Time Resolved Spectroscopy, High Sensitivity Power Spectrum & a Search for the X-Ray QPO in NGC 5548

NASA Astrophysics Data System (ADS)

Yaqoob, Tahir

1999-09-01

Controversy surrounds the EXOSAT discovery of a QPO (period ~500 s) in NGC 5548 due to the data being plagued by high background and instrumental systematics. If the NGC 5548 QPO is real, the implications for the physics of the X-ray emission mechanism and inner-most disk/black-hole system are enormous. AXAF provides the first opportunity to settle the issue, capable of yielding power spectra with unprecedented sensitivity, pushing the limit on finding new features. Using HETG/ACIS we will also perform time-resolved spectroscopy of the ionized absorption features and Fe-K emission line, search for energy-dependent time lags in the continuum, between the continuum and spectral features, and between the spectral features. These data will provide powerful constraints on models of AGN.

A Statistical Approach to Exoplanetary Molecular Spectroscopy Using Spitzer Eclipses

NASA Astrophysics Data System (ADS)

Deming, Drake; Garhart, Emily; Burrows, Adam; Fortney, Jonathan; Knutson, Heather; Todorov, Kamen

2018-01-01

Secondary eclipses of exoplanets observed using the Spitzer Space Telescope measure the total emission emergent from exoplanetary atmospheres integrated over broad photometric bands. Spitzer photometry is excellent for measuring day side temperatures, but is less well suited to the detection of molecular absorption or emission features. Even for very hot exoplanets, it can be difficult to attain the accuracy on eclipse depth that is needed to unambiguously interpret the Spitzer results in terms of molecular absorption or emission. However, a statistical approach, wherein we seek deviations from a simple blackbody planet as a function of the planet's equilibrium temperature, shows promise for defining the nature and strength of molecular absorption in ensembles of planets. In this paper, we explore such an approach using secondary eclipses observed for tens of hot exoplanets during Spitzer's Cycles 10, 12, and 13. We focus on the possibility that the hottest planets exhibit molecular features in emission, due to temperature inversions.

Free-Free Radiation Cannot Make the UV/Soft-X-Ray Excess in AGN

NASA Astrophysics Data System (ADS)

Kriss, G. A.

1994-05-01

Thermal gas always has associated atomic spectral features either in absorption or in emission. In optically thin gas the emission spectrum is dominated by line radiation and recombination continua. An example of radiation from optically thin material in accreting systems is the emission-line-dominated spectrum of a cataclysmic variable in its low state. Barvainis (1993, ApJ, 412, 513) and others have proposed that the UV/soft-X-ray excess prominent in the spectra of many AGN is due to free-free emission from gas at temperatures of 10(5) - 10(6) K. Simple arguments using only atomic data show that the recombination radiation from emission lines would produce UV, optical, and soft X-ray spectral features orders of magnitude stronger than observed. Collisional excitation produces even more line radiation under most physical conditions. As a particular example I take the Astro-1 observations of the Seyfert 1 galaxy Mrk 335 by HUT and BBXRT. Depending on the ionization state of the gas (which may be photoionized by the central source), the emission measure of the free-free radiation necessary to produce the UV continuum (3 times 10(68) cm(-3) at 8.2 times 10(5) K for H_o = 75 km s(-1) Mpc(-1) ) implies line emission from O VI, O VII, or O VIII more than a factor of 10 stronger than any features observed by HUT or BBXRT.

Intense Non-Linear Soft X-Ray Emission from a Hydride Target during Pulsed D Bombardment

NASA Astrophysics Data System (ADS)

Miley, George H.; Yang, Yang; Lipson, Andrei; Haque, Munima; Percel, Ian; Romer, Michael

Radiation emission from low-energy nuclear radiation (LENR) electrodes (both charged-particle and X-rays) represents an important feature of LENR in general. Here, calibration, measurement techniques, and soft X-ray emission results from deuterium bombardment of a Pd target (cathode) placed in a pulsed deuterium glow discharge (PGD) are described. An X-ray intensity of 13.4 mW/cm2 and a dose of 3.3 μJ/cm2 were calculated over a 0.5 ms pulse time from AXUV photodiode radiation detector measurements. A most striking feature is that X-ray energies >600 V are observed with a discharge voltage only about half of that value. To further investigate this phenomenon, emission during room temperature D-desorption from electrolytically loaded Pd:Dx cathodes was also studied. The X-ray emission energy observed was quite similar to the PGD case. However, the intensity in this case was almost 13 orders of magnitude lower due to the much lower deuterium fluxes involved.

IUE and Einstein observations of the LINER galaxy NGC 4579

NASA Technical Reports Server (NTRS)

Reichert, G. A.; Puchnarewicz, E. M.; Mason, K. O.

1990-01-01

Results of International Ultraviolet Explorer (IUE) and Einstein observations of the LINER galaxy NGC 4579 are reported. Spatial profiles of the long wavelength IUE emission show a two component structure, with an unresolved core superimposed on broader underlying emission. The core spectrum shows strong C II lambda 2326 and broad Mg II lambda 2800 emission, and perhaps emission due to blends of Fe II multiplets (2300 to 23600 angstrom). The short wavelength emission is spatially unresolved, and shows C II lambda 1335, C III lambda 1909 broad C IV lambda 1550 emission, and a broad feature at approximately 1360 angstrom which may be due to 0.1 lambda 1356. Contrary to previous reports no evidence for He II lambda 1640 is found in the spectrum. An unresolved x ray source is detected at the location of the nucleus; its spectrum is well fitted by a power law of energy slope alpha approximately -0.5. These results further support the idea that NGC 4579 may contain a dwarf Seyfert nucleus.

Observations of the Io plasma torus

NASA Technical Reports Server (NTRS)

Lane, A. L.; Moos, H. W.; Clarke, J. T.; Atreya, S. K.

1981-01-01

The short wavelength spectrography on the IUE satellite was used to obtain spectra of the plasma torus near the orbit of Io about Jupiter. Three exposures of about 8 hours each taken in March and May 1979 show emission features due to SII, SIII, and OIII. The absence of features at other wavelengths permits upper limits to be other species in the torus.

Fluorescence detection of organic molecules in the Jovian atmosphere

NASA Technical Reports Server (NTRS)

Levine, J. S.; Rogowski, R. S.

1975-01-01

A search for fluorescent emission due to the presence of possible organic molecules in the Jovian atmosphere is described. We first consider natural Jovian fluorescent emission excited by precipitating auroral particles. Due to our lack of knowledge of the Jovian precipitating particle energies and fluxes we next consider fluorescent emission excited by a laser system aboard a Jupiter spacecraft. Laser-induced fluorescence is routinely used to monitor trace constituents and pollutants in the terrestrial atmosphere. Several spacecraft laser systems are currently under development. Our calculations indicate that laser-induced fluorescent detection is approximately two orders of magnitude more sensitive than rocket ultraviolet measurements of possible Jovian absorption features at 2600 A that have been attributed to the presence of adenine or benzene.

Spitzer-IRS Spectroscopic Studies of Oxygen-Rich Asymptotic Giant Branch Star and Red Supergiant Star Dust Properties

NASA Astrophysics Data System (ADS)

Sargent, Benjamin A.; Srinivasan, Sundar; Speck, Angela; Volk, Kevin; Kemper, Ciska; Reach, William T.; Lagadec, Eric; Bernard, Jean-Philippe; McDonald, Iain; Meixner, Margaret

2015-01-01

We analyze the dust emission features seen in Spitzer Space Telescope Infrared Spectrograph (IRS) spectra of Oxygen-rich (O-rich) asymptotic giant branch (AGB) and red supergiant (RSG) stars. The spectra come from the Spitzer Legacy program SAGE-Spectroscopy (PI: F. Kemper) and other archival Spitzer-IRS programs. The broad 10 and 20 micron emission features attributed to amorphous dust of silicate composition seen in the spectra show evidence for systematic differences in the centroid of both emission features between O-rich AGB and RSG populations. Radiative transfer modeling using the GRAMS grid of models of AGB and RSG stars suggests that the centroid differences are due to differences in dust properties. We present an update of our investigation of differences in dust composition, size, shape, etc that might be responsible for these spectral differences. We explore how these differences may arise from the different circumstellar environments around RSG and O-rich AGB stars. BAS acknowledges funding from NASA ADAP grant NNX13AD54G.

Spitzer-IRS Spectroscopic Studies of the Properties of Dust from Oxygen-Rich Asymptotic Giant Branch and Red Supergiant Stars

NASA Astrophysics Data System (ADS)

Sargent, Benjamin A.; Speck, A.; Volk, K.; Kemper, C.; Reach, W. T.; Lagadec, E.; Bernard, J.; McDonald, I.; Meixner, M.; Srinivasan, S.

2014-01-01

We analyze the dust emission features seen in Spitzer Space Telescope Infrared Spectrograph (IRS) spectra of Oxygen-rich (O-rich) asymptotic giant branch (AGB) and red supergiant (RSG) stars. The spectra come from the Spitzer Legacy program SAGE-Spectroscopy (PI: F. Kemper) and other archival Spitzer-IRS programs. The broad 10 and 20 micron emission features attributed to amorphous dust of silicate composition seen in the spectra show evidence for systematic differences in the centroid of both emission features between O-rich AGB and RSG populations. Radiative transfer modeling using the GRAMS grid of models of AGB and RSG stars suggests that the centroid differences are due to differences in dust properties. We investigate differences in dust composition, size, shape, etc that might be responsible for these spectral differences. We explore how these differences may arise from the different circumstellar environments around RSG and O-rich AGB stars. BAS acknowledges funding from NASA ADAP grant NNX13AD54G.

Determination of ionic abundances in the Io torus using the Hopkins Ultraviolet Telescope

NASA Technical Reports Server (NTRS)

Moos, H. W.; Feldman, P. D.; Durrance, S. T.; Blair, W. P.; Bowers, C. W.; Davidsen, A. F.; Dixon, W. V.; Henry, R. C.; Ferguson, H. C.; Kimble, R. A.

1991-01-01

Attention is given to a 415-1864-A spectrum of the emissions from the Io torus with about 3-A resolution in first order (830-1864 A) obtained with HUT in December 1990. A list of the 31 strongest features shows that, apart from five features that are totally or partially terrestrial, all are due to O(+), S(+), S(2+), and S(3+). There is no evidence for elements other than oxygen and sulfur. The spectrum shows many additional weaker emission features so that the existence of minor species cannot be ruled out at this time. Because the HUT spectrum contains well-resolved lines for all four of the major species, the mixing ratio (Ni/ne) for each one can be determined without using models of the spectral emissions, or a detailed geometric model of the torus plasma. The relative concentration of O(+) determined from the HUT observation is 38 percent less than that obtained from the Voyager UVS data.

A Model Describing Stable Coherent Synchrotron Radiation in Storage Rings

NASA Astrophysics Data System (ADS)

Sannibale, F.; Byrd, J. M.; Loftsdóttir, Á.; Venturini, M.; Abo-Bakr, M.; Feikes, J.; Holldack, K.; Kuske, P.; Wüstefeld, G.; Hübers, H.-W.; Warnock, R.

2004-08-01

We present a model describing high power stable broadband coherent synchrotron radiation (CSR) in the terahertz frequency region in an electron storage ring. The model includes distortion of bunch shape from the synchrotron radiation (SR), which enhances higher frequency coherent emission, and limits to stable emission due to an instability excited by the SR wakefield. It gives a quantitative explanation of several features of the recent observations of CSR at the BESSYII storage ring. We also use this model to optimize the performance of a source for stable CSR emission.

Measurements of trace constituents from atmospheric infrared emission and absorption spectra, a feasibility study

NASA Technical Reports Server (NTRS)

Goldman, A.; Williams, W. J.; Murcray, D. G.

1974-01-01

The feasibility of detecting eight trace constituents (CH4, HCl, HF, HNO3, NH3, NO, NO2 and SO2) against the rest of the atmospheric background at various altitudes from infrared emission and absorption atmospheric spectra was studied. Line-by-line calculations and observational data were used to establish features that can be observed in the atmospheric spectrum due to each trace constituent. Model calculations were made for experimental conditions which approximately represent state of the art emission and absorption spectrometers.

Greenland records of aerosol source and atmospheric lifetime changes from the Eemian to the Holocene.

PubMed

Schüpbach, S; Fischer, H; Bigler, M; Erhardt, T; Gfeller, G; Leuenberger, D; Mini, O; Mulvaney, R; Abram, N J; Fleet, L; Frey, M M; Thomas, E; Svensson, A; Dahl-Jensen, D; Kettner, E; Kjaer, H; Seierstad, I; Steffensen, J P; Rasmussen, S O; Vallelonga, P; Winstrup, M; Wegner, A; Twarloh, B; Wolff, K; Schmidt, K; Goto-Azuma, K; Kuramoto, T; Hirabayashi, M; Uetake, J; Zheng, J; Bourgeois, J; Fisher, D; Zhiheng, D; Xiao, C; Legrand, M; Spolaor, A; Gabrieli, J; Barbante, C; Kang, J-H; Hur, S D; Hong, S B; Hwang, H J; Hong, S; Hansson, M; Iizuka, Y; Oyabu, I; Muscheler, R; Adolphi, F; Maselli, O; McConnell, J; Wolff, E W

2018-04-16

The Northern Hemisphere experienced dramatic changes during the last glacial, featuring vast ice sheets and abrupt climate events, while high northern latitudes during the last interglacial (Eemian) were warmer than today. Here we use high-resolution aerosol records from the Greenland NEEM ice core to reconstruct the environmental alterations in aerosol source regions accompanying these changes. Separating source and transport effects, we find strongly reduced terrestrial biogenic emissions during glacial times reflecting net loss of vegetated area in North America. Rapid climate changes during the glacial have little effect on terrestrial biogenic aerosol emissions. A strong increase in terrestrial dust emissions during the coldest intervals indicates higher aridity and dust storm activity in East Asian deserts. Glacial sea salt aerosol emissions in the North Atlantic region increase only moderately (50%), likely due to sea ice expansion. Lower aerosol concentrations in Eemian ice compared to the Holocene are mainly due to shortened atmospheric residence time, while emissions changed little.

Search for ultraviolet emission lines from a hot gaseous halo in the edge-on galaxy NGC 4244

NASA Technical Reports Server (NTRS)

Deharveng, J.-M.; Joubert, M.; Bixler, J.; Bowyer, S.; Malina, R.

1986-01-01

Short and long wavelength IUE spectra of the halo region in the edge-on galaxy NGC 4244 are analyzed in order to identify evidence of line emission at the level of 0.000001 ergs per cu cm sr/s. Features are found at 1245 A and 1402 A, having peaks four times greater than the rms intensity fluctuations of nearby spectra. The spectral features are identified with semi-forbidden N V, semi-forbidden S IV at 1240 A, and Si IV and semi-forbidden O IV multiplets at 1400 A, respectively. The appearance of high-peak features and the lack of astrophysically important lines in the sample are evidence of a gas near T = 10 exp 5.2 and emission measure (EM) equal to about 0.000001 pc. However, the case for the existence of such a gas is weakened due to the existence of two other similarly sized features with no identifiable astrophysical origin and the extremely faint nature of the candidate features. The assumed upper limit for the line intensities in NGC 4244 leads to the conclusion that at T less than 100,000 K any emitting gas is either highly clumped or has a p/k value of less than 1000 per cu cm K. It is suggested that if the observed low level features in the short wavelength spectrum are real, the temperature and emission measures allow for a single component gas in the halo of NGC 4244, and are in agreement with those derived by Paresce et al. (1983).

Single-Molecule Spectroscopy Unmasks the Lowest Exciton State of the B850 Assembly in LH2 from Rps. acidophila

PubMed Central

Kunz, Ralf; Timpmann, Kõu; Southall, June; Cogdell, Richard J.; Freiberg, Arvi; Köhler, Jürgen

2014-01-01

We have recorded fluorescence-excitation and emission spectra from single LH2 complexes from Rhodopseudomonas (Rps.) acidophila. Both types of spectra show strong temporal spectral fluctuations that can be visualized as spectral diffusion plots. Comparison of the excitation and emission spectra reveals that for most of the complexes the lowest exciton transition is not observable in the excitation spectra due to the cutoff of the detection filter characteristics. However, from the spectral diffusion plots we have the full spectral and temporal information at hand and can select those complexes for which the excitation spectra are complete. Correlating the red most spectral feature of the excitation spectrum with the blue most spectral feature of the emission spectrum allows an unambiguous assignment of the lowest exciton state. Hence, application of fluorescence-excitation and emission spectroscopy on the same individual LH2 complex allows us to decipher spectral subtleties that are usually hidden in traditional ensemble spectroscopy. PMID:24806933

Can the bump in the composite spectrum of GRB 910503 be an emission line feature of gamma-ray bursts?

NASA Astrophysics Data System (ADS)

Qin, Yi-Ping; Zhang, Fu-Wen

2005-12-01

Appearing in the composite spectral data of BATSE, EGRET and COMPTEL for GRB 910503, there is a bump at around 1600 keV. We perform a statistical analysis on the spectral data, trying to find out if the bump could be accounted for by a blue-shifted and significantly broadened rest frame line due to the Doppler effect of an expanding fireball surface. We made an F-test and adopted previously proposed criteria. The study reveals that the criteria are well satisfied and the feature can be interpreted as the blue shifted 6.4 keV line. From the fit with this line taken into account, we find the Lorentz factor of this source to be Γ = 116+9-9 (at the 68% confident level, triangleχ2 = 1) and the rest frame spectral peak energy to be E0,p = 2.96+0.24-0.18 keV. Although the existence of the emission line feature requires other independent tests to confirm, the analysis suggests that it is feasible to detect emission line features in the high energy range of GRB spectra when taking into account the Doppler effect of fireball expansion.

XMM-Newton Proposal 03033401

NASA Astrophysics Data System (ADS)

Ghosh, Kajal

2004-10-01

We have detected a highly blueshifted (7.6 keV at the source frame) emission feature in the ASCA spectra of the unusual Narrow-line Seyfert 1 galaxy RX J0136.9-3510. At ASCA resolution it is impossible to tell if the feature is a single line or a combination of lines nor if the feature is due to He-like or H-like Fe. The line profile can tell us where the bulk of the emission origin- ates: A low velocity dispersion would favor a wind/outflow origin, while a hi- gher dispersion may allow for an ionized disk reflection origin. Strong absor- ption and resonant scattering could also produce blueshifted line. To acquire better resolution spectrum to constrain the origin of the line via detailed physical modeling, we propose 50 ks XMM-Newton observations of RXJ0136.9-3510.

The hydrogen coverage of interstellar PAHs

NASA Technical Reports Server (NTRS)

Barker, J. R.; Cohen, M.; Tielens, Alexander G. G. M.; Allamandola, Louis J.; Barker, J. R.; Barker, J. R.

1986-01-01

The rate at which the CH bond in interstellar Polycyclic Aromatic Hydrocarbons (PAHs) rupture due to the absorption of a UV photon has been calculated. The results show that small PAHs (less than or equal to 25 carbon atoms) are expected to be partially dehydrogenated in regions with intense UV fields, while large PAHs (greater than or equal to 25 atoms) are expected to be completely hydrogenated in those regions. Because estimate of the carbon content of interstellar PAHs lie in the range of 20 to 25 carbon atoms, dehydrogenation is probably not very important. Because of the absence of other emission features besides the 11.3 micrometer feature in ground-based 8 to 13 micrometer spectra, it has been suggested that interstellar PAHs are partially dehydrogenated. However, IRAS 8 to 22 micrometer spectra of most sources that show strong 7.7 and 11.2 micrometer emission features also show a plateau of emission extending from about 11.3 to 14 micrometer. Like the 11.3 micrometer feature, this new feature is attributed to the CH out of plane bending mode in PAHs. This new feature shows that interstellar PAHs are not as dehydrogenated as estimated from ground-based 8 to 13 micrometer spectra. It also constrains the molecular structure of interstellar PAHs. In particular, it seems that very condensed PAHs, such as coronene and circumcoronene, dominate the interstellar PAH mixture as expected from stability arguments.

Strategic Functionalization of Single Walled Carbon Nanotubes to Manipulate Their Electronic and Optical Properties

NASA Astrophysics Data System (ADS)

Gifford, Brendan Joel

Single-walled carbon nanotubes (SWCNTs) are unique materials that exhibit chirality-specific properties due to their one-dimensional confinement. As a result, they are explored for a wide range of applications including single-photon sources in communications devices. Despite progress in this area, SWCNTs still suffer from a relatively narrow range of energies of emission features that fall short of the 1500 nm desired for long-distance lossless data transfer. One approach that is frequently used to resolve this involves chemical functionalization with aryl groups. However, this approach is met with a number of fundamental issues. First, chirality-specific SWCNTs must be acquired for subsequent functionalization. Synthesis of such samples has thus far eluded experimental efforts. As such, post-synthetic non-covalent functionalization is required to break bundles and create disperse SWCNTs that can undergo further separation, processing, and functionalization. Second, a number of low-energy emission features are introduced upon functionalization across a 200 nm range. The origin of such diverse emission features remains unknown. The research presented here focuses on computationally addressing these issues. A series of polyfluorene polymers possessing sidechains of varying length are explored using molecular mechanics to determine the impact of alkyl sidechains on SWCNT-conjugated polymer interaction strength and morphology. Additionally, density functional theory (DFT) and linear-response time-dependent DFT (TDDFT) are used to explore the effect of functionalization on emission features. A prerequisite to these calculations involves constructing finite-length SWCNT systems with similar electronic structure to their infinite counterparts: a methodological approach for the formation of such systems is presented. The optical features for aryl-functionalized SWCNTs are then explored. It is shown that the predominant effect on the energies of emission features involves the configuration of functionalization, with the identity of the functional group only playing a minor role. While the qualitative effect of such functionalization is determined, a quantitative comparison to experiment requires correction for several sources of computational error. A model to correct for such effects is also developed. This research not only explains the origin of the multiple emission features in functionalized SWCNTs for the first time but also lays the groundwork for their further computational exploration.

Fiber optic light collection system for scanning-tunneling-microscope-induced light emission.

PubMed

Watkins, Neil J; Long, James P; Kafafi, Zakya H; Mäkinen, Antti J

2007-05-01

We report a compact light collection scheme suitable for retrofitting a scanning tunneling microscope (STM) for STM-induced light emission experiments. The approach uses a pair of optical fibers with large core diameters and high numerical apertures to maximize light collection efficiency and to moderate the mechanical precision required for alignment. Bench tests indicate that efficiency reduction is almost entirely due to reflective losses at the fiber ends, while losses due to fiber misalignment have virtually been eliminated. Photon-map imaging with nanometer features is demonstrated on a stepped Au(111) surface with signal rates exceeding 10(4) counts/s.

2-45 Micron Infrared Spectroscopy of Carbon-Rich Proto-Planetary Nebulae

NASA Technical Reports Server (NTRS)

Hrivnak, Bruce J.; Volk, Kevin; Kwok, Sun

2000-01-01

Infrared Space Observatory (ISO) 2-45 micron observations of seven proto-planetary nebulae (PPNs) and two other carbon-rich objects are presented. The unidentified emission features at 21 and 30 microns are detected in six sources, including four new detections of the 30 micron feature. This previously unresolved 30 micron feature is now resolved and found to consist of a broad feature peaking at 27.2 microns (the '30 micron' feature) and a narrower feature at 25.5 microns (the '26 micron' feature). This new 26 micron feature is detected in eight sources and is particularly strong in IRAS Z02229 + 6208 and 16594-4656. The unidentified infrared (UIR) emission features at 3.3, 6.2, 7.7, and 11.3 microns which are commonly observed in planetary nebulae and H II regions, are also seen in these PPNs. However, their strengths relative to the continuum plateaus at 8 and 12 microns are weaker than in planetary nebulae. The 6.9 micron feature, seen almost exclusively in PPNs, is strong. New millimeter CO and HCN observations were made; they support the carbon-rich nature of the objects and yield the expansion velocities of the gaseous envelopes. The spectral energy distributions of these PPNs were fitted with a radiative-transfer model, taking into account the emission features at 21, 26, and 30 microns. A significant fraction of the total energy output is emitted in these features: as high as 20% in the 30 micron feature and 8% in the 21 micron feature. The fact that so much energy is carried in these features suggests that the material responsible for these features must be made of abundant elements and most likely involves carbon. SiS, appears to be ruled out as the emitter of the 21 micron feature due to the absence of a predicted companion feature.

Nitrogen airglow sources - Comparison of Triton, Titan, and earth

NASA Technical Reports Server (NTRS)

Strobel, Darrell F.; Meier, R. R.; Summers, Michael E.; Strickland, Douglas J.

1991-01-01

The individual contributions of direct solar excitation, photoelectron excitation, and magnetospheric electron excitation of Triton and Titan airglow observed by the Voyager Ultraviolet Spectrometer (UVS) are quantified. The principal spectral features of Triton's airglow are shown to be consistent with precipitation of magnetospheric electrons with power dissipation about 500 million W. Solar excitation rates of the dominant N2 and N(+) emission features are factors of 2-7 weaker than magnetospheric electron excitation. On Titan, the calculated disk center and bright limb N(+) 1085 A intensities due to solar excitation agree with observed values, while the 970 A feature is mostly N21 c5 band emission. The calculated LBH intensity by photoelectrons suggests that magnetospheric electrons play a minor role in Titan's UV airglow. On earth, solar/photoelectron excitation explains the observed N(+) 1085 A and LBH intensites and accounts for only 40 percent of the N(+) 916 A intensity.

Reaction channel coupling effects for nucleons on 16O: Induced undularity and proton-neutron potential differences

NASA Astrophysics Data System (ADS)

Keeley, N.; Mackintosh, R. S.

2018-01-01

Background: Precise fitting of scattering observables suggests that the nucleon-nucleus interaction is l dependent. Such l dependence has been shown to be S -matrix equivalent to an undulatory l -independent potential. The undulations include radial regions where the imaginary term is emissive. Purpose: To study the dynamical polarization potential (DPP) generated in proton-16O and neutron-16O interaction potentials by coupling to pickup channels. Undulatory features occurring in these DPPs can be compared with corresponding features of empirical optical model potentials (OMPs). Furthermore, the additional inclusion of coupling to vibrational states of the target will provide evidence for dynamically generated nonlocality. Methods: The fresco code provides the elastic channel S -matrix Sl j for chosen channel couplings. Inversion, Sl j→V (r ) +l .s VSO(r ) , followed by subtraction of the bare potential, yields an l -independent and local representation of the DPP due to the chosen couplings. Results: The DPPs have strongly undulatory features, including radial regions of emissivity. Certain features of empirical DPPs appear, e.g., the full inverted potential has emissive regions. The DPPs for different collective states are additive except near the nuclear center, whereas the collective and reaction channel DPPs are distinctly nonadditive over a considerable radial range, indicating dynamical nonlocality. Substantial differences between the DPPs due to pickup coupling for protons and neutrons occur; these imply a greater difference between proton and neutron OMPs than the standard phenomenological prescription. Conclusions: The onus is on those who object to undularity in the local and l -independent representation of nucleon elastic scattering to show why such undulations do not occur. This work suggests that it is not legitimate to halt model-independent fits to high-quality data at the appearance of undularity.

An alternative mechanism for production of emission features in some infrared objects

NASA Technical Reports Server (NTRS)

Apruzese, J. P.

1975-01-01

Two dust-envelope models of the M supergiant VX Sgr, which exhibits a prominent emission feature at 10 microns, are presented. The models indicate that, for certain envelope sizes, the presence of the observed emission feature does not necessarily indicate that the emitting grains possess a similar feature in their emissivity profile. The mechanism which may in some cases be producing the observed emission feature is discussed.

Diffuse radio emission in the complex merging galaxy cluster Abell2069

NASA Astrophysics Data System (ADS)

Drabent, A.; Hoeft, M.; Pizzo, R. F.; Bonafede, A.; van Weeren, R. J.; Klein, U.

2015-03-01

Context. Galaxy clusters with signs of a recent merger in many cases show extended diffuse radio features. This emission originates from relativistic electrons that suffer synchrotron losses due to the intracluster magnetic field. The mechanisms of particle acceleration and the properties of the magnetic field are still poorly understood. Aims: We search for diffuse radio emission in galaxy clusters. Here, we study the complex galaxy cluster Abell 2069, for which X-ray observations indicate a recent merger. Methods: We investigate the cluster's radio continuum emission by deep Westerbork Synthesis Radio Telescope (WSRT) observations at 346 MHz and Giant Metrewave Radio Telescope (GMRT) observations at 322 MHz. Results: We find an extended diffuse radio feature roughly coinciding with the main component of the cluster. We classify this emission as a radio halo and estimate its lower limit flux density at 25 ± 9 mJy. Moreover, we find a second extended diffuse source located at the cluster's companion and estimate its flux density at 15 ± 2 mJy. We speculate that this is a small halo or a mini-halo. If true, this cluster is the first example of a double-halo in a single galaxy cluster.

Optical and infrared spectrophotometry of the symbiotic system V1016 Cygni

NASA Technical Reports Server (NTRS)

Rudy, Richard J.; Rossano, George S.; Cohen, Ross D.; Puetter, R. C.

1990-01-01

Spectrophotometry from 0.46 to 1.3 micron of the peculiar emission-line object V1016 Cyg is presented. The optical region displays a weak continuum underlying the rich emission-line spectrum detailed in past studies. The infrared spectrum consists of prominent emission lines of H I, He I, He II, forbidden Ni, O I, and forbidden S III overlying a strong stellar continuum. The latter displays bands at 0.94 micron and 1.13 micron characteristic of a late-type, oxygen-rich giant as well as an absorption at 1.05 micron which is due to VO. The presence of these molecular features indicates a spectral class of M6 or later for the cool secondary. The reddening of the secondary does not appear to be much different from that of the emission lines. Among the infrared emission features is the rarely seen permitted transition of neutral oxygen at 1.1287 micron. Its presence at a strength comparable to O I 8446 A, together with the absence of O I 13164 A, confirms the result of Strafella that the strong O I lines arise primarily from fluorescent excitation by Ly-beta.

Fluorescence Intrinsic Characterization of Excitation-Emission Matrix Using Multi-Dimensional Ensemble Empirical Mode Decomposition

PubMed Central

Chang, Chi-Ying; Chang, Chia-Chi; Hsiao, Tzu-Chien

2013-01-01

Excitation-emission matrix (EEM) fluorescence spectroscopy is a noninvasive method for tissue diagnosis and has become important in clinical use. However, the intrinsic characterization of EEM fluorescence remains unclear. Photobleaching and the complexity of the chemical compounds make it difficult to distinguish individual compounds due to overlapping features. Conventional studies use principal component analysis (PCA) for EEM fluorescence analysis, and the relationship between the EEM features extracted by PCA and diseases has been examined. The spectral features of different tissue constituents are not fully separable or clearly defined. Recently, a non-stationary method called multi-dimensional ensemble empirical mode decomposition (MEEMD) was introduced; this method can extract the intrinsic oscillations on multiple spatial scales without loss of information. The aim of this study was to propose a fluorescence spectroscopy system for EEM measurements and to describe a method for extracting the intrinsic characteristics of EEM by MEEMD. The results indicate that, although PCA provides the principal factor for the spectral features associated with chemical compounds, MEEMD can provide additional intrinsic features with more reliable mapping of the chemical compounds. MEEMD has the potential to extract intrinsic fluorescence features and improve the detection of biochemical changes. PMID:24240806

Single-molecule spectroscopy unmasks the lowest exciton state of the B850 assembly in LH2 from Rps. acidophila.

PubMed

Kunz, Ralf; Timpmann, Kõu; Southall, June; Cogdell, Richard J; Freiberg, Arvi; Köhler, Jürgen

2014-05-06

We have recorded fluorescence-excitation and emission spectra from single LH2 complexes from Rhodopseudomonas (Rps.) acidophila. Both types of spectra show strong temporal spectral fluctuations that can be visualized as spectral diffusion plots. Comparison of the excitation and emission spectra reveals that for most of the complexes the lowest exciton transition is not observable in the excitation spectra due to the cutoff of the detection filter characteristics. However, from the spectral diffusion plots we have the full spectral and temporal information at hand and can select those complexes for which the excitation spectra are complete. Correlating the red most spectral feature of the excitation spectrum with the blue most spectral feature of the emission spectrum allows an unambiguous assignment of the lowest exciton state. Hence, application of fluorescence-excitation and emission spectroscopy on the same individual LH2 complex allows us to decipher spectral subtleties that are usually hidden in traditional ensemble spectroscopy. Copyright © 2014 Biophysical Society. Published by Elsevier Inc. All rights reserved.

[CH4 emission features of leading super-rice varieties and their relationships with the varieties growth characteristics in Yangtze Delta of China].

PubMed

Yan, Xiao-Jun; Wang, Li-Li; Jiang, Yu; Deng, Ai-Xing; Tian, Yun-Lu; Zhang, Wei-Jian

2013-09-01

A pot experiment was conducted to study the CH4 emission features of fourteen leading super-rice varieties (six Japonica rice varieties and eight Indica hybrid rice varieties) and their relationships with the varieties growth characteristics in Yangtze Delta. Two distinct peaks of CH4 emission were detected during the entire growth period of the varieties, one peak occurred at full-tillering stage, and the other appeared at booting stage. The average total CH4 emission of Japonica rice varieties was 37.6% higher than that of the Indica hybrid rice varieties (P<0.01), and the differences in the CH4 emission between rice types occurred at the post-anthesis phase. For all the varieties, there was a significant positive correlation between the total CH4 emission and the maximum leaf area, but the correlations between the CH4 emission and the other growth characteristics varied with variety type. The total CH4 emission of Japonica rice varieties had a significant positive correlation with plant height, while the correlations between the total CH4 emission of Indica hybrid rice varieties and their plant height were not significant. The total CH4 emission of Indica hybrid rice varieties had significant negative correlations with the total aboveground biomass, grain yield, and harvest index, but the correlations were not significant for Japonica rice varieties. The lower CH4 emission of Indica hybrid rice varieties was likely due to their significantly higher root biomass, as compared with Japonica rice varieties.

An optical emission-line phase of the extreme carbon star IRC +30219

NASA Technical Reports Server (NTRS)

Cohen, M.

1980-01-01

Optical spectroscopic monitoring of the extreme carbon star IRC +30219 has revealed striking changes between 1977 and 1980. The stellar photosphere was barely visible in early 1979. There was an emission line spectrum consisting of H, forbidden O I, forbidden O II, forbidden N I, forbidden N II, forbidden S II, and He I. It is likely that these lines arose in a shocked region where recent stellar mass loss encountered the extensive circumstellar envelope. By late 1979, this emission-line spectrum had vanished, and the photosphere had reappeared. The weakening of the photospheric features in early 1979 was caused by increased attenuation of starlight and overlying thermal emission, both due to recently condensed hot dust grains.

Directional Emission from Metal-Dielectric-Metal Structures: Effect of Mixed Metal Layers, Dye Location and Dielectric Thickness.

PubMed

Choudhury, Sharmistha Dutta; Badugu, Ramachandram; Ray, Krishanu; Lakowicz, Joseph R

2015-02-12

Metal-dielectric-metal (MDM) structures provide directional emission close to the surface normal, which offers opportunities for new design formats in fluorescence based applications. The directional emission arises due to near-field coupling of fluorophores with the optical modes present in the MDM substrate. Reflectivity simulations and dispersion diagrams provide a basic understanding of the mode profiles and the factors that affect the coupling efficiency and the spatial distribution of the coupled emission. This work reveals that the composition of the metal layers, the location of the dye in the MDM substrate and the dielectric thickness are important parameters that can be chosen to tune the color of the emission wavelength, the angle of observation, the angular divergence of the emission and the polarization of the emitted light. These features are valuable for displays and optical signage.

Directional Emission from Metal-Dielectric-Metal Structures: Effect of Mixed Metal Layers, Dye Location and Dielectric Thickness

PubMed Central

Choudhury, Sharmistha Dutta; Badugu, Ramachandram; Ray, Krishanu; Lakowicz, Joseph R.

2015-01-01

Metal-dielectric-metal (MDM) structures provide directional emission close to the surface normal, which offers opportunities for new design formats in fluorescence based applications. The directional emission arises due to near-field coupling of fluorophores with the optical modes present in the MDM substrate. Reflectivity simulations and dispersion diagrams provide a basic understanding of the mode profiles and the factors that affect the coupling efficiency and the spatial distribution of the coupled emission. This work reveals that the composition of the metal layers, the location of the dye in the MDM substrate and the dielectric thickness are important parameters that can be chosen to tune the color of the emission wavelength, the angle of observation, the angular divergence of the emission and the polarization of the emitted light. These features are valuable for displays and optical signage. PMID:25844110

Angle-resolved Auger electron spectra induced by neon ion impact on aluminum

NASA Technical Reports Server (NTRS)

Pepper, S. V.; Aron, P. R.

1986-01-01

Auger electron emission from aluminum bombarded with 1 to 5 keV neon ions was studied by angle-resolved electron spectroscopy. The position and shape of the spectral features depended on the incident ion energy, angle of ion incidence, and electron take-off angle with respect to the aluminum surface. These spectral dependencies were interpreted in terms of the Doppler shift given to the Auger electron velocity by the excited atom ejected into the vacuum. For oblique ion incidence it is concluded that a flux of high energy atoms are ejected in a direction close to the projection of the ion beam on the target surface. In addition, a new spectral feature was found and identified as due to Auger emission from excited neon in the aluminum matrix.

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

Hsia Chih-Hao; Sadjadi, Seyedabdolreza; Zhang Yong

An unidentified infrared emission (UIE) feature at 6.0 μ m is detected in a number of astronomical sources showing the UIE bands. In contrast to the previous suggestion that this band is due to C=O vibrational modes, we suggest that the 6.0 μ m feature arises from olefinic double-bond functional groups. These groups are likely to be attached to aromatic rings, which are responsible for the major UIE bands. The possibility that the formation of these functional groups is related to the hydrogenation process is discussed.

Research of the Electron Cyclotron Emission with Vortex Property excited by high power high frequency Gyrotron

NASA Astrophysics Data System (ADS)

Goto, Yuki; Kubo, Shin; Tsujimura, Tohru; Takubo, Hidenori

2017-10-01

Recently, it has been shown that the radiation from a single electron in cyclotron motion has vortex property. Although the cyclotron emission exists universally in nature, the vortex property has not been featured because this property is normally cancelled out due to the randomness in gyro-phase of electrons and the development of detection of the vortex property has not been well motivated. In this research, we are developing a method to generate the vortex radiation from electrons in cyclotron motion with controlled gyro-phase. Electron that rotates around the uniform static magnetic field is accelerated by right-hand circular polarized (RHCP) radiation resonantly when the cyclotron frequency coincides with the applied RHCP radiation frequency. A large number of electrons can be coherently accelerated in gyro-phase by a RHCP high power radiation so that these electrons can radiate coherent emission with vortex feature. We will show that vortex radiation created by purely rotating electrons for the first time.

Mid-infrared spectra of comet nuclei

NASA Astrophysics Data System (ADS)

Kelley, Michael S. P.; Woodward, Charles E.; Gehrz, Robert D.; Reach, William T.; Harker, David E.

2017-03-01

Comet nuclei and D-type asteroids have several similarities at optical and near-IR wavelengths, including near-featureless red reflectance spectra, and low albedos. Mineral identifications based on these characteristics are fraught with degeneracies, although some general trends can be identified. In contrast, spectral emissivity features in the mid-infrared provide important compositional information that might not otherwise be achievable. Jovian Trojan D-type asteroids have emissivity features strikingly similar to comet comae, suggesting that they have the same compositions and that the surfaces of the Trojans are highly porous. However, a direct comparison between a comet and asteroid surface has not been possible due to the paucity of spectra of comet nuclei at mid-infrared wavelengths. We present 5-35 μm thermal emission spectra of comets 10P/Tempel 2, and 49P/Arend-Rigaux observed with the Infrared Spectrograph on the Spitzer Space Telescope. Our analysis reveals no evidence for a coma or tail at the time of observation, suggesting the spectra are dominated by the comet nucleus. We fit each spectrum with the near-Earth asteroid thermal model (NEATM) and find sizes in agreement with previous values. However, the NEATM beaming parameters of the nuclei, 0.74-0.83, are systematically lower than the Jupiter-family comet population mean of 1.03 ± 0.11, derived from 16- and 22-μm photometry. We suggest this may be either an artifact of the spectral reduction, or the consequence of an emissivity low near 16 μm. When the spectra are normalized by the NEATM model, a weak 10-μm silicate plateau is evident, with a shape similar to those seen in mid-infrared spectra of D-type asteroids. A silicate plateau is also evident in previously published Spitzer spectra of the nucleus of comet 9P/Tempel 1. We compare, in detail, these comet nucleus emission features to those seen in spectra of the Jovian Trojan D-types (624) Hektor, (911) Agamemnon, and (1172) Aneas, as well as those seen in the spectra of seven comet comae. The comet comae present silicate features with two distinct shapes, either trapezoidal, or more rounded, the latter apparently due to enhanced emission near 8 to 8.5 μm. The surfaces of Tempel 2, Arend-Rigaux, and Hektor best agree with the comae that present trapezoidal features, furthering the hypothesis that the surfaces of these targets must have high porosities in order to exhibit a spectrum similar to a comet coma. An emissivity minimum at 15 μm, present in the spectra of Tempel 2, Arend-Rigaux, Hektor, and Agamemnon, is also described, the origin of which remains unidentified. The compositional similarity between D-type asteroids and comets is discussed, and our data supports the hypothesis that they have similar origins in the early Solar System.

Interpretation of satellite airglow observations during the March 22, 1979, magnetic storm, using the coupled ionosphere-thermosphere model developed at University College, London

NASA Technical Reports Server (NTRS)

Parish, H. F.; Gladstone, G. R.; Chakrabarti, S.

1994-01-01

The University of California, Berkeley, extreme ultraviolet spectrometer aboard the U.S. Air Force STP 78-1 satellite measured emission features in the Earth's dayglow due to neutral and ionized species in the atmosphere, in the 35 to 140-nm range. The spectrometer was operating between March 1979 and March 1980, including the period of the magnetic storm on March 22, 1979. Some of these measurements are interpreted using the predictions of the three-dimensional time-dependent coupled ionosphere-thermosphere model developed at University College, London. The observations show a reduction in the atomic oxygen 130.4-nm airglow emission at high northern latitudes following the storm. Model simulations show that this reduction in 130.4-nm emission is associated with an increase in the O2/O ratio. Analysis of model results using electron transport and radiative transport codes show that the brightness of 130.4-nm emission at high latitudes due to resonantly scattered sunlight is approximately twice that due to photoelectron impact excitation. However, the observed decrease in the brightness at high northern latitudes is mainly due to a change in the photoelectron impact source, which contributes approximately 75% of the total, as well as its multiple scattering component; for the photoelectron impact source at 70 deg latitude and 200 km altitude, the reduction in multiple scattering is 1.5 times greater than the reduction in the initial excitation. The reduction in the airglow emission is visible only in the norther n hemisphere because the south pole was not sunlit over the storm period. The comparison of model results with observations suggests that 130.4-nm emission may be useful as a tracer for global changes in the concentration of atomic energy.

Aerosol contribution to the rapid warming of near-term climate under RCP 2.6

NASA Astrophysics Data System (ADS)

Chalmers, N.; Highwood, E. J.; Hawkins, E.; Sutton, R.; Wilcox, L. J.

2012-09-01

The importance of aerosol emissions for near term climate projections is investigated by analysing simulations with the HadGEM2-ES model under two different emissions scenarios: RCP2.6 and RCP4.5. It is shown that the near term warming projected under RCP2.6 is greater than under RCP4.5, even though the greenhouse gas forcing is lower. Rapid and substantial reductions in sulphate aerosol emissions due to a reduction of coal burning in RCP2.6 lead to a reduction in the negative shortwave forcing due to aerosol direct and indirect effects. Indirect effects play an important role over the northern hemisphere oceans, especially the subtropical northeastern Pacific where an anomaly of 5-10 Wm-2 develops. The pattern of surface temperature change is consistent with the expected response to this surface radiation anomaly, whilst also exhibiting features that reflect redistribution of energy, and feedbacks, within the climate system. These results demonstrate the importance of aerosol emissions as a key source of uncertainty in near term projections of global and regional climate.

Spatially extended K Iλ7699 emission in the nebula of VY CMa: kinematics and geometry

NASA Astrophysics Data System (ADS)

Smith, Nathan

2004-04-01

Long-slit echelle spectra reveal bright extended emission from the K Iλ7699 resonance line in the reflection nebula surrounding the extreme red supergiant VY Canis Majoris. The central star has long been known for its unusually bright K I emission lines, but this is the first report of intrinsic emission from K I in the nebula. The extended emission is not just a reflected spectrum of the star, but is due to resonant scattering by K atoms in the outer nebula itself, and is therefore a valuable probe of the kinematics and geometry of the circumstellar environment of VY CMa. Dramatic velocity structure is seen in the long-slit spectra, and most lines of sight through the nebula intersect multiple distinct velocity components. A faint `halo' at large distances from the star does appear to show a reflected spectrum, however, and suggests a systemic velocity of +40 km s-1 with respect to the Sun. The most striking feature is blueshifted emission from the filled interior of a large shell seen in images; the kinematic structure is reminiscent of a Hubble flow, and provides strong evidence for asymmetric and episodic mass loss due to localized eruptions on the stellar surface.

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

Ballering, Nicholas P.; Rieke, George H.; Gáspár, András, E-mail: ballerin@email.arizona.edu

Observations of debris disks allow for the study of planetary systems, even where planets have not been detected. However, debris disks are often only characterized by unresolved infrared excesses that resemble featureless blackbodies, and the location of the emitting dust is uncertain due to a degeneracy with the dust grain properties. Here, we characterize the Spitzer Infrared Spectrograph spectra of 22 debris disks exhibiting 10 μm silicate emission features. Such features arise from small warm dust grains, and their presence can significantly constrain the orbital location of the emitting debris. We find that these features can be explained by themore » presence of an additional dust component in the terrestrial zones of the planetary systems, i.e., an exozodiacal belt. Aside from possessing exozodiacal dust, these debris disks are not particularly unique; their minimum grain sizes are consistent with the blowout sizes of their systems, and their brightnesses are comparable to those of featureless warm debris disks. These disks are in systems of a range of ages, though the older systems with features are found only around A-type stars. The features in young systems may be signatures of terrestrial planet formation. Analyzing the spectra of unresolved debris disks with emission features may be one of the simplest and most accessible ways to study the terrestrial regions of planetary systems.« less

Occurrence and Detectability of Thermal Anomalies on Europa

NASA Astrophysics Data System (ADS)

Hayne, Paul O.; Christensen, Philip R.; Spencer, John R.; Abramov, Oleg; Howett, Carly; Mellon, Michael; Nimmo, Francis; Piqueux, Sylvain; Rathbun, Julie A.

2017-10-01

Endogenic activity is likely on Europa, given its young surface age of and ongoing tidal heating by Jupiter. Temperature is a fundamental signature of activity, as witnessed on Enceladus, where plumes emanate from vents with strongly elevated temperatures. Recent observations suggest the presence of similar water plumes at Europa. Even if plumes are uncommon, resurfacing may produce elevated surface temperatures, perhaps due to near-surface liquid water. Detecting endogenic activity on Europa is one of the primary mission objectives of NASA’s planned Europa Clipper flyby mission.Here, we use a probabilistic model to assess the likelihood of detectable thermal anomalies on the surface of Europa. The Europa Thermal Emission Imaging System (E-THEMIS) investigation is designed to characterize Europa’s thermal behavior and identify any thermal anomalies due to recent or ongoing activity. We define “detectability” on the basis of expected E-THEMIS measurements, which include multi-spectral infrared emission, both day and night.Thermal anomalies on Europa may take a variety of forms, depending on the resurfacing style, frequency, and duration of events: 1) subsurface melting due to hot spots, 2) shear heating on faults, and 3) eruptions of liquid water or warm ice on the surface. We use numerical and analytical models to estimate temperatures for these features. Once activity ceases, lifetimes of thermal anomalies are estimated to be 100 - 1000 yr. On average, Europa’s 10 - 100 Myr surface age implies a resurfacing rate of ~3 - 30 km2/yr. The typical size of resurfacing features determines their frequency of occurrence. For example, if ~100 km2 chaos features dominate recent resurfacing, we expect one event every few years to decades. Smaller features, such as double-ridges, may be active much more frequently. We model each feature type as a statistically independent event, with probabilities weighted by their observed coverage of Europa’s surface. Our results show that if Europa is resurfaced continuously by the processes considered, there is a >99% chance that E-THEMIS will detect a thermal anomaly due to endogenic activity. Therefore, if no anomalies are detected, these models can be ruled out, or revised.

Compositional Variations of Titan's Impact Craters Indicates Active Surface Erosion

NASA Astrophysics Data System (ADS)

Werynski, Alyssa; Neish, Catherine; Le Gall, Alice; Janssen, Michael A.

2017-10-01

Titan’s crust is assumed to be mostly water-ice. However, the surface composition is not well constrained due to its thick atmosphere. Based on infrared and radiometry data, the surface appears enriched in organics, with only few areas showing evidence of exposed water-ice. Regions of water-ice enrichment include the rims and ejecta blankets of impact craters. This study utilizes these geologic features to examine compositional variations across Titan’s surface, and their subsequent modification due to erosional processes.Sixteen craters and their ejecta blankets were mapped on a Cassini RADAR mosaic. These features were selected because they are some of the best preserved craters on Titan. Composition was inferred from Cassini’s Visual and Infrared Mapping Spectrometer (VIMS) and 2-cm emissivity data from the Cassini radiometer. With VIMS, different compositional units were inferred from their reflectivity at specific wavelengths. With the emissivity data, high values suggest more organic-rich material, while lower values indicate strong volume scattering. Areas with low emissivity have been interpreted to be water-ice rich, as water-ice is a favorable medium for volume scattering.Results show fresher, well-preserved craters in the dunes regions have a low emissivity indicative of water-ice, and a VIMS spectrum consistent with an unknown material, possibly a mixture of water-ice and organics. As these craters erode over time, the VIMS spectra remain the same but the emissivity increases. Well-preserved craters in the mid-latitude plains show VIMS spectra and emissivity values consistent with water-ice. As these plain craters degrade, the VIMS spectra remain the same, but the emissivity increases. The differing VIMS signatures suggest more mixing with organics during the cratering event in the organic-rich dunes than the plains. The changes in emissivity over time are consistent with organic infilling of subsurface fractures in both regions, with limited surficial alteration. These results support the idea that compositional variations in Titan’s impact craters are related primarily to erosion and infilling, and to a lesser extent, local variations in the overlying organic material of the pre-impact substrate.

Non-Markovian dynamics of a qubit due to single-photon scattering in a waveguide

NASA Astrophysics Data System (ADS)

Fang, Yao-Lung L.; Ciccarello, Francesco; Baranger, Harold U.

2018-04-01

We investigate the open dynamics of a qubit due to scattering of a single photon in an infinite or semi-infinite waveguide. Through an exact solution of the time-dependent multi-photon scattering problem, we find the qubit's dynamical map. Tools of open quantum systems theory allow us then to show the general features of this map, find the corresponding non-Linbladian master equation, and assess in a rigorous way its non-Markovian nature. The qubit dynamics has distinctive features that, in particular, do not occur in emission processes. Two fundamental sources of non-Markovianity are present: the finite width of the photon wavepacket and the time delay for propagation between the qubit and the end of the semi-infinite waveguide.

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

Rout, Dipak; Vijaya, R.; Centre for Lasers and Photonics, Indian Institute of Technology Kanpur, Kanpur 208016

Well-ordered opaline photonic crystals are grown by inward growing self-assembly method from Rhodamine B dye-doped polystyrene colloids. Subsequent to self-assembly, the crystals are infiltrated with gold nanoparticles of 40 nm diameter. Measurements of the stopband features and photoluminescence intensity from these crystals are supplemented by fluorescence decay time analysis. The fluorescence decay times from the dye-doped photonic crystals before and after the infiltration are dramatically different from each other. A lowered fluorescence decay time was observed for the case of gold infiltrated crystal along with an enhanced emission intensity. Double-exponential decay nature of the fluorescence from the dye-doped crystal gets convertedmore » into single-exponential decay upon the infiltration of gold nanoparticles due to the resonant radiative process resulting from the overlap of the surface plasmon resonance with the emission spectrum. The influence of localized surface plasmon due to gold nanoparticles on the increase in emission intensity and decrease in decay time of the emitters is established.« less

Comparative Studies of the Dust around Red Supergiant and Oxygen-Rich Asymptotic Giant Branch Stars in the Local Universe

NASA Astrophysics Data System (ADS)

Sargent, B. A.; Srinivasan, S.; Speck, A.; Volk, K.; Kemper, F.; Reach, W.; Lagadec, E.; Bernard, J.-P.; McDonald, I.; Meixner, M.; Sloan, G. C.; Jones, O.

We analyze the dust emission features seen in Spitzer Space Telescope Infrared Spectrograph (IRS) spectra of red supergiant (RSG) and oxygen-rich asymptotic giant branch (AGB) stars in the Large Magellanic Cloud and Small Magellanic Cloud galaxies and in various Milky Way globular clusters. The spectra come from the Spitzer Legacy program SAGE-Spectroscopy (PI: F. Kemper), the Spitzer program SMC-Spec (PI: G. Sloan), and other archival Spitzer-IRS programs. The broad 10 and 20 micron emission features attributed to amorphous dust of silicate composition seen in the spectra show evidence for systematic differences in the centroid of both emission features between O-rich AGB and RSG populations. Radiative transfer modeling using the GRAMS grid of models of AGB and RSG stars suggests that the centroid differences are due to differences in dust properties. We investigate differences in dust composition, size, shape, etc that might be responsible for these spectral differences. We explore how these differences may arise from the different circumstellar environments around RSG and O-rich AGB stars and assess effects of varying metallicity (LMC versus SMC versus Milky Way globular cluster) and other properties (mass-loss rate, luminosity, etc.) on the dust originating from these stars. BAS acknowledges funding from NASA ADAP grant NNX13AD54G.

A Broad 22 Micron Emission Feature in the Carina Nebula H ii Region.

PubMed

Chan; Onaka

2000-04-10

We report the detection of a broad 22 µm emission feature in the Carina Nebula H ii region by the Infrared Space Observatory (ISO) short-wavelength spectrometer. The feature shape is similar to that of the 22 µm emission feature of newly synthesized dust observed in the Cassiopeia A supernova remnant. This finding suggests that both of the features are arising from the same carrier and that supernovae are probably the dominant production sources of this new interstellar grain. A similar broad emission dust feature is also found in the spectra of two starburst galaxies from the ISO archival data. This new dust grain could be an abundant component of interstellar grains and can be used to trace the supernova rate or star formation rate in external galaxies. The existence of the broad 22 µm emission feature complicates the dust model for starburst galaxies and must be taken into account correctly in the derivation of dust color temperature. Mg protosilicate has been suggested as the carrier of the 22 µm emission dust feature observed in Cassiopeia A. The present results provide useful information in studies on the chemical composition and emission mechanism of the carrier.

Remote air lasing for trace detection

NASA Astrophysics Data System (ADS)

Dogariu, Arthur; Michael, James B.; Miles, Richard B.

2011-05-01

We demonstrate coherent light propagating backwards from a remotely generated high gain air laser. A short ultraviolet laser pulse tuned to a two-photon atomic oxygen electronic resonance at 226 nm simultaneously dissociates the oxygen molecules in air and excites the resulting atomic oxygen fragments. Due to the focal depth of the pumping laser, a millimeter long region of high gain is created in air for the atomic oxygen stimulated emission at 845nm. We demonstrate that the gain in excess of 60 cm-1 is responsible for both forward and backwards emission of a strong, collimated, coherent laser beam. We present evidence for coherent emission and characterize the backscattered laser beam while varying the pumping conditions. The optical gain and directional emission allows for six orders of magnitude enhancement for the backscattered emission when compared with the fluorescence emission collected into the same solid angle. . This opens new opportunities for the remote detection capabilities of trace species, and provides much greater range for the detection of optical molecular and atomic features from a distant target.

The excess infrared emission of Herbig Ae/Be stars - Disks or envelopes?

NASA Technical Reports Server (NTRS)

Hartmann, Lee; Kenyon, Scott J.; Calvet, Nuria

1993-01-01

It is suggested that the near-IR emission in many Herbig Ae/Be stars arises in surrounding dusty envelopes, rather than circumstellar disks. It is shown that disks around Ae/Be stars are likely to remain optically thick at the required accretion rates. It is proposed that the IR excesses of many Ae/Be stars originate in surrounding dust nebulae instead of circumstellar disks. It is suggested that the near-IR emission of the envelope is enhanced by the same processes that produce anomalous strong continuum emission at temperatures of about 1000 K in reflection nebulae surrounding hot stars. This near-IR emission could be due to small grains transiently heated by UV photons. The dust envelopes could be associated with the primary star or a nearby companion star. Some Ae/Be stars show evidence for the 3.3-6.3-micron emission features seen in reflection nebulae around hot stars, which lends further support to this suggestion.

Study on Emission Spectral Lines of Iron, Fe in Laser-Induced Breakdown Spectroscopy (LIBS) on Soil Samples

NASA Astrophysics Data System (ADS)

Idris, Nasrullah; Lahna, Kurnia; Fadhli; Ramli, Muliadi

2017-05-01

In this work, LIBS technique has been used for detection of heavy metal especially iron, Fe in soil sample. As there are a large number of emission spectral lines due to Fe and other constituents in soil, this study is intended to identify emission spectral lines of Fe and finally to find best fit emission spectral lines for carrying out a qualitative and quantitative analysis. LIBS apparatus used in this work consists of a laser system (Neodymium Yttrium Aluminum Garnet, Nd-YAG: Quanta Ray; LAB SERIES; 1,064 nm; 500 mJ; 8 ns) and an optical multichannel analyzer (OMA) system consisting of a spectrograph (McPherson model 2061; 1,000 mm focal length; f/8.6 Czerny- Turner) and an intensified charge coupled device (ICCD) 1024x256 pixels (Andor I*Star). The soil sample was collected from Banda Aceh city, Aceh, Indonesia. For spectral data acquisition, the soil sample has been prepared by a pressing machine in the form of pellet. The laser beam was focused using a high density lens (f=+150 mm) and irradiated on the surface of the pellet for generating luminous plasma under 1 atmosphere of air surrounding. The plasma emission was collected by an optical fiber and then sent to the optical multichannel analyzer (OMA) system for acquisition of the emission spectra. It was found that there are many Fe emission lines both atomic lines (Fe I) and ionic lines (Fe II) appeared in all detection windows in the wavelength regions, ranging from 200 nm to 1000 nm. The emission lines of Fe with strong intensities occurs together with emission lines due to other atoms such as Mg, Ca, and Si. Thus, the identification of emission lines from Fe is complicated by presence of many other lines due to other major and minor elements in soil. Considering the features of the detected emission lines, several emission spectral lines of Fe I (atomic emission line), especially Fe I 404.58 nm occurring at visible range are potential to be good candidate of analytical lines in relation to detection heavy metal pollution, Fe, in soil sample.

Photoluminescence Studies of P-type Modulation Doped GaAs/AlGaAs Quantum Wells in the High Doping Regime

NASA Astrophysics Data System (ADS)

Wongmanerod, S.; Holtz, P. O.; Reginski, K.; Bugaiski, M.; Monemar, B.

The influence of high Be-acceptor doping on the modulation-doped GaAs/Al0.3Ga0.7As quantum wells structures has been optically studied by using the low-temperature photoluminescence (PL) and photoluminescence excitation (PLE) techniques.The modulation doped samples were grown by the molecular-beam epitaxy technique with a varying Be acceptor concentration ranging from 1×1018 to 8×1018cm-3. Several novels physical effects were observed. The main effect is a significant shift of the main emission towards lower energies as the doping concentrations increase. There are two contradictory mechanisms, which determine the peak energy of the main emission; the shrinkage of the effective bandgap due to many body effects and the reduction of the exciton binding energy due to the carrier screening effect. We conclude that the first one is the dominating effect. At a sufficiently high doping concentration (roughly 2×1018cm-3), the lineshape of the main PL emission is modified, and a new feature, the so called Fermi-edge singularity (FES), appears on the high energy side of the PL emission and exhibits a blue-shift as a function of doping concentration. This feature has been found to be very sensitive to a temperature change, already in the range of 4.4-50K. In addition, PLE spectra with a suitable detection energy show that the absorption edge is blue-shifted with respect to the PL main emission. The resulting Stoke shift is due to phase-space-filling of the carriers, in agreement with the FES interpretation. Finally, we have found from the PLE spectra that the exciton quenching is initiated in the same doping regime. Compared to the exciton quenching in other p-type structures, the critical acceptor concentration required to quench the excitons is significantly lower than in the case of 2D structures with acceptor doping within the well, but larger than in the case of 3D bulk.

FE K EMISSION AND ABSORPTION FEATURES IN THE XMM-EPIC SPECTRUM OF THE SEYFERT GALAXY IC 4329A

NASA Technical Reports Server (NTRS)

Markowitz, A.; Reeves, J. N.; Braito, V.

2001-01-01

We present a re-analysis of the XMM-Newton long-look of the X-ray bright Seyfert galaxy IC 4329a. The Fe K bandpass is dominated by two peaks, consistent with emission from neutral or near-neutral Fe Ka and KP. A relativistic diskline model whereby both peaks are the result of one doubly-peaked diskline profile is found to be a poor description of the data. Models using two relativistic disklines are found to describe the emission profile well. A low-inclination, moderately-relativistic dual-diskline model is possible if the contribution from narrow components, due to distant material, is small or absent. A high-inclination, moderately relativistic profile for each peak is possible if there are roughly equal contributions from both the broad and narrow components. Upper limits on Fe XXV and Fe XXVI emission and absorption at the systemic velocity of IC 4329a are obtained. We also present the results of RXTE monitoring of this source obtained so far; the combined XMM-Newton and RXTE data sets allow us to explore the time-resolved spectral behavior of this source on time scales ranging from hours to 2 years. We find no strong evidence for variability of the Fe Ka emission line on any time scale probed, likely due to the minimal level of continuum variability. We detect a narrow absorption line, at a energy of 7.68 keV in the rest frame of the source; its significance has been confirmed using Monte Carlo simulations. This feature is most likely due to absorption from Fe XXVI blueshifted to approximately 0.1c relative to the systemic velocity, making IC 4329a the lowest-redshift AGN known with a high-velocity, highly-ionized outflow component. As is often the case with similar outflows seen in high-luminosity quasars, the estimated mass outflow rate is larger than the inflow accretion rate, signaling that the outflow represents a substantial portion of the total energy budget of the AGN. The outflow could arise from a radiatively-driven disk wind, or it may be in the form of a discrete, transient blob of ejected material.

Use of Acoustic Emission and Pattern Recognition for Crack Detection of a Large Carbide Anvil

PubMed Central

Chen, Bin; Wang, Yanan; Yan, Zhaoli

2018-01-01

Large-volume cubic high-pressure apparatus is commonly used to produce synthetic diamond. Due to the high pressure, high temperature and alternative stresses in practical production, cracks often occur in the carbide anvil, thereby resulting in significant economic losses or even casualties. Conventional methods are unsuitable for crack detection of the carbide anvil. This paper is concerned with acoustic emission-based crack detection of carbide anvils, regarded as a pattern recognition problem; this is achieved using a microphone, with methods including sound pulse detection, feature extraction, feature optimization and classifier design. Through analyzing the characteristics of background noise, the cracked sound pulses are separated accurately from the originally continuous signal. Subsequently, three different kinds of features including a zero-crossing rate, sound pressure levels, and linear prediction cepstrum coefficients are presented for characterizing the cracked sound pulses. The original high-dimensional features are adaptively optimized using principal component analysis. A hybrid framework of a support vector machine with k nearest neighbors is designed to recognize the cracked sound pulses. Finally, experiments are conducted in a practical diamond workshop to validate the feasibility and efficiency of the proposed method. PMID:29382144

Use of Acoustic Emission and Pattern Recognition for Crack Detection of a Large Carbide Anvil.

PubMed

Chen, Bin; Wang, Yanan; Yan, Zhaoli

2018-01-29

Large-volume cubic high-pressure apparatus is commonly used to produce synthetic diamond. Due to the high pressure, high temperature and alternative stresses in practical production, cracks often occur in the carbide anvil, thereby resulting in significant economic losses or even casualties. Conventional methods are unsuitable for crack detection of the carbide anvil. This paper is concerned with acoustic emission-based crack detection of carbide anvils, regarded as a pattern recognition problem; this is achieved using a microphone, with methods including sound pulse detection, feature extraction, feature optimization and classifier design. Through analyzing the characteristics of background noise, the cracked sound pulses are separated accurately from the originally continuous signal. Subsequently, three different kinds of features including a zero-crossing rate, sound pressure levels, and linear prediction cepstrum coefficients are presented for characterizing the cracked sound pulses. The original high-dimensional features are adaptively optimized using principal component analysis. A hybrid framework of a support vector machine with k nearest neighbors is designed to recognize the cracked sound pulses. Finally, experiments are conducted in a practical diamond workshop to validate the feasibility and efficiency of the proposed method.

The pre- and post-accretion irradiation history of cometary ices

NASA Technical Reports Server (NTRS)

Chyba, Christopher; Sagan, Carl

1989-01-01

Comets Halley and Wilson exhibited similar 3.4 micron emission features at approx. 1 AU from the Sun. A simple model of thermal emission from organic grains fits the feature, provides optical depths in good agreement with spacecraft measurements, and explains the absence of longer-wavelength organic features as due to spectral heliocentric evolution (Chyba and Sagan, 1987). The model utilizes transmission spectra of organics synthesized in the laboratory by irradiation of candidate cometary ices; the authors have long noted that related gas-phase syntheses yield polycyclic aromatic hydrocarbons, among other organic residues (Sagan et al., 1967). The authors previously concluded (Chyba and Sagan, 1987) that Halley's loss of several meters' depth with each perihelion passage, combined with the good fit of the Halley 3.4 micron feature to that of comet Wilson (Allen and Wickramasinghe, 1987), argues for the primordial - but not necessarily interstellar - origin of cometary organics. The authors examine the relative importance to the formation of organics of the variety of radiation environments experienced by comets. They conclude that there is at present no compelling reason to choose any of three contributing mechanisms (pre-accretion UV, pre-accretion cosmic ray, and post-accretion radionuclide processing) as the most important.

Polycyclic Aromatic Hydrocarbon Emission Toward the Galactic Bulge

NASA Astrophysics Data System (ADS)

Shannon, M. J.; Peeters, E.; Cami, J.; Blommaert, J. A. D. L.

2018-03-01

We examine polycyclic aromatic hydrocarbon (PAH), dust, and atomic/molecular emission toward the Galactic bulge using Spitzer Space Telescope observations of four fields: C32, C35, OGLE, and NGC 6522. These fields are approximately centered on (l, b) = (0.°0, 1.°0), (0.°0, ‑1.°0), (0.°4, ‑2.°4), and (1.°0, ‑3.°8), respectively. Far-infrared photometric observations complement the Spitzer/IRS spectroscopic data and are used to construct spectral energy distributions. We find that the dust and PAH emission are exceptionally similar between C32 and C35 overall, in part explained due to their locations—they reside on or near boundaries of a 7 Myr old Galactic outflow event and are partly shock-heated. Within the C32 and C35 fields, we identify a region of elevated Hα emission that is coincident with elevated fine-structure and [O IV] line emission and weak PAH feature strengths. We are likely tracing a transition zone of the outflow into the nascent environment. PAH abundances in these fields are slightly depressed relative to typical ISM values. In the OGLE and NGC 6522 fields, we observe weak features on a continuum dominated by zodiacal dust. SED fitting indicates that thermal dust grains in C32 and C35 have temperatures comparable to those of diffuse, high-latitude cirrus clouds. Little variability is detected in the PAH properties between C32 and C35, indicating that a stable population of PAHs dominates the overall spectral appearance. In fact, their PAH features are exceptionally similar to that of the M82 superwind, emphasizing that we are probing a local Galactic wind environment.

Mg I absorption features in the solar spectrum near 9 and 12 microns

NASA Technical Reports Server (NTRS)

Glenar, David A.; Reuter, Dennis C.; Deming, Drake; Chang, Edward S.

1988-01-01

High-resolution FTS observations from the Kitt Peak National Solar Observatory and the Spacelab 3 ATMOS experiment have revealed additional infrared transitions due to Mg I in the spectra of both quiet sun and sunspot penumbra. In contrast to previous observations, these transitions are seen in absorption, not emission. Absorption intensities range from 1 to 7 percent of the continuum in the quiet sun. In the penumbra, the same features appear to show Zeeman splitting. Modeling of the line profiles in the photospheric spectrum shows evidence for a factor of three overabundance in the n = 5 or more levels of Mg I in the upper photosphere, but with no deviations from a Planck source function. It is concluded that whatever the process that produces the emission (including the Lemke and Holweger mechanism), it must occur well above the tau(5000) = 0.01 level.

A description of the new 3D electron gun and collector modeling tool: MICHELLE

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

Petillo, J.; Mondelli, A.; Krueger, W.

1999-07-01

A new 3D finite element gun and collector modeling code is under development at SAIC in collaboration with industrial partners and national laboratories. This development program has been designed specifically to address the shortcomings of current simulation and modeling tools. In particular, although there are 3D gun codes that exist today, their ability to address fine scale features is somewhat limited in 3D due to disparate length scales of certain classes of devices. Additionally, features like advanced emission rules, including thermionic Child's law and comprehensive secondary emission models also need attention. The program specifically targets problems classes including gridded-guns, sheet-beammore » guns, multi-beam devices, and anisotropic collectors. The presentation will provide an overview of the program objectives, the approach to be taken by the development team, and a status of the project.« less

First observations of stimulated electromagnetic emission in the ionosphere modified by the spear heating facility on Spitsbergen

NASA Astrophysics Data System (ADS)

Tereshchenko, E. D.; Yurik, R. Yu.; Yeoman, T. K.; Robinson, T. R.

2008-11-01

We present the first results of observations of the stimulated electromagnetic emission (SEE) in the ionosphere modified by the Space Plasma Exploration by Active Radar (SPEAR) heating facility. Observation of the SEE is the key method of ground-based diagnostics of the ionospheric plasma disturbances due to high-power HF radiation. The presented results were obtained during the heating campaign performed at the SPEAR facility in February-March 2007. Prominent SEE special features were observed in periods in which the critical frequency of the F 2 layer was higher than the pump-wave frequency (4.45 MHz). As an example, such special features as the downshifted maximum and the broad continuum in the region of negative detunings from the pump-wave frequency are presented. Observations clearly demonstrate that the ionosphere was efficiently excited by the SPEAR heating facility despite the comparatively low pump-wave power.

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

Yamagishi, M.; Kaneda, H.; Ishihara, D.

We present Spitzer /IRS mid-infrared spectral maps of the Galactic star-forming region M17 as well as IRSF/SIRIUS Br γ and Nobeyama 45 m/FOREST {sup 13}CO ( J = 1–0) maps. The spectra show prominent features due to polycyclic aromatic hydrocarbons (PAHs) at wavelengths of 6.2, 7.7, 8.6, 11.3, 12.0, 12.7, 13.5, and 14.2  μ m. We find that the PAH emission features are bright in the region between the H ii region traced by Br γ and the molecular cloud traced by {sup 13}CO, supporting that the PAH emission originates mostly from photo-dissociation regions. Based on the spatially resolved Spitzermore » /IRS maps, we examine spatial variations of the PAH properties in detail. As a result, we find that the interband ratio of PAH 7.7  μ m/PAH 11.3  μ m varies locally near M17SW, but rather independently of the distance from the OB stars in M17, suggesting that the degree of PAH ionization is mainly controlled by local conditions rather than the global UV environments determined by the OB stars in M17. We also find that the interband ratios of the PAH 12.0  μ m, 12.7  μ m, 13.5  μ m, and 14.2  μ m features to the PAH 11.3  μ m feature are high near the M17 center, which suggests structural changes of PAHs through processing due to intense UV radiation, producing abundant edgy irregular PAHs near the M17 center.« less

Mid-infrared interferometric variability of DG Tauri: Implications for the inner-disk structure

NASA Astrophysics Data System (ADS)

Varga, J.; Gabányi, K. É.; Ábrahám, P.; Chen, L.; Kóspál, Á.; Menu, J.; Ratzka, Th.; van Boekel, R.; Dullemond, C. P.; Henning, Th.; Jaffe, W.; Juhász, A.; Moór, A.; Mosoni, L.; Sipos, N.

2017-08-01

Context. DG Tau is a low-mass pre-main sequence star, whose strongly accreting protoplanetary disk exhibits a so-far enigmatic behavior: its mid-infrared thermal emission is strongly time-variable, even turning the 10 μm silicate feature from emission to absorption temporarily. Aims: We look for the reason for the spectral variability at high spatial resolution and at multiple epochs. Methods: Infrared interferometry can spatially resolve the thermal emission of the circumstellar disk, also giving information about dust processing. We study the temporal variability of the mid-infrared interferometric signal, observed with the VLTI/MIDI instrument at six epochs between 2011 and 2014. We fit a geometric disk model to the observed interferometric signal to obtain spatial information about the disk. We also model the mid-infrared spectra by template fitting to characterize the profile and time dependence of the silicate emission. We use physically motivated radiative transfer modeling to interpret the mid-infrared interferometric spectra. Results: The inner disk (r < 1-3 au) spectra exhibit a 10 μm absorption feature related to amorphous silicate grains. The outer disk (r > 1-3 au) spectra show a crystalline silicate feature in emission, similar to the spectra of comet Hale-Bopp. The striking difference between the inner and outer disk spectral feature is highly unusual among T Tauri stars. The mid-infrared variability is dominated by the outer disk. The strength of the silicate feature changed by more than a factor of two. Between 2011 and 2014 the half-light radius of the mid-infrared-emitting region decreased from 1.15 to 0.7 au. Conclusions: For the origin of the absorption we discuss four possible explanations: a cold obscuring envelope, an accretion heated inner disk, a temperature inversion on the disk surface and a misaligned inner geometry. The silicate emission in the outer disk can be explained by dusty material high above the disk plane, whose mass can change with time, possibly due to turbulence in the disk. Based on observations made with the ESO Very Large Telescope Interferometer at Paranal Observatory (Chile) under the programs 088.C-1007 (PI: L. Mosoni), 090.C-0040 (PI: Th. Ratzka), and 092.C-0086 (PI: Th. Ratzka).

The Identification of Complex Organic Molecules in the Interstellar Medium: Using Lasers and Matrix Isolation Spectroscopy to Simulate the Interstellar Environment

NASA Technical Reports Server (NTRS)

Stone, Bradley M.

1998-01-01

The Astrochemistry Group at NASA Ames Research Center is interested in the identification of large organic molecules in the interstellar medium Many smaller organic species (e.g. hydrocarbons, alcohols, etc.) have been previously identified by their radiofrequency signature due to molecular rotations. However, this becomes increasingly difficult to observe as the size of the molecule increases. Our group in interested in the identification of the carriers of the Diffuse Interstellar Bands (absorption features observed throughout the visible and near-infrared in the spectra of stars, due to species in the interstellar medium). Polycyclic Aromatic Hydrocarbons (PAHs) and related molecules are thought to be good candidates for these carriers. Laboratory experiments am performed at Ames to simulate the interstellar environment, and to compare spectra obtained from molecules in the laboratory to those derived astronomically. We are also interested in PAHs with respect to their possible connection to the UIR (Unidentified infrared) and ERE (Extended Red Emission) bands - emission features found to emanate from particular regions of our galaxy (e.g. Orion nebula, Red Rectangle, etc.). An old, "tried and proven spectroscopic technique, matrix isolation spectroscopy creates molecular conditions ideal for performing laboratory astrophysics.

Acoustic emission signatures of damage modes in concrete

NASA Astrophysics Data System (ADS)

Aggelis, D. G.; Mpalaskas, A. C.; Matikas, T. E.; Van Hemelrijck, D.

2014-03-01

The characterization of the dominant fracture mode may assist in the prediction of the remaining life of a concrete structure due to the sequence between successive tensile and shear mechanisms. Acoustic emission sensors record the elastic responses after any fracture event converting them into electric waveforms. The characteristics of the waveforms vary according to the movement of the crack tips, enabling characterization of the original mode. In this study fracture experiments on concrete beams are conducted. The aim is to examine the typical acoustic signals emitted by different fracture modes (namely tension due to bending and shear) in a concrete matrix. This is an advancement of a recent study focusing on smaller scale mortar and marble specimens. The dominant stress field and ultimate fracture mode is controlled by modification of the four-point bending setup while acoustic emission is monitored by six sensors at fixed locations. Conclusions about how to distinguish the sources based on waveform parameters of time domain (duration, rise time) and frequency are drawn. Specifically, emissions during the shear loading exhibit lower frequencies and longer duration than tensile. Results show that, combination of AE features may help to characterize the shift between dominant fracture modes and contribute to the structural health monitoring of concrete. This offers the basis for in-situ application provided that the distortion of the signal due to heterogeneous wave path is accounted for.

A cloud collision model for water maser excitation.

PubMed

Tarter, J C; Welch, W J

1986-06-01

High-velocity collisions between small, dense, neutral clouds or between a dense cloud and a dense shell can provide the energy source required to excite H2O maser emission. The radiative precursor from the surface of the collisional shock front rapidly diffuses through the cloud, heating the dust grains but leaving the H2 molecules cool. Transient maser emission occurs as the conditions for the Goldreich and Kwan "hot-dust cold-gas" maser pump scheme are realized locally within the cloud. In time the local maser action quenches due to the heating of the H2 molecules by collisions against the grains. Although this model cannot explain the very long-lived steady maser features, it is quite successful in explaining a number of the observed properties of the high-velocity features in such sources as Orion, W51, and W49. In particular, it provides a natural explanation for the rapid time variations, the narrow line widths, juxtaposition of high- and low-velocity features, and the short lifetimes which are frequently observed for the so-called high-velocity maser "bullets" thought to be accelerated by strong stellar winds.

POLYCYCLIC AROMATIC HYDROCARBON PROCESSING IN THE BLAST WAVE OF THE SUPERNOVA REMNANT N132D

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

Tappe, A.; Rho, J.; Boersma, C.

2012-08-01

We present Spitzer Infrared Spectrograph 14-36 {mu}m mapping observations of the supernova remnant N132D in the Large Magellanic Cloud. This study focuses on the processing of polycyclic aromatic hydrocarbons (PAHs) that we previously identified in the southern blast wave. The mid-infrared spectra show strong continuum emission from shock-heated dust and a unique, nearly featureless plateau in the 15-20 {mu}m region, which we attribute to PAH molecules. The typical PAH emission bands observed in the surrounding interstellar medium ahead of the blast wave disappear, which indicates shock processing of PAH molecules. The PAH plateau appears most strongly at the outer edgemore » of the blast wave and coincides with diffuse X-ray emission that precedes the brightest X-ray and optical filaments. This suggests that PAH molecules in the surrounding medium are swept up and processed in the hot gas of the blast wave shock, where they survive the harsh conditions long enough to be detected. We also observe a broad emission feature at 20 {mu}m appearing with the PAH plateau. We speculate that this feature is either due to FeO dust grains or connected to the processing of PAHs in the supernova blast wave shock.« less

Land Surface Microwave Emissivities Derived from AMSR-E and MODIS Measurements with Advanced Quality Control

NASA Technical Reports Server (NTRS)

Moncet, Jean-Luc; Liang, Pan; Galantowicz, John F.; Lipton, Alan E.; Uymin, Gennady; Prigent, Catherine; Grassotti, Christopher

2011-01-01

A microwave emissivity database has been developed with data from the Advanced Microwave Scanning Radiometer-EOS (AMSR-E) and with ancillary land surface temperature (LST) data from the Moderate Resolution Imaging Spectroradiometer (MODIS) on the same Aqua spacecraft. The primary intended application of the database is to provide surface emissivity constraints in atmospheric and surface property retrieval or assimilation. An additional application is to serve as a dynamic indicator of land surface properties relevant to climate change monitoring. The precision of the emissivity data is estimated to be significantly better than in prior databases from other sensors due to the precise collocation with high-quality MODIS LST data and due to the quality control features of our data analysis system. The accuracy of the emissivities in deserts and semi-arid regions is enhanced by applying, in those regions, a version of the emissivity retrieval algorithm that accounts for the penetration of microwave radiation through dry soil with diurnally varying vertical temperature gradients. These results suggest that this penetration effect is more widespread and more significant to interpretation of passive microwave measurements than had been previously established. Emissivity coverage in areas where persistent cloudiness interferes with the availability of MODIS LST data is achieved using a classification-based method to spread emissivity data from less-cloudy areas that have similar microwave surface properties. Evaluations and analyses of the emissivity products over homogeneous snow-free areas are presented, including application to retrieval of soil temperature profiles. Spatial inhomogeneities are the largest in the vicinity of large water bodies due to the large water/land emissivity contrast and give rise to large apparent temporal variability in the retrieved emissivities when satellite footprint locations vary over time. This issue will be dealt with in the future by including a water fraction correction. Also note that current reliance on the MODIS day-night algorithm as a source of LST limits the coverage of the database in the Polar Regions. We will consider relaxing the current restriction as part of future development.

