectral bands has been measured by the SunPhotometers developed at the World Radiation Center, Davos, Switzerland on board the European Retrievable Carrier between August 1992 and May 1993. Study of the variations in the visible and infrared irradiance is important for both solar and atmospheric physics. The purpose of this paper is to examine the temporal variations observed in the visible and infrared spectral bands after eliminating the trend in the data mainly related to instrument degradation. The effect of active regions in these spectral irradiances is clearly resolved. Variations in the visible and infrared irradiances are compared to total solar irradiance observed by the SOVA2 radiometer on the EURECA platform and by the ACRIMII radiometer on UARS as well as to UV observations of the UARS and NOAA9 satellites. The space-borne spectral irradiance observations are compared to the photometric sunspot deficit and CaII K irradiance measured at the San Fernando Observatory, California State University at Northridge in order to study the effect of active regions in detail.

Radiation damage of all-silica fibers in the UV region

NASA Astrophysics Data System (ADS)

Gombert, Joerg; Ziegler, M.; Assmus, J.; Klein, Karl-Friedrich; Nelson, Gary W.; Clarkin, James P.; Pross, H.; Kiefer, J.

1999-04-01

Since several years, UVI-fibers having higher solarization- resistance are well known stimulating new fiber-optic applications in the UV-region below 250 nm. Besides the description of the improved transmission properties of UV- light from different UV-sources, the mechanisms of improvement have been discussed in detail. The UV-defects, mainly the E'- center with the UV-absorption band around 215 nm, were passivated by using hydrogen-doping. Besides DUV-light, ionizing radiation like Gamma-radiation or X-rays can create similar defects in the UV-region. In the past, the radiation- damage in the UV-region was studied on silica bulk samples: again, E'-centers were generated. Up to now, no UV- transmission through a 1 m long fiber during or after Gamma- radiation had been observed. However, the hydrogen in the UVI- fibers behaves the same for Gamma-irradiation, leading to a passivation of the radiation-induced defects and an improved transmission in the UV-C region below 250 nm. On this report, the influence of total dose and fiber diameter on the UV- damage after irradiation will be described and discussed. In addition, we will include annealing studies, with and without UV-light. Based on our results, the standard process of Gamma- sterilization with a total dose of approx. 2 Mrad can be used for UVI-fibers resulting in a good UV-transmission below 320 nm. Excimer-laser light at 308 nm (XeCl) and 248 nm (KrF) and deuterium-lamp light with the full spectrum starting at 200 nm can also be transmitted.

Scanning imaging absorption spectrometer for atmospheric chartography

NASA Technical Reports Server (NTRS)

Burrows, John P.; Chance, Kelly V.

1991-01-01

The SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY is an instrument which measures backscattered, reflected, and transmitted light from the earth's atmosphere and surface. SCIAMACHY has eight spectral channels which observe simultaneously the spectral region between 240 and 1700 nm and selected windows between 1940 and 2400 nm. Each spectral channel contains a grating and linear diode array detector. SCIAMACHY observes the atmosphere in nadir, limb, and solar and lunar occultation viewing geometries.

TEMPO Specific Photochemical Reflectance Index for Monitoring Crop Productivity

NASA Astrophysics Data System (ADS)

Wulamu, A.; Fishman, J.; Maimaitiyiming, M.

2016-12-01

Chlorophyll fluorescence and Photochemical Reflectance Index (PRI) are two key indicators of plant functional status used for early stress detection. With its less than one nanometer hyperspectral resolution and hourly revisit capabilities, NASA's Tropospheric Emissions: Monitoring of Pollution (TEMPO) sensor provides new opportunities for monitoring regional food security. Chlorophyll fluorescence can be retrieved by TEMPO using Oxygen B (O2-B) absorption region at 687 nm. The Photochemical Reflectance Index (PRI) is calculated from spectral reflectance at 531 and 570. However, TEMPO spectral range covers from 290 mm - 490 nm and 540 nm -740 nm, does not provide the 531 nm measurement band for PRI. It is imperative to develop alternate wavelengths within the TEMPO spectral range for these early stress indicators so that regional crop health can be observed by TEMPO with unparalleled spectral and temporal resolutions to address food security. Combining field and airborne remote sensing experiments and radiative transfer simulations, this work proposes a TEMPO specific PRI and demonstrates that TEMPO offers a new set of high-resolution spectral data for crop monitoring.

Flash photolysis and pulse radiolysis studies on collagen Type I in acetic acid solution.

PubMed

Sionkowska, Alina

2006-07-03

An investigation of the photochemical properties of collagen Type I in acetic acid solution was carried out using nanosecond laser irradiation. The transient spectra of collagen solution excited at 266 nm show two bands. One of them with maximum at 295 nm and the second one with maximum at 400 nm. The peak at 400 nm is assigned to tyrosyl radicals. The first peak of the transient absorption spectra at 295 nm is probably due to photoionisation producing collagen radical cation. The transient for collagen solution in acetic acid at 640 nm was not observed. It is evidence that there is no hydrated electron in the irradiated collagen solution. The reactions of hydrated electrons and (*)OH radicals with collagen have been studied by pulse radiolysis. In the absorption spectra of products resulting from the reaction of collagen with e(aq)(-) no characteristic maximum absorption in UV and visible light region has been observed. In the absorption spectra of products resulting from the reaction of the hydroxyl radicals with collagen two bands have been observed. The first one at 320 nm and the second one at 405 nm. Reaction of (*)OH radicals with tyrosine residues in collagen chains gives rise to Tyr phenoxyl radicals (absorption at 400 nm).

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.

Evaluation of climate model aerosol seasonal and spatial variability over Africa using AERONET

NASA Astrophysics Data System (ADS)

Horowitz, Hannah M.; Garland, Rebecca M.; Thatcher, Marcus; Landman, Willem A.; Dedekind, Zane; van der Merwe, Jacobus; Engelbrecht, Francois A.

2017-11-01

The sensitivity of climate models to the characterization of African aerosol particles is poorly understood. Africa is a major source of dust and biomass burning aerosols and this represents an important research gap in understanding the impact of aerosols on radiative forcing of the climate system. Here we evaluate the current representation of aerosol particles in the Conformal Cubic Atmospheric Model (CCAM) with ground-based remote retrievals across Africa, and additionally provide an analysis of observed aerosol optical depth at 550 nm (AOD550 nm) and Ångström exponent data from 34 Aerosol Robotic Network (AERONET) sites. Analysis of the 34 long-term AERONET sites confirms the importance of dust and biomass burning emissions to the seasonal cycle and magnitude of AOD550 nm across the continent and the transport of these emissions to regions outside of the continent. In general, CCAM captures the seasonality of the AERONET data across the continent. The magnitude of modeled and observed multiyear monthly average AOD550 nm overlap within ±1 standard deviation of each other for at least 7 months at all sites except the Réunion St Denis Island site (Réunion St. Denis). The timing of modeled peak AOD550 nm in southern Africa occurs 1 month prior to the observed peak, which does not align with the timing of maximum fire counts in the region. For the western and northern African sites, it is evident that CCAM currently overestimates dust in some regions while others (e.g., the Arabian Peninsula) are better characterized. This may be due to overestimated dust lifetime, or that the characterization of the soil for these areas needs to be updated with local information. The CCAM simulated AOD550 nm for the global domain is within the spread of previously published results from CMIP5 and AeroCom experiments for black carbon, organic carbon, and sulfate aerosols. The model's performance provides confidence for using the model to estimate large-scale regional impacts of African aerosols on radiative forcing, but local feedbacks between dust aerosols and climate over northern Africa and the Mediterranean may be overestimated.

Particle growth in an isoprene-rich forest: Influences of urban, wildfire, and biogenic air masses

NASA Astrophysics Data System (ADS)

Gunsch, Matthew J.; Schmidt, Stephanie A.; Gardner, Daniel J.; Bondy, Amy L.; May, Nathaniel W.; Bertman, Steven B.; Pratt, Kerri A.; Ault, Andrew P.

2018-04-01

Growth of freshly nucleated particles is an important source of cloud condensation nuclei (CCN) and has been studied within a variety of environments around the world. However, there remains uncertainty regarding the sources of the precursor gases leading to particle growth, particularly in isoprene-rich forests. In this study, particle growth events were observed from the 14 total events (31% of days) during summer measurements (June 24 - August 2, 2014) at the Program for Research on Oxidants PHotochemistry, Emissions, and Transport (PROPHET) tower within the forested University of Michigan Biological Station located in northern Michigan. Growth events were observed within long-range transported air masses from urban areas, air masses impacted by wildfires, as well as stagnant, forested/regional air masses. Growth events observed during urban-influenced air masses were prevalent, with presumably high oxidant levels, and began midday during periods of high solar radiation. This suggests that increased oxidation of biogenic volatile organic compounds (BVOCs) likely contributed to the highest observed particle growth in this study (8 ± 2 nm h-1). Growth events during wildfire-influenced air masses were observed primarily at night and had slower growth rates (3 ± 1 nm h-1). These events were likely influenced by increased SO2, O3, and NO2 transported within the smoke plumes, suggesting a role of NO3 oxidation in the production of semi-volatile compounds. Forested/regional air mass growth events likely occurred due to the oxidation of regionally emitted BVOCs, including isoprene, monoterpenes, and sesquiterpenes, which facilitated multiday growth events also with slower rates (3 ± 2 nm h-1). Intense sulfur, carbon, and oxygen signals in individual particles down to 20 nm, analyzed by transmission electron microscopy with energy dispersive X-ray spectroscopy (TEM-EDX), suggest that H2SO4 and secondary organic aerosol contributed to particle growth. Overall, aerosol growth was frequently observed in a range of air masses (urban, wildfire, forested) and oxidant conditions (day vs. night), with rates ranging from 0.8 to 10.2 nm h-1.

Exoplanet Transits of Stellar Active Regions

NASA Astrophysics Data System (ADS)

Giampapa, Mark S.; Andretta, Vincenzo; Covino, Elvira; Reiners, Ansgar; Esposito, Massimiliano

2018-01-01

We report preliminary results of a program to obtain high spectral- and temporal-resolution observations of the neutral helium triplet line at 1083.0 nm in transiting exoplanet systems. The principal objective of our program is to gain insight on the properties of active regions, analogous to solar plages, on late-type dwarfs by essentially using exoplanet transits as high spatial resolution probes of the stellar surface within the transit chord. The 1083 nm helium line is a particularly appropriate diagnostic of magnetized areas since it is weak in the quiet photosphere of solar-type stars but appears strongly in absorption in active regions. Therefore, during an exoplanet transit over the stellar surface, variations in its absorption equivalent width can arise that are functions of the intrinsic strength of the feature in the active region and the known relative size of the exoplanet. We utilized the Galileo Telescope and the GIANO-B near-IR echelle spectrograph to obtain 1083 nm spectra during transits in bright, well-known systems that include HD 189733, HD 209458, and HD 147506 (HAT-P-2). We also obtained simultaneous auxiliary data on the same telescope with the HARPS-N UV-Visible echelle spectrograph. We will present preliminary results from our analysis of the observed variability of the strength of the He I 1083 nm line during transits.Acknowledgements: Based on observations made with the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Fundación Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias. The NSO is operated by AURA under a cooperative agreement with the NSF.

Transmission electron microscopy characterization of the interfacial structure of a galvanized dual-phase steel

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

Aslam, I., E-mail: ia31@msstate.edu

2016-10-15

Site-specific studies were carried out to characterize the interface of a galvanized dual-phase (DP) steel. Focused ion beam (FIB) was used to prepare specimens in the interface region (~ 100 nm thick) between the coating and the substrate. Transmission electron microscopy (TEM), scanning TEM (STEM), and high resolution TEM (HRTEM) were performed to resolve the phases and the structures at the interface between the zinc (Zn) coating and the steel substrate. The STEM and TEM results showed that a continuous manganese oxide (MnO) film with a thickness of ~ 20 nm was present on the surface of the substrate whilemore » no silicon (Si) oxides were resolved. Internal oxide particles were observed as well in the sub-surface region. Despite the presence of the continuous oxide film, a well-developed inhibition layer was observed right on top of the oxide film. The inhibition layer has a thickness of ~ 100 nm. Possible mechanisms for the growth of the inhibition layer were discussed. - Highlights: •Site-specific examinations were performed on the Zn/steel interface. •Continuous external MnO oxides (20 nm) were observed at the interface. •No Si oxides were observed at the interface. •Internal oxide particles were distributed in the subsurface. •A continuous inhibition layer grew on top of the external oxides.« less

Evidence for production and lateral transport of dissolved organic phosphorus in the eastern subtropical North Atlantic

NASA Astrophysics Data System (ADS)

Reynolds, Sarah; Mahaffey, Claire; Roussenov, Vassil; Williams, Richard G.

2014-08-01

The concentration of phosphate and dissolved organic phosphorus (DOP) is chronically low and limits phytoplankton growth in the subtropical North Atlantic relative to other ocean basins. Transport of phosphate and DOP from the productive flanks of the gyre to its interior has been hypothesized as an important phosphorus supply pathway. During a cruise in the eastern Atlantic in spring 2011, the rates of phosphate uptake, alkaline phosphatase activity (APA), and DOP production were measured in the northwest African shelf region, subtropics, and tropics. Rates of DOP production were sixfold higher in the shelf region (43 ± 41 nM d-1) relative to the subtropics (6.9 ± 4.4 nM d-1). In contrast, APA was threefold higher in the subtropics (8.0 ± 7.3 nM d-1), indicative of enhanced DOP utilization, relative to the shelf region (2.6 ± 2.1 nM d-1). Hence, observations suggest net production of DOP in the shelf region and either net consumption of DOP or a near balance in DOP production and consumption in the gyre interior. Eddy-permitting model experiments demonstrate that (i) DOP accounts for over half the total phosphorus in surface waters, (ii) DOP is transported westward from the shelf region by a combination of gyre and eddy circulations, and (iii) advected DOP supports up to 70% of the particle export over much of the subtropical gyre. Our combined observational and modeling study supports the view that the horizontal transport of DOP from the shelf region is an important mechanism supplying phosphorus to the surface subtropical North Atlantic.

2D Vis/NIR correlation spectroscopy of cooked chicken meats

NASA Astrophysics Data System (ADS)

Liu, Yongliang; Chen, Yud-Ren; Ozaki, Yukihiro

2000-03-01

Cooking of chicken meats was investigated by the generalized two-dimensional visible/near-infrared (2D Vis/NIR) correlation spectroscopy. Synchronous and asynchronous spectra in the 400-700 nm visible region suggested that the 445 and 560 nm bands be ascribed to deoxymyoglobin and oxymyoglobin, and at least one of the 475, 520, and 585 nm bands is assignable to the denatured species (metmyoglobin). The asynchronous 2D NIR correlation spectrum showed that CH bands change their spectral intensities before the OH/NH groups during the cooking process, indicating that CH fractions are easily oxidized and degraded. In addition, strong correlation peaks were observed correlating the bands in the visible and NIR spectral regions.

THE FORMATION OF IRIS DIAGNOSTICS. VIII. IRIS OBSERVATIONS IN THE C ii 133.5 nm MULTIPLET

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

Rathore, Bhavna; Pereira, Tiago M. D.; Carlsson, Mats

The C ii 133.5 nm multiplet has been observed by NASA’s Interface Region Imaging Spectrograph (IRIS) in unprecedented spatial resolution. The aims of this work are to characterize these new observations of the C ii lines, place them in context with previous work, and to identify any additional value the C ii lines bring when compared with other spectral lines. We make use of wide, long exposure IRIS rasters covering the quiet Sun and an active region. Line properties such as velocity shift and width are extracted from individual spectra and analyzed. The lines have a variety of shapes (mostlymore » single-peak or double-peak), are strongest in active regions and weaker in the quiet Sun. The ratio between the 133.4 and 133.5 nm components is always less than 1.8, indicating that their radiation is optically thick in all locations. Maps of the C ii line widths are a powerful new diagnostic of chromospheric structures, and their line shifts are a robust velocity diagnostic. Compared with earlier quiet Sun observations, we find similar absolute intensities and mean line widths, but smaller redshifts; this difference can perhaps be attributed to differences in spectral resolution and spatial coverage. The C ii intensity maps are somewhat similar to those of transition region lines, but also share some features with chromospheric maps such as those from the Mg ii k line, indicating that they are formed between the upper chromosphere and transition region. C ii intensity, width, and velocity maps can therefore be used to gather additional information about the upper chromosphere.« less

Organic molecules and nanoparticles in inorganic crystals: Vitamin C in CaCO3 as an ultraviolet absorber

NASA Astrophysics Data System (ADS)

Sato, H.; Ikeya, M.

2004-03-01

Organic molecules and nanoparticles embedded in inorganic crystalline lattices have been studied to add different properties and functions to composite materials. Calcium carbonate was precipitated by dropping an aqueous solution of CaCl2 into that of Na2CO3 containing dissolved vitamin C (ascorbic acid). The optical absorption ascribed to divalent ascorbate anions in the lattice was observed in the ultraviolet B (wavelength: 280-315 nm) region, while solid vitamin C exhibited absorption in the ultraviolet C (100-280 nm) region. The divalent ascorbate anion is only stable in CaCO3 due to the absence of oxygen molecules. Doping CaCO3 with nanoparticles of ZnO also enhanced the absorption in the ultraviolet A (315-380 nm) region. These composite materials are suggested for use as UV absorbers.

Simulated East-west differences in F-region peak electron density at Far East mid-latitude region

NASA Astrophysics Data System (ADS)

Ren, Zhipeng; Zhao, Biqiang; Wan, Weixing; Liu, Libo

2017-04-01

In the present work, using Three-Dimensional Theoretical Ionospheric Model of the Earth in Institute of Geology and Geophysics, Chinese Academy of Sciences (TIME3D-IGGCAS), we simulated the east-west differences in Fregion peak electron density (NmF2) at Far East mid-latitude region.We found that, after removing the longitudinal variations of neutral parameters, TIME3D-IGGCAS can better represent the observed relative east-west difference (Rew) features. Rew is mainly negative (West NmF2 > East NmF2) at noon and positive (East NmF2 >West NmF2) at evening-night. The magnitude of daytime negative Rew is weak at local winter and strong at local summer, and the daytime Rew show two negative peaks around two equinoxes. With the increasing of solar flux level, the magnitude of Rew mainly become larger, and two daytime negative peaks slight shifts to June Solstice. With the decreasing of geographical latitude, Rew mainly become positive, and two daytime negative peaks slight shifts to June Solstice. Our simulation also suggested that the thermospheric zonal wind combined with the geomagnetic field configuration play a pivotal role in the formation of the ionospheric east-west differences at Far East midlatitude region.

Simulated East-west differences in F-region peak electron density at Far East mid-latitude region

NASA Astrophysics Data System (ADS)

Ren, Z.; Wan, W.

2017-12-01

In the present work, using Three-Dimensional Theoretical Ionospheric Model of the Earth in Institute of Geology and Geophysics, Chinese Academy of Sciences (TIME3D-IGGCAS), we simulated the east-west differences in Fregion peak electron density (NmF2) at Far East mid-latitude region.We found that, after removing the longitudinal variations of neutral parameters, TIME3D-IGGCAS can better represent the observed relative east-west difference (Rew) features. Rew is mainly negative (West NmF2 > East NmF2) at noon and positive (East NmF2 >West NmF2) at evening-night. The magnitude of daytime negative Rew is weak at local winter and strong at local summer, and the daytime Rew show two negative peaks around two equinoxes. With the increasing of solar flux level, the magnitude of Rew mainly become larger, and two daytime negative peaks slight shifts to June Solstice. With the decreasing of geographical latitude, Rew mainly become positive, and two daytime negative peaks slight shifts to June Solstice. Our simulation also suggested that the thermospheric zonal wind combined with the geomagnetic field configuration play a pivotal role in the formation of the ionospheric east-west differences at Far East midlatitude region.

Molecular dynamics simulations reveal that water diffusion between graphene oxide layers is slow

DOE PAGES

Devanathan, Ram; Chase-Woods, Dylan; Shin, Yongsoon; ...

2016-07-08

Membranes made of stacked layers of graphene oxide (GO) hold the tantalizing promise of revolutionizing desalination and water filtration if selective transport of molecules can be controlled. We present the findings of a molecular dynamics simulation study of water intercalated between GO layers that have a C/O ratio of 4. We simulated a range of hydration levels from 1 wt.% to 23.3 wt.% water. The interlayer spacing increased upon hydration from 0.8 nm to 1.1 nm. We also synthesized GO membranes that showed an increase in spacing from about 0.7 nm to 0.8 nm and an increase in mass ofmore » about 14% on hydration. Water diffusion through GO layers is an order of magnitude slower than that in bulk water, because of strong hydrogen bonded interactions. Most of the water molecules are bound to OH groups even at the highest hydration level. We observed large water clusters that could span graphitic regions, oxidized regions and holes that have been experimentally observed in GO. As a result, slow interlayer diffusion can be consistent with experimentally observed water transport in GO if holes lead to a shorter path length than previously assumed and sorption serves as a key rate-limiting step.« less

Optical coherence tomography based imaging of dental demineralisation and cavity restoration in 840 nm and 1310 nm wavelength regions

NASA Astrophysics Data System (ADS)

Damodaran, Vani; Rao, Suresh Ranga; Vasa, Nilesh J.

2016-08-01

In this paper, a study of in-house built optical coherence tomography (OCT) system with a wavelength of 840 nm for imaging of dental caries, progress in demineralisation and cavity restoration is presented. The caries when imaged with the 840 nm OCT system showed minute demineralisation in the order of 5 μm. The OCT system was also proposed to study the growth of lesion and this was demonstrated by artificially inducing caries with a demineralisation solution of pH 4.8. The progress of carious lesion to a depth of about 50-60 μm after 60 hours of demineralisation was clearly observed with the 840 nm OCT system. The tooth samples were subjected to accelerated demineralisation condition at pH of approximately 2.3 to study the adverse effects and the onset of cavity formation was clearly observed. The restoration of cavity was also studied by employing different restorative materials (filled and unfilled). In the case of restoration without filler material (unfilled), the restoration boundaries were clearly observed. Overall, results were comparable with that of the widely used 1310 nm OCT system. In the case of restoration with filler material, the 1310 nm OCT imaging displayed better imaging capacity due to lower scattering than 840 nm imaging.

Seasonally Transported Aerosol Layers Over Southeast Atlantic are Closer to Underlying Clouds than Previously Reported

NASA Technical Reports Server (NTRS)

Rajapakshe, Chamara; Zhang, Zhibo; Yorks, John E.; Yu, Hongbin; Tan, Qian; Meyer, Kerry; Platnick, Steven; Winker, David M.

2017-01-01

From June to October, low-level clouds in the southeast (SE) Atlantic often underlie seasonal aerosol layers transported from African continent. Previously, the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) 532 nm lidar observations have been used to estimate the relative vertical location of the above-cloud aerosols (ACA) to the underlying clouds. Here we show new observations from NASA's Cloud-Aerosol Transport System (CATS) lidar. Two seasons of CATS 1064 nm observations reveal that the bottom of the ACA layer is much lower than previously estimated based on CALIPSO 532 nm observations. For about 60% of CATS nighttime ACA scenes, the aerosol layer base is within 360 m distance to the top of the underlying cloud. Our results are important for future studies of the microphysical indirect and semidirect effects of ACA in the SE Atlantic region.

Mapping Vineyard Areas Using WORLDVIEW-2 Satellite Images

NASA Astrophysics Data System (ADS)

Sertel, E.; Ozelkan, E.; Yay, I.; Seker, D. Z.; Ormeci, C.

2011-12-01

The observation of Earth surface from the space has lead to new research possibilities in many fields like agriculture, hydrology, geology, geodesy etc. Different satellite image data have been used for agricultural monitoring for different scales namely local, regional and global. It is important to monitor agricultural field in local scale to determine the crop yield, diseases, and to provide Farmer Registries. Worldview-2 is a new satellite system that could be used for agricultural applications especially in local scale. It is the first high resolution 8-band multispectral commercial satellite launched in October 2009. The satellite has an altitude of 770 kilometers and its spatial resolution for panchromatic mode and multispectral mode are 46 cm and 1.85 meter, respectively. In addition to red (630 - 690 nm), blue (450 - 510 nm), Green (510 - 580 nm) and Near Infrared (770 - 895 nm) bands, Worldview-2 has four new spectral bands lying on beginning of blue (400 - 450 nm), yellow (585 - 625 nm), red edge (705 - 745 nm) and Near Infrared (860 - 1040 nm) regions of the electromagnetic spectrum. Since Worldview-2 data are comparatively new, there have not been many studies in the literature about the usage of these new data for different applications. In this research, Worldview-2 data were used to delineate the vineyard areas and identify different grape types in Sarkoy, Turkey. Phenological observations of grape fields have been conducted for the last three years over a huge test area owned by the Government Viniculture Institute. Based on the phenological observations, it was found that July and August period is the best data acquisition time for satellite data since leaf area index is really higher. In August 2011, Worldview-2 data of the region were acquired and spectral measurements were collected in the field for different grape types using a spectroradiometer. Satellite image data and spectral measurements were correlated and satellite image data were classified to determine the location, extent and type of vineyards within the study region. A Digital Elevation Model generated from 1/25.000 scaled topographic maps was used to create slope and aspect map of the research area. These maps and vineyard parcels obtained from remote sensing techniques were integrated into a Geographic Information System. Spatial analyses were conducted in GIS to evaluate the appropriateness of vineyard areas for grape growth. Possible suitable vineyard sites for new plantation were selected through spatial queries to provide useful information to governmental authorities and farmers.

VUV Spectra observed in C-2 FRC plasma

NASA Astrophysics Data System (ADS)

Osin, Dmitry; Douglass, Jon; Tuszewski, Michel; TAE Team

2014-10-01

A grazing incidence flat-field spectrometer was installed for observation of vuv-spectra in C-2 FRC experiment. Wavelength calibration was done by observing spectra of six different gases produced by a hollow-cathode discharge lamp . In addition, in-situ calibration and alignment were performed utilizing neutral-beam heated gases. Wavelength regions between 16 nm and 170 nm was investigated with accuracy of about 0.02 nm. VUV-spectral lines of the most abundant impurity ions were identified both for Plasma Gun and C-2 plasmas. In addition to D spectrum, strong lines of O III-VI, N IV-V, C II-III, and Fe II ions were observed during the plasma lifetime. VUV radiative power losses within energy range from 7.3 eV to 81 eV were estimated based on the calculated FRC dimensions.

Optical Imaging Observation of the Geospace from the International Space Station by ISS-IMAP

NASA Astrophysics Data System (ADS)

Saito, A.; Sakanoi, T.; Yoshikawa, I.; Yamazaki, A.; Hozumi, Y.; Perwitasari, S.; Otsuka, Y.; Yamamoto, M.

2017-12-01

Optical imaging observation of the mesosphere, thermosphere, ionosphere, and plasmasphere was carried out from the International Space Station (ISS) with ISS-IMAP (Ionosphere, Mesosphere, upper Atmosphere, and Plasmasphere mapping) mission instruments. ISS-IMAP instruments was installed on the Exposed Facility of Japanese Experiment Module of the ISS in August, 2012, and removed in August, 2015. They are two imagers, Visible-light and Infrared Spectrum Imager (VISI) and Extreme UltraViolet Imager (EUVI). VISI made imaging observations of the airglow and aurora in the nadir direction. It had two slits perpendicular to the trajectory of ISS, and the movement of ISS made the two-dimensional observation whose field-of-view width is 600km at 100km altitude. It covered the wave length range from 500nm to 900nm. The airglow of 730nm (OH, Alt. 85km), 762nm (O2, Alt. 95km), and 630nm (O, Alt. 250km) were mainly observed besides the other airglow, such as 589nm (Na) and 557 (O). EUVI made imaging observation of the resonant scattering from ions. It had two telescopes, and observed the resonant scattering of He+ in 30.4nm, and O+ in 83.4nm in the limb direction. VISI captured the airglow structures whose wavelength from 80km to 500km. The concentric wave structures were frequently observed in the mesosphere and lower thermosphere region. They are strong evidence of the vertical coupling between the lower atmosphere and the upper atmosphere by vertical propagation of the atmospheric gravity waves. The other airglow structures, such as mesospheric bores, were also detected by ISS-IMAP/VISI. The meso-scale structures in the ionosphere, such as plasma bubbles, and traveling ionospheric disturbances were also observed. EUVI revealed the longitudinal structures of He+ in the top side of the ionosphere. It was attributed to the neutral wind in the thermosphere. In the presentation, the outline and results of the ISS-IMAP's VISI and EUVI observations will be discussed.

Limb Spicules from the Ground and from Space

NASA Astrophysics Data System (ADS)

Pasachoff, Jay M.; Jacobson, William A.; Sterling, Alphonse C.

2009-11-01

We amassed statistics for quiet-sun chromosphere spicules at the limb using ground-based observations from the Swedish 1-m Solar Telescope on La Palma and simultaneously from NASA’s Transition Region and Coronal Explorer (TRACE) spacecraft. The observations were obtained in July 2006. With the 0.2 arcsecond resolution obtained after maximizing the ground-based resolution with the Multi-Object Multi-Frame Blind Deconvolution (MOMFBD) program, we obtained specific statistics for sizes and motions of over two dozen individual spicules, based on movies compiled at 50-second cadence for the series of five wavelengths observed in a very narrow band at Hα, on-band and at ± 0.035 nm and ± 0.070 nm (10 s at each wavelength) using the SOUP filter, and had simultaneous observations in the 160 nm EUV continuum from TRACE. The MOMFBD restoration also automatically aligned the images, facilitating the making of Dopplergrams at each off-band pair. We studied 40 Hα spicules, and 14 EUV spicules that overlapped Hα spicules; we found that their dynamical and morphological properties fit into the framework of several previous studies. From a preliminary comparison with spicule theories, our observations are consistent with a reconnection mechanism for spicule generation, and with UV spicules being a sheath region surrounding the Hα spicules.

Soft X-ray continuum radiation from low-energy pinch discharges of hydrogen

NASA Astrophysics Data System (ADS)

Mills, R.; Booker, R.; Lu, Y.; Lu

2013-10-01

Under a study contracted by GEN3 Partners, spectra of high current pinch discharges in pure hydrogen and helium were recorded in the extreme ultraviolet radiation region at the Harvard Smithsonian Center for Astrophysics (CfA) in an attempt to reproduce experimental results published by BlackLight Power, Inc. (BLP) showing predicted continuum radiation due to hydrogen in the 10-30 nm region (Mills, R. L. and Lu, Y. 2010 Hydrino continuum transitions with cutoffs at 22.8 nm and 10.1 nm. Int. J. Hydrog. Energy 35, 8446-8456, doi:10.1016?j.ijhydene.2010.05.098). Alternative explanations were considered to the claimed interpretation of the continuum radiation as being that emitted during transitions of H to lower-energy states (hydrinos). Continuum radiation was observed at CfA in the 10-30 nm region that matched BLP's results. Considering the low energy of 5.2 J per pulse, the observed radiation in the energy range of about 120-40 eV, reference experiments and analysis of plasma gases, cryofiltration to remove contaminants, and spectra of the electrode metal, no conventional explanation was found in the prior or present work to be plausible including contaminants, electrode metal emission, and Bremsstrahlung, ion recombination, molecular or molecular ion band radiation, and instrument artifacts involving radicals and energetic ions reacting at the charge-coupled device and H2 re-radiation at the detector chamber. Moreover, predicted selective extraordinarily high-kinetic energy H was observed by the corresponding Doppler broadening of the Balmer α line.

A spectroscopic study of the microorganism model of interstellar grains

NASA Astrophysics Data System (ADS)

Yabushita, S.; Wada, K.; Takai, T.; Inagaki, T.; Young, D.; Arakawa, E. T.

1986-07-01

The microorganism model of interstellar grains is investigated by spectroscopy from the infrared, visible to the ultraviolet (UV) wave regions. E. coli, yeast and spores of Bacillus subtilis exhibit absorption bands at lambda = 3.1 and 9.7 microns; they also exhibit several absorptions at 6 to about 8 microns which are in agreement with the observed IS extinction curves. To obtain the extinction curves in the visible and UV regions, dry films of microorganism are prepared on a MgF2 plate or synthesized quartz plate and their spectra measured. In the wavelength region 190 to about 400 nm, conventional spectrophotometers are adopted for the measurement. The extinction curve of the film of E. coli is similar to the observed IS curve. For the wave-range lambda of between 100 and 400 nm, a vacuum UV spectrometer is adopted to avoid absorptions due to O2 in the atmosphere. The extinction spectra by this method are in agreement with the result obtained by the conventional method where comparison is possible. The extinction curves of E. coli and yeast are such that they increase towards the short wavelength and exhibit a peak at lambda = 190 nm, which is different from the well-known IS peak at lambda = 220 nm. It remains to be seen whether interstellar low temperatures (10 to about 40 K) can shift the peak position in the extinction curve of biochemical materials.

Low damage dry etch for III-nitride light emitters

NASA Astrophysics Data System (ADS)

Nedy, Joseph G.; Young, Nathan G.; Kelchner, Kathryn M.; Hu, Yanling; Farrell, Robert M.; Nakamura, Shuji; DenBaars, Steven P.; Weisbuch, Claude; Speck, James S.

2015-08-01

We have developed a dry etch process for the fabrication of lithographically defined features close to light emitting layers in the III-nitride material system. The dry etch was tested for its effect on the internal quantum efficiency of c-plane InGaN quantum wells using the photoluminescence of a test structure with two active regions. No change was observed in the internal quantum efficiency of the test active region when the etched surface was greater than 71 nm away. To demonstrate the application of the developed dry etch process, surface-etched air gaps were fabricated 275 nm away from the active region of an m-plane InGaN/GaN laser diode and served as the waveguide upper cladding. Electrically injected lasing was observed without the need for regrowth or recovery anneals. This dry etch opens up a new design tool that can be utilized in the next generation of GaN light emitters.

Theoretical study on sensitivity enhancement in energy-deficit region of chemically amplified resists used for extreme ultraviolet lithography

NASA Astrophysics Data System (ADS)

Kozawa, Takahiro; Santillan, Julius Joseph; Itani, Toshiro

2017-10-01

The role of photons in lithography is to transfer the energy and information required for resist pattern formation. In the information-deficit region, a trade-off relationship is observed between line edge roughness (LER) and sensitivity. However, the sensitivity can be increased without increasing LER in the energy-deficit region. In this study, the sensitivity enhancement limit was investigated, assuming line-and-space patterns with a half-pitch of 11 nm. LER was calculated by a Monte Carlo method. It was unrealistic to increase the sensitivity twofold while keeping the line width roughness (LWR) within 10% critical dimension (CD), whereas the twofold sensitivity enhancement with 20% CD LWR was feasible. The requirements are roughly that the sensitization distance should be less than 2 nm and that the total sensitizer concentration should be higher than 0.3 nm-3.

Pre-storm NmF2 enhancements at middle latitudes: delusion or reality?

NASA Astrophysics Data System (ADS)

Mikhailov, A. V.; Perrone, L.

2009-03-01

A critical analysis of recent publications devoted to the NmF2 pre-storm enhancements is performed. There are no convincing arguments that the observed cases of NmF2 enhancements at middle and sub-auroral latitudes bear a relation to the following magnetic storms. In all cases considered the NmF2 pre-storm enhancements were due to previous geomagnetic storms, moderate auroral activity or they presented the class of positive quiet time events (Q-disturbances). Therefore, it is possible to conclude that there is no such an effect as the pre-storm NmF2 enhancement as a phenomenon inalienably related to the following magnetic storm. The observed nighttime NmF2 enhancements at sub-auroral latitudes may result from plasma transfer from the plasma ring area by meridional thermospheric wind. Enhanced plasmaspheric fluxes into the nighttime F2-region resulted from westward substorm-associated electric fields is another possible source of nighttime NmF2 enhancements. Daytime positive Q-disturbances occurring under very low geomagnetic activity level may be related to the dayside cusp activity.

Tunable narrow linewidth all-fiber thulium-doped fiber laser in a 2 µm-band using two Hi-Bi fiber optical loop mirrors

NASA Astrophysics Data System (ADS)

Posada-Ramírez, B.; Durán-Sánchez, M.; Álvarez-Tamayo, R. I.; Ibarra-Escamilla, B.; Hernández-Arriaga, M. V.; Sánchez-de-la-Llave, D.; Kuzin, E. A.

2017-08-01

We propose an all-fiber Tm-doped fiber laser with a tunable and narrow laser line generated in a wavelength region of 2 µm. A single laser line with a linewidth below 0.05 nm, tunable in a wavelength range of 44.25 nm, is obtained. The laser linewidth and the discrete wavelength tuning range depend on the characteristics of the two fiber optical loop mirrors with high birefringence in the loop that forms the cavity. Dual-wavelength laser operation is also observed at tuning range limits with a wavelength separation of 47 nm. Alternate wavelength switching is also observed.

Absolute determination of the cross sections of ozone in the wavelength region 339-355 nm at temperatures 220-293 K

NASA Astrophysics Data System (ADS)

Cacciani, Marco; di Sarra, Alcide; Fiocco, Giorgio; Amoruso, Antonella

1989-06-01

Absolute measurements of the ozone absorption coefficient in the Huggins bands at different temperatures have been carried out. Ozone is produced by an electrical discharge and stored cryogenically; differential absorption measurements are subsequently obtained in a slowly evolving mixture of ozone and molecular oxygen. High resolution (to 0.012 nm) measurements cover a spectral range (339-355 nm) where the ozone absorption shows a strong dependence on temperature. Results at 293 and 220 K are reported; they are particularly interesting in view of the utilization of this spectral region as a low-absorption reference channel for the observation of atmospheric ozone profiles by active probing techniques. Coherent radiation at two wavelengths, around 355 and 353 nm, respectively, can be obtained as third harmonic of the fundamental output of an Nd:YAG laser and by H2 Raman shifting of an XeCl excimer laser output.

Development of transition metal dichalcogenide based quantum dots for light emitting diodes

NASA Astrophysics Data System (ADS)

Seth, Subhashree; Sharma, S. K.

2018-05-01

Photoluminescent quantum dots (QDs) were synthesized by facile colloidal chemical route. Its properties were characterized and analysed by utilizing Fluorescence, FTIR and UV-Vis spectrophotometers. The resultant MoS2 QD exhibits fluorescence at 470 nm for excitation wavelength 400 nm. The as prepared sample exhibits excitation dependent emission due to polydispersion of MoS2 in the dispersive medium which is the characteristics of colloidal synthesis. It is also observed that resultant MoS2 QDs show size tunable emission in the visible region. The FTIR spectrum confirms the attachment of oleic acid on the surface of MoS2. Absorption spectrum shows a band at 346 nm and a shoulder band at 400 nm. The band gap of quantum dots was obtained as 3.5 eV. CIE diagram indicates the shifting of colour coordinates towards green region with increasing excitation wavelength.

Optical effects produced by running onboard engines of low-earth-orbit spacecraft

NASA Astrophysics Data System (ADS)

Beletskiy, A. B.; Mihalev, A. V.; Hahinov, V. V.; Lebedev, V. P.

2016-12-01

This paper presents results of optical observations made during Radar-Progress Experiment performed on April 17, 2013 and July 30, 2014 after approach-correction engines (ACE) of Progress M-17M and Progress M-23M cargo spacecraft in the thermosphere had been started. A region of enhanced emission intensity was recorded during engine operation. This may have been related to the scatter of twilight solar emission along the cargo spacecraft exhaust and to the emergence of additional atomic oxygen [OI] emission at 630 nm. The maximum dimension of the observed emission region was ~330-350 km and ~250-270 km along and across the orbit respectively. For the first time after ACE had been started, an expansion rate of emission region was ~ 7 and ~ 3.5 km/s along and across the orbit respectively. The maximum intensity of the disturbance area for Progress M-17M is estimated as ~40-60 R at 2 nm. Progress M-23M Space Experiment recorded a minor disturbance of atmospheric [OI] 630.0 nm emissions, both in near and in far cargo spacecraft flight paths, which might have been associated with the ACE exhaust gas injection.

Indication of the Hanle Effect by Comparing the Scattering Polarization Observed by CLASP in the Ly α and Si iii 120.65 nm Lines

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

Ishikawa, R.; Kubo, M.; Kano, R.

The Chromospheric Lyman-Alpha Spectro-Polarimeter is a sounding rocket experiment that has provided the first successful measurement of the linear polarization produced by scattering processes in the hydrogen Ly α line (121.57 nm) radiation of the solar disk. In this paper, we report that the Si iii line at 120.65 nm also shows scattering polarization and we compare the scattering polarization signals observed in the Ly α and Si iii lines in order to search for observational signatures of the Hanle effect. We focus on four selected bright structures and investigate how the U / I spatial variations vary between themore » Ly α wing, the Ly α core, and the Si iii line as a function of the total unsigned photospheric magnetic flux estimated from Solar Dynamics Observatory /Helioseismic and Magnetic Imager observations. In an internetwork region, the Ly α core shows an antisymmetric spatial variation across the selected bright structure, but it does not show it in other more magnetized regions. In the Si iii line, the spatial variation of U / I deviates from the above-mentioned antisymmetric shape as the total unsigned photospheric magnetic flux increases. A plausible explanation of this difference is the operation of the Hanle effect. We argue that diagnostic techniques based on the scattering polarization observed simultaneously in two spectral lines with very different sensitivities to the Hanle effect, like Ly α and Si iii, are of great potential interest for exploring the magnetism of the upper solar chromosphere and transition region.« less

Study of atmospheric scattering and absorbing aerosols at 550 nm over nearby western Indian tropical sites of Thar Desert effected region

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

Vyas, B. M., E-mail: bmvyas@yahoo.com; Saxenna, Abhishek; Panwar, Chhagan

The first time experimental results based on spaced satellite observations of different kinds of aerosols properties have been described over two different contrast environmental conditions locations in western tropical Indian region specifically first at Jaisalmer (26.90°N, 69.90°E, 220 m above mean sea level (amsl)) located in central Thar dessert vicinity of western Indian site over Indian Thar Desert region and another at Udaipur (24.6° N, 73.7° E, 560 m amsl) site concerning to semi-urban and semi arid place of hilly areas. The daily values of aerosols optical depth absorption at 500nm (AOD abs 500nm), aerosols optical depth extinction at 500nmmore » (AOD ext 500nm) along with aerosols optical depth at 500nmon (AOD 500nm) of eleven year period from Jan., 2004 to Dec., 2014 are basis of primary database of the present investigation. From the synthesis if the above database and the basis of rigorous statistical approach, following some of interesting facts are noted (i) larger annual monthly AOD variation of 0.93 is noted over JSM when compared to observed annual monthly change in AOD cycle, over UDP, of only 0.50 clearly indicating the more impact of desert influence activities about more than double times over JSM than UDP (ii) The higher abundance of absorbing aerosols occurrences about two time higher are seen in JSM in comparison to UDP. It indicates the clear evidence of strong optical absorption properties of useful solar mid visible wavelength at 550nm as the results of presence of more availability of dust aerosols as mineral natural type in pre-monsoon to post-monsoon over JSM which is also more predominant over JSM than the UDP region located far away from desert activity regime (iii) The greater sharing of extinction solar radiation effect on aerosols are more effective in pre-monsoon in UDP in reference to over JSM, where as in case of UDP, the aerosols effect through the scattering mechanism gradually reduce from monsoon to winter months as compared to observed over JSM. The more detailed analysis other important results are also discussed thoroughly in this paper.« less

First analysis of solar structures in 1.21 mm full-disc ALMA image of the Sun

NASA Astrophysics Data System (ADS)

Brajša, R.; Sudar, D.; Benz, A. O.; Skokić, I.; Bárta, M.; Pontieu, B. De; Kim, S.; Kobelski, A.; Kuhar, M.; Shimojo, M.; Wedemeyer, S.; White, S.; Yagoubov, P.; Yan, Y.

2018-05-01

Context. Various solar features can be seen in emission or absorption on maps of the Sun in the millimetre and submillimetre wavelength range. The recently installed Atacama Large Millimetre/submillimetre Array (ALMA) is capable of observing the Sun in that wavelength range with an unprecedented spatial, temporal and spectral resolution. To interpret solar observations with ALMA, the first important step is to compare solar ALMA maps with simultaneous images of the Sun recorded in other spectral ranges. Aims: The first aim of the present work is to identify different structures in the solar atmosphere seen in the optical, infrared, and EUV parts of the spectrum (quiet Sun, active regions, prominences on the disc, magnetic inversion lines, coronal holes and coronal bright points) in a full-disc solar ALMA image. The second aim is to measure the intensities (brightness temperatures) of those structures and to compare them with the corresponding quiet Sun level. Methods: A full-disc solar image at 1.21 mm obtained on December 18, 2015, during a CSV-EOC campaign with ALMA is calibrated and compared with full-disc solar images from the same day in Hα line, in He I 1083 nm line core, and with various SDO images (AIA at 170 nm, 30.4 nm, 21.1 nm, 19.3 nm, and 17.1 nm and HMI magnetogram). The brightness temperatures of various structures are determined by averaging over corresponding regions of interest in the calibrated ALMA image. Results: Positions of the quiet Sun, active regions, prominences on the disc, magnetic inversion lines, coronal holes and coronal bright points are identified in the ALMA image. At the wavelength of 1.21 mm, active regions appear as bright areas (but sunspots are dark), while prominences on the disc and coronal holes are not discernible from the quiet Sun background, despite having slightly less intensity than surrounding quiet Sun regions. Magnetic inversion lines appear as large, elongated dark structures and coronal bright points correspond to ALMA bright points. Conclusions: These observational results are in general agreement with sparse earlier measurements at similar wavelengths. The identification of coronal bright points represents the most important new result. By comparing ALMA and other maps, it was found that the ALMA image was oriented properly and that the procedure of overlaying the ALMA image with other images is accurate at the 5 arcsec level. The potential of ALMA for physics of the solar chromosphere is emphasised.

1D Atmosphere Models from Inversion of Fe i 630 nm Observations with an Application to Solar Irradiance Studies

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

Cristaldi, Alice; Ermolli, Ilaria, E-mail: alice.cristaldi@oaroma.inaf.it

Present-day semi-empirical models of solar irradiance (SI) variations reconstruct SI changes measured on timescales greater than a day by using spectra computed in one dimensional atmosphere models (1D models), which are representative of various solar surface features. Various recent studies have pointed out, however, that the spectra synthesized in 1D models do not reflect the radiative emission of the inhomogenous atmosphere revealed by high-resolution solar observations. We aimed to derive observation-based atmospheres from such observations and test their accuracy for SI estimates. We analyzed spectropolarimetric data of the Fe i 630 nm line pair in photospheric regions that are representativemore » of the granular quiet-Sun pattern (QS) and of small- and large-scale magnetic features, both bright and dark with respect to the QS. The data were taken on 2011 August 6, with the CRisp Imaging Spectropolarimeter at the Swedish Solar Telescope, under excellent seeing conditions. We derived atmosphere models of the observed regions from data inversion with the SIR code. We studied the sensitivity of results to spatial resolution and temporal evolution, and discuss the obtained atmospheres with respect to several 1D models. The atmospheres derived from our study agree well with most of the 1D models we compare our results with, both qualitatively and quantitatively (within 10%), except for pore regions. Spectral synthesis computations of the atmosphere obtained from the QS observations return an SI between 400 and 2400 nm that agrees, on average, within 2.2% with standard reference measurements, and within −0.14% with the SI computed on the QS atmosphere employed by the most advanced semi-empirical model of SI variations.« less

Multispectral Evidence of Alteration from Murray Ridge to Marathon Valley Observed by the Opportunity Pancam on the Rim of Endeavour Crater, Mars

NASA Technical Reports Server (NTRS)

Farrand, W. H.; Mittlefehldt, D. W.; Bell, J. F.; Johnson, J. R.

2015-01-01

The Mars Exploration Rover Opportunity has been traversing the rim of the Noachian-aged, 22 km diameter Endeavour crater. Circa sol 3390 of its mission, Opportunity reached the northern tip of the rim segment known as Solander Point and has since been traversing the rim to the south to its current location at the break in the rim known as Marathon Valley. The rocks making up the rim are dominated by impact breccias consisting of clasts and a finer-grained matrix. Several segments of the rim are transected by fractures as observed from orbital HiRISE imagery. Pancam multispectral observations of outcrop in these fracture regions, including part of the rim crest dubbed Murray Ridge, the Hueytown fracture, and Marathon Valley have been made. Over the range of 430 to 1010 nm there are changes in the multispectral reflectance signature of the breccia matrix with an increase in 535 nm and 904 nm band depth. This is attributed to oxidation and an increase in ferric oxides in these areas. In situ observations by the rover's APXS also indicate chemical differences associated with the matrix along these fractures, including increasing Fe/Mn southward from Solander Point to a region having an Al-OH signature in CRISM spectra, and generally higher SO3 in the Hueytown fracture region and the area around Spirit of St. Louis. Overturned rocks observed on Murray Ridge were determined by the APXS to have elevated Mn and Pancam spectra of the high Mn spots have a characteristic red, featureless slope. This spectrum was also observed in association with some coatings on blocks of the sulfate-rich Grasberg formation. Spectra resembling red hematite are observed in some zones in association with the craterform feature Spirit of St. Louis outside the mouth (to the west) of Marathon Valley. Marathon Valley itself has been observed from orbital hyperspectral observations by the CRISM sensor to host occurrences of Fe/Mg smectite minerals- indicating extensive aqueous alteration in this region. Pancam observations in Marathon Valley will play an important role in surveying outcrop and making VNIR spectral comparisons with clay bearing outcrop examined earlier in the mission at the Matijevic Hill region.

Experimental observation of breathing solitons and a third harmonic in a tapered photonic crystal fiber

NASA Astrophysics Data System (ADS)

Wang, F.; Yao, C. F.; Li, C. Z.; Jia, Z. X.; Li, Q.; Wu, C. F.; Ohishi, Y.; Qin, W. P.; Qin, G. S.

2018-02-01

We report the experimental observation of breathing solitons and a third harmonic in a tapered fluorotellurite photonic crystal fiber (PCF) pumped by a 1560 nm femtosecond fiber laser. The PCF has a core diameter that varies continuously along its length, resulting in a zero-dispersion wavelength that moves from 1325 nm to 906 nm over the transition region. By finely controlling the dispersion map of the tapered PCF and increasing the order of the optical solitons, their breathing behavior is observed in the frequency domain and the number of breaths goes up to 9. Furthermore, the breathing behavior of the optical soliton is transferred to the third harmonic through inter-modal phase-matched processes in the tapered PCF, and the third harmonic also breathes with an increase in the pump power.

Extreme Ultraviolet Spectroscopy of the Thermosphere from the RAIDS Experiment on the ISS

NASA Astrophysics Data System (ADS)

Bishop, R. L.; Stephan, A. W.; Christensen, A. B.; Budzien, S. A.; Straus, P. R.; van Epps, Z.

2009-12-01

The RAIDS experiment is a suite of eight instruments to be flown aboard the Japanese Experiment Module-Exposed Facility on the International Space Station (ISS) in 2009. One of the sensors is the Extreme Ultraviolet Spectrograph (EUVS). The EUVS measures the radiance of the Earth’s airglow with a f/5 Wadsworth spectrograph fronted by a mechanical grid collimator. The 0.1 x 2.3 degree field of view is imaged onto a wedge-and-strip two dimensional detector and collapsed into a one-dimensional spectrum. The vertical profile is assembled from a series of these spectra obtained as the RAIDS platform scans in altitude. Two grating positions provide coverage of the 50.0-85.0 nm region or the 77.0-110.0 nm region at 1.2 nm spectral resolution. We will present a discussion of the scientific targets for the RAIDS EUVS and, if launched on schedule, also the first spectra observed from this sensor. The EUVS is sensitive to a number of emissions in the Earth’s dayglow including atomic and ionized oxygen and argon, ionized nitrogen, and atomic helium. One of the primary RAIDS science objectives is to use the EUVS to obtain simultaneous OII 83.4 nm and 61.7 nm limb profiles to perform an in-depth investigation of the OII excitation and emission processes in the daytime ionosphere. Some of the more dominant spectral features such as the OI (98.9, 102.7 nm), OII (83.4, 61.7 nm), and NII (108.5, 91.6 nm) lines will provide the opportunity to develop new methods to monitor thermospheric O and N2. The OI (102.7 nm) observations may also be used, in conjunction with other RAIDS measurements, to retrieve the spectrally unresolved H Lyman beta and thus a measure of atomic hydrogen. The argon emissions Ar I (104.8, 106.7 nm) and Ar II (91.96, 93.21 nm) will provide information on its relative abundance in the lower thermosphere. . Combinations of measurements, such as the EUVS OI (98.9 nm) and the RAIDS Near Infrared Spectrometer OI (799.0 nm) emission can be used to probe the details of their associated branching ratios and excitation cross sections. Finally, the very quiet solar minimum period provides a unique opportunity to observe the He I 58.4 nm emission at these altitudes. The initial RAIDS EUVS spectra will highlight this potential wealth of future ionospheric and thermospheric studies that can be accomplished using such a unique dataset.

Planning the 8-meter Chinese Giant Solar Telescope

NASA Astrophysics Data System (ADS)

Beckers, Jacques M.; Liu, Z.; Deng, Y.; Ji, H.

2013-07-01

The Chinese Giant Solar Telescope (CGST) will be a diffraction limited solar telescope optimized for the near-infrared (NIR) spectral region (0.8 - 2.5 microns). Its diffraction limit will be reached by the incorporation of Multi-Conjugate Adaptive Optics (MCAO) enhanced by image restoration techniques to achieve uniform (u.v) plane coverage over the angular spatial frequency region allowed by its 8-meter aperture. Thus it will complement the imaging capabilities of 4-meter telescopes being planned elsewhere which are optimized for the visible (VIS) spectral region (300 - 1000 nm) In the NIR spectral regions the CGST will have access to unique spectral features which will improve the diagnostics of the solar atmosphere. These include the CaII lines near 860 nm , the HeI lines near 1083 nm, the 1074 nm FeXIII coronal lines, the large Zeeman-split FeI line at 1548 nm, and (v) the H- continuum absorption minimum at 1.6 micron. Especially in sunspot umbrae the simultaneous observation of continua and lines across the NIR spectral range will cover a substantial depth range in the solar atmosphere. Of course the mid- and far- infrared regions are also available for unequalled high-angular resolution solar observations, for example, in the Hydrogen Bracket lines, CO molecular bands, and the MgI emission line at 12.3 microns. The CGST is a so-called ring telescope in which the light is captured by a 1 meter wide segmented ring or by a ring of 7 smaller off-axis aperture telescopes. The open central area of the telescope is large. The advantages of such a ring configuration is that (a) it covers all the spatial frequencies out to those corresponding to its outer diameter, (b) its circular symmetry makes it polarization neutral, (c) its large central hole helps thermal control, and (d) it provides ample space for the MCAO system and instrumentation in the Gregorian focus. Even though optimized for the NIR, we expect to use the CGST also at visible wavelengths in the so-called “Partial Adaptive Optics” (PAO) mode (Applied Optics 31,424,1992) to obtain angular resolution twice that of a 4-meter telescope if their observations indicate that higher resolution is desirable. The CGST is a Chinese solar community project.

Si III OV Bright Line of Scattering Polarized Light That Has Been Observed in the CLASP and Its Center-to-Limb Variation

NASA Technical Reports Server (NTRS)

Katsukawa, Yukio; Ishikawa, Ryoko; Kano, Ryohei; Kubo, Masahito; Noriyuki, Narukage; Kisei, Bando; Hara, Hirohisa; Yoshiho, Suematsu; Goto, Motouji; Ishikawa, Shinnosuke;

Jovian Hotspots in the NEB in the Visible and Near-IR from Hubble and Ground-Based IR Observations

NASA Astrophysics Data System (ADS)

Wittal, Matthew Michael; Orton, Glenn; Sinclair, James; Wong, Michael; Simon, Amy; Irwin, Patrick; Braude, Ashwin

2018-01-01

In order to better understand the composition and behavior of Jupiter's atmosphere, radiating regions in the infrared known as ‘hotspots’ are compared with darker spots in the visible at the same locations within the Northern Equatorial Band (NEB). Hubble images taken in across the visible and into the near-infrared (between 275 nm and 889 nm) are compared with 5.1 µm images taken using the Subaru telescope and other ground-based observations. The connection between these regions has been known for some time, and comparison between them at these wavelengths showed a general correlation between dimness in the visible and brightness in the infrared, but this was not the case in all observed locations. The origins and cause of these hotspots remains unclear, but because of their quasi-stable nature and reoccurrence at roughly 30-degree longitudes suggests a relationship with Rossby Waves. Continuous spectra from Multi Unite Spectroscopic Explorer (MUSE) also shows that measured values from the near-infrared fit well with observations, and hints at the composition of the discolored region through the use of NEMESIS software cross-correlation.

Kilohertz Cr:forsterite regenerative amplifier.

PubMed

Evans, J M; Petri Evi, V; Alfano, R R; Fu, Q

1998-11-01

We report on a tunable regenerative amplifier that is operational in the near-infrared spectral region from 1230 to 1280 nm based on the vibronic laser material Cr:forsterite. Utilizing the technique of chirped-pulse amplification, we generated pulses as short as 150 fs at 1255 nm at a repetition rate of 1 kHz. Pulse amplification of more than 5 x 10(5) times was observed, with recorded output pulse energies of 34 muJ . Implementation of a second-harmonic generator yielded 110-fs-duration pulses of 7-muJ energy at 625 nm.

Experimental observation of multiple dispersive waves emitted by multiple mid-infrared solitons in a birefringence tellurite microstuctured optical fiber.

PubMed

Cheng, Tonglei; Tuan, Tong Hoang; Xue, Xiaojei; Liu, Lai; Deng, Dinghuan; Suzuki, Takenobu; Ohishi, Yasutake

2015-08-10

We experimentally demonstrate multiple dispersive waves (DWs) emitted by multiple mid-infrared solitons in a birefringence tellurite microstuctured optical fiber (BTMOF). To the best of our knowledge, this is the first demonstration of multiple DWs in the non-silica fibers. By using a pulse of ~80 MHz and ~200 fs emitted from an optical parametric oscillator (OPO) as the pump source, DWs and solitons are investigated on the fast and slow axes of the BTMOF at the pump wavelength of ~1800 nm. With the average pump power increasing from ~200 to 450 mW, the center wavelength of the 1st DW decreases from ~956 to 890 nm, the 2nd DW from ~1039 to 997 nm, the 3rd DW from ~1101 to 1080 nm, and the 4th DW from ~1160 to 1150 nm. Meanwhile, obvious multiple soliton self-frequency shifts (SSFSs) are observed in the mid-infrared region. Furthermore, DWs and solitons at the pump wavelength of ~1400 and 2000 nm are investigated at the average pump power of ~350 mW.

Fluorescence spectroscopy of gastrointestinal tumors using δ-ALA

NASA Astrophysics Data System (ADS)

Borisova, E. G.; Vladimirov, B. G.; Angelov, I. G.; Avramov, L. A.

2007-03-01

In the recent study delta-aminolevulinic acid/Protoporphyrin IX (δ-ALA/PpIX) is used as fluorescent marker for dysplasia and tumor detection in esophagus and stomach. The δ-ALA is administered per os six hours before measurements at dose 20mg/kg weight. High-power light-emitting diode at 405 nm is used as an excitation source. Special opto-mechanical device is built to use the light guide of standard video-endoscopic system (Olimpus Corp.). Through endoscopic instrumental channel a fiber is applied to return information about fluorescence to microspectrometer (USB4000, OceanOptics Inc.). The fluorescence detected from tumor sites has very complex spectral origins. It consists of autofluorescence, fluorescence from exogenous fluorophores and re-absorption from the chromophores accumulated in the tissue investigated. Mucosa autofluorescence lies at 450-600 nm region. The fluorescence of PpIX is clearly pronounced at the 630-710 nm region. Deep minima in the tumor fluorescence signals are observed in the region 540-575 nm, related to hemoglobin re-absorption. Such high hemoglobin content is an indication of the tumors neovascularisation and it is clearly pronounced in all dysplastic and tumor sites investigated. The lack of fluorescence peaks in the red spectral area for normal mucosa is an indication for selective accumulation of δ-ALA/PpIX only in abnormal sites and gives high contrast when lesion borders are determined from clinicians during video observation in the process of diagnostic procedure. Very good correlation between fluorescence signals and histology examination results of the lesions investigated is achieved.

Photodissociation spectroscopy of (benzene-toluene) +. Charge delocalization in the hetero-dimer ion

NASA Astrophysics Data System (ADS)

Ohashi, Kazuhiko; Nakane, Youko; Inokuchi, Yoshiya; Nakai, Yasuhiro; Nishi, Nobuyuki

1998-12-01

The electronic spectrum of the benzene-toluene hetero-dimer ion is measured in the 380-1400 nm region. The spectrum shows intense bands around 1175 and 670 nm and a weaker band around 920 nm, which correspond to charge resonance (CR) bands of homo-dimer ions. The observation indicates that the positive charge stays on the benzene part in some probability, although the ionization potential of benzene is 0.4162 eV higher than that of toluene. A local excitation (LE) band is observed around 420 nm, where a π←π transition is locally excited in the charged benzene or toluene molecule. On the basis of the positions of the CR-like bands, as well as the intensity of the LE band relative to that of homo-dimer ions, the probability of finding the charge on the benzene molecule is analyzed to be approximately 36%.

VizieR Online Data Catalog: Abundances in the local region. II. F, G, and K dwarfs (Luck+, 2017)

NASA Astrophysics Data System (ADS)

Luck, R. E.

2017-06-01

The McDonald Observatory 2.1m Telescope and Sandiford Cassegrain Echelle Spectrograph provided much of the observational data for this study. High-resolution spectra were obtained during numerous observing runs, from 1996 to 2010. The spectra cover a continuous wavelength range from about 484 to 700nm, with a resolving power of about 60000. The wavelength range used demands two separate observations--one centered at about 520nm, and the other at about 630nm. Typical S/N values per pixel for the spectra are more than 150. Spectra of 57 dwarfs were obtained using the Hobby-Eberly telescope and High-Resolution Spectrograph. The spectra have a resolution of 30000, spanning the wavelength range of 400 to 785nm. They also have very high signal-to-noise ratios, >300 per resolution element in numerous cases. The last set of spectra were obtained from the ELODIE Archive (Moultaka et al. 2004PASP..116..693M). These spectra are fully processed, including order co-addition, and have a continuous wavelength span of 400 to 680nm and a resolution of 42000. The ELODIE spectra utilized here all have S/N>75 per pixel. (6 data files).

The Formation of IRIS Diagnostics. IX. The Formation of the C i 135.58 NM Line in the Solar Atmosphere

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

Lin, Hsiao-Hsuan; Carlsson, Mats; Leenaarts, Jorrit, E-mail: mats.carlsson@astro.uio.no, E-mail: jorrit.leenaarts@astro.su.se

The C i 135.58 nm line is located in the wavelength range of NASA’s Interface Region Imaging Spectrograph ( IRIS ) small explorer mission. We study the formation and diagnostic potential of this line by means of non local-thermodynamic-equilibrium modeling, employing both 1D and 3D radiation-magnetohydrodynamic models. The C i/C ii ionization balance is strongly influenced by photoionization by Ly α emission. The emission in the C i 135.58 nm line is dominated by a recombination cascade and the line forming region is optically thick. The Doppler shift of the line correlates strongly with the vertical velocity in its linemore » forming region, which is typically located at 1.5 Mm height. With IRIS , the C i 135.58 nm line is usually observed together with the O i 135.56 nm line, and from the Doppler shift of both lines, we obtain the velocity difference between the line forming regions of the two lines. From the ratio of the C i/O i line core intensity, we can determine the distance between the C i and the O i forming layers. Combined with the velocity difference, the velocity gradient at mid-chromospheric heights can be derived. The C i/O i total intensity line ratio is correlated with the inverse of the electron density in the mid-chromosphere. We conclude that the C i 135.58 nm line is an excellent probe of the middle chromosphere by itself, and together with the O i 135.56 nm line the two lines provide even more information, which complements other powerful chromospheric diagnostics of IRIS such as the Mg ii h and k lines and the C ii lines around 133.5 nm.« less

Direct comparison of neutral velocity distribution measurements and simulations in the vicinity of an absorbing boundary oblique to a magnetic field

NASA Astrophysics Data System (ADS)

Henriquez, Miguel F.; Thompson, Derek S.; Keniley, Shane; Curreli, Davide; Steinberger, Thomas E.; Caron, David D.; Jemiolo, Andrew J.; McLaughlin, Jacob W.; Dufor, Mikal T.; Neal, Luke A.; Scime, Earl E.; Siddiqui, M. Umair

2017-10-01

Plasma-boundary interactions are strongly affected by the sheath and presheath structures that form near the boundary surface. Recent measurements have observed ion transport across magnetic field lines in regions where the surface is oblique to the background magnetic field (ψ =74°) . In these boundary regions, charge exchange collisions may provide a mechanism through which neutral particles interact with the long distance presheath electric field. We report efforts to directly compare Boltzmann and particle-in-cell simulations with 3D neutral velocity distribution functions (NVDFs) using laser induced fluorescence (LIF) in a magnetized plasma boundary region. We present a novel LIF method for measuring Ar-II metastable velocity distributions, in which we observe the 738.6014 nm fluorescence (2p3 to 1s4 in Paschen's notation), that results from absorption of the 706.9167 nm (1s5 metastable to 2p3) pump laser, providing neutral temperatures and flows. We additionally describe electrostatic probe measurements in the same region.

Regional peculiarities in the inter-annual distribution of the red 630.0 nm line nightglow intensities over Abastumani

NASA Astrophysics Data System (ADS)

Toriashvili, L.; Didebulidze, G. G.; Todua, M.

2017-12-01

Peculiarities of the inter-annual distribution of atomic oxygen red OI 630.0 nm line nightglow intensity observed from Abastumani Astrophysical Observatory (41.75 N; 42.82 E) are considered, using the long-term dataset. This distribution demonstrates semi-annual and annual-like variations which occur during solar minimum, as well as maximum phases. The maximum values of the red line intensities are in Summer, however in June it is lower than in May and July, which may be due to regional effects. This phenomenon is considered as a the possible result of regional dynamical processes influencing the behavior of the ionosphere F2 layer which cause changes of electrons/ions densities in the 630.0 nm line luminous region (maximum luminous layer is at about 230-280 km). Using the red line intensities and ionosphere F2 layer electron density data of the IRI-12 model, the changes of meridional thermospheric wind velocities are estimated for this mid-latitude region. These meridional and vertical wind field changes causes of variations of the red line intensities in June can be caused by tidal wind and accompanied by atmospheric gravity waves activities.

Mirror coatings for large aperture UV optical infrared telescope optics

NASA Astrophysics Data System (ADS)

Balasubramanian, Kunjithapatham; Hennessy, John; Raouf, Nasrat; Nikzad, Shouleh; Del Hoyo, Javier; Quijada, Manuel

2017-09-01

Large space telescope concepts such as LUVOIR and HabEx aiming for observations from far UV to near IR require advanced coating technologies to enable efficient gathering of light with important spectral signatures including those in far UV region down to 90nm. Typical Aluminum mirrors protected with MgF2 fall short of the requirements below 120nm. New and improved coatings are sought to protect aluminum from oxidizing readily in normal environment causing severe absorption and reduction of reflectance in the deep UV. Choice of materials and the process of applying coatings present challenges. Here we present the progress achieved to date with experimental investigations of coatings at JPL and at GSFC and discuss the path forward to achieve high reflectance in the spectral region from 90 to 300nm without degrading performance in the visible and NIR regions taking into account durability concerns when the mirrors are exposed to normal laboratory environment as well as high humidity conditions. Reflectivity uniformity required on these mirrors is also discussed.

Emission cross sections of excited fragments produced by electron impact on BCl3

NASA Astrophysics Data System (ADS)

Tokue, Ikuo; Kudo, Mikiko; Kusakabe, Masanobu; Honda, Tomohisa; Ito, Yoshio

1992-06-01

Emission spectra in the 190-600 nm region produced by electron impact on BCl3 have been studied up to 110 eV. Emission cross sections of the B(2s2p2 2D-2p 2P0) and B(3s 2S-2p 2P0) lines and the BCl(A 1Π-X 1Σ+) band are evaluated to be 4.9±1.0, 4.5±0.7, and (1.9±0.3)×10-18 cm2, respectively, at 100 eV. Formation cross sections of these species have been determined from the analysis of their fluorescence decaying curves. Two continuous emissions observed in the 230-380 and 400-580 nm regions are attributed to the BCl*2 band. The fluorescence lifetime of BCl*2 in the 300-342 nm region is obtained to be 1.65±0.2 μs, which is nearly independent of the wavelength.

Interfacial and topological effects on the glass transition in free-standing polystyrene films

NASA Astrophysics Data System (ADS)

Lyulin, Alexey V.; Balabaev, Nikolay K.; Baljon, Arlette R. C.; Mendoza, Gerardo; Frank, Curtis W.; Yoon, Do Y.

2017-05-01

United-atom molecular-dynamics computer simulations of atactic polystyrene (PS) were performed for the bulk and free-standing films of 2 nm-20 nm thickness, for both linear and cyclic polymers comprised of 80 monomers. Simulated volumetric glass-transition temperatures (Tg) show a strong dependence on the film thickness below 10 nm. The glass-transition temperature of linear PS is 13% lower than that of the bulk for 2.5 nm-thick films, as compared to less than 1% lower for 20 nm films. Our studies reveal that the fraction of the chain-end groups is larger in the interfacial layer with its outermost region approximately 1 nm below the surface than it is in the bulk. The enhanced population of the end groups is expected to result in a more mobile interfacial layer and the consequent dependence of Tg on the film thickness. In addition, the simulations show an enrichment of backbone aliphatic carbons and concomitant deficit of phenyl aromatic carbons in the interfacial film layer. This deficit would weaken the strong phenyl-phenyl aromatic (π -π ) interactions and, hence, lead to a lower film-averaged Tg in thin films, as compared to the bulk sample. To investigate the relative importance of the two possible mechanisms (increased chain ends at the surface or weakened π -π interactions in the interfacial region), the data for linear PS are compared with those for cyclic PS. For the cyclic PS, the reduction of the glass-transition temperature is also significant in thin films, albeit not as much as for linear PS. Moreover, the deficit of phenyl carbons in the film interface is comparable to that observed for linear PS. Therefore, chain-end effects alone cannot explain the observed pronounced Tg dependence on the thickness of thin PS films; the weakened phenyl-phenyl interactions in the interfacial region seems to be an important cause as well.

Development of a solid-state sodium Doppler lidar using an all-fiber-coupled injection seeding unit for simultaneous temperature and wind measurements in the mesopause region.

PubMed

Xia, Yuan; Du, LiFang; Cheng, XueWu; Li, FaQuan; Wang, JiHong; Wang, ZeLong; Yang, Yong; Lin, Xin; Xun, YuChang; Gong, ShunSheng; Yang, GuoTao

2017-03-06

A solid-state sodium (Na) Doppler lidar developed at YanQing Station, Beijing, China (40°N, 116°E) aiming to simultaneous wind and temperature measurement of mesopause region was reported. The 589 nm pulse laser was produced by two injection seeded 1064 nm and 1319 nm Nd:YAG pulse lasers using the sum-frequency generation (SFG) technique. A fiber amplifier is implemented to boost the seed power at 1064 nm, enabling a robust, all-fiber-coupled design for seeding laser unit, absolute laser frequency locking, and cyclic three-frequency switching necessary for simultaneous temperature and wind measurements. The all-fiber-coupled injection seeding configuration together with the solid-state Nd:YAG lasers make the Na Doppler lidar more compact and greatly reduce the system maintenance, which is conducive to transportable and unattended operation. A preliminary observational result obtained with this solid-state sodium Doppler lidar was also reported in this paper.

A comparison of the DPSS UV laser ablation characteristic of 1024 and H10F WC-Co

NASA Astrophysics Data System (ADS)

See, Tian Long; Chantzis, Dimitrios; Royer, Raphael; Metsios, Ioannis; Antar, Mohammad; Marimuthu, Sundar

2017-07-01

An investigation on ablation characteristics of 1024 and H10F cobalt cemented tungsten carbide (WC-Co) with a DPSS nanosecond UV laser (50 ns pulse width, 355 nm wavelength, 90 W average power and 10 kHz repetition rate) is presented. The ablation characteristic parameters such as ablation threshold, incubation effect and optical penetration depth were evaluated based on the spot ablation diameter and depth. It was observed that the ablation threshold is significantly influenced by the number of pulses (NOP) and it decreases with increase NOP which is attributed to the incubation effect. Only one ablation region is observed at low laser fluence and an additional molten ablation region is observed at high laser fluence accompanied with cracks. The cracks formation is due to the thermal induced stress and changes in WC microstructure during laser beam irradiation. The crack depth is proportional to the thickness of the molten WC region. The ablation threshold of 1024 WC-Co and H10F WC-Co were found to be Fth1 =4.32 J/cm2 and Fth1 =4.26 J/cm2 respectively. The difference in chemical composition has insignificant effect on the ablation threshold value of the material. The incubation factor and optical penetration depth values of 1024 WC-Co and H10F WC-Co were found to be ξ=0.73, α-1 =411 nm and ξ=0.75, α-1 =397 nm respectively.

Low emissivity Ag/Ta/glass multilayer thin films deposited by sputtering

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

Park, Sun Ho; Lee, Kee Sun; Green Home Energy Technology Center, Cheonan City

Ta is deposited on a glass substrate as an interlayer for the two-dimensional growth of Ag thin films because Ta has good thermal stability and can induce a negative surface-energy change in Ag/glass. From the transmission electron microscopy results, we concluded that the Ag crystals in the bottom layer (seemingly on Ag/Ta) were flattened; this was rarely observed in the three-dimensional growth mode. Comparing Ag/Ta/glass with Ag/glass, we found that the Ta interlayer was effective in reducing both the resistance and the emissivity, accompanied by the relatively high transmittance in the visible region. In particular, Ag(9 nm)/Ta(1 nm)/glass film showedmore » 0.08 of the emissivity, including {approx}61% of the transmittance in the visible region (wavelength: 550 nm).« less

Delta-ALA-mediated fluorescence spectroscopy of gastrointestinal tumors: comparison of in vivo and in vitro results

NASA Astrophysics Data System (ADS)

Vladimirov, B.; Borisova, E.; Avramov, L.

2007-06-01

The limitations of standard endoscopy for detection of dysplastic changes of mucosa are significant challenge and initiate development of new photodiagnostic techniques, additional to diagnostic possibilities of standard endoscopic equipment. One of the most widely examined optical modalities is the laser- or light-induced fluorescence spectroscopy (LIFS), because of its rapid and highly sensitive response to early biochemical and morphological changes in biological tissues. In the recent study delta-aminolevulinic acid/protoporphyrin IX is used as fluorescent marker for dysplasia and tumor detection in esophagus and stomach. The δ -ALA is administered per os six hours before measurements at dose 20mg/kg weight. High-power light-emitting diode at 405 nm is used as an excitation source. Special opto-mechanical device is built to use the light guide of standard video-endoscopic system. Through endoscopic instrumental channel a fiber is applied to return information about fluorescence to microspectrometer. The fluorescence detected from in vivo tumor sites has very complex spectral origins. It consists of autofluorescence, fluorescence from exogenous fluorophores and re-absorption from the chromophores accumulated in the tissue investigated. Mucosa autofluorescence lies at 450-600 nm region. The fluorescence of PpIX is clearly pronounced at the 630-710 nm region. Deep minima in the tumor fluorescence signals are observed in the region 540-575 nm, related to hemoglobin re-absorption. Such high hemoglobin content is an indication of the tumors vascularization and it is clearly pronounced in all dysplastic and tumor sites investigated. After formalin conservation for in vitro samples hemoglobin absorption is strongly reduced that increases mucous fluorescence signal in green-yellow spectral region. Simultaneously the maxima at 635 nm and 720 nm are reduced.

Broadband measurements of aerosol extinction in the ultraviolet spectral region

NASA Astrophysics Data System (ADS)

Washenfelder, R. A.; Flores, J. M.; Brock, C. A.; Brown, S. S.; Rudich, Y.

2013-04-01

Aerosols influence the Earth's radiative budget by scattering and absorbing incoming solar radiation. The optical properties of aerosols vary as a function of wavelength, but few measurements have reported the wavelength dependence of aerosol extinction cross sections and complex refractive indices. We describe a new laboratory instrument to measure aerosol optical extinction as a function of wavelength, using cavity enhanced spectroscopy with a broadband light source. The instrument consists of two broadband channels which span the 360-390 and 385-420 nm spectral regions using two light emitting diodes (LED) and a grating spectrometer with charge-coupled device (CCD) detector. We determined aerosol extinction cross sections and directly observed Mie scattering resonances for aerosols that are purely scattering (polystyrene latex spheres and ammonium sulfate), slightly absorbing (Suwannee River fulvic acid), and strongly absorbing (nigrosin dye). We describe an approach for retrieving refractive indices as a function of wavelength from the measured extinction cross sections over the 360-420 nm wavelength region. The retrieved refractive indices for PSL and ammonium sulfate agree within uncertainty with the literature values for this spectral region. The refractive index determined for nigrosin is 1.78 (± 0.03) + 0.19 (± 0.08)i at 360 nm and 1.63 (± 0.03) + 0.21 (± 0.05)i at 420 nm. The refractive index determined for Suwannee River fulvic acid is 1.71 (± 0.02) + 0.07 (± 0.06)i at 360 nm and 1.66 (± 0.02) + 0.06 (± 0.04)i at 420 nm. These laboratory results support the potential for a field instrument capable of determining ambient aerosol optical extinction, average aerosol extinction cross section, and complex refractive index as a function of wavelength.

Broadband measurements of aerosol extinction in the ultraviolet spectral region

NASA Astrophysics Data System (ADS)

Washenfelder, R. A.; Flores, J. M.; Brock, C. A.; Brown, S. S.; Rudich, Y.

2013-01-01

Aerosols influence the Earth's radiative budget by scattering and absorbing incoming solar radiation. The optical properties of aerosols vary as a function of wavelength, but few measurements have reported the wavelength dependence of aerosol extinction cross-sections and complex refractive indices. We describe a new laboratory instrument to measure aerosol optical extinction as a function of wavelength, using cavity enhanced spectroscopy with a broadband light source. The instrument consists of two broadband channels which span the 360-390 and 385-420 nm spectral regions using two light emitting diodes (LED) and a grating spectrometer with charge-coupled device (CCD) detector. We determined aerosol extinction cross-sections and directly observed Mie scattering resonances for aerosols that are purely scattering (polystyrene latex spheres and ammonium sulfate), slightly absorbing (Suwannee River fulvic acid), and strongly absorbing (nigrosin dye). We describe an approach for retrieving refractive indices as a function of wavelength from the measured extinction cross-sections over the 360-420 nm wavelength region. The retrieved refractive indices for PSL and ammonium sulfate agree within uncertainty with literature values for this spectral region. The refractive index determined for nigrosin is 1.78 (±0.03) + 0.19 (±0.08) i at 360 nm and 1.53 (±0.03) + 0.21 (±0.05) i at 420 nm. The refractive index determined for Suwannee River fulvic acid is 1.71 (±0.02) + 0.07 (±0.06) i at 360 nm and 1.66 (±0.02) + 0.06 (±0.04) i at 420 nm. These laboratory results support the potential for a field instrument capable of determining ambient aerosol optical extinction, average aerosol extinction cross-section, and complex refractive index as a function of wavelength.

Analysis of extreme ultraviolet spectra from laser produced rhenium plasmas

NASA Astrophysics Data System (ADS)

Wu, Tao; Higashiguchi, Takeshi; Li, Bowen; Suzuki, Yuhei; Arai, Goki; Dinh, Thanh-Hung; Dunne, Padraig; O'Reilly, Fergal; Sokell, Emma; Liu, Luning; O'Sullivan, Gerry

2015-08-01

Extreme ultraviolet spectra of highly-charged rhenium ions were observed in the 1-7 nm region using two Nd:YAG lasers with pulse lengths of 150 ps and 10 ns, respectively, operating at a number of laser power densities. The maximum focused peak power density was 2.6 × 1014 W cm-2 for the former and 5.5 × 1012 W cm-2 for the latter. The Cowan suite of atomic structure codes and unresolved transition array (UTA) approach were used to calculate and interpret the emission properties of the different spectra obtained. The results show that n = 4-n = 4 and n = 4-n = 5 UTAs lead to two intense quasi-continuous emission bands in the 4.3-6.3 nm and 1.5-4.3 nm spectral regions. As a result of the different ion stage distributions in the plasmas induced by ps and ns laser irradiation the 1.5-4.3 nm UTA peak moves to shorter wavelength in the ps laser produced plasma spectra. For the ns spectrum, the most populated ion stage during the lifetime of this plasma that could be identified from the n = 4-n = 5 transitions was Re23+ while for the ps plasma the presence of significantly higher stages was demonstrated. For the n = 4-n = 4 4p64dN-4p54dN+1 + 4p64dN-14f transitions, the 4d-4f transitions contribute mainly in the most intense 4.7-5.5 nm region while the 4p-4d subgroup gives rise to a weaker feature in the 4.3-4.7 nm region. A number of previously unidentified spectral features produced by n = 4-n = 5 transitions in the spectra of Re XVI to Re XXXIX are identified.

Thickness dependent optical and electrical properties of CdSe thin films

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

Purohit, A., E-mail: anuradha.purohit34@gmail.com; Chander, S.; Nehra, S. P.

2016-05-06

The effect of thickness on the optical and electrical properties of CdSe thin films is investigated in this paper. The films of thickness 445 nm, 631 nm and 810 nm were deposited on glass and ITO coated glass substrates using thermal evaporation technique. The deposited thin films were thermally annealed in air atmosphere at temperature 100°C and were subjected to UV-Vis spectrophotometer and source meter for optical and electrical analysis respectively. The absorption coefficient is observed to increase with photon energy and found maximum in higher photon energy region. The extinction coefficient and refractive index are also calculated. The electrical analysis shows thatmore » the electrical resistivity is observed to be decreased with thickness.« less

Waveband specific transcriptional control of select genetic pathways in vertebrate skin (Xiphophorus maculatus).

PubMed

Walter, Ronald B; Boswell, Mikki; Chang, Jordan; Boswell, William T; Lu, Yuan; Navarro, Kaela; Walter, Sean M; Walter, Dylan J; Salinas, Raquel; Savage, Markita

2018-05-10

Evolution occurred exclusively under the full spectrum of sunlight. Conscription of narrow regions of the solar spectrum by specific photoreceptors suggests a common strategy for regulation of genetic pathways. Fluorescent light (FL) does not possess the complexity of the solar spectrum and has only been in service for about 60 years. If vertebrates evolved specific genetic responses regulated by light wavelengths representing the entire solar spectrum, there may be genetic consequences to reducing the spectral complexity of light. We utilized RNA-Seq to assess changes in the transcriptional profiles of Xiphophorus maculatus skin after exposure to FL ("cool white"), or narrow wavelength regions of light between 350 and 600 nm (i.e., 50 nm or 10 nm regions, herein termed "wavebands"). Exposure to each 50 nm waveband identified sets of genes representing discrete pathways that showed waveband specific transcriptional modulation. For example, 350-400 or 450-500 nm waveband exposures resulted in opposite regulation of gene sets marking necrosis and apoptosis (i.e., 350-400 nm; necrosis suppression, apoptosis activation, while 450-500 nm; apoptosis suppression, necrosis activation). Further investigation of specific transcriptional modulation employing successive 10 nm waveband exposures between 500 and 550 nm showed; (a) greater numbers of genes may be transcriptionally modulated after 10 nm exposures, than observed for 50 nm or FL exposures, (b) the 10 nm wavebands induced gene sets showing greater functional specificity than 50 nm or FL exposures, and (c) the genetic effects of FL are primarily due to 30 nm between 500 and 530 nm. Interestingly, many genetic pathways exhibited completely opposite transcriptional effects after different waveband exposures. For example, the epidermal growth factor (EGF) pathway exhibits transcriptional suppression after FL exposure, becomes highly active after 450-500 nm waveband exposure, and again, exhibits strong transcriptional suppression after exposure to the 520-530 nm waveband. Collectively, these results suggest one may manipulate transcription of specific genetic pathways in skin by exposure of the intact animal to specific wavebands of light. In addition, we identify genes transcriptionally modulated in a predictable manner by specific waveband exposures. Such genes, and their regulatory elements, may represent valuable tools for genetic engineering and gene therapy protocols.

