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Sample records for iii formation efficiencies

  1. Globular cluster systems in nearby dwarf galaxies - III. Formation efficiencies of old globular clusters

    NASA Astrophysics Data System (ADS)

    Georgiev, Iskren Y.; Puzia, Thomas H.; Goudfrooij, Paul; Hilker, Michael

    2010-08-01

    We investigate the origin of the shape of the globular cluster (GC) system scaling parameters as a function of galaxy mass, i.e. specific frequency (SN), specific luminosity (SL), specific mass (SM) and specific number () of GCs. In the low-mass galaxy regime (MV >~ -16 mag), our analysis is based on Hubble Space Telescope/Advanced Camera for Surveys observations of GC populations of faint, mainly late-type dwarf galaxies in low-density environments. In order to sample the entire range in galaxy mass (MV = -11 to -23mag =106- 1011Lsolar), environment and morphology we augment our sample with data of spiral and elliptical galaxies from the literature, in which old GCs are reliably detected. This large data set confirms (irrespective of the galaxy type) the increase in the specific frequencies of GCs above and below a galaxy magnitude of MV ~= -20mag. Over the full mass range, the SL value of early-type galaxies is, on average, twice that of late types. To investigate the observed trends, we derive theoretical predictions of GC system scaling parameters as a function of host galaxy mass based on the models of Dekel and Birnboim in which star formation processes are regulated by stellar and supernova feedback below a stellar mass of 3 × 1010Msolar and by virial shocks above it. We find that the analytical model describes remarkably well the shape of the GC system scaling parameter distributions with a universal specific GC formation efficiency, η, which relates the total mass in GCs to the total galaxy halo mass. Early-type and late-type galaxies show a similar mean value of η = 5.5 × 10-5, with an increasing scatter towards lower galaxy masses. This can be due to the enhanced stochastic nature of the star and star-cluster formation processes for such systems. Some massive galaxies have excess η values compared to what is expected from the mean model prediction for galaxies more luminous than MV ~= -20mag (LV >~ 1010Lsolar). This may be attributed to a very

  2. Fueling the central engine of radio galaxies. III. Molecular gas and star formation efficiency of 3C 293

    NASA Astrophysics Data System (ADS)

    Labiano, A.; García-Burillo, S.; Combes, F.; Usero, A.; Soria-Ruiz, R.; Piqueras López, J.; Fuente, A.; Hunt, L.; Neri, R.

    2014-04-01

    Context. Powerful radio galaxies show evidence of ongoing active galactic nuclei (AGN) feedback, mainly in the form of fast, massive outflows. But it is not clear how these outflows affect the star formation of their hosts. Aims: We investigate the different manifestations of AGN feedback in the evolved, powerful radio source 3C 293 and their impact on the molecular gas of its host galaxy, which harbors young star-forming regions and fast outflows of H i and ionized gas. Methods: We study the distribution and kinematics of the molecular gas of 3C 293 using high spatial resolution observations of the 12CO(1-0) and 12CO(2-1) lines, and the 3 mm and 1 continuum taken with the IRAM Plateau de Bure interferometer. We mapped the molecular gas of 3C 293 and compared it with the dust and star-formation images of the host. We searched for signatures of outflow motions in the CO kinematics, and re-examined the evidence of outflowing gas in the H i spectra. We also derived the star formation rate (SFR) and star formation efficiency (SFE) of the host with all available SFR tracers from the literature, and compared them with the SFE of young and evolved radio galaxies and normal star-forming galaxies. Results: The 12CO(1-0) emission line shows that the molecular gas in 3C 293 is distributed along a massive (M(H2) ~ 2.2 × 1010M⊙) ~24″(21 kpc-) diameter warped disk, that rotates around the AGN. Our data show that the dust and the star formation are clearly associated with the CO disk. The 12CO(2-1) emission is located in the inner 7 kpc (diameter) region around the AGN, coincident with the inner part of the 12CO(1-0) disk. Both the 12CO(1-0) and 12CO(2-1) spectra reveal the presence of an absorber against the central regions of 3C 293 that is associated with the disk. We do not detect any fast (≳500 km s-1) outflow motions in the cold molecular gas. The host of 3C 293 shows an SFE consistent with the Kennicutt-Schmidt law of normal galaxies and young radio galaxies, and it

  3. Efficient Formation of Light-Absorbing Polymeric Nanoparticles from the Reaction of Soluble Fe(III) with C4 and C6 Dicarboxylic Acids.

    PubMed

    Tran, Ashley; Williams, Geoffrey; Younus, Shagufta; Ali, Nujhat N; Blair, Sandra L; Nizkorodov, Sergey A; Al-Abadleh, Hind A

    2017-09-05

    The role of transition metals in the formation and aging of secondary organic aerosol (SOA) from aliphatic and aromatic precursors in heterogeneous/multiphase reactions is not well understood. The reactivity of soluble Fe(III) toward known benzene photooxidation products that include fumaric (trans-butenedioic) and muconic (trans,trans-2,4-hexadienedioic) acids was investigated. Efficient formation of brightly colored nanoparticles was observed that are mostly rod- or irregular-shaped depending on the structure of the organic precursor. The particles were characterized for their optical properties, growth rate, elemental composition, iron content, and oxidation state. Results indicate that these particles have mass absorption coefficients on the same order as black carbon and larger than that of biomass burning aerosols. The particles are also amorphous in nature and consist of polymeric chains of Fe centers complexed to carboxylate groups. The oxidation state of Fe was found to be in between Fe(III) and Fe(II) in standard compounds. The organic reactant to iron molar ratio and pH were found to affect the particle growth rate. Control experiments using maleic acid (cis-butenedioic acid) and succinic acid (butanedioic acid) produced no particles. The formation of particles reported herein could account for new pathways that lead to SOA and brown carbon formation mediated by transition metals. In addition, the multiple chemically active components in these particles (iron, organics, and acidic groups) may have an effect on their chemical reactivity (enhanced uptake of trace gases, catalysis, and production of reactive oxygen species) and their likely poor cloud/ice nucleation properties.

  4. Enterohemorrhagic E. coli Requires N-WASP for Efficient Type III Translocation but Not for EspFU-Mediated Actin Pedestal Formation

    PubMed Central

    Brady, Michael J.; Skehan, Brian; Battle, Scott E.; Robbins, Douglas; Kapoor, Archana; Hecht, Gail; Snapper, Scott B.; Leong, John M.

    2010-01-01

    Upon infection of mammalian cells, enterohemorrhagic E. coli (EHEC) O157:H7 utilizes a type III secretion system to translocate the effectors Tir and EspFU (aka TccP) that trigger the formation of F-actin-rich ‘pedestals’ beneath bound bacteria. EspFU is localized to the plasma membrane by Tir and binds the nucleation-promoting factor N-WASP, which in turn activates the Arp2/3 actin assembly complex. Although N-WASP has been shown to be required for EHEC pedestal formation, the precise steps in the process that it influences have not been determined. We found that N-WASP and actin assembly promote EHEC-mediated translocation of Tir and EspFU into mammalian host cells. When we utilized the related pathogen enteropathogenic E. coli to enhance type III translocation of EHEC Tir and EspFU, we found surprisingly that actin pedestals were generated on N-WASP-deficient cells. Similar to pedestal formation on wild type cells, Tir and EspFU were the only bacterial effectors required for pedestal formation, and the EspFU sequences required to interact with N-WASP were found to also be essential to stimulate this alternate actin assembly pathway. In the absence of N-WASP, the Arp2/3 complex was both recruited to sites of bacterial attachment and required for actin assembly. Our results indicate that actin assembly facilitates type III translocation, and reveal that EspFU, presumably by recruiting an alternate host factor that can signal to the Arp2/3 complex, exhibits remarkable versatility in its strategies for stimulating actin polymerization. PMID:20808845

  5. Magnetic Fields in Population III Star Formation

    SciTech Connect

    Turk, Matthew J.; Oishi, Jeffrey S.; Abel, Tom; Bryan, Greg

    2012-02-22

    We study the buildup of magnetic fields during the formation of Population III star-forming regions, by conducting cosmological simulations from realistic initial conditions and varying the Jeans resolution. To investigate this in detail, we start simulations from identical initial conditions, mandating 16, 32 and 64 zones per Jeans length, and studied the variation in their magnetic field amplification. We find that, while compression results in some amplification, turbulent velocity fluctuations driven by the collapse can further amplify an initially weak seed field via dynamo action, provided there is sufficient numerical resolution to capture vortical motions (we find this requirement to be 64 zones per Jeans length, slightly larger than, but consistent with previous work run with more idealized collapse scenarios). We explore saturation of amplification of the magnetic field, which could potentially become dynamically important in subsequent, fully-resolved calculations. We have also identified a relatively surprising phenomena that is purely hydrodynamic: the higher-resolved simulations possess substantially different characteristics, including higher infall-velocity, increased temperatures inside 1000 AU, and decreased molecular hydrogen content in the innermost region. Furthermore, we find that disk formation is suppressed in higher-resolution calculations, at least at the times that we can follow the calculation. We discuss the effect this may have on the buildup of disks over the accretion history of the first clump to form as well as the potential for gravitational instabilities to develop and induce fragmentation.

  6. MAGNETIC FIELDS IN POPULATION III STAR FORMATION

    SciTech Connect

    Turk, Matthew J.; Bryan, Greg L.; Oishi, Jeffrey S.; Abel, Tom

    2012-02-01

    We study the buildup of magnetic fields during the formation of Population III star-forming regions by conducting cosmological simulations from realistic initial conditions and varying the Jeans resolution. To investigate this in detail, we start simulations from identical initial conditions, mandating 16, 32, and 64 zones per Jeans length, and study the variation in their magnetic field amplification. We find that, while compression results in some amplification, turbulent velocity fluctuations driven by the collapse can further amplify an initially weak seed field via dynamo action, provided there is sufficient numerical resolution to capture vortical motions (we find this requirement to be 64 zones per Jeans length, slightly larger than but consistent with previous work run with more idealized collapse scenarios). We explore saturation of amplification of the magnetic field, which could potentially become dynamically important in subsequent, fully resolved calculations. We have also identified a relatively surprising phenomenon that is purely hydrodynamic: the higher-resolved simulations possess substantially different characteristics, including higher infall velocity, increased temperatures inside 1000 AU, and decreased molecular hydrogen content in the innermost region. Furthermore, we find that disk formation is suppressed in higher-resolution calculations, at least at the times that we can follow the calculation. We discuss the effect this may have on the buildup of disks over the accretion history of the first clump to form as well as the potential for gravitational instabilities to develop and induce fragmentation.

  7. Formation pathway of Population III coalescing binary black holes through stable mass transfer

    NASA Astrophysics Data System (ADS)

    Inayoshi, Kohei; Hirai, Ryosuke; Kinugawa, Tomoya; Hotokezaka, Kenta

    2017-07-01

    We study the formation of stellar mass binary black holes (BBHs) originating from Population III (PopIII) stars, performing stellar evolution simulations for PopIII binaries with mesa. We find that a significant fraction of PopIII binaries form massive BBHs through stable mass transfer between two stars in a binary, without experiencing common envelope phases. We investigate necessary conditions required for PopIII binaries to form coalescing BBHs with a semi-analytical model calibrated by the stellar evolution simulations. The BBH formation efficiency is estimated for two different initial conditions for PopIII binaries with large and small separations, respectively. Consequently, in both models, ˜10 per cent of the total PopIII binaries form BBHs only through stable mass transfer and ˜10 per cent of these BBHs merge due to gravitational wave emission within the Hubble time. Furthermore, the chirp mass of merging BBHs has a flat distribution over 15 ≲ Mchirp/M⊙ ≲ 35. This formation pathway of PopIII BBHs is presumably robust because stable mass transfer is less uncertain than common envelope evolution, which is the main formation channel for Population II BBHs. We also test the hypothesis that the BBH mergers detected by LIGO originate from PopIII stars using the total number of PopIII stars formed in the early universe as inferred from the optical depth measured by Planck. We conclude that the PopIII BBH formation scenario can explain the mass-weighted merger rate of the LIGO's O1 events with the maximal PopIII formation efficiency inferred from the Planck measurement, even without BBHs formed by unstable mass transfer or common envelope phases.

  8. Formation and survival of Population III stellar systems

    NASA Astrophysics Data System (ADS)

    Hirano, Shingo; Bromm, Volker

    2017-09-01

    The initial mass function of the first, Population III (Pop III), stars plays a vital role in shaping galaxy formation and evolution in the early Universe. One key remaining issue is the final fate of secondary protostars formed in the accretion disc, specifically whether they merge or survive. We perform a suite of hydrodynamic simulations of the complex interplay among fragmentation, protostellar accretion and merging inside dark matter minihaloes. Instead of the traditional sink particle method, we employ a stiff equation of state approach, so that we can more robustly ascertain the viscous transport inside the disc. The simulations show inside-out fragmentation because the gas collapses faster in the central region. Fragments migrate on the viscous time-scale, over which angular momentum is lost, enabling them to move towards the disc centre, where merging with the primary protostar can occur. This process depends on the fragmentation scale, such that there is a maximum scale of (1-5) × 104 au, inside which fragments can migrate to the primary protostar. Viscous transport is active until radiative feedback from the primary protostar destroys the accretion disc. The final mass spectrum and multiplicity thus crucially depends on the effect of viscosity in the disc. The entire disc is subjected to efficient viscous transport in the primordial case with viscous parameter α ≤ 1. An important aspect of this question is the survival probability of Pop III binary systems, possible gravitational wave sources to be probed with the Advanced LIGO detectors.

  9. III-V High-Efficiency Multijunction Photovoltaics (Fact Sheet)

    SciTech Connect

    Not Available

    2011-06-01

    Capabilities fact sheet that includes scope, core competencies and capabilities, and contact/web information for III-V High-Efficiency Multijunction Photovoltaics at the National Center for Photovoltaics.

  10. High efficiency III-nitride light-emitting diodes

    DOEpatents

    Crawford, Mary; Koleske, Daniel; Cho, Jaehee; Zhu, Di; Noemaun, Ahmed; Schubert, Martin F; Schubert, E. Fred

    2013-05-28

    Tailored doping of barrier layers enables balancing of the radiative recombination among the multiple-quantum-wells in III-Nitride light-emitting diodes. This tailored doping enables more symmetric carrier transport and uniform carrier distribution which help to reduce electron leakage and thus reduce the efficiency droop in high-power III-Nitride LEDs. Mitigation of the efficiency droop in III-Nitride LEDs may enable the pervasive market penetration of solid-state-lighting technologies in high-power lighting and illumination.

  11. Efficient removal of Cr(III)-organic complexes from water using UV/Fe(III) system: Negligible Cr(VI) accumulation and mechanism.

    PubMed

    Ye, Yuxuan; Jiang, Zhao; Xu, Zhe; Zhang, Xiaolin; Wang, Dandan; Lv, Lu; Pan, Bingcai

    2017-09-13

    Most available processes are incapable of removing Cr(III)-organic complexes from water due to their high solubility, extremely slow decomplexation rate, and possible formation of more toxic Cr(VI) during oxidation. Herein, we proposed a new combined process, i.e., UV/Fe(III) followed by alkaline precipitation (namely UV/Fe(III)+OH), to achieve highly efficient and environmentally benign removal of Cr(III)-organic complexes from water. The combined process could remove Cr(III)-citrate from 10.4 mg Cr/L to 0.36 mg Cr/L and ∼60% total organic carbon as well. More attractively, negligible Cr(VI) (<0.06 mg/L) was formed during the process. In the viewpoint of mechanism, the added Fe(III) generates ·OH radicals to transform Cr(III) into Cr(VI) and simultaneously released the citrate ligand to form Fe(III)-citrate simultaneously. Then, the photolysis of Fe(III)-citrate under UV irradiation involved the citrate degradation and the production of massive Fe(II) species, which in turn transformed the formed Cr(VI) back to Cr(III). The free metal ions, including Cr(III), Fe(II) and Fe(III) were removed by the subsequent alkaline precipitation. Also, the combined process is applicable to other Cr(III) complexes with EDTA, tartrate, oxalate, acetate. The applicability of the combined process was further demonstrated by treating two real tanning effluents, resulting in the residual Cr(III) below 1.5 mg/L (the discharge standard of China) and negligible formation of Cr(VI) (<0.004 mg/L) as well. In general, the combined process has a great potential for efficient removal of Cr(III) complexes from contaminated waters. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Effect of Population III Multiplicity on Dark Star Formation

    NASA Technical Reports Server (NTRS)

    Stacy, Athena; Pawlik, Andreas H.; Bromm, Volker; Loeb, Abraham

    2012-01-01

    We numerically study the mutual interaction between dark matter (DM) and Population III (Pop III) stellar systems in order to explore the possibility of Pop III dark stars within this physical scenario. We perform a cosmological simulation, initialized at z approx. 100, which follows the evolution of gas and DM. We analyze the formation of the first mini halo at z approx. 20 and the subsequent collapse of the gas to densities of 10(exp 12)/cu cm. We then use this simulation to initialize a set of smaller-scale 'cut-out' simulations in which we further refine the DM to have spatial resolution similar to that of the gas. We test multiple DM density profiles, and we employ the sink particle method to represent the accreting star-forming region. We find that, for a range of DM configurations, the motion of the Pop III star-disk system serves to separate the positions of the protostars with respect to the DM density peak, such that there is insufficient DM to influence the formation and evolution of the protostars for more than approx. 5000 years. In addition, the star-disk system causes gravitational scattering of the central DM to lower densities, further decreasing the influence of DM over time. Any DM-powered phase of Pop III stars will thus be very short-lived for the typical multiple system, and DM will not serve to significantly prolong the life of Pop III stars.

  13. Nonuniversal star formation efficiency in turbulent ISM

    SciTech Connect

    Semenov, Vadim A.; Kravtsov, Andrey V.; Gnedin, Nickolay Y.

    2016-07-29

    Here, we present a study of a star formation prescription in which star formation efficiency depends on local gas density and turbulent velocity dispersion, as suggested by direct simulations of SF in turbulent giant molecular clouds (GMCs). We test the model using a simulation of an isolated Milky Way-sized galaxy with a self-consistent treatment of turbulence on unresolved scales. We show that this prescription predicts a wide variation of local star formation efficiency per free-fall time, $\\epsilon_{\\rm ff} \\sim 0.1 - 10\\%$, and gas depletion time, $t_{\\rm dep} \\sim 0.1 - 10$ Gyr. In addition, it predicts an effective density threshold for star formation due to suppression of $\\epsilon_{\\rm ff}$ in warm diffuse gas stabilized by thermal pressure. We show that the model predicts star formation rates in agreement with observations from the scales of individual star-forming regions to the kiloparsec scales. This agreement is non-trivial, as the model was not tuned in any way and the predicted star formation rates on all scales are determined by the distribution of the GMC-scale densities and turbulent velocities $\\sigma$ in the cold gas within the galaxy, which is shaped by galactic dynamics. The broad agreement of the star formation prescription calibrated in the GMC-scale simulations with observations, both gives credence to such simulations and promises to put star formation modeling in galaxy formation simulations on a much firmer theoretical footing.

  14. Nonuniversal star formation efficiency in turbulent ISM

    SciTech Connect

    Semenov, Vadim A.; Kravtsov, Andrey V.; Gnedin, Nickolay Y.

    2016-07-29

    Here, we present a study of a star formation prescription in which star formation efficiency depends on local gas density and turbulent velocity dispersion, as suggested by direct simulations of SF in turbulent giant molecular clouds (GMCs). We test the model using a simulation of an isolated Milky Way-sized galaxy with a self-consistent treatment of turbulence on unresolved scales. We show that this prescription predicts a wide variation of local star formation efficiency per free-fall time, $\\epsilon_{\\rm ff} \\sim 0.1 - 10\\%$, and gas depletion time, $t_{\\rm dep} \\sim 0.1 - 10$ Gyr. In addition, it predicts an effective density threshold for star formation due to suppression of $\\epsilon_{\\rm ff}$ in warm diffuse gas stabilized by thermal pressure. We show that the model predicts star formation rates in agreement with observations from the scales of individual star-forming regions to the kiloparsec scales. This agreement is non-trivial, as the model was not tuned in any way and the predicted star formation rates on all scales are determined by the distribution of the GMC-scale densities and turbulent velocities $\\sigma$ in the cold gas within the galaxy, which is shaped by galactic dynamics. The broad agreement of the star formation prescription calibrated in the GMC-scale simulations with observations, both gives credence to such simulations and promises to put star formation modeling in galaxy formation simulations on a much firmer theoretical footing.

  15. Octachlorodibenzodioxin formation on Fe(III)-montmorillonite clay.

    PubMed

    Gu, Cheng; Li, Hui; Teppen, Brian J; Boyd, Stephen A

    2008-07-01

    Polychlorinated dibenzo-p-dioxins (PCDDs) are ubiquitous and highly toxic environmental contaminants found in surface and subsurface soils and in clay deposits. Interestingly, the congener profiles of such PCDDs are inexplicably dissimilar to those of known anthropogenic (e.g., pesticide manufacture, waste incineration) or natural (e.g., forest fire) sources. Characteristic features of soil or clay-associated PCDDs are the dominance of octachlorodibenzo-p-dioxin (OCDD) as the most abundant congener and very low levels of polychlorinated dibenzofurans (PCDFs). These propensities led to the hypothesis of in situ PCDD formation in soils and geologic clay deposits. In this study, we demonstrate the formation of OCDD on the naturally occurring and widely distributed clay mineral montmorillonite under environmentally relevant conditions. When pentachlorophenol (PCP)was mixed with Fe(III)-montmorillonite, significant amounts of OCDD were rapidly (minutes to days) formed (approximately 5 mg OCDD/kg clay) at ambient temperature in the presence of water. This reaction is initiated by single electron transfer from PCP to Fe(III)-montmorillonite thereby forming the PCP radical cation. Subsequent dimerization, dechlorination, and ring closure reactions result in formation of OCDD. This study provides the first direct evidence for clay-catalyzed formation of OCDD supporting the plausibility of its in situ formation in soils.

  16. Nonuniversal star formation efficiency in turbulent ISM

    DOE PAGES

    Semenov, Vadim A.; Kravtsov, Andrey V.; Gnedin, Nickolay Y.

    2016-07-29

    Here, we present a study of a star formation prescription in which star formation efficiency depends on local gas density and turbulent velocity dispersion, as suggested by direct simulations of SF in turbulent giant molecular clouds (GMCs). We test the model using a simulation of an isolated Milky Way-sized galaxy with a self-consistent treatment of turbulence on unresolved scales. We show that this prescription predicts a wide variation of local star formation efficiency per free-fall time,more » $$\\epsilon_{\\rm ff} \\sim 0.1 - 10\\%$$, and gas depletion time, $$t_{\\rm dep} \\sim 0.1 - 10$$ Gyr. In addition, it predicts an effective density threshold for star formation due to suppression of $$\\epsilon_{\\rm ff}$$ in warm diffuse gas stabilized by thermal pressure. We show that the model predicts star formation rates in agreement with observations from the scales of individual star-forming regions to the kiloparsec scales. This agreement is non-trivial, as the model was not tuned in any way and the predicted star formation rates on all scales are determined by the distribution of the GMC-scale densities and turbulent velocities $$\\sigma$$ in the cold gas within the galaxy, which is shaped by galactic dynamics. The broad agreement of the star formation prescription calibrated in the GMC-scale simulations with observations, both gives credence to such simulations and promises to put star formation modeling in galaxy formation simulations on a much firmer theoretical footing.« less

  17. Biofilms of As(III)-oxidising bacteria: formation and activity studies for bioremediation process development.

    PubMed

    Michel, C; Jean, M; Coulon, S; Dictor, M-C; Delorme, F; Morin, D; Garrido, F

    2007-11-01

    The formation and activity of an As(III)-oxidising biofilm in a bioreactor, using pozzolana as bacterial growth support, was studied for the purpose of optimising fixed-bed bioreactors for bioremediation. After 60 days of continuous functioning with an As(III)-contaminated effluent, the active biofilm was found to be located mainly near the inflow rather than homogeneously distributed. Biofilm development by the CAsO1 bacterial consortium and by Thiomonas arsenivorans was then studied both on polystyrene microplates and on pozzolana. Extra-cellular polymeric substances (EPS) and yeast extract were found to enhance bacteria attachment, and yeast extract also appears to increase the kinetics of biofilm formation. Analysis of proteins, sugars, lipids and uronic acids indicate that sugars were the main EPS components. The specific As(III)-oxidase activity of T. arsenivorans was higher (by ninefold) for planktonic cells than for sessile ones and was induced by As(III). All the results suggest that the biofilm structure is a physical barrier decreasing As(III) access to sessile cells and thus to As(III)-oxidase activity induction. The efficiency of fixed-bed reactors for the bioremediation of arsenic-contaminated waters can be thus optimised by controlling different factors such as temperature and EPS addition and/or synthesis to increase biofilm density and activity.

  18. Nonuniversal Star Formation Efficiency in Turbulent ISM

    NASA Astrophysics Data System (ADS)

    Semenov, Vadim A.; Kravtsov, Andrey V.; Gnedin, Nickolay Y.

    2016-08-01

    We present a study of a star formation prescription in which star formation efficiency (SFE) depends on local gas density and turbulent velocity dispersion, as suggested by direct simulations of SF in turbulent giant molecular clouds (GMCs). We test the model using a simulation of an isolated Milky-Way-sized galaxy with a self-consistent treatment of turbulence on unresolved scales. We show that this prescription predicts a wide variation of local SFE per free-fall time, {ɛ }{ff} ˜ 0.1%-10%, and gas depletion time, {t}{dep} ˜ 0.1-10 Gyr. In addition, it predicts an effective density threshold for star formation due to suppression of {ɛ }{ff} in warm diffuse gas stabilized by thermal pressure. We show that the model predicts star formation rates (SFRs) in agreement with observations from the scales of individual star-forming regions to the kiloparsec scales. This agreement is nontrivial, as the model was not tuned in any way and the predicted SFRs on all scales are determined by the distribution of the GMC-scale densities and turbulent velocities σ in the cold gas within the galaxy, which is shaped by galactic dynamics. The broad agreement of the star formation prescription calibrated in the GMC-scale simulations with observations both gives credence to such simulations and promises to put star formation modeling in galaxy formation simulations on a much firmer theoretical footing.

  19. Probing Population III Star Formation in a z=7 Galaxy

    NASA Astrophysics Data System (ADS)

    Fan, Xiaohui

    2011-10-01

    We propose to carry out deep WFC-3/F132N narrow-band imaging of the galaxy BDF-521 {z = 7.008+/-0.002} to measure the strength of He II 1640 emission line in this young galaxy at the end of reionization epoch. He II 1640 emission, if detected, will provide the first direct evidence of massive Population III {metal free} star formation in the early Universe. In a pilot program in Cycle-17, we obtained narrow-band imaging centered on HeII for the galaxy IOK-1 at z=6.96, and found the He II flux to be 1.2+/-1.0 x 10^-18 ergs s^-1 cm^-2, corresponding to a 1-sigma upper limit of 2 M_sun/yr in Pop-III star formation rate {SFR} assuming a top-heavy IMF. This sensitivity is 2.5x deeper than for the best previous ground-based measurement, and illustrates the power of HST narrow-band imaging in probing the earliest star formation. In this cycle, we will continue this effort by targeting galaxy BDF-521 at z=7.01 using F132N which covers the HeII emission at the galaxy redshift. The ground based photometry implies that BDF-521 has an extremely blue continuum slope with f_lambda lambda^-4, the bluest among all confirmed galaxies at z>6, suggestive of either extremely low metallicity and/or a complete lack of dust. Therefore, BDF-521 is the most promising candidate for Pop-III detection. This new HST observations will be able to detect or place the most stringent upper limit of 0.6 M_sun/yr on the Pop-III SFR {1 sigma}. We will also use short F125W and F160W broad-band observations to measure the rest-frame UV flux of BDF-521 in order to estimate its overall SFR, confirm the blue UV slope, and quantify the morphology, as well as provide continuum subtraction for narrow-band imaging.

  20. Ditopic CMPO-pillar[5]arenes as unique receptors for efficient separation of americium(III) and europium(III).

    PubMed

    Fang, Yuyu; Yuan, Xiangyang; Wu, Lei; Peng, Zhiyong; Feng, Wen; Liu, Ning; Xu, Dingguo; Li, Shoujian; Sengupta, Arijit; Mohapatra, Prasanta K; Yuan, Lihua

    2015-03-11

    A unique host-guest recognition process involving a new class of homoditopic CMPO-pillar[5]arenes and lanthanides was revealed to proceed in a stepwise manner, and correlated with the efficient separation of americium(III) and europium(III) under acidic feed conditions.

  1. 21 CFR 807.94 - Format of a class III certification.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Format of a class III certification. 807.94... IMPORTERS OF DEVICES Premarket Notification Procedures § 807.94 Format of a class III certification. (a) A class III certification submitted as part of a premarket notification shall state as follows: I...

  2. Heats of Formation and Bond Energies in Group III Compounds

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Allendorf, Mark D.; Melius, Carl F.; Arnold, James O. (Technical Monitor)

    1999-01-01

    We present heats of formation and bond energies for Group-III compounds obtained from calculations of molecular ground-state I electronic energies. Data for compounds of the form MXn are presented, where M = B, Al, Ga, and In, X = He H, Cl, and CH3, and n = 1-3. Energies for the B, Al, and Ga compounds are obtained from G2 predictions, while those for the In compounds are obtained from CCSD(T)/CBS calculations; these are the most accurate calculations for indium-containing compounds published to date. In most cases, the calculated thermochemistry is in good agreement with published values derived from experiments for those species that have well-established heats of formation. Bond energies obtained from the heats of formation follow the expected trend (Cl much greater than CH3 approx. H). However, the CH3M-(CH3)2 bond energies obtained for trimethylgallium and trimethylindium are considerably stronger (greater than 15 kcal/mol) than currently accepted values.

  3. Visualizations of Population III star formation and supernovae

    NASA Astrophysics Data System (ADS)

    Norman, M. L.; O'Shea, B. W.

    2006-06-01

    We present a visualization of a simulation of the formation of a Population III star and the resulting supernova performed with the Enzo adaptive mesh refinement cosmology code. This visualization, which will appear in the planetarium at the Denver Museum of Nature and Science, was produced in collaboration with Donna Cox, Robert Patterson, Stuart Levy, Matthew Hall and Lorne Leonard at the National Center for Supercomputing Applications. It traces the evolution of a 300 kpc/h (comoving) volume of the universe from 16 million years after the Big Bang until the collapse of the first primordial protostellar cloud at z=18, approximately 150 million years later. This star then explodes in a 30 solar mass supernova, which pollutes a region several hundred parsecs across with metals. This work was funded in part by the NSF, NASA and the Department of Energy.

  4. Addendum I, BIOPLUME III Graphics Conversion to SURFER Format

    EPA Pesticide Factsheets

    This procedure can be used to create a SURFER® compatible grid file from Bioplume III input and output graphics. The input data and results from Bioplume III can be contoured and printed directly from SURFER.

  5. Formation of Gold(III) Alkyls from Gold Alkoxide Complexes

    PubMed Central

    2017-01-01

    The gold(III) methoxide complex (C∧N∧C)AuOMe (1) reacts with tris(p-tolyl)phosphine in benzene at room temperature under O abstraction to give the methylgold product (C∧N∧C)AuMe (2) together with O=P(p-tol)3 ((C∧N∧C) = [2,6-(C6H3tBu-4)2pyridine]2–). Calculations show that this reaction is energetically favorable (ΔG = −32.3 kcal mol–1). The side products in this reaction, the Au(II) complex [Au(C∧N∧C)]2 (3) and the phosphorane (p-tol)3P(OMe)2, suggest that at least two reaction pathways may operate, including one involving (C∧N∧C)Au• radicals. Attempts to model the reaction by DFT methods showed that PPh3 can approach 1 to give a near-linear Au–O–P arrangement, without phosphine coordination to gold. The analogous reaction of (C∧N∧C)AuOEt, on the other hand, gives exclusively a mixture of 3 and (p-tol)3P(OEt)2. Whereas the reaction of (C∧N∧C)AuOR (R = But, p-C6H4F) with P(p-tol)3 proceeds over a period of hours, compounds with R = CH2CF3, CH(CF3)2 react almost instantaneously, to give 3 and O=P(p-tol)3. In chlorinated solvents, treatment of the alkoxides (C∧N∧C)AuOR with phosphines generates [(C∧N∧C)Au(PR3)]Cl, via Cl abstraction from the solvent. Attempts to extend the synthesis of gold(III) alkoxides to allyl alcohols were unsuccessful; the reaction of (C∧N∧C)AuOH with an excess of CH2=CHCH2OH in toluene led instead to allyl alcohol isomerization to give a mixture of gold alkyls, (C∧N∧C)AuR′ (R′ = −CH2CH2CHO (10), −CH2CH(CH2OH)OCH2CH=CH2 (11)), while 2-methallyl alcohol affords R′ = CH2CH(Me)CHO (12). The crystal structure of 11 was determined. The formation of Au–C instead of the expected Au–O products is in line with the trend in metal–ligand bond dissociation energies for Au(III): M–H > M–C > M–O.

  6. GMC Collisions as Triggers of Star Formation. III. Density and Magnetically Regulated Star Formation

    NASA Astrophysics Data System (ADS)

    Wu, Benjamin; Tan, Jonathan C.; Christie, Duncan; Nakamura, Fumitaka; Van Loo, Sven; Collins, David

    2017-06-01

    We study giant molecular cloud (GMC) collisions and their ability to trigger star cluster formation. We further develop our three-dimensional magnetized, turbulent, colliding GMC simulations by implementing star formation subgrid models. Two such models are explored: (1) “Density-Regulated,” i.e., fixed efficiency per free-fall time above a set density threshold and (2) “Magnetically Regulated,” i.e., fixed efficiency per free-fall time in regions that are magnetically supercritical. Variations of parameters associated with these models are also explored. In the non-colliding simulations, the overall level of star formation is sensitive to model parameter choices that relate to effective density thresholds. In the GMC collision simulations, the final star formation rates and efficiencies are relatively independent of these parameters. Between the non-colliding and colliding cases, we compare the morphologies of the resulting star clusters, properties of star-forming gas, time evolution of the star formation rate (SFR), spatial clustering of the stars, and resulting kinematics of the stars in comparison to the natal gas. We find that typical collisions, by creating larger amounts of dense gas, trigger earlier and enhanced star formation, resulting in 10 times higher SFRs and efficiencies. The star clusters formed from GMC collisions show greater spatial substructure and more disturbed kinematics.

  7. The remarkable efficiency of N-heterocyclic carbenes in lanthanide(III)/actinide(III) differentiation.

    PubMed

    Mehdoui, Thouraya; Berthet, Jean-Claude; Thuéry, Pierre; Ephritikhine, Michel

    2005-06-14

    The capacity of NHC molecules to discriminate between trivalent lanthanide and actinide ions was revealed by competition reactions of analogous U(III) and Ce(III) compounds with C3Me4N2 and a comparison of the crystal structures of the corresponding carbene adducts.

  8. Late Pop III Star Formation During the Epoch of Reionization: Results from the Renaissance Simulations

    NASA Astrophysics Data System (ADS)

    Xu, Hao; Norman, Michael L.; O'Shea, Brian W.; Wise, John H.

    2016-06-01

    We present results on the formation of Population III (Pop III) stars at redshift 7.6 from the Renaissance Simulations, a suite of extremely high-resolution and physics-rich radiation transport hydrodynamics cosmological adaptive-mesh refinement simulations of high-redshift galaxy formation performed on the Blue Waters supercomputer. In a survey volume of about 220 comoving Mpc3, we found 14 Pop III galaxies with recent star formation. The surprisingly late formation of Pop III stars is possible due to two factors: (i) the metal enrichment process is local and slow, leaving plenty of pristine gas to exist in the vast volume; and (ii) strong Lyman-Werner radiation from vigorous metal-enriched star formation in early galaxies suppresses Pop III formation in (“not so”) small primordial halos with mass less than ˜3 × 107 M ⊙. We quantify the properties of these Pop III galaxies and their Pop III star formation environments. We look for analogs to the recently discovered luminous Ly α emitter CR7, which has been interpreted as a Pop III star cluster within or near a metal-enriched star-forming galaxy. We find and discuss a system similar to this in some respects, however, the Pop III star cluster is far less massive and luminous than CR7 is inferred to be.

  9. Coordinated binding of Vps4 to ESCRT-III drives membrane neck constriction during MVB vesicle formation.

    PubMed

    Adell, Manuel Alonso Y; Vogel, Georg F; Pakdel, Mehrshad; Müller, Martin; Lindner, Herbert; Hess, Michael W; Teis, David

    2014-04-14

    Five endosomal sorting complexes required for transport (ESCRTs) mediate the degradation of ubiquitinated membrane proteins via multivesicular bodies (MVBs) in lysosomes. ESCRT-0, -I, and -II interact with cargo on endosomes. ESCRT-II also initiates the assembly of a ringlike ESCRT-III filament consisting of Vps20, Snf7, Vps24, and Vps2. The AAA-adenosine triphosphatase Vps4 disassembles and recycles the ESCRT-III complex, thereby terminating the ESCRT pathway. A mechanistic role for Vps4 in intraluminal vesicle (ILV) formation has been unclear. By combining yeast genetics, biochemistry, and electron tomography, we find that ESCRT-III assembly on endosomes is required to induce or stabilize the necks of growing MVB ILVs. Yet, ESCRT-III alone is not sufficient to complete ILV biogenesis. Rather, binding of Vps4 to ESCRT-III, coordinated by interactions with Vps2 and Snf7, is coupled to membrane neck constriction during ILV formation. Thus, Vps4 not only recycles ESCRT-III subunits but also cooperates with ESCRT-III to drive distinct membrane-remodeling steps, which lead to efficient membrane scission at the end of ILV biogenesis in vivo.

  10. Formation, disruption and energy output of Population III X-ray binaries

    NASA Astrophysics Data System (ADS)

    Ryu, Taeho; Tanaka, Takamitsu L.; Perna, Rosalba

    2016-02-01

    The first astrophysical objects shaped the cosmic environment by reionizing and heating the intergalactic medium (IGM). Particularly, X-rays are very efficient at heating the IGM before reionization is complete. High-mass X-ray binaries (HMXBs) in early stellar populations are prime candidates for driving the thermal evolution of the IGM at redshifts z ≳ 20; however, their formation efficiency is not well understood. Using N-body simulations, we estimate the HMXB formation rate via mutual gravitational interactions of nascent, small groups of the Population III stars. We run two sets of calculations: (i) stars formed in small groups of five in nearly Keplerian initial orbits and (ii) collision of two such groups (an expected outcome of mergers of host protogalaxies). We find that HMXBs form at a rate of one per ≳ 104 M⊙ in newly born stars, and that they emit with a power of ˜1041 erg s-1 in the 2-10 keV band per star formation rate. This value is a factor of ˜102 larger than what is observed in star-forming galaxies at lower redshifts; the X-ray production from early HMXBs would have been even more copious, if they also formed in situ or via migration in protostellar discs. Combining our results with earlier studies suggests that early HMXBs were highly effective at heating the IGM and leaving a strong 21-cm signature. We discuss broader implications of our results, such as the rate of long gamma-ray bursts from Population III stars and the direct collapse channel for massive black hole formation.

  11. Lanthanum(III) catalysts for highly efficient and chemoselective transesterification.

    PubMed

    Hatano, Manabu; Ishihara, Kazuaki

    2013-03-11

    A facile, atom-economical, and chemoselective esterification is crucial in modern organic synthesis, particularly in the areas of pharmaceutical, polymer, and material science. However, a truly practical catalytic transesterification of carboxylic esters with various alcohols has not yet been well established, since, with many conventional catalysts, the substrates are limited to 1°- and cyclic 2°-alcohols. In sharp contrast, if we take advantage of the high catalytic activities of La(Oi-Pr)(3), La(OTf)(3), and La(NO(3))(3) as ligand-free catalysts, ligand-assisted or additive-enhanced lanthanum(III) catalysts can be highly effective acid-base combined catalysts in transesterification. A highly active dinuclear La(III) catalyst, which is prepared in situ from lanthanum(III) isopropoxide and 2-(2-methoxyethoxy)ethanol, is effective for the practical transesterification of methyl carboxylates, ethyl acetate, weakly reactive dimethyl carbonate, and much less-reactive methyl carbamates with 1°-, 2°-, and 3°-alcohols. As the second generation, nearly neutral "lanthanum(III) nitrate alkoxide", namely La(OR)(m)(NO(3))(3-m), has been developed. This catalyst is prepared in situ from inexpensive, stable, low-toxic lanthanum(III) nitrate hydrate and methyltrioctylphosphonium methyl carbonate, and is highly useful in the non-epimerized transesterification of α-substituted chiral carboxylic esters, even under azeotropic reflux conditions. In these practical La(III)-catalyzed transesterifications, colorless esters can be obtained in small- to large-scale synthesis without the need for inconvenient work-up or careful purification procedures.

  12. Predicting Efficient Antenna Ligands for Tb(III) Emission

    SciTech Connect

    Samuel, Amanda P.S.; Xu, Jide; Raymond, Kenneth

    2008-10-06

    A series of highly luminescent Tb(III) complexes of para-substituted 2-hydroxyisophthalamide ligands (5LI-IAM-X) has been prepared (X = H, CH{sub 3}, (C=O)NHCH{sub 3}, SO{sub 3}{sup -}, NO{sub 2}, OCH{sub 3}, F, Cl, Br) to probe the effect of substituting the isophthalamide ring on ligand and Tb(III) emission in order to establish a method for predicting the effects of chromophore modification on Tb(III) luminescence. The energies of the ligand singlet and triplet excited states are found to increase linearly with the {pi}-withdrawing ability of the substituent. The experimental results are supported by time-dependent density functional theory (TD-DFT) calculations performed on model systems, which predict ligand singlet and triplet energies within {approx}5% of the experimental values. The quantum yield ({Phi}) values of the Tb(III) complex increases with the triplet energy of the ligand, which is in part due to the decreased non-radiative deactivation caused by thermal repopulation of the triplet. Together, the experimental and theoretical results serve as a predictive tool that can be used to guide the synthesis of ligands used to sensitize lanthanide luminescence.

  13. ON THE LACK OF EVOLUTION IN GALAXY STAR FORMATION EFFICIENCY

    SciTech Connect

    Behroozi, Peter S.; Wechsler, Risa H.; Conroy, Charlie

    2013-01-10

    Using reconstructed galaxy star formation histories, we calculate the instantaneous efficiency of galaxy star formation (i.e., the star formation rate divided by the baryon accretion rate) from z = 8 to the present day. This efficiency exhibits a clear peak near a characteristic halo mass of 10{sup 11.7} M{sub Sun }, which coincides with longstanding theoretical predictions for the mass scale relevant to virial shock heating of accreted gas. Above the characteristic halo mass, the efficiency falls off as the mass to the minus four-thirds power; below the characteristic mass, the efficiency falls off at an average scaling of mass to the two-thirds power. By comparison, the shape and normalization of the efficiency change very little since z = 4. We show that a time-independent star formation efficiency simply explains the shape of the cosmic star formation rate since z = 4 in terms of dark matter accretion rates. The rise in the cosmic star formation from early times until z = 2 is especially sensitive to galaxy formation efficiency. The mass dependence of the efficiency strongly limits where most star formation occurs, with the result that two-thirds of all star formation has occurred inside halos within a factor of three of the characteristic mass, a range that includes the mass of the Milky Way.

  14. POPULATION III STAR FORMATION IN LARGE COSMOLOGICAL VOLUMES. I. HALO TEMPORAL AND PHYSICAL ENVIRONMENT

    SciTech Connect

    Crosby, Brian D.; O'Shea, Brian W.; Smith, Britton D.; Turk, Matthew J.; Hahn, Oliver

    2013-08-20

    We present a semi-analytic, computationally inexpensive model to identify halos capable of forming a Population III star in cosmological simulations across a wide range of times and environments. This allows for a much more complete and representative set of Population III star forming halos to be constructed, which will lead to Population III star formation simulations that more accurately reflect the diversity of Population III stars, both in time and halo mass. This model shows that Population III and chemically enriched stars coexist beyond the formation of the first generation of stars in a cosmological simulation until at least z {approx} 10, and likely beyond, though Population III stars form at rates that are 4-6 orders of magnitude lower than chemically enriched stars by z = 10. A catalog of more than 40,000 candidate Population III forming halos were identified, with formation times temporally ranging from z = 30 to z = 10, and ranging in mass from 2.3 Multiplication-Sign 10{sup 5} M{sub Sun} to 1.2 Multiplication-Sign 10{sup 10} M{sub Sun }. At early times, the environment that Population III stars form in is very similar to that of halos hosting chemically enriched star formation. At later times Population III stars are found to form in low-density regions that are not yet chemically polluted due to a lack of previous star formation in the area. Population III star forming halos become increasingly spatially isolated from one another at later times, and are generally closer to halos hosting chemically enriched star formation than to another halo hosting Population III star formation by z {approx} 10.

  15. THE DELAY OF POPULATION III STAR FORMATION BY SUPERSONIC STREAMING VELOCITIES

    SciTech Connect

    Greif, Thomas H.; White, Simon D. M.; Klessen, Ralf S.; Springel, Volker

    2011-08-01

    It has recently been demonstrated that coherent relative streaming velocities of order 30 km s{sup -1} between dark matter and gas permeated the universe on scales below a few Mpc directly after recombination. Here we use a series of high-resolution moving-mesh calculations to show that these supersonic motions significantly influence the virialization of the gas in minihalos and delay the formation of the first stars. As the gas streams into minihalos with bulk velocities around 1 km s{sup -1} at z {approx} 20, the additional momentum and energy input reduces the gas fractions and central densities of the halos, increasing the typical virial mass required for efficient cooling by a factor of three and delaying Population III star formation by {Delta}z {approx_equal} 4. Since the distribution of the magnitude of the streaming velocities is narrowly peaked around a non-negligible value, this effect is important in most regions of the universe. As a consequence, the increased minimum halo mass implies a reduction of the absolute number of minihalos that can be expected to cool and form Population III stars by up to an order of magnitude. We further find that the streaming velocities increase the turbulent velocity dispersion of the minihalo gas, which could affect its ability to fragment and hence alter the mass function of the first stars.

  16. Spectrophotometric Determination of Iron(III)-Glycine Formation Constant in Aqueous Medium Using Competitive Ligand Binding

    ERIC Educational Resources Information Center

    Prasad, Rajendra; Prasad, Surendra

    2009-01-01

    The formation constant of iron(III) complex with glycine (Gly) ligand in aqueous acidic medium (0.2 M HNO[subscript 3], I = 0.2 M at 28 plus or minus 1 degree C) was determined spectrophotometrically in which a competing color reaction between Fe(III) and SCN[superscript -] was used as an indicator reaction. Under the specified conditions Fe(III)…

  17. Spectrophotometric Determination of Iron(III)-Glycine Formation Constant in Aqueous Medium Using Competitive Ligand Binding

    ERIC Educational Resources Information Center

    Prasad, Rajendra; Prasad, Surendra

    2009-01-01

    The formation constant of iron(III) complex with glycine (Gly) ligand in aqueous acidic medium (0.2 M HNO[subscript 3], I = 0.2 M at 28 plus or minus 1 degree C) was determined spectrophotometrically in which a competing color reaction between Fe(III) and SCN[superscript -] was used as an indicator reaction. Under the specified conditions Fe(III)…

  18. High bandgap III-V alloys for high efficiency optoelectronics

    DOEpatents

    Alberi, Kirstin; Mascarenhas, Angelo; Wanlass, Mark

    2017-01-10

    High bandgap alloys for high efficiency optoelectronics are disclosed. An exemplary optoelectronic device may include a substrate, at least one Al.sub.1-xIn.sub.xP layer, and a step-grade buffer between the substrate and at least one Al.sub.1-xIn.sub.xP layer. The buffer may begin with a layer that is substantially lattice matched to GaAs, and may then incrementally increase the lattice constant in each sequential layer until a predetermined lattice constant of Al.sub.1-xIn.sub.xP is reached.

  19. SIMULATIONS ON A MOVING MESH: THE CLUSTERED FORMATION OF POPULATION III PROTOSTARS

    SciTech Connect

    Greif, Thomas H.; White, Simon D. M.; Springel, Volker; Glover, Simon C. O.; Clark, Paul C.; Smith, Rowan J.; Klessen, Ralf S.; Bromm, Volker

    2011-08-20

    The cosmic dark ages ended a few hundred million years after the big bang, when the first stars began to fill the universe with new light. It has generally been argued that these stars formed in isolation and were extremely massive-perhaps 100 times as massive as the Sun. In a recent study, Clark and collaborators showed that this picture requires revision. They demonstrated that the accretion disks that build up around Population III stars are strongly susceptible to fragmentation and that the first stars should therefore form in clusters rather than in isolation. We here use a series of high-resolution hydrodynamical simulations performed with the moving mesh code AREPO to follow up on this proposal and to study the influence of environmental parameters on the level of fragmentation. We model the collapse of five independent minihalos from cosmological initial conditions, through the runaway condensation of their central gas clouds, to the formation of the first protostar, and beyond for a further 1000 years. During this latter accretion phase, we represent the optically thick regions of protostars by sink particles. Gas accumulates rapidly in the circumstellar disk around the first protostar, fragmenting vigorously to produce a small group of protostars. After an initial burst, gravitational instability recurs periodically, forming additional protostars with masses ranging from {approx}0.1 to 10 M{sub sun}. Although the shape, multiplicity, and normalization of the protostellar mass function depend on the details of the sink-particle algorithm, fragmentation into protostars with diverse masses occurs in all cases, confirming earlier reports of Population III stars forming in clusters. Depending on the efficiency of later accretion and merging, Population III stars may enter the main sequence in clusters and with much more diverse masses than are commonly assumed.

  20. Limits on Population III star formation with the most iron-poor stars

    NASA Astrophysics Data System (ADS)

    de Bennassuti, M.; Salvadori, S.; Schneider, R.; Valiante, R.; Omukai, K.

    2017-02-01

    We study the impact of star-forming minihaloes, and the initial mass function (IMF) of Population III (Pop III) stars, on the Galactic halo metallicity distribution function (MDF) and on the properties of C-enhanced and C-normal stars at [Fe/H] < -3. For our investigation we use a data-constrained merger tree model for the Milky Way formation, which has been improved to self-consistently describe the physical processes regulating star formation in minihaloes, including the poor sampling of the Pop III IMF. We find that only when star-forming minihaloes are included the low-Fe tail of the MDF is correctly reproduced, showing a plateau that is built up by C-enhanced metal-poor stars imprinted by primordial faint supernovae. The incomplete sampling of the Pop III IMF in inefficiently star-forming minihaloes (<10-3 M⊙ yr-1) strongly limits the formation of pair-instability supernovae (PISNe), with progenitor masses mPopIII = [140-260] M⊙, even when a flat Pop III IMF is assumed. Second-generation stars formed in environments polluted at >50 per cent level by PISNe are thus extremely rare, corresponding to ≈0.25 per cent of the total stellar population at [Fe/H] < -2, which is consistent with recent observations. The low-Fe tail of the MDF strongly depends on the Pop III IMF shape and mass range. Given the current statistics, we find that a flat Pop III IMF model with mPopIII = [10-300] M⊙ is disfavoured by observations. We present testable predictions for Pop III stars extending down to lower masses, with mPopIII = [0.1-300] M⊙.

  1. LuIII parvovirus selectively and efficiently targets, replicates in, and kills human glioma cells.

    PubMed

    Paglino, Justin C; Ozduman, Koray; van den Pol, Anthony N

    2012-07-01

    Because productive infection by parvoviruses requires cell division and is enhanced by oncogenic transformation, some parvoviruses may have potential utility in killing cancer cells. To identify the parvovirus(es) with the optimal oncolytic effect against human glioblastomas, we screened 12 parvoviruses at a high multiplicity of infection (MOI). MVMi, MVMc, MVM-G17, tumor virus X (TVX), canine parvovirus (CPV), porcine parvovirus (PPV), rat parvovirus 1A (RPV1A), and H-3 were relatively ineffective. The four viruses with the greatest oncolytic activity, LuIII, H-1, MVMp, and MVM-G52, were tested for the ability, at a low MOI, to progressively infect the culture over time, causing cell death at a rate higher than that of cell proliferation. LuIII alone was effective in all five human glioblastomas tested. H-1 progressively infected only two of five; MVMp and MVM-G52 were ineffective in all five. To investigate the underlying mechanism of LuIII's phenotype, we used recombinant parvoviruses with the LuIII capsid replacing the MVMp capsid or with molecular alteration of the P4 promoter. The LuIII capsid enhanced efficient replication and oncolysis in MO59J gliomas cells; other gliomas tested required the entire LuIII genome to exhibit enhanced infection. LuIII selectively infected glioma cells over normal glial cells in vitro. In mouse models, human glioblastoma xenografts were selectively infected by LuIII when administered intratumorally; LuIII reduced tumor growth by 75%. LuIII also had the capacity to selectively infect subcutaneous or intracranial gliomas after intravenous inoculation. Intravenous or intracranial LuIII caused no adverse effects. Intracranial LuIII caused no infection of mature mouse neurons or glia in vivo but showed a modest infection of developing neurons.

  2. LuIII Parvovirus Selectively and Efficiently Targets, Replicates in, and Kills Human Glioma Cells

    PubMed Central

    Paglino, Justin C.; Ozduman, Koray

    2012-01-01

    Because productive infection by parvoviruses requires cell division and is enhanced by oncogenic transformation, some parvoviruses may have potential utility in killing cancer cells. To identify the parvovirus(es) with the optimal oncolytic effect against human glioblastomas, we screened 12 parvoviruses at a high multiplicity of infection (MOI). MVMi, MVMc, MVM-G17, tumor virus X (TVX), canine parvovirus (CPV), porcine parvovirus (PPV), rat parvovirus 1A (RPV1A), and H-3 were relatively ineffective. The four viruses with the greatest oncolytic activity, LuIII, H-1, MVMp, and MVM-G52, were tested for the ability, at a low MOI, to progressively infect the culture over time, causing cell death at a rate higher than that of cell proliferation. LuIII alone was effective in all five human glioblastomas tested. H-1 progressively infected only two of five; MVMp and MVM-G52 were ineffective in all five. To investigate the underlying mechanism of LuIII's phenotype, we used recombinant parvoviruses with the LuIII capsid replacing the MVMp capsid or with molecular alteration of the P4 promoter. The LuIII capsid enhanced efficient replication and oncolysis in MO59J gliomas cells; other gliomas tested required the entire LuIII genome to exhibit enhanced infection. LuIII selectively infected glioma cells over normal glial cells in vitro. In mouse models, human glioblastoma xenografts were selectively infected by LuIII when administered intratumorally; LuIII reduced tumor growth by 75%. LuIII also had the capacity to selectively infect subcutaneous or intracranial gliomas after intravenous inoculation. Intravenous or intracranial LuIII caused no adverse effects. Intracranial LuIII caused no infection of mature mouse neurons or glia in vivo but showed a modest infection of developing neurons. PMID:22553327

  3. Efficient star formation in the bright bar of M83

    NASA Technical Reports Server (NTRS)

    Lord, S. D.; Strom, S. E.; Young, J. S.

    1987-01-01

    The bright molecular bar in M83 was detected standing out as a 100% enhancement of molecular emission with respect to the off-bar emission at the same radii. The spatial variations in the star formation efficiency, as traced by H alpha emission and the surface density of the interstellar gas, in M83 and M51 were compared. Both the central bar of M83 and the spiral arms of M51 are regions characterized by high massive star formation rates. For M83, it is ascribed that both the gas surface density and the star formation efficiency are high to the hydrodynamics of the central region.

  4. NIR-emissive iridium(III) corrole complexes as efficient singlet oxygen sensitizers.

    PubMed

    Sinha, Woormileela; Ravotto, Luca; Ceroni, Paola; Kar, Sanjib

    2015-10-28

    Three new iridium(iii) corrole complexes, having symmetrically and asymmetrically substituted corrole frameworks and judiciously varied axial ligands are prepared and characterized by various spectroscopic techniques including the X-ray structures of two of them. The observed phosphorescence at ambient temperature appears at much longer wavelengths than the previously reported Ir(iii) porphyrin/corrole derivatives. Efficiencies of these compounds in the generation of singlet oxygen are also studied for the first time.

  5. High Efficiency GPS Block III L1 band Envelope Tracking Power Amplifier

    DTIC Science & Technology

    2016-03-31

    envelope sign igh efficiency lope tracking a -III L1-ba katani1, Jo entric Techno position resol block-III sa an current GP provide the specially in th...RF s abstract, the of an L-band power amplif e envelope tr used by radio . In Fig. 3 the and Bock-III 5 ar function, wh expansion. A ately 5 times... power amp pe tracking ar s with digi educes the iso iplexer greatly cking (ET) a f non-constan cking, the supp d by the lope of the RF throughout th s

  6. New III-V cell design approaches for very high efficiency

    SciTech Connect

    Lundstrom, M.S.; Melloch, M.R.; Lush, G.B.; Patkar, M.P.; Young, M.P. )

    1993-04-01

    This report describes to examine new solar cell desip approaches for achieving very high conversion efficiencies. The program consists of two elements. The first centers on exploring new thin-film approaches specifically designed for M-III semiconductors. Substantial efficiency gains may be possible by employing light trapping techniques to confine the incident photons, as well as the photons emitted by radiative recombination. The thin-film approach is a promising route for achieving substantial performance improvements in the already high-efficiency, single-junction, III-V cell. The second element of the research involves exploring desip approaches for achieving high conversion efficiencies without requiring extremely high-quality material. This work has applications to multiple-junction cells, for which the selection of a component cell often involves a compromise between optimum band pp and optimum material quality. It could also be a benefit manufacturing environment by making the cell's efficiency less dependent on materialquality.

  7. Efficient phosphodiester hydrolysis by luminescent terbium(III) and europium(III) complexes.

    PubMed

    Camargo, Maryene A; Neves, Ademir; Bortoluzzi, Adailton J; Szpoganicz, Bruno; Fischer, Franciele L; Terenzi, Hernán; Serra, Osvaldo A; Santos, Vanessa G; Vaz, Boniek G; Eberlin, Marcos N

    2010-07-05

    The synthesis and structures of two new isostructural mononuclear [Ln(L)(NO(3))(H(2)O)(3)](NO(3))(2) complexes, with Ln = Tb (complex 1) and Eu (complex 2), which display high activity in the hydrolysis of the substrate 2,4-bis(dinitrophenyl)phosphate, are reported. These complexes displayed catalytic behavior similar to the mononuclear gadolinium complex [Gd(L)(NO(3))(H(2)O)(3)](NO(3))(2) previously reported by us (Inorg. Chem. 2008, 47, 2919-2921); one hydrolysis reaction in two stages where the diesterase and monoesterase activities could be monitored separately, with the first stage dependent on and the second independent of the complex concentration. Through potentiometric studies, electrospray ionization mass spectrometry (ESI-MS) analysis, and determination of the kinetic behaviors of 1 and 2 in acetonitrile/water solution, the species present in solution could be identified and suggested a dinuclear species, with one hydroxo group, as the most prominent catalyst under mild conditions. The complexes show high activity (k(1) = 7 and 18 s(-1) for 1 and 2, respectively) and catalytic efficiency. Complexes 1 and 2 were found to be active toward the cleavage of plasmid DNA, and complete kinetic studies were carried out. Studies with a radical scavenger (dimethylsulfoxide) confirmed the hydrolytic action of 1 and 2 in the cleavage of DNA. Studies on the incubation of distamycin with plasmid DNA suggested that 1 and 2 are regio-specific, interacting with the minor groove of DNA. These complexes displayed luminescent properties. Complex 1 showed higher emission intensity than 2 due to a more efficient energy transfer between triplet and emission levels of terbium (T --> (5)D(4)), along with nonradiative deactivation mechanisms of the excited states of europium via multiphonon decays and the ligand-to-metal charge transfer state. Lifetime measurements of the (5)D(4) and (5)D(0) excited levels for 1 and 2, respectively, indicated the numbers of coordinated water

  8. The evolution of galaxies. III - Metal-enhanced star formation

    NASA Technical Reports Server (NTRS)

    Talbot, R. J., Jr.; Arnett, W. D.

    1973-01-01

    The problem of the paucity of low-metal-abundance low-mass stars is discussed. One alternative to the variable-initial-mass-function (VIMF) solution is proposed. It is shown that this solution - metal-enhanced star formation - satisfies the classical test which prompted the VIMF hypothesis. Furthermore, with no additional parameters it provides improved fits to other tests - e.g., inhomogeneities in the abundances in young stars, concordance of all nucleo-cosmochronologies, and a required yield of heavy-element production which is consistent with current stellar evolution theory. In this model the age of the Galaxy is 18.6 plus or minus 5.7 b.y.

  9. The evolution of galaxies. III - Metal-enhanced star formation

    NASA Technical Reports Server (NTRS)

    Talbot, R. J., Jr.; Arnett, W. D.

    1973-01-01

    The problem of the paucity of low-metal-abundance low-mass stars is discussed. One alternative to the variable-initial-mass-function (VIMF) solution is proposed. It is shown that this solution - metal-enhanced star formation - satisfies the classical test which prompted the VIMF hypothesis. Furthermore, with no additional parameters it provides improved fits to other tests - e.g., inhomogeneities in the abundances in young stars, concordance of all nucleo-cosmochronologies, and a required yield of heavy-element production which is consistent with current stellar evolution theory. In this model the age of the Galaxy is 18.6 plus or minus 5.7 b.y.

  10. Phosphorescent iridium(III) complexes: toward high phosphorescence quantum efficiency through ligand control.

    PubMed

    You, Youngmin; Park, Soo Young

    2009-02-28

    Phosphorescent Ir(III) complexes attract enormous attention because they allow highly efficient electrophosphorescence. In pursuing the development of Ir(III) complexes during the last decade, significant progress has been made in terms of the colour-tunability, thermal- and photo-stability, phase homogeneity, and phosphorescence efficiency. By far, extensive synthetic efforts have been focused on the molecular design of ligands to achieve a wide range of phosphorescence colour that is compatible with organic light-emitting device (OLED) applications. In contrast, less has been known about a collective structure-property relationship for phosphorescence quantum efficiency. In fact, a few rule-of-thumbs for high phosphorescence quantum efficiency have been occasionally reported, but a collective rationale is yet to be investigated. In this article, we provide a comprehensive review of 8 different methods reported so far to achieve high phosphorescence quantum efficiency from Ir(III) complexes. The methods included herein are limited to the cases of intramolecular controls, and thus are discussed in terms of variations in ligand structures: (1) geometric isomer control, (2) rigid structure and restricted intramolecular motion, (3) larger mixing of 1MLCT and 3LC states, (4) de-stabilizing a thermally accessible non-emissive state, (5) introducing dendrimer structures, (6) control in substituents of ligands, (7) confining the phosphorescent region of a mixed ligand Ir(III) complex and (8) sensitized phosphorescence by using attached energy donors. Each method is closely related to intramolecular excited state interactions, which strongly affect radiative or non-radiative transitions. A comprehensive understanding of these methods leads us to conclude that the modulation in ligand structures has a profound effect on both the phosphorescence colour and phosphorescence quantum efficiency. Thus, the judicious selection of ligand structures and their chelate disposition

  11. Extended MPEG Video Format for Efficient Dynamic Voltage Scaling

    NASA Astrophysics Data System (ADS)

    Bang, Kwanhu; Bang, Sung-Yong; Chung, Eui-Young

    We present an extended MPEG video format for efficient Dynamic Voltage Scaling (DVS). DVS technique has been widely researched, but the execution time variation of a periodic task (i. e. MPEG decoding) is still a challenge to be tackled. Unlike previous works, we focus on the data (video stream) rather than the execution code to overcome such limitation. The proposed video format provides the decoding costs of frames to help the precise prediction of their execution times at client machines. The experimental results show that the extended format only increases the data size less than 1% by adding about 10bits representing the decoding cost of each frame. Also, a DVS technique adjusted for the proposed format achieves 90% of efficiency compared to the oracle case, while keeping the run time overhead of the technique negligible.

  12. Characterization of Hydrogen Complex Formation in III-V Semiconductors

    SciTech Connect

    Williams, Michael D

    2006-09-28

    Atomic hydrogen has been found to react with some impurity species in semiconductors. Hydrogenation is a methodology for the introduction of atomic hydrogen into the semiconductor for the express purpose of forming complexes within the material. Efforts to develop hydrogenation as an isolation technique for AlGaAs and Si based devices failed to demonstrate its commercial viability. This was due in large measure to the low activation energies of the formed complexes. Recent studies of dopant passivation in long wavelength (0.98 - 1.55m) materials suggested that for the appropriate choice of dopants much higher activation energies can be obtained. This effort studied the formation of these complexes in InP, This material is extensively used in optoelectronics, i.e., lasers, modulators and detectors. The experimental techniques were general to the extent that the results can be applied to other areas such as sensor technology, photovoltaics and to other material systems. The activation energies for the complexes have been determined and are reported in the scientific literature. The hydrogenation process has been shown by us to have a profound effect on the electronic structure of the materials and was thoroughly investigated. The information obtained will be useful in assessing the long term reliability of device structures fabricated using this phenomenon and in determining new device functionalities.

  13. Protostellar formation in rotation interstellar clouds. III. Nonaxisymmetric collapse

    SciTech Connect

    Boss, A.P.

    1980-05-01

    A full three spatial-dimension gravitational hydrodynamics code has been used to follow the collapse of isothermal rotating clouds subjected to various nonaxialy symmetric perturbations (NAP). An initially axially symmetric cloud collapsed to form a ring which then fragmented into a binary protostellar system. A low thermal energy cloud with a large bar-shaped NAP collapsed and fragmented directly into a binary; higher thermal energy clouds damp out such NAPs while higher rotational rotational energy clouds produce binaries with wider separations. Fragmentation into single and binary systems has been seen. The tidal effects of other nearby protostellar clouds are shown to have an important effect upon the collapse and should not be neglected. The three-dimensional calculations indicate that isothermal interstellar clouds may fragment (with or without passing through a transitory ring phase) into protostellar objects while still in the isothermal regime. The fragments obtained have masses and specific spin angular momenta roughly a 10th that of the original cloud. Interstellar clouds and their fragments may pass through successive collapse phases with fragmentation and reduction of spin angular momentum (by conversion to orbital angular momentum and preferential accretion of low angular momentum matter) terminating in the formation of pre--main-sequence stars with the observed pre--main-sequence rotation rates.

  14. Highly Efficient Cooperative Catalysis by Co(III) (Porphyrin) Pairs in Interpenetrating Metal-Organic Frameworks.

    PubMed

    Lin, Zekai; Zhang, Zhi-Ming; Chen, Yu-Sheng; Lin, Wenbin

    2016-10-24

    A series of porous twofold interpenetrated In-Co(III) (porphyrin) metal-organic frameworks (MOFs) were constructed by in situ metalation of porphyrin bridging ligands and used as efficient cooperative catalysts for the hydration of terminal alkynes. The twofold interpenetrating structure brings adjacent Co(III) (porphyrins) in the two networks parallel to each other with a distance of about 8.8 Å, an ideal distance for the simultaneous activation of both substrates in alkyne hydration reactions. As a result, the In-Co(III) (porphyrin) MOFs exhibit much higher (up to 38 times) catalytic activity than either homogeneous catalysts or MOF controls with isolated Co(III) (porphyrin) centers, thus highlighting the potential application of MOFs in cooperative catalysis. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Power-efficient III-V/silicon external cavity DBR lasers.

    PubMed

    Zilkie, A J; Seddighian, P; Bijlani, B J; Qian, W; Lee, D C; Fathololoumi, S; Fong, J; Shafiiha, R; Feng, D; Luff, B J; Zheng, X; Cunningham, J E; Krishnamoorthy, A V; Asghari, M

    2012-10-08

    We report the design and characterization of external-cavity DBR lasers built with a III-V-semiconductor reflective-SOA with spot-size converter edge-coupled to SOI waveguides containing Bragg grating mirrors. The un-cooled lasers have wall-plug-efficiencies of up to 9.5% at powers of 6 mW. The lasers are suitable for making power efficient, hybrid WDM transmitters in a CMOS-compatible SOI optical platform.

  16. Aluminium substitution in iron(II III)-layered double hydroxides: Formation and cationic order

    NASA Astrophysics Data System (ADS)

    Ruby, Christian; Abdelmoula, Mustapha; Aissa, Rabha; Medjahdi, Ghouti; Brunelli, Michela; François, Michel

    2008-09-01

    The formation and the modifications of the structural properties of an aluminium-substituted iron(II-III)-layered double hydroxide (LDH) of formula Fe4IIFe(2-6y)IIIAl6yIII (OH) 12 SO 4, 8H 2O are followed by pH titration curves, Mössbauer spectroscopy and high-resolution X-ray powder diffraction using synchrotron radiation. Rietveld refinements allow to build a structural model for hydroxysulphate green rust, GR(SO 42-), i.e. y=0, in which a bilayer of sulphate anions points to the Fe 3+ species. A cationic order is proposed to occur in both GR(SO 42-) and aluminium-substituted hydroxysulphate green rust when y<0.08. Variation of the cell parameters and a sharp decrease in average crystal size and anisotropy are detected for an aluminium content as low as y=0.01. The formation of Al-GR(SO 42-) is preceded by the successive precipitation of Fe III and Al III (oxy)hydroxides. Adsorption of more soluble Al III species onto the initially formed ferric oxyhydroxide may be responsible for this slowdown of crystal growth. Therefore, the insertion of low aluminium amount ( y˜0.01) could be an interesting way for increasing the surface reactivity of iron(II-III) LDH that maintains constant the quantity of the reactive Fe II species of the material.

  17. Photochemical Formation of Fe(II) in the Aqueous Solutions of Fe(III)- Dicarboxylates

    NASA Astrophysics Data System (ADS)

    Okada, K.; Arakaki, T.

    2007-12-01

    Although there have been many studies reporting the photochemical formation of Fe(II) in various aqueous-phase such as rain, cloud waters, seawater and aerosols, the detailed formation mechanisms are not well understood. To better understand the mechanisms of Fe(II) formation, we attempted to determine the molar absorptivity and the quantum yield of Fe(II) photoformation for individual Fe(III)-dicarboxylate species. The concentrations of Fe(II) and total dissolved Fe were measured by a Ferrozine-HPLC method. The Visual MINTEQ computer program was used to calculate the equilibrium concentrations of chemical species in the solutions of Fe(III)-dicarboxylate complexes. The molar absorptivity and the product of the quantum yield and the molar absorptivity of Fe(III)- dicarboxylate complex can be analysed by UV-VIS spectrophotometer and photochemical experiments, and these experimental data were combined with the calculated equilibrium Fe(III) speciation to determine individual molar absorptivity and quantum yield of Fe(II) photoformation for a specific Fe(III)-dicarboxylate complex. Preliminary results, using an oxalate whose quantum yield has been previously reported, indicate that this approach gives lower quantum yield values in air saturated solutions than previously reported.

  18. The First Gold(III) Formate: Evidence for β-Hydride Elimination.

    PubMed

    Kumar, Roopender; Krieger, Jean-Philippe; Gómez-Bengoa, Enrique; Fox, Thomas; Linden, Anthony; Nevado, Cristina

    2017-10-09

    The first stable gold(III) formate and experimental evidence for its β-hydride elimination are described. A catalytic dehydrogenation of formic acid together with mechanistic studies shed light on potential pathways operating in fundamental gold-catalyzed transformations. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. III-nitride quantum dots for ultra-efficient solid-state lighting

    DOE PAGES

    Wierer, Jr., Jonathan J.; Tansu, Nelson; Fischer, Arthur J.; ...

    2016-05-23

    III-nitride light-emitting diodes (LEDs) and laser diodes (LDs) are ultimately limited in performance due to parasitic Auger recombination. For LEDs, the consequences are poor efficiencies at high current densities; for LDs, the consequences are high thresholds and limited efficiencies. Here, we present arguments for III-nitride quantum dots (QDs) as active regions for both LEDs and LDs, to circumvent Auger recombination and achieve efficiencies at higher current densities that are not possible with quantum wells. QD-based LDs achieve gain and thresholds at lower carrier densities before Auger recombination becomes appreciable. QD-based LEDs achieve higher efficiencies at higher currents because of highermore » spontaneous emission rates and reduced Auger recombination. The technical challenge is to control the size distribution and volume of the QDs to realize these benefits. In conclusion, if constructed properly, III-nitride light-emitting devices with QD active regions have the potential to outperform quantum well light-emitting devices, and enable an era of ultra-efficient solidstate lighting.« less

  20. III-nitride quantum dots for ultra-efficient solid-state lighting

    SciTech Connect

    Wierer, Jr., Jonathan J.; Tansu, Nelson; Fischer, Arthur J.; Tsao, Jeffrey Y.

    2016-05-23

    III-nitride light-emitting diodes (LEDs) and laser diodes (LDs) are ultimately limited in performance due to parasitic Auger recombination. For LEDs, the consequences are poor efficiencies at high current densities; for LDs, the consequences are high thresholds and limited efficiencies. Here, we present arguments for III-nitride quantum dots (QDs) as active regions for both LEDs and LDs, to circumvent Auger recombination and achieve efficiencies at higher current densities that are not possible with quantum wells. QD-based LDs achieve gain and thresholds at lower carrier densities before Auger recombination becomes appreciable. QD-based LEDs achieve higher efficiencies at higher currents because of higher spontaneous emission rates and reduced Auger recombination. The technical challenge is to control the size distribution and volume of the QDs to realize these benefits. In conclusion, if constructed properly, III-nitride light-emitting devices with QD active regions have the potential to outperform quantum well light-emitting devices, and enable an era of ultra-efficient solidstate lighting.

  1. III-nitride quantum dots for ultra-efficient solid-state lighting

    SciTech Connect

    Wierer, Jr., Jonathan J.; Tansu, Nelson; Fischer, Arthur J.; Tsao, Jeffrey Y.

    2016-05-23

    III-nitride light-emitting diodes (LEDs) and laser diodes (LDs) are ultimately limited in performance due to parasitic Auger recombination. For LEDs, the consequences are poor efficiencies at high current densities; for LDs, the consequences are high thresholds and limited efficiencies. Here, we present arguments for III-nitride quantum dots (QDs) as active regions for both LEDs and LDs, to circumvent Auger recombination and achieve efficiencies at higher current densities that are not possible with quantum wells. QD-based LDs achieve gain and thresholds at lower carrier densities before Auger recombination becomes appreciable. QD-based LEDs achieve higher efficiencies at higher currents because of higher spontaneous emission rates and reduced Auger recombination. The technical challenge is to control the size distribution and volume of the QDs to realize these benefits. In conclusion, if constructed properly, III-nitride light-emitting devices with QD active regions have the potential to outperform quantum well light-emitting devices, and enable an era of ultra-efficient solidstate lighting.

  2. The efficiency of star formation in clustered and distributed regions

    NASA Astrophysics Data System (ADS)

    Bonnell, Ian A.; Smith, Rowan J.; Clark, Paul C.; Bate, Matthew R.

    2011-02-01

    We investigate the formation of both clustered and distributed populations of young stars in a single molecular cloud. We present a numerical simulation of a 104 M⊙ elongated, turbulent, molecular cloud and the formation of over 2500 stars. The stars form both in stellar clusters and in a distributed mode, which is determined by the local gravitational binding of the cloud. A density gradient along the major axis of the cloud produces bound regions that form stellar clusters and unbound regions that form a more distributed population. The initial mass function (IMF) also depends on the local gravitational binding of the cloud with bound regions forming full IMFs whereas in the unbound, distributed regions the stellar masses cluster around the local Jeans mass and lack both the high-mass and the low-mass stars. The overall efficiency of star formation is ≈ 15 per cent in the cloud when the calculation is terminated, but varies from less than 1 per cent in the regions of distributed star formation to ≈ 40 per cent in regions containing large stellar clusters. Considering that large-scale surveys are likely to catch clouds at all evolutionary stages, estimates of the (time-averaged) star formation efficiency (SFE) for the giant molecular cloud reported here is only ≈ 4 per cent. This would lead to the erroneous conclusion of slow star formation when in fact it is occurring on a dynamical time-scale.

  3. THE FORMATION OF SUPERMASSIVE BLACK HOLES FROM LOW-MASS POP III SEEDS

    SciTech Connect

    Whalen, Daniel J.; Fryer, Chris L.

    2012-09-01

    The existence of 10{sup 9} M{sub Sun} black holes (BHs) in massive galaxies by z {approx} 7 is one of the great unsolved mysteries in cosmological structure formation. One theory argues that they originate from the BHs of Pop III stars at z {approx} 20 and then accrete at the Eddington limit down to the epoch of reionization, which requires that they have constant access to rich supplies of fuel. Because early numerical simulations suggested that Pop III stars were {approx}>100 M{sub Sun }, the supermassive black hole (SMBH) seeds considered up to now were 100-300 M{sub Sun }. However, there is a growing numerical and observational consensus that some Pop III stars were tens of solar masses, not hundreds, and that 20-40 M{sub Sun} BHs may have been much more plentiful at high redshift. However, we find that natal kicks imparted to 20-40 M{sub Sun} Pop III BHs during formation eject them from their halos and hence their fuel supply, precluding them from Eddington-limit growth. Consequently, SMBHs are far less likely to form from low-mass Pop III stars than from very massive ones.

  4. The Biermann Battery In Cosmological Mhd Simulations Of Population III Star Formation

    SciTech Connect

    Xu, Hao; O' Shea, Brian W; Li, Hui; Li, Shengtai; Norman, Michael L; Collins, David C

    2008-01-01

    We report the results of the first self-consistent three-dimensional adaptive mesh refinement magnetohydrodynamical simulations of Population III star formation including the Biermann battery effect. We find that the Population III stellar cores formed including this effect are both qualitatively and quantitatively similar to those from hydrodynamics-only (non-MHD) cosmological simulations. We observe peak magnetic fields of {approx_equal} 10{sup -9} G in the center of our star-forming halo at z {approx_equal} 17.55 at a baryon density of n{sub B} {approx} 10{sup 10} cm{sup -3}. The magnetic fields created by the Biermann battery effect are predominantly formed early in the evolution of the primordial halo at low density and large spatial scales, and then grow through compression and by shear flows. The fields seen in this calculation are never large enough to be dynamically important (with {beta} {ge} 10{sup 15} at all times before the termination of our calculation), and should be considered the minimum possible fields in existence during Population III star formation. The lack of magnetic support lends credibility to assumptions made in previous calculations regarding the lack of importance of magnetic fields in Population III star formation. In addition, these magnetic fields may be seed fields for the stellar dynamo or the magnetorotational instability at higher densities and smaller spatial scales.

  5. Soliton communication lines based on spectrally efficient modulation formats

    SciTech Connect

    Yushko, O V; Redyuk, A A

    2014-06-30

    We report the results of mathematical modelling of optical-signal propagation in soliton fibre-optic communication lines (FOCLs) based on spectrally efficient signal modulation formats. We have studied the influence of spontaneous emission noise, nonlinear distortions and FOCL length on the data transmission quality. We have compared the characteristics of a received optical signal for soliton and conventional dispersion compensating FOCLs. It is shown that in the presence of strong nonlinearity long-haul soliton FOCLs provide a higher data transmission performance, as well as allow higher order modulation formats to be used as compared to conventional communication lines. In the context of a coherent data transmission, soliton FOCLs allow the use of phase modulation with many levels, thereby increasing the spectral efficiency of the communication line. (optical communication lines)

  6. Toluene formation from coadsorbed methanethiol and benzenethiol on the Ni(III) surface

    SciTech Connect

    Kane, S.M.; Gland, J.L.; Huntley, D.R.

    1996-04-17

    We report our observation of interspecies carbon-carbon bond formation during the reaction of coadsorbed methanethiol and benzenethiol on the Ni(III) surface. Toluene formation has been detected between 250 and 320 K in addition to methane and benzene, the hydrogenolysis products. Increased concentrations of benzenethiolate and methanethiolate, the surface intermediates, increase the amount of toluene formed. Water formation below the toluene formation temperature decreases surface hydrogen, causing toluene yield to increase substantially compared to methane and benzene yield. Toluene increases up to a factor of 20 were observed for high coadsorbed coverages. Together, these results clearly indicate that competition between hydrogen addition and alkylation controls toluene formation. 28 refs., 3 figs.

  7. Mechanistic aspects of the chemistry of mononuclear Cr(III) complexes with pendant-arm macrocyclic ligands and formation of discrete Cr(III)/Fe(II) and Cr(III)/Fe(II)/Co(III) cyano-bridged mixed valence compounds.