Exciton localization and ultralow onset ultraviolet emission in ZnO nanopencils-based heterojunction diodes.

PubMed

Jiang, Junyan; Zhang, Yuantao; Chi, Chen; Long, Yan; Han, Xu; Wu, Bin; Zhang, Baolin; Du, Guotong

2016-09-05

n-GaN/i-ZnO/p-GaN double heterojunction diodes were constructed by vertically binding p-GaN wafer on the tip of ZnO nanopencil arrays grown on n-GaN/sapphire substrates. An increased quantum confinement in the tip of ZnO nanopencils has been verified by photoluminescence measurements combined with quantitative analyses. Under forward bias, a sharp ultraviolet emission at ~375 nm due to localized excitons recombination can be observed in ZnO. The electroluminescence mechanism of the studied diode is tentatively elucidated using a simplified quantum confinement model. Additionally, the improved performance of the studied diode featuring an ultralow emission onset, a good operation stability and an enhanced ultraviolet emission shows the potential of our approach. This work provides a new route for the design and development of ZnO-based excitonic optoelectronic devices.

Feature Selection for Nonstationary Data: Application to Human Recognition Using Medical Biometrics.

PubMed

Komeili, Majid; Louis, Wael; Armanfard, Narges; Hatzinakos, Dimitrios

2018-05-01

Electrocardiogram (ECG) and transient evoked otoacoustic emission (TEOAE) are among the physiological signals that have attracted significant interest in biometric community due to their inherent robustness to replay and falsification attacks. However, they are time-dependent signals and this makes them hard to deal with in across-session human recognition scenario where only one session is available for enrollment. This paper presents a novel feature selection method to address this issue. It is based on an auxiliary dataset with multiple sessions where it selects a subset of features that are more persistent across different sessions. It uses local information in terms of sample margins while enforcing an across-session measure. This makes it a perfect fit for aforementioned biometric recognition problem. Comprehensive experiments on ECG and TEOAE variability due to time lapse and body posture are done. Performance of the proposed method is compared against seven state-of-the-art feature selection algorithms as well as another six approaches in the area of ECG and TEOAE biometric recognition. Experimental results demonstrate that the proposed method performs noticeably better than other algorithms.

Light Curve and Spectral Evolution of Type IIb Supernovae

NASA Astrophysics Data System (ADS)

Gangopadhyay, Anjasha; Misra, Kuntal; Pastorello, Andrea; Sahu, Devendra Kumar; Singh, Mridweeka; Dastidar, raya; Anapuma, Gadiyara Chakrapani; Kumar, Brijesh; Pandey, Shashi Bhushan

2018-04-01

Stripped-Envelope Supernovae constitute the sub-class of core-collapse supernovae that strip off their outer hydrogen envelope due to high stellar winds or due to interaction with a binary companion where mass transfer occurs as a result of Roche lobe overflow. We present here the photometric and spectroscopic analysis of a member of this class : SN 2015as classified as a type IIb supernova. Light curve features are similar to those of SN 2011fu while spectroscopic features are quite similar to those of SN 2008ax and SN 2011dh. Early epoch spectra have been modelled with SYN++ which indicates a photospheric velocity of 8500 km sec-1 and temperature of 6500K. Spectroscopic lines show transitioning from H to He features confirming it to be a type IIb supernova. Prominent oxygen and calcium emission features are indicative of the asymmetry of the ejecta. We also estimate the signal to noise ratio of the 3.6m telescope data. This telescope is located at ARIES, Devasthal, Nainital at an altitude of 2450m. We also show the comparison plots of spectra taken with a 2m and 4m class telescopes to enlighten the importance of spectral features displayed by bigger diameter telescopes.

Optical spectrophotometry of Wolf-Rayet galaxies

NASA Technical Reports Server (NTRS)

Vacca, William D.; Conti, Peter S.

1992-01-01

We have obtained long-slit optical spectra of 10 Wolf-Rayet galaxies and four other starburst galaxies. Using the nebular emission lines we have determined the electron temperatures, electron densities, extinctions, oxygen abundances, mass of ionized hydrogen, and numbers of ionizing photons due to hot stars in these galaxies. The various forbidden line ratios clearly indicate a stellar origin for the emission-line spectrum. From the flux of the broad He II 4686 A emission feature we have estimated the number of Wolf-Rayet stars present. We have accounted for the contribution of these stars to the total ionizing flux and have calculated the ratio of the number of these stars to the number of O stars. Wolf-Rayet galaxies are among the youngest examples of the starburst phenomenon, which we observed at a propitious moment.

A Study of the 3.3 and 3.4 μm Emission Features in Proto-Planetary Nebulae

NASA Astrophysics Data System (ADS)

Hrivnak, Bruce J.; Geballe, T. R.; Kwok, Sun

2007-06-01

Medium-resolution spectra have been obtained of seven carbon-rich proto-planetary nebulae (PPNs) and one young planetary nebula from 3.2 to 3.8 μm, an interval containing the prominent hydrocarbon CH stretches at 3.3 and 3.4 μm due to aromatic and aliphatic structures, respectively. The 3.3 μm feature is newly identified in IRAS 23304+6147, 22223+4327, and 06530-0213 and is confirmed in Z02229+6208. Three of the PPNs emit in the 3.4 μm feature, two of these being new identifications, IRAS 20000+3239 and 01005+7910, with two others showing possible detections. The 3.3 and 3.4 μm emission features in IRAS 22272+5435 are seen in the nebula offset from the star but not at the position of the central star, consistent with the 2003 results of Goto et al. A similar distribution is seen for the 3.3 μm feature in IRAS 22223+4327. All of the PPNs except IRAS 22272+5435 show Class A 3 μm emission features. These observations, when combined with those of the approximately equal number of other carbon-rich PPNs previously observed, demonstrate that there are large differences in the 3 μm emission bands, even for PPNs with central stars of similar spectral type, and thus that the behavior of the bands does not depend solely on spectral type. We also investigated other possible correlations to help explain these differences. These differences do not depend on the C/O value, since the Class B sources fall within the C/O range found for Class A. All of these 3.3 μm sources also show C2 absorption and 21 μm emission features, except IRAS 01005+7910, which is the hottest source at B0. This research is based on observations made at the W. M. Keck Observatory by Gemini staff, supported by the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., on behalf of the international Gemini partnership of Argentina, Australia, Brazil, Canada, Chile, the United Kingdom, and the United States of America. The W. M. Keck Observatory is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

Infrared Space Observatory Observations of Far-Infrared Rotational Emission Lines of Water Vapor Toward the Supergiant Star VY Canis Majoris

NASA Technical Reports Server (NTRS)

Neufeld, David A.; Feuchtgruber, Helmut; Harwit, Martin; Melnick, Gary J.

1999-01-01

We report the detection of numerous far-infrared emission lines of water vapor toward the supergiant star VY Canis Majoris. A 29.5-45 micron grating scan of VY CMa, obtained using the Short-Wavelength Spectrometer (SWS) of the Infrared Space Observatory at a spectral resolving power lambda/delat.lambda of approximately 2000, reveals at least 41 spectral features due to water vapor that together radiate a total luminosity of approximately 25 solar luminosity . In addition to pure rotational transitions within the ground vibrational state, these features include rotational transitions within the (010) excited vibrational state. The spectrum also shows the (sup 2)product(sub 1/2) (J = 5/2) left arrow (sup 2)product(sub 3/2) (J = 3/2) OH feature near 34.6 micron in absorption. Additional SWS observations of VY CMa were carried out in the instrument's Fabry-Perot mode for three water transitions: the 7(sub 25)-6(sub 16) line at 29.8367 micron, the 4(sub 41)-3(sub 12) line at 31.7721 micron, and the 4(sub 32)-3(sub 03) line at 40.6909 micron. The higher spectral resolving power lambda/delta.lambda of approximately 30,000 thereby obtained permits the line profiles to be resolved spectrally for the first time and reveals the "P Cygni" profiles that are characteristic of emission from an outflowing envelope.

Comparative Studies of the Dust around Red Supergiant and Oxygen-Rich Asymptotic Giant Branch Stars in the Local Universe

NASA Astrophysics Data System (ADS)

Sargent, Benjamin; Srinivasan, Sundar; Speck, Angela K.; Volk, Kevin; Kemper, Ciska; Reach, William; Lagadec, Eric; Bernard, Jean-Philippe; McDonald, Iain; Meixner, Margaret; Sloan, Greg; Jones, Olivia

2015-08-01

We analyze the dust emission features seen in Spitzer Space Telescope Infrared Spectrograph (IRS) spectra of red supergiant (RSG) and oxygen-rich asymptotic giant branch (AGB) stars in the Large Magellanic Cloud and Small Magellanic Cloud galaxies and in various Milky Way globular clusters. The spectra come from the Spitzer Legacy program SAGE-Spectroscopy (PI: F. Kemper), the Spitzer program SMC-Spec (PI: G. Sloan), and other archival Spitzer-IRS programs. The broad 10 and 20 μm emission features attributed to amorphous dust of silicate composition seen in the spectra show evidence for systematic differences in the centroid of both emission features between O-rich AGB and RSG populations. Radiative transfer modeling using the GRAMS grid of models of AGB and RSG stars suggests that the centroid differences are due to differences in dust properties. We investigate differences in dust composition, size, shape, etc that might be responsible for these spectral differences. We explore how these differences may arise from the different circumstellar environments around RSG and O-rich AGB stars and assess effects of varying metallicity (LMC versus SMC versus Milky Way globular cluster) and other properties (mass-loss rate, luminosity, etc.) on the dust originating from these stars. BAS acknowledges funding from NASA ADAP grant NNX13AD54G.

The anomalous 3.43 and 3.53 micron emission features toward HD 97048 and Elias 1 - C-C vibrational modes of polycyclic aromatic hydrocarbons?

NASA Technical Reports Server (NTRS)

Schutte, W. A.; Tielens, A. G. G. M.; Allamandola, L. J.; Wooden, D. H.; Cohen, M.

1990-01-01

The 5-8 micron spectra obtained toward the two protostellar sources, HD 97048 and Elias 1 exhibit strong anomalous emission features at 3.43 and 3.53 microns. Combining these results with earlier data established that the emission in the general IR features is extended on at least a 20-arcsec scale. In view of the high energy density in the emission zone, as well as the apparent correspondence of the anomalous 3.43 and 3.53 micron features with weak emission shoulders associated with the general family of IR emission bands, an explanation for these observations in terms of C-C overtones and combination tones of large or dehydrogenated polycyclic aromatic hydrocarbons is judged to be provisionally suitable.

Calibration of Radiation Thermometers up to : Effective Emissivity of the Source

NASA Astrophysics Data System (ADS)

Kozlova, O.; Briaudeau, S.; Rongione, L.; Bourson, F.; Guimier, S.; Kosmalski, S.; Sadli, M.

2015-08-01

The growing demand of industry for traceable temperature measurements up to encourages improvement of calibration techniques for industrial-type radiation thermometers in this temperature range. High-temperature fixed points can be used at such high temperatures, but due to the small diameter of apertures of their cavities (3 mm), they are not adapted for the large field-of-views commonly featured by this kind of radiation thermometers. At LNE-Cnam, a Thermo Gauge furnace of 25.4 mm source aperture diameter is used as a comparison source to calibrate customers' instruments against a reference radiation thermometer calibrated according to the ITS-90 with the lowest uncertainties achievable in the Laboratory. But the furnace blackbody radiator exhibits a large temperature gradient that degrades its effective emissivity, and increases the calibration uncertainty due to the lack of information on the working spectral band of the industrial radiation thermometer. In order to estimate the corrections to apply, the temperature distribution (radial and on-axis) of the Thermo Gauge furnace blackbody radiator was characterized and the effective emissivity of the Thermo Gauge cavity was determined by three different methods. Because of this investigation, the corrections due to different fields of view and due to the different spectral bands of the reference pyrometer and the customer's pyrometer were obtained and the uncertainties on these corrections were evaluated.

Hco+ in the Coma of Comet Hale-Bopp

NASA Astrophysics Data System (ADS)

Lovell, A. J.; Schloerb, F. P.; Bergin, E. A.; Dickens, J. E.; De Vries, C. H.; Senay, M. C.; Irvine, W. M.

1997-05-01

Maps of comet C/1995 O1 (Hale-Bopp) in the millimeter-wave emission of the ion HCO^+ revealed a local minimum near the nucleus position, with a maximum about 100,000 km in the antisolar direction. These observed features of the HCO^+ emission require a low abundance of HCO^+ due to enhanced destruction in the inner coma of the comet, within a region of low electron temperature (T_e). To set constraints on the formation of HCO^+ in the coma, as well as the location and magnitude of the transition to higher T_e, the data are compared with the results of ion-molecule chemistry models.

Bragg crystal spectroscopy on the OSO 8 satellite

NASA Technical Reports Server (NTRS)

Long, K. S.; Chanan, G. A.; Helfand, D. J.; Ku, W. H.-M.; Novick, R.

1979-01-01

Results are reported for high-resolution OSO 8 Bragg-crystal spectroscopy of a variety of cosmic X-ray sources in the energy range from 2 to 10 keV. A continuous spectrum of Sco X-1 is examined, and results of a search for narrow line emission due to iron near 6.7 keV are presented for 32 galactic X-ray sources, including Sco X-1, Cyg X-3, and Cen X-3. It is noted that the strongest evidence for iron line emission has been obtained for Cyg X-3 and that evidence for an iron line feature has also been found in the spectrum of Cen X-3.

HCO+ in the coma of comet Hale-Bopp

NASA Technical Reports Server (NTRS)

Lovell, A. J.; Schloerb, F. P.; Bergin, E. A.; Dickens, J. E.; Devries, C. H.; Senay, M. C.; Irvine, W. M.; Ferris, J. P. (Principal Investigator)

1997-01-01

Maps of comet C/1995 O1 (Hale-Bopp) in the millimeter-wave emission of the ion HCO+ revealed a local minimum near the nucleus position, with a maximum about 100,000 km in the antisolar direction. These observed features of the HCO+ emission require a low abundance of HCO+ due to enhanced destruction in the inner coma of the comet, within a region of low electron temperature (Te). To set constraints on the formation of HCO+ in the coma, as well as the location and magnitude of the transition to higher Te, the data are compared with the results of ion-molecule chemistry models.

PAHFIT: Properties of PAH Emission

NASA Astrophysics Data System (ADS)

Smith, J. D.; Draine, Bruce

2012-10-01

PAHFIT is an IDL tool for decomposing Spitzer IRS spectra of PAH emission sources, with a special emphasis on the careful recovery of ambiguous silicate absorption, and weak, blended dust emission features. PAHFIT is primarily designed for use with full 5-35 micron Spitzer low-resolution IRS spectra. PAHFIT is a flexible tool for fitting spectra, and you can add or disable features, compute combined flux bands, change fitting limits, etc., without changing the code. PAHFIT uses a simple, physically-motivated model, consisting of starlight, thermal dust continuum in a small number of fixed temperature bins, resolved dust features and feature blends, prominent emission lines (which themselves can be blended with dust features), as well as simple fully-mixed or screen dust extinction, dominated by the silicate absorption bands at 9.7 and 18 microns. Most model components are held fixed or are tightly constrained. PAHFIT uses Drude profiles to recover the full strength of dust emission features and blends, including the significant power in the wings of the broad emission profiles. This means the resulting feature strengths are larger (by factors of 2-4) than are recovered by methods which estimate the underlying continuum using line segments or spline curves fit through fiducial wavelength anchors.

From Dark to Light to Fluorescence Resonance Energy Transfer (FRET): Polarity-Sensitive Aggregation-Induced Emission (AIE)-Active Tetraphenylethene-Fused BODIPY Dyes with a Very Large Pseudo-Stokes Shift.

PubMed

Şen, Esra; Meral, Kadem; Atılgan, Serdar

2016-01-11

The work presented herein is devoted to the fabrication of large Stokes shift dyes in both organic and aqueous media by combining dark resonance energy transfer (DRET) and fluorescence resonance energy transfer (FRET) in one donor-acceptor system. In this respect, a series of donor-acceptor architectures of 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) dyes substituted by one, two, or three tetraphenylethene (TPE) luminogens were designed and synthesised. The photophysical properties of these three chromophore systems were studied to provide insight into the nature of donor-acceptor interactions in both THF and aqueous media. Because the generation of emissive TPE donor(s) is strongly polarity dependent, due to its aggregation-induced emission (AIE) feature, one might expect the formation of appreciable fluorescence emission intensity with a very large pseudo-Stokes shift in aqueous media when considering FRET process. Interestingly, similar results were also recorded in THF for the chromophore systems, although the TPE fragment(s) of the dyes are non-emissive. The explanation for this photophysical behaviour lies in the DRET. This is the first report on combining two energy-transfer processes, namely, FRET and DRET, in one polarity-sensitive donor-acceptor pair system. The accuracy of the dark-emissive donor property of the TPE luminogen is also presented for the first time as a new feature for AIE phenomena. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Automatic Jet Contrail Detection and Segmentation

NASA Technical Reports Server (NTRS)

Weiss, J.; Christopher, S. A.; Welch, R. M.

1997-01-01

Jet contrails are an important subset of cirrus clouds in the atmosphere, and thin cirrus are thought to enhance the greenhouse effect due to their semi-transparent nature. They are nearly transparent to the solar energy reaching the surface, but they reduce the planetary emission to space due to their cold ambient temperatures. Having 'seeded' the environment, contrails often elongate and widen into cirrus-like features. However, there is great uncertainty regarding the impact of contrails on surface temperature and precipitation. With increasing numbers of subsonic aircraft operating in the upper troposphere, there is the possibility of increasing cloudiness which could lead to changes in the radiation balance. Automatic detection and seg- mentation of jet contrails in satellite imagery is important because (1) it is impractical to compile a contrail climatology by hand, and (2) with the segmented images it will be possible to retrieve contrail physical properties such as optical thickness, effective ice crystal diameter and emissivity.

The anomalous 3. 43 and 3. 53 micron emission features toward HD 97048 and Elias 1 - C-C vibrational modes of polycyclic aromatic hydrocarbons

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

Schutte, W.A.; Tielens, A.G.G.M.; Allamandola, L.J.

1990-09-01

The 5-8 micron spectra obtained toward the two protostellar sources, HD 97048 and Elias 1 exhibit strong anomalous emission features at 3.43 and 3.53 microns. Combining these results with earlier data established that the emission in the general IR features is extended on at least a 20-arcsec scale. In view of the high energy density in the emission zone, as well as the apparent correspondence of the anomalous 3.43 and 3.53 micron features with weak emission shoulders associated with the general family of IR emission bands, an explanation for these observations in terms of C-C overtones and combination tones ofmore » large or dehydrogenated polycyclic aromatic hydrocarbons is judged to be provisionally suitable. 62 refs.« less

PLANET SHADOWS IN PROTOPLANETARY DISKS. II. OBSERVABLE SIGNATURES

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

Jang-Condell, Hannah

2009-07-20

We calculate simulated images of disks perturbed by embedded small planets. These 10-50 M{sub +} bodies represent the growing cores of giant planets. We examine scattered light and thermal emission from these disks over a range of wavelengths, taking into account the wavelength-dependent opacity of dust in the disk. We also examine the effect of inclination on the observed perturbations. We find that the perturbations are best observed in the visible to mid-infrared (mid-IR). Scattered light images reflect shadows produced at the surface of perturbed disks, while the infrared images follow thermal emission from the surface of the disk, showingmore » cooled/heated material in the shadowed/brightened regions. At still longer wavelengths in the submillimeter, the perturbation fades as the disk becomes optically thin and surface features become overwhelmed by emission closer toward the midplane of the disk. With the construction of telescopes such as TMT, GMT, and ALMA due in the next decade, there is a real possibility of observing planets forming in disks in the optical and submillimeter. However, having the angular resolution to observe the features in the mid-IR will remain a challenge.« less

The discovery of a new infrared emission feature at 1905 wavenumbers (5.25 microns) in the spectrum of BD + 30 deg 3639 and its relation to the polycyclic aromatic hydrocarbon model

NASA Technical Reports Server (NTRS)

Allamandola, L. J.; Bregman, J. D.; Sandford, S. A.; Tielens, A. G. G. M.; Witteborn, F. C.

1989-01-01

A new IR emission feature at 1905/cm (5.25 microns) has been discovered in the spectrum of BD + 30 deg 3639. This feature joins the family of well-known IR emission features at 3040, 2940, 1750, 1610, '1310', 1160, and 890/cm. The origin of this new feature is discussed and it is assigned to an overtone or combination band involving C-H bending modes of polycyclic aromatic hydrocarbons (PAHs). Laboratory work suggests that spectral studies of the 2000-1650/cm region may be very useful in elucidating the molecular structure of interstellar PAHs. The new feature, in conjunction with other recently discovered spectral structures, suggests that the narrow IR emission features originate in PAH molecules rather than large carbon grains.

New Infrared Emission Features and Spectral Variations in Ngc 7023

NASA Technical Reports Server (NTRS)

Werner, M. W.; Uchida, K. I.; Sellgren, K.; Marengo, M.; Gordon, K. D.; Morris, P. W.; Houck, J. R.; Stansberry, J. A.

2004-01-01

We observed the reflection nebula NGC 7023, with the Short-High module and the long-slit Short-Low and Long-Low modules of the Infrared Spectrograph on the Spitzer Space Telescope. We also present Infrared Array Camera (IRAC) and Multiband Imaging Photometer for Spitzer (MIPS) images of NGC 7023 at 3.6, 4.5, 8.0, and 24 m. We observe the aromatic emission features (AEFs) at 6.2, 7.7, 8.6, 11.3, and 12.7 m, plus a wealth of weaker features. We find new unidentified interstellar emission features at 6.7, 10.1, 15.8, 17.4, and 19.0 m. Possible identifications include aromatic hydrocarbons or nanoparticles of unknown mineralogy. We see variations in relative feature strengths, central wavelengths, and feature widths, in the AEFs and weaker emission features, depending on both distance from the star and nebular position (southeast vs. northwest).

A Search for Structure in PAH Emission in Extended Sources at 3.3 and 3.4 Microns

NASA Technical Reports Server (NTRS)

Bregman, Jesse; Temi, P.; Rank, D. M.; Sloan, G. C.; Schultz, A. S. B.; Witteborn, Fred C. (Technical Monitor)

1994-01-01

We have observed three extended sources of the infrared emission features associated with polycyclic aromatic hydrocarbons (PAHs), using a 128x128 InSb array mounted on the 1.5 m NASA/Steward telescope on Mt. Lemmon. We used a CVF (1.5% bandpass) to isolate the emission from the 3.29 and 3.40 microns PAH features in NGC 1333 #3, Sharpless 106, and the Orion Bar. In all three sources, the 3.29 and 3.40 microns emission features arise from the same regions, but show decidedly different structure. We are analyzing the images to determine the relationship of the 3.40 microns feature to the main feature at 3.29 microns. The 3.40 microns feature may be a vibrational overtone of the 3.29 microns feature, or it may arise from attached molecular sidegroups.

FAR-ULTRAVIOLET OBSERVATION OF THE AQUILA RIFT WITH FIMS/SPEAR

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

Park, S.-J.; Min, K.-W.; Seon, K.-I.

2012-07-20

We present the results of far ultraviolet (FUV) observations of the broad region around the Aquila Rift including the Galactic plane. As compared with various wavelength data sets, dust scattering is found to be the major origin of the diffuse FUV continuum in this region. The FUV intensity clearly correlates with the dust extinction level for E(B - V) < 0.2, while this correlation disappears for E(B - V) > 0.2 due to heavy dust extinction combined with the effect of nonuniform interstellar radiation fields. The FUV intensity also correlates well with H{alpha} intensity, implying that at least some fractionmore » of the observed H{alpha} emission could be the dust-scattered light of H{alpha} photons originating elsewhere in the Galaxy. Most of the Aquila Rift region is seen devoid of diffuse FUV continuum due to heavy extinction while strong emission is observed in the surrounding regions. Molecular hydrogen fluorescent emission lines are clearly seen in the spectrum of 'Aquila-Serpens', while 'Aquila-East' does not show any apparent line features. CO emission intensity is also found to be higher in the 'Aquila-Serpens' region than in the 'Aquila-East' region. In this regard, we note that regions of star formation have been found in 'Aquila-Serpens' but not in 'Aquila-East'.« less

Laboratory simulation of infrared astrophysical features. [Terrestrial silicate, meteoritic and lunar soil 10-micron spectral comparisons with comets Bennet and Kohoutek

NASA Technical Reports Server (NTRS)

Rose, L. A.

1979-01-01

Laboratory infrared emission and absorption spectra have been taken of terrestrial silicates, meteorites, and lunar soils in the form of micrometer and submicrometer grains. The emission spectra were taken in a way that imitates telescopic observations. The purpose was to see which materials best simulate the 10-micron astrophysical feature. The emission spectra of dunite, fayalite, and Allende give a good fit to the 10-micron broadband emission feature of comets Bennett and Kohoutek. A study of the effect of grain size on the presence of the 10-micron emission feature of dunite shows that for particles larger than 37 microns no feature is seen. The emission spectrum of the Murray meteorite, a Type 2 carbonaceous chrondrite, is quite similar to the intermediate-resolution spectrum of comet Kohoutek in the 10-micron region. Hydrous silicates or amorphous magnesium silicates in combination with high-temperature condensates, such as olivine or anorthite, would yield spectra that match the intermediate-resolution spectrum of comet Kohoutek in the 10-micron region. Glassy olivine and glassy anorthite in approximately equal proportions would also give a spectrum that is a good fit to the cometary 10-micron feature.

Pollutant emissions from vehicles with regenerating after-treatment systems in regulatory and real-world driving cycles.

PubMed

Alvarez, Robert; Weilenmann, Martin; Novak, Philippe

2008-07-15

Regenerating exhaust after-treatment systems are increasingly employed in passenger cars in order to comply with regulatory emission standards. These systems include pollutant storage units that occasionally have to be regenerated. The regeneration strategy applied, the resultant emission levels and their share of the emission level during normal operation mode are key issues in determining realistic overall emission factors for these cars. In order to investigate these topics, test series with four cars featuring different types of such after-treatment systems were carried out. The emission performance in legislative and real-world cycles was monitored as well as at constant speeds. The extra emissions determined during regeneration stages are presented together with the methodology applied to calculate their impact on overall emissions. It can be concluded that exhaust after-treatment systems with storage units cause substantial overall extra emissions during regeneration mode and can appreciably affect the emission factors of cars equipped with such systems, depending on the frequency of regenerations. Considering that the fleet appearance of vehicles equipped with such after-treatment systems will increase due to the evolution of statutory pollutant emission levels, extra emissions originating from regenerations of pollutant storage units consequently need to be taken into account for fleet emission inventories. Accurately quantifying these extra emissions is achieved by either conducting sufficient repetitions of emission measurements with an individual car or by considerably increasing the size of the sample of cars with comparable after-treatment systems.

piscope - A Python based software package for the analysis of volcanic SO2 emissions using UV SO2 cameras

NASA Astrophysics Data System (ADS)

Gliss, Jonas; Stebel, Kerstin; Kylling, Arve; Solvejg Dinger, Anna; Sihler, Holger; Sudbø, Aasmund

2017-04-01

UV SO2 cameras have become a common method for monitoring SO2 emission rates from volcanoes. Scattered solar UV radiation is measured in two wavelength windows, typically around 310 nm and 330 nm (distinct / weak SO2 absorption) using interference filters. The data analysis comprises the retrieval of plume background intensities (to calculate plume optical densities), the camera calibration (to convert optical densities into SO2 column densities) and the retrieval of gas velocities within the plume as well as the retrieval of plume distances. SO2 emission rates are then typically retrieved along a projected plume cross section, for instance a straight line perpendicular to the plume propagation direction. Today, for most of the required analysis steps, several alternatives exist due to ongoing developments and improvements related to the measurement technique. We present piscope, a cross platform, open source software toolbox for the analysis of UV SO2 camera data. The code is written in the Python programming language and emerged from the idea of a common analysis platform incorporating a selection of the most prevalent methods found in literature. piscope includes several routines for plume background retrievals, routines for cell and DOAS based camera calibration including two individual methods to identify the DOAS field of view (shape and position) within the camera images. Gas velocities can be retrieved either based on an optical flow analysis or using signal cross correlation. A correction for signal dilution (due to atmospheric scattering) can be performed based on topographic features in the images. The latter requires distance retrievals to the topographic features used for the correction. These distances can be retrieved automatically on a pixel base using intersections of individual pixel viewing directions with the local topography. The main features of piscope are presented based on dataset recorded at Mt. Etna, Italy in September 2015.

Circumnuclear Star Formation and AGN Activity: Clues from Surface Brightness Radial Profile of PAHs and [{\\rm{S}}\\,{\\rm{IV}}

NASA Astrophysics Data System (ADS)

Esparza-Arredondo, Donaji; González-Martín, Omaira; Dultzin, Deborah; Alonso-Herrero, Almudena; Ramos Almeida, Cristina; Díaz-Santos, Tanio; García-Bernete, Ismael; Martinez-Paredes, Mariela; Rodríguez-Espinosa, Jose Miguel

2018-06-01

We studied the circumnuclear mid-IR emission in a sample of 19 local active galactic nuclei (AGNs) with high spatial resolution spectra using T-ReCS (Gemini) and CanariCam (GTC), together with Spitzer/IRS observations. We measured the flux and the equivalent width for the 11.3 μm PAH feature and the [S IV] line emission as a function of galactocentric distance. This allowed us to study the star formation (SF) at subkiloparsec scales from the nucleus for a large sample of nearby AGNs. The [S IV] line emission could be tracing the AGN radiation field within a few thousand times the sublimation radius (R sub), but it often peaks at distances greater than 1000 R sub. One possibility is that the SF is contributing to the [S IV] total flux. We found an 11.3 μm PAH emission deficit within the inner few tens of parsecs from the AGN. This deficit might be due to the destruction of the molecules responsible for this feature or the lack of SF at these distances. We found a sensible agreement in the expected shift of the relation of the AGN bolometric luminosity and the SF rate. This indicates that numerical models attributing the link between AGN activity and host galaxy growth to mergers are in agreement with our data, for most inner galaxy parts.

Effect of growth pressure on the synthesis of vertically aligned carbon nanotubes and their growth termination.

PubMed

Park, Sangeun; Song, Wooseok; Kim, Yooseok; Song, Inkyung; Kim, Sung Hwan; Lee, Su Il; Jang, Sung Won; Parkl, Chong-Yun

2014-07-01

When vertically aligned carbon nanotubes (VACNTs) are synthesized by thermal chemical vapor deposition (TCVD), their structural features such as height and density can be determined by TCVD growth conditions. In this study we investigated the effect of growth pressure on the structural features of VACNTs. Changes in growth pressure significantly affected the height, density, and crystalinity of synthesized VACNTs. In addition, we suggest that the growth termination of VACNTs could be due to the lack of carbon feedstock supply to the center of the VACNT film induced by the pressure-dependent adsorption of amorphous carbon at the edge of the VACNT film. In addition, the field emission characteristics of the VACNT film were carried out. The turn-on voltage of the VACNT film was 1.62 V/microm and the field enhancement factor (beta) was 2478. These results provide useful information for practical applications of VACNTs, such as field emission display and X-ray source.

Outstanding features of Cu-doped ZnS nanoclusters

NASA Astrophysics Data System (ADS)

Tawfik, Wael Z.; Farghali, A. A.; Moneim, Ahmed; Imam, N. G.; El-Dek, S. I.

2018-05-01

ZnS and their Cu-doped nanoclusters (NCs) were synthesized successfully using the wet chemical route with different Cu content. The crystalline structure was investigated using x-ray powder diffraction which assured the single-phase formation in cubic symmetry. High-resolution transmission electron microscope indicated the microstructure of NCs with a size ranging from 2–4 nm. A butterfly hysteresis (M-H) loop was observed at room temperature with large values of coercivity for the Cu content of x = 0.05. Photoluminescence emission spectra were recorded from 500–615 nm for pure and Cu-doped ZnS NCs at a 350 nm excitation wavelength. The sample exhibited green fluorescence bands peaking at 535, 544, 552.5, 558.2, and 560.6 nm, which confirmed the characteristic feature of Zn2+ as luminescent centers in the lattice. The additional yellow and orange emissions are due to defect levels or/and impurity centers. The dielectric constant as well as the conductivity values increased with increasing Cu content.

DETECTING RELATIVISTIC X-RAY JETS IN HIGH-REDSHIFT QUASARS

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

McKeough, Kathryn; Siemiginowska, Aneta; Kashyap, Vinay L.

We analyze Chandra X-ray images of a sample of 11 quasars that are known to contain kiloparsec scale radio jets. The sample consists of five high-redshift ( z  ≥ 3.6) flat-spectrum radio quasars, and six intermediate redshift (2.1 <  z  < 2.9) quasars. The data set includes four sources with integrated steep radio spectra and seven with flat radio spectra. A total of 25 radio jet features are present in this sample. We apply a Bayesian multi-scale image reconstruction method to detect and measure the X-ray emission from the jets. We compute deviations from a baseline model that does not include the jet,more » and compare observed X-ray images with those computed with simulated images where no jet features exist. This allows us to compute p -value upper bounds on the significance that an X-ray jet is detected in a pre-determined region of interest. We detected 12 of the features unambiguously, and an additional six marginally. We also find residual emission in the cores of three quasars and in the background of one quasar that suggest the existence of unresolved X-ray jets. The dependence of the X-ray to radio luminosity ratio on redshift is a potential diagnostic of the emission mechanism, since the inverse Compton scattering of cosmic microwave background photons (IC/CMB) is thought to be redshift dependent, whereas in synchrotron models no clear redshift dependence is expected. We find that the high-redshift jets have X-ray to radio flux ratios that are marginally inconsistent with those from lower redshifts, suggesting that either the X-ray emissions are due to the IC/CMB rather than the synchrotron process, or that high-redshift jets are qualitatively different.« less

Recent Observations and Modeling of Narrowband Stimulated Electromagnetic Emissions SEEs at HAARP and EISCAT

NASA Astrophysics Data System (ADS)

Scales, W.; Mahmoudian, A.; Fu, H.; Bordikar, M. R.; Samimi, A.; Bernhardt, P. A.; Briczinski, S. J., Jr.; Kosch, M. J.; Senior, A.; Isham, B.

2014-12-01

There has been significant interest in so-called narrowband Stimulated Electromagnetic Emission SEE over the past several years due to recent discoveries at the High Frequency Active Auroral Research Program HAARP facility near Gakone, Alaska. Narrowband SEE (NSEE) has been defined as spectral features in the SEE spectrum typically within 1 kHz of the transmitter (or pump) frequency. SEE is due to nonlinear processes leading to re-radiation at frequencies other than the pump wave frequency during heating the ionospheric plasma with high power HF radio waves. Although NSEE exhibits a richly complex structure, it has now been shown after a substantial number of observations at HAARP, that NSEE can be grouped into two basic classes. The first are those spectral features, associated with Stimulated Brillouin Scatter SBS, which typically occur when the pump frequency is not close to electron gyro-harmonic frequencies. Typically, these spectral features are within roughly 50 Hz of the pump wave frequency where it is to be noted that the O+ ion gyro-frequency is roughly 50 Hz. The second class of spectral features corresponds to the case when the pump wave frequency is typically within roughly 10 kHz of electron gyro-harmonic frequencies. In this case, spectral features ordered by harmonics of ion gyro-frequencies are typically observed, and termed Stimulated Ion Bernstein Scatter SIBS. This presentation will first provide an overview of the recent NSEE experimental observations at HAARP. Both Stimulated Brillouin Scatter SBS and Stimulated Ion Bernstein Scatter SIBS observations will be discussed as well as their relationship to each other. Possible theoretical formulation in terms of parametric decay instabilities and computational modeling will be provided. Possible applications of NSEE will be pointed out including triggering diagnostics for artificial ionization layer formation, proton precipitation event diagnostics, electron temperature measurements in the heated volume and detection of heavy ion species. Finally potential for observing such SEE at the European Incoherent Scatter EISCAT facility will be discussed.

Cathodoluminescence studies of chevron features in semi-polar (11 2 ¯ 2 ) InGaN/GaN multiple quantum well structures

NASA Astrophysics Data System (ADS)

Brasser, C.; Bruckbauer, J.; Gong, Y.; Jiu, L.; Bai, J.; Warzecha, M.; Edwards, P. R.; Wang, T.; Martin, R. W.

2018-05-01

Epitaxial overgrowth of semi-polar III-nitride layers and devices often leads to arrowhead-shaped surface features, referred to as chevrons. We report on a study into the optical, structural, and electrical properties of these features occurring in two very different semi-polar structures, a blue-emitting multiple quantum well structure, and an amber-emitting light-emitting diode. Cathodoluminescence (CL) hyperspectral imaging has highlighted shifts in their emission energy, occurring in the region of the chevron. These variations are due to different semi-polar planes introduced in the chevron arms resulting in a lack of uniformity in the InN incorporation across samples, and the disruption of the structure which could cause a narrowing of the quantum wells (QWs) in this region. Atomic force microscopy has revealed that chevrons can penetrate over 150 nm into the sample and quench light emission from the active layers. The dominance of non-radiative recombination in the chevron region was exposed by simultaneous measurement of CL and the electron beam-induced current. Overall, these results provide an overview of the nature and impact of chevrons on the luminescence of semi-polar devices.

Infrared Space Observatory Observations of Far-Infrared Rotational Emission Lines of Water Vapor toward the Supergiant Star VY Canis Majoris

NASA Astrophysics Data System (ADS)

Neufeld, David A.; Feuchtgruber, Helmut; Harwit, Martin; Melnick, Gary J.

1999-06-01

We report the detection of numerous far-infrared emission lines of water vapor toward the supergiant star VY Canis Majoris. A 29.5-45 μm grating scan of VY CMa, obtained using the Short-Wavelength Spectrometer (SWS) of the Infrared Space Observatory at a spectral resolving power λ/Δλ of ~2000, reveals at least 41 spectral features due to water vapor that together radiate a total luminosity of ~25 Lsolar. In addition to pure rotational transitions within the ground vibrational state, these features include rotational transitions within the (010) excited vibrational state. The spectrum also shows the 2Π1/2(J=5/2)<--2Π3/2(J=3/2) OH feature near 34.6 μm in absorption. Additional SWS observations of VY CMa were carried out in the instrument's Fabry-Perot mode for three water transitions: the 725-616 line at 29.8367 μm, the 441-312 line at 31.7721 μm, and the 432-303 line at 40.6909 μm. The higher spectral resolving power λ/Δλ of approximately 30,000 thereby obtained permits the line profiles to be resolved spectrally for the first time and reveals the ``P Cygni'' profiles that are characteristic of emission from an outflowing envelope. Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands, and the UK) with the participation of ISAS and NASA.

A survey of IRAS data on 41 classical novae

NASA Astrophysics Data System (ADS)

Harrison, T. E.; Gehrz, R. D.

1988-09-01

The IRAS database has been searched for detections of 41 classical novae using coadditions of survey scans; 15 were detected. IRAS temporal observations of novae in outburst are discussed. The observed long-wavelength infrared distributions of DQ Her, and possibly HR Del, can be explained by emission from small (a of about 0.1 microns) dust grains heated by the central object. An alternative explanation for the energy distributions of DQ Her and HR Del is emission from fine-structure lines. FH Ser and LW Ser display energy distributions that have color temperatures much too hot to be due to heating of dust by the central source in any plausible scenario. Line emission is probably the best explanation of their observed energy distributions. The novae NQ Vul and LV Vul have energy distributions that may be contaminated by emission from galactic cirrus. The unusual object PL 1547.3-5612 exhibits an energy distribution that does not resemble those of planetary nebulae or other novae detected in this sample. An IRAS low-resolution spectrum of RR Tel shows the 10-micron silicate emission feature.

Ultraviolet observations of the Io torus from the IUE observatory

NASA Technical Reports Server (NTRS)

Moos, H. W.; Clarke, J. T.

1981-01-01

The short wavelength spectrograph on the International Ultraviolet Explorer (IUE) has been used to obtain 11 A resolution spectra of the Io torus from 1175-1950 A. The four spectra, obtained in the springs of 1979 and 1980, show emissions (about 40R) of S II A1256A and S III A1199A. An unidentified feature is also present at 1729 A; a tentative identification as an intercombination line of S III is proposed. Weak features, probably due to O III A1664A and S IV A1406A, appear in some of the spectra. Abundances of the ions are determined from the brightnesses of the observed features. Upper limits are also set for the abundances of a number of ionic and neutral species. An observation of Io itself does not show any additional or enhanced spectral features, permitting upper limits to be set on the injection rate for a number of species.

The similarity of broad iron lines in X-ray binaries and active galactic nuclei

NASA Astrophysics Data System (ADS)

Walton, D. J.; Reis, R. C.; Cackett, E. M.; Fabian, A. C.; Miller, J. M.

2012-05-01

We have compared the 2001 XMM-Newton spectra of the stellar mass black hole binary XTE J1650-500 and the active galaxy MCG-6-30-15, focusing on the broad, excess emission features at ˜4-7 keV displayed by both sources. Such features are frequently observed in both low-mass X-ray binaries and active galactic nuclei (AGN). For the former case it is generally accepted that the excess arises due to iron emission, but there is some controversy over whether their width is partially enhanced by instrumental processes, and hence also over the intrinsic broadening mechanism. Meanwhile, in the latter case, the origin of this feature is still subject to debate; physically motivated reflection and absorption interpretations are both able to reproduce the observed spectra. In this work we make use of the contemporaneous BeppoSAX data to demonstrate that the breadth of the excess observed in XTE J1650-500 is astrophysical rather than instrumental, and proceed to highlight the similarity of the excesses present in this source and MCG-6-30-15. Both optically thick accretion discs and optically thin coronae, which in combination naturally give rise to relativistically broadened iron lines when the disc extends close to the black hole, are commonly observed in both classes of object. The simplest solution is that the broad emission features present arise from a common process, which we argue must be reflection from the inner regions of an accretion disc around a rapidly rotating black hole; for XTE J1650-500 we find spin constraints of 0.84 ≤a*≤ 0.98 at the 90 per cent confidence level. Other interpretations proposed for AGN add potentially unnecessary complexities to the theoretical framework of accretion in strong gravity.

Design, Implementation, and Characterization of a Dedicated Breast Computed Mammotomography System for Enhanced Lesion Imaging

DTIC Science & Technology

2006-03-01

Evaluation of fully 3D emission mammotomography with a compact cadmium zinc telluride detector,” IEEE Trans. Med. Imag. (Submitted) 2005. [16] M.P...times over a few months, and the degradation due to compromised adipose tissue boundaries as well as other physical breast features are becoming...breast lesions, especially in radiographically dense breasts,2,11-13 through the removal of contrast-reducing overlying tissue ; (2) uncompressed

An Ultraviolet Spectrum of the Tidal Disruption Flare ASASSN-14li

NASA Astrophysics Data System (ADS)

Cenko, S. Bradley; Cucchiara, Antonino; Roth, Nathaniel; Veilleux, Sylvain; Prochaska, J. Xavier; Yan, Lin; Guillochon, James; Maksym, W. Peter; Arcavi, Iair; Butler, Nathaniel R.; Filippenko, Alexei V.; Fruchter, Andrew S.; Gezari, Suvi; Kasen, Daniel; Levan, Andrew J.; Miller, Jon M.; Pasham, Dheeraj R.; Ramirez-Ruiz, Enrico; Strubbe, Linda E.; Tanvir, Nial R.; Tombesi, Francesco

2016-02-01

We present a Hubble Space Telescope Space Telescope Imaging Spectrograph spectrum of ASASSN-14li, the first rest-frame ultraviolet (UV) spectrum of a tidal disruption flare (TDF). The underlying continuum is well fit by a blackbody with {T}{UV}=3.5× {10}4 K, an order of magnitude smaller than the temperature inferred from X-ray spectra (and significantly more precise than previous efforts based on optical and near-UV photometry). Superimposed on this blue continuum, we detect three classes of features: narrow absorption from the Milky Way (probably a high-velocity cloud), and narrow absorption and broad (˜2000-8000 km s-1) emission lines at or near the systemic host velocity. The absorption lines are blueshifted with respect to the emission lines by Δv = -(250-400) km s-1. Due both to this velocity offset and the lack of common low-ionization features (Mg II, Fe II), we argue these arise from the same absorbing material responsible for the low-velocity outflow discovered at X-ray wavelengths. The broad nuclear emission lines display a remarkable abundance pattern: N III], N IV], and He II are quite prominent, while the common quasar emission lines of C III] and Mg II are weak or entirely absent. Detailed modeling of this spectrum will help elucidate fundamental questions regarding the nature of the emission processes at work in TDFs, while future UV spectroscopy of ASASSN-14li would help to confirm (or refute) the previously proposed connection between TDFs and “N-rich” quasars.

An Ultraviolet Spectrum of the Tidal Disruption Flare ASASSN-14li

NASA Technical Reports Server (NTRS)

Cenko, S. Bradley; Cucchiara, Antonio; Roth, Nathaniel; Veilleux, Sylvain; Prochaska, J. Xavier; Yan, Lin; Guillochon, James; Maksym, W. Peter; Arcavi, Iair; Butler, Nathaniel R.

2016-01-01

We present a Hubble Space Telescope Space Telescope Imaging Spectrograph spectrum of ASASSN-14li, the first rest-frame ultraviolet (UV) spectrum of a tidal disruption flare (TDF). The underlying continuum is well fit by a blackbody with T(sub UV) = 3.5 x 10(exp. 4) K, an order of magnitude smaller than the temperature inferred from X-ray spectra (and significantly more precise than previous efforts based on optical and near-UV photometry).Superimposed on this blue continuum, we detect three classes of features: narrow absorption from the Milky Way (probably a high-velocity cloud), and narrow absorption and broad {approx. 2000-8000 km s(exp. -1)} emission lines at or near the systemic host velocity. The absorption lines are blueshifted with respect to the emission lines by Delta(sub v) = -(250-400) km s(exp. -1). Due both to this velocity offset and the lack of common low-ionization features (Mg II, Fe II), we argue these arise from the same absorbing material responsible for the low-velocity outflow discovered at X-ray wavelengths. The broad nuclear emission lines display a remarkable abundance pattern: N III], N IV], and He II are quite prominent, while the common quasar emission lines of C III] and Mg II are weak or entirely absent. Detailed modeling of this spectrum will help elucidate fundamental questions regarding the nature of the emission processes at work in TDFs, while future UV spectroscopy of ASASSN-14li would help to confirm (or refute) the previously proposed connection between TDFs and N-rich quasars.

Tailoring the chirality of light emission with spherical Si-based antennas.

PubMed

Zambrana-Puyalto, Xavier; Bonod, Nicolas

2016-05-21

Chirality of light is of fundamental importance in several enabling technologies with growing applications in life sciences, chemistry and photodetection. Recently, some attention has been focused on chiral quantum emitters. Consequently, optical antennas which are able to tailor the chirality of light emission are needed. Spherical nanoresonators such as colloids are of particular interest to design optical antennas since they can be synthesized at a large scale and they exhibit good optical properties. Here, we show that these colloids can be used to tailor the chirality of a chiral emitter. To this purpose, we derive an analytic formalism to model the interaction between a chiral emitter and a spherical resonator. We then compare the performances of metallic and dielectric spherical antennas to tailor the chirality of light emission. It is seen that, due to their strong electric dipolar response, metallic spherical nanoparticles spoil the chirality of light emission by yielding achiral fields. In contrast, thanks to the combined excitation of electric and magnetic modes, dielectric Si-based particles feature the ability to inhibit or to boost the chirality of light emission. Finally, it is shown that dual modes in dielectric antennas preserve the chirality of light emission.

Observation of direct infrared multiphoton pumping of the triplet manifold of biacetyl

NASA Astrophysics Data System (ADS)

Tsao, Jeffrey Y.; Black, Jerry G.; Yablonovitch, Eli; Burak, Itamar

1980-09-01

Direct collisionless multiphoton (MP) excitation of the triplet vibronic manifold of biacetyl is reported. Following a dye laser pulse which prepares some of the biacetyl molecules in the triplet metastable state, the system is irradiated by an intense 20 ns 9.6μ CO2 pulse. The CO2 radiation induces fast quenching of the phosphorescence emission from the 3Au excited molecules. It also induces an emission signal in the fluorescence spectral region of biacetyl. This signal is related to an inverse electronic relaxation (IER) from excited triplet vibronic levels into isoenergetic singlet 1Au vibronic levels. Analysis of the induced luminescence signals provides information on the collisionless MP prompted vibrational distribution. Excitation with 10.6μ CO2 pulses leads to the simultaneous MP pumping of both the ground and triplet manifolds. The generation of blue emission signals in this experiment bears a close resemblance to recent observations of prompt visible emission due to MP pumping of ground state molecules. General expressions for the emission intensities are derived with special emphasis on the specific features of MP vibrational distributions. The detectability of MP induced emission signals is discussed.

Ultraviolet Spectroscopy of Tidal Disruption Flares

NASA Astrophysics Data System (ADS)

Cenko, Stephen B.

2017-08-01

When a star passes within the sphere of disruption of a massive black hole, tidal forces will overcome self-gravity and unbind the star. While approximately half of the stellar debris is ejected at high velocities, the remaining material stays bound to the black hole and accretes, resulting in a luminous, long-lived transient known as a tidal disruption flare (TDF). In addition to serving as unique laboratories for accretion physics,TDFs offer the hope of measuring black hole masses in galaxies much too distant for resolved kinematic studies.In order to realize this potential, we must better understand the detailed processes by which the bound debris circularizes and forms an accretion disk. Spectroscopy is critical to this effort, as emission and absorption line diagnostics provide insight into the location and physical state (velocity, density, composition) of the emitting gas (in analogy with quasars). UV spectra are particularly critical, as most strong atomic features fall in this bandpass, and high-redshift TDF discoveries from LSST will sample rest-frame UV wavelengths.Here I present recent attempts to obtain UV spectra of tidal disruption flares. I describe the UV spectrum of ASASSN-14li, in which we detect three classes of features: narrow absorption from the Milky Way (probably a high-velocity cloud), and narrow absorption and broad (2000-8000 km s-1) emission lines at or near the systemic host velocity. The absorption lines are blueshifted with respect to the emission lines by 250-400 km s-1. Due both to this velocity offset and the lack of common low-ionization features (Mg II, Fe II), we argue these arise from the same absorbing material responsible for the low-velocity outflow discovered at X-ray wavelengths. The broad nuclear emission lines display a remarkable abundance pattern: N III], N IV], and He II are quite prominent, while the common quasar emission lines of C III] and Mg II are weak or entirely absent. Detailed modeling of this spectrum will help elucidate fundamental questions regarding the nature of the emission processes at work in TDFs, while future UV spectroscopy of ASASSN-14li would help to confirm (or refute) the previously proposed connection between TDFs and “N-rich” quasars.

Guilt by Association: The 13 micron Dust Feature in Circumstellar Shells and Related Spectral Features

NASA Astrophysics Data System (ADS)

Sloan, G. C.; Kraemer, K. E.; Goebel, J. H.; Price, S. D.

A study of spectra from the SWS on ISO of optically thin oxygen-rich dust shells shows that the strength of the 13 micron dust emission feature is correlated with the CO2 bands (13--17 microns) and dust emission features at 19.8 and 28.1 microns. SRb variables tend to show stronger 13 micron features than Mira variables, suggesting that the presence of the 13 micron and related features depends on pulsation mode and mass-loss rate. The absence of any correlation to dust emission features at 16.8 and 32 microns makes spinel an unlikely carrier. The most plausible carrier of the 13 micron feature remains crystalline alumina, and we suggest that the related dust features may be crystalline silicates. When dust forms in regions of low density, it may condense into crystalline grain structures.

Hazard detection in noise-related incidents - the role of driving experience with battery electric vehicles.

PubMed

Cocron, Peter; Bachl, Veronika; Früh, Laura; Koch, Iris; Krems, Josef F

2014-12-01

The low noise emission of battery electric vehicles (BEVs) has led to discussions about how to address potential safety issues for other road users. Legislative actions have already been undertaken to implement artificial sounds. In previous research, BEV drivers reported that due to low noise emission they paid particular attention to pedestrians and bicyclists. For the current research, we developed a hazard detection task to test whether drivers with BEV experience respond faster to incidents, which arise due to the low noise emission, than inexperienced drivers. The first study (N=65) revealed that BEV experience only played a minor role in drivers' response to hazards resulting from low BEV noise. The tendency to respond, reaction times and hazard evaluations were similar among experienced and inexperienced BEV drivers; only small trends in the assumed direction were observed. Still, both groups clearly differentiated between critical and non-critical scenarios and responded accordingly. In the second study (N=58), we investigated additionally if sensitization to low noise emission of BEVs had an effect on hazard perception in incidents where the noise difference is crucial. Again, participants in all groups differentiated between critical and non-critical scenarios. Even though trends in response rates and latencies occurred, experience and sensitization to low noise seemed to only play a minor role in detecting hazards due to low BEV noise. An additional global evaluation of BEV noise further suggests that even after a short test drive, the lack of noise is perceived more as a comfort feature than a safety threat. Copyright © 2014 Elsevier Ltd. All rights reserved.

Experimental investigation of starting characteristics and wave propagation from a shallow open cavity and its acoustic emission at supersonic speed

NASA Astrophysics Data System (ADS)

Pandian, S.; Desikan, S. L. N.; Niranjan, Sahoo

2018-01-01

Experiments were carried out on a shallow open cavity (L/D = 5) at a supersonic Mach number (M = 1.8) to understand its transient starting characteristics, wave propagation (inside and outside the cavity) during one vortex shedding cycle, and acoustic emission. Starting characteristics and wave propagation were visualized through time resolved schlieren images, while acoustic emissions were captured through unsteady pressure measurements. Results showed a complex shock system during the starting process which includes characteristics of the bifurcated shock system, shock train, flow separation, and shock wave boundary layer interaction. In one vortex shedding cycle, vortex convection from cavity leading edge to cavity trailing edge was observed. Flow features outside the cavity demonstrated the formation and downstream movement of a λ-shock due to the interaction of shock from the cavity leading edge and shock due to vortex and generation of waves on account of shear layer impingement at the cavity trailing edge. On the other hand, interesting wave structures and its propagation were monitored inside the cavity. In one vortex shedding cycle, two waves such as a reflected compression wave from a cavity leading edge in the previous vortex shedding cycle and a compression wave due to the reflection of Mach wave at the cavity trailing edge corner in the current vortex shedding cycle were visualized. The acoustic emission from the cavity indicated that the 2nd to 4th modes/tones are dominant, whereas the 1st mode contains broadband spectrum. In the present studies, the cavity feedback mechanism was demonstrated through a derived parameter coherence coefficient.

Quasi-continuum photoluminescence: Unusual broad spectral and temporal characteristics found in defective surfaces of silica and other materials

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

Laurence, Ted A., E-mail: laurence2@llnl.gov; Bude, Jeff D.; Shen, Nan

2014-02-28

We previously reported a novel photoluminescence (PL) with a distribution of fast decay times in fused silica surface flaws that is correlated with damage propensity by high fluence lasers. The source of the PL was not attributable to any known silica point defect. Due to its broad spectral and temporal features, we here give this PL the name quasi-continuum PL (QC-PL) and describe the features of QC-PL in more detail. The primary features of QC-PL include broad excitation and emission spectra, a broad distribution of PL lifetimes from 20 ps to 5 ns, continuous shifts in PL lifetime distributions with respectmore » to emission wavelength, and a propensity to photo-bleach and photo-brighten. We found similar PL characteristics in surface flaws of other optical materials, including CaF{sub 2}, DKDP, and quartz. Based on the commonality of the features in different optical materials and the proximity of QC-PL to surfaces, we suggest that these properties arise from interactions associated with high densities of defects, rather than a distribution over a large number of types of defects and is likely found in a wide variety of structures from nano-scale composites to bulk structures as well as in both broad and narrow band materials from dielectrics to semiconductors.« less

Untargeted Identification of Wood Type-Specific Markers in Particulate Matter from Wood Combustion.

PubMed

Weggler, Benedikt A; Ly-Verdu, Saray; Jennerwein, Maximilian; Sippula, Olli; Reda, Ahmed A; Orasche, Jürgen; Gröger, Thomas; Jokiniemi, Jorma; Zimmermann, Ralf

2016-09-20

Residential wood combustion emissions are one of the major global sources of particulate and gaseous organic pollutants. However, the detailed chemical compositions of these emissions are poorly characterized due to their highly complex molecular compositions, nonideal combustion conditions, and sample preparation steps. In this study, the particulate organic emissions from a masonry heater using three types of wood logs, namely, beech, birch, and spruce, were chemically characterized using thermal desorption in situ derivatization coupled to a GCxGC-ToF/MS system. Untargeted data analyses were performed using the comprehensive measurements. Univariate and multivariate chemometric tools, such as analysis of variance (ANOVA), principal component analysis (PCA), and ANOVA simultaneous component analysis (ASCA), were used to reduce the data to highly significant and wood type-specific features. This study reveals substances not previously considered in the literature as meaningful markers for differentiation among wood types.

Electronic modulation of infrared radiation in graphene plasmonic resonators.

PubMed

Brar, Victor W; Sherrott, Michelle C; Jang, Min Seok; Kim, Seyoon; Kim, Laura; Choi, Mansoo; Sweatlock, Luke A; Atwater, Harry A

2015-05-07

All matter at finite temperatures emits electromagnetic radiation due to the thermally induced motion of particles and quasiparticles. Dynamic control of this radiation could enable the design of novel infrared sources; however, the spectral characteristics of the radiated power are dictated by the electromagnetic energy density and emissivity, which are ordinarily fixed properties of the material and temperature. Here we experimentally demonstrate tunable electronic control of blackbody emission from graphene plasmonic resonators on a silicon nitride substrate. It is shown that the graphene resonators produce antenna-coupled blackbody radiation, which manifests as narrow spectral emission peaks in the mid-infrared. By continuously varying the nanoresonator carrier density, the frequency and intensity of these spectral features can be modulated via an electrostatic gate. This work opens the door for future devices that may control blackbody radiation at timescales beyond the limits of conventional thermo-optic modulation.

Enhanced lines and box-shaped features in the gamma-ray spectrum from annihilating dark matter in the NMSSM

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

Cerdeño, D.G.; Peiró, M.; Robles, S., E-mail: davidg.cerdeno@gmail.com, E-mail: miguel.peiro@uam.es, E-mail: sandra.robles@uam.es

2016-04-01

We study spectral features in the gamma-ray emission from dark matter (DM) annihilation in the Next-to-Minimal Supersymmetric Standard Model (NMSSM), with either neutralino or right-handed (RH) sneutrino DM . We perform a series of scans over the NMSSM parameter space, compute the DM annihilation cross section into two photons and the contribution of box-shaped features, and compare them with the limits derived from the Fermi-LAT search for gamma-ray lines using the latest Pass 8 data. We implement the LHC bounds on the Higgs sector and on the masses of supersymmetric particles as well as the constraints on low-energy observables. Wemore » also consider the recent upper limits from the Fermi-LAT satellite on the continuum gamma-ray emission from dwarf spheroidal galaxies (dSphs). We show that in the case of the RH sneutrino the constraint on gamma-ray spectral features can be more stringent than the dSph bounds. This is due to the Breit-Wigner enhancement near the ubiquitous resonances with a CP even Higgs and the contribution of scalar and pseudoscalar Higgs final states to box-shaped features. By contrast, for neutralino DM, the di-photon final state is only enhanced in the resonance with a Z boson and box-shaped features are even more suppressed. Therefore, the observation of spectral features could constitute a discriminating factor between both models. In addition, we compare our results with direct DM searches, including the SuperCDMS and LUX limits on the elastic DM-nucleus scattering cross section and show that some of these scenarios would be accessible to next generation experiments. Thus, our findings strengthen the idea of complementarity among distinct DM search strategies.« less

An Emission Inventory of Polycyclic Aromatic Hydrocarbons in China

NASA Astrophysics Data System (ADS)

Mu, Xilong; Zhu, Xianlei; Wang, Xuesong

2015-04-01

Polycyclic Aromatic Hydrocarbons (PAHs) are among the most dangerous compounds due to their high carcinogenic and mutagenic character. Emission inventory provides the primary data to account for the sources of ambient PAHs and server as a necessary database for effective PAHs pollution control. China is experiencing fast economic growth and large energy consumption, which might result in a large amount of PAHs anthropogenic emissions. Therefore, based on the previous studies and combined recently field emission measurements as well as socio-economic activity data, the development of a nationwide PAHs emission inventory is needed. In this work, the emission inventory of 16 PAHs listed as U.S. Environmental Protection Agency priority pollutants in China in the year 2012 is compiled. The emission amounts of PAHs were estimated as annual rates of emission-related activities multiplied by respective emission factors. The activities such as fuel consumption, including fossil fuel and biofuel, and socio-economic statistics were obtained from yearbook released by Chinese central government and/or provincial governments, as well as related industry reports. Emission factors were derived from the related literature. Recently reported emission factors from local measurements were used. The total emissions of PAHs were 120611 ton in 2012. In China, PAHs were emitted predominantly from domestic combustion of coal and biofuel, coking industry and motor vehicles, accounting for 72% of the total amount. PAHs emission profiles were significantly different between China and the other countries. The emission profile in China featured a relatively higher portion of high molecular weight species with carcinogenic potential due to large contributions of domestic combustion and coking industry. Domestic combustion of straw, coal and firewood emitted 19464 ton, 8831 ton, and 5062 ton of PAHs, respectively, which were much higher than those in other countries. Emission per capita showed geographical variations. In general, the southeastern provinces of China were characterized by higher emission per capita. The PAHs emissions were higher in the winter than those in the summer. In the following work, the above emission inventory will be used as an input to Chemical Transport Model to simulate the ambient PAHs concentrations in China, and the uncertainty of the inventory will be assessed based on the comparisons between simulated concentrations and available observations. Acknowledgement This work was financially supported by the Natural Science Foundation of China (Grant No. 41175102). Corresponding author: Xuesong Wang

Optical emission spectroscopic study of plasma plumes generated by IR CO2 pulsed laser on carbon targets

NASA Astrophysics Data System (ADS)

Camacho, J. J.; Díaz, L.; Santos, M.; Reyman, D.; Poyato, J. M. L.

2008-05-01

Optical emission spectroscopy studies, in the spectral range ultraviolet-visible-near infrared (UV-Vis-NIR), were performed to investigate thermal and dynamical properties of a plume produced by laser ablation of a graphite target. Ablation is carried out using a high-power IR CO2 pulsed laser at λ = 9.621 µm, power density ranging from 0.22 to 5.36 GW cm-2 and air pressures around 4 Pa. The strong emission observed in the plasma region is mainly due to electronic relaxation of excited C, ionic fragments C+, C2+ and C3+ and molecular features of C2(d 3Πg-a 3Πu Swan band system). The medium-weak emission is mainly due to excited atomic N, H, O, ionic fragment C4+ and molecular features of C2( E\\,^1\\Sigma _g^+\\--A\\,^{1}\\Pi _u ; Freymark system), C2( D\\,^1\\Sigma _u^+\\--X\\,^1\\Sigma _g^+ ; Mulliken system), CN(D 2Π-A 2Π), C2(e 3Πg-a 3Πu Fox-Herzberg system), C2(C 1Πg-A 1Πu Deslandres-d'Azambuja system), OH(A 2Σ+-X 2Π), CH(C 2Σ+-X 2Π), NH(A 3Π-X 3Σ-), CN(B 2Σ+-X 2Σ+ violet system), CH(B 2Σ+-X 2Π), CH(A 2Δ-X 2Π), C2( A\\,^{1}\\Pi_u\\--X\\,^{1}\\Sigma ^{+}_g ; Phillips system) and CN(A 2Π-X 2Σ+ red system). An excitation temperature Texc = 23 000 ± 1900 K and electron densities in the range (0.6-5.6) × 1016 cm-3 were estimated by means of C+ ionic lines. The characteristics of the spectral emission intensities from different species have been investigated as functions of the ambient pressure and laser irradiance. Estimates of vibrational temperatures of C2 and CN electronically excited species under various laser irradiance conditions are made.

DUST AROUND R CORONAE BOREALIS STARS. II. INFRARED EMISSION FEATURES IN AN H-POOR ENVIRONMENT

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

Garcia-Hernandez, D. A.; Rao, N. Kameswara; Lambert, D. L., E-mail: agarcia@iac.es, E-mail: nkrao@iiap.res.in, E-mail: dll@astro.as.utexas.edu

2013-08-20

Residual Spitzer/Infrared Spectrograph spectra for a sample of 31 R Coronae Borealis (RCB) stars are presented and discussed in terms of narrow emission features superimposed on the quasi-blackbody continuous infrared emission. A broad {approx}6-10 {mu}m dust emission complex is seen in the RCBs showing an extreme H-deficiency. A secondary and much weaker {approx}11.5-15 {mu}m broad emission feature is detected in a few RCBs with the strongest {approx}6-10 {mu}m dust complex. The Spitzer infrared spectra reveal for the first time the structure within the {approx}6-10 {mu}m dust complex, showing the presence of strong C-C stretching modes at {approx}6.3 and 8.1 {mu}mmore » as well as of other dust features at {approx}5.9, 6.9, and 7.3 {mu}m, which are attributable to amorphous carbonaceous solids with little or no hydrogen. The few RCBs with only moderate H-deficiencies display the classical ''unidentified infrared bands (UIRs)'' and mid-infrared features from fullerene-related molecules. In general, the characteristics of the RCB infrared emission features are not correlated with the stellar and circumstellar properties, suggesting that the RCB dust features may not be dependent on the present physical conditions around RCB stars. The only exception seems to be the central wavelength of the 6.3 {mu}m feature, which is blueshifted in those RCBs showing also the UIRs, i.e., the RCBs with the smallest H deficiency.« less

Comparison of the Detection Characteristics of Trace Species Using Laser-Induced Breakdown Spectroscopy and Laser Breakdown Time-of-Flight Mass Spectrometry

PubMed Central

Wang, Zhenzhen; Deguchi, Yoshihiro; Yan, Junjie; Liu, Jiping

2015-01-01

The rapid and precise element measurement of trace species, such as mercury, iodine, strontium, cesium, etc. is imperative for various applications, especially for industrial needs. The elements mercury and iodine were measured by two detection methods for comparison of the corresponding detection features. A laser beam was focused to induce plasma. Emission and ion signals were detected using laser-induced breakdown spectroscopy (LIBS) and laser breakdown time-of-flight mass spectrometry (LB-TOFMS). Multi-photon ionization and electron impact ionization in the plasma generation process can be controlled by the pressure and pulse width. The effect of electron impact ionization on continuum emission, coexisting molecular and atomic emissions became weakened in low pressure condition. When the pressure was less than 1 Pa, the plasma was induced by laser dissociation and multi-photon ionization in LB-TOFMS. According to the experimental results, the detection limits of mercury and iodine in N2 were 3.5 ppb and 60 ppb using low pressure LIBS. The mercury and iodine detection limits using LB-TOFMS were 1.2 ppb and 9.0 ppb, which were enhanced due to different detection features. The detection systems of LIBS and LB-TOFMS can be selected depending on the condition of each application. PMID:25769051

Lifecycle of laser-produced air sparks

DOE PAGES

Harilal, S. S.; Brumfield, B. E.; Phillips, M. C.

2015-06-03

Here, we investigated the lifecycle of laser-generated air sparks or plasmas using multiple plasma diagnostic tools. The sparks were generated by focusing the fundamental radiation from an Nd:YAG laser in air, and studies included early and late time spark dynamics, decoupling of the shock wave from the plasma core, emission from the spark kernel, cold gas excitation by UV radiation, shock waves produced by the air spark, and the spark's final decay and turbulence formation. The shadowgraphic and self-emission images showed similar spark morphology at earlier and late times of its lifecycle; however, significant differences are seen in the midlifemore » images. Spectroscopic studies in the visible region showed intense blackbody-type radiation at early times followed by clearly resolved ionic, atomic, and molecular emission. The detected spectrum at late times clearly contained emission from both CN and N 2 +. Additional spectral features have been identified at late times due to emission from O and N atoms, indicating some degree of molecular dissociation and excitation. Detailed spatially and temporally resolved emission analysis provides insight about various physical mechanisms leading to molecular and atomic emission by air sparks, including spark plasma excitation, heating of cold air by UV radiation emitted by the spark, and shock-heating.« less

Lifecycle of laser-produced air sparks

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

Harilal, S. S., E-mail: hari@pnnl.gov; Brumfield, B. E.; Phillips, M. C.

2015-06-15

We investigated the lifecycle of laser-generated air sparks or plasmas using multiple plasma diagnostic tools. The sparks were generated by focusing the fundamental radiation from an Nd:YAG laser in air, and studies included early and late time spark dynamics, decoupling of the shock wave from the plasma core, emission from the spark kernel, cold gas excitation by UV radiation, shock waves produced by the air spark, and the spark's final decay and turbulence formation. The shadowgraphic and self-emission images showed similar spark morphology at earlier and late times of its lifecycle; however, significant differences are seen in the midlife images.more » Spectroscopic studies in the visible region showed intense blackbody-type radiation at early times followed by clearly resolved ionic, atomic, and molecular emission. The detected spectrum at late times clearly contained emission from both CN and N{sub 2}{sup +}. Additional spectral features have been identified at late times due to emission from O and N atoms, indicating some degree of molecular dissociation and excitation. Detailed spatially and temporally resolved emission analysis provides insight about various physical mechanisms leading to molecular and atomic emission by air sparks, including spark plasma excitation, heating of cold air by UV radiation emitted by the spark, and shock-heating.« less

ALMA detection of a disk wind from HD 163296

NASA Astrophysics Data System (ADS)

Klaassen, Pamela; Juhasz, Attila; Mathews, Geoffrey; Mottram, Joseph; De Gregorio-Monsalvo, Itziar; van Dishoeck, Ewine; Takahashi, Satoko; Akiyama, Eiji; Chapillon, Edwige; Espada, Daniel; Hales, Antonio; Hogerheijde, Michiel; Rawlings, Mark; Schmalzl, Markus; Testi, Leonardo

2013-07-01

Disk winds have been postulated as a mechanism for angular momentum release in protostellar systems for decades. HD 163296 is a Herbig Ae star surrounded by a disk and has been shown to host a series of HH knots (HH 409) with bow shocks associated with the farthest knots. Here we present ALMA Science Verification data of CO J=2-1 and J=3-2 emission which are spatially coincident with the blue shifted jet of HH knots, and offset from the disk by -18.6 km/s. The emission has a double corkscrew morphology and extends more than 10'' from the disk with embedded emission clumps coincident with jet knots. We interpret this double corkscrew as emission from material in a molecular disk wind, and that the compact emission near the jet knots is being heated by the jet which is moving at much higher velocities. We show that the J=3-2 emission is likely heavily filtered by the interferometer, but the J=2-1 emission suffers less due to the larger beam and measurable angular scales. Excitation analysis suggests temperatures exceeding 900 K in these compact features. The high mass loss rate suggests that this star is dispersing the disk faster than it is funneling mass onto the star, signaling the end of the main accretion phase.

Excitation-dependent local symmetry reversal in single host lattice Ba2A(BO3)2:Eu3+ [A = Mg and Ca] phosphors with tunable emission colours.

PubMed

Jayakiruba, S; Chandrasekaran, S Selva; Murugan, P; Lakshminarasimhan, N

2017-07-05

Eu 3+ activated phosphors are widely used as red emitters in various display devices and light emitting diodes (LEDs). The emission characteristics of Eu 3+ depend on the local site symmetry. The present study demonstrates the role of excitation-dependent local symmetry changes due to the structural reorganization on the emission colour tuning of Eu 3+ from orange-red to orange in single host lattices, Ba 2 Mg(BO 3 ) 2 and Ba 2 Ca(BO 3 ) 2 . The choice of these lattices was based on the difference in the extent of strain experienced by the oxygen atoms. The samples with Eu 3+ at Ba or Mg (Ca) sites were synthesized using the conventional high-temperature solid-state reaction method. The samples were characterized using powder XRD, 11 B MAS-NMR, FT-IR, and diffuse reflectance UV-Vis spectroscopic techniques. The room temperature photoluminescence (PL) recorded using different excitation wavelengths revealed a clear difference in the PL emission features due to symmetry reversal from non-inversion to inversion symmetry around Eu 3+ . The reorganization of highly strained oxygen atoms leads to such symmetry reversal. First-principles calculations were used to deduce the optimized structures of the two borate host lattices, and local geometries and their distortions upon Eu 3+ substitution. The outcomes of these calculations support the experimental findings.

The discovery of a new infrared emission feature at 1905 wavenumbers (5.25 microns) in the spectrum of BD +30 degrees 3639 and its relation to the polycyclic aromatic hydrocarbon model

NASA Technical Reports Server (NTRS)

Allamandola, L. J.; Bregman, J. D.; Sandford, S. A.; Tielens, A. G.; Witteborn, F. C.; Wooden, D. H.; Rank, D.

1989-01-01

We have discovered a new IR emission feature at 1905 cm-1 (5.25 microns) in the spectrum of BD +30 degrees 3639. This feature joins the family of well-known IR emission features at 3040, 2940, 1750, 1610, "1310," 1160, and 890 cm-1 (3.3, 3.4, 5.7, 6.2, "7.7," 8.6, and 11.2 microns). The origin of this new feature is discussed and it is assigned to an overtone or combination band involving C-H bending modes of polycyclic aromatic hydrocarbons (PAHs). Laboratory work suggests that spectral studies of the 2000-1650 cm-1 (5.0-6.1 microns) region may be very useful in elucidating the molecular structure of interstellar PAHs. The new feature, in conjunction with other recently discovered spectral structure, suggests that the narrow IR emission features originate in PAH molecules rather than large carbon grains. Larger species are likely to be the source of the broad underlying "plateaus" seen in many of the spectra.

The effects of cloud inhomogeneities upon radiative fluxes, and the supply of a cloud truth validation dataset

NASA Technical Reports Server (NTRS)

Welch, Ronald M.

1993-01-01

A series of cloud and sea ice retrieval algorithms are being developed in support of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Science Team objectives. These retrievals include the following: cloud fractional area, cloud optical thickness, cloud phase (water or ice), cloud particle effective radius, cloud top heights, cloud base height, cloud top temperature, cloud emissivity, cloud 3-D structure, cloud field scales of organization, sea ice fractional area, sea ice temperature, sea ice albedo, and sea surface temperature. Due to the problems of accurately retrieving cloud properties over bright surfaces, an advanced cloud classification method was developed which is based upon spectral and textural features and artificial intelligence classifiers.

Mid-Infrared Spectra of Comets P/Borrelly, P/Faye, and P/Schaumasse

NASA Technical Reports Server (NTRS)

Hanner, Martha S.; Lynch, David K.; Russell, Ray W.; Hackwell, John A.; Kellogg, Robert; Blaney, Diana

1996-01-01

A 10 micron silicate emission feature has been discovered in the spectra of comets P/BorrelIy and P/Faye at R approximately 1.5 AU. These are the first short period comets in which silicate emission has definitely been detected. The broad emission features are about 25% above the continuum. No emission feature was present in the spectrum of P/Schaumasse; it is possible that the nucleus of P/Schaumasse was directly detected. If all of the observed flux originated from the nucleus, then the effective radius is about 3 km; the observed color temperature is consistent with a rapidly rotating nucleus. We present models that show how the shape of the silicate feature can depend on the way in which silicate and absorbing material are mixed in the grains.

Cigarette Design Features: Effects on Emission Levels, User Perception, and Behavior.

PubMed

Talhout, Reinskje; Richter, Patricia A; Stepanov, Irina; Watson, Christina V; Watson, Clifford H

2018-01-01

This paper describes the effects of non-tobacco, physical cigarette design features on smoke emissions, product appeal, and smoking behaviors - 3 factors that determine smoker's exposure and related health risks. We reviewed available evidence for the impact of filter ventilation, new filter types, and cigarettes dimensions on toxic emissions, smoker's perceptions, and behavior. For evidence sources we used scientific literature and websites providing product characteristics and marketing information. Whereas filter ventilation results in lower machine-generated emissions, it also leads to perceptions of lighter taste and relative safety in smokers who can unwittingly employ more intense smoking behavior to obtain the desired amount of nicotine and sensory appeal. Filter additives that modify smoke emissions can also modify sensory cues, resulting in changes in smoking behavior. Flavor capsules increase the cigarette's appeal and novelty, and lead to misperceptions of reduced harm. Slim cigarettes have lower yields of some smoke emissions, but smoking behavior can be more intense than with standard cigarettes. Physical design features significantly impact machine-measured emission yields in cigarette smoke, product appeal, smoking behaviors, and exposures in smokers. The influence of current and emerging design features is important in understanding the effectiveness of regulatory actions to reduce smoking-related harm.

Theoretical study of deuteronated PAHs as carriers for IR emission features in the ISM

NASA Astrophysics Data System (ADS)

Buragohain, Mridusmita; Pathak, Amit; Sarre, Peter; Onaka, Takashi; Sakon, Itsuki

2015-11-01

This work proposes deuteronated PAH (DPAH+) molecules as a potential carrier of the 4.4 and 4.65 μm mid-infrared emission bands that have been observationally detected towards the Orion and M17 regions. Density Functional Theory calculations have been carried out on DPAH+ molecules to see the variations in the spectral behaviour from that of a pure polycyclic aromatic hydrocarbon (PAH). DPAH+ molecules show features that arise due to the stretching of the aliphatic C-D bond. Deuterated PAHs have been previously reported as carriers for such features. However, preferred conditions of ionization of PAHs in the interstellar medium (ISM) indicates the possibility of the formation of DPAH+ molecules. Comparison of band positions of DPAH+s shows reasonable agreement with the observations. We report the effect of size of the DPAH+ molecules on band positions and intensities. This study also reports a D/H ratio ([D/H]_{sc}; the ratio of C-D stretch and C-H stretch bands per [D/H]_{num}) that is decreasing with the increasing size of DPAH+s. It is noted that large DPAH+ molecules (no. of C atoms ˜50) match the D/H ratio that has been estimated from observations. This ratio offers prospects to study the deuterium abundance and depletion in the ISM.

Impact of freeway weaving segment design on light-duty vehicle exhaust emissions.

PubMed

Li, Qing; Qiao, Fengxiang; Yu, Lei; Chen, Shuyan; Li, Tiezhu

2018-06-01

In the United States, 26% of greenhouse gas emissions is emitted from the transportation sector; these emisssions meanwhile are accompanied by enormous toxic emissions to humans, such as carbon monoxide (CO), nitrogen oxides (NO x ), and hydrocarbon (HC), approximately 2.5% and 2.44% of a total exhaust emissions for a petrol and a diesel engine, respectively. These exhaust emissions are typically subject to vehicles' intermittent operations, such as hard acceleration and hard braking. In practice, drivers are inclined to operate intermittently while driving through a weaving segment, due to complex vehicle maneuvering for weaving. As a result, the exhaust emissions within a weaving segment ought to vary from those on a basic segment. However, existing emission models usually rely on vehicle operation information, and compute a generalized emission result, regardless of road configuration. This research proposes to explore the impacts of weaving segment configuration on vehicle emissions, identify important predictors for emission estimations, and develop a nonlinear normalized emission factor (NEF) model for weaving segments. An on-board emission test was conducted on 12 subjects on State Highway 288 in Houston, Texas. Vehicles' activity information, road conditions, and real-time exhaust emissions were collected by on-board diagnosis (OBD), a smartphone-based roughness app, and a portable emission measurement system (PEMS), respectively. Five feature selection algorithms were used to identify the important predictors for the response of NEF and the modeling algorithm. The predictive power of four algorithm-based emission models was tested by 10-fold cross-validation. Results showed that emissions are also susceptible to the type and length of a weaving segment. Bagged decision tree algorithm was chosen to develop a 50-grown-tree NEF model, which provided a validation error of 0.0051. The estimated NEFs are highly correlated with the observed NEFs in the training data set as well as in the validation data set, with the R values of 0.91 and 0.90, respectively. Existing emission models usually rely on vehicle operation information to compute a generalized emission result, regardless of road configuration. In practice, while driving through a weaving segment, drivers are inclined to perform erratic maneuvers, such as hard braking and hard acceleration due to the complex weaving maneuver required. As a result, the exhaust emissions within a weaving segment vary from those on a basic segment. This research proposes to involve road configuration, in terms of the type and length of a weaving segment, in constructing an emission nonlinear model, which significantly improves emission estimations at a microscopic level.

