The origin of the red emission in n-ZnO nanotubes/p-GaN white light emitting diodes

PubMed Central

2011-01-01

In this article, the electroluminescence (EL) spectra of zinc oxide (ZnO) nanotubes/p-GaN light emitting diodes (LEDs) annealed in different ambients (argon, air, oxygen, and nitrogen) have been investigated. The ZnO nanotubes by aqueous chemical growth (ACG) technique on p-GaN substrates were obtained. The as-grown ZnO nanotubes were annealed in different ambients at 600°C for 30 min. The EL investigations showed that air, oxygen, and nitrogen annealing ambients have strongly affected the deep level emission bands in ZnO. It was concluded from the EL investigation that more than one deep level defect is involved in the red emission appearing between 620 and 750 nm and that the red emission in ZnO can be attributed to oxygen interstitials (Oi) appearing in the range from 620 nm (1.99 eV) to 690 nm (1.79 eV), and to oxygen vacancies (Vo) appearing in the range from 690 nm (1.79 eV) to 750 nm (1.65 eV). The annealing ambients, especially the nitrogen ambient, were also found to greatly influence the color-rendering properties and increase the CRI of the as - grown LEDs from 87 to 96. PMID:21711671

The origin of the red emission in n-ZnO nanotubes/p-GaN white light emitting diodes.

PubMed

Alvi, N H; Ul Hasan, Kamran; Nur, Omer; Willander, Magnus

2011-02-10

In this article, the electroluminescence (EL) spectra of zinc oxide (ZnO) nanotubes/p-GaN light emitting diodes (LEDs) annealed in different ambients (argon, air, oxygen, and nitrogen) have been investigated. The ZnO nanotubes by aqueous chemical growth (ACG) technique on p-GaN substrates were obtained. The as-grown ZnO nanotubes were annealed in different ambients at 600°C for 30 min. The EL investigations showed that air, oxygen, and nitrogen annealing ambients have strongly affected the deep level emission bands in ZnO. It was concluded from the EL investigation that more than one deep level defect is involved in the red emission appearing between 620 and 750 nm and that the red emission in ZnO can be attributed to oxygen interstitials (Oi) appearing in the range from 620 nm (1.99 eV) to 690 nm (1.79 eV), and to oxygen vacancies (Vo) appearing in the range from 690 nm (1.79 eV) to 750 nm (1.65 eV). The annealing ambients, especially the nitrogen ambient, were also found to greatly influence the color-rendering properties and increase the CRI of the as - grown LEDs from 87 to 96.

Assessment of methods for methyl iodide emission reduction and pest control using a simulation model

NASA Astrophysics Data System (ADS)

Luo, Lifang; Ashworth, Daniel J.; Šimunek, Jirka; Xuan, Richeng; Yates, Scott R.

2013-02-01

The increasing registration of the fumigant methyl iodide within the USA has led to more concerns about its toxicity to workers and bystanders. Emission mitigation strategies are needed to protect the public and environmental health while providing effective pest control. The effectiveness of various methods on emissions reduction and pest control was assessed using a process-based mathematical model in this study. Firstly, comparisons between the simulated and laboratory measured emission fluxes and cumulative emissions were made for methyl iodide (MeI) under four emission reduction treatments: 1) control, 2) using soil with high organic matter content (HOM), 3) being covered by virtually impermeable film (VIF), and 4) irrigating soil surface following fumigation (Irrigation). Then the model was extended to simulate a broader range of emission reduction strategies for MeI, including 5) being covered by high density polyethylene (HDPE), 6) increasing injection depth from 30 cm to 46 cm (Deep), 7) HDPE + Deep, 8) adding a reagent at soil surface (Reagent), 9) Reagent + Irrigation, and 10) Reagent + HDPE. Furthermore, the survivability of three types of soil-borne pests (citrus nematodes [Tylenchulus semipenetrans], barnyard seeds [Echinochloa crus-galli], fungi [Fusarium oxysporum]) was also estimated for each scenario. Overall, the trend of the measured emission fluxes as well as total emission were reasonably reproduced by the model for treatments 1 through 4. Based on the numerical simulation, the ranking of effectiveness in total emission reduction was VIF (82.4%) > Reagent + HDPE (73.2%) > Reagent + Irrigation (43.0%) > Reagent (23.5%) > Deep + HDPE (19.3%) > HOM (17.6%) > Deep (13.0%) > Irrigation (11.9%) > HDPE (5.8%). The order for pest control efficacy suggests, VIF had the highest pest control efficacy, followed by Deep + HDPE, Irrigation, Reagent + Irrigation, HDPE, Deep, Reagent + HDPE, Reagent, and HOM. Therefore, VIF is the optimal method disregarding the cost of the film since it maximizes efficacy while minimizing volatility losses. Otherwise, the integrated methods such as Deep + HDPE and Reagent + Irrigation, are recommended.

Recent distribution of lead in the Indian Ocean reflects the impact of regional emissions.

PubMed

Echegoyen, Yolanda; Boyle, Edward A; Lee, Jong-Mi; Gamo, Toshitaka; Obata, Hajime; Norisuye, Kazuhiro

2014-10-28

Humans have injected lead (Pb) massively into the earth surface environment in a temporally and spatially evolving pattern. A significant fraction is transported by the atmosphere into the surface ocean where we can observe its transport by ocean currents and sinking particles. This study of the Indian Ocean documents high Pb concentrations in the northern and tropical surface waters and extremely low Pb levels in the deep water. North of 20°S, dissolved Pb concentrations decrease from 42 to 82 pmol/kg in surface waters to 1.5-3.3 pmol/kg in deep waters. South of 20°S, surface water Pb concentrations decrease from 21 pmol/kg at 31°S to 7 pmol/kg at 62°S. This surface Pb concentration gradient reflects a southward decrease in anthropogenic Pb emissions. The upper waters of the north and central Indian Ocean have high Pb concentrations resulting from recent regional rapid industrialization and a late phase-out of leaded gasoline, and these concentrations are now higher than currently seen in the central North Pacific and North Atlantic oceans. The Antarctic sector of the Indian Ocean shows very low concentrations due to limited regional anthropogenic Pb emissions, high scavenging rates, and rapid vertical mixing, but Pb still occurs at higher levels than would have existed centuries ago. Penetration of Pb into the northern and central Indian Ocean thermocline waters is minimized by limited ventilation. Pb concentrations in the deep Indian Ocean are comparable to the other oceans at the same latitude, and deep waters of the central Indian Ocean match the lowest observed oceanic Pb concentrations.

The role of deep convection and nocturnal low-level jets for dust emission in summertime West Africa: Estimates from convection-permitting simulations

PubMed Central

Heinold, B; Knippertz, P; Marsham, JH; Fiedler, S; Dixon, NS; Schepanski, K; Laurent, B; Tegen, I

2013-01-01

[1] Convective cold pools and the breakdown of nocturnal low-level jets (NLLJs) are key meteorological drivers of dust emission over summertime West Africa, the world’s largest dust source. This study is the first to quantify their relative contributions and physical interrelations using objective detection algorithms and an off-line dust emission model applied to convection-permitting simulations from the Met Office Unified Model. The study period covers 25 July to 02 September 2006. All estimates may therefore vary on an interannual basis. The main conclusions are as follows: (a) approximately 40% of the dust emissions are from NLLJs, 40% from cold pools, and 20% from unidentified processes (dry convection, land-sea and mountain circulations); (b) more than half of the cold-pool emissions are linked to a newly identified mechanism where aged cold pools form a jet above the nocturnal stable layer; (c) 50% of the dust emissions occur from 1500 to 0200 LT with a minimum around sunrise and after midday, and 60% of the morning-to-noon emissions occur under clear skies, but only 10% of the afternoon-to-nighttime emissions, suggesting large biases in satellite retrievals; (d) considering precipitation and soil moisture effects, cold-pool emissions are reduced by 15%; and (e) models with parameterized convection show substantially less cold-pool emissions but have larger NLLJ contributions. The results are much more sensitive to whether convection is parameterized or explicit than to the choice of the land-surface characterization, which generally is a large source of uncertainty. This study demonstrates the need of realistically representing moist convection and stable nighttime conditions for dust modeling. Citation: Heinold, B., P. Knippertz, J. H. Marsham, S. Fiedler, N. S. Dixon, K. Schepanski, B. Laurent, and I. Tegen (2013), The role of deep convection and nocturnal low-level jets for dust emission in summertime West Africa: Estimates from convection-permitting simulations, J. Geophys. Res. Atmos., 118, 4385–4400, doi:10.1002/jgrd.50402. PMID:25893153

Policy Implications of Deep Decarbonization in the United States

NASA Astrophysics Data System (ADS)

Williams, J.

2015-12-01

Independent research teams from sixteen of the largest greenhouse gas (GHG) emitting countries have participated in a collaborative two-year project developing emission reduction scenarios for their own countries consistent with limiting anthropogenic warming to 2 C or less. This talk discusses the policy implications of the work done by the Deep Decarbonization Pathways Project (DDPP) at the US federal and international levels, including new ways of informing decision makers about the requirements of an energy system transformation.

Bond-center hydrogen in dilute Si1-xGex alloys: Laplace deep-level transient spectroscopy

NASA Astrophysics Data System (ADS)

Bonde Nielsen, K.; Dobaczewski, L.; Peaker, A. R.; Abrosimov, N. V.

2003-07-01

We apply Laplace deep-level transient spectroscopy in situ after low-temperature proton implantation into dilute Si1-xGex alloys and identify the deep donor state of hydrogen occupying a strained Si-Si bond-center site next to Ge. The activation energy of the electron emission from the donor is ˜158 meV when extrapolated to zero electrical field. We construct a configuration diagram of the Ge-strained site from formation and annealing data and deduce that alloying with ˜1% Ge does not significantly influence the low-temperature migration of hydrogen as compared to elemental Si. We observe two bond-center-type carbon-hydrogen centers and conclude that carbon impurities act as much stronger traps for hydrogen than the alloy Ge atoms.

Investigation of structural, morphological, luminescent and thermal properties of combusted aluminium-based iron oxide

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

Shinde, S.S.; Rajpure, K.Y., E-mail: rajpure@yahoo.co

Nanocomposites of aluminium integrated hematite {alpha}-Fe{sub 2}O{sub 3} are synthesized by combustion route using aqueous solutions of AR grade ferric trichloride and aluminium nitrate as precursors. The influence of aluminium incorporation on to the morphology, XPS, photoluminescence and thermal properties has been investigated. The FESEM and AFM micrographs depict that the samples are compact and have homogeneously distributed grains of varying sizes ({approx}20-60 nm). Chemical composition and valence states of constituent elements in hematite are analyzed by XPS. In room temperature photoluminescence (PL) study, we observed strong violet emission around 436 nm without any deep-level emission and a small PLmore » FWHM indicating that the concentrations of defects are responsible for deep-level emissions. The specific heat and thermal conductivity study shows the phonon conduction behavior is dominant. We studied interparticle interactions using complex impedance spectroscopy. We report a new potential candidate for its possible applications in optoelectronics and magnetic devices. -- Graphical abstract: Frequency and temperature dependent interparticle interactions like grains, grain boundary effects using complex impedance spectroscopy of pure and 10 at% Al:Fe{sub 2}O{sub 3} have been studied. Display Omitted« less

Surface acceptor states in MBE-grown CdTe layers

NASA Astrophysics Data System (ADS)

Wichrowska, Karolina; Wosinski, Tadeusz; Tkaczyk, Zbigniew; Kolkovsky, Valery; Karczewski, Grzegorz

2018-04-01

A deep-level hole trap associated with surface defect states has been revealed with deep-level transient spectroscopy investigations of metal-semiconductor junctions fabricated on nitrogen doped p-type CdTe layers grown by the molecular-beam epitaxy technique. The trap displayed the hole-emission activation energy of 0.33 eV and the logarithmic capture kinetics indicating its relation to extended defect states at the metal-semiconductor interface. Strong electric-field-induced enhancement of the thermal emission rate of holes from the trap has been attributed to the phonon-assisted tunneling effect from defect states involving very large lattice relaxation around the defect and metastability of its occupied state. Passivation with ammonium sulfide of the CdTe surface, prior to metallization, results in a significant decrease in the trap density. It also results in a distinct reduction in the width of the surface-acceptor-state-induced hysteresis loops in the capacitance vs. voltage characteristics of the metal-semiconductor junctions.

Local surface plasmon enhanced polarization and internal quantum efficiency of deep ultraviolet emissions from AlGaN-based quantum wells.

PubMed

Zhang, Cai; Tang, Ning; Shang, Liangliang; Fu, Lei; Wang, Weiying; Xu, Fujun; Wang, Xinqiang; Ge, Weikun; Shen, Bo

2017-05-24

We report the enhancement of the polarization and internal quantum efficiency (IQE) of deep-UV LEDs by evaporating Al nanoparticles on the device surface to induce localized surface plasmons (LSPs). The deep-UV LEDs polarization is improved due to part of TM emission turns into TE emission through LSPs coupling. The significantly enhanced IQE is attributed to LSPs coupling, which suppress the participation of delocalized and dissociated excitons to non-radiative recombination process.

Double negatively charged carbon vacancy at the h- and k-sites in 4H-SiC: Combined Laplace-DLTS and DFT study

NASA Astrophysics Data System (ADS)

Capan, Ivana; Brodar, Tomislav; Pastuović, Željko; Siegele, Rainer; Ohshima, Takeshi; Sato, Shin-ichiro; Makino, Takahiro; Snoj, Luka; Radulović, Vladimir; Coutinho, José; Torres, Vitor J. B.; Demmouche, Kamel

2018-04-01

We present results from combined Laplace-Deep Level Transient Spectroscopy (Laplace-DLTS) and density functional theory studies of the carbon vacancy (VC) in n-type 4H-SiC. Using Laplace-DLTS, we were able to distinguish two previously unresolved sub-lattice-inequivalent emissions, causing the broad Z1/2 peak at 290 K that is commonly observed by conventional DLTS in n-type 4H-SiC. This peak has two components with activation energies for electron emission of 0.58 eV and 0.65 eV. We compared these results with the acceptor levels of VC obtained by means of hybrid density functional supercell calculations. The calculations support the assignment of the Z1/2 signal to a superposition of emission peaks from double negatively charged VC defects. Taking into account the measured and calculated energy levels, the calculated relative stability of VC in hexagonal (h) and cubic (k) lattice sites, as well as the observed relative amplitude of the Laplace-DLTS peaks, we assign Z1 and Z2 to VC(h) and VC(k), respectively. We also present the preliminary results of DLTS and Laplace-DLTS measurements on deep level defects (ET1 and ET2) introduced by fast neutron irradiation and He ion implantation in 4H-SiC. The origin of ET1 and ET2 is still unclear.

Review—hexagonal boron nitride epilayers: Growth, optical properties and device applications

DOE PAGES

Jiang, H. X.; Lin, Jing Yu

2016-09-07

This paper provides a brief overview on recent advances made in authors’ laboratory in epitaxial growth and optical studies of hexagonal boron nitride (h-BN) epilayers and heterostructures. Photoluminescence spectroscopy has been employed to probe the optical properties of h-BN. It was observed that the near band edge emission of h-BN is unusually high and is more than two orders of magnitude higher than that of high quality AlN epilayers. It was shown that the unique quasi-2D nature induced by the layered structure of h-BN results in high optical absorption and emission. The impurity related and near band-edge transitions in h-BNmore » epilayers were probed for materials synthesized under varying ammonia flow rates. Our results have identified that the most dominant impurities and deep level defects in h-BN epilayers are related to nitrogen vacancies. By growing h-BN under high ammonia flow rates, nitrogen vacancy related defects can be eliminated and epilayers exhibiting pure free exciton emission have been obtained. Deep UV and thermal neutron detectors based on h-BN epilayers were shown to possess unique features. Lastly, it is our belief that h-BN will lead to many potential applications from deep UV emitters and detectors, radiation detectors, to novel 2D photonic and electronic devices.« less

Review—hexagonal boron nitride epilayers: Growth, optical properties and device applications

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

Jiang, H. X.; Lin, Jing Yu

This paper provides a brief overview on recent advances made in authors’ laboratory in epitaxial growth and optical studies of hexagonal boron nitride (h-BN) epilayers and heterostructures. Photoluminescence spectroscopy has been employed to probe the optical properties of h-BN. It was observed that the near band edge emission of h-BN is unusually high and is more than two orders of magnitude higher than that of high quality AlN epilayers. It was shown that the unique quasi-2D nature induced by the layered structure of h-BN results in high optical absorption and emission. The impurity related and near band-edge transitions in h-BNmore » epilayers were probed for materials synthesized under varying ammonia flow rates. Our results have identified that the most dominant impurities and deep level defects in h-BN epilayers are related to nitrogen vacancies. By growing h-BN under high ammonia flow rates, nitrogen vacancy related defects can be eliminated and epilayers exhibiting pure free exciton emission have been obtained. Deep UV and thermal neutron detectors based on h-BN epilayers were shown to possess unique features. Lastly, it is our belief that h-BN will lead to many potential applications from deep UV emitters and detectors, radiation detectors, to novel 2D photonic and electronic devices.« less

Thermally Stimulated Currents in Nanocrystalline Titania

PubMed Central

Bruzzi, Mara; Mori, Riccardo; Baldi, Andrea; Cavallaro, Alessandro; Scaringella, Monica

2018-01-01

A thorough study on the distribution of defect-related active energy levels has been performed on nanocrystalline TiO2. Films have been deposited on thick-alumina printed circuit boards equipped with electrical contacts, heater and temperature sensors, to carry out a detailed thermally stimulated currents analysis on a wide temperature range (5–630 K), in view to evidence contributions from shallow to deep energy levels within the gap. Data have been processed by numerically modelling electrical transport. The model considers both free and hopping contribution to conduction, a density of states characterized by an exponential tail of localized states below the conduction band and the convolution of standard Thermally Stimulated Currents (TSC) emissions with gaussian distributions to take into account the variability in energy due to local perturbations in the highly disordered network. Results show that in the low temperature range, up to 200 K, hopping within the exponential band tail represents the main contribution to electrical conduction. Above room temperature, electrical conduction is dominated by free carriers contribution and by emissions from deep energy levels, with a defect density ranging within 1014–1018 cm−3, associated with physio- and chemi-sorbed water vapour, OH groups and to oxygen vacancies. PMID:29303976

Thermally Stimulated Currents in Nanocrystalline Titania.

PubMed

Bruzzi, Mara; Mori, Riccardo; Baldi, Andrea; Carnevale, Ennio Antonio; Cavallaro, Alessandro; Scaringella, Monica

2018-01-05

A thorough study on the distribution of defect-related active energy levels has been performed on nanocrystalline TiO₂. Films have been deposited on thick-alumina printed circuit boards equipped with electrical contacts, heater and temperature sensors, to carry out a detailed thermally stimulated currents analysis on a wide temperature range (5-630 K), in view to evidence contributions from shallow to deep energy levels within the gap. Data have been processed by numerically modelling electrical transport. The model considers both free and hopping contribution to conduction, a density of states characterized by an exponential tail of localized states below the conduction band and the convolution of standard Thermally Stimulated Currents (TSC) emissions with gaussian distributions to take into account the variability in energy due to local perturbations in the highly disordered network. Results show that in the low temperature range, up to 200 K, hopping within the exponential band tail represents the main contribution to electrical conduction. Above room temperature, electrical conduction is dominated by free carriers contribution and by emissions from deep energy levels, with a defect density ranging within 10 14 -10 18 cm -3 , associated with physio- and chemi-sorbed water vapour, OH groups and to oxygen vacancies.

Phonon-assisted changes in charge states of deep level defects in germanium

NASA Astrophysics Data System (ADS)

Markevich, A. V.; Litvinov, V. V.; Emtsev, V. V.; Markevich, V. P.; Peaker, A. R.

2006-04-01

Electronic processes associated with changes in the charge states of the vacancy-oxygen center (VO or A center) and vacancy-group-V-impurity atom (P, As, Sb or Bi) pairs (E centers) in irradiated germanium crystals have been studied using deep level transient spectroscopy (DLTS), high-resolution Laplace DLTS and Hall effect measurements. It is found that the electron emission and capture processes related to transitions between the doubly and the singly negatively charged states of the A center and the E centers in Ge are phonon-assisted, i.e., they are accompanied by significant vibrations and re-arrangements of atoms in the vicinity of the defects. Manifestations of the phonon involvements are: (i) temperature-dependent electron capture cross-sections which are well described in the frame of the multi-phonon-assisted capture model; (ii) large changes in entropy related to the ionization of the defects and, associated with these, temperature-dependent positions of energy levels; and (iii) electron emission via phonon-assisted tunneling upon the application of electric field. These effects have been considered in detail for the vacancy-oxygen and the vacancy-donor complexes. On the basis of a combined analysis of the electronic processes a configuration-coordinate diagram of the acceptor states of the A and E centers is plotted. It is found that changes in the entropy of ionization and the energy for electron emission for these traps follow the empirical Meyer-Neldel rule. A model based on multi-phonon-assisted carrier emission from defects is adapted for the explanation of the origin of this rule for the case of electronic processes in Ge.

Effects of Pressure on Optically Active Deep Levels in Phosphorus Doped ZnSe

NASA Astrophysics Data System (ADS)

Weinstein, B. A.; Iota, V.

1998-03-01

We report high pressure photoluminescence (PL) and PL-excitation (PLE) studies at 8K of the 'midgap' emission in P-doped ZnSe using a diamond-cell with He medium. The dominant emission at low pressure is due to donor-acceptor-pair (DAP) transitions between shallow donors and deep trigonally relaxed P_Se acceptors.(J. Davies, et al., J. Luminescence 18/19, 322 (1979)) Its PL and PLE peaks shift by 8.2meV/kbar and 5.9meV/kbar, respectively -- Stokes shift decreasing with pressure. At 35kbar a new PL band, shifting to lower energy (-5.4meV/kbar), emerges from above the absorption edge, and concurrently the original DAP PL quenches. This shows that a resonant level, a deep donor or possibly a P_Se antibonding state,(R. Watts, et al., Phys. Rev. B3), 404 (1971) crosses the conduction edge into the gap. A third PL band is seen only with internse UV excitation. It occurs initially as a high energy shoulder of the original DAP peak, but shifts more rapidly upward (9.4meV/kbar) until it crosses the edge and quenches at 40kbar. We discuss candidates for this band, including donor-P_Se complexes, and we compare our results to similar work on the Zn vacancy in ZnSe. (figures)

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

Chavez, III, Ramiro; Cai, Min; Tlach, Brian

Four new cross-conjugated small molecules based on a central benzo[1,2-d:4,5-d']bisoxazole moiety possessing semi-independently tunable HOMO and LUMO levels were synthesized and the properties of these materials were evaluated experimentally and theoretically. The molecules were thermally stable with 5% weight loss occurring well above 350 °C. The cruciforms all exhibited blue emission in solution ranging from 433–450 nm. Host–guest OLEDs fabricated from various concentrations of these materials using the small molecule host 4,4'-bis(9-carbazolyl)-biphenyl (CBP) exhibited deep blue-emission with Commission Internationale de L'Eclairage (CIE) coordinates of (0.15 ≤ x ≤ 0.17, 0.05 ≤ y ≤ 0.11), and maximum luminance efficiencies as highmore » as ~2 cd A–1. Lastly, these results demonstrate the potential of benzobisoxazole cruciforms as emitters for developing high-performance deep blue OLEDs.« less

Water level, vegetation composition, and plant productivity explain greenhouse gas fluxes in temperate cutover fens after inundation

NASA Astrophysics Data System (ADS)

Minke, Merten; Augustin, Jürgen; Burlo, Andrei; Yarmashuk, Tatsiana; Chuvashova, Hanna; Thiele, Annett; Freibauer, Annette; Tikhonov, Vitalij; Hoffmann, Mathias

2016-07-01

Peat extraction leaves a land surface with a strong relief of deep cutover areas and higher ridges. Rewetting inundates the deep parts, while less deeply extracted zones remain at or above the water level. In temperate fens the flooded areas are colonized by helophytes such as Eriophorum angustifolium, Carex spp., Typha latifolia or Phragmites australis dependent on water depth. Reeds of Typha and Phragmites are reported as large sources of methane, but data on net CO2 uptake are contradictory for Typha and rare for Phragmites. Here, we analyze the effect of vegetation, water level and nutrient conditions on greenhouse gas (GHG) emissions for representative vegetation types along water level gradients at two rewetted cutover fens (mesotrophic and eutrophic) in Belarus. Greenhouse gas emissions were measured campaign-wise with manual chambers every 2 to 4 weeks for 2 years and interpolated by modelling. All sites had negligible nitrous oxide exchange rates. Most sites were carbon sinks and small GHG sources. Methane emissions generally increased with net ecosystem CO2 uptake. Mesotrophic small sedge reeds with water table around the land surface were small GHG sources in the range of 2.3 to 4.2 t CO2 eq. ha-1 yr-1. Eutrophic tall sedge - Typha latifolia reeds on newly formed floating mats were substantial net GHG emitters in the range of 25.1 to 39.1 t CO2 eq. ha-1 yr. They represent transient vegetation stages. Phragmites reeds ranged between -1.7 to 4.2 t CO2 eq. ha-1 yr-1 with an overall mean GHG emission of 1.3 t CO2 eq. ha-1 yr-1. The annual CO2 balance was best explained by vegetation biomass, which includes the role of vegetation composition and species. Methane emissions were obviously driven by biological activity of vegetation and soil organisms. Shallow flooding of cutover temperate fens is a suitable measure to arrive at low GHG emissions. Phragmites australis establishment should be promoted in deeper flooded areas and will lead to moderate, but variable GHG emissions or even occasional sinks. The risk of large GHG emissions is higher for eutrophic than mesotrophic peatlands. Nevertheless, flooding of eutrophic temperate fens still represents a safe GHG mitigation option because even the hotspot of our study, the floating tall sedge - Typha latifolia reeds, did not exceed the typical range of GHG emissions from drained fen grasslands and the spatially dominant Phragmites australis reed emitted by far less GHG than drained fens.

Solar activity during the deep minimum of 2009

NASA Astrophysics Data System (ADS)

Sylwester, Janusz; Siarkowski, Marek; Gburek, Szymon; Gryciuk, Magdalena; Kepa, Anna; Kowaliński, Mirosław; Mrozek, Tomek; Phillips, Kenneth J. H.; Podgórski, Piotr; Sylwester, Barbara

2014-12-01

We discuss the character of the unusually deep solar activity minimum of 2009 between Solar Cycles 23 and 24. Levels of solar activity in various parts of the solar atmosphere -- photosphere, chromosphere, transition region, and corona -- were observed to be at their lowest for a century. The soft X-ray emission from the corona (hot outer part of the Sun's atmosphere) was measured throughout most of 2009 with the Polish-built SphinX spectrophotometer. Unlike other X-ray monitoring spacecraft, this sensitive spacecraft-borne instrument was able to continue measurements throughout this extended period of low activity.

Surface plasmon coupling for suppressing p-GaN absorption and TM-polarized emission in a deep-UV light-emitting diode.

PubMed

Kuo, Yang; Su, Chia-Ying; Hsieh, Chieh; Chang, Wen-Yen; Huang, Chu-An; Kiang, Yean-Woei; Yang, C C

2015-09-15

The radiated power enhancement (suppression) of an in- (out-of-) plane-oriented radiating dipole at a desired emission wavelength in the deep-ultraviolet (UV) range when it is coupled with a surface plasmon (SP) resonance mode induced on a nearby Al nanoparticle (NP) is demonstrated. Also, it is found that the enhanced radiated power propagates mainly in the direction from the Al NP toward the dipole. Such SP coupling behaviors can be used for suppressing the transverse-magnetic (TM)-polarized emission, enhancing the transverse-electric-polarized emission, and reducing the UV absorption of the p-GaN layer in an AlGaN-based deep-UV light-emitting diode by embedding a sphere-like Al NP in its p-AlGaN layer.

Electrical characterization of deep levels created by bombarding nitrogen-doped 4H-SiC with alpha-particle irradiation

NASA Astrophysics Data System (ADS)

Omotoso, Ezekiel; Meyer, Walter E.; Auret, F. Danie; Paradzah, Alexander T.; Legodi, Matshisa J.

2016-03-01

Deep-level transient spectroscopy (DLTS) and Laplace-DLTS were used to investigate the effect of alpha-particle irradiation on the electrical properties of nitrogen-doped 4H-SiC. The samples were bombarded with alpha-particles at room temperature (300 K) using an americium-241 (241Am) radionuclide source. DLTS revealed the presence of four deep levels in the as-grown samples, E0.09, E0.11, E0.16 and E0.65. After irradiation with a fluence of 4.1 × 1010 alpha-particles-cm-2, DLTS measurements indicated the presence of two new deep levels, E0.39 and E0.62 with energy levels, EC - 0.39 eV and EC - 0.62 eV, with an apparent capture cross sections of 2 × 10-16 and 2 × 10-14 cm2, respectively. Furthermore, irradiation with fluence of 8.9 × 1010 alpha-particles-cm-2 resulted in the disappearance of shallow defects due to a lowering of the Fermi level. These defects re-appeared after annealing at 300 °C for 20 min. Defects, E0.39 and E0.42 with close emission rates were attributed to silicon or carbon vacancy and could only be separated by using high resolution Laplace-DLTS. The DLTS peaks at EC - (0.55-0.70) eV (known as Z1/Z2) were attributed to an isolated carbon vacancy (VC).

Performance status of a small robot-mounted or hand-held, solar-blind, standoff chemical, biological, and explosives (CBE) sensor

NASA Astrophysics Data System (ADS)

Hug, W. F.; Reid, R. D.; Bhartia, R.; Lane, A. L.

2009-05-01

Photon Systems and JPL are continuing development of a new technology robot-mounted or hand-held sensor for reagentless, short-range, standoff detection and identification of trace levels CBE materials on surfaces. This deep ultraviolet CBE sensor is the result of ongoing Army STTR and DTRA programs. The evolving 6 lb, 15W, lantern-size sensor can discriminate CBE from background clutter materials using a combination of deep UV excited resonance Raman (RR) and laser induced native fluorescence (LINF) emissions resulting from excitation by a new technology deep UV laser. Standoff excitation of suspicious packages, vehicles, persons, and other objects that may contain hazardous materials is accomplished using wavelengths below 250nm where RR and LINF emissions occupy distinctly different wavelength regions. This enables simultaneous detection of RR and LINF emissions with no spectral overlap or interference of LINF over RR or RR over LINF. The new eye-safe targeted ultraviolet chemical, biological, and explosives (TUCBE) sensor can detect and identify less than 1 μg/cm2 of explosives or 104 bacterial spores at 10 meters standoff, or 10 ng/cm2 of explosives or 102 bacterial spores/cm2 at 1 meter standoff. Detection and identification requires less than 1 ms and has a sample rate up to 20 Hz. Lower concentrations of contamination can be detected and identified as closer ranges and higher concentrations at longer ranges. The sensor is solar blind and can be operated in full daylight conditions as a result of excitation and detection in the deep UV and the use of a gated detection system.

Phase 2 Methyl Iodide Deep-Bed Adsorption Tests

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

Soelberg, Nick; Watson, Tony

2014-09-01

Nuclear fission produces fission products (FPs) and activation products, including iodine-129, which could evolve into used fuel reprocessing facility off-gas systems, and could require off-gas control to limit air emissions to levels within acceptable emission limits. Research, demonstrations, and some reprocessing plant experience have indicated that diatomic iodine can be captured with efficiencies high enough to meet regulatory requirements. Research on the capture of organic iodides has also been performed, but to a lesser extent. Several questions remain open regarding the capture of iodine bound in organic compounds. Deep-bed methyl iodide adsorption testing has progressed according to a multi-laboratory methylmore » iodide adsorption test plan. This report summarizes the second phase of methyl iodide adsorption work performed according to this test plan using the deep-bed iodine adsorption test system at the Idaho National Laboratory (INL), performed during the second half of Fiscal Year (FY) 2014. Test results continue to show that methyl iodide adsorption using AgZ can achieve total iodine decontamination factors (DFs, ratios of uncontrolled and controlled total iodine levels) above 1,000, until breakthrough occurred. However, mass transfer zone depths are deeper for methyl iodide adsorption compared to diatomic iodine (I2) adsorption. Methyl iodide DFs for the Ag Aerogel test adsorption efficiencies were less than 1,000, and the methyl iodide mass transfer zone depth exceeded 8 inches. Additional deep-bed testing and analyses are recommended to (a) expand the data base for methyl iodide adsorption under various conditions specified in the methyl iodide test plan, and (b) provide more data for evaluating organic iodide reactions and reaction byproducts for different potential adsorption conditions.« less

Electromagnetic interference of GSM mobile phones with the implantable deep brain stimulator, ITREL-III

PubMed Central

Kainz, Wolfgang; Alesch, François; Chan, Dulciana Dias

2003-01-01

Background The purpose was to investigate mobile phone interference with implantable deep brain stimulators by means of 10 different 900 Mega Hertz (MHz) and 10 different 1800 MHz GSM (Global System for Mobile Communications) mobile phones. Methods All tests were performed in vitro using a phantom especially developed for testing with deep brain stimulators. The phantom was filled with liquid phantom materials simulating brain and muscle tissue. All examinations were carried out inside an anechoic chamber on two implants of the same type of deep brain stimulator: ITREL-III from Medtronic Inc., USA. Results Despite a maximum transmitted peak power of mobile phones of 1 Watt (W) at 1800 MHz and 2 W at 900 MHz respectively, no influence on the ITREL-III was found. Neither the shape of the pulse form changed nor did single pulses fail. Tests with increased transmitted power using CW signals and broadband dipoles have shown that inhibition of the ITREL-III occurs at frequency dependent power levels which are below the emissions of GSM mobile phones. The ITREL-III is essentially more sensitive at 1800 MHz than at 900 MHz. Particularly the frequency range around 1500 MHz shows a very low interference threshold. Conclusion These investigations do not indicate a direct risk for ITREL-III patients using the tested GSM phones. Based on the interference levels found with CW signals, which are below the mobile phone emissions, we recommend similar precautions as for patients with cardiac pacemakers: 1. The phone should be used at the ear at the opposite side of the implant and 2. The patient should avoid carrying the phone close to the implant. PMID:12773204

Improved sensing using simultaneous deep-UV Raman and fluorescence detection-II

NASA Astrophysics Data System (ADS)

Hug, W. F.; Bhartia, R.; Sijapati, K.; Beegle, L. W.; Reid, R. D.

2014-05-01

Photon Systems in collaboration with JPL is continuing development of a new technology robot-mounted or hand-held sensor for reagentless, short-range, standoff detection and identification of trace levels chemical, biological, and explosive (CBE) materials on surfaces. This deep ultraviolet CBE sensor is the result of Army STTR and DTRA programs. The evolving 10 to 15 lb, 20 W, sensor can discriminate CBE from background clutter materials using a fusion of deep UV excited resonance Raman (RR) and laser induced native fluorescence (LINF) emissions collected is less than 1 ms. RR is a method that provides information about molecular bonds, while LINF spectroscopy is a much more sensitive method that provides information regarding the electronic configuration of target molecules. Standoff excitation of suspicious packages, vehicles, persons, and other objects that may contain hazardous materials is accomplished using excitation in the deep UV where there are four main advantages compared to near-UV, visible or near-IR counterparts. 1) Excited between 220 and 250 nm, Raman emission occur within a fluorescence-free region of the spectrum, eliminating obscuration of weak Raman signals by fluorescence from target or surrounding materials. 2) Because Raman and fluorescence occupy separate spectral regions, detection can be done simultaneously, providing an orthogonal set of information to improve both sensitivity and lower false alarm rates. 3) Rayleigh law and resonance effects increase Raman signal strength and sensitivity of detection. 4) Penetration depth into target in the deep UV is short, providing spatial/spectral separation of a target material from its background or substrate. 5) Detection in the deep UV eliminates ambient light background and enable daylight detection.

The Effect of Framing and Normative Messages in Building Support for Climate Policies

PubMed Central

Hurlstone, Mark J.; Lewandowsky, Stephan; Newell, Ben R.; Sewell, Brittany

2014-01-01

Deep cuts in greenhouse gas emissions are required to mitigate climate change. However, there is low willingness amongst the public to prioritise climate policies for reducing emissions. Here we show that the extent to which Australians are prepared to reduce their country's CO2 emissions is greater when the costs to future national income are framed as a “foregone-gain”—incomes rise in the future but not by as much as in the absence of emission cuts—rather than as a “loss”—incomes decrease relative to the baseline expected future levels (Studies 1 & 2). The provision of a normative message identifying Australia as one of the world's largest CO2 emitters did not increase the amount by which individuals were prepared to reduce emissions (Study 1), whereas a normative message revealing the emission policy preferences of other Australians did (Study 2). The results suggest that framing the costs of reducing emissions as a smaller increase in future income and communicating normative information about others' emission policy preferences are effective methods for leveraging public support for emission cuts. PMID:25501009

The effect of framing and normative messages in building support for climate policies.

PubMed

Hurlstone, Mark J; Lewandowsky, Stephan; Newell, Ben R; Sewell, Brittany

2014-01-01

Deep cuts in greenhouse gas emissions are required to mitigate climate change. However, there is low willingness amongst the public to prioritise climate policies for reducing emissions. Here we show that the extent to which Australians are prepared to reduce their country's CO2 emissions is greater when the costs to future national income are framed as a "foregone-gain"--incomes rise in the future but not by as much as in the absence of emission cuts--rather than as a "loss"--incomes decrease relative to the baseline expected future levels (Studies 1 & 2). The provision of a normative message identifying Australia as one of the world's largest CO2 emitters did not increase the amount by which individuals were prepared to reduce emissions (Study 1), whereas a normative message revealing the emission policy preferences of other Australians did (Study 2). The results suggest that framing the costs of reducing emissions as a smaller increase in future income and communicating normative information about others' emission policy preferences are effective methods for leveraging public support for emission cuts.

Donor and double-donor transitions of the carbon vacancy related EH{sub 6∕7} deep level in 4H-SiC

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

Booker, I. D., E-mail: ianbo@ifm.liu.se; Janzén, E., E-mail: erija@ifm.liu.se; Son, N. T.

Using medium- and high-resolution multi-spectra fitting of deep level transient spectroscopy (DLTS), minority carrier transient spectroscopy (MCTS), optical O-DLTS and optical-electrical (OE)-MCTS measurements, we show that the EH{sub 6∕7} deep level in 4H-SiC is composed of two strongly overlapping, two electron emission processes with thermal activation energies of 1.49 eV and 1.58 eV for EH{sub 6} and 1.48 eV and 1.66 eV for EH{sub 7}. The electron emission peaks of EH{sub 7} completely overlap while the emission peaks of EH{sub 6} occur offset at slightly different temperatures in the spectra. OE-MCTS measurements of the hole capture cross section σ{sub p0}(T) in p-type samples revealmore » a trap-Auger process, whereby hole capture into the defect occupied by two electrons leads to a recombination event and the ejection of the second electron into the conduction band. Values of the hole and electron capture cross sections σ{sub n}(T) and σ{sub p}(T) differ strongly due to the donor like nature of the deep levels and while all σ{sub n}(T) have a negative temperature dependence, the σ{sub p}(T) appear to be temperature independent. Average values at the DLTS measurement temperature (∼600 K) are σ{sub n2+}(T) ≈ 1 × 10{sup −14} cm{sup 2}, σ{sub n+}(T) ≈ 1 × 10{sup −14} cm{sup 2}, and σ{sub p0}(T) ≈ 9 × 10{sup −18} cm{sup 2} for EH{sub 6} and σ{sub n2+}(T) ≈ 2 × 10{sup −14} cm{sup 2}, σ{sub n+}(T) ≈ 2 × 10{sup −14} cm{sup 2}, σ{sub p0}(T) ≈ 1 × 10{sup −20} cm{sup 2} for EH{sub 7}. Since EH{sub 7} has already been identified as a donor transition of the carbon vacancy, we propose that the EH{sub 6∕7} center in total represents the overlapping first and second donor transitions of the carbon vacancy defects on both inequivalent lattice sites.« less

Detecting deep crustal magma movement: Exploring linkages between increased gas emission, deep seismicity, and deformation (Invited)

NASA Astrophysics Data System (ADS)

Werner, C. A.; Poland, M. P.; Power, J. A.; Sutton, A. J.; Elias, T.; Grapenthin, R.; Thelen, W. A.

2013-12-01

Typically in the weeks to days before a volcanic eruption there are indisputable signals of unrest that can be identified in geophysical and geochemical data. Detection of signals of volcanic unrest months to years prior to an eruption, however, relies on our ability to recognize and link more subtle changes. Deep long-period earthquakes, typically 10-45 km beneath volcanoes, are thought to represent magma movement and may indicate near future unrest. Carbon dioxide (CO2 ) exsolves from most magmas at similar depths and increases in CO2 discharge may also provide a months-to-years precursor as it emits at the surface in advance of the magma from which it exsolved. Without the use of sensitive monitoring equipment and routine measurements, changes in CO2 can easily go undetected. Finally, inflation of the surface, through use of InSAR or GPS stations (especially at sites tens of km from the volcano) can also indicate accumulation of magma in the deep crust. Here we present three recent examples, from Redoubt, Kilauea, and Mammoth Mountain volcanoes, where increases in CO2 emission, deep long-period earthquakes, and surface deformation data indicate either the intrusion of magma into the deep crust in the months to years preceding volcanic eruptions or a change in ongoing volcanic unrest. At Redoubt volcano, Alaska, elevated CO2 emission (~ 1200 t/d, or roughly 20 times the background emission) was measured in October, 2008, over 5 months prior to the first magmatic eruption in March, 2009. In addition to CO2 release, deep long-period earthquakes were first recorded in December, 2008, and a deep deformation signal was detected starting in May 2008, albeit retrospectively. At Kilauea, Hawaii, increases in CO2 emissions from the summit (up to nearly 25 kt/d, over three times the background emission) were measured mid-2004, roughly coincident with a change in deformation behavior from deflation to inflation. Nearly 3 years later, a change in eruptive activity occurred as a result of a burgeoning supply of magma to the volcano, which overwhelmed the ability of the ongoing east rift zone eruption to accommodate the increased flux of magma into the edifice. At Mammoth Mountain, California, diffuse CO2 degassing doubled between 2007 and 2012 following three swarms of deep earthquakes that began in 2006. In contrast to Redoubt and Kilauea, the CO2 emission rate at Mammoth is on the order of hundreds of t/d as opposed to thousands. This reasonably indicates a smaller volume of magma at depth, and changes do not suggest volcanic activity is imminent. In these examples there was no visual indication of increased CO2 emission, and geophysical signals of unrest were often subtle. Routine measurement of all volcanic gases, most importantly CO2 , coupled with a geophysical monitoring, therefore, has better potential to recognize changes in deep (10s of km) magmatic processes. Such indicators are key to better eruption forecasts, especially on the months-to years timescales that often elude volcanologists.

Ultraviolet/blue light-emitting diodes based on single horizontal ZnO microrod/GaN heterojunction.

PubMed

Du, Chia-Fong; Lee, Chen-Hui; Cheng, Chao-Tsung; Lin, Kai-Hsiang; Sheu, Jin-Kong; Hsu, Hsu-Cheng

2014-01-01

We report electroluminescence (EL) from single horizontal ZnO microrod (MR) and p-GaN heterojunction light-emitting diodes under forward and reverse bias. EL spectra were composed of two blue emissions centered at 431 and 490 nm under forward biases, but were dominated by a ultraviolet (UV) emission located at 380 nm from n-ZnO MR under high reverse biases. Light-output-current characteristic of the UV emission reveals that the rate of radiative recombination is faster than that of the nonradiative recombination. Highly efficient ZnO excitonic recombination at reverse bias is caused by electrons tunneling from deep-level states near the n-ZnO/p-GaN interface to the conduction band in n-ZnO.

Characterization of Thallium Bromide (TlBr) for Room Temperature Radiation Detectors

NASA Astrophysics Data System (ADS)

Smith, Holland McTyeire

Thallium bromide (TlBr) has emerged as a remarkably well-suited material for room temperature radiation detection. The unique combination of high-Z elements, high density, suitable band gap, and excellent electrical transport properties present in TlBr have brought device performance up to par with CdZnTe (CZT), the current market-leading room temperature radiation detector material. TlBr research is at an earlier stage than that of CZT, giving hope that the material will see even further improvement in electronic properties. Improving a resistive semiconductor material requires knowledge of deep levels present in the material and the effects of these deep levels on transport properties. Very few deep level studies have been conducted on TlBr, and none with the depth required to generate useful growth suggestions. In this dissertation, deep levels in nominally undoped and doped TlBr samples are studied with electrical and optical methods. Photo-Induced Conductivity Transient Spectroscopy (PICTS) is used to discover many deep levels in TlBr electrically. These levels are compared to sub-band gap optical transitions originating from defects observed in emission spectra. The results of this research indicate that the origin of resistivity in TlBr is likely due to deep level defects pinning the Fermi level at least ˜0.7 eV from either the conduction or valence band edge. The effect of dopants and deep levels on transport in TlBr is assessed with microwave photoconductivity decay analysis. It is found that Pb-, Se-, and O-doping decreases carrier lifetime in TlBr, whereas C-doping does not. TlBr exhibits weak ionic conductivity at room temperature, which both negatively affects the leakage current of detectors and leads to device degradation over time. Researchers are actively looking for ways to reduce or eliminate the ionic conductivity, but are faced with an intriguing challenge of materials engineering: is it possible to mitigate the ionic conduction of TlBr without harming the excellent electronic transport properties? Doping TlBr in order to control the ionic conductivity has been proposed and shown to be effective in reducing dark ionic current, but the electronic effects of the dopants has not been previously studied in detail. In this dissertation, the electronic effects of dopants introduced for ionic reasons are evaluated.

Strong ligand field effects of blue phosphorescent Ir(III) complexes with phenylpyrazole and phosphines.

PubMed

Park, Se Won; Ham, Ho Wan; Kim, Young Sik

2012-04-01

In the paper, we describe new Ir complexes for achieving efficient blue phosphorescence. New blue-emitting mixed-ligand Ir complexes comprising one cyclometalating, two phosphines trans to each other such as Ir(dppz)(PPh3)2(H)(L) (Ll= Cl, NCMe+, CN), [dppz = 3,5-Diphenylpyrazole] were synthesized and studied to tune the phosphorescence wavelength to the deep blue region and to enhance the luminescence efficiencies. To gain insight into the factors responsible for the emission color change and the variation of luminescence efficiency, we investigate the electron-withdrawing capabilities of ancillary ligands using DFT and TD-DFT calculations on the ground and excited states of the complexes. To achieve deep blue emission and increase the emission efficiency, (1) we substitute the phenyl group on the 3-position of the pyrazole ring that lowers the triplet energy enough that the quenching channel is not thermally accessible and (2) change the ancillary ligands coordinated to iridium atom to phosphine and cyano groups known as very strong field ligands. Their inclusion in the coordination sphere can increase the HOMO-LUMO gap to achieve the hypsochromic shift in emission color and lower the HOMO and LUMO energy level, which causes a large d-orbital energy splitting and avoids the quenching effect to improve the luminescence efficiency. The maximum emission spectra of Ir(dppz)(PPh3)2(H)(CI) and Ir(dppz)(PPh3)2(H)(CN) were in the ranges of 439, 432 nm, respectively.

Deep ultraviolet photoluminescence studies of aluminum-rich aluminum gallium nitride and aluminum nitride epilayers and nanostructures

NASA Astrophysics Data System (ADS)

Nepal, Neeraj

Deep ultraviolet (UV) photoluminescence (PL) spectroscopy has been employed to study optical properties of AlGaN alloys, undoped and doped AlN epilayers and nanostructure AlN photonics crystals (PCs). Using a deep UV laser system with an excitation wave length at 197 nm, continuous wave PL, temperature dependent, and time-resolved PL have been carried out on these AlGaN and AlN epilayers and nanostructures. We have measured the compositional and temperature dependence of the energy bandgap of AlxGa1-xN alloys covering the entire alloy range of x, 0 ≤ x ≤ 1 and fitted with the Varshni equation. Varshni coefficients, alpha and beta, in AlGaN alloys have a parabolic dependence with alloy concentration x. Based on the experimental data, an empirical relation was thus obtained for the energy gap of AlGaN alloys for the entire alloy concentration and at any temperature below 800 K. The exciton localization energy in AlxGa1-xN alloys the entire composition range (0 ≤ x ≤ 1) has been measured by fitting the band edge emission peak energy with the Varshni equation. Deviations of the excitonic emission peak energy from the Varshni equation at low temperatures provide directly the exciton localization energies, ELoc in AlGaN alloys. It was found that ELoc increases with x for x ≤ 0.7, and decreases with x for x ≥ 0.8. The relations between the exciton localization energy, the activation energy, and the emission linewidth have been established. It thus provides three different and independent methods to determine the exciton localization energies in AlGaN alloys. Impurity transitions in AlGaN alloys have also been investigated. Continuous wave (CW) PL spectra of Si and undoped AlGaN alloys reveals groups of impurity transitions that have been assigned to the recombination between shallow donors and an isolated triply charged cation-vacancy (VIII)3-, a doubly charged cation-vacancy-complex (VIII-complex)2- , and a singly charged cation-vacancy-complex (VIII-complex) -1. The energy levels of these deep acceptors in AlxGa 1-xN (0 ≤ x ≤ 1) alloys are pinned to a common energy level in the vacuum. AlGaN alloys predominantly exhibiting the bandedge and (V III-complex)1- transitions possess improved conductivities over those emitting predominantly (VIII)3- and (V III-complex)2- related transitions. These results thus answer the very basic question of high resistivity in Al-rich AlGaN alloys. Acceptor doped AlGaN alloys have been studied by deep UV PL. A PL emission line at 6.02 eV has been observed at 10 K in Mg-doped AlN. It is due to the recombination of an exciton bound to the neutral Mg acceptor (I1) with a binding energy, Ebx of 40 meV, which indicates large activation energy of the Mg acceptor. The observed large binding energy of the acceptor-bound exciton is consistent with relatively large binding energy of the Mg acceptor in AlN. With the energy level of 0.51 eV for Mg dopants in AlN, it is interesting and important to study other suitable acceptor dopants for AlN. Growth and optical studies of Zn-doped AlN epilayers has been carried out. The PL spectra of Zn-doped AlN epilayers exhibited two impurity emission lines at 5.40 and 4.50 eV, which were absent in undoped epilayers. They are assigned respectively, to the transitions of free electrons and electrons bound to triply positively charged nitrogen vacancies (0.90 eV deep) to the Zn0 acceptors. It was deduced that the Zn energy level is about 0.74 eV above the valence band edge, which is about 0.23 eV deeper than the Mg energy level in AlN. Nitrogen vacancies are the compensating defects in acceptor doped AlGaN alloys. A nitrogen vacancy (VN) related emission line was also observed in ion-implanted AlN at 5.87 eV and the energy level of singly charged VN1+ is found at 260 meV below the conduction band. As a consequence of large binding energy of VN 1+ as well as high formation energy, VN1+ in AlN cannot contribute significant n-type conductivity, which is consistent with experimental observation. The temperature dependent PL study of the bandedge emissions in GaN and AlN epilayers up to 800 K has been carried out, which reveals two distinctive activation processes. The first process occurring below Tt = 325 K (Tt = 500 K) for GaN (AlN) is due to the activation of free excitons to free carriers, whereas the second occurring above Tt with an activation energy of 0.29 eV (0.3 eV) for GaN (AlN) is believed to be associated with a higher lying conduction band (Gamma3) at about 0.3 eV above the conduction band minimum (Gamma1). These higher lying bands could affect device performance of GaN and AlN at elevated temperatures. Two-dimensional nanostructured AlN photonic crystals (PCs) with a varying periodicity/diameter down to 150 nm/75 nm have also been studied by deep UV PL. With PCs formation, a 20-fold enhancement in the band edge emission intensity at 208 nm over unpatterned AlN epilayer has been observed. The emission intensity increases with the decrease in the lattice constant of the AlN PCs. AlN PCs represent photonic crystals with highest (shortest) bandgap (wavelength) semiconductors, which open up new opportunities for exploring novel physical phenomena in the artificially structured photonic band gap material systems and their applications, particularly in the area of deep UV as well as nano-photonics.

Study of the effects of impurities on the properties of silicon solar cell

NASA Technical Reports Server (NTRS)

Sah, C. T.

1981-01-01

The effect of defects across the back-surface-field junction on the performance of high efficiency and thin solar cells, using a developed-perimeter device model for the three-dimensional defects is investigated. Significant degradation of open-circuit voltage can occur even if there are only a few defects distributed in the bulk of the solar cell. Two features in the thickness dependences of the fill factor and efficiency in impurity-doped back-surface-field solar cells are discovered in the exact numerical solution which are associated with the high injection level effect in the base and not predicted by the low-level analytical theory. What are believed to be the most accurate recombination parameters at the Ti center to date are also given and a theory is developed which is capable of distinguishing an acceptor-like deep level from a donor-like deep level using the measured values of the thermal emission and capture cross sections.

Emissions from simulated deep-seated fires in domestic waste.

PubMed

Lönnermark, Anders; Blomqvist, Per; Marklund, Stellan

2008-01-01

The emissions from deep-seated fires in domestic waste have been investigated. The gas phase yields of PAH, PCDD/F, PCB, HCB, particles, and metals associated to the particulate matter were analysed during a series of simulated deep-seated fires. The method of extinguishment was varied and in cases where water was used for extinguishment, the runoff water was analysed for PAH, PCDD/F, PCB, hexachlorobenzene, and metals. In total six tests were performed. In four of the tests, samples of the fire residue were analysed for PCDD/F, PCBs, and chlorobenzenes.

Tutorial: Junction spectroscopy techniques and deep-level defects in semiconductors

NASA Astrophysics Data System (ADS)

Peaker, A. R.; Markevich, V. P.; Coutinho, J.

2018-04-01

The term junction spectroscopy embraces a wide range of techniques used to explore the properties of semiconductor materials and semiconductor devices. In this tutorial review, we describe the most widely used junction spectroscopy approaches for characterizing deep-level defects in semiconductors and present some of the early work on which the principles of today's methodology are based. We outline ab-initio calculations of defect properties and give examples of how density functional theory in conjunction with formation energy and marker methods can be used to guide the interpretation of experimental results. We review recombination, generation, and trapping of charge carriers associated with defects. We consider thermally driven emission and capture and describe the techniques of Deep Level Transient Spectroscopy (DLTS), high resolution Laplace DLTS, admittance spectroscopy, and scanning DLTS. For the study of minority carrier related processes and wide gap materials, we consider Minority Carrier Transient Spectroscopy (MCTS), Optical DLTS, and deep level optical transient spectroscopy together with some of their many variants. Capacitance, current, and conductance measurements enable carrier exchange processes associated with the defects to be detected. We explain how these methods are used in order to understand the behaviour of point defects and the determination of charge states and negative-U (Hubbard correlation energy) behaviour. We provide, or reference, examples from a wide range of materials including Si, SiGe, GaAs, GaP, GaN, InGaN, InAlN, and ZnO.

Acquiring High-Performance Deep-Blue OLED Emitters through an Unexpected Blueshift Color-Tuning Effect Induced by Electron-Donating -OMe Substituents.

PubMed

Peng, Song; Zhao, Yihuan; Fu, Caixia; Pu, Xuemei; Zhou, Liang; Huang, Yan; Lu, Zhiyun

2018-06-07

A series of blue-emissive 7-(diphenylamino)-4-phenoxycoumarin derivatives bearing -CF 3 , -OMe, or -N(Me) 2 substituents on the phenoxy subunit were synthesized. Although both the -CF 3 and -N(Me) 2 modifications were found to trigger redshifted fluorescence, the -OMe substitution was demonstrated to exert an unexpected blueshift color-tuning effect toward the deep-blue region. The reason is that the moderate electron-donating -OMe group can endow coumarins with unaltered HOMO but elevated LUMO energy levels. Moreover, the -OMe substitution was found to be beneficial to the thermal stability of these coumarins. Therefore, the trimethoxy-substituted objective compound can act as a high-performance deep-blue organic light-emitting diode (OLED) emitter, and OLED based on it emits deep-blue light with CIE coordinates of (0.148, 0.084), maximum luminance of 7800 cd m -2 , and maximum external quantum efficiency of 5.1 %. These results not only shed light on the molecular design strategy for high-performance deep-blue OLED emitters through color-tuning, but also show the perspective of coumarin derivatives as deep-blue OLED emitters. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

A new miniature hand-held solar-blind reagentless standoff chemical, biological, and explosives (CBE) sensor

NASA Astrophysics Data System (ADS)

Hug, W. F.; Reid, R. D.; Bhartia, R.; Lane, A. L.

2008-04-01

Improvised explosive devices (IEDs), vehicle-borne improvised explosive devices (VBIEDs), and suicide bombers are a major threat to many countries and their citizenry. The ability to detect trace levels of these threats with a miniature, hand-held, reagentless, standoff sensor represents a major improvement in the state of the art of CBE surface sensors. Photon Systems, Inc., in collaboration with Jet Propulsion Laboratory, recently demonstrated a new technology hand-held sensor for reagentless, close-range, standoff detection and identification of trace levels CBE materials on surfaces. This targeted ultraviolet CBE (TUCBE) sensor is the result of an Army Phase I STTR program. The resulting 5lb, 5W, flashlight-sized sensor can discriminate CBE from background materials using a combination of deep UV excited resonance Raman (RR) and laser induced native fluorescence (LINF) emissions resulting from excitation by a new technology deep UV laser. Detection and identification is accomplished in less than 1ms. Standoff excitation of suspicious packages, vehicles, persons, and other objects that may contain hazardous materials is accomplished using wavelengths below 250nm where Raman and native fluorescence emissions occupy distinctly different wavelength regions. This enables simultaneous detection of RR and LINF emissions with no interferences. The sensor employs fused RR/LINF chemometric methods to extract the identity of targeted materials from background clutter. Photon Systems has demonstrated detection and identification of 100ng/cm2 of explosives materials at a distance of 1 meter using a sensor with 3.8 cm optical aperture. Expansion of the optical aperture to 38 cm in a lantern-sized sensor will enable similar detection and identification of CBE materials at standoff distances of 10 meters. As a result of excitation and detection in the deep UV and the use of a gated detection system, the sensor is solar blind and can operate in full daylight conditions.

GRB 080503: IMPLICATIONS OF A NAKED SHORT GAMMA-RAY BURST DOMINATED BY EXTENDED EMISSION

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

Perley, D. A.; Metzger, B. D.; Butler, N. R.

We report on observations of GRB 080503, a short gamma-ray burst (GRB) with very bright extended emission (about 30 times the gamma-ray fluence of the initial spike) in conjunction with a thorough comparison to other short Swift events. In spite of the prompt-emission brightness, however, the optical counterpart is extraordinarily faint, never exceeding 25 mag in deep observations starting at {approx}1 hr after the Burst Alert Telescope (BAT) trigger. The optical brightness peaks at {approx}1 day and then falls sharply in a manner similar to the predictions of Li and Paczynski (1998) for supernova-like emission following compact binary mergers. However,more » a shallow spectral index and similar evolution in X-rays inferred from Chandra observations are more consistent with an afterglow interpretation. The extreme faintness of this probable afterglow relative to the bright gamma-ray emission argues for a very low density medium surrounding the burst (a 'naked' GRB), consistent with the lack of a coincident host galaxy down to 28.5 mag in deep Hubble Space Telescope imaging. The late optical and X-ray peak could be explained by a slightly off-axis jet or by a refreshed shock. Our observations reinforce the notion that short GRBs generally occur outside regions of active star formation, but demonstrate that in some cases the luminosity of the extended prompt emission can greatly exceed that of the short spike, which may constrain theoretical interpretation of this class of events. This extended emission is not the onset of an afterglow, and its relative brightness is probably either a viewing-angle effect or intrinsic to the central engine itself. Because most previous BAT short bursts without observed extended emission are too faint for this signature to have been detectable even if it were present at typical level, conclusions based solely on the observed presence or absence of extended emission in the existing Swift sample are premature.« less

Ionization processes in a local analogue of distant clumpy galaxies: VLT MUSE IFU spectroscopy and FORS deep images of the TDG NGC 5291N

NASA Astrophysics Data System (ADS)

Fensch, J.; Duc, P.-A.; Weilbacher, P. M.; Boquien, M.; Zackrisson, E.

2016-01-01

Context. We present Integral Field Unit (IFU) observations with MUSE and deep imaging with FORS of a dwarf galaxy recently formed within the giant collisional HI ring surrounding NGC 5291. This Tidal Dwarf Galaxy (TDG) -like object has the characteristics of typical z = 1-2 gas-rich spiral galaxies: a high gas fraction, a rather turbulent clumpy interstellar medium, the absence of an old stellar population, and a moderate metallicity and star formation efficiency. Aims: The MUSE spectra allow us to determine the physical conditions within the various complex substructures revealed by the deep optical images and to scrutinize the ionization processes at play in this specific medium at unprecedented spatial resolution. Methods: Starburst age, extinction, and metallicity maps of the TDG and the surrounding regions were determined using the strong emission lines Hβ, [OIII], [OI], [NII], Hα, and [SII] combined with empirical diagnostics. Different ionization mechanisms were distinguished using BPT-like diagrams and shock plus photoionization models. Results: In general, the physical conditions within the star-forming regions are homogeneous, in particular with a uniform half-solar oxygen abundance. On small scales, the derived extinction map shows narrow dust lanes. Regions with atypically strong [OI] emission line immediately surround the TDG. The [OI]/ Hα ratio cannot be easily accounted for by the photoionization by young stars or shock models. At greater distances from the main star-foming clumps, a faint diffuse blue continuum emission is observed, both with the deep FORS images and the MUSE data. It does not have a clear counterpart in the UV regime probed by GALEX. A stacked spectrum towards this region does not exhibit any emission line, excluding faint levels of star formation, or stellar absorption lines that might have revealed the presence of old stars. Several hypotheses are discussed for the origin of these intriguing features. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile: ESO MUSE programme 60.A-9320(A) and FORS programme 382.B-0213(A).

Defect free C-axis oriented zinc oxide (ZnO) films grown at room temperature using RF magnetron sputtering

NASA Astrophysics Data System (ADS)

Kunj, Saurabh; Sreenivas, K.

2016-05-01

Radio frequency Magnetron sputtering technique was employed to fabricate ZnO thin films on quartz substrate at room temperature. The effect of varying oxygen to argon (O2/Ar) gas ratio on the structural and photoluminescence properties of the film is analyzed.X-ray diffraction (XRD) spectra reveals the formation of hexagonal wurtzite structured ZnO thin films with preferred orientation along (002) plane. Photoluminescence (PL) characterization reveals the preparation of highly crystalline films exhibiting intense Ultraviolet (UV) emission with negligible amount of defects as indicated by the absence of Deep Level Emission (DLE) in the PL spectra.

Defect free C-axis oriented zinc oxide (ZnO) films grown at room temperature using RF magnetron sputtering

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

Kunj, Saurabh, E-mail: saurabhkunj22@gmail.com; Sreenivas, K.

2016-05-23

Radio frequency Magnetron sputtering technique was employed to fabricate ZnO thin films on quartz substrate at room temperature. The effect of varying oxygen to argon (O{sub 2}/Ar) gas ratio on the structural and photoluminescence properties of the film is analyzed.X-ray diffraction (XRD) spectra reveals the formation of hexagonal wurtzite structured ZnO thin films with preferred orientation along (002) plane. Photoluminescence (PL) characterization reveals the preparation of highly crystalline films exhibiting intense Ultraviolet (UV) emission with negligible amount of defects as indicated by the absence of Deep Level Emission (DLE) in the PL spectra.

Ultraviolet/blue light-emitting diodes based on single horizontal ZnO microrod/GaN heterojunction

PubMed Central

2014-01-01

We report electroluminescence (EL) from single horizontal ZnO microrod (MR) and p-GaN heterojunction light-emitting diodes under forward and reverse bias. EL spectra were composed of two blue emissions centered at 431 and 490 nm under forward biases, but were dominated by a ultraviolet (UV) emission located at 380 nm from n-ZnO MR under high reverse biases. Light-output-current characteristic of the UV emission reveals that the rate of radiative recombination is faster than that of the nonradiative recombination. Highly efficient ZnO excitonic recombination at reverse bias is caused by electrons tunneling from deep-level states near the n-ZnO/p-GaN interface to the conduction band in n-ZnO. PMID:25232299

Combustion and NOx emission characteristics with respect to staged-air damper opening in a 600 MWe down-fired pulverized-coal furnace under deep-air-staging conditions.

PubMed

Kuang, Min; Li, Zhengqi; Wang, Zhihua; Jing, Xinjing; Liu, Chunlong; Zhu, Qunyi; Ling, Zhongqian

2014-01-01

Deep-air-staging combustion conditions, widely used in tangential-fired and wall-arranged furnaces to significantly reduce NOx emissions, are premature up to now in down-fired furnaces that are designed especially for industry firing low-volatile coals such as anthracite and lean coal. To uncover combustion and NOx emission characteristics under deep-air-staging conditions within a newly operated 600 MWe down-fired furnace and simultaneously understand the staged-air effect on the furnace performance, full-load industrial-size measurements taken of gas temperatures and species concentrations in the furnace, CO and NOx emissions in flue gas, and carbon in fly ash were performed at various staged-air damper openings of 10%, 20%, 30%, and 50%. Increasing the staged-air damper opening, gas temperatures along the flame travel (before the flame penetrating the staged-air zone) increased initially but then decreased, while those in the staged-air zone and the upper part of the hopper continuously decreased and increased, respectively. On opening the staged-air damper to further deepen the air-staging conditions, O2 content initially decreased but then increased in both two near-wall regions affected by secondary air and staged air, respectively, whereas CO content in both two regions initially increased but then decreased. In contrast to the conventional understanding about the effects of deep-air-staging conditions, here increasing the staged-air damper opening to deepen the air-staging conditions essentially decreased the exhaust gas temperature and carbon in fly ash and simultaneously increased both NOx emissions and boiler efficiency. In light of apparently low NOx emissions and high carbon in fly ash (i.e., 696-878 mg/m(3) at 6% O2 and 9.81-13.05%, respectively) developing in the down-fired furnace under the present deep-air-staging conditions, further adjustments such as enlarging the staged-air declination angle to prolong pulverized-coal residence times in the furnace should be considered to improve the deep-air-staging combustion configuration.

Transportation Energy Futures: Combining Strategies for Deep Reductions in Energy Consumption and GHG Emissions (Brochure)

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

Not Available

2013-03-01

This fact sheet summarizes actions in the areas of light-duty vehicle, non-light-duty vehicle, fuel, and transportation demand that show promise for deep reductions in energy use. Energy efficient transportation strategies have the potential to simultaneously reduce oil consumption and greenhouse gas (GHG) emissions. The Transportation Energy Futures (TEF) project examined how the combination of multiple strategies could achieve deep reductions in GHG emissions and petroleum use on the order of 80%. Led by NREL, in collaboration with Argonne National Laboratory, the project's primary goal was to help inform domestic decisions about transportation energy strategies, priorities, and investments, with an emphasismore » on underexplored opportunities. TEF findings reveal three strategies with the potential to displace most transportation-related petroleum use and GHG emissions: 1) Stabilizing energy use in the transportation sector through efficiency and demand-side approaches. 2) Using additional advanced biofuels. 3) Expanding electric drivetrain technologies.« less

Reducing greenhouse gas emissions for climate stabilization: framing regional options.

PubMed

Olabisi, Laura Schmitt; Reich, Peter B; Johnson, Kris A; Kapuscinski, Anne R; Su, Sangwon H; Wilson, Elizabeth J

2009-03-15

The Intergovernmental Panel on Climate Change (IPCC) has stated that stabilizing atmospheric CO2 concentrations will require reduction of global greenhouse gas (GHG) emissions by as much as 80% by 2050. Subnational efforts to cut emissions will inform policy development nationally and globally. We projected GHG mitigation strategies for Minnesota, which has adopted a strategic goal of 80% emissions reduction by 2050. A portfolio of conservation strategies, including electricity conservation, increased vehicle fleet fuel efficiency, and reduced vehicle miles traveled, is likely the most cost-effective option for Minnesota and could reduce emissions by 18% below 2005 levels. An 80% GHG reduction would require complete decarbonization of the electricity and transportation sectors, combined with carbon capture and sequestration at power plants, or deep cuts in other relatively more intransigent GHG-emitting sectors. In order to achieve ambitious GHG reduction goals, policymakers should promote aggressive conservation efforts, which would probably have negative net costs, while phasing in alternative fuels to replace coal and motor gasoline over the long-term.

Coexistence of strongly and weakly confined energy levels in (Cd,Zn)Se quantum dots: Tailoring the near-band-edge and defect-levels for white light emission

NASA Astrophysics Data System (ADS)

Das, Tapan Kumar; Ilaiyaraja, P.; Sudakar, C.

2017-05-01

We demonstrate white light emission (WLE) from (Cd,Zn)Se system, which is a composite of Zn alloyed CdSe quantum dot and ZnSe-amorphous (ZnSe-a) phase. Detailed structural and photoluminescence emission studies on pure CdSe and (Cd,Zn)Se show cubic zinc blende structure in the size range of 2.5 to 5 nm. (Cd,Zn)Se quantum dots (QDs) also have a significant fraction of ZnSe-a phase. The near-band-edge green-emission in crystalline CdSe and (Cd,Zn)Se is tunable between 500 to 600 nm. The (Cd,Zn)Se system also exhibits a broad, deep defect level (DL) red-emission in the range 600 to 750 nm and a sharp ZnSe near-band-edge blue-emission (ZS-NBE) between 445 to 465 nm. While DL and CdSe near-band-edge (CS-NBE) emissions significantly shift with the size of QD due to strong confinement effect, the ZS-NBE show minimal change in peak position indicating a weak confinement effect. The intensities of ZS-NBE and DL emissions also exhibit a strong dependence on the QD size. A gamut of emission colors is obtained by combining the CS-NBE with the ZS-NBE emission and broad DL emission in (Cd,Zn)Se system. Interestingly, we find the convergence of Commission Internationale de l'Eclairage (CIE) coordinates towards the white light with increasing Zn concentration in CdSe. We demonstrate by combining these three emissions in a proper weight ratio WLE can be achieved. Cd1-yZnySe (y = 0. 5; QD size ˜4.9 nm) alloy with a maximum quantum yield of 57% exhibits CIE coordinates of (0.39, 0.4), color rendering index (CRI) of 82, correlated color temperature (CCT) of 3922 K, and Duv of 0.0078 which is very promising for white light applications.

Effect of deep injection on field-scale emissions of 1,3-dichloropropene and chloropicrin from bare soil

NASA Astrophysics Data System (ADS)

Yates, S. R.; Ashworth, D. J.; Zheng, W.; Knuteson, J.; van Wesenbeeck, I. J.

2016-07-01

Fumigating soil is important for the production of many high-value vegetable, fruit, and tree crops, but fumigants are toxic pesticides with relatively high volatility, which can lead to significant atmospheric emissions. A field experiment was conducted to measure emissions and subsurface diffusion of a mixture of 1,3-dichloropropene (1,3-D) and chloropicrin after shank injection to bare soil at 61 cm depth (i.e., deep injection). Three on-field methods, the aerodynamic (ADM), integrated horizontal flux (IHF), and theoretical profile shape (TPS) methods, were used to obtain fumigant flux density and cumulative emission values. Two air dispersion models (CALPUFF and ISCST3) were also used to back-calculate the flux density using air concentration measurements surrounding the fumigated field. Emissions were continuously measured for 16 days and the daily peak emission rates for the five methods ranged from 13 to 33 μg m-2 s-1 for 1,3-D and 0.22-3.2 μg m-2 s-1 for chloropicrin. Total 1,3-D mass lost to the atmosphere was approximately 23-41 kg ha-1, or 15-27% of the applied active ingredient and total mass loss of chloropicrin was <2%. Based on the five methods, deep injection reduced total emissions by approximately 2-24% compared to standard fumigation practices where fumigant injection is at 46 cm depth. Given the relatively wide range in emission-reduction percentages, a fumigant diffusion model was used to predict the percentage reduction in emissions by injecting at 61 cm, which yielded a 21% reduction in emissions. Significant reductions in emissions of 1,3-D and chloropicrin are possible by injecting soil fumigants deeper in soil.

Urea deep placement reduces yield-scaled greenhouse gas (CH4 and N2O) and NO emissions from a ground cover rice production system.

PubMed

Yao, Zhisheng; Zheng, Xunhua; Zhang, Yanan; Liu, Chunyan; Wang, Rui; Lin, Shan; Zuo, Qiang; Butterbach-Bahl, Klaus

2017-09-12

Ground cover rice production system (GCRPS), i.e., paddy soils being covered by thin plastic films with soil moisture being maintained nearly saturated status, is a promising technology as increased yields are achieved with less irrigation water. However, increased soil aeration and temperature under GCRPS may cause pollution swapping in greenhouse gas (GHG) from CH 4 to N 2 O emissions. A 2-year experiment was performed, taking traditional rice cultivation as a reference, to assess the impacts of N-fertilizer placement methods on CH 4 , N 2 O and NO emissions and rice yields under GCRPS. Averaging across all rice seasons and N-fertilizer treatments, the GHG emissions for GCRPS were 1973 kg CO 2 -eq ha -1 (or 256 kg CO 2 -eq Mg -1 ), which is significantly lower than that of traditional cultivation (4186 kg CO 2 -eq ha -1 or 646 kg CO 2 -eq Mg -1 ). Furthermore, if urea was placed at a 10-15 cm soil depth instead of broadcasting, the yield-scaled GHG emissions from GCRPS were further reduced from 377 to 222 kg CO 2 -eq Mg -1 , as N 2 O emissions greatly decreased while yields increased. Urea deep placement also reduced yield-scaled NO emissions by 54%. Therefore, GCRPS with urea deep placement is a climate- and environment-smart management, which allows for maximal rice yields at minimal GHG and NO emissions.

Carbon-hydrogen defects with a neighboring oxygen atom in n-type Si

NASA Astrophysics Data System (ADS)

Gwozdz, K.; Stübner, R.; Kolkovsky, Vl.; Weber, J.

2017-07-01

We report on the electrical activation of neutral carbon-oxygen complexes in Si by wet-chemical etching at room temperature. Two deep levels, E65 and E75, are observed by deep level transient spectroscopy in n-type Czochralski Si. The activation enthalpies of E65 and E75 are obtained as EC-0.11 eV (E65) and EC-0.13 eV (E75). The electric field dependence of their emission rates relates both levels to single acceptor states. From the analysis of the depth profiles, we conclude that the levels belong to two different defects, which contain only one hydrogen atom. A configuration is proposed, where the CH1BC defect, with hydrogen in the bond-centered position between neighboring C and Si atoms, is disturbed by interstitial oxygen in the second nearest neighbor position to substitutional carbon. The significant reduction of the CH1BC concentration in samples with high oxygen concentrations limits the use of this defect for the determination of low concentrations of substitutional carbon in Si samples.

Energy levels distribution in supersaturated silicon with titanium for photovoltaic applications

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

Pérez, E., E-mail: eduper@ele.uva.es; Castán, H.; García, H.

2015-01-12

In the attempt to form an intermediate band in the bandgap of silicon substrates to give it the capability to absorb infrared radiation, we studied the deep levels in supersaturated silicon with titanium. The technique used to characterize the energy levels was the thermal admittance spectroscopy. Our experimental results showed that in samples with titanium concentration just under Mott limit there was a relationship among the activation energy value and the capture cross section value. This relationship obeys to the well known Meyer-Neldel rule, which typically appears in processes involving multiple excitations, like carrier capture/emission in deep levels, and itmore » is generally observed in disordered systems. The obtained characteristic Meyer-Neldel parameters were Tmn = 176 K and kTmn = 15 meV. The energy value could be associated to the typical energy of the phonons in the substrate. The almost perfect adjust of all experimental data to the same straight line provides further evidence of the validity of the Meyer Neldel rule, and may contribute to obtain a deeper insight on the ultimate meaning of this phenomenon.« less

Measurement of charged particle transverse momentum spectra in deep inelastic scattering

NASA Astrophysics Data System (ADS)

Adloff, C.; Aid, S.; Anderson, M.; Andreev, V.; Andrieu, B.; Babaev, A.; Bähr, J.; Bán, J.; Ban, Y.; Baranov, P.; Barrelet, E.; Barschke, R.; Bartel, W.; Barth, M.; Bassler, U.; Beck, H. P.; Beck, M.; Behrend, H.-J.; Belousov, A.; Berger, Ch.; Bernardi, G.; Bertrand-Coremans, G.; Besançon, M.; Beyer, R.; Biddulph, P.; Bispham, P.; Bizot, J. C.; Blobel, V.; Borras, K.; Botterweck, F.; Boudry, V.; Braemer, A.; Braunschweig, W.; Brisson, V.; Brückner, W.; Bruel, P.; Bruncko, D.; Brune, C.; Buchholz, R.; Büngener, L.; Bürger, J.; Büsser, F. W.; Buniatian, A.; Burke, S.; Burton, M. J.; Calvet, D.; Campbell, A. T.; Carli, T.; Charlet, M.; Clarke, D.; Clegg, A. B.; Clerbaux, B.; Cocks, S.; Contreras, J. G.; Cormack, C.; Coughlan, J. A.; Courau, A.; Cousinou, M.-C.; Cozzika, G.; Criegee, L.; Cussans, D. G.; Cvach, J.; Dagoret, S.; Dainton, J. B.; Dau, W. D.; Daum, K.; David, M.; Davis, C. L.; Delcourt, B.; De Roeck, A.; De Wolf, E. A.; Dirkmann, M.; Dixon, P.; Di Nezza, P.; Dlugosz, W.; Dollfus, C.; Donovan, K. T.; Dowell, J. D.; Dreis, H. B.; Droutskoi, A.; Dünger, O.; Duhm, H.; Ebert, J.; Ebert, T. R.; Eckerlin, G.; Efremenko, V.; Egli, S.; Eichler, R.; Eisele, F.; Eisenhandler, E.; Elsen, E.; Erdmann, M.; Erdmann, W.; Fahr, A. B.; Favart, L.; Fedotov, A.; Felst, R.; Feltesse, J.; Ferencei, J.; Ferrarotto, F.; Flamm, K.; Fleischer, M.; Flieser, M.; Flügge, G.; Fomenko, A.; Formánek, J.; Foster, J. M.; Franke, G.; Fretwurst, E.; Gabathuler, E.; Gabathuler, K.; Gaede, F.; Garvey, J.; Gayler, J.; Gebauer, M.; Genzel, H.; Gerhards, R.; Glazov, A.; Goerlich, L.; Gogitidze, N.; Goldberg, M.; Goldner, D.; Golec-Biernat, K.; Gonzalez-Pineiro, B.; Gorelov, I.; Grab, C.; Grässler, H.; Greenshaw, T.; Griffiths, R. K.; Grindhammer, G.; Gruber, A.; Gruber, C.; Hadig, T.; Haidt, D.; Hajduk, L.; Haller, T.; Hampel, M.; Haynes, W. J.; Heinemann, B.; Heinzelmann, G.; Henderson, R. C. W.; Henschel, H.; Herynek, I.; Hess, M. F.; Hewitt, K.; Hildesheim, W.; Hiller, K. H.; Hilton, C. D.; Hladký, J.; Höppner, M.; Hoffmann, D.; Holtom, T.; Horisberger, R.; Hudgson, V. L.; Hütte, M.; Ibbotson, M.; Itterbeck, H.; Jacholkowska, A.; Jacobsson, C.; Jaffre, M.; Janoth, J.; Jansen, D. M.; Jansen, T.; Jönson, L.; Johnson, D. P.; Jung, H.; Kalmus, P. I. P.; Kander, M.; Kant, D.; Kaschowitz, R.; Kathage, U.; Katzy, J.; Kaufmann, H. H.; Kaufmann, O.; Kausch, M.; Kazarian, S.; Kenyon, I. R.; Kermiche, S.; Keuker, C.; Kiesling, C.; Klein, M.; Kleinwort, C.; Knies, G.; Köhler, T.; Köhne, J. H.; Kolanoski, H.; Kolya, S. D.; Korbel, V.; Kostka, P.; Kotelnikov, S. K.; Krämerkämper, T.; Krasny, M. W.; Krehbiel, H.; Krücker, D.; Küster, H.; Kuhlen, M.; Kurča, T.; Kurzhöfer, J.; Lacour, D.; Laforge, B.; Landon, M. P. J.; Lange, W.; Langenegger, U.; Lebedev, A.; Lehner, F.; Levonian, S.; Lindström, G.; Lindstroem, M.; Linsel, F.; Lipinski, J.; List, B.; Lobo, G.; Loch, P.; Lomas, J. W.; Lopez, G. C.; Lubimov, V.; Liike, D.; Lytkin, L.; Magnussen, N.; Malinovski, E.; Maraček, R.; Marage, P.; Marks, J.; Marshall, R.; Martens, J.; Martin, G.; Martin, R.; Martyn, H.-U.; Martyniak, J.; Mavroidis, T.; Maxfield, S. J.; McMahon, S. J.; Mehta, A.; Meier, K.; Metlica, F.; Meyer, A.; Meyer, A.; Meyer, H.; Meyer, J.; Meyer, P.-O.; Migliori, A.; Mikocki, S.; Milstead, D.; Moeck, J.; Moreau, F.; Morris, J. V.; Mroczko, E.; Müller, D.; Müller, G.; Müller, K.; Murín, P.; Nagovizin, V.; Nahnhauer, R.; Naroska, B.; Naumann, Th.; Négri, I.; Newman, P. R.; Newton, D.; Nguyen, H. K.; Nicholls, T. C.; Niebergall, F.; Niebuhr, C.; Niedzballa, Ch.; Niggli, H.; Nowak, G.; Noyes, G. W.; Nunnemann, T.; Nyberg-Werther, M.; Oakden, M.; Oberlack, H.; Olsson, J. E.; Ozerov, D.; Palmen, P.; Panaro, E.; Panitch, A.; Pascaud, C.; Patel, G. D.; Pawletta, H.; Peppel, E.; Perez, E.; Phillips, J. P.; Pieuchot, A.; Pitzl, D.; Pope, G.; Povh, B.; Prell, S.; Rabbertz, K.; Rädel, G.; Reimer, P.; Reinshagen, S.; Rick, H.; Riepenhausen, F.; Riess, S.; Rizvi, E.; Robmann, P.; Roloff, P. H. E.; Roosen, R.; Rosenbauer, K.; Rostovtsev, A.; Rouse, F.; Royon, C.; Rüter, K.; Rusakov, S.; Rybicki, K.; Sankey, D. P. C.; Schacht, P.; Schiek, S.; Schleif, S.; Schleper, P.; von Schlippe, W.; Schmidt, D.; Schmidt, G.; Schoeffel, L.; Schöning, A.; Schröder, V.; Schuhmann, E.; Schwab, B.; Sefkow, F.; Sell, R.; Semenovy, A.; Shekelyan, V.; Sheviakov, I.; Shtarkov, L. N.; Siegmon, G.; Siewert, U.; Sirois, Y.; Skillicorni, I. O.; Smirnov, F.; Solochenko, V.; Soloviev, Y.; Specka, A.; Spiekermann, J.; Spielman, S.; Spitzer, H.; Squinabol, F.; Steffen, F.; Steinberg, F.; Steiner, H.; Steinhart, J.; Stella, B.; Stellbergr, A.; Stier, P. J.; Stiewe, J.; Stöβlein, U.; Stolze, K.; Straumann, U.; Struczinski, W.; Sutton, J. P.; Tapprogge, S.; Tagevˇský, M.; Tchernyshov, V.; Tchetchelnitski, S.; Theissen, J.; Thiebaux, C.; Thompson, G.; Tobien, N.; Todenhagen, R.; Truöl, P.; Tsipolitis, G.; Turnau, J.; Tutas, J.; Tzamariudaki, E.; Uelkes, P.; Usik, A.; Valkár, S.; Valkárová, A.; Vallée, C.; Vandenplas, D.; Van Esch, P.; Van Mechelen, P.; Vazdik, Y.; Verrecchia, P.; Villet, G.; Wacker, K.; Wagener, A.; Wagener, M.; Waugh, B.; Weber, G.; Weber, M.; Wegener, D.; Wenger, A.; Wengler, T.; Werner, M.; West, L. R.; Wilksen, T.; Willard, S.; Winde, M.; Winter, G.-G.; Wittek, C.; Wobisch, M.; Wünsch, E.; Žáček, J.; Zarbock, D.; Zhang, Z.; Zhokin, A.; Zini, P.; Zomer, F.; Zsembery, J.; Zuber, K.; zurNedden, M.; Hl Collaboration

1997-02-01

Transverse momentum spectra of charged particles produced in deep inelastic scattering are measured as a function of the kinematic variables x and Q using the H1 detector at the epcollider HERA. The data are compared to different parton emission models, either with or without ordering of the emissions in transverse momentum. The data provide evidence for a relatively large amount of parton radiation between the current and the remnant systems.

Short time variability of solar corona during recent solar cycle minimum

NASA Astrophysics Data System (ADS)

Siarkowski, Marek; Gryciuk, Magdalena; Gburek, Szymon; Sylwester, Janusz; Sylwester, Barbara; Kepa, Anna; Buczkowska, Agnieszka; Kowalinski, Miroslaw

Sphinx is the X-ray spectrophotometer designed to measure X-ray emission from the Sun in the energy range between 0.8 keV and 15 keV. The instrument is placed onboard Russian KORONAS-PHOTON satellite launched on January 30, 2009. In this paper we present the observations of coronal emission obtained between March-April and August-September 2009, i.e. the times towards the end of the last, very prolonged and deep minimum of solar activity. Prompt analysis of SphinX spectra reveal the variability of the average coronal plasma charac-teristics like the temperature and emission measure. These data are used to compare SphinX and GOES measurements, for selected times. Examples of many sub/microflare events with maxima of the X-ray flux, observed much below the GOES sensitivity threshold level will be presented.

Amplifying the Red-Emission of Upconverting Nanoparticles for Biocompatible Clinically Used Prodrug-Induced Photodynamic Therapy

DOE PAGES

Punjabi, Amol; Wu, Xiang; Tokatli-Apollon, Amira; ...

2014-09-25

A class of biocompatible upconverting nanoparticles (UCNPs) with largely amplified red-emissions was developed. The optimal UCNP shows a high absolute upconversion quantum yield of 3.2% in red-emission, which is 15-fold stronger than the known optimal β-phase core/shell UCNPs. When conjugated to aminolevulinic acid, a clinically used photodynamic therapy (PDT) prodrug, significant PDT effect in tumor was demonstrated in a deep-tissue (>1.2 cm) setting in vivo at a biocompatible laser power density. Furthermore, we show that our UCNP–PDT system with NIR irradiation outperforms clinically used red light irradiation in a deep tumor setting in vivo. This study marks a major stepmore » forward in photodynamic therapy utilizing UCNPs to effectively access deep-set tumors.Lastly, it also provides an opportunity for the wide application of upconverting red radiation in photonics and biophotonics.« less

Amplifying the red-emission of upconverting nanoparticles for biocompatible clinically used prodrug-induced photodynamic therapy.