    PubMed

    Basallote, Manuel G; Bernhardt, Paul V; Calvet, Teresa; Castillo, Carmen E; Font-Bardia, Mercè; Martínez, Manuel; Rodríguez, Carlos

    2009-11-21

    The kinetics and mechanism of the redox reaction between [Fe(II)(CN)(6)](4-) and the macrocyclic ligand complex [CrClL(15)](2+) (L(15) = 6-methyl-1,4,8,12-tetraazacyclopentadecane-6-amine) has been studied at different pH values. In acidic solution, the expected redox process occurs with no formation of any of the possible Cr(III)/Fe(II) mixed valence complexes, as those seen for the Co(III) species of the same family, due to the enhanced lability of the Cr(II) species formed on Fe(II) to Fe(III) oxidation. In alkaline conditions, the formation of the complex [Cr(L(15))(OH)(2)](+) takes place as an initial step that precedes a simple substitution process producing the expected cyano-bridged Cr(III)/Fe(II) complex. In this species the potentially pentadentate ligand, L(15), has a tetradentate coordination mode with a protonated exocyclic primary amine group and the redox potential is shifted to more negative values, thus disfavouring a redox driven reaction; the equivalent complex [CrCl(HL(14))(H(2)O)](3+) (L(14) = 6-methyl-1,4,8,11-tetraazacyclotetradecane-6-amine) has been prepared by the same method and characterized by X-ray crystallography. The final [Fe(II)(CN)(6)](4-) substituted complex, [{(HL(15))(OH)Cr(III)NC}Fe(II)(CN)(5)](-) shows pK(a) values of 3.8 and 7.4, as expected for the aqua and amino ligands, respectively. Its characterization indicated its Class II mixed valence character with a very intense MMCT band at 350 nm showing a much larger extinction coefficient than that observed for the Co(III) complexes of the same family. This fact is in good agreement with the much larger Cr(III)-Fe(II) (t(2g)-t(2g)) coupling through cyanide bridging ligands expected for these complexes. The fully mixed metal/valence/ligand trimetallic complex [{(HL(15))(OH)Cr(III)NC}{L(13)Co(III)NC}Fe(II)(CN)(4)](2+) has been prepared following the same procedures and the results are comparable. The final complex has the same Class II mixed valence character and its electronic

  8. The Pseudomonas aeruginosa Type III Translocon Is Required for Biofilm Formation at the Epithelial Barrier

    PubMed Central

    Tran, Cindy S.; Rangel, Stephanie M.; Almblad, Henrik; Kierbel, Arlinet; Givskov, Michael; Tolker-Nielsen, Tim; Hauser, Alan R.; Engel, Joanne N.

    2014-01-01

    Clinical infections by Pseudomonas aeruginosa, a deadly Gram-negative, opportunistic pathogen of immunocompromised hosts, often involve the formation of antibiotic-resistant biofilms. Although biofilm formation has been extensively studied in vitro on glass or plastic surfaces, much less is known about biofilm formation at the epithelial barrier. We have previously shown that when added to the apical surface of polarized epithelial cells, P. aeruginosa rapidly forms cell-associated aggregates within 60 minutes of infection. By confocal microscopy we now show that cell-associated aggregates exhibit key characteristics of biofilms, including the presence of extracellular matrix and increased resistance to antibiotics compared to planktonic bacteria. Using isogenic mutants in the type III secretion system, we found that the translocon, but not the effectors themselves, were required for cell-associated aggregation on the surface of polarized epithelial cells and at early time points in a murine model of acute pneumonia. In contrast, the translocon was not required for aggregation on abiotic surfaces, suggesting a novel function for the type III secretion system during cell-associated aggregation. Supernatants from epithelial cells infected with wild-type bacteria or from cells treated with the pore-forming toxin streptolysin O could rescue aggregate formation in a type III secretion mutant, indicating that cell-associated aggregation requires one or more host cell factors. Our results suggest a previously unappreciated function for the type III translocon in the formation of P. aeruginosa biofilms at the epithelial barrier and demonstrate that biofilms may form at early time points of infection. PMID:25375398

  9. The Pseudomonas aeruginosa type III translocon is required for biofilm formation at the epithelial barrier.

    PubMed

    Tran, Cindy S; Rangel, Stephanie M; Almblad, Henrik; Kierbel, Arlinet; Givskov, Michael; Tolker-Nielsen, Tim; Hauser, Alan R; Engel, Joanne N

    2014-11-01

    Clinical infections by Pseudomonas aeruginosa, a deadly Gram-negative, opportunistic pathogen of immunocompromised hosts, often involve the formation of antibiotic-resistant biofilms. Although biofilm formation has been extensively studied in vitro on glass or plastic surfaces, much less is known about biofilm formation at the epithelial barrier. We have previously shown that when added to the apical surface of polarized epithelial cells, P. aeruginosa rapidly forms cell-associated aggregates within 60 minutes of infection. By confocal microscopy we now show that cell-associated aggregates exhibit key characteristics of biofilms, including the presence of extracellular matrix and increased resistance to antibiotics compared to planktonic bacteria. Using isogenic mutants in the type III secretion system, we found that the translocon, but not the effectors themselves, were required for cell-associated aggregation on the surface of polarized epithelial cells and at early time points in a murine model of acute pneumonia. In contrast, the translocon was not required for aggregation on abiotic surfaces, suggesting a novel function for the type III secretion system during cell-associated aggregation. Supernatants from epithelial cells infected with wild-type bacteria or from cells treated with the pore-forming toxin streptolysin O could rescue aggregate formation in a type III secretion mutant, indicating that cell-associated aggregation requires one or more host cell factors. Our results suggest a previously unappreciated function for the type III translocon in the formation of P. aeruginosa biofilms at the epithelial barrier and demonstrate that biofilms may form at early time points of infection.

  10. Actin Pedestal Formation by Enterohemorrhagic Escherichia coli Enhances Bacterial Host Cell Attachment and Concomitant Type III Translocation

    PubMed Central

    Battle, Scott E.; Brady, Michael J.; Vanaja, Sivapriya Kailasan; Leong, John M.

    2014-01-01

    Attachment of enterohemorrhagic Escherichia coli (EHEC) to intestinal epithelial cells is critical for colonization and is associated with localized actin assembly beneath bound bacteria. The formation of these actin “pedestals” is dependent on the translocation of effectors into mammalian cells via a type III secretion system (T3SS). Tir, an effector required for pedestal formation, localizes in the host cell plasma membrane and promotes attachment of bacteria to mammalian cells by binding to the EHEC outer surface protein Intimin. Actin pedestal formation has been shown to foster intestinal colonization by EHEC in some animal models, but the mechanisms responsible for this remain undefined. Investigation of the role of Tir-mediated actin assembly promoting host cell binding is complicated by other, potentially redundant EHEC-encoded binding pathways, so we utilized cell binding assays that specifically detect binding mediated by Tir-Intimin interaction. We also assessed the role of Tir-mediated actin assembly in two-step assays that temporally segregated initial translocation of Tir from subsequent Tir-Intimin interaction, thereby permitting the distinction of effects on translocation from effects on cell attachment. In these experimental systems, we compromised Tir-mediated actin assembly by chemically inhibiting actin assembly or by infecting mammalian cells with EHEC mutants that translocate Tir but are specifically defective in Tir-mediated pedestal formation. We found that an inability of Tir to promote actin assembly resulted in a significant and striking decrease in bacterial binding mediated by Tir and Intimin. Bacterial mutants defective for pedestal formation translocated type III effectors to mammalian cells with reduced efficiency, but the decrease in translocation could be entirely accounted for by the decrease in host cell attachment. PMID:24958711

  11. Can the 21-cm signal probe Population III and II star formation?

    NASA Astrophysics Data System (ADS)

    Yajima, Hidenobu; Khochfar, Sadegh

    2015-03-01

    Using varying models for the star formation rate (SFR) of Population (Pop) III and II stars at z > 6 we derive the expected redshift history of the global 21-cm signal from the intergalactic medium (IGM). To recover the observed Thomson scattering optical depth of the cosmic microwave background (CMB) requires SFRs at the level of ˜ 10- 3 M⊙ yr- 1 Mpc- 3 at z ˜ 15 from Pop III stars, or ˜ 10- 1 M⊙ yr- 1 Mpc- 3 at z ˜ 7 from Pop II stars. In the case the SFR is dominated by Pop III stars, the IGM quickly heats above the CMB at z ≳ 12 due to heating from supernovae. In addition, Lyα photons from haloes hosting Pop III stars couple the spin temperature to that of the gas, resulting in a deep absorption signal. If the SFR is dominated by Pop II stars, the IGM slowly heats and exceeds the CMB temperature at z ˜ 10. However, the larger and varying fraction of Pop III stars are able to break this degeneracy. We find that the impact of the initial mass function (IMF) of Pop III stars on the 21-cm signal results in an earlier change to a positive signal if the IMF slope is ˜-1.2. Measuring the 21-cm signal at z ≳ 10 with next generation radio telescopes such as the Square Kilometre Array will be able to investigate the contribution from Pop III and Pop II stars to the global SFR.

  12. The Formation of Supermassive Black Holes from Population III.1 Seeds. I. Cosmic Formation Histories and Clustering Properties

    SciTech Connect

    Banik, Nilanjan; Tan, Jonathan C.; Monaco, Pierluigi

    2016-08-15

    We calculate the cosmic distributions in space and time of the formation sites of the first, "Pop III.1" stars, exploring a model in which these are the progenitors of all supermassive black holes (SMBHs). Pop III.1 stars are defined to form from primordial composition gas in dark matter minihalos with $\\sim10^6\\:M_\\odot$ that are isolated from neighboring astrophysical sources by a given isolation distance, $d_{\\rm{iso}}$. We assume Pop III.1 sources are seeds of SMBHs, based on protostellar support by dark matter annihilation heating that allows them to accrete a large fraction of their minihalo gas, i.e., $\\sim 10^5\\:M_\\odot$. Exploring $d_{\\rm{iso}}$ from 10--$100\\:\\rm{kpc}$ (proper distances), we predict the redshift evolution of Pop III.1 source and SMBH remnant number densities. The local, $z=0$ density of SMBHs constrains $d_{\\rm{iso}}\\lesssim 100\\:\\rm{kpc}$ (i.e., $3\\:\\rm{Mpc}$ comoving distance at $z\\simeq30$). In our simulated ($\\sim60\\:\\rm{Mpc}$)$^3$ comoving volume, Pop III.1 stars start forming just after $z=40$. Their formation is largely complete by $z\\simeq25$ to 20 for $d_{\\rm{iso}}=100$ to $50\\:\\rm{kpc}$. We follow source evolution to $z=10$, by which point most SMBHs reside in halos with $\\gtrsim10^8\\:M_\\odot$. Over this period, there is relatively limited merging of SMBHs for these values of $d_{\\rm{iso}}$. We also predict SMBH clustering properties at $z=10$: feedback suppression of neighboring sources leads to relatively flat angular correlation functions. Finally, we consider a simple "Str\\"omgren" model for $d_{\\rm iso}$, based on ionizing feedback from zero age main sequence supermassive Pop III.1 stars that may be the direct progenitors of SMBHs in this scenario. Such models naturally produce feedback effects on scales of $\\sim100\\:$kpc and thus self-consistently generate a SMBH number density similar to the observed value.

  13. Star formation in Chamaeleon I and III: a molecular line study of the starless core population

    NASA Astrophysics Data System (ADS)

    Tsitali, A. E.; Belloche, A.; Garrod, R. T.; Parise, B.; Menten, K. M.

    2015-03-01

    Context. The Chamaeleon dark molecular clouds are excellent nearby targets for low-mass star formation studies. Even though they belong to the same cloud complex, Cha I and II are actively forming stars while Cha III shows no sign of ongoing star formation. Aims: We aim to determine the driving factors that have led to the very different levels of star formation activity in Cha I and III and examine the dynamical state and possible evolution of the starless cores within them. Methods: Observations were performed in various molecular transitions with the APEX and Mopra telescopes. We examine the kinematics of the starless cores in the clouds through a virial analysis, a search for contraction motions, and velocity gradients. The chemical differences in the two clouds are explored through their fractional molecular abundances, derived from a non-LTE analysis, and comparison to predictions of chemical models. Results: Five cores are gravitationally bound in Cha I and one in Cha III. The so-called infall signature indicating contraction motions is seen toward 8-17 cores in Cha I and 2-5 cores in Cha III, which leads to a range of 13-28% of the cores in Cha I and 10-25% of the cores in Cha III that are contracting and may become prestellar. There is no significant difference in the turbulence level in the two clouds. Future dynamical interactions between the cores will not be dynamically significant in either Cha I or III, but the subregion Cha I North may experience collisions between cores within ~0.7 Myr. Turbulence dissipation in the cores of both clouds is seen in the high-density tracers N2H+ 1-0 and HC3N 10-9 which have lower non-thermal velocity dispersions compared to C17O 2-1, C18O 2-1, and C34S 2-1. Evidence of depletion in the Cha I core interiors is seen in the abundance distributions of the latter three molecules. The median fractional abundance of C18O is lower in Cha III than Cha I by a factor of ~2. The median abundances of most molecules (except

  14. Formation of Cr(III) hydroxides from chrome alum solutions. 1: Precipitation of active chromium hydroxide

    SciTech Connect

    Avena, M.J.; Giacomelli, C.E.; De Pauli, C.P.

    1996-06-25

    The hydrolysis of Cr(III) and precipitation of colloidal chromium hydroxides are important processes occurring in soils and natural waters. The formation of active chromium hydroxide, Cr(OH){sub 3}{center_dot}3H{sub 2}O, was studied through potentiometric titrations and turbidimetric measurements. UV-Vis and IR spectroscopies were also employed to characterize the synthesized solid. The rapid addition of NaOH solution to aqueous chrome alum (KCr(SO{sub 4}){sub 2}{center_dot}12H{sub 2}O) solutions caused the immediate precipitation of the active material. Only monomeric Cr(III) species seemed to be participating in the precipitation process; neither chromium polymers nor complexes with anions (SO{sub 4}{sup 2{minus}}, Cl{sup {minus}}, NO{sub 3}{sup {minus}}, ClO{sub 4}{sup {minus}}) influenced the fast formation of Cr(OH){sub 3}{center_dot}3H{sub 2}O. Titration studies allowed the determination of several hydrolysis and precipitation constants for Cr(III). Nevertheless, they cannot be used for the estimate of Cr(OH){sub 3}{sup 0} formation constant.

  15. Differential effects of Heparitinase I and Heparitinase III on endothelial tube formation in vitro

    PubMed Central

    Raman, Karthik; Kuberan, Balagurunathan

    2010-01-01

    Heparan sulfate proteoglycans (HSPGs) play vital roles in many steps of angiogenesis under physiological and pathological conditions. HSPGs on endothelial cell surfaces act as coreceptors for a variety of pro-angiogenic growth factors such as FGF and VEGF and anti-angiogenic factors such as endostatin. However, the fine structural requirements of these binding interactions are dependent on the sulfation patterns of HSPGs. Previous studies have shown that Heparitinases, heparin lyases isolated from flavobacterium heparinum, can cleave heparan sulfate chains. These enzymes have been shown to reduce tumor—derived neovascularization in vivo in mice. However, the results from these experiments could not conclusively pinpoint the origin of the HS fragments. Thus, in this study we utilized an in vitro assay to assess the differential effects of Heparitinase I (Hep I) and Heparitinase III (Hep III) on endothelial tube formation. Hep III was found to be a more potent inhibitor of tube formation than Hep I. In conclusion, differential cleavage of endothelial cell surface bound HS can affect the extent of inhibition of tube formation. PMID:20599743

  16. A high efficiency veto to increase the sensitivity of ZEPLIN-III, a WIMP detector

    SciTech Connect

    Barnes, E. J.

    2009-09-08

    An active veto detector to complement the ZEPLIN-III two phase Xenon, direct dark matter device is described. The proposed design consists of 52 plastic scintillator segments, individually read out by high efficiency photomultipliers, coupled to a Gd loaded passive polypropylene shield. Experimental work was performed to determine the plastic scintillator characteristics which were used to inform a complete end-to-end Monte Carlo simulation of the expected performance of the new instrument, both operating alone and as an active veto detector for ZEPLIN-III. The veto device will be capable of tagging over 65% of coincident nuclear recoil events in the energy range of interest in ZEPLIN-III, and over 12% for gamma ray rejection, while contributing no significant additional background. In addition it will also provide valuable diagnostic capabilities. The inclusion of the veto to ZEPLIN-III will aid to significantly improve the sensitivity to spin independent WIMP-nucleon cross sections below 10{sup -8} pb.

  17. A high efficiency veto to increase the sensitivity of ZEPLIN-III, a WIMP detector

    NASA Astrophysics Data System (ADS)

    Barnes, E. J.

    2009-09-01

    An active veto detector to complement the ZEPLIN-III two phase Xenon, direct dark matter device is described. The proposed design consists of 52 plastic scintillator segments, individually read out by high efficiency photomultipliers, coupled to a Gd loaded passive polypropylene shield. Experimental work was performed to determine the plastic scintillator characteristics which were used to inform a complete end-to-end Monte Carlo simulation of the expected performance of the new instrument, both operating alone and as an active veto detector for ZEPLIN-III. The veto device will be capable of tagging over 65% of coincident nuclear recoil events in the energy range of interest in ZEPLIN-III, and over 12% for gamma ray rejection, while contributing no significant additional background. In addition it will also provide valuable diagnostic capabilities. The inclusion of the veto to ZEPLIN-III will aid to significantly improve the sensitivity to spin independent WIMP-nucleon cross sections below 10-8 pb.

  18. Formation of Environmentally Persistent Free Radical (EPFR) in Iron(III) Cation-Exchanged Smectite Clay

    PubMed Central

    Nwosu, Ugwumsinachi G.; Roy, Amitava; dela Cruz, Albert Leo N.; Dellinger, Barry; Cook, Robert

    2016-01-01

    Environmentally persistent free radicals (EPFRs) have been found at a number of Superfund sites, with EPFRs being formed via a proposed redox process at ambient environmental conditions. The possibility of such a redox process taking place at ambient environmental conditions is studied utilizing a surrogate soil system of phenol and iron(III)-exchanged calcium montmorillonite clay, Fe(III)CaM. Sorption of phenol by the Fe(III)CaM is demonstrated by Fourier-transformed infra-red (FT-IR) spectroscopy, as evidenced by the peaks between 1345 cm−1 and 1595 cm−1, and at lower frequencies between 694 cm−1 and 806 cm−1, as well as X-ray diffraction (XRD) spectroscopy, as shown by an increase in interlayer spacing within Fe(III)CaM. The formation and characterization of the EPFRs is determined by electron paramagnetic resonance (EPR) spectroscopy, showing phenoxyl-type radical with a g-factor of 2.0034 and ΔHp-p of 6.1 G at an average concentration of 7.5 × 1017 spins/g. EPFRs lifetime data are indicative of oxygen and water molecules being responsible for EPFR decay. The change in the oxidation state of the iron redox center is studied by X-ray absorption near-edge structure (XANES) spectroscopy, showing that 23% of the Fe(III) is reduced to Fe(II). X-ray photoemission spectroscopy (XPS) results confirm the XANES results. These findings, when combined with the EPFR concentration data, demonstrate that the stoichiometry of the EPFR formation under the conditions of this study is 1.5 × 10−2 spins/Fe(II) atom. PMID:26647158

  19. Formation of environmentally persistent free radical (EPFR) in iron(III) cation-exchanged smectite clay.

    PubMed

    Nwosu, Ugwumsinachi G; Roy, Amitava; dela Cruz, Albert Leo N; Dellinger, Barry; Cook, Robert

    2016-01-01

    Environmentally persistent free radicals (EPFRs) have been found at a number of Superfund sites, with EPFRs being formed via a proposed redox process at ambient environmental conditions. The possibility of such a redox process taking place at ambient environmental conditions is studied utilizing a surrogate soil system of phenol and iron(III)-exchanged calcium montmorillonite clay, Fe(III)CaM. Sorption of phenol by the Fe(III)CaM is demonstrated by Fourier-transformed infra-red (FT-IR) spectroscopy, as evidenced by the peaks between 1345 cm(-1) and 1595 cm(-1), and at lower frequencies between 694 cm(-1) and 806 cm(-1), as well as X-ray diffraction (XRD) spectroscopy, as shown by an increase in interlayer spacing within Fe(III)CaM. The formation and characterization of the EPFRs is determined by electron paramagnetic resonance (EPR) spectroscopy, showing phenoxyl-type radical with a g-factor of 2.0034 and ΔHP-P of 6.1 G at an average concentration of 7.5 × 10(17) spins per g. EPFRs lifetime data are indicative of oxygen and water molecules being responsible for EPFR decay. The change in the oxidation state of the iron redox center is studied by X-ray absorption near-edge structure (XANES) spectroscopy, showing that 23% of the Fe(III) is reduced to Fe(II). X-ray photoemission spectroscopy (XPS) results confirm the XANES results. These findings, when combined with the EPFR concentration data, demonstrate that the stoichiometry of the EPFR formation under the conditions of this study is 1.5 × 10(-2) spins per Fe(II) atom.

  20. STAR FORMATION EFFICIENCY IN THE BARRED SPIRAL GALAXY NGC 4303

    SciTech Connect

    Momose, Rieko; Okumura, Sachiko K.; Sawada, Tsuyoshi; Koda, Jin E-mail: sokumura@nro.nao.ac.j E-mail: Jin.Koda@stonybrook.ed

    2010-09-20

    We present new {sup 12}CO (J = 1 - 0) observations of the barred galaxy NGC 4303 using the Nobeyama 45 m telescope (NRO45) and the Combined Array for Research in Millimeter-wave Astronomy (CARMA). The H{alpha} images of barred spiral galaxies often show active star formation in spiral arms, but less so in bars. We quantify the difference by measuring star formation rate (SFR) and star formation efficiency (SFE) at a scale where local star formation is spatially resolved. Our CO map covers the central 2.'3 region of the galaxy; the combination of NRO45 and CARMA provides a high fidelity image, enabling accurate measurements of molecular gas surface density. We find that SFR and SFE are twice as high in the spiral arms as in the bar. We discuss this difference in the context of the Kennicutt-Schmidt (KS) law, which indicates a constant SFR at a given gas surface density. The KS law breaks down at our native resolution ({approx}250 pc), and substantial smoothing (to 500 pc) is necessary to reproduce the KS law, although with greater scatter.

  1. New III-V cell design approaches for very high efficiency

    SciTech Connect

    Lundstrom, M.S.; Melloch, M.R.; Lush, G.B.; O'Bradovich, G.J.; Young, M.P. )

    1993-01-01

    This report describes progress during the first year of a three-year project. The objective of the research is to examine new design approaches for achieving very high conversion efficiencies. The program is divided into two areas. The first centers on exploring new thin-film approaches specifically designed for III-V semiconductors. The second area centers on exploring design approaches for achieving high conversion efficiencies without requiring extremely high quality material. Research activities consisted of an experimental study of minority carrier recombination in n-type, metal-organic chemical vapor deposition (MOCVD)-deposited GaAs, an assessment of the minority carrier lifetimes in n-GaAs grown by molecular beam epitaxy, and developing a high-efficiency cell fabrication process.

  2. Design High-Efficiency III-V Nanowire/Si Two-Junction Solar Cell

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Zhang, Y.; Zhang, D.; He, S.; Li, X.

    2015-06-01

    In this paper, we report the electrical simulation results of a proposed GaInP nanowire (NW)/Si two-junction solar cell. The NW physical dimensions are determined for optimized solar energy absorption and current matching between each subcell. Two key factors (minority carrier lifetime, surface recombination velocity) affecting power conversion efficiency (PCE) of the solar cell are highlighted, and a practical guideline to design high-efficiency two-junction solar cell is thus provided. Considering the practical surface and bulk defects in GaInP semiconductor, a promising PCE of 27.5 % can be obtained. The results depict the usefulness of integrating NWs to construct high-efficiency multi-junction III-V solar cells.

  3. Design High-Efficiency III-V Nanowire/Si Two-Junction Solar Cell.

    PubMed

    Wang, Y; Zhang, Y; Zhang, D; He, S; Li, X

    2015-12-01

    In this paper, we report the electrical simulation results of a proposed GaInP nanowire (NW)/Si two-junction solar cell. The NW physical dimensions are determined for optimized solar energy absorption and current matching between each subcell. Two key factors (minority carrier lifetime, surface recombination velocity) affecting power conversion efficiency (PCE) of the solar cell are highlighted, and a practical guideline to design high-efficiency two-junction solar cell is thus provided. Considering the practical surface and bulk defects in GaInP semiconductor, a promising PCE of 27.5 % can be obtained. The results depict the usefulness of integrating NWs to construct high-efficiency multi-junction III-V solar cells.

  4. Polarization doping and the efficiency of III-nitride optoelectronic devices

    SciTech Connect

    Kivisaari, Pyry; Oksanen, Jani; Tulkki, Jukka

    2013-11-18

    The intrinsic polarization is generally considered a nuisance in III-nitride devices, but recent studies have shown that it can be used to enhance p- and n-type conductivity and even to replace impurity doping. We show by numerical simulations that polarization-doped light-emitting diode (LED) structures have a significant performance advantage over conventional impurity-doped LED structures. Our results indicate that polarization doping decreases electric fields inside the active region and potential barriers in the depletion region, as well as the magnitude of the quantum-confined Stark effect. The simulations also predict at least an order of magnitude increase in the current density corresponding to the maximum efficiency (i.e., smaller droop) as compared to impurity-doped structures. The obtained high doping concentrations could also enable, e.g., fabrication of III-N resonant tunneling diodes and improved ohmic contacts.

  5. Toward Efficient Team Formation for Crowdsourcing in Noncooperative Social Networks.

    PubMed

    Wang, Wanyuan; Jiang, Jiuchuan; An, Bo; Jiang, Yichuan; Chen, Bing

    2016-09-07

    Crowdsourcing has become a popular service computing paradigm for requesters to integrate the ubiquitous human-intelligence services for tasks that are difficult for computers but trivial for humans. This paper focuses on crowdsourcing complex tasks by team formation in social networks (SNs) where a requester connects to a large number of workers. A good indicator of efficient team collaboration is the social connection among workers. Most previous social team formation approaches, however, either assume that the requester can maintain information of all workers and can directly communicate with them to build teams, or assume that the workers are cooperative and be willing to join the specific team built by the requester, both of which are impractical in many real situations. To this end, this paper first models each worker as a selfish entity, where the requester prefers to hire inexpensive workers that require less payment and workers prefer to join the profitable teams where they can gain high revenue. Within the noncooperative SNs, a distributed negotiation-based team formation mechanism is designed for the requester to decide which worker to hire and for the worker to decide which team to join and how much should be paid for his skill service provision. The proposed social team formation approach can always build collaborative teams by allowing team members to form a connected graph such that they can work together efficiently. Finally, we conduct a set of experiments on real dataset of workers to evaluate the effectiveness of our approach. The experimental results show that our approach can: 1) preserve considerable social welfare by comparing the benchmark centralized approaches and 2) form the profitable teams within less negotiation time by comparing the traditional distributed approaches, making our approach a more economic option for real-world applications.

  6. Efficient formation of benzylic quaternary centers via palladium catalysis.

    PubMed

    Gottumukkala, Aditya L; Suljagic, Jasmin; Matcha, Kiran; de Vries, Johannes G; Minnaard, Adriaan J

    2013-09-01

    Four's a crowd: An efficient protocol for the formation of benzylic quaternary centers via arylation of enones using a catalyst made from Pd(O2 CCF3 )2 and 2,2'-bipyridine is developed. For cyclic substrates, catalyst loadings as low as 1 mol % Pd are enough to afford excellent yields (>90%) using a variety of arylboronic acids. In case of acyclic substrates, the addition of KSbF6 was found to improve conversions and yields. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Impact of the Motor and Tail Domains of Class III Myosins on Regulating the Formation and Elongation of Actin Protrusions.

    PubMed

    Raval, Manmeet H; Quintero, Omar A; Weck, Meredith L; Unrath, William C; Gallagher, James W; Cui, Runjia; Kachar, Bechara; Tyska, Matthew J; Yengo, Christopher M

    2016-10-21

    Class III myosins (MYO3A and MYO3B) are proposed to function as transporters as well as length and ultrastructure regulators within stable actin-based protrusions such as stereocilia and calycal processes. MYO3A differs from MYO3B in that it contains an extended tail domain with an additional actin-binding motif. We examined how the properties of the motor and tail domains of human class III myosins impact their ability to enhance the formation and elongation of actin protrusions. Direct examination of the motor and enzymatic properties of human MYO3A and MYO3B revealed that MYO3A is a 2-fold faster motor with enhanced ATPase activity and actin affinity. A chimera in which the MYO3A tail was fused to the MYO3B motor demonstrated that motor activity correlates with formation and elongation of actin protrusions. We demonstrate that removal of individual exons (30-34) in the MYO3A tail does not prevent filopodia tip localization but abolishes the ability to enhance actin protrusion formation and elongation in COS7 cells. Interestingly, our results demonstrate that MYO3A slows filopodia dynamics and enhances filopodia lifetime in COS7 cells. We also demonstrate that MYO3A is more efficient than MYO3B at increasing formation and elongation of stable microvilli on the surface of cultured epithelial cells. We propose that the unique features of MYO3A, enhanced motor activity, and an extended tail with tail actin-binding motif, allow it to play an important role in stable actin protrusion length and ultrastructure maintenance.

  8. Ubisemiquinone is the electron donor for superoxide formation by complex III of heart mitochondria.

    PubMed

    Turrens, J F; Alexandre, A; Lehninger, A L

    1985-03-01

    Much evidence indicates that superoxide is generated from O2 in a cyanide-sensitive reaction involving a reduced component of complex III of the mitochondrial respiratory chain, particularly when antimycin A is present. Although it is generally believed that ubisemiquinone is the electron donor to O2, little experimental evidence supporting this view has been reported. Experiments with succinate as electron donor in the presence of antimycin A in intact rat heart mitochondria, which contain much superoxide dismutase but little catalase, showed that myxothiazol, which inhibits reduction of the Rieske iron-sulfur center, prevented formation of hydrogen peroxide, determined spectrophotometrically as the H2O2-peroxidase complex. Similarly, depletion of the mitochondria of their cytochrome c also inhibited formation of H2O2, which was restored by addition of cytochrome c. These observations indicate that factors preventing the formation of ubisemiquinone also prevent H2O2 formation. They also exclude ubiquinol, which remains reduced under these conditions, as the reductant of O2. Since cytochrome b also remains fully reduced when myxothiazol is added to succinate- and antimycin A-supplemented mitochondria, reduced cytochrome b may also be excluded as the reductant of O2. These observations, which are consistent with the Q-cycle reactions, by exclusion of other possibilities leave ubisemiquinone as the only reduced electron carrier in complex III capable of reducing O2 to O2-.

  9. Americium(iii) and europium(iii) complex formation with lactate at elevated temperatures studied by spectroscopy and quantum chemical calculations.

    PubMed

    Barkleit, Astrid; Kretzschmar, Jerome; Tsushima, Satoru; Acker, Margret

    2014-08-07

    Thermodynamic parameters for the complex formation of Am(iii) and Eu(iii) with lactate were determined with UV-vis and time-resolved laser-induced fluorescence spectroscopy (TRLFS) in a temperature range between 25 and 70 °C. The reaction enthalpy decreased with increasing ionic strength. ATR FT-IR and NMR spectroscopy in combination with density functional theory (DFT) calculations revealed structural details of the Eu(iii) lactate 1 : 1 complex: a chelating coordination mode of the lactate with a monodentate binding carboxylate group and the hydroxyl group being deprotonated.

  10. Aluminium substitution in iron(II-III)-layered double hydroxides: Formation and cationic order

    SciTech Connect

    Ruby, Christian Abdelmoula, Mustapha; Aissa, Rabha; Medjahdi, Ghouti; Brunelli, Michela; Francois, Michel

    2008-09-15

    The formation and the modifications of the structural properties of an aluminium-substituted iron(II-III)-layered double hydroxide (LDH) of formula Fe{sub 4}{sup II}Fe{sub (2-6y)}{sup III}Al{sub 6y}{sup III} (OH){sub 12} SO{sub 4}, 8H{sub 2}O are followed by pH titration curves, Moessbauer spectroscopy and high-resolution X-ray powder diffraction using synchrotron radiation. Rietveld refinements allow to build a structural model for hydroxysulphate green rust, GR(SO{sub 4}{sup 2-}), i.e. y=0, in which a bilayer of sulphate anions points to the Fe{sup 3+} species. A cationic order is proposed to occur in both GR(SO{sub 4}{sup 2-}) and aluminium-substituted hydroxysulphate green rust when y<0.08. Variation of the cell parameters and a sharp decrease in average crystal size and anisotropy are detected for an aluminium content as low as y=0.01. The formation of Al-GR(SO{sub 4}{sup 2-}) is preceded by the successive precipitation of Fe{sup III} and Al{sup III} (oxy)hydroxides. Adsorption of more soluble Al{sup III} species onto the initially formed ferric oxyhydroxide may be responsible for this slowdown of crystal growth. Therefore, the insertion of low aluminium amount (y{approx}0.01) could be an interesting way for increasing the surface reactivity of iron(II-III) LDH that maintains constant the quantity of the reactive Fe{sup II} species of the material. - Graphical abstract: (a) Crystallographical structure of sulphated green rust: SO{sub 4}{sup 2-} point to the Fe{sup 3+} cations (red) that form an ordered array with the Fe{sup 2+} cations (green). (b) Width and asymmetry of the synchrotron XRD peaks increase rapidly when some Al{sup 3+} species substitute the Fe{sup 3+} cations; z is molar ratio Al{sup 3+}/Fe{sup 3+}.

  11. Three-Coordinate Terminal Imidoiron(III) Complexes: Structure, Spectroscopy, and Mechanism of Formation

    PubMed Central

    Cowley, Ryan E.; DeYonker, Nathan J.; Eckert, Nathan A.; Cundari, Thomas R.; DeBeer, Serena; Bill, Eckhard; Ottenwaelder, Xavier; Flaschenriem, Christine; Holland, Patrick L.

    2010-01-01

    Reaction of 1-adamantyl azide with iron(I) diketiminate precursors gives metastable but isolable imidoiron(III) complexes LFe=NAd (L = bulky β-diketiminate ligand; Ad = 1-adamantyl). This paper addresses: (1) the spectroscopic and structural characterization of the Fe=N multiple bond in these interesting three-coordinate iron imido complexes, and (2) the mechanism through which the imido complexes form. The iron(III) imido complexes have been examined by 1H NMR and EPR spectroscopies and temperature-dependent magnetic susceptibility (SQUID), and structurally characterized by crystallography and/or X-ray absorption (EXAFS) measurements. These data show that the imido complexes have quartet ground states and short (1.68 ± 0.01 Å) iron-nitrogen bonds. The formation of the imido complexes proceeds through unobserved iron–RN3 intermediates, which are indicated by QM/MM computations to be best described as iron(II) with an RN3 radical anion. The radical character on the organoazide bends its NNN linkage to enable easy N2 loss and imido complex formation. The product distribution between imidoiron(III) products and hexazene-bridged diiron(II) products is solvent-dependent, and the solvent dependence can be explained by coordination of certain solvents to the iron(I) precursor prior to interaction with the organoazide. PMID:20524625

  12. Pullulanase and Starch Synthase III Are Associated with Formation of Vitreous Endosperm in Quality Protein Maize

    PubMed Central

    Wu, Hao; Clay, Kasi; Thompson, Stephanie S.; Hennen-Bierwagen, Tracie A.; Andrews, Bethany J.; Zechmann, Bernd; Gibbon, Bryan C.

    2015-01-01

    The opaque-2 (o2) mutation of maize increases lysine content, but the low seed density and soft texture of this type of mutant are undesirable. Lines with modifiers of the soft kernel phenotype (mo2) called “Quality Protein Maize” (QPM) have high lysine and kernel phenotypes similar to normal maize. Prior research indicated that the formation of vitreous endosperm in QPM might involve changes in starch granule structure. In this study, we focused on analysis of two starch biosynthetic enzymes that may influence kernel vitreousness. Analysis of recombinant inbred lines derived from a cross of W64Ao2 and K0326Y revealed that pullulanase activity had significant positive correlation with kernel vitreousness. We also found that decreased Starch Synthase III abundance may decrease the pullulanase activity and average glucan chain length given the same Zpu1 genotype. Therefore, Starch Synthase III could indirectly influence the kernel vitreousness by affecting pullulanase activity and coordinating with pullulanase to alter the glucan chain length distribution of amylopectin, resulting in different starch structural properties. The glucan chain length distribution had strong positive correlation with the polydispersity index of glucan chains, which was positively associated with the kernel vitreousness based on nonlinear regression analysis. Therefore, we propose that pullulanase and Starch Synthase III are two important factors responsible for the formation of the vitreous phenotype of QPM endosperms. PMID:26115014

  13. Star formation scales and efficiency in Galactic spiral arms

    NASA Astrophysics Data System (ADS)

    Eden, D. J.; Moore, T. J. T.; Urquhart, J. S.; Elia, D.; Plume, R.; Rigby, A. J.; Thompson, M. A.

    2015-09-01

    We positionally match a sample of infrared-selected young stellar objects, identified by combining the Spitzer Galactic Legacy Infrared Mid-Plane Survey Extraordinaire, Wide-field Infrared Survey Explorer and Herschel Space Observatory Herschel infrared Galactic Plane Survey, to the dense clumps identified in the millimetre continuum by the Bolocam Galactic Plane Survey in two Galactic lines of sight centred towards l = 30° and 40°. We calculate the ratio of infrared luminosity, LIR, to the mass of the clump, Mclump, in a variety of Galactic environments and find it to be somewhat enhanced in spiral arms compared to the interarm regions when averaged over kiloparsec scales. We find no compelling evidence that these changes are due to the mechanical influence of the spiral arm on the star formation efficiency rather than, e.g. different gradients in the star formation rate due to patchy or intermittent star formation, or local variations that are not averaged out due to small source samples. The largest variation in LIR/Mclump is found in individual clump values, which follow a lognormal distribution and have a range of over three orders of magnitude. This spread is intrinsic as no dependence of LIR/Mclump with Mclump was found. No difference was found in the luminosity distribution of sources in the arm and interarm samples and a strong linear correlation was found between LIR and Mclump.

  14. Efficiency of Natural Gas Flares Associated with Shale Formation Wells

    NASA Astrophysics Data System (ADS)

    Stirm, B.; Caulton, D.; Shepson, P.; Cambaliza, M. L.; Mccabe, D. C.; Baum, E.

    2012-12-01

    Hydraulic fracturing has increased access and economic viability of shale oil reserves. Currently the Bakken Oil field in North Dakota is experiencing a rapid increase in the drilling of shale oil wells. However, this process typically results in the simultaneous release of natural gas. Low natural gas prices and the lack of local gas pipeline infrastructure have decreased the incentive for companies to capture this natural gas, with many opting to vent or flare the natural gas instead. The impact of these operations on greenhouse gas emissions has not been well characterized. An undocumented variable of interest is the destruction efficiency of methane in active oil field flares. In situ measurements of flare efficiency are difficult to obtain because of the inaccessibility of the flares. In June of 2012 we conducted flights over shale oil wells and flares in the Bakken Formation near Williston, ND using Purdue University's Airborne Laboratory for Atmospheric Research (ALAR) which is equipped with a 0.5 Hz Picarro CO2/CH4/H2O analyzer and a Best Air Turbulence (BAT) probe that measures the wind vectors. In addition, one flare in the Marcellus Formation near Washington, PA was also sampled. Flare signals were identified based on the enhancements of CO2 above the ambient background signal and the corresponding colocated CH4 concentration. Enhancements were isolated by subtracting the background concentrations of CO2 and CH4 to obtain delta CO2 and delta CH4 values. Emission factors to be reported are obtained as the ratio delta CH4 divided by delta CO2. We will report first in situ measurements of natural gas flare efficiency. We observed a variety of meteorological conditions with winds ranging from 4 to 15 m/s and will report on the relationship between wind speed and flare efficiency. We observed very high flare efficiency even under strong winds (at least 99.8% CO2 for all flares). During flare sampling, we observed a number of CH4 enhancements that were

  15. Controlled formation of epitaxial III-V nanowires for device applications

    NASA Astrophysics Data System (ADS)

    Martensson, Thomas

    2007-03-01

    For the realization of devices with dimensions on the 10 nm scale, there is today a great interest in the possible use of self-assembly as a tool. In this talk will be described the state-of-the-art in growth of epitaxially nucleated, vertically standing semiconductor nanowires made from III-V semiconductors, with high level of control of dimensions, position and structural properties. Such wires hold great promise for use in future electronics and photonics applications. Three key aspects will be specifically addressed, namely: (1) The combination of top-down and bottom-up processes in lithographically aided formation of nanowires. A concern from industry is that bottom up techniques should suffer from ``fundamental placement problem[s], i.e. there is no practical and reliable way to precisely align and position them.'' (Chau R., et al. Opportunities and challenges of III-V nanoelectronics for future high-speed, low-power logic applications. (2005)). One way to resolve this issue is lithography where individual nanowire site control with high precision can be achieved. Electron beam lithography has the advantage of being a flexible high-resolution method, whereas nanoimprint lithography offers great opportunities for up-scaling and high-throughput processing. (2) The successful growth of III-V nanowires on silicon, including designed heterostructures. The special nanowire geometry with tens of nanometer radius and very small nanowire / substrate interface, enables monolithic integration of high-performance III-V materials on Silicon substrates. As an example, GaAsP heterostructure nanowires for photonic applications are discussed. Also the formation of InAs nanowires for high-speed and low-power-electronics directly on Si will be described. In the latter process, the use of foreign metal particles for wire growth is completely avoided, greatly reducing compatibility concerns between CMOS and nanowire technology. (3) Nanowire devices, such as field

  16. Formation of Soluble Organo-Chromium(III) Complexes after Chromate Reduction in the Presence of Cellular Organics

    SciTech Connect

    Puzon, Geoffrey J.; Roberts, Arthur G.; Kramer, David M.; Xun, Luying

    2005-04-01

    Microbial reduction of hexavalent chromium [Cr(VI)] to trivalent chromium [Cr(III)] has been investigated as a method for bioremediation of Cr(VI) contaminated environments. The produced Cr(III) is thought to be insoluble Cr(OH)3; however, recent reports suggested a more complex fate of Cr(III). A bacterial enzyme system, using NADH as the reductant, converts Cr(VI) to a soluble NAD+-Cr(III) complex, and cytochrome c-mediated Cr(VI) reduction produces cytochrome c-Cr(III) adducts. In this study, Cr(VI) reduction in the presence of cellular organic metabolites formed both soluble and insoluble organo-Cr(III) end-products. Several soluble end-products were characterized by absorbance spectroscopy and electron paramagnetic resonance spectrometry as organo-Cr(III) complexes, similar to the known ascorbate-Cr(III) complex. The complexes remained soluble and stable upon dialysis against distilled H2O and over a broad pH range. The ready formation of stable organo-Cr(III) complexes suggests that organo-Cr(III) complexes are rather common, likely representing an integral part of the natural cycling of chromium. Finally, thus, organo-Cr(III) complexes may account for the mobile form of Cr(III) detected in the environment.

  17. Bacterial Formation of As(V) and As(III) Ferric Oxyhydroxides in Acid Mine Drainage.

    NASA Astrophysics Data System (ADS)

    Morin, G.; Juillot, F.; Lebrun, S.; Casiot, C.; Elbaz-Poulichet, F.; Bruneel, O.; Personne, J.; Leblanc, M.; Ildefonse, P.; Calas, G.

    2002-12-01

    The oxidation of dissolved Fe(II) which is often promoted by acidophilic bacteria in acid mine drainage (AMD) and some hot springs, leads to the precipitation of Fe(III) oxy-hydroxides which incorporate toxic elements within their structure or adsorb them at their surface, thus limiting their mobility. In such complex natural systems, synchrotron-based techniques as X-ray absorption spectroscopy offer the opportunity to monitor surface/solution interactions as well as redox changes affecting the mobility and toxicity of trace elements as arsenic. Spatial and seasonal variations of the (bio-) oxidation of Fe(II) and As(III), and the subsequent precipitation of As-Fe gels, were followed by XANES, XRD, and SEM along the CarnoulŠs AMD (Gard, France). Chemical and mineralogical data collected on sediments, stromatolite, and bioassay samples showed that some indigenous bacteria living in the As-rich CarnoulŠs water ([As] = up to 350 mg.l-1) play an important role in the nature and composition of the solid phases that sequester arsenic at the site. The formation of nano-crystalline and amorphous As(III) ferric oxy-hydroxides has been related to the presence of bacteria able to oxidize Fe(II) but not As(III), which are only present in winter in the upstream area. A rare ferric arsenite sulfate oxy-hydroxide mineral was discovered in this context. Other types of bacteria, occurring in the downstream area whatever the season, are able to catalyze As(III) to As(V) oxidation and, provided that enough Fe(II) oxidizes, promote the formation of amorphous As(V) rich ferric oxy-hydroxides. These bacterially mediated reactions significantly reduce the concentration of dissolved As(III), which is more toxic and mobile than As(V), and might thus be helpful for designing As-removal processes. This work was supported by the French PEVS and ACI Ecologie Quantitative Programs and the PIRAMID EC program. ?Deceased, 26 October 1999 Juillot F., Ildefonse Ph., Morin G., Calas G., De

  18. High efficiency removal of dissolved As(III) using iron nanoparticle-embedded macroporous polymer composites.

    PubMed

    Savina, Irina N; English, Christopher J; Whitby, Raymond L D; Zheng, Yishan; Leistner, Andre; Mikhalovsky, Sergey V; Cundy, Andrew B

    2011-09-15

    Novel nanocomposite materials where iron nanoparticles are embedded into the walls of a macroporous polymer were produced and their efficiency for the removal of As(III) from aqueous media was studied. Nanocomposite gels containing α-Fe(2)O(3) and Fe(3)O(4) nanoparticles were prepared by cryopolymerisation resulting in a monolithic structure with large interconnected pores up to 100 μm in diameter and possessing a high permeability (ca. 3 × 10(-3) ms(-1)). The nanocomposite devices showed excellent capability for the removal of trace concentrations of As(III) from solution, with a total capacity of up to 3mg As/g of nanoparticles. The leaching of iron was minimal and the device could operate in a pH range 3-9 without diminishing removal efficiency. The effect of competing ions such as SO(4)(2-) and PO(4)(3-) was negligible. The macroporous composites can be easily configured into a variety of shapes and structures and the polymer matrix can be selected from a variety of monomers, offering high potential as flexible metal cation remediation devices.

  19. Iridium(III) Bis-Pyridine-2-Sulfonamide Complexes as Efficient and Durable Catalysts for Homogeneous Water Oxidation.

    PubMed

    Li, Mo; Takada, Kazutake; Goldsmith, Jonas I; Bernhard, Stefan

    2016-01-19

    A family of tetradentate bis(pyridine-2-sulfonamide) (bpsa) compounds was synthesized as a ligand platform for designing resilient and electronically tunable catalysts capable of performing water oxidation catalysis and other processes in highly oxidizing environments. These wrap-around ligands were coordinated to Ir(III) octahedrally, forming an anionic complex with chloride ions bound to the two remaining coordination sites. NMR spectroscopy documented that the more rigid ligand frameworks-[Ir(bpsa-Cy)Cl2](-) and [Ir(bpsa-Ph)Cl2](-)-produced C1-symmetric complexes, while the complex with the more flexible ethylene linker in [Ir(bpsa-en)Cl2](-) displays C2 symmetry. Their electronic structure was explored with DFT calculations and cyclic voltammetry in nonaqueous environments, which unveiled highly reversible Ir(III)/Ir(IV) redox processes and more complex, irreversible reduction chemistry. Addition of water to the electrolyte revealed the ability of these complexes to catalyze the water oxidation reaction efficiently. Electrochemical quartz crystal microbalance studies confirmed that a molecular species is responsible for the observed electrocatalytic behavior and ruled out the formation of active IrOx. The electrochemical studies were complemented by work on chemically driven water oxidation, where the catalytic activity of the iridium complexes was studied upon exposure to ceric ammonium nitrate, a strong, one-electron oxidant. Variation of the catalyst concentrations helped to illuminate the kinetics of these water oxidation processes and highlighted the robustness of these systems. Stable performance for over 10 days with thousands of catalyst turnovers was observed with the C1-symmetric catalysts. Dynamic light scattering experiments ascertained that a molecular species is responsible for the catalytic activity and excluded the formation of IrOx particles.

  20. Formation of crystalline titanium(IV) phosphates from titanium(III) solutions

    SciTech Connect

    Bortun, A.; Jaimez, E.; Llavona, R.; Garcia, J.R.; Rodriguez, J.

    1995-04-01

    Crystalline phases of titanium (IV) phosphate have been obtained from titanium(III) chloride in phosphoric acid solutions. The {alpha}-titanium phosphate synthesis is possible at low temperature (60--80 C). {gamma}-Titanium phosphate is obtained by reflux with very concentrated phosphoric acid in 3--5 hours by oxidation with O{sub 2}. The influence in these reactions of several factors (concentration of reagents, molar ratio P:Ti in the reaction mixture, temperature and reaction) was studied. The {alpha}-titanium phosphate formation takes place in several steps through the sequential formation of amorphous titanium(IV) phosphate, {gamma}-titanium phosphate and/or a semicrystalline titanium(IV) hydroxophosphate, Ti(OH){sub 2}(HPO{sub 4}){center_dot}H{sub 2}O.

  1. Armigeres subalbatus (Diptera: Culicidae) prophenoloxidase III is required for mosquito cuticle formation: ultrastructural study on dsRNA-knockdown mosquitoes.

    PubMed

    Tsao, I Y; Christensen, B M; Chen, C C

    2010-07-01

    We previously suggested that Armigeres subalbatus (Coquillett) prophenoloxidase III (As-pro-PO III) might be associated with morphogenesis of larvae and pupae. Because PO and its activation system are present in the insect cuticle, and cuticle formation is a major event during pupal morphogenesis, we used ultrastructural analysis to examine the effects of As-pro-PO III knockdown on the formation of pupal and adult cuticle. Inoculation of As-pro-PO III dsRNA resulted in the incomplete formation of nascent pupal endocuticle and pharate adult cuticle, i.e., significantly fewer cuticular lamellae were deposited, the helicoidal pattern of chitin microfibrils was disorganized, and numerous electron-lucent spaces were present in the cuticular protein matrix. Similar disruptions were observed in the cuticle of adults derived from As-pro-PO III dsRNA-inoculated pupae. It has long been suggested that the quinines, generated by PO-catalyzed oxidation reactions, function as cross-linking agents; therefore, it seems reasonable to suggest that the loss of As-pro-PO III-mediated protein-protein linkages causes morphological abnormalities in the protein matrix. Our findings suggest that As-pro-PO III plays a role in cuticle formation in mosquitoes, a novel function for phenol-oxidizing enzymes.

  2. On the formation of aliphatic polycarbonates from epoxides with chromium(III) and aluminum(III) metal-salen complexes.

    PubMed

    Luinstra, Gerrit A; Haas, Gerhard R; Molnar, Ferenc; Bernhart, Volker; Eberhardt, Robert; Rieger, Bernhard

    2005-10-21

    A DFT-based description is given of the CO2/epoxide copolymerization with a catalyst system consisting of metal (chromium, iron, titanium, aluminum)-salen complexes (salen = N,N'-bis(3,5-di-tert-butylsalicyliden-1,6-diaminophenyl) in combination with either chloride, acetate, or dimethylamino pyridine (DMAP) as external nucleophile. Calculations indicate that initiation proceeds through nucleophilic attack at a metal-coordinated epoxide, and the most likely propagation reaction is a bimolecular process in which a metal-bound nucleophile attacks a metal-bound epoxide. Carbon dioxide insertion occurs at a single metal center and is most likely the rate-determining step at low pressure. The prevalent chain terminating/degradation-the so-called backbiting, a reaction leading to formation of cyclic carbonate from the polymer chain-would involve attack of a carbonate nucleophile rather than an alkoxide at the last unit of the growing chain. The backbiting of a free carbonato chain end is particularly efficient. Anion dissociation from six-coordinate aluminum is appreciably easier than from chromium-salen complexes, indicating the reason why in the former case cyclic carbonate is the sole product. Experimental data were gathered for a series of chromium-, aluminum-, iron-, and zinc-salen complexes, which were used in combination with external nucleophiles like DMAP and mainly (tetraalkyl ammonium) chloride/acetate. Aluminum complexes transform PO (propylene oxide) and CO2 to give exclusively propylene carbonate. This is explained by rapid carbonate anion dissociation from a six-coordinate complex and cyclic formation. CO2 insertion or nucleophilic attack of an external nucleophile at a coordinated epoxide (at higher CO2 pressure) are the rate-determining steps. Catalysis with [Cr(salen)(acetate/chloride)] complexes leads to the formation of both cyclic carbonate and polypropylene carbonate with various quantities of ether linkages. The dependence of the activity and

  3. Application of Protocols Devised to Study Bi(III) Complex Formation by Voltammetry: The Bi(III)-Picolinic Acid System.

    PubMed

    Billing, Caren; Cukrowski, Ignacy

    2016-12-22

    Bi(III) coordination chemistry has been largely neglected due to the difficulties faced when studying these systems even though Bi(III) is used in various medicinal applications. This study of the Bi(III)-picolinic acid system by voltammetry applies the rigorous methodologies already developed to enable the study of Bi(III) systems starting in very acidic solutions to prevent precipitation. This includes calibrating the glass electrode accurately at these low pHs, compensating for the diffusion junction potential below pH 2 and determining the reduction potential of uncomplexed Bi(III) which cannot be directly measured. The importance of including nitrate from the background electrolyte as a competing species is highlighted, especially for data acquired below pH ∼ 2. From analysis of the voltammetric data, it was not clear whether a ML3OH species formed in solution or whether it was a combination of ML4 and ML4OH. Information from crystal structures and electrospray ionization-mass spectrometry measurements was thus used to propose the most probable species model. The log β values determined were 7.77 ± 0.07 for ML, 13.89 ± 0.07 for ML2, 18.61 ± 0.01 for ML3, 22.7 ± 0.2 for ML4, and 31.4 ± 0.2 for ML4OH. Application of these methodologies thus opens the door to broaden our understanding of Bi(III) complexation.

  4. Highly efficient detoxification of Cr(VI) by chitosan-Fe(III) complex: process and mechanism studies.

    PubMed

    Shen, Chensi; Chen, Hui; Wu, Shaoshuai; Wen, Yuezhong; Li, Lina; Jiang, Zheng; Li, Meichao; Liu, Weiping

    2013-01-15

    Metal-biopolymer complexes has recently gained significant attention as an effective adsorbent used for the removal of Cr(VI) from water. Unfortunately, despite increasing research efforts in the field of removal efficiency, whether this kind of complex can reduce Cr(VI) to less-toxic Cr(III) and what are the mechanisms of detoxification processes are still unknown. In this study, despite the highly adsorption efficiency (maximum adsorption capacity of 173.1 mg/g in 10 min), the significant improvement of Cr(VI) reduction by chitosan-Fe(III) complex compared with normal crosslinked chitoan has been demonstrated. In addition, the structure of chitosan-Fe(III) complex and its functional groups concerned with Cr(VI) detoxification have been characterized by the powerful spectroscopic techniques X-ray absorption fine structure (XAFS) and X-ray photoelectron spectroscopy (XPS). The XPS spectra indicated that the primary alcoholic function on C-6 served as an electron donor during Cr(VI) reduction and was oxidized to a carbonyl group. The X-ray adsorption near edge spectra (XANES) of the Cr(VI)-treated chitosan-Fe(III) complex revealed the similar geometrical arrangement of Cr species as that in Cr(III)-bound chitosan-Fe(III). Overall, a possible process and mechanism for highly efficient detoxification of Cr(VI) by chitosan-Fe(III) complex has been elucidate. Copyright © 2012 Elsevier B.V. All rights reserved.

  5. High Efficiency Nanostructured III-V Photovoltaics for Solar Concentrator Application

    SciTech Connect

    Hubbard, Seth

    2012-09-12

    The High Efficiency Nanostructured III-V Photovoltaics for Solar Concentrators project seeks to provide new photovoltaic cells for Concentrator Photovoltaics (CPV) Systems with higher cell efficiency, more favorable temperature coefficients and less sensitivity to changes in spectral distribution. The main objective of this project is to provide high efficiency III-V solar cells that will reduce the overall cost per Watt for power generation using CPV systems.This work is focused both on a potential near term application, namely the use of indium arsenide (InAs) QDs to spectrally "tune" the middle (GaAs) cell of a SOA triple junction device to a more favorable effective bandgap, as well as the long term goal of demonstrating intermediate band solar cell effects. The QDs are confined within a high electric field i-region of a standard GaAs solar cell. The extended absorption spectrum (and thus enhanced short circuit current) of the QD solar cell results from the increase in the sub GaAs bandgap spectral response that is achievable as quantum dot layers are introduced into the i-region. We have grown InAs quantum dots by OMVPE technique and optimized the QD growth conditions. Arrays of up to 40 layers of strain balanced quantum dots have been experimentally demonstrated with good material quality, low residual stain and high PL intensity. Quantum dot enhanced solar cells were grown and tested under simulated one sun AM1.5 conditions. Concentrator solar cells have been grown and fabricated with 5-40 layers of QDs. Testing of these devices show the QD cells have improved efficiency compared to baseline devices without QDs. Device modeling and measurement of thermal properties were performed using Crosslight APSYS. Improvements in a triple junction solar cell with the insertion of QDs into the middle current limiting junction was shown to be as high as 29% under one sun illumination for a 10 layer stack QD enhanced triple junction solar cell. QD devices have strong

  6. The type III protein secretion system contributes to Xanthomonas citri subsp. citri biofilm formation

    PubMed Central

    2014-01-01

    Background Several bacterial plant pathogens colonize their hosts through the secretion of effector proteins by a Type III protein secretion system (T3SS). The role of T3SS in bacterial pathogenesis is well established but whether this system is involved in multicellular processes, such as bacterial biofilm formation has not been elucidated. Here, the phytopathogen Xanthomonas citri subsp. citri (X. citri) was used as a model to gain further insights about the role of the T3SS in biofilm formation. Results The capacity of biofilm formation of different X. citri T3SS mutants was compared to the wild type strain and it was observed that this secretion system was necessary for this process. Moreover, the T3SS mutants adhered proficiently to leaf surfaces but were impaired in leaf-associated growth. A proteomic study of biofilm cells showed that the lack of the T3SS causes changes in the expression of proteins involved in metabolic processes, energy generation, exopolysaccharide (EPS) production and bacterial motility as well as outer membrane proteins. Furthermore, EPS production and bacterial motility were also altered in the T3SS mutants. Conclusions Our results indicate a novel role for T3SS in X. citri in the modulation of biofilm formation. Since this process increases X. citri virulence, this study reveals new functions of T3SS in pathogenesis. PMID:24742141

  7. Silver Nanowire Transparent Conductive Electrodes for High-Efficiency III-Nitride Light-Emitting Diodes

    NASA Astrophysics Data System (ADS)

    Oh, Munsik; Jin, Won-Yong; Jun Jeong, Hyeon; Jeong, Mun Seok; Kang, Jae-Wook; Kim, Hyunsoo

    2015-09-01

    Silver nanowires (AgNWs) have been successfully demonstrated to function as next-generation transparent conductive electrodes (TCEs) in organic semiconductor devices owing to their figures of merit, including high optical transmittance, low sheet resistance, flexibility, and low-cost processing. In this article, high-quality, solution-processed AgNWs with an excellent optical transmittance of 96.5% at 450 nm and a low sheet resistance of 11.7 Ω/sq were demonstrated as TCEs in inorganic III-nitride LEDs. The transmission line model applied to the AgNW contact to p-GaN showed that near ohmic contact with a specific contact resistance of ~10-3 Ωcm2 was obtained. The contact resistance had a strong bias-voltage (or current-density) dependence: namely, field-enhanced ohmic contact. LEDs fabricated with AgNW electrodes exhibited a 56% reduction in series resistance, 56.5% brighter output power, a 67.5% reduction in efficiency droop, and a approximately 30% longer current spreading length compared to LEDs fabricated with reference TCEs. In addition to the cost reduction, the observed improvements in device performance suggest that the AgNWs are promising for application as next-generation TCEs, to realise brighter, larger-area, cost-competitive inorganic III-nitride light emitters.

  8. Silver Nanowire Transparent Conductive Electrodes for High-Efficiency III-Nitride Light-Emitting Diodes.

    PubMed

    Oh, Munsik; Jin, Won-Yong; Jeong, Hyeon Jun; Jeong, Mun Seok; Kang, Jae-Wook; Kim, Hyunsoo

    2015-09-03

    Silver nanowires (AgNWs) have been successfully demonstrated to function as next-generation transparent conductive electrodes (TCEs) in organic semiconductor devices owing to their figures of merit, including high optical transmittance, low sheet resistance, flexibility, and low-cost processing. In this article, high-quality, solution-processed AgNWs with an excellent optical transmittance of 96.5% at 450 nm and a low sheet resistance of 11.7 Ω/sq were demonstrated as TCEs in inorganic III-nitride LEDs. The transmission line model applied to the AgNW contact to p-GaN showed that near ohmic contact with a specific contact resistance of ~10(-3) Ωcm(2) was obtained. The contact resistance had a strong bias-voltage (or current-density) dependence: namely, field-enhanced ohmic contact. LEDs fabricated with AgNW electrodes exhibited a 56% reduction in series resistance, 56.5% brighter output power, a 67.5% reduction in efficiency droop, and a approximately 30% longer current spreading length compared to LEDs fabricated with reference TCEs. In addition to the cost reduction, the observed improvements in device performance suggest that the AgNWs are promising for application as next-generation TCEs, to realise brighter, larger-area, cost-competitive inorganic III-nitride light emitters.

  9. Silver Nanowire Transparent Conductive Electrodes for High-Efficiency III-Nitride Light-Emitting Diodes

    PubMed Central

    Oh, Munsik; Jin, Won-Yong; Jun Jeong, Hyeon; Jeong, Mun Seok; Kang, Jae-Wook; Kim, Hyunsoo

    2015-01-01

    Silver nanowires (AgNWs) have been successfully demonstrated to function as next-generation transparent conductive electrodes (TCEs) in organic semiconductor devices owing to their figures of merit, including high optical transmittance, low sheet resistance, flexibility, and low-cost processing. In this article, high-quality, solution-processed AgNWs with an excellent optical transmittance of 96.5% at 450 nm and a low sheet resistance of 11.7 Ω/sq were demonstrated as TCEs in inorganic III-nitride LEDs. The transmission line model applied to the AgNW contact to p-GaN showed that near ohmic contact with a specific contact resistance of ~10−3 Ωcm2 was obtained. The contact resistance had a strong bias-voltage (or current-density) dependence: namely, field-enhanced ohmic contact. LEDs fabricated with AgNW electrodes exhibited a 56% reduction in series resistance, 56.5% brighter output power, a 67.5% reduction in efficiency droop, and a approximately 30% longer current spreading length compared to LEDs fabricated with reference TCEs. In addition to the cost reduction, the observed improvements in device performance suggest that the AgNWs are promising for application as next-generation TCEs, to realise brighter, larger-area, cost-competitive inorganic III-nitride light emitters. PMID:26333768

  10. The formation of light absorbing insoluble organic compounds from the reaction of biomass burning precursors and Fe(III)

    NASA Astrophysics Data System (ADS)

    Lavi, Avi; Lin, Peng; Bhaduri, Bhaskar; Laskin, Alexander; Rudich, Yinon

    2017-04-01

    Dust particles and volatile organic compounds from fuel or biomass burning are two major components that affect air quality in urban polluted areas. We characterized the products from the reaction of soluble Fe(III), a reactive transition metal originating from dust particles dissolution processes, with phenolic compounds , namely, guaiacol, syringol, catechol, o- and p- cresol that are known products of incomplete fuel and biomass combustion but also from other natural sources such as humic compounds degradation. We found that under acidic conditions comparable to those expected on a dust particle surface, phenolic compounds readily react with dissolved Fe(III), leading to the formation of insoluble polymeric compounds. We characterized the insoluble products by x-ray photoelectron microscopy, UV-Vis spectroscopy, mass spectrometry, elemental analysis and thermo-gravimetric analysis. We found that the major chromophores formed are oligomers (from dimers to pentamers) of the reaction precursors that efficiently absorb light between 300nm and 500nm. High variability of the mass absorption coefficient of the reaction products was observed with catechol and guaiacol showing high absorption at the 300-500nm range that is comparable to that of brown carbon (BrC) from biomass burning studies. The studied reaction is a potential source for the in-situ production of secondary BrC material under dark conditions. Our results suggest a reaction path for the formation of bio-available iron in coastal polluted areas where dust particles mix with biomass burning pollution plumes. Such mixing can occur, for instance in the coast of West Africa or North Africa during dust and biomass burning seasons

  11. A cationic Rh(III) complex that efficiently catalyzes hydrogen isotope exchange in hydrosilanes.

    PubMed

    Campos, Jesús; Esqueda, Ana C; López-Serrano, Joaquín; Sánchez, Luis; Cossio, Fernando P; de Cozar, Abel; Alvarez, Eleuterio; Maya, Celia; Carmona, Ernesto

    2010-12-01

    The synthesis and structural characterization of a mixed-sandwich (η(5)-C(5)Me(5))Rh(III) complex of the cyclometalated phosphine PMeXyl(2) (Xyl = 2,6-C(6)H(3)Me(2)) with unusual κ(4)-P,C,C',C'' coordination (compound 1-BAr(f); BAr(f) = B(3,5-C(6)H(3)(CF(3))(2))(4)) are reported. A reversible κ(4) to κ(2) change in the binding of the chelating phosphine in cation 1(+) induced by dihydrogen and hydrosilanes triggers a highly efficient Si-H/Si-D (or Si-T) exchange applicable to a wide range of hydrosilanes. Catalysis can be carried out in an organic solvent solution or without solvent, with catalyst loadings as low as 0.001 mol %, and the catalyst may be recycled a number of times.

  12. Lattice-Mismatched III-V Epilayers for High-Efficiency Photovoltaics

    SciTech Connect

    Ahrenkiel, Scott Phillip

    2013-06-30

    The project focused on development of new approaches and materials combinations to expand and improve the quality and versatility of lattice-mismatched (LMM) III-V semiconductor epilayers for use in high-efficiency multijunction photovoltaic (PV) devices. To address these goals, new capabilities for materials synthesis and characterization were established at SDSM&T that have applications in modern opto- and nano-electronics, including epitaxial crystal growth and transmission electron microscopy. Advances were made in analyzing and controlling the strain profiles and quality of compositional grades used for these technologies. In particular, quaternary compositional grades were demonstrated, and a quantitative method for characteristic X-ray analysis was developed. The project allowed enhanced collaboration between scientists at NREL and SDSM&T to address closely related research goals, including materials exchange and characterization.

  13. Dark-ages reionization and galaxy formation simulation - III. Modelling galaxy formation and the epoch of reionization

    NASA Astrophysics Data System (ADS)

    Mutch, Simon J.; Geil, Paul M.; Poole, Gregory B.; Angel, Paul W.; Duffy, Alan R.; Mesinger, Andrei; Wyithe, J. Stuart B.

    2016-10-01

    We introduce MERAXES, a new, purpose-built semi-analytic galaxy formation model designed for studying galaxy growth during reionization. MERAXES is the first model of its type to include a temporally and spatially coupled treatment of reionization and is built upon a custom (100 Mpc)3 N-body simulation with high temporal and mass resolution, allowing us to resolve the galaxy and star formation physics relevant to early galaxy formation. Our fiducial model with supernova feedback reproduces the observed optical depth to electron scattering and evolution of the galaxy stellar mass function between z = 5 and 7, predicting that a broad range of halo masses contribute to reionization. Using a constant escape fraction and global recombination rate, our model is unable to simultaneously match the observed ionizing emissivity at z ≲ 6. However, the use of an evolving escape fraction of 0.05-0.1 at z ˜ 6, increasing towards higher redshift, is able to satisfy these three constraints. We also demonstrate that photoionization suppression of low-mass galaxy formation during reionization has only a small effect on the ionization history of the intergalactic medium. This lack of `self-regulation' arises due to the already efficient quenching of star formation by supernova feedback. It is only in models with gas supply-limited star formation that reionization feedback is effective at regulating galaxy growth. We similarly find that reionization has only a small effect on the stellar mass function, with no observationally detectable imprint at M* > 107.5 M⊙. However, patchy reionization has significant effects on individual galaxy masses, with variations of factors of 2-3 at z = 5 that correlate with environment.

  14. Triggered star formation in the LMC4/Constellation III region of the Large Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    Efremov, Yuri N.; Elmegreen, Bruce G.

    1998-09-01

    The origin of a regular, 600-pc-long arc of young stars and clusters in the Constellation III region of the Large Magellanic Cloud is considered. The circular form of this arc suggests that the pre-stellar gas was uniformly swept up by a central source of pressure. In the centre of the arc are six ~30-Myr-old A-type supergiant stars and a Cepheid variable of similar age, which may be related to the source of this pressure. We calculate the expansion of a bubble around a cluster of this age, and show that it could have triggered the formation of the arc at the right time and place. Surrounding the central old stars and extending well outside the young arc is the LMC4 superbubble and giant HI shell. We show how this superbubble and shell could have formed by the continued expansion of the 15-Myr-old cavity, following star formation in the arc and the associated new pressures. The age sequence proposed here was not evident in the recent observations by Olsen et al. and Braun et al. because the first generation stars in the centre of the LMC superbubble are relatively faint and scarce compared to the more substantial population of stars less than 15 Myr old that formed throughout the region in a second generation. These considerations lead to an examination of the origin of the LMC4/Constellation III region and other large rings in the LMC and other galaxies. Their size and circularity could be the result of low galactic shear and a thick disc, with several generations of star formation in their interiors now too faint to be seen.

  15. Investigation of the Mechanism of Formation of a Thiolate-Ligated Fe(III)-OOH

    PubMed Central

    Nam, Elaine; Alokolaro, Pauline E.; Swartz, Rodney D.; Gleaves, Morgan C.; Pikul, Jessica; Kovacs, Julie A.

    2011-01-01

    Kinetic studies aimed at determining the most probable mechanism for the proton-dependent [FeII(SMe2N4(tren))]+ (1) promoted reduction of superoxide via a thiolate-ligated hydroperoxo intermediate [FeIII(SMe2N4(tren))(OOH)]+ (2) are described. Rate laws are derived for three proposed mechanisms, and it is shown that they should conceivably be distinguishable by kinetics. For weak proton donors with pKa(HA) >pKa(HO2) rates are shown to correlate with proton donor pKa, and display first-order dependence on iron, and half-order dependence on superoxide and proton donor HA. Proton donors acidic enough to convert O2− to HO2 (in tetrahydrofuran, THF), that is, those with pKa(HA) < pKa(HO2), are shown to display first-order dependence on both superoxide and iron, and rates which are independent of proton donor concentration. Relative pKa values were determined in THF by measuring equilibrium ion pair acidity constants using established methods. Rates of hydroperoxo 2 formation displays no apparent deuterium isotope effect, and bases, such as methoxide, are shown to inhibit the formation of 2. Rate constants for p-substituted phenols are shown to correlate linearly with the Hammett substituent constants σ−. Activation parameters ((ΔH‡ = 2.8 kcal/mol, ΔS‡ = −31 eu) are shown to be consistent with a low-barrier associative mechanism that does not involve extensive bond cleavage. Together, these data are shown to be most consistent with a mechanism involving the addition of HO2 to 1 with concomitant oxidation of the metal ion, and reduction of superoxide (an “oxidative addition” of sorts), in the rate-determining step. Activation parameters for MeOH- (ΔH‡ = 13.2 kcal/mol and ΔS‡ = −24.3 eu), and acetic acid- (ΔH‡ = 8.3 kcal/mol and ΔS‡ = −34 eu) promoted release of H2O2 to afford solvent-bound [FeIII(SMe2N4(tren))(OMe)]+ (3) and [FeIII(SMe2N4(tren))(O(H)Me)]+ (4), respectively, are shown to be more consistent with a reaction involving rate

  16. Phase III Advanced Anodes and Cathodes Utilized in Energy Efficient Aluminum Production Cells

    SciTech Connect

    R.A. Christini; R.K. Dawless; S.P. Ray; D.A. Weirauch, Jr.

    2001-11-05

    During Phase I of the present program, Alcoa developed a commercial cell concept that has been estimated to save 30% of the energy required for aluminum smelting. Phase ii involved the construction of a pilot facility and operation of two pilots. Phase iii of the Advanced Anodes and Cathodes Program was aimed at bench experiments to permit the resolution of certain questions to be followed by three pilot cells. All of the milestones related to materials, in particular metal purity, were attained with distinct improvements over work in previous phases of the program. NiO additions to the ceramic phase and Ag additions to the Cu metal phase of the cermet improved corrosion resistance sufficiently that the bench scale pencil anodes met the purity milestones. Some excellent metal purity results have been obtained with anodes of the following composition: Further improvements in anode material composition appear to be dependent on a better understanding of oxide solubilities in molten cryolite. For that reason, work was commissioned with an outside consultant to model the MeO - cryolite systems. That work has led to a better understanding of which oxides can be used to substitute into the NiO-Fe2O3 ceramic phase to stabilize the ferrites and reduce their solubility in molten cryolite. An extensive number of vertical plate bench electrolysis cells were run to try to find conditions where high current efficiencies could be attained. TiB2-G plates were very inconsistent and led to poor wetting and drainage. Pure TiB2 did produce good current efficiencies at small overlaps (shadowing) between the anodes and cathodes. This bench work with vertical plate anodes and cathodes reinforced the importance of good cathode wetting to attain high current efficiencies. Because of those conclusions, new wetting work was commissioned and became a major component of the research during the third year of Phase III. While significant progress was made in several areas, much work needs to be

  17. Providing for energy efficiency in homes and small buildings. Part III. Determining which practices are most effective and installing materials

    SciTech Connect

    1980-06-01

    The training program is designed to educate students and individuals in the importance of conserving energy and to provide for developing skills needed in the application of energy-saving techniques that result in energy-efficient buildings. A teacher guide and student workbook are available to supplement the basic manual. Subjects covered in Part III are: determining which practices are most efficient and economical; installing energy-saving materials; and improving efficiency of equipment.

  18. Evidence for a hyperglycaemia-dependent decrease of antithrombin III-thrombin complex formation in humans.

    PubMed

    Ceriello, A; Giugliano, D; Quatraro, A; Marchi, E; Barbanti, M; Lefèbvre, P

    1990-03-01

    In the presence of increased levels of fibrinopeptide A, decreased antithrombin III biological activity, and thrombin-antithrombin III complex levels are seen in diabetic patients. Induced-hyperglycaemia in diabetic and normal subjects decreased antithrombin III activity and thrombin-antithrombin III levels, and increased fibrinopeptide A plasma levels, while antithrombin III concentration did not change; heparin was shown to reduced these phenomena. In diabetic patients, euglycaemia induced by insulin infusion restored antithrombin III activity, thrombin-antithrombin III complex and fibrinopeptide A concentrations; heparin administration had the same effects. These data stress the role of a hyperglycaemia-dependent decrease of antithrombin III activity in precipitating thrombin hyperactivity in diabetes mellitus.

  19. Development of III-Sb Quantum Dot Systems for High Efficiency Intermediate Band Solar Cells

    SciTech Connect

    Huffaker, Diana; Hubbard, Seth; Norman, Andrew

    2015-07-31

    This project aimed to develop solar cells that can help reduce cost per watt. This work focused on developing solar cells that utilize quantum dot (QD) nanomaterials to provide multijunction solar cell efficiency at the cost of single junction solar cell. We focused on a novel concept known as intermediate band solar cells (IBSC) where an additional energy band is inserted in a single solar cell to accommodate sub-bandgap photons absorption which otherwise are lost through transmission. The additional energy band can be achieved by growing QDs within a solar cell p-n junction. Though numerous studies have been conducted to develop such QD systems, very small improvements in solar energy conversion efficiency have been reported. This is mainly due to non-optimal material parameters such as band gap, band offset etc. In this work, we identified and developed a novel QD material system that meets the requirements of IBSC more closely than the current state-of-the-art technology. To achieve these goals, we focused on three important areas of solar cell design: band structure calculations of new materials, efficient device design for high efficiency, and development of new semiconductor materials. In this project, we focused on III-Sb materials as they possess a wide range of energy bandgaps from 0.2 eV to 2eV. Despite the difficulty involved in realizing these materials, we were successfully developed these materials through a systematic approach. Materials studied in this work are AlAsSb (Aluminum Arsenide Antimonide), InAlAs (Indium Aluminum Arsenide) and InAs (Indium Arsenide). InAs was used to develop QD layers within AlAsSb and InAlAs p-n junctions. As the QDs have very small volume, up to 30 QD layers been inserted into the p-n junction to enhance light absorption. These QD multi-stack devices helped in understanding the challenges associated with the development of quantum dot solar cells. The results from this work show that the quantum dot solar cells indeed

  20. Study of damage formation and annealing of implanted III-nitride semiconductors for optoelectronic devices

    NASA Astrophysics Data System (ADS)

    Faye, D. Nd.; Fialho, M.; Magalhães, S.; Alves, E.; Ben Sedrine, N.; Rodrigues, J.; Correia, M. R.; Monteiro, T.; Boćkowski, M.; Hoffmann, V.; Weyers, M.; Lorenz, K.

    2016-07-01

    An n-GaN/n-AlGaN/p-GaN light emitting diode (LED) structure was implanted with Eu ions. High temperature high pressure annealing at 1400 °C efficiently decreases implantation damage and optically activates the Eu ions. However, the electrical properties of the p-n junction deteriorate possibly due to the formation of conducting paths along dislocations during the extreme annealing conditions.

  1. Support-dependent active species formation for CuO catalysts: Leading to efficient pollutant degradation in alkaline conditions.

    PubMed

    Li, Yibing; Guo, Lianshuang; Huang, Dekang; Jawad, Ali; Chen, Zhuqi; Yang, Jiakuan; Liu, Weidong; Shen, Yan; Wang, Mingkui; Yin, Guochuan

    2017-04-15

    Redox metal ions play the crucial role in versatile advanced oxidation technologies, in which controlling the active species formation through catalyst design is one of the key challenges in oxidant utilization. This work describes an example of different active species formations in CuO-mediated degradation just because of supporting material differences. Although three CuO catalysts were prepared by similar procedures, it was found that CuO-MgO catalyst demonstrated high efficiency in phenol degradation with bicarbonate activated H2O2, in which the superoxide radical is crucial, while hydroxyl radical and singlet oxygen are ignorable. For the CuO-MgO-Al2O3 and CuO-Al2O3 catalysts, the degradation proceeds by popular hydroxyl radical based process, however, the efficiency was poor. The EPR experiments also confirmed the absence of hydroxyl radical in CuO-MgO system but its presence in CuO-MgO-Al2O3 and CuO-Al2O3 system. The high catalytic efficiency with ignorable hydroxyl radical in the CuO-MgO system leads us to propose that an alternative Cu(III) species dominates the degradation. The basic MgO support may facilitate the formation of the Cu(III) species, whereas the neutral MgO-Al2O3 and acidic Al2O3 supports are unable to stabilize the high valent Cu(III) species, leading to the common hydroxyl radical mechanism with low efficiency of H2O2 in alkaline conditions. Copyright © 2016. Published by Elsevier B.V.

  2. Formation of III-V-on-insulator structures on Si by direct wafer bonding

    NASA Astrophysics Data System (ADS)

    Yokoyama, Masafumi; Iida, Ryo; Ikku, Yuki; Kim, Sanghyeon; Takagi, Hideki; Yasuda, Tetsuji; Yamada, Hisashi; Ichikawa, Osamu; Fukuhara, Noboru; Hata, Masahiko; Takenaka, Mitsuru; Takagi, Shinichi

    2013-09-01

    We have studied the formation of III-V-compound-semiconductors-on-insulator (III-V-OI) structures with thin buried oxide (BOX) layers on Si wafers by using developed direct wafer bonding (DWB). In order to realize III-V-OI MOSFETs with ultrathin body and extremely thin body (ETB) InGaAs-OI channel layers and ultrathin BOX layers, we have developed an electron-cyclotron resonance (ECR) O2 plasma-assisted DWB process with ECR sputtered SiO2 BOX layers and a DWB process based on atomic-layer-deposition Al2O3 (ALD-Al2O3) BOX layers. It is essential to suppress micro-void generation during wafer bonding process to achieve excellent wafer bonding. We have found that major causes of micro-void generation in DWB processes with ECR-SiO2 and ALD-Al2O3 BOX layers are desorption of Ar and H2O gas, respectively. In order to suppress micro-void generation in the ECR-SiO2 BOX layers, it is effective to introduce the outgas process before bonding wafers. On the other hand, it is a possible solution for suppressing micro-void generation in the ALD-Al2O3 BOX layers to increase the deposition temperature of the ALD-Al2O3 BOX layers. It is also another possible solution to deposit ALD-Al2O3 BOX layers on thermally oxidized SiO2 layers, which can absorb the desorption gas from ALD-Al2O3 BOX layers.

