Science.gov

Sample records for iii formation efficiencies

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. Effect of Population III multiplicity on dark star formation

    NASA Astrophysics Data System (ADS)

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

    2012-03-01

    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˜ 100, which follows the evolution of gas and DM. We analyse the formation of the first minihalo at z˜ 20 and the subsequent collapse of the gas to densities of 1012 cm-3. 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-disc 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 ˜5000 years. In addition, the star-disc 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.

  6. 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.

  7. FORMATION CRITERIA AND THE MASS OF SECONDARY POPULATION III STARS

    SciTech Connect

    Susa, Hajime; Umemura, Masayuki; Hasegawa, Kenji E-mail: umemura@ccs.tsukuba.ac.jp

    2009-09-01

    We explore the formation of secondary Population III (Pop III) stars under radiation hydrodynamic (RHD) feedback by a preformed massive star. To properly treat RHD feedback, we perform three-dimensional RHD simulations incorporating the radiative transfer of ionizing photons as well as H{sub 2} dissociating photons from a preformed star. A collapsing gas cloud is settled at a given distance from a 120 M{sub sun} Pop III star, and the evolution of the cloud is pursued including RHD feedback. We derive the threshold density depending on the distance, above which the cloud can keep collapsing owing to the shielding of H{sub 2} dissociating radiation. We find that an H{sub 2} shell formed ahead of an ionizing front works effectively to shield the H{sub 2} dissociating radiation, leading to the positive feedback for the secondary Pop III star formation. Also, near the threshold density, the envelope of gas cloud is stripped significantly by a shock associated with an ionizing front. By comparing the mass accretion timescale with the Kelvin-Helmholtz timescale, we estimate the mass of secondary Pop III stars. It turns out that the stripping by a shock can reduce the mass of secondary Pop III stars down to {approx}20 M{sub sun}.

  8. Formation of the first galaxies under Population III stellar feedback

    NASA Astrophysics Data System (ADS)

    Jeon, Myoungwon

    2015-01-01

    The first galaxies, which formed a few hundred million years after the big bang, are related to important cosmological questions. Given thatthey are thought to be the basic building blocks of large galaxies seen today, understanding their formation and properties is essentialto studying galaxy formation as a whole. In this dissertation talk, I will present the results of our highly-resolved cosmological ab-initio simulations to understand the assembly process of first galaxies under the feedback from the preceding generations of first stars, the so-called Population III (Pop III). The first stars formed at z≲30 in dark matter (DM) minihalos with M_{vir}=10^5-10^6Msun, predominately via molecular hydrogen (H_2) cooling. Radiation from Pop III stars dramatically altered the gas within their host minihalos, through photoionization, photoheating, and photoevaporation. Once a Pop III star explodes as a supernova (SN), heavy elements are dispersed, enriching the interstellar (ISM) and intergalactic medium (IGM), thus initiating the process of chemical evolution. I will begin by presenting how the SN explosion of the first stars influences early cosmic history, specifically assessing the time delay in further star formation and tracing the evolution of metal-enriched gas until the second episode star formation happens. These results will show the role of Pop III supernovae on the star formation transition from Pop III to Population II. Additionally, the more distant, diffuse IGM was heated by X-rays emitted by accreting black holes (BHs), or high-mass X-ray binaries (HMXBs), both remnants of Pop III stars. I will present results of a series of simulations where we study the impact of X-ray feedback from BHs and HMXBs on the star formation history in the early universe, and discuss the resulting implications on reionization. I will also present the role of X-rays on the early BH growth, providing constraints on models for supermassive black hole formation. Finally, I

  9. The ABC of Population III. [star formation and cosmological consequences

    NASA Technical Reports Server (NTRS)

    Carr, B. J.

    1986-01-01

    The author discusses the circumstances in which Population III stars are expected to form and examines their cosmological consequences. Consideration of their production of light, metals, and remnants places a strong constraint on their formation epoch and mass spectrum. However, these constraints would still allow Population III stars to provide the dark matter in galactic halos, a helium abundance of around 25 percent, a detectable background of gravitational waves, a possible infrared background, and the generation of large-scale cosmological structure through explosions. All of these features could be achieved by VMOs in the range 100 to 100,000 solar masses. On the other hand, the Population III scenario would be most compatible with the standard Big Bang picture if the stars were SMOs with mass around a million solar masses. Such stars could still provide the dark matter and detectable gravitational waves.

  10. Formation Rates of Population III Stars and Chemical Enrichment of Halos during the Reionization Era

    NASA Astrophysics Data System (ADS)

    Trenti, Michele; Stiavelli, Massimo

    2009-04-01

    The first stars in the universe formed out of pristine primordial gas clouds that were radiatively cooled to a few hundreds of degrees kelvin either via molecular or atomic (Lyman-α) hydrogen lines. This primordial mode of star formation was eventually quenched once radiative and/or chemical (metal enrichment) feedbacks marked the transition to Population II stars. In this paper, we present a model for the formation rate of Population III stars based on Press-Schechter modeling coupled with analytical recipes for gas cooling and radiative feedback. Our model also includes a novel treatment for metal pollution based on self-enrichment due to a previous episode of Population III star formation in progenitor halos. With this model, we derive the star formation history of Population III stars, their contribution to the reionization of the universe and the time of the transition from Population III star formation in minihalos (M ≈ 106 M sun, cooled via molecular hydrogen) to that in more massive halos (M gsim 2 × 107 M sun, where atomic hydrogen cooling is also possible). We consider a grid of models highlighting the impact of varying the values for the free parameters used, such as star formation and feedback efficiency. The most critical factor is the assumption that only one Population III star is formed in a halo. In this scenario, metal-free stars contribute only to a minor fraction of the total number of photons required to reionize the universe. In addition, metal-free star formation is primarily located in minihalos, and chemically enriched halos become the dominant locus of star formation very early in the life of the universe—at redshift z ≈ 25—even assuming a modest fraction (0.5%) of enriched gas converted in stars. If instead multiple metal-free stars are allowed to form out of a single halo, then there is an overall boost of Population III star formation, with a consequent significant contribution to the reionizing radiation budget. In addition

  11. 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.

  12. 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.

  13. 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.

  14. 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. PMID:25671799

  15. Dynamics and efficiency of type III solar radio emission

    NASA Technical Reports Server (NTRS)

    Robinson, P. A.; Cairns, I. H.; Willes, A. J.

    1994-01-01

    Existing calculations of nonlinear coupling coefficients for fundamental and harmonic emission via three-wave interactions are refined and used to calculate the conversion efficiency of Langmuir energy into electromagnetic waves when the Langmuir waves have the observed bursty form. Resulting field strengths for harmonic emission are found to be consistent with typical International Sun Earth Explorer 3 (ISSE 3) observations at 1 AU. Fundamental emission at 1 AU is found to proceed only when stimulated by the presence of a source of ion sound waves. However, it is argued that electrostatic decay of Langmuir waves can supply the necessary waves provided the driving electron beam is sufficiently fast. Under these conditions, the predicted fundamental field strengths can account for both the highest and typical fields observed; they also dominate the predicted harmonic fields, consistent with observations. This mechanism is also consistent with previous observations that fundamental emission generally occurs early in type III events, when the beam is fastest. For typical parameters it is shown that neither fundamental nor harmonic emission saturates its respective source instability, contrary to previous assumptions. However, saturation cannot be ruled out under particularly favorable conditions.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 43 CFR Appendix III to Part 11 - Format for Data Inputs and Modifications to the NRDAM/GLE

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 43 Public Lands: Interior 1 2011-10-01 2011-10-01 false Format for Data Inputs and Modifications to the NRDAM/GLE III Appendix III to Part 11 Public Lands: Interior Office of the Secretary of the Interior NATURAL RESOURCE DAMAGE ASSESSMENTS Pt. 11, App. III Appendix III to Part 11—Format for...

  1. 43 CFR Appendix III to Part 11 - Format for Data Inputs and Modifications to the NRDAM/GLE

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 43 Public Lands: Interior 1 2010-10-01 2010-10-01 false Format for Data Inputs and Modifications to the NRDAM/GLE III Appendix III to Part 11 Public Lands: Interior Office of the Secretary of the Interior NATURAL RESOURCE DAMAGE ASSESSMENTS Pt. 11, App. III Appendix III to Part 11—Format for...

  2. 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.

  3. 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.

  4. 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)…

  5. THE CHEMISTRY OF POPULATION III SUPERNOVA EJECTA. I. FORMATION OF MOLECULES IN THE EARLY UNIVERSE

    SciTech Connect

    Cherchneff, Isabelle; Dwek, Eli E-mail: eli.dwek@nasa.go

    2009-09-20

    }. This smaller efficiency at forming molecules is due to the large fraction of He{sup +} in the outer mass zone of the ejecta. Finally, we discuss the cosmological implication of molecule formation by Pop III SNe in the early universe.

  6. Complex I Function and Supercomplex Formation Are Preserved in Liver Mitochondria Despite Progressive Complex III Deficiency

    PubMed Central

    Davoudi, Mina; Kotarsky, Heike; Hansson, Eva; Fellman, Vineta

    2014-01-01

    Functional oxidative phosphorylation requires appropriately assembled mitochondrial respiratory complexes and their supercomplexes formed mainly of complexes I, III and IV. BCS1L is the chaperone needed to incorporate the catalytic subunit, Rieske iron-sulfur protein, into complex III at the final stage of its assembly. In cell culture studies, this subunit has been considered necessary for supercomplex formation and for maintaining the stability of complex I. Our aim was to assess the importance of fully assembled complex III for supercomplex formation in intact liver tissue. We used our transgenic mouse model with a homozygous c.232A>G mutation in Bcs1l leading to decreased expression of BCS1L and progressive decrease of Rieske iron-sulfur protein in complex III, resulting in hepatopathy. We studied supercomplex formation at different ages using blue native gel electrophoresis and complex activity using high-resolution respirometry. In isolated liver mitochondria of young and healthy homozygous mutant mice, we found similar supercomplexes as in wild type. In homozygotes aged 27–29 days with liver disorder, complex III was predominantly a pre-complex lacking Rieske iron-sulfur protein. However, the main supercomplex was clearly detected and contained complex III mainly in the pre-complex form. Oxygen consumption of complex IV was similar and that of complex I was twofold compared with controls. These complexes in free form were more abundant in homozygotes than in controls, and the mRNA of complex I subunits were upregulated. In conclusion, when complex III assembly is deficient, the pre-complex without Rieske iron-sulfur protein can participate with available fully assembled complex III in supercomplex formation, complex I function is preserved, and respiratory chain stability is maintained. PMID:24466228

  7. 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.

  8. Formation of Fe(III) oxyhydroxide colloids in freshwater and brackish seawater, with incorporation of phosphate and calcium

    NASA Astrophysics Data System (ADS)

    Gunnars, Anneli; Blomqvist, Sven; Johansson, Peter; Andersson, Christian

    2002-03-01

    The formation of Fe(III) oxyhydroxide colloids by oxidation of Fe(II) and their subsequent aggregation to larger particles were studied in laboratory experiments with natural water from a freshwater lake and a brackish coastal sea. Phosphate was incorporated in the solid phase during the course of hydrolysis of iron. The resulting precipitated amorphous Fe(III) oxyhydroxide phases were of varying composition, depending primarily on the initial dissolved Fe/P molar ratio, but with little influence by salinity or concentration of calcium ions. The lower limiting Fe/P ratio found for the solid phase suggests the formation of a basic Fe(III) phosphate compound with a stoichiometric Fe/P ratio of close to two. This implies that an Fe/P stoichiometry of ≈2 ultimately limits the capacity of precipitating Fe(III) to fix dissolved phosphate at oxic/anoxic boundaries in natural waters. In contrast to phosphorus, the uptake of calcium seemed to be controlled by sorption processes at the surface of the iron-rich particles formed. This uptake was more efficient in freshwater than in brackish water, suggesting that salinity restrains the uptake of calcium by newly formed Fe(III) oxyhydroxides in natural waters. Moreover, salinity enhanced the aggregation rate of the colloids formed. The suspensions were stabilised by the presence of organic matter, although this effect was less pronounced in seawater than in freshwater. Thus, in seawater of 6 to 33 ‰S, the removal of particles was fast (removal half time < 200 h), whereas the colloidal suspensions formed in freshwater were stable (removal half time > 900 h). Overall, oxidation of Fe(II) and removal of Fe(III) oxyhydroxide particles were much faster in seawater than in freshwater. This more rapid turnover results in lower iron availability in coastal seawater than in freshwater, making iron more likely to become a limiting element for chemical scavenging and biologic production.

  9. Formation of massive Population III galaxies through photoionization feedback: a possible explanation for CR 7

    NASA Astrophysics Data System (ADS)

    Visbal, Eli; Haiman, Zoltán; Bryan, Greg L.

    2016-07-01

    We explore the formation of massive high-redshift Population III (Pop III) galaxies through photoionization feedback. We consider dark matter haloes formed from progenitors that have undergone no star formation as a result of early reionization and photoevaporation caused by a nearby galaxy. Once such a halo reaches ≈109 M⊙, corresponding to the Jeans mass of the photoheated intergalactic medium at z ≈ 7, pristine gas is able to collapse into the halo, potentially producing a massive Pop III starburst. We suggest that this scenario may explain the recent observation of strong He II 1640 Å line emission in CR 7, which is consistent with ˜107 M⊙ of young Pop III stars. Such a large mass of Pop III stars is unlikely without the photoionization feedback scenario, because star formation is expected to inject metals into haloes above the atomic cooling threshold (˜108 M⊙ at z ≈ 7). We use merger trees to analytically estimate the abundance of observable Pop III galaxies formed through this channel, and find a number density of ≈10-7 Mpc-3 at z = 6.6 (the redshift of CR 7). This is approximately a factor of 10 lower than the density of Ly α emitters as bright as CR 7.

  10. 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.

  11. Lignin peroxidase compound III. Mechanism of formation and decomposition

    SciTech Connect

    Wariishi, Hiroyuki; Gold, M.H. )

    1990-02-05

    Lignin peroxidase compound III (LiPIII) was prepared via three procedures: (a) ferrous LiP + O{sub 2} (LiPIIIa), (b) ferric LiP + O{sub 2}{sup {bar {sm bullet}}} (LiPIIIb), and (c) LiP compound II + excess H{sub 2}O{sub 2} followed by treatment with catalase (LiPIIIc). LiPIIIa, b, and c each have a Soret maximum at {approximately}414 nm and visible bands at 543 and 578 nm. LiPIIIa, b, and c each slowly reverted to native ferric LiP, releasing stoichiometric amounts of O{sub 2}{sup {bar {sm bullet}}} in the process. The LiPIII reversion reactions obeyed first-order kinetics with rate constants of {approximately}1.0 {times} 10{sup {minus}3} s{sup {minus}1}. In the presence of excess peroxide, at pH 3.0, native LiP, LiPII, and LiPIIIa, b, and c are all converted to a unique oxidized species (LiPIII*) with a spectrum displaying visible bands at 543 and 578 nm, but with a Soret maximum at 419 nm, red-shifted 5 nm from that of LiPIII. LiPIII* is bleached and inactivated in the presence of excess H{sub 2}O{sub 2} via a biphasic process. The fast first phase of this bleaching reaction obeys second-order kinetics, with a rate constant of 1.7 {times} 10{sup 1} M{sup {minus}1} s{sup {minus}1}. Addition of veratryl alcohol to LiPIII* results in its rapid reversion to the native enzyme, via an apparent one-step reaction that obeys second-order kinetics, with a rate constant of 3.5 {times} 10{sup 1} M{sup {minus}1} s{sup {minus}1}. Stoichiometric amounts of O{sub 2}{sup {bar {sm bullet}}} are released during this reaction. When this reaction was run under conditions that prevented further reactions, HPLC analysis of the products demonstrated that veratryl alcohol was not oxidized. These results suggest that the binding of veratryl alcohol to LiPIII* displaces O{sub 2}{sup {bar {sm bullet}}}, thus returning the enzyme to its native state. In contrast, the addition of veratryl alcohol to LiPIII did not affect the rate of spontaneous reversion of LiPIII to the native enzyme.

  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. 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.

  14. Efficient catalytic cycloalkane oxidation employing a "helmet" phthalocyaninato iron(III) complex.

    PubMed

    Brown, Elizabeth S; Robinson, Jerome R; McCoy, Aaron M; McGaff, Robert W

    2011-06-14

    We have examined the catalytic activity of an iron(III) complex bearing the 14,28-[1,3-diiminoisoindolinato]phthalocyaninato (diiPc) ligand in oxidation reactions with three substrates (cyclohexane, cyclooctane, and indan). This modified metallophthalocyaninato complex serves as an efficient and selective catalyst for the oxidation of cyclohexane and cyclooctane, and to a far lesser extent indan. In the oxidations of cyclohexane and cyclooctane, in which hydrogen peroxide is employed as the oxidant under inert atmosphere, we have observed turnover numbers of 100.9 and 122.2 for cyclohexanol and cyclooctanol, respectively. The catalyst shows strong selectivity for alcohol (vs. ketone) formation, with alcohol to ketone (A/K) ratios of 6.7 and 21.0 for the cyclohexane and cyclooctane oxidations, respectively. Overall yields (alcohol + ketone) were 73% for cyclohexane and 92% for cyclooctane, based upon the total hydrogen peroxide added. In the catalytic oxidation of indan under similar conditions, the TON for 1-indanol was 10.1, with a yield of 12% based upon hydrogen peroxide. No 1-indanone was observed in the product mixture.

  15. Effect of the medium and the formation of nanostructures on deexcitation of electronic excitation of Eu(III) and Tb(III) chelates

    NASA Astrophysics Data System (ADS)

    Sveshnikova, E. B.; Dudar, S. S.; Shablya, A. V.; Ermolaev, V. L.

    2006-10-01

    The intensity I lum and lifetime τlum of the luminescence of complexes of Eu(III) and Tb(III) ions with β-diketones and o-phenanthroline in water-ethanol solutions of these ligands have been analyzed as functions of the concentrations of ligand, luminescing lanthanide ions, and added ions causing columinescence and of the solvent deuteration. It is shown that the formation of nanostructures from Ln complexes and their coarsening leads to an increase in τlum of Eu(III) and Tb(III) and that this increase is due to the suppression of both photochemical deexcitation of these ions and transfer of their electronic excitation energy to OH vibrations of water molecules. The disappearance of the dependence of I lum of Eu(III) on deuteration of water-ethanol solutions of n-methoxybenzoyltrifluoracetone + o-phenanthroline caused by adding Gd(III) ions is explained by the shift of the equilibrium of formation of complexes of Ln chelates to neutral hydrophoblic forms corresponding to the formation of nanostructures of these chelates in the solution. The differences in effect of La(III) and Gd(III) ions on I lum and τlum of Eu(III) and Tb(III) complexes are explained. It is shown that the widely discussed effect of columinescence not only results from the energy migration in mixed structures of Eu or Tb complexes and Gd complexes but is also due to a large extent to the decrease in τlum of Eu(III) or Tb(III) caused by their incorporation into nanostructures.

  16. 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

    2012-10-01

    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.

  17. Synthesis and characterisation of the Fe(II-III) hydroxy-formate green rust

    NASA Astrophysics Data System (ADS)

    Refait, P.; Abdelmoula, M.; Génin, J.-M. R.; Jeannin, M.

    A new methodology was envisioned in order to prepare green rust compounds build on organic anions that could intervene in microbiologically influenced corrosion processes of iron and steel. The formate ion was chosen as an example. The formation of rust was simulated by the oxidation of aqueous suspensions of Fe(OH)2 precipitated from Fe(II) lactate and sodium hydroxide, in the presence of sodium formate to promote the formation of the corresponding green rust. The evolution of the precipitate with time was followed by transmission Mössbauer spectroscopy at 15 K. It was observed that the initial hydroxide was transformed into a new GR compound. Its spectrum is composed of three quadrupole doublets, D 1 (δ=1.28 mm s-1, Δ=2.75 mm s-1) and D 2 (δ=1.28 mm s-1, Δ=2.48 mm s-1) that correspond to Fe(II) and D 3 (δ=0.49 mm s-1, Δ=0.37 mm s-1) that corresponds to Fe(III). The relative area of D 3, close to the proportion of Fe(III) in the GR, was found at 28.5±1.5% (˜2/7). Raman spectroscopy confirmed that the intermediate compound was a Fe(II-III) hydroxy-formate, GR(HCOO-).

  18. Synthesis and characterisation of the Fe(II III) hydroxy-formate green rust

    NASA Astrophysics Data System (ADS)

    Refait, P.; Abdelmoula, M.; Génin, J.-M. R.; Jeannin, M.

    2006-01-01

    A new methodology was envisioned in order to prepare green rust compounds build on organic anions that could intervene in microbiologically influenced corrosion processes of iron and steel. The formate ion was chosen as an example. The formation of rust was simulated by the oxidation of aqueous suspensions of Fe(OH)2 precipitated from Fe(II) lactate and sodium hydroxide, in the presence of sodium formate to promote the formation of the corresponding green rust. The evolution of the precipitate with time was followed by transmission Mössbauer spectroscopy at 15 K. It was observed that the initial hydroxide was transformed into a new GR compound. Its spectrum is composed of three quadrupole doublets, D 1 (δ = 1.28 mm s-1, Δ = 2.75 mm s-1) and D 2 (δ = 1.28 mm s-1, Δ = 2.48 mm s-1) that correspond to Fe(II) and D 3 (δ = 0.49 mm s-1, Δ = 0.37 mm s-1) that corresponds to Fe(III). The relative area of D 3, close to the proportion of Fe(III) in the GR, was found at 28.5 ± 1.5% (˜2/7). Raman spectroscopy confirmed that the intermediate compound was a Fe(II III) hydroxy-formate, GR(HCOO-).

  19. Empirical modeling of the cross section of damage formation in ion implanted III-V semiconductors

    SciTech Connect

    Wendler, E.; Wendler, L.

    2012-05-07

    In this letter, the cross section of damage formation per individual ion is measured for III-V compound semiconductors ion implanted at 15 K, applying Rutherford backscattering spectrometry. An empirical model is proposed that explains the measured cross sections in terms of quantities representing the primary energies deposited in the displacement of lattice atoms and in electronic interactions. The resulting formula allows the prediction of damage formation for low temperatures and low ion fluences in these materials and can be taken as a starting point for further quantitative modeling of damage formation including secondary effects such as temperature and ion flux.

  20. The Biermann Battery in Cosmological MHD Simulations of Population III Star Formation

    NASA Astrophysics Data System (ADS)

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

    2008-12-01

    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 simeq 10-9 G in the center of our star-forming halo at z simeq 17.55 at a baryon density of nB ~ 1010 cm-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 β >= 1015 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.

  1. 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.

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

    DOE PAGESBeta

    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 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

  3. Formation damage effects on horizontal-well flow efficiency

    SciTech Connect

    Renard, G.; Dupuy, J.M. )

    1991-07-01

    Wellbore damage commonly is accounted for by an apparent skin factor. A better relative index for determining the efficiency with which a well has been drilled and completed is the flow efficiency, the ration of a well's actual PI to ideal PI. The flow efficiency of horizontal wells is derived assuming steady-state flow of an incompressible fluid in a homogeneous, anisotropic medium. A comparison between the flow efficiencies of vertical and horizontal wells indicates that permeability reduction around the wellbore is less detrimental to horizontal wells. This paper shows that the effect of damage around a horizontal wellbore is reduced slightly by increasing the well length. Conversely, if the vertical permeability is less than the horizontal permeability, the anisotropy ratio, {radical} k{sub H}/k{sub V}, magnifies the influence of formation damage near the horizontal wellbore. Examples of flow efficiency calculations assuming a formation damage or a formation collapse around a liner in poorly consolidated formations are provided for horizontal and vertical wells.

  4. Recovery from Population III supernova explosions and the onset of second-generation star formation

    NASA Astrophysics Data System (ADS)

    Jeon, Myoungwon; Pawlik, Andreas H.; Bromm, Volker; Milosavljević, Miloš

    2014-11-01

    We use cosmological simulations to assess how the explosion of the first stars in supernovae (SNe) influences early cosmic history. Specifically, we investigate the impact by SNe on the host systems for Population III (Pop III) star formation and explore its dependence on halo environment and Pop III progenitor mass. We then trace the evolution of the enriched gas until conditions are met to trigger second-generation star formation. To this extent, we quantify the recovery time-scale, which measures the time delay between a Pop III SN explosion and the appearance of cold, dense gas, out of which second-generation stars can form. We find that this time-scale is highly sensitive to the Pop III progenitor mass, and less so to the halo environment. For Pop III progenitor masses, M* = 15, 25, and 40 M⊙ in a halo of 5 × 105 M⊙, recovery times are ˜10, 25, and 90 Myr, respectively. For more massive progenitors, including those exploding in pair instability SNe, second-generation star formation is delayed significantly, for up to a Hubble time. The dependence of the recovery time on the mass of the SN progenitor is mainly due to the ionizing impact of the progenitor star. Photoionization heating increases the gas pressure and initiates a hydrodynamical response that reduces the central gas density, an effect that is stronger in more massive. The gas around lower mass Pop III stars remains denser and hence the SN remnants cool more rapidly, facilitating the subsequent re-condensation of the gas and formation of a second generation of stars. In most cases, the second-generation stars are already metal enriched to ˜2-5 × 10-4 Z⊙, thus belonging to Pop II. The recovery time-scale is a key quantity governing the nature of the first galaxies, able to host low-mass, long-lived stellar systems. These in turn are the target of future deep-field campaigns with the James Webb Space Telescope.

  5. Complex formation of Am(III) and Am(IV) with phosphate ions in acetonitrile solutions

    SciTech Connect

    Perevalov, S.A.; Lebedev, I.A.; Myasoedov, B.F.

    1988-05-01

    The first dissociation constant of H/sub 3/PO/sub 4/ in acetonitrile solution (K/sub 1//sup 0/ = 1.75/centered dot/10/sup /minus/13/) and the constant of formation of H(H/sub 2/PO/sub 4/)/sub 2//sup /minus// dimers (K/sub d//sup 0/ = 8/centered dot/10/sup 2/) were determined by the method of pH-potentiometry. The complex formation of Am(III) in acetonitrile solutions containing 0.05-2.0 M H/sub 3/PO/sub 4/ was investigated by a spectrophotometric method; the stability constants of the complexes AmH/sub 2/PO/sub 4//sup 2+/ (/beta//sub 1//sup III/ = 1.0/centered dot/10/sup 12/) and Am(H/sub 2/PO/sub 4/)/sub 2//sup +/ (/beta//sub 2//sup III/ = 4.3/centered dot/10/sup 24/) were determined. The formal potentials of the couple Am/sup (IV)//Am/sup (III)/ in 0.3-1.9 M solutions of H/sub 3/PO/sub 4/ in acetonitrile were measured, and the stability constant of the phosphate complex of tetravalent americium Am(H/sub 2/PO/sub 4/)/sub 3//sup +/ (/beta//sub 3//sup IV/ = 2.5/centered dot/10/sup 46/) was calculated according to the value of the shift of the potential relative to the standard.

  6. 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

  7. 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.

  8. 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

  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

    2014-08-01

    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. Direct Copper(III) Formation from O2 and Copper(I) with Histamine Ligation.

    PubMed

    Gary, J Brannon; Citek, Cooper; Brown, Timothy A; Zare, Richard N; Wasinger, Erik C; Stack, T Daniel P

    2016-08-10

    Histamine chelation of copper(I) by a terminal histidine residue in copper hydroxylating enzymes activates dioxygen to form unknown oxidants, generally assumed as copper(II) species. The direct formation of copper(III)-containing products from the oxygenation of histamine-ligated copper(I) complexes is demonstrated here, indicating that copper(III) is a viable oxidation state in such products from both kinetic and thermodynamic perspectives. At low temperatures, both trinuclear Cu(II)2Cu(III)O2 and dinuclear Cu(III)2O2 predominate, with the distribution dependent on the histamine ligand structure and oxygenation conditions. Kinetics studies suggest the bifurcation point to these two products is an unobserved peroxide-level dimer intermediate. The hydrogen atom reactivity difference between the trinuclear and binuclear complexes at parity of histamine ligand is striking. This behavior is best attributed to the accessibility of the bridging oxide ligands to exogenous substrates rather than a difference in oxidizing abilities of the clusters. PMID:27467215

  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. 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

  14. 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.

  15. Complexation of Al(III) with gluconate in alkaline to hyperalkaline solutions: formation, stability and structure.

    PubMed

    Pallagi, Attila; Tasi, Ágost Gyula; Peintler, Gábor; Forgo, Péter; Pálinkó, István; Sipos, Pál

    2013-10-01

    Contrary to suggestions in the literature, it has been proven that Al(III) forms a 1 : 1 complex with gluconate (hereafter Gluc(-)) in strongly alkaline (pH > 12) aqueous solutions. The complex formation was proven via(27)Al and (1)H NMR, freezing-point depression, polarimetric measurements as well as potentiometric and conductometric titrations. This complexation is a pH independent process, i.e., a condensation reaction takes place. The stability constant of the complex formed was derived from (1)H NMR and polarimetric measurements, and was found to be log K = 2.4 ± 0.4. In the complex formed, Al(III) has a tetrahedral geometry, and the Al(OH)4(-) is most probably statistically distributed between the alcoholate groups of the Gluc(-). PMID:23897548

  16. A model of axial heterostructure formation in III-V semiconductor nanowires

    NASA Astrophysics Data System (ADS)

    Dubrovskii, V. G.

    2016-03-01

    A kinetic model of the formation of axial heterostructures in nanocrystalline wires (nanowires, NWs) of III-V semiconductor compounds growing according to the vapor-liquid-solid (VLS) mechanism is proposed. A general system of nonstationary equations for effective fluxes of two elements of the same group (e.g., group III) is formulated that allows the composition profile of a heterostructure to be calculated as a function of the coordinate and epitaxial growth conditions, including the flux of a group V element. Characteristic times of the composition relaxation, which determine the sharpness of the heteroboundary (heterointerface), are determined in the linear approximation. A temporal interruption (arrest) of fluxes during the switching of elements for a period exceeding these relaxation times must increase sharpness of the heteroboundary. Model calculations of the composition profile in a double GaAs/InAs/GaAs axial heterostructure have been performed for various NW radii.

  17. 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)

  18. The formation of Population III stars and their effect on cosmological structure in the early universe

    NASA Astrophysics Data System (ADS)

    O'Shea, Brian William

    2005-11-01

    The first generation of stars to form in the universe have a profound impact on their environment. These stars are responsible for beginning the universe's transition from a "cosmic dark age" where no sources of visible light existed; to the bright universe seen today. Additionally, these stars were believed to be the first sources of all elements heavier than lithium, which strongly affected the ability of gas to cool and permanently changed how star formation occurred. In this dissertation I present results from numerical simulations of the formation of the first generation of stars to form in the universe ("Population III" stars) and their effects on later structure formation. I compare Enzo, the adaptive mesh refinement cosmology code used to perform all of the simulations in this work, to GADGET, a smoothed particle hydrodynamics cosmology code. Nearly identical results can be obtained when using two extremely different numerical methods, which helps to verify the correctness of both codes and strengthen the confidence of predictions made with these tools. I perform high dynamical range calculations of the formation of an ensemble of Population III stars, varying multiple simulation parameters, in a standard cold dark matter cosmology as well as with a soft ultraviolet background and in a generic warm dark matter cosmology. I find that the accretion rates of primordial protostars have been systematically overestimated by previously published work, which has profound implications for later structure formation and the reionization of the universe. Additionally, the presence of a soft ultraviolet background and warm dark matter serves to delay the onset of star formation. I propose limits on the possible mass of a warm dark matter particle. I also present results of simulations which demonstrate the effects of the HII regions and metal enrichment from Population III stars. It appears that HII regions from these stars may hasten the formation of later generations

  19. Uniform Star Formation Efficiencies Are Due To Stabilised Galactic Disks

    NASA Astrophysics Data System (ADS)

    Meurer, Gerhardt R.; Wong, Ivy; Zheng, Zheng

    2015-08-01

    We present measurements of the star formation efficiencies (SFE here defined as SFR/M(HI)) of an HI selected sample of galaxies spanning four dex in HI mass. The sample covers a wide range of size, surface brightness, and star formation intensity, and yet a constant SFE with a scatter of 0.3 dex. We show that a model based on star formation in a constant stability disk, combined with other well known disk scaling relations, is able to successfully model the level and flatness of SFE as a function of halo circular velocity. This implies the properties of galaxies along the "main-sequence" of star forming galaxies is driven by the stabilisation galaxy disks within self-similar dark matter dominated halos.

  20. 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.

  1. Raising the Efficiency Ceiling with Multijunction III-V Concentrator Photovoltaics

    SciTech Connect

    King, R. R.; Boca, A.; Edmondson, K. M.; Romero, M. J.; Yoon, H.; Law, D. C.; Fetzer, C. M.; Haddad, M.; Zakaria, A.; Hong, W.; Mesropian, S.; Krut, D. D.; Kinsey, G. S.; Pien, R.; Sherif, R. A.; Karam, N. H.

    2008-01-01

    In this paper, we look at the question 'how high can solar cell efficiency go?' from both theoretical and experimental perspectives. First-principle efficiency limits are analyzed for some of the main candidates for high-efficiency multijunction terrestrial concentrator cells. Many of these cell designs use lattice-mismatched, or metamorphic semiconductor materials in order to tune subcell band gaps to the solar spectrum. Minority-carrier recombination at dislocations is characterized in GaInAs inverted metamorphic solar cells, with band gap ranging from 1.4 to 0.84 eV, by light I-V, electron-beam-induced current (EBIC), and cathodoluminescence (CL). Metamorphic solar cells with a 3-junction GaInP/ GaInAs/ Ge structure were the first cells to reach over 40% efficiency, with an independently confirmed efficiency of 40.7% (AM1.5D, low-AOD, 240 suns, 25 C). The high efficiency of present III-V multijunction cells now in high-volume production, and still higher efficiencies of next-generation cells, is strongly leveraging for low-cost terrestrial concentrator PV systems.

  2. 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.

  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. First-Generation Subporphyrinatoboron(III) Sensitizers Surpass the 10 % Power Conversion Efficiency Threshold.

    PubMed

    Copley, Graeme; Hwang, Daesub; Kim, Dongho; Osuka, Atsuhiro

    2016-08-22

    Subporphyrinatoboron(III) (SubB) sensitizers were synthesized for use in dye-sensitized solar cells (DSSCs). The prototype, which comprises a sterically demanding 3,5-di-tert-butylphenyl scaffold, a meso-ethynylphenyl spacer, and a cyanoacrylic acid anchoring group, achieved an open-circuit voltage VOC of 836 mV, short-circuit current density JSC of 15.3 mA cm(-2) , fill factor of 0.786, and a photon-to-current conversion efficiency of 10.1 %. Such astonishing figures suggest that a bright future lies ahead for SubB in the realm of DSSCs. PMID:27482949

  5. 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.

  6. Cerium(III) Complex Modified Gold Electrode: An Efficient Electrocatalyst for the Oxygen Evolution Reaction.

    PubMed

    Garain, Samiran; Barman, Koushik; Sinha, Tridib Kumar; Jasimuddin, Sk; Haeberle, Jörg; Henkel, Karsten; Schmeisser, Dieter; Mandal, Dipankar

    2016-08-24

    Exploring efficient and inexpensive electrocatalysts for the oxidation of water is of great importance for various electrochemical energy storage and conversion technologies. In the present study, a new water-soluble [Ce(III)(DMF) (HSO4)3] complex was synthesized and characterized by UV-vis, photoluminescence, and high-resolution X-ray photoelectron spectroscopy techniques. Owing to classic 5d → 4f transitions, an intense photoluminescence in the UV region was observed from the water-soluble [Ce(III)(DMF) (HSO4)3] complex. A stacking electrode was designed where self-assembled l-cysteine monolayer modified gold was immobilized with the synthesized cerium complex and was characterized by scanning electron microscopy, electrochemical impedance spectroscopy, and cyclic voltammetry. The resulting electrode, i.e., [Ce(III)(DMF) (HSO4)3]-l-cysteine-Au stacks shows high electrocatalytic water oxidation behavior at an overpotential of η ≈ 0.34 V under neutral pH conditions. We also demonstrated a way where the overpotential is possible to decrease upon irradiation of UV light. PMID:27490440

  7. Efficient Sporulation of Saccharomyces cerevisiae in a 96 Multiwell Format.

    PubMed

    Paulissen, Scott M; Huang, Linda S

    2016-01-01

    During times of nutritional stress, Saccharomyces cerevisiae undergoes gametogenesis, known as sporulation. Diploid yeast cells that are starved for nitrogen and carbon will initiate the sporulation process. The process of sporulation includes meiosis followed by spore formation, where the haploid nuclei are packaged into environmentally resistant spores. We have developed methods for the efficient sporulation of budding yeast in 96 multiwell plates, to increase the throughput of screening yeast cells for sporulation phenotypes. These methods are compatible with screening with yeast containing plasmids requiring nutritional selection, when appropriate minimal media is used, or with screening yeast with genomic alterations, when a rich presporulation regimen is used. We find that for this method, aeration during sporulation is critical for spore formation, and have devised techniques to ensure sufficient aeration that are compatible with the 96 multiwell plate format. Although these methods do not achieve the typical ~80% level of sporulation that can be achieved in large-volume flask based experiments, these methods will reliably achieve about 50-60% level of sporulation in small-volume multiwell plates. PMID:27684273

  8. Star Formation Efficiency in the Cool Cores of Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    McDonald, Michael; Veilleux, Sylvain; Rupke, David S. N.; Mushotzky, Richard; Reynolds, Christopher

    2011-06-01

    We have assembled a sample of high spatial resolution far-UV (Hubble Space Telescope Advanced Camera for Surveys/Solar Blind Channel) and Hα (Maryland-Magellan Tunable Filter) imaging for 15 cool core galaxy clusters. These data provide a detailed view of the thin, extended filaments in the cores of these clusters. Based on the ratio of the far-UV to Hα luminosity, the UV spectral energy distribution, and the far-UV and Hα morphology, we conclude that the warm, ionized gas in the cluster cores is photoionized by massive, young stars in all but a few (A1991, A2052, A2580) systems. We show that the extended filaments, when considered separately, appear to be star forming in the majority of cases, while the nuclei tend to have slightly lower far-UV luminosity for a given Hα luminosity, suggesting a harder ionization source or higher extinction. We observe a slight offset in the UV/Hα ratio from the expected value for continuous star formation which can be modeled by assuming intrinsic extinction by modest amounts of dust (E(B - V) ~ 0.2) or a top-heavy initial mass function in the extended filaments. The measured star formation rates vary from ~0.05 M sun yr-1 in the nuclei of non-cooling systems, consistent with passive, red ellipticals, to ~5 M sun yr-1 in systems with complex, extended, optical filaments. Comparing the estimates of the star formation rate based on UV, Hα, and infrared luminosities to the spectroscopically determined X-ray cooling rate suggests a star formation efficiency of 14+18 - 8%. This value represents the time-averaged fraction, by mass, of gas cooling out of the intracluster medium, which turns into stars and agrees well with the global fraction of baryons in stars required by simulations to reproduce the stellar mass function for galaxies. This result provides a new constraint on the efficiency of star formation in accreting systems.

  9. 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.

  10. COX7A2L Is a Mitochondrial Complex III Binding Protein that Stabilizes the III2+IV Supercomplex without Affecting Respirasome Formation.

    PubMed

    Pérez-Pérez, Rafael; Lobo-Jarne, Teresa; Milenkovic, Dusanka; Mourier, Arnaud; Bratic, Ana; García-Bartolomé, Alberto; Fernández-Vizarra, Erika; Cadenas, Susana; Delmiro, Aitor; García-Consuegra, Inés; Arenas, Joaquín; Martín, Miguel A; Larsson, Nils-Göran; Ugalde, Cristina

    2016-08-30

    Mitochondrial respiratory chain (MRC) complexes I, III, and IV associate into a variety of supramolecular structures known as supercomplexes and respirasomes. While COX7A2L was originally described as a supercomplex-specific factor responsible for the dynamic association of complex IV into these structures to adapt MRC function to metabolic variations, this role has been disputed. Here, we further examine the functional significance of COX7A2L in the structural organization of the mammalian respiratory chain. As in the mouse, human COX7A2L binds primarily to free mitochondrial complex III and, to a minor extent, to complex IV to specifically promote the stabilization of the III2+IV supercomplex without affecting respirasome formation. Furthermore, COX7A2L does not affect the biogenesis, stabilization, and function of the individual oxidative phosphorylation complexes. These data show that independent regulatory mechanisms for the biogenesis and turnover of different MRC supercomplex structures co-exist.

  11. COX7A2L Is a Mitochondrial Complex III Binding Protein that Stabilizes the III2+IV Supercomplex without Affecting Respirasome Formation.

    PubMed

    Pérez-Pérez, Rafael; Lobo-Jarne, Teresa; Milenkovic, Dusanka; Mourier, Arnaud; Bratic, Ana; García-Bartolomé, Alberto; Fernández-Vizarra, Erika; Cadenas, Susana; Delmiro, Aitor; García-Consuegra, Inés; Arenas, Joaquín; Martín, Miguel A; Larsson, Nils-Göran; Ugalde, Cristina

    2016-08-30

    Mitochondrial respiratory chain (MRC) complexes I, III, and IV associate into a variety of supramolecular structures known as supercomplexes and respirasomes. While COX7A2L was originally described as a supercomplex-specific factor responsible for the dynamic association of complex IV into these structures to adapt MRC function to metabolic variations, this role has been disputed. Here, we further examine the functional significance of COX7A2L in the structural organization of the mammalian respiratory chain. As in the mouse, human COX7A2L binds primarily to free mitochondrial complex III and, to a minor extent, to complex IV to specifically promote the stabilization of the III2+IV supercomplex without affecting respirasome formation. Furthermore, COX7A2L does not affect the biogenesis, stabilization, and function of the individual oxidative phosphorylation complexes. These data show that independent regulatory mechanisms for the biogenesis and turnover of different MRC supercomplex structures co-exist. PMID:27545886

  12. Acute physiology, age, and chronic health evaluation (APACHE) III score is an alternative efficient predictor of mortality in burn patients.

    PubMed

    Tanaka, Yohei; Shimizu, Mikio; Hirabayashi, Hidemitsu

    2007-05-01

    The present study was performed to evaluate the prognostic value of the acute physiology, age, chronic health evaluation (APACHE) III score in burn patients. We hypothesised that APACHE III score efficiently predicts mortality of burn patients as it reflects the physiological changes in the acute phase and the severity of the underlying illness. Data such as age, gender, inhalation injury, total burn surface area (TBSA), burn index (BI), prognostic burn index (PBI), APACHE III score and outcome of 105 hospitalised patients were analysed retrospectively. TBSA, BI, PBI, and APACHE III score in the mortality group were significantly higher than those of surviving group. The mean scores of surviving versus mortality groups were as follows: TBSA, 19.2+/-17.8% versus 69.1+/-28.4%, p<0.0001; BI, 12.8+/-13.1% versus 66.8+/-28.6%, p<0.0001; PBI, 68.8+/-26.0% versus 124.4+/-33.6%, p<0.0001; APACHE III score, 28.4+/-22.2% versus 71.3+/-32.1%, p<0.0001. PBI and APACHE III score showed marked associations between higher scores and higher mortality. APACHE III score showed a significant correlation with PBI (p<0.0001). The present study suggested that APACHE III score could be used as an alternative efficient predictor of mortality in burn patients.

  13. THE FORMATION OF MASSIVE POPULATION III STARS IN THE PRESENCE OF TURBULENCE

    SciTech Connect

    Latif, M. A.; Schleicher, D. R. G.; Schmidt, W.; Niemeyer, J.

    2013-07-20

    Population III stars forming in the infant universe at z = 30 heralded the end of the cosmic dark ages. They are presumed to be assembled in the so-called minihalos with virial temperatures of a few thousand K where collapse is triggered by molecular hydrogen cooling. A central question concerns their final masses, and whether fragmentation occurs during their formation. While studies employing Lagrangian codes suggest fragmentation via a self-gravitating disk, recent high-resolution simulations indicated that disk formation is suppressed. Here we report the first high-resolution large-eddy simulations performed with the Eulerian grid-based code Enzo following the evolution beyond the formation of the first peak to investigate the accretion of the central massive clump and potential fragmentation. For a total of three halos, we see that a disk forms around the first clump. The central clump reaches {approx}10 solar masses after 40 yr, while subsequent accretion is expected at a rate of 10{sup -2} solar masses per year. In one of these halos, additional clumps form as a result of fragmentation which proceeds at larger scales. We note that subgrid-scale (SGS) turbulence yields relevant contributions to the stability of the protostellar disks. Both with and without the SGS model, the disk evolution appears rather stable during the timescale considered here. We conclude that the first protostar may reach masses up to 40-100 M{sub Sun }, which are only limited by the effect of radiative feedback.

  14. CONFINED POPULATION III ENRICHMENT AND THE PROSPECTS FOR PROMPT SECOND-GENERATION STAR FORMATION

    SciTech Connect

    Ritter, Jeremy S.; Safranek-Shrader, Chalence; Milosavljevic, Milos; Bromm, Volker; Gnat, Orly

    2012-12-10

    It is widely recognized that nucleosynthetic output of the first Population III supernovae was a catalyst defining the character of subsequent stellar generations. Most of the work on the earliest enrichment was carried out assuming that the first stars were extremely massive and that the associated supernovae were unusually energetic, enough to completely unbind the baryons in the host cosmic minihalo and disperse the synthesized metals into the intergalactic medium. Recent work, however, suggests that the first stars may in fact have been somewhat less massive, with a characteristic mass scale of a few tens of solar masses. We present a cosmological simulation following the transport of the metals synthesized in a Population III supernova assuming that it had an energy of 10{sup 51} erg, compatible with standard Type II supernovae. A young supernova remnant is inserted in the first star's relic H II region in the free expansion phase and is followed for 40 Myr employing adaptive mesh refinement and Lagrangian tracer particle techniques. The supernova remnant remains partially trapped within the minihalo, and the thin snowplow shell develops pronounced instability and fingering. Roughly half of the ejecta turn around and fall back toward the center of the halo, with 1% of the ejecta reaching the center in {approx}30 kyr and 10% in {approx}10 Myr. The average metallicity of the combined returning ejecta and the pristine filaments feeding into the halo center from the cosmic web is {approx}0.001-0.01 Z{sub Sun }, but the two remain unmixed until accreting onto the central hydrostatic core that is unresolved at the end of the simulation. We conclude that if Population III stars had less extreme masses, they promptly enriched the host minihalos with metals and triggered Population II star formation.

  15. 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

  16. Complex Formation Between Ca(II), Mg(II), Al(III) Ions and Salicylglycine

    PubMed Central

    Kilyén, Melinda; Labádi, lmre; Tombácz, Etelka; Kiss, Tamás

    2003-01-01

    For modelling the interactions of proteins/peptides with hard metal ions the complex formation of salicylglycine (SalGly) with Ca(II), Mg(ll) and AI(III) ions was studied in aqueous solution using pHpotentiometric and UV-vis spectroscopic techniques. Al(lll) ion was found to form more stable complexes with SalGiy than Ca(ll) or Mg(ll) ions. While AI(III) ion forms various 1:1 complexes of different protonation states in the pH range 2-7, Ca(ll), Mg(ll) ions seem to interact with SalGly only in the basic pH range and form mixed hydroxo species MLH-1 at pH ~ 8. According to the UV-vis spectroscopic measurements in the species MLH-1 the carboxylate-O- atom and the phenolate-O- coordinate to the metal ions. SaIGiy is able to keep Al(lll) in solution through inner and outer sphere coordination to metastable amorphous AI(OH)3 particles. Deprotonation of the peptide amide Nil does not occur in these systems. PMID:18365063

  17. Star formation efficiency along the radio jet in Centaurus A

    NASA Astrophysics Data System (ADS)

    Salomé, Q.; Salomé, P.; Combes, F.; Hamer, S.; Heywood, I.

    2016-02-01

    NGC 5128 (also known as Centaurus A) is the most nearby powerful AGN, widely studied at all wavelengths. Molecular gas has been found in the halo at a distance of ~ 20 kpc from the galaxy center, associated with H i shells, through CO line detection at SEST (Charmandaris et al. 2000, A&A, 356, L1). The molecular gas lies inside some IR and UV bright star-forming filaments that have recently been observed in the direction of the radio jets. These archival data from GALEX (FUV) and Herschel (IR) show that there is dust and very weak star formation (a few 10-5-10-4M⊙ yr-1) on scales of hundreds of parsecs. NGC 5128 is thus a perfect target for detailed studies of the star formation processes at the interface of the jet/gas interaction. On top of analysing combined archival data, we have performed searches of HCN(1-0) and HCO+(1-0) emission with ATCA at the interaction of the northern filaments and the northern H i shell of Centaurus A. Measuring the dense gas is another indicator of star formation efficiency inside the filaments. However, we only derived upper limits L'HCN < 1.6×103 K km s-1 pc2 and L'HCO < 1.6×103 K km s-1 pc2 at 3σ in the synthesised beam of 3.1''. Compared with the CO luminosity, this lead to a dense-to-molecular gas fraction < 23%. We also compared the CO masses with the star formation rate estimates in order to measure a star formation efficiency. Using a standard conversion factor leads to long depletion times (7 Gyr). We then corrected the mass estimates from metallicity effect by using gas-to-dust mass ratio as a proxy. From MUSE data, we estimated the metallicity spread (0.4-0.8Z⊙) in an other region of the filament, that corresponds to gas-to-dust ratios of ~200-400. Assuming the same metallicity range in the CO-detected part of the filament, the CO/H2 conversion ratio is corrected for low metallicity by a factor between 1.4 and 3.2. Such a low-metallicity correction leads to even more massive clouds with higher depletion times (16

  18. 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.