Long-range transport of Siberian forest fire smoke to Canada's west coast identified by Lidar observations

NASA Astrophysics Data System (ADS)

Strawbridge, Kevin; Cottle, Paul; McKendry, Ian

2014-05-01

During the summer of 2012, forest fire smoke wasdetected by two CORALNet lidar systems operated by Environment Canada along Canada's west coast. Based on satellite, model and back trajectory analysis it is thought the smoke originated in Boreal Asia as a result of unusually large amounts of Siberian wildfire activity. The CORALNet lidar systems operate autonomously, measuring the vertical profile of aerosols from near ground to 18 km at a vertical resolution of 3 m and 7.5 m and a temporal resolution of 10 s and 60 s at 1064 nm and 532 nm wavelengths respectively. The lidar also measures the depolarization ratio at 532 nm: and indicator of particle shape. The lidars, located at the University of British Columbia in Vancouver and in the village of Whistler, British Columbia observed an increase in the aerosol backscatter ratio in the free troposphere as the Siberian forest fire smoke was transported across the Pacific Ocean into the region. Of particular importance was the increase in ground level particulate due to the mixing of the smoke into the boundary layer, impacting the air quality in southwestern British Columbia. Lidar depolarization ratios in the boundary layer and the free troposphere were consistent with high concentrations of smoke. Detailed lidar observations will be presented along with supporting satellite, model and ground observations revealing the magnitude of the impact on the region.

Satellite Observations of Desert Dust-induced Himalayan Snow Darkening

NASA Technical Reports Server (NTRS)

Gautam, Ritesh; Hsu, N. Christina; Lau, William K.-M.; Yasunari, Teppei J.

2013-01-01

The optically thick aerosol layer along the southern edge of the Himalaya has been subject of several recent investigations relating to its radiative impacts on the South Asian summer monsoon and regional climate forcing. Prior to the onset of summer monsoon, mineral dust from southwest Asian deserts is transported over the Himalayan foothills on an annual basis. Episodic dust plumes are also advected over the Himalaya, visible as dust-laden snow surface in satellite imagery, particularly in western Himalaya. We examined spectral surface reflectance retrieved from spaceborne MODIS observations that show characteristic reduction in the visible wavelengths (0.47 nm) over western Himalaya, associated with dust-induced solar absorption. Case studies as well as seasonal variations of reflectance indicate a significant gradient across the visible (0.47 nm) to near-infrared (0.86 nm) spectrum (VIS-NIR), during premonsoon period. Enhanced absorption at shorter visible wavelengths and the resulting VIS-NIR gradient is consistent with model calculations of snow reflectance with dust impurity. While the role of black carbon in snow cannot be ruled out, our satellite-based analysis suggests the observed spectral reflectance gradient dominated by dust-induced solar absorption during premonsoon season. From an observational viewpoint, this study underscores the importance of mineral dust deposition toward darkening of the western Himalayan snow cover, with potential implications to accelerated seasonal snowmelt and regional snow albedo feedbacks.

Uranus' post-equinox north polar brightening characterized with 2013 and 2016 IRTF SpeX observation

NASA Astrophysics Data System (ADS)

Fry, Patrick M.; Sromovsky, Lawrence A.

2017-10-01

Since its 2007 equinox, the atmosphere of Uranus, as seen in the near infrared (~800-1600 nm) has exhibited dramatic changes. Its southern polar cap, prominent prior to equinox, has faded and a similar polar cap has begun developing in the north. Karkoschka and Tomasko (2009, Icarus 202:287) demonstrated that in 2002 the south polar region, brighter than lower latitude regions when viewed at wavelengths of intermediate methane absorption, was depleted in methane compared to darker regions. Tice et al. (2013, Icarus 223:684) and Sromovsky et al. (2014, Icarus 238:137) concluded that the northern polar regions were similarly depleted. The north polar region (45N-90N) has continued to brighten; modeling of 2015 HST STIS observations (Fry et al. 2016, AAS DPS #48 421.03) suggested that the latitudinal methane distribution has remained essentially unchanged since equinox, but brightening from 2012 to 2015 was due to changes in aerosol scattering. We acquired 0.8-2.5 μm SpeX spectra in 2013 (central meridian) and 2016 (pole-aligned spectra at 0, 0.4, 0.8, and 1.2 arcsec. distant from the CM) under similar seeing conditions (0.4-0.5 arcsec.). The SpeX wavelength range gives us an additional wavelength region where H2 absorption competes with or exceeds CH4 absorption, and a wider wavelength range to characterize aerosol particle properties, compared to STIS. The multiple spectra in 2016 allow us to compare specific latitudes to 2013 at the same view angles (and to use center-to-limb constraints in modeling 2016 spectra). We will present observations, reduction procedures, comparative (2013 vs 2016) modeling of latitudinal methane abundance and vertical aerosol profiles, and compare to 2012/2015 STIS analysis. Preliminary analysis shows that lower latitudes (~30N) have not changed since 2013, but higher latitudes (~70N) have undergone continued significant brightening at pseudo-continuum wavelengths dominated by both H2 (1080 nm, up ~50%) and CH4 (1290 nm, also up ~50%) absorption , indicating a change in scattering properties.This work is supported by NASA Solar System Observations grant NNA16AH99G.

Tri-wave laser therapy for spinal cord injury, neuropathic pain management, and restoration of motor function

NASA Astrophysics Data System (ADS)

Chariff, Mark D.; Olszak, Peter

2015-03-01

A laser therapy device using three combined wavelengths 532nm, 808nm, and 1064nm has been demonstrated in clinical studies. Primarily, therapeutic lasers have used wavelengths in the ranges of 632nm through 1064nm, where the optical density (OD) < 5, to achieve pain relief and tissue regeneration. Conventional wisdom would argue against using wavelengths in the region of 532nm, due to poor penetration (OD ~ 8); however, the author's observations are to the contrary. The 532nm light is efficiently absorbed by chromophores such as oxyhemoglobin, deoxyhemoglobin, and cytochrome c oxidase thereby providing energy to accelerate the healing process. The 808nm light is known to result in Nitric Oxide production thereby reducing inflammation and oxidative stress. All three laser wavelengths likely contribute to pain relief by inhibiting nerve conduction; however, the 1064nm has the deepest penetration. Through the use of this device on over 1000 patients with a variety of acute and chronic neuro-musculoskeletal disorders, the author observed that a majority of these individuals experienced rapid relief from their presenting conditions and most patients reported a tingling sensation upon irradiation. Patient testimonials and thermal images have been collected to document the results of the laser therapy. These studies demonstrate the ability of laser therapy to rapidly alleviate pain from both acute and chronic conditions.

Solar absorption by elemental and brown carbon determined from spectral observations.

PubMed

Bahadur, Ranjit; Praveen, Puppala S; Xu, Yangyang; Ramanathan, V

2012-10-23

Black carbon (BC) is functionally defined as the absorbing component of atmospheric total carbonaceous aerosols (TC) and is typically dominated by soot-like elemental carbon (EC). However, organic carbon (OC) has also been shown to absorb strongly at visible to UV wavelengths and the absorbing organics are referred to as brown carbon (BrC), which is typically not represented in climate models. We propose an observationally based analytical method for rigorously partitioning measured absorption aerosol optical depths (AAOD) and single scattering albedo (SSA) among EC and BrC, using multiwavelength measurements of total (EC, OC, and dust) absorption. EC is found to be strongly absorbing (SSA of 0.38) whereas the BrC SSA varies globally between 0.77 and 0.85. The method is applied to the California region. We find TC (EC + BrC) contributes 81% of the total absorption at 675 nm and 84% at 440 nm. The BrC absorption at 440 nm is about 40% of the EC, whereas at 675 nm it is less than 10% of EC. We find an enhanced absorption due to OC in the summer months and in southern California (related to forest fires and secondary OC). The fractions and trends are broadly consistent with aerosol chemical-transport models as well as with regional emission inventories, implying that we have obtained a representative estimate for BrC absorption. The results demonstrate that current climate models that treat OC as nonabsorbing are underestimating the total warming effect of carbonaceous aerosols by neglecting part of the atmospheric heating, particularly over biomass-burning regions that emit BrC.

Observation and Study of Proton Aurora by using Scanning Photometer

NASA Astrophysics Data System (ADS)

Mochizuki, T.; Ono, T.; Kadokura, A.; Sato, N.

2009-12-01

The proton auroras have significant differences from electron auroras in their spectral shape. They show Doppler-shifted and broadened spectra: the spectra have Doppler-shifted (~0.5 nm shorter) peak and both bluewing (~2-4 nm) and redwing (~1.5 nm) extending. Energy spectra of precipitating protons have been estimated from this shape. Recently it is found that the intensity in the extent of the blue wing reflects more effectively by the change of the mean energy of precipitating protons than the shift of peak wavelength [Lanchester et al., 2003]. Another character of the H-beta aurora is that it is diffuse form because a proton becomes hydrogen atom due to a charge-exchange reaction with atmospheric constituent and then possible to move across the magnetic field line. By using a scanning photometer, the movement of the proton auroral belt and change of a spectrum shape associated with the variation of proton source region due to storm and substorm were reported, however, not discussed in detail yet [Deehr and Lummerzheim, 2001]. The purpose of this study is to obtain the detail characteristics of H-beta aurora for understanding of source region of energetic protons in the magnetosphere. For this purpose, a new meridian-scanning photometer (SPM) was installed at Husafell station in Iceland in last summer season and Syowa Station, Antarctica. It will contribute to investigate the distribution of energetic protons and plasma waves which cause the pitch angle scattering in the magnetosphere. The meridian-scanning photometer is able to observe at five wavelengths for H-beta emission. One channel is to measure the background level. By analyzing the data obtained by the SPM, the H-beta spectrum can be estimated by fitting a model function with it. Then it is possible to obtain distribution of precipitating protons in north-south direction. It is also possible to estimate an energy spectrum of precipitating proton, simultaneously. The instrumental parameters of the SPM is defined by the transmission characteristics of the interference filters; they are 485.7 nm (FWHM: 3.0 nm), 484.5 nm (0.6 nm), 485.5 nm (0.6 nm), 486.5 nm (0.6 nm) and 487.5 nm (0.6 nm) for H-beta auroras, and OI 630 nm (0.6 nm), N_2 1PG 670.5 nm (5.0 nm) and OI 844.6 nm (0.6 nm) for electron auroras. We analyzed the event at 2100 UT 23rd June, 2009 observed at Syowa station. This is typical auroral breakup event. And in this event, breakup occurred in FOV of the photometer and expanded to poleward. Then NS aurora appeared and pulsating aurora occurred. We calculated Doppler profile and each parameter is below. The peak intensity is 80 R/nm, wavelength at peak intensity is 486.0 nm, HWHM of bluewing is 1.7 nm and HWHM of redwing is 0.9 nm. These value are within past studies, although the Doppler shift of peak intensity is 0.1 nm and shorter than the average of past studies (0.5 nm). And intensity and Doppler profile of proton aurora changed with eqatorward moving in substorm growth phase. This suggests that the source of precipitating proton moves Earthward and its energy increases, and correspond to the result of Deehr and Lummerzheim, 2001. We are going to report the more detailed result of this event and new events of proton aurora.

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

Gelles, D. S.; Browning, James Frederick; Snow, Clark Sheldon

Er(D,T){sub 2-x} {sup 3}He{sub x}, erbium di-tritide, films of thicknesses 500 nm, 400 nm, 300 nm, 200 nm, and 100 nm were grown and analyzed by Transmission Electron Microscopy, X-Ray Diffraction, and Ion Beam Analysis to determine variations in film microstructure as a function of film thickness and age, due to the time-dependent build-up of {sup 3}He in the film from the radioactive decay of tritium. Several interesting features were observed: One, the amount of helium released as a function of film thickness is relatively constant. This suggests that the helium is being released only from the near surface regionmore » and that the helium is not diffusing to the surface from the bulk of the film. Two, lenticular helium bubbles are observed as a result of the radioactive decay of tritium into {sup 3}He. These bubbles grow along the [111] crystallographic direction. Three, a helium bubble free zone, or 'denuded zone' is observed near the surface. The size of this region is independent of film thickness. Four, an analysis of secondary diffraction spots in the Transmission Electron Microscopy study indicate that small erbium oxide precipitates, 5-10 nm in size, exist throughout the film. Further, all of the films had large erbium oxide inclusions, in many cases these inclusions span the depth of the film.« less

Host sensitized near-infrared emission in Nd3+ doped different alkaline-sodium-phosphate phosphors

NASA Astrophysics Data System (ADS)

Balakrishna, A.; Swart, H. C.; Kroon, R. E.; Ntwaeaborwa, O. M.

2018-04-01

Near-infrared (NIR) emitting phosphors of different alkaline based sodium-phosphate (MNa[PO4], where M = Mg, Ca, Sr and Ba were prepared by a conventional solution combustion method with fixed doping concentration of Nd3+ (1.0 mol%). The phosphors were characterized by powder X-ray diffraction, field emission scanning electron microscope, Fourier transform infrared spectroscopy, UV-vis spectroscopy and fluorescent spectrophotometry. The optical properties including reflectance, excitation and emission were investigated. The excitation spectra of the phosphors were characterized by a broadband extending from 450 to 900 nm. Upon excitation with a wavelength of 580 nm, the phosphor emits intensely infrared region at 872 nm, 1060 nm and 1325 nm which correspond to the 4F3/2 → 4I9/2, 4F3/2 → 4I11/2 and 4F3/2 → 4I13/2 transitions of Nd3+ ions and were found to vary for the different hosts. The strongest emission wavelength reaches 1060 nm. The most intense emission of Nd3+ was observed from Ca2+ incorporated host. The down conversion emissions of the material fall in the NIR region suggesting that the prepared phosphors have potential application in the development of photonic devices emitting in the NIR.

The Use of Transfer Radiometers in Validating the Visible through Shortwave Infrared Calibrations of Radiance Sources Used by Instruments in NASA's Earth Observing System

NASA Technical Reports Server (NTRS)

Butler, James J.; Barnes, Robert A.

2002-01-01

The detection and study of climate change over a time frame of decades requires successive generations of satellite, airborne, and ground-based instrumentation carefully calibrated against a common radiance scale. In NASA s Earth Observing System (EOS) program, the pre-launch radiometric calibration of these instruments in the wavelength region from 400 nm to 2500 nm is accomplished using internally illuminated integrating spheres and diffuse reflectance panels illuminated by irradiance standard lamps. Since 1995, the EOS Calibration Program operating within the EOS Project Science Office (PSO) has enlisted the expertise of national standards laboratories and government and university metrology laboratories in an effort to validate the radiance scales assigned to sphere and panel radiance sources by EOS instrument calibration facilities. This state-of-the-art program has been accomplished using ultra-stable transfer radiometers independently calibrated by the above participating institutions. In ten comparisons since February 1995, the agreement between the radiance measurements of the transfer radiometers is plus or minus 1.80% at 411 nm, plus or minus 1.31% at 552.5 nm, plus or minus 1.32% at 868.0 nm, plus or minus 2.54% at 1622nm, and plus or minus 2.81% at 2200nm (sigma =1).

Mechanisms for the formation and growth of nanometer-sized particles in the Amazon: New insights from GoAmazon2014 and the Tapajos Upwind Forest Flux Study (TUFFS).

NASA Astrophysics Data System (ADS)

Smith, J. N.; Park, J. H.; Kuang, C.; Bustillos, J. O. V.; Souza, R. A. F. D.; Wiedemann, K. T.; Munger, J. W.; Wofsy, S. C.; Rizzo, L. V.; Artaxo, P.; Martin, S. T.; Seco, R.; Kim, S.; Guenther, A. B.; Batalha, S. S. A.; Alves, E. G.; Tota, J.

2014-12-01

The Amazon rainforest is a unique and important place for studying aerosol formation and its impacts on atmospheric chemistry and climate. In remote areas, the atmosphere is characterized by low particle number concentrations and high humidity; perturbations in the particle number concentrations and climate-relevant physical and chemical properties could therefore have a great impact on cloud formation and thus on regional climate and precipitation. While it was previously believed that new particle formation occurs rarely in the Amazon, observations in the Amazon of a sustained steady-state particle number concentration, along with an abundance of dry and wet surfaces upon which particles may deposit, imply that sources of new particles must exist in this region. We present observations from two studies, GOAmazon2014 and Tapajos Upwind Forest Flux Study (TUFFS), which seek to identify and quantify the sources of aerosol particles in the Amazon. Measurements of the chemical composition of 20 - 100 nm diameter aerosol particles at the T3 measurement site during the wet and dry season campaigns of GOAmazon2014 show the presence of inorganic ions such as potassium ion and sulfate, as well as organic ion such as oxalate, in ambient nanoparticles. These observations, combined with 1.5 - 300 nm diameter particle number size distributions and trace gas measurements of organic compounds and sulfuric acid, are used to determine the relative importance of sulfuric acid, organic compounds, and primary biological particle emissions to nanoparticle formation and growth. Observations of 3 - 100 nm diameter particle number size distributions at the KM67 tower site during TUFFS show frequent new particle formation events during the wet season in April, transitioning to a scenario of less frequent events in July at the onset of the dry season. These observations highlight the regional nature of new particle formation in the Amazon, and suggest that additional observations at a variety of locales are needed to fully understand the roles of new particle formation in this region.

High-sensitivity optical sensing of axial strain based on microfiber with microarched transition region

NASA Astrophysics Data System (ADS)

Xia, Liang; Xing, Zengshan; Yu, Jianhui; Lu, Huihui; Guan, Heyuan; Zhong, Yongchun; Chen, Zhe

2017-11-01

We demonstrated strain sensing of a microfiber with a microarched transition region, which was fabricated by flame heated tapering. Due to multimode interference of different propagation modes of microfiber, two main transmission dips were observed at 1215.0 and 1469.8 nm. Enhanced by the microarched transition region, the depth of the dip was up to 19 dB at 1215.0 nm. The position of the dip red-shifted while the axial strain changed from 0 to 1166.2 μɛ. The axial strain sensitivity was up to 56.6 pm/μɛ, which was one order of magnitude higher than that of the traditional optical strain sensor based on microfiber or fiber Bragg grating. The linear correlation coefficient was 98.21%. This kind of microfiber with a microarched transition region can be widely used in various physical, chemical, and biological sensing and detection fields.

Broad band nonlinear optical absorption measurements of the laser dye IR26 using white light continuum Z-scan

NASA Astrophysics Data System (ADS)

Dey, Soumyodeep; Bongu, Sudhakara Reddy; Bisht, Prem Ballabh

2017-03-01

We study the nonlinear optical response of a standard dye IR26 using the Z-scan technique, but with the white light continuum. The continuum source of wavelength from 450 nm to 1650 nm has been generated from the photonic crystal fiber on pumping with 772 nm of Ti:Sapphire oscillator. The use of broadband incident pulse enables us to probe saturable absorption (SA) and reverse saturable absorption (RSA) over the large spectral range with a single Z-scan measurement. The system shows SA in the resonant region while it turns to RSA in the non-resonant regions. The low saturation intensity of the dye can be explained based on the simultaneous excitation from ground states to various higher energy levels with the help of composite energy level diagram. The cumulative effects of excited state absorption and thermal induced nonlinear optical effects are responsible for the observed RSA.

VizieR Online Data Catalog: GTC transit light curves of HAT-P-32b (Nortmann+, 2016)

NASA Astrophysics Data System (ADS)

Nortmann, L.; Palle, E.; Murgas, F.; Dreizler, S.; Iro, N.; Cabrera-Lavers, A.

2016-05-01

We provide two transit light curves of the hot Jupiter HAT-P-32b obtained on the nights of 2012/09/15 and 2012/09/30 using the OSIRIS instrument at the 10.4-m GTC telescope. The data was obtained by using OSIRIS in broad slit spectroscopy mode and covering the wavelength region between 518nm-918nm. For the night of 2012/09/30 we further provide twenty narrowband light curves which were created by summing the flux over 20-nm-wide channels instead over the whole wavelength region. We provide several auxiliary parameters of the observations which we have used to correct the data from correlated noise. These auxiliary parameters are the position drift of the stars on the CCD detector in spatial and dispersion direction, air mass and seeing (FWHM). (23 data files).

Energy transfer and optical gain properties of P{sub 2}O{sub 5}-ZnO-LiF: (Yb{sup 3+}, Er{sup 3+}) glasses

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

Reddy, C. Parthasaradhi, E-mail: cgparthasaradhi@gmail.com, E-mail: ktrkreddy@gmail.com; Naresh, V.; Reddy, K. T. Ramakrishna, E-mail: cgparthasaradhi@gmail.com, E-mail: ktrkreddy@gmail.com

2015-06-24

The present paper reports on the results pertaining to the emission properties of 0.5 mol% Er{sup 3+} and together (0.5 Yb{sup 3+} /0.5 Er{sup 3+}) doped PZL (P{sub 2}O{sub 5}-ZnO-LiF) glasses prepared by a melt quenching method. From the optical absorption data, absorption and stimulated emission cross-sections have been evaluated using McCumber’s theory and further cross-sectional gain has also been computed for Yb{sup 3+}/Er{sup 3+} doped glass. On exciting the single (Er{sup 3+}) and dual rare earth ions (Yb{sup 3+}/Er{sup 3+}) doped glass sample at λ{sub exci} = 379 nm, three emission bands in the visible region {sup 2}H{sub 11/2}→{sup 4}I{sub 15/2}more » (526 nm), {sup 4}S{sub 3/2}→{sup 4}I{sub 15/2} (549 nm) and {sup 4}F{sub 9/2}→{sup 4}I{sub 15/2} (664 nm) are observed and while at λ{sub exci} = 980 nm (Laser Diode) excitation a broad emission at 1530 nm attributed to {sup 4}H{sub 13/2}→{sup 4}I{sub 15/2} is observed in the NIR region. The enhancement in visible and NIR emission intensities with the addition of Yb{sup 3+} to Er{sup 3+} due to an energy transfer process from Yb{sup 3+} to Er{sup 3+} has been explained in terms of an energy level diagram.« less

Long-term Aerosol Lidar Measurements At CNR-IMAA

NASA Astrophysics Data System (ADS)

Mona, L.; Amodeo, A.; D'Amico, G.; Pandolfi, M.; Pappalardo, G.

2006-12-01

Actual estimations of the aerosol effect on the radiation budget are affected by a large uncertainties mainly due to the high inhomogeneity and variability of atmospheric aerosol, in terms of concentration, shape, size distribution, refractive index and vertical distribution. Long-term measurements of vertical profiles of aerosol optical properties are needed to reduce these uncertainties. At CNR-IMAA (40° 36'N, 15° 44' E, 760 m above sea level), a lidar system for aerosol study is operative since May 2000 in the framework of EARLINET (European Aerosol Research Lidar Network). Until August 2005, it provided independent measurements of aerosol extinction and backscatter at 355 nm and aerosol backscatter profiles at 532 nm. After an upgrade of the system, it provides independent measurements of aerosol extinction and backscatter profiles at 355 and 532 nm, and of aerosol backscatter profiles at 1064 nm and depolarization ratio at 532 nm. For these measurements, lidar ratio at 355 and 532 nm and Angstrom exponent profiles at 355/532 nm are also obtained. Starting on May 2000, systematic measurements are performed three times per week according to the EARLINET schedule and further measurements are performed in order to investigate particular events, like dust intrusions, volcanic eruptions and forest fires. A climatological study has been carried out in terms of the seasonal behavior of the PBL height and of the aerosol optical properties calculated inside the PBL itself. In the free troposphere, an high occurrences of Saharan dust intrusions (about 1 day of Saharan dust intrusion every 10 days) has been observed at CNR-IMAA because of the short distance from the Sahara region. During 6 years of observations, very peculiar cases of volcanic aerosol emitted by Etna volcano and aerosol released by large forest fires burning occurred in Alaska and Canada have been observed in the free troposphere at our site. Particular attention is devoted to lidar ratio both for the PBL and the free troposphere region, in order to study influences of aerosol modification/transportation processes on its values and its variability. ACKNOWLEDGMENTS The financial support of this work by the European Commission under grant RICA-025991 is gratefully acknowledged.

Review of short-wave infrared spectroscopy and imaging methods for biological tissue characterization

PubMed Central

Wilson, Robert H.; Nadeau, Kyle P.; Jaworski, Frank B.; Tromberg, Bruce J.; Durkin, Anthony J.

2015-01-01

Abstract. We present a review of short-wave infrared (SWIR, defined here as ∼1000 to 2000 nm) spectroscopy and imaging techniques for biological tissue optical property characterization. Studies indicate notable SWIR absorption features of tissue constituents including water (near 1150, 1450, and 1900 nm), lipids (near 1040, 1200, 1400, and 1700 nm), and collagen (near 1200 and 1500 nm) that are much more prominent than corresponding features observed in the visible and near-infrared (VIS-NIR, defined here as ∼400 to 1000 nm). Furthermore, the wavelength dependence of the scattering coefficient has been observed to follow a power-law decay from the VIS-NIR to the SWIR region. Thus, the magnitude of tissue scattering is lower at SWIR wavelengths than that observed at VIS or NIR wavelengths, potentially enabling increased penetration depth of incident light at SWIR wavelengths that are not highly absorbed by the aforementioned chromophores. These aspects of SWIR suggest that the tissue spectroscopy and imaging in this range of wavelengths have the potential to provide enhanced sensitivity (relative to VIS-NIR measurements) to chromophores such as water and lipids, thereby helping to characterize changes in the concentrations of these chromophores due to conditions such as atherosclerotic plaque, breast cancer, and burns. PMID:25803186

Globular and fibrous structure in barley chromosomes revealed by high-resolution scanning electron microscopy.

PubMed

Iwano, M; Fukui, K; Takaichi, S; Isogai, A

1997-08-01

Barley chromosomes were prepared for high-resolution scanning electron microscopy using a combination of enzyme maceration, treatment in acetic acid and osmium impregnation using thiocarbohydrazide. Using this technique, the three-dimensional ultrastructure of interphase nuclei and mitotic chromosomes was examined. In Interphase, different levels of chromatin condensation were observed, consisting of fibrils 10 nm in diameter, 20- to 40-nm fibres and a higher order complex. In prophase, globular and strand-like structures composed of 20- to 40-nm fibres were dominant. As the cells progressed through the cell cycle and the chromatin condensed, globular and strand-like structures (chromomeres) were coiled and packed to form chromosomes. Chromomeres were observed as globular protuberances on the surface of metaphase chromosomes. These findings indicate that the chromomere is a fundamental substructure of the higher order architecture of the chromosome. In the centromeric region, there were no globular protuberances, but 20- to 40-nm fibres were folded compactly to form a higher level organization surrounding the chromosomal axia.

UV spectroscopy of Titan's atmosphere, planetary organic chemistry and prebiological synthesis. II - Interpretation of new IUE observations in the 220-335 nm range

NASA Technical Reports Server (NTRS)

Courtin, Regis; Wagener, Richard; Mckay, Christopher P.; Caldwell, John; Fricke, Karl-Heinrich

1991-01-01

The theoretical model developed by McKay et al. (1989) to characterize the size distribution, thermal structure, and chemical composition of the stratospheric haze of Titan is applied to new 220-335-nm albedo measurements obtained with the long-wavelength prime camera of the IUE during August 1987. Data and model predictions are presented in extensive graphs and discussed in detail. It is shown that a simple model with particles of one size at a given altitude does not accurately reproduce the observed features in all spectral regions, but that good general agreement is obtained using a model with a uniformly mixed layer at 150-600 km and a bimodal distribution of small 'polymer' haze particles (radius less than 20 nm) and larger haze particles (radius 100-500 nm). The number densities implied by this model require, however, a mechanism such as electrostatic charging or reaction kinetics to inhibit coagulation of the smaller particles.

Gastric cancer target detection using near-infrared hyperspectral imaging with chemometrics

NASA Astrophysics Data System (ADS)

Yi, Weisong; Zhang, Jian; Jiang, Houmin; Zhang, Niya

2014-09-01

Gastric cancer is one of the leading causes of cancer death in the world due to its high morbidity and mortality. Hyperspectral imaging (HSI) is an emerging, non-destructive, cutting edge analytical technology that combines conventional imaging and spectroscopy in one single system. The manuscript has investigated the application of near-infrared hyperspectral imaging (900-1700 nm) (NIR-HSI) for gastric cancer detection with algorithms. Major spectral differences were observed in three regions (950-1050, 1150-1250, and 1400-1500 nm). By inspecting cancerous mean spectrum three major absorption bands were observed around 975, 1215 and 1450 nm. Furthermore, the cancer target detection results are consistent and conformed with histopathological examination results. These results suggest that NIR-HSI is a simple, feasible and sensitive optical diagnostic technology for gastric cancer target detection with chemometrics.

Silica-rich deposits and hydrated minerals at Gusev Crater, Mars: Vis-NIR spectral characterization and regional mapping

USGS Publications Warehouse

Rice, M.S.; Bell, J.F.; Cloutis, E.A.; Wang, A.; Ruff, S.W.; Craig, M.A.; Bailey, D.T.; Johnson, J. R.; De Souza, P.A.; Farrand, W. H.

2010-01-01

The Mars Exploration Rover (MER) Spirit has discovered surprisingly high concentrations of amorphous silica in soil and nodular outcrops in the Inner Basin of the Columbia Hills. In Pancam multispectral observations, we find that an absorption feature at the longest Pancam wavelength (1009 nm) appears to be characteristic of these silica-rich materials; however, spectral analyses of amorphous silica suggest that the ???1009 nm spectral feature is not a direct reflection of their silica-rich nature. Based on comparisons with spectral databases, we hypothesize that the presence of H2O or OH, either free (as water ice), adsorbed or bound in a mineral structure, is responsible for the spectral feature observed by Pancam. The Gertrude Weise soil, which is nearly pure opaline silica, may have adsorbed water cold-trapped on mineral grains. The origin of the ???1009 nm Pancam feature observed in the silica-rich nodular outcrops may result from the presence of additional hydrated minerals (specific sulfates, halides, chlorides, sodium silicates, carbonates or borates). Using the ???1009 nm feature with other spectral parameters as a "hydration signature" we have mapped the occurrence of hydrated materials along the extent of Spirit's traverse across the Columbia Hills from West Spur to Home Plate (sols 155-1696). We have also mapped this hydration signature across large panoramic images to understand the regional distribution of materials that are spectrally similar to the silica-rich soil and nodular outcrops. Our results suggest that hydrated materials are common in the Columbia Hills. ?? 2009 Elsevier Inc.

Tunable ring laser with internal injection seeding and an optically-driven photonic crystal reflector.

PubMed

Zheng, Jie; Ge, Chun; Wagner, Clark J; Lu, Meng; Cunningham, Brian T; Hewitt, J Darby; Eden, J Gary

2012-06-18

Continuous tuning over a 1.6 THz region in the near-infrared (842.5-848.6 nm) has been achieved with a hybrid ring/external cavity laser having a single, optically-driven grating reflector and gain provided by an injection-seeded semiconductor amplifier. Driven at 532 nm and incorporating a photonic crystal with an azobenzene overlayer, the reflector has a peak reflectivity of ~80% and tunes at the rate of 0.024 nm per mW of incident green power. In a departure from conventional ring or external cavity lasers, the frequency selectivity for this system is provided by the passband of the tunable photonic crystal reflector and line narrowing in a high gain amplifier. Sub - 0.1 nm linewidths and amplifier extraction efficiencies above 97% are observed with the reflector tuned to 842.5 nm.

The morphology of flare phenomena, magnetic fields, and electric currents in active regions. III - NOAA active region 6233 (1990 August)

NASA Technical Reports Server (NTRS)

De La Beaujardiere, J.-F.; Canfield, Richard C.; Leka, K. D.

1993-01-01

We investigate the spatial relationship between vertical electric currents and flare phenomena in NOAA Active Region 6233, which was observed 1990, August 28-31 at Mees Solar Observatory. The two flares studied are the 1N/M1.8 flare on August 28, 22:30 UT and the 1N/M1.6 flare on August 29, 20:35 UT. Using Stokes polarimetry we make magnetograms of the region and compute the vertical current density. Using H-alpha imaging spectroscopy we identify sites of intense nonthermal electron precipitation or of high coronal pressure. The precipitation in these flares is barely strong enough to be detectable. We find that both precipitation and high pressure tend to occur near vertical currents, but that neither phenomenon is cospatial with current maxima. In contrast with the conclusion of other authors, we argue that these observations do not support a current-interruption model for flares, unless the relevant currents are primarily horizontal. The magnetic morphology and temporal evolution of these flares suggest that an erupting filament model may be relevant, but this model does not explicitly predict the relationship between precipitation, high pressure, and vertical currents.

Enhanced stimulated Raman scattering by femtosecond ultraviolet plasma grating in water

NASA Astrophysics Data System (ADS)

Liu, Fengjiang; Yuan, Shuai; He, Boqu; Nan, Junyi; Khan, Abdul Qayyum; Ding, Liang'en; Zeng, Heping

2018-02-01

Efficient forward stimulated Raman scattering (SRS) was observed along 400-nm femtosecond (fs) laser filaments in water. SRS conversion dominated over self-phase modulation induced continuum generation as the input pulse energy was above 4 μJ (˜30 Pcr), implying that plasma in the aqueous filamentation channel played an important role in compensating for the group velocity walk-off between the pump and Stokes pulses. By overlapping two synchronous fs 400-nm filaments to form plasma grating in water, significant enhancement of SRS conversion was observed. Such a SRS enhancement originated from the ultrahigh plasma density in the intersection region of the preformed plasma grating.

The effect of surface irradiance on the absorption spectrum of chromophoric dissolved organic matter in the global ocean

NASA Astrophysics Data System (ADS)

Swan, Chantal M.; Nelson, Norman B.; Siegel, David A.; Kostadinov, Tihomir S.

2012-05-01

The cycling pathways of chromophoric dissolved organic matter (CDOM) within marine systems must be constrained to better assess the impact of CDOM on surface ocean photochemistry and remote sensing of ocean color. Photobleaching, the loss of absorption by CDOM due to light exposure, is the primary sink for marine CDOM. Herein the susceptibility of CDOM to photobleaching by sea surface-level solar radiation was examined in 15 samples collected from wide-ranging open ocean regimes. Samples from the Pacific, Atlantic, Indian and Southern Oceans were irradiated over several days with full-spectrum light under a solar simulator at in situ temperature in order to measure photobleaching rate and derive an empirical matrix, ɛsurf (m-1 μEin-1), which quantifies the effect of surface irradiance on the spectral absorption of CDOM. Irradiation responses among the ocean samples were similar within the ultraviolet (UV) region of the spectrum spanning 300-360 nm, generally exhibiting a decrease in the CDOM absorption coefficient (m-1) and concomitant increase in the CDOM spectral slope parameter, S (nm-1). However, an unexpected irradiation-induced increase in CDOM absorption between approximately 360 and 500 nm was observed for samples from high-nutrient low-chlorophyll (HNLC) environments. This finding was linked to the presence of dissolved nitrate and may explain discrepancies in action spectra for dimethylsulfide (DMS) photobleaching observed between the Equatorial Pacific and Subtropical North Atlantic Oceans. The nitrate-to-phosphate ratio explained 27-70% of observed variability in ɛsurf at observation wavelengths of 330-440 nm, while the initial spectral slope of the samples explained up to 52% of variability in ɛsurf at observation wavelengths of 310-330 nm. These results suggest that the biogeochemical and solar exposure history of the water column, each of which influence the chemical character and thus the spectral quality of CDOM and its photoreactivity, are the main factors regulating the susceptibility of CDOM to photodegradation in the surface ocean. The ɛsurf parameter reported herein may be applied to remote sensing retrievals of CDOM to estimate photobleaching at the surface on regional to global scales.

Spectral fluorescent properties of tissues in vivo with excitation in the red wavelength range

NASA Astrophysics Data System (ADS)

Stratonnikov, Alexander A.; Loschenov, Victor B.; Klimov, D. V.; Edinac, N. E.; Wolnukhin, V. A.; Strashkevich, I. A.

1997-12-01

The spectral fluorescence analysis is a promising method for differential tissue diagnostic. Usually the UV and visible light is used for fluorescence excitation with emission registration in the visible wavelength range. The light penetration length in this wavelength range is very small allowing one to analyze only the surface region of the tissue. Here we present the tissue fluorescent spectra in vivo excited in the red wavelength region. As excitation light source we used compact He-Ne laser (632.8 nm) and observed the fluorescence in 650 - 800 nm spectral range. The various tissues including normal skin, psoriasis, tumors, necrosis as well as photosensitized tissues have been measured.

Stratigraphic Correlation via Opportunity's Pancam of the Burns Formation, Meridiani Planum, Mars

NASA Astrophysics Data System (ADS)

Thompson, S. D.; Calvin, W. M.; Farrand, W. H.

2006-12-01

Spectral properties of Meridiani Planum hematite-rich Burns formation observed by Opportunity's Pancam have been described previously but not at minimum spatial scales. This study is of the fine scale visible and near- infrared spectral features within the sedimentary structures over the entire lateral extent explored by Opportunity across an 8 km traverse from Endurance to Victoria craters. Investigation of the bedrock has shown sub-centimeter thinly laminated evaporite deposits with few occurrences of festoon cross-bedding, massive bedding, and subtle differences in color and texture. Pancam data analyses of rock targets where sufficient spatial resolution (<10 mm) is achieved (within 10 m) constrain spectral parameters of laminar, erosional, and possible secondary diagenetic features. Results show differences of statistical significance in iron mineral varieties and phases in both vertical section and lateral extent of the Burns formation. Spectra exhibit a steep positive slope in the visible (432-753 nm) region and subtle changes in the near infrared (753-1009 nm) region ranging from flat, concave, to convex profiles. Maxima are typically in the 750-850 nm region but can occur as low as 673 nm and as high as 1009 nm with the latter usually from the lower albedo materials (i.e., spherules and basaltic sands). Positive slopes from 934-1009 nm in this region are consistent with the presence of hematite, commonly associated with the spherules. The higher albedo surfaces tend to have greatest negative slope in the longer wavelengths. This could result from intrinsic characteristics of the outcrop material or a significantly thick (i.e. >100 micron) dust deposit. Band depth images centered at 535 nm and 904 nm provide statistics on the relative occurrences of crystalline ferric oxide minerals. Rarely iron-rich signatures are present in individual laminations and not in the adjacent layers. Such occurrences could result from multiple iron-rich sedimentary events, secondary diagenetic products such as cementation or recrystallization, or an invasive fracture fill material. Comparisons of geomorphologic and spectroscopic mapping will be presented to show overall relationships of the Meridiani plains materials.

A catalog of stellar spectrophotometry (Adelman, et al. 1989): Documentation for the machine-readable version

NASA Technical Reports Server (NTRS)

Warren, Wayne H., Jr.; Adelman, Saul J.

1990-01-01

The machine-readable version of the catalog, as it is currently being distributed from the astronomical data centers, is described. The catalog is a collection of spectrophotometric observations made using rotating grating scanners and calibrated with the fluxes of Vega. The observations cover various wavelength regions between about 330 and 1080 nm.

Intense blue upconversion emission and intrinsic optical bistability in Tm3+/Yb3+/Zn2+ tridoped YVO4 phosphors

NASA Astrophysics Data System (ADS)

Yadav, Manglesh; Mondal, Manisha; Mukhopadhyay, Lakshmi; Rai, Vineet Kumar

2018-04-01

Tm3+/Yb3+/Zn2+:yttrium metavanadate (YVO4) phosphors prepared through chemical coprecipitation and the solid state reaction method have been structurally characterized by an x-ray diffraction (XRD) study. Photoluminescence study of the developed phosphors under ultraviolet (UV) and near infrared (NIR) excitation has been performed. The excitation spectrum of the tetragonal zircon type YVO4 phosphors corresponding to the emission at ˜476 nm exhibits a broad excitation peak in the 250-350 nm region, which is due to charge distribution in the {{{{VO}}}4}3- group. Under 980 nm CW diode laser excitation, enhancements of about ˜3000 times and ˜40 times have been observed for the blue band in the tridoped Tm3+Yb3+Zn2+:YVO4 phosphors compared to those of the Tm3+:YVO4 singly and Tm3+/Yb3+:YVO4 codoped phosphors, respectively. A downconversion (DC) emission study shows an enhancement of about ˜50 times for the blue band in the tridoped phosphors compared to that of the singly doped phosphors. Optical bistability (OB) behavior of the developed phosphors has been also investigated upon 980 nm excitation. The calculated Commission Internationale de l’Éclairage (CIE) color coordinates lie in the blue region with 96.5% color purity under 980 nm excitation, having a color temperature of ˜3400 K. Our observations show that the developed phosphors may be suitably used in dual mode luminescence spectroscopy, display devices, and UV LED chips.

Intense blue upconversion emission and intrinsic optical bistability in Tm3+/Yb3+/Zn2+ tridoped YVO4 phosphors.

PubMed

Yadav, Manglesh; Mondal, Manisha; Mukhopadhyay, Lakshmi; Rai, Vineet Kumar

2018-01-22

Tm 3+ /Yb 3+ /Zn 2+ :yttrium metavanadate (YVO 4 ) phosphors prepared through chemical coprecipitation and the solid state reaction method have been structurally characterized by an x-ray diffraction (XRD) study. Photoluminescence study of the developed phosphors under ultraviolet (UV) and near infrared (NIR) excitation has been performed. The excitation spectrum of the tetragonal zircon type YVO 4 phosphors corresponding to the emission at ∼476 nm exhibits a broad excitation peak in the 250-350 nm region, which is due to charge distribution in the [Formula: see text] group. Under 980 nm CW diode laser excitation, enhancements of about ∼3000 times and ∼40 times have been observed for the blue band in the tridoped Tm 3+ Yb 3+ Zn 2+ :YVO 4 phosphors compared to those of the Tm 3+ :YVO 4 singly and Tm 3+ /Yb 3+ :YVO 4 codoped phosphors, respectively. A downconversion (DC) emission study shows an enhancement of about ∼50 times for the blue band in the tridoped phosphors compared to that of the singly doped phosphors. Optical bistability (OB) behavior of the developed phosphors has been also investigated upon 980 nm excitation. The calculated Commission Internationale de l'Éclairage (CIE) color coordinates lie in the blue region with 96.5% color purity under 980 nm excitation, having a color temperature of ∼3400 K. Our observations show that the developed phosphors may be suitably used in dual mode luminescence spectroscopy, display devices, and UV LED chips.

Spectral characteristics of Shuttle glow

NASA Technical Reports Server (NTRS)

Viereck, R. A.; Mende, S. B.; Murad, E.; Swenson, G. R.; Pike, C. P.; Culbertson, F. L.; Springer, R. C.

1992-01-01

The glowing cloud near the ram surfaces of the Space Shuttle was observed with a hand-held, intensified spectrograph operated by the astronauts from the aft-flight-deck of the Space Shuttle. The spectral measurements were made between 400 and 800 nm with a resolution of 3 nm. Analysis of the spectral response of the instrument and the transmission of the Shuttle window was performed on orbit using earth-airglow OH Meinel bands. This analysis resulted in a correction of the Shuttle glow intensity in the spectral region between 700 and 800 nm. The data presented in this report is in better agreement with laboratory measurements of the NO2 continuum.

Overview of Key Results from SDO Extreme ultraviolet Variability Experiment (EVE)

NASA Astrophysics Data System (ADS)

Woods, Tom; Eparvier, Frank; Jones, Andrew; Mason, James; Didkovsky, Leonid; Chamberlin, Phil

2016-10-01

The SDO Extreme ultraviolet Variability Experiment (EVE) includes several channels to observe the solar extreme ultraviolet (EUV) spectral irradiance from 1 to 106 nm. These channels include the Multiple EUV Grating Spectrograph (MEGS) A, B, and P channels from the University of Colorado (CU) and the EUV SpectroPhometer (ESP) channels from the University of Southern California (USC). The solar EUV spectrum is rich in many different emission lines from the corona, transition region, and chromosphere. The EVE full-disk irradiance spectra are important for studying the solar impacts in Earth's ionosphere and thermosphere and are useful for space weather operations. In addition, the EVE observations, with its high spectral resolution of 0.1 nm and in collaboration with AIA solar EUV images, have proven valuable for studying active region evolution and explosive energy release during flares and coronal eruptions. These SDO measurements have revealed interesting results such as understanding the flare variability over all wavelengths, discovering and classifying different flare phases, using coronal dimming measurements to predict CME properties of mass and velocity, and exploring the role of nano-flares in continual heating of active regions.

Studies on pulsed optogalvanic effect in Eu/Ne hollow cathode discharge.

PubMed

Saini, V K; Kumar, P; Dixit, S K; Nakhe, S V

2014-07-01

The optogalvanic (OG) effect has been observed in a Eu/Ne hollow cathode discharge lamp using pulsed laser irradiation. An OG spectrum is recorded in dye laser wavelength region 574–602 nm using a boxcar-averager. In total 41 atomic lines are observed. Of these, 38 lines are assigned to neon transitions. Two lines observed corresponding to wavelengths 576.519 and 601.815 nm are assigned to europium transitions; (4f 7 6s 2 , S 8 7/2 →4f 7 6s6p , zP 6 7/2 ) and (4f 7 6s 2 , S 8 7/2 →4f 7 6s6p , zP 8 9/2 ), respectively, and the remaining line at 582.475 nm could not be assigned. The effect of the discharge current on europium as well as neon OG signals is also studied. At moderate discharge current values, an extra positive peak is observed in neon OG signal for the transition (1s 5 →2p 2 ) at 588.189 nm, which is explained by Penning-ionization process using the quasi-resonant energy transfer interactions between excited neon and europium atoms lying in 2p 2 and D 10 9/2 states, respectively.

Longitudinal study assessing the return of chloroquine susceptibility of Plasmodium falciparum in isolates from travellers returning from West and Central Africa, 2000–2011

PubMed Central

2013-01-01

Background Chloroquine (CQ) was the main malaria therapy worldwide from the 1940s until the 1990s. Following the emergence of CQ-resistant Plasmodium falciparum, most African countries discontinued the use of CQ, and now promote artemisinin-based combination therapy as the first-line treatment. This change was generally initiated during the last decade in West and Central Africa. The aim of this study is to describe the changes in CQ susceptibility in this African region, using travellers returning from this region as a sentinel system. Methods The study was conducted by the Malaria National Reference Centre, France. The database collated the pfcrtK76T molecular marker for CQ susceptibility and the in vitro response to CQ of parasites from travellers’ isolates returning from Senegal, Mali, Ivory Coast or Cameroon. As a proxy of drug pressure, data regarding CQ intake in febrile children were collated for the study period. Logistic regression models were used to detect trends in the proportions of CQ resistant isolates. Results A total of 2874 parasite isolates were genotyped between 2000–2011. The prevalence of the pfcrt76T mutant genotype significantly decreased for Senegal (from 78% to 47%), Ivory Coast (from 63% to 37%), Cameroon (from 90% to 59%) and remained stable for Mali. The geometric mean of the 50% inhibitory concentration (IC50) of CQ in vitro susceptibility and the proportion of resistant isolates (defining resistance as an IC50 value > 100 nM) significantly decreased for Senegal (from 86 nM (59%) to 39 nM (25%)), Mali (from 84 nM (50%) to 51 nM (31%)), Ivory Coast (from 75 nM (59%) to 29 nM (16%)) and Cameroon (from 181 nM (75%) to 51 nM (37%)). Both analyses (molecular and in vitro susceptibility) were performed for the 2004–2011 period, after the four countries had officially discontinued CQ and showed an accelerated decline of the resistant isolates for the four countries. Meanwhile, CQ use among children significantly deceased in this region (fixed effects slope = −0.3, p < 10-3). Conclusions An increase in CQ susceptibility following official withdrawal of the drug was observed in travellers returning from West and Central African countries. The same trends were observed for molecular and in vitro analysis between 2004-2011and they correlated to the decrease of the drug pressure. PMID:23351608

Longitudinal study assessing the return of chloroquine susceptibility of Plasmodium falciparum in isolates from travellers returning from West and Central Africa, 2000-2011.

PubMed

Gharbi, Myriam; Flegg, Jennifer A; Hubert, Véronique; Kendjo, Eric; Metcalf, Jessica E; Bertaux, Lionel; Guérin, Philippe J; Le Bras, Jacques; Aboubaca, Ahmed; Agnamey, Patrice; Angoulvant, Adela; Barbut, Patricia; Basset, Didier; Belkadi, Ghania; Bellanger, Anne Pauline; Bemba, Dieudonné; Benoit-Vica, Françoise; Berry, Antoine; Bigel, Marie-Laure; Bonhomme, Julie; Botterel, Françoise; Bouchaud, Olivier; Bougnoux, Marie-Elisabeth; Bourée, Patrice; Bourgeois, Nathalie; Branger, Catherine; Bret, Laurent; Buret, Bernadette; Casalino, Enrique; Chevrier, Sylviane; Conquere de Monbrison, Frédérique; Cuisenier, Bernadette; Danis, Martin; Darde, Marie-Laure; De Gentile, Ludovic; Delarbre, Jean-Marie; Delaunay, Pascal; Delaval, Anne; Desoubeaux, Guillaume; Develoux, Michel; Dunand, Jean; Durand, Rémy; Eloy, Odile; Fauchet, Nathalie; Faugere, Bernard; Faye, Alber; Fenneteau, Odile; Flori, Pierre; Fontrouge, Madeleine; Garabedian, Chantal; Gayandrieu, Françoise; Godineau, Nadine; Houzé, Pascal; Houzé, Sandrine; Hurst, Jean-Pierre; Ichou, Houria; Lachaud, Laurence; Lebuisson, Agathe; Lefevre, Magalie; LeGuern, Anne-Sophie; Le Moal, Gwenaë; Lusina, Daniel; Machouart, Marie-Claude; Malvy, Denis; Matheron, Sophie; Maubon, Danièle; Mechali, Denis; Megarbane, Bruno; Menard, Guillaume; Millon, Laurence; Aiach, Muriel Mimoun; Minodier, Philippe; Morelle, Christelle; Nevez, Gilles; Parola, Philippe; Parzy, Daniel; Patey, Olivier; Patoz, Pierre; Penn, Pascale; Perignon, Alice; Picot, Stéphane; Pilo, Jean-Etienne; Poilane, Isabelle; Pons, Denis; Poupart, Marie; Pradines, Bruno; Raffenot, Didier; Rapp, Christophe; Receveur, Marie-Catherine; Sarfati, Claudine; Senghor, Yaye; Simon, Fabrice; Siriez, Jean-Yves; Taudon, Nicolas; Thellier, Marc; Thouvenin, Maxime; Toubas, Dominique

2013-01-25

Chloroquine (CQ) was the main malaria therapy worldwide from the 1940s until the 1990s. Following the emergence of CQ-resistant Plasmodium falciparum, most African countries discontinued the use of CQ, and now promote artemisinin-based combination therapy as the first-line treatment. This change was generally initiated during the last decade in West and Central Africa. The aim of this study is to describe the changes in CQ susceptibility in this African region, using travellers returning from this region as a sentinel system. The study was conducted by the Malaria National Reference Centre, France. The database collated the pfcrtK76T molecular marker for CQ susceptibility and the in vitro response to CQ of parasites from travellers' isolates returning from Senegal, Mali, Ivory Coast or Cameroon. As a proxy of drug pressure, data regarding CQ intake in febrile children were collated for the study period. Logistic regression models were used to detect trends in the proportions of CQ resistant isolates. A total of 2874 parasite isolates were genotyped between 2000-2011. The prevalence of the pfcrt76T mutant genotype significantly decreased for Senegal (from 78% to 47%), Ivory Coast (from 63% to 37%), Cameroon (from 90% to 59%) and remained stable for Mali. The geometric mean of the 50% inhibitory concentration (IC50) of CQ in vitro susceptibility and the proportion of resistant isolates (defining resistance as an IC50 value > 100 nM) significantly decreased for Senegal (from 86 nM (59%) to 39 nM (25%)), Mali (from 84 nM (50%) to 51 nM (31%)), Ivory Coast (from 75 nM (59%) to 29 nM (16%)) and Cameroon (from 181 nM (75%) to 51 nM (37%)). Both analyses (molecular and in vitro susceptibility) were performed for the 2004-2011 period, after the four countries had officially discontinued CQ and showed an accelerated decline of the resistant isolates for the four countries. Meanwhile, CQ use among children significantly deceased in this region (fixed effects slope = -0.3, p < 10-3). An increase in CQ susceptibility following official withdrawal of the drug was observed in travellers returning from West and Central African countries. The same trends were observed for molecular and in vitro analysis between 2004-2011 and they correlated to the decrease of the drug pressure.

GADICON spectrometer for ionosphere far-ultraviolet observation: prototype design, manufacturing, and testing.

PubMed

Yu, Lei

2016-08-20

The design, manufacturing, and testing of an imaging spectrometer prototype that will address new scientific requirements by the observation of the lower atmosphere's impact on the ionosphere are presented. The two sided lateral limb observation covering 130-180 nm far-ultraviolet (FUV) region allows the instrument to perform particle measurements in the daytime and nighttime. In this paper, we focus upon the working design principle, observation, and calibration.

DNA Length Modulates the Affinity of Fragments of Genomic DNA for the Nuclear Matrix In Vitro.

PubMed

García-Vilchis, David; Aranda-Anzaldo, Armando

2017-12-01

Classical observations have shown that during the interphase the chromosomal DNA of metazoans is organized in supercoiled loops attached to a compartment known as the nuclear matrix (NM). Fragments of chromosomal DNA able to bind the isolated NM in vitro are known as matrix associated/attachment/addressed regions or MARs. No specific consensus sequence or motif has been found that may constitute a universal, defining feature of MARs. On the other hand, high-salt resistant DNA-NM interactions in situ define true DNA loop anchorage regions or LARs, that might correspond to a subset of the potential MARs but are not necessarily identical to MARs characterized in vitro, since there are several examples of MARs able to bind the NM in vitro but which are not actually bound to the NM in situ. In the present work we assayed the capacity of two LARs, as well as of shorter fragments within such LARs, for binding to the NM in vitro. Paradoxically the isolated (≈2 kb) LARs cannot bind to the NM in vitro while their shorter (≈300 pb) sub-fragments and other non-related but equally short DNA fragments, bind to the NM in a high-salt resistant fashion. Our results suggest that the ability of a given DNA fragment for binding to the NM in vitro primarily depends on the length of the fragment, suggesting that binding to the NM is modulated by the local topology of the DNA fragment in suspension that it is known to depend on the DNA length. J. Cell. Biochem. 118: 4487-4497, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

INFRARED AND ULTRAVIOLET SPECTRA OF METHANE DILUTED IN SOLID NITROGEN AND IRRADIATED WITH ELECTRONS DURING DEPOSITION AT VARIOUS TEMPERATURES

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

Chin, Chih-Hao; Chen, Sian-Cong; Liu, Meng-Chen

We recorded the infrared and ultraviolet absorption spectra of CH{sub 4}:N{sub 2} matrix samples that underwent electron bombardment during deposition in the temperature range of 10–44 K. In contrast to a previous experiment on the IR spectroscopy of electron-bombarded icy samples, methyl and azide radicals became the main products upon electron bombardment during deposition; furthermore, reduced production of nitrile species was observed for deposition at 10 and 20 K. On the other hand, for deposition above 33 K, the observed bands of the radical species (such as methyl and azide) decreased, and bands of large nitriles appeared. This observation maymore » suggest that radical species easily diffuse and recombine to form more complex molecules in solid nitrogen at higher temperatures. Further measurements of similar samples at 10–33 K in the UV region revealed the intense band of azide radicals at 272.5 nm and weak, broad, overlapping features of methyl and azide radicals in the 225–197 nm region. For deposition at 44 K, only a broad feature centered at 219.4 nm was observed, and the possible carriers of nitrile species were proposed based on the corresponding IR spectrum and theoretical predictions of excitation energy. This band is similar to the observed absorption feature of Pluto’s surface recorded by the Hubble telescope in terms of both band position and bandwidth. Our findings therefore further support the suggestion that complex nitrile species may exist on the surface of Pluto.« less

Laser-induced fluorescence spectroscopy of benign and malignant cutaneous lesions

NASA Astrophysics Data System (ADS)

Borisova, Ekaterina G.; Troyanova, P. P.; Stoyanova, V. P.; Avramov, Lachezar A.

2005-04-01

The goals of this work were investigation of pigmented skin lesions by the method of laser-induced fluorescence spectroscopy. Fluorescence spectra were obtained from malignant and benign skin lesions after excitation with nitrogen laser at 337 nm, namely: benign nevi, dysplastic nevi, malignant melanoma (MM), keratopapilloma, base-cell papilloma and base-cell carcinoma, as well as from healthy skin areas near to the lesion that were used posteriori to reveal changes between healthy and lesion skin spectra. Initially lesions were classified by ABCD-dermatscopic method. All suspicious lesions were excised and were investigated histologically. Spectrum of healthy skin consists of one main maximum at 470-500 nm spectral region and secondary maxima at in the regions round 400 and 440 nm. In the cases of nevi and melanoma significant decrease of fluorescence intensity, which correlated with the type of pigment lesion was observed. This reduction of the signal is related to the accumulation of melanin in the lesions that re-absorb strongly the fluorescence from native skin fluorophores in whole visible spectral region. In cases of papilloma and base-cell carcinoma an intensity decrease was also observed, related to accumulation of pigments in these cutaneous lesions. An relative increase of the fluorescence peak at 440 nm were registered in the case of base-cell carcinoma, and appearance of green fluorescence, related to increase of keratin content in benign papilloma lesions were detected. The results, obtained in this investigation of the different pigment lesions could be used for better comprehension of the skin optical properties. The fluorescence spectroscopy of the human skin are very prominent for early diagnosis and differentiation of cutaneous diseases and gives a wide range of possibilities related to real-time determination of existing pathological condition.

Continuous wave channel waveguide lasers in Nd:LuVO4 fabricated by direct femtosecond laser writing.

PubMed

Ren, Yingying; Dong, Ningning; Macdonald, John; Chen, Feng; Zhang, Huaijin; Kar, Ajoy K

2012-01-30

Buried channel waveguides in Nd:LuVO<4 were fabricated by femtosecond laser writing with the double-line technique. The photoluminescence properties of the bulk materials were found to be well preserved within the waveguide core region. Continuous-wave laser oscillation at 1066.4 nm was observed from the waveguide under ~809 nm optical excitation, with the absorbed pump power at threshold and laser slope efficiency of 98 mW and 14%, respectively.

Evolution and dynamics of orphan penumbrae in the solar photosphere: Analysis from multi-instrument observations

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

Zuccarello, Francesca; Guglielmino, Salvo L.; Romano, Paolo, E-mail: fzu@oact.inaf.it

2014-05-20

We investigate the dynamics and magnetic properties of orphan penumbrae observed in the solar photosphere to understand the formation process of such structures. We observed two orphan penumbrae in active region NOAA 11089 during a coordinated observing campaign carried out in 2010 July, involving the Hinode/Solar Optical Telescope (SOT) and Dutch Open Telescope (DOT), benefiting also from continuous observations acquired by the SDO satellite. We follow their evolution during about three days. The two structures form in different ways: one seems to break off the penumbra of a nearby sunspot, the other is formed through the emergence of new flux.more » Then they fragment while evolving. The SDO Helioseismic and Magnetic Imager measurements indicate the presence of strong line-of-sight motions in the regions occupied by these orphan penumbrae, lasting for several hours and decreasing with time. This is confirmed by SOT spectro-polarimetric measurements of the Fe I 630.2 nm pair. The latter also show that Stokes parameters exhibit significant asymmetries in the orphan penumbral regions, typical of an uncombed filamentary structure. The orphan penumbrae lie above polarity inversion lines, where peculiar plasma motions take place with velocities larger than ±3 km s{sup –1}. The vector magnetic field in these regions is highly inclined, with the average magnetic field strength decreasing with time. The DOT observations in the Hα line and SDO Atmospheric Imaging Assembly measurements in the He II 30.4 nm line indicate that there is no counterpart for the orphan penumbrae at midchromospheric heights or above. Our findings suggest that in at least one of the features investigated the emerging flux may be trapped in the low atmospheric layers by the overlying pre-existing fields, forming these filamentary structures.« less

Evolution and Dynamics of Orphan Penumbrae in the Solar Photosphere: Analysis from Multi-instrument Observations

NASA Astrophysics Data System (ADS)

Zuccarello, Francesca; Guglielmino, Salvo L.; Romano, Paolo

2014-05-01

We investigate the dynamics and magnetic properties of orphan penumbrae observed in the solar photosphere to understand the formation process of such structures. We observed two orphan penumbrae in active region NOAA 11089 during a coordinated observing campaign carried out in 2010 July, involving the Hinode/Solar Optical Telescope (SOT) and Dutch Open Telescope (DOT), benefiting also from continuous observations acquired by the SDO satellite. We follow their evolution during about three days. The two structures form in different ways: one seems to break off the penumbra of a nearby sunspot, the other is formed through the emergence of new flux. Then they fragment while evolving. The SDO Helioseismic and Magnetic Imager measurements indicate the presence of strong line-of-sight motions in the regions occupied by these orphan penumbrae, lasting for several hours and decreasing with time. This is confirmed by SOT spectro-polarimetric measurements of the Fe I 630.2 nm pair. The latter also show that Stokes parameters exhibit significant asymmetries in the orphan penumbral regions, typical of an uncombed filamentary structure. The orphan penumbrae lie above polarity inversion lines, where peculiar plasma motions take place with velocities larger than ±3 km s-1. The vector magnetic field in these regions is highly inclined, with the average magnetic field strength decreasing with time. The DOT observations in the Hα line and SDO Atmospheric Imaging Assembly measurements in the He II 30.4 nm line indicate that there is no counterpart for the orphan penumbrae at midchromospheric heights or above. Our findings suggest that in at least one of the features investigated the emerging flux may be trapped in the low atmospheric layers by the overlying pre-existing fields, forming these filamentary structures.

New approaches to removing cloud shadows and evaluating the 380 nm surface reflectance for improved aerosol optical thickness retrievals from the GOSAT/TANSO-Cloud and Aerosol Imager

NASA Astrophysics Data System (ADS)

Fukuda, Satoru; Nakajima, Teruyuki; Takenaka, Hideaki; Higurashi, Akiko; Kikuchi, Nobuyuki; Nakajima, Takashi Y.; Ishida, Haruma

2013-12-01

satellite aerosol retrieval algorithm was developed to utilize a near-ultraviolet band of the Greenhouse gases Observing SATellite/Thermal And Near infrared Sensor for carbon Observation (GOSAT/TANSO)-Cloud and Aerosol Imager (CAI). At near-ultraviolet wavelengths, the surface reflectance over land is smaller than that at visible wavelengths. Therefore, it is thought possible to reduce retrieval error by using the near-ultraviolet spectral region. In the present study, we first developed a cloud shadow detection algorithm that uses first and second minimum reflectances of 380 nm and 680 nm based on the difference in Rayleigh scattering contribution for these two bands. Then, we developed a new surface reflectance correction algorithm, the modified Kaufman method, which uses minimum reflectance data at 680 nm and the NDVI to estimate the surface reflectance at 380 nm. This algorithm was found to be particularly effective at reducing the aerosol effect remaining in the 380 nm minimum reflectance; this effect has previously proven difficult to remove owing to the infrequent sampling rate associated with the three-day recursion period of GOSAT and the narrow CAI swath of 1000 km. Finally, we applied these two algorithms to retrieve aerosol optical thicknesses over a land area. Our results exhibited better agreement with sun-sky radiometer observations than results obtained using a simple surface reflectance correction technique using minimum radiances.

Femtosecond laser fluorescence and propagation in very dense potassium vapor.

PubMed

Makdisi, Y; Kokaj, J; Afrousheh, K; Nair, R; Mathew, J; Pichler, G

2013-12-16

Femtosecond (fs) laser propagation and fluorescence of dense potassium vapor was studied, and the spectral region around the first and the second doublets of the principal series lines of potassium atoms was investigated. In our search we did not observe the conical emission in the far field, although it was previously observed in the case of rubidium. We discuss the possible reason of this unexpected result. The fluorescence spectrum revealed Rb impurity resonance lines in emission due to the collisional redistribution from the K(4p) levels into the Rb(5p) levels. In the forward propagation of 400 nm femtosecond light we observed the molecular band red shifted from potassium second doublet. However, no molecular spectrum was observed when the mode-locked fs laser light was discretely tuned within the wings of the first resonance lines, at 770 nm.

The influence of the pressure and temperature on the light emission of the ZnO

NASA Astrophysics Data System (ADS)

Dantas, N. O.; Couto dos Santos, M. A.; Cunha, F.; Macêdo, M. A.

2007-09-01

A new route for the preparation of zinc oxide powder is described along with its characterization. A proteic sol was prepared dissolving zinc nitrate in filtered coconut water. After calcination at 1000 °C, the powder was compressed to 1.3×10 8 Pa and ZnO pellets were obtained. The emission spectra were recorded under UV excitation at 325 and 400 nm. The powder showed no spectroscopic response, whereas one peak around 396 nm was observed for the pressed powder (pellet with no heat treatment). The pellets were then annealed for 24 h at 500, 800 and 1000 °C. In the first case, bands at 396 and 440 nm and a structure of narrow peaks around 480 nm (oxygen vacancies) were observed. Increasing the annealing temperature led to a decrease in the intensity of the emissions at 440 and 480 nm. We propose that the high pressure induces a red-shift in the UV region of the ZnO nanopowder emission peaks to 396 nm. This is an indication that the ZnO nanopowder treated under pressure and sintering temperature exhibits the spectroscopic behavior characteristic of the ZnO single crystal. The disappearance of the 440 and 480 nm lines indicate the reduction of oxygen vacancies. The atomic force micrographs suggest a coalescence thermal point.

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

Treesearch

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

2007-01-01

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

Quantitative-phase microscopy of nanosecond laser-induced micro-modifications inside silicon.

PubMed

Li, Q; Chambonneau, M; Chanal, M; Grojo, D

2016-11-20

Laser-induced permanent modification inside silicon has been recently demonstrated by using tightly focused nanosecond sources at a 1550 nm wavelength. We have developed a quantitative-phase microscope operating in the near-infrared domain to characterize the laser-induced modifications deep into silicon. By varying the number of applied laser pulses and the energy, we observe porous and densified regions in the focal region. The observed changes are associated with refractive index variations |Δn| exceeding 10^-3, enough to envision the laser writing of optical functionalities inside silicon.

Experimental and theoretical investigations on spectroscopic properties of the imidazole-fused phenanthroline and its derivatives

NASA Astrophysics Data System (ADS)

Zhong, Rongfeng; Xu, Shengxian; Wang, Jinglan; Zhao, Feng; Xia, Hongying; Wang, Yibo

2016-05-01

Two phenanthroline derivatives, 1H-imidazo[4,5-f][1,10]phenanthroline (imPhen) and 2-(9H-fluoren-2-yl)-1H-imidazo[4,5-f][1,10]phenanthroline (Flu-imPhen), have been synthesized and characterized and the corresponding absorption and emission spectroscopic properties have been studied in CH2Cl2 solution. The imPhen exhibits the main two absorption bands at 282 nm and 229 nm and these bands are assigned as the typical π → π*(Phen) state. In addition, the weak absorption bands at 313 nm associated with a shoulder near 302 nm were assigned to the π → π*(Phen) state with partial charge transfer (CT) character. A similar absorption spectra are observed in the case of the Flu-imPhen in the region of 200-300 nm, while the region of 300-400 nm of the spectra are dominated by the characteristic π → π* transition of the fluorene moiety. imPhen shows the typical ligand-centered 1π → π* emission, while Flu-imPhen emits from the mixed 1π → π*/CT states. Density functional theory (DFT) and time-dependent density functional theory (TDDFT) were employed to rationalize the photophysical properties of these ligands studied. The theoretical data confirm the assignment of the experimental absorption spectra and the nature of the emitting states.

Red photoluminescent property and modification of WO3:Eu3+ inverse opal for blue light converted LEDs

NASA Astrophysics Data System (ADS)

Ruan, Jiufeng; Yang, Zhengwen; Huang, Anjun; Chai, Zhuangzhuang; Qiu, Jianbei; Song, Zhiguo

2018-01-01

Blue light converted light-emitting diodes is of great significance as a candidate for next generation lighting. In this work, the WO3:Eu3+ inverse opal photonic crystals were prepared and their luminescence properties were studied. The results demonstrated that the main excitation peak of WO3:Eu3+ inverse opals were located at 465 nm. The red luminescence peak at the 613 nm was observed in the WO3:Eu3+ inverse opal upon 465 nm excitation, exhibiting better red color purity. The influence of photonic band gap on the photoluminescence of WO3:Eu3+ inverse opal was obtained. When the red luminescence peak is in the regions of the photonic band gap and the edge of the band-gap, the red luminescence suppression and enhancement was observed respectively. The WO3:Eu3+ inverse opals may be a promising candidate for the blue light converted LEDs.

Exploring the Origin of Blue and Ultraviolet Fluorescence in Graphene Oxide.

PubMed

Kozawa, Daichi; Miyauchi, Yuhei; Mouri, Shinichiro; Matsuda, Kazunari

2013-06-20

We studied the fluorescence (FL) properties of highly exfoliated graphene oxide (GO) in aqueous solution using continuous-wave and time-resolved FL spectroscopy. The FL spectra of highly exfoliated GO showed two distinct peaks at ∼440 (blue) and ∼300 nm [ultraviolet (UV)]. The FL of GO in the UV region at ∼300 nm was observed for the first time. The average FL lifetimes of the emission peaks at ∼440 and ∼300 nm are 8-13 and 6-8 ns, respectively. The experimentally observed peak wavelengths of pH-dependent FL, FL excitation spectra, and the FL lifetimes are nearly coincident with those of aromatic compounds bound with oxygen functional groups, which suggests that the FL comes from sp(2) fragments consisting of small numbers of aromatic rings with oxygen functional groups acting as FL centers in the GO.

Spectro-polarimetric observation in UV with CLASP to probe the chromosphere and transition region

NASA Astrophysics Data System (ADS)

Kano, Ryouhei; Ishikawa, Ryohko; Winebarger, Amy R.; Auchère, Frédéric; Trujillo Bueno, Javier; Narukage, Noriyuki; Kobayashi, Ken; Bando, Takamasa; Katsukawa, Yukio; Kubo, Masahito; Ishikawa, Shin-Nosuke; Giono, Gabriel; Hara, Hirohisa; Suematsu, Yoshinori; Shimizu, Toshifumi; Sakao, Taro; Tsuneta, Saku; Ichimoto, Kiyoshi; Goto, Motoshi; Cirtain, Jonathan W.; De Pontieu, Bart; Casini, Roberto; Manso Sainz, Rafael; Asensio Ramos, Andres; Stepan, Jiri; Belluzzi, Luca; Carlsson, Mats

2016-05-01

The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is a NASA sounding-rocket experiment that was performed in White Sands in the US on September 3, 2015. During its 5-minute ballistic flight, CLASP successfully made the first spectro-polarimetric observation in the Lyman-alpha line (121.57 nm) originating in the chromosphere and transition region. Since the Lyman-alpha polarization is sensitive to magnetic field of 10-100 G by the Hanle effect, we aim to infer the magnetic field information in such upper solar atmosphere with this experiment.The obtained CLASP data showed that the Lyman-alpha scattering polarization is about a few percent in the wings and the order of 0.1% in the core near the solar limb, as it had been theoretically predicted, and that both polarization signals have a conspicuous spatio-temporal variability. CLASP also observed another upper-chromospheric line, Si III (120.65 nm), whose critical field strength for the Hanle effect is 290 G, and showed a measurable scattering polarization of a few % in this line. The polarization properties of the Si III line could facilitate the interpretation of the scattering polarization observed in the Lyman-alpha line.In this presentation, we would like to show how the upper chromosphere and transition region are seen in the polarization of these UV lines and discuss the possible source of these complicated polarization signals.

Observation of parametric instabilities in the quarter critical density region driven by the Nike KrF laser

NASA Astrophysics Data System (ADS)

Weaver, J. L.; Oh, J.; Phillips, L.; Afeyan, B.; Seely, J.; Kehne, D.; Brown, C. M.; Obenschain, S. P.; Serlin, V.; Schmitt, A. J.; Feldman, U.; Lehmberg, R. H.; Mclean, E.; Manka, C.

2013-02-01

The krypton-fluoride (KrF) laser is an attractive choice for inertial confinement fusion due to its combination of short wavelength (λ =248 nm), large bandwidth (up to 3 THz), and superior beam smoothing by induced spatial incoherence. These qualities improve the overall hydrodynamics of directly driven pellet implosions and should allow use of increased laser intensity due to higher thresholds for laser plasma instabilities when compared to frequency tripled Nd:glass lasers (λ =351 nm). Here, we report the first observations of the two-plasmon decay instability using a KrF laser. The experiments utilized the Nike laser facility to irradiate solid plastic planar targets over a range of pulse lengths (0.35 ns≤τ≤1.25 ns) and intensities (up to 2×1015 W/cm2). Variation of the laser pulse created different combinations of electron temperature and electron density scale length. The observed onset of instability growth was consistent with the expected scaling that KrF lasers have a higher intensity threshold for instabilities in the quarter critical density region.

Capability of the CALIPSO lidar observations to detect the dust source regions

NASA Astrophysics Data System (ADS)

Kaskaoutis, D. G.; Kharol, Shailesh Kumar; Kambezidis, H. D.; Nastos, P. T.; Rani Sharma, Anu; Kvs, Badarinath

Two dust events with high aerosol optical depth (AOD) values have been observed over Athens on 4 and 6-7 February 2009. These dust events were well captured by the satellite obser-vations and are investigated in the present study by means of the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) observations, ceilometer vertical profiles and DREAM model predictions. The CALIPSO provides new insight to study the role of clouds and atmospheric aerosols in regulating Earth's weather, climate, and air quality. CALIPSO has a 98o-inclination orbit and flies at an altitude of 705 km providing daily global maps of the ver-tical distribution of aerosols and clouds. The CALIPSO satellite carries a polarization-sensitive lidar, the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP), which provides profiles of backscatter coefficient at 532 and 1064 nm. The ceilometer used in the present study is a Vaisala CL31 model. It is equipped with an InGaAs MOCVD pulsed laser, emitting at 930 nm and having an energy per pulse of 1.2 J. The emission frequency is 10 kHz while the pulse duration is 100 ns. The vertical profiles of the aerosol backscatter coefficient were obtained from 5 m up to 7.5 km at 930 nm. The CL31 is installed at the Actinometric station of the National Observatory of Athens. The CALIPSO-derived total attenuated backscatter at 532 and 1064 nm is used to identify the position of dust along the overpass trajectory. A typical example of the vertical distribution of the dust plume over the study region during nighttime on 5 Febru-ary 2009 is provided. Limiting the analysis over Libya, eastern Mediterranean and Greece (24o -37o N, 15o-19o E), the dust aerosol layer exhibits a high total attenuated backscatter at 532 nm, reaching to 0.05-0.06 km-1sr-1. CALIPSO observations clearly show that the dust plume was generated over the Sahara desert at about 24oN, 15oE near the borders of Libya, Chad and Niger. After its exposure it was uplifted to about 3-km in depth and moved northwards. As the dust layer moved towards Greece its intensity seems to decrease while its vertical extent was limited to lower altitudes within the first 2 km. The ceilometer also detected an elevated aerosol layer due to dust transport within the first 3 km, while the vertical profiles of dust predicted by DREAM were in close agreement with those of the ceilometer. The main goal of this study is the investigation via satellite vertical-profiling instrumentation not only the vertical extent and the transport of dust, but also its source region. Keywords: Dust, CALIPSO, DREAM model and AOD

Characterization of CDOM absorption of reservoirs with its linkage of regions and ages across China.

PubMed

Shang, Yingxin; Song, Kaishan; Wen, Zhidan; Lyu, Lili; Zhao, Ying; Fang, Chong; Zhang, Bai

2018-03-28

The absorption of chromophoric dissolved organic matter (CDOM) is an important part of light absorptions in aquatic systems. The increasing eutrophication of reservoirs and regional characteristics would affect the CDOM properties sensitively which would be important for the application of remote sensing monitoring. The highest (4.07 ± 2.31 m -1 ) and lowest (0.79 ± 0.67 m -1 ) CDOM concentrations of reservoirs were observed in the northeastern lake region (NER) and Tibetan Plateau lake region (TPR), respectively. The differences between S 275-295 among the five lake regions were significant (p < 0.05) in which the steepest S 275-295 (0.0173 ± 0.0026 nm -1 ) was observed in TPR and the shallowest (0.0326 ± 0.0152 nm -1 ) in Yungui Plateau lake region (YGR). The strong relationships between a CDOM (355) and DOC appeared in the NER (R 2  = 0.43), eastern lake region (EAR) (R 2  = 0.69), Mengxin lake region (MXR) (R 2  = 0.61), and YGR (R 2  = 0.79) which would be a good proxy for DOC in regional reservoirs. Most of all, the correlation between reservoir's establishing time and CDOM absorption under oligotrophic states was relatively strong in the EAR and MXR regions. It indicated that the establishing time of reservoirs affected the CDOM absorption to some extent under the oligotrophic states without much human disturbance. Our results indicate CDOM absorption varies with regions, and the relationships between CDOM and DOC are variable for different regions. Therefore, DOC estimation in reservoirs through CDOM absorption needs to be considered according to lake regions and trophic states.

Properties of transported African mineral dust aerosols in the Mediterranean region

NASA Astrophysics Data System (ADS)

Denjean, Cyrielle; Chevaillier, Servanne; Gaimoz, Cécile; Grand, Noel; Triquet, Sylvain; Zapf, Pascal; Loisil, Rodrigue; Bourrianne, Thierry; Freney, Evelyn; Dupuy, Regis; Sellegri, Karine; Schwarzenbock, Alfons; Torres, Benjamin; Mallet, Marc; Cassola, Federico; Prati, Paolo; Formenti, Paola

2015-04-01

The transport of mineral dust aerosols is a global phenomenon with strong climate implications. Depending on the travel distance over source regions, the atmospheric conditions and the residence time in the atmosphere, various transformation processes (size-selective sedimentation, mixing, condensation of gaseous species, and weathering) can modify the physical and chemical properties of mineral dust, which, in turn, can change the dust's optical properties. The model predictions of the radiative effect by mineral dust still suffer of the lack of certainty of these properties, and their temporal evolution with transport time. Within the frame of the ChArMex project (Chemistry-Aerosol Mediterranean experiment, http://charmex.lsce.ipsl.fr/), one intensive airborne campaign (ADRIMED, Aerosol Direct Radiative Impact in the regional climate in the MEDiterranean region, 06 June - 08 July 2013) has been performed over the Central and Western Mediterranean, one of the two major transport pathways of African mineral dust. In this study we have set up a systematic strategy to determine the optical, physical and optical properties of mineral dust to be compared to an equivalent dataset for dust close to source regions in Africa. This study is based on airborne observations onboard the SAFIRE ATR-42 aircraft, equipped with state of the art in situ instrumentation to measure the particle scattering and backscattering coefficients (nephelometer at 450, 550, and 700 nm), the absorption coefficient (PSAP at 467, 530, and 660 nm), the extinction coefficient (CAPS at 530 nm), the aerosol optical depth (PLASMA at 340 to 1640 nm), the size distribution in the extended range 40 nm - 30 µm by the combination of different particle counters (SMPS, USHAS, FSSP, GRIMM) and the chemical composition obtained by filter sampling. The chemistry and transport model CHIMERE-Dust have been used to classify the air masses according to the dust origin and transport. Case studies of dust transport from known but differing origins (source regions in Tunisia, Algeria, and Mauritania) and at different times after transport, will be presented. Results will be compared to equivalent measurements over source regions interpreted in terms of the evolution of the particle size distribution, chemical composition and optical properties.

LRO-LAMP Observations of Illumination Conditions in the Lunar South Pole: Multi-Dataset and Model Comparison

NASA Astrophysics Data System (ADS)

Mandt, Kathleen; Mazarico, Erwan; Greathouse, Thomas K.; Byron, Ben; Retherford, Kurt D.; Gladstone, Randy; Liu, Yang; Hendrix, Amanda R.; Hurley, Dana; Stickle, Angela; Wes Patterson, G.; Cahill, Joshua; Williams, Jean-Pierre

2017-10-01

The south pole of the Moon is an area of great interest for exploration and scientific research because many low-lying regions are permanently shaded and are likely to trap volatiles for extended periods of time, while adjacent topographic highs can experience extended periods of sunlight. One of the goals of the Lunar Reconnaissance Orbiter (LRO) mission is to characterize the temporal variability of illumination of the lunar polar regions for the benefit of future exploration efforts. We use far ultraviolet (FUV) observations made by the Lyman Alpha Mapping Project (LAMP) to evaluate illumination at the lunar south pole (within 5° of the pole).LAMP observations are made through passive remote sensing in the FUV wavelength range of 57-196 nm using reflected sunlight during daytime observations and reflected light from the IPM and UV-bright stars during nighttime observations. In this study we focused on the region within 5° of the pole, and produced maps using nighttime data taken between September 2009 and February 2014. Summing over long time periods is necessary to obtain sufficient signal to noise. Many of the maps produced for this study show excess brightness in the “Off Band”, or 155-190 nm, because sunlight scattered into the PSRs is most evident in this wavelength range.LAMP observes the highest rate of scattered sunlight in two large PSRs during nighttime observations: Haworth and Shoemaker. We focus on these craters for comparisons with an illumination model and other LRO datasets. We find that the observations of scattered sunlight do not agree with model predictions. However, preliminary results comparing LAMP maps with other LRO datasets show a correlation between LAMP observations of scattered sunlight and Diviner measurements for maximum temperature.

Exceptional aerosol pollution plume observed using a new ULA-lidar approach

NASA Astrophysics Data System (ADS)

Chazette, Patrick

2016-09-01

An exceptional particulate pollution event was sampled in June 2005 over the Ardèche region in Southern France. Airborne (at the wavelength of 355 nm) and ground-based (at the wavelength of 532 nm) lidars performed measurements simultaneously. Airborne observations were performed from an ultra-light aircraft (ULA); they offer an opportunity to test a new method for inversing lidar profiles which enables their quantitative use while the airplane flies in a scattering layer. Using the results of this approach and the ground-based lidar measurements, the aerosol plumes have been optically quantified and the diversity of particle sources (from Western Europe, North Africa and even North America) which contributed to the event has been highlighted using both spaceborne observations and multiple air mass back-trajectories.

Cathodoluminescence and transmission electron microscopy study of dark line defects in thick In(0.2)Ga(0.8)As/GaAs multiple quantum wells

NASA Technical Reports Server (NTRS)

Rich, D. H.; George, T.; Pike, W. T.; Maserjian, J.; Grunthaner, F. J.; Larsson, A.

1992-01-01

TEM and cathodoluminescence (CL) imaging and spectroscopy have been performed on In(0.2)Ga(0.8)As/GaAs MQW structures. Cross-sectional and plan-view TEM demonstrates that misfit dislocations (MDs) are confined to the MQW-to-GaAs interfacial regions. The observed large variation in the exciton luminescence intensity is interpreted as due to the presence of nonradiative recombination centers spread homogeneously in the MQW region away from interface MDs. These nonradiative recombination centers compete with exciton and midgap radiative centers at wavelengths of 950 nm and 1000-1600 nm, respectively, resulting in spatiallty correlated dark line defects for all CL imaging wavelengths.