  3. Perfluoroalkyl Cobalt(III) Fluoride and Bis(perfluoroalkyl) Complexes: Catalytic Fluorination and Selective Difluorocarbene Formation.

    PubMed

    Leclerc, Matthew C; Bayne, Julia M; Lee, Graham M; Gorelsky, Serge I; Vasiliu, Monica; Korobkov, Ilia; Harrison, Daniel J; Dixon, David A; Baker, R Tom

    2015-12-30

    Four perfluoroalkyl cobalt(III) fluoride complexes have been synthesized and characterized by elemental analysis, multinuclear NMR spectroscopy, X-ray crystallography, and powder X-ray diffraction. The remarkable cobalt fluoride (19)F NMR chemical shifts (-716 to -759 ppm) were studied computationally, and the contributing paramagnetic and diamagnetic factors were extracted. Additionally, the complexes were shown to be active in the catalytic fluorination of p-toluoyl chloride. Furthermore, two examples of cobalt(III) bis(perfluoroalkyl)complexes were synthesized and their reactivity studied. Interestingly, abstraction of a fluoride ion from these complexes led to selective formation of cobalt difluorocarbene complexes derived from the trifluoromethyl ligand. These electrophilic difluorocarbenes were shown to undergo insertion into the remaining perfluoroalkyl fragment, demonstrating the elongation of a perfluoroalkyl chain arising from a difluorocarbene insertion on a cobalt metal center. The reactions of both the fluoride and bis(perfluoroalkyl) complexes provide insight into the potential catalytic applications of these model systems to form small fluorinated molecules as well as fluoropolymers.

  4. Organometallic nickel(III) complexes relevant to cross-coupling and carbon-heteroatom bond formation reactions.

    PubMed

    Zheng, Bo; Tang, Fengzhi; Luo, Jia; Schultz, Jason W; Rath, Nigam P; Mirica, Liviu M

    2014-04-30

    Nickel complexes have been widely employed as catalysts in C-C and C-heteroatom bond formation reactions. In addition to Ni(0) and Ni(II) intermediates, several Ni-catalyzed reactions are proposed to also involve odd-electron Ni(I) and Ni(III) oxidation states. We report herein the isolation, structural and spectroscopic characterization, and organometallic reactivity of Ni(III) complexes containing aryl and alkyl ligands. These Ni(III) species undergo transmetalation and/or reductive elimination reactions to form new C-C or C-heteroatom bonds and are also competent catalysts for Kumada and Negishi cross-coupling reactions. Overall, these results provide strong evidence for the direct involvement of organometallic Ni(III) species in cross-coupling reactions and oxidatively induced C-heteroatom bond formation reactions.

  5. Resolving the Formation of Protogalaxies. III.Feedback from the First Stars

    SciTech Connect

    Wise, John H.; Abel, Tom; /KIPAC, Menlo Park

    2007-10-30

    The first stars form in dark matter halos of masses {approx}10{sup 6}M{sub {circle_dot}} as suggested by an increasing number of numerical simulations. Radiation feedback from these stars expels most of the gas from their shallow potential well of their surrounding dark matter halos. We use cosmological adaptive mesh refinement simulations that include self-consistent Population III star formation and feedback to examine the properties of assembling early dwarf galaxies. Accurate radiative transport is modeled with adaptive ray tracing. We include supernova explosions and follow the metal enrichment of the intergalactic medium. The calculations focus on the formation of several dwarf galaxies and their progenitors. In these halos, baryon fractions in 10{sup 8} M{sub {circle_dot}} halos decrease by a factor of 2 with stellar feedback and by a factor of 3 with supernova explosions. We find that radiation feedback and supernova explosions increase gaseous spin parameters up to a factor of 4 and vary with time. Stellar feedback, supernova explosions, and H{sub 2} cooling create a complex, multi-phase interstellar medium whose densities and temperatures can span up to 6 orders of magnitude at a given radius. The pair-instability supernovae of Population III stars alone enrich the halos with virial temperatures of 10{sup 4} K to approximately 10{sup -3} of solar metallicity. We find that 40% of the heavy elements resides in the intergalactic medium (IGM) at the end of our calculations. The highest metallicity gas exists in supernova remnants and very dilute regions of the IGM.

  6. LOCAL LUMINOUS INFRARED GALAXIES. III. CO-EVOLUTION OF BLACK HOLE GROWTH AND STAR FORMATION ACTIVITY?

    SciTech Connect

    Alonso-Herrero, Almudena; Hernan-Caballero, Antonio; Pereira-Santaella, Miguel; Rieke, George H.; Diamond-Stanic, Aleksandar M.; Wang Yiping; Rigopoulou, Dimitra

    2013-03-10

    Local luminous infrared (IR) galaxies (LIRGs) have both high star formation rates (SFR) and a high AGN (Seyfert and AGN/starburst composite) incidence. Therefore, they are ideal candidates to explore the co-evolution of black hole (BH) growth and star formation (SF) activity, not necessarily associated with major mergers. Here, we use Spitzer/IRS spectroscopy of a complete volume-limited sample of local LIRGs (distances of <78 Mpc). We estimate typical BH masses of 3 Multiplication-Sign 10{sup 7} M{sub Sun} using [Ne III] 15.56 {mu}m and optical [O III] {lambda}5007 gas velocity dispersions and literature stellar velocity dispersions. We find that in a large fraction of local LIRGs, the current SFR is taking place not only in the inner nuclear {approx}1.5 kpc region, as estimated from the nuclear 11.3 {mu}m PAH luminosities, but also in the host galaxy. We next use the ratios between the SFRs and BH accretion rates (BHAR) to study whether the SF activity and BH growth are contemporaneous in local LIRGs. On average, local LIRGs have SFR to BHAR ratios higher than those of optically selected Seyferts of similar active galactic nucleus (AGN) luminosities. However, the majority of the IR-bright galaxies in the revised-Shapley-Ames Seyfert sample behave like local LIRGs. Moreover, the AGN incidence tends to be higher in local LIRGs with the lowest SFRs. All of this suggests that in local LIRGs there is a distinct IR-bright star-forming phase taking place prior to the bulk of the current BH growth (i.e., AGN phase). The latter is reflected first as a composite and then as a Seyfert, and later as a non-LIRG optically identified Seyfert nucleus with moderate SF in its host galaxy.

  7. Incremental Efficiency of WISC-III Factor Scores in Predicting Achievement: What Do They Tell Us?

    ERIC Educational Resources Information Center

    Glutting, Joseph J.; Youngstrom, Eric A.; Ward, Thomas; Ward, Sandra; Hale, Robert L.

    1997-01-01

    The incremental validity of factor scores from the Wechlser Intelligence Scale for Children-III (WISC-III) in predicting scores on the Wechsler Individual Achievement Test (WIAT) was studied in 283 nonreferred children and 636 referred for evaluation. The Full Scale IQ of the WISC-III was the best predictor of WIAT achievement. (SLD)

  8. Star formation in the first galaxies - III. Formation, evolution, and characteristics of the first metal-enriched stellar cluster

    NASA Astrophysics Data System (ADS)

    Safranek-Shrader, Chalence; Montgomery, Michael H.; Milosavljević, Miloš; Bromm, Volker

    2016-01-01

    We simulate the formation of a low-metallicity (10-2 Z⊙) stellar cluster at redshift z ˜ 14. Beginning with cosmological initial conditions, the simulation utilizes adaptive mesh refinement and sink particles to follow the collapse and evolution of gas past the opacity limit for fragmentation, thus resolving the formation of individual protostellar cores. A time- and location-dependent protostellar radiation field, which heats the gas by absorption on dust, is computed by integration of protostellar evolutionary tracks. The simulation also includes a robust non-equilibrium chemical network that self-consistently treats gas thermodynamics and dust-gas coupling. The system is evolved for 18 kyr after the first protostellar source has formed. In this time span, 30 sink particles representing protostellar cores form with a total mass of 81 M⊙. Their masses range from ˜0.1 to 14.4 M⊙ with a median mass ˜0.5-1 M⊙. Massive protostars grow by competitive accretion while lower mass protostars are stunted in growth by close encounters and many-body ejections. In the regime explored here, the characteristic mass scale is determined by the cosmic microwave background temperature floor and the onset of efficient dust-gas coupling. It seems unlikely that host galaxies of the first bursts of metal-enriched star formation will be detectable with the James Webb Space Telescope or other next-generation infrared observatories. Instead, the most promising access route to the dawn of cosmic star formation may lie in the scrutiny of metal-poor, ancient stellar populations in the Galactic neighbourhood. The observable targets corresponding to the system simulated here are ultra-faint dwarf satellite galaxies such as Boötes II and Willman I.

  9. Development and Implementation of Efficiency-Improving Analysis Methods for the SAGE III on ISS Thermal Model Originating

    NASA Technical Reports Server (NTRS)

    Liles, Kaitlin; Amundsen, Ruth; Davis, Warren; Scola, Salvatore; Tobin, Steven; McLeod, Shawn; Mannu, Sergio; Guglielmo, Corrado; Moeller, Timothy

    2013-01-01

    The Stratospheric Aerosol and Gas Experiment III (SAGE III) instrument is the fifth in a series of instruments developed for monitoring aerosols and gaseous constituents in the stratosphere and troposphere. SAGE III will be delivered to the International Space Station (ISS) via the SpaceX Dragon vehicle in 2015. A detailed thermal model of the SAGE III payload has been developed in Thermal Desktop (TD). Several novel methods have been implemented to facilitate efficient payload-level thermal analysis, including the use of a design of experiments (DOE) methodology to determine the worst-case orbits for SAGE III while on ISS, use of TD assemblies to move payloads from the Dragon trunk to the Enhanced Operational Transfer Platform (EOTP) to its final home on the Expedite the Processing of Experiments to Space Station (ExPRESS) Logistics Carrier (ELC)-4, incorporation of older models in varying unit sets, ability to change units easily (including hardcoded logic blocks), case-based logic to facilitate activating heaters and active elements for varying scenarios within a single model, incorporation of several coordinate frames to easily map to structural models with differing geometries and locations, and streamlined results processing using an Excel-based text file plotter developed in-house at LaRC. This document presents an overview of the SAGE III thermal model and describes the development and implementation of these efficiency-improving analysis methods.

  10. Formation of anodic layers on InAs (111)III. Study of the chemical composition

    SciTech Connect

    Valisheva, N. A. Tereshchenko, O. E.; Prosvirin, I. P.; Kalinkin, A. V.; Goljashov, V. A.; Levtzova, T. A.; Bukhtiyarov, V. I.

    2012-04-15

    The chemical composition of {approx}20-nm-thick anodic layers grown on InAs (111)III in alkaline and acid electrolytes containing or not containing NH{sub 4}F is studied by X-ray photoelectron spectroscopy. It is shown that the composition of fluorinated layers is controlled by the relation between the concentrations of fluorine and hydroxide ions in the electrolyte and by diffusion processes in the growing layer. Fluorine accumulates at the (anodic layer)/InAs interface. Oxidation of InAs in an acid electrolyte with a low oxygen content and a high NH{sub 4}F content brings about the formation of anodic layers with a high content of fluorine and elemental arsenic and the formation of an oxygen-free InF{sub x}/InAs interface. Fluorinated layers grown in an alkaline electrolyte with a high content of O{sup 2-} and/or OH{sup -} groups contain approximately three times less fluorine and consist of indium and arsenic oxyfluorides. No distinction between the compositions of the layers grown in both types of fluorine-free electrolytes is established.

  11. X-Ray Background at High Redshifts from Pop III Remnants: Results from Pop III Star Formation Rates in the Renaissance Simulations

    NASA Astrophysics Data System (ADS)

    Xu, Hao; Ahn, Kyungjin; Norman, Michael L.; Wise, John H.; O'Shea, Brian W.

    2016-11-01

    Due to their long mean free paths, X-rays are expected to have global impacts on the properties of the intergalactic medium (IGM) by their large-scale heating and ionizing processes. At high redshifts, X-rays from Population (Pop) III binaries might have important effects on cosmic reionization and the Lyα forest. As a continuation of our previous work on Pop III binary X-rays, we use the Pop III distribution and evolution from the Renaissance Simulations, a suite of self-consistent cosmological radiation hydrodynamics simulations of the formation of the first galaxies, to calculate the X-ray luminosity density and background over the redshift range 20≥slant z≥slant 7.6. As we find that Pop III star formation continues at a low, nearly constant rate to the end of reionization, X-rays are being continuously produced at significant rates compared to other possible X-ray sources, such as AGNs and normal X-ray binaries during the same period of time. We estimate that Pop III binaries produce approximately 6 eV of energy in the X-rays per hydrogen atom. We calculate the X-ray background for different monochromatic photon energies. KeV X-rays redshift and accumulate to produce a strong X-ray background spectrum extending to roughly 500 eV. The X-ray background is strong enough to heat the IGM to ˜1000 K and to ionize a few percent of the neutral hydrogen. These effects are important for an understanding of the neutral hydrogen hyperfine transition 21 cm line signatures, the Lyα forest, and the Thomson optical depth to the CMB.

  12. Highly Efficient Cooperative Catalysis by Co III (Porphyrin) Pairs in Interpenetrating Metal-Organic Frameworks

    SciTech Connect

    Lin, Zekai; Zhang, Zhi-Ming; Chen, Yu-Sheng; Lin, Wenbin

    2016-12-02

    A series of porous twofold interpenetrated In-CoIII(porphyrin) metal–organic frameworks (MOFs) were constructed by in situ metalation of porphyrin bridging ligands and used as efficient cooperative catalysts for the hydration of terminal alkynes. The twofold interpenetrating structure brings adjacent CoIII(porphyrins) in the two networks parallel to each other with a distance of about 8.8 Å, an ideal distance for the simultaneous activation of both substrates in alkyne hydration reactions. As a result, the In-CoIII(porphyrin) MOFs exhibit much higher (up to 38 times) catalytic activity than either homogeneous catalysts or MOF controls with isolated CoIII(porphyrin) centers, thus highlighting the potential application of MOFs in cooperative catalysis.

  13. Theoretical characterization and design of highly efficient iridium (III) complexes bearing guanidinate ancillary ligand.

    PubMed

    Ren, Xin-Yao; Wu, Yong; Wang, Li; Zhao, Liang; Zhang, Min; Geng, Yun; Su, Zhong-Min

    2014-06-01

    A density functional theory/time-depended density functional theory was used to investigate the synthesized guanidinate-based iridium(III) complex [(ppy)2Ir{(N(i)Pr)2C(NPh2)}] (1) and two designed derivatives (2 and 3) to determine the influences of different cyclometalated ligands on photophysical properties. Except the conventional discussions on geometric relaxations, absorption and emission properties, many relevant parameters, including spin-orbital coupling (SOC) matrix elements, zero-field-splitting parameters, radiative rate constants (kr) and so on were quantitatively evaluated. The results reveal that the replacement of the pyridine ring in the 2-phenylpyridine ligand with different diazole rings cannot only enlarge the frontier molecular orbital energy gaps, resulting in a blue-shift of the absorption spectra for 2 and 3, but also enhance the absorption intensity of 3 in the lower-energy region. Furthermore, it is intriguing to note that the photoluminescence quantum efficiency (ΦPL) of 3 is significantly higher than that of 1. This can be explained by its large SOC value(n=3-4) and large transition electric dipole moment (μS3), which could significantly contribute to a larger kr. Besides, compared with 1, the higher emitting energy (ET1) and smaller (2) value for 3 may lead to a smaller non-radiative decay rate. Additionally, the detailed results also indicate that compared to 1 with pyridine ring, 3 with imidazole ring performs a better hole injection ability. Therefore, the designed complex 3 can be expected as a promising candidate for highly efficient guanidinate-based phosphorescence emitter for OLEDs applications.

  14. Inter-relationships of MnO 2 precipitation, siderophore-Mn (III) complex formation, siderophore degradation, and iron limitation in Mn (II)-oxidizing bacterial cultures

    NASA Astrophysics Data System (ADS)

    Parker, Dorothy L.; Morita, Takami; Mozafarzadeh, Mylene L.; Verity, Rebecca; McCarthy, James K.; Tebo, Bradley M.

    2007-12-01

    To examine the pathways that form Mn (III) and Mn (IV) in the Mn (II)-oxidizing bacterial strains Pseudomonas putida GB-1 and MnB1, and to test whether the siderophore pyoverdine (PVD) inhibits Mn (IV)O 2 formation, cultures were subjected to various protocols at known concentrations of iron and PVD. Depending on growth conditions, P. putida produced one of two oxidized Mn species - either soluble PVD-Mn (III) complex or insoluble Mn (IV)O 2 minerals - but not both simultaneously. PVD-Mn (III) was present, and MnO 2 precipitation was inhibited, both in iron-limited cultures that had synthesized 26-50 μM PVD and in iron-replete (non-PVD-producing) cultures that were supplemented with 10-550 μM purified PVD. PVD-Mn (III) arose by predominantly ligand-mediated air oxidation of Mn (II) in the presence of PVD, based on the following evidence: (a) yields and rates of this reaction were similar in sterile media and in cultures, and (b) GB-1 mutants deficient in enzymatic Mn oxidation produced PVD-Mn (III) as efficiently as wild type. Only wild type, however, could degrade PVD-Mn (III), a process linked to the production of both MnO 2 and an altered PVD with absorbance and fluorescence spectra markedly different from those of either PVD or PVD-Mn (III). Two conditions, the presence of bioavailable iron and the absence of PVD at concentrations exceeding those of Mn, both had to be satisfied for MnO 2 to appear. These results suggest that P. putida cultures produce soluble Mn (III) or MnO 2 by different and mutually inhibitory pathways: enzymatic catalysis yielding MnO 2 under iron sufficiency or PVD-promoted oxidation yielding PVD-Mn (III) under iron limitation. Since PVD-producing Pseudomonas species are environmentally prevalent Mn oxidizers, these data predict influences of iron (via PVD-Mn (III) versus MnO 2) on the global oxidation/reduction cycling of various pollutants, recalcitrant organic matter, and elements such as C, S, N, Cr, U, and Mn.

  15. Importance of the initial conditions for star formation - III. Statistical properties of embedded protostellar clusters

    NASA Astrophysics Data System (ADS)

    Girichidis, Philipp; Federrath, Christoph; Allison, Richard; Banerjee, Robi; Klessen, Ralf S.

    2012-03-01

    We investigate the formation of protostellar clusters during the collapse of dense molecular cloud cores with a focus on the evolution of potential and kinetic energy, the degree of substructure and the early phase of mass segregation. Our study is based on a series of hydrodynamic simulations of dense cores, where we vary the initial density profile and the initial turbulent velocity. In the three-dimensional adaptive mesh refinement simulations, we follow the dynamical formation of filaments and protostars until a star formation efficiency of 20 per cent. Despite the different initial configurations, the global ensemble of all protostars in a setup shows a similar energy evolution and forms sub-virial clusters with an energy ratio Ekin/|Epot|˜ 0.2. Concentrating on the innermost central region, the clusters show a roughly virialized energy balance. However, the region of virial balance only covers the innermost ˜10-30 per cent of all the protostars. In all simulations with multiple protostars, the total kinetic energy of the protostars is higher than the kinetic energy of the gas cloud, although the protostars only contain 20 per cent of the total mass. The clusters vary significantly in size, mass and number of protostars, and show different degrees of substructure and mass segregation. Flat density profiles and compressive turbulent modes produce more subclusters than centrally concentrated profiles and solenoidal turbulence. We find that dynamical relaxation and hence dynamical mass segregation is very efficient in all cases from the very beginning of the nascent cluster, i.e. during a phase when protostars constantly form and accrete.

  16. RESIDUA UPGRADING EFFICIENCY IMPROVEMENT MODELS: COKE FORMATION PREDICTABILITY MAPS

    SciTech Connect

    John F. Schabron; A. Troy Pauli; Joseph F. Rovani Jr.

    2002-05-01

    The dispersed particle solution model of petroleum residua structure was used to develop predictors for pyrolytic coke formation. Coking Indexes were developed in prior years that measure how near a pyrolysis system is to coke formation during the coke formation induction period. These have been demonstrated to be universally applicable for residua regardless of the source of the material. Coking onset is coincidental with the destruction of the ordered structure and the formation of a multiphase system. The amount of coke initially formed appears to be a function of the free solvent volume of the original residua. In the current work, three-dimensional coke make predictability maps were developed at 400 C, 450 C, and 500 C (752 F, 842 F, and 932 F). These relate residence time and free solvent volume to the amount of coke formed at a particular pyrolysis temperature. Activation energies for two apparent types of zero-order coke formation reactions were estimated. The results provide a new tool for ranking residua, gauging proximity to coke formation, and predicting initial coke make tendencies.

  17. An efficient data format for mass spectrometry-based proteomics.

    PubMed

    Shah, Anuj R; Davidson, Jennifer; Monroe, Matthew E; Mayampurath, Anoop M; Danielson, William F; Shi, Yan; Robinson, Aaron C; Clowers, Brian H; Belov, Mikhail E; Anderson, Gordon A; Smith, Richard D

    2010-10-01

    The diverse range of mass spectrometry (MS) instrumentation along with corresponding proprietary and nonproprietary data formats has generated a proteomics community driven call for a standardized format to facilitate management, processing, storing, visualization, and exchange of both experimental and processed data. To date, significant efforts have been extended towards standardizing XML-based formats for mass spectrometry data representation, despite the recognized inefficiencies associated with storing large numeric datasets in XML. The proteomics community has periodically entertained alternate strategies for data exchange, e.g., using a common application programming interface or a database-derived format. However, these efforts have yet to gain significant attention, mostly because they have not demonstrated significant performance benefits over existing standards, but also due to issues such as extensibility to multidimensional separation systems, robustness of operation, and incomplete or mismatched vocabulary. Here, we describe a format based on standard database principles that offers multiple benefits over existing formats in terms of storage size, ease of processing, data retrieval times, and extensibility to accommodate multidimensional separation systems.

  18. An efficient data format for mass spectrometry based proteomics

    SciTech Connect

    Shah, Anuj R.; Davidson, Jennifer L.; Monroe, Matthew E.; Mayampurath, Anoop M.; Danielson, William F.; Shi, Yan; Robinson, Aaron C.; Clowers, Brian H.; Belov, Mikhail E.; Anderson, Gordon A.; Smith, Richard D.

    2010-10-01

    The diverse range of mass spectrometry (MS) instrumentation along with corresponding proprietary and non-proprietary data formats has generated a proteomics community driven call for a standardized format to facilitate management, processing, storing, visualization, and exchange of both experimental and processed data. To date, significant efforts have been extended towards standardizing XML-based formats for mass spectrometry data representation, despite the recognized inefficiencies associated with storing large numeric datasets in XML. The proteomics community has periodically entertained alternate strategies for data exchange, e.g., using a common application programming interface or a database-derived format. However these efforts have yet to garner significant attention, mostly because they haven’t illustrated significant performance benefits over existing standards, but also due to issues such as extensibility to multi-dimensional separation systems, robustness of operation, and incomplete or mismatched vocabulary. Here, we describe a format based on standard database principles that offers multiple benefits over existing formats in terms of storage size, ease of processing, data retrieval times and extensibility to accommodate multi-dimensional separation systems.

  19. Formation and characterization of Co(III)-semiquinonate phenoxyl radical species.

    PubMed

    Shimazaki, Yuichi; Kabe, Ryota; Huth, Stefan; Tani, Fumito; Naruta, Yoshinori; Yamauchi, Osamu

    2007-07-23

    Co(III) complexes of N(3)O-donor tripodal ligands, 2,4-di(tert-butyl)-6-{[bis(2-pyridyl)methyl]aminomethyl}phenolate (tbuL), 2,4-di(tert-butyl)-6-{[bis(6-methyl-2-pyridyl)methyl]aminomethyl}phenolate (tbuL(Mepy)(2)), were prepared, and precursor Co(II) complexes, [Co(tbuL)Cl] (1) and [Co(tbuL(Mepy)(2))Cl] (2), and ternary Co(III) complexes, [Co(tbuL)(acac)]ClO(4) (3), [Co(tbuL)(tbu-cat)] (4), and [Co(tbuL(Mepy)(2))(tbu-SQ)]ClO(4) (5), where acac, tbu-cat, and tbu-SQ refer to pentane-2,4-dionate, 3,5-di(tert-butyl)catecholate, and 3,5-di(tert-butyl)semiquinonate, respectively, were structurally characterized by the X-ray diffraction method. Complexes 3 and 5 have a mononuclear structure with a fac-N(3)O(3) donor set, while 4 has a mer-N(3)O(3) structure. The cyclic voltammogram (CV) of complex 3 exhibited one reversible redox wave centered at 0.93 V (vs Ag/AgCl) in CH(3)CN. Complex 5 was converted to a phenoxyl radical species upon oxidation with Ce(IV), showing a characteristic pi-pi* transition band at 412 nm. The ESR spectrum at low temperature and the resonance Raman spectrum of 3 established that the radical species has a Co(III)-phenoxyl radical bond. On the other hand, the CVs showed two oxidation processes at E(1/2) = 0.01 and E(pa) = 0.92 V for 4 and E(1/2a) = 0.05 and E(1/2b) = 0.69 V for 5. The rest potential of 4 (-0.11 V) was lower than the E(1/2) value, whereas that of 5 (0.18 V) was higher, indicating that the first redox wave of 4 and 5 is assigned to the tbu-cat and the tbu-SQ redox process, respectively. One-electron oxidized 4 showed absorption, resonance Raman, and ESR spectra which are similar to those of 5, suggesting formation of a stable Co(III)-semiquinonate species, which has the same oxidation level of 5. The resonance Raman spectrum of two-electron oxidized 4 showed the nu(8a) bands of the semiquinonate and phenoxyl radical, which were absent in the spectrum of one-electron oxidized 5. Since both oxidized species were ESR inactive at 5 K

  20. Improvement of phenol photodegradation efficiency by a combined g-C3N4/Fe(III)/persulfate system.

    PubMed

    Hu, Jian-Yang; Tian, Ke; Jiang, Hong

    2016-04-01

    Graphite-like C3N4 (g-C3N4) is an efficient visible-light-driven photocatalyst commonly used in dye decolorization with very poor photocatalytic efficiency for degrading recalcitrant organic pollutants, such as phenol. In this study, we designed a g-C3N4/Fe(III)/persulfate system to significantly improve the phenol photodegradation efficacy by combining photocatalysis and light Fenton interaction. The phenol removal ratio and degradation rate of the g-C3N4/Fe(III)/persulfate system are 16.5- and 240-fold higher than those of individual g-C3N4 system. Sulfate radicals [Formula: see text] and H2O2 are detected in the g-C3N4/Fe(III)/persulfate system, suggesting that both radical decomposition and light Fenton interaction play important roles in phenol degradation. The efficient coupled photocatalytic system of g-C3N4 combined with Fe(III) and persulfate shows significant potential for application in large-scale degradation of environmental pollutants.

  1. Efficient Sensitized Z→E Photoisomerization of an Iridium(III)-Azobenzene Complex over a Wide Concentration Range.

    PubMed

    Moreno, Javier; Grubert, Lutz; Schwarz, Jutta; Bléger, David; Hecht, Stefan

    2017-09-07

    To improve the sensitized Z→E photoisomerization of azobenzenes, and circumvent the threshold concentration necessary for the bimolecular photoinduced electron transfer reaction to generate the rapidly isomerizing Z-azobenzene radical anion, an Ir(III) complex with a covalently tethered azobenzene fragment was synthesized. Selective irradiation of the (1) MLCT band of the Ir(III) complex induced an efficiently sensitized photoswitching of the dyad over a wide concentration range and even at high dilution. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Effect of RNase III on efficiency of translation of bacteriophage T7 lysozyme mRNA.

    PubMed Central

    Hagen, F S; Young, E T

    1978-01-01

    RNase III had no positive effect on the translation of bacteriophage T7 lysozyme mRNA in vivo or in vitro. The time of appearance and quanity of lysozyme in T7-infected E. coli BL107, an RNase III- strain, and T7-infected E. coli BL15, a nearly isogenic RNase III+ strain, were indistinguishable. Nearly identical patterns of lysozyme mRNA activity were obtained when RNA extracted at different times after infection of RNase III+ and RNase III- hosts was translated in cell-free extracts of E. coli containing or lacking RNase III. Exposure of RNA extracted from T7-infected E. coli BL107 (RNase III-) to purified RNase III did not increase the lysozyme mRNA activity of this RNA. The only result that implied that RNase III has a differential effect on the translatability of the lysozyme mRNA was the translation of fractionaed RNA from T7-infected E. coli BL107. Translation of the smallest and largest lysozyme messages, 0.33 x 10(6) and 4 x 10(6) to 5 x 10(6) daltons, was the most inefficient in RNase III- cell-free extracts as compared to RNase III+ cell-free translation. The translation of the most abundant, medium-sized lysozyme mRNA between 0.9 x 10(6) and 1.5 x 10(6) daltons was the least affected by the absence of RNase III. The existence of a lag between the appearance of lysozyme mRNA and the appearance of lysozyme in T7 infection was confirmed. In these studies a very rapid method of RNA extraction was used, eliminating the possibility of continued RNA transcription during cell collection and RNA extraction. With this method of analysis, the length of the lag period was established at about 3 min. The possibility that RNase III is the controlling element of the lag period was eliminated by these investigations. Images PMID:353304

  3. Star formation rates and efficiencies in the Galactic Centre

    NASA Astrophysics Data System (ADS)

    Barnes, A. T.; Longmore, S. N.; Battersby, C.; Bally, J.; Kruijssen, J. M. D.; Henshaw, J. D.; Walker, D. L.

    2017-08-01

    The inner few hundred parsecs of the Milky Way harbours gas densities, pressures, velocity dispersions, an interstellar radiation field and a cosmic ray ionization rate orders of magnitude higher than the disc; akin to the environment found in star-forming galaxies at high redshift. Previous studies have shown that this region is forming stars at a rate per unit mass of dense gas which is at least an order of magnitude lower than in the disc, potentially violating theoretical predictions. We show that all observational star formation rate diagnostics - both direct counting of young stellar objects and integrated light measurements - are in agreement within a factor two, hence the low star formation rate (SFR) is not the result of the systematic uncertainties that affect any one method. As these methods trace the star formation over different time-scales, from 0.1 to 5 Myr, we conclude that the SFR has been constant to within a factor of a few within this time period. We investigate the progression of star formation within gravitationally bound clouds on ∼parsec scales and find 1-4 per cent of the cloud masses are converted into stars per free-fall time, consistent with a subset of the considered 'volumetric' star formation models. However, discriminating between these models is obstructed by the current uncertainties on the input observables and, most importantly and urgently, by their dependence on ill-constrained free parameters. The lack of empirical constraints on these parameters therefore represents a key challenge in the further verification or falsification of current star formation theories.

  4. Concomitant Carboxylate and Oxalate Formation From the Activation of CO2 by a Thorium(III) Complex

    PubMed Central

    Formanuik, Alasdair; Ortu, Fabrizio; Inman, Christopher J.; Kerridge, Andrew; Castro, Ludovic

    2016-01-01

    Abstract Improving our comprehension of diverse CO2 activation pathways is of vital importance for the widespread future utilization of this abundant greenhouse gas. CO2 activation by uranium(III) complexes is now relatively well understood, with oxo/carbonate formation predominating as CO2 is readily reduced to CO, but isolated thorium(III) CO2 activation is unprecedented. We show that the thorium(III) complex, [Th(Cp′′)3] (1, Cp′′={C5H3(SiMe3)2‐1,3}), reacts with CO2 to give the mixed oxalate‐carboxylate thorium(IV) complex [{Th(Cp′′)2[κ2‐O2C{C5H3‐3,3′‐(SiMe3)2}]}2(μ‐κ2:κ2‐C2O4)] (3). The concomitant formation of oxalate and carboxylate is unique for CO2 activation, as in previous examples either reduction or insertion is favored to yield a single product. Therefore, thorium(III) CO2 activation can differ from better understood uranium(III) chemistry. PMID:27714966

  5. CHEMICAL ENRICHMENT OF DAMPED Ly{alpha} SYSTEMS AS A DIRECT CONSTRAINT ON POPULATION III STAR FORMATION

    SciTech Connect

    Kulkarni, Girish; Hennawi, Joseph F.; Rollinde, Emmanuel; Vangioni, Elisabeth

    2013-08-01

    Observations of damped Ly{alpha} absorbers (DLAs) can be used to measure gas-phase metallicities at large cosmological look-back times with high precision. Furthermore, relative abundances can still be measured accurately deep into the reionization epoch (z > 6) using transitions redward of Ly{alpha}, even though Gunn-Peterson absorption precludes measurement of neutral hydrogen. In this paper, we study the chemical evolution of DLAs using a model for the coupled evolution of galaxies and the intergalactic medium (IGM), which is constrained by a variety of observations. Our goal is to explore the influence of Population III stars on the abundance patterns of DLAs to determine the degree to which abundance measurements can discriminate between different Population III stellar initial mass functions (IMFs). We include effects, such as inflows onto galaxies due to cosmological accretion and outflows from galaxies due to supernova feedback. A distinct feature of our model is that it self-consistently calculates the effect of Population III star formation on the reionization of an inhomogeneous IGM, thus allowing us to calculate the thermal evolution of the IGM and implement photoionization feedback on low-mass galaxy formation. We find that if the critical metallicity of Population III to II/I transition is {approx}< 10{sup -4} Z{sub Sun }, then the cosmic Population III star formation rate drops to zero for z < 8. Nevertheless, at high redshift (z {approx} 6), chemical signatures of Population III stars remain in low-mass galaxies (halo mass {approx}< 10{sup 9} M{sub Sun }). This is because photoionization feedback suppresses star formation in these galaxies until relatively low redshift (z {approx} 10), and the chemical record of their initial generation of Population III stars is retained. We model DLAs as these low-mass galaxies, and assign to them a mass-dependent H I absorption cross-section in order to predict the expected distribution of DLA abundance ratios

  6. Efficient artificial mineralization route to decontaminate Arsenic(III) polluted water - the Tooeleite Way

    NASA Astrophysics Data System (ADS)

    Malakar, Arindam; Das, Bidisa; Islam, Samirul; Meneghini, Carlo; de Giudici, Giovanni; Merlini, Marco; Kolen'Ko, Yury V.; Iadecola, Antonella; Aquilanti, Giuliana; Acharya, Somobrata; Ray, Sugata

    2016-05-01

    Increasing exposure to arsenic (As) contaminated ground water is a great threat to humanity. Suitable technology for As immobilization and removal from water, especially for As(III) than As(V), is not available yet. However, it is known that As(III) is more toxic than As(V) and most groundwater aquifers, particularly the Gangetic basin in India, is alarmingly contaminated with it. In search of a viable solution here, we took a cue from the natural mineralization of Tooeleite, a mineral containing Fe(III) and As(III)ions, grown under acidic condition, in presence of SO42- ions. Complying to this natural process, we could grow and separate Tooeleite-like templates from Fe(III) and As(III) containing water at overall circumneutral pH and in absence of SO42- ions by using highly polar Zn-only ends of wurtzite ZnS nanorods as insoluble nano-acidic-surfaces. The central idea here is to exploit these insoluble nano-acidic-surfaces (called as INAS in the manuscript) as nucleation centres for Tooeleite growth while keeping the overall pH of the aqueous media neutral. Therefore, we propose a novel method of artificial mineralization of As(III) by mimicking a natural process at nanoscale.

  7. Efficient artificial mineralization route to decontaminate Arsenic(III) polluted water - the Tooeleite Way

    PubMed Central

    Malakar, Arindam; Das, Bidisa; Islam, Samirul; Meneghini, Carlo; De Giudici, Giovanni; Merlini, Marco; Kolen’ko, Yury V.; Iadecola, Antonella; Aquilanti, Giuliana; Acharya, Somobrata; Ray, Sugata

    2016-01-01

    Increasing exposure to arsenic (As) contaminated ground water is a great threat to humanity. Suitable technology for As immobilization and removal from water, especially for As(III) than As(V), is not available yet. However, it is known that As(III) is more toxic than As(V) and most groundwater aquifers, particularly the Gangetic basin in India, is alarmingly contaminated with it. In search of a viable solution here, we took a cue from the natural mineralization of Tooeleite, a mineral containing Fe(III) and As(III)ions, grown under acidic condition, in presence of SO42− ions. Complying to this natural process, we could grow and separate Tooeleite-like templates from Fe(III) and As(III) containing water at overall circumneutral pH and in absence of SO42− ions by using highly polar Zn-only ends of wurtzite ZnS nanorods as insoluble nano-acidic-surfaces. The central idea here is to exploit these insoluble nano-acidic-surfaces (called as INAS in the manuscript) as nucleation centres for Tooeleite growth while keeping the overall pH of the aqueous media neutral. Therefore, we propose a novel method of artificial mineralization of As(III) by mimicking a natural process at nanoscale. PMID:27189251

  8. Reaction mechanism for the highly efficient catalytic decomposition of peroxynitrite by the amphipolar iron(III) corrole 1-Fe.

    PubMed

    Avidan-Shlomovich, Shlomit; Gross, Zeev

    2015-07-21

    The amphipolar iron(III) corrole 1-Fe is one of the most efficient catalysts for the decomposition of peroxynitrite, the toxin involved in numerous diseases. This research focused on the mechanism of that reaction at physiological pH, where peroxynitrite is in equilibrium with its much more reactive conjugated acid, by focusing on the elementary steps involved in the catalytic cycle. Kinetic investigations uncovered the formation of a reaction intermediate in a process that is complete within a few milliseconds (k1 ∼ 3 × 10(7) M(-1) s(-1) at 5 °C, about 7 orders of magnitude larger than the first order rate constant for the non-catalyzed process). Multiple evidence points towards iron-catalyzed homolytic O-O bond cleavage to form nitrogen dioxide and hydroxo- or oxo-iron(iv) corrole. The iron(iv) intermediate was found to decay via multiple pathways that proceed at similar rates (k2 about 10(6) M(-1) s(-1)): reaction with nitrogen dioxide to form nitrate, nitration of the corrole macrocyclic, and dimerization to binuclear iron(iv) corrole. Catalysis in the presence of substrates affects the decay of the iron intermediate by either oxidative nitration (phenolic substrates) or reduction (ascorbate). A large enough excess of ascorbate accelerates the catalytic decomposition of PN by 1-Fe by orders of magnitude, prevents other decay routes of the iron intermediate, and eliminates nitration products as well. This suggests that the beneficial effect of the iron corrole under the reducing conditions present in most biological media might be even larger than in the purely chemical system. The acquired mechanistic insight is of prime importance for the design of optimally acting catalysts for the fast and safe decomposition of reactive oxygen and nitrogen species.

  9. THE DEPENDENCE OF STAR FORMATION EFFICIENCY ON GAS SURFACE DENSITY

    SciTech Connect

    Burkert, Andreas; Hartmann, Lee E-mail: lhartm@umich.edu

    2013-08-10

    Studies by Lada et al. and Heiderman et al. have suggested that star formation mostly occurs above a threshold in gas surface density {Sigma} of {Sigma}{sub c} {approx} 120 M{sub Sun} pc{sup -2} (A{sub K} {approx} 0.8). Heiderman et al. infer a threshold by combining low-mass star-forming regions, which show a steep increase in the star formation rate per unit area {Sigma}{sub SFR} with increasing {Sigma}, and massive cores forming luminous stars which show a linear relation. We argue that these observations do not require a particular density threshold. The steep dependence of {Sigma}{sub SFR}, approaching unity at protostellar core densities, is a natural result of the increasing importance of self-gravity at high densities along with the corresponding decrease in evolutionary timescales. The linear behavior of {Sigma}{sub SFR} versus {Sigma} in massive cores is consistent with probing dense gas in gravitational collapse, forming stars at a characteristic free-fall timescale given by the use of a particular molecular tracer. The low-mass and high-mass regions show different correlations between gas surface density and the area A spanned at that density, with A {approx} {Sigma}{sup -3} for low-mass regions and A {approx} {Sigma}{sup -1} for the massive cores; this difference, along with the use of differing techniques to measure gas surface density and star formation, suggests that connecting the low-mass regions with massive cores is problematic. We show that the approximately linear relationship between dense gas mass and stellar mass used by Lada et al. similarly does not demand a particular threshold for star formation and requires continuing formation of dense gas. Our results are consistent with molecular clouds forming by galactic hydrodynamic flows with subsequent gravitational collapse.

  10. Efficient and directed peptide bond formation in the gas phase via ion/ion reactions.

    PubMed

    McGee, William M; McLuckey, Scott A

    2014-01-28

    Amide linkages are among the most important chemical bonds in living systems, constituting the connections between amino acids in peptides and proteins. We demonstrate the controlled formation of amide bonds between amino acids or peptides in the gas phase using ion/ion reactions in a mass spectrometer. Individual amino acids or peptides can be prepared as reagents by (i) incorporating gas phase-labile protecting groups to silence otherwise reactive functional groups, such as the N terminus; (ii) converting the carboxyl groups to the active ester of N-hydroxysuccinimide; and (iii) incorporating a charge site. Protonation renders basic sites (nucleophiles) unreactive toward the N-hydroxysuccinimide ester reagents, resulting in sites with the greatest gas phase basicities being, in large part, unreactive. The N-terminal amines of most naturally occurring amino acids have lower gas phase basicities than the side chains of the basic amino acids (i.e., those of histidine, lysine, or arginine). Therefore, reagents may be directed to the N terminus of an existing "anchor" peptide to form an amide bond by protonating the anchor peptide's basic residues, while leaving the N-terminal amine unprotonated and therefore reactive. Reaction efficiencies of greater than 30% have been observed. We propose this method as a step toward the controlled synthesis of peptides in the gas phase.

  11. Efficient star formation in the spiral arms of M51

    NASA Technical Reports Server (NTRS)

    Lord, Steven D.; Young, Judith S.

    1990-01-01

    The molecular, neutral, and ionized hydrogen distributions in the Sbc galaxy M51 (NGC 5194) are compared. To estimate H2 surface densities observations of the CO (J = 1 - 0) transition were made in 60 positions out to a radius of 155 arcsec. Extinction-corrected H-alpha intensities were used to compute the detailed massive star formation rates (MSFRs) in the disk. Estimates of the gas surface density, the MSFR, and the ratio of these quantities, MSFR/sigma(p), were then examined. The spiral arms were found to exhibit an excess gas density, measuring between 1.4 and 1.6 times the interarm values at 45 arcsec resolution. The total (arm and interarm) gas content and massive star formation rates in concentric annuli in the disk of M51 were computed. The two quantities fall off together with radius, yielding a relatively constant MSFR/sigma(p) with radius. This behavior is not explained by current models of star formation in galactic disks.

  12. Mechanism of Efficient Anti-Markovnikov Olefin Hydroarylation Catalyzed by Homogeneous Ir(III) Complexes

    SciTech Connect

    Bhalla, Gaurav; Bischof, Steven M; Ganesh, Somesh K; Liu, Xiang Y; Jones, C J; Borzenko, Andrey; Tenn, William J; Ess, Daniel H; Hashiguchi, Brian G; Lokare, Kapil S; Leung, Chin Hin; Oxgaard, Jonas; Goddard, William A; Periana, Roy A

    2011-01-01

    The mechanism of the hydroarylation reaction between unactivated olefins (ethylene, propylene, and styrene) and benzene catalyzed by [(R)Ir(μ-acac-O,O,C{sup 3})-(acac-O,O){sub 2}]{sub 2} and [R-Ir(acac-O,O){sub 2}(L)] (R = acetylacetonato, CH{sub 3}, CH{sub 2}CH{sub 3}, Ph, or CH{sub 2}CH{sub 2}Ph, and L = H{sub 2}O or pyridine) Ir(III) complexes was studied by experimental methods. The system is selective for generating the anti-Markovnikov product of linear alkylarenes (61:39 for benzene + propylene and 98:2 for benzene + styrene). The reaction mechanism was found to follow a rate law with first-order dependence on benzene and catalyst, but a non-linear dependence on olefin. {sup 13}C-labelling studies with CH{sub 3}{sup 13}CH{sub 2}-Ir-Py showed that reversible β-hydride elimination is facile, but unproductive, giving exclusively saturated alkylarene products. The migration of the {sup 13}C-label from the α to β-positions was found to be slower than the C–H activation of benzene (and thus formation of ethane and Ph-d{sub 5}-Ir-Py). Kinetic analysis under steady state conditions gave a ratio of the rate constants for CH activation and β-hydride elimination (k{sub CH}: k{sub β}) of ~0.5. The comparable magnitude of these rates suggests a common rate determining transition state/intermediate, which has been shown previously with B3LYP density functional theory (DFT) calculations. Overall, the mechanism of hydroarylation proceeds through a series of pre-equilibrium dissociative steps involving rupture of the dinuclear species or the loss of L from Ph-Ir-L to the solvento, 16-electron species, Ph-Ir(acac-O,O){sub 2}-Sol (where Sol refers to coordinated solvent). This species then undergoes trans to cisisomerization of the acetylacetonato ligand to yield the pseudo octahedral species cis-Ph-Ir-Sol, which is followed by olefin insertion (the regioselective and rate determining step), and then activation of the C–H bond of an incoming benzene to generate the

  13. Magnetic Structures of Heterometallic M(II)-M(III) Formate Compounds.

    PubMed

    Mazzuca, Lidia; Cañadillas-Delgado, Laura; Rodríguez-Velamazán, J Alberto; Fabelo, Oscar; Scarrozza, Marco; Stroppa, Alessandro; Picozzi, Silvia; Zhao, Jiong-Peng; Bu, Xian-He; Rodríguez-Carvajal, Juan

    2017-01-03

    A study of the magnetic structure of the [NH2(CH3)2]n[Fe(III)M(II)(HCOO)6]n niccolite-like compounds, with M(II) = Co(II) (2) and Mn(II) (3) ions, has been carried out using neutron diffraction and compared with the previously reported Fe(II)-containing compound (1). The inclusion of two different metallic atoms into the niccolite-like structure framework leads to the formation of isostructural compounds with very different magnetic behaviors due to the compensation or not of the different spins involved in each lattice. Below TN, the magnetic order in these compounds varies from ferrimagnetic behavior for 1 and 2 to an antiferromagnetic behavior with a weak spin canting for 3. Structure refinements of 2 and 3 at low temperature (45 K) have been carried out combining synchrotron X-ray and high-resolution neutron diffraction in a multipattern approach. The magnetic structures have been determined from the difference patterns between the neutron data in the paramagnetic and the magnetically ordered regions. These difference patterns have been analyzed using a simulated annealing protocol and symmetry analysis techniques. The obtained magnetic structures have been further rationalized by means of ab initio DFT calculations. The direction of the magnetic moment of each compound has been determined. The easy axis of the M(II) for compound 1 (Fe(II)) is along the c axis; for compound 2 (Co(II)), the moments are mainly within the ab plane; finally, for compound 3 (Mn(II)), the calculations show that the moments have components both in the ab plane and along the c axis.

  14. Efficient dipyrrin-centered phosphorescence at room temperature from bis-cyclometalated iridium(III) dipyrrinato complexes.

    PubMed

    Hanson, Kenneth; Tamayo, Arnold; Diev, Vyacheslav V; Whited, Matthew T; Djurovich, Peter I; Thompson, Mark E

    2010-07-05

    A series of seven dipyrrin-based bis-cyclometalated Ir(III) complexes have been synthesized and characterized. All complexes display a single, irreversible oxidation wave and at least one reversible reduction wave. The electrochemical properties were found to be dominated by dipyrrin centered processes. The complexes were found to display room temperature luminescence with emission maxima ranging from 658 to 685 nm. Through systematic variation of the cyclometalating ligand and the meso substituent of the dipyrrin moiety, it was found that the observed room temperature emission was due to phosphorescence from a dipyrrin-centered triplet state with quantum efficiencies up to 11.5%. Bis-cyclometalated Ir(III) dipyrrin based organic light emitting diodes (OLEDs) display emission at 682 nm with maximum external quantum efficiencies up to 1.0%.

  15. Relative efficiency of North Carolina designs I and II and standard design III in three wheat crosses.

    PubMed

    Singh, S

    1979-01-01

    The efficiency of three analyses, namely, Designs I and II of Comstock and Robinson (1952) and standard Design III analysis of Kearsey and Jinks (1968), was compared in the F2s of three wheat crosses (Norteno 67 x HD 1982, HD 1982 x Moti and Sonalika x Moti) for plant height, spikelets per spike and yield per plant. The three analyses showed a remarkable agreement in estimating the additive (D) component for all three characters in all three crosses. But, as regards the estimation of dominance ] (H) component, standard Design III analysis proved to be more efficient than the other two analyses in crosses 2 (HD 1982 x Moti) and 3 (Sonalika x Moti) for all three characters except spikelets per spike in cross 3.

  16. Nanopore formation by controlled electrical breakdown: Efficient molecular-sensors

    NASA Astrophysics Data System (ADS)

    Abdalla, S.; Al-Marzouki, F. M.; Abdel-Daiem, A. M.

    2016-08-01

    A controlled electrical breakdown is used to produce efficient nanopore (NP) sensors. This phenomenon can be used to precisely fabricate these nanopore (NP) sensors through the membranes of the polydimethylsiloxane microarrays. This can be carried out, when localizing the electrical potential through a suitable microfluidic channel. Organic molecules, and other different protein-molecules, can be easily and precisely detected using this procedure referred to as controlled electrical breakdown technique.

  17. Molar Absorptivity and Concentration-Dependent Quantum Yield of Fe(II) Photo-Formation for the Aqueous Solutions of Fe(III)-Dicarboxylate Complexes

    NASA Astrophysics Data System (ADS)

    Hitomi, Y.; Arakaki, T.

    2009-12-01

    Redox cycles of iron in the aquatic environment affect formation of reactive oxygen species such as hydrogen peroxide and hydroxyl radicals, which in turn determines lifetimes of many organic compounds. Although aqueous Fe(III)-dicarboxylate complexes are considered to be important sources of photo-formed Fe(II), molar absorptivity and quantum yield of Fe(II) formation for individual species are not well understood. We initiated a study to characterize Fe(II) photo-formation from Fe(III)-dicarboxylates with the concentration ranges that are relevant to the natural aquatic environment. The Visual MINTEQ computer program was used to calculate the equilibrium concentrations of individual Fe(III)-dicarboxylate species. The molar absorptivity of Fe(III)-dicarboxylate species was obtained by UV-VIS spectrophotometer, and the product of the quantum yield and the molar absorptivity of Fe(III)-dicarboxylate species were obtained from photochemical experiments. These experimental data were combined with the calculated equilibrium Fe(III)-dicarboxylate concentrations to determine individual molar absorptivity and quantum yield of Fe(II) photo-formation for a specific Fe(III)-dicarboxylate species. We used initial concentrations of less than 10 micromolar Fe(III) to study the photochemical formation of Fe(II). Dicarboxylate compounds studied include oxalate, malonate, succinate, malate, and phthalate. We report molar absorptivity and concentration-dependent quantum yields of Fe(II) photo-formation of individual Fe(III)-dicarboxylates.

  18. Efficient removal of trace antimony(III) through adsorption by hematite modified magnetic nanoparticles.

    PubMed

    Shan, Chao; Ma, Zhiyao; Tong, Meiping

    2014-03-15

    Hematite coated magnetic nanoparticle (MNP@hematite) was fabricated through heterogeneous nucleation technique and used to remove trace Sb(III) from water. Powder X-ray diffraction, transmission electron microscopy (TEM), and alternating gradient magnetometry were utilized to characterize the prepared adsorbent. TEM image showed that MNP@hematite particles were spherical with size of 10-30nm. With saturation magnetization of 27.0emu/g, MNP@hematite particles could be easily separated from water with a simple magnetic process in short time (5min). At initial concentration of 110μg/L, Sb(III) was rapidly decreased to below 5μg/L by MNP@hematite in 10min. Sb(III) adsorption capacity of MNP@hematite was 36.7mg/g, which was almost twice that of commercial Fe3O4 nanoparticles. The removal of trace Sb(III) was not obviously affected by solution pH (over a wide range from 3 to 11), ionic strength (up to 100mM), coexisting anions (chloride, nitrate, sulfate, carbonate, silicate, and phosphate, up to 10mM) and natural organic matters (humic acid and alginate, up to 8mg/L as TOC). Moreover, MNP@hematite particles were able to remove Sb(III) and As(III) simultaneously. Trace Sb(III) could also be effectively removed from real tap water by MNP@hematite. The magnetic adsorbent could be recycled and used repeatedly. Copyright © 2014 Elsevier B.V. All rights reserved.

  19. Apelin-13 impedes foam cell formation by activating Class III PI3K/Beclin-1-mediated autophagic pathway.

    PubMed

    Yao, Feng; Lv, Yun-Cheng; Zhang, Min; Xie, Wei; Tan, Yu-Lin; Gong, Duo; Cheng, Hai-Peng; Liu, Dan; Li, Liang; Liu, Xiao-Yan; Zheng, Xi-Long; Tang, Chao-Ke

    2015-10-30

    Apelin-13, an adipokine, promotes cholesterol efflux in macrophages with antiatherosclerotic effect. Autophagy, an evolutionarily ancient response to cellular stress, has been involved in atherosclerosis. Therefore, the purpose of this study was to investigate whether apelin-13 regulates macrophage foam cell cholesterol metabolism through autophagy, and also explore the underlying mechanisms. Here, we revealed that apelin-13 decreased lipid accumulation in THP-1 derived macrophages through markedly enhancing cholesterol efflux. Our study further demonstrated that apelin-13 induced autophagy via activation of Class III phosphoinositide 3-kinase (PI3K) and Beclin-1. Inhibition of Class III PI3K and Beclin-1 suppressed the stimulatory effects of apelin-13 on autophagy activity. The present study concluded that apelin-13 reduces lipid accumulation of foam cells by activating autophagy via Class III PI3K/Beclin-1 pathway. Therefore, our results provide brand new insight about apelin-13 inhibiting foam cell formation and highlight autophagy as a promising therapeutic target in atherosclerosis.

  20. Crystal structure and solution species of Ce(III) and Ce(IV) formates: from mononuclear to hexanuclear complexes.

    PubMed

    Hennig, Christoph; Ikeda-Ohno, Atsushi; Kraus, Werner; Weiss, Stephan; Pattison, Philip; Emerich, Hermann; Abdala, Paula M; Scheinost, Andreas C

    2013-10-21

    Cerium(III) and cerium(IV) both form formate complexes. However, their species in aqueous solution and the solid-state structures are surprisingly different. The species in aqueous solutions were investigated with Ce K-edge EXAFS spectroscopy. Ce(III) formate shows only mononuclear complexes, which is in agreement with the predicted mononuclear species of Ce(HCOO)(2+) and Ce(HCOO)2(+). In contrast, Ce(IV) formate forms in aqueous solution a stable hexanuclear complex of [Ce6(μ3-O)4(μ3-OH)4(HCOO)x(NO3)y](12-x-y). The structural differences reflect the different influence of hydrolysis, which is weak for Ce(III) and strong for Ce(IV). Hydrolysis of Ce(IV) ions causes initial polymerization while complexation through HCOO(-) results in 12 chelate rings stabilizing the hexanuclear Ce(IV) complex. Crystals were grown from the above-mentioned solutions. Two crystal structures of Ce(IV) formate were determined. Both form a hexanuclear complex with a [Ce6(μ3-O)4(μ3-OH)4](12+) core in aqueous HNO3/HCOOH solution. The pH titration with NaOH resulted in a structure with the composition [Ce6(μ3-O)4(μ3-OH)4(HCOO)10(NO3)2(H2O)3]·(H2O)9.5, while the pH adjustment with NH3 resulted in [Ce6(μ3-O)4(μ3-OH)4(HCOO)10(NO3)4]·(NO3)3(NH4)5(H2O)5. Furthermore, the crystal structure of Ce(III) formate, Ce(HCOO)3, was determined. The coordination polyhedron is a tricapped trigonal prism which is formed exclusively by nine HCOO(-) ligands. The hexanuclear Ce(IV) formate species from aqueous solution is widely preserved in the crystal structure, whereas the mononuclear solution species of Ce(III) formate undergoes a polymerization during the crystallization process.

  1. Immiscible solvents enabled nanostructure formation for efficient polymer photovoltaic cells.

    PubMed

    Lee, Dong-Hyun; Michael Yang, Yang; You, Jingbi; Richard, Eric; Li, Gang

    2014-07-25

    Organic photovoltaics (OPVs) fabricated via solution processing are an attractive way to realize low cost solar energy harvesting. Bulk heterojunction (BHJ) devices are the most successful design, but their morphology is less controllable. In this manuscript, we describe a simple approach to realize 'ordered' BHJ morphology using two immiscible solvents with different boiling point and a quasi-bilayer approach. Tunable fine structures were demonstrated in poly(3-hexylthiophene) (P3HT) and [6,6]-Phenyl C61 butyric acid methyl ester (PCBM) model systems, and the devices with optimized fine structure showed a 33% efficiency enhancement compared to those with a planar bilayer structure.

  2. Chimeric antigen receptor containing ICOS signaling domain mediates specific and efficient antitumor effect of T cells against EGFRvIII expressing glioma.

    PubMed

    Shen, Chan-Juan; Yang, Yu-Xiu; Han, Ethan Q; Cao, Na; Wang, Yun-Fei; Wang, Yi; Zhao, Ying-Ying; Zhao, Li-Ming; Cui, Jian; Gupta, Puja; Wong, Albert J; Han, Shuang-Yin

    2013-05-09

    Adoptive transfer of chimeric antigen receptor (CAR)-modified T cells appears to be a promising immunotherapeutic strategy. CAR combines the specificity of antibody and cytotoxicity of cytotoxic T lymphocytes, enhancing T cells' ability to specifically target antigens and to effectively kill cancer cells. Recent efforts have been made to integrate the costimulatory signals in the CAR to improve the antitumor efficacy. Epidermal growth factor receptor variant III (EGFRvIII) is an attractive therapeutic target as it frequently expresses in glioma and many other types of cancers. Our current study aimed to investigate the specific and efficient antitumor effect of T cells modified with CAR containing inducible costimulator (ICOS) signaling domain. A second generation of EGFRvIII/CAR was generated and it contained the EGFRvIII single chain variable fragment, ICOS signaling domain and CD3ζ chain. Lentiviral EGFRvIII/CAR was prepared and human CD3+ T cells were infected by lentivirus encoding EGFRvIII/CAR. The expression of EGFRvIII/CAR on CD3+ T cells was confirmed by flow cytometry and Western blot. The functions of EGFRvIII/CAR+ T cells were evaluated using in vitro and in vivo methods including cytotoxicity assay, cytokine release assay and xenograft tumor mouse model. Chimeric EGFRvIIIscFv-ICOS-CD3ζ (EGFRvIII/CAR) was constructed and lentiviral EGFRvIII/CAR were made to titer of 106 TU/ml. The transduction efficiency of lentiviral EGFRvIII/CAR on T cells reached around 70% and expression of EGFRvIII/CAR protein was verified by immunoblotting as a band of about 57 kDa. Four hour 51Cr release assays demonstrated specific and efficient cytotoxicity of EGFRvIII/CAR+ T cells against EGFRvIII expressing U87 cells. A robust increase in the IFN-γ secretion was detected in the co-culture supernatant of the EGFRvIII/CAR+ T cells and the EGFRvIII expressing U87 cells. Intravenous and intratumor injection of EGFRvIII/CAR+ T cells inhibited the in vivo growth of the EGFRvIII

  3. Highly efficient electrochemiluminescence from iridium(III) complexes with 2-phenylquinoline ligand.

    PubMed

    Zhou, Yuyang; Li, Wanfei; Yu, Linpo; Liu, Yang; Wang, Xiaomei; Zhou, Ming

    2015-01-28

    A series of cyclometalated iridium(III) complexes with 2-phenylquinoline ligand (1-4) were designed and synthesized, which were thoroughly investigated by the photophysics, electrochemistry, theoretical calculations and electrochemiluminescence (ECL). By incorporating methyl groups into the 2-phenylquinoline, the corresponding complexes 2 and 3 displayed lower oxidative potential and higher HOMO energy levels. Most importantly, compared with tris(2,2'-bipyridyl)ruthenium(II) ([Ru(bipy)3](2+)), these iridium(III) complexes demonstrated more intense ECL in acetonitrile solutions.

  4. The catalytic efficiency of yeast ribonuclease III depends on substrate specific product release rate

    PubMed Central

    Comeau, Marc-Andre; Lafontaine, Daniel A.; Abou Elela, Sherif

    2016-01-01

    Members of the ribonuclease III (RNase III) family regulate gene expression by triggering the degradation of double stranded RNA (dsRNA). Hundreds of RNase III cleavage targets have been identified and their impact on RNA maturation and stability is now established. However, the mechanism defining substrates’ reactivity remains unclear. In this study, we developed a real-time FRET assay for the detection of dsRNA degradation by yeast RNase III (Rnt1p) and characterized the kinetic bottlenecks controlling the reactivity of different substrates. Surprisingly, the results indicate that Rnt1p cleavage reaction is not only limited by the rate of catalysis but can also depend on base-pairing of product termini. Cleavage products terminating with paired nucleotides, like the degradation signals found in coding mRNA sequence, were less reactive and more prone to inhibition than products having unpaired nucleotides found in non-coding RNA substrates. Mutational analysis of U5 snRNA and Mig2 mRNA confirms the pairing of the cleavage site as a major determinant for the difference between cleavage rates of coding and non-coding RNA. Together the data indicate that the base-pairing of Rnt1p substrates encodes reactivity determinants that permit both constitutive processing of non-coding RNA while limiting the rate of mRNA degradation. PMID:27257067

  5. Electrons initiate efficient formation of hydroperoxides from cysteine.

    PubMed

    Gebicki, Janusz M

    2016-09-01

    Amino acid and protein hydroperoxides can constitute a significant hazard if formed in vivo. It has been suggested that cysteine can form hydroperoxides after intramolecular hydrogen transfer to the commonly produced cysteine sulfur-centered radical. The resultant cysteine-derived carbon-centered radicals can react with oxygen at almost diffusion-controlled rate, forming peroxyl radicals which can oxidize other molecules and be reduced to hydroperoxides in the process. No cysteine hydroperoxides have been found so far. In this study, dilute air-saturated cysteine solutions were exposed to radicals generated by ionizing radiation and the hydroperoxides measured by an iodide assay. Of the three primary radicals present, the hydroxyl, hydrogen atoms and hydrated electrons, the first two were ineffective. However, electrons did initiate the generation of hydroperoxides by removing the -SH group and forming cysteine-derived carbon radicals. Under optimal conditions, 100% of the electrons reacting with cysteine produced the hydroperoxides with a 1:1 stoichiometry. Maximum hydroperoxide yields were at pH 5.5, with fairly rapid decline under more acid or alkaline conditions. The hydroperoxides were stable between pH 3 and 7.5, and decomposed in alkaline solutions. The results suggest that formation of cysteine hydroperoxides initiated by electrons is an unlikely event under physiological conditions.

  6. 2'-Methoxyacetophenone: An Efficient Photosensitizer for Cyclobutane Pyrimidine Dimer Formation.

    PubMed

    Liu, Lizhe; Pilles, Bert M; Reiner, Anne M; Gontcharov, Julia; Zinth, Wolfgang

    2015-11-16

    Stationary and time-resolved experiments show that 2'-methoxyacetophenone (2-M) is an interesting compound for the investigation of triplet states in thymine samples. Time-resolved emission experiments show that the fluorescence lifetime of 2-M is 660 ps. A similar time constant of 680 ps is found in transient IR experiments. The data indicate efficient intersystem crossing (≈97%) from the fluorescent singlet state to the triplet state. The lifetime of the triplet state of 2-M dissolved in D2O at room temperature and ambient oxygen concentration is 400 ns. 2-M has a strong absorption in the UV-A range and can photosensitize the triplet state of a thymidine dinucleotide with light at a wavelength of 320 nm. The experiments show that 2-M is well-suited for time-resolved experiments on the triplet-sensitizing process. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Novel Approaches to High-Efficiency III-V Nitride Heterostructure Emitters for Next-Generation Lighting Applications

    SciTech Connect

    Russell D. Dupuis

    2004-09-30

    We report research activities and technical progress on the development of high-efficiency long wavelength ({lambda} {approx} 540nm) green light emitting diodes which covers the first year of the three-year program ''Novel approaches to high-efficiency III-V nitride heterostructure emitters for next-generation lighting applications''. The first year activities were focused on the installation, set-up, and use of advanced equipment for the metalorganic chemical vapor deposition growth of III-nitride films and the characterization of these materials (Task 1) and the design, fabrication, testing of nitride LEDs (Task 4). As a progress highlight, we obtained improved quality of {approx} 2 {micro}m-thick GaN layers (as measured by the full width at half maximum of the asymmetric (102) X-ray diffraction peak of less than 350 arc-s) and higher p-GaN:Mg doping level (free hole carrier higher than 1E18 cm{sup -3}). Also in this year, we have developed the growth of InGaN/GaN active layers for long-wavelength green light emitting diodes, specifically, for emission at {lambda} {approx} 540nm. The effect of the Column III precursor (for Ga) and the post-growth thermal annealing effect were also studied. Our LED device fabrication process was developed and initially optimized, especially for low-resistance ohmic contacts for p-GaN:Mg layers, and blue-green light emitting diode structures were processed and characterized.

  8. Titanocene(III)-catalyzed 6-exo versus 7-endo cyclizations of epoxypolyprenes: efficient control and synthesis of versatile terpenic building blocks.

    PubMed

    Justicia, José; Jiménez, Tania; Miguel, Delia; Contreras-Montoya, Rafael; Chahboun, Rachid; Alvarez-Manzaneda, Enrique; Collado-Sanz, Daniel; Cárdenas, Diego J; Cuerva, Juan M

    2013-10-18

    In this article, a complete study on the selectivity of titanocene(III) cyclization of epoxypolyprenes is presented. The requirements for the formation of six- or seven-membered rings during these cyclizations are determined, taking into account the different substitution pattern in the epoxypolyprene precursor. Thus, a complete selectivity to 6-exo or 7-endo cyclization process has been achieved, yielding mono-, bi-, and even tricyclic compounds, constituting a new and efficient access to this type of derivative. Additionally, this procedure opens the possibility to prepare excellent building blocks for the synthesis of polycyclic compounds with a trisubstituted oxygenated function, which is present in several natural terpenes. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Formation of molecular glasses and the aggregation in solutions for lanthanum(III), calcium(II), and yttrium(III) complexes of octanoyl-DL-alaninate.

    PubMed

    Naren, Gerile; Masuda, Rie; Iida, Masayasu; Harada, Masafumi; Kurosu, Hiromichi; Suzuki, Toshiharu; Kimura, Takayoshi

    2008-04-07

    Octanoylalaninato-metal (metal = calcium(II), yttrium(III), lanthanum(III), and zinc(II)) complexes were prepared and the first three metal complexes were found to readily form transparent and stable molecular glasses from methanol and chloroform solutions. The process of glass formation from solution was studied in detail. The effect of the central metal ions on the formation of glassy states was remarkable: the lanthanum and calcium complexes assumed glassy or crystalline states depending on the isolation method and the yttrium complex had a large tendency to assume an amorphous state, whereas the zinc complex did not assume a pure and stable glassy-state. The glass transition temperatures were 50 degrees C for the yttrium complex and 70-75 degrees C for the lanthanum and calcium complexes when these complexes are monohydrates prepared by a solvent-cast method, whereas they increase by 10-30 degrees for the hemihydrates which were obtained by an annealing treatment at 110 degrees C. The coordinated water was eliminated from the solid above the glass transition temperature. The glassy state was regarded as a result of the self-aggregation of the metal complex in solution by an entanglement of the methylene chains with one another. SAXS showed the presence of two disordered bilayer structures with 2.2 nm and 4.5 nm periods in the glassy states. The structures of the molecular assemblies in the solid states and solutions were compared by SAXS and NMR studies. EXAFS studies confirmed the coordination numbers of oxygen atoms around the yttrium and lanthanum atoms in the glassy states for the yttrium and lanthanum complexes to be about 7.

  10. Bis-Tridentate Ir(III) Metal Phosphors for Efficient Deep-Blue Organic Light-Emitting Diodes.

    PubMed

    Kuo, Hsin-Hung; Chen, Yi-Ting; Devereux, Leon R; Wu, Chung-Chih; Fox, Mark A; Kuei, Chu-Yun; Chi, Yun; Lee, Gene-Hsiang

    2017-09-01

    Emissive Ir(III) metal complexes possessing two tridentate chelates (bis-tridentate) are known to be more robust compared to those with three bidentate chelates (tris-bidentate). Here, the deep-blue-emitting, bis-tridentate Ir(III) metal phosphors bearing both the dicarbene pincer ancillary such as 2,6-diimidazolylidene benzene and the 6-pyrazolyl-2-phenoxylpyridine chromophoric chelate are synthesized. A deep-blue organic light-emitting diode from one phosphor exhibits Commission Internationale de l'Eclairage (CIE(x,y) ) coordinates of (0.15, 0.17) with maximum external quantum efficiency (max. EQE) of 20.7% and EQE = 14.6% at the practical brightness of 100 cd m(-2) . © 2017 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. An inconvenient influence of iridium(III) isomer on OLED efficiency.

    PubMed

    Baranoff, Etienne; Bolink, Henk J; De Angelis, Filippo; Fantacci, Simona; Di Censo, Davide; Djellab, Karim; Grätzel, Michael; Nazeeruddin, Md Khaja

    2010-10-14

    The recently reported heteroleptic cyclometallated iridium(III) complex [Ir(2-phenylpyridine)(2)(2-carboxy-4-dimethylaminopyridine)] N984 and its isomer N984b have been studied more in detail. While photo- and electrochemical properties are very similar, DFT/TDDFT calculations show that the two isomers have different HOMO orbital characteristics. As a consequence, solution processed OLEDs made using a mixture of N984 and isomer N984b similar to vacuum processed devices show that the isomer has a dramatic detrimental effect on the performances of the device. In addition, commonly used thermogravimetric analysis is not suitable for showing the isomerization process. The isomer could impact performances of vacuum processed OLEDs using heteroleptic cyclometallated iridium(III) complexes as dopant.

  12. Radiation Transfer of Models of Massive Star Formation. III. The Evolutionary Sequence

    NASA Astrophysics Data System (ADS)

    Zhang, Yichen; Tan, Jonathan C.; Hosokawa, Takashi

    2014-06-01

    We present radiation transfer simulations of evolutionary sequences of massive protostars forming from massive dense cores in environments of high mass surface densities, based on the Turbulent Core Model. The protostellar evolution is calculated with a multi-zone numerical model, with the accretion rate regulated by feedback from an evolving disk wind outflow cavity. The disk evolution is calculated assuming a fixed ratio of disk to protostellar mass, while the core envelope evolution assumes an inside-out collapse of the core with a fixed outer radius. In this framework, an evolutionary track is determined by three environmental initial conditions: the core mass Mc , the mass surface density of the ambient clump Σcl, and the ratio of the core's initial rotational to gravitational energy β c . Evolutionary sequences with various Mc , Σcl, and β c are constructed. We find that in a fiducial model with Mc = 60 M ⊙, Σcl = 1 g cm-2, and β c = 0.02, the final mass of the protostar reaches at least ~26 M ⊙, making the final star formation efficiency >~ 0.43. For each of the evolutionary tracks, radiation transfer simulations are performed at selected stages, with temperature profiles, spectral energy distributions (SEDs), and multiwavelength images produced. At a given stage, the envelope temperature depends strongly on Σcl, with higher temperatures in a higher Σcl core, but only weakly on Mc . The SED and MIR images depend sensitively on the evolving outflow cavity, which gradually widens as the protostar grows. The fluxes at <~ 100 μm increase dramatically, and the far-IR peaks move to shorter wavelengths. The influence of Σcl and β c (which determines disk size) are discussed. We find that, despite scatter caused by different Mc , Σcl, β c , and inclinations, sources at a given evolutionary stage appear in similar regions of color-color diagrams, especially when using colors with fluxes at >~ 70 μm, where scatter due to inclination is minimized

  13. Resolving Early Stages of Homogeneous Iron(III) Oxyhydroxide Formation from Iron(III) Nitrate Solutions at pH 3 Using Time-Resolved SAXS

    PubMed Central

    2015-01-01

    Small angle X-ray scattering (SAXS) measurements coupled to a stopped-flow device has permitted the observation of the kinetics of Fe(III) oxyhydroxide (FeOx) formation and transformation from around 1 s to 30 min after initiation under environmentally relevant conditions at pH 3. The Unified Model approach was used to determine the evolution of multiple key parameters (particle scattering mass, mean particle volume, particle concentration, particle dimensionality, and particle size) for two separate structural levels as a function of time, with the results obtained enabling clarification of the mechanisms underlying FeOx formation and transformation under these conditions. Colloidal primary particles (radius of gyration 2–10 nm) that were observable by SAXS formed within 1 s of stopping the flow and subsequently grew over several minutes, first by cluster–cluster addition and then by a monomer-addition mechanism. Aggregation of these primary particles via a secondary cluster–cluster addition mechanism simultaneously resulted in a distinct population of larger (25–40 nm radius of gyration) secondary particles. The primary particles evolved into compact spheroidal forms with fractally rough surfaces, while the secondary particles were relatively open mass fractal structures. Comparison of the observed rates of these processes with those predicted for Fe polymerization indicates that kinetics of primary particle formation were likely controlled initially by rates of exchange between water molecules coordinated with Fe and those in the bulk solution. These findings provide new insights into the mechanisms underlying FeOx formation and transformation, and the kinetics of these mechanisms, at pH 3. PMID:24601665

  14. Simulated efficiency of range beef production. III. Culling strategies and nontraditional management systems.

    PubMed

    Bourdon, R M; Brinks, J S

    1987-10-01

    A modified version of the Texas A&M Beef Cattle Production Model was used to simulate life-cycle biological and economic efficiency of various culling strategies and non-traditional management systems in a northern plains, range environment. Biological efficiency was defined as the ratio of TDN input (kg) to product output (kg), and economic efficiency was defined as the ratio of cost ($) to product output (100 kg), where products were live weight at weaning (LWW), empty body weight at slaughter (EBW) and fat-free weight at slaughter (FFW). Several economic scenarios were simulated. Culling cows at younger ages increased biological efficiency, but not necessarily economic efficiency. The simulated optimal age at culling was 8 yr, the same age at which simulated feed intake and milk production began to decline. Finishing young cows in the feedlot had little effect on biological efficiency and generally increased economic efficiency, although specific results depended on feed prices and relative values of cull cows vs fed animals. A simulated sex-controlled system in which only heifer calves were produced, while extremely biologically efficient for production of lean, resulted in relatively little output and was not economically efficient in most cases. Sex control combined with feeding of 2-yr-old cows was economically efficient, but not markedly more efficient than a conventional system. Results suggest that sex-controlled systems may be more appropriate where emphasis is on lean product and heifers can be bred at very early ages. General results indicate that producers should pay attention to relative values of cull cows and fed animals in choosing culling strategies and management systems.

  15. Formation, expansion, and interconversion of metallarings in a sulfur-bridged Au(I) Co(III) coordination system.

    PubMed

    Oji, Katsuya; Igashira-Kamiyama, Asako; Yoshinari, Nobuto; Konno, Takumi

    2014-02-10

    A novel Au(I) Co(III) coordination system that is derived from the newly prepared [Co(D-nmp)2 ](-) (1(-) ; D-nmp=N-methyl-D-penicillaminate) and a gold(I) precursor Au(I) is reported. Complex 1(-) acts as a sulfur-donating metallaligand and reacts with the gold(I) precursor to give [Au2 Co2 (D-nmp)4 ] (2), which has an eight-membered Au(I) 2 Co(III) 2 metallaring. Treatment of 2 with [Au2 (dppe)2 ](2+) (dppe=1,2-bis(diphenylphosphino)ethane) leads to the formation of [Au4 Co2 (dppe)2 (D-nmp)4 ](2+) (3(2+) ), which consists of an 18-membered Au(I) 4 Co(III) 2 metallaring that accommodates a tetrahedral anion (BF4 (-) , ClO4 (-) , ReO4 (-) ). In solution, the metallaring structure of 3(2+) is readily interconvertible with the nine-membered Au(I) 2 Co(III) metallaring structure of [Au2 Co(dppe)(D-nmp)2 ](+) (4(+) ); this process depends on external factors, such as solvent, concentration, and nature of the counteranion. These results reveal the lability of the AuS and AuP bonds, which is essential for metallaring expansion and contraction. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Highly efficient catalysts for Co(II/III) redox couples in dye-sensitized solar cells.

    PubMed

    Wang, Liang; Diau, Eric Wei-Guang; Wu, Mingxing; Lu, Hsueh-Pei; Ma, Tingli

    2012-03-07

    We developed several low-cost catalysts with high catalytic activity, which were used as counter electrodes in dye-sensitized solar cells (DSCs). They showed higher efficiencies than that of Pt. The efficiencies were improved by 18-42% for the DSCs composed of active carbon, niobium dioxide, ordered mesoporous carbon and commercial titanium carbide.

  17. Energy-level matching of Fe(III) ions grafted at surface and doped in bulk for efficient visible-light photocatalysts.

    PubMed

    Liu, Min; Qiu, Xiaoqing; Miyauchi, Masahiro; Hashimoto, Kazuhito

    2013-07-10

    Photocatalytic reaction rate (R) is determined by the multiplication of light absorption capability (α) and quantum efficiency (QE); however, these two parameters generally have trade-off relations. Thus, increasing α without decreasing QE remains a challenging issue for developing efficient photocatalysts with high R. Herein, using Fe(III) ions grafted Fe(III) doped TiO2 as a model system, we present a novel method for developing visible-light photocatalysts with efficient R, utilizing the concept of energy level matching between surface-grafted Fe(III) ions as co-catalysts and bulk-doped Fe(III) ions as visible-light absorbers. Photogenerated electrons in the doped Fe(III) states under visible-light efficiently transfer to the surface grafted Fe(III) ions co-catalysts, as the doped Fe(III) ions in bulk produced energy levels below the conduction band of TiO2, which match well with the potential of Fe(3+)/Fe(2+) redox couple in the surface grafted Fe(III) ions. Electrons in the surface grafted Fe(III) ions efficiently cause multielectron reduction of adsorbed oxygen molecules to achieve high QE value. Consequently, the present Fe(III)-FexTi1-xO2 nanocomposites exhibited the highest visible-light R among the previously reported photocatalysts for decomposition of gaseous organic compounds. The high R can proceed even under commercial white-light emission diode irradiation and is very stable for long-term use, making it practically useful. Further, this efficient method could be applied in other wide-band gap semiconductors, including ZnO or SrTiO3, and may be potentially applicable for other photocatalysis systems, such as water splitting, CO2 reduction, NOx removal, and dye decomposition. Thus, this method represents a strategic approach to develop new visible-light active photocatalysts for practical uses.

  18. Selectively Modulating Triplet Exciton Formation in Host Materials for Highly Efficient Blue Electrophosphorescence.

    PubMed

    Li, Huanhuan; Bi, Ran; Chen, Ting; Yuan, Kai; Chen, Runfeng; Tao, Ye; Zhang, Hongmei; Zheng, Chao; Huang, Wei

    2016-03-23

    The concept of limiting the triplet exciton formation to fundamentally alleviate triplet-involved quenching effects is introduced to construct host materials for highly efficient and stable blue phosphorescent organic light-emitting diodes (PhOLEDs). The low triplet exciton formation is realized by small triplet exciton formation fraction and rate with high binding energy and high reorganization energy of triplet exciton. Demonstrated in two analogue molecules in conventional donor-acceptor molecule structure for bipolar charge injection and transport with nearly the same frontier orbital energy levels and triplet excited energies, the new concept host material shows significantly suppressed triplet exciton formation in the host to avoid quenching effects, leading to much improved device efficiencies and stabilities. The low-voltage-driving blue PhOLED devices exhibit maximum efficiencies of 43.7 cd A(-1) for current efficiency, 32.7 lm W(-1) for power efficiency, and 20.7% for external quantum efficiency with low roll-off and remarkable relative quenching effect reduction ratio up to 41%. Our fundamental solution for preventing quenching effects of long-lived triplet excitons provides exciting opportunities for fabricating high-performance devices using the advanced host materials with intrinsically small triplet exciton formation cross section.