  19. The Arabidopsis Endosomal Sorting Complex Required for Transport III Regulates Internal Vesicle Formation of the Prevacuolar Compartment and Is Required for Plant Development1[C][W][OPEN

    PubMed Central

    Cai, Yi; Zhuang, Xiaohong; Gao, Caiji; Wang, Xiangfeng; Jiang, Liwen

    2014-01-01

    We have established an efficient transient expression system with several vacuolar reporters to study the roles of endosomal sorting complex required for transport (ESCRT)-III subunits in regulating the formation of intraluminal vesicles of prevacuolar compartments (PVCs)/multivesicular bodies (MVBs) in plant cells. By measuring the distributions of reporters on/within the membrane of PVC/MVB or tonoplast, we have identified dominant negative mutants of ESCRT-III subunits that affect membrane protein degradation from both secretory and endocytic pathways. In addition, induced expression of these mutants resulted in reduction in luminal vesicles of PVC/MVB, along with increased detection of membrane-attaching vesicles inside the PVC/MVB. Transgenic Arabidopsis (Arabidopsis thaliana) plants with induced expression of ESCRT-III dominant negative mutants also displayed severe cotyledon developmental defects with reduced cell size, loss of the central vacuole, and abnormal chloroplast development in mesophyll cells, pointing out an essential role of the ESCRT-III complex in postembryonic development in plants. Finally, membrane dissociation of ESCRT-III components is important for their biological functions and is regulated by direct interaction among Vacuolar Protein Sorting-Associated Protein20-1 (VPS20.1), Sucrose Nonfermenting7-1, VPS2.1, and the adenosine triphosphatase VPS4/SUPPRESSOR OF K+ TRANSPORT GROWTH DEFECT1. PMID:24812106

  20. Local Luminous Infrared Galaxies. III. Co-evolution of Black Hole Growth and Star Formation Activity?

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

    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 × 107 M ⊙ using [Ne III] 15.56 μm and optical [O III] λ5007 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 ~1.5 kpc region, as estimated from the nuclear 11.3 μm 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. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under NASA contract 1407.

  1. 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.

  2. 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.

  3. 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

  4. 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

  5. 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

    2015-01-01

    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) 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.

  6. 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.

  7. Complex formation reactions of lanthanum(III), cerium(III), thorium(IV), dioxouranyl(IV) complexes with tricine.

    PubMed

    Mohamed, Mahmoud M A

    2007-08-01

    Equilibrium studies for the heavy metal ions La(III), Ce(III), Th(IV) and UO2(IV) (M) complexes of the zwitterionic buffer tricine (L) in aqueous solution are investigated. Stoichiometry and stability constants for the different complexes formed as well as hydrolysis products of the metal cations are determined at 25 degrees C and ionic strength 0.1 M NaNO3. The stability of the formed complexes are discussed in terms of the nature of the heavy metal cation. The solid complexes are synthesized and characterized by means of elemental analysis, FTIR, and TG analysis. The general molecular formulae of the obtained complexes is suggested to be [M(L)2](NO3)n-2(H2O)x, where n = the charge of the metal cation, x = no. of water molecules.

  8. Efficient, tunable flip-chip-integrated III-V/Si hybrid external-cavity laser array.

    PubMed

    Lin, Shiyun; Zheng, Xuezhe; Yao, Jin; Djordjevic, Stevan S; Cunningham, John E; Lee, Jin-Hyoung; Shubin, Ivan; Luo, Ying; Bovington, Jock; Lee, Daniel Y; Thacker, Hiren D; Raj, Kannan; Krishnamoorthy, Ashok V

    2016-09-19

    We demonstrate a surface-normal coupled tunable hybrid silicon laser array for the first time using passively-aligned, high-accuracy flip chip bonding. A 2x6 III-V reflective semiconductor optical amplifier (RSOA) array with integrated total internal reflection mirrors is bonded to a CMOS SOI chip with grating couplers and silicon ring reflectors to form a tunable hybrid external-cavity laser array. Waveguide-coupled wall plug efficiency (wcWPE) of 2% and output power of 3 mW has been achieved for all 12 lasers. We further improved the performance by reducing the thickness of metal/dielectric stacks and achieved 10mW output power and 5% wcWPE with the same integration techniques. This non-invasive, one-step back end of the line (BEOL) integration approach provides a promising solution to high density laser sources for future large-scale photonic integrated circuits. PMID:27661885

  9. 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.

  10. Efficient, tunable flip-chip-integrated III-V/Si hybrid external-cavity laser array.

    PubMed

    Lin, Shiyun; Zheng, Xuezhe; Yao, Jin; Djordjevic, Stevan S; Cunningham, John E; Lee, Jin-Hyoung; Shubin, Ivan; Luo, Ying; Bovington, Jock; Lee, Daniel Y; Thacker, Hiren D; Raj, Kannan; Krishnamoorthy, Ashok V

    2016-09-19

    We demonstrate a surface-normal coupled tunable hybrid silicon laser array for the first time using passively-aligned, high-accuracy flip chip bonding. A 2x6 III-V reflective semiconductor optical amplifier (RSOA) array with integrated total internal reflection mirrors is bonded to a CMOS SOI chip with grating couplers and silicon ring reflectors to form a tunable hybrid external-cavity laser array. Waveguide-coupled wall plug efficiency (wcWPE) of 2% and output power of 3 mW has been achieved for all 12 lasers. We further improved the performance by reducing the thickness of metal/dielectric stacks and achieved 10mW output power and 5% wcWPE with the same integration techniques. This non-invasive, one-step back end of the line (BEOL) integration approach provides a promising solution to high density laser sources for future large-scale photonic integrated circuits.

  11. The OGLE-III planet detection efficiency from six years of microlensing observations (2003-2008)

    NASA Astrophysics Data System (ADS)

    Tsapras, Y.; Hundertmark, M.; Wyrzykowski, Ł.; Horne, K.; Udalski, A.; Snodgrass, C.; Street, R.; Bramich, D. M.; Dominik, M.; Bozza, V.; Figuera Jaimes, R.; Kains, N.; Skowron, J.; Szymański, M. K.; Pietrzyński, G.; Soszyński, I.; Ulaczyk, K.; Kozłowski, S.; Pietrukowicz, P.; Poleski, R.

    2016-04-01

    We use six years (2003-2008) of Optical Gravitational Lensing Experiment-III microlensing observations to derive the survey detection efficiency for a range of planetary masses and projected distances from the host star. We perform an independent analysis of the microlensing light curves to extract the event parameters and compute the planet detection probability given the data. 2433 light curves satisfy our quality selection criteria and are retained for further processing. The aggregate of the detection probabilities over the range explored yields the expected number of microlensing planet detections. We employ a Galactic model to convert this distribution from dimensionless to physical units, α/au and M⊕. The survey sensitivity to small planets is highest in the range 1-4 au, shifting to slightly larger separations for more massive ones.

  12. Ethanol oxidation by imidorhenium(V) complexes: formation of amidorhenium(III) complexes.

    PubMed

    Suing, A L; Dewan, C R; White, P S; Thorp, H H

    2000-12-25

    The reaction of Re(NC6H4R)Cl3(PPh3)2 (R = H, 4-Cl, 4-OMe) with 1,2-bis(diphenylphosphino)ethane (dppe) is investigated in refluxing ethanol. The reaction produces two major products, Re(NC6H4R)Cl(dppe)(2)2+ (R = H, 1-H; R = Cl, 1-Cl; R = OMe, 1-OMe) and the rhenium(III) species Re(NHC6H4R)Cl(dppe)2+ (R = H, 2-H; R = Cl, 2-Cl). Complexes 1-H (orthorhombic, Pcab, a = 22.3075(10) A, b = 23.1271(10) A, c = 23.3584(10) A, Z = 8), 1-Cl (triclinic, P1, a = 11.9403(6) A, b = 14.6673(8) A, c = 17.2664(9) A, alpha = 92.019(1) degrees, beta = 97.379(1) degrees, gamma = 90.134(1) degrees, Z = 2), and 1-OMe (triclinic, P1, a = 11.340(3) A, b = 13.134(4) A, c = 13.3796(25) A, alpha = 102.370(20) degrees, beta = 107.688(17) degrees, gamma = 114.408(20) degrees, Z = 1) are crystallographically characterized and show an average Re-N bond length (1.71 A) typical of imidorhenium(V) complexes. There is a small systematic decrease in the Re-N bond length on going from Cl to H to OMe. Complex 2-Cl (monoclinic, Cc, a = 24.2381(11) A, b = 13.4504(6) A, c = 17.466(8) A, beta = 97.06900(0) degrees, Z = 4) is also crystallographically characterized and shows a Re-N bond length (1.98 A) suggestive of amidorhenium(III). The rhenium(III) complexes exhibit unusual proton NMR spectra where all of the resonances are found at expected locations except those for the amido protons, which are at 37.8 ppm for 2-Cl and 37.3 ppm for 1-H. The phosphorus resonances are also unremarkable, but the 13C spectrum of 2-Cl shows a significantly shifted resonance at 177.3 ppm, which is assigned to the ipso carbon of the phenylamido ligand. The extraordinary shifts of the amido hydrogen and ipso carbon are attributed to second-order magnetism that is strongly focused along the axially compressed amido axis. The reducing equivalents for the formation of the Re(III) product are provided by oxidation of the ethanol solvent, which produces acetal and acetaldehyde in amounts as much as 30 equiv based on the quantity of

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Rapid and efficient sonochemical formation of gold nanoparticles under ambient conditions using functional alkoxysilane.

    PubMed

    Wei, Ming-Yuan; Famouri, Leila; Carroll, Lloyd; Lee, Yongkuk; Famouri, Parviz

    2013-01-01

    Gold nanoparticles (NPs) are rapidly and efficiently formed under ambient conditions with a novel and highly-efficient sonochemical promoter. Despite of the presence of free oxygen, 3-glycidoxypropyltrimethoxysilane (GPTMS) showed remarkable efficiency in promoting the reduction rate of Au (III) than that of conventional promoters (primary alcohols). This is likely attributed to the formation of a variety of radical scavengers, which are alcoholic products from sonochemical hydrolysis of the epoxide group and methoxysilane moieties of GPTMS under weakly acidic conditions. Interestingly, the promotion is quenched by amine- or thiol-functionalized alkoxysilane, thereby producing marginal amounts of gold NPs. Furthermore, products of hydrolyzed GPTMS were confirmed to attach on the surface of gold NPs by attenuated total reflectance-Fourier transform infrared spectroscopy. However, according to transmission electron microscopy images, gold NPs that were produced in the presence of GPTMS tend to fuse with each other as condensation of silanols occurs, forming worm- or nugget-like gold nanostructures. The use of long chain surfactants (i.e. polyethylene glycol terminated with hydroxyl or carboxyl) inhibited the fusion, leading to mono-dispersed gold NPs. Additionally, the fact that this approach requires neither an ultrasound source with high frequency nor anaerobic conditions provides a huge advantage. These findings could potentially open an avenue for rapid and large-scale green-synthesis of gold NPs in future work. PMID:22938998

  19. Characterizing uniform star formation efficiencies with marginally stable galactic discs

    NASA Astrophysics Data System (ADS)

    Wong, O. Ivy; Meurer, G. R.; Zheng, Z.; Heckman, T. M.; Thilker, D. A.; Zwaan, M. A.

    2016-07-01

    We examine the H I-based star formation efficiency (SFE_{{H I}}), the ratio of star formation rate to the atomic hydrogen (H I) mass, in the context of a constant stability star-forming disc model. Our observations of H I-selected galaxies show SFE_{{H I}} to be fairly constant (log SFE_{{H I}}=-9.65 yr-1 with a dispersion of 0.3 dex) across ˜5 orders of magnitude in stellar masses. We present a model to account for this result, whose main principle is that the gas within galaxies forms a uniform stability disc and that stars form within the molecular gas in this disc. We test two versions of the model differing in the prescription that determines the molecular gas fraction, based on either the hydrostatic pressure or the stellar surface density of the disc. For high-mass galaxies such as the Milky Way, we find that either prescription predicts SFE_{{H I}} similar to the observations. However, the hydrostatic pressure prescription is a more accurate SFE_{{H I}} predictor for low-mass galaxies. Our model is the first model that links the uniform SFE_{{H I}} observed in galaxies at low redshifts to star-forming discs with constant marginal stability. While the rotational amplitude Vmax is the primary driver of disc structure in our model, we find that the specific angular momentum of the galaxy may play a role in explaining a weak correlation between SFE_{{H I}} and effective surface brightness of the disc.

  20. 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.

  1. Phenolic lipid synthesis by type III polyketide synthases is essential for cyst formation in Azotobacter vinelandii.

    PubMed

    Funa, Nobutaka; Ozawa, Hiroki; Hirata, Aiko; Horinouchi, Sueharu

    2006-04-18

    Cysts of Azotobacter vinelandii are resting cells that are surrounded by a protective coat, conferring resistance to various chemical and physical agents. The major chemical components of the cyst coat are alkylresorcinols, which are amphiphilic molecules possessing an aromatic ring with a long aliphatic carbon chain. Although alkylresorcinols are widely distributed in bacteria, fungi, plants, and animals, no enzyme systems for their biosynthesis are known. We report here an ars operon in A. vinelandii that is responsible for the biosynthesis of the alkylresorcinols in the cysts. The ars operon consisted of four genes, two of which encoded a type III polyketide synthase, ArsB and ArsC. In vitro experiments revealed that ArsB and ArsC, sharing 71% amino acid sequence identity, were an alkylresorcinol synthase and an alkylpyrone synthase, respectively, indicating that ArsB and ArsC are not isozymes but enzymatically distinct polyketide synthases. In addition, ArsB and ArsC accepted several acyl-CoAs with various lengths of the side chain as a starter substrate and gave corresponding alkylresorcinols and alkylpyrones, respectively, which suggests that the mode of the ring folding is uninfluenced by the structure of the starter substrates. The importance of the alkylresorcinols for encystment was confirmed by gene inactivation experiments; the lack of alkylresorcinols synthesis caused by ars mutations resulted in the formation of severely impaired cysts, as observed by electron microscopy.

  2. Propionibacterium-Produced Coproporphyrin III Induces Staphylococcus aureus Aggregation and Biofilm Formation

    PubMed Central

    Wollenberg, Michael S.; Claesen, Jan; Escapa, Isabel F.; Aldridge, Kelly L.; Fischbach, Michael A.

    2014-01-01

    ABSTRACT The majority of bacteria detected in the nostril microbiota of most healthy adults belong to three genera: Propionibacterium, Corynebacterium, and Staphylococcus. Among these staphylococci is the medically important bacterium Staphylococcus aureus. Almost nothing is known about interspecies interactions among bacteria in the nostrils. We observed that crude extracts of cell-free conditioned medium from Propionibacterium spp. induce S. aureus aggregation in culture. Bioassay-guided fractionation implicated coproporphyrin III (CIII), the most abundant extracellular porphyrin produced by human-associated Propionibacterium spp., as a cause of S. aureus aggregation. This aggregation response depended on the CIII dose and occurred during early stationary-phase growth, and a low pH (~4 to 6) was necessary but was not sufficient for its induction. Additionally, CIII induced plasma-independent S. aureus biofilm development on an abiotic surface in multiple S. aureus strains. In strain UAMS-1, CIII stimulation of biofilm depended on sarA, a key biofilm regulator. This study is one of the first demonstrations of a small-molecule-mediated interaction among medically relevant members of the nostril microbiota and the first description of a role for CIII in bacterial interspecies interactions. Our results indicate that CIII may be an important mediator of S. aureus aggregation and/or biofilm formation in the nostril or other sites inhabited by Propionibacterium spp. and S. aureus. PMID:25053784

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. Water formation at low temperatures by surface O2 hydrogenation III: Monte Carlo simulation.

    PubMed

    Lamberts, Thanja; Cuppen, Herma M; Ioppolo, Sergio; Linnartz, Harold

    2013-06-01

    Water is the most abundant molecule found in interstellar icy mantles. In space it is thought to be efficiently formed on the surfaces of dust grains through successive hydrogenation of O, O2 and O3. The underlying physico-chemical mechanisms have been studied experimentally in the past decade and in this paper we extend this work theoretically, using Continuous-Time Random-Walk Monte Carlo simulations to disentangle the different processes at play during hydrogenation of molecular oxygen. CTRW-MC offers a kinetic approach to compare simulated surface abundances of different species to the experimental values. For this purpose, the results of four key experiments-sequential hydrogenation as well as co-deposition experiments at 15 and 25 K-are selected that serve as a reference throughout the modeling stage. The aim is to reproduce all four experiments with a single set of parameters. Input for the simulations consists of binding energies as well as reaction barriers (activation energies). In order to understand the influence of the parameters separately, we vary a single process rate at a time. Our main findings are: (i) The key reactions for the hydrogenation route starting from O2 are H + O2, H + HO2, OH + OH, H + H2O2, H + OH. (ii) The relatively high experimental abundance of H2O2 is due to its slow destruction. (iii) The large consumption of O2 at a temperature of 25 K is due to a high hydrogen diffusion rate. (iv) The diffusion of radicals plays an important role in the full reaction network. The resulting set of 'best fit' parameters is presented and discussed for use in future astrochemical modeling.

  8. 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.

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

    PubMed

    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 SO4(2-) 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 SO4(2-) 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

  10. 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

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

    PubMed

    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

    2016-05-18

    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 SO4(2-) 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 SO4(2-) 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.

  12. Reactivity of Cys4 zinc finger domains with gold(III) complexes: insights into the formation of "gold fingers".

    PubMed

    Jacques, Aurélie; Lebrun, Colette; Casini, Angela; Kieffer, Isabelle; Proux, Olivier; Latour, Jean-Marc; Sénèque, Olivier

    2015-04-20

    Gold(I) complexes such as auranofin or aurothiomalate have been used as therapeutic agents for the treatment of rheumatoid arthritis for several decades. Several gold(I) and gold(III) complexes have also shown in vitro anticancer properties against human cancer cell lines, including cell lines resistant to cisplatin. Because of the thiophilicity of gold, cysteine-containing proteins appear as likely targets for gold complexes. Among them, zinc finger proteins have attracted attention and, recently, gold(I) and gold(III) complexes have been shown to inhibit poly(adenosine diphosphate ribose)polymerase-1 (PARP-1), which is an essential protein involved in DNA repair and in cancer resistance to chemotherapies. In this Article, we characterize the reactivity of the gold(III) complex [Au(III)(terpy)Cl]Cl2 (Auterpy) with a model of Zn(Cys)4 "zinc ribbon" zinc finger by a combination of absorption spectroscopy, circular dichroism, mass spectrometry, high-performance liquid chromatography analysis, and X-ray absorption spectroscopy. We show that the Zn(Cys)4 site of Zn·LZR is rapidly oxidized by Auterpy to form a disulfide bond. The Zn(2+) ion is released, and the two remaining cysteines coordinate the Au(+) ion that is produced during the redox reaction. Subsequent oxidation of these cysteines can take place in conditions of excess gold(III) complex. In the presence of excess free thiols mimicking the presence of glutathione in cells, mixing of the zinc finger model and gold(III) complex yields a different product: complex (Au(I))2·LZR with two Au(+) ions bound to cysteines is formed. Thus, on the basis of detailed speciation and kinetic measurements, we demonstrate herein that the destruction of Zn(Cys)4 zinc fingers by gold(III) complexes to achieve the formation of "gold fingers" is worth consideration, either directly or mediated by reducing agents.

  13. Sunlight-driven formation and dissociation of a dynamic mixed-valence thallium(III)/thallium(I) porphyrin complex.

    PubMed

    Ndoyom, Victoria; Fusaro, Luca; Dorcet, Vincent; Boitrel, Bernard; Le Gac, Stéphane

    2015-03-16

    Inspired by a Newton's cradle device and interested in the development of redox-controllable bimetallic molecular switches, a mixed-valence thallium(III)/thallium(I) bis-strap porphyrin complex, with Tl(III) bound out of the plane of the N core and Tl(I) hung to a strap on the opposite side, was formed by the addition of TlOAc to the free base and exposure to indirect sunlight. In this process, oxygen photosensitization by the porphyrin allows the oxidation of Tl(I) to Tl(III). The bimetallic complex is dynamic as the metals exchange their positions symmetrically to the porphyrin plane with Tl(III) funneling through the macrocycle. Further exposure of the complex to direct sunlight leads to thallium dissociation and to total recovery of the free base. Hence, the porphyrin plays a key role at all stages of the cycle of the complex: It hosts two metal ions, and by absorbing light, it allows the formation and dissociation of Tl(III). These results constitute the basis for the further design of innovative light-driven bimetallic molecular devices.

  14. Formation of a compact toroid for enhanced efficiency

    SciTech Connect

    Mozgovoy, A. G.; Romadanov, I. V.; Ryzhkov, S. V.

    2014-02-15

    We report here our results on the formation of a plasma configuration with the generic name of compact toroid (CT). A method of compact toroid formation to confine, heat and compress a plasma is investigated. Formation of a compact torus using an additional toroidal magnetic field helps to increase the plasma current to a maintainable level of the original magnetic field. We design the Compact Toroid Challenge (CTC) experiment in order to improve the magnetic flux trapping during field reversal in the formation of a compact toroid. The level of the magnetic field immersed in the plasma about 70% of the primary field is achieved. The CTC device and scheme of high level capturing of magnetic flux are presented.

  15. Highly efficient phosphorescent materials based on Ir(iii) complexes-grafted on a polyhedral oligomeric silsesquioxane core.

    PubMed

    Yu, Tianzhi; Xu, Zixuan; Su, Wenming; Zhao, Yuling; Zhang, Hui; Bao, Yanjun

    2016-09-14

    A new iridium(iii) complex containing a coumarin derivative as the cyclometalated ligand (L) and a carbazole-functionalized β-diketonate (Cz-acac-allyl) as the ancillary ligand, namely, Ir(iii) bis(3-(pyridin-2-yl)coumarinato-N,C(4))(1-(9-butyl-9H-carbazol-3-yl)hept-6-ene-1,3-dionato-O,O) [Ir(L)2(Cz-acac-allyl)], was firstly synthesized as the emissive iridium(iii) complex. Then three new phosphorescent polyhedral oligomeric silsesquioxane (POSS) materials, consisting of the emissive Ir(iii) complex and carbazole moieties covalently attached to a polyhedral oligomeric silsesquioxane (POSS) core were successfully synthesized by hydrosilylation reaction in the presence of platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane (Pt-dvs) as the catalyst. These phosphorescent POSS materials offer many advantages including amorphous properties, good thermal stabilities, and good solubility in common solvents, and high purity via column chromatography. The photoluminescence spectra of the POSS materials in solution and in the solid state indicate a reduction in the degrees of interactions among the Ir(iii) complex units and concentration quenching due to the bulky POSS core. Solution processed light-emitting devices based on these phosphorescent POSS materials exhibit a maximum external quantum efficiency (EQE) of 9.77%. PMID:27501335

  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

    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.

  18. FUEL EFFICIENT GALAXIES: SUSTAINING STAR FORMATION WITH STELLAR MASS LOSS

    SciTech Connect

    Leitner, Samuel N.; Kravtsov, Andrey V.

    2011-06-10

    We examine the importance of secular stellar mass loss for fueling ongoing star formation in disk galaxies during the late stages of their evolution. For a galaxy of a given stellar mass, we calculate the total mass loss rate of its entire stellar population using star formation histories derived from the observed evolution of the M{sub *}-star formation rate (SFR) relation, along with the predictions of standard stellar evolution models for stellar mass loss for a variety of initial stellar mass functions. Our model shows that recycled gas from stellar mass loss can provide most or all of the fuel required to sustain the current level of star formation in late-type galaxies. Stellar mass loss can therefore remove the tension between the low gas infall rates that are derived from observations and the relatively rapid star formation occurring in disk galaxies. For galaxies where cold gas infall rates have been estimated, we demonstrate explicitly that stellar mass loss can account for most of the deficit between their SFR and infall rate.

  19. Recyclable hypervalent iodine(III) reagent iodosodilactone as an efficient coupling reagent for direct esterification, amidation, and peptide coupling.

    PubMed

    Tian, Jun; Gao, Wen-Chao; Zhou, Dong-Mei; Zhang, Chi

    2012-06-15

    A hypervalent iodine(III) reagent plays a novel role as an efficient coupling reagent to promote the direct condensation between carboxylic acids and alcohols or amines to provide esters, macrocyclic lactones, amides, as well as peptides without racemization. The regeneration of iodosodilactone (1) can also be readily achieved. The intermediate acyloxyphosphonium ion C from the activation of a carboxylic acid is thought to be involved in the present esterification reaction.

  20. Molecular cloud formation and the star formation efficiency in M 33. Molecule and star formation in M 33

    NASA Astrophysics Data System (ADS)

    Braine, J.; Gratier, P.; Kramer, C.; Schuster, K. F.; Tabatabaei, F.; Gardan, E.

    2010-09-01

    Does star formation proceed in the same way in large spirals such as the Milky Way and in smaller chemically younger galaxies? Earlier work suggests a more rapid transformation of H2 into stars in these objects but (1) a doubt remains about the validity of the H2 mass estimates and (2) there is currently no explanation for why star formation should be more efficient. M 33, a local group spiral with a mass ~10% and a metallicity half that of the Galaxy, represents a first step towards the metal poor Dwarf Galaxies. We have searched for molecular clouds in the outer disk of M 33 and present here a set of detections of both 12CO and 13CO, including the only detections (for both lines) beyond the R25 radius in a subsolar metallicity galaxy. The spatial resolution enables mass estimates for the clouds and thus a measure of the N(H2)/ICO ratio, which in turn enables a more reliable calculation of the H2 mass. Our estimate for the outer disk of M 33 is N(H2)/ICO(1-0) ~ 5 × 1020 cm-2/(K km s-1) with an estimated uncertainty of a factor ≤2. While the 12/13CO line ratios do not provide a reliable measure of N(H2)/ICO, the values we find are slightly greater than Galactic and corroborate a somewhat higher N(H2)/ICO value. Comparing the CO observations with other tracers of the interstellar medium, no reliable means of predicting where CO would be detected was identified. In particular, CO detections were often not directly on local HI or FIR or Hα peaks, although generally in regions with FIR emission and high HI column density. The results presented here provide support for the quicker transformation of H2 into stars in M 33 than in large local universe spirals.

  1. Synthetic RNA Polymerase III Promoters Facilitate High-Efficiency CRISPR-Cas9-Mediated Genome Editing in Yarrowia lipolytica.

    PubMed

    Schwartz, Cory M; Hussain, Murtaza Shabbir; Blenner, Mark; Wheeldon, Ian

    2016-04-15

    The oleaginous yeast Yarrowia lipolytica is a valuable microbial host for chemical production because it has a high capacity to synthesize, modify, and store intracellular lipids; however, rapid strain development has been hampered by the limited availability of genome engineering tools. We address this limitation by adapting the CRISPR-Cas9 system from Streptococcus pyogenes for markerless gene disruption and integration in Y. lipolytica. Single gene disruption efficiencies of 92% and higher were achieved when single guide RNAs (sgRNA) were transcribed with synthetic hybrid promoters that combine native RNA polymerase III (Pol III) promoters with tRNA. The Pol III-tRNA hybrid promoters exploit endogenous tRNA processing to produce mature sgRNA for Cas9 targeting. The highest efficiencies were achieved with a SCR1'-tRNA(Gly) promoter and Y. lipolytica codon-optimized Cas9 expressed from a UAS1B8-TEF promoter. Cotransformation of the Cas9 and sgRNA expressing plasmid with a homologous recombination donor plasmid resulted in markerless homologous recombination efficiency of over 64%. Homologous recombination was observed in 100% of transformants when nonhomologous end joining was disrupted. The end result of these studies was the development of pCRISPRyl, a modular tool for markerless gene disruption and integration in Y. lipolytica.

  2. Efficient suppression of biofilm formation by a nucleic acid aptamer.

    PubMed

    Ning, Yi; Cheng, Lijuan; Ling, Min; Feng, Xinru; Chen, Lingli; Wu, Minxi; Deng, Le

    2015-08-01

    Biofilms are microbial communities that are attached to a solid surface using extracellular polymeric substances. Motility and initial attachment mediated by flagella are required for biofilm formation. Therefore, blocking the motility of flagella is a potential strategy to inhibit biofilm formation. In this study, single-stranded DNA aptamers specific to the Salmonella choleraesuis were selected after 14 cycles of the systematic evolution of ligands by exponential enrichment. Among the selected aptamers, the aptamer 3 showed the highest affinity for S. choleraesuis with a dissociation constant (Kd) of 41 ± 2 nM. Aptamer 3, conjugated with magnetic beads, was then used to capture its binding target on the bacteria. After mass spectrometry and specific binding analysis, the flagellin was identified as the target captured by aptamer 3. Furthermore, inhibition experiments, inverted microscopy and atomic force microscopy demonstrated that aptamer 3 was able to control the biofilm formation and promote the inhibitory effect of an antibiotic on bacterial biofilms. Single-stranded DNA aptamers therefore have great potential as inhibitors of biofilm formation.

  3. 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.

  4. 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

  5. Dark-matter halo mergers as a fertile environment for low-mass Population III star formation

    NASA Astrophysics Data System (ADS)

    Bovino, S.; Latif, M. A.; Grassi, T.; Schleicher, D. R. G.

    2014-07-01

    While Population III (Pop III) stars are typically thought to be massive, pathways towards lower mass Pop III stars may exist when the cooling of the gas is particularly enhanced. A possible route is enhanced HD cooling during the merging of dark-matter haloes. The mergers can lead to a high ionization degree catalysing the formation of HD molecules and may cool the gas down to the cosmic microwave background temperature. In this paper, we investigate the merging of mini-haloes with masses of a few 105 M⊙ and explore the feasibility of this scenario. We have performed three-dimensional cosmological hydrodynamics calculations with the ENZO code, solving the thermal and chemical evolution of the gas by employing the astrochemistry package KROME. Our results show that the HD abundance is increased by two orders of magnitude compared to the no-merging case and the halo cools down to ˜60 K triggering fragmentation. Based on Jeans estimates, the expected stellar masses are about 10 M⊙. Our findings show that the merging scenario is a potential pathway for the formation of low-mass stars.

  6. The N-terminal domain of antithrombin-III is essential for heparin binding and complex-formation with, but not cleavage by, alpha-thrombin.

    PubMed Central

    Austin, R C; Sheffield, W P; Rachubinski, R A; Blajchman, M A

    1992-01-01

    Normal and mutant forms of human antithrombin-III (AT-III) were synthesized in a cell-free system in order to identify putative functional domains required for heparin binding and complex-formation with alpha-thrombin. Heparin-Sepharose chromatography resulted in the elution of approx. 70% of cell-free-derived normal AT-III-(1-432)-polypeptide as a peak between 0.2 M- and 0.7 M-NaCl. The cell-free-derived normal AT-III also reacted with alpha-thrombin. Approx. 15% of this AT-III formed covalent complexes with alpha-thrombin in 2 min. Unfractionated heparin accelerated the rate of formation of such complexes. Two truncated forms of AT-III (amino acid residues 219-432 and 251-432), containing only the putative thrombin-binding domain, were synthesized independently in this cell-free system. These truncated AT-III polypeptides did not bind heparin and were unable to form stable covalent complexes with alpha-thrombin. However, both of these AT-III polypeptides were cleaved by alpha-thrombin, presumably at the reactive centre Arg-393-Ser-394. The formation of the disulphide bond between Cys-247 and Cys-430 in AT-III-(219-432)-polypeptide had no effect on the results obtained. Mutations in full-length AT-III at Cys-430 had no effect on the ability of AT-III to bind heparin. There was, however, a slight decrease in the formation of stable inhibitory complexes with alpha-thrombin. A cell-free-derived AT-III mutant, devoid of amino acid residues 41-49, which comprise heparin-binding region 1 of AT-III, had slightly decreased heparin binding compared with cell-free-derived normal AT-III-(1-432)-polypeptide. This mutant AT-III polypeptide was unable, however, to form a stable complex with alpha-thrombin. We conclude therefore that the N-terminal domain of AT-III is essential for both heparin binding and complex-formation with alpha-thrombin, but not for the cleavage of AT-III at its reactive centre by alpha-thrombin. Images Fig. 1. Fig. 2. Fig. 4. Fig. 5. Fig. 6. Fig. 7. PMID

  7. Rhodium(III)-catalyzed C-H activation/[4+3] annulation of N-phenoxyacetamides and α,β-unsaturated aldehydes: an efficient route to 1,2-oxazepines at room temperature.

    PubMed

    Duan, Pingping; Lan, Xia; Chen, Ying; Qian, Shao-Song; Li, Jie Jack; Lu, Liang; Lu, Yanbo; Chen, Bo; Hong, Mei; Zhao, Jing

    2014-10-18

    An efficient Rh(III)-catalyzed coupling reaction of N-phenoxyacetamides with α,β-unsaturated aldehydes to give 1,2-oxazepines via C-H activation/[4+3] annulation has been developed. This transformation does not require oxidants and features C-C/C-N bond formation to yield seven-membered oxazepine rings at room temperature. Further derivation of 1,2-oxazepines leads to important chroman derivatives.

  8. COLLISIONLESS SHOCKS IN A PARTIALLY IONIZED MEDIUM. III. EFFICIENT COSMIC RAY ACCELERATION

    SciTech Connect

    Morlino, G.; Blasi, P.; Bandiera, R.; Amato, E.; Caprioli, D.

    2013-05-10

    In this paper, we present the first formulation of the theory of nonlinear particle acceleration in collisionless shocks in the presence of neutral hydrogen in the acceleration region. The dynamical reaction of the accelerated particles, the magnetic field amplification, and the magnetic dynamical effects on the shock are also included. The main new aspect of this study, however, consists of accounting for charge exchange and the ionization of a neutral hydrogen, which profoundly change the structure of the shock, as discussed in our previous work. This important dynamical effect of neutrals is mainly associated with the so-called neutral return flux, namely the return of hot neutrals from the downstream region to upstream, where they deposit energy and momentum through charge exchange and ionization. We also present the self-consistent calculation of Balmer line emission from the shock region and discuss how to use measurements of the anomalous width of the different components of the Balmer line to infer cosmic ray acceleration efficiency in supernova remnants showing Balmer emission: the broad Balmer line, which is due to charge exchange of hydrogen atoms with hot ions downstream of the shock, is shown to become narrower as a result of the energy drainage into cosmic rays, while the narrow Balmer line, due to charge exchange in the cosmic-ray-induced precursor, is shown to become broader. In addition to these two well-known components, the neutral return flux leads to the formation of a third component with an intermediate width: this too contains information on ongoing processes at the shock.

  9. 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

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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. PMID:22409244

  15. On the formation of intermetalloid clusters: titanocene(III)diammin as a versatile reactant toward nonastannide Zintl clusters.

    PubMed

    Benda, Christian B; Waibel, Markus; Fässler, Thomas F

    2015-01-01

    The reactivity of TiCp2Cl2 (d(0)) towards Zintl clusters was studied in liquid ammonia (Cp = cyclopentadienyl). Reduction of Ti(IV)Cp2Cl2 and ligand exchange led to the formation of [Ti(III)Cp2(NH3)2](+), also obtainable by recrystallization of [CpTi(III)Cl]2. Upon reaction with [K4Sn9], ligand exchange leads to [TiCp2(η(1)-Sn9)(NH3)](3-). A small variation of the stoichiometry led to the formation of [Ti(η(4)-Sn8)Cp](3-), which cocrystallizes with [TiCp2(NH3)2](+) and [TiCp2(η(1)-Sn9)(NH3)](3-). Finally, the large intermetalloid cluster anion [Ti4Sn15Cp5](n-) (n = 4 or 5) was obtained from the reaction of K12Sn17 and TiCp2Cl2 in liquid ammonia. The isolation of three side products, [K([18]crown-6)]Cp, [K([18]crown-6)]Cp(NH3), and [K([2.2]crypt)]Cp, suggests a stepwise elimination of the Cl(-) and Cp(-) ligands from TiCp2Cl2 and thus gives a hint to the mechanism of the product formation in which [Ti(η(4+2)-Sn8)Cp](3-) has a key role.

  16. 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.

  17. Al(III) -catalysed formation of poly(limonene)carbonate: DFT analysis of the origin of stereoregularity.

    PubMed

    Peña Carrodeguas, Leticia; González-Fabra, Joan; Castro-Gómez, Fernando; Bo, Carles; Kleij, Arjan W

    2015-04-13

    Amino-triphenolate derived Al(III) complexes combined with suitable nucleophiles have been investigated as binary catalysts for the coupling of limonene oxide and carbon dioxide to afford alternating polycarbonates. These catalysts are able to produce stereoregular, perfectly alternating trans-polymers from cis-limonene oxide, whereas the pure trans isomer and cis/trans mixture give rise to lower degrees of stereoregularity. The best Al(III) catalyst shows the potential to mediate the conversion of both stereoisomers of limonene oxide with high conversion levels of up to 71 % under neat conditions, indicating the high degree of robustness and atom-efficiency of this catalytic process. Computational studies have revealed unique features of the binary catalyst system, among which is the preferred nucleophilic attack on the quaternary carbon centre in the limonene oxide substrate.

  18. 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.

  19. Endoplasmic Reticulum-Localized Iridium(III) Complexes as Efficient Photodynamic Therapy Agents via Protein Modifications.

    PubMed

    Nam, Jung Seung; Kang, Myeong-Gyun; Kang, Juhye; Park, Sun-Young; Lee, Shin Jung C; Kim, Hyun-Tak; Seo, Jeong Kon; Kwon, Oh-Hoon; Lim, Mi Hee; Rhee, Hyun-Woo; Kwon, Tae-Hyuk

    2016-08-31

    Protein inactivation by reactive oxygen species (ROS) such as singlet oxygen ((1)O2) and superoxide radical (O2(•-)) is considered to trigger cell death pathways associated with protein dysfunction; however, the detailed mechanisms and direct involvement in photodynamic therapy (PDT) have not been revealed. Herein, we report Ir(III) complexes designed for ROS generation through a rational strategy to investigate protein modifications by ROS. The Ir(III) complexes are effective as PDT agents at low concentrations with low-energy irradiation (≤ 1 J cm(-2)) because of the relatively high (1)O2 quantum yield (> 0.78), even with two-photon activation. Furthermore, two types of protein modifications (protein oxidation and photo-cross-linking) involved in PDT were characterized by mass spectrometry. These modifications were generated primarily in the endoplasmic reticulum and mitochondria, producing a significant effect for cancer cell death. Consequently, we present a plausible biologically applicable PDT modality that utilizes rationally designed photoactivatable Ir(III) complexes. PMID:27494510

  20. Synthesis and evaluation of gold(III) complexes as efficient DNA binders and cytotoxic agents.

    PubMed

    Patel, Mohan N; Bhatt, Bhupesh S; Dosi, Promise A

    2013-06-01

    In recent years, great interest has been focused on gold(III) complexes as cytotoxic and antitumor drugs. Recent studies demonstrated that simple bidentate or polydentate ligands containing nitrogen donor atoms may offer sufficient redox stabilization to produce viable Au(III) anticancer drug targets under physiologic conditions. So, we have synthesized square planer Au(III) complexes of type [Au(A(n))Clx]·Cly and characterized them using UV-Vis absorption, C, H, N elemental analysis, FT-IR, LC-MS, (1)H and (13)C NMR spectroscopy. These compounds manifested significant cytotoxic properties in vitro for brine shrimp lethality bioassay. The metal complexes were screened for series of DNA binding activity using UV-Vis absorption titration, hydrodynamic measurement and thermal DNA denaturation study. The nucleolytic activity was performed on plasmid pUC19 DNA. The Michaelis-Menten kinetic studies were performed to evaluate rate of enhancement in metal complexes mediated DNA cleavage over the non-catalyzed DNA cleavage.

  1. Synthesis and evaluation of gold(III) complexes as efficient DNA binders and cytotoxic agents

    NASA Astrophysics Data System (ADS)

    Patel, Mohan N.; Bhatt, Bhupesh S.; Dosi, Promise A.

    2013-06-01

    In recent years, great interest has been focused on gold(III) complexes as cytotoxic and antitumor drugs. Recent studies demonstrated that simple bidentate or polydentate ligands containing nitrogen donor atoms may offer sufficient redox stabilization to produce viable Au(III) anticancer drug targets under physiologic conditions. So, we have synthesized square planer Au(III) complexes of type [Au(An)Clx]·Cly and characterized them using UV-Vis absorption, C, H, N elemental analysis, FT-IR, LC-MS, 1H and 13C NMR spectroscopy. These compounds manifested significant cytotoxic properties in vitro for brine shrimp lethality bioassay. The metal complexes were screened for series of DNA binding activity using UV-Vis absorption titration, hydrodynamic measurement and thermal DNA denaturation study. The nucleolytic activity was performed on plasmid pUC19 DNA. The Michaelis-Menten kinetic studies were performed to evaluate rate of enhancement in metal complexes mediated DNA cleavage over the non-catalyzed DNA cleavage.

  2. 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.

  3. 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.

  4. Enthalpies of formation of rare earths and actinide(III) hydroxides: Their acid-base relationships and estimation of their thermodynamic properties

    SciTech Connect

    Morss, L.R.; Williams, C.W.

    1991-12-31

    This paper reviews the literature on rare earth(III) and actinide(III) hydroxide thermodynamics, in particular the determination of their enthalpies of formation at 25{degree}C. The hydroxide unit-cell volumes, lanthanide/actinide ion sizes, and solid-solution stability trends have been correlated with a generalized acid-base strength model for oxides to estimate properties for heterogeneous equilibria that are relevant to nuclear waste modeling and to characterization of potential actinide environmental interactions. Enthalpies of formation and solubility-product constants of actinide(III) hydroxides are estimated.

  5. Enthalpies of formation of rare earths and actinide(III) hydroxides: Their acid-base relationships and estimation of their thermodynamic properties

    SciTech Connect

    Morss, L.R.; Williams, C.W.

    1991-01-01

    This paper reviews the literature on rare earth(III) and actinide(III) hydroxide thermodynamics, in particular the determination of their enthalpies of formation at 25{degree}C. The hydroxide unit-cell volumes, lanthanide/actinide ion sizes, and solid-solution stability trends have been correlated with a generalized acid-base strength model for oxides to estimate properties for heterogeneous equilibria that are relevant to nuclear waste modeling and to characterization of potential actinide environmental interactions. Enthalpies of formation and solubility-product constants of actinide(III) hydroxides are estimated.

  6. Cp*Rh(III)-Catalyzed Cross-Coupling of Alkyltrifluoroborate with α-Diazomalonates for C(sp(3))-C(sp(3)) Bond Formation.

    PubMed

    Lu, Yin-Suo; Yu, Wing-Yiu

    2016-03-18

    A Cp*Rh(III)-catalyzed cross-coupling of alkyltrifluoroborate with α-diazomalonates was developed; the C(sp(3))-C(sp(3)) bond coupled products were formed in up to 97% yields. The reaction tolerates some useful functional groups, including ketone, ester, amide, ether, sulfonyl, and thiophene. Electrospray ionization mass spectrometry (ESI-MS) analysis revealed the formation of a distinct molecular species corresponding to σ-alkylrhodium(III) complexes. The successful diazo coupling reaction may be attributed to coordination of the amide group that promotes stability of the alkylrhodium(III) complex through the formation of a five-membered metallacycle. PMID:26926387

  7. Star formation efficiency in the outer filaments of Centaurus A

    NASA Astrophysics Data System (ADS)

    Salomé, Q.; Salomé, P.; Combes, F.; Hamer, S.; Heywood, I.

    2015-12-01

    We present a multi-wavelength study of the northern filaments of Centaurus A (at a distance of ˜ 20 kpc from the galaxy center) based on FUV (GALEX), FIR (Herschel) and CO (SEST and ALMA) emission. We also searched for HCN and HCO^+ (ATCA) and observed optical emission lines (VLT/MUSE) in different places of the filament. An upper limit of the dense gas of L'_{HCN}<4.8× 10^3 K.km.s^{-1}.pc^2 at 3σ leads to a dense-to-molecular gas fraction <23% in this region. We compared the CO masses with the SFR estimates and found very long depletion times (11 Gyr on 730 pc scales) and a large scatter in the KS-relation with a standard conversion factor. Applying a metallicity correction to the CO/H_2 conversion factor would lead to even more massive clouds with higher depletion times. Using ALMA archive data, we found 3 unresolved CO(2-1) clumps of size <37× 21 pc and masses around 10^4 M_⊙. The 3 clumps show resolved line profiles (Δ v˜ 10 km.s^{-1}) and are all three dynamically clearly separated by ˜ 10-20 km.s^{-1}. We derived a virial parameter α_{vir}˜ 10-16 which indicates that the clumps are not gravitationally bound and input of energy likely inhibits star formation.

  8. 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.

  9. Stellar Populations and the Star Formation Histories of LSB Galaxies: III. Stellar Population Models

    NASA Astrophysics Data System (ADS)

    Schombert, James; McGaugh, Stacy

    2014-09-01

    A series of population models are designed to explore the star formation history of gas-rich, low surface brightness (LSB) galaxies. LSB galaxies are unique in having properties of very blue colors, low Hα emission and high gas fractions that indicated a history of constant star formation (versus the declining star formation models used for most spirals and irregulars). The model simulations use an evolving multi-metallicity composite population that follows a chemical enrichment scheme based on Milky Way observations. Color and time sensitive stellar evolution components (i.e., BHB, TP-AGB and blue straggler stars) are included, and model colors are extended into the Spitzer wavelength regions for comparison to new observations. In general, LSB galaxies are well matched to the constant star formation scenario with the variation in color explained by a fourfold increase/decrease in star formation over the last 0.5 Gyrs (i.e., weak bursts). Early-type spirals, from the S4G sample, are better fit by a declining star formation model where star formation has decreased by 40% in the last 12 Gyrs.

  10. The hydrogen salicylate ion as ligand. Complex formation equilibria with dioxouranium (VI), neodymium (III) and lead (II).

    PubMed

    Furia, Emilia; Porto, Raffaella

    2004-11-01

    The complexation equilibria of the hydrogen salicylate ion, HL(-), have been studied, at 25 degrees C, by potentiometric measurements with a glass electrode in 1 M NaClO4 for uranyl and Nd(III) ions and in 3 M NaClO4 for Pb(II) ion. The ligand concentration (CL) was varied between 10(-3) and 0.05 M. In the system with U(VI) the concentrations ranged between: 10(-3) < or = [U(VI)] < or = 0.01 M, 0.5 < or = CL /[U(VI)] < or = 10 and 10(-2) < or = [H+] < or = 10(-5) M; for neodymium system: 2 x 10(-3) < or = [Nd(III)] < or = 0.01, 1 < or = CL /[Nd(III)] < or = 10 and 10(-2) < or = [H+] < or = 10(-7) M; for lead system: 10(-3) < or = [Pb(II) < or = 3 x 10(-3), 1 < or = CL /Pb(II)] < or = 2 and 10(-5) < or = [H+] < or = 10(-7.3) M. The experimental data have been explained with the formation of UO2HL+, UO2L, UO2(OH)L(-), (UO2)2(OH)L2(-) UO2(HL)L(-), NdHL(2+), NdL(+), Nd(OH)L, PbHL(+), PbL and PbL2(2-). Equilibrium constants are given for the investigated ionic media and at infinite dilution.

  11. 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. PMID:9535191

  12. Remarkable efficiency of ultrafine superparamagnetic iron(III) oxide nanoparticles toward arsenate removal from aqueous environment.

    PubMed

    Kilianová, Martina; Prucek, Robert; Filip, Jan; Kolařík, Jan; Kvítek, Libor; Panáček, Aleš; Tuček, Jiří; Zbořil, Radek

    2013-11-01

    Arsenates, when present in water resources, constitute a risk to human health. In order to remove them, various technologies have been developed; out of them, sorption approach is widely adopted employing a wide spectrum of suitable sorbent materials. Nanoparticles of iron oxide are frequently used due to a high surface area and ability to control them by external magnetic field. In this work, we report on a simple and cheap synthesis of ultrafine iron(III) oxide nanoparticles with a narrow size distribution and their exploitation in the field of arsenate removal from aqueous environment. It is shown that the adsorption capacity is enhanced by a mesoporous nature of nanoparticle arrangement in their system due to strong magnetic interactions they evolve between nanoparticles. A complete arsenate removal is achieved at Fe/As ratio equal to ∼20/1 and at pH in the range from 5 to 7.6. Under these conditions, the arsenates are completely removed within several minutes of treatment. Among iron-oxide-based nanosystems synthesized and employed in arsenate remediation issues so far, our assembly of iron(III) oxide nanoparticles shows the highest Freundlich adsorption coefficient and equilibrium sorption capacity under conditions maintained. Taking into account simple and low-cost preparation procedure, product high yields, almost monodispersed character, room-temperature superparamagnetic behavior, and strong magnetic response under small applied magnetic fields, the synthesized iron(III) oxide nanoparticles can be regarded as a promising candidate for exploitation in the field of removing undesired toxic pollutants from various real water systems.

  13. An estimate of star formation efficiency in molecular clouds

    NASA Technical Reports Server (NTRS)

    Rengarajan, T. N.

    1984-01-01

    From the existing data in the literature it is shown that there is a linear correlation between cloud mass derived from CO observations and the associated luminosity obtained from far-IR observations over a large luminosity range of 10 to the 4th to 10 to the 8th solar luminosities. The mean value of luminosity per unit mass for a giant molecular cloud is 5.6 solar-L/solar-M. The star-forming efficiency of the molecular cloud over its lifetime of 5-10 x 10 to the 7th yr is found to be 0.2-0.3, which yields the present star-forming rate of 6-11 solar masses per year. Furthermore, the integral luminosity distribution is a power-law with an exponent of about -0.5. The correlation between cloud mass and the far-IR luminosity observed for a sample of nuclei of external galaxies corresponds to molecular clouds similar to those in the Galaxy.

  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. PMID:26660060

  15. 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.