Response of the Ionospheric F-region in the Latin American Sector During the Intense Geomagnetic Storm of 21-22 January 2005

NASA Astrophysics Data System (ADS)

Sahai, Y.; Fagundes, P. R.; de Jesus, R.; de Abreu, A. J.; Crowley, G.; Pillat, V. G.; Guarnieri, F. L.; Abalde, J. R.; Bittencourt, J. A.

2009-12-01

Ionospheric storms are closely associated with geomagnetic storms and are an extreme example of space weather events. The response of the ionosphere to storms is rather complicated. In the present investigation, we have studied the response of the ionospheric F-region in the Latin American sector during the intense geomagnetic storm of 21-22 January 2005 (with storm sudden commencement (SSC) at 1712 UT on 21 January). This geomagnetic storm is anomalous (minimum Dst reached -105 nT at 0700 UT on 22 January) because the main phase occurred during the northward excursion of the Bz component of interplanetary magnetic fields (IMFs). The monthly mean F10.7 solar flux for the month of January 2005 was 99.0 sfu. The ionospheric F-region parameters observed at Ramey (18.5 N, 67.1 W; RAM), Puerto Rico, Jicamarca (12.0 S, 76.8 W; JIC), Peru, Manaus (2.9 S, 60.0 W; MAN), and São José dos Campos (23.2 S, 45.9 W; SJC), Brazil, during 21-22 January (geomagnetically disturbed) and 25 January (geomagnetically quiet) have been analyzed. Both JIC and MAN, the equatorial stations, show unusually rapid uplifting of the F-region peak heights(hpF2/hmF2) and a decrease in the NmF2 coincident with the time of SSC. At both RAM and SJC an uplifting of the F-region peak height is observed at about 2000 UT. The low-latitude station SJC shows a coincident decrease in NmF2 with the uplifting, whereas the mid-latitude station RAM shows a decrease in NmF2 earlier than the uplifting. Also, the observed variations in the F-region ionospheric parameters are compared with the TIMEGCM model run for 21-22 January and the model results show both similarities and differences from the observed results. Average GPS-TEC (21-22 and 25 January) and phase fluctuations (21, 22, 25, 26 January) observed at Belem (1.5 S, 48.5 W; BELE), Brasilia (15.9 S, 47.9 W; BRAZ), Presidente Prudente (22.3o S, 51.4 W; UEPP), and Porto Alegre (30.1 S, 51.1 W; POAL), Brazil, are also presented. These GPS stations belong to the RBMC/IBGE network of Brazil. Few hours after the onset of the storm, large enhancements in VTEC between 2000 and 2400 UT on 21 January was observed at all the stations. However, the increase in VTEC was greater at the near equatorial station and enhancements in VTEC decreased with latitude. No phase fluctuations were observed during the pre-reversal time during the geomagnetic disturbance (21 January).

Selective-area growth of GaN nanocolumns on Si(111) substrates for application to nanocolumn emitters with systematic analysis of dislocation filtering effect of nanocolumns

NASA Astrophysics Data System (ADS)

Kishino, Katsumi; Ishizawa, Shunsuke

2015-06-01

The growth of highly uniform arrays of GaN nanocolumns with diameters from 122 to 430 nm on Si (111) substrates was demonstrated. The employment of GaN film templates with flat surfaces (root mean square surface roughness of 0.84 nm), which were obtained using an AlN/GaN superlattice (SL) buffer on Si, contributed to the high-quality selective-area growth of nanocolumns using a thin Ti mask of 5 nm thickness by rf-plasma-assisted molecular beam epitaxy. Although the GaN template included a large number of dislocations (dislocation density ˜1011 cm-2), the dislocation filtering effect of nanocolumns was enhanced with decreasing nanocolumn diameters (D). Systematic transmission electron microscopy (TEM) observation enabled us to explain the dependence of the dislocation propagation behavior in nanocolumns on the nanocolumn diameter for the first time. Plan-view TEM analysis was performed for nanocolumns with D = 120-324 nm by slicing the nanocolumns horizontally at a height of ˜300 nm above their bottoms and dislocation propagation through the nanocolumns was analyzed by the cross-sectional TEM observation of nanocolumns with D ˜ 200 nm. It was clarified that dislocations were effectively filtered in the bottom 300 nm region of the nanocolumns, the dislocation density of the nanocolumns decreased with decreasing D, and for narrow nanocolumns with D < 200 nm, dislocation-free crystals were obtained in the upper part of the nanocolumns. The dramatic improvement in the emission properties of GaN nanocolumns observed with decreasing diameter is discussed in relation to the decreased dislocation density. The laser action of InGaN/GaN-based nanocolumn arrays with a nanocolumn diameter of 170 nm and a period of 200 nm on Si under optical excitation was obtained with an emission wavelength of 407 nm. We also fabricated red-emitting InGaN-based nanocolumn light-emitting diodes on Si that operated at a wavelength of 652 nm, demonstrating vertical conduction through the AlN/GaN SL buffer to the Si substrate.

Solar irradiance variability: a six-year comparison between SORCE observations and the SATIRE model

NASA Astrophysics Data System (ADS)

Ball, W. T.; Unruh, Y. C.; Krivova, N. A.; Solanki, S.; Harder, J. W.

2011-06-01

Aims: We investigate how well modeled solar irradiances agree with measurements from the SORCE satellite, both for total solar irradiance and broken down into spectral regions on timescales of several years. Methods: We use the SATIRE model and compare modeled total solar irradiance (TSI) with TSI measurements over the period 25 February 2003 to 1 November 2009. Spectral solar irradiance over 200-1630 nm is compared with the SIM instrument on SORCE over the period 21 April 2004 to 1 November 2009. We discuss the overall change in flux and the rotational and long-term trends during this period of decline from moderate activity to the recent solar minimum in ~10 nm bands and for three spectral regions of significant interest: the UV integrated over 200-300 nm, the visible over 400-691 nm and the IR between 972-1630 nm. Results: The model captures 97% of the observed TSI variation. This is on the order at which TSI detectors agree with each other during the period considered. In the spectral comparison, rotational variability is well reproduced, especially between 400 and 1200 nm. The magnitude of change in the long-term trends is many times larger in SIM at almost all wavelengths while trends in SIM oppose SATIRE in the visible between 500 and 700 nm and again between 1000 and 1200 nm. We discuss the remaining issues with both SIM data and the identified limits of the model, particularly with the way facular contributions are dealt with, the limit of flux identification in MDI magnetograms during solar minimum and the model atmospheres in the IR employed by SATIRE. However, it is unlikely that improvements in these areas will significantly enhance the agreement in the long-term trends. This disagreement implies that some mechanism other than surface magnetism is causing SSI variations, in particular between 2004 and 2006, if the SIM data are correct. Since SATIRE was able to reproduce UV irradiance between 1991 and 2002 from UARS, either the solar mechanism for SSI variation fundamentally changed around the peak of cycle 23, or there is an inconsistency between UARS and SORCE UV measurements. We favour the second explanation.

Multispectral VNIR Observations by the Opportunity Rover Pancam of Multiple Episodes of Aqueous Alteration in Marathon Valley, Endeavour Crater, Mars

NASA Technical Reports Server (NTRS)

Farrand, William H.; Bell, James F., III; Johnson, Jeffrey R.; Arvidson, Raymond E.; Mittlefehldt, David W.; Ruff, Steven W.; Rice, Melissa S.

2016-01-01

Since early 2015, the Mars Exploration Rover Opportunity has been exploring the break in the rim of Endeavour Crater dubbed Marathon Valley by the rover team. Marathon Valley was identified by orbital hyperspectral data from the MRO CRISM as having a relatively strong spectral feature in the 2.3 micrometer region indicative of an Mg or Fe-OH combination overtone absorption band indicative of smectite clay. Earlier in its mission, Opportunity examined the Matijevic Hill region on the more northerly Cape York crater rim segment and found evidence for smectite clays in a stratigraphically lower, pre-impact formed unit dubbed the Matijevic formation. However, the smectite exposures in Marathon Valley appear to be associated with the stratigraphically higher Shoemaker formation impact breccia. Evidence for alteration in this unit in Marathon Valley is provided by Pancam multispectral observations in the 430 to 1010 nm visible/near infrared (VNIR) spectral range. Sinuous troughs ("red zones") contain fragmented cobbles and pebbles displaying higher blue-to-red slopes, moderately higher 535 nm band depths, elevated 754 to 934 nm, and negative 934 to 1009 nm slopes. The lack of an absorption at 864 to 904 nm indicates the lack of crystalline red hematite in these red zones, but likely an enrichment in nanophase ferric oxides. The negative 934 to 1009 nm slope is potentially indicative of the presence of adsorbed or structurally bound water. A scuff in a red zone near the southern wall of Marathon Valley uncovered light-toned soils and a pebble with an 803 to 864 nm absorption resembling that of light-toned Fe-sulfate bearing soils uncovered by the Spirit rover in the Columbia Hills of Gusev crater. APXS chemical measurements indicated enrichments of Mg and S in the scuff soils and the pebble, Joseph Field, with the strongest 803 nm band- consistent with Mg and Fe sulfates. The presence of Fe and Mg sulfates can be interpreted as evidence of a potentially later episode of aqueous alteration with an earlier, neutral to alkaline pH episode forming the Fe/Mg smectites and a later acid pH episode forming the Fe and Mg sulfates.

Novel quantum well gallium arsenide-based lasers for all transmission windows in optical communication

NASA Astrophysics Data System (ADS)

Tansu, Nelson

The thesis covers the development of novel active regions for high-performance edge-emitting lasers (EEL) and vertical cavity surface-emitting lasers (VCSELs) in optical communication. Three main themes of the thesis cover the design, fabrication, and physics of the novel and alternative active regions for GaAs-based VCSELs for the three optical communications windows at wavelength regimes of 850-nm, 1300-nm, and 1500-nm, with the emphases on the 1300-nm InGaAsN QW GaAs-based active regions and on the novel design of 1500-nm GaAs-based active regions. The studies include the utilization of compressively-strained InGaAsP quantum well (QW) active regions for the 850-nm VCSELs. The research on the long-wavelength lasers covers the design, growth, temperature analysis, carrier transport, and gain analysis of the InGaAsN (lambda = 1.3 mum) quantum well lasers. The novel and original design of the GaAsSb-(In)GaAsN type-II QWs to achieve 1500--3000 nm GaAs-based active regions is discussed in detail.

Concentric circular focusing reflector realized using high index contrast gratings

NASA Astrophysics Data System (ADS)

Fang, Wenjing; Huang, Yongqing; Fei, Jiarui; Duan, Xiaofeng; Liu, Kai; Ren, Xiaomin

2017-11-01

A non-periodic concentric circular high index contrast grating (CC-HCG) focusing reflector on 500 nm silicon-on-insulator (SOI) platform is fabricated and experimentally demonstrated. The proposed mirror is realized with phase modulation of wave front in a high reflectivity region. The circular structure based HCG focusing reflector has a spot of high concentration at the 10.87 mm with normal incidence for radially polarization, along with the center wavelength set at 1550 nm. The FWHM spot size of the focusing beam decreases to 260 μm, and the intensity increases to 1.26 compared with the incident beam. The focusing efficiency of about 80% is observed at 1550 nm in the experimental measurement.

Design of a grazing incidence EUV imaging spectrometer for the solar orbiter ESA mission

NASA Astrophysics Data System (ADS)

Da Deppo, Vania; Poletto, Luca

2017-11-01

The paper describes the optical design and performance of an extreme-ultraviolet (EUV) spectrometer for imaging spectroscopy to be part of the scientific payload of the Solar Orbiter (SOLO) mission. The main scientific objectives are to study the solar polar region and observe in detail the evolution of corona structures from a favourable point of view at only 45 solar radii from the Sun (0.2 AU). The instrument concept is based on a grazing incidence telescope, (1200 m focal length, 18 arcmin x 18 arcmin FoV), in Wolter configuration couple to a normalincidence VLS grating spectrometer, which preserve the stigmaticity in an extended spectral region and in the whole field-of-view. The spectral range covered by the instrument is the 116-126 nm region at the first order and the 57-63 nm region at the second order. The spectral resolving element is 65 mÅ (I order), corresponding to a velocity resolution of 16 km/s.

Self-organization of a wedge-shaped surfactant in monolayers and multilayers.

PubMed

Cain, Nicholas; Van Bogaert, Josh; Gin, Douglas L; Hammond, Scott R; Schwartz, Daniel K

2007-01-16

The self-organization behavior of a wedge-shaped surfactant, disodium-3,4,5-tris(dodecyloxy)phenylmethylphosphonate, was studied in Langmuir monolayers (at the air-water interface), Langmuir-Blodgett (LB) monolayers and multilayers, and films adsorbed spontaneously from isooctane solution onto a mica substrate (self-assembled films). This compound forms an inverted hexagonal lyotropic liquid crystal phase in the bulk and in thick adsorbed films. Surface pressure isotherm and Brewster angle microscope (BAM) studies of Langmuir monolayers revealed three phases: gas (G), liquid expanded (LE), and liquid condensed (LC). The surface pressure-temperature phase diagram was determined in detail; a triple point was found at approximately 10 degrees C. Atomic force microscope (AFM) images of LB monolayers transferred from various regions of the phase diagram were consistent with the BAM images and indicated that the LE regions are approximately 0.5 nm thinner than the LC regions. AFM images were also obtained of self-assembled films after various adsorption times. For short adsorption times, when monolayer self-assembly was incomplete, the film topography indicated the coexistence of two distinct monolayer phases. The height difference between these two phases was again 0.5 nm, suggesting a correspondence with the LE/LC coexistence observed in the Langmuir monolayers. For longer immersion times, adsorbed multilayers assembled into highly organized periodic arrays of inverse cylindrical micelles. Similar periodic structures, with the same repeat distance of 4.5 nm, were also observed in three-layer LB films. However, the regions of organized periodic structure were much smaller and more poorly correlated in the LB multilayers than in the films adsorbed from solution. Collectively, these observations indicate a high degree of similarity between the molecular organization in Langmuir layers/LB films and adsorbed self-assembled films. In both cases, monolayers progress through an LE phase, into LE/LC coexistence, and finally into LC phase as surface density increases. Following the deposition of an additional bilayer, the film reorganizes to form an array of inverted cylindrical micelles.

Why is gas phase 2-nitrophenol photolysis a potentially important source of OH radicals in the polluted atmosphere?

NASA Astrophysics Data System (ADS)

Zhu, L.

2017-12-01

2-Nitrophenol is an important component of "brown carbon" in the atmosphere. The concentration of 2-nitrophenol is higher in polluted urban areas where there are increased emissions of aromatic hydrocarbons. To assess the air quality impacts of pollutant emissions, it is important to understand the oxidant formation potential of the emitted species. Photolysis is the dominant atmospheric removal process for 2-nitrophenol. Although photodissociation dynamics studies of 2-nitrophenol have reported OH formation at photolysis wavelengths of 266 nm, 355 nm, and over the 361-390 nm range, and HONO has been observed as a product from 2-nitrophenol photolysis in an environmental chamber, the lack of quantitative absorption cross section and product quantum yield information has prevented quantitative assessment of the extent of oxidant formation from the photolysis of 2-nitrophenol in the atmosphere. My group determined the gas phase absorption cross sections of 2-nitrophenol in the 295-400 nm region by using cavity ring-down spectroscopy. The OH, HONO, and NO2 formation channels following the gas phase photolysis of 2-nitrophenol at 308 and 351 nm were investigated. Direct NO2 formation was not observed. OH and HONO were direct products from the 2-nitrophenol photolysis, and their quantum yields were obtained. The sum of the OH and the HONO quantum yields was about unity at both photolysis wavelengths. The estimated photolysis rate constant of 2-nitrophenol was about twice that of NO2. I will discuss the importance of 2-nitrophenol gas phase photolysis as a potential source of OH and HONO in regions of high anthropogenic emissions.

Optical Properties of Boreal Region Biomass Burning Aerosols in Central Alaska and Seasonal Variation of Aerosol Optical Depth at an Arctic Coastal Site

NASA Technical Reports Server (NTRS)

Eck, T. F.; Holben, B. N.; Reid, J. S.; Sinyuk, A.; Hyer, E. J.; O'Neill, N. T.; Shaw, G. E.; VandeCastle, J. R.; Chapin, F. S.; Dubovik, O.;

Gallium nitride based logpile photonic crystals.

PubMed

Subramania, Ganapathi; Li, Qiming; Lee, Yun-Ju; Figiel, Jeffrey J; Wang, George T; Fischer, Arthur J

2011-11-09

We demonstrate a nine-layer logpile three-dimensional photonic crystal (3DPC) composed of single crystalline gallium nitride (GaN) nanorods, ∼100 nm in size with lattice constants of 260, 280, and 300 nm with photonic band gap in the visible region. This unique GaN structure is created through a combined approach of a layer-by-layer template fabrication technique and selective metal organic chemical vapor deposition (MOCVD). These GaN 3DPC exhibit a stacking direction band gap characterized by strong optical reflectance between 380 and 500 nm. By introducing a "line-defect" cavity in the fifth (middle) layer of the 3DPC, a localized transmission mode with a quality factor of 25-30 is also observed within the photonic band gap. The realization of a group III nitride 3DPC with uniform features and a band gap at wavelengths in the visible region is an important step toward realizing complete control of the electromagnetic environment for group III nitride based optoelectronic devices.

XUV generation from the interaction of pico- and nanosecond laser pulses with nanostructured targets

NASA Astrophysics Data System (ADS)

Barte, Ellie Floyd; Lokasani, Ragava; Proska, Jan; Stolcova, Lucie; Maguire, Oisin; Kos, Domagoj; Sheridan, Paul; O'Reilly, Fergal; Sokell, Emma; McCormack, Tom; O'Sullivan, Gerry; Dunne, Padraig; Limpouch, Jiri

2017-05-01

Laser-produced plasmas are intense sources of XUV radiation that can be suitable for different applications such as extreme ultraviolet lithography, beyond extreme ultraviolet lithography and water window imaging. In particular, much work has focused on the use of tin plasmas for extreme ultraviolet lithography at 13.5 nm. We have investigated the spectral behavior of the laser produced plasmas formed on closely packed polystyrene microspheres and porous alumina targets covered by a thin tin layer in the spectral region from 2.5 to 16 nm. Nd:YAG lasers delivering pulses of 170 ps (Ekspla SL312P )and 7 ns (Continuum Surelite) duration were focused onto the nanostructured targets coated with tin. The intensity dependence of the recorded spectra was studied; the conversion efficiency (CE) of laser energy into the emission in the 13.5 nm spectral region was estimated. We have observed an increase in CE using high intensity 170 ps Nd:YAG laser pulses as compared with a 7 ns pulse.

SO_2 Absorption Cross Sections and N_2 VUV Oscillator Strengths for Planetary Atmosphere Studies

NASA Astrophysics Data System (ADS)

Smith, Peter L.; Stark, G.; Rufus, J.; Pickering, J. C.; Cox, G.; Huber, K. P.

1998-09-01

The determination of the chemical composition of the atmosphere of Io from Hubble Space Telescope observations in the 190-220 nm wavelength region requires knowledge of the photoabsorption cross sections of SO_2 at temperatures ranging from about 110 K to 300 K. We are engaged in a laboratory program to measure SO_2 absorption cross sections with very high resolving power (lambda /delta lambda =~ 450,000) and at a range of temperatures appropriate to the Io atmosphere. Previous photoabsorption measurements, with lambda /delta lambda =~ 100,000, have been unable to resolve the very congested SO_2 spectrum, and, thus, to elucidate the temperature dependence of the cross sections. Our measurements are being performed at Imperial College, London, using an ultraviolet Fourier transform spectrometer. We will present our recently completed room temperature measurements of SO_2 cross sections in the 190-220 nm region and plans for extending these to ~ 195 K. Analyses of Voyager VUV occultation measurements of the N_2-rich atmospheres of Titan and Triton have been hampered by the lack of fundamental spectroscopic data for N_2, in particular, by the lack of reliable f-values and line widths for electronic bands of N_2 in the 80-100 nm wavelength region. We are continuing our program of measurements of band oscillator strengths for the many (approximately 100) N_2 bands between 80 and 100 nm. We report new f-values, derived from data obtained at the Photon Factory (Tsukuba, Japan) synchrotron radiation facility with lambda /delta lambda =~ 130,000, of 37 bands in the 80-86 nm region and 21 bands in the 90-95 nm region. We have also begun the compilation of a searchable archive of N_2 data on the World Wide Web; see http://cfa-www.harvard. edu/amp/data/n2/n2home.html. The archive, covering the spectroscopy of N_2 between 80 and 100 nm, will include published and unpublished (14) N_2, (14) N(15) N, and (15) N_2 line lists and spectroscopic identifications, excited state energy levels, band and line f-values, a summary of published band f-value and line width measurements, and a cross-referenced summary of the relevant N_2 literature.

[Resolving characteristic of CDOM by excitation-emission matrix spectroscopy combined with parallel factor analysis in the seawater of outer Yangtze Estuary in Autumn in 2010].

PubMed

Yan, Li-Hong; Chen, Xue-Jun; Su, Rong-Guo; Han, Xiu-Rong; Zhang, Chuan-Song; Shi, Xiao-Yong

2013-01-01

The distribution and estuarine behavior of fluorescent components of chromophoric dissolved organic matter in the seawater of outer Yangtze Estuary were determined by fluorescence excitation emission matrix spectra combined with parallel factor analysis. Six individual fluorescent components were identified by PARAFAC models, including three terrestrial humic-like components C1 [330 nm/390(430) nm], C2 (390 nm/480 nm), C3 (360 nm/440 nm), marine biological production component C5 (300 nm/400 nm) and protein-like components C4 (290 nm/350 nm) and C6 (275 nm/300 nm). The results indicated that C1, C2, and C3 showed a conservative mixing behavior in the whole estuarine region, especially in high-salinity region. And the fluorescence intensity proportion of C1 and C3 decreased with increase of salinity and fluorescence intensity proportion of C2 kept constant with increase of salinity in the whole estuarine region. While C4 showed conservative mixing behavior in low-salinity region and non-conservative mixing behavior in high-salinity region, and fluorescence intensity proportion of C4 increased with increase of salinity. However, C5 and C6 showed a non-conservative mixing behavior and fluorescence intensity proportion increased with increase of salinity in high-salinity region. Significantly spatial difference was recorded for CDOM absorption coefficient in the coastal region and in the open water areas with the highest value in coastal region and the lowest value in the open water areas. The scope of absorption coefficient and absorption slope was higher in coastal region than that in the open water areas. Significantly positive correlations were found between CDOM absorption coefficient and the fluorescence intensities of C1, C2, C3, and C4, but no significant correlation was found between C5 and C6, suggesting that the river inputs contributed to the coastal areas, while CDOM in the open water areas was affected by terrestrial inputs and phytoplankton degradation.

Picosecond time-resolved absorption and fluorescence dynamics in the artificial bacteriorhodopsin pigment BR6.11.

PubMed

Brack, T L; Delaney, J K; Atkinson, G H; Albeck, A; Sheves, M; Ottolenghi, M

1993-08-01

The picosecond molecular dynamics in an artificial bacteriorhodopsin (BR) pigment containing a structurally modified all-trans retinal chromphore with a six-membered ring bridging the C11=C12-C13 positions (BR6.11) are measured by picosecond transient absorption and picosecond time-resolved fluorescence spectroscopy. Time-dependent intensity and spectral changes in absorption in the 570-650-nm region are monitored for delays as long as 5 ns after the 7-ps, 573-nm excitation of BR6.11. Two intermediates, J6.11 and K6.11/1, both with enhanced absorption to the red (> 600 nm) of the BR6.11 spectrum are observed within approximately 50 ps. The J6.11 intermediate decays with a time constant of 12 +/- 3 ps to form K6.11/1. The K6.11/1 intermediate decays with an approximately 100-ps time constant to form a third intermediate, K6.11/2, which is observed through diminished 650-nm absorption (relative to that of K6.11/1). No other transient absorption changes are found during the remainder of the initial 5-ns period of the BR6.11 photoreaction. Fluorescence in the 650-900-nm region is observed from BR6.11, K6.11/1, and K6.11/2, but no emission assignable to J6.11 is found. The BR6.11 fluroescence spectrum has a approximately 725-nm maximum which is blue-shifted by approximately 15 nm relative to that of native BR-570 and is 4.2 +/- 1.5 times larger in intensity (same sample optical density). No differences in the profile of the fluorescence spectra of BR6.11 and the intermediates K6.11/1 and K6.11/2 are observed. Following ground-state depletion of the BR6.11 population, the time-resolved fluroescence intensity monitored at 725 nm increases with two time constants, 12 +/- 3 and approximately 100 ps, both of which correlate well with changes in the picosecond transient absorption data. The resonance Raman spectrum of ground-state BR6.11, measured with low-energy, 560-nm excitation, is significantly different from the spectrum of native BR-570, thus confirming that the picosecond transient absorption and picosecond time resolved fluorescence data are assignable to BR6.11 and its photoreaction alone and not to BR-570 reformed during there constitution process (<5% of the BR6.11 sample could be attributed to native BR-570).The J6.11 and K6.11 absorption and fluorescence data presented here are generally analogous to those measured for native J-625 and K-590, respectively, and therefore, the primary events in the BR6.11 photoreaction can be correlated with those in the native BR photocycle. The BR6.11 photoreaction, however, exhibits important differences including slower formation rates for J and K intermediates as well as the presence of a second K intermediate. These results demonstrate that the restricted motion in the C11=C12-C13 region of retinal found in BR6.11 does not greatly change the overall photoreaction mechanism,but does alter the rates at which processes occur.

Geomagnetically conjugate observation of plasma bubbles and thermospheric neutral winds at low latitudes

NASA Astrophysics Data System (ADS)

Fukushima, D.; Shiokawa, K.; Otsuka, Y.; Nishioka, M.; Kubota, M.; Tsugawa, T.; Nagatsuma, T.; Komonjinda, S.; Yatini, C. Y.

2015-03-01

This is the first paper that reports simultaneous observations of zonal drift of plasma bubbles and the thermospheric neutral winds at geomagnetically conjugate points in both hemispheres. The plasma bubbles were observed in the 630 nm nighttime airglow images taken by using highly sensitive all-sky airglow imagers at Kototabang, Indonesia (geomagnetic latitude (MLAT): 10.0°S), and Chiang Mai, Thailand (MLAT: 8.9°N), which are nearly geomagnetically conjugate stations, for 7 h from 13 to 20 UT (from 20 to 03 LT) on 5 April 2011. The bubbles continuously propagated eastward with velocities of 100-125 m/s. The 630 nm images at Chiang Mai and those mapped to the conjugate point of Kototabang fit very well, which indicates that the observed plasma bubbles were geomagnetically connected. The eastward thermospheric neutral winds measured by two Fabry-Perot interferometers were 70-130 m/s at Kototabang and 50-90 m/s at Chiang Mai. We compared the observed plasma bubble drift velocity with the velocity calculated from the observed neutral winds and the model conductivity, to investigate the F region dynamo contribution to the bubble drift velocity. The estimated drift velocities were 60-90% of the observed velocities of the plasma bubbles, suggesting that most of the plasma bubble velocity can be explained by the F region dynamo effect.

Effect of geomagnetic storm conditions on the equatorial ionization anomaly and equatorial temperature anomaly

NASA Astrophysics Data System (ADS)

Bharti, Gaurav; Bag, T.; Sunil Krishna, M. V.

2018-03-01

The effect of the geomagnetic storm on the equatorial ionization anomaly (EIA) and equatorial temperature anomaly (ETA) has been studied using the atomic oxygen dayglow emissions at 577.7 nm (OI 557.7 nm) and 732.0 nm (OII 732.0 nm). For the purpose of this study, four intense geomagnetic storms during the ascending phase of solar cycle 24 have been considered. This study is primarily based on the results obtained using photochemical models with necessary inputs from theoretical studies and experimental observations. The latest reaction rate coefficients, quantum yields and the corresponding cross-sections have also been incorporated in these models. The volume emission rate of airglow emissions has been calculated using the neutral densities from NRLMSISE-00 and charged densities from IRI-2012 model. The modeled volume emission rate (VER) for OI 557.7 nm shows a positive correlation with the Dst index at 150 km and negative correlation with Dst at 250 and 280 km altitudes. Latitudinal profile of the greenline emission rate at different altitudes show a distinct behaviour similar to what has been observed in EIA with crests on either sides of the equator. The EIA crests are found to show poleward movement in the higher altitude regions. The volume emission rate of 732.0 nm emission shows a strong enhancement during the main phase of the storm. The changes observed in the airglow emission rates are explained with the help of variations induced in neutral densities and parameters related to EIA and ETA. The latitudinal variation of 732.0 nm emission rate is correlated to the variability in EIA during the storm period.

A Study of Extreme Events in Subseasonal Forecasts Made by a High Resolution Version of the NCEP Climate Forecast System

NASA Astrophysics Data System (ADS)

Saha, S.; Vandendool, H. M.; Johansson, A.; Vintzileos, A.; Pan, H.; Thiaw, C.

2005-05-01

Actual estimations of the aerosol effect on the radiation budget are affected by a large uncertainties mainly due to the high inhomogeneity and variability of atmospheric aerosol, in terms of concentration, shape, size distribution, refractive index and vertical distribution. Long-term measurements of vertical profiles of aerosol optical properties are needed to reduce these uncertainties. At CNR-IMAA (40° 36'N, 15° 44' E, 760 m above sea level), a lidar system for aerosol study is operative since May 2000 in the framework of EARLINET (European Aerosol Research Lidar Network). Until August 2005, it provided independent measurements of aerosol extinction and backscatter at 355 nm and aerosol backscatter profiles at 532 nm. After an upgrade of the system, it provides independent measurements of aerosol extinction and backscatter profiles at 355 and 532 nm, and of aerosol backscatter profiles at 1064 nm and depolarization ratio at 532 nm. For these measurements, lidar ratio at 355 and 532 nm and Angstrom exponent profiles at 355/532 nm are also obtained. Starting on May 2000, systematic measurements are performed three times per week according to the EARLINET schedule and further measurements are performed in order to investigate particular events, like dust intrusions, volcanic eruptions and forest fires. A climatological study has been carried out in terms of the seasonal behavior of the PBL height and of the aerosol optical properties calculated inside the PBL itself. In the free troposphere, an high occurrences of Saharan dust intrusions (about 1 day of Saharan dust intrusion every 10 days) has been observed at CNR-IMAA because of the short distance from the Sahara region. During 6 years of observations, very peculiar cases of volcanic aerosol emitted by Etna volcano and aerosol released by large forest fires burning occurred in Alaska and Canada have been observed in the free troposphere at our site. Particular attention is devoted to lidar ratio both for the PBL and the free troposphere region, in order to study influences of aerosol modification/transportation processes on its values and its variability. ACKNOWLEDGMENTS The financial support of this work by the European Commission under grant RICA-025991 is gratefully acknowledged.

Michelson Interferometer for Global High-Resolution Thermospheric Imaging (MIGHTI): Instrument Design and Calibration

NASA Astrophysics Data System (ADS)

Englert, Christoph R.; Harlander, John M.; Brown, Charles M.; Marr, Kenneth D.; Miller, Ian J.; Stump, J. Eloise; Hancock, Jed; Peterson, James Q.; Kumler, Jay; Morrow, William H.; Mooney, Thomas A.; Ellis, Scott; Mende, Stephen B.; Harris, Stewart E.; Stevens, Michael H.; Makela, Jonathan J.; Harding, Brian J.; Immel, Thomas J.

2017-10-01

The Michelson Interferometer for Global High-resolution Thermospheric Imaging (MIGHTI) instrument was built for launch and operation on the NASA Ionospheric Connection Explorer (ICON) mission. The instrument was designed to measure thermospheric horizontal wind velocity profiles and thermospheric temperature in altitude regions between 90 km and 300 km, during day and night. For the wind measurements it uses two perpendicular fields of view pointed at the Earth's limb, observing the Doppler shift of the atomic oxygen red and green lines at 630.0 nm and 557.7 nm wavelength. The wavelength shift is measured using field-widened, temperature compensated Doppler Asymmetric Spatial Heterodyne (DASH) spectrometers, employing low order échelle gratings operating at two different orders for the different atmospheric lines. The temperature measurement is accomplished by a multichannel photometric measurement of the spectral shape of the molecular oxygen A-band around 762 nm wavelength. For each field of view, the signals of the two oxygen lines and the A-band are detected on different regions of a single, cooled, frame transfer charge coupled device (CCD) detector. On-board calibration sources are used to periodically quantify thermal drifts, simultaneously with observing the atmosphere. The MIGHTI requirements, the resulting instrument design and the calibration are described.

Enhancement in ferroelectric, pyroelectric and photoluminescence properties in dye doped TGS crystals

NASA Astrophysics Data System (ADS)

Sinha, Nidhi; Goel, Neeti; Singh, B. K.; Gupta, M. K.; Kumar, Binay

2012-06-01

Pure and dye doped (0.1 and 0.2 mol%) Triglycine Sulfate (TGS) single crystals were grown by slow evaporation technique. A pyramidal coloring pattern, along with XRD and FT-IR studies confirmed the dye doping. Decrease in dielectric constant and increase in Curie temperature (Tc) were observed with increasing doping concentration. Low absorption cut off (231 nm) and high optical transparency (>90%) resulting in large band gap was observed in UV-VIS studies. In addition, strong hyper-luminescent emission bands at 350 and 375 nm were observed in which the relative intensity were found to be reversed as a result of doping. In P-E hysteresis loop studies, a higher curie temperature and an improved and more uniform figure of merit over a large region of the ferroelectric phase were observed. The improved dielectric, optical and ferroelectric/pyroelectric properties make the dye doped TGS crystals better candidate for various opto- and piezo-electronics applications.

Static Electric Fields and Lightning Over Land and Ocean in Florida Thunderstorms

NASA Technical Reports Server (NTRS)

Wilson, J. G.; Cummins, K. L.; Simpson, A. A.; Hinckley, A.

2017-01-01

Natural cloud-to-ground (CG) lightning and the charge structure of the associated clouds behave differently over land and ocean. Existing literature has raised questions over the years on the behavior of thunderstorms and lightning over oceans, and there are still open scientific questions. We expand on the observational datasets by obtaining identical electric field observations over coastal land, near-shore, and deep ocean regions during both clear air and thunderstorm periods. Oceanic observations were obtained using two 3-meter NOAA buoys that were instrumented with Campbell Scientific electric field mills to measure the static electric fields. These data were compared to selected electric field records from the existing on-shore electric field mill suite of 31 sensors at Kennedy Space Center (KSC). CG lightning occurrence times, locations and peak current values for both on-shore and ocean were provided by the U.S. National Lightning Detection Network. The buoy instruments were first evaluated on-shore at the Florida coast, to calibrate field enhancements and to confirm proper behavior of the system in elevated-field environments. The buoys were then moored 20NM and 120NM off the coast of KSC in February (20NM) and August (120NM) 2014. Statistically larger CG peak currents were reported over the deep ocean for first strokes and for subsequent strokes with new contacts points. Storm-related static fields were significantly larger at both oceanic sites, likely due to decreased screening by nearby space charge. Time-evolution of the static field during storm development and propagation indicated weak or missing lower positive charge regions in most storms that initiated over the deep ocean, supporting one mechanism for the observed high peak currents in negative first strokes over the deep ocean. This project also demonstrated the practicality of off-shore electric field measurements for safety-related decision making at KSC.

The emission characteristics of uranium hexafluoride at high temperatures

NASA Technical Reports Server (NTRS)

Krascella, N. L.

1976-01-01

Relative emission measurements were made for UF6/Argon mixtures heated in a plasma torch over a range of temperatures from 800 to about 3600 K over a wavelength range from 80 to 600 nm. Total pressures were varied from 1 to approximately 1.7 atm. Similarly absorption measurements were carried out in the visible region from 420 to 580 nm over a temperature range from about 1000 to 1800 K. Total pressure for these measurements was 1.0 atm. The emission results exhibited relatively no emission at wavelengths below 250 nm over the range of temperatures investigated. At temperatures in excess of 1800 K an additional emission band centered at 310 nm appears and becomes more well defined at higher temperatures. Essentially no pressure effect was observed with respect to emission at pressures up to 1.7 atm.

1.6 μm microchip laser

NASA Astrophysics Data System (ADS)

Šulc, J.; Jelínková, H.; Ryba-Romanowski, W.; Lukasiewicz, T.

2009-03-01

Properties of new pulsed-diode-pumped Er:YVO4 and Er:YVO4+CaO microchip lasers working in an ``eye-safe'' spectral region were investigated. As a pumping source, a fiber coupled (core diameter-200 μm) laser diode emitting radiation at wavelength 976 nm was used. The laser diode was operating in pulsed regime with 3 ms pulse width, and 20 Hz repetition rate. The result obtained was 175 mW and 152 mW output peak power for the Er:YVO4 and Er:YVO4+CaO lasers, respectively. The maximal efficiency with respect to the absorbed power was ~ 5%. The laser emission for Er:YVO4 microchip was observed in detail in the range 1593 nm to 1604 nm with respect to pumping. However, for Er:YVO4+CaO crystal only 1604 nm was generated.

Ultrastructural networks in growth cones and neurites of cultured central nervous system neurons.

PubMed

Tsui, H C; Ris, H; Klein, W L

1983-09-01

We have examined growth cones and neurites of cultured central nervous system neurons by high-voltage electron microscopy. Embryonic chicken retina cells were cultured on polylysine-treated and Formvar-coated gold grids for 2-6 days, fixed, and critical point dried. Growth cones and neurites were examined as unembedded whole mounts. Three-dimensional images from stereo-pair electron micrographs of these regions showed a high degree of ultrastructural articulation, with distinct, non-tapering filaments (5-9 nm in diameter) joining both cytoskeletal and membranous components. In the central regions of growth cones, interconnected structures included microtubules, large membranous sacs (up to 400 nm), and irregular vesicles (25-75 nm). A denser filamentous network was prevalent at the edges of growth cones. This network, which frequently adjoined the surface membrane, linked vesicles of uniform size (35-40 nm). Such vesicles often were seen densely packed in growth cone protrusions that were about the size of small synaptic boutons. Prevalent structural interconnections within growth cones conceivably could play a logistic role in specific membrane assembly, intracellular transport, endocytosis, and secretion. Because such processes are not unique to growth cones, the extensive linkages we have observed may have implications for cytoplasmic structure in general.

Modeling of N2 and O optical emissions for ionosphere HF powerful heating experiments

NASA Astrophysics Data System (ADS)

Sergienko, T.; Gustavsson, B.

Analyses of experiments of F region ionosphere modification by HF powerful radio waves show that optical observations are very useful tools for diagnosing of the interaction of the probing radio wave with the ionospheric plasma Hitherto the emissions usually measured in the heating experiment have been the 630 0 nm and the 557 7 nm lines of atomic oxygen Other emissions for instance O 844 8 nm and N2 427 8 nm have been measured episodically in only a few experiments although the very rich optical spectrum of molecular nitrogen potentially involves important information about ionospheric plasma in the heated region This study addresses the modeling of optical emissions from the O and the N2 triplet states first positive second positive Vegard-Kaplan infrared afterglow and Wu-Benesch band systems excited under a condition of the ionosphere heating experiment The auroral triplet state population distribution model was modified for the ionosphere heating conditions by using the different electron distribution functions suggested by Mishin et al 2000 2003 and Gustavsson at al 2004 2005 Modeling results are discussed from the point of view of efficiency of measurements of the N2 emissions in future experiments

Spatial Heterodyne Observation of Water (SHOW) from a high altitude aircraft

NASA Astrophysics Data System (ADS)

Bourassa, A. E.; Langille, J.; Solheim, B.; Degenstein, D. A.; Letros, D.; Lloyd, N. D.; Loewen, P.

2017-12-01

The Spatial Heterodyne Observations of Water instrument (SHOW) is limb-sounding satellite prototype that is being developed in collaboration between the University of Saskatchewan, York University, the Canadian Space Agency and ABB. The SHOW instrument combines a field-widened SHS with an imaging system to observe limb-scattered sunlight in a vibrational band of water (1363 nm - 1366 nm). Currently, the instrument has been optimized for deployment on NASA's ER-2 aircraft. Flying at an altitude of 70, 000 ft the ER-2 configuration and SHOW viewing geometry provides high spatial resolution (< 500 m) limb-measurements of water vapor in the Upper troposphere and lower stratosphere region. During an observation campaign from July 15 - July 22, the SHOW instrument performed 10 hours of observations from the ER-2. This paper describes the SHOW measurement technique and presents the preliminary analysis and results from these flights. These observations are used to validate the SHOW measurement technique and demonstrate the sampling capabilities of the instrument.

VizieR Online Data Catalog: Abundances in the local region. I. G and K giants (Luck, 2015)

NASA Astrophysics Data System (ADS)

Luck, R. E.

2015-10-01

At the start of this program, the observation list for giants was set to sample the G/K giants of the local region out to about 100pc from the Sun in all directions. The region was subdivided into cubes that were 25pc on a side; from each sub-volume, appropriate stars were selected north of declination -30°. This sample yielded the 286 G/K giants found in Luck et al. 2007 (cat. J/AJ/133/2464). This data set was also augmented by the addition of numerous G/K giants, increasing the number in the 100pc volume to 594 stars. Because the volume selection criteria used in Luck et al. 2007 (cat. J/AJ/133/2464) formally extended out to 115pc, a more precise comparison is that the current sample has 740 stars out to the older limit. Additional stars from the Bright Star Catalog (Hoffleit & Jaschek, 1991bsc..book.....H) were added, driving the sample out to about 200pc. The spectral database was supplemented using the ELODIE and ESO Archives. The ESO addition adds the southern sky. The bulk of the northern stars were observed using the McDonald Observatory Struve Telescope and Sandiford Cassegrain Echelle Spectrograph. For the ELODIE and ESO data archives, a list of all stars available was obtained and spectral type for each from SIMBAD was retrieved. Stars having a spectral type of F, G, or K III were then processed. The ESO data derives from the HARPS and UVES spectrographs. Basic observational data for the program stars can be found in Table1, along with some derived quantities, such as distance. The primary source of observational data for this study is a set of high signal-to-noise ratio (S/N) spectra obtained during numerous observing runs between 1997 and 2010 at McDonald Observatory using the 2.1m Struve Telescope and the Sandiford Cassegrain Echelle Spectrograph. The spectra continuously cover a wavelength range from about 484 to 700nm, with a resolving power of about 60000. Typical S/N values for the spectra are in excess of 150. To enable cancellation of telluric lines, broad-lined B stars were regularly observed with S/N exceeding that of the program stars. The 726 stars observed with the Sandiford spectrograph are marked with an "S" in column "Sce" of Table1. A further 120 spectra were obtained from the ELODIE Archive. These echelle spectra are fully processed through order co-addition with a continuous wavelength span from about 400 to 680 nm and a resolution of 42000. Only spectra with S/N>50 were utilized in this analysis. An "E" in Table1, column "Sce", marks these stars. The ESO Archive was used to obtain spectra from the ESO 3.6m telescope and HARPS spectrograph. The HARPS spectra cover a continuous wavelength range from about 400 to 680nm with a native resolving power of 120000. To match the resolution of the Sandiford data and to increase the S/N of the data, these spectra were co-added to a resolution of 60000. Typical maximum S/N values (per pixel) for the spectra are in excess of 150. In Table1, column "Sce", these stars are marked with an "H." Spectra from the UVES spectrograph and VLT/UT2 were also utilized. These spectra are rather heterogeneous, having resolutions of 40000-80000 and non-continuous spectral coverages in the range 400-700nm. A number of the spectra from UVES stop at about 625nm, meaning that [O I] 630nm and Li I 670nm were not observed. In Table 1, "U" denotes the stars observed with UVES spectrograph. (5 data files).

Multispectral sensing of citrus young tree decline

NASA Technical Reports Server (NTRS)

Edwards, G. J.; Ducharme, E. P.; Schehl, T.

1975-01-01

Computer processing of MSS data to identify and map citrus trees affected by young tree decline is analyzed. The data were obtained at 1500-feet altitude in six discrete spectral bands covering regions from 0.53 to 1.3 millimicrons as well as from instrumental ground truths of tree crowns. Measurable spectral reflectance intensity differences are observed in the leaves of healthy and diseased trees, especially at wavelengths of 500 to 600 nm and 700 to 800 nm. The overall accuracy of the method is found to be 89%.

Quantum dots transparent display (QDs-TPD) using a liquid QDs layer and N2 barrier discharge

NASA Astrophysics Data System (ADS)

Kim, Hong Tak; Lee, Sung-Youp; Sohn, Sang Ho

2017-07-01

Quantum dots transparent display (QDs-TPD) was realized using a liquid QDs layer and N2 barrier discharge panel. In the N2 discharge, the 2nd+ lines of N2 in the range of 300 - 400 nm (C3Πu - B3Πg), and the 1st- lines of N2+ at 391.4 and 427.8 nm (B2Σu+ - X2 Σg+) were mainly observed, while the visible emission lines were rarely observed. This implies the N2 discharge is suitable for the excitation source of the QDs, due to the strong ultra-violet radiations and the weak visible emissions. The emission centers for red, green, and blue color in QDs-TPD were positioned at 452, 540, and 638 nm, respectively, and the N2 emission peaks were seldom observed in the visible region. The transmittance of QDs-TPD was approximately 40% in the visible region and the luminescence was about 70 cd/m2. The CIE (x, y) coordinates of red, green, and blue colors were (0.670, 0.309), (0.378, 0.640), and (0.183, 0.118), respectively, and the color gamut was 71% of a NTSC standard. Thus, the QDs-TPD is expected as a way for realizing the TPD, due to its good transparency, excellent visibility, wide viewing-angle, aesthetical design, low cost production, and good scalability to large sizes.

GREGOR Fabry-Pérot interferometer and its companion the blue imaging solar spectrometer

NASA Astrophysics Data System (ADS)

Puschmann, Klaus G.; Denker, Carsten; Balthasar, Horst; Louis, Rohan E.; Popow, Emil; Woche, Manfred; Beck, Christian; Seelemann, Thomas; Volkmer, Reiner

2013-08-01

The GREGOR Fabry-Pérot Interferometer (GFPI) is one of three first-light instruments of the German 1.5-m GREGOR solar telescope at the Observatorio del Teide, Tenerife, Spain. The GFPI allows fast narrow-band imaging and postfactum image restoration. The retrieved physical parameters will be a fundamental building block for understanding the dynamic sun and its magnetic field at spatial scales down to ˜50 km on the solar surface. The GFPI is a tunable dual-etalon system in a collimated mounting. It is designed for spectrometric and spectropolarimetric observations between 530-860 nm and 580-660 nm, respectively, and possesses a theoretical spectral resolution of R≈250,000. Large-format, high-cadence charged coupled device detectors with sophisticated computer hard- and software enable the scanning of spectral lines in time-spans equivalent to the evolution time of solar features. The field-of-view (FOV) of 50″×38″ covers a significant fraction of the typical area of active regions in the spectroscopic mode. In case of Stokes-vector spectropolarimetry, the FOV reduces to 25″×38″. The main characteristics of the GFPI including advanced and automated calibration and observing procedures are presented. Improvements in the optical design of the instrument are discussed and first observational results are shown. Finally, the first concrete ideas for the integration of a second FPI, the blue imaging solar spectrometer, are laid out, which will explore the blue spectral region below 530 nm.

RELEVANT ASPECTS OF MEDIUM-SCALE TIDs RELATED WITH MIDLATITUDES SPREAD- F OBSERVED BY ALL-SKY IMAGING SYSTEM IN THE SOUTHERN HEMISPHERE OVER TWO FULL SOLAR CYCLES

NASA Astrophysics Data System (ADS)

Pimenta, A. A.

2009-12-01

Using ground-based measurements we investigate the occurrence of medium-scale TIDs (MSTIDs) in the OI 630 nm nightglow emission all-sky images in the Brazilian low latitudes region related with midlatitude Spread F, during over two full solar cycles. The OI 630 nm images obtained during these periods show thermospheric dark band structures (MSTIDs) in low latitudes region propagating from southeast to northwest. These dark patches moved with average speed of about 50-200 m/s. Only during low solar activity period (LSA), ascending solar activity period (ASA) and descending solar activity period the DBS occurrences were observed in the OI630 nm nightglow emission all-sky images. However, during high solar activity (HAS) we didn’t observe the DBS in the all-sky images. In addition, ionospheric data over two stations in Brazil, one at the magnetic equator (São Luís) and the other close to the southern crest of the equatorial ionization anomaly (Cachoeira Paulista) were used to study this kind of structures during high and low solar activity periods. It should be pointed out that these thermospheric/ionospheric events are not related to geomagnetic disturbed conditions. In this work, we present and discuss this phenomenon in the Brazilian sector over two full solar cycles under different solar activity conditions. A possible mechanism for generation of these dark band structures is presented.

CRISM/HiRISE Correlative Spectroscopy

NASA Astrophysics Data System (ADS)

Seelos, F. P.; Murchie, S. L.; McGovern, A.; Milazzo, M. P.; Herkenhoff, K. E.

2011-12-01

The Mars Reconnaissance Orbiter (MRO) Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) and High Resolution Imaging Science Experiment (HiRISE) are complementary investigations with high spectral resolution and broad wavelength coverage (CRISM ~20 m/pxl; ~400 - 4000 nm, 6.55 nm sampling) and high spatial resolution with broadband color capability (HiRISE ~25 cm/pxl; ~500, 700, 900 nm band centers, ~200-300 nm FWHM). Over the course of the MRO mission it has become apparent that spectral variations in the IR detected by CRISM (~1000 nm - 4000 nm) sometimes correlate spatially with visible and near infrared 3-band color variations observed by HiRISE. We have developed a data processing procedure that establishes a numerical mapping between HiRISE color and CRISM VNIR and IR spectral data and provides a statistical evaluation of the uncertainty in the mapping, with the objective of extrapolating CRISM-inferred mineralogy to the HiRISE spatial scale. The MRO mission profile, spacecraft capabilities, and science planning process emphasize coordinated observations - the simultaneous observation of a common target by multiple instruments. The commonalities of CRISM/HiRISE coordinated observations present a unique opportunity for tandem data analysis. Recent advances in the systematic processing of CRISM hyperspectral targeted observations account for gimbal-induced photometric variations and transform the data to a synthetic nadir acquisition geometry. The CRISM VNIR (~400 nm - 1000 nm) data can then be convolved to the HiRISE Infrared, Red, and Blue/Green (IRB) response functions to generate a compatible CRISM IRB product. Statistical evaluation of the CRISM/HiRISE spatial overlap region establishes a quantitative link between the data sets. IRB spectral similarity mapping for each HiRISE color spatial pixel with respect to the CRISM IRB product allows a given HiRISE pixel to be populated with information derived from the coordinated CRISM observation, including correlative VNIR or IR spectral data, spectral summary parameters, or browse products. To properly characterize the quality and fidelity of the IRB correlation, a series of ancillary information bands that record the numerical behavior of the procedure are also generated. Prototype CRISM/HiRISE correlative data products have been generated for a small number of coordinated observation pairs. The resulting products have the potential to support integrated spectral and morphological mapping at sub-meter spatial scales. Such data products would be invaluable for strategic and tactical science operations on landed missions, and would allow observations from a landed platform to be evaluated in a CRISM-based spectral and mineralogical context.

1.319 μm excited intense 800 nm frequency upconversion emission in Tm{sup 3+}-doped fluorogermanate glass

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

Gouveia-Neto, A. S.; Vermelho, M. V. D.; Gouveia, E. A.

2015-11-23

Generation of near-infrared light within the first biological optical window via frequency upconversion in Tm{sup 3+}-doped PbGeO{sub 3}-PbF{sub 2}-CdF{sub 2} glass excited within the second biological window at 1.319 μm is reported. The upconversion emission at 800 nm is the sole light signal observed in the entire ultraviolet-visible-near-infrared spectral region making it possible obtaining high contrast imaging. The dependence of the 800 nm signal upon the sample temperature was investigated and results showed an increase by a factor of ×2.5 in the 30–280 °C range. Generation of detectable 690 nm for temperatures above 100 °C in addition to the intense 800 nm main signal was also observed.more » The proposed excitation mechanism for the 800 nm thulium emitting level is assigned to a multiphonon-assisted excitation from the ground-state {sup 3}H{sub 6} to the {sup 3}H{sub 5} excited-state level, a rapid relaxation to the {sup 3}F{sub 4} level and followed by an excited-state absorption of the pump photons mediated by multiphonons connecting the {sup 3}F{sub 4} level to the {sup 3}H{sub 4} emitting level.« less

Fine structure of meiotic prophase chromosomes and modified synaptonemal complexes in diploid and triploid Rhoeo spathacea.

PubMed

Lin, Y J

1979-06-01

The synaptonemal complex (SC) in the diploid Rhoeo consists of 2 amorphous lateral elements, each about 46.0 nm thick, and one amorphous central element about 30.0 nm thick. The central region is about 115.0 nm wide. SC in the triploid have essentially the same dimensions as those of the diploid; both lateral (46.0 nm) and central (30.0 nm) elements are amorphous, and the central region is about 117.5 nm wide. The coil, observed in both diploid and triploid, is a modified short segment of SC with several twists at the end of a synapsed bivalent that is attached to the nuclear membrane. Serial sections in a diploid cell reveal that a coil extends inwards about 3.5 micron from the nuclear membrane and makes a complete turn at a distance of every 0.5 micron. There is a correlation between the modified ends of SC and terminal chiasmata in Rhoeo. The coils might have a positive role in the process of crossing over, or alternatively might be involved in ring formation by holding chromosome ends together while chiasmata are not involved. SC are present in chromocentres of both diploid and triploid. Chromocentres in diploid and triploid are indistinguishable, and appear to be formed from the aggregation of pericentromeric heterochromatin as a result of translocations which occured close to the centromeres. 3-dimensional hypothetical pachytene configuration of the diploid is presented.

Eu/Tb codoped spindle-shaped fluorinated hydroxyapatite nanoparticles for dual-color cell imaging

NASA Astrophysics Data System (ADS)

Ma, Baojin; Zhang, Shan; Qiu, Jichuan; Li, Jianhua; Sang, Yuanhua; Xia, Haibing; Jiang, Huaidong; Claverie, Jerome; Liu, Hong

2016-06-01

Lanthanide doped fluorinated hydroxyapatite (FAp) nanoparticles are promising cell imaging nanomaterials but they are excited at wavelengths which do not match the light sources usually found in a commercial confocal laser scanning microscope (CLSM). In this work, we have successfully prepared spindle-shaped Eu/Tb codoped FAp nanoparticles by a hydrothermal method. Compared with single Eu doped FAp, Eu/Tb codoped FAp can be excited by a 488 nm laser, and exhibit both green and red light emission. By changing the amounts of Eu and Tb peaks, the emission in the green region (500-580 nm) can be decreased to the benefit of the emission in the red region (580-720 nm), thus reaching a balanced dual color emission. Using MC3T3-E1 cells co-cultured with Eu/Tb codoped FAp nanoparticles, it is observed that the nanoparticles are cytocompatible even at a concentration as high as 800 μg ml-1. The Eu/Tb codoped FAp nanoparticles are located in the cytoplasm and can be monitored by dual color--green and red imaging with a single excitation light at 488 nm. At a concentration of 200 μg ml-1, the cytoplasm is saturated in 8 hours, and Eu/Tb codoped FAp nanoparticles retain their fluorescence for at least 3 days. The cytocompatible Eu/Tb codoped FAp nanoparticles with unique dual color emission will be of great use for cell and tissue imaging.Lanthanide doped fluorinated hydroxyapatite (FAp) nanoparticles are promising cell imaging nanomaterials but they are excited at wavelengths which do not match the light sources usually found in a commercial confocal laser scanning microscope (CLSM). In this work, we have successfully prepared spindle-shaped Eu/Tb codoped FAp nanoparticles by a hydrothermal method. Compared with single Eu doped FAp, Eu/Tb codoped FAp can be excited by a 488 nm laser, and exhibit both green and red light emission. By changing the amounts of Eu and Tb peaks, the emission in the green region (500-580 nm) can be decreased to the benefit of the emission in the red region (580-720 nm), thus reaching a balanced dual color emission. Using MC3T3-E1 cells co-cultured with Eu/Tb codoped FAp nanoparticles, it is observed that the nanoparticles are cytocompatible even at a concentration as high as 800 μg ml-1. The Eu/Tb codoped FAp nanoparticles are located in the cytoplasm and can be monitored by dual color--green and red imaging with a single excitation light at 488 nm. At a concentration of 200 μg ml-1, the cytoplasm is saturated in 8 hours, and Eu/Tb codoped FAp nanoparticles retain their fluorescence for at least 3 days. The cytocompatible Eu/Tb codoped FAp nanoparticles with unique dual color emission will be of great use for cell and tissue imaging. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr02137a

Photodetachment of electrons from amide and arsenide ions - The electron affinities of NH2., and AsH2.

NASA Technical Reports Server (NTRS)

Smyth, K. C.; Brauman, J. I.

1972-01-01

The relative cross section for the gas-phase photodetachment of electrons has been determined for NH2(-) in the wavelength region of 1195 to 1695 nm and for AsH2(-) in the region from 620 to 1010 nm. An ion cyclotron resonance spectrometer was used to generate, trap, and detect negative ions. A 1000-W xenon arc lamp with a grating monochromator was used as the light source, except for one series of experiments in which a tunable laser was employed. Single sharp thresholds were observed in both cross sections, and the following electron affinity values were determined: 0.744 (plus or minus 0.022) eV for NH2. and 1.27 (plus or minus 0.03) eV for AsH2.

Time-resolved photoluminescence measurements of InP/ZnS quantum dots

NASA Astrophysics Data System (ADS)

Thi Thuy, Pham; Thi Dieu Thuy, Ung; Chi, Tran Thi Kim; Phuong, Le Quang; Liem, Nguyen Quang; Li, Liang; Reiss, Peter

2009-09-01

This paper reports the results on the time-resolved photoluminescence study of InP/ZnS core/shell quantum dots. The ZnS shell played a decisive role to passivate imperfections on the surface of InP quantum dots, consequently giving rise to a strong enhancement of the photoluminescence from the InP core. Under appropriate excitation conditions, not only the emission from the InP core but also that from the ZnS shell was observed. The emission peak in InP core quantum dots varied as a function of quantum dots size, ranging in the 600 - 700 nm region; while the ZnS shell showed emission in the blue region around 470 nm, which is interpreted as resulting from defects in ZnS.

The 67P nucleus composition and temporal variations observed by the OSIRIS cameras onboard Rosetta

NASA Astrophysics Data System (ADS)

Fornasier, Sonia; Barucci, Maria Antonietta; Feller, Clement; Deshapriya, Prasanna J. D.; Pommerol, Antoine; Lara, Luisa; Oklay, Nilda; A'Hearn, Mike; Davidsson, Bjorn; Perna, Davide; Sierks, Holger

2015-11-01

Since August 2014, the comet 67P/Churyumov-Gerasimenko has been mapped by the NAC and WAC cameras of the OSIRIS imaging system in the 250-1000 nm wavelength range. OSIRIS got the most detailed maps at the highest spatial resolution of a comet nucleus surface. Here we report on the colors and spectrophotometry of the whole 67P nucleus from images acquired since the first Rosetta bound orbits in August 2014 up to the comet perihelion passage. Globally, the nucleus shows a red spectral behavior and it has spectrophotometric properties similar to those of bare cometary nuclei, of primitive D-type asteroids such us Jupiter Trojans, and of the moderately red Transneptunians. No clear absorption bands have been identified yet in the UV-VIS-NIR range, except for a potential absorption centered at 290 nm, possibly due to SO2 ice. The nucleus shows an important phase reddening, with disk-averaged spectral slopes increasing from 11%/(100 nm) to 16%/(100 nm) in the 1.3-54° phase angle range. On the basis of the spectral slope, we identified three different groups of regions, characterized by a low, medium, and high spectral slope, respectively. The three groups are distributed everywhere on the nucleus, with no evident distinction between the two lobes of the comet. The comet southern hemisphere, that has been observed by Rosetta since April 2015, shows a lack of spectrally red regions associated to the absence of wide spread smooth or dust covered terrains. Several local bright and spectrally blue patches have been identified on the nucleus and attributed to exposed water ice on the surface. In particular we observed big (> 1500 m2) bright ice rich areas in the southern hemisphere which completely sublimated in a few weeks. We see evidence of very bright patches in the NUV-blue region close to the morning shadows that are compatible with the presence of frosts/ices. These patches disappear when fully illuminated by the Sun indicating that important processes of sublimation and recondensation of volatiles are taking place on the nucleus.

Correlating Metastable-Atom Density, Reduced Electric Field, and Electron Energy Distribution in the Initiation, Transient, and Post-Transient Stages of a Pulsed Argon Discharge

NASA Astrophysics Data System (ADS)

Franek, James B.

Argon emission lines, particularly those in the near-infrared region (700-900nm), are used to determine plasma properties in low-temperature, partially ionized plasmas to determine effective electron temperature [Boffard et al., 2012], and argon excited state density [Boffard et al., 2009] using appropriately assumed electron energy distributions. While the effect of radiation trapping influences the interpretation of plasma properties from emission-line ratio analysis, eliminating the need to account for these effects by directly observing the 3px-to-1sy transitions [ Boffard et al., 2012] is preferable in most cases as this simplifies the analysis. In this dissertation, a 1-Torr argon, pulsed positive column in a hollow-cathode discharge is used to study the correlation between four quantities: 420.1-419.8nm emission-line ratio, metastable-atom density, reduced electric field, and electron energy distribution. The extended coronal model is used to acquire an expression for 420.1-419.8nm emission-line ratio, which is sensitive to direct electron-impact excitation of argon excited states as well as stepwise electron-impact excitation of argon excited states for the purpose of inferring plasma quantities from experimental measurements. Initial inspection of the 420.1-419.8nm emission-line ratio suggests the pulse may be empirically divided into three distinct stages labelled the Initiation Stage, Transient Stage, and Post-Transient stage. Using equilibrium electron energy distributions from simulation to deduce excitation rates [Adams et al., 2012] in the extended coronal model affords agreement between predicted and observed metastable density in the Post-Transient stage of the discharge [Franek et al., 2015]. Applying this model-assisted diagnostic technique to the characterization of plasma systems utilizing lower-resolution spectroscopic systems is not straightforward, however, as the 419.8nm and 420.1nm emission-line profiles are convolved and become insufficiently resolved for treating the convolution as two separate emission-lines. To remedy this, the argon 425.9nm emission-line is evaluated as a proxy for the 419.8 nm emission-line. Both emission-lines (419.8nm and 425.9nm) are attributed to direct excitation from the argon ground state. The intensity of the 425.9nm emission-line is compared to the intensity of the 419.8nm emission-line over a range of plasma conditions to infer the same plasma quantities from similar experimental measurements. Discrepancies between the observed intensities of the emission-lines (419.8nm, 425.9nm) are explained by electron-impact cross-sections of their parent states. It is shown that the intensity of the argon 425.9nm emission-line is similar to that of the 419.8nm emission-line. The difference between the observed emission lines (425.9nm, 419.8nm) is attributed to the electron energy distribution in the plasma.

Tuning all-Optical Analog to Electromagnetically Induced Transparency in nanobeam cavities using nanoelectromechanical system.

PubMed

Shi, Peng; Zhou, Guangya; Deng, Jie; Tian, Feng; Chau, Fook Siong

2015-09-29

We report the observations of all-optical electromagnetically induced transparency in nanostructures using waveguide side-coupled with photonic crystal nanobeam cavities, which has measured linewidths much narrower than individual resonances. The quality factor of transparency resonance can be 30 times larger than those of measured individual resonances. When the gap between cavity and waveguide is reduced to 10 nm, the bandwidth of destructive interference region can reach 10 nm while the width of transparency resonance is 0.3 nm. Subsequently, a comb-drive actuator is introduced to tune the line shape of the transparency resonance. The width of the peak is reduced to 15 pm and the resulting quality factor exceeds 10(5).

Conductance enhancement of InAs/InP heterostructure nanowires by surface functionalization with oligo(phenylene vinylene)s.

PubMed

Schukfeh, Muhammed Ihab; Storm, Kristian; Mahmoud, Ahmed; Søndergaard, Roar R; Szwajca, Anna; Hansen, Allan; Hinze, Peter; Weimann, Thomas; Svensson, Sofia Fahlvik; Bora, Achyut; Dick, Kimberly A; Thelander, Claes; Krebs, Frederik C; Lugli, Paolo; Samuelson, Lars; Tornow, Marc

2013-05-28

We have investigated the electronic transport through 3 μm long, 45 nm diameter InAs nanowires comprising a 5 nm long InP segment as electronic barrier. After assembly of 12 nm long oligo(phenylene vinylene) derivative molecules onto these InAs/InP nanowires, we observed a pronounced, nonlinear I-V characteristic with significantly increased currents of up to 1 μA at 1 V bias, for a back-gate voltage of 3 V. As supported by our model calculations based on a nonequilibrium Green Function approach, we attribute this effect to charge transport through those surface-bound molecules, which electrically bridge both InAs regions across the embedded InP barrier.

Ion beam synthesis of ZrC{sub x}O{sub y} nanoparticles in cubic zirconia

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

Velişa, Gihan, E-mail: gihan@tandem.nipne.ro; Horia Hulubei National Institute for Physics and Nuclear Engineering, P.O.B. MG-6, 077125 Magurele; Mylonas, Stamatis

2016-04-28

{110}-oriented yttria-stabilized zirconia single crystals have been implanted with low-energy C ions in an axial direction, at room temperature and at 550 °C. Room temperature ion implantation generated a damage layer that contains the expected dislocation loop clusters. Strikingly, the high temperature implantation produced zirconium oxycarbide nanoparticles (ZrC{sub x}O{sub y}) at a shallow depth in the yttria-stabilized cubic zirconia crystal, with a diameter in the range of 4–10 nm. Moreover, in the high concentration region of implanted C ions, between 100 and 150 nm below the surface, a number of large precipitates, up to 20 nm, were observed.

Comparisons of Airborne HSRL and Modeled Aerosol Profiles

NASA Astrophysics Data System (ADS)

Ferrare, R. A.; Burton, S. P.; Hostetler, C. A.; Hair, J. W.; Ismail, S.; Rogers, R. R.; Notari, A.; Berkoff, T.; Butler, C. F.; Collins, J. E., Jr.; Fenn, M. A.; Scarino, A. J.; Clayton, M.; Mueller, D.; Chemyakin, E.; Fast, J. D.; Berg, L. K.; Randles, C. A.; Colarco, P. R.; daSilva, A.

2014-12-01

Aerosol profiles derived from a regional and a global model are compared with aerosol profiles acquired by NASA Langley Research Center (LaRC) airborne High Spectral Resolution Lidars (HSRLs) during recent field missions. We compare simulated aerosol profiles obtained from the WRF-Chem regional model with those measured by the airborne HSRL-2 instrument over the Atlantic Ocean east of Cape Cod in July 2012 during the Department of Energy Two-Column Aerosol Project (TCAP). While deployed on the LaRC King Air during TCAP, HSRL-2 acquired profiles of aerosol extinction at 355 and 532 nm, as well as aerosol backscatter and depolarization at 355, 532, and 1064 nm. Additional HSRL-2 data products include profiles of aerosol type, mixed layer depth, and aerosol microphysical parameters (e.g. effective radius, concentration). The HSRL-2 and WRF-Chem aerosol profiles are compared along the aircraft flight tracks. HSRL-2 profiles acquired during the NASA Deriving Information on Surface Conditions from COlumn and VERtically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) mission over Houston during September 2013 are compared with the NASA Goddard Earth Observing System global model, version 5 (GEOS-5) profiles. In addition to comparing backscatter and extinction profiles, the fraction of aerosol extinction and optical thickness from various aerosol species from GEOS-5 are compared with aerosol extinction and optical thickness contributed by aerosol types derived from HSRL-2 data. We also compare aerosol profiles modeled by GEOS-5 with those measured by the airborne LaRC DIAL/HSRL instrument during August and September 2013 when it was deployed on the NASA DC-8 for the Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) mission. DIAL/HSRL measured extinction (532 nm), backscatter (532 and 1064 nm), and depolarization profiles (532 and 1064 nm) in both nadir and zenith directions during long transects over the continental United States. DIAL/HSRL measurements acquired during SEAC4RS allow comparisons with GEOS-5 simulations of forest fire smoke over the western U.S. The fraction of aerosol extinction attributed to dust derived from the DIAL/HSRL depolarization measurements are compared with the corresponding GEOS-5 dust simulations.

Wide spectral range multiple orders and half-wave achromatic phase retarders fabricated from two lithium tantalite single crystal plates

NASA Astrophysics Data System (ADS)

Emam-Ismail, M.

2015-11-01

In a broad spectral range (300-2500 nm), we report the use of channeled spectra formed from the interference of polarized white light to extract the dispersion of the phase birefringence Δnp(λ) of the x- and y-cuts of lithium tantalite (LiTaO3:LT) plates. A new method named as wavenumber difference method is used to extract the spectral behavior of the phase birefringence of the x- and y- cuts of LT plates. The correctness of the obtained birefringence data is confirmed by using Jones vector method through recalculating the plates thicknesses. The spectral variation of the phase birefringence Δnp(λ) of the x- and y-cuts of LT plates is fitted to Cauchy dispersion function with relative error for both x- and y-cuts of order 2.4×10-4. The group birefringence dispersion Δng (λ) of the x- and y-cuts of LT plates is also calculated and fitted to Ghosh dispersion function with relative error for both x- and y-cuts of order 2.83×10-4. Furthermore, the phase retardation introduced by the x- and y-cuts of LT plates is also calculated. It is found that the amount of phase retardation confirms that the x- and y-cuts of LT plates can act as a multiple order half- and quarter-wave plates working at many different wavelengths through the spectral range 300-2500 nm. For the x- and y-cuts of LT plates, a large difference between group and phase birefringence is observed at a short wavelength (λ=300 nm); while such difference progressively diminished at longer wavelength (λ=2000 nm). In the near infrared region (NIR) region (700-2500 nm), a broad spectral full width at half maximum (FWHM) is observed for either x- or y-cut of LT plate which can act as if it is working as a zero order wave plate. Finally, an achromatic half-wave plate working at 598 nm and covering a wide spectral range (300-900 nm) is demonstrated experimentally by combining both x- and y-cuts of LT plates.

Identification of vacancy-oxygen complexes in oxygen-implanted silicon probed with slow positrons

NASA Astrophysics Data System (ADS)

Fujinami, M.; Miyagoe, T.; Sawada, T.; Suzuki, R.; Ohdaira, T.; Akahane, T.

2004-04-01

Defects and their annealing behavior for low (2×1015/cm2) and high (1.7×1018/cm2) doses of 180 keV oxygen-implanted silicon have been investigated by the coincidence Doppler broadening (CDB) and lifetime measurements in variable-energy positron annihilation spectroscopy. In the low-dose sample, divacancies are induced throughout the entire implantation region. In the vacancy-oxygen coexisting region (300-500 nm depths), by raising the annealing temperature to 600 °C, vacancy-oxygen VxOy complexes with one vacant site are formed and, simultaneously, the migration of oxygen begins to takes place. In the vacancy-rich region (-200 nm depths), the evolution of simple vacancy clusters to V4 is mainly observed below 600 °C. From CDB and lifetime measurements, it has been proven that after annealing at 800 °C, the VxOy complexes are formed throughout the implanted region and they contain four vacant sites and a high ratio of y to x. On the other hand, high-dose implantation at 550 °C produces the VxOy complexes with a lifetime of a 430 ps in the near-surface region (less than 200 nm deep) and annealing at 1100 °C leads to the highest ratio of y to x. These complexes cannot be annealed out even by annealing at 1350 °C, and their structure is found to be very similar to that for the electron-irradiated amorphous SiO2.

Real-time photoacoustic imaging of rat deep brain: hemodynamic responses to hypoxia

NASA Astrophysics Data System (ADS)

Kawauchi, Satoko; Iwazaki, Hideaki; Ida, Taiichiro; Hosaka, Tomoya; Kawaguchi, Yasushi; Nawashiro, Hiroshi; Sato, Shunichi

2013-03-01

Hemodynamic responses of the brain to hypoxia or ischemia are one of the major interests in neurosurgery and neuroscience. In this study, we performed real-time transcutaneous PA imaging of the rat brain that was exposed to a hypoxic stress and investigated depth-resolved responses of the brain, including the hippocampus. A linear-array 8ch 10-MHz ultrasonic sensor (measurement length, 10 mm) was placed on the shaved scalp. Nanosecond, 570-nm and 595- nm light pulses were used to excite PA signals indicating cerebral blood volume (CBV) and blood deoxygenation, respectively. Under spontaneous respiration, inhalation gas was switched from air to nitrogen, and then reswitched to oxygen, during which real-time PA imaging was performed continuously. High-contrast PA signals were observed from the depth regions corresponding to the scalp, skull, cortex and hippocampus. After starting hypoxia, PA signals at 595 nm increased immediately in both the cortex and hippocampus for about 1.5 min, showing hemoglobin deoxygenation. On the other hand, PA signals at 570 nm coming from these regions did not increase in the early phase but started to increase at about 1.5 min after starting hypoxia, indicating reactive hyperemia to hypoxia. During hypoxia, PA signals coming from the scalp decreased transiently, which is presumably due to compensatory response in the peripheral tissue to preserve blood perfusion in the brain. The reoxygenation caused a gradual recovery of these PA signals. These findings demonstrate the usefulness of PA imaging for real-time, depth-resolved observation of cerebral hemodynamics.

BrO, OClO and HCHO Observations from the EOS-Aura Ozone Monitoring Instrument

NASA Astrophysics Data System (ADS)

Kurosu, T. P.; Chance, K.; Sioris, C. E.

2004-12-01

The Ozone Monitoring Instrument (OMI) was launched on 15 July 2004 on the EOS-Aura platform into a sun-synchronous, polar orbit with an equator crossing time of 13:45h (ascending node). OMI is a nadir-viewing near-UV/Visible spectrometer, covering the spectral region of 270 nm to 500 nm with a resolution between 0.45 nm and 1.0 nm and a nominal ground footprint of 13 km×24 km. Global coverage is achieved in one day. The very high spatial resolution of OMI measurements sets a new standard for trace gas and air quality monitoring from space. Combined with daily global coverage, this significantly advances our ability to answer outstanding questions on air pollution, including the determination of BrO sources in mid and low latitudes, BrO--O3 anti-correlations as a function of latitude, and the production of formaldehyde in cities of the developing world. We introduce the design of the OMI operational retrieval algorithm for BrO, OClO and HCHO. Based on a direct (non-DOAS) non-linear fitting approach, it includes wavelength calibration for radiances and irradiances, an undersampling correction, and the characterization of the instrument slit function. We will present results of BrO (global distribution, and tropospheric contributions from the break-up ice shelves and volcanic emissions), formaldehyde (over regions of isoprene emissions, forest fires, and heavy urban pollution), and, contingent upon the availability of suitable OMI observations, OClO (under ozone hole conditions). Where available, trace gas retrievals from OMI will be compared to results from the SCIAMACHY and GOME instruments.

First Evaluation of the CCAM Aerosol Simulation over Africa: Implications for Regional Climate Modeling

NASA Astrophysics Data System (ADS)

Horowitz, H.; Garland, R. M.; Thatcher, M. J.; Naidoo, M.; van der Merwe, J.; Landman, W.; Engelbrecht, F.

2015-12-01

An accurate representation of African aerosols in climate models is needed to understand the regional and global radiative forcing and climate impacts of aerosols, at present and under future climate change. However, aerosol simulations in regional climate models for Africa have not been well-tested. Africa contains the largest single source of biomass-burning smoke aerosols and dust globally. Although aerosols are short-lived relative to greenhouse gases, black carbon in particular is estimated to be second only to carbon dioxide in contributing to warming on a global scale. Moreover, Saharan dust is exported great distances over the Atlantic Ocean, affecting nutrient transport to regions like the Amazon rainforest, which can further impact climate. Biomass burning aerosols are also exported from Africa, westward from Angola over the Atlantic Ocean and off the southeastern coast of South Africa to the Indian Ocean. Here, we perform the first extensive quantitative evaluation of the Conformal-Cubic Atmospheric Model (CCAM) aerosol simulation against monitored data, focusing on aerosol optical depth (AOD) observations over Africa. We analyze historical regional simulations for 1999 - 2012 from CCAM consistent with the experimental design of CORDEX at 50 km global horizontal resolution, through the dynamical downscaling of ERA-Interim data reanalysis data, with the CMIP5 emissions inventory (RCP8.5 scenario). CCAM has a prognostic aerosol scheme for organic carbon, black carbon, sulfate, and dust, and non-prognostic sea salt. The CCAM AOD at 550nm was compared to AOD (observed at 440nm, adjusted to 550nm with the Ångström exponent) from long-term AERONET stations across Africa. Sites strongly impacted by dust and biomass burning and with long continuous records were prioritized. In general, the model captures the monthly trends of the AERONET data. This presentation provides a basis for understanding how well aerosol particles are represented over Africa in regional climate modeling and the potential impact on climate predictions, and is the first large scale climate model-measurement verification of aerosols over Africa that we are aware of. CCAM is widely used for regional climate modeling applications, and we also discuss further improvements to the aerosol parameterizations based on our results.

UV excited downconversion luminescence properties of Eu3+: NaZnPO4 phosphors

NASA Astrophysics Data System (ADS)

Mukhopadhyay, Lakshmi; Rai, Vineet Kumar

2018-05-01

The structural and optical properties of Eu3+: NaZnPO4 phosphors prepared by chemical coprecipitation method have been studied. The phase formation and morphology of the phosphors have been confirmed by the X-ray diffraction (XRD) and Field emission scanning electron microscopy (FESEM) analysis. The downconversion emission spectra upon 392 nm excitation exhibit five emission bands centred at ˜ 575 nm, ˜ 590 nm, ˜ 612 nm, ˜ 660 nm and ˜ 702 nm corresponding to the 5D0→7F0, 5D0→7F1, 5D0→7F2, 5D0→7F3 and 5D0→7F4 transitions of Eu3+ ions respectively. The observed downconversion emission peaks can be explained with the help of suitable energy level diagram. The CIE chromaticity diagram shows the purity of the emitted colour from the prepared phosphors. The present phosphors emit in intense red region which shows the applicability of the phosphors in red light emitting display devices.

High-resolution, vacuum-ultraviolet absorption spectrum of boron trifluoride

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

Hughes, Patrick P.; Thompson, Alan K.; Vest, Robert E.

2014-11-21

In the course of investigations of thermal neutron detection based on mixtures of {sup 10}BF{sub 3} with other gases, knowledge was required of the photoabsorption cross sections of {sup 10}BF{sub 3} for wavelengths between 135 and 205 nm. Large discrepancies in the values reported in existing literature led to the absolute measurements reported in this communication. The measurements were made at the SURF III Synchrotron Ultraviolet Radiation Facility at the National Institute of Standards and Technology. The measured absorption cross sections vary from 10{sup −20} cm{sup 2} at 135 nm to less than 10{sup −21} cm{sup 2} in the regionmore » from 165 to 205 nm. Three previously unreported absorption features with resolvable structure were found in the regions 135–145 nm, 150–165 nm, and 190–205 nm. Quantum mechanical calculations, using the TD-B3LYP/aug-cc-pVDZ variant of time-dependent density functional theory implemented in Gaussian 09, suggest that the observed absorption features arise from symmetry-changing adiabatic transitions.« less

Tunable Photonic Band Gap of PS-b-P2VP Lamellar Film Using Metal Ions and pH Gradation.

PubMed

Baek, Young-Bin; Choi, Soo-Hyung; Shin, Dong-Myung

2015-02-01

Optical properties of photonic crystal film were investigated by tuning photonic band gap (PBG). The lamellar-forming photonic films were prepared by nearly symmetric poly(styrene-b-2-vinyl pyridine) (PS-b-P2VP) block copolymers. Molecular weight of PS block and P2VP block is 52 kg/mol, and 57 kg/mol, respectively. When submerged in water, the lamellar films were swollen and show Bragg reflection in visible light region. We observed that the reflection color can be tuned by ion concentration (e.g., hydrogen or metal ion) in water. The higher concentration of hydrogen ion in solution, the longer reflectance wavelength shifted (from 537 nm to 743 nm). In addition, max-reflectance wavelength is dependent on both metal ion and the concentration. The max-reflectance wavelength is shifted from 653 nm (i.e., in water without ion) to 430 nm, 465 nm, and 505 nm for 120 mM of Ca2+, Fe2+, and Cu2+, respectively. Therefore, we can control the photonic band gap of photonic devices by changing the condition of swelling solution.

Growth directions of C8-BTBT thin films during drop-casting

NASA Astrophysics Data System (ADS)

Iizuka, Naoki; Zanka, Tomohiko; Onishi, Yosuke; Fujieda, Ichiro

2016-02-01

Because charge transport in a single crystal is anisotropic, control of its orientation is important for enhancing electrical characteristics and reducing variations among devices. For growing an organic thin film, a solution process such as inkjet printing offers advantages in throughput. We have proposed to apply an external temperature gradient during drop-casting and to control the direction of solvent evaporation. In experiment, a temperature gradient was generated in a bare Si substrate by placing it on a Si plate bridging two heat stages. When a solution containing 2,7-dioctyl [1]benzothieno[3,2-b]benzothiophene (C8-BTBT) was dropped on the substrate, evaporation started at the hotter side of the droplet and proceeded toward the colder side. The front line of the liquid was not pinned and the solution extended toward the colder region. As a result, a thin film was formed in a 7mm-long region. The peripheral region of the film was significantly thicker due to the coffee ring effect. The surface of the rest of the film was mostly smooth and terrace structures with 2.6nm steps were observed. The step roughly corresponds to the length of the C8-BTBT molecule. The film thickness varied from 20nm to 50nm over the distance of 3mm. Another film was grown on a glass substrate under a similar condition. Observation of the film with a polarizing microscope revealed that fan-shaped domains were formed in the film and that their optical axes were mostly along the directions of the solvent evaporation.

Breakdown of Shape Memory Effect in Bent Cu-Al-Ni Nanopillars: When Twin Boundaries Become Stacking Faults.

PubMed

Liu, Lifeng; Ding, Xiangdong; Sun, Jun; Li, Suzhi; Salje, Ekhard K H

2016-01-13

Bent Cu-Al-Ni nanopillars (diameters 90-750 nm) show a shape memory effect, SME, for diameters D > 300 nm. The SME and the associated twinning are located in a small deformed section of the nanopillar. Thick nanopillars (D > 300 nm) transform to austenite under heating, including the deformed region. Thin nanopillars (D < 130 nm) do not twin but generate highly disordered sequences of stacking faults in the deformed region. No SME occurs and heating converts only the undeformed regions into austenite. The defect-rich, deformed region remains in the martensite phase even after prolonged heating in the stability field of austenite. A complex mixture of twins and stacking faults was found for diameters 130 nm < D < 300 nm. The size effect of the SME in Cu-Al-Ni nanopillars consists of an approximately linear reduction of the SME between 300 and 130 nm when the SME completely vanishes for smaller diameters.

Near-infrared luminescence from Y2O3:Eu3+, Yb3+ prepared by sol-gel method.