PubMed

Punjabi, Amol; Wu, Xiang; Tokatli-Apollon, Amira; El-Rifai, Mahmoud; Lee, Hyungseok; Zhang, Yuanwei; Wang, Chao; Liu, Zhuang; Chan, Emory M; Duan, Chunying; Han, Gang

2014-10-28

A class of biocompatible upconverting nanoparticles (UCNPs) with largely amplified red-emissions was developed. The optimal UCNP shows a high absolute upconversion quantum yield of 3.2% in red-emission, which is 15-fold stronger than the known optimal β-phase core/shell UCNPs. When conjugated to aminolevulinic acid, a clinically used photodynamic therapy (PDT) prodrug, significant PDT effect in tumor was demonstrated in a deep-tissue (>1.2 cm) setting in vivo at a biocompatible laser power density. Furthermore, we show that our UCNP-PDT system with NIR irradiation outperforms clinically used red light irradiation in a deep tumor setting in vivo. This study marks a major step forward in photodynamic therapy utilizing UCNPs to effectively access deep-set tumors. It also provides an opportunity for the wide application of upconverting red radiation in photonics and biophotonics.

Amplifying the Red-Emission of Upconverting Nanoparticles for Biocompatible Clinically Used Prodrug-Induced Photodynamic Therapy

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

Punjabi, Amol; Wu, Xiang; Tokatli-Apollon, Amira

A class of biocompatible upconverting nanoparticles (UCNPs) with largely amplified red-emissions was developed. The optimal UCNP shows a high absolute upconversion quantum yield of 3.2% in red-emission, which is 15-fold stronger than the known optimal β-phase core/shell UCNPs. When conjugated to aminolevulinic acid, a clinically used photodynamic therapy (PDT) prodrug, significant PDT effect in tumor was demonstrated in a deep-tissue (>1.2 cm) setting in vivo at a biocompatible laser power density. Furthermore, we show that our UCNP–PDT system with NIR irradiation outperforms clinically used red light irradiation in a deep tumor setting in vivo. This study marks a major stepmore » forward in photodynamic therapy utilizing UCNPs to effectively access deep-set tumors.Lastly, it also provides an opportunity for the wide application of upconverting red radiation in photonics and biophotonics.« less

Feasibility and Costs of Natural Gas as a Bridge to Deep Decarbonization in the United States

NASA Astrophysics Data System (ADS)

Jones, A. D.; McJeon, H. C.; Muratori, M.; Shi, W.

2015-12-01

Achieving emissions reductions consistent with a 2 degree Celsius global warming target requires nearly complete replacement of traditional fossil fuel combustion with near-zero carbon energy technologies in the United States by 2050. There are multiple technological change pathways consistent with this deep decarbonization, including strategies that rely on renewable energy, nuclear, and carbon capture and storage (CCS) technologies. The replacement of coal-fired power plants with natural gas-fired power plants has also been suggested as a bridge strategy to achieve near-term emissions reduction targets. These gas plants, however, would need to be replaced by near-zero energy technologies or retrofitted with CCS by 2050 in order to achieve longer-term targets. Here we examine the costs and feasibility of a natural gas bridge strategy. Using the Global Change Assessment (GCAM) model, we develop multiple scenarios that each meet the recent US Intended Nationally Determined Contribution (INDC) to reduce GHG emissions by 26%-28% below its 2005 levels in 2025, as well as a deep decarbonization target of 80% emissions reductions below 1990 levels by 2050. We find that the gas bridge strategy requires that gas plants be retired on average 20 years earlier than their designed lifetime of 45 years, a potentially challenging outcome to achieve from a policy perspective. Using a more idealized model, we examine the net energy system costs of this gas bridge strategy compared to one in which near-zero energy technologies are deployed in the near tem. We explore the sensitivity of these cost results to four factors: the discount rate applied to future costs, the length (or start year) of the gas bridge, the relative capital cost of natural gas vs. near-zero energy technology, and the fuel price of natural gas. The discount rate and cost factors are found to be more important than the length of the bridge. However, we find an important interaction as well. At low discount rates, the gas bridge is more expensive and a shorter bridge is preferred. At high discount rates, the gas bridge is less expensive and a longer bridge is preferred. This result indicates that the valuation of future expenditures relative to present day expenditures is a major factor in determining the merits of a gas bridge strategy.

Zinc vacancy and oxygen interstitial in ZnO revealed by sequential annealing and electron irradiation

NASA Astrophysics Data System (ADS)

Knutsen, K. E.; Galeckas, A.; Zubiaga, A.; Tuomisto, F.; Farlow, G. C.; Svensson, B. G.; Kuznetsov, A. Yu.

2012-09-01

By combining results from positron annihilation and photoluminescence spectroscopy with data from Hall effect measurements, the characteristic deep level emission centered at ˜1.75 eV and exhibiting an activation energy of thermal quenching of 11.5 meV is associated with the zinc vacancy. Further, a strong indication that oxygen interstitials act as a dominating acceptor is derived from the analysis of charge carrier losses induced by electron irradiation with variable energy below and above the threshold for Zn-atom displacement. We also demonstrate that the commonly observed green emission is related to an extrinsic acceptorlike impurity, which may be readily passivated by oxygen vacancies.

Deep-UV emission at 219 nm from ultrathin MBE GaN/AlN quantum heterostructures

NASA Astrophysics Data System (ADS)

Islam, S. M.; Protasenko, Vladimir; Lee, Kevin; Rouvimov, Sergei; Verma, Jai; Xing, Huili Grace; Jena, Debdeep

2017-08-01

Deep ultraviolet (UV) optical emission below 250 nm (˜5 eV) in semiconductors is traditionally obtained from high aluminum containing AlGaN alloy quantum wells. It is shown here that high-quality epitaxial ultrathin binary GaN quantum disks embedded in an AlN matrix can produce efficient optical emission in the 219-235 nm (˜5.7-5.3 eV) spectral range, far above the bulk bandgap (3.4 eV) of GaN. The quantum confinement energy in these heterostructures is larger than the bandgaps of traditional semiconductors, made possible by the large band offsets. These molecular beam epitaxy-grown extreme quantum-confinement GaN/AlN heterostructures exhibit an internal quantum efficiency of 40% at wavelengths as short as 219 nm. These observations together with the ability to engineer the interband optical matrix elements to control the direction of photon emission in such binary quantum disk active regions offer unique advantages over alloy AlGaN quantum well counterparts for the realization of deep-UV light-emitting diodes and lasers.

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.

Water level, vegetation composition and plant productivity explain greenhouse gas fluxes in temperate cutover fens after inundation

NASA Astrophysics Data System (ADS)

Minke, M.; Augustin, J.; Burlo, A.; Yarmashuk, T.; Chuvashova, H.; Thiele, A.; Freibauer, A.; Tikhonov, V.; Hoffmann, M.

2015-10-01

Rewetting of temperate continental cutover peatlands generally implies the creation of flooded areas, which are - dependent on water depth - colonized by helophytes such as Eriophorum angustifolium, Carex spp., Typha latifolia or Phragmites australis. Reeds of Typha and Phragmites are reported to be large sources of methane, but data on net CO2 uptake are contradictory for Typha and rare for Phragmites. This paper describes the effect of vegetation, water level and nutrient conditions on greenhouse gas (GHG) emissions for representative vegetation types along water level gradients at two rewetted cutover fens (mesotrophic and eutrophic) in Belarus. Greenhouse emissions were measured with manual chambers in weekly to few - weekly intervals over a two years period and interpolated by modelling. All sites had negligible nitrous oxide exchange rates. Most sites were carbon sinks and small GHG sources. Methane emissions were generally associated with net ecosystem CO2 uptake. Small sedges were minor methane emitters and net CO2 sinks, while Phragmites australis sites released large amounts of methane and sequestered very much CO2. Variability of both fluxes increased with site productivity. Floating mats composed of Carex tussocks and Typha latifolia were a source for both methane and CO2. We conclude that shallow, stable flooding is a better measure to arrive at low GHG emissions than deep flooding, and that the risk of high GHG emissions consequent on rewetting is larger for eutrophic than for mesotrophic peatlands.

Geocoronal Imaging from the Deep Space Gateway

NASA Astrophysics Data System (ADS)

Waldrop, L.; Immel, T.; Clarke, J.; Fillingim, M.; Rider, K.; Qin, J.; Bhattacharyya, D.; Doe, R.

2018-02-01

UV imaging of geocoronal emission at high spatial and temporal resolution from deep space would provide crucial new constraints on global exospheric structure and dynamics, significantly advancing models of space weather and atmospheric escape.

Role of future scenarios in understanding deep uncertainty in long-term air quality management.

PubMed

Gamas, Julia; Dodder, Rebecca; Loughlin, Dan; Gage, Cynthia

2015-11-01

The environment and its interactions with human systems, whether economic, social, or political, are complex. Relevant drivers may disrupt system dynamics in unforeseen ways, making it difficult to predict future conditions. This kind of "deep uncertainty" presents a challenge to organizations faced with making decisions about the future, including those involved in air quality management. Scenario Planning is a structured process that involves the development of narratives describing alternative future states of the world, designed to differ with respect to the most critical and uncertain drivers. The resulting scenarios are then used to understand the consequences of those futures and to prepare for them with robust management strategies. We demonstrate a novel air quality management application of Scenario Planning. Through a series of workshops, important air quality drivers were identified. The most critical and uncertain drivers were found to be "technological development" and "change in societal paradigms." These drivers were used as a basis to develop four distinct scenario storylines. The energy and emissions implications of each storyline were then modeled using the MARKAL energy system model. NOx emissions were found to decrease for all scenarios, largely a response to existing air quality regulations, whereas SO2 emissions ranged from 12% greater to 7% lower than 2015 emissions levels. Future-year emissions differed considerably from one scenario to another, however, with key differentiating factors being transition to cleaner fuels and energy demand reductions. Application of scenarios in air quality management provides a structured means of sifting through and understanding the dynamics of the many complex driving forces affecting future air quality. Further, scenarios provide a means to identify opportunities and challenges for future air quality management, as well as a platform for testing the efficacy and robustness of particular management options across wide-ranging conditions.

Understanding the contribution of non-carbon dioxide gases in deep mitigation scenarios

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

Gernaat, David; Calvin, Katherine V.; Lucas, Paul

2015-07-01

The combined 2010 emissions of methane (CH4), nitrous oxide (N2O) and the fluorinated gasses (F-gas) account for about 20-30% of total emissions and about 30% of radiative forcing. At the moment, most studies looking at reaching ambitious climate targets project the emission of carbon dioxide (CO2) to be reduced to zero (or less) by the end of the century. As for non-CO2 gases, the mitigation potential seem to be more constrained, we find that by the end of the century in the current deep mitigation scenarios non-CO2 emissions could form the lion’s share of remaining greenhouse gas emissions. In ordermore » to support effective climate policy strategies, in this paper we provide a more in-depth look at the role of non-CO2¬ emission sources (CH4, N2O and F-gases) in achieving deep mitigation targets (radiative forcing target of 2.8 W/m2 in 2100). Specifically, we look at the sectorial mitigation potential and the remaining non-CO2 emissions. By including a set of different models, we provide some insights into the associated uncertainty. Most of the remaining methane emissions in 2100 in the climate mitigation scenario come from the livestock sector. Strong reductions are seen in the energy supply sector across all models. For N2O, less reduction potential is seen compared to methane and the sectoral differences are larger between the models. The paper shows that the assumptions on remaining non-CO2 emissions are critical for the feasibility of reaching ambitious climate targets and the associated costs.« less

Three-year decline of magmatic CO2 emissions from soils of a Mammoth Mountain tree kill: Horseshoe Lake, CA, 1995-1997

USGS Publications Warehouse

Gerlach, T.M.; Doukas, M.P.; McGee, K.A.; Kessler, R.

1998-01-01

We used the closed chamber method to measure soil CO2 efflux over a three-year period at the Horseshoe Lake tree kill (HLTK) - the largest tree kill on Mammoth Mountain in central eastern California. Efflux contour maps show a significant decline in the areas and rates of CO2 emission from 1995 to 1997. The emission rate fell from 350 t d-1 (metric tons per day) in 1995 to 130 t d-1 in 1997. The trend suggests a return to background soil CO2 efflux levels by early to mid 1999 and may reflect exhaustion of CO2 in a deep reservoir of accumulated gas and/or mechanical closure or sealing of fault conduits transmitting gas to the surface. However, emissions rose to 220 t d-1 on 23 September 1997 at the onset of a degassing event that lasted until 5 December 1997. Recent reservoir recharge and/or extension-enhanced gas flow may have caused the degassing event.

Demonstration of miniaturized 20mW CW 280nm and 266nm solid-state UV laser sources

NASA Astrophysics Data System (ADS)

Landru, Nicolas; Georges, Thierry; Beaurepaire, Julien; Le Guen, Bruno; Le Bail, Guy

2015-02-01

Visible 561 nm and 532 nm laser emissions from 14-mm long DPSS monolithic cavities are frequency converted to deep UV 280 nm and 266 nm in 16-mm long monolithic external cavities. Wavelength conversion is fully insensitive to mechanical vibrations and the whole UV laser sources fit in a miniaturized housing. More than 20 mW deep UV laser emission is demonstrated with high power stability, low noise and good beam quality. Aging tests are in progress but long lifetimes are expected thanks to the cavity design. Protein detection and deep UV resonant Raman spectroscopy are applications that could benefit from these laser sources.

Vertical transport of ozone and CO during super cyclones in the Bay of Bengal as detected by Tropospheric Emission Spectrometer.

PubMed

Fadnavis, S; Beig, G; Buchunde, P; Ghude, Sachin D; Krishnamurti, T N

2011-02-01

Vertical profiles of carbon monoxide (CO) and ozone retrieved from Tropospheric Emission Spectrometer have been analyzed during two super cyclone systems Mala and Sidr. Super cyclones Mala and Sidr traversed the Bay of Bengal (BOB) region on April 24-29, 2006 and November 12-16, 2007 respectively. The CO and ozone plume is observed as a strong enhancement of these pollutants in the upper troposphere over the BOB, indicating deep convective transport. Longitude-height cross-section of these pollutants shows vertical transport to the upper troposphere. CO mixing ratio ~90 ppb is observed near the 146-mb level during the cyclone Mala and near 316 mb during the cyclone Sidr. Ozone mixing ratio ~60-100 ppb is observed near the 316-mb level during both the cyclones. Analysis of National Centers for Environmental Prediction (NCEP) reanalysis vertical winds (omega) confirms vertical transport in the BOB.

Tuning of deep level emission in highly oriented electrodeposited ZnO nanorods by post growth annealing treatments

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

Simimol, A.; Department of Physics, National Institute of Technology, Calicut 673601; Manikandanath, N. T.

Highly dense and c-axis oriented zinc oxide (ZnO) nanorods with hexagonal wurtzite facets were deposited on fluorine doped tin oxide coated glass substrates by a simple and cost-effective electrodeposition method at low bath temperature (80 °C). The as-grown samples were then annealed at various temperatures (T{sub A} = 100–500 °C) in different environments (e.g., zinc, oxygen, air, and vacuum) to understand their photoluminescence (PL) behavior in the ultra-violet (UV) and the visible regions. The PL results revealed that the as-deposited ZnO nanorods consisted of oxygen vacancy (V{sub O}), zinc interstitial (Zn{sub i}), and oxygen interstitial (O{sub i}) defects and these can be reduced significantlymore » by annealing in different environments at optimal annealing temperatures. However, the intensity of deep level emission increased for T{sub A} greater than the optimized values for the respective environments due to the introduction of various defect centers. For example, for T{sub A} ≥ 450 °C in the oxygen and air environments, the density of O{sub i} defects increased, whereas, the green emission associated with V{sub O} is dominant in the vacuum annealed (T{sub A} = 500 °C) ZnO nanorods. The UV peak red shifted after the post-growth annealing treatments in all the environments and the vacuum annealed sample exhibited highest UV peak intensity. The observations from the PL data are supported by the micro-Raman spectroscopy. The present study gives new insight into the origin of different defects that exist in the electrodeposited ZnO nanorods and how these defects can be precisely controlled in order to get the desired emissions for the opto-electronic applications.« less

Origin of the Electroluminescence from Annealed-ZnO/GaN Heterojunction Light-Emitting Diodes

PubMed Central

Hsu, Kai-Chiang; Hsiao, Wei-Hua; Lee, Ching-Ting; Chen, Yan-Ting; Liu, Day-Shan

2015-01-01

This paper addressed the effect of post-annealed treatment on the electroluminescence (EL) of an n-ZnO/p-GaN heterojunction light-emitting diode (LED). The bluish light emitted from the 450 °C-annealed LED became reddish as the LED annealed at a temperature of 800 °C under vacuum atmosphere. The origins of the light emission for these LEDs annealed at various temperatures were studied using measurements of electrical property, photoluminescence, and Auger electron spectroscopy (AES) depth profiles. A blue-violet emission located at 430 nm was associated with intrinsic transitions between the bandgap of n-ZnO and p-GaN, the green-yellow emission at 550 nm mainly originating from the deep-level transitions of native defects in the n-ZnO and p-GaN surfaces, and the red emission at 610 nm emerging from the Ga-O interlayer due to interdiffusion at the n-ZnO/p-GaN interface. The above-mentioned emissions also supported the EL spectra of LEDs annealed at 700 °C under air, nitrogen, and oxygen atmospheres, respectively. PMID:28793675

Origin of the Electroluminescence from Annealed-ZnO/GaN Heterojunction Light-Emitting Diodes.

PubMed

Hsu, Kai-Chiang; Hsiao, Wei-Hua; Lee, Ching-Ting; Chen, Yan-Ting; Liu, Day-Shan

2015-11-16

This paper addressed the effect of post-annealed treatment on the electroluminescence (EL) of an n -ZnO/ p -GaN heterojunction light-emitting diode (LED). The bluish light emitted from the 450 °C-annealed LED became reddish as the LED annealed at a temperature of 800 °C under vacuum atmosphere. The origins of the light emission for these LEDs annealed at various temperatures were studied using measurements of electrical property, photoluminescence, and Auger electron spectroscopy (AES) depth profiles. A blue-violet emission located at 430 nm was associated with intrinsic transitions between the bandgap of n -ZnO and p -GaN, the green-yellow emission at 550 nm mainly originating from the deep-level transitions of native defects in the n -ZnO and p -GaN surfaces, and the red emission at 610 nm emerging from the Ga-O interlayer due to interdiffusion at the n -ZnO/ p -GaN interface. The above-mentioned emissions also supported the EL spectra of LEDs annealed at 700 °C under air, nitrogen, and oxygen atmospheres, respectively.

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

Kobulnicky, Henry A.; Alexander, Michael J.; Babler, Brian L.

We characterize the completeness of point source lists from Spitzer Space Telescope surveys in the four Infrared Array Camera (IRAC) bandpasses, emphasizing the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) programs (GLIMPSE I, II, 3D, 360; Deep GLIMPSE) and their resulting point source Catalogs and Archives. The analysis separately addresses effects of incompleteness resulting from high diffuse background emission and incompleteness resulting from point source confusion (i.e., crowding). An artificial star addition and extraction analysis demonstrates that completeness is strongly dependent on local background brightness and structure, with high-surface-brightness regions suffering up to five magnitudes of reduced sensitivity to pointmore » sources. This effect is most pronounced at the IRAC 5.8 and 8.0 {mu}m bands where UV-excited polycyclic aromatic hydrocarbon emission produces bright, complex structures (photodissociation regions). With regard to diffuse background effects, we provide the completeness as a function of stellar magnitude and diffuse background level in graphical and tabular formats. These data are suitable for estimating completeness in the low-source-density limit in any of the four IRAC bands in GLIMPSE Catalogs and Archives and some other Spitzer IRAC programs that employ similar observational strategies and are processed by the GLIMPSE pipeline. By performing the same analysis on smoothed images we show that the point source incompleteness is primarily a consequence of structure in the diffuse background emission rather than photon noise. With regard to source confusion in the high-source-density regions of the Galactic Plane, we provide figures illustrating the 90% completeness levels as a function of point source density at each band. We caution that completeness of the GLIMPSE 360/Deep GLIMPSE Catalogs is suppressed relative to the corresponding Archives as a consequence of rejecting stars that lie in the point-spread function wings of saturated sources. This effect is minor in regions of low saturated star density, such as toward the Outer Galaxy; this effect is significant along sightlines having a high density of saturated sources, especially for Deep GLIMPSE and other programs observing closer to the Galactic center using 12 s or longer exposure times.« less

The MUSE Hubble Ultra Deep Field Survey. VII. Fe II* emission in star-forming galaxies

NASA Astrophysics Data System (ADS)

Finley, Hayley; Bouché, Nicolas; Contini, Thierry; Paalvast, Mieke; Boogaard, Leindert; Maseda, Michael; Bacon, Roland; Blaizot, Jérémy; Brinchmann, Jarle; Epinat, Benoît; Feltre, Anna; Marino, Raffaella Anna; Muzahid, Sowgat; Richard, Johan; Schaye, Joop; Verhamme, Anne; Weilbacher, Peter M.; Wisotzki, Lutz

2017-11-01

Non-resonant Fe II* (λ2365, λ2396, λ2612, λ2626) emission can potentially trace galactic winds in emission and provide useful constraints to wind models. From the 3.15' × 3.15' mosaic of the Hubble Ultra Deep Field (UDF) obtained with the VLT/MUSE integral field spectrograph, we identify a statistical sample of 40 Fe II* emitters and 50 MgIII (λλ2796,2803) emitters from a sample of 271 [O II]λλ3726,3729 emitters with reliable redshifts from z = 0.85-1.50 down to 2 × 10-18 (3σ) ergs s-1 cm-2 (for [O II]), covering the M⋆ range from 108-1011 M⊙. The Fe II* and Mg II emitters follow the galaxy main sequence, but with a clear dichotomy. Galaxies with masses below 109 M⊙ and star formation rates (SFRs) of ≲ 1 M⊙ yr-1 have MgIII emission without accompanying Fe II* emission, whereas galaxies with masses above 1010 M⊙ and SFRs ≳ 10 M⊙ yr-1 have Fe II* emission without accompanying MgIII emission. Between these two regimes, galaxies have both MgIII and Fe II* emission, typically with MgIII P Cygni profiles. Indeed, the MgIII profile shows a progression along the main sequence from pure emission to P Cygni profiles to strong absorption, due to resonant trapping. Combining the deep MUSE data with HST ancillary information, we find that galaxies with pure MgIII emission profiles have lower SFR surface densities than those with either MgIII P Cygni profiles or Fe II* emission. These spectral signatures produced through continuum scattering and fluorescence, MgIII P Cygni profiles and Fe II* emission, are better candidates for tracing galactic outflows than pure MgIII emission, which may originate from HIII regions. We compare the absorption and emission rest-frame equivalent widths for pairs of FeIII transitions to predictions from outflow models and find that the observations consistently have less total re-emission than absorption, suggesting either dust extinction or non-isotropic outflow geometries.

Greenhouse Gas Emissions from Three Cage Layer Housing Systems

PubMed Central

Fournel, Sébastien; Pelletier, Frédéric; Godbout, Stéphane; Lagacé, Robert; Feddes, John

2011-01-01

Simple Summary Greenhouse gas (GHG) emissions were measured from three different cage layer housing systems. A comparative study was conducted to identify the housing system with the least impact on the environment. The results showed that liquid manure from deep-pit housing systems produces greater emissions of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) than natural and forced dried manure from belt housing systems. The influencing factors appeared to be the manure removal frequency and the dry matter content of the manure. Abstract Agriculture accounts for 10 to 12% of the World’s total greenhouse gas (GHG) emissions. Manure management alone is responsible for 13% of GHG emissions from the agricultural sector. During the last decade, Québec’s egg production systems have shifted from deep-pit housing systems to manure belt housing systems. The objective of this study was to measure and compare carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) emissions from three different cage layer housing systems: a deep liquid manure pit and a manure belt with natural or forced air drying. Deep liquid manure pit housing systems consist of “A” frame layer cages located over a closed pit containing the hens’ droppings to which water is added to facilitate removal by pumping. Manure belt techniques imply that manure drops on a belt beneath each row of battery cages where it is either dried naturally or by forced air until it is removed. The experiment was replicated with 360 hens reared into twelve independent bench-scale rooms during eight weeks (19–27 weeks of age). The natural and forced air manure belt systems reduced CO2 (28.2 and 28.7 kg yr−1 hen−1, respectively), CH4 (25.3 and 27.7 g yr−1 hen−1, respectively) and N2O (2.60 and 2.48 g yr−1 hen−1, respectively) emissions by about 21, 16 and 9% in comparison with the deep-pit technique (36.0 kg CO2 yr−1 hen−1, 31.6 g CH4 yr−1 hen−1 and 2.78 g N2O yr−1 hen−1). The shift to manure belt systems needs to be encouraged since this housing system significantly decreases the production of GHG. PMID:26486772

Growth of PBI 2 single crystals from stoichiometric and Pb excess melts

NASA Astrophysics Data System (ADS)

Hayashi, T.; Kinpara, M.; Wang, J. F.; Mimura, K.; Isshiki, M.

2008-01-01

We have successfully grown high-purity and -quality PbI 2 single crystals by the vertical Bridgman method. The rocking curves of four-crystal X-ray diffraction (XRD) show 120 arcsec in full-width at half-maximum (FWHM). The photoluminescence (PL) spectra at 7.8 K show the resolved intensive exciton emission line and the weak DAP emission band. The deep-level emissions are not observed. The measurement of the electrical and radiographic properties show that Leadiodide (PbI 2) single crystal has a resistivity of 5×10 10 Ω cm and imager lag is 8 s, respectively. In order to improve the controllability of crystal growth, PbI 2 single crystals were also grown from a lead (Pb) excess PbI 2 source. The experimental results show very good reproducibility. In addition, the growth models of crystal are proposed, and the growth mechanism is discussed.

Study of GaN nanorods converted from β-Ga2O3

NASA Astrophysics Data System (ADS)

Li, Yuewen; Xiong, Zening; Zhang, Dongdong; Xiu, Xiangqian; Liu, Duo; Wang, Shuang; Hua, Xuemei; Xie, Zili; Tao, Tao; Liu, Bin; Chen, Peng; Zhang, Rong; Zheng, Youdou

2018-05-01

We report here high-quality β-Ga2O3 nanorods (NRs) grown on sapphire substrates by hydrothermal method. Ammoniating the β-Ga2O3 NRs results in strain-free wurtzite gallium nitride (GaN) NRs. It was shown by XRD and Raman spectroscopy that β-Ga2O3 was partially converted to GaN/β-Ga2O3 at 1000 °C and then completely converted to GaN NRs at 1050 °C, as confirmed by high-resolution transmission electron microscopy (HRTEM). There is no band-edge emission of β-Ga2O3 in the cathodoluminescence spectrum, and only a deep-level broad emission observed at 3.68-3.73 eV. The band edge emission (3.39 eV) of GaN NRs converted from β-Ga2O3 can also be observed.

Pure ultraviolet emission from ZnO quantum dots-based/GaN heterojunction diodes by MgO interlayer

NASA Astrophysics Data System (ADS)

Chen, Cheng; Liang, Renli; Chen, Jingwen; Zhang, Jun; Wang, Shuai; Zhao, Chong; Zhang, Wei; Dai, Jiangnan; Chen, Changqing

2017-07-01

We demonstrate the fabrication and characterization of ZnO/GaN-based heterojunction light-emitting diodes (LEDs) by using air-stable and solution-processable ZnO quantum dots (QDs) with a thin MgO interlayer acting as an electron blocking layer (EBL). The ZnO QDs/MgO/ p-GaN heterojunction can only display electroluminescence (EL) characteristic in reverse bias regime. Under sufficient reverse bias, a fairly pure ultraviolet EL emission located at 370 nm deriving from near band edge of ZnO with a full width at half maximum (FWHM) of 8.3 nm had been obtained, while the deep-level emission had been almost totally suppressed. The EL origination and corresponding carrier transport mechanisms were investigated qualitatively in terms of photoluminescence (PL) results and energy band diagram.[Figure not available: see fulltext.

Excellent deep-blue emitting materials based on anthracene derivatives for non-doped organic light-emitting diodes

NASA Astrophysics Data System (ADS)

Wang, Zhiqiang; Liu, Wei; Xu, Chen; Ji, Baoming; Zheng, Caijun; Zhang, Xiaohong

2016-08-01

Two deep-blue emitting materials 2-tert-butyl-9,10-bis(3,5-diphenylphenyl)anthracene (An-1) and 2-tert-butyl-9,10-bis(3,5-diphenylbiphenyl-4‧-yl)anthracene (An-2) were successfully synthesized by the Pd-catalyzed Suzuki coupling reaction. Both of these compounds have high thermal stabilities and show strong deep-blue emission as solid-state film as well as in n-hexane solution. Two non-doped electroluminescent devices employing An-1 and An-2 as emitting layers were fabricated by vacuum vapor deposition. These devices exhibited highly efficient and stable deep-blue emission with high color purity. The CIE coordinate and maximum EQE of An-1 based device are 4.2% and (0.16, 0.06), respectively. Device based on An-2 achieved a maximum EQE of 4.0% and a CIE coordinate of (0.16, 0.10).

Highly efficient deep-blue organic light emitting diode with a carbazole based fluorescent emitter

NASA Astrophysics Data System (ADS)

Sahoo, Snehasis; Dubey, Deepak Kumar; Singh, Meenu; Joseph, Vellaichamy; Thomas, K. R. Justin; Jou, Jwo-Huei

2018-04-01

High efficiency deep-blue emission is essential to realize energy-saving, high-quality display and lighting applications. We demonstrate here a deep-blue organic light emitting diode using a novel carbazole based fluorescent emitter 7-[4-(diphenylamino)phenyl]-9-(2-ethylhexyl)-9H-carbazole-2-carbonitrile (JV234). The solution processed resultant device shows a maximum luminance above 1,750 cd m-2 and CIE coordinates (0.15,0.06) with a 1.3 lm W-1 power efficiency, 2.0 cd A-1 current efficiency, and 4.1% external quantum efficiency at 100 cd m-2. The resulting deep-blue emission enables a greater than 100% color saturation. The high efficiency may be attributed to the effective host-to-guest energy transfer, suitable device architecture facilitating balanced carrier injection and low doping concentration preventing efficiency roll-off caused by concentration quenching.

The Impact of the Aerosol Direct Radiative Forcing on Deep Convection and Air Quality in the Pearl River Delta Region

NASA Astrophysics Data System (ADS)

Liu, Z.; Yim, Steve H. L.; Wang, C.; Lau, N. C.

2018-05-01

Literature has reported the remarkable aerosol impact on low-level cloud by direct radiative forcing (DRF). Impacts on middle-upper troposphere cloud are not yet fully understood, even though this knowledge is important for regions with a large spatial heterogeneity of emissions and aerosol concentration. We assess the aerosol DRF and its cloud response in June (with strong convection) in Pearl River Delta region for 2008-2012 at cloud-resolving scale using an air quality-climate coupled model. Aerosols suppress deep convection by increasing atmospheric stability leading to less evaporation from the ground. The relative humidity is reduced in middle-upper troposphere due to induced reduction in both evaporation from the ground and upward motion. The cloud reduction offsets 20% of the aerosol DRF. The weaker vertical mixing further increases surface aerosol concentration by up to 2.90 μg/m3. These findings indicate the aerosol DRF impact on deep convection and in turn regional air quality.

Glacial CO2 Cycles: A Composite Scenario

NASA Astrophysics Data System (ADS)

Broecker, W. S.

2015-12-01

There are three main contributors to the glacial drawdown of atmospheric CO2 content: starvation of the supply of carbon to the ocean-atmosphere reservoir, excess CO2 storage in the deep sea, and surface-ocean cooling. In this talk, I explore a scenario in which all three play significant roles. Key to this scenario is the assumption that deep ocean storage is related to the extent of nutrient stratification of the deep Atlantic. The stronger this stratification, the larger the storage of respiration CO2. Further, it is my contention that the link between Milankovitch insolation cycles and climate is reorganizations of the ocean's thermohaline circulation leading to changes in the deep ocean's CO2 storage. If this is the case, the deep Atlantic d13C record kept in benthic foraminifera shells tells us that deep ocean CO2 storage follows Northern Hemisphere summer insolation cycles and thus lacks the downward ramp so prominent in the records of sea level, benthic 18O and CO2. Rather, the ramp is created by the damping of planetary CO2 emissions during glacial time intervals. As it is premature to present a specific scenario, I provide an example as to how these three contributors might be combined. As their magnitudes and shapes remain largely unconstrained, the intent of this exercise is to provoke creative thinking.

The origins of near band-edge transitions in hexagonal boron nitride epilayers

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

Du, X. Z.; Li, J.; Lin, J. Y.

2016-02-01

Photoluminescence spectroscopy has been employed to probe the near band-edge transitions in hexagonal BN (h-BN) epilayers synthesized under varying ammonia flow rates. The results suggest that the quasi-donor-acceptor pair emission line at 5.3 eV is due to the transition between the nitrogen vacancy and a deep acceptor, whereas the 5.5 eV emission line is due to the recombination of an exciton bound to a deep acceptor formed by carbon impurity occupying the nitrogen site. By growing h-BN under high ammonia flow rates, nitrogen vacancy related peaks can be eliminated and epilayers exhibiting pure free exciton emission have been obtained.

Regulating low-NOx and high-burnout deep-air-staging combustion under real-furnace conditions in a 600 MWe down-fired supercritical boiler by strengthening the staged-air effect.

PubMed

Kuang, Min; Wang, Zhihua; Zhu, Yanqun; Ling, Zhongqian; Li, Zhengqi

2014-10-21

A 600 MW(e) down-fired pulverized-coal supercritical boiler, which was equipped with a deep-air-staging combustion system for reducing the particularly high NOx emissions, suffered from the well-accepted contradiction between low NOx emissions and high carbon in fly ash, in addition to excessively high gas temperatures in the hopper that jeopardized the boiler's safe operations. Previous results uncovered that under low-NOx conditions, strengthening the staged-air effect by decreasing the staged-air angle and simultaneously increasing the staged-air damper opening alleviated the aforementioned problems to some extent. To establish low-NOx and high-burnout circumstances and control the aforementioned hopper temperatures, a further staged-air retrofit with horizontally redirecting staged air through an enlarged staged-air slot area was performed to greatly strengthen the staged-air effect. Full-load industrial-size measurements were performed to confirm the availability of this retrofit. The present data were compared with those published results before the retrofit. High NOx emissions, low carbon in fly ah, and high hopper temperatures (i.e., levels of 1036 mg/m(3) at 6% O2, 3.72%, and about 1300 °C, respectively) appeared under the original conditions with the staged-air angle of 45° and without overfire air (OFA) application. Applying OFA and reducing the angle to 20° achieved an apparent NOx reduction and a moderate hopper temperature decrease while a sharp increase in carbon in fly ash (i.e., levels of 878 mg/m(3) at 6% O2, about 1200 °C, and 9.81%, respectively). Fortunately, the present staged-air retrofit was confirmed to be applicable in regulating low-NOx, high-burnout, and low hopper temperature circumstances (i.e., levels of 867 mg/m(3) at 6% O2, 5.40%, and about 1100 °C, respectively).

Ammonia and hydrogen sulfide emissions from swine production facilities in North America: a meta-analysis.

PubMed

Liu, Z; Powers, W; Murphy, J; Maghirang, R

2014-04-01

Literature on NH3 and H2S emissions from swine production facilities in North America was reviewed, and a meta-analysis was conducted on measured emissions data from swine houses and manure storage facilities as well as concentration data in the vicinity of swine production facilities. Results from more than 80 studies were compiled with results from the 11 swine sites in the National Air Emissions Monitoring Study (NAEMS). Data across studies were analyzed statistically using the MIXED procedures of SAS. The median emission rates from swine houses across various production stages and manure handling systems were 2.78 and 0.09 kg/yr per pig for NH3 and H2S, respectively. The median emission rates from swine storage facilities were 2.08 and 0.20 kg/yr per pig for NH3 and H2S, respectively. The size of swine farm that may trigger the need to report NH3 emissions under the Emergency Planning and Community Right-to-Know Act (EPCRA) is 3,410 pigs on the basis of the median NH3 emission rate (4.86 kg/yr per pig), but the threshold can be as low as 992 pigs on the basis of the 90th-percentile emission rates (16.71 kg/yr per pig). Swine hoop houses had significantly higher NH3 emission rate (14.80 kg/yr per pig) than other manure-handling systems (P < 0.01), whereas deep-pit houses had the highest H2S emission rate (16.03 kg/yr per pig, P = 0.03). Farrowing houses had the highest H2S emission rate (2.50 kg/yr per pig), followed by gestation houses, and finishing houses had the lowest H2S emission rate (P < 0.01). Regression models for NH3 and H2S emission rates were developed for finishing houses with deep pits, recharge pits, and lagoons. The NH3 emission rates increased with increasing air temperature, but effects of air temperature on H2S emission rates were not significant. The recharge interval of manure pits significantly affected H2S but not NH3 emission rates. The H2S emission rates were also influenced by the size of the operation. Although NH3 and H2S concentrations at the edge of swine houses or lagoons were often higher than corresponding acute or intermediate minimum risk levels (MRL), they decreased quickly to less than corresponding chronic or intermediate MRL as distances from emission sources increased. At the distances 30 to 1,185 m from emission sources, the average ambient concentrations for NH3 and H2S were 46 ± 46 µg/m(3) and 4.3 ± 8.6 µg/m(3) respectively.

Controlled electroluminescence of n-ZnMgO/p-GaN light-emitting diodes

NASA Astrophysics Data System (ADS)

Goh, E. S. M.; Yang, H. Y.; Han, Z. J.; Chen, T. P.; Ostrikov, K.

2012-12-01

Effective control of room-temperature electroluminescence of n-ZnMgO/p-GaN light-emitting diodes (LEDs) over both emission intensity and wavelength is demonstrated. With varied Mg concentration, the intensity of LEDs in the near-ultraviolet region is increased due to the effective radiative recombination in the ZnMgO layer. Furthermore, the emission wavelength is shifted to the green/yellow spectral region by employing an indium-tin-oxide thin film as the dopant source, where thermally activated indium diffusion creates extra deep defect levels for carrier recombination. These results clearly demonstrate the effectiveness of controlled metal incorporation in achieving high energy efficiency and spectral tunability of the n-ZnMgO/p-GaN LED devices.

Deep Uncertainty Surrounding Coastal Flood Risk Projections: A Case Study for New Orleans

NASA Astrophysics Data System (ADS)

Wong, Tony E.; Keller, Klaus

2017-10-01

Future sea-level rise drives severe risks for many coastal communities. Strategies to manage these risks hinge on a sound characterization of the uncertainties. For example, recent studies suggest that large fractions of the Antarctic ice sheet (AIS) may rapidly disintegrate in response to rising global temperatures, leading to potentially several meters of sea-level rise during the next few centuries. It is deeply uncertain, for example, whether such an AIS disintegration will be triggered, how much this would increase sea-level rise, whether extreme storm surges intensify in a warming climate, or which emissions pathway future societies will choose. Here, we assess the impacts of these deep uncertainties on projected flooding probabilities for a levee ring in New Orleans, LA. We use 18 scenarios, presenting probabilistic projections within each one, to sample key deeply uncertain future projections of sea-level rise, radiative forcing pathways, storm surge characterization, and contributions from rapid AIS mass loss. The implications of these deep uncertainties for projected flood risk are thus characterized by a set of 18 probability distribution functions. We use a global sensitivity analysis to assess which mechanisms contribute to uncertainty in projected flood risk over the course of a 50-year design life. In line with previous work, we find that the uncertain storm surge drives the most substantial risk, followed by general AIS dynamics, in our simple model for future flood risk for New Orleans.

Implications of Deep Decarbonization for Carbon Cycle Science

NASA Astrophysics Data System (ADS)

Jones, A. D.; Williams, J.; Torn, M. S.

2016-12-01

The energy-system transformations required to achieve deep decarbonization in the United States, defined as a reduction of greenhouse gas emissions of 80% or more below 1990 levels by 2050, have profound implications for carbon cycle science, particularly with respect to 4 key objectives: understanding and enhancing the terrestrial carbon sink, using bioenergy sustainably, controlling non-CO2 GHGs, and emissions monitoring and verification. (1) As a source of mitigation, the terrestrial carbon sink is pivotal but uncertain, and changes in the expected sink may significantly affect the overall cost of mitigation. Yet the dynamics of the sink under changing climatic conditions, and the potential to protect and enhance the sink through land management, are poorly understood. Policy urgently requires an integrative research program that links basic science knowledge to land management practices. (2) Biomass resources can fill critical energy needs in a deeply decarbonized system, but current understanding of sustainability and lifecycle carbon aspects is limited. Mitigation policy needs better understanding of the sustainable amount, types, and cost of bioenergy feedstocks, their interactions with other land uses, and more efficient and reliable monitoring of embedded carbon. (3) As CO2 emissions from energy decrease under deep decarbonization, the relative share of non-CO2 GHGs grows larger and their mitigation more important. Because the sources tend to be distributed, variable, and uncertain, they have been under-researched. Policy needs a better understanding of mitigation priorities and costs, informed by deeper research in key areas such as fugitive CH4, fertilizer-derived N2O, and industrial F-gases. (4) The M&V challenge under deep decarbonization changes with a steep decrease in the combustion CO2 sources due to widespread electrification, while a greater share of CO2 releases is net-carbon-neutral. Similarly, gas pipelines may carry an increasing share of methane from biogenic or other net carbon-neutral sources. Improved lifecycle analysis will be needed to verify carbon neutrality, while the signal-to-noise challenge for attributing CO2 to fossil or biogenic fuels becomes more challenging.

Dynamic Geospatial Modeling of the Building Stock to Project Urban Energy Demand.

PubMed

Breunig, Hanna Marie; Huntington, Tyler; Jin, Ling; Robinson, Alastair; Scown, Corinne Donahue

2018-06-26

In the United States, buildings account for more than 40 percent of total energy consumption, and the evolution of the urban form will impact the effectiveness of strategies to reduce energy use and mitigate emissions. This paper presents a broadly applicable approach for modeling future commercial, residential, and industrial floorspace, thermal consumption (heating and cooling), and associated GHG emissions at the tax assessor land parcel level. The approach accounts for changing building standards and retrofitting, climate change, and trends in housing and industry. We demonstrate the automated workflow for California, and project building stock, thermal energy consumption, and associated GHG emissions out to 2050. Our results suggest that if buildings in California have long lifespans, and minimal energy efficiency improvements compared to building codes reflective of 2008, then the state will face a 20% or higher increase in thermal energy consumption by 2050. Baseline annual GHG emissions associated with thermal energy consumption in the modeled building stock in 2016 is 34% below 1990 levels (110 Mt CO2eq/y).While the 2020 targets for the reduction of GHG emissions set by the California Senate Bill 350 have already been met, none of our scenarios achieve >80% reduction from 1990 levels by 2050, despite assuming an 86% reduction in electricity carbon intensity in our "Low Carbon" scenario. The results highlight the challenge California faces in meeting its new energy efficiency targets unless the State's building stock undergoes timely and strategic turnover, paired with deep retrofitting of existing buildings and natural gas equipment.

Deep mantle: Enriched carbon source detected

NASA Astrophysics Data System (ADS)

Barry, Peter H.

2017-09-01

Estimates of carbon in the deep mantle vary by more than an order of magnitude. Coupled volcanic CO2 emission data and magma supply rates reveal a carbon-rich mantle plume source region beneath Hawai'i with 40% more carbon than previous estimates.

The 2007 and 2014 eruptions of Stromboli at match: monitoring the potential occurrence of effusion-driven basaltic paroxysmal explosions from a volcanic CO2 flux perspective

NASA Astrophysics Data System (ADS)

Liuzzo, Marco; Aiuppa, Alessandro; Salerno, Giuseppe; Burton, Mike; Federico, Cinzia; Caltabiano, Tommaso; Giudice, Gaetano; Giuffrida, Giovanni

2015-04-01

The recent effusive unrests of Stromboli occurred in 2002 and 2007 were both punctuated by short-lived, violent paroxysmal explosions generated from the volcano's summit craters. When effusive activity recently resumed on Stromboli, on 6 August 2014, much concern was raised therefore on whether or not a paroxysm would have occurred again. The occurrence of these potentially hazardous events has stimulated research toward understanding the mechanisms through which effusive eruptions can perturb the volcano's plumbing system, to eventually trigger a paroxysm. The anomalously large CO2 gas emissions measured prior to the 15 March 2007 paroxysmal explosion of Stromboli [1] have first demonstrated the chance to predict days in advance the effusive-to-explosive transition. Here 2007 and 2014 volcanic CO2 flux records have been compared for exploring causes/conditions that had not triggered any paroxysm event in the 2014 case. We show that the 2007 and 2014 datasets shared both similarities and remarkable differences. The pre-eruptive trends of CO2 and SO2 flux emissions were strikingly similar in both 2007 and 2014, indicating similar conditions within the plumbing system prior to onset of both effusive crises. In both events, the CO2 flux substantially accelerated (relative to the pre-eruptive mean flux) after onset of the effusion. However, this CO2 flux acceleration was a factor 3 lower in 2014 than in 2007, and the excess CO2 flux (the fraction of CO2 not associated with the shallowly emplaced/erupted magma, and therefore contributed by the deep magmatic system) never returned to the very high levels observed prior to the 15 March 2007 paroxysm. We conclude therefore that, although similar quantities of magma were effusively erupted in 2007 and 2014, the deep magmatic system was far less perturbed in the most recent case. We speculate that the rate at which the deep magmatic system is decompressed, rather than the level of de-compression itself, determine if the deep Stromboli's plumbing system is prone to erupt in a paroxysm, or not. [1] A. Aiuppa et al., Geophys Res Lett, 2010.

Overall evaluation of combustion and NO(x) emissions for a down-fired 600 MW(e) supercritical boiler with multiple injection and multiple staging.

PubMed

Kuang, Min; Li, Zhengqi; Liu, Chunlong; Zhu, Qunyi

2013-05-07

To achieve significant reductions in NOx emissions and to eliminate strongly asymmetric combustion found in down-fired boilers, a deep-air-staging combustion technology was trialed in a down-fired 600 MWe supercritical utility boiler. By performing industrial-sized measurements taken of gas temperatures and species concentrations in the near wing-wall region, carbon in fly ash and NOx emissions at various settings, effects of overfire air (OFA) and staged-air damper openings on combustion characteristics, and NOx emissions within the furnace were experimentally determined. With increasing the OFA damper opening, both fluctuations in NOx emissions and carbon in fly ash were initially slightly over OFA damper openings of 0-40% but then lengthened dramatically in openings of 40-70% (i.e., NOx emissions reduced sharply accompanied by an apparent increase in carbon in fly ash). Decreasing the staged-air declination angle clearly increased the combustible loss but slightly influenced NOx emissions. In comparison with OFA, the staged-air influence on combustion and NOx emissions was clearly weaker. Only at a high OFA damper opening of 50%, the staged-air effect was relatively clear, i.e., enlarging the staged-air damper opening decreased carbon in fly ash and slightly raised NOx emissions. By sharply opening the OFA damper to deepen the air-staging conditions, although NOx emissions could finally reduce to 503 mg/m(3) at 6% O2 (i.e., an ultralow NOx level for down-fired furnaces), carbon in fly ash jumped sharply to 15.10%. For economical and environment-friendly boiler operations, an optimal damper opening combination (i.e., 60%, 50%, and 50% for secondary air, staged-air, and OFA damper openings, respectively) was recommended for the furnace, at which carbon in fly ash and NOx emissions attained levels of about 10% and 850 mg/m(3) at 6% O2, respectively.

Activation of an intense near band edge emission from ZnTe/ZnMgTe core/shell nanowires grown on silicon.

PubMed

Wojnar, P; Szymura, M; Zaleszczyk, W; Kłopotowski, L; Janik, E; Wiater, M; Baczewski, L T; Kret, S; Karczewski, G; Kossut, J; Wojtowicz, T

2013-09-13

The absence of luminescence in the near band edge energy region of Te-anion based semiconductor nanowires grown by gold catalyst assisted molecular beam epitaxy has strongly limited their applications in the field of photonics. In this paper, an enhancement of the near band edge emission intensity from ZnTe/ZnMgTe core/shell nanowires grown on Si substrates is reported. A special role of the use of Si substrates instead of GaAs substrates is emphasized, which results in an increase of the near band edge emission intensity by at least one order of magnitude accompanied by a simultaneous reduction of the defect related luminescence. A possible explanation of this effect relies on the presence of Ga-related deep level defects in structures grown on GaAs substrates, which are absent when Si substrates are used. Monochromatic mapping of the cathodoluminescence clearly confirms that the observed emission originates, indeed, from the ZnTe/ZnMgTe core/shell nanowires, whereas individual objects are studied by means of microphotoluminescence.

Detection of z~2 Type IIn Supernovae

NASA Astrophysics Data System (ADS)

Cooke, Jeff; Sullivan, Mark; Barton, Elizabeth J.

2009-05-01

Type IIn supernovae (SNe IIn) result from the deaths of massive stars. The broad magnitude distribution of SNe IIn make these some of the most luminous SN events ever recorded. In addition, they are the most luminous SN type in the rest-frame UV which make them ideal targets for wide-field optical high redshift searches. We briefly describe our method to detect z~2 SNe IIn events that involves monitoring color-selected galaxies in deep stacked images and our program that applies this method to the CFHTLS survey. Initial results have detected four compelling photometric candidates from their subtracted images and light curves. SNe IIn spectra exhibit extremely bright narrow emission lines as a result of the interaction between the SN ejecta and the circumstellar material released in pre-explosion outbursts. These emission lines remain bright for years after outburst and are above the thresholds of current 8 m-class telescope sensitivities to z~3. The deep spectroscopy required to confirm z~2 host galaxies has the potential to detect the SN emission lines and measure their energies. Finally, planned deep, wide-field surveys have the capability to detect and confirm SNe IIn to z~6. The emission lines of such high-redshift events are expected to be above the sensitivity of future 30 m-class telescopes and the James Webb Space Telescope.

The Metal Abundances across Cosmic Time (MACT) Survey. I. Optical Spectroscopy in the Subaru Deep Field

NASA Astrophysics Data System (ADS)

Ly, Chun; Malhotra, Sangeeta; Malkan, Matthew A.; Rigby, Jane R.; Kashikawa, Nobunari; de los Reyes, Mithi A.; Rhoads, James E.

2016-09-01

Deep rest-frame optical spectroscopy is critical for characterizing and understanding the physical conditions and properties of the ionized gas in galaxies. Here, we present a new spectroscopic survey called “Metal Abundances across Cosmic Time” or { M }{ A }{ C }{ T }, which will obtain rest-frame optical spectra for ˜3000 emission-line galaxies. This paper describes the optical spectroscopy that has been conducted with MMT/Hectospec and Keck/DEIMOS for ≈1900 z = 0.1-1 emission-line galaxies selected from our narrowband and intermediate-band imaging in the Subaru Deep Field. In addition, we present a sample of 164 galaxies for which we have measured the weak [O III]λ4363 line (66 with at least 3σ detections and 98 with significant upper limits). This nebular emission line determines the gas-phase metallicity by measuring the electron temperature of the ionized gas. This paper presents the optical spectra, emission-line measurements, interstellar properties (e.g., metallicity, gas density), and stellar properties (e.g., star formation rates, stellar mass). Paper II of the { M }{ A }{ C }{ T } survey (Ly et al.) presents the first results on the stellar mass-gas metallicity relation at z ≲ 1 using the sample with [O III]λ4363 measurements.

Seismic reflection imaging of shallow oceanographic structures

NASA Astrophysics Data System (ADS)

Piété, Helen; Marié, Louis; Marsset, Bruno; Thomas, Yannick; Gutscher, Marc-André

2013-05-01

Multichannel seismic (MCS) reflection profiling can provide high lateral resolution images of deep ocean thermohaline fine structure. However, the shallowest layers of the water column (z < 150 m) have remained unexplored by this technique until recently. In order to explore the feasibility of shallow seismic oceanography (SO), we reprocessed and analyzed four multichannel seismic reflection sections featuring reflectors at depths between 10 and 150 m. The influence of the acquisition parameters was quantified. Seismic data processing dedicated to SO was also investigated. Conventional seismic acquisition systems were found to be ill-suited to the imaging of shallow oceanographic structures, because of a high antenna filter effect induced by large offsets and seismic trace lengths, and sources that typically cannot provide both a high level of emission and fine vertical resolution. We considered a test case, the imagery of the seasonal thermocline on the western Brittany continental shelf. New oceanographic data acquired in this area allowed simulation of the seismic acquisition. Sea trials of a specifically designed system were performed during the ASPEX survey, conducted in early summer 2012. The seismic device featured: (i) four seismic streamers, each consisting of six traces of 1.80 m; (ii) a 1000 J SIG sparker source, providing a 400 Hz signal with a level of emission of 205 dB re 1 μPa @ 1 m. This survey captured the 15 m thick, 30 m deep seasonal thermocline in unprecedented detail, showing images of vertical displacements most probably induced by internal waves.

Effect of deep injection on field-scale emissions of 1,3-dichloropropene and chloropicrin from bare soil

USDA-ARS?s Scientific Manuscript database

Fumigating soil is important for the production of many high-value vegetable, fruit, and tree crops, but fumigants are toxic and highly volatile which can lead to significant atmospheric emissions. A field experiment was conducted to measure emissions and subsurface diffusion of a mixture of 1,3-di...

Turmoil at Turrialba Volcano (Costa Rica): Degassing and eruptive processes inferred from high-frequency gas monitoring.

PubMed

de Moor, J Maarten; Aiuppa, A; Avard, G; Wehrmann, H; Dunbar, N; Muller, C; Tamburello, G; Giudice, G; Liuzzo, M; Moretti, R; Conde, V; Galle, B

2016-08-01

Eruptive activity at Turrialba Volcano (Costa Rica) has escalated significantly since 2014, causing airport and school closures in the capital city of San José. Whether or not new magma is involved in the current unrest seems probable but remains a matter of debate as ash deposits are dominated by hydrothermal material. Here we use high-frequency gas monitoring to track the behavior of the volcano between 2014 and 2015 and to decipher magmatic versus hydrothermal contributions to the eruptions. Pulses of deeply derived CO 2 -rich gas (CO 2 /S total  > 4.5) precede explosive activity, providing a clear precursor to eruptive periods that occurs up to 2 weeks before eruptions, which are accompanied by shallowly derived sulfur-rich magmatic gas emissions. Degassing modeling suggests that the deep magmatic reservoir is ~8-10 km deep, whereas the shallow magmatic gas source is at ~3-5 km. Two cycles of degassing and eruption are observed, each attributed to pulses of magma ascending through the deep reservoir to shallow crustal levels. The magmatic degassing signals were overprinted by a fluid contribution from the shallow hydrothermal system, modifying the gas compositions, contributing volatiles to the emissions, and reflecting complex processes of scrubbing, displacement, and volatilization. H 2 S/SO 2 varies over 2 orders of magnitude through the monitoring period and demonstrates that the first eruptive episode involved hydrothermal gases, whereas the second did not. Massive degassing (>3000 T/d SO 2 and H 2 S/SO 2  > 1) followed, suggesting boiling off of the hydrothermal system. The gas emissions show a remarkable shift to purely magmatic composition (H 2 S/SO 2  < 0.05) during the second eruptive period, reflecting the depletion of the hydrothermal system or the establishment of high-temperature conduits bypassing remnant hydrothermal reservoirs, and the transition from phreatic to phreatomagmatic eruptive activity.

Turmoil at Turrialba Volcano (Costa Rica): Degassing and eruptive processes inferred from high‐frequency gas monitoring

PubMed Central

Aiuppa, A.; Avard, G.; Wehrmann, H.; Dunbar, N.; Muller, C.; Tamburello, G.; Giudice, G.; Liuzzo, M.; Moretti, R.; Conde, V.; Galle, B.

2016-01-01

Abstract Eruptive activity at Turrialba Volcano (Costa Rica) has escalated significantly since 2014, causing airport and school closures in the capital city of San José. Whether or not new magma is involved in the current unrest seems probable but remains a matter of debate as ash deposits are dominated by hydrothermal material. Here we use high‐frequency gas monitoring to track the behavior of the volcano between 2014 and 2015 and to decipher magmatic versus hydrothermal contributions to the eruptions. Pulses of deeply derived CO2‐rich gas (CO2/Stotal > 4.5) precede explosive activity, providing a clear precursor to eruptive periods that occurs up to 2 weeks before eruptions, which are accompanied by shallowly derived sulfur‐rich magmatic gas emissions. Degassing modeling suggests that the deep magmatic reservoir is ~8–10 km deep, whereas the shallow magmatic gas source is at ~3–5 km. Two cycles of degassing and eruption are observed, each attributed to pulses of magma ascending through the deep reservoir to shallow crustal levels. The magmatic degassing signals were overprinted by a fluid contribution from the shallow hydrothermal system, modifying the gas compositions, contributing volatiles to the emissions, and reflecting complex processes of scrubbing, displacement, and volatilization. H2S/SO2 varies over 2 orders of magnitude through the monitoring period and demonstrates that the first eruptive episode involved hydrothermal gases, whereas the second did not. Massive degassing (>3000 T/d SO2 and H2S/SO2 > 1) followed, suggesting boiling off of the hydrothermal system. The gas emissions show a remarkable shift to purely magmatic composition (H2S/SO2 < 0.05) during the second eruptive period, reflecting the depletion of the hydrothermal system or the establishment of high‐temperature conduits bypassing remnant hydrothermal reservoirs, and the transition from phreatic to phreatomagmatic eruptive activity. PMID:27774371

Turmoil at Turrialba Volcano (Costa Rica): Degassing and eruptive processes inferred from high-frequency gas monitoring

NASA Astrophysics Data System (ADS)

de Moor, J. Maarten; Aiuppa, A.; Avard, G.; Wehrmann, H.; Dunbar, N.; Muller, C.; Tamburello, G.; Giudice, G.; Liuzzo, M.; Moretti, R.; Conde, V.; Galle, B.

2016-08-01

Eruptive activity at Turrialba Volcano (Costa Rica) has escalated significantly since 2014, causing airport and school closures in the capital city of San José. Whether or not new magma is involved in the current unrest seems probable but remains a matter of debate as ash deposits are dominated by hydrothermal material. Here we use high-frequency gas monitoring to track the behavior of the volcano between 2014 and 2015 and to decipher magmatic versus hydrothermal contributions to the eruptions. Pulses of deeply derived CO2-rich gas (CO2/Stotal > 4.5) precede explosive activity, providing a clear precursor to eruptive periods that occurs up to 2 weeks before eruptions, which are accompanied by shallowly derived sulfur-rich magmatic gas emissions. Degassing modeling suggests that the deep magmatic reservoir is 8-10 km deep, whereas the shallow magmatic gas source is at 3-5 km. Two cycles of degassing and eruption are observed, each attributed to pulses of magma ascending through the deep reservoir to shallow crustal levels. The magmatic degassing signals were overprinted by a fluid contribution from the shallow hydrothermal system, modifying the gas compositions, contributing volatiles to the emissions, and reflecting complex processes of scrubbing, displacement, and volatilization. H2S/SO2 varies over 2 orders of magnitude through the monitoring period and demonstrates that the first eruptive episode involved hydrothermal gases, whereas the second did not. Massive degassing (>3000 T/d SO2 and H2S/SO2 > 1) followed, suggesting boiling off of the hydrothermal system. The gas emissions show a remarkable shift to purely magmatic composition (H2S/SO2 < 0.05) during the second eruptive period, reflecting the depletion of the hydrothermal system or the establishment of high-temperature conduits bypassing remnant hydrothermal reservoirs, and the transition from phreatic to phreatomagmatic eruptive activity.

Enhancement of external quantum efficiency and quality of heterojunction white LEDs by varying the size of ZnO nanorods.

PubMed

Bano, N; Hussain, I; Sawaf, S; Alshammari, Abeer; Saleemi, F

2017-06-16

The size of ZnO nanorods (NRs) plays an important role in tuning the external quantum efficiency (EQE) and quality of light generated by white light emitting diodes (LEDs). In this work, we report on the enhancement of EQE and the quality of ZnO NR-based hetrojunction white LEDs fabricated on a p-GaN substrate using a low temperature solution method. Cathodoluminescence spectra demonstrate that ultraviolet (UV) emission decreases and visible deep band emission increases with an increase in the length of the ZnO NRs. The UV emission could be internally reabsorbed by the ZnO NR excitation, thus enhancing the emission intensity of the visible deep band. Photocurrent measurements validated the fact that the EQE depends on the size of ZnO NRs, increasing by 87% with an increase in the length of the ZnO NRs. Furthermore, the quality of white light was measured and clearly indicated an increase in the color rendering indices of the LEDs with an increase in the length of the ZnO NRs, confirming that the quality of light generated by LEDs can be tuned by varying the length of the ZnO NRs. These results suggest that the EQE and visible deep band emission from n-ZnONRs/p-GaN heterojunction LEDs can be effectively controlled by adjusting the length of the ZnO NRs, which can be useful for realizing tunable white LEDs.

Enhancement of external quantum efficiency and quality of heterojunction white LEDs by varying the size of ZnO nanorods

NASA Astrophysics Data System (ADS)

Bano, N.; Hussain, I.; Sawaf, S.; Alshammari, Abeer; Saleemi, F.

2017-06-01

The size of ZnO nanorods (NRs) plays an important role in tuning the external quantum efficiency (EQE) and quality of light generated by white light emitting diodes (LEDs). In this work, we report on the enhancement of EQE and the quality of ZnO NR-based hetrojunction white LEDs fabricated on a p-GaN substrate using a low temperature solution method. Cathodoluminescence spectra demonstrate that ultraviolet (UV) emission decreases and visible deep band emission increases with an increase in the length of the ZnO NRs. The UV emission could be internally reabsorbed by the ZnO NR excitation, thus enhancing the emission intensity of the visible deep band. Photocurrent measurements validated the fact that the EQE depends on the size of ZnO NRs, increasing by 87% with an increase in the length of the ZnO NRs. Furthermore, the quality of white light was measured and clearly indicated an increase in the color rendering indices of the LEDs with an increase in the length of the ZnO NRs, confirming that the quality of light generated by LEDs can be tuned by varying the length of the ZnO NRs. These results suggest that the EQE and visible deep band emission from n-ZnONRs/p-GaN heterojunction LEDs can be effectively controlled by adjusting the length of the ZnO NRs, which can be useful for realizing tunable white LEDs.

Airborne reduced nitrogen: ammonia emissions from agriculture and other sources.

PubMed

Anderson, Natalie; Strader, Ross; Davidson, Cliff

2003-06-01

Ammonia is a basic gas and one of the most abundant nitrogen-containing compounds in the atmosphere. When emitted, ammonia reacts with oxides of nitrogen and sulfur to form particles, typically in the fine particle size range. Roughly half of the PM(2.5) mass in eastern United States is ammonium sulfate, according to the US EPA. Results from recent studies of PM(2.5) show that these fine particles are typically deposited deep in the lungs and may lead to increased morbidity and/or mortality. Also, these particles are in the size range that will degrade visibility. Ammonia emission inventories are usually constructed by multiplying an activity level by an experimentally determined emission factor for each source category. Typical sources of ammonia include livestock, fertilizer, soils, forest fires and slash burning, industry, vehicles, the oceans, humans, pets, wild animals, and waste disposal and recycling activities. Livestock is the largest source category in the United States, with waste from livestock responsible for about 3x10(9) kg of ammonia in 1995. Volatilization of ammonia from livestock waste is dependent on many parameters, and thus emission factors are difficult to predict. Despite a seasonal variation in these values, the emission factors for general livestock categories are usually annually averaged in current inventories. Activity levels for livestock are from the USDA Census of Agriculture, which does not give information about animal raising practices such as housing types and grazing times, waste handling systems, and approximate animal slurry spreading times or methods. Ammonia emissions in the United States in 1995 from sources other than livestock are much lower; for example, annual emissions are roughly 8x10(8) kg from fertilizer, 7x10(7) kg from industry, 5x10(7) kg from vehicles and 1x10(8) kg from humans. There is considerable uncertainty in the emissions from soil and vegetation, although this category may also be significant. Recommendations for future directions in ammonia research include designing experiments to improve emission factors and their resolution in all significant source categories, developing mass balance models, and refining of the livestock activity level data by eliciting judgment from experts in this field.

Methane efflux measured by eddy covariance in Alaskan upland tundra undergoing permafrost degradation

NASA Astrophysics Data System (ADS)

Taylor, M.; Celis, G.; Ledman, J.; Bracho, R. G.; Schuur, E.

2017-12-01

Permafrost thaw can increase landscape heterogeneity, leading to wetter and drier soil conditions that affect the magnitude and form (carbon dioxide - CO2 and methane - CH4) of carbon produced via microbial decomposition. Environmental controls on CH4 emissions, especially in drier upland tundra systems, are not well understood. In degrading upland tundra permafrost, cold season CH4 fluxes may contribute significantly to annual emissions from CH4 production within unfrozen layers deep in the soil profile. Eight Mile Lake (EML), located in Interior Alaska near Denali National Park, is a moist acidic tussock tundra ecosystem undergoing permafrost degradation. Perennially frozen soils have warmed between 1985 and 2016 from -1.2 to -0.75˚C resulting in a deeper active layer depth from 61 to 70 cm between 2004-2016. Depth from the soil/moss surface to the water table perched on the permafrost surface has decreased from 30 to 20 cm over the same interval. Here we present the first year of continuous CH4 flux measurements made at EML (May 2016 - May 2017). The site was a net source of low-level CH4 emissions throughout the year. Annual CH4 emissions (1.3 g C yr-1) made up 8.8% of total annual C emissions (14.7 g m-2yr-1). Methane flux is related with soil temperatures during both summer and non-summer seasons. Emissions increased throughout the summer season as thaw depth and soil temperatures increased. In contrast with wetland sites where water table is at or above the soil surface for much of the growing season, EML is relatively dry and there was no relationship between soil moisture and emissions. Non-summer season CH4 emissions are related to increases in atmospheric and shallow soil temperatures. Winter season emissions account for 37% of the annual CH4 budget, the bulk of which occurred between October and January when deep soils remained thawed. Non-summer season CH4 and CO2 pulses appear to be coupled, suggesting a similar mechanism for release. We hypothesize that this relationship is the result of surface soils warming and cracking, allowing for the escape of microbially produced gases at depth. While annual CH4 emissions made up 8.8% of total annual C emissions at this site, taking into account the greenhouse warming potential of CH4 relative to CO2, the climate impact of CH4 is 15.6 g m-2yr-1, or 69% of the C budget.

Deep ultraviolet semiconductor light sources for sensing and security

NASA Astrophysics Data System (ADS)

Shatalov, Max; Bilenko, Yuri; Yang, Jinwei; Gaska, Remis

2009-09-01

III-Nitride based deep ultraviolet (DUV) light emitting diodes (LEDs) rapidly penetrate into sensing market owing to several advantages over traditional UV sources (i.e. mercury, xenon and deuterium lamps). Small size, a wide choice of peak emission wavelengths, lower power consumption and reduced cost offer flexibility to system integrators. Short emission wavelength offer advantages for gas detection and optical sensing systems based on UV induced fluorescence. Large modulation bandwidth for these devices makes them attractive for frequency-domain spectroscopy. We will review present status of DUV LED technology and discuss recent advances in short wavelength emitters and high power LED lamps.

Deep Blue Phosphorescent Organic Light-Emitting Diodes with CIEy Value of 0.11 and External Quantum Efficiency up to 22.5.

PubMed

Li, Xiaoyue; Zhang, Juanye; Zhao, Zifeng; Wang, Liding; Yang, Hannan; Chang, Qiaowen; Jiang, Nan; Liu, Zhiwei; Bian, Zuqiang; Liu, Weiping; Lu, Zhenghong; Huang, Chunhui

2018-03-01

Organic light-emitting diodes (OLEDs) based on red and green phosphorescent iridium complexes are successfully commercialized in displays and solid-state lighting. However, blue ones still remain a challenge on account of their relatively dissatisfactory Commission International de L'Eclairage (CIE) coordinates and low efficiency. After analyzing the reported blue iridium complexes in the literature, a new deep-blue-emitting iridium complex with improved photoluminescence quantum yield is designed and synthesized. By rational screening host materials showing high triplet energy level in neat film as well as the OLED architecture to balance electron and hole recombination, highly efficient deep-blue-emission OLEDs with a CIE at (0.15, 0.11) and maximum external quantum efficiency (EQE) up to 22.5% are demonstrated. Based on the transition dipole moment vector measurement with a variable-angle spectroscopic ellipsometry method, the ultrahigh EQE is assigned to a preferred horizontal dipole orientation of the iridium complex in doped film, which is beneficial for light extraction from the OLEDs. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Plasmonic based light manipulation and applications in AIGaN deep-UV devices (Conference Presentation)

NASA Astrophysics Data System (ADS)

Yin, Jun; Li, Jing; Kang, Junyong

2016-09-01

Recently, surface plasmon (SP)-exciton coupling has been wildly applied in nitride semiconductors in order to improve the spontaneous radiative recombination rate [1-3]. However, most works have been focused on the emission enhancement in InGaN-based blue or green light emitting diodes (LEDs). Practically, it is significantly important to improve the emission efficiency in deep-UV AlGaN-base quantum well (QW) structure due to its intrinsically low internal quantum efficiency (IQE) induced by the high defect density in its epitaxy layer [4]. But, the effective SP-exciton coupling with matched energy in deep-UV region is still a challenge issue due to the lack of appropriate metal structures and compatible fabrication techniques. In this work, the Al nanoparticles (NPs) were introduced by the nanosphere lithography (NSL) and deposition techniques into the AlGaN based MQWs with optimized size and structure. Due to the local surface plasmon (LSP) coupling with the excitons in QWs, emission enhancement in deep UV region has been achieved in the Al NPs decorated AlGaN MQWs structure with comparison to the bare MQWs. Theoretical calculations on the energy subbands of AlGaN QWs were further carried out to investigate the corresponding mechanisms, in which the hot carrier transition activated by SP-exciton coupling was believed to be mainly responsible for the enhancement. This work demonstrated a low cost, wafer scale fabrication process, which can be potentially employed to the practical SP-enhanced AlGaN-based deep UV LEDs with high IQEs.

Heterojunction light emitting diodes fabricated with different n-layer oxide structures on p-GaN layers by magnetron sputtering

NASA Astrophysics Data System (ADS)

Kong, Bo Hyun; Han, Won Suk; Kim, Young Yi; Cho, Hyung Koun; Kim, Jae Hyun

2010-06-01

We grew heterojunction light emitting diode (LED) structures with various n-type semiconducting layers by magnetron sputtering on p-type GaN at high temperature. Because the undoped ZnO used as an active layer was grown under oxygen rich atmosphere, all LED devices showed the EL characteristics corresponding to orange-red wavelength due to high density of oxygen interstitial, which was coincident with the deep level photoluminescence emission of undoped ZnO. The use of the Ga doped layers as a top layer provided the sufficient electron carriers to active region and resulted in the intense EL emission. The LED sample with small quantity of Mg incorporated in MgZnO as an n-type top layer showed more intense emission than the LED with ZnO, in spite of the deteriorated electrical and structural properties of the MgZnO film. This might be due to the improvement of output extraction efficiency induced by rough surface.

Effect of Eu3+ doping on the structural, morphological and luminescence properties ZnO nanostructures

NASA Astrophysics Data System (ADS)

Vinoditha, U.; Balakrishna, K. M.; Sarojini, B. K.; Narayana, B.; Kumara, K.

2018-05-01

Pure and Eu3+ ions (1, 3, 5 atomic wt%) doped ZnO nanostructures are synthesized by a surfactant assisted hydrothermal method. The effect of doping concentrations on structural, morphological and optical properties of ZnO nanostructures is studied. The XRD analysis shows good crystallinity and the phase purity of the ZnO nanostructures. A shift in the standard Zn-O stretching mode after Eu3+ doping is observed in the FTIR spectra. The images of FESEM demonstrate the morphological variations from hexagonal nanorods to nanoflowers on varying the dopant concentrations. Substitution of Eu3+ ions into Zn2+ sites is confirmed by EDX analysis. The dominance of particle shape over the UV-Visible absorption properties of the prepared samples is noticed. The photoluminescence (PL) emission of undoped and doped ZnO nanostructures show dominant near band edge emission (NBE) in the UV region and minor defect induced deep level emissions in the visible region.

Observational and modeling constraints on global anthropogenic enrichment of mercury.

PubMed

Amos, Helen M; Sonke, Jeroen E; Obrist, Daniel; Robins, Nicholas; Hagan, Nicole; Horowitz, Hannah M; Mason, Robert P; Witt, Melanie; Hedgecock, Ian M; Corbitt, Elizabeth S; Sunderland, Elsie M

2015-04-07

Centuries of anthropogenic releases have resulted in a global legacy of mercury (Hg) contamination. Here we use a global model to quantify the impact of uncertainty in Hg atmospheric emissions and cycling on anthropogenic enrichment and discuss implications for future Hg levels. The plausibility of sensitivity simulations is evaluated against multiple independent lines of observation, including natural archives and direct measurements of present-day environmental Hg concentrations. It has been previously reported that pre-industrial enrichment recorded in sediment and peat disagree by more than a factor of 10. We find this difference is largely erroneous and caused by comparing peat and sediment against different reference time periods. After correcting this inconsistency, median enrichment in Hg accumulation since pre-industrial 1760 to 1880 is a factor of 4.3 for peat and 3.0 for sediment. Pre-industrial accumulation in peat and sediment is a factor of ∼ 5 greater than the precolonial era (3000 BC to 1550 AD). Model scenarios that omit atmospheric emissions of Hg from early mining are inconsistent with observational constraints on the present-day atmospheric, oceanic, and soil Hg reservoirs, as well as the magnitude of enrichment in archives. Future reductions in anthropogenic emissions will initiate a decline in atmospheric concentrations within 1 year, but stabilization of subsurface and deep ocean Hg levels requires aggressive controls. These findings are robust to the ranges of uncertainty in past emissions and Hg cycling.

Investigation of intrinsic and extrinsic defects effective role on producing intense red emission in ZnO:Eu nanostructures

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

Najafi, Mehrdad, E-mail: najafi@shahroodut.ac.ir; Haratizadeh, Hamid

2015-05-15

Highlights: • Effective role of defects on producing red emission at indirect excitation. • V{sub Zn} and V{sub O} defects have important role on energy transfer. • Mg related defects and Zn{sub i} defects were responsible for blue emission. • Extrinsic and intrinsic defects mediated energy transfer to sensitize Eu{sup 3+} ions. • Decrease of red emission because of diminishing in oxygen vacancy. - Abstract: Europium doped ZnO nanorads and nanosheets were synthesized by hydrothermal method. Effects of Mg doping, morphology and annealing in oxygen ambient on structural and optical properties of ZnO nanostructures were investigated using X-ray diffraction (XRD),more » particle size analysis (PSA), thermo gravimetric analysis (TGA), differential thermal analysis (DTA), differential thermo gravimetry (DTG), scanning electron microscopy (SEM) and photoluminescence spectroscopy (PL). This study recommends that both of intrinsic and extrinsic defects facilitate energy transfer (ET) from the ZnO host to Eu{sup 3+} ions and consequently have efficient role on producing intense red emission at indirect excitation. The results also showed that annealing process improved the crystal structure of ZnO nanosheets due to decrease of surface defects; however decreased ET and red emission because of diminishing in oxygen vacancy. In addition in ZnO nanorods sample with more surface area in comparison with ZnO nanosheets sample deep level emissions are enhanced.« less

Long term monitoring of Gamma-Ray emission from the BL Lacertae object (1ES 2200+420)

NASA Astrophysics Data System (ADS)

Gunawardhana, Isuru; VERITAS Collaboration

2016-03-01

Blazars are a class of Active Galactic Nuclei (AGN) that have relativistic jets pointing along the observer line of sight. Blazars exhibit variable emission extending from radio to TeV energies. The variability timescale of the TeV flux is a key component of understanding the location of the very high energy emission zones. Deep observations of the quiescent state measurements are also required to disentangle the flaring state emission from quiescent state emission, a prerequisite for understanding the origin of blazar spectral variability. BL Lacertae (also known as 1ES 2200+420), as the namesake for all BL Lac objects, is a prime example of one such blazar. The VERITAS Observatory, an Imaging Atmospheric Cherenkov Telescope (IACT) array sensitive to gamma rays in the range from 85 GeV to 30 TeV, dedicates approximately 110 hours per year on deep observations of known gamma-ray blazars. In this talk, I will describe the TeV photon flux variability of BL Lacertae measured by VERITAS from 2013 to 2015.

Deep peat warming increases surface methane and carbon dioxide emissions in a black spruce-dominated ombrotrophic bog.

PubMed

Gill, Allison L; Giasson, Marc-André; Yu, Rieka; Finzi, Adrien C

2017-12-01

Boreal peatlands contain approximately 500 Pg carbon (C) in the soil, emit globally significant quantities of methane (CH 4 ), and are highly sensitive to climate change. Warming associated with global climate change is likely to increase the rate of the temperature-sensitive processes that decompose stored organic carbon and release carbon dioxide (CO 2 ) and CH 4 . Variation in the temperature sensitivity of CO 2 and CH 4 production and increased peat aerobicity due to enhanced growing-season evapotranspiration may alter the nature of peatland trace gas emission. As CH 4 is a powerful greenhouse gas with 34 times the warming potential of CO 2 , it is critical to understand how factors associated with global change will influence surface CO 2 and CH 4 fluxes. Here, we leverage the Spruce and Peatland Responses Under Changing Environments (SPRUCE) climate change manipulation experiment to understand the impact of a 0-9°C gradient in deep belowground warming ("Deep Peat Heat", DPH) on peat surface CO 2 and CH 4 fluxes. We find that DPH treatments increased both CO 2 and CH 4 emission. Methane production was more sensitive to warming than CO 2 production, decreasing the C-CO 2 :C-CH 4 of the respired carbon. Methane production is dominated by hydrogenotrophic methanogenesis but deep peat warming increased the δ 13 C of CH 4 suggesting an increasing contribution of acetoclastic methanogenesis to total CH 4 production with warming. Although the total quantity of C emitted from the SPRUCE Bog as CH 4 is <2%, CH 4 represents >50% of seasonal C emissions in the highest-warming treatments when adjusted for CO 2 equivalents on a 100-year timescale. These results suggest that warming in boreal regions may increase CH 4 emissions from peatlands and result in a positive feedback to ongoing warming. © 2017 John Wiley & Sons Ltd.

A DEEP HUBBLE SPACE TELESCOPE SEARCH FOR ESCAPING LYMAN CONTINUUM FLUX AT z {approx} 1.3: EVIDENCE FOR AN EVOLVING IONIZING EMISSIVITY

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

Siana, Brian; Bridge, Carrie R.; Teplitz, Harry I.

We have obtained deep Hubble Space Telescope far-UV images of 15 starburst galaxies at z {approx} 1.3 in the GOODS fields to search for escaping Lyman continuum (LyC) photons. These are the deepest far-UV images (m{sub AB} = 28.7, 3{sigma}, 1'' diameter) over this large an area (4.83 arcmin{sup 2}) and provide some of the best escape fraction constraints for any galaxies at any redshift. We do not detect any individual galaxies, with 3{sigma} limits to the LyC ({approx}700 A) flux 50-149 times fainter (in f{sub {nu}}) than the rest-frame UV (1500 A) continuum fluxes. Correcting for the mean intergalacticmore » medium (IGM) attenuation (factor {approx}2), as well as an intrinsic stellar Lyman break (factor {approx}3), these limits translate to relative escape fraction limits of f{sub esc,rel} < [0.03, 0.21]. The stacked limit is f{sub esc,rel}(3{sigma}) < 0.02. We use a Monte Carlo simulation to properly account for the expected distribution of line-of-sight IGM opacities. When including constraints from previous surveys at z {approx} 1.3 we find that, at the 95% confidence level, no more than 8% of star-forming galaxies at z {approx} 1.3 can have relative escape fractions greater than 0.50. Alternatively, if the majority of galaxies have low, but non-zero, escaping LyC, the escape fraction cannot be more than 0.04. In light of some evidence for strong LyC emission from UV-faint regions of Lyman break galaxies (LBGs) at z {approx} 3, we also stack sub-regions of our galaxies with different surface brightnesses and detect no significant LyC flux at the f{sub esc,rel} < 0.03 level. Both the stacked limits and the limits from the Monte Carlo simulation suggest that the average ionizing emissivity (relative to non-ionizing UV emissivity) at z {approx} 1.3 is significantly lower than has been observed in LBGs at z {approx} 3. If the ionizing emissivity of star-forming galaxies is in fact increasing with redshift, it would help to explain the high photoionization rates seen in the IGM at z>4 and reionization of the IGM at z>6.« less

Jovian meterology: Large-scale moist convection without a lower boundary

NASA Technical Reports Server (NTRS)

Gierasch, P. J.

1975-01-01

It is proposed that Jupiter's cloud bands represent large scale convection whose character is determined by the phase change of water at a level where the temperature is about 275K. It is argued that there are three important layers in the atmosphere: a tropopause layer where emission to space occurs; an intermediate layer between the tropopause and the water cloud base; and the deep layer below the water cloud. All arguments are only semi-quantitative. It is pointed out that these ingredients are essential to Jovian meteorology.

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

Veysey, Jason; Octaviano, Claudia; Calvin, Katherine

Mexico’s climate policy sets ambitious national greenhouse gas (GHG) emission reduction targets—30% versus a business-as-usual baseline by 2020, 50% versus 2000 by 2050. However, these goals are at odds with recent energy and emission trends in the country. Both energy use and GHG emissions in Mexico have grown substantially over the last two decades. Here, we investigate how Mexico might reverse current trends and reach its mitigation targets by exploring results from energy system and economic models involved in the CLIMACAP-LAMP project. To meet Mexico’s emission reduction targets, all modeling groups agree that decarbonization of electricity is needed, along withmore » changes in the transport sector, either to more efficient vehicles or a combination of more efficient vehicles and lower carbon fuels. These measures reduce GHG emissions as well as emissions of other air pollutants. The models find different energy supply pathways, with some solutions based on renewable energy and others relying on biomass or fossil fuels with carbon capture and storage. The economy-wide costs of deep mitigation could range from 2% to 4% of GDP in 2030, and from 7% to 15% of GDP in 2050. Our results suggest that Mexico has some flexibility in designing deep mitigation strategies, and that technological options could allow Mexico to achieve its emission reduction targets, albeit at a cost to the country.« less

Global Emissions of Nitrous Oxide: Key Source Sectors, their Future Activities and Technical Opportunities for Emission Reduction

NASA Astrophysics Data System (ADS)

Winiwarter, W.; Höglund-Isaksson, L.; Klimont, Z.; Schöpp, W.; Amann, M.

2017-12-01

Nitrous oxide originates primarily from natural biogeochemical processes, but its atmospheric concentrations have been strongly affected by human activities. According to IPCC, it is the third largest contributor to the anthropogenic greenhouse gas emissions (after carbon dioxide and methane). Deep decarbonization scenarios, which are able to constrain global temperature increase within 1.5°C, require strategies to cut methane and nitrous oxide emissions on top of phasing out carbon dioxide emissions. Employing the Greenhouse gas and Air pollution INteractions and Synergies (GAINS) model, we have estimated global emissions of nitrous oxide until 2050. Using explicitly defined emission reduction technologies we demonstrate that, by 2030, about 26% ± 9% of the emissions can be avoided assuming full implementation of currently existing reduction technologies. Nearly a quarter of this mitigation can be achieved at marginal costs lower than 10 Euro/t CO2-eq with the chemical industry sector offering important reductions. Overall, the largest emitter of nitrous oxide, agriculture, also provides the largest emission abatement potentials. Emission reduction may be achieved by precision farming methods (variable rate technology) as well as by agrochemistry (nitrification inhibitors). Regionally, the largest emission reductions are achievable where intensive agriculture and industry are prevalent (production and application of mineral fertilizers): Centrally Planned Asia including China, North and Latin America, and South Asia including India. Further deep cuts in nitrous oxide emissions will require extending reduction efforts beyond strictly technological solutions, i.e., considering behavioral changes, including widespread adoption of "healthy diets" minimizing excess protein consumption.

An automatic microseismic or acoustic emission arrival identification scheme with deep recurrent neural networks

NASA Astrophysics Data System (ADS)

Zheng, Jing; Lu, Jiren; Peng, Suping; Jiang, Tianqi

2018-02-01

The conventional arrival pick-up algorithms cannot avoid the manual modification of the parameters for the simultaneous identification of multiple events under different signal-to-noise ratios (SNRs). Therefore, in order to automatically obtain the arrivals of multiple events with high precision under different SNRs, in this study an algorithm was proposed which had the ability to pick up the arrival of microseismic or acoustic emission events based on deep recurrent neural networks. The arrival identification was performed using two important steps, which included a training phase and a testing phase. The training process was mathematically modelled by deep recurrent neural networks using Long Short-Term Memory architecture. During the testing phase, the learned weights were utilized to identify the arrivals through the microseismic/acoustic emission data sets. The data sets were obtained by rock physics experiments of the acoustic emission. In order to obtain the data sets under different SNRs, this study added random noise to the raw experiments' data sets. The results showed that the outcome of the proposed method was able to attain an above 80 per cent hit-rate at SNR 0 dB, and an approximately 70 per cent hit-rate at SNR -5 dB, with an absolute error in 10 sampling points. These results indicated that the proposed method had high selection precision and robustness.

Fabrication of n-ZnO/ p-Si (100) and n-ZnO:Al/ p-Si (100) Heterostructures and Study of Current-Voltage, Capacitance-Voltage and Room-Temperature Photoluminescence

NASA Astrophysics Data System (ADS)

Shah, M. A. H.; Khan, M. K. R.; Tanveer Karim, A. M. M.; Rahman, M. M.; Kamruzzaman, M.