Non-methane volatile organic compounds in Africa: A view from space

NASA Astrophysics Data System (ADS)

Marais, Eloise Ann

Isoprene emissions affect human health, air quality, and the oxidative capacity of the atmosphere. Globally anthropogenic non-methane volatile organic compounds (NMVOC) emissions are lower than that of isoprene, but local hotspots are hazardous to human health and air quality. In Africa the tropics are a large source of isoprene, while Nigeria appears as a large contributor to regional anthropogenic NMVOC emissions. I make extensive use of space-based formaldehyde (HCHO) observations from the Ozone Monitoring Instrument (OMI) and the chemical transport model (CTM) GEOS-Chem to estimate and examine seasonality of isoprene emissions across Africa, and identify sources and air quality consequences of anthropogenic NMVOC emissions in Nigeria. To estimate isoprene emissions I first developed a filtering scheme to remove (1) contamination from biomass burning and anthropogenic influences; and (2) displacement of HCHO from the isoprene emission source diagnosed with the GEOS-Chem CTM. Conversion to isoprene emissions is with NOx-dependent GEOS-Chem HCHO yields, obtained as the local sensitivity S of the HCHO column ΩHCHO to a perturbation Delta in isoprene emissions EISOP (S = DeltaΩHCHO/DeltaE ISOP). The error in OMI-derived isoprene emissions is 40% at low levels of NOx and 40-90% under high-NOx conditions and is reduced by spatial and temporal averaging to the extent that errors are random. Weak isoprene emission seasonality in equatorial forests is driven predominantly by temperature, while large seasonality in northern and southern savannas is driven by temperature and leaf area index. The largest contribution of African isoprene emissions to surface ozone and particulate matter, determined with GEOS-Chem, of 8 ppbv and 1.5 μg m-3, respectively, is over West Africa. The OMI HCHO data feature a large enhancement over Nigeria that is due to anthropogenic NMVOC emissions. With the OMI HCHO data, coincident satellite observations of atmospheric composition, aircraft measurements, and GEOS-Chem I estimate Nigerian NMVOC emissions that are higher per capita than China (5.7 Tg C a-1). Should Nigeria develop its electricity sector to sustain economic growth with local natural gas and coal reserves NO x emissions will exacerbate wintertime (December-February) surface ozone pollution that exceeds 90 ppbv due to poor ventilation and the Harmattan inversion layer.

VizieR Online Data Catalog: CaII H&K to CaII IRT echelle spectra (Montes+, 2000)

NASA Astrophysics Data System (ADS)

Montes, D.; Fernandez-Figueroa, M. J.; de Castro, E.; Cornide, M.; Latorre, A.; Sanz-Forcada, J.

2000-11-01

This is the third paper of a series aimed at studying the chromosphere of active binary systems using the information provided for several optical spectroscopic features. High resolution echelle spectra including all the optical chromospheric activity indicators from the CaII H&K to CaII IRT lines are analysed here for 16 systems. The chromospheric contribution in these lines has been determined using the spectral subtraction technique. Very broad wings have been found in the subtracted Hα profile of the very active star HU Vir. These profiles are well matched using a two-component Gaussian fit (narrow and broad) and the broad component can be interpreted as arising from microflaring. Red-shifted absorption features in the Hα line have been detected in several systems and excess emission in the blue wing of FG UMa was also detected. These features indicate that several dynamical processes, or a combination of them, may be involved. Using the EHα/EHβ ratio as a diagnostic we have detected prominence-like extended material viewed off the limb in many stars of the sample, and prominences viewed against the disk at some orbital phases in the dwarfs OU Gem and BF Lyn. The He I D3 line has been detected as an absorption feature in mainly all the giants of the sample. Total filling-in of the He I D3, probably due to microflaring activity, is observed in HU Vir. Self-absorption with red asymmetry is detected in the CaII H&K lines of the giants 12 Cam, FG UMa and BM CVn. All the stars analysed show clear filled-in CaII IRT lines or even notable emission reversal. The small values of the E8542/E8498 ratio we have found indicate CaII IRT emission arises from plage-like regions. Orbital phase modulation of the chromospheric emission has been detected in some systems, in the case of HU Vir evidence of an active longitude area has been found. (5 data files).

Titan's Aerosol and Condensation Cloud Properties in the Far-IR Between 2005 and 2010

NASA Technical Reports Server (NTRS)

Anderson, Carrie; Samuelson, Robert

2011-01-01

Analyses of far-IR spectra between 20 and 560 cm(exp -1) (500 to 18 micron) recorded by the Cassini Composite Infrared Spectrometer (CIRS) yield the spectral dependence and the vertical distribution of Titan's photochemical aerosol and ice clouds. Titan's aerosol appears to be well mixed between the surface and an altitude of 300 km, with a spectral shape that does not change with latitude or time. The aerosol exhibits an extremely broad emission feature with a spectral peak at 140 cm(exp -1) (71 micron), which is not evident in laboratory simulated Titan aerosols (tholin). This low- energy aerosol emission feature may arise from low-energy molecules such as polycyclic aromatic hydrocarbons and/or nitrogenated aromatics. Unlike the vertically well-mixed aerosol, Titan's condensate clouds are located in highly restricted altitudes in the lower stratosphere, ranging between 60 and 100 km at low and moderate latitudes, to between 150 and 165 km at high northern latitudes during northern winter. Such clouds are located at altitudes where nitrile vapors are expected to condense and appear to be dominated by HCN and HC3N, which are the two most abundant nitriles in Titan's atmosphere. Associated with this ice cloud is a broad emission feature that spectrally peaks near 160 cm(exp -1) (62.5 micron). This ice composite appears to chemically change with altitude and latitude, probably as a result of differences in vapor abundance and condensation temperature, and the ice cloud appears to be global in extent. Both CIRS and the Huygens Descent Imager and Spectral Radiometer (DISR) show evidence of cloud layering in Titan's lower stratosphere. The 15 km difference in cloud altitude indicated by the two instruments suggests a difference in ice composition. CIRS also indicates a second ice cloud that exists at isolated latitudes and is consistent with hydrocarbon condensation above the tropopause. This cloud exhibits an emission feature that spectrally peaks near 80 cm(exp -1) (125 micron), possibly due to C2H6 ice or dominated by an ethane-acetylene composite ice, given that CzH6 then C2H2 are the two most abundant hydrocarbons next to methane in Titan's atmosphere.

Interaction of surface plasmon polaritons in heavily doped GaN microstructures with terahertz radiation

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

Melentev, G. A., E-mail: gamelen@spbstu.ru; Shalygin, V. A.; Vorobjev, L. E.

2016-03-07

We present the results of experimental and theoretical studies of the surface plasmon polariton excitations in heavily doped GaN epitaxial layers. Reflection and emission of radiation in the frequency range of 2–20 THz including the Reststrahlen band were investigated for samples with grating etched on the sample surface, as well as for samples with flat surface. The reflectivity spectrum for p-polarized radiation measured for the sample with the surface-relief grating demonstrates a set of resonances associated with excitations of different surface plasmon polariton modes. Spectral peculiarities due to the diffraction effect have been also revealed. The characteristic features of themore » reflectivity spectrum, namely, frequencies, amplitudes, and widths of the resonance dips, are well described theoretically by a modified technique of rigorous coupled-wave analysis of Maxwell equations. The emissivity spectra of the samples were measured under epilayer temperature modulation by pulsed electric field. The emissivity spectrum of the sample with surface-relief grating shows emission peaks in the frequency ranges corresponding to the decay of the surface plasmon polariton modes. Theoretical analysis based on the blackbody-like radiation theory well describes the main peculiarities of the observed THz emission.« less

Spectral Selectivity of Plasmonic Interactions between Individual Up-Converting Nanocrystals and Spherical Gold Nanoparticles.

PubMed

Piątkowski, Dawid; Schmidt, Mikołaj K; Twardowska, Magdalena; Nyk, Marcin; Aizpurua, Javier; Maćkowski, Sebastian

2017-08-04

We experimentally demonstrate strong spectral selectivity of plasmonic interaction that occurs between α-NaYF₄:Er 3+ /Yb 3+ nanocrystals, which feature two emission bands, and spherical gold nanoparticles, with plasmon frequency resonant with one of the emission bands. Spatially-resolved luminescence intensity maps acquired for individual nanocrystals, together with microsecond luminescence lifetime images, show two qualitatively different effects that result from the coupling between plasmon excitations in metallic nanoparticles and emitting states of the nanocrystals. On the one hand, we observe nanocrystals, whose emission intensity is strongly enhanced for both resonant and non-resonant bands with respect to the plasmon resonance. Importantly, this increase is accompanied with shortening of luminescence decays times. In contrast, a significant number of nanocrystals exhibits almost complete quenching of the emission resonant with the plasmon resonance of gold nanoparticles. Theoretical analysis indicates that such an effect can occur for emitters placed at distances of about 5 nm from gold nanoparticles. While under these conditions, both transitions experience significant increases of the radiative emission rates due to the Purcell effect, the non-radiative energy transfer between resonant bands results in strong quenching, which in that situation nullifies the enhancement.

Spectroscopic properties of the 1.4 microm emission of Tm3+ ions in TeO2-WO3-PbO glasses.

PubMed

Balda, R; Lacha, L M; Fernández, J; Arriandiaga, M A; Fernández-Navarro, J M; Muñoz-Martin, D

2008-08-04

In this work, we report the spectroscopic properties of the infrared 3H4-->3F4 emission of Tm3+ ions in two different compositions of glasses based on TeO2, WO3, and PbO for three Tm2O3 concentrations (0.1,0.5, and 1 wt%). Judd-Ofelt intensity parameters have been determined and used to calculate the radiative transition probabilities and radiative lifetimes. The infrared emission at around 1490 nm corresponding to the 3H4-->F4 transition has two noticeable features if compared to fluoride glasses used for S-band amplifiers. On one hand, it is broader by nearly 30 nm, and on the other, the stimulated emission cross section is twice the value for fluoride glasses. Both the relative intensity ratio of the 1490 nm emission to 1820 nm and the measured lifetime of the 3H4 level decrease as concentration increases, due to the existence of energy transfer via cross-relaxation among Tm3+ ions. The analysis of the decays from the 3H4 level with increasing concentration indicates the presence of a dipole-dipole quenching process assisted by energy migration.

Diagnostic features of Alzheimer's disease extracted from PET sinograms

NASA Astrophysics Data System (ADS)

Sayeed, A.; Petrou, M.; Spyrou, N.; Kadyrov, A.; Spinks, T.

2002-01-01

Texture analysis of positron emission tomography (PET) images of the brain is a very difficult task, due to the poor signal to noise ratio. As a consequence, very few techniques can be implemented successfully. We use a new global analysis technique known as the Trace transform triple features. This technique can be applied directly to the raw sinograms to distinguish patients with Alzheimer's disease (AD) from normal volunteers. FDG-PET images of 18 AD and 10 normal controls obtained from the same CTI ECAT-953 scanner were used in this study. The Trace transform triple feature technique was used to extract features that were invariant to scaling, translation and rotation, referred to as invariant features, as well as features that were sensitive to rotation but invariant to scaling and translation, referred to as sensitive features in this study. The features were used to classify the groups using discriminant function analysis. Cross-validation tests using stepwise discriminant function analysis showed that combining both sensitive and invariant features produced the best results, when compared with the clinical diagnosis. Selecting the five best features produces an overall accuracy of 93% with sensitivity of 94% and specificity of 90%. This is comparable with the classification accuracy achieved by Kippenhan et al (1992), using regional metabolic activity.

Time dependent emission line profiles in the radially streaming particle model of Seyfert galaxy nuclei and quasi-stellar objects

NASA Technical Reports Server (NTRS)

Hubbard, R.

1974-01-01

The radially-streaming particle model for broad quasar and Seyfert galaxy emission features is modified to include sources of time dependence. The results are suggestive of reported observations of multiple components, variability, and transient features in the wings of Seyfert and quasi-stellar emission lines.

On the 10 μm Silicate Feature in Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Nikutta, Robert; Elitzur, Moshe; Lacy, Mark

2009-12-01

The 10 μm silicate feature observed with Spitzer in active galactic nuclei (AGNs) reveals some puzzling behavior. It (1) has been detected in emission in type 2 sources, (2) shows broad, flat-topped emission peaks shifted toward long wavelengths in several type 1 sources, and (3) is not seen in deep absorption in any source observed so far. We solve all three puzzles with our clumpy dust radiative transfer formalism. Addressing (1), we present the spectral energy distribution (SED) of SST1721+6012, the first type 2 quasar observed to show a clear 10 μm silicate feature in emission. Such emission arises in models of the AGN torus easily when its clumpy nature is taken into account. We constructed a large database of clumpy torus models and performed extensive fitting of the observed SED. We find that the cloud radial distribution varies as r -1.5 and the torus contains 2-4 clouds along radial equatorial rays, each with optical depth at visual ~60-80. The source bolometric luminosity is ~3 × 1012 Lsun. Our modeling suggests that lsim35% of objects with tori sharing these characteristics and geometry would have their central engines obscured. This relatively low obscuration probability can explain the clear appearance of the 10 μm emission feature in SST1721+6012 together with its rarity among other QSO2. Investigating (2), we also fitted the SED of PG1211+143, one of the first type 1 QSOs with a 10 μm silicate feature detected in emission. Together with other similar sources, this QSO appears to display an unusually broadened feature whose peak is shifted toward longer wavelengths. Although this led to suggestions of non-standard dust chemistry in these sources, our analysis fits such SEDs with standard galactic dust; the apparent peak shifts arise from simple radiative transfer effects. Regarding (3), we find additionally that the distribution of silicate feature strengths among clumpy torus models closely resembles the observed distribution, and the feature never occurs deeply absorbed. Comparing such distributions in several AGN samples we also show that the silicate emission feature becomes stronger in the transition from Seyfert to quasar luminosities.

Spectra of galaxies in the Case Low-Dispersion Sky Survey in the direction of the Bootes void

NASA Technical Reports Server (NTRS)

Weistrop, Donna; Downes, Ronald A.

1988-01-01

A sample of 34 galaxies selected from the Case Low-Dispersion Northern Sky Survey in the direction of the Bootes void. Emission-line redshifts were obtained for 33 objects; the spectrum of the thirty-fourth galaxy contains no obvious features. Three of the emission-line galaxies are lcoated within the boundaries of the Bootes void, including one not previously reported. To date, all the galaxies discovered in the void have emission-line spectra. Although more than half the galaxies in the sample are fainter than M(B) = -21.0 mag, all five of the galaxies that were detected by IRAS are brighter than M(B) = 21.5 mag. The relative strengths of the emission lines in most of the galaxies, including those in the void, indicate the lines are excited by photoionization due to young, hot O and B stars. Possible causes for the star formation occurring in these galaxies include interaction with nearby galaxies, star formation induced by nuclear activity, and/or recent development of physical conditions required for star formation.

Time-resolved EPR study on the photochemical reactions of benzil

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

Mukai, Masahiro; Yamnauchi, Seigo; Hirota, Noboru

1992-04-16

TREPR and optical studies on the photochemical reactions of benzil in 2-propanol and benzene-TEA conclude that emissive signals are due to the reaction from T{sub n} produced via the S{sub n} pointing right T{sub n} intersystem crossing process. The free-pair radical-pair mechanism can account for the main features of the slow rise component of the chemically induced dynamic electron polarization signal of the ketyl radical in 2-propanol. 27 refs., 10 figs., 2 tabs.

Detection of a weak maser emission pedestal associated with the SiO maser. [in variable late stars

NASA Technical Reports Server (NTRS)

Snyder, L. E.; Dickinson, D. F.; Brown, L. W.; Buhl, D.

1978-01-01

Results are reported for high-spectral-resolution observations of the v = 1, J = 1-0 SiO maser sources at 43,122.027 MHz (6.95 mm wavelength) associated with the variable stars Omega Cet, NML Tau, VY CMa, R Leo, W Hya, VX Sgr, NML Cyg, and R Cas. A weak underlying maser emission pedestal is clearly observed in the spectra of all but NML Cyg and R Cas. The data indicate that the underlying pedestal of SiO emission appears to originate in a shell-like region around the star, has a thermal appearance even though it must be due to weak maser emission, and appears to be part of the spectral signature of SiO maser emission from late-type stars. It is found that the center velocities of the pedestals may be used to determine stellar radial velocities. Observations of large-scale time variations in the intensity of the Ori A SiO maser and the detection of weak maser pedestals associated with each of the two strong emission-feature groups in Orion are also discussed. It is suggested that the Orion molecular cloud might contain two late-type long-period variable stars that may be semiregular variables.

Estimating fire severity and carbon emissions over Australian tropical savannas based on passive microwave satellite observations

NASA Astrophysics Data System (ADS)

Chen, X.; Liu, Y.; Evans, J. P.; Parinussa, R.

2017-12-01

Carbon emissions from large-scale fire activity over the Australian tropical savannas have strong inter-annual variability, due mainly to variations in fuel accumulation in response to rainfall. We investigated the use of a recently developed satellite-based vegetation optical depth (VOD) dataset to estimate fire severity and carbon emission. VOD is sensitive to the dynamics of all aboveground vegetation and available nearly every two days. For areas burned during 2003 - 2010, we calculated the VOD change (ΔVOD) pre- and post-fire and the associated loss in above ground biomass carbon. Both results compare well with widely-accepted approaches: ΔVOD agreed well with the Normalized Burn Ratio change (ΔNBR) and carbon loss with modelled emissions from the Global Fire Emissions Database (GFED). We found that the ΔVOD and ΔNBR are generally linearly related. The Pearson correlation coefficients (R) between VOD- and GFED-based fire carbon emissions for monthly and annual total estimates are very high, 0.92 and 0.96 respectively. A key feature of fire carbon emissions is the strong inter-annual variation, ranging from 21.1 million tonnes in 2010 to 84.3 million tonnes in 2004. This study demonstrates that a reasonable estimate of fire carbon emissions can be achieved in a timely manner based on multiple satellite observations over the regions where the emissions are primarily from aboveground vegetation loss, which can be complementary to the currently used approaches.

A short dive into the complexity of Jupiter's aurorae - invited

NASA Astrophysics Data System (ADS)

Bonfond, Bertrand

2015-04-01

Aurorae are the atmospheric signatures of energetic processes taking place far in the magnetosphere. One of the most important results brought by high resolution imaging of the UV aurorae at Jupiter is the realization that there isn't such a thing as «the aurora» at Jupiter; as these light emissions appear to arise from a variety of processes. Some are related to the interaction of the magnetospheric plasma with the moons (the satellite footprints). Others are linked with the radial motion of flux tubes through centrifugal instabilities (the injection auroral signatures). Some diffuse emissions are connected with wave-particle interaction (the equatorward diffuse emissions). Another feature is associated with the magnetosphere-ionosphere coupling (the main emission/oval). Some auroral spots are related to internally driven reconnection (the polar dawn spots). Finally, the polar-most emissions remain to be understood and this list is still incomplete. In order to illustrate the discrepancies between these various features, I will show a set of recent results derived from the analysis of Hubble Space Telescope observations. For example, I will compare the vertical profile of satellite footprints and the main emissions, and show that the energy population of the precipitating particles varies from feature to feature. Moreover, even within a single feature, spatial variations do exist. As an example, I will characterize the dawn-dusk brightness discrepancy of the main emissions and discuss its implication regarding the magnetospheric currents. And finally, the dynamics of the features also helps differentiating one type of aurora from another. This will be shown through the description of the morphological evolution of the transient flares in the polar region.

Photochemical modeling of emissions trading of highly reactive volatile organic compounds in Houston, Texas. 1. Reactivity based trading and potential for ozone hot spot formation.

PubMed

Wang, Linlin; Thompson, Tammy; McDonald-Buller, Elena C; Webb, Alba; Allen, David T

2007-04-01

As part of the State Implementation Plan for attaining the National Ambient Air Quality Standard for ozone, the Texas Commission of Environmental Quality has created a Highly Reactive Volatile Organic Compounds (HRVOC) Emissions Cap and Trade Program for industrial point sources in the Houston/Galveston/Brazoria area. This program has a number of unique features, including its focus on a limited group of ozone precursors and its provisions for trading emissions based on atmospheric reactivity. This series of papers examines the potential air quality impacts of this new emission trading program through photochemical modeling of potential trading scenarios; this first paper in the series describes the air quality modeling methods used to assess potential trades, the potential for localized increases in ozone concentrations (ozone "hot spots") due to HRVOC emission trading, and the use of reactivity scales in the trading. When HRVOC emissions are traded on a mass basis, the simulations indicate that trading of HRVOC allowances between facilities resulted in less than 0.15 ppb (<0.13%) and 0.06 ppb (<0.06%) increases in predicted maximum, area-wide 1-h averaged and 8-h averaged ozone concentrations, respectively. Maximum decreases in ozone concentrations associated with trading, as opposed to across-the-board reductions, were larger than the increases. All of these changes are small compared to the maximum changes in ozone concentrations due to the VOC emissions from these sources (up to 5-10 ppb for 8 h averages; up to 30 ppb for 1-h averages). When emissions of HRVOCs are traded for other, less reactive emissions, on a reactivity weighted basis, air quality simulations indicate that daily maximum ozone concentrations increased by less than 0.3%. Because these relatively small changes (< 1%) are for unlikely trading scenarios designed to produce a maximum change in ozone concentrations (all emissions traded into localized regions), the simulations indicate that the implementation of the trading program, as currently configured and possibly expanded, is unlikely to cause localized increases in ozone concentrations ("hot spots").

Recent progress of carbon nanotube field emitters and their application.

PubMed

Seelaboyina, Raghunandan; Choi, Wonbong

2007-01-01

The potential of utilizing carbon nanotube field emission properties is an attractive feature for future vacuum electronic devices including: high power microwave, miniature x-ray, backlight for liquid crystal displays and flat panel displays. Their high emission current, nano scale geometry, chemical inertness and low threshold voltage for emission are attractive features for the field emission applications. In this paper we review the recent developments of carbon nanotube field emitters and their device applications. We also discuss the latest results on field emission current amplification achieved with an electron multiplier microchannel plate, and emission performance of multistage field emitter based on oxide nanowire operated in poor vacuum.

Monte Carlo simulations of secondary electron emission due to ion beam milling

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

Mahady, Kyle; Tan, Shida; Greenzweig, Yuval

We present a Monte Carlo simulation study of secondary electron emission resulting from focused ion beam milling of a copper target. The basis of this study is a simulation code which simulates ion induced excitation and emission of secondary electrons, in addition to simulating focused ion beam sputtering and milling. This combination of features permits the simulation of the interaction between secondary electron emission, and the evolving target geometry as the ion beam sputters material. Previous ion induced SE Monte Carlo simulation methods have been restricted to predefined target geometries, while the dynamic target in the presented simulations makes thismore » study relevant to image formation in ion microscopy, and chemically assisted ion beam etching, where the relationship between sputtering, and its effects on secondary electron emission, is important. We focus on a copper target, and validate our simulation against experimental data for a range of: noble gas ions, ion energies, ion/substrate angles and the energy distribution of the secondary electrons. We then provide a detailed account of the emission of secondary electrons resulting from ion beam milling; we quantify both the evolution of the yield as high aspect ratio valleys are milled, as well as the emission of electrons within these valleys that do not escape the target, but which are important to the secondary electron contribution to chemically assisted ion induced etching.« less

A Highly Doppler Blueshifted Fe-K Emission Line in the High-Redshift QSO PKS 2149-306.

PubMed

Yaqoob; George; Nandra; Turner; Zobair; Serlemitsos

1999-11-01

We report the results from an ASCA observation of the high-luminosity, radio-loud quasar PKS 2149-306 (redshift 2.345), covering the approximately 1.7-30 keV band in the quasar frame. We find the source to have a luminosity approximately 6x1047 ergs s-1 in the 2-10 keV band (quasar frame). We detect an emission line centered at approximately 17 keV in the quasar frame. Line emission at this energy has not been observed in any other active galaxy or quasar to date. We present evidence rejecting the possibility that this line is the result of instrumental artifacts or a serendipitous source. The most likely explanation is blueshifted Fe-K emission (the equivalent width is EW approximately 300+/-200 eV, quasar frame). Bulk velocities of the order of 0.75c are implied by the data. We show that Fe-K line photons originating in an accretion disk and Compton scattering off a leptonic jet aligned along the disk axis can account for the emission line. Curiously, if the emission-line feature recently discovered in another quasar (PKS 0637-752, z=0.654) at 1.6 keV in the quasar frame is due to blueshifted O vii emission, the Doppler blueshifting factor in both quasars is similar ( approximately 2.7-2.8).

Extreme Ultraviolet Emission Spectrum of CO_2 Induced by Electron Impact at 200 eV

NASA Technical Reports Server (NTRS)

Kanik, I.; Ajello, J. M.; James, G. K.

1993-01-01

We present the extreme ultraviolet (EUV) emission spectrum of CO_2 induced by electronimpact at 200 eV. There are 36 spectral features which are identified with a resolution of 0.5 nmover the wavelength range of 40 to 125 nm. Absolute emission cross sections were obtained for eachof these features. The EUV emission spectrum induced by electron impact consist of atomicmultiplets of CI,II and OI,II,III as well as CO and CO^+ molecular band systems produced bydissociative excitation. The CI (119.4 nm) multiplet is the strongest feature of CI with a peak crosssection of 3.61 x 10^(-19) cm^2 at 200 eV. The strongest feature of OI in the EUV spectrum is theOI (99.0 nm) multiplet with a peak cross section of 3.59 x 10^(-19) cm^2 at 200 eV.

Spectral observations of the extreme ultraviolet background.

PubMed

Labov, S E; Bowyer, S

1991-04-20

A grazing incidence spectrometer was designed to measure the diffuse extreme ultraviolet background. It was flown on a sounding rocket, and data were obtained on the diffuse background between 80 and 650 angstroms. These are the first spectral measurements of this background below 520 angstroms. Several emission features were detected, including interplanetary He I 584 angstroms emission and geocoronal He II 304 angstroms emission. Other features observed may originate in a hot ionized interstellar gas, but if this interpretation is correct, gas at several different temperatures is present. The strongest of these features is consistent with O V emission at 630 angstroms. This emission, when combined with upper limits for other lines, restricts the temperature of this component to 5.5 < log T < 5.7, in agreement with temperatures derived from O VI absorption studies. A power-law distribution of temperatures is consistent with this feature only if the power-law coefficient is negative, as is predicted for saturated evaporation of clouds in a hot medium. In this case, the O VI absorption data confine the filling factor of the emission of f < or = 4% and the pressure to more than 3.7 x 10(4) cm-3 K, substantially above ambient interstellar pressure. Such a pressure enhancement has been predicted for clouds undergoing saturated evaporation. Alternatively, if the O V emission covers a considerable fraction of the sky, it would be a major source of ionization. A feature centered at about 99 angstroms is well fitted by a cluster of Fe XVIII and Fe XIX lines from gas at log T = 6.6-6.8. These results are consistent with previous soft X-ray observations with low-resolution detectors. A feature found near 178 angstroms is consistent with Fe X and Fe XI emission from gas at log T = 6; this result is consistent with results from experiments employing broad-band soft X-ray detectors.

Enhanced emission and photoconductivity due to photo-induced charge transfer from Au nanoislands to ZnO

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

Wu, Shang-Hsuan; Chan, Ching-Hsiang; Liang, Ching-Tarng

2016-01-25

We report systematic studies based on photoluminescence, Hall, and photoconductivity measurements together with theoretical modeling in order to identify mechanisms for the photo-induced charge transfer effects in ZnO thin film incorporated with the Au nano-islands (AuNIs). Significant enhancement of near band edge emission and improvement in conductivity of ZnO/AuNIs samples after illumination are observed, which are attributed to the photo-induced hot electrons in Au which are then transferred into the conduction band of ZnO as long as the excitation energy is higher than the offset between the ZnO conduction-band minimum and Au Fermi level. Our experimental results are consistent withmore » the general features predicted by first principles calculations.« less

Role of atomic bonding for compound and glass formation in Ni-Si, Pd-Si, and Ni-B systems

NASA Astrophysics Data System (ADS)

Tanaka, K.; Saito, T.; Suzuki, K.; Hasegawa, R.

1985-11-01

Valence electronic structures of crystalline compounds and glassy alloys of Ni silicides, Pd silicides, and Ni borides are studied by soft-x-ray spectroscopy over wide ranges of Si and B concentrations. The samples prepared include bulk compounds, glassy ribbons, and amorphous sputtered films. Silicon Kβ emissions of Ni and Pd silicides generally consist of a prominent peak fixed at ~=4.5 and ~=5.8 eV below the Fermi level EF, respectively, with a shoulder near EF which grows and shifts toward lower energy with increasing Si concentration. The former is identified as due to Si p-like states forming Si 3p-Ni 3d or Si 3p-Pd 4d bonding states while the latter as due to the corresponding antibonding states. Ni L3 and Pd L3 emissions of these silicides indicate that Ni 3d and Pd 4d states lie between the above two states. These local electronic configurations are consistent with partial-density-of-states (PDOS) calculations performed by Bisi and Calandra. Similar electronic configurations are suggested for Ni borides from B Kα and Ni L3 emissions. Differences of emission spectra between compounds and glasses of similar compositions are rather small, but some enhancement of the contribution of antibonding states to the PDOS near EF is suggested for certain glasses over that of the corresponding compounds. These features are discussed in connection with the compound stability and glass formability.

The emission-line regions in the nucleus of NGC 1313 probed with GMOS-IFU: a supergiant/hypergiant candidate and a kinematically cold nucleus

NASA Astrophysics Data System (ADS)

Menezes, R. B.; Steiner, J. E.

2017-04-01

NGC 1313 is a bulgeless nearby galaxy, classified as SB(s)d. Its proximity allows high spatial resolution observations. We performed the first detailed analysis of the emission-line properties in the nuclear region of NGC 1313, using an optical data cube obtained with the Gemini Multi-object Spectrograph. We detected four main emitting areas, three of them (regions 1, 2 and 3) having spectra typical of H II regions. Region 1 is located very close to the stellar nucleus and shows broad spectral features characteristic of Wolf-Rayet stars. Our analysis revealed the presence of one or two WC4-5 stars in this region, which is compatible with results obtained by previous studies. Region 4 shows spectral features (as a strong Hα emission line, with a broad component) typical of a massive emission-line star, such as a luminous blue variable, a B[e] supergiant or a B hypergiant. The radial velocity map of the ionized gas shows a pattern consistent with rotation. A significant drop in the values of the gas velocity dispersion was detected very close to region 1, which suggests that the young stars there were formed from this cold gas, possibly keeping low values of velocity dispersion. Therefore, although detailed measurements of the stellar kinematics were not possible (due to the weak stellar absorption spectrum of this galaxy), we predict that NGC 1313 may also show a drop in the values of the stellar velocity dispersion in its nuclear region.

The Unique OMI HCHO/NO2 Feature During the 2008 Beijing Summer Olympics: Implications for Ozone Production Sensitivity

NASA Technical Reports Server (NTRS)

Witte, J. C.; Duncan, B. N.; Douglass, A. R.; Kurosu, T. P.; Chance, K.; Retscher, C.

2010-01-01

In preparation of the Beijing Summer Olympic and Paralympics Games, strict controls were imposed between July and September 2008 on motor vehicle traffic and industrial emissions to improve air quality for the competitors. We assessed chemical sensitivity of ozone production to these controls using Ozone Monitoring Instrument (OMI) column measurements of formaldehyde (HCHO) and nitrogen dioxide (NO2), where their ratio serves as a proxy for the sensitivity. During the emission controls, HCHO/NO2 increased and indicated a NOx-limited regime, in contrast to the same period in the preceding three years when the ratio indicates volatile organic carbon (VOC)-limited and mixed NOx-VOC-limited regimes. After the emission controls were lifted, observed NO2 and HCHO/NO2 returned to their previous values. The 2005-2008 OMI record shows that this transition in regimes was unique as ozone production in Beijing was rarely NOx-limited. OMI measured summertime increases in HCHO of around 13% in 2008 compared to prior years, the same time period during which MODIS vegetation indices increased. The OMI HCHO increase may be due to higher biogenic emissions of HCHO precursors, associated with Beijing's greening initiative for the Olympics. However, NO2 and HCHO were also found to be well-correlated during the summer months. This indicates an anthropogenic VOC contribution from vehicle emissions to OMI HCHO and is a plausible explanation for the relative HCHO minimum observed in August 2008, concurrent with a minimum in traffic emissions. We calculated positive trends in 2005-2008 OMI HCHO and NO2 of about +1 x 10(exp 14) Molec/ square M-2 and +3 x 10(exp 13) molec CM-2 per month, respectively. The positive trend in NO2 may be an indicator of increasing vehicular traffic since 2005, while the positive trend in HCHO may be due to a combined increase in anthropogenic and biogenic emissions since 2005.

Wet soil cover applicability and design

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

Hunter, F.; Feenstra, S.; Hwang, D.

1996-12-31

As part of a focused feasibility study for the Tyson Superfund site, Daekyoo Hwang, then with ERM, developed a flooding/flushing option. It was not considered a viable option due to concerns over contaminated groundwater control. The concept, however, had several attractive features: control of VOC emissions; the downward movement of water prevents contamination of the overlying clean soil by the upward movement of contaminated soil vapor; and some natural attenuation of the contaminated lagoon area soils. The new concept employs a near saturated soil layer to prevent VOC emission and the downward movement of water to prevent contamination of surfacemore » soil. The wet soil cover became one of five alternatives submitted as part of the focused feasibility study. It was selected as the remedial option for the site by the USEPA. The study was reviewed by the public and they also were positive as to the use of a wet soil cover to control VOC emissions at the site. The wet soil cover is currently being designed by Smith Environmental.« less

Recent high energy gamma-ray results from SAS-2

NASA Technical Reports Server (NTRS)

Thompson, D. J.; Fichtel, C. E.; Hartman, R. C.; Kniffen, D. A.; Bignami, G. F.; Ogelman, H. B.; Ozel, M. E.; Tumer, T.; Lamb, R. C.

1977-01-01

Recent developments in gamma-ray astronomy due to the results from SAS-2 have focused on two areas. First, the emission from the plane of the Galaxy is the dominant feature in the gamma-ray sky. The galactic latitude and longitude distributions are consistent with the concept that the high-energy radiation originates from cosmic rays interacting with interstellar matter, and the measurements support a galactic origin for cosmic rays. Second, searches of the SAS-2 data for emission from localized sources have shown three strong discrete gamma-ray sources: the Crab nebula and PSR 0531 + 21, the Vela supernova remnant and PSR 0833-45, and a source near galactic coordinates 193 deg longitude, +3 deg latitude, which does not appear to be associated with other known celestial objects. Evidence has also been found for pulsed gamma-ray emission from two other radio pulsars, PSR 1818-04 and PSR 1747-46. A localized source near longitudes 76-80 deg may be associated with the X-ray source Cyg X-3.

General Relativistic Radiative Transfer and General Relativistic MHD Simulations of Accretion and Outflows of Black Holes

NASA Technical Reports Server (NTRS)

Fuerst, Steven V.; Mizuno, Yosuke; Nishikawa, Ken-Ichi; Wu, Kinwah

2007-01-01

We have calculated the emission from relativistic flows in black hole systems using a fully general relativistic radiative transfer, with flow structures obtained by general relativistic magnetohydrodynamic simulations. We consider thermal free-free emission and thermal synchrotron emission. Bright filament-like features are found protruding (visually) from the accretion disk surface, which are enhancements of synchrotron emission when the magnetic field is roughly aligned with the line-of-sight in the co-moving frame. The features move back and forth as the accretion flow evolves, but their visibility and morphology are robust. We propose that variations and location drifts of the features are responsible for certain X-ray quasi-periodic oscillations (QPOs) observed in black-hole X-ray binaries.

General Relativistic Radiative Transfer and GeneralRelativistic MHD Simulations of Accretion and Outflows of Black Holes

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

Fuerst, Steven V.; /KIPAC, Menlo Park; Mizuno, Yosuke

2007-01-05

We calculate the emission from relativistic flows in black hole systems using a fully general relativistic radiative transfer formulation, with flow structures obtained by general relativistic magneto-hydrodynamic simulations. We consider thermal free-free emission and thermal synchrotron emission. Bright filament-like features protrude (visually) from the accretion disk surface, which are enhancements of synchrotron emission where the magnetic field roughly aligns with the line-of-sight in the co-moving frame. The features move back and forth as the accretion flow evolves, but their visibility and morphology are robust. We propose that variations and drifts of the features produce certain X-ray quasi-periodic oscillations (QPOs) observedmore » in black-hole X-ray binaries.« less

The heliocentric evolution of cometary infrared spectra - Results from an organic grain model

NASA Technical Reports Server (NTRS)

Chyba, Christopher F.; Sagan, Carl; Mumma, Michael J.

1989-01-01

An emission feature peaking near 3.4 microns that is typical of C-H stretching in hydrocarbons and which fits a simple, two-component thermal emission model for dust in the cometary coma, has been noted in observations of Comets Halley and Wilson. A noteworthy consequence of this modeling is that, at about 1 AU, emission features at wavelengths longer than 3.4 microns come to be 'diluted' by continuum emission. A quantitative development of the model shows it to agree with observational data for Comet Halley for certain, plausible values of the optical constants; the observed heliocentric evolution of the 3.4-micron feature thereby furnishes information on the composition of the comet's organic grains.

SUBARU/HDS STUDY OF HE 1015-2050: SPECTRAL EVIDENCE OF R CORONAE BOREALIS LIGHT DECLINE

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

Goswami, Aruna; Aoki, Wako, E-mail: aruna@iiap.res.in

2013-02-01

Hydrogen deficiency and a sudden optical light decline of about 6-8 mag are two principal characteristics of R Coronae Borealis (RCB) stars. The high latitude carbon star HE 1015-2050 was identified as a hydrogen-deficient carbon star from low-resolution spectroscopy. Photometric data of the Catalina Real-Time Transient Survey gathered between 2006 February and 2012 May indicate that the object exhibits no variability. However, a high-resolution (R {approx} 50, 000) optical spectrum of this object obtained with the 8.2 m Subaru telescope using High Dispersion Spectrograph on the 2012 January 13 offers sufficient spectral evidence that the object is a cool HdCmore » star of RCB type undergoing light decline. In contrast to the Na I D broad absorption features seen in the low-resolution spectra on several occasions, the high-resolution spectrum exhibits Na I D{sub 2} and D{sub 1} features in emission. A few emission lines due to Mg I, Sc II, Ti I, Ti II, Fe II, and Ba I are also observed in the spectrum of this object for the first time. Such emission features combined with neutral and singly ionized lines of Ca, Ti, Fe, etc., in absorption are reportedly seen in RCBs spectra in the early stage of decline or during the recovery to maximum. Further, the light decline of RCBs is ascribed to the formation of a cloud of soot that obscures the visible photosphere. The presence of such circumstellar material is evident from the polarimetric observations with an estimated V-band percentage polarization of {approx}1.7% for this object.« less

Binarity and Accretion in AGB Stars: HST/STIS Observations of UV Flickering in Y Gem

NASA Astrophysics Data System (ADS)

Sahai, R.; Sánchez Contreras, C.; Mangan, A. S.; Sanz-Forcada, J.; Muthumariappan, C.; Claussen, M. J.

2018-06-01

Binarity is believed to dramatically affect the history and geometry of mass loss in AGB and post-AGB stars, but observational evidence of binarity is sorely lacking. As part of a project to search for hot binary companions to cool AGB stars using the GALEX archive, we discovered a late-M star, Y Gem, to be a source of strong and variable UV and X-ray emission. Here we report UV spectroscopic observations of Y Gem obtained with the Hubble Space Telescope that show strong flickering in the UV continuum on timescales of ≲20 s, characteristic of an active accretion disk. Several UV lines with P-Cygni-type profiles from species such as Si IV and C IV are also observed, with emission and absorption features that are red- and blueshifted by velocities of ∼500 {km} {{{s}}}-1 from the systemic velocity. Our model for these (and previous) observations is that material from the primary star is gravitationally captured by a companion, producing a hot accretion disk. The latter powers a fast outflow that produces blueshifted features due to the absorption of UV continuum emitted by the disk, whereas the redshifted emission features arise in heated infalling material from the primary. The outflow velocities support a previous inference by Sahai et al. that Y Gem’s companion is a low-mass main-sequence star. Blackbody fitting of the UV continuum implies an accretion luminosity of about 13 L ⊙, and thus a mass-accretion rate >5 × 10‑7 M ⊙ yr‑1 we infer that Roche-lobe overflow is the most likely binary accretion mode for Y Gem.

Mid-Infrared Silicate Dust Features in Seyfert 1 Spectra

NASA Astrophysics Data System (ADS)

Thompson, Grant D.; Levenson, N. A.; Sirocky, M. M.; Uddin, S.

2007-12-01

Silicate dust emission dominates the mid-infrared spectra of galaxies, and the dust produces two spectral features, at 10 and 18 μm. These features' strengths (in emission or absorption) and peak wavelengths reveal the geometry of the dust distribution, and they are sensitive to the dust composition. We examine mid-infrared spectra of 32 Seyfert 1 active galactic nuclei (AGN), observed with the Infrared Spectrograph aboard the Spitzer Space Telescope. In the spectra, we typically find the shorter-wavelength feature in emission, at an average peak wavelength of 10.0 μm, although it is known historically as the "9.7 μm" feature. In addition, peak wavelength increases with feature strength. The 10 and 18 μm feature strengths together are sensitive to the dust geometry surrounding the central heating engine. Numerical calculations of radiative transfer distinguish between clumpy and smooth distributions, and we find that the surroundings of these AGN (the obscuring "tori" of unified AGN schemes) are clumpy. Polycyclic aromatic hydrocarbon (PAH) features are associated with star formation, and we find strong PAH emission (luminosity ≥ 1042 erg/s) in only four sources, three of which show independent evidence for starbursts. We will explore the effects of luminosity on dust geometry and chemistry in a comparison sample of quasars. We acknowledge work supported by the NSF under grant number 0237291.

Novel High Efficient Organic Photovoltaic Materials

NASA Technical Reports Server (NTRS)

Sun, Sam; Haliburton, James; Wang, Yi-Qing; Fan, Zhen; Taft, Charles; Maaref, Shahin; Bailey, Sheila (Technical Monitor)

2003-01-01

Solar energy is a renewable, nonpolluting, and most abundant energy source for human exploration of a remote site or outer space. In order to generate appreciable electrical power in space or on the earth, it is necessary to collect sunlight from large areas and with high efficiency due to the low density of sunlight. Future organic or polymer (plastic) solar cells appear very attractive due to their unique features such as light weight, flexible shape, tunability of energy band-gaps via versatile molecular or supramolecular design, synthesis, processing and device fabrication schemes, and much lower cost on large scale industrial production. It has been predicted that supramolecular and nano-phase separated block copolymer systems containing electron rich donor blocks and electron deficient acceptor blocks may facilitate the charge carrier separation and migration due to improved electronic ultrastructure and morphology in comparison to polymer composite system. This presentation will describe our recent progress in the design, synthesis and characterization of a novel block copolymer system containing donor and acceptor blocks covalently attached. Specifically, the donor block contains an electron donating alkyloxy derivatized polyphenylenevinylene (RO-PPV), the acceptor block contains an electron withdrawing alkyl-sulfone derivatized polyphenylenevinylene (SF-PPV). The key synthetic strategy includes the synthesis of each individual block first, then couple the blocks together. While the donor block has a strong PL emission at around 560 nm, and acceptor block has a strong PL emission at around 520 nm, the PL emissions of final block copolymers are severely quenched. This verifies the expected electron transfer and charge separation due to interfaces of donor and acceptor nano phase separated blocks. The system therefore has potential for variety light harvesting applications, including high efficient photovoltaic applications.

Tool Wear Prediction in Ti-6Al-4V Machining through Multiple Sensor Monitoring and PCA Features Pattern Recognition.

PubMed

Caggiano, Alessandra

2018-03-09

Machining of titanium alloys is characterised by extremely rapid tool wear due to the high cutting temperature and the strong adhesion at the tool-chip and tool-workpiece interface, caused by the low thermal conductivity and high chemical reactivity of Ti alloys. With the aim to monitor the tool conditions during dry turning of Ti-6Al-4V alloy, a machine learning procedure based on the acquisition and processing of cutting force, acoustic emission and vibration sensor signals during turning is implemented. A number of sensorial features are extracted from the acquired sensor signals in order to feed machine learning paradigms based on artificial neural networks. To reduce the large dimensionality of the sensorial features, an advanced feature extraction methodology based on Principal Component Analysis (PCA) is proposed. PCA allowed to identify a smaller number of features ( k = 2 features), the principal component scores, obtained through linear projection of the original d features into a new space with reduced dimensionality k = 2, sufficient to describe the variance of the data. By feeding artificial neural networks with the PCA features, an accurate diagnosis of tool flank wear ( VB max ) was achieved, with predicted values very close to the measured tool wear values.

Tool Wear Prediction in Ti-6Al-4V Machining through Multiple Sensor Monitoring and PCA Features Pattern Recognition

PubMed Central

2018-01-01

Machining of titanium alloys is characterised by extremely rapid tool wear due to the high cutting temperature and the strong adhesion at the tool-chip and tool-workpiece interface, caused by the low thermal conductivity and high chemical reactivity of Ti alloys. With the aim to monitor the tool conditions during dry turning of Ti-6Al-4V alloy, a machine learning procedure based on the acquisition and processing of cutting force, acoustic emission and vibration sensor signals during turning is implemented. A number of sensorial features are extracted from the acquired sensor signals in order to feed machine learning paradigms based on artificial neural networks. To reduce the large dimensionality of the sensorial features, an advanced feature extraction methodology based on Principal Component Analysis (PCA) is proposed. PCA allowed to identify a smaller number of features (k = 2 features), the principal component scores, obtained through linear projection of the original d features into a new space with reduced dimensionality k = 2, sufficient to describe the variance of the data. By feeding artificial neural networks with the PCA features, an accurate diagnosis of tool flank wear (VBmax) was achieved, with predicted values very close to the measured tool wear values. PMID:29522443

Thermal infrared spectroscopy and modeling of experimentally shocked plagioclase feldspars

USGS Publications Warehouse

Johnson, J. R.; Horz, F.; Staid, M.I.

2003-01-01

Thermal infrared emission and reflectance spectra (250-1400 cm-1; ???7???40 ??m) of experimentally shocked albite- and anorthite-rich rocks (17-56 GPa) demonstrate that plagioclase feldspars exhibit characteristic degradations in spectral features with increasing pressure. New measurements of albite (Ab98) presented here display major spectral absorptions between 1000-1250 cm-1 (8-10 ??m) (due to Si-O antisymmetric stretch motions of the silica tetrahedra) and weaker absorptions between 350-700 cm-1 (14-29 ??m) (due to Si-O-Si octahedral bending vibrations). Many of these features persist to higher pressures compared to similar features in measurements of shocked anorthite, consistent with previous thermal infrared absorption studies of shocked feldspars. A transparency feature at 855 cm-1 (11.7 ??m) observed in powdered albite spectra also degrades with increasing pressure, similar to the 830 cm-1 (12.0 ??m) transparency feature in spectra of powders of shocked anorthite. Linear deconvolution models demonstrate that combinations of common mineral and glass spectra can replicate the spectra of shocked anorthite relatively well until shock pressures of 20-25 GPa, above which model errors increase substantially, coincident with the onset of diaplectic glass formation. Albite deconvolutions exhibit higher errors overall but do not change significantly with pressure, likely because certain clay minerals selected by the model exhibit absorption features similar to those in highly shocked albite. The implication for deconvolution of thermal infrared spectra of planetary surfaces (or laboratory spectra of samples) is that the use of highly shocked anorthite spectra in end-member libraries could be helpful in identifying highly shocked calcic plagioclase feldspars.

Detection of silicate emission features in the 8- to 13-micron spectra of main belt asteroids

NASA Technical Reports Server (NTRS)

Feierberg, M. A.; Witteborn, F. C.; Lebofsky, L. A.

1983-01-01

A presentation is given of 8.0-13.0 micron spectra (Delta lambda/lambda = 0.02-0.03) for six main belt asteroids, which range from 58 to 220 km in diameter and sample the five principal taxonomic classes (C, S, M, R and E). Narrow, well-defined silicate emission features are present on two of the asteroids, the C-type 19 Fortuna and the M-type 21 Lutetia. No comparable emission features are observed on the S-types 11 Parthenope and 14 Irene, the R-type 349 Dembowska or the E-type 64 Angelina.

GHRS observations of cool, low-gravity stars. 1: The far-ultraviolet spectrum of alpha Orionis (M2 Iab)

NASA Technical Reports Server (NTRS)

Carpenter, Kenneth G.; Robinson, Richard D.; Wahlgren, Glenn M.; Linsky, Jeffrey L.; Brown, Alexander

1994-01-01

We present far-UV (1200-1930 A) observations of the prototypical red supergiant star alpha Ori, obtained with the Goddard High Resolution Spectrograph (GHRS) on the Hubble Space Telescope (HST). The observations, obtained in both low- (G140L) and medium- (G160/200M) resolution modes, unamibiguously confirm that the UV 'continuum' tentatively seen with (IUE) is in fact a true continuum and is not due to a blend of numerous faint emission features or scattering inside the IUE spectrograph. This continuum appears to originate in the chromospheric of the star at temperatures ranging from 3000-5000 K, and we argue that it is not related to previously reported putative companions or to bright spots on the stellar disk. Its stellar origin is further confirmed by overlying atomic and molecular absorptions from the chromosphere and circumstellar shell. The dominant structure in this spectral region is due to nine strong, broad absorption bands of the fourth-positive A-X system of CO, superposed on this continuum in the 1300-1600 A region. Modeling of this CO absorption indicates that it originates in the circumstellar shell in material characterized by T = 500 K, N(CO) = 1.0 x 10(exp 18) per sq cm, and V(sub turb) = 5.0 km per sec. The numerous chromospheric emission features are attributed mostly to fluorescent lines of Fe II and Cr II (both pumped by Lyman Alpha) and S I lines, plus a few lines of O I, C I, and Si II. The O I and C I UV 2 multiplets are very deficient in flux, compared to both the flux observed in lines originating from common upper levels but with markedly weaker intrinsic strength (i.e., O I UV 146 and C I UV 32) and to the UV 2 line fluxes seen in other cool, less luminous stars. This deficiency appears to be caused by strong self-absorption of these resonance lines in the circumstellar shell and/or upper chromosphere of alpha Ori. Atomic absorption features, primarily due to C I and Fe II are clearly seen in the G160M spectrum centered near 1655 A. These Fe II features are formed at temperatures that can occur only in the chromosphere of the star and are clearly not photospheric or circumstellar in origin.

CN rings in full protoplanetary disks around young stars as probes of disk structure

NASA Astrophysics Data System (ADS)

Cazzoletti, P.; van Dishoeck, E. F.; Visser, R.; Facchini, S.; Bruderer, S.

2018-01-01

Aims: Bright ring-like structure emission of the CN molecule has been observed in protoplanetary disks. We investigate whether such structures are due to the morphology of the disk itself or if they are instead an intrinsic feature of CN emission. With the intention of using CN as a diagnostic, we also address to which physical and chemical parameters CN is most sensitive. Methods: A set of disk models were run for different stellar spectra, masses, and physical structures via the 2D thermochemical code DALI. An updated chemical network that accounts for the most relevant CN reactions was adopted. Results: Ring-shaped emission is found to be a common feature of all adopted models; the highest abundance is found in the upper outer regions of the disk, and the column density peaks at 30-100 AU for T Tauri stars with standard accretion rates. Higher mass disks generally show brighter CN. Higher UV fields, such as those appropriate for T Tauri stars with high accretion rates or for Herbig Ae stars or for higher disk flaring, generally result in brighter and larger rings. These trends are due to the main formation paths of CN, which all start with vibrationally excited H_2^* molecules, that are produced through far ultraviolet (FUV) pumping of H2. The model results compare well with observed disk-integrated CN fluxes and the observed location of the CN ring for the TW Hya disk. Conclusions: CN rings are produced naturally in protoplanetary disks and do not require a specific underlying disk structure such as a dust cavity or gap. The strong link between FUV flux and CN emission can provide critical information regarding the vertical structure of the disk and the distribution of dust grains which affects the UV penetration, and could help to break some degeneracies in the SED fitting. In contrast with C2H or c-C3H2, the CN flux is not very sensitive to carbon and oxygen depletion.

Preliminary Results on Irradiance Measurements from Lyra and Swap

NASA Astrophysics Data System (ADS)

Kumara, S. T.; Kariyappa, R.; Dominique, M.; Berghmans, D.; Damé, L.; Hochedez, J. F.; Doddamani, V. H.; Chitta, Lakshmi Pradeep

The first and preliminary results of the photometry of Large Yield Radiometer (LYRA) and Sun Watcher using Active Pixel system detector and Image Processing (SWAP) onboard PROBA2 are presented in this paper. To study the day-to-day variations of LYRA irradiance, we have compared the LYRA irradiance values (observed Sun as a star) measured in Aluminum filter channel (171Å-500Å) with spatially resolved full-disk integrated intensity values measured with SWAP (174Å) and Ca II K 1 Å index values (ground-based observations from NSO/Sac Peak) for the period from 01 April 2010 to 15 Mar 2011. We found that there is a good correlation between these parameters. This indicates that the spatial resolution of SWAP complements the high temporal resolution of LYRA. Hence SWAP can be considered as an additional radiometric channel. Also the K emission index is the integrated intensity (or flux) over a 1 Å band centered on the K line and is proportional to the total emission from the chromosphere; this comparison clearly explains that the LYRA irradiance variations are due to the various magnetic features, which are contributing significantly. In addition to this we have made an attempt to segregate coronal features from full-disk SWAP images. This will help to understand and determine the actual contribution of the individual coronal feature to LYRA irradiance variations.

The 2.5-12 micrometers spectrum of comet Halley from the IKS-VEGA experiment.

PubMed

Combes, M; Moroz, V I; Crovisier, J; Encrenaz, T; Bibring, J P; Grigoriev, A V; Sanko, N F; Coron, N; Crifo, J F; Gispert, R; Bockelée-Morvan, D; Nikolsky YuV; Krasnopolsky, V A; Owen, T; Emerich, C; Lamarre, J M; Rocard, F

1988-01-01

The infrared instrument IKS flown on board the VEGA space probes was designed for the detection of emission bands of parent molecules, and for a measurement of the size and temperature of the thermal emitting nuclear region. The instrument had three channels with cooled detectors: an "imaging channel" designed to modulate the signal of the nucleus and two spectroscopic channels operating at 2.5-5 and 6-12 micrometers, respectively, equipped with circular variable filters of resolving power approximately 50. This paper presents and discusses the results from the spectral channels. On VEGA 1, usable spectra were obtained at distances D from the comet nucleus ranging from 250,000 to 40,000 km corresponding to fields of view 4000 and 700 km in diameter, respectively. The important internal background signal caused by the instrument itself, which could not be cooled, had to be eliminated. Since no sky chopping was performed, we obtain difference spectra between the current spectrum and a reference spectrum with little or no cometary signal taken at the beginning of the observing sequence (D approximately 200,000 km). Final discrimination between cometary signal and instrumental background is achieved using their different time evolution, since the instrumental background is proportional to the slow temperature drift of the instrument, and the cometary signal due to parent molecules or dust grains is expected to vary in first order as D-1. The 2.5-5 micrometers IKS spectra definitely show strong narrow signals at 2.7 and 4.25 micrometers, attributed to the nu 3 vibrational bands of H2O and CO2, respectively, and a broader signal in the region 3.2-3.5 micrometers, which may be attributed to CH-bearing molecules. All these signals present the expected D-1 intensity variation. Weaker emission features at 3.6 and 4.7 micrometers could correspond to the nu 1 and nu 5 bands of H2CO and the (1 - 0) band of CO, respectively. Molecular production rates are derived from the observed emissions, assuming that they are due to resonance fluorescence excited by the Sun's infrared radiation. For the strong bands of H2O and CO2, the rovibrational lines are optically thick, and radiative transfer is taken into account. We derive production rates, at the moment of the VEGA 1 flyby, of approximately 10(30) sec-1 for H2O, approximately 2.7 x 10(28) sec-1 for CO2, approximately 5 x 10(28) sec-1 for CO, and 4 x 10(28) sec-1 for H2CO, if attributions to CO and H2CO are correct. The production rate of carbon atoms in CH-bearing molecules is approximately 9 x 10(29) sec-1 assuming fluorescence of molecules in the gas phase, but could be much less if the 3.2-3.5 micrometers emission is attributed to C-H stretch in polycyclic aromatic hydrocarbons or small organic grains. In addition, marginal features are present at 4.85 and 4.45 micrometers, tentatively attributed to OCS and molecules with the CN group, respectively. Broad absorption at 2.8-3.0 micrometers, as well as a narrow emission at 3.15 micrometers, which follow well the D-1 intensity variation, might be due to water ice. Emission at 2.8 micrometers is also possibly present, and might be due to OH created in vibrationally excited states after water photodissociation. The 6-12 micrometers spectrum does not show any molecular emission, nor emission in the 7.5-micrometers region. The spectrum is dominated by silicate emission showing a double structure with maxima at 9.0 and 11.2 micrometers, which suggests the presence of olivine.

Significance of the impact of motion compensation on the variability of PET image features

NASA Astrophysics Data System (ADS)

Carles, M.; Bach, T.; Torres-Espallardo, I.; Baltas, D.; Nestle, U.; Martí-Bonmatí, L.

2018-03-01

In lung cancer, quantification by positron emission tomography/computed tomography (PET/CT) imaging presents challenges due to respiratory movement. Our primary aim was to study the impact of motion compensation implied by retrospectively gated (4D)-PET/CT on the variability of PET quantitative parameters. Its significance was evaluated by comparison with the variability due to (i) the voxel size in image reconstruction and (ii) the voxel size in image post-resampling. The method employed for feature extraction was chosen based on the analysis of (i) the effect of discretization of the standardized uptake value (SUV) on complementarity between texture features (TF) and conventional indices, (ii) the impact of the segmentation method on the variability of image features, and (iii) the variability of image features across the time-frame of 4D-PET. Thirty-one PET-features were involved. Three SUV discretization methods were applied: a constant width (SUV resolution) of the resampling bin (method RW), a constant number of bins (method RN) and RN on the image obtained after histogram equalization (method EqRN). The segmentation approaches evaluated were 40% of SUVmax and the contrast oriented algorithm (COA). Parameters derived from 4D-PET images were compared with values derived from the PET image obtained for (i) the static protocol used in our clinical routine (3D) and (ii) the 3D image post-resampled to the voxel size of the 4D image and PET image derived after modifying the reconstruction of the 3D image to comprise the voxel size of the 4D image. Results showed that TF complementarity with conventional indices was sensitive to the SUV discretization method. In the comparison of COA and 40% contours, despite the values not being interchangeable, all image features showed strong linear correlations (r  >  0.91, p\\ll 0.001 ). Across the time-frames of 4D-PET, all image features followed a normal distribution in most patients. For our patient cohort, the compensation of tumor motion did not have a significant impact on the quantitative PET parameters. The variability of PET parameters due to voxel size in image reconstruction was more significant than variability due to voxel size in image post-resampling. In conclusion, most of the parameters (apart from the contrast of neighborhood matrix) were robust to the motion compensation implied by 4D-PET/CT. The impact on parameter variability due to the voxel size in image reconstruction and in image post-resampling could not be assumed to be equivalent.

A study of extreme carbon stars. I - Silicon carbide emission features

NASA Technical Reports Server (NTRS)

Cohen, M.

1984-01-01

10-micron spectra of many extreme carbon stars reveal a prominent emission feature near 11 microns. This is compared with laboratory spectra of SiC grains. Two distinct types of features are found, perhaps indicative of different mechanisms of grain formation in different stars. Estimates are made of probable column densities and total masses of SiC in the circumstellar shells.

[Fe II] emissions associated with the young interacting binary UY Aurigae

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

Pyo, Tae-Soo; Hayashi, Masahiko; Beck, Tracy L.

We present high-resolution 1.06-1.28 μm spectra toward the interacting binary UY Aur obtained with GEMINI/NIFS and the adaptive optics system Altair. We have detected [Fe II] λ1.257 μm and He I λ1.083 μm lines from both UY Aur A (the primary source) and UY Aur B (the secondary). In [Fe II] UY Aur A drives fast and widely opening outflows with an opening angle of ∼90° along a position angle of ∼40°, while UY Aur B is associated with a redshifted knot. The blueshifted and redshifted emissions show a complicated structure between the primary and secondary. The radial velocities ofmore » the [Fe II] emission features are similar for UY Aur A and B: ∼ –100 km s{sup –1} for the blueshifted emission and ∼ +130 km s{sup –1} for the redshifted component. The He I line profile observed toward UY Aur A comprises a central emission feature with deep absorptions at both blueshifted and redshifted velocities. These absorption features may be explained by stellar wind models. The He I line profile of UY Aur B shows only an emission feature.« less

Characterizing the Dust-Correlated Anomalous Emission in LDN 1622

NASA Astrophysics Data System (ADS)

Cleary, Kieran; Casassus, Simon; Dickinson, Clive; Lawrence, Charles; Sakon, Itsuki

2008-03-01

The search for 'dust-correlated microwave emission' was started by the surprising excess correlation of COBE-DMR maps, at 31.5, 53 and 91GHz, with DIRBE dust emission at 140 microns. It was first thought to be Galactic free-free emission from the Warm Ionized Medium (WIM). However, Leitch et al. (1997) ruled out a link with free-free by comparing with Halpha templates and first confirmed the anomalous nature of this emission. Since then, this emission has been detected by a number of experiments in the frequency range 5-60 GHz. The most popular explanation is emission from ultra-small spinning dust grains (first postulated by Erickson, 1957), which is expected to have a spectrum that is highly peaked at about 20 GHz. Spinning dust models appear to be broadly consistent with microwave data at high latitudes, but the data have not been conclusive, mainly due to the difficulty of foreground separation in CMB data. LDN 1622 is a dark cloud that lies within the Orion East molecular cloud at a distance of 120 pc. Recent cm-wave observations, in combination with WMAP data, have verified the detection of anomalous dust-correlated emission in LDN 1622. This mid-IR-cm correlation in LDN 1622 is currently the only observational evidence that very small grains VSG emit at GHz frequencies. We propose a programme of spectroscopic observations of LDN 1622 with Spitzer IRS to address the following questions: (i) Are the IRAS 12 and 25 microns bands tracing VSG emission in LDN 1622? (ii) What Mid-IR features and continuum bands best correlate with the cm-wave emission? and (iii) How do the dust properties vary with the cm-wave emission? These questions have important implications for high-sensitivity CMB experiments.

X-Rays from Saturn and its Rings

NASA Technical Reports Server (NTRS)

Bhardwaj, Anil; Elsner, Ron F.; Waite, J. Hunter; Gladstone, G. Randall; Cravens, Tom E.; Ford, Peter G.

2005-01-01

In January 2004 Saturn was observed by Chandra ACIS-S in two exposures, 00:06 to 11:00 UT on 20 January and 14:32 UT on 26 January to 01:13 UT on 27 January. Each continuous observation lasted for about one full Saturn rotation. These observations detected an X-ray flare from the Saturn's disk and indicate that the entire Saturnian X-ray emission is highly variable -- a factor of $\\sim$4 variability in brightness in a week time. The Saturn X-ray flare has a time and magnitude matching feature with the solar X-ray flare, which suggests that the disk X-ray emission of Saturn is governed by processes happening on the Sun. These observations also unambiguously detected X-rays from Saturn's rings. The X-ray emissions from rings are present mainly in the 0.45-0.6 keV band centered on the atomic OK$\\alpha$ fluorescence line at 525 eV: indicating the production of X-rays due to oxygen atoms in the water icy rings. The characteristics of X-rays from Saturn's polar region appear to be statistically consistent with those from its disk X-rays, suggesting that X-ray emission from the polar cap region might be an extension of the Saturn disk X-ray emission.

Follow-up FOCAS Spectroscopy for [O iii] Blobs at z 0.7

NASA Astrophysics Data System (ADS)

Yuma, Suraphong

2014-01-01

We propose FOCAS spectroscopy for our eight newly selected [O_iii] blobs at z~0.7, showing remarkably extended [O_iii] emission larger than 30 kpc down to 1.2x10^{-18} erg^{-1}cm^{-2} arcsec^{-2} in continuum-subtracted narrowband images. This extended oxygen nebulae beyond stellar component is thought to be hot metal-right gas outflowing from galaxies. However, without spectroscopy to verify gas motion of the system, we cannot certainly conclude that the extended feature of [O_iii] emission is caused by gas outflow. With FOCAS, we expect to observe Fe_ii, Mg_ii absorption lines and [O_ii}], Hbeta, and [O_iii] emission lines, which all fall into optical window at this redshift. We will 1) confirm the outflow of these blobs through Fe_ii and/or Mg_ii absorption lines, 2) constrain energy source of the outflow (AGN or stellar feedback) through line-ratio diagnostic diagram, and 3) for the first time investigate if the extended oxygen emission is just due to the photo-ionized outflowing gas or involving shock heating process through [O_ii]/[O_iii] ratios in extended regions. The last goal can only be accomplished with FOCAS optical spectroscopy, which can observe both [O_ii] and [O_iii] emission lines simultaneously.

MOLECULAR AND IONIZED HYDROGEN IN 30 DORADUS. I. IMAGING OBSERVATIONS

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

Yeh, Sherry C. C.; Seaquist, Ernest R.; Matzner, Christopher D.

2015-07-10

We present the first fully calibrated H{sub 2} 1–0 S(1) image of the entire 30 Doradus nebula. The observations were conducted using the NOAO Extremely Wide-field Infrared Imager (NEWFIRM) on the CTIO 4 m Blanco Telescope. Together with a NEWFIRM Brγ image of 30 Doradus, our data reveal the morphologies of the warm molecular gas and ionized gas in 30 Doradus. The brightest H{sub 2}-emitting area, which extends from the northeast to the southwest of R136, is a photodissociation region (PDR) viewed face-on, while many clumps and pillar features located at the outer shells of 30 Doradus are PDRs viewedmore » edge-on. Based on the morphologies of H{sub 2}, Brγ, CO, and 8 μm emission, the H{sub 2} to Brγ line ratio, and Cloudy models, we find that the H{sub 2} emission is formed inside the PDRs of 30 Doradus, 2–3 pc to the ionization front of the H ii region, in a relatively low-density environment <10{sup 4} cm{sup −3}. Comparisons with Brγ, 8 μm, and CO emission indicate that H{sub 2} emission is due to fluorescence, and provide no evidence for shock excited emission of this line.« less

SSULI/SSUSI UV Tomographic Images of Large-Scale Plasma Structuring

NASA Astrophysics Data System (ADS)

Hei, M. A.; Budzien, S. A.; Dymond, K.; Paxton, L. J.; Schaefer, R. K.; Groves, K. M.

2015-12-01

We present a new technique that creates tomographic reconstructions of atmospheric ultraviolet emission based on data from the Special Sensor Ultraviolet Limb Imager (SSULI) and the Special Sensor Ultraviolet Spectrographic Imager (SSUSI), both flown on the Defense Meteorological Satellite Program (DMSP) Block 5D3 series satellites. Until now, the data from these two instruments have been used independently of each other. The new algorithm combines SSULI/SSUSI measurements of 135.6 nm emission using the tomographic technique; the resultant data product - whole-orbit reconstructions of atmospheric volume emission within the satellite orbital plane - is substantially improved over the original data sets. Tests using simulated atmospheric emission verify that the algorithm performs well in a variety of situations, including daytime, nighttime, and even in the challenging terminator regions. A comparison with ALTAIR radar data validates that the volume emission reconstructions can be inverted to yield maps of electron density. The algorithm incorporates several innovative new features, including the use of both SSULI and SSUSI data to create tomographic reconstructions, the use of an inversion algorithm (Richardson-Lucy; RL) that explicitly accounts for the Poisson statistics inherent in optical measurements, and a pseudo-diffusion based regularization scheme implemented between iterations of the RL code. The algorithm also explicitly accounts for extinction due to absorption by molecular oxygen.

Review of modern low emissions combustion technologies for aero gas turbine engines

NASA Astrophysics Data System (ADS)

Liu, Yize; Sun, Xiaoxiao; Sethi, Vishal; Nalianda, Devaiah; Li, Yi-Guang; Wang, Lu

2017-10-01

Pollutant emissions from aircraft in the vicinity of airports and at altitude are of great public concern due to their impact on environment and human health. The legislations aimed at limiting aircraft emissions have become more stringent over the past few decades. This has resulted in an urgent need to develop low emissions combustors in order to meet legislative requirements and reduce the impact of civil aviation on the environment. This article provides a comprehensive review of low emissions combustion technologies for modern aero gas turbines. The review considers current high Technologies Readiness Level (TRL) technologies including Rich-Burn Quick-quench Lean-burn (RQL), Double Annular Combustor (DAC), Twin Annular Premixing Swirler combustors (TAPS), Lean Direct Injection (LDI). It further reviews some of the advanced technologies at lower TRL. These include NASA multi-point LDI, Lean Premixed Prevaporised (LPP), Axially Staged Combustors (ASC) and Variable Geometry Combustors (VGC). The focus of the review is placed on working principles, a review of the key technologies (includes the key technology features, methods of realising the technology, associated technology advantages and design challenges, progress in development), technology application and emissions mitigation potential. The article concludes the technology review by providing a technology evaluation matrix based on a number of combustion performance criteria including altitude relight auto-ignition flashback, combustion stability, combustion efficiency, pressure loss, size and weight, liner life and exit temperature distribution.

Spatial variations of the 3 micron emission features within UV-excited nebulae - Photochemical evolution of interstellar polycyclic aromatic hydrocarbons

NASA Technical Reports Server (NTRS)

Geballe, T. R.; Tielens, A. G. G. M.; Allamandola, L. J.; Moorhouse, A.; Brand, P. W. J. L.

1989-01-01

Spectra at 3 microns have been obtained at several positions in the Orion Bar region and in the nebula surrounding HD 44179. Weak emission features at 3.40, 3.46, 3.51, and 3.57 microns are prominent in the Orion Bar region. The 3.40- and 3.51-micron features increase in intensity relative to the dominant 3.29-micron feature. The spectrum obtained in the Red Rectangle region 5 arcsecs north of HD 44179 are similar to those in the Orion Bar, with a weak, broad 3.40-micron feature at the position of HD 44179. The spatial behavior of the weak emission features is explained in terms of hot bands of the CH stretch and overtones, and combination bands of other fundamental vibrations in simple PAHs. Based on the susceptibility of PAHs to destruction by the far UV fields in both regions, PAH sizes are estimated at 20-50 carbon atoms.

Laser spectroscopy of CaNC and SrNC

NASA Astrophysics Data System (ADS)

Douay, M.; Bernath, P. F.

1990-11-01

Low-resolution laser excitation and dispersed laser-induced fluorescence spectra of CaNC and SrNC were recorded. The laser excitation spectra of the overlineB2Σ+-overlineX2Σ+ and overlineA2Π-overlineX2Σ+ transitions of SrNC are consistent with a linear,isocyanide structure. For both CaNC and SrNC, additional strong, non-resonant features occur to the red of the overlineB2Σ+-overlineX2Σ+ and overlineA2Π-overlineX2Σ+ transitions in the dispersed fluorescence spectra. Although these features remain unassigned, they might be due to emission from the isomeric,linear cyanides, CaCN and SrCN. In this case, the excited state potential curves need to have a small barrier between the cyanide and the isocyanide forms.

Switching behaviour of individual Ag-TCNQ nanowires: an in situ transmission electron microscopy study

NASA Astrophysics Data System (ADS)

Ran, Ke; Rösner, Benedikt; Butz, Benjamin; Fink, Rainer H.; Spiecker, Erdmann

2016-10-01

The organic semiconductor silver-tetracyanoquinodimethane (Ag-TCNQ) exhibits electrical switching and memory characteristics. Employing a scanning tunnelling microscopy setup inside a transmission electron microscope, the switching behaviour of individual Ag-TCNQ nanowires (NWs) is investigated in detail. For a large number of NWs, the switching between a high (OFF) and a low (ON) resistance state was successfully stimulated by negative bias sweeps. Fitting the experimental I-V curves with a Schottky emission function makes the switching features prominent and thus enables a direct evaluation of the switching process. A memory cycle including writing, reading and erasing features is demonstrated at an individual NW. Moreover, electronic failure mechanisms due to Joule heating are discussed. These findings have a significant impact on our understanding of the switching behaviour of Ag-TCNQ.

Herschel-PACS Observations of Far-IR CO Line Emission in NGC 1068: Highly Excited Molecular Gas in the Circumnuclear Disk

DTIC Science & Technology

2012-08-10

local radiation density. At millimeter wavelengths the background is dominated by the cosmic microwave background (CMB; Kamenetzky et al. 2011), but the...the observed continuum flux density Fν,obs as Jν,ext = Iν,CB + 9 16 Fν,obs Ω , (1) where Iν,CB is the sum of the CMB and cosmic IR background . We take...data, likely due to an imperfect subtraction of the telescope background , and we remove this feature using a higher order baseline fit. The integrated

Direct spectroscopic evidence for ionized polycyclic aromatic hydrocarbons in the interstellar medium.

PubMed

Sloan, G C; Hayward, T L; Allamandola, L J; Bregman, J D; DeVito, B; Hudgins, D M

1999-03-01

Long-slit 8-13 micrometers spectroscopy of the nebula around NGC 1333 SVS 3 reveals spatial variations in the strength and shape of emission features that are probably produced by polycyclic aromatic hydrocarbons (PAHs). Close to SVS 3, the 11.2 micrometers feature develops an excess at approximately 10.8-11.0 micrometers and a feature appears at approximately 10 micrometers. These features disappear with increasing distance from the central source, and they show striking similarities to recent laboratory data of PAH cations, providing the first identification of emission features arising specifically from ionized PAHs in the interstellar medium.

Interferometric Observation of the Highly Polarized SiO Maser Emission from the v = 1, J = 5-4 Transition Associated with VY Canis Majoris

NASA Astrophysics Data System (ADS)

Shinnaga, Hiroko; Moran, James M.; Young, Ken H.; Ho, Paul T. P.

2004-11-01

We used the Submillimeter Array to image the SiO maser emission in the v=1, J=5-4 transition associated with the peculiar red supergiant VY Canis Majoris. We identified seven maser components and measured their relative positions and linear polarization properties. Five of the maser components are coincident to within about 150 mas (~200 AU at the distance of 1.5 kpc); most of them may originate in the circumstellar envelope at a radius of about 50 mas from the star along with the SiO masers in the lowest rotational transitions. Our measurements show that two of the maser components may be offset from the inner stellar envelope (at the 3 σ level of significance) and may be part of a larger bipolar outflow associated with VY CMa identified by Shinnaga et al. The strongest maser feature at a velocity of 35.9 km s-1 has a 60% linear polarization, and its polarization direction is aligned with the bipolar axis. Such a high degree of polarization suggests that maser inversion is due to radiative pumping. Five of the other maser features have significant linear polarization.

Infrared imaging of the crime scene: possibilities and pitfalls.

PubMed

Edelman, Gerda J; Hoveling, Richelle J M; Roos, Martin; van Leeuwen, Ton G; Aalders, Maurice C G

2013-09-01

All objects radiate infrared energy invisible to the human eye, which can be imaged by infrared cameras, visualizing differences in temperature and/or emissivity of objects. Infrared imaging is an emerging technique for forensic investigators. The rapid, nondestructive, and noncontact features of infrared imaging indicate its suitability for many forensic applications, ranging from the estimation of time of death to the detection of blood stains on dark backgrounds. This paper provides an overview of the principles and instrumentation involved in infrared imaging. Difficulties concerning the image interpretation due to different radiation sources and different emissivity values within a scene are addressed. Finally, reported forensic applications are reviewed and supported by practical illustrations. When introduced in forensic casework, infrared imaging can help investigators to detect, to visualize, and to identify useful evidence nondestructively. © 2013 American Academy of Forensic Sciences.

Fast-ion distributions from third harmonic ICRF heating studied with neutron emission spectroscopy

NASA Astrophysics Data System (ADS)

Hellesen, C.; Gatu Johnson, M.; Andersson Sundén, E.; Conroy, S.; Ericsson, G.; Eriksson, J.; Sjöstrand, H.; Weiszflog, M.; Johnson, T.; Gorini, G.; Nocente, M.; Tardocchi, M.; Kiptily, V. G.; Pinches, S. D.; Sharapov, S. E.; EFDA Contributors, JET

2013-11-01

The fast-ion distribution from third harmonic ion cyclotron resonance frequency (ICRF) heating on the Joint European Torus is studied using neutron emission spectroscopy with the time-of-flight spectrometer TOFOR. The energy dependence of the fast deuteron distribution function is inferred from the measured spectrum of neutrons born in DD fusion reactions, and the inferred distribution is compared with theoretical models for ICRF heating. Good agreements between modelling and measurements are seen with clear features in the fast-ion distribution function, that are due to the finite Larmor radius of the resonating ions, replicated. Strong synergetic effects between ICRF and neutral beam injection heating were also seen. The total energy content of the fast-ion population derived from TOFOR data was in good agreement with magnetic measurements for values below 350 kJ.

Hybrid Wing Body Configuration Scaling Study

NASA Technical Reports Server (NTRS)

Nickol, Craig L.

2012-01-01

The Hybrid Wing Body (HWB) configuration is a subsonic transport aircraft concept with the potential to simultaneously reduce fuel burn, noise and emissions compared to conventional concepts. Initial studies focused on very large applications with capacities for up to 800 passengers. More recent studies have focused on the large, twin-aisle class with passenger capacities in the 300-450 range. Efficiently scaling this concept down to the single aisle or smaller size is challenging due to geometric constraints, potentially reducing the desirability of this concept for applications in the 100-200 passenger capacity range or less. In order to quantify this scaling challenge, five advanced conventional (tube-and-wing layout) concepts were developed, along with equivalent (payload/range/technology) HWB concepts, and their fuel burn performance compared. The comparison showed that the HWB concepts have fuel burn advantages over advanced tube-and-wing concepts in the larger payload/range classes (roughly 767-sized and larger). Although noise performance was not quantified in this study, the HWB concept has distinct noise advantages over the conventional tube-and-wing configuration due to the inherent noise shielding features of the HWB. NASA s Environmentally Responsible Aviation (ERA) project will continue to investigate advanced configurations, such as the HWB, due to their potential to simultaneously reduce fuel burn, noise and emissions.

PAH Emission From ULIRGs: Evidence For Unusual Grain Properties?

NASA Astrophysics Data System (ADS)

Marshall, Jason A.; Armus, L.; Spoon, H. W. W.