PubMed

Xie, Ying; Xiao, Lin J; Yan, Feng Q; Chen, Yong J; Li, Wen Z; Geng, Xiu J

2014-06-01

Eu3+ and Yb3+ codoped Y2O3 phosphors were synthesized by the sol-gel method. The phosphors possess absorption in the region of 300-550 nm, exhibiting an intense NIR emission of Yb3+ around 1000 nm, which is suitable for matching the maximum spectral response of c-Si solar cells. The optimum composition of Eu3+ and Yb3+ codoped Y2O3 was (Y1.94Yb0.04Eu0.02)2O3. It is observed that two-step energy transfer occurs from the 5D2 level of Eu3+ situated around (466 nm) exciting two neighboring Yb3+ ions to the 2F5/2 level (1000 nm). The down-conversion material based on Eu(3+)- Yb3+ couple may have great potential applications in c-Si solar cells to enhance their photovoltaic conversion efficiency via spectral modification.

Detection of polychlorinated biphenyls in transformer oils in Vietnam by multiphoton ionization mass spectrometry using a far-ultraviolet femtosecond laser as an ionization source.

PubMed

Duong, Vu Thi Thuy; Duong, Vu; Lien, Nghiem Thi Ha; Imasaka, Tomoko; Tang, Yuanyuan; Shibuta, Shinpei; Hamachi, Akifumi; Hoa, Do Quang; Imasaka, Totaro

2016-03-01

Polychlorinated biphenyls (PCBs) in transformer and food oils were measured using gas chromatography combined with multiphoton ionization mass spectroscopy. An ultrashort laser pulse emitting in the far-ultraviolet region was utilized for efficient ionization of the analytes. Numerous signal peaks were clearly observed for a standard sample mixture of PCBs when the third and fourth harmonic emissions (267 and 200nm) of a femtosecond Ti:sapphire laser (800nm) were employed. The signal intensities were found to be greater when measured at 200nm compared with those measured at 267nm, providing lower detection limits especially for highly chlorinated PCBs at shorter wavelengths. After simple pretreatment using disposable columns, PCB congeners were measured and found to be present in the transformer oils used in Vietnam. Copyright © 2015 Elsevier B.V. All rights reserved.

Absolute spectral response measurements of different photodiodes useful for applications in the UV spectral region

NASA Astrophysics Data System (ADS)

Pelizzo, Maria G.; Ceccherini, Paolo; Garoli, Denis; Masut, Pietro; Nicolosi, Piergiorgio

2004-09-01

Long UV radiation exposure can result in damages of biological tissues, as burns, skin aging, erythema and even melanoma cancer. In the past years an increase of melanoma cancer has been observed and associated to the atmospheric ozone deployment. Attendance of sun tanning unit centers has become a huge social phenomena, and the maximum UV radiation dose that a human being can receive is regulated by law. On the other side, UV radiation is largely used for therapeutic and germicidal purposes. In all these areas, spectroradiometer and radiomenter are needed for monitoring UVA (315-400 nm), UVB (280-315 nm) and UVC (100-280 nm) irradiance. We have selected some commercial photodiodes which can be used as solid state detectors in these instruments. We have characterized them by measuring their absolute spectral response in the 200 - 400 nm spectral range.

Absolute ozone absorption cross section in the Huggins Chappuis minimum (350-470 nm) at 296 K

NASA Astrophysics Data System (ADS)

Axson, J. L.; Washenfelder, R. A.; Kahan, T. F.; Young, C. J.; Vaida, V.; Brown, S. S.

2011-11-01

We report the ozone absolute absorption cross section between 350-470 nm, the minimum between the Huggins and Chappuis bands, where the ozone cross section is less than 10-22 cm2. Ozone spectra were acquired using an incoherent broadband cavity enhanced absorption spectrometer, with three channels centered at 365, 405, and 455 nm. The accuracy of the measured cross section is 4-30%, with the greatest uncertainty near the minimum absorption at 375-390 nm. Previous measurements vary by more than an order of magnitude in this spectral region. The measurements reported here provide much greater spectral coverage than the most recent measurements. The effect of O3 concentration and water vapor partial pressure were investigated, however there were no observable changes in the absorption spectrum most likely due to the low optical density of the complex.

Optical, physical and chemical properties of transported African mineral dust aerosols in the Mediterranean region

NASA Astrophysics Data System (ADS)

Denjean, Cyrielle; Di Biagio, Claudia; Chevaillier, Servanne; Gaimoz, Cécile; Grand, Noel; Loisil, Rodrigue; Triquet, Sylvain; Zapf, Pascal; Roberts, Greg; Bourrianne, Thierry; Torres, Benjamin; Blarel, Luc; Sellegri, Karine; Freney, Evelyn; Schwarzenbock, Alfons; Ravetta, François; Laurent, Benoit; Mallet, Marc; Formenti, Paola

2014-05-01

The transport of mineral dust aerosols is a global phenomenon with strong climate implications. Depending on the travel distance over source regions, the atmospheric conditions and the residence time in the atmosphere, various transformation processes (size-selective sedimentation, mixing, condensation of gaseous species, and weathering) can modify the physical and chemical properties of mineral dust, which, in turn, can change the dust's optical properties. The model predictions of the radiative effect by mineral dust still suffer of the lack of certainty of these properties, and their temporal evolution with transport time. Within the frame of the ChArMex project (Chemistry-Aerosol Mediterranean experiment, http://charmex.lsce.ipsl.fr/), two intensive airborne campaigns (TRAQA, TRansport and Air QuAlity, 18 June - 11 July 2012, and ADRIMED, Aerosol Direct Radiative Impact in the regional climate in the MEDiterranean region, 06 June - 08 July 2013) have been performed over the Central and Western Mediterranean, one of the two major transport pathways of African mineral dust. In this study we have set up a systematic strategy to determine the optical, physical and optical properties of mineral dust to be compared to an equivalent dataset for dust close to source regions in Africa. This study is based on airborne observations onboard the SAFIRE ATR-42 aircraft, equipped with state of the art in situ instrumentation to measure the particle scattering and backscattering coefficients (nephelometer at 450, 550, and 700 nm), the absorption coefficient (PSAP at 467, 530, and 660 nm), the extinction coefficient (CAPS at 530 nm), the aerosol optical depth (PLASMA at 340 to 1640 nm), the size distribution in the extended range 40 nm - 30 µm by the combination of different particle counters (SMPS, USHAS, FSSP, GRIMM) and the chemical composition obtained by filter sampling. The chemistry and transport model CHIMERE-Dust have been used to classify the air masses according to the dust origin and transport. Case studies of dust transport from known but differing origins (source regions in Tunisia, Algeria, and Mauritania) and at different times after transport, will be presented. Results will be compared to equivalent measurements over source regions interpreted in terms of the evolution of the particle size distribution, chemical composition and optical properties.

Remote sensing of potential lunar resources. 2: High spatial resolution mapping of spectral reflectance ratios and implications for nearside mare TiO2 content`

NASA Technical Reports Server (NTRS)

Melendrez, David E.; Johnson, Jeffrey R.; Larson, Stephen M.; Singer, Robert B.

1994-01-01

High spatial resolution maps illustrating variations in spectral reflectance 400/560 nm ratio values have been generated for the following mare regions: (1) the border between southern Mare Serenitatis and northern Mare Tranquillitatis (including the MS-2 standard area and Apollo 17 landing site), (2) central Mare Tranquillitatis, (3) Oceanus Procellarum near Seleucus, and (4) southern Oceanus Procellarum and Flamsteed. We have also obtained 320-1000 nm reflectance spectra of several sites relative to MS-2 to facilitate scaling of the images and provide additional information on surface composition. Inferred TiO2 abundances for these mare regions have been determined using an empirical calibration which relates the weight percent TiO2 in mature mare regolith to the observed 400/560 nm ratio. Mare areas with high TiO2 abundances are probably rich in ilmenite (FeTiO3) a potential lunar resource. The highest potential TiO2 concentrations we have identified in the nearside maria occur in central Mare Tranquillitatis. Inferred TiO2 contents for these areas are greater than 9 wt% and are spatially consistent with the highest-TiO2 regions mapped previously at lower spatial resolution. We note that the morphology of surface units with high 400/560 nm ratio values increases in complexity at higher spatial resolutions. Comparisons have been made with previously published geologic maps, Lunar Orbiter IV, and ground-based images, and some possible morphologic correlatins have been found between our mapped 400/560 nm ratio values and volcanic landforms such as lava flows, mare domes, and collapse pits.

Radiometry from Bio-Argo Floats: a New Strategy to Validate Ocean Color Products at the Global Scale.

NASA Astrophysics Data System (ADS)

Organelli, E.; Claustre, H.; Serra, R.; Bricaud, A.; Schmechtig, C.; D'Ortenzio, F.; Poteau, A.; Mangin, A.; Leymarie, E.; Obolensky, G.; Prieur, L. M.; Dall'Olmo, G.; Xing, X.

2016-02-01

Thanks to a new generation of Bio-Argo floats equipped with sensors for PAR (Photosynthetically Available Irradiance) and downward irradiance measurements at selected wavelengths (i.e., 380, 412 and 490 nm), the number of radiometric measurements has been dramatically increasing and data are available for diverse open ocean systems, including winter periods with harsh seas when ships can hardly sample. More than 6500 radiometric profiles have so far been acquired around solar noon in the upper 250 m of the ocean. These radiometric profiles, acquired simultaneously to other key biogeochemical and bio-optical variables (chlorophyll a, CDOM, light backscattering), represent a fruitful data source for validation of Ocean Color (OC) products. Two different strategies can be implemented: direct validation of satellite OC products and identification of regions characterized by bio-optical anomalies. Diffuse attenuation coefficients (Kd) derived from these profiles, after a specifically developed quality control, are used for these purposes.A good agreement is observed between satellite-derived Kd values at 490 nm and their Bio-Argo counterparts. However, satellite overestimates low in situ Kd values found in very clear waters (e.g., Atlantic and Pacific Sub-Tropical Gyres). The analysis of the spectral Kd variability in the surface ocean shows the potential of Bio-Argo floats in identifying those regions with optical properties departing from global bio-optical relationships. Divergences of the ratio between Kd values at 380 nm and those at 490 nm from global bio-optical models are observed in areas such as the Mediterranean Sea and the North Atlantic in winter. This might cause difficulties in retrieving biogeochemical parameters from satellite data. Hence, delineation of "anomalous" regions by Bio-Argo floats represents a useful strategy for planning dedicated cruises, setting mooring buoys or using CAL/VAL floats in order to improve Ocean Color applications.

Operational trace gas column observations from GOME-2 on MetOp

NASA Astrophysics Data System (ADS)

Valks, Pieter; Hao, Nan; Pinardi, Gaia; Hedelt, Pascal; Liu, Song; Van Roozendael, Michel; De Smedt, Isabelle; Theys, Nicolas; Koukouli, MariLiza; Balis, Dimitris

2017-04-01

This contribution focuses on the operational GOME-2 trace gas column products developed in the framework of EUMETSAT's Satellite Application Facility on Atmospheric Composition Monitoring (AC-SAF). We present an overview of the retrieval algorithms for ozone, OClO, NO2, SO2 and formaldehyde, and we show examples of various applications such as air quality and climate monitoring, using observations from the GOME-2 instruments on MetOp-A and MetOp-B. Total ozone and the minor trace gas columns from GOME-2 are retrieved with the latest version 4.8 of the GOME Data Processor (GDP), which uses an optimized Differential Optical Absorption Spectroscopy (DOAS) algorithm, with air mass factor conversions based on the LIDORT model. Improved total and tropospheric NO2 columns are retrieved in the visible wavelength region between 425 and 497 nm. SO2 emissions from volcanic and anthropogenic sources can be measured by GOME-2 using the UV wavelength region around 320 nm. For formaldehyde, an optimal DOAS fitting window around 335 nm has been determined for GOME-2. The GOME-2 trace gas columns have reached the operational EUMETSAT product status, and are available to the users in near real time (within two hours after sensing by GOME-2). The use of trace gas observations from the GOME-2 instruments on MetOp-A and MetOp-B for air quality purposed will be illustrated, e.g. for South-East Asia and Europe. Furthermore, comparisons of the GOME-2 satellite observations with ground-based measurements will be shown. Finally, the use of GOME-2 trace-gas column data in the Copernicus Atmosphere Monitoring Service (CAMS) will be presented.

234 nm and 246 nm AlN-Delta-GaN quantum well deep ultraviolet light-emitting diodes

NASA Astrophysics Data System (ADS)

Liu, Cheng; Ooi, Yu Kee; Islam, S. M.; Xing, Huili Grace; Jena, Debdeep; Zhang, Jing

2018-01-01

Deep ultraviolet (DUV) AlN-delta-GaN quantum well (QW) light-emitting diodes (LEDs) with emission wavelengths of 234 nm and 246 nm are proposed and demonstrated in this work. Our results reveal that the use of AlN-delta-GaN QW with ˜1-3 monolayer GaN delta-layer can achieve a large transverse electric (TE)-polarized spontaneous emission rate instead of transverse magnetic-polarized emission, contrary to what is observed in conventional AlGaN QW in the 230-250 nm wavelength regime. The switching of light polarization in the proposed AlN-delta-GaN QW active region is attributed to the rearrangement of the valence subbands near the Γ-point. The light radiation patterns obtained from angle-dependent electroluminescence measurements for the Molecular Beam Epitaxy (MBE)-grown 234 nm and 246 nm AlN-delta-GaN QW LEDs show that the photons are mainly emitted towards the surface rather than the edge, consistent with the simulated patterns achieved by the finite-difference time-domain modeling. The results demonstrate that the proposed AlN-delta-GaN QWs would potentially lead to high-efficiency TE-polarized surface-emitting DUV LEDs.

Raman Spectrum of Er-Y-codoped ZrO2 and Fluorescence Properties of Er3+

NASA Astrophysics Data System (ADS)

He, Jun; Luo, Meng-fei; Jin, Ling-yun; He, Mai; Fang, Ping; Xie, Yun-long

2007-02-01

Er-Y-codoped ZrO2 mixed oxides with monoclinic, tetragonal and cubic structures were prepared by a sol-gel method. The crystal structure of ZrO2 matrix and the effect of the ZrO2 phases on the fluorescence properties of Er3+ were studied using Raman spectroscopy. The results indicated that the fluorescence properties of Er3+ depend on its local ZrO2 crystal structures. As ZrO2 matrix transferred from monoclinic to tetragonal and cubic phase, the Raman and fluorescence bands of Er3+ decreased in intensities and tended to form a single peak. With 632.8 nm excitation, the bands between 640 and 680 nm were attributed to the fluorescence of Er3+ in the ZrO2 environment. However, only the fluorescence was observed and no Raman spectra were seen under 514.5 nm excitation, while only Raman spectra were observed under 325 nm excitation. UV Raman spectroscopy was found to be more sensitive in the surface region while the information provided by XRD mainly came from the bulk. The phase with lower symmetry forms more easily on the surface than in the bulk.

Scintillation properties of Ce-doped (Gd0.32Y0.68)3Al5O12 transparent ceramics

NASA Astrophysics Data System (ADS)

Hirano, Shotaro; Okada, Go; Kawaguchi, Noriaki; Yagi, Hideki; Yanagitani, Takagimi; Yanagida, Takayuki

2017-04-01

In this work, we have investigated optical and scintillation properties of 0.35-0.65% Ce:(Gd0.32Y0.68)3Al5O12 (Ce:GYAG) transparent ceramics prepared by the vacuum sintering method. Obtained samples showed high transmittance in the spectral region longer than 500 nm, and two strong absorption bands were clearly observed below 380 nm and between 400 and 500 nm due to the 4f-5d transitions of Ce3+. Under UV and X-rays, we have also observed emission due to the 5d-4f transitions of Ce3+ which appeared around 500-700 nm. The emission decay profile of PL consisted of a single exponential decay component with the decay time of 62.7-64.1 ns while the scintillation decay profile was approximated by a second-order exponential decay function with the decay times of 87.3-100 ns and 1.14-1.32 μs. In addition, it has been revealed that 0.65% Ce:GYAG transparent ceramic showed a notable light yield of 18,000 ph/MeV and low afterglow (13 ppm).

Absolute absorption cross sections of ozone at 300 K, 228 K and 195 K in the wavelength region 185-240 nm

NASA Technical Reports Server (NTRS)

Yoshino, K.; Parkinson, W. H.; Freeman, D. E.

1992-01-01

An account is given of progress of work on absorption cross section measurements of ozone at 300 K, 228 K and 195 K in the wavelength region 185-240 nm. In this wavelength region, the penetration of solar radiation into the Earth's atmosphere is controlled by O2 and O3. The transmitted radiation is available to dissociate trace species such as halocarbons and nitrous oxide. We have recently measured absolute absorption cross sections of O3 in the wavelength region 240-350 nm (Freeman et al., 1985; Yoshino et al., 1988). We apply these proven techniques to the determination of the absorption cross section of O3 at 300 K, 228 K and 195 K throughout the wavelength region 185-240 nm. A paper titled 'Absolute Absorption Cross Section Measurements of Ozone in the Wavelength Region 185-254 nm and the Temperature Dependence' has been submitted for publication in the Journal of Geophysical Research.

Coordinated Global Measurements of TLEs from the Space Shuttle and Ground Stations during MEIDEX

NASA Astrophysics Data System (ADS)

Yair, Y.; Price, C.; Levin, Z.; Israelevitch, P.; Devir, A.; Ziv, B.; Jospeh, J.; Mekler, Y.

2001-12-01

The Mediterranean Israeli Dust Experiment (MEIDEX) is scheduled to fly on-board the Columbia in May 2002, in a 39º inclination orbit for 16 days, passing over the major thunderstorm regions on Earth. The primary science instrument is a Xybion IMC-201 image-intensified radiometric camera with 6 narrow band filters (340nm, 380nm, 470nm, 555nm, 665nm, 860nm). A Sekai color video camera is a boresighted wide-FOV viewfinder. The cameras are mounted on a single-axis gimbal with a cross-track scan of ±22º degrees, inside a pressurized canister sealed with a coated quartz window that is mounted in the shuttle cargo bay. Data will be recorded in 3 digital VCRs and downlinked to the ground. During the night-side of the orbit there will be dedicated observations toward the Earth's limb above areas of active thunderstorms, in an effort to image TLEs from space. While earlier shuttle flights have succeeded in recording several ionospheric discharges by using cargo bay video cameras, MEIDEX offers a unique opportunity to conduct targeted observations with a calibrated, multispectral instrument. The Xybion camera has a rectangular FOV of 14.04(H) x 10.76 (V) degrees, that covers a volume of 466km (H) x 358km (V) at the Earth's limb, 1900km away from the shuttle. The spatial resolution is 665m (H) x 745m (V) per pixel, enabling to resolve some structural features of TLEs. Optical observations from space will be conducted with the 665nm filter that matches the observed wide peak centered at 670nm that typifies red sprites, and also with the 380 and 470nm filters to record blue jets. Observations will consist of a continuous recording of the Earth's limb, from the direction of the dusk terminator towards the night side. Areas of high convective activity will be forecast by using global aviation SIG maps, and uplinked to the crew before the observation. The astronaut will direct the camera toward areas with lightning activity, observed visually through the windows and on monitors in the crew cabin. Simultaneously with the optical observations from space, dedicated ground measurements will be conducted on a global scale. Two field sites in the Negev Desert in Israel will be used to collect electromagnetic data in the ELF and VLF frequency range. Additional ground stations in Germany, Hungary, USA, Antarctica, Chile, South Africa, Australia, Taiwan and Japan will also record Schumann Resonance and VLF signals. The coordinated measurements from various locations on Earth and from space will enable us to triangulate the location, and determine the polarity and charge moment of the parent lightning of the optically observed TLEs. The success of the campaign will further clarify the global picture of TLE occurrence.

Protein-Induced Fluorescence Enhancement Based Detection of Plasmodium falciparum Glutamate Dehydrogenase Using Carbon Dot Coupled Specific Aptamer.

PubMed

Singh, Naveen Kumar; Chakma, Babina; Jain, Priyamvada; Goswami, Pranab

2018-06-11

A novel 90-mer long ssDNA aptamer (NG3) covering a 40-mer random region targeting Plasmodium falciparum glutamate dehydrogenase ( PfGDH) developed through systematic evolution of ligands by exponential enrichment (SELEX) technique. The binding affinity of the aptamer to PfGDH discerned by circular dichroism (CD) was 0.5 ± 0.04 μM. The specificity of the aptamer toward the target was confirmed by gel electrophoresis and CD studies. The presence of two quadruplex forming regions, two big and four small stem loop structures with a δG of -7.99 kcal mol -1 for NG3 were deduced by computational studies. The spherical carbon dots (Cdots) of size 2-4 nm, synthesized by pyrolysis method using l-glutamate as a substrate were covalently linked to the amine modified aptamer. The Cdot with a band gap of 2.8 eV and a quantum yield of 34% produced fluorescence at ∼ λ 410 nm when excited at λ 320nm . The quantum yield of Cdot-aptamer assembly was increased up to 40% in the presence of the PfGDH in solution. A linear relationship with a dynamic range of 0.5 nM to 25 nM (R 2 = 0.98) and a limit of detection (LOD) of 0.48 nM was observed between the fluorescence intensity of the Cdots-aptamer conjugate and the concentration of PfGDH. The method could detect PfGDH with an LOD of 2.85 nM in diluted serum sample. This novel simple, sensitive and specific protein induced fluorescence enhancement based detection of PfGDH has a great potential to develop as a method for malaria detection.

Vertical Distribution and Columnar Optical Properties of Springtime Biomass-Burning Aerosols over Northern Indochina during the 7-SEAS/BASELInE field campaign

NASA Astrophysics Data System (ADS)

Lin, N. H.; Wang, S. H.; Welton, E. J.; Holben, B. N.; Tsay, S. C.; Giles, D. M.; Stewart, S. A.; Janjai, S.; Anh, N. X.; Hsiao, T. C.; Chen, W. N.; Lin, T. H.; Buntoung, S.; Chantara, S.; Wiriya, W.

2015-12-01

In this study, the aerosol optical properties and vertical distributions in major biomass-burning emission area of northern Indochina were investigated using ground-based remote sensing (i.e., four Sun-sky radiometers and one lidar) during the Seven South East Asian Studies/Biomass-burning Aerosols & Stratocumulus Environment: Lifecycles & Interactions Experiment conducted during spring 2014. Despite the high spatial variability of the aerosol optical depth (AOD; which at 500 nm ranged from 0.75 to 1.37 depending on the site), the temporal variation of the daily AOD demonstrated a consistent pattern among the observed sites, suggesting the presence of widespread smoke haze over the region. Smoke particles were characterized as small (Ångström exponent at 440-870 nm of 1.72 and fine mode fraction of 0.96), strongly absorbing (single-scattering albedo at 440 nm of 0.88), mixture of black and brown carbon particles (absorption Ångström exponent at 440-870 nm of 1.5) suspended within the planetary boundary layer (PBL). Smoke plumes driven by the PBL dynamics in the mountainous region reached as high as 5 km above sea level; these plumes subsequently spread out by westerly winds over northern Vietnam, southern China, and the neighboring South China Sea. Moreover, the analysis of diurnal variability of aerosol loading and optical properties as well as vertical profile in relation to PBL development, fire intensity, and aerosol mixing showed that various sites exhibited different variability based on meteorological conditions, fuel type, site elevation, and proximity to biomass-burning sources. These local factors influence the aerosol characteristics in the region and distinguish northern Indochina smoke from other biomass-burning regions in the world.

Trend analysis of aerosol optical thickness and Ångström exponent derived from the global AERONET spectral observations

NASA Astrophysics Data System (ADS)

Yoon, J.; von Hoyningen-Huene, W.; Kokhanovsky, A. A.; Vountas, M.; Burrows, J. P.

2012-06-01

Regular aerosol observations based on well-calibrated instruments have led to a better understanding of the aerosol radiative budget on Earth. In recent years, these instruments have played an important role in the determination of the increase of anthropogenic aerosols by means of long-term studies. Only few investigations regarding long-term trends of aerosol optical characteristics (e.g. aerosol optical thickness (AOT) and Ångström exponent (ÅE)) have been derived from ground-based observations. This paper aims to derive and discuss linear trends of AOT (440, 675, 870, and 1020 nm) and ÅE (440-870 nm) using AErosol RObotic NETwork (AERONET) level 2.0 spectral observations. Additionally, temporal trends of coarse- and fine-mode dominant AOTs (CdAOT and FdAOT) have been estimated by applying an aerosol classification based on accurate ÅE and Ångström exponent difference (ÅED). In order to take into account the fact that cloud disturbance is having a significant influence on the trend analysis of aerosols, we introduce a weighted least squares regression depending on two weights: (1) monthly standard deviation (σt) and (2) number of observations per month (nt). Temporal increase of FdAOTs (440 nm) prevails over newly industrializing countries in East Asia (weighted trends; +6.23% yr-1 at Beijing) and active agricultural burning regions in South Africa (+1.89% yr-1 at Mongu). On the other hand, insignificant or negative trends for FdAOTs are detected over Western Europe (+0.25% yr-1 at Avignon and -2.29% yr-1 at Ispra) and North America (-0.52% yr-1 for GSFC and -0.01% yr-1 at MD_Science_Center). Over desert regions, both increase and decrease of CdAOTs (+3.37% yr-1 at Solar_Village and -1.18% yr-1 at Ouagadougou) are observed depending on meteorological conditions.

Optical remote sensing of penetration into the lower thermosphere of neutral wind and composition perturbations driven by magnetospheric forcing

NASA Astrophysics Data System (ADS)

Conde, M. G.; Anderson, C.; Hecht, J. H.

2011-12-01

Numerous observations of thermospheric neutral winds at altitudes of 240 km and higher clearly show wind structures occurring at auroral latitudes in response to magnetospheric forcing. It is also known from observations that magnetospheric forcing is not a major driver of winds down at mesopause heights and below. Because it is difficult to measure winds in the intervening "transition region" between these height regimes, very little is known about how deeply the magnetospherically driven neutral wind structures penetrate into the lower thermosphere, what factors affect this penetration, and what consequences it may have for transport of chemical species. Here we will show neutral wind maps obtained at F-region and E-region heights in the auroral zone using Fabry-Perot Doppler spectroscopy of the 630 nm and 558 nm optical emissions. Although thermospheric neutral winds are smoothed by viscosity and inertia, observed responses to magnetospheric forcing still include wind responses on time scales as short as 10 minutes or less, and on length scales shorter than 100 km horizontally and 5 km vertically. The data also show that the degree of penetration of magnetospheric forcing into the lower thermospheric wind field is highly variable from day to day. Signatures of magnetospheric forcing are sometimes seen at altitudes as low as 120 km, whereas at other times the E-region does not seem to respond at all. Possible links will be explored between this variability and the day to day differences seen in the column integrated thermospheric [O]/[N2] ratio over Alaska.

Investigation of formalin influence over hard and soft biological tissues fluorescent spectra in vitro

NASA Astrophysics Data System (ADS)

Borisova, E.; Uzunov, Tz.; Vladimirov, B.; Avramov, L.

2007-05-01

In order to investigate the formalin influence over fluorescence properties of hard and soft biological tissues during conservation, emission spectra have been registered. Nitrogen laser at 337 nm and light-emitting diode with maximum at 405 nm have been used as excitation sources. For investigation of formalin influence over hard tissues, an experiment was made on teeth samples. Sound teeth were demineralized with a phosphoric acid for 10 seconds to obtain enamel structure near to the tooth lesion, and were fixed in formalin. Before and after teeth treatment spectra from the areas of interest were detected. There were not observed changes in the shape of the teeth spectra, related to the introduction of formalin fluorescence. Samples from mucosa of esophagus and stomach, where initially an ALA/Protoporphyrin IX diagnosis was applied, were used as soft tissue specimens. After fluorescent diagnosis in vivo biopsy samples were obtained from normal and cancerous areas and were conserved in formalin. Initially, spectrum observed has one autofluorescence maximum from the mucous tissue at 500-600 nm and secondary maxima from the protoporphyrin fluorescence at 635 nm and 720 nm, as well as pronounced minima at 540 and 575 nm related to hemoglobin absorption. After formalin conservation hemoglobin absorption was strongly reduced that increases mucous emission signal in green-yellow spectral region. Simultaneously the maxima at 635 nm and 720 nm were reduced. As conclusion we could say that formalin has negligible influence over fluorescence spectra of conserved hard tissues and has more pronounced influence over fluorescence spectra obtained in the case of soft tissue conservation, which has to be taking into account in measurements in vitro.

Hyperspectral-based predictive modelling of grapevine water status in the Portuguese Douro wine region

NASA Astrophysics Data System (ADS)

Pôças, Isabel; Gonçalves, João; Costa, Patrícia Malva; Gonçalves, Igor; Pereira, Luís S.; Cunha, Mario

2017-06-01

In this study, hyperspectral reflectance (HySR) data derived from a handheld spectroradiometer were used to assess the water status of three grapevine cultivars in two sub-regions of Douro wine region during two consecutive years. A large set of potential predictors derived from the HySR data were considered for modelling/predicting the predawn leaf water potential (Ψpd) through different statistical and machine learning techniques. Three HySR vegetation indices were selected as final predictors for the computation of the models and the in-season time trend was removed from data by using a time predictor. The vegetation indices selected were the Normalized Reflectance Index for the wavelengths 554 nm and 561 nm (NRI554;561), the water index (WI) for the wavelengths 900 nm and 970 nm, and the D1 index which is associated with the rate of reflectance increase in the wavelengths of 706 nm and 730 nm. These vegetation indices covered the green, red edge and the near infrared domains of the electromagnetic spectrum. A large set of state-of-the-art analysis and statistical and machine-learning modelling techniques were tested. Predictive modelling techniques based on generalized boosted model (GBM), bagged multivariate adaptive regression splines (B-MARS), generalized additive model (GAM), and Bayesian regularized neural networks (BRNN) showed the best performance for predicting Ψpd, with an average determination coefficient (R2) ranging between 0.78 and 0.80 and RMSE varying between 0.11 and 0.12 MPa. When cultivar Touriga Nacional was used for training the models and the cultivars Touriga Franca and Tinta Barroca for testing (independent validation), the models performance was good, particularly for GBM (R2 = 0.85; RMSE = 0.09 MPa). Additionally, the comparison of Ψpd observed and predicted showed an equitable dispersion of data from the various cultivars. The results achieved show a good potential of these predictive models based on vegetation indices to support irrigation scheduling in vineyard.

Ionospheric tomography over South Africa: Comparison of MIDAS and ionosondes measurements

NASA Astrophysics Data System (ADS)

Giday, Nigussie M.; Katamzi, Zama T.; McKinnell, Lee-Anne

2016-01-01

This paper aims to show the results of an ionospheric tomography algorithm called Multi-Instrument Data Analysis System (MIDAS) over the South African region. Recorded data from a network of 49-53 Global Positioning System (GPS) receivers over the South African region was used as input for the inversion. The inversion was made for April, July, October and December representing the four distinct seasons (Autumn, Winter, Spring and Summer respectively) of the year 2012. MIDAS reconstructions were validated by comparing maximum electron density of the F2 layer (NmF2) and peak height (hmF2) values predicted by MIDAS to those derived from three South African ionosonde measurements. The diurnal and seasonal trends of the MIDAS NmF2 values were in good agreement with the respective NmF2 values derived from the ionosondes. In addition, good agreement was found between the two measurements with minimum and maximum coefficients of determination (r2) between 0.84 and 0.96 in all the stations and validation days. The seasonal trend of the NmF2 values over the South Africa region has been reproduced using this inversion which was in good agreement with the ionosonde measurements. Moreover, a comparison of the International Reference Ionosphere (IRI-2012) model NmF2 values with the respective ionosonde derived NmF2 values showed to have higher deviation than a similar comparison between the MIDAS reconstruction and the ionosonde measurements. However, the monthly averaged hmF2 values derived from IRI 2012 model showed better agreement than the respective MIDAS reconstructed hmF2 values compared with the ionosonde derived hmF2 values.The performance of the MIDAS reconstruction was observed to deteriorate with increased geomagnetic conditions. MIDAS reconstructed electron density were slightly elevated during three storm periods studied (24 April, 15 July and 8 October) which was in good agreement with the ionosonde measurements.

Blocking germanium diffusion inside silicon dioxide using a co-implanted silicon barrier

NASA Astrophysics Data System (ADS)

Barba, D.; Wang, C.; Nélis, A.; Terwagne, G.; Rosei, F.

2018-04-01

We investigate the effect of co-implanting a silicon sublayer on the thermal diffusion of germanium ions implanted into SiO2 and the growth of Ge nanocrystals (Ge-ncs). High-resolution imaging obtained by transmission electron microscopy and energy dispersive spectroscopy measurements supported by Monte-Carlo calculations shows that the Si-enriched region acts as a diffusion barrier for Ge atoms. This barrier prevents Ge outgassing during thermal annealing at 1100 °C. Both the localization and the reduced size of Ge-ncs formed within the sample region co-implanted with Si are observed, as well as the nucleation of mixed Ge/Si nanocrystals containing structural point defects and stacking faults. Although it was found that the Si co-implantation affects the crystallinity of the formed Ge-ncs, this technique can be implemented to produce size-selective and depth-ordered nanostructured systems by controlling the spatial distribution of diffusing Ge. We illustrate this feature for Ge-ncs embedded within a single SiO2 monolayer, whose diameters were gradually increased from 1 nm to 5 nm over a depth of 100 nm.

Broadband infrared light-emitting patterns in optical glass by laser-induced nanostructuring of NiO-doped alkali-gallium germanosilicates.

PubMed

Lotarev, S V; Lipatiev, A S; Golubev, N V; Ignat'eva, E S; Malashkevich, G E; Mudryi, A V; Priseko, Y S; Lorenzi, R; Paleari, A; Sigaev, V N

2013-02-15

In this Letter, we show functionalization of NiO-doped 7.5Li(2)O·2.5Na(2)O·20Ga(2)O(3)·35SiO(2)·35GeO(2) glass by space-selective nanocrystallization via exposure to the focused beam of a pulsed copper vapor laser (510.6 and 578.2 nm) at temperature close to the glass transition point (570°C). Irradiated areas drastically change their color, caused by electronic transitions of Ni(2+) dopant ions, without any alteration of the optical quality. Importantly, irradiated regions acquire broadband infrared luminescence (centered at about 1400 nm and possessing 400 nm effective bandwidth) typical of Ni(2+) ions in crystalline environment, and by positive change of refractive index (more than 10(-3)). Spectroscopic and diffractometric data of the irradiated regions indeed resemble those previously observed in thermally nanocrystallized glass, with Ni(2+) ions embedded in γ-Ga(2)O(3) nanocrystals. The results demonstrate the possibility of laser writing nanocrystallized multifunction patterns in germanosilicate glasses for the fabrication of active integrated devices.

Fourier transform emission spectroscopy of the TiF radical in the 407 nm region

NASA Astrophysics Data System (ADS)

Imajo, Takashi; Kobayashi, Yuki; Nakashima, Yoshihiro; Tanaka, Keiichi; Tanaka, Takehiko

2005-04-01

Ultraviolet emission spectra of the TiF radical in the 407 nm region have been observed at a resolution of 0.04 cm -1 using a Fourier transform spectrometer. A new electronic assignment of 4Γ- X4Φ has been proposed. Rotational analysis has been obtained for the 0-0 and 1-1 vibrational bands of the 4Γ 5/2- X4Φ 3/2, 4Γ 9/2- X4Φ 7/2, and 4Γ 11/2- X4Φ 9/2 subbands and the 0-0 band of 4Γ 7/2- X4Φ 5/2. The lower state rotational and centrifugal distortion constants are consistent with the previous results [J. Mol. Spectrosc. 184 (1997) 186; J. Chem. Phys. 119 (2003) 9496], to the conformation that the lower state of the 407 nm band is the 4Φ ground electronic state. Rough estimates of the vibrational interval Δ G(1/2) and the spin-orbit coupling constant A in the 4Γ state were also obtained.

Development of a solid-state sodium Doppler lidar using an all-fiber-coupled injection seeding unit for simultaneous temperature and wind measurements in the mesopause region

NASA Astrophysics Data System (ADS)

Yang, Guotao; Xia, Yuan; Cheng, Xuewu; Du, Lifang; Wang, Jihong; Xun, Yuchang

2017-04-01

We present a solid-state sodium (Na) Doppler lidar developed at YanQing Station, Beijing, China (40°N, 116°E) to achieve simultaneous wind and temperature measurements of mesopause region. The 589nm pulse laser is produced by two injection seeded 1064nm and 1319nm Nd:YAG pulse lasers using the sum-frequency generation (SFG) technique. An all-fiber-coupled seeding laser unit was designed to enable absolute laser frequency locking and cycling the measurements among three different operating frequencies. Experimental observations were carried out using this Na lidar system and the preliminary results were described and compared with the temperature of the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) and the horizontal wind of the meteor Radar, demonstrating the reliability and good performance of this lidar system. The all-fiber-coupled injection seeding configuration together with the solid-state Nd:YAG lasers make the Na Doppler lidar more compact and greatly reduce the system maintenance, which is conducive to transportable and unattended operation.

Thermoluminescent properties of nanocrystalline ZnTe thin films: Structural and morphological studies

NASA Astrophysics Data System (ADS)

Rajpal, Shashikant; Kumar, S. R.

2018-04-01

Zinc Telluride (ZnTe) is a binary II-VI direct band gap semiconducting material with cubic structure and having potential applications in different opto-electronic devices. Here we investigated the effects of annealing on the thermoluminescence (TL) of ZnTe thin films. A nanocrystalline ZnTe thin film was successfully electrodeposited on nickel substrate and the effect of annealing on structural, morphological, and optical properties were studied. The TL emission spectrum of as deposited sample is weakly emissive in UV region at ∼328 nm. The variation in the annealing temperature results into sharp increase in emission intensity at ∼328 nm along with appearance of a new peak at ∼437 nm in visible region. Thus, the deposited nanocrystalline ZnTe thin films exhibited excellent thermoluminescent properties upon annealing. Furthermore, the influence of annealing (annealed at 400 °C) on the solid state of ZnTe were also studied by XRD, SEM, EDS, AFM. It is observed that ZnTe thin film annealed at 400 °C after deposition provide a smooth and flat texture suited for optoelectronic applications.

Group-III nitride VCSEL structures grown by molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Ng, HockMin; Moustakas, Theodore D.

2000-07-01

III-nitride VCSEL structures designed for electron-beam pumping have been grown by molecular beam epitaxy (MBE). The structures consist of a sapphire substrate on which an AlN/GaN distributed Bragg reflector (DBR) with peak reflectance >99% at 402 nm is deposited. The active region consists of a 2-(lambda) cavity with 25 In0.1Ga0.9N/GaN multiquantum wells (MQWs) whose emission coincides with the high reflectance region of the DBR. The thicknesses of the InGaN wells and the GaN barriers are 35 angstrom and 75 angstrom respectively. The top reflector consists of a silver metallic mirror which prevents charging effects during electron-beam pumping. The structure was pumped from the top- side with a cw electron-beam using a modified cathodoluminescence (CL) system mounted on a scanning electron microscope chamber. Light output was collected from the polished sapphire substrate side. Measurements performed at 100 K showed intense emission at 407 nm with narrowing of the linewidth with increasing beam current. A narrow emission linewidth of 0.7 nm was observed indicating the onset of stimulated emission.

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

Lu, Hsiao-Chi; Lo, Jen-Iu; Peng, Yu-Chain

Irradiation of solid nitrogen at 4 K with far-ultraviolet light from a synchrotron caused excitation to the upper state of the Vegard–Kaplan (VK) system; the emission in that system was simultaneously recorded in wavelength region 200–440 nm. The lifetimes of emission lines for VK (0, 1) to (0, 12) transitions were measured in the range of 2.12 ∼ 2.65 s. The threshold wavelength to observe the VK emission was 175.0 ± 3.5 nm, corresponding to energy 7.08 ± 0.14 eV. This investigation of the generation of icy VK nitrogen enhances our understanding of its photochemistry in space.

Vertical profiles and ground-based measurements of Black Carbon, Particulate matter and Optical properties over New Delhi during the foggy winters of 2015-16

NASA Astrophysics Data System (ADS)

Tiwari, S.; Bisht, D. S.; Srivastava, A. K.; Hopke, P. K.; Chakrabarty, R. K.

2016-12-01

Ground level and vertical observations of particulate matter were made as part of a pilot experiment using an air-quality monitory tethered balloon flown in the lower troposphere (1000 m) during the foggy winters of New Delhi, India. Measurements of black carbon (BC), the dominant absorber of visible light, particulate matter (PM), and the particulate optical properties along with meteorological parameters were conducted during the winter of 2015-16 in Delhi. During the study period, the mean concentrations of PM2.5, BC370nm, and BC880nm were observed to be 144.0 ± 39.7, 25.3 ± 8.5, and 19.4 ± 6.9 μg/m3, respectively. The mean value of PM2.5 is 12 times higher than the daily US-EPA air quality standard. The contribution of BC370nm in PM2.5 is 18 %. During the foggy period, the ground level concentrations of fine (PM2.5) and soot (BC370nm) particles increased substantially (59% and 26%, respectively) in comparison to clear days. Also, the aerosol light extinction coefficient (σext) was much higher (mean: 610 Mm-1) indicating that atmosphere was not transparent resulting in lower visibility. High concentrations of PM2.5 (89 µg/m3) and BC880nm (25.7 µg/m3) were observed up to 200 m (fog persists in this layer) in January. The BC880nm and PM2.5 concentrations near 1 km were significantly higher ( 1.9 and 12 µg/m3), respectively. Direct radiative forcing (DRF) due to BC was estimated at the top of the atmosphere (TOA), surface (SFC), and atmospheric (ATM) and its resultant forcing were - 46.2 Wm-2 at SFC indicates the cooling effect. However, a positive value ( 20.8 Wm-2) of BC DRF at TOA indicates the warming effect over the study region. The resultant ATM DRF due to BC was positive (67.0 Wm-2) indicating a net warming effect in the atmosphere. The contribution of fossil fuel climate forcing due to BC was 79% and 21% was due to burning of biomass/biofuels. The higher mean atmospheric heating rate (2.05 K day-1) by BC in the winter season would probably strengthen the temperature inversion leading to poor dispersion and affecting the formation of clouds. Based on this study, serious detrimental impacts of high concentrations of BC and PM (especially PM2.5) on regional climate are likely, thereby highlighting the need for immediate, stringent measures to improve the regional air quality in northern India.

Ultrastructural networks in growth cones and neurites of cultured central nervous system neurons.

PubMed Central

Tsui, H C; Ris, H; Klein, W L

1983-01-01

We have examined growth cones and neurites of cultured central nervous system neurons by high-voltage electron microscopy. Embryonic chicken retina cells were cultured on polylysine-treated and Formvar-coated gold grids for 2-6 days, fixed, and critical point dried. Growth cones and neurites were examined as unembedded whole mounts. Three-dimensional images from stereo-pair electron micrographs of these regions showed a high degree of ultrastructural articulation, with distinct, non-tapering filaments (5-9 nm in diameter) joining both cytoskeletal and membranous components. In the central regions of growth cones, interconnected structures included microtubules, large membranous sacs (up to 400 nm), and irregular vesicles (25-75 nm). A denser filamentous network was prevalent at the edges of growth cones. This network, which frequently adjoined the surface membrane, linked vesicles of uniform size (35-40 nm). Such vesicles often were seen densely packed in growth cone protrusions that were about the size of small synaptic boutons. Prevalent structural interconnections within growth cones conceivably could play a logistic role in specific membrane assembly, intracellular transport, endocytosis, and secretion. Because such processes are not unique to growth cones, the extensive linkages we have observed may have implications for cytoplasmic structure in general. Images PMID:6577454

Tuning from green to red the upconversion emission of Y2O3:Er3+-Yb3+ nanophosphors

NASA Astrophysics Data System (ADS)

Diaz-Torres, L. A.; Salas, P.; Oliva, J.; Resendiz-L, E.; Rodriguez-Gonzalez, C.; Meza, O.

2017-01-01

In this work, the structural, morphological and luminescent properties of Y2O3 nanophosphors doped with Er3+ (1 mol%) and different Yb3+ concentrations (2-12 mol%) have been studied. Those nanophosphors were synthesized using a simple hydrothermal method. XRD analysis indicates that all the samples presented a pure cubic phase even for Yb concentrations as high as 12 mol%. In addition, SEM images show nanoparticles with quasi-spherical shapes with average sizes in the range of 300-340 nm. Photoluminescence measurements obtained after excitation at 967 nm revealed that our samples have strong green (563 nm) and red emissions (660 nm) corresponding to 2H11/2 + 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions of Er3+ ions, respectively. We also observed that the green band is quenched and the red emission enhanced as the Yb concentration increases. In consequence, the CIE coordinates changed from (0.35, 0.64) in the green region to (0.59, 0.39) in the red region. Thus, the tuning properties of Y2O3 nanophosphors suggest that they are good candidates for applications in lighting.

Structure and photoluminescence studies of CeO2·CuAlO2 mixed metal oxide fabricated by co-precipitation method.

PubMed

Subhan, Md Abdus; Ahmed, Tanzir; Awal, M R; Kim, B Moon

2015-01-25

A novel mixed metal oxide, CeO2·CuAlO2 was fabricated by co-precipitation method in aqueous medium. CeO2·CuAlO2 was characterized by XRD, SEM, EDS, TEM, FTIR and PL spectra. The optical properties of the nanoparticles were studied by photoluminescence (PL) spectra. PL spectra at different excitations were recorded. The composite showed emission in UV, visible and NIR region depending on the excitation wavelength. The special spectral feature observed for this composite is that it showed six emission bands at 364, 409, 434, 448, 465 and 481 nm when excited at 298 nm. The green and red emissions observed at 512 and 669 nm are originated from cubic CeO2 phase when excited at 450 nm. The PL spectra were found to be dependent on excitation wavelength violating Kasha's rule. The X-ray diffraction reveals a cubic CeO2 phase and hexagonal CuAlO2 phase. EDS spectra revealed the presence of cerium (Ce), copper (Cu), aluminum (Al) and oxygen (O) elements. The particle size of the CeO2·CuAlO2 mixed oxide was estimated using Scherrer's formula, which was found to be in the range of 17.2-34.2 nm. The TEM image showed particles are almost uniform size of approximately 15-50 nm with spherical morphology. Copyright © 2014 Elsevier B.V. All rights reserved.

Structure and photoluminescence studies of CeO2·CuAlO2 mixed metal oxide fabricated by co-precipitation method

NASA Astrophysics Data System (ADS)

Subhan, Md Abdus; Ahmed, Tanzir; Awal, M. R.; Kim, B. Moon

2015-01-01

A novel mixed metal oxide, CeO2·CuAlO2 was fabricated by co-precipitation method in aqueous medium. CeO2·CuAlO2 was characterized by XRD, SEM, EDS, TEM, FTIR and PL spectra. The optical properties of the nanoparticles were studied by photoluminescence (PL) spectra. PL spectra at different excitations were recorded. The composite showed emission in UV, visible and NIR region depending on the excitation wavelength. The special spectral feature observed for this composite is that it showed six emission bands at 364, 409, 434, 448, 465 and 481 nm when excited at 298 nm. The green and red emissions observed at 512 and 669 nm are originated from cubic CeO2 phase when excited at 450 nm. The PL spectra were found to be dependent on excitation wavelength violating Kasha's rule. The X-ray diffraction reveals a cubic CeO2 phase and hexagonal CuAlO2 phase. EDS spectra revealed the presence of cerium (Ce), copper (Cu), aluminum (Al) and oxygen (O) elements. The particle size of the CeO2·CuAlO2 mixed oxide was estimated using Scherrer's formula, which was found to be in the range of 17.2-34.2 nm. The TEM image showed particles are almost uniform size of approximately 15-50 nm with spherical morphology.

Proteomic analysis of the nuclear matrix in the early stages of rat liver carcinogenesis: Identification of differentially expressed and MAR-binding proteins

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

Barboro, Paola; D'Arrigo, Cristina; Repaci, Erica

Tumor progression is characterized by definite changes in the protein composition of the nuclear matrix (NM). The interactions of chromatin with the NM occur via specific DNA sequences called MARs (matrix attachment regions). In the present study, we applied a proteomic approach along with a Southwestern assay to detect both differentially expressed and MAR-binding NM proteins, in persistent hepatocyte nodules (PHN) in respect with normal hepatocytes (NH). In PHN, the NM undergoes changes both in morphology and in protein composition. We detected over 500 protein spots in each two dimensional map and 44 spots were identified. Twenty-three proteins were differentiallymore » expressed; among these, 15 spots were under-expressed and 8 spots were over-expressed in PHN compared to NH. These changes were synchronous with several modifications in both NM morphology and the ability of NM proteins to bind nuclear RNA and/or DNA containing MARs sequences. In PHN, we observed a general decrease in the expression of the basic proteins that bound nuclear RNA and the over-expression of two species of Mw 135 kDa and 81 kDa and pI 6.7-7.0 and 6.2-7.4, respectively, which exclusively bind to MARs. These results suggest that the deregulated expression of these species might be related to large-scale chromatin reorganization observed in the process of carcinogenesis by modulating the interaction between MARs and the scaffold structure.« less

Direct observation of gold nanoparticle assemblies with the porin MspA on mica.

PubMed

Basel, Matthew T; Dani, Raj Kumar; Kang, Myungshim; Pavlenok, Mikhail; Chikan, Viktor; Smith, Paul E; Niederweis, Michael; Bossmann, Stefan H

2009-02-24

The octameric porin MspA from Mycobacterium smegmatis is sufficiently stable to form a nonmembrane-supported stand-alone porin on mica surfaces. About 98% of all MspA octamers were found to stand upright on mica, with their periplasmic loop regions bound to the hydrophilic mica surface. Both, small (d = 3.7 nm) and large (d = 17 nm) gold nanoparticles bind to MspA, however, in different positions: small gold nanoparticles bind within the MspA pore, whereas the large gold nanoparticles bind to the upper region of MspA. These experiments demonstrate that gold nanoparticles can be positioned at different, well-defined distances from the underlying surface using the MspA pore as a template. These findings represent a significant step toward the use of electrically insulating stable proteins in combination with metal nanoparticles in nanodevices.

Two-photon excitation spectrum of light-harvesting complex II and fluorescence upconversion after one- and two-photon excitation of the carotenoids

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

Walla, P.J.; Yom, J.; Krueger, B.P.

2000-05-18

The two-photon excitation (TPE) spectrum of light-harvesting complex II (LHC II) has been measured in the spectral region of 1,000--1,600 nm, corresponding to one-photon wavelengths of 500--800 nm. The authors observed a band with an origin at {approximately}2 x 660 nm (ca. 15,100 {+-} 300 cm{sup {minus}1}) and a maximum at {approximately}2 x 600 nm. The line shape and origin of this band strongly suggest that the observed signal is due to the two-photon-allowed S{sub 1} state of the energy-transferring carotenoids (Car ) in LHC II. The authors also report the time dependence of the upconverted chlorophyll (Chl) fluorescence aftermore » TPE at the maximum of the observed band. Surprisingly, a fast rise of 250 {+-} 50 fs followed by a multiexponential decay on the picosecond time scale was observed. This result provides strong indication that there is a fast energy transfer even from the dipole-forbidden Car S{sub 1} state to the Chl's. The sub picosecond energy transfer from the Car S{sub 1} state is likely a consequence of the large number of energy-accepting Chls in van der Waals contact with the central Car's in LHC II. They also present upconversion data of the Car S{sub 2}, Chl a, and Chl b fluorescence observed after one-photon excitation into the dipole-allowed Car S{sub 2} state. The lifetime of the Car S{sub 2} state is {approximately}120 {+-} 30 fs. With the observed time constants they are able to calculate quantum yields for the different possible pathways contributing to the overall Car to Chl energy transfer in LHC II.« less

Investigating the 3.3 micron infrared fluorescence from naphthalene following ultraviolet excitation

NASA Technical Reports Server (NTRS)

Williams, Richard M.; Leone, Stephen R.

1994-01-01

Polycyclic aromatic hydrocarbon (PAH) type molecules are proposed as the carriers of the unidentified infrared (UIR) bands. Detailed studies of the 3.3 micrometer infrared emission features from naphthalene, the simplest PAH, following ultraviolet laser excitation are used in the interpretation of the 3.29 micrometer (3040 cm(sup -1)) UIR band. A time-resolved Fourier transform spectrometer is used to record the infrared emission spectrum of gas-phase naphthalene subsequent to ultraviolet excitation facilitated by an excimer laser operated at either 193 nm or 248 nm. The emission spectra differ significantly from the absorption spectrum in the same spectral region. Following 193 nm excitation the maximum in the emission profile is red-shifted 45 cm(sup -1) relative to the absorption maximum; a 25 cm(sup -1) red-shift is observed after 248 nm excitation. The red-shifting of the emission spectrum is reduced as collisional and radiative relaxation removes energy from the highly vibrationally excited molecules. Coupling between the various vibrational modes is thought to account for the differences between absorption and emission spectra. Strong visible emission is also observed following ultraviolet excitation. Visible emission may play an important role in the rate of radiative relaxation, which according to the interstellar PAH hypothesis occurs only by the slow emission of infrared photons. Studying the visible emission properties of PAH type molecules may be useful in the interpretation of the DIB's observed in absorption.

Scattering properties of Saturn's rings in the far ultraviolet from Cassini UVIS spectra

NASA Astrophysics Data System (ADS)

Bradley, E. Todd; Colwell, Joshua E.; Esposito, Larry W.

2013-07-01

We use Cassini UVIS data to determine the scattering properties of Saturn's ring particles in the FUV. We have replaced the scattering function from the classical Chandrasekhar single scattering radiative transfer equation for reflectance with a ring wake model for the A and B rings derived from stellar occultations. The free parameters in this model are the ring particle Bond albedo, AB, and the ring particle asymmetry parameter, g, which equals the cosine of the most probable scattering angle of a photon from a ring particle. The spectrum of Saturn's rings from 140 to 190 nm shows an absorption feature due to water ice shortward of 165 nm. We compare our model values for I/F to lit-side data at 155 nm and at 180 nm for regions in both the A and B rings. We used the unmodified Chandrasekhar model for the C ring and Cassini Division, and in all cases we determined AB and g in the FUV for the first time. Values of AB vary between 0.04 and 0.091 at 180 nm and between 0.012 and 0.019 at 155 nm. The variations across the ring of AB at 180 nm is consistent with a greater abundance of non-ice contaminant in the C ring and Cassini Division and a minimum in contaminant abundance in the outer B ring. There is little variation in AB at 155 nm across the rings, which suggests that the reflectance of the water ice and non-water ice material shortward of the 165 nm absorption edge are about the same. Values of g vary between -0.68 and -0.78 at 180 nm and between -0.63 and -0.77 at 155 nm showing that the ring particles are highly backscattering in the FUV. We find that the wavelength of the absorption feature varies with ring region and viewing geometry indicating a different photon mean path length, L, through the outer layer of the ring particle (Bradley, E.T., Colwell, J.E., Esposito, L.W., Cuzzi, J.N., Tollerud, H., Chambers, L. [2010]. Icarus 206 (2), 458-466). We compared I/F from 152 to 185 nm to a radiative transfer spectral model developed by Shkuratov et al. (Shkuratov, Y., Starukhina, L., Hoffmann, H., Arnold, G. [1999]. Icarus 137, 235-246) and modified by Poulet et al. (Poulet, F., Cuzzi, J.N., Cruikshank, D.P., Roush, T., Dalle Ore, C.M. [2002]. Icarus 160, 313-324). We find that L is positively correlated with phase angle, which we attribute to multiple scattering within the particle on length scales comparable to L. We extrapolate L to zero phase angle and find values of L at zero phase ranging from ˜2 to 3 μm. This provides a direct measure of the distance from the surface of a ring particle to the first scattering center. L at zero phase is roughly constant across the rings suggesting the outermost 1.25 μm of the ring particles have the same structural properties in all ring regions. We azimuthally binned and interpolated observations of the unlit side of the A ring taken during Saturn orbit insertion to a 100 km resolution radial profile. We see halos (enhanced brightness) surrounding the Janus 4:3 and Janus 5:4 density waves. We also computed I/F across the A ring using the SOI observational geometry along with AB and the power-law index, n, derived from the retrieval approach from lit side observations. I/F determined by this technique agrees with results from the lit side analysis for the A2 ring but diverge for the inner and outer A ring, which we attribute to multiple scattering effects.

Discovery of Short-Timescale Oscillations in the Transition Region by CLASP

NASA Technical Reports Server (NTRS)

Kubo, M.; Katsukawa, Y.; Kano, R.; Winebarger, A.; Kobayashi, K.; Ishikawa, R.; Narukage, N.; Bando, T.; Suematsu, Y.; Giono, G.;

Intersubband absorption in GaN nanowire heterostructures at mid-infrared wavelengths.

PubMed

Ajay, Akhil; Blasco, Rodrigo; Polaczynski, Jakub; Spies, Maria; den Hertog, Martien; Monroy, Eva

2018-06-27

In this paper, we study intersubband characteristics of GaN/AlN and GaN/Al0.4Ga0.6N heterostructures in GaN nanowires structurally designed to absorb in the mid-infrared wavelength region. Increasing the GaN well width from 1.5 to 5.7 nm leads to a red shift of the intersubband absorption from 1.4 to 3.4 µm. The red shift in larger quantum wells is amplified by the fact that one of the GaN/AlN heterointerfaces (corresponding to the growth of GaN on AlN) is not sharp but rather a graded alloy extending around 1.5-2 nm. Using AlGaN instead of AlN for the same barrier dimensions, we observe the effects of reduced polarization, which blue shifts the band-to-band transitions and red shifts the intersubband transitions. In heavily doped GaN/AlGaN nanowires, a broad absorption band is observed in the 4.5-6.4 µm spectral region. © 2018 IOP Publishing Ltd.

Generation of silicon nanocrystals by damage free continuous wave laser annealing of substrate-bound SiO{sub x} films

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

Fricke-Begemann, T., E-mail: fricke-begemann@llg-ev.de; Ihlemann, J.; Wang, N.

2015-09-28

Silicon nanocrystals have been generated by laser induced phase separation in SiO{sub x} films. A continuous wave laser emitting at 405 nm is focused to a 6 μm diameter spot on 530 nm thick SiO{sub x} films deposited on fused silica substrates. Irradiation of lines is accomplished by focus scanning. The samples are investigated by atomic force microscopy, TEM, Raman spectroscopy, and photoluminescence measurements. At a laser power of 35 mW corresponding to an irradiance of about 1.2 × 10{sup 5 }W/cm{sup 2}, the formation of Si-nanocrystals in the film without any deterioration of the surface is observed. At higher laser power, the centralmore » irradiated region is oxidized to SiO{sub 2} and exhibits some porous character, while the surface remains optically smooth, and nanocrystals are observed beside and beneath this oxidized region. Amorphous Si-nanoclusters are formed at lower laser power and around the lines written at high power.« less

Antibacterial effect of light emitting diodes of visible wavelengths on selected foodborne pathogens at different illumination temperatures.

PubMed

Ghate, Vinayak S; Ng, Kheng Siang; Zhou, Weibiao; Yang, Hyunsoo; Khoo, Gek Hoon; Yoon, Won-Byong; Yuk, Hyun-Gyun

2013-09-16

The antibacterial effect of light emitting diodes (LEDs) in the visible region (461, 521 and 642 nm) of the electromagnetic spectrum was investigated on Escherichia coli O157:H7, Salmonella typhimurium, Listeria monocytogenes and Staphylococcus aureus. The irradiances of the 461, 521 and 642 nm LEDs were 22.1, 16 and 25.4 mW/cm², respectively. Bacterial cultures suspended in tryptic soy broth were illuminated by 10-watt LEDs at a distance of 4.5 cm for 7.5h at 20, 15 and 10 °C. Regardless of the bacterial strains, bacterial inactivation was observed with the range of 4.6-5.2 logCFU/ml at 10 and 15 °C after illumination with the 461 nm LED, while illumination with the 521 nm LED resulted in only 1.0-2.0 log reductions after 7.5h. On the other hand, no antibacterial effect was observed using the 642 nm LED treatment. The photodynamic inactivation by 461 and 521 nm LEDs was found to be greater at the set temperatures of 10 and 15 °C than at 20 °C. The D-values for the four bacterial strains at 10 and 15 °C after the illumination of 461 nm LED ranged from 1.29 to 1.74 h, indicating that there was no significant difference in the susceptibility of the bacterial strains to the LED illumination between 10 and 15 °C, except for L. monocytogenes. Regardless of the illumination temperature, sublethal injury was observed in all bacterial strains during illumination with the 461 and the 521 nm LED and the percentage of injured cells increased as the treatment time increased. Thus, the results show that the antibacterial effect of the LEDs was highly dependent on the wavelength and the illumination temperature. This study suggests the potential of 461 and 521 nm LEDs in combination with chilling to be used as a novel food preservation technology. © 2013 Elsevier B.V. All rights reserved.

Polarization retention in ultra-thin barium titanate films on Ge(001)

NASA Astrophysics Data System (ADS)

Cho, Yujin; Ponath, Patrick; Zheng, Lu; Hatanpaa, Benjamin; Lai, Keji; Demkov, Alexander A.; Downer, Michael C.

2018-04-01

We investigate polarization retention in 10 to 19 nm thick ferroelectric BaTiO3 (BTO) grown on Ge(001) by molecular beam epitaxy. The out-of-plane direction and reversibility of electric polarization were confirmed using piezoresponse force microscopy. After reverse-poling selected regions of the BTO films to a value P with a biased atomic-force microscope tip, we monitored relaxation of their net polarization for as long as several weeks using optical second-harmonic generation microscopy. All films retained reversed polarization throughout the observation period. 10 nm-thick BTO films relaxed monotonically to a saturation value of 0.9 P after 27 days and 19 nm films to 0.75 P after 24 h. Polarization dynamics are discussed in the context of a 1D polarization relaxation/kinetics model.

Colloidal silver nanoparticles prepared by UV-light induced citrate reduction technique for the quantitative detection of uric acid

NASA Astrophysics Data System (ADS)

Maity, Anupam; Panda, Sovan Kumar

2018-04-01

Reddish-yellow color colloid consisting of silver nanoparticles (Ag NPs) has been synthesized by reducing aqueous AgNO3 solution by photo-induced citrate reduction technique under UV light. As prepared colloid exhibits single and intense plasmonic absorption peak in the violet region of the visible spectra with the peak centered at 405 nm. The NPs are fine and spherical with diameter ranging from 5 to 10 nm. These colloidal NPs have been used for the quantitative detection of uric acid by UV-VIS spectroscopy. A linear red shifting of the characteristics Plasmonic absorption peak of Ag NPs is observed with uric acid concentration. Uric acid can be detected by UV-VIS spectroscopy down to 5 nM limit using the prepared colloid.

Characteristics of indium-gallium-nitride multiple-quantum-well blue laser diodes grown by MOCVD

NASA Astrophysics Data System (ADS)

Mack, M. P.; Abare, A. C.; Hansen, M.; Kozodoy, P.; Keller, S.; Mishra, U.; Coldren, L. A.; DenBaars, S. P.

1998-06-01

Room temperature (RT) pulsed operation of blue (420 nm) nitride-based multi-quantum well (MQW) laser diodes grown on c-plane sapphire substrates has been demonstrated. Atmospheric pressure MOCVD was used to grow the active region of the device which consisted of a 10 pair In 0.21Ga 0.79N (2.5 nm)/In 0.07Ga 0.93N (5 nm) InGaN MQW. Threshold current densities as low as 12.6 kA/cm 2 were observed for 10×1200 μm lasers with uncoated reactive ion etched (RIE) facets. The emission is strongly TE polarized and has a sharp transition in the far-field pattern above threshold. Laser diodes were tested under pulsed conditions lasted up to 6 h at room temperature.

Protection of Nomex from Ultraviolet Degradation

DTIC Science & Technology

1977-03-01

absorbs UV radiation beginning at approximately 390 nano- meters (nm) and extending into the near UV with a peak at approximately 360 nm. This absorption is...the region near 290 nm [ 5 ]. Sunlight is much richer in radiation at 360 nm than at 290 nm and this fact undoubt- edly accounts for the much greater...function as UV screening agents. The absorption spectrum of Nomex in the near UV and visible region which is responsible for Nomex photodegra- dation is

Spectrophotometer properties of vein blood plasma in UF-region patients with sharp surgical pathology of abdominal region organs

NASA Astrophysics Data System (ADS)

Guminestskij, S. G.; Polianski, I. J.; Motrich, A. V.; Grunchuk, F. W.

2006-05-01

It is set that there are two maximums in UF- region absorption of vein blood plasma of a man: at λ = 235 nm and at λ = 280 nm. It is shown that there are the substantial changes of values of the optical density D comparative with controls (for donors) exactly in a maximum at development of sharp surgical diseases of organs of abdominal region λ = 280 nm, in that time as maximum at λ = 235 nm in this plan is not informing. Resulted results of researches of dynamics of changes of optical properties of vein blood plasma in UF- region of patients with pathology of abdominal region organs in after operating period (sharp appendicitis, sharp pancreatitis, intestinal impassability and others like that), which can have the diagnostic value.

The red edge in arid region vegetation: 340-1060 nm spectra

NASA Technical Reports Server (NTRS)

Ray, Terrill W.; Murray, Bruce C.; Chehbouni, A.; Njoku, Eni

1993-01-01

The remote sensing study of vegetated regions of the world has typically been focused on the use of broad-band vegetation indices such as NDVI. Various modifications of these indices have been developed in attempts to minimize the effect of soil background, e.g., SAVI, or to reduce the effect of the atmosphere, e.g., ARVI. Most of these indices depend on the so-called 'red edge,' the sharp transition between the strong absorption of chlorophyll pigment in visible wavelengths and the strong scattering in the near-infrared from the cellular structure of leaves. These broadband indices tend to become highly inaccurate as the green canopy cover becomes sparse. The advent of high spectral resolution remote sensing instrument such as the Airborne Visible and Infrared Imaging Spectrometer (AVIRIS) has allowed the detection of narrow spectral features in vegetation and there are reports of detection of the red edge even for pixels with very low levels of green vegetation cover by Vane et al. and Elvidge et al., and to characterize algal biomass in coastal areas. Spectral mixing approaches similar to those of Smith et al. can be extended into the high spectral resolution domain allowing for the analysis of more endmembers, and potentially, discrimination between material with narrow spectral differences. Vegetation in arid regions tends to be sparse, often with small leaves such as the creosote bush. Many types of arid region vegetation spend much of the year with their leaves in a senescent state, i.e., yellow, with lowered chlorophyll pigmentation. The sparseness of the leaves of many arid region plants has the dual effect of lowering the green leaf area which can be observed and of allowing more of the sub-shrub soil to be visible which further complicates the spectrum of a region covered with arid region vegetation. Elvidge examined the spectral characteristics of dry plant materials showing significant differences in the region of the red edge and the diagnostic ligno-cellulose absorptions at 2090 nm and 2300 nm. Ray et al. detected absorption at 2100 nm in AVIRIS spectra of an abandoned field known to be covered by a great deal of dead plant litter. In order to better study arid region vegetation remote sensing data, it is necessary to better characterize the reflectance spectra of in situ, living, arid region plants.

Trend analysis of the Aerosol Optical Thickness and Ångström Exponent derived from the global AERONET spectral observations

NASA Astrophysics Data System (ADS)

Yoon, J.; von Hoyningen-Huene, W.; Kokhanovsky, A. A.; Vountas, M.; Burrows, J. P.

2011-08-01

Regular aerosol observations based on well-calibrated instruments have led to a better understanding of the aerosol radiative budget on Earth. In recent years, these instruments have played an important role in the determination of the increase of anthropogenic aerosols by means of long-term studies. Only few investigations regarding long-term trends of aerosol optical characteristics (e.g. Aerosol Optical Thickness (AOT) and Ångström Exponent (ÅE)) have been derived from ground-based observations. This paper aims to derive and discuss linear trends of AOT (440, 675, 870, and 1020 nm) and ÅE (440-870 nm) using AErosol RObotic NETwork (AERONET) spectral observations. Additionally, temporal trends of Coarse- and Fine-mode dominant AOTs (CAOT and FAOT) have been estimated by applying an aerosol classification based on accurate ÅE and Ångström Exponent Difference (ÅED). In order to take into account the fact that cloud disturbance is having a significant influence on the trend analysis of aerosols, we introduce a weighted least squares regression depending on two weights: (1) monthly standard deviation and (2) Number of Observations (NO) per month. Temporal increase of FAOTs prevails over regions dominated by emerging economy or slash-burn agriculture in East Asia and South Africa. On the other hand, insignificant or negative trends for FAOTs are detected over Western Europe and North America. Over desert regions, both increase and decrease of CAOTs are observed depending on meteorological conditions.

High-Power Arctic Lidar for observations of Sodium layer and Calcium Ion Cyclotron Resonance Heating

NASA Astrophysics Data System (ADS)

Wuerker, R. F.; Foley, J.; Kidd, P.; Wong, A. Y.

1998-11-01

The UCLA HIPAS Observatory is located at 64o 54' 22"N, 146o 50' 33" W. It passes under the auroral oval, has a 2.7 m diameter liquid mirror collector (LMT), and two bistatic laser illuminators; a Doubled YAG pumped dye laser and a Doubled (tunable) Alexandrite laser. The first emits 0.1 J - 10 ns pulses at 590nm (Na) at 20 Hz. The second laser emits 0.15 J -10 ns pulses at 393 nm (Ca+) and 391.4 nm (N2) at 10 Hz. New sporadic sodium layers have been observed during the passage of the electrojet and auroras in periods of 20-30 seconds, indicating that sodium is liberated from micrometeors during auroral precipitations. The Laser Induced Fluorescence techniques will be used to observe the acceleration of the Ca+ ions when they are driven by the 80 MW (ERP) 2.85MHz RF array, modulated at the Ca+ ion Cyclotron Frequency. 1. Ionospheric Modifaction and Enviromental Research in the Auroral Region in Plasma Science and the Environment. Publisher: AIP Press, Woodbury, NY. Editors: W. Manheimer, L. Sugiyama, T. Stix; Chapter 3, pgs. 41-75, 1997. Research supported by ONR N00014-96-C-0040

Long Periodic Structure of a Room-Temperature Ionic Liquid by High-Pressure Small-Angle X-Ray Scattering and Wide-Angle X-Ray Scattering: 1-Decyl-3-Methylimidazolium Chloride.

PubMed

Abe, Hiroshi; Hamaya, Nozomu; Koyama, Yoshihiro; Kishimura, Hiroaki; Takekiyo, Takahiro; Yoshimura, Yukihiro; Wakabayashi, Daisuke; Funamori, Nobumasa; Matsuishi, Kiyoto

2018-04-23

The Bragg reflections of 1-decyl-3-methylimidazolium chloride ([C 10 mim][Cl]), a room-temperature ionic liquid, are observed in a lowly scattered wavevector (q) region using high-pressure (HP) small-angle X-ray scattering methods. The HP crystal of [C 10 mim][Cl] was characterized by an extremely long periodic structure. The peak position at the lowest q (1.4 nm -1 ) was different from that of the prepeak observed in the liquid state (2.3 nm -1 ). Simultaneously, Bragg reflections at high-q were detected using HP wide-angle X-ray scattering. The longest lattice constant was estimated to be 4.3 nm using structural analysis. The crystal structure of HP differed from that of the low-temperature (LT) crystal and the LT liquid crystal. With increasing pressure, Bragg reflections in the high-q component became much broader, and were accompanied by phase transition, although those in the low-q component were observed to be relatively sharp. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Density patterns in metal films produced by laser interference.

PubMed

Peláez, R J; Afonso, C N; Škereň, M; Bulíř, J

2015-01-26

Fringed periodic patterns have been produced by laser interference at 193 nm in an almost continuous 9.5 nm-thick Ag film that exhibits a number density of ≈189 μm(-2) holes. Patterns with four periods in the range of 1.8-10.2 μm were produced by changing the projection optics. At high fluences, the film breaks up into nanostructures around the regions exposed to intensity maxima due to laser-induced melting. At low fluences, a new process is observed that is triggered at the initial holes of the film by solid-state dewetting. Once the fluence is high enough to prevent the temperature balance across the pattern, mass transport from cold to hot regions is observed, leading to film densification in regions around intensity maxima sites. The novel patterns are thus formed by fringes of material that is more/less dense than the as-grown film, each of which is located at intensity maxima/minima sites, and have negligible topography. Comparing the present results to earlier reports in the literature shows that the thermal gradient across the pattern is influenced by the initial film microstructure, rather than by the thickness. The existence of a minimum period, which is achievable depending on the thermal continuity of the film, is also discussed.

Atmospheric dayglow diagnostics involving the O2(b-X) Atmospheric band emission: Global Oxygen and Temperature (GOAT) mapping

NASA Astrophysics Data System (ADS)

Slanger, T. G.; Pejaković, D. A.; Kostko, O.; Matsiev, D.; Kalogerakis, K. S.

2017-03-01

The terrestrial dayglow displays prominent emission features from the 0-0 and 1-1 bands of the O2 Atmospheric band system in the 760-780 nm region. We present an analysis of observations in this wavelength region recorded by the Space Shuttle during the Arizona Airglow Experiment. A major conclusion is that the dominant product of O(1D) + O2 energy transfer is O2(b, v = 1), a result that corroborates our previous laboratory studies. Moreover, critical to the interpretation of dayglow is the possible interference by N2 and N2+ bands in the 760-780 nm region, where the single-most important component is the N2 1PG 3-1 band that overlaps with the O2(b-X) 0-0 band. When present, this background must be accounted for to reveal the O2(b-X) 0-0 and 1-1 bands for altitudes at which the O2 and N2/N2+ emissions coincide. Finally, we exploit the very different collisional behavior of the two lowest O2(b) vibrational levels to outline a remote sensing technique that provides information on Atmospheric composition and temperature from space-based observations of the 0-0 and 1-1 O2 atmospheric bands.

Observations of Cirrus Clouds over the Pacific Region by the NASA Multiwavelength Lidar System

NASA Technical Reports Server (NTRS)

Ismail, Syed; Browell, Edward V.; Fenn, Marta A.; Nowicki, Greg D.

1992-01-01

As part of the Pacific Exploratory Mission-West Campaign that took place during 16 Sep. - 21 Oct. 1991, lidar measurements were made from the ARC DC-8 aircraft at an altitude of approximately 9 km. This mission provided a unique opportunity to make cirrus cloud observations around the Pacific region covering the latitude range from 5 to 55 deg N and the longitude range from -114 to 120 deg E. Cirrus clouds were observed on most of these flights providing a unique data base. The latitudinal coverage of cirrus observations was further extended to -5 deg S from observations on 30 Jan. 1992 as part of the Airborne Arctic Stratospheric Expedition 2. During this latter mission, aerosol depolarizations at 622 and 1064 nm were also measured. The optical characteristics and statistics related to these cirrus cloud observations are summarized.

Continuation of Global NO2 and SO2 Monitoring with Suomi NPP OMPS

NASA Astrophysics Data System (ADS)

Yang, K.; Zhang, H.; Wang, J.; Ge, C.; Wang, Y.

2017-12-01

We have produced high-quality NO2 and SO2 standard products (named NMNO2 and NMSO2 respectively) from the SNPP OMPS-NM daily global observations. These OMPS standard products have been archived and publicly released at NASA Goddard Earth Sciences Data and Information Services Center (https://daac.gsfc.nasa.gov/information/news/595e9675624016d1af392c73/omps-nm-no- 2-and-so-2-l-2-data-products-released). Analyses and comparisons have demonstrated that the qualities of these OMPS standard products match or surpass those of the corresponding OMI products, enabling the continuity and extension of these two key standard Earth System Data Records (ESDRs) that begun with NASA's EOS Aura mission using the SNPP observations. In this presentation, we summarize the new techniques and algorithm advances that improve the accuracy and consistency of these ESDRs from satellite observations, and highlight the regional changes in NO2 and SO2 detected from half a decade of SNPP OMPS observations.

Leaf Level Chlorophyll Fluorescence Emission Spectra: Narrow Band versus Full 650-800 nm Retrievals

NASA Astrophysics Data System (ADS)

Middleton, E.; Zhang, Q.; Campbell, P. K.; Huemmrich, K. F.; Corp, L.; Cheng, Y.

2012-12-01

Recently, chlorophyll fluorescence (ChlF) retrievals in narrow spectral regions (< 1 nm, between 750-770 nm) of the near infrared (NIR) region of Earth's reflected radiation have been achieved from satellites, including the Japanese GOSAT and the European Space Agency's Sciamachy/Envisat. However, these retrievals sample the total full-spectrum ChlF and are made at non-optimal wavelengths since they are not located at the peak fluorescence emission features. We wish to estimate the total full-spectrum ChlF based on emissions obtained at selected wavelengths. For this, we drew upon leaf emission spectra measured on corn leaves obtained from a USDA experimental cornfield in MD (USA). These emission spectra were determined for the adaxial and abaxial (i.e., top and underside) surfaces of leaves measured throughout the 2008 and 2011 growing seasons (n>400) using a laboratory instrument (Fluorolog-3, Horiba Scientific, USA), recorded in either 1 nm or 5 nm increments with monochromatic excitation wavelengths of either 532 or 420 nm. The total ChlF signal was computed as the area under the continuous spectral emission curves, summing the emission intensities (counts per second) per waveband. The individual narrow (1 or 5 nm) waveband emission intensities were linearly related to full emission values, with variable success across the spectrum. Equations were developed to estimate total ChlF from these individual wavebands. Here, we report the results for the average adaxial/abaxial emissions. Very strong relationships were achieved for the relatively high fluorescence intensities at the red chlorophyll peak, centered at 685 nm (r2= 0.98, RMSE = 5.53 x 107 photons/s) and in the nearby O2-B atmospheric absorption feature centered at 688 nm (r2 = 0.94, RMSE = 4.04 x 107), as well as in the far-red peak centered at 740 nm (r2=0.94, RMSE = 5.98 x107). Very good retrieval success occurred for the O2-A atmospheric absorption feature on the declining NIR shoulder centered at 760 nm (r2 = 0.88, RMSE = 7.54 x 107). When perfect retrievals were assumed (0% noise), retrievals remained good in the low emission regions on either side of the peaks-- those associated with the H alpha line at 655 nm (r2 = 0.83, RMSE =8.87 x 107) and the far-NIR wavelengths recently utilized for satellite retrievals: a K line at 770 nm (r2 = 0.85, RMSE = 8.36 x 107) and the 750-770 nm interval (r2 = 0.88, RMSE = 6.92 x 107). However, the atmosphere and satellite observations are expected to add noise to retrievals. Adding 5% random error to these relationships did not seriously impair the retrieval successes in the red and far-red peaks (r2 ~ 0.85, RMSEs = 6.31 x 107). A greater impact occurred (reducing retrieval success by ~10%) when adding 5% noise for the far-NIR narrow band at 770 nm (r2 ~ 0.70, RMSE ~ 8.5 x 107). When a 10% random error was added, the retrieval successes fell to ~68 ± 7% for all retrieval wavebands, and RMSEs increased by a factor of 10. This laboratory approach will be critical to calibrate space borne retrievals, but additional information across plant species is needed. Furthermore, this experiment indicates that ChlF retrievals from space should include information from the red and far-red peak emission regions, since the true total fluorescence signal is the desired parameter for Earth carbon and energy budgets.

Point-of-use water disinfection using ultraviolet and visible light-emitting diodes.

PubMed

Lui, Gough Yumu; Roser, David; Corkish, Richard; Ashbolt, Nicholas J; Stuetz, Richard

2016-05-15

Improvements in point-of-use (POU) drinking water disinfection technologies for remote and regional communities are urgently needed. Conceptually, UV-C light-emitting diodes (LEDs) overcome many drawbacks of low-pressure mercury tube based UV devices, and UV-A or visible light LEDs also show potential. To realistically evaluate the promise of LED disinfection, our study assessed the performance of a model 1.3 L reactor, similar in size to solar disinfection bottles. In all, 12 different commercial or semi-commercial LED arrays (270-740 nm) were compared for their ability to inactivate Escherichia coli K12 ATCC W3110 and Enterococcus faecalis ATCC 19433 over 6h. Five log10 and greater reductions were consistently achieved using the 270, 365, 385 and 405 nm arrays. The output of the 310 nm array was insufficient for useful disinfection while 430 and 455 nm performance was marginal (≈ 4.2 and 2.3-log10s E. coli and E. faecalis over the 6h). No significant disinfection was observed with the 525, 590, 623, 660 and 740 nm arrays. Delays in log-phase inactivation of E. coli were observed, particularly with UV-A wavelengths. The radiation doses required for >3-log10 reduction of E. coli and E. faecalis differed by 10 fold at 270 nm but only 1.5-2.5 fold at 365-455 nm. Action spectra, consistent with the literature, were observed with both indicators. The design process revealed cost and technical constraints pertaining to LED electrical efficiency, availability and lifetime. We concluded that POU LED disinfection using existing LED technology is already technically possible. UV-C LEDs offer speed and energy demand advantages, while UV-A/violet units are safer. Both approaches still require further costing and engineering development. Our study provides data needed for such work. Copyright © 2016 Elsevier B.V. All rights reserved.

An Erupting Active Region Filament: Three-Dimensional Trajectory and Hydrogen Column Density

NASA Astrophysics Data System (ADS)

Penn, M. J.

2000-05-01

From 15:33-16:02 UT on 13 June 1998 observations of an erupting filament as it crossed solar disk center were obtained with the NSO/KPVT and SoHO/CDS instruments as part of the SoHO Joint Observing Program 70. Context observations show that this event was the eruption of the north-east section of a small active region filament associated with NOAA 8237, that the photospheric magnetic field was changing in this active region from 12 through 14 June 1998, that a coronal Moreton-wave disk event occurred, as well as a white-light CME off the south-west solar limb. The NSO/KPVT imaging spectroscopy sho the He I 1083 nm absorption line blue-shifted to velocities of between 200 and 300 km s-1. The true solar trajectory of the eruption is obtained by using the projected solar coordinates and by integrating the Doppler velocity. The filament travels with a total velocity of about 300 km s-1 along a path inclined roughly 49 degrees to the solar surface and rises to a height of just over 1.5 solar radii. The KPVT data show no Stokes V profiles in the Doppler shifted He I 1083 nm absorption to a limit of roughly 3 x 10-3 times the continuum intensity. The SoHO/CDS data scanned the center of the KPVT FOV using seven EUV lines; Doppler shifted filament emission is seen in six lines from representing temperatures from about 2 x 104K through 1 x 106K. Bound-free continuum absorption from H I, free from confusion from foreground emission and line emission, is seen as the filament obscures underlying chromospheric emission. A fit to the wavelength dependence of the absorption from five lines between 55.5 to 63.0 nm yields a column density ξ HI = 1.7 x 1018cm-2. Spatial maps show that this filament absorption is more confined than the regions which show emission. This work was made possible by 1997 and 1999 SoHO Guest Investigator awards NASA #W-19,142 Basic and NASA NAG5-8004.

Black carbon aerosol characterization in a remote area of Qinghai-Tibetan Plateau, western China.

PubMed

Wang, Qiyuan; Schwarz, J P; Cao, Junji; Gao, Rushan; Fahey, D W; Hu, Tafeng; Huang, R-J; Han, Yongming; Shen, Zhenxing

2014-05-01

The concentrations, size distributions, and mixing states of refractory black carbon (rBC) aerosols were measured with a ground-based Single Particle Soot Photometer (SP2), and aerosol absorption was measured with an Aethalometer at Qinghai Lake (QHL), a rural area in the Northeastern Tibetan Plateau of China in October 2011. The area was not pristine, with an average rBC mass concentration of 0.36 μg STP-m(-3) during the two-week campaign period. The rBC concentration peaked at night and reached the minimal in the afternoon. This diurnal cycle of concentration is negatively correlated with the mixed layer depth and ventilation. When air masses from the west of QHL were sampled in late afternoon to early evening, the average rBC concentration of 0.21 μg STP-m(-3) was observed, representing the rBC level in a larger Tibetan Plateau region because of the highest mixed layer depth. A lognormal primary mode with mass median diameter (MMD) of ~175 nm, and a small secondary lognormal mode with MMD of 470-500 nm of rBC were observed. Relative reduction in the secondary mode during a snow event supports recent work that suggested size dependent removal of rBC by precipitation. About 50% of the observed rBC cores were identified as thickly coated by non-BC material. A comparison of the Aethalometer and SP2 measurements suggests that non-BC species significantly affect the Aethalometer measurements in this region. A scaling factor for the Aethalometer data at a wavelength of 880 nm is therefore calculated based on the measurements, which may be used to correct other Aethalometer datasets collected in this region for a more accurate estimate of the rBC loading. The results present here significantly improve our understanding of the characteristics of rBC aerosol in the less studied Tibetan Plateau region and further highlight the size dependent removal of BC via precipitation. Copyright © 2014 Elsevier B.V. All rights reserved.