  16. The Relation between [O III]/Hβ and Specific Star Formation Rate in Galaxies at z ∼ 2

    NASA Astrophysics Data System (ADS)

    Mackay Dickey, Claire; van Dokkum, Pieter G.; Oesch, Pascal A.; Whitaker, Katherine E.; Momcheva, Ivelina G.; Nelson, Erica J.; Leja, Joel; Brammer, Gabriel B.; Franx, Marijn; Skelton, Rosalind E.

    2016-09-01

    Recent surveys have identified a seemingly ubiquitous population of galaxies with elevated [O iii]/Hβ emission line ratios at z > 1, although the nature of this phenomenon continues to be debated. The [O iii]/Hβ line ratio is of interest because it is a main component of the standard diagnostic tools used to differentiate between active galactic nuclei and star-forming galaxies as well as the gas-phase metallicity indicators O 23 and R 23. Here, we investigate the primary driver of increased [O iii]/Hβ ratios by median-stacking rest-frame optical spectra for a sample of star-forming galaxies in the 3D-HST survey in the redshift range z ∼ 1.4–2.2. Using N = 4220 star-forming galaxies, we stack the data in bins of mass and specific star formation rates (sSFRs), respectively. After accounting for stellar Balmer absorption, we measure [O iii]λ5007 Å/Hβ down to M ∼ 109.2 M ⊙ and sSFR ∼ 10‑9.6 yr‑1, greater than an order of magnitude lower than previous work at similar redshifts. We find an offset of 0.59 ± 0.05 dex between the median ratios at z ∼ 2 and z ∼ 0 at fixed stellar mass, in agreement with existing studies. However, with respect to sSFR, the z ∼ 2 stacks all lie within 1σ of the median SDSS ratios, with an average offset of only ‑0.06 ± 0.05. We find that the excitation properties of galaxies are tightly correlated with their sSFR at both z ∼ 2 and z ∼ 0, with a relation that appears to be roughly constant over the last 10 Gyr of cosmic time.

  17. Efficiency of heating methods for polymer fibers with formation of adhesion compounds

    SciTech Connect

    Markova, L.V.; Markov, E.M.; Pinchuk, I.S.

    1995-12-01

    Efficiency of contact and contactless methods of heating of a fiber polymer material upon formation of adhesion compounds between its layers is analyzed. The advisability of contact heating in the preliminary stage and contactless heating in the final stage of formation of compounds is shown.

  18. 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.

  19. 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.

  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. 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…

  2. 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.

  3. 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

  4. Composition, Formation, and Regulation of the Cytosolic C-ring, a Dynamic Component of the Type III Secretion Injectisome

    PubMed Central

    Diepold, Andreas; Kudryashev, Mikhail; Delalez, Nicolas J.; Berry, Richard M.; Armitage, Judith P.

    2015-01-01

    Many gram-negative pathogens employ a type III secretion injectisome to translocate effector proteins into eukaryotic host cells. While the structure of the distal “needle complex” is well documented, the composition and role of the functionally important cytosolic complex remain less well understood. Using functional fluorescent fusions, we found that the C-ring, an essential and conserved cytosolic component of the system, is composed of ~22 copies of SctQ (YscQ in Yersinia enterocolitica), which require the presence of YscQC, the product of an internal translation initiation site in yscQ, for their cooperative assembly. Photoactivated localization microscopy (PALM) reveals that in vivo, YscQ is present in both a free-moving cytosolic and a stable injectisome-bound state. Notably, fluorescence recovery after photobleaching (FRAP) shows that YscQ exchanges between the injectisome and the cytosol, with a t½ of 68 ± 8 seconds when injectisomes are secreting. In contrast, the secretin SctC (YscC) and the major export apparatus component SctV (YscV) display minimal exchange. Under non-secreting conditions, the exchange rate of YscQ is reduced to t½ = 134 ± 16 seconds, revealing a correlation between C-ring exchange and injectisome activity, which indicates a possible role for C-ring stability in regulation of type III secretion. The stabilization of the C-ring depends on the presence of the functional ATPase SctN (YscN). These data provide new insights into the formation and composition of the injectisome and present a novel aspect of type III secretion, the exchange of C-ring subunits, which is regulated with respect to secretion. PMID:25591178

  5. Facile formation and redox of benzoxazole-2-thiolate-bridged dinuclear Pt(II/III) complexes.

    PubMed

    Wang, Zhe; Jiang, Lu; Liu, Zhi-Pan; Gan, C R Raymond; Liu, Zhaolin; Zhang, Xin-Hai; Zhao, Jin; Hor, T S Andy

    2012-10-28

    Reaction of [Pt(L)(μ-Cl)](2) (L = ppy (2-phenylpyridine) or bzq (benzo[h]quinoline)) with 2-mercaptobenzoxazole (NOSH) and NaOAc in THF at r.t. yields the dinuclear Pt(II) d(8)-d(8) complexes [Pt(2)L(2)(μ-NOS-κN,S)(2)] (L = ppy, 1; L = bzq, 2) and the Pt(III) d(7)-d(7) complexes [Pt(2)(ppy)(2)(μ-NOS-κN,S)(2)(NOS-κS)(2)] (L = ppy, 3; L = bzq, 4) in one pot. The C,N-cyclometalated ligand is chelating whereas the N,S-donating benzoxazole-2-thiolates doubly bridge the two metal centers. The Pt···Pt separations of 3.0204(3) and 2.9726(8) Å in 1 and 2 contract to 2.685(1) Å in 3 and 2.6923(3) Å in 4, respectively, when two S-bound thiolate ligands coordinate trans- to the Pt···Pt axis. However, cyclometalation is preserved and there is minimum perturbation of the bridging ligands. Complexes 3 and 4 can be also obtained by oxidative addition of the thiolate ligand. In the presence of NaBH(4), 3 and 4 can be reduced to 1 and 2, respectively. At r.t., 1 and 2 exhibit intense orange-red luminescence at 625 nm and 631 nm, respectively. The electrochemical properties of 1-4 have been also discussed.

  6. 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.

  7. Kinetics of formation and dissociation of aquocobalt(III) complexes with some carboxylic acids in acid perchlorate solution.

    PubMed

    Davies, Geoffrey

    2007-06-21

    The rates of formation and dissociation of monocarboxylic complexes of aquocobalt(III) cations with propionic, malonic, and 2-ethylmalonic acids have been measured with the stopped-flow method over a range of concentrations and temperatures in acid perchlorate media at an ionic strength 3.0 M. Although the rate constants for reactions of CoOHaq2+ with neutral ligands cover only a small range, indicating a dissociative mechanism, the associated activation parameters change cooperatively. These variations are discussed in terms of differences in the structure, proton distribution, and rates of water loss in the ion-pair precursors for the different ligands. Similar activation enthalpies of dissociation indicate a common mode of coordination, and the positive activation entropies for dissociation are consistent with a neutral leaving group.

  8. 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.

  9. The influence of the cluster environment on the star formation efficiency of 12 Virgo spiral galaxies

    NASA Astrophysics Data System (ADS)

    Vollmer, B.; Wong, O. I.; Braine, J.; Chung, A.; Kenney, J. D. P.

    2012-07-01

    The influence of the environment on gas surface density and star formation efficiency of cluster spiral galaxies is investigated. We extend previous work on radial profiles by a pixel-to pixel analysis looking for asymmetries due to environmental interactions. The star formation rate is derived from GALEX UV and Spitzer total infrared data based on the 8, 24, 70, and 160 μm data. As in field galaxies, the star formation rate for most Virgo galaxies is approximately proportional to the molecular gas mass. Except for NGC 4438, the cluster environment does not affect the star formation efficiency with respect to the molecular gas. Gas truncation is not associated with major changes in the total gas surface density distribution of the inner disk of Virgo spiral galaxies. In three galaxies (NGC 4430, NGC 4501, and NGC 4522), possible increases in the molecular fraction and the star formation efficiency with respect to the total gas, of factors of 1.5 to 2, are observed on the windward side of the galactic disk. A significant increase of the star formation efficiency with respect to the molecular gas content on the windward side of ram pressure-stripped galaxies is not observed. The ram-pressure stripped extraplanar gas of 3 highly inclined spiral galaxies (NGC 4330, NGC 4438, and NGC 4522) shows a depressed star formation efficiency with respect to the total gas, and one of them (NGC 4438) shows a depressed rate even with respect to the molecular gas. The interpretation is that stripped gas loses the gravitational confinement and associated pressure of the galactic disk, and the gas flow is diverging, so the gas density decreases and the star formation rate drops. We found two such regions of low star formation efficiency in the more face-on galaxies NGC 4501 and NGC 4654 which are both undergoing ram pressure stripping. These regions show low radio continuum emission or unusually steep radio spectral index. However, the stripped extraplanar gas in one highly inclined

  10. Facile formation and redox of benzoxazole-2-thiolate-bridged dinuclear Pt(II/III) complexes.

    PubMed

    Wang, Zhe; Jiang, Lu; Liu, Zhi-Pan; Gan, C R Raymond; Liu, Zhaolin; Zhang, Xin-Hai; Zhao, Jin; Hor, T S Andy

    2012-10-28

    Reaction of [Pt(L)(μ-Cl)](2) (L = ppy (2-phenylpyridine) or bzq (benzo[h]quinoline)) with 2-mercaptobenzoxazole (NOSH) and NaOAc in THF at r.t. yields the dinuclear Pt(II) d(8)-d(8) complexes [Pt(2)L(2)(μ-NOS-κN,S)(2)] (L = ppy, 1; L = bzq, 2) and the Pt(III) d(7)-d(7) complexes [Pt(2)(ppy)(2)(μ-NOS-κN,S)(2)(NOS-κS)(2)] (L = ppy, 3; L = bzq, 4) in one pot. The C,N-cyclometalated ligand is chelating whereas the N,S-donating benzoxazole-2-thiolates doubly bridge the two metal centers. The Pt···Pt separations of 3.0204(3) and 2.9726(8) Å in 1 and 2 contract to 2.685(1) Å in 3 and 2.6923(3) Å in 4, respectively, when two S-bound thiolate ligands coordinate trans- to the Pt···Pt axis. However, cyclometalation is preserved and there is minimum perturbation of the bridging ligands. Complexes 3 and 4 can be also obtained by oxidative addition of the thiolate ligand. In the presence of NaBH(4), 3 and 4 can be reduced to 1 and 2, respectively. At r.t., 1 and 2 exhibit intense orange-red luminescence at 625 nm and 631 nm, respectively. The electrochemical properties of 1-4 have been also discussed. PMID:22960665

  11. Synaptotagmin III is a critical factor for the formation of the perinuclear endocytic recycling compartment and determination of secretory granules size.

    PubMed

    Grimberg, Elena; Peng, Ze; Hammel, Ilan; Sagi-Eisenberg, Ronit

    2003-01-01

    Early endosomes and a perinuclear, Rab-11-positive compartment have been implicated in the recycling of internalized receptors. In this study, we show that synaptotagmin III (Syt III), a member of the Syt family of proteins, is required for the formation and delivery of cargo to the perinuclear endocytic recycling compartment (ERC). We demonstrate that rat basophilic leukemia (RBL-2H3) mast cells endogenously express Syt III, and >70% of this protein colocalizes with early endosomal markers, such as EEA1, annexin II and syntaxin 7, and the remaining protein colocalizes with secretory granule (SG) markers such as beta-hexosaminidase, histamine and serotonin. To study the functional role of Syt III, we stably transfected RBL cells with Syt III antisense cDNA and monitored the route of transferrin (Tfn) internalization in cells that displayed substantially reduced (<90%) levels of Syt III (RBL-Syt III(-)). In these cells, Tfn binding and internalization into early endosomes were unaltered. However, whereas in the mock-transfected cells Tfn was subsequently delivered to the ERC, in the RBL-Syt III(-) cells, Tfn remained associated with dispersed peripheral vesicles and Rab 11 remained cytosolic. Nevertheless, the rates of Tfn internalization and recycling were not affected. RBL-Syt III(-) cells also displayed enlarged SGs, reminiscent of the SGs present in Chediak-Higashi (beige) mice. However, morphometric analyses suggested that granule formation was unaltered and that the calculated unit granule volume is the same in both cell lines. Therefore, our results implicate Syt III as a critical factor for the generation and delivery of internalized cargo to the perinuclear endocytic recycling compartment and suggest a possible link between ERC and recycling from immature SGs during the process of SG maturation.

  12. 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. PMID:26647114

  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. 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.

  15. 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.

  16. Genetic Algorithm for Innovative Device Designs in High-Efficiency III-V Nitride Light-Emitting Diodes

    NASA Astrophysics Data System (ADS)

    Zhu, Di; Schubert, Martin F.; Cho, Jaehee; Schubert, E. Fred; Crawford, Mary H.; Koleske, Daniel D.; Shim, Hyunwook; Sone, Cheolsoo

    2012-01-01

    Light-emitting diodes are becoming the next-generation light source because of their prominent benefits in energy efficiency, versatility, and benign environmental impact. However, because of the unique polarization effects in III-V nitrides and the high complexity of light-emitting diodes, further breakthroughs towards truly optimized devices are required. Here we introduce the concept of artificial evolution into the device optimization process. Reproduction and selection are accomplished by means of an advanced genetic algorithm and device simulator, respectively. We demonstrate that this approach can lead to new device structures that go beyond conventional approaches. The innovative designs originating from the genetic algorithm and the demonstration of the predicted results by implementing structures suggested by the algorithm establish a new avenue for complex semiconductor device design and optimization.

  17. Gold(III) reduction by the rhizobacterium Azospirillum brasilense with the formation of gold nanoparticles.

    PubMed

    Tugarova, Anna V; Burov, Andrei M; Burashnikova, Marina M; Kamnev, Alexander A

    2014-01-01

    For the soil nitrogen-fixing bacterium Azospirillum brasilense, the ability to reduce [AuCl4](-) and to form gold nanoparticles (GNPs) has been demonstrated, with the appearance of a mauve tint of the culture. To validate the shapes and chemical nature of nanoparticles, transmission electron microscopy (TEM) and X-ray fluorescence analysis were used. For the widely studied agriculturally important wild-type strains A. brasilense Sp7 and Sp245, GNPs formed after 10 days of incubation of cell biomass with 0.25 mM [AuCl4](-) were shown (using TEM) to be mainly of spherical form (5 to 20 nm in diameter), with rare occasional triangles. In the course of cultivation with [AuCl4](-), after 5 days, a mauve tint was already visible for cells of strain Sp245.5, after 6 days for Sp245 and after 10 days for Sp7. Thus, for the mutant strain Sp245.5 (which has significant differences in the structure and composition of cell-surface polysaccharides as compared with Sp245), a more rapid formation of GNPs was observed. Moreover, their TEM images (also obtained after 10 days) showed different shapes: nano-sized spheres, triangles, hexagons and rods, as well as larger round-shaped flower-like nanoparticles about 100 nm in size. Since by the time of GNP formation in our experiments the cells were found to be already not viable, this confirms the dominating role of cell surface structure and chemical composition in shaping the GNPs formed in the course of [AuCl4](-) reduction to Au(0). This finding may be useful for understanding the natural biogeochemical mechanisms of gold reduction and formation of GNPs involving microorganisms. The data obtained may also help in developing protocols for environmentally friendly synthesis of nanoparticles and possible use of bacterial cells with modified surface structure and composition for their fabrication.

  18. 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.

  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. 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.

  2. 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. PMID:25788096

  3. 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.

  4. Alternative Formats to Achieve More Efficient Energy Codes for Commercial Buildings

    SciTech Connect

    Conover, David R.; Rosenberg, Michael I.; Halverson, Mark A.; Taylor, Zachary T.; Makela, Eric J.

    2013-01-26

    This paper identifies and examines several formats or structures that could be used to create the next generation of more efficient energy codes and standards for commercial buildings. Pacific Northwest National Laboratory (PNNL) is funded by the U.S. Department of Energy’s Building Energy Codes Program (BECP) to provide technical support to the development of ANSI/ASHRAE/IES Standard 90.1. While the majority of PNNL’s ASHRAE Standard 90.1 support focuses on developing and evaluating new requirements, a portion of its work involves consideration of the format of energy standards. In its current working plan, the ASHRAE 90.1 committee has approved an energy goal of 50% improvement in Standard 90.1-2013 relative to Standard 90.1-2004, and will likely be considering higher improvement targets for future versions of the standard. To cost-effectively achieve the 50% goal in manner that can gain stakeholder consensus, formats other than prescriptive must be considered. Alternative formats that include reducing the reliance on prescriptive requirements may make it easier to achieve these aggressive efficiency levels in new codes and standards. The focus on energy code and standard formats is meant to explore approaches to presenting the criteria that will foster compliance, enhance verification, and stimulate innovation while saving energy in buildings. New formats may also make it easier for building designers and owners to design and build the levels of efficiency called for in the new codes and standards. This paper examines a number of potential formats and structures, including prescriptive, performance-based (with sub-formats of performance equivalency and performance targets), capacity constraint-based, and outcome-based. The paper also discusses the pros and cons of each format from the viewpoint of code users and of code enforcers.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  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. 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.

  14. Massive star formation in Wolf-Rayet galaxies. III. Analysis of the O and WR populations

    NASA Astrophysics Data System (ADS)

    López-Sánchez, Á. R.; Esteban, C.

    2010-06-01

    observations are needed to detect the red WR bump because of the decreasing of the WR luminosities with decreasing metallicity. Although available models reproduce the WR properties at high metallicities fairly well, new evolutionary synthesis models for young starbursts including all involved parameters (age, metallicity, star-formation history, IMF and WR stars properties such as metallicity-dependent WR luminosities, stellar rotation and the WR binnary channel) are absolutely needed to perform an appropriate comparison with the observational data. Based on observations made with NOT (Nordic Optical Telescope), INT (Isaac Newton Telescope) and WHT (William Herschel Telescope) operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway and Sweden (NOT) or the Isaac Newton Group (INT, WHT) in the Spanish Observatorio del Roque de Los Muchachos of the Instituto de Astrofísica de Canarias.

  15. 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.

  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. The formation of a luminescent Mn(III,IV) intermediate of bis(2-pyridylmethyl)amine and acetone assistant its intramolecular C-H oxidation.

    PubMed

    Zhou, Dong-Fang; Chen, Qiu-Yun; Fu, Hai-Jian; Yan, Qi-

    2011-10-15

    The dinuclear Mn(II) complexes of bis(2-pyridylmethyl)amine (dpa) reacted with H(2)O(2) producing a fluorescent dioxodimanganese(III,IV) intermediate [(dpa)Mn(2)Cl(2)(μ-O(2))(OHdpa)](3+), which was characterized by IR, UV, ESR, ES-MS and fluorescence spectra. ES-MS data show that this intermediate could bind an acetone molecule forming dioxodimanganese(III,IV)-acetone adduct [(dpa)Mn(2)Cl(2)(μ-O)(CH(3)COCH(3))(OHdpa)](3+). The emission of dioxodimanganese(III,IV)-acetone at 378 nm was stronger than that of dioxodimanganese(III,IV) complex. Excess acetone molecules promoted the intramolecular C-H oxidation and the formation of one dimensional chain Mn(II) complex [(2-picolinic-acid)Mn(H(2)O)(2)Cl(O)](n) through possible intramolecular oxygen transfer reaction.

  18. 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).

  19. Crystal structure of a mixed-ligand terbium(III) coordination polymer containing oxalate and formate ligands, having a three-dimensional fcu topology.

    PubMed

    Kittipong, Chainok; Khemthong, Phailyn; Kielar, Filip; Zhou, Yan

    2016-01-01

    The title compound, poly[(μ 3-formato)(μ 4-oxalato)terbium(III)], [Tb(CHO2)(C2O4)] n , is a three-dimensional coordination polymer, and is isotypic with the La(III), Ce(III) and Sm(III) analogues. The asymmetric unit contains one Tb(III) ion, one formate anion (CHO2 (-)) and half of an oxalate anion (C2O4 (2-)), the latter being completed by application of inversion symmetry. The Tb(III) ion is nine-coordinated in a distorted tricapped trigonal-prismatic manner by two chelating carboxyl-ate groups from two C2O4 (2-) ligands, two carboxyl-ate oxygen atoms from another two C2O4 (2-) ligands and three oxygen atoms from three CHO2 (-) ligands, with the Tb-O bond lengths and the O-Tb-O bond angles ranging from 2.4165 (19) to 2.478 (3) Å and 64.53 (6) to 144.49 (4)°, respectively. The CHO2 (-) and C2O4 (2-) anions adopt μ 3-bridging and μ 4-chelating-bridging coordination modes, respectively, linking adjacent Tb(III) ions into a three-dimensional 12-connected fcu topology with point symbol (3(24).4(36).5(6)). The title compound exhibits thermal stability up to 623 K, and also displays strong green photoluminescence in the solid state at room temperature.

  20. 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

    2014-04-01

    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).

  1. 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.

  2. 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.

  3. The effect of vortex formation on left ventricular filling and mitral valve efficiency.

    PubMed

    Pierrakos, Olga; Vlachos, Pavlos P

    2006-08-01

    A new mechanism for quantifying the filling energetics in the left ventricle (LV) and past mechanical heart valves (MHV) is identified and presented. This mechanism is attributed to vortex formation dynamics past MHV leaflets. Recent studies support the conjecture that the natural healthy left ventricle (LV) performs in an optimum, energy-preserving manner by redirecting the flow with high efficiency. Yet to date, no quantitative proof has been presented. The present work provides quantitative results and validation of a theory based on the dynamics of vortex ring formation, which is governed by a critical formation number (FN) that corresponds to the dimensionless time at which the vortex ring has reached its maximum circulation content, in support of this hypothesis. Herein, several parameters (vortex ring circulation, vortex ring energy, critical FN, hydrodynamic efficiencies, vortex ring propagation speed) have been quantified and presented as a means of bridging the physics of vortex formation in the LV. In fact, the diastolic hydrodynamic efficiencies were found to be 60, 41, and 29%, respectively, for the porcine, anti-anatomical, and anatomical valve configurations. This assessment provides quantitative proof of vortex formation, which is dependent of valve design and orientation, being an important flow characteristic and associated to LV energetics. Time resolved digital particle image velocimetry with kilohertz sampling rate was used to study the ejection of fluid into the LV and resolve the spatiotemporal evolution of the flow. The clinical significance of this study is quantifying vortex formation and the critical FN that can potentially serve as a parameter to quantify the LV filling process and the performance of heart valves.

  4. Efficient isolation of Pseudomonas aeruginosa type III secretion translocators and assembly of heteromeric transmembrane pores in model membranes.

    PubMed

    Romano, Fabian B; Rossi, Kyle C; Savva, Christos G; Holzenburg, Andreas; Clerico, Eugenia M; Heuck, Alejandro P

    2011-08-23

    Translocation of bacterial toxins or effectors into host cells using the type III secretion (T3S) system is a conserved mechanism shared by many Gram-negative pathogens. Pseudomonas aeruginosa injects different proteins across the plasma membrane of target cells, altering the normal metabolism of the host. Protein translocation presumably occurs through a proteinaceous transmembrane pore formed by two T3S secreted protein translocators, PopB and PopD. Unfolded translocators are secreted through the T3S needle prior to insertion into the target membrane. Purified PopB and PopD form pores in model membranes. However, their tendency to form heterogeneous aggregates in solution had hampered the analysis of how these proteins undergo the transition from a denatured state to a membrane-inserted state. Translocators were purified as stable complexes with the cognate chaperone PcrH and isolated from the chaperone using 6 M urea. We report here the assembly of stable transmembrane pores by dilution of urea-denatured translocators in the presence of membranes. PopB and PopD spontaneously bound liposomes containing anionic phospholipids and cholesterol in a pH-dependent manner as observed by two independent assays, time-resolved Förster resonance energy transfer and sucrose-step gradient ultracentrifugation. Using Bodipy-labeled proteins, we found that PopB interacts with PopD on the membrane surface as determined by excitation energy migration and fluorescence quenching. Stable transmembrane pores are more efficiently assembled at pH <5.0, suggesting that acidic residues might be involved in the initial membrane binding and/or insertion. Altogether, the experimental setup described here represents an efficient method for the reconstitution and analysis of membrane-inserted translocators.

  5. 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.

  6. Efficient generation of perfluoroalkyl radicals from sodium perfluoroalkanesulfinates and a hypervalent iodine(iii) reagent: mild, metal-free synthesis of perfluoroalkylated organic molecules.

    PubMed

    Sakamoto, Ryu; Kashiwagi, Hirotaka; Selvakumar, Sermadurai; Moteki, Shin A; Maruoka, Keiji

    2016-07-01

    This article describes an efficient method for the introduction of perfluoroalkyl groups into N-acrylamides, 2-isocyanides, olefins, and other heterocycles using perfluoroalkyl radicals that were generated from the reaction between sodium perfluoroalkanesulfinates and a hypervalent iodine(iii) reagent. This approach represents a simple, scalable perfluoroalkylation method under mild and metal-free conditions.

  7. 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.

  8. 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

  9. Monocyclometalated gold(III) monoaryl complexes--a new class of triplet phosphors with highly tunable and efficient emission properties.

    PubMed

    Szentkuti, Alexander; Bachmann, Michael; Garg, Jai Anand; Blacque, Olivier; Venkatesan, Koushik

    2014-02-24

    Highly tunable and rich phosphorescent emission properties based on the stable monocyclometalated gold(III) monoaryl structural motif are reported. Monochloro complexes of the type cis-[(N^C)Au(C6 H2 (CF3)3)(Cl)] N^C=2-phenylpyridine (ppy)] (1), [N^C=benzo[h]quinoline (bzq)] (2), [N^C=2-(5-Methyl-2-thienyl)pyridine (5m-thpy)] (3) were successfully prepared in modest to good yields by reacting an excess of 2, 4, 6-tris(trifluoromethyl)phenyl lithium (LiFmes) with the corresponding dichloride complexes cis-[(N^C)AuCl2]. Subsequent replacement of the chloride ligand in 1 with strong ligand field strength such as cyanide and terminal alkynes resulted in complexes of the type cis-[(ppy)Au(Fmes)(R)] R=CN (4), I (5), C≡C-C6 H5 (6) and C≡C-C6 H4 N(C6 H5)-p (7). Single crystal X-ray diffraction studies of all the complexes except 7 were performed to further corroborate their chemical identity. Thermogravimetric analysis (TGA) studies of the uncommon cis configured aryl alkyne complex 7 confirmed the high stability of this complex. Detailed photophysical investigations carried out in solution at room temperature, at 77 K (2-MeTHF) in rigidified media, solid state and 5 wt % PMMA revealed the phosphorescent nature of emission in these complexes. Additionally, their behavior was found to be governed based on both the nature of the cyclometalated ligand and the electronic properties of the ancillary ligands. Highly efficient interligand charge transfer in complex 7 provides access to a wide range of emission colors (solvent-dependent) from deep blue to red with phosphorescence emission quantum yield of 30 % (441 nm) and 39 % (622 nm) in solution and solid state, respectively, and is the highest reported for any Au(III) complexes. DFT and TDDFT calculations carried out further validated the observations and assignments based on the photophysical experimental findings. PMID:24481957

  10. 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.

  11. 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. PMID:25108829

  12. 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

    2016-08-01

    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.

  13. 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.

  14. 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.

  15. Multicopper Oxidase Involvement in Both Mn(II) and Mn(III) Oxidation during Bacterial Formation of MnO2

    PubMed Central

    Soldatova, Alexandra V.; Butterfield, Cristina; Oyerinde, Oyeyemi F.; Tebo, Bradley M.; Spiro, Thomas G.

    2013-01-01

    Global cycling of environmental manganese requires catalysis by bacteria and fungi for MnO2 formation, since abiotic Mn(II) oxidation is slow under ambient conditions. Genetic evidence from several bacteria implicates multicopper oxidases (MCOs) as being required for MnO2 formation. However, MCOs catalyze one-electron oxidations, whereas conversion of Mn(II) to MnO2 is a two-electron process. Trapping experiments with pyrophosphate (PP), a Mn(III) chelator, have demonstrated that Mn(III) is an intermediate in Mn(II) oxidation when mediated by exosporium from the Mn-oxidizing bacterium Bacillus SG-1. The reaction of Mn(II) depends on O2 and is inhibited by azide, consistent with MCO catalysis. We show that the subsequent conversion of Mn(III) to MnO2 also depends on O2 and is inhibited by azide. Thus, both oxidation steps appear to be MCO-mediated, likely by the same enzyme, indicated by genetic evidence to be the MnxG gene product. We propose a model of how the manganese oxidase active site may be organized to couple successive electron transfers to the formation of polynuclear Mn(IV) complexes as precursors to MnO2 formation. PMID:22892957

  16. Multicopper oxidase involvement in both Mn(II) and Mn(III) oxidation during bacterial formation of MnO(2).

    PubMed

    Soldatova, Alexandra V; Butterfield, Cristina; Oyerinde, Oyeyemi F; Tebo, Bradley M; Spiro, Thomas G

    2012-12-01

    Global cycling of environmental manganese requires catalysis by bacteria and fungi for MnO(2) formation, since abiotic Mn(II) oxidation is slow under ambient conditions. Genetic evidence from several bacteria indicates that multicopper oxidases (MCOs) are required for MnO(2) formation. However, MCOs catalyze one-electron oxidations, whereas the conversion of Mn(II) to MnO(2) is a two-electron process. Trapping experiments with pyrophosphate (PP), a Mn(III) chelator, have demonstrated that Mn(III) is an intermediate in Mn(II) oxidation when mediated by exosporium from the Mn-oxidizing bacterium Bacillus SG-1. The reaction of Mn(II) depends on O(2) and is inhibited by azide, consistent with MCO catalysis. We show that the subsequent conversion of Mn(III) to MnO(2) also depends on O(2) and is inhibited by azide. Thus, both oxidation steps appear to be MCO-mediated, likely by the same enzyme, which is indicated by genetic evidence to be the MnxG gene product. We propose a model of how the manganese oxidase active site may be organized to couple successive electron transfers to the formation of polynuclear Mn(IV) complexes as precursors to MnO(2) formation. PMID:22892957

  17. 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.

  18. Tetrathiafulvalene-amido-2-pyridine-N-oxide as efficient charge-transfer antenna ligand for the sensitization of Yb(III) luminescence in a series of lanthanide paramagnetic coordination complexes.

    PubMed

    Pointillart, Fabrice; Cauchy, Thomas; Maury, Olivier; Le Gal, Yann; Golhen, Stéphane; Cador, Olivier; Ouahab, Lahcène

    2010-10-18

    The tetrathiafulvalene-amido-2-pyridine-N-oxide (L) ligand has been employed to coordinate 4f elements. The architecture of the complexes mainly depends on the ionic radii of the lanthanides. Thus, the reaction of L in the same experimental protocol leads to three different molecular structure series. Binuclear [Ln(2)(hfac)(5)(O(2)CPhCl)(L)(3)]·2 H(2)O (hfac(-)=1,1,1,5,5,5-hexafluoroacetylacetonate anion, O(2)CPhCl(-)=3-chlorobenzoate anion) and mononuclear [Ln(hfac)(3)(L)(2)] complexes were obtained by using rare-earth ions with either large (Ln(III)=Pr, Gd) or small (Ln(III)=Y, Yb) ionic radius, respectively, whereas the use of Tb(III) that possesses an intermediate ionic radius led to the formation of a binuclear complex of formula [Tb(2)(hfac)(4)(O(2)CPhCl)(2)(L)(2)]. Antiferromagnetic interactions have been observed in the three dinuclear compounds by using an extended empirical method. Photophysical properties of the coordination complexes have been studied by solid-state absorption spectroscopy, whereas time-dependent density functional theory (TD-DFT) calculations have been carried out on the diamagnetic Y(III) derivative to build a molecular orbital diagram and to reproduce the absorption spectrum. For the [Yb(hfac)(3)(L)(2)] complex, the excitation at 19,600 cm(-1) of the HOMO→LUMO+1/LUMO+2 charge-transfer transition induces both line-shape emissions in the near-IR spectral range assigned to the (2)F(5/2)→(2)F(7/2) (9860 cm(-1)) ytterbium-centered transition and a residual charge-transfer emission around 13,150 cm(-1). An efficient antenna effect that proceeds through energy transfer from the singlet excited state of the tetrathiafulvalene-amido-2-pyridine-N-oxide chromophore is evidence of the Yb(III) sensitization.

  19. 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. PMID:19864064

  20. 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.

  1. Crystal structure of a mixed-ligand terbium(III) coordination polymer containing oxalate and formate ligands, having a three-dimensional fcu topology

    PubMed Central

    Kittipong, Chainok; Khemthong, Phailyn; Kielar, Filip; Zhou, Yan

    2016-01-01

    The title compound, poly[(μ 3-formato)(μ 4-oxalato)terbium(III)], [Tb(CHO2)(C2O4)]n, is a three-dimensional coordination polymer, and is isotypic with the LaIII, CeIII and SmIII analogues. The asymmetric unit contains one TbIII ion, one formate anion (CHO2 −) and half of an oxalate anion (C2O4 2−), the latter being completed by application of inversion symmetry. The TbIII ion is nine-coordinated in a distorted tricapped trigonal–prismatic manner by two chelating carboxyl­ate groups from two C2O4 2− ligands, two carboxyl­ate oxygen atoms from another two C2O4 2− ligands and three oxygen atoms from three CHO2 − ligands, with the Tb—O bond lengths and the O—Tb—O bond angles ranging from 2.4165 (19) to 2.478 (3) Å and 64.53 (6) to 144.49 (4)°, respectively. The CHO2 − and C2O4 2− anions adopt μ 3-bridging and μ 4-chelating-bridging coordination modes, respectively, linking adjacent TbIII ions into a three-dimensional 12-connected fcu topology with point symbol (324.436.56). The title compound exhibits thermal stability up to 623 K, and also displays strong green photoluminescence in the solid state at room temperature. PMID:26870593

  2. 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

  3. 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

  4. 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.

  5. Analyses of Group III Secreted Phospholipase A2 Transgenic Mice Reveal Potential Participation of This Enzyme in Plasma Lipoprotein Modification, Macrophage Foam Cell Formation, and Atherosclerosis*S⃞

    PubMed Central

    Sato, Hiroyasu; Kato, Rina; Isogai, Yuki; Saka, Go-ichi; Ohtsuki, Mitsuhiro; Taketomi, Yoshitaka; Yamamoto, Kei; Tsutsumi, Kae; Yamada, Joe; Masuda, Seiko; Ishikawa, Yukio; Ishii, Toshiharu; Kobayashi, Tetsuyuki; Ikeda, Kazutaka; Taguchi, Ryo; Hatakeyama, Shinji; Hara, Shuntaro; Kudo, Ichiro; Itabe, Hiroyuki; Murakami, Makoto

    2008-01-01

    Among the many mammalian secreted phospholipase A2 (sPLA2) enzymes, PLA2G3 (group III secreted phospholipase A2) is unique in that it possesses unusual N- and C-terminal domains and in that its central sPLA2 domain is homologous to bee venom PLA2 rather than to other mammalian sPLA2s. To elucidate the in vivo actions of this atypical sPLA2, we generated transgenic (Tg) mice overexpressing human PLA2G3. Despite marked increases in PLA2 activity and mature 18-kDa PLA2G3 protein in the circulation and tissues, PLA2G3 Tg mice displayed no apparent abnormality up to 9 months of age. However, alterations in plasma lipoproteins were observed in PLA2G3 Tg mice compared with control mice. In vitro incubation of low density (LDL) and high density (HDL) lipoproteins with several sPLA2s showed that phosphatidylcholine was efficiently converted to lysophosphatidylcholine by PLA2G3 as well as by PLA2G5 and PLA2G10, to a lesser extent by PLA2G2F, and only minimally by PLA2G2A and PLA2G2E. PLA2G3-modified LDL, like PLA2G5- or PLA2G10-treated LDL, facilitated the formation of foam cells from macrophages ex vivo. Accumulation of PLA2G3 was detected in the atherosclerotic lesions of humans and apoE-deficient mice. Furthermore, following an atherogenic diet, aortic atherosclerotic lesions were more severe in PLA2G3 Tg mice than in control mice on the apoE-null background, in combination with elevated plasma lysophosphatidylcholine and thromboxane A2 levels. These results collectively suggest a potential functional link between PLA2G3 and atherosclerosis, as has recently been proposed for PLA2G5 and PLA2G10. PMID:18801741

  6. 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

  7. 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%.

  8. Hydration and ion pair formation in common aqueous La(III) salt solutions--a Raman scattering and DFT study.

    PubMed

    Rudolph, Wolfram W; Irmer, Gert

    2015-01-01

    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.

  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. Type III Secretion System Translocon Component EseB Forms Filaments on and Mediates Autoaggregation of and Biofilm Formation by Edwardsiella tarda.

    PubMed

    Gao, Zhi Peng; Nie, Pin; Lu, Jin Fang; Liu, Lu Yi; Xiao, Tiao Yi; Liu, Wei; Liu, Jia Shou; Xie, Hai Xia

    2015-09-01

    The type III secretion system (T3SS) of Edwardsiella tarda plays an important role in infection by translocating effector proteins into host cells. EseB, a component required for effector translocation, is reported to mediate autoaggregation of E. tarda. In this study, we demonstrate that EseB forms filamentous appendages on the surface of E. tarda and is required for biofilm formation by E. tarda in Dulbecco's modified Eagle's medium (DMEM). Biofilm formation by E. tarda in DMEM does not require FlhB, an essential component for assembling flagella. Dynamic analysis of EseB filament formation, autoaggregation, and biofilm formation shows that the formation of EseB filaments occurs prior to autoaggregation and biofilm formation. The addition of an EseB antibody to E. tarda cultures before bacterial autoaggregation prevents autoaggregation and biofilm formation in a dose-dependent manner, whereas the addition of the EseB antibody to E. tarda cultures in which biofilm is already formed does not destroy the biofilm. Therefore, EseB filament-mediated bacterial cell-cell interaction is a prerequisite for autoaggregation and biofilm formation.

  11. Type III Secretion System Translocon Component EseB Forms Filaments on and Mediates Autoaggregation of and Biofilm Formation by Edwardsiella tarda

    PubMed Central

    Gao, Zhi Peng; Nie, Pin; Lu, Jin Fang; Liu, Lu Yi; Xiao, Tiao Yi; Liu, Wei

    2015-01-01

    The type III secretion system (T3SS) of Edwardsiella tarda plays an important role in infection by translocating effector proteins into host cells. EseB, a component required for effector translocation, is reported to mediate autoaggregation of E. tarda. In this study, we demonstrate that EseB forms filamentous appendages on the surface of E. tarda and is required for biofilm formation by E. tarda in Dulbecco's modified Eagle's medium (DMEM). Biofilm formation by E. tarda in DMEM does not require FlhB, an essential component for assembling flagella. Dynamic analysis of EseB filament formation, autoaggregation, and biofilm formation shows that the formation of EseB filaments occurs prior to autoaggregation and biofilm formation. The addition of an EseB antibody to E. tarda cultures before bacterial autoaggregation prevents autoaggregation and biofilm formation in a dose-dependent manner, whereas the addition of the EseB antibody to E. tarda cultures in which biofilm is already formed does not destroy the biofilm. Therefore, EseB filament-mediated bacterial cell-cell interaction is a prerequisite for autoaggregation and biofilm formation. PMID:26116669

  12. 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

    2016-02-01

    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. PMID:26780000

  13. 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

    2016-02-01

    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.

  14. 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

  15. Optical Features of Efficient Europium(III) Complexes with β-Diketonato and Auxiliary Ligands and Mechanistic Investigation of Energy Transfer Process.

    PubMed

    Bala, Manju; Kumar, Satish; Taxak, V B; Boora, Priti; Khatkar, S P

    2016-09-01

    Two new europium (III) complexes have been synthesized with 1,3-[bis(4-methoxyphenyl)]propane-1,3-dionato (HBMPD) as main ligand and 2,2'-bipyridyl (bipy) or 1,10-phenanthroline (phen) as an auxiliary ligand. The main ligand HBMPD has been synthesized by ecofriendly microwave approach and complexes by solution precipitation method. The resulting materials are characterized by IR, (1)H-NMR, elemental analysis, X-ray diffraction, UV-visible and TG-DTG techniques. The photoluminescence (PL) spectroscopy depicts the detail analysis of photophysical properties of the complexes, their results show that the ligand interact with Eu (III) ion which act as antenna and transfers the absorbed energy to the central europium(III) ion via sensitization process efficiently. As a consequence of this interaction, these materials exhibit excellent luminescent intensity, long decay time (τ), high quantum efficiency (η) and Judd-Ofelt intensity parameter (Ω2). The CIE coordinates fall under the deep red region, matching well with the NTSC (National Television Standard Committee) standard. Hence, these highly efficient optical materials can be used as a red component in organic light emitting diodes (OLEDs) and full color flat panel displays. PMID:27444962

  16. Ycs4 is Required for Efficient Double-Strand Break Formation and Homologous Recombination During Meiosis.

    PubMed

    Hong, Soogil; Choi, Eui-Hwan; Kim, Keun Pil

    2015-07-01

    Condensin is not only responsible for chromosome condensation, but is also involved in double-strand break (DSB) processing in the cell cycle. During meiosis, the condensin complex serves as a component of the meiotic chromosome axis, and mediates both proper assembly of the synaptonemal complex and DSB repair, in order to ensure proper homologous chromosome segregation. Here, we used the budding yeast Saccharomyces cerevisiae to show that condensin participates in a variety of chromosome organization processes and exhibits crucial molecular functions that contribute to meiotic recombination during meiotic prophase I. We demonstrate that Ycs4 is required for efficient DSB formation and establishing homolog bias at the early stage of meiotic prophase I, which allows efficient formation of interhomolog recombination products. In the Ycs4 meiosis-specific allele (ycs4S), interhomolog products were formed at substantial levels, but with the same reduction in crossovers and noncrossovers. We further show that, in prophase chromosomal events, ycs4S relieved the defects in the progression of recombination interactions induced as a result of the absence of Rec8. These results suggest that condensin is a crucial coordinator of the recombination process and chromosome organization during meiosis.

  17. 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.

  18. Rapid and efficient generation of neurons from human pluripotent stem cells in a multititre plate format.

    PubMed

    Zhang, Miao; Schöler, Hans R; Greber, Boris

    2013-01-01

    Existing protocols for the generation of neurons from human pluripotent stem cells (hPSCs) are often tedious in that they are multistep procedures involving the isolation and expansion of neural precursor cells, prior to terminal differentiation. In comparison to these time-consuming approaches, we have recently found that combined inhibition of three signaling pathways, TGFβ/SMAD2, BMP/SMAD1, and FGF/ERK, promotes rapid induction of neuroectoderm from hPSCs, followed by immediate differentiation into functional neurons. Here, we have adapted our procedure to a novel multititre plate format, to further enhance its reproducibility and to make it compatible with mid-throughput applications. It comprises four days of neuroectoderm formation in floating spheres (embryoid bodies), followed by a further four days of differentiation into neurons under adherent conditions. Most cells obtained with this protocol appear to be bipolar sensory neurons. Moreover, the procedure is highly efficient, does not require particular expert skills, and is based on a simple chemically defined medium with cost-efficient small molecules. Due to these features, the procedure may serve as a useful platform for further functional investigation as well as for cell-based screening approaches requiring human sensory neurons or neurons of any type. PMID:23486189

  19. 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

  20. Research on Efficiency of Ozonation and Bromate Formation in Low Temperature and Low Turbidity Water

    NASA Astrophysics Data System (ADS)

    Zhu, Qi; Liu, Dongmei; Cui, Fuyi; Fang, Lei; Zhao, Zhiwei; Liu, Tongmian

    2010-11-01

    The efficiency of ozonation and the influence factor of bromate formation were studied in filtered water at low temperature and low turbidity in Harbin Shaohe water treatment plant, of which source water was from Songhua river. The results showed that when adding 3 mg/L O3 to the filtered water, the average removal rate of UV254 were 22.31%, the removal rate of TOC in filtered water were 6.33%. When adding 2 mg/L O3 and 4 mg/L O3 to the filtered water, the CODMn decreased by 21.53% and 24.68%, respectively. Ozonation had no obvious effect on reducing turbidity and the content of ammonia nitrogen of filtered water in Shaohe water treatment plant. It could be found that the formation amount of BrO3- would increase with the concentration of Br- increasing in low temperature and low turbidity water. When Ct value of filtered water in Shaohe water treatment plant was less than 30 mgṡL-1ṡmin, the formation amount of BrO3- could be controlled under 10 μg/L.

  1. 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.

  2. 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)].

  3. 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.

  4. 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

  5. Pseudomonas aeruginosa Exhibits Deficient Biofilm Formation in the Absence of Class II and III Ribonucleotide Reductases Due to Hindered Anaerobic Growth.

    PubMed

    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

  6. Pseudomonas aeruginosa Exhibits Deficient Biofilm Formation in the Absence of Class II and III Ribonucleotide Reductases Due to Hindered Anaerobic Growth.

    PubMed

    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

  7. 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.

  8. mu-1,2-Peroxobridged di-iron(III) dimer formation in human H-chain ferritin.

    PubMed Central

    Bou-Abdallah, Fadi; Papaefthymiou, Georgia C; Scheswohl, Danielle M; Stanga, Sean D; Arosio, Paolo; Chasteen, N Dennis

    2002-01-01

    Biomineralization of the ferritin iron core involves a complex series of events in which H(2)O(2) is produced during iron oxidation by O(2) at a dinuclear centre, the 'ferroxidase site', located on the H-subunit of mammalian proteins. Rapid-freeze quench Mössbauer spectroscopy was used to probe the early events of iron oxidation and mineralization in recombinant human ferritin containing 24 H-subunits. The spectra reveal that a mu-1,2-peroxodiFe(III) intermediate (species P) with Mössbauer parameters delta (isomer shift)=0.58 mm/s and DeltaE(Q) (quadrupole splitting)=1.07 mm/s at 4.2 K is formed within 50 ms of mixing Fe(II) with the apoprotein. This intermediate accounts for almost all of the iron in the sample at 160 ms. It subsequently decays within 10 s to form a mu-oxodiFe(III)-protein complex (species D), which partially vacates the ferroxidase sites of the protein to generate Fe(III) clusters (species C) at a reaction time of 10 min. The intermediate peroxodiFe(III) complex does not decay under O(2)-limiting conditions, an observation suggesting inhibition of decay by unreacted Fe(II), or a possible role for O(2) in ferritin biomineralization in addition to that of direct oxidation of iron(II). PMID:11988076

  9. The citric acid-Mn III,IVO 2(birnessite) reaction. Electron transfer, complex formation, and autocatalytic feedback

    NASA Astrophysics Data System (ADS)

    Wang, Yun; Stone, Alan T.

    2006-09-01

    Citrate released by plants, bacteria, and fungi into soils is subject to abiotic oxidation by MnO 2(birnessite), yielding 3-ketoglutarate, acetoacetate, and Mn II. Citrate loss and generation of products as a function of time all yield S-shaped curves, indicating autocatalysis. Increasing the citrate concentration decreases the induction period. The maximum rate ( rmax) along the reaction coordinate follows a Langmuir-Hinshelwood dependence on citrate concentration. Increases in pH decrease rmax and increase the induction time. Adding Mn II, Zn II, orthophosphate, or pyrophosphate at the onset of reaction decreases rmax. Mn II addition eliminates the induction period, while orthophosphate and pyrophosphate addition increase the induction period. These findings indicate that two parallel processes are responsible. The first, relatively slow process involves the oxidation of free citrate by surface-bound Mn III,IV, yielding Mn II and citrate oxidation products. The second process, which is subject to strong positive feedback, involves electron transfer from Mn II-citrate complexes to surface-bound Mn III,IV, generating Mn III-citrate and Mn II. Subsequent intramolecular electron transfer converts Mn III-citrate into Mn II and citrate oxidation products.

  10. Magnetic bead-based enzyme-chromogenic substrate system for ultrasensitive colorimetric immunoassay accompanying cascade reaction for enzymatic formation of squaric acid-iron(III) chelate.

    PubMed

    Lai, Wenqiang; Tang, Dianping; Zhuang, Junyang; Chen, Guonan; Yang, Huanghao

    2014-05-20

    This work reports on a simple and feasible colorimetric immunoassay with signal amplification for sensitive determination of prostate-specific antigen (PSA, used as a model) at an ultralow concentration by using a new enzyme-chromogenic substrate system. We discovered that glucose oxidase (GOx), the enzyme broadly used in enzyme-linked immunosorbent assay (ELISA), has the ability to stimulate in situ formation of squaric acid (SQA)-iron(III) chelate. GOx-catalyzed oxidization of glucose leads to the formation of gluconic acid and hydrogen peroxide (H2O2). The latter can catalytically oxidize iron(II) to iron(III), which can rapidly (<1 min) coordinate with the SQA. Formation of the iron-squarate complex causes the color of the solution to change from bluish purple to bluish red accompanying the increasing absorbance with the increment of iron(III) concentration. On the basis of the SQA-iron(III) system, a new immunoassay protocol with GOx-labeled anti-PSA detection antibody can be designed for the detection of target PSA on capture antibody-functionalized magnetic immunosensing probe, monitored by recording the color or absorbance (λ = 468 nm) of the generated SQA-iron(III) chelate. The absorbance intensity shows to be dependent on the concentration of target PSA. A linear dependence between the absorbance and target PSA concentration is obtained under optimal conditions in the range from 1.0 pg mL(-1) to 30 ng mL(-1) with a detection limit (LOD) of 0.5 pg mL(-1) (0.5 ppt) estimated at the 3Sblank level. The sensitivity displays to be 3-5 orders of magnitude better than those of most commercialized human PSA ELISA kits. In addition, the developed colorimetric immunoassay was validated by assaying 12 human serum samples, receiving in good accordance with those obtained by the commercialized PSA ELISA kit. Importantly, the SQA-based immunosensing system can be further extended for the detection of other low-abundance proteins or biomarkers by controlling the target

  11. 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

    2015-07-01

    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.

  12. 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.