2018-01-01

Heterojunction diodes of n-ZnO/ p-Si (100) and n-ZnO:Al/ p-Si (100) were fabricated by spray pyrolysis technique. X-ray diffraction (XRD), energy dispersive x-ray spectroscopy (EDX), and field emission scanning electron microscopy (FESEM) were used to characterize the as-prepared samples. The XRD pattern indicates the hexagonal wurzite structure of zinc oxide (ZnO) and Al-doped ZnO (AZO) thin films grown on Si (100) substrate. The compositional analysis by EDX indicates the presence of Al in the AZO structure. The FESEM image indicates the smooth and compact surface of the heterostructures. The current-voltage characteristics of the heterojunction confirm the rectifying diode behavior at different temperatures and illumination intensities. For low forward bias voltage, the ideality factors were determined to be 1.24 and 1.38 for un-doped and Al-doped heterostructures at room temperature (RT), respectively, which indicates the good diode characteristics. The capacitance-voltage response of the heterojunctions was studied for different oscillation frequencies. From the 1/ C 2- V plot, the junction built-in potentials were found 0.30 V and 0.40 V for un-doped and Al-doped junctions at RT, respectively. The differences in built-in potential for different heterojunctions indicate the different interface state densities of the junctions. From the RT photoluminescence (PL) spectrum of the n-ZnO/ p-Si (100) heterostructure, an intense main peak at near band edge (NBE) 378 nm (3.28 eV) and weak deep-level emissions (DLE) centered at 436 nm (2.84 eV) and 412 nm (3.00 eV) were observed. The NBE emission is attributed to the radiative recombination of the free and bound excitons and the DLE results from the radiative recombination through deep level defects.

Poole-Frenkel effect in sputter-deposited CuAlO2+x nanocrystals

NASA Astrophysics Data System (ADS)

Narayan Banerjee, Arghya; Joo, Sang Woo

2013-04-01

Field-assisted thermionic emission within a sputter-deposited, nanocrystalline thin film of CuAlO2.06 is observed for the first time, and explained in terms of the Poole-Frenkel model. The presence of adsorbed oxygen ions as trap-states at the grain boundary regions of the nanostructured thin film is considered to manifest this phenomenon. Under an applied field, the barrier of the trap potential is lowered and thermal emission of charge carriers takes place at different sample temperatures to induce nonlinearity in the current (I)-voltage (V) characteristics of the nanomaterial. Fitting of the Poole-Frenkel model with the I-V data shows that the nonlinearity is effective above 50 V under the operating conditions. Calculations of the energy of the trap level, acceptor level and Fermi level reveal the existence of deep level trap-states and a shallow acceptor level with acceptor concentration considerably higher than the trap-states. Hall measurements confirm the p-type semiconductivity of the film, with a hole concentration around 1018 cm-3. Thermopower measurements give a room-temperature Seebeck coefficient around 130 μV K-1. This temperature-dependent conductivity enhancement within CuAlO2 nanomaterial may find interesting applications in transparent electronics and high-voltage applications for power supply networks.

Poole-Frenkel effect in sputter-deposited CuAlO(2+x) nanocrystals.

PubMed

Banerjee, Arghya Narayan; Joo, Sang Woo

2013-04-26

Field-assisted thermionic emission within a sputter-deposited, nanocrystalline thin film of CuAlO2.06 is observed for the first time, and explained in terms of the Poole-Frenkel model. The presence of adsorbed oxygen ions as trap-states at the grain boundary regions of the nanostructured thin film is considered to manifest this phenomenon. Under an applied field, the barrier of the trap potential is lowered and thermal emission of charge carriers takes place at different sample temperatures to induce nonlinearity in the current (I)-voltage (V) characteristics of the nanomaterial. Fitting of the Poole-Frenkel model with the I-V data shows that the nonlinearity is effective above 50 V under the operating conditions. Calculations of the energy of the trap level, acceptor level and Fermi level reveal the existence of deep level trap-states and a shallow acceptor level with acceptor concentration considerably higher than the trap-states. Hall measurements confirm the p-type semiconductivity of the film, with a hole concentration around 10(18) cm(-3). Thermopower measurements give a room-temperature Seebeck coefficient around 130 μV K(-1). This temperature-dependent conductivity enhancement within CuAlO2 nanomaterial may find interesting applications in transparent electronics and high-voltage applications for power supply networks.

Effect of pressure-assisted thermal annealing on the optical properties of ZnO thin films.

PubMed

Berger, Danielle; Kubaski, Evaldo Toniolo; Sequinel, Thiago; da Silva, Renata Martins; Tebcherani, Sergio Mazurek; Varela, José Arana

2013-01-01

ZnO thin films were prepared by the polymeric precursor method. The films were deposited on silicon substrates using the spin-coating technique, and were annealed at 330 °C for 32 h under pressure-assisted thermal annealing and under ambient pressure. Their structural and optical properties were characterized, and the phases formed were identified by X-ray diffraction. No secondary phase was detected. The ZnO thin films were also characterized by field-emission scanning electron microscopy, Fourier transform infrared spectroscopy, photoluminescence and ultraviolet emission intensity measurements. The effect of pressure on these thin films modifies the active defects that cause the recombination of deep level states located inside the band gap that emit yellow-green (575 nm) and orange (645 nm) photoluminescence. Copyright © 2012 John Wiley & Sons, Ltd.

Transportation Energy Futures Series: Alternative Fuel Infrastructure Expansion: Costs, Resources, Production Capacity, and Retail Availability for Low-Carbon Scenarios

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

Melaina, W.; Heath, Garvin; Sandor, Debra

2013-04-01

The petroleum-based transportation fuel system is complex and highly developed, in contrast to the nascent low-petroleum, low-carbon alternative fuel system. This report examines how expansion of the low-carbon transportation fuel infrastructure could contribute to deep reductions in petroleum use and greenhouse gas (GHG) emissions across the U.S. transportation sector. Three low-carbon scenarios, each using a different combination of low-carbon fuels, were developed to explore infrastructure expansion trends consistent with a study goal of reducing transportation sector GHG emissions to 80% less than 2005 levels by 2050.These scenarios were compared to a business-as-usual (BAU) scenario and were evaluated with respect tomore » four criteria: fuel cost estimates, resource availability, fuel production capacity expansion, and retail infrastructure expansion.« less

Luminescence from Zinc Oxide Nanostructures and Polymers and their Hybrid Devices

PubMed Central

Willander, Magnus; Nur, Omer; Sadaf, Jamil Rana; Qadir, Muhammad Israr; Zaman, Saima; Zainelabdin, Ahmed; Bano, Nargis; Hussain, Ijaz

2010-01-01

Zinc oxide (ZnO) is a strong luminescent material, as are several polymers. These two materials have distinct drawbacks and advantages, and they can be combined to form nanostructures with many important applications, e.g., large-area white lighting. This paper discusses the origin of visible emission centers in ZnO nanorods grown with different approaches. White light emitting diodes (LEDs) were fabricated by combining n-ZnO nanorods and hollow nanotubes with different p-type materials to form heterojunctions. The p-type component of the hybrids includes p-SiC, p-GaN, and polymers. We conclude by analyzing the electroluminescence of the different light emitting diodes we fabricated. The observed optical, electrical, and electro-optical characteristics of these LEDs are discussed with an emphasis on the deep level centers that cause the emission.

Highly Efficient Solution-Processed Deep-Red Organic Light-Emitting Diodes Based on an Exciplex Host Composed of a Hole Transporter and a Bipolar Host.

PubMed

Huang, Manli; Jiang, Bei; Xie, Guohua; Yang, Chuluo

2017-10-19

With the aim to achieve highly efficient deep-red emission, we introduced an exciplex forming cohost, 4,4',4″-tris(3-methylphenylphenylamino)triphenylamine (m-MTDATA): 2,5-bis(2-(9H-carbazol-9-yl)phenyl)-1,3,4-oxadiazole (o-CzOXD) (1:1). Due to the efficient triplet up-conversion processes upon the exciplex forming cohost, excellent performances of the devices were achieved with deep-red emission. Using the heteroleptic iridium complexes as the guest dopants, the solution-processed deep-red phosphorescent organic light-emitting diodes (PhOLEDs) with the iridium(III) bis(6-(4-(tert-butyl)phenyl)phenanthridine)acetylacetonate [(TP-BQ) 2 Ir(acac)]-based phosphorescent emitter exhibited an electroluminescent peak at 656 nm and a maximum external quantum efficiency (EQE) of 11.9%, which is 6.6 times that of the device based on the guest emitter doped in the polymer-based cohost. The unique exciplex with a typical hole transporter and a bipolar material is ideal and universal for hosting the red PhOLEDs and tremendously improves the device performances.

Rigid biimidazole ancillary ligands as an avenue to bright deep blue cationic iridium(iii) complexes.

PubMed

Henwood, Adam F; Evariste, Sloane; Slawin, Alexandra M Z; Zysman-Colman, Eli

2014-01-01

Herein we report the synthesis and optoelectronic characterisation of three deep blue-emitting cationic iridium complexes, of the form [Ir(dFppy)(2)(N^N)]PF(6), bearing biimidazole-type N^N ancillary ligands (dFppyH = 2-(2,4-difluorophenyl)pyridine). Complex 1 contains the parent biimidazole, biim, while 2 contains a dimethylated analog, dMebiim, and 3 contains an ortho-xylyl-tethered biimidzole, o-xylbiim. We explore a strategy of tethering the biimidazole in order to rigidify the complex and increase the photoluminescent quantum yield, culminating in deep blue (λ(max): 457 nm in MeOH at 298 K) ligand-centered emission with a very high photoluminescent quantum yield of 68% and microsecond emission lifetime. Density functional theory calculations elucidate the origin of such disparate excited state kinetics across this series, especially in light of virtually identical optoelectronic properties observed for these compounds.

Deep-Ultraviolet Luminescence of Rocksalt-Structured Mg x Zn1-x O (x > 0.5) Films on MgO Substrates

NASA Astrophysics Data System (ADS)

Kaneko, Kentaro; Tsumura, Keiichi; Ishii, Kyohei; Onuma, Takayoshi; Honda, Tohru; Fujita, Shizuo

2018-04-01

Rocksalt-structured Mg x Zn1-x O films with Mg composition x of 0.47, 0.57, and 0.64 were grown on (100)-oriented MgO substrates using mist chemical vapor deposition. Cathodoluminescence measurements showed deep ultraviolet (DUV) emission peaking at 4.88 eV (254 nm), 5.15 eV (241 nm), and 5.21 eV (238 nm), respectively, at 12 K. The peak energies were lower than the band gap energies by ca. 1 eV, suggesting that the deep ultraviolet (DUV) emission may be recognized as near band edge luminescence but is associated with impurities, defects, or band fluctuations. The use of carbon-free precursors in the growth is suggested to eliminate carbon impurities and to improve the optical properties of Mg x Zn1-x O.

Quicklook Constituent Abundance and Stretch Parameter Retrieval for the Juno Microwave Radiometer using Neural Networks

NASA Astrophysics Data System (ADS)

Bellotti, A.; Steffes, P. G.

2016-12-01

The Juno Microwave Radiometer (MWR) has six channels ranging from 1.36-50 cm and the ability to peer deep into the Jovian atmosphere. An Artifical Neural Network algorithm has been developed to rapidly perform inversion for the deep abundance of ammonia, the deep abundance of water vapor, and atmospheric "stretch" (a parameter that reflects the deviation from a wet adiabate in the higher atmosphere). This algorithm is "trained" by using simulated emissions at the six wavelengths computed using the Juno atmospheric microwave radiative transfer (JAMRT) model presented by Oyafuso et al. (This meeting). By exploiting the emission measurements conducted at six wavelengths and at various incident angles, the neural network can provide preliminary results to a useful precison in a computational method hundreds of times faster than conventional methods. This can quickly provide important insights into the variability and structure of the Jovian atmosphere.

Could US mayors achieve the entire US Paris climate target?

NASA Astrophysics Data System (ADS)

Gurney, K. R.; Huang, J.; Hutchins, M.; Liang, J.

2017-12-01

After the recent US Federal Administration announcement not to adhere to the Paris Accords, 359 mayors (and counting) in the US pledged to maintain their commitments, reducing emissions within their jurisdictions by 26-28% from their 2005 levels by the year 2025. While important, this leaves a large portion of the US landscape, and a large amount of US emissions, outside of the Paris commitment. With Federal US policy looking unlikely to change, could additional effort by US cities overcome the gap in national policy and achieve the equivalent US national Paris commitment? How many cities would be required and how deep would reductions need to be? Up until now, this question could not be reliably resolved due to lack of data at the urban scale. Here, we answer this question with new data - the Vulcan V3.0 FFCO2 emissions data product - through examination of the total US energy related CO2 emissions from cities. We find that the top 500 urban areas in the US could meet the national US commitment to the Paris Accords with a reduction of roughly 30% below their 2015 levels by the year 2025. This is driven by the share of US emissions emanating from cities, particularly the largest cohort. Indeed, as the number of urban areas taking on CO2 reduction targets grows, the less the reduction burden on any individual city. In this presentation, we provide an analysis of US urban CO2 emissions and US climate policy, accounting for varying definitions of urban areas, emitting sectors and the tradeoff between the number of policy-active cities and the CO2 reduction burden.

Deep Sea Memory of High Atmospheric CO2 Concentration

NASA Astrophysics Data System (ADS)

Mathesius, Sabine; Hofmann, Matthias; Caldeira, Ken; Schellnhuber, Hans Joachim

2015-04-01

Carbon dioxide removal (CDR) from the atmosphere has been proposed as a powerful measure to mitigate global warming and ocean acidification. Planetary-scale interventions of that kind are often portrayed as "last-resort strategies", which need to weigh in if humankind keeps on enhancing the climate-system stock of CO2. Yet even if CDR could restore atmospheric CO2 to substantially lower concentrations, would it really qualify to undo the critical impacts of past emissions? In the study presented here, we employed an Earth System Model of Intermediate Complexity (EMIC) to investigate how CDR might erase the emissions legacy in the marine environment, focusing on pH, temperature and dissolved oxygen. Against a background of a world following the RCP8.5 emissions path ("business-as-usual") for centuries, we simulated the effects of two massive CDR interventions with CO2 extraction rates of 5 GtC yr-1 and 25 GtC yr-1, respectively, starting in 2250. We found that the 5 GtC yr-1 scheme would have only minor ameliorative influence on the oceans, even after several centuries of application. By way of contrast, the extreme 25 GtC yr-1 scheme eventually leads to tangible improvements. However, even with such an aggressive measure, past CO2 emissions leave a substantial legacy in the marine environment within the simulated period (i.e., until 2700). In summary, our study demonstrates that anthropogenic alterations of the oceans, caused by continued business-as-usual emissions, may not be reversed on a multi-centennial time scale by the most aspirational geoengineering measures. We also found that a transition from the RCP8.5 state to the state of a strong mitigation scenario (RCP2.6) is not possible, even under the assumption of extreme extraction rates (25 GtC yr-1). This is explicitly demonstrated by simulating additional scenarios, starting CDR already in 2150 and operating until the atmospheric CO2 concentration reaches 280 ppm and 180 ppm, respectively. The simulated massive CDR interventions eventually bring down the global mean pH value to the RCP2.6 level, yet cannot restore a similarly homogenous distribution - while the pH of the upper ocean returns to the preindustrial value or even exceed it (in the 180 ppm scenario), the deep ocean remains acidified. The deep ocean is out of contact with the atmosphere and therefore unreachable by atmospheric CDR. Our results suggest that the proposition that the marine consequences of early emissions reductions are comparable to those of delayed reductions plus CDR is delusive and that a policy that allows for emitting CO2 today in the hopes of removing it tomorrow is bound to generate substantial regrets.

Decarbonizing the international shipping industry: Solutions and policy recommendations.

PubMed

Wan, Zheng; El Makhloufi, Abdel; Chen, Yang; Tang, Jiayuan

2018-01-01

Ship-source greenhouse gas (GHG) emissions could increase by up to 250% by 2050 from their 2012 levels, owing to increasing global freight volumes. Binding international legal agreements to regulate GHGs, however, are lacking as technical solutions remain expensive, and crucial industrial support is absent. In 2003, the International Maritime Organization adopted Resolution A.963 (23) to regulate shipping CO 2 emissions via technical, operational, and market-based routes. However, progress has been slow and uncertain; there is no concrete emission reduction target or definitive action plan. Yet, a full-fledged roadmap may not even emerge until 2023. In this policy analysis, we revisit the progress of technical, operational, and market-based routes and the associated controversies. We argue that 1) a performance-based index, though good-intentioned, has loopholes affecting meaningful CO 2 emission reductions driven by technical advancements; 2) using slow steaming to cut energy consumption stands out among all operational solutions thanks to its immediate and obvious results, but with the already slow speed in practice, this single source has limited emission reduction potential; 3) without a technology-savvy shipping industry, a market-based approach is essentially needed to address the environmental impact. To give shipping a 50:50 chance for contributing fairly and proportionately to keep global warming below 2°C, deep emission reductions should occur soon. Copyright © 2017 Elsevier Ltd. All rights reserved.

Gaseous and particulate polycyclic aromatic hydrocarbons (PAHs) emissions from commercial restaurants in Hong Kong.

PubMed

Chen, Yi; Ho, Kin Fai; Ho, Steven Sai Hang; Ho, Wing Kei; Lee, Shun Cheng; Yu, Jian Zhen; Sit, Elber Hoi Leung

2007-12-01

Commercial cooking emissions are important air pollution sources in a heavily urbanized city. Exhaust samples were collected in six representative commercial kitchens including Chinese restaurants, Western restaurants, and Western fast-food restaurants in Hong Kong during peak lunch hours. Both gaseous and particulate emissions were evaluated. Eight gaseous and twenty-two particulate polycyclic aromatic hydrocarbons (PAHs) were quantified in this study. In the gaseous phase, naphthalene (67-89%) was the most abundant PAH in all of the exhaust samples. The contribution of acenaphthylene in the gaseous phase was significantly higher in emissions from the Chinese restaurants, whereas fluorene was higher in emissions from the Western cooking style restaurants (i.e., Western restaurants and Western fast-food restaurants). Pyrene is the most abundant particulate PAH in the Chinese restaurants (14-49%) while its contribution was much lower in the Western cooking style restaurants (10-22%). Controlled cooking conditions were monitored in a staff canteen to compare the emissions from several different local cooking styles, including deep frying, steaming, and mixed cooking styles (combination of steaming and frying). Deep frying produced the highest amount of total gaseous PAHs, 6 times higher than the steaming. However, steaming produced the highest particulate emissions. The estimated annual gaseous PAH emissions for the Chinese restaurants, Western restaurants, and Western fast-food restaurants were 255, 173, and 20.2 t y(-1) whereas 252, 1.9, and 0.4 t y(-1) were estimated for particulate phase PAH emissions. The study provides useful information and estimates for PAH emissions from commercial cooking exhaust in Hong Kong.

New ultra deep blue emitters based on chrysene chromophores

NASA Astrophysics Data System (ADS)

Shin, Hwangyu; Kang, Seokwoo; Jung, Hyocheol; Lee, Hayoon; Lee, Jaehyun; Kim, Beomjin; Park, Jongwook

2016-09-01

Chrysene, which has a wide band gap, was selected as an emission core to develop and study new materials that emit ultra-deep-blue light with high efficiency. Six compounds introducing various side groups were designed and synthesized: 6, 12-bis(30,50-diphenylphenyl)chrysene (TP-C-TP), 6-(30,50-diphenylphenyl)-12-(3,5-diphenylbiphenyl-400-yl)chrysene (TP-C-TPB) and 6,12-bis(300,500-diphenylbiphenyl-40-yl)chrysene (TPB-C-TPB), which contained bulky aromatic si de groups; and N,N,N0 ,N0-tetraphenyl-chrysene-6,12-diamine (DPA-C-DPA), [12-(4-diphenylamino-phenyl)-chrysene-6-yl]-diphenylamine(DPA-C-TPA) and 6,12-bis[4-(diphenylamino)phenyl]chrysene (TPA-C-TPA), which contained aromatic amine groups, were designed to afford improved hole injection properties. The synthesized materials showed maxi mum absorption wavelengths at 342-402 nm in the film state and exhibited deep-blue photoluminescence (PL) emission s at 417-464 nm. The use of TP-C-TPB in a non-doped organic light emitting diode (OLED) device resulted in ultra-deep-blue emission with an external quantum efficiency (EQE) of 4.02% and Commission Internationale de L'Eclairage coo rdinates (CIE x, y) of (0.154, 0.042) through effective control of the internal conjugation length and suppression of the p -p* stacking. The use of TPA-C-TPA, which includes an aromatic amine side group, afforded an excellent EQE of 4.83 % and excellent color coordinates CIE x, y of (0.147, 0.077).

Atmospheric Hg emissions from preindustrial gold and silver extraction in the Americas: a reevaluation from lake-sediment archives.

PubMed

Engstrom, Daniel R; Fitzgerald, William F; Cooke, Colin A; Lamborg, Carl H; Drevnick, Paul E; Swain, Edward B; Balogh, Steven J; Balcom, Prentiss H

2014-06-17

Human activities over the last several centuries have transferred vast quantities of mercury (Hg) from deep geologic stores to actively cycling earth-surface reservoirs, increasing atmospheric Hg deposition worldwide. Understanding the magnitude and fate of these releases is critical to predicting how rates of atmospheric Hg deposition will respond to future emission reductions. The most recently compiled global inventories of integrated (all-time) anthropogenic Hg releases are dominated by atmospheric emissions from preindustrial gold/silver mining in the Americas. However, the geophysical evidence for such large early emissions is equivocal, because most reconstructions of past Hg-deposition have been based on lake-sediment records that cover only the industrial period (1850-present). Here we evaluate historical changes in atmospheric Hg deposition over the last millennium from a suite of lake-sediment cores collected from remote regions of the globe. Along with recent measurements of Hg in the deep ocean, these archives indicate that atmospheric Hg emissions from early mining were modest as compared to more recent industrial-era emissions. Although large quantities of Hg were used to extract New World gold and silver beginning in the 16th century, a reevaluation of historical metallurgical methods indicates that most of the Hg employed was not volatilized, but rather was immobilized in mining waste.

Pathways to Mexico’s climate change mitigation targets: A multi-model analysis

DOE PAGES

Veysey, Jason; Octaviano, Claudia; Calvin, Katherine; ...

2015-04-25

Mexico’s climate policy sets ambitious national greenhouse gas (GHG) emission reduction targets—30% versus a business-as-usual baseline by 2020, 50% versus 2000 by 2050. However, these goals are at odds with recent energy and emission trends in the country. Both energy use and GHG emissions in Mexico have grown substantially over the last two decades. Here, we investigate how Mexico might reverse current trends and reach its mitigation targets by exploring results from energy system and economic models involved in the CLIMACAP-LAMP project. To meet Mexico’s emission reduction targets, all modeling groups agree that decarbonization of electricity is needed, along withmore » changes in the transport sector, either to more efficient vehicles or a combination of more efficient vehicles and lower carbon fuels. These measures reduce GHG emissions as well as emissions of other air pollutants. The models find different energy supply pathways, with some solutions based on renewable energy and others relying on biomass or fossil fuels with carbon capture and storage. The economy-wide costs of deep mitigation could range from 2% to 4% of GDP in 2030, and from 7% to 15% of GDP in 2050. Our results suggest that Mexico has some flexibility in designing deep mitigation strategies, and that technological options could allow Mexico to achieve its emission reduction targets, albeit at a cost to the country.« less

Comparing (Semi-) Analytic Solutions Used to Model the Impact of Deep Carbon Injection on the Displacement and Pressurization of the Resident Brine

EPA Science Inventory

Injection of carbon dioxide into deep saline formations is seen as one possible technology for mitigating carbon emissions from utilities. The safety of the sequestered carbon dioxide is the focus of many studies with leakage through faults or abandoned wells as some of the main...

Stability of peatland carbon to rising temperatures

Treesearch

R. M. Wilson; A. M. Hopple; M. M. Tfaily; S. D. Sebestyen; C. W. Schadt; L. Pfeifer-Meister; C. Medvedeff; K. J. McFarlane; J. E. Kostka; M. Kolton; R.K. Kolka; L. A. Kluber; J. K. Keller; T. P. Guilderson; N. A. Griffiths; J. P. Chanton; S. D. Bridgham; P. J. Hanson

2016-01-01

Peatlands contain one-third of soil carbon (C), mostly buried in deep, saturated anoxic zones (catotelm). The response of catotelm C to climate forcing is uncertain, because prior experiments have focused on surface warming. We show that deep peat heating of a 2 m-thick peat column results in an exponential increase in CH4 emissions. However,...

Demonstration of transverse-magnetic deep-ultraviolet stimulated emission from AlGaN multiple-quantum-well lasers grown on a sapphire substrate

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

Li, Xiao-Hang, E-mail: xli@gatech.edu, E-mail: dupuis@gatech.edu; Kao, Tsung-Ting; Satter, Md. Mahbub

2015-01-26

We demonstrate transverse-magnetic (TM) dominant deep-ultraviolet (DUV) stimulated emission from photo-pumped AlGaN multiple-quantum-well lasers grown pseudomorphically on an AlN/sapphire template by means of photoluminescence at room temperature. The TM-dominant stimulated emission was observed at wavelengths of 239, 242, and 243 nm with low thresholds of 280, 250, and 290 kW/cm{sup 2}, respectively. In particular, the lasing wavelength of 239 nm is shorter compared to other reports for AlGaN lasers grown on foreign substrates including sapphire and SiC. The peak wavelength difference between the transverse-electric (TE)-polarized emission and TM-polarized emission was approximately zero for the lasers in this study, indicating the crossover of crystal-fieldmore » split-off hole and heavy-hole valence bands. The rapid variation of polarization between TE- and TM-dominance versus the change in lasing wavelength from 243 to 249 nm can be attributed to a dramatic change in the TE-to-TM gain coefficient ratio for the sapphire-based DUV lasers in the vicinity of TE-TM switch.« less

Cadmium-free quantum dot light emitting devices: energy-transfer realizing pure blue emission.

PubMed

Ji, Wenyu; Jing, Pengtao; Fan, Yi; Zhao, Jialong; Wang, Yunjun; Kong, Xianggui

2013-01-01

In this study, deep blue, pure electroluminescence (EL) at 441.5 nm from a ZnSe/ZnS quantum dot light-emitting device (QD-LED) is obtained by using poly (4-butylphenyl-diphenyl-amine) (poly-TPD) as the hole-transport layer (HTL) to open up the channel for energy transfer from poly-TPD to QDs. The emission originating from HTL is observed in the QD-LED with N,N'-bis (tolyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine functionalized with two styryl groups (2-TPD) as the HTL due to inefficient energy-transfer from 2-TPD to QDs. The poly-TPD based device exhibits color-saturated blue emission with a narrow spectral bandwidth of full width at half maximum (~17.2 nm). These results explore the operating mechanism of the QD EL and signify a remarkable progress in deep blue QD-LEDs based on environmental-friendly QD materials.

Mid-Holocene change in types of degassing volcanoes, using indium in Antarctic ice as a tracer of volcanic source type

USGS Publications Warehouse

Hinkley, T.; Matsumoto, A.

2007-01-01

Proportions of trace metals in Antarctic ice samples indicate that the type of volcanoes that dominated atmospheric emissions changed at about the middle of the Holocene from relatively mafic, deep source volcanoes to more silicic, shallower-source volcanoes. We base this inference on the strong contrast in the abundances of the trace metal indium (In), relative to other trace metals present in ice, deposited at different times in the past, and on contrasting In abundances in modern emissions of volcanoes of different types. Indium is more abundant in the emissions of deep-source mafic volcanoes than in more felsic, shallower-source volcanoes. Earlier workers have shown, on the basis of petrologic and some meteoritic evidence, that In may be partitioned to the interiors (stony mantles) of differentiated planets, or enriched in the liquids of partly crystallized mafic melts.

Non-Ideal Properties of Gallium Nitride Based Light-Emitting Diodes

NASA Astrophysics Data System (ADS)

Shan, Qifeng

The spectacular development of gallium nitride (GaN) based light-emitting diodes (LEDs) in recent years foreshadows a new era for lighting. There are still several non-ideal properties of GaN based LEDs that hinder their widespread applications. This dissertation studies these non-ideal properties including the large reverse leakage current, large subthreshold forward leakage current, an undesired parasitic cyan luminescence and high-concentration deep levels in GaInN blue LEDs. This dissertation also studies the thermal properties of GaInN LEDs. Chapter 1 gives a brief introduction of non-ideal properties of GaN based LEDs. The leakage current of GaN based LEDs, defects in epitaxially grown GaN devices, and doping problems of p-type GaN materials are discussed. The transient junction temperature measurement technique for GaN based LEDs is introduced. The leakage current of an LED includes the subthreshold forward leakage current and the reverse leakage current. The leakage current of GaN based LEDs affects the reliability, electrostatic discharge resilience, and sub-threshold power consumption. In Chapter 2, the reverse leakage current of a GaInN LED is analyzed by temperaturedependent current-voltage measurements. At low temperature, the reverse leakage current is attributed to the variable-range-hopping conduction. At high temperature, the reverse leakage current is attributed to a thermally-assisted multi-step tunneling. The thermal activation energies (95 meV ~ 162 meV), extracted from the Arrhenius plot for the reverse current in the high-temperature range, indicate a thermally activated tunneling process. Additional room-temperature capacitance-voltage (C-V) measurements are performed to obtain information on the depletion width and doping concentration of the LED. The average internal electric field is estimated by the C-V measurements. The strong internal electric field enhances the thermal emission of electrons in the thermally-assisted multi-step tunneling process. Another problem of GaInN blue LEDs is the undesired parasitic cyan emission band. The undesired parasitic emission band strongly influence the electrical and optical properties of GaInN blue LEDs including the subthreshold forward leakage current and the color purity of the emission. In Chapter 3 , GaInN blue LEDs emitting at 445 nm with a parasitic cyan (blue-green) emission band (480 nm), which dominates the emission spectrum at low injection current, are analyzed. Photoluminescence using resonant optical excitation shows that the cyan emission originates from the active region of the LED. The current- and excitation-density-dependent blue-to-cyan intensity ratio reveals that the cyan emission is due to a transition from the conduction band to a Mg acceptor having diffused into the last-grown quantum well of the active region. The Mg in the active region provides an additional carrier-transport path, and therefore can explain the high subthreshold forward leakage current that is measured in these LEDs. Deep levels in GaN-based materials strongly affect the electrical and optical properties of GaN-based LEDs. Chapter 4 describes the basic principle and the setup of a deep-level transient spectroscopy (DLTS) measurement system. This DLTS system is used to determine the concentration and thermal activation energy of deep levels in the depletion region of the GaInN LED. Two types of hole traps in the n-type side of the depletion region are observed in the DLTS measurement. The thermal activation energies of these two types of hole traps are compared with the results reported in literature. The hole trap associated with the major DLTS peak with a thermal activation energy of 0.80 eV is presumably related to the “yellow luminescence band”. Self-heating of LEDs is an important issue that affects the efficiency and reliability. In Chapter 5, the thermal properties, including thermal time constants, of GaN LEDs are analyzed. The transient-junction-temperature behavior of unpackaged LED chips is described by a single time constant, which is the product of a thermal resistance Rth and a thermal capacitance Cth. Furthermore, a multistage RthCth thermal model for packaged LEDs is developed. The transient response of the junction temperature of LEDs after the power is switched on or switched off can be described by a multi-exponential function. Each time constant of this function is approximately the product of a thermal resistance, Rth, and a thermal capacitance, Cth. The transient junction temperature after the power is switched off is measured for a high-power flip-chip LED by the forward-voltage method. A two-stage RthCth model is used to analyze the thermal properties of the packaged LED. Two time constants, 2.72 ms and 18.7 ms are extracted from the junction temperature decay measurement and attributed to the thermal time constant of the LED GaN / sapphire chip and LED Si submount, respectively.

Impacts of National Decarbonization Targets for Subnational Societal Priorities

NASA Astrophysics Data System (ADS)

Peng, W.; Iyer, G.

2017-12-01

Carbon mitigation has well-recognized linkages with other environmental and socioeconomic priorities, such as air pollution, economic development, employment, etc. While climate change is a global issue, many other societal priorities are local concerns. Since local efforts form the pillars of achieving co-benefits and avoiding dis-benefits at the national level, it is critical to go beyond national-level analyses and focus on the synergies and tradeoffs at the subnational level. Here we use the United States as an example to evaluate the impacts of mid-century national-level deep decarbonization target for state-level societal priorities. Based on the Global Change Assessment Model with state-level details for the US (GCAM-USA), we design two mid-century scenarios: A Reference scenario that assumes the U.S. undertakes no additional climate mitigation policy, and a Deep Decarbonization Scenario that assumes the U.S. achieves the NDC goal through 2025 (26-28% reduction relative to 2005 levels) and then follows a straight-line trajectory to 80% reductions in economy-wide GHG emissions by 2050 relative to 2005. We then compare these two scenarios for a variety of metrics of carbon mitigation and other societal priorities in 2050. We highlight two findings. First, the synergies and tradeoffs of carbon mitigation with other societal goals at the subnational level can be quite different from the national level. For example, while deep decarbonization could improve national energy security by reducing the overall dependence on energy imports, it may exacerbate energy independence goals for some states by increasing inter-state electricity imports. Second, achieving national-level decarbonization target could result in unequal regional impacts across states. We find uneven geographic impacts for air pollution (more co-reductions occur in the eastern states), economic costs (energy prices increase more in the northeastern states) and employment (jobs increase in the western states where renewable capacity scales up, and decrease in the northeast due to reduced mining activities). Therefore, local decision makers may find decarbonization in line or contradicting with the most urgent local priority to address, highlighting the importance of evaluating the synergies and tradeoffs at the subnational level.

Deep Reductions in Greenhouse Gas Emissions from the California Transportation Sector: Dynamics in Vehicle Fleet and Energy Supply Transitions to Achieve 80% Reduction in Emissions from 1990 Levels by 2050

NASA Astrophysics Data System (ADS)

Leighty, Wayne Waterman

California's "80in50" target for reducing greenhouse gas emissions to 80 percent below 1990 levels by the year 2050 is based on climate science rather than technical feasibility of mitigation. As such, it raises four fundamental questions: is this magnitude of reduction in greenhouse gas emissions possible, what energy system transitions over the next 40 years are necessary, can intermediate policy goals be met on the pathway toward 2050, and does the path of transition matter for the objective of climate change mitigation? Scenarios for meeting the 80in50 goal in the transportation sector are modelled. Specifically, earlier work defining low carbon transport scenarios for the year 2050 is refined by incorporating new information about biofuel supply. Then transition paths for meeting 80in50 scenarios are modelled for the light-duty vehicle sub-sector, with important implications for the timing of action, rate of change, and cumulative greenhouse gas emissions. One aspect of these transitions -- development in the California wind industry to supply low-carbon electricity for plug-in electric vehicles -- is examined in detail. In general, the range of feasible scenarios for meeting the 80in50 target is narrow enough that several common themes are apparent: electrification of light-duty vehicles must occur; continued improvements in vehicle efficiency must be applied to improving fuel economy; and energy carriers must de-carbonize to less than half of the carbon intensity of gasoline and diesel. Reaching the 80in50 goal will require broad success in travel demand reduction, fuel economy improvements and low-carbon fuel supply, since there is little opportunity to increase emission reductions in one area if we experience failure in another. Although six scenarios for meeting the 80in50 target are defined, only one also meets the intermediate target of reducing greenhouse gas emissions to 1990 levels by the year 2020. Furthermore, the transition path taken to reach any one of these scenarios can differ in cumulative emissions by more than 25 percent. Since cumulative emissions are the salient factor for climate change mitigation and the likelihood of success is an important consideration, initiating action immediately to begin the transitions indicated for achieving the 80in50 goal is found to be prudent.

Electrical current flow at conductive nanowires formed in GaN thin films by a dislocation template technique

NASA Astrophysics Data System (ADS)

Amma, Shin-ichi; Tokumoto, Yuki; Edagawa, Keiichi; Shibata, Naoya; Mizoguchi, Teruyasu; Yamamoto, Takahisa; Ikuhara, Yuichi

2010-05-01

Conductive nanowires were fabricated in GaN thin film by selectively doping of Al along threading dislocations. Electrical current flow localized at the nanowires was directly measured by a contact mode atomic force microscope. The current flow at the nanowires was considered to be Frenkel-Poole emission mode, suggesting the existence of the deep acceptor level along the nanowires as a possible cause of the current flow. The results obtained in this study show the possibility for fabricating nanowires using pipe-diffusion at dislocations in solid thin films.

Characterisation of retention properties of charge-trapping memory cells at low temperatures

NASA Astrophysics Data System (ADS)

Yurchuk, E.; Bollmann, J.; Mikolajick, T.

2009-09-01

The density of states of deep level centers in silicon oxynitride layer of SONOS memory cells are calculated from temperature dependent retention measurement. The dominating charge loss mechanisms are direct trap-to-band tunneling (TB) and thermally stimulated emission (TE). Retention measurements at low temperatures (80 - 300K) will be dominated by TE from more "shallow" traps with energies below 1eV and by TB. Taking into account both independent and rival processes the density of states could be calculated self consisting. The results are in excellent agreement with elsewhere published data.

Seismic risk mitigation in deep level South African mines by state of the art underground monitoring - Joint South African and Japanese study

NASA Astrophysics Data System (ADS)

Milev, A.; Durrheim, R.; Nakatani, M.; Yabe, Y.; Ogasawara, H.; Naoi, M.

2012-04-01

Two underground sites in a deep level gold mine in South Africa were instrumented by the Council for Scientific and Industrial Research (CSIR) with tilt meters and seismic monitors. One of the sites was also instrumented by JApanese-German Underground Acoustic emission Research in South Africa (JAGUARS) with a small network, approximately 40m span, of eight Acoustic Emission (AE) sensors. The rate of tilt, defined as quasi-static deformations, and the seismic ground motion, defined as dynamic deformations, were analysed in order to understand the rock mass behavior around deep level mining. In addition the high frequency AE events recorded at hypocentral distances of about 50m located at 3300m below the surface were analysed. A good correspondence between the dynamic and quasi-static deformations was found. The rate of coseismic and aseismic tilt, as well as seismicity recorded by the mine seismic network, are approximately constant until the daily blasting time, which takes place from about 19:30 until shortly before 21:00. During the blasting time and the subsequent seismic events the coseismic and aseismic tilt shows a rapid increase.Much of the quasi-static deformation, however, occurs independently of the seismic events and was described as 'slow' or aseismic events. During the monitoring period a seismic event with MW 2.2 occurred in the vicinity of the instrumented site. This event was recorded by both the CSIR integrated monitoring system and JAGUARS acoustic emotion network. The tilt changes associated with this event showed a well pronounced after-tilt. The aftershock activities were also well recorded by the acoustic emission and the mine seismic networks. More than 21,000 AE aftershocks were located in the first 150 hours after the main event. Using the distribution of the AE events the position of the fault in the source area was successfully delineated. The distribution of the AE events following the main shock was related to after tilt in order to quantify post slip behavior of the source. An attempt to associate the different type of deformations with the various fracture regions and geological structures around the stopes was carried out. A model, was introduced in which the coseismic deformations are associated with the stress regime outside the stope fracture envelope and very often located on existing geological structures, while the aseismic deformations are associated with mobilization of fractures and stress relaxation within the fracture envelope. Further research to verify this model is strongly recommended. This involves long term underground monitoring using a wide variety of instruments such as tilt, closure and strain meters, a highly sensitive AE fracture monitoring system, as well as strong ground motion monitors. A large amount of numerical modeling is also required.

Deep Extragalactic X-Ray Surveys

NASA Astrophysics Data System (ADS)

Brandt, W. N.; Hasinger, G.

2005-09-01

Deep surveys of the cosmic X-ray background are reviewed in the context of observational progress enabled by the Chandra X-Ray Observatory and the X-Ray Multi-Mirror Mission-Newton. The sources found by deep surveys are described along with their redshift and luminosity distributions, and the effectiveness of such surveys at selecting active galactic nuclei (AGN) is assessed. Some key results from deep surveys are highlighted, including (a) measurements of AGN evolution and the growth of supermassive black holes, (b) constraints on the demography and physics of high-redshift AGN, (c) the X-ray AGN content of infrared and submillimeter galaxies, and (d) X-ray emission from distant starburst and normal galaxies. We also describe some outstanding problems and future prospects for deep extragalactic X-ray surveys.

PRODUCTION, MANAGEMENT AND THE ENVIRONMENT SYMPOSIUM: Measurement and mitigation of reactive nitrogen species from swine and poultry production.

PubMed

Powers, W; Capelari, M

2017-05-01

Reactive nitrogen (Nr) species include oxides of nitrogen [N; nitric oxide, nitrogen dioxide and nitrous oxide (NO)], anions (nitrate and nitrite), and amine derivatives [ammonia (NH), ammonium salts and urea]. Of the different Nr species, air emissions from swine and poultry facilities are predominantly NH followed by NO. Excreta emissions are NH, ammonium ions, and urea with trace amounts of nitrate and nitrite. Farm systems and practices that handle manure as a wet product without pH modification favor almost exclusive NH production. Systems and practices associated with dry manure handling and bedded systems emit more NH than NO. Results from a turkey grow-out study estimated that just under 1% of consumed N was emitted as NO from housing, compared with just under 11% emitted as NH. Despite generally less NO emissions from animal housing compared with crop field emissions, NO emissions from housing are often greater than estimated. Lagoon systems emit more NO than either slurry or deep pit swine systems. Deep pit swine buildings emit only one-third the NO that is emitted from deep bedded swine systems. Laying hen, broiler chicken, and turkey buildings emit over 4 times as much NO as swine housing, on a weight-adjusted basis. Critical control points for mitigation center on: 1) reducing the amount of N excreted and, therefore, excreted N available for loss to air or water during housing, manure storage, or following land application of manures; 2) capturing excreted N to prevent release of N-containing compounds to air, water, or soil resources; or 3) conversion or treatment of N-containing compounds to non-reactive N gas.

The ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: Implications for Spectral Line Intensity Mapping at Millimeter Wavelengths and CMB Spectral Distortions

NASA Astrophysics Data System (ADS)

Carilli, C. L.; Chluba, J.; Decarli, R.; Walter, F.; Aravena, M.; Wagg, J.; Popping, G.; Cortes, P.; Hodge, J.; Weiss, A.; Bertoldi, F.; Riechers, D.

2016-12-01

We present direct estimates of the mean sky brightness temperature in observing bands around 99 and 242 GHz due to line emission from distant galaxies. These values are calculated from the summed line emission observed in a blind, deep survey for spectral line emission from high redshift galaxies using ALMA (the ALMA spectral deep field observations “ASPECS” survey). In the 99 GHz band, the mean brightness will be dominated by rotational transitions of CO from intermediate and high redshift galaxies. In the 242 GHz band, the emission could be a combination of higher order CO lines, and possibly [C II] 158 μm line emission from very high redshift galaxies (z ˜ 6-7). The mean line surface brightness is a quantity that is relevant to measurements of spectral distortions of the cosmic microwave background, and as a potential tool for studying large-scale structures in the early universe using intensity mapping. While the cosmic volume and the number of detections are admittedly small, this pilot survey provides a direct measure of the mean line surface brightness, independent of conversion factors, excitation, or other galaxy formation model assumptions. The mean surface brightness in the 99 GHZ band is: T B = 0.94 ± 0.09 μK. In the 242 GHz band, the mean brightness is: T B = 0.55 ± 0.033 μK. These should be interpreted as lower limits on the average sky signal, since we only include lines detected individually in the blind survey, while in a low resolution intensity mapping experiment, there will also be the summed contribution from lower luminosity galaxies that cannot be detected individually in the current blind survey.

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

Renno, Nilton O.; Ruf, Christopher S., E-mail: renno@alum.mit.edu

Ruf et al. used the Deep Space Network (DSN) to search for the emission of non-thermal radiation by martian dust storms, theoretically predicted by Renno et al. They detected the emission of non-thermal radiation that they were searching for, but were surprised that it contained spectral peaks suggesting modulation at various frequencies and their harmonics. Ruf et al. hypothesized that the emission of non-thermal radiation was caused by electric discharges in a deep convective dust storm, modulated by Schumann resonances (SRs). Anderson et al. used the Allen Telescope Array (ATA) to search for similar emissions. They stated that they foundmore » only radio frequency interference (RFI) during their search for non-thermal emission by martian dust storms and implicitly suggested that the signal detected by Ruf et al. was also RFI. However, their search was not conducted during the dust storm season when deep convective storms are most likely to occur. Here, we show that the ubiquitous dust devils and small-scale dust storms that were instead likely present during their observations are too shallow to excite SRs and produce the signals detected by Ruf et al. We also show that the spectral and temporal behavior of the signals detected by Anderson et al. corroborates the idea that they originated from man-made pulse-modulated telecommunication signals rather than martian electric discharges. In contrast, an identical presentation of the signals detected by Ruf et al. demonstrates that they do not resemble man-made signals. The presentation indicates that the DSN signals were consistent with modulation by martian SRs, as originally hypothesized by Ruf et al. We propose that a more comprehensive search for electrostatic discharges be conducted with either the ATA or DSN during a future martian dust storm season to test the hypothesis proposed by Ruf et al.« less

Deep Fabry-Perot Hα observations of two Sculptor group galaxies, NGC 247 and 300

NASA Astrophysics Data System (ADS)

Hlavacek-Larrondo, J.; Marcelin, M.; Epinat, B.; Carignan, C.; de Denus-Baillargeon, M.-M.; Daigle, O.; Hernandez, O.

2011-09-01

It has been suggested that diffuse ionized gas can extend all the way to the end of the H I disc, and even beyond, such as in the case of the warped galaxyNGC 253 (Bland-Hawthorn et al.). Detecting ionized gas at these radii could carry significant implications as to the distribution of dark matter in galaxies. With the aim of detecting this gas, we carried out a deep Hα kinematical analysis of two Sculptor group galaxies, NGC 247 and 300. The Fabry-Perot data were taken at the 36-cm Marseille Telescope in La Silla, Chile, offering a large field of view. With almost 20 hours of observations for each galaxy, very faint diffuse emission is detected. Typical emission measures of 0.1 cm-6 pc are reached. For NGC 247, emission extending up to a radius comparable with that of the H I disc (r˜ 13 arcmin) is found, but no emission is seen beyond the H I disc. For NGC 300, we detect ionized gas on the entirety of our field of view (rmax˜ 14 arcmin), and find that the bright H II regions are embedded in a diffuse background. Using the deep data, extended optical rotation curves are obtained, as well as mass models. These are the most extended optical rotation curves thus far for these galaxies. We find no evidence suggesting that NGC 247 has a warped disc, and to account for our non-detection of Hα emission beyond its H I disc, as opposed to the warped galaxy NGC 253, our results favour the model in which, only through a warp, ionization by hot young stars in the central region of a galaxy can let photons escape and ionize the interstellar medium in the outer parts.

Magma at depth: A retrospective analysis of the 1975 unrest at Mount Baker, Washington, USA

USGS Publications Warehouse

Crider, Juliet G.; Frank, David; Malone, Stephen D.; Poland, Michael P.; Werner, Cynthia; Caplan-Auerbach, Jacqueline

2011-01-01

Mount Baker volcano displayed a short interval of seismically-quiescent thermal unrest in 1975, with high emissions of magmatic gas that slowly waned during the following three decades. The area of snow-free ground in the active crater has not returned to pre-unrest levels, and fumarole gas geochemistry shows a decreasing magmatic signature over that same interval. A relative microgravity survey revealed a substantial gravity increase in the ~30 years since the unrest, while deformation measurements suggest slight deflation of the edifice between 1981-83 and 2006-07. The volcano remains seismically quiet with regard to impulsive volcano-tectonic events, but experiences shallow (10 km) long-period earthquakes. Reviewing the observations from the 1975 unrest in combination with geophysical and geochemical data collected in the decades that followed, we infer that elevated gas and thermal emissions at Mount Baker in 1975 resulted from magmatic activity beneath the volcano: either the emplacement of magma at mid-crustal levels, or opening of a conduit to a deep existing source of magmatic volatiles. Decadal-timescale, multi-parameter observations were essential to this assessment of magmatic activity.

Negative thermal quenching of photoluminescence in zinc oxide nanowire-core/graphene-shell complexes.

PubMed

Lin, S S; Chen, B G; Xiong, W; Yang, Y; He, H P; Luo, J

2012-09-10

Graphene is an atomic thin two-dimensional semimetal whereas ZnO is a direct wide band gap semiconductor with a strong light-emitting ability. In this paper, we report on photoluminescence (PL) of ZnO-nanowires (NWs)-core/Graphene-shell heterostructures, which shows a negative thermal quenching (NTQ) behavior both for the near band-edge and deep level emission. The abnormal PL behavior was understood through the charging and discharging processes between ZnO NWs and graphene. The NTQ properties are most possibly induced by the unique rapidly increasing density of states of graphene as a function of Fermi level, which promises a higher quantum tunneling probability between graphene and ZnO at a raised temperature.

Dual-wavelength excited photoluminescence spectroscopy of deep-level hole traps in Ga(In)NP

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

Dagnelund, D.; Huang, Y. Q.; Buyanova, I. A.

2015-01-07

By employing photoluminescence (PL) spectroscopy under dual-wavelength optical excitation, we uncover the presence of deep-level hole traps in Ga(In)NP alloys grown by molecular beam epitaxy (MBE). The energy level positions of the traps are determined to be at 0.56 eV and 0.78 eV above the top of the valance band. We show that photo-excitation of the holes from the traps, by a secondary light source with a photon energy below the bandgap energy, can lead to a strong enhancement (up to 25%) of the PL emissions from the alloys under a primary optical excitation above the bandgap energy. We further demonstrate thatmore » the same hole traps can be found in various MBE-grown Ga(In)NP alloys, regardless of their growth temperatures, chemical compositions, and strain. The extent of the PL enhancement induced by the hole de-trapping is shown to vary between different alloys, however, likely reflecting their different trap concentrations. The absence of theses traps in the GaNP alloy grown by vapor phase epitaxy suggests that their incorporation could be associated with a contaminant accompanied by the N plasma source employed in the MBE growth, possibly a Cu impurity.« less

Stoichiometric control for heteroepitaxial growth of smooth ɛ-Ga2O3 thin films on c-plane AlN templates by mist chemical vapor deposition

NASA Astrophysics Data System (ADS)

Tahara, Daisuke; Nishinaka, Hiroyuki; Morimoto, Shota; Yoshimoto, Masahiro

2017-07-01

Epitaxial ɛ-Ga2O3 thin films with smooth surfaces were successfully grown on c-plane AlN templates by mist chemical vapor deposition. Using X-ray diffraction 2θ-ω and φ scans, the out-of-plane and in-plane epitaxial relationship was determined to be (0001) ɛ-Ga2O3 [10\\bar{1}0] ∥ (0001)AlN[10\\bar{1}0]. The gallium/oxygen ratio was controlled by varying the gallium precursor concentration in the solution. While scanning electron microscopy showed the presence of large grains on the surfaces of the films formed for low concentrations of oxygen species, no large grains were observed under stoichiometric conditions. Cathodoluminescence measurements showed a deep-level emission ranging from 1.55-3.7 eV; however, no band-edge emission was observed.

Origin and enhancement of the 1.3 μm luminescence from GaAs treated by ion-implantation and flash lamp annealing

NASA Astrophysics Data System (ADS)

Gao, Kun; Prucnal, S.; Skorupa, W.; Helm, M.; Zhou, Shengqiang

2013-09-01

GaAs and GaAs based materials have outstanding optoelectronic properties and are widely used as light emitting media in devices. Many approaches have been applied to GaAs to generate luminescence at 0.88, 1.30, and 1.55 μm which are transmission windows of optical fibers. In this paper, we present the photoluminescence at 1.30 μm from deep level defects in GaAs treated by ion-implantation and flash lamp annealing (FLA). Such emission, which exhibits superior temperature stability, can be obtained from FLA treated virgin GaAs as well as doped GaAs. Indium-doping in GaAs can greatly enhance the luminescence. By photoluminescence, Raman measurements, and positron annihilation spectroscopy, we conclude that the origin of the 1.30 μm emission is from transitions between the VAs-donor and X-acceptor pairs.

Relationships between Fungal Biomass and Nitrous Oxide Emission in Upland Rice Soils under No Tillage and Cover Cropping Systems.

PubMed

Zhaorigetu; Komatsuzaki, Masakazu; Sato, Yoshinori; Ohta, Hiroyuki

2008-01-01

The relationships between soil microbial properties and nitrous oxide emission were examined in upland soil under different tillage systems [no tillage (NT), rotary and plow tillage] and cover crop systems (fallow, cereal rye, and hairy vetch) in 2004 and 2005. Microbiological analyses included the determination of soil ergosterol as an indicator of fungal biomass, bacterial plate counting, and MPN estimations of ammonia oxidizers and denitrifiers. The combined practice of NT with rye-cover crop treatment increased fungal biomass but not bacterial populations in 0-10 cm deep soils. Such increase in fungal biomass was not found in 10-20 cm and 20-30 cm deep cover-cropped NT soil. The combined practice of NT with rye-cover cropping resulted in higher in situ N(2)O emission rates compared with rotary- and plow-till treatments. N(2)O flux was positively correlated with soil ergosterol content but not with denitrifier MPN and other soil chemical properties. These results suggested a significant contribution of fungi to N(2)O emission in cover-cropped NT soils.

White/blue-emitting, water-dispersible CdSe quantum dots prepared by counter ion-induced polymer collapse

NASA Astrophysics Data System (ADS)

Wang, Jing; Goh, Jane Betty; Goh, M. Cynthia; Giri, Neeraj Kumar; Paige, Matthew F.

2015-09-01

The synthesis and characterization of water-dispersible, luminescent CdSe/ZnS semiconductor quantum dots that exhibit nominal "white" fluorescence emission and have potential applications in solid-state lighting is described. The nanomaterials, prepared through counter ion-induced collapse and UV cross-linking of high-molecular weight polyacrylic acid in the presence of appropriate aqueous inorganic ions, were of ∼2-3 nm diameter and could be prepared in gram quantities. The quantum dots exhibited strong luminescence emission in two bands, the first in the blue-region (band edge) of the optical spectrum and the second, a broad emission in the red-region (attributed to deep trap states) of the optical spectrum. Because of the relative strength of emission of the band edge and deep trap state luminescence, it was possible to achieve visible white luminescence from the quantum dots in aqueous solution and in dried, solid films. The optical spectroscopic properties of the nanomaterials, including ensemble and single-molecule spectroscopy, was performed, with results compared to other white-emitting quantum dot systems described previously in the literature.

Distinguishing triplet energy transfer and trap-assisted recombination in multi-color organic light-emitting diode with an ultrathin phosphorescent emissive layer

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

Xue, Qin, E-mail: xueqin19851202@163.com; Liu, Shouyin; Xie, Guohua

2014-03-21

An ultrathin layer of deep-red phosphorescent emitter tris(1-phenylisoquinoline) iridium (III) (Ir(piq){sub 3}) is inserted within different positions of the electron blocking layer fac-tris (1-phenylpyrazolato-N,C{sup 2′})-iridium(III) (Ir(ppz){sub 3}) to distinguish the contribution of the emission from the triplet exciton energy transfer/diffusion from the adjacent blue phosphorescent emitter and the trap-assisted recombination from the narrow band-gap emitter itself. The charge trapping effect of the narrow band-gap deep-red emitter which forms a quantum-well-like structure also plays a role in shaping the electroluminescent characteristics of multi-color organic light-emitting diodes. By accurately controlling the position of the ultrathin sensing layer, it is considerably easy tomore » balance the white emission which is quite challenging for full-color devices with multiple emission zones. There is nearly no energy transfer detectable if 7 nm thick Ir(ppz){sub 3} is inserted between the blue phosphorescent emitter and the ultrathin red emitter.« less

Structural defects and recombination behavior of excited carriers in Cu(In,Ga)Se2 solar cells

NASA Astrophysics Data System (ADS)

Yang, J.; Du, H. W.; Li, Y.; Gao, M.; Wan, Y. Z.; Xu, F.; Ma, Z. Q.

2016-08-01

The carriers' behavior in neutral region (NTR) and space charged region (SCR) of Cu(In,Ga)Se2 thin film based solar cells has been investigated by temperature dependent photoluminescence (PL-T), electroluminescence (EL-T) and current-voltage (IV-T) from 10 to 300 K. PL-T spectra show that three kinds of defects, namely VSe, InCu and (InCu+VCu), are localized within the band gap of NTR and SCR of CIGS layer, corresponding to the energy levels of EC-0.08, EC-0.20 and EC-0.25 eV, respectively. The InCu and (InCu+VCu) deep level defects are non-radiative recombination centers at room temperature. The IV-T and EL-T analysis reveals that the injection modes of electrons from ZnO conduction band into Cu(In,Ga)Se2 layer are tunneling, thermally-excited tunneling and thermionic emission under 10-40, 60-160, and 180-300 K, respectively. At 10-160 K, the electrons tunnel into (InCu+VCu) and Vse defect levels in band gap of SCR and the drifting is involved in the emission bands at 0.96 and 1.07 eV, which is the direct evidence for a tunneling assisted recombination. At 180-300 K, the electrons are directly injected into the Cu(In,Ga)Se2 conduction band, and the emission of 1.13 eV are ascribed to the transitions from the conduction band to the valence band.

Global Scale Attribution of Anthropogenic and Natural Dust Sources and their Emission Rates Based on MODIS Deep Blue Aerosol Products

NASA Technical Reports Server (NTRS)

Ginoux, Paul; Prospero, Joseph M.; Gill, Thomas E.; Hsu, N. Christina; Zhao, Ming

2012-01-01

Our understanding of the global dust cycle is limited by a dearth of information about dust sources, especially small-scale features which could account for a large fraction of global emissions. Here we present a global-scale high-resolution (0.1 deg) mapping of sources based on Moderate Resolution Imaging Spectroradiometer (MODIS) Deep Blue estimates of dust optical depth in conjunction with other data sets including land use. We ascribe dust sources to natural and anthropogenic (primarily agricultural) origins, calculate their respective contributions to emissions, and extensively compare these products against literature. Natural dust sources globally account for 75% of emissions; anthropogenic sources account for 25%. North Africa accounts for 55% of global dust emissions with only 8% being anthropogenic, mostly from the Sahel. Elsewhere, anthropogenic dust emissions can be much higher (75% in Australia). Hydrologic dust sources (e.g., ephemeral water bodies) account for 31% worldwide; 15% of them are natural while 85% are anthropogenic. Globally, 20% of emissions are from vegetated surfaces, primarily desert shrublands and agricultural lands. Since anthropogenic dust sources are associated with land use and ephemeral water bodies, both in turn linked to the hydrological cycle, their emissions are affected by climate variability. Such changes in dust emissions can impact climate, air quality, and human health. Improved dust emission estimates will require a better mapping of threshold wind velocities, vegetation dynamics, and surface conditions (soil moisture and land use) especially in the sensitive regions identified here, as well as improved ability to address small-scale convective processes producing dust via cold pool (haboob) events frequent in monsoon regimes.

Deep-Ultraviolet Hyperbolic Metacavity Laser.

PubMed

Shen, Kun-Ching; Ku, Chen-Ta; Hsieh, Chiieh; Kuo, Hao-Chung; Cheng, Yuh-Jen; Tsai, Din Ping

2018-05-01

Given the high demand for miniaturized optoelectronic circuits, plasmonic devices with the capability of generating coherent radiation at deep subwavelength scales have attracted great interest for diverse applications such as nanoantennas, single photon sources, and nanosensors. However, the design of such lasing devices remains a challenging issue because of the long structure requirements for producing strong radiation feedback. Here, a plasmonic laser made by using a nanoscale hyperbolic metamaterial cube, called hyperbolic metacavity, on a multiple quantum-well (MQW), deep-ultraviolet emitter is presented. The specifically designed metacavity merges plasmon resonant modes within the cube and provides a unique resonant radiation feedback to the MQW. This unique plasmon field allows the dipoles of the MQW with various orientations into radiative emission, achieving enhancement of spontaneous emission rate by a factor of 33 and of quantum efficiency by a factor of 2.5, which is beneficial for coherent laser action. The hyperbolic metacavity laser shows a clear clamping of spontaneous emission above the threshold, which demonstrates a near complete radiation coupling of the MQW with the metacavity. This approach shown here can greatly simplify the requirements of plasmonic nanolaser with a long plasmonic structure, and the metacavity effect can be extended to many other material systems. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Spectroscopic Chemical Analysis Methods and Apparatus

NASA Technical Reports Server (NTRS)

Hug, William F.; Reid, Ray D.

2012-01-01

This invention relates to non-contact spectroscopic methods and apparatus for performing chemical analysis and the ideal wavelengths and sources needed for this analysis. It employs deep ultraviolet (200- to 300-nm spectral range) electron-beam-pumped wide bandgap semiconductor lasers, incoherent wide bandgap semiconductor lightemitting devices, and hollow cathode metal ion lasers. Three achieved goals for this innovation are to reduce the size (under 20 L), reduce the weight [under 100 lb (.45 kg)], and reduce the power consumption (under 100 W). This method can be used in microscope or macroscope to provide measurement of Raman and/or native fluorescence emission spectra either by point-by-point measurement, or by global imaging of emissions within specific ultraviolet spectral bands. In other embodiments, the method can be used in analytical instruments such as capillary electrophoresis, capillary electro-chromatography, high-performance liquid chromatography, flow cytometry, and related instruments for detection and identification of unknown analytes using a combination of native fluorescence and/or Raman spectroscopic methods. This design provides an electron-beampumped semiconductor radiation-producing method, or source, that can emit at a wavelength (or wavelengths) below 300 nm, e.g. in the deep ultraviolet between about 200 and 300 nm, and more preferably less than 260 nm. In some variations, the method is to produce incoherent radiation, while in other implementations it produces laser radiation. In some variations, this object is achieved by using an AlGaN emission medium, while in other implementations a diamond emission medium may be used. This instrument irradiates a sample with deep UV radiation, and then uses an improved filter for separating wavelengths to be detected. This provides a multi-stage analysis of the sample. To avoid the difficulties related to producing deep UV semiconductor sources, a pumping approach has been developed that uses ballistic electron beam injection directly into the active region of a wide bandgap semiconductor material.

Lyman Break Galaxies in the Hubble Ultra Deep Field through Deep U-Band Imaging

NASA Astrophysics Data System (ADS)

Rafelski, Marc; Wolfe, A. M.; Cooke, J.; Chen, H. W.; Armandroff, T. E.; Wirth, G. D.

2009-12-01

We introduce an extremely deep U-band image taken of the Hubble Ultra Deep Field (HUDF), with a one sigma depth of 30.7 mag arcsec-2 and a detection limiting magnitude of 28 mag arcsec-2. The observations were carried out on the Keck I telescope using the LRIS-B detector. The U-band image substantially improves the accuracy of photometric redshift measurements of faint galaxies in the HUDF at z=[2.5,3.5]. The U-band for these galaxies is attenuated by lyman limit absorption, allowing for more reliable selections of candidate Lyman Break Galaxies (LBGs) than from photometric redshifts without U-band. We present a reliable sample of 300 LBGs at z=[2.5,3.5] in the HUDF. Accurate redshifts of faint galaxies at z=[2.5,3.5] are needed to obtain empirical constraints on the star formation efficiency of neutral gas at high redshift. Wolfe & Chen (2006) showed that the star formation rate (SFR) density in damped Ly-alpha absorption systems (DLAs) at z=[2.5,3.5] is significantly lower than predicted by the Kennicutt-Schmidt law for nearby galaxies. One caveat to this result that we wish to test is whether LBGs are embedded in DLAs. If in-situ star formation is occurring in DLAs, we would see it as extended low surface brightness emission around LBGs. We shall use the more accurate photometric redshifts to create a sample of LBGs around which we will look for extended emission in the more sensitive and higher resolution HUDF images. The absence of extended emission would put limits on the SFR density of DLAs associated with LBGs at high redshift. On the other hand, detection of faint emission on scales large compared to the bright LBG cores would indicate the presence of in situ star formation in those DLAs. Such gas would presumably fuel the higher star formation rates present in the LBG cores.

Climate change impacts on lake thermal dynamics and ecosystem vulnerabilities

USGS Publications Warehouse

Sahoo, G. B; Forrest, A. L; Schladow, S. G ;; Reuter, J. E; Coats, R.; Dettinger, Michael

2016-01-01

Using water column temperature records collected since 1968, we analyzed the impacts of climate change on thermal properties, stability intensity, length of stratification, and deep mixing dynamics of Lake Tahoe using a modified stability index (SI). This new SI is easier to produce and is a more informative measure of deep lake stability than commonly used stability indices. The annual average SI increased at 16.62 kg/m2/decade although the summer (May–October) average SI increased at a higher rate (25.42 kg/m2/decade) during the period 1968–2014. This resulted in the lengthening of the stratification season by approximately 24 d. We simulated the lake thermal structure over a future 100 yr period using a lake hydrodynamic model driven by statistically downscaled outputs of the Geophysical Fluid Dynamics Laboratory Model (GFDL) for two different green house gas emission scenarios (the A2 in which greenhouse-gas emissions increase rapidly throughout the 21st Century, and the B1 in which emissions slow and then level off by the late 21st Century). The results suggest a continuation and intensification of the already observed trends. The length of stratification duration and the annual average lake stability are projected to increase by 38 d and 12 d and 30.25 kg/m2/decade and 8.66 kg/m2/decade, respectively for GFDLA2 and GFDLB1, respectively during 2014–2098. The consequences of this change bear the hallmarks of climate change induced lake warming and possible exacerbation of existing water quality, quantity and ecosystem changes. The developed methodology could be extended and applied to other lakes as a tool to predict changes in stratification and mixing dynamics.

Variability of passive gas emissions, seismicity, and deformation during crater lake growth at White Island Volcano, New Zealand, 2002-2006

USGS Publications Warehouse

Werner, C.; Hurst, T.; Scott, B.; Sherburn, S.; Christenson, B.W.; Britten, K.; Cole-Baker, J.; Mullan, B.

2008-01-01

We report on 4 years of airborne measurements of CO2, SO2, and H2S emission rates during a quiescent period at White Island volcano, New Zealand, beginning in 2003. During this time a significant crater lake emerged, allowing scrubbig processes to be investigated. CO2 emissions varied from a baseline of 250 to >2000 t d-1 and demonstrated clear annual cycling that was consistent with numbers of earthquake detections and annual changes in sea level. The annual variability was found to be most likely related to increases in the strain on the volcano during sea level highs, temporarily causing fractures to reduce in size in the upper conduit. SO2 emissions varied from 0 to >400 t d-1 and were clearly affected by scrubbing processes within the first year of take development. Scrubbing caused increases of SO42- and Cl- in lake waters, and the ratio of carbon to total sulphur suggested that elemental sulphur deposition was also significant in the lake during the first year. Careful measurements of the lake level and chemistry allowed estimates of the rate of H2O(g) and HCl(g) input into the lake and suggested that the molar abundances of major gas species (H2O, CO2, SO2, and HCl) during this quiescent phase were similar to fumarolic ratios observed between earlier eruptive periods. The volume of magma estimated from CO2 emissions (0.0 15-0.04 km3) was validated by Cl- increases in the lake, suggesting that the gas and magma are transported from deep to shallow depths as a closed system and likely become open in the upper conduit region. The absence of surface deformation further leads to a necessity of magma convection to supply and remove magma from the degassing depths. Two models of convection configurations are discussed. Copyright 2008 by the American Geophysical Union.

Variability of passive gas emissions, seismicity, and deformation during crater lake growth at White Island Volcano, New Zealand, 2002-2006

NASA Astrophysics Data System (ADS)

Werner, C.; Hurst, T.; Scott, B.; Sherburn, S.; Christenson, B. W.; Britten, K.; Cole-Baker, J.; Mullan, B.

2008-01-01

We report on 4 years of airborne measurements of CO2, SO2, and H2S emission rates during a quiescent period at White Island volcano, New Zealand, beginning in 2003. During this time a significant crater lake emerged, allowing scrubbing processes to be investigated. CO2 emissions varied from a baseline of 250 to >2000 t d-1 and demonstrated clear annual cycling that was consistent with numbers of earthquake detections and annual changes in sea level. The annual variability was found to be most likely related to increases in the strain on the volcano during sea level highs, temporarily causing fractures to reduce in size in the upper conduit. SO2 emissions varied from 0 to >400 t d-1 and were clearly affected by scrubbing processes within the first year of lake development. Scrubbing caused increases of SO42- and Cl- in lake waters, and the ratio of carbon to total sulphur suggested that elemental sulphur deposition was also significant in the lake during the first year. Careful measurements of the lake level and chemistry allowed estimates of the rate of H2O(g) and HCl(g) input into the lake and suggested that the molar abundances of major gas species (H2O, CO2, SO2, and HCl) during this quiescent phase were similar to fumarolic ratios observed between earlier eruptive periods. The volume of magma estimated from CO2 emissions (0.015-0.04 km3) was validated by Cl- increases in the lake, suggesting that the gas and magma are transported from deep to shallow depths as a closed system and likely become open in the upper conduit region. The absence of surface deformation further leads to a necessity of magma convection to supply and remove magma from the degassing depths. Two models of convection configurations are discussed.

2-(2-Hydroxyphenyl)imidazole-based four-coordinate organoboron compounds with efficient deep blue photoluminescence and electroluminescence.

PubMed

Zhang, Zhenyu; Zhang, Zuolun; Zhang, Hongyu; Wang, Yue

2017-12-19

Two new four-coordinate organoboron compounds with 2-(2-hydroxyphenyl)imidazole derivatives as the chelating ligands have been synthesized. They possess high thermal stability and are able to form an amorphous glass state. Crystallographic analyses indicate that the differences in ligand structure cause the change of ππ stacking character. The CH 2 Cl 2 solutions and thin films of these compounds display bright blue emission, and these compounds have appropriate HOMO and LUMO energy levels for carrier injection in OLEDs. By utilizing the good thermal and luminescent properties, as well as the proper frontier orbital energy levels, bright non-doped OLEDs with a simple structure have been realized. Notably, these simple devices show deep blue electroluminescence with the Commission Internationale de l'Éclairage (CIE) coordinate of ca. (0.16, 0.08), which is close to the CIE coordinate of (0.14, 0.08) for standard blue defined by the National Television System Committee. In addition, one of the devices exhibits good performance, showing brightness, current efficiency, power efficiency and external quantum efficiency up to 2692 cd m -2 , 2.50 cd A -1 , 1.81 lm W -1 and 3.63%, respectively. This study not only provides good deep-blue emitting OLED materials that are rarely achieved by using four-coordinate organoboron compounds, but also allows a deeper understanding of the structure-property relationship of 2-(2-hydroxyphenyl)imidazole-based boron complexes, which benefits the further structural design of this type of material.

New applications of laser-induced breakdown and stand-off Raman spectroscopy

NASA Astrophysics Data System (ADS)

Snyder, Marion Lawrence

Two novel spectroscopic applications, with the common theme of remote spectroscopy are described. In one application, laser-induced breakdown spectroscopy (LIBS) is investigated for deep ocean measurements of hydrothermal vent chemistry. This technique is demonstrated for the first time for solution measurements at pressures corresponding to those found at hydrothermal vent sites, at ocean depths of one to three kilometers. In the other application, Raman spectroscopy is investigated for stand-off detection of high explosive (HE) materials. We demonstrate several HE materials in silica can be measured at 50-meter range under ambient light conditions, a new record for this application. Chapters one through three of this dissertation contain published and recently submitted articles describing LIBS for in situ multi-elemental detection in high-pressure aqueous environments such as the deep ocean. Initial work shows the potential of single-pulse LIBS (SP-LIBS) to measure dissolved elements (e.g., Na, Ca, Li, K, and Mn) at the part-per-million level in aqueous solutions at pressures exceeding 276 bar. Dual-pulse LIBS (DP-LIBS) of high-pressure aqueous solutions is also presented. We show significant DP-LIBS enhancements are achieved through excitation of a vapor bubble formed by laser-induced breakdown of the solution with a previous laser pulse, thereby increasing the sensitivity of LIBS and allowing additional elements to be measured. Preliminary findings show that increasing solution pressure has a detrimental effect on DP-LIBS emission intensities, such that little if any DP-LIBS emission was observed above approximately 100 bar. Recent results suggest a direct relationship exists between the size of the bubble and the resulting DP-LIBS emission, and that reduction in bubble size and lifetime at elevated pressure lead to the decreased DP-LIBS emission. Chapter four contains published work examining the potential of stand-off Raman spectroscopy for remote HE detection. A small, transportable, telescope-based standoff Raman system is demonstrated for detection of HE materials, including RDX, TNT, and PETN, and simulants at distances up to 50 meters in ambient light conditions. Possible detection limits on the hundreds of parts-per-million level and detection ranges of hundreds of meters are suggested. Merits of pulsed laser excitation sources and intensified charge-coupled devices (ICCD) for detection are discussed.

Trap Depth Engineering of SrSi2O2N2:Ln2+,Ln3+ (Ln2+ = Yb, Eu; Ln3+ = Dy, Ho, Er) Persistent Luminescence Materials for Information Storage Applications.

PubMed

Zhuang, Yixi; Lv, Ying; Wang, Le; Chen, Wenwei; Zhou, Tian-Liang; Takeda, Takashi; Hirosaki, Naoto; Xie, Rong-Jun

2018-01-17

Deep-trap persistent luminescence materials exhibit unique properties of energy storage and controllable photon release under additional stimulation, allowing for both wavelength and intensity multiplexing to realize high-capacity storage in the next-generation information storage system. However, the lack of suitable persistent luminescence materials with deep traps is the bottleneck of such storage technologies. In this study, we successfully developed a series of novel deep-trap persistent luminescence materials in the Ln 2+ /Ln 3+ -doped SrSi 2 O 2 N 2 system (Ln 2+ = Yb, Eu; Ln 3+ = Dy, Ho, Er) by applying the strategy of trap depth engineering. Interestingly, the trap depth can be tailored by selecting different codopants, and it monotonically increases from 0.90 to 1.18 eV in the order of Er, Ho, and Dy. This is well explained by the energy levels indicated in the host-referred binding energy scheme. The orange-red-emitting SrSi 2 O 2 N 2 :Yb,Dy and green-emitting SrSi 2 O 2 N 2 :Eu,Dy phosphors are demonstrated to be good candidates of information storage materials, which are attributed to their deep traps, narrow thermoluminescence glow bands, high emission efficiency, and excellent chemical stability. This work not only validates the suitability of deep-trap persistent luminescence materials in the information storage applications, but also broadens the avenue to explore such kinds of new materials for applications in anticounterfeiting and advanced displays.

Ammonia and greenhouse gas emissions from a modern U.S. swine breeding-gestation-farrowing system

NASA Astrophysics Data System (ADS)

Stinn, John P.; Xin, Hongwei; Shepherd, Timothy A.; Li, Hong; Burns, Robert T.

2014-12-01

Aerial emissions from livestock production continue to be an area of attention and concern for both the potential health and environmental impacts. However, information of gaseous, especially greenhouse gas (GHG), emissions for swine breeding/gestation and farrowing production systems is limited. The purpose of this study was to quantify ammonia (NH3), carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) concentrations and emissions from a modern breeding-gestation-farrowing system located in central Iowa, USA. A 4300-sow farm was selected for the extensive field monitoring which employed a Mobile Air Emission Monitoring Unit equipped with state-of-the-art gas analyzers and a data acquisition system. The monitored portion of the farm facility consisted of a deep-pit breeding/early gestation (B/EG) barn (1800 head), a deep-pit late gestation (LG) barn (1800 head), and two shallow-pit (pull-plug) farrowing rooms (40 head per room). A dynamic flux chamber was used to monitor gaseous emissions from the external manure storage for the farrowing rooms. Data were collected for 29 consecutive months (January 2011 through June 2013). Daily indoor NH3, CO2, N2O, and CH4 concentrations (ppm, mean ± SD) were 12.0 (±7.6), 1594 (±797), 0.31 (±0.11), and 28.5 (±9.8), respectively, in the breeding/gestation barns; and 9.7 (±4.1), 1536 (±701), 0.30 (±0.10), and 78.3 (±37), respectively, in the farrowing rooms. Daily emissions per animal unit (AU, 500 kg live weight) were 35.1 g NH3, 7.46 kg CO2, 0.17 g N2O, and 263.4 g CH4 for sows in the B/EG barn; and 28.2 g NH3, 6.50 kg CO2, 0.12 g N2O, and 201.3 g CH4 for sows in the LG barn. The average daily emissions per AU (sow and piglets) of the farrowing rooms during the lactation period (birth to weaning) were: 59.7 g NH3, 16.4 kg CO2, 0.73 g N2O, and 107 g CH4. For the monitored period, the external manure storage had the following average daily emission per m2 surface area: 1.26 g NH3, 137 g CO2, and 94.8 g CH4, which was equivalent to daily emissions per AU in the farrowing rooms of 12.2 g NH3, 1.055 kg CO2, and 867 g CH4. Average daily emissions per AU for the total operation (including house-level and manure storage emissions) were 38.5 g NH3, 8.73 kg CO2 (including 7.3 kg from animal respiration), 0.25 g N2O, and 301 g CH4.

Enhancing absorption in coated semiconductor nanowire/nanorod core-shell arrays using active host matrices

NASA Astrophysics Data System (ADS)

Jule, Leta; Dejene, Francis; Roro, Kittessa

2016-12-01

In the present work, we investigated theoretically and experimentally the interaction of radiation field phenomena interacting with arrays of nanowire/nanorod core-shell embedded in active host matrices. The optical properties of composites are explored including the case when the absorption of propagating wave by dissipative component is completely compensated by amplification in active (lasing) medium. On the basis of more elaborated modeling approach and extended effective medium theory, the effective polarizability and the refractive index of electromagnetic mode dispersion of the core-shell nanowire arrays are derived. ZnS(shell)-coated by sulphidation process on ZnO(shell) nanorod arrays grown on (100) silicon substrate by chemical bath deposition (CBD) has been used for theoretical comparison. Compared with the bare ZnO nanorods, ZnS-coated core/shell nanorods exhibit a strongly reduced ultraviolet (UV) emission and a dramatically enhanced deep level (DL) emission. Obviously, the UV and DL emission peaks are attributed to the emissions of ZnO nanorods within ZnO/ZnS core/shell nanorods. The reduction of UV emission after ZnS coating seems to agree with the charge separation mechanism of type-II band alignment that holes transfer from the core to shell, which would quench the UV emission to a certain extent. Our theoretical calculations and numerical simulation demonstrate that the use of active host (amplifying) medium to compensate absorption at metallic inclusions. Moreover the core-shell nanorod/nanowire arrays create the opportunity for broad band absorption and light harvesting applications.

A 60-yr record of atmospheric carbon monoxide reconstructed from Greenland firn air

NASA Astrophysics Data System (ADS)

Petrenko, V. V.; Martinerie, P.; Novelli, P.; Etheridge, D. M.; Levin, I.; Wang, Z.; Blunier, T.; Chappellaz, J.; Kaiser, J.; Lang, P.; Steele, L. P.; Hammer, S.; Mak, J.; Langenfelds, R. L.; Schwander, J.; Severinghaus, J. P.; Witrant, E.; Petron, G.; Battle, M. O.; Forster, G.; Sturges, W. T.; Lamarque, J.-F.; Steffen, K.; White, J. W. C.

2012-08-01

We present a reconstruction of the Northern Hemisphere (NH) high latitude atmospheric carbon monoxide (CO) mole fraction from Greenland firn air. Firn air samples were collected at three deep ice core sites in Greenland (NGRIP in 2001, Summit in 2006 and NEEM in 2008). CO records from the three sites agree well with each other as well as with recent atmospheric measurements, indicating that CO is well preserved in the firn at these sites. CO atmospheric history was reconstructed back to the year 1950 from the measurements using a combination of two forward models of gas transport in firn and an inverse model. The reconstructed history suggests that Arctic CO was already higher in 1950 than it is today. CO mole fractions rose gradually until the 1970s and peaked in the 1970s or early 1980s, followed by a decline to today's levels. We compare the CO history with the atmospheric histories of methane, light hydrocarbons, molecular hydrogen, CO stable isotopes and hydroxyl radical (OH), as well as with published CO emission inventories and results of a historical run from a chemistry-transport model. We find that the reconstructed Greenland CO history cannot be reconciled with available emission inventories unless large changes in OH are assumed. We argue that the available CO emission inventories chronically underestimate NH emissions, and fail to capture the emission decline starting in the late 1970s, which was most likely due to reduced emissions from road transportation in North America and Europe.

High efficiency blue and white phosphorescent organic light emitting devices

NASA Astrophysics Data System (ADS)

Eom, Sang-Hyun

Organic light-emitting devices (OLEDs) have important applications in full-color flat-panel displays and as solid-state lighting sources. Achieving high efficiency deep-blue phosphorescent OLEDs (PHOLEDs) is necessary for high performance full-color displays and white light sources with a high color rendering index (CRI); however it is more challenging compared to the longer wavelength light emissions such as green and red due to the higher energy excitations for the deep-blue emitter as well as the weak photopic response of deep-blue emission. This thesis details several effective strategies to enhancing efficiencies of deep-blue PHOLEDs based on iridium(III) bis(4',6'-difluorophenylpyridinato)tetrakis(1-pyrazolyl)borate (FIr6), which are further employed to demonstrate high efficiency white OLEDs by combining the deep-blue emitter with green and red emitters. First, we have employed 1,1-bis-(di-4-tolylaminophenyl) cyclohexane (TAPC) as the hole transporting material to enhance electron and triplet exciton confinement in Fir6-based PHOLEDs, which increased external quantum efficiency up to 18 %. Second, dual-emissive-layer (D-EML) structures consisting of an N,N -dicarbazolyl-3,5-benzene (mCP) layer doped with 4 wt % FIr6 and a p-bis (triphenylsilyly)benzene (UGH2) layer doped with 25 wt % FIr6 was employed to maximize exciton generation in the emissive layer. Combined with the p-i-n device structure, high power efficiencies of (25 +/- 2) lm/W at 100 cd/m2 and (20 +/- 2) lm/W at 1000 cd/m 2 were achieved. Moreover, the peak external quantum efficiency of (20 +/- 1) % was achieved by employing tris[3-(3-pyridyl)mesityl]borane (3TPYMB) as the electron transporting material, which further improves the exciton confinement in the emissive layer. With Cs2CO3 doping in the 3TPYMB layer to greatly increase its electrical conductivity, a peak power efficiency up to (36 +/- 2) lm/W from the deep-blue PHOLED was achieved, which also maintains Commission Internationale de L'Eclairage (CIE) coordinates of (0.16, 0.28). High efficiency white PHOLEDs are also demonstrated by incorporating green and red phosphorescent emitters together with the deep-blue emitter FIr6. Similar to the FIr6-only devices, the D-EML structure with high triplet energy charge transport materials leads to a maximum external quantum efficiency of (19 +/- 1) %. Using the p-i-n device structure, a peak power efficiency of (40 +/- 2) lm/W and (36 +/- 2) lm/W at 100 cd/m2 were achieved, and the white PHOLED possesses a CRI of 79 and CIE coordinates of (0.37, 0.40). The limited light extraction from the planar-type OLEDs is also one of the remaining challenges to the OLED efficiency. Here we have developed a simple soft lithography technique to fabricate a transparent, close-packed hemispherical microlens arrays. The application of such microlens arrays to the glass surface of the large-area fluorescent OLEDs enhanced the light extraction efficiency up to (70 +/- 7)%. It is also shown that the light extraction efficiency of the OLEDs is affected by microlens contact angle, OLEDs size, and detailed layer structure of the OLEDs.

Energy demand for materials in an international context.

PubMed

Worrell, Ernst; Carreon, Jesus Rosales

2017-06-13

Materials are everywhere and have determined society. The rapid increase in consumption of materials has led to an increase in the use of energy and release of greenhouse gas (GHG) emissions. Reducing emissions in material-producing industries is a key challenge. If all of industry switched to current best practices, the energy-efficiency improvement potential would be between 20% and 35% for most sectors. While these are considerable potentials, especially for sectors that have historically paid a lot of attention to energy-efficiency improvement, realization of these potentials under current 'business as usual' conditions is slow due to a large variety of barriers and limited efforts by industry and governments around the world. Importantly, the potentials are not sufficient to achieve the deep reductions in carbon emissions that will be necessary to stay within the climate boundaries as agreed in the 2015 Paris Conference of Parties. Other opportunities need to be included in the menu of options to mitigate GHG emissions. It is essential to develop integrated policies combining energy efficiency, renewable energy and material efficiency and material demand reduction, offering the most economically attractive way to realize deep reductions in carbon emissions.This article is part of the themed issue 'Material demand reduction'. © 2017 The Author(s).