2007-12-01

The tremendous power emerging from ultraluminous infrared galaxies (ULIRGs) is driven both by high levels of star-formation activity and AGN-related accretion. Observations of star-forming regions in the Milky Way and external star-forming galaxies provide evidence that the first of these energy generation mechanisms often also gives rise to emission from PAH molecules in the form of characteristic mid-IR features. Given the composite nature of ULIRGs, it is not surprising that many also exhibit significant emission from PAHs. Perhaps more surprising, however, is that some ULIRGs believed to be powered primarily by AGNs also show emission from PAHs, although typically at lower levels relative to their total dust output. To investigate the nature of the PAH emission from galaxies powered either by star-formation or AGN accretion alone, as well as emission from composite systems such as ULIRGs powered by both mechanisms, we present a detailed study of the PAH emission spectra from galaxies of each type. We use the CAFE spectral energy distribution decomposition software we have developed to derive and extinction correct the spectra of PAH emission from a sample of 100 galaxies with Spitzer/IRS observations, and use the results of this analysis to calculate the ratios of the various mid-IR PAH feature luminosities. In particular, we investigate to what extent these relative feature strengths vary as a function of the optical classification of galaxies, and we inquire into whether or not the derived feature strength ratios provide evidence for unusual grain properties in the extreme conditions within ULIRGs.

Sources of the 13 microns Emission Feature Associated with Silicate Dust

NASA Astrophysics Data System (ADS)

Levan, P. D.; Sloan, G. C.; Little-Marenin, I. R.

1993-05-01

We have carefully searched the Atlas of Low-resolution Spectra (IRAS Science Team 1986, A&A Suppl., 65, 607; Volk and Cohen 1989, AJ, 98, 931) for sources of the 13 microns emission feature associated with silicate emission at 10 microns first discussed by Little-Marenin and Little (1988, ApJ, 303, 305). We have identified 73 spectra for which the 13 microns feature is detected at 4sigma or better. In several cases, we have confirmed the existence of the feature using GLADYS, the Air Force long-slit 10 microns spectrometer, at the Wyoming Infrared Observatory. Our sample of 13 microns emission sources are nearly all late M giants, the majority of type M6 or M7. Variability types exist for 54; over half are SRb variables, while the remainder are fairly evenly divided among Miras and classes SRa and Lb. Most of the sources have LRS characterizations of 14, 15, or 21-24, i.e. weak silicate emission at 10 microns. The shape of the silicate emission feature varies from a nearly classic 10 microns profile broadened at longer wavelengths to a double-humped profile with peaks at both 10 and 11 microns. In the scheme of Little-Marenin and Little, these shapes would be characterized as Sil+, Sil++, and 3-component. The root mean square radial velocity of our sample is 31 km/sec. The mean angle from the galactic plane is 29 degrees, and there are no obvious dependencies with galactic longitude. These properties indicate that our sample consists of old Population I AGB stars. We have also investigated how the strength of the 13 microns emission varies with spectral type, class and period of variability, LRS characterization, 10 microns feature width, and galactic position. We find no correlation with any of these properties, indicating that the 13 microns emission is not unique to any specific class of Population I AGB stars. There is no strong evidence for the contention that the 13 microns sources are precursors to S stars.

Polycyclic aromatic hydrocarbons and the unidentified infrared emission bands - Auto exhaust along the Milky Way

NASA Technical Reports Server (NTRS)

Allamandola, L. J.; Tielens, A. G. G. M.; Barker, J. R.

1985-01-01

The unidentified infrared emission features (UIR bands) are attributed to a collection of partially hydrogenated, positively charged polycyclic aromatic hydrocarbons (PAHs). This assignment is based on a spectroscopic analysis of the UIR bands. Comparison of the observed interstellar 6.2 and 7.7-micron bands with the laboratory measured Raman spectrum of a collection of carbon-based particulates (auto exhaust) shows a very good agreement, supporting this identification. The infrared emission is due to relaxation from highly vibrationally and electronically excited states. The excitation is probably caused by UV photon absorption. The infrared fluorescence of one particular, highly vibrationally excited PAH (chrysene) is modeled. In this analysis the species is treated as a molecule rather than bulk material and the non-thermodynamic equilibrium nature of the emission is fully taken into account. From a comparison of the observed ratio of the 3.3 to 11.3-micron UIR bands with the model calculations, the average number of carbon atoms per molecule is estimated to be about 20. The abundance of interstellar PAHs is calculated to be about 2 x 10 to the -7th with respect to hydrogen.

High-Directivity Emissions with Flexible Beam Numbers and Beam Directions Using Gradient-Refractive-Index Fractal Metamaterial

PubMed Central

Xu, He-Xiu; Wang, Guang-Ming; Tao, Zui; Cui, Tie Jun

2014-01-01

A three-dimensional (3D) highly-directive emission system is proposed to enable beam shaping and beam steering capabilities in wideband frequencies. It is composed of an omnidirectional source antenna and several 3D gradient-refractive-index (GRIN) lenses. To engineer a broadband impedance match, the design method for these 3D lenses is established under the scenario of free-space excitation by using a planar printed monopole. For realizations and demonstrations, a kind of GRIN metamaterial is proposed, which is constructed by non-uniform fractal geometries. Due to the non-resonant and deep-subwavelength features of the fractal elements, the resulting 3D GRIN metamaterial lenses have extra wide bandwidth (3 to 7.5 GHz), and are capable of manipulating electromagnetic wavefronts accurately, advancing the state of the art of available GRIN lenses. The proposal for the versatile highly-directive emissions has been confirmed by simulations and measurements, showing that not only the number of beams can be arbitrarily tailored but also the beam directions can be steerable. The proposal opens a new way to control broadband highly-directive emissions with pre-designed directions, promising great potentials in modern wireless communication systems. PMID:25034268

Chromospheres of late-type active and quiescent dwarfs. III - Variability of CA II H emission profiles

NASA Astrophysics Data System (ADS)

Garcia Lopez, R. J.; Crivellari, L.; Beckman, J. E.; Rebolo, R.

1992-08-01

We have used high-resolution spectra of the Ca II H resonance line in late-type dwarfs, obtained with high S:N ratios, over a period of four years to widen our understanding of the dynamical behavior of the Ca II emission cores. All of the stars dealt with in this article, which are chromospherically active, show variability both in core emission flux and line width. They also show significant wavelength shifts with time of order hundreds of meters per second in the mean core wavelength, and with lower amplitude in the H3 self-absorption, compared to the photospheric rest wavelength of Ca II H. Comparing the emission core shifts with those observed in the H3 features, we find, for the first time, direct prima facie evidence for vertical chromospheric velocity fields, which show stability in sense over periods of years in a given star, with notable modulation in gradient, and which differ in gradient from star to star. We present evidence to show that the observed effects are almost certainly not due to projected rotational modulation, and offer new prospects, given spectral measurements closely sampled in time, for investigating the vertical velocity structures of chromospheres.

Bioinspired Orientation of β-Substituents on Porphyrin Antenna Ligands Switches Ytterbium(III) NIR Emission with Thermosensitivity.

PubMed

Ning, Yingying; Ke, Xian-Sheng; Hu, Ji-Yun; Liu, Yi-Wei; Ma, Fang; Sun, Hao-Ling; Zhang, Jun-Long

2017-02-20

"Configurational isomerism" is an important approach found in naturally occurring chlorophylls to modulate light harvesting function without significant structural changes; however, this feature has been seldom applied in design of antenna ligands for lanthanide (Ln) sensitization. In this work, we introduced a bioinspired approach by orientation of β-dilactone moieties on porphyrinates, namely cis-/trans-porphodilactones, to modulate the energy transfer process from the lowest triplet excited state of the ligand (T 1 ) to the emitting level of ytterbium(III) ( 2 F 5/2 , Yb*). Interestingly, near-infrared (NIR) emission of Yb(III) could be switched "on" by the cis-porphodilactone ligand, while the trans-isomer renders Yb(III) emission "off" and the ratio of quantum yields is ∼8. Analysis of the structure-photophysical properties relationship suggests that the significant emission difference is correlated to the energy gaps between T 1 and Yb* (1152 cm -1 in the cis- vs -25 cm -1 in the trans-isomer). More interestingly, due to back energy transfer (BEnT), the Yb(III) complex of cis-porphodilactone exhibits NIR emission with high thermosensitivity (4.0%°C -1 in solution and 4.9%°C -1 in solid state), comparable to previously reported terbium (Tb) and europium (Eu) visible emitters, in contrast to the trivial emission changes of the trans-isomer and porphyrin and porpholactone analogues. This work opens up new access to design NIR emissive Ln complexes by bioinspired modification of antenna ligands.

Synchronization of spontaneous otoacoustic emissions in the tokay gecko

NASA Astrophysics Data System (ADS)

Roongthumskul, Yuttana; Hudspeth, A. J.

2018-05-01

Spontaneous otoacoustic emissions (SOAEs) are a universal feature of all classes of tetrapods. Although the generation mechanism of SOAEs are incompletely understood, these emissions are undoubtedly associated with the active process of the inner ear. In most lizards, unlike mammals and amphibians, robust SOAEs can ordinarily be detected from both ears. In this work, we investigated the interactions between emissions recorded simultaneously from the two ears of tokay geckos. We found that the frequency spectra of SOAEs from both ears of an individual animal are partially correlated: the peaks of several emissions occur at identical frequencies. To investigate the underlying mechanisms of these identical-frequency SOAEs, we perturbed the emissions from one or both ears by manipulating the pressure in the ear canals or by decreasing the local temperature in the vicinity of one inner ear. Suppression of SOAEs due to large positive pressures revealed that some identical-frequency emissions were generated unilaterally, whereas others were contributed by both ears at identical or slightly different frequencies. These bilaterally generated SOAEs became desynchronized as their frequency detuning grew sufficiently large, a phenomenon consistent with the synchronization of two active oscillators. Finally, we found that manipulations of the volume of the oral cavity or altering the impedance of the tympanum strongly affected the synchronization of SOAEs. These findings agreed with previous studies suggesting that the tokay gecko, like other lizards, exhibits strong acoustic coupling between its tympani through the oral cavity.

ALMA detection of the rotating molecular disk wind from the young star HD 163296

NASA Astrophysics Data System (ADS)

Klaassen, P. D.; Juhasz, A.; Mathews, G. S.; Mottram, J. C.; De Gregorio-Monsalvo, I.; van Dishoeck, E. F.; Takahashi, S.; Akiyama, E.; Chapillon, E.; Espada, D.; Hales, A.; Hogerheijde, M. R.; Rawlings, M.; Schmalzl, M.; Testi, L.

2013-07-01

Disk winds have been postulated as a mechanism for angular momentum release in protostellar systems for decades. HD 163296 is a Herbig Ae star surrounded by a disk and has been shown to host a series of HH knots (HH 409) with bow shocks associated with the farthest knots. Here we present ALMA science verification data of CO J = 2-1 and J = 3-2 emission, which are spatially coincident with the blue shifted jet of HH knots, and offset from the disk by -18.6 km s-1. The emission has a double corkscrew morphology and extends more than 10'' from the disk with embedded emission clumps coincident with jet knots. We interpret this double corkscrew as emission from material in a molecular disk wind, and that the compact emission near the jet knots is being heated by the jet that is moving at much higher velocities. We show that the J = 3-2 emission is likely heavily filtered by the interferometer, but the J = 2-1 emission suffers less due to the larger beam and sensitivity to larger scale structures. Excitation analysis suggests temperatures exceeding 900 K in these compact features, with the wind mass, momentum and energy being of order 10-5 M⊙, 10-4 M⊙ km s-1 and 1040 erg, respectively. The high mass loss rate suggests that this star is dispersing the disk faster than it is funneling mass onto the star.

Intrinsic fluorescence excitation-emission matrix spectral features of cottonseed protein fractions and the effects of denaturants

USDA-ARS?s Scientific Manuscript database

To better understand the functional and physicochemical properties of cottonseed protein, we investigated the intrinsic fluorescence excitation-emission matrix (EEM) spectral features of cottonseed protein isolate (CSPI) and sequentially extracted water (CSPw) and alkali (CSPa) protein fractions, an...

X-ray Spectral Formation In High-mass X-ray Binaries: The Case Of Vela X-1

NASA Astrophysics Data System (ADS)

Akiyama, Shizuka; Mauche, C. W.; Liedahl, D. A.; Plewa, T.

2007-05-01

We are working to develop improved models of radiatively-driven mass flows in the presence of an X-ray source -- such as in X-ray binaries, cataclysmic variables, and active galactic nuclei -- in order to infer the physical properties that determine the X-ray spectra of such systems. The models integrate a three-dimensional time-dependent hydrodynamics capability (FLASH); a comprehensive and uniform set of atomic data, improved calculations of the line force multiplier that account for X-ray photoionization and non-LTE population kinetics, and X-ray emission-line models appropriate to X-ray photoionized plasmas (HULLAC); and a Monte Carlo radiation transport code that simulates Compton scattering and recombination cascades following photoionization. As a test bed, we have simulated a high-mass X-ray binary with parameters appropriate to Vela X-1. While the orbital and stellar parameters of this system are well constrained, the physics of X-ray spectral formation is less well understood because the canonical analytical wind velocity profile of OB stars does not account for the dynamical and radiative feedback effects due to the rotation of the system and to the irradiation of the stellar wind by X-rays from the neutron star. We discuss the dynamical wind structure of Vela X-1 as determined by the FLASH simulation, where in the binary the X-ray emission features originate, and how the spatial and spectral properties of the X-ray emission features are modified by Compton scattering, photoabsorption, and fluorescent emission. This work was performed under the auspices of the U.S. Department of Energy by University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.

Broadband Observations of High Redshift Blazars

NASA Astrophysics Data System (ADS)

Paliya, Vaidehi S.; Parker, M. L.; Fabian, A. C.; Stalin, C. S.

2016-07-01

We present a multi-wavelength study of four high redshift blazars, S5 0014+81 (z = 3.37), CGRaBS J0225+1846 (z = 2.69), BZQ J1430+4205 (z = 4.72), and 3FGL J1656.2-3303 (z = 2.40) using quasi-simultaneous data from the Swift, Nuclear Spectroscopic Telescope Array (NuSTAR) and the Fermi-Large Area Telescope (LAT) and also archival XMM-Newton observations. Other than 3FGL J1656.2-3303, none of the sources were known as γ-ray emitters, and our analysis of ˜7.5 yr of LAT data reveals the first time detection of statistically significant γ-ray emission from CGRaBS J0225+1846. We generate the broadband spectral energy distributions (SED) of all the objects, centering at the epoch of NuSTAR observations and reproduce them using a one-zone leptonic emission model. The optical-UV emission in all the objects can be explained by radiation from the accretion disk, whereas the X-ray to γ-ray windows of the SEDs are found to be dominated by inverse Compton scattering off the broad line region photons. All of them host black holes that are billions of solar masses. Comparing the accretion disk luminosity and the jet power of these sources with a large sample of blazars, we find them to occupy a high disk luminosity-jet power regime. We also investigate the X-ray spectral properties of the sources in detail with a major focus on studying the causes of soft X-ray deficit, a feature generally seen in high redshift radio-loud quasars. We summarize that this feature could be explained based on the intrinsic curvature in the jet emission rather than being due to the external effects predicted in earlier studies, such as host galaxy and/or warm absorption.

Infrared Spectroscopy of HR 4796A's Bright Outer Cometary Ring + Tenuous Inner Hot Dust Cloud

NASA Astrophysics Data System (ADS)

Lisse, C. M.; Sitko, M. L.; Marengo, M.; Vervack, R. J., Jr.; Fernandez, Y. R.; Mittal, T.; Chen, C. H.

2017-11-01

We have obtained new NASA/IRTF SpeX spectra of the HR 4796A debris ring system. We find a unique red excess flux that extends out to ˜9 μm in Spitzer IRS spectra, where thermal emission from cold, ˜100 K dust from the system’s ring at ˜75 au takes over. Matching imaging ring photometry, we find the excess consists of NIR reflectance from the ring, which is as red as that of old, processed comet nuclei, plus a tenuous thermal emission component from close-in, T ˜ 850 K circumstellar material evincing an organic/silicate emission feature complex at 7-13 μm. Unusual, emission-like features due to atomic Si, S, Ca, and Sr were found at 0.96-1.07 μm, likely sourced by rocky dust evaporating in the 850 K component. An empirical cometary dust phase function can reproduce the scattered light excess and 1:5 balance of scattered versus thermal energy for the ring with optical depth < τ > ≥slant 0.10 in an 8 au wide belt of 4 au vertical height and M dust > 0.1-0.7 M Mars. Our results are consistent with HR 4796A, consisting of a narrow shepherded ring of devolatilized cometary material associated with multiple rocky planetesimal subcores and a small steady stream of dust inflowing from this belt to a rock sublimation zone at ˜1 au from the primary. These subcores were built from comets that have been actively emitting large, reddish dust for >0.4 Myr at ˜100 K, the temperature at which cometary activity onset is seen in our solar system.

Annual land cover change mapping using MODIS time series to improve emissions inventories.

NASA Astrophysics Data System (ADS)

López Saldaña, G.; Quaife, T. L.; Clifford, D.

2014-12-01

Understanding and quantifying land surface changes is necessary for estimating greenhouse gas and ammonia emissions, and for meeting air quality limits and targets. More sophisticated inventories methodologies for at least key emission source are needed due to policy-driven air quality directives. Quantifying land cover changes on an annual basis requires greater spatial and temporal disaggregation of input data. The main aim of this study is to develop a methodology for using Earth Observations (EO) to identify annual land surface changes that will improve emissions inventories from agriculture and land use/land use change and forestry (LULUCF) in the UK. First goal is to find the best sets of input features that describe accurately the surface dynamics. In order to identify annual and inter-annual land surface changes, a times series of surface reflectance was used to capture seasonal variability. Daily surface reflectance images from the Moderate Resolution Imaging Spectroradiometer (MODIS) at 500m resolution were used to invert a Bidirectional Reflectance Distribution Function (BRDF) model to create the seamless time series. Given the limited number of cloud-free observations, a BRDF climatology was used to constrain the model inversion and where no high-scientific quality observations were available at all, as a gap filler. The Land Cover Map 2007 (LC2007) produced by the Centre for Ecology & Hydrology (CEH) was used for training and testing purposes. A prototype land cover product was created for 2006 to 2008. Several machine learning classifiers were tested as well as different sets of input features going from the BRDF parameters to spectral Albedo. We will present the results of the time series development and the first exercises when creating the prototype land cover product.

Fluorescence and absorption spectroscopy for warm dense matter studies and ICF plasma diagnostics

NASA Astrophysics Data System (ADS)

Hansen, Stephanie

2017-10-01

The burning core of an inertial confinement fusion (ICF) plasma at stagnation is surrounded by a shell of warm, dense matter whose properties are difficult both to model (due to a complex interplay of thermal, degeneracy, and strong coupling effects) and to diagnose (due to low emissivity and high opacity). We demonstrate a promising technique to study the warm dense shells of ICF plasmas based on the fluorescence emission of dopants or impurities in the shell material. This emission, which is driven by x-rays produced in the hot core, exhibits signature changes in response to compression and heating. High-resolution measurements of absorption and fluorescence features can refine our understanding of the electronic structure of material under high compression, improve our models of density-driven phenomena such as ionization potential depression and plasma polarization shifts, and help diagnose shell density, temperature, mass distribution, and residual motion in ICF plasmas at stagnation. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525. This work was supported by the U.S. Department of Energy, Office of Science Early Career Research Program, Office of Fusion Energy Sciences under FWP-14-017426.

Trend of cancer risk of Chinese inhabitants to dioxins due to changes in dietary patterns: 1980-2009

NASA Astrophysics Data System (ADS)

Huang, Tao; Jiang, Wanyanhan; Ling, Zaili; Zhao, Yuan; Gao, Hong; Ma, Jianmin

2016-02-01

Food ingestion is a major route for human exposure and body burden to dioxins. We estimated the potential influence of changes in dietary patterns in Chinese population on human health risk to 2,3,7,8-TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) over the last three decades. We performed multiple modeling scenario investigations to discriminate the contribution of 2,3,7,8-TCDD emissions and changes in dietary patterns to the cancer risks (CR) to dioxins. Results showed that changes in dietary patterns, featured by decreasing consumption of total grain (including all unprocessed grains) and vegetables and increasing intake of animal-derived foodstuffs, caused increasing CR from 7.3 × 10-8 in 1980 to 1.1 × 10-7 in 2009. Varying dietary patterns contributed 17% to the CR of Chinese population in 2009 under the fixed emission in 1980. The CR to 2,3,7,8-TCDD in urban and eastern China residents was higher considerably than those who lived in rural area and western China, attributable to higher emissions, household income, and greater intake of animal-derived foodstuffs in urban and eastern China inhabitants. On the other hand, more rapid increasing trend of the CR was found in rural residents due to their more rapid increase in the consumption of fat-dominated foods as compared with urban residents.

The influence of rotation on optical emission profiles of O stars

NASA Astrophysics Data System (ADS)

Hillier, D. John; Bouret, Jean-Claude; Lanz, Thierry; Busche, Joseph R.

2012-10-01

We study the formation of photospheric emission lines in O stars and show that the rectangular profiles, sometimes double peaked, that are observed for some stars are a direct consequence of rotation, and it is unnecessary to invoke an enhanced density structure in the equatorial regions. Emission lines, such as N IV λ4058 and the N III λλ4634-4640-4642 multiplet, exhibit non-standard 'limb-darkening' laws. The lines can be in absorption for rays striking the centre of the star and in emission for rays near the limb. Weak features in the flux spectrum do not necessarily indicate an intrinsically weak feature - instead the feature can be weak because of cancellation between absorption in 'core' rays and emission from rays near the limb. Rotation also modifies line profiles of wind diagnostics such as He II λ4686 and Hα and should not be neglected when inferring the actual stratification, level and nature of wind structures.

Blinded by the light: on the relationship between CO first overtone emission and mass accretion rate in massive young stellar objects

NASA Astrophysics Data System (ADS)

Ilee, J. D.; Oudmaijer, R. D.; Wheelwright, H. E.; Pomohaci, R.

2018-07-01

To date, there is no explanation as to why disc-tracing CO first overtone (or `bandhead') emission is not a ubiquitous feature in low- to medium-resolution spectra of massive young stellar objects (MYSOs), but instead is only detected towards approximately 25 per cent of their spectra. In this paper, we investigate the hypothesis that only certain mass accretion rates result in detectable bandhead emission in the near-infrared spectra of MYSOs. Using an analytic disc model combined with an LTE model of the CO emission, we find that high accretion rates (≳10-4 M⊙ yr-1) result in large dust sublimation radii, a larger contribution to the K-band continuum from hot dust at the dust sublimation radius, and therefore correspondingly lower CO emission with respect to the continuum. On the other hand, low accretion rates (≲10-6 M⊙ yr-1) result in smaller dust sublimation radii, a correspondingly smaller emitting area of CO, and thus also lower CO emission with respect to the continuum. In general, moderate accretion rates produce the most prominent, and therefore detectable, CO first overtone emission. We compare our findings to a recent near-infrared spectroscopic survey of MYSOs, finding results consistent with our hypothesis. We conclude that the detection rate of CO bandhead emission in the spectra of MYSOs could be the result of MYSOs exhibiting a range of mass accretion rates, perhaps due to the variable accretion suggested by recent multi-epoch observations of these objects.

Blinded by the light: on the relationship between CO first overtone emission and mass accretion rate in massive young stellar objects

NASA Astrophysics Data System (ADS)

Ilee, J. D.; Oudmaijer, R. D.; Wheelwright, H. E.; Pomohaci, R.

2018-04-01

To date, there is no explanation as to why disc-tracing CO first overtone (or `bandhead') emission is not a ubiquitous feature in low- to medium-resolution spectra of massive young stellar objects, but instead is only detected toward approximately 25 per cent of their spectra. In this paper, we investigate the hypothesis that only certain mass accretion rates result in detectable bandhead emission in the near infrared spectra of MYSOs. Using an analytic disc model combined with an LTE model of the CO emission, we find that high accretion rates (≳ 10-4 M⊙yr-1) result in large dust sublimation radii, a larger contribution to the K-band continuum from hot dust at the dust sublimation radius, and therefore correspondingly lower CO emission with respect to the continuum. On the other hand, low accretion rates (≲ 10-6 M⊙yr-1) result in smaller dust sublimation radii, a correspondingly smaller emitting area of CO, and thus also lower CO emission with respect to the continuum. In general, moderate accretion rates produce the most prominent, and therefore detectable, CO first overtone emission. We compare our findings to a recent near-infrared spectroscopic survey of MYSOs, finding results consistent with our hypothesis. We conclude that the detection rate of CO bandhead emission in the spectra of MYSOs could be the result of MYSOs exhibiting a range of mass accretion rates, perhaps due to the variable accretion suggested by recent multi-epoch observations of these objects.

Heterodyne detection of CO2 emission lines and wind velocities in the atmosphere of Venus

NASA Technical Reports Server (NTRS)

Betz, A. L.; Johnson, M. A.; Mclaren, R. A.; Sutton, E. C.

1975-01-01

Strong 10 micrometer line emission from (c-12)(o-16)2 in the upper atmosphere of Venus was detected by heterodyne techniques. Observations of the absolute Doppler shift of the emission features indicate mean zonal wind velocities less than 10 m/sec in the upper atmosphere near the equator. No evidence was found of the 100 m/sec wind velocity implied by the apparent 4-day rotation period of ultraviolet cloud features.

INTRAGROUP AND GALAXY-LINKED DIFFUSE X-RAY EMISSION IN HICKSON COMPACT GROUPS

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

Desjardins, Tyler D.; Gallagher, Sarah C.; Tzanavaris, Panayiotis

2013-02-15

Isolated compact groups (CGs) of galaxies present a range of dynamical states, group velocity dispersions, and galaxy morphologies with which to study galaxy evolution, particularly the properties of gas both within the galaxies and in the intragroup medium. As part of a large, multiwavelength examination of CGs, we present an archival study of diffuse X-ray emission in a subset of nine Hickson compact groups (HCGs) observed with the Chandra X-Ray Observatory. We find that seven of the groups in our sample exhibit detectable diffuse emission. However, unlike large-scale emission in galaxy clusters, the diffuse features in the majority of themore » detected groups are linked to the individual galaxies, in the form of both plumes and halos likely as a result of vigourous star formation or activity in the galaxy nucleus, as well as in emission from tidal features. Unlike previous studies from earlier X-ray missions, HCGs 31, 42, 59, and 92 are found to be consistent with the L{sub X} -T relationship from clusters within the errors, while HCGs 16 and 31 are consistent with the cluster L{sub X} -{sigma} relation, though this is likely coincidental given that the hot gas in these two systems is largely due to star formation. We find that L{sub X} increases with decreasing group H I to dynamical-mass ratio with tentative evidence for a dependence in X-ray luminosity on H I morphology whereby systems with intragroup H I indicative of strong interactions are considerably more X-ray luminous than passively evolving groups. We also find a gap in the L{sub X} of groups as a function of the total group specific star formation rate. Our findings suggest that the hot gas in these groups is not in hydrostatic equilibrium and these systems are not low-mass analogs of rich groups or clusters, with the possible exception of HCG 62.« less

Intragroup and Galaxy-linked Diffuse X-ray Emission In Hickson Compact Groups

NASA Technical Reports Server (NTRS)

Desjardins, Tyler D.; Gallagher, Sarah C.; Tzanavaris, Panayiotis; Mulchaey, John S.; Brandt, William N.; Charlton, Jane C.; Garmire, Gordon P.; Gronwall, Caryl; Cardiff, Ann; Johnson, Kelsey E.;

THE ORIGIN AND OPTICAL DEPTH OF IONIZING RADIATION IN THE 'GREEN PEA' GALAXIES

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

Jaskot, A. E.; Oey, M. S.

2013-04-01

Although Lyman-continuum (LyC) radiation from star-forming galaxies likely drove the reionization of the universe, observations of star-forming galaxies at low redshift generally indicate low LyC escape fractions. However, the extreme [O III]/[O II] ratios of the z = 0.1-0.3 Green Pea galaxies may be due to high escape fractions of ionizing radiation. To analyze the LyC optical depths and ionizing sources of these rare, compact starbursts, we compare nebular photoionization and stellar population models with observed emission lines in the Peas' Sloan Digital Sky Survey (SDSS) spectra. We focus on the six most extreme Green Peas, the galaxies with themore » highest [O III]/[O II] ratios and the best candidates for escaping ionizing radiation. The Balmer line equivalent widths and He I {lambda}3819 emission in the extreme Peas support young ages of 3-5 Myr, and He II {lambda}4686 emission in five extreme Peas signals the presence of hard ionizing sources. Ionization by active galactic nuclei or high-mass X-ray binaries is inconsistent with the Peas' line ratios and ages. Although stacked spectra reveal no Wolf-Rayet (WR) features, we tentatively detect WR features in the SDSS spectra of three extreme Peas. Based on the Peas' ages and line ratios, we find that WR stars, chemically homogeneous O stars, or shocks could produce the observed He II emission. If hot stars are responsible, then the Peas' optical depths are ambiguous. However, accounting for emission from shocks lowers the inferred optical depth and suggests that the Peas may be optically thin. The Peas' ages likely optimize the escape of LyC radiation; they are old enough for supernovae and stellar winds to reshape the interstellar medium, but young enough to possess large numbers of UV-luminous O or WR stars.« less

Projecting U.S. climate forcing and criteria pollutant emissions through 2050

EPA Science Inventory

Presentation highlighting a method for translating emission scenarios to model-ready emission inventories. The presentation highlights new features for spatially allocating emissions to counties and grid cells and identifies areas of potential improvement, such as updating tempor...

Thermal infrared spectroscopy and modeling of experimentally shocked basalts

USGS Publications Warehouse

Johnson, J. R.; Staid, M.I.; Kraft, M.D.

2007-01-01

New measurements of thermal infrared emission spectra (250-1400 cm-1; ???7-40 ??m) of experimentally shocked basalt and basaltic andesite (17-56 GPa) exhibit changes in spectral features with increasing pressure consistent with changes in the structure of plagioclase feldspars. Major spectral absorptions in unshocked rocks between 350-700 cm-1 (due to Si-O-Si octahedral bending vibrations) and between 1000-1250 cm-1 (due to Si-O antisymmetric stretch motions of the silica tetrahedra) transform at pressures >20-25 GPa to two broad spectral features centered near 950-1050 and 400-450 cm-1. Linear deconvolution models using spectral libraries composed of common mineral and glass spectra replicate the spectra of shocked basalt relatively well up to shock pressures of 20-25 GPa, above which model errors increase substantially, coincident with the onset of diaplectic glass formation in plagioclase. Inclusion of shocked feldspar spectra in the libraries improves fits for more highly shocked basalt. However, deconvolution models of the basaltic andesite select shocked feldspar end-members even for unshocked samples, likely caused by the higher primary glass content in the basaltic andesite sample.

Understanding reconstructed Dante spectra using high resolution spectroscopy

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

May, M. J., E-mail: may13@llnl.gov; Widmann, K.; Kemp, G. E.

2016-11-15

The Dante is an 18 channel filtered diode array used at the National Ignition Facility (NIF) to measure the spectrally and temporally resolved radiation flux between 50 eV and 20 keV from various targets. The absolute flux is determined from the radiometric calibration of the x-ray diodes, filters, and mirrors and a reconstruction algorithm applied to the recorded voltages from each channel. The reconstructed spectra are very low resolution with features consistent with the instrument response and are not necessarily consistent with the spectral emission features from the plasma. Errors may exist between the reconstructed spectra and the actual emissionmore » features due to assumptions in the algorithm. Recently, a high resolution convex crystal spectrometer, VIRGIL, has been installed at NIF with the same line of sight as the Dante. Spectra from L-shell Ag and Xe have been recorded by both VIRGIL and Dante. Comparisons of these two spectroscopic measurements yield insights into the accuracy of the Dante reconstructions.« less

Recent Observations and Modeling of Narrowband Stimulated Electromagnetic Emissions SEEs at the HAARP Facility

NASA Astrophysics Data System (ADS)

Scales, Wayne; Bernhardt, Paul; McCarrick, Michael; Briczinski, Stanley; Mahmoudian, Alireza; Fu, Haiyang; Ranade Bordikar, Maitrayee; Samimi, Alireza

There has been significant interest in so-called narrowband Stimulated Electromagnetic Emission SEE over the past several years due to recent discoveries at the High Frequency Active Auroral Research Program HAARP facility near Gakone, Alaska. Narrowband SEE (NSEE) has been defined as spectral features in the SEE spectrum typically within 1 kHz of the transmitter (or pump) frequency. SEE is due to nonlinear processes leading to re-radiation at frequencies other than the pump wave frequency during heating the ionospheric plasma with high power HF radio waves. Although NSEE exhibits a richly complex structure, it has now been shown after a substantial number of observations at HAARP, that NSEE can be grouped into two basic classes. The first are those spectral features, associated with Stimulated Brillouin Scatter SBS, which typically occur when the pump frequency is not close to electron gyro-harmonic frequencies. Typically, these spectral features are within roughly 50 Hz of the pump wave frequency where it is to be noted that the O+ ion gyro-frequency is roughly 50 Hz. The second class of spectral features corresponds to the case when the pump wave frequency is typically within roughly 10 kHz of electron gyro-harmonic frequencies. In this case, spectral features ordered by harmonics of ion gyro-frequencies are typically observed, and termed Stimulated Ion Bernstein Scatter SIBS. There is also important parametric behavior on both classes of NSEE depending on the pump wave parameters including the field strength, antenna beam angle, and electron gyro-harmonic number. This presentation will first provide an overview of the recent NSEE experimental observations at HAARP. Both Stimulated Brillouin Scatter SBS and Stimulated Ion Bernstein Scatter SIBS observations will be discussed as well as their relationship to each other. Possible theoretical formulation in terms of parametric decay instabilities will be provided. Computer simulation model results will be presented to provide insight into associated higher order nonlinear effects including particle acceleration and wave-wave processes. Both theory and model results will be put into the context of the experimental observations. Finally, possible applications of NSEE will be pointed out including triggering diagnostics for artificial ionization layer formation, proton precipitation event diagnostics, and electron temperature measurements in the heated volume.

The 11 Micron Emissions of Carbon Stars

NASA Technical Reports Server (NTRS)

Goebel, J. H.; Cheeseman, P.; Gerbault, F.

1995-01-01

A new classification scheme of the IRAS LRS carbon stars is presented. It comprises the separation of 718 probable carbon stars into 12 distinct self-similar spectral groupings. Continuum temperatures are assigned and range from 470 to 5000 K. Three distinct dust species are identifiable: SiC, alpha:C-H, and MgS. In addition to the narrow 11 + micron emission feature that is commonly attributed to SiC, a broad 11 + micron emission feature, that is correlated with the 8.5 and 7.7 micron features, is found and attributed to alpha:C-H. SiC and alpha:C-H band strengths are found to correlate with the temperature progression among the Classes. We find a spectral sequence of Classes that reflects the carbon star evolutionary sequence of spectral types, or alternatively developmental sequences of grain condensation in carbon-rich circumstellar shells. If decreasing temperature corresponds to increasing evolution, then decreasing temperature corresponds to increasing C/O resulting in increasing amounts of carbon rich dust, namely alpha:C-H. If decreasing the temperature corresponds to a grain condensation sequence, then heterogeneous, or induced nucleation scenarios are supported. SiC grains precede alpha:C-H and form the nuclei for the condensation of the latter material. At still lower temperatures, MgS appears to be quite prevalent. No 11.3 micron PAH features are identified in any of the 718 carbon stars. However, one of the coldest objects, IRAS 15048-5702, and a few others, displays an 11.9 micron emission feature characteristic of laboratory samples of coronene. That feature corresponds to the C-H out of plane deformation mode of aromatic hydrocarbon. This band indicates the presence of unsaturated, sp(sup 3), hydrocarbon bonds that may subsequently evolve into saturated bonds, sp(sup 2), if, and when, the star enters the planetary nebulae phase of stellar evolution. The effusion of hydrogen from the hydrocarbon grain results in the evolution in wavelength of this 11.9 micron emission feature to the 11.3 micron feature.

The 11 Micron Emissions of Cabon Stars

NASA Technical Reports Server (NTRS)

Goebel, J. H.; Cheeseman, P.; Gerbault, F.

1995-01-01

A new classification scheme of the IRAS LRS carbon stars is presented. It comprises the separation of 718 probable carbon stars into 12 distinct self-similar spectral groupings. Continuum temperatures are assigned and range from 470 to 5000 K. Three distinct dust species are identifiable: SiC, alpha:C-H, and MgS. In addition to the narrow 11 + micron emission feature that is commonly attributed to SiC, a broad 11 + micron emission feature, that is correlated with the 8.5 and 7.7 micron features, is found and attributed to alpha:C-H. SiC and alpha:C-H band strengths are found to correlate with the temperature progression among the Classes. We find a spectral sequence of Classes that reflects the carbon star evolutionary sequence of spectral types, or alternatively developmental sequences of grain condensation in carbon-rich circumstellar shells. If decreasing temperature corresponds to increasing evolution, then decreasing temperature corresponds to increasing CIO resulting in increasing amounts of carbon rich dust, namely alpha:C-H. If decreasing the temperature corresponds to a grain condensation sequence, then heterogeneous, or induced nucleation scenarios are supported. SiC grains precede alpha:C-H and form the nuclei for the condensation of the latter material. At still lower temperatures, MgS appears to be quite prevalent. No 11.3 micron PAH features are identified in any of the 718 carbon stars. However, one of the coldest objects, IRAS 15048-5702, and a few others, displays an 11.9 micron emission feature characteristic of laboratory samples of coronene. That feature corresponds to the C-H out of plane deformation mode of aromatic hydrocarbon. This band indicates the presence of unsaturated, sp(sup 3), hydrocarbon bonds that may subsequently evolve into saturated bonds, sp(sup 2), if, and when, the star enters the planetary nebulae phase of stellar evolution. The effusion of hydrogen from the hydrocarbon grain results in the evolution in wavelength of this 11.9 micron emission feature to the 11.3 micron feature.

Path-integral method for the source apportionment of photochemical pollutants

NASA Astrophysics Data System (ADS)

Dunker, A. M.

2015-06-01

A new, path-integral method is presented for apportioning the concentrations of pollutants predicted by a photochemical model to emissions from different sources. A novel feature of the method is that it can apportion the difference in a species concentration between two simulations. For example, the anthropogenic ozone increment, which is the difference between a simulation with all emissions present and another simulation with only the background (e.g., biogenic) emissions included, can be allocated to the anthropogenic emission sources. The method is based on an existing, exact mathematical equation. This equation is applied to relate the concentration difference between simulations to line or path integrals of first-order sensitivity coefficients. The sensitivities describe the effects of changing the emissions and are accurately calculated by the decoupled direct method. The path represents a continuous variation of emissions between the two simulations, and each path can be viewed as a separate emission-control strategy. The method does not require auxiliary assumptions, e.g., whether ozone formation is limited by the availability of volatile organic compounds (VOCs) or nitrogen oxides (NOx), and can be used for all the species predicted by the model. A simplified configuration of the Comprehensive Air Quality Model with Extensions (CAMx) is used to evaluate the accuracy of different numerical integration procedures and the dependence of the source contributions on the path. A Gauss-Legendre formula using three or four points along the path gives good accuracy for apportioning the anthropogenic increments of ozone, nitrogen dioxide, formaldehyde, and nitric acid. Source contributions to these increments were obtained for paths representing proportional control of all anthropogenic emissions together, control of NOx emissions before VOC emissions, and control of VOC emissions before NOx emissions. There are similarities in the source contributions from the three paths but also differences due to the different chemical regimes resulting from the emission-control strategies.

Path-integral method for the source apportionment of photochemical pollutants

NASA Astrophysics Data System (ADS)

Dunker, A. M.

2014-12-01

A new, path-integral method is presented for apportioning the concentrations of pollutants predicted by a photochemical model to emissions from different sources. A novel feature of the method is that it can apportion the difference in a species concentration between two simulations. For example, the anthropogenic ozone increment, which is the difference between a simulation with all emissions present and another simulation with only the background (e.g., biogenic) emissions included, can be allocated to the anthropogenic emission sources. The method is based on an existing, exact mathematical equation. This equation is applied to relate the concentration difference between simulations to line or path integrals of first-order sensitivity coefficients. The sensitivities describe the effects of changing the emissions and are accurately calculated by the decoupled direct method. The path represents a continuous variation of emissions between the two simulations, and each path can be viewed as a separate emission-control strategy. The method does not require auxiliary assumptions, e.g., whether ozone formation is limited by the availability of volatile organic compounds (VOC's) or nitrogen oxides (NOx), and can be used for all the species predicted by the model. A simplified configuration of the Comprehensive Air Quality Model with Extensions is used to evaluate the accuracy of different numerical integration procedures and the dependence of the source contributions on the path. A Gauss-Legendre formula using 3 or 4 points along the path gives good accuracy for apportioning the anthropogenic increments of ozone, nitrogen dioxide, formaldehyde, and nitric acid. Source contributions to these increments were obtained for paths representing proportional control of all anthropogenic emissions together, control of NOx emissions before VOC emissions, and control of VOC emissions before NOx emissions. There are similarities in the source contributions from the three paths but also differences due to the different chemical regimes resulting from the emission-control strategies.

Infrared images of reflection nebulae and Orion's bar: Fluorescent molecular hydrogen and the 3.3 micron feature

NASA Technical Reports Server (NTRS)

Burton, Michael G.; Moorhouse, Alan; Brand, P. W. J. L.; Roche, Patrick F.; Geballe, T. R.

1989-01-01

Images were obtained of the (fluorescent) molecular hydrogen 1-0 S(1) line, and of the 3.3 micron emission feature, in Orion's Bar and three reflection nebulae. The emission from these species appears to come from the same spatial locations in all sources observed. This suggests that the 3.3 micron feature is excited by the same energetic UV-photons which cause the molecular hydrogen to fluoresce.

CARBON MONOXIDE EMISSIONS FROM ROAD DRIVING: EVIDENCE OF EMISSIONS DUE TO POWER ENRICHMENT

EPA Science Inventory

The paper examines one aspect of motor vehicle emissions behavior; i.e. emissions due to engine power enrichment, a factor not well represented in existing models. Database reflecting 46 instrumented vehicles was used to analyze the importance of enrichment emissions to overall v...

High-resolution spectra of the 3.29 micron interstellar emission feature - A summary

NASA Technical Reports Server (NTRS)

Tokunaga, A. T.; Sellgren, K.; Smith, R. G.; Nagata, T.; Sakata, A.; Nakada, Y.

1991-01-01

High spectral resolution observations of the 3.29-micron interstellar emission feature show two types of profiles. Type 1 has a central wavelength of 3.289-micron and is observed in extended objects such as planetary nebulae and H II regions. Type 2 has a central wavelength of 3.296 microns and is observed around a small number of stellar sources. Type 2 has a full width at half-maximum of 0.020 micron; Type 1 has a broader FWHM, perhaps as much as 0.042 micron, but this is uncertain because of contamination by Pf(delta) emission. These profiles are tabulated for comparison to laboratory data. It is found that no proposed identification for the 3.29-micron emission feature definitely matches the observational spectra, although amorphous aromatic materials and heated polycyclic aromatic hydrocarbons tend to fit the best.

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

Peteanu, Linda A.; Chowdhury, Sanchari; Wildeman, Jurjen

One measure of exciton mobility in an aggregate is the efficiency of exciton–exciton annihilation (EEA). Both exciton mobilities and EEA are enhanced for aggregate morphologies in which the distances between chromophores and their relative orientations are favorable for Förster energy transfer. Here this principle is applied to gauge the strength of interchain interactions in aggregates of two substituted PPV oligomers of 7 (OPPV7) and 13 (OPPV13) phenylene rings. These are models of the semiconducting conjugated polymer MEH–PPV. The aggregates were formed by adding a poor solvent (methanol or water) to the oligomers dissolved in a good solvent. Aggregates formed frommore » the longer-chain oligomer and/or by addition of the more polar solvent showed the largest contribution of EEA in their emission decay dynamics. This was found to correlate with the degree to which the steady-state emission spectrum of the monomer is altered by aggregation. Furthermore, the wavelength dependence of the EEA signal was also shown to be useful in differentiating emission features due to monomeric and aggregated chains when their spectra overlap significantly.« less

Early Emission from Type Ia Supernovae

NASA Astrophysics Data System (ADS)

Rabinak, Itay; Livne, Eli; Waxman, Eli

2012-09-01

A unique feature of deflagration-to-detonation (DDT) white dwarf explosion models of supernovae of type Ia is the presence of a strong shock wave propagating through the outer envelope. We consider the early emission expected in such models, which is produced by the expanding shock-heated outer part of the ejecta and precedes the emission driven by radioactive decay. We expand on earlier analyses by considering the modification of the pre-detonation density profile by the weak shocks generated during the deflagration phase, the time evolution of the opacity, and the deviation of the post-shock equation of state from that obtained for radiation pressure domination. A simple analytic model is presented and shown to provide an acceptable approximation to the results of one-dimensional numerical DDT simulations. Our analysis predicts a ~103 s long UV/optical flash with a luminosity of ~1 to ~3 × 1039 erg s-1. Lower luminosity corresponds to faster (turbulent) deflagration velocity. The luminosity of the UV flash is predicted to be strongly suppressed at t > t drop ~ 1 hr due to the deviation from pure radiation domination.

Exciton–exciton annihilation as a probe of interchain interactions in PPV–oligomer aggregates

DOE PAGES

Peteanu, Linda A.; Chowdhury, Sanchari; Wildeman, Jurjen; ...

2017-01-20

One measure of exciton mobility in an aggregate is the efficiency of exciton–exciton annihilation (EEA). Both exciton mobilities and EEA are enhanced for aggregate morphologies in which the distances between chromophores and their relative orientations are favorable for Förster energy transfer. Here this principle is applied to gauge the strength of interchain interactions in aggregates of two substituted PPV oligomers of 7 (OPPV7) and 13 (OPPV13) phenylene rings. These are models of the semiconducting conjugated polymer MEH–PPV. The aggregates were formed by adding a poor solvent (methanol or water) to the oligomers dissolved in a good solvent. Aggregates formed frommore » the longer-chain oligomer and/or by addition of the more polar solvent showed the largest contribution of EEA in their emission decay dynamics. This was found to correlate with the degree to which the steady-state emission spectrum of the monomer is altered by aggregation. Furthermore, the wavelength dependence of the EEA signal was also shown to be useful in differentiating emission features due to monomeric and aggregated chains when their spectra overlap significantly.« less

Exciton-Exciton Annihilation as a Probe of Interchain Interactions in PPV-Oligomer Aggregates.

PubMed

Peteanu, Linda A; Chowdhury, Sanchari; Wildeman, Jurjen; Sfeir, Matthew Y

2017-02-23

One measure of exciton mobility in an aggregate is the efficiency of exciton-exciton annihilation (EEA). Both exciton mobilities and EEA are enhanced for aggregate morphologies in which the distances between chromophores and their relative orientations are favorable for Förster energy transfer. Here this principle is applied to gauge the strength of interchain interactions in aggregates of two substituted PPV oligomers of 7 (OPPV7) and 13 (OPPV13) phenylene rings. These are models of the semiconducting conjugated polymer MEH-PPV. The aggregates were formed by adding a poor solvent (methanol or water) to the oligomers dissolved in a good solvent. Aggregates formed from the longer-chain oligomer and/or by addition of the more polar solvent showed the largest contribution of EEA in their emission decay dynamics. This was found to correlate with the degree to which the steady-state emission spectrum of the monomer is altered by aggregation. The wavelength dependence of the EEA signal was also shown to be useful in differentiating emission features due to monomeric and aggregated chains when their spectra overlap significantly.

Aggregation-Induced Emission of Multiphenyl-Substituted 1,3-Butadiene Derivatives: Synthesis, Property and Application.

PubMed

Zhang, Yahui; Mao, Huiling; Xu, Weiquan; Shi, Jianbing; Cai, Zhengxu; Tong, Bin; Dong, Yuping

2018-05-29

Organic functional materials, including conjugated molecules and fluorescent dyes, have been rapidly developed in recent years because they can be applied in many fields, such as solar cells, biosensing and bioimaging, and medical adjuvant therapy. Organic functional materials with aggregation-induced emission or aggregation-enhanced emission (AIE/AEE) characteristics have increasingly attracted attention due to their high quantum efficiency in the aggregated or solid state. A large variety of AIE/AEE materials have been designed and applied during the exponential growth of research interest in the abovementioned fields. Multiphenyl-substituted 1,3-butadiene (MPB), as a core structure that includes tetraphenyl-1,3-butadiene, hexaphenyl-1,3-butadiene and their derivatives, show a typical AIE/AEE feature and can be potentially used in all the abovementioned fields. This review summarizes the design principles, the corresponding syntheses, and the structure-property relationships of MPBs, as well as their excellent innovative functionalities and applications. This review will be very useful for scientists conducting chemistry, materials, and biomedical research in AIE/AEE-related fields. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Nature of the Optical "Jets" in the Spiral Galaxy NGC 1097

NASA Technical Reports Server (NTRS)

Wehrle, Ann E.; Keel, William C.; Jones, Dayton L.

1997-01-01

We present new observations of the jet features in the barred spiral galaxy NGC 1097, including optical spectroscopy of the brightest jet features, two-color optical imagery, new VLA mapping at 327 MHz, and archival 1.4 GHz VLA data reprocessed for improved sensitivity. No optical emission lines appear to an equivalent width limit of 15-30 A (depending on the line wavelength). The jets are uniformly blue, with B - V = 0.45 for the two well-observed jets R1 and R2. No radio emission from the jets is detected at either frequency; the 327-MHz data set particularly stringent limits on "fossil" emission from aging synchrotron electrons. The morphology of the jets is shown to be inconsistent with any conical distribution of emission enhanced by edge-brightening; their combination of transverse profile and relative narrowness cannot be reproduced with cone models. The optical colors, lack of radio emission, and morphology of the features lead us to conclude that they are tidal manifestations, perhaps produced by multiple encounters of the small elliptical companion NGC 1097A with the disk of NGC 1097. We present photometric and morphological comparisons to the tail of NGC 465 1, which is similar in scale and morphology to the northeast "dogleg" feature R1 in NGC 1097.

Note: Enhancement of the extreme ultraviolet emission from a potassium plasma by dual laser irradiation

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

Higashiguchi, Takeshi, E-mail: higashi@cc.utsunomiya-u.ac.jp; Yamaguchi, Mami; Otsuka, Takamitsu

2014-09-15

Emission spectra from multiply charged potassium ions ranging from K{sup 3+} to K{sup 5+} have been obtained in the extreme ultraviolet (EUV) spectral region. A strong emission feature peaking around 38 nm, corresponding to a photon energy of 32.6 eV, is the dominant spectral feature at time-averaged electron temperatures in the range of 8−12 eV. The variation of this emission with laser intensity and the effects of pre-pulses on the relative conversion efficiency (CE) have been explored experimentally and indicate that an enhancement of about 30% in EUV CE is readily attainable.

Mexico City, Mexico as seen from STS-62

NASA Image and Video Library

1994-03-05

STS062-84-028 (4-18 March 1994) --- According to NASA scientists this image is the clearest photo of Mexico City taken from United States manned spacecraft. North is to the upper right. Mexico City sits in a basin surrounded by large volcanoes. The restricted atmospheric circulation in the basin, coupled with the inevitable air emissions produced by a city of 20 million people has created a critical air pollution problem for the city. In most photographs of the region, Mexico City is obscured by haze. Scientists feel the clear atmosphere in this photograph may be due, in part, to the stringent air emission restrictions now in place. The clarity of the photograph allows many key cultural features to be identified, including all of the major boulevards, the horse track (western part of the city), the university (south of the city), and the museum areas. Large, man-made ponds east of the city also stand out.

Photoluminescence quenching processes by NO2 adsorption in ZnO nanostructured films

NASA Astrophysics Data System (ADS)

Cretı, A.; Valerini, D.; Taurino, A.; Quaranta, F.; Lomascolo, M.; Rella, R.

2012-04-01

The optical response by NO2 gas adsorption at different concentrations has been investigated, at room temperature, in ZnO nanostructured films grown by controlled vapor phase deposition. The variation (quenching) in the photoluminescence signal from excitonic and defects bands, due to the interactions between the oxidizing gas molecules and the sample surface, has been detected and dynamic responses and calibration curves as a function of gas concentration have been obtained and analyzed for each band. We showed that the sensing response results larger in excitonic band than in defect one and that the emission signal rises from two different quenchable and unquenchable states. A simple model was proposed in order to explain the quenching processes on the emission intensity and to correlate them to the morphological features of the samples. Finally, the reversibility of the quenching effects has also been tested at high gas concentration.

Morphology of a Hot Coronal Cavity Core as Observed by Hinode/XRT

NASA Technical Reports Server (NTRS)

Reeves, K. K.; Gibson, S. E.; Kucera, T. A.; Hudson, H. S.

2010-01-01

We follow a coronal cavity that was observed by Hinode/XRT during the summer of 2008. This cavity has a persistent area of relatively bright X-ray emission in its center. We use multifilter data from XRT to study the thermal emission from this cavity, and find that the bright center is hotter than the surrounding cavity plasma with temperatures of about 1.6 MK. We follow the morphology of this hot feature as the cavity structure rotates over the limb during the several days between July 19 - 23 2008. We find that the hot structure at first looks fairly circular, then appears to expand and elongate, and then shrinks again to a compact circular shape. We interpret this apparent change in shape as being due to the morphology of the filament channel associated with the cavity, and the change in viewing angle as the structure rotates over the limb of the Sun.

Present knowledge and perspectives on the role of copper in brake materials and related environmental issues: A critical assessment.

PubMed

Straffelini, Giovanni; Ciudin, Rodica; Ciotti, Alessandro; Gialanella, Stefano

2015-12-01

This critical review presents several aspects related to the use of copper as a main component in brake pads in road vehicles. The compositions of these materials are attracting increasing interest and concern due to the relative contribution of wear products to particulate matter emissions in the environment as a result of braking action even though there has been a reduction in exhaust products from internal combustion engines. We review the data on the main wear mechanisms in brake systems and highlight the positive role of copper. However, similar to other heavy metal emissions, even the release of copper into the atmosphere may have important environmental and health effects. Thus, several replacement strategies are being pursued, and the positive and negative features will be critically reviewed. Additionally, the future perspectives in materials development will be discussed. Copyright © 2015 Elsevier Ltd. All rights reserved.

Blowing Dust on Highway Safety: Characterizing and Modeling of Dust Emission Hot Spots in the Southern Plains

NASA Astrophysics Data System (ADS)

Blackwell, J., III; Li, J. J.; Kandakji, T.; Collins, J. D., Jr.; Lee, J.; Gill, T. E.

2016-12-01

Blowing dust and highway safety have become increasingly prevalent problems concerning human safety and welfare. Two factors precipitate wind-blown dust accidents: sudden loss of visibility, and loss of traction due to soil particles on the road surface. The project, using remote sensing and in situ measurements of surface and subsurface characteristics, will identify the location of dust emission "hotspots" and associated geomorphic features within the southwest region and panhandle (New Mexico, Texas, and Oklahoma), measure the threshold shear velocity and vegetative cover and model the results. The results of this study will provide critical information for land managers, policy makers, and highway authorities when making timely and informed potentially life-saving decisions and modifications here, in the southwest region and panhandle, as well as, anywhere else in the world where blowing dust is a hazard to highway safety.

Bright luminescence from pure DNA-curcumin-based phosphors for bio hybrid light-emitting diodes

NASA Astrophysics Data System (ADS)

Reddy, M. Siva Pratap; Park, Chinho

2016-08-01

Recently, significant advances have occurred in the development of phosphors for bio hybrid light-emitting diodes (Bio-HLEDs), which have created brighter, metal-free, rare-earth phosphor-free, eco-friendly, and cost-competitive features for visible light emission. Here, we demonstrate an original approach using bioinspired phosphors in Bio-HLEDs based on natural deoxyribonucleic acid (DNA)-curcumin complexes with cetyltrimethylammonium (CTMA) in bio-crystalline form. The curcumin chromophore was bound to the DNA double helix structure as observed using field emission tunnelling electron microscopy (FE-TEM). Efficient luminescence occurred due to tightly bound curcumin chromophore to DNA duplex. Bio-HLED shows low luminous drop rate of 0.0551 s-1. Moreover, the solid bio-crystals confined the activating bright luminescence with a quantum yield of 62%, thereby overcoming aggregation-induced quenching effect. The results of this study herald the development of commercially viable large-scale hybrid light applications that are environmentally benign.

Road traffic emission factors for heavy metals

NASA Astrophysics Data System (ADS)

Johansson, Christer; Norman, Michael; Burman, Lars

Quantifying the emissions and concentrations of heavy metals in urban air is a prerequisite for assessing their health effects. In this paper a combination of measurements and modelling is used to assess the contribution from road traffic emissions. Concentrations of particulate heavy metals in air were measured simultaneously during 1 year at a densely trafficked street and at an urban background site in Stockholm, Sweden. Annual mean concentrations of cadmium were 50 times lower than the EU directive and for nickel and arsenic concentrations were 10 and six times lower, respectively. More than a factor of two higher concentrations was in general observed at the street in comparison to roof levels indicating the strong influence from local road traffic emissions. The only compound with a significantly decreasing trend in the urban background was Pb with 9.1 ng m -3 in 1995/96 compared to 3.4 ng m -3 2003/04. This is likely due to decreased emissions from wear of brake linings and reduced emissions due to oil and coal combustion in central Europe. Total road traffic emission factors for heavy metals were estimated using parallel measurements of NOx concentrations and knowledge of NOx emission factors. In general, the emission factors for the street were higher than reported in road tunnel measurements. This could partly be due to different driving conditions, since especially for metals which are mainly emitted from brake wear, more stop and go driving in the street compared to in road tunnels is likely to increase emissions. Total emissions were compared with exhaust emissions, obtained from the COPERT model and brake wear emissions based on an earlier study in Stockholm. For Cu, Ni and Zn the sum of brake wear and exhaust emissions agreed very well with estimated total emission factors in this study. More than 90% of the road traffic emissions of Cu were due to brake wear. For Ni more than 80% is estimated to be due to exhaust emissions and for Zn around 40% of road traffic emissions are estimated to be due to exhaust emissions. Pb is also mainly due to exhaust emissions (90%); a fuel Pb content of only 0.5 mg L -1 would give similar emission factor as that based on the concentration increment at the street. This is the first study using simultaneous measurements of heavy metals at street and roof enabling calculations of emission factors using a tracer technique.

Line Identifications in the Far Ultraviolet Spectrum of the Eclipsing Binary System 31 Cygni

NASA Astrophysics Data System (ADS)

Hagen Bauer, Wendy; Bennett, P. D.

2011-05-01

The eclipsing binary system 31 Cygni (K4 Ib + B3 V) was observed at several phases with the Far Ultraviolet Spectrosocopic Explorer (FUSE) satellite. During total eclipse, a rich emission spectrum was observed, produced by scattering of hot star photons in the extended wind of the K supergiant. The system was observed during deep chromospheric eclipse, and 2.5 months after total eclipse ended. We present an atlas of line identifications in these spectra. During total eclipse, emission features from C II , C III, N I, N II, N III, O I, Si II, P II, P III, S II, S III, Ar I, Cr III, Fe II, Fe III, and Ni II were detected. The strongest emission features arise from N II. These lines appear strongly in absorption during chromospheric eclipse, and even 2.5 months after total eclipse, the absorption bottoms out on the underlying emission seen during total eclipse. The second strongest features in the emission spectrum arise from Fe III. Any chromospheric Fe III absorption is buried within strong chromospheric absorption from other species, mainly Fe II. The emission profiles of most of the doubly-ionized species are red-shifted relative to the systemic velocity, with asymmetric profiles with a steeper long-wavelength edge. Emission profiles from singly-ionized species tend to be more symmetric and centered near the systemic velocity. In deep chromospheric eclipse, absorption features are seen from neutral and singly-ionized species, arising from lower levels up to 3 eV. Many strong chromospheric features are doubled in the observation obtained during egress from eclipse. The 31 Cygni spectrum taken 2.5 months after total eclipse ended ws compared to single-star B spectra from the FUSE archives. There was still some additional chromospheric absorption from strong low-excitation Fe II, O I and Ar I.

Emission from water vapor and absorption from other gases at 5-7.5 μm in Spitzer-IRS Spectra Of Protoplanetary Disks

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

Sargent, B. A.; Forrest, W.; Watson, Dan M.

We present spectra of 13 T Tauri stars in the Taurus-Auriga star-forming region showing emission in Spitzer Space Telescope Infrared Spectrograph 5-7.5 μm spectra from water vapor and absorption from other gases in these stars' protoplanetary disks. Seven stars' spectra show an emission feature at 6.6 μm due to the ν{sub 2} = 1-0 bending mode of water vapor, with the shape of the spectrum suggesting water vapor temperatures >500 K, though some of these spectra also show indications of an absorption band, likely from another molecule. This water vapor emission contrasts with the absorption from warm water vapor seenmore » in the spectrum of the FU Orionis star V1057 Cyg. The other 6 of the 13 stars have spectra showing a strong absorption band, peaking in strength at 5.6-5.7 μm, which for some is consistent with gaseous formaldehyde (H{sub 2}CO) and for others is consistent with gaseous formic acid (HCOOH). There are indications that some of these six stars may also have weak water vapor emission. Modeling of these stars' spectra suggests these gases are present in the inner few AU of their host disks, consistent with recent studies of infrared spectra showing gas in protoplanetary disks.« less

Investigation of the Contribution of Lower Charger State Ar Ions to the Unknown Faint X-Ray Feature Found in the Stacked Spectrum of Galaxy Clusters

NASA Astrophysics Data System (ADS)

Gall, Amy

Driven by the recent detection of an unidentified emission line previously reported at 3.55-3.57 keV in a stacked spectrum of galaxy clusters, in this work we investigated the resonant dielectronic recombination (DR) process in Li-like Ar as a possible source of, or contributor to, the emission line. The Li-like transition 1s22l-1s2l3l' was suggested to produce a 3.62 keV photon [1] near the unidentified line at 3.57 keV and was the primary focus of our study. The Electron Beam Ion Trap at NIST was used to produce and trap the highly-charged ions of argon. The energy of the quasi-monoenergetic electron beam was incremented in steps of 15 eV to scan over all of the Li-like Ar DR resonances. A Johann-type crystal spectrometer and a solid-state germanium detector were used to take x-ray measurements perpendicular to the electron beam. Our broadband results allowed us to identify the processes that produced specific spectral features, while our high-resolution spectra allowed the experimental separation of features that are less than 2 eV apart. We have used the collisional radiative model NOMAD [2] aided by atomic data calculations by FAC [3] to interpret our observations and account for corrections. Experimental results were compared to the atomic database AtomDB, used to fit the galaxy cluster spectra. We found a number of measured features due to DR in lower charge state Ar ions not included in the database, close in energy to the identified line at 3.57 keV, and suggest their inclusion for improved interpretation and diagnosis of other astrophysical spectra.

Near-Infrared [Fe II] and H2 Study of the Galactic Supernova Remnants

NASA Astrophysics Data System (ADS)

Lee, Yong-Hyun; Koo, Bon-Chul; Lee, Jae-Joon; Jaffe, Daniel T.; Burton, Michael G.; Ryder, Stuart D.

2018-01-01

We have searched for near-infrared (NIR) [Fe II] (1.644 μm) and H2 1-0 S(1) (2.122 μm) emission features associated with Galactic supernova remnants (SNRs) using the narrow-band imaging surveys UWIFE / UWISH2 (UKIRT Widefield Infrared Survey for [Fe II] / H2). Both surveys cover about 180 square degrees of the first Galactic quadrant (7° < l < 65° -1.3° < b < +1.3°), and a total of 79 SNRs are falling in the survey area. We have found 19 [Fe II]- and 19 H2-emitting SNRs, giving a detection rate of 24%. Eleven SNRs show both emission features. Some of the SNRs show bright, complex, and interesting structures that have never been reported in previous studies. The brightest SNR in the both emission is W49B, contributing ~70% of the total [Fe II] luminosity of the detected SNRs. The total [Fe II] luminosity, however, is considerably less than what we would expect from the SN rate of our Galaxy.Among the SNRs showing both [Fe II] and H2 emission lines, some SNRs show the “[Fe II]-H2 reversal” phenomenon, i.e., the H2 emission features are detected outside the [Fe II] emission boundary. We carried out high resolution (R~40,000) NIR H- and K-band spectroscopy of the five SNRs showing the [Fe II]-H2 reversal (G11.2-0.3, KES 73, W44, 3C 396, W49B) using IGRINS (Immersion GRating INfrared Spectrograph). Various ro-vibrational H2 lines have been detected, which are used to derive the kinematic distances to the SNRs and to investigate the origin of the H2 emission. The detected H2 lines show broad line width (> 10 km s-1) and line flux ratios of thermal excitation. We discuss the origin of the extended H2 emission features beyond the the [Fe II] emission boundary.

Outflow of chromospheric emission features from the rim of a sunspot

NASA Technical Reports Server (NTRS)

Liu, S.-Y.

1973-01-01

In viewing a 16 mm movie made from a time sequence of spectroheliograms, some of these emission features are found to move outward from the rim of the sunspot until they are eventually lost in the small plage. There are two interpretations for the streaming of the magnetic features. It is possible that kinks in the line of force propagate along a horizontal extension of the penumbral magnetic field. Alternatively, fragments of the sunspot magnetic field are carried away by the photospheric velocity field.

Inclusion of Paracetamol into β-cyclodextrin nanocavities in solution and in the solid state

NASA Astrophysics Data System (ADS)

El-Kemary, Maged; Sobhy, Saffaa; El-Daly, Samy; Abdel-Shafi, Ayman

2011-09-01

We report on steady-state UV-visible absorption and emission characteristics of Paracetamol, drug used as antipyretic agent, in water and within cyclodextrins (CDs): β-CD, 2-hydroxypropyl- β-CD (HP- β-CD) and 2,6-dimethyl- β-CD (Me- β-CD). The results reveal that Paracetamol forms a 1:1 inclusion complex with CD. Upon encapsulation, the emission intensity enhances, indicating a confinement effect of the nanocages on the photophysical behavior of the drug. Due to its methyl groups, the Me- β-CD shows the largest effect for the drug. The observed binding constant showing the following trend: Me- β-CD > HP- β-CD > β-CD. The less complexing effectiveness of HP- β-CD is due to the steric effect of the hydroxypropyl-substituents, which can hamper the inclusion of the guest molecules. The solid state inclusion complex was prepared by co-precipitation method and its characterization was investigated by Fourier transform infrared spectroscopy, 1H NMR and X-ray diffractometry. These approaches indicated that Paracetamol was able to form an inclusion complex with CDs, and the inclusion compounds exhibited different spectroscopic features and properties from Paracetamol.

Theoretical studies of the infrared emission from circumstellar dust shells: the infrared characteristics of circumstellar silicates and the mass-loss rate of oxygen-rich late-type giants

NASA Technical Reports Server (NTRS)

Schutte, W. A.; Tielens, A. G.; Allamandola, L. J. (Principal Investigator)

1989-01-01

We have modeled the infrared emission of spherically symmetric, circumstellar dust shells with the aim of deriving the infrared absorption properties of circumstellar silicate grains and the mass-loss rates of the central stars. As a basis for our numerical studies, a simple semianalytical formula has been derived that illustrates the essential characteristics of the infrared emission of such dust shells. A numerical radiative transfer program has been developed and applied to dust shells around oxygen-rich late-type giants. Free parameters in such models include the absorption properties and density distribution of the dust. An approximate, analytical expression is derived for the density distribution of circumstellar dust driven outward by radiation pressure from a central source. A large grid of models has been calculated to study the influence of the free parameters on the emergent spectrum. These results form the basis for a comparison with near-infrared observations. Observational studies have revealed a correlation between the near-infrared color temperature, Tc, and the strength of the 10 micrometers emission or absorption feature, A10. This relationship, which essentially measures the near-infrared optical depth in terms of the 10 micrometers optical depth, is discussed. Theoretical A10-Tc relations have been calculated and compared to the observations. The results show that this relation is a sensitive way to determine the ratio of the near-infrared to 10 micrometers absorption efficiency of circumstellar silicates. These results as well as previous studies show that the near-infrared absorption efficiency of circumstellar silicate grains is much higher than expected from terrestrial minerals. We suggest that this enhanced absorption is due to the presence of ferrous iron (Fe2+) color centers dissolved in the circumstellar silicates. By using the derived value for the ratio of the near-infrared to 10 micrometers absorption efficiency, the observed A10-Tc relation can be calibrated in terms of the total dust column density of the circumstellar shell and thus the mass-loss rate of late-type giants can easily be derived. Detailed models have been made of the infrared emission of three well-studied Miras: R Cas, IRC 10011, and OH 26.5+0.6, with the emphasis on the shape of the 10 micrometers emission or absorption feature. The results show that the intrinsic shape of the 10 micrometers resonance varies from a very broad feature in R Cas to a relatively narrower feature in OH 26.5+0.6, with IRC 10011 somewhere in between. Possible origins of this variation are discussed. The mass-loss rates from these objects are calculated to be 3 x 10(-7), 2 x 10(-5), and 2 x 10(-4) M Sun yr-1 for R Cas, IRC 10011, and OH 26.5+0.6, respectively. These results are compared to other determinations in the literature.

A comparison between the observed and predicted Fe II spectrum in different plasmas

NASA Astrophysics Data System (ADS)

Johansson, S.

This paper gives a survey of the spectral distribution of emission lines of Fe II, predicted from a single atomic model. The observed differences between the recorded and the predicted spectrum are discussed in terms of deficiencies of the model and interactions within the emitting plasma. A number of illustrative examples of unexpected features with applications to astrophysics are given. Selective population, due to charge transfer and resonant photo excitation, is elucidated. The future need of more laboratory data for Fe II as regards energy levels and line classification is also discussed.

A study of areas of low radio-thermal emissivity on Venus

NASA Astrophysics Data System (ADS)

Wilt, Robert Joseph

1992-01-01

Observations performed by the Magellan radiometer experiment have confirmed previous findings that a few regions on Venus, primarily at higher elevations, possess unexpectedly low values of radiothermal emissivity, occasionally reaching as low as 0.3. Values of emissivity below 0.7 occur over about 1.5 percent of the surface, and are associated with several types of features, including highlands, volcanoes, tectonically uplifted terrain, and impact craters. There is a strong correlation of low emissivity and high elevation, but rather than decreasing gradually with elevation, the emissivity drops rapidly in a small altitude range above a certain 'critical radius'. The altitude at which the change in emissive properties occurs varies from feature to feature; on average, it lies at a planetary radius of about 6054 km. Notable exceptions to the association of low emissivity and high elevation exist; for example, Lakshmi Planum, Maat Mons, and the summits of many volcanoes display high emissivities at high elevations, while in some impact craters and plains areas we find low emissivities at low elevations. Two possible explanations for low emissivities have been advanced: (1) emission from a highly reflective single interface between the atmosphere and a surface material having a bulk dielectric constant of order 80 ('high-dielectric' model); and (2) emission from the surface of a low-loss soil having a more usual permittivity (of order 2) which contains subsurface scatterers composed of ordinary rock materials ('volume scattering' model). Theoretical results and Monte Carlo simulations are used to show that the previously proposed volume scattering model cannot account for the observed emissivities; however, scattering from a material with very low loss (loss factor of order 10-3 or less) containing subsurface voids could produce the observed results. Consideration of the two models in light of the Magellan observations leads us to believe that the low emissivities on Venus result from the creation of a high-dielectic material by surface-atmosphere interaction, probably a loaded dielectric containing a conductive mineral.

The Detection of 6.9 μm Emission Features in the Infrared Spectra of IRAS 04296+3429, IRAS 05341+0852, and IRAS 22272+5435: Evidence for the Presence of Hn-PAHs in Post-AGB Stars

NASA Astrophysics Data System (ADS)

Materese, Christopher K.; Bregman, Jesse D.; Sandford, Scott A.

2017-12-01

Polycyclic aromatic hydrocarbons (PAHs) are generally believed to be ubiquitous in space and responsible for numerous telltale interstellar infrared emission bands. In Sandford et al., we suggested that PAHs with excess hydrogenation at their periphery ({{{H}}}{{n}}-PAHs) may be an important subclass of these molecules in some astrophysical environments. These molecules are candidates to explain objects with anomalously large 3.4 μm features, which are presumed to be associated with the aliphatic C-H stretching vibrations of the excess hydrogen. In that work, we suggest that for Hn-PAHs to be a viable candidate as the source for this 3.4 μm feature, we must also expect to observe methylene scissoring modes at 6.9 μm. In this work, we continue to develop the {{{H}}}{{n}} - {PAH} hypothesis with a focus on the 6.9 μm feature. We also present some new observations of three post-asymptotic giant branch (post-AGB) objects with abnormally large 3.4 μm features, IRAS 04296+3429, IRAS 05341+0852, and IRAS 22272+5435, in addition to one post-AGB object with normal PAH emissions, IRAS 20000+3239. These observations were made using the FORCAST instrument in grism mode on the Stratospheric Observatory for Infrared Astronomy aircraft and demonstrate the presence of a 6.9 μm feature for the three objects with abnormally large 3.4 μm features and no detectable 6.9 μm feature for the normal PAH emitter. These results are consistent with the hypothesis that Hn-PAHs are a possible source of these infrared emission bands.

ON IRON MONOXIDE NANOPARTICLES AS A CARRIER OF THE MYSTERIOUS 21 μm EMISSION FEATURE IN POST-ASYMPTOTIC GIANT BRANCH STARS

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

Li, Aigen; Jiang, B. W.; Liu, J. M., E-mail: lia@missouri.edu, E-mail: bjiang@bnu.edu.cn

2013-11-10

A prominent mysterious emission feature peaking at ∼20.1 μm—historically known as the '21 μm' feature—is seen in over two dozen Galactic and Magellanic Cloud carbon-rich, post-asymptotic giant branch (post-AGB) stars. The nature of its carrier remains unknown since the first detection of the 21 μm feature in 1989. Over a dozen materials have been suggested as possible carrier candidates. However, none of them has been accepted: they either require too much material (compared to what is available in the circumstellar shells around these post-AGB stars), or exhibit additional emission features that are not seen in these 21 μm sources. Recently,more » iron monoxide (FeO) nanoparticles seem to be a promising carrier candidate as Fe is an abundant element and FeO emits exclusively at ∼21 μm. In this work, using the proto-typical protoplanetary nebula HD 56126 as a test case, we examine FeO nanoparticles as a carrier for the 21 μm feature by modeling their infrared emission, with FeO being stochastically heated by single stellar photons. We find that FeO emits too broad a 21 μm feature to explain that observed and the Fe abundance required to be locked up in FeO exceeds what is available in HD 56126. We therefore conclude that FeO nanoparticles are not likely to be responsible for the 21 μm feature.« less

Separation of Atmospheric and Surface Spectral Features in Mars Global Surveyor Thermal Emission Spectrometer (TES) Spectra

NASA Technical Reports Server (NTRS)

Smith, Michael D.; Bandfield, Joshua L.; Christensen, Philip R.

2000-01-01

We present two algorithms for the separation of spectral features caused by atmospheric and surface components in Thermal Emission Spectrometer (TES) data. One algorithm uses radiative transfer and successive least squares fitting to find spectral shapes first for atmospheric dust, then for water-ice aerosols, and then, finally, for surface emissivity. A second independent algorithm uses a combination of factor analysis, target transformation, and deconvolution to simultaneously find dust, water ice, and surface emissivity spectral shapes. Both algorithms have been applied to TES spectra, and both find very similar atmospheric and surface spectral shapes. For TES spectra taken during aerobraking and science phasing periods in nadir-geometry these two algorithms give meaningful and usable surface emissivity spectra that can be used for mineralogical identification.

Optically active red-emitting Cu nanoclusters originating from complexation and redox reaction between copper(ii) and d/l-penicillamine

NASA Astrophysics Data System (ADS)

Long, Tengfei; Guo, Yanjia; Lin, Min; Yuan, Mengke; Liu, Zhongde; Huang, Chengzhi

2016-05-01

Despite a significant surge in the number of investigations into both optically active Au and Ag nanostructures, there is currently only limited knowledge about optically active Cu nanoclusters (CuNCs) and their potential applications. Here, we have succeeded in preparing a pair of optically active red-emitting CuNCs on the basis of complexation and redox reaction between copper(ii) and penicillamine (Pen) enantiomers, in which Pen serves as both a reducing agent and a stabilizing ligand. Significantly, the CuNCs feature unique aggregation induced emission (AIE) characteristics and therefore can serve as pH stimuli-responsive functional materials. Impressively, the ligand chirality plays a dramatic role for the creation of brightly emissive CuNCs, attributed to the conformation of racemic Pen being unfavorable for the electrostatic interaction, and thus suppressing the formation of cluster aggregates. In addition, the clusters display potential toward cytoplasmic staining and labelling due to the high photoluminescence (PL) quantum yields (QYs) and remarkable cellular uptake, in spite that no chirality-dependent effects in autophagy and subcellular localization are observed in the application of chiral cluster enantiomer-based cell imaging.Despite a significant surge in the number of investigations into both optically active Au and Ag nanostructures, there is currently only limited knowledge about optically active Cu nanoclusters (CuNCs) and their potential applications. Here, we have succeeded in preparing a pair of optically active red-emitting CuNCs on the basis of complexation and redox reaction between copper(ii) and penicillamine (Pen) enantiomers, in which Pen serves as both a reducing agent and a stabilizing ligand. Significantly, the CuNCs feature unique aggregation induced emission (AIE) characteristics and therefore can serve as pH stimuli-responsive functional materials. Impressively, the ligand chirality plays a dramatic role for the creation of brightly emissive CuNCs, attributed to the conformation of racemic Pen being unfavorable for the electrostatic interaction, and thus suppressing the formation of cluster aggregates. In addition, the clusters display potential toward cytoplasmic staining and labelling due to the high photoluminescence (PL) quantum yields (QYs) and remarkable cellular uptake, in spite that no chirality-dependent effects in autophagy and subcellular localization are observed in the application of chiral cluster enantiomer-based cell imaging. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01492e

Anatomy of the AGN in NGC 5548. IX. Photoionized emission features in the soft X-ray spectra

NASA Astrophysics Data System (ADS)

Mao, Junjie; Kaastra, J. S.; Mehdipour, M.; Gu, Liyi; Costantini, E.; Kriss, G. A.; Bianchi, S.; Branduardi-Raymont, G.; Behar, E.; Di Gesu, L.; Ponti, G.; Petrucci, P.-O.; Ebrero, J.

2018-04-01

The X-ray narrow emission line region (NELR) of the archetypal Seyfert 1 galaxy NGC 5548 has been interpreted as a single-phase photoionized plasma that is absorbed by some of the warm absorber components. This scenario requires those overlaying warm absorber components to have larger distance (to the central engine) than the X-ray NELR, which is not fully consistent with the distance estimates found in the literature. Therefore, we reanalyze the high-resolution spectra obtained in 2013-2014 with the Reflection Grating Spectrometer (RGS) aboard XMM-Newton to provide an alternative interpretation of the X-ray narrow emission features. We find that the X-ray narrow emission features in NGC 5548 can be described by a two-phase photoionized plasma with different ionization parameters (logξ = 1.3 and 0.1) and kinematics (vout = -50 and -400 km s-1), and no further absorption by the warm absorber components. The X-ray and optical NELR might be the same multi-phase photoionized plasma. Both X-ray and optical NELR have comparable distances, asymmetric line profiles, and the underlying photoionized plasma is turbulent and compact in size. The X-ray NELR is not the counterpart of the UV/X-ray absorber outside the line of sight because their distances and kinematics are not consistent. In addition, X-ray broad emission features that we find in the spectrum can be accounted for by a third photoionized emission component. The RGS spectrum obtained in 2016 is analyzed as well, where the luminosity of most prominent emission lines (the O VII forbidden line and O VIII Lyα line) are the same (at a 1σ confidence level) as in 2013-2014.

The Structure of Dark Molecular Gas in the Galaxy. I. A Pilot Survey for 18 cm OH Emission Toward l≈ 105°, b≈ +1°

NASA Astrophysics Data System (ADS)

Allen, Ronald J.; Hogg, David E.; Engelke, Philip D.