  13. An HDAC inhibitor enhances cancer therapeutic efficiency of RNA polymerase III promoter-driven IDO shRNA.

    PubMed

    Yen, M-C; Weng, T-Y; Chen, Y-L; Lin, C-C; Chen, C-Y; Wang, C-Y; Chao, H-L; Chen, C-S; Lai, M-D

    2013-06-01

    Histone deacetylase (HDAC) inhibitors are used in treating certain human malignancies. Our laboratories demonstrated their capability in enhancing antitumor effect of DNA vaccine driven by an RNA polymerase II (RNA pol II) promoter. However, it is unknown whether HDAC inhibitors enhance the therapeutic short hairpin RNA (shRNA) expressed by an RNA polymerase III (RNA pol III) promoter. We investigated whether HDAC inhibitors augmented antitumor effect of indoleamine 2,3 dioxygenase (IDO) shRNA. HDAC inhibitor OSU-HDAC42 and suberoylanilide hydroxamic acid enhanced RNA pol III-driven U6 and H1 promoter activity in three different cell types in vitro: 293, NIH3T3 and dendritic cell line DC2.4. Subcutaneous injection of OSU-HDAC42 enhanced U6 and H1 promoter activity on abdominal skin of mice in vivo. Combination of IDO shRNA and OSU-HDAC42 increased antitumor effect of IDO shRNA in MBT-2 murine bladder tumor model. IDO shRNA induced tumor-infiltrating CD8⁺ and CD4⁺ T cells, whereas OSU-HDAC42 treatment induced tumor-infiltrating CD4⁺ T cells. Combination of OSU-HDAC42 and IDO shRNA further induced tumor-infiltrating natural killer cells and enhanced interferon-γ in lymphocytes, but suppressed interleukin (IL)-4 expression of lymphocytes. In addition, OSU-HDAC42 treatment did not alter mRNA expression of IL-12 and tumor necrosis factor-α. In conclusion, HDAC inhibitor OSU-HDAC42 may serve as adjuvant of the therapeutic shRNA expressed by an RNA pol III promoter.

  14. 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⊙.

  15. An efficient means to mitigate wavefront curvature effects in polar format processed SAR imagery

    NASA Astrophysics Data System (ADS)

    Linnehan, Robert; Yasuda, Mark; Doerry, Armin

    2012-06-01

    Synthetic aperture radar (SAR) images processed using the polar format algorithm (PFA) may exhibit distortion if the curvature of the spherical wavefronts are not accounted for. The distortion manifests in geometric shifts and defocusing of targets, and intensifies as distances between pixels and the scene reference position increase. In this work, we demonstrate a method to mitigate the effects of wavefront curvature by applying localized (space-variant) phase corrections to sub-regions selected from the polar format processed image. The modified sub-images are then reassembled into a full image. To minimize discontinuities in the reconstructed image, the spatially variant phase adjustments are made to regions larger than the sub-images, and pared down before being reinserted into the complete image. The result is a SAR process that retains the efficiency of the PFA, yet avoids scene size limitations due to wavefront curvature distortions. The method is illustrated and validated using simulations and real data collected by the General Atomics Aeronautical Systems, Inc. (GA-ASI) Lynx® Multi-mode Radar System.

  16. 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.

  17. Efficient Isoprene Secondary Organic Aerosol Formation from a Non-IEPOX Pathway.

    PubMed

    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.

  18. Efficient Isoprene Secondary Organic Aerosol Formation from a Non-IEPOX Pathway.

    PubMed

    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. PMID:27548285

  19. 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.

  20. 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

  1. New calcareous soil-alginate composites for efficient uptake of Fe(III), Mn(II) and As(V) from water.

    PubMed

    El-Sherbiny, Ibrahim M; Abdel-Hamid, Mohammed I; Rashad, Mohamed; Ali, Abdelnaser S M; Azab, Yehia A

    2013-07-25

    In the present study, various grades of sodium alginates were extracted from different brown macro-algae and their characteristics were investigated using FTIR, UV-vis and EA. The alginates were used in combination with different proportions of calcareous soil to develop new composite microparticles as potential sorbents for efficient uptake of Fe(III), Mn(II) and As(V) from water. Under the investigated conditions (1g of composite equilibrated in 100ml of standard metal ion solution), the composites have removed almost 100% of Fe(III) in the concentration range of 0.5-16.0 mg l(-1). Soil, alginate and composites exhibited the highest removal (about 89%) of Mn(II) at 0.5 mg l(-1). Reasonable removal efficiency (50-60%) was recorded at 0.5 mg l(-1) of As(V) whereas, increasing the initial As(V) concentration resulted in marked decrease in removal efficiency. The collected equilibrium data were also fitted to both Langmuir and Freundlich isotherms for all the developed composites. PMID:23768586

  2. 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.

  3. 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

  4. Simulated influence of postweaning production system on performance of different biological types of cattle: III. Biological efficiency.

    PubMed

    Williams, C B; Bennett, G L; Keele, J W

    1995-03-01

    Methods were developed and incorporated into a previously published computer model to predict ME intake and calculate biological efficiencies in terms of grams of empty BW (EBW) and fat-free matter (FFM) gained/megacalorie of ME consumed from weaning to slaughter. Efficiencies were calculated for steers from F1 crosses of 16 sire breeds (Hereford, Angus, Jersey, South Devon, Limousin, Simmental, Charolais, Red Poll, Brown Swiss, Gelbvieh, Maine Anjou, Chianina, Brahman, Sahiwal, Pinzgauer, and Tarentaise) mated to Hereford and Angus dams, grown under nine backgrounding systems, finished at either a low (1.0 kg) or high (1.36 kg) ADG, and slaughtered at 300 kg carcass weight, small or greater degree of marbling, and 28% carcass fat. Backgrounding systems were high ADG (.9 kg) for 111, 167, or 222 d, medium ADG (.5 kg) for 200, 300, or 400 d, and low ADG (.25 kg) for 300 or 400 d, and 0 d backgrounding. The high ADG finishing system was more biologically efficient than the low ADG finishing system, and generally backgrounding systems were less biologically efficient than direct finishing after weaning (0 d backgrounding). Large-framed breeds were more efficient at the constant carcass weight and carcass fatness end point, and breeds that achieved the marbling end point at low levels of carcass fatness were more efficient at this end point. Some small-framed breeds gained EBW more efficiently but gained FFM less efficiently than some of the large-framed breeds. Variation in efficiency between genotypes was greatest with 0 d backgrounding and decreased in the other backgrounding systems. PMID:7608001

  5. Simulated influence of postweaning production system on performance of different biological types of cattle: III. Biological efficiency.

    PubMed

    Williams, C B; Bennett, G L; Keele, J W

    1995-03-01

    Methods were developed and incorporated into a previously published computer model to predict ME intake and calculate biological efficiencies in terms of grams of empty BW (EBW) and fat-free matter (FFM) gained/megacalorie of ME consumed from weaning to slaughter. Efficiencies were calculated for steers from F1 crosses of 16 sire breeds (Hereford, Angus, Jersey, South Devon, Limousin, Simmental, Charolais, Red Poll, Brown Swiss, Gelbvieh, Maine Anjou, Chianina, Brahman, Sahiwal, Pinzgauer, and Tarentaise) mated to Hereford and Angus dams, grown under nine backgrounding systems, finished at either a low (1.0 kg) or high (1.36 kg) ADG, and slaughtered at 300 kg carcass weight, small or greater degree of marbling, and 28% carcass fat. Backgrounding systems were high ADG (.9 kg) for 111, 167, or 222 d, medium ADG (.5 kg) for 200, 300, or 400 d, and low ADG (.25 kg) for 300 or 400 d, and 0 d backgrounding. The high ADG finishing system was more biologically efficient than the low ADG finishing system, and generally backgrounding systems were less biologically efficient than direct finishing after weaning (0 d backgrounding). Large-framed breeds were more efficient at the constant carcass weight and carcass fatness end point, and breeds that achieved the marbling end point at low levels of carcass fatness were more efficient at this end point. Some small-framed breeds gained EBW more efficiently but gained FFM less efficiently than some of the large-framed breeds. Variation in efficiency between genotypes was greatest with 0 d backgrounding and decreased in the other backgrounding systems.

  6. Robust and efficient amide-based nonheme manganese(III) hydrocarbon oxidation catalysts: substrate and solvent effects on involvement and partition of multiple active oxidants.

    PubMed

    Song, Young Joo; Lee, Sun Hwa; Park, Hyun Min; Kim, Soo Hyun; Goo, Hyo Geun; Eom, Geun Hee; Lee, Ju Hoon; Lah, Myoung Soo; Kim, Youngmee; Kim, Sung-Jin; Lee, Ju Eun; Lee, Hong-In; Kim, Cheal

    2011-06-20

    Two new mononuclear nonheme manganese(III) complexes of tetradentate ligands containing two deprotonated amide moieties, [Mn(bpc)Cl(H(2)O)] (1) and [Mn(Me(2)bpb)Cl(H(2)O)]⋅CH(3)OH (2), were prepared and characterized. Complex 2 has also been characterized by X-ray crystallography. Magnetic measurements revealed that the complexes are high spin (S = 5/2) Mn(III) species with typical magnetic moments of 4.76 and 4.95 μ(B), respectively. These nonheme Mn(III) complexes efficiently catalyzed olefin epoxidation and alcohol oxidation upon treatment with MCPBA under mild experimental conditions. Olefin epoxidation by these catalysts is proposed to involve the multiple active oxidants Mn(V)=O, Mn(IV)=O, and Mn(III)-OO(O)CR. Evidence for this approach was derived from reactivity and Hammett studies, KIE (k(H)/k(D)) values, H(2)(18)O-exchange experiments, and the use of peroxyphenylacetic acid as a mechanistic probe. In addition, it has been proposed that the participation of Mn(V)=O, Mn(IV)=O, and Mn(III)-OOR could be controlled by changing the substrate concentration, and that partitioning between heterolysis and homolysis of the O-O bond of a Mn-acylperoxo intermediate (Mn-OOC(O)R) might be significantly affected by the nature of solvent, and that the O-O bond of the Mn-OOC(O)R might proceed predominantly by heterolytic cleavage in protic solvent. Therefore, a discrete Mn(V)=O intermediate appeared to be the dominant reactive species in protic solvents. Furthermore, we have observed close similarities between these nonheme Mn(III) complex systems and Mn(saloph) catalysts previously reported, suggesting that this simultaneous operation of the three active oxidants might prevail in all the manganese-catalyzed olefin epoxidations, including Mn(salen), Mn(nonheme), and even Mn(porphyrin) complexes. This mechanism provides the greatest congruity with related oxidation reactions by using certain Mn complexes as catalysts.

  7. Formation and movement of Fe(III) in horse spleen, H- and L-recombinant ferritins. A fluorescence study.

    PubMed Central

    Cavallo, S.; Mei, G.; Stefanini, S.; Rosato, N.; Finazzi-Agrò, A.; Chiancone, E.

    1998-01-01

    Iron oxidation and incorporation into apoferritins of different subunit composition, namely the recombinant H and L homopolymers and the natural horse spleen heteropolymer (10-15% H), have been followed by steady-state and time-resolved fluorescence. After aerobic addition of 100 Fe(II) atoms/polymer, markedly different kinetic profiles are observed. In the rL-homopolymer a slow monotonic fluorescence quenching is observed which reflects binding, slow oxidation at the threefold apoferritin channels, and diffusion into the protein cavity. In the rH-homopolymer a fast fluorescence quenching is followed by a partial, slow recovery. The two processes have been attributed to Fe(II) binding and oxidation at the ferroxidase centers and to Fe(III) released into the cavity, respectively. The fluorescence kinetics of horse spleen apoferritin is dominated by the H chain contribution and resembles that of the H homopolymer. It brings out clearly that the rate of the overall process is limited by the rate at which Fe(III) leaves the ferroxidase centers of the H chains where binding of incoming Fe(II) and its oxidation take place. The data obtained upon stepwise addition of iron and the results of optical absorption measurements confirm this picture. The correspondence between steady-state and time-resolved data is remarkably good; this is manifest when the latter are used to calculate the change in fluorescence intensity as apparent in the steady-state measurements. PMID:9521120

  8. 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.

  9. Enhanced formation of silver nanoparticles in Ag+-NOM-iron(II, III) systems and antibacterial activity studies.

    PubMed

    Adegboyega, Nathaniel F; Sharma, Virender K; Siskova, Karolina M; Vecerova, Renata; Kolar, Milan; Zbořil, Radek; Gardea-Torresdey, Jorge L

    2014-03-18

    This work reports the role of iron redox pair (Fe(3+)/Fe(2+)) in the formation of naturally occurring silver nanoparticles (AgNPs) in the aquatic environment. The results showed that Fe(3+) or Fe(2+) ions in the mixtures of Ag(+) and natural organic matter enhanced the formation of AgNPs. The formation of AgNPs depended on pH and types of organic matter. Increase in pH enhanced the formation of AgNPs, and humic acids as ligands showed higher formation of AgNPs compared to fulvic acids. The observed results were described by considering the potentials of redox pairs of silver and iron species and the possible species involved in reducing silver ions to AgNPs. Dynamic light scattering and transmission electron microscopy measurements of AgNPs revealed mostly bimodal size distribution with decrease in size of AgNPs due to iron species in the reaction mixture. Minimum inhibitory concentration of AgNPs needed to inhibit the growth of various bacterial species suggested the role of surfaces of tested Gram-positive and Gram-negative bacteria. Stability study of AgNPs, formed in Ag(+)-humic acid/fulvic acids-Fe(3+) mixtures over a period of several months showed high stability of the particles with significant increase in surface plasmon resonance peak. The environmental implications of the results in terms of fate, transport, and ecotoxicity of organic-coated AgNPs are briefly presented. PMID:24524189

  10. 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.

  11. The Type III TGF-β receptor regulates filopodia formation via a Cdc42-mediated IRSP53: NWASP interaction in epithelial cells

    PubMed Central

    Oh, Sun Young; Knelson, Erik. H.; Blobe, Gerard C.; Mythreye, Karthikeyan

    2014-01-01

    Synopsis Cell adhesion and migration are tightly controlled by regulated changes in the actin cytoskeleton. Previously we reported that the TGF-β superfamily coreceptor, the type III TGF-β receptor (TβRIII/betaglycan), regulates cell adhesion, migration and invasion and suppresses cancer progression in part, through activation of the small GTPase, Cdc42, and Cdc42-dependent alterations to the actin cytoskeleton. Here we demonstrate that TβRIII specifically promotes filopodial formation and extension in MCF10A and HMEC mammary epithelial cells. Mechanistically, cell surface TβRIII and Cdc42 colocalize to filopodial structures and co-complex in a β-arrestin2 dependent, and a TβRI/TβRII independent manner. The β-arrestin2-mediated interaction between TβRIII and Cdc42 increases complex formation between the Cdc42 effectors, IRSp53 with N-WASP, to increase filopodial formation. We demonstrate a function link between filopodial structures and epithelial cell adhesion as regulated by the TβRIII-Cdc42 interaction. These studies identify TβRIII as a novel regulator of IRSP53/NWASP via Cdc42 to regulate filopodial formation and cell adhesion. PMID:23750457

  12. 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.

  13. 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.

  14. 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.

  15. On breaking the age-metallicity degeneracy in early-type galaxies: outflows versus star formation efficiency

    NASA Astrophysics Data System (ADS)

    Ferreras, Ignacio; Silk, Joseph

    2000-08-01

    A simple model of chemical enrichment in cluster early-type galaxies is presented where the main parameters driving the formation of the stellar component are reduced to four: the infall time-scale (τf), the formation epoch (zF), the star formation efficiency (Ceff) and the fraction of gas ejected in outflows (Bout). We find that only variations in Bout or Ceff can account for the colour-magnitude relation, so that the most luminous galaxies had low values of ejected gas and high efficiencies. Less massive galaxies can be related either to a lower star formation efficiency (Ceff sequence) or to an increased outflow rate (Bout sequence). The combination of chemical enrichment tracks with population synthesis models is used to explore the correlation between mass-to-light ratios and masses. A significant slope mismatch is found between stellar and total ML ratios, which cannot be explained by an age spread and implies a non-linear correlation between total and stellar mass: MTOT ∝ M1.2ST. The sequences driven by star formation efficiency (Ceff) and outflows (Bout) are shown to predict different trends at high redshift. The variation with redshift of the slope of the fundamental plane will increase significantly in the efficiency sequence - driven by age - and will slightly decrease in the outflow sequence - driven by metallicity. The evolution of the zero-point is similar in both cases and within the observational errors of current observations. Measurement of the dependence of the tilt of the fundamental plane on redshift will break the degeneracy between outflows and star formation efficiency, which will enable us to determine whether the colour-magnitude relation is controlled by age or metallicity.

  16. Role of Viral RNA and Co-opted Cellular ESCRT-I and ESCRT-III Factors in Formation of Tombusvirus Spherules Harboring the Tombusvirus Replicase

    PubMed Central

    Kovalev, Nikolay; de Castro Martín, Isabel Fernández; Pogany, Judit; Barajas, Daniel; Pathak, Kunj; Risco, Cristina

    2016-01-01

    ABSTRACT Plus-stranded RNA viruses induce membrane deformations in infected cells in order to build viral replication complexes (VRCs). Tomato bushy stunt virus (TBSV) co-opts cellular ESCRT (endosomal sorting complexes required for transport) proteins to induce the formation of vesicle (spherule)-like structures in the peroxisomal membrane with tight openings toward the cytosol. In this study, using a yeast (Saccharomyces cerevisiae) vps23Δ bro1Δ double-deletion mutant, we showed that the Vps23p ESCRT-I protein (Tsg101 in mammals) and Bro1p (ALIX) ESCRT-associated protein, both of which bind to the viral p33 replication protein, play partially complementary roles in TBSV replication in cells and in cell extracts. Dual expression of dominant-negative versions of Arabidopsis homologs of Vps23p and Bro1p inhibited tombusvirus replication to greater extent than individual expression in Nicotiana benthamiana leaves. We also demonstrated the critical role of Snf7p (CHMP4), Vps20p, and Vps24p ESCRT-III proteins in tombusvirus replication in yeast and in vitro. Electron microscopic imaging of vps23Δ yeast revealed the lack of tombusvirus-induced spherule-like structures, while crescent-like structures are formed in ESCRT-III deletion yeasts replicating TBSV RNA. In addition, we also showed that the length of the viral RNA affects the sizes of spherules formed in N. benthamiana cells. The 4.8-kb genomic RNA is needed for the formation of spherules 66 nm in diameter, while spherules formed during the replication of the ∼600-nucleotide (nt)-long defective interfering RNA in the presence of p33 and p92 replication proteins are 42 nm. We propose that the viral RNA serves as a “measuring string” during VRC assembly and spherule formation. IMPORTANCE Plant positive-strand RNA viruses, similarly to animal positive-strand RNA viruses, replicate in membrane-bound viral replicase complexes in the cytoplasm of infected cells. Identification of cellular and viral factors

  17. Organic solvent vapor sensitive methylammonium lead trihalide film formation for efficient hybrid perovskite solar cells

    DOE PAGESBeta

    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 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

  18. 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.

  19. 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.

  20. 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.

  1. EARLY-TYPE GALAXIES AT z {approx} 1.3. III. ON THE DEPENDENCE OF FORMATION EPOCHS AND STAR FORMATION HISTORIES ON STELLAR MASS AND ENVIRONMENT

    SciTech Connect

    Rettura, A.; Stanford, S. A.; Jee, M. J.; Mei, S.; Ford, H. C.; Huertas-Company, M.; Raichoor, A.; Moran, S.; Holden, B.; Illingworth, G.; Ellis, R.; Nakata, F.; Nonino, M.; Treu, T.; Blakeslee, J. P.; Demarco, R.; Eisenhardt, P.; Kodama, T.

    2011-05-10

    We study the environmental dependence of stellar population properties at z {approx} 1.3. We derive galaxy properties (stellar masses, ages, and star formation histories) for samples of massive, red, passive early-type galaxies (ETGs) in two high-redshift clusters, RXJ0849+4452 and RXJ0848+4453 (with redshifts of z = 1.26 and 1.27, respectively), and compare them with those measured for the RDCS1252.9-2927 cluster at z = 1.24 and with those measured for a similarly mass-selected sample of field contemporaries drawn from the GOODS-South field. Robust estimates of the aforementioned parameters have been obtained by comparing a large grid of composite stellar population models with extensive 8- to 10-band photometric coverage, from the rest-frame far-ultraviolet to the infrared. We find no variations of the overall stellar population properties among the different samples of cluster ETGs. However, when comparing cluster versus field stellar population properties we find that, even if the ages are similar and depend only on galaxy mass, the ones in the field do employ longer timescales to assemble their final mass. We find that, approximately 1 Gyr after the onset of star formation, the majority (75%) of cluster galaxies have already assembled most (>80%) of their final mass, while, by the same time, fewer (35%) field ETGs have. Thus, we conclude that while galaxy mass regulates the timing of galaxy formation, the environment regulates the timescale of their star formation histories.

  2. 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.; Barbera, F. La

    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

  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. Cr(1/3)Zr₂P₃O₁₂ with unusual tetrahedral coordination of Cr(III): peculiarities of the formation, thermal stability and application as a pigment.

    PubMed

    Gorodylova, Nataliia; Kosinová, Veronika; Šulcová, Petra; Bělina, Petr; Vlček, Milan

    2014-11-01

    All the known chromium(III) NASICON-related phosphates are considered to be solid solutions. In these compounds chromium atoms share their position in the basic framework of the crystal lattice with other structure forming elements such as zirconium. In our study, we have hypothesised a completely new way of structural organisation of the chromium(III) zirconium(IV) NASICON framework, consisting in the distribution of chromium over the charge-compensating atom sites with tetrahedral oxygen coordination. The possibility of formation of the corresponding phosphate, Cr(1/3)Zr2P3O12, was studied using a classical ceramic route and a sol-gel method. Structural affiliation of the obtained pure phase product was studied using XRD analysis. The results confirmed that the Cr(1/3)Zr2P3O12 phosphate belongs to monoclinic SW-subtype of the NASICON family. In this structure, chromium atoms occupy charge-compensating sites with a strongly distorted tetrahedral oxygen environment. To the best of our knowledge, it is the first example of tetrahedral coordination of chromium(III) in phosphates. Along with the unusual crystallographic characteristics of chromium, special attention in this paper is devoted to the thermal stability of this phosphate and to its performance as an inorganic pigment. The sample was characterised by heating microscopy and DTA study, particle size distribution analysis, and IR- and VIS-spectroscopy. The stability of the obtained powder in a glaze environment, its colouring performance and lightfastness are discussed as well. PMID:25189199

  5. Direct formation of small Cu2O nanocubes, octahedra, and octapods for efficient synthesis of triazoles

    NASA Astrophysics Data System (ADS)

    Tsai, Ya-Huei; Chanda, Kaushik; Chu, Yi-Ting; Chiu, Chun-Ya; Huang, Michael H.

    2014-07-01

    In most studies describing the preparation of Cu2O crystals of various morphologies, the particle sizes are normally hundreds of nanometers to micrometers due to rapid particle growth, so they are not exactly nanocrystals. Here we report surfactant-free formation of sub-100 nm Cu2O nanocrystals with systematic shape evolution from cubic to octahedral structures by preparing an aqueous mixture of Cu(OAc)2, NaOH, and N2H4 solution. Adjustment of the hydrazine volume enables the particle shape control. Uniform nanocubes and octahedra were synthesized with edge lengths of 37 and 67 nm, respectively. Novel Cu2O octapods with an edge length of 135 nm were also produced by mixing CuCl2 solution, SDS surfactant, NaOH solution, and NH2OH.HCl reductant solution. All of them are nearly the smallest Cu2O nanocrystals of the same shapes ever reported. These small cubes, octahedra, and octapods were employed as catalysts in the direct synthesis of 1,2,3-triazoles from the reaction of alkynes, organic halides, and NaN3 at 55 °C. All of them displayed high product yields in short reaction times. The octahedra enclosed by the {111} facets are the best catalysts, and can catalyze this cycloaddition reaction with high yields in just 2 h when different alkynes were used to make diverse triazole products. Hence, the small Cu2O particles provide time-saving, energy-efficient, and high product yield benefits to organocatalysis.In most studies describing the preparation of Cu2O crystals of various morphologies, the particle sizes are normally hundreds of nanometers to micrometers due to rapid particle growth, so they are not exactly nanocrystals. Here we report surfactant-free formation of sub-100 nm Cu2O nanocrystals with systematic shape evolution from cubic to octahedral structures by preparing an aqueous mixture of Cu(OAc)2, NaOH, and N2H4 solution. Adjustment of the hydrazine volume enables the particle shape control. Uniform nanocubes and octahedra were synthesized with edge

  6. 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.

  7. 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.

  8. 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.

  9. Biphasic modulation of Wnt signaling supports efficient foregut endoderm formation from human pluripotent stem cells.

    PubMed

    Hoepfner, Jeannine; Kleinsorge, Mandy; Papp, Oliver; Ackermann, Mania; Alfken, Susanne; Rinas, Ursula; Solodenko, Wladimir; Kirschning, Andreas; Sgodda, Malte; Cantz, Tobias

    2016-05-01

    Pluripotent stem cells (embryonic stem cells and induced pluripotent stem cells) are of great promise in regenerative medicine, including molecular studies of disease mechanisms, if the affected cell type can be authentically generated during in vitro differentiation. Most existing protocols aim to mimic embryonic development steps by the supplementation of specific cytokines and small molecules, but the involved signaling pathways need further exploration. In this study, we investigated enhanced initial activation of Wnt signaling for definitive endoderm formation and subsequent rapid shutdown of Wnt signaling for proper foregut endoderm specification using 3 μM CHIR99021 and 0.5 μg/mL of secreted frizzled-related protein 5 (sFRP-5) for biphasic modulation of the Wnt pathway. The definitive endoderm and foregut endoderm differentiation capabilities of Wnt pathway-modulated cells were determined based on the expression levels of the endodermal transcription factors SOX17 and FOXA2 and those of the transcription activator GATA4 and the α-fetoprotein (AFP) gene, respectively. Furthermore, the resulting biphasic Wnt pathway modulation was investigated at the protein level by analyzing phosphorylation of glycogen synthase kinase 3 beta (GSK3β) and β-catenin. Finally, Wnt target gene expression was determined using an improved lentiviral reporter construct that enabled robust T-cell transcription factor 4 (TCF4)/lymphoid enhancer-binding factor 1 (LEF1)-mediated luciferase expression in differentiating pluripotent stem cells. In conclusion, we demonstrated robust, homogeneous, and efficient derivation of foregut endodermal cells by inducing a biphasic modulation of the Wnt signaling pathway. PMID:26861571

  10. 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

  11. An efficient Rh/O2 catalytic system for oxidative C-H activation/annulation: evidence for Rh(I) to Rh(III) oxidation by molecular oxygen.

    PubMed

    Zhang, Guoying; Yang, Lei; Wang, Yanyu; Xie, Yinjun; Huang, Hanmin

    2013-06-19

    A novel and efficient Rh/O2 catalytic system has been developed and shown to catalyze highly efficient oxidative C-H activation/annulation reactions, producing a broad range of isoquinolinium salts with high turnover numbers (up to 740). Mechanistic studies provided strong evidence of facile oxidation of Rh(I) to Rh(III) by molecular oxygen facilitated by acid.

  12. Polymer induced crystallization III. PEO-CdCl 2 and in situ formation of PEO-CdS composite

    NASA Astrophysics Data System (ADS)

    Radhakrishnan, S.

    1994-08-01

    The "in situ" formation of cadmium sulphide in a polyethylene oxide matrix has been studied starting with its complex with cadmium chloride. It has been found that the complex crystallizes in orthorhombic configuration with lattice parameters of a = 8.42 Å, b = 15.39 Å and c = 18.49 Å, and that its morphology is spherulitic. At high concentrations (>1:4 per monomer), the added salt gets excluded out of the spherulites and deposits in the interspherulitic regions. The cadmium sulphide formed from such a complex has mixed α and β phases and its crystallite/particle size depends on the initial concentration of the cadmium chloride.

  13. Efficient Energy Transfer and Metal Coupling in Cyanide-Bridged Heterodinuclear Complexes Based on (Bipyridine)(terpyridine)ruthenium(II) and (Phenylpyridine)iridium(III) Complexes.

    PubMed

    Barthelmes, Kevin; Jäger, Michael; Kübel, Joachim; Friebe, Christian; Winter, Andreas; Wächtler, Maria; Dietzek, Benjamin; Schubert, Ulrich S

    2016-06-01

    We report a series of cyanide-bridged, heterodinuclear iridium(III)-ruthenium(II) complexes with the generalized formula [Ir((R2)2-ppy)2(CN)(μ-CN)Ru(bpy)(tpy-R1)]PF6 (ppy = 2-phenylpyridine, bpy = 2,2'-bipyridine, and tpy = 2,2':6',2″-terpyridine). The structural, spectroscopic, and electrochemical properties were analyzed in the context of variation of the electron-withdrawing (e.g., -F, -Br, -CHO) and -donating (e.g., -Me) and extended π-conjugated groups at several positions. In total, ten dinuclear complexes and the appropriate model complexes have been prepared. The iridium(III)-based emission is almost fully quenched in these complexes, and only the ruthenium(II)-based emission is observed, which indicates an efficient energy transfer toward the Ru center. Upon oxidation of the Ru center, the fluorinated complexes 2 exhibit a broad intervalence charge-transfer transition in the near-infrared region. The complexes are assigned to a weakly coupled class II system according to the Robin-Day classification. The electronic structure was evaluated by density functional theory (DFT) and time-dependent DFT calculations to corroborate the experimental data. PMID:27214264

  14. On the correlation of the Auger generated hot electron emission and efficiency droop in III-N light-emitting diodes

    SciTech Connect

    Sadi, Toufik; Kivisaari, Pyry; Oksanen, Jani; Tulkki, Jukka

    2014-09-01

    Recent experiments presented in by Iveland et al. [Phys. Rev. Lett. 110, 177406 (2013)] demonstrated that hot electron emission from cesiated p-contacts of III-nitride quantum-well (QW) light-emitting diodes (LEDs) coincides with the onset of the efficiency droop. We have carried out Monte Carlo simulations of hot-electron transport in realistic III-N LEDs. The simulations account for the hole population and all relevant electron scattering and recombination processes. We show that Auger recombination generates a significant hot electron population, which is temporarily trapped in the conduction band side-valleys, without decaying completely before reaching the p-contact. The leakage current due to electron overflow and thermal escape from the QWs is shown to have a minimal impact on the droop. We conclude that the experimentally observed hot electrons are created by Auger recombination in QWs, and that the Auger effect as the origin of the droop is the only consistent explanation for the experimental findings of Iveland et al., [Phys. Rev. Lett. 110, 177406 (2013)].

  15. 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.

  16. 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.

  17. 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

  18. Adamantyl-group containing mixed-mode acrylamide-based continuous beds for capillary electrochromatography. Part III. Optimization of the chromatographic efficiency.

    PubMed

    Al-Massaedh, Ayat Allah; Pyell, Ute

    2014-01-17

    In a previous article we described the synthesis of amphiphilic monolithic stationary phases by in situ free radical copolymerization of cyclodextrin-solubilized N-adamantyl acrylamide, piperazinediacrylamide, methacrylamide and vinylsulfonic acid in aqueous medium in pre-treated fused silica capillaries of 100μ.m I.D. In this work, a series of N-adamantyl-group containing acrylamide-based continuous beds is synthesized under variation of different synthesis parameters. The studied synthesis parameters are (i) concentration of the lyotropic salt ammonium sulfate, (ii) concentration of the initiator ammonium persulfate, and (iii) concentration of the negatively charged monomer vinylsulfonic acid in the polymerization mixture. The influence of the synthesis parameters on the chromatographic efficiency is studied under isocratic conditions for a homologues series of alkylphenones in the reversed-phase mode at constant composition of the mobile phase via capillary electrochromatography with varied electric field strength. With varied concentration of the lyotropic salt ammonium sulfate or varied concentration of the initiator ammonium persulfate in the polymerization mixture, a strong impact on the chromatographic efficiency is observed, while there is only a minor influence when varying the molar fraction of the charged monomer VSA. The absence of a significant influence of extra-column band broadening effects on the determined efficiency is confirmed. There is a good repeatability (with respect to capillary-to-capillary variation and run-to-run variation) reached for the theoretical plate heights obtained for DMF and selected alkylphenones in the reversed-phase mode. PMID:24296296

  19. X-ray conversion efficiency and radiation non-uniformity in the hohlraum experiments at Shenguang-III prototype laser facility

    SciTech Connect

    Zhang, Huasen; Song, Peng; Zou, Shiyang Zhao, Yiqing; Zheng, Wudi; Gu, Peijun; Pei, Wenbing; Yang, Dong; Li, Sanwei; Li, Zhichao; Guo, Liang; Wang, Feng; Peng, Xiaoshi; Wei, Huiyue; Xu, Tao; Jiang, Shaoen; Ding, Yongkun

    2014-11-15

    The hohlraum radiation properties are studied experimentally by the Shenguang-III prototype laser facility and numerically by the two-dimensional code LARED with the multi-group radiation transfer model. The measured radiation temperature is consistent with the prediction of the simulations in a wide laser energy range, suggesting that the x-ray conversion efficiency is around 75% at the peak radiation temperature. The delicate hohlraum experiments further show that the radiation intensity inside the hohlraum is significantly non-uniform. The measured radiation flux of the hot spot region is over twice higher than that of the re-emitted wall region. Good agreements between the experiments and simulations further demonstrate the validity of the LARED code to study the hohlraum radiation properties.

  20. The structure of star formation regions. III - Individual regions - Spatial extent, mass, and age of SFR Sagittarius I

    NASA Astrophysics Data System (ADS)

    Stalbovsky, O. I.; Shevchenko, V. S.

    1981-02-01

    Photoelectric UBV photometry was used to study selected stars in the clusters NGC 6530, 6531, 6611, 6613 and near the nebulae M17 and M20. These clusters as well as Bo 14, NGC 6544, 6546, 6595, 6604, Cr 367 and Cr 469, along with field stars in the region and the molecular cloud common to all the objects, make up the unified star formation region Sgr I. Distended along the galactic plane, this region measures 900 x 140 pc. Its stars have a combined mass of about 100,000 solar masses; the mass of the molecular cloud is 10 million to 40 million solar masses. Thirteen Cepheids occur in the region; CR Ser and X Sct are about 50 million years old. The age of the oldest clusters in the region is 20 million to 30 million years old; Sgr I itself is more than 100 million years old.

  1. 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.

  2. 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.

  3. The initial conditions for stellar protocluster formation. III. The Herschel counterparts of the Spitzer Dark Cloud catalogue

    NASA Astrophysics Data System (ADS)

    Peretto, N.; Lenfestey, C.; Fuller, G. A.; Traficante, A.; Molinari, S.; Thompson, M. A.; Ward-Thompson, D.

    2016-05-01

    Context. Galactic plane surveys of pristine molecular clouds are key for establishing a Galactic-scale view of star formation. For this reason, an unbiased sample of infrared dark clouds in the 10° < | l | < 65°, | b | < 1° region of the Galactic plane was built using Spitzer 8 μm extinction. However, intrinsic fluctuations in the mid-infrared background can be misinterpreted as foreground clouds. Aims: The main goal of this study is to disentangle real clouds in the Spitzer Dark Cloud (SDC) catalogue from artefacts due to fluctuations in the mid-infrared background. Methods: We constructed H2 column density maps at ~18″ resolution using the 160 μm and 250 μm data from the Herschel Galactic plane survey Hi-GAL. We also developed an automated detection scheme that confirms the existence of a SDC through its association with a peak on these Herschel column density maps. Detection simulations, along with visual inspection of a small sub-sample of SDCs, have been performed to get more insight into the limitations of our automated identification scheme. Results: Our analysis shows that 76( ± 19)% of the catalogued SDCs are real. This fraction drops to 55( ± 12)% for clouds with angular diameters larger than ~1 arcmin. The contamination of the PF09 catalogue by large spurious sources reflects the large uncertainties associated to the construction of the 8 μm background emission, a key stage in identiying SDCs. A comparison of the Herschel confirmed SDC sample with the BGPS and ATLASGAL samples shows that SDCs probe a unique range of cloud properties, reaching down to more compact and lower column density clouds than any of these two (sub-)millimetre Galactic plane surveys. Conclusions: Even though about half of the large SDCs are spurious sources, the vast majority of the catalogued SDCs do have a Herschel counterpart. The Herschel-confirmed sample of SDCs offers a unique opportunity to study the earliest stages of both low- and high-mass star formation across

  4. 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

  5. Type III Methyltransferase M.NgoAX from Neisseria gonorrhoeae FA1090 Regulates Biofilm Formation and Interactions with Human Cells.

    PubMed

    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) × 10(5) for mutant and 4.67 (±3.09) × 10(4) 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

  6. The acid-catalyzed decompostion of phenacylcobalamin: evidence for the formation of an enol-Co(III) pi-complex intermediate.

    PubMed

    Brown, K L; Chu, M M; Ingraham, L L

    1976-04-01

    Phenacylcobalamin has been synthesized and characterized by thin-layer chromatography and uv-visible spectroscopy, as well as identification of the cobalt-containing and organic products of its cleavage in acid and base and by aerobic photolysis. The major organic product from all three cleavage reactions is acetophenone and the cobalt-containing product is aquacobalamin (or hydroxocobalamin, its conjugate base). In aqueous acidic solution (pH 0 to 7.3, ionic strength 1.0 M, and 25.0 degrees C), the kinetics of the formation of aquacobalamin are biphasic representing the linear sum of two exponential terms. The pH dependence of the first-order rate constant of both phases shows a first-order dependence on proton concentration but with an inflection point ot pH 3.55 for the faster phase and at pH 4.03 for the slower phase. This behavior is interpreted in terms of the specific acid catalyzed formation of an intermediate from both "base on" and "base off" phenacylcobalamin with different second-order rate constants for each form, followed by an intermediate decompotion step with a similar formal mechanism. The nature of the intermediate is discussed and it is concluded to be a pi-complex between cob(III)alamin and the enol of acetophenone. PMID:4086

  7. FORMATION OF COMPACT STELLAR CLUSTERS BY HIGH-REDSHIFT GALAXY OUTFLOWS. III. OBSERVABILITY AND CONNECTION TO HALO GLOBULAR CLUSTERS

    SciTech Connect

    Gray, William J.; Scannapieco, Evan

    2011-12-01

    The early universe hosted a large population of low-mass virialized 'minihalos', that were not massive enough to form stars on their own. While most minihalos were photoevaporated by ionizing photons from star-forming galaxies, these galaxies also drove large outflows, which in some cases would have reached the minihalos in advance of ionization fronts. In the previous papers in this series, we carried out high-resolution, three-dimensional adaptive mesh refinement simulations of outflow-minihalo interactions that included non-equilibrium chemistry, radiative cooling, and turbulent mixing. We found that, for a fiducial set of parameters, minihalos were transformed into dense, chemically homogenous stellar clusters. Here we conduct a suite of simulations that follow these interactions over a wide range of parameters including minihalo mass, minihalo formation redshift, outflow energy, outflow redshift, distance, concentration, and spin. In almost all cases, the shocked minihalos form molecules through non-equilibrium reactions and then cool rapidly to become compact, chemically homogenous stellar clusters. Furthermore, we show that the unique properties of these clusters make them a prime target for direct study with the next generation of telescopes, and that there are many reasons to suspect that their low-redshift counterparts are the observed population of halo globular clusters.

  8. Mutagen formation in a model beef boiling system. III. Purification and identification of three heterocyclic amine mutagens-carcinogens

    SciTech Connect

    Taylor, R.T.; Fultz, E.; Knize, M.

    1985-01-01

    An extensively boiled supernatant/sub 2/ (S/sub 2/) fraction from beef round steak contains two major Salmonella frameshift mutagens, designated as HPLC peaks A and B. These same mutagens arise, but in different proportions, when S/sub 2/ is boiled with creatine phosphate (CP), and they are produced in much greater quantities from a boiled mixture of S/sub 2/ + L-tryptophan (Trp) + CP + FeSO/sub 4/ (S/sub 2//sup */). A third mutagen, peak C, is also generated in the S/sub 2//sup */ mixture. Mutagen peaks A, B, and C were purified to homogeneity and shown by their absorption spectra, mass fragmentation patterns, and other data to be 2-amino-3-methylimidazo(4,5-f)quinoline (IQ), 3-amino-1-methyl-5H-pyrido(4,3-b)-indole (Trp-P-2), and 3-amino-1,4-dimethyl-5H-pyrido(4,3-b)indole (Trp-P-1), respectively. This is the first demonstration that IQ, Trp-P-2, and Trp-P-1 can form under aqueous conditions at 100/sup 0/C from reactions between low molecular weight precursors that are present in meat juice. Further simplification of and studies with the S/sub 2/ fraction of beef muscle should provide relevant information about the mechanisms of frameshift mutagen formation during the cooking of meats and fish.

  9. 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

    2011-10-01

    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. PMID:21842053

  10. 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

  11. Analysis of irrigation pumping and application efficiency in the central Ogallala formation

    SciTech Connect

    Mapp, H.P. Jr.

    1983-01-01

    This study evaluates irrigation technologies designed to increase pumping and application efficiency for irrigated grain sorghum in the Oklahoma Panhandle region. A dynamic grain sorghum plant growth model is incorporated into a farm level simulation model to derive the effects of alternative irrigation schedules on crop yields, water use and producer net returns. Comparisons of proposed irrigation schedules is accomplished using stochastic efficiency and optimal control procedures.

  12. Evolution of the H β + [O III] and [O II] luminosity functions and the [O II] star formation history of the Universe up to z ˜ 5 from HiZELS

    NASA Astrophysics Data System (ADS)

    Khostovan, A. A.; Sobral, D.; Mobasher, B.; Best, P. N.; Smail, I.; Stott, J. P.; Hemmati, S.; Nayyeri, H.

    2015-10-01

    We investigate the evolution of the H β + [O III] and [O II] luminosity functions from z ˜ 0.8 to ˜5 in four redshift slices per emission line using data from the High-z Emission Line Survey (HiZELS). This is the first time that the H β + [O III] and [O II] luminosity functions have been studied at these redshifts in a self-consistent analysis. This is also the largest sample of [O II] and H β + [O III] emitters (3475 and 3298 emitters, respectively) in this redshift range, with large comoving volumes ˜1 × 106 Mpc-3 in two independent volumes (COSMOS and UDS), greatly reducing the effects of cosmic variance. The emitters were selected by a combination of photometric redshift and colour-colour selections, as well as spectroscopic follow-up, including recent spectroscopic observations using DEIMOS and MOSFIRE on the Keck Telescopes and FMOS on Subaru. We find a strong increase in L⋆ and a decrease in φ⋆ for both H β + [O III] and [O II] emitters. We derive the [O II] star formation history of the Universe since z ˜ 5 and find that the cosmic star formation rate density (SFRD) rises from z ˜ 5 to ˜3 and then drops towards z ˜ 0. We also find that our star formation history is able to reproduce the evolution of the stellar mass density up to z ˜ 5 based only on a single tracer of star formation. When comparing the H β + [O III] SFRDs to the [O II] and H α SFRD measurements in the literature, we find that there is a remarkable agreement, suggesting that the H β + [O III] sample is dominated by star-forming galaxies at high-z rather than AGNs.

  13. A CHANDRA STUDY OF THE ROSETTE STAR-FORMING COMPLEX. III. THE NGC 2237 CLUSTER AND THE REGION'S STAR FORMATION HISTORY

    SciTech Connect

    Wang Junfeng; Feigelson, Eric D.; Townsley, Leisa K.; Broos, Patrick S.; Garmire, Gordon; Roman-Zuniga, Carlos G.; Lada, Elizabeth

    2010-06-10

    We present high spatial resolution Chandra X-ray images of the NGC 2237 young stellar cluster on the periphery of the Rosette Nebula. We detect 168 X-ray sources, 80% of which have stellar counterparts in USNO, Two Micron All Sky Survey, and deep FLAMINGOS images. These constitute the first census of the cluster members with 0.2 {approx}< M {approx}< 2 M {sub sun}. Star locations in near-infrared color-magnitude diagrams indicate a cluster age around 2 Myr with a visual extinction of 1 {approx}< A{sub V} {approx}< 3 at 1.4 kpc, the distance of the Rosette Nebula's main cluster NGC 2244. We derive the K-band luminosity function and the X-ray luminosity function of the cluster, which indicate a population {approx}400-600 stars. The X-ray-selected sample shows a K-excess disk frequency of 13%. The young Class II counterparts are aligned in an arc {approx}3 pc long suggestive of a triggered formation process induced by the O stars in NGC 2244. The diskless Class III sources are more dispersed. Several X-ray emitting stars are located inside the molecular cloud and around gaseous pillars projecting from the cloud. These stars, together with a previously unreported optical outflow originating inside the cloud, indicate that star formation is continuing at a low level and the cluster is still growing. This X-ray view of young stars on the western side of the Rosette Nebula complements our earlier studies of the central cluster NGC 2244 and the embedded clusters on the eastern side of the Nebula. The large-scale distribution of the clusters and molecular material is consistent with a scenario in which the rich central NGC 2244 cluster formed first, and its expanding H II region triggered the formation of the now-unobscured satellite clusters Rosette Molecular Cloud (RMC) XA and NGC 2237. A large swept-up shell material around the H II region is now in a second phase of collect-and-collapse fragmentation, leading to the recent formation of subclusters. Other clusters deeper

  14. A Chandra Study of the Rosette Star-forming Complex. III. The NGC 2237 Cluster and the Region's Star Formation History

    NASA Astrophysics Data System (ADS)

    Wang, Junfeng; Feigelson, Eric D.; Townsley, Leisa K.; Broos, Patrick S.; Román-Zúñiga, Carlos G.; Lada, Elizabeth; Garmire, Gordon

    2010-06-01

    We present high spatial resolution Chandra X-ray images of the NGC 2237 young stellar cluster on the periphery of the Rosette Nebula. We detect 168 X-ray sources, 80% of which have stellar counterparts in USNO, Two Micron All Sky Survey, and deep FLAMINGOS images. These constitute the first census of the cluster members with 0.2 <~ M <~ 2 M sun. Star locations in near-infrared color-magnitude diagrams indicate a cluster age around 2 Myr with a visual extinction of 1 <~ AV <~ 3 at 1.4 kpc, the distance of the Rosette Nebula's main cluster NGC 2244. We derive the K-band luminosity function and the X-ray luminosity function of the cluster, which indicate a population ~400-600 stars. The X-ray-selected sample shows a K-excess disk frequency of 13%. The young Class II counterparts are aligned in an arc ~3 pc long suggestive of a triggered formation process induced by the O stars in NGC 2244. The diskless Class III sources are more dispersed. Several X-ray emitting stars are located inside the molecular cloud and around gaseous pillars projecting from the cloud. These stars, together with a previously unreported optical outflow originating inside the cloud, indicate that star formation is continuing at a low level and the cluster is still growing. This X-ray view of young stars on the western side of the Rosette Nebula complements our earlier studies of the central cluster NGC 2244 and the embedded clusters on the eastern side of the Nebula. The large-scale distribution of the clusters and molecular material is consistent with a scenario in which the rich central NGC 2244 cluster formed first, and its expanding H II region triggered the formation of the now-unobscured satellite clusters Rosette Molecular Cloud (RMC) XA and NGC 2237. A large swept-up shell material around the H II region is now in a second phase of collect-and-collapse fragmentation, leading to the recent formation of subclusters. Other clusters deeper in the molecular cloud appear unaffected by the

  15. Efficient generation of volatile cadmium species using Ti(III) and Ti(IV) and application to determination of cadmium by cold vapor generation inductively coupled plasma mass spectrometry (CVG-ICP-MS)†

    PubMed Central

    Arslan, Zikri; Yilmaz, Vedat; Rose, LaKeysha

    2015-01-01

    In this study, a highly efficient chemical vapor generation (CVG) approach is reported for determination of cadmium (Cd). Titanium (III) and titanium (IV) were investigated for the first time as catalytic additives along with thiourea, L-cysteine and potassium cyanide (KCN) for generation of volatile Cd species. Both Ti(III) and Ti(IV) provided the highest enhancement with KCN. The improvement with thiourea was marginal (ca. 2-fold), while L-cysteine enhanced signal slightly only with Ti(III) in H2SO4. Optimum CVG conditions were 4% (v/v) HCl + 0.03 M Ti(III) + 0.16 M KCN and 2% (v/v) HNO3 + 0.03 M Ti(IV) + 0.16 M KCN with a 3% (m/v) NaBH4 solution. The sensitivity was improved about 40-fold with Ti(III) and 35-fold with Ti(IV). A limit of detection (LOD) of 3.2 ng L−1 was achieved with Ti(III) by CVG-ICP-MS. The LOD with Ti(IV) was 6.4 ng L−1 which was limited by the blank signals in Ti(IV) solution. Experimental evidence indicated that Ti(III) and Ti(IV) enhanced Cd vapor generation catalytically; for best efficiency mixing prior to reaction with NaBH4 was critical. The method was highly robust against the effects of transition metal ions. No significant suppression was observed in the presence of Co(II), Cr(III), Cu(II), Fe(III), Mn(II), Ni(II) and Zn(II) up to 1.0 μg mL−1. Among the hydride forming elements, no interference was observed from As(III) and Se(IV) at 0.5 μg mL−1 level. The depressive effects from Pb(II) and Sb(III) were not significant at 0.1 μg mL−1 while those from Bi(III) and Sn(II) were marginal. The procedures were validated with determination of Cd by CVG-ICP-MS in a number certified reference materials, including Nearshore seawater (CASS-4), Bone ash (SRM 1400), Dogfish liver (DOLT-4), Mussel tissue (SRM 2976) and Domestic Sludge (SRM 2781). PMID:26251554

  16. 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.

  17. Redox activation of Fe(III)-thiosemicarbazones and Fe(III)-bleomycin by thioredoxin reductase: specificity of enzymatic redox centers and analysis of reactive species formation by ESR spin trapping

    PubMed Central

    Myers, Judith M.; Cheng, Qing; Antholine, William E.; Kalyanaraman, Balaraman; Filipovska, Aleksandra; Arnér, ArnerElias S.J.; Myers, Charles R.