Measurement of the hadronic final state in deep inelastic scattering at HERA

NASA Astrophysics Data System (ADS)

Ahmed, T.; Andreev, V.; Andrieu, B.; Arpagaus, M.; Babaev, A.; Bärwolff, H.; Bán, J.; Baranov, P.; Barrelet, E.; Bartel, W.; Bassler, U.; Beck, G. A.; Beck, H. P.; Behrend, H.-J.; Belousov, A.; Berger, Ch.; Bergstein, H.; Bernardi, G.; Bernet, R.; Berthon, U.; Bertrand-Coremans, G.; Besançon, M.; Biddulph, P.; Binder, E.; Bizot, J. C.; Blobel, V.; Borras, K.; Bosetti, P. C.; Boudry, V.; Bourdarios, C.; Brasse, F.; Braun, U.; Braunschweig, W.; Brisson, V.; Bruncko, D.; Bürger, J.; Büsser, F. W.; Buniatian, A.; Burke, S.; Buschhorn, G.; Campbell, A. J.; Carli, T.; Charles, F.; Clarke, D.; Clegg, A. B.; Colombo, M.; Coughlan, J. A.; Courau, A.; Coutures, Ch.; Cozzika, G.; Criegee, L.; Cvach, J.; Dainton, J. B.; Danilov, M.; Dann, A. W. E.; Dau, W. D.; David, M.; Deffur, E.; Delcourt, B.; Del Buono, L.; Devel, M.; De Roeck, A.; Dingus, P.; Dollfus, C.; Dowell, J. D.; Dreis, H. B.; Drescher, A.; Duboc, J.; Düllmann, D.; Dünger, O.; Duhm, H.; Eberle, M.; Ebert, J.; Ebert, T. R.; Eckerlin, G.; Efremenko, V.; Egli, S.; Eichenberger, S.; Eichler, R.; Eisele, F.; Eisenhandler, E.; Ellis, N. N.; Ellison, R. J.; Elsen, E.; Erdmann, M.; Evrard, E.; Favart, L.; Fedotov, A.; Feeken, D.; Felst, R.; Feltesse, J.; Feng, Y.; Fensome, I. F.; Ferencei, J.; Ferrarotto, F.; Flauger, W.; Fleischer, M.; Flower, P. S.; Flügge, G.; Fomenko, A.; Fominykh, B.; Forbush, M.; Formánek, J.; Foster, J. M.; Franke, G.; Fretwurst, E.; Fuhrmann, P.; Gabathuler, E.; Gamerdinger, K.; Garvey, J.; Gayler, J.; Gellrich, A.; Gennis, M.; Gensch, U.; Genzel, H.; Gerhards, R.; Gillespie, D.; Godfrey, L.; Goerlach, U.; Goerlich, L.; Goldberg, M.; Goodall, A. M.; Gorelov, I.; Goritchev, P.; Grab, C.; Grässler, H.; Grässler, R.; Greenshaw, T.; Greif, H.; Grindhammer, G.; Gruber, C.; Haack, J.; Haidt, D.; Hajduk, L.; Hamon, O.; Handschuh, D.; Hanlon, E. M.; Hapke, M.; Haries, J.; Hartz, P.; Haydar, R.; Haynes, W. J.; Heatherington, J.; Hedberg, V.; Hedgecock, R.; Heinzelmann, G.; Henderson, R. C. W.; Henschel, H.; Herma, R.; Herynek, I.; Hildesheim, W.; Hill, P.; Hilton, C. D.; Hladký, J.; Hoeger, K. C.; Huet, Ph.; Hufnagel, H.; Huot, N.; Ibbotson, M.; Jabiol, M. A.; Jacholkowska, A.; Jacobsson, C.; Jaffre, M.; Jöhnsson, L.; Johannsen, K.; Johnson, D. P.; Johnson, L.; Jung, H.; Kalmus, P. I. P.; Kasarian, S.; Kaschowitz, R.; Kasselmann, P.; Kathage, U.; Kaufmann, H. H.; Kenyon, I. R.; Kermiche, S.; Kiesling, C.; Klein, M.; Kleinwort, C.; Knies, G.; Köhler, T.; Kolanoski, H.; Kole, F.; Kolya, S. D.; Korbel, V.; Korn, M.; Kostka, P.; Kotelnikov, S. K.; Krasny, M. W.; Krehbiel, H.; Krücker, D.; Krüger, U.; Kubenka, J. P.; Küster, H.; Kuhlen, M.; Kurça, T.; Kurzhöfer, J.; Kuznik, B.; Lander, R.; London, M. P. J.; Langkau, R.; Lanius, P.; Laporte, J. F.; Lebedev, A.; Lebedev, A.; Leuschner, A.; Leverenz, C.; Levin, D.; Levonian, S.; Ley, Ch.; Lindner, A.; Lindström, G.; Loch, P.; Lohmander, H.; Lopez, G. C.; Lüers, D.; Magnussen, N.; Malinovski, E.; Mani, S.; Marage, P.; Marks, J.; Marshall, R.; Martens, J.; Martin, R.; Martyn, H.-U.; Martyniak, J.; Masson, S.; Mavroidis, A.; Maxfield, S. J.; McMahon, S. J.; Mehta, A.; Meier, K.; Merz, T.; Meyer, C. A.; Meyer, H.; Meyer, J.; Mikocki, S.; Milone, V.; Monnier, E.; Moreau, F.; Moreels, J.; Morris, J. V.; Morton, J. M.; Müller, K.; Murín, P.; Murray, S. A.; Nagovizin, V.; Naroska, B.; Naumann, Th.; Newton, D.; Nguyen, H. K.; Niebergall, F.; Nisius, R.; Nowak, G.; Noyes, G. W.; Nyberg, M.; Oberlack, H.; Obrock, U.; Olsson, J. E.; Orenstein, S.; Ould-Saada, F.; Pascaud, C.; Patel, G. D.; Peppel, E.; Peters, S.; Phillips, H. T.; Phillips, J. P.; Pichler, Ch.; Pilgram, W.; Pitzl, D.; Prosi, R.; Raupach, F.; Rauschnabel, K.; Reimer, P.; Ribarics, P.; Riech, V.; Riedlberger, J.; Rietz, M.; Robertson, S. M.; Robmann, P.; Roosen, R.; Rostovtsev, A.; Royon, C.; Rudowicz, M.; Ruffer, M.; Rusakov, S.; Rybicki, K.; Ryseck, E.; Sacton, J.; Sahlmann, N.; Sanchez, E.; Sankey, D. P. C.; Savitsky, M.; Schacht, P.; Schleper, P.; von Schlippe, W.; Schmidt, C.; Schmidt, D.; Schmitz, W.; Schröder, V.; Schulz, M.; Schwind, A.; Scobel, W.; Seehausen, U.; Sell, R.; Seman, M.; Semenov, A.; Shekelyan, V.; Sheviakov, I.; Shooshtari, H.; Siegmon, G.; Siewert, U.; Sirois, Y.; Skillicorn, I. O.; Smirnov, P.; Smith, J. R.; Smolik, L.; Soloviev, Y.; Spitzer, H.; Staroba, P.; Steenbock, M.; Steffen, P.; Steinberg, R.; Steiner, H.; Stella, B.; Stephens, K.; Stier, J.; Strachota, J.; Straumann, U.; Struczinski, W.; Sutton, J. P.; Taylor, R. E.; Thompson, G.; Thompson, R. J.; Tichomirov, I.; Trenkel, C.; Truöl, P.; Tchernyshov, V.; Turnau, J.; Tutas, J.; Urban, L.; Usik, A.; Valkar, S.; Valkarova, A.; Vallee, C.; Van Esch, P.; Vartapetian, A.; Vazdik, Y.; Vecko, M.; Verrecchia, P.; Vick, R.; Villet, G.; Vogel, E.; Wacker, K.; Walker, I. W.; Walther, A.; Weber, G.; Wegener, D.; Wegner, A.; Wellisch, H. P.; Willard, S.; Winde, M.; Winter, G.-G.; Wolff, Th.; Womersley, L. A.; Wright, A. E.; Wulff, N.; Yiou, T. P.; Ząçek, J.; Závada, P.; Zeitnitz, C.; Ziaeepour, H.; Zimmer, M.; Zimmermann, W.; Zomer, F.; H1 Collaboration

1993-01-01

We report on the first experimental study of the hadronic final state in deep inelastic electron-proton scattering with the H1 detector at HERA. Energy flow and transverse momentum characteristics are measured and presented both in the laboratory and in the hadronic center of mass frames. Comparison is made with QCD models distinguished by their different treatment of parton emission.

Deep two-photon microscopic imaging through brain tissue using the second singlet state from fluorescent agent chlorophyll α in spinach leaf

NASA Astrophysics Data System (ADS)

Shi, Lingyan; Rodríguez-Contreras, Adrián; Budansky, Yury; Pu, Yang; An Nguyen, Thien; Alfano, Robert R.

2014-06-01

Two-photon (2P) excitation of the second singlet (S) state was studied to achieve deep optical microscopic imaging in brain tissue when both the excitation (800 nm) and emission (685 nm) wavelengths lie in the "tissue optical window" (650 to 950 nm). S2 state technique was used to investigate chlorophyll α (Chl α) fluorescence inside a spinach leaf under a thick layer of freshly sliced rat brain tissue in combination with 2P microscopic imaging. Strong emission at the peak wavelength of 685 nm under the 2P S state of Chl α enabled the imaging depth up to 450 μm through rat brain tissue.

Deep two-photon microscopic imaging through brain tissue using the second singlet state from fluorescent agent chlorophyll α in spinach leaf.

PubMed

Shi, Lingyan; Rodríguez-Contreras, Adrián; Budansky, Yury; Pu, Yang; Nguyen, Thien An; Alfano, Robert R

2014-06-01

Two-photon (2P) excitation of the second singlet (S₂) state was studied to achieve deep optical microscopic imaging in brain tissue when both the excitation (800 nm) and emission (685 nm) wavelengths lie in the "tissue optical window" (650 to 950 nm). S₂ state technique was used to investigate chlorophyll α (Chl α) fluorescence inside a spinach leaf under a thick layer of freshly sliced rat brain tissue in combination with 2P microscopic imaging. Strong emission at the peak wavelength of 685 nm under the 2P S₂ state of Chl α enabled the imaging depth up to 450 μm through rat brain tissue.

Manipulating the Electronic Excited State Energies of Pyrimidine-Based Thermally Activated Delayed Fluorescence Emitters To Realize Efficient Deep-Blue Emission.

PubMed

Komatsu, Ryutaro; Ohsawa, Tatsuya; Sasabe, Hisahiro; Nakao, Kohei; Hayasaka, Yuya; Kido, Junji

2017-02-08

The development of efficient and robust deep-blue emitters is one of the key issues in organic light-emitting devices (OLEDs) for environmentally friendly, large-area displays or general lighting. As a promising technology that realizes 100% conversion from electrons to photons, thermally activated delayed fluorescence (TADF) emitters have attracted considerable attention. However, only a handful of examples of deep-blue TADF emitters have been reported to date, and the emitters generally show large efficiency roll-off at practical luminance over several hundreds to thousands of cd m -2 , most likely because of the long delayed fluorescent lifetime (τ d ). To overcome this problem, we molecularly manipulated the electronic excited state energies of pyrimidine-based TADF emitters to realize deep-blue emission and reduced τ d . We then systematically investigated the relationships among the chemical structure, properties, and device performances. The resultant novel pyrimidine emitters, called Ac-XMHPMs (X = 1, 2, and 3), contain different numbers of bulky methyl substituents at acceptor moieties, increasing the excited singlet (E S ) and triplet state (E T ) energies. Among them, Ac-3MHPM, with a high E T of 2.95 eV, exhibited a high external quantum efficiency (η ext,max ) of 18% and an η ext of 10% at 100 cd m -2 with Commission Internationale de l'Eclairage chromaticity coordinates of (0.16, 0.15). These efficiencies are among the highest values to date for deep-blue TADF OLEDs. Our molecular design strategy provides fundamental guidance to design novel deep-blue TADF emitters.

A study of the red-shift of a neutral donor bound exciton in GaN nanorods by hydrogenation

NASA Astrophysics Data System (ADS)

Park, Byung-Guon; Lee, Sang-Tae; Reddeppa, Maddaka; Kim, Moon-Deock; Oh, Jae-Eung; Lee, Sang-Kwon

2017-09-01

In this paper we account for the physics behind the exciton peak shift in GaN nanorods (NRs) due to hydrogenation. GaN NRs were selectively grown on a patterned Ti/Si(111) substrate using plasma-assisted molecular beam epitaxy, and the effect of hydrogenation on their optical properties was investigated in detail using low-temperature photoluminescence measurements. Due to hydrogenation, the emissions corresponding to the donor-acceptor pair and yellow luminescence in GaN NRs were strongly suppressed, while the emission corresponding to the neutral to donor bound exciton (D0X) exhibited red-shift. Thermal annealing of hydrogenated GaN NRs demonstrated the recovery of the D0X and deep level emission. To determine the nature of the D0X peak shift due to hydrogenation, comparative studies were carried out on various diameters of GaN NRs, which can be controlled by different growth conditions and wet-etching times. Our experimental results reveal that the D0X shift depends on the diameter of the GaN NRs after hydrogenation. The results clearly demonstrate that the hydrogenation leads to band bending of GaN NRs as compensated by hydrogen ions, which causes a red-shift in the D0X emission.

A study of the red-shift of a neutral donor bound exciton in GaN nanorods by hydrogenation.

PubMed

Park, Byung-Guon; Lee, Sang-Tae; Reddeppa, Maddaka; Kim, Moon-Deock; Oh, Jae-Eung; Lee, Sang-Kwon

2017-09-08

In this paper we account for the physics behind the exciton peak shift in GaN nanorods (NRs) due to hydrogenation. GaN NRs were selectively grown on a patterned Ti/Si(111) substrate using plasma-assisted molecular beam epitaxy, and the effect of hydrogenation on their optical properties was investigated in detail using low-temperature photoluminescence measurements. Due to hydrogenation, the emissions corresponding to the donor-acceptor pair and yellow luminescence in GaN NRs were strongly suppressed, while the emission corresponding to the neutral to donor bound exciton (D 0 X) exhibited red-shift. Thermal annealing of hydrogenated GaN NRs demonstrated the recovery of the D 0 X and deep level emission. To determine the nature of the D 0 X peak shift due to hydrogenation, comparative studies were carried out on various diameters of GaN NRs, which can be controlled by different growth conditions and wet-etching times. Our experimental results reveal that the D 0 X shift depends on the diameter of the GaN NRs after hydrogenation. The results clearly demonstrate that the hydrogenation leads to band bending of GaN NRs as compensated by hydrogen ions, which causes a red-shift in the D 0 X emission.

Infiltrated Zinc Oxide in Poly(methyl methacrylate): An Atomic Cycle Growth Study

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

Ocola, Leonidas E.; Connolly, Aine; Gosztola, David J.

We have investigated the growth of zinc oxide in a polymer matrix by sequential infiltration synthesis (SiS). The atomic cycle-by-cycle self-terminating reaction growth investigation was done using photoluminescence (PL), Raman, and X-ray photoemission spectroscopy (XPS). Results show clear differences between Zn atom configurations at the initial stages of growth. Mono Zn atoms (O-Zn and O-Zn-O) exhibit pure UV emission with little evidence of deep level oxygen vacancy states (VO). Dimer Zn atoms (O-Zn-O-Zn and O-Zn-O-Zn-O) show strong UV and visible PL emission from VO states 20 times greater than that from the mono Zn atom configuration. After three precursor cycles,more » the PL emission intensity drops significantly exhibiting first evidence of crystal formation as observed with Raman spectroscopy via the presence of longitudinal optical phonons. We also report a first confirmation of energy transfer between polymer and ZnO where the polymer absorbs light at 241 nm and emits at 360 nm, which coincides with the ZnO UV emission peak. Our work shows that ZnO dimers are unique ZnO configurations with high PL intensity, unique O1s oxidation states, and sub-10 ps absorption and decay, which are interesting properties for novel quantum material applications.« less

Nanoscale Imaging of Light-Matter Coupling Inside Metal-Coated Cavities with a Pulsed Electron Beam.

PubMed

Moerland, Robert J; Weppelman, I Gerward C; Scotuzzi, Marijke; Hoogenboom, Jacob P

2018-05-02

Many applications in (quantum) nanophotonics rely on controlling light-matter interaction through strong, nanoscale modification of the local density of states (LDOS). All-optical techniques probing emission dynamics in active media are commonly used to measure the LDOS and benchmark experimental performance against theoretical predictions. However, metal coatings needed to obtain strong LDOS modifications in, for instance, nanocavities, are incompatible with all-optical characterization. So far, no reliable method exists to validate theoretical predictions. Here, we use subnanosecond pulses of focused electrons to penetrate the metal and excite a buried active medium at precisely defined locations inside subwavelength resonant nanocavities. We reveal the spatial layout of the spontaneous-emission decay dynamics inside the cavities with deep-subwavelength detail, directly mapping the LDOS. We show that emission enhancement converts to inhibition despite an increased number of modes, emphasizing the critical role of optimal emitter location. Our approach yields fundamental insight in dynamics at deep-subwavelength scales for a wide range of nano-optical systems.

Low threshold Amplified Spontaneous Emission properties in deep blue of poly[(9,9-dioctylfluorene-2,7-dyil)-alt-p-phenylene] thin films

NASA Astrophysics Data System (ADS)

Lattante, Sandro; De Giorgi, Maria Luisa; Pasini, Mariacecilia; Anni, Marco

2017-10-01

Amongst the different optoelectronic applications of conjugated polymers, the development of new active materials for optically pumped organic lasers is still an open question particularly in the blue-near UV spectral range. We investigate the emission properties of poly[(9,9-dioctylfluorene-2,7-dyil)- alt-p-phenylene] (PFP) neat films under nanosecond pump. We demonstrate that thanks to the introduction of a phenylene moiety between two fluorene units it is possible to obtain Amplified Spontaneous Emission (ASE) with a lower threshold and a blue shifted wavelength with respect to poly(9,9-dioctylfluorene) (PFO). We demonstrate efficient ASE with a minimum threshold as low as 23 μJcm-2 and a minimum ASE wavelength of 436 nm. A maximum net optical gain of about 26 cm-1 is measured at an excitation density of 0.23 mJcm-2. These results make the PFP a good active material for optically pumped deep blue organic lasers.

Click beetle luciferase mutant and near infrared naphthyl-luciferins for improved bioluminescence imaging.

PubMed

Hall, Mary P; Woodroofe, Carolyn C; Wood, Monika G; Que, Ivo; Van't Root, Moniek; Ridwan, Yanto; Shi, Ce; Kirkland, Thomas A; Encell, Lance P; Wood, Keith V; Löwik, Clemens; Mezzanotte, Laura

2018-01-09

The sensitivity of bioluminescence imaging in animals is primarily dependent on the amount of photons emitted by the luciferase enzyme at wavelengths greater than 620 nm where tissue penetration is high. This area of work has been dominated by firefly luciferase and its substrate, D-luciferin, due to the system's peak emission (~ 600 nm), high signal to noise ratio, and generally favorable biodistribution of D-luciferin in mice. Here we report on the development of a codon optimized mutant of click beetle red luciferase that produces substantially more light output than firefly luciferase when the two enzymes are compared in transplanted cells within the skin of black fur mice or in deep brain. The mutant enzyme utilizes two new naphthyl-luciferin substrates to produce near infrared emission (730 nm and 743 nm). The stable luminescence signal and near infrared emission enable unprecedented sensitivity and accuracy for performing deep tissue multispectral tomography in mice.

Synthesis of ZnSe and ZnSe:Cu quantum dots by a room temperature photochemical (UV-assisted) approach using Na2 SeO3 as Se source and investigating optical properties.

PubMed

Khafajeh, R; Molaei, M; Karimipour, M

2017-06-01

In this study, ZnSe and ZnSe:Cu quantum dots (QDs) were synthesized using Na 2 SeO 3 as the Se source by a rapid and room temperature photochemical (UV-assisted) approach. Thioglycolic acid (TGA) was employed as the capping agent and UV illumination activated the chemical reactions. Synthesized QDs were successfully characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), photoluminescence (PL) and UV-visible (UV-vis) spectroscopy, Fourier transform-infrared (FT-IR), and energy dispersive X-ray spectroscopy (EDX). XRD analysis demonstrated the cubic zinc blend phase QDs. TEM images indicated that round-shaped particles were formed, most of which had a diameter of about 4 nm. The band gap of the ZnSe QDs was higher than that for ZnSe in bulk. PL spectra indicated an emission with three peaks related to the excitonic, surface trap states and deep level (DL) states. The band gap and QD emission were tunable only by UV illumination time during synthesis. ZnSe:Cu showed green emission due to transition of electrons from the Conduction band (CB) or surface trap states to the 2 T 2 acceptor levels of Cu 2 + . The emission was increased by increasing the Cu 2 + ion concentration, such that the optimal value of PL intensity was obtained for the nominal mole ratio of Cu:Zn 1.5%. Copyright © 2016 John Wiley & Sons, Ltd.

Sustained climate warming drives declining marine biological productivity

NASA Astrophysics Data System (ADS)

Moore, J. Keith; Fu, Weiwei; Primeau, Francois; Britten, Gregory L.; Lindsay, Keith; Long, Matthew; Doney, Scott C.; Mahowald, Natalie; Hoffman, Forrest; Randerson, James T.

2018-03-01

Climate change projections to the year 2100 may miss physical-biogeochemical feedbacks that emerge later from the cumulative effects of climate warming. In a coupled climate simulation to the year 2300, the westerly winds strengthen and shift poleward, surface waters warm, and sea ice disappears, leading to intense nutrient trapping in the Southern Ocean. The trapping drives a global-scale nutrient redistribution, with net transfer to the deep ocean. Ensuing surface nutrient reductions north of 30°S drive steady declines in primary production and carbon export (decreases of 24 and 41%, respectively, by 2300). Potential fishery yields, constrained by lower–trophic-level productivity, decrease by more than 20% globally and by nearly 60% in the North Atlantic. Continued high levels of greenhouse gas emissions could suppress marine biological productivity for a millennium.

Long Baseline Nulling Interferometry with the Keck Telescopes: A Progress Report

NASA Technical Reports Server (NTRS)

Mennesson, Bertrand; Akeson, R.; Appleby, E.; Bell, J.; Booth, A.; Colavita, M. M.; Crawford, S.; Creech-Eakman, M. J.; Dahl, W.; Fanson, J.;

Long-term noise statistics from the Gulf of Mexico

NASA Astrophysics Data System (ADS)

Eller, Anthony I.; Ioup, George E.; Ioup, Juliette W.; Larue, James P.

2003-04-01

Long-term, omnidirectional acoustic noise measurements were conducted in the northeastern Gulf of Mexico during the summer of 2001. These efforts were a part of the Littoral Acoustic Demonstration Center project, Phase I. Initial looks at the noise time series, processed in standard one-third-octave bands from 10 to 5000 Hz, show noise levels that differ substantially from customary deep-water noise spectra. Contributing factors to this highly dynamic noise environment are an abundance of marine mammal emissions and various industrial noises. Results presented here address long-term temporal variability, temporal coherence times, the fluctuation spectrum, and coherence of fluctuations across the frequency spectrum. [Research supported by ONR.

Feasibility of infrared Earth tracking for deep-space optical communications.

PubMed

Chen, Yijiang; Hemmati, Hamid; Ortiz, Gerry G

2012-01-01

Infrared (IR) Earth thermal tracking is a viable option for optical communications to distant planet and outer-planetary missions. However, blurring due to finite receiver aperture size distorts IR Earth images in the presence of Earth's nonuniform thermal emission and limits its applicability. We demonstrate a deconvolution algorithm that can overcome this limitation and reduce the error from blurring to a negligible level. The algorithm is applied successfully to Earth thermal images taken by the Mars Odyssey spacecraft. With the solution to this critical issue, IR Earth tracking is established as a viable means for distant planet and outer-planetary optical communications. © 2012 Optical Society of America

Spatial distribution of marine crenarchaeota group I in the vicinity of deep-sea hydrothermal systems.

PubMed

Takai, Ken; Oida, Hanako; Suzuki, Yohey; Hirayama, Hisako; Nakagawa, Satoshi; Nunoura, Takuro; Inagaki, Fumio; Nealson, Kenneth H; Horikoshi, Koki

2004-04-01

Distribution profiles of marine crenarchaeota group I in the vicinity of deep-sea hydrothermal systems were mapped with culture-independent molecular techniques. Planktonic samples were obtained from the waters surrounding two geographically and geologically distinct hydrothermal systems, and the abundance of marine crenarchaeota group I was examined by 16S ribosomal DNA clone analysis, quantitative PCR, and whole-cell fluorescence in situ hybridization. A much higher proportion of marine crenarchaeota group I within the microbial community was detected in deep-sea hydrothermal environments than in normal deep and surface seawaters. The highest proportion was always obtained from the ambient seawater adjacent to hydrothermal emissions and chimneys but not from the hydrothermal plumes. These profiles were markedly different from the profiles of epsilon-Proteobacteria, which are abundant in the low temperatures of deep-sea hydrothermal environments.

The Stacked LYα Emission Profile from the Circum-Galactic Medium of z ˜ 2 Quasars

NASA Astrophysics Data System (ADS)

Arrigoni Battaia, Fabrizio; Hennawi, Joseph F.; Cantalupo, Sebastiano; Prochaska, J. Xavier

2016-09-01

In the context of the FLASHLIGHT survey, we obtained deep narrowband images of 15 z ˜ 2 quasars with the Gemini Multi-object Spectrograph on Gemini South in an effort to measure Lyα emission from circum- and intergalactic gas on scales of hundreds of kpc from the central quasar. We do not detect bright giant Lyα nebulae (SB ˜ 10-17 erg s-1 cm-2 arcsec-2 at distances >50 kpc) around any of our sources, although we routinely (≃47%) detect smaller-scale <50 kpc Lyα emission at this surface brightness level emerging from either the extended narrow emission line regions powered by the quasars or by star formation in their host galaxies. We stack our 15 deep images to study the average extended Lyα surface brightness profile around z ˜ 2 quasars, carefully PSF-subtracting the unresolved emission component and paying close attention to sources of systematic error. Our analysis, which achieves an unprecedented depth, reveals a surface brightness of SBLyα ˜ 10-19 erg s-1 cm-2 arcsec-2 at ˜200 kpc, with a 2.3σ detection of Lyα emission at SB {}{Lyα }=(5.5+/- 3.1)× {10}-20 erg s-1 cm-2 arcsec-2 within an annulus spanning 50 kpc < R < 500 kpc from the quasars. Assuming that this Lyα emission is powered by fluorescence from highly ionized gas illuminated by the bright central quasar, we deduce an average volume density of n H = 0.6 × 10-2 cm-3 on these large scales. Our results are in broad agreement with the densities suggested by cosmological hydrodynamical simulations of massive (M ≃ 1012.5 M ⊙) quasar hosts; however, they indicate that the typical quasars at these redshifts are surrounded by gas that is a factor of ˜100 times less dense than the (˜1 cm-3) gas responsible for the giant bright Lyα nebulae around quasars recently discovered by our group. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência, Tecnologia e Inovação (Brazil), and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina).

Biochemical Detection and Identification False Alarm Rate Dependence on Wavelength Using Laser Induced Fluorescence

NASA Technical Reports Server (NTRS)

Bhartia, R.; Hug, W. F.; Sala, E. C.; Sijapati, K.; Lane, A. L.; Reid, R. D.; Conrad, P. G.

2006-01-01

Most organic and many inorganic materials absorb strongly in specific wavelength ranges in the deep UV between about 220nm and 300nm. Excitation within these absorption bands results in native fluorescence emission. Each compound or composite material, such as a bacterial spore, has a unique excitation-emission fingerprint that can be used to provide information about the material. The sensitivity and specificity with which these materials can be detected and identified depends on the excitation wavelength and the number and location of observation wavelengths.We will present data on our deep ultraviolet Targeted Ultraviolet Chemical Sensors that demonstrate the sensitivity and specificity of the sensors. In particular, we will demonstrate the ability to quantitatively differentiate a wide range of biochemical agent targets against a wide range of background materials. We will describe the relationship between spectral resolution and specificity in target identification, as well as simple, fast, algorithms to identify materials.Hand-held, battery operated instruments using a deep UV laser and multi-band detection have been developed and deployed on missions to the Antarctic, the Arctic, and the deep ocean with the capability of detecting a single bacterial spore and to differentiate a wide range of organic and biological compounds.

Spatial scales of bacterial community diversity at cold seeps (Eastern Mediterranean Sea)

PubMed Central

Pop Ristova, Petra; Wenzhöfer, Frank; Ramette, Alban; Felden, Janine; Boetius, Antje

2015-01-01

Cold seeps are highly productive, fragmented marine ecosystems that form at the seafloor around hydrocarbon emission pathways. The products of microbial utilization of methane and other hydrocarbons fuel rich chemosynthetic communities at these sites, with much higher respiration rates compared with the surrounding deep-sea floor. Yet little is known as to the richness, composition and spatial scaling of bacterial communities of cold seeps compared with non-seep communities. Here we assessed the bacterial diversity across nine different cold seeps in the Eastern Mediterranean deep-sea and surrounding seafloor areas. Community similarity analyses were carried out based on automated ribosomal intergenic spacer analysis (ARISA) fingerprinting and high-throughput 454 tag sequencing and were combined with in situ and ex situ geochemical analyses across spatial scales of a few tens of meters to hundreds of kilometers. Seep communities were dominated by Deltaproteobacteria, Epsilonproteobacteria and Gammaproteobacteria and shared, on average, 36% of bacterial types (ARISA OTUs (operational taxonomic units)) with communities from nearby non-seep deep-sea sediments. Bacterial communities of seeps were significantly different from those of non-seep sediments. Within cold seep regions on spatial scales of only tens to hundreds of meters, the bacterial communities differed considerably, sharing <50% of types at the ARISA OTU level. Their variations reflected differences in porewater sulfide concentrations from anaerobic degradation of hydrocarbons. This study shows that cold seep ecosystems contribute substantially to the microbial diversity of the deep-sea. PMID:25500510

Effect of swift heavy ion irradiation on deep levels in Au /n-Si (100) Schottky diode studied by deep level transient spectroscopy

NASA Astrophysics Data System (ADS)

Kumar, Sandeep; Katharria, Y. S.; Kumar, Sugam; Kanjilal, D.

2007-12-01

In situ deep level transient spectroscopy has been applied to investigate the influence of 100MeV Si7+ ion irradiation on the deep levels present in Au/n-Si (100) Schottky structure in a wide fluence range from 5×109to1×1012ions cm-2. The swift heavy ion irradiation introduces a deep level at Ec-0.32eV. It is found that initially, trap level concentration of the energy level at Ec-0.40eV increases with irradiation up to a fluence value of 1×1010cm-2 while the deep level concentration decreases as irradiation fluence increases beyond the fluence value of 5×1010cm-2. These results are discussed, taking into account the role of energy transfer mechanism of high energy ions in material.

Effect of air-staging on anthracite combustion and NOx formation

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

Weidong Fan; Zhengchun Lin; Youyi Li

Experiments were carried out in a multipath air inlet one-dimensional furnace to assess NOx emission characteristics of the staged combustion of anthracite coal. These experiments allowed us to study the impact of pulverized coal fineness and burnout air position on emission under both deep and shallow air-staged combustion conditions. We also studied the impact of char-nitrogen release on both the burning-out process of the pulverized coal and the corresponding carbon content in fly ash. We found that air-staged combustion affects a pronounced reduction in NOx emissions from the combustion of anthracite coal. The more the air is staged, the moremore » NOx emission is reduced. In shallow air-staged combustion (f{sub M} = 0.85), the fineness of the pulverized coal strongly influences emissions, and finer coals result in lower emissions. Meanwhile, the burnout air position has only a weak effect. In the deep air-staged combustion (f{sub M} = 0.6), the effect of coal fineness is smaller, and the burnout air position has a stronger effect. When the primary combustion air is stable, NOx emissions increase with increasing burnout air. This proves that, in the burnout zone, coal char is responsible for the discharge of fuel-nitrogen that is oxidized to NOx. The measurement of secondary air staging in a burnout zone can help inhibit the oxidization of NO caused by nitrogen release. Air-staged combustion has little effect on the burnout of anthracite coal, which proves to be suitable for air-staged combustion. 31 refs., 11 figs., 1 tab.« less

CHEERS Results on Mrk 573: A Study of Deep Chandra Observations

NASA Astrophysics Data System (ADS)

Paggi, Alessandro; Wang, Junfeng; Fabbiano, Giuseppina; Elvis, Martin; Karovska, Margarita

2012-09-01

We present results on Mrk 573 obtained as part of the CHandra survey of Extended Emission-line Regions in nearby Seyfert galaxies (CHEERS). Previous studies showed that this source features a biconical emission in the soft X-ray band closely related to the narrow-line region as mapped by the [O III] emission line and the radio emission, though on a smaller scale; we investigate the properties of soft X-ray emission from this source with new deep Chandra observations. Making use of the subpixel resolution of the Chandra/ACIS image and point-spread function deconvolution, we resolve and study substructures in each ionizing cone. The two cone spectra are fitted with a photoionization model, showing a mildly photoionized phase diffused over the bicone. Thermal collisional gas at about ~1.1 keV and ~0.8 keV appears to be located between the nucleus and the "knots" resolved in radio observations, and between the "arcs" resolved in the optical images, respectively; this can be interpreted in terms of shock interaction with the host galactic plane. The nucleus shows a significant flux decrease across the observations indicating variability of the active galactic nucleus (AGN), with the nuclear region featuring a higher ionization parameter with respect to the bicone region. The long exposure allows us to find extended emission up to ~7 kpc from the nucleus along the bicone axis. Significant emission is also detected in the direction perpendicular to the ionizing cones, disagreeing with the fully obscuring torus prescribed in the AGN unified model and suggesting instead the presence of a clumpy structure.

The total hemispheric emissivity of painted aluminum honeycomb at cryogenic temperatures

NASA Astrophysics Data System (ADS)

Tuttle, J.; Canavan, E.; DiPirro, M.; Li, X.; Knollenberg, P.

2014-01-01

NASA uses high-emissivity surfaces on deep-space radiators and thermal radiation absorbers in test chambers. Aluminum honeycomb core material, when coated with a high-emissivity paint, provides a lightweight, mechanically robust, and relatively inexpensive black surface that retains its high emissivity down to low temperatures. At temperatures below about 100 Kelvin, this material performs much better than the paint itself. We measured the total hemispheric emissivity of various painted honeycomb configurations using an adaptation of an innovative technique developed for characterizing thin black coatings. These measurements were performed from room temperature down to 30 Kelvin. We describe the measurement technique and compare the results with predictions from a detailed thermal model of each honeycomb configuration.

The Total Hemispheric Emissivity of Painted Aluminum Honeycomb at Cryogenic Temperatures

NASA Technical Reports Server (NTRS)

Tuttle, J.; Canavan, E.; DiPirro, M.; Li, X.; Knollenberg, K.

2013-01-01

NASA uses high-emissivity surfaces on deep-space radiators or thermal radiation absorbers in test chambers. Aluminum honeycomb core material, when coated with a high-emissivity paint, provides a lightweight, mechanically robust, and relatively inexpensive black surface that retains its high emissivity down to low temperatures. At temperatures below about 100 Kelvin, this material performs much better than the paint itself. We measured the total hemispheric emissivity of various painted honeycomb configurations using an adaptation of an innovative technique developed for characterizing thin black coatings. These measurements were performed from room temperature down to 30 Kelvin. We describe the measurement technique and compare the results with predictions from a detailed thermal model of each honeycomb configuration.

The Evolution of Normal Galaxy X-Ray Emission Through Cosmic History: Constraints from the 6 MS Chandra Deep Field-South

NASA Technical Reports Server (NTRS)

Lehmer, B. D.; Basu-Zych, A. R.; Mineo, S.; Brandt, W. N.; Eurfrasio, R. T.; Fragos, T.; Hornschemeier, A. E.; Lou, B.; Xue, Y. Q.; Bauer, F. E.;

Comparison of Landfill Methane Oxidation Measured Using Stable Isotope Analysis and CO2/CH4 Fluxes Measured by the Eddy Covariance Method

NASA Astrophysics Data System (ADS)

Xu, L.; Chanton, J.; McDermitt, D. K.; Li, J.; Green, R. B.

2015-12-01

Methane plays a critical role in the radiation balance and chemistry of the atmosphere. Globally, landfill methane emission contributes about 10-19% of the anthropogenic methane burden into the atmosphere. In the United States, 18% of annual anthropogenic methane emissions come from landfills, which represent the third largest source of anthropogenic methane emissions, behind enteric fermentation and natural gas and oil production. One uncertainty in estimating landfill methane emissions is the fraction of methane oxidized when methane produced under anaerobic conditions passes through the cover soil. We developed a simple stoichiometric model to estimate methane oxidation fraction when the anaerobic CO2 / CH4 production ratio is known, or can be estimated. The model predicts a linear relationship between CO2 emission rates and CH4 emission rates, where the slope depends on anaerobic CO2 / CH4 production ratio and the fraction of methane oxidized, and the intercept depends on non-methane-dependent oxidation processes. The model was tested using carbon dioxide emission rates (fluxes) and methane emission rates (fluxes) measured using the eddy covariance method over a one year period at the Turkey Run landfill in Georgia, USA. The CO2 / CH4 production ratio was estimated by measuring CO2 and CH4 concentrations in air sampled under anaerobic conditions deep inside the landfill. We also used a mass balance approach to independently estimate fractional oxidation based on stable isotope measurements (δ13C of methane) of gas samples taken from deep inside the landfill and just above the landfill surface. Results from the two independent methods agree well. The model will be described and methane oxidation will be discussed in relation to wind direction, location at the landfill, and age of the deposited refuse.

Single and double acceptor-levels of a carbon-hydrogen defect in n-type silicon

NASA Astrophysics Data System (ADS)

Stübner, R.; Scheffler, L.; Kolkovsky, Vl.; Weber, J.

2016-05-01

In the present study, we discuss the origin of two dominant deep levels (E42 and E262) observed in n-type Si, which is subjected to hydrogenation by wet chemical etching or a dc H-plasma treatment. Their activation enthalpies determined from Laplace deep level transient spectroscopy measurements are EC-0.06 eV (E42) and EC-0.51 eV (E262). The similar annealing behavior and identical depth profiles of E42 and E262 correlate them with two different charge states of the same defect. E262 is attributed to a single acceptor state due to the absence of the Poole-Frenkel effect and the lack of a capture barrier for electrons. The emission rate of E42 shows a characteristic enhancement with the electric field, which is consistent with the assignment to a double acceptor state. In samples with different carbon and hydrogen content, the depth profiles of E262 can be explained by a defect with one H-atom and one C-atom. From a comparison with earlier calculations [Andersen et al., Phys. Rev. B 66, 235205 (2002)], we attribute E42 to the double acceptor and E262 to the single acceptor state of the CH1AB configuration, where one H atom is directly bound to carbon in the anti-bonding position.

Single and double acceptor-levels of a carbon-hydrogen defect in n-type silicon

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

Stübner, R.; Scheffler, L.; Kolkovsky, Vl., E-mail: kolkov@ifpan.edu.pl

In the present study, we discuss the origin of two dominant deep levels (E42 and E262) observed in n-type Si, which is subjected to hydrogenation by wet chemical etching or a dc H-plasma treatment. Their activation enthalpies determined from Laplace deep level transient spectroscopy measurements are E{sub C}-0.06 eV (E42) and E{sub C}-0.51 eV (E262). The similar annealing behavior and identical depth profiles of E42 and E262 correlate them with two different charge states of the same defect. E262 is attributed to a single acceptor state due to the absence of the Poole-Frenkel effect and the lack of a capture barrier formore » electrons. The emission rate of E42 shows a characteristic enhancement with the electric field, which is consistent with the assignment to a double acceptor state. In samples with different carbon and hydrogen content, the depth profiles of E262 can be explained by a defect with one H-atom and one C-atom. From a comparison with earlier calculations [Andersen et al., Phys. Rev. B 66, 235205 (2002)], we attribute E42 to the double acceptor and E262 to the single acceptor state of the CH{sub 1AB} configuration, where one H atom is directly bound to carbon in the anti-bonding position.« less

The influence of biopreparations on the reduction of energy consumption and CO2 emissions in shallow and deep soil tillage.

PubMed

Naujokienė, Vilma; Šarauskis, Egidijus; Lekavičienė, Kristina; Adamavičienė, Aida; Buragienė, Sidona; Kriaučiūnienė, Zita

2018-06-01

The application of innovation in agriculture technologies is very important for increasing the efficiency of agricultural production, ensuring the high productivity of plants, production quality, farm profitability, the positive balance of used energy, and the requirements of environmental protection. Therefore, it is a scientific problem that solid and soil surfaces covered with plant residue have a negative impact on the work, traction resistance, energy consumption, and environmental pollution of tillage machines. The objective of this work was to determine the dependence of the reduction of energy consumption and CO 2 gas emissions on different biopreparations. Experimental research was carried out in a control (SC1) and seven different biopreparations using scenarios (SC2-SC8) using bacterial and non-bacterial biopreparations in different consistencies (with essential and mineral oils, extracts of various grasses and sea algae, phosphorus, potassium, humic and gibberellic acids, copper, zinc, manganese, iron, and calcium), estimating discing and plowing as the energy consumption parameters of shallow and deep soil tillage machines, respectively. CO 2 emissions were determined by evaluating soil characteristics (such as hardness, total porosity and density). Meteorological conditions such average daily temperatures (2015-20.3 °C; 2016-16.90 °C) and precipitations (2015-6.9 mm; 2016-114.9 mm) during the month strongly influenced different results in 2015 and 2016. Substantial differences between the averages of energy consumption identified in approximately 62% of biological preparation combinations created usage scenarios. Experimental research established that crop field treatments with biological preparations at the beginning of vegetation could reduce the energy consumption of shallow tillage machines by up to approximately 23%, whereas the energy consumption of deep tillage could be reduced by up to approximately 19.2% compared with the control treatment. The experimental research results reveal the reduction of CO 2 emissions in shallow tillage to approximately 20.14% (and that in deep tillage to approximately 19.16%) when works were performed by different biological preparation usage scenarios. This experimental research demonstrates the efficient use of the special adaptation of a new biotechnological method for the reduction of the energy consumption and CO 2 gas emissions of agricultural machinery. Copyright © 2018 Elsevier B.V. All rights reserved.

THE ALMA SPECTROSCOPIC SURVEY IN THE HUBBLE ULTRA DEEP FIELD: IMPLICATIONS FOR SPECTRAL LINE INTENSITY MAPPING AT MILLIMETER WAVELENGTHS AND CMB SPECTRAL DISTORTIONS

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

Carilli, C. L.; Walter, F.; Chluba, J.

We present direct estimates of the mean sky brightness temperature in observing bands around 99 and 242 GHz due to line emission from distant galaxies. These values are calculated from the summed line emission observed in a blind, deep survey for spectral line emission from high redshift galaxies using ALMA (the ALMA spectral deep field observations “ASPECS” survey). In the 99 GHz band, the mean brightness will be dominated by rotational transitions of CO from intermediate and high redshift galaxies. In the 242 GHz band, the emission could be a combination of higher order CO lines, and possibly [C ii]more » 158 μ m line emission from very high redshift galaxies ( z  ∼ 6–7). The mean line surface brightness is a quantity that is relevant to measurements of spectral distortions of the cosmic microwave background, and as a potential tool for studying large-scale structures in the early universe using intensity mapping. While the cosmic volume and the number of detections are admittedly small, this pilot survey provides a direct measure of the mean line surface brightness, independent of conversion factors, excitation, or other galaxy formation model assumptions. The mean surface brightness in the 99 GHZ band is: T{sub B}  = 0.94 ± 0.09 μ K. In the 242 GHz band, the mean brightness is: T{sub B}  = 0.55 ± 0.033 μ K. These should be interpreted as lower limits on the average sky signal, since we only include lines detected individually in the blind survey, while in a low resolution intensity mapping experiment, there will also be the summed contribution from lower luminosity galaxies that cannot be detected individually in the current blind survey.« less

Origin of the lethal gas burst from Lake Monoun, Cameroun

NASA Astrophysics Data System (ADS)

Sigurdsson, H.; Devine, J. D.; Tchua, F. M.; Presser, F. M.; Pringle, M. K. W.; Evans, W. C.

1987-03-01

On 15 August, 1984, a lethal gas burst issued from a submerged 96-m-deep crater in Lake Monoun in Cameroun, western Africa, killing 37 people. The event was associated with a landslide from the eastern crater rim, which slumped into deep water. Waters below 50 m are anoxic, dominated by high Fe 2+ (˜600 mg/l) and HCO 3- (≥ 1900 mg/l), anoxic and supersaturated with siderite, which is a major component of the crater floor sediments. The unusually high Fe 2+ levels are attributed to reduction of laterite-derived ferric iron gradually brought into the lake as loess and in river input. Sulfur compounds are below detection limits in both water and gas. Gases effervescing from depressurized deep waters are dominantly CO 2 with minor CH 4, having δ 13C of -7.18 and -54.8 per mil, respectively. Bacterial decomposition of organic matter may account for the methane, but 14C of lake water indicates that only 10% of the carbon is modern, giving an apparent age of 18,000 years. The dominant source of carbon is therefore attributed to long-term emission of CO 2 as volcanic exhalation from vents within the crater, which led to gradual build-up of HCO 3- in the lake. The density stratification of the lake may have been upset by an earthquake and underwater landslide on 15 August, which triggered overturn of the lake and caused nucleation of CO 2 in the deep water. The resultant ebullition of CO 2 from deep lake waters led to a gas burst at the surface and locally generated a water wave up to 5 m high. People travelling through the gas cloud were asphyxiated, presumably from CO 2, and suffered skin discoloration from unidentified components.

Origin of the lethal gas burst from Lake Monoun, Cameroun

USGS Publications Warehouse

Sigurdsson, Haraldur; Devine, J.D.; Tchua, F.M.; Presser, F.M.; Pringle, M.K.W.; Evans, William C.

1987-01-01

On 15 August, 1984, a lethal gas burst issued from a submerged 96-m-deep crater in Lake Monoun in Cameroun, western Africa, killing 37 people. The event was associated with a landslide from the eastern crater rim, which slumped into deep water. Waters below 50 m are anoxic, dominated by high Fe2+ (???600 mg/l) and HCO3- (??? 1900 mg/l), anoxic and supersaturated with siderite, which is a major component of the crater floor sediments. The unusually high Fe2+ levels are attributed to reduction of laterite-derived ferric iron gradually brought into the lake as loess and in river input. Sulfur compounds are below detection limits in both water and gas. Gases effervescing from depressurized deep waters are dominantly CO2 with minor CH4, having ??13C of -7.18 and -54.8 per mil, respectively. Bacterial decomposition of organic matter may account for the methane, but 14C of lake water indicates that only 10% of the carbon is modern, giving an apparent age of 18,000 years. The dominant source of carbon is therefore attributed to long-term emission of CO2 as volcanic exhalation from vents within the crater, which led to gradual build-up of HCO3- in the lake. The density stratification of the lake may have been upset by an earthquake and underwater landslide on 15 August, which triggered overturn of the lake and caused nucleation of CO2 in the deep water. The resultant ebullition of CO2 from deep lake waters led to a gas burst at the surface and locally generated a water wave up to 5 m high. People travelling through the gas cloud were asphyxiated, presumably from CO2, and suffered skin discoloration from unidentified components. ?? 1987.

Thermal quenching effect of an infrared deep level in Mg-doped p-type GaN films

NASA Astrophysics Data System (ADS)

Kim, Keunjoo; Chung, Sang Jo

2002-03-01

The thermal quenching of an infrared deep level of 1.2-1.5 eV has been investigated on Mg-doped p-type GaN films, using one- and two-step annealing processes and photocurrent measurements. The deep level appeared in the one-step annealing process at a relatively high temperature of 900 °C, but disappeared in the two-step annealing process with a low-temperature step and a subsequent high-temperature step. The persistent photocurrent was residual in the sample including the deep level, while it was terminated in the sample without the deep level. This indicates that the deep level is a neutral hole center located above a quasi-Fermi level, estimated with an energy of EpF=0.1-0.15 eV above the valence band at a hole carrier concentration of 2.0-2.5×1017/cm3.

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.

A Deep Extragalactic Survey with the ART-XC Telescope of the Spectrum-RG Observatory: Simulations and Expected Results

NASA Astrophysics Data System (ADS)

Mereminskiy, I. A.; Filippova, E. V.; Burenin, R. A.; Sazonov, S. Yu.; Pavlinsky, M. N.; Tkachenko, A. Yu.; Lapshov, I. Yu.; Shtykovskiy, A. E.; Krivonos, R. A.

2018-02-01

To choose the best strategy for conducting a deep extragalactic survey with the ART-XC X-ray telescope onboard the Spectrum-Röntgen-Gamma (SRG) observatory and to estimate the expected results, we have simulated the observations of a 1.1° × 1.1° field in the 5-11 and 8-24 keV energy bands. For this purpose, we have constructed a model of the active galactic nuclei (AGN) population that reflects the properties of the X-ray emission from such objects. The photons that "arrived" from these sources were passed through a numerical model of the telescope, while the resulting data were processed with the standard ART-XC data processing pipeline. We show that several hundred AGNs at redshifts up to z ≈ 3 will be detected in such a survey over 1.2 Ms of observations with the expected charged particle background levels. Among them there will be heavily obscured AGNs, which will allow a more accurate estimate of the fraction of such objects in the total population to be made. Source confusion is expected at fluxes below 2 × 10-14 erg s-1 cm-2 (5-11 keV). Since this value can exceed the source detection threshold in a deep survey at low particle background levels, it may turn out to be more interesting to conduct a survey of larger area (several square degrees) but smaller depth, obtaining a sample of approximately four hundred bright AGNs as a result.

Potential Interference from Wireless Water Tank Transmitters at Goldstone

NASA Astrophysics Data System (ADS)

Ho, C.

2008-02-01

The Deep Space Network (DSN) facility in the Goldstone, California, area is considering installation of a new type of wireless transmitter (M2400S) within the facility. The transmitters will be used to monitor the water levels in several water tanks. Then these water-level signals will be transmitted to the nearby DSN facilities using transmitters operating in the UHF band (900-MHz) or S-band (2.4-GHz). This study is to evaluate the interference effects from the transmitters in adjacent DSN receiving stations. First we perform a terrain profile analysis to identify if there is a line of sight between each transmitter and the nearby DSN stations. After taking into account terrain shielding using high-resolution data, total propagation losses are calculated along each path. Then we perform the link analysis for each site to identify if the interference power exceeds the protection threshold of DSN receiving stations. As a result, we find that, because there is no bandpass filter installed in the transmitter system, interference power from the new transmitter at S-band will greatly exceed the protection criteria of broadband radio astronomy services (RAS) at S-band, such as Deep Space Station (DSS) 12 and DSS 28, by about 50 dB. The interference may also cause problems on all deep-space research stations at S-band, such as the Mars, Apollo, Venus, and Gemini sites. Without a sharp bandpass filter to suppress the out-of-band emissions in the frequency bands that the DSN station and RAS use, the author recommends not installing this type of transmitter within the Goldstone DSN facility area.

Carbonyl-based blue autofluorescence of proteins and amino acids

PubMed Central

Niyangoda, Chamani; Miti, Tatiana; Breydo, Leonid; Uversky, Vladimir

2017-01-01

Intrinsic protein fluorescence is inextricably linked to the near-UV autofluorescence of aromatic amino acids. Here we show that a novel deep-blue autofluorescence (dbAF), previously thought to emerge as a result of protein aggregation, is present at the level of monomeric proteins and even poly- and single amino acids. Just as its aggregation-related counterpart, this autofluorescence does not depend on aromatic residues, can be excited at the long wavelength edge of the UV and emits in the deep blue. Differences in dbAF excitation and emission peaks and intensities from proteins and single amino acids upon changes in solution conditions suggest dbAF’s sensitivity to both the chemical identity and solution environment of amino acids. Autofluorescence comparable to dbAF is emitted by carbonyl-containing organic solvents, but not those lacking the carbonyl group. This implicates the carbonyl double bonds as the likely source for the autofluorescence in all these compounds. Using beta-lactoglobulin and proline, we have measured the molar extinction coefficients and quantum yields for dbAF in the monomeric state. To establish its potential utility in monitoring protein biophysics, we show that dbAF emission undergoes a red-shift comparable in magnitude to tryptophan upon thermal denaturation of lysozyme, and that it is sensitive to quenching by acrylamide. Carbonyl dbAF therefore provides a previously neglected intrinsic optical probe for investigating the structure and dynamics of amino acids, proteins and, by extension, DNA and RNA. PMID:28542206

Diverse origins of Arctic and Subarctic methane point source emissions identified with multiply-substituted isotopologues

NASA Astrophysics Data System (ADS)

Douglas, P. M. J.; Stolper, D. A.; Smith, D. A.; Walter Anthony, K. M.; Paull, C. K.; Dallimore, S.; Wik, M.; Crill, P. M.; Winterdahl, M.; Eiler, J. M.; Sessions, A. L.

2016-09-01

Methane is a potent greenhouse gas, and there are concerns that its natural emissions from the Arctic could act as a substantial positive feedback to anthropogenic global warming. Determining the sources of methane emissions and the biogeochemical processes controlling them is important for understanding present and future Arctic contributions to atmospheric methane budgets. Here we apply measurements of multiply-substituted isotopologues, or clumped isotopes, of methane as a new tool to identify the origins of ebullitive fluxes in Alaska, Sweden and the Arctic Ocean. When methane forms in isotopic equilibrium, clumped isotope measurements indicate the formation temperature. In some microbial methane, however, non-equilibrium isotope effects, probably related to the kinetics of methanogenesis, lead to low clumped isotope values. We identify four categories of emissions in the studied samples: thermogenic methane, deep subsurface or marine microbial methane formed in isotopic equilibrium, freshwater microbial methane with non-equilibrium clumped isotope values, and mixtures of deep and shallow methane (i.e., combinations of the first three end members). Mixing between deep and shallow methane sources produces a non-linear variation in clumped isotope values with mixing proportion that provides new constraints for the formation environment of the mixing end-members. Analyses of microbial methane emitted from lakes, as well as a methanol-consuming methanogen pure culture, support the hypothesis that non-equilibrium clumped isotope values are controlled, in part, by kinetic isotope effects induced during enzymatic reactions involved in methanogenesis. Our results indicate that these kinetic isotope effects vary widely in microbial methane produced in Arctic lake sediments, with non-equilibrium Δ18 values spanning a range of more than 5‰.

A Deep Narrowband Imaging Search for C IV and He II Emission from Lyα Blobs

NASA Astrophysics Data System (ADS)

Arrigoni Battaia, Fabrizio; Yang, Yujin; Hennawi, Joseph F.; Prochaska, J. Xavier; Matsuda, Yuichi; Yamada, Toru; Hayashino, Tomoki

2015-05-01

We conduct a deep narrowband imaging survey of 13 Lyα blobs (LABs) located in the SSA22 proto-cluster at z ˜ 3.1 in the C iv and He ii emission lines in an effort to constrain the physical process powering the Lyα emission in LABs. Our observations probe down to unprecedented surface brightness (SB) limits of (2.1-3.4) × 10-18 erg s-1 cm-2 arcsec-2 per 1 arcsec2 aperture (5σ) for the He ii λ1640 and C iv λ1549 lines, respectively. We do not detect extended He ii and C iv emission in any of the LABs, placing strong upper limits on the He ii/Lyα and C iv/Lyα line ratios, of 0.11 and 0.16, for the brightest two LABs in the field. We conduct detailed photoionization modeling of the expected line ratios and find that, although our data constitute the deepest ever observations of these lines, they are still not deep enough to rule out a scenario where the Lyα emission is powered by the ionizing radiation from an obscured active galactic nucleus. Our models can accommodate He ii/Lyα and C iv/Lyα ratios as low as ≃0.05 and ≃0.07, respectively, implying that one needs to reach SB as low as (1-1.5) × 10-18 erg s-1 cm-2 arcsec-2 (at 5σ) in order to rule out a photoionization scenario. These depths will be achievable with the new generation of image-slicing integral field units such as the Multi Unit Spectroscopic Explorer (MUSE) on VLT and the Keck Cosmic Web Imager (KCWI). We also model the expected He ii/Lyα and C iv/Lyα in a different scenario, where Lyα emission is powered by shocks generated in a large-scale superwind, but find that our observational constraints can only be met for shock velocities vs ≳ 250 km s-1, which appear to be in conflict with recent observations of quiescent kinematics in LABs. .

A Chandra Study of the Stellar X-Ray Emissivity of Globular Clusters in the M31 Bulge

NASA Astrophysics Data System (ADS)

Xu, Xiao-jie; Li, Zhiyuan

2018-03-01

The X-ray emissivity (i.e., luminosity per unit stellar mass) of globular clusters (GCs) is an important indicator of their dynamical evolution history. Based on deep archival Chandra observations, we report a stacking analysis of 44 GCs with 0.5–8 keV luminosities L X ≲ 1035 erg s‑1 in the M31 bulge, which are supposed to be dominated by cataclysmic variables (CVs) and coronally active binaries (ABs). We obtain a significant detection at the 5σ level in 0.5–8 keV band. The average X-ray luminosity per GC and the average X-ray emissivity are determined to be 5.3 ± 1.6 × 1033 erg s‑1 and 13.2 ± 4.3 × 1027 erg s‑1 {M}ȯ -1, respectively. Both of these values are consistent with those of Milky Way GCs. Moreover, the measured emissivity of M31 GCs is also consistent with that of the Milky Way field stars. Massive GCs have X-ray luminosities that are marginally higher than those of less massive ones. Massive GCs also show a lower emissivity (5.0+/- 2.5× {10}27 {erg} {{{s}}}-1 {M}ȯ -1) than less massive ones (26.5+/- 14.3× {10}27 {erg} {{{s}}}-1 {M}ȯ -1), which is consistent with the scenario that the (progenitors of) CVs and ABs were more efficiently destroyed via stellar encounters in the more massive GCs. No dependence of the X-ray emissivity on GC color or on the projected galactocentric distance of GCs is found.

Far red bioluminescence from two deep-sea fishes.

PubMed

Widder, E A; Latz, M I; Herring, P J; Case, J F

1984-08-03

Spectral measurements of red bioluminescence were obtained from the deep-sea stomiatoid fishes Aristostomias scintillans (Gilbert) and Malacosteus niger (Ayres). Red luminescence from suborbital light organs extends to the near infrared, with peak emission at approximately 705 nanometers in the far red. These fishes also have postorbital light organs that emit blue luminescence with maxima between 470 and 480 nanometers. The red bioluminescence may be due to an energy transfer system and wavelength-selective filtering.

Application of positron annihilation lifetime technique to the study of deep level transients in semiconductors

NASA Astrophysics Data System (ADS)

Deng, A. H.; Shan, Y. Y.; Fung, S.; Beling, C. D.

2002-03-01

Unlike its conventional applications in lattice defect characterization, positron annihilation lifetime technique was applied to study temperature-dependent deep level transients in semiconductors. Defect levels in the band gap can be determined as they are determined by conventional deep level transient spectroscopy (DLTS) studies. The promising advantage of this application of positron annihilation over the conventional DLTS is that it could further extract extra microstructure information of deep-level defects, such as whether a deep level defect is vacancy related or not. A demonstration of EL2 defect level transient study in GaAs was shown and the EL2 level of 0.82±0.02 eV was obtained by a standard Arrhenius analysis, similar to that in conventional DLTS studies.

Room temperature ammonia and VOC sensing properties of CuO nanorods

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

Bhuvaneshwari, S.; Gopalakrishnan, N., E-mail: ngk@nitt.edu

Here, we report a NH{sub 3} and Volatile Organic Compounds (VOCs) sensing prototype of CuO nanorods with peculiar sensing characteristics at room temperature. High quality polycrystalline nanorods were synthesized by a low temperature hydrothermal method. The rods are well oriented with an aspect ratio of 5.71. Luminescence spectrum of CuO nanorods exhibited a strong UV-emission around 415 nm (2.98 eV) which arises from the electron-hole recombination phenomenon. The absence of further deep level emissions establishes the lack of defects such as oxygen vacancies and Cu interstitials. At room temperature, the sensor response was recorded over a range of gas concentrations frommore » 100-600 ppm of ammonia, ethanol and methanol. The sensor response showed power law dependence with the gas concentration. This low temperature sensing can be validated by the lower value of calculated activation energy of 1.65 eV observed from the temperature dependent conductivity measurement.« less

Growth mechanism and optical properties of aligned hexagonal ZnO nanoprisms synthesized by noncatalytic thermal evaporation.

PubMed

Umar, Ahmad; Karunagaran, B; Kim, S H; Suh, E-K; Hahn, Y B

2008-05-19

Vertically aligned perfectly hexagonal-shaped ZnO nanoprisms have been grown on a Si(100) substrate via a noncatalytic thermal evaporation process by using metallic zinc powder in the presence of oxygen gas. The as-grown nanoprisms consist of ultra smooth Zn-terminated (0001) facets bounded with the {0110} surfaces. The as-synthesized products are single-crystalline with the wurtzite hexagonal phase and grown along the [0001] direction, as confirmed from the detailed structural investigations. The presence of a sharp and strong nonpolar optical phonon high-E2 mode at 437 cm(-1) in the Raman scattering spectrum further confirms good crystallinity and wurtzite hexagonal phase for the as-grown products. The as-grown nanoprisms exhibit a strong near-band-edge emission with a very weak deep-level emission in the room-temperature and low-temperature photoluminescence measurements, confirming good optical properties for the deposited products. Moreover, systematic time-dependent experiments were also performed to determine the growth process of the grown vertically aligned nanoprisms.

Controllable dimension of ZnO nanowalls on GaN/c-Al2O3 substrate by vapor phase epitaxy method.

PubMed

Song, W Y; Shin, T I; Kang, S M; Kim, S W; Yang, J H; Park, M H; Yang, C W; Yoon, D H

2008-09-01

Vertically well-aligned ZnO nanowalls were successfully synthesized at 950-1050 degrees C. Ar gas was introduced into the furnace at a flow rate of 2000-2500 sccm. An Au thin film with a thickness of 3 nm was used as a catalyst. The ZnO nanowalls were successfully grown on the substrate and most of them had nearly the same thickness and were oriented perpendicular to the substrate. The morphology and chemical composition of the ZnO nanowalls were examined as a function of the growth conditions examined. It was found that the grown ZnO nanowalls have a single-crystalline hexagonal structure and preferred c-axis growth orientation based on the X-ray diffraction and high-resolution transmission electron microscope measurements. The room temperature photoluminescence showed a strong free-exciton emission band with negligible deep level emission, indicating the high optical property of our ZnO nanowall samples.

Non-invasive imaging and cellular tracking of pulmonary emboli by near-infrared fluorescence and positron-emission tomography

PubMed Central

Page, Michael J.; Lourenço, André L.; David, Tovo; LeBeau, Aaron M.; Cattaruzza, Fiore; Castro, Helena C.; VanBrocklin, Henry F.; Coughlin, Shaun R.; Craik, Charles S.

2015-01-01

Functional imaging of proteolytic activity is an emerging strategy to quantify disease and response to therapy at the molecular level. We present a new peptide-based imaging probe technology that advances these goals by exploiting enzymatic activity to deposit probes labelled with near-infrared (NIR) fluorophores or radioisotopes in cell membranes of disease-associated proteolysis. This strategy allows for non-invasive detection of protease activity in vivo and ex vivo by tracking deposited probes in tissues. We demonstrate non-invasive detection of thrombin generation in a murine model of pulmonary embolism using our protease-activated peptide probes in microscopic clots within the lungs with NIR fluorescence optical imaging and positron-emission tomography. Thrombin activity is imaged deep in tissue and tracked predominantly to platelets within the lumen of blood vessels. The modular design of our probes allows for facile investigation of other proteases, and their contributions to disease by tailoring the protease activation and cell-binding elements. PMID:26423607

Multiple-component Decomposition from Millimeter Single-channel Data

NASA Astrophysics Data System (ADS)

Rodríguez-Montoya, Iván; Sánchez-Argüelles, David; Aretxaga, Itziar; Bertone, Emanuele; Chávez-Dagostino, Miguel; Hughes, David H.; Montaña, Alfredo; Wilson, Grant W.; Zeballos, Milagros

2018-03-01

We present an implementation of a blind source separation algorithm to remove foregrounds off millimeter surveys made by single-channel instruments. In order to make possible such a decomposition over single-wavelength data, we generate levels of artificial redundancy, then perform a blind decomposition, calibrate the resulting maps, and lastly measure physical information. We simulate the reduction pipeline using mock data: atmospheric fluctuations, extended astrophysical foregrounds, and point-like sources, but we apply the same methodology to the Aztronomical Thermal Emission Camera/ASTE survey of the Great Observatories Origins Deep Survey–South (GOODS-S). In both applications, our technique robustly decomposes redundant maps into their underlying components, reducing flux bias, improving signal-to-noise ratio, and minimizing information loss. In particular, GOODS-S is decomposed into four independent physical components: one of them is the already-known map of point sources, two are atmospheric and systematic foregrounds, and the fourth component is an extended emission that can be interpreted as the confusion background of faint sources.

Effect of precursor on epitaxially grown of ZnO thin film on p-GaN/sapphire (0 0 0 1) substrate by hydrothermal technique

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

Sahoo, Trilochan; Ju, Jin-Woo; Kannan, V.

2008-03-04

Single crystalline ZnO thin film on p-GaN/sapphire (0 0 0 1) substrate, using two different precursors by hydrothermal route at a temperature of 90 deg. C were successfully grown. The effect of starting precursor on crystalline nature, surface morphology and optical emission of the films were studied. ZnO thin films were grown in aqueous solution of zinc acetate and zinc nitrate. X-ray diffraction analysis revealed that all the thin films were single crystalline in nature and exhibited wurtzite symmetry and c-axis orientation. The thin films obtained with zinc nitrate had a more pitted rough surface morphology compared to the filmmore » grown in zinc acetate. However the thickness of the films remained unaffected by the nature of the starting precursor. Sharp luminescence peaks were observed from the thin films almost at identical energies but deep level emission was slightly prominent for the thin film grown in zinc nitrate.« less

Photoelectrochemical properties of highly mobilized Li-doped ZnO thin films.

PubMed

Shinde, S S; Bhosale, C H; Rajpure, K Y

2013-03-05

Li-doped ZnO thin films with preferred (002) orientation have been prepared by spray pyrolysis technique in aqueous medium on to the corning glass substrates. The effect of Li-doping on to the photoelectrochemical, structural, morphological, optical, luminescence, electrical and thermal properties has been investigated. XRD and Raman study indicates that the films have hexagonal crystal structure. The transmittance, reflectance, refractive index, extinction coefficient and bandgap have been analyzed by optical study. PL spectra consist of a near band edge and visible emission due to the electronic defects, which are related to deep level emissions, such as oxide antisite (OZn), interstitial zinc (Zni), interstitial oxygen (Oi) and zinc vacancy (VZn). The Li-doped ZnO films prepared for 1at% doping possesses the highest electron mobility of 102cm(2)/Vs and carrier concentration of 3.62×10(19)cm(-3). Finally, degradation of 2,4,6-Trinitrotoluene using Li-doped ZnO thin films has been reported. Copyright © 2013 Elsevier B.V. All rights reserved.

Absorbance detector for high performance liquid chromatography based on a deep-UV light-emitting diode at 235nm.

PubMed

da Silveira Petruci, João Flavio; Liebetanz, Michael G; Cardoso, Arnaldo Alves; Hauser, Peter C

2017-08-25

In this communication, we describe a flow-through optical absorption detector for HPLC using for the first time a deep-UV light-emitting diode with an emission band at 235nm as light source. The detector is also comprised of a UV-sensitive photodiode positioned to enable measurement of radiation through a flow-through cuvette with round aperture of 1mm diameter and optical path length of 10mm, and a second one positioned as reference photodiode; a beam splitter and a power supply. The absorbance was measured and related to the analyte concentration by emulating the Lambert-Beer law with a log-ratio amplifier circuitry. This detector showed noise levels of 0.30mAU, which is comparable with our previous LED-based detectors employing LEDs at 280 and 255nm. The detector was coupled to a HPLC system and successfully evaluated for the determination of the anti-diabetic drugs pioglitazone and glimepiride in an isocratic separation and the benzodiazepines flurazepam, oxazepam and clobazam in a gradient elution. Good linearities (r>0.99), a precision better than 0.85% and limits of detection at sub-ppm levels were achieved. Copyright © 2017 Elsevier B.V. All rights reserved.

MaGa, a web-based collaborative database for gas emissions: a tool to improve the knowledge on Earth degassing

NASA Astrophysics Data System (ADS)

Frigeri, A.; Cardellini, C.; Chiodini, G.; Frondini, F.; Bagnato, E.; Aiuppa, A.; Fischer, T. P.; Lehnert, K. A.

2014-12-01

The study of the main pathways of carbon flux from the deep Earth requires the analysis of a large quantity and variety of data on volcanic and non-volcanic gas emissions. Hence, there is need for common frameworks to aggregate available data and insert new observations. Since 2010 we have been developing the Mapping Gas emissions (MaGa) web-based database to collect data on carbon degassing form volcanic and non-volcanic environments. MaGa uses an Object-relational model, translating the experience of field surveyors into the database schema. The current web interface of MaGa allows users to browse the data in tabular format or by browsing an interactive web-map. Enabled users can insert information as measurement methods, instrument details as well as the actual values collected in the field. Measurements found in the literature can be inserted as well as direct field observations made by human-operated instruments. Currently the database includes fluxes and gas compositions from active craters degassing, diffuse soil degassing and fumaroles both from dormant volcanoes and open-vent volcanoes from literature survey and data about non-volcanic emission of the Italian territory. Currently, MaGa holds more than 1000 volcanic plume degassing fluxes, data from 30 sites of diffuse soil degassing from italian volcanoes, and about 60 measurements from fumarolic and non volcanic emission sites. For each gas emission site, the MaGa holds data, pictures, descriptions on gas sampling, analysis and measurement methods, together with bibliographic references and contacts to researchers having experience on each site. From 2012, MaGa developments started to be focused towards the framework of the Deep Earth Carbon Degassing research initiative of the Deep Carbon Observatory. Whithin the DECADE initiative, there are others data systems, as EarthChem and the Smithsonian Institution's Global Volcanism Program. An interoperable interaction between the DECADE data systems is being planned. MaGa is showing good potentials to improve the knowledge on Earth degassing firstly by making data more accessible and encouraging participation among researchers, and secondly by allowing to observe and explore, for the first time, a gas emission dataset with spatial and temporal extents never analyzed before.

The deep-sea under global change.

PubMed

Danovaro, Roberto; Corinaldesi, Cinzia; Dell'Anno, Antonio; Snelgrove, Paul V R

2017-06-05

The deep ocean encompasses 95% of the oceans' volume and is the largest and least explored biome of Earth's Biosphere. New life forms are continuously being discovered. The physiological mechanisms allowing organisms to adapt to extreme conditions of the deep ocean (high pressures, from very low to very high temperatures, food shortage, lack of solar light) are still largely unknown. Some deep-sea species have very long life-spans, whereas others can tolerate toxic compounds at high concentrations; these characteristics offer an opportunity to explore the specialized biochemical and physiological mechanisms associated with these responses. Widespread symbiotic relationships play fundamental roles in driving host functions, nutrition, health, and evolution. Deep-sea organisms communicate and interact through sound emissions, chemical signals and bioluminescence. Several giants of the oceans hunt exclusively at depth, and new studies reveal a tight connection between processes in the shallow water and some deep-sea species. Limited biological knowledge of the deep-sea limits our capacity to predict future response of deep-sea organisms subject to increasing human pressure and changing global environmental conditions. Molecular tools, sensor-tagged animals, in situ and laboratory experiments, and new technologies can enable unprecedented advancement of deep-sea biology, and facilitate the sustainable management of deep ocean use under global change. Copyright © 2017. Published by Elsevier Ltd.

The State, Potential Distribution, and Biological Implications of Methane in the Martian Crust

NASA Technical Reports Server (NTRS)

Max, Michael D.; Clifford, Stephen M.

2000-01-01

The search for life on Mars has recently focused on its potential survival in deep (>2 km) subpermafrost aquifers where anaerobic bacteria, similar to those found in deep subsurface ecosystems on Earth, may have survived in an environment that has remained stable for billions of years. An anticipated by-product of this biological activity is methane. The detection of large deposits of methane gas and hydrate in the Martian cryosphere, or as emissions from deep fracture zones, would provide persuasive evidence of indigenous life and confirm the presence of a valuable in situ resource for use by future human explorers.

A physically based algorithm for non-blackbody correction of the cloud top temperature for the convective clouds

NASA Astrophysics Data System (ADS)

Wang, C.; Luo, Z. J.; Chen, X.; Zeng, X.; Tao, W.; Huang, X.

2012-12-01

Cloud top temperature is a key parameter to retrieval in the remote sensing of convective clouds. Passive remote sensing cannot directly measure the temperature at the cloud tops. Here we explore a synergistic way of estimating cloud top temperature by making use of the simultaneous passive and active remote sensing of clouds (in this case, CloudSat and MODIS). Weighting function of the MODIS 11μm band is explicitly calculated by feeding cloud hydrometer profiles from CloudSat retrievals and temperature and humidity profiles based on ECMWF ERA-interim reanalysis into a radiation transfer model. Among 19,699 tropical deep convective clouds observed by the CloudSat in 2008, the averaged effective emission level (EEL, where the weighting function attains its maximum) is at optical depth 0.91 with a standard deviation of 0.33. Furthermore, the vertical gradient of CloudSat radar reflectivity, an indicator of the fuzziness of convective cloud top, is linearly proportional to, d_{CTH-EEL}, the distance between the EEL of 11μm channel and cloud top height (CTH) determined by the CloudSat when d_{CTH-EEL}<0.6km. Beyond 0.6km, the distance has little sensitivity to the vertical gradient of CloudSat radar reflectivity. Based on these findings, we derive a formula between the fuzziness in the cloud top region, which is measurable by CloudSat, and the MODIS 11μm brightness temperature assuming that the difference between effective emission temperature and the 11μm brightness temperature is proportional to the cloud top fuzziness. This formula is verified using the simulated deep convective cloud profiles by the Goddard Cumulus Ensemble model. We further discuss the application of this formula in estimating cloud top buoyancy as well as the error characteristics of the radiative calculation within such deep-convective clouds.

ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: Survey Description

NASA Astrophysics Data System (ADS)

Walter, Fabian; Decarli, Roberto; Aravena, Manuel; Carilli, Chris; Bouwens, Rychard; da Cunha, Elisabete; Daddi, Emanuele; Ivison, R. J.; Riechers, Dominik; Smail, Ian; Swinbank, Mark; Weiss, Axel; Anguita, Timo; Assef, Roberto; Bacon, Roland; Bauer, Franz; Bell, Eric F.; Bertoldi, Frank; Chapman, Scott; Colina, Luis; Cortes, Paulo C.; Cox, Pierre; Dickinson, Mark; Elbaz, David; Gónzalez-López, Jorge; Ibar, Edo; Inami, Hanae; Infante, Leopoldo; Hodge, Jacqueline; Karim, Alex; Le Fevre, Olivier; Magnelli, Benjamin; Neri, Roberto; Oesch, Pascal; Ota, Kazuaki; Popping, Gergö; Rix, Hans-Walter; Sargent, Mark; Sheth, Kartik; van der Wel, Arjen; van der Werf, Paul; Wagg, Jeff

2016-12-01

We present the rationale for and the observational description of ASPECS: the ALMA SPECtroscopic Survey in the Hubble Ultra-Deep Field (UDF), the cosmological deep field that has the deepest multi-wavelength data available. Our overarching goal is to obtain an unbiased census of molecular gas and dust continuum emission in high-redshift (z > 0.5) galaxies. The ˜1‧ region covered within the UDF was chosen to overlap with the deepest available imaging from the Hubble Space Telescope. Our ALMA observations consist of full frequency scans in band 3 (84-115 GHz) and band 6 (212-272 GHz) at approximately uniform line sensitivity ({L}{CO}\\prime ˜ 2 × 109 K km s-1 pc2), and continuum noise levels of 3.8 μJy beam-1 and 12.7 μJy beam-1, respectively. The molecular surveys cover the different rotational transitions of the CO molecule, leading to essentially full redshift coverage. The [C II] emission line is also covered at redshifts 6.0\\lt z\\lt 8.0. We present a customized algorithm to identify line candidates in the molecular line scans and quantify our ability to recover artificial sources from our data. Based on whether multiple CO lines are detected, and whether optical spectroscopic redshifts as well as optical counterparts exist, we constrain the most likely line identification. We report 10 (11) CO line candidates in the 3 mm (1 mm) band, and our statistical analysis shows that <4 of these (in each band) are likely spurious. Less than one-third of the total CO flux in the low-J CO line candidates are from sources that are not associated with an optical/NIR counterpart. We also present continuum maps of both the band 3 and band 6 observations. The data presented here form the basis of a number of dedicated studies that are presented in subsequent papers.

Ultraviolet and Radio Emission from the Northern Middle Lobe of Centaurus A

NASA Technical Reports Server (NTRS)

Neff, Susan

2009-01-01

We present deep GALEX ultraviolet (135 - 280 nm) images of the Northern Middle Lobe (NML) of the nearby radio galaxy Centaurus A. We find that the ultraviolet emission appears to have a complex interaction with soft X-ray, H-alpha emission, and radio emission, which should help constrain various models of energy transport in the NML. We also present new 90cm VLA images of the NML. The radio morphology at this wavelength is indicative of a more complex system than either a straightforward flaring jet (Morganti et al. 1999) or a bubble with trailing stem (Saxton et al. 2001). New limits are placed on the lack of radio emission from any corresponding southern counterpart to the NML.

Is the Eagle Nebula powered by a hidden supernova remnant ?

NASA Astrophysics Data System (ADS)

Boulanger, Francois

2008-10-01

Spitzer observations of the Eagle nebula (M16) reveal the presence of a large (8 pc diameter) shell of dust heated to anomalously high temperatures. Modeling of dust excitation shows that the shell emission cannot be powered by the cluster UV radiation but that it can be accounted for by collisionally heated dust in a young (a few 1000 yrs) supernova remnant. We have re-analyzed deep Chandra observations that show diffuse emission consistent with this hypothesis, but also with galactic ridge emission. We propose a 50 ksec XMM observation to probe the spatial extent of the diffuse X-ray emission beyond the Spitzer shell. Absence of emission outside of this shell will strongly support the supernova remnant interpretation

The total hemispheric emissivity of painted aluminum honeycomb at cryogenic temperatures

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

Tuttle, J.; Canavan, E.; DiPirro, M.

NASA uses high-emissivity surfaces on deep-space radiators and thermal radiation absorbers in test chambers. Aluminum honeycomb core material, when coated with a high-emissivity paint, provides a lightweight, mechanically robust, and relatively inexpensive black surface that retains its high emissivity down to low temperatures. At temperatures below about 100 Kelvin, this material performs much better than the paint itself. We measured the total hemispheric emissivity of various painted honeycomb configurations using an adaptation of an innovative technique developed for characterizing thin black coatings. These measurements were performed from room temperature down to 30 Kelvin. We describe the measurement technique and comparemore » the results with predictions from a detailed thermal model of each honeycomb configuration.« less

MAGA, a new database of gas natural emissions: a collaborative web environment for collecting data.

NASA Astrophysics Data System (ADS)

Cardellini, Carlo; Chiodini, Giovanni; Frigeri, Alessandro; Bagnato, Emanuela; Frondini, Francesco; Aiuppa, Alessandro

2014-05-01

The data on volcanic and non-volcanic gas emissions available online are, as today, are incomplete and most importantly, fragmentary. Hence, there is need for common frameworks to aggregate available data, in order to characterize and quantify the phenomena at various scales. A new and detailed web database (MAGA: MApping GAs emissions) has been developed, and recently improved, to collect data on carbon degassing form volcanic and non-volcanic environments. MAGA database allows researchers to insert data interactively and dynamically into a spatially referred relational database management system, as well as to extract data. MAGA kicked-off with the database set up and with the ingestion in to the database of the data from: i) a literature survey on publications on volcanic gas fluxes including data on active craters degassing, diffuse soil degassing and fumaroles both from dormant closed-conduit volcanoes (e.g., Vulcano, Phlegrean Fields, Santorini, Nysiros, Teide, etc.) and open-vent volcanoes (e.g., Etna, Stromboli, etc.) in the Mediterranean area and Azores, and ii) the revision and update of Googas database on non-volcanic emission of the Italian territory (Chiodini et al., 2008), in the framework of the Deep Earth Carbon Degassing (DECADE) research initiative of the Deep Carbon Observatory (DCO). For each geo-located gas emission site, the database holds images and description of the site and of the emission type (e.g., diffuse emission, plume, fumarole, etc.), gas chemical-isotopic composition (when available), gas temperature and gases fluxes magnitude. Gas sampling, analysis and flux measurement methods are also reported together with references and contacts to researchers expert of each site. In this phase data can be accessed on the network from a web interface, and data-driven web service, where software clients can request data directly from the database, are planned to be implemented shortly. This way Geographical Information Systems (GIS) and Virtual Globes (e.g., Google Earth) could easily access the database, and data could be exchanged with other database. At the moment the database includes: i) more than 1000 flux data about volcanic plume degassing from Etna and Stromboli volcanoes, ii) data from ~ 30 sites of diffuse soil degassing from Napoletan volcanoes, Azores, Canary, Etna, Stromboli, and Vulcano Island, several data on fumarolic emissions (~ 7 sites) with CO2 fluxes; iii) data from ~ 270 non volcanic gas emission site in Italy. We believe MAGA data-base is an important starting point to develop a large scale, expandable data-base aimed to excite, inspire, and encourage participation among researchers. In addition, the possibility to archive location and qualitative information for gas emission/sites not yet investigated, could stimulate the scientific community for future researches and will provide an indication on the current uncertainty on deep carbon fluxes global estimates

Sustained climate warming drives declining marine biological productivity

DOE PAGES

Moore, J. Keith; Fu, Weiwei; Primeau, Francois; ...

2018-03-01

Climate change projections to the year 2100 may miss physical-biogeochemical feedbacks that emerge later from the cumulative effects of climate warming. In a coupled climate simulation to the year 2300, the westerly winds strengthen and shift poleward, surface waters warm, and sea ice disappears, leading to intense nutrient trapping in the Southern Ocean. The trapping drives a global-scale nutrient redistribution, with net transfer to the deep ocean. Ensuing surface nutrient reductions north of 30°S drive steady declines in primary production and carbon export (decreases of 24 and 41%, respectively, by 2300). Potential fishery yields, constrained by lower–trophic-level productivity, decrease bymore » more than 20% globally and by nearly 60% in the North Atlantic. Continued high levels of greenhouse gas emissions could suppress marine biological productivity for a millennium.« less

Sustained climate warming drives declining marine biological productivity

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

Moore, J. Keith; Fu, Weiwei; Primeau, Francois

Climate change projections to the year 2100 may miss physical-biogeochemical feedbacks that emerge later from the cumulative effects of climate warming. In a coupled climate simulation to the year 2300, the westerly winds strengthen and shift poleward, surface waters warm, and sea ice disappears, leading to intense nutrient trapping in the Southern Ocean. The trapping drives a global-scale nutrient redistribution, with net transfer to the deep ocean. Ensuing surface nutrient reductions north of 30°S drive steady declines in primary production and carbon export (decreases of 24 and 41%, respectively, by 2300). Potential fishery yields, constrained by lower–trophic-level productivity, decrease bymore » more than 20% globally and by nearly 60% in the North Atlantic. Continued high levels of greenhouse gas emissions could suppress marine biological productivity for a millennium.« less

Interpretation of deep levels in Si-GaAs crystals observed by photo-induced current transient spectroscopy

NASA Astrophysics Data System (ADS)

Hlinomaz, P.; Šmíd, V.; Krištofik, J.

1993-05-01

Deep levels measured by Photo-Induced Current Transient Spectroscopy (PICTS) are interpreted taking into account different bulk and surface properties of semi-insulating crystals, results of directly measured isothermal transients and types of observed deep levels determined from the measurements with different voltage polarity. The principal interest is focused on the temperature interval 250-450 K where peaks related to the deep levels causing semiinsulating properties are observed in the PICTS spectra. Majority of deep levels observed in various samples may be ascribed to the EL2, EL3, EL4, HL1 and HL9 levels. Maxima exhibiting inverse polarity in PICTS spectra are not related to EL2 or HL1.

Typhoon Ioke in the Western Pacific

NASA Technical Reports Server (NTRS)

2006-01-01

[figure removed for brevity, see original site] [figure removed for brevity, see original site] Microwave ImageVisible Light Image

These infrared, microwave, and visible images were created with data retrieved by the Atmospheric Infrared Sounder (AIRS) on NASA's Aqua satellite.

Infrared Image Because infrared radiation does not penetrate through clouds, AIRS infrared images show either the temperature of the cloud tops or the surface of the Earth in cloud-free regions. The lowest temperatures (in purple) are associated with high, cold cloud tops that make up the top of the storm. In cloud-free areas the AIRS instrument will receive the infrared radiation from the surface of the Earth, resulting in the warmest temperatures (orange/red).

Microwave Image In the AIRS microwave imagery, deep blue areas in storms show where the most precipitation occurs, or where ice crystals are present in the convective cloud tops. Outside of these storm regions, deep blue areas may also occur over the sea surface due to its low radiation emissivity. On the other hand, land appears much warmer due to its high radiation emissivity.

In the AIRS microwave imagery, deep blue areas in storms show where the most precipitation occurs, or where ice crystals are present in the convective cloud tops. Outside of these storm regions, deep blue areas may also occur over the sea surface due to its low radiation emissivity. On the other hand, land appears much warmer due to its high radiation emissivity.

Microwave radiation from Earth's surface and lower atmosphere penetrates most clouds to a greater or lesser extent depending upon their water vapor, liquid water and ice content. Precipitation, and ice crystals found at the cloud tops where strong convection is taking place, act as barriers to microwave radiation. Because of this barrier effect, the AIRS microwave sensor detects only the radiation arising at or above their location in the atmospheric column. Where these barriers are not present, the microwave sensor detects radiation arising throughout the air column and down to the surface. Liquid surfaces (oceans, lakes and rivers) have 'low emissivity' (the signal isn't as strong) and their radiation brightness temperature is therefore low. Thus the ocean also appears 'low temperature' in the AIRS microwave images and is assigned the color blue. Therefore deep blue areas in storms show where the most precipitation occurs, or where ice crystals are present in the convective cloud tops. Outside of these storm regions, deep blue areas may also occur over the sea surface due to its low radiation emissivity. Land appears much warmer due to its high radiation emissivity.

Vis/NIR Image The AIRS instrument suite contains a sensor that captures radiation in four bands of the visible/near-infrared portion of the electromagetic spectrum. Data from three of these bands are combined to create 'visible' images similar to a snapshot taken with your camera.

The Atmospheric Infrared Sounder Experiment, with its visible, infrared, and microwave detectors, provides a three-dimensional look at Earth's weather. Working in tandem, the three instruments can make simultaneous observations all the way down to the Earth's surface, even in the presence of heavy clouds. With more than 2,000 channels sensing different regions of the atmosphere, the system creates a global, 3-D map of atmospheric temperature and humidity and provides information on clouds, greenhouse gases, and many other atmospheric phenomena. The AIRS Infrared Sounder Experiment flies onboard NASA's Aqua spacecraft and is managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., under contract to NASA. JPL is a division of the California Institute of Technology in Pasadena.

Convective transport over the central United States and its role in regional CO and ozone budgets

NASA Technical Reports Server (NTRS)

Thompson, Anne M.; Pickering, Kenneth E.; Dickerson, Russell R.; Ellis, William G., Jr.; Jacob, Daniel J.; Scala, John R.; Tao, Wei-Kuo; Mcnamara, Donna P.; Simpson, Joanne

1994-01-01

We have constructed a regional budget for boundary layer carbon monoxide over the central United States (32.5 deg - 50 deg N, 90 deg - 105 deg W), emphasizing a detailed evaluation of deep convective vertical fluxes appropriate for the month of June. Deep convective venting of the boundary layer (upward) dominates other components of the CO budget, e.g., downward convective transport, loss of CO by oxidation, anthropogenic emissions, and CO produced from oxidation of methane, isoprene, and anthropogenic nonmethane hydrocarbons (NMHCs). Calculations of deep convective venting are based on the method pf Pickering et al.(1992a) which uses a satellite-derived deep convective cloud climatology along with transport statistics from convective cloud model simulations of observed prototype squall line events. This study uses analyses of convective episodes in 1985 and 1989 and CO measurements taken during several midwestern field campaigns. Deep convective venting of the boundary layer over this moderately polluted region provides a net (upward minus downward) flux of 18.1 x 10(exp 8) kg CO/month to the free troposphere during early summer. Shallow cumulus and synoptic-scale weather systems together make a comparable contribution (total net flux 16.2 x 10(exp 8) kg CO/month). Boundary layer venting of CO with other O3 precursors leads to efficient free troposheric O3 formation. We estimate that deep convective transport of CO and other precursors over the central United States in early summer leads to a gross production of 0.66 - 1.1 Gmol O3/d in good agreement with estimates of O3 production from boundary layer venting in a continental-scale model (Jacob et al., 1993a, b). On this respect the central U.S. region acts as s `chimney' for the country, and presumably this O3 contributes to high background levels of O3 in the eastern United States and O3 export to the North Atlantic.