2015-04-01

We report the first results from a survey for 1665, 1667, and 1720 MHz OH emission over a small region of the Outer Galaxy centered at l≈ 105\\buildrel{\\circ}\\over{.} 0,b≈ +1\\buildrel{\\circ}\\over{.} 0. This sparse, high-sensitivity survey ({Δ }{{T}A}≈ {Δ }{{T}mb}≈ 3.0-3.5 mK rms in 0.55 km s-1 channels), was carried out as a pilot project with the Robert C. Byrd Green Bank Telescope (GBT) (FWHM ≈ 7\\buildrel{ \\prime}\\over{.} 6 ) on a 3 × 9 grid at 0\\buildrel{\\circ}\\over{.} 5 spacing. The pointings were chosen to correspond with those of the existing 12CO(1-0) CfA survey of the Galaxy done at a similar resolution (8.‧4). With 2 hr integrations, 1667 MHz OH emission was detected with the GBT at ≳ 21 of the 27 survey positions (≥slant 78% ), confirming the ubiquity of molecular gas in the ISM as traced by this spectral line. With few exceptions, the main OH lines at 1665 and 1667 MHz appear in the ratio of 5:9 characteristic of LTE at our sensitivity levels. No OH absorption features are recorded in the area of the present survey, in agreement with the low levels of continuum background emission in this direction. At each pointing the OH emission appears in several components extending over a wide range of radial velocity and coinciding with well-known features of Galactic structure such as the Local Arm and the Perseus Arm. In contrast, little CO emission is seen in the survey area; less than half of the ≳ 50 identified OH spectral features show detectable CO counterparts at the CfA sensitivity levels, and these are generally relatively faint. There are no CO features without corresponding OH emission in our survey. With very few exceptions, peaks in the OH profiles coincide with peaks in the GBT H i spectra (obtained concurrently, FWHM 8.‧9), although the converse is not true. We conclude that main-line OH emission is a promising tracer for the “dark molecular gas” in the Galaxy discovered earlier in far-IR and gamma-ray emission, although further work is needed to establish the quantitative details of the connection. Further aspects of the OH \\Leftrightarrow CO relation are revealed in a scatter plot of CO versus OH line strengths. This plot suggests a rough proportionality between the bright envelope of the CO emission (when present) and level of the accompanying 1667 MHz OH emission. Finally, we note several cases of anomalous OH emission. One survey position shows several narrow OH spectral features which are not well correlated with the H i spectrum; these features have been identified with a nearby known OH-IR star. Also, nine neighboring survey positions show enhanced emission at 1720 MHz, consistent with earlier observations and with models involving extended regions of elevated particle density.

Crystal Phase Quantum Well Emission with Digital Control.

PubMed

Assali, S; Lähnemann, J; Vu, T T T; Jöns, K D; Gagliano, L; Verheijen, M A; Akopian, N; Bakkers, E P A M; Haverkort, J E M

2017-10-11

One of the major challenges in the growth of quantum well and quantum dot heterostructures is the realization of atomically sharp interfaces. Nanowires provide a new opportunity to engineer the band structure as they facilitate the controlled switching of the crystal structure between the zinc-blende (ZB) and wurtzite (WZ) phases. Such a crystal phase switching results in the formation of crystal phase quantum wells (CPQWs) and quantum dots (CPQDs). For GaP CPQWs, the inherent electric fields due to the discontinuity of the spontaneous polarization at the WZ/ZB junctions lead to the confinement of both types of charge carriers at the opposite interfaces of the WZ/ZB/WZ structure. This confinement leads to a novel type of transition across a ZB flat plate barrier. Here, we show digital tuning of the visible emission of WZ/ZB/WZ CPQWs in a GaP nanowire by changing the thickness of the ZB barrier. The energy spacing between the sharp emission lines is uniform and is defined by the addition of single ZB monolayers. The controlled growth of identical quantum wells with atomically flat interfaces at predefined positions featuring digitally tunable discrete emission energies may provide a new route to further advance entangled photons in solid state quantum systems.

Realizing Highly Efficient Solution-Processed Homojunction-Like Sky-Blue OLEDs by Using Thermally Activated Delayed Fluorescent Emitters Featuring an Aggregation-Induced Emission Property.

PubMed

Wu, Kailong; Wang, Zian; Zhan, Lisi; Zhong, Cheng; Gong, Shaolong; Xie, Guohua; Yang, Chuluo

2018-04-05

Two new blue emitters, i.e., bis-[2-(9,9-dimethyl-9,10-dihydroacridine)-phenyl]-sulfone ( o-ACSO2) and bis-[3-(9,9-dimethyl-9,10-dihydroacridine)-phenyl]-sulfone ( m-ACSO2), with reserved fine thermally activated delayed fluorescent (TADF) nature and simply tuned thermal and optoelectronic properties, were synthesized by isomer engineering. The meta-linking compound, i.e., m-ACSO2, obtains the highest photoluminescence quantum yield with a small singlet-triplet energy gap, a moderate delayed fluorescent lifetime, excellent solubility, and neat film homogeneity. Due to its unique aggregation-induced emission (AIE) character, neat film-based heterojunction-like organic light-emitting diodes (OLEDs) are achievable. By inserting an excitonic inert exciton-blocking layer, the PN heterojunction-like emission accompanied by intefacial exciplex was shifted to a homojunction-like channel mainly from the AIE emitter itself, providing a new tactic to generate efficient blue color from neat films. The solution-processed nondoped sky-blue OLED employing m-ACSO2 as emitter with homojunction-like emission achieved a maximum external quantum efficiency of 17.2%. The design strategies presented herein provide practical methods to construct efficient blue TADF dyes and realize high-performance blue TADF devices.

CO2 Condensation Models for Mars

NASA Technical Reports Server (NTRS)

Colaprete, A.; Haberle, R.

2004-01-01

During the polar night in both hemispheres of Mars, regions of low thermal emission, frequently referred to as "cold spots", have been observed by Mariner 9, Viking and Mars Global Surveyor (MGS) spacecraft. These cold spots vary in time and appear to be associated with topographic features suggesting that they are the result of a spectral-emission effect due to surface accumulation of fine-grained frost or snow. Presented here are simulations of the Martian polar night using the NASA Ames General Circulation Cloud Model. This cloud model incorporates all the microphysical processes of carbon dioxide cloud formation, including nucleation, condensation and sedimentation and is coupled to a surface frost scheme that includes both direct surface condensation and precipitation. Using this cloud model we simulate the Mars polar nights and compare model results to observations from the Thermal Emission Spectrometer (TES) and the Mars Orbiter Laser Altimeter (MOLA). Model predictions of "cold spots" compare well with TES observations of low emissivity regions, both spatially and as a function of season. The model predicted frequency of CO2 cloud formation also agrees well with MOLA observations of polar night cloud echoes. Together the simulations and observations in the North indicate a distinct shift in atmospheric state centered about Ls 270 which we believe may be associated with the strength of the polar vortex.

Isotopic dependence of the fragments' internal temperatures determined from multifragment emission

NASA Astrophysics Data System (ADS)

Souza, S. R.; Donangelo, R.

2018-05-01

The internal temperatures of fragments produced by an excited nuclear source are investigated by using the microcanonical version of the statistical multifragmentation model, with discrete energy. We focus on the fragments' properties at the breakup stage, before they have time to deexcite by particle emission. Since the adopted model provides the excitation energy distribution of these primordial fragments, it allows one to calculate the temperatures of different isotope families and to make inferences about the sensitivity to their isospin composition. It is found that, due to the functional form of the nuclear density of states and the excitation energy distribution of the fragments, proton-rich isotopes are hotter than neutron-rich isotopes. This property has been taken to be an indication of earlier emission of the former from a source that cools down as it expands and emits fragments. Although this scenario is incompatible with the prompt breakup of a thermally equilibrated source, our results reveal that the latter framework also provides the same qualitative features just mentioned. Therefore they suggest that this property cannot be taken as evidence for nonequilibrium emission. We also found that this sensitivity to the isotopic composition of the fragments depends on the isospin composition of the source, and that it is weakened as the excitation energy of the source increases.

Rapid-Response Low Infrared Emission Broadband Ultrathin Plasmonic Light Absorber

PubMed Central

Tagliabue, Giulia; Eghlidi, Hadi; Poulikakos, Dimos

2014-01-01

Plasmonic nanostructures can significantly advance broadband visible-light absorption, with absorber thicknesses in the sub-wavelength regime, much thinner than conventional broadband coatings. Such absorbers have inherently very small heat capacity, hence a very rapid response time, and high light power-to-temperature sensitivity. Additionally, their surface emissivity can be spectrally tuned to suppress infrared thermal radiation. These capabilities make plasmonic absorbers promising candidates for fast light-to-heat applications, such as radiation sensors. Here we investigate the light-to-heat conversion properties of a metal-insulator-metal broadband plasmonic absorber, fabricated as a free-standing membrane. Using a fast IR camera, we show that the transient response of the absorber has a characteristic time below 13 ms, nearly one order of magnitude lower than a similar membrane coated with a commercial black spray. Concurrently, despite the small thickness, due to the large absorption capability, the achieved absorbed light power-to-temperature sensitivity is maintained at the level of a standard black spray. Finally, we show that while black spray has emissivity similar to a black body, the plasmonic absorber features a very low infra-red emissivity of almost 0.16, demonstrating its capability as selective coating for applications with operating temperatures up to 400°C, above which the nano-structure starts to deform. PMID:25418040

Emission spectra of a pulse needle-to-plane corona-like discharge in conductive aqueous solutions

NASA Astrophysics Data System (ADS)

Šimek, Milan; Člupek, Martin; Babický, Václav; Lukeš, Petr; Šunka, Pavel

2012-10-01

We explored basic optical and electrical characteristics of a positive corona-like discharge produced in conductive aqueous solutions by periodic high-voltage pulses. Emission spectra of the discharge were acquired in a needle-to-plate electrode geometry and analysed in the UV-vis-NIR spectral range with nanosecond time resolution for the solution conductivity of 100 and 500 µS cm-1. The most important emission features are due to electronic excitation of HI, OI, OII and OH species. We found evidence of significant time-dependent line-shape broadening of selected HI and OI transitions. The observed broadening is attributed to the dynamic Stark and pressure broadening mechanisms and significantly increases with the aqueous solution conductivity. Electron densities were estimated by fitting a single Voigt peak function to the observed Hα profiles, and can reach as much as ne ≅ 4 × 1018 cm-3 (tD = 300 ns at 100 µS cm-1 solution conductivity) and ne ≅ 5 × 1018 cm-3 (tD = 1 µs at 500 µS cm-1). Temporal evolution of the partially resolved rotational structure of the OH emission reaches a maximum during the discharge decay, with the onset significantly delayed with respect to the streamer ignition.

A new process for NOx reduction in combustion systems for the generation of energy from waste.

PubMed

Gohlke, Oliver; Weber, Toralf; Seguin, Philippe; Laborel, Yann

2010-07-01

In the EU, emissions from energy from waste plants are largely reduced by applying the Waste Incineration Directive with its limit of 200 mg/m3(s) for NO(x) emissions. The need for further improvement is reflected by new German legislation effective as of 27 January 2009, requiring 100 mg/m3(s). Other countries are expected to follow this example due to the national emission ceilings of the Gothenburg protocol and the concluding EU directive 2001/81/EC. On the other hand, an increase in energy efficiency will be encouraged by the EU Waste Framework Directive. This is why there is a need for new technologies that make it possible to reconcile both requirements: reduced emissions and increased energy efficiency. A new process combining the internal recirculation of flue gas with ammonia or urea injection in order to achieve less then 80 mg/m3(s) of NO(x) is described. Important additional features of the process are an R1 efficiency above the required 0.65 of the EU Waste Framework Directive even with standard steam parameters of 40 bar/380 degrees C as well as low ammonia slip in the flue gas at the boiler outlet of below 10 mg/m3(s). Copyright (c) 2010 Elsevier Ltd. All rights reserved.

Tidal interaction, star formation and chemical evolution in blue compact dwarf galaxy Mrk 22

NASA Astrophysics Data System (ADS)

Paswan, A.; Omar, A.; Jaiswal, S.

2018-02-01

The optical spectroscopic and radio interferometric H I 21 cm-line observations of the blue compact dwarf galaxy Mrk 22 are presented. The Wolf-Rayet (WR) emission-line features corresponding to high ionization lines of He II λ4686 and C IV λ5808 from young massive stars are detected. The ages of two prominent star-forming regions in the galaxy are estimated as ∼10 and ∼ 4 Myr. The galaxy has non-thermal radio deficiency, which also indicates a young starburst and lack of supernovae events from the current star formation activities, consistent with the detection of WR emission-line features. A significant N/O enrichment is seen in the fainter star-forming region. The gas-phase metallicities [12 + log(O/H)] for the bright and faint regions are estimated as 7.98±0.07 and 7.46±0.09, respectively. The galaxy has a large diffuse H I envelop. The H I images reveal disturbed gas kinematics and H I clouds outside the optical extent of the galaxy, indicating recent tidal interaction or merger in the system. The results strongly indicate that Mrk 22 is undergoing a chemical and morphological evolution due to ongoing star formation, most likely triggered by a merger.

Drill wear monitoring in cortical bone drilling.

PubMed

Staroveski, Tomislav; Brezak, Danko; Udiljak, Toma

2015-06-01

Medical drills are subject to intensive wear due to mechanical factors which occur during the bone drilling process, and potential thermal and chemical factors related to the sterilisation process. Intensive wear increases friction between the drill and the surrounding bone tissue, resulting in higher drilling temperatures and cutting forces. Therefore, the goal of this experimental research was to develop a drill wear classification model based on multi-sensor approach and artificial neural network algorithm. A required set of tool wear features were extracted from the following three types of signals: cutting forces, servomotor drive currents and acoustic emission. Their capacity to classify precisely one of three predefined drill wear levels has been established using a pattern recognition type of the Radial Basis Function Neural Network algorithm. Experiments were performed on a custom-made test bed system using fresh bovine bones and standard medical drills. Results have shown high classification success rate, together with the model robustness and insensitivity to variations of bone mechanical properties. Features extracted from acoustic emission and servomotor drive signals achieved the highest precision in drill wear level classification (92.8%), thus indicating their potential in the design of a new type of medical drilling machine with process monitoring capabilities. Copyright © 2015 IPEM. Published by Elsevier Ltd. All rights reserved.

Failed Collapsar Jets to Explain Low Luminosity GRB Properties

NASA Astrophysics Data System (ADS)

Hamidani, Hamid; Umeda, Hideyuki; Takahashi, Koh

Using the collapsar scenario for long GRBs [1], we present series of numerical simulations to investigate properties of expanding jets, driven by engines deploying the same total energy (1052 erg), differently. We include a wide range of engine durations (Tinj), from 0.1 to 100 s, as well as different initial opening angles (θ0) for the deployed energy. We employ an AMR 2D special relativistic hydrodynamical code, using a 25 solar mass Wolf-Rayet star as the progenitor [2]. We analyze the effect of the engine duration on the jet's hydrodynamic properties, and discuss the implications on GRB and SN emissions. Our results show that the expanding jet's hydrodynamical properties significantly differ, in particular outflow collimation and relativistic acceleration. The implication of this is that brief engines (with Tinj < Tbreakout, either due to a short Tinj or to a large θ0) represent excellent systems to explain the debated low-luminosity GRBs (llGRBs), displaying two of llGRBs peculiar features: i) the estimated llGRBs rate at least about 100 times higher than that of GRBs [3,4,5], and ii) potentially energetic SN emission [6]. We find that these two features only arise from brief engines. The conclusion is that brief engines dominate collapsars, at least at low redshift.

ISO Spectroscopy of Proto-Planetary Nebulae

NASA Technical Reports Server (NTRS)

Hrivnak, Bruce J.

2000-01-01

The goal of this program was to determine the chemical properties of the dust shells around protoplanetary nebulae (PPNs) through a study of their short-wavelength (6-45 micron) infrared spectra. PPNs are evolved stars in transition from the asymptotic giant branch to the planetary nebula stages. Spectral features in the 10 to 20 gm region indicate the chemical nature (oxygen- or carbon-rich), and the strengths of the features relate to the physical properties of the shells. A few bright carbon-rich PPNs have been observed to show PAH features and an unidentified 21 micron emission feature. We used the Infrared Space Observatory (ISO) to observe a sample of IRAS sources that have the expected properties of PPNs and for which we have accurate positions. Some of these have optical counterparts (proposal SWSPPN01) and some do not (SWSPPN02). We had previously observed these from the ground with near-infrared photometry and, for those with visible counterparts, visible photometry and spectroscopy, which we have combined with these new ISO data in the interpretation of the spectra. We have completed a study of the unidentified emission feature at 21 micron in eight sources. We find the shape of the feature to be the same in all of the sources, with no evidence of any substructure. The ratio of the emission peak to continuum ranges from 0.13 to 1.30. We have completed a study of seven PPNs and two other carbon-rich objects for which we had obtained ISO 2-45 micron observations. The unidentified emission features at 21 and 30 micron were detected in six sources, including four new detections of the 30 micron feature. This previously unresolved 30 micron feature was resolved and found to consist of a broad feature peaking at 27.2 micron (the "30 micron" feature) and a narrower feature peaking at 25.5 micron (the "26 micron" feature). This new 26 micron feature is detected in eight sources and is particularly strong in IRAS Z02229+6208 and 16594-4656. The unidentified features at 3.3, 6,2, 7.7, and 11.3 micron, which are commonly observed in planetary nebulae and HII regions, are also seen in these PPNs. However, their strengths relative to the continuum plateaus at 8 and 12 micron are weaker than in planetary nebulae. The 6.9 micron feature, seen almost exclusively in PPNs, is strong. The spectral energy distributions of these PPNs were fitted with a radiative-transfer model, taking into account the emission features at 21, 26, and 30 micron. A significant fraction of the total energy output is emitted in these features: as high as 20% in the 30 micron feature and 8% in the 21 micron feature. The fact that so much energy is carried in these features suggests that the material responsible for this feature must be made of abundant elements, and most likely involves carbon. The change in the in feature strengths from stronger aliphatic bonds in PPNs to stronger aromatic bonds in PNs suggests a chemical and physical evolution in the carbonaceous circumstellar dust during this transition time scale of a few thousand years.

Wavelet Based Characterization of Low Radio Frequency Solar Emissions

NASA Astrophysics Data System (ADS)

Suresh, A.; Sharma, R.; Das, S. B.; Oberoi, D.; Pankratius, V.; Lonsdale, C.

2016-12-01

Low-frequency solar radio observations with the Murchison Widefield Array (MWA) have revealed the presence of numerous short-lived, narrow-band weak radio features, even during quiet solar conditions. In their appearance in in the frequency-time plane, they come closest to the solar type III bursts, but with much shorter spectral spans and flux densities, so much so that they are not detectable with the usual swept frequency radio spectrographs. These features occur at rates of many thousand features per hour in the 30.72 MHz MWA bandwidth, and hence necessarily require an automated approach to determine robust statistical estimates of their properties, e.g., distributions of spectral widths, temporal spans, flux densities, slopes in the time-frequency plane and distribution over frequency. To achieve this, a wavelet decomposition approach has been developed for feature recognition and subsequent parameter extraction from the MWA dynamic spectrum. This work builds on earlier work by the members of this team to achieve a reliable flux calibration in a computationally efficient manner. Preliminary results show that the distribution of spectral span of these features peaks around 3 MHz, most of them last for less than two seconds and are characterized by flux densities of about 60% of the background solar emission. In analogy with the solar type III bursts, this non-thermal emission is envisaged to arise via coherent emission processes. There is also an exciting possibility that these features might correspond to radio signatures of nanoflares, hypothesized (Gold, 1964; Parker, 1972) to explain coronal heating.

Iron K Features in the Quasar E 1821+643: Evidence for Gravitationally Redshifted Absorption?

NASA Technical Reports Server (NTRS)

Yaqoob, Tahir; Serlemitsos, Peter

2005-01-01

We report a Chandra high-energy grating detection of a narrow, redshifted absorption line superimposed on the red wing of a broad Fe K line in the z = 0.297 quasar E 1821+643. The absorption line is detected at a confidence level, estimated by two different methods, in the range approx. 2 - 3 sigma. Although the detection significance is not high enough to exclude a non-astrophysical origin, accounting for the absorption feature when modeling the X-ray spectrum implies that the Fe-K emission line is broad, and consistent with an origin in a relativistic accretion disk. Ignoring the apparent absorption feature leads to the conclusion that the Fe-K emission line is narrower, and also affects the inferred peak energy of the line (and hence the inferred ionization state of Fe). If the absorption line (at approx. 6.2 keV in the quasar frame) is real, we argue that it could be due to gravitationally redshifted Fe XXV or Fe XXVI resonance absorption within approx. 10 - 20 gravitational radii of the putative central black hole. The absorption line is not detected in earlier ASCA and Chandra low-energy grating observations, but the absorption line is not unequivocally ruled out by these data. The Chandra high-energy grating Fe-K emission line is consistent with an origin predominantly in Fe I-XVII or so. In an ASCA observation eight years earlier, the Fe-K line peaked at approx. 6.6 keV, closer to the energies of He-like Fe triplet lines. Further, in a Chandra low-energy grating observation the Fe-K line profile was double-peaked, one peak corresponding to Fe I-XVII or so, the other peak to Fe XXVI Ly alpha. Such a wide range in ionization state of Fe is not ruled out by the HEG and ASCA data either, and is suggestive of a complex structure for the line-emitter.

Overview of the diagenetic features analyzed by ChemCam onboard Curiosity

NASA Astrophysics Data System (ADS)

Mangold, N.; Forni, O.; Nachon, M.; Blaney, D. L.; Wiens, R. C.; Kah, L. C.; Kronyak, R. E.; Clegg, S. M.; Cousin, A.; Fisk, M. R.; Gasnault, O.; Grotzinger, J. P.; Lanza, N.; Lasue, J.; Le Deit, L.; Le Mouelic, S.; Maurice, S.; Meslin, P. Y.; Rapin, W.; Newsom, H. E.; Sumner, D. Y.

2015-12-01

The Curiosity rover has encountered a variety of sedimentary rocks with significant variations in both texture and composition. Most of the sandstones and mudstones are interpreted as having been deposited in a fluvio-lacustrine environment, as analyzed in details in the waypoints named Yellowknife Bay, Kimberley and Pahrump. All of these sediments have been crossed by diagenetic features of different composition. Light-toned Ca-sulfate veins observed initially at Yellowknife Bay were observed along the traverse, and in high density at the Pahrump location. As they appear in all sediments and show straight fractures, they correspond to late-stage diagenetic features, due to fluid circulation, with fractures probably due to hydraulic stress at depth. In contrast to light-toned veins, earlier-stage diagenetic features have shown variable composition in the three areas. At Yellowknife Bay, raised ridges display enriched Mg proportion, probably linked to Mg-clay whereas outcrops at Kimberley display fracture fills enriched in Mn and Zn. Pahrump displays a large variety of diagenetic features distinct from these previous examples. Mg-enriched concretions contain S and abundant Ni. Mg enrichments have also been observed in resistant zones along fractures and in resistant layers. Locally concretions also display high Fe, S-bearing material interpreted as Fe-sulfate, probably jarosite. A special location named Garden City at the top of the Parhump sequence displays a complex area with light-toned veins surrounded by darker veins. The latter display strong Ca signatures correlated with F, interpreted as fluorite. No C or S emissions were observed that could alternatively explain the high Ca abundance by carbonates or sulfates. The dark tone of the F-bearing minerals may be due to the presence of Fe. These specific dark veins could derive from the leaching of F-apatite, a mineral that has been observed both in the sandstones and in some of the igneous clasts analyzed by ChemCam during the traverse. Altogether, these diagenetic features show that aqueous sediments were modified by a series of distinct diagenetic episodes, with strong local variability.

Complete fluorescent fingerprints of extremophilic and photosynthetic microbes

NASA Astrophysics Data System (ADS)

Dartnell, Lewis R.; Storrie-Lombardi, Michael C.; Ward, John M.

2010-10-01

The work reported here represents a study into the total fluorescence exhibited by a broad selection of model, extremophilic and photosynthetic bacterial strains, over a great range of excitation and emission wavelengths from ultraviolet (UV) through visible to near infrared. The aim is to identify distinctive fluorescent features that may serve as detectable biosignatures of remnant microbial life on the Martian surface. A lab-bench fluorescence spectrometer was used to generate an excitation-emission matrix (EEM) for the unpigmented Escherichia coli, radiation-resistant Deinococcus radiodurans, Antarctic Dry Valley isolates Brevundimonas sp. MV.7 and Rhodococcus sp. MV.10, and the cyanobacterium Synechocystis sp. PCC 6803. Detailed EEMs, representing the fluorescence signature of each organism, are presented, and the most significant features suitable for biosignature surveys are identified, including small-molecule cellular metabolites, light-harvesting photosynthetic pigments and extracellular UV-screening compounds. E. coli exhibits the most intense emission from tryptophan, presumably due to the absence of UV-screening pigments that would shield the organism from short-wavelength light-exciting intracellular fluorescence. The efficacy of commonly available laser diodes for exciting cellular fluorescence is treated, along with the most appropriate filter wavelengths for imaging systems. The best combination of available laser diodes and PanCam filters aboard the ExoMars probe is proposed. The possibility of detecting fluorescence excited by solar UV radiation in freshly exposed surface samples by imaging when both sunlit and shadowed, perhaps by the body of the rover itself, is discussed. We also study how these biological fluorophore molecules may be degraded, and thus the potential biosignatures erased, by the high flux of far-ultraviolet light on Mars.

A Deep Chandra ACIS Study of NGC 4151. III. The Line Emission and Spectral Analysis of the Ionization Cone

NASA Astrophysics Data System (ADS)

Wang, Junfeng; Fabbiano, Giuseppina; Elvis, Martin; Risaliti, Guido; Karovska, Margarita; Zezas, Andreas; Mundell, Carole G.; Dumas, Gaelle; Schinnerer, Eva

2011-11-01

This paper is the third in a series in which we present deep Chandra ACIS-S imaging spectroscopy of the Seyfert 1 galaxy NGC 4151, devoted to study its complex circumnuclear X-ray emission. Emission features in the soft X-ray spectrum of the bright extended emission (L 0.3-2 keV ~ 1040 erg s-1) at r > 130 pc (2'') are consistent with blended brighter O VII, O VIII, and Ne IX lines seen in the Chandra HETGS and XMM-Newton RGS spectra below 2 keV. We construct emission line images of these features and find good morphological correlations with the narrow-line region clouds mapped in [O III] λ5007. Self-consistent photoionization models provide good descriptions of the spectra of the large-scale emission, as well as resolved structures, supporting the dominant role of nuclear photoionization, although displacement of optical and X-ray features implies a more complex medium. Collisionally ionized emission is estimated to be lsim12% of the extended emission. Presence of both low- and high-ionization spectral components and extended emission in the X-ray image perpendicular to the bicone indicates leakage of nuclear ionization, likely filtered through warm absorbers, instead of being blocked by a continuous obscuring torus. The ratios of [O III]/soft X-ray flux are approximately constant (~15) for the 1.5 kpc radius spanned by these measurements, indicating similar relative contributions from the low- and high-ionization gas phases at different radial distances from the nucleus. If the [O III] and X-ray emission arise from a single photoionized medium, this further implies an outflow with a wind-like density profile. Using spatially resolved X-ray features, we estimate that the mass outflow rate in NGC 4151 is ~2 M ⊙ yr-1 at 130 pc and the kinematic power of the ionized outflow is 1.7 × 1041 erg s-1, approximately 0.3% of the bolometric luminosity of the active nucleus in NGC 4151.

LIBS Spectral Data for a Mixed Actinide Fuel Pellet Containing Uranium, Plutonium, Neptunium and Americium

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

Judge, Elizabeth J.; Berg, John M.; Le, Loan A.

2012-06-18

Laser-induced breakdown spectroscopy (LIBS) was used to analyze a mixed actinide fuel pellet containing 75% UO{sub 2}/20% PuO{sub 2}/3% AmO{sub 2}/2% NpO{sub 2}. The preliminary data shown here is the first report of LIBS analysis of a mixed actinide fuel pellet, to the authors knowledge. The LIBS spectral data was acquired in a plutonium facility at Los Alamos National Laboratory where the sample was contained within a glove box. The initial installation of the glove box was not intended for complete ultraviolet (UV), visible (VIS) and near infrared (NIR) transmission, therefore the LIBS spectrum is truncated in the UV andmore » NIR regions due to the optical transmission of the window port and filters that were installed. The optical collection of the emission from the LIBS plasma will be optimized in the future. However, the preliminary LIBS data acquired is worth reporting due to the uniqueness of the sample and spectral data. The analysis of several actinides in the presence of each other is an important feature of this analysis since traditional methods must chemically separate uranium, plutonium, neptunium, and americium prior to analysis. Due to the historic nature of the sample fuel pellet analyzed, the provided sample composition of 75% UO{sub 2}/20% PuO{sub 2}/3% AmO{sub 2}/2% NpO{sub 2} cannot be confirm without further analytical processing. Uranium, plutonium, and americium emission lines were abundant and easily assigned while neptunium was more difficult to identify. There may be several reasons for this observation, other than knowing the exact sample composition of the fuel pellet. First, the atomic emission wavelength resources for neptunium are limited and such techniques as hollow cathode discharge lamp have different dynamics than the plasma used in LIBS which results in different emission spectra. Secondly, due to the complex sample of four actinide elements, which all have very dense electronic energy levels, there may be reactions and interactions occurring within the plasma, such as collisional energy transfer, that might be a factor in the reduction in neptunium emission lines. Neptunium has to be analyzed alone using LIBS to further understand the dynamics that may be occurring in the plasma of the mixed actinide fuel pellet sample. The LIBS data suggests that the emission spectrum for the mixed actinide fuel pellet is not simply the sum of the emission spectra of the pure samples but is dependent on the species present in the plasma and the interactions and reactions that occur within the plasma. Finally, many of the neptunium lines are in the near infrared region which is drastically reduced in intensity by the current optical setup and possibly the sensitivity of the emission detector in the spectral region. Once the optics are replaced and the optical collection system is modified and optimized, the probability of observing emission lines for neptunium might be increased significantly. The mixed actinide fuel pellet was analyzed under the experimental conditions listed in Table 1. The LIBS spectra of the fuel pellet are shown in Figures 1-49. The spectra are labeled with the observed wavelength and atomic species (both neutral (I) and ionic (II)). Table 2 is a complete list of the observed and literature based emission wavelengths. The literature wavelengths have references including NIST Atomic Spectra Database (NIST), B.A. Palmer et al. 'An Atlas of Uranium Emission Intensities in a Hollow Cathode Discharge' taken at the Kitt Peak National Observatory (KPNO), R.L. Kurucz 1995 Atomic Line Data from the Smithsonian Astrophysical Observatory (SAO), J. Blaise et al. 'The Atomic Spectrum of Plutonium' from Argonne National Laboratory (BFG), and M. Fred and F.S. Tomkins, 'Preliminary Term Analysis of Am I and Am II Spectra' (FT). The dash (-) shown under Ionic State indicates that the ionic state of the transition was not available. In the spectra, the dash (-) is replaced with a question mark (?). Peaks that are not assigned are most likely real features and not noise but cannot be confidently assigned to a transition without further investigation. Several peaks have multiple assignments due to limited resolution of the spectrometer used (20,000, {lambda}/{Delta}{lambda}) and without the availability, at this point in time, of pure PuO{sub 2}, AmO{sub 2}, and NpO{sub 2} to confirm the identity of the peaks. A different spectrometer was used in the plutonium facility to collect the mixed actinide fuel pellet data (Echelle 3000) than the DUO{sub 2}, ThO{sub 2} and uranium ore previously reported [6-8] (Echelle 4000) which accounts for the slight shift in the observed wavelength of the uranium emission lines.« less

New Dust Features Observed with ISO

NASA Technical Reports Server (NTRS)

Tielens, Alexander G. G. M.; Young, Richard E. (Technical Monitor)

1997-01-01

This paper will review our current knowledge of circumstellar and interstellar dust with the emphasis on infrared spectroscopy with ISO. Objects embedded in or located behind molecular clouds show a wealth of absorption features due to simple molecules in an icy mantle. The SWS on ISO has provided us, for the first time, with complete 3-45 um spectra which allow an inventory of interstellar ice. Among the species identified are H2O, CH3OH, CH4, CO2, CO, and OCS. These species are formed through simple reactions among gas phase species accreted on grain surfaces, possibly modified by FUV photolysis and warm-up (ie., outgassing). The implications of the observations for our understanding of these processes will be reviewed. The IR spectra of many UV bright objects are dominated by strong emission features at 3.3, 6.2, 7.7, and 11.3 micrometers. These are generally attributed to Polycyclic Aromatic Hydrocarbons (PAHs) molecules. The observational evidence will be reviewed. The emphasis will be on recent data which show widespread spectral variations, particularly among protoplanetary and planetary nebulae, and their implications. One of the most exciting, recent discoveries on interstellar and circumstellar dust has been the detection of spectral structure due to crystalline olivine and enstatite in a variety of objects surrounded by circumstellar silicates. These spectra will be reviewed and circumstellar silicate mineralogy will be discussed.

Evidence for Ni-56 yields Co-56 yields Fe-56 decay in type Ia supernovae

NASA Technical Reports Server (NTRS)

Kuchner, Marc J.; Kirshner, Robert P.; Pinto, Philip A.; Leibundgut, Bruno

1994-01-01

In the prevailing picture of Type Ia supernovae (SN Ia), their explosive burning produces Ni-56, and the radioactive decay chain Ni-56 yields Co-56 yields Fe-56 powers the subsequent emission. We test a central feature of this theory by measuring the relative strengths of a (Co III) emission feature near 5900 A and a (Fe III) emission feature near 4700 A. We measure 38 spectra from 13 SN Ia ranging from 48 to 310 days after maximum light. When we compare the observations with a simple multilevel calculation, we find that the observed Fe/Co flux ratio evolves as expected when the Fe-56/Co-56 abundance ratio follows from Ni-56 yields Co-56 yields Fe-56 decay. From this agreement, we conclude that the cobalt and iron atoms we observe through SN Ia emission lines are produced by the radioactive decay of Ni-56, just as predicted by a wide range of models for SN Ia explosions.

A two component model for thermal emission from organic grains in Comet Halley

NASA Technical Reports Server (NTRS)

Chyba, Christopher; Sagan, Carl

1988-01-01

Observations of Comet Halley in the near infrared reveal a triple-peaked emission feature near 3.4 micrometer, characteristic of C-H stretching in hydrocarbons. A variety of plausible cometary materials exhibit these features, including the organic residue of irradiated candidate cometary ices (such as the residue of irradiated methane ice clathrate, and polycyclic aromatic hydrocarbons. Indeed, any molecule containing -CH3 and -CH2 alkanes will emit at 3.4 micrometer under suitable conditions. Therefore tentative identifications must rest on additional evidence, including a plausible account of the origins of the organic material, a plausible model for the infrared emission of this material, and a demonstration that this conjunction of material and model not only matches the 3 to 4 micrometer spectrum, but also does not yield additional emission features where none is observed. In the case of the residue of irradiated low occupancy methane ice clathrate, it is argued that the lab synthesis of the organic residue well simulates the radiation processing experienced by Comet Halley.

Spectral reflectance and emissivity features of broad leaf plants: Prospects for remote sensing in the thermal infrared (8.0-14.0 μm)

USGS Publications Warehouse

Ribeiro da Luz, Beatriz; Crowley, James K.

2007-01-01

In contrast to visible and short-wave infrared data, thermal infrared spectra of broad leaf plants show considerable spectral diversity, suggesting that such data eventually could be utilized to map vegetation composition. However, remotely measuring the subtle emissivity features of leaves still presents major challenges. To be successful, sensors operating in the 8–14 μm atmospheric window must have high signal-to-noise and a small enough instantaneous field of view to allow measurements of only a few leaf surfaces. Methods for atmospheric compensation, temperature–emissivity separation, and spectral feature analysis also will need to be refined to allow the recognition, and perhaps, exploitation of leaf thermal infrared spectral properties.

Effect of water and heat transport processes on methane emissions from paddy soils: a process-based model analysis

NASA Astrophysics Data System (ADS)

Rizzo, Anacleto; Boano, Fulvio; Revelli, Roberto; Ridolfi, Luca

2013-04-01

High CH4 fluxes are emitted from paddy fields worldwide and represent a considerable issue for the rice production eco-sustainability. Water and heat transport fluxes are known to strongly influence biogeochemical cycles in wetland environments, and therefore also CH4 emissions from paddy soils. Water percolation affects the dynamics of many compounds (e.g. DOC, O2) influencing CH4 fate. On the other hand, heat fluxes strongly influence CH4 production in submerged rice crops, and lowering ponding water temperature (LPWT) can reduce microbial activities and consequently decrease CH4 emissions. Moreover, as long as the optimal temperature range for rice growth is maintained, LPWT can lower CH4 emissions without rice yield limitation. Hence, a process-based model is proposed and applied to investigate the role of water flow on CH4 emissions, and to analyse the efficiency of LPWT as mitigation strategy for CH4 production and release. The process-based model relies on a system of partial differential mass balance equations to describe the vertical dynamics of the chemical compounds leading to CH4 production. Many physico-chemical processes and features characteristic of paddy soil are included: paddy soil stratigraphy; spatio-temporal variations of plant-root compartment; water and heat transport; SOC decomposition; heterotrophic reactions in both aerobic and anaerobic conditions; root radial oxygen loss; root solute uptake; DOC root exudation; plant-mediated, ebullition, and diffusion gas exchange pathways. LPWT is included as a temperature shift subtracted directly to the ponding water temperature. Model results confirm the importance of water flow on CH4 emission, since simulations that do not include water fluxes show a considerable overestimation of CH4 emissions due to a different DOC spatio-temporal dynamics. Particularly, when water fluxes are not modeled the overestimation can reach 67 % of the total CH4 emission over the whole growing season. Moreover, model results also suggest that roots influence CH4 dynamics principally due to their solute uptake, while root effect on advective flow plays a minor role. In addition, the analysis of CH4 transport fluxes show the limiting effect of upward dispersive transport fluxes on the downward CH4 percolation. Finally, LPWT is confirmed to be a valid mitigation strategy for CH4 emissions from paddy soils, since the reduction of CH4 emission reach about -50 % with a LPWT equal to only 2°C over the whole growing season.

Breast cancer detection in rotational thermography images using texture features

NASA Astrophysics Data System (ADS)

Francis, Sheeja V.; Sasikala, M.; Bhavani Bharathi, G.; Jaipurkar, Sandeep D.

2014-11-01

Breast cancer is a major cause of mortality in young women in the developing countries. Early diagnosis is the key to improve survival rate in cancer patients. Breast thermography is a diagnostic procedure that non-invasively images the infrared emissions from breast surface to aid in the early detection of breast cancer. Due to limitations in imaging protocol, abnormality detection by conventional breast thermography, is often a challenging task. Rotational thermography is a novel technique developed in order to overcome the limitations of conventional breast thermography. This paper evaluates this technique's potential for automatic detection of breast abnormality, from the perspective of cold challenge. Texture features are extracted in the spatial domain, from rotational thermogram series, prior to and post the application of cold challenge. These features are fed to a support vector machine for automatic classification of normal and malignant breasts, resulting in a classification accuracy of 83.3%. Feature reduction has been performed by principal component analysis. As a novel attempt, the ability of this technique to locate the abnormality has been studied. The results of the study indicate that rotational thermography holds great potential as a screening tool for breast cancer detection.

The composition of Martian aeolian sands: Thermal emissivity from Viking IRTM observations

NASA Technical Reports Server (NTRS)

Edgett, Kenneth S.; Christensen, Philip R.

1992-01-01

Aeolian sands provide excellent surfaces for the remote determination of the mineralogic composition of Martian materials, because such deposits consist of relatively well-sorted, uniform particle sizes and might consist of chemically unaltered, primary mineral grains derived from bedrock. Dark features on the floors of Martian craters are controlled by aeolian processes and many consist largely of unconsolidated, windblown sand. Measurement of the thermal emissivity of geologic materials provides a way to identify mid-infrared absorption bands, the strength and positions of which vary with mineral structure and composition. The Viking Infrared Thermal Mapper (IRTM) had four surface-sensing mid-IR bands, three of which, the 7, 9, and 11 micron channels, correspond to absorption features characteristic of carbonates, sialic, and mafic minerals, respectively. In this study, the highest quality IRTM data were constrained so as to avoid the effects of atmospheric dust, clouds, surface frosts, and particle size variations (the latter using data obtained between 7 and 9 H, and they were selected for dark intracrater features such that only data taken directly from the dark feature were used, so as to avoid thermal contributions from adjacent but unrelated materials. Three-point emissivity spectra of Martian dart intracrater features were compared with laboratory emission spectra of minerals and terrestrial aeolian sands convolved using the IRTM response function to the four IRTM spectral channels.

Velocities along Byrd Glacier, East Antarctica, derived from Automatic Feature Tracking

NASA Astrophysics Data System (ADS)

Stearns, L. A.; Hamilton, G. S.

2003-12-01

Automatic feature tracking techniques are applied to recently acquired ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) imagery in order to determine the velocity field of Byrd Glacier, East Antarctica. The software IMCORR tracks the displacement of surface features (crevasses, drift mounds) in time sequential images, to produce the velocity field. Due to its high resolution, ASTER imagery is ideally suited for detecting small features changes. The produced result is a dense array of velocity vectors, which allows more thorough characterization of glacier dynamics. Byrd Glacier drains approximately 20.5 km3 of ice into the Ross Ice Shelf every year. Previous studies have determined ice velocities for Byrd Glacier by using photogrammetry, field measurements and manual feature tracking. The most recent velocity data is from 1986 and, as evident in the West Antarctic ice streams, substantial changes in velocity can occur on decadal time scales. The application of ASTER-based velocities fills this time lapse, and increased temporal resolution allows for a more complete analysis of Byrd Glacier. The ASTER-derived ice velocities are used in updating mass balance and force budget calculations to assess the stability of Byrd Glacier. Ice thickness information from BEDMAP, surface slopes from the OSUDEM and a compilation of accumulation rates are used to complete the calculations.

Comparison of the 3.36 micrometer feature to the ISM

NASA Technical Reports Server (NTRS)

Tokunaga, Alan T.; Brooke, Timothy Y.

1988-01-01

It has been noted that the 3.36 micrometer emission feature is not the same as that of any ISM band at 3.4 micrometer. This is documented herein. There is no convincing analog to the cometary 3.36 micrometer emission feature seen in the Interstellar Matter band. This fact suggests that if the carbonaceous material in comets came from the ISM, it was either further processed in the solar nebula or has a different appearance because of the different excitation environment of the sun and ISM.

RADIO AND DEEP CHANDRA OBSERVATIONS OF THE DISTURBED COOL CORE CLUSTER ABELL 133

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

Randall, S. W.; Nulsen, P. E. J.; Forman, W. R.

2010-10-10

We present results based on new Chandra and multi-frequency radio observations of the disturbed cool core cluster Abell 133. The diffuse gas has a complex bird-like morphology, with a plume of emission extending from two symmetric wing-like features. The plume is capped with a filamentary radio structure that has been previously classified as a radio relic. X-ray spectral fits in the region of the relic indicate the presence of either high-temperature gas or non-thermal emission, although the measured photon index is flatter than would be expected if the non-thermal emission is from inverse Compton scattering of the cosmic microwave backgroundmore » by the radio-emitting particles. We find evidence for a weak elliptical X-ray surface brightness edge surrounding the core, which we show is consistent with a sloshing cold front. The plume is consistent with having formed due to uplift by a buoyantly rising radio bubble, now seen as the radio relic, and has properties consistent with buoyantly lifted plumes seen in other systems (e.g., M87). Alternatively, the plume may be a gas sloshing spiral viewed edge-on. Results from spectral analysis of the wing-like features are inconsistent with the previous suggestion that the wings formed due to the passage of a weak shock through the cool core. We instead conclude that the wings are due to X-ray cavities formed by displacement of X-ray gas by the radio relic. The central cD galaxy contains two small-scale cold gas clumps that are slightly offset from their optical and UV counterparts, suggestive of a galaxy-galaxy merger event. On larger scales, there is evidence for cluster substructure in both optical observations and the X-ray temperature map. We suggest that the Abell 133 cluster has recently undergone a merger event with an interloping subgroup, initialing gas sloshing in the core. The torus of sloshed gas is seen close to edge-on, leading to the somewhat ragged appearance of the elliptical surface brightness edge. We show that the additional buoyant force from a passing subcluster can have a significant effect on the rise trajectories of buoyant bubbles, although this effect alone cannot fully explain the morphology of Abell 133. The radio observations reveal a large-scale double-lobed structure not previously identified in the literature. We conclude that this structure represents a previously unreported background giant radio galaxy at z = 0.293, the northern lobe of which overlies the radio relic in the core of Abell 133. A rough estimate indicates that the contribution of this background lobe to the total radio emission in the region of the relic is modest (<13%).« less

SILICATES ON IAPETUS FROM CASSINI’S COMPOSITE INFRARED SPECTROMETER

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

Young, Cindy L.; Wray, James J.; Clark, Roger N.

We present the first spectral features obtained from Cassini’s Composite Infrared Spectrometer (CIRS) for any icy moon. The spectral region covered by CIRS focal planes (FP) 3 and 4 is rich in emissivity features, but previous studies at these wavelengths have been limited by low signal-to-noise ratios (S/Ns) for individual spectra. Our approach is to average CIRS FP3 spectra to increase the S/N and use emissivity spectra to constrain the composition of the dark material on Iapetus. We find an emissivity feature at ∼855 cm{sup −1} and a possible doublet at 660 and 690 cm{sup −1} that do not correspondmore » to any known instrument artifacts. We attribute the 855 cm{sup −1} feature to fine-grained silicates, similar to those found in dust on Mars and in meteorites, which are nearly featureless at shorter wavelengths. Silicates on the dark terrains of Saturn’s icy moons have been suspected for decades, but there have been no definitive detections until now. Serpentines reported in the literature at ambient temperature and pressure have features near 855 and 660 cm{sup −1}. However, peaks can shift depending on temperature and pressure, so measurements at Iapetus-like conditions are necessary for more positive feature identifications. As a first investigation, we measured muscovite at 125 K in a vacuum and found that this spectrum does match the emissivity feature near 855 cm{sup −1} and the location of the doublet. Further measurements are needed to robustly identify a specific silicate, which would provide clues regarding the origin and implications of the dark material.« less

Unidentified emission features in the R Coronae Borealis star V854 Centauri

NASA Astrophysics Data System (ADS)

Oostrum, L. C.; Ochsendorf, B. B.; Kaper, L.; Tielens, A. G. G. M.

2018-02-01

During its 2012 decline, the R Coronae Borealis star (RCB) V854 Cen was spectroscopically monitored with X-shooter on the ESO Very Large Telescope. The obscured optical and near-infrared spectrum exhibits many narrow and several broad emission features, as previously observed. The envelope is spatially resolved along the slit and allows for a detailed study of the circumstellar material. In this Letter, we report on the properties of a number of unidentified visual emission features (UFs), including the detection of a new feature at 8692 Å. These UFs have been observed in the Red Rectangle (RR), but their chemical and physical nature is still a mystery. The previously known UFs behave similarly in the RR and in V854 Cen, but are not detected in six other observed RCBs. Some hydrogen might be required for the formation of their carrier(s). The λ8692 UF is present in all RCBs. Its carrier is likely of a carbonaceous molecular nature, presumably different from that of the other UFs.

New emission features in the 11-13 micron region and their relationship to polycyclic aromatic hydrocarbons

NASA Technical Reports Server (NTRS)

Witteborn, F. C.; Sandford, S. A.; Bregman, J. D.; Allamandola, L. J.; Cohen, M.; Wooden, D. H.; Graps, A. L.

1989-01-01

Moderate-resolution spectra of NGC 7027, HD 44179, IRAS 2182+5050, and BD +30 deg 3639 are presented, showing that the 11.3-micron feature actually peaks at 11.22 microns. Evidence is found for new emission features near 11.9 and 12.7 microns, supporting an origin from PAHs. Also, the observed asymmetry of the 11.3-micron band is consistent with the anharmonicity expected in the C-H out-of-plane bending mode in PAHs. The analysis of the 11-13-micron emission suggests that the molecular structures of the most intensely emitting free PAHs vary between the high-excitation environment in NGC 7027 and the low-excitation but high-flux environment close to HD 44179. In addition, a series of regularly spaced features between 10 and 11 microns is detected in the spectrum of HD 44179, suggesting that a simple polyatomic hydride is present in the object's gas phase.

Hydrogenated Polycyclic Aromatic Hydrocarbons and the 2940 and 2850 Wavenumber (3.40 and 3.51 micron) Infrared Emission Features

NASA Technical Reports Server (NTRS)

Bernstein, Max P.; Sandford, Scott A.; Allamadola, Louis J.

1996-01-01

The 3150-2700/cm (3.17-3.70 micron) range of the spectra of a number of Ar-matrix-isolated PAHs containing excess H atoms (H(sub n)-PAHS) are presented. This region covers features produced by aromatic and aliphatic C-H stretching vibrations as well as overtone and combination bands involving lower lying fundamentals. The aliphatic C-H stretches in molecules of this type having low to modest excess H coverage provide excellent fits to a number of the weak emission features superposed on the plateau between 3080 and 2700/cm (3.25 and 3.7 micron) in the spectra of many planetary nebulae, reflection nebulae, and H II regions. Higher H coverage is implied for a few objects. We compare these results in context with the other suggested identifications of the emission features in the 2950-2700/cm (3.39-3.70 micron) region and briefly discuss their astrophysical implications.

Implications of the IRAS data for galactic gamma ray astronomy and EGRET

NASA Technical Reports Server (NTRS)

Stecker, Floyd W.

1990-01-01

Using the results of gamma-ray, millimeter wave and far surveys of the galaxy, logically consistent picture of the large scale distribution of galactic gas and cosmic rays was derived, tied to the overall processes of stellar birth and destruction on a galactic scale. Using the results of the IRAS far-infrared survey of te galaxy, the large scale radial distributions of galactic far-infrared emission independently was obtained for both the Northern and Southern Hemisphere sides of the Galaxy. The dominant feature in these distributions was found to be a broad peak coincident with the 5 kpc molecular gas cloud ring. Evidence was found for spiral arm features. Strong correlations are evident between the large scale galactic distributions of far-infrared emission, gamma-ray emission and total CO emission. There is particularly tight correlation between the distribution of warm molecular clouds and far-infrared emission on a galactic scale. The 5 kpc ring was evident in existing galactic gamma-ray data. The extent to which the more detailed spiral arm features are evident in the more resolved EGRET (Energetic Gamma-Ray Experimental Telescope) data will help to determine more precisely the propagation characteristics of cosmic rays.

The far-ultraviolet /1180-1950 A/ emission spectrum of Arcturus

NASA Technical Reports Server (NTRS)

Mckinney, W. R.; Giles, J. W.; Moos, H. W.

1976-01-01

The far-ultraviolet (1180-1950 A) emission spectrum of the K2 IIIp star, Arcturus, has been obtained with a rocket-borne multichannel spectrometer. The use of multiple detectors gave an increase in effective observing time and permitted an improvement in spectral resolution over two previous rocket measurements. H I at 1216-A and O I at 1304 A are the only identified emissions, and the observed H I 1216-A flux is low compared with previous observations. A third unidentified feature was observed at 1511 A. The absence of many lines found in emission from the sun is striking. The absence of certain features implies that the coronal temperature must be either below 50,000 K or above 350,000 K.

White-Light Emission from Layered Halide Perovskites.

PubMed

Smith, Matthew D; Karunadasa, Hemamala I

2018-03-20

With nearly 20% of global electricity consumed by lighting, more efficient illumination sources can enable massive energy savings. However, effectively creating the high-quality white light required for indoor illumination remains a challenge. To accurately represent color, the illumination source must provide photons with all the energies visible to our eye. Such a broad emission is difficult to achieve from a single material. In commercial white-light sources, one or more light-emitting diodes, coated by one or more phosphors, yield a combined emission that appears white. However, combining emitters leads to changes in the emission color over time due to the unequal degradation rates of the emitters and efficiency losses due to overlapping absorption and emission energies of the different components. A single material that emits broadband white light (a continuous emission spanning 400-700 nm) would obviate these problems. In 2014, we described broadband white-light emission upon near-UV excitation from three new layered perovskites. To date, nine white-light-emitting perovskites have been reported by us and others, making this a burgeoning field of study. This Account outlines our work on understanding how a bulk material, with no obvious emissive sites, can emit every color of the visible spectrum. Although the initial discoveries were fortuitous, our understanding of the emission mechanism and identification of structural parameters that correlate with the broad emission have now positioned us to design white-light emitters. Layered hybrid halide perovskites feature anionic layers of corner-sharing metal-halide octahedra partitioned by organic cations. The narrow, room-temperature photoluminescence of lead-halide perovskites has been studied for several decades, and attributed to the radiative recombination of free excitons (excited electron-hole pairs). We proposed that the broad white emission we observed primarily stems from exciton self-trapping. Here, the exciton couples strongly to the lattice, creating transient elastic lattice distortions that can be viewed as "excited-state defects". These deformations stabilize the exciton affording a broad emission with a large Stokes shift. Although material defects very likely contribute to the emission width, our mechanistic studies suggest that the emission mostly arises from the bulk material. Ultrafast spectroscopic measurements support self-trapping, with new, transient, electronic states appearing upon photoexcitation. Importantly, the broad emission appears common to layered Pb-Br and Pb-Cl perovskites, albeit with a strong temperature dependence. Although the emission is attributed to light-induced defects, it still reflects changes in the crystal structure. We find that greater out-of-plane octahedral tilting increases the propensity for the broad emission, enabling synthetic control over the broad emission. Many of these perovskites have color rendering abilities that exceed commercial requirements and mixing halides affords both "warm" and "cold" white light. The most efficient white-light-emitting perovskite has a quantum efficiency of 9%. Improving this value will make these phosphors attractive for solid-state lighting, particularly as large-area coatings that can be deposited inexpensively. The emission mechanism can also be extended to other low-dimensional systems. We hope this Account aids in expanding the phase space of white-light emitters and controlling their exciton dynamics by the synthetic, spectroscopic, theoretical, and engineering communities.

Guilt by Association: The 13 Micron Dust Emission Feature and Its Correlation to Other Gas and Dust Features

NASA Astrophysics Data System (ADS)

Sloan, G. C.; Kraemer, Kathleen E.; Goebel, J. H.; Price, Stephan D.

2003-09-01

A study of all full-scan spectra of optically thin oxygen-rich circumstellar dust shells in the database produced by the Short Wavelength Spectrometer on ISO reveals that the strength of several infrared spectral features correlates with the strength of the 13 μm dust feature. These correlated features include dust features at 19.8 and 28.1 μm and the bands produced by warm carbon dioxide molecules (the strongest of which are at 13.9, 15.0, and 16.2 μm). The database does not provide any evidence for a correlation of the 13 μm feature with a dust feature at 32 μm, and it is more likely that a weak emission feature at 16.8 μm arises from carbon dioxide gas rather than dust. The correlated dust features at 13, 20, and 28 μm tend to be stronger with respect to the total dust emission in semiregular and irregular variables associated with the asymptotic giant branch than in Mira variables or supergiants. This family of dust features also tends to be stronger in systems with lower infrared excesses and thus lower mass-loss rates. We hypothesize that the dust features arise from crystalline forms of alumina (13 μm) and silicates (20 and 28 μm). Based on observations with the ISO, a European Space Agency (ESA) project with instruments funded by ESA member states (especially the Principal Investigator countries: France, Germany, the Netherlands, and the United Kingdom) and with the participation of the Institute of Space and Astronautical Science (ISAS) and the National Aeronautics and Space Administration (NASA).

40 CFR 51.358 - Test equipment.

Code of Federal Regulations, 2013 CFR

2013-07-01

... vehicle description, including license plate number, vehicle identification number, and odometer reading... emissions test on subject vehicles. (a) Performance features of computerized emission test systems. The...) Emission test equipment shall be capable of testing all subject vehicles and shall be updated from time to...

40 CFR 51.358 - Test equipment.

Code of Federal Regulations, 2011 CFR

2011-07-01

... vehicle description, including license plate number, vehicle identification number, and odometer reading... emissions test on subject vehicles. (a) Performance features of computerized emission test systems. The...) Emission test equipment shall be capable of testing all subject vehicles and shall be updated from time to...

40 CFR 51.358 - Test equipment.

Code of Federal Regulations, 2012 CFR

2012-07-01

... vehicle description, including license plate number, vehicle identification number, and odometer reading... emissions test on subject vehicles. (a) Performance features of computerized emission test systems. The...) Emission test equipment shall be capable of testing all subject vehicles and shall be updated from time to...

A slippery molecular assembly allows water as a self-erasable security marker

PubMed Central

Thirumalai, Rajasekaran; Mukhopadhyay, Rahul Dev; Praveen, Vakayil K.; Ajayaghosh, Ayyappanpillai

2015-01-01

Protection of currency and valuable documents from counterfeit continues to be a challenge. While there are many embedded security features available for document safety, they are not immune to forgery. Fluorescence is a sensitive property, which responds to external stimuli such as solvent polarity, temperature or mechanical stress, however practical use in security applications is hampered due to several reasons. Therefore, a simple and specific stimuli responsive security feature that is difficult to duplicate is of great demand. Herein we report the design of a fluorescent molecular assembly on which water behaves as a self-erasable security marker for checking the authenticity of documents at point of care. The underlying principle involves the disciplined self-assembly of a tailor-made fluorescent molecule, which initially form a weak blue fluorescence (λem = 425 nm, Φf = 0.13) and changes to cyan emission (λem = 488 nm,Φf = 0.18) in contact with water due to a reversible molecular slipping motion. This simple chemical tool, based on the principles of molecular self-assembly and fluorescence modulation, allows creation of security labels and optically masked barcodes for multiple documents authentication. PMID:25940779

A slippery molecular assembly allows water as a self-erasable security marker.

PubMed

Thirumalai, Rajasekaran; Mukhopadhyay, Rahul Dev; Praveen, Vakayil K; Ajayaghosh, Ayyappanpillai

2015-05-05

Protection of currency and valuable documents from counterfeit continues to be a challenge. While there are many embedded security features available for document safety, they are not immune to forgery. Fluorescence is a sensitive property, which responds to external stimuli such as solvent polarity, temperature or mechanical stress, however practical use in security applications is hampered due to several reasons. Therefore, a simple and specific stimuli responsive security feature that is difficult to duplicate is of great demand. Herein we report the design of a fluorescent molecular assembly on which water behaves as a self-erasable security marker for checking the authenticity of documents at point of care. The underlying principle involves the disciplined self-assembly of a tailor-made fluorescent molecule, which initially form a weak blue fluorescence (λem = 425 nm, Φf = 0.13) and changes to cyan emission (λem = 488 nm,Φf = 0.18) in contact with water due to a reversible molecular slipping motion. This simple chemical tool, based on the principles of molecular self-assembly and fluorescence modulation, allows creation of security labels and optically masked barcodes for multiple documents authentication.

Spectral Emissivity (6 - 38 µm) of Jupiter's Trojan Asteroids

NASA Astrophysics Data System (ADS)

Martin, Audrey; Emery, Joshua P.; Lindsay, Sean S.

2016-10-01

Jovian Trojan asteroids, located in Jupiter's stable Lagrange points, are an extensive population of primitive bodies in the Solar System. Previous work in the visible and NIR shows Trojans have featureless, red-sloped spectra and low albedos, making mineralogical characterization difficult. However, it has been shown that three Trojans exhibit silicate emissivity features in the thermal IR (6 - 38 μm Emery et al. 2006, Icarus 182). The detected features indicate the presence of fine-grained (micron-sized) silicate dust on the surfaces, and closely resemble spectral features measured of cometary comae. We hypothesize that Trojan surface mineralogy is fairly uniform and is similar to comet dust. The principal goal of this work is, therefore, to derive primary surface mineralogy from thermal emission spectra. We present thermal IR spectra of 12 Trojans observed with NASA's Spitzer space telescope, using the InfraRed Spectrograph (IRS) in Staring Mode from June 2006 to June 2007. Eight objects were observed over the 5.2 - 38 µm spectral range, and four objects over the 7.5 - 38 µm range. Using the NEATM thermal model, we have computed size, albedo, and beaming parameter for the 12 Trojans. Results for these physical parameters are comparable to those derived from WISE data (Grav et al. 2011, ApJ 742 (1); Grav et al. 2012, ApJ 759 (49)). There are, however, some discrepancies, especially with 2797 Teucer. The emissivity spectra fall into groups that directly correlate with the red and less-red spectral slope groupings described in Emery et al. (2011, ApJ, 141(1)). Strong 10 µm emission features appear in each object, suggesting the presence of fine-grained silicates. Features found between 12-13 µm, and 18-19 µm are also observed in all spectra. We will present these new Trojan asteroid data with mineralogical estimates derived from the emissivity spectra.

Simultaneous NuSTAR/Chandra Observations of the Bursting Pulsar GRO J1744-28 During its Third Reactivation

NASA Technical Reports Server (NTRS)

Younes, G.; Kouveliotou, C.; Grefenstette, B. W.; Tomsick, J. A.; Tennant, A.; Finger, M. H.; Furst, F.; Pottschmidt, K.; Bhalerao, V.; Boggs, S. E.;

ISM DUST GRAINS AND N-BAND SPECTRAL VARIABILITY IN THE SPATIALLY RESOLVED SUBARCSECOND BINARY UY Aur

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

Skemer, Andrew J.; Close, Laird M.; Hinz, Philip M.

2010-03-10

The 10 {mu}m silicate feature is an essential diagnostic of dust-grain growth and planet formation in young circumstellar disks. The Spitzer Space Telescope has revolutionized the study of this feature, but due to its small (85 cm) aperture, it cannot spatially resolve small/medium-separation binaries ({approx}<3''; {approx}< 420 AU) at the distances of the nearest star-forming regions ({approx}140 pc). Large, 6-10 m ground-based telescopes with mid-infrared instruments can resolve these systems. In this paper, we spatially resolve the 0.''88 binary, UY Aur, with MMTAO/BLINC-MIRAC4 mid-infrared spectroscopy. We then compare our spectra to Spitzer/IRS (unresolved) spectroscopy, and resolved images from IRTF/MIRAC2, Keck/OSCIR,more » and Gemini/Michelle, which were taken over the past decade. We find that UY Aur A has extremely pristine, interstellar medium (ISM)-like grains and that UY Aur B has an unusually shaped silicate feature, which is probably the result of blended emission and absorption from foreground extinction in its disk. We also find evidence for variability in both UY Aur A and UY Aur B by comparing synthetic photometry from our spectra with resolved imaging from previous epochs. The photometric variability of UY Aur A could be an indication that the silicate emission itself is variable, as was recently found in EX Lupi. Otherwise, the thermal continuum is variable, and either the ISM-like dust has never evolved, or it is being replenished, perhaps by UY Aur's circumbinary disk.« less

Allocating emissions to 4 km and 1 km horizontal spatial resolutions and its impact on simulated NOx and O3 in Houston, TX

NASA Astrophysics Data System (ADS)

Pan, Shuai; Choi, Yunsoo; Roy, Anirban; Jeon, Wonbae

2017-09-01

A WRF-SMOKE-CMAQ air quality modeling system was used to investigate the impact of horizontal spatial resolution on simulated nitrogen oxides (NOx) and ozone (O3) in the Greater Houston area (a non-attainment area for O3). We employed an approach recommended by the United States Environmental Protection Agency to allocate county-based emissions to model grid cells in 1 km and 4 km horizontal grid resolutions. The CMAQ Integrated Process Rate analyses showed a substantial difference in emissions contributions between 1 and 4 km grids but similar NOx and O3 concentrations over urban and industrial locations. For example, the peak NOx emissions at an industrial and urban site differed by a factor of 20 for the 1 km and 8 for the 4 km grid, but simulated NOx concentrations changed only by a factor of 1.2 in both cases. Hence, due to the interplay of the atmospheric processes, we cannot expect a similar level of reduction of the gas-phase air pollutants as the reduction of emissions. Both simulations reproduced the variability of NASA P-3B aircraft measurements of NOy and O3 in the lower atmosphere (from 90 m to 4.5 km). Both simulations provided similar reasonable predictions at surface, while 1 km case depicted more detailed features of emissions and concentrations in heavily polluted areas, such as highways, airports, and industrial regions, which are useful in understanding the major causes of O3 pollution in such regions, and to quantify transport of O3 to populated communities in urban areas. The Integrated Reaction Rate analyses indicated a distinctive difference of chemistry processes between the model surface layer and upper layers, implying that correcting the meteorological conditions at the surface may not help to enhance the O3 predictions. The model-observation O3 bias in our studies (e.g., large over-prediction during the nighttime or along Gulf of Mexico coastline), were due to uncertainties in meteorology, chemistry or other processes. Horizontal grid resolution is unlikely the major contributor to these biases.

Phase-Resolved Spectroscopy of the Low-Mass X-ray Binary V801 Ara

NASA Astrophysics Data System (ADS)

Brauer, Kaley; Vrtilek, Saeqa Dil; Peris, Charith; McCollough, Michael

2018-06-01

We present phase-resolved optical spectra of the low mass X-ray binary system V801 Ara. The spectra, obtained in 2014 with IMACS on the Magellan/Baade telescope at Las Campanas Observatory, cover the full binary orbit of 3.8 hours. They contain strong emission features allowing us to map the emission of Hα, Hβ, He II λ4686, and the Bowen blend at λ4640. The radial velocity curves of the Bowen blend shows significantly stronger modulation at the orbital period than Hα as expected for the former originating on the secondary with the latter consistent with emission dominated by the disk. Our tomograms of Hα and Hβ are the most detailed studies of these lines for V801 to date and they clearly detect the accretion disk. The Hβ emission extends to higher velocities than Hα, suggesting emission from closer to the neutron star and differentiating temperature variance in the accretion disk for the first time. The center of the accretion disk appears offset from the center-of-mass of the neutron star as has been seen in several other X-ray binaries. This is often interpreted to imply disk eccentricity. Our tomograms do not show strong evidence for a hot spot at the point where the accretion stream hits the disk. This could imply a reduced accretion rate or could be due to the spot being drowned out by bright accretion flow around it. There is enhanced emission further along the disk, however, which implies gas stream interaction downstream of the hot spot.

Ionospheric-thermospheric UV tomography: 3. A multisensor technique for creating full-orbit reconstructions of atmospheric UV emission

NASA Astrophysics Data System (ADS)

Hei, Matthew A.; Budzien, Scott A.; Dymond, Kenneth F.; Nicholas, Andrew C.; Paxton, Larry J.; Schaefer, Robert K.; Groves, Keith M.

2017-07-01

We present the Volume Emission Rate Tomography (VERT) technique for inverting satellite-based, multisensor limb and nadir measurements of atmospheric ultraviolet emission to create whole-orbit reconstructions of atmospheric volume emission rate. The VERT approach is more general than previous ionospheric tomography methods because it can reconstruct the volume emission rate field irrespective of the particular excitation mechanisms (e.g., radiative recombination, photoelectron impact excitation, and energetic particle precipitation in auroras); physical models are then applied to interpret the airglow. The technique was developed and tested using data from the Special Sensor Ultraviolet Limb Imager and Special Sensor Ultraviolet Spectrographic Imager instruments aboard the Defense Meteorological Satellite Program F-18 spacecraft and planned for use with upcoming remote sensing missions. The technique incorporates several features to optimize the tomographic solutions, such as the use of a nonnegative algorithm (Richardson-Lucy, RL) that explicitly accounts for the Poisson statistics inherent in optical measurements, capability to include extinction effects due to resonant scattering and absorption of the photons from the lines of sight, a pseudodiffusion-based regularization scheme implemented between iterations of the RL code to produce smoother solutions, and the capability to estimate error bars on the solutions. Tests using simulated atmospheric emissions verify that the technique performs well in a variety of situations, including daytime, nighttime, and even in the challenging terminator regions. Lastly, we consider ionospheric nightglow and validate reconstructions of the nighttime electron density against Advanced Research Project Agency (ARPA) Long-range Tracking and Identification Radar (ALTAIR) incoherent scatter radar data.

The Spectrum of Isotropic Diffuse Gamma-Ray Emission Between 100 Mev and 820 Gev

NASA Technical Reports Server (NTRS)

Ackermann, M.; Ajello, M.; Albert, A.; Atwood, W. B.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Brandt, T. J.; Hays, E.;

N2O, NO, N2 and CO2 emissions from tropical savanna and grassland of northern Australia: an incubation experiment with intact soil cores

NASA Astrophysics Data System (ADS)

Werner, C.; Reiser, K.; Dannenmann, M.; Hutley, L. B.; Jacobeit, J.; Butterbach-Bahl, K.

2014-11-01

Strong seasonal variability of hygric and thermal soil conditions are a defining environmental feature in northern Australia. However, how such changes affect the soil-atmosphere exchange of nitrous oxide (N2O), nitric oxide (NO) and dinitrogen (N2) is still not well explored. By incubating intact soil cores from four sites (three savanna, one pasture) under controlled soil temperatures (ST) and soil moisture (SM) we investigated the release of the trace gas fluxes of N2O, NO and carbon dioxide (CO2). Furthermore, the release of N2 due to denitrification was measured using the helium gas flow soil core technique. Under dry pre-incubation conditions NO and N2O emissions were very low (<7.0 ± 5.0 μg NO-N m-2 h-1; <0.0 ± 1.4 μg N2O-N m-2 h-1) or in the case of N2O, even a net soil uptake was observed. Substantial NO (max: 306.5 μg N m-2 h-1) and relatively small N2O pulse emissions (max: 5.8 ± 5.0 μg N m-2 h-1) were recorded following soil wetting, but these pulses were short lived, lasting only up to 3 days. The total atmospheric loss of nitrogen was generally dominated by N2 emissions (82.4-99.3% of total N lost), although NO emissions contributed almost 43.2% to the total atmospheric nitrogen loss at 50% SM and 30 °C ST incubation settings (the contribution of N2 at these soil conditions was only 53.2%). N2O emissions were systematically higher for 3 of 12 sample locations, which indicates substantial spatial variability at site level, but on average soils acted as weak N2O sources or even sinks. By using a conservative upscale approach we estimate total annual emissions from savanna soils to average 0.12 kg N ha-1 yr-1 (N2O), 0.68 kg N ha-1 yr-1 (NO) and 6.65 kg N ha-1 yr-1 (N2). The analysis of long-term SM and ST records makes it clear that extreme soil saturation that can lead to high N2O and N2 emissions only occurs a few days per year and thus has little impact on the annual total. The potential contribution of nitrogen released due to pulse events compared to the total annual emissions was found to be of importance for NO emissions (contribution to total: 5-22%), but not for N2O emissions. Our results indicate that the total gaseous release of nitrogen from these soils is low and clearly dominated by loss in the form of inert nitrogen. Effects of seasonally varying soil temperature and moisture were detected, but were found to be low due to the small amounts of available nitrogen in the soils (total nitrogen <0.1%).

Impact of active geomagnetic conditions on stimulated radiation during ionospheric second electron gyroharmonic heating

NASA Astrophysics Data System (ADS)

Bordikar, M. R.; Scales, W. A.; Mahmoudian, A.; Kim, H.; Bernhardt, P. A.; Redmon, R.; Samimi, A. R.; Brizcinski, S.; McCarrick, M. J.

2014-01-01

Recently, narrowband emissions ordered near the H+ (proton) gyrofrequency (fcH) were reported in the stimulated electromagnetic emission (SEE) spectrum during active geomagnetic conditions. This work presents new observations and theoretical analysis of these recently discovered emissions. These emission lines are observed in the stimulated electromagnetic emission (SEE) spectrum when the transmitter is tuned near the second electron gyroharmonic frequency (2fce) during recent ionospheric modification experiments at the High Frequency Active Auroral Research (HAARP) facility near Gakona, Alaska. The spectral lines are typically shifted below and above the pump wave frequency by harmonics of a frequency roughly 10% less than fcH (≈ 800 Hz) with a narrow emission bandwidth less than the O+ gyrofrequency (≈ 50 Hz). However, new observations and analysis of emission lines ordered by a frequency approximately 10% greater than fcH are presented here for the first time as well. The interaction altitude for the heating for all the observations is in the range of 160 km up to 200 km. As described previously, proton precipitation due to active geomagnetic conditions is considered as the reason for the presence of H+ ions known to be a minor background constituent in this altitude region. DMSP satellite observations over HAARP during the heating experiments and ground-based magnetometer and riometer data validate active geomagnetic conditions. The theory of parametric decay instability in multi-ion component plasma including H+ ions as a minority species described in previous work is expanded in light of simultaneously observed preexisting SEE features to interpret the newly reported observations. Impact of active geomagnetic conditions on the SEE spectrum as a diagnostic tool for proton precipitation event characterization is discussed.

THE ORIGIN OF THE HOT GAS IN THE GALACTIC HALO: TESTING GALACTIC FOUNTAIN MODELS' X-RAY EMISSION

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

Henley, David B.; Shelton, Robin L.; Kwak, Kyujin

2015-02-20

We test the X-ray emission predictions of galactic fountain models against XMM-Newton measurements of the emission from the Milky Way's hot halo. These measurements are from 110 sight lines, spanning the full range of Galactic longitudes. We find that a magnetohydrodynamical simulation of a supernova-driven interstellar medium, which features a flow of hot gas from the disk to the halo, reproduces the temperature but significantly underpredicts the 0.5-2.0 keV surface brightness of the halo (by two orders of magnitude, if we compare the median predicted and observed values). This is true for versions of the model with and without anmore » interstellar magnetic field. We consider different reasons for the discrepancy between the model predictions and the observations. We find that taking into account overionization in cooled halo plasma, which could in principle boost the predicted X-ray emission, is unlikely in practice to bring the predictions in line with the observations. We also find that including thermal conduction, which would tend to increase the surface brightnesses of interfaces between hot and cold gas, would not overcome the surface brightness shortfall. However, charge exchange emission from such interfaces, not included in the current model, may be significant. The faintness of the model may also be due to the lack of cosmic ray driving, meaning that the model may underestimate the amount of material transported from the disk to the halo. In addition, an extended hot halo of accreted material may be important, by supplying hot electrons that could boost the emission of the material driven out from the disk. Additional model predictions are needed to test the relative importance of these processes in explaining the observed halo emission.« less

The Origin of the Hot Gas in the Galactic Halo: Testing Galactic Fountain Models' X-Ray Emission

NASA Astrophysics Data System (ADS)

Henley, David B.; Shelton, Robin L.; Kwak, Kyujin; Hill, Alex S.; Mac Low, Mordecai-Mark

2015-02-01

We test the X-ray emission predictions of galactic fountain models against XMM-Newton measurements of the emission from the Milky Way's hot halo. These measurements are from 110 sight lines, spanning the full range of Galactic longitudes. We find that a magnetohydrodynamical simulation of a supernova-driven interstellar medium, which features a flow of hot gas from the disk to the halo, reproduces the temperature but significantly underpredicts the 0.5-2.0 keV surface brightness of the halo (by two orders of magnitude, if we compare the median predicted and observed values). This is true for versions of the model with and without an interstellar magnetic field. We consider different reasons for the discrepancy between the model predictions and the observations. We find that taking into account overionization in cooled halo plasma, which could in principle boost the predicted X-ray emission, is unlikely in practice to bring the predictions in line with the observations. We also find that including thermal conduction, which would tend to increase the surface brightnesses of interfaces between hot and cold gas, would not overcome the surface brightness shortfall. However, charge exchange emission from such interfaces, not included in the current model, may be significant. The faintness of the model may also be due to the lack of cosmic ray driving, meaning that the model may underestimate the amount of material transported from the disk to the halo. In addition, an extended hot halo of accreted material may be important, by supplying hot electrons that could boost the emission of the material driven out from the disk. Additional model predictions are needed to test the relative importance of these processes in explaining the observed halo emission.

Atmospheric emission of mercury due to combustion of steam coal and domestic coal in China

NASA Astrophysics Data System (ADS)

Wang, Shaobin; Luo, Kunli

2017-08-01

To study the mercury emission due to the combustion of steam coal and domestic coal in China, we analyzed the mercury contents of coal, fly ash, bottom ash and sluicing water in thermal power plants, steam boilers as well as domestic coal-stoves, in Shaanxi, Shanxi, Shandong and Yunnan Provinces. This study conduct an estimate of the Hg emission rates from steam coal and domestic coal combustion based on the method of mass distribution ratio of fly ash and bottom ash. The results show that the Hg emission rate of coal combustion in thermal power plants is about 50.21% (electrostatic precipitators + wet flue gas desulfurization), and that in heating boilers is about 67.23%, and 92.28% in industrial boilers without flue gas desulphurisation equipment. Furthermore, Hg emission rate is 83.61% due to domestic coal combustion in coal-stoves. The Hg emission amount into the atmosphere from power and heat generation, industrial boilers, domestic coal-stoves and spontaneous combustion of coal gangue is roughly estimated to be 133 ± 4, 100 ± 17, 11 ± 0.1 and 47 ± 26 tons in China in 2014, respectively, and the total Hg emission amount from this paper is estimated at 292 tons. The trends of Hg emission in China from 1991 to 2014 show an accelerating growth after 2002. The proportion of mercury emission due to thermal power, heating generation and industrial energy utilization continuously increased. The atmospheric emission of mercury due to combustion of steam coal, domestic coal and coal gangue accounts nearly 50% in total anthropogenic Hg emissions in China, indicating one of the largest sources of Hg emission in China which should draw more public and scientific attention in the future.

The Infrared Spectra of Polycyclic Aromatic Hydrocarbons with Excess Peripheral H Atoms (H(sub n)-PAHs) and their Relation to the 3.4 and 6.9 Micrometer PAH Emission Features

NASA Technical Reports Server (NTRS)

Sandford, Scott A.; Bernstein, Max P.; Materese, Christopher K.

2013-01-01

A population of polycyclic aromatic hydrocarbons (PAHs) and related materials are thought to be responsible for the family of infrared emission features that are seen towards a wide variety of astrophysical environments. A potentially important subclass of these materials are polycyclic aromatic hydrocarbons whose edges contain excess H atoms (H(sub n)-PAHs). While it has been suggested that this type of compound may be present in the interstellar population, it has been difficult to properly assess this possibility because of a lack of suitable infrared laboratory spectra to assist with analysis of the astronomical data. We present the 4000-500 cm(exp -1) (2.5-20 micrometers) infrared spectra of 23 H(sub n)-PAHs and related molecules isolated in argon matrices, under conditions suitable for use in the interpretation of astronomical data. The spectra of molecules with mixed aromatic and aliphatic domains show unique characteristics that distinguish them from their fully aromatic PAH equivalents. We discuss the changes to the spectra of these types of molecules as they transition from fully aromatic to fully aliphatic forms. The implications for the interpretation of astronomical spectra are discussed with specific emphasis on the 3.4 and 6.9 micrometer features. Laboratory data is compared with emission spectra from IRAS 21282+5050, an object with normal PAH emission features, in addition to IRAS 22272+5435 and IRAS 0496+3429, two protoplanetary nebulae with abnormally large 3.4 micrometer features. We show that 'normal' PAH emission objects contain relatively few H(sub n)-PAHs in their emitter populations, but less evolved protoplanetary nebulae may contain significant abundances of these molecules.

The Infrared Spectra of Polycyclic Aromatic Hydrocarbons with Excess Peripheral H Atoms (Hn-PAHs) and their Relation to the 3.4 and 6.9 µm PAH Emission Features

PubMed Central

Sandford, Scott A.; Bernstein, Max P.; Materese, Christopher K.