  19. Efficient stereoscopic contents file format on the basis of ISO base media file format

    NASA Astrophysics Data System (ADS)

    Kim, Kyuheon; Lee, Jangwon; Suh, Doug Young; Park, Gwang Hoon

    2009-02-01

    A lot of 3D contents haven been widely used for multimedia services, however, real 3D video contents have been adopted for a limited applications such as a specially designed 3D cinema. This is because of the difficulty of capturing real 3D video contents and the limitation of display devices available in a market. However, diverse types of display devices for stereoscopic video contents for real 3D video contents have been recently released in a market. Especially, a mobile phone with a stereoscopic camera has been released in a market, which provides a user as a consumer to have more realistic experiences without glasses, and also, as a content creator to take stereoscopic images or record the stereoscopic video contents. However, a user can only store and display these acquired stereoscopic contents with his/her own devices due to the non-existence of a common file format for these contents. This limitation causes a user not share his/her contents with any other users, which makes it difficult the relevant market to stereoscopic contents is getting expanded. Therefore, this paper proposes the common file format on the basis of ISO base media file format for stereoscopic contents, which enables users to store and exchange pure stereoscopic contents. This technology is also currently under development for an international standard of MPEG as being called as a stereoscopic video application format.

  20. Observational probes of the connection between Star Formation Efficiency and Dark Matter halo mass of galaxies

    NASA Astrophysics Data System (ADS)

    Kalinova, Veselina; Colombo, Dario; Rosolowsky, Erik

    2015-08-01

    Modern simulations predict that the stellar mass and the star formation efficiency of a galaxy are tightly linked to the dark matter (DM) halo mass of that galaxy. This prediction relies on a specific model of galaxy evolution and so testing this prediction directly tests our best models of galaxy formation and evolution. Recent DM numerical studies propose relationships between star formation efficiency and the DM halo mass with two domains based on SF feedback (low-mass) vs. AGN feedback (high-mass), see Moster et al. (2013). The observational probe of such parameters in the relationship imply globally important physics that are fundamental as, e.g., the star formation law (e.g., Kennicutt et al., 1998), the universal depletion time (Leroy et al. 2008), and the origin of the cold gas phase with respect to the stellar disc (Davis et al.2011). Thus, we can directly measure whether this parameterization is correct by estimating the stellar mass, star formation efficiency and dynamical (DM) mass for a set of galaxies at strategically selected points to test if they fall on the predicted relationship.We use CO data from the Extragalactic Database for Galaxy Evolution survey (EDGE) in conjunction with archival 21-cm data and spectroscopic data from Calar Alto Legacy Integral Field spectroscopy Area survey (CALIFA) to measure the stellar vs. halo mass and star-formation-efficiency vs. halo mass relations of the galaxies. We also analyze archival 21-cm spectra to estimate rotation speeds, atomic gas masses and halo masses for a set of EDGE galaxies. Data from CALIFA are used for high quality star formation efficiency and stellar mass measurements. By linking these three parameters - stellar mass, star formation efficiency (SFE) and DM halo mass - we can test the simulation models of how the gas is cooling in the potential wells of the dark matter halos and then forms stars.

  1. Enhancing the photocytotoxic potential of curcumin on terpyridyl lanthanide(III) complex formation.

    PubMed

    Hussain, Akhtar; Somyajit, Kumar; Banik, Bhabatosh; Banerjee, Samya; Nagaraju, Ganesh; Chakravarty, Akhil R

    2013-01-07

    Lanthanide(III) complexes [Ln(R-tpy)(cur)(NO3)2] (Ln = La(III) in 1, 2; Gd(III) in 5, 6) and [Ln(R-tpy)(scur)(NO3)2] (Ln = La(III) in 3, 4; Gd(III) in 7, 8), where R-tpy is 4′-phenyl-2,2′:6′,2′′-terpyridine (ph-tpy in 1, 3, 5, 7), 4′-(1-pyrenyl)-2,2′:6′,2′′-terpyridine (py-tpy in 2, 4, 6, 8), Hcur is curcumin (in 1, 2, 5, 6) and Hscur is diglucosylcurcumin (in 3, 4, 7, 8), were prepared and their DNA photocleavage activity and photocytotoxicity studied. Complexes [La(ph-tpy)(cur)(NO3)2] (1) and [Gd(ph-tpy)(cur)(NO3)2] (5) were structurally characterized. The complexes in aqueous-DMF showed an absorption band near 430 nm and an emission band near 515 nm when excited at 420 nm. The complexes are moderate binders to calf-thymus DNA. They cleave plasmid supercoiled DNA to its nicked circular form in UV-A (365 nm) and visible light (454 nm) via (1)O2 and ˙OH pathways. The complexes are remarkably photocytotoxic in HeLa cells in visible light (λ = 400–700 nm) and are non-toxic in the dark. FACScan analysis of the HeLa cells treated with 2 and 4 showed cell death via an apoptotic pathway. Nuclear localization of 1–4 is evidenced from confocal imaging on HeLa cells. The hydrolytic instability of curcumin gets significantly reduced upon binding to the lanthanide ions while retaining its photocytotoxic potential.

  2. Critical thickness for the formation of misfit dislocations originating from prismatic slip in semipolar and nonpolar III-nitride heterostructures

    NASA Astrophysics Data System (ADS)

    Smirnov, A. M.; Young, E. C.; Bougrov, V. E.; Speck, J. S.; Romanov, A. E.

    2016-01-01

    We calculate the critical thickness for misfit dislocation (MD) formation in lattice mismatched semipolar and nonpolar III-nitride wurtzite semiconductor layers for the case of MDs originated from prismatic slip (PSMDs). It has been shown that there is a switch of stress relaxation modes from generation of basal slip originated MDs to PSMDs after the angle between c-axis in wurtzite crystal structure and the direction of semipolar growth reaches a particular value, e.g., ˜70° for Al0.13Ga0.87N/GaN ( h 0 h ¯ 1 ) semipolar heterostructures. This means that for some semipolar growth orientations of III-nitride heterostructures biaxial relaxation of misfit stress can be realized. The results of modeling are compared to experimental data on the onset of plastic relaxation in AlxGa1-xN/GaN heterostructures.

  3. THE NATURE OF STARBURSTS. III. THE SPATIAL DISTRIBUTION OF STAR FORMATION

    SciTech Connect

    McQuinn, Kristen B. W.; Skillman, Evan D.; Dalcanton, Julianne J.; Weisz, Daniel R.; Williams, Benjamin F.; Cannon, John M.; Dolphin, Andrew E.; Holtzman, Jon

    2012-11-01

    We map the spatial distribution of recent star formation over a few Multiplication-Sign 100 Myr timescales in 15 starburst dwarf galaxies using the location of young blue helium burning stars identified from optically resolved stellar populations in archival Hubble Space Telescope observations. By comparing the star formation histories from both the high surface brightness central regions and the diffuse outer regions, we measure the degree to which the star formation has been centrally concentrated during the galaxies' starbursts, using three different metrics for the spatial concentration. We find that the galaxies span a full range in spatial concentration, from highly centralized to broadly distributed star formation. Since most starbursts have historically been identified by relatively short timescale star formation tracers (e.g., H{alpha} emission), there could be a strong bias toward classifying only those galaxies with recent, centralized star formation as starbursts, while missing starbursts that are spatially distributed.

  4. Synthesis of Ce(III)-doped Fe3O4 magnetic particles for efficient removal of antimony from aqueous solution.

    PubMed

    Qi, Zenglu; Joshi, Tista Prasai; Liu, Ruiping; Liu, Huijuan; Qu, Jiuhui

    2017-05-05

    Aqueous antimony (Sb) pollution from human activity is of great concern in drinking water due to its adverse health effect. Magnetic Fe3O4 particles, with high separation ability from solution, have been considered as a low-cost Sb adsorbent for contaminants. However, the limited adsorption capacity has restricted its practical application. In this study, a solvothermal approach was developed for doping Ce(III) into Fe3O4, thereby increasing the adsorption efficacy for both Sb(III) and Sb(V). In contrast to un-doped Fe3O4, the adsorption capacity towards Sb(III) and Sb(V) in Ce-doped materials increased from 111.4 to 224.2mg/g and from 37.2 to 188.1mg/g at neutral pH, respectively. Based on the combined results of XPS, XRD, and FTIR, it confirmed that Ce atom successfully doped into the Fe3O4 structure, resulting in the decreased particle size, increased the surface area, and isoelectric point. Furthermore, the vibrating sample magnetometer (VSM) results showed that the Ce doping process had some side effects on the primitive magnetic property, but remaining the high separation potential during water treatment. According to the high removal efficiency and magnetic property, the Ce-doped Fe3O4 of great simplicity should be a promising adsorbent for aqueous Sb removal. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Bis-cyclometalated Ir(III) complexes as efficient singlet oxygen sensitizers.

    PubMed

    Gao, Ruomei; Ho, David G; Hernandez, Billy; Selke, Matthias; Murphy, Drew; Djurovich, Peter I; Thompson, Mark E

    2002-12-18

    We report the singlet oxygen sensitization properties of a series of bis-cyclometalated Ir(III) complexes (i.e., (bt)2Ir(acac), (bsn)2Ir(acac), and (pq)2Ir(acac); bt = 2-phenylbenzothiazole, bsn = 2-(1-naphthyl)benzothiazole, pq = 2-phenylquinoline, and acac = acetylacetonate). Complexes with acetylacetonate ancillary ligands give singlet oxygen quantum yields near unity (PhiDelta = (0.7-1.0) +/- 0.1), whether exciting the ligand-based state or the lowest energy excited state (MLCT + 3LC). The singlet oxygen quenching rates for these beta-diketonate complexes were found to be small [(5 +/- 2) x 105 to (6 +/- 0.2) x 106 M-1 s-1], roughly 3 orders of magnitude slower than the corresponding phosphorescence quenching rate. Similar complexes were prepared with glycine or pyridine tethered to the Ir(III) center (i.e., (bsn)2Ir(gly) and (bt)2Ir(py)Cl; gly = glycine and py = pyridine). The glycine and pyridine derivatives give high singlet oxygen yields (PhiDelta = (0.7-1.0) +/- 0.1).

  6. Reactivity of Ir(III) carbonyl complexes with water: alternative by-product formation pathways in catalytic methanol carbonylation.

    PubMed

    Elliott, Paul I P; Haak, Susanne; Meijer, Anthony J H M; Sunley, Glenn J; Haynes, Anthony

    2013-12-21

    The reactions of water with a number of iridium(III) complexes relevant to the mechanism for catalytic methanol carbonylation are reported. The iridium acetyl, [Ir(CO)2I3(COMe)](-), reacts with water under mild conditions to release CO2 and CH4, rather than the expected acetic acid. Isotopic labeling and kinetic experiments are consistent with a mechanism involving nucleophilic attack by water on a terminal CO ligand of [Ir(CO)2I3(COMe)](-) to give an (undetected) hydroxycarbonyl species. Subsequent decarboxylation and elimination of methane gives [Ir(CO)2I2](-). Similar reactions with water are observed for [Ir(CO)2I3Me](-), [Ir(CO)2(NCMe)I2(COMe)] and [Ir(CO)3I2Me] with the neutral complexes exhibiting markedly higher rates. The results demonstrate that CO2 formation during methanol carbonylation is not restricted to the conventional water gas shift mechanism mediated by [Ir(CO)2I4](-) or [Ir(CO)3I3], but can arise directly from key organo-iridium(III) intermediates in the carbonylation cycle. An alternative pathway for methane formation not involving the intermediacy of H2 is also suggested. A mechanism is proposed for the conversion MeOH + CO → CO2 + CH4, which may account for the similar rates of formation of the two gaseous by-products during iridium-catalysed methanol carbonylation.

  7. Formation and Stabilization of Environmentally Persistent Free Radicals Induced by the Interaction of Anthracene with Fe(III)-Modified Clays.

    PubMed

    Jia, Hanzhong; Nulaji, Gulimire; Gao, Hongwei; Wang, Fu; Zhu, Yunqing; Wang, Chuanyi

    2016-06-21

    Environmentally persistent free radicals (EPFRs) are occasionally detected in Superfund sites but the formation of EPFRs induced by polycyclic aromatic hydrocarbons (PAHs) is not well understood. In the present work, the formation of EPFRs on anthracene-contaminated clay minerals was quantitatively monitored via electron paramagnetic resonance (EPR) spectroscopy, and surface/interface-related environmental influential factors were systematically explored. The obtained results suggest that EPFRs are more readily formed on anthracene-contaminated Fe(III)-montmorillonite than in other tested systems. Depending on the reaction condition, more than one type of organic radicals including anthracene-based radical cations with g-factors of 2.0028-2.0030 and oxygenic carbon-centered radicals featured by g-factors of 2.0032-2.0038 were identified. The formed EPFRs are stabilized by their interaction with interlayer surfaces, and such surface-bound EPFRs exhibit slow decay with 1/e-lifetime of 38.46 days. Transformation pathway and possible mechanism are proposed on the basis of experimental results and quantum mechanical simulations. Overall, the formation of EPFRs involves single-electron-transfer from anthracene to Fe(III) initially, followed by H2O addition on formed aromatic radical cation. Because of their potential exposure in soil and atmosphere, such clay surface-associated EPFRs might induce more serious toxicity than PAHs and exerts significant impacts on human health.

  8. Formation of layered Fe(II)-Al(III)-hydroxides during reaction of Fe(II) with aluminum oxide.

    PubMed

    Elzinga, Evert J

    2012-05-01

    The reactivity of aqueous Fe(II) with aluminum oxide in anoxic solutions was investigated with batch kinetic experiments combined with Fe K edge X-ray absorption spectroscopy measurements to characterize Fe(II) sorption products. Formation of Fe(II)-Al(III)-layered double hydroxides with an octahedral sheet structure similar to nikischerite (NaFe(II)(6) Al(3)(SO(4))(2)(OH)(18) (H(2)O)(12)) was observed within a few hours during sorption at pH 7.5 and aqueous Fe(II) concentrations of 1-3 mM. These Fe(II) phases are composed of brucite-like Fe(II)(OH)(2) sheets with partial substitution of Al(III) for Fe(II), charge balanced by anions coordinated along the basal planes. Their fast rate of formation suggests that these previously unrecognized Fe(II) phases, which are structurally and compositionally similar to green rust, may be an important sink of Fe(II) in suboxic and anoxic geochemical environments, and impact the fate of structurally compatible trace metals, such as Co(II), Ni(II), and Zn(II), as well as redox-reactive species including Cr(VI) and U(VI). Further studies are required to assess the thermodynamics, formation kinetics, and stability of these Fe(II) minerals under field conditions.

  9. Porphyrin-sensitized solar cells with cobalt (II/III)-based redox electrolyte exceed 12 percent efficiency.

    PubMed

    Yella, Aswani; Lee, Hsuan-Wei; Tsao, Hoi Nok; Yi, Chenyi; Chandiran, Aravind Kumar; Nazeeruddin, Md Khaja; Diau, Eric Wei-Guang; Yeh, Chen-Yu; Zakeeruddin, Shaik M; Grätzel, Michael

    2011-11-04

    The iodide/triiodide redox shuttle has limited the efficiencies accessible in dye-sensitized solar cells. Here, we report mesoscopic solar cells that incorporate a Co((II/III))tris(bipyridyl)-based redox electrolyte in conjunction with a custom synthesized donor-π-bridge-acceptor zinc porphyrin dye as sensitizer (designated YD2-o-C8). The specific molecular design of YD2-o-C8 greatly retards the rate of interfacial back electron transfer from the conduction band of the nanocrystalline titanium dioxide film to the oxidized cobalt mediator, which enables attainment of strikingly high photovoltages approaching 1 volt. Because the YD2-o-C8 porphyrin harvests sunlight across the visible spectrum, large photocurrents are generated. Cosensitization of YD2-o-C8 with another organic dye further enhances the performance of the device, leading to a measured power conversion efficiency of 12.3% under simulated air mass 1.5 global sunlight.

  10. The first plant type III polyketide synthase that catalyzes formation of aromatic heptaketide.

    PubMed

    Abe, Ikuro; Utsumi, Yoriko; Oguro, Satoshi; Noguchi, Hiroshi

    2004-03-26

    A cDNA encoding a novel plant type III polyketide synthase (PKS) was cloned from rhubarb (Rheum palmatum). A recombinant enzyme expressed in Escherichia coli accepted acetyl-CoA as a starter, carried out six successive condensations with malonyl-CoA and subsequent cyclization to yield an aromatic heptaketide, aloesone. The enzyme shares 60% amino acid sequence identity with chalcone synthases (CHSs), and maintains almost identical CoA binding site and catalytic residues conserved in the CHS superfamily enzymes. Further, homology modeling predicted that the 43-kDa protein has the same overall fold as CHS. This provides new insights into the catalytic functions of type III PKSs, and suggests further involvement in the biosynthesis of plant polyketides.

  11. On the formation of iron(III) oxides via oxidation of iron(II)

    SciTech Connect

    Bongiovanni, R.; Pelizzetti, E.; Borgarello, E.; Meisel, D.

    1994-09-01

    Formation of iron oxides in aqueous salt solutions is reviewed. The discussion is focused on the oxidation of iron(II) and the following hydrolysis process that leads to the formation of a solid phase from homogeneous solutions. Results from our own studies on the kinetics of the oxidation reactions and the ensuing growth processes are presented.

  12. On the Temperature Dependence of the Formation Constant of Thiocyanatopentaaquochromium (III) in Acidic Solution.

    DTIC Science & Technology

    1983-04-01

    constants for metal ion complexes Bflandamer’s method Chromium (III) complexes Heat capacity of activation Equilibrium and kinetics of reactions in solution...20 ABSTRACT (Continue on reveree aide if neceetary and Identify by block number) The equilibrium constants for the ionization of carboxylic acids in...water pass through a maximum as temperature changes. If the equilibrium constant repre- sents a one-step process, then the attendant thermodynamic

  13. To the understanding of the formation of the droplet-epitaxial III-V based nanostructures

    SciTech Connect

    Nemcsics, Ákos

    2014-05-15

    In this work, we discuss the evolution of the self-assembling III-V based nanostructures. These nano-structures were prepared by droplet epitaxial technique. The different nanostructures such as quantum dot, quantum ring, double quantum ring, or nanohole form similarly from an initial Ga droplet but under different substrate temperature and various arsenic pressures. Started from few atomic courses, we give here a qualitative description of the key processes for all of the aforementioned nanostructures.

  14. Organic-inorganic hybrid supermicroporous iron(III) phosphonate nanoparticles as an efficient catalyst for the synthesis of biofuels.

    PubMed

    Pramanik, Malay; Bhaumik, Asim

    2013-06-24

    Here we report a novel family of crystalline, supermicroporous iron(III) phosphonate nanomaterials (HFeP-1-3, HFeP-1-2, and HFeP-1-4) with different Fe(III)-to-organophosphonate ligand mole ratios. The materials were synthesized by using a hydrothermal reaction between benzene-1,3,5-triphosphonic acid and iron(III) chloride under acidic conditions (pH ≈ 4.0). Powder X-ray diffraction, N2 sorption, transmission and scanning electron microscopy (TEM and SEM) image analysis, thermogravimetric and differential thermal analysis (TGA-DTA), and FTIR spectroscopic tools were used to characterize the materials. The triclinic crystal phase [P1(2) space group] of the hybrid iron phosphonate was established by a Rietveld refinement of the PXRD analysis of HFeP-1-3 by using the MAUD program. The unit cell parameters are a = 8.749(1), b = 8.578(1), c = 17.725(3) Å; α = 104.47(3), β = 97.64(1), γ = 113.56(3)°; and V = 1013.41 Å(3). With these crystal parameters, we proposed an 24-membered-ring open framework structure for HFeP-1. Compound HFeP-1-3, with an starting Fe/ligand molar ratio of 3.0, shows the highest Brunauer-Emmett-Telller (BET) surface area of 556 m(2) g(-1) and uniform supermicropores of approximately 1.1 nm. The acidic surface of the porous iron(III) phosphonate nanoparticles was used in a highly efficient and recyclable catalytic transesterification reaction for the synthesis of biofuels under mild reaction conditions. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Enhanced Conversion Efficiency of III-V Triple-junction Solar Cells with Graphene Quantum Dots.

    PubMed

    Lin, Tzu-Neng; Santiago, Svette Reina Merden S; Zheng, Jie-An; Chao, Yu-Chiang; Yuan, Chi-Tsu; Shen, Ji-Lin; Wu, Chih-Hung; Lin, Cheng-An J; Liu, Wei-Ren; Cheng, Ming-Chiang; Chou, Wu-Ching

    2016-12-16

    Graphene has been used to synthesize graphene quantum dots (GQDs) via pulsed laser ablation. By depositing the synthesized GQDs on the surface of InGaP/InGaAs/Ge triple-junction solar cells, the short-circuit current, fill factor, and conversion efficiency were enhanced remarkably. As the GQD concentration is increased, the conversion efficiency in the solar cell increases accordingly. A conversion efficiency of 33.2% for InGaP/InGaAs/Ge triple-junction solar cells has been achieved at the GQD concentration of 1.2 mg/ml, corresponding to a 35% enhancement compared to the cell without GQDs. On the basis of time-resolved photoluminescence, external quantum efficiency, and work-function measurements, we suggest that the efficiency enhancement in the InGaP/InGaAs/Ge triple-junction solar cells is primarily caused by the carrier injection from GQDs to the InGaP top subcell.

  16. Efficient production of a ring derivative of chromosome III by the mating-type switching mechanism in Saccharomyces cerevisiae.

    PubMed Central

    Klar, A J; Strathern, J N; Hicks, J B; Prudente, D

    1983-01-01

    The mating-type switches in the yeast Saccharomyces cerevisiae occur by unidirectional transposition of replicas of unexpressed genetic information, residing at HML or HMR, into the mating-type locus (MAT). The source loci, HML and HMR, remain unchanged. Interestingly, when the HM cassettes are expressed, as in marl strains, the HML and HMR cassettes can also efficiently switch, apparently by obtaining genetic information from either of the other two cassettes (Klar et al., Cell 25:517-524, 1981). We have isolated a novel chromosome III rearrangement in heterothallic (marl ho) strains, which is also produced efficiently in marl HO cells, presumably the consequence of a recombination event between HML and HMR. The fusion results in the loss of sequences which are located distal to HML and to HMR and produces a ring derivative of chromosome III. Cells containing such a ring chromosome are viable as haploids; apparently, no essential loci are located distal to the HM loci. The fusion cassette behaves as a standard HM locus with respect to both regulation by the MAR/SIR control and its role in switching MAT. Images PMID:6346056

  17. Boosting the Efficiency of III-V/Si Tandem Solar Cells

    SciTech Connect

    Essig, Stephanie; Allebe, Christophe; Geisz, John F.; Steiner, Myles A.; Paviet-Salomon, Bertrand; Descoeudres, Antoine; Tamboli, Adele; Barraud, Loris; Ward, Scott; Badel, Nicolas; LaSalvia, Vincenzo; Levrat, Jacques; Despeisse, Matthieu; Ballif, Christophe; Stradins, Paul; Young, David L.

    2016-11-21

    We have developed Si-based tandem solar cells with a certified 1-sun efficiency of 29.8% (AM1.5g). The four-terminal tandem devices consist of 1.8 eV rear-heterojunction GaInP top cells and silicon heterojunction bottom cells. The two subcells were fabricated independently in two different labs and merged using an optically transparent, electrically insulating epoxy. Work is ongoing to further improve the performance of each subcell and to push the tandem cell efficiency to > 30%.

  18. What Sets the Massive Star Formation Rates and Efficiencies of Giant Molecular Clouds?

    NASA Astrophysics Data System (ADS)

    Ochsendorf, Bram B.; Meixner, Margaret; Roman-Duval, Julia; Rahman, Mubdi; Evans, Neal J., II

    2017-06-01

    Galactic star formation scaling relations show increased scatter from kpc to sub-kpc scales. Investigating this scatter may hold important clues to how the star formation process evolves in time and space. Here, we combine different molecular gas tracers, different star formation indicators probing distinct populations of massive stars, and knowledge of the evolutionary state of each star-forming region to derive the star formation properties of ˜150 star-forming complexes over the face of the Large Magellanic Cloud (LMC). We find that the rate of massive star formation ramps up when stellar clusters emerge and boost the formation of subsequent generations of massive stars. In addition, we reveal that the star formation efficiency of individual giant molecular clouds (GMCs) declines with increasing cloud gas mass ({M}{cloud}). This trend persists in Galactic star-forming regions and implies higher molecular gas depletion times for larger GMCs. We compare the star formation efficiency per freefall time ({ɛ }{ff}) with predictions from various widely used analytical star formation models. While these models can produce large dispersions in {ɛ }{ff} similar to those in observations, the origin of the model-predicted scatter is inconsistent with observations. Moreover, all models fail to reproduce the observed decline of {ɛ }{ff} with increasing {M}{cloud} in the LMC and the Milky Way. We conclude that analytical star formation models idealizing global turbulence levels and cloud densities and assuming a stationary star formation rate (SFR) are inconsistent with observations from modern data sets tracing massive star formation on individual cloud scales. Instead, we reiterate the importance of local stellar feedback in shaping the properties of GMCs and setting their massive SFR.

  19. Providing for Energy Efficiency in Homes and Small Buildings, Part III.

    ERIC Educational Resources Information Center

    American Association for Vocational Instructional Materials, Athens, GA.

    Presented is part three of a training program designed to educate students and individuals in the importance of conserving energy and to provide for developing skills needed in the application of energy-saving techniques that result in energy efficient buildings. Alternatives are provided in this program to allow for specific instruction in…

  20. Effectiveness and Efficiency of Nursing Education Programs. Volume III: Analysis of the Literature.

    ERIC Educational Resources Information Center

    Cresap, McCormick, and Paget, Inc., Washington, DC.

    The three volume study is a review of the available literature to determine the relative effectiveness and efficiency of diploma, associate degree, and baccalaureate nursing education programs in producing the number and quality of registered nurses needed in the nation; and to analyze the cost of nursing education. Volume three notes that a mild…

  1. Effectiveness and Efficiency of Nursing Education Programs. Volume III: Analysis of the Literature.

    ERIC Educational Resources Information Center

    Cresap, McCormick, and Paget, Inc., Washington, DC.

    The three volume study is a review of the available literature to determine the relative effectiveness and efficiency of diploma, associate degree, and baccalaureate nursing education programs in producing the number and quality of registered nurses needed in the nation; and to analyze the cost of nursing education. Volume three notes that a mild…

  2. Ion-pair formation of Bi(III)-iodide with some nitrogenous drugs and its application to pharmaceutical preparations.

    PubMed

    Abdel-Gawad, F M

    1998-01-01

    A systematic spectrophotometric study on the ion-pair formation of Bi(III)-iodide with amineptine hydrochloride, piribedil and trimebutine maleate is carried out. The optimal experimental conditions pH, concentration of Bi(III) nitrate, potassium iodide; and the nature and amount of organic solvent have been studied. The ion pairs are soluble in 1,2-dichloroethane and the optimum pH range is 2.0-2.8. By application of the methods of Sommer and Job involving non-equimolar solutions, the conditional stability constant (log K') of the Bi(III) piridedil ion pair (1:1) at the optimum pH of 2.4 and an ionic strength (mu) 0.1 M, was found to be 5.436. The validity of Beer's law has been tested in the concentration range 5-50 microg ml(-1) in the organic layer, the relative standard deviation is less than 1%. The method is applied to the determination of these drugs in tablets without interference.

  3. Diagnostic efficiency of demographically corrected Wechsler Adult Intelligence Scale-III and Wechsler Memory Scale-III indices in moderate to severe traumatic brain injury and lower education levels.

    PubMed

    Walker, Alexandra J; Batchelor, Jennifer; Shores, E Arthur; Jones, Mike

    2009-11-01

    Despite the sensitivity of neuropsychological tests to educational level, improved diagnostic accuracy for demographically corrected scores has yet to be established. Diagnostic efficiency statistics of Wechsler Adult Intelligence Scale-III (WAIS-III) and Wechsler Memory Scale-III (WMS-III) indices that were corrected for education, sex, and age (demographically corrected) were compared with age corrected indices in individuals aged 16 to 75 years with moderate to severe traumatic brain injury (TBI) and 12 years or less education. TBI participants (n = 100) were consecutive referrals to an outpatient rehabilitation service and met careful selection criteria. Controls (n = 100) were obtained from the WAIS-III/WMS-III standardization sample. Demographically corrected indices did not provide higher diagnostic efficiency than age corrected indices and this result was supported by reanalysis of the TBI group against a larger and unmatched control group. Processing Speed Index provided comparable diagnostic accuracy to that of combined indices. Demographically corrected indices were associated with higher cut-scores to maximize overall classification, reflecting the upward adjustment of those scores in a lower education sample. This suggests that, in clinical practice, the test results of individuals with limited education may be more accurately interpreted with the application of demographic corrections. Diagnostic efficiency statistics are presented, and future research directions are discussed.

  4. Photochemical Ignition Studies. 3. Ignition by Efficient and Resonant Multiphoton Photochemical Formation of Microplasmas

    DTIC Science & Technology

    1987-06-01

    Security Ct14sfIcation) PHOTOCHEMICAL IGNITION STUDIES. I11. IGNITION BY EFFICIENT AND RESONANT MULTIPHOTON PHOTOCHEMICAL FORMATION OF MICROPLASMAS 12... Microplasmas 07 04ý 19. ABSTRACT (Coninu On 06 it= iP rwouiry and ikti n~jnilW) ;;is is the third of a series of reports concerning the activation...p--spectral studies were carried out on 02 and N 0 flows alone. These indicated a resonant formation of a microplasma with a fifetime on the order

  5. Improvement of III-nitride visible and ultraviolet light-emitting diode performance, including extraction efficiency, electrical efficiency, thermal management and efficiency maintenance at high current densities

    NASA Astrophysics Data System (ADS)

    Vampola, Kenneth

    In this work, highly efficient broad-area LEDs on bulk GaN substrates were developed and the fabrication process and device layout were optimized. This optimization relied in part on electrical, optical, thermal and recombination models. The peak external quantum efficiency of the 450 nm LEDs was over 68% when biased at 20 mA. The efficiency characteristic showed a typical droop curve, decreasing at high current densities. The cause of this droop is unknown. An exploratory experiment was conducted to characterize electron overflow and its role in efficiency droop. Novel device structures were developed, allowing direct measurement of overflow electrons in LED-like structures under electrical injection. In these test structures, electrons were observed in the p-type region of the LED only at current densities where efficiency droop was active. The onset of efficiency droop was preceded by the onset of electron overflow. However, the magnitude of the overflow current could not be measured and it is undetermined whether the dominant cause of efficiency droop is electron overflow or some other process such as Auger recombination. Calibration structures allowing measurement of the magnitude of the overflow are proposed. Work on deep-ultraviolet, 275 nm, LEDs is also presented. Demonstration of direct-wafer bonded LEDs to beta-Ga2O3 is presented. A SiC substrate removal process is discussed. LEDs fabricated by this flip-chip process exhibited up to 1.8 times greater power compared to LEDs fabricated by a standard process but suffered from increased forward voltage and premature failure. Further process development leading to electrically efficient operation is proposed.

  6. Unexpected formation of a novel pyridinium-containing catecholate ligand and its manganese(III) complex.

    PubMed

    Sheriff, Tippu S; Watkinson, Michael; Motevalli, Majid; Lesin, Jocelyne F

    2010-01-07

    Nucleophilic aromatic substitution of tetrachloro-o-benzoquinone by pyridine and reduction of the o-quinone to the catechol by hydroxylamine forms 1,2-dihydroxy-3,5,6-trichlorobenzene-4-pyridinium chloride. This compound reacts with manganese(II) acetate in air to form chlorobis(3,5,6-trichlorobenzene 4-pyridinium catecholate)manganese(III), which represents the first complex of this ligand class to be structurally characterized by X-ray diffraction; this complex is active in the catalytic reduction of dioxygen to hydrogen peroxide under ambient conditions and turnover frequencies (TOFs) >10,000 h(-1) can be obtained.

  7. Highly efficient star formation in NGC 5253 possibly from stream-fed accretion.

    PubMed

    Turner, J L; Beck, S C; Benford, D J; Consiglio, S M; Ho, P T P; Kovács, A; Meier, D S; Zhao, J-H

    2015-03-19

    Gas clouds in present-day galaxies are inefficient at forming stars. Low star-formation efficiency is a critical parameter in galaxy evolution: it is why stars are still forming nearly 14 billion years after the Big Bang and why star clusters generally do not survive their births, instead dispersing to form galactic disks or bulges. Yet the existence of ancient massive bound star clusters (globular clusters) in the Milky Way suggests that efficiencies were higher when they formed ten billion years ago. A local dwarf galaxy, NGC 5253, has a young star cluster that provides an example of highly efficient star formation. Here we report the detection of the J = 3→2 rotational transition of CO at the location of the massive cluster. The gas cloud is hot, dense, quiescent and extremely dusty. Its gas-to-dust ratio is lower than the Galactic value, which we attribute to dust enrichment by the embedded star cluster. Its star-formation efficiency exceeds 50 per cent, tenfold that of clouds in the Milky Way. We suggest that high efficiency results from the force-feeding of star formation by a streamer of gas falling into the galaxy.

  8. Global and radial variations in the efficiency of massive star formation among galaxies

    NASA Technical Reports Server (NTRS)

    Allen, Lori E.; Young, Judith S.

    1990-01-01

    In order to determine the regions within galaxies which give rise to the most efficient star formation and to test the hypothesis that galaxies with high infrared luminosities per unit molecular mass are efficiently producing high mass stars, researchers have undertaken an H alpha imaging survey in galaxies whose CO distributions have been measured as part of the Five College Radio Astronomy Observatory (FCRAO) Extragalactic CO Survey. From these images researchers have derived global H alpha fluxes and distributions for comparison with far infrared radiation (FIR) fluxes and CO fluxes and distributions. Here, researchers present results on the global massive star formation efficiency (SFE = L sub H sub alpha/M(H2)) as a function of morphological type and environment, and on the radial distribution of the SFE within both peculiar and isolated galaxies. On the basis of comparison of the global L sub H sub alpha/M(H2) and L sub FIR/M(H2) for 111 galaxies, researchers conclude that environment rather than morphological type has the strongest effect on the global efficiency of massive star formation. Based on their study of a small sample, they find that the largest radial gradients are observed in the interacting/peculiar galaxies, indicating that environment affects the star formation efficiency within galaxies as well.

  9. Highly efficient multiple-layer CdS quantum dot sensitized III-V solar cells.

    PubMed

    Lin, Chien-Chung; Han, Hau-Vei; Chen, Hsin-Chu; Chen, Kuo-Ju; Tsai, Yu-Lin; Lin, Wein-Yi; Kuo, Hao-Chung; Yu, Peichen

    2014-02-01

    In this review, the concept of utilization of solar spectrum in order to increase the solar cell efficiency is discussed. Among the three mechanisms, down-shifting effect is investigated in detail. Organic dye, rare-earth minerals and quantum dots are three most popular down-shift materials. While the enhancement of solar cell efficiency was not clearly observed in the past, the advances in quantum dot fabrication have brought strong response out of the hybrid platform of a quantum dot solar cell. A multiple layer structure, including PDMS as the isolation layer, is proposed and demonstrated. With the help of pulse spray system, precise control can be achieved and the optimized concentration can be found.

  10. Plasma processing of III-V materials for energy efficient electronics applications

    NASA Astrophysics Data System (ADS)

    Thayne, Iain; Li, Xu; Millar, David; Fu, Yen-Chun; Peralagu, Uthayasankararan

    2017-03-01

    This paper reviews some recent activity at the James Watt Nanofabrication Centre in the University of Glasgow in the area of plasma processing for energy efficient compound semiconductor-based transistors. Atomic layer etching suitable for controllable recess etching in GaN power transistors will be discussed. In addition, plasma based surface passivation techniques will be reviewed for a variety of compound semiconductor materials ((100) and (110) oriented InGaAs and InGaSb).

  11. Formation of nanofilms on cell surfaces to improve the insertion efficiency of a nanoneedle into cells

    SciTech Connect

    Amemiya, Yosuke; Kawano, Keiko; Matsusaki, Michiya; Akashi, Mitsuru; Nakamura, Noriyuki; Nakamura, Chikashi

    2012-04-13

    Highlights: Black-Right-Pointing-Pointer We examined the insertion efficiency of nanoneedles into fibroblast and neural cells. Black-Right-Pointing-Pointer Nanofilms formed on cell surfaces improved the insertion efficiency of nanoneedles. Black-Right-Pointing-Pointer Nanofilms improved the insertion efficiency even in Y27632-treated cells. -- Abstract: A nanoneedle, an atomic force microscope (AFM) tip etched to 200 nm in diameter and 10 {mu}m in length, can be inserted into cells with the aid of an AFM and has been used to introduce functional molecules into cells and to analyze intracellular information with minimal cell damage. However, some cell lines have shown low insertion efficiency of the nanoneedle. Improvement in the insertion efficiency of a nanoneedle into such cells is a significant issue for nanoneedle-based cell manipulation and analysis. Here, we have formed nanofilms composed of extracellular matrix molecules on cell surfaces and found that the formation of the nanofilms improved insertion efficiency of a nanoneedle into fibroblast and neural cells. The nanofilms were shown to improve insertion efficiency even in cells in which the formation of actin stress fibers was inhibited by the ROCK inhibitor Y27632, suggesting that the nanofilms with the mesh structure directly contributed to the improved insertion efficiency of a nanoneedle.

  12. Europium (III) Organic Complexes in Porous Boron Nitride Microfibers: Efficient Hybrid Luminescent Material

    PubMed Central

    Lin, Jing; Feng, Congcong; He, Xin; Wang, Weijia; Fang, Yi; Liu, Zhenya; Li, Jie; Tang, Chengchun; Huang, Yang

    2016-01-01

    We report the design and synthesis of a novel kind of organic-inorganic hybrid material via the incorporation of europium (III) β-diketonate complexes (Eu(TTA)3, TTA = 2-thenoyltrifluoroacetone) into one-dimensional (1D) porous boron nitride (BN) microfibers. The developed Eu(TTA)3@BN hybrid composites with typical 1D fibrous morphology exhibit bright visible red-light emission on UV illumination. The confinement of Eu(TTA)3 within pores of BN microfibers not only decreases the aggregation-caused quenching in solid Eu(TTA)3, but also improves their thermal stabilities. Moreover, The strong interactions between Eu(TTA)3 and porous BN matrix result in an interesting energy transfer process from BN host to TTA ligand and TTA ligand to Eu3+ ions, leading to the remarkable increase of red emission. The synthetic approach should be a very promising strategy which can be easily expanded to other hybrid luminescent materials based on porous BN. PMID:27687246

  13. Heptanuclear Co(II)5Co(III)2 Cluster as Efficient Water Oxidation Catalyst.

    PubMed

    Xu, Jia-Heng; Guo, Ling-Yu; Su, Hai-Feng; Gao, Xiang; Wu, Xiao-Fan; Wang, Wen-Guang; Tung, Chen-Ho; Sun, Di

    2017-02-06

    Inspired by the transition-metal-oxo cubical Mn4CaO5 in photosystem II, we herein report a disc-like heptanuclear mixed-valent cobalt cluster, [Co(II)5Co(III)2(mdea)4(N3)2(CH3CN)6(OH)2(H2O)2·4ClO4] (1, H2mdea = N-methyldiethanolamine), for photocatalytic oxygen evolution. The topology of the Co7 core resembles a small piece of cobaltate protected by terminal H2O, N3(-), CH3CN, and multidentate N-methyldiethanolamine at the periphery. Under the optimal photocatalytic conditions, 1 exhibits water oxidation activity with a turnover number (TON) of 210 and a turnover frequency (TOFinitial) of 0.23 s(-1). Importantly, electrospray mass spectrometry (ESI-MS) was used to not only identify the possible main active species in the water oxidation reaction but also monitor the evolutions of oxidation states of cobalt during the photocatalytic reactions. These results shed light on the design concept of new water oxidation catalysts and mechanism-related issues such as the key active intermediate and oxidation state evolution in the oxygen evolution process. The magnetic properties of 1 were also discussed in detail.

  14. Formation of W/O microemulsions in the extraction of Nd(iii) by bis(2,4,4-trimethylpentyl)dithiophosphinic acid and its effects on Nd(iii) coordination.

    PubMed

    Sun, Taoxiang; Xu, Chao; Chen, Jing

    2016-01-21

    The formation of water-in-oil (W/O) microemulsions during the extraction of Nd(iii) by bis(2,4,4-trimethylpentyl)dithiophosphinic acid (also known as purified Cyanex 301, denoted as HC301) was studied. Results from the measurement of the concentration of Nd(iii), Na(+) and NO3(-) in the organic phase, IR spectroscopy, and dynamic light scattering (DLS) all indicated that W/O microemulsions could form as the ratio of the neutralized ligand to Nd(iii) in the aqueous phase is over 3 : 1. The coordination environment of Nd(iii) in the extracted complexes was monitored by absorption spectroscopy and extended X-ray absorption fine structure (EXAFS) and was found to vary significantly with the formation of W/O microemulsions. When only 10% of HC301 was neutralized, with no formation of W/O microemulsions, the inner coordination shell of Nd(iii) in the organic phase was occupied dominantly by sulfur atoms from HC301. As HC301 was further neutralized, the coordinated sulfur atoms around Nd(iii) were replaced gradually by the oxygen atoms from water. This work provides further insights into the extraction mechanism in the extraction system using purified Cyanex 301 as an extractant.

  15. STAR FORMATION IN DISK GALAXIES. III. DOES STELLAR FEEDBACK RESULT IN CLOUD DEATH?

    SciTech Connect

    Tasker, Elizabeth J.; Wadsley, James; Pudritz, Ralph

    2015-03-01

    Stellar feedback, star formation, and gravitational interactions are major controlling forces in the evolution of giant molecular clouds (GMCs). To explore their relative roles, we examine the properties and evolution of GMCs forming in an isolated galactic disk simulation that includes both localized thermal feedback and photoelectric heating. The results are compared with the three previous simulations in this series, which consists of a model with no star formation, star formation but no form of feedback, and star formation with photoelectric heating in a set with steadily increasing physical effects. We find that the addition of localized thermal feedback greatly suppresses star formation but does not destroy the surrounding GMC, giving cloud properties closely resembling the run in which no stellar physics is included. The outflows from the feedback reduce the mass of the cloud but do not destroy it, allowing the cloud to survive its stellar children. This suggests that weak thermal feedback such as the lower bound expected for a supernova may play a relatively minor role in the galactic structure of quiescent Milky-Way-type galaxies, compared to gravitational interactions and disk shear.

  16. Star Formation in Disk Galaxies. III. Does Stellar Feedback Result in Cloud Death?

    NASA Astrophysics Data System (ADS)

    Tasker, Elizabeth J.; Wadsley, James; Pudritz, Ralph

    2015-03-01

    Stellar feedback, star formation, and gravitational interactions are major controlling forces in the evolution of giant molecular clouds (GMCs). To explore their relative roles, we examine the properties and evolution of GMCs forming in an isolated galactic disk simulation that includes both localized thermal feedback and photoelectric heating. The results are compared with the three previous simulations in this series, which consists of a model with no star formation, star formation but no form of feedback, and star formation with photoelectric heating in a set with steadily increasing physical effects. We find that the addition of localized thermal feedback greatly suppresses star formation but does not destroy the surrounding GMC, giving cloud properties closely resembling the run in which no stellar physics is included. The outflows from the feedback reduce the mass of the cloud but do not destroy it, allowing the cloud to survive its stellar children. This suggests that weak thermal feedback such as the lower bound expected for a supernova may play a relatively minor role in the galactic structure of quiescent Milky-Way-type galaxies, compared to gravitational interactions and disk shear.

  17. On the Origin of Sub-subgiant Stars. III. Formation Frequencies

    NASA Astrophysics Data System (ADS)

    Geller, Aaron M.; Leiner, Emily M.; Chatterjee, Sourav; Leigh, Nathan W. C.; Mathieu, Robert D.; Sills, Alison

    2017-06-01

    Sub-subgiants (SSGs) are a new class of stars that are optically redder than normal main-sequence stars and fainter than normal subgiant stars. SSGs, as well as the possibly related red stragglers (which fall to the red of the giant branch), occupy a region of the color-magnitude diagram that is predicted to be devoid of stars by standard stellar evolution theory. In previous papers we presented the observed demographics of these sources and defined possible theoretical formation channels through isolated binary evolution, the rapid stripping of a subgiant’s envelope, and stellar collisions. SSGs offer key tests for single- and binary-star evolution and stellar collision models. In this paper, we synthesize these findings to discuss the formation frequencies through each of these channels. The empirical data, our analytic formation rate calculations, and analyses of SSGs in a large grid of Monte Carlo globular cluster models suggest that the binary evolution channels may be the most prevalent, though all channels appear to be viable routes to SSG creation (especially in higher-mass globular clusters). Multiple formation channels may operate simultaneously to produce the observed SSG population. Finally, many of these formation pathways can produce stars in both the SSG and red straggler (and blue straggler) regions of the color-magnitude diagram, in some cases as different stages along the same evolutionary sequence.

  18. Highly efficient hydrogen storage system based on ammonium bicarbonate/formate redox equilibrium over palladium nanocatalysts.

    PubMed

    Su, Ji; Yang, Lisha; Lu, Mi; Lin, Hongfei

    2015-03-01

    A highly efficient, reversible hydrogen storage-evolution process has been developed based on the ammonium bicarbonate/formate redox equilibrium over the same carbon-supported palladium nanocatalyst. This heterogeneously catalyzed hydrogen storage system is comparable to the counterpart homogeneous systems and has shown fast reaction kinetics of both the hydrogenation of ammonium bicarbonate and the dehydrogenation of ammonium formate under mild operating conditions. By adjusting temperature and pressure, the extent of hydrogen storage and evolution can be well controlled in the same catalytic system. Moreover, the hydrogen storage system based on aqueous-phase ammonium formate is advantageous owing to its high volumetric energy density.

  19. Constraints on the Star Formation Efficiency of Galaxies During Cosmic Reionization

    NASA Astrophysics Data System (ADS)

    Sun, Guochao; Furlanetto, Steven R.

    2016-01-01

    Cosmic reionization is thought to have occurred in the redshift range of 6 < z < 9, which is now being probed by both deep galaxy surveys and CMB observations. Using halo abundance matching over the redshift range 5 < z < 8 and an analytic prescription of gas accretion, we develop a model for the star formation efficiency f* of dark matter halos at z > 6 that matches the measured galaxy luminosity functions at these redshifts. We find that the star formation efficiency peaks near ˜ 10% at halo masses M ˜ 1011-1012 M⊙, in qualitative agreement with its behavior at lower redshifts. Recent lensing observations of z ˜ 7 galaxies suggest that the efficiency declines toward smaller masses, with f* proportional to M1/2 down to M ˜ 1010 M⊙ as expected by models of stellar feedback, albeit with large uncertainties. We then investigate the cosmic star formation histories and the corresponding models of cosmic reionization for a range of extrapolations to small halo masses. We compare these to a variety of observations, using them to further constrain the characteristics of the galaxy populations. Our approach provides an empirically-calibrated, physically-motivated model for the properties of star-forming galaxies sourcing the epoch of reionization. By modeling the redshift evolution of f*, we find a generally slower evolution of the cosmic star formation rate density compared to that predicted by f* fixed in time. In the case where star formation in low-mass halos is maximally efficient, an average escape fraction ˜ 0.1 can reproduce the CMB optical depth observed by Planck, whereas less efficient star formation in these halos requires about twice as many UV photons to escape, or an escape fraction that increases towards higher redshifts. Our models also predict how future observations with JWST can improve our understanding of these galaxy populations.

  20. INSIDE-OUT PLANET FORMATION. III. PLANET–DISK INTERACTION AT THE DEAD ZONE INNER BOUNDARY

    SciTech Connect

    Hu, Xiao; Tan, Jonathan C.; Chatterjee, Sourav; Zhu, Zhaohuan

    2016-01-01

    The Kepler mission has discovered more than 4000 exoplanet candidates. Many of them are in systems with tightly packed inner planets. Inside-out planet formation (IOPF) has been proposed as a scenario to explain these systems. It involves sequential in situ planet formation at the local pressure maximum of a retreating dead zone inner boundary (DZIB). Pebbles accumulate at this pressure trap, which builds up a pebble ring and then a planet. The planet is expected to grow in mass until it opens a gap, which helps to both truncate pebble accretion and also induce DZIB retreat that sets the location of formation of the next planet. This simple scenario may be modified if the planet undergoes significant migration from its formation location. Thus, planet–disk interactions play a crucial role in the IOPF scenario. Here we present numerical simulations that first assess the degree of migration for planets of various masses that are forming at the DZIB of an active accretion disk, where the effective viscosity is undergoing a rapid increase in the radially inward direction. We find that torques exerted on the planet by the disk tend to trap the planet at a location very close to the initial pressure maximum where it formed. We then study gap opening by these planets to assess at what mass a significant gap is created. Finally, we present a simple model for DZIB retreat due to penetration of X-rays from the star to the disk midplane. Overall, these simulations help to quantify both the mass scale of first (“Vulcan”) planet formation and the orbital separation to the location of second planet formation.

  1. Inside-out Planet Formation. III. Planet-Disk Interaction at the Dead Zone Inner Boundary

    NASA Astrophysics Data System (ADS)

    Hu, Xiao; Zhu, Zhaohuan; Tan, Jonathan C.; Chatterjee, Sourav

    2016-01-01

    The Kepler mission has discovered more than 4000 exoplanet candidates. Many of them are in systems with tightly packed inner planets. Inside-out planet formation (IOPF) has been proposed as a scenario to explain these systems. It involves sequential in situ planet formation at the local pressure maximum of a retreating dead zone inner boundary (DZIB). Pebbles accumulate at this pressure trap, which builds up a pebble ring and then a planet. The planet is expected to grow in mass until it opens a gap, which helps to both truncate pebble accretion and also induce DZIB retreat that sets the location of formation of the next planet. This simple scenario may be modified if the planet undergoes significant migration from its formation location. Thus, planet-disk interactions play a crucial role in the IOPF scenario. Here we present numerical simulations that first assess the degree of migration for planets of various masses that are forming at the DZIB of an active accretion disk, where the effective viscosity is undergoing a rapid increase in the radially inward direction. We find that torques exerted on the planet by the disk tend to trap the planet at a location very close to the initial pressure maximum where it formed. We then study gap opening by these planets to assess at what mass a significant gap is created. Finally, we present a simple model for DZIB retreat due to penetration of X-rays from the star to the disk midplane. Overall, these simulations help to quantify both the mass scale of first (“Vulcan”) planet formation and the orbital separation to the location of second planet formation.

  2. III-V photocathode with nitrogen doping for increased quantum efficiency

    NASA Technical Reports Server (NTRS)

    James, L. W. (Inventor)

    1976-01-01

    An increase in the quantum efficiency of a 3-5 photocathode is achieved by doping its semiconductor material with an acceptor and nitrogen, a column-5 isoelectronic element, that introduces a spatially localized energy level just below the conduction band similar to a donor level to which optical transitions can occur. This increases the absorption coefficient, alpha without compensation of the acceptor dopant. A layer of a suitable 1-5, 1-6 or 1-7 compound is included as an activation layer on the electron emission side to lower the work function of the photocathode.

  3. SAGE III

    Atmospheric Science Data Center

    2017-01-13

    SAGE III Data and Information The Stratospheric Aerosol and Gas ... on the spacecraft. SAGE III produced L1 and L2 scientific data from 5/07/2002 until 12/31/2005. The flight of the second instrument is as ... Additional Info:  Data Format: HDF-EOS or Big Endian/IEEE Binary SCAR-B Block:  ...

  4. The IMACS Cluster Building Survey. III. The Star Formation Histories of Field Galaxies

    NASA Astrophysics Data System (ADS)

    Oemler, Augustus, Jr.; Dressler, Alan; Gladders, Michael G.; Fritz, Jacopo; Poggianti, Bianca M.; Vulcani, Benedetta; Abramson, Louis

    2013-06-01

    Using data from the IMACS Cluster Building Survey and from nearby galaxy surveys, we examine the evolution of the rate of star formation in field galaxies from z = 0.60 to the present. Fitting the luminosity function to a standard Schechter form, we find a rapid evolution of M_B^* consistent with that found in other deep surveys; at the present epoch M_B^* is evolving at the rate of 0.38 Gyr-1, several times faster than the predictions of simple models for the evolution of old, coeval galaxies. The evolution of the distribution of specific star formation rates (SSFRs) is also too rapid to explain by such models. We demonstrate that starbursts cannot, even in principle, explain the evolution of the SSFR distribution. However, the rapid evolution of both M_B^* and the SSFR distribution can be explained if some fraction of galaxies have star formation rates characterized by both short rise and fall times and by an epoch of peak star formation more recent than the majority of galaxies. Although galaxies of every stellar mass up to 1.4 × 1011 M ⊙ show a range of epochs of peak star formation, the fraction of "younger" galaxies falls from about 40% at a mass of 4 × 1010 M ⊙ to zero at a mass of 1.4 × 1011 M ⊙. The incidence of younger galaxies appears to be insensitive to the density of the local environment; but does depend on group membership: relatively isolated galaxies are much more likely to be young than are group members. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

  5. A unique palladium catalyst for efficient and selective alkoxycarbonylation of olefins with formates.

    PubMed

    Fleischer, Ivana; Jennerjahn, Reiko; Cozzula, Daniela; Jackstell, Ralf; Franke, Robert; Beller, Matthias

    2013-03-01

    Forget about CO! Carbonylations are among the most important homogeneously catalyzed reactions in the chemical industry, but typically require carbon monoxide. Instead, straightforward and efficient alkoxycarbonylations of olefins can proceed with alkyl formates in the presence of a specific palladium catalyst. Aromatic, terminal aliphatic, and internal olefins are carbonylated to give industrially important linear esters at low catalyst loadings.

  6. Can the removal of molecular cloud envelopes by external feedback affect the efficiency of star formation?

    NASA Astrophysics Data System (ADS)

    Lucas, William E.; Bonnell, Ian A.; Forgan, Duncan H.

    2017-01-01

    We investigate how star formation efficiency can be significantly decreased by the removal of a molecular cloud's envelope by feedback from an external source. Feedback from star formation has difficulties halting the process in dense gas but can easily remove the less dense and warmer envelopes where star formation does not occur. However, the envelopes can play an important role keeping their host clouds bound by deepening the gravitational potential and providing a constraining pressure boundary. We use numerical simulations to show that removal of the cloud envelopes results in all cases in a fall in the star formation efficiency (SFE). At 1.38 free-fall times our 4 pc cloud simulation experienced a drop in the SFE from 16 to six percent, while our 5 pc cloud fell from 27 to 16 per cent. At the same time, our 3 pc cloud (the least bound) fell from an SFE of 5.67 per cent to zero when the envelope was lost. The star formation efficiency per free-fall time varied from zero to ≈0.25 according to α, defined to be the ratio of the kinetic plus thermal to gravitational energy, and irrespective of the absolute star forming mass available. Furthermore the fall in SFE associated with the loss of the envelope is found to even occur at later times. We conclude that the SFE will always fall should a star forming cloud lose its envelope due to stellar feedback, with less bound clouds suffering the greatest decrease.

  7. Metallothioneins (I+II) and thyroid-thymus axis efficiency in old mice: role of corticosterone and zinc supply.

    PubMed

    Mocchegiani, Eugenio; Giacconi, Robertina; Cipriano, Catia; Gasparini, Nazzarena; Orlando, Fiorenza; Stecconi, Rosalia; Muzzioli, Mario; Isani, Gloria; Carpenè, Emilio

    2002-03-31

    Thymic atrophy or thymus absence causes depressed thyroid-thymus axis (TTA) efficiency in old, young propyl-thiouracil (PTU) (experimental hypothyroidism) and in young-adult thymectomised (Tx) mice, respectively. Altered zinc turnover may be also involved in depressed TTA efficiency. Zinc turnover is under the control of zinc-bound metallothioneins (Zn-MTs) synthesis. Thyroid hormones, corticosterone and nutritional zinc affect Zn-MT induction. Zn-MT releases zinc in young-adult age during transient oxidative stress for prompt immune response. In constant oxidative stress (ageing and liver regeneration after partial hepatectomy), high liver Zn-MTs, low zinc ion bioavailability and depressed TTA efficiency appear. This last finding suggested that MT might not release zinc during constant oxidative stress leading to impaired TTA efficiency. The aim of this work/study is to clarify the role of Zn-MTs (I+II) in TTA efficiency during development and ageing. The main results are (1) Old and PTU mice display high corticosterone, enhanced liver MTmRNA, low zinc and depressed TTA efficiency restored by zinc supply. Increased survival and no significant increments in basal liver Zn-MTs proteins occur in old and PTU mice after zinc supply. (2) Lot of zinc ions bound with MT in the liver from old mice than young (HPLC). (3) Young-adult Tx mice, evaluated at 15 days from thymectomy, display high MTmRNA and nutritional-endocrine-immune damage restored by zinc supply or by thymus grafts from old zinc-treated mice. (4) Young-adult Tx mice, but evaluated at 40 days from thymectomy, display natural normalisation in MTmRNA and nutritional-endocrine-immune profile with survival similar to normal mice. (5) Stressed (constant dark for 10 days) mice overexpressing MT display low zinc, depressed immunity, reduced thymic cortex, high corticosterone, altered thyroid hormones turnover showing a likeness with old mice. These findings, taken altogether, show that corticosterone is pivotal in

  8. Molar Absorptivity and Quantum Yield of Fe(II) Photo-formation for the Aqueous Solutions of Fe(III)-Dicarboxylate Comlexes

    NASA Astrophysics Data System (ADS)

    Hitomi, Y.; Arakaki, T.

    2009-04-01

    Fe(III)/Fe(II) cycle in the environment affects formation of active oxygen species such as hydrogen peroxide and hydroxyl radicals, which in turn determines lifetimes of many organic compounds. Although aqueous Fe(III)-dicarboxylate complexes are considered to be an important source of photo-chemically formed Fe(II), molar absorptivity and quantum yield of Fe(II) formation for individual species are not well understood. The Visual MINTEQ computer program was used to calculate the equilibrium concentrations of individual Fe(III)-dicarboxylate species in the aqueous solutions of Fe(III)-dicarboxylate complexes. The molar absorptivity and the product of the quantum yield and the molar absorptivity of Fe(III)-dicarboxylate species were obtained by UV-VIS spectrophotometer and photochemical experiments, and these experimental data were combined with the calculated equilibrium Fe(III)-dicarboxylate concentrations to determine individual molar absorptivity and quantum yield of Fe(II) photo-formation for a specific Fe(III)-dicarboxylate species. Dicarboxylate compounds studied were oxalate, malonate, succinate, malate, and phthalate.

  9. Coherent nanocavity structures for enhancement in internal quantum efficiency of III-nitride multiple quantum wells

    SciTech Connect

    Kim, T.; Liu, B.; Smith, R.; Athanasiou, M.; Gong, Y.; Wang, T.

    2014-04-21

    A “coherent” nanocavity structure has been designed on two-dimensional well-ordered InGaN/GaN nanodisk arrays with an emission wavelength in the green spectral region, leading to a massive enhancement in resonance mode in the green spectra region. By means of a cost-effective nanosphere lithography technique, we have fabricated such a structure on an InGaN/GaN multiple quantum well epiwafer and have observed the “coherent” nanocavity effect, which leads to an enhanced spontaneous emission (SE) rate. The enhanced SE rate has been confirmed by time resolved photoluminescence measurements. Due to the coherent nanocavity effect, we have achieved a massive improvement in internal quantum efficiency with a factor of 88, compared with the as-grown sample, which could be significant to bridge the “green gap” in solid-state lighting.

  10. Calorimetric study of the energy efficiency for ultrasound-induced radical formation.

    PubMed

    Kuijpers, M W A; Kemmere, M F; Keurentjes, J T F

    2002-05-01

    Energy conversion in sonochemistry is known to be an important factor for the development of industrial applications, however, the strong influence of the physical properties of the liquid on the ultrasound characteristics usually prevents an accurate determination of the chemical effects. In this study, the energy efficiency of the ultrasound-induced radical formation from methyl methacrylate has been investigated. The energy yield can be quantified by comparison of the ultrasonic power that is transferred to the liquid and the radical formation kinetics. Based on this method the influence of temperature and amplitude of the ultrasound horn on the energy efficiency has been determined. The energy yield for the formation of radicals from ultrasonic waves appears to be in the order of 5 x 10(-6) J/J. The energy conversion is the highest at low temperatures and at low amplitudes.

  11. GLOBULAR CLUSTER FORMATION EFFICIENCIES FROM BLACK HOLE X-RAY BINARY FEEDBACK

    SciTech Connect

    Justham, Stephen; Peng, Eric W.; Schawinski, Kevin

    2015-08-10

    We investigate a scenario in which feedback from black hole X-ray binaries (BHXBs) sometimes begins inside young star clusters before strong supernova (SN) feedback. Those BHXBs could reduce the gas fraction inside embedded young clusters while maintaining virial equilibrium, which may help globular clusters (GCs) to stay bound when SN-driven gas ejection subsequently occurs. Adopting a simple toy model with parameters guided by BHXB population models, we produce GC formation efficiencies consistent with empirically inferred values. The metallicity dependence of BHXB formation could naturally explain why GC formation efficiency is higher at lower metallicity. For reasonable assumptions about that metallicity dependence, our toy model can produce a GC metallicity bimodality in some galaxies without a bimodality in the field-star metallicity distribution.

  12. Formation of thin films of organic-inorganic perovskites for high-efficiency solar cells.

    PubMed

    Stranks, Samuel D; Nayak, Pabitra K; Zhang, Wei; Stergiopoulos, Thomas; Snaith, Henry J

    2015-03-09

    Organic-inorganic perovskites are currently one of the hottest topics in photovoltaic (PV) research, with power conversion efficiencies (PCEs) of cells on a laboratory scale already competing with those of established thin-film PV technologies. Most enhancements have been achieved by improving the quality of the perovskite films, suggesting that the optimization of film formation and crystallization is of paramount importance for further advances. Here, we review the various techniques for film formation and the role of the solvents and precursors in the processes. We address the role chloride ions play in film formation of mixed-halide perovskites, which is an outstanding question in the field. We highlight the material properties that are essential for high-efficiency operation of solar cells, and identify how further improved morphologies might be achieved. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Interstellar matter in early-type galaxies. III - Radio emission and star formation

    NASA Technical Reports Server (NTRS)

    Walsh, D. E. P.; Knapp, G. R.; Wrobel, J. M.; Kim, D.-W.

    1989-01-01

    The relationship between the IR and radio luminosity in early-type galaxies is examined using the correlation among spiral galaxies as a diagnostic of the presence of star formation. For ellipticals, the presence of long-wavelength IR emission enhances the probability that the galaxy is a radio source and is also correlated with the strength of that source. These findings are consistent with the idea that active radio nuclei are due to black holes being fueled by accretion of gas. The majority of S0s detected in both radio and far-IR have a similar ratio of IR to radio luminosity as has been found in spirals, and which is considered to be indicative of recent star formation. Sensitive radio limits for several galaxies reveal another substantial population of S0s with moderately strong IR emission unaccompanied by radio power.

  14. Gas Content and Star Formation Efficiency of Massive Main Sequence Galaxies at z~3-4

    NASA Astrophysics Data System (ADS)

    Schinnerer, Eva; Groves, Brent; Karim, Alexander; Sargent, Mark T.; Oesch, Pascal; Le Fevre, Olivier; Tasca, Lidia; Magnelli, Benjamin; Cassata, Paolo; Smolcic, Vernesa

    2016-01-01

    Recent observations have shown that the neutral gas content and star formation efficiency of massive (with log(stellar masses) > 10), normal star forming galaxies, i.e. they reside on the main sequence of star forming galaxies, are steadily decreasing from the peak of star formation activity (at redshifts of z~2) till today. This decrease is coincident with the observed decline in the cosmic star formation rate density over this time range. However, only few observations have probed the evolution of the gas content and star formation efficiency beyond this peak epoch when the cosmic star formation rate density has been increasing, i.e. at redshifts of z~3-4.We will present new ALMA rest-frame 250um continuum detections of 45 massive, normal star forming galaxies in this critical redshift interval selected in the COSMOS deep field. Using the sub-mm continnum as proxy for the cold neutral gas content, we find gas mass fractions and depletions similar to those reported during the peak epoch of star formation. We will discuss our findings in the context of results from lower redshift observations and model expectations.

  15. When Feedback Fails: The Scaling and Saturation of Star Formation Efficiency

    NASA Astrophysics Data System (ADS)

    Y Grudic, Michael; Hopkins, Philip F.; Faucher-Giguere, Claude-Andre; Quataert, Eliot; Murray, Norman W.; Keres, Dusan

    2017-06-01

    We present a suite of 3D multi-physics MHD simulations following star formation in isolated turbulent molecular gas disks ranging from 5 to 500 parsecs in radius. These simulations are designed to survey the range of surface densities between those typical of Milky Way GMCs (˜100 M⊙pc-2) and extreme ULIRG environments (˜104M⊙pc-2) so as to map out the scaling of star formation efficiency (SFE) between these two regimes. The simulations include prescriptions for supernova, stellar wind, and radiative feedback, which we find to be essential in determining both the instantaneous (ɛff) and integrated (ɛint) star formation efficiencies. In all simulations, the gas disks form stars until a critical stellar mass has been reached and the remaining gas is blown out by stellar feedback. We find that surface density is the best predictor of ɛint of all of the gas cloud's global properties, as suggested by analytic force balance arguments from previous works. Furthermore, SFE eventually saturates to ˜1 at high surface density, with very good agreement across different spatial scales. We also find a roughly proportional relationship between ɛff and ɛint. These results have implications for star formation in galactic disks, the nature and fate of nuclear starbursts, and the formation of bound star clusters. The scaling of ɛff also contradicts star formation models in which ɛff˜1% universally, including popular subgrid models for galaxy simulations.

  16. Panchromatic Hubble Andromeda Treasury. XVI. Star Cluster Formation Efficiency and the Clustered Fraction of Young Stars

    NASA Astrophysics Data System (ADS)

    Johnson, L. Clifton; Seth, Anil C.; Dalcanton, Julianne J.; Beerman, Lori C.; Fouesneau, Morgan; Lewis, Alexia R.; Weisz, Daniel R.; Williams, Benjamin F.; Bell, Eric F.; Dolphin, Andrew E.; Larsen, Søren S.; Sandstrom, Karin; Skillman, Evan D.

    2016-08-01

    We use the Panchromatic Hubble Andromeda Treasury survey data set to perform spatially resolved measurements of star cluster formation efficiency (Γ), the fraction of stellar mass formed in long-lived star clusters. We use robust star formation history and cluster parameter constraints, obtained through color-magnitude diagram analysis of resolved stellar populations, to study Andromeda’s cluster and field populations over the last ˜300 Myr. We measure Γ of 4%-8% for young, 10-100 Myr-old populations in M31. We find that cluster formation efficiency varies systematically across the M31 disk, consistent with variations in mid-plane pressure. These Γ measurements expand the range of well-studied galactic environments, providing precise constraints in an H i-dominated, low-intensity star formation environment. Spatially resolved results from M31 are broadly consistent with previous trends observed on galaxy-integrated scales, where Γ increases with increasing star formation rate surface density (ΣSFR). However, we can explain observed scatter in the relation and attain better agreement between observations and theoretical models if we account for environmental variations in gas depletion time (τ dep) when modeling Γ, accounting for the qualitative shift in star formation behavior when transitioning from a H2-dominated to a H i-dominated interstellar medium. We also demonstrate that Γ measurements in high ΣSFR starburst systems are well-explained by τ dep-dependent fiducial Γ models.

  17. UNDERSTANDING COMPACT OBJECT FORMATION AND NATAL KICKS. III. THE CASE OF CYGNUS X-1

    SciTech Connect

    Wong, Tsing-Wai; Valsecchi, Francesca; Kalogera, Vassiliki; Fragos, Tassos E-mail: francesca@u.northwestern.edu E-mail: tfragos@cfa.harvard.edu

    2012-03-10

    In recent years, accurate observational constraints have become available for an increasing number of Galactic X-ray binaries (XRBs). Together with proper-motion measurements, we could reconstruct the full evolutionary history of XRBs back to the time of compact object formation. In this paper, we present the first study of the persistent X-ray source Cygnus X-1 that takes into account all available observational constraints. Our analysis accounts for three evolutionary phases: orbital evolution and motion through the Galactic potential after the formation of a black hole (BH), and binary orbital dynamics at the time of core collapse. We find that the mass of the BH immediate progenitor is 15.0-20.0 M{sub Sun }, and at the time of core collapse, the BH has potentially received a small kick velocity of {<=}77 km s{sup -1} at 95% confidence. If the BH progenitor mass is less than {approx}17 M{sub Sun }, a non-zero natal kick velocity is required to explain the currently observed properties of Cygnus X-1. Since the BH has only accreted mass from its companion's stellar wind, the negligible amount of accreted mass does not explain the observationally inferred BH spin of a{sub *} > 0.95, and the origin of this extreme BH spin must be connected to the BH formation itself. Right after the BH formation, we find that the BH companion is a 19.8-22.6 M{sub Sun} main-sequence star, orbiting the BH at a period of 4.7-5.2 days. Furthermore, recent observations show that the BH companion is currently super-synchronized. This super-synchronism indicates that the strength of tides exerted on the BH companion should be weaker by a factor of at least two compared to the usually adopted strength.

  18. Efficient callus formation and plant regeneration are heritable characters in sugar beet (Beta vulgaris L.).

    PubMed

    Kagami, Hiroyo; Taguchi, Kazunori; Arakawa, Takumi; Kuroda, Yosuke; Tamagake, Hideto; Kubo, Tomohiko

    2016-01-01

    Obtaining dedifferentiated cells (callus) that can regenerate into whole plants is not always feasible for many plant species. Sugar beet is known to be recalcitrant for dedifferentiation and plant regeneration. These difficulties were major obstacles for obtaining transgenic sugar beets through an Agrobacterium-mediated transformation procedure. The sugar beet line 'NK-219mm-O' is an exceptional line that forms callus efficiently and is easy to regenerate, but the inheritance of these characters was unknown. Another concern was whether these characters could coexist with an annual habitat that makes it possible to breed short life-cycle sugar beet suitable for molecular genetic analysis. Five sugar beet lines including NK-219mm-O were crossed with each other and subjected to in vitro culture to form callus. F1s with a NK-219mm-O background generally formed callus efficiently compared to the others, indicating that efficient callus formation is heritable. The regeneration potential was examined based on the phenotypes of calli after placement on regeneration medium. Five phenotypes were observed, of which two phenotypes regenerated shoots or somatic embryo-like structures. Vascular differentiation was evident in regenerable calli, whereas non-regenerable calli lacked normally developed vascular tissues. In a half-diallel cross, the callus-formation efficiency and the regeneration potential of reciprocal F1s progeny having a NK-219mm-O background were high. Finally, we crossed NK-219mm-O with an annual line that had a poor in vitro performance. The callus-formation efficiency and the regeneration potential of reciprocal F1 were high. The regenerated plants showed an annual habitat. Efficient callus formation and the high plant regeneration potential of NK-219mm-O were inherited and expressed in the F1. The annual habitat does not impair these high in vitro performances.

  19. Yersinia enterocolitica type III secretion-translocation system: channel formation by secreted Yops.

    PubMed Central

    Tardy, F; Homblé, F; Neyt, C; Wattiez, R; Cornelis, G R; Ruysschaert, J M; Cabiaux, V

    1999-01-01

    'Type III secretion' allows extracellular adherent bacteria to inject bacterial effector proteins into the cytosol of their animal or plant host cells. In the archetypal Yersinia system the secreted proteins are called Yops. Some of them are intracellular effectors, while YopB and YopD have been shown by genetic analyses to be dedicated to the translocation of these effectors. Here, the secretion of Yops by Y.enterocolitica was induced in the presence of liposomes, and some Yops, including YopB and YopD, were found to be inserted into liposomes. The proteoliposomes were fused to a planar lipid membrane to characterize the putative pore-forming properties of the lipid-bound Yops. Electrophysiological experiments revealed the presence of channels with a 105 pS conductance and no ionic selectivity. Channels with those properties were generated by mutants devoid of the effectors and by lcrG mutants, as well as by wild-type bacteria. In contrast, mutants devoid of YopB did not generate channels and mutants devoid of YopD led to current fluctuations that were different from those observed with wild-type bacteria. The observed channel could be responsible for the translocation of Yop effectors. PMID:10581252

  20. Yersinia enterocolitica type III secretion-translocation system: channel formation by secreted Yops.

    PubMed

    Tardy, F; Homblé, F; Neyt, C; Wattiez, R; Cornelis, G R; Ruysschaert, J M; Cabiaux, V

    1999-12-01

    'Type III secretion' allows extracellular adherent bacteria to inject bacterial effector proteins into the cytosol of their animal or plant host cells. In the archetypal Yersinia system the secreted proteins are called Yops. Some of them are intracellular effectors, while YopB and YopD have been shown by genetic analyses to be dedicated to the translocation of these effectors. Here, the secretion of Yops by Y.enterocolitica was induced in the presence of liposomes, and some Yops, including YopB and YopD, were found to be inserted into liposomes. The proteoliposomes were fused to a planar lipid membrane to characterize the putative pore-forming properties of the lipid-bound Yops. Electrophysiological experiments revealed the presence of channels with a 105 pS conductance and no ionic selectivity. Channels with those properties were generated by mutants devoid of the effectors and by lcrG mutants, as well as by wild-type bacteria. In contrast, mutants devoid of YopB did not generate channels and mutants devoid of YopD led to current fluctuations that were different from those observed with wild-type bacteria. The observed channel could be responsible for the translocation of Yop effectors.

  1. Ultra-flat galaxies selected from RFGC catalog. III. Star formation rate

    NASA Astrophysics Data System (ADS)

    Melnyk, O. V.; Karachentseva, V. E.; Karachentsev, I. D.

    2017-01-01

    We examine the star formation properties of galaxies with very thin disks selected from the Revised FlatGalaxy Catalog (RFGC). The sample contains 333 ultra-flat galaxies (UFG) at high Galactic latitudes, |b| > 10°, with a blue major angular diameter of a ≥ 1.'2, blue and red apparent axial ratios of ( a/b)b > 10, ( a/b)r > 8.5 and radial velocities within 10 000 kms-1. As a control sample for them we use a population of 722 more thick RFGC galaxies with ( a/b)b > 7, situated in the same volume. The UFG distribution over the sky indicates them as a population of quite isolated galaxies.We found that the specific star formation rate, sSFR FUV, determined via the FUV GALEX flux, increases steadily from the early type to late type disks for both the UFG and RFGC-UFG samples, showing no significant mutual difference within each morphological type T. The population of UFG disks has the average HI-mass-to-stellarmass ratio by (0.25 ± 0.03) dex higher than that of RFGC-UFG galaxies. Being compared with arbitrary orientated disks of the same type, the ultra-flat edge-on galaxies reveal that their total HI mass is hidden by self-absorption on the average by approximately 0.20 dex.We demonstrate that using the robust stellar mass estimate via < B-K>-color and galaxy type T for the thin disks, together with a nowaday accounting for internal extinction, yields their sSFR quantities definitely lying below the limit of -9.4 dex (yr-1). The collected observational data on UFG disks imply that their average star formation rate in the past has been approximately three times the current SFR. The UFG galaxies have also sufficient amount of gas to support their observed SFR over the following nearly 9 Gyrs.

  2. Efficient quantum-classical method for computing thermal rate constant of recombination: application to ozone formation.

    PubMed

    Ivanov, Mikhail V; Babikov, Dmitri

    2012-05-14

    Efficient method is proposed for computing thermal rate constant of recombination reaction that proceeds according to the energy transfer mechanism, when an energized molecule is formed from reactants first, and is stabilized later by collision with quencher. The mixed quantum-classical theory for the collisional energy transfer and the ro-vibrational energy flow [M. Ivanov and D. Babikov, J. Chem. Phys. 134, 144107 (2011)] is employed to treat the dynamics of molecule + quencher collision. Efficiency is achieved by sampling simultaneously (i) the thermal collision energy, (ii) the impact parameter, and (iii) the incident direction of quencher, as well as (iv) the rotational state of energized molecule. This approach is applied to calculate third-order rate constant of the recombination reaction that forms the (16)O(18)O(16)O isotopomer of ozone. Comparison of the predicted rate vs. experimental result is presented.

  3. Ligand basicity and rigidity control formation of macrocyclic polyamino carboxylate complexes of gadolinium(III)

    SciTech Connect

    Kumar, K.; Tweedle, M.F. )

    1993-09-29

    The formation reaction rates of some macrocyclic polyamino carboxylate complexes of gadolinium, GdL (where L is DO3A = 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid, H[sub 3]L, HP-DO3A = 10-(hydroxyproyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid, H[sub 3]L, and DO3MA = (1R,4R,7R)-[alpha],[alpha][prime],[alpha][double prime]-trimethyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-triacetic acid, H[sub 3]L), have been measured at 25.0 [+-] 0.1 [degrees]C and at a constant ionic strength of 1.0 (NaCl) by an indicator method. The formation reactions are first order in the limiting reagent (ligand) and nearly independent of the excess reagent (gadolinium ion). A mechanism of the formation of the gadolinium complexes involves the formation of a precursor (intermediate) complex, Gd(*HL), in an equilibrium step followed by its deprotonation and reorganization to the final product in the rate-determining step. The stability constants (log K[sub Gd(*HL)]) of the intermediate have been determined from the kinetic data and the values are 8.9 (DO3A), 9.0(HP-DO3A), and 10.7 (DO3MA). The nature of the intermediate is proposed in which the metal is coordinated to oxygens and at least one nitrogen of the ligand. Deprotonation and reorganization of the intermediate are specific-base assisted. The second-order rate constants (k[sub OH], M[sup [minus]1]s[sup [minus]1]) for the reorganization of the intermediate, Gd(*HL) (L are given in the parentheses), are (2.1 [+-] 0.1) x 10[sup 7] (DO3A), (1.23 [+-] 0.04) x 10[sup 7] (HP-DO3A), and (7.2 [+-] 0.3) x 10[sup 4] (DO3MA), compared to the literature data (7.1 [+-] 1) x 10[sup 7] (NOTA) and (5.9 [+-] 0.2) x 10[sup 6] (DOTA). The specific-base assisted rate of reorganization of the intermediate, Gd(*HL), is correlated with the ligand strain energy and its first protonation constant.

  4. Human RNase P ribonucleoprotein is required for formation of initiation complexes of RNA polymerase III

    PubMed Central

    Serruya, Raphael; Orlovetskie, Natalie; Reiner, Robert; Dehtiar-Zilber, Yana; Wesolowski, Donna; Altman, Sidney; Jarrous, Nayef

    2015-01-01

    Human RNase P is implicated in transcription of small non-coding RNA genes by RNA polymerase III (Pol III), but the precise role of this ribonucleoprotein therein remains unknown. We here show that targeted destruction of HeLa nuclear RNase P inhibits transcription of 5S rRNA genes in whole cell extracts, if this precedes the stage of initiation complex formation. Biochemical purification analyses further reveal that this ribonucleoprotein is recruited to 5S rRNA genes as a part of proficient initiation complexes and the activity persists at reinitiation. Knockdown of RNase P abolishes the assembly of initiation complexes by preventing the formation of the initiation sub-complex of Pol III. Our results demonstrate that the structural intactness, but not the endoribonucleolytic activity per se, of RNase P is critical for the function of Pol III in cells and in extracts. PMID:25953854

  5. Fuel Efficient Strategies for Reducing Contrail Formations in United States Air Space

    NASA Technical Reports Server (NTRS)

    Sridhar, Banavar; Chen, Neil Y.; Ng, Hok K.