Discussion of vicarious calibration of GOSAT/TANSO-CAI UV-band (380nm) and aerosol retrieval in wildfire region in the OCO-2 and GOSAT observation campaign at Railroad Valley in 2016

NASA Astrophysics Data System (ADS)

Hashimoto, M.; Kuze, A.; Bruegge, C. J.; Shiomi, K.; Kataoka, F.; Kikuchi, N.; Arai, T.; Kasai, K.; Nakajima, T.

2016-12-01

The GOSAT (Greenhouse Gases Observing Satellite) / TANSO-CAI (Cloud and Aerosol Imager, CAI) is an imaging sensor to measure cloud and aerosol properties and observes reflected sunlight from the atmosphere and surface of the ground. The sensor has four bands from near ultraviolet (near-UV) to shortwave infrared, 380, 674, 870 and 1600nm. The field of view size is 0.5 km for band-1 through band-3, and 1.5km for band-4. Band-1 (380nm) is one of unique function of the CAI. The near-UV observation offers several advantages for the remote sensing of aerosols over land: Low reflectance of most surfaces; Sensitivity to absorbing aerosols; Absorption of trace gases is weak (Höller et al., 2004). CAI UV-band is useful to distinguish absorbing aerosol (smoke) from cloud. GOSAT-2/TANSO-CAI-2 that will be launched in the future also has UV-bands, 340 and 380nm. We carried out an experiment to calibrate CAI UV-band radiance using data taken in a field campaign of OCO-2 and GOSAT at Railroad Valley in 2016. The campaign period is June 27 to July 3 in 2016. We measured surface reflectance by using USB4000 Spectrometer with 74-UV collimating lens (Ocean Optics) and Spectralon (Labsphere). USB4000 is a UV spectrometer, and its measurement range from 300 to 520nm. We simulated CAI UV-band radiance using a vector type of radiation transfer code, i.e. including polarization calculation, pstar3 (Ota et al., 2010) using measured surface reflectance and atmospheric data, pressure and relative humidity by radiosonde in the same campaign, and aerosol optical depth by AERONET, etc. Then, we evaluated measured UV radiances with the simulated data. We show the result of vicarious calibration of CAI UV-band in the campaign, and discuss about this method for future sensor, CAI-2. Around the campaign period, there was wildfire around Los Angeles, and aerosol optical thickness (AOT) observed by AERONET at Rail Road valley and Caltech sites is also high. We tried to detect and retrieve aerosol properties using CAI data around campaign region by the multi-wavelength and multi-pixel method (MWPM) (Hashimoto AGU Fall meeting, 2014) using CAI UV-band. In the analysis, we use CAI four bands to retrieve aerosol optical properties including cloud optical characteristics. We also like to introduce the analysis result of aerosol optical properties during wildfire.

Oxytocin receptor binding sites in the periphery of the neonatal mouse

PubMed Central

Greenwood, Maria A.

2017-01-01

Oxytocin (OXT) is a pleiotropic regulator of physiology and behavior. An emerging body of evidence demonstrates a role for OXT in the transition to postnatal life of the infant. To identify potential sites of OXT action via the OXT receptor (OXTR) in the newborn mouse, we performed receptor autoradiography on 20 μm sagittal sections of whole postnatal day 0 male and female mice on a C57BL/6J background using the 125iodinated ornithine vasotocin analog ([125I]-OVTA) radioligand. A competitive binding assay on both wild-type (WT) and OXTR knockout (OXTR KO) tissue was used to assess the selectivity of [125I]-OVTA for neonatal OXTR. Radioactive ligand (0.05 nM [125I]-OVTA) was competed against concentrations of 0 nM, 10 nM, and 1000 nM excess unlabeled OXT. Autoradiographs demonstrated the high selectivity of the radioligand for infant peripheral OXTR. Specific ligand binding activity for OXTR was observed in the oronasal cavity, the eye, whisker pads, adrenal gland, and anogenital region in the neonatal OXTR WT mouse, but was absent in neonatal OXTR KO. Nonspecific binding was observed in areas with a high lipid content such as the scapular brown adipose tissue and the liver: in these regions, binding was present in both OXTR WT and KO mice, and could not be competed away with OXT in either WT or KO mice. Collectively, these data confirm novel OXT targets in the periphery of the neonate. These peripheral OXTR sites, coupled with the immaturity of the neonate’s own OXT system, suggest a role for exogenous OXT in modulating peripheral physiology and development. PMID:28235051

A sea surface reflectance model for (A)ATSR, and application to aerosol retrievals

NASA Astrophysics Data System (ADS)

Sayer, A. M.; Thomas, G. E.; Grainger, R. G.

2010-07-01

A model of the sea surface bidirectional reflectance distribution function (BRDF) is presented for the visible and near-IR channels (over the spectral range 550 nm to 1.6 μm) of the dual-viewing Along-Track Scanning Radiometers (ATSRs). The intended application is as part of the Oxford-RAL Aerosols and Clouds (ORAC) retrieval scheme. The model accounts for contributions to the observed reflectance from whitecaps, sun-glint and underlight. Uncertainties in the parametrisations used in the BRDF model are propagated through into the forward model and retrieved state. The new BRDF model offers improved coverage over previous methods, as retrievals are possible into the sun-glint region, through the ATSR dual-viewing system. The new model has been applied in the ORAC aerosol retrieval algorithm to process Advanced ATSR (AATSR) data from September 2004 over the south-eastern Pacific. The assumed error budget is shown to be generally appropriate, meaning the retrieved states are consistent with the measurements and a priori assumptions. The resulting field of aerosol optical depth (AOD) is compared with colocated MODIS-Terra observations, AERONET observations at Tahiti, and cruises over the oceanic region. MODIS and AATSR show similar spatial distributions of AOD, although MODIS reports values which are larger and more variable. It is suggested that assumptions in the MODIS aerosol retrieval algorithm may lead to a positive bias in MODIS AOD of order 0.01 at 550 nm over ocean regions where the wind speed is high.

A sea surface reflectance model for (A)ATSR, and application to aerosol retrievals

NASA Astrophysics Data System (ADS)

Sayer, A. M.; Thomas, G. E.; Grainger, R. G.

2010-03-01

A model of the sea surface bidirectional reflectance distribution function (BRDF) is presented for the visible and near-IR channels (over the spectral range 550 nm to 1.6 μm) of the dual-viewing Along-Track Scanning Radiometers (ATSRs). The intended application is as part of the Oxford-RAL Aerosols and Clouds (ORAC) retrieval scheme. The model accounts for contributions to the observed reflectance from whitecaps, sun-glint and underlight. Uncertainties in the parametrisations used in the BRDF model are propagated through into the forward model and retrieved state. The new BRDF model offers improved coverage over previous methods, as retrievals are possible into the sun-glint region, through the ATSR dual-viewing system. The new model has been applied in the ORAC aerosol retrieval algorithm to process Advanced ATSR (AATSR) data from September 2004 over the south-eastern Pacific. The assumed error budget is shown to be generally appropriate, meaning the retrieved states are consistent with the measurements and a priori assumptions. The resulting field of aerosol optical depth (AOD) is compared with colocated MODIS-Terra observations, AERONET observations at Tahiti, and cruises over the oceanic region. MODIS and AATSR show similar spatial distributions of AOD, although MODIS reports values which are larger and more variable. It is suggested that assumptions in the MODIS aerosol retrieval algorithm may lead to a positive bias in MODIS AOD of order 0.01 at 550 nm over ocean regions where the wind speed is high.

Asteroid (21) Lutetia: Disk-resolved photometric analysis of Baetica region

NASA Astrophysics Data System (ADS)

Hasselmann, P. H.; Barucci, M. A.; Fornasier, S.; Leyrat, C.; Carvano, J. M.; Lazzaro, D.; Sierks, H.

2016-03-01

(21) Lutetia has been visited by Rosetta mission on July 2010 and observed with a phase angle ranging from 0.15° to 156.8°. The Baetica region, located at the north pole has been extensively observed by OSIRIS cameras system. Baetica encompass a region called North Pole Crater Cluster (NPCC), shows a cluster of superposed craters which presents signs of variegation at the small phase angle images. For studying the location, we used 187 images distributed throughout 14 filter recorded by the NAC (Narrow Angle Camera) and WAC (Wide Angle Camera) of the OSIRIS system on-board Rosetta taken during the fly-by. Then, we photometrically modeled the region using Minnaert disk-function and Akimov phase function to obtain a resolved spectral slope map at phase angles of 5 ° and 20 ° . We observed a dichotomy between Gallicum and Danuvius-Sarnus Labes in the NPCC, but no significant phase reddening (- 0.04 ± 0.045 % μm-1deg-1). In the next step, we applied the Hapke (Hapke, B. [2008]. Icarus 195, 918-926; Hapke, B. [2012]. Theory of Reflectance and Emittance Spectroscopy, second ed. Cambridge University Press) model for the NAC F82+F22 (649.2 nm), WAC F13 (375 nm) and WAC F17 (631.6 nm) and we obtained normal albedo maps and Hapke parameter maps for NAC F82+F22. On Baetica, at 649.2 nm, the geometric albedo is 0.205 ± 0.005 , the average single-scattering albedo is 0.181 ± 0.005 , the average asymmetric factor is - 0.342 ± 0.003 , the average shadow-hiding opposition effect amplitude and width are 0.824 ± 0.002 and 0.040 ± 0.0007 , the average roughness slope is 11.45 ° ± 3 ° and the average porosity is 0.85 ± 0.002 . We are unable to confirm the presence of coherent-backscattering mechanism. In the NPCC, the normal albedo variegation among the craters walls reach 8% brighter for Gallicum Labes and 2% fainter for Danuvius Labes. The Hapke parameter maps also show a dichotomy at the opposition effect coefficients, single-scattering albedo and asymmetric factor, that may be attributed to the maturation degree of the regolith or to compositonal variation. In addition, we compared the Hapke (Hapke, B. [2008]. Icarus 195, 918-926; Hapke, B. [2012]. Theory of Reflectance and Emittance Spectroscopy, second ed. Cambridge University Press) and Hapke (Hapke, B. [1993]. Theory of Reflectance and Emittance Spectroscopy) parameters with laboratory samples and other small Solar System bodies visited by space missions.

Evidence of differentiated near-surface plutons on Vesta in integrated Dawn color images and spectral datasets

NASA Astrophysics Data System (ADS)

Cheek, L.; Sunshine, J.

2014-07-01

Introduction: Recent analyses of Visible and Infrared Mapping Spectrometer (VIR) data from the Dawn mission [1] revealed isolated areas on the asteroid (4) Vesta that contain enhanced abundances of olivine [2,3]. However, this olivine component is only subtly expressed in the VIR data, superimposed on spectrally dominant pyroxene absorptions. The highly ''mixed'' nature of these spectra is likely due, in part, to the relatively coarse spatial resolution of VIR (˜190 m/pixel in HAMO-2) [4], which averages the spectral characteristics of potentially heterogeneous meter-scale outcrops. The capability to resolve the olivine-enhanced regions at a finer scale may reveal a spectrally-dominant olivine component that would facilitate characterization of 1) the distribution and context of the olivine-enhanced exposures, and 2) the spectral properties of the olivine component, providing clues to mineral composition. In order to access finer spatial scales while preserving the detailed mineralogic information offered by the hyperspectral VIR instrument, we use an approach developed for the Moon by [5] that is based on an inversion of the Spectral Mixture Analysis (SMA) framework [6]. Here, we project the VIR data onto co-located, multispectral Framing Camera (FC) data with a spatial resolution of ˜50 m/pixel (HAMO-2) [7]. The analysis was carried out using georeferenced VIR and FC calibrated mosaics for the olivine-enhanced region containing Bellicia and Arruntia craters in the northern hemisphere of Vesta. The approach produces a set of four calculated VIR end members, as well as a projected image cube that contains a calculated VIR spectrum for each FC pixel in the scene. An important advantage of this approach is that it can be applied to co-located multi- and hyperspectral datasets on other planetary bodies. Initial Results: We find that VIR observations for diverse areas across the scene are well described by the following hyperspectral end members: two spectra resembling pyroxenes, one of which has a subtle ˜600-nm absorption; one spectrum that resembles a pyroxene but displays a somewhat distorted 1000-nm band shape that may be indicative of residual calibration issues in the VIR data; and one spectrum strongly resembling a pure olivine. The olivine-like calculated end member spectrum provides important validation of the interpretation that the spectral character of VIR data in the Bellicia/Arruntia region is due to the spectral influence of an olivine component. In addition, the ˜600-nm feature in one of the calculated pyroxene end members is an unexpected and compelling result. Coordinated petrologic and spectral analyses of unbrecciated eucrites by [8] indicate that a similar ˜600-nm absorption is observable in relatively primitive, Cr-rich pyroxenes. This observation suggested that the presence of a ˜600-nm absorption in remote-sensing data for Dawn may be a straightforward indicator of the presence of primitive materials - a prediction that is borne out in these results. Evaluation of the hyperspectral projected cube reveals that discrete regions of spectrally pure olivine are indeed present throughout the walls of Bellicia and, to a lesser extent, Arruntia. Spectra of the Arruntia ejecta in the projected cube contain less of an olivine component than the walls, but important spatial variations are apparent. In particular, the proximal Arruntia ejecta (< 1 crater radius) appear to contain very little olivine, whereas spectra of the more distal ejecta (> 1 crater radius) do display an apparent olivine component. This observation strongly suggests that the Arruntia impact has revealed a compositionally stratified subsurface, with an enhanced olivine component occurring at slightly deeper levels. Projected spectra displaying pyroxene bands with a superimposed ˜600-nm feature occur primarily on crater walls, often in association with olivine- dominated spectra. The co-occurrence of Cr-rich pyroxene and olivine in this unique region of Vesta suggests that a primitive lithology is locally exposed at the surface. We interpret these observations as indicating the presence of one or more differentiated plutons in the Bellicia/Arruntia region.

EFFECT OF VISIBLE RANGE ELECTROMAGNETIC RADIATIONS ON ESCHERICHIA COLI.

PubMed

Azeemi, Samina T Yousuf; Shaukat, Saleem Farooq; Azeemi, Khawaja Shamsuddin; Khan, Idrees; Mahmood, Khalid; Naz, Farah

2017-01-01

Escherichia coli is the agent responsible for a range of clinical diseases. With emerging antimicrobial resistance, other treatment options including solar/photo-therapy are becoming increasingly common. Visible Range Radiation Therapy/Colour Therapy is an emerging technique in the field of energy/vibrational medicine that uses visible spectrum of Electromagnetic Radiations to cure different diseases. In this study, our goal was to understand the effect of Visible Range Electromagnetic Radiations on E. coli (in vitro) and therefore find out the most appropriate visible range radiation for the treatment of diseases caused by E. coli. A total of 6 non-repetitive E. coli isolates were obtained from urine samples obtained from hospitalized patients with UTI. Single colony of E. coli was inoculated in 3 ml of Lysogeny Broth (LB) and 40 μl of this E. coli suspension was poured into each of the plastic tubes which were then irradiated with six different wavelengths in the visible region (Table. 1) after 18 hours with one acting as a control. The Optical Densities of these irradiated samples were then measured. Furthermore, scanning electron microscopy (TEFCAN ZEGA3) was carried out. The analysis of the microscopic and SEM images of irradiated E. coli samples with six different visible range radiations is representative of The fact that E. coli responded differently to every applied radiation in the visible region and the most profound inhibitory effects were that of 538nm Visible Range Radiation (Green) which proved to be bactericidal and 590nm Visible Range Radiation (yellow) which was bacteriostatic. The enhanced growth of E. coli with varying degrees was clearly observed in 610nm (orange), 644nm (red), 464nm (Purple) and 453nm (blue). It can be concluded that 538nm (Green) and 590nm (Yellow) can effectively be used for treating E. coli borne diseases.

EFFECT OF VISIBLE RANGE ELECTROMAGNETIC RADIATIONS ON ESCHERICHIA COLI

PubMed Central

Azeemi, Samina T. Yousuf; Shaukat, Saleem Farooq; Azeemi, Khawaja Shamsuddin; Khan, Idrees; Mahmood, Khalid; Naz, Farah

2017-01-01

Background: Escherichia coli is the agent responsible for a range of clinical diseases. With emerging antimicrobial resistance, other treatment options including solar/photo-therapy are becoming increasingly common. Visible Range Radiation Therapy/Colour Therapy is an emerging technique in the field of energy/vibrational medicine that uses visible spectrum of Electromagnetic Radiations to cure different diseases. In this study, our goal was to understand the effect of Visible Range Electromagnetic Radiations on E. coli (in vitro) and therefore find out the most appropriate visible range radiation for the treatment of diseases caused by E. coli. Materials and Methods: A total of 6 non-repetitive E. coli isolates were obtained from urine samples obtained from hospitalized patients with UTI. Single colony of E. coli was inoculated in 3 ml of Lysogeny Broth (LB) and 40 μl of this E. coli suspension was poured into each of the plastic tubes which were then irradiated with six different wavelengths in the visible region (Table. 1) after 18 hours with one acting as a control. The Optical Densities of these irradiated samples were then measured. Furthermore, scanning electron microscopy (TEFCAN ZEGA3) was carried out. Results: The analysis of the microscopic and SEM images of irradiated E. coli samples with six different visible range radiations is representative of The fact that E. coli responded differently to every applied radiation in the visible region and the most profound inhibitory effects were that of 538nm Visible Range Radiation (Green) which proved to be bactericidal and 590nm Visible Range Radiation (yellow) which was bacteriostatic. The enhanced growth of E. coli with varying degrees was clearly observed in 610nm (orange), 644nm (red), 464nm (Purple) and 453nm (blue). Conclusion: It can be concluded that 538nm (Green) and 590nm (Yellow) can effectively be used for treating E. coli borne diseases. PMID:28331912

Plasmonic resonance in planer split ring trimer

NASA Astrophysics Data System (ADS)

Xu, Haiqing; Li, Hongjian; Xiao, Gang

2014-12-01

We have numerically investigated the plasmon properties supported by asymmetry planer split ring trimer structures. We investigate the modification of gap distance, thickness and gap width on the transmission properties of the weak coupling model (g is larger than or equal to 120 nm, d=48 nm, t is larger than 30 nm, w1=200 nm, and w2=40 nm), as the coupling becomes weaker, the first peak sharply attenuates, the second peak slightly decreases, the transmission dip in the near-infrared region becomes shallow, and they are very sensitive to the gap distance between two small split ring pairs and the thickness and gap width of the big split ring. We also study the change of gap distance on the strong coupling model (g is smaller than or equal to 40 nm, d=24 nm, t=10 nm, w1=80 nm, and w2=20 nm), there exists a new Fano resonance peak, the strongest peak in visible region becomes symmetry, while the peak in near-infrared region becomes asymmetry. The resonator design strategy opens up a rich pathway for the implementation of optimized optical properties for specific applications.

Nanostructured polymer brushes.

PubMed

Schmelmer, Ursula; Paul, Anne; Küller, Alexander; Steenackers, Marin; Ulman, Abraham; Grunze, Michael; Gölzhäuser, Armin; Jordan, Rainer

2007-03-01

Nanopatterned polymer brushes with sub-50-nm resolution were prepared by a combination of electron-beam chemical lithography (EBCL) of self-assembled monolayers (SAMs) and surface-initiated photopolymerization (SIPP). As a further development of our previous work, selective EBCL was performed with a highly focused electron beam and not via a mask, to region-selectively convert a SAM of 4'-nitro-1,1'-biphenyl-4-thiol to defined areas of crosslinked 4'-amino-1,1'-biphenyl-4-thiol. These "written" structures were then used to prepare surface-bonded, asymmetric, azo initiator sites of 4'-azomethylmalonodinitrile-1,1'-biphenyl-4-thiol. In the presence of bulk styrene, SIPP amplified the primary structures of line widths from 500 to 10 nm to polystyrene structures of line widths 530 nm down to approximately 45 nm at a brush height of 10 or 7 nm, respectively, as measured by scanning electron microscopy and atomic force microscopy (AFM). The relative position of individual structures was within a tolerance of a few nanometers, as verified by AFM. At line-to-line spacings down to 50-70 nm, individual polymer brush structures are still observable. Below this threshold, neighboring structures merge due to chain overlap.

THE SPECTRUM OF THORIUM FROM 250 nm TO 5500 nm: RITZ WAVELENGTHS AND OPTIMIZED ENERGY LEVELS

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

Redman, Stephen L.; Nave, Gillian; Sansonetti, Craig J.

2014-03-01

We have made precise observations of a thorium-argon hollow cathode lamp emission spectrum in the region between 350 nm and 1175 nm using a high-resolution Fourier transform spectrometer. Our measurements are combined with results from seven previously published thorium line lists to re-optimize the energy levels of neutral, singly, and doubly ionized thorium (Th I, Th II, and Th III). Using the optimized level values, we calculate accurate Ritz wavelengths for 19, 874 thorium lines between 250 nm and 5500 nm (40, 000 cm{sup –1} to 1800 cm{sup –1}). We have also found 102 new thorium energy levels. A systematicmore » analysis of previous measurements in light of our new results allows us to identify and propose corrections for systematic errors in Palmer and Engleman and typographical errors and incorrect classifications in Kerber et al. We also found a large scatter with respect to the thorium line list of Lovis and Pepe. We anticipate that our Ritz wavelengths will lead to improved measurement accuracy for current and future spectrographs that make use of thorium-argon or thorium-neon lamps as calibration standards.« less

An Investigation of Magneto-Optical Effects

NASA Technical Reports Server (NTRS)

Adams, Mitzi L.; Hagyard, Mona J.; West, Edward A.

1998-01-01

We exhibit the effects of Faraday rotation on the direction of the transverse component of the magnetic field in a simple, symmetric sunspot. A set of 35 polarization filtergrams of NOAA active region 4662 (June 9, 1985) were obtained with the Marshall Space Flight Center (MSFC) vector magnetograph. These filtergrams measured the Stokes I, Q, U, and V intensities averaged over the instrument's filter bandpass (0.0125 nm) for wavelengths from 0.017 nm in the red wing to 0.017 nm in the blue wing of the Lambda525.22 nm spectral line in steps of 0.001 nm. These data were used to derive the azimuth phi of the vector field as a function of wavelength over the field of view of the sunspot. We interpret the observed variations of this azimuth with wavelength as the effects of Faraday rotation and verify this interpretation by comparing these variations with those predicted from magneto-optical theory. In the theoretical calculations we use the line-profile parameters and magnetic field strength derived in previous work by Balasubramaniam and West (Astrophys. J 382, p. 699, 1991).

Interface influence on the properties of Co90Fe10 films on soft magnetic underlayers - Magnetostrictive and Mössbauer spectrometry studies

NASA Astrophysics Data System (ADS)

Szumiata, Tadeusz; Gzik-Szumiata, Małgorzata; Brzózka, Katarzyna; Górka, Bogumił; Gawroński, Michał; Caruana Finkel, Anastasia; Reeves-McLaren, Nik; Morley, Nicola A.

2016-03-01

The main aim of the work was to show the correlation between magnetostrictive properties and microstructure of 25 nm thick Co90Fe10 films deposited on soft magnetic underlayers. A special attention was paid to the role of the interface region. In the case of Co90Fe10 on 25 nm and 35 nm thick METGLAS underlayers one can resolve in conversion electron Mössbauer spectra two hyperfine field distributions (high-field and medium-field ones) corresponding to both constituents of bilayers. Analogical distributions describe the spectra of Co90Fe10 on 25 nm and 35 nm thick Ni81Fe19 underlayers, however an additional low-field, smeared component has been observed. It has been attributed to the interface layer (of partially disordered structure) between magnetostrictive layer and soft magnetic layer. Such interpretation is backed up by the obtained strong correlation between mean hyperfine field value and magnetostriction constant of the films. The investigated bilayers are good candidates for MRAM devices.

Femtosecond Measurements Of Size-Dependent Spin Crossover In FeII(pyz)Pt(CN)4 Nanocrystals

DOE PAGES

Sagar, D. M.; Baddour, Frederick G.; Konold, Patrick; ...

2016-01-07

We report a femtosecond time-resolved spectroscopic study of size-dependent dynamics in nanocrystals (NCs) of Fe(pyz)Pt(CN) 4. We observe that smaller NCs (123 or 78 nm cross section and < 25 nm thickness) exhibit signatures of spin crossover (SCO) with time constants of ~ 5-10 ps whereas larger NCs with 375 nm cross section and 43 nm thickness exhibit a weaker SCO signature accompanied by strong spectral shifting on a ~20 ps time scale. For the small NCs, the fast dynamics appear to result from thermal promotion of residual low-spin states to high-spin states following nonradiative decay, and the size dependencemore » is postulated to arise from differing high-spin vs low-spin fractions in domains residing in strained surface regions. The SCO is less efficient in larger NCs owing to their larger size and hence lower residual LS/HS fractions. Our results suggest that size-dependent dynamics can be controlled by tuning surface energy in NCs with dimensions below ~25 nm for use in energy harvesting, spin switching, and other applications.« less

Investigation of Upconversion, downshifting and quantum –cutting behavior of Eu3+, Yb3+, Bi3+ co-doped LaNbO4 phosphor as a spectral conversion material

NASA Astrophysics Data System (ADS)

Dwivedi, A.; Mishra, K.; Rai, S. B.

2018-06-01

This work presents the spectral conversion characteristics [upconversion (UC), downshifting (DS) and quantum–cutting (QC) optical processes] of Eu3+, Yb3+ and Bi3+ co-doped LaNbO4 (LBO) phosphor samples synthesized by solid state reaction technique. The crystal structure and the pure phase formation have been confirmed by x-ray diffraction (XRD) measurements. The surface morphology and particle size are studied by scanning electron microscopy (SEM). The rarely observed intense red UC emission from Eu3+ ion has been successfully obtained in Eu3+/Yb3+ co-doped LaNbO4 phosphor (on excitation with 980 nm) by optimizing the concentrations of Eu3+ and Yb3+ ions. The downshifting (DS) behavior has been studied by photoluminescence (PL) measurements on excitation with 265 nm wavelength from a Xe lamp source. A broad blue emission in the region 300–550 nm with its maximum ∼415 nm due to charge transfer band (CTB) of the host and large number of sharp peaks due to f-f transitions of Eu3+ ion have been observed. The energy transfer has been observed from (NbO4)3‑ to Eu3+ ion and the fluorescence emission has been optimized by varying the concentration of Eu3+ ion. An intense red emission has also been observed corresponding to 5D0 → 7F2 transition of Eu3+ ion at 611 nm in LBO: 0.09Eu3+ phosphor on excitation with 394 nm. The luminescence properties of Eu3+ ion are enhanced further through the sensitization effect of Bi3+ ion. The near infra-red (NIR) quantum cutting (QC) behavior due to Yb3+ ion has been monitored on excitation with 265 as well as 394 nm. The NIR QC is observed due to 2F5/2 → 2F7/2 transition of Yb3+ ion via co-operative energy transfer (CET) process from (NbO4)3‑ as well as Eu3+ ions to Yb3+ ion. This multimodal behavior (UC, DS and QC) makes this a promising phosphor material for multi-purpose spectral converter.

Assessing the Extent of Black Carbon Absorption Enhancements from Field Observations

NASA Astrophysics Data System (ADS)

Cappa, C. D.; Zhang, X.; Metcalf, A. R.; Kim, H.; Zhang, Q.; Zimmermann, K.; Bertram, T. H.; Corrigan, A. L.; Russell, L. M.

2013-12-01

Black carbon (BC) and brown carbon (BrC) play important roles as short-lived climate forcers (SLCFs) as a result of their short atmospheric lifetimes and ability to absorb solar radiation. The direct impacts of BC on climate depend on just how efficiently a given BC particle absorbs solar radiation, while the impacts of BrC depend on the specific properties of the BrC. The addition of 'coatings' to BC particles can theoretically increase the absorption by a given particle, and this theoretical 'lensing' enhancement has been confirmed through laboratory experiments. However, recent field observations (from the CalNex and CARES studies; Cappa et al. 2012), using a novel thermodenuder-absorption method, have suggested that the actual enhancement for ambient particles is substantially less than theoretically expected. Here, we will discuss results from similar measurements made during two recent field studies, the 2013 DISCOVER-AQ Fresno study and the 2013 SOAS Look Rock study. DISCOVER-AQ took place in Jan/Feb 2013 in Fresno, CA. This region is severely impacted by particulate matter from local and regional residential biomass burning, and thus provides a sharp contrast to the previous CalNex and CARES studies. SOAS took place during June/July 2013 at Look Rock National Park, TN, a relatively remote region strongly impacted by biogenic emissions (predominately isoprene) and located approximately 30 miles away from Knoxville, TN. The difference in absorption for dry, ambient particles will be compared with absorption measured for particles that have been passed through a thermodenuder. Additionally, variations in the mass absorption coefficient, determined from comparison of the measured light absorption and refractory black carbon concentrations, will be examined. The relative contributions of BrC and BC to total absorption at 405 nm, 532 nm and 870 nm will be discussed. The overall measurements suggest a relatively small role for lensing-induced absorption enhancements for ambient particles in these regions.

Rotated grating coupled surface plasmon resonance on wavelength-scaled shallow rectangular gratings

NASA Astrophysics Data System (ADS)

Szalai, A.; Szekeres, G.; Balázs, J.; Somogyi, A.; Csete, Maria

2013-09-01

Theoretical investigation of rotated grating coupling phenomenon was performed on a multilayer comprising 416-nmperiodic shallow rectangular polymer grating on bimetal film made of gold and silver layers. During the multilayer illumination by 532 nm wavelength p-polarized light the polar and azimuthal angles were varied. In presence of 0-35 nm, 0-50 nm and 15-50 nm thick polymer-layers at the valleys and hills splitting was observed on the dual-angle dependent reflectance in two regions: (i) close to 0° azimuthal angle corresponding to incidence plane parallel to the periodic pattern (P-orientation); and (ii) around ~33.5°/29°/30° azimuthal angle (C-orientation), in agreement with our previous experimental studies. The near-field study revealed that in P-orientation the E-field is enhanced at the glass side with p/2 periodicity at the first minimum appearing at 49°/50°/52° polar angles, and comprises maxima below both the valleys and hills; while E-field enhancement is observable both at the glass and polymer side with p-periodicity at the second minimum developing at 55°/63/64° tilting, comprising maxima intermittently below the valleys or above the hills. In Corientation coupled plasmonic modes are observable, involving modes propagating along the valleys at the secondary maxima appearing at ~35°/32°/32° azimuthal and ~49°/51°/56° polar angles, while modes confined along the polymer hills are observable at the primary minima, which are coupled most strongly at the ~31.5°/25°/28° azimuthal and ~55°/63°/66° polar angles. The secondary peak observable in C-orientation is proposed for biosensing applications, since the supported modes are confined along the valleys, where biomolecules prefer to attach.

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

Coarse-Grained Simulation of Solvated Cellulose Ib Microfibril

NASA Astrophysics Data System (ADS)

Fan, Bingxin; Maranas, Janna; Zhong, Linghao; Zhen Zhao Collaboration

2013-03-01

We construct a coarse-grained (CG) model of cellulose microfibrils in water. The force field is derived from atomistic simulation of a 40 glucose-unit-long microfibril by requiring consistency between the chain configuration, intermolecular packing and hydrogen bonding of the two levels of modeling. Intermolecular interactions such as hydrogen bonding are added sequentially until the force field holds the microfibril crystal structure. This stepwise process enables us to evaluate the importance of each potential and provides insight to ordered and disordered regions. We simulate cellulose microfibrils with 100 to 400 residues, comparable to the smallest observed microfibrils. Microfibrils longer than 100nm would form a bending region along their longitudinal direction. Multiple bends are observed in the microfibril containing 400 residues. Although the cause is not clear, the bending regions may provide us insights about the periodicity and the behavior of the disordered regions in the microfibril.

Stress response in Caenorhabditis elegans caused by optical tweezers: wavelength, power, and time dependence.

PubMed Central

Leitz, Guenther; Fällman, Erik; Tuck, Simon; Axner, Ove

2002-01-01

Optical tweezers have emerged as a powerful technique for micromanipulation of living cells. Although the technique often has been claimed to be nonintrusive, evidence has appeared that this is not always the case. This work presents evidence that near-infrared continuous-wave laser light from optical tweezers can produce stress in Caenorhabditis elegans. A transgenic strain of C. elegans, carrying an integrated heat-shock-responsive reporter gene, has been exposed to laser light under a variety of illumination conditions. It was found that gene expression was most often induced by light of 760 nm, and least by 810 nm. The stress response increased with laser power and irradiation time. At 810 nm, significant gene expression could be observed at 360 mW of illumination, which is more than one order of magnitude above that normally used in optical tweezers. In the 700-760-nm range, the results show that the stress response is caused by photochemical processes, whereas at 810 nm, it mainly has a photothermal origin. These results give further evidence that the 700-760-nm wavelength region is unsuitable for optical tweezers and suggest that work at 810 nm at normal laser powers does not cause stress at the cellular level. PMID:11916877

Exciplex electroluminescence and photoluminescence spectra of the new organic materials based on zinc complexes of sulphanylamino-substituted ligands.

PubMed

Kaplunov, Mikhail G; Krasnikova, Svetlana S; Nikitenko, Sergey L; Sermakasheva, Natalia L; Yakushchenko, Igor K

2012-04-03

We have investigated the electroluminescence spectra of the electroluminescent devices based on the new zinc complexes of amino-substituted benzothiazoles and quinolines containing the C-N-M-N chains in their chelate cycles. The spectra exhibit strong exciplex bands in the green to yellow region 540 to 590 nm due to interaction of the excited states of zinc complexes and triaryl molecules of the hole-transporting layer. For some devices, the intrinsic luminescence band of 460 nm in the blue region is also observed along with the exciplex band giving rise to an almost white color of the device emission. The exciplex band can be eliminated if the material of the hole-transporting layer is not a triarylamine derivative. We have also found the exciplex emission in the photoluminescence spectra of the films containing blends of zinc complex and triphenylamine material.

Exciplex electroluminescence and photoluminescence spectra of the new organic materials based on zinc complexes of sulphanylamino-substituted ligands

PubMed Central

2012-01-01

We have investigated the electroluminescence spectra of the electroluminescent devices based on the new zinc complexes of amino-substituted benzothiazoles and quinolines containing the C-N-M-N chains in their chelate cycles. The spectra exhibit strong exciplex bands in the green to yellow region 540 to 590 nm due to interaction of the excited states of zinc complexes and triaryl molecules of the hole-transporting layer. For some devices, the intrinsic luminescence band of 460 nm in the blue region is also observed along with the exciplex band giving rise to an almost white color of the device emission. The exciplex band can be eliminated if the material of the hole-transporting layer is not a triarylamine derivative. We have also found the exciplex emission in the photoluminescence spectra of the films containing blends of zinc complex and triphenylamine material. PMID:22471942

Direct Observation of Gold Nanoparticle Assemblies with the Porin MspA on Mica

PubMed Central

Basel, Matthew T.; Dani, Raj Kumar; Kang, Myungshim; Pavlenok, Mikhail; Chikan, Viktor; Smith, Paul E.; Niederweis, Michael

2009-01-01

The octameric porin MspA from Mycobacterium smegmatis is sufficiently stable to form a non-membrane-supported stand-alone porin on Mica surfaces. About 98% of all MspA octamers were found to stand upright on Mica, with their periplasmic loop regions bound to the hydrophilic Mica surface. Both, small (d = 3.7 nm) and large (d = 17 nm) gold nanoparticles bind to MspA, however in different positions: small gold nanoparticles bind within the MspA pore, whereas the large gold nanoparticles bind to the upper region of MspA. These experiments demonstrate that gold nanoparticles can be positioned at different, well-defined distances from the underlying surface using the MspA pore as a template. These findings represent a significant step towards the use of electrically insulating stable proteins in combination with metal nanoparticles in nanodevices. PMID:19236086

Seismotectonic, structural, volcanologic, and geomorphic study of New Zealand; indigenous forest assessment in New Zealand; mapping, land use, and environmental studies in New Zealand, volume 1

NASA Technical Reports Server (NTRS)

Probine, M. C.; Suggate, R. P.; Mcgreevy, M. G.; Stirling, I. F. (Principal Investigator)

1977-01-01

The author has identified the following significant results. Results of the atmospheric extinction measurements show clearly the greater opacity of the atmosphere in MSS band 4 which is due to Rayleigh scattering. Atmospheric water vapor absorbs strongly in a wide region between 900 nm and 1000 nm, and this results in a consistently higher extinction coefficient than would otherwise be expected in MSS band 7. The short term fluctuations tend to be greater in band 7 than in the other bands, and this effect is probably due to variations of water vapor concentration in the instrument line of sight. These high extinction coefficients and short term fluctuations in band 7 were observed at Menindee which is in a semi-desert region in western New South Wales.

Microstructural characterization of Ti-6Al-4V metal chips by focused ion beam (FIB) and transmission electron microscopy (TEM)

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

Schneider, Judy; Dong, Lei; Howe, Jane Y

2011-01-01

The microstructure of the secondary deformation zone (SDZ) near the cutting surface in metal chips of Ti-6Al-4V formed during machining was investigated using focused ion beam (FIB) specimen preparation and transmission electron microscopy (TEM) imaging. Use of the FIB allowed precise extraction of the specimen across this region to reveal its inhomogeneous microstructure resulting from the non-uniform distribution of strain, strain rate, and temperature generated during the cutting process. Initial imaging from conventional TEM foil preparation revealed microstructures ranging from heavily textured to regions of fine grains. Using FIB preparation, the transverse microstructure could be interpreted as fine grains nearmore » the cutting surface which transitioned to coarse grains toward the free surface. At the cutting surface a 10 nm thick recrystallized layer was observed capping a 20 nm thick amorphous layer.« less

A rocket-borne airglow photometer

NASA Technical Reports Server (NTRS)

Paarmann, L. D.; Smith, L. G.

1977-01-01

The design of a rocket-borne photometer to measure the airglow emission of ionized molecular nitrogen in the 391.4 nm band is presented. This airglow is a well known and often observed phenomenon of auroras, where the principal source of ionization is energetic electrons. It is believed that at some midlatitude locations energetic electrons are also a source of nighttime ionization in the E region of the ionosphere. If this is so, then significant levels of 391.4 nm airglow should be present. The intensity of this airglow will be measured in a rocket payload which also contains instrumentation to measured in a rocket payload which also contains instrumentation to measure energetic electron differential flux and the ambient electron density. An intercomparison of the 3 experiments in a nightime launch will allow a test of the importance of energetic electrons as a nighttime source of ionization in the upper E region.

Absorption Properties of Mediterranean Aerosols Obtained from Multi-year Ground-based and Satellite Remote Sensing Observations

NASA Technical Reports Server (NTRS)

Mallet, M.; Dubovik, O.; Nabat, P.; Dulac, F.; Kahn, R.; Sciare, J.; Paronis, D.; Leon, J. F.

2013-01-01

Aerosol absorption properties are of high importance to assess aerosol impact on regional climate. This study presents an analysis of aerosol absorption products obtained over the Mediterranean Basin or land stations in the region from multi-year ground-based AERONET and satellite observations with a focus on the Absorbing Aerosol Optical Depth (AAOD), Single Scattering Albedo (SSA) and their spectral dependence. The AAOD and Absorption Angstrom Exponent (AAE) data set is composed of daily averaged AERONET level 2 data from a total of 22 Mediterranean stations having long time series, mainly under the influence of urban-industrial aerosols and/or soil dust. This data set covers the 17 yr period 1996-2012 with most data being from 2003-2011 (approximately 89 percent of level-2 AAOD data). Since AERONET level-2 absorption products require a high aerosol load (AOD at 440 nm greater than 0.4), which is most often related to the presence of desert dust, we also consider level-1.5 SSA data, despite their higher uncertainty, and filter out data with an Angstrom exponent less than 1.0 in order to study absorption by carbonaceous aerosols. The SSA data set includes both AERONET level-2 and satellite level-3 products. Satellite-derived SSA data considered are monthly level 3 products mapped at the regional scale for the spring and summer seasons that exhibit the largest aerosol loads. The satellite SSA dataset includes the following products: (i) Multi-angle Imaging SpectroRadiometer (MISR) over 2000-2011, (ii) Ozone Monitoring Instrument (OMI) near-UV algorithm over 2004-2010, and (iii) MODerate resolution Imaging Spectroradiometer (MODIS) Deep-Blue algorithm over 2005-2011, derived only over land in dusty conditions. Sun-photometer observations show that values of AAOD at 440 nm vary between 0.024 +/- 0.01 (resp. 0.040 +/- 0.01) and 0.050 +/- 0.01 (0.055 +/- 0.01) for urban (dusty) sites. Analysis shows that the Mediterranean urban-industrial aerosols appear "moderately" absorbing with values of SSA close to approximately 0.94-0.95 +/- 0.04 (at 440 nm) in most cases except over the large cities of Rome and Athens, where aerosol appears more absorbing (SSA approximately 0.89-0.90 +/- 0.04). The aerosol Absorption Angstrom Exponent (AAE, estimated using 440 and 870 nm) is found to be larger than 1 for most sites over the Mediterranean, a manifestation of mineral dust (iron) and/or brown carbon producing the observed absorption. AERONET level-2 sun-photometer data indicate the existence of a moderate East-West gradient, with higher values over the eastern basin (AAEEast. = 1.39/AAEWest. = 1.33) due to the influence of desert dust. The North-South AAE gradient is more pronounced, especially over the western basin. Our additional analysis of AERONET level-1.5 data also shows that organic absorbing aerosols significantly affect some Mediterranean sites. These results indicate that current climate models treating organics as nonabsorbing over the Mediterranean certainly underestimate the warming effect due to carbonaceous aerosols. Acomparative analysis of the regional SSA variability has been attempted using satellite data. OMI and MODIS data show an absorbing zone (SSA approximately 0.90 at 470-500 nm) over Northeastern Africa that does not appear in the MISR retrievals. In contrast, MISR seems able to observe the East-West SSA gradient during summer, as also detected by AERONET. Also, the analysis of SSA provided by satellites indicates that the aerosol over the Mediterranean Sea appears less absorbing during spring (MAM) than summer (JJA).

Measurements of absolute absorption cross sections of ozone in the 185- to 254-nm wavelength region and the temperature dependence

NASA Technical Reports Server (NTRS)

Yoshino, K.; Esmond, J. R.; Freeman, D. E.; Parkinson, W. H.

1993-01-01

Laboratory measurements of the relative absorption cross sections of ozone at temperatures 195, 228, and 295 K have been made throughout the 185 to 254 nm wavelength region. The absolute absorption cross sections at the same temperatures have been measured at several discrete wavelengths in the 185 to 250 nm region. The absolute cross sections of ozone have been used to put the relative cross sections on a firm absolute basis throughout the 185 to 255 nm region. These recalibrated cross sections are slightly lower than those of Molina and Molina (1986), but the differences are within a few percent and would not be significant in atmospheric applications.

Long term change in atmospheric dust absorption, dust scattering and black carbon aerosols scattering coefficient parameters over western Indian locations

NASA Astrophysics Data System (ADS)

Satoliya, Anil Kumar; Vyas, B. M.; Shekhawat, M. S.

2018-05-01

The first time satellite space based measurement of atmospheric black carbon (BC) aerosols scattering coefficient at 550nm (BC SC at 550nm), dust aerosols scattering and dust aerosols extinction coefficient (DSC at 550nm and DEC at 550nm) parameters have been used to understand their long term trend of natural and anthropogenic aerosols behavior with its close association with ground based measured precipitation parameters such as Total Rain Fall (TRF), and Total Number of Rainy Days (TNRD) for the same period over western Indian regions concerned to the primary aerosols sources of natural activities. The basic objective of this study is an attempt to investigate the inter-correlation between dust and black carbon aerosols loading characteristics with a variation of rainfall pattern parameters as indirect aerosols induced effect i.e., aerosols-cloud interaction. The black carbon aerosols generated by diverse anthropogenic or human made activities are studied by choosing of measured atmospheric BC SC at 550nm parameter, whereas desert dust mineral aerosols primarily produced by varieties of natural activities pre-dominated of dust mineral desert aerosols mainly over Thar desert influenced area of hot climate and rural tropical site are investigated by selecting DSC at 550nm and DEC at 550nm of first semi-urban site i.e., Udaipur (UDP, 24.6°N, 73.35°E, 580m above surface level (asl)) situated in southern Rajasthan part as well as over other two Great Indian Thar desert locations i.e., Jaisalmer (JSM, 26.90°N, 69.90°E, 220m asl)) and Bikaner (BKN, 28.03°N, 73.30°E, 224m asl) located in the vicinity of the Thar desert region situated in Rajasthan state of the western Indian region. The source of the present study would be collection of longer period of monthly values of the above parameters of spanning 35 years i.e., 1980 to 2015. Such types of atmospheric aerosols-cloud monsoon interaction investigation is helpful in view of understanding their direct and indirect aerosols active role of optical absorption and scattering of solar light radiation at useful wavelength 550nm as well as heating of clouds over least explored region, i.e., the Thar desert region and also away from less dust dominated influenced provinces for longer period. The analysis of the above the result would also give a clear scientific evidence of alteration in enhancement in DSC at 550nm and DEC at 550nm and BC SC at 550nm variables with simultaneous corresponding reduction in the five yearly mean precipitation activity parameters such as TRF and TNRD. It is quite evident that anthropogenic BC aerosols activity are showing the significant increasing trend at all three locations, but it is more prominent over central Thar Desert influenced regime, i.e., JSM and BKN relative to semi-urban region i.e., UDP. The systematic increasing pattern of average monthly mean value of DSC at 550nm and DEC at 550nm or increasing aerosol loading have been revealed from acquiring their lowest value in January month and the highest values in July and retained with the broad peak values in pre-monsoon months. Subsequently, their respective values reduce sharply downward from August to December onwards. The mountain value of dust aerosols parameters, i.e., DSC at 550nm and DEC at 550nm are systematically enhanced toward from UDP to BKN and then maximized at JSM. It is clearly obvious fact that the following ascending order of desert aerosols loading influenced activity in different areas has been recorded, i.e., JSM> BKN>UDP. Several other interesting features of the earth-climate change implication in reference to the altering nature of reduction of precipitation parameter pattern with simultaneous observed elevated dust aerosol and BC aerosol loading have been also noticed in the course of present investigation. Overall reduction in rainfall pattern effect with increasing of dust aerosols loading or vice versa are seen more pronounced over JSM and lees prevalence over UDP. The more detailed investigations about other interesting results of Aerosols-Indian monsoon over western Indian locations are also discussed thoroughly in this paper.

Novel behaviors of anomalous Hall effect in TbFeCo ferrimagnetic thin films

NASA Astrophysics Data System (ADS)

Ando, Ryo; Komine, Takashi; Sato, Shiori; Kaneta, Shingo; Hara, Yoshiaki

2018-05-01

We investigate the temperature dependence and the thickness dependence of anomalous Hall effect (AHE) of TbFeCo ultra-thin films under high magnetic field. The sign change on temperature dependence of AHE in 20nm-thick TbFeCo film with rare-earth (RE) rich composition was observed. The AHE sign at low temperature is negative while it gradually becomes positive as the temperature increases. Moreover, the AHE sign for 5nm-thick TbFeCo film remains positive while that for 50nm-thick TbFeCo film remains negative at temperature in the range from 5 K to 400 K. The similar thickness dependence of AHE in TM-rich samples was also observed. From the mean-field approximation, the sign change temperature in AHE is related to the compensation temperature and the existence of interfacial region, which has the TM-rich composition and the weak anisotropy. Therefore, We clarified that the novel behavior of AHE sign changes in TbFeCo thin films with different thickness can be explained by the interfacial layer with weak anisotropy and two phase model.

Solar Spectral Irradiance Changes During Cycle 24

NASA Technical Reports Server (NTRS)

Marchenko, Sergey; Deland, Matthew

2014-01-01

We use solar spectra obtained by the Ozone Monitoring Instrument (OMI) on board the Aura satellite to detect and follow long-term (years) and short-term (weeks) changes in the solar spectral irradiance (SSI) in the 265-500 nm spectral range. During solar Cycle 24, in the relatively line-free regions the SSI changed by approximately 0.6% +/- 0.2% around 265 nm. These changes gradually diminish to 0.15% +/- 0.20% at 500 nm. All strong spectral lines and blends, with the notable exception of the upper Balmer lines, vary in unison with the solar "continuum." Besides the lines with strong chromospheric components, the most involved species include Fe I blends and all prominent CH, NH, and CN spectral bands. Following the general trend seen in the solar "continuum," the variability of spectral lines also decreases toward longer wavelengths. The long-term solar cycle SSI changes are closely, to within the quoted 0.1%-0.2% uncertainties, matched by the appropriately adjusted short-term SSI variations derived from the 27 day rotational modulation cycles. This further strengthens and broadens the prevailing notion about the general scalability of the UV SSI variability to the emissivity changes in the Mg II 280 nm doublet on timescales from weeks to years. We also detect subtle deviations from this general rule: the prominent spectral lines and blends at lambda approximately or greater than 350 nm show slightly more pronounced 27 day SSI changes when compared to the long-term (years) trends. We merge the solar data from Cycle 21 with the current Cycle 24 OMI and GOME-2 observations and provide normalized SSI variations for the 170-795 nm spectral region.

Electrically-inactive phosphorus re-distribution during low temperature annealing

NASA Astrophysics Data System (ADS)

Peral, Ana; Youssef, Amanda; Dastgheib-Shirazi, Amir; Akey, Austin; Peters, Ian Marius; Hahn, Giso; Buonassisi, Tonio; del Cañizo, Carlos

2018-04-01

An increased total dose of phosphorus (P dose) in the first 40 nm of a phosphorus diffused emitter has been measured after Low Temperature Annealing (LTA) at 700 °C using the Glow Discharge Optical Emission Spectrometry technique. This evidence has been observed in three versions of the same emitter containing different amounts of initial phosphorus. A stepwise chemical etching of a diffused phosphorus emitter has been carried out to prepare the three types of samples. The total P dose in the first 40 nm increases during annealing by 1.4 × 1015 cm-2 for the sample with the highly doped emitter, by 0.8 × 1015 cm-2 in the middle-doped emitter, and by 0.5 × 1015 cm-2 in the lowest-doped emitter. The presence of surface dislocations in the first few nanometers of the phosphorus emitter might play a role as preferential sites of local phosphorus gettering in phosphorus re-distribution, because the phosphorus gettering to the first 40 nm is lower when this region is etched stepwise. This total increase in phosphorus takes place even though the calculated electrically active phosphorus concentration shows a reduction, and the measured sheet resistance shows an increase after annealing at a low temperature. The reduced electrically active P dose is around 0.6 × 1015 cm-2 for all the emitters. This can be explained with phosphorus-atoms diffusing towards the surface during annealing, occupying electrically inactive configurations. An atomic-scale visual local analysis is carried out with needle-shaped samples of tens of nm in diameter containing a region of the highly doped emitter before and after LTA using Atom Probe Tomography, showing phosphorus precipitates of 10 nm and less before annealing and an increased density of larger precipitates after annealing (25 nm and less).

Optical and morphological properties of sol gel derived titanium dioxide films

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

Sharma, A. B.; Sharma, S. K.; M, Vishwas

2015-08-28

Titanium oxide (Titania) thin films were synthesized on different substrates via the sol-gel dip-coating method using alkoxide solution. Some selected samples were also prepared with different percentage of Lead (Pb). The influence of Pb addition in precursor sol on the optical properties of titanium dioxide thin films was studied. The optical transmittance in the visible region has increased with increase in weight percentage of lead. The refractive index was slightly decreased with Pb addition. Crystallization of these coatings was achieved through thermal annealing at temperatures above 400 °C. The structural properties and surface morphology of the crystallized coatings were studiedmore » by Scanning Electron Microscopy. Increase in average grain size from 250 nm to 350 nm with increase in Pb concentration is observed. Films were appeared to more coarse with increase in Pb addition. An increase in Pb addition resulted increase in average roughness from 12 nm to 25 nm.« less

Absolute ozone absorption cross section in the Huggins Chappuis minimum (350-470 nm) at 296 K

NASA Astrophysics Data System (ADS)

Axson, J. L.; Washenfelder, R. A.; Kahan, T. F.; Young, C. J.; Vaida, V.; Brown, S. S.

2011-08-01

We report the ozone absolute absorption cross section between 350-470 nm, the minimum between the Huggins and Chappuis bands, where the ozone cross section is less than 10-22 cm2. Ozone spectra were acquired using an incoherent broadband cavity enhanced absorption spectrometer, with three channels centered at 365, 405, and 455 nm. The accuracy of the measured cross section is 2 %. Previous measurements vary by more than an order of magnitude in this spectral region. The measurements reported here provide much greater spectral coverage than the most recent measurements. We report a minimum absorption cross section of 3.4×10-24 cm2 at 381.8 nm, which is 22 % lower than the previously reported value. The effect of O3 concentration and water vapor partial pressure were investigated, however there were no observable changes in the absorption spectrum most likely due to the low optical density of the complex.

Au 329–xAg x(SR) 84 Nanomolecules: Plasmonic Alloy Faradaurate-329

DOE PAGES

Kumara, Chanaka; Zuo, Xiaobing; Cullen, David A.; ...

2015-08-10

Though significant progress has been made to improve the monodispersity of larger (>10 nm) alloy metal nanoparticles, there still exists a significant variation in nanoparticle composition, ranging from ±1000s of atoms. Here in this paper, for the first time, we report the synthesis of atomically precise (±0 metal atom variation) Au 329–xAg x(SCH 2CH 2Ph) 84 alloy nanomolecules. The composition was determined using high resolution electrospray ionization mass spectrometry. In contrast to larger (>10 nm) Au–Ag nanoparticles, the surface plasmon resonance (SPR) peak does not show a major shift, but a minor ~10 nm red-shift, upon increasing silver content. Themore » intensity of the SPR peak also varies in an intriguing manner, where a dampening is observed with medium silver incorporation, and a significant sharpening is observed upon higher Ag content. The report outlines (a) an unprecedented advance in nanoparticle mass spectrometry of high mass at atomic precision; and (b) the unexpected optical behavior of Au–Ag alloys in the region where nascent SPR emerges; specifically, in this work, the SPR-like peak does not show a major ~100 nm blue-shift with Ag alloying of Au 329 nanomolecules, as shown to be common in larger nanoparticles.« less

Rapid amyloid fiber formation from the fast-folding WW domain FBP28.

PubMed

Ferguson, Neil; Berriman, John; Petrovich, Miriana; Sharpe, Timothy D; Finch, John T; Fersht, Alan R

2003-08-19

The WW domains are small proteins that contain a three-stranded, antiparallel beta-sheet. The 40-residue murine FBP28 WW domain rapidly formed twirling ribbon-like fibrils at physiological temperature and pH, with morphology typical of amyloid fibrils. These ribbons were unusually wide and well ordered, making them highly suitable for structural studies. Their x-ray and electron-diffraction patterns displayed the characteristic amyloid fiber 0.47-nm reflection of the cross-beta diffraction signature. Both conventional and electron cryomicroscopy showed clearly that the ribbons were composed of many 2.5-nm-wide subfilaments that ran parallel to the long axis of the fiber. There was a region of lower density along the center of each filament. Lateral association of these filaments generated twisted, often interlinked, sheets up to 40 nm wide and many microns in length. The pitch of the helix varied from 60 to 320 nm, depending on the width of the ribbon. The wild-type FBP28 fibers were formed under conditions in which multiexponential folding kinetics is observed in other studies and which was attributed to a change in the mechanism of folding. It is more likely that those phases result from initial events in the off-pathway aggregation observed here.

Development of an online UV-visible microspectrophotometer for a macromolecular crystallography beamline.

PubMed

Shimizu, Nobutaka; Shimizu, Tetsuya; Baba, Seiki; Hasegawa, Kazuya; Yamamoto, Masaki; Kumasaka, Takashi

2013-11-01

Measurement of the UV-visible absorption spectrum is a convenient technique for detecting chemical changes of proteins, and it is therefore useful to combine spectroscopy and diffraction studies. An online microspectrophotometer for the UV-visible region was developed and installed on the macromolecular crystallography beamline, BL38B1, at SPring-8. This spectrophotometer is equipped with a difference dispersive double monochromator, a mercury-xenon lamp as the light source, and a photomultiplier as the detector. The optical path is mostly constructed using mirrors, in order to obtain high brightness in the UV region, and the confocal optics are assembled using a cross-slit diaphragm like an iris to eliminate stray light. This system can measure optical densities up to a maximum of 4.0. To study the effect of radiation damage, preliminary measurements of glucose isomerase and thaumatin crystals were conducted in the UV region. Spectral changes dependent on X-ray dose were observed at around 280 nm, suggesting that structural changes involving Trp or Tyr residues occurred in the protein crystal. In the case of the thaumatin crystal, a broad peak around 400 nm was also generated after X-ray irradiation, suggesting the cleavage of a disulfide bond. Dose-dependent spectral changes were also observed in cryo-solutions alone, and these changes differed with the composition of the cryo-solution. These responses in the UV region are informative regarding the state of the sample; consequently, this device might be useful for X-ray crystallography.

Photoionization bands of rubidium molecule

NASA Astrophysics Data System (ADS)

Rakić, M.; Pichler, G.

2018-03-01

We studied the absorption spectrum of dense rubidium vapor generated in a T-type sapphire cell with a special emphasis on the structured photoionization continuum observed in the 200-300 nm spectral region. The photoionization spectrum has a continuous atomic contribution with a pronounced Seaton-Cooper minimum at about 250 nm and a molecular photoionization contribution with many broad bands. We discuss the possible origin of the photoionization bands as stemming from the absorption from the ground state of the Rb2 molecule to excited states of Rb2+* and to doubly excited autoionizing states of Rb2** molecule. All these photoionization bands are located above the Rb+ and Rb2+ ionization limits.

Bayesian model for matching the radiometric measurements of aerospace and field ocean color sensors.

PubMed

Salama, Mhd Suhyb; Su, Zhongbo

2010-01-01

A Bayesian model is developed to match aerospace ocean color observation to field measurements and derive the spatial variability of match-up sites. The performance of the model is tested against populations of synthesized spectra and full and reduced resolutions of MERIS data. The model derived the scale difference between synthesized satellite pixel and point measurements with R(2) > 0.88 and relative error < 21% in the spectral range from 400 nm to 695 nm. The sub-pixel variabilities of reduced resolution MERIS image are derived with less than 12% of relative errors in heterogeneous region. The method is generic and applicable to different sensors.

Random Telegraph Signal Amplitudes in Sub 100 nm (Decanano) MOSFETs: A 3D 'Atomistic' Simulation Study

NASA Technical Reports Server (NTRS)

Asenov, Asen; Balasubramaniam, R.; Brown, A. R.; Davies, J. H.; Saini, Subhash

2000-01-01

In this paper we use 3D simulations to study the amplitudes of random telegraph signals (RTS) associated with the trapping of a single carrier in interface states in the channel of sub 100 nm (decanano) MOSFETs. Both simulations using continuous doping charge and random discrete dopants in the active region of the MOSFETs are presented. We have studied the dependence of the RTS amplitudes on the position of the trapped charge in the channel and on the device design parameters. We have observed a significant increase in the maximum RTS amplitude when discrete random dopants are employed in the simulations.

Enhanced photoresponsivity in graphene-silicon slow-light photonic crystal waveguides

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

Zhou, Hao, E-mail: zhoufirst@scu.edu.cn, E-mail: tg2342@columbia.edu, E-mail: cheewei.wong@ucla.edu; Optical Nanostructures Laboratory, Columbia University, New York, New York 10027; Gu, Tingyi, E-mail: zhoufirst@scu.edu.cn, E-mail: tg2342@columbia.edu, E-mail: cheewei.wong@ucla.edu

2016-03-14

We demonstrate the enhanced fast photoresponsivity in graphene hybrid structures by combining the ultrafast dynamics of graphene with improved light-matter interactions in slow-light photonic crystal waveguides. With a 200 μm interaction length, a 0.8 mA/W photoresponsivity is achieved in a graphene-silicon Schottky-like photodetector, with an operating bandwidth in excess of 5 GHz and wavelength range at least from 1480 nm to 1580 nm. Fourfold enhancement of the photocurrent is observed in the slow light region, compared to the wavelength far from the photonic crystal bandedge, for a chip-scale broadband fast photodetector.

Electronic absorption spectral studies of Pr(III) chelates with some amino acids

NASA Astrophysics Data System (ADS)

Kachhawa, Chanchal; Solanki, Kanika; Bhandari, H. S.

2018-05-01

Investigations on Pr(III) systems with 1:1 metal-ligand stoichiometric ratio have been carried out in different solvents. β - Alanine, Taurine and anthranilic acid have been opted as ligands for the investigations. The Study is based on doped crystal phenomenon. The Slater-Condon, spin-orbit, nephelauxetic, bonding, Racah and Judd-Ofelt parameters have been explored during the study. Four bands for Pr(III) have been observed and recorded in the region 350 nm to 900nm. Partial regression method has been used for calculations. Use of computational chemistry has been explored in order to develop better and easier methods of calculations.

Nitrous Oxide Emissions from Biofuel Crops and Atmospheric Aerosols: Associations with Air Quality and Regional Climate

NASA Astrophysics Data System (ADS)

Pillai, Priya Ramachandran

Emissions of greenhouse gases (GHG) and primary release and secondary formation of aerosols alter the earth's radiative balance and therefore have important climatic implications. Savings in carbon dioxide (CO2) emissions accomplished by replacing fossil fuels with biofuels may increase the nitrous oxide (N2O) emissions. Among various atmospheric trace gases, N2O, irrespective of its low atmospheric concentration, is the fourth most important gas in causing the global greenhouse effect. Major processes, those affect the concentration of atmospheric N2O, are soil microbial activities leading to nitrification and denitrification. Therefore, anthropogenic activities such as industrial emissions, and agricultural practices including application of nitrogenous fertilizers, land use changes, biomass combustion all contribute to the atmospheric N2O concentration. The emission rates of N2O related to biofuel production depend on the nitrogen (N) fertilizer uptake efficiency of biofuel crops. However, crops with less N demand, such as switchgrass may have more favorable climate impacts when compared to crops with high N demands, such as corn. Despite its wide environmental tolerance, the regional adaptability of the potential biofuel crop switch grass varies considerably. Therefore, it is important to regionally quantify the GHG emissions and crop yield in response to N-fertilization. A major objective of this study is to quantify soil emissions of N2O from switchgrass and corn fields as a function of N-fertilization. The roles of soil moisture and soil temperature on N2O fluxes were analyzed. These N2O observations may be used to parameterize the biogeochemical models to better understand the impact of different N2O emission scenarios. This study allows for improvements in climate models that focus on understanding the environmental impacts of the climate change mitigation strategy of replacing fossil fuels with biofuels. As a second major objective, the top of the atmosphere (TOA) shortwave aerosol direct radiative forcing (SWARF) by regionally nucleated particles over a forest site in the Southeastern United States was estimated. Particle size distributions (aerodynamic diameter, Dp 10.2 nm to 250 nm), total number concentrations of nucleation mode (Dp < 25 nm) and fine mode (25 < Dp < 250 nm) particles, and growth rates were analyzed to identify regional nucleation events during November 2005 to September 2007. Shortwave flux from Clouds and Earth's Radiant Energy System (CERES) and aerosol optical depth at 550 nm (AOD, tau550) from Moderate Resolution Imaging Spectroradiometer (MODIS) instruments onboard the Earth Observing System (EOS) Terra satellite were used to estimate SWARF. AOD was highest (0.38 +/- 0.20) in summer (period of highest particle growth rate) and lowest (0.06 +/- 0.05) in winter (period of lowest particle growth rate). The nucleation day SWARF forcing was -24 +/- 11 Wm-2 in summer and -15 +/- 19 Wm-2 in spring. The radiative forcing efficiency was lower (-54 Wm-2, tau550 -1) in summer (period of highest tau550 and organic PM2.5 concentrations) as compared to spring (-93 Wm-2, tau550 -1). The results show that, during spring and summer 2006 and 2007, the radiative forcing efficiency of regionally nucleated aerosols was -73 Wm-2, tau550 -1. Formations of particles during regional nucleation events introduced significant radiative forcing that need to examine for other regions of the globe where intense regional nucleation events occur frequently.

Photoluminescence properties and structure of double perovskite Ba2ZnWO6:Eu3+, Li+ as a novel red emitting phosphor

NASA Astrophysics Data System (ADS)

Chen, Peng; Yang, Dingming; Hu, Wenyuan; Zhang, Jing; Wu, Yadong

2017-12-01

Novel red-emitting Ba2Zn1-x-yWO6:xEu3+, yLi+ phosphors were prepared using a high-temperature solid-state method, and the crystal structure, the photoluminescence properties and the doping concentrations of Eu3+ and Li+ were investigated. The results show that these phosphors can be excited by near-ultraviolet light (250-400 nm) and co-doped Li+ can significantly enhance their PL performance. An intense red emission peak at 598 nm (5D0-7F1 transitions) was observed with an excitation wavelength of 316 nm. The CIE chromaticity coordinates of the phosphors are located in the red region, indicating that the BZW:Eu3+, Li+ phosphor holds promise as a red phosphor for near-ultraviolet excited WLEDs.

In situ conductance measurements of copper phthalocyanine thin film growth on sapphire [0001].

PubMed

Murdey, Richard; Sato, Naoki

2011-06-21

The current flowing through a thin film of copper phthalocyanine vacuum deposited on a single crystal sapphire [0001] surface was measured during film growth from 0 to 93 nm. The results, expressed as conductance vs. nominal film thickness, indicate three distinct film growth regions. Conductive material forms below about 5 nm and again above 35 nm, but in the intermediate thicknesses the film conductance was observed to decrease with increasing film thickness. With the aid of ac-AFM topology images taken ex situ, the conductance results are explained based on the Stranski-Krastanov (2D + 3D) film growth mechanism, in which the formation of a thin wetting layer is followed by the growth of discrete islands that eventually coalesce into an interpenetrating, conductive network. © 2011 American Institute of Physics

Fast determination of total ginsenosides content in ginseng powder by near infrared reflectance spectroscopy

NASA Astrophysics Data System (ADS)

Chen, Hua-cai; Chen, Xing-dan; Lu, Yong-jun; Cao, Zhi-qiang

2006-01-01

Near infrared (NIR) reflectance spectroscopy was used to develop a fast determination method for total ginsenosides in Ginseng (Panax Ginseng) powder. The spectra were analyzed with multiplicative signal correction (MSC) correlation method. The best correlative spectra region with the total ginsenosides content was 1660 nm~1880 nm and 2230nm~2380 nm. The NIR calibration models of ginsenosides were built with multiple linear regression (MLR), principle component regression (PCR) and partial least squares (PLS) regression respectively. The results showed that the calibration model built with PLS combined with MSC and the optimal spectrum region was the best one. The correlation coefficient and the root mean square error of correction validation (RMSEC) of the best calibration model were 0.98 and 0.15% respectively. The optimal spectrum region for calibration was 1204nm~2014nm. The result suggested that using NIR to rapidly determinate the total ginsenosides content in ginseng powder were feasible.

Color tunable emission through energy transfer from Yb3+ co-doped SrSnO3: Ho3+ perovskite nano-phosphor

NASA Astrophysics Data System (ADS)

Jain, Neha; Singh, Rajan Kr.; Sinha, Shriya; Singh, R. A.; Singh, Jai

2018-04-01

First time color tunable lighting observed from Ho3+ and Yb3+ co-doped SrSnO3 perovskite. Down-conversion and up-conversion (UC) photoluminescence emission spectra were recorded to understand the whole mechanism of energy migration between Ho3+ and Yb3+ ions. The intensity of green and red emission varies with Yb3+ doping which causes multicolour emissions from nano-phosphor. The intensity of UC red emission (654 nm) obtained from 1 at.% Ho3+ and 3 at.% Yb3+ co-doped nano-phosphor is nine times higher than from 1 at.% Ho3+ doped SrSnO3 nano-phosphor. Enhanced brightness of 654 nm in UC process belongs in biological transparency window so that it might be a promising phosphor in the bio-medical field. Moreover, for the other Yb3+ co-doped nano-phosphor, Commission Internationale de l'Éclairage chromaticity co-ordinates were found near the white region and their CCT values lie in the range 4900-5100 K indicating cool white. Decay time was measured for 545 nm emission of Ho3+ ion found in 7.652 and 8.734 µs at 355 nm excitation. The variation in lifetime was observed in ascending order with increasing Yb3+ concentration which supports PL emission spectra observation that with increasing Yb3+ concentration, rate of transition has changed. These studies reveal that Ho3+ and Yb3+ co-doped phosphor is useful for fabrication of white LEDs.

Comparative Morphology of Mg+ and O+ Ions Made by the HIRAAS Experiment

NASA Astrophysics Data System (ADS)

Dymond, K.

2017-12-01

We present coincident observations of the spatial distribution of the Mg+ ion and O+ ions made by the High Resolution Airglow and Aurora Spectroscopy (HIRAAS) experiment that flew on the United States Air Force Advanced Research and Global Observing Satellite (ARGOS) mission during 1999-2002. The HIRAAS experiment featured two instruments that made coincident ultraviolet limb scan measurements viewing aft of the satellite. In the first year of mission operations, the Ionospheric Spectroscopy and Atmospheric Chemistry (ISAAC) instrument made observations of the Mg+ emission near 280 nm with a cadence of 100 s and altitude resolution of 5 km. The Low Resolution Airglow and Aurora Spectrograph (LORAAS) instrument made measurements of the 80-170 nm region of the Earth's airglow spectrum, including the 91.1 nm emission produced by radiative recombination of O+ and electrons, at 100 s cadence and 5 km altitude resolution. We use the recently developed Volume Emission Rate Tomography (VERT) technique to invert the UV measurements and produce the Mg+ and O+ ion distributions in the orbit plane of the satellite. We present our approach and comparisons of the distributions to each other and the International Reference Ionosphere model. Similar to previous metal ion density measurements, we see considerable variability over the globe with extended plumes of Mg+ ion density extending upward from 100 km to greater than 700 km and small compact layers. However, the O+ ion densities do not show similar structures, indicating that the Mg+ structures are likely driven by processes that act below the F-region ionosphere where O+ is a minor species. The global distribution of the Mg+ ions, which is related to the development of Sporadic-E, is of particular interest in this study.

[Worker exposure to ultrafine particles during carbon black treatment].

PubMed

Mikołajczyk, Urszula; Bujak-Pietrek, Stella; Szadkowska-Stańczyk, Irena

2015-01-01

The aim of the project was to assess the exposure of workers to ultrafine particles released during handling and packing of carbon black. The assessment included the results of the measurements performed in a carbon black handling plant before, during, and after work shift. The number concentration of particles within the dimension range 10-1000 nm and 10-100 nm was assayed by a condensation particle counter (CPC). The mass concentration of particles was determined by a DustTrak II DRX aerosol concentration monitor. The surface area concentration of the particles potentially deposited in the alveolar (A) and tracheo-bronchial (TB) regions was estimated by an AeroTrak 9000 nanoparticle monitor. An average mass concentration of particles during the process was 6-fold higher than that before its start, while a 3-fold increase in the average number concentration of particles within the dimension range 10-1000 nm and 10-100 nm was observed during the process. At the same time a 4-fold increase was found in the surface area concentration of the particles potentially deposited in the A and TB regions. During the process of carbon black handling and packing a significantly higher values of each of the analysed parameters, characterizing the exposure to ultrafine particles, were noted. This work is available in Open Access model and licensed under a CC BY-NC 3.0 PL license.

Tunable Narrow Band Emissions from Dye-Sensitized Core/Shell/Shell Nanocrystals in the Second Near-Infrared Biological Window

PubMed Central

Shao, Wei; Chen, Guanying; Kuzmin, Andrey; Kutscher, Hilliard L.; Pliss, Artem; Ohulchanskyy, Tymish Y.; Prasad, Paras N.

2017-01-01

We introduce a hybrid organic–inorganic system consisting of epitaxial NaYF4:Yb3+/X3+@NaYbF4@NaYF4:Nd3+ (X = null, Er, Ho, Tm, or Pr) core/shell/shell (CSS) nanocrystal with organic dye, indocyanine green (ICG) on the nanocrystal surface. This system is able to produce a set of narrow band emissions with a large Stokes-shift (>200 nm) in the second biological window of optical transparency (NIR-II, 1000–1700 nm), by directional energy transfer from light-harvesting surface ICG, via lanthanide ions in the shells, to the emitter X3+ in the core. Surface ICG not only increases the NIR-II emission intensity of inorganic CSS nanocrystals by ~4-fold but also provides a broadly excitable spectral range (700–860 nm) that facilitates their use in bioapplications. We show that the NIR-II emission from ICG-sensitized Er3+-doped CSS nanocrystals allows clear observation of a sharp image through 9 mm thick chicken breast tissue, and emission signal detection through 22 mm thick tissue yielding a better imaging profile than from typically used Yb/Tm-codoped upconverting nanocrystals imaged in the NIR-I region (700–950 nm). Our result on in vivo imaging suggests that these ICG-sensitized CSS nanocrystals are suitable for deep optical imaging in the NIR-II region. PMID:27935695

Divertor impurity monitor for the International Thermonuclear Experimental Reactor

NASA Astrophysics Data System (ADS)

Sugie, T.; Ogawa, H.; Nishitani, T.; Kasai, S.; Katsunuma, J.; Maruo, M.; Ebisawa, K.; Ando, T.; Kita, Y.

1999-01-01

The divertor impurity monitoring system of the International Thermonuclear Experimental Reactor has been designed. The main functions of this system are to identify impurity species and to measure the two-dimensional distributions of the particle influxes in the divertor plasmas. The wavelength range is 200-1000 nm. The viewing fans are realized by molybdenum mirrors located in the divertor cassette. With additional viewing fans seeing through the gap between the divertor cassettes, the region approximately from the divertor leg to the x point will be observed. The light from the divertor region passes through the quartz windows on the divertor port plug and the cryostat, and goes through the dog-leg optics in the biological shield. Three different type of spectrometers: (i) survey spectrometers for impurity species monitoring, (ii) filter spectrometers for the particle influx measurement with the spatial resolution of 10 mm and the time resolution of 1 ms, and (iii) high dispersion spectrometers for high resolution wavelength measurements are designed. These spectrometers are installed just behind the biological shield (for λ<450 nm) to prevent the transmission loss in fiber and in the diagnostic room (for λ⩾450 nm) from the point of view of accessibility and flexibility. The optics have been optimized by a ray trace analysis. As a result, 10-15 mm spatial resolution will be achieved in all regions of the divertor.

Chlorophyll as a biomarker for early disease diagnosis

NASA Astrophysics Data System (ADS)

Manzoor Atta, Babar; Saleem, M.; Ali, Hina; Arshad, Hafiz Muhammad Imran; Ahmed, M.

2018-06-01

The current study was designed to identify the stage for the diagnosis of disease before visible symptoms appeared. Fluorescence spectroscopy has been employed to identify disease signatures for its early diagnosis in rice plant leaves. Bacterial leaf blight (BLB) diseased and healthy leaf samples were collected from the rice fields in September, 2017 which were then used to record spectra using an excitation wavelength at 410 nm. The spectral range of emission was set from 420 to 800 nm which covers the blue–green and the chlorophyll bands. It was found that diseased leaves have a narrower ‘chlorophyll a’ band than healthy ones, and furthermore, that the emission band at 730 nm was either declined or depleted in the sample with high infection symptoms. In contrast, the blue–green region was observed to increase due to the emergence of disease. As the band intensity of chlorophyll decreases during infection, this decrease in chlorophyll content and increase in the blue–green spectral region could provide a new approach for predicting BLB at an early stage. The important finding was that the chlorophyll degradation and rise in the blue–green region take place in leaves with BLB or during BLB infection. Principal component analysis has been applied to spectral data which successfully separated diseased samples from healthy ones even with very small spectral variations.

Some new features of ionospheric plasma depletions over the Indian zone using all sky optical imaging

NASA Astrophysics Data System (ADS)

Sinha, H. S. S.; Raizada, S.

2000-08-01

An all sky optical imaging system was operated from Sriharikota rocket range (SHAR) (14° N, 80° E, 5.5° N dip latitude) during January-March, 1993 to observe ionospheric plasma depletions through 630 nm and 777.4 nm night glow emissions. Strong plasma depletions were observed only on four nights viz., 14, 17, 19 and 21 February, 1993. Except the 17 February, which was a magnetically disturbed day, all the other nights pertained to magnetically quiet period. A number of plasma depletion parameters such as, degree of depletion, east-west extent, tilt with respect to the geomagnetic field, inter-depletion distance, drift velocity and plasma enhancements or brightness patterns were estimated. Some of the important results are: (a) It was found that the east-west extent of plasma depletions varied with the degree of depletion; for the 630 nm images the degree of depletion ranged between 6-9% per 100 km east-west extent and for 777.4 nm images it was 3% per 100 km east-west extent, (b) The average inter-depletion distance (IDD) was in the range of 1500±100 km during the magnetically disturbed period and 740±60 km during quiet periods. This is suggestive of gravity wave modulation of the bottom side of the F-region. While the large scale gravity waves (1500±100 km) of auroral origin could be responsible during magnetically disturbed period, smaller scale gravity waves (740±60 km) having their origin in the lower atmosphere could produce initial perturbation in the bottom side of the F-region, (c) Plasma depletions are observed to have an eastward tilt in the range of 10-15° with respect to the geomagnetic field. It has been suggested here that these tilts are associated with the variation of plasma drift with altitude, (d) plasma depletions are observed to be moving eastwards with drift velocities in the range of 40-190 ms-1, and (e) Strong plasma enhancements or brightness patterns were observed on three nights. The degree of enhancement was by a factor of 1.4-3.8. These enhancements lasted for more than 15 minutes. Although, prima facie, these observations look similar to the transient brightness wave reported by Mendillo et al. (1997a), the high degree of enhancement and an extended duration of more than 15 minutes, observed in the present case, need to be understood.

Global and Seasonal Aerosol Optical Depths Derived From Ultraviolet Observations by Satellites (TOMS)

NASA Technical Reports Server (NTRS)

Herman, J. R.; Torres, O.

1999-01-01

It has been shown that absorbing aerosols (dust, smoke, volcanic ash) can be detected in the ultraviolet wavelengths (331 nm to 380 nm) from satellite observations (TOMS, Total Ozone Mapping Spectrometer) over both land and water. The theoretical basis for these observations and their conversions to optical depths is discussed in terms of an aerosol index AI or N-value residue (assigned positive for absorbing aerosols). The theoretical considerations show that negative values of the AI frequently represent the presence of non-absorbing aerosols (NA) in the troposphere (mostly pollution in the form of sulfates, hydrocarbons, etc., and some natural sulfate aerosols) with particle sizes near 0.1 to 0.2 microns or less. The detection of small-particle non-absorbing aerosols from the measured backscattered radiances is based on the observed wavelength dependence from Mie scattering after the background Rayleigh scattering is subtracted. The Mie scattering from larger particles, 1 micron or more (e.g., cloud water droplets) has too small a wavelength dependence to be detected by this method. In regions that are mostly cloud free, aerosols of all sizes can be seen in the single channel 380 nm or 360 nm radiance data. The most prominent Al feature observed is the strong asymmetry in aerosol amount between the Northern and Southern Hemispheres, with the large majority of NA occurring above 20degN latitude. The maximum values of non-absorbing aerosols are observed over the eastern U.S. and most of western Europe corresponding to the areas of highest industrial pollution. Annual cycles in the amount of NA are observed over Europe and North America with maxima occurring in the summer corresponding to times of minimum wind transport. Similarly, the maxima in the winter over the Atlantic Ocean occurs because of wind borne transport from the land. Most regions of the world have the maximum amount of non-absorbing aerosol in the December to January period except for the eastern North America and Europe. Comparisons of the estimated TOMS aerosol optical depths show good agreement in magnitude and seasonal dependence with sun-photometer optical depths obtained at Goddard Space Flight Center (39degN 76.88degW) in the U.S. and in Lille (50.63degN 3.07degE) in France. The study of these aerosols is important for detecting the sources of industrial pollution and its redistribution by winds on a global basis, as well as its effect on reducing the UV irradiance at the Earth's surface.

Extreme dust storm over the eastern Mediterranean in September 2015: satellite, lidar, and surface observations in the Cyprus region

NASA Astrophysics Data System (ADS)

Mamouri, Rodanthi-Elisavet; Ansmann, Albert; Nisantzi, Argyro; Solomos, Stavros; Kallos, George; Hadjimitsis, Diofantos G.

2016-11-01

A record-breaking dust storm originating from desert regions in northern Syria and Iraq occurred over the eastern Mediterranean in September 2015. In this contribution of a series of two articles (part 1, observations; part 2, atmospheric modeling), we provide a comprehensive overview of the aerosol conditions during this extreme dust outbreak in the Cyprus region. These observations are based on satellite observations (MODIS, moderate resolution imaging spectroradiometer) of aerosol optical thickness (AOT) and Ångström exponent, surface particle mass (PM10) concentrations measured at four sites in Cyprus, visibility observations at three airports in southern Cyprus and corresponding conversion products (particle extinction coefficient, dust mass concentrations), EARLINET (European Aerosol Research Lidar Network) lidar observations of dust vertical layering over Limassol, particle optical properties (backscatter, extinction, lidar ratio, linear depolarization ratio), and derived profiles of dust mass concentrations. Maximum 550 nm AOT exceeded values of 5.0, according to MODIS, and the mass loads were correspondingly > 10 g m-2 over Larnaca and Limassol during the passage of an extremely dense dust front on 8 September 2015. Hourly mean PM10 values were close to 8000 µg m-3 and the observed meteorological optical range (visibility) was reduced to 300-750 m at Larnaca and Limassol. The visibility observations suggest peak values of the near-surface total suspended particle (TSP) extinction coefficients of 6000 Mm-1 and thus TSP mass concentrations of 10 000 µg m-3. The Raman polarization lidar observations mainly indicated a double layer structure of the dust plumes (reaching to about 4 km height), pointing to at least two different dust source regions. Dust particle extinction coefficients (532 nm) already exceeded 1000 Mm-1 and the mass concentrations reached 2000 µg m-3 in the elevated dust layers on 7 September, more than 12 h before the peak dust front on 8 September reached the Limassol lidar station around local noon. Typical Middle Eastern dust lidar ratios around 40 sr were observed in the dense dust plumes. The particle depolarization ratio decreased from around 0.3 in the lofted dense dust layers to 0.2 at the end of the dust period (11 September), indicating an increasing impact of anthropogenic haze.

Radiative Characteristics of Aerosol During Extreme Fire Event over Siberia in Summer 2012

NASA Technical Reports Server (NTRS)

Zhuravleva, Tatiana B.; Kabanov, Dmitriy M.; Nasrtdinov, Ilmir M.; Russkova, Tatiana V.; Sakerin, Sergey M.; Smirnov, Alexander; Holben, Brent N.