Distribution of atmospheric mercury in northern Southeast Asia and South China Sea during Dongsha Experiment

NASA Astrophysics Data System (ADS)

Sheu, Guey-Rong; Lin, Neng-Huei; Lee, Chung-Te; Wang, Jia-Lin; Chuang, Ming-Tung; Wang, Sheng-Hsiang; Chi, Kai Hsine; Ou-Yang, Chang-Feng

2013-10-01

Northern South China Sea (SCS) is adjacent to major atmospheric mercury (Hg) emission source regions; however, studies concerning regional atmospheric Hg distribution and cycling are very limited. Accordingly, measurements of atmospheric Hg were conducted in March and April during the 2010 Dongsha Experiment to study its spatial and temporal distribution. Atmospheric Hg was measured at Hengchun and Dongsha Island (Taiwan), Da Nang (Vietnam), Chiang Mai (Thailand) and over the northern SCS. Atmospheric Hg concentrations ranged between 1.54 and 6.83 ng m-3, mostly higher than the Northern Hemisphere background value. Regional wind fields and backward trajectories indicated that the atmospheric Hg concentrations over northern SCS should principally reflect the export of the East Asian Hg emissions by northeast monsoon. However, significantly elevated Hg concentrations were always observed at Da Nang, possibly due to the influence of local Hg emissions. Chiang Mai is located in the intense biomass burning region in northern Thailand. Therefore, atmospheric Hg concentrations at Chiang Mai reflected the influence of regional biomass burning Hg emissions. Two dust storms were encountered at Dongsha Island, one on March 16 and the other on March 21, with atmospheric Hg enhancements. Compared with the 2008 summer values, elevated Hg levels were observed at Dongsha Island in the spring of 2010. Summer air masses were mainly from the deep SCS, representing relatively clean marine air. On the other hand, air masses were from the north in spring, passing eastern China or Taiwan prior to reaching Dongsha Island. Results of this research thus demonstrated the transport of atmospheric Hg from the East Asian continent to northern SCS by regional monsoon activity in spring, but special events, such as biomass burning and dust storms, can also cause enhancements of ambient Hg levels.

Shallow outgassing changes disrupt steady lava lake activity, Kilauea Volcano

NASA Astrophysics Data System (ADS)

Patrick, M. R.; Orr, T. R.; Swanson, D. A.; Lev, E.

2015-12-01

Persistent lava lakes are a testament to sustained magma supply and outgassing in basaltic systems, and the surface activity of lava lakes has been used to infer processes in the underlying magmatic system. At Kilauea Volcano, Hawai`i, the lava lake in Halema`uma`u Crater has been closely studied for several years with webcam imagery, geophysical, petrological and gas emission techniques. The lava lake in Halema`uma`u is now the second largest on Earth, and provides an unprecedented opportunity for detailed observations of lava lake outgassing processes. We observe that steady activity is characterized by continuous southward motion of the lake's surface and slow changes in lava level, seismic tremor and gas emissions. This normal, steady activity can be abruptly interrupted by the appearance of spattering - sometimes triggered by rockfalls - on the lake surface, which abruptly shifts the lake surface motion, lava level and gas emissions to a more variable, unstable regime. The lake commonly alternates between this a) normal, steady activity and b) unstable behavior several times per day. The spattering represents outgassing of shallowly accumulated gas in the lake. Therefore, although steady lava lake behavior at Halema`uma`u may be deeply driven by upwelling of magma, we argue that the sporadic interruptions to this behavior are the result of shallow processes occurring near the lake surface. These observations provide a cautionary note that some lava lake behavior is not representative of deep-seated processes. This behavior also highlights the complex and dynamic nature of lava lake activity.

An elegant route to overcome fundamentally-limited light extraction in AlGaN deep-ultraviolet light-emitting diodes: Preferential outcoupling of strong in-plane emission

PubMed Central

Lee, Jong Won; Kim, Dong Yeong; Park, Jun Hyuk; Schubert, E. Fred; Kim, Jungsub; Lee, Jinsub; Kim, Yong-Il; Park, Youngsoo; Kim, Jong Kyu

2016-01-01

While there is an urgent need for semiconductor-based efficient deep ultraviolet (DUV) sources, the efficiency of AlGaN DUV light-emitting diodes (LEDs) remains very low because the extraction of DUV photons is significantly limited by intrinsic material properties of AlGaN. Here, we present an elegant approach based on a DUV LED having multiple mesa stripes whose inclined sidewalls are covered by a MgF2/Al omni-directional mirror to take advantage of the strongly anisotropic transverse-magnetic polarized emission pattern of AlGaN quantum wells. The sidewall-emission-enhanced DUV LED breaks through the fundamental limitations caused by the intrinsic properties of AlGaN, thus shows a remarkable improvement in light extraction as well as operating voltage. Furthermore, an analytic model is developed to understand and precisely estimate the extraction of DUV photons from AlGaN DUV LEDs, and hence to provide promising routes for maximizing the power conversion efficiency. PMID:26935402

An elegant route to overcome fundamentally-limited light extraction in AlGaN deep-ultraviolet light-emitting diodes: Preferential outcoupling of strong in-plane emission

NASA Astrophysics Data System (ADS)

Lee, Jong Won; Kim, Dong Yeong; Park, Jun Hyuk; Schubert, E. Fred; Kim, Jungsub; Lee, Jinsub; Kim, Yong-Il; Park, Youngsoo; Kim, Jong Kyu

2016-03-01

While there is an urgent need for semiconductor-based efficient deep ultraviolet (DUV) sources, the efficiency of AlGaN DUV light-emitting diodes (LEDs) remains very low because the extraction of DUV photons is significantly limited by intrinsic material properties of AlGaN. Here, we present an elegant approach based on a DUV LED having multiple mesa stripes whose inclined sidewalls are covered by a MgF2/Al omni-directional mirror to take advantage of the strongly anisotropic transverse-magnetic polarized emission pattern of AlGaN quantum wells. The sidewall-emission-enhanced DUV LED breaks through the fundamental limitations caused by the intrinsic properties of AlGaN, thus shows a remarkable improvement in light extraction as well as operating voltage. Furthermore, an analytic model is developed to understand and precisely estimate the extraction of DUV photons from AlGaN DUV LEDs, and hence to provide promising routes for maximizing the power conversion efficiency.

Synthesis and influence of ultrasonic treatment on luminescence of Mn incorporated ZnS nanoparticles

NASA Astrophysics Data System (ADS)

Cadis, A.-I.; Muresan, L. E.; Perhaita, I.; Munteanu, V.; Karabulut, Y.; Garcia Guinea, J.; Canimoglu, A.; Ayvacikli, M.; Can, N.

2017-10-01

Manganese (Mn) doping of ZnS phosphors was achieved by precipitation method using different ultrasound (US) maturation times. The structural and luminescence properties of the samples were carried out by means of X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), photoluminescence (PL), and cathodoluminescence (CL). The real amount of manganese incorporated in ZnS lattice was calculated based on ICP-OES results. According with XRD patterns, the phase structure of ZnS:Mn samples is cubic. EDS spectra reveal deviations of the Mn dopant concentration from the target composition. Both 300 K PL and CL emission spectra of the Mn doped ZnS phosphors display intense orange emission at 590 and 600 nm, respectively, which is characteristic emission of Mn ion corresponding to a 4T1→6A1 transition. Both PL and CL spectra confirmed manganese is substitutionally incorporated into the ZnS host as Mn2+. However, it is suggested that the origin of broad blue emission around 400 nm appeared in CL is due to the radiative recombination at deep level defect states in the ZnS. The ultrasound treatment at first enhances the luminescent intensity by ∼3 times in comparison with samples prepared by classical way. This study gives rise to an optimization guideline, which is extremely demanded for the development of new luminescent materials.

Effect of an Electrochemically Oxidized ZnO Seed Layer on ZnO Nanorods Grown by using Electrodeposition

NASA Astrophysics Data System (ADS)

Jeon, Woosung; Leem, Jae-Young

2018-05-01

ZnO nanorods were prepared on a Si substrate with and without a ZnO seed layer formed by electro-oxidation to investigate the effect of the seed layer on their growth. The ZnO nanorods grown on the ZnO seed layer had top surfaces that were flat whereas those grown without it had rough top surfaces, as observed in field-emission scanning electron microscopy images. In the Xray diffraction analysis, all ZnO nanorods showed preferential orientation with the (002) plane. In the case of ZnO nanorods prepared with a ZnO seed layer, the residual stress decreased, and the full width at half maximum of the ZnO (002) plane peak decreased. The photoluminescence spectra show a strong and narrow near-band-edge emission peak and high near-band-edge emission to deep-level emission peak ratio for the ZnO nanorods prepared with the seed layer. With respect to the photoresponse properties, the ZnO nanorods grown with the ZnO seed layer showed higher responsivity and faster rise/decay curves than those grown without it. Thus, the ZnO seed layer formed by electro-oxidation improves the structural, optical, and photoresponse properties of the ZnO nanorods formed on it. This method could serve as a new route for improving the properties of optoelectronic devices.

Wavelength-modulated photocapacitance spectroscopy

NASA Technical Reports Server (NTRS)

Kamieniecki, E.; Lagowski, J.; Gatos, H. C.

1980-01-01

Derivative deep-level spectroscopy was achieved with wavelength-modulated photocapacitance employing MOS structures and Schottky barriers. The energy position and photoionization characteristics of deep levels of melt-grown GaAs and the Cr level in high-resistivity GaAs were determined. The advantages of this method over existing methods for deep-level spectroscopy are discussed.

Deep-Subwavelength Resolving and Manipulating of Hidden Chirality in Achiral Nanostructures.

PubMed

Zu, Shuai; Han, Tianyang; Jiang, Meiling; Lin, Feng; Zhu, Xing; Fang, Zheyu

2018-04-24

The chiral state of light plays a vital role in light-matter interactions and the consequent revolution of nanophotonic devices and advanced modern chiroptics. As the light-matter interaction goes into the nano- and quantum world, numerous chiroptical technologies and quantum devices require precise knowledge of chiral electromagnetic modes and chiral radiative local density of states (LDOS) distributions in detail, which directly determine the chiral light-matter interaction for applications such as chiral light detection and emission. With classical optical techniques failing to directly measure the chiral radiative LDOS, deep-subwavelength imaging and control of circular polarization (CP) light associated phenomena are introduced into the agenda. Here, we simultaneously reveal the hidden chiral electromagnetic mode and acquire its chiral radiative LDOS distribution of a single symmetric nanostructure at the deep-subwavelength scale by using CP-resolved cathodoluminescence (CL) microscopy. The chirality of the symmetric nanostructure under normally incident light excitation, resulting from the interference between the symmetric and antisymmetric modes of the V-shaped nanoantenna, is hidden in the near field with a giant chiral distribution (∼99%) at the arm-ends, which enables the circularly polarized CL emission from the radiative LDOS hot-spot and the following active helicity control at the deep-subwavelength scale. The proposed V-shaped nanostructure as a functional unit is further applied to the helicity-dependent binary encoding and the two-dimensional display applications. The proposed physical principle and experimental configuration can promote the future chiral characterization and manipulation at the deep-subwavelength scale and provide direct guidelines for the optimization of chiral light-matter interactions for future quantum studies.

Synthesis and photophysical studies of blue phosphorescent Ir(III) complexes with dimethylphenylphospine.

PubMed

Ham, Ho-Wan; Jung, Kyung-Yoon; Kim, Young-Sik

2012-02-01

New blue emitting mixed ligand iridium(III) complexes comprising one cyclometalating, two phosphines trans to each other such as Ir{(CF3)2Meppy}(PPhMe3)2(H)(L) [L = CI, NCMe, CN] [(CF3)2Meppy = 2-(3', 5'-bis-trifluoromethylphenyl)-4-methylpyridine] were synthesized and studied to tune the phosphorescence wavelength to the deep blue region and to enhance the luminescence efficiencies. To achieve deep blue emission, the trifluoromethyl group substituted on the phenyl ring and the methyl group substituted on the pyridyl ring increased HOMO-LUMO gap and achieved the hypsochromic shift. To gain insight into the factors responsible for the emission color change and the different luminescence efficiency, we investigate the electron-withdrawing capabilities of ancillary ligands using the DFT and TD-DFT calculations on the ground and excited states of the complexes. From these results, we discuss how the ancillary ligand influences the emission peak as well as the metal to ligand charge transfer (MLCT) transition efficiency. The maximum emission spectra of Ir{(CF3)2Meppy}(PPhMe3)2(H)(Cl), [Ir{(CF3),Meppy)(PPhMe3),(H)(NCMe)]+ and Ir{(CF3)2Meppy}(PPhMe3)2(H)(CN) were in the ranges of 441, 435, 434 nm, respectively.

Effects of cooking method, cooking oil, and food type on aldehyde emissions in cooking oil fumes.

PubMed

Peng, Chiung-Yu; Lan, Cheng-Hang; Lin, Pei-Chen; Kuo, Yi-Chun

2017-02-15

Cooking oil fumes (COFs) contain a mixture of chemicals. Of all chemicals, aldehydes draw a great attention since several of them are considered carcinogenic and formation of long-chain aldehydes is related to fatty acids in cooking oils. The objectives of this research were to compare aldehyde compositions and concentrations in COFs produced by different cooking oils, cooking methods, and food types and to suggest better cooking practices. This study compared aldehydes in COFs produced using four cooking oils (palm oil, rapeseed oil, sunflower oil, and soybean oil), three cooking methods (stir frying, pan frying, and deep frying), and two foods (potato and pork loin) in a typical kitchen. Results showed the highest total aldehyde emissions in cooking methods were produced by deep frying, followed by pan frying then by stir frying. Sunflower oil had the highest emissions of total aldehydes, regardless of cooking method and food type whereas rapeseed oil and palm oil had relatively lower emissions. This study suggests that using gentle cooking methods (e.g., stir frying) and using oils low in unsaturated fatty acids (e.g., palm oil or rapeseed oil) can reduce the production of aldehydes in COFs, especially long-chain aldehydes such as hexanal and t,t-2,4-DDE. Copyright © 2016 Elsevier B.V. All rights reserved.

Al x Ga1‑ x N-based semipolar deep ultraviolet light-emitting diodes

NASA Astrophysics Data System (ADS)

Akaike, Ryota; Ichikawa, Shuhei; Funato, Mitsuru; Kawakami, Yoichi

2018-06-01

Deep ultraviolet (UV) emission from Al x Ga1‑ x N-based light-emitting diodes (LEDs) fabricated on semipolar (1\\bar{1}02) (r-plane) AlN substrates is presented. The growth conditions are optimized. A high NH3 flow rate during metalorganic vapor phase epitaxy yields atomically flat Al y Ga1‑ y N (y > x) on which Al x Ga1‑ x N/Al y Ga1‑ y N multiple quantum wells with abrupt interfaces and good periodicity are fabricated. The fabricated r-Al x Ga1‑ x N-based LED emits at 270 nm, which is in the germicidal wavelength range. Additionally, the emission line width is narrow, and the peak wavelength is stable against the injection current, so the semipolar LED shows promise as a UV emitter.

A theory for narrow-banded radio bursts at Uranus - MHD surface waves as an energy driver

NASA Technical Reports Server (NTRS)

Farrell, W. M.; Curtis, S. A.; Desch, M. D.; Lepping, R. P.

1992-01-01

A possible scenario for the generation of the narrow-banded radio bursts detected at Uranus by the Voyager 2 planetary radio astronomy experiment is described. In order to account for the emission burstiness which occurs on time scales of hundreds of milliseconds, it is proposed that ULF magnetic surface turbulence generated at the frontside magnetopause propagates down the open/closed field line boundary and mode-converts to kinetic Alfven waves (KAW) deep within the polar cusp. The oscillating KAW potentials then drive a transient electron stream that creates the bursty radio emission. To substantiate these ideas, Voyager 2 magnetometer measurements of enhanced ULF magnetic activity at the frontside magnetopause are shown. It is demonstrated analytically that such magnetic turbulence should mode-convert deep in the cusp at a radial distance of 3 RU.

Deep Chandra Observations of HCG 16. I. Active Nuclei, Star Formation, and Galactic Winds

NASA Astrophysics Data System (ADS)

O'Sullivan, E.; Zezas, A.; Vrtilek, J. M.; Giacintucci, S.; Trevisan, M.; David, L. P.; Ponman, T. J.; Mamon, G. A.; Raychaudhury, S.

2014-10-01

We present new, deep Chandra X-ray and Giant Metrewave Radio Telescope 610 MHz observations of the spiral-galaxy-rich compact group HCG 16, which we use to examine nuclear activity, star formation, and high-luminosity X-ray binary populations in the major galaxies. We confirm the presence of obscured active nuclei in NGC 833 and NGC 835, and identify a previously unrecognized nuclear source in NGC 838. All three nuclei are variable on timescales of months to years, and for NGC 833 and NGC 835 this is most likely caused by changes in accretion rate. The deep Chandra observations allow us to detect for the first time an Fe Kα emission line in the spectrum of the Seyfert 2 nucleus of NGC 835. We find that NGC 838 and NGC 839 are both starburst-dominated systems, with only weak nuclear activity, in agreement with previous optical studies. We estimate the star formation rates in the two galaxies from their X-ray and radio emission, and compare these results with estimates from the infrared and ultraviolet bands to confirm that star formation in both galaxies is probably declining after galaxy-wide starbursts were triggered ~400-500 Myr ago. We examine the physical properties of their galactic superwinds, and find that both have temperatures of ~0.8 keV. We also examine the X-ray and radio properties of NGC 848, the fifth largest galaxy in the group, and show that it is dominated by emission from its starburst.

Decadal trends in deep ocean salinity and regional effects on steric sea level

NASA Astrophysics Data System (ADS)

Purkey, S. G.; Llovel, W.

2017-12-01

We present deep (below 2000 m) and abyssal (below 4000 m) global ocean salinity trends from the 1990s through the 2010s and assess the role of deep salinity in local and global sea level budgets. Deep salinity trends are assessed using all deep basins with available full-depth, high-quality hydrographic section data that have been occupied two or more times since the 1980s through either the World Ocean Circulation Experiment (WOCE) Hydrographic Program or the Global Ship-Based Hydrographic Investigations Program (GO-SHIP). All salinity data is calibrated to standard seawater and any intercruise offsets applied. While the global mean deep halosteric contribution to sea level rise is close to zero (-0.017 +/- 0.023 mm/yr below 4000 m), there is a large regional variability with the southern deep basins becoming fresher and northern deep basins becoming more saline. This meridional gradient in the deep salinity trend reflects different mechanisms driving the deep salinity variability. The deep Southern Ocean is freshening owing to a recent increased flux of freshwater to the deep ocean. Outside of the Southern Ocean, the deep salinity and temperature changes are tied to isopycnal heave associated with a falling of deep isopycnals in recent decades. Therefore, regions of the ocean with a deep salinity minimum are experiencing both a halosteric contraction with a thermosteric expansion. While the thermosteric expansion is larger in most cases, in some regions the halosteric compensates for as much as 50% of the deep thermal expansion, making a significant contribution to local sea level rise budgets.

Irreversible ocean thermal expansion under carbon dioxide removal

NASA Astrophysics Data System (ADS)

Ehlert, Dana; Zickfeld, Kirsten

2018-03-01

In the Paris Agreement in 2015 countries agreed on holding global mean surface air warming to well below 2 °C above pre-industrial levels, but the emission reduction pledges under that agreement are not ambitious enough to meet this target. Therefore, the question arises of whether restoring global warming to this target after exceeding it by artificially removing CO2 from the atmosphere is possible. One important aspect is the reversibility of ocean heat uptake and associated sea level rise, which have very long (centennial to millennial) response timescales. In this study the response of sea level rise due to thermal expansion to a 1 % yearly increase of atmospheric CO2 up to a quadrupling of the pre-industrial concentration followed by a 1 % yearly decline back to the pre-industrial CO2 concentration is examined using the University of Victoria Earth System Climate Model (UVic ESCM). We find that global mean thermosteric sea level (GMTSL) continues to rise for several decades after atmospheric CO2 starts to decline and does not return to pre-industrial levels for over 1000 years after atmospheric CO2 is restored to the pre-industrial concentration. This finding is independent of the strength of vertical sub-grid-scale ocean mixing implemented in the model. Furthermore, GMTSL rises faster than it declines in response to a symmetric rise and decline in atmospheric CO2 concentration partly because the deep ocean continues to warm for centuries after atmospheric CO2 returns to the pre-industrial concentration. Both GMTSL rise and decline rates increase with increasing vertical ocean mixing. Exceptions from this behaviour arise if the overturning circulations in the North Atlantic and Southern Ocean intensify beyond pre-industrial levels in model versions with lower vertical mixing, which leads to rapid cooling of the deep ocean.

Effects of the ZnO layer on the structure and white light emission properties of a ZnS:Mn/GaN nanocomposite system.

PubMed

Wang, Cai-Feng; Hu, Bo

2017-10-01

ZnO films were inserted between the ZnS:Mn films and GaN substrates by pulsed laser deposition (PLD). The structure, morphology, and optical properties of the ZnS:Mn/ZnO/GaN nanocomposite systems have been investigated. X-ray diffraction results show that there are three diffraction peaks located at 28.4°, 34.4°, and 34.1°, which correspond to the β-ZnS(111), ZnO(002), and GaN(002) planes, respectively. Due to the insertion of ZnO films, the diffraction peak intensity of ZnS:Mn in ZnS:Mn/ZnO/GaN is stronger than that of ZnS:Mn in ZnS:Mn/GaN, and the full width at half-maximum is smaller. Though the transmittance of ZnS:Mn/ZnO films is slightly lower than that of ZnS:Mn films, the transmittance is still higher than 80%. Compared with ZnS:Mn/GaN, an ultraviolet (UV) emission at 387 nm (originated from the near-band emission of ZnO) and a green light emission at about 520 nm appeared in the photoluminescence (PL) spectra of ZnS:Mn/ZnO/GaN, in addition to the blue emission at 435 nm and the orange-red emission at 580 nm. The emission at 520 nm may be related to the deep-level emission from ZnO and the interface of ZnS:Mn/ZnO. The PL spectrum of ZnS:Mn/ZnO/GaN covers the visible region from the blue light to the red light (400-700 nm), and its color coordinate and color temperature are (0.3103,0.3063) and 6869 K, respectively, presenting strong white light emission.

Localized-Surface-Plasmon Enhanced the 357 nm Forward Emission from ZnMgO Films Capped by Pt Nanoparticles

PubMed Central

2009-01-01

The Pt nanoparticles (NPs), which posses the wider tunable localized-surface-plasmon (LSP) energy varying from deep ultraviolet to visible region depending on their morphology, were prepared by annealing Pt thin films with different initial mass-thicknesses. A sixfold enhancement of the 357 nm forward emission of ZnMgO was observed after capping with Pt NPs, which is due to the resonance coupling between the LSP of Pt NPs and the band-gap emission of ZnMgO. The other factors affecting the ultraviolet emission of ZnMgO, such as emission from Pt itself and light multi-scattering at the interface, were also discussed. These results indicate that Pt NPs can be used to enhance the ultraviolet emission through the LSP coupling for various wide band-gap semiconductors. PMID:20596433

Electroluminescence and other diagnostic techniques for the study of hot-electron effects in compound semiconductor devices

NASA Astrophysics Data System (ADS)

Zanoni, Enrico; Meneghesso, Gaudenzio; Menozzi, Roberto

2000-03-01

Hot electron in III-V FETs can be indirectly monitored by measuring the current coming out from the gate when the device is biased at high electric fields. This negative current is due to the collection of holes generated by impact ionization in the gate-to drain region. Electroluminescence represents a powerful tool in order to characterize not only hot electrons but also material properties. By using spatially resolved emission microscopy it is possible to show that the light due to cold electron/hole recombination is emitted between the gate and the source (low electric field region), while the contribution due to hot electrons is emitted between the gate and the drain (high electric field region). Deep-traps created in the device by hot carriers can be analysed by means of drain current deep level transient spectroscopy and by transconductance frequency dispersion. Cathodoluminescence, optical beam induced current, X-ray spectroscopy, electron energy loss spectroscopy in combination with a transmission electron microscopy are powerful tools in order to identify and localize surface modification following hot-electron stress tests.

Probing the Nature of Short Swift Bursts via Deep INTEGRAL Monitoring of GRB 050925

NASA Technical Reports Server (NTRS)

Sakamoto, T.; Barbier, L.; Barthelmy, S. D.; Cummings, J. R.; Fenimore, E. E.; Gehrels, N.; Krimm, H. A.; Markwardt, C. B.; Palmer, D. M.; Parsons, A. M.;

The Moon as Possible Calibration Reference for Microwave Radiometers

NASA Astrophysics Data System (ADS)

Burgdorf, Martin; Buehler, Stefan; Hans, Imke; Lang, Theresa; Michel, Simon

2016-04-01

Instruments on satellites for Earth observation on polar orbits usually employ a two-point calibration technique, in which deep space and an on-board calibration target provide two reference flux levels. As the direction of the deep space view is in general close to the celestial equator, the Moon moves sometimes through the field of view and introduces an unwelcome additional signal. One can take advantage of this intrusion, however, by using the Moon as a third flux standard, and this has actually been done for checking the lifetime stability of sensors operating at visible wavelengths. We discuss the advantages and problems of extending this concept to microwaves, concentrating on the frequency of appearances of the Moon in the deep space view, the factors limiting the accuracy of both measurements and models of the Moon's brightness, as well as benefits from complementing the naturally occurring appearances of the Moon with dedicated spacecraft maneuvers. Such pre-planned rotations of the instrument would allow to observe the Moon at a well-defined phase angle and to put it at the exact center of the field of view. This way they would eliminate the need for a model of the Moon's brightness temperature when checking instrumental stability. Finally we investigate the question, whether foreground emission from objects other than the Moon can contaminate the measurements of the Cosmic Microwave Background, which provides the low reference flux in the deep space view. We show that even the brightest discreet sources do not increase significantly the signal from a single scan.

Deep Radio Imaging with MERLIN of the Supernova Remnants in M82

NASA Astrophysics Data System (ADS)

Muxlow, T. W. B.; Pedlar, A.; Riley, J. D.; McDonald, A. R.; Beswick, R. J.; Wills, K. A.

An 8 day MERLIN deep integration at 5GHz of the central region of the starburst galaxy M82 has been used to investigate the radio structure of a number of supernova remnants in unprecedented detail revealing new shells and partial shell structures for the first time. In addition, by comparing the new deep 2002 image with an astrometrically aligned image from 36 hours of data taken in 1992, it has been possible to directly measure the expansion velocities of 4 of the most compact remnants in M82. For the two most compact remnants, 41.95+575 and 43.31+592, expansion velocities of 2800 ± 300 km s-1 and 8750 ± 400 km s-1 have been derived. These confirm and refine the measured expansion velocities which have been derived from VLBI multi-epoch studies. For remnants 43.18+583 and 44.01+596, expansion velocities of 10500 ± 750 km s -1 and 2400 ± 250 km s-1 have been measured for the first time. In addition, the peak of the radio emission for SNR 45.17+612 has moved between the two epochs implying velocities around 7500km s-1. The relatively compact remnants in M82 are thus found to be expanding over a wide range of velocities which appear unrelated to their size. The new 2002 map is the most sensitive high-resolution image yet made of M82, achieving an rms noise level of 17µJy beam-1. This establishes a first epoch for subsequent deep studies of expansion velocities for many SNR within M82.

Structural defects and recombination behavior of excited carriers in Cu(In,Ga)Se{sub 2} solar cells

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

Yang, J.; Du, H. W.; Li, Y.

2016-08-15

The carriers’ behavior in neutral region (NTR) and space charged region (SCR) of Cu(In,Ga)Se{sub 2} thin film based solar cells has been investigated by temperature dependent photoluminescence (PL-T), electroluminescence (EL-T) and current-voltage (IV-T) from 10 to 300 K. PL-T spectra show that three kinds of defects, namely V{sub Se}, In{sub Cu} and (In{sub Cu}+V{sub Cu}), are localized within the band gap of NTR and SCR of CIGS layer, corresponding to the energy levels of E{sub C}-0.08, E{sub C}-0.20 and E{sub C}-0.25 eV, respectively. The In{sub Cu} and (In{sub Cu}+V{sub Cu}) deep level defects are non-radiative recombination centers at room temperature.more » The IV-T and EL-T analysis reveals that the injection modes of electrons from ZnO conduction band into Cu(In,Ga)Se{sub 2} layer are tunneling, thermally-excited tunneling and thermionic emission under 10-40, 60-160, and 180-300 K, respectively. At 10-160 K, the electrons tunnel into (In{sub Cu}+V{sub Cu}) and V{sub se} defect levels in band gap of SCR and the drifting is involved in the emission bands at 0.96 and 1.07 eV, which is the direct evidence for a tunneling assisted recombination. At 180-300 K, the electrons are directly injected into the Cu(In,Ga)Se{sub 2} conduction band, and the emission of 1.13 eV are ascribed to the transitions from the conduction band to the valence band.« less

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

Li, Gaoming; Key Laboratory of OptoElectronic Science and Technology for Medicine, Ministry of Education, Fujian Normal University, Fuzhou 350007; Gao, Fei

Multiple stimulated emission fluorescence photoacoustic (MSEF-PA) phenomenon is demonstrated in this letter. Under simultaneous illumination of pumping light and stimulated emission light, the fluorescence emission process is speeded up by the stimulated emission effect. This leads to nonlinear enhancement of photoacoustic signal while the quantity of absorbed photons is more than that of fluorescent molecules illuminated by pumping light. The electronic states' specificity of fluorescent molecular can also be labelled by the MSEF-PA signals, which can potentially be used to obtain fluorescence excitation spectrum in deep scattering tissue with nonlinearly enhanced photoacoustic detection. In this preliminary study, the fluorescence excitationmore » spectrum is reconstructed by MSEF-PA signals through sweeping the wavelength of exciting light, which confirms the theoretical derivation well.« less

Towards a parameterization of convective wind gusts in Sahel

NASA Astrophysics Data System (ADS)

Largeron, Yann; Guichard, Françoise; Bouniol, Dominique; Couvreux, Fleur; Birch, Cathryn; Beucher, Florent

2014-05-01

West Africa is responsible for between 25 and 50 % of the global emissions of mineral dust (cf [Engelstaedter et al., 2006]) and these dust emissions have a huge impact on climate (cf [Carslaw et al., 2010]) and soil erosion. Numerous studies have focused on the quantification of the dust emission fluxes from knowledges of the soil surface characteristics, leading to the formulation of a threshold wind friction velocity (cf [Marticorena and Bergametti, 1995]) above which the dust can be uplifted. That flux varies with the cube of the surface wind speed above the threshold and is therefore particularly sensitive to the way the wind speed is modeled (cf [Menut, 2008]). Moreover, in the Sahelian belt, about half of the dust uplift happens during isolated events which generate violent cold pool outflows from moist deep convection, and associated high surface wind speeds. Therefore, the representation of convectively generated winds appears critical (cf [Marsham et al., 2011], [Knippertz and Todd, 2012]). The present study is motivated by these issues, and is carried out within the CAVIARS French Research National Agency (ANR) project. First, we examine the ERA interim reanalysis of the ECMWF, frequently used as an input wind field for off-line dust emission models (cf [Pierre et al., 2012]). The comparison with high-frequency local measurements shows that, not unexpectedly, the increase of the surface wind speed from deep convection is not represented in large-scale reanalysis. Therefore, following [Redelsperger et al., 2000], we propose a statistical approach to introduce a formulation of the surface wind gusts during deep convection, based on the analysis of convection-permitting high resolution simulations made with the UKMO atmospheric model (CASCADE project), the AROME operational model from Meteo-France, and the MesoNH Large Eddy Simulations model. High-frequency observations are also used to complement the analysis. However, unlike [Redelsperger et al., 2000] who focused on the wet tropical Pacific region, and linked wind gusts to convective precipitation rates alone, here, we also analyse the subgrid wind distribution during convective events, and quantify the statistical moments (variance, skewness and kurtosis) in terms of mean wind speed and convective indexes such as DCAPE. Next step of the work will be to formulate a parameterization of the cold pool convective gust from those probability density functions and analytical formulaes obtained from basic energy budget models. References : [Carslaw et al., 2010] A review of natural aerosol interactions and feedbacks within the earth system. Atmospheric Chemistry and Physics, 10(4):1701{1737. [Engelstaedter et al., 2006] North african dust emissions and transport. Earth-Science Reviews, 79(1):73{100. [Knippertz and Todd, 2012] Mineral dust aerosols over the sahara: Meteorological controls on emission and transport and implications for modeling. Reviews of Geophysics, 50(1). [Marsham et al., 2011] The importance of the representation of deep convection for modeled dust-generating winds over west africa during summer.Geophysical Research Letters, 38(16). [Marticorena and Bergametti, 1995] Modeling the atmospheric dust cycle: 1. design of a soil-derived dust emission scheme. Journal of Geophysical Research, 100(D8):16415{16. [Menut, 2008] Sensitivity of hourly saharan dust emissions to ncep and ecmwf modeled wind speed. Journal of Geophysical Research: Atmospheres (1984{2012), 113(D16). [Pierre et al., 2012] Impact of vegetation and soil moisture seasonal dynamics on dust emissions over the sahel. Journal of Geophysical Research: Atmospheres (1984{2012), 117(D6). [Redelsperger et al., 2000] A parameterization of mesoscale enhancement of surface fluxes for large-scale models. Journal of climate, 13(2):402{421.

Anthropogenic and volcanic emission impacts on SO2 dynamics and acid rain profiles. Numerical study using WRF-Chem in a high-resolution modeling

NASA Astrophysics Data System (ADS)

Vela, A. V.; González, C. M.; Ynoue, R.; Rojas, N. Y.; Aristizábal, B. H.; Wahl, M.

2017-12-01

Eulerian 3-D chemistry transport models (CTM) have been widely used for the study of air quality in urban environments, becoming an essential tool for studying the impacts and dynamics of gases and aerosols on air quality. However, their use in Colombia is scarce, especially in medium-sized cities, which are experimenting a fast urban growth, increasing the risk associated with possible air pollution episodes. In the densely populated medium-sized Andean city of Manizales, Colombia - a city located on the western slopes of the central range of the Andes (urban population 368000; 2150 m.a.s.l), there is an influence of the active Nevado del Ruiz volcano, located 28 km to the southwest. This natural source emits daily gas and particle fluxes, which could influence the atmospheric chemistry of the city and neighboring towns. Hence, the zone presents a unique combination of anthropogenic and volcanic sulfur gas emissions, which affects SO2 dynamics in the urban area, influencing also in the formation of acid rain phenomenon in the city. Therefore, studies analyzing the relative contribution of anthropogenic and volcanic emission could contribute with a deep understanding about causes and dynamics of both acid rain phenomenon and ambient SO2 levels in Manizales. This work aimed to analyze the influence of anthropogenic (on-road vehicular and industrial point-sources) and volcanic sulfur emissions in SO2 atmospheric chemistry dynamics, evaluating its possible effects on acid rain profiles. Ambient SO2 levels and day-night rain samples were measured and used to analyze results obtained from the application of the fully-coupled on-line WRF-Chem model. Two high-resolution simulations were performed during two dry and wet one-week periods in 2015. Analysis of SO2 dispersion patterns and comparison with SO2 observations in the urban area were performed for three different scenarios in which natural and anthropogenic emissions were simulated separately. Results suggest that industrial point-source emissions had a higher influence in urban SO2 formation, suggesting also reasons of higher acidity levels during daytime periods, pattern obtained when comparing acid rain day-night profiles from rain samples measurements.

The ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: Search for [CII] Line and Dust Emission in 6

NASA Astrophysics Data System (ADS)

Aravena, M.; Decarli, R.; Walter, F.; Bouwens, R.; Oesch, P. A.; Carilli, C. L.; Bauer, F. E.; Da Cunha, E.; Daddi, E.; Gónzalez-López, J.; Ivison, R. J.; Riechers, D. A.; Smail, I.; Swinbank, A. M.; Weiss, A.; Anguita, T.; Bacon, R.; Bell, E.; Bertoldi, F.; Cortes, P.; Cox, P.; Hodge, J.; Ibar, E.; Inami, H.; Infante, L.; Karim, A.; Magnelli, B.; Ota, K.; Popping, G.; van der Werf, P.; Wagg, J.; Fudamoto, Y.

2016-12-01

We present a search for [C II] line and dust continuum emission from optical dropout galaxies at z > 6 using ASPECS, our Atacama Large Millimeter submillimeter Array Spectroscopic Survey in the Hubble Ultra-deep Field (UDF). Our observations, which cover the frequency range of 212-272 GHz, encompass approximately the range of 6 < z < 8 for [C II] line emission and reach a limiting luminosity of L [C II] ˜ (1.6-2.5) × 108 L ⊙. We identify 14 [C II] line emitting candidates in this redshift range with significances >4.5σ, two of which correspond to blind detections with no optical counterparts. At this significance level, our statistical analysis shows that about 60% of our candidates are expected to be spurious. For one of our blindly selected [C II] line candidates, we tentatively detect the CO(6-5) line in our parallel 3 mm line scan. None of the line candidates are individually detected in the 1.2 mm continuum. A stack of all [C II] candidates results in a tentative detection with S 1.2 mm = 14 ± 5 μJy. This implies a dust-obscured star-formation rate (SFR) of (3 ± 1) M ⊙ yr-1. We find that the two highest-SFR objects have candidate [C II] lines with luminosities that are consistent with the low-redshift L [C II] versus SFR relation. The other candidates have significantly higher [C II] luminosities than expected from their UV-based SFR. At the current sensitivity, it is unclear whether the majority of these sources are intrinsically bright [C II] emitters, or spurious sources. If only one of our line candidates was real (a scenario greatly favored by our statistical analysis), we find a source density for [C II] emitters at 6 < z < 8 that is significantly higher than predicted by current models and some extrapolations from galaxies in the local universe.

Time-resolved fluorescence and ultrafast energy transfer in a zinc (hydr)oxide-graphite oxide mesoporous composite

NASA Astrophysics Data System (ADS)

Secor, Jeff; Narinesingh, Veeshan; Seredych, Mykola; Giannakoudakis, Dimitrios A.; Bandosz, Teresa; Alfano, Robert R.

2015-01-01

Ultrafast energy decay kinetics of a zinc (hydr)oxide-graphite oxide (GO) composite is studied via time-resolved fluorescence spectroscopy. The time-resolved emission is spectrally decomposed into emission regions originating from the zinc (hydr)oxide optical gap, surface, and defect states of the composite material. The radiative lifetime of deep red emission becomes an order of magnitude longer than that of GO alone while the radiative lifetime of the zinc optical gap is shortened in the composite. An energy transfer scheme from the zinc (hydr)oxide to GO is considered.

The Bose-Einstein correlations in deep inelastic μ p interactions at 280 GeV

NASA Astrophysics Data System (ADS)

Arneodo, M.; Arvidson, A.; Aubert, J. J.; Badelek, B.; Beaufays, J.; Bee, C. P.; Benchouk, C.; Berghoff, G.; Bird, I.; Blum, D.; Böhm, E.; de Bouard, X.; Brasse, F. W.; Braun, H.; Broll, C.; Brown, S.; Brück, H.; Calen, H.; Chima, J. S.; Ciborowski, J.; Cliftt, R.; Coignet, G.; Combley, F.; Coughlan, J.; D'Agostini, G.; Dahlgren, S.; Dengler, F.; Derado, I.; Dreyer, T.; Drees, J.; Düren, M.; Eckardt, V.; Edwards, A.; Edwards, M.; Ernst, T.; Eszes, G.; Favier, J.; Ferrero, M. I.; Figiel, J.; Flauger, W.; Foster, J.; Gabathuler, E.; Gajewski, J.; Gamet, R.; Gayler, J.; Geddes, N.; Grafström, P.; Grard, F.; Haas, J.; Hagberg, E.; Hasert, F. J.; Hayman, P.; Heusse, P.; Jaffre, M.; Jacholkowska, A.; Janata, F.; Jancso, G.; Johnson, A. S.; Kabuss, E. M.; Kellner, G.; Korbel, V.; Krüger, J.; Kullander, S.; Landgraf, U.; Lanske, D.; Loken, J.; Long, K.; Maire, M.; Malecki, P.; Manz, A.; Maselli, S.; Mohi, W.; Montanet, F.; Montgomery, H. E.; Nagy, E.; Nassalski, J.; Norton, P. R.; Oakham, F. G.; Osborne, A. M.; Osborne, L. S.; Pascaud, C.; Pawlik, B.; Payre, P.; Peroni, C.; Peschel, H.; Pessard, H.; Pettingale, J.; Pietrzyk, B.; Pönsgen, B.; Pötsch, M.; Renton, P.; Ribarics, P.; Rith, K.; Rondio, E.; Sandacz, A.; Scheer, M.; Schlagböhmer, A.; Schiemann, H.; Schmitz, N.; Schneegans, M.; Sholz, M.; Schröder, T.; Schouten, M.; Schultze, K.; Sloan, T.; Stier, H. E.; Studt, M.; Taylor, G. N.; Thenard, J. M.; Thompson, J. C.; de La Torre, A.; Toth, J.; Urban, L.; Urban, L.; Wallucks, W.; Whalley, M.; Wheeler, S.; Williams, W. S. C.; Wimpenny, S. J.; Windmolders, R.; Wolf, G.

1986-03-01

The Bose-Einstein correlation has been observed for pions in deep inelastic μ p interactions at 280 GeV. The importance of non-interference correlations in the sample of like charge pion pairs and in the sample used for reference is discussed. The pion emission region is found to be roughly spherical in the pair rest frame with a radius of 0.46 0.84 fm and the chaos factor λ is 0.60 1.08.

Soil gas geochemistry in relation to eruptive fissures on Timanfaya volcano, Lanzarote Island (Canary Islands, Spain)

NASA Astrophysics Data System (ADS)

Padrón, Eleazar; Padilla, Germán; Hernández, Pedro A.; Pérez, Nemesio M.; Calvo, David; Nolasco, Dácil; Barrancos, José; Melián, Gladys V.; Dionis, Samara; Rodríguez, Fátima

2013-01-01

We report herein the first results of an extensive soil gas survey performed on Timanfaya volcano on May 2011. Soil gas composition at Timanfaya volcano indicates a main atmospheric source, slightly enriched in CO2 and He. Soil CO2 concentration showed a very slight deep contribution of the Timanfaya volcanic system, with no clear relation to the main eruptive fissures of the studied area. The existence of soil helium enrichments in Timanfaya indicates a shallow degassing of crustal helium and other possible deeper sources probably form cooling magma bodies at depth. The main soil helium enrichments were observed in good agreement with the main eruptive fissures of the 1730-36 eruption, with the highest values located at those areas with a higher density of recent eruptive centers, indicating an important structural control for the leakage of helium at Timanfaya volcano. Atmospheric air slightly polluted by deep-seated helium emissions, CO2 degassed from a cooling magma body, and biogenic CO2, might be the most plausible explanation for the existence of soil gas. Helium is a deep-seated gas, exhibiting important emission rates along the main eruptive fissure of the 1730-36 eruption of Timanfaya volcano.

Historic and Industrial Lead within the Northwest Pacific Ocean Evidenced by Lead Isotopes in Seawater.

PubMed

Zurbrick, Cheryl M; Gallon, Céline; Flegal, A Russell

2017-02-07

We report the continued lead (Pb) contamination of the Northwest Pacific Ocean in 2002 and present the first comprehensive Pb isotope data set for that region. In the upper ocean, a Pb concentration maxima (64-113 pmol kg -1 ) extended throughout the entire North Pacific Subtropical Gyre (NPSG). We determined most of the Pb in this feature was from industrial emissions by many nations in the 1980s and 1990s, with the largest contributions from leaded gasoline emissions. In contrast, the deep water (>1000 m) Pb concentrations were lower (6-37 pmol kg -1 ), and constituted a mix of background (natural) Pb and anthropogenic Pb inputs from preceding decades. Deep water below the Western Subarctic Gyre (WSAG) contained more industrial Pb than below the NPSG, which was attributed to a calculated 60-fold greater flux of particulate Pb to abyssal waters near the Asian continent. Assuming Pb isotope compositions in the North Pacific Ocean were homogeneous prior to large-scale 20th century anthropogenic inputs, this evidence suggests a relatively faster change in Pb isotope ratios of North Pacific deep water below the WSAG versus the NPSG.

The deep levels in InGaAlP epilayers grown by metalorganic chemical vapor deposition using tertiarybutylphosphine

NASA Astrophysics Data System (ADS)

Izumiya, T.; Ishikawa, H.; Mashita, M.

1994-12-01

InGaAlP epilayers and double-hetero structure light emitting diodes (LEDs) were grown by metalorganic chemical vapor deposition (MOCVD) using tertiarybutylphosphine (TBP). The photoluminescence (PL) intensities were low compared with the epilayer grown using PH 3, and depended markedly on the TBP synthesis lots. Deep levels, were studied and two oxygen related levels were observed in the epilayers with small PL intensities. An intimate relation between the deep levels and the photoluminescence (PL) intensity has been found. A larger TBP flow rate reduced the deep level concentrations and improved the PL intensity.

Ozone Depletion Caused by Rocket Engine Emissions: A Fundamental Limit on the Scale and Viability of Space-Based Geoengineering Schemes

NASA Astrophysics Data System (ADS)

Ross, M. N.; Toohey, D.

2008-12-01

Emissions from solid and liquid propellant rocket engines reduce global stratospheric ozone levels. Currently ~ one kiloton of payloads are launched into earth orbit annually by the global space industry. Stratospheric ozone depletion from present day launches is a small fraction of the ~ 4% globally averaged ozone loss caused by halogen gases. Thus rocket engine emissions are currently considered a minor, if poorly understood, contributor to ozone depletion. Proposed space-based geoengineering projects designed to mitigate climate change would require order of magnitude increases in the amount of material launched into earth orbit. The increased launches would result in comparable increases in the global ozone depletion caused by rocket emissions. We estimate global ozone loss caused by three space-based geoengineering proposals to mitigate climate change: (1) mirrors, (2) sunshade, and (3) space-based solar power (SSP). The SSP concept does not directly engineer climate, but is touted as a mitigation strategy in that SSP would reduce CO2 emissions. We show that launching the mirrors or sunshade would cause global ozone loss between 2% and 20%. Ozone loss associated with an economically viable SSP system would be at least 0.4% and possibly as large as 3%. It is not clear which, if any, of these levels of ozone loss would be acceptable under the Montreal Protocol. The large uncertainties are mainly caused by a lack of data or validated models regarding liquid propellant rocket engine emissions. Our results offer four main conclusions. (1) The viability of space-based geoengineering schemes could well be undermined by the relatively large ozone depletion that would be caused by the required rocket launches. (2) Analysis of space- based geoengineering schemes should include the difficult tradeoff between the gain of long-term (~ decades) climate control and the loss of short-term (~ years) deep ozone loss. (3) The trade can be properly evaluated only if our understanding of the stratospheric impact of rocket emissions is significantly improved. (4) Such an improved understanding requires a concerted effort of research including new in situ measurements in a variety of rocket plumes and a multi-scale modeling program similar in scope to the effort required to address the climate and ozone impacts of aircraft emissions.

Spectral properties of X-ray selected narrow emission line galaxies

NASA Astrophysics Data System (ADS)

Romero-Colmenero, E.

1998-03-01

This thesis reports a study of the X-ray and optical properties of two samples of X-ray selected Narrow Emission Line Galaxies (NELGs), and their comparison with the properties of broad line Active Galactic Nuclei (AGN). One sample (18 NELGs) is drawn from the ROSAT International X-ray Optical Survey (RIXOS), the other (19 NELGs and 33 AGN) from the ROSAT UK Deep Survey. ROSAT multi-channel X-ray spectra have been extracted and fitted with power-law, bremsstrahlung and black body models for the brighter RIXOS sources. In most cases, power-law and bremsstrahlung models provide the best results. The average spectral energy index, alpha, of the RIXOS NELGs is 0.96 +/- 0.07, similar to that of AGN (alpha~1). For the fainter RIXOS NELGs, as well as for all the UK Deep Survey sources, counts in three spectral bands have been extracted and fitted with a power-law model, assuming the Galactic value for N_H. The brighter RIXOS sources demonstrated that the results obtained by these two different extraction and fitting procedures provide consistent results. Two average X-ray spectra, one for the NELGs and another for the AGN, were created from the UK Deep Survey sources. The power-law slope of the average NELG is alpha = 0.45 +/- 0.09, whilst that of the AGN is alpha = 0.96 +/- 0.03. ROSAT X-ray surveys have shown that the fractional surface density of NELGs increases with respect to AGN at faint fluxes (<= 2e-15 ergs cm-2 s-1), thus suggesting that NELGs are important contributors to the residual soft (<2 keV) X-ray background (XRB). Moreover, the spectral slope of this background (alpha~0.4, 1-10 keV) is harder than that of AGN (alpha~1), which are known to contribute most of the XRB at higher flux levels. The work presented in this thesis shows unequivocally for the first time that the integrated spectrum of the faintest NELGs (alpha~0.4) is consistent with that of the soft X-ray background, finally reconciling it with the properties of the sources that are thought to constitute it. Furthermore, by combining both samples of NELGs, I find a tendency for sources at lower fluxes to display harder slopes (95% confidence level), further strengthening the case for NELGs to be major contributors to the XRB at the fainter fluxes. The analysis of optical spectroscopy, obtained on La Palma and Hawaii, shows that NELGs form a very heterogeneous group, made up of a mixture of Seyfert 2, LINER and HII-region like galaxies. Seyfert 2 galaxies are found to possess in general the steepest X-ray slopes. Ways to explain this in the context of the unified model of AGN are discussed. The FWHM of some emission lines (Halpha, Hbeta, [NII]) in the NELGs appears to increase with steepening X-ray spectral slope. In the case of the Balmer lines, this is at variance with what is observed in broad line AGN. The FWHM of the Balmer lines is also correlated to the FWHM of the forbidden lines, indicating that they must originate in regions of similar velocity fields. Unfortunately, the number of sources uniquely classified is not sufficient to investigate these relationships on a source type basis. The optical emission line ratios of a bright RIXOS source (aka Arp 185, NGC 6217), classified as a starburst galaxy in the literature, indicate that this is in fact a weak-[OI] LINER, powered either by emission from hot O stars or by hot stars together with a non-stellar continuum. Spatially resolved spectroscopic analysis suggests that the Balmer emission lines are concentrated in the inner regions of the nucleus, while the forbidden lines arise from a more extended region. Line ratios do not indicate a change in the ionizing continuum of this source with distance from the centre.

Spectral properties of x-ray selected narrow emission line galaxies

NASA Astrophysics Data System (ADS)

Romero Colmenero, Encarnacion

This thesis reports a study of the X-ray and optical properties of two samples of X-ray selected Narrow Emission Line Galaxies (NELGs), and their comparison with the properties of broad line Active Galactic Nuclei (AGN). One sample (18 NELGs) is drawn from the ROSAT International X-ray Optical Survey (RIXOS), the other (19 NELGs and 33 AGN) from the ROSAT UK Deep Survey. ROSAT multi-channel X-ray spectra have been extracted and fitted with power-law, bremsstrahlung and black body models for the brighter RIXOS sources. In most cases, power-law and bremsstrahlung models provide the best results. The average spectral energy index, alpha, of the RIXOS NELGs is 0.96 +/- 0.07, similar to that of AGN (alpha ~ 1). For the fainter RIXOS NELGs, as well as for all the UK Deep Survey sources, counts in three spectral bands have been extracted and fitted with a power-law model, assuming the Galactic value for NH. The brighter RIXOS sources demonstrated that the results obtained by these two different extraction and fitting procedures provide consistent results. Two average X-ray spectra, one for the NELGs and another for the AGN, were created from the UK Deep Survey sources. The power-law spectral slope of the average NELG is S = 0.45 +/- 0.09, whilst that of the AGN is S = 0.96 +/- 0.03. ROSAT X-ray surveys have shown that the fractional surface density of NELGs increases with respect to AGN at faint fluxes (< 2 x 10-15erg cm-2 s -1), thus suggesting that NELGs are important contributors to the residual soft (< 2 keV) X-ray background (XRB). Moreover, the spectral slope of this background (S ~ 0.4, 1-10 keV) is harder than that of AGN (S ~ 1), which are known to contribute most of the XRB at higher flux levels. The work presented in this thesis shows unequivocally for the first time that the integrated spectrum of the faintest NELGs (alpha ~ 0.4) is consistent with that of the soft X-ray background, finally reconciling it with the properties of the sources that are thought to constitute it. Furthermore, by combining both samples of NELGs, I find a tendency for sources at lower fluxes to display harder slopes (95% confidence level), further strengthening the case for NELGs to be major contributors to the XRB at the fainter fluxes. The analysis of optical spectroscopy, obtained on La Palma and Hawaii, shows that NELGs form a very heterogeneous group, made up of a mixture of Seyfert 2, LINER and HII-region like galaxies. Seyfert 2 galaxies are found to possess in general the steepest X-ray slopes. Ways to explain this in the context of the unified model of AGN are discussed. The FWHM of some emission lines (H, [NH]) in the NELGs appears to increase with steepening X-ray spectral slope. In the case of the Balmer lines, this at variance with what is observed in broad line AGN. The FWHM of the Balmer lines is also correlated to the FWHM of the forbidden lines, indicating that they must originate in regions of similar velocity fields. Unfortunately, the number of sources uniquely classified is not sufficient to investigate these relationships on a source type basis. The optical emission line ratios of a bright RIXOS source (aka Arp 185, NGC 6217), classified as a starburst galaxy in the literature, indicate that this is in fact a weak-[OI] LINER, powered either by emission from hot O stars or by hot stars together with a non-stellar continuum. Spatially resolved spectroscopic analysis suggests that the Balmer emission lines are concentrated in the inner regions of the nucleus, while the forbidden lines arise from a more extended region. Line ratios do not indicate a change in the ionizing continuum of this source with distance from the centre.

The Number Density Evolution of Extreme Emission Line Galaxies in 3D-HST: Results from a Novel Automated Line Search Technique for Slitless Spectroscopy

NASA Astrophysics Data System (ADS)

Maseda, Michael V.; van der Wel, Arjen; Rix, Hans-Walter; Momcheva, Ivelina; Brammer, Gabriel B.; Franx, Marijn; Lundgren, Britt F.; Skelton, Rosalind E.; Whitaker, Katherine E.

2018-02-01

The multiplexing capability of slitless spectroscopy is a powerful asset in creating large spectroscopic data sets, but issues such as spectral confusion make the interpretation of the data challenging. Here we present a new method to search for emission lines in the slitless spectroscopic data from the 3D-HST survey utilizing the Wide-Field Camera 3 on board the Hubble Space Telescope. Using a novel statistical technique, we can detect compact (extended) emission lines at 90% completeness down to fluxes of 1.5(3.0)× {10}-17 {erg} {{{s}}}-1 {{cm}}-2, close to the noise level of the grism exposures, for objects detected in the deep ancillary photometric data. Unlike previous methods, the Bayesian nature allows for probabilistic line identifications, namely redshift estimates, based on secondary emission line detections and/or photometric redshift priors. As a first application, we measure the comoving number density of Extreme Emission Line Galaxies (restframe [O III] λ5007 equivalent widths in excess of 500 Å). We find that these galaxies are nearly 10× more common above z ∼ 1.5 than at z ≲ 0.5. With upcoming large grism surveys such as Euclid and WFIRST, as well as grisms featured prominently on the NIRISS and NIRCam instruments on the James Webb Space Telescope, methods like the one presented here will be crucial for constructing emission line redshift catalogs in an automated and well-understood manner. This work is based on observations taken by the 3D-HST Treasury Program and the CANDELS Multi-Cycle Treasury Program with the NASA/ESA HST, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

Investigation and characterization of ZnO single crystal microtubes

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

Al-Naser, Qusay A.H.; Zhou, Jian, E-mail: jianzhou@whut.edu.cn; Liu, Guizhen

2016-04-15

Morphological, structural, and optical characterization of microwave synthesized ZnO single crystal microtubes were investigated in this work. The structure and morphology of the ZnO microtubes are characterized using X-ray diffraction (XRD), single crystal diffraction (SCD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM). The results reveal that the as-synthesized ZnO microtube has a highly regular hexagonal cross section and smooth surfaces with an average length of 650–700 μm, an average outer diameter of 50 μm and wall thickness of 1–3 μm, possessing a single crystal wurtzite hexagonal structure. Optical properties of ZnOmore » single crystal microtubes were investigated by photoluminescence (PL) and ultraviolet-visible (UV-vis) absorption techniques. Room-temperature PL spectrum of the microtube reveal a strong UV emission peak at around 375.89 nm and broad and a weak visible emission with a main peak identified at 577 nm, which was assigned to the nearest band-edge emission and the deep-level emission, respectively. The band gap energy of ZnO microtube was found to be 3.27 eV. - Highlights: • ZnO microtube length of 650–700 μm, diameter of 50 μm, wall thickness of 1–3 μm • ZnO microtube possesses a single crystal wurtzite hexagonal structure. • The crystal system is hexahedral oriented along a-axis with indices of (100). • A strong and sharp UV emission at 375.89 nm (3.29 eV) • One prominent absorption band around 378.88 nm (3.27 eV)« less

A 60 yr record of atmospheric carbon monoxide reconstructed from Greenland firn air

NASA Astrophysics Data System (ADS)

Petrenko, V. V.; Martinerie, P.; Novelli, P.; Etheridge, D. M.; Levin, I.; Wang, Z.; Blunier, T.; Chappellaz, J.; Kaiser, J.; Lang, P.; Steele, L. P.; Hammer, S.; Mak, J.; Langenfelds, R. L.; Schwander, J.; Severinghaus, J. P.; Witrant, E.; Petron, G.; Battle, M. O.; Forster, G.; Sturges, W. T.; Lamarque, J.-F.; Steffen, K.; White, J. W. C.

2013-08-01

We present the first reconstruction of the Northern Hemisphere (NH) high latitude atmospheric carbon monoxide (CO) mole fraction from Greenland firn air. Firn air samples were collected at three deep ice core sites in Greenland (NGRIP in 2001, Summit in 2006 and NEEM in 2008). CO records from the three sites agree well with each other as well as with recent atmospheric measurements, indicating that CO is well preserved in the firn at these sites. CO atmospheric history was reconstructed back to the year 1950 from the measurements using a combination of two forward models of gas transport in firn and an inverse model. The reconstructed history suggests that Arctic CO in 1950 was 140-150 nmol mol-1, which is higher than today's values. CO mole fractions rose by 10-15 nmol mol-1 from 1950 to the 1970s and peaked in the 1970s or early 1980s, followed by a ≈ 30 nmol mol-1 decline to today's levels. We compare the CO history with the atmospheric histories of methane, light hydrocarbons, molecular hydrogen, CO stable isotopes and hydroxyl radicals (OH), as well as with published CO emission inventories and results of a historical run from a chemistry-transport model. We find that the reconstructed Greenland CO history cannot be reconciled with available emission inventories unless unrealistically large changes in OH are assumed. We argue that the available CO emission inventories strongly underestimate historical NH emissions, and fail to capture the emission decline starting in the late 1970s, which was most likely due to reduced emissions from road transportation in North America and Europe.

Radio-Optical Reference Frame Link Using the U.S. Naval Observatory Astrograph and Deep CCD Imaging

NASA Astrophysics Data System (ADS)

Zacharias, N.; Zacharias, M. I.

2014-05-01

Between 1997 and 2004 several observing runs were conducted, mainly with the CTIO 0.9 m, to image International Celestial Reference Frame (ICRF) counterparts (mostly QSOs) in order to determine accurate optical positions. Contemporary to these deep CCD images, the same fields were observed with the U.S. Naval Observatory astrograph in the same bandpass. They provide accurate positions on the Hipparcos/Tycho-2 system for stars in the 10-16 mag range used as reference stars for the deep CCD imaging data. Here we present final optical position results of 413 sources based on reference stars obtained by dedicated astrograph observations that were reduced following two different procedures. These optical positions are compared to radio very long baseline interferometry positions. The current optical system is not perfectly aligned to the ICRF radio system with rigid body rotation angles of 3-5 mas (= 3σ level) found between them for all three axes. Furthermore, statistically, the optical-radio position differences are found to exceed the total, combined, known errors in the observations. Systematic errors in the optical reference star positions and physical offsets between the centers of optical and radio emissions are both identified as likely causes. A detrimental, astrophysical, random noise component is postulated to be on about the 10 mas level. If confirmed by future observations, this could severely limit the Gaia to ICRF reference frame alignment accuracy to an error of about 0.5 mas per coordinate axis with the current number of sources envisioned to provide the link. A list of 36 ICRF sources without the detection of an optical counterpart to a limiting magnitude of about R = 22 is provided as well.

Neuroinflammatory component of gray matter pathology in multiple sclerosis.

PubMed

Herranz, Elena; Giannì, Costanza; Louapre, Céline; Treaba, Constantina A; Govindarajan, Sindhuja T; Ouellette, Russell; Loggia, Marco L; Sloane, Jacob A; Madigan, Nancy; Izquierdo-Garcia, David; Ward, Noreen; Mangeat, Gabriel; Granberg, Tobias; Klawiter, Eric C; Catana, Ciprian; Hooker, Jacob M; Taylor, Norman; Ionete, Carolina; Kinkel, Revere P; Mainero, Caterina

2016-11-01

In multiple sclerosis (MS), using simultaneous magnetic resonance-positron emission tomography (MR-PET) imaging with 11 C-PBR28, we quantified expression of the 18kDa translocator protein (TSPO), a marker of activated microglia/macrophages, in cortex, cortical lesions, deep gray matter (GM), white matter (WM) lesions, and normal-appearing WM (NAWM) to investigate the in vivo pathological and clinical relevance of neuroinflammation. Fifteen secondary-progressive MS (SPMS) patients, 12 relapsing-remitting MS (RRMS) patients, and 14 matched healthy controls underwent 11 C-PBR28 MR-PET. MS subjects underwent 7T T2*-weighted imaging for cortical lesion segmentation, and neurological and cognitive evaluation. 11 C-PBR28 binding was measured using normalized 60- to 90-minute standardized uptake values and volume of distribution ratios. Relative to controls, MS subjects exhibited abnormally high 11 C-PBR28 binding across the brain, the greatest increases being in cortex and cortical lesions, thalamus, hippocampus, and NAWM. MS WM lesions showed relatively modest TSPO increases. With the exception of cortical lesions, where TSPO expression was similar, 11 C-PBR28 uptake across the brain was greater in SPMS than in RRMS. In MS, increased 11 C-PBR28 binding in cortex, deep GM, and NAWM correlated with neurological disability and impaired cognitive performance; cortical thinning correlated with increased thalamic TSPO levels. In MS, neuroinflammation is present in the cortex, cortical lesions, deep GM, and NAWM, is closely linked to poor clinical outcome, and is at least partly linked to neurodegeneration. Distinct inflammatory-mediated factors may underlie accumulation of cortical and WM lesions. Quantification of TSPO levels in MS could prove to be a sensitive tool for evaluating in vivo the inflammatory component of GM pathology, particularly in cortical lesions. Ann Neurol 2016;80:776-790. © 2016 American Neurological Association.

Radio-optical reference frame link using the U.S. Naval observatory astrograph and deep CCD imaging

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

Zacharias, N.; Zacharias, M. I., E-mail: nz@usno.navy.mil

2014-05-01

Between 1997 and 2004 several observing runs were conducted, mainly with the CTIO 0.9 m, to image International Celestial Reference Frame (ICRF) counterparts (mostly QSOs) in order to determine accurate optical positions. Contemporary to these deep CCD images, the same fields were observed with the U.S. Naval Observatory astrograph in the same bandpass. They provide accurate positions on the Hipparcos/Tycho-2 system for stars in the 10-16 mag range used as reference stars for the deep CCD imaging data. Here we present final optical position results of 413 sources based on reference stars obtained by dedicated astrograph observations that were reducedmore » following two different procedures. These optical positions are compared to radio very long baseline interferometry positions. The current optical system is not perfectly aligned to the ICRF radio system with rigid body rotation angles of 3-5 mas (= 3σ level) found between them for all three axes. Furthermore, statistically, the optical-radio position differences are found to exceed the total, combined, known errors in the observations. Systematic errors in the optical reference star positions and physical offsets between the centers of optical and radio emissions are both identified as likely causes. A detrimental, astrophysical, random noise component is postulated to be on about the 10 mas level. If confirmed by future observations, this could severely limit the Gaia to ICRF reference frame alignment accuracy to an error of about 0.5 mas per coordinate axis with the current number of sources envisioned to provide the link. A list of 36 ICRF sources without the detection of an optical counterpart to a limiting magnitude of about R = 22 is provided as well.« less

Processing-Induced Electrically Active Defects in Black Silicon Nanowire Devices.

PubMed

Carapezzi, Stefania; Castaldini, Antonio; Mancarella, Fulvio; Poggi, Antonella; Cavallini, Anna

2016-04-27

Silicon nanowires (Si NWs) are widely investigated nowadays for implementation in advanced energy conversion and storage devices, as well as many other possible applications. Black silicon (BSi)-NWs are dry etched NWs that merge the advantages related to low-dimensionality with the special industrial appeal connected to deep reactive ion etching (RIE). In fact, RIE is a well established technique in microelectronics manufacturing. However, RIE processing could affect the electrical properties of BSi-NWs by introducing deep states into their forbidden gap. This work applies deep level transient spectroscopy (DLTS) to identify electrically active deep levels and the associated defects in dry etched Si NW arrays. Besides, the successful fitting of DLTS spectra of BSi-NWs-based Schottky barrier diodes is an experimental confirmation that the same theoretical framework of dynamic electronic behavior of deep levels applies in bulk as well as in low dimensional structures like NWs, when quantum confinement conditions do not occur. This has been validated for deep levels associated with simple pointlike defects as well as for deep levels associated with defects with richer structures, whose dynamic electronic behavior implies a more complex picture.

The Grism Lens-Amplified Survey from Space (GLASS). III. A Census of Lyα Emission at z ≳ 7 from HST Spectroscopy

NASA Astrophysics Data System (ADS)

Schmidt, K. B.; Treu, T.; Bradač, M.; Vulcani, B.; Huang, K.-H.; Hoag, A.; Maseda, M.; Guaita, L.; Pentericci, L.; Brammer, G. B.; Dijkstra, M.; Dressler, A.; Fontana, A.; Henry, A. L.; Jones, T. A.; Mason, C.; Trenti, M.; Wang, X.

2016-02-01

We present a census of Lyα emission at z≳ 7, utilizing deep near-infrared Hubble Space Telescope grism spectroscopy from the first six completed clusters of the Grism Lens-Amplified Survey from Space (GLASS). In 24/159 photometrically selected galaxies we detect emission lines consistent with Lyα in the GLASS spectra. Based on the distribution of signal-to-noise ratios and on simulations, we expect the completeness and the purity of the sample to be 40%-100% and 60%-90%, respectively. For the objects without detected emission lines we show that the observed (not corrected for lensing magnification) 1σ flux limits reach 5 × 10-18 erg s-1 cm-2 per position angle over the full wavelength range of GLASS (0.8-1.7 μm). Based on the conditional probability of Lyα emission measured from the ground at z˜ 7, we would have expected 12-18 Lyα emitters. This is consistent with the number of detections, within the uncertainties, confirming the drop in Lyα emission with respect to z˜ 6. Deeper follow-up spectroscopy, here exemplified by Keck spectroscopy, is necessary to improve our estimates of completeness and purity and to confirm individual candidates as true Lyα emitters. These candidates include a promising source at z = 8.1. The spatial extent of Lyα in a deep stack of the most convincing Lyα emitters with < z> = 7.2 is consistent with that of the rest-frame UV continuum. Extended Lyα emission, if present, has a surface brightness below our detection limit, consistent with the properties of lower-redshift comparison samples. From the stack we estimate upper limits on rest-frame UV emission line ratios and find {f}{{C}{{IV}}}/{f}{Lyα }≲ 0.32 and {f}{{C}{{III}}]}/{f}{Lyα }≲ 0.23, in good agreement with other values published in the literature.

Large eddy simulation of reactive pollutants in a deep urban street canyon: Coupling dynamics with O3-NOx-VOC chemistry.

PubMed

Zhong, Jian; Cai, Xiao-Ming; Bloss, William James

2017-05-01

A large eddy simulation (LES) model coupled with O 3 -NO x -VOC chemistry is implemented to simulate the coupled effects of emissions, mixing and chemical pre-processing within an idealised deep (aspect ratio = 2) urban street canyon under a weak wind condition. Reactive pollutants exhibit significant spatial variations in the presence of two vertically aligned unsteady vortices formed in the canyon. Comparison of the LES results from two chemical schemes (simple NO x -O 3 chemistry and a more comprehensive Reduced Chemical Scheme (RCS) chemical mechanism) shows that the concentrations of NO 2 and O x inside the street canyon are enhanced by approximately 30-40% via OH/HO 2 chemistry. NO, NO x , O 3 , OH and HO 2 are chemically consumed, while NO 2 and O x (total oxidant) are chemically produced within the canyon environment. Within-canyon pre-processing increases oxidant fluxes from the canyon to the overlying boundary layer, and this effect is greater for deeper street canyons (as found in many traditional European urban centres) than shallower (lower aspect ratio) streets. There is clear evidence of distinct behaviours for emitted chemical species and entrained chemical species, and positive (or negative) values of intensities of segregations are found between pairs of species with similar (or opposite) behaviour. The simplified two-box model underestimated NO and O 3 levels, but overestimated NO 2 levels for both the lower and upper canyon compared with the more realistic LES-chemistry model. This suggests that the segregation effect due to incomplete mixing reduces the chemical conversion rate of NO to NO 2 . This study reveals the impacts of nonlinear O 3 -NO x -VOC photochemical processes in the incomplete mixing environment and provides a better understanding of the pre-processing of emissions within canyons, prior to their release to the urban boundary layer, through the coupling of street canyon dynamics and chemistry. Copyright © 2017 Elsevier Ltd. All rights reserved.

Deep learning aided decision support for pulmonary nodules diagnosing: a review.

PubMed

Yang, Yixin; Feng, Xiaoyi; Chi, Wenhao; Li, Zhengyang; Duan, Wenzhe; Liu, Haiping; Liang, Wenhua; Wang, Wei; Chen, Ping; He, Jianxing; Liu, Bo

2018-04-01

Deep learning techniques have recently emerged as promising decision supporting approaches to automatically analyze medical images for different clinical diagnosing purposes. Diagnosing of pulmonary nodules by using computer-assisted diagnosing has received considerable theoretical, computational, and empirical research work, and considerable methods have been developed for detection and classification of pulmonary nodules on different formats of images including chest radiographs, computed tomography (CT), and positron emission tomography in the past five decades. The recent remarkable and significant progress in deep learning for pulmonary nodules achieved in both academia and the industry has demonstrated that deep learning techniques seem to be promising alternative decision support schemes to effectively tackle the central issues in pulmonary nodules diagnosing, including feature extraction, nodule detection, false-positive reduction, and benign-malignant classification for the huge volume of chest scan data. The main goal of this investigation is to provide a comprehensive state-of-the-art review of the deep learning aided decision support for pulmonary nodules diagnosing. As far as the authors know, this is the first time that a review is devoted exclusively to deep learning techniques for pulmonary nodules diagnosing.

Aquifer disposal of carbon dioxide for greenhouse effect mitigation

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

Gupta, N.; Naymik, T.G.; Bergman, P.

1998-07-01

Deep aquifer sequestration of carbon dioxide (CO{sup 2}), generated from power plant and other industrial emissions, is being evaluated as one of the potential options for the reduction of atmospheric greenhouse gas emissions. The major advantages of using deep aquifers are that the disposal facilities may be located close to the sources, thus reducing the CO{sub 2} transport costs. The potential capacity is much larger than the projected CO{sub 2} emissions over the next century, and it is a long-term/permanent sequestration option, because a large portion of the injected CO{sub 2} may be fixed into the aquifer by dissolution ormore » mineralization. The major limitations include the potentially high cost, the risk of upward migration, and the public perception of risk. Most of the cost is due to the need to separate CO{sub 2} from other flue gases, rather than the actual cost of disposal. Hazardous liquid waste and acid gas disposal in deep sedimentary formations is a well-established practice. There are also numerous facilities for storage of natural gases in depleted oil and gas reservoirs. The only current facility for aquifer disposal of CO{sub 2} is the offshore injection well at Sleipner Vest in the North Sea in Norway operated by Statoil. Exxon and Pertamina are planning an offshore aquifer disposal facility at Natuna gas field in Indonesia. A major evaluation of the feasibility of CO{sub 2} disposal in the European Union and Norway has been conducted under project Joule II. The data and experience obtained from the existing deep-waste disposal facilities and from the Sleipner Vest site form a strong foundation for further research and development on CO{sub 2} sequestration. Federal Energy Technology Center (FETC) is currently leading a project that uses data from an existing hazardous waste disposal facility injecting in the Mt. Simon Sandstone aquifer in Ohio to evaluate hydrogeologic, geochemical, and social issues related to CO{sub 2} disposal.« less

Aquifer disposal of carbon dioxide for greenhouse effect mitigation

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

Gupta, N.; Naymik, T.G.; Bergman, P.

1998-04-01

Deep aquifer sequestration of carbon dioxide (CO{sub 2}) generated from power plant and other industrial emissions, is being evaluated as one of the potential options for the reduction of atmospheric greenhouse gas emissions. The major advantages of using deep aquifers are that the disposal facilities may be located close to the sources, thus reducing the CO{sub 2} transport costs. The potential capacity is much larger than the projected CO{sub 2} emissions over the next century, and it is a long-term/permanent sequestration option, because a large portion of the injected CO{sub 2} may be fixed into the aquifer by dissolution ormore » mineralization. The major limitations include the potentially high cost, the risk of upward migration, and the public perception of risk. Most of the cost is due to the need to separate CO{sub 2} from other flue gases, rather than the actual cost of disposal. Hazardous liquid waste and acid gas disposal in deep sedimentary formations is a well-established practice. There are also numerous facilities for storage of natural gases in depleted oil and gas reservoirs. The only current facility for aquifer disposal of CO{sub 2} is the offshore injection well at Sleipner Vest in the North Sea in Norway operated by Statoil. Exxon and Pertamina are planning an offshore aquifer disposal facility at Natuna gas field in Indonesia. A major evaluation of the feasibility of CO{sub 2} disposal in the European Union and Norway has been conducted under project Joule II. The data and experience obtained from the existing deep-waste disposal facilities and from the Sleipner Vest site form a strong foundation for further research and development on CO{sub 2} sequestration. Federal Energy Technology Center (FETC) is currently leading a project that uses data from an existing hazardous waste disposal facility injecting in the Mt. Simon Sandstone aquifer in Ohio to evaluate hydrogeologic, geochemical, and social issues related to CO{sub 2} disposal.« less

Setup for in situ deep level transient spectroscopy of semiconductors during swift heavy ion irradiation.

PubMed

Kumar, Sandeep; Kumar, Sugam; Katharria, Y S; Safvan, C P; Kanjilal, D

2008-05-01

A computerized system for in situ deep level characterization during irradiation in semiconductors has been set up and tested in the beam line for materials science studies of the 15 MV Pelletron accelerator at the Inter-University Accelerator Centre, New Delhi. This is a new facility for in situ irradiation-induced deep level studies, available in the beam line of an accelerator laboratory. It is based on the well-known deep level transient spectroscopy (DLTS) technique. High versatility for data manipulation is achieved through multifunction data acquisition card and LABVIEW. In situ DLTS studies of deep levels produced by impact of 100 MeV Si ions on Aun-Si(100) Schottky barrier diode are presented to illustrate performance of the automated DLTS facility in the beam line.

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

Archer, D.

A two-dimensional model of a passive continental margin was adapted to the simulation of the methane cycle on Siberian continental shelf and slope, attempting to account for the impacts of glacial/interglacial cycles in sea level, alternately exposing the continental shelf to freezing conditions with deep permafrost formation during glacial times, and immersion in the ocean in interglacial times. The model is used to gauge the impact of the glacial cycles, and potential anthropogenic warming in the deep future, on the atmospheric methane emission flux, and the sensitivities of that flux to processes such as permafrost formation and terrestrial organic carbonmore » (Yedoma) deposition. Hydrological forcing drives a freshening and ventilation of pore waters in areas exposed to the atmosphere, which is not quickly reversed by invasion of seawater upon submergence, since there is no analogous saltwater pump. This hydrological pump changes the salinity enough to affect the stability of permafrost and methane hydrates on the shelf. Permafrost formation inhibits bubble transport through the sediment column, by construction in the model. The impact of permafrost on the methane budget is to replace the bubble flux by offshore groundwater flow containing dissolved methane, rather than accumulating methane for catastrophic release when the permafrost seal fails during warming. By far the largest impact of the glacial/interglacial cycles on the atmospheric methane flux is attenuation by dissolution of bubbles in the ocean when sea level is high. Methane emissions are highest during the regression (soil freezing) part of the cycle, rather than during transgression (thawing). The model-predicted methane flux to the atmosphere in response to a warming climate is small, relative to the global methane production rate, because of the ongoing flooding of the continental shelf. A slight increase due to warming could be completely counteracted by sea level rise on geologic time scales, decreasing the efficiency of bubble transit through the water column. The methane cycle on the shelf responds to climate change on a long time constant of thousands of years, because hydrate is excluded thermodynamically from the permafrost zone by water limitation, leaving the hydrate stability zone at least 300 m below the sediment surface.« less

A Zero-Dimensional Organic Seesaw-Shaped Tin Bromide with Highly Efficient Strongly Stokes-Shifted Deep-Red Emission

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

Zhou, Chenkun; Lin, Haoran; Shi, Hongliang

The synthesis and characterization is reported of (C 9NH 20) 2SnBr 4, a novel organic metal halide hybrid with a zero-dimensional (0D) structure, in which individual seesaw-shaped tin (II) bromide anions (SnBr 4 2-) are co-crystallized with 1-butyl-1-methylpyrrolidinium cations (C 9NH 20 +). Upon photoexcitation, the bulk crystals exhibit a highly efficient broadband deep-red emission peaked at 695 nm, with a large Stokes shift of 332 nm and a high quantum efficiency of around 46 %. Furthermore, the unique photophysical properties of this hybrid material are attributed to two major factors: 1) the 0D structure allowing the bulk crystals tomore » exhibit the intrinsic properties of individual SnBr 4 2- species, and 2) the seesaw structure then enables a pronounced excited state structural deformation as confirmed by density functional theory (DFT) calculations.« less

Deep Limits on the X-ray and Radio Emission From the Nearby Type Iax SN2014dt

NASA Astrophysics Data System (ADS)

Stauffer, Candice; Margutti, Raffaella; Coppejans, Deannne

2018-01-01

Type Iax Supernovae (SN Iax) have been recently recognized as a new class of stellar explosions in 2012. SN Iax constitute the largest class of ``peculiar thermonuclear explosions'' from white dwarf (WD) stellar progenitors in binary systems. They are characterized by lower ejecta velocity, lower luminsity and non-standard late-time spectral evolution, when compared to the more common Type Ia SNe. Here I present deep radio and X-ray observations of the closest type Iax SN yet discovered, SN2014dt. The SN shock interaction with the medium is a very well known source of radio and X-ray emission. My observations of SN2014dt uniquely constrain the density in the SN sub-pc environment (which cannot be investigated otherwise), and allow me to put constraints on the mysterious nature of the stellar companion.

Carbon emissions and resources use by Chinese economy 2007: A 135-sector inventory and input-output embodiment

NASA Astrophysics Data System (ADS)

Chen, G. Q.; Chen, Z. M.

2010-11-01

A 135-sector inventory and embodiment analysis for carbon emissions and resources use by Chinese economy 2007 is presented in this paper by an ecological input-output modeling based on the physical entry scheme. Included emissions and resources belong to six categories as: (1) greenhouse gas (GHG) in terms of CO 2, CH 4, and N 2O; (2) energy in terms of coal, crude oil, natural gas, hydropower, nuclear power, and firewood; (3) water in terms of freshwater; (4) exergy in terms of coal, crude oil, natural gas, grain, bean, tuber, cotton, peanut, rapeseed, sesame, jute, sugarcane, sugar beet, tobacco, silkworm feed, tea, fruits, vegetables, wood, bamboo, pulp, meat, egg, milk, wool, aquatic products, iron ore, copper ore, bauxite, lead ore, zinc ore, pyrite, phosphorite, gypsum, cement, nuclear fuel, and hydropower; (5) and (6) solar and cosmic emergies in terms of sunlight, wind power, deep earth heat, chemical power of rain, geopotential power of rain, chemical power of stream, geopotential power of stream, wave power, geothermal power, tide power, topsoil loss, coal, crude oil, natural gas, ferrous metal ore, non-ferrous metal ore, non-metal ore, cement, and nuclear fuel. Accounted based on the embodied intensities are carbon emissions and resources use embodied in the final use as rural consumption, urban consumption, government consumption, gross fixed capital formation, change in inventories, and export, as well as in the international trade balance. The resulted database is basic to environmental account of carbon emissions and resources use at various levels.

Local Group dSph radio survey with ATCA - II. Non-thermal diffuse emission

NASA Astrophysics Data System (ADS)

Regis, Marco; Richter, Laura; Colafrancesco, Sergio; Profumo, Stefano; de Blok, W. J. G.; Massardi, Marcella

2015-04-01

Our closest neighbours, the Local Group dwarf spheroidal (dSph) galaxies, are extremely quiescent and dim objects, where thermal and non-thermal diffuse emissions lack, so far, of detection. In order to possibly study the dSph interstellar medium, deep observations are required. They could reveal non-thermal emissions associated with the very low level of star formation, or to particle dark matter annihilating or decaying in the dSph halo. In this work, we employ radio observations of six dSphs, conducted with the Australia Telescope Compact Array in the frequency band 1.1-3.1 GHz, to test the presence of a diffuse component over typical scales of few arcmin and at an rms sensitivity below 0.05 mJy beam-1. We observed the dSph fields with both a compact array and long baselines. Short spacings led to a synthesized beam of about 1 arcmin and were used for the extended emission search. The high-resolution data mapped background sources, which in turn were subtracted in the short-baseline maps, to reduce their confusion limit. We found no significant detection of a diffuse radio continuum component. After a detailed discussion on the modelling of the cosmic ray (CR) electron distribution and on the dSph magnetic properties, we present bounds on several physical quantities related to the dSphs, such that the total radio flux, the angular shape of the radio emissivity, the equipartition magnetic field, and the injection and equilibrium distributions of CR electrons. Finally, we discuss the connection to far-infrared and X-ray observations.

Post-polymerization C-H Borylation of Donor-Acceptor Materials Gives Highly Efficient Solid State Near-Infrared Emitters for Near-IR-OLEDs and Effective Biological Imaging.

PubMed

Crossley, Daniel L; Urbano, Laura; Neumann, Robert; Bourke, Struan; Jones, Jennifer; Dailey, Lea Ann; Green, Mark; Humphries, Martin J; King, Simon M; Turner, Michael L; Ingleson, Michael J

2017-08-30

Post-polymerization modification of the donor-acceptor polymer, poly(9,9-dioctylfluorene-alt-benzothiadiazole), PF8-BT, by electrophilic C-H borylation is a simple method to introduce controllable quantities of near-infrared (near-IR) emitting chromophore units into the backbone of a conjugated polymer. The highly stable borylated unit possesses a significantly lower LUMO energy than the pristine polymer resulting in a reduction in the band gap of the polymer by up to 0.63 eV and a red shift in emission of more than 150 nm. Extensively borylated polymers absorb strongly in the deep red/near-IR and are highly emissive in the near-IR region of the spectrum in solution and solid state. Photoluminescence quantum yield (PLQY) values are extremely high in the solid state for materials with emission maxima ≥ 700 nm with PLQY values of 44% at 700 nm and 11% at 757 nm for PF8-BT with different borylation levels. This high brightness enables efficient solution processed near-IR emitting OLEDs to be fabricated and highly emissive borylated polymer loaded conjugated polymer nanoparticles (CPNPs) to be prepared. The latter are bright, photostable, low toxicity bioimaging agents that in phantom mouse studies show higher signal to background ratios for emission at 820 nm than the ubiquitous near-IR emissive bioimaging agent indocyanine green. This methodology represents a general approach for the post-polymerization functionalization of donor-acceptor polymers to reduce the band gap as confirmed by the C-H borylation of poly((9,9-dioctylfluorene)-2,7-diyl-alt-[4,7-bis(3-hexylthien-5-yl)-2,1,3-benzothiadiazole]-2c,2cc-diyl) (PF8TBT) resulting in a red shift in emission of >150 nm, thereby shifting the emission maximum to 810 nm.

A Poor Relationship Between Sea Level and Deep-Water Sand Delivery

NASA Astrophysics Data System (ADS)

Harris, Ashley D.; Baumgardner, Sarah E.; Sun, Tao; Granjeon, Didier

2018-08-01

The most commonly cited control on delivery of sand to deep water is the rate of relative sea-level fall. The rapid rate of accommodation loss on the shelf causes sedimentation to shift basinward. Field and experimental numerical modeling studies have shown that deep-water sand delivery can occur during any stage of relative sea level position and across a large range of values of rate of relative sea-level change. However, these studies did not investigate the impact of sediment transport efficiency on the relationship between rate of relative sea-level change and deep-water sand delivery rate. We explore this relationship using a deterministic nonlinear diffusion-based numerical stratigraphic forward model. We vary across three orders of magnitude the diffusion coefficient value for marine settings, which controls sediment transport efficiency. We find that the rate of relative sea-level change can explain no more than 1% of the variability in deep-water sand delivery rates, regardless of sediment transport efficiency. Model results show a better correlation with relative sea level, with up to 55% of the variability in deep water sand delivery rates explained. The results presented here are consistent with studies of natural settings which suggest stochastic processes such as avulsion and slope failure, and interactions among such processes, may explain the remaining variance. Relative sea level is a better predictor of deep-water sand delivery than rate of relative sea-level change because it is the sea-level fall itself which promotes sand delivery, not the rate of the fall. We conclude that the poor relationship between sea level and sand delivery is not an artifact of the modeling parameters but is instead due to the inadequacy of relative sea level and the rate of relative sea-level change to fully describe the dimensional space in which depositional systems reside. Subsequently, sea level itself is unable to account for the interaction of multiple processes that contribute to sand delivery to deep water.

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.