    2010-01-01

    This paper describes a class of strategies for reducing persistent contrail formation in the United States airspace. The primary objective is to minimize potential contrail formation regions by altering the aircraft's cruising altitude in a fuel-efficient way. The results show that the contrail formations can be reduced significantly without extra fuel consumption and without adversely affecting congestion in the airspace. The contrail formations can be further reduced by using extra fuel. For the day tested, the maximal reduction strategy has a 53% contrail reduction rate. The most fuel-efficient strategy has an 8% reduction rate with 2.86% less fuel-burnt compared to the maximal reduction strategy. Using a cost function which penalizes extra fuel consumed while maximizing the amount of contrail reduction provides a flexible way to trade off between contrail reduction and fuel consumption. It can achieve a 35% contrail reduction rate with only 0.23% extra fuel consumption. The proposed fuel-efficient contrail reduction strategy provides a solution to reduce aviation-induced environmental impact on a daily basis.

  6. Low-metallicity Star Formation and Pop III-II Transition

    NASA Astrophysics Data System (ADS)

    Omukai, Kazuyuki

    2010-10-01

    The first stars in the universe were typically very massive, but those near us are not. The metallicity in the star-forming gas is thought to have played a key role in this transition of characteristic stellar mass scale. By studying the evolution of low-metallicity star-forming clouds up to the formation of protostars by way of radiation hydrodynamics with spherical symmetry, we discuss their fragmentation mass scales. The critical metallicity for low-mass fragmentation is in the range of Zcr = 10-6-10-5Zsolar. Although the exact value is still unknown due to uncertain dust nature in the early universe, the small value of Zcr means that low-mass star formation begun just after the first episode of metal enrichment. We also evaluate the upper limit on the stellar mass by the stellar feedback. Owing to the higher density in the envelope and thus higher protostellar accretion rate, the upper limit of stellar mass increases toward lower matallicity.

  7. Transfection efficiency and transgene expression kinetics of mRNA delivered in naked and nanoparticle format.

    PubMed

    Phua, Kyle K L; Leong, Kam W; Nair, Smita K

    2013-03-28

    Transfection efficiencies and transgene expression kinetics of messenger RNA (mRNA), an emerging class of nucleic acid-based therapeutics, have been poorly characterized. In this study, we evaluated transfection efficiencies of mRNA delivered in naked and nanoparticle format in vitro and in vivo using GFP and luciferase as reporters. While mRNA nanoparticles transfect primary human and mouse dendritic cells (DCs) efficiently in vitro, naked mRNA could not produce any detectable gene product. The protein expression of nanoparticle-mediated transfection in vitro peaks rapidly within 5-7h and decays in a biphasic manner. In vivo, naked mRNA is more efficient than mRNA nanoparticles when administered subcutaneously. In contrast, mRNA nanoparticle performs better when administered intranasally and intravenously. Gene expression is most transient when delivered intravenously in nanoparticle format with an apparent half-life of 1.4h and lasts less than 24h, and most sustained when delivered in the naked format subcutaneously at the base of tail with an apparent half-life of 18h and persists for at least 6days. Notably, exponential decreases in protein expression are consistently observed post-delivery of mRNA in vivo regardless of the mode of delivery (naked or nanoparticle) or the site of administration. This study elucidates the performance of mRNA transfection and suggests a niche for mRNA therapeutics when predictable in vivo transgene expression kinetics is imperative.

  8. Formation and Function of the Manganese(IV)/Iron(III) Cofactor in Chlamydia trachomatis Ribonucleotide Reductase†

    PubMed Central

    Jiang, Wei; Yun, Danny; Saleh, Lana; Bollinger, J. Martin; Krebs, Carsten

    2009-01-01

    The β2 subunit of a class Ia or Ib ribonucleotide reductase (RNR) is activated when its carboxylate-bridged Fe2II/II cluster reacts with O2 to oxidize a nearby tyrosine (Y) residue to a stable radical (Y•). During turnover, the Y• in β2 is thought to reversibly oxidize a cysteine (C) in the α2 subunit to a thiyl radical (C•) by a long-distance (~35 Å) proton-coupled electron-transfer (PCET) step. The C• in α2 then initiates reduction of the 2' position of the ribonucleoside-5'-diphosphate substrate by abstracting the hydrogen atom from C3'. The class I RNR from Chlamydia trachomatis (Ct) is the prototype of a newly recognized subclass (Ic), which is characterized by the presence of a phenylalanine (F) residue at the site of β2 where the essential radical-harboring Y is normally found. We recently demonstrated that Ct RNR employs a heterobinuclear MnIV/FeIII cluster for radical initiation. In essence, the MnIV ion of the cluster functionally replaces the Y• of the conventional class I RNR. The Ct β2 protein also auto-activates by reaction of its reduced (MnII/FeII) metal cluster with O2. In this reaction, an unprecedented MnIV/FeIV intermediate accumulates almost stoichiometrically and decays by one-electron reduction of the FeIV site. This reduction is mediated by the near-surface residue, Y222, a residue with no functional counterpart in the well-studied conventional class I RNRs. In this review, we recount the discovery of the novel Mn/Fe redox cofactor in Ct RNR and summarize our current understanding of how it assembles and initiates nucleotide reduction. PMID:19061340

  9. On the Role of the ΩΓ Limit in the Formation of Population III Massive Stars

    NASA Astrophysics Data System (ADS)

    Lee, Hunchul; Yoon, Sung-Chul

    2016-04-01

    We explore the role of the modified Eddington limit due to rapid rotation (the so-called ΩΓ limit) in the formation of Population III stars. We performed one-dimensional stellar evolution simulations of zero-metallicity protostars accreting mass at a very high rate (\\dot{M}˜ {10}-3\\quad {M}⊙ \\quad {{yr}}-1) and dealt with stellar rotation as a separate post-process. The protostar would reach the Keplerian rotation very soon after the onset of mass accretion, but mass accretion would continue as stellar angular momentum is transferred outward to the accretion disk by viscous stress. The envelope of the protostar expands rapidly when the stellar mass reaches ~5-7 M⊙ and the Eddington factor increases sharply. This makes the protostar rotate critically at a rate that is significantly below the Keplerian value (i.e., the ΩΓ limit). The resultant positive gradient of the angular velocity in the boundary layer between the protostar and the Keplerian disk prohibits angular momentum transport from the star to the disk, and consequently further rapid mass accretion. This would prevent the protostar from growing significantly beyond 20-40 M⊙. Another important consequence of the ΩΓ limit is that the protostar can remain fairly compact (R ≲ 50 R⊙) and avoid a fluffy structure (R ≳ 500 R⊙) that is usually found with a very high rate of mass accretion. This effect would make the protostar less prone to binary interactions during the protostar phase. Although our analysis is based on Population III protostar models, this role of the ΩΓ limit would be universal in the formation process of massive stars, regardless of metallicity.

  10. Me-3,2-HOPO Complexes of Near Infra-Red (NIR) Emitting Lanthanides: Efficient Sensitization of Yb(III) and Nd(III) in Aqueous Solution

    SciTech Connect

    Moore, Evan G.; Xu, Jide; Dodani, Sheel; Jocher, Christoph; D'Aleo, Anthony; Seitz, Michael; Raymond, Kenneth

    2009-11-10

    The synthesis, X-ray structure, solution stability, and photophysical properties of several trivalent lanthanide complexes of Yb(III) and Nd(III) using both tetradentate and octadentate ligand design strategies and incorporating the 1-methyl-3-hydroxy-pyridin-2-one (Me-3,2-HOPO) chelate group are reported. Both the Yb(III) and Nd(III) complexes have emission bands in the Near Infra-Red (NIR) region, and this luminescence is retained in aqueous solution ({Phi}{sub tot}{sup Yb} {approx} 0.09-0.22%). Furthermore, the complexes demonstrate very high stability (pYb {approx} 18.8-21.9) in aqueous solution, making them good candidates for further development as probes for NIR imaging. Analysis of the low temperature (77 K) photophysical measurements for a model Gd(III) complex were used to gain an insight into the electronic structure, and were found to agree well with corresponding TD-DFT calculations at the B3LYP/6-311G{sup ++}(d,p) level of theory for a simplified model monovalent sodium complex.

  11. Me-3,2-HOPO Complexes of Near Infra-Red (NIR) Emitting Lanthanides: Efficient Sensitization of Yb(III) and Nd(III) in Aqueous Solution

    PubMed Central

    Moore, Evan G.; Xu, Jide; Dodani, Sheel C.; Jocher, Christoph J.; D'Aléo, Anthony; Seitz, Michael; Raymond, Kenneth N.

    2011-01-01

    The synthesis, X-ray structure, solution stability, and photophysical properties of several trivalent lanthanide complexes of Yb(III) and Nd(III) using both tetradentate and octadentate ligand design strategies and incorporating the 1-methyl-3-hydroxy-pyridin-2-one (Me-3,2-HOPO) chelate group are reported. Both the Yb(III) and Nd(III) complexes have emission bands in the Near Infra-Red (NIR) region, and this luminescence is retained in aqueous solution (ΦtotYb~0.09−0.22%). Furthermore, the complexes demonstrate very high stability (pYb ~ 18.8 – 21.9) in aqueous solution, making them good candidates for further development as probes for NIR imaging. Analysis of the low temperature (77 K) photophysical measurements for a model Gd(III) complex were used to gain an insight into the electronic structure, and were found to agree well with corresponding TD-DFT calculations at the B3LYP/6-311G++(d,p) level of theory for a simplified model monovalent sodium complex. PMID:20364838

  12. New III-V cell design approaches for very high efficiency. Annual subcontract report, 1 August 1991--31 July 1992

    SciTech Connect

    Lundstrom, M.S.; Melloch, M.R.; Lush, G.B.; Patkar, M.P.; Young, M.P.

    1993-04-01

    This report describes to examine new solar cell desip approaches for achieving very high conversion efficiencies. The program consists of two elements. The first centers on exploring new thin-film approaches specifically designed for M-III semiconductors. Substantial efficiency gains may be possible by employing light trapping techniques to confine the incident photons, as well as the photons emitted by radiative recombination. The thin-film approach is a promising route for achieving substantial performance improvements in the already high-efficiency, single-junction, III-V cell. The second element of the research involves exploring desip approaches for achieving high conversion efficiencies without requiring extremely high-quality material. This work has applications to multiple-junction cells, for which the selection of a component cell often involves a compromise between optimum band pp and optimum material quality. It could also be a benefit manufacturing environment by making the cell`s efficiency less dependent on materialquality.

  13. Kinetics and Mechanisms of Cr(VI) Formation via the Oxidation of Cr(III) Solid Phases by Chlorine in Drinking Water.

    PubMed

    Chebeir, Michelle; Liu, Haizhou

    2016-01-19

    Hexavalent chromium Cr(VI), typically existing as the oxyanion form of CrO4(2-), is being considered for more stringent drinking water standards by regulatory agencies. Cr(VI) can be inadvertently produced via the oxidation of trivalent chromium Cr(III) solids. This study investigated the kinetics and mechanisms of Cr(III) solids oxidation by chlorine in drinking water and associated Cr(VI) formation. Batch experiments were carried out with three Cr(III) solids of environmental relevance, i.e., chromium hydroxide Cr(OH)3(s), chromium oxide Cr2O3(s), and copper chromite Cu2Cr2O5(s). Impacts of water chemical parameters including pH (6.0-8.5) and bromide concentration (0-5 mg/L) were examined. Results showed that the rapid oxidation of Cr(III) solid phases by chlorine was accompanied by Cr(VI) formation and an unexpected production of dissolved oxygen. Analysis of reaction stoichiometry indicated the existence of Cr intermediate species that promoted the autocatalytic decay of chlorine. An increase in pH modestly enhanced Cr(VI) formation due to changes of reactive Cr(III) surface hydroxo species. Bromide, a trace chemical constituent in source waters, exhibited a catalytic effect on Cr(VI) formation due to an electron shuttle mechanism between Cr(III) and chlorine and the bypass of Cr intermediate formation. The kinetics data obtained from this study suggest that the oxidation of Cr(III) solids by chlorine in water distribution systems can contribute to Cr(VI) occurrence in tap water, especially in the presence of a trace level of bromide.

  14. Equilibrium and Formation/Dissociation Kinetics of some Lanthanide(III)-PCTA complexes

    PubMed Central

    Tircsó, Gyula; Kovács, Zoltán; Sherry, A. Dean

    2008-01-01

    The protonation constants (KiH) of 3,6,9,15-tetraazabicyclo[9.3.1]pentadeca-1(15),11,13-triene-3,6,9,-triacetic acid (PCTA) and stability constants of complexes formed between this pyridine containing macrocycle and several different metal ions have been determined in 1.0 M KCl, 25°C and compared to previous literature values. The first protonation constant was found to be 0.5-0.6 log units higher than the value reported previously and a total five protonation steps were detected (log KiH = 11.36, 7.35, 3.83, 2.12 and 1.29). The stability constants of complexes formed between PCTA and Mg2+, Ca2+, Cu2+ and Zn2+ were also somewhat higher than those previously reported but this difference could be largely attributed to the higher first protonation constant of the ligand. Stability constants of complexes formed between PCTA and the Ln3+ series of ions and Y3+ were determined by using an “out-of-cell” potentiometric method. These values ranged from log K = 18.15 for Ce(PCTA) to log K = 20.63 for Yb(PCTA), increasing along the lanthanide series in proportion to decreasing Ln3+ cation size. The rates of complex formation for Ce(PCTA), Eu(PCTA), Y(PCTA) and Yb(PCTA) were followed by conventional UV-VIS spectroscopy in the pH range pH=3.5 - 4.4. First order rate constants (saturation kinetics) obtained for different ligand / metal ion ratios were consistent with rapid formation of a diprotonated intermediate, Ln(H2PCTA)2+. The stabilities of the intermediates as determined from the kinetic data were 2.81, 3.12, 2.97 and 2.69 log K units for Ce(H2PCTA), Eu(H2PCTA), Y(H2PCTA) and Yb(H2PCTA), respectively. Rearrangement of these intermediates to the fully chelated complexes was the rate determining step and the rate constant (kr) for this process was found to be inversely proportional to the proton concentration. The formation rates (kOH) increased with a decrease in lanthanide ion size (9.68×107 M-1s-1, 1.74×108 M-1s-1, 1.13×108 M-1s-1 and 1.11×109 M-1s-1 for Ce

  15. Semiconductor structural damage attendant to contact formation in III-V solar cells

    NASA Technical Reports Server (NTRS)

    Fatemi, Navid S.; Weizer, Victor G.

    1991-01-01

    In order to keep the resistive losses in solar cells to a minimum, it is often necessary for the ohmic contacts to be heat treated to lower the metal-semiconductor contact resistivity to acceptable values. Sintering of the contacts, however can result in extensive mechanical damage of the semiconductor surface under the metallization. An investigation of the detailed mechanisms involved in the process of contact formation during heat treatment may control the structural damage incurred by the semiconductor surface to acceptable levels, while achieving the desired values of contact resistivity for the ohmic contacts. The reaction kinetics of sintered gold contacts to InP were determined. It was found that the Au-InP interaction involves three consecutive stages marked by distinct color changes observed on the surface of the Au, and that each stage is governed by a different mechanism. A detailed description of these mechanisms and options to control them are presented.

  16. Catalysts on the basis of activated aluminum alloys: III. Formation of oxide alumina catalysts

    SciTech Connect

    Yakerson, V.I.; Dykh, Zh.L.; Subbotin, A.N.

    1995-11-01

    The formation of the bulk and surface of a new generation of oxide alumina catalysts is studied by XRD, thermal analysis, adsorption, and IR spectroscopy. The oxide alumina catalysts exhibit a developed surface area (up to 320 m{sup 2}/g) and diverse porous structures. Three types of non-associated OH groups, characterized by the different number of adjacent Al atoms, as well as OH groups with a strong hydrogen bond are found at the surface. Lewis, but not Br6ensted, acidic properties (revealed by pyridine adsorption) are inherent to the catalyst surface. The number of Lewis acid sites increases from 1.0 to 2.2 {mu}mol/m{sup 2} with an increasing concentration of activating agents from 2 to 20 wt %.

  17. Equilibrium and formation/dissociation kinetics of some Ln(III)PCTA complexes.

    PubMed

    Tircsó, Gyula; Kovacs, Zoltan; Sherry, A Dean

    2006-11-13

    The protonation constants () of 3,6,9,15-tetraazabicyclo[9.3.1]pentadeca-1(15),11,13-triene-3,6,9-triacetic acid (PCTA) and stability constants of complexes formed between this pyridine-containing macrocycle and several different metal ions have been determined in 1.0 M KCl at 25 degrees C and compared to previous literature values. The first protonation constant was found to be 0.5-0.6 log units higher than the value reported previously, and a total of five protonation steps were detected (log = 11.36, 7.35, 3.83, 2.12, and 1.29). The stability constants of complexes formed between PCTA and Mg2+, Ca2+, Cu2+, and Zn2+ were also somewhat higher than those previously reported, but this difference could be largely attributed to the higher first protonation constant of the ligand. Stability constants of complexes formed between PCTA and the Ln3+ series of ions and Y3+ were determined by using an "out-of-cell" potentiometric method. These values ranged from log K = 18.15 for Ce(PCTA) to log K = 20.63 for Yb(PCTA), increasing along the Ln series in proportion to decreasing Ln3+ cation size. The rates of complex formation for Ce(PCTA), Eu(PCTA), Y(PCTA), and Yb(PCTA) were followed by conventional UV-vis spectroscopy in the pH range 3.5-4.4. First-order rate constants (saturation kinetics) obtained for different ligand-to-metal ion ratios were consistent with the rapid formation of a diprotonated intermediate, Ln(H(2)PCTA)(2+). The stabilities of the intermediates as determined from the kinetic data were 2.81, 3.12, 2.97, and 2.69 log K units for Ce(H(2)PCTA), Eu(H(2)PCTA), Y(H(2)PCTA), and Yb(H(2)PCTA), respectively. Rearrangement of these intermediates to the fully chelated complexes was the rate-determining step, and the rate constant (k(r)) for this process was found to be inversely proportional to the proton concentration. The formation rates (k(OH)) increased with a decrease in the lanthanide ion size [9.68 x 10(7), 1.74 x 10(8), 1.13 x 10(8), and 1.11 x 10(9) M(-1

  18. The SILCC project - III. Regulation of star formation and outflows by stellar winds and supernovae

    NASA Astrophysics Data System (ADS)

    Gatto, Andrea; Walch, Stefanie; Naab, Thorsten; Girichidis, Philipp; Wünsch, Richard; Glover, Simon C. O.; Klessen, Ralf S.; Clark, Paul C.; Peters, Thomas; Derigs, Dominik; Baczynski, Christian; Puls, Joachim

    2017-04-01

    We study the impact of stellar winds and supernovae on the multiphase interstellar medium using three-dimensional hydrodynamical simulations carried out with FLASH. The selected galactic disc region has a size of (500 pc)2 × ±5 kpc and a gas surface density of 10 M⊙ pc-2. The simulations include an external stellar potential and gas self-gravity, radiative cooling and diffuse heating, sink particles representing star clusters, stellar winds from these clusters that combine the winds from individual massive stars by following their evolution tracks, and subsequent supernova explosions. Dust and gas (self-) shielding is followed to compute the chemical state of the gas with a chemical network. We find that stellar winds can regulate star (cluster) formation. Since the winds suppress the accretion of fresh gas soon after the cluster has formed, they lead to clusters that have lower average masses (102-104.3 M⊙) and form on shorter time-scales (10-3-10 Myr). In particular, we find an anticorrelation of cluster mass and accretion time-scale. Without winds, the star clusters easily grow to larger masses for ∼5 Myr until the first supernova explodes. Overall, the most massive stars provide the most wind energy input, while objects beginning their evolution as B-type stars contribute most of the supernova energy input. A significant outflow from the disc (mass loading ≳1 at 1 kpc) can be launched by thermal gas pressure if more than 50 per cent of the volume near the disc mid-plane can be heated to T > 3 × 105 K. Stellar winds alone cannot create a hot volume-filling phase. The models that are in best agreement with observed star formation rates drive either no outflows or weak outflows.

  19. ANALYTICAL THEORY FOR THE INITIAL MASS FUNCTION. III. TIME DEPENDENCE AND STAR FORMATION RATE

    SciTech Connect

    Hennebelle, Patrick

    2013-06-20

    The present paper extends our previous theory of the stellar initial mass function (IMF) by including time dependence and by including the impact of the magnetic field. The predicted mass spectra are similar to the time-independent ones with slightly shallower slopes at large masses and peak locations shifted toward smaller masses by a factor of a few. Assuming that star-forming clumps follow Larson-type relations, we obtain core mass functions in good agreement with the observationally derived IMF, in particular, when taking into account the thermodynamics of the gas. The time-dependent theory directly yields an analytical expression for the star formation rate (SFR) at cloud scales. The SFR values agree well with the observational determinations of various Galactic molecular clouds. Furthermore, we show that the SFR does not simply depend linearly on density, as is sometimes claimed in the literature, but also depends strongly on the clump mass/size, which yields the observed scatter. We stress, however, that any SFR theory depends, explicitly or implicitly, on very uncertain assumptions like clump boundaries or the mass of the most massive stars that can form in a given clump, making the final determinations uncertain by a factor of a few. Finally, we derive a fully time dependent model for the IMF by considering a clump, or a distribution of clumps accreting at a constant rate and thus whose physical properties evolve with time. In spite of its simplicity, this model reproduces reasonably well various features observed in numerical simulations of converging flows. Based on this general theory, we present a paradigm for star formation and the IMF.

  20. HERSCHEL EXPLOITATION OF LOCAL GALAXY ANDROMEDA (HELGA). III. THE STAR FORMATION LAW IN M31

    SciTech Connect

    Ford, George P.; Gear, Walter K.; Smith, Matthew W. L.; Eales, Steve A.; Gomez, Haley L.; Kirk, Jason; Baes, Maarten; De Looze, Ilse; Fritz, Jacopo; Gentile, Gianfranco; Gordon, Karl D.; Verstappen, Joris; Bendo, George J.; Boquien, Mederic; Boselli, Alessandro; Cooray, Asantha R.; Lebouteiller, Vianney; O'Halloran, Brian; Spinoglio, Luigi; Wilson, Christine D.

    2013-05-20

    We present a detailed study of how the star formation rate (SFR) relates to the interstellar medium (ISM) of M31 at {approx}140 pc scales. The SFR is calculated using the far-ultraviolet and 24 {mu}m emission, corrected for the old stellar population in M31. We find a global value for the SFR of 0.25{sup +0.06}{sub -0.04} M{sub sun} yr{sup -1} and compare this with the SFR found using the total far-infrared luminosity. There is general agreement in regions where young stars dominate the dust heating. Atomic hydrogen (H I) and molecular gas (traced by carbon monoxide, CO) or the dust mass is used to trace the total gas in the ISM. We show that the global surface densities of SFR and gas mass place M31 among a set of low-SFR galaxies in the plot of Kennicutt. The relationship between SFR and gas surface density is tested in six radial annuli across M31, assuming a power law relationship with index, N. The star formation (SF) law using total gas traced by H I and CO gives a global index of N = 2.03 {+-} 0.04, with a significant variation with radius; the highest values are observed in the 10 kpc ring. We suggest that this slope is due to H I turning molecular at {Sigma}{sub Gas} {approx} 10 M{sub Sun} pc{sup -2}. When looking at H{sub 2} regions, we measure a higher mean SFR suggesting a better spatial correlation between H{sub 2} and SF. We find N {approx} 0.6 with consistent results throughout the disk-this is at the low end of values found in previous work and argues against a superlinear SF law on small scales.

  1. Herschel Exploitation of Local Galaxy Andromeda (HELGA). III. The Star Formation Law in M31

    NASA Astrophysics Data System (ADS)

    Ford, George P.; Gear, Walter K.; Smith, Matthew W. L.; Eales, Steve A.; Baes, Maarten; Bendo, George J.; Boquien, Médéric; Boselli, Alessandro; Cooray, Asantha R.; De Looze, Ilse; Fritz, Jacopo; Gentile, Gianfranco; Gomez, Haley L.; Gordon, Karl D.; Kirk, Jason; Lebouteiller, Vianney; O'Halloran, Brian; Spinoglio, Luigi; Verstappen, Joris; Wilson, Christine D.

    2013-05-01

    We present a detailed study of how the star formation rate (SFR) relates to the interstellar medium (ISM) of M31 at ~140 pc scales. The SFR is calculated using the far-ultraviolet and 24 μm emission, corrected for the old stellar population in M31. We find a global value for the SFR of 0.25^{+0.06}_{-0.04}\\,M_{\\odot }\\,yr^{-1} and compare this with the SFR found using the total far-infrared luminosity. There is general agreement in regions where young stars dominate the dust heating. Atomic hydrogen (H I) and molecular gas (traced by carbon monoxide, CO) or the dust mass is used to trace the total gas in the ISM. We show that the global surface densities of SFR and gas mass place M31 among a set of low-SFR galaxies in the plot of Kennicutt. The relationship between SFR and gas surface density is tested in six radial annuli across M31, assuming a power law relationship with index, N. The star formation (SF) law using total gas traced by H I and CO gives a global index of N = 2.03 ± 0.04, with a significant variation with radius; the highest values are observed in the 10 kpc ring. We suggest that this slope is due to H I turning molecular at ΣGas ~ 10 M ⊙ pc-2. When looking at H2 regions, we measure a higher mean SFR suggesting a better spatial correlation between H2 and SF. We find N ~ 0.6 with consistent results throughout the disk—this is at the low end of values found in previous work and argues against a superlinear SF law on small scales. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  2. Galaxy formation in the Planck cosmology - III. The high-redshift universe

    NASA Astrophysics Data System (ADS)

    Clay, Scott J.; Thomas, Peter A.; Wilkins, Stephen M.; Henriques, Bruno M. B.

    2015-08-01

    We present high-redshift predictions of the star formation rate distribution function (SFRDF), UV luminosity function (UVLF), galactic stellar mass function (GSMF), and specific star formation rates (sSFRs) of galaxies from the latest version of the Munich semi-analytic model L-GALAXIES. We find a good fit to both the shape and normalization of the SFRDF at z = 4-7, apart from a slight underprediction at the low-SFR end at z = 4. Likewise, we find a good fit to the faint number counts for the observed UVLF at brighter magnitudes our predictions lie below the observations, increasingly so at higher redshifts. At all redshifts and magnitudes, the raw (unattenuated) number counts for the UVLF lie above the observations. Because of the good agreement with the SFR we interpret our underprediction as an overestimate of the amount of dust in the model for the brightest galaxies, especially at high redshift. While the shape of our GSMF matches that of the observations, we lie between (conflicting) observations at z = 4-5, and underpredict at z = 6-7. The sSFRs of our model galaxies show the observed trend of increasing normalization with redshift, but do not reproduce the observed mass dependence. Overall, we conclude that the latest version of L-GALAXIES, which is tuned to match observations at z ≤ 3, does a fair job of reproducing the observed properties of galaxies at z ≥ 4. More work needs to be done on understanding observational bias at high redshift, and upon the dust model, before strong conclusions can be drawn on how to interpret remaining discrepancies between the model and observations.

  3. Impact of Protostellar Outflows on Turbulence and Star Formation Efficiency in Magnetized Dense Cores

    NASA Astrophysics Data System (ADS)

    Offner, Stella S. R.; Chaban, Jonah

    2017-10-01

    The star-forming efficiency of dense gas is thought to be set within cores by outflow and radiative feedback. We use magnetohydrodynamic simulations to investigate the relation between protostellar outflow evolution, turbulence, and star formation efficiency. We model the collapse and evolution of isolated dense cores for ≳0.5 Myr including the effects of turbulence, radiation transfer, and both radiation and outflow feedback from forming protostars. We show that outflows drive and maintain turbulence in the core environment even with strong initial fields. The star formation efficiency decreases with increasing field strength, and the final efficiencies are 15%–40%. The Stage 0 lifetime, during which the protostellar mass is lower than that of the dense envelope, increases proportionally with the initial magnetic field strength and ranges from ∼ 0.1 {to} 0.4 {Myr}. The average accretion rate is well represented by a tapered turbulent core model, which is a function of the final protostellar mass and is independent of the magnetic field strength. By tagging material launched in the outflow, we demonstrate that the outflow entrains about three times the actual launched gas mass, a ratio that remains roughly constant in time regardless of the initial magnetic field strength. However, turbulent driving increases for stronger fields since momentum is more efficiently imparted to non-outflow material. The protostellar outflow momentum is highest during the first 0.1 Myr and declines thereafter by a factor of ≳ 10 as the accretion rate diminishes.

  4. Ytterbium(III) porpholactones: β-lactonization of porphyrin ligands enhances sensitization efficiency of lanthanide near-infrared luminescence.

    PubMed

    Ke, Xian-Sheng; Yang, Bo-Yan; Cheng, Xin; Chan, Sharon Lai-Fung; Zhang, Jun-Long

    2014-04-07

    The near-infrared (NIR) luminescence efficiency of lanthanide complexes is largely dependent on the electronic and photophysical properties of antenna ligands. Although porphyrin ligands are efficient sensitizers of lanthanide NIR luminescence, non-pyrrolic porphyrin analogues, which have unusual symmetry and electronic states, have been much less studied. In this work, we used porpholactones, a class of β-pyrrolic-modified porphyrins, as ligands and investigated the photophysical properties of lanthanide porpholactones Yb-1 a-5 a. Compared with Yb porphyrin complexes, the porpholactone complexes displayed remarkable enhancement of NIR emission (50-120 %). Estimating the triplet-state levels of porphyrin and porpholactone in Gd complexes revealed that β-lactonization of porphyrinic ligands lowers the ligand T1 state and results in a narrow energy gap between this state and the lowest excited state of Yb(3+) . Transient absorption spectra showed that Yb(III) porpholactone has a longer transient decay lifetime at the Soret band than the porphyrin analogue (30.8 versus 17.0 μs). Thus, the narrower energy gap and longer lifetime arising from β-lactonization are assumed to enhance NIR emission of Yb porpholactones. To demonstrate the potential applications of Yb porpholactone, a water-soluble Yb bioprobe was constructed by conjugating glucose to Yb-1 a. Interestingly, the NIR emission of this Yb porpholactone could be specifically switched on in the presence of glucose oxidase and then switched off by addition of glucose. This is the first demonstration that non-pyrrolic porphyrin ligands enhance the sensitization efficiency of lanthanide luminescence and also display switchable NIR emission in the region of biological analytes (800-1400 nm).

  5. Fe(II) sorption on pyrophyllite: Effect of structural Fe(III) (impurity) in pyrophyllite on nature of layered double hydroxide (LDH) secondary mineral formation

    SciTech Connect

    Starcher, Autumn N.; Li, Wei; Kukkadapu, Ravi K.; Elzinga, Evert J.; Sparks, Donald L.

    2016-11-01

    Fe(II)-Al(III)-LDH (layered double hydroxide) phases have been shown to form from reactions of aqueous Fe(II) with Fe-free Al-bearing minerals (phyllosilicate/clays and Al-oxides). To our knowledge, the effect of small amounts of structural Fe(III) impurities in “neutral” clays on such reactions, however, were not studied. In this study to understand the role of structural Fe(III) impurity in clays, laboratory batch studies with pyrophyllite (10 g/L), an Al-bearing phyllosilicate, containing small amounts of structural Fe(III) impurities and 0.8 mM and 3 mM Fe(II) (both natural and enriched in 57Fe) were carried out at pH 7.5 under anaerobic conditions (4% H2 – 96% N2 atmosphere). Samples were taken up to 4 weeks for analysis by Fe-X-ray absorption spectroscopy and 57Fe Mössbauer spectroscopy. In addition to the precipitation of Fe(II)-Al(III)-LDH phases as observed in earlier studies with pure minerals (no Fe(III) impurities in the minerals), the analyses indicated formation of small amounts of Fe(III) containing solid(s), most probably hybrid a Fe(II)-Al(III)/Fe(III)-LDH phase. The mechanism of Fe(II) oxidation was not apparent but most likely was due to interfacial electron transfer from the sorbed Fe(II) to the structural Fe(III) and/or surface-sorption-induced electron-transfer from the sorbed Fe(II) to the clay lattice. Increase in the Fe(II)/Al ratio of the LDH with reaction time further indicated the complex nature of the samples. This research provides evidence for the formation of both Fe(II)-Al(III)-LDH and Fe(II)-Fe(III)/Al(III)-LDH-like phases during reactions of Fe(II) in systems that mimic the natural environments. Better understanding Fe phase formation in complex laboratory studies will improve models of natural redox systems.

  6. Comparative analysis of pixel resolution of standard digital imaging formats to Generation III image intensifiers based on nighttime man-size target recognition

    NASA Astrophysics Data System (ADS)

    Estrera, Joseph P.

    2009-05-01

    This paper presents a comparative analysis of pixel resolution of standard digital imaging formats to the imaging output of a Generation III image intensifier. The comparative analysis will focus on the application of recognition of a man size target at a specified distance in nighttime (starlight conditions) utilizing a 1X night vision system with 40° field of view (FOV). Simple geometric theory will be applied to determine image intensified pixel format, digital imaging formats, and man size target pixel coverage for respective imaging pixel format. Daylight and night time experiments are described in detail using the several digital CCD formats (640×480, 1280×1024, and 2615×1471) through a standard Generation III image intensifier (64 lp/mm) in a night vision monocular system (AN/PVS-14). Detailed image analysis is conducted and presented on experimental data. Paper has been cleared by DOD/OSR for Public Release under Ref: 05-S-0347 on December 13, 2004.

  7. The Mechanical Properties of III-V Compound Semiconductors Used in High Efficiency Multijunction Photovoltaic Cells

    NASA Astrophysics Data System (ADS)

    Zakaria, Abdallah

    Lattice-mismatched heteroepitaxy enables the fabrication of metamorphic solar cells that have reached record light conversion efficiencies in the last five years. These devices are accelerating the commercialization of concentrator photovoltaics that can compete with fossil fuels for terrestrial energy production. A critical part of metamorphic structures is the graded buffer layer (GBL) needed to progressively change the lattice constant of the substrate to that the epilayer of interest. The effectiveness of the graded buffer layer in relieving misfit strain affects the quality of the device grown and depends on a variety of parameters. This study focuses on the mechanical properties of semiconductor compounds used in graded buffer layers. First, the effect of compound semiconductor spontaneous atomic ordering on hardness is assessed. In1--xGaxP was deposited on Ge wafers in two structures. A surfactant was used in experiment A to induce a lower degree of order. High resolution x-ray diffraction (HRXRD) estimated a theoretical band gap energy Eg corrected for strain effects. Photoluminescence measured the actual Eg. By comparing the two, the degree of order eta was determined to be 0.12-0.15 for samples A and 0.43-0.44 for samples B. Atomic force microscopy (AFM) demonstrated that all wafers had an equivalent surface roughness of 6.1-7.4 A. Nanoindentation measurements determined that the degree of order has no effect on the hardness of InGaP. Using 1/2 (115) superlattice reflection scans, the InGaP ordered domains size was estimated to be 28.5 nm for sample B1. No superlattice peak was detected in sample A1. The large ordered domain size in B1 explains why no order-hardening behavior was observed in InGaP. Second, a correlation between the composition of a ternary compound semiconductor and hardness is established and the effect of oxidation is determined. A structure consisting of three different AlxGa1--xAs layers separated by In0.01Ga0.99As etch stops was

  8. A synthetic peptide from the heparin-binding domain III (repeats III4-5) of fibronectin promotes stress-fibre and focal-adhesion formation in melanoma cells.

    PubMed Central

    Moyano, José V; Maqueda, Alfredo; Albar, Juan P; Garcia-Pardo, Angeles

    2003-01-01

    Cell adhesion to fibronectin results in formation of actin stress fibres and focal adhesions. In fibroblasts, this response requires two co-operative signals provided by interactions of the RGD sequence with alpha5beta1 integrin and the heparin-binding domain II (Hep II) domain with syndecan-4. Within Hep II, this activity was mapped to repeat III13 and to the peptide FN-C/H-V(WQPPRARITGY, repeat III14). We previously described that the synthetic heparin-binding peptide/III5 (HBP/III5) (WTPPRAQITGYRLTVGLTRR, repeat III5) binds heparin and mediates cell adhesion via chondroitin sulphate proteoglycans. We have now studied whether HBP/III5 co-operates with alpha5beta1 and drives a full cytoskeletal response in melanoma cells. SKMEL-178 cells attached and spread on the RGD-containing FNIII7-FNIII10 (FNIII7-10) fragment, but did not form stress fibres or focal adhesions. Co-immobilization of HBP/III5 with FNIII7-10 or adding soluble HBP/III5 to cells prespread on FNIII7-10, effectively induced these structures. Cell transfection with dominant-negative N19RhoA, a member of the small GTPase family, abolished the HBP/III5 effect. Both chondroitinase and heparitinase diminished focal adhesions, indicating that both types of proteoglycans bound HBP/III5 in melanoma cells. We have mapped the active sequence of HBP/III5 to YRLTVGLTRR, which is a novel sequence in fibronectin with focal-adhesion-promoting activity. The last two arginine (R) residues of this sequence are required for activity, since their replacement by alanine completely abrogated the HBP/III5 cytoskeletal effect. Moreover, this sequence is also active in the context of large fibronectin fragments. Our results establish that the Hep III region provides co-operative signals to alpha5beta1 for the progression of the cytoskeletal response and that these include activation of RhoA. PMID:12519080

  9. A new combined process for efficient removal of Cu(II) organic complexes from wastewater: Fe(III) displacement/UV degradation/alkaline precipitation.

    PubMed

    Xu, Zhe; Gao, Guandao; Pan, Bingcai; Zhang, Weiming; Lv, Lu

    2015-12-15

    Efficient removal of heavy metals complexed with organic ligands from water is still an important but challenging task now. Herein, a novel combined process, i.e., Fe(III)-displacement/UV degradation/alkaline precipitation (abbreviated as Fe(III)/UV/OH) was developed to remove copper-organic complexes from synthetic solution and real electroplating effluent, and other processes including alkaline precipitation, Fe(III)/OH, UV/OH were employed for comparison. By using the Fe(III)/UV/OH process, some typical Cu(II) complexes, such as Cu(II)-ethylenediaminetetraacetic acid (EDTA), Cu(II)-nitrilotriacetic acid (NTA), Cu(II)-citrate, Cu(II)-tartrate, and Cu(II)-sorbate, each at 19.2 mg Cu/L initially, were efficiently removed from synthetic solution with the residual Cu below 1 mg/L. Simultaneously, 30-48% of total organic carbon was eliminated with exception of Cu(II)-sorbate. Comparatively, the efficiency of other processes was much lower than the Fe(III)/UV/OH process. With Cu(II)-citrate as the model complex, the optimal conditions for the combined process were obtained as: initial pH for Fe(III) displacement, 1.8-5.4; molar ratio of [Fe]/[Cu], 4:1; UV irradiation, 10 min; precipitation pH, 6.6-13. The mechanism responsible for the process involved the liberation of Cu(II) ions from organic complexes as a result of Fe(III) displacement, decarboxylation of Fe(III)-ligand complexes subjected to UV irradiation, and final coprecipitation of Cu(II) and Fe(II)/Fe(III) ions. Up to 338.1 mg/L of Cu(II) in the electroplating effluent could be efficiently removed by the process with the residual Cu(II) below 1 mg/L and the removal efficiency of ∼99.8%, whereas direct precipitation by using NaOH could only result in total Cu(II) removal of ∼8.6%. In addition, sunlight could take the place of UV to achieve similar removal efficiency with longer irradiation time (90 min).

  10. In situ gelation of Al(III)-4-tert-butylpyridine based metal-organic gel electrolyte for efficient quasi-solid-state dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Dong, Yu-Jie; Rao, Hua-Shang; Cao, Yang; Chen, Hong-Yan; Kuang, Dai-Bin; Su, Cheng-Yong

    2017-03-01

    A novel Al(III)-4-tert-butylpyridine (TBP) gel electrolyte is successfully achieved by a simple and facile in situ gelation method and applied as quasi-solid-state electrolyte for dye-sensitized solar cells (DSSCs). Through directly adding Al3+ into the TBP solution, the induced hydrolysis of Al3+ and the coordination interaction between Al3+ and TBP facilitates the formation of metal-organic gels(MOGs), in which such bi-functional TBP molecules will act as both gelators and active additives to tailor the performance of electrolytes. In addition, the gel electrolytes can largely preserve the properties of liquid electrolyte and penetrate well into the TiO2 photoanode film. Both Al3+ and TBP in the gel electrolytes affect the performance of cells. The Jsc of gel electrolytes decrease with the increasing concentration of gelators due to the enhanced strength and viscosity of the gel electrolytes, while the competition between Al3+ and TBP causes conduction band edge shift and electron recombination, leading to a variation of Voc. Herein, by tuning the molar ratio of Al3+/TBP, an impressive conversion efficiency of 8.25% is obtained, indicating a promising protocol of preparing MOGs not only to achieve high performance in solar cells, but also opens up extended scopes in other energy-related fields such as catalysis.

  11. Ozone process insights from field experiments - Part III: extent of reaction and ozone formation

    NASA Astrophysics Data System (ADS)

    Blanchard, Charles L.

    The analysis of ambient data offers a means of developing a qualitative understanding of the sensitivity of ozone formation at specific times and places to changes in VOC and NO x concentrations. The Integrated Empirical Rate (IER) model (Johnson, 1984, Proceedings of the Eighth International Clean Air Conference, Melbourne, Australia, pp. 715-731) and two revisions known as the Smog Production (SP) algorithm (Blanchard et al., 1999, Atmospheric Environment 33, 369-381; Chang et al., 1997, Atmospheric Environment 31, 2787-2794) are reviewed. Applied to ambient data, the algorithm requires measurements of ozone, NO, and either NO x or NO y and computes a quantity known as the extent of reaction. The extent of reaction is shown to be related to photochemical age and serves as an indicator of the sensitivity of instantaneous ozone production to changes in VOC or NO x concentrations. Extent of reaction alone is insufficient as an indicator of the sensitivity of ozone concentration to a complex upwind history of emission changes. Consideration of daily, hourly, and spatial patterns of extent of reaction is needed to interpret applications of the SP algorithm.

  12. Geosynthesis of organic compounds: III. Formation of alkyltoluenes and alkylxylenes in sediments

    NASA Astrophysics Data System (ADS)

    Ellis, Leroy; Singh, Raj K.; Alexander, Robert; Kagi, Robert I.

    1995-12-01

    Heating ortho-undecyltoluene with an acidic clay catalyst and hexamethylbenzene as a methylating agent resulted in the formation of hydrocarbon mixtures containing undecyltoluenes and dimethylundecylbenzenes. At short heating times, methylation at ring positions 4 and 5 forming 2,4- and 2,5-dimethylundecylbenzenes occurred predominantly, while at longer heating times, methylation and isomerization/transalkylation reactions resulted in higher concentrations of more stable alkylxylene isomers. The distributions of undecyltoluenes and dimethylundecylbenzenes in two mature crude oils were also compared to those formed in the laboratory heating experiments. One crude oil derived from carbonate sediments was shown to have a predominance of ortho-undecyltoluene and 2,4- and 2,5-dimethylundecylbenzenes, similar to the reaction products formed from short-term laboratory heating experiments. The other crude oil, derived from clastic sediments containing abundant clays, was shown to contain a mixture of the undecyltoluenes and dimethylundecylbenzenes similar to the reaction products generated from longer-term heating experiments. These observations suggest that alkylxylenes in crude oils result from sedimentary methylation of ortho-alkyltoluenes, as the ortho-alkyltoluenes isomers are often the most abundant isomers in low maturity sediments. The initial products formed under kinetic control then undergo clay-catalyzed isomerization/transalkylation reactions to yield mixtures with higher abundances of the more thermodynamically stable isomers.

  13. Stratigraphic sections of the Phosphoria formation in Idaho, 1947-48, Part III

    USGS Publications Warehouse

    O'Malley, F.W.; Davidson, D.F.; Hoppin, R.A.; Sheldon, R.P.

    1951-01-01

    .The U.S. Geological Survey has measured and sampled the Phosphoria formation at many localities in Idaho and other western states. These data will not be fully synthesized and analyzed for several years but segments of the data, accompanied by little or no interpretation, are published as preliminary reports as they are assembled. This report, which contains abstracts of many of the sections in southeastern Idaho (fig. 1), is one of this series and is the third report of data gathered in Idaho during 1947 and 1948. The field and laboratory procedures adopted in these investigations are described rather fully in a companion report (McKelvey and others, 1953). Many people have taken part in this investigation, which was organized and supervised by V. E. McKelvey. D. A. Bostwick, R. M. Campbell, R. A. Gulbrandsen, R. A. Harris, R. L. Parker, R. A. Smart, J. E. Smedley, R. H. Thurston, and R. G. Waring participated in the description of strata and collection of samples referred to in this report. D. B. Dimick, Jack George, W. S. Hunziker, J. E. Jones, H. A. Larsen, and T. K. Rigby assisted in the preparation of trenches and collection, crushing, and splitting of samples in the field. The laboratory preparation of samples for chemical analysis was done in Denver, Colo., under the direction of W. P. Huleatt.

  14. The effect of cerium (III) on the chlorophyll formation in spinach.

    PubMed

    Fashui, Hong; Ling, Wang; Xiangxuan, Meng; Zheng, Wei; Guiwen, Zhao

    2002-12-01

    The effect of Ce(3+) on the chlorophyll (chl) of spinach was studied in pot culture experiments. The results showed that Ce(3+) could obviously stimulate the growth of spinach and increase its chlorophyll contents and photosynthetic rate. It could also improve the PSII formation and enhance its electron transport rate of PSII as well. By inductively coupled plasma-mass spectroscopy and atom absorption spectroscopy methods, it was revealed that the rare-earth-element (REE) distribution pattern in the Ce(3+)-treated spinach was leaf > root > shoot in Ce(3+) contents. The spinach leaves easily absorbed REEs. The Ce(3+) contents of chloroplast and chlorophyll of the Ce(3+)-treated spinach were higher than that of any other rare earth and were much higher than that of the control; it was also suggested that Ce(3+) could enter the chloroplast and bind easily to chlorophyll and might replace magnesium to form Ce-chlorophyll. By ultraviolet-visible, Fourier transform infrared, and extended X-ray absorption fine structure (EXAFS) methods, Ce(3+)-coordinated nitrogen of porphyrin rings with eight coordination numbers and average length of the Ce-N bond of 0.251 nm.

  15. Layered double hydroxide stability. 2. Formation of Cr(III)-containing layered double hydroxides directly from solution

    NASA Technical Reports Server (NTRS)

    Boclair, J. W.; Braterman, P. S.; Jiang, J.; Lou, S.; Yarberry, F.

    1999-01-01

    Solutions containing divalent metal [M(II) = Mg2+, Zn2+, Co2+, Ni2+, Mn2+] chlorides and CrCl3 6H2O were titrated with NaOH to yield, for M(II) = Zn, Co, and Ni, hydrotalcite-like layered double hydroxides (LDHs), [[M(II)]1-z[Cr(III)]z(OH)2][Cl]z yH2O, in a single step, without intermediate formation of chromium hydroxide. Analysis of the resultant titration curves yields solubility constants for these compounds. These are in the order Zn < Ni approximately Co, with a clear preference for formation of the phase with z = 1/3. With Mg2+ as chloride, titration gives a mixture of Cr(OH)3 and Mg(OH)2, but the metal sulfates give Mg2Cr(OH)6 1/2(SO4) by a two-step process. Titrimetric and spectroscopic evidence suggests short-range cation order in the one-step LDH systems.

  16. Layered double hydroxide stability. 2. Formation of Cr(III)-containing layered double hydroxides directly from solution

    NASA Technical Reports Server (NTRS)

    Boclair, J. W.; Braterman, P. S.; Jiang, J.; Lou, S.; Yarberry, F.

    1999-01-01

    Solutions containing divalent metal [M(II) = Mg2+, Zn2+, Co2+, Ni2+, Mn2+] chlorides and CrCl3 6H2O were titrated with NaOH to yield, for M(II) = Zn, Co, and Ni, hydrotalcite-like layered double hydroxides (LDHs), [[M(II)]1-z[Cr(III)]z(OH)2][Cl]z yH2O, in a single step, without intermediate formation of chromium hydroxide. Analysis of the resultant titration curves yields solubility constants for these compounds. These are in the order Zn < Ni approximately Co, with a clear preference for formation of the phase with z = 1/3. With Mg2+ as chloride, titration gives a mixture of Cr(OH)3 and Mg(OH)2, but the metal sulfates give Mg2Cr(OH)6 1/2(SO4) by a two-step process. Titrimetric and spectroscopic evidence suggests short-range cation order in the one-step LDH systems.

  17. Higher-order modulation formats for spectral-efficient high-speed metro systems

    NASA Astrophysics Data System (ADS)

    Freund, R.; Nölle, M.; Seimetz, M.; Hilt, J.; Fischer, J.; Ludwig, R.; Schubert, C.; Bach, H.-G.; Velthaus, K.-O.; Schell, M.

    2011-01-01

    Worldwide, higher-order modulation formats are intensively investigated to further increase the spectral efficiency for building the next generation of high-speed metro systems. IQ-modulators, coherent receivers and electronic equalizers are hereby discussed as key devices. We report on system design issues as well as on HHI's latest achievements in developing InP based high-speed modulators and coherent receiver frontends.

  18. Turbulence and star formation efficiency in molecular clouds: solenoidal versus compressive motions in Orion B

    NASA Astrophysics Data System (ADS)

    Orkisz, Jan H.; Pety, Jérôme; Gerin, Maryvonne; Bron, Emeric; Guzmán, Viviana V.; Bardeau, Sébastien; Goicoechea, Javier R.; Gratier, Pierre; Le Petit, Franck; Levrier, François; Liszt, Harvey; Öberg, Karin; Peretto, Nicolas; Roueff, Evelyne; Sievers, Albrecht; Tremblin, Pascal

    2017-03-01

    Context. The nature of turbulence in molecular clouds is one of the key parameters that control star formation efficiency: compressive motions, as opposed to solenoidal motions, can trigger the collapse of cores, or mark the expansion of Hii regions. Aims: We try to observationally derive the fractions of momentum density (ρv) contained in the solenoidal and compressive modes of turbulence in the Orion B molecular cloud and relate these fractions to the star formation efficiency in the cloud. Methods: The implementation of a statistical method applied to a 13CO(J = 1-0) datacube obtained with the IRAM-30 m telescope, enables us to retrieve 3-dimensional quantities from the projected quantities provided by the observations, which yields an estimate of the compressive versus solenoidal ratio in various regions of the cloud. Results: Despite the Orion B molecular cloud being highly supersonic (mean Mach number 6), the fractions of motion in each mode diverge significantly from equipartition. The cloud's motions are, on average, mostly solenoidal (excess > 8% with respect to equipartition), which is consistent with its low star formation rate. On the other hand, the motions around the main star forming regions (NGC 2023 and NGC 2024) prove to be strongly compressive. Conclusions: We have successfully applied to observational data a method that has so far only been tested on simulations, and we have shown that there can be a strong intra-cloud variability of the compressive and solenoidal fractions, these fractions being in turn related to the star formation efficiency. This opens a new possibility for star formation diagnostics in galactic molecular clouds. Based on observations carried out at the IRAM-30 m single-dish telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).

  19. The formation of IRIS diagnostics. III. Near-ultraviolet spectra and images

    SciTech Connect

    Pereira, T. M. D.; Leenaarts, J.; De Pontieu, B.; Carlsson, M.; Uitenbroek, H. E-mail: jorritl@astro.uio.no E-mail: mats.carlsson@astro.uio.no

    2013-12-01

    The Mg II h and k lines are the prime chromospheric diagnostics of NASA's Interface Region Imaging Spectrograph (IRIS). In the previous papers of this series, we used a realistic three-dimensional radiative magnetohydrodynamics model to calculate the h and k lines in detail and investigated how their spectral features relate to the underlying atmosphere. In this work, we employ the same approach to investigate how the h and k diagnostics fare when taking into account the finite resolution of IRIS and different noise levels. In addition, we investigate the diagnostic potential of several other photospheric lines and near-continuum regions present in the near-ultraviolet (NUV) window of IRIS and study the formation of the NUV slit-jaw images. We find that the instrumental resolution of IRIS has a small effect on the quality of the h and k diagnostics; the relations between the spectral features and atmospheric properties are mostly unchanged. The peak separation is the most affected diagnostic, but mainly due to limitations of the simulation. The effects of noise start to be noticeable at a signal-to-noise ratio (S/N) of 20, but we show that with noise filtering one can obtain reliable diagnostics at least down to a S/N of 5. The many photospheric lines present in the NUV window provide velocity information for at least eight distinct photospheric heights. Using line-free regions in the h and k far wings, we derive good estimates of photospheric temperature for at least three heights. Both of these diagnostics, in particular the latter, can be obtained even at S/Ns as low as 5.

  20. DNA ligase III promotes alternative nonhomologous end-joining during chromosomal translocation formation.

    PubMed

    Simsek, Deniz; Brunet, Erika; Wong, Sunnie Yan-Wai; Katyal, Sachin; Gao, Yankun; McKinnon, Peter J; Lou, Jacqueline; Zhang, Lei; Li, James; Rebar, Edward J; Gregory, Philip D; Holmes, Michael C; Jasin, Maria

    2011-06-01

    Nonhomologous end-joining (NHEJ) is the primary DNA repair pathway thought to underlie chromosomal translocations and other genomic rearrangements in somatic cells. The canonical NHEJ pathway, including DNA ligase IV (Lig4), suppresses genomic instability and chromosomal translocations, leading to the notion that a poorly defined, alternative NHEJ (alt-NHEJ) pathway generates these rearrangements. Here, we investigate the DNA ligase requirement of chromosomal translocation formation in mouse cells. Mammals have two other DNA ligases, Lig1 and Lig3, in addition to Lig4. As deletion of Lig3 results in cellular lethality due to its requirement in mitochondria, we used recently developed cell lines deficient in nuclear Lig3 but rescued for mitochondrial DNA ligase activity. Further, zinc finger endonucleases were used to generate DNA breaks at endogenous loci to induce translocations. Unlike with Lig4 deficiency, which causes an increase in translocation frequency, translocations are reduced in frequency in the absence of Lig3. Residual translocations in Lig3-deficient cells do not show a bias toward use of pre-existing microhomology at the breakpoint junctions, unlike either wild-type or Lig4-deficient cells, consistent with the notion that alt-NHEJ is impaired with Lig3 loss. By contrast, Lig1 depletion in otherwise wild-type cells does not reduce translocations or affect microhomology use. However, translocations are further reduced in Lig3-deficient cells upon Lig1 knockdown, suggesting the existence of two alt-NHEJ pathways, one that is biased toward microhomology use and requires Lig3 and a back-up pathway which does not depend on microhomology and utilizes Lig1.

  1. DNA Ligase III Promotes Alternative Nonhomologous End-Joining during Chromosomal Translocation Formation

    PubMed Central

    Wong, Sunnie Yan-Wai; Katyal, Sachin; Gao, Yankun; McKinnon, Peter J.; Lou, Jacqueline; Zhang, Lei; Li, James; Rebar, Edward J.; Gregory, Philip D.; Holmes, Michael C.; Jasin, Maria

    2011-01-01

    Nonhomologous end-joining (NHEJ) is the primary DNA repair pathway thought to underlie chromosomal translocations and other genomic rearrangements in somatic cells. The canonical NHEJ pathway, including DNA ligase IV (Lig4), suppresses genomic instability and chromosomal translocations, leading to the notion that a poorly defined, alternative NHEJ (alt-NHEJ) pathway generates these rearrangements. Here, we investigate the DNA ligase requirement of chromosomal translocation formation in mouse cells. Mammals have two other DNA ligases, Lig1 and Lig3, in addition to Lig4. As deletion of Lig3 results in cellular lethality due to its requirement in mitochondria, we used recently developed cell lines deficient in nuclear Lig3 but rescued for mitochondrial DNA ligase activity. Further, zinc finger endonucleases were used to generate DNA breaks at endogenous loci to induce translocations. Unlike with Lig4 deficiency, which causes an increase in translocation frequency, translocations are reduced in frequency in the absence of Lig3. Residual translocations in Lig3-deficient cells do not show a bias toward use of pre-existing microhomology at the breakpoint junctions, unlike either wild-type or Lig4-deficient cells, consistent with the notion that alt-NHEJ is impaired with Lig3 loss. By contrast, Lig1 depletion in otherwise wild-type cells does not reduce translocations or affect microhomology use. However, translocations are further reduced in Lig3-deficient cells upon Lig1 knockdown, suggesting the existence of two alt-NHEJ pathways, one that is biased toward microhomology use and requires Lig3 and a back-up pathway which does not depend on microhomology and utilizes Lig1. PMID:21655080

  2. Constraints on the star formation efficiency of galaxies during the epoch of reionization

    NASA Astrophysics Data System (ADS)

    Sun, G.; Furlanetto, S. R.

    2016-07-01

    Reionization is thought to have occurred in the redshift range of 6 < z < 9, which is now being probed by both deep galaxy surveys and CMB observations. Using halo abundance matching over the redshift range 5 < z < 8 and assuming smooth, continuous gas accretion, we develop a model for the star formation efficiency f⋆ of dark matter haloes at z > 6 that matches the measured galaxy luminosity functions at these redshifts. We find that f⋆ peaks at ˜30 per cent at halo masses M ˜ 1011-1012 M⊙, in qualitative agreement with its behaviour at lower redshifts. We then investigate the cosmic star formation histories and the corresponding models of reionization for a range of extrapolations to small halo masses. We use a variety of observations to further constrain the characteristics of the galaxy populations, including the escape fraction of UV photons. Our approach provides an empirically calibrated, physically motivated model for the properties of star-forming galaxies sourcing the epoch of reionization. In the case where star formation in low-mass haloes is maximally efficient, an average escape fraction ˜0.1 can reproduce the optical depth reported by Planck, whereas inefficient star formation in these haloes requires either about twice as many UV photons to escape, or an escape fraction that increases towards higher redshifts. Our models also predict how future observations with James Webb Space Telescope can improve our understanding of these galaxy populations.

  3. Innovative design of composite structures: Use of curvilinear fiber format to improve structural efficiency

    NASA Technical Reports Server (NTRS)

    Hyer, M. W.; Charette, R. F.

    1987-01-01

    To increase the effectiveness and efficiency of fiber-reinforced materials, the use of fibers in a curvilinear rather than the traditional straightline format is explored. The capacity of a laminated square plate with a central circular hole loaded in tension is investigated. The orientation of the fibers is chosen so that the fibers in a particular layer are aligned with the principle stress directions in that layer. Finite elements and an iteration scheme are used to find the fiber orientation. A noninteracting maximum strain criterion is used to predict load capacity. The load capacities of several plates with different curvilinear fibers format are compared with the capacities of more conventional straightline format designs. It is found that the most practical curvilinear design sandwiches a group of fibers in a curvilinear format between a pair of +/-45 degree layers. This design has a 60% greater load capacity than a conventional quasi-isotropic design with the same number of layers. The +/-45 degree layers are necessary to prevent matrix cracking in the curvilinear layers due to stresses perpendicular to the fibers in those layers. Greater efficiencies are achievable with composite structures than now realized.

  4. Molecule formation and infrared emission in fast interstellar shocks. III - Results for J shocks in molecular clouds

    NASA Technical Reports Server (NTRS)

    Hollenbach, David; Mckee, Christopher F.

    1989-01-01

    The structure and emission spectrum of J shocks in molecular gas are studied over a broad range of conditions. It is found that at high densities chemistry has a profound effect on the emission spectrum: the density behind the shock is sufficiently high that some of the internal energy of the newly formed H2 molecules is transformed to the gas as heat by collisional deexcitations, producing the H2 formation plateau. In this temperature plateau, endothermal reactions and neutral-neutral chemical reactions with activation energies can proceed efficiently, producing significant quantities of warm H2, CO, OH, and H2O and enhanced columns of warm atoms and ions. The heat generated by the H2 formation is radiated in collisionally excited atomic fine-structure lines.

  5. POLARIZED LINE FORMATION IN MULTI-DIMENSIONAL MEDIA. III. HANLE EFFECT WITH PARTIAL FREQUENCY REDISTRIBUTION

    SciTech Connect

    Anusha, L. S.; Nagendra, K. N.

    2011-09-01

    In two previous papers, we solved the polarized radiative transfer (RT) equation in multi-dimensional (multi-D) geometries with partial frequency redistribution as the scattering mechanism. We assumed Rayleigh scattering as the only source of linear polarization (Q/I, U/I) in both these papers. In this paper, we extend these previous works to include the effect of weak oriented magnetic fields (Hanle effect) on line scattering. We generalize the technique of Stokes vector decomposition in terms of the irreducible spherical tensors T{sup K}{sub Q}, developed by Anusha and Nagendra, to the case of RT with Hanle effect. A fast iterative method of solution (based on the Stabilized Preconditioned Bi-Conjugate-Gradient technique), developed by Anusha et al., is now generalized to the case of RT in magnetized three-dimensional media. We use the efficient short-characteristics formal solution method for multi-D media, generalized appropriately to the present context. The main results of this paper are the following: (1) a comparison of emergent (I, Q/I, U/I) profiles formed in one-dimensional (1D) media, with the corresponding emergent, spatially averaged profiles formed in multi-D media, shows that in the spatially resolved structures, the assumption of 1D may lead to large errors in linear polarization, especially in the line wings. (2) The multi-D RT in semi-infinite non-magnetic media causes a strong spatial variation of the emergent (Q/I, U/I) profiles, which is more pronounced in the line wings. (3) The presence of a weak magnetic field modifies the spatial variation of the emergent (Q/I, U/I) profiles in the line core, by producing significant changes in their magnitudes.

  6. Polarized Line Formation in Multi-dimensional Media. III. Hanle Effect with Partial Frequency Redistribution

    NASA Astrophysics Data System (ADS)

    Anusha, L. S.; Nagendra, K. N.

    2011-09-01

    In two previous papers, we solved the polarized radiative transfer (RT) equation in multi-dimensional (multi-D) geometries with partial frequency redistribution as the scattering mechanism. We assumed Rayleigh scattering as the only source of linear polarization (Q/I, U/I) in both these papers. In this paper, we extend these previous works to include the effect of weak oriented magnetic fields (Hanle effect) on line scattering. We generalize the technique of Stokes vector decomposition in terms of the irreducible spherical tensors {T}^K_Q, developed by Anusha & Nagendra, to the case of RT with Hanle effect. A fast iterative method of solution (based on the Stabilized Preconditioned Bi-Conjugate-Gradient technique), developed by Anusha et al., is now generalized to the case of RT in magnetized three-dimensional media. We use the efficient short-characteristics formal solution method for multi-D media, generalized appropriately to the present context. The main results of this paper are the following: (1) a comparison of emergent (I, Q/I, U/I) profiles formed in one-dimensional (1D) media, with the corresponding emergent, spatially averaged profiles formed in multi-D media, shows that in the spatially resolved structures, the assumption of 1D may lead to large errors in linear polarization, especially in the line wings. (2) The multi-D RT in semi-infinite non-magnetic media causes a strong spatial variation of the emergent (Q/I, U/I) profiles, which is more pronounced in the line wings. (3) The presence of a weak magnetic field modifies the spatial variation of the emergent (Q/I, U/I) profiles in the line core, by producing significant changes in their magnitudes.

  7. Novel Approaches to High-Efficiency III-V Nitride Heterostructure Emitters for Next-Generation Lighting Applications

    SciTech Connect

    Russell D. Dupuis

    2006-01-01

    We report research activities and technical progress on the development of high-efficiency long wavelength ({lambda} {approx} 540nm) green light emitting diodes which covers the second year of the three-year program ''Novel approaches to high-efficiency III-V nitride heterostructure emitters for next-generation lighting applications''. The second year activities were focused on the development of p-type layer that has less/no detrimental thermal annealing effect on green LED active region as well as excellent structural and electrical properties and the development of green LED active region that has superior luminescence quality for {lambda} {approx}540nm green LEDs. We have also studied the thermal annealing effect on blue and green LED active region during the p-type layer growth. As a progress highlight, we obtained green-LED-active-region-friendly In{sub 0.04}Ga{sub 0.96}N:Mg exhibiting low resistivity with higher hole concentration (p=2.0 x 10{sup 18} cm{sup -3} and a low resistivity of 0.5 {Omega}-cm) and improved optical quality green LED active region emitting at {lambda} {approx}540nm by electroluminescence. The active region of the green LEDs was found to be much more sensitive to the thermal annealing effect during the p-type layer growth than that of the blue LEDs. We have designed grown, fabricated green LED structures for both 520 nm and 540 nm for the evaluation of second year green LED development.

  8. Novel Approaches to High-Efficiency III-V Nitride Heterostructure Emitters for Next-Generation Lighting Applications

    SciTech Connect

    Russell Dupuis

    2007-06-30

    We report research activities and technical progress on the development of high-efficiency long wavelength ({lambda} {approx} 540nm) green light emitting diodes which covers whole years of the three-year program 'Novel approaches to high-efficiency III-V nitride heterostructure emitters for next-generation lighting applications'. The research activities were focused on the development of p-type layer that has less/no detrimental thermal annealing effect on as well as excellent structural and electrical properties and the development of green LED active region that has superior luminescence quality for {lambda}{approx}540nm green LEDs. We have also studied (1) the thermal annealing effect on blue and green LED active region during the p-type layer growth; (2) the effect of growth parameters and structural factors for LED active region on electroluminescence properties; (3) the effect of substrates and orientation on electrical and electro-optical properties of green LEDs. As a progress highlight, we obtained green-LED-active-region-friendly In{sub 0.04}Ga{sub 0.96}N:Mg exhibiting low resistivity with higher hole concentration (p=2.0 x 10{sup 18} cm{sup -3} and a low resistivity of 0.5 {omega}-cm) and improved optical quality green LED active region emitting at {approx}540nm by electroluminescence. The LEDs with p-InGaN layer can act as a quantum-confined Stark effect mitigation layer by reducing strain in the QW. We also have achieved (projected) peak IQE of {approx}25% at {lambda}{approx}530 nm and of {approx}13% at {lambda}{approx}545 nm. Visible LEDs on a non-polar substrate using (11-20) {alpha}-plane bulk substrates. The absence of quantum-confined Stark effect was confirmed but further improvement in electrical and optical properties is required.

  9. An efficient 2-linked carbazolyl β-diketonate europium(III) complex as red phosphor applied in LED

    NASA Astrophysics Data System (ADS)

    He, P.; Wang, H. H.; Liu, S. G.; Shi, J. X.; Gong, M. L.

    2010-06-01

    An efficient 2-linked carbazolyl β-diketonate europium(III) complex Eu(ETFMCTFBD)3phen was designed and synthesized, where ETFMCTFBD was 1-(9-ethyl-7-(trifluoromethyl)-9H-carbazol-2-yl)-4,4,4-trifluorobutane-1,3-dione and phen was 1,10-phenanthroline. Eu(ETFMCTFBD)3phen exhibits high thermal stability and excellent photoluminescence properties. The CIE chromaticity coordinates ( x=0.668, y=0.331) are close to the National Television Standard Committee (NTSC) standard values for red. The lowest triplet energy was measured and suggests the photoluminescence process as a ligand-sensitized luminescence process (antenna effect). A bright red light-emitting diode was fabricated by coating the complex phosphor onto a ˜395 nm-emitting InGaN chip. All the results indicate that Eu(ETFMCTFBD)3phen is a good candidate as a red component in the fabrication of white LEDs with a high color-rendering index.

  10. Electrochemical determination of Ga(III) through formation of Ga(III)-deferrioxamine B nanostructures on the glassy carbon electrode surface.

    PubMed

    Karimi Shervedani, Reza; Garavand, Somayeh; Samiei Foroushani, Marzieh; Yaghoobi, Fatemeh

    2016-03-01

    Selective and sensitive determination of Ga(III) in the presence of Fe(III), as the main interfering ion is studied by using glassy carbon electrode modified with deferrioxamine B (GC-DFO). Characterization and analytical application are performed by different methods including cyclic and differential pulse voltammetry (CV and DPV), electrochemical impedance spectroscopy (EIS), and Field Emission Scanning Electron Microscopy (FESEM). The DPV measurements showed two reduction peaks around -0.630 and -0.830V. While the current of both peaks varied linearly with Ga(III) concentration of the accumulation solution, the latter was more sensitive and used for construction of the calibration curve. The experimental parameters are studied and optimized. A dynamic calibration curve (6.0×10(-11) to 1.4×10(-9)molL(-1)), including a linear part, from 6.0×10(-11) to 1.0×10(-9)molL(-1) with mean RSDs of 5.3% for n=3 at 4.0×10(-10)molL(-1) Ga(III), and a detection limit of 2.0×10(-11) mol L(-1) Ga(III) is observed at the optimized conditions. The validity of the method and applicability of the sensor are successfully tested by determining of Ga(III) in natural (river) waters, rice and coal samples. The experimental data are presented and discussed from which the new sensor is characterized.

  11. Construction of Identical [2 + 2] Schiff-Base Macrocyclic Ligands by Ln(III) and Zn(II) Template Ions Including Efficient Yb(III) Near-Infrared Sensitizers.

    PubMed

    Zhang, Kun; Zhang, Lei; Zhang, Song; Hu, Yong; Zheng, Youxuan; Huang, Wei

    2015-06-01

    Identical 34-membered [2 + 2] pendent-armed Schiff-base macrocyclic ligands (H4La and H4Lb) can be constructed via the condensation reactions between rigid o-phenylenediamine and extended dialdehydes (H2hpdd/H2pdd) in the presence of either Ln(III) or Zn(II) template with remarkable distinction on the ion radii and charge. X-ray single-crystal diffraction analyses reveal the formation of mononuclear Ln(III) complexes (1-4 and 7) and dinuclear Zn(II) complexes (5 and 6). It is noted that Ln(III) macrocyclic complexes have eight-coordinate sandwich-like mononuclear structures fully surrounded by flexible and large-sized macrocyclic ligands. Photophysical studies have demonstrated that both H4La and H4Lb can serve as effective sensitizers for the Yb(III) ion (2 and 7) exhibiting near-infrared emission at 974 nm with high quantum yields in solution (C2H5OH and CH3OH, ∼1%). Moreover, the quantum yields of two Yb(III) complexes 2 and 7 could be increased ∼15% in CH3OH under weak alkaline condition (pH = 8-9), while no significant changes are observed in C2H5OH by contrast. We think the unique sandwich-like macrocyclic structures of Yb(III) complexes 2 and 7 play important roles in simultaneously guaranteeing the effective match of the energy levels of Yb(III) centers as well as shielding from the solvent molecules and counterions.

  12. Dew and hoarfrost frequency, formation efficiency and chemistry in Wroclaw, Poland

    NASA Astrophysics Data System (ADS)

    Gałek, G.; Sobik, M.; Błaś, M.; Polkowska, Ż.; Cichała-Kamrowska, K.; Wałaszek, K.

    2015-01-01

    This article presents the results of a research study concerning a comparison of frequency, formation efficiency and basic physico-chemical properties of dew and hoarfrost in urban conditions. Longer than two-year series of measurements was carried out from 1 February 2008 to 10 March 2010 in Wroclaw, Poland. Sampling of atmospheric deposits was made by means of insulated plain passive radiative condensers, which allowed to collect 222 dew and 96 hoarfrost samples. The results indicate that the frequency of dew days was about threefold greater than hoarfrost days. The formation efficiency of both types of deposits was almost the same, and reached a mean value of about 100 mL·m- 2 per day. The conducted analysis of several meteorological parameters showed that dew and hoarfrost, despite seasonal weather changes, were formed in very similar meteorological conditions. Only water vapor pressure values were in average twice higher in the case of dew and the impact of this parameter on dew and hoarfrost formation efficiency seems to be more complex than expected. The role of night duration in counterbalancing of smaller amount of available moisture in hoarfrost days is not clear. The investigation showed also, that there was an expected clear positive dependence of dew and hoarfrost formation efficiency on relative humidity, and not so evident in the case of temperature inversion, and wind velocity. The physico-chemical analysis indicated that the pH of dew was only slightly lower than the hoarfrost ones, regardless of the deposit formation intensity. Simultaneously, the lower pH values were much more frequent in the case of dew, which resulted from more effective absorption of anthropogenic NO3- and SO42 - ions. For both types of deposits, the average pH was low (4.5-4.8) in relation to majority of studies reported in literature. In spite of seasonal changes of pollutant concentration, various weather conditions and different mechanisms of pollutant absorption of dew

  13. Spectrophotometric and electrochemical determination of the formation constants of the complexes Curcumin-Fe(III)-water and Curcumin-Fe(II)-water.

    PubMed

    Bernabé-Pineda, Marganta; Ramírez-Silva, Maria Teresa; Romero-Romo, Mario Alberto; González-Vergara, Enrique; Rojas-Hernández, Alberto

    2004-04-01

    The formation of complexes among the Curcumin, Fe(III) and Fe(II) was studied in aqueous media within the 5-11 pH range by means of UV-Vis spectrophotometry and cyclic voltammetry. When the reaction between the Curcumin and the ions present in basic media took place, the resulting spectra of the systems Curcumin-Fe(III) and Curcumin-Fe(II) presented a similar behaviour. The cyclic voltammograms in basic media indicated that a chemical reaction has taken place between the Curcumin and Fe(III) before that of the formation of complexes. Data processing with SQUAD permitted to calculate the formation constants of the complexes Curcumin-Fe(III), corresponding to the species FeCur (lob beta110 = 22.25 +/- 0.03) and FeCur(OH)- (log beta111 = 12.14 +/- 0.03), while for the complexes Curcumin-Fe(II) the corresponding formation constants of the species FeCur- (log beta110 = 9.20 +/- 0.04), FeHCur (log beta111 = 19.76 +/- 0.03), FeH2Cur+ (log beta112 = 28.11 +/- 0.02).

  14. REVERSAL OF FORTUNE: INCREASED STAR FORMATION EFFICIENCIES IN THE EARLY HISTORIES OF DWARF GALAXIES?

    SciTech Connect

    Madau, Piero; Weisz, Daniel R.; Conroy, Charlie

    2014-08-01

    On dwarf galaxy scales, the different shapes of the galaxy stellar mass function and the dark halo mass function require a star-formation efficiency (SFE) in these systems that is currently more than 1 dex lower than that of Milky Way-size halos. Here, we argue that this trend may actually be reversed at high redshift. Specifically, by combining the resolved star-formation histories of nearby isolated dwarfs with the simulated mass-growth rates of dark matter halos, we show that the assembly of these systems occurs in two phases: (1) an early, fast halo accretion phase with a rapidly deepening potential well, characterized by a high SFE; and (2) a late, slow halo accretion phase where, perhaps as a consequence of reionization, the SFE is low. Nearby dwarfs have more old stars than predicted by assuming a constant or decreasing SFE with redshift, a behavior that appears to deviate qualitatively from the trends seen among more massive systems. Taken at face value, the data suggest that at sufficiently early epochs, dwarf galaxy halos above the atomic cooling mass limit can be among the most efficient sites of star formation in the universe.

  15. An efficient and extensible format, library, and API for binary trajectory data from molecular simulations.

    PubMed

    Lundborg, Magnus; Apostolov, Rossen; Spångberg, Daniel; Gärdenäs, Anders; van der Spoel, David; Lindahl, Erik

    2014-01-30

    Molecular dynamics simulations is an important application in theoretical chemistry, and with the large high-performance computing resources available today the programs also generate huge amounts of output data. In particular in life sciences, with complex biomolecules such as proteins, simulation projects regularly deal with several terabytes of data. Apart from the need for more cost-efficient storage, it is increasingly important to be able to archive data, secure the integrity against disk or file transfer errors, to provide rapid access, and facilitate exchange of data through open interfaces. There is already a whole range of different formats used, but few if any of them (including our previous ones) fulfill all these goals. To address these shortcomings, we present "Trajectory Next Generation" (TNG)--a flexible but highly optimized and efficient file format designed with interoperability in mind. TNG both provides state-of-the-art multiframe compression as well as a container framework that will make it possible to extend it with new compression algorithms without modifications in programs using it. TNG will be the new file format in the next major release of the GROMACS package, but it has been implemented as a separate library and API with liberal licensing to enable wide adoption both in academic and commercial codes.

  16. Mn(2+)-mediated homogeneous Fenton-like reaction of Fe(III)-NTA complex for efficient degradation of organic contaminants under neutral conditions.

    PubMed

    Li, Yifan; Sun, Jianhui; Sun, Sheng-Peng

    2016-08-05

    In this work, we report a novel Mn(2+)-mediated Fenton-like process based on Fe(III)-NTA complex that is super-efficient at circumneutral pH range. Kinetics experiments showed that the presence of Mn(2+) significantly enhanced the effectiveness of Fe(III)-NTA complex catalyzed Fenton-like reaction. The degradation rate constant of crotamiton (CRMT), a model compound, by the Fe(III)- NTA_Mn(2+) Fenton-like process was at least 1.6 orders of magnitude larger than that in the absence of Mn(2+). Other metal ions such as Ca(2+), Mg(2+), Co(2+) and Cu(2+) had no impacts or little inhibitory effect on the Fe(III)-NTA complex catalyzed Fenton-like reaction. The generation of hydroxyl radical (HO) and superoxide radical anion (O2(-)) in the Fe(III)-NTA_Mn(2+) Fenton-like process were suggested by radicals scavenging experiments. The degradation efficiency of CRMT was inhibited significantly (approximately 92%) by the addition of HO scavenger 2-propanol, while the addition of O2(-) scavenger chloroform resulted in 68% inhibition. Moreover, the results showed that other chelating agents such as EDTA- and s,s-EDDS-Fe(III) catalyzed Fenton-like reactions were also enhanced significantly by the presence of Mn(2+). The mechanism involves an enhanced generation of O2(-) from the reactions of Mn(2+)-chelates with H2O2, indirectly promoting the generation of HO by accelerating the reduction rate of Fe(III)-chelates to Fe(II)- chelates. Copyright © 2016 Elsevier B.V. All rights reserved.

  17. Facile and highly efficient removal of trace Gd(III) by adsorption of colloidal graphene oxide suspensions sealed in dialysis bag.

    PubMed

    Chen, Weifan; Wang, Linlin; Zhuo, Mingpeng; Liu, Yue; Wang, Yiping; Li, Yongxiu

    2014-08-30

    A facile, highly efficient and second-pollution-free strategy to remove trace Gd(III) from aqueous solutions by adsorption of colloidal graphene oxide (GO) suspensions in dialysis bag has been developed. The effects of pH, ionic strength and temperature on Gd(III) adsorption, and the pH-dependent desorption were investigated. The maximum adsorption capacity of Gd(III)on GO at pH=5.9±0.1 and T=303K was 286.86mgg(-1), higher than any other currently reported. The Gd(III)-saturated GO suspension could resume colloidal state in 0.1M HNO3 with desorption rate of 85.00% in the fifth adsorption-desorption cycle. Gd(III) adsorption rate on GO was dependent more on pH and ionic strength than on temperature. The abundant oxygen-containing functional groups such as carboxyl and hydroxyl played a vital role on adsorption. The thermodynamics and kinetics investigations revealed that the adsorption of Gd(III) on GO was an endothermic, spontaneous and monolayer absorption process, which well fitted the pseudo-second-order model. GO could be a promising adsorbent applied in the enrichment and removal of lanthanides from aqueous solutions. More significantly, the combination of colloidal GO suspension with dialysis membrane facilely solves the re-pollution of the treated solutions due to the great difficulties in separation and recovery of GO.

  18. Novel red phosphorescent polymers bearing both ambipolar and functionalized Ir(III) phosphorescent moieties for highly efficient organic light-emitting diodes.

    PubMed

    Zhao, Jiang; Lian, Meng; Yu, Yue; Yan, Xiaogang; Xu, Xianbin; Yang, Xiaolong; Zhou, Guijiang; Wu, Zhaoxin

    2015-01-01

    A series of novel red phosphorescent polymers is successfully developed through Suzuki cross-coupling among ambipolar units, functionalized Ir(III) phosphorescent blocks, and fluorene-based silane moieties. The photophysical and electrochemical investigations indicate not only highly efficient energy-transfer from the organic segments to the phosphorescent units in the polymer backbone but also the ambipolar character of the copolymers. Benefiting from all these merits, the phosphorescent polymers can furnish organic light-emitting diodes (OLEDs) with exceptional high electroluminescent (EL) efficiencies with a current efficiency (η L ) of 8.31 cd A(-1) , external quantum efficiency (η ext ) of 16.07%, and power efficiency (η P ) of 2.95 lm W(-1) , representing the state-of-the-art electroluminescent performances ever achieved by red phosphorescent polymers. This work here might represent a new pathway to design and synthesize highly efficient phosphorescent polymers.