    2013-01-01

    Thiosemicarbazones such as triapine (Tp) and Dp44mT are tridentate iron (Fe) chelators that have well-documented anti-neoplastic activity. While Fe-thiosemicarbazones can undergo redox-cycling to generate reactive species that may have important roles in their cytotoxicity, there is only limited insight into specific cellular agents that can rapidly reduce Fe(III)-thiosemicarbazones and thereby promote their redox activity. Here we report that thioredoxin reductase-1 (TrxR1) and glutathione reductase (GR) have this activity, and that there is considerable specificity to the interactions between specific redox centers in these enzymes and different Fe(III) complexes. Site-directed variants of TrxR1 demonstrate that the selenocysteine (Sec) of the enzyme is not required, whereas the C59 residue and the flavin have important roles. While TrxR1 and GR have analogous C59/flavin motifs, TrxR is considerably faster than GR. For both enzymes, Fe(III)(Tp)2 is reduced faster than Fe(III)(Dp44mT)2. This reduction promotes redox cycling and the generation of hydroxyl radical (HO•) in a peroxide-dependent manner, even with low μM levels of Fe(Tp)2. TrxR also reduces Fe(III)-bleomycin and this activity is Sec-dependent. TrxR cannot reduce Fe(III)-EDTA at significant rates. Our findings are the first to demonstrate pro-oxidant reductive activation of Fe(III)-based antitumor thiosemicarbazones by interactions with specific enzyme species. The marked elevation of TrxR in many tumors could contribute to the selective tumor toxicity of these drugs by enhancing the redox activation of Fe(III)-thiosemicarbazones and the generation of reactive oxygen species such as HO• PMID:23485585

  18. Photophysical efficiency-boost of aqueous aluminium phthalocyanine by hybrid formation with nano-clays.

    PubMed

    Staniford, Mark C; Lezhnina, Marina M; Gruener, Malte; Stegemann, Linda; Kuczius, Rauni; Bleicher, Vera; Strassert, Cristian A; Kynast, Ulrich H

    2015-09-11

    Novel organic-inorganic hybrid materials comprising nanoscaled layered silicates and native aluminium hydroxide phthalocyanine (Al(OH)Pc) allowed for the first time the exploitation of their unique photophysical properties in aqueous ambience. In particular, we were able to observe the efficient emission of Al(OH)Pc-nanoclay hybrids and generation of singlet oxygen in aqueous solution.

  19. Photophysical efficiency-boost of aqueous aluminium phthalocyanine by hybrid formation with nano-clays.

    PubMed

    Staniford, Mark C; Lezhnina, Marina M; Gruener, Malte; Stegemann, Linda; Kuczius, Rauni; Bleicher, Vera; Strassert, Cristian A; Kynast, Ulrich H

    2015-09-11

    Novel organic-inorganic hybrid materials comprising nanoscaled layered silicates and native aluminium hydroxide phthalocyanine (Al(OH)Pc) allowed for the first time the exploitation of their unique photophysical properties in aqueous ambience. In particular, we were able to observe the efficient emission of Al(OH)Pc-nanoclay hybrids and generation of singlet oxygen in aqueous solution. PMID:26221639

  20. 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}).

  1. H5MD: A structured, efficient, and portable file format for molecular data

    NASA Astrophysics Data System (ADS)

    de Buyl, Pierre; Colberg, Peter H.; Höfling, Felix

    2014-06-01

    We propose a new file format named "H5MD" for storing molecular simulation data, such as trajectories of particle positions and velocities, along with thermodynamic observables that are monitored during the course of the simulation. H5MD files are HDF5 (Hierarchical Data Format) files with a specific hierarchy and naming scheme. Thus, H5MD inherits many benefits of HDF5, e.g., structured layout of multi-dimensional datasets, data compression, fast and parallel I/O, and portability across many programming languages and hardware platforms. H5MD files are self-contained, and foster the reproducibility of scientific data and the interchange of data between researchers using different simulation programs and analysis software. In addition, the H5MD specification can serve for other kinds of data (e.g. experimental data) and is extensible to supplemental data, or may be part of an enclosing file structure.

  2. Tunable storage of optical data packets modulated in spectrally efficient formats

    NASA Astrophysics Data System (ADS)

    Schneider, Thomas

    2013-03-01

    An all-optical telecommunications network requires all-optical routers. These routers would be able to process optical signals directly, without the transformation to the electrical domain. Thus, optical routers have the potential to accelerate telecommunications, i.e. to enhance the data rate and to minimize the latency times. Furthermore, since the double transformation at each network node can be omitted, they could be able to reduce the energy consumption of telecommunications. Key elements of optical routers are optical buffers, which are able to store the optical packets prior to processing in order to avoid congestion. Therefore, many different concepts for the realization of optical buffers have been presented so far. Most of these can just store or delay on-off keyed (OOK) signals. However, in optical telecommunications advanced modulation formats will be increasingly used because they are able to improve the transmission properties and to take advantage of the capacity of optical fibers. Thus, advanced modulation formats can drastically increase the transmissible data rates. Most of these advanced formats modulate the carrier's phase or are a combination of amplitude and phase modulation. Here the storage of amplitude and phase modulated data packets with the so called quasi-light-storage (QLS) method will be shown. The QLS relies on the time-bandwidth coherence of each signal. Thus, as long as the sampling theorem in the frequency domain is not violated, a distortion-free storage of optical data packets with a delay-bandwidth product (DBP) of several thousand bits is possible. Here we will discuss the applicability of the QLS method to advanced modulation formats and we show experimental results of the tunable alloptical storage of OOK modulated signals with a DBP of 160 bit and the storage of phase shift keyed signals with a DBP of 60 bits.

  3. Catalysis of peptide formation by inorganic oxides: high efficiency of alumina under mild conditions on the Earth-like planets.

    PubMed

    Basiuk, V A; Sainz-Rojas, J

    2001-01-01

    Amino acid condensation catalyzed by inorganic oxides is a widely recognized way for prebiotic peptide formation. Silica and alumina are widely distributed in the Earth-like planets' crust as minerals of different complexity, and thus are attractive model catalysts for the studies of abiotic peptide synthesis. Experiments performed in other laboratories have shown that this process can be efficient at > 80 degrees C, which is not easy to find on the planetary surface in combination with sufficient concentrations of amino acids and necessary catalysts. In the present work we tested catalytic activity of three forms of alumina (which proved to be an efficient catalyst for this process) in the intermolecular condensation of L-alanine. We expanded the temperature interval down to 55 degrees C and used the simplest permanent heating procedure, without employing fluctuating drying/wetting conditions. The most important finding is that even under the lowest temperature considered (i.e. 55 degrees C), short peptide formation can be detected already after 10-30 days of heating. This fact implies that the abiotic peptide formation might occur in a wide variety of planetary environments, without need for high temperatures, given the presence of amino acid building blocks and alumina-containing minerals.

  4. Efficient inhibition of the formation of joint adhesions by ERK2 small interfering RNAs

    SciTech Connect

    Li, Fengfeng; Ruan, Hongjiang; Fan, Cunyi; Zeng, Bingfang; Wang, Chunyang; Wang, Xiang

    2010-01-01

    Transforming growth factor-{beta}1 and fibroblast growth factor-2 play very important roles in fibroblast proliferation and collagen expression. These processes lead to the formation of joint adhesions through the SMAD and MAPK pathways, in which extracellular signal-regulated kinase (ERK)2 is considered to be crucial. Based on these theories, we examined the effects of a lentivirus-mediated small interfering RNA (siRNA) targeting ERK2 on the suppression of joint adhesion formation in vivo. The effects were assessed in vivo from different aspects including the adhesion score, histology and joint contracture angle. We found that the adhesions in the ERK2 siRNA group became soft and weak, and were easily stretched. Accordingly, the flexion contracture angles in the ERK2 siRNA group were also reduced (P < 0.05 compared with the control group). The animals appeared healthy, with no signs of impaired wound healing. In conclusion, local delivery of a lentivirus-mediated siRNA targeting ERK2 can ameliorate joint adhesion formation effectively and safely.

  5. Short- and long-term efficiency of carboxymethylcellulose (CMC) to prevent crystal formation in South African wine.

    PubMed

    Greeff, A E; Robillard, B; du Toit, W J

    2012-01-01

    Crystal formation in bottled wine occurs due to the over-saturation of wine with potassium bitartrate (KHT) salt when exposed to low temperatures. In this study, special focus was given to the efficiency of a crystallisation-inhibiting additive, carboxymethylcellulose (CMC), which is widely used in the food industry. In 2008, CMC was authorised by the International Organisation of Vine and Wine (OIV) for use in white and sparkling wines, but is not yet officially permitted in all wine-producing countries. The use of CMC could be of economical importance to the wine industry because energy costs due to cooling can be reduced. Unlike traditional cooling methods, the use of CMC theoretically prevents the loss of acidity. In this study, the short- and long-term efficiencies of CMC were investigated in South African white, rosé and red wines. Efficiency was determined primarily by measuring changes in potassium (K(+)) and tartaric acid (H(2)T) concentrations and visual crystal formation. As part of this study CMC's efficiency was compared with several other crystal inhibition treatments, and was also evaluated for its temperature stability over a year. CMC's effect on colour and total phenols was also assessed. The results reveal a high efficiency in preventing losses in K(+) and H(2)T concentrations in white wines, even with an ageing period of up to 12 months. The addition of CMC to rosé wines also delivered certain positive results, but less so for red wine. Three different commercial CMCs were also compared with mannoproteins to prevent changes in K(+) and H(2)T concentrations in three different wines. Furthermore, sensory evaluation was performed to determine certain organoleptic changes as a result of CMC treatments. PMID:22762479

  6. Structures and standard molar enthalpies of formation of a series of Ln(III)–Cu(II) heteronuclear compounds with pyrazine-2,3-dicarboxylic acid

    SciTech Connect

    Yang, Qi; Xie, Gang; Wei, Qing; Chen, Sanping Gao, Shengli

    2014-07-01

    Fifteen lanthanide–copper heteronuclear compounds, formulated as [CuLn{sub 2}(pzdc){sub 4}(H{sub 2}O){sub 6}]·xH{sub 2}O (1–6(x=2), 8(x=3), 9–10(x=4)); [CuLn{sub 2}(pzdc){sub 4}(H{sub 2}O){sub 4}]·xH{sub 2}O (7, 12–13, 15(x=4), 14(x=5), 11(x=8)) (Ln(III)=La(1); Ce(2); Pr(3); Nd(4); Sm(5); Eu(6); Gd(7); Tb(8); Dy(9); Ho(10); Er(11); Tm(12); Yb(13); Lu(14); Y(15); H{sub 2}pzdc (C{sub 6}H{sub 4}N{sub 2}O{sub 4})=pyrazine-2,3-dicarboxylic acid) have been hydrothermally synthesized. All compounds were characterized by element analysis, IR spectroscopy, single-crystal X-ray diffraction and thermal analysis. X-ray diffraction analyses confirm that all compounds are isostructural and feature a 3D brick-like framework structure with (4.6{sup 2}){sub 2}(4{sup 2}.6{sup 2}.8{sup 2})(6{sup 3}){sup 2}(6{sup 5}.8){sub 2} topology. Using 1 mol cm{sup −3} HCl(aq) as calorimetric solvent, with an isoperibol solution–reaction calorimeter, the standard molar enthalpies of formation of all compounds were determined by a designed thermochemical cycle. In addition, solid state luminescence properties of compounds 5, 6, 8 and 9 were studied in the solid state. - Graphical abstract: According to Hess' rule, the standard molar enthalpies of formation of Ln–Cu heterometallic coordination compounds were determined by a designed thermochemical cycle. - Highlights: • Fifteen lanthanide–copper heteronuclear isostructural compounds. • Structurally characterization by IR, X-ray diffraction and thermal analysis. • The standard molar enthalpy of formation. • Isoperibol solution–reaction calorimetry.

  7. Development of advanced drilling, completion, and stimulation systems for minimum formation damage and improved efficiency: A program overview

    SciTech Connect

    Layne, A.W.; Yost, A.B. II

    1994-07-01

    The Department of Energy`s (DOE) Natural Gas Resource and Extraction Program consists of industry/government co-sponsored research, development, and demonstration (RD&D) projects, which focus on gas recovery from both conventional and nonconventional resources. The Drilling, Completion, and Stimulation (DCS) Project focuses on advanced, non-damaging technology systems and equipment for improving gas recovery from conventional and nonconventional reservoirs. As operators move from development of current day economically attractive gas-field development to the lower permeability geologic regions of domestic onshore plays, increasing the emphasis on minimum formation damage DCS will permit economic development of gas reserves. The objective of the Project is to develop and demonstrate cost-effective, advanced technology to accelerate widespread use and acceptance of minimum formation damage DCS systems. The goal of this product development effort is to reduce costs and improve the overall efficiency of vertical, directional, and horizontally drilled wells in gas formations throughout the US. The current focus of the Project is on the development of underbalanced drilling technology and minimum formation damage stimulation technology concurrently with the appropriate completion hardware to improve the economics of domestic natural gas field development. Ongoing drilling technology projects to be discussed include development of an electromagnetic measurement while drilling system for directional and horizontal drilling in underbalanced drilling applications and the development of a steerable air percussion drilling system for hard formation drilling and improved penetration rates. Ongoing stimulation technology projects to be discussed include introduction of carbon dioxide/sand fracturing technology for minimal formation damage.

  8. Efficient Formation of Site-Specific Protein-DNA Hybrids Using Copper-Free Click Chemistry.

    PubMed

    Mukhortava, Ann; Schlierf, Michael

    2016-07-20

    Protein-DNA hybrids have become increasingly popular molecular building blocks in bionanotechnology and single-molecule studies to synergistically combine the programmability of DNA with the chemical diversity of proteins. The growing demand for protein-DNA hybrids requires powerful strategies for their conjugation. Here, we present an efficient two-step method for protein-DNA assembly based on copper-free click chemistry. The method allows site-specificity and high coupling efficiency, while maintaining the conservation of protein activity. We compare our method to a commonly used protocol of direct linkage of maleimide-modified oligos. We demonstrate the significantly higher yield with a protein-DNA conjugate, which is analyzed using single-molecule force spectroscopy. PMID:27322198

  9. An efficient initial guess formation of broken-symmetry solutions by using localized natural orbitals

    NASA Astrophysics Data System (ADS)

    Shoji, Mitsuo; Yoshioka, Yasunori; Yamaguchi, Kizashi

    2014-07-01

    A novel procedure to generate initial broken-symmetry solutions is proposed. Conventional methods for the initial broken-symmetry solutions are the MO alter, HOMO-LUMO mixing and fragment methods. These procedures, however, are quite complex. Our new approach is efficient, automatic and highly practical especially for large QM systems. This approach, called the LNO method, is applied to the following four typical open-shell systems: H2, dicarbene and two iron-sulfur clusters of Rieske-type [2Fe-2S] and [4Fe-4S]. The performance and the efficiency as an electronic structural analysis are discussed. The LNO method will be applicable for general systems in the complicated broken symmetry states.

  10. Liquid metal heat exchanger for efficient heating of soils and geologic formations

    SciTech Connect

    DeVault, Robert C; Wesolowski, David J

    2010-02-23

    Apparatus for efficient heating of subterranean earth includes a well-casing that has an inner wall and an outer wall. A heater is disposed within the inner wall and is operable within a preselected operating temperature range. A heat transfer metal is disposed within the outer wall and without the inner wall, and is characterized by a melting point temperature lower than the preselected operating temperature range and a boiling point temperature higher than the preselected operating temperature range.

  11. Universal formation of compositionally graded bulk heterojunction for efficiency enhancement in organic photovoltaics.

    PubMed

    Xiao, Zhengguo; Yuan, Yongbo; Yang, Bin; VanDerslice, Jeremy; Chen, Jihua; Dyck, Ondrej; Duscher, Gerd; Huang, Jinsong

    2014-05-21

    A universal method is reported to form graded bulk heterojunction (BHJ) organic photovoltaic devices (OPVs) by a simple solvent-fluxing process. Donors are enriched at the anode and acceptors are enriched at cathode side, matching the gradient electron and hole current across the film. Efficiency enhancements by 15-50% are achieved for all BHJ systems tested compared with the optimized regular BHJ OPVs.

  12. Enhancing the efficiency of sortase-mediated ligations through nickel-peptide complex formation.

    PubMed

    David Row, R; Roark, Travis J; Philip, Marina C; Perkins, Lorena L; Antos, John M

    2015-08-14

    A modified sortase A recognition motif containing a masked Ni(2+)-binding peptide was employed to boost the efficiency of sortase-catalyzed ligation reactions. Deactivation of the Ni(2+)-binding peptide using a Ni(2+) additive improved reaction performance at low to equimolar ratios of the glycine amine nucleophile and sortase substrate. The success of this approach was demonstrated with both peptide and protein substrates. PMID:26152789

  13. An Efficient Format for Nearly Constant-Time Access to Arbitrary Time Intervals in Large Trace Files

    DOE PAGESBeta

    Chan, Anthony; Gropp, William; Lusk, Ewing

    2008-01-01

    A powerful method to aid in understanding the performance of parallel applications uses log or trace files containing time-stamped events and states (pairs of events). These trace files can be very large, often hundreds or even thousands of megabytes. Because of the cost of accessing and displaying such files, other methods are often used that reduce the size of the tracefiles at the cost of sacrificing detail or other information. This paper describes a hierarchical trace file format that provides for display of an arbitrary time window in a time independent of the total size of the file andmore » roughly proportional to the number of events within the time window. This format eliminates the need to sacrifice data to achieve a smaller trace file size (since storage is inexpensive, it is necessary only to make efficient use of bandwidth to that storage). The format can be used to organize a trace file or to create a separate file of annotations that may be used with conventional trace files. We present an analysis of the time to access all of the events relevant to an interval of time and we describe experiments demonstrating the performance of this file format.« less

  14. Efficient surface formation route of interstellar hydroxylamine through NO hydrogenation. II. The multilayer regime in interstellar relevant ices

    NASA Astrophysics Data System (ADS)

    Fedoseev, G.; Ioppolo, S.; Lamberts, T.; Zhen, J. F.; Cuppen, H. M.; Linnartz, H.

    2012-08-01

    Hydroxylamine (NH2OH) is one of the potential precursors of complex pre-biotic species in space. Here, we present a detailed experimental study of hydroxylamine formation through nitric oxide (NO) surface hydrogenation for astronomically relevant conditions. The aim of this work is to investigate hydroxylamine formation efficiencies in polar (water-rich) and non-polar (carbon monoxide-rich) interstellar ice analogues. A complex reaction network involving both final (N2O, NH2OH) and intermediate (HNO, NH2O., etc.) products is discussed. The main conclusion is that hydroxyl-amine formation takes place via a fast and barrierless mechanism and it is found to be even more abundantly formed in a water-rich environment at lower temperatures. In parallel, we experimentally verify the non-formation of hydroxylamine upon UV photolysis of NO ice at cryogenic temperatures as well as the non-detection of NC- and NCO-bond bearing species after UV processing of NO in carbon monoxide-rich ices. Our results are implemented into an astrochemical reaction model, which shows that NH2OH is abundant in the solid phase under dark molecular cloud conditions. Once NH2OH desorbs from the ice grains, it becomes available to form more complex species (e.g., glycine and β-alanine) in gas phase reaction schemes.

  15. Efficient electron-induced removal of oxalate ions and formation of copper nanoparticles from copper(II) oxalate precursor layers

    PubMed Central

    Rückriem, Kai; Grotheer, Sarah; Vieker, Henning; Penner, Paul; Beyer, André; Gölzhäuser, Armin

    2016-01-01

    Summary Copper(II) oxalate grown on carboxy-terminated self-assembled monolayers (SAM) using a step-by-step approach was used as precursor for the electron-induced synthesis of surface-supported copper nanoparticles. The precursor material was deposited by dipping the surfaces alternately in ethanolic solutions of copper(II) acetate and oxalic acid with intermediate thorough rinsing steps. The deposition of copper(II) oxalate and the efficient electron-induced removal of the oxalate ions was monitored by reflection absorption infrared spectroscopy (RAIRS). Helium ion microscopy (HIM) reveals the formation of spherical nanoparticles with well-defined size and X-ray photoelectron spectroscopy (XPS) confirms their metallic nature. Continued irradiation after depletion of oxalate does not lead to further particle growth giving evidence that nanoparticle formation is primarily controlled by the available amount of precursor. PMID:27547602

  16. Variations in the Star Formation Efficiency of the Dense Molecular Gas across the Disks of Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Usero, Antonio; Leroy, Adam K.; Walter, Fabian; Schruba, Andreas; García-Burillo, Santiago; Sandstrom, Karin; Bigiel, Frank; Brinks, Elias; Kramer, Carsten; Rosolowsky, Erik; Schuster, Karl-Friedrich; de Blok, W. J. G.

    2015-10-01

    We present a new survey of HCN(1–0) emission, a tracer of dense molecular gas, focused on the little-explored regime of normal star-forming galaxy disks. Combining HCN, CO, and infrared (IR) emission, we investigate the role of dense gas in star formation, finding systematic variations in both the apparent dense gas fraction (traced by the HCN-to-CO ratio) and the apparent star formation efficiency of dense gas (traced by the IR-to-HCN ratio). The latter may be unexpected, given the recent popularity of gas density threshold models to explain star formation scaling relations. Our survey used the IRAM 30 m telescope to observe HCN(1–0), CO(1–0), and several other emission lines across 29 nearby disk galaxies whose CO(2–1) emission has previously been mapped by the HERACLES survey. We detected HCN in 48 out of 62 observed positions. Because our observations achieve a typical resolution of ∼1.5 kpc and span a range of galaxies and galactocentric radii (56% lie at {r}{gal}\\gt 1 kpc), we are able to investigate the properties of the dense gas as a function of local conditions in a galaxy disk. We focus on how the ratios IR-to-CO, HCN-to-CO, and IR-to-HCN (observational cognates of the star formation efficiency, dense gas fraction, and dense gas star formation efficiency) depend on the stellar surface density, {{{Σ }}}{star}, and the molecular-to-atomic gas ratio, {{{Σ }}}{mol}/{{{Σ }}}{atom}. The HCN-to-CO ratio is low, often ∼1/30, and correlates tightly with both the molecular-to-atomic ratio and the stellar mass surface density across a range of 2.1 dex (factor of ≈125) in both parameters. Thus for the assumption of fixed CO-to-H2 and HCN-to-dense gas conversion factors, the dense gas fraction depends strongly on location in the disk, being higher in the high surface density, highly molecular parts of galaxies. At the same time, the IR-to-HCN ratio (closely related to the star formation efficiency of dense molecular gas) decreases systematically

  17. Mesophilic co-digestion of dairy manure and lipid rich solid slaughterhouse wastes: process efficiency, limitations and floating granules formation.

    PubMed

    Pitk, Peep; Palatsi, Jordi; Kaparaju, Prasad; Fernández, Belén; Vilu, Raivo

    2014-08-01

    Lipid and protein rich solid slaughterhouse wastes are attractive co-substrates to increase volumetric biogas production in co-digestion with dairy manure. Addition of decanter sludge (DS), containing 42.2% of lipids and 35.8% of proteins (total solids basis), up to 5% of feed mixture resulted in a stable process without any indication of long chain fatty acids (LCFA) or free ammonia (NH3) inhibition and in 3.5-fold increase of volumetric biogas production. Contrary, only lipids addition as technical fat (TF) at over 2% of feed mixture resulted in formation of floating granules (FG) and process efficiency decrease. Formed FG had low biodegradability and its organic part was composed of lipids and calcium salts of LCFAs. Anaerobic digestion process intentionally directed to FG formation, could be a viable option for mitigation and control of lipids overload and derived LCFA inhibition. PMID:24907576

  18. Efficient CO2 capture by tertiary amine-functionalized ionic liquids through Li+-stabilized zwitterionic adduct formation

    PubMed Central

    Yang, Zhen-Zhen

    2014-01-01

    Summary Highly efficient CO2 absorption was realized through formation of zwitterionic adducts, combining synthetic strategies to ionic liquids (ILs) and coordination. The essence of our strategy is to make use of multidentate cation coordination between Li+ and an organic base. Also PEG-functionalized organic bases were employed to enhance the CO2-philicity. The ILs were reacted with CO2 to form the zwitterionic adduct. Coordination effects between various lithium salts and neutral ligands, as well as the CO2 capacity of the chelated ILs obtained were investigated. For example, the CO2 capacity of PEG150MeBu2N increased steadily from 0.10 to 0.66 (mol CO2 absorbed per mol of base) through the formation of zwitterionic adducts being stabilized by Li+. PMID:25246955

  19. Efficient electron-induced removal of oxalate ions and formation of copper nanoparticles from copper(II) oxalate precursor layers.

    PubMed

    Rückriem, Kai; Grotheer, Sarah; Vieker, Henning; Penner, Paul; Beyer, André; Gölzhäuser, Armin; Swiderek, Petra

    2016-01-01

    Copper(II) oxalate grown on carboxy-terminated self-assembled monolayers (SAM) using a step-by-step approach was used as precursor for the electron-induced synthesis of surface-supported copper nanoparticles. The precursor material was deposited by dipping the surfaces alternately in ethanolic solutions of copper(II) acetate and oxalic acid with intermediate thorough rinsing steps. The deposition of copper(II) oxalate and the efficient electron-induced removal of the oxalate ions was monitored by reflection absorption infrared spectroscopy (RAIRS). Helium ion microscopy (HIM) reveals the formation of spherical nanoparticles with well-defined size and X-ray photoelectron spectroscopy (XPS) confirms their metallic nature. Continued irradiation after depletion of oxalate does not lead to further particle growth giving evidence that nanoparticle formation is primarily controlled by the available amount of precursor. PMID:27547602

  20. Efficient capture of CO{sub 2} from simulated flue gas by formation of TBAB or TBAF semiclathrate hydrates

    SciTech Connect

    Shuanshi Fan; Shifeng Li; Jingqu Wang; Xuemei Lang; Yanhong Wang

    2009-08-15

    Capturing CO{sub 2} by forming hydrate is an attractive technology for reducing the greenhouse effect. The most primary challenges are high energy consumption, low hydrate formation rate, and separation efficiency. This work presents efficient capture of CO{sub 2} from simulated flue gas (CO{sub 2} (16.60 mol %)/N{sub 2} binary mixtures) by formation of semiclathrate hydrates at 4.5 and 7.1{sup o}C and feed pressures ranging from 2.19 to 7.31 MPa. The effect of 0.293 mol % tetra-n-butyl ammonium bromide (TBAB) and tetra-n-butyl ammonium fluoride (TBAF) on the hydrate formation rate, reactor space velocity, and CO{sub 2} separation efficiency was studied in a 1 L stirred reactor. The results showed the hydrate formation rate constant increased with increasing feed pressure and reached the maximum at 2.82 x 10{sup -7} mol{sup 2}/(s.J) with TBAB and 8.26 x 10{sup -7} mol{sup 2}/(s.J) with TBAF. The space velocity of the hydrate reactor increased with increasing feed pressure and reached a maximum of 13.46 h{sup -1} with TBAB and 25.96 h{sup -1} with TBAF. CO{sub 2} recovery was about 50%, and the optimum CO{sub 2} separation factor with TBAF was 36.98, which was about 4 times higher than that with TBAB in the range of feed pressure. CO{sub 2} could be enriched to 90.40 mol % from simulated flue gas under low feed pressure by two stages of hydrate separation with TBAF. The results demonstrated that TBAB, especially TBAF, could accelerate hydrate formation. The space velocity of the hydrate reactor with TBAB or TBAF was higher than that with THF. CO{sub 2} could be easily enriched in the hydrate phase by two stages of hydrate separation under gentle conditions. 27 refs., 8 figs., 5 tabs.

  1. Observational evidence of a slow downfall of star formation efficiency in massive galaxies during the past 10 Gyr

    NASA Astrophysics Data System (ADS)

    Schreiber, C.; Elbaz, D.; Pannella, M.; Ciesla, L.; Wang, T.; Koekemoer, A.; Rafelski, M.; Daddi, E.

    2016-05-01

    We study the causes of the reported mass-dependence in the slope of the SFR-M∗ relation, the so-called main sequence of star-forming galaxies, and discuss its implication on the physical processes that shaped the star formation history of massive galaxies over cosmic time. We made use of the near-infrared high-resolution imaging from the Hubble Space Telescope in the CANDELS fields to perform a careful bulge-to-disk decomposition of distant galaxies and measure for the first time the slope of the SFR-Mdisk relation at z = 1. We find that this relation very closely follows the shape of the nominal SFR-M∗ correlation, still with a pronounced flattening at the high-mass end. This clearly excludes, at least at z = 1, the progressive growth of quiescent stellar bulges in star-forming galaxies as the main driver for the change of slope of the main sequence. Then, by stacking the Herschel data available in the CANDELS field, we estimated the gas mass (Mgas = MH i + MH2) and the star formation efficiency (SFE ≡ SFR/Mgas) at different positions on the SFR-M∗ relation. We find that the relatively low SFRs observed in massive galaxies (M∗> 5 × 1010 M⊙) are not caused by a reduced gas content, but by a star formation efficiency that is lower by up to a factor of 3 than in galaxies with lower stellar mass. The trend at the lowest masses is probably linked to the dominance of atomic over molecular gas. We argue that this stellar-mass-dependent SFE can explain the varying slope of the main sequence since z = 1.5, hence over 70% of the Hubble time. The drop in SFE occurs at lower masses in the local Universe (M∗> 2 × 1010 M⊙) and is not present at z = 2. Altogether, this provides evidence for a slow decrease in star formation efficiency in massive main sequence galaxies. The resulting loss of star formation is found to be rising starting from z = 2 to reach a level similar to the mass growth of the quiescent population by z = 1. We finally discuss the possible

  2. Increased efficiency of evolved group I intron spliceozymes by decreased side product formation

    PubMed Central

    Amini, Zhaleh N.; Müller, Ulrich F.

    2015-01-01

    The group I intron ribozyme from Tetrahymena was recently reengineered into a trans-splicing variant that is able to remove 100-nt introns from pre-mRNA, analogous to the spliceosome. These spliceozymes were improved in this study by 10 rounds of evolution in Escherichia coli cells. One clone with increased activity in E. coli cells was analyzed in detail. Three of its 10 necessary mutations extended the substrate binding duplexes, which led to increased product formation and reduced cleavage at the 5′-splice site. One mutation in the conserved core of the spliceozyme led to a further reduction of cleavage at the 5′-splice site but an increase in cleavage side products at the 3′-splice site. The latter was partially reduced by six additional mutations. Together, the mutations increased product formation while reducing activity at the 5′-splice site and increasing activity at the 3′-splice site. These results show the adaptation of a ribozyme that evolved in nature for cis-splicing to trans-splicing, and they highlight the interdependent function of nucleotides within group I intron ribozymes. Implications for the possible use of spliceozymes as tools in research and therapy, and as a model for the evolution of the spliceosome, are discussed. PMID:26106216

  3. Experimental and DFT Studies Explain Solvent Control of C-H Activation and Product Selectivity in the Rh(III)-Catalyzed Formation of Neutral and Cationic Heterocycles.

    PubMed

    Davies, David L; Ellul, Charles E; Macgregor, Stuart A; McMullin, Claire L; Singh, Kuldip

    2015-08-01

    A range of novel heterocyclic cations have been synthesized by the Rh(III)-catalyzed oxidative C-N and C-C coupling of 1-phenylpyrazole, 2-phenylpyridine, and 2-vinylpyridine with alkynes (4-octyne and diphenylacetylene). The reactions proceed via initial C-H activation, alkyne insertion, and reductive coupling, and all three of these steps are sensitive to the substrates involved and the reaction conditions. Density functional theory (DFT) calculations show that C-H activation can proceed via a heteroatom-directed process that involves displacement of acetate by the neutral substrate to form charged intermediates. This step (which leads to cationic C-N coupled products) is therefore favored by more polar solvents. An alternative non-directed C-H activation is also possible that does not involve acetate displacement and so becomes favored in low polarity solvents, leading to C-C coupled products. Alkyne insertion is generally more favorable for diphenylacetylene over 4-octyne, but the reverse is true of the reductive coupling step. The diphenylacetylene moiety can also stabilize unsaturated seven-membered rhodacycle intermediates through extra interaction with one of the Ph substituents. With 1-phenylpyrazole this effect is sufficient to suppress the final C-N reductive coupling. A comparison of a series of seven-membered rhodacycles indicates the barrier to coupling is highly sensitive to the two groups involved and follows the trend C-N(+) > C-N > C-C (i.e., involving the formation of cationic C-N, neutral C-N, and neutral C-C coupled products, respectively). PMID:26115418

  4. Rapid and High-Efficiency Laser-Alloying Formation of ZnMgO Nanocrystals

    NASA Astrophysics Data System (ADS)

    Liu, Peisheng; Wang, Hao; Chen, Jun; Li, Xiaoming; Zeng, Haibo

    2016-06-01

    Applications of ZnMgO nanocrystals (NCs), especially in photoelectric detectors, have significant limitations because of the unresolved phase separation in the synthesis process. Here, we propose a rapid and highly efficient ZnMgO NC alloying method based on pulsed laser ablation in liquid. The limit value of homogeneous magnesium (Mg) is pushed from 37% to 62%, and the optical band gap is increased to 3.7 eV with high doping efficiency (>100%). Further investigations on the lattice geometry of ZnMgO NCs indicate that all ZnMgO NCs are hexagonal wurtzite structures, and the (002) and (100) peaks shift to higher diffraction angles with the increase in Mg doping content. The calculated results of the lattice constants a and c slightly decrease based on Bragg’s law and lattice geometry equations. Furthermore, the relationship between annealing temperature and the limit value of homogeneous Mg is examined, and the results reveal that the latter decreases with the former because of the phase separation of MgO. A probable mechanism of zinc magnesium alloy is introduced to expound on the details of the laser-alloying process.

  5. Rapid and High-Efficiency Laser-Alloying Formation of ZnMgO Nanocrystals.

    PubMed

    Liu, Peisheng; Wang, Hao; Chen, Jun; Li, Xiaoming; Zeng, Haibo

    2016-01-01

    Applications of ZnMgO nanocrystals (NCs), especially in photoelectric detectors, have significant limitations because of the unresolved phase separation in the synthesis process. Here, we propose a rapid and highly efficient ZnMgO NC alloying method based on pulsed laser ablation in liquid. The limit value of homogeneous magnesium (Mg) is pushed from 37% to 62%, and the optical band gap is increased to 3.7 eV with high doping efficiency (>100%). Further investigations on the lattice geometry of ZnMgO NCs indicate that all ZnMgO NCs are hexagonal wurtzite structures, and the (002) and (100) peaks shift to higher diffraction angles with the increase in Mg doping content. The calculated results of the lattice constants a and c slightly decrease based on Bragg's law and lattice geometry equations. Furthermore, the relationship between annealing temperature and the limit value of homogeneous Mg is examined, and the results reveal that the latter decreases with the former because of the phase separation of MgO. A probable mechanism of zinc magnesium alloy is introduced to expound on the details of the laser-alloying process. PMID:27324296

  6. Rapid and High-Efficiency Laser-Alloying Formation of ZnMgO Nanocrystals

    PubMed Central

    Liu, Peisheng; Wang, Hao; Chen, Jun; Li, Xiaoming; Zeng, Haibo

    2016-01-01

    Applications of ZnMgO nanocrystals (NCs), especially in photoelectric detectors, have significant limitations because of the unresolved phase separation in the synthesis process. Here, we propose a rapid and highly efficient ZnMgO NC alloying method based on pulsed laser ablation in liquid. The limit value of homogeneous magnesium (Mg) is pushed from 37% to 62%, and the optical band gap is increased to 3.7 eV with high doping efficiency (>100%). Further investigations on the lattice geometry of ZnMgO NCs indicate that all ZnMgO NCs are hexagonal wurtzite structures, and the (002) and (100) peaks shift to higher diffraction angles with the increase in Mg doping content. The calculated results of the lattice constants a and c slightly decrease based on Bragg’s law and lattice geometry equations. Furthermore, the relationship between annealing temperature and the limit value of homogeneous Mg is examined, and the results reveal that the latter decreases with the former because of the phase separation of MgO. A probable mechanism of zinc magnesium alloy is introduced to expound on the details of the laser-alloying process. PMID:27324296

  7. Drug interactions. III. Formation of nitrosamines from therapeutic drugs. Formation, mutagenic properties and safety assessment of propranolol hydrochloride with respect to the intragastric formation of N-nitrosopropranolol under conditions found in patients.

    PubMed

    Raisfeld-Danse, I H; Chen, J

    1983-06-01

    In the preceding report, the kinetics of formation of N-nitrosopropranolol (NNP) from propranolol and inorganic nitrite were determined in solutions of hydrochloric acid over the range of pH similar to that found in the human stomach. In this communication, NNP formation was examined in human gastric juice and in the presence of organic nitrate ester vasodilator drugs. In comparison to HCl solutions, equivalent concentrations of propranolol and nitrite produced similar amounts of NNP in gastric juice; however, the yield increased as the pH was lowered and the kinetics of nitrosamine formation were different. Endogenous nitrite concentrations in 22 samples of human gastric juice were below the minimum concentration (10(-5) M) required for production of detectable levels of NNP. Maximal therapeutic dosages of propranolol (10(-2) M) incubated with isosorbide dinitrate (3,4-6.8 X 10(-3) M) or nitroglycerin (8.6 X 10(-4) M) also failed to produce NNP. However, NNP formed adventitiously during the concentration of aqueous and methylene chloride solutions that contained propranolol and organic nitrates, underscoring the importance of avoiding artifactual formation of nitrosamines. Furthermore, synthetic NNP was not mutagenic in either the Ames tester strains (TA92, TA98, TA100, TA1535, TA1537 and TA1538) or the hepatocyte-mediated mammalian cell mutagenesis assay. We conclude that NNP is unlikely to form in the stomach under conditions normally present in patients. Moreover, even if NNP formed under exceptional circumstances, this compound is unlikely to be a carcinogen. With respect to the potential formation of nitrosamines during drug dissolution in the stomach, long-term therapy with propranolol hydrochloride appears to be safe. PMID:6345752

  8. Highly efficient peptide formation from N-acetylaminoacyl-AMP anhydride and free amino acid

    NASA Technical Reports Server (NTRS)

    Mullins, D. W., Jr.; Lacey, J. C., Jr.

    1983-01-01

    The kinetics of formation of the N-blocked dipeptide, N-acetylglycylglycine, from N-acetylglycyl adenylate anhydride and glycine in aqueous solution at 25 C, and at various PH's are reported. The reaction is of interest in that over a physiologically relevant pH range (6-8), peptide synthesis proceeds more rapidly than hydrolysis, even at those pH's at which this compound becomes increasingly susceptible to base-catalyzed hydrolysis. Under similar conditions, the corresponding unblocked aminoacyl adenylate anhydrides are considerably more unstable, and undergo appreciable hydrlysis in the presence of free amino acid. Because N-blocked aminoacyl adenylate anhydrides serve as model compounds of peptidyl adenylate anhydrides, these results suggest that primitive amino acid polymerization systems may have operated by cyclic reactivation of the peptidyl carboxyl group, rather than that of the incoming amino acid.

  9. Mitotic rounding alters cell geometry to ensure efficient bipolar spindle formation.

    PubMed

    Lancaster, Oscar M; Le Berre, Maël; Dimitracopoulos, Andrea; Bonazzi, Daria; Zlotek-Zlotkiewicz, Ewa; Picone, Remigio; Duke, Thomas; Piel, Matthieu; Baum, Buzz

    2013-05-13

    Accurate animal cell division requires precise coordination of changes in the structure of the microtubule-based spindle and the actin-based cell cortex. Here, we use a series of perturbation experiments to dissect the relative roles of actin, cortical mechanics, and cell shape in spindle formation. We find that, whereas the actin cortex is largely dispensable for rounding and timely mitotic progression in isolated cells, it is needed to drive rounding to enable unperturbed spindle morphogenesis under conditions of confinement. Using different methods to limit mitotic cell height, we show that a failure to round up causes defects in spindle assembly, pole splitting, and a delay in mitotic progression. These defects can be rescued by increasing microtubule lengths and therefore appear to be a direct consequence of the limited reach of mitotic centrosome-nucleated microtubules. These findings help to explain why most animal cells round up as they enter mitosis.

  10. A format standard for efficient interchange of high-contrast direct imaging science products

    NASA Astrophysics Data System (ADS)

    Choquet, Élodie; Vigan, Arthur; Soummer, Rémi; Chauvin, Gaël.; Pueyo, Laurent; Perrin, Marshall D.; Hines, Dean C.

    2014-07-01

    The present and next few years will see the arrival of several new coronagraphic instruments dedicated to the detection and characterization of planetary systems. These ground- and space-based instruments (Gemini/GPI, VLT/SPHERE, Subaru/ CHARIS, JWST NIRCam and MIRI coronagraphs among others), will provide a large number of new candidates, through multiple nearby-star surveys and will complete and extend those acquired with current generation instruments (Palomar P1640, VLT/NACO, Keck, HST). To optimize the use of the wealth of data, including non-detection results, the science products of these instruments will require to be shared among the community. In the long term such data exchange will significantly ease companion confirmations, planet characterization via different type of instruments (integral field spectrographs, polarimetric imagers, etc.), and Monte-Carlo population studies from detection and non-detection results. In this context, we initiated a collaborative effort between the teams developing the data reduction pipelines for SPHERE, GPI, and the JWST coronagraphs, and the ALICE (Archival Legacy Investigations of Circumstellar Environment) collaboration, which is currently reprocessing all the HST/NICMOS coronagraphic surveys. We are developing a standard format for the science products generated by high-contrast direct imaging instruments (reduced image, sensitivity limits, noise image, candidate list, etc.), that is directly usable for astrophysical investigations. In this paper, we present first results of this work and propose a preliminary format adopted for the science product. We call for discussions in the high-contrast direct imaging community to develop this effort, reach a consensus and finalize this standard. This action will be critical to enable data interchange and combination in a consistent way between several instruments and to stiffen the scientific production in the community.

  11. The formation efficiency of high-mass X-ray binaries in our two nearest star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Antoniou, Vallia; Zezas, Andreas

    2016-04-01

    We present the results of our investigation of the link between high-mass X-ray binaries (HMXBs) and star formation in the Magellanic Clouds, our nearest star-forming galaxies. Using the most complete census of HMXBs in the Large Magellanic Cloud (LMC) and the published spatially resolved star-formation history map of this galaxy, we find that the HMXBs (and as expected the X-ray pulsars) are present in regions with star-formation bursts ˜6-25 Myr ago. In contrast, this population peaks at later ages (˜25-60 Myr ago) in the Small Magellanic Cloud (SMC). Thus, this study (in combination with previous works) reinforces the idea that the HMXBs are associated with young stellar populations of ages ˜10-40 Myr. In addition, we estimate an HMXB production rate of 1 system per ˜(23.0-4.1+4.4)×10-3 M⊙/yr or 1 system per ˜143M⊙ of stars formed during the associated star-formation episode. Therefore, the formation efficiency of HMXBs in the LMC is ˜17 times lower than that in the SMC. We attribute this difference primarily in the different ages and metallicity of the HMXB populations in the two galaxies. We also set limits on the kicks imparted on the neutron star during the supernova explosion. We find that the time elapsed since the supernova kick is ˜3 times shorter in the LMC than the SMC. This in combination with the average offsets of the HMXBs from their nearest star clusters results in ˜4 times faster transverse velocities for HMXBs in the LMC than in the SMC.

  12. Molecular beam epitaxy of III-P{sub x}As{sub 1−x} solid solutions: Mechanism of composition formation in the sublattice of a group V element

    SciTech Connect

    Emelyanov, E. A. Putyato, M. A.; Semyagin, B. R.; Feklin, D. F.; Preobrazhensky, V. V.

    2015-02-15

    The effect of substrate temperature, As{sub 2} and P{sub 2} molecular flux densities, and growth rate on the composition of III-P{sub x}As{sub 1−x} solid solution layers prepared by molecular beam epitaxy is experimentally investigated. Experimental data in a wide range of growth conditions are analyzed. The results obtained are presented in the form of a kinetic model for describing the process of formation of the composition in the Group V sublattice of the III-P{sub x}As{sub 1−x} solid solution upon molecular beam epitaxy. The model can be used for choosing the growth conditions of the III-P{sub x}As{sub 1−x} (001) solid-solution layers of a specified composition.

  13. Hydrothermal Synthesis of FeS2 as a High-Efficiency Fenton Reagent to Degrade Alachlor via Superoxide-Mediated Fe(II)/Fe(III) Cycle.

    PubMed

    Liu, Wei; Wang, Yueyao; Ai, Zhihui; Zhang, Lizhi

    2015-12-30

    In this study, we demonstrate that hydrothermally synthesized FeS2 (syn-FeS2) is highly efficient at catalyzing the H2O2 decomposition for alachlor degradation at a wide range of initial pH (3.2-9.2). The alachlor degradation rate of syn-FeS2 heterogeneous Fenton system was almost 55 times that of its commercial pyrite (com-FeS2) counterpart at an initial pH of 6.2. Experimental results revealed that the alachlor oxidation enhancement in the syn-FeS2 Fenton system was attributed to the molecular oxygen activation induced by more surface-bound ferrous ions on syn-FeS2. The molecular oxygen activation process could generate superoxide anions to accelerate the Fe(II)/Fe(III) cycle on the syn-FeS2 surface, which favored the H2O2 decomposition to generate more hydroxyl radicals for the alachlor oxidation. It was found that the hydroxyl radicals generation rate constant of syn-FeS2 Fenton system was 71 times that of its com-FeS2 counterpart, and even 1-3 orders of magnitude larger than those of commonly used Fe-bearing heterogeneous catalysts. We detected the alachlor degradation intermediates with gas chromatography-mass spectrometry to propose tentatively a possible alachlor degradation pathway. These interesting findings could provide some new insights on the molecular oxygen activation induced by FeS2 minerals and the subsequent heterogeneous Fenton degradation of organic pollutants in the environment. PMID:26646468

  14. Oxidation of Benzene by Persulfate in the Presence of Fe(III)- and Mn(IV)-Containing Oxides: Stoichiometric Efficiency and Transformation Products.

    PubMed

    Liu, Haizhou; Bruton, Thomas A; Li, Wei; Buren, Jean Van; Prasse, Carsten; Doyle, Fiona M; Sedlak, David L

    2016-01-19

    Sulfate radical (SO4(•-)) is a strong, short-lived oxidant that is produced when persulfate (S2O8(2-)) reacts with transition metal oxides during in situ chemical oxidation (ISCO) of contaminated groundwater. Although engineers are aware of the ability of transition metal oxides to activate persulfate, the operation of ISCO remediation systems is hampered by an inadequate understanding of the factors that control SO4(•-) production and the overall efficiency of the process. To address these shortcomings, we assessed the stoichiometric efficiency and products of transition metal-catalyzed persulfate oxidation of benzene with pure iron- and manganese-containing minerals, clays, and aquifer solids. For most metal-containing solids, the stoichiometric efficiency, as determined by the loss of benzene relative to the loss of persulfate, approached the theoretical maximum. Rates of production of SO4(•-) or hydroxyl radical (HO(•)) generated from radical chain reactions were affected by the concentration of benzene, with rates of S2O8(2-) decomposition increasing as the benzene concentration increased. Under conditions selected to minimize the loss of initial transformation products through reaction with radicals, the production of phenol only accounted for 30%-60% of the benzene lost in the presence of O2. The remaining products included a ring-cleavage product that appeared to contain an α,β-unsaturated aldehyde functional group. In the absence of O2, the concentration of the ring-cleavage product increased relative to phenol. The formation of the ring-cleavage product warrants further studies of its toxicity and persistence in the subsurface.

  15. In situ formation of cobalt oxide nanocubanes as efficient oxygen evolution catalysts.

    PubMed

    Hutchings, Gregory S; Zhang, Yan; Li, Jian; Yonemoto, Bryan T; Zhou, Xinggui; Zhu, Kake; Jiao, Feng

    2015-04-01

    Oxygen evolution from water poses a significant challenge in solar fuel production because it requires an efficient catalyst to bridge the one-electron photon capture process with the four-electron oxygen evolution reaction (OER). Here, a new strategy was developed to synthesize nonsupported ultrasmall cobalt oxide nanocubanes through an in situ phase transformation mechanism using a layered Co(OH)(OCH3) precursor. Under sonication, the precursor was exfoliated and transformed into cobalt oxide nanocubanes in the presence of NaHCO3-Na2SiF6 buffer solution. The resulting cobalt catalyst with an average particle size less than 2 nm exhibited a turnover frequency of 0.023 per second per cobalt in photocatalytic water oxidation. X-ray absorption results suggested a unique nanocubane structure, where 13 cobalt atoms fully coordinated with oxygen in an octahedral arrangement to form 8 Co4O4 cubanes, which may be responsible for the exceptionally high OER activity.

  16. [Role of Bacterial Adhesin RAPA1 in Formation of Efficient Symbiosis of Rhizobium leguminosarum with Bean Plants].

    PubMed

    Nigmatullina, L R; Lavina, A M; Vershinina, Z R; Baimiev, Al Kh

    2015-01-01

    Bacterial adhesins, the proteins responsible for attachment of plant growth-promoting rhizobacteria to plant roots, are involved in formation of stable associative symbioses. In the present work enhanced expression of the rapA1 adhesin gene in Rhizobium leguminosarum PVu5 was shown to improve the efficiency of nodulation on bean roots inoculated with the modified strain. The rapA1 gene was cloned into the pJN105Turbo plasmid, this construct was used for transformation of R. leguminosarum PVu5, bean plants were inoculated by this transgenic strain, and efficiency of root nodule formation was determined. In the plants treated with rapA1-transgenic rhizobia, the number of root nodules was on average two times higher than in the plants inoculated with the original strain. Aggregation of R. leguminosarum was achieved when the rapA1 gene expression was enhanced either in rhizobia or in the co-cultured modified strain E. coli pJN105TurboRapA1.