Study of Jovian synchrotron emission with the NASA's Deep Space Network for Juno mission

NASA Astrophysics Data System (ADS)

Garcia-Miro, Cristina; Horiuchi, Shinji; Levin, Steve; Orton, Glenn S.; Bolton, Scott; Jauncey, David; Kuiper, T. B. H.; Teitelbaum, Lawrence

2016-10-01

We are monitoring Jupiter's synchrotron emission with the purpose of connecting the measurements of the Juno mission's MicroWave Radiometer (MWR) experiment to the historical baseline of non-thermal emission, using NASA's Deep Space Network (DSN). The DSN has the most sensitive network of antennas dedicated to tracking spacecraft that are exploring deep space, whose state-of-the-art receivers are considered among the best radio telescopes in the world. Availability for radio astronomy studies is subject to demand from space projects using the DSN. These antennas have previously contributed to the study of the Jovian non-thermal synchroton emission [1].NASA's New Frontiers Juno mission was placed into a nominal orbit on the 4th of July, 2016, allowing it to begin a detailed exploration of Jupiter. Among its scientific objectives is the characterization and exploration of the 3D structure of Jupiter's polar magnetosphere and auroras. It is important to provide a means to connect these detailed MWR measurements with the historical record of synchrotron emission. Ideally, these measurements should be performed on a regular basis during the whole extent of the mission. The DSN has the advantage of being able to perform uninterrupted 24-hour observations using antennas from the different complexes located in USA, Australia and Spain.Additionally, this monitoring program links with and validates the Jupiter observations currently performed by the triplet of educational programs GAVRT, STARS and PARTNeR in USA, Australia and Spain, respectively. These educational programs are partially supported by the DSN and use some of its antennas for teaching purposes, involving students in professional research and exploration.We will describe the DSN single-dish continuum observations of Jupiter in detail: the antennas, receivers and the equipment used to collect the data, the observing procedure, and the data-reduction process. Preliminary results of the Jupiter beaming curve will also be presented.References[1] Bolton, S.J., Janssen, M., Thorne, R., et al.: Ultra-relativistic electrons in Jupiter's radiation belts, Nature, 415, 2002.

Optical Emission Associated with the Galactic Supernova Remnant G179.0+2.6

NASA Astrophysics Data System (ADS)

How, Thomas G.; Fesen, Robert A.; Neustadt, Jack M. M.; Black, Christine S.; Outters, Nicolas

2018-04-01

Narrow passband optical images of the large Galactic supernova remnant G179.0+2.6 reveal a faint but nearly complete emission shell dominated by strong [O 3] 4959,5007 Å line emission. The remnant's optical emission, which consists of both diffuse and filamentary features, is brightest along its southern and northeastern limbs. Deep Hα images detect little coincidence emission indicating an unusually high [O 3]/Hα emission ratio for such a large and apparently old remnant. Low-dispersion optical spectra of several regions confirm large [O 3]/Hα line ratios with typical values around 10. The dominance of [O 3] emission for the majority of the remnant's optical filaments suggests shock velocities above 100 km s-1 are present throughout most of the remnant, likely reflecting a relatively low density ambient ISM. The remnant's unusually strong [O 3] emission adds to the remnant's interesting set of properties which include a thick radio emission shell, radial polarization of its radio emission like that typically seen in young supernova remnants, and an unusually slow-rotating gamma-ray pulsar with a characteristic spin-down age ≃ 50 kyr.

A New Observation of the Quiet Sun Soft X-ray (0.5-5 keV) Spectrum

NASA Astrophysics Data System (ADS)

Caspi, A.; Woods, T. N.; Stone, J.

2012-12-01

The solar corona is the brightest source of X-rays in the solar system, and the X-ray emission is highly variable with solar activity. While this is particularly true during solar flares, when emission can be enhanced by many orders of magnitude up to gamma-ray energies, even the so-called "quiet Sun" is bright in soft X-rays (SXRs), as the ~1-2 MK ambient plasma of the corona emits significant thermal bremsstrahlung up to ~5 keV. However, the actual solar SXR (0.5-5 keV) spectrum is not well known, particularly during quiet periods, as, with few exceptions, this energy range has not been systematically studied in many years. Previous observations include ultra-high-resolution but very narrow-band spectra from crystral spectrometers (e.g. Yohkoh/BCS), or integrated broadband irradiances from photometers (e.g. GOES/XRS, TIMED/XPS, etc.) that lack detailed spectral information. In recent years, broadband measurements with fair energy resolution (~0.5-0.7 keV FWHM) were made by SphinX on CORONAS-Photon and XRS on MESSENGER, although they did not extend below ~1 keV. We present observations of the quiet Sun SXR emission obtained using a new SXR spectrometer flown on the third SDO/EVE underflight calibration rocket (NASA 36.286). The commercial off-the-shelf Amptek X123 silicon drift detector, with an 8-micron Be window and custom aperture, measured the solar SXR emission from ~0.5 to >10 keV with ~0.15 keV FWHM resolution (though, due to hardware limitations, with only ~0.12 keV binning) and 2-sec cadence over ~5 minutes on 23 June 2012. Despite the rising solar cycle, activity on 23 June 2012 was abnormally low, with no visible active regions and GOES XRS emission near 2010 levels; we measured no solar counts above ~4 keV during the observation period. We compare our X123 measurements with spectra and broadband irradiances from other instruments, including the SphinX observations during the deep solar minimum of 2009, and with upper limits of >3 keV quiet Sun emission determined from RHESSI. We discuss the possible implications for X-ray-producing physical processes in the quiescent, active-region-free corona. The X123 spectrum could potentially serve as a reference for ~0.5-4 keV quiet Sun emission, to help improve solar spectral models such as CHIANTI and XPS Level 4. Our comparisons indicate that XPS Level 4 likely requires significant revisions in the SXR range, which may have downstream implications for the Earth ionosphere models that have used XPS Level 4 as their solar input.

A New Observation of the Quiet Sun Soft X-ray (0.5-5 keV) Spectrum

NASA Astrophysics Data System (ADS)

Caspi, Amir; Woods, Thomas N.; Stone, Jordan

2013-03-01

The solar corona is the brightest source of X-rays in the solar system, and the X-ray emission is highly variable with solar activity. While this is particularly true during solar flares, when emission can be enhanced by many orders of magnitude up to gamma-ray energies, even the so-called "quiet Sun" is bright in soft X-rays (SXRs), as the 1-2 MK ambient plasma of the corona emits significant thermal bremsstrahlung up to 5 keV. However, the actual solar SXR (0.5-5 keV) spectrum is not well known, particularly during quiet periods, as, with few exceptions, this energy range has not been systematically studied in many years. Previous observations include ultra-high-resolution but very narrow-band spectra from crystral spectrometers (e.g. Yohkoh/BCS), or integrated broadband irradiances from photometers (e.g. GOES/XRS, TIMED/XPS, etc.) that lack detailed spectral information. In recent years, broadband measurements with fair energy resolution ( 0.5-0.7 keV FWHM) were made by SphinX on CORONAS-Photon and XRS on MESSENGER, although they did not extend below 1 keV. We present observations of the quiet Sun SXR emission obtained using a new SXR spectrometer flown on the third SDO/EVE underflight calibration rocket (NASA 36.286). The commercial off-the-shelf Amptek X123 silicon drift detector, with an 8-micron Be window and custom aperture, measured the solar SXR emission from 0.5 to >10 keV with 0.15 keV FWHM resolution (though, due to hardware limitations, with only 0.12 keV binning) and 2-sec cadence over 5 minutes on 23 June 2012. Despite the rising solar cycle, activity on 23 June 2012 was abnormally low, with no visible active regions and GOES XRS emission near 2010 levels; we measured no solar counts above 4 keV during the observation period. We compare our X123 measurements with spectra and broadband irradiances from other instruments, including the SphinX observations during the deep solar minimum of 2009, and with upper limits of >3 keV quiet Sun emission determined from RHESSI. We discuss the possible implications for X-ray-producing physical processes in the quiescent, active-region-free corona. The X123 spectrum could potentially serve as a reference for 0.5-4 keV quiet Sun emission, to help improve solar spectral models such as CHIANTI and XPS Level 4. Our comparisons indicate that XPS Level 4 likely requires significant revisions in the SXR range, which may have downstream implications for the Earth ionosphere models that have used XPS Level 4 as their solar input.

Deep-sea bioluminescence blooms after dense water formation at the ocean surface.

PubMed

Tamburini, Christian; Canals, Miquel; Durrieu de Madron, Xavier; Houpert, Loïc; Lefèvre, Dominique; Martini, Séverine; D'Ortenzio, Fabrizio; Robert, Anne; Testor, Pierre; Aguilar, Juan Antonio; Samarai, Imen Al; Albert, Arnaud; André, Michel; Anghinolfi, Marco; Anton, Gisela; Anvar, Shebli; Ardid, Miguel; Jesus, Ana Carolina Assis; Astraatmadja, Tri L; Aubert, Jean-Jacques; Baret, Bruny; Basa, Stéphane; Bertin, Vincent; Biagi, Simone; Bigi, Armando; Bigongiari, Ciro; Bogazzi, Claudio; Bou-Cabo, Manuel; Bouhou, Boutayeb; Bouwhuis, Mieke C; Brunner, Jurgen; Busto, José; Camarena, Francisco; Capone, Antonio; Cârloganu, Christina; Carminati, Giada; Carr, John; Cecchini, Stefano; Charif, Ziad; Charvis, Philippe; Chiarusi, Tommaso; Circella, Marco; Coniglione, Rosa; Costantini, Heide; Coyle, Paschal; Curtil, Christian; Decowski, Patrick; Dekeyser, Ivan; Deschamps, Anne; Donzaud, Corinne; Dornic, Damien; Dorosti, Hasankiadeh Q; Drouhin, Doriane; Eberl, Thomas; Emanuele, Umberto; Ernenwein, Jean-Pierre; Escoffier, Stéphanie; Fermani, Paolo; Ferri, Marcelino; Flaminio, Vincenzo; Folger, Florian; Fritsch, Ulf; Fuda, Jean-Luc; Galatà, Salvatore; Gay, Pascal; Giacomelli, Giorgio; Giordano, Valentina; Gómez-González, Juan-Pablo; Graf, Kay; Guillard, Goulven; Halladjian, Garadeb; Hallewell, Gregory; van Haren, Hans; Hartman, Joris; Heijboer, Aart J; Hello, Yann; Hernández-Rey, Juan Jose; Herold, Bjoern; Hößl, Jurgen; Hsu, Ching-Cheng; de Jong, Marteen; Kadler, Matthias; Kalekin, Oleg; Kappes, Alexander; Katz, Uli; Kavatsyuk, Oksana; Kooijman, Paul; Kopper, Claudio; Kouchner, Antoine; Kreykenbohm, Ingo; Kulikovskiy, Vladimir; Lahmann, Robert; Lamare, Patrick; Larosa, Giuseppina; Lattuada, Dario; Lim, Gordon; Presti, Domenico Lo; Loehner, Herbert; Loucatos, Sotiris; Mangano, Salvatore; Marcelin, Michel; Margiotta, Annarita; Martinez-Mora, Juan Antonio; Meli, Athina; Montaruli, Teresa; Moscoso, Luciano; Motz, Holger; Neff, Max; Nezri, Emma Nuel; Palioselitis, Dimitris; Păvălaş, Gabriela E; Payet, Kevin; Payre, Patrice; Petrovic, Jelena; Piattelli, Paolo; Picot-Clemente, Nicolas; Popa, Vlad; Pradier, Thierry; Presani, Eleonora; Racca, Chantal; Reed, Corey; Riccobene, Giorgio; Richardt, Carsten; Richter, Roland; Rivière, Colas; Roensch, Kathrin; Rostovtsev, Andrei; Ruiz-Rivas, Joaquin; Rujoiu, Marius; Russo, Valerio G; Salesa, Francisco; Sánchez-Losa, Augustin; Sapienza, Piera; Schöck, Friederike; Schuller, Jean-Pierre; Schussler, Fabian; Shanidze, Rezo; Simeone, Francesco; Spies, Andreas; Spurio, Maurizio; Steijger, Jos J M; Stolarczyk, Thierry; Taiuti, Mauro G F; Toscano, Simona; Vallage, Bertrand; Van Elewyck, Véronique; Vannoni, Giulia; Vecchi, Manuela; Vernin, Pascal; Wijnker, Guus; Wilms, Jorn; de Wolf, Els; Yepes, Harold; Zaborov, Dmitry; De Dios Zornoza, Juan; Zúñiga, Juan

2013-01-01

The deep ocean is the largest and least known ecosystem on Earth. It hosts numerous pelagic organisms, most of which are able to emit light. Here we present a unique data set consisting of a 2.5-year long record of light emission by deep-sea pelagic organisms, measured from December 2007 to June 2010 at the ANTARES underwater neutrino telescope in the deep NW Mediterranean Sea, jointly with synchronous hydrological records. This is the longest continuous time-series of deep-sea bioluminescence ever recorded. Our record reveals several weeks long, seasonal bioluminescence blooms with light intensity up to two orders of magnitude higher than background values, which correlate to changes in the properties of deep waters. Such changes are triggered by the winter cooling and evaporation experienced by the upper ocean layer in the Gulf of Lion that leads to the formation and subsequent sinking of dense water through a process known as "open-sea convection". It episodically renews the deep water of the study area and conveys fresh organic matter that fuels the deep ecosystems. Luminous bacteria most likely are the main contributors to the observed deep-sea bioluminescence blooms. Our observations demonstrate a consistent and rapid connection between deep open-sea convection and bathypelagic biological activity, as expressed by bioluminescence. In a setting where dense water formation events are likely to decline under global warming scenarios enhancing ocean stratification, in situ observatories become essential as environmental sentinels for the monitoring and understanding of deep-sea ecosystem shifts.

Origin and roles of oxygen impurities in hexagonal boron nitride epilayers

NASA Astrophysics Data System (ADS)

Grenadier, S. J.; Maity, A.; Li, J.; Lin, J. Y.; Jiang, H. X.

2018-04-01

Photoluminescence emission spectroscopy and electrical transport measurements have been employed to study the origin and roles of oxygen impurities in hexagonal boron nitride (h-BN) epilayers grown on sapphire substrates. The temperature dependence of the electrical resistivity revealed the presence of a previously unnoticed impurity level of about 0.6 eV in h-BN epilayers grown at high temperatures. The results suggested that in addition to the common nitrogen vacancy (VN) shallow donors in h-BN, oxygen impurities diffused from sapphire substrates during high temperature growth also act as substitutional donors (ON). The presence of ON gives rise to an additional emission peak in the photoluminescence spectrum, corresponding to a donor-acceptor pair recombination involving the ON donor and the CN (carbon occupying nitrogen site) deep level acceptor. Moreover, due to the presence of ON donors, the majority charge carrier type changed to electrons in epilayers grown at high temperatures, in contrast to typical h-BN epilayers which naturally exhibit "p-type" character. The results provided a more coherent picture for common impurities/defects in h-BN as well as a better understanding of the growth mediated impurities in h-BN epilayers, which will be helpful for finding possible ways to further improve the quality and purity of this emerging material.

Potential restrictions for CO2 sequestration sites due to shale and tight gas production.

PubMed

Elliot, T R; Celia, M A

2012-04-03

Carbon capture and geological sequestration is the only available technology that both allows continued use of fossil fuels in the power sector and reduces significantly the associated CO(2) emissions. Geological sequestration requires a deep permeable geological formation into which captured CO(2)can be injected, and an overlying impermeable formation, called a caprock, that keeps the buoyant CO(2) within the injection formation. Shale formations typically have very low permeability and are considered to be good caprock formations. Production of natural gas from shale and other tight formations involves fracturing the shale with the explicit objective to greatly increase the permeability of the shale. As such, shale gas production is in direct conflict with the use of shale formations as a caprock barrier to CO(2) migration. We have examined the locations in the United States where deep saline aquifers, suitable for CO(2) sequestration, exist, as well as the locations of gas production from shale and other tight formations. While estimated sequestration capacity for CO(2) sequestration in deep saline aquifers is large, up to 80% of that capacity has areal overlap with potential shale-gas production regions and, therefore, could be adversely affected by shale and tight gas production. Analysis of stationary sources of CO(2) shows a similar effect: about two-thirds of the total emissions from these sources are located within 20 miles of a deep saline aquifer, but shale and tight gas production could affect up to 85% of these sources. These analyses indicate that colocation of deep saline aquifers with shale and tight gas production could significantly affect the sequestration capacity for CCS operations. This suggests that a more comprehensive management strategy for subsurface resource utilization should be developed.

Connecting Surface Emissions, Convective Uplifting, and Long-Range Transport of Carbon Monoxide in the Upper Troposphere: New Observations from the Aura Microwave Limb Sounder

NASA Technical Reports Server (NTRS)

Jiang, Jonathan H.; Livesey, Nathaniel J.; Su, Hui; Neary, Lori; McConnell, John C.; Richards, Nigel A. D.

2007-01-01

Two years of observations of upper tropospheric (UT) carbon monoxide (CO) from the Aura Microwave Limb Sounder are analyzed; in combination with the CO surface emission climatology and data from the NCEP analyses. It is shown that spatial distribution, temporal variation and long-range transport of UT CO are closely related to the surface emissions, deep-convection and horizontal winds. Over the Asian monsoon region, surface emission of CO peaks in boreal spring due to high biomass burning in addition to anthropogenic emission. However, the UT CO peaks in summer when convection is strongest and surface emission of CO is dominated by anthropogenic source. The long-range transport of CO from Southeast Asia across the Pacific to North America, which occurs most frequently during boreal summer, is thus a clear imprint of Asian anthropogenic pollution influencing global air quality.

Investigation of the Charge Balance in Green Phosphorescent Organic Light-Emitting Diodes by Controlling the Mixed Host Emission Layer.

PubMed

Lee, Jeonghyun; Choi, Pyungho; Kim, Minsoo; Lim, Kiwon; Hyeon, Younghwan; Kim, Soonkon; Koo, Kwangjun; Kim, Sangsoo; Choi, Byoungdeog

2018-09-01

In this paper, we investigated the use of a mixed host emission layer (MH-EML) in green phosphorescent organic light-emitting diodes (OLEDs). The hole transport type (p-type) material (4,4'-Bis(N-carbazolyl)-1,1'-biphenyl (CBP)) and electron transport type (N-type) material (2,2',2″-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi)) were mixed with different ratios. The electrons were easily injected through the lowest unoccupied molecular orbital (LUMO) of TPBi in the mixed host system. Also, holes were confined in the EML because of the deep highest occupied molecular orbital (HOMO) level of TPBi (6.7 eV). These results indicate that excitons were formed effectively and the recombination zone became wider under a high electric field in MH-EML devices. For these reasons, the lifetime of the MH-OLED device was 1.36 times higher than that of a single host emission layer (SH-EML) device and showed a reduction in Joule heating. Finally, the external quantum efficiency (EQE) roll-off ratio from 1 mA/cm2 to 100 mA/cm2 in the optimized device (30.46%) was 18.12%p lower than that of the SH-EML (48.58%).

Air Pollution Control Policies in China: A Retrospective and Prospects.

PubMed

Jin, Yana; Andersson, Henrik; Zhang, Shiqiu

2016-12-09

With China's significant role on pollution emissions and related health damage, deep and up-to-date understanding of China's air pollution policies is of worldwide relevance. Based on scientific evidence for the evolution of air pollution and the institutional background of environmental governance in China, we examine the development of air pollution control policies from the 1980s and onwards. We show that: (1) The early policies, until 2005, were ineffective at reducing emissions; (2) During 2006-2012, new instruments which interact with political incentives were introduced in the 11th Five-Year Plan, and the national goal of reducing total sulfur dioxide (SO₂) emissions by 10% was achieved. However, regional compound air pollution problems dominated by fine particulate matter (PM 2.5 ) and ground level ozone (O₃) emerged and worsened; (3) After the winter-long PM 2.5 episode in eastern China in 2013, air pollution control policies have been experiencing significant changes on multiple fronts. In this work we analyze the different policy changes, the drivers of changes and key factors influencing the effectiveness of policies in these three stages. Lessons derived from the policy evolution have implications for future studies, as well as further reforming the management scheme towards air quality and health risk oriented directions.

Developed and developing world responsibilities for historical climate change and CO2 mitigation.

PubMed

Wei, Ting; Yang, Shili; Moore, John C; Shi, Peijun; Cui, Xuefeng; Duan, Qingyun; Xu, Bing; Dai, Yongjiu; Yuan, Wenping; Wei, Xin; Yang, Zhipeng; Wen, Tijian; Teng, Fei; Gao, Yun; Chou, Jieming; Yan, Xiaodong; Wei, Zhigang; Guo, Yan; Jiang, Yundi; Gao, Xuejie; Wang, Kaicun; Zheng, Xiaogu; Ren, Fumin; Lv, Shihua; Yu, Yongqiang; Liu, Bin; Luo, Yong; Li, Weijing; Ji, Duoying; Feng, Jinming; Wu, Qizhong; Cheng, Huaqiong; He, Jiankun; Fu, Congbin; Ye, Duzheng; Xu, Guanhua; Dong, Wenjie

2012-08-07

At the United Nations Framework Convention on Climate Change Conference in Cancun, in November 2010, the Heads of State reached an agreement on the aim of limiting the global temperature rise to 2 °C relative to preindustrial levels. They recognized that long-term future warming is primarily constrained by cumulative anthropogenic greenhouse gas emissions, that deep cuts in global emissions are required, and that action based on equity must be taken to meet this objective. However, negotiations on emission reduction among countries are increasingly fraught with difficulty, partly because of arguments about the responsibility for the ongoing temperature rise. Simulations with two earth-system models (NCAR/CESM and BNU-ESM) demonstrate that developed countries had contributed about 60-80%, developing countries about 20-40%, to the global temperature rise, upper ocean warming, and sea-ice reduction by 2005. Enacting pledges made at Cancun with continuation to 2100 leads to a reduction in global temperature rise relative to business as usual with a 1/3-2/3 (CESM 33-67%, BNU-ESM 35-65%) contribution from developed and developing countries, respectively. To prevent a temperature rise by 2 °C or more in 2100, it is necessary to fill the gap with more ambitious mitigation efforts.

Air Pollution Control Policies in China: A Retrospective and Prospects

PubMed Central

Jin, Yana; Andersson, Henrik; Zhang, Shiqiu

2016-01-01

With China’s significant role on pollution emissions and related health damage, deep and up-to-date understanding of China’s air pollution policies is of worldwide relevance. Based on scientific evidence for the evolution of air pollution and the institutional background of environmental governance in China, we examine the development of air pollution control policies from the 1980s and onwards. We show that: (1) The early policies, until 2005, were ineffective at reducing emissions; (2) During 2006–2012, new instruments which interact with political incentives were introduced in the 11th Five-Year Plan, and the national goal of reducing total sulfur dioxide (SO2) emissions by 10% was achieved. However, regional compound air pollution problems dominated by fine particulate matter (PM2.5) and ground level ozone (O3) emerged and worsened; (3) After the winter-long PM2.5 episode in eastern China in 2013, air pollution control policies have been experiencing significant changes on multiple fronts. In this work we analyze the different policy changes, the drivers of changes and key factors influencing the effectiveness of policies in these three stages. Lessons derived from the policy evolution have implications for future studies, as well as further reforming the management scheme towards air quality and health risk oriented directions. PMID:27941665

Deep Chandra Observations of ESO 428-G014. II. Spectral Properties and Morphology of the Large-scale Extended X-Ray Emission

NASA Astrophysics Data System (ADS)

Fabbiano, G.; Paggi, A.; Karovska, M.; Elvis, M.; Maksym, W. P.; Risaliti, G.; Wang, Junfeng

2018-03-01

We present a deep Chandra spectral and spatial study of the kpc-scale diffuse X-ray emission of the Compton-thick (CT) active galactic nucleus (AGN) ESO 428-G014. The entire spectrum is best fit with composite photoionization + thermal models. The diffuse emission is more extended at lower energies (<3 keV). The smaller extent of the hard continuum and Fe Kα profiles implies that the optically thicker clouds responsible for this scattering may be relatively more prevalent closer to the nucleus. These clouds must not prevent soft ionizing X-rays from the AGN escaping to larger radii, in order to have photoionized ISM at larger radii. This suggests that at smaller radii, there may be a larger population of molecular clouds to scatter the hard X-rays, as in the Milky Way. The diffuse emission is also significantly extended in the cross-cone direction, where the AGN emission would be mostly obscured by the torus in the standard AGN model. Our results suggest that the transmission of the obscuring region in the cross-cone direction is ∼10% of that in the cone direction. In the 0.3–1.5 keV band, the ratio of cross-cone to cone photons increases to ∼84%, suggesting an additional soft diffuse emission component disjoint from the AGN. This could be due to hot ISM trapped in the potential of the galaxy. The luminosity of this component, ∼5 × 1038 erg s‑1, is roughly consistent with the thermal component suggested by the spectral fits in the 170–900 pc annulus.

Deep Chandra observations of HCG 16. I. Active nuclei, star formation, and galactic winds

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

O'Sullivan, E.; Zezas, A.; Vrtilek, J. M.

2014-10-01

We present new, deep Chandra X-ray and Giant Metrewave Radio Telescope 610 MHz observations of the spiral-galaxy-rich compact group HCG 16, which we use to examine nuclear activity, star formation, and high-luminosity X-ray binary populations in the major galaxies. We confirm the presence of obscured active nuclei in NGC 833 and NGC 835, and identify a previously unrecognized nuclear source in NGC 838. All three nuclei are variable on timescales of months to years, and for NGC 833 and NGC 835 this is most likely caused by changes in accretion rate. The deep Chandra observations allow us to detect formore » the first time an Fe Kα emission line in the spectrum of the Seyfert 2 nucleus of NGC 835. We find that NGC 838 and NGC 839 are both starburst-dominated systems, with only weak nuclear activity, in agreement with previous optical studies. We estimate the star formation rates in the two galaxies from their X-ray and radio emission, and compare these results with estimates from the infrared and ultraviolet bands to confirm that star formation in both galaxies is probably declining after galaxy-wide starbursts were triggered ∼400-500 Myr ago. We examine the physical properties of their galactic superwinds, and find that both have temperatures of ∼0.8 keV. We also examine the X-ray and radio properties of NGC 848, the fifth largest galaxy in the group, and show that it is dominated by emission from its starburst.« less

Deep Emission-Line Imaging of Local Galactic Winds with NEWFIRM: Part II.

NASA Astrophysics Data System (ADS)

Veilleux, Sylvain; Trippe, Margaret; Swaters, Rob; Rupke, David; McCormick, Alex

2010-08-01

Galactic winds are the primary mechanism by which energy and metals are recycled in galaxies and deposited into the IGM. New observations are revealing the ubiquity of this process, particularly at high redshift. Measurements have shown that winds contain cool (molecular/neutral), warm (partly ionized), and hot (fully ionized) gases. Though most of the wind mass is likely contained in the dusty molecular gas, very little is known about this component. However, our recent observations of M 82 with NEWFIRM on the Mayall 4-m show that H_2 emission can be used as a sensitive tracer of the cool molecular wind component. We propose to use NEWFIRM to study the NIR emission- line properties of a small but representative set of local wind galaxies. Deep images of these objects will be obtained at H_2 2.122 (micron) and [Fe II] 1.644 (micron) and combined with existing optical emission-line maps to (1) constrain the importance of molecular gas in the energetics of these winds and (2) determine the nature of the interaction between the central energy injection zone and the wind material. 5 nights were allocated for this program in 10B; we now request to observe the rest of the sample. These data will complement an approved Spitzer program to constrain the hot dust content of these winds, and likely become part of A. McCormick's PhD thesis.

SPECTROSCOPIC CONFIRMATION OF FAINT LYMAN BREAK GALAXIES NEAR REDSHIFT FIVE IN THE HUBBLE ULTRA DEEP FIELD

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

Rhoads, James E.; Malhotra, Sangeeta; Cohen, Seth

We present the faintest spectroscopically confirmed sample of z {approx} 5 Lyman break galaxies (LBGs) to date. The sample is based on slitless grism spectra of the Hubble Ultra Deep Field region from the Grism ACS Program for Extragalactic Science (GRAPES) and Probing Evolution and Reionization Spectroscopically (PEARS) projects, using the G800L grism on the Hubble Space Telescope Advanced Camera for Surveys. We report here confirmations of 39 galaxies, preselected as candidate LBGs using photometric selection criteria. We compare a 'traditional' V-dropout selection, based on the work of Giavalisco et al., to a more liberal one (with V - imore » > 0.9), and find that the traditional criteria are about 64% complete and 81% reliable. We also study the Ly{alpha} emission properties of our sample. We find that Ly{alpha} emission is detected in {approx}1/4 of the sample, and that the liberal V-dropout color selection includes {approx}55% of previously published line-selected Ly{alpha} sources. Finally, we examine our stacked two-dimensional spectra. We demonstrate that strong, spatially extended ({approx}1'') Ly{alpha} emission is not a generic property of these LBGs, but that a modest extension of the Ly{alpha} photosphere (compared to the starlight) may be present in those galaxies with prominent Ly{alpha} emission.« less

Techniques to minimize adjacent band emissions from Earth Exploration Satellites to protect the Space Research (Category B) Earth Stations in the 8400-8450 MHz band

NASA Technical Reports Server (NTRS)

Wang, Charles C.; Sue, Miles K.; Manshadi, Farzin

2004-01-01

The Earth Exploration Satellites operating in the 8025-8400 MHz band can have strong adjacent band emissions on the8400-8450 MHz band which is allocated for Space Research (Category-B). The unwanted emission may exceed the protection criterion establish by the ITU-R for the protection of the Space Research (Category B) earth stations, i.e., deep-space earth stations. An SFCG Action Item (SF 23/14) was created during the 23rd SFCG meeting to explore technical and operational techniques to reduce the adjacent band emissions. In response to this action item, a study was conducted and results are presented in this document.

Commander’s Guide Renewable Energy

DTIC Science & Technology

2011-08-01

water deep underground. The most common way of capturing the energy from geothermal sources is to tap into naturally occurring hydrothermal ...Emissions: smoke and condensation plume impacts on atmospheric opacity (visual and other spectra), odors, noise, and boiler ash. Commanders

A 16 deg2 survey of emission-line galaxies at z < 1.5 in HSC-SSP Public Data Release 1

NASA Astrophysics Data System (ADS)

Hayashi, Masao; Tanaka, Masayuki; Shimakawa, Rhythm; Furusawa, Hisanori; Momose, Rieko; Koyama, Yusei; Silverman, John D.; Kodama, Tadayuki; Komiyama, Yutaka; Leauthaud, Alexie; Lin, Yen-Ting; Miyazaki, Satoshi; Nagao, Tohru; Nishizawa, Atsushi J.; Ouchi, Masami; Shibuya, Takatoshi; Tadaki, Ken-ichi; Yabe, Kiyoto

2018-01-01

We present initial results from the Subaru Strategic Program (SSP) with Hyper Suprime-Cam (HSC) on a comprehensive survey of emission-line galaxies at z < 1.5 based on narrowband imaging. The first Public Data Release provides us with data from two narrowband filters, specifically NB816 and NB921 over 5.7 deg2 and 16.2 deg2 respectively. The 5 σ limiting magnitudes are 25.2 mag (UltraDeep layer, 1.4 deg2) and 24.8 mag (Deep layer, 4.3 deg2) for NB816, and 25.1 mag (UltraDeep, 2.9 deg2) and 24.6-24.8 mag (Deep, 13.3 deg2) for NB921. The wide-field imaging allows us to construct unprecedentedly large samples of 8054 H α emitters at z ≈ 0.25 and 0.40, 8656 [O III] emitters at z ≈ 0.63 and 0.84, and 16877 [O II] emitters at z ≈ 1.19 and 1.47. We map the cosmic web on scales out to about 50 comoving Mpc that includes galaxy clusters, identified by red sequence galaxies, located at the intersection of filamentary structures of star-forming galaxies. The luminosity functions of emission-line galaxies are measured with precision and are consistent with published studies. The wide field coverage of the data enables us to measure the luminosity functions up to brighter luminosities than previous studies. The comparison of the luminosity functions between the different HSC-SSP fields suggests that a survey volume of >5 × 105 Mpc3 is essential to overcome cosmic variance. Since the current data have not reached the full depth expected for the HSC-SSP, the color cut in i - NB816 or z - NB921 induces a bias towards star-forming galaxies with large equivalent widths, primarily seen in the stellar mass functions for the H α emitters at z ≈ 0.25-0.40. Even so, the emission-line galaxies clearly cover a wide range of luminosity, stellar mass, and environment, thus demonstrating the usefulness of the narrowband data from the HSC-SSP for investigating star-forming galaxies at z < 1.5.

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

NASA Astrophysics Data System (ADS)

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

2018-01-01

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

Detection prospects for GeV neutrinos from collisionally heated gamma-ray bursts with IceCube/DeepCore.

PubMed

Bartos, I; Beloborodov, A M; Hurley, K; Márka, S

2013-06-14

Jet reheating via nuclear collisions has recently been proposed as the main mechanism for gamma-ray burst (GRB) emission. In addition to producing the observed gamma rays, collisional heating must generate 10-100 GeV neutrinos, implying a close relation between the neutrino and gamma-ray luminosities. We exploit this theoretical relation to make predictions for possible GRB detections by IceCube + DeepCore. To estimate the expected neutrino signal, we use the largest sample of bursts observed by the Burst and Transient Source Experiment in 1991-2000. GRB neutrinos could have been detected if IceCube + DeepCore operated at that time. Detection of 10-100 GeV neutrinos would have significant implications, shedding light on the composition of GRB jets and their Lorentz factors. This could be an important target in designing future upgrades of the IceCube + DeepCore observatory.

ROSAT Pointed Observations of Cool Magnetic White Dwarfs

NASA Technical Reports Server (NTRS)

Musielak, Z. E.; Porter, J. G.; Davis, J. M.

1995-01-01

Observational evidence for the existence of a chromosphere on the cool magnetic white dwarf GD 356 has been reported. In addition, there has been theoretical speculations that cool magnetic white dwarfs may be sources of coronal X-ray emission. This emission, if it exists, would be distinct from the two types of X-ray emission (deep photospheric and shocked wind) that have already been observed from hot white dwarfs. We have used the PSPC instrument on ROSAT to observe three of the most prominent DA white dwarf candidates for coronal X-ray emission: GD 356, KUV 2316+123, and GD 90. The data show no significant emission for these stars. The derived upper limits for the X-ray luminosities provide constraints for a revision of current theories of the generation of nonradiative energy in white dwarfs.

Effects of the impurity-host interactions on the nonradiative processes in ZnS:Cr

NASA Astrophysics Data System (ADS)

Tablero, C.

2010-11-01

There is a great deal of controversy about whether the behavior of an intermediate band in the gap of semiconductors is similar or not to the deep-gap levels. It can have significant consequences, for example, on the nonradiative recombination. In order to analyze the behavior of an intermediate band, we have considered the effect of the inward and outward displacements corresponding to breathing and longitudinal modes of Cr-doped ZnS and on the charge density for different processes involved in the nonradiative recombination using first-principles. This metal-doped zinc chalcogenide has a partially filled band within the host semiconductor gap. In contrast to the properties exhibited by deep-gap levels in other systems, we find small variations in the equilibrium configurations, forces, and electronic density around the Cr when the nonradiative recombination mechanisms modify the intermediate band charge. The charge density around the impurity is equilibrated in response to the perturbations in the equilibrium nuclear configuration and the charge of the intermediate band. The equilibration follows a Le Chatelier principle through the modification of the contribution from the impurity to the intermediate band and to the valence band. The intermediate band introduced by Cr in ZnS for the concentrations analyzed makes the electronic capture difficult and later multiphonon emission in the charge-transfer processes, in accordance with experimental results.

Sea-level and deep-sea-temperature variability over the past 5.3 million years.

PubMed

Rohling, E J; Foster, G L; Grant, K M; Marino, G; Roberts, A P; Tamisiea, M E; Williams, F

2014-04-24

Ice volume (and hence sea level) and deep-sea temperature are key measures of global climate change. Sea level has been documented using several independent methods over the past 0.5 million years (Myr). Older periods, however, lack such independent validation; all existing records are related to deep-sea oxygen isotope (δ(18)O) data that are influenced by processes unrelated to sea level. For deep-sea temperature, only one continuous high-resolution (Mg/Ca-based) record exists, with related sea-level estimates, spanning the past 1.5 Myr. Here we present a novel sea-level reconstruction, with associated estimates of deep-sea temperature, which independently validates the previous 0-1.5 Myr reconstruction and extends it back to 5.3 Myr ago. We find that deep-sea temperature and sea level generally decreased through time, but distinctly out of synchrony, which is remarkable given the importance of ice-albedo feedbacks on the radiative forcing of climate. In particular, we observe a large temporal offset during the onset of Plio-Pleistocene ice ages, between a marked cooling step at 2.73 Myr ago and the first major glaciation at 2.15 Myr ago. Last, we tentatively infer that ice sheets may have grown largest during glacials with more modest reductions in deep-sea temperature.

Modification of optical and electrical properties of zinc oxide-coated porous silicon nanostructures induced by swift heavy ion

PubMed Central

2012-01-01

Morphological and optical characteristics of radio frequency-sputtered zinc aluminum oxide over porous silicon (PS) substrates were studied before and after irradiating composite films with 130 MeV of nickel ions at different fluences varying from 1 × 1012 to 3 × 1013 ions/cm2. The effect of irradiation on the composite structure was investigated by scanning electron microscopy, X-ray diffraction (XRD), photoluminescence (PL), and cathodoluminescence spectroscopy. Current–voltage characteristics of ZnO-PS heterojunctions were also measured. As compared to the granular crystallites of zinc oxide layer, Al-doped zinc oxide (ZnO) layer showed a flaky structure. The PL spectrum of the pristine composite structure consists of the emission from the ZnO layer as well as the near-infrared emission from the PS substrate. Due to an increase in the number of deep-level defects, possibly oxygen vacancies after swift ion irradiation, PS-Al-doped ZnO nanocomposites formed with high-porosity PS are shown to demonstrate a broadening in the PL emission band, leading to the white light emission. The broadening effect is found to increase with an increase in the ion fluence and porosity. XRD study revealed the relative resistance of the film against the irradiation, i.e., the irradiation of the structure failed to completely amorphize the structure, suggesting its possible application in optoelectronics and sensing applications under harsh radiation conditions. PMID:22748164

Multi-angle ZnO microstructures grown on Ag nanorods array for plasmon-enhanced near-UV-blue light emitter

NASA Astrophysics Data System (ADS)

Pal, Anil Kumar; Bharathi Mohan, D.

2017-10-01

Metal enhanced ultraviolet light emission has been explored in ZnO/Ag hybrid structures prepared by hydrothermal growth of multi-angled ZnO nanorods on slanted Ag nanorods array fabricated by the thermal evaporation technique. Slanted Ag nanorods are realized to be the stacking of non-spherical Ag nanoparticles, resulting in asymmetric surface plasmon resonance spectra. The surface roughness of Ag nanorod array films significantly influences the growth mechanism of ZnO nanorods, leading to the formation of multi-angled ZnO microflowers. ZnO/Ag hybrid structures facilitate the interfacial charge transfer from Ag to ZnO with the realization of negative shift in binding energy of Ag 3d orbitals by ˜0.8 eV. These high quality ZnO nanorods in ZnO/Ag hybrid nanostructures exhibit strong ultraviolet emission in the 383-396 nm region without broad deep level emission, which can be explained by a suitable band diagram. The metal enhanced photoluminescence is witnessed mainly due to interfacial charge transfer with its dependence on surface roughness of bottom layer Ag nanorods, number density of ZnO nanorods and diversity in the interfacial area between Ag and ZnO nanorods. The existence of strong ultraviolet light with minor blue light emission and appearance of CIE shade in strong violet-blue region by ZnO/Ag hybrid structures depict exciting possibilities towards near UV-blue light emitting devices.

Multi-angle ZnO microstructures grown on Ag nanorods array for plasmon-enhanced near-UV-blue light emitter.

PubMed

Pal, Anil Kumar; Mohan, D Bharathi

2017-10-13

Metal enhanced ultraviolet light emission has been explored in ZnO/Ag hybrid structures prepared by hydrothermal growth of multi-angled ZnO nanorods on slanted Ag nanorods array fabricated by the thermal evaporation technique. Slanted Ag nanorods are realized to be the stacking of non-spherical Ag nanoparticles, resulting in asymmetric surface plasmon resonance spectra. The surface roughness of Ag nanorod array films significantly influences the growth mechanism of ZnO nanorods, leading to the formation of multi-angled ZnO microflowers. ZnO/Ag hybrid structures facilitate the interfacial charge transfer from Ag to ZnO with the realization of negative shift in binding energy of Ag 3d orbitals by ∼0.8 eV. These high quality ZnO nanorods in ZnO/Ag hybrid nanostructures exhibit strong ultraviolet emission in the 383-396 nm region without broad deep level emission, which can be explained by a suitable band diagram. The metal enhanced photoluminescence is witnessed mainly due to interfacial charge transfer with its dependence on surface roughness of bottom layer Ag nanorods, number density of ZnO nanorods and diversity in the interfacial area between Ag and ZnO nanorods. The existence of strong ultraviolet light with minor blue light emission and appearance of CIE shade in strong violet-blue region by ZnO/Ag hybrid structures depict exciting possibilities towards near UV-blue light emitting devices.

Broad visible emission from GaN nanowires grown on n-Si (1 1 1) substrate by PVD for solar cell application

NASA Astrophysics Data System (ADS)

Saron, K. M. A.; Hashim, M. R.

2013-04-01

Nanostructured gallium nitrides (GaNs) were grown on a catalyst-free Si (1 1 1) substrates using physical vapor deposition via thermal evaporation of GaN powder at 1150 °C in the absence of NH3 gas for different deposition time. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometer (EDX) results indicated that the growth of GaN nanostructure varies with deposition time. Both X-ray diffraction (XRD) patterns and Raman spectra reveals a hexagonal GaN with wurtzite structure. Photoluminescence (PL) showed that the UV emission was suppressed, and the visible band emission was enhanced with increasing deposition time. Enhancement of visible band emission from the GaN NWs is due to the increasement of deep level states, which was resulted from growth process. Current-voltage (IV) characteristics of GaN/Si heterostructure were measured and good rectifying behavior was observed for this photodiode (PD). The forward current under illumination was almost three times than that in the dark current at +5 V. Responsivity of the photodetector was 10.5 A/W at range from 350 nm to 500 nm, which rapidly increased to 13.6 A/W at 700 nm. We found that the fabricated photodiode PD has an infra-red (IR) photoresponse behavior. The analysis of optical and electrical properties indications that the grown GaN in the absent of NH3 is a promising optical material and has potential applications in photo voltage solar cell.

Studies on annealed ZnO:V thin films deposited by nebulised spray pyrolysis method

NASA Astrophysics Data System (ADS)

Malini, D. Rachel

2018-04-01

Structural, optical and photoluminescence properties of annealed ZnO:V thin films deposited by nebulized spray pyrolysis technique by varying vanadium concentration are studied. Thickness of thin films varies from 1.52µm to 7.78µm. V2O5, VO2 and ZnO peaks are observed in XRD patterns deposited with high vanadium concentration and the intensity of peaks corresponding to ZnO decreases in those samples. Morphological properties were studied by analysing SEM images and annealed thin films deposited at ZnO:V = 50:50 possess dumb bell shape grains. Emission peaks corresponding to both Augur transition and deep level transition are observed in the PL spectra of the samples.

The development of a new database of gas emissions: MAGA, a collaborative web environment for collecting data

NASA Astrophysics Data System (ADS)

Cardellini, C.; Chiodini, G.; Frigeri, A.; Bagnato, E.; Aiuppa, A.; McCormick, B.

2013-12-01

The data on volcanic and non-volcanic gas emissions available online are, as today, incomplete and most importantly, fragmentary. Hence, there is need for common frameworks to aggregate available data, in order to characterize and quantify the phenomena at various spatial and temporal scales. Building on the Googas experience we are now extending its capability, particularly on the user side, by developing a new web environment for collecting and publishing data. We have started to create a new and detailed web database (MAGA: MApping GAs emissions) for the deep carbon degassing in the Mediterranean area. This project is part of the Deep Earth Carbon Degassing (DECADE) research initiative, lunched in 2012 by the Deep Carbon Observatory (DCO) to improve the global budget of endogenous carbon from volcanoes. MAGA database is planned to complement and integrate the work in progress within DECADE in developing CARD (Carbon Degassing) database. MAGA database will allow researchers to insert data interactively and dynamically into a spatially referred relational database management system, as well as to extract data. MAGA kicked-off with the database set up and a complete literature survey on publications on volcanic gas fluxes, by including data on active craters degassing, diffuse soil degassing and fumaroles both from dormant closed-conduit volcanoes (e.g., Vulcano, Phlegrean Fields, Santorini, Nysiros, Teide, etc.) and open-vent volcanoes (e.g., Etna, Stromboli, etc.) in the Mediterranean area and Azores. For each geo-located gas emission site, the database holds images and description of the site and of the emission type (e.g., diffuse emission, plume, fumarole, etc.), gas chemical-isotopic composition (when available), gas temperature and gases fluxes magnitude. Gas sampling, analysis and flux measurement methods are also reported together with references and contacts to researchers expert of the site. Data can be accessed on the network from a web interface or as a data-driven web service, where software clients can request data directly from the database. This way Geographical Information Systems (GIS) and Virtual Globes (e.g., Google Earth) can easily access the database, and data can be exchanged with other database. In details the database now includes: i) more than 1000 flux data about volcanic plume degassing from Etna (4 summit craters and bulk degassing) and Stromboli volcanoes, with time averaged CO2 fluxes of ~ 18000 and 766 t/d, respectively; ii) data from ~ 30 sites of diffuse soil degassing from Napoletan volcanoes, Azores, Canary, Etna, Stromboli, and Vulcano Island, with a wide range of CO2 fluxes (from les than 1 to 1500 t/d) and iii) several data on fumarolic emissions (~ 7 sites) with CO2 fluxes up to 1340 t/day (i.e., Stromboli). When available, time series of compositional data have been archived in the database (e.g., for Campi Flegrei fumaroles). We believe MAGA data-base is an important starting point to develop a large scale, expandable data-base aimed to excite, inspire, and encourage participation among researchers. In addition, the possibility to archive location and qualitative information for gas emission/sites not yet investigated, could stimulate the scientific community for future researches and will provide an indication on the current uncertainty on deep carbon fluxes global estimates.

Calculated emission rates for barium releases in space

NASA Technical Reports Server (NTRS)

Stenbaek-Nielsen, H. C.

1989-01-01

The optical emissions from barium releases in space are caused by resonance and fluorescent scattering of sunlight. Emission rates for the dominant ion and neutral lines are calculated assuming the release to be optically thin and the barium to be in radiative equilibrium with the solar radiation. The solar spectrum has deep Fraunhofer absorption lines at the primary barium ion resonances. A velocity component toward or away from the sun will Doppler shift the emission lines relative to the absorption lines and the emission rates will increase many-fold over the rest value. The Doppler brightening is important in shaped charge or satellite releases where the barium is injected at high velocities. Emission rates as a function of velocity are calculated for the 4554, 4934, 5854, 6142 and 6497 A ion emission lines and the dominant neutral line at 5535 A. Results are presented for injection parallel to the ambient magnetic field, B, and for injection at an angle to B.

Achieving deep-red-to-near-infrared emissions in Sn-doped Cu-In-S/ZnS quantum dots for red-enhanced white LEDs and near-infrared LEDs.

PubMed

Chen, Jixin; Li, Ye; Wang, Le; Zhou, Tianliang; Xie, Rong-Jun

2018-05-16

Semiconductor quantum dots (QDs) are promising luminescent materials for use in lighting, display and bio-imaging, and the color tuning is a necessity for such applications. In this work, we report tunable colors and deep-red or near infrared (NIR) emissions in Cu-In-S and Cu-In-S/ZnS QDs by incorporating Sn. These QDs (with a size of 5 nm) with varying Sn concentrations and/or Cu/In ratios were synthesized by a non-injection method, and characterized by a variety of analytical techniques (i.e., XRD, TEM, XPS, absorption, photoluminescence, decay time, etc.). The Cu-Sn-In-S and Cu-Sn-In-S/ZnS QDs with Cu/In = 1/2 show the emission maximum in the ranges of 701-894 nm and 628-785 nm, respectively. The red-shift in emission is ascribed to the decrease of the band gap with the Sn doping. The highest quantum yield of 75% is achieved in Cu-Sn-In-S/ZnS with 0.1 mmol Sn and Cu/In = 1/2. Both the white and NIR LEDs were fabricated by using Cu-Sn-In-S/ZnS QDs and a 365 nm LED chip. The white LED exhibits superhigh color rendering indices of Ra = 97.2 and R9 = 91 and a warm color temperature of 2700 K. And the NIR LED shows an interesting broadband near-infrared emission centered at 741 nm, allowing for applications in optical communication, sensing and medical devices.

A search for radio emission from Galactic supersoft X-ray sources

NASA Astrophysics Data System (ADS)

Ogley, R. N.; Chaty, S.; Crocker, M.; Eyres, S. P. S.; Kenworthy, M. A.; Richards, A. M. S.; Rodríguez, L. F.; Stirling, A. M.

2002-03-01

We have made a deep search for radio emission from all the northern hemisphere supersoft X-ray sources using the Very Large Array (VLA) and multi-element radio-linked interferometer network (MERLIN) telescopes, at 5 and 8.4GHz. Three previously undetected sources, T Pyx, V1974 Cygni and RX J0019.8+2156, were imaged in quiescence using the VLA in order to search for any persistent emission. No radio emission was detected in any of the VLA fields down to a typical 1σ rms noise of 20μJybeam-1, however, 17 new point sources were detected in the fields with 5-GHz fluxes between 100 and 1500μJy, giving an average 100-μJy source density of ~200deg-2, comparable to what was found in the MERLIN Hubble Deep Field survey. The persistent source AG Draconis was observed by MERLIN to provide a confirmation of previous VLA observations and to investigate the source at a higher resolution. The core is resolved at the milliarcsec scale into two components that have a combined flux of ~1mJy. It is possible that we are detecting nebulosity, which is becoming resolved out by the higher MERLIN resolution. We have investigated possible causes of radio emission from a wind environment, both directly from the secondary star, and also consequently, of the high X-ray luminosity from the white dwarf. There is an order of magnitude discrepancy between observed and modelled values that can be explained by the uncertainty in fundamental quantities within these systems.

Investigating the TeV Morphology of MGRO J1908+06 with VERITAS

NASA Astrophysics Data System (ADS)

Aliu, E.; Archambault, S.; Aune, T.; Behera, B.; Beilicke, M.; Benbow, W.; Berger, K.; Bird, R.; Buckley, J. H.; Bugaev, V.; Cardenzana, J. V.; Cerruti, M.; Chen, X.; Ciupik, L.; Collins-Hughes, E.; Connolly, M. P.; Cui, W.; Dumm, J.; Dwarkadas, V. V.; Errando, M.; Falcone, A.; Federici, S.; Feng, Q.; Finley, J. P.; Fleischhack, H.; Fortin, P.; Fortson, L.; Furniss, A.; Galante, N.; Gall, D.; Gillanders, G. H.; Griffin, S.; Griffiths, S. T.; Grube, J.; Gyuk, G.; Hanna, D.; Holder, J.; Hughes, G.; Humensky, T. B.; Kaaret, P.; Kertzman, M.; Khassen, Y.; Kieda, D.; Krennrich, F.; Kumar, S.; Lang, M. J.; Madhavan, A. S.; Maier, G.; McCann, A. J.; Meagher, K.; Millis, J.; Moriarty, P.; Mukherjee, R.; Nieto, D.; O'Faoláin de Bhróithe, A.; Ong, R. A.; Otte, A. N.; Pandel, D.; Park, N.; Pohl, M.; Popkow, A.; Prokoph, H.; Quinn, J.; Ragan, K.; Rajotte, J.; Ratliff, G.; Reyes, L. C.; Reynolds, P. T.; Richards, G. T.; Roache, E.; Rousselle, J.; Sembroski, G. H.; Shahinyan, K.; Sheidaei, F.; Smith, A. W.; Staszak, D.; Telezhinsky, I.; Tsurusaki, K.; Tucci, J. V.; Tyler, J.; Varlotta, A.; Vassiliev, V. V.; Vincent, S.; Wakely, S. P.; Ward, J. E.; Weinstein, A.; Welsing, R.; Wilhelm, A.

2014-06-01

We report on deep observations of the extended TeV gamma-ray source MGRO J1908+06 made with the VERITAS very high energy gamma-ray observatory. Previously, the TeV emission has been attributed to the pulsar wind nebula (PWN) of the Fermi-LAT pulsar PSR J1907+0602. We detect MGRO J1908+06 at a significance level of 14 standard deviations (14σ) and measure a photon index of 2.20 ± 0.10stat ± 0.20sys. The TeV emission is extended, covering the region near PSR J1907+0602 and also extending toward SNR G40.5-0.5. When fitted with a two-dimensional Gaussian, the intrinsic extension has a standard deviation of σsrc = 0.°44 ± 0.°02. In contrast to other TeV PWNe of similar age in which the TeV spectrum softens with distance from the pulsar, the TeV spectrum measured near the pulsar location is consistent with that measured at a position near the rim of G40.5-0.5, 0.°33 away.

Estimation of Crack Initiation and Propagation Thresholds of Confined Brittle Coal Specimens Based on Energy Dissipation Theory

NASA Astrophysics Data System (ADS)

Ning, Jianguo; Wang, Jun; Jiang, Jinquan; Hu, Shanchao; Jiang, Lishuai; Liu, Xuesheng

2018-01-01

A new energy-dissipation method to identify crack initiation and propagation thresholds is introduced. Conventional and cyclic loading-unloading triaxial compression tests and acoustic emission experiments were performed for coal specimens from a 980-m deep mine with different confining pressures of 10, 15, 20, 25, 30, and 35 MPa. Stress-strain relations, acoustic emission patterns, and energy evolution characteristics obtained during the triaxial compression tests were analyzed. The majority of the input energy stored in the coal specimens took the form of elastic strain energy. After the elastic-deformation stage, part of the input energy was consumed by stable crack propagation. However, with an increase in stress levels, unstable crack propagation commenced, and the energy dissipation and coal damage were accelerated. The variation in the pre-peak energy-dissipation ratio was consistent with the coal damage. This new method demonstrates that the crack initiation threshold was proportional to the peak stress ( σ p) for ratios that ranged from 0.4351 to 0.4753 σ p, and the crack damage threshold ranged from 0.8087 to 0.8677 σ p.

Hierarchical feature representation and multimodal fusion with deep learning for AD/MCI diagnosis.

PubMed

Suk, Heung-Il; Lee, Seong-Whan; Shen, Dinggang

2014-11-01

For the last decade, it has been shown that neuroimaging can be a potential tool for the diagnosis of Alzheimer's Disease (AD) and its prodromal stage, Mild Cognitive Impairment (MCI), and also fusion of different modalities can further provide the complementary information to enhance diagnostic accuracy. Here, we focus on the problems of both feature representation and fusion of multimodal information from Magnetic Resonance Imaging (MRI) and Positron Emission Tomography (PET). To our best knowledge, the previous methods in the literature mostly used hand-crafted features such as cortical thickness, gray matter densities from MRI, or voxel intensities from PET, and then combined these multimodal features by simply concatenating into a long vector or transforming into a higher-dimensional kernel space. In this paper, we propose a novel method for a high-level latent and shared feature representation from neuroimaging modalities via deep learning. Specifically, we use Deep Boltzmann Machine (DBM)(2), a deep network with a restricted Boltzmann machine as a building block, to find a latent hierarchical feature representation from a 3D patch, and then devise a systematic method for a joint feature representation from the paired patches of MRI and PET with a multimodal DBM. To validate the effectiveness of the proposed method, we performed experiments on ADNI dataset and compared with the state-of-the-art methods. In three binary classification problems of AD vs. healthy Normal Control (NC), MCI vs. NC, and MCI converter vs. MCI non-converter, we obtained the maximal accuracies of 95.35%, 85.67%, and 74.58%, respectively, outperforming the competing methods. By visual inspection of the trained model, we observed that the proposed method could hierarchically discover the complex latent patterns inherent in both MRI and PET. Copyright © 2014 Elsevier Inc. All rights reserved.

Hierarchical Feature Representation and Multimodal Fusion with Deep Learning for AD/MCI Diagnosis

PubMed Central

Suk, Heung-Il; Lee, Seong-Whan; Shen, Dinggang

2014-01-01

For the last decade, it has been shown that neuroimaging can be a potential tool for the diagnosis of Alzheimer’s Disease (AD) and its prodromal stage, Mild Cognitive Impairment (MCI), and also fusion of different modalities can further provide the complementary information to enhance diagnostic accuracy. Here, we focus on the problems of both feature representation and fusion of multimodal information from Magnetic Resonance Imaging (MRI) and Positron Emission Tomography (PET). To our best knowledge, the previous methods in the literature mostly used hand-crafted features such as cortical thickness, gray matter densities from MRI, or voxel intensities from PET, and then combined these multimodal features by simply concatenating into a long vector or transforming into a higher-dimensional kernel space. In this paper, we propose a novel method for a high-level latent and shared feature representation from neuroimaging modalities via deep learning. Specifically, we use Deep Boltzmann Machine (DBM)1, a deep network with a restricted Boltzmann machine as a building block, to find a latent hierarchical feature representation from a 3D patch, and then devise a systematic method for a joint feature representation from the paired patches of MRI and PET with a multimodal DBM. To validate the effectiveness of the proposed method, we performed experiments on ADNI dataset and compared with the state-of-the-art methods. In three binary classification problems of AD vs. healthy Normal Control (NC), MCI vs. NC, and MCI converter vs. MCI non-converter, we obtained the maximal accuracies of 95.35%, 85.67%, and 74.58%, respectively, outperforming the competing methods. By visual inspection of the trained model, we observed that the proposed method could hierarchically discover the complex latent patterns inherent in both MRI and PET. PMID:25042445

Turning Paris into reality at the University of California

NASA Astrophysics Data System (ADS)

Victor, David G.; Abdulla, Ahmed; Auston, David; Brase, Wendell; Brouwer, Jack; Brown, Karl; Davis, Steven J.; Kappel, Carrie V.; Meier, Alan; Modera, Mark; Zarin Pass, Rebecca; Phillips, David; Sager, Jordan; Weil, David; TomKat Natural Gas Exit Strategies Working Group

2018-03-01

The Paris Agreement highlights the need for local climate leadership. The University Of California's approach to deep decarbonization offers lessons in efficiency, alternative fuels and electrification. Bending the emissions curve globally requires efforts that blend academic insights with practical solutions.

MUSE deep-fields: the Ly α luminosity function in the Hubble Deep Field-South at 2.91 < z < 6.64

NASA Astrophysics Data System (ADS)

Drake, Alyssa B.; Guiderdoni, Bruno; Blaizot, Jérémy; Wisotzki, Lutz; Herenz, Edmund Christian; Garel, Thibault; Richard, Johan; Bacon, Roland; Bina, David; Cantalupo, Sebastiano; Contini, Thierry; den Brok, Mark; Hashimoto, Takuya; Marino, Raffaella Anna; Pelló, Roser; Schaye, Joop; Schmidt, Kasper B.

2017-10-01

We present the first estimate of the Ly α luminosity function using blind spectroscopy from the Multi Unit Spectroscopic Explorer, MUSE, in the Hubble Deep Field-South. Using automatic source-detection software, we assemble a homogeneously detected sample of 59 Ly α emitters covering a flux range of -18.0 < log10 (F) < -16.3 (erg s-1 cm-2), corresponding to luminosities of 41.4 < log10 (L) < 42.8 (erg s-1). As recent studies have shown, Ly α fluxes can be underestimated by a factor of 2 or more via traditional methods, and so we undertake a careful assessment of each object's Ly α flux using a curve-of-growth analysis to account for extended emission. We describe our self-consistent method for determining the completeness of the sample, and present an estimate of the global Ly α luminosity function between redshifts 2.91 < z < 6.64 using the 1/Vmax estimator. We find that the luminosity function is higher than many number densities reported in the literature by a factor of 2-3, although our result is consistent at the 1σ level with most of these studies. Our observed luminosity function is also in good agreement with predictions from semi-analytic models, and shows no evidence for strong evolution between the high- and low-redshift halves of the data. We demonstrate that one's approach to Ly α flux estimation does alter the observed luminosity function, and caution that accurate flux assessments will be crucial in measurements of the faint-end slope. This is a pilot study for the Ly α luminosity function in the MUSE deep-fields, to be built on with data from the Hubble Ultra Deep Field that will increase the size of our sample by almost a factor of 10.

Deep Learning and Developmental Learning: Emergence of Fine-to-Coarse Conceptual Categories at Layers of Deep Belief Network.

PubMed

Sadeghi, Zahra

2016-09-01

In this paper, I investigate conceptual categories derived from developmental processing in a deep neural network. The similarity matrices of deep representation at each layer of neural network are computed and compared with their raw representation. While the clusters generated by raw representation stand at the basic level of abstraction, conceptual categories obtained from deep representation shows a bottom-up transition procedure. Results demonstrate a developmental course of learning from specific to general level of abstraction through learned layers of representations in a deep belief network. © The Author(s) 2016.

Analysis of Deep and Shallow Traps in Semi-Insulating CdZnTe

DOE PAGES

Kim, Kihyun; Yoon, Yongsu; James, Ralph B.

2018-03-13

Trap levels which are deep or shallow play an important role in the electrical and the optical properties of a semiconductor; thus, a trap level analysis is very important in most semiconductor devices. Deep-level defects in CdZnTe are essential in Fermi level pinning at the middle of the bandgap and are responsible for incomplete charge collection and polarization effects. However, a deep level analysis in semi-insulating CdZnTe (CZT) is very difficult. Theoretical capacitance calculation for a metal/insulator/CZT (MIS) device with deep-level defects exhibits inflection points when the donor/acceptor level crosses the Fermi level in the surface-charge layer (SCL). Three CZTmore » samples with different resistivities, 2 × 10 4 (n-type), 2 × 10 6 (p-type), and 2 × 10 10 (p-type) Ω·cm, were used in fabricating the MIS devices. These devices showed several peaks in their capacitance measurements due to upward/downward band bending that depend on the surface potential. In conclusion, theoretical and experimental capacitance measurements were in agreement, except in the fully compensated case.« less

Analysis of Deep and Shallow Traps in Semi-Insulating CdZnTe

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

Kim, Kihyun; Yoon, Yongsu; James, Ralph B.

Trap levels which are deep or shallow play an important role in the electrical and the optical properties of a semiconductor; thus, a trap level analysis is very important in most semiconductor devices. Deep-level defects in CdZnTe are essential in Fermi level pinning at the middle of the bandgap and are responsible for incomplete charge collection and polarization effects. However, a deep level analysis in semi-insulating CdZnTe (CZT) is very difficult. Theoretical capacitance calculation for a metal/insulator/CZT (MIS) device with deep-level defects exhibits inflection points when the donor/acceptor level crosses the Fermi level in the surface-charge layer (SCL). Three CZTmore » samples with different resistivities, 2 × 10 4 (n-type), 2 × 10 6 (p-type), and 2 × 10 10 (p-type) Ω·cm, were used in fabricating the MIS devices. These devices showed several peaks in their capacitance measurements due to upward/downward band bending that depend on the surface potential. In conclusion, theoretical and experimental capacitance measurements were in agreement, except in the fully compensated case.« less

Steps towards understanding deep atmospheric heating in flares

NASA Technical Reports Server (NTRS)

Mauas, Pablo J. D.; Machado, Marcos E.

1986-01-01

Different aspects of the heating of the deep solar atmosphere during flares, including temperature minimum enhancements and white light emission, are discussed. The proper treatment of H(-) radiative losses is discussed, and compared with previous studies, as well as a quantitative analysis of the ionizing effect of nonthermal particles and ultraviolet radiation. It is concluded that temperature minimum heating may be a natural consequence of the global radiation transport in flares. The implications of these results are discussed within the context of homogeneous and inhomogeneous models of the solar atmosphere.

Theory of Semiconducting Superlattices and Microstructures

DTIC Science & Technology

1992-03-01

theory elucidated the various factors affecting deep levels, sets forth the conditions for obtaining shallow-deep transitions, and predicts that Si (a...theory elucidates the various factors affecting deep levels, sets forth the conditions for obtaining shallow-deep transitions, and predicts that Si (a...ondenotes the anion vacancy, which can be thought any quantitative theoretical factor are theof as originating from Column-O of the Period strengths of

Deep-Sea Bioluminescence Blooms after Dense Water Formation at the Ocean Surface

PubMed Central

Tamburini, Christian; Canals, Miquel; Durrieu de Madron, Xavier; Houpert, Loïc; Lefèvre, Dominique; Martini, Séverine; D'Ortenzio, Fabrizio; Robert, Anne; Testor, Pierre; Aguilar, Juan Antonio; Samarai, Imen Al; Albert, Arnaud; André, Michel; Anghinolfi, Marco; Anton, Gisela; Anvar, Shebli; Ardid, Miguel; Jesus, Ana Carolina Assis; Astraatmadja, Tri L.; Aubert, Jean-Jacques; Baret, Bruny; Basa, Stéphane; Bertin, Vincent; Biagi, Simone; Bigi, Armando; Bigongiari, Ciro; Bogazzi, Claudio; Bou-Cabo, Manuel; Bouhou, Boutayeb; Bouwhuis, Mieke C.; Brunner, Jurgen; Busto, José; Camarena, Francisco; Capone, Antonio; Cârloganu, Christina; Carminati, Giada; Carr, John; Cecchini, Stefano; Charif, Ziad; Charvis, Philippe; Chiarusi, Tommaso; Circella, Marco; Coniglione, Rosa; Costantini, Heide; Coyle, Paschal; Curtil, Christian; Decowski, Patrick; Dekeyser, Ivan; Deschamps, Anne; Donzaud, Corinne; Dornic, Damien; Dorosti, Hasankiadeh Q.; Drouhin, Doriane; Eberl, Thomas; Emanuele, Umberto; Ernenwein, Jean-Pierre; Escoffier, Stéphanie; Fermani, Paolo; Ferri, Marcelino; Flaminio, Vincenzo; Folger, Florian; Fritsch, Ulf; Fuda, Jean-Luc; Galatà, Salvatore; Gay, Pascal; Giacomelli, Giorgio; Giordano, Valentina; Gómez-González, Juan-Pablo; Graf, Kay; Guillard, Goulven; Halladjian, Garadeb; Hallewell, Gregory; van Haren, Hans; Hartman, Joris; Heijboer, Aart J.; Hello, Yann; Hernández-Rey, Juan Jose; Herold, Bjoern; Hößl, Jurgen; Hsu, Ching-Cheng; de Jong, Marteen; Kadler, Matthias; Kalekin, Oleg; Kappes, Alexander; Katz, Uli; Kavatsyuk, Oksana; Kooijman, Paul; Kopper, Claudio; Kouchner, Antoine; Kreykenbohm, Ingo; Kulikovskiy, Vladimir; Lahmann, Robert; Lamare, Patrick; Larosa, Giuseppina; Lattuada, Dario; Lim, Gordon; Presti, Domenico Lo; Loehner, Herbert; Loucatos, Sotiris; Mangano, Salvatore; Marcelin, Michel; Margiotta, Annarita; Martinez-Mora, Juan Antonio; Meli, Athina; Montaruli, Teresa; Motz, Holger; Neff, Max; Nezri, Emma nuel; Palioselitis, Dimitris; Păvălaş, Gabriela E.; Payet, Kevin; Payre, Patrice; Petrovic, Jelena; Piattelli, Paolo; Picot-Clemente, Nicolas; Popa, Vlad; Pradier, Thierry; Presani, Eleonora; Racca, Chantal; Reed, Corey; Riccobene, Giorgio; Richardt, Carsten; Richter, Roland; Rivière, Colas; Roensch, Kathrin; Rostovtsev, Andrei; Ruiz-Rivas, Joaquin; Rujoiu, Marius; Russo, Valerio G.; Salesa, Francisco; Sánchez-Losa, Augustin; Sapienza, Piera; Schöck, Friederike; Schuller, Jean-Pierre; Schussler, Fabian; Shanidze, Rezo; Simeone, Francesco; Spies, Andreas; Spurio, Maurizio; Steijger, Jos J. M.; Stolarczyk, Thierry; Taiuti, Mauro G. F.; Toscano, Simona; Vallage, Bertrand; Van Elewyck, Véronique; Vannoni, Giulia; Vecchi, Manuela; Vernin, Pascal; Wijnker, Guus; Wilms, Jorn; de Wolf, Els; Yepes, Harold; Zaborov, Dmitry; De Dios Zornoza, Juan; Zúñiga, Juan

2013-01-01

The deep ocean is the largest and least known ecosystem on Earth. It hosts numerous pelagic organisms, most of which are able to emit light. Here we present a unique data set consisting of a 2.5-year long record of light emission by deep-sea pelagic organisms, measured from December 2007 to June 2010 at the ANTARES underwater neutrino telescope in the deep NW Mediterranean Sea, jointly with synchronous hydrological records. This is the longest continuous time-series of deep-sea bioluminescence ever recorded. Our record reveals several weeks long, seasonal bioluminescence blooms with light intensity up to two orders of magnitude higher than background values, which correlate to changes in the properties of deep waters. Such changes are triggered by the winter cooling and evaporation experienced by the upper ocean layer in the Gulf of Lion that leads to the formation and subsequent sinking of dense water through a process known as “open-sea convection”. It episodically renews the deep water of the study area and conveys fresh organic matter that fuels the deep ecosystems. Luminous bacteria most likely are the main contributors to the observed deep-sea bioluminescence blooms. Our observations demonstrate a consistent and rapid connection between deep open-sea convection and bathypelagic biological activity, as expressed by bioluminescence. In a setting where dense water formation events are likely to decline under global warming scenarios enhancing ocean stratification, in situ observatories become essential as environmental sentinels for the monitoring and understanding of deep-sea ecosystem shifts. PMID:23874425

A Green Fluorescent Protein with Photoswitchable Emission from the Deep Sea

PubMed Central

Vogt, Alexander; D'Angelo, Cecilia; Oswald, Franz; Denzel, Andrea; Mazel, Charles H.; Matz, Mikhail V.; Ivanchenko, Sergey; Nienhaus, G. Ulrich; Wiedenmann, Jörg

2008-01-01

A colorful variety of fluorescent proteins (FPs) from marine invertebrates are utilized as genetically encoded markers for live cell imaging. The increased demand for advanced imaging techniques drives a continuous search for FPs with new and improved properties. Many useful FPs have been isolated from species adapted to sun-flooded habitats such as tropical coral reefs. It has yet remained unknown if species expressing green fluorescent protein (GFP)-like proteins also exist in the darkness of the deep sea. Using a submarine-based and -operated fluorescence detection system in the Gulf of Mexico, we discovered ceriantharians emitting bright green fluorescence in depths between 500 and 600 m and identified a GFP, named cerFP505, with bright fluorescence emission peaking at 505 nm. Spectroscopic studies showed that ∼15% of the protein bulk feature reversible ON/OFF photoswitching that can be induced by alternating irradiation with blue und near-UV light. Despite being derived from an animal adapted to essentially complete darkness and low temperatures, cerFP505 maturation in living mammalian cells at 37°C, its brightness and photostability are comparable to those of EGFP and cmFP512 from shallow water species. Therefore, our findings disclose the deep sea as a potential source of GFP-like molecular marker proteins. PMID:19018285

Coseismic and aseismic deformations of the rock mass around deep level mining in South Africa - Joint South African and Japanese study

NASA Astrophysics Data System (ADS)

Milev, A. M.; Yabe, Y.; Naoi, M. M.; Nakatani, M.; Durrheim, R. J.; Ogasawara, H.; Scholz, C. H.

2010-12-01

Two underground sites in a deep level gold mine in South Africa were instrumented by the Council for Scientific and Industrial Research (CSIR) with tilt meters and seismic monitors. One of the sites was also instrumented by JApanese-German Underground Acoustic emission Research in South Africa (JAGUARS) with a small network, approx. 40 m span, of eight Acoustic Emission (AE) sensors. The rate of tilt, defined as quasi-static deformations, and the seismic ground motion, defined as dynamic deformations, were analysed in order to understand the rock mass behavior around deep level mining. In addition the high frequency AE events recorded at hypocentral distances of about 50m were analysed. This was the first implementation of high frequency AE events at such a great depth (3300m below the surface). A good correspondence between the dynamic and quasi-static deformations was found. The rate of coseismic and aseismic tilt, as well as seismicity recorded by the mine seismic network, are approximately constant until the daily blasting time, which takes place from about 19:30 until shortly before 21:00. During the blasting time and the subsequent seismic events the coseismic and aseismic tilt shows a rapid increase indicated by a rapid change of the tilt during the seismic event. Much of the quasi-static deformation, however, occurs independently of the seismic events and was described as ‘slow’ or aseismic events. During the monitoring period a seismic event with MW 1.9 (2.1) occurred in the vicinity of the instrumented site. This event was recorded by both the CSIR integrated monitoring system and JAGUARS acoustic emotion network. The tilt changes associated with this event showed a well pronounced after-tilt. More than 21,000 AE aftershocks were located in the first 150 hours after the main event. Using the distribution of the AE events the position of the fault in the source area was successfully delineated. The distribution of the AE events following the main shock was related to after tilt in order to quantify post slip behavior of the source. There was no evidence found for coseismic expansion of the source after the main slip. An attempt to associate the different type of deformations with the various fracture regions and geological structures around the stopes was carried out. A model, was introduced in which the coseismic deformations are associated with the stress regime outside the stope fracture envelope and very often located on existing geological structures, while the aseismic deformations are associated with mobilization of fractures and stress relaxation within the fracture envelope.

Deep learning aided decision support for pulmonary nodules diagnosing: a review

PubMed Central

Yang, Yixin; Feng, Xiaoyi; Chi, Wenhao; Li, Zhengyang; Duan, Wenzhe; Liu, Haiping; Liang, Wenhua; Wang, Wei; Chen, Ping

2018-01-01

Deep learning techniques have recently emerged as promising decision supporting approaches to automatically analyze medical images for different clinical diagnosing purposes. Diagnosing of pulmonary nodules by using computer-assisted diagnosing has received considerable theoretical, computational, and empirical research work, and considerable methods have been developed for detection and classification of pulmonary nodules on different formats of images including chest radiographs, computed tomography (CT), and positron emission tomography in the past five decades. The recent remarkable and significant progress in deep learning for pulmonary nodules achieved in both academia and the industry has demonstrated that deep learning techniques seem to be promising alternative decision support schemes to effectively tackle the central issues in pulmonary nodules diagnosing, including feature extraction, nodule detection, false-positive reduction, and benign-malignant classification for the huge volume of chest scan data. The main goal of this investigation is to provide a comprehensive state-of-the-art review of the deep learning aided decision support for pulmonary nodules diagnosing. As far as the authors know, this is the first time that a review is devoted exclusively to deep learning techniques for pulmonary nodules diagnosing. PMID:29780633

Photoinduced current transient spectroscopy of deep levels and transport mechanisms in iron-doped GaN thin films grown by low pressure-metalorganic vapor phase epitaxy

NASA Astrophysics Data System (ADS)

Muret, P.; Pernot, J.; Azize, M.; Bougrioua, Z.

2007-09-01

Electrical transport and deep levels are investigated in GaN:Fe layers epitaxially grown on sapphire by low pressure metalorganic vapor phase epitaxy. Photoinduced current transient spectroscopy and current detected deep level spectroscopy are performed between 200 and 650 K on three Fe-doped samples and an undoped sample. A detailed study of the detected deep levels assigns dominant centers to a deep donor 1.39 eV below the conduction band edge EC and to a deep acceptor 0.75 eV above the valence band edge EV at low electric field. A strong Poole-Frenkel effect is evidenced for the donor. Schottky diodes characteristics and transport properties in the bulk GaN:Fe layer containing a homogenous concentration of 1019 Fe/cm3 are typical of a compensated semiconductor. They both indicate that the bulk Fermi level is located typically 1.4 eV below EC, in agreement with the neutrality equation and dominance of the deep donor concentration. This set of results demonstrates unambiguously that electrical transport in GaN:Fe is governed by both types, either donor or acceptor, of the iron impurity, either substitutional in gallium sites or associated with other defects.

Geochemical signatures of possible deep-seated ore deposits in Tertiary volcanic centers, Arizona and New Mexico, U.S.A.

USGS Publications Warehouse

Watts, K.C.; Hassemer, J.R.

1989-01-01

A reconnaissance geochemical survey of stream drainages within 21,000 km2 of southeastern Arizona and southwestern New Mexico shows broad zones of low-level to moderate contrast anomalies, many associated with mid-Tertiary eruptive centers and Tertiary fault zones. Of these eruptive centers, few are known to contain metallic deposits, and most of those known are minor. This, however, may be more a function of shallow erosion level than an indication of the absence of mineralization, since hydrothermal alteration and Fe-Mn-oxide staining are widespread, and geochemical anomalies are pervasive over a larger part of the region than outcrop observations would predict. Accordingly, interpretations of the geochemical data use considerations of relative erosion levels, and inferred element zonalities, to focus on possible undiscovered deposits in the subsurface of base-, precious-, and rare-metal deposits of plutonic-volcanic association. In order to enhance the identification of specific deep targets, we use the empirically determined ratio: Ag+Mn+Pb+Zn+Ba Au+Mo+Cu+Bi+W This ratio is based on reported metal contents of nonmagnetic heavy-mineral samples from the drainage sediment, determined by emission spectrographic analysis. Before the ratio was computed for each sample site, the data were normalized to a previously estimated regional threshold value. A regional isopleth map was then prepared, using a cell-averaging computer routine, with contours drawn at the 25th, 50th, 75th, 80th, 90th, 95th and 99th percentiles of the computed data. ?? 1989.

IBS-like Symptoms in Patients with Ulcerative Colitis in Deep Remission Are Associated with Increased Levels of Serum Cytokines and Poor Psychological Well-being.

PubMed

Jonefjäll, Börje; Öhman, Lena; Simrén, Magnus; Strid, Hans

2016-11-01

Gastrointestinal symptoms (GI) compatible with irritable bowel syndrome (IBS) are common in patients with ulcerative colitis (UC) in remission. The causes of these symptoms remain to be clarified. Our aim was to investigate prevalence and factors associated with IBS-like symptoms in patients with UC in deep remission. We included 298 patients with UC and used Mayo score, sigmoidoscopy, and fecal calprotectin to define deep remission versus active disease. Presence of IBS-like symptoms according to the Rome III criteria, severity of GI, extraintestinal and psychological symptoms, stress levels, and quality of life were measured with validated questionnaires. Serum cytokines and high-sensitive C-reactive peptide were determined. The criteria for deep remission was fulfilled by 132 patients (44%) and 24 of these fulfilled the Rome III criteria for IBS (18%). Patients with UC in deep remission with IBS-like symptoms had comparable levels of GI symptoms, non-GI somatic symptoms, and quality of life as patients with active UC. The patients with UC in deep remission with IBS-like symptoms had similar levels of fecal calprotectin as patients in deep remission without IBS-like symptoms (18 versus 31 μg/g, P = 0.11), but higher levels of serum cytokines (interleukin [IL]-1β, IL-6, IL-13, IL-10 and IL-8, P < 0.05) and higher levels of anxiety (P < 0.001), depression (P = 0.02) and perceived stress (P = 0.03). IBS-like symptoms in patients with UC in deep remission are common, but not as prevalent as previously reported. Poor psychological well-being and increased serum cytokine levels, but not colonic low-grade inflammation, were associated with IBS-like symptoms.

Factors influencing CO2 and CH4 emissions from coastal wetlands in the Liaohe Delta, Northeast China

NASA Astrophysics Data System (ADS)

Olsson, L.; Ye, S.; Yu, X.; Wei, M.; Krauss, K. W.; Brix, H.

2015-08-01

Many factors are known to influence greenhouse gas emissions from coastal wetlands, but it is still unclear which factors are most important under field conditions when they are all acting simultaneously. The objective of this study was to assess the effects of water table, salinity, soil temperature and vegetation on CH4 emissions and ecosystem respiration (Reco) from five coastal wetlands in the Liaohe Delta, Northeast China: two Phragmites australis (common reed) wetlands, two Suaeda salsa (sea blite) marshes and a rice (Oryza sativa) paddy. Throughout the growing season, the Suaeda wetlands were net CH4 sinks whereas the Phragmites wetlands and the rice paddy were net CH4 sources emitting 1.2-6.1 g CH4 m-2 yr-1. The Phragmites wetlands emitted the most CH4 per unit area and the most CH4 relative to CO2. The main controlling factors for the CH4 emissions were water table, temperature, soil organic carbon and salinity. The CH4 emission was accelerated at high and constant (or managed) water tables and decreased at water tables below the soil surface. High temperatures enhanced CH4 emissions, and emission rates were consistently low (< 1 mg CH4 m-2 h-1) at soil temperatures < 18 °C. At salinity levels > 18 ppt, the CH4 emission rates were always low (< 1 mg CH4 m-2 h-1) probably because methanogens were out-competed by sulphate-reducing bacteria. Saline Phragmites wetlands can, however, emit significant amounts of CH4 as CH4 produced in deep soil layers are transported through the air-space tissue of the plants to the atmosphere. The CH4 emission from coastal wetlands can be reduced by creating fluctuating water tables, including water tables below the soil surface, as well as by occasional flooding by high-salinity water. The effects of water management schemes on the biological communities in the wetlands must, however, be carefully studied prior to the management in order to avoid undesirable effects on the wetland communities.

Factors influencing CO2 and CH4 emissions from coastal wetlands in the Liaohe Delta, Northeast China

NASA Astrophysics Data System (ADS)

Olsson, L.; Ye, S.; Yu, X.; Wei, M.; Krauss, K. W.; Brix, H.

2015-02-01

Many factors are known to influence greenhouse gas emissions from coastal wetlands, but it is still unclear which factors are most important under field conditions when they are all acting simultaneously. The objective of this study was to assess the effects of water table, salinity, soil temperature and vegetation on CH4 emissions and ecosystem respiration (Reco) from five coastal wetlands in the Liaohe Delta, northeast China: two Phragmites australis (common reed) wetlands, two Suaeda salsa (sea blite) marshes and a rice (Oryza sativa) paddy. Throughout the growing season, the Suaeda wetlands were net CH4 sinks whereas the Phragmites wetlands and the rice paddy were net CH4 sources emitting 1.2-6.1 g CH4 m-2 y-1. The Phragmites wetlands emitted the most CH4 per unit area and the most CH4 relative to CO2. The main controlling factors for the CH4 emissions were water table, temperature and salinity. The CH4 emission was accelerated at high and constant (or managed) water tables and decreased at water tables below the soil surface. High temperatures enhanced CH4 emissions, and emission rates were consistently low (< 1 mg CH4 m-2 h) at soil temperatures <18 °C. At salinity levels > 18 ppt, the CH4 emission rates were always low (< 1 mg CH4 m-2 h-1) probably because methanogens were outcompeted by sulphate reducing bacteria. Saline Phragmites wetlands can, however, emit significant amounts of CH4 as CH4 produced in deep soil layers are transported through the air-space tissue of the plants to the atmosphere. The CH4 emission from coastal wetlands can be reduced by creating fluctuating water tables, including water tables below the soil surface, as well as by occasional flooding by high-salinity water. The effects of water management schemes on the biological communities in the wetlands must, however, be carefully studied prior to the management in order to avoid undesirable effects on the wetland communities.

Nitrous oxide emission by aquatic macrofauna

PubMed Central

Stief, Peter; Poulsen, Morten; Nielsen, Lars Peter; Brix, Hans; Schramm, Andreas

2009-01-01

A large variety of aquatic animals was found to emit the potent greenhouse gas nitrous oxide when nitrate was present in the environment. The emission was ascribed to denitrification by ingested bacteria in the anoxic animal gut, and the exceptionally high N2O-to-N2 production ratio suggested delayed induction of the last step of denitrification. Filter- and deposit-feeding animal species showed the highest rates of nitrous oxide emission and predators the lowest, probably reflecting the different amounts of denitrifying bacteria in the diet. We estimate that nitrous oxide emission by aquatic animals is quantitatively important in nitrate-rich aquatic environments like freshwater, coastal marine, and deep-sea ecosystems. The contribution of this source to overall nitrous oxide emission from aquatic environments might further increase because of the projected increase of nitrate availability in tropical regions and the numeric dominance of filter- and deposit-feeders in eutrophic ecosystems. PMID:19255427

An intensity map of hydrogen 21-cm emission at redshift z approximately 0.8.

PubMed

Chang, Tzu-Ching; Pen, Ue-Li; Bandura, Kevin; Peterson, Jeffrey B

2010-07-22

Observations of 21-cm radio emission by neutral hydrogen at redshifts z approximately 0.5 to approximately 2.5 are expected to provide a sensitive probe of cosmic dark energy. This is particularly true around the onset of acceleration at z approximately 1, where traditional optical cosmology becomes very difficult because of the infrared opacity of the atmosphere. Hitherto, 21-cm emission has been detected only to z = 0.24. More distant galaxies generally are too faint for individual detections but it is possible to measure the aggregate emission from many unresolved galaxies in the 'cosmic web'. Here we report a three-dimensional 21-cm intensity field at z = 0.53 to 1.12. We then co-add neutral-hydrogen (H i) emission from the volumes surrounding about 10,000 galaxies (from the DEEP2 optical galaxy redshift survey). We detect the aggregate 21-cm glow at a significance of approximately 4sigma.

Levels-of-processing effects on a task of olfactory naming.

PubMed

Royet, Jean-Pierre; Koenig, Olivier; Paugam-Moisy, Helene; Puzenat, Didier; Chasse, Jean-Luc

2004-02-01

The effects of odor processing were investigated at various analytical levels, from simple sensory analysis to deep or semantic analysis, on a subsequent task of odor naming. Students (106 women, 23.6 +/- 5.5 yr. old; 65 men, 25.1 +/- 7.1 yr. old) were tested. The experimental procedure included two successive sessions, a first session to characterize a set of 30 odors with criteria that used various depths of processing and a second session to name the odors as quickly as possible. Four processing conditions rated the odors using descriptors before naming the odor. The control condition did not rate the odors before naming. The processing conditions were based on lower-level olfactory judgments (superficial processing), higher-level olfactory-gustatory-somesthetic judgments (deep processing), and higher-level nonolfactory judgments (Deep-Control processing, with subjects rating odors with auditory and visual descriptors). One experimental condition successively grouped lower- and higher-level olfactory judgments (Superficial-Deep processing). A naming index which depended on response accuracy and the subjects' response time were calculated. Odor naming was modified for 18 out of 30 odorants as a function of the level of processing required. For 94.5% of significant variations, the scores for odor naming were higher following those tasks for which it was hypothesized that the necessary olfactory processing was carried out at a deeper level. Performance in the naming task was progressively improved as follows: no rating of odors, then superficial, deep-control, deep, and superficial-deep processings. These data show that the deepest olfactory encoding was later associated with progressively higher performance in naming.