  19. Synthesis, Spectroscopic and Thermal Characterization of Copper(II) and Iron(III) Complexes of Folic Acid and Their Absorption Efficiency in the Blood

    PubMed Central

    Hamed, E.; Attia, M. S.; Bassiouny, K.

    2009-01-01

    The absorption efficiency of any drug in blood is of prime importance. Compounds having the general formula: Kn[M(FO)2(H2O)2] · xH2O, where (M = Cu(II) or Fe(III), n = 2 or 1, FO = folate anion, x = 2 or 3 with respect), were prepared, and their absorption efficiency in rodent's blood was determined. The obtained compounds were characterized by elemental analysis, infrared as well as thermogravimetric analysis and polarization of light. The results suggest that the two folate complexes were formed in 1 : 2 molar ratio (metal : folic acid) which acted as a bidentate ligand through both carboxylic groups. Polarization of light proved that the folate complexes have symmetric geometry. Biological application proved that Cu(II) and Fe(III) complexes were absorbed more efficiently in rodent blood than folic acid itself. PMID:19746175

  20. MMTF—An efficient file format for the transmission, visualization, and analysis of macromolecular structures

    PubMed Central

    Pavelka, Antonín; Valasatava, Yana; Prlić, Andreas

    2017-01-01

    Recent advances in experimental techniques have led to a rapid growth in complexity, size, and number of macromolecular structures that are made available through the Protein Data Bank. This creates a challenge for macromolecular visualization and analysis. Macromolecular structure files, such as PDB or PDBx/mmCIF files can be slow to transfer, parse, and hard to incorporate into third-party software tools. Here, we present a new binary and compressed data representation, the MacroMolecular Transmission Format, MMTF, as well as software implementations in several languages that have been developed around it, which address these issues. We describe the new format and its APIs and demonstrate that it is several times faster to parse, and about a quarter of the file size of the current standard format, PDBx/mmCIF. As a consequence of the new data representation, it is now possible to visualize structures with millions of atoms in a web browser, keep the whole PDB archive in memory or parse it within few minutes on average computers, which opens up a new way of thinking how to design and implement efficient algorithms in structural bioinformatics. The PDB archive is available in MMTF file format through web services and data that are updated on a weekly basis. PMID:28574982

  1. Efficient automatic OCR word validation using word partial format derivation and language model

    NASA Astrophysics Data System (ADS)

    Chen, Siyuan; Misra, Dharitri; Thoma, George R.

    2010-01-01

    In this paper we present an OCR validation module, implemented for the System for Preservation of Electronic Resources (SPER) developed at the U.S. National Library of Medicine.1 The module detects and corrects suspicious words in the OCR output of scanned textual documents through a procedure of deriving partial formats for each suspicious word, retrieving candidate words by partial-match search from lexicons, and comparing the joint probabilities of N-gram and OCR edit transformation corresponding to the candidates. The partial format derivation, based on OCR error analysis, efficiently and accurately generates candidate words from lexicons represented by ternary search trees. In our test case comprising a historic medico-legal document collection, this OCR validation module yielded the correct words with 87% accuracy and reduced the overall OCR word errors by around 60%.

  2. An Efficient Implementation of the Sign LMS Algorithm Using Block Floating Point Format

    NASA Astrophysics Data System (ADS)

    Chakraborty, Mrityunjoy; Shaik, Rafiahamed; Lee, Moon Ho

    2007-12-01

    An efficient scheme is presented for implementing the sign LMS algorithm in block floating point format, which permits processing of data over a wide dynamic range at a processor complexity and cost as low as that of a fixed point processor. The proposed scheme adopts appropriate formats for representing the filter coefficients and the data. It also employs a scaled representation for the step-size that has a time-varying mantissa and also a time-varying exponent. Using these and an upper bound on the step-size mantissa, update relations for the filter weight mantissas and exponent are developed, taking care so that neither overflow occurs, nor are quantities which are already very small multiplied directly. Separate update relations are also worked out for the step size mantissa. The proposed scheme employs mostly fixed-point-based operations, and thus achieves considerable speedup over its floating-point-based counterpart.

  3. Efficacy and efficiency in formative assessment: an informed reflection on the value of partial marking

    NASA Astrophysics Data System (ADS)

    Seaton, Katherine A.

    2013-10-01

    This article presents an informed reflection on the evolution of teacher-to-learner feedback provided on written assignments in first-year university mathematics subjects. The feedback provided addresses not only mathematical accuracy and skills, but also the development of graduate attributes, such as discipline-appropriate written communication. Effective and efficient practices that have been collectively refined and enhanced, for more than a decade, are described and examined. This model for formative assessment in mathematics subjects is critiqued in the light of the scholarly literature on feedback and assessment.

  4. A Highly Efficient Heterogenized Iridium Complex for the Catalytic Hydrogenation of Carbon Dioxide to Formate.

    PubMed

    Park, Kwangho; Gunasekar, Gunniya Hariyanandam; Prakash, Natarajan; Jung, Kwang-Deog; Yoon, Sungho

    2015-10-26

    A heterogenized catalyst on a highly porous covalent triazine framework was synthesized and characterized to have a coordination environment similar to that of its homogeneous counterpart. The catalyst efficiently converted CO2 into formate through hydrogenation with a turnover number of 5000 after 2 h and an initial turnover frequency of up to 5300 h(-1) ; both of these values are the highest reported to date for a heterogeneous catalyst, which makes it attractive toward industrial application. Furthermore, the synthesized catalyst was found to be stable in air and was recycled by simple filtration without significant loss of catalytic activity.

  5. βIII Spectrin Is Necessary for Formation of the Constricted Neck of Dendritic Spines and Regulation of Synaptic Activity in Neurons.

    PubMed

    Efimova, Nadia; Korobova, Farida; Stankewich, Michael C; Moberly, Andrew H; Stolz, Donna B; Wang, Junling; Kashina, Anna; Ma, Minghong; Svitkina, Tatyana

    2017-07-05

    Dendritic spines are postsynaptic structures in neurons often having a mushroom-like shape. Physiological significance and cytoskeletal mechanisms that maintain this shape are poorly understood. The spectrin-based membrane skeleton maintains the biconcave shape of erythrocytes, but whether spectrins also determine the shape of nonerythroid cells is less clear. We show that βIII spectrin in hippocampal and cortical neurons from rodent embryos of both sexes is distributed throughout the somatodendritic compartment but is particularly enriched in the neck and base of dendritic spines and largely absent from spine heads. Electron microscopy revealed that βIII spectrin forms a detergent-resistant cytoskeletal network at these sites. Knockdown of βIII spectrin results in a significant decrease in the density of dendritic spines. Surprisingly, the density of presynaptic terminals is not affected by βIII spectrin knockdown. However, instead of making normal spiny synapses, the presynaptic structures in βIII spectrin-depleted neurons make shaft synapses that exhibit increased amplitudes of miniature EPSCs indicative of excessive postsynaptic excitation. Thus, βIII spectrin is necessary for formation of the constricted shape of the spine neck, which in turn controls communication between the synapse and the parent dendrite to prevent excessive excitation. Notably, mutations of SPTNB2 encoding βIII spectrin are associated with neurodegenerative syndromes, spinocerebellar ataxia Type 5, and spectrin-associated autosomal recessive cerebellar ataxia Type 1, but molecular mechanisms linking βIII spectrin functions to neuronal pathologies remain unresolved. Our data suggest that spinocerebellar ataxia Type 5 and spectrin-associated autosomal recessive cerebellar ataxia Type 1 pathology likely arises from poorly controlled synaptic activity that leads to excitotoxicity and neurodegeneration.SIGNIFICANCE STATEMENT Dendritic spines are small protrusions from neuronal

  6. CO observations of infrared bright galaxies - The efficiency of star formation

    NASA Technical Reports Server (NTRS)

    Young, J. S.; Schloerb, F. P.; Kenney, J. D.; Lord, S. D.

    1986-01-01

    CO emission has been detected in each of 14 of the IR-bright galaxies listed in IRAS Circular 15; for the nine galaxies of the largest angular size, the CO emission distributions along the major axis have been mapped. A strong correlation is noted between total CO luminosities and IR ones for galaxies in each of three ranges of dust temperature. The ratio of IR/CO luminosities increases with the ratio of 60/100-micron flux densities, consistent with emission of thermal origin at the characteristic temperature given by the dust temperature. If this luminosity ratio is a measure of the emergent stellar luminosity/unit molecular mass, or the efficiency of star formation, this efficiency varies over almost two orders of magnitude from one galaxy to another.

  7. Effect of temperature on carrier formation efficiency in organic photovoltaic cells

    NASA Astrophysics Data System (ADS)

    Moritomo, Yutaka; Yonezawa, Kouhei; Yasuda, Takeshi

    2014-08-01

    The internal quantum efficiency ( ϕ IQ) of an organic photovoltaic cell is governed by plural processes. Here, we propose that ϕ IQ can be experimentally decomposed into carrier formation ( ϕ CF) and carrier transfer ( ϕ CT) efficiencies. By combining femtosecond time-resolved and electrochemical spectroscopy, we clarified the effect of temperature on ϕ CF in a regioregular poly(3-hexylthiophene) (rr-P3HT)/[6,6]-phenyl C61-butyric acid methyl ester blend film. We found that ϕ CF ( = 0.55 ) at 80 K is the same as that (=0.55) at 300 K. The temperature insensitivity of ϕ CF indicates that the electron-hole pairs at the D/A interface are seldom subjected to coulombic binding energy.

  8. CO observations of infrared bright galaxies - The efficiency of star formation

    NASA Technical Reports Server (NTRS)

    Young, J. S.; Schloerb, F. P.; Kenney, J. D.; Lord, S. D.

    1986-01-01

    CO emission has been detected in each of 14 of the IR-bright galaxies listed in IRAS Circular 15; for the nine galaxies of the largest angular size, the CO emission distributions along the major axis have been mapped. A strong correlation is noted between total CO luminosities and IR ones for galaxies in each of three ranges of dust temperature. The ratio of IR/CO luminosities increases with the ratio of 60/100-micron flux densities, consistent with emission of thermal origin at the characteristic temperature given by the dust temperature. If this luminosity ratio is a measure of the emergent stellar luminosity/unit molecular mass, or the efficiency of star formation, this efficiency varies over almost two orders of magnitude from one galaxy to another.

  9. Effect of temperature on carrier formation efficiency in organic photovoltaic cells

    SciTech Connect

    Moritomo, Yutaka Yonezawa, Kouhei; Yasuda, Takeshi

    2014-08-18

    The internal quantum efficiency (ϕ{sub IQ}) of an organic photovoltaic cell is governed by plural processes. Here, we propose that ϕ{sub IQ} can be experimentally decomposed into carrier formation (ϕ{sub CF}) and carrier transfer (ϕ{sub CT}) efficiencies. By combining femtosecond time-resolved and electrochemical spectroscopy, we clarified the effect of temperature on ϕ{sub CF} in a regioregular poly(3-hexylthiophene) (rr-P3HT)/[6,6]-phenyl C{sub 61}-butyric acid methyl ester blend film. We found that ϕ{sub CF} (=0.55) at 80 K is the same as that (=0.55) at 300 K. The temperature insensitivity of ϕ{sub CF} indicates that the electron-hole pairs at the D/A interface are seldom subjected to coulombic binding energy.

  10. Highly efficient removal of heavy metals by polymer-supported nanosized hydrated Fe(III) oxides: behavior and XPS study.

    PubMed

    Pan, Bingjun; Qiu, Hui; Pan, Bingcai; Nie, Guangze; Xiao, Lili; Lv, Lu; Zhang, Weiming; Zhang, Quanxing; Zheng, Shourong

    2010-02-01

    The present study developed a polymer-based hybrid sorbent (HFO-001) for highly efficient removal of heavy metals [e.g., Pb(II), Cd(II), and Cu(II)] by irreversibly impregnating hydrated Fe(III) oxide (HFO) nanoparticles within a cation-exchange resin D-001 (R-SO(3)Na), and revealed the underlying mechanism based on X-ray photoelectron spectroscopy (XPS) study. HFO-001 combines the excellent handling, flow characteristics, and attrition resistance of conventional cation-exchange resins with the specific affinity of HFOs toward heavy metal cations. As compared to D-001, sorption selectivity of HFO-001 toward Pb(II), Cu(II), and Cd(II) was greatly improved from the Ca(II) competition at greater concentration. Column sorption results indicated that the working capacity of HFO-001 was about 4-6 times more than D-001 with respect to removal of three heavy metals from simulated electroplating water (pH approximately 4.0). Also, HFO-001 is particularly effective in removing trace Pb(II) and Cd(II) from simulated natural waters to meet the drinking water standard, with treatment volume orders of magnitude higher than D-001. The superior performance of HFO-001 was attributed to the Donnan membrane effect exerted by the host D-001 as well as to the impregnated HFO nanoparticles of specific interaction toward heavy metal cations, as further confirmed by XPS study on lead sorption. More attractively, the exhausted HFO-001 beads can be effectively regenerated by HCl-NaCl solution (pH 3) for repeated use without any significant capacity loss.

  11. Efficiently Visible-Light Driven Photoelectrocatalytic Oxidation of As(III) at Low Positive Biasing Using Pt/TiO2 Nanotube Electrode

    NASA Astrophysics Data System (ADS)

    Qin, Yanyan; Li, Yilian; Tian, Zhen; Wu, Yangling; Cui, Yanping

    2016-01-01

    A constant current deposition method was selected to load highly dispersed Pt nanoparticles on TiO2 nanotubes in this paper, to extend the excited spectrum range of TiO2-based photocatalysts to visible light. The morphology, elemental composition, and light absorption capability of as-obtained Pt/TiO2 nanotubes electrodes were characterized by FE-SEM, energy dispersive spectrometer (EDS), X-ray photoelectron spectrometer (XPS), and UV-vis spectrometer. The photocatalytic and photoelectrocatalytic oxidation of As(III) using a Pt/TiO2 nanotube arrays electrode under visible light ( λ > 420 nm) irradiation were investigated in a divided anode/cathode electrolytic tank. Compared with pure TiO2 which had no As(III) oxidation capacity under visible light, Pt/TiO2 nanotubes exhibited excellent visible-light photocatalytic performance toward As(III), even at dark condition. In anodic cell, As(III) could be oxidized with high efficiency by photoelectrochemical process with only 1.2 V positive biasing. Experimental results showed that photoelectrocatalytic oxidation process of As(III) could be well described by pseudo-first-order kinetic model. Rate constants depended on initial concentration of As(III), applied bias potential and solution pH. At the same time, it was interesting to find that in cathode cell, As(III) was also continuously oxidized to As(V). Furthermore, high-arsenic groundwater sample (25 m underground) with 0.32 mg/L As(III) and 0.35 mg/L As(V), which was collected from Daying Village, Datong basin, Northern China, could totally transform to As(V) after 200 min under visible light in this system.

  12. Efficiently Visible-Light Driven Photoelectrocatalytic Oxidation of As(III) at Low Positive Biasing Using Pt/TiO2 Nanotube Electrode.

    PubMed

    Qin, Yanyan; Li, Yilian; Tian, Zhen; Wu, Yangling; Cui, Yanping

    2016-12-01

    A constant current deposition method was selected to load highly dispersed Pt nanoparticles on TiO2 nanotubes in this paper, to extend the excited spectrum range of TiO2-based photocatalysts to visible light. The morphology, elemental composition, and light absorption capability of as-obtained Pt/TiO2 nanotubes electrodes were characterized by FE-SEM, energy dispersive spectrometer (EDS), X-ray photoelectron spectrometer (XPS), and UV-vis spectrometer. The photocatalytic and photoelectrocatalytic oxidation of As(III) using a Pt/TiO2 nanotube arrays electrode under visible light (λ > 420 nm) irradiation were investigated in a divided anode/cathode electrolytic tank. Compared with pure TiO2 which had no As(III) oxidation capacity under visible light, Pt/TiO2 nanotubes exhibited excellent visible-light photocatalytic performance toward As(III), even at dark condition. In anodic cell, As(III) could be oxidized with high efficiency by photoelectrochemical process with only 1.2 V positive biasing. Experimental results showed that photoelectrocatalytic oxidation process of As(III) could be well described by pseudo-first-order kinetic model. Rate constants depended on initial concentration of As(III), applied bias potential and solution pH. At the same time, it was interesting to find that in cathode cell, As(III) was also continuously oxidized to As(V). Furthermore, high-arsenic groundwater sample (25 m underground) with 0.32 mg/L As(III) and 0.35 mg/L As(V), which was collected from Daying Village, Datong basin, Northern China, could totally transform to As(V) after 200 min under visible light in this system.

  13. 2-and 1-D coordination polymers of Dy(III) and Ho(III) with near infrared and visible luminescence by efficient charge-transfer antenna ligand

    NASA Astrophysics Data System (ADS)

    Oylumluoglu, Gorkem; Coban, Mustafa Burak; Kocak, Cagdas; Aygun, Muhittin; Kara, Hulya

    2017-10-01

    Two new lanthanide-based coordination complexes, [Dy(2-stp).2(H2O)]n (1) and {[Ho(2-stp).3(H2O)]·(H2O)}n (2) [2-stp = 2-sulfoterephthalic acid] were synthesized by hydrothermal reaction and characterized by elemental analysis, UV, IR, single crystal X-ray diffraction and solid state photoluminescence. DyIII and HoIII atoms are eight-coordinated and adopt a distorted square-antiprismatic geometry in complexes 1 and 2, respectively. In compound 1, Dy atoms are coordinated by four bridging 2-stp ligands forming two-dimensional (2D) layer, while Ho atoms by three bridging 2-stp ligands creating one dimensional (1D) double chains in 2. In addition, complexes 1 and 2 display in the solid state and at room temperature an intense yellow emission, respectively; this photoluminescence is achieved by an indirect process (antenna effect). The excellent luminescent performances make these complexes very good candidates for potential luminescence materials.

  14. Rh(III)/Cu(II)-cocatalyzed synthesis of 1H-indazoles through C-H amidation and N-N bond formation.

    PubMed

    Yu, Da-Gang; Suri, Mamta; Glorius, Frank

    2013-06-19

    Substituted 1H-indazoles can be formed from readily available arylimidates and organo azides by Rh(III)-catalyzed C-H activation/C-N bond formation and Cu-catalyzed N-N bond formation. For the first time the N-H-imidates are demonstrated to be good directing groups in C-H activation, also capable of undergoing intramolecular N-N bond formation. The process is scalable and green, with O2 as the terminal oxidant and N2 and H2O formed as byproducts. Moreover, the products could be transformed to diverse important derivatives.

  15. Subtask 2.17 - CO{sub 2} Storage Efficiency in Deep Saline Formations

    SciTech Connect

    Gorecki, Charles; Liu, Guoxiang; Braunberger, Jason; Klenner, Robert; Ayash, Scott; Dotzenrod, Neil; Steadman, Edward; Harju, John

    2014-02-01

    As the field of carbon capture and storage (CCS) continues to advance, and large-scale implementation of geologic carbon dioxide (CO{sub 2}) storage progresses, it will be important to understand the potential of geologic formations to store meaningful amounts of CO{sub 2}. Geologic CO{sub 2} storage in deep saline formations (DSFs) has been suggested as one of the best potential methods for reducing anthropogenic CO{sub 2} emission to the atmosphere, and as such, updated storage resource estimation methods will continue to be an important component for the widespread deployment of CCS around the world. While there have been several methodologies suggested in the literature, most of these methods are based on a volumetric calculation of the pore volume of the DSF multiplied by a storage efficiency term and do not consider the effect of site-specific dynamic factors such as injection rate, injection pattern, timing of injection, pressure interference between injection locations, and overall formation pressure buildup. These volumetric methods may be excellent for comparing the potential between particular formations or basins, but they have not been validated through real-world experience or full-formation injection simulations. Several studies have also suggested that the dynamic components of geologic storage may play the most important role in storing CO{sub 2} in DSFs but until now have not directly compared CO{sub 2} storage resource estimates made with volumetric methodologies to estimates made using dynamic CO{sub 2} storage methodologies. In this study, two DSFs, in geographically separate areas with geologically diverse properties, were evaluated with both volumetric and dynamic CO{sub 2} storage resource estimation methodologies to compare the results and determine the applicability of both approaches. In the end, it was determined that the dynamic CO{sub 2} storage resource potential is timedependent and it asymptotically approaches the volumetric CO

  16. Synthesis, characterization, and catalase activity of a water-soluble diMn(III) complex of a sulphonato-substituted Schiff base ligand: an efficient catalyst for H2O2 disproportionation.

    PubMed

    Palopoli, Claudia; Bruzzo, Natalia; Hureau, Christelle; Ladeira, Sonia; Murgida, Daniel; Signorella, Sandra

    2011-09-19

    A new diMn(III) complex, Na[Mn(2)(3-Me-5-SO(3)-salpentO)(μ-MeO)(μ-AcO)(H(2)O)]·4H(2)O (1), where salpentOH = 1,5-bis(salicylidenamino) pentan-3-ol, was synthesized and structurally characterized. The complex possesses a bis(μ-alkoxo)(μ-acetato) triply bridged diMn(III) core, the structure of which is retained upon dissolution. Complex 1 is highly efficient to disproportionate H(2)O(2) in an aqueous solution of pH ≥ 8.5 or in DMF, with only a slight decrease of activity. Electrospray ionization mass spectrometry, EPR, and UV-vis spectroscopy used to monitor the H(2)O(2) disproportionation in buffered basic medium, suggest that the major active form of the catalyst during cycling occurs in the Mn(III)(2) oxidation state and that the starting complex retains the dinuclearity and composition during catalysis, with the acetate that moves from bridging to terminal ligand. UV-vis and Raman spectroscopy of H(2)O(2) + 1 + Bu(4)NOH mixtures in DMF suggest that the catalytic cycle involves Mn(III)(2)/Mn(IV)(2) oxidation levels. At pH 10.6 in an Et(3)N/Et(3)NH(+) buffer, complex 1 catalyzes dismutation of H(2)O(2) with saturation kinetics on the substrate, first order dependence on the catalyst, and k(cat)/K(M) = 16(1) × 10(2) s(-1) M(-1). During catalysis, the exogenous base contributes to retain the integrity of the bis(μ-alkoxo) doubly bridged diMn core and favors the formation of the catalyst-peroxide adduct (low value of K(M)), rendering 1 a highly efficient catalyst for H(2)O(2) disproportionation.

  17. DUST PRODUCTION FACTORIES IN THE EARLY UNIVERSE: FORMATION OF CARBON GRAINS IN RED-SUPERGIANT WINDS OF VERY MASSIVE POPULATION III STARS

    SciTech Connect

    Nozawa, Takaya; Yoon, Sung-Chul; Maeda, Keiichi; Kozasa, Takashi; Nomoto, Ken'ichi; Langer, Norbert

    2014-06-01

    We investigate the formation of dust in a stellar wind during the red-supergiant (RSG) phase of a very massive Population III star with a zero-age main sequence mass of 500 M {sub ☉}. We show that, in a carbon-rich wind with a constant velocity, carbon grains can form with a lognormal-like size distribution, and that all of the carbon available for dust formation finally condenses into dust for wide ranges of the mass-loss rate ((0.1-3) × 10{sup –3} M {sub ☉} yr{sup –1}) and wind velocity (1-100 km s{sup –1}). We also find that the acceleration of the wind, driven by newly formed dust, suppresses the grain growth but still allows more than half of the gas-phase carbon to finally be locked up in dust grains. These results indicate that, at most, 1.7 M {sub ☉} of carbon grains can form during the RSG phase of 500 M {sub ☉} Population III stars. Such a high dust yield could place very massive primordial stars as important sources of dust at the very early epoch of the universe if the initial mass function of Population III stars was top-heavy. We also briefly discuss a new formation scenario of carbon-rich ultra-metal-poor stars, considering feedback from very massive Population III stars.

  18. Heterogeneous oxidation of Fe(II) on iron oxides in aqueous systems: Identification and controls of Fe(III) product formation

    NASA Astrophysics Data System (ADS)

    Larese-Casanova, Philip; Kappler, Andreas; Haderlein, Stefan B.

    2012-08-01

    The aqueous Fe(II)-oxide Fe(III) system is a reactant for many classes of redox sensitive compounds via an interfacial Fe(II) sorption and electron transfer process. The poorly soluble Fe(III) products formed as a result of contaminant reduction and Fe(II) oxidation on iron oxides may be capable of modifying iron oxide surfaces and affecting subsequent reduction rates of contaminants such as halogenated ethenes or nitroaromatic compounds. The scope of this study was to identify the secondary Fe(III) mineral phases formed after Fe(II) oxidation on common iron oxides during heterogeneous contaminant reduction by directly targeting the secondary minerals using Mössbauer-active isotopes. Fe(III) mineral characterization was performed using 57Fe-Mössbauer spectroscopy, μ-X-ray diffraction, and electron microscopy after oxidation of dissolved 57Fe(II) using nitrobenzenes as a model oxidant in pH-buffered suspensions of 56hematite, 56goethite, 56magnetite, and 56maghemite. Mössbauer spectra confirmed sorbed 57Fe(II) becomes oxidized by the parent 56Fe(III)-oxide sorbent and assimilated as the sorbent oxide prior to any nitrobenzene reduction, consistent with several reports in the literature. In addition to oxide sorbent growth, Fe(II) sorption and oxidation by nitrobenzene result also in the formation of secondary Fe(III) minerals. Goethite formed on three hematite morphologies (rhombohedra, needles, and hexagonal platelets), and acicular needle shapes typical of goethite appeared on the micron-sized hexagonal platelets, at times aligned in 60° orientations on (0 0 1) faces. The proportion of goethite formation on the three hematites was linked to number of surface sites. Only goethite was observed to form on a goethite sorbent. In contrast, lepidocrocite was observed to form on magnetite and maghemite sorbents (consistent with homogeneous Fe(II) oxidation by O2) and assumed spherulite morphologies. All secondary Fe(III) phases were confirmed within

  19. Evaluation of siderite and magnetite formation in BIFs by pressure-temperature experiments of Fe(III) minerals and microbial biomass

    NASA Astrophysics Data System (ADS)

    Halama, Maximilian; Swanner, Elizabeth D.; Konhauser, Kurt O.; Kappler, Andreas

    2016-09-01

    Anoxygenic phototrophic Fe(II)-oxidizing bacteria potentially contributed to the deposition of Archean banded iron formations (BIFs), before the evolution of cyanobacterially-generated molecular oxygen (O2), by using sunlight to oxidize aqueous Fe(II) and precipitate Fe(III) (oxyhydr)oxides. Once deposited at the seafloor, diagenetic reduction of the Fe(III) (oxyhydr)oxides by heterotrophic bacteria produced secondary Fe(II)-bearing minerals, such as siderite (FeCO3) and magnetite (Fe3O4), via the oxidation of microbial organic carbon (i.e., cellular biomass). During deeper burial at temperatures above the threshold for life, thermochemical Fe(III) reduction has the potential to form BIF-like minerals. However, the role of thermochemical Fe(III) reduction of primary BIF minerals during metamorphism, and its impact on mineralogy and geochemical signatures in BIFs, is poorly understood. Consequently, we simulated the metamorphism of the precursor and diagenetic iron-rich minerals (ferrihydrite, goethite, hematite) at low-grade metamorphic conditions (170 °C, 1.2 kbar) for 14 days by using (1) mixtures of abiotically synthesized Fe(III) minerals and either microbial biomass or glucose as a proxy for biomass, and (2) using biogenic minerals formed by phototrophic Fe(II)-oxidizing bacteria. Mössbauer spectroscopy and μXRD showed that thermochemical magnetite formation was limited to samples containing ferrihydrite and glucose, or goethite and glucose. No magnetite was formed from Fe(III) minerals when microbial biomass was present as the carbon and electron sources for thermochemical Fe(III) reduction. This could be due to biomass-derived organic molecules binding to the mineral surfaces and preventing solid-state conversion to magnetite. Mössbauer spectroscopy revealed siderite contents of up to 17% after only 14 days of incubation at elevated temperature and pressure for all samples with synthetic Fe(III) minerals and biomass, whereas 6% of the initial Fe(III) was

  20. Efficient near ultraviolet light induced formation of hydrogen by ferrous hydroxide. [in primitive earth

    NASA Technical Reports Server (NTRS)

    Borowska, Zofia K.; Mauzerall, David C.

    1987-01-01

    A possible origin of early hydrogen by UV-induced photoreduction of ferrous ions was investigated by measuring the rate of H2 formation from irradiated FeSO4 solutions as a function of pH and the range of UV sources. It was found that, in addition to the known reaction in acid solution which decreases in yield with increasing pH and requires far-UV light, there is an efficient reaction occurring between pH 6 and 9 which utilizes near-UV light (of a 200-W mercury arc lamp). This latter reaction is a linear function of both the concentration of Fe(2+) and the light intensity. These results support the suggestion of Braterman et al. (1983) that the near-UV-driven photooxidation of ferrous ions may be responsible for the origin of the banded iron formations on the early earth. The efficient photoreaction could also explain the source of reducing equivalents for CO2 reduction.

  1. Efficient near ultraviolet light induced formation of hydrogen by ferrous hydroxide. [in primitive earth

    NASA Technical Reports Server (NTRS)

    Borowska, Zofia K.; Mauzerall, David C.

    1987-01-01

    A possible origin of early hydrogen by UV-induced photoreduction of ferrous ions was investigated by measuring the rate of H2 formation from irradiated FeSO4 solutions as a function of pH and the range of UV sources. It was found that, in addition to the known reaction in acid solution which decreases in yield with increasing pH and requires far-UV light, there is an efficient reaction occurring between pH 6 and 9 which utilizes near-UV light (of a 200-W mercury arc lamp). This latter reaction is a linear function of both the concentration of Fe(2+) and the light intensity. These results support the suggestion of Braterman et al. (1983) that the near-UV-driven photooxidation of ferrous ions may be responsible for the origin of the banded iron formations on the early earth. The efficient photoreaction could also explain the source of reducing equivalents for CO2 reduction.

  2. Interfacial confined formation of mesoporous spherical TiO2 nanostructures with improved photoelectric conversion efficiency.

    PubMed

    Shao, Wei; Gu, Feng; Li, Chunzhong; Lu, Mengkai

    2010-06-21

    Uniform mesoporous TiO(2) nanospheres were successfully developed via an interfacial confined formation process for application in dye-sensitized solar cells. The mesoporous spherical structures greatly promote the dye-loading capacity, electron transfer, and light scattering, resulting in remarkable enhancement of the cell performance. The designed interfacial platform caused a reaction-limited aggregation of the TiO(2) nanocrystals, resulting in the formation of mesoporous spherical nanostructures with sphere diameter of 216 nm and pore size of 8 nm. The oriented attachment of adjacent TiO(2) nanocrystals facilitated the electron transfer process when the mesoporous TiO(2) nanospheres were used as electrode films. The dye coverage was enhanced remarkably in the mesoporous spherical TiO(2) samples. Owing to the enhanced light-harvesting efficiency, solar conversion efficiency was enhanced about 30% for the dye-sensitized solar cell (DSSC) based on mesoporous spherical TiO(2) in comparison with that made by commercial TiO(2) nanoparticles.

  3. The influence of sodium salts (iodide, chloride and sulfate) on the formation efficiency of sulfamerazine nanocrystals.

    PubMed

    Lou, Hao; Liu, Min; Qu, Wen; Johnson, James; Brunson, Ed; Almoazen, Hassan

    2014-08-01

    The purpose of this study is to evaluate the influence of sodium iodide, sodium chloride and sodium sulfate on the formation efficiency of sulfamerazine nanocrystals by wet ball milling. Sulfamerazine was milled using zirconium oxide beads in a solution containing polyvinylpyrrolidone (PVP) and a sodium salt (iodide, chloride or sulfate). Particle size distributions were evaluated by light diffraction before and after milling. High-performance liquid chromatography was utilized to determine the amount of PVP adsorbed onto sulfamerazine surface. Lyophilized nanocrystals were further characterized by differential scanning calorimetry and dissolution testing. Sulfate ion had more profound effect on reducing particle size via milling than iodide or chloride. We linked our findings to Hofmeister ion series, which indicates that sulfate ions tends to break the water structure, increases the surface tension and lowers the solubility of hydrocarbons in water. We hypothesized that the addition of sulfate ions dehydrated the PVP molecules and enhanced its adsorption onto the sulfamerazine particle surfaces. Consequently, the adsorbed PVP helped to stabilize of the nanosuspension. The nanocrystals that were obtained from the lyophilized milled suspensions exhibited a notable increase in dissolution rate. The addition of sodium sulfate enhanced the formation efficiency of sulfamerazine nanocrystals.

  4. The effect of butterfly scales on flight efficiency and leading edge vortex formation

    NASA Astrophysics Data System (ADS)

    Lang, Amy; Wilroy, Jacob; Wahidi, Redha; Slegers, Nathan; Heilman, Micahel; Cranford, Jacob

    2016-11-01

    It is hypothesized that the scales on a butterfly wing lead to increased flight efficiency. Recent testing of live butterflies tracked their motion over 246 flights for 11 different specimens. Results show a 37.8 percent mean decrease in flight efficiency and a flapping amplitude reduction of 6.7 percent once the scales were removed. This change could be largely a result of how the leading edge vortex (LEV) interacts with the wing. To simplify this complex flow problem, an experiment was designed to focus on the alteration of 2-D vortex development with a variation in surface patterning. Specifically, the secondary vorticity generated by the LEV interacting at the patterned surface was studied, as well as the subsequent effect on the LEV's growth rate and peak circulation. For this experiment butterfly inspired grooves were created using additive manufacturing and were attached to a flat plate with a chordwise orientation, thus increasing plate surface area. The vortex generated by the grooved plate was then compared to a smooth case as the plate translated vertically through a tow tank at Re = 1500, 3000, and 6000. Using DPIV, the vortex formation was documented and a maximum vortex formation time of 4.22 was found based on the flat plate travel distance and chord length. Results indicate that the patterned surface slows down the growth of the vortex which corroborates the flight test results. Funding from NSF CBET Fluid Dynamcis is gratefully acknowledged.

  5. Three-step effluent chlorination increases disinfection efficiency and reduces DBP formation and toxicity.

    PubMed

    Li, Yu; Zhang, Xiangru; Yang, Mengting; Liu, Jiaqi; Li, Wanxin; Graham, Nigel J D; Li, Xiaoyan; Yang, Bo

    2017-02-01

    Chlorination is extensively applied for disinfecting sewage effluents, but it unintentionally generates disinfection byproducts (DBPs). Using seawater for toilet flushing introduces a high level of bromide into domestic sewage. Chlorination of sewage effluent rich in bromide causes the formation of brominated DBPs. The objectives of achieving a disinfection goal, reducing disinfectant consumption and operational costs, as well as diminishing adverse effects to aquatic organisms in receiving water body remain a challenge in sewage treatment. In this study, we have demonstrated that, with the same total chlorine dosage, a three-step chlorination (dosing chlorine by splitting it into three equal portions with a 5-min time interval for each portion) was significantly more efficient in disinfecting a primary saline sewage effluent than a one-step chlorination (dosing chlorine at one time). Compared to one-step chlorination, three-step chlorination enhanced the disinfection efficiency by up to 0.73-log reduction of Escherichia coli. The overall DBP formation resulting from one-step and three-step chlorination was quantified by total organic halogen measurement. Compared to one-step chlorination, the DBP formation in three-step chlorination was decreased by up to 23.4%. The comparative toxicity of one-step and three-step chlorination was evaluated in terms of the development of embryo-larva of a marine polychaete Platynereis dumerilii. The results revealed that the primary sewage effluent with three-step chlorination was less toxic than that with one-step chlorination, indicating that three-step chlorination could reduce the potential adverse effects of disinfected sewage effluents to aquatic organisms in the receiving marine water. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. Dense Gas Fraction and Star-formation Efficiency Variations in the Antennae Galaxies

    NASA Astrophysics Data System (ADS)

    Bigiel, F.; Leroy, A. K.; Blitz, L.; Bolatto, A. D.; da Cunha, E.; Rosolowsky, E.; Sandstrom, K.; Usero, A.

    2015-12-01

    We use the Combined Array for Research in Millimeter-wave Astronomy (CARMA) millimeter interferometer to map the Antennae Galaxies (NGC 4038/39), tracing the bulk of the molecular gas via the 12CO(1-0) line and denser molecular gas via the high density transitions HCN(1-0), HCO+(1-0), CS(2-1), and HNC(1-0). We detect bright emission from all tracers in both the two nuclei and three locales in the overlap region between the two nuclei. These three overlap region peaks correspond to previously identified “supergiant molecular clouds.” We combine the CARMA data with Herschel infrared (IR) data to compare observational indicators of the star formation efficiency (star formation rate/H2 ∝ IR/CO), dense gas fraction (HCN/CO), and dense gas star formation efficiency (IR/HCN). Regions within the Antennae show ratios consistent with those seen for entire galaxies, but these ratios vary by up to a factor of six within the galaxy. The five detected regions vary strongly in both their integrated intensities and these ratios. The northern nucleus is the brightest region in millimeter-wave line emission, while the overlap region is the brightest part of the system in the IR. We combine the CARMA and Herschel data with ALMA CO data to report line ratio patterns for each bright point. CO shows a declining spectral line energy distribution, consistent with previous studies. HCO+ (1-0) emission is stronger than HCN (1-0) emission, perhaps indicating either more gas at moderate densities or higher optical depth than is commonly seen in more advanced mergers.

  7. DENSE GAS FRACTION AND STAR FORMATION EFFICIENCY VARIATIONS IN THE ANTENNAE GALAXIES

    SciTech Connect

    Bigiel, F.; Leroy, A. K.; Blitz, L.; Bolatto, A. D.; Da Cunha, E.; Rosolowsky, E.; Sandstrom, K.; Usero, A.

    2015-12-20

    We use the Combined Array for Research in Millimeter-wave Astronomy (CARMA) millimeter interferometer to map the Antennae Galaxies (NGC 4038/39), tracing the bulk of the molecular gas via the {sup 12}CO(1–0) line and denser molecular gas via the high density transitions HCN(1–0), HCO{sup +}(1–0), CS(2–1), and HNC(1–0). We detect bright emission from all tracers in both the two nuclei and three locales in the overlap region between the two nuclei. These three overlap region peaks correspond to previously identified “supergiant molecular clouds.” We combine the CARMA data with Herschel infrared (IR) data to compare observational indicators of the star formation efficiency (star formation rate/H{sub 2} ∝ IR/CO), dense gas fraction (HCN/CO), and dense gas star formation efficiency (IR/HCN). Regions within the Antennae show ratios consistent with those seen for entire galaxies, but these ratios vary by up to a factor of six within the galaxy. The five detected regions vary strongly in both their integrated intensities and these ratios. The northern nucleus is the brightest region in millimeter-wave line emission, while the overlap region is the brightest part of the system in the IR. We combine the CARMA and Herschel data with ALMA CO data to report line ratio patterns for each bright point. CO shows a declining spectral line energy distribution, consistent with previous studies. HCO{sup +} (1–0) emission is stronger than HCN (1–0) emission, perhaps indicating either more gas at moderate densities or higher optical depth than is commonly seen in more advanced mergers.

  8. The W43-MM1 mini-starburst ridge, a test for star formation efficiency models

    NASA Astrophysics Data System (ADS)

    Louvet, F.; Motte, F.; Hennebelle, P.; Maury, A.; Bonnell, I.; Bontemps, S.; Gusdorf, A.; Hill, T.; Gueth, F.; Peretto, N.; Duarte-Cabral, A.; Stephan, G.; Schilke, P.; Csengeri, T.; Nguyen Luong, Q.; Lis, D. C.

    2014-10-01

    Context. Star formation efficiency (SFE) theories are currently based on statistical distributions of turbulent cloud structures and a simple model of star formation from cores. They remain poorly tested, especially at the highest densities. Aims: We investigate the effects of gas density on the SFE through measurements of the core formation efficiency (CFE). With a total mass of ~2 × 104 M⊙, the W43-MM1 ridge is one of the most convincing candidate precursors of Galactic starburst clusters and thus one of the best places to investigate star formation. Methods: We used high-angular resolution maps obtained at 3 mm and 1 mm within the W43-MM1 ridge with the IRAM Plateau de Bure Interferometer to reveal a cluster of 11 massive dense cores, and, one of the most massive protostellar cores known. A Herschel column density image provided the mass distribution of the cloud gas. We then measured the "instantaneous" CFE and estimated the SFE and the star formation rate (SFR) within subregions of the W43-MM1 ridge. Results: The high SFE found in the ridge (~6% enclosed in ~8 pc3) confirms its ability to form a starburst cluster. There is, however, a clear lack of dense cores in the eastern part of the ridge, which may be currently assembling. The CFE and the SFE are observed to increase with volume gas density, while the SFR per free fall time steeply decreases with the virial parameter, αvir. Statistical models of the SFR may describe the outskirts of the W43-MM1 ridge well, but struggle to reproduce its inner part, which corresponds to measurements at low αvir. It may be that ridges do not follow the log-normal density distribution, Larson relations, and stationary conditions forced in the statistical SFR models. Final IRAM/PdBI FITS cube is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/570/A15

  9. Can the removal of molecular cloud envelopes by external feedback affect the efficiency of star formation?

    NASA Astrophysics Data System (ADS)

    Lucas, William E.; Bonnell, Ian A.; Forgan, Duncan H.

    2017-04-01

    We investigate how star formation efficiency (SFE) can be significantly decreased by the removal of a molecular cloud's envelope by feedback from an external source. Feedback from star formation has difficulties halting the process in dense gas but can easily remove the less dense and warmer envelopes where star formation does not occur. However, the envelopes can play an important role keeping their host clouds bound by deepening the gravitational potential and providing a constraining pressure boundary. We use numerical simulations to show that removal of the cloud envelopes results in all cases in a fall in the SFE. At 1.38 free-fall times, our 4 pc cloud simulation experienced a drop in the SFE from 16 to 6 per cent, while our 5 pc cloud fell from 27 to 16 per cent. At the same time, our 3 pc cloud (the least bound) fell from an SFE of 5.67 per cent to zero when the envelope was lost. The SFE per free-fall time varied from zero to ≈0.25 according to α, defined to be the ratio of the kinetic plus thermal to gravitational energy, and irrespective of the absolute star-forming mass available. Furthermore, the fall in SFE associated with the loss of the envelope is found to even occur at later times. We conclude that the SFE will always fall should a star-forming cloud lose its envelope due to stellar feedback, with less bound clouds suffering the greatest decrease.

  10. Molecular gas observations and enhanced massive star formation efficiencies in M 100.

    NASA Astrophysics Data System (ADS)

    Knapen, J. H.; Beckman, J. E.; Cepa, J.; Nakai, N.

    1996-04-01

    We present new J=1->0 ^12^CO observations along the northern spiral arm of the grand-design spiral galaxy M 100 (NGC 4321), and study the distribution of molecular hydrogen as derived from these observations, comparing the new data with a set of data points on the southern arm published previously. We compare these measurements on both spiral arms and on the interarm regions with observations of the atomic and ionized hydrogen components. We determine massive star formation efficiency parameters, defined as the ratio of Hα luminosity to total gas mass, along the arms and compare the values to those in the interarm regions adjacent to the arms. We find that these parameters in the spiral arms are on average a factor of 3 higher than outside the arms, a clear indication of triggering of the star formation in the spiral arms. We discuss possible mechanisms for this triggering, and conclude that a density wave system is probably responsible for it. We discuss several possible systematical effects in some detail, and infer that the conclusions on triggering are sound. We specifically discuss the possible effects of extinction in Hα, or a non-standard CO to H_2_ conversion factor (X), and find that our conclusions on the enhancement of the efficiencies in the arms are reinforced rather than weakened by these considerations. A simple star forming scheme involving threshold densities for gravitational collapse is discussed for NGC 4321, and comparison is made with M 51. We find that the gas between the arms is generally stable against gravitational collapse whereas the gas in the arms is not, possibly leading to the observed arm-interarm differences in efficiency, but also note that these results, unlike the others obtained in this paper, do depend critically on the assumed value for the conversion factor.

  11. Interactions between Type III receptor tyrosine phosphatases and growth factor receptor tyrosine kinases regulate tracheal tube formation in Drosophila.

    PubMed

    Jeon, Mili; Scott, Matthew P; Zinn, Kai

    2012-06-15

    The respiratory (tracheal) system of the Drosophila melanogaster larva is an intricate branched network of air-filled tubes. Its developmental logic is similar in some ways to that of the vertebrate vascular system. We previously described a unique embryonic tracheal tubulogenesis phenotype caused by loss of both of the Type III receptor tyrosine phosphatases (RPTPs), Ptp4E and Ptp10D. In Ptp4E Ptp10D double mutants, the linear tubes in unicellular and terminal tracheal branches are converted into bubble-like cysts that incorporate apical cell surface markers. This tube geometry phenotype is modulated by changes in the activity or expression of the epidermal growth factor receptor (Egfr) tyrosine kinase (TK). Ptp10D physically interacts with Egfr. Here we demonstrate that the Ptp4E Ptp10D phenotype is the consequence of the loss of negative regulation by the RPTPs of three growth factor receptor TKs: Egfr, Breathless and Pvr. Reducing the activity of any of the three kinases by tracheal expression of dominant-negative mutants suppresses cyst formation. By competing dominant-negative and constitutively active kinase mutants against each other, we show that the three RTKs have partially interchangeable activities, so that increasing the activity of one kinase can compensate for the effects of reducing the activity of another. This implies that SH2-domain downstream effectors that are required for the phenotype are likely to be able to interact with phosphotyrosine sites on all three receptor TKs. We also show that the phenotype involves increases in signaling through the MAP kinase and Rho GTPase pathways.

  12. Interactions between Type III receptor tyrosine phosphatases and growth factor receptor tyrosine kinases regulate tracheal tube formation in Drosophila

    PubMed Central

    Jeon, Mili; Scott, Matthew P.; Zinn, Kai

    2012-01-01

    Summary The respiratory (tracheal) system of the Drosophila melanogaster larva is an intricate branched network of air-filled tubes. Its developmental logic is similar in some ways to that of the vertebrate vascular system. We previously described a unique embryonic tracheal tubulogenesis phenotype caused by loss of both of the Type III receptor tyrosine phosphatases (RPTPs), Ptp4E and Ptp10D. In Ptp4E Ptp10D double mutants, the linear tubes in unicellular and terminal tracheal branches are converted into bubble-like cysts that incorporate apical cell surface markers. This tube geometry phenotype is modulated by changes in the activity or expression of the epidermal growth factor receptor (Egfr) tyrosine kinase (TK). Ptp10D physically interacts with Egfr. Here we demonstrate that the Ptp4E Ptp10D phenotype is the consequence of the loss of negative regulation by the RPTPs of three growth factor receptor TKs: Egfr, Breathless and Pvr. Reducing the activity of any of the three kinases by tracheal expression of dominant-negative mutants suppresses cyst formation. By competing dominant-negative and constitutively active kinase mutants against each other, we show that the three RTKs have partially interchangeable activities, so that increasing the activity of one kinase can compensate for the effects of reducing the activity of another. This implies that SH2-domain downstream effectors that are required for the phenotype are likely to be able to interact with phosphotyrosine sites on all three receptor TKs. We also show that the phenotype involves increases in signaling through the MAP kinase and Rho GTPase pathways. PMID:23213447

  13. Metal Reduction and Mineral formation by a Psychrotolerant Fe(III)-Reducing Bacterium Isolated from an Iron-Rich Waters near a Hydrothermal Vent

    NASA Astrophysics Data System (ADS)

    Roh, Y.; Vali, H.; Stapleton, R. D.; Fields, M. M.; Phelps, T. J.; Zhou, J.

    2002-12-01

    Although dissimilatory metal reduction and mineral formation under mesophilic and thermophilic conditions are extensively examined, they are poorly understood under low temperature. The objective of this study was to examine metal reduction and mineral formation using a psychrotolerant iron-reducing bacterium (Shewanella alga, PV-4) isolated from iron-rich waters associated with the Naha vents off the Hawaiian coast. The psychrotolerant iron-reducing bacterium was able to use lactate, formate, and hydrogen as an electron donor while reducing Fe(III)-citrate, Fe(III)-EDTA, Co(III)-EDTA, Cr(VI), Mn(IV), and iron oxyhydroxide (FeOOH) at temperatures between 0 and 37°C. The psychrotolerant bacterium exhibited diverse mineral precipitation capabilities including the formation of magnetite (Fe3O4), siderite (FeCO3), and rhodochrosite (MnCO3). Transmission electron microscopic data showed that PV-4 formed mainly superparamagnetic magnetite at temperatures ranging from 0 to 14°C and formed mainly single-domain magnetite at temperatures ranging from 18 to 37°C. This study indicats that iron-reducing bacteria may contribute to the biogeochemical cycling of metals and carbon at low temperatures and may contribute to the natural remnant magnetism of marine sediments.

  14. Quantum efficiency performances of the NIR European Large Format Array detectors tested at ESTEC

    NASA Astrophysics Data System (ADS)

    Crouzet, P.-E.; Duvet, L.; de Wit, F.; Beaufort, T.; Blommaert, S.; Butler, B.; Van Duinkerken, G.; ter Haar, J.; Heijnen, J.; van der Luijt, K.; Smit, H.

    2015-10-01

    Publisher's Note: This paper, originally published on 10/12/2015, was replaced with a corrected/revised version on 10/23/2015. If you downloaded the original PDF but are unable to access the revision, please contact SPIE Digital Library Customer Service for assistance. The Payload Technology Validation Section (SRE-FV) at ESTEC has the goal to validate new technology for future or on-going mission. In this framework, a test set up to characterize the quantum efficiency of near-infrared (NIR) detectors has been created. In the context of the NIR European Large Format Array ("LFA"), 3 deliverables detectors coming from SELEX-UK/ATC (UK) on one side, and CEA/LETI- CEA/IRFU-SOFRADIR (FR) on the other side were characterized. The quantum efficiency of an HAWAII-2RG detector from Teledyne was as well measured. The capability to compare on the same setup detectors from different manufacturers is a unique asset for the future mission preparation office. This publication will present the quantum efficiency results of a HAWAII-2RG detector from Teledyne with a 2.5um cut off compared to the LFA European detectors prototypes developed independently by SELEX-UK/ATC (UK) on one side, and CEA/LETI- CEA/IRFU-SOFRADIR (FR) on the other side.

  15. Third phase formation in the extraction of Nd(III) by octyl(phenyl)-N,N-diisobutyl carbamoyl methyl phosphine oxide (O{Phi}CMPO)

    SciTech Connect

    Suresh, A.; Brahmmananda Rao, C.V.S.; Sabharwal, K.N.; Srinivasan, T.G.; Vasudeva Rao, P.R.

    1999-01-01

    Third phase formation in the extraction of Nd(III) by 0.2 M Octyl(Phenyl)-N,N-Diisobutyl Carbamoyl methyl phosphine oxide (O{Phi}CMPO) in n-dodecane has been studied with tri-n-butyl phosphate (TBP) and tri-n-amyl phosphate (TAP) as modifiers to provide a comparison between these two modifier systems. The effect of concentration of TAP as modifier for the extraction of Nd(III) by 0.2 M O{Phi}CMPO has been studied. The extraction of Nd(III) by TAP/n-dodecane in the absence of O{Phi}CMPO has also been studied and the results are reported here.

  16. Rapid Ti(III) reduction of perchlorate in the presence of beta-alanine: kinetics, pH effect, complex formation, and beta-alanine effect.

    PubMed

    Wang, Chao; Huang, Zhengdao; Lippincott, Lee; Meng, Xiaoguang

    2010-03-15

    Ti(III) reduction of perchlorate might be a useful method for the treatment of highly perchlorate-contaminated water. Though the reaction rate was usually low, we observed that beta-alanine (HOOCCH(2)CH(2)NH(2)) could significantly promote the reaction. A complete (>99.9%) perchlorate removal was obtained in a solution containing [ClO(4)(-)]=1.0mM, [Ti(III)]=40 mM, and [beta-alanine]=120 mM after 2.5h of reaction under 50 degrees C. The effects of both pH and complex formation on the reaction were then studied. The results showed that without beta-alanine the optimal pH was 2.3. When pH increased from 1.6 to 2.3, the reduction rate increased remarkably. In the pH range >2.3, however, the reduction was significantly inhibited, attributed to the formation of Ti(III) precipitate. The presence of beta-alanine at a molar ratio of [beta-alanine]:[Ti(III)]=3:1 significantly increased the reduction rate of perchlorate even at near neutral pH. This is because beta-alanine formed complexes with Ti(III), which greatly improved the total soluble [Ti(III)] in the pH range between 3.5 and 6. The findings may lead to the development of rapid treatment methods for intermittent and small stream of highly perchlorate-contaminated water, which are resulted from the manufacturing, storage, handling, use and/or disposal of large quantities of perchlorate salts.

  17. Intensely colored mixed-valence iron(II) iron(III) formate analogue of Prussian Blue exhibits néel N-type ferrimagnetism.

    PubMed

    Hagen, Karl S; Naik, Sunil G; Huynh, Boi Hanh; Masello, Antonio; Christou, George

    2009-06-10

    The reaction of colorless iron(II) formate or the mixed-valence cluster Fe(3)O(MeCOO)(6)(H(2)O)(3) with formic acid in dimethylformamide exposed to air at 110 degrees C affords black crystals of the mixed-valence (Me(2)NH(2))[Fe(II)Fe(III)(HCOO)(6)] three-dimensional (3D) structure in which the cations occupy half of the channels. The structure consists of alternating layers of Fe(II)O(6) [Fe(1)-O(1), 2.119(1) A] and Fe(III)O(6) [Fe(2)-O(2), 2.0049(9) A] octahedra bridged by anti-anti-bonded formates to afford an open-framework 3D structure. The structure is very similar to those of (Me(2)NH(2))[Fe(II)(HCOO)(3)] and [Fe(III)(HCOO)(3)].HCOOH, both of which are colorless. The black crystals appear dark-purple (lambda(max) approximately 520 nm) when powdered. The room-temperature Mössbauer spectrum confirms the 1:1 ratio of Fe(II) (delta = 1.03 mm/s, DeltaE(Q) = 1.16 mm/s) and Fe(III) (delta = 0.62 mm/s, DeltaE (Q) = 0.49 mm/s). Magnetic ordering that includes negative magnetization at low fields occurs at low temperature. The only molecular-based magnetic materials in which this phenomenon has been observed are the 2D polyiron(II,III) oxalates A[Fe(II)Fe(III)(C(2)O(4))(3)] (A = R(4)N(+) cation).

  18. Impact of a star formation efficiency profile on the evolution of open clusters

    NASA Astrophysics Data System (ADS)

    Shukirgaliyev, B.; Parmentier, G.; Berczik, P.; Just, A.

    2017-09-01

    Aims: We study the effect of the instantaneous expulsion of residual star-forming gas on star clusters in which the residual gas has a density profile that is shallower than that of the embedded cluster. This configuration is expected if star formation proceeds with a given star-formation efficiency per free-fall time in a centrally concentrated molecular gas clump. Methods: We performed direct N-body simulations whose initial conditions were generated by the program "mkhalo" from the package "falcON", adapted for our models. Our model clusters initially had a Plummer profile and are in virial equilibrium with the gravitational potential of the cluster-forming clump. The residual gas contribution was computed based on a local-density driven clustered star formation model. Our simulations included mass loss by stellar evolution and the tidal field of a host galaxy. Results: We find that a star cluster with a minimum global star formation efficiency (SFE) of 15 percent is able to survive instantaneous gas expulsion and to produce a bound cluster. Its violent relaxation lasts no longer than 20 Myr, independently of its global SFE and initial stellar mass. At the end of violent relaxation, the bound fractions of the surviving clusters with the same global SFEs are similar, regardless of their initial stellar mass. Their subsequent lifetime in the gravitational field of the Galaxy depends on their bound stellar masses. Conclusions: We therefore conclude that the critical SFE needed to produce a bound cluster is 15 percent, which is roughly half the earlier estimates of 33 percent. Thus we have improved the survival likelihood of young clusters after instantaneous gas expulsion. Young clusters can now survive instantaneous gas expulsion with a global SFEs as low as the SFEs observed for embedded clusters in the solar neighborhood (15-30 percent). The reason is that the star cluster density profile is steeper than that of the residual gas. However, in terms of the

  19. Carbon dots preparation as a fluorescent sensing platform for highly efficient detection of Fe(III) ions in biological systems.

    PubMed

    Hamishehkar, Hamed; Ghasemzadeh, Bahar; Naseri, Abdolhossein; Salehi, Roya; Rasoulzadeh, Farzaneh

    2015-01-01

    Water-soluble carbon dots (CDs) were prepared, using a facile hydrothermal oxidation route of cyclic oligosaccharide α-CD, as carbon sources, and alkali as additives. The successful synthesis of CDs was confirmed by scanning electron microscopy (SEM), dynamic light scattering (DLS), FTIR, UV-visible absorption, and emission fluorescence. The characterizations showed that the prepared CDs are spherical and well-dispersed in water with average diameters of approximately 2 nm. These water-soluble CDs have excellent photo stability towards photo bleaching during 30 days. The obtained CDs showed a strong emission at the wavelength of 450 nm, with an optimum excitation of 360 nm. The fluorescence quenching of CDs in the presence of Fe(III) ions was used as fluorescent probes for quantifying Fe(III) ions in aqueous solution. Under optimum condition, the fluorescence intensity versus Fe(III) concentration gave a linear response, according to Stern-Volmer equation. The linearity range of the calibration curve and the limit of detection were 1.60×10(-5) to 16.6×10(-5) mol L(-1), and 6.05×10(-6) mol L(-1), respectively, which was in the range for serum analysis of Fe(III). It was concluded that the prepared CDs had a great potential as fluorescent probes for applications in analysis of Fe(III) ions in the blood serum samples, which is hardly interfered by other ions.

  20. Pentachlorophenol radical cations generated on Fe(III)-montmorillonite initiate octachlorodibenzo-p-dioxin formation in clays: DFT and FTIR studies

    PubMed Central

    Gu, Cheng; Liu, Cun; Johnston, Cliff T.; Teppen, Brian J.; Li, Hui; Boyd, Stephen A.

    2011-01-01

    Octachlorodibenzodioxin (OCDD) forms spontaneously from pentachlorophenol (PCP) on the surfaces of Fe(III)-saturated smectite clay (1). Here, we used in situ FTIR methods and quantum mechanical calculations to determine the mechanism by which this reaction is initiated. As the clay was dehydrated, vibrational spectra showed new peaks that grew and then reversibly disappeared as the clay rehydrated. First principle DFT calculations of hydrated Fe-PCP clusters reproduced these transient FTIR peaks when inner-sphere complexation and concomitant electron transfer produced Fe(II) and PCP radical cations. Thus, our experimental (FTIR) and theoretical (quantum mechanical) results mutually support the hypothesis that OCDD formation on Fe-smectite surfaces is initiated by the reversible formation of metastable PCP radical cations via single electron transfer from PCP to Fe(III). The negatively charged clay surface apparently selects for this reaction mechanism by stabilizing PCP radical cations. PMID:21254769

  1. C2-domain mediated nano-cluster formation increases calcium signaling efficiency

    PubMed Central

    Bonny, Mike; Hui, Xin; Schweizer, Julia; Kaestner, Lars; Zeug, André; Kruse, Karsten; Lipp, Peter

    2016-01-01

    Conventional protein kinase Cs (cPKCs) are key signaling proteins for transducing intracellular Ca2+ signals into downstream phosphorylation events. However, the lifetime of individual membrane-bound activated cPKCs is an order of magnitude shorter than the average time needed for target-protein phosphorylation. Here, we employed intermolecular Förster resonance energy transfer (FRET) in living cells combined with computational analysis to study the spatial organization of cPKCs bound to the plasma membrane. We discovered Ca2+-dependent cPKC nano-clusters that significantly extend cPKC’s plasma-membrane residence time. These protein patterns resulted from self-assembly mediated by Ca2+-binding C2-domains, which are widely used for membrane-targeting of Ca2+-sensing proteins. We also established clustering of other unrelated C2-domain containing proteins, suggesting that nano-cluster formation is a key step for efficient cellular Ca2+-signaling. PMID:27808106

  2. C2-domain mediated nano-cluster formation increases calcium signaling efficiency.

    PubMed

    Bonny, Mike; Hui, Xin; Schweizer, Julia; Kaestner, Lars; Zeug, André; Kruse, Karsten; Lipp, Peter

    2016-11-03

    Conventional protein kinase Cs (cPKCs) are key signaling proteins for transducing intracellular Ca(2+) signals into downstream phosphorylation events. However, the lifetime of individual membrane-bound activated cPKCs is an order of magnitude shorter than the average time needed for target-protein phosphorylation. Here, we employed intermolecular Förster resonance energy transfer (FRET) in living cells combined with computational analysis to study the spatial organization of cPKCs bound to the plasma membrane. We discovered Ca(2+)-dependent cPKC nano-clusters that significantly extend cPKC's plasma-membrane residence time. These protein patterns resulted from self-assembly mediated by Ca(2+)-binding C2-domains, which are widely used for membrane-targeting of Ca(2+)-sensing proteins. We also established clustering of other unrelated C2-domain containing proteins, suggesting that nano-cluster formation is a key step for efficient cellular Ca(2+)-signaling.

  3. An Efficient Method for the Preparation of Styrene Derivatives via Rh(III)-Catalyzed Direct C—H Vinylation

    PubMed Central

    Otley, Kate D.; Ellman, Jonathan A.

    2015-01-01

    The development of a method for the Rh(III)-catalyzed direct vinylation of an aromatic C—H bond to give functionalized styrenes in good yield, using vinyl acetate as a convenient and inexpensive vinyl source is reported. High functional group tolerance is demonstrated for electronically distinct arenes as well as different directing groups. Mechanistic investigation resulted in the characterization of a novel rhodium-metallacycle, which represents the first x-ray structure of a [1,2]-Rh(III)-alkenyl addition adduct. PMID:25715077

  4. N-type molecular electrical doping in organic semiconductors: formation and dissociation efficiencies of charge transfer complex

    NASA Astrophysics Data System (ADS)

    Kim, Jae-Min; Yoo, Seung-Jun; Moon, Chang-Ki; Sim, Bomi; Lee, Jae-Hyun; Lim, Heeseon; Kim, Jeong Won; Kim, Jang-Joo

    2016-09-01

    Electrical doping is an important method in organic electronics to enhance device efficiency by controlling Fermi level, increasing conductivity, and reducing injection barrier from electrode. To understand the charge generation process of dopant in doped organic semiconductors, it is important to analyze the charge transfer complex (CTC) formation and dissociation into free charge carrier. In this paper, we correlate charge generation efficiency with the CTC formation and dissociation efficiency of n-dopant in organic semiconductors (OSs). The CTC formation efficiency of Rb2CO3 linearly decreases from 82.8% to 47.0% as the doping concentration increases from 2.5 mol% to 20 mol%. The CTC formation efficiency and its linear decrease with doping concentration are analytically correlated with the concentration-dependent size and number of dopant agglomerates by introducing the degree of reduced CTC formation. Lastly, the behavior of dissociation efficiency is discussed based on the picture of the statistical semiconductor theory and the frontier orbital hybridization model.

  5. Efficient Isoprene Secondary Organic Aerosol Formation from a Non-IEPOX Pathway

    DOE PAGES

    Liu, Jiumeng; D’Ambro, Emma L.; Lee, Ben H.; ...

    2016-09-20

    With a large global emission rate and high reactivity, isoprene has a profound effect upon atmospheric chemistry and composition. The atmospheric pathways by which isoprene converts to secondary organic aerosol (SOA) and how anthropogenic pollutants such as nitrogen oxides and sulfur affect this process are subjects of intense research because particles affect Earth’s climate and local air quality. In the absence of both nitrogen oxides and reactive aqueous seed particles, we measure SOA mass yields from isoprene photochemical oxidation of up to 15%, which are factors of 2 or more higher than those typically used in coupled chemistry climate models.more » SOA yield is initially constant with the addition of increasing amounts of nitric oxide (NO) but then sharply decreases for input concentrations above 50 ppbv. Online measurements of aerosol molecular composition show that the fate of second-generation RO2 radicals is key to understanding the efficient SOA formation and the NOx-dependent yields described here and in the literature. These insights allow for improved quantitative estimates of SOA formation in the preindustrial atmosphere and in biogenic-rich regions with limited anthropogenic impacts and suggest that a more-complex representation of NOx-dependent SOA yields may be important in models« less

  6. Efficient Isoprene Secondary Organic Aerosol Formation from a Non-IEPOX Pathway

    SciTech Connect

    Liu, Jiumeng; D’Ambro, Emma L.; Lee, Ben H.; Lopez-Hilfiker, Felipe D.; Zaveri, Rahul A.; Rivera-Rios, Jean C.; Keutsch, Frank N.; Iyer, Siddharth; Kurten, Theo; Zhang, Zhenfa; Gold, Avram; Surratt, Jason D.; Shilling, John E.; Thornton, Joel A.

    2016-09-20

    With a large global emission rate and high reactivity, isoprene has a profound effect upon atmospheric chemistry and composition. The atmospheric pathways by which isoprene converts to secondary organic aerosol (SOA) and how anthropogenic pollutants such as nitrogen oxides and sulfur affect this process are a subject of intense research because particles affect Earth’s climate and local air quality. In the absence of both nitrogen oxides and reactive aqueous seed particles, we measure SOA mass yields from isoprene photochemical oxidation of up to 15%, which are factors of 2, or more, higher than those typically used in coupled chemistry-climate models. SOA yield is initially constant with the addition of increasing amounts of nitric oxide (NO) but then sharply decreases for input concentrations above 10 ppbv. Online measurements of aerosol molecular composition show that the fate of second-generation RO2 radicals is key to understanding the efficient SOA formation and the NOx dependent yields described here and in the literature. These insights allow for improved quantitative estimates of SOA formation in the pre-industrial atmosphere and in biogenic-rich regions with limited anthropogenic impacts and suggest a more complex representation of NOx dependent SOA yields may be important in models.

  7. The formation efficiency of close-in planets via Lidov-Kozai migration: analytic calculations

    NASA Astrophysics Data System (ADS)

    Muñoz, Diego J.; Lai, Dong; Liu, Bin

    2016-07-01

    Lidov-Kozai oscillations of planets in stellar binaries, combined with tidal dissipation, can lead to the formation of hot Jupiters (HJs) or tidal disruption of planets. Recent population synthesis studies have found that the fraction of systems resulting in HJs ({F}_HJ) depends strongly on the planet mass, host stellar type and tidal dissipation strength, while the total migration fraction {F}_mig ={F}_HJ+{F}_dis (including both HJ formation and tidal disruption) exhibits much weaker dependence. We present an analytical method for calculating {F}_HJ and {F}_mig in the Lidov-Kozai migration scenario. The key ingredient of our method is to determine the critical initial planet-binary inclination angle that drives the planet to reach sufficiently large eccentricity for efficient tidal dissipation or disruption. This calculation includes the effects of the octupole potential and short-range forces on the planet. Our analytical method reproduces the planet migration/disruption fractions obtained from population synthesis, and can be easily implemented for various planet and stellar/companion types, and for different distributions of initial planetary semimajor axes, binary separations and eccentricities. We extend our calculations to planets in the super-Earth mass range and discuss the conditions for such planets to survive Lidov-Kozai migration and form close-in rocky planets.

  8. CO observations of nearby galaxies and the efficiency of star formation

    NASA Technical Reports Server (NTRS)

    Young, Judith S.

    1987-01-01

    The CO distributions and total molecular content of 160 galaxies were observed using the 14 meter millimeter telescope of the FCRAO. For the luminous, relatively face-on Sc galaxies, the azimuthally averaged CO distributions are centrally peaked, while for the Sb and Sa galaxies the Co distributions often exhibit central CO holes up to 5 kpc across. None of the Sc galaxies have CO distributions which resemble the Milky Way. A general correlation was found between total CO and IR luminosities in galaxies. The scatter in this relation is highly correlated with dust temperature. No strong correlation of IR luminosities was found with HI masses, and it was thereby concluded that the infrared emission is more directly tied to the molecular content of galaxies. It is suggested that galaxies which have high Star Formation Effiencies (SFEs) produce more stars per unit molecular mass, thereby increasing the average temperature of the dust in the star forming regions. Irregular galaxies and galaxies previously identified as mergers have the highest observed star formation efficiencies. For the mergers, evidence was found that the IR/CO luminosity ratio increases with the merger age estimated by Joseph and Wright (1985).

  9. Efficient Isoprene Secondary Organic Aerosol Formation from a Non-IEPOX Pathway

    SciTech Connect

    Liu, Jiumeng; D’Ambro, Emma L.; Lee, Ben H.; Lopez-Hilfiker, Felipe D.; Zaveri, Rahul A.; Rivera-Rios, Jean C.; Keutsch, Frank N.; Iyer, Siddharth; Kurten, Theo; Zhang, Zhenfa; Gold, Avram; Surratt, Jason D.; Shilling, John E.; Thornton, Joel A.

    2016-09-20

    With a large global emission rate and high reactivity, isoprene has a profound effect upon atmospheric chemistry and composition. The atmospheric pathways by which isoprene converts to secondary organic aerosol (SOA) and how anthropogenic pollutants such as nitrogen oxides and sulfur affect this process are subjects of intense research because particles affect Earth’s climate and local air quality. In the absence of both nitrogen oxides and reactive aqueous seed particles, we measure SOA mass yields from isoprene photochemical oxidation of up to 15%, which are factors of 2 or more higher than those typically used in coupled chemistry climate models. SOA yield is initially constant with the addition of increasing amounts of nitric oxide (NO) but then sharply decreases for input concentrations above 50 ppbv. Online measurements of aerosol molecular composition show that the fate of second-generation RO2 radicals is key to understanding the efficient SOA formation and the NOx-dependent yields described here and in the literature. These insights allow for improved quantitative estimates of SOA formation in the preindustrial atmosphere and in biogenic-rich regions with limited anthropogenic impacts and suggest that a more-complex representation of NOx-dependent SOA yields may be important in models

  10. Pericellular matrix formation alters the efficiency of intracellular uptake of oligonucleotides in osteosarcoma cells.

    PubMed

    Suzuki, Yoshitaka; Nishida, Yoshihiro; Naruse, Takahiro; Gemba, Takefumi; Ishiguro, Naoki

    2009-03-01

    One of the crucial roles of tumor extracellular matrix is to act as a barrier to drug delivery. In this study, we analyzed the relationship between the formation of tumor extracellular matrix and the efficiency of intracellular uptake of oligonucleotides in human osteosarcoma cell lines, HOS, and MG-63. Oligonucleotides used in this study were nuclear factor-kappa B (NF-kappaB) decoy, which might be a therapeutic tool for neoplasms. Pericellular matrix formation was examined by particle exclusion assay. Cellular uptake of fluorescein isothiocyanate-labeled NF-kappaB decoy was evaluated by fluorescent microscopy and flow cytometry. Effects of NF-kappaB decoy on cell viability and cell cycle arrest in MG-63 cells were determined by MTT assay and flow cytometry, respectively. MG-63 cells exhibited abundant pericellular matrix with time compared with HOS cells. Uptake of fluorescein isothiocyanate-labeled NF-kappaB decoy decreased in MG-63 cells with time but not in HOS cells in both monolayer and three-dimensional culture using matrigel. However, after enzymatic removal of pericellular matrix, the uptake markedly recovered in MG-63 cells. NF-kappaB decoy inhibited cell proliferation and induced G0/G1 cell cycle arrest in MG-63 cells. These results suggest that abundant pericellular matrix might disturb the uptake of NF-kappaB decoy, and modification of pericellular matrix composition would increase the efficacy of exogenous oligonucleotides treatment for neoplasms.

  11. The Cosmological Impact of Luminous TeV Blazars. III. Implications for Galaxy Clusters and the Formation of Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Pfrommer, Christoph; Chang, Philip; Broderick, Avery E.

    2012-06-01

    A subset of blazars are powerful TeV emitters, dominating the extragalactic component of the very high energy gamma-ray universe (E >~ 100 GeV). These TeV gamma rays generate ultrarelativistic electron-positron pairs via pair production with the extragalactic background light. While it has generally been assumed that the kinetic energy of these pairs cascades to GeV gamma rays via inverse Compton scattering, we have argued in Broderick et al. (Paper I in this series) that plasma beam instabilities are capable of dissipating the pairs' energy locally on timescales short in comparison to the inverse Compton cooling time, heating the intergalactic medium (IGM) with a rate that is independent of density. This dramatically increases the entropy of the IGM after redshift z ~ 2, with a number of important implications for structure formation: (1) this suggests a scenario for the origin of the cool core (CC)/non-cool core (NCC) bimodality in galaxy clusters and groups. Early-forming galaxy groups are unaffected because they can efficiently radiate the additional entropy, developing a CC. However, late-forming groups do not have sufficient time to cool before the entropy is gravitationally reprocessed through successive mergers—counteracting cooling and potentially raising the core entropy further. This may result in a population of X-ray dim groups/clusters, consistent with X-ray stacking analyses of optically selected samples. Hence, blazar heating works differently than feedback by active galactic nuclei, which we show can balance radiative cooling but is unable to transform CC into NCC clusters on the buoyancy timescale due to the weak coupling between the mechanical energy to the cluster gas. (2) We predict a suppression of the Sunyaev-Zel'dovich (SZ) power spectrum template on angular scales smaller than 5' due to the globally reduced central pressure of groups and clusters forming after z ~ 1. This allows for a larger rms amplitude of the density power spectrum,

  12. THE COSMOLOGICAL IMPACT OF LUMINOUS TeV BLAZARS. III. IMPLICATIONS FOR GALAXY CLUSTERS AND THE FORMATION OF DWARF GALAXIES

    SciTech Connect

    Pfrommer, Christoph; Chang, Philip; Broderick, Avery E. E-mail: aeb@cita.utoronto.ca

    2012-06-10

    A subset of blazars are powerful TeV emitters, dominating the extragalactic component of the very high energy gamma-ray universe (E {approx}> 100 GeV). These TeV gamma rays generate ultrarelativistic electron-positron pairs via pair production with the extragalactic background light. While it has generally been assumed that the kinetic energy of these pairs cascades to GeV gamma rays via inverse Compton scattering, we have argued in Broderick et al. (Paper I in this series) that plasma beam instabilities are capable of dissipating the pairs' energy locally on timescales short in comparison to the inverse Compton cooling time, heating the intergalactic medium (IGM) with a rate that is independent of density. This dramatically increases the entropy of the IGM after redshift z {approx} 2, with a number of important implications for structure formation: (1) this suggests a scenario for the origin of the cool core (CC)/non-cool core (NCC) bimodality in galaxy clusters and groups. Early-forming galaxy groups are unaffected because they can efficiently radiate the additional entropy, developing a CC. However, late-forming groups do not have sufficient time to cool before the entropy is gravitationally reprocessed through successive mergers-counteracting cooling and potentially raising the core entropy further. This may result in a population of X-ray dim groups/clusters, consistent with X-ray stacking analyses of optically selected samples. Hence, blazar heating works differently than feedback by active galactic nuclei, which we show can balance radiative cooling but is unable to transform CC into NCC clusters on the buoyancy timescale due to the weak coupling between the mechanical energy to the cluster gas. (2) We predict a suppression of the Sunyaev-Zel'dovich (SZ) power spectrum template on angular scales smaller than 5' due to the globally reduced central pressure of groups and clusters forming after z {approx} 1. This allows for a larger rms amplitude of the density

  13. Effect of Oxidation Rate and Fe(II) State on Microbial Nitrate-Dependent Fe(III) Mineral Formation

    PubMed Central

    Senko, John M.; Dewers, Thomas A.; Krumholz, Lee R.

    2005-01-01

    A nitrate-dependent Fe(II)-oxidizing bacterium was isolated and used to evaluate whether Fe(II) chemical form or oxidation rate had an effect on the mineralogy of biogenic Fe(III) (hydr)oxides resulting from nitrate-dependent Fe(II) oxidation. The isolate (designated FW33AN) had 99% 16S rRNA sequence similarity to Klebsiella oxytoca. FW33AN produced Fe(III) (hydr)oxides by oxidation of soluble Fe(II) [Fe(II)sol] or FeS under nitrate-reducing conditions. Based on X-ray diffraction (XRD) analysis, Fe(III) (hydr)oxide produced by oxidation of FeS was shown to be amorphous, while oxidation of Fe(II)sol yielded goethite. The rate of Fe(II) oxidation was then manipulated by incubating various cell concentrations of FW33AN with Fe(II)sol and nitrate. Characterization of products revealed that as Fe(II) oxidation rates slowed, a stronger goethite signal was observed by XRD and a larger proportion of Fe(III) was in the crystalline fraction. Since the mineralogy of Fe(III) (hydr)oxides may control the extent of subsequent Fe(III) reduction, the variables we identify here may have an effect on the biogeochemical cycling of Fe in anoxic ecosystems. PMID:16269756

  14. Binding of europium(III) ions to RNA stem loops: role of the primary hydration sphere in complex formation.

    PubMed

    Mundoma, Claudius; Greenbaum, Nancy L

    2003-05-01

    Understanding the process by which RNA molecules fold into stable structures includes study of the role of site-bound metal ions. Because the alkaline earth metal ions typically associated with RNA structure [most often Mg(II)] do not provide convenient spectroscopic signals, replacement with metal ions having spectroscopically useful properties has been a valuable approach. The luminescence properties of the lanthanide(III) series, in particular europium(III), have made them useful in the study of complexation with biomolecules. We review the physical, chemical, and spectroscopic characteristics of Eu(III) that contribute to its value as a probe of RNA-metal ion interactions, and examples of information obtained from studies of Eu(III) bound to small RNA stem loops. Although Eu(III) has similar site preference to Mg(II), luminescence and isothermal titration calorimetry measurements indicate that Ln(III) loses water molecules from the inner hydration sphere more readily than does Mg(II), resulting in more direct coordination between RNA and the metal ion and very different energetics of binding. In some cases, e.g., a GAAA tetraloop, binding appears to occur by a lock and key process; in the same base sequence containing certain deoxynucleoside substitutions that alter loop structure, binding appears to occur by an induced fit process. Copyright 2003 Wiley Periodicals, Inc.

  15. Effect of the oxidation rate and Fe(II) state on microbial nitrate-dependent Fe(III) mineral formation

    USGS Publications Warehouse

    Senko, John M.; Dewers , Thomas A.; Krumholz, Lee R.

    2005-01-01

    A nitrate-dependent Fe(II)-oxidizing bacterium was isolated and used to evaluate whether Fe(II) chemical form or oxidation rate had an effect on the mineralogy of biogenic Fe(III) (hydr)oxides resulting from nitrate-dependent Fe(II) oxidation. The isolate (designated FW33AN) had 99% 16S rRNA sequence similarity to Klebsiella oxytoca. FW33AN produced Fe(III) (hydr)oxides by oxidation of soluble Fe(II) [Fe(II)sol] or FeS under nitrate-reducing conditions. Based on X-ray diffraction (XRD) analysis, Fe(III) (hydr)oxide produced by oxidation of FeS was shown to be amorphous, while oxidation of Fe(II)sol yielded goethite. The rate of Fe(II) oxidation was then manipulated by incubating various cell concentrations of FW33AN with Fe(II)sol and nitrate. Characterization of products revealed that as Fe(II) oxidation rates slowed, a stronger goethite signal was observed by XRD and a larger proportion of Fe(III) was in the crystalline fraction. Since the mineralogy of Fe(III) (hydr)oxides may control the extent of subsequent Fe(III) reduction, the variables we identify here may have an effect on the biogeochemical cycling of Fe in anoxic ecosystems.