  17. neuTube 1.0: A New Design for Efficient Neuron Reconstruction Software Based on the SWC Format.

    PubMed

    Feng, Linqing; Zhao, Ting; Kim, Jinhyun

    2015-01-01

    Brain circuit mapping requires digital reconstruction of neuronal morphologies in complicated networks. Despite recent advances in automatic algorithms, reconstruction of neuronal structures is still a bottleneck in circuit mapping due to a lack of appropriate software for both efficient reconstruction and user-friendly editing. Here we present a new software design based on the SWC format, a standardized neuromorphometric format that has been widely used for analyzing neuronal morphologies or sharing neuron reconstructions via online archives such as NeuroMorpho.org. We have also implemented the design in our open-source software called neuTube 1.0. As specified by the design, the software is equipped with parallel 2D and 3D visualization and intuitive neuron tracing/editing functions, allowing the user to efficiently reconstruct neurons from fluorescence image data and edit standard neuron structure files produced by any other reconstruction software. We show the advantages of neuTube 1.0 by comparing it to two other software tools, namely Neuromantic and Neurostudio. The software is available for free at http://www.neutracing.com, which also hosts complete software documentation and video tutorials. PMID:26464967

  18. [Role of Bacterial Adhesin RAPA1 in Formation of Efficient Symbiosis of Rhizobium leguminosarum with Bean Plants].

    PubMed

    Nigmatullina, L R; Lavina, A M; Vershinina, Z R; Baimiev, Al Kh

    2015-01-01

    Bacterial adhesins, the proteins responsible for attachment of plant growth-promoting rhizobacteria to plant roots, are involved in formation of stable associative symbioses. In the present work enhanced expression of the rapA1 adhesin gene in Rhizobium leguminosarum PVu5 was shown to improve the efficiency of nodulation on bean roots inoculated with the modified strain. The rapA1 gene was cloned into the pJN105Turbo plasmid, this construct was used for transformation of R. leguminosarum PVu5, bean plants were inoculated by this transgenic strain, and efficiency of root nodule formation was determined. In the plants treated with rapA1-transgenic rhizobia, the number of root nodules was on average two times higher than in the plants inoculated with the original strain. Aggregation of R. leguminosarum was achieved when the rapA1 gene expression was enhanced either in rhizobia or in the co-cultured modified strain E. coli pJN105TurboRapA1. PMID:26964360

  19. neuTube 1.0: A New Design for Efficient Neuron Reconstruction Software Based on the SWC Format 123

    PubMed Central

    Feng, Linqing

    2015-01-01

    Abstract Brain circuit mapping requires digital reconstruction of neuronal morphologies in complicated networks. Despite recent advances in automatic algorithms, reconstruction of neuronal structures is still a bottleneck in circuit mapping due to a lack of appropriate software for both efficient reconstruction and user-friendly editing. Here we present a new software design based on the SWC format, a standardized neuromorphometric format that has been widely used for analyzing neuronal morphologies or sharing neuron reconstructions via online archives such as NeuroMorpho.org. We have also implemented the design in our open-source software called neuTube 1.0. As specified by the design, the software is equipped with parallel 2D and 3D visualization and intuitive neuron tracing/editing functions, allowing the user to efficiently reconstruct neurons from fluorescence image data and edit standard neuron structure files produced by any other reconstruction software. We show the advantages of neuTube 1.0 by comparing it to two other software tools, namely Neuromantic and Neurostudio. The software is available for free at http://www.neutracing.com, which also hosts complete software documentation and video tutorials. PMID:26464967

  20. Evaluation of Injection Efficiency of Carbon Dioxide Using an Integrated Injection Well and Geologic Formation Numerical Simulation Scheme

    NASA Astrophysics Data System (ADS)

    Kihm, J.; Park, S.; Kim, J.; SNU CO2 GEO-SEQ TEAM

    2011-12-01

    A series of integrated injection well and geologic formation numerical simulations was performed to evaluate the injection efficiency of carbon dioxide using a multiphase thermo-hydrological numerical model. The numerical simulation results show that groundwater flow, carbon dioxide flow, and heat transport in both injection well and sandstone formation can be simultaneously analyzed, and thus the injection efficiency (i.e., injection rate and injectivity) of carbon dioxide can be quantitatively evaluated using the integrated injection well and geologic formation numerical simulation scheme. The injection rate and injectivity of carbon dioxide increase rapidly during the early period of time (about 10 days) and then increase slightly up to about 2.07 kg/s (equivalent to 0.065 Mton/year) and about 2.84 × 10-7 kg/s/Pa, respectively, until 10 years for the base case. The sensitivity test results show that the injection pressure and temperature of carbon dioxide at the wellhead have significant impacts on its injection rate and injectivity. The vertical profile of the fluid pressure in the injection well becomes almost a hydrostatical equilibrium state within 1 month for all the cases. The vertical profile of the fluid temperature in the injection well becomes a monotonously increasing profile with the depth due to isenthalpic or adiabatic compression within 6 months for all the cases. The injection rate of carbon dioxide increases linearly with the fluid pressure difference between the well bottom and the sandstone formation far from the injection well. In contrast, the injectivity of carbon dioxide varies unsystematically with the fluid pressure difference. On the other hand, the reciprocal of the kinematic viscosity of carbon dioxide at the well bottom has an excellent linear relationship with the injectivity of carbon dioxide. It indicates that the above-mentioned variation of the injectivity of carbon dioxide can be corrected using this linear relationship. The

  1. Structural, magnetic and phonon properties of Cr(III)-doped perovskite metal formate framework [(CH3)2NH2][Mn(HCOO)3

    NASA Astrophysics Data System (ADS)

    Mączka, Mirosław; Gągor, Anna; Hermanowicz, Krzysztof; Sieradzki, Adam; Macalik, Lucyna; Pikul, Adam

    2016-05-01

    We have incorporated Cr(III) into [(CH3)2NH2][Mn(HCOO)3] (DMMn) multiferroic metal organic framework (MOF). The highest concentration of Cr(III) in the synthesized samples reached 15.9 mol%. The obtained samples were characterized by powder and single-crystal X-ray diffraction, DSC, magnetic susceptibility, dielectric, EPR, Raman and IR methods. These methods and the performed chemical analysis revealed that electrical charge neutrality after substitution of Cr(III) for Mn(II) is maintained by partial replacement of dimethylammonium (DMA+) cations by neutral HCOOH molecules. These changes in the chemical composition are responsible for weakening of the hydrogen bonds and decreased flexibility of the framework. This in turn leads to lowering of the ferroelectric phase transition temperature, observed around 185 K for undoped DMMn and around 155 K for the sample containing 3.1 mol% of Cr(III), and lack of macroscopic phase transition for the samples with Cr(III) content of 8.2 and 15.9 mol %. Another interesting effect observed for the studied samples is pronounced strengthening of the weak ferromagnetism of in Cr(III)-doped samples, associated with slight decrease of the ferromagnetic ordering temperature from 8.5 K for DMMn to 7.0 K for the sample with 15.9 mol % Cr(III) content.

  2. Efficient surface formation route of interstellar hydroxylamine through NO hydrogenation. I. The submonolayer regime on interstellar relevant substrates.

    PubMed

    Congiu, E; Chaabouni, H; Laffon, C; Parent, P; Baouche, S; Dulieu, F

    2012-08-01

    Dust grains in the interstellar medium are known to serve as the first chemical laboratory where the rich inventory of interstellar molecules are synthesized. Here we present a study of the formation of hydroxylamine--NH(2)OH--via the non-energetic route NO + H (D) on crystalline H(2)O and amorphous silicate under conditions relevant to interstellar dense clouds. Formation of nitrous oxide (N(2)O) and water (H(2)O, D(2)O) is also observed and the reaction network is discussed. Hydroxylamine and water results are detected in temperature-programmed desorption (TPD) experiments, while N(2)O is detected by both reflection-absorption IR spectroscopy and TPD techniques. The solid state NO + H reaction channel proves to be a very efficient pathway to NH(2)OH formation in space and may be a potential starting point for prebiotic species in dark interstellar clouds. The present findings are an important step forward in understanding the inclusion of interstellar nitrogen into a non-volatile aminated species since NH(2)OH provides a solid state nitrogen reservoir along the whole evolutionary process of interstellar ices from dark clouds to planetary systems.

  3. In situ formation of graphene layers on graphite surfaces for efficient anodes of microbial fuel cells.

    PubMed

    Tang, Jiahuan; Chen, Shanshan; Yuan, Yong; Cai, Xixi; Zhou, Shungui

    2015-09-15

    Graphene can be used to improve the performance of the anode in a microbial fuel cell (MFC) due to its good biocompatibility, high electrical conductivity and large surface area. However, the chemical production and modification of the graphene on the anode are environmentally hazardous because of the use of various harmful chemicals. This study reports a novel method based on the electrochemical exfoliation of a graphite plate (GP) for the in situ formation of graphene layers on the surface of a graphite electrode. When the resultant graphene-layer-based graphite plate electrode (GL/GP) was used as an anode in an MFC, a maximum power density of 0.67 ± 0.034 W/m(2) was achieved. This value corresponds to 1.72-, 1.56- and 1.26-times the maximum power densities of the original GP, exfoliated-graphene-modified GP (EG/GP) and chemically-reduced-graphene-modified GP (rGO/GP) anodes, respectively. Electrochemical measurements revealed that the high performance of the GL/GP anode was attributable to its macroporous structure, improved electron transfer and high electrochemical capacitance. The results demonstrated that the proposed method is a facile and environmentally friendly synthesis technique for the fabrication of high-performance graphene-based electrodes for use in microbial energy harvesting. PMID:25950933

  4. In situ formation of graphene layers on graphite surfaces for efficient anodes of microbial fuel cells.

    PubMed

    Tang, Jiahuan; Chen, Shanshan; Yuan, Yong; Cai, Xixi; Zhou, Shungui

    2015-09-15

    Graphene can be used to improve the performance of the anode in a microbial fuel cell (MFC) due to its good biocompatibility, high electrical conductivity and large surface area. However, the chemical production and modification of the graphene on the anode are environmentally hazardous because of the use of various harmful chemicals. This study reports a novel method based on the electrochemical exfoliation of a graphite plate (GP) for the in situ formation of graphene layers on the surface of a graphite electrode. When the resultant graphene-layer-based graphite plate electrode (GL/GP) was used as an anode in an MFC, a maximum power density of 0.67 ± 0.034 W/m(2) was achieved. This value corresponds to 1.72-, 1.56- and 1.26-times the maximum power densities of the original GP, exfoliated-graphene-modified GP (EG/GP) and chemically-reduced-graphene-modified GP (rGO/GP) anodes, respectively. Electrochemical measurements revealed that the high performance of the GL/GP anode was attributable to its macroporous structure, improved electron transfer and high electrochemical capacitance. The results demonstrated that the proposed method is a facile and environmentally friendly synthesis technique for the fabrication of high-performance graphene-based electrodes for use in microbial energy harvesting.

  5. Structure-guided alteration of coenzyme specificity of formate dehydrogenase by saturation mutagenesis to enable efficient utilization of NADP+.

    PubMed

    Andreadeli, Aggeliki; Platis, Dimitris; Tishkov, Vladimir; Popov, Vladimir; Labrou, Nikolaos E

    2008-08-01

    Formate dehydrogenase from Candida boidinii (CboFDH) catalyses the oxidation of formate anion to carbon dioxide with concomitant reduction of NAD(+) to NADH. CboFDH is highly specific to NAD(+) and virtually fails to catalyze the reaction with NADP(+). Based on structural information for CboFDH, the loop region between beta-sheet 7 and alpha-helix 10 in the dinucleotide-binding fold was predicted as a principal determinant of coenzyme specificity. Sequence alignment with other formate dehydrogenases revealed two residues (Asp195 and Tyr196) that could account for the observed coenzyme specificity. Positions 195 and 196 were subjected to two rounds of site-saturation mutagenesis and screening and enabled the identification of a double mutant Asp195Gln/Tyr196His, which showed a more than 2 x 10(7)-fold improvement in overall catalytic efficiency with NADP(+) and a more than 900-fold decrease in the efficiency with NAD(+) as cofactors. The results demonstrate that the combined polar interactions and steric factors comprise the main structural determinants responsible for coenzyme specificity. The double mutant Asp195Gln/Tyr196His was tested for practical applicability in a cofactor recycling system composed of cytochrome P450 monooxygenase from Bacillus subtilis, (CYP102A2), NADP(+), formic acid and omega-(p-nitrophenyl)dodecanoic acid (12-pNCA). Using a 1250-fold excess of 12-pNCA over NADP(+) the first order rate constant was determined to be equal to k(obs) = 0.059 +/- 0.004 min(-1).

  6. Functionalization with C-terminal cysteine enhances transfection efficiency of cell-penetrating peptides through dimer formation

    SciTech Connect

    Amand, Helene L.

    2012-02-17

    Highlights: Black-Right-Pointing-Pointer Reversible CPP dimerisation is a simple yet efficient strategy to improve delivery. Black-Right-Pointing-Pointer Dimer formation enhances peptiplex stability, resulting in increased transfection. Black-Right-Pointing-Pointer By dimerisation, the CPP EB1 even gain endosomal escape properties while lowering cytotoxicity. -- Abstract: Cell-penetrating peptides have the ability to stimulate uptake of macromolecular cargo in mammalian cells in a non-toxic manner and therefore hold promise as efficient and well tolerated gene delivery vectors. Non-covalent peptide-DNA complexes ('peptiplexes') enter cells via endocytosis, but poor peptiplex stability and endosomal entrapment are considered as main barriers to peptide-mediated delivery. We explore a simple, yet highly efficient, strategy to improve the function of peptide-based vectors, by adding one terminal cysteine residue. This allows the peptide to dimerize by disulfide bond formation, increasing its affinity for nucleic acids by the 'chelate effect' and, when the bond is reduced intracellularly, letting the complex dissociate to deliver the nucleic acid. By introducing a single C-terminal cysteine in the classical CPP penetratin and the penetratin analogs PenArg and EB1, we show that this minor modification greatly enhances the transfection capacity for plasmid DNA in HEK293T cells. We conclude that this effect is mainly due to enhanced thermodynamic stability of the peptiplexes as endosome-disruptive chloroquine is still required for transfection and the effect is more pronounced for peptides with lower inherent DNA condensation capacity. Interestingly, for EB1, addition of one cysteine makes the peptide able to mediate transfection in absence of chloroquine, indicating that dimerisation can also improve endosomal escape properties. Further, the cytotoxicity of EB1 peptiplexes is considerably reduced, possibly due to lower concentration of free peptide dimer resulting from

  7. [Formation Mechanism of Aerobic Granular Sludge and Removal Efficiencies in Integrated ABR-CSTR Reactor].

    PubMed

    Wu, Kai-cheng; Wu, Peng; Xu, Yue-zhong; Li, Yue-han; Shen, Yao-liang

    2015-08-01

    Anaerobic Baffled Reactor (ABR) was altered to make an integrated anaerobic-aerobic reactor. The research investigated the mechanism of aerobic sludge granulation, under the condition of continuous-flow. The last two compartments of the ABR were altered into aeration tank and sedimentation tank respectively with seeded sludge of anaerobic granular sludge in anaerobic zone and conventional activated sludge in aerobic zone. The HRT was gradually decreased in sedimentation tank from 2.0 h to 0.75 h and organic loading rate was increased from 1.5 kg x (M3 x d)(-1) to 2.0 kg x (M3 x d)(-1) while the C/N of 2 was controlled in aerobic zone. When the system operated for 110 days, the mature granular sludge in aerobic zone were characterized by compact structure, excellent sedimentation performance (average sedimentation rate was 20.8 m x h(-1)) and slight yellow color. The system performed well in nitrogen and phosphorus removal under the conditions of setting time of 0.75 h and organic loading rate of 2.0 kg (m3 x d)(-1) in aerobic zone, the removal efficiencies of COD, NH4+ -N, TP and TN were 90%, 80%, 65% and 45%, respectively. The results showed that the increasing selection pressure and the high organic loading rate were the main propulsions of the aerobic sludge granulation.

  8. Fused porphyrin-single-walled carbon nanotube hybrids: efficient formation and photophysical characterization.

    PubMed

    Zhong, Qiwen; Diev, Vyacheslav V; Roberts, Sean T; Antunez, Priscilla D; Brutchey, Richard L; Bradforth, Stephen E; Thompson, Mark E

    2013-04-23

    A systematic study of the interaction between π-extended porphyrins and single-walled carbon nanotubes (SWNTs) is reported here. Zinc porphyrins with 1-pyrenyl groups in the 5,15-meso positions, 1, as well as compounds where one or both of the pyrene groups have been fused at the meso and β positions of the porphyrin core, 2 and 3, respectively, have been examined. The strongest binding to SWNTs is observed for porphyrin 3, leading to debundling of the nanotubes and formation of stable suspensions of 3-SWNT hybrids in a range of common organic solvents. Absorption spectra of 3-SWNT suspensions are broad and continuous (λ=400-1400 nm), and the Q-band of 3 displays a significant bathochromic shift of 33 nm. The surface coverage of the SWNTs in the nanohybrids was estimated by spectroscopic and analytical methods and found to reach 64% for (7,6) nanotubes. The size and shape of π-conjugated porphyrins were found to be important factors in determining the strength of the π-π interactions, as the linear anti-3 isomer displays more than 90% binding selectivity compared to the bent syn-3 isomer. Steady-state photoluminescence measurements show quenching of porphyrin emission from the nanohybrids. Femtosecond transient absorption spectroscopy reveals that this quenching results from ultrafast electron transfer from the photoexcited porphyrin to the SWNT (1/kCT=260 fs) followed by rapid charge recombination on a picosecond time scale. Overall, our data demonstrate that direct π-π interaction between fused porphyrins and SWNTs leads to electronically coupled stable nanohybrids.

  9. Transformation of ranitidine during water chlorination and ozonation: Moiety-specific reaction kinetics and elimination efficiency of NDMA formation potential.

    PubMed

    Jeon, Dahee; Kim, Jisoo; Shin, Jaedon; Hidayat, Zahra Ramadhany; Na, Soyoung; Lee, Yunho

    2016-11-15

    Ranitidine can produce high yields of N-nitrosodimethylamine (NDMA) upon chloramination and its presence in water resources is a concern for water utilities using chloramine disinfection. This study assessed the efficiency of water chlorination and ozonation in transforming ranitidine and eliminating its NDMA formation potential (NDMA-FP) by determining moiety-specific reaction kinetics, stoichiometric factors, and elimination levels in real water matrices. Despite the fact that chlorine reacts rapidly with the acetamidine and thioether moieties of ranitidine (k>10(8)M(-1)s(-1) at pH 7), the NDMA-FP decreases significantly only when chlorine reacts with the less reactive tertiary amine (k=3×10(3)M(-1)s(-1) at pH 7) or furan moiety (k=81M(-1)s(-1) at pH 7). Ozone reacts rapidly with all four moieties of ranitidine (k=1.5×10(5)-1.6×10(6)M(-1)s(-1) at pH 7) and its reaction with the tertiary amine or furan moiety leads to complete elimination of the NDMA-FP. Treatments of ranitidine-spiked real water samples have shown that ozonation can efficiently deactivate ranitidine in water and wastewater treatment, while chlorination can be efficient for water containing low concentration of ammonia. This result can be applied to the other structurally similar, potent NDMA precursors. PMID:27381234

  10. The Kiloparsec-scale Star Formation Law at Redshift 4: Widespread, Highly Efficient Star Formation in the Dust-obscured Starburst Galaxy GN20

    NASA Astrophysics Data System (ADS)

    Hodge, J. A.; Riechers, D.; Decarli, R.; Walter, F.; Carilli, C. L.; Daddi, E.; Dannerbauer, H.

    2015-01-01

    We present high-resolution observations of the 880 μm (rest-frame FIR) continuum emission in the z = 4.05 submillimeter galaxy GN20 from the IRAM Plateau de Bure Interferometer (PdBI). These data resolve the obscured star formation (SF) in this unlensed galaxy on scales of 0.''3 × 0.''2 (~2.1 × 1.3 kpc). The observations reveal a bright (16 ± 1 mJy) dusty starburst centered on the cold molecular gas reservoir and showing a bar-like extension along the major axis. The striking anti-correlation with the Hubble Space Telescope/Wide Field Camera 3 imaging suggests that the copious dust surrounding the starburst heavily obscures the rest-frame UV/optical emission. A comparison with 1.2 mm PdBI continuum data reveals no evidence for variations in the dust properties across the source within the uncertainties, consistent with extended SF, and the peak star formation rate surface density (119 ± 8 M ⊙ yr-1 kpc-2) implies that the SF in GN20 remains sub-Eddington on scales down to 3 kpc2. We find that the SF efficiency (SFE) is highest in the central regions of GN20, leading to a resolved SF law with a power-law slope of ΣSFR ~ Σ _H_2^2.1+/- 1.0, and that GN20 lies above the sequence of normal star-forming disks, implying that the dispersion in the SF law is not due solely to morphology or choice of conversion factor. These data extend previous evidence for a fixed SFE per free-fall time to include the star-forming medium on ~kiloparsec scales in a galaxy 12 Gyr ago. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

  11. THE IMPACT OF INTERACTIONS, BARS, BULGES, AND ACTIVE GALACTIC NUCLEI ON STAR FORMATION EFFICIENCY IN LOCAL MASSIVE GALAXIES

    SciTech Connect

    Saintonge, Amelie; Fabello, Silvia; Wang Jing; Catinella, Barbara; Tacconi, Linda J.; Genzel, Reinhard; Gracia-Carpio, Javier; Wuyts, Stijn; Kramer, Carsten; Moran, Sean; Heckman, Timothy M.; Schiminovich, David; Schuster, Karl

    2012-10-20

    Using atomic and molecular gas observations from the GASS and COLD GASS surveys and complementary optical/UV data from the Sloan Digital Sky Survey and the Galaxy Evolution Explorer, we investigate the nature of the variations in the molecular gas depletion time observed across the local massive galaxy population. The large and unbiased COLD GASS sample allows us for the first time to statistically assess the relative importance of galaxy interactions, bar instabilities, morphologies, and the presence of active galactic nuclei (AGNs) in regulating star formation efficiency. We find that both the H{sub 2} mass fraction and depletion time vary as a function of the distance of a galaxy from the main sequence traced by star-forming galaxies in the SFR-M {sub *} plane. The longest gas depletion times are found in below-main-sequence bulge-dominated galaxies ({mu}{sub *} >5 Multiplication-Sign 10{sup 8} M {sub Sun} kpc{sup -2}, C > 2.6) that are either gas-poor (M{sub H{sub 2}}/M {sub *} <1.5%) or else on average less efficient by a factor of {approx}2 than disk-dominated galaxies at converting into stars any cold gas they may have. We find no link between the presence of AGNs and these long depletion times. In the regime where galaxies are disk-dominated and gas-rich, the galaxies undergoing mergers or showing signs of morphological disruptions have the shortest molecular gas depletion times, while those hosting strong stellar bars have only marginally higher global star formation efficiencies as compared to matched control samples. Our interpretation is that the molecular gas depletion time variations are caused by changes in the ratio between the gas mass traced by the CO(1-0) observations and the gas mass in high-density star-forming cores (as traced by observations of, e.g., HCN(1-0)). While interactions, mergers, and bar instabilities can locally increase pressure and raise the ratio of efficiently star-forming gas to CO-detected gas (therefore lowering the CO

  12. Trapping of Cr by formation of ferrihydrite during the reduction of chromate ions by Fe(II)-Fe(III) hydroxysalt green rusts

    SciTech Connect

    Loyaux-Lawniczak, S.; Refait, P.; Ehrhardt, J.J.; LeComte, P.; Genin, J.M.R.

    2000-02-01

    Hexavalent chromium, a byproduct of many industrial processes, is toxic and produces mobile aqueous oxyanions, whereas Cr(III) is relatively immobile in the environment and, moreover, essential in human glucidic metabolism. For this reason, Fe(II)-Fe(III) layered double hydroxysalt green rusts, recently identified as a mineral in hydromorphic soils, were evaluated as potential Fe(II)-bearing phases for hexavalent chromium reduction. Both considered synthetic varieties, the hydroxysulfate GR(SO{sub 4}{sup 2{minus}}) and the hydroxychloride GR(Cl{sup {minus}}), proved to be very reactive; their interaction with potassium chromate solutions leads to the rapid and complete reduction of Cr(VI) into Cr(III). The Cr(III)-bearing solid phase, studied by X-ray diffraction, Moessbauer, X-ray photoelectron, and Raman spectroscopies, was determined to be a poorly ordered Cr(III)-Fe(III) oxyhydroxide, similar to the 2 the line ferrihydrite. The comparison between the experimental redox potential and pH values for a theoretical equilibrium diagram bearing Cr and Fe phases indicated that the solubility of this solid solution, which may govern the behavior of chromium in the environment, is of the same order as that of pure Cr(OH){sub 3}.

  13. SAGE III

    Atmospheric Science Data Center

    2016-06-15

    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 ... Guide Documents:  Project Guide Data Products User's Guide  (PDF) Relevant Documents:  ...

  14. Human DNA ligase III bridges two DNA ends to promote specific intermolecular DNA end joining

    PubMed Central

    Kukshal, Vandna; Kim, In-Kwon; Hura, Gregory L.; Tomkinson, Alan E.; Tainer, John A.; Ellenberger, Tom

    2015-01-01

    Mammalian DNA ligase III (LigIII) functions in both nuclear and mitochondrial DNA metabolism. In the nucleus, LigIII has functional redundancy with DNA ligase I whereas LigIII is the only mitochondrial DNA ligase and is essential for the survival of cells dependent upon oxidative respiration. The unique LigIII zinc finger (ZnF) domain is not required for catalytic activity but senses DNA strand breaks and stimulates intermolecular ligation of two DNAs by an unknown mechanism. Consistent with this activity, LigIII acts in an alternative pathway of DNA double strand break repair that buttresses canonical non-homologous end joining (NHEJ) and is manifest in NHEJ-defective cancer cells, but how LigIII acts in joining intermolecular DNA ends versus nick ligation is unclear. To investigate how LigIII efficiently joins two DNAs, we developed a real-time, fluorescence-based assay of DNA bridging suitable for high-throughput screening. On a nicked duplex DNA substrate, the results reveal binding competition between the ZnF and the oligonucleotide/oligosaccharide-binding domain, one of three domains constituting the LigIII catalytic core. In contrast, these domains collaborate and are essential for formation of a DNA-bridging intermediate by adenylated LigIII that positions a pair of blunt-ended duplex DNAs for efficient and specific intermolecular ligation. PMID:26130724

  15. Transformation efficiency and formation of transformation products during photochemical degradation of TCE and PCE at micromolar concentrations

    PubMed Central

    2014-01-01

    Background Trichloroethene and tetrachloroethene are the most common pollutants in groundwater and two of the priority pollutants listed by the U.S. Environmental Protection Agency. In previous studies on TCE and PCE photolysis and photochemical degradation, concentration ranges exceeding environmental levels by far with millimolar concentrations of TCE and PCE have been used, and it is not clear if the obtained results can be used to explain the degradation of these contaminants at more realistic environmental concentration levels. Methods Experiments with micromolar concentrations of TCE and PCE in aqueous solution using direct photolysis and UV/H2O2 have been conducted and product formation as well as transformation efficiency have been investigated. SPME/GC/MS, HPLC/UV and ion chromatography with conductivity detection have been used to determine intermediates of degradation. Results The results showed that chloride was a major end product in both TCE and PCE photodegradation. Several intermediates such as formic acid, dichloroacetic acid, dichloroacetaldehyede, chloroform, formaldehyde and glyoxylic acid were formed during both, UV and UV/H2O2 treatment of TCE. However chloroacetaldehyde and chloroacetic acid were only detected during direct UV photolysis of TCE and oxalic acid was only formed during the UV/H2O2 process. For PCE photodegradation, formic acid, di- and trichloroacetic acids were detected in both UV and UV/H2O2 systems, but formaldehyde and glyoxylic acid were only detected during direct UV photolysis. Conclusions For water treatment UV/H2O2 seems to be favorable over direct UV photolysis because of its higher degradation efficiency and lower risk for the formation of harmful intermediates. PMID:24401763

  16. Eucalyptus hairy roots, a fast, efficient and versatile tool to explore function and expression of genes involved in wood formation.

    PubMed

    Plasencia, Anna; Soler, Marçal; Dupas, Annabelle; Ladouce, Nathalie; Silva-Martins, Guilherme; Martinez, Yves; Lapierre, Catherine; Franche, Claudine; Truchet, Isabelle; Grima-Pettenati, Jacqueline

    2016-06-01

    Eucalyptus are of tremendous economic importance being the most planted hardwoods worldwide for pulp and paper, timber and bioenergy. The recent release of the Eucalyptus grandis genome sequence pointed out many new candidate genes potentially involved in secondary growth, wood formation or lineage-specific biosynthetic pathways. Their functional characterization is, however, hindered by the tedious, time-consuming and inefficient transformation systems available hitherto for eucalypts. To overcome this limitation, we developed a fast, reliable and efficient protocol to obtain and easily detect co-transformed E. grandis hairy roots using fluorescent markers, with an average efficiency of 62%. We set up conditions both to cultivate excised roots in vitro and to harden composite plants and verified that hairy root morphology and vascular system anatomy were similar to wild-type ones. We further demonstrated that co-transformed hairy roots are suitable for medium-throughput functional studies enabling, for instance, protein subcellular localization, gene expression patterns through RT-qPCR and promoter expression, as well as the modulation of endogenous gene expression. Down-regulation of the Eucalyptus cinnamoyl-CoA reductase1 (EgCCR1) gene, encoding a key enzyme in lignin biosynthesis, led to transgenic roots with reduced lignin levels and thinner cell walls. This gene was used as a proof of concept to demonstrate that the function of genes involved in secondary cell wall biosynthesis and wood formation can be elucidated in transgenic hairy roots using histochemical, transcriptomic and biochemical approaches. The method described here is timely because it will accelerate gene mining of the genome for both basic research and industry purposes. PMID:26579999

  17. Limitation of thiamine pyrophosphate supply to growing Escherichia coli switches metabolism to efficient D-lactate formation.

    PubMed

    Tian, Kangming; Niu, Dandan; Liu, Xiaoguang; Prior, Bernard A; Zhou, Li; Lu, Fuping; Singh, Suren; Wang, Zhengxiang

    2016-01-01

    Efficient production of D-lactate by engineered Escherichia coli entails balancing cell growth and product synthesis. To develop a metabolic switch to implement a desirable transition from cell growth to product fermentation, a thiamine auxotroph B0013-080A was constructed in a highly efficient D-lactate producer E. coli strain B0013-070. This was achieved by inactivation of thiE, a gene encoding a thiamine phosphate synthase for biosynthesis of thiamine monophosphate. The resultant mutant B0013-080A failed to grow on the medium in the absence of thiamine yet growth was restored when exogenous thiamine was provided. A linear relationship between cell mass formation and amount of thiamine supplemented was mathematically determined in a shake flask experiment and confirmed in a 7-L bioreactor system. This calculation revealed that ∼ 95-96 thiamine molecules per cell were required to satisfy cell growth. This relationship was employed to develop a novel fermentation process for D-lactate production by using thiamine as a limiting condition. A D-lactate productivity of 4.11 g · L(-1) · h(-1) from glycerol under microaerobic condition and 3.66 g · L(-1) · h(-1) from glucose under anaerobic condition was achieved which is 19.1% and 10.2% higher respectively than the parental strain. These results revealed a convenient and reliable method to control cell growth and improve D-lactate fermentation. This control strategy could be applied to other biotechnological processes that require optimal allocation of carbon between cell growth and product formation.

  18. Application of acid-treated yeast cell wall (AYC) as a pharmaceutical additive. III. AYC aqueous coating onto granules and film formation mechanism of AYC.

    PubMed

    Yuasa, Hiroshi; Kaneshige, Junichi; Ozeki, Tetsuya; Kasai, Takahide; Eguchi, Takahiro; Ishiwaki, Naomu

    2002-04-26

    From the viewpoint of effective utilization of natural resources and development of new pharmaceutical materials, acid-treated yeast cell wall (AYC) was prepared via a novel approach involving acidification of brewers' yeast cell wall. AYC aqueous dispersion containing 5% (w/v) AYC and 0.5% (w/v) glycerol was prepared. Subsequently, AYC was coated onto core granules containing acetaminophen (AAP). Spray mist size under various spray conditions and viscosity of the AYC aqueous dispersion at various AYC concentrations were measured. AYC spray mists were optically observed. The surface of AYC cast film and AYC-coated granules were observed with a confocal scanning laser microscope. We attempted to show the utility of AYC as a novel material for granule coating, following the tablet coating in our previous report. In addition, the film formation mechanism of AYC was investigated. A smooth surface of the AYC-coated granules was obtained at a coating ratio of only 5%, which generally requires approximately 15-30% coating against the core granule weight, with no aggregation. These results are attributable to the fact that the granules were coated with a large number of small mists of AYC and the coating progressed efficiently, and the thin film layer of AYC was formed on the granules by mutual tangling of the hydrogel layers of AYC polysaccharides. AAP release from AYC-coated granules was obviously rapid, suggesting the high utility of AYC as a coating material for the rapidly releasing granules.

  19. Enhancement of CO(3-2)/CO(1-0) ratios and star formation efficiencies in supergiant H II regions

    SciTech Connect

    Miura, Rie E.; Espada, Daniel; Komugi, Shinya; Nakanishi, Kouichiro; Sawada, Tsuyoshi; Fujii, Kosuke; Kawabe, Ryohei; Kohno, Kotaro; Tosaki, Tomoka; Hirota, Akihiko; Minamidani, Tetsuhiro; Okumura, Sachiko K.; Kuno, Nario; Muraoka, Kazuyuki; Onodera, Sachiko; Kaneko, Hiroyuki

    2014-06-20

    We present evidence that super giant H II regions (GHRs) and other disk regions of the nearby spiral galaxy, M33, occupy distinct locations in the correlation between molecular gas, Σ{sub H{sub 2}}, and the star formation rate surface density, Σ{sub SFR}. This result is based on wide-field and high-sensitivity CO(3-2) observations at 100 pc resolution. Star formation efficiencies (SFEs), defined as Σ{sub SFR}/Σ{sub H{sub 2}}, in GHRs are found to be ∼1 dex higher than in other disk regions. The CO(3-2)/CO(1-0) integrated intensity ratio, R {sub 3-2/1-0}, is also higher than the average over the disk. Such high SFEs and R {sub 3-2/1-0} can reach the values found in starburst galaxies, which suggests that GHRs may be the elements building up a larger-scale starburst region. Three possible contributions to high SFEs in GHRs are investigated: (1) the I {sub CO}-N(H{sub 2}) conversion factor, (2) the dense gas fraction traced by R {sub 3-2/1-0}, and (3) the initial mass function (IMF). We conclude that these starburst-like properties in GHRs can be interpreted by a combination of both a top-heavy IMF and a high dense gas fraction, but not by changes in the I {sub CO}-N(H{sub 2}) conversion factor.

  20. Efficient hydrogenation of organic carbonates, carbamates and formates indicates alternative routes to methanol based on CO2 and CO

    NASA Astrophysics Data System (ADS)

    Balaraman, Ekambaram; Gunanathan, Chidambaram; Zhang, Jing; Shimon, Linda J. W.; Milstein, David

    2011-08-01

    Catalytic hydrogenation of organic carbonates, carbamates and formates is of significant interest both conceptually and practically, because these compounds can be produced from CO2 and CO, and their mild hydrogenation can provide alternative, mild approaches to the indirect hydrogenation of CO2 and CO to methanol, an important fuel and synthetic building block. Here, we report for the first time catalytic hydrogenation of organic carbonates to alcohols, and carbamates to alcohols and amines. Unprecedented homogeneously catalysed hydrogenation of organic formates to methanol has also been accomplished. The reactions are efficiently catalysed by dearomatized PNN Ru(II) pincer complexes derived from pyridine- and bipyridine-based tridentate ligands. These atom-economical reactions proceed under neutral, homogeneous conditions, at mild temperatures and under mild hydrogen pressures, and can operate in the absence of solvent with no generation of waste, representing the ultimate ‘green’ reactions. A possible mechanism involves metal-ligand cooperation by aromatization-dearomatization of the heteroaromatic pincer core.

  1. THE KILOPARSEC-SCALE STAR FORMATION LAW AT REDSHIFT 4: WIDESPREAD, HIGHLY EFFICIENT STAR FORMATION IN THE DUST-OBSCURED STARBURST GALAXY GN20

    SciTech Connect

    Hodge, J. A.; Riechers, D.; Decarli, R.; Walter, F.; Carilli, C. L.; Daddi, E.

    2015-01-01

    We present high-resolution observations of the 880 μm (rest-frame FIR) continuum emission in the z = 4.05 submillimeter galaxy GN20 from the IRAM Plateau de Bure Interferometer (PdBI). These data resolve the obscured star formation (SF) in this unlensed galaxy on scales of 0.''3 × 0.''2 (∼2.1 × 1.3 kpc). The observations reveal a bright (16 ± 1 mJy) dusty starburst centered on the cold molecular gas reservoir and showing a bar-like extension along the major axis. The striking anti-correlation with the Hubble Space Telescope/Wide Field Camera 3 imaging suggests that the copious dust surrounding the starburst heavily obscures the rest-frame UV/optical emission. A comparison with 1.2 mm PdBI continuum data reveals no evidence for variations in the dust properties across the source within the uncertainties, consistent with extended SF, and the peak star formation rate surface density (119 ± 8 M {sub ☉} yr{sup –1} kpc{sup –2}) implies that the SF in GN20 remains sub-Eddington on scales down to 3 kpc{sup 2}. We find that the SF efficiency (SFE) is highest in the central regions of GN20, leading to a resolved SF law with a power-law slope of Σ{sub SFR} ∼ Σ{sub H{sub 2}{sup 2.1±1.0}}, and that GN20 lies above the sequence of normal star-forming disks, implying that the dispersion in the SF law is not due solely to morphology or choice of conversion factor. These data extend previous evidence for a fixed SFE per free-fall time to include the star-forming medium on ∼kiloparsec scales in a galaxy 12 Gyr ago.

  2. THE WIDESPREAD OF Fe(III)-REDUCING BACTERIA IN NATURAL ECOSYSTEMS OF ECUADOR.

    PubMed

    Tashyrev, O B; Govorukha, V M

    2015-01-01

    The widespread of Fe(III)-reducing microorganisms in natural ecosystems of Ecuador of La Favorita, Tungurahua volcano and Papallacta areas was experimentally proved. High efficiency of microbial precipitation of soluble iron compounds was also demonstrated. Obtained results indicate the potential ability of Fe(III)-reducing microorganisms to influence the formation of carbon and iron vector fluxes in ecosystems, as well as development of effective biotechnologies of water purification from iron compounds.

  3. THE WIDESPREAD OF Fe(III)-REDUCING BACTERIA IN NATURAL ECOSYSTEMS OF ECUADOR.

    PubMed

    Tashyrev, O B; Govorukha, V M

    2015-01-01

    The widespread of Fe(III)-reducing microorganisms in natural ecosystems of Ecuador of La Favorita, Tungurahua volcano and Papallacta areas was experimentally proved. High efficiency of microbial precipitation of soluble iron compounds was also demonstrated. Obtained results indicate the potential ability of Fe(III)-reducing microorganisms to influence the formation of carbon and iron vector fluxes in ecosystems, as well as development of effective biotechnologies of water purification from iron compounds. PMID:26422925

  4. Method for making graded I-III-VI.sub.2 semiconductors and solar cell obtained thereby

    DOEpatents

    Devaney, Walter E.

    1987-08-04

    Improved cell photovoltaic conversion efficiencies are obtained by the simultaneous elemental reactive evaporation process of Mickelsen and Chen for making semiconductors by closer control of the evaporation rates and substrate temperature during formation of the near contact, bulk, and near junction regions of a graded I-III-VI.sub.2, thin film, semiconductor, such as CuInSe.sub.2 /(Zn,Cd)S or another I-III-VI.sub.2 /II-VI heterojunction.

  5. Dynamic regulation of GacA in type III secretion, pectinase gene expression, pellicle formation, and pathogenicity of Dickeya dadantii (Erwinia chrysanthemi 3937).

    PubMed

    Yang, Shihui; Peng, Quan; Zhang, Qiu; Yi, Xuan; Choi, Chang Jae; Reedy, Ralph M; Charkowski, Amy O; Yang, Ching-Hong

    2008-01-01

    Dickeya dadantii (Erwinia chrysanthemi 3937) secretes exoenzymes, including pectin-degrading enzymes, leading to the loss of structural integrity of plant cell walls. A type III secretion system (T3SS) is essential for full virulence of this bacterium within plant hosts. The GacS/GacA two-component signal transduction system participates in important biological roles in several gram-negative bacteria. In this study, a gacA deletion mutant (Ech137) of D. dadantii was constructed to investigate the effect of this mutation on pathogenesis and other phenotypes. Compared with wild-type D. dadantii, Ech137 had a delayed biofilm-pellicle formation. The production of pectate lyase (Pel), protease, and cellulase was diminished in Ech137 compared with the wild-type cells. Reduced transcription of two endo-Pel genes, pelD and pelL, was found in Ech137 using a green fluorescence protein-based fluorescence-activated cell sorter promoter activity assay. In addition, the transcription of T3SS genes dspE (an effector), hrpA (a structural protein of the T3SS pilus), and hrpN (a T3SS harpin) was reduced in Ech137. A lower amount of rsmB regulatory RNA was found in gacA mutant Ech137 compared with the wild-type bacterium by quantitative reverse-transcription polymerase chain reaction. Compared with wild-type D. dadantii, a lower amount of hrpL mRNA was observed in Ech137 at 12 h grown in medium. Although the role of RsmA, rsmB, and RsmC in D. dadantii is not clear, from the regulatory pathway revealed in E. carotovora, the lower expression of dspE, hrpA, and hrpN in Ech137 may be due to a post-transcriptional regulation of hrpL through the Gac-Rsm regulatory pathway. Consequently, the reduced exoenzyme production and Pel gene expression in the mutant may be sue partially to the regulatory role of rsmB-RsmA on exoenzyme expression. Similar to in vitro results, a lower expression of T3SS and pectinase genes of Ech137 also was observed in bacterial cells inoculated into Saintpaulia

  6. Rainforest burning and the global carbon budget: Biomass, combustion efficiency, and charcoal formation in the Brazilian Amazon

    SciTech Connect

    Fearnside, P.M.; Leal, N. Jr.; Fernandes, F.M.

    1993-09-20

    Biomass present before and after burning was measured in forest cleared for pasture in a cattle ranch (Fazenda Dimona) near Manaus, Amazonas, Brazil. Aboveground dry weight biomass loading averaged 265 t ha{sup {minus}1} (standard deviation (SD) = 110, n = 6 quadrats) at Fazenda Dimonas. Postburn aboveground biomass loading was evaluated by cutting and weighing of 100 m{sup 2} quadrats and by line intersect sampling. Quadrats had a mean dry weight of 187 t ha{sup {minus}1} (SD = 69, n = 10), a 29.3% reduction from the preburn mean in the same clearing. Line intersect estimates in 1.65 km of transects indicated that 265 m{sup 3} ha{sup {minus}1} (approximately 164 t ha{sup {minus}1} of aboveground dry matter) survived burning. Using carbon contents measured for different biomass components (all {approximately} 50% carbon) and assuming a carbon content of 74.8% for charcoal (from other studies near Manaus), the destructive measurements imply a 27.6% reduction of aboveground carbon pools. Charcoal composed 2.5% of the dry weight of the remains in the postburn destructive quadrats and 2.8% of the volume in the line intersect transects. Thus approximately 2.7% of the preburn aboveground carbon stock was converted to charcoal, substantially less than is generally assumed in global carbon models. The findings confirm high values for biomass in central Amazonia. High variability indicates the need for further studies in many localities and for making maximum use of less laborious indirect methods of biomass estimation. While indirect methods are essential for regional estimates of average biomass, only direct weighing such as that reported here can yield information on combustion efficiency and charcoal formation. Both high biomass and low percentage of charcoal formation suggest the significant potential contribution of forest burning to global climate changes from CO{sub 2} and trace gases. 66 refs., 6 figs., 2 tabs.

  7. THE RICH GLOBULAR CLUSTER SYSTEM OF ABELL 1689 AND THE RADIAL DEPENDENCE OF THE GLOBULAR CLUSTER FORMATION EFFICIENCY

    SciTech Connect

    Alamo-Martínez, K. A.; González-Lópezlira, R. A.; Blakeslee, J. P.; Côté, P.; Ferrarese, L.; Jee, M. J.; Jordán, A.; Meurer, G. R.; Peng, E. W.; West, M. J.

    2013-09-20

    We study the rich globular cluster (GC) system in the center of the massive cluster of galaxies Abell 1689 (z = 0.18), one of the most powerful gravitational lenses known. With 28 Hubble Space Telescope/Advanced Camera for Surveys orbits in the F814W bandpass, we reach a magnitude I{sub 814} = 29 with ∼>90% completeness and sample the brightest ∼5% of the GC system. Assuming the well-known Gaussian form of the GC luminosity function (GCLF), we estimate a total population of N{sup total}{sub GC}= 162,850{sup +75,450}{sub -51,310} GCs within a projected radius of 400 kpc. As many as half of the GCs may comprise an intracluster component. Even with the sizable uncertainties, which mainly result from the uncertain GCLF parameters, this system is by far the largest GC population studied to date. The specific frequency S{sub N} is high, but not uncommon for central galaxies in massive clusters, rising from S{sub N} ≈ 5 near the center to ∼12 at large radii. Passive galaxy fading would increase S{sub N} by ∼20% at z = 0. We construct the radial mass profiles of the GCs, stars, intracluster gas, and lensing-derived total mass, and we compare the mass fractions as a function of radius. The estimated mass in GCs, M{sub GC}{sup total} = 3.9 × 10{sup 10} M{sub ☉}, is comparable to ∼80% of the total stellar mass of the Milky Way. The shape of the GC mass profile appears intermediate between those of the stellar light and total cluster mass. Despite the extreme nature of this system, the ratios of the GC mass to the baryonic and total masses, and thus the GC formation efficiency, are typical of those in other rich clusters when comparing at the same physical radii. The GC formation efficiency is not constant, but varies with radius, in a manner that appears similar for different clusters; we speculate on the reasons for this similarity in profile.

  8. Disproportionation of hydroxylamine by water-soluble iron(III) porphyrinate compounds.

    PubMed

    Bari, Sara E; Amorebieta, Valentín T; Gutiérrez, María M; Olabe, José A; Doctorovich, Fabio

    2010-01-01

    The reactions of hydroxylamine (HA) with several water-soluble iron(III) porphyrinate compounds, namely iron(III) meso-tetrakis-(N-ethylpyridinium-2yl)-porphyrinate ([Fe(III)(TEPyP)](5+)), iron(III) meso-tetrakis-(4-sulphonatophenyl)-porphyrinate ([Fe(III)(TPPS)](3-)), and microperoxidase 11 ([Fe(III)(MP11)]) were studied for different [Fe(III)(Porph)]/[HA] ratios, under anaerobic conditions at neutral pH. Efficient catalytic processes leading to the disproportionation of HA by these iron(III) porphyrinates were evidenced for the first time. As a common feature, only N(2) and N(2)O were found as gaseous, nitrogen-containing oxidation products, while NH(3) was the unique reduced species detected. Different N(2)/N(2)O ratios obtained with these three porphyrinates strongly suggest distinctive mechanistic scenarios: while [Fe(III)(TEPyP)](5+) and [Fe(III)(MP11)] formed unknown steady-state porphyrinic intermediates in the presence of HA, [Fe(III)(TPPS)](3-) led to the well characterized soluble intermediate, [Fe(II)(TPPS)NO](4-). Free-radical formation was only evidenced for [Fe(III)(TEPyP)](5+), as a consequence of a metal centered reduction. We discuss the catalytic pathways of HA disproportionation on the basis of the distribution of gaseous products, free radicals formation, the nature of porphyrinic intermediates, the Fe(II)/Fe(III) redox potential, the coordinating capabilities of each complex, and the kinetic analysis. The absence of NO(2)(-) revealed either that no HAO-like activity was operative under our reaction conditions, or that NO(2)(-), if formed, was consumed in the reaction milieu.

  9. MTBE oxidation by conventional ozonation and the combination ozone/hydrogen peroxide: efficiency of the processes and bromate formation.

    PubMed

    Acero, J L; Haderlein, S B; Schmidt, T C; Suter, M J; von Gunten, U

    2001-11-01

    The present study investigates the oxidation of methyl tert-butyl ether (MTBE) by conventional ozonation and the advanced oxidation process (AOP) ozone/hydrogen peroxide under drinking water treatment conditions. The major degradation products identified were tert-butyl formate (TBF), tert-butyl alcohol (TBA), 2-methoxy-2-methyl propionaldehyde (MMP), acetone (AC), methyl acetate (MA), hydroxyisobutyraldehyde (HiBA), and formaldehyde (FA). The rate constants of the reaction of ozone and OH radicals with MTBE were found to be 0.14 and 1.9 x 10(9) M(-1) s(-1), respectively. The rate constants for the same oxidation processes were also measured for the degradation products TBF, MMP, MA, and HiBA (k(O3-TBF) = 0.78 M(-1) s(-1); k(OH-TBF) = 7.0 x 10(8) M(-1) s(-1); k(O3-MMP) = 5 M(-1) s(-1); k(OH-MMP) = 3 x 10(9) M(-1) s(-1), k(O3-MA) = 0.09 M(-1) s(-1), k(O3-HiBA) = 5 M(-1) s(-1); k(OH-HiBA) = 3 x 10(9) M(-1) s(-1)). Since all compounds reacted slowly with molecular ozone, only the degradation pathway of MTBE with OH radicals has been determined, including the formation of primary degradation products. In experiments performed with several natural waters, the efficiency of MTBE elimination and the formation of bromate as disinfection byproduct have been measured. With a bromide level of 50 microg/L, only 35-50% of MTBE could be eliminated by the AOP O3/H2O2 without exceeding the current drinking water standard of bromate (10 microg/L). The transient concentrations of MTBE and its primary degradation products were modeled using a combination of kinetic parameters (degradation product distribution and rate constants) together with the ozone and OH radical concentration and were in good agreement with the experimental results.