2017-01-01

Microphysical and optical properties of aerosol were studied during a mega-fire event in summer 2012 over Siberia using ground-based measurements of spectral solarradiation at the AERONET site in Tomsk and satellite observations. The data were analyzed using multi-year (2003-2013) measurements of aerosol characteristics under back-ground conditions and for less intense fires, differing in burning biomass type, stage of fire, remoteness from observation site, etc. (ordinary smoke). In June-August 2012, the average aerosol optical depth (AOD, 500 nm) had been 0.95+/-0.86, about a factor of 6 larger than background values (0.16+/-0.08), and a factor of 2.5 larger than in ordinary smoke. The AOD values were extremely high on 24-28 July and reached 3-5. A comparison with satellite observations showed that ground-based measurements in the region of Tomsk not only reflect the local AOD features, but are also characteristic for the territory of Western Siberia as a whole. Single scattering albedo (SSA, 440 nm) in this period ranged from 0.91 to 0.99 with an average of approx. 0.96 in the entire wavelength range of 440-1020 nm. The increase in absorptance of aerosol particles (SSA(440 nm)=0.92) and decrease in SSA with wavelength observed in ordinary smoke agree with the data from multi-year observations in analogous situations in the boreal zone of USA and Canada. Volume aerosol size distribution in extreme and ordinary smoke had a bimodal character with significant prevalence of fine-mode particles, but in summer 2012 the mean median radius and the width of the fine-mode distribution somewhat increased. In contrast to data from multi-year observations, in summer 2012 an increase in the volume concentration and median radius of the coarse mode was observed with growing AOD.

UV 380 nm reflectivity of the Earth's surface, clouds and aerosols

NASA Astrophysics Data System (ADS)

Herman, J. R.; Celarier, E.; Larko, D.

2001-03-01

The 380 nm radiance measurements of the Total Ozone Mapping Spectrometer (TOMS) have been converted into a global data set of daily (1979-1992) Lambert equivalent reflectivities R of the Earth's surface and boundary layer (clouds, aerosols, surface haze, and snow/ice) and then corrected to RPC for the presence of partly clouded scenes. Since UV surface reflectivity is between 2 and 8% for both land and water during all seasons of the year (except for ice and snow cover), reflectivities larger than the surface value indicate the presence of clouds, haze, or aerosols in the satellite field of view. A statistical analysis of 14 years of daily reflectivity data shows that most snow-/ice-free scenes observed by TOMS have a reflectivity less than 10% for the majority of days during a year. The 380 nm reflectivity data show that the true surface reflectivity is 2-3% lower than the most frequently occurring reflectivity value for each TOMS scene as seen from space. Most likely the cause is a combination of frequently occurring boundary layer water and/or aerosol haze. For most regions the observation of extremely clear conditions needed to estimate the surface reflectivity from space is a comparatively rare occurrence. Certain areas (e.g., Australia, southern Africa, portions of northern Africa) are cloud-free more than 80% of the year, which exposes these regions to larger amounts of UV radiation than at comparable latitudes in the Northern Hemisphere. Regions over rain forests, jungle areas, Europe and Russia, the bands surrounding the Arctic and Antarctic regions, and many ocean areas have significant cloud cover (R>15%) more than half of each year. In the low to middle latitudes the areas with the heaviest cloud cover (highest reflectivity for most of the year) are the forest areas of northern South America, southern Central America, the jungle areas of equatorial Africa, and high mountain regions such as the Himalayas or the Andes. The TOMS reflectivity data show both the presence of large nearly clear ocean areas and the effects of the major ocean currents on cloud production.

A UV-Vis photoacoustic spectrophotometer.

PubMed

Wiegand, Joseph R; Mathews, L Dalila; Smith, Geoffrey D

2014-06-17

A novel photoacoustic spectrophotometer (PAS) for the measurement of gas-phase and aerosol absorption over the UV-visible region of the spectrum is described. Light from a broadband Hg arc lamp is filtered in eight separate bands from 300 to 700 nm using bandpass interference filters (centered at 301 nm, 314 nm, 364 nm, 405 nm, 436 nm, 546 nm, 578 and 687 nm) and modulated with an optical chopper before entering the photoacoustic cell. All wavelength bands feature a 20-s detection limit of better than 3.0 Mm(-1) with the exception of the lower-intensity 687 nm band for which it is 10.2 Mm(-1). Validation measurements of gas-phase acetone and nigrosin aerosol absorption cross sections at several wavelengths demonstrate agreement to within 10% with those measured previously (for acetone) and those predicted by Mie theory (for nigrosin). The PAS instrument is used to measure the UV-visible absorption spectrum of ambient aerosol demonstrating a dramatic increase in the UV region with absorption increasing by 300% from 405 to 301 nm. This type of measurement throughout the UV-visible region and free from artifacts associated with filter-based methods has not been possible previously, and we demonstrate its promise for classifying and quantifying different types of light-absorbing ambient particles.

Miroirs multicouches C/SI a incidence normale pour la region spectrale 25-40 nanometres

NASA Astrophysics Data System (ADS)

Grigonis, Marius

Nous avons propose la nouvelle combinaison de materiaux, C/Si, pour la fabrication de miroirs multicouches a incidence normale dans la region spectrale 25-40 nm. Les resultats experimentaux montrent que cette combinaison possede une reflectivite d'environ ~25% dans la region spectrale 25-33 nm et une reflectivite d'environ ~23% dans la region spectrale 33-40 nm. Ces valeurs de reflectivite sont les plus grandes obtenues jusqu'a maintenant dans la region spectrale 25-40 nm. Les miroirs multicouches ont ete par la suite caracterises par microscopie electronique a transmission, par diverses techniques de diffraction des rayons X et par spectroscopies d'electrons AES et ESCA. La resistance des miroirs aux temperatures elevees a ete egalement etudiee. Les resultats fournis par les methodes de caracterisation indiquent que cette combinaison possede des caracteristiques tres prometteuses pour son application comme miroir pour les rayons X mous.

Hyperspectral remote sensing of paddy crop using insitu measurement and clustering technique

NASA Astrophysics Data System (ADS)

Moharana, S.; Dutta, S.

2014-11-01

Rice Agriculture, mainly cultivated in South Asia regions, is being monitored for extracting crop parameter, crop area, crop growth profile, crop yield using both optical and microwave remote sensing. Hyperspectral data provide more detailed information of rice agriculture. The present study was carried out at the experimental station of the Regional Rainfed Low land Rice Research Station, Assam, India (26.1400° N, 91.7700° E) and the overall climate of the study area comes under Lower Brahmaputra Valley (LBV) Agro Climatic Zones. The hyperspectral measurements were made in the year 2009 from 72 plots that include eight rice varieties along with three different level of nitrogen treatments (50, 100, 150 kg/ha) covering rice transplanting to the crop harvesting period. With an emphasis to varieties, hyperspectral measurements were taken in the year 2014 from 24 plots having 24 rice genotypes with different crop developmental ages. All the measurements were performed using a spectroradiometer with a spectral range of 350-1050 nm under direct sunlight of a cloud free sky and stable condition of the atmosphere covering more than 95 % canopy. In this study, reflectance collected from canopy of rice were expressed in terms of waveforms. Furthermore, generated waveforms were analysed for all combinations of nitrogen applications and varieties. A hierarchical clustering technique was employed to classify these waveforms into different groups. By help of agglomerative clustering algorithm a few number of clusters were finalized for different rice varieties along with nitrogen treatments. By this clustering approach, observational error in spectroradiometer reflectance was also nullified. From this hierarchical clustering, appropriate spectral signature for rice canopy were identified and will help to create rice crop classification accurately and therefore have a prospect to make improved information on rice agriculture at both local and regional scales. From this hierarchical clustering, spectral signature library for rice canopy were identified which will help to create rice crop classification maps and critical wave bands like green (519,559 nm), red (649 nm), red edge (729 nm) and NIR region (779,819 nm) were marked sensitive to nitrogen which will further help in nitrogen mapping of paddy agriculture over therefore have the prospect to make improved informed decisions.

Confinement and the Glass Transition Temperature in Supported Polymer Films: Molecular Weight, Repeat Unit Modification, and Cooperativity Length Scale Investigations

NASA Astrophysics Data System (ADS)

Mundra, Manish K.

2005-03-01

It is well known that the glass transition temperatures, Tgs, of supported polystyrene (PS) films decrease dramatically with decreasing film thickness below 60-80 nm. However, a detailed understanding of the cause of this effect is lacking. We have investigated the impact of several parameters, including polymer molecular weight (MW), repeat unit structure, and the length scale of cooperatively rearranging regions in bulk. There is no significant effect of PS MW on the Tg-confinement effect over a range of 5,000 to 3,000,000 g/mol. In contrast, the strength of the Tg reduction and the onset of the confinement effect increase dramatically upon changing the polymer from PS to poly(4-tert-butylstyrene) (PTBS), with PTBS exhibiting a Tg reduction relative to bulk at a thickness of 300-400 nm. PTBS also shows a Tg reduction relative to bulk of 47 K in a 21-nm-thick film, more than twice that observed in a PS film of identical thickness. Characterization of the length scale of cooperatively rearranging regions has been done by differential scanning calorimetry but reveals at best a limited correlation with the confinement effect.

A comparative computational study of Csbnd N and Csbnd C bonding visible to NIR absorbing croconines

NASA Astrophysics Data System (ADS)

Chetti, Prabhakar; Tripathi, Anuj

2018-03-01

The lowest electronic excitations and charge transfer properties in two series of croconine dyes; 1) molecules with Csbnd N bonding, having an absorption in the visible region (400-600 nm) and 2) molecules with Csbnd C bonding, showing absorption in visible to near infrared (NIR) region (600-1100 nm) are analyzed by quantum-chemical calculations. The absorption maxima in Csbnd C bonding croconines (CCR) are always having 200-300 nm red shifted than its corresponding Csbnd N bonding croconines (NCR). The reason for this drastic red shift in CCR series than its corresponding NCR has been systematically studied by DFT, TDDFT and SAC-CI methods. It is found that, CCR series are with less charge transfer in nature and are having larger diradical character, whereas NCR series molecules showing larger charge transfer with lower diradical character. The change in bonding mode of central five membered croconate ring, from Csbnd N to Csbnd C, destabilization and/stabilization of HOMO LUMO levels were observed. This study may helpful in the design and synthesis of new visible to NIR absorbing croconine dyes which are useful in materials applications.

Invisible liposomes: refractive index matching with sucrose enables flow dichroism assessment of peptide orientation in lipid vesicle membrane.

PubMed

Ardhammar, Malin; Lincoln, Per; Nordén, Bengt

2002-11-26

Valuable information on protein-membrane organization may in principle be obtained from polarized-light absorption (linear dichroism, LD) measurement on shear-aligned lipid vesicle bilayers as model membranes. However, attempts to probe LD in the UV wavelength region (<250 nm) have so far failed because of strong polarized light scattering from the vesicles. Using sucrose to match the refractive index and suppress the light scattering of phosphatidylcholine vesicles, we have been able to detect LD bands also in the peptide-absorbing region (200-230 nm). The potential of refractive index matching in vesicle LD as a general method for studying membrane protein structure was investigated for the membrane pore-forming oligopeptide gramicidin incorporated into the liposome membranes. In the presence of sucrose, the LD signals arising from oriented tryptophan side chains as well as from n-->pi* and pi-->pi* transitions of the amide chromophore of the polypeptide backbone could be studied. The observation of a strongly negative LD for the first exciton transition ( approximately 204 nm) is consistent with a membrane-spanning orientation of two intertwined parallel gramicidin helices, as predicted by coupled-oscillator theory.

Cathodoluminescence microscopy and spectroscopy of forsterite from Kaba meteorite: An application to the study of hydrothermal alteration of parent body

NASA Astrophysics Data System (ADS)

Gucsik, Arnold; Endo, Taro; Nishido, Hirotsugu; Ninagawa, Kiyotaka; Kayama, Masahiro; Bérczi, Szaniszló; Nagy, Szabolcs; Ábrahám, Péter; Kimura, Yuki; Miura, Hitoshi; Gyollai, Ildikó; Simonia, Irakli; Rózsa, Péter; Posta, József; Apai, Dániel; Mihályi, Krisztián; Nagy, Mihály; Ott, Ulrich

2013-12-01

Highly forsteritic olivine (Fo: 99.2-99.7) in the Kaba meteorite emits bright cathodoluminescence (CL). CL spectra of red luminescent forsterite grains have two broad emission bands at approximately 630 nm (impurity center of divalent Mn ions) in the red region and above 700 nm (trivalent Cr ions) in the red-IR region. The cores of the grains show CL blue luminescence giving a characteristic broad band emission at 400 nm, also associated with minor red emissions related to Mn and Cr ions. CL color variation of Kaba forsterite is attributed to structural defects. Electron probe microanalyzer (EPMA) analysis shows concentrations of Ca, Al, and Ti in the center of the forsterite grain. The migration of diffusible ions of Mn, Cr, and Fe to the rim of the Kaba meteoritic forsterite was controlled by the hydrothermal alteration at relatively low temperature (estimated at about 250 °C), while Ca and Al ions might still lie in the core. A very unusual phase of FeO (wüstite) was also observed, which may be a terrestrial alteration product of FeNi-metal.

Self-consistent performance modeling for dual band MIS UV photodetectors based on Si/SiO2 multilayer structure.

PubMed

Rostami, A; Leilaeioun, M; Golmmohamadi, S; Rasooli Saghai, H

2012-06-01

In this paper, we present a self-consistent theoretical model for a metal-insulator semiconductor (MIS) dual band ultraviolet (UV) photodetector with a modified structure implying an arbitrarily defined insulating potential barrier as its active region. Utilizing our proposed model, the dark and photocurrent density-voltage (J-V) characteristics of MIS UV photodetectors with multi-quantum wells of silicon (MQWs) are calculated. We demonstrate that dark current is reduced in the suggested structure, because the electron-tunneling probability becomes unity at energies coincident with the peak detection wavelength. This is due to the resonant tunneling and decreases at energies that are significantly smaller than this optimum value. In consequence, the number of carriers contributing to the dark current, which have a broad energy distribution at high temperatures, will decrease. It is also shown that the designed structure could detect two individual UV wavelengths, simultaneously. The width of each Si quantum well has been considered at around 1.2 nm, in order to observe these two absorption peaks in the middle and near UV regions of photon spectrum (about 365 nm, 175 nm).

Integrated Duo Wavelength VCSEL Using an Electrically Pumped GaInAs/AlGaAs 980 nm Cavity at the Bottom and an Optically Pumped GaInAs/AlGaInAs 1550 nm Cavity on the Top

PubMed Central

Islam, Samiha Ishrat; Islam, Arnob; Islam, Saiful

2014-01-01

In this work, an integrated single chip dual cavity VCSEL has been designed which comprises an electrically pumped 980 nm bottom VCSEL section fabricated using GaInAs/AlGaAs MQW active region and a 1550 nm top VCSEL section constructed using GaInAs/AlGaInAs MQW active region but optically pumped using half of the produced 980 nm light entering into it from the electrically pumped bottom cavity. In this design, the active region of the intracavity structure 980 nm VCSEL consists of 3 quantum wells (QWs) using Ga0.847In0.153As, 2 barriers using Al0.03Ga0.97As, and 2 separate confinement heterostructures (SCH) using the same material as the barrier. The active region of the top emitting 1550 nm VCSEL consists of 3 QWs using Ga0.47In0.52As, 2 barriers using Al0.3Ga0.17In0.53As, and 2 SCHs using the same material as the barrier. The top DBR and the bottom DBR mirror systems of the 1550 nm VCSEL section plus the top and bottom DBR mirror systems of the 980 nm VCSEL section have been formed using GaAs/Al0.8Ga0.2As. Computations show that the VCSEL is capable of producing 8.5 mW of power at 980 nm from the bottom side and 2 mW of power at the 1550 nm from top side. PMID:27379335

Tethered balloon-born and ground-based measurements of black carbon and particulate profiles within the lower troposphere during the foggy period in Delhi, India.

PubMed

Bisht, D S; Tiwari, S; Dumka, U C; Srivastava, A K; Safai, P D; Ghude, S D; Chate, D M; Rao, P S P; Ali, K; Prabhakaran, T; Panickar, A S; Soni, V K; Attri, S D; Tunved, P; Chakrabarty, R K; Hopke, P K

2016-12-15

The ground and vertical profiles of particulate matter (PM) were mapped as part of a pilot study using a Tethered balloon within the lower troposphere (1000m) during the foggy episodes in the winter season of 2015-16 in New Delhi, India. Measurements of black carbon (BC) aerosol and PM <2.5 and 10μm (PM 2.5 & PM 10 respectively) concentrations and their associated particulate optical properties along with meteorological parameters were made. The mean concentrations of PM 2.5 , PM 10 , BC 370 nm, and BC 880 nm were observed to be 146.8±42.1, 245.4±65.4, 30.3±12.2, and 24.1±10.3μgm -3 , respectively. The mean value of PM 2.5 was ~12 times higher than the annual US-EPA air quality standard. The fraction of BC in PM 2.5 that contributed to absorption in the shorter visible wavelengths (BC 370 nm ) was ~21%. Compared to clear days, the ground level mass concentrations of PM 2.5 and BC 370 nm particles were substantially increased (59% and 24%, respectively) during the foggy episode. The aerosol light extinction coefficient (σ ext ) value was much higher (mean: 610Mm -1 ) during the lower visibility (foggy) condition. Higher concentrations of PM 2.5 (89μgm -3 ) and longer visible wavelength absorbing BC 880 nm (25.7μgm -3 ) particles were observed up to 200m. The BC 880 nm and PM 2.5 aerosol concentrations near boundary layer (1km) were significantly higher (~1.9 and 12μgm -3 ), respectively. The BC (i.e BC tot ) aerosol direct radiative forcing (DRF) values were estimated at the top of the atmosphere (TOA), surface (SFC), and atmosphere (ATM) and its resultant forcing were - 75.5Wm -2 at SFC indicating the cooling effect at the surface. A positive value (20.9Wm -2 ) of BC aerosol DRF at TOA indicated the warming effect at the top of the atmosphere over the study region. The net DRF value due to BC aerosol was positive (96.4Wm -2 ) indicating a net warming effect in the atmosphere. The contribution of fossil and biomass fuels to the observed BC aerosol DRF values was ~78% and ~22%, respectively. The higher mean atmospheric heating rate (2.71Kday -1 ) by BC aerosol in the winter season would probably strengthen the temperature inversion leading to poor dispersion and affecting the formation of clouds. Serious detrimental impacts on regional climate due to the high concentrations of BC and PM (especially PM 2.5 ) aerosol are likely based on this study and suggest the need for immediate, stringent measures to improve the regional air quality in the northern India. Copyright © 2016 Elsevier B.V. All rights reserved.

Near IR observations of Quiet Chromosphere

NASA Astrophysics Data System (ADS)

Prasad Choudhary, Debi; Deng, N.; Tejamoortula, U.; Penn, M. J.

2009-05-01

We have carried out the observations of quiet solar limb during April 29 to May 1, 2008, March 9-13, 2009 using the vertical spectrograph at the focal plane of McMath-Pierce telescope at Kitt Peak National Observatory. The solar limb was mostly featureless during the observations. The New Infrared Array (NAC) at the exit port of the spectrograph has been used to record the limb spectrum at HeI 1083.0 nm, Hydrogen Paschen beta at 1281.8 nm and Brackett gamma 2165.5 nm wavelength regions. The NAC is a 1024 x 1024 InSb Alladin III Detector operating over 1-5 micron range with high density sampling at 0.018 arc second/pixel. The all-reflective optical train minimizes number of surfaces and eliminates ghosts leading to low scatter, ghost-free optics. The close-cycle cryogenic provides a stable cooling environment over six hour period with an accuracy of about 0.01K leading to low dark current. The low read out noise combined with low scattered light and dark current makes NAC an ideal detector for making high quality infrared spectral observations of solar limb. In this presentation, we shall compare the line parameters of these lines around the solar disk. Acknowledgements: This work is supported by NSF under grant ATM 05-48952 and by NASA under grant NNX08AQ32G.

Plasma assisted molecular beam epitaxy growth and effect of varying buffer thickness on the formation of ultra-thin In{sub 0.17}Al{sub 0.83}N/GaN heterostructure on Si(111)

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

Chowdhury, Subhra, E-mail: subhra1109@gmail.com; Biswas, Dhrubes; Department of E and E C E, Indian Institute of Technology Kharagpur, Kharagpur 721302

2015-02-23

This work reports on the detailed plasma-assisted molecular beam epitaxy (PAMBE) growth of ultra-thin In{sub 0.17}Al{sub 0.83}N/GaN heterostructures on Si(111) substrate with three different buffer thickness (600 nm, 400 nm, and 200 nm). Growth through critical optimization of growth conditions is followed by the investigation of impact of varying buffer thickness on the formation of ultra-thin 1.5 nm, In{sub 0.17}Al{sub 0.83}N–1.25 nm, GaN–1.5 nm, In{sub 0.17}Al{sub 0.83}N heterostructure, in terms of threading dislocation (TD) density. Analysis reveals a drastic reduction of TD density from the order 10{sup 10 }cm{sup −2} to 10{sup 8 }cm{sup −2} with increasing buffer thickness resulting smooth ultra-thin active region for thick buffer structure.more » Increasing strain with decreasing buffer thickness is studied through reciprocal space mapping analysis. Surface morphology through atomic force microscopy analysis also supports our study by observing an increase of pits and root mean square value (0.89 nm, 1.2 nm, and 1.45 nm) with decreasing buffer thickness which are resulted due to the internal strain and TDs.« less

Plasma flows and magnetic field interplay during the formation of a pore

NASA Astrophysics Data System (ADS)

Ermolli, I.; Cristaldi, A.; Giorgi, F.; Giannattasio, F.; Stangalini, M.; Romano, P.; Tritschler, A.; Zuccarello, F.

2017-04-01

Aims: Recent simulations of solar magneto-convection have offered new levels of understanding of the interplay between plasma motions and magnetic fields in evolving active regions. We aim at verifying some aspects of the formation of magnetic regions derived from recent numerical studies in observational data. Methods: We studied the formation of a pore in the active region (AR) NOAA 11462. We analysed data obtained with the Interferometric Bidimensional Spectrometer (IBIS) at the Dunn Solar Telescope on April 17, 2012, consisting of full Stokes measurements of the Fe I 617.3 nm lines. Furthermore, we analysed SDO/HMI observations in the continuum and vector magnetograms derived from the Fe I 617.3 nm line data taken from April 15 to 19, 2012. We estimated the magnetic field strength and vector components and the line-of-sight (LOS) and horizontal motions in the photospheric region hosting the pore formation. We discuss our results in light of other observational studies and recent advances of numerical simulations. Results: The pore formation occurs in less than 1 h in the leading region of the AR. We observe that the evolution of the flux patch in the leading part of the AR is faster (<12 h) than the evolution (20-30 h) of the more diffuse and smaller scale flux patches in the trailing region. During the pore formation, the ratio between magnetic and dark area decreases from 5 to 2. We observe strong downflows at the forming pore boundary and diverging proper motions of plasma in the vicinity of the evolving feature that are directed towards the forming pore. The average values and trends of the various quantities estimated in the AR are in agreement with results of former observational studies of steady pores and with their modelled counterparts, as seen in recent numerical simulations of a rising-tube process. The agreement with the outcomes of the numerical studies holds for both the signatures of the flux emergence process (e.g. appearance of small-scale mixed polarity patterns and elongated granules) and the evolution of the region. The processes driving the formation of the pore are identified with the emergence of a magnetic flux concentration and the subsequent reorganization of the emerged flux, by the combined effect of velocity and magnetic field, in and around the evolving structure. Movies associated to Figs. 1 and 4 are available at http://www.aanda.org

Further study on the solar activity variation of daytime NmF2

NASA Astrophysics Data System (ADS)

Chen, Yiding; Liu, Libo

2010-12-01

The ionosonde observations in the East Asia-Australia sector are collected to further investigate the solar activity variation of daytime (0800 ˜ 1600 LT) NmF2. The linear increase rate of NmF2 with F10.7 at lower solar activity levels is remarkably dependent on latitude, season, and local time. The rate is largest in equinoxes (with an equinoctial asymmetry) and higher in the morning (afternoon) in local winter (summer) at geomagnetic midlatitudes; particularly, the maximum rates in local winter are obviously larger than those in local summer at northern midlatitudes. In the equatorial ionization anomaly (EIA) crest regions, the rates in equinoxes and December (June) solstice are remarkably higher than those in June (December) solstice at the northern (southern) EIA crest, and the rate grows from the morning sector to the afternoon sector. The variation trend of NmF2 with F10.7 also shows latitudinal, seasonal, and local time dependences. The saturation effect dominates in all seasons in the EIA regions; at midlatitudes, NmF2 nearly increases linearly with F10.7 in local winter so that a linear fit is a good approximation for NmF2 modeling, while the saturation effect still dominates in other seasons. The saturation effect is more significant in the afternoon, and the strongest saturation effect appears at the EIA crest latitudes in equinox afternoon. Discussions indicate that the variations of neutral atmosphere and hmF2 are responsible for the seasonal and local time dependences of the linear increase rate of NmF2 with F10.7 at midlatitudes, and the seasonal variation of neutral atmosphere is the primary reason for the seasonal dependence of the variation trend of NmF2 with F10.7, while dynamics processes are the more important factors controlling the linear increase rate and the variation trend of NmF2 with F10.7 at low latitudes. Furthermore, dynamics processes are important for the saturation effect, and the fountain effect is related to the strongest saturation effect appearing at the EIA crests.

Genetic structure of cougar populations across the Wyoming basin: Metapopulation or megapopulation

USGS Publications Warehouse

Anderson, C.R.; Lindzey, F.G.; McDonald, D.B.

2004-01-01

We examined the genetic structure of 5 Wyoming cougar (Puma concolor) populations surrounding the Wyoming Basin, as well as a population from southwestern Colorado. When using 9 microsatellite DNA loci, observed heterozygosity was similar among populations (HO = 0.49-0.59) and intermediate to that of other large carnivores. Estimates of genetic structure (FST = 0.028, RST = 0.029) and number of migrants per generation (Nm) suggested high gene flow. Nm was lowest between distant populations and highest among adjacent populations. Examination of these data, plus Mantel test results of genetic versus geographic distance (P ??? 0.01), suggested both isolation by distance and an effect of habitat matrix. Bayesian assignment to population based on individual genotypes showed that cougars in this region were best described as a single panmictic population. Total effective population size for cougars in this region ranged from 1,797 to 4,532 depending on mutation model and analytical method used. Based on measures of gene flow, extinction risk in the near future appears low. We found no support for the existence of metapopulation structure among cougars in this region.

403 nm cavity ring-down measurements of brown carbon aerosol

NASA Astrophysics Data System (ADS)

Kwon, D.; Grassian, V. H.; Kleiber, P.; Young, M. A.

2017-12-01

Atmospheric aerosol influences Earth's climate by absorbing and scattering incoming solar radiation and outgoing terrestrial radiation. One class of secondary organic aerosol (SOA), called brown carbon (BrC), has attracted attention for its wavelength dependent light absorbing properties with absorption coefficients that generally increase from the visible (Vis) to ultraviolet (UV) regions. Here we report results from our investigation of the optical properties of BrC aerosol products from the aqueous phase reaction of ammonium sulfate (AS) with methylglyoxal (MG) using cavity ring-down spectroscopy (CRDS) at 403 nm wavelength. We have measured the optical constants of BrC SOA from the AS/MG reaction as a function of reaction time. Under dry flow conditions, we observed no apparent variation in the BrC refractive index with aging over the course of 22 days. The retrieved BrC optical constants are similar to those of AS with n = 1.52 for the real component. Despite significant UV absorption observed from the bulk BrC solution, the imaginary index value at 403 nm is below our minimum detection limit which puts an upper bound of k as 0.03. These observations are in agreement with results from our recent studies of the light scattering properties of this BrC aerosol.

Role of Ni2+(d8) ions in electrical, optical and magnetic properties of CdS nanowires for optoelectronic and spintronic applications

NASA Astrophysics Data System (ADS)

Arshad Kamran, Muhammad

2018-06-01

For the first time, 1D Ni ion doped CdS nanowires (NWs) were synthesized via chemical vapour deposition (CVD). The synthesized Cd0.886Ni0.114S NWs were single crystalline. We have reported here the investigation of optical, electrical and magnetic properties of prepared NWs for optoelectronic and spintronic applications. Successful incorporation of Ni ions in an individual CdS NW has been confirmed through several characterization tools: significantly higher angle and phonon mode shift were observed in the XRD and Raman spectra. SEM-EDX and XPS analysis also confirmed the presence of Ni2+ ions. Room temperature photoluminescence (RT-PL) showed multiple peaks: two emission peaks in the visible region centered at 517.1 nm (green), 579.2 nm (orange), and a broad-band near infra-red (NIR) emission centered at 759.9 nm. The first peak showed 5 nm red shift upon Ni2+ doping, hinting at the formation of exciton magnetic polarons (EMPs), and broad NIR emission was observed in both chlorides and bromides, which was assigned to d‑d transition of Ni ions whose energy levels lying at 749.51 nm (13 342 cm–1) and 750.98 nm (13 316 cm–1) are very close to NIR emission. Orange emission not only remained at same peak position—its PL intensity was also significantly enhanced at 78 K; this was assigned to d‑d transition (3A2g → 1Eg) of Ni2+ ions. It was observed that 11.4% Ni2+ ion doping enhanced the conductivity of our sample around 20 times, and saturation magnetization (Ms) increased from 7.2 × 10‑5 Am2/Kg to 1.17 × 10‑4 Am2/Kg, which shows promise for optoelectronic and spintronic applications.

Role of Ni2+(d8) ions in electrical, optical and magnetic properties of CdS nanowires for optoelectronic and spintronic applications.

PubMed

Kamran, Muhammad Arshad

2018-06-29

For the first time, 1D Ni ion doped CdS nanowires (NWs) were synthesized via chemical vapour deposition (CVD). The synthesized Cd 0.886 Ni 0.114 S NWs were single crystalline. We have reported here the investigation of optical, electrical and magnetic properties of prepared NWs for optoelectronic and spintronic applications. Successful incorporation of Ni ions in an individual CdS NW has been confirmed through several characterization tools: significantly higher angle and phonon mode shift were observed in the XRD and Raman spectra. SEM-EDX and XPS analysis also confirmed the presence of Ni 2+ ions. Room temperature photoluminescence (RT-PL) showed multiple peaks: two emission peaks in the visible region centered at 517.1 nm (green), 579.2 nm (orange), and a broad-band near infra-red (NIR) emission centered at 759.9 nm. The first peak showed 5 nm red shift upon Ni 2+ doping, hinting at the formation of exciton magnetic polarons (EMPs), and broad NIR emission was observed in both chlorides and bromides, which was assigned to d-d transition of Ni ions whose energy levels lying at 749.51 nm (13 342 cm -1 ) and 750.98 nm (13 316 cm -1 ) are very close to NIR emission. Orange emission not only remained at same peak position-its PL intensity was also significantly enhanced at 78 K; this was assigned to d-d transition ( 3 A 2g  →  1 E g ) of Ni 2+ ions. It was observed that 11.4% Ni 2+ ion doping enhanced the conductivity of our sample around 20 times, and saturation magnetization (M s ) increased from 7.2 × 10 -5 Am 2 /Kg to 1.17 × 10 -4 Am 2 /Kg, which shows promise for optoelectronic and spintronic applications.

Optical Properties of Nickel(ii) and Radiation Defects in Magnesium-Fluoride and Manganese-Fluoride

NASA Astrophysics Data System (ADS)

Feuerhelm, Leonard Norman

1980-12-01

Scope and Method of Study. A study has been made of the radiation defects in pure MgF(,2) by observating the polarized absorption, luminescence, and excitation spectra in electron-irradiated MgF(,2). Additionally, studies of the absorption, emission, excitation, and temperature dependence of the lifetimes of transitions in nickel-doped MgF(,2) and MnF(,2) have been accomplished, as well as the observation of radiation effects on these crystals. Findings and Conclusions. The absorption band at about 320 nm in irradiated MgF(,2) is identified to be due to the F(,2)(D(,2h)) center, and to have an emission at about 450 nm. Analysis of the temperature dependence of this band indicates a dominant phonon mode of 255 cm(' -1) for the excited state. The F(,2)(C(,1)) center is identified with an absorption of about 360 nm and an emission of 410 nm. An absorption peak at 300 nm, for which no corresponding emission has been found, is tentatively identified to be the F(,3)-center, and to have a dominant phonon mode of 255 cm('-1). The temperature dependence of the lifetimes of transitions in nickel-doped MgF(,2) have been analyzed by the quantum mechanical single configuration coordinate model of Struck and Fonger, and a complete configuration coordinate model has been made for this crystal. Similar studies have been made in MnF(,2):Ni, but energy transfer between Mn('2+) ions and Ni('2+) ions prevents completion of the complete model. Energy transfer in this crystal was studied, with the finding that a gain of about 2 in luminescence output was possible for excitation in the visible region (400-600 nm) as compared with MgF(,2):Ni. The effects of radiation upon the Ni('2+) transitions in these crystals were studied with the finding that no observable change occurred in the Ni('2+) transitions with radiation, although other radiation effects were noted in the crystal.

The distribution of methylated sulfur compounds, DMS and DMSP, in Canadian subarctic and Arctic marine waters during summer 2015

NASA Astrophysics Data System (ADS)

Jarníková, Tereza; Dacey, John; Lizotte, Martine; Levasseur, Maurice; Tortell, Philippe

2018-04-01

We present seawater concentrations of dimethyl sulfide (DMS) and dimethylsulfoniopropionate (DMSP) measured across a transect from the Labrador Sea to the Canadian Arctic Archipelago during summer 2015. Using an automated ship-board gas chromatography system and a membrane-inlet mass spectrometer, we measured a wide range of DMS (˜ 1 to 18 nM) and DMSP (˜ 1 to 150 nM) concentrations. The highest DMS and DMSP concentrations occurred in a localized region of Baffin Bay, where surface waters were characterized by high chlorophyll a (chl a) fluorescence, indicative of elevated phytoplankton biomass. Across the full sampling transect, there were only weak relationships between DMS(P), chl a fluorescence and other measured variables, including positive relationships between DMSP : chl a ratios and several taxonomic marker pigments, and elevated DMS(P) concentrations in partially ice-covered areas. Our high spatial resolution measurements allowed us to examine DMS variability over small scales (< 1 km), documenting strong DMS concentration gradients across surface hydrographic frontal features. Our new observations fill in an important observational gap in the Arctic Ocean and provide additional information on sea-air DMS fluxes from this ocean region. In addition, this study constitutes a significant contribution to the existing Arctic DMS(P) dataset and provides a baseline for future measurements in the region.

In-vitro micro-Raman study of tissue samples for detecting cervical and ovarian cancer with 785-nm laser excitation

NASA Astrophysics Data System (ADS)

Sharma, S. K.; Kamemoto, L. E.; Misra, A. K.; Goodman, M. T.; Luk, H. W.; Killeen, J. L.

2010-04-01

We present results of in vitro micro-Raman spectroscopy of normal and cancerous cervical and ovarian tissues excited with 785 nm near-infrared (NIR) laser. Micro- Raman spectra of squamous cervical cells of both cervix and ovarian tissues show significant differences in the spectra of normal and cancerous cells. In particular, several well-defined Raman peaks in the 775-975 cm-1 region are observed in the spectra of normal cervix squamous cells but are completely missing in the spectra of invasive cervical cancer cells. In the high-frequency 2800-3100 cm-1 region it is shown that the peak area under CH stretching band is much lower than the corresponding area in the spectra of normal cells. In the case of ovarian tissues, the micro-Raman spectra show noticeable spectral differences between normal cells and ovarian serous cancer cells. In particular, we observed the accumulation of β-carotene in ovarian serous cancer cells compared to normal ovarian cells from women with no ovarian cancer. The NIR micro-Raman spectroscopy offers a potential molecular technique for detecting cervical and ovarian cancer from the respective tissues.

Tunable optical response of bowtie nanoantenna arrays on thermoplastic substrates

NASA Astrophysics Data System (ADS)

Sharac, N.; Sharma, H.; Veysi, M.; Sanderson, R. N.; Khine, M.; Capolino, F.; Ragan, R.

2016-03-01

Thermally responsive polymers present an interesting avenue for tuning the optical properties of nanomaterials on their surfaces by varying their periodicity and shape using facile processing methods. Gold bowtie nanoantenna arrays are fabricated using nanosphere lithography on prestressed polyolefin (PO), a thermoplastic polymer, and optical properties are investigated via a combination of spectroscopy and electromagnetic simulations to correlate shape evolution with optical response. Geometric features of bowtie nanoantennas evolve by annealing at temperatures between 105 °C and 135 °C by releasing the degree of prestress in PO. Due to the higher modulus of Au versus PO, compressive stress occurs on Au bowtie regions on PO, which leads to surface buckling at the two highest annealing temperatures; regions with a 5 nm gap between bowtie nanoantennas are observed and the average reduction is 75%. Reflectance spectroscopy and full-wave electromagnetic simulations both demonstrate the ability to tune the plasmon resonance wavelength with a window of approximately 90 nm in the range of annealing temperatures investigated. Surface-enhanced Raman scattering measurements demonstrate that maximum enhancement is observed as the excitation wavelength approaches the plasmon resonance of Au bowtie nanoantennas. Both the size and morphology tunability offered by PO allows for customizing optical response.

Wide band antireflective coatings Al2O3 / HfO2 / MgF2 for UV region

NASA Astrophysics Data System (ADS)

Winkowski, P.; Marszałek, Konstanty W.

2013-07-01

Deposition technology of the three layers antireflective coatings consists of hafnium compound are presented in this paper. Oxide films were deposited by means of e-gun evaporation in vacuum of 5x10-5 mbar in presence of oxygen and fluoride films by thermal evaporation. Substrate temperature was 250°C. Coatings were deposited onto optical lenses made from quartz glass (Corning HPFS). Thickness and deposition rate were controlled by thickness measuring system Inficon XTC/2. Simulations leading to optimization of thickness and experimental results of optical measurements carried during and after deposition process were presented. Physical thickness measurements were made during deposition process and were equal to 43 nm/74 nm/51 nm for Al2O3 / HfO2 / MgF2 respectively. Optimization was carried out for ultraviolet region from 230nm to the beginning of visible region 400 nm. In this region the average reflectance of the antireflective coating was less than 0.5% in the whole range of application.

Long wavelength vertical cavity surface emitting laser

DOEpatents

Choquette, Kent D.; Klem, John F.

2005-08-16

Selectively oxidized vertical cavity lasers emitting near 1300 nm using InGaAsN quantum wells are reported for the first time which operate continuous wave below, at and above room temperature. The lasers employ two n-type Al.sub.0.94 Ga.sub.0.06 As/GaAs distributed Bragg reflectors each with a selectively oxidized current aperture adjacent to the active region, and the top output mirror contains a tunnel junction to inject holes into the active region. Continuous wave single mode lasing is observed up to 55.degree. C.

A medium-scale traveling ionospheric disturbance observed from the ground and from space

NASA Astrophysics Data System (ADS)

Dymond, K. F.; Watts, C.; Coker, C.; Budzien, S. A.; Bernhardt, P. A.; Kassim, N.; Lazio, T. J.; Weiler, K.; Crane, P. C.; Ray, P. S.; Cohen, A.; Clarke, T.; Rickard, L. J.; Taylor, G. B.; Schinzel, F.; Pihlstrom, Y.; Kuniyoshi, M.; Close, S.; Colestock, P.; Myers, S.; Datta, A.

2011-10-01

We report ultraviolet optical observations from space of a Medium-Scale Traveling Ionospheric Disturbance (MSTID) made during the Combined Radio Interferometry and COSMIC Experiment in Tomography Campaign (CRICKET) held on September 15, 2007 at ˜8:30 UT. The experiment used a Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC also known as FORMOSAT-3) satellite in conjunction with the Very Large Array (VLA) radio telescope, located near Socorro, NM, to study the ionosphere from the global scale down to the regional scale while the TIDs propagated through it. The COSMIC/FORMOSAT-3 satellite measured the F region electron density both horizontally and with altitude while the VLA measured the directions and speeds of the TIDs. These observations provide new information on this poorly understood class of TID and demonstrate the possibility of studying MSTIDs using space-based optical instruments.

The Effect of Temperature on Reflectance of Materials Space Weathered by Laser Irradiation: Implications for Increased Albedo Measured by LOLA

NASA Astrophysics Data System (ADS)

Corley, L. M.; Gillis-Davis, J.; Lucey, P. G.; Trang, D.

2016-12-01

Space weathering significantly changes the optical properties of airless planetary bodies, resulting in decreased albedo, spectral reddening, and subdued absorption bands. These optical changes are caused by the presence of submicroscopic iron (SMFe) in agglutinates and patina glass, which is observed in lunar soils returned by the Apollo and Luna missions. Micrometeorite impacts and solar wind irradiation are key processes that produce SMFe. The Lunar Orbiter Laser Altimeter (LOLA) onboard the Lunar Reconnaissance Orbiter measured a trend of increased albedo at 1064 nm with decreasing temperature and a spike in 1064-nm albedo in permanently shadowed regions (PSRs). Although the LOLA albedo increase could be due to the presence of ice, increased reflectance is also consistent with reduced space weathering. It is currently unknown how temperature influences the production of SMFe and the resulting spectral effects. Low temperatures of polar regions and PSRs (as low as 50K) may affect the volume of impact melt/vaporization produced and the subsequent development of SMFe. To test this hypothesis we compare visible to near-infrared (VNIR) reflectance spectra of materials laser space weathered at low temperature and room temperature. Olivine irradiated at 88K is brighter at 1064 nm and exhibits less reddening than olivine irradiated at 295K. Radiative transfer modeling provided abundance estimates for SMFe. Based on these estimates, olivine irradiated at 88K contains 65-70% the abundance of SMFe of olivine irradiated at 295K. Laser weathering of a highlands analog at 85K results in reduced reddening but does not yield a statistically significant increased brightness at 1064 nm with lower temperature. Hence, our results show that laser weathering at low temperatures produces a measurable effect in VNIR spectra for olivine and less so for a plagioclase dominated soil. We attribute this mineral dependent observation to a decrease in the production of SMFe, and we will confirm this hypothesis with transmission electron microscopy. The 5% greater reflectance at 1064 nm for the 88K sample of olivine is consistent with the observed anticorrelation trend between temperature and LOLA albedo. Thus, reduced space weathering may contribute to the trend of increased albedo with decreasing temperature measured by LOLA.

Multi-instrument Observations of Storm Enhanced Density (SED) During the Oct. 24-25 2011 Storm: Implications for SED Formation Processes (Invited)

NASA Astrophysics Data System (ADS)

Zou, S.; Ridley, A. J.; Moldwin, M.; Nicolls, M. J.; Coster, A. J.; Thomas, E. G.; Ruohoniemi, J.

2013-12-01

Ionospheric density often exhibits significant variations, which affect the propagation of radio signals that pass through or are reflected by the ionosphere. One example of these effects is the loss of phase lock and range errors in Global Navigation Satellite Systems (GNSS) signals. Because our modern society increasingly relies on ground-to-ground and ground-to-space communications and navigation, understanding the sources of the ionospheric density variability and monitoring its dynamics during space weather events has great importance. Storm-enhanced density (SED) is one of the most prominent ionospheric density structures that can have significant space weather impact. We present multi-instrument observations of a SED event during the Oct. 24-25, 2011 intense geomagnetic storm. Formation and the subsequent evolution of the SED and the mid-latitude trough are revealed by global GPS vertical total electron content (VTEC) maps. In addition, we present high time resolution Poker Flat Incoherent Scatter Radar (PFISR) observations of ionospheric properties within the SED. The SED structure observed by PFISR is found to consist of two parts with different properties. Both parts are characterized by elevated ionospheric peak height (HmF2) and TEC, compared to quiet time values. However, the two parts of the SED have different characteristics in the electron temperature (Te), the F-region peak density (NmF2) and convection flows. The first part of the SED is associated with enhanced Te in the lower F region and reduced Te in the upper F region, and is collocated with northward convection flows. The NmF2 was lower than quiet time values. The second part of the SED is associated with significantly increased NmF2, elevated Te at all altitudes, and is located near the equatorward boundary of large northwestward flow, which is probably subauroral polarization stream (SAPS). Based on these observations, we suggest that the mechanisms responsible for the formation of the two parts of the SED are different. The first part is due to equatorward expansion of the convection pattern and the projection of northward convection flows in the vertical direction, which lifts the ionospheric plasma to higher altitudes and thus reduces the loss rate of plasma recombination. The formation mechanism of the second part appears more complex. Besides equatorward expansion of the convection pattern and large upward flows, evidence of other mechanisms, including horizontal advection due to SAPS flows, energetic particle precipitation, and enhanced thermospheric wind in the topside ionosphere, is also present in the observations. Our estimates show that contribution from precipitating energetic protons accounts for at most ~10% of the total F-region density. The thermospheric wind also plays a minor role in this case.

POP emissions from a large sinter plant in Taranto (Italy) over a five-year period following enforcement of new legislation.

PubMed

Esposito, Vittorio; Maffei, Annamaria; Bruno, Donato; Varvaglione, Berenice; Ficocelli, Salvatore; Capoccia, Carmelo; Spartera, Maria; Giua, Roberto; Blonda, Massimo; Assennato, Giorgio

2014-09-01

PCDD/F in exhaust gas emission samples was determined by the Environmental Agency of Apulia for a sinter plant located in Taranto (Italy) starting from June 2007 following an Agreement Act between plant owners and the Regional Government with the aim to assess and improve the environmental performances of the plant. The first two sampling campaigns yielded results ranging between 3.42 and 8.34 ng I-TE/Nm(3) that were soon considered revelatory of a high potential impact on the surrounding environment and the public, prompting for immediate action. As a first outcome, a Regional Regulation (LR 44/2008) was enforced in order to reduce PCDD/F emissions by plants operating in the metal sector, including sinter plants. After installation of a urea addition plant to the sinter mix as a process-integrated abatement technique the emissions ranged from 0.86 to 3.59 ng I-TE/Nm(3). In order to reach compliance to the newly introduced emission limit value of 0.4 ng I-TE/Nm(3) the urea plant was removed in favour of active-carbon injection as an end-of-pipe technique. Subsequently, during year 2011 emission values ranged from 0.095 to 1.97 ng I-TE/Nm(3), while in 2012 the observed range was 0.058 to 0.91 ng I-TE/Nm(3). As a better evaluation of the potential impact of the sinter plant emissions, a yearly mass-flow was estimated using exhaust gas PCDD/F concentrations and plant operational parameters (3.4 M Nm(3)/h). Mass-flow was estimated to be as high as 165 g I-TE/year for 2007 using yearly average concentrations or 248 g I-TE/year using the peak-value of 8.34 ng I-TE/Nm(3). Copyright © 2014 Elsevier B.V. All rights reserved.

Co-registered Topographical, Band Excitation Nanomechanical, and Mass Spectral Imaging Using a Combined Atomic Force Microscopy/Mass Spectrometry Platform

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

Ovchinnikova, Olga S.; Tai, Tamin; Bocharova, Vera

The advancement of a hybrid atomic force microscopy/mass spectrometry imaging platform demonstrating for the first time co-registered topographical, band excitation nanomechanical, and mass spectral imaging of a surface using a single instrument is reported. The mass spectrometry-based chemical imaging component of the system utilized nanothermal analysis probes for pyrolytic surface sampling followed by atmospheric pressure chemical ionization of the gas phase species produced with subsequent mass analysis. We discuss the basic instrumental setup and operation and the multimodal imaging capability and utility are demonstrated using a phase separated polystyrene/poly(2-vinylpyridine) polymer blend thin film. The topography and band excitation images showedmore » that the valley and plateau regions of the thin film surface were comprised primarily of one of the two polymers in the blend with the mass spectral chemical image used to definitively identify the polymers at the different locations. Data point pixel size for the topography (390 nm x 390 nm), band excitation (781 nm x 781 nm), mass spectrometry (690 nm x 500 nm) images was comparable and submicrometer in all three cases, but the data voxel size for each of the three images was dramatically different. The topography image was uniquely a surface measurement, whereas the band excitation image included information from an estimated 10 nm deep into the sample and the mass spectral image from 110-140 nm in depth. Moreover, because of this dramatic sampling depth variance, some differences in the band excitation and mass spectrometry chemical images were observed and were interpreted to indicate the presence of a buried interface in the sample. The spatial resolution of the mass spectral image was estimated to be between 1.5 m 2.6 m, based on the ability to distinguish surface features in that image that were also observed in the other images.« less

Co-registered Topographical, Band Excitation Nanomechanical, and Mass Spectral Imaging Using a Combined Atomic Force Microscopy/Mass Spectrometry Platform

DOE PAGES

Ovchinnikova, Olga S.; Tai, Tamin; Bocharova, Vera; ...

2015-03-18

The advancement of a hybrid atomic force microscopy/mass spectrometry imaging platform demonstrating for the first time co-registered topographical, band excitation nanomechanical, and mass spectral imaging of a surface using a single instrument is reported. The mass spectrometry-based chemical imaging component of the system utilized nanothermal analysis probes for pyrolytic surface sampling followed by atmospheric pressure chemical ionization of the gas phase species produced with subsequent mass analysis. We discuss the basic instrumental setup and operation and the multimodal imaging capability and utility are demonstrated using a phase separated polystyrene/poly(2-vinylpyridine) polymer blend thin film. The topography and band excitation images showedmore » that the valley and plateau regions of the thin film surface were comprised primarily of one of the two polymers in the blend with the mass spectral chemical image used to definitively identify the polymers at the different locations. Data point pixel size for the topography (390 nm x 390 nm), band excitation (781 nm x 781 nm), mass spectrometry (690 nm x 500 nm) images was comparable and submicrometer in all three cases, but the data voxel size for each of the three images was dramatically different. The topography image was uniquely a surface measurement, whereas the band excitation image included information from an estimated 10 nm deep into the sample and the mass spectral image from 110-140 nm in depth. Moreover, because of this dramatic sampling depth variance, some differences in the band excitation and mass spectrometry chemical images were observed and were interpreted to indicate the presence of a buried interface in the sample. The spatial resolution of the mass spectral image was estimated to be between 1.5 m 2.6 m, based on the ability to distinguish surface features in that image that were also observed in the other images.« less

Earth Glint Observations Conducted During the Deep Impact Spacecraft Flyby

NASA Technical Reports Server (NTRS)

Barry, R. K.; Deming, L. D.; Robinson, T.; Hewagama, T.

2010-01-01

We describe observations of Earth conducted using the High Resolution Instrument (HRI) - a 0.3 m f/35 telescope - on the Deep Impact (DI) spacecraft during its recent flybys. Earth was observed on five occasions: 2008-Mar-18 18:18 UT, 2008-May-28 20:05 UT, 2008-Jun-4 16:57 UT, 2009-Mar-27 16:19 and 2009-Oct-4 09:37 UT. Each set of observations was conducted over a full 24-hour rotation of Earth and a total of thirteen NIR spectra were taken on two-hour intervals during each observing period. Photometry in the 450, SSO, 650 and 8S0 nm filters was taken every fifteen minutes and every hour for the 350, 750 and 950 nm filters. The spacecraft was located over the equator for the three sets of observations in 2008, while the 2009- Mar and 2009-Oct were taken over the north and south Polar Regions, respectively. Observations of calibrator stars Canopus and Achernar were conducted on multiple occasions through all filters. The observations detected a strong specular glint not necessarily associated with a body of water. We describe spectroscopic characterization of the glint and evidence for the possibility of detection of reflection from high cirrus clouds. We describe implications for observations of extrasolar planets.

Spectrometric Estimation of Total Nitrogen Concentration in Douglas-Fir Foliage

NASA Technical Reports Server (NTRS)

Johnson, Lee F.; Billow, Christine R.; Peterson, David L. (Technical Monitor)

1995-01-01

Spectral measurements of fresh and dehydrated Douglas-fir foliage, from trees cultivated under three fertilization treatments, were acquired with a laboratory spectrophotometer. The slope (first-derivative) of the fresh- and dry-leaf absorbance spectra at locations near known protein absorption features was strongly correlated with total nitrogen (TN) concentration of the foliage samples. Particularly strong correlation was observed between the first-derivative spectra in the 2150-2170 nm region and TN, reaching a local maximum in the fresh-leaf spectra of -0.84 at 2 160 nm. Stepwise regression was used to generate calibration equations relating first derivative spectra from fresh, dry/intact, and dry/ground samples to TN concentration. Standard errors of calibration were 1.52 mg g-1 (fresh), 1.33 (dry/intact), and 1.20 (dry/ground), with goodness-of-fit 0.94 and greater. Cross-validation was performed with the fresh-leaf dataset to examine the predictive capability of the regression method; standard errors of prediction ranged from 1.47 - 2.37 mg g(exp -1) across seven different validation sets, prediction goodness of fit ranged from .85-.94, and wavelength selection was fairly insensitive to the membership of the calibration set. All regressions in this study tended to select wavelengths in the 2100-2350 nm region, with the primary selection in the 2142-2172 nm region. The study provides positive evidence concerning the feasibility of assessing TN status of fresh-leaf samples by spectrometric means. We assert that the ability to extract biochemical information from fresh-leaf spectra is a necessary but insufficient condition regarding the use of remote sensing for canopy-level biochemical estimation.

Comparative Analysis of Red-Edge Hyperspectral Indices

NASA Astrophysics Data System (ADS)

Gupta, R.; Vijayan, D.; Prasad, T.

The spectrally continuous observations of 3 nm bandwidth in 680 to 800 nm range over the growth cycle of wheat were subjected to first order differentiation to identify the point of inflection in red to near-IR transition zone. During 40 to 84 days after sowing (DAS), the point of inflection was observed in 723 to 735 nm region with peak response at 729 nm for 64 DAS . For differentiated curve pertaining to 25 DAS (initial vegetative) and 90 DAS (initial senescence) phenological stages, the point of inflection was in 690-693 and 744-747 nm spectral region, respectively. The ratios corresponding to 1dB (RI1dB = R 735 /R720), 2dB (RI 2dB = R738/R 720), 3dB (RI3dB = R741 /R 717) down signal levels and half signal level (RIhalf = R747/R 708 ) were computed. For nomenclature point of view, R41 refers to reflectance for 3 nm7 bandwidth centered at 741 nm. Correlations for these developed RIs were studied with reference to indices given by Vogelmann i.e., VOG a = R 740 /R720 , VOG b = [(R 734-R747)/(R715+R720)] and red edge spectral parameter (RESP) = R750 /R 710. VOG a and RESP conceptually resemble with developed RI 2dB and RIhalf , respectively. All RIs were found correlated with VOGa , VOG b and RESP with r2 in the range of 0.96 to 0.99; r2 was 0.998 for RI2dB and VOG a pair and 0.996 for RI half and RESP pair; the slope factor of regression relationship improved by about 50% from RI dB to2 RI3dB and by about 125% from RI3dB to RIhalf with r2 in 0.97-0.99 range. Thus, theoretical basis for VOG a and RESP in terms of dB based indices has been provided. The wavelengths used in VOGb are noticed in dB based indices ; to provide stability to small magnitude R720, the sum of R720 and R715 has been used in VOGb. Based on regression analysis of these indices with LAI in its growth and decline phases separately, the slope value for VOG b, RI 2dB, VOG a, RIhalf, RESP and area under 680 to 760 nm for first order derivative curve (area) were in 0.08-0.11, 0.24 - 0.34, 0.27-0.38, 0.86-1.18, 0.89-1.27 and 7.6-13.87 range, respectively. Here, the first value in the range refers to slope value for the growth phase of LAI while the second value in the range refers to that for the decline phase of LAI. To judge the sensitivity for the rate of change in red - edge, the change in area for ratio indices and normalized indices in 680 to 760 nm (red-near IR transition region) with 673 nm were analysed. The rate of change for area under the red edge as a function of DAS was more for ratio indices as compared to that for normalized indices.

Broad Band Antireflection Coating on Zinc Sulphide Window for Shortwave infrared cum Night Vision System

NASA Astrophysics Data System (ADS)

Upadhyaya, A. S.; Bandyopadhyay, P. K.

2012-11-01

In state of art technology, integrated devices are widely used or their potential advantages. Common system reduces weight as well as total space covered by its various parts. In the state of art surveillance system integrated SWIR and night vision system used for more accurate identification of object. In this system a common optical window is used, which passes the radiation of both the regions, further both the spectral regions are separated in two channels. ZnS is a good choice for a common window, as it transmit both the region of interest, night vision (650 - 850 nm) as well as SWIR (0.9 - 1.7 μm). In this work a broad band anti reflection coating is developed on ZnS window to enhance the transmission. This seven layer coating is designed using flip flop design method. After getting the final design, some minor refinement is done, using simplex method. SiO2 and TiO2 coating material combination is used for this work. The coating is fabricated by physical vapour deposition process and the materials were evaporated by electron beam gun. Average transmission of both side coated substrate from 660 to 1700 nm is 95%. This coating also acts as contrast enhancement filter for night vision devices, as it reflect the region of 590 - 660 nm. Several trials have been conducted to check the coating repeatability, and it is observed that transmission variation in different trials is not very much and it is under the tolerance limit. The coating also passes environmental test for stability.

Bio-optical observations of the 2004 Labrador Sea phytoplankton bloom

NASA Astrophysics Data System (ADS)

Strutton, Peter G.; Martz, Todd R.; Degrandpre, Michael D.; McGillis, Wade R.; Drennan, William M.; Boss, Emmanuel

2011-11-01

A unique time series of moored bio-optical measurements documented the 2004 spring-summer bloom in the southern Labrador Sea. In situ and satellite chlorophyll data show that chlorophyll levels in the 2004 bloom were at the upper end of those typically observed in this region. Satellite chlorophyll and profiling float temperature/salinity data show that the main bloom, which typically peaks in June/July, is often preceded by ephemeral mixed layer shoaling and a lesser, short-lived bloom in May; this was the case in 2004. The particulate backscatter to beam attenuation ratio (bbp[470 nm]/Cp[660 nm]) showed peaks in the relative abundance of small particles at bloom initiation and during the decline of the bloom, while larger particles dominated during the bloom. Chlorophyll/Cp and bbp/chlorophyll were correlated with carbon export and dominated by changes in the pigment per cell associated with lower light levels due to enhanced attenuation of solar radiation during the bloom. An NPZ (nutrients, phytoplankton, zooplankton) model captured the phytoplankton bloom and an early July peak in zooplankton. Moored acoustic Doppler current profiler (ADCP) data showed an additional mid-June peak in zooplankton biomass which was attributed to egg-laying copepods. The data reported here represent one of the few moored time series of Cp, bbp and chlorophyll extending over several months in an open ocean region. Interpretation of data sets such as this will become increasingly important as these deployments become more commonplace via ocean observing systems. Moreover, these data contribute to the understanding of biological-physical coupling in a biogeochemically important, yet poorly studied region.

Advantages of using gold hollow nanoshells in cancer photothermal therapy

NASA Astrophysics Data System (ADS)

Abbasi, Sattar; Servatkhah, Mojtaba; Keshtkar, Mohammad Mehdi

2016-08-01

Lots of studies have been conducted on the optical properties of gold nanoparticles in the first region of near infrared (650 nm-950 nm), however new findings show that the second region of near-infrared (1000 nm-1350 nm) penetrates to the deeper tissues of the human body. Therefore, using the above-mentioned region in photo-thermal therapy (PTT) of cancer will be more appropriate. In this paper, absorption efficiency is calculated for gold spherical and rod-shaped nanoshells by the finite element method (FEM). The results show that the surface plasmon frequency of these nanostructures is highly dependent on the dimension and thickness of shell and it can be adjusted to the second region of near-infrared. Thus, due to their optical tunability and their high absorption efficiency the hollow nanoshells are the most appropriate options for eradicating cancer tissues.

Auroral LSTIDs and SAR Arc Occurrences in Northern California During Geomagnetic Storms

NASA Astrophysics Data System (ADS)

Bhatt, A.; Kendall, E. A.

2015-12-01

A 630nm allsky imager has been operated for two years in northern California at the Hat Creek Radio Observatory. F-region airglow data captured by the imager ranges from approximately L=1.7 -2.7. Since installation of the imager several geomagnetic storms have occurred with varying intensities. Two main manifestations of the geomagnetic storms are observed in the 630 nm airglow data: large-scale traveling ionospheric disturbances that are launched from the auroral zone and Stable Auroral Red (SAR) arcs during more intense geomagnetic storms. We will present a statistical analysis of these storm-time phenomena in northern California for the past eighteen months. This imager is part of a larger all-sky imaging network across the continental United States, termed MANGO (Midlatitude All-sky-imaging Network for Geophysical Observations). Where available, we will add data from networked imagers located at similar L-shell in other states as well.

Ultrastructural observations on giardiasis in a mouse model. II. Endosymbiosis and organelle distribution in Giardia muris and Giardia lamblia.

PubMed

Nemanic, P C; Owen, R L; Stevens, D P; Mueller, J C

1979-08-01

Ultrastructural observations of Giardia muris in a mouse model revealed endosymbiotic microbes not previously reported in Giardia. Endosymbionts 240--360 nm wide, 600--1,400 nm long, and with an internal structure similar to that of bacilli were not seen entering Giardia but were found and appeared to divide within Giardia. No evidence was found of digestion of the endosymbionts by the giardia host in either the trophozoite or the cyst form. Endosymbionts were concentrated centrally around the nuclear area and were uncommon in peripheral feeding regions. The same cellular organelles seen in G. muris were found in Giardia lamblia from human jejunal biopsy material, but no endosymbionts were identified in G. lamblia trophozoites from the seven patients examined. Endosymbionts within Giardia may be found to alter trophozoite pathogenicity, metabolism, range of infectivity, antigenic surface characteristics, and host specificity, as they do in other protozoa.

Interference of birefractive waves in CdGa2S4 crystals

NASA Astrophysics Data System (ADS)

Syrbu, N. N.; Tiron, A. V.; Parvan, V. I.; Zalamai, V. V.; Tiginyanu, I. M.

2015-04-01

In СdGа2S4 crystals the Fabry-Perot and birefringence interference spectra were investigated. Spectral dependences of refraction indexes for ordinary (no) and extraordinary (ne) light waves are defined. The spectral dependence Δn=ne-no from the short and long-wavelength parts of isotropic wavelength λ0=485.7 nm (300 K) is determined. It is established that at λ>λ0 Δn is positive and at λ<λ0 Δn is negative. Wavelength λ0=485.7 nm shifts with decreasing temperature to short-wavelengths. The phase difference of ordinary and extraordinary light waves for λ>λ0 and λ<λ0 was determined. The band in reflection spectra observed at the isotropic wavelength has a small halfwidth (∽3-5 Å). Another isotropic wavelength was found in the short-wavelength region (433 nm) for crystals obtained by iodine transport method.

Study of photoluminescence properties of CaAl{sub 2}O{sub 4}: Eu{sup 2+} prepared by combustion synthesis method

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

Hingwe, V. S., E-mail: vishwas.hingwe@yahoo.in; Omanwar, S. K.; Bajaj, N. S.

2016-05-06

Eu{sup 2+} doped alkaline earth metals such as strontium aluminate, calcium aluminate and barium aluminate prepared by using modified combustion synthesis method at 600°C with Urea as fuel. Crystal structure is determined by using XRD and the sample confirmation by using the FTIR. The effect of the host material on the photoluminescence (PL) and phosphorescence properties were studied by using the Hitachi F-7000 spectrofluorimeter equipped with a 450W Xenon lamp, in the range 200-650 nm. The emission spectra of Eu{sup 2+} range from 450 to 500 nm in the Blue to aqua region and the transition 4f{sup 7}-4f{sup 6} 5d{sup 1}.more » The observed emission in CaAl{sub 2}O{sub 4} is 440 nm.« less

Fabrication of Ta nanoparticles induced by nanosecond laser ablation in ethanol: the study of laser fluence effects

NASA Astrophysics Data System (ADS)

Azadi Kenari, Fariba; Moniri, Samira; Hantehzadeh, Mohammad Reza; Dorranian, Davoud; Ghoranneviss, Mahmood

2018-05-01

Tantalum nanoparticles (Ta NPs) were synthesized in ethanol solution by ablation with a 1064 nm Nd:YAG laser. Prepared NPs were investigated by UV-visible absorption spectroscopy, Transmission electron microscopy, X-ray diffraction and Photoluminescence measurement. The average sizes of NPs were calculated to be in the range of 12-18 nm. From the UV-visible studies, the plasmon peak position of Ta NPs was observed in the spectral range of 206-208 nm. The XRD spectra clearly showed the crystalline structure of NPs and various peaks of Ta and Ta2O5. Moreover, the UV region in the PL spectrum included the free exciton and the bound exciton emission correlated with the defect concentration. In fact, the laser ablation in the organic and inorganic solvents is a strong technique to obtain some NPs with particular structures, which are impossible to produce by conventional methods.

UV absorption spectrum of allene radical cations in solid argon

NASA Astrophysics Data System (ADS)

Chin, Chih-Hao; Lin, Meng-Yeh; Huang, Tzu-Ping; Wu, Yu-Jong

2018-05-01

Electron bombardment during deposition of an Ar matrix containing a small proportion of allene generated allene cations. Further irradiation of the matrix sample at 385 nm destroyed the allene cations and formed propyne cations in solid Ar. Both cations were identified according to previously reported IR absorption bands. Using a similar technique, we recorded the ultraviolet absorption spectrum of allene cations in solid Ar. The vibrationally resolved progression recorded in the range of 266-237 nm with intervals of about 800 cm-1 was assigned to the A2E ← X2E transition of allene cations, and the broad continuum absorption recorded in the region of 229-214 nm was assigned to their B2A1 ← X2E transition. These assignments were made based on the observed photolytic behavior of the progressions and the vertical excitation energies and oscillator strengths calculated using time-dependent density functional theory.

Photo-induced persistent inversion of germanium in a 200-nm-deep surface region.

PubMed

Prokscha, T; Chow, K H; Stilp, E; Suter, A; Luetkens, H; Morenzoni, E; Nieuwenhuys, G J; Salman, Z; Scheuermann, R

2013-01-01

The controlled manipulation of the charge carrier concentration in nanometer thin layers is the basis of current semiconductor technology and of fundamental importance for device applications. Here we show that it is possible to induce a persistent inversion from n- to p-type in a 200-nm-thick surface layer of a germanium wafer by illumination with white and blue light. We induce the inversion with a half-life of ~12 hours at a temperature of 220 K which disappears above 280 K. The photo-induced inversion is absent for a sample with a 20-nm-thick gold capping layer providing a Schottky barrier at the interface. This indicates that charge accumulation at the surface is essential to explain the observed inversion. The contactless change of carrier concentration is potentially interesting for device applications in opto-electronics where the gate electrode and gate oxide could be replaced by the semiconductor surface.

Fluorescent and scattering contrast agents in a mouse model of colorectal cancer

NASA Astrophysics Data System (ADS)

Winkler, Amy M.; Rice, Photini F. S.; Troutman, Timothy S.; Backer, Marina V.; Backer, Joseph M.; Drezek, Rebekah A.; Romanowski, Marek; Barton, Jennifer K.

2008-02-01

In previous work we have demonstrated the utility of laser-induced fluorescence (LIF) and optical coherence tomography (OCT) to identify adenoma in mouse models of colorectal cancer with high sensitivity and specificity. However, improved sensitivity to early disease, as well as the ability to distinguish confounders (e.g. fecal contamination, natural variations in mucosal thickness), is desired. In this study, we investigated the signal enhancement of fluorescent and scattering contrast agents in the colons of AOM-treated mice. The fluorescent tracer scVEGF/Cy, targeted to receptors for vascular endothelial growth factor, was visualized on a dual modality OCT/LIF endoscopic system with 1300-nm center wavelength OCT source and 635-nm LIF excitation. Scattering agents were tested with an 890-nm center wavelength endoscopic OCT system. Agents included nanoshells, 120-nm in diameter, and nanorods, 20-nm in diameter by 80-nm in length. Following imaging, colons were excised. Tissue treated with fluorophore was imaged on an epifluorescence microscope. Histological sections were obtained and stained with H&E and silver enhancer to verify disease and identify regions of gold uptake, respectively. Non-specific signal enhancement was observed with the scattering contrast agents. Specificity for adenoma was seen with the scVEGF/Cy dye.

Influence of 2D electrostatic effects on the high-frequency noise behavior of sub-100-nm scaled MOSFETs

NASA Astrophysics Data System (ADS)

Rengel, Raul; Pardo, Daniel; Martin, Maria J.

2004-05-01

In this work, we have performed an investigation of the consequences of dowscaling the bulk MOSFET beyond the 100 nm range by means of a particle-based Monte Carlo simulator. Taking a 250 nm gate-length ideal structure as the starting point, the constant field scaling rules (also known as "classical" scaling) are considered and the high-frequency dynamic and noise performance of transistors with 130 nm, 90 nm and 60 nm gate-lengths are studied in depth. The analysis of internal quantities such as electric fields, velocity and energy of carriers or conduction band profiles shows the increasing importance of electrostatic two-dimensional effects due to the proximity of source and drain regions even when the most ideal bias conditions are imposed. As a consequence, a loss of the transistor action for the smallest MOSFET and the degradation of the most important high-frequency figures of merit is observed. Whereas the comparative values of intrinsic noise sources (SID, SIG) are improved when reducing the dimensions and the bias voltages, the poor dynamic performance yields an overall worse noise behaviour than expected (especially for Rn and Gass), limiting at the same time the useful bias ranges and conditions for a proper low-noise configuration.

A 23-dB bismuth-doped optical fiber amplifier for a 1700-nm band

PubMed Central

Firstov, Sergei V.; Alyshev, Sergey V.; Riumkin, Konstantin E.; Khopin, Vladimir F.; Guryanov, Alexey N.; Melkumov, Mikhail A.; Dianov, Evgeny M.

2016-01-01

It is now almost twenty-five years since the first Erbium-Doped Fiber Amplifier (EDFA) was demonstrated. Currently, the EDFA is one of the most important elements widely used in different kinds of fiber-optic communication systems. However, driven by a constantly increasing demand, the network traffic, growing exponentially over decades, will lead to the overload of these systems (“capacity crunch”) because the operation of the EDFA is limited to a spectral region of 1530–1610 nm. It will require a search for new technologies and, in this respect, the development of optical amplifiers for new spectral regions can be a promising approach. Most of fiber-optic amplifiers are created using rare-earth-doped materials. As a result, wide bands in shorter (1150–1530 nm) and longer wavelength (1600–1750 nm) regions with respect to the gain band of Er-doped fibers are still uncovered. Here we report on the development of a novel fiber amplifier operating in a spectral region of 1640–1770 nm pumped by commercially available laser diodes at 1550 nm. This amplifier was realized using bismuth-doped high-germania silicate fibers fabricated by MCVD technique. PMID:27357592

Observation of an optical vortex beam from a helical undulator in the XUV region.

PubMed

Kaneyasu, Tatsuo; Hikosaka, Yasumasa; Fujimoto, Masaki; Iwayama, Hiroshi; Hosaka, Masahito; Shigemasa, Eiji; Katoh, Masahiro

2017-09-01

The observation of an optical vortex beam at 60 nm wavelength, produced as the second-harmonic radiation from a helical undulator, is reported. The helical wavefront of the optical vortex beam was verified by measuring the interference pattern between the vortex beam from a helical undulator and a normal beam from another undulator. Although the interference patterns were slightly blurred owing to the relatively large electron beam emittance, it was possible to observe the interference features thanks to the helical wavefront of the vortex beam. The experimental results were well reproduced by simulation.

Plasma bubble monitoring by TEC map and 630 nm airglow image

NASA Astrophysics Data System (ADS)

Takahashi, H.; Wrasse, C. M.; Otsuka, Y.; Ivo, A.; Gomes, V.; Paulino, I.; Medeiros, A. F.; Denardini, C. M.; Sant'Anna, N.; Shiokawa, K.

2015-08-01

Equatorial ionosphere plasma bubbles over the South American continent were successfully observed by mapping the total electron content (TECMAP) using data provided by ground-based GNSS receiver networks. The TECMAP could cover almost all of the continent within ~4000 km distance in longitude and latitude, monitoring TEC variability continuously with a time resolution of 10 min. Simultaneous observations of OI 630 nm all-sky image at Cachoeira Paulista (22.7°S, 45.0°W) and Cariri (7.4°S, 36.5°W) were used to compare the bubble structures. The spatial resolution of the TECMAP varied from 50 km to 1000 km, depending on the density of the observation sites. On the other hand, optical imaging has a spatial resolution better than 15 km, depicting the fine structure of the bubbles but covering a limited area (~1600 km diameter). TECMAP has an advantage in its spatial coverage and the continuous monitoring (day and night) form. The initial phase of plasma depletion in the post-sunset equatorial ionization anomaly (PS-EIA) trough region, followed by development of plasma bubbles in the crest region, could be monitored in a progressive way over the magnetic equator. In December 2013 to January 2014, periodically spaced bubble structures were frequently observed. The longitudinal spacing between the bubbles was around 600-800 km depending on the day. The periodic form of plasma bubbles may suggest a seeding process related to the solar terminator passage in the ionosphere.

Observations of and Influences on Low-Latitude Vertical Plasma Drifts

NASA Astrophysics Data System (ADS)

Miller, E. S.; Chartier, A.; Paxton, L. J.

2016-12-01

Many workers have suggested that the morphology (position and relative intensities) of the crests of the equatorial ionization anomaliesis related to the time history of the equatorial vertical drift. In this work, we compare observations of the vertical drift using an HF radiosignals of opportunity in the Central Pacific with UV 135.6-nm observations of the equatorial anomalies from the DMSP/SSUSI andTIMED/GUVI instruments. Furthermore, we explore the role of E region density in modulating the vertical plasma drift using a passive HFsounding experiment in the Caribbean. Coupling between nighttime medium-scale traveling ionospheric disturbances (MSTIDs) and sporadic-Elayers has been suggested as a growth-rate-increasing process. While we observe sporadic-E in the local hemisphere coincident to increases in thealtitude of the F-region altitude, we also observe uplifts without sporadic-E in the local hemisphere. Apart from the trivial explanation that sporadic-E is occurring in the conjugate hemisphere, another possible explanation is that the E region may enhance the vertical drift, but is not required to produce enhanced vertical drifts. These studies represent fruitful areas of future intersection between ground-based observations and ICON and GOLD science.

Detection of low-concentration ammonia using differential laser-induced fluorescence on vapochromic coordination polymers

NASA Astrophysics Data System (ADS)

Yin, Dawei; Chapman, Glenn H.; Stevens, David; Gray, Bonnie; Leznoff, Daniel

2018-02-01

The detection of ammonia in parts per millions range has been challenging in sensors research, and is of great importance for industrial applications. In previous literature, Vapochromic Coordination Polymers (VCP) were developed to achieve luminescence upon a targeted gas exposures. We investigate a specific VCP, Zn[Au(CN)2]2,as an ammonia sensing material. Upon high concentration ammonia exposure, the fluorescent peak under near-UV stimulation undergoes a spectral shift from 460nm to 520nm, while the intensity increases by 3 4X. However, at ammonia concentrations < 50ppm, the spectral shift becomes hidden within the overall changing fluorescent spectrum shape. Then simple methods, such as detecting the peak wavelength or subtracting post-exposure from pre-exposure spectrums do not work. We developed further excitation and data processing techniques to detect ammonia at lower concentrations. A low-cost 405nm blue-ray DVD laser diode was used as the excitation source, providing a narrow band-width (4nm) stimulation that is separated from the emission peak. We measured the emission using a portable spectrometer (Photon Control SPM-002), and processed the data by separating the spectrum into two regions; (A) from 425 nm to 460 nm and (B) from 460nm to 500nm. Next, the integrated emissions under both regions were computed, and the value of shorter wavelength region (A) was subtracted from the longer wavelength one (B). When exposed to ammonia, region (A) reduces overall intensity while region (B) increases, resulting a signal starting from negative value and gradually increases to positive values, enabling the detection of 5ppm ammonia in less than 30 seconds gas exposure.

308-nm excimer laser for the treatment of alopecia areata.

PubMed

Al-Mutairi, Nawaf

2007-12-01

Alopecia areata is loss of hair from localized or diffuse areas of hair-bearing area of the skin. Recently there are reports of efficacy of the 308-nm excimer radiation for this condition. To study the effect of the 308-nm excimer laser in the treatment of alopecia areata. Eighteen patients with 42 recalcitrant patches (including 1 adult with alopecia totalis) were enrolled in this study. The lesions were treated with the 308-nm excimer laser twice a week for a period of 12 weeks; one lesion on each patient was left as a control for comparison. There were 7 males and 11 females in this study. Regrowth of hair was observed in 17 (41.5%) patches. Thirteen of the 18 lesions in scalp showed a complete regrowth of hair. The extremity regions failed to show a response. Atopic diatheses had an unfavorable effect on the outcome in our patients. The 308-nm excimer laser is an effective therapeutic option for patchy alopecia areata of the scalp and for some cases with patchy alopecia areata of the beard area. It does not work for patchy alopecia areata of the extremities.

Strong coupling between adenine nucleobases in DNA single strands revealed by circular dichroism using synchrotron radiation

NASA Astrophysics Data System (ADS)

Kadhane, Umesh; Holm, Anne I. S.; Hoffmann, Søren Vrønning; Nielsen, Steen Brøndsted

2008-02-01

Circular dichroism (CD) experiments on DNA single strands (dAn) at the ASTRID synchrotron radiation facility reveal that eight adenine (A) bases electronically couple upon 190nm excitation. After n=8 , the CD signal increases linearly with n with a slope equal to the sum of the coupling terms. Nearest neighbor interactions account for only 24% of the CD signal whereas electronic communication is limited to nearest neighbors for two other exciton bands observed at 218 and 251nm (i.e., dimer excited states). Electronic coupling between bases in DNA is important for nonradiative deexcitation of electronically excited states since the hazardous energy is spread over a larger spatial region.

Bayesian Model for Matching the Radiometric Measurements of Aerospace and Field Ocean Color Sensors

PubMed Central

Salama, Mhd. Suhyb; Su, Zhongbo

2010-01-01

A Bayesian model is developed to match aerospace ocean color observation to field measurements and derive the spatial variability of match-up sites. The performance of the model is tested against populations of synthesized spectra and full and reduced resolutions of MERIS data. The model derived the scale difference between synthesized satellite pixel and point measurements with R2 > 0.88 and relative error < 21% in the spectral range from 400 nm to 695 nm. The sub-pixel variabilities of reduced resolution MERIS image are derived with less than 12% of relative errors in heterogeneous region. The method is generic and applicable to different sensors. PMID:22163615

The Emission, Lifetimes, and Formation Threshold of the Vegard-Kaplan Transition of Solid Nitrogen Exposed to Far-ultraviolet Radiation

NASA Astrophysics Data System (ADS)

Lu, Hsiao-Chi; Lo, Jen-Iu; Peng, Yu-Chain; Chou, Sheng-Lung; Lin, Meng-Yeh; Cheng, Bing-Ming

2016-11-01

Irradiation of solid nitrogen at 4 K with far-ultraviolet light from a synchrotron caused excitation to the upper state of the Vegard-Kaplan (VK) system; the emission in that system was simultaneously recorded in wavelength region 200-440 nm. The lifetimes of emission lines for VK (0, 1) to (0, 12) transitions were measured in the range of 2.12 ˜ 2.65 s. The threshold wavelength to observe the VK emission was 175.0 ± 3.5 nm, corresponding to energy 7.08 ± 0.14 eV. This investigation of the generation of icy VK nitrogen enhances our understanding of its photochemistry in space.

Bipolar resistive switching in metal-insulator-semiconductor nanostructures based on silicon nitride and silicon oxide

NASA Astrophysics Data System (ADS)

Koryazhkina, M. N.; Tikhov, S. V.; Mikhaylov, A. N.; Belov, A. I.; Korolev, D. S.; Antonov, I. N.; Karzanov, V. V.; Gorshkov, O. N.; Tetelbaum, D. I.; Karakolis, P.; Dimitrakis, P.

2018-03-01

Bipolar resistive switching in metal-insulator-semiconductor (MIS) capacitor-like structures with an inert Au top electrode and a Si3N4 insulator nanolayer (6 nm thick) has been observed. The effect of a highly doped n +-Si substrate and a SiO2 interlayer (2 nm) is revealed in the changes in the semiconductor space charge region and small-signal parameters of parallel and serial equivalent circuit models measured in the high- and low-resistive capacitor states, as well as under laser illumination. The increase in conductivity of the semiconductor capacitor plate significantly reduces the charging and discharging times of capacitor-like structures.

[Study on the movement of the carrier recombination region in organic light-emitting diodes (OLEDs) based on DPVBi/Alq3].

PubMed

Yan, Guang; Zhao, Su-ling; Xu, Zheng; Zhang, Fu-jun; Kong, Chao; Liu, Xiao-dong; Gong, Wei; Gao, Li-yan

2011-07-01

Series of organic light emitting devices with basic structure of ITO/PCBM: PVK(x Wt%, approximately 40 nm)/DPVBi(30 nm)/Alq3 (30 nm)/Al were fabricated in order to investigate the carrier recombination region movement in these devices. The carrier injection-dependent, the carrier transport-dependent and the voltage-dependent carrier recombination region movements were investigated respectively by modifying cathode with lithium fluoride, by changing the doping concentration of PCBM and by changing the voltage on the devices. The physical mechanism behind the voltage-dependent carrier recombination region movement was discussed.

Solar Spectral Irradiance Variability of Some Chromospheric Emission Lines Through the Solar Activity Cycles 21-23

NASA Astrophysics Data System (ADS)

Göker, Ü. D.; Gigolashvili, M. Sh.; Kapanadze, N.

2017-06-01

A study of variations of solar spectral irradiance (SSI) in the wavelength ranges 121.5 nm-300.5 nm for the period 1981-2009 is presented. We used various data for ultraviolet (UV) spectral lines and international sunspot number (ISSN) from interactive data centers such as SME (NSSDC), UARS (GDAAC), SORCE (LISIRD) and SIDC, respectively. We reduced these data by using the MATLAB software package. In this respect, we revealed negative correlations of intensities of UV (289.5 nm-300.5 nm) spectral lines originating in the solar chromosphere with the ISSN index during the unusually prolonged minimum between the solar activity cycles (SACs) 23 and 24. We also compared our results with the variations of solar activity indices obtained by the ground-based telescopes. Therefore, we found that plage regions decrease while facular areas are increasing in SAC 23. However, the decrease in plage regions is seen in small sunspot groups (SGs), contrary to this, these regions in large SGs are comparable to previous SACs or even larger as is also seen in facular areas. Nevertheless, negative correlations between ISSN and SSI data indicate that these variations are in close connection with the classes of sunspots/SGs, faculae and plage regions. Finally, we applied the time series analysis of spectral lines corresponding to the wavelengths 121.5 nm-300.5 nm and made comparisons with the ISSN data. We found an unexpected increase in the 298.5 nm line for the Fe II ion. The variability of Fe II ion 298.5 nm line is in close connection with the facular areas and plage regions, and the sizes of these solar surface indices play an important role for the SSI variability, as well. So, we compared the connection between the sizes of faculae and plage regions, sunspots/SGs, chemical elements and SSI variability. Our future work will be the theoretical study of this connection and developing of a corresponding model.

Optimum spectral resolution for computing atmospheric heating and photodissociation rates

NASA Astrophysics Data System (ADS)

Stamnes, K.; Tsay, S.-C.