2015-01-01

Polycyclic aromatic hydrocarbons (PAHs) are likely responsible for the family of infrared emission features seen in a wide variety of astrophysical environments. A potentially important subclass of these materials are PAHs whose edges contain excess H atoms (Hn-PAHs). This type of compound may be present in space, but it has been difficult to assess this possibility because of a lack of suitable laboratory spectra to assist with analysis of astronomical data. We present 4000-500 cm−1 (2.5–20 µm) infrared spectra of 23 Hn-PAHs and related molecules isolated in argon matrices under conditions suitable for interpretation of astronomical data. Spectra of molecules with mixed aromatic and aliphatic domains show characteristics that distinguish them from fully aromatic PAH equivalents. Two major changes occur as PAHs become more hydrogenated: (1) aromatic C-H stretching bands near 3.3 µm weaken and are replaced with stronger aliphatic bands near 3.4 µm, and (2) aromatic C-H out-of-plane bending mode bands in the 11–15 µm region shift and weaken concurrent with growth of a strong aliphatic -CH2-deformation mode near 6.9 µm. Implications for interpreting astronomical spectra are discussed with emphasis on the 3.4 and 6.9 µm features. Laboratory data is compared with emission spectra from IRAS 21282+5050, an object with normal PAH emission features, and IRAS 22272+5435 and IRAS 0496+3429, two protoplanetary nebulae with abnormally large 3.4 µm features. We show that ‘normal’ PAH emission objects contain relatively few Hn-PAHs in their emitter populations, but less evolved protoplanetary nebulae may contain significant abundances of these molecules. PMID:26435553

Soil cover patterns and SOC dynamics impacts on the soil processes, land management and ecosystem services in Central Region of Russia

NASA Astrophysics Data System (ADS)

Vasenev, Ivan; Chernikov, Vladimir; Yashin, Ivan; Geraskin, Mikhail; Morev, Dmitriy

2014-05-01

In the Central Region of Russia (CRR) the soil cover patterns usually play the very important role in the soil forming and degradation processes (SFP & SDP) potential and current rates, soil organic carbon (SOC) dynamics and pools, greenhouse gases (GHG) emissions and soluble SOC fluxes that we need take into attention for better assessment of the natural and especially man-changed ecosystems' services and for best land-use practices development. Central Region of Russia is the biggest one in RF according to its population and role in the economy. CRR is characterized by high spatial variability of soil cover due to as original landscape heterogeneity as complicated history of land-use practices during last 700 years. Our long-term researches include the wide zonal-provincial set of representative ecosystems and soil cover patterns with different types and history of land-use (forest, meadow-steppe and agricultural ones) from middle-taiga to steppe zones with different level of continentality. The carried out more than 30-years region- and local-scale researches of representative natural and rural landscapes in Tver', Yaroslavl', Kaluga, Moscow, Vladimir, Saransk (Mordovia), Kursk, Orel, Tambov, Voronezh and Saratov oblasts give us the interregional multi-factorial matrix of elementary soil cover patterns (ESCP) with different soil forming and degradation processes rates and soil organic carbon dynamics due to regionally specific soil-geomorphologic features, environmental and dominated microclimate conditions, land-use current practices and history. The validation and ranging of the limiting factors of SFP and SDP develop¬ment, soil carbon dynamics and sequestration potential, ecosystem (agroecosystem) principal services, land functional qualities and agroecological state have been done for dominating and most dynamical components of ESCP regional-typological forms - with application of SOC structure analysis, regional and local GIS, soil spatial patterns detail mapping, traditional regression kriging, correlation tree models and DSS adapted to concrete region and agrolandscape conditions. The outcomes of statistical process modeling show the essential amplification of erosion, dehumification, CO2, CH4 and N2O emission, soluble SOC fluxes, acidification or alkalization, disaggregation and overcompaction processes due to violation of environmentally sound land-use systems and traditional balances of organic matter, nutrients, Ca and Na in agrolandscapes. Due to long-term intensive and out-of-balance land-use practices the most zonal soils and soil cover pattern essentially lost not only their unique natural features (humus horizons depth till 1 m and more in case of Chernozems, 2-6 % of SOC and favorable agrophysical features), but ecosystem services and ecological functions including terrestrial ecosystem carbon balance and the GHG fluxes control. Key-site monitoring results and regional generalized data showed 1-1.5% SOC lost during last 50 years period and active processes of CO2 emission and humus profile eluvial-illuvial redistribution too. A drop of Corg content below threshold "humus limiting content" values (for different soils they vary from 1 to 3-4% of SOC) considerably reduces effectiveness of used fertilizers and possibility of sustai¬nable agronomy here. Forest-steppe Chernozems are usually characterized by higher stability than steppe ones. The ratio between erosive and biological losses in humus supplies can be ten-tatively estimated as fifty-fifty with strong spatial variability due to slope and land-use parameters. These processes have essentially different sets of environmental consequences and ecosystem services that we need to understand in frame of environmental and agroecological problems development prediction.

Fine flow structures in the transition region small-scale loops

NASA Astrophysics Data System (ADS)

Yan, L.; Peter, H.; He, J.; Wei, Y.

2016-12-01

The observation and model have suggested that the transition region EUV emission from the quiet sun region is contributed by very small scale loops which have not been resolved. Recently, the observation from IRIS has revealed that this kind of small scale loops. Based on the high resolution spectral and imaging observation from IRIS, much more detail work needs to be done to reveal the fine flow features in this kind of loop to help us understand the loop heating. Here, we present a detail statistical study of the spatial and temporal evolution of Si IV line profiles of small scale loops and report the spectral features: there is a transition from blue (red) wing enhancement dominant to red (blue) wing enhancement dominant along the cross-section of the loop, which is independent of time. This feature appears as the loop appear and disappear as the loop un-visible. This is probably the signature of helical flow along the loop. The result suggests that the brightening of this kind of loop is probably due to the current dissipation heating in the twisted magnetic field flux tube.

Density and temperature structure over northern Europe

NASA Technical Reports Server (NTRS)

Philbrick, C. R.; Schmidlin, F. J.; Grossmann, K. U.; Lange, G.; Offermann, D.; Baker, K. D.; Krankowsky, D.; Von Zahn, U.

1985-01-01

During the Energy Budget Campaign, a number of profiles of the density and temperature were obtained to study the structure and variability of the atmosphere. The measurements were made using rocketborne instrumentation launched from Esrange, Sweden, and Andoya Rocket Range, Norway, during November and December 1980. The techniques included meteorological temperature sondes, passive falling sphere, accelerometer instrumented falling spheres, density gauges, mass spectrometers and infrared emission experiments. The instruments provided data covering the altitude range from 20 to 150 km. The measurements were made during periods which have been grouped into three categories by level of geomagnetic activity. Analysis has been made to compare the results and to examine the wave features and variations in the vertical profiles for scales ranging between hundreds of meters and tens of kilometers. Most of the features observed fit qualitatively within the range expected for internal gravity waves. However, the features in the profiles during one of the measurement periods are unusual and may be due to aurorally generated shock waves. The geomagnetic storm conditions caused temperature increases in the lower thermosphere which maximized in the 120-140 km region.

In situ high temperature oxidation analysis of Zircaloy-4 using acoustic emission coupled with thermogravimetry

NASA Astrophysics Data System (ADS)

Omar, Al Haj; Véronique, Peres; Eric, Serris; François, Grosjean; Jean, Kittel; François, Ropital; Michel, Cournil

2015-06-01

Zircaloy-4 oxidation behavior at high temperature (900 °C), which can be reached in case of severe accidental situations in nuclear pressurised water reactor, was studied using acoustic emission analysis coupled with thermogravimetry. Two different atmospheres were used to study the oxidation of Zircaloy-4: (a) helium and pure oxygen, (b) helium and oxygen combined with slight addition of air. The experiments with 20% of oxygen confirm the dependence on oxygen anions diffusion in the oxide scale. Under a mixture of oxygen and air in helium, an acceleration of the corrosion was observed due to the detrimental effect of nitrogen. The kinetic rate increased significantly after a kinetic transition (breakaway). This acceleration was accompanied by an acoustic emission activity. Most of the acoustic emission bursts were recorded after the kinetic transition (post-transition) or during the cooling of the sample. The characteristic features of the acoustic emission signals appear to be correlated with the different populations of cracks and their occurrence in the ZrO2 layer or in the α-Zr(O) layer. Acoustic events were recorded during the isothermal dwell time at high temperature under air. They were associated with large cracks in the zirconia porous layer. Acoustic events were also recorded during cooling after oxidation tests both under air or oxygen. For the latter, cracks were observed in the oxygen enriched zirconium metal phase and not in the dense zirconia layer after 5 h of oxidation.

The IR emission features - Emission from PAH molecules and amorphous carbon particles

NASA Technical Reports Server (NTRS)

Allamandola, L. J.; Tielens, A. G. G. M.; Barker, J. R.

1987-01-01

Given the current understanding of polycyclic aromatic hydrocarbons (PAHs), the spectroscopic data suggest that are at least two components which contribute to the interstellar emission spectrum: (1) free molecule-sized PAHs producing the narrow features and (2) amorphous carbon particles (which are primarily composed of an irregular 'lattice' of PAHs) contributing to the broad underlying components. An exact treatment of the IR fluorescence from highly vibrationally excited large molecules demonstrates that species containing between 20 and 30 carbon atoms are responsible for the narrow features, although the spectra match more closely with the spectra of amorphous carbon particles. It is concluded that, since little is known about the spectroscopic properties of free PAHs and PAH clusters, much laboratory work is required along with an observational program focusing on the spatial characteristics of the spectra.

Silicate Emission in the TW Hydrae Association

NASA Astrophysics Data System (ADS)

Sitko, Michael L.; Lynch, David K.; Russell, Ray W.

2000-11-01

The TW Hydrae association is the nearest young stellar association. Among its members are HD 98800, HR 4796A, and TW Hydrae itself, the nearest known classical T Tauri star. We have observed these three stars spectroscopically between 3 and 13 μm. In TW Hya, the spectrum shows a silicate emission feature that is similar to many other young stars' with protostellar disks. The 11.2 μm feature indicative of significant amounts of crystalline olivine is not as strong as in some young stars and solar system comets. In HR 4796A, the thermal emission in the silicate feature is very weak, suggesting little in the way of (small silicate) grains near the star. The silicate band of HD 98800 (observed by us, but also reported by Sylvester & Skinner) is intermediate in strength between TW Hya and HR 4796A.

On- and off-axis spectral emission features from laser-produced gas breakdown plasmas

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

Harilal, S. S.; Skrodzki, P. J.; Miloshevsky, A.

Laser-heated gas breakdown plasmas or sparks emit profoundly in the ultraviolet and visible region of the electromagnetic spectrum with contributions from ionic, atomic, and molecular species. Laser created kernels expand into a cold ambient with high velocities during its early lifetime followed by confinement of the plasma kernel and eventually collapse. However, the plasma kernels produced during laser breakdown of gases are also capable of exciting and ionizing the surrounding ambient medium. Two mechanisms can be responsible for excitation and ionization of surrounding ambient: viz. photoexcitation and ionization by intense ultraviolet emission from the sparks produced during the early timesmore » of its creation and/or heating by strong shocks generated by the kernel during its expansion into the ambient. In this study, an investigation is made on the spectral features of on- and off-axis emission features of laser-induced plasma breakdown kernels generated in atmospheric pressure conditions with an aim to elucidate the mechanisms leading to ambient excitation and emission. Pulses from an Nd:YAG laser emitting at 1064 nm with 6 ns pulse duration are used to generate plasma kernels. Laser sparks were generated in air, argon, and helium gases to provide different physical properties of expansion dynamics and plasma chemistry considering the differences in laser absorption properties, mass density and speciation. Point shadowgraphy and time-resolved imaging were used to evaluate the shock wave and spark self-emission morphology at early and late times while space and time resolved spectroscopy is used for evaluating the emission features as well as for inferring plasma fundaments at on- and off-axis. Structure and dynamics of the plasma kernel obtained using imaging techniques are also compared to numerical simulations using computational fluid dynamics code. The emission from the kernel showed that spectral features from ions, atoms and molecules are separated in time with an early time temperatures and densities in excess of 35000 K and 4×10 18 /cm 3 with an existence of thermal equilibrium. However, the emission from the off-kernel positions from the breakdown plasmas showed enhanced ultraviolet radiation with the presence of N 2 bands and represented by non-LTE conditions. Finally, our results also highlight that the ultraviolet radiation emitted during early time of spark evolution is the predominant source of the photo-excitation of the surrounding medium.« less

On- and off-axis spectral emission features from laser-produced gas breakdown plasmas

DOE PAGES

Harilal, S. S.; Skrodzki, P. J.; Miloshevsky, A.; ...

2017-06-01

Laser-heated gas breakdown plasmas or sparks emit profoundly in the ultraviolet and visible region of the electromagnetic spectrum with contributions from ionic, atomic, and molecular species. Laser created kernels expand into a cold ambient with high velocities during its early lifetime followed by confinement of the plasma kernel and eventually collapse. However, the plasma kernels produced during laser breakdown of gases are also capable of exciting and ionizing the surrounding ambient medium. Two mechanisms can be responsible for excitation and ionization of surrounding ambient: viz. photoexcitation and ionization by intense ultraviolet emission from the sparks produced during the early timesmore » of its creation and/or heating by strong shocks generated by the kernel during its expansion into the ambient. In this study, an investigation is made on the spectral features of on- and off-axis emission features of laser-induced plasma breakdown kernels generated in atmospheric pressure conditions with an aim to elucidate the mechanisms leading to ambient excitation and emission. Pulses from an Nd:YAG laser emitting at 1064 nm with 6 ns pulse duration are used to generate plasma kernels. Laser sparks were generated in air, argon, and helium gases to provide different physical properties of expansion dynamics and plasma chemistry considering the differences in laser absorption properties, mass density and speciation. Point shadowgraphy and time-resolved imaging were used to evaluate the shock wave and spark self-emission morphology at early and late times while space and time resolved spectroscopy is used for evaluating the emission features as well as for inferring plasma fundaments at on- and off-axis. Structure and dynamics of the plasma kernel obtained using imaging techniques are also compared to numerical simulations using computational fluid dynamics code. The emission from the kernel showed that spectral features from ions, atoms and molecules are separated in time with an early time temperatures and densities in excess of 35000 K and 4×1018 /cm3 with an existence of thermal equilibrium. However, the emission from the off-kernel positions from the breakdown plasmas showed enhanced ultraviolet radiation with the presence of N2 bands and represented by non-LTE conditions. Our results also highlight that the ultraviolet radiation emitted during early time of spark evolution is the predominant source of the photo-excitation of the surrounding medium.« less

40 CFR 51.358 - Test equipment.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 2 2014-07-01 2014-07-01 false Test equipment. 51.358 Section 51.358....358 Test equipment. Computerized emission test systems are required for performing an official emissions test on subject vehicles. (a) Performance features of computerized emission test systems. The...

40 CFR 265.1090 - Recordkeeping requirements.

Code of Federal Regulations, 2010 CFR

2010-07-01

... applicable to the facility. Except for air emission control equipment design documentation and information... the operating record for a minimum of 3 years. Air emission control equipment design documentation... explain: How use of the required air emission controls on the tanks would affect the tank design features...

40 CFR 265.1090 - Recordkeeping requirements.

Code of Federal Regulations, 2011 CFR

2011-07-01

... applicable to the facility. Except for air emission control equipment design documentation and information... the operating record for a minimum of 3 years. Air emission control equipment design documentation... explain: How use of the required air emission controls on the tanks would affect the tank design features...

40 CFR 265.1090 - Recordkeeping requirements.

Code of Federal Regulations, 2012 CFR

2012-07-01

... applicable to the facility. Except for air emission control equipment design documentation and information... the operating record for a minimum of 3 years. Air emission control equipment design documentation... explain: How use of the required air emission controls on the tanks would affect the tank design features...

40 CFR 51.358 - Test equipment.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 2 2010-07-01 2010-07-01 false Test equipment. 51.358 Section 51.358....358 Test equipment. Computerized emission test systems are required for performing an official emissions test on subject vehicles. (a) Performance features of computerized emission test systems. The...

Modeling the emission, transport and deposition of contaminated dust from a mine tailing site.

PubMed

Stovern, Michael; Betterton, Eric A; Sáez, A Eduardo; Villar, Omar Ignacio Felix; Rine, Kyle P; Russell, Mackenzie R; King, Matt

2014-01-01

Mining operations are potential sources of airborne particulate metal and metalloid contaminants through both direct smelter emissions and wind erosion of mine tailings. The warmer, drier conditions predicted for the Southwestern US by climate models may make contaminated atmospheric dust and aerosols increasingly important, due to potential deleterious effects on human health and ecology. Dust emissions and dispersion of contaminants from the Iron King Mine tailings in Dewey-Humboldt, Arizona, a Superfund site, are currently being investigated through in situ field measurements and computational fluid dynamics modeling. These tailings are significantly contaminated with lead and arsenic with an average soil concentration of 1616 and 1420 ppm, respectively. Similar levels of these contaminants have also been measured in soil samples taken from the area surrounding the mine tailings. Using a computational fluid dynamics model, we have been able to model dust transport from the mine tailings to the surrounding region. The model includes a distributed Eulerian model to simulate fine aerosol transport and a Lagrangian approach to model fate and transport of larger particles. In order to improve the accuracy of the dust transport simulations both regional topographical features and local weather patterns have been incorporated into the model simulations.

Acoustic Transmitters for Underwater Neutrino Telescopes

PubMed Central

Ardid, Miguel; Martínez-Mora, Juan A.; Bou-Cabo, Manuel; Larosa, Giuseppina; Adrián-Martínez, Silvia; Llorens, Carlos D.

2012-01-01

In this paper acoustic transmitters that were developed for use in underwater neutrino telescopes are presented. Firstly, an acoustic transceiver has been developed as part of the acoustic positioning system of neutrino telescopes. These infrastructures are not completely rigid and require a positioning system in order to monitor the position of the optical sensors which move due to sea currents. To guarantee a reliable and versatile system, the transceiver has the requirements of reduced cost, low power consumption, high pressure withstanding (up to 500 bars), high intensity for emission, low intrinsic noise, arbitrary signals for emission and the capacity of acquiring and processing received signals. Secondly, a compact acoustic transmitter array has been developed for the calibration of acoustic neutrino detection systems. The array is able to mimic the signature of ultra-high-energy neutrino interaction in emission directivity and signal shape. The technique of parametric acoustic sources has been used to achieve the proposed aim. The developed compact array has practical features such as easy manageability and operation. The prototype designs and the results of different tests are described. The techniques applied for these two acoustic systems are so powerful and versatile that may be of interest in other marine applications using acoustic transmitters. PMID:22666022

Photoluminescence and contactless electroreflectance characterization of BexCd1-xSe alloys

NASA Astrophysics Data System (ADS)

Huang, P. J.; Huang, Y. S.; Firszt, F.; Meczynska, H.; Maksimov, O.; Tamargo, M. C.; Tiong, K. K.

2007-01-01

A detailed optical characterization of a Bridgman-grown wurtzite- (WZ-) type Be0.075Cd0.925Se mixed crystal and three zinc-blende (ZB) BexCd1-xSe epilayers grown by MBE on InP substrates has been carried out via photoluminescence (PL) and contactless electroreflectance (CER) in the temperature range of 15-400 K. The PL spectrum of the WZ-BeCdSe at low temperature consists of an exciton line, an edge emission feature due to recombination of donor-acceptor pairs, and a broad band related to recombination through deep-level defects, while the PL emission peaks of the ZB-BeCdSe epilayers show an asymmetric shape with a tail on the low-energy side. Various interband transitions, originating from the band edge and spin-orbit splitting critical points, of the samples have been observed in the CER spectra. The peak positions of the exciton emission lines in the PL spectra correspond quite well to the energies of the fundamental transitions determined from electromodulation data. The parameters that describe the temperature dependence of the fundamental and spin split-off bandgaps and the broadening function of the band-edge exciton are evaluated and discussed.

The Extraordinary Outburst in the Massive Protostellar System NGC 6334I-MM1: Emergence of Strong 6.7 GHz Methanol Masers

NASA Astrophysics Data System (ADS)

Hunter, T. R.; Brogan, C. L.; MacLeod, G. C.; Cyganowski, C. J.; Chibueze, J. O.; Friesen, R.; Hirota, T.; Smits, D. P.; Chandler, C. J.; Indebetouw, R.

2018-02-01

We report the first sub-arcsecond VLA imaging of 6 GHz continuum, methanol maser, and excited-state hydroxyl maser emission toward the massive protostellar cluster NGC 6334I following the recent 2015 outburst in (sub)millimeter continuum toward MM1, the strongest (sub)millimeter source in the protocluster. In addition to detections toward the previously known 6.7 GHz Class II methanol maser sites in the hot core MM2 and the UCHII region MM3 (NGC 6334F), we find new maser features toward several components of MM1, along with weaker features ∼1″ north, west, and southwest of MM1, and toward the nonthermal radio continuum source CM2. None of these areas have heretofore exhibited Class II methanol maser emission in three decades of observations. The strongest MM1 masers trace a dust cavity, while no masers are seen toward the strongest dust sources MM1A, 1B, and 1D. The locations of the masers are consistent with a combination of increased radiative pumping due to elevated dust grain temperature following the outburst, the presence of infrared photon propagation cavities, and the presence of high methanol column densities as indicated by ALMA images of thermal transitions. The nonthermal radio emission source CM2 (2″ north of MM1) also exhibits new maser emission from the excited 6.035 and 6.030 GHz OH lines. Using the Zeeman effect, we measure a line-of-sight magnetic field of +0.5 to +3.7 mG toward CM2. In agreement with previous studies, we also detect numerous methanol and excited OH maser spots toward the UCHII region MM3, with predominantly negative line-of-sight magnetic field strengths of ‑2 to ‑5 mG and an intriguing south–north field reversal.

Relationship of Topside Ionospheric Ion Outflows to Auroral Forms and Precipitations, Plasma Waves, and Convection Observed by POLAR

NASA Technical Reports Server (NTRS)

Hirahara, M.; Horwitz, J. L.; Moore, T. E.; Germany, G. A.; Spann, J. F.; Peterson, W. K.; Shelley, E. G.; Chandler, M. O.; Giles, B. L.; Craven, P. D.;

Relationship of Topside Ionospheric Ion Outflows to Auroral Forms and Precipitation, Plasma Waves, and Convection Observed by Polar

NASA Technical Reports Server (NTRS)

Hirahara, M.; Horwitz, J. L.; Moore, T. E.; Germany, G. A.; Spann, J. F.; Peterson, W. K.; Shelley, E. G.; Chandler, M. O.; Giles, B. L.; Craven, P. D.;

BROADBAND OBSERVATIONS OF HIGH REDSHIFT BLAZARS

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

Paliya, Vaidehi S.; Parker, M. L.; Fabian, A. C.

We present a multi-wavelength study of four high redshift blazars, S5 0014+81 ( z = 3.37), CGRaBS J0225+1846 ( z = 2.69), BZQ J1430+4205 ( z = 4.72), and 3FGL J1656.2−3303 ( z = 2.40) using quasi-simultaneous data from the Swift , Nuclear Spectroscopic Telescope Array ( NuSTAR ) and the Fermi -Large Area Telescope (LAT) and also archival XMM-Newton observations. Other than 3FGL J1656.2−3303, none of the sources were known as γ -ray emitters, and our analysis of ∼7.5 yr of LAT data reveals the first time detection of statistically significant γ -ray emission from CGRaBS J0225+1846. We generatemore » the broadband spectral energy distributions (SED) of all the objects, centering at the epoch of NuSTAR observations and reproduce them using a one-zone leptonic emission model. The optical−UV emission in all the objects can be explained by radiation from the accretion disk, whereas the X-ray to γ -ray windows of the SEDs are found to be dominated by inverse Compton scattering off the broad line region photons. All of them host black holes that are billions of solar masses. Comparing the accretion disk luminosity and the jet power of these sources with a large sample of blazars, we find them to occupy a high disk luminosity–jet power regime. We also investigate the X-ray spectral properties of the sources in detail with a major focus on studying the causes of soft X-ray deficit, a feature generally seen in high redshift radio-loud quasars. We summarize that this feature could be explained based on the intrinsic curvature in the jet emission rather than being due to the external effects predicted in earlier studies, such as host galaxy and/or warm absorption.« less

A Search for HI Self-Absorption in the SGPS

NASA Astrophysics Data System (ADS)

Kavars, D. W.; Dickey, J. D.; McClure-Griffiths, N. M.; Gaensler, B. M.; Green, A. J.

2003-12-01

Using data from the Southern Galactic Plane Survey(SGPS) we present a routine to search for cold HI clouds in the Galaxy, based on their HI self-absorption(HISA) signature. The data was obtained using the Australia Telescope Compact Array and the Parkes Radio Telescope. The SGPS, because of its good angular and velocity resolution, is excellent for searching for HISA clouds. We have already analyzed a few of the more prominent HISA features, finding spin temperatures, Ts ˜ 20K, column densities, NHI ˜ 2 x 1020}cm{-2, and optical depths of ˜ 1. The next step is to search the entire SGPS. A search by eye is possible, but is biased towards the most pronounced features. To better understand the role HISA plays in the ISM, an automated search technique is required. Our routine takes the first and second derivatives of the HI emission brightness temperature with respect to velocity. Due to the sharp drop in the emission profile through a HISA cloud, the derivative profiles show characteristic positive and/or negative peaks. These peaks represent a population of clouds separate from random HI emission fluctuations. By setting thresholds on the derivative maps and defining HISA only if it passes both derivative tests, we can build an unbiased catalog of HISA candidates in the Galaxy. The number distribution can be used to put constraints on the parameters used to find the spin temperature and optical depth, allowing us to more accurately determine the temperature, column density, and optical depth distribution of HISA clouds. We also compare HISA with 12CO emission. In the Inner Galaxy from l=313 deg to l=338 deg we find 30-50% of HISA is associated with 12CO at a brightness temperature of at least 1K. This work was supported by NSF grant AST 97-32695 to the University of Minnesota.

40 CFR 61.32 - Emission standard.

Code of Federal Regulations, 2010 CFR

2010-07-01

... frequency of calibration. (b) Method of sample analysis. (c) Averaging technique for determining 30-day...) Plant and sampling area plots showing emission points and sampling sites. Topographic features...

On the inorganic carriers of the 21 micron emission feature in post-AGB stars

NASA Astrophysics Data System (ADS)

Zhang, Ke; Jiang, Biwei; Li, Aigen

2008-10-01

The mysterious 21 μm emission feature seen in only 12 C-rich proto-planetary nebulae (PPNe) remains unidentified since its discovery in 1989. Over a dozen materials have been suggested as the carrier candidates while none of them has received general acceptance. We investigate the inorganic carrier candidates by applying the observational constraints of the feature strength and associated features. It is found that: (1) three candidates, TiC clusters, fullerenes with Ti impurity atoms, and SiS2, are not abundant enough to account for the emission power of the 21 μm band, (2) five candidates, doped-SiC, SiO2-mantled SiC dust, carbon and silicon mixtures, Fe2O3, and Fe3O4, all show associated features which are either not detected in the 21 μm sources or detected but with a much lower strength, and (3) FeO, which satisfies the abundance constraints, does not display any associated features which are not seen in the 21 μm sources. Moreover, FeO is more likely to survive in the C-rich environment than Fe2O3 and Fe3O4. Thus FeO seems to be the most plausible one among the inorganic carrier candidates.

The onset of Wolf-Rayet wind outflow and the nature of the hot component in the symbiotic nova PU Vulpecula

NASA Technical Reports Server (NTRS)

Sion, Edward M.; Shore, Steven N.; Ready, Christian J.; Scheible, Maureen P.

1993-01-01

We have analyzed temporal variations in the far ultraviolet He II (1640), Si IV (1393, 1402), and C IV (1548, 1550) line profiles in eight high dispersion, International Ultraviolet Explorer Short Wavelength Prime spectra of the symbiotic nova PU Vul by comparatively examining these profiles on a common velocity scale. We see clear evidence of the onset of a Wolf-Rayet-like wind outflow from the bloated, contracting white dwarf hot component with terminal velocity of approximately equals -550 to -600 km/s. We have quantitatively analyzed the complicated He II (1640) emission region for the first time and show that the discrete absorption features seen in the He II region occur at precisely the same velocites in each spectrum, thus demonstrating that the absorbing source is steady and not affected by any orbital motion. We demonstrate that there is an underlying He II wind emission feature whose true shape is hidden by superposed absorption due to the foreground red giant wind flowing in front of the white dwarf and abscuring the white dwarf's wind outflow. We present synthetic spectra of He II emission behind an absorbing slab with u = 20 km/s, T = 5000 K, and column densities in the range N = 1 x 10(exp 22) and 1 x 10(exp 23)/sq cm which explain these absorptions. Our analysis of the Si IV and C IV resonance doublets, in velocity space, reveal temporal variations in the profile between 1987 and 1991 with the emergence of clear P Cygni profiles in Si IV by 1990. A nebular emission feature in C III 1909 also appears in the most recent spectra (e.g., SW42538H) while it was absent or extremely weak in the earliest spectra (e.g., SW36332H), thus strengthening evidence that the nebular emission, as seen in permitted and semiforbidden lines, intensities in step with the onset of the hot, fast, wind outflow. We also report the first detection of narrow interstellar (circumbinary shell?) absorption lines near -1 km/s, most strongly in Al III (1854, 1862) and Si IV (1392, 1402). We have carried out a rough quantitative analysis of the He II wind emission by using the theoretical He II Wolf-Rayet profiles of Hamann & Schmutz (1987). We obtain a lower limit to the He II net emission equivalent width of approximately 1 A, a hot component temperature in the range 25,000 to 35,000 K, a hot component radius in the range 5 solar radius to 30 solar radius, a maximum wind velocity of approximately equals -600 km/s and a rough upper limit to the mass-loss rate of less than 1 x 10(exp -5) solar mass/yr. To our knowledge, this is the first quantitative wind analysis, albeit crude, to be carried out for the hot component of a symbiotic nova or symbiotic variable.

Optical emission spectroscopy of microwave-plasmas at atmospheric pressure applied to the growth of organosilicon and organotitanium nanopowders

NASA Astrophysics Data System (ADS)

Kilicaslan, A.; Levasseur, O.; Roy-Garofano, V.; Profili, J.; Moisan, M.; Côté, C.; Sarkissian, A.; Stafford, L.

2014-03-01

An atmospheric-pressure plasma sustained by an electromagnetic surface wave (SW) in the microwave regime combined with a bubbler/flash evaporator for the injection of liquid precursors was used to produce organosilicon and organotitanium nanopowders. Following the addition of hexamethyldisiloxane (HMDSO) vapors in the nominally pure argon plasma, optical emission spectra revealed the apparition of strong C2 molecular bands along with Si and Balmer H emission lines. Such features were not observed in our atmospheric-pressure Ar/HMDSO discharges controlled by dielectric barriers, indicating that microwave plasmas are characterized by much higher fragmentation levels of the precursors due to much higher electron densities. Emission spectra from the Ar/HMDSO SW plasma further showed a high-intensity continuum, the intensity of which decreased with time as powders started to form on the discharge tube walls. In presence of titanium isopropoxide (TTIP) vapors in the nominally pure Ar plasma, the emission was dominated by Ar and Ti lines, with no trace of carbon and no continuum. Fourier-Transform Infrared (FTIR) Spectroscopy of the powders formed in Ar/HMDSO plasmas showed very strong Si-(CH3)x and O-Si-(CH3)x bands, which is consistent with the formation of silicon oxycarbide. Transmission Electron Microscopy (TEM) further showed tube and sheet-like nanofeatures as well as larger structures consisting of agglomerated primary clusters. On the other hand, introduction of O2 in Ar/HMDSO plasmas produced only round-like nanoparticles with strong Si-O-Si bands and no trace of carbon, consistent with the formation of SiOx. The average size of the silica nanoparticles was 50 nm. FTIR spectra of powders formed in Ar/TTIP plasmas showed strong Ti-O signals, even without the addition of O2 in the gas phase. Corresponding TEM analysis showed nano- and agglomerated features comparable to those obtained in Ar/HMDSO although the average size of the titanate nanoparticles was smaller (10 nm). This set of data indicates that SW plasmas represent a promising parametric tool not only to achieve nanopowders with tailored properties for applications, but also for fundamental studies of nanodusty plasmas at atmospheric-pressure.

Vacuum ultraviolet spectra of the late twilight airglow.

NASA Technical Reports Server (NTRS)

Buckley, J. L.; Moos, H. W.

1971-01-01

Evaluation of sounding rocket spectra of the late twilight (solar-zenith angle of 120 deg) ultraviolet airglow between 1260 and 1900 A. The only observed features are O I 1304 and 1356. When the instrument looked at an elevation of 17 deg above the western horizon, the brightnesses were 70 and 33 rayleighs, respectively. The upper limits on the total intensity of the Lyman-Birge-Hopfield and Vegard-Kaplan systems of N2 were 26 plus or minus 26 and 55 plus or minus 55 rayleighs, respectively. An estimate shows that a large part of the O I emissions may be due to excitation by conjugate-point electrons.

Engineering cyanobacteria as photosynthetic feedstock factories

PubMed Central

Hays, Stephanie G.; Ducat, Daniel C.

2018-01-01

Carbohydrate feedstocks are at the root of bioindustrial production and are needed in greater quantities than ever due to increased prioritization of renewable fuels and reduction of carbon emissions. Cyanobacteria possess a number of features that make them well-suited as an alternative feedstock crop in comparison to traditional, terrestrial plant species. Recent advances in genetic engineering, as well as promising preliminary investigations of cyanobacteria in a number of distinct production regimes have illustrated the potential of these aquatic phototrophs as biosynthetic chasses. Further improvements in strain productivities and design, along with enhanced understanding of photosynthetic metabolism in cyanobacteria may pave the way to translate cyanobacterial theoretical potential into realized application. PMID:24526260

The 7.5- to 13.5-micron spectrum of Saturn

NASA Technical Reports Server (NTRS)

Gillett, F. C.; Forrest, W. J.

1974-01-01

A medium-resolution spectrum of Saturn in the 7.5-13.5 micron range is presented. The observed low brightness temperature between 9 and 11 microns of about 100-105 K rules out gaseous NH3 as the dominant absorber in this spectral range. Absorption features due to PH3 may be present around 10 microns and cloud particles could be an important source of opacity in this wavelength range. There are strong indications of a temperature inversion in the upper atmosphere, including high brightness temperature in the 7.7-micron CH4 band, and possible emission from C2H6 around 12 microns.

Raman Scattered He II 4332 and Photoionization Model in the Symbiotic Star V1016 Cygni

NASA Astrophysics Data System (ADS)

Lee, H.-W.; Heo, J.-E.; Lee, B.-C.

2014-08-01

Symbiotic stars are wide binary systems of a white dwarf and a mass losing giant. They exhibit unique Raman scattered features as a result of inelastic scattering of far UV line photons by atomic hydrogen. Co-existence of a far UV He II emission region and a thick H I region in symbiotic stars is necessary for the formation of Raman-scattered features blueward of hydrogen Balmer emission lines. Being a single electron atom, He II has the same atomic structure as the hydrogen atom and hence emits far UV emission lines that are slightly blueward of hydrogen Lyman lines. These far UV He II emission lines can be Raman scattered to appear blueward of hydrogen Balmer lines. In particular, the symbiotic star V1016 Cyg is found to exhibit Raman scattered He II 4332 feature in the BOES high resolution spectrum. Our profile fitting of Raman scattered He II 4332 is consistent with the mass loss geometry proposed by Jung & Lee (2004). We use the photoionization code ‘ CLOUDY' to estimate the far UV He II emission lines and make comparisons with the observed Raman scattered He II 4332 blueward of Hγ in the high resolution echelle V1016 Cyg. The emission nebula is assumed to be of uniform density of 108 cm-3 that is illuminated by a black body characterized by its temperature and total luminosity. With our comparisons we conclude that the Raman scattered He II features are consistent with the existence of a photoionized nebula by a hot black body source with temperature 7-8× 104 K with a luminosity 1038erg s-1.

Astrophysical data on 5 eV to 1 keV radiation from the radiative decay of fundamental particles - Current limits and prospects for improvement

NASA Technical Reports Server (NTRS)

Bowyer, Stuart; Malina, Roger F.

1986-01-01

Line emission from the decay of fundamental particles, integrated over cosmological distances, can give rise to detectable spectral features in the diffuse astronomical background between 5 eV and 1 keV. Spectroscopic observations may allow these features to be separated from line emission from the numerous local sources of radiation. The current observational status and existing evidence for such features are reviewed. No definitive detections of nongalactic line features have been made. Several local sources of background mask the features at many wavelengths and confuse the interpretation of the data. No systematic spectral observations have been carried out to date. Upcoming experiments which can be expected to provide significantly better constraints on the presence of spectral features in the diffuse background from 5 eV to 1 keV are reviewed.

Principal factors of soil spatial heterogeneity and ecosystem services at the Central Chernozemic Region of Russia

NASA Astrophysics Data System (ADS)

Vasenev, Ivan; Valentini, Riccardo

2013-04-01

The essential spatial heterogeneity is mutual feature for most natural and man-changed soils at the Central Chernozemic Region of Russia which is not only one of the biggest «food baskets» in RF but very important regulator of ecosystem principal services at the European territory of Russia. The original spatial heterogeneity of dominated here forest-steppe and steppe Chernozems and the other soils has been further complicated by a specific land-use history and different-direction soil successions due to environmental changes and more than 1000-year history of human impacts. The carried out long-term researches of representative natural, rural and urban landscapes in Kursk, Orel, Tambov and Voronezh oblasts give us the regional multi-factorial matrix of elementary soil cover patterns (ESCP) with different land-use practices and history, soil-geomorphologic features, environmental and microclimate conditions. The validation and ranging of the limiting factors of ESCP regulation and development, ecosystem principal services, land functional qualities and agroecological state have been done for dominating and most dynamical components of ESCP regional-typological forms - with application of regional and local GIS, soil spatial patterns mapping, traditional regression kriging, correlation tree models. The outcomes of statistical modeling show the essential amplification of erosion, dehumification and CO2 emission, acidification and alkalization, disaggregation and overcompaction processes due to violation of agroecologically sound land-use systems and traditional balances of organic matter, nutrients, Ca and Na in agrolandscapes. Due to long-term intensive and out-of-balance land-use practices the famous Russian Chernozems begin to lose not only their unique natural features of (around 1 m of humus horizon, 4-6% of Corg and favorable agrophysical features), but traditional soil cover patterns, ecosystem services and agroecological functions. Key-site monitoring results and regional generalized data showed 1-1.5 % Corg lost during last 50 years period and active processes of CO2 emission and humus profile eluvial-illuvial redistribution too. Forest-steppe Chernozems are usually characterized by higher stability than steppe ones. The ratio between erosive and biological losses in humus supplies can be ten¬tatively estimated as fifty-fifty with strong spatial variability due to slope and land-use parameters. These processes have essentially different sets of environmental consequences and ecosystem services that we need to understand in frame of agroecological problems development prediction. A drop of Corg content below threshold "humus limiting content" values (3-4% of Corg) considerably reduces effectiveness of used fertilizers and possibility of sustainable agronomy here. This problem environmental and agroecological situation can be essentially improved by new federal law on environmentally friendly agriculture but it's draft is still in the process of deliberation. Quantitative analysis of principal ecosystem services, soil cover patterns and degradation processes in parameters of land qualities help us in developing different-scale projects for agricultural and urban land-use, taking into attention not only economical benefits but environmental functions too. The conceptions of ecosystem services and local land resource management are becoming more and more popular at the Central Chernozemic Region of Russia due to innovation application of basic agroecology, ecological monitoring and soil science achievements.

OH masers towards IRAS 19092+0841

NASA Astrophysics Data System (ADS)

Edris, K. A.; Fuller, G. A.; Etoka, S.; Cohen, R. J.

2017-12-01

Context. Maser emission is a strong tool for studying high-mass star-forming regions and their evolutionary stages. OH masers in particular can trace the circumstellar material around protostars and determine their magnetic field strengths at milliarcsecond resolution. Aims: We seek to image OH maser emission towards high-mass protostellar objects to determine their evolutionary stages and to locate the detected maser emission in the process of high-mass star formation. Methods: In 2007, we surveyed OH maser emission towards 217 high-mass protostellar objects to study its presence. In this paper, we present follow-up MERLIN observations of a ground-state OH maser emission towards one of these objects, IRAS 19092+0841. Results: We detect emissions from the two OH main spectral lines, 1665 and 1667 MHz, close to the central object. We determine the positions and velocities of the OH maser features. The masers are distributed over a region of 5'' corresponding to 22 400 AU (or 0.1 pc) at a distance of 4.48 kpc. The polarization properties of the OH maser features are determined as well. We identify three Zeeman pairs from which we inferred a magnetic field strength of 4.4 mG pointing towards the observer. Conclusions: The relatively small velocity spread and relatively wide spacial distribution of the OH maser features support the suggestion that this object could be in an early evolutionary state before the presence of disk, jets or outflows.

A search for the 10-micron silicate feature in periodic Comet Grigg-Skjellerup

NASA Technical Reports Server (NTRS)

Hanner, M.; Aitken, D.; Roche, P.; Whitmore, B.

1984-01-01

A 10-micron spectrum of periodic Comet Grigg-Skjellerup was obtained on 22 June 1982 with the UCL array spectrometer at the United Kingdom Infrared Telescope, Mauna Kea. No emission feature is obvious in the spectrum. The observed spectrum can be fit equally well by a model of small hot absorbing grains or by a composite model with less than or equal to 30 percent (3sigma) warm, 'dirty' silicate grains. The latter model is consistent with the silicate abundance in Comet Kohoutek, which did display an emission feature at 10 microns.

Verifying mixing in dilution tunnels How to ensure cookstove emissions samples are unbiased

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

Wilson, Daniel L.; Rapp, Vi H.; Caubel, Julien J.

A well-mixed diluted sample is essential for unbiased measurement of cookstove emissions. Most cookstove testing labs employ a dilution tunnel, also referred to as a “duct,” to mix clean dilution air with cookstove emissions before sampling. It is important that the emissions be well-mixed and unbiased at the sampling port so that instruments can take representative samples of the emission plume. Some groups have employed mixing baffles to ensure the gaseous and aerosol emissions from cookstoves are well-mixed before reaching the sampling location [2, 4]. The goal of these baffles is to to dilute and mix the emissions stream withmore » the room air entering the fume hood by creating a local zone of high turbulence. However, potential drawbacks of mixing baffles include increased flow resistance (larger blowers needed for the same exhaust flow), nuisance cleaning of baffles as soot collects, and, importantly, the potential for loss of PM2.5 particles on the baffles themselves, thus biasing results. A cookstove emission monitoring system with baffles will collect particles faster than the duct’s walls alone. This is mostly driven by the available surface area for deposition by processes of Brownian diffusion (through the boundary layer) and turbophoresis (i.e. impaction). The greater the surface area available for diffusive and advection-driven deposition to occur, the greater the particle loss will be at the sampling port. As a layer of larger particle “fuzz” builds on the mixing baffles, even greater PM2.5 loss could occur. The micro structure of the deposited aerosol will lead to increased rates of particle loss by interception and a tendency for smaller particles to deposit due to impaction on small features of the micro structure. If the flow stream could be well-mixed without the need for baffles, these drawbacks could be avoided and the cookstove emissions sampling system would be more robust.« less

Atypical dust species in the ejecta of classical novae

NASA Astrophysics Data System (ADS)

Helton, L. A.; Evans, A.; Woodward, C. E.; Gehrz, R. D.

2011-03-01

A classical nova outburst arises from a thermonuclear runaway in the hydrogen-rich material accreted onto the surface of a white dwarf in a binary system. These explosions can produce copious amounts of heavy element enriched material that are ejected violently into the surrounding interstellar medium. In some novae, conditions in the ejecta are suitable for the formation of dust of various compositions, including silicates, amorphous carbon, silicon carbide, and hydrocarbons. Multiple dust grain types are sometimes produced in the same system. CO formation in novae may not reach saturation, thus invalidating the usual paradigm in which the C:O ratio determines the dust species. A few novae, such as V705 Cas and DZ Cru, have exhibited emission features near 6, 8, and 11 μmthat are similar to "Unidentified Infrared" (UIR) features, but with significant differences in position and band structure. Here, we present Spitzer IRS spectra of two recent dusty novae, V2361 Cyg and V2362 Cyg, that harbor similar peculiar emission structures superimposed on features arising from carbonaceous grains. In other astronomical objects, such as star forming regions and young stellar objects, emission peaks at 6.2, 7.7, and 11.3 μmhave been associated with polycyclic aromatic hydrocarbon (PAH) complexes. We suggest that hydrogenated amorphous carbon (HAC) may be the source of these features in novae based upon the spectral behavior of the emission features and the conditions under which the dust formed.

Detection of CN emission from (2060) Chiron

NASA Technical Reports Server (NTRS)

Bowell, Edward

1991-01-01

Spectrophotometric observations of (2060) Chiron were obtained. Their primary goal was to look for the subtle differences in color between Chiron and its surrounding coma, and to search for possible absorption or emission features in Chiron's spectrum. The presence of the CN(0-0) emission band was identified. It proves Chiron's cometary nature and breaks the record heliocentric distance for cometary gaseous emission.

The X-ray spectra of the black hole candidate 4U 1630-47 during its 2012 outburst

NASA Astrophysics Data System (ADS)

Wang, Y.; Mendez, M.

2015-07-01

Diaz Trigo et al. (2013) reported the detection of three Doppler-shifted emission lines arising from baryonic matter in the jet of 4U 1630-47 during its 2012 outburst. Here we propose an alternative model that, without the need of the lines from the jet, and with less free parameters, fits the same data equally well. In our model we allow the abundances of S and Fe in the interstellar medium to vary; the best-fitting values are, respectively, 1.5 and 0.5 times solar, consistent with recent findings. Our model also includes a moderately broad emission line and a narrow absorption line due to highly ionised Fe. (These lines are also present in the other observations of this source during the 2012 outburst.) This model fits well all the XMM-Newton observations of this source, both in burst and timing mode. In addition to the components that we fitted to the burst-mode data, the timing-mode observations show several absorption features due to ionised Fe and Ni, which reveal the presence of a highly-ionised absorber close to the source. Our model also fits well the burst-mode data using the most recent calibration files (March 2015), whereas the model from Diaz Trigo et al. does not.

Coherent emission mechanisms in astrophysical plasmas

NASA Astrophysics Data System (ADS)

Melrose, D. B.

2017-12-01

Three known examples of coherent emission in radio astronomical sources are reviewed: plasma emission, electron cyclotron maser emission (ECME) and pulsar radio emission. Plasma emission is a multi-stage mechanism with the first stage being generation of Langmuir waves through a streaming instability, and subsequent stages involving partial conversion of the Langmuir turbulence into escaping radiation at the fundamental (F) and second harmonic (H) of the plasma frequency. The early development and subsequent refinements of the theory, motivated by application to solar radio bursts, are reviewed. The driver of the instability is faster electrons outpacing slower electrons, resulting in a positive gradient ({d}f(v_allel )/{d}v_allel >0) at the front of the beam. Despite many successes of the theory, there is no widely accepted explanation for type I bursts and various radio continua. The earliest models for ECME were purely theoretical, and the theory was later adapted and applied to Jupiter (DAM), the Earth (AKR), solar spike bursts and flare stars. ECME strongly favors the x mode, whereas plasma emission favors the o mode. Two drivers for ECME are a ring feature (implying {d}f(v)/{d}v>0) and a loss-cone feature. Loss-cone-driven ECME was initially favored for all applications. The now favored driver for AKR is the ring-feature in a horseshoe distribution, which results from acceleration by a parallel electric on converging magnetic field lines. The driver in DAM and solar and stellar applications is uncertain. The pulsar radio emission mechanism remains an enigma. Ingredients needed in discussing possible mechanisms are reviewed: general properties of pulsars, pulsar electrodynamics, the properties of pulsar plasma and wave dispersion in such plasma. Four specific emission mechanisms (curvature emission, linear acceleration emission, relativistic plasma emission and anomalous Doppler emission) are discussed and it is argued that all encounter difficulties. Coherent radio emission from extensive air showers in the Earth's atmosphere is reviewed briefly. The difference in theoretical approach from astrophysical theories is pointed out and discussed. Fine structures in DAM and in pulsar radio emission are discussed, and it is suggested that trapping in a large-amplitude wave, as in a model for discrete VLF emission, provides a plausible explanation. A possible direct measure of coherence is pointed out.

Application of pattern recognition techniques to acousto-ultrasonic testing of Kevlar composite panels

NASA Astrophysics Data System (ADS)

Hinton, Yolanda L.

An acousto-ultrasonic evaluation of panels fabricated from woven Kevlar and PVB/phenolic resin is being conducted. The panels were fabricated with various simulated defects. They were examined by pulsing with one acoustic emission sensor, and detecting the signal with another sensor, on the same side of the panel at a fixed distance. The acoustic emission signals were filtered through high (400-600 KHz), low (100-300 KHz) and wide (100-1200 KHz) bandpass filters. Acoustic emission signal parameters, including amplitude, counts, rise time, duration, 'energy', rms, and counts to peak, were recorded. These were statistically analyzed to determine which of the AE parameters best characterize the simulated defects. The wideband filtered acoustic emission signal was also digitized and recorded for further processing. Seventy-one features of the signals in both the time and frequency domains were calculated and compared to determine which subset of these features uniquely characterize the defects in the panels. The objective of the program is to develop a database of AE signal parameters and features to be used in pattern recognition as an inspection tool for material fabricated from these materials.

Deep Optical Spectroscopy of Planetary Nebulae: The Search for Neutron-Capture Elements

NASA Astrophysics Data System (ADS)

Sterling, Nicholas C.; Garofali, K.; Dinerstein, H. L.; Hwang, S.; Redfield, S.

2013-01-01

We present deep, high-resolution (R=36,700) optical spectra of five planetary nebulae (PNe), taken with the 2D-coude echelle spectrograph on the 2.7-m Harlan J. Smith Telescope at McDonald Observatory. These observations are part of a larger optical survey of PNe, designed to unambiguously detect emission lines from neutron(n)-capture elements (atomic number Z>30). The abundances of these elements are of particular interest in PNe, since they can be produced by slow n-capture nucleosynthesis (the ``s-process'') during the asymptotic giant branch (AGB) stage of evolution of PN progenitor stars. The first large-scale investigation of n-capture element abundances in PNe (Sterling & Dinerstein 2008, ApJS, 174, 157) surveyed [Kr III] and [Se IV] transitions in the K band spectra of more than 80 PNe. However, the abundances derived from these data relied on ionization corrections that were often large and uncertain due to the detection of only one ion per element. Transitions of other Se and Kr ions, as well as many other trans-iron species, reside at optical wavelengths. High-resolution spectra are essential to unequivocally identify these lines and resolve potential blends with other species. The spectra we present are rich in emission features, with between 125 and 600 distinct lines detected in each PN. Emission from at least one Kr ion is detected in all five objects, and two (Hb 12 and J 900) exhibit emission from multiple Kr ions. We detected multiple Xe ions in J 900, as well as Se, Br, and Rb lines. Hb 12 also exhibits Xe emission, and the first detection of [Se II] in a PN to our knowledge. The spectra display a wealth of other emission lines, including permitted features of second-row elements and forbidden transitions of several iron-peak elements (e.g., Cr, Mn, Fe, Co, Ni, and Cu). Our survey makes it possible to derive more accurate Se and Kr abundances in PNe, and reveals the enrichment of other trans-iron elements. This enables more accurate s-process enrichment factors to be derived for PNe, providing important constraints to models of AGB nucleosynthesis and the chemical evolution of trans-iron nuclides. This research was supported by NSF awards AST-0708425 and AST-901432.

Retrieval of Garstang's emission function from all-sky camera images

NASA Astrophysics Data System (ADS)

Kocifaj, Miroslav; Solano Lamphar, Héctor Antonio; Kundracik, František

2015-10-01

The emission function from ground-based light sources predetermines the skyglow features to a large extent, while most mathematical models that are used to predict the night sky brightness require the information on this function. The radiant intensity distribution on a clear sky is experimentally determined as a function of zenith angle using the theoretical approach published only recently in MNRAS, 439, 3405-3413. We have made the experiments in two localities in Slovakia and Mexico by means of two digital single lens reflex professional cameras operating with different lenses that limit the system's field-of-view to either 180º or 167º. The purpose of using two cameras was to identify variances between two different apertures. Images are taken at different distances from an artificial light source (a city) with intention to determine the ratio of zenith radiance relative to horizontal irradiance. Subsequently, the information on the fraction of the light radiated directly into the upward hemisphere (F) is extracted. The results show that inexpensive devices can properly identify the upward emissions with adequate reliability as long as the clear sky radiance distribution is dominated by a largest ground-based light source. Highly unstable turbidity conditions can also make the parameter F difficult to find or even impossible to retrieve. The measurements at low elevation angles should be avoided due to a potentially parasitic effect of direct light emissions from luminaires surrounding the measuring site.

UVIT view of ram-pressure stripping in action: Star formation in the stripped gas of the GASP jellyfish galaxy JO201 in Abell 85

NASA Astrophysics Data System (ADS)

George, K.; Poggianti, B. M.; Gullieuszik, M.; Fasano, G.; Bellhouse, C.; Postma, J.; Moretti, A.; Jaffé, Y.; Vulcani, B.; Bettoni, D.; Fritz, J.; Côté, P.; Ghosh, S. K.; Hutchings, J. B.; Mohan, R.; Sreekumar, P.; Stalin, C. S.; Subramaniam, A.; Tandon, S. N.

2018-06-01

Jellyfish are cluster galaxies that experience strong ram-pressure effects that strip their gas. Their Hα images reveal ionized gas tails up to 100 kpc, which could be hosting ongoing star formation. Here we report the ultraviolet (UV) imaging observation of the jellyfish galaxy JO201 obtained at a spatial resolution ˜ 1.3 kpc. The intense burst of star formation happening in the tentacles is the focus of the present study. JO201 is the "UV-brightest cluster galaxy" in Abell 85 (z ˜ 0.056) with knots and streams of star formation in the ultraviolet. We identify star forming knots both in the stripped gas and in the galaxy disk and compare the UV features with the ones traced by Hα emission. Overall, the two emissions remarkably correlate, both in the main body and along the tentacles. Similarly, also the star formation rates of individual knots derived from the extinction-corrected FUV emission agree with those derived from the Hα emission and range from ˜ 0.01 -to- 2.07 M⊙ yr-1. The integrated star formation rate from FUV flux is ˜ 15 M⊙ yr-1. The unprecedented deep UV imaging study of the jellyfish galaxy JO201 shows clear signs of extraplanar star-formation activity due to a recent/ongoing gas stripping event.

Defect-induced infrared electroluminescence from radial GaInP/AlGaInP quantum well nanowire array light- emitting diodes

NASA Astrophysics Data System (ADS)

Hussain, Laiq; Karimi, Mohammad; Berg, Alexander; Jain, Vishal; Borgström, Magnus T.; Gustafsson, Anders; Samuelson, Lars; Pettersson, Håkan

2017-12-01

Radial GaInP/AlGaInP nanowire array light-emitting diodes (LEDs) are promising candidates for novel high-efficiency solid state lighting due to their potentially large strain-free active emission volumes compared to planar LEDs. Moreover, by proper tuning of the diameter of the nanowires, the fraction of emitted light extracted can be significantly enhanced compared to that of planar LEDs. Reports so far on radial growth of nanowire LED structures, however, still point to significant challenges related to obtaining defect-free radial heterostructures. In this work, we present evidence of optically active growth-induced defects in a fairly broad energy range in vertically processed radial GaInP/AlGaInP quantum well nanowire array LEDs using a variety of complementary experimental techniques. In particular, we demonstrate strong infrared electroluminescence in a spectral range centred around 1 eV (1.2 μm) in addition to the expected red light emission from the quantum well. Spatially resolved cathodoluminescence studies reveal a patchy red light emission with clear spectral features along the NWs, most likely induced by variations in QW thickness, composition and barriers. Dark areas are attributed to infrared emission generated by competing defect-assisted radiative transitions, or to trapping mechanisms involving non-radiative recombination processes. Possible origins of the defects are discussed.

Polarization effects in cutaneous autofluorescent spectra

NASA Astrophysics Data System (ADS)

Borisova, E.; Angelova, L.; Jeliazkova, Al.; Genova, Ts.; Pavlova, E.; Troyanova, P.; Avramov, L.

2014-05-01

Used polarized light for fluorescence excitation one could obtain response related to the anisotropy features of extracellular matrix. The fluorophore anisotropy is attenuated during lesions' growth and level of such decrease could be correlated with the stage of tumor development. Our preliminary investigations are based on in vivo point-by-point measurements of excitation-emission matrices (EEM) from healthy volunteers skin on different ages and from different anatomical places using linear polarizer and analyzer for excitation and emission light detected. Measurements were made using spectrofluorimeter FluoroLog 3 (HORIBA Jobin Yvon, France) with fiber-optic probe in steady-state regime using excitation in the region of 280-440 nm. Three different situations were evaluated and corresponding excitation-emission matrices were developed - with parallel and perpendicular positions for linear polarizer and analyzer, and without polarization of excitation and fluorescence light detected from a forearm skin surface. The fluorescence spectra obtained reveal differences in spectral intensity, related to general attenuation, due to filtering effects of used polarizer/analyzer couple. Significant spectral shape changes were observed for the complex autofluorescence signal detected, which correlated with collagen and protein cross-links fluorescence, that could be addressed to the tissue extracellular matrix and general condition of the skin investigated, due to morphological destruction during lesions' growth. A correlation between volunteers' age and the fluorescence spectra detected was observed during our measurements. Our next step is to increase developed initial database and to evaluate all sources of intrinsic fluorescent polarization effects and found if they are significantly altered from normal skin to cancerous state of the tissue, this way to develop a non-invasive diagnostic tool for dermatological practice.

An organic dye with very large Stokes-shift and broad tunability of fluorescence: Potential two-photon probe for bioimaging and ultra-sensitive solid-state gas sensor

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

He, Tingchao; Tian, Xiaoqing; Lin, Xiaodong, E-mail: linxd@szu.edu.cn, E-mail: hdsun@ntu.edu.sg

Light-emitting nonlinear optical molecules, especially those with large Stokes shifts and broad tunability of their emission wavelength, have attracted considerable attention for various applications including biomedical imaging and fluorescent sensors. However, most fluorescent chromophores have only limited potential for such applications due to small Stokes shifts, narrow tunability of fluorescence emissions, and small optical nonlinearity in highly polar solvents. In this work, we demonstrate that a two-photon absorbing stilbene chromophore exhibits a large two-photon absorption action cross-section (ηδ = 320 GM) in dimethylsulfoxide (DMSO) and shows broad fluorescence tunability (125 nm) by manipulating the polarity of the surrounding medium. Importantly, a very large Stokesmore » shift of up to 227 nm is achieved in DMSO. Thanks to these features, this chromophore can be utilized as a two-photon probe for bioimaging applications and in an ultrasensitive solid-state gas detector.« less

Manifestation of anharmonic resonance in the interaction of intense ultrashort laser pulses with microstructured targets

NASA Astrophysics Data System (ADS)

Dalui, Malay; Kundu, M.; Madhu Trivikram, T.; Ray, Krishanu; Krishnamurthy, M.

2016-10-01

Identification of the basic processes responsible for an efficient heating of intense laser produced plasmas is one of the important features of high intensity laser matter interaction studies. Collisionless absorption due to the anharmonicity in the self-consistent electrostatic potential of the plasma, known as anharmonic resonance (AHR), has been proposed to be a basic mechanism but a clear experimental demonstration is needed. Here, we show that microstructured targets enhance X-ray emission and the polarization dependence ascribes the enhancement to anharmonic resonance heating. It is found that p-polarized pulses of 5 ×1017 W/cm2 intensity bring in a 16-fold enhancement in the X-ray emission in the energy range 20-350 keV compared to s-polarized pulses with microstructured targets. This ratio is 2 for the case of polished targets under otherwise identical conditions. Particle-in-cell simulations clearly show that AHR is the key absorption mechanism responsible for this effect.

Long-Distance Single Photon Transmission from a Trapped Ion via Quantum Frequency Conversion

NASA Astrophysics Data System (ADS)

Walker, Thomas; Miyanishi, Koichiro; Ikuta, Rikizo; Takahashi, Hiroki; Vartabi Kashanian, Samir; Tsujimoto, Yoshiaki; Hayasaka, Kazuhiro; Yamamoto, Takashi; Imoto, Nobuyuki; Keller, Matthias

2018-05-01

Trapped atomic ions are ideal single photon emitters with long-lived internal states which can be entangled with emitted photons. Coupling the ion to an optical cavity enables the efficient emission of single photons into a single spatial mode and grants control over their temporal shape. These features are key for quantum information processing and quantum communication. However, the photons emitted by these systems are unsuitable for long-distance transmission due to their wavelengths. Here we report the transmission of single photons from a single 40Ca+ ion coupled to an optical cavity over a 10 km optical fiber via frequency conversion from 866 nm to the telecom C band at 1530 nm. We observe nonclassical photon statistics of the direct cavity emission, the converted photons, and the 10 km transmitted photons, as well as the preservation of the photons' temporal shape throughout. This telecommunication-ready system can be a key component for long-distance quantum communication as well as future cloud quantum computation.

Modeling of Fine-Particle Formation in Turbulent Flames

NASA Astrophysics Data System (ADS)

Raman, Venkat; Fox, Rodney O.

2016-01-01

The generation of nanostructured particles in high-temperature flames is important both for the control of emissions from combustion devices and for the synthesis of high-value chemicals for a variety of applications. The physiochemical processes that lead to the production of fine particles in turbulent flames are highly sensitive to the flow physics and, in particular, the history of thermochemical compositions and turbulent features they encounter. Consequently, it is possible to change the characteristic size, structure, composition, and yield of the fine particles by altering the flow configuration. This review describes the complex multiscale interactions among turbulent fluid flow, gas-phase chemical reactions, and solid-phase particle evolution. The focus is on modeling the generation of soot particles, an unwanted pollutant from automobile and aircraft engines, as well as metal oxides, a class of high-value chemicals sought for specialized applications, including emissions control. Issues arising due to the numerical methods used to approximate the particle number density function, the modeling of turbulence-chemistry interactions, and model validation are also discussed.

Bright luminescence from pure DNA-curcumin–based phosphors for bio hybrid light-emitting diodes

PubMed Central

Reddy, M. Siva Pratap; Park, Chinho

2016-01-01

Recently, significant advances have occurred in the development of phosphors for bio hybrid light-emitting diodes (Bio-HLEDs), which have created brighter, metal-free, rare-earth phosphor-free, eco-friendly, and cost-competitive features for visible light emission. Here, we demonstrate an original approach using bioinspired phosphors in Bio-HLEDs based on natural deoxyribonucleic acid (DNA)-curcumin complexes with cetyltrimethylammonium (CTMA) in bio-crystalline form. The curcumin chromophore was bound to the DNA double helix structure as observed using field emission tunnelling electron microscopy (FE-TEM). Efficient luminescence occurred due to tightly bound curcumin chromophore to DNA duplex. Bio-HLED shows low luminous drop rate of 0.0551 s−1. Moreover, the solid bio-crystals confined the activating bright luminescence with a quantum yield of 62%, thereby overcoming aggregation-induced quenching effect. The results of this study herald the development of commercially viable large-scale hybrid light applications that are environmentally benign. PMID:27572113

Sensing Properties of a Novel Temperature Sensor Based on Field Assisted Thermal Emission.

PubMed

Pan, Zhigang; Zhang, Yong; Cheng, Zhenzhen; Tong, Jiaming; Chen, Qiyu; Zhang, Jianpeng; Zhang, Jiaxiang; Li, Xin; Li, Yunjia

2017-02-27

The existing temperature sensors using carbon nanotubes (CNTs) are limited by low sensitivity, complicated processes, or dependence on microscopy to observe the experimental results. Here we report the fabrication and successful testing of an ionization temperature sensor featuring non-self-sustaining discharge. The sharp tips of nanotubes generate high electric fields at relatively low voltages, lowering the work function of electrons emitted by CNTs, and thereby enabling the safe operation of such sensors. Due to the temperature effect on the electron emission of CNTs, the collecting current exhibited an exponential increase with temperature rising from 20 °C to 100 °C. Additionally, a higher temperature coefficient of 0.04 K -1 was obtained at 24 V voltage applied on the extracting electrode, higher than the values of other reported CNT-based temperature sensors. The triple-electrode ionization temperature sensor is easy to fabricate and converts the temperature change directly into an electrical signal. It shows a high temperature coefficient and good application potential.

Sensing Properties of a Novel Temperature Sensor Based on Field Assisted Thermal Emission

PubMed Central

Pan, Zhigang; Zhang, Yong; Cheng, Zhenzhen; Tong, Jiaming; Chen, Qiyu; Zhang, Jianpeng; Zhang, Jiaxiang; Li, Xin; Li, Yunjia

2017-01-01

The existing temperature sensors using carbon nanotubes (CNTs) are limited by low sensitivity, complicated processes, or dependence on microscopy to observe the experimental results. Here we report the fabrication and successful testing of an ionization temperature sensor featuring non-self-sustaining discharge. The sharp tips of nanotubes generate high electric fields at relatively low voltages, lowering the work function of electrons emitted by CNTs, and thereby enabling the safe operation of such sensors. Due to the temperature effect on the electron emission of CNTs, the collecting current exhibited an exponential increase with temperature rising from 20 °C to 100 °C. Additionally, a higher temperature coefficient of 0.04 K−1 was obtained at 24 V voltage applied on the extracting electrode, higher than the values of other reported CNT-based temperature sensors. The triple-electrode ionization temperature sensor is easy to fabricate and converts the temperature change directly into an electrical signal. It shows a high temperature coefficient and good application potential. PMID:28264427

The changing source of X-ray reflection in the radio-intermediate Seyfert 1 galaxy III Zw 2

NASA Astrophysics Data System (ADS)

Gonzalez, A. G.; Waddell, S. G. H.; Gallo, L. C.

2018-03-01

We report on X-ray observations of the radio-intermediate, X-ray bright Seyfert 1 galaxy, III Zw 2, obtained with XMM-Newton, Suzaku, and Swift over the past 17 yr. The source brightness varies significantly over yearly time-scales, but more modestly over periods of days. Pointed observations with XMM-Newton in 2000 and Suzaku in 2011 show spectral differences despite comparable X-ray fluxes. The Suzaku spectra are consistent with a power-law continuum and a narrow Gaussian emission feature at ˜6.4 keV, whereas the earlier XMM-Newton spectrum requires a broader Gaussian profile and soft-excess below ˜2 keV. A potential interpretation is that the primary power-law emission, perhaps from a jet base, preferentially illuminates the inner accretion disc in 2000, but the distant torus in 2011. The interpretation could be consistent with the hypothesized precessing radio jet in III Zw 2 that may have originated from disc instabilities due to an ongoing merging event.

The effects of pre-ionization using a shunt resistor on reproducibility of the x-ray emission in a dense plasma focus device

NASA Astrophysics Data System (ADS)

Piriaei, D.; Yousefi, H. R.; Mahabadi, T. D.; SalarElahi, A.; Ghoranneviss, M.

2017-08-01

In this research, the effects of pre-ionization using a shunt resistor on reproducibility of x-ray emission in a Mather type plasma focus device have been studied. This technique increased the intensities of the emitted x-rays from argon as the filling gas of the device and made the x-ray yields with similar intensities reproducible. A Mirnov coil was also used to record the variations of the plasma's magnetic field, and the wavelet spectrums of these recorded signals showed the reduced instabilities due to the application of the pre-ionization technique. Moreover, it was demonstrated that this technique was capable of reducing the number of initial runaway electrons that could increase the impurities and instabilities inside the plasma. In addition to the above-mentioned features, this technique could improve the uniform formation of the current sheath during the breakdown phase that might later lead to a high quality pinch and high intensity emitted x-rays.

Physics and Engineering Design of the ITER Electron Cyclotron Emission Diagnostic

NASA Astrophysics Data System (ADS)

Rowan, W. L.; Austin, M. E.; Houshmandyar, S.; Phillips, P. E.; Beno, J. H.; Ouroua, A.; Weeks, D. A.; Hubbard, A. E.; Stillerman, J. A.; Feder, R. E.; Khodak, A.; Taylor, G.; Pandya, H. K.; Danani, S.; Kumar, R.

2015-11-01

Electron temperature (Te) measurements and consequent electron thermal transport inferences will be critical to the non-active phases of ITER operation and will take on added importance during the alpha heating phase. Here, we describe our design for the diagnostic that will measure spatial and temporal profiles of Te using electron cyclotron emission (ECE). Other measurement capability includes high frequency instabilities (e.g. ELMs, NTMs, and TAEs). Since results from TFTR and JET suggest that Thomson Scattering and ECE differ at high Te due to driven non-Maxwellian distributions, non-thermal features of the ITER electron distribution must be documented. The ITER environment presents other challenges including space limitations, vacuum requirements, and very high-neutron-fluence. Plasma control in ITER will require real-time Te. The diagnosic design that evolved from these sometimes-conflicting needs and requirements will be described component by component with special emphasis on the integration to form a single effective diagnostic system. Supported by PPPL/US-DA via subcontract S013464-C to UT Austin.

Information Security due to Electromagnetic Environments

NASA Astrophysics Data System (ADS)

Sekiguchi, Hidenori; Seto, Shinji

Generally, active electronic devices emit slightly unintentional electromagnetic noise. From long ago, electromagnetic emission levels have been regulated from the aspect of electromagnetic compatibility (EMC). Also, it has been known the electromagnetic emissions have been generated from the ON/OFF of signals in the device. Recently, it becomes a topic of conversation on the information security that the ON/OFF on a desired signal in the device can be reproduced or guessed by receiving the electromagnetic emission. For an example, a display image on a personal computer (PC) can be reconstructed by receiving and analyzing the electromagnetic emission. In sum, this fact makes known information leakage due to electromagnetic emission. “TEMPEST" that has been known as a code name originated in the U. S. Department of Defense is to prevent the information leakage caused by electromagnetic emissions. This paper reports the brief summary of the information security due to electromagnetic emissions from information technology equipments.

Saturns Thermal Emission at 2.2-cm Wavelength as Imaged by the Cassini RADAR Radiometer

NASA Technical Reports Server (NTRS)

Janssen, M. A.; Ingersoll, A. P.; Allison, M. D.; Gulkis, S.; Laraia, A. L.; Baines, K. H.; Edgington, S. G.; Anderson, Y. Z.; Kelleher, K.; Oyafuso, F. A.

2013-01-01

We present well-calibrated, high-resolution maps of Saturn's thermal emission at 2.2-cm wavelength obtained by the Cassini RADAR radiometer through the Prime and Equinox Cassini missions, a period covering approximately 6 years. The absolute brightness temperature calibration of 2% achieved is more than twice better than for all previous microwave observations reported for Saturn, and the spatial resolution and sensitivity achieved each represent nearly an order of magnitude improvement. The brightness temperature of Saturn in the microwave region depends on the distribution of ammonia, which our radiative transfer modeling shows is the only significant source of absorption in Saturn's atmosphere at 2.2-cm wavelength. At this wavelength the thermal emission comes from just below and within the ammonia cloud-forming region, and yields information about atmospheric circulations and ammonia cloud-forming processes. The maps are presented as residuals compared to a fully saturated model atmosphere in hydrostatic equilibrium. Bright regions in these maps are readily interpreted as due to depletion of ammonia vapor in, and, for very bright regions, below the ammonia saturation region. Features seen include the following: a narrow equatorial band near full saturation surrounded by bands out to about 10deg planetographic latitude that demonstrate highly variable ammonia depletion in longitude; narrow bands of depletion at -35deg latitude; occasional large oval features with depleted ammonia around -45deg latitude; and the 2010-2011 storm, with extensive saturated and depleted areas as it stretched halfway around the planet in the northern hemisphere. Comparison of the maps over time indicates a high degree of stability outside a few latitudes that contain active regions.

The noseleaf of Rhinolophus formosae focuses the Frequency Modulated (FM) component of the calls

PubMed Central

Vanderelst, Dieter; Lee, Ya-Fu; Geipel, Inga; Kalko, Elisabeth K. V.; Kuo, Yen-Min; Peremans, Herbert

2013-01-01

Bats of the family Rhinolophidae emit their echolocation calls through their nostrils and feature elaborate noseleaves shaping the directionality of the emissions. The calls of these bats consist of a long constant-frequency component preceded and/or followed by short frequency-modulated sweeps. While Rhinolophidae are known for their physiological specializations for processing the constant frequency part of the calls, previous evidence suggests that the noseleaves of these animals are tuned to the frequencies in the frequency modulated components of the calls. In this paper, we seek further support for this hypothesis by simulating the emission beam pattern of the bat Rhinolophus formosae. Filling the furrows of lancet and removing the basal lappets (i.e., two flaps on the noseleaf) we find that these conspicuous features of the noseleaf focus the emitted energy mostly for frequencies in the frequency-modulated components. Based on the assumption that this component of the call is used by the bats for ranging, we develop a qualitative model to assess the increase in performance due to the furrows and/or the lappets. The model confirms that both structures decrease the ambiguity in selecting relevant targets for ranging. The lappets and the furrows shape the emission beam for different spatial regions and frequency ranges. Therefore, we conclude that the presented evidence is in line with the hypothesis that different parts of the noseleaves of Rhinolophidae are tuned to different frequency ranges with at least some of the most conspicuous ones being tuned to the frequency modulated components of the calls—thus yielding strong evidence for the sensory importance of the component. PMID:23882226

The polarization and ultraviolet spectrum of Markarian 231

NASA Technical Reports Server (NTRS)

Smith, Paul S.; Schmidt, Gary D.; Allen, Richard G.; Angel, J. R. P.

1995-01-01

Ultraviolet spectropolarimetry acquired with the Hubble Space Telescope (HST) of the peculiar Seyfert galaxy Mrk 231 is combined with new high-quality ground-based measurements to provide the first, nearly complete, record of its linear polarization from 1575 to 7900 A. The accompanying ultraviolet spectrum portrays the heavily extinguished emission-line spectrum of the active nucleus plus the emergence of a blue continuum shortward of approximately 2400 A. In addition, absorption features due to He I lambda 3188, Mg I lambda 2853, Mg II lambda 2798, and especially several resonance multiplets of Fe II are identified with a well-known optical absorption system blueshifted approximately 4600 km/s with respect to emission lines. The continuum is attributed to approximately 10(exp 5) hot, young stars surrounding the nucleus. This component dilutes the polarized nuclear light, implying that the intrinsic polarization of the active galactic nucleus (AGN) spectrum approaches 20% at 2800 A. The rapid decline in degree of polarization toward longer wavelengths is best explained by the strongly frequency-dependent scattering cross section of dust grains coupled with modest starlight dilution. Peculiar S-shaped inflections in both the degree and position angle of polarization through H alpha and other major emission lines are interpreted as effects of scattering from two regions offset in velocity by several hundred km/s. A third source of (weakly) polarized flux is required to explain a nearly 40 deg rotation in position angle between 3200 and 1800 A. The displaced absorption features, polarimetry, and optical/infrared properties of Mrk 231 all point to its classification as a low-ionization, or Mg II broad absorption line quasar, in which most, if not all, lines of sight to the active nucleus are heavily obscured by dust and low-ionization gas clouds.

Water vapour masers in long-period variable stars. I. RX Bootis and SV Pegasi

NASA Astrophysics Data System (ADS)

Winnberg, A.; Engels, D.; Brand, J.; Baldacci, L.; Walmsley, C. M.

2008-05-01

Context: Water vapour maser emission from late-type stars characterises them as asymptotic-giant-branch stars with oxygen-rich chemistry that are losing mass at a substantial rate. Further conclusions on the properties of the stars, however, are hampered by the strong variability of the emission. Aims: We wish to understand the reasons for the strong variability of H2O masers in circumstellar shells of late-type stars. In this paper we study RX Bootis and SV Pegasi as representatives of semiregular variable stars (SRVs). Methods: We monitored RX Boo and SV Peg in the 22-GHz maser line of water vapour with single-dish telescopes. The monitoring period covered two decades for RX Boo (1987-2007) and 12 years for SV Peg (1990-1995, 2000-2007). In addition, maps were obtained of RX Boo with the Very Large Array over several years. Results: We find that most of the emission in the circumstellar shell of RX Boo is located in an incomplete ring with an inner radius of 91 mas (15 AU). A velocity gradient is found in a NW-SE direction. The maser region can be modelled as a shell with a thickness of 22 AU, which is only partially filled. The gas crossing time is 16.5 years. The ring-like structure and the velocity gradient remained stable for at least 11 years, while the maser line profiles varied strongly. This suggests that the spatial asymmetry is not accidental, so that either the mass loss process or the maser excitation conditions in RX Boo are not spherically symmetric. The strong variability of the maser spectral features is mainly due to incoherent intensity fluctuations of maser emission spots, which have lifetimes of the order of 1 year. We found no correlation between the optical and the maser variability in either star. The variability properties of the SV Peg masers do not differ substantially from those of RX Boo. There were fewer spectral features present, and the range of variations was narrower. The maser was active on the >10-Jy level only 1990-1992 and 2006/2007. At other times the maser was either absent (<1 Jy) or barely detectable. Conclusions: The variability of H2O masers in the SRVs RX Boo and SV Peg is due to the emergence and disappearance of maser clouds with lifetimes of ~1 year. The emission regions do not evenly fill the shell of RX Boo leading to asymmetry in the spatial distribution, which persists at least an order of magnitude longer. Appendix A is only available in electronic form at http://www.aanda.org

The Embedded Ring-like Feature and Star Formation Activities in G35.673-00.847

NASA Astrophysics Data System (ADS)

Dewangan, L. K.; Devaraj, R.; Ojha, D. K.

2018-02-01

We present a multiwavelength study to probe the star formation (SF) process in the molecular cloud linked with the G35.673-00.847 site (hereafter MCG35.6), which is traced in a velocity range of 53–62 km s‑1. Multiwavelength images reveal a semi-ring-like feature (associated with ionized gas emission) and an embedded face-on ring-like feature (without the NVSS 1.4 GHz radio emission, where 1σ ∼ 0.45 mJy beam‑1) in MCG35.6. The semi-ring-like feature is originated by the ionizing feedback from a star with spectral type B0.5V–B0V. The central region of the ring-like feature does not contain detectable ionized gas emission, indicating that the ring-like feature is unlikely to be produced by the ionizing feedback from a massive star. Several embedded Herschel clumps and young stellar objects (YSOs) are identified in MCG35.6, tracing the ongoing SF activities within the cloud. The polarization information from the Planck and GPIPS data trace the plane-of-sky magnetic field, which is oriented parallel to the major axis of the ring-like feature. At least five clumps (having M clump ∼ 740–1420 M ⊙) seem to be distributed in an almost regularly spaced manner along the ring-like feature and contain noticeable YSOs. Based on the analysis of the polarization and molecular line data, three subregions containing the clumps are found to be magnetically supercritical in the ring-like feature. Altogether, the existence of the ring-like feature and the SF activities on its edges can be explained by the magnetic field mediated process as simulated by Li & Nakamura.

Observations of Ellerman bomb emission features in He I D3 and He I 10 830 Å

NASA Astrophysics Data System (ADS)

Libbrecht, Tine; Joshi, Jayant; Rodríguez, Jaime de la Cruz; Leenaarts, Jorrit; Ramos, Andrés Asensio

2017-02-01

Context. Ellerman bombs (EBs) are short-lived emission features, characterised by extended wing emission in hydrogen Balmer lines. Until now, no distinct signature of EBs has been found in the He I 10 830 Å line, and conclusive observations of EBs in He I D3 have never been reported. Aims: We aim to study the signature of EBs in neutral helium triplet lines. Methods: The observations consisted of ten consecutive SST/TRIPPEL raster scans close to the limb, featuring the Hβ, He I D3 and He I 10 830 Å spectral regions. We also obtained raster scans with IRIS and made use of the SDO/AIA 1700 Å channel. We used Hazel to invert the neutral helium triplet lines. Results: Three EBs in our data show distinct emission signatures in neutral helium triplet lines, most prominently visible in the He I D3 line. The helium lines have two components: a broad and blueshifted emission component associated with the EB, and a narrower absorption component formed in the overlying chromosphere. One of the EBs in our data shows evidence of strong velocity gradients in its emission component. The emission component of the other two EBs could be fitted using a constant slab. Our analysis hints towards thermal Doppler motions having a large contribution to the broadening for helium and IRIS lines. We conclude that the EBs must have high temperatures to exhibit emission signals in neutral helium triplet lines. An order of magnitude estimate places our observed EBs in the range of T 2 × 104-105 K. Movies associated to Figs. 3-5 are available at http://www.aanda.org

Time series analysis of tool wear in sheet metal stamping using acoustic emission

NASA Astrophysics Data System (ADS)

Vignesh Shanbhag, V.; Pereira, P. Michael; Rolfe, F. Bernard; Arunachalam, N.