Gas phase emissions from cooking processes and their secondary aerosol production potential

NASA Astrophysics Data System (ADS)

Klein, Felix; Platt, Stephen; Bruns, Emily; Termime-roussel, Brice; Detournay, Anais; Mohr, Claudia; Crippa, Monica; Slowik, Jay; Marchand, Nicolas; Baltensperger, Urs; Prevot, Andre; El Haddad, Imad

2014-05-01

Long before the industrial evolution and the era of fossil fuels, high concentrations of aerosol particles were alluded to in heavily populated areas, including ancient Rome and medieval London. Recent radiocarbon measurements (14C) conducted in modern megacities came as a surprise: carbonaceous aerosol (mainly organic aerosol, OA), a predominant fraction of particulate matter (PM), remains overwhelmingly non-fossil despite extensive fossil fuel combustion. Such particles are directly emitted (primary OA, POA) or formed in-situ in the atmosphere (secondary OA, SOA) via photochemical reactions of volatile organic compounds (VOCs). Urban levels of non-fossil OA greatly exceed the levels measured in pristine environments strongly impacted by biogenic emissions, suggesting a contribution from unidentified anthropogenic non-fossil sources to urban OA. Positive matrix factorization (PMF) techniques applied to ambient aerosol mass spectrometer (AMS, Aerodyne) data identify primary cooking emissions (COA) as one of the main sources of primary non-fossil OA in major cities like London (Allan et al., 2010), New York (Sun et al., 2011) and Beijing (Huang et al., 2010). Cooking processes can also emit VOCs that can act as SOA precursors, potentially explaining in part the high levels of oxygenated OA (OOA) identified by the AMS in urban areas. However, at present, the chemical nature of these VOCs and their secondary aerosol production potential (SAPP) remain virtually unknown. The approach adopted here involves laboratory quantification of PM and VOC emission factors from the main primary COA emitting processes and their SAPP. Primary emissions from deep-fat frying, vegetable boiling, vegetable frying and meat cooking for different oils, meats and vegetables were analysed under controlled conditions after ~100 times dilution. A high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and a high resolution proton transfer time-of-flight mass spectrometer (PTR-ToF-MS) were used to quantify OA and VOC emissions, respectively. SOA production potential of the different emissions was quantified by introducing them into the PSI mobile smog chamber and a potential aerosol chamber (PAM) where they were photochemically aged. The measurements of primary emissions suggest that the COA factor identified in ambient atmospheric aerosols is mostly related to fat release from frying with vegetable oils or grilling fatty-meats. In contrast, vegetable cooking (boiling and frying) was associated with significant VOC emissions. The VOC emissions from frying consist mainly of aldehydes which are formed through breaking of fatty acids. Gas phase composition, emission factors and SAPP from all these processes will be presented. This work was supported by the Swiss National Science Foundation as well as the Swiss Federal Office for the Environment. The research leading to these results has received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement n.° 290605 (COFUND: PSI-FELLOW). J. Allan et al, Atmos. Chem. Phys. 10, 647-668 (2010) X.-F. Huang et al, Atmos. Chem. Phys. 10, 8933-8945 (2010) Y.-L. Sun et al, Atmos. Chem. Phys. 11, 1581-1602 (2011)

Effect of land use change for bioenergy on greenhouse gas emissions from a wet marginal soil in New York State, USA.

NASA Astrophysics Data System (ADS)

Stoof, Cathelijne; Mason, Cedric; Steenhuis, Tammo; Richards, Brian

2013-04-01

Millions of hectares of marginal lands in the Northeast USA no longer used for agriculture are suitable for production of second-generation cellulosic bioenergy crops, offering the potential for regional bioenergy production without inducing food vs. fuel competition for prime farmland. Abundant water resources, close proximity between production and markets, and compatibility with existing agricultural systems all favor development in the region. Yet, little is known about how sustainable bioenergy crop production on marginal lands is regarding greenhouse gas emissions. In a 10-ha field trial on wet marginal soils in upstate New York, we are assessing the effect of land use change (from fallow land to perennial grass stands) on N2O and CH4 emissions. The deep clay loam is unsuited for row-crop agriculture because it is too dry in summer and too wet in winter. Monthly chamber campaigns were performed from April to November 2012 to monitor large scale (10-20 m resolution) differences caused by land cover type (n=4 for both switchgrass, reed-canary grass and a 50-yr unplowed control) across soil moisture gradients (n=5 soil moisture levels per replicate). Additional weekly campaigns assessed the smaller scale spatial and temporal variability in emissions at meter-scale. Here we present results of both the large and small-scale patterns in greenhouse gas emissions from this marginal soil, and discuss effects of soil properties and hydrologic conditions as potential drivers. Insight gained about the environmental impact of bioenergy crops can be used to assess the sustainability of using this region's underutilized land base for energy production.

High-efficiency emitting materials based on phenylquinoline/carbazole-based compounds for organic light emitting diode applications

NASA Astrophysics Data System (ADS)

Jin, Sung-Ho

2009-08-01

Highly efficient light-emitting materials based on phenylquinoline-carbazole derivative has been synthesized for organic-light emitting diodes (OLEDs). The materials form high quality amorphous thin films by thermal evaporation and the energy levels can be easily adjusted by the introduction of different electron donating and electron withdrawing groups on carbazoylphenylquinoline. Non-doped deep-blue OLEDs using Et-CVz-PhQ as the emitter show bright emission (CIE coordinates, x=0.156, y=0.093) with an external quantum efficiency of 2.45 %. Furthermore, the material works as an excellent host material for BCzVBi to get high-performance OLEDs with excellent deep-blue CIE coordinates (x=0.155, y=0.157), high power efficiency (5.98 lm/W), and high external quantum efficiency (5.22 %). Cyclometalated Ir(III) μ-chloride bridged dimers were synthesized by iridium trichloride hydrate with an excess of our developed deep-blue emitter, Et-CVz-PhQ. The Ir(III) complexes were prepared by the dimers with the corresponding ancillary ligands. The chloride bridged diiridium complexes can be easily converted to mononuclear Ir(III) complexes by replacing the two bridging chlorides with bidentate monoanionic ancillary ligands. Among the various types of ancillary ligands, we firstly used picolinic acid N-oxide, including picolinic acid and acetylacetone as an ancillary ligands for Ir(III) complexes. The PhOLEDs also shows reasonably high brightness and good luminance efficiency of 20,000 cd/m2 and 12 cd/A, respectively.

Multicriteria approach to interpret the variability of the levels of particulate matter and gaseous pollutants in the Madrid metropolitan area, during the 1999-2012 period

NASA Astrophysics Data System (ADS)

Salvador, P.; Artíñano, B.; Viana, M. M.; Alastuey, A.; Querol, X.

2015-05-01

The evolution of the mean levels of particulate matter (PM) and gaseous pollutants recorded in the Madrid metropolitan area from 1999 to 2012, were investigated focussing on the impact of mitigation strategies and economic scenarios. Temporal trends have shown that SO2, CO, NO, PM10 and NO2 levels at Madrid kerbside and urban-background sites have been decreasing over the 1999-2012 period, with statistical significance. A small contribution to the annual decreasing rates of SO2, NO and NO2 obtained at these sites could be attributed to the reduction in the regional background levels. The reduction in the emissions of atmospheric pollutants from specific sources of the urban agglomeration, explained most of the annual decreasing rates obtained at the kerbside and urban-background sites. From 1999 to 2007 a reduction of the emissions from road traffic and residential heating was produced, as a consequence of the implementation of a number of management strategies promoted and adopted by European and national public administrations. In contrast, from 2008 to 2012 a deep decrease in fuel consumption and a reduction of construction-demolition and roadwork activities took place in the Madrid metropolitan area, as a consequence of the economic recession. The expected overcoming of the economic crisis within the next few years, will presumably give rise to similar levels of PM and gaseous pollutants as those existing previously to the crisis period. The introduction of new Euro 6/VI vehicles which emit considerably less NOx than previous generation diesel vehicles, as well as the implementation of strategies aimed at reducing resuspended mineral dust from road traffic and construction-demolition activities are thus encouraged.

MUSE Integral Field Observations of the Oxygen-rich SNR 1E 0102.2-7219

NASA Astrophysics Data System (ADS)

Seitenzahl, Ivo R.; Vogt, Frédéric P. A.; Terry, Jason P.; Dopita, Michael A.; Ruiter, Ashley J.; Ghavamian, Parviz; Sukhbold, Tuguldur

2017-02-01

We have observed the oxygen-rich SNR 1E 0102.2-7219 with the integral field spectrograph WiFeS at Siding Spring Observatory and discovered sulfur-rich ejecta for the first time. Follow-up deep DDT observations with MUSE on the VLT (8100 s on source) reaching down to a noise level of ~5 × 10-20ergs-1cm-2Å-1spaxel-1 have led to the additional discovery of fast-moving hydrogen as well as argon-rich and chlorine-rich material. The detection of fast-moving hydrogen knots challenges the interpretation that the progenitor of 1E 0102 was a compact core of a Wolf-Rayet star that had shed its entire envelope. In addition to the detection of hydrogen and the products of oxygen-burning, this unprecedented sharp (0.2'' spaxel size at ~0.7'' seeing) and deep MUSE view of an oxygen-rich SNR in the Magellanic Clouds reveals further exciting discoveries, including [Fe xiv]λ5303 and [Fe xi]λ7892 emission, which we associate with the forward shock. We present this exciting data set and discuss some of its implications for the explosion mechanism and nucleosynthesis of the associated supernova.

Fabrication of cerium-doped β-Ga2O3 epitaxial thin films and deep ultraviolet photodetectors.

PubMed

Li, Wenhao; Zhao, Xiaolong; Zhi, Yusong; Zhang, Xuhui; Chen, Zhengwei; Chu, Xulong; Yang, Hujiang; Wu, Zhenping; Tang, Weihua

2018-01-20

High-quality cerium-doped β-Ga 2 O 3 (Ga 2 O 3 :Ce) thin films could be achieved on (0001)α-Al 2 O 3 substrates using a pulsed-laser deposition method. The impact of dopant contents concentration on crystal structure, optical absorption, photoluminescence, and photoelectric properties has been intensively studied. X-ray diffraction analysis results have shown that Ga 2 O 3 :Ce films are highly (2¯01) oriented, and the lattice spacing of the (4¯02) planes is sensitive to the Ce doping level. The prepared Ga 2 O 3 :Ce films show a sharp absorption edge at about 250 nm, meaning a high transparency to deep ultraviolet (DUV) light. The photoluminescence results revealed that the emissions were in the violet-blue-green region, which are associated with the donor-acceptor transitions with the Ce 3+ and oxygen vacancies related defects. A simple DUV photodetector device with a metal-semiconductor-metal structure has also been fabricated based on Ga 2 O 3 :Ce thin film. A distinct DUV photoresponse was obtained, suggesting a potential application in DUV photodetector devices.

Nature of Pre-Earthquake Phenomena and their Effects on Living Organisms

PubMed Central

Freund, Friedemann; Stolc, Viktor

2013-01-01

Simple Summary Earthquakes are invariably preceded by a period when stresses increase deep in the Earth. Animals appear to be able to sense impending seismic events. During build-up of stress, electronic charge carriers are activated deep below, called positive holes. Positive holes have unusual properties: they can travel fast and far into and through the surrounding rocks. As they flow, they generate ultralow frequency electromagnetic waves. When they arrive at the Earth surface, they can ionize the air. When they flow into water, they oxidize it to hydrogen peroxides. All these physical and chemical processes can have noticeable effects on animals. Abstract Earthquakes occur when tectonic stresses build up deep in the Earth before catastrophic rupture. During the build-up of stress, processes that occur in the crustal rocks lead to the activation of highly mobile electronic charge carriers. These charge carriers are able to flow out of the stressed rock volume into surrounding rocks. Such outflow constitutes an electric current, which generates electromagnetic (EM) signals. If the outflow occurs in bursts, it will lead to short EM pulses. If the outflow is continuous, the currents may fluctuate, generating EM emissions over a wide frequency range. Only ultralow and extremely low frequency (ULF/ELF) waves travel through rock and can reach the Earth surface. The outflowing charge carriers are (i) positively charged and (ii) highly oxidizing. When they arrive at the Earth surface from below, they build up microscopic electric fields, strong enough to field-ionize air molecules. As a result, the air above the epicentral region of an impending major earthquake often becomes laden with positive airborne ions. Medical research has long shown that positive airborne ions cause changes in stress hormone levels in animals and humans. In addition to the ULF/ELF emissions, positive airborne ions can cause unusual reactions among animals. When the charge carriers flow into water, they oxidize water to hydrogen peroxide. This, plus oxidation of organic compounds, can cause behavioral changes among aquatic animals. PMID:26487415

Deep magmatic degassing versus scrubbing: Elevated CO2 emissions and C/S in the lead-up to the 2009 eruption of Redoubt Volcano, Alaska

USGS Publications Warehouse

Werner, Cynthia A.; Evans, William C.; Kelly, Peter; McGimsey, Robert G.; Pfeffer, Melissa; Doukas, Michael P.; Neal, Christina

2012-01-01

We report CO2, SO2, and H2S emission rates and C/S ratios during the five months leading up to the 2009 eruption of Redoubt Volcano, Alaska. CO2emission rates up to 9018 t/d and C/S ratios ≥30 measured in the months prior to the eruption were critical for fully informed forecasting efforts. Observations of ice-melt rates, meltwater discharge, and water chemistry suggest that surface waters represented drainage from surficial, perched reservoirs of condensed magmatic steam and glacial meltwater. These fluids scrubbed only a few hundred tonnes/day of SO2, not the >2100 t/d SO2expected from degassing of magma in the mid- to upper crust (3–6.5 km), where petrologic analysis shows the final magmatic equilibration occurred. All data are consistent with upflow of a CO2-rich magmatic gas for at least 5 months prior to eruption, and minimal scrubbing of SO2by near-surface groundwater. The high C/S ratios observed could reflect bulk degassing of mid-crustal magma followed by nearly complete loss of SO2in a deep magmatic-hydrothermal system. Alternatively, high C/S ratios could be attributed to decompressional degassing of low silica andesitic magma that intruded into the mid-crust in the 5 months prior to eruption, thereby mobilizing the pre-existing high silica andesite magma or mush in this region. The latter scenario is supported by several lines of evidence, including deep long-period earthquakes (−28 to −32 km) prior to and during the eruption, and far-field deformation following the onset of eruptive activity.

Deep Restricted Kernel Machines Using Conjugate Feature Duality.

PubMed

Suykens, Johan A K

2017-08-01

The aim of this letter is to propose a theory of deep restricted kernel machines offering new foundations for deep learning with kernel machines. From the viewpoint of deep learning, it is partially related to restricted Boltzmann machines, which are characterized by visible and hidden units in a bipartite graph without hidden-to-hidden connections and deep learning extensions as deep belief networks and deep Boltzmann machines. From the viewpoint of kernel machines, it includes least squares support vector machines for classification and regression, kernel principal component analysis (PCA), matrix singular value decomposition, and Parzen-type models. A key element is to first characterize these kernel machines in terms of so-called conjugate feature duality, yielding a representation with visible and hidden units. It is shown how this is related to the energy form in restricted Boltzmann machines, with continuous variables in a nonprobabilistic setting. In this new framework of so-called restricted kernel machine (RKM) representations, the dual variables correspond to hidden features. Deep RKM are obtained by coupling the RKMs. The method is illustrated for deep RKM, consisting of three levels with a least squares support vector machine regression level and two kernel PCA levels. In its primal form also deep feedforward neural networks can be trained within this framework.

A direct calibration of the IRX-β relation in Lyman-break Galaxies at z=3-5

NASA Astrophysics Data System (ADS)

Koprowski, M. P.; Coppin, K. E. K.; Geach, J. E.; McLure, R. J.; Almaini, O.; Blain, A. W.; Bremer, M.; Bourne, N.; Chapman, S. C.; Conselice, C. J.; Dunlop, J. S.; Farrah, D.; Hartley, W.; Karim, A.; Knudsen, K. K.; Michałowski, M. J.; Scott, D.; Simpson, C.; Smith, D. J. B.; van der Werf, P. P.

2018-06-01

We use a sample of 4209 Lyman break galaxies (LBGs) at z ≃ 3, 4 and 5 in the UKIRT Infrared Deep Sky Survey (UKIDSS) Ultra Deep Survey (UDS) field to investigate the relationship between the observed slope of the stellar continuum emission in the ultraviolet, β, and the thermal dust emission, as quantified via the so-called `infrared excess' (IRX ≡ LIR/LUV). Through a stacking analysis we directly measure the 850μm flux density of LBGs in our deep (0.9 mJy) James Clerk Maxwell Telescope (JCMT) SCUBA-2 850-μm map, as well as deep public Herschel/SPIRE 250-, 350- and 500-μm imaging. We establish functional forms for the IRX-β relation to z ˜ 5, confirming that there is no significant redshift evolution of the relation and that the resulting average IRX-β curve is consistent with a Calzetti-like attenuation law. By comparing our results with recent works in the literature, we confirm that discrepancies in the slope of the IRX-β relation are driven by biases in the methodology used to determine the ultraviolet slopes. Consistent results are found when IRX-β is evaluated by stacking in bins of stellar mass, and we argue that the near-linear IRX-M⋆ relationship is a better proxy for correcting observed UV luminosities to total star formation rates, provided an accurate handle on M⋆ can be had, and also gives clues as to the physical driver of the role of dust-obscured star formation in high-redshift galaxies.

DECADE web portal: toward the integration of MaGa, EarthChem and VOTW data systems to further the knowledge on Earth degassing

NASA Astrophysics Data System (ADS)

Cardellini, Carlo; Frigeri, Alessandro; Lehnert, Kerstin; Ash, Jason; McCormick, Brendan; Chiodini, Giovanni; Fischer, Tobias; Cottrell, Elizabeth

2015-04-01

The release of volatiles from the Earth's interior takes place in both volcanic and non-volcanic areas of the planet. The comprehension of such complex process and the improvement of the current estimates of global carbon emissions, will greatly benefit from the integration of geochemical, petrological and volcanological data. At present, major online data repositories relevant to studies of degassing are not linked and interoperable. In the framework of the Deep Earth Carbon Degassing (DECADE) initiative of the Deep Carbon Observatory (DCO), we are developing interoperability between three data systems that will make their data accessible via the DECADE portal: (1) the Smithsonian Institutionian's Global Volcanism Program database (VOTW) of volcanic activity data, (2) EarthChem databases for geochemical and geochronological data of rocks and melt inclusions, and (3) the MaGa database (Mapping Gas emissions) which contains compositional and flux data of gases released at volcanic and non-volcanic degassing sites. The DECADE web portal will create a powerful search engine of these databases from a single entry point and will return comprehensive multi-component datasets. A user will be able, for example, to obtain data relating to compositions of emitted gases, compositions and age of the erupted products and coincident activity, of a specific volcano. This level of capability requires a complete synergy between the databases, including availability of standard-based web services (WMS, WFS) at all data systems. Data and metadata can thus be extracted from each system without interfering with each database's local schema or being replicated to achieve integration at the DECADE web portal. The DECADE portal will enable new synoptic perspectives on the Earth degassing process allowing to explore Earth degassing related datasets over previously unexplored spatial or temporal ranges.

SphinX Measurements of the 2009 Solar Minimum X-Ray Emission

NASA Astrophysics Data System (ADS)

Sylwester, J.; Kowalinski, M.; Gburek, S.; Siarkowski, M.; Kuzin, S.; Farnik, F.; Reale, F.; Phillips, K. J. H.; Bakała, J.; Gryciuk, M.; Podgorski, P.; Sylwester, B.

2012-06-01

The SphinX X-ray spectrophotometer on the CORONAS-PHOTON spacecraft measured soft X-ray emission in the 1-15 keV energy range during the deep solar minimum of 2009 with a sensitivity much greater than GOES. Several intervals are identified when the X-ray flux was exceptionally low, and the flux and solar X-ray luminosity are estimated. Spectral fits to the emission at these times give temperatures of 1.7-1.9 MK and emission measures between 4 × 1047 cm-3 and 1.1 × 1048 cm-3. Comparing SphinX emission with that from the Hinode X-ray Telescope, we deduce that most of the emission is from general coronal structures rather than confined features like bright points. For one of 27 intervals of exceptionally low activity identified in the SphinX data, the Sun's X-ray luminosity in an energy range roughly extrapolated to that of ROSAT (0.1-2.4 keV) was less than most nearby K and M dwarfs.

Particulate matter adjacent to cattle deep-bedded monoslope facilities

USDA-ARS?s Scientific Manuscript database

Purpose: Confined cattle facilities are an increasingly common housing system in the Northern Great Plains region. Many of these facilities add organic bedding material to the pens once or twice per week. Particulate matter concentrations and emissions from these facilities have not been evaluate...

Structural determinants of electric vehicle market growth : a National Center for Sustainable Transportation research report.

DOT National Transportation Integrated Search

2017-02-01

Zero emission vehicles (ZEV) and plug-in electric vehicles (PEV) are critical technologies to attain deep reductions in greenhouse gases from transportation. PEV markets, however, have grown more slowly than anticipated by many observers. In this stu...

Changes in VEGF and nitric oxide after deep dermal injury in the female, red Duroc pig-further similarities between female, Duroc scar and human hypertrophic scar.

PubMed

Zhu, Kathy Q; Engrav, Loren H; Armendariz, Rebecca; Muangman, Pornprom; Klein, Matthew B; Carrougher, Gretchen J; Deubner, Heike; Gibran, Nicole S

2005-02-01

Despite decades of research, our understanding of human hypertrophic scar is limited. A reliable animal model could significantly increase our understanding. We previously confirmed similarities between scarring in the female, red, Duroc pig and human hypertrophic scarring. The purpose of this study was to: (1) measure vascular endothelial growth factor (VEGF) and nitric oxide (NO) levels in wounds on the female Duroc; and (2) to compare the NO levels to those reported for human hypertrophic scar. Shallow and deep wounds were created on four female Durocs. VEGF levels were measured using ELISA and NO levels with the Griess reagent. VEGF and NO levels were increased in deep wounds at 10 days when compared to shallow wounds (p < 0.05). At 15 weeks, VEGF and NO levels had returned to the level of shallow wounds. At 21 weeks, VEGF and NO levels had declined below baseline levels in deep wounds and the NO levels were significantly lower (p < 0.01). We found that VEGF and NO exhibit two distinctly different temporal patterns in shallow and deep wounds on the female Durocs. Furthermore, NO is decreased in female, Duroc scar as it is in human, hypertrophic scar further validating the usefulness of the model.

Intense deep blue exciplex electroluminescence from NPB/TPBi:PPh3O-based OLEDs and their intrinsic degradation mechanisms (Conference Presentation)

NASA Astrophysics Data System (ADS)

Shinar, Joseph; Hippola, Chamika; Danilovic, Dusan; Bhattacharjee, Ujjal; Petrich, Jacob W.; Shinar, Ruth

2016-09-01

We describe intense and efficient deep blue (430 - 440 nm) exciplex emission from NPB/TPBi:PPh3O OLEDs where the luminous efficiency approaches 4 Cd/A and the maximal brightness exceeds 22,000 Cd/m2. Time resolved PL measurements confirm the exciplex emission from NPB:TPBi, as studied earlier by Monkman and coworkers [Adv. Mater. 25, 1455 (2013)]. However, the inclusion of PPh3O improves the OLED performance significantly. The effect of PPh3O on the EL and PL will be discussed. The NPB/TPBi:PPh3O-based OLEDs were also studied by optically and electrically detected magnetic resonance (ODMR and EDMR, respectively). In particular, the amplitude of the negative (EL- and current-quenching) spin 1/2 resonance, previously attributed to enhanced formation of strongly EL-quenching positive bipolarons, increases as the OLEDs degrade in a dry nitrogen atmosphere. This degradation mechanism is discussed in relation to degradation induced by hot polarons that are energized by exciton annihilation.

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

Djavid, Mehrdad; Mi, Zetian, E-mail: zetian.mi@mcgill.ca

The performance of conventional AlGaN deep ultraviolet light emitting diodes has been limited by the extremely low light extraction efficiency (<10%), due to the unique transverse magnetic (TM) polarized light emission. Here, we show that, by exploiting the lateral side emission, the extraction efficiency of TM polarized light can be significantly enhanced in AlGaN nanowire structures. Using the three-dimensional finite-difference time domain simulation, we demonstrate that the nanowire structures can be designed to inhibit the emission of guided modes and redirect trapped light into radiated modes. A light extraction efficiency of more than 70% can, in principle, be achieved bymore » carefully optimizing the nanowire size, nanowire spacing, and p-GaN thickness.« less

Emission-Line Galaxies from the PEARS Hubble Ultra Deep Field: A 2-D Detection Method and First Results

NASA Technical Reports Server (NTRS)

Gardner, J. P.; Straughn, Amber N.; Meurer, Gerhardt R.; Pirzkal, Norbert; Cohen, Seth H.; Malhotra, Sangeeta; Rhoads, james; Windhorst, Rogier A.; Gardner, Jonathan P.; Hathi, Nimish P.;

Multi-band Emission Light Curves of Jupiter: Insights on Brown Dwarfs and Directly Imaged Exoplanets

NASA Astrophysics Data System (ADS)

Zhang, Xi; Ge, Huazhi; Orton, Glenn S.; Fletcher, Leigh N.; Sinclair, James; Fernandes, Joshua; Momary, Thomas W.; Kasaba, Yasumasa; Sato, Takao M.; Fujiyoshi, Takuya

2016-10-01

Many brown dwarfs exhibit significant infrared flux variability (e.g., Artigau et al. 2009, ApJ, 701, 1534; Radigan et al. 2012, ApJ, 750, 105), ranging from several to twenty percent of the brightness. Current hypotheses include temperature variations, cloud holes and patchiness, and cloud height and thickness variations (e.g., Apai et al. 2013, ApJ, 768, 121; Robinson and Marley 2014, ApJ, 785, 158; Zhang and Showman 2014, ApJ, 788, L6). Some brown dwarfs show phase shifts in the light curves among different wavelengths (e.g., Buenzli et al. 2012, ApJ, 760, L31; Yang et al. 2016, arXiv:1605.02708), indicating vertical variations of the cloud distribution. The current observational technique can barely detect the brightness changes on the surfaces of nearby brown dwarfs (Crossfield et al. 2014, Nature, 505, 654) let alone resolve detailed weather patterns that cause the flux variability. The infrared emission maps of Jupiter might shed light on this problem. Using COMICS at Subaru Telescope, VISIR at Very Large Telescope (VLT) and NASA's Infrared Telescope Facility (IRTF), we obtained infrared images of Jupiter over several nights at multiple wavelengths that are sensitive to several pressure levels from the stratosphere to the deep troposphere below the ammonia clouds. The rotational maps and emission light curves are constructed. The individual pixel brightness varies up to a hundred percent level and the variation of the full-disk brightness is around several percent. Both the shape and amplitude of the light curves are significantly distinct at different wavelengths. Variation of light curves at different epochs and phase shift among different wavelengths are observed. We will present principle component analysis to identify dominant emission features such as stable vortices, cloud holes and eddies in the belts and zones and strong emissions in the aurora region. A radiative transfer model is used to simulate those features to get a more quantitative understanding. This work provides rich insights on the relationship between observed light curves and weather on brown dwarfs and perhaps on directly imaged exoplanets in the future.

Sources of nitrous oxide and other climate relevant gases on surface area in a dairy free stall barn with solid floor and outside slurry storage

NASA Astrophysics Data System (ADS)

Schmithausen, Alexander J.; Trimborn, Manfred; Büscher, Wolfgang

2018-04-01

Livestock production systems in agriculture are one of the major emitters of greenhouse gases. So far, the focus of research in the dairy farm sector was primarily on ruminal methane (CH4) emissions. Emissions of nitrous oxide (N2O) usually arise from solid manure or in deep litter free stall barns. Release of N2O occurs as a result of interactions between organic material, nitrogen and moisture. Data of N2O emissions from modern dairy barns and liquid manure management systems are rare. Thus, the goal of this research was to determine the main sources of trace gas emissions at the dairy farm level, including N2O. Areas such as the scraped surface area where dry and wet conditions alternate are interesting. Possible sources of trace gases within and outside the barn were localised by measuring trace gas concentration rates from different dairy farm areas (e.g., areas covered with urine and excrement or slurry storage system) via the closed chamber technique. The results indicate typical emission ratios of carbon dioxide (CO2), CH4 and N2O in the various areas to generate comparable equivalent values. Calculated on the basis of nitrogen excretion from dairy cows, total emissions of N2O were much lower from barns than typically measured in fields. However, there were also areas within the barn with individual events and unexpected release factors of N2O concentrations such as urine patches, polluted areas and cubicles. Emission factors of N2O ranged from 1.1 to 5.0 mg m-2 d-1, respectively, for cleaned areas and urine patches. By considering the release factors of these areas and their proportion of the entire barn, total emission rates of 371 CO2-eq. LU-1 a-1, 36 CO2-eq. LU-1 a-1, and 1.7 kg CO2-eq. LU-1 a-1 for CO2, CH4 and N2O, respectively, were measured for the whole barn surface area. The CH4 emissions from surface area were stronger climate relevant comparing to N2O emissions, but compared to CH4 emissions from slurry storage or ruminal fermentation (not measured) even insignificant.

A SUCCESSFUL BROADBAND SURVEY FOR GIANT Ly{alpha} NEBULAE. II. SPECTROSCOPIC CONFIRMATION

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

Prescott, Moire K. M.; Dey, Arjun; Jannuzi, Buell T., E-mail: mkpresco@physics.ucsb.edu

2013-01-01

Using a systematic broadband search technique, we have carried out a survey for large Ly{alpha} nebulae (or Ly{alpha} {sup b}lobs{sup )} at 2 {approx}< z {approx}< 3 within 8.5 deg{sup 2} of the NOAO Deep Wide-Field Survey Booetes field, corresponding to a total survey comoving volume of Almost-Equal-To 10{sup 8} h {sup -3} {sub 70} Mpc{sup 3}. Here, we present our spectroscopic observations of candidate giant Ly{alpha} nebulae. Of 26 candidates targeted, 5 were confirmed to have Ly{alpha} emission at 1.7 {approx}< z {approx}< 2.7, 4 of which were new discoveries. The confirmed Ly{alpha} nebulae span a range of Ly{alpha}more » equivalent widths, colors, sizes, and line ratios, and most show spatially extended continuum emission. The remaining candidates did not reveal any strong emission lines, but instead exhibit featureless, diffuse, blue continuum spectra. Their nature remains mysterious, but we speculate that some of these might be Ly{alpha} nebulae lying within the redshift desert (i.e., 1.2 {approx}< z {approx}< 1.6). Our spectroscopic follow-up confirms the power of using deep broadband imaging to search for the bright end of the Ly{alpha} nebula population across enormous comoving volumes.« less

Role of future scenarios in understanding deep uncertainty in ...

EPA Pesticide Factsheets

The environment and its interactions with human systems, whether economic, social or political, are complex. Relevant drivers may disrupt system dynamics in unforeseen ways, making it difficult to predict future conditions. This kind of deep uncertainty presents a challenge to organizations faced with making decisions about the future, including those involved in air quality management. Scenario Planning is a structured process that involves the development of narratives describing alternative future states of the world, designed to differ with respect to the most critical and uncertain drivers. The resulting scenarios are then used to understand the consequences of those futures and to prepare for them with robust management strategies. We demonstrate a novel air quality management application of Scenario Planning. Through a series of workshops, important air quality drivers were identified. The most critical and uncertain drivers were found to be “technological development” and “change in societal paradigms.” These drivers were used as a basis to develop four distinct scenario storylines. The energy and emission implications of each storyline were then modeled using the MARKAL energy system model. NOX and SO2 emissions were found to decrease for all scenarios, largely a response to existing air quality regulations. Future-year emissions differed considerably from one scenario to another, however, with key differentiating factors being transition

A transient, flat spectrum radio pulsar near the Galactic Centre

NASA Astrophysics Data System (ADS)

Dexter, J.; Degenaar, N.; Kerr, M.; Deller, A.; Deneva, J.; Lazarus, P.; Kramer, M.; Champion, D.; Karuppusamy, R.

2017-06-01

Recent studies have shown possible connections between highly magnetized neutron stars ('magnetars'), whose X-ray emission is too bright to be powered by rotational energy, and ordinary radio pulsars. In addition to the magnetar SGR J1745-2900, one of the radio pulsars in the Galactic Centre (GC) region, PSR J1746-2850, had timing properties implying a large magnetic field strength and young age, as well as a flat spectrum. All characteristics are similar to those of rare, transient, radio-loud magnetars. Using several deep non-detections from the literature and two new detections, we show that this pulsar is also transient in the radio. Both the flat spectrum and large amplitude variability are inconsistent with the light curves and spectral indices of three radio pulsars with high magnetic field strengths. We further use frequent, deep archival imaging observations of the GC in the past 15 yr to rule out a possible X-ray outburst with a luminosity exceeding the rotational spin-down rate. This source, either a transient magnetar without any detected X-ray counterpart or a young, strongly magnetized radio pulsar producing magnetar-like radio emission, further blurs the line between the two categories. We discuss the implications of this object for the radio emission mechanism in magnetars and for star and compact object formation in the GC.

Clusters, Groups, and Filaments in the Chandra Deep Field-South up to Redshift 1

NASA Astrophysics Data System (ADS)

Dehghan, S.; Johnston-Hollitt, M.

2014-03-01

We present a comprehensive structure detection analysis of the 0.3 deg2 area of the MUSYC-ACES field, which covers the Chandra Deep Field-South (CDFS). Using a density-based clustering algorithm on the MUSYC and ACES photometric and spectroscopic catalogs, we find 62 overdense regions up to redshifts of 1, including clusters, groups, and filaments. We also present the detection of a relatively small void of ~10 Mpc2 at z ~ 0.53. All structures are confirmed using the DBSCAN method, including the detection of nine structures previously reported in the literature. We present a catalog of all structures present, including their central position, mean redshift, velocity dispersions, and classification based on their morphological and spectroscopic distributions. In particular, we find 13 galaxy clusters and 6 large groups/small clusters. Comparison of these massive structures with published XMM-Newton imaging (where available) shows that 80% of these structures are associated with diffuse, soft-band (0.4-1 keV) X-ray emission, including 90% of all objects classified as clusters. The presence of soft-band X-ray emission in these massive structures (M 200 >= 4.9 × 1013 M ⊙) provides a strong independent confirmation of our methodology and classification scheme. In the closest two clusters identified (z < 0.13) high-quality optical imaging from the Deep2c field of the Garching-Bonn Deep Survey reveals the cD galaxies and demonstrates that they sit at the center of the detected X-ray emission. Nearly 60% of the clusters, groups, and filaments are detected in the known enhanced density regions of the CDFS at z ~= 0.13, 0.52, 0.68, and 0.73. Additionally, all of the clusters, bar the most distant, are found in these overdense redshift regions. Many of the clusters and groups exhibit signs of ongoing formation seen in their velocity distributions, position within the detected cosmic web, and in one case through the presence of tidally disrupted central galaxies exhibiting trails of stars. These results all provide strong support for hierarchical structure formation up to redshifts of 1.

Vertical wind shear characteristics that promote supercell-to-MCS transitions

NASA Astrophysics Data System (ADS)

Peters, J. M.

2017-12-01

What causes supercells to transition into MCSs in some situations, but not others? To explore this question, I first examined observed environmental characteristics of supercell events when MCSs formed, and compared them to the analogous environmental characteristics of supercell events when MCSs did not form. During events when MCS growth occurred, 0-1 km (low-level) vertical wind shear was stronger and 0-10 km (deep-layer) vertical wind shear was weaker than the wind shear during events when MCS growth did not occur. Next, I used idealized simulations of supercell thunderstorms to understand the connections between low-level and deep-layer shear and MCS growth. Compared to simulations with strong deep-layer shear, the simulations with weak deep-layer shear had rain in the storm's forward-flank downdraft (FFD) that fell closer to the updraft, fell through storm-moistened air and evaporated less, and produced a more intense FFD. Compared to simulations with weak low-level shear, the simulations with stronger low-level shear showed enhanced northward low-level hydrometeor transport into the FFD. Environments with strong low-level shear and weak deep-layer shear therefore conspired to produce a storm with a more intense FFD cold pool, when compared to environments with weak low-level shear and/or strong deep-layer shear. This strong FFD periodically disrupted the supercells' mesocyclones, and favorably interacted with westerly wind shear to produce widespread linear convection initiation, which drove MCS growth. These results suggest that increasing low-level wind shear after dark - while commonly assumed to enhance tornado potential - may in fact drive MCS growth and reduce tornado potential, unless it is combined with sufficiently strong deep layer shear.

Clean Air Act, TRI drive emission reduction

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

Heller, K.

1994-06-22

When asked to rank priority environmental engineering projects, many chemical firms put emissions reduction first. The chief motivators are the need to comply with rules governing major sources of hazardous air pollutants (HAPS) under the Clean Air Act Amendments of 1990 (CAA), along with the need to reduce the volumes of chemicals on EPA`s Toxics Release Inventory (TRI). Deep-welling of toxics is getting special attention as the practice adds considerably to TRI numbers. {open_quotes}We want to eliminate our air toxics so that we can get entirely out of the [CAA] Maximum Achievable Control Technology (MACT) requirements,{close_quotes} says Thomas Zosel, manager/pollutionmore » prevention programs for 3M (St. Paul, MN). He estimates that 3M`s 1993 total research expenditures for environmental improvements were at least $200 million, out of an annual research budget of a little more than $1 billion. And, he says, the spending level is not expected to drop. Among its many efforts, 3M is striving to move away from solvents in all of its processes. To help reach that goal, the company developed a {open_quotes}waste measurement metric{close_quotes} that calculates the wastes produced by each of the company`s 50 operating divisions. In the case of Magic Tape, the company eliminated solvent emission by switching to a water-based adhesive that does not require a solvent.« less

Ultrafine Particles from Traffic Emissions and Children's Health (UPTECH) in Brisbane, Queensland (Australia): study design and implementation.

PubMed

Ezz, Wafaa Nabil; Mazaheri, Mandana; Robinson, Paul; Johnson, Graham R; Clifford, Samuel; He, Congrong; Morawska, Lidia; Marks, Guy B

2015-02-02

Ultrafine particles are particles that are less than 0.1 micrometres (µm) in diameter. Due to their very small size they can penetrate deep into the lungs, and potentially cause more damage than larger particles. The Ultrafine Particles from Traffic Emissions and Children's Health (UPTECH) study is the first Australian epidemiological study to assess the health effects of ultrafine particles on children's health in general and peripheral airways in particular. The study is being conducted in Brisbane, Australia. Continuous indoor and outdoor air pollution monitoring was conducted within each of the twenty five participating school campuses to measure particulate matter, including in the ultrafine size range, and gases. Respiratory health effects were evaluated by conducting the following tests on participating children at each school: spirometry, forced oscillation technique (FOT) and multiple breath nitrogen washout test (MBNW) (to assess airway function), fraction of exhaled nitric oxide (FeNO, to assess airway inflammation), blood cotinine levels (to assess exposure to second-hand tobacco smoke), and serum C-reactive protein (CRP) levels (to measure systemic inflammation). A pilot study was conducted prior to commencing the main study to assess the feasibility and reliably of measurement of some of the clinical tests that have been proposed for the main study. Air pollutant exposure measurements were not included in the pilot study.

Ultrafine Particles from Traffic Emissions and Children’s Health (UPTECH) in Brisbane, Queensland (Australia): Study Design and Implementation

PubMed Central

Ezz, Wafaa Nabil; Mazaheri, Mandana; Robinson, Paul; Johnson, Graham R.; Clifford, Samuel; He, Congrong; Morawska, Lidia; Marks, Guy B.

2015-01-01

Ultrafine particles are particles that are less than 0.1 micrometres (µm) in diameter. Due to their very small size they can penetrate deep into the lungs, and potentially cause more damage than larger particles. The Ultrafine Particles from Traffic Emissions and Children’s Health (UPTECH) study is the first Australian epidemiological study to assess the health effects of ultrafine particles on children’s health in general and peripheral airways in particular. The study is being conducted in Brisbane, Australia. Continuous indoor and outdoor air pollution monitoring was conducted within each of the twenty five participating school campuses to measure particulate matter, including in the ultrafine size range, and gases. Respiratory health effects were evaluated by conducting the following tests on participating children at each school: spirometry, forced oscillation technique (FOT) and multiple breath nitrogen washout test (MBNW) (to assess airway function), fraction of exhaled nitric oxide (FeNO, to assess airway inflammation), blood cotinine levels (to assess exposure to second-hand tobacco smoke), and serum C-reactive protein (CRP) levels (to measure systemic inflammation). A pilot study was conducted prior to commencing the main study to assess the feasibility and reliably of measurement of some of the clinical tests that have been proposed for the main study. Air pollutant exposure measurements were not included in the pilot study. PMID:25648226

Positron-induced Auger-electron study of the Ge(100) surface: Positron thermal desorption and surface condition

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

Soininen, E.; Schwab, A.; Lynn, K.G.

1991-05-01

Positron-annihilation-induced Auger-electron spectroscopy (PAES) was used to study the effects of oxygen, residual gases, and temperature on a Ge(100) surface. Three low-energy Auger peaks were detected at 50, 90, and 100--150 eV, attributed to {ital M}{sub 2,3}{ital M4}{ital M4}, {ital M}{sub 2,3}{ital M4}{ital V}, and {ital M}{sub 1}{ital M4}{ital M4} Auger transitions, respectively. An estimated (4{plus minus}1)% of the surface-trapped positrons annihilate with Ge 3{ital p}--level electrons. The sensitivity of PAES to the surface condition is demonstrated. The PAES yield from a Ge(100) surface is reduced at elevated temperatures, in accord with an activation process earlier found in several positroniummore » (Ps) -fraction experiments. A desorption model adopted from these studies does not describe accurately the PAES results at higher temperatures ({gt}500 {degree}C), where the PAES intensity levels off to 5% of the room-temperature value. Possible sources for the discrepancy are discussed and models for positron trapping to deep surface traps are introduced. On the Ge(100) surface, an upper limit for Ps emission near the melting point is 97%. The error in calibration parameters due to the earlier assumption of 100% Ps emission seems to introduce only small errors into the Ps-fraction measurements.« less

Ethanol emission from loose corn silage and exposed silage particles

NASA Astrophysics Data System (ADS)

Hafner, Sasha D.; Montes, Felipe; Rotz, C. Alan; Mitloehner, Frank

2010-11-01

Silage on dairy farms has been identified as a major source of volatile organic compound (VOC) emissions. However, rates of VOC emission from silage are not accurately known. In this work, we measured ethanol (a dominant silage VOC) emission from loose corn silage and exposed corn silage particles using wind tunnel systems. Flux of ethanol was highest immediately after exposing loose silage samples to moving air (as high as 220 g m -2 h -1) and declined by as much as 76-fold over 12 h as ethanol was depleted from samples. Emission rate and cumulative 12 h emission increased with temperature, silage permeability, exposed surface area, and air velocity over silage samples. These responses suggest that VOC emission from silage on farms is sensitive to climate and management practices. Ethanol emission rates from loose silage were generally higher than previous estimates of total VOC emission rates from silage and mixed feed. For 15 cm deep loose samples, mean cumulative emission was as high as 170 g m -2 (80% of initial ethanol mass) after 12 h of exposure to an air velocity of 5 m s -1. Emission rates measured with an emission isolation flux chamber were lower than rates measured in a wind tunnel and in an open setting. Results show that the US EPA emission isolation flux chamber method is not appropriate for estimating VOC emission rates from silage in the field.

Estimated Emissions from the Prime-Movers of Unconventional Natural Gas Well Development Using Recently Collected In-Use Data in the United States.

PubMed

Johnson, Derek; Heltzel, Robert; Nix, Andrew; Darzi, Mahdi; Oliver, Dakota

2018-05-01

Natural gas from shale plays dominates new production and growth. However, unconventional well development is an energy intensive process. The prime movers, which include over-the-road service trucks, horizontal drilling rigs, and hydraulic fracturing pumps, are predominately powered by diesel engines that impact air quality. Instead of relying on certification data or outdated emission factors, this model uses new in-use emissions and activity data combined with historical literature to develop a national emissions inventory. For the diesel only case, hydraulic fracturing engines produced the most NO x emissions, while drilling engines produced the most CO emissions, and truck engines produced the most THC emissions. By implementing dual-fuel and dedicated natural gas engines, total fuel energy consumed, CO 2 , CO, THC, and CH 4 emissions would increase, while NO x emissions, diesel fuel consumption, and fuel costs would decrease. Dedicated natural gas engines offered significant reductions in NO x emissions. Additional scenarios examined extreme cases of full fleet conversions. While deep market penetrations could reduce fuel costs, both technologies could significantly increase CH 4 emissions. While this model is based on a small sample size of engine configurations, data were collected during real in-use activity and is representative of real world activity.

VizieR Online Data Catalog: CANDELS z~2 galaxy properties (Trump+, 2014)

NASA Astrophysics Data System (ADS)

Trump, J. R.; Barro, G.; Juneau, S.; Weiner, B. J.; Luo, B.; Brammer, G. B.; Bell, E. F.; Brandt, W. N.; Dekel, A.; Guo, Y.; Hopkins, P. F.; Koo, D. C.; Kocevski, D. D.; McIntosh, D. H.; Momcheva, I.; Faber, S. M.; Ferguson, H. C.; Grogin, N. A.; Kartaltepe, J.; Koekemoer, A. M.; Lotz, J.; Maseda, M.; Mozena, M.; Nandra, K.; Rosario, D. J.; Zeimann, G. R.

2017-04-01

We select a sample of 44 clumpy galaxies from the Great Observatories Origins Deep Survey South (GOODS-S; Giavalisco et al. 2004ApJ...600L..93G) region of CANDELS. For comparison, we also construct mass-matched samples of 41 smooth (non-clumpy) and 35 intermediate galaxies. All galaxies have H<24 (to ensure reliable classification of clumpiness) and have [O III] detected at the 3σ level (for reliable AGN line ratio diagnostics) in the redshift range 1.3

Semiconductor-based narrow-line and high-brilliance 193-nm laser system for industrial applications

NASA Astrophysics Data System (ADS)

Opalevs, D.; Scholz, M.; Stuhler, J.; Gilfert, C.; Liu, L. J.; Wang, X. Y.; Vetter, A.; Kirner, R.; Scharf, T.; Noell, W.; Rockstuhl, C.; Li, R. K.; Chen, C. T.; Voelkel, R.; Leisching, P.

2018-02-01

We present a novel industrial-grade prototype version of a continuous-wave 193 nm laser system entirely based on solid state pump laser technology. Deep-ultraviolet emission is realized by frequency-quadrupling an amplified diode laser and up to 20 mW of optical power were generated using the nonlinear crystal KBBF. We demonstrate the lifetime of the laser system for different output power levels and environmental conditions. The high stability of our setup was proven in > 500 h measurements on a single spot, a crystal shifter multiplies the lifetime to match industrial requirements. This laser improves the relative intensity noise, brilliance, wall-plug efficiency and maintenance cost significantly. We discuss first lithographic experiments making use of this improvement in photon efficiency.

Deep Levels of Processing Elicit a Distinctiveness Heuristic: Evidence from the Criterial Recollection Task

ERIC Educational Resources Information Center

Gallo, David A.; Meadow, Nathaniel G.; Johnson, Elizabeth L.; Foster, Katherine T.

2008-01-01

Thinking about the meaning of studied words (deep processing) enhances memory on typical recognition tests, relative to focusing on perceptual features (shallow processing). One explanation for this levels-of-processing effect is that deep processing leads to the encoding of more distinctive representations (i.e., more unique semantic or…

Methane and nitrous oxide measurements onboard the UK Atmospheric Research Aircraft using quantum cascade laser spectrometry (QCL)

NASA Astrophysics Data System (ADS)

Muller, J. B.; O'Shea, S.; Dorsey, J.; Bauguitte, S.; Cain, M.; Allen, G.; Percival, C. J.; Gallagher, M. W.

2012-12-01

A Aerodyne Research© Mini-Quantum Cascade Laser (QCL) spectrometer was installed on the UK Facility of Airborne Atmospheric Measurements (FAAM) BAe-146 research aircraft and employed during summer 2012. Methane (CH4) and nitrous oxide (N2O) concentrations were measured within the Arctic Circle as part of the MAMM project (Methane and other greenhouse gases in the Arctic - Measurements, process studies and Modelling) as well as around the UK as part of the ClearfLo project (Clean Air for London). A range of missions were flown, including deep vertical profiles up to the stratosphere, providing concentration profiles of CH4 and N2O, as well as low altitude level runs exploring near surface diffuse emission sources such as the wetlands in Arctic Lapland and point emissions sources such as gas platforms off the UK coast. Significant pollution plumes were observed both in the Arctic and around the UK with elevated CH4 concentrations, as well as enhanced CO, O3 and aerosol levels. The NAME Lagrangian particle dispersion model will be used to investigate the origins of these CH4 plumes to identify the locations of the emissions sources. The first set of flights using QCL on the FAAM research aircraft have been successful and regular in-flight calibrations (high/low span) and target concentrations were used to determine instrument accuracy and precision. Additional data quality control checks could be made by comparison with an onboard Los Gatos Fast Greenhouse Gas Analyser (FGGA) for CO2 and CH4 and provide the basis for further instrument development and implementation for future Arctic MAMM flights during spring and summer 2013.

A Celestial Reference Frame at X/ka-Band (8.4/32 Ghz) for Deep Space Navigation

NASA Technical Reports Server (NTRS)

Jacobs, C. S.; Clark, J. E.; Garcia-Miro, C.; Horiuchi, S.; Romero-Wolf, A.; Snedeker, L.; Sotuela, I.

2012-01-01

Deep space tracking and navigation are done in a quasi-inertial reference frame based upon the angular positions of distant active galactic nuclei (AGN). These objects, which are found at extreme distances characterized by median redshifts of z = 1, are ideal for reference frame definition because they exhibit no measurable parallax or proper motion. They are thought to be powered by super massive black holes whose gravitational energy drives galactic sized relativistic jets. These jets produce synchrotron emissions which are detectable by modern radio techniques such as Very Long baseline Interferometry (VLBI).

Hydrogen-bearing iron peroxide and its implications to the deep Earth

NASA Astrophysics Data System (ADS)

Liu, J.; Hu, Q.; Kim, D. Y.; Wu, Z.; Wang, W.; Alp, E. E.; Yang, L.; Xiao, Y.; Meng, Y.; Chow, P.; Greenberg, E.; Prakapenka, V. B.; Mao, H. K.; Mao, W. L.

2017-12-01

Hydrous materials subducted into the deep mantle may play a significant role in the geophysical and geochemical processes of the lower mantle through geological time, but their roles have not become clear yet in the region. Hydrogen-bearing iron peroxide (FeO2Hx) was recently discovered to form through dehydrogenation of goethite (e.g., FeOOH) and the reaction between hematite (Fe2O3) and water under deep lower mantle conditions. We conducted synchrotron Mössbauer, X-ray absorption, and X-ray emission spectroscopy measurements to investigate the electronic spin and valence states of iron in hydrogen-bearing iron peroxide (FeO2Hx) in-situ at high pressures. Combined with theoretical calculations and other high-pressure experiments (i.e., nuclear resonant inelastic x-ray scattering spectroscopy and X-ray diffraction coupled with laser-heated diamond-anvil cell techniques), we find that the intriguing properties of FeO2Hx could shed light on the origin of a number of the observed geochemical and geophysical anomalies in the deep Earth.

Designed Er(3+)-singly doped NaYF4 with double excitation bands for simultaneous deep macroscopic and microscopic upconverting bioimaging.

PubMed

Wen, Xuanyuan; Wang, Baoju; Wu, Ruitao; Li, Nana; He, Sailing; Zhan, Qiuqiang

2016-06-01

Simultaneous deep macroscopic imaging and microscopic imaging is in urgent demand, but is challenging to achieve experimentally due to the lack of proper fluorescent probes. Herein, we have designed and successfully synthesized simplex Er(3+)-doped upconversion nanoparticles (UCNPs) with double excitation bands for simultaneous deep macroscopic and microscopic imaging. The material structure and the excitation wavelength of Er(3+)-singly doped UCNPs were further optimized to enhance the upconversion emission efficiency. After optimization, we found that NaYF4:30%Er(3+)@NaYF4:2%Er(3+) could simultaneously achieve efficient two-photon excitation (2PE) macroscopic tissue imaging and three-photon excitation (3PE) deep microscopic when excited by 808 nm continuous wave (CW) and 1480 nm CW lasers, respectively. In vitro cell imaging and in vivo imaging have also been implemented to demonstrate the feasibility and potential of the proposed simplex Er(3+)-doped UCNPs as bioprobe.

Dual-wavelength photo-Hall effect spectroscopy of deep levels in high resistive CdZnTe with negative differential photoconductivity

NASA Astrophysics Data System (ADS)

Musiienko, A.; Grill, R.; Moravec, P.; Korcsmáros, G.; Rejhon, M.; Pekárek, J.; Elhadidy, H.; Šedivý, L.; Vasylchenko, I.

2018-04-01

Photo-Hall effect spectroscopy was used in the study of deep levels in high resistive CdZnTe. The monochromator excitation in the photon energy range 0.65-1.77 eV was complemented by a laser diode high-intensity excitation at selected photon energies. A single sample characterized by multiple unusual features like negative differential photoconductivity and anomalous depression of electron mobility was chosen for the detailed study involving measurements at both the steady and dynamic regimes. We revealed that the Hall mobility and photoconductivity can be both enhanced and suppressed by an additional illumination at certain photon energies. The anomalous mobility decrease was explained by an excitation of the inhomogeneously distributed deep level at the energy Ev + 1.0 eV, thus enhancing potential non-uniformities. The appearance of negative differential photoconductivity was interpreted by an intensified electron occupancy of that level by a direct valence band-to-level excitation. Modified Shockley-Read-Hall theory was used for fitting experimental results by a model comprising five deep levels. Properties of the deep levels and their impact on the device performance were deduced.

Photoluminescence characteristics of ZnTe bulk crystal and ZnTe epilayer grown on GaAs substrate by MOVPE

NASA Astrophysics Data System (ADS)

Lü, Hai-Yan; Mu, Qi; Zhang, Lei; Lü, Yuan-Jie; Ji, Zi-Wu; Feng, Zhi-Hong; Xu, Xian-Gang; Guo, Qi-Xin

2015-12-01

Excitation power and temperature-dependent photoluminescence (PL) spectra of the ZnTe epilayer grown on (100) GaAs substrate and ZnTe bulk crystal are investigated. The measurement results show that both the structures are of good structural quality due to their sharp bound excitonic emissions and absence of the deep level structural defect-related emissions. Furthermore, in contrast to the ZnTe bulk crystal, although excitonic emissions for the ZnTe epilayer are somewhat weak, perhaps due to As atoms diffusing from the GaAs substrate into the ZnTe epilayer and/or because of the strain-induced degradation of the crystalline quality of the ZnTe epilayer, neither the donor-acceptor pair (DAP) nor conduction band-acceptor (e-A) emissions are observed in the ZnTe epilayer. This indicates that by further optimizing the growth process it is possible to obtain a high-crystalline quality ZnTe heteroepitaxial layer that is comparable to the ZnTe bulk crystal. Project supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20120131110006), the Key Science and Technology Program of Shandong Province, China (Grant No. 2013GGX10221), the Key Laboratory of Functional Crystal Materials and Device (Shandong University, Ministry of Education), China (Grant No. JG1401), the National Natural Science Foundation of China (Grant No. 61306113), the Major Research Plan of the National Natural Science Foundation of China (Grant No. 91433112), and the Partnership Project for Fundamental Technology Researches of the Ministry of Education, Culture, Sports, Science and Technology, Japan.

The Mechanics of Deep Earthquakes: An Experimental Investigation of Slab Phase Changes

NASA Astrophysics Data System (ADS)

Santangeli, J. R.; Dobson, D. P.; Hunt, S. A.; Meredith, P. G.

2014-12-01

The mechanics of deep earthquakes have remained a puzzle for researchers since 1928 when they were first accurately identified by Kiyoo Wadati1 in Japan. Deep earthquakes show a split distribution, with peaks centered around ~370-420km and ~520-550km. As these events are limited to subducting slabs, it is accepted that they may be due to phase changes in metastable slab material. Indeed, conditions at ~350km depth are nominally appropriate for the olivine - wadsleyite transition, consistent with the anticrack mechanism previously observed in (Mg,Fe)2SiO42. The additional peak around 520km suggests that there is another siesmogenic phase change; candidates include Ca-garnet -> Ca-perovskite, wadsleyite -> ringwoodite and enstatite -> majorite or ilmenite. Importantly, for large scale seismogenesis to occur candidate phase changes must be susceptible to a runaway mechanism. Typically this involves the release of heat during exothermic reactions, which acts to increase reaction and nucleation rates. It is worth noting that the post-spinel reaction (sp -> pv + fp) marks the cessation of deep earthquakes; possibly as a result of being endothermic. This research aims to identify which of these candidates could be responsible for seismogenesis. We use high-pressure split cylinder multi-anvil experiments with acoustic emission detection. Low-pressure analogue materials have been used to allow greater cell sizes and thus sample volumes to enable accurate location of AE to within the sample. The candidate phase is annealed below its phase boundary, and then taken through the boundary by further compression. Acoustic emissions, if generated, are observed in real time and later processed to ensure they emanate from within the sample volume. Initial results indicate that the pryroxene -> ilmenite transition in MgGeO3 is seismogenic, with several orders of magnitude increase in the energy of AE concurrent with the phase boundary. References:1) Wadati, K. (1928) Shallow and deep earthquakes. Geophysical Magazine. 1, 162-202 2) Green, H., W., & Burnley, P., C. (1989) A new self-organizing mechanism for deep-focus earthquakes. Nature. 341, 733-737

Computational Modeling of the Geologic Sequestration of Carbon Dioxide

EPA Science Inventory

Geologic sequestration of CO2 is a component of C capture and storage (CCS), an emerging technology for reducing CO2 emissions to the atmosphere, and involves injection of captured CO2 into deep subsurface formations. Similar to the injection of hazardous wastes, before injection...

SUBSURFACE PROPERTY RIGHTS: IMPLICATIONS FOR GEOLOGIC CO2 STORAGE

EPA Science Inventory

The paper discusses subsurface property rights as they apply to geologic sequestration (GS) of carbon dioxide (CO2). GS projects inject captured CO2 into deep (greater than ~1 km) geologic formations for the explicit purpose of avoiding atmospheric emission of CO2. Because of the...

SUBSURFACE PROPERTY RIGHTS: IMPLICATIONS FOR GEOLOGIC CO2 SEQUESTRATION

EPA Science Inventory

The chapter discusses subsurface property rights as they apply to geologic sequestration (GS) of carbon dioxide (CO2). GS projects inject captured CO2 into deep (greater than ~1 km) geologic formations for the explicit purpose of avoiding atmospheric emission of CO2. Because of t...

40 CFR Table Jj-7 to Subpart Jj of... - Nitrous Oxide Emission Factors (kg N2O-N/kg Kjdl N)

Code of Federal Regulations, 2011 CFR

2011-07-01

...) 0.07 Deep bedding for cattle and swine (no mix) 0.01 Manure Composting (in vessel) 0.006 Manure Composting (intensive) 0.1 Manure Composting (passive) 0.01 Manure Composting (static) 0.006 Aerobic...

Measurement of stimulated Hawking emission in an analogue system.

PubMed

Weinfurtner, Silke; Tedford, Edmund W; Penrice, Matthew C J; Unruh, William G; Lawrence, Gregory A

2011-01-14

Hawking argued that black holes emit thermal radiation via a quantum spontaneous emission. To address this issue experimentally, we utilize the analogy between the propagation of fields around black holes and surface waves on moving water. By placing a streamlined obstacle into an open channel flow we create a region of high velocity over the obstacle that can include surface wave horizons. Long waves propagating upstream towards this region are blocked and converted into short (deep-water) waves. This is the analogue of the stimulated emission by a white hole (the time inverse of a black hole), and our measurements of the amplitudes of the converted waves demonstrate the thermal nature of the conversion process for this system. Given the close relationship between stimulated and spontaneous emission, our findings attest to the generality of the Hawking process.

Imaging AGN Feedback in NGC 3393 with CHEERS

NASA Astrophysics Data System (ADS)

Maksym, W. Peter; Fabbiano, Giuseppina; Elvis, Martin; Karovska, Margarita; Paggi, Alessandro; Wang, Junfeng; Storchi-Bergmann, Thaisa

2016-01-01

The CHandra Extended Emission-line Region Survey (CHEERS) is the 'ultimate' resolution X-ray imaging survey of nearby far-IR selected AGN. By comparing deep Chandra observations with complementary HST and radio data, we investigate the morphology of the extended narrow-line region on scales of <100 pc. We present new results on the gas surrounding the compton-thick AGN NGC 3393. The luminous extended narrow-line X-ray emission from this gas allows us to study the role and extent of AGN feedback as sub-kpc jets interact with the surrounding ISM.

Imaging AGN Feedback in NGC 3393 with CHEERS

NASA Astrophysics Data System (ADS)

Paggi, Alessandro; Maksym, W. Peter; Fabbiano, Giuseppina; Elvis, Martin; Karovska, Margarita; Wang, Junfeng; Storchi-Bergmann, Thaisa

2016-04-01

The CHandra Extended Emission-line Region Survey (CHEERS) is the 'ultimate' resolution X-ray imaging survey of nearby far-IR selected AGN. By comparing deep Chandra observations with complementary HST and radio data, we investigate the morphology of the extended narrow-line region on scales of <100 pc. We present new results on the gas surrounding the compton-thick AGN NGC 3393. The luminous extended narrow-line X-ray emission from this gas allows us to study the role and extent of AGN feedback as sub-kpc jets interact with the surrounding ISM.

Extended Hard-X-Ray Emission in the Inner Few Parsecs of the Galaxy

NASA Technical Reports Server (NTRS)

Perez, Kerstin; Hailey, Charles J.; Bauer, Franz E.; Krivonos, Roman A.; Mori, Kaya; Baganoff, Frederick K.; Barriere, Nicholas M.; Boggs, Steven E.; Christensen, Finn E.; Craig, William W.;

A Late-time Flattening of Light Curves in Gamma-Ray Burst Afterglows

NASA Astrophysics Data System (ADS)

Sironi, Lorenzo; Giannios, Dimitrios

2013-12-01

The afterglow emission from gamma-ray bursts (GRBs) is usually interpreted as synchrotron radiation from relativistic electrons accelerated at the GRB external shock. We investigate the temporal decay of the afterglow emission at late times, when the bulk of the shock-accelerated electrons are non-relativistic (the "deep Newtonian phase," as denoted by Huang and Cheng). We assume that the electron spectrum in the deep Newtonian phase is a power-law distribution in momentum with slope p, as dictated by the theory of Fermi acceleration in non-relativistic shocks. For a uniform circumburst medium, the deep Newtonian phase begins at t{_{\\scriptsize {DN}}}\\sim 3\\,\\epsilon _{e,-1}^{5/6}t{_{\\scriptsize {ST}}}, where t ST marks the transition of the blast wave to the non-relativistic, spherically symmetric Sedov-Taylor (ST) solution, and epsilon e = 0.1 epsilon e, -1 quantifies the amount of shock energy transferred to the electrons. For typical parameters, the deep Newtonian stage starts ~0.5 to several years after the GRB. The radio flux in this phase decays as F νvpropt -3(p + 1)/10vpropt -(0.9÷1.2), for a power-law slope 2 < p < 3. This is shallower than the scaling F νvpropt -3(5p - 7)/10vpropt -(0.9÷2.4) derived by Frail et al., which only applies if the GRB shock is non-relativistic, but the electron distribution still peaks at ultra-relativistic energies (a regime that is relevant for a narrow time interval, and only if t DN >~ t ST, namely, epsilon e >~ 0.03). We discuss how the deep Newtonian phase can be reliably used for GRB calorimetry, and we comment on the good detection prospects of trans-relativistic blast waves at 0.1÷10 GHz with the Karl G. Jansky Very Large Array and LOw-Frequency ARray.

Interactions between atmospheric circulation, nutrient deposition, and tropical forest primary production (Invited)

NASA Astrophysics Data System (ADS)

Randerson, J. T.; Chen, Y.; Rogers, B. M.; Morton, D. C.; van der Werf, G.; Mahowald, N. M.

2010-12-01

Tropical forests influence regional and global climate by means of several pathways, including by modifying surface energy exchange and by forming clouds. High levels of precipitation, leaching, and soil weathering limit nutrient availability in these ecosystems. Phosphorus (P) is a key element limiting net primary production, and in some areas, including forests recovering from prior disturbance, nitrogen (N) also may limit some components of production. Here we quantified atmospheric P and N inputs to these forests from fires using satellite-derived estimates of emissions and atmospheric models. In Africa and South America, cross-biome transport of fire-emitted aerosols and reactive N gases from savannas and areas near the deforestation frontier increased deposition of P and N in interior forests. Equatorward atmospheric transport during the dry (fire) season in one hemisphere was linked with surface winds moving toward the inter-tropical convergence zone (ITCZ) in the other hemisphere. Deposition levels were higher in tropical forests in Africa than in South America because of large savanna areas with high levels of fire emissions in both southern and northern Africa. We conclude by describing a potential feedback loop by which equatorward transport of fire emissions, dust, and spores sustains the productivity of tropical forests. We specifically assessed evidence that savanna-to-forest atmospheric transport of nutrients increases forest productivity, height, and rates of evapotranspiration (ET). In parallel, we examined the degree to which increases in ET and surface roughness in tropical forests have the potential to strengthen several components of the Hadley circulation, including deep convection, equatorward return flow (near the surface), and the intensity of seasonal drought in the subtropics (thereby increasing fires). These interactions are important for understanding biogeochemical - climate interactions on millennial timescales and for quantifying how contemporary changes in fire activity and land use are changing the global carbon cycle.

Laboratory measurements of the 3.7-20 cm wavelength opacity of sulfur dioxide and carbon dioxide under simulated conditions for the deep atmosphere of Venus

NASA Astrophysics Data System (ADS)

Steffes, Paul G.; Shahan, Patrick; Christopher Barisich, G.; Bellotti, Amadeo

2015-01-01

In the past two decades, multiple observations of Venus have been made at X-Band (3.6 cm) using the Jansky Very Large Array (VLA), and maps have been created of the 3.6 cm emission from Venus (see, e.g., Devaraj, K. [2011]. The Centimeter- and Millimeter-Wavelength Ammonia Absorption Spectra under Jovian Conditions. PhD Thesis, Georgia Institute of Technology, Atlanta, GA). Since the emission morphology is related both to surface features and to deep atmospheric absorption from CO2 and SO2 (see, e.g., Butler, B.J., Steffes, P.G., Suleiman, S.H., Kolodner, M.A., Jenkins, J.M. [2001]. Icarus 154, 226-238), knowledge of the microwave absorption properties of sulfur dioxide in a carbon dioxide atmosphere under conditions for the deep atmosphere of Venus is required for proper interpretation. Except for a single measurement campaign conducted at a single wavelength (3.2 cm) over 40 years ago (Ho, W., Kaufman, I.A., Thaddeus, P. [1966]. J. Geophys. Res. 71, 5091-5108), no measurements of the centimeter-wavelength properties of any Venus atmospheric constituent have been conducted under conditions characteristic of the deep atmosphere (pressures from 10 to 92 bars and temperatures from 400 to 700 K). New measurements of the microwave properties of SO2 and CO2 at wavelengths from 3.7 to 20 cm have been conducted under simulated conditions for the deep atmosphere of Venus, using a new high-pressure system. Results from this measurement campaign conducted at temperatures from 430 K to 560 K and at pressures up to 92 bars are presented. Results indicate that the model for the centimeter-wavelength opacity from pure CO2 (Ho, W., Kaufman, I.A., Thaddeus, P. [1966]. J. Geophys. Res. 71, 5091-5108), is valid over the entire centimeter-wavelength range under simulated conditions for the deep atmosphere of Venus. Additionally, the laboratory results indicate that both of the models for the centimeter-wavelength opacity of SO2 in a CO2 atmosphere from Suleiman et al. (Suleiman, S.H., Kolodner, M.A., Steffes, P.G. [1996]. J. Geophys. Res. 101, 4623-4635) and from Fahd and Steffes (Fahd, A.K., Steffes, P.G. [1992]. Icarus 97, 200-210) can reliably be used under conditions of the deep atmosphere of Venus.

Effect of retrapping on the persistent luminescence in strontium silicate orange–yellow phosphor

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

Xu, Xuhui; Yu, Xue, E-mail: yuyu6593@126.com; Zhou, Dacheng

2013-10-15

The orange–yellow long persistent luminescence in Sr{sub 3}SiO{sub 5}:Eu{sup 2+}, Er{sup 3+} with the chromaticity coordination of (0.48, 0.49) can persist for over 20 h above the recognizable intensity level (≥0.32 mcd/m{sup 2}) because of retrapping carriers by the deep traps. The incorporation of Er{sup 3+} into Sr{sub 3}SiO{sub 5}:Eu{sup 2+} generates a large number of shallow traps responsible for the fast decay component as well as deep traps responsible for the decay tail of the LPL. It demonstrates that the retrapping of the carrier released from a trap plays an important role in the persistent luminescence process. - Graphicalmore » abstract: LPL decay curves of Sr{sub 3−x−y}SiO{sub 5}:xEu{sup 2+}, yEr{sup 3+} (x=0.0025, y=0, 0.0025). Inset: Orange–yellow emission images recorded using a classic Reflex digital camera with exposure times varying with the persistent luminescence times. Display Omitted - Highlights: • The persistence time of Sr{sub 3}SiO{sub 5}:Eu{sup 2+}, Er{sup 3+} lasts over 20 h above the recognizable intensity level. • The incorporation of Er{sup 3+} into Sr{sub 3}SiO{sub 5}:Eu{sup 2+} generates a large number of shallow traps. • The experimental results provide an evidence for the retrapping process in LPL processes.« less

DeepMirTar: a deep-learning approach for predicting human miRNA targets.

PubMed

Wen, Ming; Cong, Peisheng; Zhang, Zhimin; Lu, Hongmei; Li, Tonghua

2018-06-01

MicroRNAs (miRNAs) are small noncoding RNAs that function in RNA silencing and post-transcriptional regulation of gene expression by targeting messenger RNAs (mRNAs). Because the underlying mechanisms associated with miRNA binding to mRNA are not fully understood, a major challenge of miRNA studies involves the identification of miRNA-target sites on mRNA. In silico prediction of miRNA-target sites can expedite costly and time-consuming experimental work by providing the most promising miRNA-target-site candidates. In this study, we reported the design and implementation of DeepMirTar, a deep-learning-based approach for accurately predicting human miRNA targets at the site level. The predicted miRNA-target sites are those having canonical or non-canonical seed, and features, including high-level expert-designed, low-level expert-designed, and raw-data-level, were used to represent the miRNA-target site. Comparison with other state-of-the-art machine-learning methods and existing miRNA-target-prediction tools indicated that DeepMirTar improved overall predictive performance. DeepMirTar is freely available at https://github.com/Bjoux2/DeepMirTar_SdA. lith@tongji.edu.cn, hongmeilu@csu.edu.cn. Supplementary data are available at Bioinformatics online.

Highly Efficient Deep Blue Organic Light-Emitting Diodes Based on Imidazole: Significantly Enhanced Performance by Effective Energy Transfer with Negligible Efficiency Roll-off.

PubMed

Shan, Tong; Liu, Yulong; Tang, Xiangyang; Bai, Qing; Gao, Yu; Gao, Zhao; Li, Jinyu; Deng, Jian; Yang, Bing; Lu, Ping; Ma, Yuguang

2016-10-26

Great efforts have been devoted to develop efficient deep blue organic light-emitting diodes (OLEDs) materials meeting the standards of European Broadcasting Union (EBU) standard with Commission International de L'Eclairage (CIE) coordinates of (0.15, 0.06) for flat-panel displays and solid-state lightings. However, high-performance deep blue OLEDs are still rare for applications. Herein, two efficient deep blue emitters, PIMNA and PyINA, are designed and synthesized by coupling naphthalene with phenanthreneimidazole and pyreneimidazole, respectively. The balanced ambipolar transporting natures of them are demonstrated by single-carrier devices. Their nondoped OLEDs show deep blue emissions with extremely small CIE y of 0.034 for PIMNA and 0.084 for PyINA, with negligible efficiency roll-off. To take advantage of high photoluminescence quantum efficiency of PIMNA and large fraction of singlet exciton formation of PyINA, doped devices are fabricated by dispersing PyINA into PIMNA. A significantly improved maximum external quantum efficiency (EQE) of 5.05% is obtained through very effective energy transfer with CIE coordinates of (0.156, 0.060), and the EQE remains 4.67% at 1000 cd m -2 , which is among the best of deep blue OLEDs reported matching stringent EBU standard well.

Deep-convection events foster carbonate ion reduction in deep coral reefs

NASA Astrophysics Data System (ADS)

Perez, Fiz F.; Fontela, Marcos; Garcia-Ibañez, Maribel I.; Lherminier, Pascale; Zunino, Patricia; de la Paz, Mercedes; Padín, Xose A.; Alonso-Pérez, Fernando; Velo, Anton; Guallart, Elisa F.; Mercier, Herle

2017-04-01

Since millennial times, water mass circulation and deep-convection events have been transforming warm upper waters at high latitudes into cold and well-oxygenated deep waters. These processes have filled the deep North Atlantic Ocean with waters moderately saturated in calcium carbonate, thus promoting the growth of stony corals, which are hotspots of biodiversity. During the Anthropocene, the meridional circulation has been conveying cumulative amounts of more acidified waters with lower calcium carbonate saturation levels due to the incorporation of anthropogenic carbon dioxide, with very harsh conditions for deep cold-water corals projected by 2100. We evaluate the diminution of calcium carbonate saturation levels (aragonite form) due to the increase in anthropogenic carbon dioxide during the last two decades (2002-2016). We observe a strong decrease in the aragonite saturation levels concomitant with the reduction in the volume transport of aragonite-saturated waters. We estimate a 30-35% reduction in the transport of ion carbonate excess over the saturation levels with respect to the natural carbon cycle for the period 2002-2016. This reduction is associated with an increase in the downward transport of hydrogen ions. We also observe a heaving of the aragonite saturation horizons during the last 25 years, which is estimated at 6 m year-1 for the deep waters and 12-14 m year-1 for the intermediated waters. The harsh winters of 2015 and 2016 have fostered the fast addition of more acidified water into the lower layers of the North Atlantic through deep-convection events. In the future scenario of 2oC warming, the anthropogenic carbon dioxide in the water column would be double than today and the associated transport of hydrogen ions towards the bottom water would reduce the aragonite saturation levels to 60-80% with respect to preindustrial levels. This reduction in the aragonite saturation levels would suppose a strong diminution of the North Atlantic habitats where stony corals will be able to inhabit.

Using glow stick chemistry for biological imaging.

PubMed

Tseng, Jen-Chieh; Bailey, Dyane; Tupper, Tanya; Kung, Andrew L

2014-08-01

This study describes an imaging strategy based on glow stick chemistry to non-invasively image oxidative stress and reactive oxygen species (ROS) production in living animals. Upon stimulation, phagocytes produce toxic levels of ROS to kill engulfed microorganisms. The mitochondrial respiratory chain continually generates low levels of superoxide (O2·(-)) that serve as a source for generation of downstream ROS, which function as regulatory signaling intermediaries. A ROS-reacting substrate, 2-methyl-6-[4-methoxyphenyl]-3,7-dihydroimidazo[1,2-a]pyrazin-3-one hydrochloride, was used as the chemical energy donor for generating energy transfer luminescence in phagosomes and mitochondria. Using targeted photoluminescent dyes with specific subcellular localization that serve as chemical energy recipients, our imaging data demonstrate proof-of-concept for using glow stick chemistry to visualize ROS production associated with phagocytosis and mitochondrial respiration in living mice. Glow stick imaging is a complementary hybrid of chemiluminescence and photoluminescence imaging, capable of generating red or far-red emission for deep tissue imaging.

Optoelectronically probing the density of nanowire surface trap states to the single state limit

NASA Astrophysics Data System (ADS)

Dan, Yaping

2015-02-01

Surface trap states play a dominant role in the optoelectronic properties of nanoscale devices. Understanding the surface trap states allows us to properly engineer the device surfaces for better performance. But characterization of surface trap states at nanoscale has been a formidable challenge using the traditional capacitive techniques. Here, we demonstrate a simple but powerful optoelectronic method to probe the density of nanowire surface trap states to the single state limit. In this method, we choose to tune the quasi-Fermi level across the bandgap of a silicon nanowire photoconductor, allowing for capture and emission of photogenerated charge carriers by surface trap states. The experimental data show that the energy density of nanowire surface trap states is in a range from 109 cm-2/eV at deep levels to 1012 cm-2/eV near the conduction band edge. This optoelectronic method allows us to conveniently probe trap states of ultra-scaled nano/quantum devices at extremely high precision.

Temperature and moisture effects on greenhouse gas emissions from deep active-layer boreal soils

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

Bond-Lamberty, Ben; Smith, A. Peyton; Bailey, Vanessa L.

Rapid climatic changes, rising air temperatures, and increased fires are expected to drive permafrost degradation and alter soil carbon (C) cycling in many high-latitude ecosystems. How these soils will respond to changes in their temperature, moisture, and overlying vegetation is uncertain but critical to understand given the large soil C stocks in these regions. We used a laboratory experiment to examine how temperature and moisture control CO 2 and CH 4 emissions from mineral soils sampled from the bottom of the annual active layer, i.e., directly above permafrost, in an Alaskan boreal forest. Gas emissions from 30 cores, subjected tomore » two temperatures and either field moisture conditions or experimental drought, were tracked over a 100-day incubation; we also measured a variety of physical and chemical characteristics of the cores. Gravimetric water content was 0.31 ± 0.12 (unitless) at the beginning of the incubation; cores at field moisture were unchanged at the end, but drought cores had declined to 0.06 ± 0.04. Daily CO 2 fluxes were positively correlated with incubation chamber temperature, core water content, and percent soil nitrogen. They also had a temperature sensitivity ( Q 10) of 1.3 and 1.9 for the field moisture and drought treatments, respectively. Daily CH 4 emissions were most strongly correlated with percent nitrogen, but neither temperature nor water content was a significant first-order predictor of CH 4 fluxes. The cumulative production of C from CO 2 was over 6 orders of magnitude higher than that from CH 4; cumulative CO 2 was correlated with incubation temperature and moisture treatment, with drought cores producing 52–73 % lower C. Cumulative CH 4 production was unaffected by any treatment. These results suggest that deep active-layer soils may be sensitive to changes in soil moisture under aerobic conditions, a critical factor as discontinuous permafrost thaws in interior Alaska. Furthermore, deep but unfrozen high-latitude soils have been shown to be strongly affected by long-term experimental warming, and these results provide insight into their future dynamics and feedback potential with future climate change.« less

Temperature and moisture effects on greenhouse gas emissions from deep active-layer boreal soils

DOE PAGES

Bond-Lamberty, Ben; Smith, A. Peyton; Bailey, Vanessa L.

2016-12-21

Rapid climatic changes, rising air temperatures, and increased fires are expected to drive permafrost degradation and alter soil carbon (C) cycling in many high-latitude ecosystems. How these soils will respond to changes in their temperature, moisture, and overlying vegetation is uncertain but critical to understand given the large soil C stocks in these regions. We used a laboratory experiment to examine how temperature and moisture control CO 2 and CH 4 emissions from mineral soils sampled from the bottom of the annual active layer, i.e., directly above permafrost, in an Alaskan boreal forest. Gas emissions from 30 cores, subjected tomore » two temperatures and either field moisture conditions or experimental drought, were tracked over a 100-day incubation; we also measured a variety of physical and chemical characteristics of the cores. Gravimetric water content was 0.31 ± 0.12 (unitless) at the beginning of the incubation; cores at field moisture were unchanged at the end, but drought cores had declined to 0.06 ± 0.04. Daily CO 2 fluxes were positively correlated with incubation chamber temperature, core water content, and percent soil nitrogen. They also had a temperature sensitivity ( Q 10) of 1.3 and 1.9 for the field moisture and drought treatments, respectively. Daily CH 4 emissions were most strongly correlated with percent nitrogen, but neither temperature nor water content was a significant first-order predictor of CH 4 fluxes. The cumulative production of C from CO 2 was over 6 orders of magnitude higher than that from CH 4; cumulative CO 2 was correlated with incubation temperature and moisture treatment, with drought cores producing 52–73 % lower C. Cumulative CH 4 production was unaffected by any treatment. These results suggest that deep active-layer soils may be sensitive to changes in soil moisture under aerobic conditions, a critical factor as discontinuous permafrost thaws in interior Alaska. Furthermore, deep but unfrozen high-latitude soils have been shown to be strongly affected by long-term experimental warming, and these results provide insight into their future dynamics and feedback potential with future climate change.« less

Temperature and moisture effects on greenhouse gas emissions from deep active-layer boreal soils

NASA Astrophysics Data System (ADS)

Bond-Lamberty, Ben; Smith, A. Peyton; Bailey, Vanessa

2016-12-01

Rapid climatic changes, rising air temperatures, and increased fires are expected to drive permafrost degradation and alter soil carbon (C) cycling in many high-latitude ecosystems. How these soils will respond to changes in their temperature, moisture, and overlying vegetation is uncertain but critical to understand given the large soil C stocks in these regions. We used a laboratory experiment to examine how temperature and moisture control CO2 and CH4 emissions from mineral soils sampled from the bottom of the annual active layer, i.e., directly above permafrost, in an Alaskan boreal forest. Gas emissions from 30 cores, subjected to two temperatures and either field moisture conditions or experimental drought, were tracked over a 100-day incubation; we also measured a variety of physical and chemical characteristics of the cores. Gravimetric water content was 0.31 ± 0.12 (unitless) at the beginning of the incubation; cores at field moisture were unchanged at the end, but drought cores had declined to 0.06 ± 0.04. Daily CO2 fluxes were positively correlated with incubation chamber temperature, core water content, and percent soil nitrogen. They also had a temperature sensitivity (Q10) of 1.3 and 1.9 for the field moisture and drought treatments, respectively. Daily CH4 emissions were most strongly correlated with percent nitrogen, but neither temperature nor water content was a significant first-order predictor of CH4 fluxes. The cumulative production of C from CO2 was over 6 orders of magnitude higher than that from CH4; cumulative CO2 was correlated with incubation temperature and moisture treatment, with drought cores producing 52-73 % lower C. Cumulative CH4 production was unaffected by any treatment. These results suggest that deep active-layer soils may be sensitive to changes in soil moisture under aerobic conditions, a critical factor as discontinuous permafrost thaws in interior Alaska. Deep but unfrozen high-latitude soils have been shown to be strongly affected by long-term experimental warming, and these results provide insight into their future dynamics and feedback potential with future climate change.

Long term stable deep red light-emitting electrochemical cells based on an emissive, rigid cationic Ir(iii) complex

DOE PAGES

Namanga, Jude E.; Ruhr-Univ. Bochum, Bochum; Gerlitzki, Niels; ...

2017-02-17

Here, the new cationic iridium complex [Ir(bzq) 2(biq)][PF 6] (bzq = benzo[ h]quinolinato and biq = 2,2'-biquinoline) has been synthesized for application as an emitter in light emitting electrochemical cells (LECs). The molecular structure and crystal packing of this complex were established by single X-ray diffraction (SXRD). The electrochemical and photophysical properties of the complex were examined to determine the frontier orbital energies as well as the optical transitions that led to photoemission. The complex was found to emit at 644 nm and 662 nm for powder and thin films, respectively. A high powder photoluminescence quantum yield of 25% wasmore » determined, which is attributed to a reduction in vibrational modes of the complex due to the use of the rigid cyclometalated (C^N) bzq ligand. A LEC with [Ir(bzq) 2(biq)][PF 6] as the emitter was fabricated which showed a deep red emission (662 nm) with a luminance of 33.65 cd m –2, yielding a current efficiency of 0.33 cd A –1 and a power efficiency of 0.2 lm W –1. Most importantly, the LEC based on [Ir(bzq) 2(biq)][PF 6] demonstrated a lifetime of 280 hours which is among the longest device lifetimes reported for any deep red light emitting LEC.« less

Long term stable deep red light-emitting electrochemical cells based on an emissive, rigid cationic Ir(iii) complex

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

Namanga, Jude E.; Ruhr-Univ. Bochum, Bochum; Gerlitzki, Niels

Here, the new cationic iridium complex [Ir(bzq) 2(biq)][PF 6] (bzq = benzo[ h]quinolinato and biq = 2,2'-biquinoline) has been synthesized for application as an emitter in light emitting electrochemical cells (LECs). The molecular structure and crystal packing of this complex were established by single X-ray diffraction (SXRD). The electrochemical and photophysical properties of the complex were examined to determine the frontier orbital energies as well as the optical transitions that led to photoemission. The complex was found to emit at 644 nm and 662 nm for powder and thin films, respectively. A high powder photoluminescence quantum yield of 25% wasmore » determined, which is attributed to a reduction in vibrational modes of the complex due to the use of the rigid cyclometalated (C^N) bzq ligand. A LEC with [Ir(bzq) 2(biq)][PF 6] as the emitter was fabricated which showed a deep red emission (662 nm) with a luminance of 33.65 cd m –2, yielding a current efficiency of 0.33 cd A –1 and a power efficiency of 0.2 lm W –1. Most importantly, the LEC based on [Ir(bzq) 2(biq)][PF 6] demonstrated a lifetime of 280 hours which is among the longest device lifetimes reported for any deep red light emitting LEC.« less

Super-nonlinear fluorescence microscopy for high-contrast deep tissue imaging

NASA Astrophysics Data System (ADS)

Wei, Lu; Zhu, Xinxin; Chen, Zhixing; Min, Wei

2014-02-01

Two-photon excited fluorescence microscopy (TPFM) offers the highest penetration depth with subcellular resolution in light microscopy, due to its unique advantage of nonlinear excitation. However, a fundamental imaging-depth limit, accompanied by a vanishing signal-to-background contrast, still exists for TPFM when imaging deep into scattering samples. Formally, the focusing depth, at which the in-focus signal and the out-of-focus background are equal to each other, is defined as the fundamental imaging-depth limit. To go beyond this imaging-depth limit of TPFM, we report a new class of super-nonlinear fluorescence microscopy for high-contrast deep tissue imaging, including multiphoton activation and imaging (MPAI) harnessing novel photo-activatable fluorophores, stimulated emission reduced fluorescence (SERF) microscopy by adding a weak laser beam for stimulated emission, and two-photon induced focal saturation imaging with preferential depletion of ground-state fluorophores at focus. The resulting image contrasts all exhibit a higher-order (third- or fourth- order) nonlinear signal dependence on laser intensity than that in the standard TPFM. Both the physical principles and the imaging demonstrations will be provided for each super-nonlinear microscopy. In all these techniques, the created super-nonlinearity significantly enhances the imaging contrast and concurrently extends the imaging depth-limit of TPFM. Conceptually different from conventional multiphoton processes mediated by virtual states, our strategy constitutes a new class of fluorescence microscopy where high-order nonlinearity is mediated by real population transfer.

A model of the methane cycle, permafrost, and hydrology of the Siberian continental margin

DOE PAGES

Archer, D.