  10. Three-Dimensional Reduced Graphene Oxide Coupled with Mn3O4 for Highly Efficient Removal of Sb(III) and Sb(V) from Water.

    PubMed

    Zou, Jian-Ping; Liu, Hui-Long; Luo, Jinming; Xing, Qiu-Ju; Du, Hong-Mei; Jiang, Xun-Heng; Luo, Xu-Biao; Luo, Sheng-Lian; Suib, Steven L

    2016-07-20

    Highly porous, three-dimensional (3D) nanostructured composite adsorbents of reduced graphene oxides/Mn3O4 (RGO/Mn3O4) were fabricated by a facile method of a combination of reflux condensation and solvothermal reactions and systemically characterized. The as-prepared RGO/Mn3O4 possesses a mesoporous 3D structure, in which Mn3O4 nanoparticles are uniformly deposited on the surface of the reduced graphene oxide. The adsorption properties of RGO/Mn3O4 to antimonite (Sb(III)) and antimonate (Sb(V)) were investigated using batch experiments of adsorption isotherms and kinetics. Experimental results show that the RGO/Mn3O4 composite has fast liquid transport and superior adsorption capacity toward antimony (Sb) species in comparison to six recent adsorbents reported in the literature and summarized in a table in this paper. Theoretical maximum adsorption capacities of RGO/Mn3O4 toward Sb(III) and Sb(V) are 151.84 and 105.50 mg/g, respectively, modeled by Langmuir isotherms. The application of RGO/Mn3O4 was demonstrated by using drinking water spiked with Sb (320 μg/L). Fixed-bed column adsorption experiments indicate that the effective breakthrough volumes were 859 and 633 mL bed volumes (BVs) for the Sb(III) and Sb(V), respectively, until the maximum contaminant level of 5 ppb was reached, which is below the maximum limits allowed in drinking water according to the most stringent regulations. The advantages of being nontoxic, highly stable, and resistant to acid and alkali and having high adsorption capacity toward Sb(III) and Sb(V) confirm the great potential application of RGO/Mn3O4 in Sb-spiked water treatment. PMID:27355752

  11. Efficient water oxidation with electromodified Langmuir-Blodgett films of procatalytic [Co(III)(N2O3)] metallosurfactants on electrodes.

    PubMed

    Gonawala, Sunalee; Baydoun, Habib; Wickramasinghe, Lanka; Verani, Cláudio N

    2016-06-28

    Electromodified Langmuir-Blodgett films of a phenolate-rich [Co(III)(L(N2O3))H2O] metallosurfactant support water oxidation at an overpotential of 0.5 V. Gradual enhancement of catalytic activity is observed between 1 and 9 deposited layers. Upon application of a potential bias the molecular species rearranges into a catalytic layer that yields estimated turnover numbers of 54 000 ± 1500 h(-1).

  12. Efficient induction of formate hydrogen lyase of aerobically grown Escherichia coli in a three-step biohydrogen production process.

    PubMed

    Yoshida, Akihito; Nishimura, Taku; Kawaguchi, Hideo; Inui, Masayuki; Yukawa, Hideaki

    2007-03-01

    A three-step biohydrogen production process characterized by efficient anaerobic induction of the formate hydrogen lyase (FHL) of aerobically grown Escherichia coli was established. Using E. coli strain SR13 (fhlA (++), DeltahycA) at a cell density of 8.2 g/l medium in this process, a specific hydrogen productivity (28.0 +/- 5.0 mmol h(-1) g(-1) dry cell) of one order of magnitude lower than we previously reported was realized after 8 h of anaerobic incubation. The reduced productivity was attributed partly to the inhibitory effects of accumulated metabolites on FHL induction. To avoid this inhibition, strain SR14 (SR13 DeltaldhA DeltafrdBC) was constructed and used to the effect that specific hydrogen productivity increased 1.3-fold to 37.4 +/- 6.9 mmol h(-1) g(-1). Furthermore, a maximum hydrogen production rate of 144.2 mmol h(-1) g(-1) was realized when a metabolite excretion system that achieved a dilution rate of 2.0 h(-1) was implemented. These results demonstrate that by avoiding anaerobic cultivation altogether, more economical harvesting of hydrogen-producing cells for use in our biohydrogen process was made possible.

  13. A highly-efficient blue-light excitable red phosphor: intramolecular π-stacking interactions in one dinuclear europium(iii) complex.

    PubMed

    Wang, Zhengliang; Yang, Hui; He, Pei; He, Yonghui; Zhao, Jishou; Tang, Huaijun

    2016-02-21

    A series of ternary dinuclear europium(iii) complexes [Eu2(2,7-BTFDBC)3-n(DBM)2n(Phen)2] (n = 0, 1, or 2) were synthesized by using 2,7-bis(4'4'4'-trifluoro-1,3-dioxobutyl)-(9-ethyl-9H-carbazole) (2,7-BTFDBC), dibenzoylmethane (DBM), 1,10-phenanthroline (Phen) and europium(iii) ions. All these complexes display a broad excitation band in the blue region and high intensity emission with high colour purity. The intensity of emission significantly increases with the increase of DBM in [Eu2(2,7-BTFDBC)3-n(DBM)2n(Phen)2] (n = 0, 1, or 2). The theoretical predictions of the molecular geometry and electronic absorption spectrum of [Eu2(2,7-BTFDBC)(DBM)4(Phen)2] confirm that the pendant phenyl domains engage in multiple T-shaped and parallel-displaced π-stacking interactions with the coordination sphere of two europium(iii) centers. Using [Eu2(2,7-BTFDBC)(DBM)4(Phen)2] as a red phosphor, a single red LED has been obtained with a ∼460 nm-emitting GaN chip. PMID:26673545

  14. Formation of iron(III) (hydr)oxides on polyaspartate- and alginate-coated substrates: effects of coating hydrophilicity and functional group.

    PubMed

    Ray, Jessica R; Lee, Byeongdu; Baltrusaitis, Jonas; Jun, Young-Shin

    2012-12-18

    To better understand the transport of contaminants in aqueous environments, we need more accurate information about heterogeneous and homogeneous nucleation of iron(III) hydroxide nanoparticles in the presence of organics. We combined synchrotron-based grazing incidence small-angle X-ray scattering (GISAXS) and SAXS and other nanoparticle and substrate surface characterization techniques to observe iron(III) (hydr)oxide [10⁻⁴ M Fe(NO₃)₃ in 10 mM NaNO₃] precipitation on quartz and on polyaspartate- and alginate-coated glass substrates and in solution (pH = 3.7 ± 0.2). Polyaspartate was determined to be the most negatively charged substrate and quartz the least; however, after 2 h, total nanoparticle volume calculations--from GISAXS--indicate that positively charged precipitation on quartz is twice that of alginate and 10 times higher than on polyaspartate, implying that electrostatics do not govern iron(III) (hydr)oxide nucleation. On the basis of contact angle measurements and surface characterization, we concluded that the degree of hydrophilicity may control heterogeneous nucleation on quartz and organic-coated substrates. The arrangement of functional groups at the substrate surface (--OH and --COOH) may also contribute. These results provide new information for elucidating the effects of polymeric organic substrate coatings on the size, volume, and location of nucleating iron hydroxides, which will help predict nanoparticle interactions in natural and engineered systems.

  15. Adsorption of Eu(III) on a heterogeneous surface studied by time-resolved laser fluorescence microscopy (TRLFM).

    PubMed

    Ishida, Keisuke; Kimura, Takaumi; Saito, Takumi; Tanaka, Satoru

    2009-03-15

    Time-resolved laser fluorescence microscopy (TRLFM) is a useful tool to simultaneously investigate the intensity, location, type, and surrounding chemical environment of a fluorophore. In this study, we demonstrated the applicability of TRLFM for the adsorption of Eu(III) on a natural heterogeneous surface. Different adsorption species of Eu(III) were observed on the Makabe granite surface and its constituents (biotite, plagioclase, potassium feldspar, and quartz). Eu(III) heterogeneously adsorbed on biotite, plagioclase, and quartz and homogeneously on potassium feldspar. The histograms of the fluorescence decay rates of adsorbed Eu(III) indicated efficient quenching of Eu(III) fluorescence probably due to Eu(III)-surface interaction or the formation polynuclear hydoxo Eu(III) species on the surfaces. It was also revealed that single species of Eu(III) was observed on biotite and two species on plagioclase and potassium feldspar. The adsorption of Eu(III) on the granite surface was highly heterogeneous. The TRLFM measurements of different regions of the granite surface turned into the finding of Eu(III) with different fluorescence decay rates. Comparing with the fluorescence decay histograms of the mineral constituents, Eu(III) clearly adsorbed on the feldspar family. It was also found that Eu(III) adsorbed as an outer-sphere complex and on an altered mineral of the granite.

  16. Synthesis of crystalline americium hydroxide, Am(OH){sub 3}, and determination of its enthalpy of formation; estimation of the solubility-product constants of actinide(III) hydroxides

    SciTech Connect

    Morss, L.R.; Williams, C.W.

    1993-12-31

    This paper reports a new synthesis of pure, microcrystalline Am(OH){sub 3}, its characterization by x-ray powder diffraction and infrared spectroscopy, and the calorimetric determination of its enthalpy of solution in dilute hydrochloric acid. From the enthalpy of solution the enthalpy of formation of Am(OH){sub 3} has been calculated to be {minus}1371.2{plus_minus}7.9 kj{center_dot}mol{sup {minus}1}, which represents the first experimental determination of an enthalpy of formation of any actinide hydroxide. The free energy of formation and solubility product constant of Am(OH){sub 3} (K{sub sp} = 7 {times} 10{sup {minus}31}) have been calculated from our enthalpy of formation and entropy estimates and are compared with literature measurements under near-equilibrium conditions. Since many properties of the tripositive lanthanide and actinide ions (e.g., hydrolysis, complex-ion formation, and thermochemistry) change in a regular manner, these properties can be interpreted systematically in terms of ionic size. This paper compares the thermochemistry of Am(OH){sub 3} with thermochemical studies of lanthanide hydroxides. A combined structural and acid-base model is used to explain the systematic differences in enthalpies of solution between the oxides and hydroxides of the 4f{sup n} and 5f{sup n} subgroups and to predict solubility-product constants for the actinide(III) hydroxides of Pu through Cf.

  17. Star formation properties in barred galaxies. III. Statistical study of bar-driven secular evolution using a sample of nearby barred spirals

    SciTech Connect

    Zhou, Zhi-Min; Wu, Hong; Cao, Chen E-mail: hwu@bao.ac.cn

    2015-01-01

    Stellar bars are important internal drivers of secular evolution in disk galaxies. Using a sample of nearby spiral galaxies with weak and strong bars, we explore the relationships between the star formation feature and stellar bars in galaxies. We find that galaxies with weak bars tend coincide with low concentrical star formation activity, while those with strong bars show a large scatter in the distribution of star formation activity. We find enhanced star formation activity in bulges toward stronger bars, although not predominantly, consistent with previous studies. Our results suggest that different stages of the secular process and many other factors may contribute to the complexity of the secular evolution. In addition, barred galaxies with intense star formation in bars tend to have active star formation in their bulges and disks, and bulges have higher star formation densities than bars and disks, indicating the evolutionary effects of bars. We then derived a possible criterion to quantify the different stages of the bar-driven physical process, while future work is needed because of the uncertainties.

  18. In vitro colonization of the muscle extracellular matrix components by Escherichia coli O157:H7: the influence of growth medium, temperature and pH on initial adhesion and induction of biofilm formation by collagens I and III.

    PubMed

    Chagnot, Caroline; Agus, Allison; Renier, Sandra; Peyrin, Frédéric; Talon, Régine; Astruc, Thierry; Desvaux, Mickaël

    2013-01-01

    Enterohemorrhagic Escherichia coli (EHEC) O157:H7 are responsible for repeated food-poisoning cases often caused by contaminated burgers. EHEC infection is predominantly a pediatric illness, which can lead to life-threatening diseases. Ruminants are the main natural reservoir for EHEC and food contamination almost always originates from faecal contamination. In beef meat products, primary bacterial contamination occurs at the dehiding stage of slaughtering. The extracellular matrix (ECM) is the most exposed part of the skeletal muscles in beef carcasses. Investigating the adhesion to the main muscle fibrous ECM proteins, insoluble fibronectin, collagen I, III and IV, laminin-α2 and elastin, results demonstrated that the preceding growth conditions had a great influence on subsequent bacterial attachment. In the tested experimental conditions, maximal adhesion to fibril-forming collagens I or III occurred at 25°C and pH 7. Once initially adhered, exposure to lower temperatures, as applied to meat during cutting and storage, or acidification, as in the course of post-mortem physiological modifications of muscle, had no effect on detachment, except at pHu. In addition, dense biofilm formation occurred on immobilized collagen I or III and was induced in growth medium supplemented with collagen I in solution. From this first comprehensive investigation of EHEC adhesion to ECM proteins with respect to muscle biology and meat processing, new research directions for the development of innovative practices to minimize the risk of meat contamination are further discussed. PMID:23516631

  19. In vitro colonization of the muscle extracellular matrix components by Escherichia coli O157:H7: the influence of growth medium, temperature and pH on initial adhesion and induction of biofilm formation by collagens I and III.

    PubMed

    Chagnot, Caroline; Agus, Allison; Renier, Sandra; Peyrin, Frédéric; Talon, Régine; Astruc, Thierry; Desvaux, Mickaël

    2013-01-01

    Enterohemorrhagic Escherichia coli (EHEC) O157:H7 are responsible for repeated food-poisoning cases often caused by contaminated burgers. EHEC infection is predominantly a pediatric illness, which can lead to life-threatening diseases. Ruminants are the main natural reservoir for EHEC and food contamination almost always originates from faecal contamination. In beef meat products, primary bacterial contamination occurs at the dehiding stage of slaughtering. The extracellular matrix (ECM) is the most exposed part of the skeletal muscles in beef carcasses. Investigating the adhesion to the main muscle fibrous ECM proteins, insoluble fibronectin, collagen I, III and IV, laminin-α2 and elastin, results demonstrated that the preceding growth conditions had a great influence on subsequent bacterial attachment. In the tested experimental conditions, maximal adhesion to fibril-forming collagens I or III occurred at 25°C and pH 7. Once initially adhered, exposure to lower temperatures, as applied to meat during cutting and storage, or acidification, as in the course of post-mortem physiological modifications of muscle, had no effect on detachment, except at pHu. In addition, dense biofilm formation occurred on immobilized collagen I or III and was induced in growth medium supplemented with collagen I in solution. From this first comprehensive investigation of EHEC adhesion to ECM proteins with respect to muscle biology and meat processing, new research directions for the development of innovative practices to minimize the risk of meat contamination are further discussed.

  20. Development of a C3-symmetric benzohydroxamate tripod: Trimetallic complexation with Fe(III), Cr(III) and Al(III)

    NASA Astrophysics Data System (ADS)

    Baral, Minati; Gupta, Amit; Kanungo, B. K.

    2016-06-01

    The design, synthesis and physicochemical characterization of a C3-symmetry Benzene-1,3,5-tricarbonylhydroxamate tripod, noted here as BTHA, are described. The chelator was built from a benzene as an anchor, symmetrically extended by three hydroxamate as ligating moieties, each bearing O, O donor sites. A combination of absorption spectrophotometry, potentiometry and theoretical investigations are used to explore the complexation behavior of the ligand with some trivalent metal ions: Fe(III), Cr(III), and Al(III). Three protonation constants were calculated for the ligand in a pH range of 2-11 in a highly aqueous medium (9:1 H2O: DMSO). A high rigidity in the molecular structure restricts the formation of 1:1 (M/L) metal encapsulation but shows a high binding efficiency for a 3:1 metal ligand stoichiometry giving formation constant (in β unit) 28.73, 26.13 and 19.69 for [M3L]; Mdbnd Fe(III), Al(III) and Cr(III) respectively, and may be considered as an efficient Fe-carrier. The spectrophotometric study reveals of interesting electronic transitions occurred during the complexation. BTHA exhibits a peak at 238 nm in acidic pH and with the increase of pH, a new peak appeared at 270 nm. A substantial shifting in both of the peaks in presence of the metal ions implicates a s coordination between ligand and metal ions. Moreover, complexation of BTHA with iron shows three distinct colors, violet, reddish orange and yellow in different pH, enables the ligand to be considered for the use as colorimetric sensor.

  1. Welding III.

    ERIC Educational Resources Information Center

    Allegheny County Community Coll., Pittsburgh, PA.

    Instructional objectives and performance requirements are outlined in this course guide for Welding III, an advanced course in arc welding offered at the Community College of Allegheny County to provide students with the proficiency necessary for industrial certification. The course objectives, which are outlined first, specify that students will…

  2. Rapid preparation of (methyl)malonyl coenzyme A and enzymatic formation of unusual polyketides by type III polyketide synthase from Aquilaria sinensis.

    PubMed

    Gao, Bo-Wen; Wang, Xiao-Hui; Liu, Xiao; Shi, She-Po; Tu, Peng-Fei

    2015-03-15

    (Methyl)malonyl coenzyme A was rapidly and effectively synthesized by a two-step procedure involving preparation of N-hydroxysuccinimidyl (methyl)malonate from (methyl)Meldrum's acid, and followed by transesterification with coenzyme A. The synthesized (methyl)malonyl coenzyme A could be well accepted and assembled to 4-hydroxy phenylpropionyl coenzyme A by type III polyketide synthase from Aquilaria sinensis to produce dihydrochalcone and 4-hydroxy-3,5-dimethyl-6-(4-hydroxyphenethyl)-2H-pyrone as well as 4-hydroxy-3,5-dimethyl-6-(5-(4-hydroxyphenyl)-3-oxopentan-2-yl)-2H-pyrone.

  3. Efficient transport of Am(III) from nitric acid medium using a new conformationally constrained (N,N,N',N'-tetra-2-ethylhexyl)7-oxabicyclo[2.2.1]heptane-2,3-dicarboxamide across a supported liquid membrane.

    PubMed

    Sharma, S; Panja, S; Ghosh, S K; Dhami, P S; Gandhi, P M

    2016-03-15

    Am(III) is one of the most hazardous radionuclide present in nuclear fuel cycle. A new conformationally constrained diamide, (N,N,N',N'-tetra-2-ethylhexyl)7-oxabicyclo[2.2.1]heptane-2,3-dicarboxamide (OBDA) was studied for Am(III) transport from HNO3 medium across a Supported Liquid Membrane. Transport rate was observed to be significantly fast with ∼95% transport of Am(III) within 1h using 0.1M OBDA in the presence of 15% isodecyl alcohol (IDA)/n-dodecane as carrier. The mechanism of transport was investigated by studying various parameters like feed HNO3/NaNO3 concentration, OBDA concentration in the membrane, membrane pore size, membrane thickness etc. From these studies, the mechanism of transport was found to be diffusion controlled with diffusion co-efficient value of 5.1×10(-6)cm(2)/s. The membrane was found to be highly selective for tri- and tetra-valent actinides, and trivalent lanthanides. OBDA based membrane was found to be stable for at least for ten consecutive cycles of operation. PMID:26685064

  4. Ionic Polymer Microspheres Bearing a Co(III) -Salen Moiety as a Bifunctional Heterogeneous Catalyst for the Efficient Cycloaddition of CO2 and Epoxides.

    PubMed

    Leng, Yan; Lu, Dan; Zhang, Chenjun; Jiang, Pingping; Zhang, Weijie; Wang, Jun

    2016-06-01

    We report a unique strategy to obtain the bifunctional heterogeneous catalyst TBB-Bpy@Salen-Co (TBB=1,2,4,5-tetrakis(bromomethyl)benzene, Bpy=4,4'-bipyridine, Salen-Co=N,N'-bis({4-dimethylamino}salicylidene)ethylenediamino cobalt(III) acetate) by combining a cross-linked ionic polymer with a Co(III) -salen Schiff base. The catalyst showed extra high activity for CO2 fixation under mild, solvent-free reaction conditions with no requirement for a co-catalyst. The synthesized catalyst possessed distinctive spherical structural features, abundant halogen Br(-) anions with good leaving group ability, and accessible Lewis acidic Co metal centers. These unique features, together with the synergistic role of the Co and Br(-) functional sites, allowed TBB-Bpy@Salen-Co to exhibit enhanced catalytic conversion of CO2 into cyclic carbonates relative to the corresponding monofunctional analogues. This catalyst can be easily recovered and recycled five times without significant leaching of Co or loss of activity. Moreover, based on our experimental results and previous work, a synergistic cycloaddition reaction mechanism was proposed.

  5. Kiloparsec-Scale Simulations of Star Formation in Disk Galaxies III. Structure and Dynamics of Filaments and Clumps in Giant Molecular Clouds

    NASA Astrophysics Data System (ADS)

    Butler, Michael J.; Tan, Jonathan C.; Van Loo, Sven

    2015-05-01

    We present hydrodynamic simulations of self-gravitating dense gas in a galactic disk, exploring scales ranging from 1 kpc down to ˜0.1 pc. Our primary goal is to understand how dense filaments form in giant molecular clouds (GMCs). These structures, often observed as infrared dark clouds (IRDCs) in the Galactic plane, are thought to be the precursors to massive stars and star clusters, so their formation may be the rate-limiting step controlling global star formation rates in galactic systems as described by the Kennicutt-Schmidt relation. Our study follows on from Van Loo et al., which carried out simulations to 0.5 pc resolution and examined global aspects of the formation of dense gas clumps and the resulting star formation rate. Here, using our higher resolution, we examine the detailed structural, kinematic, and dynamical properties of dense filaments and clumps, including mass surface density (Σ) probability distribution functions, filament mass per unit length and its dispersion, lateral Σ profiles, filament fragmentation, filament velocity gradients and infall, and degree of filament and clump virialization. Where possible, these properties are compared to observations of IRDCs. By many metrics, especially too large mass fractions of high {Σ }\\gt 1 g c{{m}-2} material, too high mass per unit length dispersion due to dense clump formation, too high velocity gradients, and too high velocity dispersion for a given mass per unit length, the simulated filaments differ from observed IRDCs. We thus conclude that IRDCs do not form from global fast collapse of GMCs. Rather, we expect that IRDC formation and collapse are slowed significantly by the influence of dynamically important magnetic fields, which may thus play a crucial role in regulating galactic star formation rates.

  6. The PdBI Arcsecond Whirlpool Survey (PAWS) III. How Dynamical Environments Regulate the Structure of the Molecular Gas and Star Formation in M51

    NASA Astrophysics Data System (ADS)

    Meidt, Sharon; Schinnerer, E.; Hughes, A.; Garcia Burillo, S.; Colombo, D.; Pety, J.; Leroy, A. K.; Dobbs, C.; Dumas, G.; Schuster, K. F.; Thompson, T. A.; Kramer, C.

    2013-01-01

    Gas kinematics on the scales of Giant Molecular Clouds (GMCs) are essential for probing the framework that links the large-scale organization of interstellar gas to cloud formation and subsequent star formation. We will present an overview of our results on the importance of dynamical environment for molecular gas and star formation from the PdBI Arcsecond Whirlpool Survey (PAWS, PI: E. Schinnerer), which has mapped CO(1-0) emission in the nearby grand-design spiral galaxy M51 at 40pc resolution and is sensitive to giant molecular clouds (GMCs) with masses above 10^5 Msun. The observed gas motions suggest a strong response to the gravitational forces exerted by the stellar spiral arms, and we find that the properties of the CO emission in M51 show significant variation that can be linked to the (galactic) dynamical environment in which the molecular gas is located. Dynamically distinct regions exhibit different GMC properties and mass spectra, as well as distinct patterns of star formation. We have analyzed how the stability of GMCs depends on dynamical environment (including the effects of pressure, shear, turbulence). We will discuss the impact of our results on the interpretation of standard GMC scaling relations and as a potential source of the observed scatter in extragalactic star formation laws.

  7. Efficient cross-coupling of aryl Grignard reagents with alkyl halides by recyclable ionic iron(III) complexes bearing a bis(phenol)-functionalized benzimidazolium cation.

    PubMed

    Xia, Chong-Liang; Xie, Cun-Fei; Wu, Yu-Feng; Sun, Hong-Mei; Shen, Qi; Zhang, Yong

    2013-12-14

    A novel bis(phenol)-functionalized benzimidazolium salt, 1,3-bis(3,5-di-tert-butyl-2-hydroxybenzyl)benzimidazolium chloride (H3LCl, 1), was designed and used to prepare ionic iron(III) complexes of the type [H3L][FeX4] (X = Cl, 2; X = Br, 3). Both 2 and 3 were characterized by elemental analysis, Raman spectroscopy, electrospray ionization mass spectrometry and X-ray crystallography. The catalytic performances of 2 and 3 in cross-coupling reactions using aryl Grignard reagents with primary and secondary alkyl halides bearing β-hydrogens were studied. This analysis shows that complex 2 has good potential for alkyl chloride-mediated coupling. In comparison, complex 3 showed slightly lower catalytic activity. After decanting the product contained in the ethereal layer, complex 2 could be recycled at least eight times without significant loss of catalytic activity.

  8. Efficient cross-coupling of aryl Grignard reagents with alkyl halides by recyclable ionic iron(III) complexes bearing a bis(phenol)-functionalized benzimidazolium cation.

    PubMed

    Xia, Chong-Liang; Xie, Cun-Fei; Wu, Yu-Feng; Sun, Hong-Mei; Shen, Qi; Zhang, Yong

    2013-12-14

    A novel bis(phenol)-functionalized benzimidazolium salt, 1,3-bis(3,5-di-tert-butyl-2-hydroxybenzyl)benzimidazolium chloride (H3LCl, 1), was designed and used to prepare ionic iron(III) complexes of the type [H3L][FeX4] (X = Cl, 2; X = Br, 3). Both 2 and 3 were characterized by elemental analysis, Raman spectroscopy, electrospray ionization mass spectrometry and X-ray crystallography. The catalytic performances of 2 and 3 in cross-coupling reactions using aryl Grignard reagents with primary and secondary alkyl halides bearing β-hydrogens were studied. This analysis shows that complex 2 has good potential for alkyl chloride-mediated coupling. In comparison, complex 3 showed slightly lower catalytic activity. After decanting the product contained in the ethereal layer, complex 2 could be recycled at least eight times without significant loss of catalytic activity. PMID:24145602

  9. Performance of Single-Stage Turbine of Mark 25 Torpedo Power Plant with Two Special Nozzles. III; Efficiency with Standard Rotor Blades

    NASA Technical Reports Server (NTRS)

    Schum, Harold J.; Whitney, Warren J.

    1949-01-01

    A Mark 25 torpedo power plant modified to operate as a single-stage turbine was investigated to determine the performance with two nozzle designs and a standard first-stage rotor having 0.40-inch blades with a 17O met-air angle. Both nozzles had smaller port cross-sectional areas than those nozzles of similar design, which were previously investigated. The performance of the two nozzles was compared on the basis of blade, rotor, and brake efficiencies as a function of blade-jet speed ratio for pressure ratios of 8, 15 (design), and 20. At pressure ratios of 15 and 20, the blade efficiency obtained with the nozzle having circular passages (K) was higher than that obtained with the nozzle having rectangular passages (J). At a pressure ratio of 8, the efficiencies obtained with the two nozzles were comparable for blade-jet speed ratios of less than 0.260. For blade-jet speed ratios exceeding this value, nozzle K yielded slightly higher efficiencies. The maximum blade efficiency of 0.569 was obtained with nozzle K at a pressure ratio of 8 and a blade-jet speed ratio of 0.295. At design speed and pressure ratio, nozzle K yielded a maximum blade efficiency of 0.534, an increase of 0.031 over that obtained with nozzle J. When the blade efficiencies of the two nozzles were compared with those of four other nozzles previously investigated, the maximum difference for the six nozzles with this rotor was 0.050. From, this comparison, no specific effect of nozzles size or shape on over-all performance was discernible.

  10. Reduction of SeO{sub 4}{sup 2{minus}} anions and anoxic formation of iron(II)-Iron(III) hydroxy-selenate green rust

    SciTech Connect

    Refait, P.; Simon, L.; Genin, J.M.R.

    2000-03-01

    Iron(II)-iron(III) hydroxy-salts known as green rusts were recently discovered as minerals present in hydromorphic soils and sediments. Due to their high reactivity, they are envisioned as potential reducing agents of a number of pollutants such as nitrate, chromate, or selenate. The interaction of selenate ions with such iron(II)-containing hydroxy compounds was studied by monitoring the oxidation processes of the iron phases with transmission Moessbauer spectroscopy measured at 14 K and by following the evolution of Se(VI) in solution by capillary electrophoresis. This interaction involved the hydroxy-selenate green rust, a compound isomorphous to the hydroxy-sulfate GR(SO{sub 4}{sup 2{minus}}). Its chemical composition, Fe{sub y}{sup II}Fe{sub 2}{sup III}(OH){sub 2(y+2)}SeO{sub 4}{center_dot}8H{sub 2}O, varied with time since y starts at 5.5 and ends at 4. GR(SeO{sub 4}{sup 2{minus}}) was obtained from Fe(OH){sub 2} precipitates by simultaneous accumulation of SeO{sub 4}{sup 2{minus}} anions inside the solid phase and reduction of an equal amount of SeO{sub 4}{sup 2{minus}} anions to Se(IV) species. These species were found to be less mobile, partially bound to iron compounds and/or forming iron salts. Finally, the hydroxy-selenate GR2(SeO{sub 4}{sup 2{minus}}) can form without any other oxidizing agent than selenate itself.

  11. Loss of GltB Inhibits Biofilm Formation and Biocontrol Efficiency of Bacillus subtilis Bs916 by Altering the Production of γ-Polyglutamate and Three Lipopeptides

    PubMed Central

    Luo, Chuping; Fang, Xianwen; Xiang, Yaping; Wang, Xiaoyu; Zhang, Rongsheng; Chen, Zhiyi

    2016-01-01

    Aims This study examined the contribution of GltB on biofilm formation and biocontrol efficiency of B. subtilis Bs916. Methods and Results The gltB gene was identified through a biofilm phenotype screen and a bioinformatics analysis of serious biofilm formation defects, and then a gltB single knockout mutant was constructed using homologous recombination. This mutant demonstrated severe deficits in biofilm formation and colonisation along with significantly altered production ofγ-polyglutamate (γ-PGA) and three lipopeptide antibiotics (LPs) as measured by a transcriptional analysis of both the wild type B. subtilis Bs916 and the gltB mutant. Consequently, the mutant strain retained almost no antifungal activity against Rhizoctonia solani and exhibited decreased biocontrol efficiency against rice sheath blight. Very few gltB mutant cells colonised the rice stem, and they exhibited no significant nutrient chemotaxis compared to the wild type B. subtilis Bs916. The mechanism underlying these deficits in the gltB mutant appears to be decreased significantly in production of γ-PGA and a reduction in the production of both bacillomycin L and fengycin. Biofilm restoration of gltB mutant by additionγ-PGA in the EM medium demonstrated that biofilm formation was able to restore significantly at 20 g/L. Conclusions GltB regulates biofilm formation by altering the production ofγ-PGA, the LPs bacillomycin L and fengcin and influences bacterial colonisation on the rice stem, which consequently leads to poor biocontrol efficiency against rice sheath blight. Significance and Impact of Study This is the first report of a key regulatory protein (GltB) that is involved in biofilm regulation and its regulation mechanism and biocontrol efficiency by B. subtilis. PMID:27223617

  12. IOMIDAZOLIUM-BASED INDIUM(III) TETRAHIDES: RECYCLABLE CATALYSTS FOR EFFICIENT COUPLING OF CARBON DIOXIDE WITH EXPOXIDES TO FORM CYCLIC CARBONATES

    EPA Science Inventory

    The transformation of CO2 an abundant greenhouse gas, into cyclic carbonates by coupling reaction with epoxides is receiving well-deserved attention. A series of imidazolium-based indium tetrahalides, prepared efficiently via microwave assisted reaction of InX3 with [1-R-3-metht...

  13. Efficient enhancement of the visible-light absorption of cyclometalated Ir(III) complexes triplet photosensitizers with Bodipy and applications in photooxidation and triplet-triplet annihilation upconversion.

    PubMed

    Sun, Jifu; Zhong, Fangfang; Yi, Xiuyu; Zhao, Jianzhang

    2013-06-01

    We report molecular designing strategies to enhance the effective visible-light absorption of cyclometalated Ir(III) complexes. Cationic cyclometalated Ir(III) complexes were prepared in which boron-dipyrromethene (Bodipy) units were attached to the 2,2'-bipyridine (bpy) ligand via -C≡C- bonds at either the meso-phenyl (Ir-2) or 2 position of the π core of Bodipy (Ir-3). For the first time the effect of π conjugating (Ir-3) or tethering (Ir-2) of a light-harvesting chromophore to the coordination center on the photophysical properties was compared in detail. Ir(ppy)2(bpy) (Ir-1; ppy = 2-phenylpyridine) was used as model complex, which gives the typical weak absorption in visible range (ε < 4790 M(-1) cm(-1) in region > 400 nm). Ir-2 and Ir-3 showed much stronger absorption in the visible range (ε = 71,400 M(-1) cm(-1) at 499 nm and 83,000 M(-1) cm(-1) at 527 nm, respectively). Room-temperature phosphorescence was only observed for Ir-1 (λ(em) = 590 nm) and Ir-3 (λ(em) = 742 nm). Ir-3 gives RT phosphorescence of the Bodipy unit. On the basis of the 77 K emission spectra, nanosecond transient absorption spectra, and spin density analysis, we proposed that Bodipy-localized long-lived triplet excited states were populated for Ir-2 (τT = 23.7 μs) and Ir-3 (87.2 μs). Ir-1 gives a much shorter triplet-state lifetime (0.35 μs). Complexes were used as singlet oxygen ((1)O2) photosensitizers in photooxidation. The (1)O2 quantum yield of Ir-3 (ΦΔ = 0.97) is ca. 2-fold of Ir-2 (ΦΔ = 0.52). Complexes were also used as triplet photosensitizer for TTA upconversion; upconversion quantum yields of 1.2% and 2.8% were observed for Ir-2 and Ir-3, respectively. Our results proved that the strong absorption of visible light of Ir-2 failed to enhance production of a triplet excited state. These results are useful for designing transition metal complexes that show effective strong visible-light absorption and long-lived triplet excited states, which can be used as ideal

  14. Quasi-elastic light scattering from migrating chemotactic bands of Escherichia coli. III. Studies of band formation propagation and motility in oxygen and serine substrates.

    PubMed Central

    Wang, P C; Chen, S H

    1986-01-01

    A series of light scattering experiments have been performed to study both macroscopic aspects of band formation and propagation and microscopic motility parameters of Escherichia coli in the combined substrate gradients of oxygen and serine. From the band formation experiment the conclusion is drawn that a minimum threshold gradient of the substrate is required for bacteria to form a band. From the band propagation experiment in the serine substrate the motility coefficient mu and chemotactic coefficient delta are determined. A separate quasi-elastic scattering experiment has been made with a propagating band to obtain three microscopic motility parameters: mean twiddle time tau 1, mean run time tau 2, and mean run speed V2. Finally, a scaling argument is made to connect the macroscopic parameters mu and delta with the microscopic parameters tau 1, tau 2, and V2, thus achieving a unified understanding of macroscopic and microscopic aspect of chemotaxis. Images FIGURE 1 PMID:3087435

  15. Biotransformation of Two-Line Silica-Ferrihydrite by a Dissimilatory Fe(III)-Reducing Bacterium: Formation of Carbonate Green Rust in the Presence of Phosphate

    SciTech Connect

    Kukkadapu, Ravi K.; Zachara, John M.; Fredrickson, Jim K.; Kennedy, David W.

    2004-07-01

    The reductive biotransformation of two Si-ferrihydrite (0.01 and 0.05 mole% Si) coprecipiates by Shewanella putrefaciens, strain CN32, was investigated in 1,4-piperazinediethanesulfonic acid-buffered media (pH ~7) with lactate as the electron donor. Anthraquinone-2,6-disulfonate (electron shuttle) that stimulates respiration was present in the media. Experiments were performed without and with PO43- (ranging from 1 to 20 mmol/L in media containing 50 mmol/L Fe). Our objectives were to define the combined effects of SiO44- and PO43- on the bioreducibility and biomineralization of ferrihydrites under anoxic conditions. Iron reduction was measured as a function of time, solids were characterized by powder X-ray diffraction (XRD) and Mossbauer spectroscopy, and aqueous solutions were analyzed for Si, P, Cl- and inorganic carbon. Both of the ferrihydrites were rapidly reduced regardless of the Si content. Si concentration had no effect on the reduction rate or mineralization products. Magnetite was formed in the absence of PO43- whereas carbonate green rust GR(CO32-) ([FeII(6-x)FeIIIx(OH)12]x+(CO32-)0.5x.yH2O) and vivianite [Fe3(PO4)2.8H2O], were formed when PO43- was present. GR(CO32-) dominated as a mineral product in samples with < 4 mmol/L PO43-. The Fe(II)/Fe(III) ratio of GR(CO32-) varied with PO43- concentration; it was 2 in the 1 mmol/L PO43- and approached 1 in the 4- and 10-mmol/L PO43- samples. GR appeared to form by solid-state transformation of ferrihydrite. Medium PO43- concentration dictated the mechanism of transformation. In 1 mmol/L PO43- media, an intermediate Fe(II)/Fe(III) phase with structural Fe(II), which we tentatively assigned to a protomagnetite phase, slowly transformed to GR with time. In contrast, in medium with >4 mmol/L PO43-, a residual ferrihydrite with sorbed Fe2+ phase transformed to GR. Despite similar chemistries, PO43- was shown to have a profound effect on ferrihydrite biotransformations while that of SiO44- was minimal.

  16. Biotransformation of two-line silica-ferrihydrite by a dissimilatory Fe(III)-reducing bacterium: formation of carbonate green rust in the presence of phosphate

    NASA Astrophysics Data System (ADS)

    Kukkadapu, Ravi K.; Zachara, John M.; Fredrickson, James K.; Kennedy, David W.

    2004-07-01

    The reductive biotransformation of two Si-ferrihydrite coprecipitates (1 and 5 mole % Si) by Shewanella putrefaciens, strain CN32, was investigated in 1,4-piperazinediethanesulfonic acid-buffered media (pH ˜7) with lactate as the electron donor. Anthraquinone-2,6-disulfonate, an electron shuttle, was present in the media. Experiments were performed without and with PO 43- (P) (1 to 20 mmol/L) in media containing 50 mmol/L Fe. Our objectives were to define the combined effects of SiO 44- (Si) and P on the bioreducibility and biomineralization of ferrihydrites under anoxic conditions. Iron reduction was measured as a function of time, solids were characterized by powder X-ray diffraction and Mössbauer spectroscopy, and aqueous solutions were analyzed for Si, P, Cl - and inorganic carbon. Both of the ferrihydrites were rapidly reduced regardless of the Si and P content. Si concentration had no effect on the reduction rate or mineralization products. Magnetite was formed in the absence of P whereas carbonate green rust GR(CO 32-) ([Fe (6-x)IIFe IIIx(OH) 12] x+(CO 32-) 0.5x · yH 2O) and vivianite [Fe 3(PO 4) 2 · 8H 2O], were formed when P was present. GR(CO 32-) dominated as a mineral product in samples with <4 mmol/L P. The Fe(II)/Fe(III) ratio of GR(CO 32-) varied with P concentration; the ratio was 2 in 1 mmol/L P and approached 1 with 4- and 10 mmol/L P. Green rust appeared to form by solid-state transformation of ferrihydrite. Media P and Si concentration dictated the mechanism of transformation. In the 1 mole % Si coprecipitate with 1 mmol/L P, an intermediate Fe(II)/Fe(III) phase with structural Fe(II) slowly transformed to GR with time. In contrast, when ferrihydrite contained more Si (5 mole %) and/or contained higher P (4 mmol/L), sorbed Fe(II) and residual ferrihydrite together transformed to GR. Despite similar chemistries, P was shown to have a profound effect on extent of ferrihydrite reduction and biotransformations while that of Si was minimal.

  17. Similar quartz crystallographic textures in rocks of continental earth's crust (by neutron diffraction data): III. Relation of quartz texture types with means and conditions of texture formation

    SciTech Connect

    Nikitin, A. N. Ivankina, T. I.; Ullemeyer, K.; Vasin, R. N.

    2008-09-15

    Examples of different rocks collected in different regions of the continental earth's crust are presented. Groups of quartz crystallographic textures of the same type are selected for these rocks. The relationship between the types of textures and the physical means and conditions of their formation is analyzed. The effect of the {alpha}-{beta} phase transition in quartz on the texture transformations in rocks is considered.

  18. Reactivity of boranes with a titanium(IV) amine tris(phenolate) alkoxide complex; formation of a Ti(IV) tetrahydroborate complex, a Ti(III) dimer and a Ti(IV) hydroxide Lewis acid adduct.

    PubMed

    Johnson, Andrew L; Davidson, Matthew G; Mahon, Mary F

    2007-12-14

    Treatment of the titanium(IV) alkoxide complex [Ti(Oi Pr)(OC6Me2H(2)CH2)3N] (2) with BH3.THF, as part of a study into the utility and reactivity of (2) in the metal mediated borane reduction of acetophenone, results in alkoxide-hydride exchange and formation of the structurally characterised titanium(iv) tetrahydroborate complex [Ti{BH4}(OC6Me2H2CH2)3N] (3). Complex (3) readily undergoes reduction to form the isolable titanium(III) species [Ti(OC6Me2H2CH2)3N]2 (4). Reaction of (2) with B(C6F5)3 results in formation of the Lewis acid adduct [Ti(OC6Me2H2CH2)3N][HO.B(C6F5)3] (5). In comparison, treatment of the less sterically encumbered alkoxide Ti(Oi Pr)4 with B(C6F5)3 results in alkoxide-aryl exchange and formation of the organometallic titanium complex [Ti(Oi Pr)3(C6F5)]2 (6). The molecular structures of 3, 4, 5 and 6 have been determined by X-ray diffraction.

  19. Dihydrogen catalysis of the reversible formation and cleavage of C-H and N-H bonds of aminopyridinate ligands bound to (η(5) -C5 Me5 )Ir(III.).

    PubMed

    Zamorano, Ana; Rendón, Nuria; López-Serrano, Joaquín; Valpuesta, José E V; Álvarez, Eleuterio; Carmona, Ernesto

    2015-02-01

    This study focuses on a series of cationic complexes of iridium that contain aminopyridinate (Ap) ligands bound to an (η(5) -C5 Me5 )Ir(III) fragment. The new complexes have the chemical composition [Ir(Ap)(η(5) -C5 Me5 )](+) , exist in the form of two isomers (1(+) and 2(+) ) and were isolated as salts of the BArF (-) anion (BArF =B[3,5-(CF3 )2 C6 H3 ]4 ). Four Ap ligands that differ in the nature of their bulky aryl substituents at the amido nitrogen atom and pyridinic ring were employed. In the presence of H2 , the electrophilicity of the Ir(III) centre of these complexes allows for a reversible prototropic rearrangement that changes the nature and coordination mode of the aminopyridinate ligand between the well-known κ(2) -N,N'-bidentate binding in 1(+) and the unprecedented κ-N,η(3) -pseudo-allyl-coordination mode in isomers 2(+) through activation of a benzylic C-H bond and formal proton transfer to the amido nitrogen atom. Experimental and computational studies evidence that the overall rearrangement, which entails reversible formation and cleavage of H-H, C-H and N-H bonds, is catalysed by dihydrogen under homogeneous conditions. PMID:25504864

  20. Dihydrogen catalysis of the reversible formation and cleavage of C-H and N-H bonds of aminopyridinate ligands bound to (η(5) -C5 Me5 )Ir(III.).

    PubMed

    Zamorano, Ana; Rendón, Nuria; López-Serrano, Joaquín; Valpuesta, José E V; Álvarez, Eleuterio; Carmona, Ernesto

    2015-02-01

    This study focuses on a series of cationic complexes of iridium that contain aminopyridinate (Ap) ligands bound to an (η(5) -C5 Me5 )Ir(III) fragment. The new complexes have the chemical composition [Ir(Ap)(η(5) -C5 Me5 )](+) , exist in the form of two isomers (1(+) and 2(+) ) and were isolated as salts of the BArF (-) anion (BArF =B[3,5-(CF3 )2 C6 H3 ]4 ). Four Ap ligands that differ in the nature of their bulky aryl substituents at the amido nitrogen atom and pyridinic ring were employed. In the presence of H2 , the electrophilicity of the Ir(III) centre of these complexes allows for a reversible prototropic rearrangement that changes the nature and coordination mode of the aminopyridinate ligand between the well-known κ(2) -N,N'-bidentate binding in 1(+) and the unprecedented κ-N,η(3) -pseudo-allyl-coordination mode in isomers 2(+) through activation of a benzylic C-H bond and formal proton transfer to the amido nitrogen atom. Experimental and computational studies evidence that the overall rearrangement, which entails reversible formation and cleavage of H-H, C-H and N-H bonds, is catalysed by dihydrogen under homogeneous conditions.

  1. Solvent assisted formation of ruthenium(III) and ruthenium(II) hydrazone complexes in one-pot with potential in vitro cytotoxicity and enhanced LDH, NO and ROS release.

    PubMed

    Jayanthi, Eswaran; Kalaiselvi, Sivalingam; Padma, Viswanatha Vijaya; Bhuvanesh, Nattamai S P; Dharmaraj, Nallasamy

    2016-01-28

    A set each of new bivalent and trivalent ruthenium complexes, [Ru(III)(HL)Cl2(EPh3)2] and [Ru(II)(L)(CO)(EPh3)2] (E = P (complexes and ) or As (complexes and )) were synthesised from the reactions of [Ru(III)Cl3(EPh3)3] with 2-hydroxynaphthaldehyde benzoic acid hydrazone (H2L) in methanol-chloroform and characterized by elemental analysis, spectral data and XRD study. A suitable mechanism to account for the formation of bivalent ruthenium carbonyl complexes from the corresponding trivalent precursors is provided by considering the role of added base in the reaction. Interaction of complexes with CT-DNA/bovine serum albumin was analysed with absorption and emission spectral titration studies. In vitro cytotoxic potential of the above ruthenium hydrazone complexes assayed against the A549 cell line revealed a significant growth inhibition. The test complexes added in IC50 concentration into the cell culture medium enhanced the release of lactate dehydrogenase, NO and reactive oxygen species in comparison with the control. Cell death induced by the complexes was studied using a propidium iodide staining assay and showed noticeable changes in the cell morphology which resembled apoptosis.

  2. Solvent assisted formation of ruthenium(III) and ruthenium(II) hydrazone complexes in one-pot with potential in vitro cytotoxicity and enhanced LDH, NO and ROS release.

    PubMed

    Jayanthi, Eswaran; Kalaiselvi, Sivalingam; Padma, Viswanatha Vijaya; Bhuvanesh, Nattamai S P; Dharmaraj, Nallasamy

    2016-01-28

    A set each of new bivalent and trivalent ruthenium complexes, [Ru(III)(HL)Cl2(EPh3)2] and [Ru(II)(L)(CO)(EPh3)2] (E = P (complexes and ) or As (complexes and )) were synthesised from the reactions of [Ru(III)Cl3(EPh3)3] with 2-hydroxynaphthaldehyde benzoic acid hydrazone (H2L) in methanol-chloroform and characterized by elemental analysis, spectral data and XRD study. A suitable mechanism to account for the formation of bivalent ruthenium carbonyl complexes from the corresponding trivalent precursors is provided by considering the role of added base in the reaction. Interaction of complexes with CT-DNA/bovine serum albumin was analysed with absorption and emission spectral titration studies. In vitro cytotoxic potential of the above ruthenium hydrazone complexes assayed against the A549 cell line revealed a significant growth inhibition. The test complexes added in IC50 concentration into the cell culture medium enhanced the release of lactate dehydrogenase, NO and reactive oxygen species in comparison with the control. Cell death induced by the complexes was studied using a propidium iodide staining assay and showed noticeable changes in the cell morphology which resembled apoptosis. PMID:26699435

  3. Directly imaging damped Ly α galaxies at z > 2 - III. The star formation rates of neutral gas reservoirs at z ˜ 2.7

    NASA Astrophysics Data System (ADS)

    Fumagalli, Michele; O'Meara, John M.; Prochaska, J. Xavier; Rafelski, Marc; Kanekar, Nissim

    2015-01-01

    We present results from a survey designed to probe the star formation properties of 32 damped Lyman α systems (DLAs) at z ˜ 2.7. By using the `double-DLA' technique that eliminates the glare of the bright background quasars, we directly measure the rest-frame far-ultraviolet flux from DLAs and their neighbouring galaxies. At the position of the absorbing gas, we place stringent constraints on the unobscured star formation rates (SFRs) of DLAs to 2σ limits of dot{ψ }<0.09-0.27M⊙ yr-1, corresponding to SFR surface densities Σsfr < 10-2.6-10-1.5M⊙ yr-1 kpc-2. The implications of these limits for the star formation law, metal enrichment, and cooling rates of DLAs are examined. By studying the distribution of impact parameters as a function of SFRs for all the galaxies detected around these DLAs, we place new direct constraints on the bright end of the UV luminosity function of DLA hosts. We find that ≤13 per cent of the hosts have dot{ψ }≥2M⊙ yr-1 at impact parameters b_dla ≤ (dot{ψ }/{M_{⊙} yr^{-1}})^{0.8}+6 kpc, differently from current samples of confirmed DLA galaxies. Our observations also disfavour a scenario in which the majority of DLAs arise from bright Lyman-break galaxies at distances 20 ≤ bdla < 100 kpc. These new findings corroborate a picture in which DLAs do not originate from highly star-forming systems that are coincident with the absorbers, and instead suggest that DLAs are associated with faint, possibly isolated, star-forming galaxies. Potential shortcomings of this scenario and future strategies for further investigation are discussed.