  16. Hydration and ion pair formation in common aqueous La(III) salt solutions--a Raman scattering and DFT study.

    PubMed

    Rudolph, Wolfram W; Irmer, Gert

    2015-01-07

    Raman spectra of aqueous lanthanum perchlorate, triflate (trifluorosulfonate), chloride and nitrate solutions were measured over a broad concentration (0.121-3.050 mol L(-1)) range at room temperature (23 °C). A very weak mode at 343 cm(-1) with a full width at half height at 49 cm(-1) in the isotropic spectrum suggests that the nona-aqua La(III) ion is thermodynamically stable in dilute perchlorate solutions (∼0.2 mol L(-1)) while in concentrated perchlorate solutions outer-sphere ion pairs and contact ion pairs are formed. The La(3+) nona-hydrate was also detected in a 1.2 mol L(-1) La(CF3SO3)3(aq). In lanthanum chloride solutions chloro-complex formation was detected over the measured concentration range from 0.5-3.050 mol L(-1). The chloro-complexes in LaCl3(aq) are fairly weak and disappear with dilution. At a concentration <0.1 mol L(-1) almost all complexes disappeared. In LaCl3 solutions, with additional HCl, a series of chloro-complexes of the type [La(OH2)(9-n)Cln](+3-n) (n = 1-3) were formed. The La(NO3)3(aq) spectra were compared with a spectrum of a 0.409 mol L(-1) NaNO3(aq) and it was concluded that in La(NO3)3(aq) over the concentration range from 0.121-1.844 mol L(-1), nitrato-complexes, [La(OH2)(9-n)(NO3)n](+3-n) (n = 1, 2) were formed. These nitrato-complexes are quite weak and disappear with dilution <0.01 mol L(-1). DFT geometry optimizations and frequency calculations are reported for a lanthanum-nona-hydrate with a polarizable dielectric continuum in order to take the solvent into account. The bond distances and angles for the cluster geometry of [La(OH2)9](3+) with the polarizable dielectric continuum are in good agreement with data from recent structural experimental measurements and high quality simulations. The DFT frequency of the La-O stretching mode at 328.2 cm(-1), is only slightly smaller than the experimental one.

  17. Sulfate formation catalyzed by coal fly ash, mineral dust and iron(iii) oxide: variable influence of temperature and light.

    PubMed

    Gankanda, Aruni; Coddens, Ellen M; Zhang, Yaping; Cwiertny, David M; Grassian, Vicki H

    2016-12-08

    Recent atmospheric field and modeling studies have highlighted a lack of understanding of the processes responsible for high levels of sulfate aerosol in the atmosphere, ultimately arising from a dearth of experimental data on such processes. Here we investigated the effect of temperature and simulated solar radiation on the catalytic oxidation of S(iv) to S(vi) (i.e., sulfite to sulfate) in aqueous suspensions of several metal-containing, atmospherically relevant particles including coal fly ash (FA), Arizona test dust (ATD) and an iron oxide (γ-Fe2O3). The effect of temperature and light on S(iv) oxidation was found to be very different for these three samples. For example, in the presence of FA and γ-Fe2O3 the temporal evolution of dissolved Fe(ii) (formed via reductive particle dissolution) correlated with S(iv) oxidation. Accordingly, we propose that S(iv) oxidation in most of these systems initially occurs primarily at the particle surface (i.e., a heterogeneous reaction pathway), although a solution-phase (i.e., homogeneous) catalytic pathway also contributes over later timescales due to the formation and accumulation of dissolved Fe(iii) (generated via oxidation of dissolved Fe(ii) by O2). It is likely that the homogeneous reaction pathway is operative at initial times in the presence of γ-Fe2O3 at 25 °C. In contrast, S(iv) oxidation in the presence of ATD appears to proceed entirely via a heterogeneous reaction, which notably does not lead to any iron dissolution. In fact, the greater overall rate of S(iv) loss in the presence of ATD compared to FA and γ-Fe2O3 suggests that other factors, including greater adsorption of sulfite, transition metal ion (TMI) catalysis by other metal ions (e.g., Ti), or different species of iron in ATD, play a role. Overall these studies suggest that the rate, extent and products of atmospheric S(iv) oxidation can be highly variable and dependent upon the nature of aerosol sources and ambient conditions (e.g., temperature

  18. Efficient removal of detergents from proteins and peptides in a spin column format.

    PubMed

    Antharavally, Babu S; Mallia, Krishna A; Rosenblatt, Michael M; Salunkhe, Ashok M; Rogers, John C; Haney, Paul; Haghdoost, Navid

    2011-09-01

    Detergents are commonly used in protein-chemistry protocols and may be necessary for protein extraction, solubilization, and denaturation; however, their presence interferes with many downstream analysis techniques, including mass spectrometry (MS). To enable downstream analysis, it is critical to remove unbound detergents from protein and peptide samples. In this study, we describe a high-performance resin that offers exceptional detergent removal for proteins and peptides. When used in a spin column format, this resin dramatically improves protein and peptide MS results by more than 95% removal of 1-5% detergents, including sodium dodecyl sulfate (SDS), sodium deoxycholate, Chaps, Triton X-100, Triton X-114, NP-40, Brij-35, octyl glucoside, octyl thioglucoside, and lauryl maltoside, with high recovery of proteins and peptides. Postcolumn liquid chromatography-tandem MS (LC-MS/MS) analysis of trypsin digests of bovine serum albumin (BSA) and HeLa cell lysate revealed excellent sequence coverage, indicating successful removal of detergent from the peptides. Matrix-assisted laser desorption/ionization (MALDI)-MS analysis of unprocessed and processed samples further confirmed efficient removal of detergents. The advantages of this method include speed (<15min), efficient detergent removal, and high recovery of proteins and peptides.

  19. Formative evaluation of antiretroviral therapy scale-up efficiency in sub-Saharan Africa.

    PubMed

    Wagner, Glenn; Ryan, Gery; Taylor, Stephanie

    2007-11-01

    With millions in need of HIV antiretroviral therapy (ART) in the developing world, and scarce human and fiscal resources available, we conducted a formative evaluation of scale-up operations at clinics associated with AIDS Healthcare Foundation in Africa to identify lessons learned for improving scale-up efficiency. Site visits were made to six selected clinics in Uganda, Zambia, and South Africa, during which semistructured interviews with key stake-holders and observation of client flows and clinic operations were performed. This evaluation revealed the following lessons related to factors that are critical to efficient ART scale-up: (1) to ensure steady ART uptake, it is important to involve the community and community leaders in outreach, HIV education, and program decision-making; (2) minimizing bottlenecks to smooth patient flow requires efficient staff allocation to appropriate clinical duties, streamlined clinic visit schedule protocols, and tapping clients and the HIV community as a key source of labor; (3) to minimize clients dropping out of care, structures should be developed that enable clients to provide support and a "safety net" for helping each other remain in care; (4) computerized record management systems are essential for accurate antiretroviral inventory and dispensing records, quality assurance monitoring, and client enrollment records and visit scheduling; (5) effective organizational management and human resource policies are essential to maintain high job performance and satisfaction and limit burnout; (6) to maximize impact on social and economic health, it is important for ART programs to develop effective mechanisms for coordinating and referring clients to support service organizations.

  20. Supermassive star formation via episodic accretion: protostellar disc instability and radiative feedback efficiency

    NASA Astrophysics Data System (ADS)

    Sakurai, Y.; Vorobyov, E. I.; Hosokawa, T.; Yoshida, N.; Omukai, K.; Yorke, H. W.

    2016-06-01

    The formation of supermassive stars (SMSs) is a potential pathway to seed supermassive black holes in the early universe. A critical issue for forming SMSs is stellar UV feedback, which may limit the stellar mass growth via accretion. In this paper, we study the evolution of an accreting SMS and its UV emissivity with realistic variable accretion from a circumstellar disc. First we conduct a 2D hydrodynamical simulation to follow the protostellar accretion until the stellar mass exceeds 104 M⊙. The disc fragments by gravitational instability, creating many clumps that migrate inward to fall on to the star. The resulting accretion history is highly time-dependent: short episodic accretion bursts are followed by longer quiescent phases. We show that the disc for the direct collapse model is more unstable and generates greater variability than normal Pop III cases. Next, we conduct a stellar evolution calculation using the obtained accretion history. Our results show that, regardless of the variable accretion, the stellar radius monotonically increases with almost constant effective temperature at Teff ≃ 5000 K as the stellar mass increases. The resulting UV feedback is too weak to hinder accretion due to the low flux of stellar UV photons. The insensitivity of stellar evolution to variable accretion is attributed to the fact that time-scales of variability, ≲103 yr, are too short to affect the stellar structure. We argue that this evolution will continue until the SMS collapses to produce a black hole by the general relativistic instability after the mass reaches ≳105 M⊙.

  1. Mechanisms of Loss in Internal Quantum Efficiency in III-Nitride-based Blue-and Green-Light Emitting Diodes

    NASA Astrophysics Data System (ADS)

    Huang, Li

    The overarching goals of the research conducted for this dissertation have been to understand the scientific reasons for the losses in the internal quantum efficiency (IQE) in Group III-nitride-based blue and especially green light-emitting diodes (LEDs) containing a multi-quantum well (MQW) active region and to simultaneously develop LED epitaxial structures to ameliorate these losses. The p-type AlGaN EBL was determined to be both mandatory and effective in the prevention of electron overflow from the MQW region into the p-type cladding layer and the resultant lowering of the IQE. The overflow phenomenon was partially due to the low concentration (˜ 5 x 1017 cm-3) and mobility (˜ 10 cm2/(V•s)) of the holes injected into the active region. Electroluminescence (EL) studies of LEDs without an EBL revealed a dominant emission from donor-acceptor pair recombination in the p-type GaN layer. The incorporation of a 90 nm compositionally graded In0-0.1 Ga1-0.9N buffer layer between each MQW and n-GaN cladding layer grown on an Al/SiC substrate resulted in an increase in the luminescence intensity and a blue-shift in the emission wavelength, as observed in photoluminescence (PL) spectra. The graded InGaN buffer layer reduced the stress and thus the piezoelectric field across the MQW; this improved the electron/hole overlap that, in turn, resulted in an enhanced radiative recombination rate and an increase in efficiency. A direct correlation was observed between an increase in the IQE measured in temperature-dependent PL (TDPL) and an increase in the roughness of all the upper InGaN QW/GaN barrier interfaces, as determined using cross-sectional transmission electron microscopy of the MQW. These results agreed in general with the average surface roughness values of the pit-free region on the top GaN barrier determined via atomic force microscopy and the average roughness values of all the interfaces in the MQW calculated from the FWHM of the emission peak in the PL

  2. Balancing the Need for Reliability and Time Efficiency: Short Forms of the Wechsler Adult Intelligence Scale-III

    ERIC Educational Resources Information Center

    Jeyakumar, Sharon L. E.; Warriner, Erin M.; Raval, Vaishali V.; Ahmad, Saadia A.

    2004-01-01

    Tables permitting the conversion of short-form composite scores to full-scale IQ estimates have been published for previous editions of the Wechsler Adult Intelligence Scale (WAIS). Equivalent tables are now needed for selected subtests of the WAIS-III. This article used Tellegen and Briggs's formulae to convert the sum of scaled scores for four…

  3. Balancing the Need for Reliability and Time Efficiency: Short Forms of the Wechsler Adult Intelligence Scale-III

    ERIC Educational Resources Information Center

    Jeyakumar, Sharon L. E.; Warriner, Erin M.; Raval, Vaishali V.; Ahmad, Saadia A.

    2004-01-01

    Tables permitting the conversion of short-form composite scores to full-scale IQ estimates have been published for previous editions of the Wechsler Adult Intelligence Scale (WAIS). Equivalent tables are now needed for selected subtests of the WAIS-III. This article used Tellegen and Briggs's formulae to convert the sum of scaled scores for four…

  4. Hierarchical Assembly of a {Mn(II)15Mn(III)4} Brucite Disc: Step-by-Step Formation and Ferrimagnetism.

    PubMed

    Deng, Yong-Kai; Su, Hai-Feng; Xu, Jia-Heng; Wang, Wen-Guang; Kurmoo, Mohamedally; Lin, Shui-Chao; Tan, Yuan-Zhi; Jia, Jiong; Sun, Di; Zheng, Lan-Sun

    2016-02-03

    In search of functional molecular materials and the study of their formation mechanism, we report the elucidation of a hierarchical step-by-step formation from monomer (Mn) to heptamer (Mn7) to nonadecamer (Mn19) satisfying the relation 1 + Σn6n, where n is the ring number of the Brucite structure using high-resolution electrospray ionization mass spectrometry (HRESI-MS). Three intermediate clusters, Mn10, Mn12, and Mn14, were identified. Furthermore, the Mn19 disc remains intact when dissolved in acetonitrile with a well-resolved general formula of [Mn19(L)x(OH)y(N3)36-x-y](2+) (x = 18, 17, 16; y = 8, 7, 6; HL = 1-(hydroxymethyl)-3,5-dimethylpyrazole) indicating progressive exchange of N3(-) for OH(-). The high symmetry (R-3) Mn19 crystal structure consists of a well-ordered discotic motif where the peripheral organic ligands form a double calix housing the anions and solvent molecules. From the formula and valence bond sums, the charge state is mixed-valent, [Mn(II)15Mn(III)4]. Its magnetic properties and electrochemistry have been studied. It behaves as a ferrimagnet below 40 K and has a coercive field of 2.7 kOe at 1.8 K, which can be possible by either weak exchange between clusters through the anions and solvents or through dipolar interaction through space as confirmed by the lack of ordering in frozen CH3CN. The moment of nearly 50 NμB suggests Mn(II)-Mn(II) and Mn(III)-Mn(III) are ferromagnetically coupled while Mn(II)-Mn(III) is antiferromagnetic which is likely if the Mn(III) are centrally placed in the cluster. This compound displays the rare occurrence of magnetic ordering from nonconnected high-spin molecules.

  5. Dependence of the star formation efficiency on global parameters of molecular clouds

    NASA Astrophysics Data System (ADS)

    Rosas-Guevara, Yetli; Vázquez-Semadeni, Enrique; Gómez, Gilberto C.; Jappsen, A.-Katharina

    2010-08-01

    We investigate the response of the star formation efficiency (SFE) to the main parameters of simulations of molecular cloud formation and evolution (growth and star formation) by the collision of warm diffuse medium [warm neutral medium (WNM)] cylindrical streams, and compare our results with theoretical predictions for this dependence. The parameters we vary are the Mach number of the inflow velocity of the streams, , the rms Mach number, , of the initial background turbulence in the WNM and the total mass contained in the colliding gas streams, Minf, which is eventually deposited in the forming clouds. Because the SFE is a function of time, we define two estimators for it, the `absolute' SFE, measured at t = 25Myr into the simulation's evolution (SFEabs,25), and the `relative' SFE, measured 5Myr after the onset of star formation in each simulation (SFErel,5). The latter is close to the `SFE per free-fall time' for gas at n = 100cm-3. Our simulations suggest that the dominant parameter controlling the SFE is Minf. The SFE in general decreases as this parameter is decreased, presumably because, with the other parameters being equal, smaller fragments are more weakly gravitationally bound. In terms of the initial virial parameter (α ≡ 2Ekin/|Egrav|) of the clouds, our results are qualitatively consistent with the theoretical prediction by Krumholz & McKee that the SFE decreases with increasing α. However, quantitatively, their prediction lies beyond the 1σ error of our observed trend. This may be due to the fact that the simulated clouds develop significant gravitational contraction motions, which overwhelm the initial turbulent motions, contrary to Krumholz & McKee's assumption of stationary turbulent support. We also observe that the SFE decreases (moderately) with increasing , although the SFR increases. The decrease of the SFE with is thus a consequence of the cloud mass accretion rate from the WNM increasing more steeply with this parameter than the SFR

  6. New III-V cell design approaches for very high efficiency. Annual subcontract report, 1 August 1990--31 July 1991

    SciTech Connect

    Lundstrom, M.S.; Melloch, M.R.; Lush, G.B.; O`Bradovich, G.J.; Young, M.P.

    1993-01-01

    This report describes progress during the first year of a three-year project. The objective of the research is to examine new design approaches for achieving very high conversion efficiencies. The program is divided into two areas. The first centers on exploring new thin-film approaches specifically designed for III-V semiconductors. The second area centers on exploring design approaches for achieving high conversion efficiencies without requiring extremely high quality material. Research activities consisted of an experimental study of minority carrier recombination in n-type, metal-organic chemical vapor deposition (MOCVD)-deposited GaAs, an assessment of the minority carrier lifetimes in n-GaAs grown by molecular beam epitaxy, and developing a high-efficiency cell fabrication process.

  7. A fungal conserved gene from the basidiomycete Hebeloma cylindrosporum is essential for efficient ectomycorrhiza formation.

    PubMed

    Doré, Jeanne; Marmeisse, Roland; Combier, Jean-Philippe; Gay, Gilles

    2014-10-01

    We used Agrobacterium-mediated insertional mutagenesis to identify genes in the ectomycorrhizal fungus Hebeloma cylindrosporum that are essential for efficient mycorrhiza formation. One of the mutants presented a dramatically reduced ability to form ectomycorrhizas when grown in the presence of Pinus pinaster. It failed to form mycorrhizas in the presence of glucose at 0.5 g liter(-1), a condition favorable for mycorrhiza formation by the wild-type strain. However, it formed few mycorrhizas when glucose was replaced by fructose or when glucose concentration was increased to 1 g liter(-1). Scanning electron microscopy examination of these mycorrhizas revealed that this mutant was unable to differentiate true fungal sheath and Hartig net. Molecular analyses showed that the single-copy disrupting T-DNA was integrated 6,884 bp downstream from the start codon, of an open reading frame potentially encoding a 3,096-amino-acid-long protein. This gene, which we named HcMycE1, has orthologs in numerous fungi as well as different other eukaryotic microorganisms. RNAi inactivation of HcMycE1 in the wild-type strain also led to a mycorrhizal defect, demonstrating that the nonmycorrhizal phenotype of the mutant was due to mutagenic T-DNA integration in HcMycE1. In the wild-type strain colonizing P. pinaster roots, HcMycE1 was transiently upregulated before symbiotic structure differentiation. Together with the inability of the mutant to differentiate these structures, this suggests that HcMycE1 plays a crucial role upstream of the fungal sheath and Hartig net differentiation. This study provides the first characterization of a fungal mutant altered in mycorrhizal ability.

  8. Hemolytic lectin CEL-III heptamerizes via a large structural transition from α-helices to a β-barrel during the transmembrane pore formation process.

    PubMed

    Unno, Hideaki; Goda, Shuichiro; Hatakeyama, Tomomitsu

    2014-05-02

    CEL-III is a hemolytic lectin isolated from the sea cucumber Cucumaria echinata. This lectin is composed of two carbohydrate-binding domains (domains 1 and 2) and one oligomerization domain (domain 3). After binding to the cell surface carbohydrate chains through domains 1 and 2, domain 3 self-associates to form transmembrane pores, leading to cell lysis or death, which resembles other pore-forming toxins of diverse organisms. To elucidate the pore formation mechanism of CEL-III, the crystal structure of the CEL-III oligomer was determined. The CEL-III oligomer has a heptameric structure with a long β-barrel as a transmembrane pore. This β-barrel is composed of 14 β-strands resulting from a large structural transition of α-helices accommodated in the interface between domains 1 and 2 and domain 3 in the monomeric structure, suggesting that the dissociation of these α-helices triggered their structural transition into a β-barrel. After heptamerization, domains 1 and 2 form a flat ring, in which all carbohydrate-binding sites remain bound to cell surface carbohydrate chains, stabilizing the transmembrane β-barrel in a position perpendicular to the plane of the lipid bilayer.

  9. Heat Shock Protein 90 Ensures Efficient Mumps Virus Replication by Assisting with Viral Polymerase Complex Formation.

    PubMed

    Katoh, Hiroshi; Kubota, Toru; Nakatsu, Yuichiro; Tahara, Maino; Kidokoro, Minoru; Takeda, Makoto

    2017-03-15

    Paramyxoviral RNAs are synthesized by a viral RNA-dependent RNA polymerase (RdRp) consisting of the large (L) protein and its cofactor phosphoprotein (P protein). The L protein is a multifunctional protein that catalyzes RNA synthesis, mRNA capping, and mRNA polyadenylation. Growing evidence shows that the stability of several paramyxovirus L proteins is regulated by heat shock protein 90 (Hsp90). In this study, we demonstrated that Hsp90 activity was important for mumps virus (MuV) replication. The Hsp90 activity was required for L-protein stability and activity because an Hsp90-specific inhibitor, 17-allylamino-17-demethoxygeldanamycin (17-AAG), destabilized the MuV L protein and suppressed viral RNA synthesis. However, once the L protein formed a mature polymerase complex with the P protein, Hsp90 activity was no longer required for the stability and activity of the L protein. When the Hsp90 activity was inhibited, the MuV L protein was degraded through the CHIP (C terminus of Hsp70-interacting protein)-mediated proteasomal pathway. High concentrations of 17-AAG showed strong cytotoxicity to certain cell types, but combined use of an Hsp70 inhibitor, VER155008, potentiated degradation of the L protein, allowing a sufficient reduction of 17-AAG concentration to block MuV replication with minimum cytotoxicity. Regulation of the L protein by Hsp90 and Hsp70 chaperones was also demonstrated for another paramyxovirus, the measles virus. Collectively, our data show that the Hsp90/Hsp70 chaperone machinery assists in the maturation of the paramyxovirus L protein and thereby in the formation of a mature RdRp complex and efficient viral replication.IMPORTANCE Heat shock protein 90 (Hsp90) is nearly universally required for viral protein homeostasis. Here, we report that Hsp90 activity is required for efficient propagation of mumps virus (MuV). Hsp90 functions in the maintenance of the catalytic subunit of viral polymerase, the large (L) protein, prior to formation of a

  10. Formation of a cobalt(III)-phenoxyl radical complex by acetic acid promoted aerobic oxidation of a Co(II)salen complex.

    PubMed

    Vinck, Evi; Murphy, Damien M; Fallis, Ian A; Strevens, Robert R; Van Doorslaer, Sabine

    2010-03-01

    The activation of N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexane-diamino Co(II), [Co(II)(1)], by the addition of acetic acid under aerobic conditions has been investigated by a range of spectroscopic techniques including continuous-wave EPR, HYSCORE, pulsed ENDOR, and resonance Raman. These measurements have revealed for the first time the formation of a coordinated cobalt(III)-bound phenoxyl radical labeled [Co(III)(1(*))(OAc)(n)](OAc)(m) (n = m = 1 or n = 2, m = 0). This cobalt(III)-bound phenoxyl radical is characterized by the following spin Hamiltonian parameters: g(x) = 2.0060, g(y) = 2.0031, g(z) = 1.9943, A(x) = 17 MHz, A(y) = 55 MHz, and A(z) = 14 MHz. Although the radical contains coordinated acetate(s), the experiments unambiguously proved that the phenoxyl radical is situated on ligand (1) as opposed to a phenoxyl radical ligated to cobalt in the axial position. Density functional theory computations on different models corroborate the stability of such a phenoxyl radical species and suggest the ligation of one or two acetate molecules to the complex. A mechanism is proposed, which accounts for the formation of this unusual and extremely robust phenoxyl radical, never previously observed for [Co(1)].

  11. Pseudomonas aeruginosa Exhibits Deficient Biofilm Formation in the Absence of Class II and III Ribonucleotide Reductases Due to Hindered Anaerobic Growth

    PubMed Central

    Crespo, Anna; Pedraz, Lucas; Astola, Josep; Torrents, Eduard

    2016-01-01

    Chronic lung infections by the ubiquitous and extremely adaptable opportunistic pathogen Pseudomonas aeruginosa correlate with the formation of a biofilm, where bacteria grow in association with an extracellular matrix and display a wide range of changes in gene expression and metabolism. This leads to increased resistance to physical stress and antibiotic therapies, while enhancing cell-to-cell communication. Oxygen diffusion through the complex biofilm structure generates an oxygen concentration gradient, leading to the appearance of anaerobic microenvironments. Ribonucleotide reductases (RNRs) are a family of highly sophisticated enzymes responsible for the synthesis of the deoxyribonucleotides, and they constitute the only de novo pathway for the formation of the building blocks needed for DNA synthesis and repair. P. aeruginosa is one of the few bacteria encoding all three known RNR classes (Ia, II, and III). Class Ia RNRs are oxygen dependent, class II are oxygen independent, and class III are oxygen sensitive. A tight control of RNR activity is essential for anaerobic growth and therefore for biofilm development. In this work we explored the role of the different RNR classes in biofilm formation under aerobic and anaerobic initial conditions and using static and continuous-flow biofilm models. We demonstrated the importance of class II and III RNR for proper cell division in biofilm development and maturation. We also determined that these classes are transcriptionally induced during biofilm formation and under anaerobic conditions. The molecular mechanism of their anaerobic regulation was also studied, finding that the Anr/Dnr system is responsible for class II RNR induction. These data can be integrated with previous knowledge about biofilms in a model where these structures are understood as a set of layers determined by oxygen concentration and contain cells with different RNR expression profiles, bringing us a step closer to the understanding of this

  12. Testing the universality of the star-formation efficiency in dense molecular gas

    NASA Astrophysics Data System (ADS)

    Shimajiri, Y.; André, Ph.; Braine, J.; Könyves, V.; Schneider, N.; Bontemps, S.; Ladjelate, B.; Roy, A.; Gao, Y.; Chen, H.

    2017-08-01

    Context. Recent studies with, for example, Spitzer and Herschel have suggested that star formation in dense molecular gas may be governed by essentially the same "law" in Galactic clouds and external galaxies. This conclusion remains controversial, however, in large part because different tracers have been used to probe the mass of dense molecular gas in Galactic and extragalactic studies. Aims: We aimed to calibrate the HCN and HCO+ lines commonly used as dense gas tracers in extragalactic studies and to test the possible universality of the star-formation efficiency in dense gas (≳104 cm-3), SFEdense. Methods: We conducted wide-field mapping of the Aquila, Ophiuchus, and Orion B clouds at 0.04 pc resolution in the J = 1 - 0 transition of HCN, HCO+, and their isotopomers. For each cloud, we derived a reference estimate of the dense gas mass MHerschelAV > 8, as well as the strength of the local far-ultraviolet (FUV) radiation field, using Herschel Gould Belt survey data products, and estimated the star-formation rate from direct counting of the number of Spitzer young stellar objects. Results: The H13CO+(1-0) and H13CN(1-0) lines were observed to be good tracers of the dense star-forming filaments detected with Herschel. Comparing the luminosities LHCN and LHCO+ measured in the HCN and HCO+ lines with the reference masses MHerschelAV > 8, the empirical conversion factors αHerschel - HCN (=MHerschelAV > 8/LHCN) and αHerschel - HCO+ (=MHerschelAV > 8/LHCO+) were found to be significantly anti-correlated with the local FUV strength. In agreement with a recent independent study of Orion B by Pety et al., the HCN and HCO+ lines were found to trace gas down to AV ≳ 2. As a result, published extragalactic HCN studies must be tracing all of the moderate density gas down to nH2 ≲ 103 cm-3. Estimating the contribution of this moderate density gas from the typical column density probability distribution functions in nearby clouds, we obtained the following G0

  13. Organic solvent vapor sensitive methylammonium lead trihalide film formation for efficient hybrid perovskite solar cells

    DOE PAGES

    Lian, Jiarong; Wang, Qi; Yuan, Yongbo; ...

    2015-03-25

    In this study, the anisotropic electronic properties of the perovskite crystals originating from their non-cubic crystal structures can potentially give rise to the grain orientation correlated photovoltaic device performance. Here we report that an organic solvent vapor atmosphere introduced during the spin-coating and formation of perovskite films changes the orientation and size of perovskite grains. It was found that slightly larger but much more oriented methylammonium lead trihalide (CH3NH3PbI3) grains could be obtained under 1,2-dichlorobenzene (DCB) and dimethyl sulfoxide (DMSO) vapor atmospheres. The devices with more oriented grains outperformed regular devices with more random grains by a 50 mV largermore » open circuit voltage as well as a slightly increased fill factor. The device efficiency enhancement can be attributed to the longer charge recombination lifetime resulting from the reduced trap density and oriented grains. This result is important in providing guidelines for comparing the results from various groups because organic solvent vapors are generally present in a sealed glovebox for perovskite solar cell fabrication.« less

  14. Organic solvent vapor sensitive methylammonium lead trihalide film formation for efficient hybrid perovskite solar cells

    SciTech Connect

    Lian, Jiarong; Wang, Qi; Yuan, Yongbo; Shao, Yuchuan; Huang, Jinsong

    2015-03-25

    In this study, the anisotropic electronic properties of the perovskite crystals originating from their non-cubic crystal structures can potentially give rise to the grain orientation correlated photovoltaic device performance. Here we report that an organic solvent vapor atmosphere introduced during the spin-coating and formation of perovskite films changes the orientation and size of perovskite grains. It was found that slightly larger but much more oriented methylammonium lead trihalide (CH3NH3PbI3) grains could be obtained under 1,2-dichlorobenzene (DCB) and dimethyl sulfoxide (DMSO) vapor atmospheres. The devices with more oriented grains outperformed regular devices with more random grains by a 50 mV larger open circuit voltage as well as a slightly increased fill factor. The device efficiency enhancement can be attributed to the longer charge recombination lifetime resulting from the reduced trap density and oriented grains. This result is important in providing guidelines for comparing the results from various groups because organic solvent vapors are generally present in a sealed glovebox for perovskite solar cell fabrication.

  15. AN EFFICIENT, NON-LINEAR STABILITY ANALYSIS FOR DETECTING PATTERN FORMATION IN REACTION DIFFUSION SYSTEMS

    PubMed Central

    HOLMES, WILLIAM R.

    2014-01-01

    Reaction diffusion systems are often used to study pattern formation in biological systems. However, most methods for understanding their behavior are challenging and can rarely be applied to complex systems common in biological applications. I present a relatively simple and efficient, non-linear stability technique that greatly aids such analysis when rates of diffusion are substantially different. This technique reduces a system of reaction diffusion equations to a system of ordinary differential equations tracking the evolution of a large amplitude, spatially localized perturbation of a homogeneous steady state. Stability properties of this system, determined using standard bifurcation techniques and software, describe both linear and non-linear patterning regimes of the reaction diffusion system. I describe the class of systems this method can be applied to and demonstrate its application. Analysis of Schnakenberg and substrate inhibition models is performed to demonstrate the methods capabilities in simplified settings and show that even these simple models have non-linear patterning regimes not previously detected. The real power of this technique however is its simplicity and applicability to larger complex systems where other non-linear methods become intractable. This is demonstrated through analysis of a chemotaxis regulatory network comprised of interacting proteins and phospholipids. In each case, predictions of this method are verified against results of numerical simulation, linear stability, asymptotic, and / or full PDE bifurcation analyses. PMID:24158538

  16. Efficient Large-Scale Coating Microstructure Formation Using Realistic CFD Models

    NASA Astrophysics Data System (ADS)

    Wiederkehr, Thomas; Müller, Heinrich

    2015-02-01

    For the understanding of physical effects during the formation of thermally sprayed coating layers and the deduction of the macroscopic properties of a coating, microstructure modeling and simulation techniques play an important role. In this contribution, a coupled simulation framework consisting of a detailed, CFD-based single splat simulation, and a large-scale coating build-up simulation is presented that is capable to compute large-scale, three-dimensional, porous microstructures by sequential drop impingement of more than 10,000 individual particles on multicore workstation hardware. Due to the geometry-based coupling of the two simulations, the deformation, cooling, and solidification of every particle is sensitive to the hit surface area and thereby pores develop naturally in the model. The single splat simulation employs the highly parallel Lattice-Boltzmann method, which is well suited for GPU-acceleration. In order to save splat calculations, the coating simulation includes a database-driven approach that re-uses already computed splats for similar underground shapes at the randomly chosen impact sites. For a fast database search, three different methods of efficient pre-selection of candidates are described and compared against each other.

  17. Efficient formation of bipolar microtubule bundles requires microtubule-bound γ-tubulin complexes

    PubMed Central

    Janson, Marcel E.; Setty, Thanuja Gangi; Paoletti, Anne; Tran, P.T.

    2005-01-01

    The mechanism for forming linear microtubule (MT) arrays in cells such as neurons, polarized epithelial cells, and myotubes is not well understood. A simpler bipolar linear array is the fission yeast interphase MT bundle, which in its basic form contains two MTs that are bundled at their minus ends. Here, we characterize mto2p as a novel fission yeast protein required for MT nucleation from noncentrosomal γ-tubulin complexes (γ-TuCs). In interphase mto2Δ cells, MT nucleation was strongly inhibited, and MT bundling occurred infrequently and only when two MTs met by chance in the cytoplasm. In wild-type 2, we observed MT nucleation from γ-TuCs bound along the length of existing MTs. We propose a model on how these nucleation events can more efficiently drive the formation of bipolar MT bundles in interphase. Key to the model is our observation of selective antiparallel binding of MTs, which can both explain the generation and spatial separation of multiple bipolar bundles. PMID:15837798

  18. Efficient Super Energy Transfer Collisions Through Reactive-Complex Formation: H + SO2

    NASA Astrophysics Data System (ADS)

    Smith, Jonathan M.; Wilhelm, Michael J.; Ma, Jianqiang; Dai, HAI-LUNG

    2015-06-01

    Translational-to-vibrational energy transfer (ET) from a hyperthermal H atom to ambient SO2 was characterized using time-resolved Fourier transform infrared emission spectroscopy. Vibrational excitation of SO2, following collisions with H atoms containing 59 kcal/mol of kinetic energy, generated from the 193 nm photolysis of HBr, is detected in two distinct energy distributions: one with excitation predominantly at the fundamental vibrational levels is attributable to classical impulsive collisions, while the other, accounting for 80% of the excited SO2 with vibrational energy as high as 14,000 wn, is proposed to arise from the formation of a transient reactive-complex during the collision. The cross-section for this super ET collision is determined to be 0.53±0.05 Å2, or roughly 2% of all hard sphere collisions. This observation reveals that in collisions between a hyperthermal atom and an ambient molecule, for which a reactive-complex exists on the potential energy surface, a large quantity of translational energy can be transferred to the molecule with high efficiency.

  19. Electrical properties of III-Nitride LEDs: Recombination-based injection model and theoretical limits to electrical efficiency and electroluminescent cooling

    SciTech Connect

    David, Aurelien Hurni, Christophe A.; Young, Nathan G.; Craven, Michael D.

    2016-08-22

    The current-voltage characteristic and ideality factor of III-Nitride quantum well light-emitting diodes (LEDs) grown on bulk GaN substrates are investigated. At operating temperature, these electrical properties exhibit a simple behavior. A model in which only active-region recombinations have a contribution to the LED current is found to account for experimental results. The limit of LED electrical efficiency is discussed based on the model and on thermodynamic arguments, and implications for electroluminescent cooling are examined.

  20. Electrical properties of III-Nitride LEDs: Recombination-based injection model and theoretical limits to electrical efficiency and electroluminescent cooling

    NASA Astrophysics Data System (ADS)

    David, Aurelien; Hurni, Christophe A.; Young, Nathan G.; Craven, Michael D.

    2016-08-01

    The current-voltage characteristic and ideality factor of III-Nitride quantum well light-emitting diodes (LEDs) grown on bulk GaN substrates are investigated. At operating temperature, these electrical properties exhibit a simple behavior. A model in which only active-region recombinations have a contribution to the LED current is found to account for experimental results. The limit of LED electrical efficiency is discussed based on the model and on thermodynamic arguments, and implications for electroluminescent cooling are examined.

  1. Energy Transfer in a Hybrid Ir(III) Carbene-Pt(II) Acetylide Assembly for Efficient Hydrogen Production.

    PubMed

    Yu, Zhen-Tao; Yuan, Yong-Jun; Chen, Xin; Cai, Jian-Guang; Zou, Zhi-Gang

    2015-07-06

    A new heterometallic supramolecular complex, consisting of an iridium carbene-based unit appended to a platinum terpyridine acetylide unit, representing a new Ir(III) -Pt(II) structural motif, was designed and developed to act as an active species for photocatalytic hydrogen production. The results also suggested that a light-harvesting process is essential to realize the solar-to-fuel conversion in an artificial system as illustrated in the natural photosynthetic system. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Formation of Light Absorbing Soluble Secondary Organics and Insoluble Polymeric Particles from the Dark Reaction of Catechol and Guaiacol with Fe(III).

    PubMed

    Slikboer, Samantha; Grandy, Lindsay; Blair, Sandra L; Nizkorodov, Sergey A; Smith, Richard W; Al-Abadleh, Hind A

    2015-07-07

    Transition metals such as iron are reactive components of environmentally relevant surfaces. Here, dark reaction of Fe(III) with catechol and guaiacol was investigated in an aqueous solution at pH 3 under experimental conditions that mimic reactions in the adsorbed phase of water. Using UV-vis spectroscopy, liquid chromatography, mass spectrometry, elemental analysis, dynamic light scattering, and electron microscopy techniques, we characterized the reactants, intermediates, and products as a function of reaction time. The reactions of Fe(III) with catechol and guaiacol produced significant changes in the optical spectra of the solutions due to the formation of light absorbing secondary organics and colloidal organic particles. The primary steps in the reaction mechanism were shown to include oxidation of catechol and guaiacol to hydroxy- and methoxy-quinones. The particles formed within a few minutes of reaction and grew to micron-size aggregates after half an hour reaction. The mass-normalized absorption coefficients of the particles were comparable to those of strongly absorbing brown carbon compounds produced by biomass burning. These results could account for new pathways that lead to atmospheric secondary organic aerosol formation and abiotic polymer formation on environmental surfaces mediated by transition metals.

  3. Stereoselective formation and catalytic activity of hydrido(acylphosphane)(chlorido)(pyrazole)rhodium(III) complexes. Experimental and DFT studies.

    PubMed

    San Nacianceno, Virginia; Azpeitia, Susan; Ibarlucea, Lourdes; Mendicute-Fierro, Claudio; Rodríguez-Diéguez, Antonio; Seco, José M; San Sebastian, Eider; Garralda, María A

    2015-08-07

    The reaction of [{RhCl(COD)}2] (COD = 1,5-cyclooctadiene) with L = pyrazole (Hpz), 3(5)-methylpyrazole (Hmpz) or 3,5-dimethylpyrazole (Hdmpz) and PPh2(o-C6H4CHO) (Rh : L : P = 1 : 2 : 1) gives hydridoacyl complexes [RhHCl{PPh2(o-C6H4CO)}(L)2] (). Stereoselective formation of and with pyrazoles trans to hydrido and phosphorus and hydrogen bond formation with O-acyl and chlorido occur. is a mixture of two linkage isomers in a 9 : 1 ratio, with two 5-methylpyrazole ligands or with one 3- and one 5-methylpyrazole ligand, respectively. Fluxional undergoes metallotropic tautomerization and is a mixture of equal amounts of and , with hydrido trans to pyrazole or chlorido, respectively. Complexes readily exchange hydrido by chlorido to afford [RhCl2{PPh2(o-C6H4CO)}(L)2] (, and ) as single isomers with cis chloridos and two N-HCl hydrogen bonds. The reaction of with PPh3 or PPh2OH affords static [RhHCl{PPh2(o-C6H4CO)}(PPh3)L] () or [RhHCl{PPh2(o-C6H4CO)}(PPh2OH)L] () respectively with trans P-atoms and pyrazoles forming N-HCl hydrogen bonds. and contain single species with hydrido cis to chlorido, while is a mixture of equal amounts of and . Complexes , with an additional O-HO hydrogen bond, selectively contain only the cis-H,Cl species with all the three ligands. The reaction of [{RhCl(COD)}2] with L and PPh2(o-C6H4CHO) (Rh : L : P = 1 : 1 : 2) led to complexes with trans P-atoms, [RhHCl{PPh2(o-C6H4CO)}{PPh2(o-C6H4CHO)-κP}L] (, and ), at room temperature, and to [RhCl{PPh2(o-C6H4CO)}{PPh2(o-C6H4CHOH)}(Hmpz)] () or [RhCl{PPh2(o-C6H4CO)}2L] () with hydrogen evolution in refluxing benzene. DFT calculations were used to predict the correct isomers, their ratios and the particular intramolecular hydrogen bonds in these complexes. Single crystal X-ray diffraction analysis was performed on , and . Complexes are efficient homogeneous catalysts (0.5 mol% loading) in the hydrolysis of amine- or ammonia-borane (AB) to generate up to 3 equivalents

  4. Combustion studies of coal derived solid fuels by thermogravimetric analysis. III. Correlation between burnout temperature and carbon combustion efficiency

    USGS Publications Warehouse

    Rostam-Abadi, M.; DeBarr, J.A.; Chen, W.T.

    1990-01-01

    Burning profiles of 35-53 ??m size fractions of an Illinois coal and three partially devolatilized coals prepared from the original coal were obtained using a thermogravimetric analyzer. The burning profile burnout temperatures were higher for lower volatile fuels and correlated well with carbon combustion efficiencies of the fuels when burned in a laboratory-scale laminar flow reactor. Fuels with higher burnout temperatures had lower carbon combustion efficiencies under various time-temperature conditions in the laboratory-scale reactor. ?? 1990.

  5. Synthetic control to achieve lanthanide(III)/pyrimidine-4,6-dicarboxylate compounds by preventing oxalate formation: structural, magnetic, and luminescent properties.

    PubMed

    Cepeda, Javier; Balda, Rolindes; Beobide, Garikoitz; Castillo, Oscar; Fernández, Joaquín; Luque, Antonio; Pérez-Yáñez, Sonia; Román, Pascual

    2012-07-16

    Control over the synthetic conditions in many metal/diazinedicarboxylato systems is crucial to prevent oxalate formation, since dicarboxylato ligands easily undergo degradation in the presence of metal salts. We report here an efficient route to obtain oxalato-free compounds for the lanthanide/pyrimidine-4,6-dicarboxylato (pmdc) system on the basis of the reaction temperature and nonacidic pH or oxygen free atmosphere. Two different crystal architectures have been obtained: {[Ln(μ-pmdc)(1.5)(H(2)O)(3)]·xH(2)O}(n) (1-Ln) and {[Ln(2)(μ(4)-pmdc)(2)(μ-pmdc)(H(2)O)(2)]·H(2)O}(n) (2-Ln) with Ln(III) = La-Yb, except Pm. Both crystal structures are built from distorted two-dimensional honeycomb networks based on the recurrent double chelating mode established by the pmdc. In compounds 1-Ln, the tricapped trigonal prismatic coordination environment of the lanthanides is completed by three water molecules, precluding a further increase in the dimensionality. Crystallization water molecules are arranged in the interlamellar space, giving rise to highly flexible supramolecular clusters that are responsible for the modulation found in compound 1-Gd. Two of the coordinated water molecules are replaced by nonchelating carboxylate oxygen atoms of pmdc ligands in compounds 2-Ln, joining the metal-organic layers together and thus providing a compact three-dimensional network. The crystal structure of the compounds is governed by the competition between two opposing factors: the ionic size and the reaction temperature. The lanthanide contraction rejects the sterically hindered coordination geometries whereas high-temperature entropy driven desolvation pathway favors the release of solvent molecules leading to more compact frameworks. The characteristic luminescence of the Nd, Eu, and Tb centers is improved when moving from 1-Ln to 2-Ln compounds as a consequence of the decrease of the O-H oscillators. The magnetic properties of the compounds are dominated by the spin

  6. The Star Formation Histories of Local Group Dwarf Galaxies. III. Characterizing Quenching in Low-mass Galaxies

    NASA Astrophysics Data System (ADS)

    Weisz, Daniel R.; Dolphin, Andrew E.; Skillman, Evan D.; Holtzman, Jon; Gilbert, Karoline M.; Dalcanton, Julianne J.; Williams, Benjamin F.

    2015-05-01

    We explore the quenching of low-mass galaxies (104 ≲ {{M}\\star } ≲ 108 {{M}⊙ }) as a function of lookback time using the star formation histories (SFHs) of 38 Local Group dwarf galaxies. The SFHs were derived by analyzing color-magnitude diagrams of resolved stellar populations in archival Hubble Space Telescope/Wide Field Planetary Camera 2 imaging. We find: (1) lower-mass galaxies quench earlier than higher-mass galaxies; (2) inside of Rvirial there is no correlation between a satellite’s current proximity to a massive host and its quenching epoch; and (3) there are hints of systematic differences in the quenching times of M31 and Milky Way (MW) satellites, although the sample size and uncertainties in the SFHs of M31 dwarfs prohibit definitive conclusions. Combined with results from the literature, we qualitatively consider the redshift evolution (z = 0-1) of the quenched galaxy fraction over ˜7 dex in stellar mass (104 ≲ {{M}\\star } ≲ 1011.5 {{M}⊙ }). The quenched fraction of all galaxies generally increases toward the present, with both the lowest and highest-mass systems exhibiting the largest quenched fractions at all redshifts. In contrast, galaxies between {{M}\\star } ˜ 108-1010 {{M}⊙ } have the lowest quenched fractions. We suggest that such intermediate-mass galaxies are the least efficient at quenching. Finally, we compare our quenching times with predictions for infall times for low-mass galaxies associated with the MW. We find that some of the lowest-mass satellites (e.g., CVn II, Leo IV) may have been quenched before infall, while higher-mass satellites (e.g., Leo I, Fornax) typically quench ˜1-4 Gyr after infall. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA constract NAS 5-26555.

  7. Polyaspartic acid facilitates oxolation within iron(iii) oxide pre-nucleation clusters and drives the formation of organic-inorganic composites

    NASA Astrophysics Data System (ADS)

    Scheck, J.; Drechsler, M.; Ma, X.; Stöckl, M. T.; Konsek, J.; Schwaderer, J. B.; Stadler, S. M.; De Yoreo, J. J.; Gebauer, D.

    2016-12-01

    The interplay between polymers and inorganic minerals during the formation of solids is crucial for biomineralization and bio-inspired materials, and advanced material properties can be achieved with organic-inorganic composites. By studying the reaction mechanisms, basic questions on organic-inorganic interactions and their role during material formation can be answered, enabling more target-oriented strategies in future synthetic approaches. Here, we present a comprehensive study on the hydrolysis of iron(iii) in the presence of polyaspartic acid. For the basic investigation of the formation mechanism, a titration assay was used, complemented by microscopic techniques. The polymer is shown to promote precipitation in partly hydrolyzed reaction solutions at the very early stages of the reaction by facilitating iron(iii) hydrolysis. In unhydrolyzed solutions, no significant interactions between the polymer and the inorganic solutes can be observed. We demonstrate that the hydrolysis promotion by the polymer can be understood by facilitating oxolation in olation iron(iii) pre-nucleation clusters. We propose that the adsorption of olation pre-nucleation clusters on the polymer chains and the resulting loss in dynamics and increased proximity of the reactants is the key to this effect. The resulting composite material obtained from the hydrolysis in the presence of the polymer was investigated with additional analytical techniques, namely, scanning and transmission electron microscopies, light microscopy, atomic force microscopy, zeta potential measurements, dynamic light scattering, and thermogravimetric analyses. It consists of elastic, polydisperse nanospheres, ca. 50-200 nm in diameter, and aggregates thereof, exhibiting a high polymer and water content.

  8. Detecting population III galaxies with HST and JWST

    NASA Astrophysics Data System (ADS)

    Zackrisson, E.

    2012-09-01

    A small fraction of the atomic-cooling halos assembling at z < 15 may form out of minihalos that never experienced any prior star formation, and could in principle host small galaxies of chemically unenriched stars. Since the prospects of detecting isolated population III stars appear bleak even with the upcoming James Webb Space Telescope (JWST), these population III galaxies may offer one of the best probes of population III stars in the foreseeable future. By projecting the results from population III galaxy simulations through cluster magnification maps, we predict the fluxes and surface number densities of pop III galaxy galaxies as a function of their typical star formation efficiency. We argue that a small number of lensed population III galaxies in principle could turn up at z ~ 7-10 in the ongoing Hubble Space Telecope survey CLASH, which covers a total of 25 low-redshift galaxy clusters.

  9. Fusion of blastomeres in mouse embryos under the action of femtosecond laser radiation. Efficiency of blastocyst formation and embryo development

    NASA Astrophysics Data System (ADS)

    Osychenko, A. A.; Zalesskii, A. D.; Krivokharchenko, A. S.; Zhakhbazyan, A. K.; Ryabova, A. V.; Nadtochenko, V. A.

    2015-05-01

    Using the method of femtosecond laser surgery we study the fusion of two-cell mouse embryos under the action of tightly focused femtosecond laser radiation with the fusion efficiency reaching 60%. The detailed statistical analysis of the efficiency of blastomere fusion and development of the embryo up to the blastocyst stage after exposure of the embryos from different mice to a femtosecond pulse is presented. It is shown that the efficiency of blastocyst formation essentially depends on the biological characteristics of the embryo, namely, the strain and age of the donor mouse. The possibility of obtaining hexaploid embryonal cells using the methods of femtosecond laser surgery is demonstrated.

  10. New La(III) complex immobilized on 3-aminopropyl-functionalized silica as an efficient and reusable catalyst for hydrolysis of phosphate ester bonds.

    PubMed

    Muxel, Alfredo A; Neves, Ademir; Camargo, Maryene A; Bortoluzzi, Adailton J; Szpoganicz, Bruno; Castellano, Eduardo E; Castilho, Nathalia; Bortolotto, Tiago; Terenzi, Hernán

    2014-03-17

    Described herein is the synthesis, structure, and monoesterase and diesterase activities of a new mononuclear [La(III)(L(1))(NO3)2] (1) complex (H2L(1) = 2-bis[{(2-pyridylmethyl)-aminomethyl}-6-[N-(2-pyridylmethyl) aminomethyl)])-4-methyl-6-formylphenol) in the hydrolysis of 2,4-bis(dinitrophenyl)phosphate (2,4-BDNPP). When covalently linked to 3-aminopropyl-functionalized silica, 1 undergoes disproportionation to form a dinuclear species (APS-1), whose catalytic efficiency is increased when compared to the homogeneous reaction due to second coordination sphere effects which increase the substrate to complex association constant. The anchored catalyst APS-1 can be recovered and reused for subsequent hydrolysis reactions (five times) with only a slight loss in activity. In the presence of DNA, we suggest that 1 is also converted into the dinuclear active species as observed with APS-1, and both were shown to be efficient in DNA cleavage.

  11. High-efficiency III-V//Si tandem solar cells enabled by the Pd nanoparticle array-mediated “smart stack” approach

    NASA Astrophysics Data System (ADS)

    Mizuno, Hidenori; Makita, Kikuo; Tayagaki, Takeshi; Mochizuki, Toshimitsu; Sugaya, Takeyoshi; Takato, Hidetaka

    2017-07-01

    Smart stack is a handy technique to produce two-terminal tandem structures from various photovoltaic materials using Pd nanoparticle arrays as bonding mediators. Because of the increasing interest in III-V/Si integration, we herein demonstrated smart stack-based triple-junction cells consisting of InGaP/GaAs and crystalline Si subcells. Despite the use of classic Al-back surface field-type Si subcells, current matching with the InGaP/GaAs subcells was realized, and the promising efficiency of 25.1% was successfully achieved. The potential and versatility of the smart stack approach as a fabrication tool for high-efficiency multi-junction cells were further enhanced through this study.

  12. Mechanistic insights on iodine(III) promoted metal-free dual C-H activation involved in the formation of a spirocyclic bis-oxindole.

    PubMed

    Sreenithya, A; Sunoj, Raghavan B

    2014-12-05

    The mechanism of a metal-free, phenyliodine(III) bis(trifluoroacetate) promoted, dual aryl C-H activation of an anilide to a spirocyclic bis-oxindole is examined using density functional theory (M06-2X). The most preferred pathway proceeds through the involvement of a novel iodonium ion intermediate and a pivotal trifluoroacetate counterion. The two sequential aryl C-H activations, assisted by trifluoroacetate as well as the superior leaving group ability of PhI, facilitate the formation of spirocyclic bis-oxindole.

  13. Highly efficient luminescent hybrid materials covalently linking with europium(III) complexes via a novel fluorinated beta-diketonate ligand: synthesis, characterization and photophysical properties.

    PubMed

    Francis, Biju; Ambili Raj, D B; Reddy, M L P

    2010-09-14

    A novel highly fluorinated beta-diketonate ligand, 1-(3,5-bis(benzyloxy)phenyl)-4,4,5,5,5-pentafluoropentane-1,3-dione (HBBPPF) and its corresponding europium(III) ternary complex, Eu(BBPPF)(3)(DDXPO) [DDXPO = 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene oxide] were synthesized via a dexterously designed routine, characterized and its photophysical properties (PL) investigated. PL measurement results indicated that the europium(III) ternary complex exhibits intense red emission under UV light excitation with a solid-state quantum yield of 39%. An organic-inorganic mesoporous luminescent hybrid material was also constructed by linking the ternary europium(III) complex to the functionalized hexagonal mesoporous MCM-41 through the modified beta-diketonate ligand (SiBBPPF-Na). Beta-diketonate grafted to the coupling agent 3-(triethoxysilyl)propyl isocyanate was used as the precursor for the preparation of mesoporous materials. A modified MCM-41 mesoporous material containing ternary europium(iii) complex covalently bonded to the silica-based network, designated as Eu(BBPPF-Si)(3)(DDXPO)/MCM-41, was obtained by interacting SiBBPPF-Na with europium nitrate, DDXPO and MCM-41 via a ligand-exchange reaction. The new mesoporous hybrid material was characterized by powder X-ray diffraction, nitrogen adsorption-desorption, thermogravimetry, transmission electron microscopy, dynamic light scattering, FT-IR, (29)Si CP MAS NMR and (13)C NMR solid-state techniques, and photoluminescence spectroscopy. Eu(BBPPF-Si)(3)(DDXPO)/MCM-41 exhibits an efficient intramolecular energy transfer process from the silylated beta-diketonate to the central Eu(3+), namely, the "antenna effect", which favours a strong luminescent intensity (quantum yield = 43%). Thermogravimetric analysis on Eu(BBPPF-Si)(3)(DDXPO)/MCM-41 demonstrated that the thermal stability of the lanthanide complex was evidently improved as it was covalently bonded to the mesoporous MCM-41 matrix.

  14. He II emitters in the VIMOS VLT Deep Survey: Population III star formation or peculiar stellar populations in galaxies at 2 < z < 4.6?

    NASA Astrophysics Data System (ADS)

    Cassata, P.; Le Fèvre, O.; Charlot, S.; Contini, T.; Cucciati, O.; Garilli, B.; Zamorani, G.; Adami, C.; Bardelli, S.; Le Brun, V.; Lemaux, B.; Maccagni, D.; Pollo, A.; Pozzetti, L.; Tresse, L.; Vergani, D.; Zanichelli, A.; Zucca, E.

    2013-08-01

    Aims: The aim of this work is to identify He II emitters at 2 < z < 4.6 and to constrain the source of the hard ionizing continuum that powers the He II emission. Methods: We assembled a sample of 277 galaxies with a highly reliable spectroscopic redshift at 2 < z < 4.6 from the VIMOS-VLT Deep Survey (VVDS) Deep and Ultra-Deep data, and we identified 39 He II λ1640 emitters. We studied their spectral properties, measuring the fluxes, equivalent widths (EW), and full width at half maximum (FWHM) for most relevant lines, including He II λ1640, Lyα line, Si II λ1527, and C IV λ1549. Results: About 10% of galaxies at z ~ 3 and iAB ≤ 24.75 show He II in emission, with rest frame equivalent widths EW0 ~ 1-7 Å, equally distributed between galaxies with Lyα in emission or in absorption. We find 11 (3.9% of the global population) reliable He II emitters with unresolved He II lines (FWHM0 < 1200 km s-1), 13 (4.6% of the global population) reliable emitters with broad He II emission (FWHM0 > 1200 km s-1), 3 active galactic nuclei (AGN), and an additional 12 possible He II emitters. The properties of the individual broad emitters are in agreement with expectations from a Wolf-Rayet (W-R) model. Instead, the properties of the narrow emitters are not compatible with this model, nor with predictions of gravitational cooling radiation produced by gas accretion, unless this is severely underestimated by current models by more than two orders of magnitude. Rather, we find that the EW of the narrow He II line emitters are in agreement with expectations for a Population III (PopIII) star formation, if the episode of star formation is continuous, and we calculate that a PopIII star formation rate (SFR) of 0.1-10 M⊙ yr-1 alone is enough to sustain the observed He II flux. Conclusions: We conclude that narrow He II emitters are powered either by the ionizing flux from a stellar population rare at z ~ 0 but much more common at z ~ 3, or by PopIII star formation. As proposed by

  15. PAA-PAMPS copolymers as an efficient tool to control CaCO3 scale formation.

    PubMed

    Dietzsch, Michael; Barz, Matthias; Schüler, Timo; Klassen, Stefanie; Schreiber, Martin; Susewind, Moritz; Loges, Niklas; Lang, Michael; Hellmann, Nadja; Fritz, Monika; Fischer, Karl; Theato, Patrick; Kühnle, Angelika; Schmidt, Manfred; Zentel, Rudolf; Tremel, Wolfgang

    2013-03-05

    Scale formation, the deposition of certain minerals such as CaCO3, MgCO3, and CaSO4·2H2O in industrial facilities and household devices, leads to reduced efficiency or severe damage. Therefore, incrustation is a major problem in everyday life. In recent years, double hydrophilic block copolymers (DHBCs) have been the focus of interest in academia with regard to their antiscaling potential. In this work, we synthesized well-defined blocklike PAA-PAMPS copolymers consisting of acrylic acid (AA) and 2-acrylamido-2-methyl-propane sulfonate (AMPS) units in a one-step reaction by RAFT polymerization. The derived copolymers had dispersities of 1.3 and below. The copolymers have then been investigated in detail regarding their impact on the different stages of the crystallization process of CaCO3. Ca(2+) complexation, the first step of a precipitation process, and polyelectrolyte stability in aqueous solution have been investigated by potentiometric measurements, isothermal titration calorimetry (ITC), and dynamic light scattering (DLS). A weak Ca(2+) induced copolymer aggregation without concomitant precipitation was observed. Nucleation, early particle growth, and colloidal stability have been monitored in situ with DLS. The copolymers retard or even completely suppress nucleation, most probably by complexation of solution aggregates. In addition, they stabilize existing CaCO3 particles in the nanometer regime. In situ AFM was used as a tool to verify the coordination of the copolymer to the calcite (104) crystal surface and to estimate its potential as a growth inhibitor in a supersaturated CaCO3 environment. All investigated copolymers instantly stopped further crystal growth. The carboxylate richest copolymer as the most promising antiscaling candidate proved its enormous potential in scale inhibition as well in an industrial-filming test (Fresenius standard method).

  16. Forming Different Planetary Architectures. I. The Formation Efficiency of Hot Jupiters from High-eccentricity Mechanisms

    NASA Astrophysics Data System (ADS)

    Wang, Ying; Zhou, Ji-lin; hui-gen, Liu; Meng, Zeyang

    2017-10-01

    Exoplanets discovered over the past decades have provided a new sample of giant exoplanets: hot Jupiters. For lack of enough materials in the current locations of hot Jupiters, they are perceived to form outside the snowline. Then, they migrate to the locations observed through interactions with gas disks or high-eccentricity mechanisms. We examined the efficiencies of different high-eccentricity mechanisms for forming hot Jupiters in near-coplanar multi-planet systems. These mechanisms include planet–planet scattering, the Kozai–Lidov mechanism, coplanar high-eccentricity migration, and secular chaos, as well as other two new mechanisms that we present in this work, which can produce hot Jupiters with high inclinations even in retrograde. We find that the Kozai–Lidov mechanism plays the most important role in producing hot Jupiters among these mechanisms. Secular chaos is not the usual channel for the formation of hot Jupiters due to the lack of an angular momentum deficit within {10}7{T}{in} (periods of the inner orbit). According to comparisons between the observations and simulations, we speculate that there are at least two populations of hot Jupiters. One population migrates into the boundary of tidal effects due to interactions with the gas disk, such as ups And b, WASP-47 b, and HIP 14810 b. These systems usually have at least two planets with lower eccentricities, and remain dynamically stable in compact orbital configurations. Another population forms through high-eccentricity mechanisms after the excitation of eccentricity due to dynamical instability. These kinds of hot Jupiters usually have Jupiter-like companions in distant orbits with moderate or high eccentricities.

  17. Star formation efficiencies of molecular clouds in a galactic centre environment

    NASA Astrophysics Data System (ADS)

    Bertram, Erik; Glover, Simon C. O.; Clark, Paul C.; Klessen, Ralf S.

    2015-08-01

    We use the AREPO moving mesh code to simulate the evolution of molecular clouds exposed to a harsh environment similar to that found in the galactic centre (GC), in an effort to understand why the star formation efficiency (SFE) of clouds in this environment is so small. Our simulations include a simplified treatment of time-dependent chemistry and account for the highly non-isothermal nature of the gas and the dust. We model clouds with a total mass of 1.3 × 105 M⊙ and explore the effects of varying the mean cloud density and the virial parameter, α = Ekin/|Epot|. We vary the latter from α = 0.5 to 8.0, and so many of the clouds that we simulate are gravitationally unbound. We expose our model clouds to an interstellar radiation field (ISRF) and cosmic ray flux (CRF) that are both a factor of 1000 higher than the values found in the solar neighbourhood. As a reference, we also run simulations with local solar neighbourhood values of the ISRF and the CRF in order to better constrain the effects of the extreme conditions in the GC on the SFE. Despite the harsh environment and the large turbulent velocity dispersions adopted, we find that all of the simulated clouds form stars within less than a gravitational free-fall time. Increasing the virial parameter from α = 0.5 to 8.0 decreases the SFE by a factor of ˜4-10, while increasing the ISRF/CRF by a factor of 1000 decreases the SFE again by a factor of ˜2-6. However, even in our most unbound clouds, the SFE remains higher than that inferred for real GC clouds. We therefore conclude that high levels of turbulence and strong external heating are not enough by themselves to lead to a persistently low SFE at the centre of the Galaxy.

  18. Efficient callus formation and plant regeneration of goosegrass [Eleusine indica (L.) Gaertn.].

    PubMed

    Yemets, A I; Klimkina, L A; Tarassenko, L V; Blume, Y B

    2003-02-01

    Efficient methods in totipotent callus formation, cell suspension culture establishment and whole-plant regeneration have been developed for the goosegrass [ Eleusine indica (L.) Gaertn.] and its dinitroaniline-resistant biotypes. The optimum medium for inducing morphogenic calli consisted of N6 basal salts and B5 vitamins supplemented with 1-2 mg l(-1) 2,4-dichlorophenoxyacetic acid (2,4-D), 2 mg l(-1) glycine, 100 mg l(-1) asparagine, 100 mg l(-1) casein hydrolysate, 30 g l(-1) sucrose and 0.6% agar, pH 5.7. The presence of organogenic and embryogenic structures in these calli was histologically documented. Cell suspension cultures derived from young calli were established in a liquid medium with the same composition. Morphogenic structures of direct shoots and somatic embryos were grown into rooted plantlets on medium containing MS basal salts, B5 vitamins, 1 mg l(-1) kinetin (Kn) and 0.1 mg l(-1) indole-3-acetic acid (IAA), 3% sucrose, 0.6% agar, pH 5.7. Calli derived from the R-biotype of E. indica possessed a high resistance to trifluralin (dinitroaniline herbicide) and cross-resistance to a structurally non-related herbicide, amiprophosmethyl (phosphorothioamidate herbicide), as did the original resistant plants. Embryogenic cell suspension culture was a better source of E. indica protoplasts than callus or mesophyll tissue. The enzyme solution containing 1.5% cellulase Onozuka R-10, 0.5% driselase, 1% pectolyase Y-23, 0.5% hemicellulase and N(6) mineral salts with an additional 0.2 M KCl and 0.1 M CaCl(2) (pH 5.4-5.5) was used for protoplast isolation. The purified protoplasts were cultivated in KM8p liquid medium supplemented with 2 mg l(-1) 2,4-D and 0.2 mg l(-1) Kn.

  19. Preliminary protein corona formation stabilizes gold nanoparticles and improves deposition efficiency

    NASA Astrophysics Data System (ADS)

    Luby, Alexandra O.; Breitner, Emily K.; Comfort, Kristen K.

    2016-08-01

    Due to their advantageous characteristics, gold nanoparticles (AuNPs) are being increasingly utilized in a vast array of biomedical applications. However, the efficacy of these procedures are highly dependent upon strong interactions between AuNPs and the surrounding environment. While the field of nanotechnology has grown exponentially, there is still much to be discovered with regards to the complex interactions between NPs and biological systems. One area of particular interest is the generation of a protein corona, which instantaneously forms when NPs encounter a protein-rich environment. Currently, the corona is viewed as an obstacle and has been identified as the cause for loss of application efficiency in physiological systems. To date, however, no study has explored if the protein corona could be designed and advantageously utilized to improve both NP behavior and application efficacy. Therefore, we sought to identify if the formation of a preliminary protein corona could modify both AuNP characteristics and association with the HaCaT cell model. In this study, a corona comprised solely of epidermal growth factor (EGF) was successfully formed around 10-nm AuNPs. These EGF-AuNPs demonstrated augmented particle stability, a modified corona composition, and increased deposition over stock AuNPs, while remaining biocompatible. Analysis of AuNP dosimetry was repeated under dynamic conditions, with lateral flow significantly disrupting deposition and the nano-cellular interface. Taken together, this study demonstrated the plausibility and potential of utilizing the protein corona as a means to influence NP behavior; however, fluid dynamics remains a major challenge to progressing NP dosimetry.

  20. Significant role of Mn(III) sites in e(g)(1) configuration in manganese oxide catalysts for efficient artificial water oxidation.

    PubMed

    Indra, Arindam; Menezes, Prashanth W; Schuster, Felix; Driess, Matthias

    2015-11-01

    Development of efficient bio-inspired water oxidation system with transition metal oxide catalyst has been considered as the one of the most challenging task in the recent years. As the oxygen evolving center of photosystem II consists of Mn4CaO5 cluster, most of the water oxidation study was converged to build up manganese oxide based catalysts. Here we report the synthesis of efficient artificial water oxidation catalysts by transferring the inactive manganese monooxide (MnO) under highly oxidizing conditions with ceric ammonium nitrate (CAN) and ozone (O3). MnO was partially oxidized to form mixed-valent manganese oxide (MnOx) with CAN whereas completely oxidized to mineral phase of ε-MnO2 (Akhtenskite) upon treatment of O3 in acidic solution, which we explore first time as a water oxidation catalyst. Chemical water oxidation, as well as the photochemical water oxidation in the presence of sacrificial electron acceptor and photosensitizer with the presented catalysts were carried out that followed the trends: MnOx>MnO2>MnO. Structural and activity correlation reveals that the presence of larger extent of Mn(III) in MnOx is the responsible factor for higher activity compared to MnO2. Mn(III) species in octahedral system with eg(1) configuration furnishes and facilitates the Mn-O and Mn-Mn bond enlargement with required structural flexibility and disorder in the manganese oxide structure which indeed facilitates water oxidation.

  1. Osmium(III) and osmium(V) complexes bearing a macrocyclic ligand: a simple and efficient catalytic system for cis-dihydroxylation of alkenes with hydrogen peroxide.

    PubMed

    Sugimoto, Hideki; Ashikari, Kenji; Itoh, Shinobu

    2013-09-01

    A simple protocol that uses [Os(III)(OH)(H2O)(L-N4Me2)](PF6)2 (1; L-N4Me2 = N,N'-dimethyl-2,11-diaza[3.3](2,6)pyridinophane) as a catalyst and H2O2 as a terminal oxidant for efficient cis-1,2-dihydroxylation of alkenes is presented. Unfunctionalized (or aliphatic) alkenes and alkenes/styrenes containing electron-withdrawing groups are selectively oxidized to the corresponding vicinal diols in good to excellent yields (46-99 %). In the catalytic reactions, the stoichiometry of alkene:H2O2 is 1:1, and thus the oxidant efficiency is very high. For the dihydroxylation of cyclohexene, the catalytic amount of 1 can be reduced to 0.01 mol % to achieve a very high turnover number of 5500. The active oxidant is identified as the Os(V)(O)(OH) species (2), which is formed via the hydroperoxide adduct, an Os(III)(OOH) species. The active oxidant 2 is successfully isolated and crystallographically characterized. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. A Novel Periplasmic Protein, VrpA, Contributes to Efficient Protein Secretion by the Type III Secretion System in Xanthomonas spp.

    PubMed

    Zhou, Xiaofeng; Hu, Xiufang; Li, Jinyun; Wang, Nian

    2015-02-01

    Efficient secretion of type III effector proteins from the bacterial cytoplasm to host cell cytosol via a type III secretion system (T3SS) is crucial for virulence of plant-pathogenic bacterium. Our previous study revealed a conserved hypothetical protein, virulence-related periplasm protein A (VrpA), which was identified as a critical virulence factor for Xanthomonas citri subsp. citri. In this study, we demonstrate that mutation of vrpA compromises X. citri subsp. citri virulence and hypersensitive response induction. This deficiency is also observed in the X. campestris pv. campestris strain, suggesting a functional conservation of VrpA in Xanthomonas spp. Our study indicates that VrpA is required for efficient protein secretion via T3SS, which is supported by multiple lines of evidence. A CyaA reporter assay shows that VrpA is involved in type III effector secretion; quantitative reverse-transcription polymerase chain reaction analysis suggests that the vrpA mutant fails to activate citrus-canker-susceptible gene CsLOB1, which is transcriptionally activated by transcription activator-like effector PthA4; in vitro secretion study reveals that VrpA plays an important role in secretion of T3SS pilus, translocon, and effector proteins. Our data also indicate that VrpA in X. citri subsp. citri localizes to bacterial periplasmic space and the periplasmic localization is required for full function of VrpA and X. citri subsp. citri virulence. Protein-protein interaction studies show that VrpA physically interacts with periplasmic T3SS components HrcJ and HrcC. However, the mutation of VrpA does not affect T3SS gene expression. Additionally, VrpA is involved in X. citri subsp. citri tolerance of oxidative stress. Our data contribute to the mechanical understanding of an important periplasmic protein VrpA in Xanthomonas spp.

  3. Semipolar III-nitride light-emitting diodes with negligible efficiency droop up to ˜1 W

    NASA Astrophysics Data System (ADS)

    Oh, Sang Ho; Yonkee, Benjamin P.; Cantore, Michael; Farrell, Robert M.; Speck, James S.; Nakamura, Shuji; DenBaars, Steven P.

    2016-10-01

    We demonstrate 1 mm2 blue light-emitting diodes with a negligible efficiency droop up to ˜1 W. LEDs with 12- to 14-nm-thick single quantum wells were grown by metalorganic chemical vapor deposition on a free-standing semipolar (20\\bar{2}\\bar{1}) GaN substrate. Packaged devices showed an external quantum efficiency of 42.3% at 20 A/cm2 with a negligible efficiency droop up to 991 mW at 900 mA. At 900 mA, the thermal droop and hot/cold factor were 8.2% and 0.92, respectively. The adoption of a thick active region resulted in excellent optical and thermal performance characteristics that are suitable for high-power lighting applications.

  4. Modeling, synthesis and study of highly efficient solar cells based on III-nitride nanowire arrays grown on Si substrates

    NASA Astrophysics Data System (ADS)

    Mozharov, A. M.; Bolshakov, A. D.; Kudryashov, D. A.; Kryzhanovskaya, N. V.; Cirlin, G. E.; Mukhin, I. S.; Harmand, J. C.; Tchernysheva, M.

    2015-11-01

    In this letter we investigate photovoltaic properties of GaN nanowires (NWs) - Si substrate heterostructure obtained by molecular beam epitaxy (MBE). Antireflection properties of the NW array were studied theoretically and experimentally to show an order of magnitude enhancement in antireflection comparing to the pure Si surface (2.5% vs. 33.8%). In order to determine optimal morphology and doping levels of the structure with maximum possible efficiency we simulated it's properties using a finite difference method. The carried out simulation showed that a maximum efficiency should be 20%.

  5. Pd/C synthesized with citric acid: an efficient catalyst for hydrogen generation from formic acid/sodium formate.

    PubMed

    Wang, Zhi-Li; Yan, Jun-Min; Wang, Hong-Li; Ping, Yun; Jiang, Qing

    2012-01-01

    A highly efficient hydrogen generation from formic acid/sodium formate aqueous solution catalyzed by in situ synthesized Pd/C with citric acid has been successfully achieved at room temperature. Interestingly, the presence of citric acid during the formation and growth of the Pd nanoparticles on carbon can drastically enhance the catalytic property of the resulted Pd/C, on which the conversion and turnover frequency for decomposition of formic acid/sodium formate system can reach the highest values ever reported of 85% within 160 min and 64 mol H(2) mol(-1) catalyst h(-1), respectively, at room temperature. The present simple, low cost, but highly efficient CO-free hydrogen generation system at room temperature is believed to greatly promote the practical application of formic acid system on fuel cells.

  6. Pd/C Synthesized with Citric Acid: An Efficient Catalyst for Hydrogen Generation from Formic Acid/Sodium Formate

    PubMed Central

    Wang, Zhi-Li; Yan, Jun-Min; Wang, Hong-Li; Ping, Yun; Jiang, Qing

    2012-01-01

    A highly efficient hydrogen generation from formic acid/sodium formate aqueous solution catalyzed by in situ synthesized Pd/C with citric acid has been successfully achieved at room temperature. Interestingly, the presence of citric acid during the formation and growth of the Pd nanoparticles on carbon can drastically enhance the catalytic property of the resulted Pd/C, on which the conversion and turnover frequency for decomposition of formic acid/sodium formate system can reach the highest values ever reported of 85% within 160 min and 64 mol H2 mol−1 catalyst h−1, respectively, at room temperature. The present simple, low cost, but highly efficient CO-free hydrogen generation system at room temperature is believed to greatly promote the practical application of formic acid system on fuel cells. PMID:22953041

  7. Sterically Congested 2,6‐Disubstituted Anilines from Direct C−N Bond Formation at an Iodine(III) Center

    PubMed Central

    Lucchetti, Nicola; Scalone, Michelangelo; Fantasia, Serena

    2016-01-01

    Abstract 2,6‐Disubstituted anilines are readily prepared from the direct reaction between amides and diaryliodonium salts. As demonstrated for 24 different examples, the reaction is of unusually broad scope with respect to the sterically congested arene and the nitrogen source, occurs without the requirement for any additional promoter, and proceeds through a direct reductive elimination at the iodine(III) center. The efficiency of the coupling procedure is further demonstrated within the short synthesis of a chemerin binding inhibitor. PMID:27651117

  8. Reactions of the class II peroxidases, lignin peroxidase and Arthromyces ramosus peroxidase, with hydrogen peroxide. Catalase-like activity, compound III formation, and enzyme inactivation.

    PubMed

    Hiner, Alexander N P; Hernández-Ruiz, Josefa; Rodríguez-López, José Neptuno; García-Cánovas, Francisco; Brisset, Nigel C; Smith, Andrew T; Arnao, Marino B; Acosta, Manuel

    2002-07-26

    The reactions of the fungal enzymes Arthromyces ramosus peroxidase (ARP) and Phanerochaete chrysosporium lignin peroxidase (LiP) with hydrogen peroxide (H(2)O(2)) have been studied. Both enzymes exhibited catalase activity with hyperbolic H(2)O(2) concentration dependence (K(m) approximately 8-10 mm, k(cat) approximately 1-3 s(-1)). The catalase and peroxidase activities of LiP were inhibited within 10 min and those of ARP in 1 h. The inactivation constants were calculated using two independent methods; LiP, k(i) approximately 19 x 10(-3) s(-1); ARP, k(i) approximately 1.6 x 10(-3) s(-1). Compound III (oxyperoxidase) was detected as the majority species after the addition of H(2)O(2) to LiP or ARP, and its formation was accompanied by loss of enzyme activity. A reaction scheme is presented which rationalizes the turnover and inactivation of LiP and ARP with H(2)O(2). A similar model is applicable to horseradish peroxidase. The scheme links catalase and compound III forming catalytic pathways and inactivation at the level of the [compound I.H(2)O(2)] complex. Inactivation does not occur from compound III. All peroxidases studied to date are sensitive to inactivation by H(2)O(2), and it is suggested that the model will be generally applicable to peroxidases of the plant, fungal, and prokaryotic superfamily.

  9. Unveiling the Crystal Formation of Cesium Lead Mixed-Halide Perovskites for Efficient and Stable Solar Cells.

    PubMed

    Nam, Jae Keun; Jung, Myung Sun; Chai, Sung Uk; Choi, Yung Ji; Kim, Dongho; Park, Jong Hyeok

    2017-07-06

    Thermal instability of organic-inorganic hybrid perovskites will be an inevitable hurdle for commercialization. Recently, all-inorganic cesium lead halide perovskites, in particular, CsPbI2Br, have emerged as thermally stable and efficient photovoltaic light absorbers. However, the fundamental properties of this material have not been studied in detail. The crystal formation behavior of CsPbI2Br is investigated by examining the surface morphology, crystal structure, and chemical state of the perovskite films. We discover a previously uncharacterized feature that the formation of black polymorph through optimal annealing temperature proves to be critical to both solar cell efficiency and phase stability. Our optimized planar heterojunction solar cell exhibits a J-V scan efficiency of 10.7% and open-circuit voltage of 1.23 V, which far outperforms the preceding literature.

  10. The effects of stimulated star formation on the evolution of the galaxy. III - The chemical evolution of nonlinear systems

    NASA Technical Reports Server (NTRS)

    Shore, Steven N.; Ferrini, Federico; Palla, Francesco

    1987-01-01

    The evolution of models for star formation in galaxies with disk and halo components is discussed. Two phases for the halo (gas and stars) and three for the disk (including clouds) are used in these calculations. The star-formation history is followed using nonlinear phase-coupling models which completely determine the populations of the phases as a function of time. It is shown that for a wide range of parameters, including the effects of both spontaneous and stimulated star formation and mass exchange between the spatial components of the system, the observed chemical history of the galaxy can easily be obtained. The most sensitive parameter in the detailed metallicity and star-formation history for the system is the rate of return of gas to the diffuse phase upon stellar death.

  11. Efficient stabilization of copper(III) in tetraaza pseudo-macrocyclic oxime-and-hydrazide ligands with adjustable cavity size.

    PubMed

    Fritsky, Igor O; Kozłowski, Henryk; Kanderal, Olga M; Haukka, Matti; Swiatek-Kozłowska, Jolanta; Gumienna-Kontecka, Elzbieta; Meyer, Franc

    2006-10-21

    Substitution of the amide donors in open-chain {2N(oxime), 2N(amide)} ligands by hydrazide donors gives new pseudo-macrocyclic copper complexes that show a significant decrease of the Cu(3+/2+) redox potentials in both mono- and polynuclear systems, thus demonstrating a pronounced capacity of such ligand systems to efficiently stabilize the trivalent copper.

  12. Preliminary analysis of problem of determining experimental performance of air-cooled turbine III : methods for determining power and efficiency

    NASA Technical Reports Server (NTRS)

    Ellerbrock, Herman H , Jr; Ziemer, Robert R

    1950-01-01

    Suggested formula are given for determining air-cooled turbine-performance characteristics, such as power and efficiency, as functions of certain parameters. These functions, generally being unknown, are determined from experimental data obtained from specific investigations. Special plotting methods for isolating the effect of each parameter are outlined.

  13. Sensitizer design for efficient triplet-triplet annihilation upconversion: annihilator-appended tris-cyclometalated Ir(III) complexes.

    PubMed

    Peng, Jiang; Jiang, Xinpeng; Guo, Xinyan; Zhao, Dahui; Ma, Yuguo

    2014-07-25

    Enhanced triplet-triplet annihilation upconversion efficiency is achieved with two tris-cyclometalated iridium sensitizers covalently tethered with a pyrene annihilator. The improved sensitizing ability and very long phosphorescence lifetimes (1-2 ms) of these bichromophore molecules are both attributed to the intramolecular energy transfer between the iridium complex and appended pyrene group.

  14. Syntheses, photophysics, and application of iridium(III) phosphorescent emitters for highly efficient, long-life organic light-emitting diodes.