2017-09-01

Galling is an adhesive wear mode that often affects the lifespan of stamping tools. Since stamping tools represent significant economic cost, even a slight improvement in maintenance cost is of high importance for the stamping industry. In other manufacturing industries, online tool condition monitoring has been used to prevent tool wear-related failure. However, monitoring the acoustic emission signal from a stamping process is a non-trivial task since the acoustic emission signal is non-stationary and non-transient. There have been numerous studies examining acoustic emissions in sheet metal stamping. However, very few have focused in detail on how the signals change as wear on the tool surface progresses prior to failure. In this study, time domain analysis was applied to the acoustic emission signals to extract features related to tool wear. To understand the wear progression, accelerated stamping tests were performed using a semi-industrial stamping setup which can perform clamping, piercing, stamping in a single cycle. The time domain features related to stamping were computed for the acoustic emissions signal of each part. The sidewalls of the stamped parts were scanned using an optical profilometer to obtain profiles of the worn part, and they were qualitatively correlated to that of the acoustic emissions signal. Based on the wear behaviour, the wear data can be divided into three stages: - In the first stage, no wear is observed, in the second stage, adhesive wear is likely to occur, and in the third stage severe abrasive plus adhesive wear is likely to occur. Scanning electron microscopy showed the formation of lumps on the stamping tool, which represents galling behavior. Correlation between the time domain features of the acoustic emissions signal and the wear progression identified in this study lays the basis for tool diagnostics in stamping industry.

The spectrum of HM Sagittae: A planetary nebula excited by a Wolf-Rayet star

NASA Technical Reports Server (NTRS)

Brown, L. W.; Feibelman, W. A.; Hobbs, R. W.; Mccracken, C. W.

1977-01-01

A total of image tube spectrograms of HM Sagittae were obtained. More than 70 emission lines, including several broad emission features, were identified. An analysis of the spectra indicates that HM Sagittae is a planetary nebula excited by a Wolf-Rayet star. The most conspicuous Wolf-Rayet feature is that attributed to a blend of C III at 4650 A and He II at 4686 A.

Laboratory investigation of nitrile ices of Titan's stratospheric clouds

NASA Astrophysics Data System (ADS)

Nna Mvondo, D.; Anderson, C. M.; McLain, J. L.; Samuelson, R. E.

2017-09-01

Titan's mid to lower stratosphere contains complex cloud systems of numerous organic ice particles comprised of both hydrocarbon and nitrile compounds. Most of these stratospheric ice clouds form as a result of vapor condensation formation processes. However, there are additional ice emission features such as dicyanoacetylene (C4N2) and the 220 cm-1 ice emission feature (the "Haystack") that are difficult to explain since there are no observed vapor emission features associated with these ices. In our laboratory, using a high-vacuum chamber coupled to a FTIR spectrometer, we are engaged in a dedicated investigation of Titan's stratospheric ices to interpret and constrain Cassini Composite InfraRed Spectrometer (CIRS) far-IR data. We will present laboratory transmittance spectra obtained for propionitrile (CH3CH2CN), cyanogen (C2N2) and hydrogen cyanide (HCN) ices, as well as various combinations of their mixtures, to better understand the cloud chemistry occurring in Titan's stratosphere.

Methods of editing cloud and atmospheric layer affected pixels from satellite data

NASA Technical Reports Server (NTRS)

Nixon, P. R. (Principal Investigator); Wiegand, C. L.; Richardson, A. J.; Johnson, M. P.; Goodier, B. G.

1981-01-01

The location and migration of cloud, land and water features were examined in spectral space (reflective VIS vs. emissive IR). Daytime HCMM data showed two distinct types of cloud affected pixels in the south Texas test area. High altitude cirrus and/or cirrostratus and "subvisible cirrus" (SCi) reflected the same or only slightly more than land features. In the emissive band, the digital counts ranged from 1 to over 75 and overlapped land features. Pixels consisting of cumulus clouds, or of mixed cumulus and landscape, clustered in a different area of spectral space than the high altitude cloud pixels. Cumulus affected pixels were more reflective than land and water pixels. In August the high altitude clouds and SCi were more emissive than similar clouds were in July. Four-channel TIROS-N data were examined with the objective of developing a multispectral screening technique for removing SCi contaminated data.

Polycyclic aromatic hydrocarbon molecules in astrophysics

NASA Astrophysics Data System (ADS)

Rastogi, Shantanu; Pathak, Amit; Maurya, Anju

2013-06-01

Polycyclic aromatic hydrocarbon (PAH) molecules are responsible for the mid-infrared emission features. Their ubiquitous presence in almost all types of astrophysical environments and related variations in their spectral profilesmake them an important tool to understand the physics and chemistry of the interstellar medium. The observed spectrum is generally a composite superposition of all different types of PAHs possible in the region. In the era of space telescopes the spectral richness of the emission features has enhanced their importance as probe and also the need to understand the variations with respect to PAH size, type and ionic state. Quantum computational studies of PAHs have proved useful in elucidating the profile variations and put constraints on the possible types of PAHs in different environments. The study of PAHs has also significantly contributed to the problems of diffuse interstellar bands (DIBs), UV extinction and understanding the chemistry of the formation of complex organics in space. The review highlights the results of various computational models for the understanding of infrared emission features, the PAH-DIB relation, formation of prebiotics and possible impact in the understanding of far-infrared features.

Application of the laguerre deconvolution method for time-resolved fluorescence spectroscopy to the characterization of atherosclerotic plaques.

PubMed

Jo, J A; Fang, Q; Papaioannou, T; Qiao, J H; Fishbein, M C; Beseth, B; Dorafshar, A H; Reil, T; Baker, D; Freischlag, J; Marcu, L

2005-01-01

This study investigates the ability of time-resolved laser-induced fluorescence spectroscopy (TR-LIFS) to detect inflammation in atherosclerotic lesion, a key feature of plaque vulnerability. A total of 348 TR-LIFS measurements were taken from carotid plaques of 30 patients, and subsequently analyzed using the Laguerre deconvolution technique. The investigated spots were classified as Early, Fibrotic/Calcified or Inflamed lesions. A stepwise linear discriminant analysis algorithm was developed using spectral and TR features (normalized intensity values and Laguerre expansion coefficients at discrete emission wavelengths, respectively). Features from only three emission wavelengths (390, 450 and 500 nm) were used in the classifier. The Inflamed lesions were discriminated with sensitivity > 80% and specificity > 90 %, when the Laguerre expansion coefficients were included in the feature space. These results indicate that TR-LIFS information derived from the Laguerre expansion coefficients at few selected emission wavelengths can discriminate inflammation in atherosclerotic plaques. We believe that TR-LIFS derived Laguerre expansion coefficients can provide a valuable additional dimension for the detection of vulnerable plaques.

A TALE OF THREE MYSTERIOUS SPECTRAL FEATURES IN CARBON-RICH EVOLVED STARS: THE 21 μm, 30 μm, AND “UNIDENTIFIED INFRARED” EMISSION FEATURES

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

Mishra, Ajay; Li, Aigen; Jiang, B. W., E-mail: amishra@mail.missouri.edu, E-mail: lia@missouri.edu, E-mail: bjiang@bnu.edu.cn

2015-03-20

The mysterious “21 μm” emission feature seen almost exclusively in the short-lived protoplanetary nebula (PPN) phase of stellar evolution remains unidentified since its discovery two decades ago. This feature is always accompanied by the equally mysterious, unidentified “30 μm” feature and the so-called “unidentified infrared” (UIR) features at 3.3, 6.2, 7.7, 8.6, and 11.3 μm which are generally attributed to polycyclic aromatic hydrocarbon (PAH) molecules. The 30 μm feature is commonly observed in all stages of stellar evolution from the asymptotic giant branch through PPN to the planetary nebula phase. We explore the interrelations among the mysterious 21, 30 μm,more » and UIR features of the 21 μm sources. We derive the fluxes emitted in the observed UIR, 21, and 30 μm features from published Infrared Space Observatory or Spitzer/IRS spectra. We find that none of these spectral features correlate with each other. This argues against a common carrier (e.g., thiourea) for both the 21 μm feature and the 30 μm feature. This also does not support large PAH clusters as a possible carrier for the 21 μm feature.« less

Mid-infrared spectroscopy to better characterize icy moon surface compositions

NASA Astrophysics Data System (ADS)

Young, Cindy L.; Wray, James J.; Hand, Kevin P.; Poston, Michael; Carlson, Robert W.; Clark, Roger Nelson; Spencer, John R.; Jennings, Donald

2016-10-01

Previous spectroscopy work on icy moons has focused primarily on the visible and near-IR portion of the spectrum due to challenges presented by a low signal to noise ratio at the longer wavelengths. However, the mid-IR is the region of the strongest fundamental vibrations of many important types of molecules (e.g., organics) and has the potential to reveal unique compositional information [1]. We use the wealth of data that is now available from Cassini's Composite Infrared Spectrometer (CIRS) to average spectra over similar regions to improve the signal to noise, helping to reveal spectral features never before observed.Our initial work has already led to the detection and tentative laboratory identification of the first spectral features observed for any icy moon in the mid-IR [2]. On Iapetus' dark terrain, we found an emissivity feature at ~855 cm-1 and a possible doublet at 660 and 690 cm-1 that does not correspond to any known instrument artifacts. We attributed the 855 cm-1 feature to fine-grained silicates, similar to those found in dust on Mars and in meteorites, which are nearly featureless at shorter wavelengths [e.g., 3, 4]. Silicates on the dark terrains of Saturn's icy moons have been suspected for decades, but there have been no definitive detections until this work.We measured the vacuum, low temperature mid-IR spectra of various fine-grained powdered silicates, including Mg-rich serpentines, often present in meteorites. Some of these materials do have emissivity features near 855 cm-1 and exhibit a doublet. Presently, we are continuing to comb the CIRS icy moon database for spectral features (particularly focusing on the warmer surfaces in the Saturn system) and are performing further vacuum chamber measurements to experiment with more sample types and ice/sample mixtures to determine the impacts of changing conditions in the chamber on features. We are also working to understand how surface porosity and mixing with various darkening agents may impact our spectra.[1] Flasar, F. M., et al. (2004), Space Sci Rev, 115, 169.[2] Young, C. L., et al. (2015), ApJ Lett., 811, L27.[3] Christensen, P. R., et al. (2004), Sci, 306, 1733.[4] McAdam, M. M., et al. (2015), Icar, 245, 320.

Spatially extended polycyclic aromatic hydrocarbons in circumstellar disks around T Tauri and Herbig Ae stars

NASA Astrophysics Data System (ADS)

Geers, V. C.; van Dishoeck, E. F.; Visser, R.; Pontoppidan, K. M.; Augereau, J.-C.; Habart, E.; Lagrange, A. M.

2007-12-01

Aims:Our aim is to determine the presence and location of the emission from polycyclic aromatic hydrocarbons (PAHs) towards low and intermediate mass young stars with disks using large aperture telescopes. Methods: VLT-VISIR N-band spectra and VLT-ISAAC and VLT-NACO L-band spectra of 29 sources are presented, spectrally resolving the 3.3, 8.6, 11.2, and 12.6 μm PAH features. Spatial-extent profiles of the features and the continuum emission have been derived and used to associate the PAH emission with the disks. The results are discussed in the context of recent PAH-emission disk models. Results: The 3.3, 8.6, and 11.2 μm PAH features are detected toward a small fraction of the T Tauri stars, with typical upper limits between 1 × 10-15 and 5 × 10-17 W m-2. All 11.2 μm detections from a previous Spitzer survey are confirmed with (tentative) 3.3 μm detections, and both the 8.6 and the 11.2 μm features are detected in all PAH sources. For 6 detections, the spatial extent of the PAH features is confined to scales typically smaller than 0.12-0.34'', consistent with the radii of 12-60 AU disks at their distances (typically 150 pc). For 3 additional sources, WL 16, HD 100546, and TY CrA, one or more of the PAH features are more extended than the hot dust continuum of the disk, whereas for Oph IRS 48, the size of the resolved PAH emission is confirmed as smaller than for the large grains. For HD 100546, the 3.3 μm emission is confined to a small radial extent of 12±3 AU, most likely associated with the outer rim of the gap in this disk. Gaps with radii out to 10-30 AU may also affect the observed PAH extent for other sources. For both Herbig Ae and T Tauri stars, the small measured extents of the 8.6 and 11.2 μm features are consistent with larger (≥100 carbon atoms) PAHs. Based on observations obtained at the European Southern Observatory, Paranal, Chile, within the observing programs 164.I-0605 (ISAAC May 2002), 074.C-0413 (NACO, March/April 2005), 075.C-0420 (ISAAC August 2005), 077.C-0668 (VISIR/ISAAC April/May 2006). Appendix A is only available in electronic form at http://www.aanda.org

High spatial and spectral resolution measurements of Jupiter's auroral regions using Gemini-North-TEXES

NASA Astrophysics Data System (ADS)

Sinclair, J. A.; Orton, G. S.; Greathouse, T. K.; Lacy, J.; Giles, R.; Fletcher, L. N.; Vogt, M.; Irwin, P. G.

2017-12-01

Jupiter exhibits auroral emission at a multitude of wavelengths. Auroral emission at X-ray, ultraviolet and near-infrared wavelengths demonstrate the precipitation of ion and electrons in Jupiter's upper atmosphere, at altitudes exceeding 250 km above the 1-bar level. Enhanced mid-infrared emission of CH4, C2H2, C2H4 and further hydrocarbons is also observed coincident with Jupiter's auroral regions. Retrieval analyses of infrared spectra from IRTF-TEXES (Texas Echelon Cross Echelle Spectrograph on NASA's Infrared Telescope Facility) indicate strong heating at the 1-mbar level and evidence of ion-neutral chemistry, which enriches the abundances of unsaturated hydrocarbons (Sinclair et al., 2017b, doi:10.1002/2017GL073529, Sinclair et al., 2017c (under review)). The extent to which these phenomena in the stratosphere are correlated and coupled physically with the shorter-wavelength auroral emission originating from higher altitudes has been a challenge due to the limited spatial resolution available on the IRTF. Smaller-scale features observed in the near-infrared and ultraviolet emission, such as the main `oval', transient `swirls' and dusk-active regions within the main oval (e.g. Stallard et al., 2014, doi:10.1016/j/Icarus.2015.12.044, Nichols et al., 2017, doi: 10.1002/2017GL073029) are potentially being blurred in the mid-infrared by the diffraction-limited resolution (0.7") of IRTF's 3-metre primary aperture. However, on March 17-19th 2017, we obtained spectral measurements of H2 S(1), CH4, C2H2, C2H4 and C2H6 emission of Jupiter's high latitudes using TEXES on Gemini-North, which has a 8-metre primary aperture. This rare opportunity combines the superior spectral resolving power of TEXES and the high spatial resolution provided by Gemini-North's 8-metre aperture. We will perform a retrieval analyses to determine the 3D distributions of temperature, C2H2, C2H4 and C2H6. The morphology will be compared with near-contemporaneous measurements of H3+ emission from IRTF-SpeX and Juno-JIRAM/UVS to assess the extent of coupling between the stratosphere and ionosphere. In addition, a magnetospheric mapping tool (Vogt et al. 2011, doi:10.1029/2010JA016148) will be used to determine whether small-scale features are likely linked to the solar wind or the magnetosphere.

KVN observations reveal multiple γ-ray emission regions in 3C 84?

NASA Astrophysics Data System (ADS)

Hodgson, Jeffrey A.; Rani, Bindu; Lee, Sang-Sung; Algaba, Juan Carlos; Kino, Motoki; Trippe, Sascha; Park, Jong-Ho; Zhao, Guang-Yao; Byun, Do-Young; Kang, Sincheol; Kim, Jae-Young; Kim, Jeong-Sook; Kim, Soon-Wook; Miyazaki, Atsushi; Wajima, Kiyoaki; Oh, Junghwan; Kim, Dae-won; Gurwell, Mark

2018-03-01

3C 84 (NGC 1275) is a well-studied misaligned sctive galactic nucleus (AGN), which has been active in γ-rays since at least 2008. We have monitored the source at four wavelengths (14, 7, 3, and 2 mm) using the Korean VLBI network (KVN) since 2013 as part of the interferometric monitoring of γ-ray bright AGN (iMOGABA) programme, and it exhibits bright radio emission both near the central SMBH and in a slowly moving feature located to the south known as C3. Other facilities have also detected these short-term variations above a slowly rising trend at shorter wavelengths, such as in γ-ray and 1-mm total intensity light curves. We find that the variations in the γ-rays and 1-mm total intensity light curves are correlated, with the γ-ray leading and lagging the radio emission. Analysis of the 2-mm KVN data shows that both the γ-rays and 1-mm total intensity short-term variations are better correlated with the SMBH region than C3, likely placing the short-term variations in C1. We interpret the emission as being due to the random alignment of spatially separated emission regions. We place the slowly rising trend in C3, consistent with previous results. Spectral analysis of the γ-ray data shows that the γ-ray flaring is inconsistent with blazar-like γ-ray emission. Additionally, we report that since mid-2015, a large mm-wave radio flare has been occurring in C3, with a large γ-ray flare coincident with the onset of this flare at all radio wavelengths.

Thermal Emissions Spanning the Prompt and the Afterglow Phases of the Ultra-long GRB 130925A

NASA Astrophysics Data System (ADS)

Basak, Rupal; Rao, A. R.

2015-07-01

GRB 130925A is an ultra-long gamma-ray burst (GRB), and it shows clear evidence for thermal emission in the soft X-ray data of the Swift/X-ray Telescope (XRT; ∼0.5 keV), lasting until the X-ray afterglow phase. Due to the long duration of the GRB, the burst could be studied in hard X-rays with high-resolution focusing detectors (NuSTAR). The blackbody temperature, as measured by the Swift/XRT, shows a decreasing trend until the late phase (Piro et al.) whereas the high-energy data reveal a significant blackbody component during the late epochs at an order of magnitude higher temperature (∼5 keV) compared to contemporaneous low energy data (Bellm et al.). We resolve this apparent contradiction by demonstrating that a model with two black bodies and a power law (2BBPL) is consistent with the data right from the late prompt emission to the afterglow phase. Both blackbodies show a similar cooling behavior up to late times. We invoke a structured jet, having a fast spine and a slower sheath layer, to identify the location of these blackbodies. Independent of the physical interpretation, we propose that the 2BBPL model is a generic feature of the prompt emission of all long GRBs, and the thermal emission found in the afterglow phase of different GRBs reflects the lingering thermal component of the prompt emission with different timescales. We strengthen this proposal by pointing out a close similarity between the spectral evolutions of this GRB and GRB 090618, a source with significant wide band data during the early afterglow phase.

Red-luminescence band: A tool for the quality assessment of germanium and silicon nanocrystals

NASA Astrophysics Data System (ADS)

Fraj, I.; Favre, L.; David, T.; Abbarchi, M.; Liu, K.; Claude, J. B.; Ronda, A.; Naffouti, M.; Saidi, F.; Hassen, F.; Maaref, H.; Aqua, J. N.; Berbezier, I.

2017-10-01

We present the photoluminescence (PL) emission of Silicon and Germanium nanocrystals (NCs) of different sizes embedded in two different matrices. Formation of the NCs is achieved via solid-state dewetting during annealing in a molecular beam epitaxy ultra-high vacuum system of ultrathin amorphous Si and Ge layers deposited at room temperature on SiO2. During the dewetting process, the bi-dimensional amorphous layers transform into small pseudo-spherical islands whose mean size can be tuned directly with the deposited thickness. The nanocrystals are capped either ex situ by silicon dioxide or in situ by amorphous Silicon. The surface-state dependent emission (typically in the range 1.74 eV-1.79 eV) exhibited higher relative PL quantum yields compared to the emission originating from the band gap transition. This red-PL emission comes from the radiative transitions between a Si band and an interface level. It is mainly ascribed to the NCs and environment features deduced from morphological and structural analyses. Power dependent analysis of the photoluminescence intensity under continuous excitation reveals a conventional power law with an exponent close to 1, in agreement with the type II nature of the emission. We show that Ge-NCs exhibit much lower quantum efficiency than Si-NCs due to non-radiative interface states. Low quantum efficiency is also obtained when NCs have been exposed to air before capping, even if the exposure time is very short. Our results indicate that a reduction of the non-radiative surface states is a key strategy step in producing small NCs with increased PL emission for a variety of applications. The red-PL band is then an effective tool for the quality assessment of NCs based structures.

The Environmental Impact of Intra-Cluster Medium on the Interstellar Medium in Early Type Galaxies

NASA Technical Reports Server (NTRS)

Trinchieri, Ginevra

1997-01-01

High resolution X-ray images of three early type galaxies observed with the ROSAT HRI are presented. Data for NGC 1553 and NGC 5846 indicate that the emission is highly irregular, with interesting features on scales from a few arcsec to a few arcmin. The gas temperatures also vary both with the galactocentric radius and in correspondence to regions of higher emission and denser material. Strikingly similar features are observed in the X-ray and H(alpha) morphologies of NGC 1553 and NGC 5846, while smoother, more regular isophotes are observed in NGC 4649 at both wavelengths. A connection between these two kinds of emission therefore seems likely. In the light of our observations we discuss possible scenarios that can and account for the connection between X-ray and H(alpha) emissions.

Mid-Infrared Spectrum of the Zodiacal Emission: Detection of Crystalline Silicates in Interplanetary Dust

NASA Technical Reports Server (NTRS)

Ootsubo, T.; Onaka, T.; Yamamura, I.; Ishihara, D.; Tanabe, T.; Roellig, T. L.

2003-01-01

Within a few astronomical units of the Sun the solar system is filled with interplanetary dust, which is believed to be dust of cometary and asteroidal origin. Spectroscopic observations of the zodiacal emission with moderate resolution provide key information on the composition and size distribution of the dust in the interplanetary space. They can be compared directly to laboratory measurements of candidate materials, meteorites, and dust particles collected in the stratosphere. Recently mid-infrared spectroscopic observations of the zodiacal emission have been made by two instruments on board the Infrared Space Observatory; the camera (ISOCAM) and the spectrophotometer (ISOPHOT-S). A broad excess emission feature in the 9-11 micron range is reported in the ISOCAM spectrum, whereas the ISOPHOT-S spectra in 6-12 microns can be well fitted by a blackbody radiation without spectral features.

Characterizing the emission implications of future natural gas production and use in the U.S. and Rocky Mountain region: A scenario-based energy system modeling approach

NASA Astrophysics Data System (ADS)

McLeod, Jeffrey

The recent increase in U.S. natural gas production made possible through advancements in extraction techniques including hydraulic fracturing has transformed the U.S. energy supply landscape while raising questions regarding the balance of environmental impacts associated with natural gas production and use. Impact areas at issue include emissions of methane and criteria pollutants from natural gas production, alongside changes in emissions from increased use of natural gas in place of coal for electricity generation. In the Rocky Mountain region, these impact areas have been subject to additional scrutiny due to the high level of regional oil and gas production activity and concerns over its links to air quality. Here, the MARKAL (MArket ALlocation) least-cost energy system optimization model in conjunction with the EPA-MARKAL nine-region database has been used to characterize future regional and national emissions of CO 2, CH4, VOC, and NOx attributed to natural gas production and use in several sectors of the economy. The analysis is informed by comparing and contrasting a base case, business-as-usual scenario with scenarios featuring variations in future natural gas supply characteristics, constraints affecting the electricity generation mix, carbon emission reduction strategies and increased demand for natural gas in the transportation sector. Emission trends and their associated sensitivities are identified and contrasted between the Rocky Mountain region and the U.S. as a whole. The modeling results of this study illustrate the resilience of the short term greenhouse gas emission benefits associated with fuel switching from coal to gas in the electric sector, but also call attention to the long term implications of increasing natural gas production and use for emissions of methane and VOCs, especially in the Rocky Mountain region. This analysis can help to inform the broader discussion of the potential environmental impacts of future natural gas production and use by illustrating links between relevant economic and environmental variables.

OT2_pgolds01_6: Herschel [NII] Observations to Define the Source of [CII] Emission

NASA Astrophysics Data System (ADS)

Goldsmith, P.

2011-09-01

The 158 micron line of ionized carbon is the strongest single long-wavelength emission feature from the interstellar medium and is the most important coolant of gas in which hydrogen is in atomic form. It is a key determinant of the evolution of these largely atomic regions into denser, cooler molecular clouds in which new stars are formed, and is widely used as a tracer of star formation in the Milky Way and other galaxies. There is, however, an ongoing, serious controversy about the origin of the [CII] emission, which has been asserted to come from the extended low-density warm interstellar medium, but has more generally been associated with the primarily molecular photon dominated regions (PDRs) intimately associated with massive, young stars. We propose a combined HIFI and PACS study of the two far-infrared [NII] fine structure lines in order to resolve the important question of the fraction of CII emission that arises in ionized gas. Specifically, we will (1) utilize the fact that due to its ionization potential NII is found only in HII regions, and with PACS 122 and 205 micron observations, determine electron densities in a sample of such regions in the Galactic plane; (2) utilize available data on radio free-free and H-alpha emission to determine the NII column densities and from this the CII column densities in the HII regions; (3) use the electron densities to determine the fraction of CII emission arising in the ionized interstellar medium. These observations will be carried out at 150 of the positions in the Galactic plane observed in [CII] by the GOT-C+ project. We will also carry out HIFI observations of 10 selected positions in the 205 micron line to determine spectral characteristics of the NII emission line, which with CII, CI, and CO profiles already in hand will serve as a further discriminant among the proposed sources of CII emission.

Near-infrared spectroscopy of the proto-planetary nebula CRL 618 and the origin of the hydrocarbon dust component in the interstellar medium.

PubMed

Chiar, J E; Pendleton, Y J; Geballe, T R; Tielens, A G

1998-11-01

A new 2.8-3.8 micrometers spectrum of the carbon-rich protoplanetary nebula CRL 618 confirms the previous detection of a circumstellar 3.4 micrometers absorption feature in this object (Lequeux & Jourdain de Muizon). The high resolution and high signal-to-noise ratio of our spectrum allow us to derive the detailed profile of this absorption feature, which is very similar to that observed in the spectrum of the Galactic center and also resembles the strong 3.4 micrometers emission feature in some post-asymptotic giant branch stars. A weak 3.3 micrometers unidentified infrared band, marginally detected in the CRL 618 spectrum of Lequeux & Jourdain de Muizon, is present in our spectrum. The existence of the 3.4 micrometers feature implies the presence of relatively short-chained, aliphatic hydrocarbon materials (-CH2-/-CH3 approximately = 2-2.5) in the circumstellar environment around CRL 618. It also implies that the carriers of the interstellar 3.4 micrometers feature are produced at least in part in circumstellar material, and it calls into question whether any are produced by the processing of interstellar ices in dense interstellar clouds, as has been previously proposed. Other features in the spectrum are recombination lines of hydrogen, rotational and vibration-rotation lines of molecular hydrogen, and a broad absorption probably due to a blend of HCN and C2H2 bands.

Near-infrared spectroscopy of the proto-planetary nebula CRL 618 and the origin of the hydrocarbon dust component in the interstellar medium

NASA Technical Reports Server (NTRS)

Chiar, J. E.; Pendleton, Y. J.; Geballe, T. R.; Tielens, A. G.

1998-01-01

A new 2.8-3.8 micrometers spectrum of the carbon-rich protoplanetary nebula CRL 618 confirms the previous detection of a circumstellar 3.4 micrometers absorption feature in this object (Lequeux & Jourdain de Muizon). The high resolution and high signal-to-noise ratio of our spectrum allow us to derive the detailed profile of this absorption feature, which is very similar to that observed in the spectrum of the Galactic center and also resembles the strong 3.4 micrometers emission feature in some post-asymptotic giant branch stars. A weak 3.3 micrometers unidentified infrared band, marginally detected in the CRL 618 spectrum of Lequeux & Jourdain de Muizon, is present in our spectrum. The existence of the 3.4 micrometers feature implies the presence of relatively short-chained, aliphatic hydrocarbon materials (-CH2-/-CH3 approximately = 2-2.5) in the circumstellar environment around CRL 618. It also implies that the carriers of the interstellar 3.4 micrometers feature are produced at least in part in circumstellar material, and it calls into question whether any are produced by the processing of interstellar ices in dense interstellar clouds, as has been previously proposed. Other features in the spectrum are recombination lines of hydrogen, rotational and vibration-rotation lines of molecular hydrogen, and a broad absorption probably due to a blend of HCN and C2H2 bands.

Observations of neutral iron emission in twilight spectra

NASA Technical Reports Server (NTRS)

Tepley, C. A.; Meriwether, J. W., Jr.; Walker, J. C. G.; Mathews, J. D.

1981-01-01

A method is presented for the analysis of twilight airglow spectra that may be contaminated by atmospheric continuum emission of unknown brightness. The necessity of correcting for this continuum emission when measuring weak airglow features in twilight is illustrated by application of the method to the neutral iron line at 3860 A.

Titan's Aerosol and Stratospheric Ice Opacities Between 18 and 500 Micrometers: Vertical and Spectral Characteristics from Cassini CIRS

NASA Technical Reports Server (NTRS)

Anderson, Carrie M.; Samuelson, Robert E.

2011-01-01

Vertical distributions and spectral characteristics of Titan's photochemical aerosol and stratospheric ices are determined between 20 and 560 per centimeter (500-18 micrometers) from the Cassini Composite Infrared Spectrometer (CIRS). Results are obtained for latitudes of 15 N, 15 S, and 58 S, where accurate temperature profiles can be independently determined. In addition, estimates of aerosol and ice abundances at 62 N relative to those at 15 S are derived. Aerosol abundances are comparable at the two latitudes, but stratospheric ices are approximately 3 times more abundant at 62 N than at 15 S. Generally, nitrile ice clouds (probably HCN and HC3N), as inferred from a composite emission feature at approximately 160 per centimeter, appear to be located over a narrow altitude range in the stratosphere centered at approximately 90 km. Although most abundant at high northern latitudes, these nitrile ice clouds extend down through low latitudes and into mid southern latitudes, at least as far as 58 S. There is some evidence of a second ice cloud layer at approximately 60 km altitude at 58 S associated with an emission feature at approximately 80 per centimeter. We speculate that the identify of this cloud may be due to C2H6 ice, which in the vapor phase is the most abundant hydrocarbon (next to CH4) in the stratosphere of Titan. Unlike the highly restricted range of altitudes (50-100 km) associated with organic condensate clouds, Titan's photochemical aerosol appears to be well-mixed from the surface to the top of the stratosphere near an altitude of 300 km, and the spectral shape does not appear to change between 15 N and 58 S latitude. The ratio of aerosol-to-gas scale heights range from 1.3-2.4 at about 160 km to 1.1-1.4 at 300 km, although there is considerable variability with latitude, The aerosol exhibits a very broad emission feature peaking at approximately 140 per centimeter. Due to its extreme breadth and low wavenumber, we speculate that this feature may be caused by low-energy vibrations of two-dimensional lattice structures of large molecules. Examples of such molecules include polycyclic aromatic hydrocarbons (PAHs) and nitrogenated aromatics. Finally, volume extinction coefficients N chi EPSILON derived from 15 S CIRS data at a wavelength of lambda = 62.5 micrometers are compared with those derived from the 10 S Huygens Descent Imager/Spectral Radiometer (DISR) data at 1.583 micrometers. This comparison yields volume extinction coefficient ratios N chi EPSILON (1.583 micrometers)/N chi EPSILON (62.5 micrometers) of roughly 70 and 20, respectively, for Titan's aerosol and stratospheric ices, The inferred particle cross-section ratios chi EPSILON(1.583 micrometers)/chi EPSILON (62.5 micrometers) appear to be consistent with sub-micron size aerosol particles, and effective radii of only a few microns for stratospheric ice cloud particles.

Silicate Phases on the Surfaces of Trojan Asteroids

NASA Astrophysics Data System (ADS)

Martin, Audrey; Emery, Joshua P.; Lindsay, Sean S.

2017-10-01

Determining the origin of asteroids provides an effective means of constraining the solar system’s dynamic past. Jupiter Trojan asteroids (hereafter Trojans) may help in determining the amount of radial mixing that occurred during giant planet migration. Previous studies aimed at characterizing surface composition show that Trojans have low albedo surfaces and are spectrally featureless in the near infrared. The thermal infrared (TIR) wavelength range has advantages for detecting silicates on low albedo asteroids such as Trojans. The 10 μm region exhibits strong features due to the Si-O fundamental molecular vibrations. Silicates that formed in the inner solar system likely underwent thermal annealing, and thus are crystalline, whereas silicates that accreted in the outer solar system experienced less thermal processing, and therefore are more likely to have remained in an amorphous phase. We hypothesize that the Trojans formed in the outer solar system (i.e., the Kuiper Belt), and therefore will have a more dominant amorphous spectral silicate component. With TIR spectra from the Spitzer Space Telescope, we identify mineralogical features from the surface of 11 Trojan asteroids. Fine-grain mixtures of crystalline pyroxene and olivine exhibit a 10 μm feature with sharp cutoffs between about 9 μm and 12 μm, which create a broad flat plateau. Amorphous phases, when present, smooth the sharp emission features, resulting in a dome-like shape. Preliminary results indicate that the surfaces of analyzed Trojans contain primarily amorphous silicates. Emissivity spectra of asteroids 1986 WD and 4709 Ennomos include small peaks in the 10 μm region, diagnostic of small amounts of crystalline olivine. One explanation is that Trojans formed in the same region as Kuiper Belt objects, and when giant planet migration ensued, they were swept into Jupiter’s stable Lagrange points where they are found today. As such, it is possible that an ancestral group of Kuiper Belt objects were separated from Trojans during large planet migration.

A review of fundamental drivers governing the emissions, dispersion and exposure to vehicle-emitted nanoparticles at signalised traffic intersections

NASA Astrophysics Data System (ADS)

Goel, Anju; Kumar, Prashant

2014-11-01

Signalised traffic intersections (TIs) are considered as pollution hot-spots in urban areas, but the knowledge of fundamental drivers governing emission, dispersion and exposure to vehicle-emitted nanoparticles (represented by particle number concentration, PNC) at TIs is yet to be established. A number of following key factors, which are important for developing an emission and exposure framework for nanoparticles at TIs, are critically evaluated as a part of this review article. In particular, (i) how do traffic- and wind-flow features affect emission and dispersion of nanoparticles? (ii) What levels of PNCs can be typically expected under diverse signal- and traffic-conditions? (iii) How does the traffic driving condition affect the particle number (PN) emissions and the particle number emission factors (PNEF)? (iv) What is the relative importance of particle transformation processes in affecting the PNCs? (v) What are important considerations for the dispersion modelling of nanoparticles? (vi) What is extent of exposure at TIs with respect to other locations in urban settings? (vii) What are the gaps in current knowledge on this topic where the future research should focus? We found that the accurate consideration of dynamic traffic flow features at TIs is essential for reliable estimates of PN emissions. Wind flow features at TIs are generally complex to generalise. Only a few field studies have monitored PNCs at TIs until now, reporting over an order of magnitude larger peak PNCs (0.7-5.4 × 105 cm-3) compared with average PNCs at typical roadsides (˜0.3 × 105 cm-3). The PN emission and thus the PNEFs can be up to an order of magnitude higher during acceleration compared with steady speed conditions. The time scale analysis suggests nucleation as the fastest transformation process, followed by dilution, deposition, coagulation and condensation. Consideration of appropriate flow features, PNEFs and transformation processes emerged as important parameters for reliable modelling of PNCs at TIs. Computation of respiratory deposition doses (RDD) based on the available PNC data suggest that the peak RDD at TIs can be up to 12-times higher compared with average RDD at urban roadsides. Systematic field and modelling studies are needed to develop a sound understanding of the emissions, dispersion and exposure of nanoparticles at the TIs.

Unraveling Pr3+ 5d-4f emission in LiLa9(SiO4)6O2 crystals doped with Pr3+ ions

NASA Astrophysics Data System (ADS)

Ivanovskikh, Konstantin V.; Shi, Qiufeng; Bettinelli, Marco; Pustovarov, Vladimir A.

2018-05-01

LiLa9(SiO4)6O2 (LLSO) crystals doped with Pr3+ ions were grown using the slow cooling flux method. The crystals were characterized by means of luminescence and optical spectroscopy and luminescence decay measurements upon excitation in UV, VUV and X-ray range including using synchrotron radiation sources. The spectroscopic data revealed the presence Pr3+ 5d↔4f emission and excitation bands related to Pr3+ ions replacing La3+ in two nonequivalent positions, and features related Pr3+ 4f→4f emission. The photon cascade emission is not observed in LLSO:Pr3+, since Pr3+1S0 state is above the bottom of 4fn-15d mixed-states band. Apart from the emission features related to Pr3+, a defect-related emission was observed upon UV, VUV, and ionizing radiation excitation. Presence of the defects was shown with thermoluminescence measurements and suggested to be the main reason for suppression the 5d→4f emission. Peculiarities of host-to-impurity energy transfer are analyzed and discussed.

Bayesian Multiscale Analysis of X-Ray Jet Features in High Redshift Quasars

NASA Astrophysics Data System (ADS)

McKeough, Kathryn; Siemiginowska, A.; Kashyap, V.; Stein, N.

2014-01-01

X-ray emission of powerful quasar jets may be a result of the inverse Compton (IC) process in which the Cosmic Microwave Background (CMB) photons gain energy by interactions with the jet’s relativistic electrons. However, there is no definite evidence that IC/CMB process is responsible for the observed X-ray emission of large scale jets. A step toward understanding the X-ray emission process is to study the Radio and X-ray morphologies of the jet. We implement a sophisticated Bayesian image analysis program, Low-count Image Reconstruction and Analysis (LIRA) (Esch et al. 2004; Conners & van Dyk 2007), to analyze jet features in 11 Chandra images of high redshift quasars (z ~ 2 - 4.8). Out of the 36 regions where knots are visible in the radio jets, nine showed detectable X-ray emission. We measured the ratios of the X-ray and radio luminosities of the detected features and found that they are consistent with the CMB radiation relationship. We derived a range of the bulk lorentz factor (Γ) for detected jet features under the CMB jet emission model. There is no discernible trend of Γ with redshift within the sample. The efficiency of the X-ray emission between the detected jet feature and the corresponding quasar also shows no correlation with redshift. This work is supported in part by the National Science Foundation REU and the Department of Defense ASSURE programs under NSF Grant no.1262851 and by the Smithsonian Institution, and by NASA Contract NAS8-39073 to the Chandra X-ray Center (CXC). This research has made use of data obtained from the Chandra Data Archive and Chandra Source Catalog, and software provided by the CXC in the application packages CIAO, ChIPS, and Sherpa. We thank Teddy Cheung for providing the VLA radio images. Connors, A., & van Dyk, D. A. 2007, Statistical Challenges in Modern Astronomy IV, 371, 101 Esch, D. N., Connors, A., Karovska, M., & van Dyk, D. A. 2004, ApJ, 610, 1213

Red and near-infrared fluorophores inspired by chlorophylls: consideration of practical brightness in multicolor flow cytometry and biomedical sciences

NASA Astrophysics Data System (ADS)

Taniguchi, Masahiko; Hu, Gongfang; Liu, Rui; Du, Hai; Lindsey, Jonathan S.

2018-02-01

Demands in flow cytometry for increased multiplexing (for detection of multiple antigens) and brightness (for detection of rare entities) require new fluorophores (i.e., "colors") with spectrally distinct fluorescence outside the relatively congested visible spectral region. Flow cytometry fluorophores typically must function in aqueous solution upon bioconjugation and ideally should exhibit a host of photophysical features: (i) strong absorption, (ii) sizable Stokes shift, (iii) modest if not strong fluorescence, and (iv) narrow fluorescence band. Tandem dyes have long been pursued to achieve a large effective Stokes shift, increased brightness, and better control over the excitation and emission wavelengths. Here, the attractive photophysical features of chlorophylls and bacteriochlorophylls - Nature's chosen photoactive pigments for photosynthesis - are described with regards to use in flow cytometry. A chlorophyll (or bacteriochlorophyll) constitutes an intrinsic tandem dye given the red (or near-infrared) fluorescence upon excitation in the higher energy ultraviolet (UV) or visible absorption bands (due to rapid internal conversion to the lowest energy state). Synthetic (bacterio)chlorins are available with strong absorption (near-UV molar absorption coefficient ɛ(λexc) 105 M-1cm-1), modest fluorescence quantum yield (Φf = 0.05-0.30), and narrow fluorescence band (10-25 nm) tunable from 600-900 nm depending on synthetic design. The "relative practical brightness" is given by intrinsic brightness [ɛ(λexc) x Φf] times ηf, the fraction of the fluorescence band that is captured by an emission filter in a multicolor experiment. The spectroscopic features of (bacterio)chlorins are evaluated quantitatively to illustrate practical brightness for this novel class of fluorophores in a prospective 8-color panel.

The 2006-2007 Active Phase of Anomalous X-Ray Pulsar 4U 0142+61: Radiative and Timing Changes, Bursts,and Burst Spectral Features

NASA Technical Reports Server (NTRS)

Gavriil, Fotis P.; Dib, Rim; Kaspi, Victoria M.

2011-01-01

After at least 6 years of quiescence, Anomalous X-ray Pulsar (AXP) 4U 0142+61 entered an active phase in 2006 March that lasted several months and included six X-ray bursts as well as many changes in the persistent X-ray emission. The bursts, the first seen from this AXP in > 11 years of Rossi X-ray Timing Explorer monitoring, all occurred in the interval between 2006 April 6 and 2007 February 7. The burst durations ranged from 0.4 - 1.8 x 10(exp 3) s. The first five burst spectra are well modeled by blackbodies, with temperatures kT approx 2 - 9 keV. However, the sixth burst had a complicated spectrum that is well characterized by a blackbody plus two emission features whose amplitude varied throughout the burst. The most prominent feature was at 14.0 keV. Upon entry into the active phase the pulsar showed a significant change in pulse morphology and a likely timing glitch. The glitch had a total frequency jump of (1.9+/-0.4) x 10(exp -7) Hz, which recovered with a decay time of 17+/-2 days by more than the initial jump, implying a net spin-down of the pulsar. Within the framework of the magnetar model, the net spin-down of the star could be explained by regions of the superfluid that rotate. slower than the rest. The bursts, flux enhancements, and pulse morphology changes can be explained as arising from crustal deformations due to stresses imposed by the highly twisted internal magnetic field. However, unlike other AXP outbursts, we cannot account for a major twist being implanted in the magnetosphere.

ISM Dust Grains and N-band Spectral Variability in the Spatially Resolved Subarcsecond Binary UY Aur

NASA Astrophysics Data System (ADS)

Skemer, Andrew J.; Close, Laird M.; Hinz, Philip M.; Hoffmann, William F.; Greene, Thomas P.; Males, Jared R.; Beck, Tracy L.

2010-03-01

The 10 μm silicate feature is an essential diagnostic of dust-grain growth and planet formation in young circumstellar disks. The Spitzer Space Telescope has revolutionized the study of this feature, but due to its small (85 cm) aperture, it cannot spatially resolve small/medium-separation binaries (lsim3''; <~ 420 AU) at the distances of the nearest star-forming regions (~140 pc). Large, 6-10 m ground-based telescopes with mid-infrared instruments can resolve these systems. In this paper, we spatially resolve the 0farcs88 binary, UY Aur, with MMTAO/BLINC-MIRAC4 mid-infrared spectroscopy. We then compare our spectra to Spitzer/IRS (unresolved) spectroscopy, and resolved images from IRTF/MIRAC2, Keck/OSCIR, and Gemini/Michelle, which were taken over the past decade. We find that UY Aur A has extremely pristine, interstellar medium (ISM)-like grains and that UY Aur B has an unusually shaped silicate feature, which is probably the result of blended emission and absorption from foreground extinction in its disk. We also find evidence for variability in both UY Aur A and UY Aur B by comparing synthetic photometry from our spectra with resolved imaging from previous epochs. The photometric variability of UY Aur A could be an indication that the silicate emission itself is variable, as was recently found in EX Lupi. Otherwise, the thermal continuum is variable, and either the ISM-like dust has never evolved, or it is being replenished, perhaps by UY Aur's circumbinary disk. The observations reported here were partially obtained at the Infrared Telescope Facility, which is operated by the University of Hawaii under Cooperative Agreement no. NCC 5-538 with the National Aeronautics and Space Administration, Science Mission Directorate, Planetary Astronomy Program.

The Luminous Polycyclic Aromatic Hydrocarbon Emission Features: Applications to High Redshift Galaxies and Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Shipley, Heath V.

2016-01-01

For decades, significant work has been applied to calibrating emission from the ultra-violet, nebular emission lines, far-infrared, X-ray and radio as tracers of the star-formation rate (SFR) in distant galaxies. Understanding the exact rate of star-formation and how it evolves with time and galaxy mass has deep implications for how galaxies form. The co-evolution of star-formation and supermassive black hole (SMBH) accretion is one of the key problems in galaxy formation theory. But, many of these SFR indicators are influenced by SMBH accretion in galaxies and result in unreliable SFRs. Utilizing the luminous polycyclic aromatic hydrocarbon (PAH) emission features, I provide a new robust SFR calibration using the luminosity emitted from the PAHs at 6.2μm, 7.7μm and 11.3μm to solve this. The PAH features emit strongly in the mid-infrared (mid-IR; 5-25μm) mitigating dust extinction, containing on average 5-10% of the total IR luminosity in galaxies. I use a sample of 105 star-forming galaxies covering a range of total IR luminosity, LIR = L(8-1000μm) = 109 - 1012 L⊙ and redshift 0 < z < 0.4, with mid-IR spectroscopy from the Spitzer Infrared Spectrograph (IRS), and data covering other SFR indicators (Hα emission and rest-frame 24μm continuum emission). The PAH luminosity correlates linearly with the SFR as measured by the Hα luminosity (corrected for attenuation using the mono-chromatic rest-frame 24μm emission), with a tight scatter of <0.15 dex. The scatter is comparable to that between SFRs derived from the Paα and dust-corrected Hα emission lines. We present a case study in advance of JWST, which will be capable of measuring SFRs (from 8μm rest-frame photometry, i.e. PAHs) in distant galaxies (z ≤ 2) with JWST/MIRI to SFRs as low as ~10 M⊙yr-1, because the PAH features are so bright. We use Spitzer/IRS observations of PAH features in lensed star-forming galaxies at 1 < z < 3 to demonstrate the utility of the PAHs to derive SFRs that agree with those available from Paα. This new SFR indicator will be useful for probing the peak of the SFR density in the universe (1 < z < 3) and for studying the co-evolution of star-formation and supermassive blackhole accretion contemporaneously in a galaxy.

Implications of the IRAS data for galactic gamma-ray astronomy and EGRET

NASA Technical Reports Server (NTRS)

Stecker, F. W.

1990-01-01

Using the results of gamma-ray, millimeter wave and far infrared surveys of the galaxy, one can derive a logically consistent picture of the large scale distribution of galactic gas and cosmic rays, one tied to the overall processes of stellar birth and destruction on a galactic scale. Using the results of the IRAS far-infrared survey of the galaxy, the large scale radial distribution of galactic far-infrared emission were obtained independently for both the Northern and Southern Hemisphere sides of the Galaxy. It was found that the dominant feature in these distributions to be a broad peak coincident with the 5 kpc molecular gas cloud ring. Also found was evidence of spiral arm features. Strong correlations are evident between the large scale galactic distributions of far infrared emission, gamma-ray emission and total CO emission. There is a particularly tight correlation between the distribution of warm molecular clouds and far-infrared emission on a galactic scale.

Interstellar polycyclic aromatic hydrocarbons - The infrared emission bands, the excitation/emission mechanism, and the astrophysical implications

NASA Technical Reports Server (NTRS)

Allamandola, L. J.; Tielens, G. G. M.; Barker, J. R.

1989-01-01

A comprehensive study of the PAH hypothesis is presented, including the interstellar, IR spectral features which have been attributed to emission from highly vibrationally excited PAHs. Spectroscopic and IR emission features are discussed in detail. A method for calculating the IR fluorescence spectrum from a vibrationally excited molecule is described. Analysis of interstellar spectrum suggests that the PAHs which dominate the IR spectra contain between 20 and 40 C atoms. The results are compared with results from a thermal approximation. It is found that, for high levels of vibrational excitation and emission from low-frequency modes, the two methods produce similar results. Also, consideration is given to the relationship between PAH molecules and amorphous C particles, the most likely interstellar PAH molecular structures, the spectroscopic structure produced by PAHs and PAH-related materials in the UV portion of the interstellar extinction curve, and the influence of PAH charge on the UV, visible, and IR regions.

Surface wind accuracy for modeling mineral dust emissions: Comparing two regional models in a Bodélé case study

NASA Astrophysics Data System (ADS)

Laurent, B.; Heinold, B.; Tegen, I.; Bouet, C.; Cautenet, G.

2008-05-01

After a decade of research on improving the description of surface and soil features in desert regions to accurately model mineral dust emissions, we now emphasize the need for deeper evaluating the accuracy of modeled 10-m surface wind speeds U 10 . Two mesoscale models, the Lokal-Modell (LM) and the Regional Atmospheric Modeling System (RAMS), coupled with an explicit dust emission model have previously been used to simulate mineral dust events in the Bodélé region. We compare LM and RAMS U 10 , together with measurements at the Chicha site (BoDEx campaign) and Faya-Largeau meteorological station. Surface features and soil schemes are investigated to correctly simulate U 10 intensity and diurnal variability. The uncertainties in dust emissions computed with LM and RAMS U 10 and different soil databases are estimated. This sensitivity study shows the importance of accurate computation of surface winds to improve the quantification of regional dust emissions from the Bodélé

High temperature structure in cool binary stars

NASA Technical Reports Server (NTRS)

Dupree, A. K.; Brickhouse, Nancy S.; Hanson, G. J.

1995-01-01

Strong high temperature emission lines in the EUVE spectra of binary stars containing cool components (Alpha Aur (Capella), 44 iota Boo, Lambda And, and VY Ari) provide the basis to define reliably the differential emission measure of hot plasma. The emission measure distributions for the short-period (P less than or equal to 13 d) binary systems show a high temperature enhancement over a relatively narrow temperature region similar to that originally found in Capella (Dupree et al. 1993). The emission measure distributions of rapidly rotating single stars 31 Com and AB Dor also contain a local enhancement of the emission measure although at different temperatures and width from Capella, suggesting that the enhancement in these objects may be characteristic of rapid rotation of a stellar corona. This feature might be identified with a (polar) active region, although its density and absolute size are unknown; in the binaries Capella and VY Ari, the feature is narrow and it may arise from an interaction region between the components.

The parsec-scale relationship between ICO and AV in local molecular clouds

NASA Astrophysics Data System (ADS)

Lee, Cheoljong; Leroy, Adam K.; Bolatto, Alberto D.; Glover, Simon C. O.; Indebetouw, Remy; Sandstrom, Karin; Schruba, Andreas

2018-03-01

We measure the parsec-scale relationship between integrated CO intensity (ICO) and visual extinction (AV) in 24 local molecular clouds using maps of CO emission and dust optical depth from Planck. This relationship informs our understanding of CO emission across environments, but clean Milky Way measurements remain scarce. We find uniform ICO for a given AV, with the results bracketed by previous studies of the Pipe and Perseus clouds. Our measured ICO-AV relation broadly agrees with the standard Galactic CO-to-H2 conversion factor, the relation found for the Magellanic clouds at coarser resolution, and numerical simulations by Glover & Clark (2016). This supports the idea that CO emission primarily depends on shielding, which protects molecules from dissociating radiation. Evidence for CO saturation at high AV and a threshold for CO emission at low AV varies remains uncertain due to insufficient resolution and ambiguities in background subtraction. Resolution of order 0.1 pc may be required to measure these features. We use this ICO-AV relation to predict how the CO-to-H2 conversion factor (XCO) would change if the Solar Neighbourhood clouds had different dust-to-gas ratio (metallicity). The calculations highlight the need for improved observations of the CO emission threshold and H I shielding layer depth. They are also sensitive to the shape of the column density distribution. Because local clouds collectively show a self-similar distribution, we predict a shallow metallicity dependence for XCO down to a few tenths of solar metallicity. However, our calculations also imply dramatic variations in cloud-to-cloud XCO at subsolar metallicity.

The nuclear region of low luminosity flat radio spectrum sources. II. Emission-line spectra

NASA Astrophysics Data System (ADS)

Gonçalves, A. C.; Serote Roos, M.

2004-01-01

We report on the spectroscopic study of 19 low luminosity Flat Radio Spectrum (LL FRS) sources selected from Marchã's et al. (\\cite{March96}) 200 mJy sample. In the optical, these objects are mainly dominated by the host galaxy starlight. After correcting the data for this effect, we obtain a new set of spectra clearly displaying weak emission lines; such features carry valuable information concerning the excitation mechanisms at work in the nuclear regions of LL FRS sources. We have used a special routine to model the spectra and assess the intensities and velocities of the emission lines; we have analyzed the results in terms of diagnostic diagrams. Our analysis shows that 79% of the studied objects harbour a Low Ionization Nuclear Emission-line Region (or LINER) whose contribution was swamped by the host galaxy starlight. The remaining objects display a higher ionization spectrum, more typical of Seyferts; due to the poor quality of the spectra, it was not possible to identify any possible large Balmer components. The fact that we observe a LINER-type spectrum in LL FRS sources supports the idea that some of these objects could be undergoing an ADAF phase; in addition, such a low ionization emission-line spectrum is in agreement with the black hole mass values and sub-Eddington accretion rates published for some FRS sources. Based on observations collected at the Multiple Mirror Telescope on Mt. Hopkins. Full Fig. 1 is only available in electronic form at http://www.edpsciences.org

Interaction of the accretion flows in corona and disk near the black hole in active galactic nuclei

NASA Astrophysics Data System (ADS)

Meyer-Hofmeister, E.; Liu, B. F.; Qiao, E.

2017-11-01

Context. Accretion flows toward black holes can be of a quite different nature, described as an optically thick cool gas flow in a disk for high accretion rates or as a hot coronal optically thin gas flow for low accretion rates, possibly affected by outflowing gas. Aims: The detection of broad iron emission lines in active galactic nuclei (AGN) indicates the coexistence of corona and disk. The appearance and relative strength of such flows essentially depends on their interaction. Liu et al. suggested that condensation of gas from the corona to the disk allows to understand accretion flows of comparable strength of emission. Matter inflow due to gravitational capture of gas is important for the condensation process. We discuss observational features predicted by the model. Methods: Data from simultaneous observations of AGN with Swift's X-ray and UV-optical telescopes are compared with the theoretical predictions. Results: The frequent detection of broad iron Kα emission lines and the dependence of the emitted spectra on the Eddington ratio, described by the values of the photon index Γ and the two-point spectral index αox are in approximate agreement with the predictions of the condensation model; the latter, however, with a large scatter. The model further yields a coronal emission concentrated in a narrow inner region as is also deduced from the analysis of emissivity profiles. Conclusions: The accretion flows in bright AGN could be described by the accretion of stellar wind or interstellar medium and its condensation into a thin disk.

Constraints on two active galactic nuclei in the merger remnant cosmos J100043.15+020637.2

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

Wrobel, J. M.; Comerford, J. M.; Middelberg, E., E-mail: jwrobel@nrao.edu, E-mail: julie.comerford@colorado.edu, E-mail: middelberg@astro.rub.de

2014-02-20

COSMOS J100043.15+020637.2 is a merger remnant at z = 0.36 with two optical nuclei, NW and SE, offset by 500 mas (2.5 kpc). Prior studies suggest two competing scenarios for these nuclei: (1) SE is an active galactic nucleus (AGN) lost from NW due to a gravitational-wave recoil. (2) NW and SE each contain an AGN, signaling a gravitational-slingshot recoil or inspiralling AGNs. We present new images from the Very Large Array (VLA) at a frequency ν = 9.0 GHz and a FWHM resolution θ = 320 mas (1.6 kpc), and the Very Long Baseline Array (VLBA) at ν =more » 1.52 GHz and θ = 15 mas (75 pc). The VLA imaging is sensitive to emission driven by AGNs and/or star formation, while the VLBA imaging is sensitive only to AGN-driven emission. No radio emission is detected at these frequencies. Folding in prior results, we find: (a) The properties of SE and its adjacent X-ray feature resemble those of the Type 1 AGN in NGC 4151, albeit with a much higher narrow emission-line luminosity. (b) The properties of NW are consistent with it hosting a Compton-thick AGN that warms ambient dust, photoionizes narrow emission-line gas, and is free-free absorbed by that gas. Finding (a) is consistent with scenarios (a) and (b). Finding (b) weakens the case for scenario (a) and strengthens the case for scenario (b). Follow-up observations are suggested.« less

Near-Infrared Emission Lines of Nova Cassiopeiae 1995

NASA Astrophysics Data System (ADS)

Rudy, R. J.; Lynch, D. K.; Mazuk, S. M.; Venturini, C. C.; Puetter, R. C.

2000-12-01

The slow nova V 723 Cas (Nova Cas 1995) exhibits comparatively narrow emission features (FWHM 500 km sec-1) that make it ideal for classifying weak lines and lines blended with stronger features. We present spectra from 0.8-2.5 microns that track the gradual incrase in excitation of Nova Cas and discuss the emission lines that were present. During the period encompassed by these observations Nova Cas reached only moderate excitation-the most energetic coronal lines were [S VIII] 9913 and [Al IX] 20444; lines such as [S IX] 12523 that are prominent in some novae were not detected. Additional coronal lines present include [Si VI] 19641, [Ca VIII] 23205, and [Si VII] 24807. New lines identified include features of [Fe V], [Fe VI]. These iron features are not coronal lines, arising from transitions among low-lying terms rather than within the ground term itself. Also detected was [Ti VI] 17151 that was first identified in V1974 Cygni (Nova Cyg 1992), and possibly [Ti VII] 22050. Accurate wavelengths for a number of unidentified lines are also presented. These unidentified features are discussed with regard to their likely level of excitation and their presence in other novae. This work was supported by the IR&D program of the Aerospace Corporation. RCP acknowledges support from NASA.

Young Debris Disks With Newly Discovered Emission Features

NASA Astrophysics Data System (ADS)

Ballering, N.

2014-04-01

We analyzed the Spitzer/IRS spectra of young A and F stars that host debris disks with previously unidentified silicate emission features. Such features probe small, warm dust grains in the inner regions of these young systems where terrestrial planet formation may be proceeding (Lisse et al. 2009). For most systems, these regions are too near their host star to be directly seen with high-contrast imaging and too warm to be imaged with submillimeter interferometers. Mid-infrared excess spectra - originating from the thermal emission of the debris disk dust - remain the best data to constrain the properties of the debris in these regions. For each target, we fit physically-motivated model spectra to the data. Typical spectra of unresolved debris disks are featureless and suffer severe degeneracies between the dust location and the grain properties; however, spectra with solid-state emission features provide significantly more information, allowing for a more accurate determination of the dust size, composition, and location (e.g. Chen et al. 2006; Olofsson et al. 2012). Our results shed light on the dynamic properties occurring in the terrestrial regions of these systems. For instance, the sizes of the smallest grains and the nature of the grain size distribution reveal whether the dust originates from steady-state collisional cascades or from stochastic collisions. The properties of the dust grains - such as their crystalline or amorphous structure - can inform us of grain processing mechanisms in the disk. The location of this debris illuminates where terrestrial planet forming activity is occurring. We used results from the Beta Pictoris - which has a well-resolved debris disk with emission features (Li et al. 2012) - to place our results in context. References: Chen et al. 2006, ApJS, 166, 351 Li et al. 2012, ApJ, 759, 81 Lisse et al. 2009, ApJ, 701, 2019 Olofsson et al. 2012, A&A, 542, A90

A search for inversion layers in hot Jupiters with high-resolution spectroscopy

NASA Astrophysics Data System (ADS)

Hood, Callie; Birkby, Jayne; Lopez-Morales, Mercedes

2017-01-01

At present, the existence of thermal inversion layers in hot Jupiter atmospheres is uncertain due to conflicting results on their detection. However, understanding the thermal structure of exoplanet atmospheres is crucial to measuring their chemical compositions because the two quantities are highly interdependent. Here, we present high-resolution infrared spectroscopy of a hot Jupiter taken at 3.5 μm with CRIRES (R~100,000) on the Very Large Telescope. We directly detect the spectrum of the planet by tracing the radial-velocity shift of water features in its atmosphere during approximately one tenth of its orbit. We removed telluric contamination effects and the lines of the host star from our observed combined light spectra using singular value decomposition, then cross-correlated these processed spectra with a grid of high spectral resolution molecular templates containing features from water, methane, and carbon dioxide. The templates included atmospheric profiles with and without thermal inversion i.e. emission and absorption lines, respectively. We find evidence of water emission features in the planet’s dayside spectrum at a signal-to-noise of 4.7, indicative of a thermal inversion in the planet's atmosphere within the pressures ranges probed by our observations. The direct detection of emission lines at high spectral resolution in the planet spectrum make it one of the most unambiguous detections of a thermal inversion layer in an exoplanet atmosphere to date. However, we are carrying out further data analysis to ensure the robustness of the signal. Future observations of other molecules that could cause inversion layers, e.g. titanium oxide, would provide strong additional evidence of the inversion and help further our understanding of the behavior of highly irradiated giant planet atmospheres.The SAO REU program is funded in part by the National Science Foundation REU and Department of Defense ASSURE programs under NSF Grant no. 1262851, and by the Smithsonian Institution. This work was performed in part under contract with the California Institute of Technology/Jet Propulsion Laboratory funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute.

AUSTRALIA TELESCOPE COMPACT ARRAY RADIO CONTINUUM 1384 AND 2368 MHz OBSERVATIONS OF SAGITTARIUS B

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

Jones, David I.; Protheroe, Raymond J.; Crocker, Roland M.

2011-03-15

We present images of the Sagittarius (Sgr) B giant molecular cloud at 1384 and 2368 MHz obtained using new, multi-configuration Australia Telescope Compact Array observations. We have combined these observations with archival single-dish observations yielding images at resolutions of 47'' x 14'' and 27'' x 8'' at 1384 and 2368 MHz, respectively. These observations were motivated by our theoretical work indicating the possibility that synchrotron emission from secondary electrons and positrons created in hadronic cosmic ray (CR) collisions with the ambient matter of the Sgr B2 cloud could provide a detectable (and possibly linearly polarized) non-thermal radio signal. We findmore » that the only detectable non-thermal emission from the Sgr B region is from a strong source to the south of Sgr B2, which we label Sgr B2 Southern Complex (SC). We find Sgr B2(SC) integrated flux densities of 1.2 {+-} 0.2 Jy at 1384 MHz and 0.7 {+-} 0.1 Jy at 2368 MHz for a source of FWHM size at 1384 MHz of {approx}54''. Despite its non-thermal nature, the synchrotron emission from this source is unlikely to be dominated due to secondary electrons and positrons. Failing to find clear evidence of non-thermal emission due to secondary electrons and positrons, we use polarization data to place 5{sigma} upper limits on the level of polarized intensity from the Sgr B2 cloud of 3.5 and 3 mJybeam{sup -1} at 1384 and 2368 MHz, respectively. We also use the angular distribution of the total intensity of archival 330 MHz Very Large Array and the total intensity and polarized emission of our new 1384 and 2368 MHz data to constrain the diffusion coefficient for transport of the parent hadronic CRs into the dense core of Sgr B2 to be no larger than about 1% of that in the Galactic disk. Finally, we have also used the data to perform a spectral and morphological study of the features of the Sgr B cloud and compare and contrast these to previous studies.« less

Evaluation of the Committed Carbon Emissions and Global Warming due to the Permafrost Carbon Feedback

NASA Astrophysics Data System (ADS)

Elshorbany, Y. F.; Schaefer, K. M.; Jafarov, E. E.; Yumashev, D.; Hope, C.

2017-12-01

We quantify the increase in carbon emissions and temperature due to Permafrost Carbon feedback (PCF), defined as the amplification of anthropogenic warming due to carbon emissions from thawing permafrost (i.e., of near-surface layers to 3 m depth). We simulate the Committed PCF emissions, the cumulative total emissions from thawing permafrost by 2300 for a given global temperature increase by 2100, and investigate the resulting global warming using the Simple Biosphere/Carnegie-Ames-Stanford Approach SiBCASA model. We estimate the committed PCF emissions and warming for the Fifth Assessment Report, Representative Concentration Pathway scenarios 4.5 and 8.5 using two ensembles of five projections. For the 2 °C warming target of the global climate change treaty, committed PCF emissions increase to 24 Gt C by 2100 and 76 Gt C by 2300 and the committed PCF warming is 0.23 °C by 2300. Our calculations show that as the global temperature increase by 2100 approaches 5.8 °C, the entire stock of frozen carbon thaws out, resulting in maximum committed PCF emissions of 560 Gt C by 2300.

Diffuse X-ray Emission from M101

NASA Technical Reports Server (NTRS)

Kuntz, K. D.; Snowden, S. L.; Pence, W. D.; Mukai, K.; White, Nicholas E. (Technical Monitor)

2002-01-01

The total 0.45-2.0 keV luminosity of M101 is 3.1 x 10(exp 39) ergs/s, of which 2.2 x 10(exp 39) ergs/s is due to diffuse emission. Of the diffuse emission, no more than 6% can be due to unresolved point sources such as X-ray binaries, and approx. 11% is due to dwarf stars. The diffuse emission traces the spiral arms and is roughly correlated with the H alpha and FUV (far ultraviolet) emission. The radial distribution closely follows the optical profile. The bulk of the diffuse emission is characterized by a two thermal component spectrum with kT = 0.20,0.75 keV, and the ratios of the emission measures of the two components is roughly constant as a function of both radius and surface brightness. The softer component has a sufficiently large covering factor that the bulk of the emission is likely extra-planar. We find no evidence of an extended axisymmetric X-ray halo, suggesting that any such halo has a strength much smaller than current predictions.

Development and application of a high resolution hybrid modelling system for the evaluation of urban air quality

NASA Astrophysics Data System (ADS)

Pepe, N.; Pirovano, G.; Lonati, G.; Balzarini, A.; Toppetti, A.; Riva, G. M.; Bedogni, M.

2016-09-01

A hybrid modelling system (HMS) was developed to provide hourly concentrations at the urban local scale. The system is based on the combination of a meteorological model (WRF), a chemical and transport eulerian model (CAMx), which computes concentration levels over the regional domains, and a lagrangian dispersion model (AUSTAL2000), accounting for dispersion phenomena within the urban area due to local emission sources; a source apportionment algorithm is also included in the HMS in order to avoid the double counting of local emissions. The HMS was applied over a set of nested domains, the innermost covering a 1.6 × 1.6 km2 area in Milan city center with 20 m grid resolution, for NOX simulation in 2010. For this paper the innermost domain was defined as ;local;, excluding usual definition of urban areas. WRF model captured the overall evolution of the main meteorological features, except for some very stagnant situations, thus influencing the subsequent performance of regional scale model CAMx. Indeed, CAMx was able to reproduce the spatial and temporal evolution of NOX concentration over the regional domain, except a few episodes, when observed concentrations were higher than 100 ppb. The local scale model AUSTAL2000 provided high-resolution concentration fields that sensibly mirrored the road and traffic pattern in the urban domain. Therefore, the first important outcome of the work is that the application of the hybrid modelling system allowed a thorough and consistent description of urban air quality. This result represents a relevant starting point for future evaluation of pollution exposure within an urban context. However, the overall performance of the HMS did not provide remarkable improvements with respect to stand-alone CAMx at the two only monitoring sites in Milan city center. HMS results were characterized by a smaller average bias, that improved about 6-8 ppb corresponding to 12-13% of the observed concentration, but by a lower correlation, that worsened around 1-3% (e.g. from 0.84 to 0.81 at Senato site), due to the concentration peaks produced by AUSTAL2000 during nighttime stable conditions. Additionally, the HMS results showed that it was unable to correctly take into account some local scale features (e.g. urban canyon effects), pointing out that the emission spatialization and time modulation criteria, especially those from road traffic, need further improvement. Nevertheless, a second important outcome of the work is that some of the most relevant discrepancies between modelled and observed concentrations were not related to the horizontal resolution of the dispersion models but to larger scale meteorological features not captured by the meteorological model, especially during winter period. Finally, the estimated contribution of the local emission sources accounted on the annual average for about 25-30% of the computed concentration levels in the innermost urban domain. This confirmed that the whole Milan urban area as well as the outside background areas, accounting all sources outside the innermost domain, play a key role on air quality. The result suggests that strictly local emission policies could have a limited and indecisive effect on urban air quality, although this finding could be partially biased by model underestimation of the observed concentration.

Clusterization in Ternary Fission

NASA Astrophysics Data System (ADS)

Kamanin, D. V.; Pyatkov, Y. V.

This lecture notes are devoted to the new kind of ternary decay of low excited heavy nuclei called by us "collinear cluster tri-partition" (CCT) due to the features of the effect observed, namely, decay partners fly away almost collinearly and at least one of them has magic nucleon composition. At the early stage of our work the process of "true ternary fission" (fission of the nucleus into three fragments of comparable masses) was considered to be undiscovered for low excited heavy nuclei. Another possible prototype—three body cluster radioactivity—was also unknown. The most close to the CCT phenomenon, at least cinematically, stands so called "polar emission", but only very light ions (up to isotopes of Be) were observed so far.

The 1.4-2.7 micron spectrum of the point source at the galactic center

NASA Technical Reports Server (NTRS)

Treffers, R. R.; Fink, U.; Larson, H. P.; Gautier, T. N., III

1976-01-01

The spectrum of the 2-micron point source at the galactic center is presented over the range from 1.4 to 2.7 microns. The two-level-transition CO band heads are seen near 2.3 microns, confirming that the radiation from this source is due to a cool supergiant star. The heliocentric radial velocity is found to be - 173 (+ or -90) km/s and is consistent with the star being in orbit about a dense galactic nucleus. No evidence is found for Brackett-gamma emission, and no interstellar absorption features are seen. Upper limits for the column densities of interstellar H2, CH4, CO, and NH3 are derived.

Dust Spectroscopy and the Nature of Grains

NASA Technical Reports Server (NTRS)

Tielens, A. G. G. M.

2006-01-01

Ground-based, air-borne and space-based, infrared spectra of a wide variety of objects have revealed prominent absorption and emission features due to large molecules and small dust grains. Analysis of this data reveals a highly diverse interstellar and circumstellar grain inventory, including both amorphous materials and highly crystalline compounds (silicates and carbon). This diversity points towards a wide range of physical and chemical birthsites as well as a complex processing of these grains in the interstellar medium. In this talk, I will review the dust inventory contrasting and comparing both the interstellar and circumstellar reservoirs. The focus will be on the processes that play a role in the lifecycle of dust in the interstellar medium.

New features in Saturn's atmosphere revealed by high-resolution thermal infrared images

NASA Technical Reports Server (NTRS)

Gezari, D. Y.; Mumma, M. J.; Espenak, F.; Deming, D.; Bjoraker, G.; Woods, L.; Folz, W.

1989-01-01

Observations of the stratospheric IR emission structure on Saturn are presented. The high-spatial-resolution global images show a variety of new features, including a narrow equatorial belt of enhanced emission at 7.8 micron, a prominent symmetrical north polar hotspot at all three wavelengths, and a midlatitude structure which is asymmetrically brightened at the east limb. The results confirm the polar brightening and reversal in position predicted by recent models for seasonal thermal variations of Saturn's stratosphere.

The Gum Nebula.

NASA Technical Reports Server (NTRS)

Maran, S. P.

1971-01-01

A historical review of observations on the Gum Nebula is given together with a survey of knowledge on its size, emission features, and dynamics of expansion. The ultraviolet spectrum of Zeta Puppis is examined in terms of features caused by various absorption lines, and radio emission from Vela X is analyzed, together with the effects of nebular plasma on the propagation of radio pulses from pulsars in the Nebula. The density distribution and the possibility of being produced by the Vela X supernova are discussed.

PAH emission from Nova Cen 1986

NASA Technical Reports Server (NTRS)

Hyland, A. R. Harry; Mcgregor, P. J.

1989-01-01

The discovery of broad emission features between 3.2 and 3.6 microns were reported in the spectrum of Nova Cen 1986 (V842 Cen) some 300 days following outburst and remaining prominent for several months. The general characteristics of these features are similar to those attributed to polycyclic hydrocarbon (PAH) molecules in other dusty sources, although the relative strengths are different, and these observations provide the first clear evidence for molecular constituents other than graphite particles in the ejecta of novae.

LETTER TO THE EDITOR: Green emission and bandgap narrowing due to two-photon excitation in thin film CdS formed by spray pyrolysis

NASA Astrophysics Data System (ADS)

Ullrich, B.; Schroeder, R.

2001-08-01

Thin (10 µm) film CdS on Pyrex® formed by spray pyrolysis is excited below the gap at 804 nm with 200 fs laser pulses at room temperature. Excitation intensities up to 250 GW cm-2 evoke green bandgap emission due to two-photon transitions. This two-photon photoluminescence does not show a red emission contribution in contrast to the single-photon excited emission, which is dominated by broad emission in the red spectral range. It is demonstrated that two-photon excitation causes photo-induced bandgap narrowing due to Debye screening. At 250 GW cm-2 bandgap narrowing of 47 meV is observed, which corresponds to an excited electron density of 1.6×1018 cm-3.

High resolution of black carbon and organic carbon emissions in the Pearl River Delta region, China.

PubMed

Zheng, Junyu; He, Min; Shen, Xingling; Yin, Shasha; Yuan, Zibing

2012-11-01

A high-resolution regional black carbon (BC) and organic carbon (OC) emission inventory for the year 2009 was developed for the Pearl River Delta (PRD) region, China, based on the collected activity data and the latest emission factors. PM(2.5), BC and OC emissions were estimated to be 303 kt, 39 kt and 31 kt, respectively. Industrial processes were major contributing sources to PM(2.5) emissions. BC emissions were mainly from mobile sources, accounting for 65.0%, while 34.1% of OC emissions were from residential combustion. The primary OC/BC ratios for individual cities in the PRD region were dependent on the levels of economic development due to differences in source characteristics, with high ratios in the less developed cities and low ratios in the central and southern developed areas. The preliminary temporal profiles were established, showing the highest OC emissions in winter and relatively constant BC emissions throughout the year. The emissions were spatially allocated into grid cells with a resolution of 3 km × 3 km. Large amounts of BC emissions were distributed over the central-southern PRD city clusters, while OC emissions exhibited a relatively even spatial distribution due to the significant biomass burning emissions from the outlying area of the PRD region. Uncertainties in carbonaceous aerosol emissions were usually higher than in other primary pollutants like SO(2), NO(x), and PM(10). One of the key uncertainty sources was the emission factor, due to the absence of direct measurements of BC and OC emission rates. Copyright © 2012 Elsevier B.V. All rights reserved.

Competition Between Resonant Plasmonic Coupling and Electrostatic Interaction in Reduced Graphene Oxide Quantum Dots.

PubMed

Karna, Sanjay; Mahat, Meg; Choi, Tae-Youl; Shimada, Ryoko; Wang, Zhiming; Neogi, Arup

2016-11-22

The light emission from reduced graphene oxide quantum dots (rGO-QDs) exhibit a significant enhancement in photoluminescence (PL) due to localized surface plasmon (LSP) interactions. Silver and gold nanoparticles (NPs) coupled to rGO nanoparticles exhibit the effect of resonant LSP coupling on the emission processes. Enhancement of the radiative recombination rate in the presence of Ag-NPs induced LSP tuned to the emission energy results in a four-fold increase in PL intensity. The localized field due to the resonantly coupled LSP modes induces n-π* transitions that are not observed in the absence of the resonant interaction of the plasmons with the excitons. An increase in the density of the Ag-NPs result in a detuning of the LSP energy from the emission energy of the nanoparticles. The detuning is due to the cumulative effect of the red-shift in the LSP energy and the electrostatic field induced blue shift in the PL energy of the rGO-QDs. The detuning quenches the PL emission from rGO-QDs at higher concentration of Ag NPs due to non-dissipative effects unlike plasmon induced Joule heating that occurs under resonance conditions. An increase in Au nanoparticles concentration results in an enhancement of PL emission due to electrostatic image charge effect.

Infrared molecular emissions from comets

NASA Technical Reports Server (NTRS)

Weaver, H. A.; Mumma, M. J.

1983-01-01

The possibility of detecting IR molecular line emission from cometary parent molecules is explored. Due to the non-LTE conditions in the inner coma and the large amount of near IR solar flux, IR fluorescence will be a significant source of cometary emission and, in fact, will dominate the grain radiation in a sufficiently high resolution instrument. The detection of this line emission will be difficult due to absorption in the terrestrial atmosphere, but it appears possible to measure cometary H2O emission from airplane altitudes. As IR molecular line emission represents one of the few promising methods of detecting cometary parent molecules directly, further research on this problem should be vigorously pursued.

Arctic shipping emissions inventories and future scenarios

NASA Astrophysics Data System (ADS)

Corbett, J. J.; Lack, D. A.; Winebrake, J. J.; Harder, S.; Silberman, J. A.; Gold, M.

2010-10-01

This paper presents 5 km×5 km Arctic emissions inventories of important greenhouse gases, black carbon and other pollutants under existing and future (2050) scenarios that account for growth of shipping in the region, potential diversion traffic through emerging routes, and possible emissions control measures. These high-resolution, geospatial emissions inventories for shipping can be used to evaluate Arctic climate sensitivity to black carbon (a short-lived climate forcing pollutant especially effective in accelerating the melting of ice and snow), aerosols, and gaseous emissions including carbon dioxide. We quantify ship emissions scenarios which are expected to increase as declining sea ice coverage due to climate change allows for increased shipping activity in the Arctic. A first-order calculation of global warming potential due to 2030 emissions in the high-growth scenario suggests that short-lived forcing of ~4.5 gigagrams of black carbon from Arctic shipping may increase global warming potential due to Arctic ships' CO2 emissions (~42 000 gigagrams) by some 17% to 78%. The paper also presents maximum feasible reduction scenarios for black carbon in particular. These emissions reduction scenarios will enable scientists and policymakers to evaluate the efficacy and benefits of technological controls for black carbon, and other pollutants from ships.

The nature of pulsar radio emission

NASA Astrophysics Data System (ADS)

Dyks, J.; Rudak, B.; Demorest, P.

2010-01-01

High-quality averaged radio profiles of some pulsars exhibit double, highly symmetric features both in emission and in absorption. It is shown that both types of feature are produced by a split fan beam of extraordinary-mode curvature radiation that is emitted/absorbed by radially extended streams of magnetospheric plasma. With no emissivity in the plane of the stream, such a beam produces bifurcated emission components (BFCs) when our line of sight passes through the plane. An example of a double component created in this way is present in the averaged profile of the 5-ms pulsar J1012+5307. We show that the component can indeed be very well fitted by the textbook formula for the non-coherent beam of curvature radiation in the polarization state that is orthogonal to the plane of electron trajectory. The observed width of the BFC decreases with increasing frequency at a rate that confirms the curvature origin. Likewise, the double absorption features (double notches) are produced by the same beam of the extraordinary-mode curvature radiation, when it is eclipsed by thin plasma streams. The intrinsic property of curvature radiation to create bifurcated fan beams explains the double features in terms of a very natural geometry and implies the curvature origin of pulsar radio emission. Similarly, the `double conal' profiles of class D result from a cut through a wider stream with finite extent in magnetic azimuth. Therefore, their width reacts very slowly to changes of viewing geometry resulting from geodetic precession. The stream-cut interpretation implies a highly non-orthodox origin of both the famous S-swing of polarization angle and the low-frequency pulse broadening in D profiles. The azimuthal structure of polarization modes in the curvature radiation beam provides an explanation for the polarized `multiple imaging' and the edge depolarization of pulsar profiles.

Potential of Diesel Engine, Emission Technology

DOT National Transportation Integrated Search

1980-03-01

This report surveys diesel engine emission technologies applicable to passenger cars and light trucks. The general design and operating features are presented and discussed. Current and state-of-the-art concepts are reviewed with the focus on control...

The fuel market effects of biofuel policies and implications for regulations based on lifecycle emissions

NASA Astrophysics Data System (ADS)

Rajagopal, Deepak

2013-06-01

The absence of a globally-consistent and binding commitment to reducing greenhouse emissions provides a rationale for partial policies, such as renewable energy mandates, product emission standards, etc to target lifecycle emissions of the regulated products or services. While appealing in principle, regulation of lifecycle emissions presents several practical challenges. Using biofuels as an illustrative example, we highlight some outstanding issues in the design and implementation of life cycle-based policies and discuss potential remedies. We review the literature on emissions due to price effects in fuel markets, which are akin to emissions due to indirect land use change, but are, unlike the latter, ignored under all current life cycle emissions-based regulations. We distinguish the current approaches to regulating indirect emissions into hard and soft approaches and discuss their implications.