1990-06-01

Rapid, reliable and accurate computations of atmospheric heating rates are needed in climate models aimed at predicting the impact of greenhouse gases on the surface temperature. Photolysis rates play a major role in photochemical models used to assess potential changes in atmospheric ozone abundance due to man's release of chlorofluorocarbons. Both rates depend directly on the amount of solar radiation available at any level in the atmosphere. We present a very efficient method of computing these rates in which integration over the solar spectrum is reduced to a minimum number of monochromatic (or pseudogray) problems by appealing to the continuum features of the ozone absorption cross-sections. To explore the resolutions needed to obtain adequate results we have divided the spectral range between 175 and 700 nm into four regions. Within each of these regions we may vary the resolution as we wish. Accurate results are obtained for very coarse spectral resolution provided all cross-sections are averaged by weighting them with the solar flux across any bin. By using this procedure we find that heating rate errors are less than 20% for all altitudes when only four spectral bands across the entire wavelength region from 175 to 700 nm are used to compute the heating rate profile. Similarly, we find that the error in the photodissociation of ozone is less than a few percent when 10 nm resolution is used in the Hartley and Huggins bands (below 330 nm), while an average over the entire wavelength region from 400 to 700 nm yields similar accuracy for the Chappuis band. For integrated u.v. dose estimates a resolution slightly better than 10 nm is required in the u.v.B region (290-315 nm) to yield an accuracy better than 10%, but we may treat the u.v.A region (315-400 nm) as a single band and yet have an accuracy better than 2%.

Detecting Thermal Barrier Coating Delamination Using Visible and Near-Infrared Luminescence from Erbium-Doped Sublayers

NASA Technical Reports Server (NTRS)

Eldridge, J. I.; Bencic, T. J.; Martin, R. E.; Singh, J.; Wolfe, D. E.

2007-01-01

Nondestructive diagnostic tools are needed to monitor early stages of delamination progression in thermal barrier coatings (TBCs) because the risk of delamination induced coating failure will compromise engine performance and safety. Previous work has demonstrated that for TBCs composed of yttria-stabilized zirconia (YSZ), luminescence from a buried europium-doped sublayer can be utilized to identify the location of TBC delamination from the substantially higher luminescence intensity observed from the delaminated regions of the TBC. Luminescence measurements from buried europium-doped layers depend on sufficient transmittance of the 532 nm excitation and 606 nm emission wavelengths through the attenuating undoped YSZ overlayer to produce easily detected luminescence. In the present work, improved delamination indication is demonstrated using erbium-doped YSZ sublayers. For visible-wavelength luminescence, the erbium-doped sublayer offers the advantage of a very strong excitation peak at 517 nm that can be conveniently excited a 514 nm Ar ion laser. More importantly, the erbium-doped sublayer also produces near-infrared luminescence at 1550 nm that is effectively excited by a 980 nm laser diode. Both the 980 nm excitation and the 1550 nm emission are transmitted through the TBC with much less attenuation than visible wavelengths and therefore show great promise for delamination monitoring through thicker or more highly scattering TBCs. The application of this approach for both electron beam physical vapor deposited (EB-PVD) and plasma-sprayed TBCs is discussed.

The High-Excitation Planetary Nebula NCG 246: Optical and Near-Ultraviolet Observations and Two-dimensional Numerical Models

NASA Technical Reports Server (NTRS)

Szentgyorgyi, Andrew; Raymond, John; Franco, Jose; Villaver, Eva; Lopez-Martin, Luis

2003-01-01

We have imaged the planetary nebula (PN) NGC 246 in the near-ultraviolet wavelengths [Ne v] 342.6 nm, the Bowen fluorescence line of 0 111 at 344.4 nm, and a nearby line-free region centered on 338.6 nm, as well as H(alpha), [O III] 500.7 nm, and [S II] 673.0 and 671.5 nm. Imaging in the 344.4 nm line is necessary to deconvolve contamination of the [Ne v] images by O III 342.9 nm. The emission from the shell and inner parts of the nebula is detected in [Ne v]. The radial profiles of the [Ne v] brightness decrease with radius from the exciting star, indicating that the bulk of the emission from this ion is due to the hard UV stellar radiation field, with a (probably) marginal contribution from collisional ionization in a shock between the PN shell and the interstellar medium (ISM). In contrast, the radial profiles of the emission in H(alpha), [0 III] 500.7 nm, and [S II] are flatter and peak at the location of the shell. The emission of [S II] probably traces the interaction of the PN with the ambient ISM. We also present two-dimensional numerical simulations for this PN-ISM interaction. The simulations consider the stellar motion with respect to the ambient ISM, with a velocity of 85 km/s , and include the time evolution of the wind parameters and UV radiation field from the progenitor star.

The design of broad band anti-reflection coatings for solar cell applications

NASA Astrophysics Data System (ADS)

Siva Rama Krishna, Angirekula; Sabat, Samrat Lagnajeet; Ghanashyam Krishna, Mamidipudi

2017-01-01

The design of broadband anti-reflection coatings (ARCs) for solar cell applications using multiobjective differential evolutionary (MODE) algorithms is reported. The effect of thickness and refractive index contrast within the layers of the ARC on the bandwidth of reflectance is investigated in detail. In the case of the hybrid plasmonic ARC structures the effect of size, shape and filling fraction of silver (Ag) nanoparticles on the reflectance is studied. Bandwidth is defined as the spectral region of wavelengths over which the reflectance is below 2%. Single, two and three layers ARCs (consisting of MgF2, Al2O3, Si3N4, TiO2 and ZnS or combinations of these materials) were simulated for performance evaluation on an a-Si photovoltaic cell. It is observed that the three layer ARC consisting of MgF2/Si3N4/TiO2(ZnTe) of 81/42/36 nm thicknesses, respectively, exhibited a weighted reflectance of 1.9% with a bandwidth of 450 nm over the wavelength range of 300-900 nm. The ARC bandwidth could be further improved by embedding randomly distributed Ag nanoparticles of size between 100 and 120 nm on a two layer ARC consisting of Al2O3/TiO2 with thickness of 42 nm and 56 nm respectively. This plasmon-dielectric hybrid ARC design exhibited a weighted reflectance of 0.6% with a bandwidth of 560 nm over the wavelength range of 300-900 nm.

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

Sharma, Rabindar K.; Reddy, G. B.

In this work, we have successfully developed plasma assisted paste sublimation route to deposit vertically aligned MoO{sub 3} nanoflakes (NFs) on nickel coated glass substrate in oxygen plasma ambience with the assistant of Ni thin layer as a catalyst. In our case, sublimation source (Mo strip surface) is resistively heated by flowing current across it. The structural, morphological, and optical properties of NFs have been investigated systematically using x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) with selected area electron diffraction (SAED), High resolution transmission electron microscopy (HRTEM), micro-Raman spectroscopy, and Photoluminescence (PL) spectroscopy. Studies reveal thatmore » the presence of oxygen plasma and the nickel thin layer are very essential for the growth of vertically aligned NFs. The observed results divulge that α-MoO{sub 3} NFs are deposited uniformly on large scale with very high aspect (height/thickness) ratio more than 30 and well aligned along [0 k 0] crystallographic direction where k is even (2, 4, 6). Raman spectrum shows a significant size effect on the vibrational property of MoO{sub 3} nanoflakes. The PL spectrum of MoO{sub 3} NFs was recorded at room temperature and four prominent peaks at 365 nm, 395 nm, 452 nm, and 465 nm corresponding to UV-visible region were observed. In this paper, a three step growth strategy for the formation of MoO{sub 3} NFs has been proposed in detail.« less

Which colors would extraterrestrial civilizations use to transmit signals?: The ;magic wavelengths; for optical SETI

NASA Astrophysics Data System (ADS)

Narusawa, Shin-ya; Aota, Tatusya; Kishimoto, Ryo

2018-04-01

In the case of radio SETI, there are predicted frequencies which extraterrestrial beings select to send messages to other civilizations. Those are called ;magic frequencies. Considering the optical region, terrestrial technologies can not transmit arbitrary wavelengths of high-power optical lasers, easily. In this article, we discuss communications among civilizations with the same level of technology as us to enhance the persuasive power. It might be possible to make a reasonable assumption about the laser wavelengths transmitted by extraterrestrial intelligences to benefit optical SETI (OSETI) methods. Therefore, we propose some ;magic wavelengths; for spectroscopic OSETI observations in this article. From the senders point of view, we argue that the most favorable wavelength used for interstellar communication would be the one of YAG lasers, at 1.064 μm or its Second Harmonic Generation (532.1 nm). On the contrary, there are basic absorption lines in the optical spectra, which are frequently observed by astrophysicists on Earth. It is possible that the extraterrestrials used lasers, which wavelengths are tuned to such absorption lines for sending messages. In that case, there is a possibility that SHG and/or Sum Frequency Generation of YAG and YLF lasers are used. We propose three lines at, 393.8 nm (near the Ca K line), 656.5 nm (near the Hα line) and 589.1 nm (Na D2 line) as the magic wavelengths.

Size resolved Internally Mixed Black Carbon and the Absorption Enhancement in the Indo-Gangetic Plain due to internally mixed BC

NASA Astrophysics Data System (ADS)

Tripathi, S. N.; Thamban, N.

2017-12-01

Indo-Gangetic Plain (IGP) is one of the most populated and polluted regions in northern India. Even though IGP is a well-known "absorbing aerosol hotspot", information of BC mixing state in IGP is mostly unknown. Our calculation on size resolved mixing state in IGP shown that the mixing state of BC changes with the core diameter of BC. The majority of BC particle were thickly coated ( 80%) at lower diameter (75-125 nm) and the externally mixed BC fraction was gradually increased at higher core diameter of BC (125-250 nm). The mean fraction of "thickly coated BC" particles (fTCBC) was found to be 61.6% for a BC core diameter of 70 to 450 nm, indicating that a large fraction of BC particles was internally mixed in IGP. The fTCBC increased after sunrise with a peak at about noontime, indicating that the formation of secondary organic aerosol under active photochemistry can enhance organic coating on a core of black carbon. A positive correlation between the fTCBC and the mass absorption cross-section at 781nm (MAC781) was also observed (r=0.58). Our results identify that the observed fTCBC in IGP could amplify the MAC781 approximately by a factor of 1.8, which may catalyze the positive radiative forcing.

An analysis of dissolved organic matter from freshwater Karelian Lakes using reversed-phase high-performance liquid chromatography with online absorbance and fluorescence analysis

NASA Astrophysics Data System (ADS)

Khundzhua, D. A.; Patsaeva, S. V.; Trubetskoj, O. A.; Trubetskaya, O. E.

2017-01-01

The spectral and optical properties of the fractionated components of dissolved organic matter (DOM) of three freshwater lakes in Karelia were studied using reversed-phase high-performance liquid chromatography (RP-HPLC) with online detection of fluorescence and absorption spectra. It is shown that the DOM fractions are qualitatively similar, but differ quantitatively in the ratio of components and consist of at least three types of fluorophores: (1) hydrophilic "humic-like" fluorophore(s) with the emission maximum in the region of 420 nm and an absorption band at 260-270 nm; (2) hydrophobic "humic-like" fluorophore(s) with the emission maximum at approximately 450 nm that has no characteristic absorption maxima in the region from 220 to 400 nm; and (3) a "protein-like" fluorophore with the emission maximum in the region of 340-350 nm, which is typical of proteins and peptides containing tryptophan.

High photon-to-heat conversion efficiency in the wavelength region of 250–1200 nm based on a thermoelectric Bi2Te3 film structure

PubMed Central

Hu, Er-Tao; Yao, Yuan; Zang, Kai-Yan; Liu, Xin-Xing; Jiang, An-Qing; Zheng, Jia-Jin; Yu, Ke-Han; Wei, Wei; Zheng, Yu-Xiang; Zhang, Rong-Jun; Wang, Song-You; Zhao, Hai-Bin; Yoshie, Osamu; Lee, Young-Pak; Wang, Cai-Zhuang; Lynch, David W.; Guo, Jun-Peng; Chen, Liang-Yao

2017-01-01

In this work, 4-layered SiO2/Bi2Te3/SiO2/Cu film structures were designed and fabricated and the optical properties investigated in the wavelength region of 250–1200 nm for their promising applications for direct solar-thermal-electric conversion. A typical 4-layered film sample with the structure SiO2 (66.6 nm)/Bi2Te3 (7.0 nm)/SiO2 (67.0 nm)/Cu (>100.0 nm) was deposited on a Si or K9-glass substrate by magnetron sputtering. The experimental results agree well with the simulated ones showing an average optical absorption of 96.5%, except in the shorter wavelength region, 250–500 nm, which demonstrates the superior absorption property of the 4-layered film due to the randomly rough surface of the Cu layer resulting from the higher deposition power. The high reflectance of the film structure in the long wavelength region of 2–20 μm will result in a low thermal emittance, 0.064 at 600 K. The simpler 4-layered structure with the thermoelectric Bi2Te3 used as the absorption layer may provide a straightforward way to obtain solar-thermal-electric conversion more efficiently through future study. PMID:28300178

Studies of ionospheric F-region response in the Latin American sector during the geomagnetic storm of 21-22 January 2005

NASA Astrophysics Data System (ADS)

Sahai, Y.; Fagundes, P. R.; de Jesus, R.; de Abreu, A. J.; Crowley, G.; Kikuchi, T.; Huang, C.-S.; Pillat, V. G.; Guarnieri, F. L.; Abalde, J. R.; Bittencourt, J. A.

2011-05-01

In the present investigation, we have studied the response of the ionospheric F-region in the Latin American sector during the intense geomagnetic storm of 21-22 January 2005. This geomagnetic storm has been considered "anomalous" (minimum Dst reached -105 nT at 07:00 UT on 22 January) because the main storm phase occurred during the northward excursion of the Bz component of interplanetary magnetic fields (IMFs). The monthly mean F10.7 solar flux for the month of January 2005 was 99.0 sfu. The F-region parameters observed by ionosondes at Ramey (RAM; 18.5° N, 67.1° W), Puerto Rico, Jicamarca (JIC; 12.0° S, 76.8° W), Peru, Manaus (MAN; 2.9° S, 60.0° W), and São José dos Campos (SJC; 23.2° S, 45.9° W), Brazil, during 21-22 January (geomagnetically disturbed) and 25 January (geomagnetically quiet) have been analyzed. Both JIC and MAN, the equatorial stations, show unusually rapid uplifting of the F-region peak heights (hpF2/hmF2) and a decrease in the NmF2 coincident with the time of storm sudden commencement (SSC). The observed variations in the F-region ionospheric parameters are compared with the TIMEGCM model run for 21-22 January and the model results show both similarities and differences from the observed results. Average GPS-TEC (21, 22 and 25 January) and phase fluctuations (21, 22, 25, 26 January) observed at Belem (BELE; 1.5° S, 48.5° W), Brasilia (BRAZ; 15.9° S, 47.9° W), Presidente Prudente (UEPP; 22.3° S, 51.4° W), and Porto Alegre (POAL; 30.1° S, 51.1° W), Brazil, are also presented. These GPS stations belong to the RBMC/IBGE network of Brazil. A few hours after the onset of the storm, large enhancements in the VTEC and NmF2 between about 20:00 and 24:00 UT on 21 January were observed at all the stations. However, the increase in VTEC was greatest at the near equatorial station (BELE) and enhancements in VTEC decreased with latitude. It should be pointed out that no phase fluctuations or spread-F were observed in the Latin American sector during the post-sunset pre-reversal time in the geomagnetic disturbance (21 January). The disturbance dynamo electric field possibly resulted in downward drift of the F-region plasma and inhibited the formation of spread-F.

Ocular fundus auto-fluorescence observations at different wavelengths in patients with age-related macular degeneration and diabetic retinopathy.

PubMed

Hammer, Martin; Königsdörffer, Ekkehart; Liebermann, Christiane; Framme, Carsten; Schuch, Günter; Schweitzer, Dietrich; Strobel, Jürgen

2008-01-01

Post-translational protein modification by lipid peroxidation products or glycation is a feature of aging as well as pathologic processes in postmitotic cells at the ocular fundus exposed to an oxidative environment. The accumulation of modified proteins such as those found in lipofuscin and advanced glycation end products (AGEs) contribute greatly to the fundus auto-fluorescence. The distinct fluorescence spectra of lipofuscin and AGE enable their differentiation in multispectral fundus fluorescence imaging. A dual-centre consecutive case series of 78 pseudo-phacic patients is reported. Digital colour fundus photographs as well as auto-fluorescence images were taken from 33 patients with age related macular degeneration (AMD), 13 patients with diabetic retinopathy (RD), or from 32 cases without pathologic findings (controls). Fluorescence was excited at 475-515 nm or 476-604 nm and recorded in the emission bands 530-675 nm or 675-715 nm, respectively. Fluorescence images excited at 475-515 nm were taken by a colour CCD-camera (colour-fluorescence imaging) enabling the separate recording of green and red fluorescence. The ratio of green versus red fluorescence was calculated within a representative region of each image. The 530-675 nm auto-fluorescence in AMD patients was dominated by the red emission (green vs. red ratio, g/r = 0.861). In comparison, the fluorescence of the diabetics was green-shifted (g/r = 0.946; controls: g/r = 0.869). Atrophic areas (geographic atrophy, laser scars) showed massive hypo-fluorescence in both emission bands. Hyper-fluorescent drusen and exudates, unobtrusive in the colour fundus images as well as in the fluorescence images with emission >667 nm, showed an impressive green-shift in the colour-fluorescence image. Lipofuscin is the dominant fluorophore at long wavelengths (>675 nm or red channel of the colour fluorescence image). In the green spectral region, we found an additional emission of collagen and elastin (optic disc, sclera) as well as deposits in drusen and exudates. The green shift of the auto-fluorescence in RD may be a hint of increased AGE concentrations.

Stark-assisted population control of coherent CS(2) 4f and 5p Rydberg wave packets studied by femtosecond time-resolved photoelectron spectroscopy.

PubMed

Knappenberger, Kenneth L; Lerch, Eliza-Beth W; Wen, Patrick; Leone, Stephen R

2007-09-28

A two-color (3+1(')) pump-probe scheme is employed to investigate Rydberg wave packet dynamics in carbon disulfide (CS(2) (*)). The state superpositions are created within the 4f and 5p Rydberg manifolds by three photons of the 400 nm pump pulse, and their temporal evolution is monitored with femtosecond time-resolved photoelectron spectroscopy using an 800 nm ionizing probe pulse. The coherent behavior of the non-stationary superpositions are observed through wavepacket revivals upon ionization to either the upper (12) or lower (32) spin-orbit components of CS(2) (+). The results show clearly that the composition of the wavepacket can be efficiently controlled by the power density of the excitation pulse over a range from 500 GWcm(2) to 10 TWcm(2). The results are consistent with the anticipated ac-Stark shift for 400 nm light and demonstrate an effective method for population control in molecular systems. Moreover, it is shown that Rydberg wavepackets can be formed in CS(2) with excitation power densities up to 10 TWcm(2) without significant fragmentation. The exponential 1e population decay (T(1)) of specific excited Rydberg states are recovered by analysis of the coherent part of the signal. The dissociation lifetimes of these states are typically 1.5 ps. However, a region exhibiting a more rapid decay ( approximately 800 fs) is observed for states residing in the energy range of 74 450-74 550 cm(-1), suggestive of an enhanced surface crossing in this region.

Zonal drift velocities of the ionospheric plasma bubbles over brazilian region using oi630nm airglow digital images

NASA Astrophysics Data System (ADS)

Arruda, D. C. S.; Sobral, J. H. A.; Abdu, M. A.; Castilho, V. M.; Takahashi, H.

The zonal drift velocities of the ionospheric plasma bubbles over the Brazilian region are analyzed in this study that is based on OI630nm airglow digital images. These digital images were obtained by an all-sky imager system between October 1998 and August 2000, at Cachoeira Paulista (22.5°S, 45°W), a low latitude region. In this period, 138 nights of OI 630 nm airglow experiments were carried out of which 30 nights detected the ionospheric plasma bubbles. These 30 nights correspond to magnetically quiet days (ΣK_P<24+) and were grouped according approximately to their season. KEY WORDS: Imager System, Ionospheric Plasma Bubbles, Zonal drift velocities, OI630nm.

HST Multicolor (255-1042 nm) Photometry of Saturn's Main Rings. 1; Radial Profiles, Phase and Opening Angle Variations, and Regional Spectra

NASA Technical Reports Server (NTRS)

Cuzzi, Jeffrey N.; French, Richard G.; Dones, Luke; DeVincenzi, Donald (Technical Monitor)

2001-01-01

The main rings of Saturn were observed with the Planetary Camera of the WFPC2 instrument on the Hubble Space Telescope (HST) from September 1996 to August 2000 as the'ring opening angle to Earth and Sun increased from 4 deg to 24 deg, with a spread of phase angles between 0.3 deg and 6 deg at each opening angle. The rings were routinely observed in the five HST wideband UBVRI filters (F336W, F439W, F555W, F675W, and F814W) and occasionally in the F255W, F785LP, and F1042M filters. The emphasis in this series of papers will be on radial color (implying compositional) variations. In this first paper we describe the analysis technique and calibration procedure, note revisions in a previously published Voyager ring color data analysis, and present new results based on over 100 HST images. In the 300-600 nm spectral range where the rings are red, the 555nm/336nm ratio increases by about 14% as the phase angle increases from 0.3 deg to 6 deg. This effect, never reported previously for the rings, is significantly larger than the phase reddening which characterizes other icy objects, primarily because of the redness of the rings. However, there is no discernible tendency for color to vary with ring opening angle at a given phase angle, and there is no phase variation of color where the spectrum is flat. We infer from this combination of facts that multiple intraparticle scattering, either in a regolith or between facets of an unusually rough surface, is important in these geometries, but that multiple interparticle scattering in a vertically extended layer is not. Voyager color ratios at a phase angle of 14 deg are compatible with this trend, but calibration uncertainties prevent their use in quantitative modeling. Overall ring-average spectra are compatible with those of earlier work within calibration uncertainties, but ring spectra vary noticeably with region. We refine and subdivide the regions previously defined by others. The variation seen between radial profiles of ratios between different wavelength suggests the presence of multiple compositional components with different radial distributions. We present new radial profiles of far UV color ratio (F336W/F255W) showing, substantial global variations having a different radial structure than seen between 555 and 336nm. We also find evidence for absorption in the 850nm spectral range (a feature previously only weakly indicated in ring-averaged spectra) primarily through its radial variation; it is located primarily in the C ring, where the particles are known to have lower albedo, and is consistent with "interplanetary pollution" of the rings.

Source of the dayside cusp aurora.

PubMed

Mende, S B; Frey, H U; Angelopoulos, V

2016-08-01

Monochromatic all-sky imagers at South Pole and other Antarctic stations of the Automatic Geophysical Observatory chain recorded the aurora in the region where the Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellites crossed the dayside magnetopause. In several cases the magnetic field lines threading the satellites when mapped to the atmosphere were inside the imagers' field of view. From the THEMIS magnetic field and the plasma density measurements, we were able to locate the position of the magnetopause crossings and map it to the ionosphere using the Tsyganenko-96 field model. Field line mapping is reasonably accurate on the dayside subsolar region where the field is strong, almost dipolar even though compressed. From these coordinated observations, we were able to prove that the dayside cusp aurora of high 630 nm brightness is on open field lines, and it is therefore direct precipitation from the magnetosheath. The cusp aurora contained significant highly structured N 2 + 427.8 nm emission. The THEMIS measurements of the magnetosheath particle energy and density taken just outside the magnetopause compared to the intensity of the structured N 2 + 427.8 nm emissions showed that the precipitating magnetosheath particles had to be accelerated. The most likely electron acceleration mechanism is by dispersive Alfvén waves propagating along the field line. Wave-accelerated suprathermal electrons were seen by FAST and DMSP. The 427.8 nm wavelength channel also shows the presence of a lower latitude hard-electron precipitation zone originating inside the magnetosphere.

Source of the dayside cusp aurora

PubMed Central

Frey, H. U.; Angelopoulos, V.

2016-01-01

Abstract Monochromatic all‐sky imagers at South Pole and other Antarctic stations of the Automatic Geophysical Observatory chain recorded the aurora in the region where the Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellites crossed the dayside magnetopause. In several cases the magnetic field lines threading the satellites when mapped to the atmosphere were inside the imagers' field of view. From the THEMIS magnetic field and the plasma density measurements, we were able to locate the position of the magnetopause crossings and map it to the ionosphere using the Tsyganenko‐96 field model. Field line mapping is reasonably accurate on the dayside subsolar region where the field is strong, almost dipolar even though compressed. From these coordinated observations, we were able to prove that the dayside cusp aurora of high 630 nm brightness is on open field lines, and it is therefore direct precipitation from the magnetosheath. The cusp aurora contained significant highly structured N2 + 427.8 nm emission. The THEMIS measurements of the magnetosheath particle energy and density taken just outside the magnetopause compared to the intensity of the structured N2 + 427.8 nm emissions showed that the precipitating magnetosheath particles had to be accelerated. The most likely electron acceleration mechanism is by dispersive Alfvén waves propagating along the field line. Wave‐accelerated suprathermal electrons were seen by FAST and DMSP. The 427.8 nm wavelength channel also shows the presence of a lower latitude hard‐electron precipitation zone originating inside the magnetosphere. PMID:27867797

Effectively infinite optical path-length created using a simple cubic photonic crystal for extreme light trapping

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

Frey, Brian J.; Kuang, Ping; Hsieh, Mei-Li

A 900 nm thick TiO 2 simple cubic photonic crystal with lattice constant 450 nm was fabricated and used to experimentally validate a newly-discovered mechanism for extreme light-bending. Absorption enhancement was observed extending 1–2 orders of magnitude over that of a reference TiO 2 film. Several enhancement peaks in the region from 600–950 nm were identified, which far exceed both the ergodic fundamental limit and the limit based on surface-gratings, with some peaks exceeding 100 times enhancement. These results are attributed to radically sharp refraction where the optical path length approaches infinity due to the Poynting vector lying nearly parallelmore » to the photonic crystal interface. The observed phenomena follow directly from the simple cubic symmetry of the photonic crystal, and can be achieved by integrating the light-trapping architecture into the absorbing volume. These results are not dependent on the material used, and can be applied to any future light trapping applications such as phosphor-converted white light generation, water-splitting, or thin-film solar cells, where increased response in areas of weak absorption is desired.« less

Optical and electrical properties of TiOPc doped Alq3 thin films

NASA Astrophysics Data System (ADS)

Ramar, M.; Suman, C. K.; Tyagi, Priyanka; Srivastava, R.

2015-06-01

The Titanyl phthalocyanine (TiOPc) was doped in Tris (8-hydroxyquinolinato) aluminum (Alq3) with different concentration. The thin film of optimized doping concentration was studied extensively for optical and electrical properties. The optical properties, studied using ellipsometry, absorption and photoluminescence. The absorption peak of Alq3 and TiOPc was observed at 387 nm and 707 nm and the photo-luminescence intensity (PL) peak of doped thin film was observed at 517 nm. The DC and AC electrical properties of the thin film were studied by current density-voltage (J-V) characteristics and impedance over a frequency range of 100 Hz - 1 MHz. The electron mobility calculated from trap-free space-charge limited region (SCLC) is 0.17×10-5 cm2/Vs. The Cole-Cole plots shows that the TiOPc doped Alq3 thin film can be represented by a single parallel resistance RP and capacitance CP network with a series resistance RS (10 Ω). The value of RP and CP at zero bias was 1587 Ω and 2.568 nF respectively. The resistance RP decreases with applied bias whereas the capacitance CP remains almost constant.

Effectively infinite optical path-length created using a simple cubic photonic crystal for extreme light trapping

DOE PAGES

Frey, Brian J.; Kuang, Ping; Hsieh, Mei-Li; ...

2017-06-23

A 900 nm thick TiO 2 simple cubic photonic crystal with lattice constant 450 nm was fabricated and used to experimentally validate a newly-discovered mechanism for extreme light-bending. Absorption enhancement was observed extending 1–2 orders of magnitude over that of a reference TiO 2 film. Several enhancement peaks in the region from 600–950 nm were identified, which far exceed both the ergodic fundamental limit and the limit based on surface-gratings, with some peaks exceeding 100 times enhancement. These results are attributed to radically sharp refraction where the optical path length approaches infinity due to the Poynting vector lying nearly parallelmore » to the photonic crystal interface. The observed phenomena follow directly from the simple cubic symmetry of the photonic crystal, and can be achieved by integrating the light-trapping architecture into the absorbing volume. These results are not dependent on the material used, and can be applied to any future light trapping applications such as phosphor-converted white light generation, water-splitting, or thin-film solar cells, where increased response in areas of weak absorption is desired.« less

Analysis of laser produced plasmas of gold in the 1-7 nm region

NASA Astrophysics Data System (ADS)

Li, Bowen; Higashiguchi, Takeshi; Otsuka, Takamitsu; Yugami, Noboru; Dunne, Padraig; Kilbane, Deirdre; Sokell, Emma; O'Sullivan, Gerry

2014-04-01

Extreme ultraviolet (EUV) spectra from gold laser produced plasmas were recorded in the 1-7 nm region using two Nd:YAG lasers with pulse lengths of 150 ps and 10 ns, respectively, operating at a range of power densities. The maximum focused peak power density was 9.5 × 1013 W cm-2 for the former and 5.3 × 1012 W cm-2 for the latter. Two intense quasicontinuous intensity bands resulting from n = 4-n = 4 and n = 4-n = 5 unresolved transition arrays dominate the 4-5.5 and 1.5-3.6 nm regions of both spectra. Comparison with atomic structure calculations performed with the Cowan suite of atomic structure codes as well as consideration of previous experimental and theoretical results aided identification of the most prominent features in the spectra. For the ns spectrum, the highest ion stage that could be identified from the n = 4-n = 5 arrays was Au28+ while for the ps plasma the presence of significantly higher stages was deduced and lines due to 4d104f-4d94f2 transitions in Ag-like Au32+ give rise to the strongest observed features within the n = 4-n = 4 array while in the n = 4-n = 5 array it was possible to identify a number of previously unidentified spectral features as resulting from 4f-5g transitions in the spectra of Au XX to Au XXXIII.

VizieR Online Data Catalog: Spectroscopy and HST imaging in ONC (O'Dell+, 2015)

NASA Astrophysics Data System (ADS)

O'Dell, C. R.; Ferland, G. J.; Henney, W. J.; Peimbert, M.; Garcia-Diaz, Ma. T.; Rubin, R. H.

2016-02-01

We are able to draw on both new and existing observational data for both imaging and spectroscopy. Since the ionization range of the Orion Nebula is quite low, we use the high signal-to-noise ratio (S/N) F658N and F502N images in our analysis Our new imaging observations were made with Hubble Space Telescope (HST)'s WFC3 as part of program GO 12543. Observations were made (2012 January 7) with the narrowband emission line filters F487N (Hβ409s), F502N ([OIII]348s), F656N (Hα349s), F658N ([NII]602s), and F673N ([SII]700s), in addition to observations with the continuum sampling intermediate-width filter F547M (348s). The characteristics of these filters and their calibration have been described by O'Dell et al. (2013AJ....145...92O). The images are the highest angular resolution (0.04''/pixel sampling) optical images of a portion of the Huygens Region. When used alone, we employed the original images in combination with one another. When used for comparison with earlier (undersampled) WFPC2 images (0.0996''/pixel), we processed them with IRAF task "Gauss" to match their broader image cores. We have been able to use earlier HST observations made with the WFPC2 (program GO 5085 (FOV5) on MJD49737; program GO 5469 on MJD49797; program GO 11038 (FOV1) on MJD54406; program GO 12543 on MJD55935). The most useful data set of spectra is the compilation of north-south orientation long-slit spectra by Garcia-Diaz et al. (2008RMxAA..44..181G). In addition to their original observations (Garcia-Diaz & Henney, 2007AJ....133..952G) in low-ionization lines, they recalibrate the high-ionization spectra of Doi et al. 2004 (cat. J/AJ/127/3456) and present combined results for emission lines from a wide variety of ionization states ([OI]630.0nm, [SII]671.6nm+673.1nm, [NII]658.4nm, [SIII]631.2nm, Hα656.3nm, [OIII]500.7nm) calibrated to 2km/s accuracy and a resolution of about 10km/s. We will refer to this as the Spectroscopic Atlas, or simply the Atlas. New observations were made at the San Pedro Martir Observatory in 2013 February in the [OIII] 500.7nm line in essentially the same manner as the earlier low-ionization line observations, except that the slit was oriented east-west. The slit center was at 5:35:15.9. Fifteen spectra were obtained in steps of 1.4'' starting at 23'' south of θ1Ori C and proceeding south. Their total exposure time in each slit of 300 or 600s, depending on the source brightness, with the 2.1m telescope's MEZCAL spectrograph gave higher-S/N images than the earlier observations made at the Kitt Peak National Observatory with the 4m telescope's echelle spectrograph by Doi et al. 2004 (cat. J/AJ/127/3456). The [NII] 658.3nm and [OIII] 500.7nm archived spectra had an instrumental FWHM intensity of about 10km/s, and the new [OIII] spectra's FWHM are slightly smaller. The quadratic addition of the instrumental and thermal FWHM values gives an expected observed FWHM of 11.5km/s for [NII] and 11.4km/s for [OIII]. The tangential velocities determined from HST images are presented in Table6. The radial velocities of features not directly associated with the Main Ionization Front (MIF) are presented in Table7, using data from the spectroscopic Atlas. (2 data files).

Evidence for Phyllosilicates near the Lunar South Pole

NASA Technical Reports Server (NTRS)

Vilas, Faith; Jensen, E.; Domingue, Deborah; McFadden, L.; Coombs, Cassandraa; Mendell, Wendell

1998-01-01

While theoretically water ice could be stable in permanently shadowed areas near the lunar poles, there is conflicting observational evidence for the existence of water ice at either pole. Clementine's bistatic radar resumed a weak signal commensurate with water ice in the South Pole Aitken Basin; however, groundbased radar searches have not detected such a signal at either pole. Lunar Prospector measured large amounts of H (attributed to water) at both poles; however, Galileo near-infrared spectral measurements of the north polar region did not detect the prominent 3.0 micron absorption feature due to interlayer and adsorbed water in phyllosilicates. Evidence for the existence of water at the lunar poles is still ambiguous and controversial. We present evidence, based on the analysis of Galileo SSI images, for the presence of phyllosilicates near the lunar south pole. Using the color image sequence (560 nm, 670 nm, 756 nm, and 889 nm) of Lunmap 14 taken during the Galileo Earth-Moon pass I, we have identified areas that show evidence for a 0.7 microns absorption feature present in Fe-bearing phyllosilicates.

Measurement of the fluorescence of crop residues: A tool for controlling soil erosion

NASA Technical Reports Server (NTRS)

Daughtry, C. S. T.; Mcmurtrey, J. E., III; Chappelle, E. W.; Hunter, W. J.

1994-01-01

Management of crop residues, the portion of a crop left in the field after harvest, is an important conservation practice for minimizing soil erosion and for improving water quality. Quantification of crop residue cover is required to evaluate the effectiveness of conservation tillage practices. Methods are needed to quantify residue cover that are rapid, accurate, and objective. The fluorescence of crop residue was found to be a broadband phenomenon with emission maxima at 420 to 495 nm for excitations of 350 to 420 nm. Soils had low intensity broadband emissions over the 400 to 690 nm region for excitations of 300 to 600 nm. The range of relative fluorescence intensities for the crop residues was much greater than the fluorescence observed of the soils. As the crop residues decompose their blue fluorescence values approach the fluorescence of the soil. Fluorescence techniques are concluded to be less ambiguous and better suited for discriminating crop residues and soils than reflectance methods. If properly implemented, fluorescence techniques can be used to quantify, not only crop residue cover, but also photosynthetic efficiency in the field.

X-ray microfocusing with off-axis ellipsoidal mirror

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

Yumoto, Hirokatsu, E-mail: yumoto@spring8.or.jp; Koyama, Takahisa; Matsuyama, Satoshi

2016-07-27

High-precision ellipsoidal mirrors for two-dimensionally focusing X-rays to nanometer sizes have not been realized because of technical problems in their fabrication processes. The objective of the present study is to develop fabrication techniques for ellipsoidal focusing mirrors in the hard-X-ray region. We design an off-axis ellipsoidal mirror for use under total reflection conditions up to the X-ray energy of 8 keV. We fabricate an ellipsoidal mirror with a surface roughness of 0.3 nm RMS (root-mean-square) and a surface figure error height of 3.0 nm RMS by utilizing a surface profiler and surface finishing method developed by us. The focusing propertiesmore » of the mirror are evaluated at the BL29XUL beamline in SPring-8. A focusing beam size of 270 nm × 360 nm FWHM (full width at half maximum) at an X-ray energy of 7 keV is observed with the use of the knife-edge scanning method. We expect to apply the developed fabrication techniques to construct ellipsoidal nanofocusing mirrors.« less

Crystal Growth and Luminescence Properties of Yb-doped Gd3Al2Ga3O12 Infra-red Scintillator

NASA Astrophysics Data System (ADS)

Suzuki, Akira; Kurosawa, Shunsuke; Nagata, Shinji; Yamamura, Tomoo; Pejchal, Jan; Yamaji, Akihiro; Yokota, Yuui; Shirasaki, Kenji; Homma, Yoshiya; Aoki, Dai; Shikama, Tatsuo; Yoshikawa, Akira

2014-07-01

1-mol%-Yb-doped Gd3Al2Ga3O12 infra-red scintillator crystal has been studied as a novel implantable radiation monitor in radiation therapy. Powder X-ray diffraction measurement and chemical analysis with a field emission scanning microscope and wavelength dispersive spectrometer determined its garnet structure and average chemical composition of Yb0.03±0.01Gd2.99±0.07Al2.21±0.08Ga2.64±0.09O12.10±0.09. Transmittance measurements reached high values of approximately 70% in the human body transparency region between 650 to 1200 nm. Photoluminescence peaks were detected around 970 and 1030 nm under the 940 nm excitation with a Xe lamp. Infra-red scintillation emissions were clearly observed around 970 and 1030 nm due to Yb3+ 4f-4f transitions under X-ray excitation. Therefore, these results suggest that Yb-doped Gd3Al2Ga3O12 might be used as an infra-red scintillator material.

Tb3+ and Eu3+ doped zinc phosphate glasses for solid state lighting applications

NASA Astrophysics Data System (ADS)

Jha, Kaushal; Vishwakarma, Amit K.; Jayasimhadri, M.; Haranath, D.; Jang, Kiwan

2018-04-01

Tb3+ and Eu3+ doped zinc phosphate (ZP) glasses were prepared by conventional melt-quenching technique and their photoluminescence properties were investigated in detail. For, Tb3+ doped glasses the intense emission was at 545 nm corresponding to 5D4→7F5 transition under 377 nm n-UV excitation. The optimized concentration for Tb3+ doped zinc phosphate glass was 3 mol% and above this concentration quenching takes place. The Eu3+ doped zinc phosphate glass revealed intense emission at 613 nm attributed to the 5D0→7F2 transition under intense 392 nm n-UV excitation. The concentration quenching phenomenon was not observed in the Eu3+ doped ZP glasses. The CIE chromaticity coordinates for 3 mol% Tb3+ and 5 mol% Eu3+ doped ZP glasses were found to (0.283, 0.615) and (0.652, 0.331) lying in the green and red regions, respectively. The above mentioned results indicate that the prepared glass are suitable for application in the field of lighting and display devices.

Deep-UV emission at 219 nm from ultrathin MBE GaN/AlN quantum heterostructures

NASA Astrophysics Data System (ADS)

Islam, S. M.; Protasenko, Vladimir; Lee, Kevin; Rouvimov, Sergei; Verma, Jai; Xing, Huili Grace; Jena, Debdeep

2017-08-01

Deep ultraviolet (UV) optical emission below 250 nm (˜5 eV) in semiconductors is traditionally obtained from high aluminum containing AlGaN alloy quantum wells. It is shown here that high-quality epitaxial ultrathin binary GaN quantum disks embedded in an AlN matrix can produce efficient optical emission in the 219-235 nm (˜5.7-5.3 eV) spectral range, far above the bulk bandgap (3.4 eV) of GaN. The quantum confinement energy in these heterostructures is larger than the bandgaps of traditional semiconductors, made possible by the large band offsets. These molecular beam epitaxy-grown extreme quantum-confinement GaN/AlN heterostructures exhibit an internal quantum efficiency of 40% at wavelengths as short as 219 nm. These observations together with the ability to engineer the interband optical matrix elements to control the direction of photon emission in such binary quantum disk active regions offer unique advantages over alloy AlGaN quantum well counterparts for the realization of deep-UV light-emitting diodes and lasers.

Measurements of the weak UV absorptions of isoprene and acetone at 261-275 nm using cavity ringdown spectroscopy for evaluation of a potential portable ringdown breath analyzer.

PubMed

Sahay, Peeyush; Scherrer, Susan T; Wang, Chuji

2013-06-26

The weak absorption spectra of isoprene and acetone have been measured in the wavelength range of 261-275 nm using cavity ringdown spectroscopy. The measured absorption cross-sections of isoprene in the wavelength region of 261-266 nm range from 3.65 × 10⁻²¹ cm².molecule⁻¹ at 261 nm to 1.42 × 10⁻²¹ cm².molecule⁻¹ at 266 nm; these numbers are in good agreement with the values reported in the literature. In the longer wavelength range of 270-275 nm, however, where attractive applications using a single wavelength compact diode laser operating at 274 nm is located, isoprene has been reported in the literature to have no absorption (too weak to be detected). Small absorption cross-sections of isoprene in this longer wavelength region are measured using cavity ringdown spectroscopy for the first time in this work, i.e., 6.20 × 10⁻²³ cm².molecule⁻¹ at 275 nm. With the same experimental system, wavelength-dependent absorption cross-sections of acetone have also been measured. Theoretical detection limits of isoprene and comparisons of absorbance of isoprene, acetone, and healthy breath gas in this wavelength region are also discussed.

Improving Soft X-Ray Spectral Irradiance Models for Use Throughout the Solar System

NASA Astrophysics Data System (ADS)

Eparvier, F. G.; Thiemann, E.; Woods, T. N.

2017-12-01

Understanding the effects of solar variability on planetary atmospheres has been hindered by the lack of accurate models and measurements of the soft x-ray (SXR) spectral irradiance (0-6 nm). Most measurements of the SXR have been broadband and are difficult to interpret due to changing spectral distribution under the pass band of the instruments. Models that use reference spectra for quiet sun, active region, and flaring contributions to irradiance have been made, but with limited success. The recent Miniature X-ray Solar Spectrometer (MinXSS) CubeSat made spectral measurements in the 0.04 - 3 nm range from June 2016 to May 2017, observing the Sun at many different levels of activity. In addition, the Solar Dynamics Observatory (SDO) EUV Variability Experiment (EVE) has observed the Sun since May 2010, in both broad bands (including a band at 0-7 nm) and spectrally resolved (6-105 nm at 0.1 nm resolution). We will present an improved model of the SXR based on new reference spectra from MinXSS and SDO-EVE. The non-flaring portion of the model is driven by broadband SXR measurements for determining activity level and relative contributions of quiet and active sun. Flares are modeled using flare temperatures from the GOES X-Ray Sensors. The improved SXR model can be driven by any sensors that provide a measure of activity level and flare temperature from any vantage point in the solar system. As an example, a version of the model is using the broadband solar irradiance measurements from the MAVEN EUV Monitor at Mars will be presented.

Determination of phenolic compounds using spectral and color transitions of rhodium nanoparticles.

PubMed

Gatselou, Vasiliki; Christodouleas, Dionysios C; Kouloumpis, Antonios; Gournis, Dimitrios; Giokas, Dimosthenis L

2016-08-17

This work reports a new approach for the determination of phenolic compounds based on their interaction with citrate-capped rhodium nanoparticles. Phenolic compounds (i.e., catechins, gallates, cinnamates, and dihydroxybenzoic acids) were found to cause changes in the size and localized surface plasmon resonance of rhodium nanoparticles, and therefore, give rise to analyte-specific spectral and color transitions in the rhodium nanoparticle suspensions. Upon reaction with phenolic compounds (mainly dithydroxybenzoate derivatives, and trihydroxybenzoate derivatives), new absorbance peaks at 350 nm and 450 nm were observed. Upon reaction with trihydroxybenzoate derivatives, however, an additional absorbance peak at 580 nm was observed facilitating the speciation of phenolic compounds in the sample. Both absorbance peaks at 450 nm and 580 nm increased with increasing concentration of phenolic compounds over a linear range of 0-500 μM. Detection limits at the mid-micromolar levels were achieved, depending on the phenolic compound involved, and with satisfactory reproducibility (<7.3%). On the basis of these findings, two rhodium nanoparticles-based assays for the determination of the total phenolic content and total catechin content were developed and applied in tea samples. The obtained results correlated favorably with commonly used methods (i.e., Folin-Ciocalteu and aluminum complexation assay). Not the least, the finding that rhodium nanoparticles can react with analytes and exhibit unique localized surface plasmon resonance bands in the visible region, can open new opportunities for developing new optical and sensing analytical applications. Copyright © 2016 Elsevier B.V. All rights reserved.

Electro-thermo-optical simulation of vertical-cavity surface-emitting lasers

NASA Astrophysics Data System (ADS)

Smagley, Vladimir Anatolievich

Three-dimensional electro-thermal simulator based on the double-layer approximation for the active region was coupled to optical gain and optical field numerical simulators to provide a self-consistent steady-state solution of VCSEL current-voltage and current-output power characteristics. Methodology of VCSEL modeling had been established and applied to model a standard 850-nm VCSEL based on GaAs-active region and a novel intracavity-contacted 400-nm GaN-based VCSEL. Results of GaAs VCSEL simulation were in a good agreement with experiment. Correlations between current injection and radiative mode profiles have been observed. Physical sub-models of transport, optical gain and cavity optical field were developed. Carrier transport through DBRs was studied. Problem of optical fields in VCSEL cavity was treated numerically by the effective frequency method. All the sub-models were connected through spatially inhomogeneous rate equation system. It was shown that the conventional uncoupled analysis of every separate physical phenomenon would be insufficient to describe VCSEL operation.

Faint Luminescent Ring over Saturn’s Polar Hexagon

NASA Astrophysics Data System (ADS)

Adriani, Alberto; Moriconi, Maria Luisa; D'Aversa, Emiliano; Oliva, Fabrizio; Filacchione, Gianrico

2015-07-01

Springtime insolation is presently advancing across Saturn's north polar region. Early solar radiation scattered through the gaseous giant's atmosphere gives a unique opportunity to sound the atmospheric structure at its upper troposphere/lower stratosphere at high latitudes. Here, we report the detection of a tenuous bright structure in Saturn's northern polar cap corresponding to the hexagon equatorward boundary, observed by Cassini Visual and Infrared Mapping Spectrometer on 2013 June. The structure is spectrally characterized by an anomalously enhanced intensity in the 3610-3730 nm wavelength range and near 2500 nm, pertaining to relatively low opacity windows between strong methane absorption bands. Our first results suggest that a strong forward scattering by tropospheric clouds, higher in respect to the surrounding cloud deck, can be responsible for the enhanced intensity of the feature. This can be consistent with the atmospheric dynamics associated with the jet stream embedded in the polar hexagon. Further investigations at higher spectral resolution are needed to better assess the vertical distribution and microphysics of the clouds in this interesting region.

The effect of nanoparticle size on the ability to cross the blood-brain barrier: an in vivo study.

PubMed

Betzer, Oshra; Shilo, Malka; Opochinsky, Renana; Barnoy, Eran; Motiei, Menachem; Okun, Eitan; Yadid, Gal; Popovtzer, Rachela

2017-07-01

Our goal was to develop an efficient nanoparticle-based system that can overcome the restrictive mechanism of the blood-brain barrier (BBB) by targeting insulin receptors and would thus enable drug delivery to the brain. Insulin-coated gold nanoparticles (INS-GNPs) were synthesized to serve as a BBB transport system. The effect of nanoparticle size (20, 50 and 70 nm) on their ability to cross the BBB was quantitatively investigated in Balb/C mice. The most widespread biodistribution and highest accumulation within the brain were observed using 20 nm INS-GNPs, 2 h post injection. In vivo CT imaging revealed that particles migrated to specific brain regions, which are involved in neurodegenerative and neuropsychiatric disorders. These findings promote the optimization of nanovehicles for transport of drugs through the BBB. The insulin coating of the particles enabled targeting of specific brain regions, suggesting the potential use of INS-GNPs for delivery of various treatments for brain-related disorders.

Tunable color emission via energy transfer in co-doped Ce3+/Dy3+: Li2O-LiF-B2O3-ZnO glasses for photonic applications

NASA Astrophysics Data System (ADS)

Vijayalakshmi, L.; Naveen Kumar, K.; Srinivasa Rao, K.; Hwang, Pyung

2017-10-01

A set of co-doped (Ce3+/Dy3+): LBZ glasses were prepared by standard melt quenching technique. The pertinent absorption bands were observed in the optical absorption spectrum of co-doped Ce3+/Dy3+: LBZ glasses. We have been observed a prominent blue and yellow emission pertaining to Dy3+ ions at 0.5 mol % under the excitation of 385 nm doped glasses. However, the photoluminescence intensities were remarkably enhanced by co-doping with Ce3+ ions to Dy3+: LBZ glasses due to energy transfer from Ce3+ to Dy3+. The emission spectra of co-doped (Ce3+/Dy3+): LBZ glass exhibits three strong emissions at 440 nm, 480 nm and 574 nm which are assigned with corresponding electronic transitions of 4I15/2 → 6H15/2, 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 respectively. The Commission International de E'clairage coordinates were calculated from their emission spectra of single doped Dy3+ and co-doped (Ce3+/Dy3+): LBZ glasses. The obtained CIE chromaticity coordinates for optimized co-doped glass are found to be very close to the standard white region. Based on the concentration of Ce3+, the emitting color of the co-doped glass can be changed from blue to white color. The transformation of the color from blue to white region due to energy transfer from Ce3+ to Dy3+. The energy transfer mechanism was substantiated by various fluorescence dynamics such as overlapped spectral profiles, photoluminescence, lifetime decay and CIE color coordinate analysis. These results could be suggested that the obtained co-doped (Ce3+/Dy3+): LBZ glasses are promising candidates for commercial white light applications.

Characteristics of dayside auroral displays in relation to magnetospheric processes

NASA Astrophysics Data System (ADS)

Minow, Joseph I.

1997-09-01

The use of dayside aurorae as a ground based monitor of magnetopause activity is explored in this thesis. The origin of diffuse (OI) 630.0 nm emissions in the midday auroral oval is considered first. Analysis of low altitude satellite records of precipitating charged particles within the cusp show an unstructured electron component that will produce a 0.5-1 kR 630.0 nm emission throughout the cusp. Distribution of the electrons is controlled by the requirement of charge neutrality in the cusp, predicting a diffuse 630.0 nm background even if the magnetosheath plasma is introduced into the magnetosphere in discrete merging events. Cusp electron fluxes also contain a structured component characterized by enhancements in the electron energy and energy flux over background values in narrow regions a few 10's of kilometers in width. These structured features are identified as the source of the transient midday arcs. An auroral model is developed to study the morphology of (OI) 630.0 nm auroral emissions produced by the transient arcs. The model demonstrates that a diffuse 630.0 nm background emission is produced by transient arcs due to the long lifetime of the O(1D) state. Two sources of diffuse 630.0 nm background emissions exist in the cusp which may originate in discrete merging events. The conclusion is that persistent 630.0 nm emissions cannot be interpreted as prima facie evidence for continuous particle transport from the magnetosheath across the magnetopause boundary and into the polar cusp. The second subject that is considered is the analysis of temporal and spatial variations of the diffuse 557.7 nm pulsating aurora in relation to the 630.0 nm dominated transient aurora. Temporal variations at the poleward boundary of the diffuse 557.7 nm aurora correlate with the formation of the 630.0 nm transient aurorae suggesting that the two events are related. The character of the auroral variations is consistent with the behavior of particle populations reported during satellite observations of flux transfer events near the dayside magnetopause. An interpretation of the events in terms of impulsive magnetic reconnection yields a new observation that relates the poleward moving transient auroral arcs in the midday sector to the flux transfer events.

Jupiter Equatorial Region in a Methane Band Time Set 1

NASA Image and Video Library

1998-03-06

Mosaic of an equatorial "hotspot" on Jupiter at 889 nanometers (nm). The mosaic covers an area of 34,000 kilometers by 11,000 kilometers. Light at 889 nm is strongly absorbed by atmospheric methane. This image shows the features of a hazy cloud layer tens of kilometers above Jupiter's main visible cloud deck. This haze varies in height but appears to be present over the entire region. Small patches of very bright clouds may be similar to terrestrial thunderstorms. The dark region near the center of the mosaic is an equatorial "hotspot" similar to the Galileo Probe entry site. These features are holes in the bright, reflective, equatorial cloud layer where warmer thermal emission from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance. North is at the top. The mosaic covers latitudes 1 to 10 degrees and is centered at longitude 336 degrees West. The smallest resolved features are tens of kilometers in size. These images were taken on December 17, 1996, at a range of 1.5 million kilometers by the Solid State Imaging system aboard NASA's Galileo spacecraft. http://photojournal.jpl.nasa.gov/catalog/PIA01200

Time-resolved photoluminescence characterization of oxygen-related defect centers in AlN

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

Genji, Kumihiro; Uchino, Takashi, E-mail: uchino@kobe-u.ac.jp

2016-07-11

Time-resolved photoluminescence (PL) spectroscopy has been employed to investigate the emission characteristics of oxygen-related defects in AlN in the temperature region from 77 to 500 K. Two PL components with different decay constants are observed in the near-ultraviolet to visible regions. One is the PL component with decay time of <10 ns and its peak position shifts to longer wavelengths from ∼350 to ∼500 nm with increasing temperature up to 500 K. This PL component is attributed to the radiative relaxation of photoexcited electrons from the band-edge states to the ground state of the oxygen-related emission centers. In the time region from tens tomore » hundreds of nanoseconds, the second PL component emerges in the wavelength region from 300 to 400 nm. The spectral shape and the decay profiles are hardly dependent on temperature. This temperature-independent PL component most likely results from the transfer of photoexcited electrons from the band-edge states to the localized excited state of the oxygen-related emission centers. These results provide a detailed insight into the radiative relaxation processes of the oxygen-related defect centers in AlN immediately after the photoexcitation process.« less

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

Economy, David Ross; Mara, Nathan A.; Schoeppner, R.

In complex loading conditions (e.g. sliding contact), mechanical properties, such as strain hardening and initial hardness, will dictate the long-term performance of materials systems. With this in mind, the strain hardening behaviors of Cu/Nb nanoscale metallic multilayer systems were examined by performing nanoindentation tests within nanoscratch wear boxes and undeformed, as-deposited regions. Both the architecture and substrate influence were examined by utilizing three different individual layer thicknesses (2, 20, and 100 nm) and two total film thicknesses (1 and 10 μm). After nano-wear deformation, multilayer systems with thinner layers showed less volume loss as measured by laser scanning microscopy. Additionally,more » the hardness of the deformed regions significantly rose with respect to the as-deposited measurements, which further increased with greater wear loads. Strain hardening exponents for multilayers with thinner layers (2 and 20 nm, n ≈ 0.018 and n ≈ 0.022 respectively) were less than was determined for 100 nm systems (n ≈ 0.041). These results suggest that singledislocation based deformation mechanisms observed for the thinner systems limit the extent of achievable strain hardening. This conclusion indicates that impacts of both architecture strengthening and strain hardening must be considered to accurately predict multilayer performance during sliding contact across varying length scales.« less

Development of a spectro-electrochemical cell for soft X-ray photon-in photon-out spectroscopy

NASA Astrophysics Data System (ADS)

Ishihara, Tomoko; Tokushima, Takashi; Horikawa, Yuka; Kato, Masaru; Yagi, Ichizo

2017-10-01

We developed a spectro-electrochemical cell for X-ray absorption and X-ray emission spectroscopy, which are element-specific methods to study local electronic structures in the soft X-ray region. In the usual electrochemical measurement setup, the electrode is placed in solution, and the surface/interface region of the electrode is not normally accessible by soft X-rays that have low penetration depth in liquids. To realize soft X-ray observation of electrochemical reactions, a 15-nm-thick Pt layer was deposited on a 150-nm-thick film window with an adhesive 3-nm-thick Ti layer for use as both the working electrode and the separator window between vacuum and a sample liquid under atmospheric pressure. The designed three-electrode electrochemical cell consists of a Pt film on a SiC window, a platinized Pt wire, and a commercial Ag|AgCl electrode as the working, counter, and reference electrodes, respectively. The functionality of the cell was tested by cyclic voltammetry and X-ray absorption and emission spectroscopy. As a demonstration, the electroplating of Pb on the Pt/SiC membrane window was measured by X-ray absorption and real-time monitoring of fluorescence intensity at the O 1s excitation.

Preparation of high-quality ultrathin transmission electron microscopy specimens of a nanocrystalline metallic powder.

PubMed

Riedl, Thomas; Gemming, Thomas; Mickel, Christine; Eymann, Konrad; Kirchner, Alexander; Kieback, Bernd

2012-06-01

This article explores the achievable transmission electron microscopy specimen thickness and quality by using three different preparation methods in the case of a high-strength nanocrystalline Cu-Nb powder alloy. Low specimen thickness is essential for spatially resolved analyses of the grains in nanocrystalline materials. We have found that single-sided as well as double-sided low-angle Ar ion milling of the Cu-Nb powders embedded into epoxy resin produced wedge-shaped particles of very low thickness (<10 nm) near the edge. By means of a modified focused ion beam lift-out technique generating holes in the lamella interior large micrometer-sized electron-transparent regions were obtained. However, this lamella displayed a higher thickness at the rim of ≥30 nm. Limiting factors for the observed thicknesses are discussed including ion damage depths, backscattering, and surface roughness, which depend on ion type, energy, current density, and specimen motion. Finally, sections cut by ultramicrotomy at low stroke rate and low set thickness offered vast, several tens of square micrometers uniformly thin regions of ∼10-nm minimum thickness. As major drawbacks, we have detected a thin coating on the sections consisting of epoxy deployed as the embedding material and considerable nanoscale thickness variations. Copyright © 2011 Wiley Periodicals, Inc.

Identifying Deformation and Strain Hardening Behaviors of Nanoscale Metallic Multilayers Through Nano-wear Testing

DOE PAGES

Economy, David Ross; Mara, Nathan A.; Schoeppner, R.; ...

2016-01-13

In complex loading conditions (e.g. sliding contact), mechanical properties, such as strain hardening and initial hardness, will dictate the long-term performance of materials systems. With this in mind, the strain hardening behaviors of Cu/Nb nanoscale metallic multilayer systems were examined by performing nanoindentation tests within nanoscratch wear boxes and undeformed, as-deposited regions. Both the architecture and substrate influence were examined by utilizing three different individual layer thicknesses (2, 20, and 100 nm) and two total film thicknesses (1 and 10 μm). After nano-wear deformation, multilayer systems with thinner layers showed less volume loss as measured by laser scanning microscopy. Additionally,more » the hardness of the deformed regions significantly rose with respect to the as-deposited measurements, which further increased with greater wear loads. Strain hardening exponents for multilayers with thinner layers (2 and 20 nm, n ≈ 0.018 and n ≈ 0.022 respectively) were less than was determined for 100 nm systems (n ≈ 0.041). These results suggest that singledislocation based deformation mechanisms observed for the thinner systems limit the extent of achievable strain hardening. This conclusion indicates that impacts of both architecture strengthening and strain hardening must be considered to accurately predict multilayer performance during sliding contact across varying length scales.« less

Comparison of AIS Versus TMS Data Collected over the Virginia Piedmont

NASA Technical Reports Server (NTRS)

Bell, R.; Evans, C. S.

1985-01-01

The Airborne Imaging Spectrometer (AIS, NS001 Thematic Mapper Simlulator (TMS), and Zeiss camera collected remotely sensed data simultaneously on October 27, 1983, at an altitude of 6860 meters (22,500 feet). AIS data were collected in 32 channels covering 1200 to 1500 nm. A simple atmospheric correction was applied to the AIS data, after which spectra for four cover types were plotted. Spectra for these ground cover classes showed a telescoping effect for the wavelength endpoints. Principal components were extracted from the shortwave region of the AIS (1200 to 1280 nm), full spectrum AIS (1200 to 1500 nm) and TMS (450 to 12,500 nm) to create three separate three-component color image composites. A comparison of the TMS band 5 (1000 to 1300 nm) to the six principal components from the shortwave AIS region (1200 to 1280 nm) showed improved visual discrimination of ground cover types. Contrast of color image composites created from principal components showed the AIS composites to exhibit a clearer demarcation between certain ground cover types but subtle differences within other regions of the imagery were not as readily seen.

Creating biomimetic polymeric surfaces by photochemical attachment and patterning of dextran

PubMed Central

Ferrer, M. Carme Coll; Yang, Shu; Eckmann, David M.; Composto, Russell J.

2010-01-01

In this work, we report the preparation of photoactive dextran and demonstrate its utility by photochemically attaching it onto various polymeric substrates. The attachment of homogeneous and patterned dextran films was performed on polyurethane and polystyrene, with detailed analysis of surface morphology, swelling behavior, and the protein resistance of these substrates. The described photoactive dextran and attachment procedure is applicable to a wide variety of substrates while accommodating surfaces with complex surface and geometries. Dextran with azide content between 22 to 0.3 wt% was produced by esterification with p-azidobenzoic acid. Dextran (1.2 wt% azide) was photografted onto plasma oxidized polyurethane and polystyrene and displayed thicknesses of 5 ± 3 nm and 7 ± 3 nm, respectively. The patterned dextran on oxidized polyurethane was patchy with a nominal height difference between dextranized and non-dextranized regions. The azidated dextran on oxidized polystyrene exhibited a distinct step in height. In the presence of PBS buffer, the dextranized regions became smoother and more uniform without affecting the height difference at the oxidized polyurethane boundary. However, the dextranized regions on oxidized polyurethane were observed to swell by a factor of 3 relative to the dried thickness. These dissimilarities were attributed to hydrogen bonding between the dextran and oxidized polyurethane and were confirmed by the photoimmobiliization in the presence of LiCl. The resulting surface was the smoothest of all the azidated dextran samples (RRMS = 1 ± 0.3 nm) and swelled up to 2 times its dried thickness in PBS buffer. The antifouling properties of dextran functionalized surfaces were verified by the selective adsorption of FITC-labeled human albumin only on the non-dextranized regions of the patterned polyurethane and polystyrene substrates. PMID:20712352

Saturn's equatorial jet structure from Cassini/ISS

NASA Astrophysics Data System (ADS)

García-Melendo, Enrique; Legarreta, Jon; Sánchez-Lavega, Agustín.; Pérez-Hoyos, Santiago; Hueso, Ricardo

2010-05-01

Detailed wind observations of the equatorial regions of the gaseous giant planets, Jupiter and Saturn, are crucial for understanding the basic problem of the global circulation and obtaining new detailed information on atmospheric phenomena. In this work we present high resolution data of Saturn's equatorial region wind profile from Cassini/ISS images. To retrieve wind measurements we applied an automatic cross correlator to image pairs taken by Cassini/ISS with the MT1, MT2, MT3 filters centred at the respective three methane absorbing bands of 619nm, 727nm, and 889nm, and with the adjacent continuum CB1, CB2, and CB3 filters. We obtained a complete high resolution coverage of Saturn's wind profile in the equatorial region. The equatorial jet displays an overall symmetric structure similar to that shown the by same region in Jupiter. This result suggests that, in accordance to some of the latest compressible atmosphere computer models, probably global winds in gaseous giants are deeply rooted in the molecular hydrogen layer. Wind profiles in the methane absorbing bands show the effect of strong vertical shear, ~40m/s per scale height, confirming previous results and an important decay in the wind intensity since the Voyager era (~100 m/s in the continuum and ~200 m/s in the methane absorbing band). We also report the discovery of a new feature, a very strong and narrow jet on the equator, about only 5 degrees wide, that despite the vertical shear maintains its intensity (~420 m/s) in both, the continuum and methane absorbing band filters. Acknowledgements: Work supported by the Spanish MICIIN AYA2009-10701 with FEDER and Grupos Gobierno Vasco IT-464-07.

Radiation damage in Tb-implanted CaF 2 observed by channeling and luminescence measurements

NASA Astrophysics Data System (ADS)

Aono, K.; Kumagai, M.; Iwaki, M.; Aoyagi, Y.; Namba, S.

1993-06-01

The effects of 100 keV Tb ion implantation in CaF 2 single crystals have been investigated using Rutherford backscattering/channeling technique and luminescence spectra during ion implantation, depending on ion doses. Terbium ions were implanted into (111)-cut CaF 2 single crystals in random directions with doses ranging from 1 × 10 13 to 1 × 10 17 Tb +/cm 2 at -100°C, 25°C and 100°C. The luminescence signals were measured by 100 keV Ar ion beam irradiation at room temperature to Tb-implanted specimens in order to detect the ionic state of Tb. Two broad emission peaks (near 380 and 545 nm) in visible regions were observed, originating from Tb 3+ in CaF 2. The same luminescence was also observed even during Tb implantation to CaF 2. The luminescence near 380 nm is identified as an emission of 5D 3→ 7F 6 and that near 545 nm is 5D 4→ 7F 5. The emission peak intensities depend on ion dose. Channeling measurements suggest that most of the Tb atoms occupy substitutional lattice sites. Intensities of luminescence and Tb depth profiles depend on the target temperature. In conclusion, implanted Tb atoms occupy Ca lattice sites and emit green luminescence light.

All-silica fiber with low or medium OH-content for broadband applications in astronomy

NASA Astrophysics Data System (ADS)

Ferwana, Saleh; Eckhardt, Hanns-Simon; Simon, Thorsten; Klein, Karl-Friedrich; Haynes, Roger; Khalilov, Valery K.; Nelson, Gary W.

2004-09-01

For astronomical applications, different types of step-index all-silica fibers with high-transparency in the whole spectral region from UV (300 nm) to NIR (1100 nm) will be introduced. The light-guiding core-material consists of high-purity silica, especially with low or medium OH-content. In UV region, the losses are mainly influenced by Rayleigh scattering, while the losses in the IR region are limited by traces of OH-groups (in the order of approx. 2 ppm) and fundamental vibration-bands. Due to processing, typical UV-defects below 280 nm can be suppressed significantly within fibers with medium or low OH-content. Especially, one fiber-type with low-OH content in the core possess high resistance against UV radiation in the DUV-region down to 200 nm, which is comparable to high-OH all-silica fibers specially developed for UV-application below 250 nm. In addition, a medium-OH will be presented. The properties of these new fibers in respect to basic attenuation and spectral damage in the UV-region will be discussed, in comparison to high-OH fibers, based on the same measurement-technique. In addition, first results on focal ratio degradation (FRD) and additional loss related to higher propagation angles will be shown, in comparison to standard high-OH fibers.

Haze and cloud structure of Saturn's North Pole and Hexagon Wave from Cassini/ISS imaging

NASA Astrophysics Data System (ADS)

Sanz-Requena, J. F.; Pérez-Hoyos, S.; Sánchez-Lavega, A.; Antuñano, A.; Irwin, Patrick G. J.

2018-05-01

In this paper we present a study of the vertical haze and cloud structure in the upper two bars of Saturn's Northern Polar atmosphere using the Imaging Science Subsystem (ISS) instrument onboard the Cassini spacecraft. We focus on the characterization of latitudes from 53° to 90° N. The observations were taken during June 2013 with five different filters (VIO, BL1, MT2, CB2 and MT3) covering spectral range from the 420 nm to 890 nm (in a deep methane absorption band). Absolute reflectivity measurements of seven selected regions at all wavelengths and several illumination and observation geometries are compared with the values produced by a radiative transfer model. The changes in reflectivity at these latitudes are mostly attributed to changes in the tropospheric haze. This includes the haze base height (from 600 ± 200 mbar at the lowest latitudes to 1000 ± 300 mbar in the pole), its particle number density (from 20 ± 2 particles/cm3 to 2 ± 0.5 particles/cm3 at the haze base) and its scale height (from 18 ± 0.1 km to 50 ± 0.1 km). We also report variability in the retrieved particle size distribution and refractive indices. We find that the Hexagonal Wave dichotomizes the studied stratospheric and tropospheric hazes between the outer, equatorward regions and the inner, Polar Regions. This suggests that the wave or the jet isolates the particle distribution at least at tropospheric levels.

Imaging the equilibrium state and magnetization dynamics of partially built hard disk write heads

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

Valkass, R. A. J., E-mail: rajv202@ex.ac.uk; Yu, W.; Shelford, L. R.

Four different designs of partially built hard disk write heads with a yoke comprising four repeats of NiFe (1 nm)/CoFe (50 nm) were studied by both x-ray photoemission electron microscopy (XPEEM) and time-resolved scanning Kerr microscopy (TRSKM). These techniques were used to investigate the static equilibrium domain configuration and the magnetodynamic response across the entire structure, respectively. Simulations and previous TRSKM studies have made proposals for the equilibrium domain configuration of similar structures, but no direct observation of the equilibrium state of the writers has yet been made. In this study, static XPEEM images of the equilibrium state of writer structures weremore » acquired using x-ray magnetic circular dichroism as the contrast mechanism. These images suggest that the crystalline anisotropy dominates the equilibrium state domain configuration, but competition with shape anisotropy ultimately determines the stability of the equilibrium state. Dynamic TRSKM images were acquired from nominally identical devices. These images suggest that a longer confluence region may hinder flux conduction from the yoke into the pole tip: the shorter confluence region exhibits clear flux beaming along the symmetry axis, whereas the longer confluence region causes flux to conduct along one edge of the writer. The observed variations in dynamic response agree well with the differences in the equilibrium magnetization configuration visible in the XPEEM images, confirming that minor variations in the geometric design of the writer structure can have significant effects on the process of flux beaming.« less

Liposome formation in microgravity.

PubMed

Claassen, D E; Spooner, B S

1996-01-01

Liposomes are artificial vesicles with a phospholipid bilayer membrane. The formation of liposomes is a self-assembly process that is driven by the amphipathic nature of phospholipid molecules and can be observed during the removal of detergent from phospholipids dissolved in detergent micelles. As detergent concentration in the mixed micelles decreases, the non-polar tail regions of phospholipids produce a hydrophobic effect that drives the micelles to fuse and form planar bilayers in which phospholipids orient with tail regions to the center of the bilayer and polar head regions to the external surface. Remaining detergent molecules shield exposed edges of the bilayer sheet from the aqueous environment. Further removal of detergent leads to intramembrane folding and membrane folding and membrane vesiculation, forming liposomes. We have observed that the formation of liposomes is altered in microgravity. Liposomes that were formed at 1-g did not exceed 150 nm in diameter, whereas liposomes that were formed during spaceflight exhibited diameters up to 2000 nm. Using detergent-stabilized planar bilayers, we determined that the stage of liposome formation most influenced by gravity is membrane vesiculation. In addition, we found that small, equipment-induced fluid disturbances increased vesiculation and negated the size-enhancing effects of microgravity. However, these small disturbances had no effect on liposome size at 1-g, likely due to the presence of gravity-induced buoyancy-driven fluid flows (e.g., convection currents). Our results indicate that fluid disturbances, induced by gravity, influence the vesiculation of membranes and limit the diameter of forming liposomes.

Liposome formation in microgravity

NASA Astrophysics Data System (ADS)

Claassen, D. E.; Spooner, B. S.

Liposomes are artificial vesicles with a phospholipid bilayer membrane. The formation of liposomes is a self-assembly process that is driven by the amphipathic nature of phospholipid molecules and can be observed during the removal of detergent from phospholipids dissolved in detergent micelles. As detergent concentration in the mixed micelles decreases, the non-polar tail regions of phospholipids produce a hydrophobic effect that drives the micelles to fuse and form planar bilayers in which phospholipids orient with tail regions to the center of the bilayer and polar head regions to the external surface. Remaining detergent molecules shield exposed edges of the bilayer sheet from the aqueous environment. Further removal of detergent leads to intramembrane folding and membrane vesiculation, forming liposomes. We have observed that the formation of liposomes is altered in microgravity. Liposomes that were formed at 1-g did not exceed 150 nm in diameter, whereas liposomes that were formed during spaceflight exhibited diameters up to 2000 nm. Using detergent-stabilized planar bilayers, we determined that the stage of liposome formation most influenced by gravity is membrane vesiculation. In addition, we found that small, equipment-induced fluid disturbances increased vesiculation and negated the size-enhancing effects of microgravity. However, these small disturbances had no effect on liposome size at 1-g, likely due to the presence of gravity-induced buoyancy-driven fluid flows (e.g., convection currents). Our results indicate that fluid disturbances, induced by gravity, influence the vesiculation of membranes and limit the diameter of forming liposomes.

Raman imaging of carrier distribution in the channel of an ionic liquid-gated transistor fabricated with regioregular poly(3-hexylthiophene)

NASA Astrophysics Data System (ADS)

Wada, Y.; Enokida, I.; Yamamoto, J.; Furukawa, Y.

2018-05-01

Raman images of carriers (positive polarons) at the channel of an ionic liquid-gated transistor (ILGT) fabricated with regioregular poly(3-hexylthiophene) (P3HT) have been measured with excitation at 785 nm. The observed spectra indicate that carriers generated are positive polarons. The intensities of the 1415 cm-1 band attributed to polarons in the P3HT channel were plotted as Raman images; they showed the carrier density distribution. When the source-drain voltage VD is lower than the source-gate voltage VG (linear region), the carrier density was uniform. When VD is nearly equal to VG (saturation region), a negative carrier density gradient from the source electrode towards the drain electrode was observed. This carrier density distribution is associated with the observed current-voltage characteristics, which is not consistent with the "pinch-off" theory of inorganic semiconductor transistors.

Periodic disorder along ramie cellulose microfibrils.

PubMed

Nishiyama, Yoshiharu; Kim, Ung-Jin; Kim, Dae-Young; Katsumata, Kyoko S; May, Roland P; Langan, Paul

2003-01-01

Small angle neutron scattering studies have been carried out on cellulose fibers from ramie and Populus maximowicii (cotton wood). Labile hydrogen atoms were replaced by deuterium atoms, in water-accessible disordered regions of the fibers, to increase the neutron scattering contrast between the disordered and crystalline regions. A meridional Bragg reflection, corresponding to a longitudinal periodicity of 150 nm, was observed when scattering collected from hydrogenated and deuterated dry ramie fibers was subtracted. No Bragg reflection was observed with the cotton wood fibers, probably because of lower orientation of the microfibrils in the cell wall. The ramie fibers were then subjected to electron microscopy, acid hydrolysis, gel permeation chromatography, and viscosity studies. The leveling off degree of polymerization (LODP) of the hydrolyzed samples matched exactly the periodicity observed in the diffraction studies. The weight loss related to the LODP was only about 1.5%, and thus, the microfibrils can be considered to have 4-5 disordered residues every 300 residues.

Remote compositional mapping of lunar titanium and surface maturity

NASA Technical Reports Server (NTRS)

Johnson, J. R.; Larson, S. M.; Singer, Robert B.

1991-01-01

Lunar ilmenite (FeTiO3) is a potential resource capable of providing oxygen for life support and spacecraft propellant for future lunar bases. Estimates of TiO2 content in mature mare soils can be made using an empirical relation between the 400/500 nm reflectance ratio and TiO2 wt percent. A TiO2 abundance map was constructed for the entire near-side lunar maria accurate to + or - 2 wt percent TiO2 using CCD images obtained at the Tumamoc Hill 0.5 m telescope in Tucson, employing bandpass filters centered at 400 and 560 nm. Highest TiO2 regions in the maria are located in western Mare Tranquillitatis. Greater contrast differences between regions on the lunar surface can be obtained using 400/730 nm ratio images. The relation might well be refined to accommodate this possibly more sensitive indicator of TiO2 content. Another potential lunar resource is solar wind-implanted He-3 which may be used as a fuel for fusion reactors. Relative soil maturity, as determined by agglutinate content, can be estimated from 950/560 nm ration images. Immature soils appear darker in this ratio since such soils contain abundant pyroxene grains which cause strong absorption centered near 950 nm due Fe(2+) crystal field transitions. A positive correlation exists between the amount of He-3 and TiO2 content in lunar soils, suggesting that regions high in TiO2 should also be high in He-3. Reflectance spectrophotometry in the region 320 to 870 nm was also obtained for several regions. Below about 340 nm, these spectra show variations in relative reflectance that are caused by as yet unassigned near-UV absorptions due to compositional differences.

Estimation of 557.7 nm Emission Altitude using Co-located Lidars and Photometers over Arecibo

NASA Astrophysics Data System (ADS)

Franco, E.; Raizada, S.; Lautenbach, J.; Brum, C. G. M.

2017-12-01

Airglow at 557.7 nm (green line emission) is generated through the Barth mechanism in the E-region altitude and is sometimes associated with red line (630.0 nm) originating at F-region altitudes. Photons at 557.7 nm are produced through the quenching of excited atomic oxygen atoms, O(1S), while 630.0 nm results through the de-excitation of O(1D) atoms. Even though, the contribution of the green line from F-region is negligible and the significant component comes from the mesosphere, this uncertainty gives rise to a question related to its precise altitude. Previous studies have shown that perturbations generated by atmospheric gravity Waves (GWs) alter the airglow intensity and can be used for studying dynamics of the region where it originates. The uncertainty in the emission altitude of green line can be resolved by using co-located lidars, which provide altitude resolved metal densities. At Arecibo, the resonance lidars tuned to Na and K resonance wavelengths at 589 nm and 770 nm can be used in conjunction with simultaneous measurements from green line photometer to resolve this issue. Both photometer and lidars have narrow field of view as compared to airglow imagers, and hence provide an added advantage that these instruments sample same GW spectrum. Hence, correlation between density perturbations inferred from lidars and airglow intensity perturbations can shed light on the exact altitude of green line emission.

He behavior in Ni and Ni-based equiatomic solid solution alloy

NASA Astrophysics Data System (ADS)

Yan, Zhanfeng; Liu, Shaoshuai; Xia, Songqin; Zhang, Yong; Wang, Yugang; Yang, Tengfei

2018-07-01

In the current work, pure nickel (99.99 wt.%) and Ni-containing single phase equiatomic solid solution alloy Fe-Co-Cr-Ni were irradiated with 190 keV He ions at room temperature with different fluences and He behavior in both materials are compared. At 1 × 1017 cm-2, TEM observation reveals that only isolated and small He bubbles (1-2 nm) are formed in Fe-Co-Cr-Ni alloy while many small suspected "string"-like He bubbles are observed in nickel at the concentration peak region (5.5 at.%). When the fluence is increased to 5 × 1017 cm-2, average bubble size in nickel increases to ∼8 nm which is almost equal to that in Fe-Co-Cr-Ni, but a higher bubble density is observed in nickel. At the highest dose of 1 × 1018 cm-2, numerous surface blisters and exfoliations occur in nickel which are consistent with TEM observation, while the Fe-Co-Cr-Ni alloy only shows a slight surface blister. Bubble coarsening upon annealing at 500 °C (2 h) is observed at 5 × 1017 cm-2 in both alloys, but a significant larger bubble growth is observed in nickel, suggesting a relatively better resistance to He bubble growth for Fe-Co-Cr-Ni alloy.

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.

Structural and thermoelectric properties of epitaxially grown Bi2Te3 thin films and superlattices

NASA Astrophysics Data System (ADS)

Peranio, N.; Eibl, O.; Nurnus, J.

2006-12-01

Multi-quantum-well structures of Bi2Te3 are predicted to have a high thermoelectric figure of merit ZT. Bi2Te3 thin films and Bi2Te3/Bi2(Te0.88Se0.12)3 superlattices (SLs) were grown epitaxially by molecular beam epitaxy on BaF2 substrates with periods of 12 and 6nm, respectively. Reflection high-energy electron diffraction confirmed a layer-by-layer growth, x-ray diffraction yielded the lattice parameters and SL periods and proved epitaxial growth. The in-plane transport coefficients were measured and the thin films and SL had power factors between 28 and 35μW /cmK2. The lattice thermal conductivity varied between 1.60W/mK for Bi2Te3 thin films and 1.01W/mK for a 10nm SL. The best figures of merit ZT were achieved for the SL; however, the values are slightly smaller than those in bulk materials. Thin films and superlattices were investigated in plan view and cross section by transmission electron microscopy. In the Bi2Te3 thin film and SL the dislocation density was found to be 2×1010cm-2. Bending of the SL with amplitudes of 30nm (12nm SL) and 15nm (6nm SL) and a wavelength of 400nm was determined. Threading dislocations were found with a density greater than 2×109cm-2. The superlattice interfaces are strongly bent in the region of the threading dislocations, undisturbed regions have a maximum lateral sie of 500nm. Thin films and SL showed a structural modulation [natural nanostructure (nns)] with a wavelength of 10nm and a wave vector parallel to (1,0,10). This nns was also observed in Bi2Te3 bulk materials and turned out to be of general character for Bi2Te3. The effect of the microstructure on the thermoelectric properties is discussed. The microstructure is governed by the superlattice, the nns, and the dislocations that are present in the films. Our results indicate that the microstructure directly affects the lattice thermal conductivity. Thermopower and electrical conductivity were found to be negatively correlated and no clear dependence of the two quantities on the microstructure could be found.

Earthquake Hazard and Risk Assessment based on Unified Scaling Law for Earthquakes: Altai-Sayan Region

NASA Astrophysics Data System (ADS)

Kossobokov, V. G.; Nekrasova, A.

2017-12-01

We continue applying the general concept of seismic risk analysis in a number of seismic regions worldwide by constructing regional seismic hazard maps based on morphostructural analysis, pattern recognition, and the Unified Scaling Law for Earthquakes, USLE, which generalizes the Gutenberg-Richter relationship making use of naturally fractal distribution of earthquake sources of different size in a seismic region. The USLE stands for an empirical relationship log10N(M, L) = A + B·(5 - M) + C·log10L, where N(M, L) is the expected annual number of earthquakes of a certain magnitude M within an seismically prone area of linear dimension L. We use parameters A, B, and C of USLE to estimate, first, the expected maximum credible magnitude in a time interval at seismically prone nodes of the morphostructural scheme of the region under study, then map the corresponding expected ground shaking parameters (e.g. peak ground acceleration, PGA, or macro-seismic intensity etc.). After a rigorous testing against the available seismic evidences in the past (usually, the observed instrumental PGA or the historically reported macro-seismic intensity), such a seismic hazard map is used to generate maps of specific earthquake risks for population, cities, and infrastructures (e.g., those based on census of population, buildings inventory, etc.). This, USLE based, methodology of seismic hazard and risks assessment is applied to the territory of Altai-Sayan Region, of Russia. The study supported by the Russian Science Foundation Grant No. 15-17-30020.

EPOXI at Earth's Poles: Empirical Test for Observations of an Exoplanet at High Obliquity

NASA Astrophysics Data System (ADS)

Livengood, Timothy A.; A'Hearn, M. F.; Deming, D.; Charbonneau, D.; Barry, R. K.; Hewagama, T.; Lisse, C. M.; McFadden, L.; Meadows, V.; Seager, S.; Wellnitz, D.; EPOXI-EPOCh Science Team

2009-09-01

Observations of the Earth have been obtained by the EPOXI mission to investigate empirically the visible-to-near infrared spectral distribution and lightcurve variations of the Earth as a model for terrestrial exoplanets. Exoplanetary systems may be at arbitrary inclination to the solar system, and may include planets of arbitrary obliquity. The EPOXI mission has previously observed the Earth from within the ecliptic plane and has now acquired measurements at high northern and southern sub-spacecraft latitude with nearly identical phase angle and range. On 27-28 Mar 2009 UT, the whole disc of the Earth was observed from a sub-spacecraft latitude of 62°N at 87° phase angle (53.5% illumination) and 0.114 AU range. On 27 Sep 2009, Earth will have been observed from a sub-spacecraft latitude of 74°S at 87° phase angle (52.7% illumination) and 0.115 AU range. The Earth was near the spring equinox of each pole as it was observed. The visible-light signal was sampled with 7 filters of approximately 100 nm width at 100 nm spacing over 350-950 nm central wavelength, at 15-minute intervals in 4 selected filters and 1-hour intervals in the remaining 3 filters. Near-IR spectroscopy at 1-4.8 µm was obtained at 2-hour intervals. These polar data, capturing the polar ice caps and high latitude climatic regions, will be compared to similar data previously acquired from over the equator, to investigate distinctions in the ability to discern from the global average the spectroscopic signature of vegetation and biogenic gas species. This work is supported by the NASA Discovery Program.