2014-06-03

A two-dimensional model of a passive continental margin was adapted to the simulation of the methane cycle on Siberian continental shelf and slope, attempting to account for the impacts of glacial/interglacial cycles in sea level, alternately exposing the continental shelf to freezing conditions with deep permafrost formation during glacial times, and immersion in the ocean in interglacial times. The model is used to gauge the impact of the glacial cycles, and potential anthropogenic warming in the deep future, on the atmospheric methane emission flux, and the sensitivities of that flux to processes such as permafrost formation and terrestrial organic carbonmore » (Yedoma) deposition. Hydrological forcing drives a freshening and ventilation of pore waters in areas exposed to the atmosphere, which is not quickly reversed by invasion of seawater upon submergence, since there is no analogous saltwater pump. This hydrological pump changes the salinity enough to affect the stability of permafrost and methane hydrates on the shelf. Permafrost formation inhibits bubble transport through the sediment column, by construction in the model. The impact of permafrost on the methane budget is to replace the bubble flux by offshore groundwater flow containing dissolved methane, rather than accumulating methane for catastrophic release when the permafrost seal fails during warming. By far the largest impact of the glacial/interglacial cycles on the atmospheric methane flux is attenuation by dissolution of bubbles in the ocean when sea level is high. Methane emissions are highest during the regression (soil freezing) part of the cycle, rather than during transgression (thawing). The model-predicted methane flux to the atmosphere in response to a warming climate is small, relative to the global methane production rate, because of the ongoing flooding of the continental shelf. A slight increase due to warming could be completely counteracted by sea level rise on geologic time scales, decreasing the efficiency of bubble transit through the water column. The methane cycle on the shelf responds to climate change on a long time constant of thousands of years, because hydrate is excluded thermodynamically from the permafrost zone by water limitation, leaving the hydrate stability zone at least 300 m below the sediment surface.« less

Geological Sequestration of CO2 A Brief Overview and Potential for Application for Oklahoma

EPA Science Inventory

Geologic sequestration of CO2 is a component of C capture and storage (CCS), an emerging technology for reducing CO2 emissions to the atmosphere, and involves injection of captured CO2 into deep subsurface formations. Similar to the injection of hazardous wastes, before injection...

An automated scraper system for swine confinement facilities

USDA-ARS?s Scientific Manuscript database

Odor and air emissions released by some commercial, large swine operations can be a nuisance. Research has shown that some swine confinement buildings can emit significant amounts of odors, hydrogen sulfide (H2S) and other gases, especially from deep pit buildings with long-term manure storage. A m...

SUBSURFACE PROPERTY RIGHTS: IMPLICATIONS FOR GEOLOGIC CO2 SEQUESTRATION (PRESENTATION)

EPA Science Inventory

The paper discusses subsurface property rights as they apply to geologic sequestration (GS) of carbon dioxide (CO2). GS projects inject captured CO2 into deep (greater than ~1 km) geologic formations for the explicit purpose of avoiding atmospheric emission of CO2. Because of the...

Deep-red to near-infrared fluorescent dyes: Synthesis, photophysical properties, and application in cell imaging

NASA Astrophysics Data System (ADS)

Li, Qi; Liu, Weimin; Wu, Jiasheng; Zhou, Bingjiang; Niu, Guangle; Zhang, Hongyan; Ge, Jiechao; Wang, Pengfei

2016-07-01

More and more attention has been paid to the design of new fluorescent imaging agents with good photostability and water solubility, especially those with emissions in the deep-red and near-infrared regions. In this work, we designed and synthesized four novel fluorescent dyes with deep-red or NIR fluorescence by hybridizing coumarin and pyronin moieties based on our previous work. Introduction of carboxylic acid in the dyes not only imparted the dyes with water solubility but also provided a versatile sensing platform for designing the fluorescent probes and sensors of biomolecules. The photophysical properties of these new dyes were investigated through absorption and fluorescence spectroscopy. Cell imaging experiments showed that esterification products could selectively stain lysosomes with good photostability, thereby indicating that they could be useful in the development of fluorescent probes for bioimaging.

Policy Needs for Carbon Capture & Storage

NASA Astrophysics Data System (ADS)

Peridas, G.

2007-12-01

Climate change is one of the most pressing environmental problems of our time. The widespread consensus that exists on climate science requires deep cuts in greenhouse gas emissions, on the order of 50-80% globally from current levels. Reducing energy demand, increasing energy efficiency and sourcing our energy from renewable sources will, and should, play a key role in achieving these cuts. Fossil fuels however are abundant, relatively inexpensive, and still make up the backbone of our energy system. Phasing out fossil fuel use will be a gradual process, and is likely to take far longer than the timeframe dictated by climate science for reducing emissions. A reliable way of decarbonizing the use of fossil fuels is needed. Carbon capture and storage (CCS) has already proven to be a technology that can safely and effectively accomplish this task. The technological know-how and the underground capacity exist to store billions of tons of carbon dioxide in mature oil and gas fields, and deep saline formations. Three large international commercial projects and several other applications have proved this, but substantial barriers remain to be overcome before CCS becomes the technology of choice in all major emitting sectors. Government has a significant role to play in surmounting these barriers. Without mandatory limits on greenhouse gas emissions and a price on carbon, CCS is likely to linger in the background. The expected initial carbon price levels and their potential volatility under such a scheme dictates that further policies be used in the early years in order for CCS to be implemented. Such policies could include a new source performance standard for power plants, and a low carbon generation obligation that would relieve first movers by spreading the additional cost of the technology over entire sectors. A tax credit for capturing and permanently sequestering anthropogenic CO2 would aid project economics. Assistance in the form of loan guarantees for components of the technology that make financing problematic due to insufficient performance guarantees would help first movers. The development of a pipeline network for transporting CO2 will require centralized planning in order to materialize and make use of economies of scale. The federal government should significantly accelerate its research, development and demonstration program, with particular emphasis on multi-megaton injections in representative geological settings. Finally, a comprehensive regulatory framework for large-scale injections is a high priority item that can and should be developed now, with scope for revision after our experience with CCS projects grows.

Iron and intrinsic deep level states in Ga2O3

NASA Astrophysics Data System (ADS)

Ingebrigtsen, M. E.; Varley, J. B.; Kuznetsov, A. Yu.; Svensson, B. G.; Alfieri, G.; Mihaila, A.; Badstübner, U.; Vines, L.

2018-01-01

Using a combination of deep level transient spectroscopy, secondary ion mass spectrometry, proton irradiation, and hybrid functional calculations, we identify two similar deep levels that are associated with Fe impurities and intrinsic defects in bulk crystals and molecular beam epitaxy and hydride vapor phase epitaxi-grown epilayers of β-Ga2O3. First, our results indicate that FeGa, and not an intrinsic defect, acts as the deep acceptor responsible for the often dominating E2 level at ˜0.78 eV below the conduction band minimum. Second, by provoking additional intrinsic defect generation via proton irradiation, we identified the emergence of a new level, labeled as E2*, having the ionization energy very close to that of E2, but exhibiting an order of magnitude larger capture cross section. Importantly, the properties of E2* are found to be consistent with its intrinsic origin. As such, contradictory opinions of a long standing literature debate on either extrinsic or intrinsic origin of the deep acceptor in question converge accounting for possible contributions from E2 and E2* in different experimental conditions.

SELFI: an object-based, Bayesian method for faint emission line source detection in MUSE deep field data cubes

NASA Astrophysics Data System (ADS)

Meillier, Céline; Chatelain, Florent; Michel, Olivier; Bacon, Roland; Piqueras, Laure; Bacher, Raphael; Ayasso, Hacheme

2016-04-01

We present SELFI, the Source Emission Line FInder, a new Bayesian method optimized for detection of faint galaxies in Multi Unit Spectroscopic Explorer (MUSE) deep fields. MUSE is the new panoramic integral field spectrograph at the Very Large Telescope (VLT) that has unique capabilities for spectroscopic investigation of the deep sky. It has provided data cubes with 324 million voxels over a single 1 arcmin2 field of view. To address the challenge of faint-galaxy detection in these large data cubes, we developed a new method that processes 3D data either for modeling or for estimation and extraction of source configurations. This object-based approach yields a natural sparse representation of the sources in massive data fields, such as MUSE data cubes. In the Bayesian framework, the parameters that describe the observed sources are considered random variables. The Bayesian model leads to a general and robust algorithm where the parameters are estimated in a fully data-driven way. This detection algorithm was applied to the MUSE observation of Hubble Deep Field-South. With 27 h total integration time, these observations provide a catalog of 189 sources of various categories and with secured redshift. The algorithm retrieved 91% of the galaxies with only 9% false detection. This method also allowed the discovery of three new Lyα emitters and one [OII] emitter, all without any Hubble Space Telescope counterpart. We analyzed the reasons for failure for some targets, and found that the most important limitation of the method is when faint sources are located in the vicinity of bright spatially resolved galaxies that cannot be approximated by the Sérsic elliptical profile. The software and its documentation are available on the MUSE science web service (muse-vlt.eu/science).

Recent NASA/GSFC cryogenic measurements of the total hemispheric emissivity of black surface preparations

NASA Astrophysics Data System (ADS)

Tuttle, J.; Canavan, E.

2015-12-01

High-emissivity (black) surfaces are commonly used on deep-space radiators and thermal radiation absorbers in test chambers. Since 2011 NASA Goddard Space Flight Center has measured the total hemispheric emissivity of such surfaces from 20 to 300 K using a test apparatus inside a small laboratory cryostat. We report the latest data from these measurements, including Aeroglaze Z307 paint, Black Kapton, and a configuration of painted aluminum honeycomb that was not previously tested. We also present the results of batch-to- batch reproducibility studies in Ball Infrared BlackTM and painted aluminum honeycomb. Finally, we describe a recently-adopted temperature control method which significantly speeds the data acquisition, and we discuss efforts to reduce the noise in future data.

On the outer atmospheres of hybrid stars

NASA Technical Reports Server (NTRS)

Hartmann, L.; Dupree, A. K.; Jordan, C.; Brown, A.

1985-01-01

Deep exposures with the IUE satellite have been obtained in order to search for high-temperature emission from stars with cool winds. Iota Aur and Theta Her are confirmed as hybrid stars, and an additional hybrid object, Gamma Aql, has been discovered. The emission line fluxes of the hybrid stars are analyzed to establish the emission measure distribution and, as far as possible, the electron density. The discovery of variable, high-velocity Mg II circumstellar absorption in Gamma Aql, Theta Her, and Alpha TrA is reported. Very long exposure of the latter show that cool material is being accelerated to velocities of at least 180 km/s. These observations suggest that high-velocity mass loss is more common than previously thought.

The effects of illumination on deep levels observed in as-grown and low-energy electron irradiated high-purity semi-insulating 4H-SiC

NASA Astrophysics Data System (ADS)

Alfieri, G.; Knoll, L.; Kranz, L.; Sundaramoorthy, V.

2018-05-01

High-purity semi-insulating 4H-SiC can find a variety of applications, ranging from power electronics to quantum computing applications. However, data on the electronic properties of deep levels in this material are scarce. For this reason, we present a deep level transient spectroscopy study on HPSI 4H-SiC substrates, both as-grown and irradiated with low-energy electrons (to displace only C-atoms). Our investigation reveals the presence of four deep levels with activation energies in the 0.4-0.9 eV range. The concentrations of three of these levels increase by at least one order of magnitude after irradiation. Furthermore, we analyzed the behavior of these traps under sub- and above-band gap illumination. The nature of the traps is discussed in the light of the present data and results reported in the literature.

Tropical Storm Ernesto over Cuba

NASA Technical Reports Server (NTRS)

2006-01-01

[figure removed for brevity, see original site] Microwave Image

These infrared, microwave, and visible images were created with data retrieved by the Atmospheric Infrared Sounder (AIRS) on NASA's Aqua satellite.

Infrared Image Because infrared radiation does not penetrate through clouds, AIRS infrared images show either the temperature of the cloud tops or the surface of the Earth in cloud-free regions. The lowest temperatures (in purple) are associated with high, cold cloud tops that make up the top of the storm. In cloud-free areas the AIRS instrument will receive the infrared radiation from the surface of the Earth, resulting in the warmest temperatures (orange/red).

Microwave Image In the AIRS microwave imagery, deep blue areas in storms show where the most precipitation occurs, or where ice crystals are present in the convective cloud tops. Outside of these storm regions, deep blue areas may also occur over the sea surface due to its low radiation emissivity. On the other hand, land appears much warmer due to its high radiation emissivity.

Microwave radiation from Earth's surface and lower atmosphere penetrates most clouds to a greater or lesser extent depending upon their water vapor, liquid water and ice content. Precipitation, and ice crystals found at the cloud tops where strong convection is taking place, act as barriers to microwave radiation. Because of this barrier effect, the AIRS microwave sensor detects only the radiation arising at or above their location in the atmospheric column. Where these barriers are not present, the microwave sensor detects radiation arising throughout the air column and down to the surface. Liquid surfaces (oceans, lakes and rivers) have 'low emissivity' (the signal isn't as strong) and their radiation brightness temperature is therefore low. Thus the ocean also appears 'low temperature' in the AIRS microwave images and is assigned the color blue. Therefore deep blue areas in storms show where the most precipitation occurs, or where ice crystals are present in the convective cloud tops. Outside of these storm regions, deep blue areas may also occur over the sea surface due to its low radiation emissivity. Land appears much warmer due to its high radiation emissivity.

The Atmospheric Infrared Sounder Experiment, with its visible, infrared, and microwave detectors, provides a three-dimensional look at Earth's weather. Working in tandem, the three instruments can make simultaneous observations all the way down to the Earth's surface, even in the presence of heavy clouds. With more than 2,000 channels sensing different regions of the atmosphere, the system creates a global, 3-D map of atmospheric temperature and humidity and provides information on clouds, greenhouse gases, and many other atmospheric phenomena. The AIRS Infrared Sounder Experiment flies onboard NASA's Aqua spacecraft and is managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., under contract to NASA. JPL is a division of the California Institute of Technology in Pasadena.

Long-term changes in quiescent degassing at Mount Baker Volcano, Washington, USA; Evidence for a stalled intrusion in 1975 and connection to a deep magma source

USGS Publications Warehouse

Werner, Cynthia A.; Evans, William C.; Poland, Michael P.; Doukas, Michael P.; Tucker, D.S.

2009-01-01

Long-term changes have occurred in the chemistry, isotopic ratios, and emission rates of gas at Mount Baker volcano following a major thermal perturbation in 1975. In mid-1975 a large pulse in sulfur and carbon dioxide output was observed both in emission rates and in fumarole samples. Emission rates of CO2 and H2S were ??? 950 and 112??t/d, respectively, in 1975; these decreased to ??? 150 and < 1??t/d by 2007. During the peak of the activity the C/S ratio was the lowest ever observed in the Cascade Range and similar to magmatic signatures observed at other basaltic-andesite volcanoes worldwide. Increases in the C/S ratio and decreases in the CO2/CH4 ratio since 1975 suggest a long steady trend back toward a more hydrothermal gas signature. The helium isotope ratio is very high (> 7??Rc/RA), but has declined slightly since the mid-1970s, and ??13C-CO2 has decreased by ??? 1??? over time. Both trends are expected from a gradually crystallizing magma. While other scenarios are investigated, we conclude that magma intruded the mid- to shallow-crust beneath Mount Baker during the thermal awakening of 1975. Since that time, evidence for fresh magma has waned, but the continued emission of CO2 and the presence of a long-term hydrothermal system leads us to suspect some continuing connection between the surface and deep convecting magma.

A Deep X-Ray View of the Synchrotron-dominated Supernova Remnant G330.2+1.0

NASA Astrophysics Data System (ADS)

Williams, Brian J.; Hewitt, John W.; Petre, Robert; Temim, Tea

2018-03-01

We present moderately deep (125 ks) XMM-Newton observations of supernova remnant G330.2+1.0. This remnant is one of only a few known that fall into the “synchrotron-dominated” category, with the emission almost entirely dominated by a nonthermal continuum. Previous X-ray observations could only characterize the spectra of a few regions. Here, we examine the spectra from 14 regions surrounding the entire rim, finding that the spectral properties of the nonthermal emission do not vary significantly in any systematic way from one part of the forward shock to another, unlike several other remnants of this class. We confirm earlier findings that the power-law index, Γ, ranges from about 2.1–2.5, while the absorbing column density is generally between (2.0–2.6) × 1022 cm‑2. Fits with the srcut model find values of the roll-off frequency in the range of 1017.1–1017.5 Hz, implying energies of accelerated electrons of ∼100 TeV. These values imply a high shock velocity of ∼4600 km s‑1, favoring a young age of the remnant. Diffuse emission from the interior is nonthermal in origin as well, and fits to these regions yield similar values to those along the rim, also implying a young age. Thermal emission is present in the east, and the spectrum is consistent with a ∼650 km s‑1 shock wave encountering interstellar or circumstellar material with a density of ∼1 cm‑3.

Near-UV OH Prompt Emission in the Innermost Coma of 103P/Hartley 2

NASA Astrophysics Data System (ADS)

La Forgia, Fiorangela; Bodewits, Dennis; A'Hearn, Michael F.; Protopapa, Silvia; Kelley, Michael S. P.; Sunshine, Jessica; Feaga, Lori; Farnham, Tony

2017-11-01

The Deep Impact spacecraft flyby of comet 103P/Hartley 2 occurred on 2010 November 4, 1 week after perihelion with a closest approach (CA) distance of about 700 km. We used narrowband images obtained by the Medium Resolution Imager on board the spacecraft to study the gas and dust in the innermost coma. We derived an overall dust reddening of 15%/100 nm between 345 and 749 nm and identified a blue enhancement in the dust coma in the sunward direction within 5 km from the nucleus, which we interpret as a localized enrichment in water ice. OH column density maps show an anti-sunward enhancement throughout the encounter, except for the highest-resolution images, acquired at CA, where a radial jet becomes visible in the innermost coma, extending up to 12 km from the nucleus. The OH distribution in the inner coma is very different from that expected for a fragment species. Instead, it correlates well with the water vapor map derived by the HRI-IR instrument on board Deep Impact. Radial profiles of the OH column density and derived water production rates show an excess of OH emission during CA that cannot be explained with pure fluorescence. We attribute this excess to a prompt emission process where photodissociation of H2O directly produces excited OH*(A 2Σ+) radicals. Our observations provide the first direct imaging of near-UV prompt emission of OH. We therefore suggest the use of a dedicated filter centered at 318.8 nm to directly trace the water in the coma of comets.

A physical classification scheme for blazars

NASA Astrophysics Data System (ADS)

Landt, Hermine; Padovani, Paolo; Perlman, Eric S.; Giommi, Paolo

2004-06-01

Blazars are currently separated into BL Lacertae objects (BL Lacs) and flat spectrum radio quasars based on the strength of their emission lines. This is performed rather arbitrarily by defining a diagonal line in the Ca H&K break value-equivalent width plane, following Marchã et al. We readdress this problem and put the classification scheme for blazars on firm physical grounds. We study ~100 blazars and radio galaxies from the Deep X-ray Radio Blazar Survey (DXRBS) and 2-Jy radio survey and find a significant bimodality for the narrow emission line [OIII]λ5007. This suggests the presence of two physically distinct classes of radio-loud active galactic nuclei (AGN). We show that all radio-loud AGN, blazars and radio galaxies, can be effectively separated into weak- and strong-lined sources using the [OIII]λ5007-[OII]λ3727 equivalent width plane. This plane allows one to disentangle orientation effects from intrinsic variations in radio-loud AGN. Based on DXRBS, the strongly beamed sources of the new class of weak-lined radio-loud AGN are made up of BL Lacs at the ~75 per cent level, whereas those of the strong-lined radio-loud AGN include mostly (~97 per cent) quasars.

Phosphorus Doping in Si Nanocrystals/SiO2 msultilayers and Light Emission with Wavelength compatible for Optical Telecommunication

PubMed Central

Lu, Peng; Mu, Weiwei; Xu, Jun; Zhang, Xiaowei; Zhang, Wenping; Li, Wei; Xu, Ling; Chen, Kunji

2016-01-01

Doping in semiconductors is a fundamental issue for developing high performance devices. However, the doping behavior in Si nanocrystals (Si NCs) has not been fully understood so far. In the present work, P-doped Si NCs/SiO2 multilayers are fabricated. As revealed by XPS and ESR measurements, P dopants will preferentially passivate the surface states of Si NCs. Meanwhile, low temperature ESR spectra indicate that some P dopants are incorporated into Si NCs substitutionally and the incorporated P impurities increase with the P doping concentration or annealing temperature increasing. Furthermore, a kind of defect states will be generated with high doping concentration or annealing temperature due to the damage of Si crystalline lattice. More interestingly, the incorporated P dopants can generate deep levels in the ultra-small sized (~2 nm) Si NCs, which will cause a new subband light emission with the wavelength compatible with the requirement of the optical telecommunication. The studies of P-doped Si NCs/SiO2 multilayers suggest that P doping plays an important role in the electronic structures and optoelectronic characteristics of Si NCs. PMID:26956425

Towards microalbuminuria determination on a disposable diagnostic microchip with integrated fluorescence detection based on thin-film organic light emitting diodes.

PubMed

Hofmann, Oliver; Wang, Xuhua; Demello, John C; Bradley, Donal D C; Demello, Andrew J

2005-08-01

As a first step towards a fully disposable stand-alone diagnostic microchip for determination of urinary human serum albumin (HSA), we report the use of a thin-film organic light emitting diode (OLED) as an excitation source for microscale fluorescence detection. The OLED has a peak emission wavelength of 540 nm, is simple to fabricate on flexible or rigid substrates, and operates at drive voltages below 10 V. In a fluorescence assay, HSA is reacted with Albumin Blue 580, generating a strong emission at 620 nm when excited with the OLED. Filter-less discrimination between excitation light and generated fluorescence is achieved through an orthogonal detection geometry. When the assay is performed in 800 microm deep and 800 microm wide microchannels on a poly(dimethylsiloxane)(PDMS) microchip at flow rates of 20 microL min(-1), HSA concentrations down to 10 mg L(-1) can be detected with a linear range from 10 to 100 mg L(-1). This sensitivity is sufficient for the determination of microalbuminuria (MAU), an increased urinary albumin excretion indicative of renal disease (clinical cut-off levels: 15-40 mg L(-1)).

Gate oxide thickness dependence of the leakage current mechanism in Ru/Ta2O5/SiON/Si structures

NASA Astrophysics Data System (ADS)

Ťapajna, M.; Paskaleva, A.; Atanassova, E.; Dobročka, E.; Hušeková, K.; Fröhlich, K.

2010-07-01

Leakage conduction mechanisms in Ru/Ta2O5/SiON/Si structures with rf-sputtered Ta2O5 with thicknesses ranging from 13.5 to 1.8 nm were systematically studied. Notable reaction at the Ru/Ta2O5 interface was revealed by capacitance-voltage measurements. Temperature-dependent current-voltage characteristics suggest the bulk-limited conduction mechanism in all metal-oxide-semiconductor structures. Under gate injection, Poole-Frenkel emission was identified as a dominant mechanism for 13.5 nm thick Ta2O5. With an oxide thickness decreasing down to 3.5 nm, the conduction mechanism transforms to thermionic trap-assisted tunnelling through the triangular barrier. Under substrate injection, the dominant mechanism gradually changes with decreasing thickness from thermionic trap-assisted tunnelling to trap-assisted tunnelling through the triangular barrier; Poole-Frenkel emission was not observed at all. A 0.7 eV deep defect level distributed over Ta2O5 is assumed to be responsible for bulk-limited conduction mechanisms and is attributed to H-related defects or oxygen vacancies in Ta2O5.

Anomalous luminescence phenomena of indium-doped ZnO nanostructures grown on Si substrates by the hydrothermal method

PubMed Central

2012-01-01

In recent years, zinc oxide (ZnO) has become one of the most popular research materials due to its unique properties and various applications. ZnO is an intrinsic semiconductor, with a wide bandgap (3.37 eV) and large exciton binding energy (60 meV) making it suitable for many optical applications. In this experiment, the simple hydrothermal method is used to grow indium-doped ZnO nanostructures on a silicon wafer, which are then annealed at different temperatures (400°C to 1,000°C) in an abundant oxygen atmosphere. This study discusses the surface structure and optical characteristic of ZnO nanomaterials. The structure of the ZnO nanostructures is analyzed by X-ray diffraction, the superficial state by scanning electron microscopy, and the optical measurements which are carried out using the temperature-dependent photoluminescence (PL) spectra. In this study, we discuss the broad peak energy of the yellow-orange emission which shows tendency towards a blueshift with the temperature increase in the PL spectra. This differs from other common semiconductors which have an increase in their peak energy of deep-level emission along with measurement temperature. PMID:22647253

Electrical and optical characteristics of n-Zno/p-GaN hetero-junction diode fabricated by ultra-high vacuum sputter.

PubMed

Cho, Seong Gook; Lee, Dong Uk; Kim, Eun Kyu

2013-09-01

We investigated the electrical and optical properties of n-ZnO/p-GaN hetero-junction diode fabricated by an ultra-high vacuum radio frequency magnetron sputter. A physical relationship between the rotation rate during deposition process and post annealing conditions after deposited ZnO layer on p-GaN layer was discussed. When the rotation rates during deposition process of n-ZnO layer were 5 rpm and 15 rpm, the full width at half maximum of photoluminescence spectra of ZnO layer on the p-GaN layer was about 106 and 133 meV, respectively. Also, the ratio of deep level emission to near band edge emission was dramatically increased as increasing the rotation rate from 5 to 15 rpm. The n-ZnO/p-GaN hetero-junction diode grown at 5 rpm has a higher ratio of forward to reverse currents than the diode grown at 15 rpm. Also, the 600 degrees C-annealed diodes with 5 rpm showed good rectifying behavior with the barrier height of 0.74 eV, the ideality factor of 12.2, and the forward to reverse current ratio of 614 at +/- 8 V.

Status of miniature integrated UV resonance fluorescence and Raman sensors for detection and identification of biochemical warfare agents

NASA Astrophysics Data System (ADS)

Hug, William F.; Bhartia, Rohit; Taspin, Alexandre; Lane, Arthur; Conrad, Pamela; Sijapati, Kripa; Reid, Ray D.

2005-11-01

Laser induced native fluorescence (LINF) is the most sensitive method of detection of biological material including microorganisms, virus', and cellular residues. LINF is also a sensitive method of detection for many non-biological materials as well. The specificity with which these materials can be classified depends on the excitation wavelength and the number and location of observation wavelengths. Higher levels of specificity can be obtained using Raman spectroscopy but a much lower levels of sensitivity. Raman spectroscopy has traditionally been employed in the IR to avoid fluorescence. Fluorescence rarely occurs at wavelength below about 270nm. Therefore, when excitation occurs at a wavelength below 250nm, no fluorescence background occurs within the Raman fingerprint region for biological materials. When excitation occurs within electronic resonance bands of the biological target materials, Raman signal enhancement over one million typically occurs. Raman sensitivity within several hundred times fluorescence are possible in the deep UV where most biological materials have strong absorption. Since the Raman and fluorescence emissions occur at different wavelength, both spectra can be observed simultaneously, thereby providing a sensor with unique sensitivity and specificity capability. We will present data on our integrated, deep ultraviolet, LINF/Raman instruments that are being developed for several applications including life detection on Mars as well as biochemical warfare agents on Earth. We will demonstrate the ability to discriminate organic materials based on LINF alone. Together with UV resonance Raman, higher levels of specificity will be demonstrated. In addition, these instruments are being developed as on-line chemical sensors for industrial and municipal waste streams and product quality applications.

Countdown to Drawdown: an initial overview of exponential scaling of potential societal tipping points for deep decarbonization of global energy infrastructure by 2050

NASA Astrophysics Data System (ADS)

McCaffrey, Mark; Bhowmik, Avit

2017-04-01

The 194 signatories to the Paris Agreement range in size from small island nations (Tuvalu, less than 10,000 people) to massive states (India and China, which between them have 2.6 billion people). Their cultural backgrounds, political, economic and social systems vary widely. What they all share is an agreement for climate stabilisation at 1.5-2˚ C. A roadmap outlining potential exponential transitions towards a carbon-free economy may benefit from a logarithmic "powers of ten" framework that sets aside backgrounds and systems to examine the relative population concentration scales-from the individual (100) to local/neighborhood (103) to the national/transnational scales (108) and ultimately the global population of around 10 billion anticipated in 2050 (1010). What are the related targets and indicators for successful engagement at each level for rapid and radical reductions of carbon emissions and concentrations? What are the possible interventions and barriers that may be applied at different levels of population concentration? What "drawdown" strategies are most appropriate for different scales? Could focusing demonstrations of clean energy and sustainable practices on the local/neighborhood to urban scale (103-104) provide a leverage that has not been achieved at more complex national and transnational scales? Ultimately, backgrounds and systems are important factors in the equation, but the "powers of 10" scaling framework may provide a compass to assist in identifying the challenges, opportunities and related thresholds and tipping points for achieving deep decarbonization and transformation of the global energy infrastructure at every level of society over the next thirty-three years.

Excitation of Molecular Hydrogen in the Orion Bar Photodissociation Region from a Deep Near-infrared IGRINS Spectrum

NASA Astrophysics Data System (ADS)

Kaplan, Kyle F.; Dinerstein, Harriet L.; Oh, Heeyoung; Mace, Gregory N.; Kim, Hwihyun; Sokal, Kimberly R.; Pavel, Michael D.; Lee, Sungho; Pak, Soojong; Park, Chan; Sok Oh, Jae; Jaffe, Daniel T.

2017-04-01

We present a deep near-infrared spectrum of the Orion Bar Photodissociation Region (PDR) taken with the Immersion Grating INfrared Spectrometer (IGRINS) on the 2.7 m telescope at the McDonald Observatory. IGRINS has high spectral resolution (R˜ {{45,000}}) and instantaneous broad wavelength coverage (1.45-2.45 μm), enabling us to detect 87 emission lines from rovibrationally excited molecular hydrogen (H2) that arise from transitions out of 69 upper rovibration levels of the electronic ground state. These levels cover a large range of rotational and vibrational quantum numbers and excitation energies, making them excellent probes of the excitation mechanisms of H2 and physical conditions within the PDR. The Orion Bar PDR is thought to consist of cooler high density clumps or filaments (T=50{--}250 K, {n}H={10}5{--}{10}7 cm-3) embedded in a warmer lower density medium (T=250{--}1000 K, {n}H={10}4{--}{10}5 cm-3). We fit a grid of constant temperature and density Cloudy models, which recreate the observed H2 level populations well, to constrain the temperature to a range of 600-650 K and the density to {n}H=2.5× {10}3{--}{10}4 cm-3. The best-fit model gives T = 625 K and {n}H=5× {10}3 cm-3. This well-constrained warm temperature is consistent with kinetic temperatures found by other studies for the Orion Bar’s lower density medium. However, the range of densities well fit by the model grid is marginally lower than those reported by other studies. We could be observing lower density gas than the surrounding medium, or perhaps a density-sensitive parameter in our models is not properly estimated.

The Northern Middle Lobe of Centaurus A: Circumgalactic Gas in a Starburst Wind

NASA Technical Reports Server (NTRS)

Neff, S. G.; Eilek, J. A.; Owen, F. N.; Schiminovich, D.; Seibert, M.; Thilker, D.

2012-01-01

We present deep ultraviolet (GALEX), radio continuum (VLA) and H-alpha (Magellan) images of the circumgalactic medium around Centaurus A (NGC5128). We focus on the Northern Middle Lobe (NML), a region extending more than 50kpc beyond the galaxy and known to host a collection of striking phenomena: emission line filaments, recent star formation, disrupted HI/molecular gas streams, and short-lived X-ray clouds. Far UV emission is tightly correlated with H-alpha emission for more than 50kpc, and loosely associated with a filament of X-ray clouds and with the radio continuum emission. The radio emission in the NML region does not appear to be an extension of the inner radio jet (10kpc) or a typical radio lobe. We speculate that the "weather" seen in the NML region is a short-lived phenomenon, caused by an outflow encountering cool gas deposited by one of the recent merger/encounter events which have characterized the history of NGC5128.

A Multiwavelength Exploration of the Grand Design Spiral M83: Diffuse X-ray Emission

NASA Astrophysics Data System (ADS)

Kuntz, K. D.; Long, K. S.; Blair, W. P.; Plucinsky, P. P.; Soria, R.; Winkler, P. F.

2013-01-01

We have obtained a series of deep X-ray images of the nearby galaxy M83, with a total exposure 729 ksec with the Chandra ACIS-S array. Since the bulk of the X-ray emitting disk falls within the BI chip, these observations allow a detailed study of the soft diffuse emission in the disk. Most of the diffuse emission is related to star-formation regions and must be powered by supernovae and stellar winds, though the amount of emission due to identifiable SNR is only a few percent. The relation between the spectral shape and surface brightness that was seen in M101 suggests that the properties of the X-ray emission in spiral disks are shaped by the local hot gas production rate (traced by the local star-formation rate) or the disk mid-plane pressure, but it is unclear which physical mechanism dominates. To illuminate this problem, we will compare M83 with the previous Chandra studies of M101 and M33.

Tunable room-temperature single-photon emission at telecom wavelengths from sp 3 defects in carbon nanotubes

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

He, Xiaowei; Hartmann, Nicolai F.; Ma, Xuedan

Generating quantum light emitters that operate at room temperature and at telecom wavelengths remains a significant materials challenge. To achieve this goal requires light sources that emit in the near-infrared wavelength region and that, ideally, are tunable to allow desired output wavelengths to be accessed in a controllable manner. Here, we show that exciton localization at covalently introduced aryl sp 3 defect sites in single-walled carbon nanotubes provides a route to room-temperature single-photon emission with ultrahigh single-photon purity (99%) and enhanced emission stability approaching the shot-noise limit. Moreover, we demonstrate that the inherent optical tunability of single-walled carbon nanotubes, presentmore » in their structural diversity, allows us to generate room-temperature single-photon emission spanning the entire telecom band. Furthermore, single-photon emission deep into the centre of the telecom C band (1.55 um) is achieved at the largest nanotube diameters we explore (0.936 nm).« less

Tunable room-temperature single-photon emission at telecom wavelengths from sp 3 defects in carbon nanotubes

DOE PAGES

He, Xiaowei; Hartmann, Nicolai F.; Ma, Xuedan; ...

2017-07-31

Generating quantum light emitters that operate at room temperature and at telecom wavelengths remains a significant materials challenge. To achieve this goal requires light sources that emit in the near-infrared wavelength region and that, ideally, are tunable to allow desired output wavelengths to be accessed in a controllable manner. Here, we show that exciton localization at covalently introduced aryl sp 3 defect sites in single-walled carbon nanotubes provides a route to room-temperature single-photon emission with ultrahigh single-photon purity (99%) and enhanced emission stability approaching the shot-noise limit. Moreover, we demonstrate that the inherent optical tunability of single-walled carbon nanotubes, presentmore » in their structural diversity, allows us to generate room-temperature single-photon emission spanning the entire telecom band. Furthermore, single-photon emission deep into the centre of the telecom C band (1.55 um) is achieved at the largest nanotube diameters we explore (0.936 nm).« less

New Chandra observations of the jet in 3C273. 1. Softer X-ray than radio spectra and the X-ray emission mechanism

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

Jester, Sebastian; /Fermilab; Harris, D.E.

2006-05-01

The jet in 3C273 is a high-power quasar jet with radio, optical and X-ray emission whose size and brightness allow a detailed study of the emission processes acting in it. We present deep Chandra observations of this jet and analyze the spectral properties of the jet emission from radio through X-rays. We find that the X-ray spectra are significantly softer than the radio spectra in all regions of the bright part of the jet except for the first bright ''knot A'', ruling out a model in which the X-ray emission from the entire jet arises from beamed inverse-Compton scattering ofmore » cosmic microwave background photons in a single-zone jet flow. Within two-zone jet models, we find that a synchrotron origin for the jet's X-rays requires fewer additional assumptions than an inverse-Compton model, especially if velocity shear leads to efficient particle acceleration in jet flows.« less

A regional estimate of convective transport of CO from biomass burning

NASA Technical Reports Server (NTRS)

Pickering, Kenneth E.; Scala, John R.; Thompson, Anne M.; Tao, Wei-Kuo; Simpson, Joanne

1992-01-01

A regional-scale estimate of the fraction of biomass burning emissions that are transported to the free troposphere by deep convection is presented. The focus is on CO and the study region is a part of Brazil that underwent intensive deforestation in the 1980s. The method of calculation is stepwise, scaling up from a prototype convective event, the dynamics of which are well-characterized, to the vertical mass flux of carbon monoxide over the region. Given uncertainties in CO emissions from biomass burning and the representativeness of the prototype event, it is estimated that 10-40 percent of CO emissions from the burning region may be rapidly transported to the free troposphere over the burning region. These relatively fresh emissions will produce O3 efficiently in the free troposphere where O3 has a longer lifetime than in the boundary layer.

Cities’ Role in Mitigating United States Food System Greenhouse Gas Emissions

PubMed Central

2018-01-01

Current trends of urbanization, population growth, and economic development have made cities a focal point for mitigating global greenhouse gas (GHG) emissions. The substantial contribution of food consumption to climate change necessitates urban action to reduce the carbon intensity of the food system. While food system GHG mitigation strategies often focus on production, we argue that urban influence dominates this sector’s emissions and that consumers in cities must be the primary drivers of mitigation. We quantify life cycle GHG emissions of the United States food system through data collected from literature and government sources producing an estimated total of 3800 kg CO2e/capita in 2010, with cities directly influencing approximately two-thirds of food sector GHG emissions. We then assess the potential for cities to reduce emissions through selected measures; examples include up-scaling urban agriculture and home delivery of grocery options, which each may achieve emissions reductions on the order of 0.4 and ∼1% of this total, respectively. Meanwhile, changes in waste management practices and reduction of postdistribution food waste by 50% reduce total food sector emissions by 5 and 11%, respectively. Consideration of the scale of benefits achievable through policy goals can enable cities to formulate strategies that will assist in achieving deep long-term GHG emissions targets. PMID:29717606

Cities' Role in Mitigating United States Food System Greenhouse Gas Emissions.

PubMed

Mohareb, Eugene A; Heller, Martin C; Guthrie, Peter M

2018-05-15

Current trends of urbanization, population growth, and economic development have made cities a focal point for mitigating global greenhouse gas (GHG) emissions. The substantial contribution of food consumption to climate change necessitates urban action to reduce the carbon intensity of the food system. While food system GHG mitigation strategies often focus on production, we argue that urban influence dominates this sector's emissions and that consumers in cities must be the primary drivers of mitigation. We quantify life cycle GHG emissions of the United States food system through data collected from literature and government sources producing an estimated total of 3800 kg CO 2 e/capita in 2010, with cities directly influencing approximately two-thirds of food sector GHG emissions. We then assess the potential for cities to reduce emissions through selected measures; examples include up-scaling urban agriculture and home delivery of grocery options, which each may achieve emissions reductions on the order of 0.4 and ∼1% of this total, respectively. Meanwhile, changes in waste management practices and reduction of postdistribution food waste by 50% reduce total food sector emissions by 5 and 11%, respectively. Consideration of the scale of benefits achievable through policy goals can enable cities to formulate strategies that will assist in achieving deep long-term GHG emissions targets.

A look at some systemic properties of self-bioluminescent emission

NASA Astrophysics Data System (ADS)

Creath, Katherine

2008-08-01

Self-bioluminescent emission (SBE) is a type of biological chemiluminescence where photons are emitted as part of chemical reactions occurring during metabolic processes. This emission is also known as biophoton emission, ultraweak photon emission and ultraweak bioluminescence. This paper outlines research over the past century on some systemic properties of SBE as measured with biological detectors, photomultiplier detectors and ultra-sensitive imaging arrays. There is an apparent consensus in the literature that emission in the deep blue and ultraviolet (150-450nm) is related to DNA / RNA processes while emission in the red and near infrared (600-1000nm) is related to mitochondria and oxidative metabolisms involving reactive oxygen species, singlet oxygen and free radicals in plant, animal and human cells along with chlorophyll fluorescent decay in plants. Additionally, there are trends showing that healthy, unstressed and uninjured samples have less emission than samples that are unhealthy, stressed or injured. Mechanisms producing this emission can be narrowed down by isolating the wavelength region of interest and waiting for short-term fluorescence to decay leaving the ultraweak long-term metabolic emission. Examples of imaging this emission in healthy versus unhealthy, stressed versus unstressed, and injured versus uninjured plant parts are shown. Further discussion poses questions still to be answered related to properties such as coherence, photon statistics, and methodological means of isolating mechanisms.

Processes governing transient responses of the deep ocean buoyancy budget to a doubling of CO2

NASA Astrophysics Data System (ADS)

Palter, J. B.; Griffies, S. M.; Hunter Samuels, B. L.; Galbraith, E. D.; Gnanadesikan, A.

2012-12-01

Recent observational analyses suggest there is a temporal trend and high-frequency variability in deep ocean buoyancy in the last twenty years, a phenomenon reproduced even in low-mixing models. Here we use an earth system model (GFDL's ESM2M) to evaluate physical processes that influence buoyancy (and thus steric sea level) budget of the deep ocean in quasi-steady state and under a doubling of CO2. A new suite of model diagnostics allows us to quantitatively assess every process that influences the buoyancy budget and its temporal evolution, revealing surprising dynamics governing both the equilibrium budget and its transient response to climate change. The results suggest that the temporal evolution of the deep ocean contribution to sea level rise is due to a diversity of processes at high latitudes, whose net effect is then advected in the Eulerian mean flow to mid and low latitudes. In the Southern Ocean, a slowdown in convection and spin up of the residual mean advection are approximately equal players in the deep steric sea level rise. In the North Atlantic, the region of greatest deep steric sea level variability in our simulations, a decrease in mixing of cold, dense waters from the marginal seas and a reduction in open ocean convection causes an accumulation of buoyancy in the deep subpolar gyre, which is then advected equatorward.

Comparison and Interpretation of Admittance Spectroscopy and Deep Level Transient Spectroscopy from Co-Evaporated and Solution-Deposited Cu2ZnSn(Sx, Se1-x)4 Solar Cells

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

Caruso, A. E.; Lund, E. A.; Kosyak, V.

2016-11-21

Cu2ZnSn(S, Se)4 (CZTSe) is an earth-abundant semiconductor with potential for economical thin-film photovoltaic devices. Short minority carrier lifetimes contribute to low open circuit voltage and efficiency. Deep level defects that may contribute to lower minority carrier lifetimes in kesterites have been theoretically predicted, however very little experimental characterization of these deep defects exists. In this work we use admittance spectroscopy (AS) and deep level transient spectroscopy (DLTS) to characterize devices built using CZTSSe absorber layers deposited via both coevaporation and solution processing. AS reveals a band of widely-distributed activation energies for traps or energy barriers for transport, especially in themore » solution deposited case. DLTS reveals signatures of deep majority and minority traps within both types of samples.« less

40 CFR 86.098-28 - Compliance with emission standards.

Code of Federal Regulations, 2010 CFR

2010-07-01

... useful life relative to the evaporative emission level at 4,000 miles as follows: (1) Factor = Evaporative emission level at the useful life mileage for that standard minus the evaporative emission level... applicable usefule life relative to the refueling emission level at 4,000 miles as follows: (1) Factor...

40 CFR 86.098-28 - Compliance with emission standards.

Code of Federal Regulations, 2011 CFR

2011-07-01

... useful life relative to the evaporative emission level at 4,000 miles as follows: (1) Factor = Evaporative emission level at the useful life mileage for that standard minus the evaporative emission level... applicable usefule life relative to the refueling emission level at 4,000 miles as follows: (1) Factor...

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

Danno, Katsunori; Kimoto, Tsunenobu

The authors have investigated deep levels in as-grown and electron-irradiated p-type 4H-SiC epilayers by deep level transient spectroscopy. In as-grown epilayers, the D center and four deep levels are observed. In p-type 4H-SiC, reactive ion etching followed by thermal treatment (at 1150 degree sign C) induces the HK0 (E{sub V}+0.79 eV) and HK2 (E{sub V}+0.84 eV) centers. By the electron irradiation, two deep levels at 0.98 eV (EP1) and 1.44 eV (EP2) are observed in all the samples irradiated at 116-400 keV, while two additional deep levels (EP3 and EP4) are observed only in the samples irradiated at 400 keV.more » After annealing at 950 degree sign C, these centers are annealed out, and the HK4 (E{sub V}+1.44 eV) concentration is increased. By the electron irradiation at more than 160 keV followed by annealing at 950 degree sign C, three deep levels are always observed at 0.30 eV (UK1), 0.58 eV (UK2), and 1.44 eV (HK4). These centers may be defect complexes including carbon displacement-related defects. All the centers except for the D center are reduced to below the detection limit (1-3x10{sup 11} cm{sup -3}) by annealing at 1550 degree sign C for 30 min.« less

Two-step narrow ridge cascade diode lasers emitting near $$2~\\mu$$ m

DOE PAGES

Feng, Tao; Hosoda, Takashi; Shterengas, Leon; ...

2017-01-02

Nearly diffraction limited GaSb-based type-I quantum well cascade diode lasers emitting in the spectral region 1.95-2 μm were designed and fabricated. Two-step 5.5-μm-wide shallow and 14-μm-wide deep etched ridge waveguide design yielded devices generating stable single lobe beams with 250 mW of continuous wave output power at 20 °C. Quantum well radiative recombination current contributes about 13% to laser threshold as estimated from true spontaneous emission and modal gain analysis. Here, recombination at etched sidewalls of the 14-μmwide deep ridges controls about 30% of the threshold.

Brain changes due to hypoxia during light anaesthesia can be prevented by deepening anaesthesia; a study in rats

PubMed Central

Kalmar, Alain F.; Doorduin, Janine; Struys, Michel M. R. F.; Schoemaker, Regien G.; Absalom, Anthony R.

2018-01-01

In anaesthetic practice the risk of cerebral ischemic/hypoxic damage is thought to be attenuated by deep anaesthesia. The rationale is that deeper anaesthesia reduces cerebral oxygen demand more than light anaesthesia, thereby increasing the tolerance to ischemia or hypoxia. However, evidence to support this is scarce. We thus investigated the influence of light versus deep anaesthesia on the responses of rat brains to a period of hypoxia. In the first experiment we exposed adult male Wistar rats to deep or light propofol anaesthesia and then performed [18F]- Fludeoxyglucose (FDG) Positron Emission Tomography (PET) scans to verify the extent of cerebral metabolic suppression. In subsequent experiments, rats were subjected to light/deep propofol anaesthesia and then exposed to a period of hypoxia or ongoing normoxia (n = 9–11 per group). A further 5 rats, not exposed to anaesthesia or hypoxia, served as controls. Four days later a Novel Object Recognition (NOR) test was performed to assess mood and cognition. After another 4 days, the animals were sacrificed for later immunohistochemical analyses of neurogenesis/neuroplasticity (Doublecortin; DCX), Brain Derived Neurotrophic Factor (BDNF) expression and neuroinflammation (Ionized calcium-binding adaptor protein-1; Iba-1) in hippocampal and piriform cortex slices. The hippocampi of rats subjected to hypoxia during light anaesthesia showed lower DCX positivity, and therefore lower neurogenesis, but higher BDNF levels and microglia hyper-ramification. Exploration was reduced, but no significant effect on NOR was observed. In the piriform cortex, higher DCX positivity was observed, associated with neuroplasticity. All these effects were attenuated by deep anaesthesia. Deepening anaesthesia attenuated the brain changes associated with hypoxia. Hypoxia during light anaesthesia had a prolonged effect on the brain, but no impairment in cognitive function was observed. Although reduced hippocampal neurogenesis may be considered unfavourable, higher BDNF expression, associated with microglia hyper-ramification may suggest activation of repair mechanisms. Increased neuroplasticity observed in the piriform cortex supports this, and might reflect a prolonged state of alertness rather than damage. PMID:29451906

Sub-250nm room temperature optical gain from AlGaN materials with strong compositional fluctuations

NASA Astrophysics Data System (ADS)

Pecora, Emanuele; Zhang, Wei; Sun, Haiding; Nikiforov, A.; Yin, Jian; Paiella, Roberto; Moustakas, Theodore; Dal Negro, Luca

2013-03-01

Compact and portable deep-UV LEDs and laser sources are needed for a number of engineering applications including optical communications, gas sensing, biochemical agent detection, disinfection, biotechnology and medical diagnostics. We investigate the deep-UV optical emission and gain properties of AlxGa1-xN/AlyGa1-yN multiple quantum wells structure. These structures were grown by molecular-beam epitaxy on 6H-SiC substrates resulting in either homogeneous wells or various degrees of band-structure compositional fluctuations in the form of cluster-like features within the wells. We measured the TE-polarized amplified spontaneous emission in the sample with cluster-like features and quantified the optical absorption/gain coefficients and gain spectra by the Variable Stripe Length (VSL) technique under ultrafast optical pumping. We report blue-shift and narrowing of the emission, VSL traces, gain spectra, polarization studies, and the validity of the Schalow-Townes relation to demonstrate a maximum net modal gain of 120 cm-1 at 250 nm in the sample with strong compositional fluctuations. Moreover, we measure a very low gain threshold (15 μJ/cm2) . On the other hand, we found that samples with homogeneous quantum wells lead to absorption only. In addition, we report gain measurements in graded-index-separate-confined heterostructure (GRINSCH) designed to increase the device optical confinement factor.

A Search for Lyα Emission from Galaxies AT 6 < z < 8 Using Deep HST Grism Observations: Discovery of a z = 7.5 Galaxy

NASA Astrophysics Data System (ADS)

Larson, Rebecca L.; Finkelstein, Steven; Pirzkal, Nor; Ryan, Russell; Tilvi, Vithal; Malhotra, Sangeeta; Rhoads, James; Finkelstein, Keely; Jung, Intae; Christensen, Lise; Cimatti, Andrea; Ferreras, Ignacio; Grogin, Norman; Koekemoer, Anton; Hathi, Nimish; O'Connell, Robert; Östlin, Göran; Pasquali, Anna; Rothberg, Barry; Windhorst, Rogier; FIGS Team

2018-01-01

We have built an automated detection method to find Lyα emission lines in HST grism data from 6 < z < 8 galaxies in order to spectroscopically confirm their redshifts and to probe the ionization state of the intergalactic medium (IGM) during the epoch of reionization. We use 160 orbits of G102 slitless spectroscopy obtained from HST/WFC3 for the Faint Infrared Grism Survey (FIGS; PI: Malhotra) that were optimized to sample previously-identified high-redshift galaxy candidates. This dataset has already been used to identify one of these candidates, at redshift z = 7.51, which has been observed to have Lyα emission detectable with the HST Grism (Finkelstein et al. 2013; Tilvi et al. 2016). The FIGS data use five separate roll-angles of HST in an effort to mitigate the overall contamination effects of nearby galaxies and we have created a method that accounts for and removes the contamination from surrounding galaxies, while also removing any dispersed continuum light from each individual spectrum (Pirzkal et al. 2017). Using our new automated process we searched for significant (> 3σ) emission lines via two different methods. First, we compared the results for each galaxy across all roll angles and identified significant lines detected in more than one roll angle. Second, we performed a fit to all five roll angles simultaneously, accounting for the total flux of the emission line across all of our spectra. We have examined the spectra for 64 z > 7 candidates in our sample and found one new candidate Lyα emission line at a (> 5σ) level at 1.03µm (FIGS ID: GS2 1406 also named CANDELS ID: z7 PAR2 2909). After comparing this emission line with the broadband photometric colors, we conclude that this line is Lyα at z = 7.542 ± 0.003. This galaxy has the highest Lyα rest-frame equivalent width (EWLyα) yet published at z > 7 (110 ± 14 A).

XMM-Newton Observations of Solar Wind Charge Exchange Emission

NASA Technical Reports Server (NTRS)

Snowden, S. L.; Collier, M. R.; Kuntz, K. D.

2004-01-01

We present an XMM-Newton spectrum of diffuse X-ray emission from within the solar system. The spectrum is dominated by O VII and O VIII lines at 0.57 keV and 0.65 keV, O VIII (and possibly Fe XVII) lines at approximately 0.8 keV, Ne IX lines at approximately 0.92 keV, and Mg XI lines at approximately 1.35 keV. This spectrum is consistent with what is expected from charge exchange emission between the highly ionized solar wind and either interstellar neutrals in the heliosphere or material from Earth's exosphere. The emission is clearly seen as a low-energy ( E less than 1.5 keV) spectral enhancement in one of a series of observations of the Hubble Deep Field North. The X-ray enhancement is concurrent with an enhancement in the solar wind measured by the ACE satellite. The solar wind enhancement reaches a flux level an order of magnitude more intense than typical fluxes at 1 AU, and has ion ratios with significantly enhanced higher ionization states. Whereas observations of the solar wind plasma made at a single point reflect only local conditions which may only be representative of solar wind properties with spatial scales ranging from less than half of an Earth radii (approximately 10 s) to 100 Earth radii, X-ray observations of solar wind charge exchange are remote sensing measurements which may provide observations which are significantly more global in character. Besides being of interest in its own right for studies of the solar system, this emission can have significant consequences for observations of more cosmological objects. It can provide emission lines at zero redshift which are of particular interest (e.g., O VII and O VIII) in studies of diffuse thermal emission, and which can therefore act as contamination in objects which cover the entire detector field of view. We propose the use of solar wind monitoring data, such as from the ACE and Wind spacecraft, as a diagnostic to screen for such possibilities.

Acute and chronic changes in brain activity with deep brain stimulation for refractory depression.

PubMed

Conen, Silke; Matthews, Julian C; Patel, Nikunj K; Anton-Rodriguez, José; Talbot, Peter S

2018-04-01

Deep brain stimulation is a potential option for patients with treatment-refractory depression. Deep brain stimulation benefits have been reported when targeting either the subgenual cingulate or ventral anterior capsule/nucleus accumbens. However, not all patients respond and optimum stimulation-site is uncertain. We compared deep brain stimulation of the subgenual cingulate and ventral anterior capsule/nucleus accumbens separately and combined in the same seven treatment-refractory depression patients, and investigated regional cerebral blood flow changes associated with acute and chronic deep brain stimulation. Deep brain stimulation-response was defined as reduction in Montgomery-Asberg Depression Rating Scale score from baseline of ≥50%, and remission as a Montgomery-Asberg Depression Rating Scale score ≤8. Changes in regional cerebral blood flow were assessed using [ 15 O]water positron emission tomography. Remitters had higher relative regional cerebral blood flow in the prefrontal cortex at baseline and all subsequent time-points compared to non-remitters and non-responders, with prefrontal cortex regional cerebral blood flow generally increasing with chronic deep brain stimulation. These effects were consistent regardless of stimulation-site. Overall, no significant regional cerebral blood flow changes were apparent when deep brain stimulation was acutely interrupted. Deep brain stimulation improved treatment-refractory depression severity in the majority of patients, with consistent changes in local and distant brain regions regardless of target stimulation. Remission of depression was reached in patients with higher baseline prefrontal regional cerebral blood flow. Because of the small sample size these results are preliminary and further evaluation is necessary to determine whether prefrontal cortex regional cerebral blood flow could be a predictive biomarker of treatment response.

Photophysical properties of ortho-metalated monomeric and dimeric complexes containing rhodium(III) and iridium(III) metal centers

NASA Astrophysics Data System (ADS)

Marshall, Jason Alexander

Photophysical properties of dichloro-bridged dimers and monomeric tris complexes of the type [M(NC)2Cl]2 and M(NC)3, where NC refers to the ortho-metalating ligands 2-phenylpyridine (ppy), benzo[h]quinoline (bzq), or 2-(p-tolyl)pyridine (ptpy) and M is Rh(III) or Ir(III), were investigated. Excited-state emission of Rh(III) complexes are highly structured and independent of temperature from 4--100 K in glassy media, with long lifetimes (102 mus to ms). Emission is not observed from the pale yellow, fluid solutions of Rh(III) complexes at room temperature. Below 7K, decay kinetics are sensitive to temperature and are complicated, requiring multi-exponential fits in 4:1 EtOH/MeOH. The spectroscopic properties are consistent with the assignment of a lowest 3pipi* excited-state manifold perturbed by an admixture of higher-lying states possessing strong spin-orbit interactions. The complicated decays are attributed to spin-relaxation-limited behavior between spin-levels in the 3pipi* manifold. Deep yellow solutions of Ir(III) complexes in 4:1 EtOH/MeOH are observed to emit in both glassy media and in fluid solution, displaying severe changes in spectral shape as the glass softens which are not attributable to rigidochromic shifts. Low-temperature spectra are structured with emission origins in the range 496--520 nm whereas room-temperature emission of complexes in fluid solution are characteristically broad structureless bands with maxima redshifted from spectra measured in rigid media. Both the emission and the excited-state lifetimes display temperature dependence, with lifetimes in the microsecond to tens of microseconds range at 77 K, increasing by more than an order of magnitude as the temperature is decreased to 4 K. Each of these characteristic band shapes arises from separate components of the emission which have been time-resolved from the low-temperature spectrum. A long-lived, structured component of the emission, only observed in rigid media, has been assigned as 3pipi*. The spectroscopic properties of the short-lived component, observed in the time-resolved low-temperature emission spectrum and in the room-temperature fluid-solution emission spectrum, are consistent with a lowest 3MLCT excited state manifold.

Factors influencing CO2 and CH4 emissions from coastal wetlands in the Liaohe Delta, northeast China

USGS Publications Warehouse

Olsson, Linda; Ye, Siyuan; Yu, Xueyang; Wei, Mengjie; Krauss, Ken W.; Brix, Hans

2015-01-01

Many factors are known to influence greenhouse gas emissions from coastal wetlands, but it is still unclear which factors are most important under field conditions when they are all acting simultaneously. The objective of this study was to assess the effects of water table, salinity, soil temperature and vegetation on CH4 emissions and ecosystem respiration (Reco) from five coastal wetlands in the Liaohe Delta, northeast China: two Phragmites australis (common reed) wetlands, two Suaeda salsa (sea blite) marshes and a rice (Oryza sativa) paddy. Throughout the growing season, the Suaeda wetlands were net CH4 sinks whereas the Phragmites wetlands and the rice paddy were net CH4sources emitting 1.2–6.1 g CH4 m−2 y−1. The Phragmites wetlands emitted the most CH4 per unit area and the most CH4 relative to CO2. The main controlling factors for the CH4 emissions were water table, temperature and salinity. The CH4 emission was accelerated at high and constant (or managed) water tables and decreased at water tables below the soil surface. High temperatures enhanced CH4 emissions, and emission rates were consistently low (< 1 mg CH4 m−2 h) at soil temperatures <18 °C. At salinity levels > 18 ppt, the CH4 emission rates were always low (< 1 mg CH4 m−2 h−1) probably because methanogens were outcompeted by sulphate reducing bacteria. Saline Phragmites wetlands can, however, emit significant amounts of CH4 as CH4 produced in deep soil layers are transported through the air-space tissue of the plants to the atmosphere. The CH4 emission from coastal wetlands can be reduced by creating fluctuating water tables, including water tables below the soil surface, as well as by occasional flooding by high-salinity water. The effects of water management schemes on the biological communities in the wetlands must, however, be carefully studied prior to the management in order to avoid undesirable effects on the wetland communities.

Mechanism of the 1996-97 non-eruptive volcano-tectonic earthquake swarm at Iliamna Volcano, Alaska

USGS Publications Warehouse

Roman, D.C.; Power, J.A.

2011-01-01

A significant number of volcano-tectonic(VT) earthquake swarms, some of which are accompanied by ground deformation and/or volcanic gas emissions, do not culminate in an eruption.These swarms are often thought to represent stalled intrusions of magma into the mid- or shallow-level crust.Real-time assessment of the likelihood that a VTswarm will culminate in an eruption is one of the key challenges of volcano monitoring, and retrospective analysis of non-eruptive swarms provides an important framework for future assessments. Here we explore models for a non-eruptive VT earthquake swarm located beneath Iliamna Volcano, Alaska, in May 1996-June 1997 through calculation and inversion of fault-plane solutions for swarm and background periods, and through Coulomb stress modeling of faulting types and hypocenter locations observed during the swarm. Through a comparison of models of deep and shallow intrusions to swarm observations,we aim to test the hypothesis that the 1996-97 swarm represented a shallow intrusion, or "failed" eruption.Observations of the 1996-97 swarm are found to be consistent with several scenarios including both shallow and deep intrusion, most likely involving a relatively small volume of intruded magma and/or a low degree of magma pressurization corresponding to a relatively low likelihood of eruption. ?? 2011 Springer-Verlag.

Optical Properties of ZnO-Alloyed Nanocrystalline Films

DOE PAGES

Che, Hui; Huso, Jesse; Morrison, John L.; ...

2012-01-01

ZnO is emore » merging as one of the materials of choice for UV applications. It has a deep excitonic energy level and a direct bandgap of ~3.4 eV. Alloying ZnO with certain atomic constituents adds new optical and electronic functionalities to ZnO. This paper presents research on M g x Z n 1 − x O and Z n S 1 − x O x nanocrystalline flexible films, which enable tunable optical properties in the deep-UV and in the visible range. The ZnO and Mg 0 .3 Zn 0 .7 O films were found to have bandgaps at 3.35 and 4.02 eV, respectively. The photoluminescence of the Mg 0 .3 Zn 0 .7 O exhibited a bandedge emission at 3.95 eV, and at lower energy 3.38 eV due to the limited solubility inherent to these alloys. ZnS 0 .76 O 0 .24 and ZnS 0 .16 O 0 .84 were found to have bandgaps at 3.21 and 2.65 eV, respectively. The effect of nitrogen doping on ZnS 0 .16 O 0 .84 is discussed in terms of the highly lattice mismatched nature of these alloys and the resulting valence-band modification.« less

Lyα emitters in the GOODS-S field. A powerful pure nebular SED with N IV] emission at z = 5.563

NASA Astrophysics Data System (ADS)

Raiter, A.; Fosbury, R. A. E.; Teimoorinia, H.

2010-02-01

Context. The Great Observatories Origins Deep Survey (GOODS) has provided us with one of the deepest multi-wavelength views of the distant universe. The combination of multi-band photometry and optical spectroscopy has resulted in the identification of sources whose redshifts extend to values in excess of six. Amongst these distant sources are Lyα emitters whose nature must be deduced by clearly identifying the different components that contribute to the measured SED. Aims: From a sample of Lyα emitters in the GOODS-S field with uncontaminated photometry and optical (red) spectroscopy, we select a spatially compact object at a redshift of 5.563 (Lyα) that shows a second emission line, identified as N IV] 1486 Å. The SED is modelled in a way that accounts for both the N IV] line emission and the photometry in a self-consistent way. Methods: The photoionization code CLOUDY is used to calculate a range of nebular models as a function of stellar ionizing source temperature, ionization parameter, density and nebular metallicity. We compare the theoretical and observed magnitudes and search for the model parameters that also reproduce the observed N IV] luminosity and equivalent width. Results: A nebular model with a hot blackbody ionizing source of around 100 kK and a nebular metallicity of ~5% of solar is able to fit the observed SED and, in particular, explain the large apparent Balmer break which is inferred from the pure stellar population model fitting conventionally applied to multi-band photometric observations. In our model, an apparent spectral break is produced by strong [O III] 4959, 5007 Å emission falling in one of the IR bands (IRAC1 in this case). A lower limit on the total baryonic mass of a model of this type is 3.2 ×10^8~M⊙. Conclusions: It is argued that objects with Lyα emission at high redshift that show an apparent Balmer break may have their SED dominated by nebular emission and so could possibly be identified with very young starbursting galaxies rather than massive evolved stellar populations. Detailed studies of these emission nebulæ with large telescopes will provide a unique insight into very early chemical evolution. Based on observations made at the European Southern Observatory, Paranal, Chile (ESO programme 170.A-0788) The Great Observatories Origins Deep Survey: ESO Public Observations of the SIRTF Legacy/HST Treasury/Chandra Deep Field South.); on observations obtained with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc.; and on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA.

A Noninvasive Imaging Approach to Understanding Speech Changes following Deep Brain Stimulation in Parkinson's Disease

ERIC Educational Resources Information Center

Narayana, Shalini; Jacks, Adam; Robin, Donald A.; Poizner, Howard; Zhang, Wei; Franklin, Crystal; Liotti, Mario; Vogel, Deanie; Fox, Peter T.

2009-01-01

Purpose: To explore the use of noninvasive functional imaging and "virtual" lesion techniques to study the neural mechanisms underlying motor speech disorders in Parkinson's disease. Here, we report the use of positron emission tomography (PET) and transcranial magnetic stimulation (TMS) to explain exacerbated speech impairment following…

Minimize emissions and improve efficacy with low permeability tarp and deep injection in soil fumigation

USDA-ARS?s Scientific Manuscript database

Soil fumigation targets high pest control efficiency and low environmental impact. Earlier field data show that most fumigated treatments provided 100% kill for plant parasitic nematodes in the soil above 3 ft depth, but not below due to insufficient fumigant delivery. A fumigation trial was conduct...

Li 2Se as a Neutron Scintillator

DOE PAGES

Du, Mao-Hua; Shi, Hongliang; Singh, David J.

2015-06-23

We show that Li 2Se:Te is a potential neutron scintillator material based on density functional calculations. Li 2Se exhibits a number of properties favorable for efficient neutron detection, such as a high Li concentration for neutron absorption, a small effective atomic mass and a low density for reduced sensitivity to background gamma rays, and a small band gap for a high light yield. Our calculations show that Te doping should lead to the formation of deep acceptor complex V Li-Te Se, which can facilitate efficient light emission, similar to the emission activation in Te doped ZnSe.

Neural Imaging Using Single-Photon Avalanche Diodes

PubMed Central

Karami, Mohammad Azim; Ansarian, Misagh

2017-01-01

Introduction: This paper analyses the ability of single-photon avalanche diodes (SPADs) for neural imaging. The current trend in the production of SPADs moves toward the minimum dark count rate (DCR) and maximum photon detection probability (PDP). Moreover, the jitter response which is the main measurement characteristic for the timing uncertainty is progressing. Methods: The neural imaging process using SPADs can be performed by means of florescence lifetime imaging (FLIM), time correlated single-photon counting (TCSPC), positron emission tomography (PET), and single-photon emission computed tomography (SPECT). Results: This trend will result in more precise neural imaging cameras. While achieving low DCR SPADs is difficult in deep submicron technologies because of using higher doping profiles, higher PDPs are reported in green and blue part of light. Furthermore, the number of pixels integrated in the same chip is increasing with the technology progress which can result in the higher resolution of imaging. Conclusion: This study proposes implemented SPADs in Deep-submicron technologies to be used in neural imaging cameras, due to the small size pixels and higher timing accuracies. PMID:28446946

CO2 diffuse emission from maar lake: An example in Changbai volcanic field, NE China

NASA Astrophysics Data System (ADS)

Sun, Yutao; Guo, Zhengfu; Liu, Jiaqi; Du, Jianguo

2018-01-01

Numerous maars and monogenetic volcanic cones are distributed in northeast China, which are related to westward deep subduction of the Pacific Ocean lithosphere, comprising a significant part of the "Pacific Ring of Fire". It is well known that diffuse CO2 emissions from monogenetic volcanoes, including wet (e.g., maar lake) and dry degassing systems (e.g., soil diffuse emission, fault degassing, etc.), may contribute to budget of globally nature-derived greenhouse gases. However, their relationship between wet (e.g., maar lake) and concomitant dry degassing systems (e.g., soil diffuse emission, fault degassing, etc.) related to monogenetic volcanic field is poorly understood. Yuanchi maar, one of the typical monogenetic volcanic systems, is located on the eastern flank of Tianchi caldera in Changbai volcanic field of northeast China, which displays all of three forms of CO2 degassing including the maar lake, soil micro-seepage and fault degassing. Measurements of efflux of CO2 diffusion from the Yuanchi maar system (YMS) indicate that the average values of CO2 emissions from soil micro-seepage, fault degassing and water-air interface diffusion are 24.3 ± 23.3 g m- 2 d- 1, 39.2 ± 22.4 g m- 2 d- 1 and 2.4 ± 1.1 g m- 2 d- 1, respectively. The minimum output of CO2 diffuse emission from the YMS to the atmosphere is about 176.1 ± 88.3 ton/yr, of which 80.4% results from the dry degassing system. Degassing from the fault contributes to the most of CO2 emissions in all of the three forms of degassing in the YMS. Contributions of mantle, crust, air and organic CO2 to the soil gas are 0.01-0.10%, 10-20%, 32-36% and 48-54%, respectively, which are quantitatively constrained by a He-C isotope coupling calculation model. We propose that CO2 exsolves from the upper mantle melting beneath the Tianchi caldera, which migrates to the crustal magma chamber and further transports to the surface of YMS along the deep fault system. During the transportation processes, the emission of gas experiences crustal contamination, influence of magma chamber beneath the YMS, sub-surface processes and air dilution.

Deep blue exciplex organic light-emitting diodes with enhanced efficiency; P-type or E-type triplet conversion to singlet excitons?

PubMed

Jankus, Vygintas; Chiang, Chien-Jung; Dias, Fernando; Monkman, Andrew P

2013-03-13

Simple trilayer, deep blue, fluorescent exciplex organic light-emitting diodes (OLEDs) are reported. These OLEDs emit from an exciplex state formed between the highest occupied molecular orbital (HOMO) of N,N'-bis(1-naphthyl)N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (NPB) and lowest unoccupied molecular orbital (LUMO) of 1,3,5-tri(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl (TPBi) and the NPB singlet manifold, yielding 2.7% external quantum efficiency at 450 nm. It is shown that the majority of the delayed emission in electroluminescence arises from P-type triplet fusion at NPB sites not E-type reverse intersystem crossing because of the presence of the NPB triplet state acting as a deep trap. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Direct observation of keyhole characteristics in deep penetration laser welding with a 10 kW fiber laser.

PubMed

Zhang, Mingjun; Chen, Genyu; Zhou, Yu; Li, Shichun

2013-08-26

Keyhole formation is a prerequisite for deep penetration laser welding. Understanding of the keyhole dynamics is essential to improve the stability of the keyhole. Direct observation of the keyhole during deep penetration laser welding of a modified "sandwich" specimen with a 10 kW fiber laser is presented. A distinct keyhole wall and liquid motion along the wall are observed directly for the first time. The moving liquid "shelf" on the front keyhole wall and the accompanying hydrodynamic and vapor phenomena are observed simultaneously. Micro-droplets torn off the keyhole wall and the resultant bursts of vapor are also visualized. The hydrodynamics on the keyhole wall has a dominant effect on the weld defects. The emission spectrum inside the keyhole is captured accurately using a spectrometer to calculate the characteristics of the keyhole plasma plume.

Cellular imaging of deep organ using two-photon Bessel light-sheet nonlinear structured illumination microscopy

PubMed Central

Zhao, Ming; Zhang, Han; Li, Yu; Ashok, Amit; Liang, Rongguang; Zhou, Weibin; Peng, Leilei

2014-01-01

In vivo fluorescent cellular imaging of deep internal organs is highly challenging, because the excitation needs to penetrate through strong scattering tissue and the emission signal is degraded significantly by photon diffusion induced by tissue-scattering. We report that by combining two-photon Bessel light-sheet microscopy with nonlinear structured illumination microscopy (SIM), live samples up to 600 microns wide can be imaged by light-sheet microscopy with 500 microns penetration depth, and diffused background in deep tissue light-sheet imaging can be reduced to obtain clear images at cellular resolution in depth beyond 200 microns. We demonstrate in vivo two-color imaging of pronephric glomeruli and vasculature of zebrafish kidney, whose cellular structures located at the center of the fish body are revealed in high clarity by two-color two-photon Bessel light-sheet SIM. PMID:24876996

CO2 storage capacity estimation: Methodology and gaps

USGS Publications Warehouse

Bachu, S.; Bonijoly, D.; Bradshaw, J.; Burruss, R.; Holloway, S.; Christensen, N.P.; Mathiassen, O.M.

2007-01-01

Implementation of CO2 capture and geological storage (CCGS) technology at the scale needed to achieve a significant and meaningful reduction in CO2 emissions requires knowledge of the available CO2 storage capacity. CO2 storage capacity assessments may be conducted at various scales-in decreasing order of size and increasing order of resolution: country, basin, regional, local and site-specific. Estimation of the CO2 storage capacity in depleted oil and gas reservoirs is straightforward and is based on recoverable reserves, reservoir properties and in situ CO2 characteristics. In the case of CO2-EOR, the CO2 storage capacity can be roughly evaluated on the basis of worldwide field experience or more accurately through numerical simulations. Determination of the theoretical CO2 storage capacity in coal beds is based on coal thickness and CO2 adsorption isotherms, and recovery and completion factors. Evaluation of the CO2 storage capacity in deep saline aquifers is very complex because four trapping mechanisms that act at different rates are involved and, at times, all mechanisms may be operating simultaneously. The level of detail and resolution required in the data make reliable and accurate estimation of CO2 storage capacity in deep saline aquifers practical only at the local and site-specific scales. This paper follows a previous one on issues and development of standards for CO2 storage capacity estimation, and provides a clear set of definitions and methodologies for the assessment of CO2 storage capacity in geological media. Notwithstanding the defined methodologies suggested for estimating CO2 storage capacity, major challenges lie ahead because of lack of data, particularly for coal beds and deep saline aquifers, lack of knowledge about the coefficients that reduce storage capacity from theoretical to effective and to practical, and lack of knowledge about the interplay between various trapping mechanisms at work in deep saline aquifers. ?? 2007 Elsevier Ltd. All rights reserved.

No evidence for Lyman α emission in spectroscopy of z > 7 candidate galaxies

NASA Astrophysics Data System (ADS)

Caruana, Joseph; Bunker, Andrew J.; Wilkins, Stephen M.; Stanway, Elizabeth R.; Lacy, Mark; Jarvis, Matt J.; Lorenzoni, Silvio; Hickey, Samantha

2012-12-01

We present Gemini/Gemini Near Infrared Spectrograph (GNIRS) spectroscopic observations of four z-band (z ≈ 7) dropout galaxies and Very Large Telescope (VLT)/XSHOOTER observations of one z-band dropout and three Y-band (z ≈ 8-9) dropout galaxies in the Hubble Ultra Deep Field, which were selected with Wide Field Camera 3 imaging on the Hubble Space Telescope. We find no evidence of Lyman α emission with a typical 5σ sensitivity of 5 × 10-18 erg cm-2 s-1, and use the upper limits on Lyman α flux and the broad-band magnitudes to constrain the rest-frame equivalent widths for this line emission. Accounting for incomplete spectral coverage, we survey 3.0 z-band dropouts and 2.9 Y-band dropouts to a Lyman α rest-frame equivalent width limit >120 Å (for an unresolved emission line); for an equivalent width limit of 50 Å the effective numbers of drop-outs surveyed fall to 1.2 z-band drop-outs and 1.5 Y-band drop-outs. A simple model where the fraction of high rest-frame equivalent width emitters follows the trend seen at z = 3-6.5 is inconsistent with our non-detections at z = 7-9 at the ≈1σ level for spectrally unresolved lines, which may indicate that a significant neutral H I fraction in the intergalactic medium suppresses the Lyman α line in z-drop and Y-drop galaxies at z > 7. Based on observations collected at the European Organization for Astronomical Research in the Southern Hemisphere, Chile, as part of programme 086.A-0968(B).

A modeling comparison of deep greenhouse gas emissions reduction scenarios by 2030 in California

DOE PAGES

Yeh, Sonia; Yang, Christopher; Gibbs, Michael; ...

2016-10-21

California aims to reduce greenhouse gas (GHG) emissions to 40% below 1990 levels by 2030. We compare six energy models that have played various roles in informing the state policymakers in setting climate policy goals and targets. These models adopt a range of modeling structures, including stock-turnover back-casting models, a least-cost optimization model, macroeconomic/macro-econometric models, and an electricity dispatch model. Results from these models provide useful insights in terms of the transformations in the energy system required, including efficiency improvements in cars, trucks, and buildings, electrification of end-uses, low- or zero-carbon electricity and fuels, aggressive adoptions of zero-emission vehicles (ZEVs),more » demand reduction, and large reductions of non-energy GHG emissions. Some of these studies also suggest that the direct economic costs can be fairly modest or even generate net savings, while the indirect macroeconomic benefits are large, as shifts in employment and capital investments could have higher economic returns than conventional energy expenditures. These models, however, often assume perfect markets, perfect competition, and zero transaction costs. They also do not provide specific policy guidance on how these transformative changes can be achieved. Greater emphasis on modeling uncertainty, consumer behaviors, heterogeneity of impacts, and spatial modeling would further enhance policymakers' ability to design more effective and targeted policies. Here, this paper presents an example of how policymakers, energy system modelers and stakeholders interact and work together to develop and evaluate long-term state climate policy targets. Lastly, even though this paper focuses on California, the process of dialogue and interactions, modeling results, and lessons learned can be generally adopted across different regions and scales.« less

Fabrication of high responsivity deep UV photo-detector based on Na doped ZnO nanocolumns

NASA Astrophysics Data System (ADS)

Agrawal, Jitesh; Dixit, Tejendra; Palani, I. A.; Ramachandra Rao, M. S.; Singh, Vipul

2018-05-01

We report a variety of the hydrothermally synthesized ZnO nanostructures with a significant suppression in defect-related emission and huge enhancement in the photo-current to the dark current ratio (approximately six orders of magnitude) upon UV light illumination. Interestingly, the photo-detector shows lower dark current of 1.6 nA with high responsivity of 507 A W‑1 at 254 nm. Here, a systematic analysis of the growth process as well as the physical, chemical and electrical properties of as-grown ZnO nanostructures has been performed. We have utilized the duo effect of both the inorganic (KMnO4) and organic (Na3C6H5O7) additives, which has facilitated the precise tuning of the morphology and intrinsic defects in nanostructures that have made an impact on the photo-responsivity, photoluminescence (PL) and adhesivity of the film on to the underlying substrate. PL analysis of as-grown ZnO nanostructures has suggested 11 times improvement in the near band emission (NBE) to defect level emission (DLE) ratio. Interestingly, thermal annealing of the samples has shown a dramatic change in the morphology with significant improvement in the crystallinity. Notably, the band gap was observed to be modulated from 3.3 eV to 3.1 eV after annealing. In addition to UV photo-detector based applications, the work presented here has provided a subtle solution towards the rectification of various problems pertaining to hydrothermal processes like poor adhesivity, feeble UV emission and problem in precise tuning of the morphology along with the bandgap in one go. Therefore, these investigations assume critical significance towards the development of next-generation optoelectronic devices.

Green engineered ZnO nanopowders by Banyan Tree and E. tirucalli plant latex: auto ignition route, photoluminescent and photocatalytic properties

NASA Astrophysics Data System (ADS)

Anilkumar, M. R.; Nagaswarupa, H. P.; Anantharaju, K. S.; Gurushantha, K.; Pratapkumar, C.; Prashantha, S. C.; Shashi Shekhar, T. R.; Nagabhushana, H.; Sharma, S. C.; Vidya, Y. S.; Prasad, Daruka

2015-03-01

A simple and eco-friendly solution combustion route was used to prepare ZnO nanoparticles (ZNPs) using Banyan Tree (BT) and Euphorbia tirucalli (ET) plant latexes as fuels. The final products were characterized by powder x-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), UV-visible, scanning electron microcopy (SEM) and transmission electron microscopy (TEM). The PXRD result reveals the formation of hexagonal phase with Wurtzite structure. The crystallite size obtained from TEM was found to be ˜20-25 nm. SEM results reveal rose-like morphology with BT latex and hexagonal shaped with ET latex. The energy band gap of ZNPs obtained by BT and ET latex were found to be 3.20 and 3.38 eV, respectively. Photoluminescence (PL) emission peaks at ˜421, 458, 505, 522, 628 and 695 nm were observed in both the samples when excited at 383 nm. These emission peaks were mainly attributed to deep level oxygen (blue-green) defect and exciton (UV) defects, respectively. The international commission on illumination (CIE) chromaticity co-ordinates, as well as co-ordinated color temperature (CCT), were estimated from the emission spectra; the values (x, y) were very close to national television system committee (NTSC) standard values of pure white emission. Photocatalytic activity (PCA) of ZNPs prepared was studied in detail. The ZNPs prepared using BT latex showed highest PCA under sunlight. The results demonstrate that the synthesized product could be quite useful for display applications as well as photocatalyst. Further, the material prepared by this route was found to be non-toxic, environmentally friendly and could be a potential alternative to economical routes.

[Ultra] luminous infrared galaxies selected at 90 μm in the AKARI deep field: a study of AGN types contributing to their infrared emission

NASA Astrophysics Data System (ADS)

Małek, K.; Bankowicz, M.; Pollo, A.; Buat, V.; Takeuchi, T. T.; Burgarella, D.; Goto, T.; Malkan, M.; Matsuhara, H.

2017-02-01

Aims: The aim of this work is to characterize physical properties of ultra luminous infrared galaxies (ULIRGs) and luminous infrared galaxies (LIRGs) detected in the far-infrared (FIR) 90 μm band in the AKARI Deep Field-South (ADF-S) survey. In particular, we want to estimate the active galactic nucleus (AGN) contribution to the LIRGs and ULIRGs' infrared emission and which types of AGNs are related to their activity. Methods: We examined 69 galaxies at redshift ≥0.05 detected at 90 μm by the AKARI satellite in the ADF-S, with optical counterparts and spectral coverage from the ultraviolet to the FIR. We used two independent spectral energy distribution fitting codes: one fitting the SED from FIR to FUV (CIGALE) (we use the results from CIGALE as a reference) and gray-body + power spectrum fit for the infrared part of the spectra (CMCIRSED) in order to identify a subsample of ULIRGs and LIRGs, and to estimate their properties. Results: Based on the CIGALE SED fitting, we have found that LIRGs and ULIRGs selected at the 90 μm AKARI band compose 56% of our sample (we found 17 ULIRGs and 22 LIRGs, spanning over the redshift range 0.06

Electrically driven deep ultraviolet MgZnO lasers at room temperature

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

Suja, Mohammad; Bashar, Sunayna Binte; Debnath, Bishwajit

Semiconductor lasers in the deep ultraviolet (UV) range have numerous potential applications ranging from water purification and medical diagnosis to high-density data storage and flexible displays. Nevertheless, very little success was achieved in the realization of electrically driven deep UV semiconductor lasers to date. Here, we report the fabrication and characterization of deep UV MgZnO semiconductor lasers. These lasers are operated with continuous current mode at room temperature and the shortest wavelength reaches 284 nm. The wide bandgap MgZnO thin films with various Mg mole fractions were grown on c-sapphire substrate using radio-frequency plasma assisted molecular beam epitaxy. Metal-semiconductor-metal (MSM)more » random laser devices were fabricated using lithography and metallization processes. Besides the demonstration of scalable emission wavelength, very low threshold current densities of 29-33 A/cm 2 are achieved. Furthermore, numerical modeling reveals that impact ionization process is responsible for the generation of hole carriers in the MgZnO MSM devices. The interaction of electrons and holes leads to radiative excitonic recombination and subsequent coherent random lasing.« less

Electrically driven deep ultraviolet MgZnO lasers at room temperature

DOE PAGES

Suja, Mohammad; Bashar, Sunayna Binte; Debnath, Bishwajit; ...

2017-06-01

Semiconductor lasers in the deep ultraviolet (UV) range have numerous potential applications ranging from water purification and medical diagnosis to high-density data storage and flexible displays. Nevertheless, very little success was achieved in the realization of electrically driven deep UV semiconductor lasers to date. Here, we report the fabrication and characterization of deep UV MgZnO semiconductor lasers. These lasers are operated with continuous current mode at room temperature and the shortest wavelength reaches 284 nm. The wide bandgap MgZnO thin films with various Mg mole fractions were grown on c-sapphire substrate using radio-frequency plasma assisted molecular beam epitaxy. Metal-semiconductor-metal (MSM)more » random laser devices were fabricated using lithography and metallization processes. Besides the demonstration of scalable emission wavelength, very low threshold current densities of 29-33 A/cm 2 are achieved. Furthermore, numerical modeling reveals that impact ionization process is responsible for the generation of hole carriers in the MgZnO MSM devices. The interaction of electrons and holes leads to radiative excitonic recombination and subsequent coherent random lasing.« less

Low-temperature emission of Al0.48In0.52As under high pressures

NASA Astrophysics Data System (ADS)

Zhou, H. P.; Sotomayor Torres, C. M.

1994-04-01

We investigated the low-temperature emission of Al0.48In0.52As under high pressures from 1 bar up to 92 kbar, paying special attention to the changes in luminescence mechanisms that occur concurrently with the crossover between the Γ- and the X-related states. By investigating the temperature and excitation power dependence of the photoluminescence together with the photoluminescence excitation, we demonstrate the low-temperature emission of Al0.48In0.52As is due to neutral donor-acceptor-pair (D0,A0) transitions with a relatively deep acceptor. This occurs in both the Γ- and the X-related states. We suggest the shallow donor ground states associated with the X and the Γ conduction bands seem to be tied quite rigidly to these conduction bands. Variations in the donor binding energies with the pressure and the Γ-X related state crossover seem to be minor. The linear pressure coefficients αΓ and αX of the (D0,A0) related to the Γ and the X levels in the conduction band are 7.9±0.1 and -2.9±0.1 meV/kbar, respectively. The Γ-X related state crossover occurs at ˜52.5±0.5 kbar at 2 K. The direct band gap EΓg and the indirect band gap Exg of Al0.48In0.52As are ˜1.61 and ˜2.17 eV at 1 bar and 2 K, respectively.

Positron deep level transient spectroscopy — a new application of positron annihilation to semiconductor physics

NASA Astrophysics Data System (ADS)

Beling, C. D.; Fung, S.; Au, H. L.; Ling, C. C.; Reddy, C. V.; Deng, A. H.; Panda, B. K.

1997-05-01

Recent positron mobility and lifetime measurements made on ac-biased metal on semi-insulating GaAs junctions, which have identified the native EL2 defect through a determination of the characteristic ionization energy of the donor level, are reviewed. It is shown that these measurements point towards a new spectroscopy, tentatively named positron-DLTS (deep level transient spectroscopy), that is the direct complement to conventional DLTS in that it monitors transients in the electric field of the depletion region rather than the inversely related depletion width, as deep levels undergo ionization. In this new spectroscopy, which may be applied to doped material by use of a suitable positron beam, electric field transients are monitored through the Doppler shift of the annihilation radiation resulting from the drift velocity of the positron in the depletion region. Two useful extensions of the new spectroscopy beyond conventional capacitance-DLTS are suggested. The first is that in some instances information on the microstructure of the defect causing the deep level may be inferred from the sensitivity of the positron to vacancy defects of negative and neutral charge states. The second is that the positron annihilation technique is intrinsically much faster than conventional DLTS with the capability of observing transients some 10 6 times faster, thus allowing deep levels (and even shallow levels) to be investigated without problems associated with carrier freeze-out.