Destruction and survival of polycyclic aromatic hydrocarbons in active galaxies

NASA Technical Reports Server (NTRS)

Voit, G. M.

1992-01-01

Infrared spectra of dusty galactic environments often contain emission features attributed to polycyclic aromatic hydrocarbons or PAHs, which can be considered to be very small grains or very large molecules. Although IR spectra of starburst galaxies almost always show these emission features, similar spectra of active galaxies are usually featureless. Even in those active galaxies that do exhibit PAH emission, the PAHs still appear to be eradicated from the nuclear region. This dichotomy suggests that PAHs are destroyed by the intense hard radiation field from an AGN. Laboratory experiments show that certain PAHs are, in fact, so effectively destroyed by individual EUV and X-ray photons that they cannot survive even at kiloparsec distances from active nuclei. Regions within active galaxies that do show PAH emission must therefore be shielded from the central X-ray source by a substantial column density of X-ray absorbing gas.

Can acoustic emission detect the initiation of fatigue cracks: Application to high-strength light alloys used in aeronautics

NASA Technical Reports Server (NTRS)

Bathias, C.; Brinet, B.; Sertour, G.

1978-01-01

Acoustic emission was used for the detection of fatigue cracking in a number of high-strength light alloys used in aeronautical structures. Among the features studied were: the influence of emission frequency, the effect of surface oxidation, and the influence of grains. It was concluded that acoustic emission is an effective nondestructive technique for evaluating the initiation of fatigue cracking in such materials.

Aurora and Non-Auroral X-ray Emissions from Jupiter: A Comparative View

NASA Technical Reports Server (NTRS)

Bhardwal, Anil; Elsner, Ron; Gladstone, Randy; Waite, Hunter, Jr.; Lugaz, Noe; Cravens, Tom; Branduardi-Raymont, Graziella; Ramsay, Gavin; Soria, Rob; Ford, Peter

2004-01-01

Jovian X-rays can be broadly classified into two categories: (1) auroral emission, which is confined to high-latitudes (approximately greater than 60 deg.) at both polar regions, and (2) dayglow emission, which originates from the sunlit low-latitude (approximately less than 50 deg.) regions of the disk (hereafter called disk emissions). Recent X-ray observations of Jupiter by chandra and XMM-Newton have shown that these two types of X-ray emission from Jupiter have different morphological, temporal, and spectral characteristics. In particular: 1) contrary to the auroral X-rays, which are concentrated in a spot in the north and in a band that runs half-way across the planet in the south, the low-latitude X-ray disk is almost uniform; 2) unlike the approximately 40 plus or minus 20-min periodic oscillations seen in the auroral X-ray emissions, the disk emissions do not show any periodic oscillations; 3) the disk emission is harder and extends to higher energies than the auroral spectrum; and 4) the disk X-ray emission show time variability similar to that seen in solar X-rays. These differences and features imply that the processes producing X-rays are different at these two latitude regions on Jupiter. We will present the details of these and other features that suggest the differences between these two classes of X-ray emissions from Jupiter, and discuss the current scenario of the production mechanism of them.

Bacterial bioluminescence onset and quenching: a dynamical model for a quorum sensing-mediated property

PubMed Central

Side, Domenico Delle; Nassisi, Vincenzo; Pennetta, Cecilia; Alifano, Pietro; Di Salvo, Marco; Talà, Adelfia; Chechkin, Aleksei; Seno, Flavio

2017-01-01

We present an effective dynamical model for the onset of bacterial bioluminescence, one of the most studied quorum sensing-mediated traits. Our model is built upon simple equations that describe the growth of the bacterial colony, the production and accumulation of autoinducer signal molecules, their sensing within bacterial cells, and the ensuing quorum activation mechanism that triggers bioluminescent emission. The model is directly tested to quantitatively reproduce the experimental distributions of photon emission times, previously measured for bacterial colonies of Vibrio jasicida, a luminescent bacterium belonging to the Harveyi clade, growing in a highly drying environment. A distinctive and novel feature of the proposed model is bioluminescence ‘quenching’ after a given time elapsed from activation. Using an advanced fitting procedure based on the simulated annealing algorithm, we are able to infer from the experimental observations the biochemical parameters used in the model. Such parameters are in good agreement with the literature data. As a further result, we find that, at least in our experimental conditions, light emission in bioluminescent bacteria appears to originate from a subtle balance between colony growth and quorum activation due to autoinducers diffusion, with the two phenomena occurring on the same time scale. This finding is consistent with a negative feedback mechanism previously reported for Vibrio harveyi. PMID:29308273

Emission shaping in fluorescent proteins: role of electrostatics and π-stacking.

PubMed

Park, Jae Woo; Rhee, Young Min

2016-02-07

For many decades, simulating the excited state properties of complex systems has been an intriguing but daunting task due to its high computational cost. Here, we apply molecular dynamics based techniques with interpolated potential energy surfaces toward calculating fluorescence spectra of the green fluorescent protein (GFP) and its variants in a statistically meaningful manner. With the GFP, we show that the diverse electrostatic tuning can shape the emission features in many different ways. By computationally modulating the electrostatic interactions between the chromophore phenoxy oxygen and its nearby residues, we demonstrate that we indeed can shift the emission to the blue or to the red side in a predictable manner. We rationalize the shifting effects of individual residues in the GFP based on the responses of both the adiabatic and the diabatic electronic states of the chromophore. We next exhibit that the yellow emitting variant, the Thr203Tyr mutant, generates changes in the electrostatic interactions and an additional π-stacking interaction. These combined effects indeed induce a red shift to emit the fluorescence into the yellow region. With the series of demonstrations, we suggest that our approach can provide sound rationales and useful insights in understanding different responses of various fluorescent complexes, which may be helpful in designing new light emitting proteins and other related systems in future studies.

Bacterial bioluminescence onset and quenching: a dynamical model for a quorum sensing-mediated property.

PubMed

Side, Domenico Delle; Nassisi, Vincenzo; Pennetta, Cecilia; Alifano, Pietro; Di Salvo, Marco; Talà, Adelfia; Chechkin, Aleksei; Seno, Flavio; Trovato, Antonio

2017-12-01

We present an effective dynamical model for the onset of bacterial bioluminescence, one of the most studied quorum sensing-mediated traits. Our model is built upon simple equations that describe the growth of the bacterial colony, the production and accumulation of autoinducer signal molecules, their sensing within bacterial cells, and the ensuing quorum activation mechanism that triggers bioluminescent emission. The model is directly tested to quantitatively reproduce the experimental distributions of photon emission times, previously measured for bacterial colonies of Vibrio jasicida , a luminescent bacterium belonging to the Harveyi clade, growing in a highly drying environment. A distinctive and novel feature of the proposed model is bioluminescence 'quenching' after a given time elapsed from activation. Using an advanced fitting procedure based on the simulated annealing algorithm, we are able to infer from the experimental observations the biochemical parameters used in the model. Such parameters are in good agreement with the literature data. As a further result, we find that, at least in our experimental conditions, light emission in bioluminescent bacteria appears to originate from a subtle balance between colony growth and quorum activation due to autoinducers diffusion, with the two phenomena occurring on the same time scale. This finding is consistent with a negative feedback mechanism previously reported for Vibrio harveyi .

Three new 5-fold interpenetrating diamondoid frameworks constructed by rigid diimidazole and dicarboxylate ligands

NASA Astrophysics Data System (ADS)

Huo, Jianqiang; Yan, Shuai; Li, Haiqiang; Yu, Donghui; Arulsamy, Navamoney

2018-03-01

A series of three-dimensional coordination polymers, namely, [Cd(BIMB)(SCA)]n (1), [M(BIMB)(trans-CHDC)]n (2, M = Cd2+; 3, M = Co2+), where BIMB = 1,4-di(1H-imidazol-1-yl)benzene, SCA2- = succinate dianion, CHDC2- = cyclohexane-1,4-dicarboxylate dianion) are synthesized hydro/solvatothermal methods. The products are characterized by elemental analysis and single-crystal X-ray diffraction data. Both the dianion and BIMB bridge different pairs of the metal ions, the three complexes are polymeric and their three-dimensional topology feature a diamond-like metal-organic framework (MOF). Owing to the length of the two bridging ligands, moderate size voids are formed in the diamondoid networks. However, the voids are filled by mutual interpenetration of four independent equivalent frameworks in a 5-fold interpenetrating architecture, and there is no sufficient void volume available for any guest molecules. The phase purity and thermal stability of the compounds are verified by powder X-ray diffraction (PXRD) and thermogravimetric (TG) data. The solid-state fluorescence spectra for the 3d10 Cd2+ MOF's 1 and 2 reveal significant enhancement in their emission intensities in comparison to the non-metallated BIMB. The enhanced emission is attributed to perturbation of intra-ligand emission states due to Cd2+ coordination.

INFERENCE OF HEATING PROPERTIES FROM “HOT” NON-FLARING PLASMAS IN ACTIVE REGION CORES. II. NANOFLARE TRAINS

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

Barnes, W. T.; Bradshaw, S. J.; Cargill, P. J., E-mail: will.t.barnes@rice.edu, E-mail: stephen.bradshaw@rice.edu, E-mail: p.cargill@imperial.ac.uk

2016-12-20

Despite its prediction over two decades ago, the detection of faint, high-temperature (“hot”) emission due to nanoflare heating in non-flaring active region cores has proved challenging. Using an efficient two-fluid hydrodynamic model, this paper investigates the properties of the emission expected from repeating nanoflares (a nanoflare train) of varying frequency as well as the separate heating of electrons and ions. If the emission measure distribution (EM(T)) peaks at T = T{sub m} , we find that EM(T{sub m}) is independent of details of the nanoflare train, and EM(T) above and below T{sub m} reflects different aspects of the heating. Belowmore » T{sub m} , the main influence is the relationship of the waiting time between successive nanoflares to the nanoflare energy. Above T{sub m}, power-law nanoflare distributions lead to an extensive plasma population not present in a mono-energetic train. Furthermore, in some cases, characteristic features are present in EM(T). Such details may be detectable given adequate spectral resolution and a good knowledge of the relevant atomic physics. In the absence of such resolution we propose some metrics that can be used to infer the presence of “hot” plasma.« less

Characterization and Modeling of Dust Emissions from an Instrumented Mine Tailings Site

NASA Astrophysics Data System (ADS)

Betterton, E. A.; Stovern, M.; Saez, A.; Csavina, J. L.; Felix Villar, O. I.; Field, J. P.; Rine, K. P.; Russell, M. R.; Saliba, P.

2012-12-01

Mining operations are potential sources of airborne particulate metal and metalloid contaminants through both direct smelter emissions and wind erosion of mine tailings. The warmer, drier conditions predicted for the Southwestern US by climate models may make contaminated atmospheric dust and aerosols increasingly important, due to potential deleterious effects on human health and ecology. Dust emissions and dispersion of contaminants from the Iron King Mine tailings in Dewey-Humboldt, Arizona, a Superfund site, are currently being investigated through in situ field measurements and computational fluid dynamics modeling. These tailings are heavily contaminated with lead and arsenic. We report on the chemical characterization of atmospheric dust and aerosol sampled near the mine tailings. Instrumented eddy flux towers were also setup on the mine tailings to give both spatial and temporal dust observations. The eddy flux towers have multiple DUSTTRAK monitors as well as weather stations. These in situ observations allow us to assess spatial distribution of suspended particulate. Using the DUSTTRAK flux tower observations at 10-second resolution in conjunction with a computational fluid dynamics model, we have been able to model dust transport from the mine tailings to downwind areas. In order to improve the accuracy of the dust transport simulations both regional topographical features and local weather patterns have been incorporated into the model simulations.

Highly Efficient Defect Emission from ZnO:Zn and ZnO:S Powders

NASA Astrophysics Data System (ADS)

Everitt, Henry

2013-03-01

Bulk Zinc Oxide (ZnO) is a wide band gap semiconductor with an ultraviolet direct band gap energy of 3.4 eV and a broad, defect-related visible wavelength emission band centered near 2 eV. We have shown that the external quantum efficiency can exceed 50% for this nearly white emission band that closely matches the human dark-adapted visual response. To explore the potential of ZnO as a rare earth-free white light phosphor, we investigated the mechanism of efficient defect emission in three types of ZnO powders: unannealed, annealed, and sulfur-doped. Annealing and sulfur-doping of ZnO greatly increase the strength of defect emission while suppressing the UV band edge emission. Continuous wave and ultrafast one- and two-photon excitation spectroscopy are used to examine the defect emission mechanism. Low temperature photoluminescence (PL) and PL excitation (PLE) spectra were measured for all three compounds, and it was found that bound excitons mediate the defect emission. Temperature-dependent PLE spectra for the defect and band edge emission were measured to estimate trapping and activation energies of the bound excitons and clarify the role they play in the defect emission. Time-resolved techniques were used to ascertain the role of exciton diffusion, the effects of reabsorption, and the spatial distributions of radiative and non-radiative traps. In unannealed ZnO we find that defect emission is suppressed and UV band edge emission is inefficient (< 2%) because of reabsorption and non-radiative recombination due to a high density of non-radiative bulk traps. By annealing ZnO, bulk trap densities are reduced, and a high density of defects responsible for the broad visible emission are created near the surface. Interestingly, nearly identical PLE spectra are found for both the band edge and the defect emission, one of many indications that the defect emission is deeply connected to bound excitons. Quantum efficiency, also measured as a function of excitation wavelength, closely mirrors the PLE spectra for both emission bands. Sulfur-doped ZnO exhibits additional PLE and X-ray features indicative of a ZnS-rich surface shell that correlates with even more efficient defect emission. The results presented here offer hope that engineering defects in ZnO materials may significantly improve the quantum efficiency for white light phosphor applications. This work was supported by the Army's in-house laboratory innovative research program.

Cometary crystalline silicate before and after perihelion passage II

NASA Astrophysics Data System (ADS)

Ootsubo, Takafumi

2014-01-01

Crystalline silicate is often observed in comets as an 11.3-micron resonant emission feature, and may be used for probing the early solar nebula. Because the formation of the crystalline silicate requires high temperature, they are thought to have been born from amorphous silicate at the inner region, and then transported toward the outer regions where comets were born. This transportation can produce the difference in the crystalline fraction in the cometary silicate dust between two dynamical types of comets, Oort-cloud comets (OCs) and Ecliptic comets (ECs), due to the different heliocentric distances of their birth places. The study of peak wavelengths in crystalline features is important to investigate the conditions of the crystalline silicate formation as well. Thus far, we don't have enough observational samples of OCs. Fortunately, we can observe comet C/2012 K1 (PanSTARRS) along with C/2013 A1 (Siding Spring) in this semester. In particular, the comet C/2012 K1 (PanSTARRS) is a bright and good target for this silicate peak feature study. Observations at pre- and post-perihelion provide us precious information on the dust evolution of the comet.

Optical Asymmetry and Nonlinear Light Scattering from Colloidal Gold Nanorods.

PubMed

Lien, Miao-Bin; Kim, Ji-Young; Han, Myung-Geun; Chang, You-Chia; Chang, Yu-Chung; Ferguson, Heather J; Zhu, Yimei; Herzing, Andrew A; Schotland, John C; Kotov, Nicholas A; Norris, Theodore B

2017-06-27

A systematic study is presented of the intensity-dependent nonlinear light scattering spectra of gold nanorods under resonant excitation of the longitudinal surface plasmon resonance (SPR). The spectra exhibit features due to coherent second and third harmonic generation as well as a broadband feature that has been previously attributed to multiphoton photoluminescence arising primarily from interband optical transitions in the gold. A detailed study of the spectral dependence of the scaling of the scattered light with excitation intensity shows unexpected scaling behavior of the coherent signals, which is quantitatively accounted for by optically induced damping of the SPR mode through a Fermi liquid model of the electronic scattering. The broadband feature is shown to arise not from luminescence, but from scattering of the second-order longitudinal SPR mode with the electron gas, where efficient excitation of the second order mode arises from an optical asymmetry of the nanorod. The electronic-temperature-dependent plasmon damping and the Fermi-Dirac distribution together determine the intensity dependence of the broadband emission, and the structure-dependent absorption spectrum determines the spectral shape through the fluctuation-dissipation theorem. Hence a complete self-consistent picture of both coherent and incoherent light scattering is obtained with a single set of physical parameters.

Titan's Far-Infrared 220 cm(exp -1) Cloud Seen for the First Time in the South

NASA Technical Reports Server (NTRS)

Jennings, Donald; Anderson, Carrie; Samuelson, Robert; Nixon, Conor; Flasar, Michael; Teanby, Nick; deKok, Remco; Coustenis, Athena; Vinatier, Sandrine

2013-01-01

In 2012 an emission feature at 220 cm(exp -1) in Titan's far-infrared spectrum was seen for the first time in the south. Attributed to a stratosphere ice cloud formed at the winter pole, the 220 (exp -1) emission had previously been seen only at high northern latitudes where it bad been decreasing since the arrival of Cassini in 2004. Our far-infrared observations were performed With the Composite Infrared Spectrometer (CIRS) on Caasini. Although it bad been expected that the 220 cm(exp -1) emission would eventnal1y appear in the south, the emission appeared rather suddenly, increasing by a factor of at least four between February (when it was not detected) and July 2012. At the time of our observations, one Titan month after equinox, the 220 cm(exp -1) feature was present in both the north and south and showed a trend of continued slow decrease in the north and steep increase in the south. As has been the case in the north, the emission in the south was confined to high latitudes associated with winter polar shadowing. Our spectroscopic detection of the southern 220 cm(exp -1) ice cloud coincided with the rapid formation in 2012 of a haze hood and vortex at the south pole as seen in Cassini image. The 220 cm(exp -1) feature was first observed by the Infrared Interferometer Spectrometer (IRIS) on Voyager I and has been extensively studied in the north by CIRS. Until now the 220 cm(exp -1) emission, like the polar hood, has been associated solely with the north, owing to the fact that Voyager and Cassini have viewed Titan only during winter-spring. In 2012 we witnessed the start of a seasonal shift of this pattern to the south. The 220 cm(exp -1) emission arises from altitudes of 80-150 km and peaks sharply near 140 km. The material responsible for the spectral feature is not known, but indirect evidence hints at a condensate arising from complex nitriles, which also tend to be present only at high winter latitudes.

The hot DOA1 degenerate HZ 21 - A search for circumstellar/photospheric metals and peculiar absorption at He II

NASA Technical Reports Server (NTRS)

Fritz, M. L.; Leckenby, H.; Sion, E. M.; Vauclair, G.; Liebert, J.

1990-01-01

A high-resolution IUE spectrum of the hot DO1 degenerate HZ 21 was obtained by combining US1 + European 2 low-background observing shifts. The SWP image reveals a rich spectrum of interstellar absorption lines with an average velocity in the line of sight to HZ 21 of -30 km/s. However, there is no clear evidence of any highly or lowly ionized metal features which could be attributed to circumstellar, wind, or photospheric absorption. There is, however, a broad absorption trough at He II (1640) which was not unexpected, given the clear presence of He II (4686) absorption in this star's optical spectrum. The velocity width of He II (1640) appears consistent with photospheric absorption wings which appear to flank the geocoronal Ly-alpha emission feature. The He II (1640) feature reveals what appears to be a broad (310 km/s) emission reversal. Evidence is provided that the emission reversal is probably real.

Reducing the environmental impact of methane emissions from dairy farms by anaerobic digestion of cattle waste.

PubMed

Marañón, E; Salter, A M; Castrillón, L; Heaven, S; Fernández-Nava, Y

2011-08-01

Four dairy cattle farms considered representative of Northern Spain milk production were studied. Cattle waste was characterised and energy consumption in the farms was inventoried. Methane emissions due to slurry/manure management and fuel consumption on the farms were calculated. The possibility of applying anaerobic digestion to the slurry to minimise emissions and of using the biogas produced to replace fossil fuels on the farm was considered. Methane emissions due to slurry management (storage and use as fertiliser) ranged from 34 to 66kg CH(4)cow(-1)year(-1) for dairy cows and from 13 to 25kg CH(4)cow(-1)year(-1) for suckler calves. Cattle on these farms are housed for most of the year, and the contribution from emissions from manure dropped in pastures is insignificant due to the very low methane conversion factors. If anaerobic digestion were implemented on the farms, the potential GHG emissions savings per livestock unit would range from 978 to 1776kg CO(2)eq year(-1), with the main savings due to avoided methane emissions during slurry management. The methane produced would be sufficient to supply digester heating needs (35-55% of the total methane produced) and on-farm fuel energy requirements. Copyright © 2011 Elsevier Ltd. All rights reserved.

On the carriers of the 21μm emission feature in post-asymptotic giant branch stars

NASA Astrophysics Data System (ADS)

Zhang, Ke; Jiang, B. W.; Li, Aigen

2009-07-01

The mysterious 21μm emission feature seen in sixteen C-rich proto-planetary nebulae (PPNe) remains unidentified since its discovery in 1989. Over a dozen of materials are suggested as the carrier candidates. In this work, we quantitatively investigate eight inorganic and one organic carrier candidates in terms of elemental abundance constraints, while previous studies mostly focus on their spectral profiles (which could be largely affected by grain size, shape and clustering effects). It is found that: (1) five candidates (TiC nanoclusters, fullerenes coordinated with Ti atoms, SiS2, doped-SiC and SiO2-coated SiC dust) violate the abundance constraints (i.e. they require too much Ti, S or Si to account for the emission power of the 21μm band, (2) three candidates (carbon and silicon mixtures, Fe2O3 and Fe3O4), while satisfying the abundance constraints, exhibit secondary features which are not detected in the 21μm sources and (3) nano FeO, neither exceeding the abundance budget nor producing undetected secondary features, seems to be a viable candidate, supporting the suggestions of Posch, Mutschke & Andersen.

Spitzer Quasar and ULIRG Evolution Study (QUEST). II. The Spectral Energy Distributions of Palomar-Green Quasars

NASA Astrophysics Data System (ADS)

Netzer, Hagai; Lutz, Dieter; Schweitzer, Mario; Contursi, Alessandra; Sturm, Eckhard; Tacconi, Linda J.; Veilleux, Sylvain; Kim, D.-C.; Rupke, David; Baker, Andrew J.; Dasyra, Kalliopi; Mazzarella, Joseph; Lord, Steven

2007-09-01

This is the second paper studying the QSOs in the Spitzer QUEST sample. Previously we presented new PAH measurements and argued that most of the observed far-infrared (FIR) radiation is due to star-forming activity. Here we present spectral energy distributions (SEDs) by supplementing our data with optical, NIR, and FIR observations. We define two subgroups, of ``weak FIR'' and ``strong FIR'' QSOs, and a third group of FIR nondetections. Assuming a starburst origin for the FIR, we obtain ``intrinsic'' active galactic nucleus (AGN) SEDs by subtracting a starburst template from the mean SEDs. The resulting SEDs are remarkably similar for all groups. They show three distinct peaks corresponding to two silicate emission features and a 3 μm bump, which we interpret as the signature of the hottest AGN dust. They also display drops beyond ~20 μm that we interpret as the signature of the minimum temperature (~200 K) dust. This component must be optically thin to explain the silicate emission and the slope of the long-wavelength continuum. We discuss the merits of an alternative model in which most of the FIR emission is due to AGN heating. Such models are unlikely to explain the properties of our QSOs, but they cannot be ruled out for more luminous objects. We also find correlations between the luminosity at 5100 Å and two infrared starburst indicators: L(60 μm) and L(PAH 7.7 μm). The correlation of L(5100 Å) with L(60 μm) can be used to measure the relative growth rates and lifetimes of the black hole and the new stars.

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

NASA Technical Reports Server (NTRS)

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

1996-01-01

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

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

NASA Technical Reports Server (NTRS)

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

1996-01-01

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

Voyager planetary radio astronomy studies

NASA Technical Reports Server (NTRS)

Staelin, David H.; Eikenberry, Stephen S.

1993-01-01

Analysis of nonthermal radio emission data obtained by the Planetary Radio Astronomy (PRA) spectrometers on the Voyager 1 and 2 spacecraft was performed. This PRA data provided unique insights into the radio emission characteristics of the outer planets because of PRA's unique spectral response below the terrestrial ionospheric plasma frequency and its unprecedented proximity to the source. Of those results which were documented or published, this final report surveys only the highlights and cites references for more complete discussions. Unpublished results for Uranus, Neptune, and theoretical Ionian current distributions are presented at greater length. The most important conclusion to be drawn from these observations is that banded spectral emission is common to the radio emission below 1-2 MHz observed from all four Jovian planets. In every case multiple spectral features evolve on time scales of seconds to minutes. To the extent these features drift in frequency, they appear never to cross one another. The Neptunian spectral features appear to drift little or not at all, their evolution consisting principally of waxing and waning. Since other evidence strongly suggests that most or all of this radio emission is occurring near the local magnetospheric electron cyclotron frequency, this implies that this emission preferentially occurs at certain continually changing planetary radii. It remains unknown why certain radii might be favored, unless radial electric field components or other means serve to differentiate radially the magnetospheric plasma density, particle energy vectors, or particle coherence. Calculation of the spatial distribution and intensity of the Io-generated magnetospheric currents are also presented; these currents may be limited principally by wave impedance and local field strengths.

A far-infrared emission feature in carbon-rich stars and planetary nebulae

NASA Technical Reports Server (NTRS)

Forrest, W. J.; Houck, J. R.; Mccarthy, J. F.

1981-01-01

The 16-30 micron spectra of several carbon stars and the planetary nebulae IC 418 and NGC 6572 have been obtained using the NASA C-141 Kuiper Airborne Observatory. A newly observed emission feature appears in the spectrum of IRC +10216 and several other carbon stars at wavelengths greater than 24 microns. The feature is interpreted as resulting from a solid-state resonance in the dust grains which have condensed around these stars. A similar feature appears in the spectra of IC 418 and NGC 6572, implying that the same type of dust is present. Since the dust probably condensed from a carbon-rich gas, this indicates an evolutionary link between carbon stars and these planetary nebulae. No identification for the grain material has been found, but some clues are apparent which could aid in the identification.

Light Curves and Spectra from a Unimodal Core-collapse Supernova

DOE PAGES

Wollaeger, Ryan T.; Hungerford, Aimee L.; Fryer, Chris L.; ...

2017-08-23

To assess the effectiveness of optical emission as a probe of spatial asymmetry in core-collapse supernovae (CCSNe), we apply in this paper the radiative transfer software SuperNu to a unimodal CCSN model. The SNSPH radiation hydrodynamics software was used to simulate an asymmetric explosion of a 16more » $${M}_{\\odot }$$ zero-age main-sequence binary star. The ejecta has 3.36 $${M}_{\\odot }$$ with 0.024 $${M}_{\\odot }$$ of radioactive 56Ni, with unipolar asymmetry along the z-axis. For 96 discrete angular views, we find a ratio between maximum and minimum peak total luminosities of ~1.36. The brightest light curves emerge from views orthogonal to the z-axis. Multigroup spectra from UV to IR are obtained. We find a shift in wavelength with viewing angle in a near-IR Ca ii emission feature, consistent with Ca being mostly in the unimode. We compare emission from the gray gamma-ray transfer in SuperNu and from the detailed gamma-ray transfer code Maverick. Relative to the optical light curves, the brightness of the gamma-ray emission is more monotonic with respect to viewing angle. UBVRI broadband light curves are also calculated. Parallel with the unimode, the U and B bands have excess luminosity at $$\\gtrsim 10$$ days post-explosion, due to 56Ni on the unimode. Finally, we compare our CCSN model with SN 2002ap, which is thought to have a similar ejecta morphology.« less

Calibration of VIIRS F1 Sensor Fire Detection Band Using lunar Observations

NASA Technical Reports Server (NTRS)

McIntire, Jeff; Efremova, Boryana; Xiong, Xiaoxiong

2012-01-01

Visible Infrared Imager Radiometer Suite (VIIRS) Fight 1 (Fl) sensor includes a fire detection band at roughly 4 microns. This spectral band has two gain states; fire detection occurs in the low gain state above approximately 345 K. The thermal bands normally utilize an on-board blackbody to provide on-orbit calibration. However, as the maximum temperature of this blackbody is 315 K, the low gain state of the 4 micron band cannot be calibrated in the same manner as the rest of the thermal bands. Regular observations of the moon provide an alternative calibration source. The lunar surface temperature has been recently mapped by the DIVINER sensor on the LRO platform. The periodic on-board high gain calibration along with the DIVINER surface temperatures was used to determine the emissivity and solar reflectance of the lunar surface at 4 microns; these factors and the lunar data are then used to fit the low gain calibration coefficients of the 4 micron band. Furthermore, the emissivity of the lunar surface is well known near 8.5 microns due to the Christiansen feature (an emissivity maximum associated with Si-O stretching vibrations) and the solar reflectance is negligible. Thus, the 8.5 micron band is used for relative calibration with the 4 micron band to de-trend any temporal variations. In addition, the remaining thermal bands are analyzed in a similar fashion, with both calculated emissivities and solar reflectances produced.

Light Curves and Spectra from a Unimodal Core-collapse Supernova

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

Wollaeger, Ryan T.; Hungerford, Aimee L.; Fryer, Chris L.

To assess the effectiveness of optical emission as a probe of spatial asymmetry in core-collapse supernovae (CCSNe), we apply in this paper the radiative transfer software SuperNu to a unimodal CCSN model. The SNSPH radiation hydrodynamics software was used to simulate an asymmetric explosion of a 16more » $${M}_{\\odot }$$ zero-age main-sequence binary star. The ejecta has 3.36 $${M}_{\\odot }$$ with 0.024 $${M}_{\\odot }$$ of radioactive 56Ni, with unipolar asymmetry along the z-axis. For 96 discrete angular views, we find a ratio between maximum and minimum peak total luminosities of ~1.36. The brightest light curves emerge from views orthogonal to the z-axis. Multigroup spectra from UV to IR are obtained. We find a shift in wavelength with viewing angle in a near-IR Ca ii emission feature, consistent with Ca being mostly in the unimode. We compare emission from the gray gamma-ray transfer in SuperNu and from the detailed gamma-ray transfer code Maverick. Relative to the optical light curves, the brightness of the gamma-ray emission is more monotonic with respect to viewing angle. UBVRI broadband light curves are also calculated. Parallel with the unimode, the U and B bands have excess luminosity at $$\\gtrsim 10$$ days post-explosion, due to 56Ni on the unimode. Finally, we compare our CCSN model with SN 2002ap, which is thought to have a similar ejecta morphology.« less

Observational Evidence Linking Interstellar UV Absorption to PAH Molecules

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

Blasberger, Avi; Behar, Ehud; Perets, Hagai B.

The 2175 Å UV extinction feature was discovered in the mid-1960s, yet its physical origin remains poorly understood. One suggestion is absorption by polycyclic aromatic hydrocarbon (PAH) molecules, which is supported by theoretical molecular structure computations and by laboratory experiments. PAHs are positively detected by their 3.3, 6.2, 7.7, 8.6, 11.3, and 12.7 μ m IR emission bands, which are specified by their modes of vibration. A definitive empirical link between the 2175 Å UV extinction and the IR PAH emission bands, however, is still missing. We present a new sample of hot stars that have both 2175 Å absorptionmore » and IR PAH emission. We find significant shifts of the central wavelength of the UV absorption feature, up to 2350 Å, but predominantly in stars that also have IR PAH emission. These UV shifts depend on stellar temperature in a fashion that is similar to the shifts of the 6.2 and 7.7 μ m IR PAH bands, that is, the features are increasingly more redshifted as the stellar temperature decreases, but only below ∼15 kK. Above 15 kK both UV and IR features retain their nominal values. Moreover, we find a suggestive correlation between the UV and IR shifts. We hypothesize that these similar dependences of both the UV and IR features on stellar temperature hint at a common origin of the two in PAH molecules and may establish the missing link between the UV and IR observations. We further suggest that the shifts depend on molecular size, and that the critical temperature of ∼15 kK above which no shifts are observed is related to the onset of UV-driven hot-star winds and their associated shocks.« less

Observational Evidence Linking Interstellar UV Absorption to PAH Molecules

NASA Astrophysics Data System (ADS)

Blasberger, Avi; Behar, Ehud; Perets, Hagai B.; Brosch, Noah; Tielens, Alexander G. G. M.

2017-02-01

The 2175 Å UV extinction feature was discovered in the mid-1960s, yet its physical origin remains poorly understood. One suggestion is absorption by polycyclic aromatic hydrocarbon (PAH) molecules, which is supported by theoretical molecular structure computations and by laboratory experiments. PAHs are positively detected by their 3.3, 6.2, 7.7, 8.6, 11.3, and 12.7 μm IR emission bands, which are specified by their modes of vibration. A definitive empirical link between the 2175 Å UV extinction and the IR PAH emission bands, however, is still missing. We present a new sample of hot stars that have both 2175 Å absorption and IR PAH emission. We find significant shifts of the central wavelength of the UV absorption feature, up to 2350 Å, but predominantly in stars that also have IR PAH emission. These UV shifts depend on stellar temperature in a fashion that is similar to the shifts of the 6.2 and 7.7 μm IR PAH bands, that is, the features are increasingly more redshifted as the stellar temperature decreases, but only below ˜15 kK. Above 15 kK both UV and IR features retain their nominal values. Moreover, we find a suggestive correlation between the UV and IR shifts. We hypothesize that these similar dependences of both the UV and IR features on stellar temperature hint at a common origin of the two in PAH molecules and may establish the missing link between the UV and IR observations. We further suggest that the shifts depend on molecular size, and that the critical temperature of ˜15 kK above which no shifts are observed is related to the onset of UV-driven hot-star winds and their associated shocks.

Changes in inorganic fine particulate matter sensitivities to precursors due to large-scale US emissions reductions.

PubMed

Holt, Jareth; Selin, Noelle E; Solomon, Susan

2015-04-21

We examined the impact of large US emissions changes, similar to those estimated to have occurred between 2005 and 2012 (high and low emissions cases, respectively), on inorganic PM2.5 sensitivities to further NOx, SO2, and NH3 emissions reductions using the chemical transport model GEOS-Chem. Sensitivities to SO2 emissions are larger year-round and across the US in the low emissions case than the high emissions case due to more aqueous-phase SO2 oxidation. Sensitivities to winter NOx emissions are larger in the low emissions case, more than 2× those of the high emissions case in parts of the northern Midwest. Sensitivities to NH3 emissions are smaller (∼40%) in the low emissions case, year-round, and across the US. Differences in NOx and NH3 sensitivities indicate an altered atmospheric acidity. Larger sensitivities to SO2 and NOx in the low emissions case imply that reducing these emissions may improve air quality more now than they would have in 2005; conversely, NH3 reductions may not improve air quality as much as previously assumed.

On- and off-axis spectral emission features from laser-produced gas breakdown plasmas

NASA Astrophysics Data System (ADS)

Harilal, S. S.; Skrodzki, P. J.; Miloshevsky, A.; Brumfield, B. E.; Phillips, M. C.; Miloshevsky, G.

2017-06-01

Laser-heated gas breakdown plasmas or sparks emit profoundly in the ultraviolet and visible region of the electromagnetic spectrum with contributions from ionic, atomic, and molecular species. Laser created kernels expand into a cold ambient with high velocities during their early lifetime followed by confinement of the plasma kernel and eventually collapse. However, the plasma kernels produced during laser breakdown of gases are also capable of exciting and ionizing the surrounding ambient medium. Two mechanisms can be responsible for excitation and ionization of the surrounding ambient: photoexcitation and ionization by intense ultraviolet emission from the sparks produced during the early times of their creation and/or heating by strong shocks generated by the kernel during its expansion into the ambient. In this study, an investigation is made on the spectral features of on- and off-axis emission of laser-induced plasma breakdown kernels generated in atmospheric pressure conditions with an aim to elucidate the mechanisms leading to ambient excitation and emission. Pulses from an Nd:YAG laser emitting at 1064 nm with a pulse duration of 6 ns are used to generate plasma kernels. Laser sparks were generated in air, argon, and helium gases to provide different physical properties of expansion dynamics and plasma chemistry considering the differences in laser absorption properties, mass density, and speciation. Point shadowgraphy and time-resolved imaging were used to evaluate the shock wave and spark self-emission morphology at early and late times, while space and time resolved spectroscopy is used for evaluating the emission features and for inferring plasma physical conditions at on- and off-axis positions. The structure and dynamics of the plasma kernel obtained using imaging techniques are also compared to numerical simulations using the computational fluid dynamics code. The emission from the kernel showed that spectral features from ions, atoms, and molecules are separated in time with early time temperatures and densities in excess of 35 000 K and 4 × 1018/cm3 with an existence of thermal equilibrium. However, the emission from the off-kernel positions from the breakdown plasmas showed enhanced ultraviolet radiation with the presence of N2 bands and is represented by non-local thermodynamic equilibrium (non-LTE) conditions. Our results also highlight that the ultraviolet radiation emitted during the early time of spark evolution is the predominant source of the photo-excitation of the surrounding medium.

Redefining the importance of nitrate during haze pollution to help optimize an emission control strategy

NASA Astrophysics Data System (ADS)

Pan, Yuepeng; Wang, Yuesi; Zhang, Junke; Liu, Zirui; Wang, Lili; Tian, Shili; Tang, Guiqian; Gao, Wenkang; Ji, Dongsheng; Song, Tao; Wang, Yonghong

2016-09-01

Nitrate salts represent a major component of fine mode aerosols, which play an important role in air pollution worldwide. Based on on-line and off-line aerosol measurements in urban Beijing for both clean and haze conditions, we demonstrate that the absolute and relative concentrations of nitrate increased with visibility degradation (relative humidity), whereas the variations of organics tracked the patterns of mixing-layer height and temperature. We propose that the increase in the relative contribution of nitrate to PM1 observed during the early stages of haze pollution was due to new particle formation, whereas the nitrate formed in PM1-2.5 during the latter stages was due to heterogeneous formation and hygroscopic growth. The increasing trend of nitrate (and also sulfate and ammonium) but decreasing trends of organics during haze development, together with the increase of the NO2/SO2 molar ratio with increasing proximity to downtown Beijing and with visibility degradation, provide further evidence that controlling NOx emissions should be a priority for improving air quality in mega cities. Additional large-scale investigation is required to adequately characterize the regional features of NOx-induced haze pollution in China. Such studies may provide insight into the formation of critical nuclei or the subsequent growth of freshly nucleated particles and advance our understanding of the role of nitrate in new particle formation.

NICMOS Narrow-band Images of OMC-1

NASA Technical Reports Server (NTRS)

Schultz, Angela S. B.; Colgan, Sean W. J.; Erickson, E. F.; Kaufman, M. J.; Hollenbach, D. J.; O'Dell, C. R.; Young, E. T.; Chen, H.

1998-01-01

We present images of a 90in. x 90in. field centered on BN in OMC-1, taken with the Near-Infrared Camera and MultiObject Spectrograph (NICMOS) aboard the Hubble Space Telescope. The observed lines are H2 1-0 S(l), Pa, [FeII] 1.64 pm, and the adjacent continua. The region is rich in interesting structures. The most remarkable are the streamers or "fingers" of H2 emission which extend from 15in. to 50in. from IRc2, seen here in unprecedented detail. Unlike the northern H2 fingers, the inner fingers do not exhibit significant [FeII] emission at theirdips, which we suggest is due to lower excitation. These observations also show that the general morphology of the Pa and [FeII] emission (both imaged for the first time in this region) bears a striking resemblance to that of the Ha and [SII] emission previously observed with WFPC2. This implies that these IR and optical lines are produced by radiative excitation on the surface of the molecular cloud. The Pa morphology of HH 202 is also very similar to its H a and [OIII] emission, again suggesting that the Pa in this object is photo-excited by the Trapezium, as has been suggested for the optical emission. We find evidence of shock-excited [FeII] in HH 208, where it again closely follows the morphology of [SII]. There is also H2 coincident with the [SII] and [FeII] emission, which may be associated with HH 208. Finally, we note some interesting continuum features: diffuse "tails" trailing from IRc3 and IRc4, more extensive observations of the "crescent" found by Stolovy, et al. (1998), and new observations of a similar oval object nearby. We also find a "V"-shaped region which may be the boundary of a cavity being cleared by IRc2.

Temporalization of Electric Generation Emissions for Improved Representation of Peak Air Quality Episodes

NASA Astrophysics Data System (ADS)

Farkas, C. M.; Moeller, M.; Carlton, A. G.

2013-12-01

Photochemical transport models routinely under predict peak air quality events. This deficiency may be due, in part, to inadequate temporalization of emissions from the electric generating sector. The National Emissions Inventory (NEI) reports emissions from Electric Generating Units (EGUs) by either Continuous Emission Monitors (CEMs) that report hourly values or as an annual total. The Sparse Matrix Operator Kernel Emissions preprocessor (SMOKE), used to prepare emissions data for modeling with the CMAQ air quality model, allocates annual emission totals throughout the year using specific monthly, weekly, and hourly weights according to standard classification code (SCC) and location. This approach represents average diurnal and seasonal patterns of electricity generation but does not capture spikes in emissions due to episodic use as with peaking units or due to extreme weather events. In this project we use a combination of state air quality permits, CEM data, and EPA emission factors to more accurately temporalize emissions of NOx, SO2 and particulate matter (PM) during the extensive heat wave of July and August 2006. Two CMAQ simulations are conducted; the first with the base NEI emissions and the second with improved temporalization, more representative of actual emissions during the heat wave. Predictions from both simulations are evaluated with O3 and PM measurement data from EPA's National Air Monitoring Stations (NAMS) and State and Local Air Monitoring Stations (SLAMS) during the heat wave, for which ambient concentrations of criteria pollutants were often above NAAQS. During periods of increased photochemistry and high pollutant concentrations, it is critical that emissions are most accurately represented in air quality models.

Effects of nitrogen fertilizer application on greenhouse gas emissions and economics of corn production.

PubMed

Kim, Seungdo; Dale, Bruce E

2008-08-15

Nitrogen fertilizer plays an important role in corn cultivation in terms of both economic and environmental aspects. Nitrogen fertilizer positively affects corn yield and the soil organic carbon level, but it also has negative environmental effects through nitrogen-related emissions from soil (e.g., N20, NOx, NO3(-) leaching, etc.). Effects of nitrogen fertilizer on greenhouse gas emissions associated with corn grain are investigated via life cycle assessment. Ecoefficiency analysis is also used to determine an economically and environmentally optimal nitrogen application rate (NAR). The ecoefficiency index in this study is defined as the ratio of economic return due to nitrogen fertilizer to the greenhouse gas emissions of corn cultivation. Greenhouse gas emissions associated with corn grain decrease as NAR increases at a lower NAR until a minimum greenhouse gas emission level is reached because corn yield and soil organic carbon level increase with NAR. Further increasing NAR after a minimum greenhouse gas emission level raises greenhouse gas emissions associated with corn grain. Increased greenhouse gas emissions of corn grain due to nitrous oxide emissions from soil are much higher than reductions of greenhouse gas emissions of corn grain due to corn yield and changes in soil organic carbon levels at a higher NAR. Thus, there exists an environmentally optimal NAR in terms of greenhouse gas emissions. The trends of the ecoefficiency index are similar to those of economic return to nitrogen and greenhouse gas emissions associated with corn grain. Therefore, an appropriate NAR could enhance profitability as well as reduce greenhouse gas emissions associated with corn grain.

Multi-Model Simulations of Aerosol and Ozone Radiative Forcing Due to Anthropogenic Emission Changes During the Period 1990-2015

NASA Technical Reports Server (NTRS)

Myhre, Gunnar; Aas, Wenche; Ribu, Cherian; Collins, William; Faluvegi, Gregory S.; Flanner, Mark; Forster, Piers; Hodnebrog, Oivind; Klimont, Zbigniew; Lund, Marianne T.

2017-01-01

Over the past few decades, the geographical distribution of emissions of substances that alter the atmospheric energy balance has changed due to economic growth and air pollution regulations. Here, we show the resulting changes to aerosol and ozone abundances and their radiative forcing using recently updated emission data for the period 1990-2015, as simulated by seven global atmospheric composition models. The models broadly reproduce large-scale changes in surface aerosol and ozone based on observations (e.g. 1 to 3 percent per year in aerosols over the USA and Europe). The global mean radiative forcing due to ozone and aerosol changes over the 1990-2015 period increased by 0.17 plus or minus 0.08 watts per square meter, with approximately one-third due to ozone. This increase is more strongly positive than that reported in IPCC AR5 (Intergovernmental Panel on Climate Change Fifth Assessment Report). The main reasons for the increased positive radiative forcing of aerosols over this period are the substantial reduction of global mean SO2 emissions, which is stronger in the new emission inventory compared to that used in the IPCC analysis, and higher black carbon emissions.

Infrared molecular emissions from comets

NASA Technical Reports Server (NTRS)

Weaver, H. A.; Mumma, M. J.

1984-01-01

The possibility of detecting IR molecular line emission from cometary parent molecules is explored. Due to the non-LTE conditions in the inner coma and the large amount of near IR solar flux, IR fluorescence will be a significant source of cometary emission and, in fact, will dominate the grain radiation in a sufficiently high resolution instrument. The detection of this line emission will be difficult due to absorption in the terrestrial atmosphere, but it appears possible to measure cometary H2O emission from airplane altitudes. As IR molecular line emission represents one of the few promising methods of detecting cometary parent molecules directly, further research on this problem should be vigorously pursued. Previously announced in STAR as N83-30344

Factors Affecting Aerosol Radiative Forcing from Both Production-based and Consumption-based View

NASA Astrophysics Data System (ADS)

Wang, J.; Lin, J.; Ni, R.

2017-12-01

Aerosol radiative forcing (RF) is determined by emissions and various chemical-transport-radiative processes in the atmosphere, a multi-factor problem whose individual contributors have not been well quantified. This problem becomes more complicated when taking into account the role of international trade, which means reallocated aerosol RF due to separation of regions producing goods and emissions and regions consuming those goods. Here we analyze major factors affecting RF of secondary inorganic aerosols (SIOAs, including sulfate, nitrate and ammonium), primary organic aerosol (POA) and black carbon (BC), extending the work of Lin et al. (2016, Nature Geoscience). We contrast five factors determining production-based (RFp, due to a region's production of goods) and consumption-based (RFc, due to a region's consumption) forcing by 11 major regions, including population size, per capita output, emission intensity (emission per output), chemical efficiency (mass per unit emission) and radiative efficiency (RF per unit mass). Comparing across the 11 regions, East Asia produces the strongest RFp and RFc of SIOA and BC and the second largest RFp and RFc of POA primarily due to its high emission intensity. Although Middle East and North Africa has low emissions, its RFp is strengthened by its largest chemical efficiency for POA and BC and second largest chemical efficiency for SIOA. However, RFp of South-East Asia and Pacific is greatly weakened by its lowest chemical efficiency. Economic trade means that net importers (Western Europe, North America and Pacific OECD) have higher RFc than RFp by 50-100%. And such forcing difference is mainly due to the high emission intensity of the exporters supplying these regions. For North America, SIOA's RFc is 50% stronger than RFp, for that emission intensity of SIOA is 5.2 times in East Asia and 2.5 times in Latin America and Caribbean compared with that in North America, and the chemical efficiency in the top four exporters are 1.4-2.1 times of North America. For East Asia, the RFc of SIOA is 20% lower than RFp due to the relatively low emission intensity and chemical efficiency of the top two exporters (Pacific OECD and Western Europe). Overall, economic, emission and atmospheric factors all play important roles in differentiating regions' RFp and RFc.

A 0.8-2.4 μm Transmission spectrum of the hot Jupiter CoRoT-1b

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

Schlawin, E.; Herter, T.; Zhao, M.

Hot Jupiters with brightness temperatures ≳2000 K can have TiO and VO molecules as gaseous species in their atmospheres. The TiO and VO molecules can potentially induce temperature inversions in hot Jupiter atmospheres and also have an observable signature of large optical to infrared transit depth ratios. Previous transmission spectra of very hot Jupiters have shown a lack of TiO and VO, but only in planets that also appear to lack temperature inversions. We measure the transmission spectrum of CoRoT-1b, a hot Jupiter that was predicted to have a temperature inversion potentially due to significant TiO and VO in itsmore » atmosphere. We employ the multi-object spectroscopy method using the SpeX and MORIS instruments on the Infrared Telescope Facility (IRTF) and the Gaussian process method to model red noise. By using a simultaneous reference star on the slit for calibration and a wide slit to minimize slit losses, we achieve transit depth precision of 0.03%-0.09%, comparable to the atmospheric scale height but detect no statistically significant molecular features. We combine our IRTF data with optical CoRoT transmission measurements to search for differences in the optical and near-infrared absorption that would arise from TiO/VO. Our IRTF spectrum and the CoRoT photometry disfavor a TiO/VO-rich spectrum for CoRoT-1b, suggesting that the atmosphere has another absorber that could create a temperature inversion or that the blackbody-like emission from the planet is due to a spectroscopically flat cloud, dust, or haze layer that smoothes out molecular features in both CoRoT-1b's emission and transmission spectra. This system represents the faintest planet hosting star (K = 12.2) with a measured planetary transmission spectrum.« less

Characterization of submicron aerosols at a rural site in Pearl River Delta of China using an Aerodyne High-Resolution Aerosol Mass Spectrometer

NASA Astrophysics Data System (ADS)

Huang, X.-F.; He, L.-Y.; Hu, M.; Canagaratna, M. R.; Kroll, J. H.; Ng, N. L.; Zhang, Y.-H.; Lin, Y.; Xue, L.; Sun, T.-L.; Liu, X.-G.; Shao, M.; Jayne, J. T.; Worsnop, D. R.

2010-11-01

The Pearl River Delta (PRD) region in South China is one of the most economically developed regions in China, but it is also noted for its severe air pollution due to industrial/metropolitan emissions. In order to continuously improve the understanding and quantification of air pollution in this region, an intensive campaign was executed in PRD during October-November 2008. Here, we report and analyze Aerodyne High-Resolution Aerosol Mass Spectrometer measurements at Kaiping, a rural site downwind of the highly-polluted central PRD area, to characterize the general features of submicron particulate pollution in the regional air. The mean measured PM1 mass concentration was 33.1 ± 18.1 μg m-3 during the campaign and composed of organic matter (33.8%), sulfate (33.7%), ammonium (14.0%), nitrate (10.7%), black carbon (6.7%), and chloride (1.1%), which is characterized by high fractions of inorganic ions due to huge emissions of SO2 and NOx in PRD. The average size distributions of the species (except BC) were all dominated by an accumulation mode peaking at ~450 nm in vacuum aerodynamic diameter. Calculations based on high-resolution organic mass spectra indicate that C, H, O, and N on average contributed 56.6, 7.0, 35.1, and 1.3% to the total organic mass, respectively, corresponding to an organic matter mass to organic carbon mass ratio (OM/OC) of 1.77 ± 0.08. Based on the high-resolution organic mass spectral dataset observed, Positive Matrix Factorization (PMF) analysis differentiated the organic aerosol into three components, i.e., biomass burning (BBOA) and two oxygenated (LV-OOA and SV-OOA) organic aerosols, which on average accounted for 24.5, 39.6 and 35.8% of the total organic mass, respectively. The BBOA showed strong features of biomass burning emissions and has been mainly attributed to field rice straw burning after harvest. The LV-OOA and SV-OOA were found to correspond to more aged (and thus less-volatile) and fresher (and semi-volatile) secondary organic aerosol, respectively. Analysis of meteorological influence supported that regional transport from the central PRD area was the major origin of the PM1 components observed at the Kaiping site.

40 CFR 63.1653 - Opacity standards.

Code of Federal Regulations, 2014 CFR

2014-07-01

... Silicomanganese § 63.1653 Opacity standards. No owner or operator shall cause emissions exiting from a shop due... particulate emissions from a shop due solely to operation of a semi-closed submerged arc furnace, may exceed...

40 CFR 63.1653 - Opacity standards.

Code of Federal Regulations, 2013 CFR

2013-07-01

... Silicomanganese § 63.1653 Opacity standards. No owner or operator shall cause emissions exiting from a shop due... particulate emissions from a shop due solely to operation of a semi-closed submerged arc furnace, may exceed...

40 CFR 63.1653 - Opacity standards.

Code of Federal Regulations, 2012 CFR

2012-07-01

... Silicomanganese § 63.1653 Opacity standards. No owner or operator shall cause emissions exiting from a shop due... particulate emissions from a shop due solely to operation of a semi-closed submerged arc furnace, may exceed...

Physical properties of erupting plasma associated with coronal mass ejections

NASA Astrophysics Data System (ADS)

Lee, J.; Raymond, J. C.; Reeves, K. K.; Moon, Y.; Kim, K.

2013-12-01

We investigate the physical properties (temperature, density, and mass) of erupting plasma observed in X-rays and EUV, which are all associated with coronal mass ejections observed by SOHO/LASCO. The erupting plasmas are observed as absorption or emission features in the low corona. The absorption feature provides a lower limit to the cold mass while the emission feature provides an upper limit to the mass of observed plasma in X-ray and EUV. We compare the mass constraints for each temperature response and find that the mass estimates in EUV and XRT are smaller than the total mass in the coronagraph. Several events were observed by a few passbands in the X-rays, which allows us to determine the temperature of the eruptive plasma using a filter ratio method. The temperature of one event is estimated at about 8.6 MK near the top of the erupting plasma. This measurement is possibly an average temperature for higher temperature plasma because the XRT is more sensitive at higher temperatures. In addition, a few events show that the absorption features of a prominence or a loop change to emission features with the beginning of their eruptions in all EUV wavelengths of SDO/AIA, which indicates the heating of the plasma. By estimating the physical properties of the erupting plasmas, we discuss the heating of the plasmas associated with coronal mass ejections in the low corona.

Structural health monitoring and damage evaluation for steel confined reinforced concrete column using the acoustic emission technique

NASA Astrophysics Data System (ADS)

Du, Fangzhu; Li, Dongsheng

2018-03-01

As a new kind of composite structures, the using of steel confined reinforced concrete column attract increasing attention in civil engineer. During the damage process, this new structure offers highly complex and invisible failure mechanism due to the combination effects of steel tubes, concrete, and steel rebar. Acoustic emission (AE) technique has been extensively studied in nondestructive testing (NDT) and is currently applied in civil engineering for structural health monitoring (SHM) and damage evaluation. In the present study, damage property and failure evolution of steel confined and unconfined reinforced concrete (RC) columns are investigated under quasi-static loading through (AE) signal. Significantly improved loading capacity and excellent energy dissipation characteristic demonstrated the practicality of that proposed structure. AE monitoring results indicated that the progressive deformation of the test specimens occur in three stages representing different damage conditions. Sentry function compares the logarithm ratio between the stored strain energy (Es) and the released acoustic energy (Ea); explicitly disclose the damage growth and failure mechanism of the test specimens. Other extended AE features including index of damage (ID), and relax ratio are calculated to quantitatively evaluate the damage severity and critical point. Complicated temporal evolution of different AE features confirms the potential importance of integrated analysis of two or more parameters. The proposed multi-indicators analysis is capable of revealing the damage growth and failure mechanism for steel confined RC columns, and providing critical warning information for structure failure.

Kβ Mainline X-ray Emission Spectroscopy as an Experimental Probe of Metal–Ligand Covalency

PubMed Central

2015-01-01

The mainline feature in metal Kβ X-ray emission spectroscopy (XES) has long been recognized as an experimental marker for the spin state of the metal center. However, even within a series of metal compounds with the same nominal oxidation and spin state, significant changes are observed that cannot be explained on the basis of overall spin. In this work, the origin of these effects is explored, both experimentally and theoretically, in order to develop the chemical information content of Kβ mainline XES. Ligand field expressions are derived that describe the behavior of Kβ mainlines for first row transition metals with any dn count, allowing for a detailed analysis of the factors governing mainline shape. Further, due to limitations associated with existing computational approaches, we have developed a new methodology for calculating Kβ mainlines using restricted active space configuration interaction (RAS–CI) calculations. This approach eliminates the need for empirical parameters and provides a powerful tool for investigating the effects that chemical environment exerts on the mainline spectra. On the basis of a detailed analysis of the intermediate and final states involved in these transitions, we confirm the known sensitivity of Kβ mainlines to metal spin state via the 3p–3d exchange coupling. Further, a quantitative relationship between the splitting of the Kβ mainline features and the metal–ligand covalency is established. Thus, this study furthers the quantitative electronic structural information that can be extracted from Kβ mainline spectroscopy. PMID:24914450

Estimating PM2.5-associated mortality increase in California due to the Volkswagen emission control defeat device

NASA Astrophysics Data System (ADS)

Wang, Tianyang; Jerrett, Michael; Sinsheimer, Peter; Zhu, Yifang

2016-11-01

The Volkswagen Group of America (VW) was found by the US Environmental Protection Agency (EPA) and the California Air Resources Board (CARB) to have installed "defeat devices" and emit more oxides of nitrogen (NOx) than permitted under current EPA standards. In this paper, we quantify the hidden NOx emissions from this so-called VW scandal and the resulting public health impacts in California. The NOx emissions are calculated based on VW road test data and the CARB Emission Factors (EMFAC) model. Cumulative hidden NOx emissions from 2009 to 2015 were estimated to be over 3500 tons. Adult mortality changes were estimated based on ambient fine particulate matter (PM2.5) change due to secondary nitrate formation and the related concentration-response functions. We estimated that hidden NOx emissions from 2009 to 2015 have resulted in a total of 12 PM2.5-associated adult mortality increases in California. Most of the mortality increase happened in metropolitan areas, due to their high population and vehicle density.

Source Attribution of Methane Emissions in Northeastern Colorado Using Ammonia to Methane Emission Ratios

NASA Astrophysics Data System (ADS)

Eilerman, S. J.; Neuman, J. A.; Peischl, J.; Aikin, K. C.; Ryerson, T. B.; Perring, A. E.; Robinson, E. S.; Holloway, M.; Trainer, M.

2015-12-01

Due to recent advances in extraction technology, oil and natural gas extraction and processing in the Denver-Julesburg basin has increased substantially in the past decade. Northeastern Colorado is also home to over 250 concentrated animal feeding operations (CAFOs), capable of hosting over 2 million head of ruminant livestock (cattle and sheep). Because of methane's high Global Warming Potential, quantification and attribution of methane emissions from oil and gas development and agricultural activity are important for guiding greenhouse gas emission policy. However, due to the co-location of these different sources, top-down measurements of methane are often unable to attribute emissions to a specific source or sector. In this work, we evaluate the ammonia:methane emission ratio directly downwind of CAFOs using a mobile laboratory. Several CAFOs were chosen for periodic study over a 12-month period to identify diurnal and seasonal variation in the emission ratio as well as differences due to livestock type. Using this knowledge of the agricultural ammonia:methane emission ratio, aircraft measurements of ammonia and methane over oil and gas basins in the western US during the Shale Oil and Natural Gas Nexus (SONGNEX) field campaign in March and April 2015 can be used for source attribution of methane emissions.

A spectroscopic search for colliding stellar winds in O-type close binary systems. III - 29 UW Canis Majoris

NASA Technical Reports Server (NTRS)

Wiggs, Michael S.; Gies, Douglas R.

1993-01-01

The orbital-phase variations in the optical emission lines and UV P Cygni lines of the massive O-type binary 29 UW Canis Majoris are investigated in a search for evidence of colliding winds. High SNR spectra of the H-alpha and He I 6678-A emission lines are presented, and radial velocity curves for several features associated with the photosphere of the more luminous primary star are given. The H-alpha features consists of a P Cygni component that shares the motion of the primary, and which probably originates at the base of its wind, and a broad, stationary emission component. It is proposed that the broad emission forms in a plane midway between the stars where the winds collide. A simple geometric model is used to show that this placement of the broad component can explain the lack of orbital velocity shifts, the near-constancy of the emission strength throughout the orbit, the large velocities associated with the H-alpha wings, and the constancy of the velocity range observed.

X-ray and optical emission-line filaments in the cooling flow cluster 2A 0335 + 096

NASA Technical Reports Server (NTRS)

Sarazin, Craig L.; O'Connell, Robert W.; Mcnamara, Brian R.

1992-01-01

We present a new high-resolution X-ray image of the 2A 0335 + 096 cluster of galaxies obtained with the High Resolution Imager (HRI) aboard the ROSAT satellite. The presence of dense gas having a very short cooling time in the central regions confirms its earlier identification as a cooling flow. The X-ray emission from the central regions of the cooling flow shows a great deal of filamentary structure. Using the crude spectral resolution of the HRI, we show that these filaments are the result of excess emission, rather than foreground X-ray absorption. Although there are uncertainties in the pointing, many of the X-ray features in the cooling flow region correspond to features in H-alpha optical line emission. This suggests that the optical emission line gas has resulted directly from the cooling of X-ray-emitting gas. The filament material cannot be in hydrostatic equilibrium, and it is likely that other forces such as rotation, turbulence, and magnetic fields influence the dynamical state of the gas.

X-Ray Spectral Diagnostics of Gamma-Ray Burst Environments.

PubMed

Paerels; Kuulkers; Heise; Liedahl

2000-05-20

Recently, detection of discrete features in the X-ray afterglow spectra of GRB 970508 and GRB 970828 was reported. The most natural interpretation of these features is that they are redshifted Fe K emission complexes. The identification of the line emission mechanism has drastic implications for the inferred mass of radiating material and hence the nature of the burst site. X-ray spectroscopy provides a direct observational constraint on these properties of gamma-ray bursters. We briefly discuss how these constraints arise in the context of an application to the spectrum of GRB 970508.

Detection of 12 micron Mg I and OH lines in stellar spectra

NASA Technical Reports Server (NTRS)

Jennings, D. E.; Deming, D.; Wiedemann, G. R.; Keady, J. J.

1986-01-01

Infrared lines of Mg I and OH have been detected in stellar spectra near 12.3 microns. The Mg I 7i-6h transition was seen in Alpha Ori and Alpha Tau, and the R2e(23.5) and R1f(24.5) transitions of OH were seen in Alpha Ori. All lines appear in absorption, in contrast to the solar spectrum where the Mg I line shows a prominent emission core. The lack of emission in these low surface gravity stars is due to a greatly reduced volume recombination rate for the high-n states of Mg I, which is not fully compensated by the increased chromospheric scale height. The OH equivalent widths are sensitive to the temperature structure of the upper photosphere of Alpha Ori, and they indicate that the photosphere near tau 5000 of about 10 to the -5th is approximately 100 K hotter than is given by flux constant models. The OH measurements agree more closely with the 1981 semiemprical model of Basri, Linsky, and Eriksson (1981), which is based on Ca II and Mg II ultraviolet features.

WASP-121b: An ultrahot gas-giant exoplanet with a stratosphere

NASA Astrophysics Data System (ADS)

Kataria, Tiffany; Evans, Thomas M.; Sing, David; Goyal, Jayesh; Nikolov, Nikolay; Wakeford, Hannah R.; Deming, Drake; Marley, Mark S.; PanCET Team

2018-01-01

Stratospheres are ubiquitous in the atmospheres of solar system planets, and provide crucial information about an atmosphere’s chemical composition, vertical temperature structure, and energy budget. While it has been suggested that stratospheres could form in highly irradiated exoplanets, the extent to which this occurs has so far been unresolved both theoretically and observationally. Here we present secondary eclipse observations of the ultra-hot (Teq ~ 2500 K) gas giant exoplanet WASP-121b made using HST/WFC3 in spectroscopic mode across the 1.12-1.64 micron wavelength range. The spectrum is inconsistent with an isothermal atmosphere and has spectrally-resolved water features in emission, providing a detection of an exoplanet stratosphere at 5-sigma confidence. WASP-121b is one of the standout exoplanets available for atmospheric characterization, both in transmission and emission, due to its large radius (1.8 Rjup), high temperature, and bright host star (H=9.4mag). As such, we will also discuss follow-up observations of WASP-121b with HST and JWST to probe the longitudinal extent of its stratosphere, and the molecular absorbers that may produce it.

High Resolution Integral Field Spectroscopy of Europa's Sodium Clouds: Evidence for a Component with Origins in Iogenic Plasma.

NASA Astrophysics Data System (ADS)

Schmidt, C.; Johnson, R. E.; Mendillo, M.; Baumgardner, J. L.; Moore, L.; O'Donoghue, J.; Leblanc, F.

2015-12-01

With the object of constraining Iogenic contributions and identifying drivers for variability, we report new observations of neutral sodium in Europa's exosphere. An R~20000 integral field spectrograph at McDonald Observatory is used to generate Doppler maps of sodium cloud structures with a resolution of 2.8 km/s/pixel. In the five nights of observations since 2011, measurements on UT 6.15-6.31 May 2015 uniquely feature fast (10s of km/s) neutral sodium clouds extending nearly 100 Europa radii, more distant than in any previous findings. During these measurements, the satellite geometry was favorable for the transfer of Na from Io to Europa, located at 1:55 to 4:00 and 3:38 to 4:39 Jovian local time, respectively. Eastward emission (away from Jupiter) extends 10-20 Europa radii retaining the moon's rest velocity, while westward emission blue-shifts with distance, and a broad range of velocities are measured, reaching at least 70 km/s at 80 Europa radii. These cloud features are distinct from Io's "banana" and "stream" features, the distant Jupiter-orbiting nebula, and from terrestrial OH and Na contaminant emissions. Io's production was quiescent during this observation, following an extremely active phase in February 2015. These results are consistent with previous findings that Europa's Na exosphere has peak emission between midnight and dawn Jovian local time and support the idea that sodium escape from Io can significantly enhance the emission intensity measured at Europa.

The first full-resolution measurements of Auroral Medium Frequency Burst Emissions

NASA Astrophysics Data System (ADS)

Bunch, N. L.; Labelle, J.; Weatherwax, A.; Hughes, J.

2008-12-01

Auroral MF burst is a naturally occurring auroral radio emission which appears unstructured on resolution of previous measurements, is observed in the frequency range of 0.8-4.5 MHz, and has typical amplitudes of around 10-14 V2/m2Hz, and durations of a few minutes. The emission occurs at substorm onset. Since Sept 2006, Dartmouth has operated a broadband (0-5 MHz) interferometer at Toolik Lake, Alaska (68° 38' N, 149° 36' W, 68.51 deg. magnetic latitude), designed for the study of auroral MF burst emissions. Normal operation involves taking snapshots of waveforms from four spaced antennas from which wave spectral and directional information is obtained. However, the experiment can also be run in "continuous mode" whereby the signal from a selected antenna is sampled continuously at 10 M samples/second. A "continuous mode" campaign was run 0800-1200 UT (~2200-0200 MLT) daily from March 21 to April 19, 2008. During this campaign more than twenty auroral MF burst emissions were observed, including three extraordinarily intense examples lasting approximately two minutes each. These observations represent the highest time and frequency resolution data ever collected of MF burst emissions. These data allow us to better characterize the null near twice the electron gyrofrequency identified in previous experiments, since examples of this feature observed during this campaign display a strong null ~50 kHz in bandwidth, with sharp boundaries and occasionally coincident with 2 fce auroral roar. These data also allow us to search for frequency-time structures embedded in MF-burst. One prominent feature appears to be a strong single frequency emission which broadens down to lower frequencies over time, spreading to approximately 500 kHz in bandwidth over ~10 ms. Among other features observed are a diffuse and unstructured emission, as well as what could potentially be several separate emission sources, with multiple emissions occurring simultaneously, appearing as weaker "ghosts" behind the main MF burst emission. These data in will additionally allow us to search for the presence of sub-millisecond wave packets, sometimes quasi-periodic, reported by LaBelle et al. [1997, J. Geophys. Res. 102, 22221]. Finally, a search for frequency dispersion or absence thereof will provide a test of theories which speculate that different frequencies originate at different altitudes in the ionosphere.

The spectrum of isotropic diffuse gamma-ray emission between 100 MeV and 820 GeV

DOE PAGES

Ackermann, M.; Ajello, M.; Albert, A.; ...

2015-01-19

We present that the γ-ray sky can be decomposed into individually detected sources, diffuse emission attributed to the interactions of Galactic cosmic rays with gas and radiation fields, and a residual all-sky emission component commonly called the isotropic diffuse γ-ray background (IGRB). The IGRB comprises all extragalactic emissions too faint or too diffuse to be resolved in a given survey, as well as any residual Galactic foregrounds that are approximately isotropic. The first IGRB measurement with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope (Fermi) used 10 months of sky-survey data and considered an energy rangemore » between 200 MeV and 100 GeV. Improvements in event selection and characterization of cosmic-ray backgrounds, better understanding of the diffuse Galactic emission (DGE), and a longer data accumulation of 50 months allow for a refinement and extension of the IGRB measurement with the LAT, now covering the energy range from 100 MeV to 820 GeV. The IGRB spectrum shows a significant high-energy cutoff feature and can be well described over nearly four decades in energy by a power law with exponential cutoff having a spectral index of 2.32 ± 0.02 and a break energy of (279 ± 52) GeV using our baseline DGE model. In conclusion, the total intensity attributed to the IGRB is (7.2 ± 0.6) × 10 –6 cm –2 s –1 sr –1 above 100 MeV, with an additional +15%/–30% systematic uncertainty due to the Galactic diffuse foregrounds.« less

Development of a compact bushing for NBI

NASA Astrophysics Data System (ADS)

de Esch, H. P. L.; Simonin, A.; Grand, C.; Lepetit, B.; Lemoine, D.; Márquez-Mijares, M.; Minea, T.; Caillault, L.; Seznec, B.; Jager, T.; Odic, E.; Kirkpatrick, M. J.; Teste, Ph.; Dessante, Ph.; Almaksour, K.

2017-08-01

Research into a novel type of compact bushing is being conducted through the HVIV (High Voltage holding In Vacuum) partnership between CEA-Cadarache1, GeePs-Centralesupélec4, LPGP3 and LCAR2. The bushing aims to concentrate the high electric field inside its interior, rather than in the vacuum tank. Hence the field emission current is also concentrated inside the bushing and it can be attempted to suppress this so-called dark current by conditioning the internal surfaces and by adding gas. LCAR have performed theoretical quantum mechanical studies of electron field emission and the role of adsorbates in changing the work function. LPGP studied the ionization of gas due to field emission current and the behavior of micro particles exposed to emissive electron current in the vacuum gap under high electric fields. Experiments at Geeps have clarified the role of surface conditioning in reducing the dark current. Geeps also found that adding low pressure nitrogen gas to the vacuum is much more effective than helium in reducing the field emission. An interesting observation is the growth of carbon structures after exposure of an electrode to the electric field. Finally, IRFM have performed experiments on a single stage test bushing that features a 36 cm high porcelain insulator and two cylindrical electrode surfaces in vacuum or low-pressure gas. Using 0.1 Pa N2 gas, the voltage holding exceeded 185 kV over a 40 mm "vacuum" gap without dark current. Above this voltage, exterior breakdowns occurred over the insulator, which was in air. The project will finish with the fabrication of a 2-stage compact bushing, capable to withstand 400 kV.

Development of combined low-emissions burner devices for low-power boilers

NASA Astrophysics Data System (ADS)

Roslyakov, P. V.; Proskurin, Yu. V.; Khokhlov, D. A.

2017-08-01

Low-power water boilers are widely used for autonomous heat supply in various industries. Firetube and water-tube boilers of domestic and foreign manufacturers are widely represented on the Russian market. However, even Russian boilers are supplied with licensed foreign burner devices, which reduce their competitiveness and complicate operating conditions. A task of developing efficient domestic low-emissions burner devices for low-power boilers is quite acute. A characteristic property of ignition and fuel combustion in such boilers is their flowing in constrained conditions due to small dimensions of combustion chambers and flame tubes. These processes differ significantly from those in open combustion chambers of high-duty power boilers, and they have not been sufficiently studied yet. The goals of this paper are studying the processes of ignition and combustion of gaseous and liquid fuels, heat and mass transfer and NO x emissions in constrained conditions, and the development of a modern combined low-emissions 2.2 MW burner device that provides efficient fuel combustion. A burner device computer model is developed and numerical studies of its operation on different types of fuel in a working load range from 40 to 100% of the nominal are carried out. The main features of ignition and combustion of gaseous and liquid fuels in constrained conditions of the flame tube at nominal and decreased loads are determined, which differ fundamentally from the similar processes in steam boiler furnaces. The influence of the burner devices design and operating conditions on the fuel underburning and NO x formation is determined. Based on the results of the design studies, a design of the new combined low-emissions burner device is proposed, which has several advantages over the prototype.

Metal plasmon-coupled fluorescence imaging and label free coenzyme detection in cells

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

Zhang, Jian, E-mail: jian@cfs.bioment.umaryland.edu; Fu, Yi; Li, Ge

2012-08-31

Highlights: Black-Right-Pointing-Pointer Metal nanoparticle for fluorescence cell imaging. Black-Right-Pointing-Pointer Non-invasive emission detection of coenzyme in cell on time-resolved confocal microscope. Black-Right-Pointing-Pointer Near-field interaction of flavin adenine dinucleotide with silver substrate. Black-Right-Pointing-Pointer Isolation of emissions by coenzymes from cellular autofluorescence on fluorescence cell imaging. -- Abstract: Flavin adenine dinucleotide (FAD) is a key metabolite in cellular energy conversion. Flavin can also bind with some enzymes in the metabolic pathway and the binding sites may be changed due to the disease progression. Thus, there is interest on studying its expression level, distribution, and redox state within the cells. FAD is naturally fluorescent,more » but it has a modest extinction coefficient and quantum yield. Hence the intrinsic emission from FAD is generally too weak to be isolated distinctly from the cellular backgrounds in fluorescence cell imaging. In this article, the metal nanostructures on the glass coverslips were used as substrates to measure FAD in cells. Particulate silver films were fabricated with an optical resonance near the absorption and the emission wavelengths of FAD which can lead to efficient coupling interactions. As a result, the emission intensity and quantum yield by FAD were greatly increased and the lifetime was dramatically shortened resulting in less interference from the longer lived cellular background. This feature may overcome the technical limits that hinder the direct observation of intrinsically fluorescent coenzymes in the cells by fluorescence microscopy. Fluorescence cell imaging on the metallic particle substrates may provide a non-invasive strategy for collecting the information of coenzymes in cells.« less

POLYCYCLIC AROMATIC HYDROCARBON EMISSION IN SPITZER/IRS MAPS. I. CATALOG AND SIMPLE DIAGNOSTICS

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

Stock, D. J.; Choi, W. D.-Y.; Moya, L. G. V.

2016-03-01

We present a sample of resolved galactic H ii regions and photodissociation regions (PDRs) observed with the Spitzer infrared spectrograph in spectral mapping mode between the wavelengths of 5–15 μm. For each object we have spectral maps at a spatial resolution of ∼4″ in which we have measured all of the mid-infrared emission and absorption features. These include the polycyclic aromatic hydrocarbon (PAH) emission bands, primarily at 6.2, 7.7, 8.6, 11.2, and 12.7 μm, as well as the spectral emission lines of neon and sulfur and the absorption band caused by silicate dust at around 9.8 μm. In this work wemore » describe the data in detail, including the data reduction and measurement strategies, and subsequently present the PAH emission band intensity correlations for each of the objects and the sample as a whole. We find that there are distinct differences between the sources in the sample, with two main groups: the first comprising the H ii regions and the second the reflection nebulae (RNe). Three sources—the reflection nebula NGC 7023, the Horsehead nebula PDR (an interface between the H ii region IC 434 and the Orion B molecular cloud), and M17—resist this categorization, with the Horsehead PDR points mimicking the RNe and the NGC 7023 fluxes displaying a unique bifurcated appearance in our correlation plots. These discrepancies seem to be due to the very low radiation field experienced by the Horsehead PDR and the very clean separation between the PDR environment and a diffuse environment in the NGC 7023 observations.« less

The Ozone Monitoring Instrument (OMI): towards a 14 Year Data Record and Applications in the Air Quality and Climate Domain

NASA Astrophysics Data System (ADS)

Levelt, P.; Joiner, J.; Tamminen, J.; Veefkind, P.; Bhartia, P. K.; Court, A. J.; Vlemmix, T.

2017-12-01

Keywords: emission monitoring, air quality, climate, atmospheric composition The Ozone Monitoring Instrument (OMI), launched on board of NASA's EOS-Aura spacecraft on July 15, 2004, provides unique contributions to the monitoring of the ozone layer, air quality and climate from space. With a data record of 13 years, OMI provides the longest NO2 and SO2 record from space, which is essential to understand the changes to emissions globally. The combination of urban scale resolution (13 x 24 km2 in nadir) and daily global coverage proved to be key features for the air quality community. Due to the operational Very Fast Delivery (VFD / direct readout) and Near Real Time (NRT) availability of the data, OMI also plays an important role in the early developments of operational services in the atmospheric chemistry domain. For example, OMI data is currently used operationally for improving air quality forecasts, for inverting high-resolution emission maps, the UV forecast and for volcanic plume warning systems for aviation. An overview of air quality applications, emission inventory inversions and trend analyses based on the OMI data record will be presented. An outlook will be given on the potentials of augmenting this record with the high resolution air quality measurements of TROPOMI (3,5 x 7 km2) and new satellite instrumentation entering the imaging domain, such as the TROPOLITE instrument ( 1 x 1 km2). Potential of imaging type of NO2 measurements in the the climate and air quality domain will be given, most notably on the use of high resolution NO2 measurements for pin-pointing anthropogenic CO2 emissions.

Evidence for hot clumpy accretion flow in the transitional millisecond pulsar PSR J1023+0038

NASA Astrophysics Data System (ADS)

Shahbaz, T.; Dallilar, Y.; Garner, A.; Eikenberry, S.; Veledina, A.; Gandhi, P.

2018-06-01

We present simultaneous optical and near-infrared (IR) photometry of the millisecond pulsar PSR J1023+0038 during its low-mass X-ray binary phase. The r΄- and Ks-band light curves show rectangular, flat-bottomed dips, similar to the X-ray mode-switching (active-passive state transitions) behaviour observed previously. The cross-correlation function (CCF) of the optical and near-IR data reveals a strong, broad negative anticorrelation at negative lags, a broad positive correlation at positive lags, with a strong, positive narrow correlation superimposed. The shape of the CCF resembles the CCF of black hole X-ray binaries but the time-scales are different. The features can be explained by reprocessing and a hot accretion flow close to the neutron star's magnetospheric radius. The optical emission is dominated by the reprocessed component, whereas the near-IR emission contains the emission from plasmoids in the hot accretion flow and a reprocessed component. The rapid active-passive state transition occurs when the hot accretion flow material is channelled on to the neutron star and is expelled from its magnetosphere. During the transition the optical reprocessing component decreases resulting in the removal of a blue spectral component. The accretion of clumpy material through the magnetic barrier of the neutron star produces the observed near-IR/optical CCF and variability. The dip at negative lags corresponds to the suppression of the near-IR synchrotron component in the hot flow, whereas the broad positive correlation at positive lags is driven by the increased synchrotron emission of the outflowing plasmoids. The narrow peak in the CCF is due to the delayed reprocessed component, enhanced by the increased X-ray emission.

THE SPECTRUM OF ISOTROPIC DIFFUSE GAMMA-RAY EMISSION BETWEEN 100 MeV AND 820 GeV

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

Ackermann, M.; Buehler, R.; Ajello, M.

2015-01-20

The γ-ray sky can be decomposed into individually detected sources, diffuse emission attributed to the interactions of Galactic cosmic rays with gas and radiation fields, and a residual all-sky emission component commonly called the isotropic diffuse γ-ray background (IGRB). The IGRB comprises all extragalactic emissions too faint or too diffuse to be resolved in a given survey, as well as any residual Galactic foregrounds that are approximately isotropic. The first IGRB measurement with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope (Fermi) used 10 months of sky-survey data and considered an energy range between 200 MeV and 100 GeV. Improvementsmore » in event selection and characterization of cosmic-ray backgrounds, better understanding of the diffuse Galactic emission (DGE), and a longer data accumulation of 50 months allow for a refinement and extension of the IGRB measurement with the LAT, now covering the energy range from 100 MeV to 820 GeV. The IGRB spectrum shows a significant high-energy cutoff feature and can be well described over nearly four decades in energy by a power law with exponential cutoff having a spectral index of 2.32 ± 0.02 and a break energy of (279 ± 52) GeV using our baseline DGE model. The total intensity attributed to the IGRB is (7.2 ± 0.6) × 10{sup –6} cm{sup –2} s{sup –1} sr{sup –1} above 100 MeV, with an additional +15%/–30% systematic uncertainty due to the Galactic diffuse foregrounds.« less