Derivative Analysis of Absorption Features in Hyperspectral Remote Sensing Data of Carbonate Sediments

DTIC Science & Technology

2002-12-30

reflectance of carbonate sediments and application to shallow water benthic habitat classification,” Doctoral Dissertation, University of Miami. Chap.3...resolve overlapping features. A primary application has been to analyze pigment and chemical composition of leaves in order to track physiological...final absorption feature was observed at 630 nm, in a region associated with the biliprotein, phycocyanin [16,17]. As biliproteins are water soluble

Discrimination of tomatoes bred by spaceflight mutagenesis using visible/near infrared spectroscopy and chemometrics

NASA Astrophysics Data System (ADS)

Shao, Yongni; Xie, Chuanqi; Jiang, Linjun; Shi, Jiahui; Zhu, Jiajin; He, Yong

2015-04-01

Visible/near infrared spectroscopy (Vis/NIR) based on sensitive wavelengths (SWs) and chemometrics was proposed to discriminate different tomatoes bred by spaceflight mutagenesis from their leafs or fruits (green or mature). The tomato breeds were mutant M1, M2 and their parent. Partial least squares (PLS) analysis and least squares-support vector machine (LS-SVM) were implemented for calibration models. PLS analysis was implemented for calibration models with different wavebands including the visible region (400-700 nm) and the near infrared region (700-1000 nm). The best PLS models were achieved in the visible region for the leaf and green fruit samples and in the near infrared region for the mature fruit samples. Furthermore, different latent variables (4-8 LVs for leafs, 5-9 LVs for green fruits, and 4-9 LVs for mature fruits) were used as inputs of LS-SVM to develop the LV-LS-SVM models with the grid search technique and radial basis function (RBF) kernel. The optimal LV-LS-SVM models were achieved with six LVs for the leaf samples, seven LVs for green fruits, and six LVs for mature fruits, respectively, and they outperformed the PLS models. Moreover, independent component analysis (ICA) was executed to select several SWs based on loading weights. The optimal LS-SVM model was achieved with SWs of 550-560 nm, 562-574 nm, 670-680 nm and 705-715 nm for the leaf samples; 548-556 nm, 559-564 nm, 678-685 nm and 962-974 nm for the green fruit samples; and 712-718 nm, 720-729 nm, 968-978 nm and 820-830 nm for the mature fruit samples. All of them had better performance than PLS and LV-LS-SVM, with the parameters of correlation coefficient (rp), root mean square error of prediction (RMSEP) and bias of 0.9792, 0.2632 and 0.0901 based on leaf discrimination, 0.9837, 0.2783 and 0.1758 based on green fruit discrimination, 0.9804, 0.2215 and -0.0035 based on mature fruit discrimination, respectively. The overall results indicated that ICA was an effective way for the selection of SWs, and the Vis/NIR combined with LS-SVM models had the capability to predict the different breeds (mutant M1, mutant M2 and their parent) of tomatoes from leafs and fruits.

Variations in Ionospheric Peak Electron Density During Sudden Stratospheric Warmings in the Arctic Region

NASA Astrophysics Data System (ADS)

Yasyukevich, A. S.

2018-04-01

The focus of the paper is the ionospheric disturbances during sudden stratospheric warming (SSW) events in the Arctic region. This study examines the ionospheric behavior during 12 SSW events, which occurred in the Northern Hemisphere over 2006-2013, based on vertical sounding data from DPS-4 ionosonde located in Norilsk (88.0°E, 69.2°N). Most of the addressed events show that despite generally quiet geomagnetic conditions, notable changes in the ionospheric behavior are observed during SSWs. During the SSW evolution and peak phases, there is a daytime decrease in NmF2 values at 10-20% relative to background level. After the SSW maxima, in contrast, midday NmF2 surpasses the average monthly values for 10-20 days. These changes in the electron density are observed for both strong and weak stratospheric warmings occurring at midwinter. The revealed SSW effects in the polar ionosphere are assumed to be associated with changes in the thermospheric neutral composition, affecting the F2-layer electron density. Analysis of the Global Ultraviolet Imager data revealed the positive variations in the O/N2 ratio within the thermosphere during SSW peak and recovery periods. Probable mechanisms for SSW impact on the state of the high-latitude neutral thermosphere and ionosphere are discussed.

Galileo Ultraviolet Spectrometer experiment

NASA Technical Reports Server (NTRS)

Hord, C. W.; Mcclintock, W. E.; Stewart, A. I. F.; Barth, C. A.; Esposito, L. W.; Thomas, G. E.; Sandel, B. R.; Hunten, D. M.; Broadfoot, A. L.; Shemansky, D. E.

1992-01-01

The Galileo ultraviolet spectrometer experiment uses data obtained by the Ultraviolet Spectrometer (UVS) mounted on the pointed orbiter scan platform and from the Extreme Ultraviolet Spectrometer (EUVS) mounted on the spinning part of the orbiter with the field of view perpendicular to the spin axis. The UVS is a Ebert-Fastie design that covers the range 113-432 nm with a wavelength resolution of 0.7 nm below 190 and 1.3 nm at longer wavelengths. The UVS spatial resolution is 0.4 deg x 0.1 deg for illuminated disk observations and 1 deg x 0.1 deg for limb geometries. The EUVS is a Voyager design objective grating spectrometer, modified to cover the wavelength range from 54 to 128 nm with wavelength resolution 3.5 nm for extended sources and 1.5 nm for point sources and spatial resolution of 0.87 deg x 0.17 deg. The EUVS instrument will follow up on the many Voyager UVS discoveries, particularly the sulfur and oxygen ion emissions in the Io torus and molecular and atomic hydrogen auroral and airglow emissions from Jupiter. The UVS will obtain spectra of emission, absorption, and scattering features in the unexplored, by spacecraft, 170-432 nm wavelength region. The UVS and EUVS instruments will provide a powerful instrument complement to investigate volatile escape and surface composition of the Galilean satellites, the Io plasma torus, micro- and macro-properties of the Jupiter clouds, and the composition structure and evolution of the Jupiter upper atmosphere.

Understanding Vegetation Response To Climate Variability From Space: The Scientific Objectives< The Approach and The Concept of The Spectra Mission

NASA Astrophysics Data System (ADS)

Menenti, M.; Rast, M.; Baret, F.; Mauser, W.; Miller, J.; Schaepman, M.; Schimel, D.; Verstraete, M.

The response of vegetation to climate variability is a major scientific question. The monitoring of the carbon stock in terrestrial environments, as well as the improved understanding of the surface-atmosphere interactions controlling the exchange of mat- ter, energy and momentum, is of immediate interest for an improved assessment of the various components of the global carbon cycle. Studies of the Earth System processes at the global scale rely on models that require an advanced understanding and proper characterization of processes at smaller scales. The goal of the SPECTRA mission is to improve the description of those processes by means of better constraints on and parameterizations of the associated models. Many vegetation properties are related to features of reflectance spectra in the region 400 nm U 2500 nm. Detailed observa- tions of spectral reflectance reveal subtle features related to biochemical components of leaves such as chlorophyll and water. The architecture of vegetation canopies de- termines complex changes of observed reflectance spectra with view and illumination angle. Quantitative analysis of reflectance spectra requires, therefore, an accurate char- acterization of the anisotropy of reflected radiance. This can be achieved with nearly U simultaneous observations at different view angles. Exchange of energy between the biosphere and the atmosphere is an important mechanism determining the response of vegetation to climate variability. This requires measurements of the component tem- perature of foliage and soil. The prime objective of SPECTRA is to determine the amount, assess the conditions and understand the response of terrestrial vegetation to climate variability and its role in the coupled cycles of energy, water and carbon. The amount and state of vegetation will be determined by the combination of observed vegetation properties and data assimilation. Specifically, the mission will character- ize the amount and state of vegetation with observations of the following variables: 1) Fractional vegetation cover; 2) Fraction Absorbed Photosynthetically Active Radi- ation (FAPAR); 3) Albedo; 4) Leaf Area Index (LAI); 5) Leaf chlorophyll content; 6)Leaf water content; 7) Foliage temperature; 8) Soil temperature; 9) Fractional cover of living and dead biomass. SPECTRA will provide spatially distributed observations (maps) of the key vegetation properties at the spatial resolution of one image pixel and 1 a temporal frequency of one week or lower. Each map will cover an area of 50 km x 50 km. The SPECTRA mission is being studied by the European Space Agency to ad- dress these scientific issues. The mission comprises the following elements: A. Space segment consisting of an imaging spectrometer covering the region 400 nm U 2400 nm with a nominal spectral resolution of 10 nm and of an agile platform to perform subsequent, along track observations at seven view angles between -70 and + 70. B. Ground segment consisting of a core data processing facility and specialized Centers of Excellence to guarantee to a wide and diverse community access to higher level data products and to specialized data assimilation systems. C. Field segment consist- ing of 50 to 100 dedicated sites where teams of investigators evaluate the observations and assimilate them in models describing the functioning of terrestrial ecosystems. 2

Picosecond time-resolved fluorescence spectroscopy of K-590 in the bacteriorhodopsin photocycle.

PubMed Central

Atkinson, G H; Blanchard, D; Lemaire, H; Brack, T L; Hayashi, H

1989-01-01

The fluorescence spectrum of a distinct isometric and conformational intermediate formed on the 10(-11) s time scale during the bacteriorhodopsin (BR) photocycle is observed at room temperature using a two laser, pump-probe technique with picosecond time resolution. The BR photocycle is initiated by pulsed (8 ps) excitation at 565 nm, whereas the fluorescence is generated by 4-ps laser pulses at 590 nm. The unstructured fluorescence extends from 650 to 880 nm and appears in the same general spectral region as the fluorescence spectrum assigned to BR-570. The transient fluorescence spectrum can be distinguished from that assigned to BR-570 by a larger emission quantum yield (approximately twice that of BR-570) and by a maximum intensity near 731 nm (shifted 17 nm to higher energy from the maximum of the BR-570 fluorescence spectrum). The fluorescence spectrum of BR-570 only is measured with low energy, picosecond pulsed excitation at 590 nm and is in good agreement with recent data in the literature. The assignment of the transient fluorescence spectrum to the K-590 intermediate is based on its appearance at time delays longer than 40 ps. The K-590 fluorescence spectrum remains unchanged over the entire 40-100-ps interval. The relevance of these fluorescence data with respect to the molecular mechanism used to model the primary processes in the BR photocycle also is discussed. PMID:2713439

Transient Resonance Raman Spectroscopy of a Light-Driven Sodium-Ion-Pump Rhodopsin from Indibacter alkaliphilus.

PubMed

Kajimoto, Kousuke; Kikukawa, Takashi; Nakashima, Hiroki; Yamaryo, Haruki; Saito, Yuta; Fujisawa, Tomotsumi; Demura, Makoto; Unno, Masashi

2017-05-04

Sodium-ion-pump rhodopsin (NaR) is a microbial rhodopsin that transports Na + during its photocycle. Here we explore the photocycle mechanism of NaR from Indibacter alkaliphilus with transient absorption and transient resonance Raman spectroscopy. The transient absorption data indicate that the photocycle of NaR is K (545 nm) → L (490 nm)/M (420 nm) → O 1 (590 nm) → O 2 (560 nm) → NaR, where the L and M are formed as equilibrium states. The presence of K, L, M, and O intermediates was confirmed by the resonance Raman spectra with 442 and 532 nm excitation. The main component of the transient resonance Raman spectra was due to L which contains a 13-cis retinal protonated Schiff base. The presence of an enhanced hydrogen out-of-plane band as well as its sensitivity to the H/D exchange indicate that the retinal chromophore is distorted near the Schiff base region in L. Moreover, the retinal Schiff base of the L state forms a hydrogen bond that is stronger than that of the dark state. These observations are consistent with a Na + pumping mechanism that involves a proton transfer from the retinal Schiff base to a key aspartate residue (Asp116 in Krokinobacter eikastus rhodopsin 2) in the L/M states.

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.

Synthesis and photophysical properties of a series of cyclopenta[b]naphthalene solvatochromic fluorophores.

PubMed

Benedetti, Erica; Kocsis, Laura S; Brummond, Kay M

2012-08-01

The synthesis and photophysical properties of a series of naphthalene-containing solvatochromic fluorophores are described within. These novel fluorophores are prepared using a microwave-assisted dehydrogenative Diels-Alder reaction of styrene, followed by a palladium-catalyzed cross coupling reaction to install an electron donating amine group. The new fluorophores are structurally related to Prodan. Photophysical properties of the new fluorophores were studied and intriguing solvatochromic behavior was observed. For most of these fluorophores, high quantum yields (60-99%) were observed in methylene chloride in addition to large Stokes shifts (95-226 nm) in this same solvent. As the solvent polarity increased, so did the observed Stokes shift with one derivative displaying a Stokes shift of ~300 nm in ethanol. All fluorophore emission maxima, and nearly all absorption maxima were significantly red-shifted when compared to Prodan. Shifting the absorption and emission maxima of a fluorophore into the visible region increases its utility in biological applications. Moreover, the cyclopentane portion of the fluorophore structure provides an attachment point for biomolecules that will minimize disruptions of the photophysical properties.

CHROMOSPHERIC MASS MOTIONS AND INTRINSIC SUNSPOT ROTATIONS FOR NOAA ACTIVE REGIONS 10484, 10486, AND 10488 USING ISOON DATA

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

Hardersen, Paul S.; Balasubramaniam, K. S.; Shkolyar, Svetlana, E-mail: Hardersen@space.edu

2013-08-10

This work utilizes Improved Solar Observing Optical Network continuum (630.2 nm) and H{alpha} (656.2 nm) data to: (1) detect and measure intrinsic sunspot rotations occurring in the photosphere and chromosphere, (2) identify and measure chromospheric filament mass motions, and (3) assess any large-scale photospheric and chromospheric mass couplings. Significant results from 2003 October 27-29, using the techniques of Brown et al., indicate significant counter-rotation between the two large sunspots in NOAA AR 10486 on October 29, as well as discrete filament mass motions in NOAA AR 10484 on October 27 that appear to be associated with at least one C-classmore » solar flare.« less

Generic Superconducting Inhomogeneity in Single Crystal Fe(Te1-xSex) Probed by Nanostructure-transport

NASA Astrophysics Data System (ADS)

Yue, Chunlei; Hu, Jin; Liu, Xue; Mao, Zhiqiang; Wei, Jiang

2015-03-01

We have investigated the nano-scale electronic properties of the iron-based unconventional superconductor Fe(Te1-xSex) with optimal Se content x = 0.5. Using the microexfoliation method and ion milling thinning, we successfully produced Fe(Te1-xSex) devices with thickness varying from 90nm down to 12nm. Our transport measurements revealed a suppression of superconductivity coinciding with the loss of normal state metallicity. Through the simulation of the formation of superconducting region in nano-scale thin flakes, we show that our observation is in line with the nano-scale inhomogeneity proposed for this material; therefore it provides a more direct evidence for the nano-scale inhomogeneous superconductivity in Fe(Te1-xSex) .

Scintillation and storage luminescence properties of MgF2 transparent ceramics doped with Ce3+

NASA Astrophysics Data System (ADS)

Nakamura, Fumiya; Kato, Takumi; Okada, Go; Kawaguchi, Noriaki; Fukuda, Kentaro; Yanagida, Takayuki

2017-10-01

In this paper, we report basic optical properties and scintillation and storage luminescence properties of MgF2:Ce transparent ceramics with different doping concentrations of Ce (0.01, 0.1 and 1%) synthesized by spark plasma sintering (SPS). In scintillation, thermally-stimulated luminescence (TSL) and optically-stimulated luminescence (OSL), the dominant emissions were due to the 5d-4f transitions of Ce3+ which appeared in the near-UV region peaking around 320 and 360 nm. The scintillation was evaluated by X-ray irradiation while OSL was observed under 540 nm stimulation. In particular, the TSL sensitivity was high and showed a good linearity from 0.1 mGy to 1000 mGy.

[Multiply upconversion emission in oxyfluoride ceramics].

PubMed

Xiao, Si-guo; Yang, Xiao-liang; Liu, Zhen-wei

2003-02-01

Oxyfluoride ceramics with the host composition of SiO2 and PbF2 have been prepared. X-ray diffraction analysis of the ceramics revealed that fluoride type beta-PbF2 solid solution regions are precipitated in the glass matrix. Rare earth ions in the beta-PbF2 solid solution show highly efficient upconversion performance due to the very small multi-phonon relaxation rates. Eight upconversion emission bands whose central wavelength are 846, 803, 665, 549, 523, 487, 456 and 411 nm have been observed when the sample was excited with 930 nm diode light. Four possible energy transfer processes between Er3+ and Yb3+ cause the electronic population of high energy level of Er3+ and realize the abound upconversion luminescence bands.

Antimicrobial photodisinfection with Zn(II) phthalocyanine adsorbed on TiO2 upon UVA and red irradiation

NASA Astrophysics Data System (ADS)

Mantareva, Vanya; Eneva, Ivelina; Kussovski, Vesselin; Borisova, Ekaterina; Angelov, Ivan

2015-01-01

The light exposure on a daily basis has been well accepted as a competitive method for decontamination of wastewater. The catalytic properties of TiO2 offer a great potential to reduce the transmission of pathogens in the environment. Although the titanium dioxide shows high activity against pathogens, its general usage in water cleaning is limited due to the insufficient excitation natural light (about 3% of the solar spectrum). A hydrophobic dodecylpyridyloxy Zn(II)-phthalocyanine with four peripheral hydrocarbon chains of C12 (ZnPcDo) was immobilized on a photocatalyst TiO2 anatase (P25). The resulted greenish colored nanoparticles of phthalocyanine were characterized by the means of absorption, fluorescence and infrared spectroscopy. The laser scanning confocal fluorescence microscopy was used to visualize the phthalocyanine dye by the red fluorescence emission (650 - 740 nm). The intensive Q-band in the far red visible spectral region (~ 690 nm) suggested a monomeric state of phthalocyanine on TiO2 nanoparticles. Two pathogenic bacterial strains (methicillin-resistant Staphylococcus aureus - MRSA and Salmonella enteritidis) associated with wastewater were photoinactivated with the suspension of the particles. The effective photoinactivation was observed with 1 g.L-1 TiO2 anatase at irradiation with UVA 364 nm as with UVA 364 nm and LED 643 nm. The gram-negative Salmonella enteritidis was fully photoinactivated with ZnPcDo-TiO2 and TiO2 alone at UVA 346 nm and at irradiation with two light sources (364 nm + 643 nm). The proposed conjugate appears as an useful composite material for antibacterial disinfection.

OBSERVING CASCADES OF SOLAR BULLETS AT HIGH RESOLUTION. II

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

Scullion, E.; Engvold, O.; Lin, Y.

High resolution observations from the Swedish 1-m Solar Telescope revealed bright, discrete, blob-like structures (which we refer to as solar bullets) in the Hα 656.28 nm line core that appear to propagate laterally across the solar atmosphere as clusters in active regions (ARs). These small-scale structures appear to be field aligned and many bullets become triggered simultaneously and traverse collectively as a cluster. Here, we conduct a follow-up study on these rapidly evolving structures with coincident observations from the Solar Dynamics Observatory/Atmospheric Imaging Assembly. With the co-aligned data sets, we reveal (a) an evolving multithermal structure in the bullet clustermore » ranging from chromospheric to at least transition region temperatures, (b) evidence for cascade-like behavior and corresponding bidirectional motions in bullets within the cluster, which indicate that there is a common source of the initial instability leading to bullet formation, and (c) a direct relationship between co-incident bullet velocities observed in Hα and He ii 30.4 nm and an inverse relationship with respect to bullet intensity in these channels. We find evidence supporting that bullets are typically composed of a cooler, higher density core detectable in Hα with a less dense, hotter, and fainter co-moving outer sheath. Bullets unequivocally demonstrate the finely structured nature of the AR corona. We have no clear evidence for bullets being associated with locally heated (or cooled), fast flowing plasma. Fast MHD pulses (such as solitons) could best describe the dynamic properties of bullets whereas the presence of a multithermal structure is new.« less

Structural and optical studies of Er3+-doped alkali/alkaline oxide containing zinc boro-aluminosilicate glasses for 1.5 μm optical amplifier applications

NASA Astrophysics Data System (ADS)

Kaky, Kawa M.; Lakshminarayana, G.; Baki, S. O.; Lira, A.; Caldiño, U.; Meza-Rocha, A. N.; Falcony, C.; Kityk, I. V.; Taufiq-Yap, Y. H.; Halimah, M. K.; Mahdi, M. A.

2017-07-01

In the present work, we report on the optical spectral properties of Er3+-doped zinc boro-aluminosilicate glasses with an addition of 10 mol % alkali/alkaline modifier regarding the fabrication of new optical materials for optical amplifiers. A total of 10 glasses were prepared using melt-quenching technique with the compositions (40-x)B2O3 - 10SiO2 - 10Al2O3 - 30ZnO - 10Li2O - xEr2O3 and (40-x)B2O3 - 10SiO2 - 10Al2O3 - 30ZnO - 10MgO - xEr2O3 (x = 0.1, 0.25, 0.5, 1.0, and 2.0 mol %). We confirm the amorphous-like structure for all the prepared glasses using X-ray diffraction (XRD). To study the functional groups of the glass composition after the melt-quenching process, Raman spectroscopy was used, and various structural units such as triangular and tetrahedral-borates (BO3 and BO4) have been identified. All the samples were characterized using optical absorption for UV, visible and NIR regions. Judd-Ofelt (JO) intensity parameters (Ωλ, λ = 2, 4 and 6) were calculated from the optical absorption spectra of two glasses LiEr 2.0 and MgEr 2.0 (doped with 2 mol % of Er3+). JO parameters for LiEr 2.0 and MgEr 2.0 glasses follow the trend as Ω6>Ω2>Ω4. Using Judd-Ofelt intensity parameters, we obtained radiative probability A (S-1), branching ratios (β), radiative decay lifetimes τrad (μs) of emissions from excited Er+3 ions in LiEr 2.0 and MgEr 2.0 to all lower levels. Quantum efficiency (η) of 4I13/2 and 4S3/2 levels for LiEr 2.0 and MgEr 2.0 with and without 4D7/2 level was calculated using the radiative decay lifetimes τrad. (μs) and measured lifetimes τexp. (μs). We measured the visible photoluminescence under 377 nm excitation for both LiEr and MgEr glass series within the region 390-580 nm. Three bands were observed in the visible region at 407 nm, 530 nm, and 554 nm, as a result of 2H9/2 → 4I15/2, 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 transitions, respectively. Decay lifetimes for emissions at 407 nm, 530 nm, and 554 nm were measured and they show single exponential behavior for all the LiEr and MgEr glass series. From the photoluminescence and radiative decay lifetimes (τrad), we calculated the full-width at half-maximum (FWHM), emission cross-section (σPE) and bandwidth gain (FWHM × σPE) parameters. Near-infrared photoluminescence under 980 nm excitation was measured for all the LiEr and MgEr glass series in the region 1420-1620 nm. NIR emissions show a broadband centered at ∼1530 nm due to the transition of Er3+: 4I13/2 → 4I15/2. Decay lifetimes for NIR emission at ∼1530 nm were measured and they show a quite exponential nature for all the LiEr and MgEr glass series. From the NIR emission spectra and decay lifetimes, we calculated the full-width at half-maximum (FWHM), the emission cross-section (σPE) and the bandwidth gain (FWHM × σPE) for the NIR emission and it shows FWHM of 50-70 nm for prepared glasses, emission cross-section of (∼3.5) × 10-20 cm2, while bandwidth gain was (∼25) × 10-26 cm3.

Measurements of the Weak UV Absorptions of Isoprene and Acetone at 261–275 nm Using Cavity Ringdown Spectroscopy for Evaluation of a Potential Portable Ringdown Breath Analyzer

PubMed Central

Sahay, Peeyush; Scherrer, Susan T.; Wang, Chuji

2013-01-01

The weak absorption spectra of isoprene and acetone have been measured in the wavelength range of 261–275 nm using cavity ringdown spectroscopy. The measured absorption cross-sections of isoprene in the wavelength region of 261–266 nm range from 3.65 × 10−21 cm2·molecule−1 at 261 nm to 1.42 × 10−21 cm2·molecule−1 at 266 nm; these numbers are in good agreement with the values reported in the literature. In the longer wavelength range of 270–275 nm, however, where attractive applications using a single wavelength compact diode laser operating at 274 nm is located, isoprene has been reported in the literature to have no absorption (too weak to be detected). Small absorption cross-sections of isoprene in this longer wavelength region are measured using cavity ringdown spectroscopy for the first time in this work, i.e., 6.20 × 10−23 cm2·molecule−1 at 275 nm. With the same experimental system, wavelength-dependent absorption cross-sections of acetone have also been measured. Theoretical detection limits of isoprene and comparisons of absorbance of isoprene, acetone, and healthy breath gas in this wavelength region are also discussed. PMID:23803787

Hubble Space Telescope - New view of an ancient universe

NASA Technical Reports Server (NTRS)

Leckrone, David S.; Longair, Malcolm S.; Stockman, Peter; Olivier, Jean R.

1989-01-01

Scheduled for a March 1990 Shuttle launch, the Hubble Space Telescope (HST) will give astronomers a tool of unprecedented accuracy to observe the universe: an optically superb instrument free of the atmospheric turbulence, distortion, and brightness that plague all earthbound telescopes. The observatory will carry into orbit two cameras, a pair of spectrographs, a photometer, and fine guidance sensors optimized for astrometry. The diffraction limit for the 2.4-m aperture of the HST corresponds to 90 percent of the radiation from a point source falling within a circle of 0.1 arcsec angular radius at a wavelength of 633 nm. The 15-year mission will make observations in the ultraviolet as well as the optical spectral region, thus, widening the wavelength window to a range extending from the Lyman alpha wavelengnth of 122 nm to just about 2 microns. The observational program that awaits the HST will include the study of planetary atmospheres, in particular the search for aerosols; the study of globular star clusters within the Galaxy; and the determination of the present rate of expansion of the universe. The HST will achieve resolutions of 0.1 arcsec consistently, regardless of observation duration. The HST engineering challenge is also discussed.

Raman Scattering from Atmospheric Nitrogen in the Stratosphere

NASA Technical Reports Server (NTRS)

Garvey, M. J.; Kent, G. S.

1973-01-01

The Mark II laser radar system at Kingston, Jamaica, has been used to make observations on the Raman shifted line from atmospheric nitrogen at 828.5 nm. The size of the system makes it possible to detect signals from heights of up to 40 kilometres. The effects of aerosol scattering observed using a single wavelength are almost eliminated, and a profile of nitrogen density may be obtained. Assuming a constant mixing ratio, this may be interpreted as a profile of atmospheric density whose accuracy is comparable to that obtained from routine meteorological soundings. In order to obtain an accurate profile several interfering effects have had to be examined and, where necessary, eliminated. These include: 1) Fluorescence in optical components 2) Leakage of signal at 694.3 nm. 3) Overload effects and non-linearities in the receiving and counting electronics. Most of these effects have been carefully examined and comparisons are being made between the observed atmospheric density profiles and local meteorological radio-sonde measurements. Good agreement has been obtained over the region of overlap (15 - 30 KID), discrepancies being of the same order as the experimental accuracy (1-10%), depending on height and length of period of observation.

Retinoids, 585-nm laser, and carbon dioxide laser: a numeric comparison of neocollagen formation in photoaged hairless mouse skin.

PubMed

Lee, C J; Park, J H; Ciesielski, T E; Thomson, J G; Persing, J A

2008-11-01

A variety of new methods for treating photoaging have been recently introduced. There has been increasing interest in comparing the relative efficacy of multiple methods for photoaging. However, the efficacy of a single method is difficult to assess from the data reported in the literature. Photoaged hairless mice were randomly divided into seven treatment groups: control, retinoids (tretinoin and adapalene), lasers (585 nm and CO(2)), and combination groups (585 nm + adapalene and CO(2 )+ adapalene). Biopsies were taken from the treated regions, and the results were analyzed based on the repair zone. The repair zones of the various methods for photoaging were compared. Retinoids produced a wider repair zone than the control condition. The 585-nm and CO(2) laser resurfacing produced a result equivalent to that of the control condition. A combination of these lasers with adapalene produced a wider repair zone than the lasers alone, but the combination produced a result equivalent to that of adapalene alone. Retinoids are potent stimuli for neocollagen formation. The 585-nm or CO(2) laser alone did not induce more neocollagen than the control condition. In addition, no synergistic effect was observed with the combination treatments. The repair zone of the combination treatment is mainly attributable to adapalene.

Conductive atomic force microscopy measurements of nanopillar magnetic tunnel junctions

NASA Astrophysics Data System (ADS)

Evarts, E. R.; Hogg, C.; Bain, J. A.; Majetich, S. A.

2009-03-01

Magnetic tunnel junctions have been studied extensively for their magnetoresistance and potential uses in magnetic logic and data storage devices, but little is known about how their performance will scale with size. Here we examined the electronic behavior of 12 nm diameter magnetic tunnel junctions fabricated by a novel nanomasking process. Scanning electron microscopy images indicated feature diameter of 12 nm, and atomic force microscopy showed a height of 5 nm suggesting that unmasked regions have been milled on average to the oxide barrier layer, and areas should have the remnants of the free layer exposed with no remaining nanoparticle. Electrical contact was made to individual nanopillars using a doped-diamond-coated atomic force microscopy probe with a 40 nm radius of curvature at the tip. Off pillar we observed a resistance of 8.1 x 10^5 φ, while on pillar we found a resistance of 2.85 x 10^6 φ. Based on the RA product for this film, 120 φ-μm^2, a 12 nm diameter cylinder with perfect contact would have a resistance of 1.06 x 10^6 φ. The larger experimental value is consistent with a smaller contact area due to damaging the pillar during the ion milling process. The magnetoresistance characteristics of these magnetic tunnel junctions will be discussed.

Determination of phosphorus in steel by the combined technique of laser induced breakdown spectrometry with laser induced fluorescence spectrometry

NASA Astrophysics Data System (ADS)

Kondo, Hiroyuki; Hamada, Naoya; Wagatsuma, Kazuaki

2009-09-01

Laser induced breakdown spectrometry (LIBS) combined with laser induced fluorescence spectrometry (LIFS) has been applied for detection of trace-level phosphorus in steel. The plasma induced by irradiation of Nd:YAG laser pulse for ablation was illuminated by the 3rd harmonic of Ti:Sapphire laser tuned to one of the resonant lines for phosphorus in the wavelength region of 253-256 nm. An excitation line for phosphorus was selected to give the highest signal-to-noise ratio. Fluorescence signals, P213.62 and P214.91 nm, were observed with high selectivity at the contents as low as several tens µg g - 1 . Fluorescence intensities were in a good linear correlation with the contents. Fluorescence intensity ratio of a collisionally assisted line (213.62 nm) to a direct transition line (214.91 nm) was discussed in terms of the analytical conditions and experimental results were compared with a calculation based on rate equations. Since the fluorescence signal light in the wavelength range longer than 200 nm can be transmitted relatively easily, even through fiber optics of moderate length, LIBS/LIFS would be a versatile technique in on-site applications for the monitoring of phosphorus contents in steel.

Size dependence of magnetization switching and its dispersion of Co/Pt nanodots under the assistance of radio frequency fields

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

Furuta, Masaki, E-mail: furutam@mail.tagen.tohoku.ac.jp; Okamoto, Satoshi; Kikuchi, Nobuaki

2014-04-07

We have studied the dot size dependence of microwave assisted magnetization switching (MAS) on perpendicular magnetic Co/Pt multilayer dot array. The significant microwave assistance effect has been observed over the entire dot size D ranging from 50 nm to 330 nm examined in the present study. The MAS behavior, however, critically depends on D. The excitation frequency dependence of the switching field is well consistent with the spin wave theory, indicating that the magnetization precession in MAS is in accordance with the well defined eigenmodes depending on the dot diameter. The lowest order spin wave is only excited for D ≤ 100 nm, and thenmore » the MAS effect is well consistent with that of the single macrospin prediction. On the other hand, higher order spin waves are excited for D > 100 nm, giving rise to the significant enhancement of the MAS effect. The dispersion of MAS effect also depends on D and is significantly reduced for the region of D > 100 nm. This significant reduction of the dispersion is attributed to the essential feature of the MAS effect which is insensitive to the local fluctuation of anisotropy field, such as defect, damaged layer, and so on.« less

Surface plasmon resonance sensor based on photonic crystal fiber filled with gold-silica-gold multilayer nanoshells

NASA Astrophysics Data System (ADS)

Liu, Baolin; Lu, Ying; Yang, Xianchao; Yao, Jianquan

2017-12-01

We present a surface plasmon resonance sensor based on photonic crystal fiber filled with gold-silica-gold (GSG) multilayer nanoshells for measurement of the refractive index of liquid analyte. The GSG multilayer nanoshells, composed of a silica-coated gold nanosphere surrounded by a gold shell layer, are designed to be the functional material of the sensor because of their attractive optical properties. Two resonant peaks are obtained due to the hybridization of nanosphere plasmon modes and nanoshell plasmon modes. It is demonstrated that the resonant wavelength of the two peaks can be precisely tuned in 560-716 nm and 849-2485 nm, respectively, by varying the structural parameters of the GSG multilayer nanoshells in a compact, sub-200 nm size range. The excellent spectral tunability makes the sensor attractive in a wide range of applications, especially in biosensing in near-infrared region. Furthermore, the influences of the parameters on the performance of the sensor are systematically simulated and discussed. It is observed that the spectral sensitivities of 1894.3 nm/RIU and 3011.4 nm/RIU can be achieved respectively by the two resonant peaks in the sensing range of 1.33-1.38. The existence of two loss peaks also provides the possibility to realize self-reference in the sensing process.

Monochromatic imaging observation of sprites with the Reimei satellite

NASA Astrophysics Data System (ADS)

Sakanoi, T.; Adachi, T.; Sato, M.; Yamazaki, A.; Asamura, K.; Hirahara, M.

2012-12-01

The sprite emission is characterized by vertically extending fine structures (called as streamer, halo, etc.) in the approximate altitude range from 40 to 90 km. Satellite observation is useful to investigate the global distributions of sprite since an optical instrument on a satellite can measure the sprite in the wide range without atmospheric absorption. However, the sprite has been measured mainly by ground-based instruments, and there is no monochromatic imaging data from space. The multi-spectral camera (MAC) on Reimei was originally designed to measure auroral emissions in the polar region taking the monochromatic images at wavelengths of 428 nm, 558 nm, and 670 nm. Since March 2008, MAC has been operated in the mid- and low-latitudes viewing the limb direction with an exposure time of 957 ms to measure the monochromatic image of sprite emission. The spatial resolution at a tangential point is approximately 4 km. According to the noon-midnight sun-synchronous orbit of Reimei at an altitude of 640 km, the observation is made around the midnight sector. So far, we found seven sprits events in N2 1P (670 nm) images, and on six events the simultaneous observations between N2+ 1N (428nm) and N2 1P were performed. The electron temperature and electric field associated with a sprite can be estimated from the intensity ratio between emission of N2+ 1N and that of N2 1P. However, we did not obtain the N2+ 1N emission intensity due to the low sensitivity of 428 nm channel of MAC. Therefore, the N2+ 1N intensities of sprites are estimated to be less than the noise level (26 - 54 R), while the measured N2 1P intensities of sprites are 2.9 - 3.6 kR. Using these data, we estimated the upper limit of electron temperature and electric field associated with sprites. The altitude of sprite emission was accurately determined with the satellite attitude data and the field-of-view direction of MAC. On the 2008 Sep.2 case, we obtained sprite events at 26.6 GLAT and 107.6 GELON, and determined its height range from 47 to 81 km. In this presentation, we report the estimation of temperatures and electric fields associated with the sprite events.

Ionospheric variations during sudden stratospheric warming in the high- and mid-latitude regions

NASA Astrophysics Data System (ADS)

Yasyukevich, Anna; Voeykov, Sergey; Mylnikova, Anna

2017-04-01

The ionospheric dynamic in the high- and middle-latitude regions during the periods of sudden stratospheric warmings (SSW) was studied by using the international network of phase dual-frequency GPS/GLONASS receivers and the vertical sounding data. Twelve SSW events that occurred in the Northern Hemisphere 2006 through 2013 were considered. In order to identify the possible response of the ionosphere to SSW events, we carried out the analysis of the total electron (TEC) and the F2-layer maximum electron density (NmF2) deviations from the background level. We have also studied changes of the level of total electron content (TEC) wave-like variations characterized by a special index WTEC. The index reflects the intensity of medium- and large-scale traveling ionospheric disturbances. The dynamics of the high- and middle-latitude ionosphere at the points near the SSW areas was found to differ from the regular. For a large number of events, it is shown that, despite quiet geomagnetic conditions, a noticeable decrease in the NmF2 and TEC values (by 5-10% relative to the background level) is observed during the SSW evolution and maximum stages. On the contrary, for 10-20 days after the SSW maxima, NmF2 and TEC significantly exceed the monthly averaged values. Moreover, these electron density changes are observed for both strong and weak stratospheric warmings, and are recorded mainly during daytime. The observed SSW effects in the polar and mid-latitude ionosphere are assumed to be probably associated with the changes in the neutral composition at the thermospheric heights that affect the F2-layer electron density. The study is supported by the Russian Foundation for Basic Research under Grant No. 16-35-60018, as well as by the RF President Grant of Public Support for RF Leading Scientific Schools (NSh-6894.2016.5).

An optimal-estimation-based aerosol retrieval algorithm using OMI near-UV observations

NASA Astrophysics Data System (ADS)

Jeong, U.; Kim, J.; Ahn, C.; Torres, O.; Liu, X.; Bhartia, P. K.; Spurr, R. J. D.; Haffner, D.; Chance, K.; Holben, B. N.

2016-01-01

An optimal-estimation(OE)-based aerosol retrieval algorithm using the OMI (Ozone Monitoring Instrument) near-ultraviolet observation was developed in this study. The OE-based algorithm has the merit of providing useful estimates of errors simultaneously with the inversion products. Furthermore, instead of using the traditional look-up tables for inversion, it performs online radiative transfer calculations with the VLIDORT (linearized pseudo-spherical vector discrete ordinate radiative transfer code) to eliminate interpolation errors and improve stability. The measurements and inversion products of the Distributed Regional Aerosol Gridded Observation Network campaign in northeast Asia (DRAGON NE-Asia 2012) were used to validate the retrieved aerosol optical thickness (AOT) and single scattering albedo (SSA). The retrieved AOT and SSA at 388 nm have a correlation with the Aerosol Robotic Network (AERONET) products that is comparable to or better than the correlation with the operational product during the campaign. The OE-based estimated error represented the variance of actual biases of AOT at 388 nm between the retrieval and AERONET measurements better than the operational error estimates. The forward model parameter errors were analyzed separately for both AOT and SSA retrievals. The surface reflectance at 388 nm, the imaginary part of the refractive index at 354 nm, and the number fine-mode fraction (FMF) were found to be the most important parameters affecting the retrieval accuracy of AOT, while FMF was the most important parameter for the SSA retrieval. The additional information provided with the retrievals, including the estimated error and degrees of freedom, is expected to be valuable for relevant studies. Detailed advantages of using the OE method were described and discussed in this paper.

An Optimal-Estimation-Based Aerosol Retrieval Algorithm Using OMI Near-UV Observations

NASA Technical Reports Server (NTRS)

Jeong, U; Kim, J.; Ahn, C.; Torres, O.; Liu, X.; Bhartia, P. K.; Spurr, R. J. D.; Haffner, D.; Chance, K.; Holben, B. N.

2016-01-01

An optimal-estimation(OE)-based aerosol retrieval algorithm using the OMI (Ozone Monitoring Instrument) near-ultraviolet observation was developed in this study. The OE-based algorithm has the merit of providing useful estimates of errors simultaneously with the inversion products. Furthermore, instead of using the traditional lookup tables for inversion, it performs online radiative transfer calculations with the VLIDORT (linearized pseudo-spherical vector discrete ordinate radiative transfer code) to eliminate interpolation errors and improve stability. The measurements and inversion products of the Distributed Regional Aerosol Gridded Observation Network campaign in northeast Asia (DRAGON NE-Asia 2012) were used to validate the retrieved aerosol optical thickness (AOT) and single scattering albedo (SSA). The retrieved AOT and SSA at 388 nm have a correlation with the Aerosol Robotic Network (AERONET) products that is comparable to or better than the correlation with the operational product during the campaign. The OEbased estimated error represented the variance of actual biases of AOT at 388 nm between the retrieval and AERONET measurements better than the operational error estimates. The forward model parameter errors were analyzed separately for both AOT and SSA retrievals. The surface reflectance at 388 nm, the imaginary part of the refractive index at 354 nm, and the number fine-mode fraction (FMF) were found to be the most important parameters affecting the retrieval accuracy of AOT, while FMF was the most important parameter for the SSA retrieval. The additional information provided with the retrievals, including the estimated error and degrees of freedom, is expected to be valuable for relevant studies. Detailed advantages of using the OE method were described and discussed in this paper.

Observations of rock spectral classes by the Opportunity rover's Pancam on northern Cape York and on Matijevic Hill, Endeavour Crater, Mars

NASA Astrophysics Data System (ADS)

Farrand, W. H.; Bell, J. F.; Johnson, J. R.; Rice, M. S.; Jolliff, B. L.; Arvidson, R. E.

2014-11-01

The Opportunity rover's exploration of the portion of the rim of Endeavour crater known as Cape York included examination of the sulfate-bearing Grasberg formation and the Matijevic Hill region. Multispectral visible and near-infrared (VNIR) Pancam observations were used to characterize reflectance properties of rock units. Using spectral end-member detection and classification approaches including a principal components/n-dimensional visualization, automatic sequential maximum angle convex cone method, and classification through hierarchical clustering, six main spectral classes of rock surfaces were identified: light-toned veins, Grasberg fm., the smectite-bearing Matijevic formation, the hematitic "blueberry" spherules, resistant spherules within the Matijevic fm. dubbed "newberries," and the Shoemaker formation impact breccia. Some of these could be divided into spectral subclasses. There were three types of veins: veins in the bench unit of Cape York, thinner veins in the Matijevic fm., and boxwork pattern-forming veins. The bench unit veins had higher 535 nm band depths than the other two vein subclasses and a steeper 934 to 1009 nm slope. The Grasberg fm. has VNIR spectral features that are interpreted to indicate higher fractions of red hematite than in the sulfate-bearing Burns Fm. The Matijevic fm. includes both light-toned, fine-grained matrix, and dark-toned veneers. The latter has a weak near-infrared absorption band centered near 950 nm consistent with nontronite. Observations of Rock Abrasion Tool brushed and ground newberries indicated that cuttings from the RAT grind had a longer wavelength reflectance maximum and deeper 535 nm band depth, consistent with more oxidized materials. Greater oxidation of cementing materials in the newberries is consistent with a diagenetic concretion origin.

Involvement of microtubules and 10-nm filaments in the movement and positioning of nuclei in syncytia

PubMed Central

1979-01-01

Previous studies (Holmes, K.V., and P.W. Choppin. J. Exp. Med. 124:501- 520; J. Cell Biol. 39:526-543) showed that infection of baby hamster kidney (BHK21-F) cells with the parainfluenza virus SV5 causes extensive cell fusion, that nuclei migrate in the syncytial cytoplasm and align in tightly-packed rows, and that microtubules are involved in nuclear movement and alignment. The role of microtubules, 10-nm filaments, and actin-containing microfilaments in this process has been investigated by immunofluorescence microscopy using specific antisera, time-lapse cinematography, and electron microscopy. During cell fusion, micro tubules and 10-nm filaments from many cells form large bundles which are localized between rows of nuclei. No organized bundles of actin fibers were detected in these areas, although actin fibers were observed in regions away from the aligned nuclei. Although colchicine disrupts microtubules and inhibits nuclear movement, cytochalasin B (CB; 20-50 microgram/ml) does not inhibit cell fusion or nuclear movement. However, CB alters the shape of the syncytium, resulting in long filamentous processes extending from a central region. When these processes from neighboring cells make contact, fusion occurs, and nuclei migrate through the channels which are formed. Electron and immunofluorescence microscopy reveal bundles of microtubules and 10-nm filaments in parallel arrays within these processes, but no bundles of microfilaments were detected. The effect of CB on the structural integrity of microfilaments at this high concentration (20 microgram/ml) was demonstrated by the disappearance of filaments interacting with heavy meromyosin. Cycloheximide (20 microgram/ml) inhibits protein synthesis but does not affect cell fusion, the formation of microtubules and 10-nm filament bundles, or nuclear migration and alignment; thus, continued protein synthesis is not required. The association of microtubules and 10-nm filaments with nuclear migration and alignment suggests that microtubules and 10-nm filaments are two components in a system which serves both cytoskeletal and force-generating functions in intracellular movement and position of nuclei. PMID:227913

Internal quantum efficiency and carrier dynamics in semipolar (2021) InGaN/GaN light-emitting diodes

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

Okur, Serdal; Nami, Mohsen; Rishinaramangalam, Ashwin K.

Here, the internal quantum efficiencies (IQE) and carrier lifetimes of semipolar (more » $$20\\bar{2}$$$\\bar{1}$$) InGaN/GaN LEDs with different active regions are measured using temperature-dependent, carrier-density-dependent, and time-resolved photoluminescence. Three active regions are investigated: one 12-nm-thick single quantum well (SQW), two 6-nm-thick QWs, and three 4-nm-thick QWs. The IQE is highest for the 12-nm-thick SQW and decreases as the well width decreases. The radiative lifetimes are similar for all structures, while the nonradiative lifetimes decrease as the well width decreases. The superior IQE and longer nonradiative lifetime of the SQW structure suggests using thick SQW active regions for high brightness semipolar ($$20\\bar{2}$$$\\bar{1}$$) LEDs.« less

Internal quantum efficiency and carrier dynamics in semipolar (2021) InGaN/GaN light-emitting diodes

DOE PAGES

Okur, Serdal; Nami, Mohsen; Rishinaramangalam, Ashwin K.; ...

2017-01-26

Here, the internal quantum efficiencies (IQE) and carrier lifetimes of semipolar (more » $$20\\bar{2}$$$\\bar{1}$$) InGaN/GaN LEDs with different active regions are measured using temperature-dependent, carrier-density-dependent, and time-resolved photoluminescence. Three active regions are investigated: one 12-nm-thick single quantum well (SQW), two 6-nm-thick QWs, and three 4-nm-thick QWs. The IQE is highest for the 12-nm-thick SQW and decreases as the well width decreases. The radiative lifetimes are similar for all structures, while the nonradiative lifetimes decrease as the well width decreases. The superior IQE and longer nonradiative lifetime of the SQW structure suggests using thick SQW active regions for high brightness semipolar ($$20\\bar{2}$$$\\bar{1}$$) LEDs.« less

Crystal Initiation Structures in Developing Enamel: Possible Implications for Caries Dissolution of Enamel Crystals

PubMed Central

Robinson, Colin; Connell, Simon D.

2017-01-01

Investigations of developing enamel crystals using Atomic and Chemical Force Microscopy (AFM, CFM) have revealed a subunit structure. Subunits were seen in height images as collinear swellings about 30 nM in diameter on crystal surfaces. In friction mode they were visible as positive regions. These were similar in size (30–50 nM) to collinear spherical structures, presumably mineral matrix complexes, seen in developing enamel using a freeze fracturing/freeze etching procedure. More detailed AFM studies on mature enamel suggested that the 30–50 nM structures were composed of smaller units, ~10–15 nM in diameter. These were clustered in hexagonal or perhaps a spiral arrangement. It was suggested that these could be the imprints of initiation sites for mineral precipitation. The investigation aimed at examining original freeze etched images at high resolution to see if the smaller subunits observed using AFM in mature enamel were also present in developing enamel i.e., before loss of the organic matrix. The method used was freeze etching. Briefly samples of developing rat enamel were rapidly frozen, fractured under vacuum, and ice sublimed from the fractured surface. The fractured surface was shadowed with platinum or gold and the metal replica subjected to high resolution TEM. For AFM studies high-resolution tapping mode imaging of human mature enamel sections was performed in air under ambient conditions at a point midway between the cusp and the cervical margin. Both AFM and freeze etch studies showed structures 30–50 nM in diameter. AFM indicated that these may be clusters of somewhat smaller structures ~10–15 nM maybe hexagonally or spirally arranged. High resolution freeze etching images of very early enamel showed ~30–50 nM spherical structures in a disordered arrangement. No smaller units at 10–15 nM were clearly seen. However, when linear arrangements of 30–50 nM units were visible the picture was more complex but also smaller units including ~10–15 nM units could be observed. Conclusions: Structures ~10–15 nM in diameter were detected in developing enamel. While the appearance was complex, these were most evident when the 30–5 nM structures were in linear arrays. Formation of linear arrays of subunits may be associated with the development of mineral initiation sites and attendant processing of matrix proteins. PMID:28670283

UV/vis and NIR light-responsive spiropyran self-assembled monolayers.

PubMed

Ivashenko, Oleksii; van Herpt, Jochem T; Feringa, Ben L; Rudolf, Petra; Browne, Wesley R

2013-04-02

Self-assembled monolayers of a 6-nitro BIPS spiropyran (SP) modified with a disulfide-terminated aliphatic chain were prepared on polycrystalline gold surfaces and characterized by UV/vis absorption, surface-enhanced Raman scattering (SERS), and X-ray photoelectron spectroscopies (XPS). The SAMs obtained are composed of the ring-closed form (i.e., spiropyran) only. Irradiation with UV light results in conversion of the monolayer to the merocyanine form (MC), manifested in the appearance of an N(+) contribution in the N 1s region of the XPS spectrum of the SAMs, the characteristic absorption band of the MC form in the visible region at 555 nm, and the C-O stretching band in the SERS spectrum. Recovery of the initial state of the monolayer was observed both thermally and after irradiation with visible light. Several switching cycles were performed and monitored by SERS spectroscopy, demonstrating the stability of the SAMs during repeated switching between SP and MC states. A key finding in the present study is that ring-opening of the surface-immobilized spiropyrans can be induced by irradiation with continuous wave NIR (785 nm) light as well as by irradiation with UV light. We demonstrate that ring-opening by irradiation at 785 nm proceeds by a two-photon absorption pathway both in the SAMs and in the solid state. Hence, spiropyran SAMs on gold can undergo reversible photochemical switching from the SP to the MC form with both UV and NIR and the reverse reaction induced by irradiation with visible light or heating. Furthermore, the observation of NIR-induced switching with a continuous wave source holds important consequences in the study of photochromic switches on surfaces using SERS and emphasizes the importance of the use of multiple complementary techniques in characterizing photoresponsive SAMs.

Vertical distribution of aerosol optical properties based on aircraft measurements over the Loess Plateau in China.

PubMed

Li, Junxia; Liu, Xingang; Yuan, Liang; Yin, Yan; Li, Zhanqing; Li, Peiren; Ren, Gang; Jin, Lijun; Li, Runjun; Dong, Zipeng; Li, Yiyu; Yang, Junmei

2015-08-01

Vertical distributions of aerosol optical properties based on aircraft measurements over the Loess Plateau were measured for the first time during a summertime aircraft campaign, 2013 in Shanxi, China. Data from four flights were analyzed. The vertical distributions of aerosol optical properties including aerosol scattering coefficients (σsc), absorption coefficients (σab), Angström exponent (α), single scattering albedo (ω), backscattering ratio (βsc), aerosol mass scattering proficiency (Qsc) and aerosol surface scattering proficiency (Qsc(')) were obtained. The mean statistical values of σsc were 77.45 Mm(-1) (at 450 nm), 50.72 Mm(-1) (at 550n m), and 32.02 Mm(-1) (at 700 nm). The mean value of σab was 7.62 Mm(-1) (at 550 nm). The mean values of α, βsc and ω were 1.93, 0.15, and 0.91, respectively. Aerosol concentration decreased with altitude. Most effective diameters (ED) of aerosols were less than 0.8 μm. The vertical profiles of σsc,, α, βsc, Qsc and Qsc(') showed that the aerosol scattering properties at lower levels contributed the most to the total aerosol radiative forcing. Both α and βsc had relatively large values, suggesting that most aerosols in the observational region were small particles. The mean values of σsc, α, βsc, Qsc, Qsc('), σab and ω at different height ranges showed that most of the parameters decreased with altitude. The forty-eight hour backward trajectories of air masses during the observation days indicated that the majority of aerosols in the lower level contributed the most to the total aerosol loading, and most of these particles originated from local or regional pollution emissions. Copyright © 2015. Published by Elsevier B.V.

Spectroscopic study of Pr3+ ions doped Zinc Lead Tungsten Tellurite glasses for visible photonic device applications

NASA Astrophysics Data System (ADS)

Sharma, Ritu; Rao, A. S.; Deopa, Nisha; Venkateswarlu, M.; Jayasimhadri, M.; Haranath, D.; Prakash, G. Vijaya

2018-04-01

Zinc Lead Tungsten Tellurite (ZnPbWTe) glasses doped with different Pr3+ ion concentrations having the composition 5ZnO + 15PbO + 20WO3 + (60-x)TeO2 + xPr6O11 (where x = 0.5, 1, 1.5, 2.0 and 2.5 mol%) were prepared by using sudden quenching technique and characterized to understand their visible emission characteristic features using spectroscopic techniques such as absorption, excitation and emission. The Judd-Ofelt (J-O) theory has been applied to the absorption spectral features with an aim to evaluate various radiative properties for the prominent fluorescent levels of Pr3+ions in the as-prepared glasses. The emission spectra recorded for the as-prepared glasses under 468 nm excitation show three prominent emission transitions 3P0→3H6, 3P0→3F2 and 3P1→3F4, of which 3P0→3F2 observed in visible red region (648 nm), is relatively more intense. The intensity of 3P0→3F2 emission transition in the titled glasses increases up to 1mol% of Pr3+ ions and beyond concentration quenching is observed. Branching ratios (βR) and emission cross-sections (σse) were estimated for 3P0→3F2 transition to understand the luminescence efficiency in visible red region (648 nm). The CIE chromaticity coordinates were also evaluated in order to understand the suitability of these glasses for visible red luminescence devices. From the emission cross-sections, quantum efficiency and CIE coordinates, it was concluded that 1mol% of Pr3+ ions in ZnPbWTe glasses are quite suitable for preparing visible reddish orange luminescent devices.

Synthesis, structure, optical, photoluminescence and magnetic properties of K2[Co(C2O4)2(H2O)2]·4H2O

NASA Astrophysics Data System (ADS)

Narsimhulu, M.; Hussain, K. A.

2018-06-01

The synthesis, crystal structure, optical, photoluminescence and magnetic behaviour of potassium bis(oxalato)cobaltate(II)tertrahydrate{K2[Co(C2O4)2(H2O)2]·4H2O} are described. The compound was grown at room temperature from mixture of aqueous solutions by slow evaporation method. The X-ray crystallographic data showed that the compound belongs to the monoclinic crystal system with P21/n space group and Z = 4. The UV-visible diffuse absorbance spectra exhibited bands at 253, 285 and 541 nm in the visible and ultraviolet regions. The optical band gap of the compound was estimated as 3.4 eV. At room temperature, an intense photoluminescence was observed from this material around 392 nm when it excited at 254 nm. The variable temperature dc magnetic susceptibility measurements exposed paramagnetic behaviour at high temperatures and antiferromagnetic ordering at low temperatures.

Denaturing of single electrospun fibrinogen fibers studied by deep ultraviolet fluorescence microscopy.

PubMed

Kim, Jeongyong; Song, Hugeun; Park, Inho; Carlisle, Christine R; Bonin, Keith; Guthold, Martin

2011-03-01

Deep ultraviolet (DUV) microscopy is a fluorescence microscopy technique to image unlabeled proteins via the native fluorescence of some of their amino acids. We constructed a DUV fluorescence microscope, capable of 280 nm wavelength excitation by modifying an inverted optical microscope. Moreover, we integrated a nanomanipulator-controlled micropipette into this instrument for precise delivery of picoliter amounts of fluid to selected regions of the sample. In proof-of-principle experiments, we used this instrument to study, in situ, the effect of a denaturing agent on the autofluorescence intensity of single, unlabeled, electrospun fibrinogen nanofibers. Autofluorescence emission from the nanofibers was excited at 280 nm and detected at ∼350 nm. A denaturant solution was discretely applied to small, select sections of the nanofibers and a clear local reduction in autofluorescence intensity was observed. This reduction is attributed to the dissolution of the fibers and the unfolding of proteins in the fibers. Copyright © 2010 Wiley-Liss, Inc.

Efficient continuous-wave, broadly tunable and passive Q-switching lasers based on a Tm3+:CaF2 crystal

NASA Astrophysics Data System (ADS)

Liu, Jingjing; Zhang, Cheng; Zu, Yuqian; Fan, Xiuwei; Liu, Jie; Guo, Xinsheng; Qian, Xiaobo; Su, Liangbi

2018-04-01

Laser operations in the continuous-wave as well as in the pulsed regime of a 4 at.% Tm3+:CaF2 crystal are reported. For the continuous-wave operation, a maximum average output power of 1.15 W was achieved, and the corresponding slope efficiency was more than 64%. A continuous tuning range of about 160 nm from 1877-2036 nm was achieved using a birefringent filter. Using Argentum nanorods as a saturable absorber, the significant pulsed operation of a passively Q-switched Tm3+:CaF2 laser was observed at 1935.4 nm for the first time, to the best of our knowledge. A maximum output power of 385 mW with 41.4 µJ pulse energy was obtained under an absorbed pump power of 2.04 W. The present results indicate that the Tm3+:CaF2 lasers could be promising laser sources to operate in the eye-safe spectral region.

Detection of hidden mineral deposits by airborne spectral analysis of forest canopies. [Spirit Lake, Washington; Catheart Mountain, Maine; Blacktail Mountain, Montana; and Cotter Basin, Montana

NASA Technical Reports Server (NTRS)

Collins, W.; Chang, S. H.; Kuo, J. T.

1984-01-01

Data from field surveys and biogeochemical tests conducted in Maine, Montana, and Washington strongly correlate with results obtained using high resolution airborne spectroradiometer which detects an anomalous spectral waveform that appears definitely associated with sulfide mineralization. The spectral region most affected by mineral stress is between 550 nm and 750 nm. Spectral variations observed in the field occur on the wings of the red chlorophyll band centered at about 690 nm. The metal-stress-induced variations on the absorption band wing are most successfully resolved in the high spectral resolution field data using a waveform analysis technique. The development of chlorophyll pigments was retarded in greenhouse plants doped with copper and zinc in the laboratory. The lowered chlorophyll production resulted in changes on the wings of the chlorophyll bands of reflectance spectra of the plants. The airborne spectroradiometer system and waveform analysis remains the most sensitive technique for biogeochemical surveys.

ZrO2:Sm3+ nanophosphor: synthesis, Rietveld refinement, optical and thermoluminescent properties

NASA Astrophysics Data System (ADS)

Ponkumar, S.; Janaki, K.; Prakashbabu, D.; Ramalingam, H. B.; Munirathnam, K.; Sreekanth, T. V. M.; Dhoble, S. J.

2018-02-01

We have synthesized undoped and Sm3+ ions doped ZrO2 nanophosphors by solution combustion method. These nanophosphors crystallized in cubic structure. Rietveld refinement of the samples was performed to estimate lattice parameters. Spherical particles with the sizes of 10-25 nm were observed by transmission electron microscopy. Photoluminescence and thermoluminescence (TL) properties of samples were investigated. Under 400 nm excitation, the nanophosphors have intense red emission at 600 nm. The color coordinates (0.67, 0.33) were located in the red region of CIE diagram. TL properties of nanophosphors were studied by exposing the samples to γ-rays. 5 mol% Sm3+ doped ZrO2 nanophosphor has shown maximum TL intensity after γ-irradiation. To test suitability of the nanophosphors for practical application in dosimetry, the 5 mol% Sm3+ doped ZrO2 sample was irradiated by 14 MeV electron beam in various electron fluence ranging from 100 to 900 Gy and their TL response was recorded.

Arsenic- and selenium-induced changes in spectral reflectance and morphology of soybean plants

USGS Publications Warehouse

Milton, N.M.; Ager, C.M.; Eiswerth, B.A.; Power, M.S.

1989-01-01

Soybean (Glycine max) plants were grown in hydroponic solutions treated with high concentrations of either arsenic or selenium. Spectral reflectance changes in arsenic-dosed plants included a shift to shorter wavelengths in the long-wavelength edge of the chlorophyll absorption band centered at 680 nm (the red edge) and higher reflectance in the 550-650 nm region. These results are consistent with vegetation reflectance anomalies observed in previous greenhouse experiments and in airborne radiometer studies. The selenium-dosed plants contrast, exhibited a shift to longer wavelengths of the red edge and lower reflectance between 550 nm and 650 wh when compared with control plants. Morphological effects of arsenic uptake included lower overall biomass, stunted and discolored roots, and smaller leaves oriented more vertically than leaves of control plants. Selenium-dosed plants also displayed morphological changes, but root and leaf biomass were less affected than were those of arsenic-dosed plants when compared to control plants. ?? 1989.

Packaging-induced failure of semiconductor lasers and optical telecommunications components

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

Sharps, J.A.

1996-12-31

Telecommunications equipment for field deployment generally have specified lifetimes of > 100,000 hr. To achieve this high reliability, it is common practice to package sensitive components in hermetic, inert gas environments. The intent is to protect components from particulate and organic contamination, oxidation, and moisture. However, for high power density 980 nm diode lasers used in optical amplifiers, the authors found that hermetic, inert gas packaging induced a failure mode not observed in similar, unpackaged lasers. They refer to this failure mode as packaging-induced failure, or PIF. PIF is caused by nanomole amounts of organic contamination which interact with highmore » intensity 980 nm light to form solid deposits over the emitting regions of the lasers. These deposits absorb 980 nm light, causing heating of the laser, narrowing of the band gap, and eventual thermal runaway. The authors have found PIF is averted by packaging with free O{sub 2} and/or a getter material that sequesters organics.« less

Effect of pH on ionic liquid mediated synthesis of gold nanoparticle using elaiseguineensis (palm oil) kernel extract

NASA Astrophysics Data System (ADS)

Irfan, Muhammad; Ahmad, Tausif; Moniruzzaman, Muhammad; Abdullah, Bawadi

2017-05-01

This study was conducted for microwave assisted synthesis of stable gold nanoparticles (AuNPs) by reduction of chloroauric acid with Elaeis Guineensis (palm oil) kernel (POK) extract which was prepared in aqueous solution of ionic liquid, [EMIM][OAc], 1-Ethyl-3-methylimidazolium acetate. Effect of initial pH of reaction mixture (3.5 - 8.5) was observed on SPR absorbance, maximum wavelength (λmax ) and size distribution of AuNPs. Change of pH of reaction mixture from acidic to basic region resulted in appearance of strong SPR absorption peaks and blue shifting of λmax from 533 nm to 522 nm. TEM analysis revealed the formation of predominantly spherical AuNPs with mean diameter of 8.51 nm. Presence of reducing moieties such as flavonoids, phenolic and carboxylic groups in POK extract was confirmed by FTIR analysis. Colloidal solution of AuNPs was remained stable at room temperature and insignificant difference in zeta value was recorded within experimental tenure of 4 months.

Blueish green photoluminescence from nitrided GaAs(100) surfaces

NASA Astrophysics Data System (ADS)

Shimaoka, Goro; Udagawa, Takashi

1999-04-01

Optical and structural studies were made on the Si-doped (100)GaAs surfaces nitrided at a temperature between 650° and 750°C for 15 min in the flowing NH 3 gas. The wavelength of photoluminescence (PL) spectra were observed to be shortened from 820 nm of the GaAs nitrided at 650°C with increasing nitridation temperature. Blueish green PL with wavelengths of approx. 490 nm and 470 nm were emitted from the nitrided surfaces at 700° and 750°C, respectively. Results of AES and SIMS indicated that the surfaces are nitrided as GaAs 1- xN x, (0< x≤1) alloy layer, and the nitrided region also tended to increase as the temperature raised. High-resolution transmission electron microscopic (HRTEM), transmission electron diffraction (TED) and energy dispersive X-ray (EDX) results showed that films peeled off from the nitrided surfaces consisted mainly of hexagonal, wurtzite-type gallium nitride (GaN) with stacking faults and microtwins.

Laser-induced autofluorescence properties of base-cell lesions: analysis and algorithms for diagnosis and differentiation

NASA Astrophysics Data System (ADS)

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

2006-09-01

The goals of this work were investigation of base-cell skin lesions by the method of laser-induced autofluorescence spectroscopy. Fluorescence spectra were obtained from benign base-cell papilloma and malignant base-cell carcinoma, as well as from healthy skin areas near to the lesions that were used posteriori to reveal changes between healthy and lesion skin spectra. Preliminarily lesions were classified by dermatoscopic method (MoleMax II, DERMA Instruments). All suspicious lesions were excised and were investigated histologically. The experimental set-up consists of a nitrogen laser (337 nm, 14 μJ, 10 Hz), lenses, filters, optical fibers, and a microspectrometer (PC2000, "Ocean Optics"). A computer controls this system. Spectrum of healthy skin consists of one main maximum at 470-500 nm spectral region and secondary maxima at in the regions around 400 and 440 nm. In cases of papilloma and base-cell carcinoma an intensity decrease was observed, related to accumulation of pigments in these cutaneous lesions. An relative increase of the fluorescence peak at 440 nm were registered in the case of base-cell carcinoma, related to metabolism activity increase, and appearance of green fluorescence, related to increase of keratin content in benign papilloma lesions were detected. The results, obtained were used to develop multispectral diagnostic algorithm of these base-cell lesions. An sensitivity of 89,4% and 91,0% and specificity of 99,6% and 97,4% for differentiation between normal skin and papilloma and carcinoma respectively were obtained. The capability of the human skin fluorescence spectroscopy for early diagnosis and differentiation of cutaneous lesions is shown.

An observationally constrained estimate of global dust aerosol optical depth

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

Ridley, David A.; Heald, Colette L.; Kok, Jasper F.

Here, the role of mineral dust in climate and ecosystems has been largely quantified using global climate and chemistry model simulations of dust emission, transport, and deposition. However, differences between these model simulations are substantial, with estimates of global dust aerosol optical depth (AOD) that vary by over a factor of 5. Here we develop an observationally based estimate of the global dust AOD, using multiple satellite platforms, in situ AOD observations and four state-of-the-science global models over 2004–2008. We estimate that the global dust AOD at 550 nm is 0.030 ± 0.005 (1σ), higher than the AeroCom model medianmore » (0.023) and substantially narrowing the uncertainty. The methodology used provides regional, seasonal dust AOD and the associated statistical uncertainty for key dust regions around the globe with which model dust schemes can be evaluated. Exploring the regional and seasonal differences in dust AOD between our observationally based estimate and the four models in this study, we find that emissions in Africa are often overrepresented at the expense of Asian and Middle Eastern emissions and that dust removal appears to be too rapid in most models.« less

An observationally constrained estimate of global dust aerosol optical depth

DOE PAGES

Ridley, David A.; Heald, Colette L.; Kok, Jasper F.; ...

2016-12-06

Here, the role of mineral dust in climate and ecosystems has been largely quantified using global climate and chemistry model simulations of dust emission, transport, and deposition. However, differences between these model simulations are substantial, with estimates of global dust aerosol optical depth (AOD) that vary by over a factor of 5. Here we develop an observationally based estimate of the global dust AOD, using multiple satellite platforms, in situ AOD observations and four state-of-the-science global models over 2004–2008. We estimate that the global dust AOD at 550 nm is 0.030 ± 0.005 (1σ), higher than the AeroCom model medianmore » (0.023) and substantially narrowing the uncertainty. The methodology used provides regional, seasonal dust AOD and the associated statistical uncertainty for key dust regions around the globe with which model dust schemes can be evaluated. Exploring the regional and seasonal differences in dust AOD between our observationally based estimate and the four models in this study, we find that emissions in Africa are often overrepresented at the expense of Asian and Middle Eastern emissions and that dust removal appears to be too rapid in most models.« less

Investigation of the bandwidth of multimode optical fibers used with 1550-nm LED and laser sources

NASA Technical Reports Server (NTRS)

White, Preston A., III

1992-01-01

Multimode optical fibers are not intended to be used with 1550-nm sources; however, it is desirable to utilize 1300/1550-nm wavelength division multiplexing (WDM) on some multimode fibers at Kennedy Space Center (KSC). No information from fiber vendors nor from the literature is available to support this use. Preliminary studies at KSC have suggested that these fibers might be usable at 1550-nm if the fibers possessed enough bandwidth when sourced by LEDs. Detailed bandwidth studies were made on 12 multimode fibers using 1300- and 1550-nm lasers and LEDs. The results showed that the modal bandwidth at 1550-nm was about 50 percent of the 1300-nm value and that the chromatic dispersion could be predicted by extrapolating the vendor's specifications for wavelengths outside the 1550-nm region. Utilizing these data, predictions of the fiber's optical bandwidth were accurately made. Problems with launch conditions and possible differential attenuation at connectors was noted at 1300-nm but was less significant at 1550-nm. It appears that the multimode fibers studied will offer adequate performance in the 1550-nm region for a number of current KSC needs. Studies of additional fibers are encouraged to gain more confidence and better understanding of the 1550-nm bandwidth of KSC's multimode optical fibers before committing to 1300/1550-nm WDM.

Mechanical Strength and Broadband Transparency Improvement of Glass Wafers via Surface Nanostructures.

PubMed

Kumar, Amarendra; Kashyap, Kunal; Hou, Max T; Yeh, J Andrew

2016-06-17

In this study, we mechanically strengthened a borosilicate glass wafer by doubling its bending strength and simultaneously enhancing its transparency using surface nanostructures for different applications including sensors, displays and panels. A fabrication method that combines dry and wet etching is used for surface nanostructure fabrication. Specifically, we improved the bending strength of plain borosilicate glass by 96% using these surface nanostructures on both sides. Besides bending strength improvement, a limited optical transmittance enhancement of 3% was also observed in the visible light wavelength region (400-800 nm). Both strength and transparency were improved by using surface nanostructures of 500 nm depth on both sides of the borosilicate glass without affecting its bulk properties or the glass manufacturing process. Moreover, we observed comparatively smaller fragments during the breaking of the nanostructured glass, which is indicative of strengthening. The range for the nanostructure depth is defined for different applications with which improvements of the strength and transparency of borosilicate glass substrate are obtained.

SrAl2O4:Eu2+ (1%) luminescence under UV, VUV and electron beam excitation

NASA Astrophysics Data System (ADS)

Nazarov, M.; Mammadova, S.; Spassky, D.; Vielhauer, S.; Abdullayeva, S.; Huseynov, A.; Jabbarov, R.

2018-01-01

This paper reports the luminescence properties of nanosized SrAl2O4:Eu2+ (1%) phosphors. The samples were prepared by combustion method at 600 °C, followed by annealing of the resultant combustion ash at 1000 °C in a reductive (Ar + H2) atmosphere. X-ray diffraction (XRD), photo luminescence (PL) and cathodoluminescence (CL) analysis and thermal stimulated luminescence (TSL) method were applied to characterize the phosphor. For the first time a peak at 375 nm was observed in CL spectra of SrAl2O4:Eu2+ (1%) nanophosphors. Luminescence excitation spectra analysis have shown that this peak is related to crystal defects. Also in TSL curve one strong peak was observed in the region above room temperature (T = 325 K), which is attributed to lattice defects, namely oxygen vacancies. A green LED was fabricated by the combination of the SrAl2O4:Eu2+ (1%) nanosized phosphor and a 365 nm UV InGaN chip.

Observation of strong amplification at 8.8 nm in the TCE scheme by a table-top pumping system

NASA Astrophysics Data System (ADS)

Kawachi, Tetsuya; Tanaka, Momoko; Sasaki, Akira; Kishimoto, Maki; Nishiuchi, Mamiko; Yasuike, Kazuhito; Hasegawa, Noboru; Kilpio, Alexander V.; Lu, Peixiang; Tai, Renzhong

2002-11-01

We observed strong amplification of the transition of 4d 4p, J = 0 1 (the transition from (3d3/2, 4d3/2)0 to (3d3/2, 4p1/2)1) of the Ni-like lanthanum (La) ions at a wavelength of 8.8 nm pumped by a compact CPA Nd:Glass laser light at a wavelength of 1.053 mum with a pumping energy of 18 J. The experimental gain coefficient and the achieved gain-length product was 14.5 cm-1 and 7.7, respectively. In this experiment, the pumping laser pulse consisted of a pre-pulse with a duration of 200 ps and a 7ps-duration main pulse, separated by 250 ps. A hydrodynamics simulation coupled with a collisional-radiative model showed that the present experimental condition generated a pre-formed plasma with small volume and made it possible by the main pulse to heat the high density region effectively.

A review of colour center and nanostructure creation in LiF under heavy ion irradiation

NASA Astrophysics Data System (ADS)

Schwartz, K.; Maniks, J.; Manika, I.

2015-09-01

A study of radiation damage in LiF crystals under irradiation with MeV-GeV energy ions, from 12C to 238U, at temperatures varying from 8 to 300 K, depending on the ion energy, energy loss and irradiation temperature, is presented. For light ions (12C, 14N) at low fluences, it is mainly color centers that are created. Increasing the fluence leads to the overlapping of tracks and the creation of more complex color centers, defect aggregates and dislocations. For ions with an energy loss above a threshold value (dE/dx = 10 keV nm-1) the tracks exhibit a central core damage region with a radius of 1-2 nm, surrounded by an extended halo which mainly contains single color centers. In this case, ion-induced nanostructuring is observed. Novel effects of radiation damage creation under ion irradiation at 8 K are observed. The role of energy loss and irradiation temperature in damage creation is discussed.

Mechanical Strength and Broadband Transparency Improvement of Glass Wafers via Surface Nanostructures

PubMed Central

Kumar, Amarendra; Kashyap, Kunal; Hou, Max T.; Yeh, J. Andrew

2016-01-01

In this study, we mechanically strengthened a borosilicate glass wafer by doubling its bending strength and simultaneously enhancing its transparency using surface nanostructures for different applications including sensors, displays and panels. A fabrication method that combines dry and wet etching is used for surface nanostructure fabrication. Specifically, we improved the bending strength of plain borosilicate glass by 96% using these surface nanostructures on both sides. Besides bending strength improvement, a limited optical transmittance enhancement of 3% was also observed in the visible light wavelength region (400–800 nm). Both strength and transparency were improved by using surface nanostructures of 500 nm depth on both sides of the borosilicate glass without affecting its bulk properties or the glass manufacturing process. Moreover, we observed comparatively smaller fragments during the breaking of the nanostructured glass, which is indicative of strengthening. The range for the nanostructure depth is defined for different applications with which improvements of the strength and transparency of borosilicate glass substrate are obtained. PMID:27322276

Heterogeneous structure and mechanical hardness of biomedical β-type Ti-29Nb-13Ta-4.6Zr subjected to high-pressure torsion.

PubMed

Yilmazer, H; Niinomi, M; Nakai, M; Hieda, J; Todaka, Y; Akahori, T; Miyazaki, T

2012-06-01

A novel β-type titanium alloy, Ti-29Nb-13Ta-4.6Zr (TNTZ), has been developed as a candidate for biomedical applications. TNTZ exhibits non-toxicity and a low Young's modulus close to that of bone (10-30 GPa). Such a low Young's modulus of this alloy is achieved by comprising a single metastable β phase. Greater mechanical biocompatibility, which implies higher mechanical strength and hardness while maintaining a low Young's modulus, has been aimed for TNTZ. Therefore, strengthening by grain refinement and increasing dislocation density is expected to provide TNTZ high mechanical strength while keeping a low Young's modulus because they keep the original β phase. In this case, high-pressure torsion (HPT) processing is one of the effective ways to obtain these properties simultaneously in TNTZ. Thus, in this study, the effect of HPT processing on the microstructure and mechanical hardness of TNTZ was systematically investigated at rotation numbers (N) of 1 to 20 under a pressure of around 1.25 GPa at room temperature. On the cross sections of TNTZ subjected to HPT processing (TNTZ(HPT)) after cold rolling (TNTZ(CR)) at any rotation number, a heterogeneous microstructure consisting of a matrix and a non-etched band, which is not corroded by etching solution, can be observed. The thickness of non-etched band increases as rotation number and distance from specimen center increase. Both matrix and non-etched band comprise a single β phase, but their grain geometries are different each other. Equiaxed grains and elongated grains are observed in the matrix and the non-etched band, respectively. The equiaxed grain diameter, which is ranged from 155 nm to 44 nm, in the matrix decreases with increasing rotation number. Contrastingly, the elongated grains with a length of around 300 nm and a width of 30 nm, which are nearly constant with rotation number, are observed in the non-etched band. The mechanical hardness of TNTZ(HPT) is consistently much higher than that of TNTZ(CR). The mechanical hardness distribution on the surface of TNTZ(HPT) is heterogeneous in the radial and depth directions, while that of TNTZ(CR) is homogeneous; the mechanical hardness is higher in the peripheral region than in the central region on the surfaces of TNTZ(HPT) at all N. Further, the mechanical hardness distribution on the cross sections of TNTZ(HPT) at all N is also heterogeneous in depth direction; the mechanical hardness is higher in the peripheral region than in the central region. The heterogeneous mechanical hardness distribution depending on the position on the surface and cross section of TNTZ(HPT) is considered to be related to grain refinement and imposed strain due to HPT processing. Copyright © 2012 Elsevier Ltd. All rights reserved.

Laser optogalvanic wavelength calibration with a commercial hollow cathode iron - neon discharge lamp

NASA Technical Reports Server (NTRS)

Zhu, Xinming; Nur, Abdullahi H.; Misra, Prabhakar

1994-01-01

351 optogalvanic transitions have been observed in the 337 - 598 nm wavelength region using an iron - neon hollow cathode discharge lamp and a pulsed tunable dye laser. 223 of these have been identified as transitions associated with neon energy levels. These optogalvanic transitions have allowed, in conjunction with interference fringes recorded concomitantly with an etalon, the calibration of the dye laser wavelength with 0.3/cm accuracy.

[Resolving excitation emission matrix spectroscopy of estuarine CDOM with parallel factor analysis and its application in organic pollution monitoring].

PubMed

Guo, Wei-Dong; Huang, Jian-Ping; Hong, Hua-Sheng; Xu, Jing; Deng, Xun

2010-06-01

The distribution and estuarine behavior of fluorescent components of chromophoric dissolved organic matter (CDOM) from Jiulong Estuary were determined by fluorescence excitation emission matrix spectroscopy (EEMs) combined with parallel factor analysis (PARAFAC). The feasibility of these components as tracers for organic pollution in estuarine environments was also evaluated. Four separate fluorescent components were identified by PARAFAC, including three humic-like components (C1: 240, 310/382 nm; C2: 230, 250, 340/422 nm; C4: 260, 390/482 nm) and one protein-like components (C3: 225, 275/342 nm). These results indicated that UV humic-like peak A area designated by traditional "peak-picking method" was not a single peak but actually a combination of several fluorescent components, and it also had inherent links to so-called marine humic-like peak M or terrestrial humic-like peak C. Component C2 which include peak M decreased with increase of salinity in Jiulong Estuary, demonstrating that peak M can not be thought as the specific indicator of the "marine" humic-like component. Two humic-like components C1 and C2 showed additional behavior in the turbidity maximum region (salinity < 6) and then conservative mixing behavior for the rest estuarine region, while humic-like components C4 showed conservative mixing behavior for the whole estuarine region. However, the protein-like component C3 showed nonconservative mixing behavior, suggesting it had autochthonous estuarine origin. EEMs-PARAFAC can provide fluorescent fingerprint to differentiate the DOM features for three tributaries of Jiulong River. The observed linear relationships between humic-like components and absorption coefficient a (280) with chemical oxygen demand (COD) and biological oxygen demand (BOD5) suggest that the optical properties of CDOM may provide a fast in-situ way to monitor the variation of the degree of organic pollution in estuarine environments.

Laboratory estimate of the regional shortwave refractive index and single scattering albedo of mineral dust from major sources worldwide

NASA Astrophysics Data System (ADS)

Di Biagio, C.; Formenti, P.; Caponi, L.; Cazaunau, M.; Pangui, E.; Journet, E.; Nowak, S.; Caquineau, S.; Andreae, M. O.; Kandler, K.; Saeed, T.; Piketh, S.; Seibert, D.; Williams, E.; Balkanski, Y.; Doussin, J. F.

2017-12-01

Mineral dust is one of the most abundant aerosol species in the atmosphere and strongly contributes to the global and regional direct radiative effect. Still large uncertainties persist on the magnitude and overall sign of the dust direct effect, where indeed one of the main unknowns is how much mineral dust absorbs light in the shortwave (SW) spectral range. Aerosol absorption is represented both by the imaginary part (k) of the complex refractive index or the single scattering albedo (SSA, i.e. the ratio of the scattering to extinction coefficient). In this study we present a new dataset of SW complex refractive indices and SSA for mineral dust aerosols obtained from in situ measurements in the 4.2 m3 CESAM simulation chamber at LISA (Laboratoire Interuniversitaire des Systemes Atmospheriques) in Créteil, France. Investigated dust aerosol samples were issued from major desert sources worldwide, including the African Sahara and Sahel, Eastern Asia, the Middle East, Southern Africa, Australia, and the Americas, with differing iron oxides content. Results from the present study provide a regional mapping of the SW absorption by dust and show that the imaginary part of the refractive index largely varies (by up to a factor 6, 0.003-0.02 at 370 nm and 0.001-0.003 at 950 nm) for the different source areas due to the change in the particle iron oxide content. The SSA for dust varies between 0.75-0.90 at 370 nm and 0.95-0.99 at 950 nm, with the largest absorption observed for Sahelian and Australian dust aerosols. Our range of variability for k and SSA is well bracketed by already published literature estimates, but suggests that regional‒dependent values should be used in models. The possible relationship between k and the dust iron oxides content is investigated with the aim of providing a parameterization of the regional‒dependent dust absorption to include in climate models.

Experimental verification of the rainbow trapping effect in adiabatic plasmonic gratings

PubMed Central

Gan, Qiaoqiang; Gao, Yongkang; Wagner, Kyle; Vezenov, Dmitri; Ding, Yujie J.; Bartoli, Filbert J.

2011-01-01

We report the experimental observation of a trapped rainbow in adiabatically graded metallic gratings, designed to validate theoretical predictions for this unique plasmonic structure. One-dimensional graded nanogratings were fabricated and their surface dispersion properties tailored by varying the grating groove depth, whose dimensions were confirmed by atomic force microscopy. Tunable plasmonic bandgaps were observed experimentally, and direct optical measurements on graded grating structures show that light of different wavelengths in the 500–700-nm region is “trapped” at different positions along the grating, consistent with computer simulations, thus verifying the “rainbow” trapping effect. PMID:21402936

Different regions of line formation in the envelope of the early emission line star HD 190073

NASA Technical Reports Server (NTRS)

Ringuelet, A. E.; Rovira, M.; Cidale, L.; Sahade, J.

1987-01-01

A description is presented of the spectral features that characterize the spectrum of HD 190073 both in the photographic region (360-660 nm), and in the IUE UV (115-320 nm). A number of different types of profiles can be distinguished, and this seems to imply that many different 'broad' regions of line formation coexist in the extended envelope of the star, including regions with densities differing in several orders of magnitude.

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Science.gov Websites

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