    PubMed

    Lee, Tsang-Chi; Chang, Chiung-Fang; Chiu, Yuan-Chieh; Chi, Yun; Chan, Tzu-Ying; Cheng, Yi-Ming; Lai, Chin-Hung; Chou, Pi-Tai; Lee, Gene-Hsiang; Chien, Chen-Han; Shu, Ching-Fong; Leonhardt, Jens

    2009-05-04

    Rational design and synthesis of Ir(III) complexes (1-3) bearing two cyclometalated ligands (C--N) and one 2-(diphenylphosphino)phenolate chelate (P--O) as well as the corresponding Ir(III) derivatives (4-6) with only one (C--N) ligand and two P--O chelates are reported, where (C--NH)=phenylpyridine (ppyH), 1-phenylisoquinoline (piqH), and 4-phenylquinazoline (nazoH). Single crystal X-ray diffraction studies of 3 reveal a distorted octahedral coordination geometry, in which two nazo ligands adopt an eclipsed configuration, with the third P--O ligand located trans to the phenyl group of both nazo ligands, confirming the general skeletal pattern for 1-3. In sharp contrast, complex 4 reveals a trans-disposition for the PPh2 groups, along with the phenolate groups residing opposite the unique cyclometalated ppy ligand, which is the representative structure for 4-6. These Ir(III) complexes exhibit green-to-red photoluminescence with moderate to high quantum efficiencies in the degassed fluid state and bright emission in the solid state. For 1-6, the resolved emission spectroscopy and relaxation dynamics are well rationalized by the computational approach. OLEDs fabricated using 12 wt. % of 3 doped in CBP and with BCP as hole blocking material, give bright electroluminescence with lambda(max)=628 nm and CIE(xy) coordinates (0.65, 0.34). The turn-on voltage is 3.2 V, while the current efficiency and the power efficiency reach 11.2 cd A(-1) and 4.5 lm W(-1) at 20 mA cm(-2). The maximum efficiency reaches 14.7 cd A(-1)and 6.8 lm W(-1) upon switching to TPBI as hole blocking material. For evaluating device lifespan, the tested device incorporating CuPc as a passivation layer, 3 doped in CTP as an emitting layer, and BAlq as hole blocking material, shows a remarkably long lifetime up to 36,000 h at an initial luminance of 500 cd m(-2).

  15. Formation, reactivity, and aging of ferric oxide particles formed from Fe(II) and Fe(III) sources: Implications for iron bioavailability in the marine environment

    NASA Astrophysics Data System (ADS)

    Bligh, Mark W.; Waite, T. David

    2011-12-01

    Freshly formed amorphous ferric oxides (AFO) in the water column are potentially highly reactive, but with reactivity declining rapidly with age, and have the capacity to partake in reactions with dissolved species and to be a significant source of bioavailable iron. However, the controls on reactivity in aggregated oxides are not well understood. Additionally, the mechanism by which early rapid aging occurs is not clear. Aging is typically considered in terms of changes in crystallinity as the structure of an iron oxide becomes more stable and ordered with time thus leading to declining reactivity. However, there has been recognition of the role that aggregation can play in determining reactivity, although it has received limited attention. Here, we have formed AFO in seawater in the laboratory from either an Fe(II) or Fe(III) source to produce either AFO(II) or AFO(III). The changes in reactivity of these two oxides following formation was measured using both ligand-promoted dissolution (LPD) and reductive dissolution (RD). The structure of the two oxides was examined using light scattering and X-ray adsorption techniques. The dissolution rate of AFO(III) was greater than that of AFO(II), as measured by both dissolution techniques, and could be attributed to both the less ordered molecular structure and smaller primary particle size of AFO(III). From EXAFS analysis shortly (90 min) following formation, AFO(II) and AFO(III) were shown to have the same structure as aged lepidocrocite and ferrihydrite respectively. Both oxides displayed a rapid decrease in dissolution rate over the first hours following formation in a pattern that was very similar when normalised. The early establishment and little subsequent change of crystal structure for both oxides undermined the hypothesis that increasing crystallinity was responsible for early rapid aging. Also, an aging model describing this proposed process could only be fitted to the data with kinetic parameters that were

  16. A Coherent Study of Emission Lines from Broadband Photometry: Specific Star Formation Rates and [O iii]/Hβ Ratio at 3 > z > 6

    NASA Astrophysics Data System (ADS)

    Faisst, A. L.; Capak, P.; Hsieh, B. C.; Laigle, C.; Salvato, M.; Tasca, L.; Cassata, P.; Davidzon, I.; Ilbert, O.; Le Fèvre, O.; Masters, D.; McCracken, H. J.; Steinhardt, C.; Silverman, J. D.; de Barros, S.; Hasinger, G.; Scoville, N. Z.

    2016-04-01

    We measure the Hα and [O iii] emission line properties as well as specific star formation rates (sSFRs) of spectroscopically confirmed 3 < z < 6 galaxies in COSMOS from their observed colors versus redshift evolution. Our model describes consistently the ensemble of galaxies including intrinsic properties (age, metallicity, star formation history), dust attenuation, and optical emission lines. We forward-model the measured Hα equivalent widths (EW) to obtain the sSFR out to z ˜ 6 without stellar mass fitting. We find a strongly increasing rest-frame Hα EW that is flattening off above z ˜ 2.5 with average EWs of 300-600 Å at z ˜ 6. The sSFR is increasing proportionally to {(1+z)}2.4 at z < 2.2 and to {(1+z)}1.5 at higher redshifts, indicative of a fast build-up of mass in high-z galaxies within e-folding times of 100-200 Myr at z ˜ 6. The redshift evolution at z > 3 cannot be fully explained in a picture of growth driven by cold accretion. We find a progressively increasing [O iii]λ5007/Hβ ratio out to z ˜ 6, consistent with the ratios in local galaxies selected by increasing Hα EW (i.e., sSFR). This demonstrates the potential of using “local high-z analogs” to investigate the spectroscopic properties and relations of galaxies in the re-ionization epoch.

  17. Exposure to Umbelliferone Reduces Ralstonia solanacearum Biofilm Formation, Transcription of Type III Secretion System Regulators and Effectors and Virulence on Tobacco

    PubMed Central

    Yang, Liang; Li, Shili; Qin, Xiyun; Jiang, Gaofei; Chen, Juanni; Li, Bide; Yao, Xiaoyuan; Liang, Peibo; Zhang, Yong; Ding, Wei

    2017-01-01

    Ralstonia solanacearum is one of the most devastating phytopathogens and causes bacterial wilt, which leads to severe economic loss due to its worldwide distribution and broad host range. Certain plant-derived compounds (PDCs) can impair bacterial virulence by suppressing pathogenic factors of R. solanacearum. However, the inhibitory mechanisms of PDCs in bacterial virulence remain largely unknown. In this study, we screened a library of coumarins and derivatives, natural PDCs with fused benzene and α-pyrone rings, for their effects on expression of the type III secretion system (T3SS) of R. solanacearum. Here, we show that umbelliferone (UM), a 7-hydroxycoumarin, suppressed T3SS regulator gene expression through HrpG–HrpB and PrhG–HrpB pathways. UM decreased gene expression of six type III effectors (RipX, RipD, RipP1, RipR, RipTAL, and RipW) of 10 representative effector genes but did not alter T2SS expression. In addition, biofilm formation of R. solanacearum was significantly reduced by UM, though swimming activity was not affected. We then observed that UM suppressed the wilting disease process by reducing colonization and proliferation in tobacco roots and stems. In summary, the findings reveal that UM may serve as a plant-derived inhibitor to manipulate R. solanacearum T3SS and biofilm formation, providing proof of concept that these key virulence factors are potential targets for the integrated control of bacterial wilt. PMID:28713361

  18. Impact of Microcystis aeruginosa Exudate on the Formation and Reactivity of Iron Oxide Particles Following Fe(II) and Fe(III) Addition.

    PubMed

    Garg, Shikha; Wang, Kai; Waite, T David

    2017-05-16

    Impact of the organic exudate secreted by a toxic strain of Microcystis aeruginosa on the formation, aggregation, and reactivity of iron oxides that are formed on addition of Fe(II) and Fe(III) salts to a solution of the exudate is investigated in this study. The exudate has a stabilizing effect on the particles formed with decreased aggregation rate and increased critical coagulant concentration required for diffusion-limited aggregation to occur. These results suggest that the presence of algal exudates from Microcystis aeruginosa may significantly influence particle aggregation both in natural water bodies where Fe(II) oxidation results in oxide formation and in water treatment where Fe(III) salts are commonly added to aid particle growth and contaminant capture. The exudate also affects the reactivity of iron oxide particles formed with exudate coated particles undergoing faster dissolution than bare iron oxide particles. This has implications to iron availability, especially where algae procure iron via dissolution of iron oxide particles as a result of either reaction with reducing moieties, light-mediated ligand to metal charge transfer and/or reaction with siderophores. The increased reactivity of exudate coated particles is attributed, for the most part, to the smaller size of these particles, higher surface area and increased accessibility of surface sites.

  19. Axonal Type III Nrg1 Controls Glutamate Synapse Formation and GluA2 Trafficking in Hippocampal-Accumbens Connections

    PubMed Central

    Akmentin, Wendy

    2017-01-01

    Abstract Altered neuregulin 1 (Nrg1)/ErbB signaling and glutamatergic hypofunction have been implicated in the pathophysiology of schizophrenia. Here, we employed gene chimeric ventral hippocampus (vHipp)-nucleus accumbens (nAcc) coculture from mouse, electrophysiology, immunocytochemistry, FM1-43 vesicle fusion, and electron microscopy techniques to examine the pre- and postsynaptic mechanisms of genetic deficits in Nrg1/ErbB signaling-induced glutamatergic dysfunctions. Reduced presynaptic type III Nrg1 expression along vHipp axons decreases the number of glutamate synapses and impairs GluA2 trafficking in the postsynaptic nAcc neurons, resulting in decreased frequency and amplitude of miniature EPSCs (mEPSCs). Reduced expression of axonal type III Nrg1 along vHipp projections also decreases functional synaptic vesicle (SV) clustering and vesicular trafficking to presynaptic vHipp axonal terminals. These findings suggest that Nrg1/ErbB signaling modulate glutamatergic transmission via both pre- and postsynaptic mechanisms. PMID:28275713

  20. Catalytic efficiency of iron(III) oxides in decomposition of hydrogen peroxide: competition between the surface area and crystallinity of nanoparticles.

    PubMed

    Hermanek, Martin; Zboril, Radek; Medrik, Ivo; Pechousek, Jiri; Gregor, Cenek

    2007-09-05

    Various iron(III) oxide catalysts were prepared by controlled decomposition of a narrow layer (ca. 1 mm) of iron(II) oxalate dihydrate, FeC(2)O(4).2H(2)O, in air at the minimum conversion temperature of 175 degrees C. This thermally induced solid-state process allows for simple synthesis of amorphous Fe(2)O(3) nanoparticles and their controlled one-step crystallization to hematite (alpha-Fe(2)O(3)). Thus, nanopowders differing in surface area and particle crystallinity can be produced depending on the reaction time. The phase composition of iron(III) oxides was monitored by XRD and (57)Fe Mössbauer spectroscopy including in-field measurements, providing information on the relative contents of amorphous and crystalline phases. The gradual changes in particle size and surface area accompanying crystallization were evaluated by HRTEM and BET analysis, respectively. The catalytic efficiency of the synthesized nanoparticles was tested by tracking the decomposition of hydrogen peroxide. The obtained kinetic data gave an unconventional nonmonotone dependence of the rate constant on the surface area of the samples. The amorphous nanopowder with the largest surface area of 401 m(2) g(-1) revealed the lowest catalytic efficiency, while the highest efficiency was achieved with the sample having a significantly lower surface area, 337 m(2) g(-1), exhibiting a prevailing content of crystalline alpha-Fe(2)O(3) phase. The obtained rate constant, 26.4 x 10(-3) min(-1) (g/L)(-1), is currently the highest value published. The observed rare catalytic phenomenon, where the particle crystallinity prevails over the surface area effects, is discussed with respect to other processes of heterogeneous catalysis.

  1. Annealing group III-V compound doped silicon-germanium alloy for improved thermo-electric conversion efficiency

    NASA Technical Reports Server (NTRS)

    Vandersande, Jan W. (Inventor); Wood, Charles (Inventor); Draper, Susan L. (Inventor)

    1989-01-01

    The thermoelectric conversion efficiency of a GaP doped SiGe alloy is improved about 30 percent by annealing the alloy at a temperature above the melting point of the alloy, preferably stepwise from 1200 C to 1275 C in air to form large grains having a size over 50 microns and to form a GeGaP rich phase and a silicon rich phase containing SiP and SiO2 particles.

  2. Continuum models for gas in disturbed galaxies. III. Bifurcations and chaos in a deterministic model for bursts of star formation

    SciTech Connect

    Struck-Marcell, C.; Scalo, J.M.

    1987-05-01

    A study of the nonlinear behavior of model equations describing the Oort model for interstellar cloud evolution and star formation is presented. One-zone cloud fluid equations for the Oort model are given, and it is shown how, as the time-delay parameter T(d) is increased, the system bifurcates to limit-cycle behavior accompanied by star formation bursts and, with further increase in T(d), suffers further bifurcations leading to chaotic behavior. A linear stability analysis, including time delay, is used to demonstrate that the behavior of the Oort model does not depend sensitively on the other parameters involved. It is also shown that the onset of bifurcation to a limit cycle can be predicted analytically. The major predictions of the calculations are compared with available relevant observations of star formation activity in galaxies, especially tidally interacting galaxies. 112 references.

  3. Coordination Modes in the Formation of Ternary Complexes of Am(III), Cm(III) and Eu(III) with EDTA and NTA: TRLFS, 13C NMR, EXAFS, and Thermodynamics of the complexation.

    SciTech Connect

    Mathur,J.; Thakur, P.; Dodge, C.; Francis, A.; Choppin, G.

    2006-01-01

    The formation and the structure of the ternary complexes of trivalent Am, Cm, and Eu with mixtures of EDTA+NTA (ethylenediamine tetraacetate and nitrilotriacetate) have been studied by time-resolved laser fluorescence spectroscopy, {sup 13}C NMR, extended X-ray absorption fine structure, and two-phase metal ion equilibrium distribution at 6.60 m (NaClO{sub 4}) and a hydrogen ion concentration value (pcH) between 3.60 and 11.50. In the ternary complexes, EDTA binds via four carboxylates and two nitrogens, while the binding of the NTA varies with the hydrogen ion concentration, pcH, and the concentration ratios of the metal ion and the ligand. When the concentration ratios of the metal to ligand is low (1:1:1-1:1:2), two ternary complexes, M(EDTA)(NTAH){sup 3-} and M(EDTA)(NTA){sup 4-}, are formed at pcH ca. 9.00 in which NTA binds via three carboxylates, via two carboxylates and one nitrogen, or via two carboxylates and a H{sub 2}O. At higher ratios (1:1:20 and 1:10:10) and pcH's of ca. 9.00 and 11.50, one ternary complex, M(EDTA)(NTA){sup 4-}, is formed in which NTA binds via three carboxylates and not via nitrogen. The two-phase equilibrium distribution studies at tracer concentrations of Am, Cm, and Eu have also confirmed the formation of the ternary complex M(EDTA)(NTA){sup 4-} at temperatures between 0 and 60 {sup o}C. The stability constants (log{beta}{sub 111}) for these metal ions increase with increasing temperature. The endothermic enthalpy and positive entropy indicated a significant effect of cation dehydration in the formation of the ternary complexes at high ionic strength.

  4. Efficient biodegradation of acephate by Pseudomonas pseudoalcaligenes PS-5 in the presence and absence of heavy metal ions [Cu(II) and Fe(III)], and humic acid.

    PubMed

    Singh, Simranjeet; Kumar, Vijay; Upadhyay, Niraj; Singh, Joginder; Singla, Sourav; Datta, Shivika

    2017-08-01

    The present study was intended to investigate the biodegradation of acephate in aqueous media in the presence and in the absence of metal ions [Fe(III) and Cu(II)], and humic acid (HA). Biodegradations were performed using Pseudomonas pseudoalcaligenes PS-5 (PS-5) isolated from the heavy metal polluted site. Biodegradations were monitored by UV-Visible, FTIR, and electron spray ionization-mass spectrometry (ESI-MS) analyses. ESI-MS analysis revealed that PS-5 degraded acephate to two metabolites showing intense ions at mass-to-charge ratios (m/z) 62 and 97. The observed kinetic was the pseudo-first order, and half-life periods (t1/2) were 2.79 d(-1) (of PS-5 + acephate), 3.45 d(-1) [of PS-5 + acephate + Fe(III)], 3.16 d(-1) [of PS-5 + acephate + Cu(II)], and 5.54 d(-1) (of PS-5 + acephate + HA). A significant decrease in degradation rate of acephate was noticed in the presence of HA, and the same was confirmed by UV-Visible and TGA analyses. Strong aggregation behavior of acephate with humic acid in aqueous media was the major cause behind the slow degradation rate of acephate . New results on acephate metabolism by strain PS-5 in the presence and in the absence of metal ions [Fe(III) and Cu(II)] and humic acid were obtained. Results confirmed that Pseudomonas pseudoalcaligenes strain PS-5 was capable of mineralization of the acephate without formation of toxic metabolite methamidophos. More significantly, the Pseudomonas pseudoalcaligenes strain PS-5 could be useful as potential biological agents in effective bioremediation campaign for multi-polluted environments.

  5. Stellar mass to halo mass relation from galaxy clustering in VUDS: a high star formation efficiency at z ≃ 3

    NASA Astrophysics Data System (ADS)

    Durkalec, A.; Le Fèvre, O.; de la Torre, S.; Pollo, A.; Cassata, P.; Garilli, B.; Le Brun, V.; Lemaux, B. C.; Maccagni, D.; Pentericci, L.; Tasca, L. A. M.; Thomas, R.; Vanzella, E.; Zamorani, G.; Zucca, E.; Amorín, R.; Bardelli, S.; Cassarà, L. P.; Castellano, M.; Cimatti, A.; Cucciati, O.; Fontana, A.; Giavalisco, M.; Grazian, A.; Hathi, N. P.; Ilbert, O.; Paltani, S.; Ribeiro, B.; Schaerer, D.; Scodeggio, M.; Sommariva, V.; Talia, M.; Tresse, L.; Vergani, D.; Capak, P.; Charlot, S.; Contini, T.; Cuby, J. G.; Dunlop, J.; Fotopoulou, S.; Koekemoer, A.; López-Sanjuan, C.; Mellier, Y.; Pforr, J.; Salvato, M.; Scoville, N.; Taniguchi, Y.; Wang, P. W.

    2015-04-01

    The relation between the galaxy stellar mass M⋆ and the dark matter halo mass Mh gives important information on the efficiency in forming stars and assembling stellar mass in galaxies. We present measurements of the ratio of stellar mass to halo mass (SMHR) at redshifts 2 < z < 5, obtained from the VIMOS Ultra Deep Survey. We use halo occupation distribution (HOD) modelling of clustering measurements on ~3000 galaxies with spectroscopic redshifts to derive the dark matter halo mass Mh, and spectral energy density fitting over a large set of multi-wavelength data to derive the stellar mass M⋆ and compute the SMHR = M⋆/Mh. We find that the SMHR ranges from 1% to 2.5% for galaxies with M⋆ = 1.3 × 109 M⊙ to M⋆ = 7.4 × 109 M⊙ in DM halos with Mh = 1.3 × 1011 M⊙ to Mh = 3 × 1011 M⊙. We derive the integrated star formation efficiency (ISFE) of these galaxies and find that the star formation efficiency is a moderate 6-9% for lower mass galaxies, while it is relatively high at 16% for galaxies with the median stellar mass of the sample ~ 7 × 109 M⊙. The lower ISFE at lower masses may indicate that some efficient means of suppressing star formation is at work (like SNe feedback), while the high ISFE for the average galaxy at z ~ 3 indicates that these galaxies efficiently build up their stellar mass at a key epoch in the mass assembly process. Based on our results, we propose a possible scenario in which the average massive galaxy at z ~ 3 begins to experience truncation of its star formation within a few million years. Based on data obtained with the European Southern Observatory Very Large Telescope, Paranal, Chile, under Large Program 185.A-0791.

  6. Raising the one-sun conversion efficiency of III-V/Si solar cells to 32.8% for two junctions and 35.9% for three junctions

    NASA Astrophysics Data System (ADS)

    Essig, Stephanie; Allebé, Christophe; Remo, Timothy; Geisz, John F.; Steiner, Myles A.; Horowitz, Kelsey; Barraud, Loris; Ward, J. Scott; Schnabel, Manuel; Descoeudres, Antoine; Young, David L.; Woodhouse, Michael; Despeisse, Matthieu; Ballif, Christophe; Tamboli, Adele

    2017-09-01

    Today's dominant photovoltaic technologies rely on single-junction devices, which are approaching their practical efficiency limit of 25-27%. Therefore, researchers are increasingly turning to multi-junction devices, which consist of two or more stacked subcells, each absorbing a different part of the solar spectrum. Here, we show that dual-junction III-V//Sidevices with mechanically stacked, independently operated III-V and Si cells reach cumulative one-sun efficiencies up to 32.8%. Efficiencies up to 35.9% were achieved when combining a GaInP/GaAs dual-junction cell with a Si single-junction cell. These efficiencies exceed both the theoretical 29.4% efficiency limit of conventional Si technology and the efficiency of the record III-V dual-junction device (32.6%), highlighting the potential of Si-based multi-junction solar cells. However, techno-economic analysis reveals an order-of-magnitude disparity between the costs for III-V//Si tandem cells and conventional Si solar cells, which can be reduced if research advances in low-cost III-V growth techniques and new substrate materials are successful.

  7. Internal quantum efficiency of III-nitride quantum dot superlattices grown by plasma-assisted molecular-beam epitaxy

    SciTech Connect

    Gacevic, Z.; Kehagias, Th.; Koukoula, T.; Komninou, Ph.

    2011-05-15

    We present a study of the optical properties of GaN/AlN and InGaN/GaN quantum dot (QD) superlattices grown via plasma-assisted molecular-beam epitaxy, as compared to their quantum well (QW) counterparts. The three-dimensional/two-dimensional nature of the structures has been verified using atomic force microscopy and transmission electron microscopy. The QD superlattices present higher internal quantum efficiency as compared to the respective QWs as a result of the three-dimensional carrier localization in the islands. In the QW samples, photoluminescence (PL) measurements point out a certain degree of carrier localization due to structural defects or thickness fluctuations, which is more pronounced in InGaN/GaN QWs due to alloy inhomogeneity. In the case of the QD stacks, carrier localization on potential fluctuations with a spatial extension smaller than the QD size is observed only for the InGaN QD-sample with the highest In content (peak emission around 2.76 eV). These results confirm the efficiency of the QD three-dimensional confinement in circumventing the potential fluctuations related to structural defects or alloy inhomogeneity. PL excitation measurements demonstrate efficient carrier transfer from the wetting layer to the QDs in the GaN/AlN system, even for low QD densities ({approx}10{sup 10} cm{sup -3}). In the case of InGaN/GaN QDs, transport losses in the GaN barriers cannot be discarded, but an upper limit to these losses of 15% is deduced from PL measurements as a function of the excitation wavelength.

  8. Thioether-triphenolate bimetallic iron(III) complexes as robust and highly efficient catalysts for cycloaddition of carbon dioxide to epoxides.

    PubMed

    Buonerba, Antonio; Della Monica, Francesco; De Nisi, Assunta; Luciano, Ermanno; Milione, Stefano; Grassi, Alfonso; Capacchione, Carmine; Rieger, Bernhard

    2015-01-01

    The selective and effective synthesis of organic carbonates under mild conditions, starting from carbon dioxide and oxiranes, catalyzed by metal complexes is currently a focus of interest for both industrial and academic researchers. We recently developed a novel thioether-triphenolate iron(III) catalyst (Ct-BU) that has proven to be highly active for the coupling of CO2 with epoxides, resulting in cyclic organic carbonates under solvent-free conditions. In the current work, the properties of this novel class of catalysts were extensively investigated. In particular, the steric properties of the ligand were modulated by changing the substituents of the aromatic rings in order to obtain a deeper knowledge of the relationship between the complex structure and catalytic performance/selectivity for these iron complexes. Notably, the less steric demanding iron(III) CH complex synthesized shows, when activated by n-tetrabutylammonium bromide, an impressive turnover frequency (TOF) of 3800 h(-1) for the formation of propylene carbonate and glycerol carbonate which are, by far, the highest reported for an iron based catalyst and compares well with the most active catalyst based on other metals.

  9. Deployment of the Burkholderia glumae type III secretion system as an efficient tool for translocating pathogen effectors to monocot cells.

    PubMed

    Sharma, Shailendra; Sharma, Shiveta; Hirabuchi, Akiko; Yoshida, Kentaro; Fujisaki, Koki; Ito, Akiko; Uemura, Aiko; Terauchi, Ryohei; Kamoun, Sophien; Sohn, Kee Hoon; Jones, Jonathan D G; Saitoh, Hiromasa

    2013-05-01

    Genome sequences of plant fungal pathogens have enabled the identification of effectors that cooperatively modulate the cellular environment for successful fungal growth and suppress host defense. Identification and characterization of novel effector proteins are crucial for understanding pathogen virulence and host-plant defense mechanisms. Previous reports indicate that the Pseudomonas syringae pv. tomato DC3000 type III secretion system (T3SS) can be used to study how non-bacterial effectors manipulate dicot plant cell function using the effector detector vector (pEDV) system. Here we report a pEDV-based effector delivery system in which the T3SS of Burkholderia glumae, an emerging rice pathogen, is used to translocate the AVR-Pik and AVR-Pii effectors of the fungal pathogen Magnaporthe oryzae to rice cytoplasm. The translocated AVR-Pik and AVR-Pii showed avirulence activity when tested in rice cultivars containing the cognate R genes. AVR-Pik reduced and delayed the hypersensitive response triggered by B. glumae in the non-host plant Nicotiana benthamiana, indicative of an immunosuppressive virulence activity. AVR proteins fused with fluorescent protein and nuclear localization signal were delivered by B. glumae T3SS and observed in the nuclei of infected cells in rice, wheat, barley and N. benthamiana. Our bacterial T3SS-enabled eukaryotic effector delivery and subcellular localization assays provide a useful method for identifying and studying effector functions in monocot plants. © 2013 The Authors The Plant Journal © 2013 John Wiley & Sons Ltd.

  10. Hst3p, a histone deacetylase, promotes maintenance of Saccharomyces cerevisiae chromosome III lacking efficient replication origins.

    PubMed

    Irene, Carmela; Theis, James F; Gresham, David; Soteropoulos, Patricia; Newlon, Carol S

    2016-02-01

    Long gaps between active replication origins probably occur frequently during chromosome replication, but little is known about how cells cope with them. To address this issue, we deleted replication origins from S. cerevisiae chromosome III to create chromosomes with long interorigin gaps and identified mutations that destabilize them [originless fragment maintenance (Ofm) mutations]. ofm6-1 is an allele of HST3, a sirtuin that deacetylates histone H3K56Ac. Hst3p and Hst4p are closely related, but hst4Δ does not cause an Ofm phenotype. Expressing HST4 under the control of the HST3 promoter suppressed the Ofm phenotype of hst3Δ, indicating Hst4p, when expressed at the appropriate levels and/or at the correct time, can fully substitute for Hst3p in maintenance of ORIΔ chromosomes. H3K56Ac is the Hst3p substrate critical for chromosome maintenance. H3K56Ac-containing nucleosomes are preferentially assembled into chromatin behind replication forks. Deletion of the H3K56 acetylase and downstream chromatin assembly factors suppressed the Ofm phenotype of hst3, indicating that persistence of H3K56Ac-containing chromatin is deleterious for the maintenance of ORIΔ chromosomes, and experiments with synchronous cultures showed that it is replication of H3K56Ac-containing chromatin that causes chromosome loss. This work shows that while normal chromosomes can tolerate hyperacetylation of H3K56Ac, deacetylation of histone H3K56Ac by Hst3p is required for stable maintenance of a chromosome with a long interorigin gap. The Ofm phenotype is the first report of a chromosome instability phenotype of an hst3 single mutant.

  11. The EHEC type III effector NleL is an E3 ubiquitin ligase that modulates pedestal formation

    USDA-ARS?s Scientific Manuscript database

    Enterohemorrhagic Escherichia coli (EHEC) O157:H7 causes hemorrhagic colitis and may result in potentially fatal hemolytic uremia syndrome in humans. EHEC colonize the intestinal mucosa and promote formation of “pedestals” in the tissue beneath the adherent bacteria. Secreted proteins are key playe...

  12. Spectro-photometric evolution of elliptical galaxies. III. Infall models with gradients in mass density and star formation

    NASA Astrophysics Data System (ADS)

    Tantalo, R.; Chiosi, C.; Bressan, A.; Marigo, P.; Portinari, L.

    1998-07-01

    In this study we present a simple model of elliptical galaxies aimed at interpreting the gradients in colours and narrow band indices observed across these systems. Salient features of the model are the gradients in mass density and star formation and infall of primordial gas aimed at simulating the collapse of a galaxy into the potential well of dark matter. Adopting a multi-zone model we follow in detail the history of star formation, gas consumption, and chemical enrichment of the galaxy and also allow for the occurrence of galactic winds according to the classical supernova (and stellar winds) energy deposit. The outline of the model, the time scale of gas accretion and rate of star formation as a function of the galacto-centric distance in particular, seek to closely mimic the results from Tree-SPH dynamical models. Although some specific ingredients of the model can be questioned from many points of view (of which we are well aware), the model has to be considered as a gross tool for exploring the consequences of different recipes of gas accretion and star formation in which the simple one-zone scheme is abandoned. With the aid of this model we discuss the observational data on the gradients in metallicity, colours, and narrow band indices across elliptical galaxies. Tables~4 and 6 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http:// cdsweb.u-strasbg.fr/Abstract.html

  13. DsbA directs efficient expression of outer membrane secretin EscC of the enteropathogenic Escherichia coli type III secretion apparatus.

    PubMed

    Miki, Tsuyoshi; Okada, Nobuhiko; Kim, Yeongsuk; Abe, Akio; Danbara, Hirofumi

    2008-02-01

    The formation of disulfide bond is essential for the folding, activity, and stability of many secreted proteins of Gram-negative bacteria. The disulfide oxidoreductase, DsbA, introduces disulfide bonds into exported proteins from the cytoplasm. In pathogenic bacteria, DsbA is required to process virulence determinants for their folding and assembly. In this study, we investigated the role of DsbA in enteropathogenic Escherichia coli. Here, we show that the DsbA is required for stable expression of outer membrane secretin EscC. DsbA has no effect on LEE transcription as measured with LEE-lacZ fusions. Replacement of either cysteine residue 136 or 155 of EscC with a serine resulted in reduced level of EscC, similar to the effect of the dsbA mutation. These results demonstrate the role of DsbA in assembly of the type III secretion apparatus.

  14. Formation and evolution of early-type galaxies - III. Dependence of the star formation history on the total mass and initial overdensity

    NASA Astrophysics Data System (ADS)

    Merlin, E.; Chiosi, C.; Piovan, L.; Grassi, T.; Buonomo, U.; La Barbera, F.

    2012-12-01

    We investigate the influence of the initial overdensities and masses of proto-galaxies on their subsequent evolution (the star formation history in particular) to understand whether these key parameters are sufficient to account for the varied properties of the galactic populations. By means of fully hydrodynamical N-body simulations performed with the code EVOL, we produce 12 self-similar models of early-type galaxies of different initial masses and overdensities, and follow their evolution from the early epochs (detachment from the linear regime and Hubble flow at z ≥ 20) down to the stage when mass assembly is complete, i.e. z ≤ 1 (in some cases the models are calculated up to z = 0). The simulations include radiative cooling, star formation, stellar energy feedback, re-ionizing photo-heating background and chemical enrichment of the interstellar medium; we do not consider the possible presence of active nuclei. We find a strong correlation between the initial properties of the proto-haloes and their subsequent star formation histories. Massive (Mtot ≃ 1013 M⊙) haloes experience a single, intense burst of star formation (with rates ≥103 M⊙ yr-1) at early epochs, consistently with observations, with less pronounced dependence on the initial overdensity; intermediate-mass (Mtot ≃ 1011 M⊙) haloes have histories that strongly depend on their initial overdensity, whereas low-mass haloes (Mtot ≃ 109 M⊙) always have erratic, bursting like star-forming histories, due to the 'galactic breathing' phenomenon. The model galaxies have morphological, structural and chemical properties resembling those of real galaxies, even though some disagreement still occurs, likely a consequence of some numerical choices. We conclude that total mass and initial overdensity drive the star formation histories of early-type galaxies. The model galaxies belong to the so-called quasi-monolithic (or early hierarchical) scenario in the sense that the aggregation of lumps of

  15. Free energy of formation for green rust sodium sulphate (NaFe II6Fe III3(OH) 18(SO 4) 2(s))

    NASA Astrophysics Data System (ADS)

    Davesne, E.; Dideriksen, K.; Christiansen, B. C.; Sonne, M.; Ayala-Luis, K. B.; Koch, C. Bender; Hansen, H. C. B.; Stipp, S. L. S.

    2010-11-01

    In a recent study, sulphate-bearing green rust (GR) was shown to incorporate Na + in its structure (NaFe II6Fe III3(OH) 18(SO 4) 2(s); GR). The compound was synthesised by aerial oxidation of Fe(OH) 2(s) in the presence of NaOH. This paper reports on its free energy of formation (ΔGf0). Freshly synthesised GR was titrated with 0.5 M H 2SO 4 in an inert atmosphere at 25 °C, producing dissolved Fe 2+ and magnetite or goethite. Solution concentrations, PHREEQC and the MINTEQ database were used to calculate reaction constants for the reactions: 2NaFeII6 FeIII3 (OH)18(SO)+12H+(aq) ⇆9Fe2+(aq) +2Na+(aq) +4SO42-(aq) +3FeFeIII2 O+24HO,K=10 and NaFeII6 FeIII3 (OH)18(SO)+9H(aq)+⇆6Fe2+(aq) +Na+(aq) +2SO42-(aq) +3α-FeOOH+12HO,K=10. From the determined equilibrium constants and published ΔGf0 values for the other compounds, we derived ΔGf0 = -6366 ± 18 kJ/mol for anhydrous GR. The solubility product at 25 °C and atmospheric pressure is K = 10 -210.5±3.2. It is not yet known if the extent of Na + incorporation in GR depends on formation pathway; it cannot be excluded that both Na-free GR and GR exist. If so, uncertainty in ΔGf0 determined from acid titration is such that the EH-pH stability fields of the two phases are statistically indistinguishable for Na + concentrations as low as ˜30 μM (2 SD level; 0.036 M SO 42- concentration). In sea water, where Na + and SO 42- concentrations are high, but soluble Fe 2+ is low, GR is expected to form where local conditions increase concentration gradients, such as for corrosion of metallic iron and steel. Another example of an environment that would provide GR-favourable conditions is a degrading concrete and steel radioactive waste storage facility, where groundwater is saline. Green rust is a well-known sink for redox-active trace components, making it a compound that should be considered in risk assessment modelling of groundwater quality. Phase stability is critical in such simulations.

  16. New triarylamine sensitizers for high efficiency dye-sensitized solar cells: Recombination kinetics of cobalt(III) complexes at titania/dye interface

    NASA Astrophysics Data System (ADS)

    Gao, Weixue; Liang, Mao; Tan, Yulin; Wang, Min; Sun, Zhe; Xue, Song

    2015-06-01

    A new generation of dye-sensitized solar cells (DSCs) is based on a combination of D-π-A organic dyes in conjunction with cobalt-based redox mediators. Here, two new triarylamine organic dyes (M36 and M37) toward cobalt electrolytes are constructed and employed as photosensitizers for dye-sensitized solar cells. The photoelectrochemical properties and photovoltaic performance of dyes are sensitive to the slightly structural modification of the terminal donor in triarylamine. Recombination kinetics of cobalt(III) complexes at titania/dye interface are also studied using electrochemical impedance spectroscopy and controlled intensity modulated photovoltage spectroscopy measurements. Our results show that, for M36 sensitized DSCs, a Marcus inverted region can be reached for the charge recombination kinetics behavior of cobalt(III) species. While that for DSCs based on M37 just lies in the Marcus normal region. The results can be attributed to differences in the retarding charge recombination ability of the dye layer. Benefiting from a Marcus inverted region behavior, the M36 dye exhibits a good compatibility with the [Co(phen)3]2+/3+ redox couples, achieving a high overall power conversion efficiency (PCE) of 9.58% under full sun illumination.

  17. An Amine‐Functionalized Iron(III) Metal–Organic Framework as Efficient Visible‐Light Photocatalyst for Cr(VI) Reduction

    PubMed Central

    Shi, Li; Wang, Tao; Zhang, Huabin; Chang, Kun; Meng, Xianguang; Liu, Huimin

    2015-01-01

    The photocatalytic reduction of Cr(VI) is investigated over iron(III)‐based metal–organic frameworks (MOFs) structured as MIL‐88B. It is found that MIL‐88B (Fe) MOFs, containing Fe3‐μ3‐oxo clusters, can be used as photocatalyst for the reduction of Cr(VI) under visible light irradiation, which is due to the direct excitation of Fe3‐μ3‐oxo clusters. The amine‐functionalized MIL‐88B (Fe) MOFs (denoted as NH2–MIL‐88B (Fe)) shows much higher efficiency for the photocatalytic Cr(VI) reduction under visible‐light irradiation compared with MIL‐88B (Fe). It is revealed that in addition to the direct excitation of Fe3‐μ3‐oxo clusters, the amine functionality in NH2–MIL‐88B (Fe) can also be excited and then transferred an electron to Fe3‐μ3‐oxo clusters, which is responsible for the enhanced photocatalytic activity for Cr(VI) reduction. The enhanced photocatalytic activity for Cr(VI) reduction is also achieved for other two amine‐functionalized iron(III)‐based MOFs (NH2–MIL‐53 (Fe) and NH2–MIL‐101 (Fe)). PMID:27980927

  18. An ultraviolet-selected galaxy redshift survey - III. Multicolour imaging and non-uniform star formation histories

    NASA Astrophysics Data System (ADS)

    Sullivan, Mark; Treyer, Marie A.; Ellis, Richard S.; Mobasher, Bahram

    2004-05-01

    We present panoramic u' and optical ground-based imaging observations of a complete sample of low-redshift (0 < z < 0.4) galaxies selected in the ultraviolet (UV) at 2000 Å using the balloon-borne FOCA instrument of Milliard et al. This survey is highly sensitive to newly formed massive stars and hence to actively star-forming galaxies. We use the new data to investigate further the optical, stellar population and star formation properties of this unique sample, deriving accurate galaxy types and k-corrections based on the broad-band spectral energy distributions. When combined with our earlier spectroscopic surveys, these new data allow us to compare star formation measures derived from aperture-corrected Hα line fluxes, and UV(2000 Å) and u'(3600 Å) continuum fluxes on a galaxy-by-galaxy basis. As expected from our earlier studies, we find broad correlations over several decades in luminosity between the different dust-corrected star formation diagnostics, though the scatter is larger than that from observational errors, with significant offsets from trends expected according to simple models of the star formation histories (SFHs) of galaxies. Popular galaxy spectral synthesis models with varying metallicities and/or initial mass functions seem unable to explain the observed discrepancies. We investigate the star formation properties further by modelling the observed spectroscopic and photometric properties of the galaxies in our survey. We find that nearly half of the galaxies surveyed possess features that appear incompatible with simple constant or smoothly declining SFHs, favouring instead irregular or temporally varying SFHs. We demonstrate how this can reconcile the majority of our observations, enabling us to determine empirical corrections that can be used to calculate intrinsic star formation rates (as derived from Hα luminosities) from measures based on UV (or u') continuum observations alone. We discuss the broader implications of our finding that

  19. Mono- and dinuclear manganese(III) complexes showing efficient catechol oxidase activity: syntheses, characterization and spectroscopic studies.

    PubMed

    Banu, Kazi Sabnam; Chattopadhyay, Tanmay; Banerjee, Arpita; Mukherjee, Madhuparna; Bhattacharya, Santanu; Patra, Goutam Kumar; Zangrando, Ennio; Das, Debasis

    2009-10-28

    Four side-off compartmental ligands L1-L4 [L1 = N,N'-ethylenebis(3-formyl-5-methyl-salicylaldimine), L2 = N,N'-1-methylethylenebis(3-formyl-5-methylsalicylaldimine), L3 = N,N'-1,1-dimethylethylenebis(3-formyl-5-methylsalicylaldimine) and L4= N,N'-cyclohexenebis(3-formyl-5-methylsalicylaldimine)] having two binding sites, N2O2 and O4, have been chosen to synthesize mononuclear and dinuclear manganese(III) complexes with the aim to study their catecholase activity using 3,5-di-tert-butylcatechol (3,5-DTBC) as substrate in the presence of molecular oxygen. In all cases only mononuclear manganese complexes (1-4) were obtained, with manganese coordination taking place at the N2O2 binding site only, irrespective of the amount of manganese salt used. All these complexes have been characterized by routine physico-chemical techniques. Complex MnL2Cl.4H2O (2) has further been structurally characterized by X-ray single crystal structure analysis. Four dinuclear manganese complexes, 5-8, were obtained after condensing the two pending formyl groups on each ligand (L1-L4) with aniline followed by reaction with MnCl2 to put the second Mn atom onto another N2O2 site. The catalytic activity of all complexes 1-8 has been investigated following the oxidation of 3,5-di-tert-butylcatechol (3,5-DTBC) to 3,5-di-tert-butylbenzoquinone (3,5-DTBQ) with molecular oxygen in two different solvents, methanol and acetonitrile. The study reveals that the catalytic activity is influenced by the solvent and to a significant extent by the backbone of the diamine and the behavior seems to be related mainly to steric rather than electronic factors. Experimental data suggest that a correlation, the lower the E(1/2) value the higher the catalytic activity, can be drawn between E(1/2) and Vmax of the complexes in a particular solvent. The EPR measurements suggest that the catalytic property of the complexes is related to the metal center(s) participation rather than to a radical mechanism.

  20. Studies of efficient heteroleptic Ir(III) complexes containing tpy and dfppy ligands for phosphorescent organic light-emitting devices.

    PubMed

    Lee, Seung Chan; Seo, Ji Hyun; Kim, Young Kwan; Kim, Young Sik

    2009-12-01

    To increase the luminescent efficiency by avoiding T-T annihilation and reducing the number of luminescent ligands, we designed and synthesized Ir(dfppy)(tpy)2 and Ir(dfppy)2(tpy), where dfppy and tpy represent 2,4-difluoro-phenylpyridine and 2-(p-tolyl)pyridine. The emission wavelength of Ir(dfppy)(tpy)2 and Ir(dfppy)2(tpy) are observed at 494 and 490 nm, respectively. The luminescence mechanism in the heteroleptic iridium complex determined the decay rates and the triplet energy between two different ligands. To confirm the color tuning by the substitution, we have measured UV-absorption and photoluminescence (PL) spectra. In addition, to predict the energy level of the iridium complex, we calculated these complexes theoretically by the density functional theory (DFT) methods.

  1. The molecular content of interacting and isolated galaxies The effect of environment on the efficiency of star formation

    NASA Technical Reports Server (NTRS)

    Young, Judith S.; Kenney, Jeffrey D.; Tacconi, Linda; Claussen, M. J.; Huang, Y.-L.

    1986-01-01

    Molecular gas observations of merging/interacting and isolated galaxies are presented in order to study the relationship between environment and the efficiency of star formation. The two galaxy samples differ primarily in their IR properties and are quite similar in their molecular gas contents. The ratios of IR luminosity to H2 mass have a mean value of 78 and 12 solar luminosity/solar mass for interacting and isolated galaxies, respectively. The highest star formation efficiencies (SFEs) appear to occur in the merging and interacting pairs. The SFE in merging/interacting galaxies is greater than that found in the spiral arms of M51 and may be roughly proportional to the rate of cloud-cloud collisions in the interacting systems.

  2. FliH and FliI ensure efficient energy coupling of flagellar type III protein export in Salmonella.

    PubMed

    Minamino, Tohru; Kinoshita, Miki; Inoue, Yumi; Morimoto, Yusuke V; Ihara, Kunio; Koya, Satomi; Hara, Noritaka; Nishioka, Noriko; Kojima, Seiji; Homma, Michio; Namba, Keiichi

    2016-06-01

    For construction of the bacterial flagellum, flagellar proteins are exported via its specific export apparatus from the cytoplasm to the distal end of the growing flagellar structure. The flagellar export apparatus consists of a transmembrane (TM) export gate complex and a cytoplasmic ATPase complex consisting of FliH, FliI, and FliJ. FlhA is a TM export gate protein and plays important roles in energy coupling of protein translocation. However, the energy coupling mechanism remains unknown. Here, we performed a cross-complementation assay to measure robustness of the energy transduction system of the export apparatus against genetic perturbations. Vibrio FlhA restored motility of a Salmonella ΔflhA mutant but not that of a ΔfliH-fliI flhB(P28T) ΔflhA mutant. The flgM mutations significantly increased flagellar gene expression levels, allowing Vibrio FlhA to exert its export activity in the ΔfliH-fliI flhB(P28T) ΔflhA mutant. Pull-down assays revealed that the binding affinities of Vibrio FlhA for FliJ and the FlgN-FlgK chaperone-substrate complex were much lower than those of Salmonella FlhA. These suggest that Vibrio FlhA requires the support of FliH and FliI to efficiently and properly interact with FliJ and the FlgN-FlgK complex. We propose that FliH and FliI ensure robust and efficient energy coupling of protein export during flagellar assembly. © 2016 The Authors. MicrobiologyOpen published by John Wiley & Sons Ltd.

  3. The formation and alteration of the Renazzo-like carbonaceous chondrites III: Toward understanding the genesis of ferromagnesian chondrules

    NASA Astrophysics Data System (ADS)

    Schrader, Devin L.; Connolly, Harold C.; Lauretta, Dante S.; Zega, Thomas J.; Davidson, Jemma; Domanik, Kenneth J.

    2015-01-01

    To better understand the formation conditions of ferromagnesian chondrules from the Renazzo-like carbonaceous (CR) chondrites, a systematic study of 210 chondrules from 15 CR chondrites was conducted. The texture and composition of silicate and opaque minerals from each observed FeO-rich (type II) chondrule, and a representative number of FeO-poor (type I) chondrules, were studied to build a substantial and self-consistent data set. The average abundances and standard deviations of Cr2O3 in FeO-rich olivine phenocrysts are consistent with previous work that the CR chondrites are among the least thermally altered samples from the early solar system. Type II chondrules from the CR chondrites formed under highly variable conditions (e.g., precursor composition, redox conditions, cooling rate), with each chondrule recording a distinct igneous history. The opaque minerals within type II chondrules are consistent with formation during chondrule melting and cooling, starting as S- and Ni-rich liquids at 988-1350 °C, then cooling to form monosulfide solid solution (mss) that crystallized around olivine/pyroxene phenocrysts. During cooling, Fe,Ni-metal crystallized from the S- and Ni-rich liquid, and upon further cooling mss decomposed into pentlandite and pyrrhotite, with pentlandite exsolving from mss at 400-600 °C. The composition, texture, and inferred formation temperature of pentlandite within chondrules studied here is inconsistent with formation via aqueous alteration. However, some opaque minerals (Fe,Ni-metal versus magnetite and panethite) present in type II chondrules are a proxy for the degree of whole-rock aqueous alteration. The texture and composition of sulfide-bearing opaque minerals in Graves Nunataks 06100 and Grosvenor Mountains 03116 suggest that they are the most thermally altered CR chondrites.

  4. Size-Dependent Activity of Palladium Nanoparticles: Efficient Conversion of CO2 into Formate at Low Overpotentials.

    PubMed

    Rahaman, Motiar; Dutta, Abhijit; Broekmann, Peter

    2017-04-22

    Remarkable size-dependent activity of palladium nanoparticles (PdNPs) towards formate production is evident at very low overpotentials (-0.1 to -0.5 V vs. RHE). Size-selective PdNPs, chemically synthesized at sizes of 3.8-10.7 nm, effected an electrochemical CO2 reduction reaction in aqueous 0.5 m NaHCO3 . The faradaic efficiency of formate production (FEformate ) on 3.8 nm PdNPs exceeded 86 % at E=-0.1 V versus RHE, whereas on 6.5 nm PdNPs an even higher FEformate of 98 % was observed. However, FEformate decreased for larger PdNPs. The superior efficiency towards formate production at low overpotentials is rationalized in terms of a changed catalytic pathway through PdH phases. The observed maximum in the formate efficiency for a mean particle size of about 6.5 nm is discussed in terms of counterbalancing the size-dependent effects of a competing CO2 reduction reaction and a parasitic hydrogen evolution reaction. Production rates of formate are also remarkably high at -0.3 V versus RHE with 539.9 and 452.3 ppm h(-1)  mgPd(-1) for the 6.5 and 3.8 nm PdNPs, respectively. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Sequential Carbon-Carbon/Carbon-Selenium Bond Formation Mediated by Iron(III) Chloride and Diorganyl Diselenides: Synthesis and Reactivity of 2-Organoselenyl-Naphthalenes.

    PubMed

    Recchi, Ana M S; Back, Davi F; Zeni, Gilson

    2017-03-03

    In this paper, we report an intramolecular cyclization of benzylic-substituted propargyl alcohols promoted by iron(III) chloride and diorganyl diselenides to give 2-organoselenyl-naphthalenes via a sequential carbon-carbon/carbon-selenium bond formation. The present reaction tolerated a wide range of substituents in both propargyl alcohols and diorganyl diselenides to give the desired 2-organoselenyl-naphthalenes in good yields with high selectivity. In addition, O-acyl protected propargyl alcohol and propargyl bromide were also subjected to this protocol giving the corresponding 2-organoselenyl-naphthalenes. We found that dichalcogenide species affected the formation of cyclized products, whereas diorganyl diselenides gave high yields, moderate yields were obtained with diorganyl disulfides, and no product formation was found with diorganyl ditellurides. The key transformations could be attributed to the carbon-carbon triple bond activation of benzylic-substituted propargyl alcohols by a seleniranium ion, antiattack of the electron cloud from the aromatic ring at the activated triple bond, and cyclization via an exclusive 6-endo-dig process. We also found that the corresponding 2-organoselenyl-naphthalenes are suitable substrates to the selenium-lithium exchange reactions followed by trapping with aldehydes affording the corresponding secondary alcohols.

  6. Numerical Simulation of Impacts of Hydrological Properties of Geologic Storage Formations on Injection Efficiency of Carbon Dioxide

    NASA Astrophysics Data System (ADS)

    Kihm, J.; Kim, J.

    2010-12-01

    A series of numerical simulations using a multiphase thermo-hydrological numerical model is performed to analyze groundwater flow, carbon dioxide flow, and heat transport due to geologic storage of carbon dioxide in a geologic storage formation (sandstone aquifer) and to evaluate impacts of its saturated (i.e., porosity and intrinsic permeability) and unsaturated (i.e., residual water saturation, residual gas saturation, gas-entry pressure, and van Genuchten’s exponent) hydrological properties on the injection efficiency of carbon dioxide. The numerical simulation results show that the hydrological properties of the storage formation have significant effects on the injection efficiency of carbon dioxide. Under a constant injection pressure of carbon dioxide, the injection rate and injectivity of carbon dioxide increase rapidly during the early period of carbon dioxide injection (about 2 weeks) and then increases monotonously until the end of carbon dioxide injection. The injection rate and injectivity of carbon dioxide are most sensitive to variations in the intrinsic permeability and van Genuchten’s exponent of the storage formation. They increase significantly as the intrinsic permeability and van Genuchten’s exponent of the storage formation increase, whereas they decrease slightly as the porosity and the residual gas saturation of the storage formation increase. However, they are most insensitive to variations in the residual water saturation and the gas-entry pressure of the storage formation. These results indicate that the injection efficiency of carbon dioxide is significantly dependent on the relative permeability, which is a function of the unsaturated hydrological properties (i.e., residual water saturation, residual gas saturation, gas-entry pressure, and van Genuchten’s exponent) of the storage formation, as well as its saturated hydrological properties (i.e., porosity and intrinsic permeability) in different degrees. Therefore it may be

  7. The effect of direct addition of iron(III) on anaerobic digestion efficiency and odor causing compounds.

    PubMed

    Park, Chang Min; Novak, John T

    2013-01-01

    The role of iron addition to sewage sludge prior to anaerobic digestion was evaluated to determine the effect of iron on digestion performance and generation of odor-causing compounds. Hydrogen sulfide (H2S) and volatile organic sulfur compounds (VOSCs) were the odorous gases evaluated in this study. Samples were obtained from seven municipal wastewater treatment plants (WWTPs), and batch anaerobic digestion tests were conducted using primary and secondary sludges at 30 day solids retention time (SRT) under mesophilic conditions. Volatile solid removal (VSR) was highly predictable with background iron concentrations measured in the combined sludge. They were likely to increase as influent iron content increased. 1.25% w/w ferric chloride (FeCl3) was added to the anaerobic digester feed in order to simulate iron addition for sulfide control in full-scale WWTPs. The results showed that it had a positive impact on digestion performance with higher VSR and odor control with reduced H2S and TVOSCs in the headspace gas of dewatered biosolids considered in the tests. Ferric chloride is considered a beneficial additive as a strategy for an odor mitigation, not to mention more efficient digestion under anaerobic conditions.

  8. Fusion of blastomeres in mouse embryos under the action of femtosecond laser radiation. Efficiency of blastocyst formation and embryo development

    SciTech Connect

    Osychenko, A A; Zalesskii, A D; Krivokharchenko, A S; Zhakhbazyan, A K; Nadtochenko, V A; Ryabova, A V

    2015-05-31

    Using the method of femtosecond laser surgery we study the fusion of two-cell mouse embryos under the action of tightly focused femtosecond laser radiation with the fusion efficiency reaching 60%. The detailed statistical analysis of the efficiency of blastomere fusion and development of the embryo up to the blastocyst stage after exposure of the embryos from different mice to a femtosecond pulse is presented. It is shown that the efficiency of blastocyst formation essentially depends on the biological characteristics of the embryo, namely, the strain and age of the donor mouse. The possibility of obtaining hexaploid embryonal cells using the methods of femtosecond laser surgery is demonstrated. (extreme light fields and their applications)

  9. Oligomeric states of the Shigella translocator protein IpaB provide structural insights into formation of the type III secretion translocon

    PubMed Central

    Dickenson, Nicholas E; Choudhari, Shyamal P; Adam, Philip R; Kramer, Ryan M; Joshi, Sangeeta B; Middaugh, C Russell; Picking, Wendy L; Picking, William D

    2013-01-01

    The Shigella flexneri Type III secretion system (T3SS) senses contact with human intestinal cells and injects effector proteins that promote pathogen entry as the first step in causing life threatening bacillary dysentery (shigellosis). The Shigella Type III secretion apparatus (T3SA) consists of an anchoring basal body, an exposed needle, and a temporally assembled tip complex. Exposure to environmental small molecules recruits IpaB, the first hydrophobic translocator protein, to the maturing tip complex. IpaB then senses contact with a host cell membrane, forming the translocon pore through which effectors are delivered to the host cytoplasm. Within the bacterium, IpaB exists as a heterodimer with its chaperone IpgC; however, IpaB's structural state following secretion is unknown due to difficulties isolating stable protein. We have overcome this by coexpressing the IpaB/IpgC heterodimer and isolating IpaB by incubating the complex in mild detergents. Interestingly, preparation of IpaB with n-octyl-oligo-oxyethylene (OPOE) results in the assembly of discrete oligomers while purification in N,N-dimethyldodecylamine N-oxide (LDAO) maintains IpaB as a monomer. In this study, we demonstrate that IpaB tetramers penetrate phospholipid membranes to allow a size-dependent release of small molecules, suggesting the formation of discrete pores. Monomeric IpaB also interacts with liposomes but fails to disrupt them. From these and additional findings, we propose that IpaB can exist as a tetramer having inherent flexibility, which allows it to cooperatively interact with and insert into host cell membranes. This event may then lay the foundation for formation of the Shigella T3SS translocon pore. PMID:23456854

  10. Methane destruction efficiency of natural gas flares associated with shale formation wells.

    PubMed

    Caulton, Dana R; Shepson, Paul B; Cambaliza, Maria O L; McCabe, David; Baum, Ellen; Stirm, Brian H

    2014-08-19

    Flaring to dispose of natural gas has increased in the United States and is typically assumed to be 98% efficient, accounting for both incomplete combustion and venting during unintentional flame termination. However, no in situ measurements of flare emissions have been reported. We used an aircraft platform to sample 10 flares in North Dakota and 1 flare in Pennsylvania, measuring CO2, CH4, and meteorological data. Destruction removal efficiency (DRE) was calculated by assuming a flare natural gas input composition of 60-100% CH4. In all cases flares were >99.80 efficient at the 25% quartile. Crosswinds up to 15 m/s were observed, but did not significantly adversely affect efficiency. During analysis unidentified peaks of CH4, most likely from unknown venting practices, appeared much larger in magnitude than emissions from flaring practices. Our analysis suggests 98% efficiency for nonsputtering flares is a conservative estimate for incomplete combustion and that the unidentified venting is a greater contributor to CH4 emissions.

  11. Simultaneous Au(III) Extraction and In Situ Formation of Polymeric Membrane-Supported Au Nanoparticles: A Sustainable Process with Application in Catalysis.

    PubMed

    Mora-Tamez, Lucía; Esquivel-Peña, Vicente; Ocampo, Ana L; Rodríguez de San Miguel, Eduardo; Grande, Daniel; de Gyves, Josefina

    2017-04-10

    A polymeric membrane-supported catalyst with immobilized gold nanoparticles (AuNPs) was prepared through the extraction and in situ reduction of Au(III) salts in a one-step strategy. Polymeric inclusion membranes (PIMs) and polymeric nanoporous membranes (PNMs) were tested as different membrane-support systems. Transport experiments indicated that PIMs composed of cellulose triacetate, 2-nitrophenyloctyl ether, and an aliphatic tertiary amine (Adogen 364 or Alamine 336) were the most efficient supports for Au(III) extraction. The simultaneous extraction and reduction processes were proven to be the result of a synergic phenomenon in which all the membrane components were involved. Scanning electron microscopy characterization of cross-sectional samples suggested a distribution of AuNPs throughout the membrane. Transmission electron microscopy characterization of the AuNPs indicated average particle sizes of 36.7 and 2.9 nm for the PIMs and PNMs, respectively. AuNPs supported on PIMs allowed for >95.4 % reduction of a 0.05 mmol L(-1) 4-nitrophenol aqueous solution with 10 mmol L(-1) NaBH4 solution within 25 min. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Near-IR Emitting Iridium(III) Complexes with Heteroaromatic β-Diketonate Ancillary Ligands for Efficient Solution-Processed OLEDs: Structure-Property Correlations.

    PubMed

    Kesarkar, Sagar; Mróz, Wojciech; Penconi, Marta; Pasini, Mariacecilia; Destri, Silvia; Cazzaniga, Marco; Ceresoli, Davide; Mussini, Patrizia R; Baldoli, Clara; Giovanella, Umberto; Bossi, Alberto

    2016-02-18

    Three NIR-emitting neutral Ir(III) complexes [Ir(iqbt)2 (dpm)] (1), [Ir(iqbt)2 (tta)] (2), and [Ir(iqbt)2 (dtdk)] (3) based on the 1-(benzo[b]thiophen-2-yl)-isoquinolinate (iqtb) were synthesized and characterized (dpm=2,2,6,6-tetramethyl-3,5-heptanedionate; tta=2-thienoyltrifluoroacetonate; dtdk=1,3-di(thiophen-2-yl)propane-1,3-dionate). The compounds emit between λ=680 and 850 nm with high luminescence quantum yields (up to 16 %). By combining electrochemistry, photophysical measurements, and computational modelling, the relationship between the structure, energy levels, and properties were investigated. NIR-emitting, solution-processed phosphorescent organic light-emitting devices (PHOLEDs) were fabricated using the complexes. The devices show remarkable external quantum efficiencies (above 3 % with 1) with negligible efficiency roll-off values, exceeding the highest reported values for solution-processible NIR emitters. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Monopropionate analogues of DOTA4- and DTPA5-: kinetics of formation and dissociation of their lanthanide(III) complexes.

    PubMed

    Balogh, Edina; Tripier, Raphaël; Fousková, Petra; Reviriego, Felipe; Handel, Henri; Tóth, Eva

    2007-08-28

    The replacement of an acetate function of the macrocyclic DOTA4-(DO3A-Nprop4-) or the acyclic DTPA5- in terminal position (DTTA-Nprop5-) has been recently shown to result in a significant increase of the water exchange rate on the Gd3+ complexes, which makes these chelates potential contrast agents for MRI applications. Here, two novel and straightforward synthetic routes to H4DO3A-Nprop are described. Protonation constants of DO3A-Nprop4- and stability constants with several alkaline earth and transition metal ions have been determined by potentiometry. For each metal, the thermodynamic stability constant is decreased in comparison to the DOTA chelates. The formation reaction of LnDO3A-Nprop- complexes (Ln=Ce, Gd and Yb) proceeds via the rapid formation of a diprotonated intermediate and its subsequent deprotonation and rearrangement in a slow, OH- catalyzed process. The stability of the LnH2DO3A-Nprop* intermediates is similar to those reported for the corresponding DOTA analogues. The rate constants of the OH- catalyzed deprotonation step increase with decreasing lanthanide ion size, and are slightly higher than for DOTA complexes. The kinetic inertness of GdDTTA-Nprop2- was characterized by the rates of its exchange reactions with Zn2+ and Eu3+. The rate of the reaction between GdDTTA-Nprop2- and Zn2+ increases with Zn2+ concentration, while it is independent of pH, implying that the exchange takes place predominantly via direct attack of the metal ion on the complex. In the Eu3+ exchange, the rate decreases with increasing concentration of the exchanging ion which is accounted for by the transitional formation of a dinuclear GdDTTA-NpropEu+ species. The kinetic inertness of the monopropionate GdDTTA-Nprop2- is decreased in comparison to GdDTPA2-: all rate constants, characterizing the dissociation reaction via either proton- or metal-catalyzed pathways being higher by 1-2 orders of magnitude. Similarly, a study of the acid-catalyzed dissociation of the

  14. Efficiency of pyrimidine dimer formation in Escherichia coli across UV wavelengths.

    PubMed

    Eischeid, A C; Linden, K G

    2007-11-01

    Inactivation of Escherichia coli as a function of ultraviolet (UV) wavelength was investigated by using the endonuclease-sensitive site (ESS) assay to quantify pyrimidine dimer formation. Ultraviolet dose-response curves were determined based on both log reduction in colony-forming units (CFU) and endonuclease-sensitive sites per kb DNA (ESS/kb) for monochromatic 254-nm low-pressure (LP) UV, polychromatic medium-pressure (MP) UV, 228 and 289-nm UV irradiation. UV irradiation from LP and MP UV sources were approx. equal in both CFU reduction and pyrimidine dimer formation at all UV doses studied; 228-nm irradiation was less effective than LP or MP, and 289-nm irradiation was the least effective in both CFU reduction and pyrimidine dimer formation. These results are in qualitative agreement with the absorption spectrum of pyrimidine bases in DNA. Results indicated an approx. linear relationship between ESS/kb and log CFU reduction. Formation of pyrimidine dimers in genomic DNA is primarily responsible for UV inactivation of E. coli. This work contributed to fundamental understanding of UV disinfection and aids in UV reactor design.

  15. Iron(III) chloride as an efficient catalyst for stereoselective synthesis of glycosyl azides and a cocatalyst with Cu(0) for the subsequent click chemistry.

    PubMed

    Salunke, Santosh B; Babu, N Seshu; Chen, Chien-Tien

    2011-10-07

    A highly efficient and mild method for azido glycosylation of glycosyl β-peracetates to 1,2-trans glycosyl azides was developed by using inexpensive FeCl(3) as the catalyst. In addition, we demonstrated, for the first time, that FeCl(3) in combination with copper powder can promote 1,3-dipolar cycloaddition (click chemistry) of azido glycosides with terminal alkynes. Good to excellent yields were obtained with exclusive formation of a single isomer in both glycosyl azidation and subsequent cycloaddition processes. This journal is © The Royal Society of Chemistry 2011

  16. Silicon isotope fractionation during microbial reduction of Fe(III)-Si gels under Archean seawater conditions and implications for iron formation genesis

    NASA Astrophysics Data System (ADS)

    Reddy, Thiruchelvi R.; Zheng, Xin-Yuan; Roden, Eric E.; Beard, Brian L.; Johnson, Clark M.

    2016-10-01

    Microbial dissimilatory iron reduction (DIR) is a deeply rooted metabolism in the Bacteria and Archaea. In the Archean and Proterozoic, the most likely electron acceptor for DIR in marine environments was Fe(III)-Si gels. It has been recently suggested that the Fe and Si cycles were coupled through sorption of aqueous Si to iron oxides/hydroxides, and through release of Si during DIR. Evidence for the close association of the Fe and Si cycles comes from banded iron formations (BIFs), which consist of alternating bands of Fe-bearing minerals and quartz (chert). Although there has been extensive study of the stable Fe isotope fractionations produced by DIR of Fe(III)-Si gels, as well as studies of stable Fe isotope fractionations in analogous abiologic systems, no studies to date have investigated stable Si isotope fractionations produced by DIR. In this study, the stable Si isotope fractionations produced by microbial reduction of Fe(III)-Si gels were investigated in simulated artificial Archean seawater (AAS), using the marine iron-reducing bacterium Desulfuromonas acetoxidans. Microbial reduction produced very large 30Si/28Si isotope fractionations between the solid and aqueous phase at ∼23 °C, where Δ30Sisolid-aqueous isotope fractionations of -3.35 ± 0.16‰ and -3.46 ± 0.09‰ were produced in two replicate experiments at 32% Fe(III) reduction (solid-phase Fe(II)/FeTotal = 0.32). This isotopic fractionation was substantially greater than that observed in two abiologic controls that had solid-phase Fe(II)/FeTotal = 0.02-0.03, which produced Δ30Sisolid-aqueous isotope fractionations of -2.83 ± 0.24‰ and -2.65 ± 0.28‰. In a companion study, the equilibrium Δ30Sisolid-aqueous isotope fractionation was determined to be -2.3‰ for solid-phase Fe(II)/FeTotal = 0. Collectively, these results highlight the importance of Fe(II) in Fe-Si gels in producing large changes in Si isotope fractionations. These results suggest that DIR should produce highly

  17. Ozone interaction with rodent lung. III. Oxidation of reduced glutathione and formation of mixed disulfides between protein and nonprotein sulfhydryls.

    PubMed Central

    DeLucia, A J; Mustafa, M G; Hussain, M Z; Cross, C E

    1975-01-01

    Nonprotein sulfhydryls (NPSH), a major source of cellular reducing substances, were examined in lung tissue after short-term exposure of rats to O3. While the NPSH level was unaffected by low-level exposures (e.g., 0.8 ppm for up to 24 h or 1.5 ppm for up to 8 h), it was significantly lowered by higher exposure regimens (e.g., 25 per cent after 2 ppm for 8 h and 49 per cent after 4 ppm for 6 h). After exposure to 4 ppm O3 for 6 h the level of reduced glutathione (GSH), which accounted for approximately 90 per cent of NPSH in the lung, decreased 40 per cent but without a rise in the level of oxidized gluathione (GSSG). Treatment of lung homogenate with borohydride led to recovery of NPSH in exposed lungs to control values, suggesting that NPSH or GSH oxidation during in vivo O3 exposure resulted in formation of mixed disulfides with other sulfhydryl (SH) groups of lung tissue. Extracts of borohydride-treated particulate and supernatant fractions of lung homogenate were analyzed for NPSH by paper chromatography. From this analysis GSH appeared to be the only NPSH bound to lung tissue proteins via mixed disulfide linkage. The formation of mixed disulfides appeared to be a transient phenomenon. Immediately after a 4-h exposure to 3 ppm O3 the level of mixed disulfides was small (15 per cent of the total NPSH) but attained a peak (equivalent to 0.6 mumol NPSH/lung) after a recovery for 24 h. However, the level diminished considerably within 48 h of recovery. PMID:1120782

  18. Galaxy pairs in the Sloan Digital Sky Survey - III. Evidence of induced star formation from optical colours

    NASA Astrophysics Data System (ADS)

    Patton, David R.; Ellison, Sara L.; Simard, Luc; McConnachie, Alan W.; Mendel, J. Trevor

    2011-03-01

    We have assembled a large, high-quality catalogue of galaxy colours from the Sloan Digital Sky Survey Data Release 7 and have identified 21 347 galaxies in pairs spanning a range of projected separations (rp < 80 h-170 kpc), relative velocities (Δv < 10 000 km s-1, which includes projected pairs that are essential for quality control) and stellar mass ratios (from 1:10 to 10:1). We find that the red fraction of galaxies in pairs is higher than that of a control sample matched in stellar mass and redshift, and demonstrate that this difference is likely due to the fact that galaxy pairs reside in higher density environments than non-paired galaxies. We detect clear signs of interaction-induced star formation within the blue galaxies in pairs, as evidenced by a higher fraction of extremely blue galaxies, along with blueward offsets between the colours of paired versus control galaxies. These signs are strongest in close pairs (rp < 30 h-170 kpc and Δv < 200 km s-1), diminish for more widely separated pairs (rp > 60 h-170 kpc and Δv < 200 km s-1) and disappear for close projected pairs (rp < 30 h-170 kpc and Δv > 3000 km s-1). These effects are also stronger in central (fibre) colours than in global colours and are found primarily in low- to medium-density environments. Conversely, no such trends are seen in red galaxies, apart from a small reddening at small separations, which may result from residual errors with photometry in crowded fields. When interpreted in conjunction with a simple model of induced starbursts, these results are consistent with a scenario in which close pericentre passages trigger induced star formation in the centres of galaxies which are sufficiently gas rich, after which time the galaxies gradually redden as they separate and their starbursts age.

  19. Reduction of uranium(VI) by mixed iron(II)/iron(III) hydroxide (green rust): formation of UO2 nanoparticles.

    PubMed

    O'Loughlin, Edward J; Kelly, Shelly D; Cook, Russell E; Csencsits, Roseann; Kemner, Kenneth M

    2003-02-15

    Green rusts, which are mixed ferrous/ferric hydroxides, are found in many suboxic environments and are believed to play a central role in the biogeochemistry of Fe. Analysis by U LIII-edge X-ray absorption near edge spectroscopy of aqueous green rust suspensions spiked with uranyl (U(VI)) showed that U(VI) was readily reduced to U(IV) by green rust The extended X-ray absorption fine structure (EXAFS) date for uranium reduced by green rust indicate the formation of a UO2 phase. A theoretical model based on the crystal structure of UO2 was generated by using FEFF7 and fitted to the data for the UO2 standard and the uranium in the green rust samples. The model fits indicate that the number of nearest-neighbor uranium atoms decreases from 12 for the UO2 structure to 5.4 forthe uranium-green rust sample. With an assumed four near-neighbor uranium atoms per uranium atom on the surface of UO2, the best-fit value for the average number of uranium atoms indicates UO2 particles with an average diameter of 1.7 +/- 0.6 nm. The formation of nanometer-scale particles of UO2, suggested by the modeling of the EXAFS data, was confirmed by high-resolution transmission electron microscopy, which showed discrete particles (approximately 2-9 nm in diameter) of crystalline UO2. Our results clearly indicate that U(VI) (as soluble uranyl ion) is readily reduced by green rust to U(IV) in the form of relatively insoluble UO2 nanoparticles, suggesting that the presence of green rusts in the subsurface may have significant effects on the mobility of uranium, particularly under iron-reducing conditions.

  20. Complex Formation in the Ternary System Tl(III)-CN(-)-Cl(-) in Aqueous Solution. A (205)Tl NMR Study.

    PubMed

    Berg, Katja E.; Blixt, Johan; Glaser, Julius

    1996-11-20

    The existence of mixed complexes of the general formula Tl(CN)(m)()Cl(n)()(3)(-)(m)()(-)(n)() (m + n formation constants for addition of one cyanide ligand, log K(CN), show linear dependence on both the spin-spin coupling constants, (1)J((205)Tl-(13)C), and the chemical shifts, delta(Tl). Also the interatomic distance, d(Tl-C), is linearly correlated to the spin-spin coupling constant. The correlations are discussed in terms of the Ramsey equation, involving bond properties, stereochemistry, and stability of the complexes. Since (1)J((205)Tl-(13)C) also shows linear dependence on the Tl-CN force constant, it is concluded that the above correlations reflect the Tl-CN bond strength. Thus, the most important factor contributing to the thermodynamic stability of the complexes is the enthalpy term, dominated by formation of very strong sigma-bonds between cyanide and thallium. These trends may prove useful for spectral/structural assignments but also for estimation of metal-to-ligand bond distances and stability constants for complexes which exist only in low concentration.

  1. The effect of dosage on the efficiency of LLLT in new bone formation at the expanded suture in rats.

    PubMed

    Altan, Ayse Burcu; Bicakci, Ali Altug; Avunduk, Mustafa Cihat; Esen, Hasan

    2015-01-01

    The aim of this study was to investigate the effect that dosage has on the efficiency of low-level laser therapy (LLLT) in bone formation in a rat study model. Twenty-eight rats were divided into four groups as only expansion (OE), expansion + low dose (0.15 J) (LD), expansion + medium dose (0.65 J) (MD), and expansion + high dose (198 J) (HD) laser therapy groups. The midpalatal suture was expanded during 5 days. Afterwards, irradiations were started and performed with an 820 nm, continuous wave, Ga-Al-As diode laser (Doris, CTL-1106MX, Warsaw, Poland). At the end of experiment, the premaxillae of the animals were dissected. The sections were transferred into PC environment and analyzed by using Image Analysis program. Number of osteoblasts, osteoclasts, fibroblasts, vessels, transforming growth factor beta (TGF-β) expression, and new bone formation were evaluated with this program. Amount of expansion did not show any difference among the groups. All parameters except the number of osteoclasts were increased in all lased groups while that parameter was significantly decreased. Vessels, TGF-β expression, and new bone formation were mostly increased in LD group followed by HD group. Among the lased groups, a significant difference was observed only for the amount of new bone formation, which was between the LD and the MD groups. On the other hand, the difference in this parameter was insignificant between OE and MD groups. Low-level laser therapy with both 5 and 6,300 J/cm(2) doses was found to be significantly effective, while the 20 J/cm(2) dose did not show a significant effect in increasing new bone formation. This finding reveals that the efficiency of the therapy is affected by the dosage.

  2. Numerical Simulations of Turbulent Molecular Clouds Regulated by Radiation Feedback Forces. I. Star Formation Rate and Efficiency

    NASA Astrophysics Data System (ADS)

    Raskutti, Sudhir; Ostriker, Eve C.; Skinner, M. Aaron

    2016-10-01

    Radiation feedback from stellar clusters is expected to play a key role in setting the rate and efficiency of star formation in giant molecular clouds. To investigate how radiation forces influence realistic turbulent systems, we have conducted a series of numerical simulations employing the Hyperion radiation hydrodynamics solver, considering the regime that is optically thick to ultraviolet and optically thin to infrared radiation. Our model clouds cover initial surface densities between Σ cl,0∼ 10--300 M⊙ pc-2, with varying initial turbulence. We follow them through turbulent, self-gravitating collapse, star cluster formation, and cloud dispersal by stellar radiation. All our models display a log-normal distribution of gas surface density Σ for an initial virial parameter αvir,0=2, the log-normal standard deviation is σln Σ =1-1.5 and the star formation rate coefficient ɛff,ρ=0.3-0.5, both of which are sensitive to turbulence but not radiation feedback. The net star formation efficiency (SFE) ɛfinal increases with Σcl,0 and decreases with α vir,0. We interpret these results via a simple conceptual framework, whereby steady star formation increases the radiation force, such that local gas patches at successively higher Σ become unbound. Based on this formalism (with fixed σln Σ), we provide an analytic upper bound on ɛfinal, which is in good agreement with our numerical results. The final SFE depends on the distribution of Eddington ratios in the cloud and is strongly increased by the turbulent compression of gas.

  3. Coalescence of Multiple Plasmoids as a Means of Efficient Spheromak Formation

    SciTech Connect

    Woodruff, S; McLean, H S; Stallard, B W

    2002-02-28

    We have produced single bursts of helicity from the source in the SSPX spheromak in order to study the efficiency of the simplest example of helicity injection. We find that the helicity injection rate can be written in terms of the injected current and an inductance, and that a simple circuit analogue demonstrates unambiguously the relationship of helicity to energy: helicity injection is the addition of inductive loops. While helicity balance points to the conservation of helicity, the electrical efficiency is around 15%. However, in the expulsion of the loop, electrical energy is converted to directional motion, which may be recoverable usefully as heat by collisions, thus the efficiency of the injection process is arguably quite high. Integral to this notion of helicity injection is the idea that reconnection is necessary: without disconnection from the source by a reconnection event, the spheromak fields are just proportional to the injected current. Sometimes the multiple bursts occur spontaneously and cause a step-wise increase in the field (and helicity). However, in all instances when the current remains above the ejection threshold for t > 50 {micro}s, the n=l mode initiates and builds field, although with much reduced efficiency, and to a level which is symptomatic of no reconnection (B{sub spheromak} {proportional_to} I{sub inj}).

  4. Luminous Infrared Galaxies. III. Multiple Merger, Extended Massive Star Formation, Galactic Wind, and Nuclear Inflow in NGC 3256

    NASA Astrophysics Data System (ADS)

    Lípari, S.; Díaz, R.; Taniguchi, Y.; Terlevich, R.; Dottori, H.; Carranza, G.

    2000-08-01

    We report detailed evidence for multiple merger, extended massive star formation, galactic wind, and circular/noncircular motions in the luminous infrared galaxy NGC 3256, based on observations of high-resolution imaging (Hubble Space Telescope, ESO NTT), and extensive spectroscopic data (more than 1000 spectra, collected at Estación Astrofísica de Bosque Alegre, Complejo Astronómico el Leoncito, Cerro Tololo InterAmerican Observatory, and IUE observatories). We find in a detailed morphological study (resolution ~15 pc) that the extended massive star formation process detected previously in NGC 3256 shows extended triple asymmetrical spiral arms (r~5 kpc), emanating from three different nuclei. The main optical nucleus shows a small spiral disk (r~500 pc), which is a continuation of the external one and reaches the very nucleus. The core shows blue elongated structure (50 pc×25 pc) and harbors a blue stellar cluster candidate (r~8 pc). We discuss this complex morphology in the framework of an extended massive star formation driven by a multiple merger process (models of Hernquist et al. and Taniguchi et al.). We study the kinematics of this system and present a detailed Hα velocity field for the central region (40''×40'' rmax~30''~5 kpc), with a spatial resolution of 1" and errors of +/-15 km s-1. The color and isovelocity maps show mainly (1) a kinematic center of circular motion with ``spider'' shape, located between the main optical nucleus and the close (5") mid-IR nucleus and (2) noncircular motions in the external parts. We obtained three ``sinusoidal rotation curves'' (from the Hα velocity field) around position angle (P.A.) ~55°, ~90°, and ~130°. In the main optical nucleus we found a clear ``outflow component'' associated with galactic winds plus an ``inflow radial motion.'' The outflow component was also detected in the central and external regions (r<=5-6 kpc). The main axis of the inflow region (P.A.~80deg) is practically perpendicular to the

  5. Type III Methyltransferase M.NgoAX from Neisseria gonorrhoeae FA1090 Regulates Biofilm Formation and Interactions with Human Cells

    PubMed Central

    Kwiatek, Agnieszka; Mrozek, Agnieszka; Bacal, Pawel; Piekarowicz, Andrzej; Adamczyk-Popławska, Monika

    2015-01-01

    Neisseria gonorrhoeae is the etiological factor of the sexually transmitted gonorrhea disease that may lead, under specific conditions, to systemic infections. The gonococcal genome encodes many restriction modification (RM) systems, which main biological role is to defend the pathogen from potentially harmful foreign DNA. However, RM systems seem also to be involved in several other functions. In this study, we examined the effect of inactivation the N. gonorrhoeae FA1090 ngoAXmod gene encoding M.NgoAX methyltransferase on the global gene expression, biofilm formation, interactions with human epithelial host cells and overall bacterial growth. Expression microarrays showed at least a twofold deregulation of a total of 121 genes in the NgoAX knock-out mutant compared to the wild-type (wt) strain under standard grow conditions. Genes with changed expression levels encoded mostly proteins involved in cell metabolism, DNA replication and repair or regulating cellular processes and signaling (such as cell wall/envelop biogenesis). As determined by the assay with crystal violet, the NgoAX knock-out strain formed a slightly larger biofilm biomass per cell than the wt strain. Live biofilm observations showed that the biofilm formed by the gonococcal ngoAXmod gene mutant is more relaxed, dispersed and thicker than the one formed by the wt strain. This more relaxed feature of the biofilm, in respect to adhesion and bacterial interactions, can be involved in pathogenesis. Moreover, the overall adhesion of mutant bacterial cells to human cells was lower than adhesion of the wt gonococci [adhesion index = 0.672 (±0.2) and 2.15 (±1.53), respectively]; yet, a higher number of mutant than wt bacteria were found inside the Hec-1-B epithelial cells [invasion index = 3.38 (±0.93) × 105 for mutant and 4.67 (±3.09) × 104 for the wt strain]. These results indicate that NgoAX knock-out cells have lower ability to attach to human cells, but more easily penetrate inside the host