  4. Directly Imaging Damped Ly-Alpha Galaxies at Redshifts Greater Than 2. III: The Star Formation Rates of Neutral Gas Reservoirs at Redshifts of Approximately 2.7

    NASA Technical Reports Server (NTRS)

    Fumagalli, Michele; OMeara, John M.; Prochaska, J. Xavier; Rafelski, Marc; Kanekar, Nissim

    2014-01-01

    We present results from a survey designed to probe the star formation properties of 32 damped Ly alpha systems (DLAs) at redshifts of approximately 2.7. By using the "double-DLA" technique that eliminates the glare of the bright background quasars, we directly measure the rest-frame FUV flux from DLAs and their neighbouring galaxies. At the position of the absorbing gas, we place stringent constraints on the unobscured star formation rates (SFRs) of DLAs to 2 sigma limits of psi less than 0.09-0.27 solar mass yr(exp -1), corresponding to SFR surface densities sigma(sub sfr) less than 10(exp -2.6)-10(exp -1.5) solar mass yr(exp -1) kpc(exp -2). The implications of these limits for the star formation law, metal enrichment, and cooling rates of DLAs are examined. By studying the distribution of impact parameters as a function of SFRs for all the galaxies detected around these DLAs, we place new direct constraints on the bright end of the UV luminosity function of DLA hosts. We find that less than or equal to 13% of the hosts have psi greater than or equal to 2 solar mass yr(exp -1) at impact parameters b(sub dla) less than or equal to (psi/solar mass yr(exp -1))(exp 0.8) + 6 kpc, differently from current samples of confirmed DLA galaxies. Our observations also disfavor a scenario in which the majority of DLAs arise from bright LBGs at distances 20 less than or equal to b(sub dla) less than 100 kpc. These new findings corroborate a picture in which DLAs do not originate from highly star forming systems that are coincident with the absorbers, and instead suggest that DLAs are associated with faint, possibly isolated, star-forming galaxies. Potential shortcomings of this scenario and future strategies for further investigation are discussed.

  5. mzDB: a file format using multiple indexing strategies for the efficient analysis of large LC-MS/MS and SWATH-MS data sets.

    PubMed

    Bouyssié, David; Dubois, Marc; Nasso, Sara; Gonzalez de Peredo, Anne; Burlet-Schiltz, Odile; Aebersold, Ruedi; Monsarrat, Bernard

    2015-03-01

    The analysis and management of MS data, especially those generated by data independent MS acquisition, exemplified by SWATH-MS, pose significant challenges for proteomics bioinformatics. The large size and vast amount of information inherent to these data sets need to be properly structured to enable an efficient and straightforward extraction of the signals used to identify specific target peptides. Standard XML based formats are not well suited to large MS data files, for example, those generated by SWATH-MS, and compromise high-throughput data processing and storing. We developed mzDB, an efficient file format for large MS data sets. It relies on the SQLite software library and consists of a standardized and portable server-less single-file database. An optimized 3D indexing approach is adopted, where the LC-MS coordinates (retention time and m/z), along with the precursor m/z for SWATH-MS data, are used to query the database for data extraction. In comparison with XML formats, mzDB saves ∼25% of storage space and improves access times by a factor of twofold up to even 2000-fold, depending on the particular data access. Similarly, mzDB shows also slightly to significantly lower access times in comparison with other formats like mz5. Both C++ and Java implementations, converting raw or XML formats to mzDB and providing access methods, will be released under permissive license. mzDB can be easily accessed by the SQLite C library and its drivers for all major languages, and browsed with existing dedicated GUIs. The mzDB described here can boost existing mass spectrometry data analysis pipelines, offering unprecedented performance in terms of efficiency, portability, compactness, and flexibility.

  6. mzDB: A File Format Using Multiple Indexing Strategies for the Efficient Analysis of Large LC-MS/MS and SWATH-MS Data Sets*

    PubMed Central

    Bouyssié, David; Dubois, Marc; Nasso, Sara; Gonzalez de Peredo, Anne; Burlet-Schiltz, Odile; Aebersold, Ruedi; Monsarrat, Bernard

    2015-01-01

    The analysis and management of MS data, especially those generated by data independent MS acquisition, exemplified by SWATH-MS, pose significant challenges for proteomics bioinformatics. The large size and vast amount of information inherent to these data sets need to be properly structured to enable an efficient and straightforward extraction of the signals used to identify specific target peptides. Standard XML based formats are not well suited to large MS data files, for example, those generated by SWATH-MS, and compromise high-throughput data processing and storing. We developed mzDB, an efficient file format for large MS data sets. It relies on the SQLite software library and consists of a standardized and portable server-less single-file database. An optimized 3D indexing approach is adopted, where the LC-MS coordinates (retention time and m/z), along with the precursor m/z for SWATH-MS data, are used to query the database for data extraction. In comparison with XML formats, mzDB saves ∼25% of storage space and improves access times by a factor of twofold up to even 2000-fold, depending on the particular data access. Similarly, mzDB shows also slightly to significantly lower access times in comparison with other formats like mz5. Both C++ and Java implementations, converting raw or XML formats to mzDB and providing access methods, will be released under permissive license. mzDB can be easily accessed by the SQLite C library and its drivers for all major languages, and browsed with existing dedicated GUIs. The mzDB described here can boost existing mass spectrometry data analysis pipelines, offering unprecedented performance in terms of efficiency, portability, compactness, and flexibility. PMID:25505153

  7. Formation of [Ni(III)(κ(1)-S2CH)(P(o-C6H3-3-SiMe3-2-S)3)]- via CS2 insertion into nickel(III) hydride containing [Ni(III)(H)(P(o-C6H3-3-SiMe3-2-S)3)]-.

    PubMed

    Lai, Kuan-Ting; Ho, Wei-Chieh; Chiou, Tzung-Wen; Liaw, Wen-Feng

    2013-04-15

    Insertion of CS2 into the thermally unstable nickel(III) hydride [PPN][Ni(H)(P(o-C6H3-3-SiMe3-2-S)3)] (1), freshly prepared from the reaction of [PPN][Ni(OC6H5)P(C6H3-3-SiMe3-2-S)3] and 4,4,5,5-tetramethyl-1,3,2-dioxaborolane (HBpin; pin = OCMe2CMe2O) in tetrahydrofuran at -80 °C via a metathesis reaction, readily affords [PPN][Ni(III)(κ(1)-S2CH)(P(o-C6H3-3-SiMe3-2-S)3)] (2) featuring a κ(1)-S2CH moiety. PMID:23541028

  8. The importance of nodule CO2 fixation for the efficiency of symbiotic nitrogen fixation in pea at vegetative growth and during pod formation.

    PubMed

    Fischinger, Stephanie Anastasia; Schulze, Joachim

    2010-05-01

    Nodule CO2 fixation is of pivotal importance for N2 fixation. The process provides malate for bacteroids and oxaloacetate for nitrogen assimilation. The hypothesis of the present paper was that grain legume nodules would adapt to higher plant N demand and more restricted carbon availability at pod formation through increased nodule CO2 fixation and a more efficient N2 fixation. Growth, N2 fixation, and nodule composition during vegetative growth and at pod formation were studied in pea plants (Pisum sativum L.). In parallel experiments, 15N2 and 13CO2 uptake, as well as nodule hydrogen and CO2 release, was measured. Plants at pod formation showed higher growth rates and N2 fixation per plant when compared with vegetative growth. The specific activity of active nodules was about 25% higher at pod formation. The higher nodule activity was accompanied by higher amino acid concentration in nodules and xylem sap with a higher share of asparagine. Nodule 13CO2 fixation was increased at pod formation, both per plant and per 15N2 fixed unit. However, malate concentration in nodules was only 40% of that during vegetative growth and succinate was no longer detectable. The data indicate that increased N2 fixation at pod formation is connected with strongly increased nodule CO2 fixation. While the sugar concentration in nodules at pod formation was not altered, the concentration of organic acids, namely malate and succinate, was significantly lower. It is concluded that strategies to improve the capability of nodules to fix CO2 and form organic acids might prolong intensive N2 fixation into the later stages of pod formation and pod filling in grain legumes.

  9. Development and testing of a high efficiency advanced coal combustor phase III industrial boiler retrofit. Quarterly technical progress report No. 9, 1 October 1993--31 December 1993

    SciTech Connect

    Jennings, P.; Borio, R.; McGowan, J.G.

    1994-03-01

    This report documents the technical aspects of this project during the ninth quarter of the program. During this quarter, the natural gas baseline testing at the Penn State demonstration boiler was completed, results were analyzed and are presented here. The burner operates in a stable manner over an 8/1 turndown, however due to baghouse temperature limitations (300{degrees}F for acid dewpoint), the burner is not operated for long periods of time below 75% load. Boiler efficiency averaged 83.1% at the 100 percent load rate while increasing to 83.7% at 75% load. NO{sub x} emissions ranged from a low of 0.17 Lbs/MBtu to a high of 0.24 Lbs/MBtu. After the baseline natural gas testing was completed, work continued on hardware optimization and testing with the goal of increasing carbon conversion efficiency on 100% coal firing from {approx}95% to 98%. Several coal handling and feeding problems were encountered during this quarter and no long term testing was conducted. While resolving these problems several shorter term (less than 6 hour) tests were conducted. These included, 100% coal firing tests, 100% natural gas firing tests, testing of air sparges on coal to simulate more primary air and a series of cofiring tests. For 100% coal firing, the carbon conversion efficiency (CCE) obtained this quarter did not exceed the 95-96% barrier previously reached. NO{sub x} emissions on coal only ranged from {approx} 0.42 to {approx} 0.78 Lbs/MBtu. The burner has not been optimized for low NO{sub x} yet, however, due to the short furnace residence time, meeting the goals of 98% CCE and <0.6 Lbs/MBtu NO{sub x} simultaneously will be difficult. Testing on 100% natural gas in the boiler after coal firing indicated no changes in efficiency due to firing in a `dirty` boiler. The co-firing tests showed that increased levels of natural gas firing proportionately decreased NO{sub x}, SO{sub 2}, and CO.

  10. Direct detection of RNA in vitro and in situ by target-primed RCA: The impact of E. coli RNase III on the detection efficiency of RNA sequences distanced far from the 3′-end

    PubMed Central

    Merkiene, Egle; Gaidamaviciute, Edita; Riauba, Laurynas; Janulaitis, Arvydas; Lagunavicius, Arunas

    2010-01-01

    We improved the target RNA-primed RCA technique for direct detection and analysis of RNA in vitro and in situ. Previously we showed that the 3′ → 5′ single-stranded RNA exonucleolytic activity of Phi29 DNA polymerase converts the target RNA into a primer and uses it for RCA initiation. However, in some cases, the single-stranded RNA exoribonucleolytic activity of the polymerase is hindered by strong double-stranded structures at the 3′-end of target RNAs. We demonstrate that in such hampered cases, the double-stranded RNA-specific Escherichia coli RNase III efficiently assists Phi29 DNA polymerase in converting the target RNA into a primer. These observations extend the target RNA-primed RCA possibilities to test RNA sequences distanced far from the 3′-end and customize this technique for the inner RNA sequence analysis. PMID:20584897

  11. EVA thin film with thermo- and moisture-stable luminescent copolymer beads composed of Eu(III) complexes for improvement of energy conversion efficiency on silicon solar cell

    NASA Astrophysics Data System (ADS)

    Kataoka, Hisataka; Omagari, Shun; Nakanishi, Takayuki; Hasegawa, Yasuchika

    2015-04-01

    Luminescent beads composed of Eu(hfa)3(TPPO)2 (hfa: hexafluoroacetylacetonate, TPPO: triphenylphosphine oxide) in PMMA copolymer (polymethylmethacrylate- styrene and polymethylmethacrylate-trifluoromethylmethacrylate copolymers), PMMA-St-Eu and PMMA-TF-Eu have been reported for improvement of energy conversion efficiency on silicon solar cell. The PMMA-St-Eu and PMMA-TF-Eu beads are prepared using radical initiator AIBN (2,2-azobisisobutyronitrile) without BPO (Benzoyl peroxide) which promotes decomposition of Eu(hfa)3(TPPO)2. The emission properties of EVA (ethylene vinyl acetate) film with PMMA-St-Eu or PMMA-TF-Eu beads are characterized by the emission spectra and lifetimes. Thermo- and moisture-stabilities of the EVA films are performed under high temperature and high moisture condition (85°C85%RH). Increase percentage the solar cell short circuit current efficiency in the solar cell modulation using with EVA film containing PMMA-St-Eu beads with size in 70 μm was estimated to 1.2%. Thermo- and moisture-stable PMMA-St-Eu and PMMA-TF-Eu beads for solar sealing film are demonstrated for the first time.

  12. Development of advanced drilling, completion, and stimulation systems for minimum formation damage and improved efficiency: A program overview

    SciTech Connect

    Layne, A.W.; Yost, A.B. II

    1994-12-31

    The Department of Energy`s (DOE) Natural Gas Resource and Extraction Program consists of industry/government co-sponsored research, development, and demonstration (RD and D) projects, which focus on gas recovery from both conventional and nonconventional resources. The current focus of the Project is on the development of underbalanced drilling technology and minimum formation damage stimulation technology concurrently with the appropriate completion hardware to improve the economics of domestic natural gas field development. Ongoing drilling technology projects to be discussed include development of an electromagnetic measurement while drilling system for directional and horizontal drilling in underbalanced drilling applications and the development of a steerable air percussion drilling system for hard formation drilling and improved penetration rates. Ongoing stimulation technology projects to be discussed include introduction of carbon dioxide/sand fracturing technology for minimal formation damage.

  13. X-ray sources in regions of star formation. III - Naked T Tauri stars associated with the Taurus-Auriga complex

    NASA Technical Reports Server (NTRS)

    Walter, Frederick M.; Brown, A.; Mathieu, R. D.; Myers, P. C.; Vrba, F. J.

    1988-01-01

    Ground-based and IRAS optical and IR spectroscopic and photometric observations are reported for 90 stars in or near 59 Einstein Observatory X-ray error circles in the Tau-Aur region. The data are presented in extensive tables and sample spectra and characterized in detail, with particular attention to 28 newly discovered 'naked' T Tau stars, which are shown to be normal stars with no significant IR or UV excess and ages of 1-40 Myr. These stars are found to outnumber normal T Tau stars by a factor of 10 in an area near the Tau-Aur dark clouds, and it is argued that their evolution toward the ZAMS is typical for low-mass stars. The implications of this finding for the time scales of circumstellar-disk dissipation and planet formation are discussed.

  14. Geomechanical variability within the D-E Member of the lower Tuscaloosa Formation supporting the SECARB Phase III CO2 Injection Program

    NASA Astrophysics Data System (ADS)

    Rinehart, A. J.; Dewers, T. A.; Broome, S.; Newell, P.

    2014-12-01

    We characterize the mechanical properties at near in-situ conditions of Lower Tuscaloosa lithologies at the Cranfield-site Southeast Regional Carbon Sequestration Partnership (SECARB) Phase III injection program. Four lithofacies in the injection horizon are chosen for strength testing, including: chlorite-cemented conglomeratic sandstone (CSS); mixed chlorite- and quartz-cemented cross-bedded fine sandstone (XSS); quartz-cemented tabular very fine sandstone (TSS); and quartz-cemented siltstone (SiS). Each lithofacies had 25-mm diameter by at least 50-mm length samples plugged. We performed a suite of compression tests for the sandstone at 100°C and pore pressure of 30 MPa, including near-zero effective confining pressure triaxial test, axisymmetric compression tests, and hydrostatic compression test. Sandstones were saturated with supercritical CO2-equilibrated brine with 30 MPa pore pressure. SiS samples were equilibrated at a constant relative humidity of 77% at 100°C. TSS had the largest yield and failure envelopes. XSS had slightly smaller yield and failure envelopes. CSS was by far the weakest. The sandy facies' effective unconfined tests showed rounded peaks, indicating viscous deformation during damage. SiS had strengths intermediate to TSS and XSS, and CSS. The chemical environment mechanically changed CSS, with cement type exerting control on strength. Constitutive behavior is modeled with elasto-plastic and viscous models. Essential features describing mechanical behavior include non-associative plasticity, stress-invariant dependent failure, elliptical cap surface, kinematic and isotropic hardening, non linear elasticity and elastic-plastic coupling. We discuss the influence of CO2 injection on geomechanical properties. This material is based upon work supported as part of the Center for Frontiers of Subsurface Energy Security, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy

  15. Hubble Tarantula Treasury Project. III. Photometric Catalog and Resulting Constraints on the Progression of Star Formation in the 30 Doradus Region

    NASA Astrophysics Data System (ADS)

    Sabbi, E.; Lennon, D. J.; Anderson, J.; Cignoni, M.; van der Marel, R. P.; Zaritsky, D.; De Marchi, G.; Panagia, N.; Gouliermis, D. A.; Grebel, E. K.; Gallagher, J. S., III; Smith, L. J.; Sana, H.; Aloisi, A.; Tosi, M.; Evans, C. J.; Arab, H.; Boyer, M.; de Mink, S. E.; Gordon, K.; Koekemoer, A. M.; Larsen, S. S.; Ryon, J. E.; Zeidler, P.

    2016-01-01

    We present and describe the astro-photometric catalog of more than 800,000 sources found in the Hubble Tarantula Treasury Project (HTTP). HTTP is a Hubble Space Telescope Treasury program designed to image the entire 30 Doradus region down to the sub-solar (˜0.5 M⊙) mass regime using the Wide Field Camera 3 and the Advanced Camera for Surveys. We observed 30 Doradus in the near-ultraviolet (F275W, F336W), optical (F555W, F658N, F775W), and near-infrared (F110W, F160W) wavelengths. The stellar photometry was measured using point-spread function fitting across all bands simultaneously. The relative astrometric accuracy of the catalog is 0.4 mas. The astro-photometric catalog, results from artificial star experiments, and the mosaics for all the filters are available for download. Color-magnitude diagrams are presented showing the spatial distributions and ages of stars within 30 Dor as well as in the surrounding fields. HTTP provides the first rich and statistically significant sample of intermediate- and low-mass pre-main sequence candidates and allows us to trace how star formation has been developing through the region. The depth and high spatial resolution of our analysis highlight the dual role of stellar feedback in quenching and triggering star formation on the giant H ii region scale. Our results are consistent with stellar sub-clustering in a partially filled gaseous nebula that is offset toward our side of the Large Magellanic Cloud. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA Inc., under NASA contract NAS 5-26555.

  16. Sr2+/Ca2+ and 44Ca/40Ca fractionation during inorganic calcite formation: III. Impact of salinity/ionic strength

    PubMed Central

    Tang, Jianwu; Niedermayr, Andrea; Köhler, Stephan J.; Böhm, Florian; Kısakürek, Basak; Eisenhauer, Anton; Dietzel, Martin

    2012-01-01

    In order to apply Sr/Ca and 44Ca/40Ca fractionation during calcium carbonate (CaCO3) formation as a proxy to reconstruct paleo-environments, it is essential to evaluate the impact of various environmental factors. In this study, a CO2 diffusion technique was used to crystallize inorganic calcite from aqueous solutions at different ionic strength/salinity by the addition of NaCl at 25 °C. Results show that the discrimination of Sr2+ versus Ca2+ during calcite formation is mainly controlled by precipitation rate (R in μmol/m2/h) and is weakly influenced by ionic strength/salinity. In analogy to Sr incorporation, 44Ca/40Ca fractionation during precipitation of calcite is weakly influenced by ionic strength/salinity too. At 25 °C the calcium isotope fractionation between calcite and aqueous calcium ions (Δ44/40Cacalcite-aq = δ44/40Cacalcite − δ44/40Caaq) correlates inversely to log R values for all experiments. In addition, an inverse relationship between Δ44/40Cacalcite-aq and log DSr, which is independent of temperature, precipitation rate, and aqueous (Sr/Ca)aq ratio, is not affected by ionic strength/salinity either. Considering the log DSr and Δ44/40Cacalcite-aq relationship, Sr/Ca and δ44/40Cacalcite values of precipitated calcite can be used as an excellent multi-proxy approach to reconstruct environmental conditions (e.g., temperature, precipitation rate) of calcite growth and diagenetic alteration. PMID:22347722

  17. Small molecular glasses based on multiposition encapsulated phenyl benzimidazole iridium(III) complexes: toward efficient solution-processable host-free electrophosphorescent diodes.

    PubMed

    Xu, Hui; Yu, Dong-Hui; Liu, Le-Le; Yan, Peng-Fei; Jia, Li-Wei; Li, Guang-Ming; Yue, Zheng-Yu

    2010-01-14

    Three electrophosphorescent small molecular Ir(3+) complexes, Ir(HexPhBI)(3) 1 (HexPhBI = 1-Hexyl-2-phenyl-1H-benzo[d]imidazole), Ir(CzPhBI)(3) 2 (CzPhBI = 9-(6-(2-phenyl-1H-benzo[d]imidazol-1-yl)hexyl)-9H-carbazole), and Ir(Cz(2)PhBI)(3) 3 (Cz(2)PhBI = 9-(6-(4-(1-(6-(9H-carbazol-9-yl)hexyl)-1H-benzo[d]imidazol-2-yl)phenoxy)hexyl)-9H-carbazole), were synthesized in which 3 was designed with the structure of multiposition encapsulation. Compared to the hexyl-substituted 1, 2 and 3 end-capped with the conjugated carbazole moieties have improved thermal stability. X-ray diffraction analysis proved the amorphous state of 2 and 3. High-photoluminescent efficiencies of 3 are achieved as 72% in solution and 61% in solid. It indicates that the peripheral carbazoles not only facilitate the separation of triplet-emission cores and reduce the intermolecular aggregation but also supply a routine for the intermolecular energy transfer. Electrochemical analysis showed the more oxidation states of 3, which might be anticipated to make it superior to 1 and 2 in hole injection and transporting. The important role of the peripheral carbazole moieties in carrier injection/transporting and the optical properties of the complexes were further investigated by Gaussian simulation. A dramatic electroluminescent (EL) performance, including external quantum efficiency of nearly 6%, low turn-on voltage of 2.5 V, and high brightness over 6000 cd m(-2), from the host-free spin-coated device of 3 was achieved. The superiority of multiencapsulation in EL was proved by comparing the EL performance of 2 and 3. By making comparison between the host-free and phosphor-doping devices, it indicated that the combined modification of the aliphatic chains and functional groups in multipositions is a feasible approach to realize the high-efficiency small molecular phosphorescent materials. PMID:19954149

  18. THE ACS NEARBY GALAXY SURVEY TREASURY. X. QUANTIFYING THE STAR CLUSTER FORMATION EFFICIENCY OF NEARBY DWARF GALAXIES

    SciTech Connect

    Cook, David O.; Dale, Daniel A.; Seth, Anil C.; Johnson, L. Clifton; Weisz, Daniel R.; Fouesneau, Morgan; Dalcanton, Julianne J.; Olsen, Knut A. G.; Engelbracht, Charles W.

    2012-06-01

    We study the relationship between the field star formation and cluster formation properties in a large sample of nearby dwarf galaxies. We use optical data from the Hubble Space Telescope and from ground-based telescopes to derive the ages and masses of the young (t{sub age} {approx}< 100 Myr) cluster sample. Our data provide the first constraints on two proposed relationships between the star formation rate (SFR) of galaxies and the properties of their cluster systems in the low SFR regime. The data show broad agreement with these relationships, but significant galaxy-to-galaxy scatter exists. In part, this scatter can be accounted for by simulating the small number of clusters detected from stochastically sampling the cluster mass function. However, this stochasticity does not fully account for the observed scatter in our data, suggesting that there may be true variations in the fraction of stars formed in clusters in dwarf galaxies. Comparison of the cluster formation and the brightest cluster in our sample galaxies also provide constraints on cluster destruction models.

  19. Oxidative damage-induced PCNA complex formation is efficient in xeroderma pigmentosum group A but reduced in Cockayne syndrome group B cells.

    PubMed

    Balajee, A S; Dianova, I; Bohr, V A

    1999-11-15

    Proliferating cell nuclear antigen (PCNA), a processivity factor for DNA polymerases delta and epsilon, is essential for both DNA replication and repair. PCNA is required in the resynthesis step of nucleotide excision repair (NER). After UV irradiation, PCNA translocates into an insoluble protein complex, most likely associated with the nuclear matrix. It has not previously been investigated in vivo whether PCNA complex formation also takes place after oxidative stress. In this study, we have examined the involvement of PCNA in the repair of oxidative DNA damage. PCNA complex formation was studied in normal human cells after treatment with hydrogen peroxide, which generates a variety of oxidative DNA lesions. PCNA was detected by two assays, immunofluorescence and western blot analyses. We observed that PCNA redistributes from a soluble to a DNA-bound form during the repair of oxidative DNA damage. PCNA complex formation was analyzed in two human natural mutant cell lines defective in DNA repair: xeroderma pigmentosum group A (XP-A) and Cockayne syndrome group B (CS-B). XP-A cells are defective in overall genome NER while CS-B cells are defective only in the preferential repair of active genes. Immunofluorescent detection of PCNA complex formation was similar in normal and XP-A cells, but was reduced in CS-B cells. Consistent with this observation, western blot analysis in CS-B cells showed a reduction in the ratio of PCNA relocated as compared to normal and XP-A cells. The efficient PCNA complex formation observed in XP-A cells following oxidative damage suggests that formation of PCNA-dependent repair foci may not require the XPA gene product. The reduced PCNA complex formation observed in CS-B cells suggests that these cells are defective in the processing of oxidative DNA damage. PMID:10536158

  20. STUDIES CONCERNING THE SITE OF RENIN FORMATION IN THE KIDNEY : III. THE APPARENT SITE OF RENIN FORMATION IN THE TUBULES OF THE MESONEPHROS AND METANEPHROS OF THE HOG FETUS.

    PubMed

    Kaplan, A; Friedman, M

    1942-09-01

    1. Renin was found in both the mesonephric and metanephric kidneys of the smallest hog fetuses examined. These were from 17 to 24 mm. in length in the case of the former, and 25 to 49 mm. in that of the latter. 2. No evidence was found in either type of kidney of juxtaglomerular cells described by Goormaghtigh as the probable site of renin formation. 3. The renin content in both the mesonephros and the metanephros was found to be independent of its arteriologlomerular component but directly dependent upon the number, size, and functional state of the tubular component. It increased in amount with increasing tubular proliferation during the course of embryonic development, and decreased with the progressive tubular atrophy and degeneration incident thereto. 4. The site of renin formation is discussed.

  1. The Star Formation Rate Efficiency of Neutral Atomic-dominated Hydrogen Gas in the Outskirts of Star-forming Galaxies from z ~ 1 to z ~3

    NASA Astrophysics Data System (ADS)

    Rafelski, Marc; Gardner, Jonathan P.; Fumagalli, Michele; Neeleman, Marcel; Teplitz, Harry I.; Grogin, Norman; Koekemoer, Anton M.; Scarlata, Claudia

    2016-07-01

    Current observational evidence suggests that the star formation rate (SFR) efficiency of neutral atomic hydrogen gas measured in damped Lyα systems (DLAs) at z˜ 3 is more than 10 times lower than predicted by the Kennicutt-Schmidt (KS) relation. To understand the origin of this deficit, and to investigate possible evolution with redshift and galaxy properties, we measure the SFR efficiency of atomic gas at z ˜ 1, z ˜ 2, and z˜ 3 around star-forming galaxies. We use new robust photometric redshifts in the Hubble Ultra Deep Field to create galaxy stacks in these three redshift bins, and measure the SFR efficiency by combining DLA absorber statistics with the observed rest-frame UV emission in the galaxies’ outskirts. We find that the SFR efficiency of H i gas at z\\gt 1 is ˜1%-3% of that predicted by the KS relation. Contrary to simulations and models that predict a reduced SFR efficiency with decreasing metallicity and thus with increasing redshift, we find no significant evolution in the SFR efficiency with redshift. Our analysis instead suggests that the reduced SFR efficiency is driven by the low molecular content of this atomic-dominated phase, with metallicity playing a secondary effect in regulating the conversion between atomic and molecular gas. This interpretation is supported by the similarity between the observed SFR efficiency and that observed in local atomic-dominated gas, such as in the outskirts of local spiral galaxies and local dwarf galaxies.

  2. Antisites in III-V semiconductors: Density functional theory calculations

    NASA Astrophysics Data System (ADS)

    Chroneos, A.; Tahini, H. A.; Schwingenschlögl, U.; Grimes, R. W.

    2014-07-01

    Density functional based simulation, corrected for finite size effects, is used to investigate systematically the formation of antisite defects in III-V semiconductors (III = Al, Ga, and In and V = P, As, and Sb). Different charge states are modelled as a function of the Fermi level and under different growth conditions. The formation energies of group III antisites ( III V q) decrease with increasing covalent radius of the group V atom though not group III radius, whereas group V antisites ( V I I I q) show a consistent decrease in formation energies with increase in group III and group V covalent radii. In general, III V q defects dominate under III-rich conditions and V I I I q under V-rich conditions. Comparison with equivalent vacancy formation energy simulations shows that while antisite concentrations are always dominant under stoichiometric conditions, modest variation in growth or doping conditions can lead to a significantly higher concentration of vacancies.

  3. STELLAR KINEMATICS AND STRUCTURAL PROPERTIES OF VIRGO CLUSTER DWARF EARLY-TYPE GALAXIES FROM THE SMAKCED PROJECT. III. ANGULAR MOMENTUM AND CONSTRAINTS ON FORMATION SCENARIOS

    SciTech Connect

    Toloba, E.; Guhathakurta, P.; Peletier, R. F.; Emsellem, E.; Lisker, T.; Van de Ven, G.; Simon, J. D.; Adams, J. J.; Benson, A. J.; Falcón-Barroso, J.; Ryś, A.; Gorgas, J.; Hensler, G.; Janz, J.; Laurikainen, E.; Salo, H.; Paudel, S.

    2015-02-01

    We analyze the stellar kinematics of 39 dwarf early-type galaxies (dEs) in the Virgo Cluster. Based on the specific stellar angular momentum λ{sub Re} and the ellipticity, we find 11 slow rotators and 28 fast rotators. The fast rotators in the outer parts of the Virgo Cluster rotate significantly faster than fast rotators in the inner parts of the cluster. Moreover, 10 out of the 11 slow rotators are located in the inner 3° (D < 1 Mpc) of the cluster. The fast rotators contain subtle disk-like structures that are visible in high-pass filtered optical images, while the slow rotators do not exhibit these structures. In addition, two of the dEs have kinematically decoupled cores and four more have emission partially filling in the Balmer absorption lines. These properties suggest that Virgo Cluster dEs may have originated from late-type star-forming galaxies that were transformed by the environment after their infall into the cluster. The correlation between λ{sub Re} and the clustercentric distance can be explained by a scenario where low luminosity star-forming galaxies fall into the cluster, their gas is rapidly removed by ram-pressure stripping, although some of it can be retained in their core, their star formation is quenched but their stellar kinematics are preserved. After a long time in the cluster and several passes through its center, the galaxies are heated up and transformed into slow rotating dEs.

  4. Formation of the Integral Ecological Quality Index of the Technological Processes in Machine Building Based on Their Energy Efficiency

    ERIC Educational Resources Information Center

    Egorov, Sergey B.; Kapitanov, Alexey V.; Mitrofanov, Vladimir G.; Shvartsburg, Leonid E.; Ivanova, Natalia A.; Ryabov, Sergey A.

    2016-01-01

    The aim of article is to provide development of a unified assessment methodology in relation to various technological processes and the actual conditions of their implementation. To carry the energy efficiency analysis of the technological processes through comparison of the established power and the power consumed by the actual technological…

  5. Megacity pollution by modern Diesel cars: New insights into the nature and formation of volatile nano-particles with high lung intrusion efficiency

    NASA Astrophysics Data System (ADS)

    Arnold, F.; Reichl, U.; Muschik, Ch.; Roiger, A.; Schlager, H.; Pirjola, L.; Rönkkö, T.; Keskinen, J.; Rothe, D.; Lähde, T.

    2009-04-01

    Aerosol particles generated by Diesel vehicles represent mayor health affecting air pollutants in cities and near motor ways. To mitigate the Diesel particle pollution problem, Diesel vehicles become increasingly fitted or retro-fitted with modern exhaust after treatment systems (ATS), which remove most engine-generated primary particles, particularly soot. Unfortunately however, ATS have undesired side effects including also the formation of low vapour pressure gases, which may undergo nucleation and condensation leading to volatile nucleation particles (NUP). NUP are substantially smaller (diameters: 5-15 nm) than soot particles (diameters: 40-100 nm), and therefore may be termed real nano-particles. NUP can intrude with maximum efficiency the lowest, least protected, and most vulnerable compartment of the human lung. However, the chemical nature and mechanism of formation of NUP are only poorly explored. Using a novel mass spectrometric method, we have made the first on line and off line measurements of low vapour pressure NUP precursor gases in the exhaust of a modern heavy duty Diesel vehicle engine, operated with and without ATS and combusting low and ultra-low sulphur fuels including also bio fuel. In addition, we have made accompanying NUP measurements and NUP model simulations. The on line measurements involved a CIMS (Chemical Ionization Mass Spectrometry) method originally developed by MPIK. They took place directly in the Diesel exhaust and had a large sensitivity and a fast time response (1 s). The off line measurements involved adsorption of exhaust gases on stainless steel, followed by thermo desorption and detection of desorbed exhaust molecules by CIMS. We find that modern Diesel ATS strongly increase the formation of hydroxyl radicals, which induce conversion of fuel sulphur to the important NUP precursor gaseous sulphuric acid. We also find that appreciable amounts of di-carboxylic acids survive the passage of the ATS or are even formed by the

  6. Kinematics of Metal-poor Stars in the Galaxy. III. Formation of the Stellar Halo and Thick Disk as Revealed from a Large Sample of Nonkinematically Selected Stars

    NASA Astrophysics Data System (ADS)

    Chiba, Masashi; Beers, Timothy C.

    2000-06-01

    We present a detailed analysis of the space motions of 1203 solar-neighborhood stars with metal abundances [Fe/H]<=-0.6, on the basis of a catalog, of metal-poor stars selected without kinematic bias recently revised and supplemented by Beers et al. This sample, having available proper motions, radial velocities, and distance estimates for stars with a wide range of metal abundances, is by far the largest such catalog to be assembled to date. We show that the stars in our sample with [Fe/H]<=-2.2, which likely represent a ``pure'' halo component, are characterized by a radially elongated velocity ellipsoid (σU,σV,σW)=(141+/-11, 106+/-9, 94+/-8) km s-1 and small prograde rotation =30 to 50 km s-1, consistent with previous analysis of this sample by Beers and Sommer-Larsen based on radial velocity information alone. In contrast to the previous analysis, we find a decrease in with increasing distance from the Galactic plane for stars that are likely to be members of the halo population (Δ/Δ|Z|=-52+/-6 km s-1 kpc-1), which may represent the signature of a dissipatively formed flattened inner halo. Unlike essentially all previous kinematically selected catalogs, the metal-poor stars in our sample exhibit a diverse distribution of orbital eccentricities, e, with no apparent correlation between [Fe/H] and e. This demonstrates, clearly and convincingly, that the evidence offered in 1962 by Eggen, Lynden-Bell, & Sandage for a rapid collapse of the Galaxy, an apparent correlation between the orbital eccentricity of halo stars with metallicity, is basically the result of their proper-motion selection bias. However, even in our nonkinematically selected sample, we have identified a small concentration of high-e stars at [Fe/H]~-1.7, which may originate, in part, from infalling gas during the early formation of the Galaxy. We find no evidence for an additional thick disk component for stellar abundances [Fe/H]<=-2.2. The kinematics of the intermediate

  7. UV-based advanced oxidation processes for the treatment of odour compounds: efficiency and by-product formation.

    PubMed

    Zoschke, Kristin; Dietrich, Norman; Börnick, Hilmar; Worch, Eckhard

    2012-10-15

    The occurrence of the taste and odour compounds geosmin and 2-methyl isoborneol (2-MIB) affects the organoleptic quality of raw waters from drinking water reservoirs worldwide. UV-based oxidation processes for the removal of these substances are an alternative to adsorption and biological processes, since they additionally provide disinfection of the raw water. We could show that the concentration of geosmin and 2-MIB could be reduced by VUV irradiation and the combination of UV irradiation with ozone and hydrogen peroxide in pure water and water from a drinking water reservoir. The figure of merit EE/O is an appropriate tool to compare the AOPs and showed that VUV and UV/O(3) yielded the lowest treatment costs for the odour compounds in pure and raw water, respectively. Additionally, VUV irradiation with addition of ozone, generated by the VUV lamp, was evaluated. The generation of ozone and the irradiation were performed in a single reactor system using the same low-pressure mercury lamp, thereby reducing the energy consumption of the treatment process. The formation of the undesired by-products nitrite and bromate was investigated. The combination of VUV irradiation with ozone produced by a VUV lamp avoided the formation of relevant concentrations of the by-products. The internal generation of ozone is capable to produce ozone concentrations sufficient to reduce EE/O below 1 kWh m(-3) and without the risk of the formation of nitrite or bromate above the maximum contaminant level.

  8. A comparative study of nitrite reduction by synthetic and biogenic Fe(II-III) hydroxysalts green rusts: Evidence for hydroxyl-nitrite green rust formation as an intermediate reaction product.

    NASA Astrophysics Data System (ADS)

    Ona-Nguema, G.; Guerbois, D.; Morin, G.; Zhang, Y.; Noel, V.; Brest, J.

    2013-12-01

    The occurrence of high nitrite concentrations as a result of anthropogenic activities is an important water quality concern as it is highly toxic to human and fauna, and it is used as a nitrogen source for the assimilation process. The toxicity of nitrite is related to its transformation into carcinogenic N-nitroso compounds, which are suspected to be responsible for some gastric cancers, and to its ability to convert the hemoglobin to methaemoglobin what is then unable to fix oxygen and to transport it to the tissues, involving hypoxia and the blue-baby syndrome [1]. To reduce the adverse effect of nitrite on human health and on macroalgal blooms, any process enhancing the transformation of nitrite ions to nitrogen gas is of interest for the remediation of natural environments. To achieve this purpose the use of processes involving Fe(II)-containing minerals could be considered as one of the best options. Green-rusts are mixed Fe(II-III) layered double hydroxides commonly found in anoxic zones of natural environments such as sediments and hydromorphic soils. In such anoxic environments, green rust minerals play an important role in the biogeochemical redox cycling of iron and nitrogen, and can affect the speciation and mobility of many organic and inorganic contaminants. The present study investigates the reduction of nitrite by two synthetic and two biogenic green rusts. On the one hand, Fe(II-III) hydroxychloride and Fe(II-III) hydroxycarbonate green rusts were used as synthetic interlayer forms of GR, which are referred to as ';syn-GR(CO3)' and ';syn-GR(Cl)', respectively. On the other hand, the study was performed with biogenic Fe(II-III) hydroxycarbonate green rusts obtained from the bioreduction of two ferric precursors, either Fe(III)-oxyhydroxycarbonate or lepidocrocite; these biogenic green rusts are referred to as ';bio-GR(CO3)F' and ';bio-GR(CO3)L', respectively. For synthetic green rusts, results showed that the oxidation of both syn-GR(CO3) and syn

  9. Hot ammonia around young O-type stars. III. High-mass star formation and hot core activity in W51 Main

    NASA Astrophysics Data System (ADS)

    Goddi, C.; Ginsburg, A.; Zhang, Q.

    2016-05-01

    Context. This paper is the third in a series of NH3 multilevel imaging studies in well-known, high-mass star-forming regions. The main goal is to characterize kinematics and physical conditions of (hot and dense) circumstellar molecular gas around O-type young stars. Aims: We want to map at subarcsecond resolution highly excited inversion lines of NH3 in the high-mass star-forming region W51 Main (distance = 5.4 kpc), which is an ideal target to constrain theoretical models of high-mass star formation. Methods: Using the Karl Jansky Very Large Array (JVLA), we mapped the hot and dense molecular gas in W51 Main with ~0.2 arcsec-0.3 arcsec angular resolution in five metastable (J = K) inversion transitions of ammonia (NH3): (J,K) = (6, 6), (7, 7), (9, 9), (10, 10), and (13, 13). These lines arise from energy levels between ~400 K and ~1700 K above the ground state. We also made maps of the (free-free) continuum emission at frequencies between 25 and 36 GHz. Results: We have identified and characterized two main centers of high-mass star formation in W51 Main, which excite hot cores and host one or multiple high-mass young stellar objects (YSOs) at their centers: the W51e2 complex and the W51e8 core (~6'' southward of W51e2). The former breaks down into three further subcores: W51e2-W, which surrounds the well-known hypercompact (HC) HII region, where hot NH3 is observed in absorption, and two additional dusty cores, W51e2-E (~0.8 arcsec to the East) and W51e2-NW (~1'' to the North), where hot NH3 is observed in emission. The velocity maps toward the HC HII region show a clear velocity gradient along the east-west in all lines. The gradient may indicate rotation, although any Keplerian motion must be on smaller scales (<1000 AU) as we do not directly observe a Keplerian velocity profile. The absence of outflow and/or maser activity and the low amount of molecular gas available for accretion (~5 M⊙, assuming [NH3]/[H2] = 10-7) with respect to the mass of the central

  10. Improved Agrobacterium-mediated transformation and high efficiency of root formation from hypocotyl meristem of spring Brassica napus 'Precocity' cultivar.

    PubMed

    Liu, X X; Lang, S R; Su, L Q; Liu, X; Wang, X F

    2015-01-01

    Rape seed (Brassica napus L.) is one of the most important oil seed crops in the world. Genetic manipulation of rapeseed requires a suitable tissue culture system and an efficient method for plant regeneration, as well as an efficient transformation procedure. However, development of transgenic B. napus has been problematic, and current studies are limited to cultivated varieties. In this study, we report a protocol for regeneration of transgenic rape after Agrobacterium-mediated transformation of hypocotyls from the spring B. napus 'Precocity' cultivar. We analyzed the effects of plant growth regulators in the medium on regeneration. Additionally, factors affecting the transformation efficiency, including seedling age, Agrobacterium concentration, infection time, and co-cultivation time, were assessed by monitoring GUS expression. Results from these experiments revealed that transformation was optimized when the meristematic parts of the hypocotyls were taken from 8 day-old seedlings, cultured on Murashinge and Skoog basal media containing 0.1 mg/L 1-naphthaleneacetic acid and 2.5 mg/L 6-benzylaminopurine, and incubated in Agrobacterium suspension (OD600 = 0.5) for 3 to 5 min, followed by 2 days of co-cultivation. Integration of T-DNA into the plant genome was confirmed by polymerase chain reaction (PCR), b-glucuronidase histochemical staining, and quantitative real-time PCR. The protocols developed for regeneration, transformation, and rooting described in this study could help to accelerate the development of transgenic spring rape varieties with novel features. PMID:26681030

  11. Improved Agrobacterium-mediated transformation and high efficiency of root formation from hypocotyl meristem of spring Brassica napus 'Precocity' cultivar.

    PubMed

    Liu, X X; Lang, S R; Su, L Q; Liu, X; Wang, X F

    2015-12-14

    Rape seed (Brassica napus L.) is one of the most important oil seed crops in the world. Genetic manipulation of rapeseed requires a suitable tissue culture system and an efficient method for plant regeneration, as well as an efficient transformation procedure. However, development of transgenic B. napus has been problematic, and current studies are limited to cultivated varieties. In this study, we report a protocol for regeneration of transgenic rape after Agrobacterium-mediated transformation of hypocotyls from the spring B. napus 'Precocity' cultivar. We analyzed the effects of plant growth regulators in the medium on regeneration. Additionally, factors affecting the transformation efficiency, including seedling age, Agrobacterium concentration, infection time, and co-cultivation time, were assessed by monitoring GUS expression. Results from these experiments revealed that transformation was optimized when the meristematic parts of the hypocotyls were taken from 8 day-old seedlings, cultured on Murashinge and Skoog basal media containing 0.1 mg/L 1-naphthaleneacetic acid and 2.5 mg/L 6-benzylaminopurine, and incubated in Agrobacterium suspension (OD600 = 0.5) for 3 to 5 min, followed by 2 days of co-cultivation. Integration of T-DNA into the plant genome was confirmed by polymerase chain reaction (PCR), b-glucuronidase histochemical staining, and quantitative real-time PCR. The protocols developed for regeneration, transformation, and rooting described in this study could help to accelerate the development of transgenic spring rape varieties with novel features.

  12. Revisiting the First Galaxies: The Effects of Population III Stars on their Host Galaxies

    NASA Astrophysics Data System (ADS)

    Muratov, Alexander L.; Gnedin, Oleg Y.; Gnedin, Nickolay Y.; Zemp, Marcel

    2013-08-01

    We revisit the formation and evolution of the first galaxies using new hydrodynamic cosmological simulations with the adaptive refinement tree code. Our simulations feature a recently developed model for H2 formation and dissociation, and a star formation recipe that is based on molecular rather than atomic gas. Here, we develop and implement a recipe for the formation of metal-free Population III (Pop III) stars in galaxy-scale simulations that resolve primordial clouds with sufficiently high density. We base our recipe on the results of prior zoom-in simulations that resolved the protostellar collapse in pre-galactic objects. We find the epoch during which Pop III stars dominated the energy and metal budget of the first galaxies to be short-lived. Galaxies that host Pop III stars do not retain dynamical signatures of their thermal and radiative feedback for more than 108 years after the lives of the stars end in pair-instability supernovae, even when we consider the maximum reasonable efficiency of the feedback. Though metals ejected by the supernovae can travel well beyond the virial radius of the host galaxy, they typically begin to fall back quickly, and do not enrich a large fraction of the intergalactic medium. Galaxies with a total mass in excess of 3 × 106 M ⊙ re-accrete most of their baryons and transition to metal-enriched Pop II star formation.

  13. REVISITING THE FIRST GALAXIES: THE EFFECTS OF POPULATION III STARS ON THEIR HOST GALAXIES

    SciTech Connect

    Muratov, Alexander L.; Gnedin, Oleg Y.; Zemp, Marcel; Gnedin, Nickolay Y.

    2013-08-01

    We revisit the formation and evolution of the first galaxies using new hydrodynamic cosmological simulations with the adaptive refinement tree code. Our simulations feature a recently developed model for H{sub 2} formation and dissociation, and a star formation recipe that is based on molecular rather than atomic gas. Here, we develop and implement a recipe for the formation of metal-free Population III (Pop III) stars in galaxy-scale simulations that resolve primordial clouds with sufficiently high density. We base our recipe on the results of prior zoom-in simulations that resolved the protostellar collapse in pre-galactic objects. We find the epoch during which Pop III stars dominated the energy and metal budget of the first galaxies to be short-lived. Galaxies that host Pop III stars do not retain dynamical signatures of their thermal and radiative feedback for more than 10{sup 8} years after the lives of the stars end in pair-instability supernovae, even when we consider the maximum reasonable efficiency of the feedback. Though metals ejected by the supernovae can travel well beyond the virial radius of the host galaxy, they typically begin to fall back quickly, and do not enrich a large fraction of the intergalactic medium. Galaxies with a total mass in excess of 3 Multiplication-Sign 10{sup 6} M{sub Sun} re-accrete most of their baryons and transition to metal-enriched Pop II star formation.

  14. Rh(III)-catalyzed selective coupling of N-methoxy-1H-indole-1-carboxamides and aryl boronic acids.

    PubMed

    Zheng, Jing; Zhang, Yan; Cui, Sunliang

    2014-07-01

    A Rh(III)-catalyzed selective coupling of N-methoxy-1H-indole-1-carboxamide and aryl boronic acids is reported. The coupling is mild and efficient toward diverse product formation, with selective C-C and C-C/C-N bond formation. Kinetic isotope effects studies were conducted to reveal a mechanism of C-H activation and electrophilic addition. PMID:24959967

  15. EFFECTS OF LASER RADIATION ON MATTER: Efficient surface-erosion plasma formation in air due to the action of pulse-periodic laser radiation

    NASA Astrophysics Data System (ADS)

    Min'ko, L. Ya; Chumakou, A. N.; Bosak, N. A.

    1990-11-01

    A study was made of the interaction of a series of periodic laser (λ = 1.06 μm) pulses with a number of materials (aluminum, copper, graphite, ebonite) in air at laser radiation power densities q = 107-109 W/cm2 and repetition frequencies f<=50 kHz. The radiation was concentrated in spots of ~ 10 - 2 cm2 area. Efficient formation of plasma as a result of laser erosion (q > 2 × 108 W/cm2, f>=5 kHz) was observed. A screening layer of an air plasma created by the first pulse of the series was expelled from the interaction zone and this was followed by erosion plasma formation under conditions of slight screening of the target during the action of the subsequent laser pulses.

  16. High SO{sub 2} removal efficiency testing: Results of DBA and sodium formate additive tests at Southwestern Electric Power company`s Pirkey Station

    SciTech Connect

    1996-05-30

    Tests were conducted at Southwestern Electric Power Company`s (SWEPCo) Henry W. Pirkey Station wet limestone flue gas desulfurization (FGD) system to evaluate options for achieving high sulfur dioxide removal efficiency. The Pirkey FGD system includes four absorber modules, each with dual slurry recirculation loops and with a perforated plate tray in the upper loop. The options tested involved the use of dibasic acid (DBA) or sodium formate as a performance additive. The effectiveness of other potential options was simulated with the Electric Power Research Institute`s (EPRI) FGD PRocess Integration and Simulation Model (FGDPRISM) after it was calibrated to the system. An economic analysis was done to determine the cost effectiveness of the high-efficiency options. Results are-summarized below.

  17. Defining Binding Efficiency and Specificity of Auxins for SCFTIR1/AFB-Aux/IAA Co-receptor Complex Formation

    PubMed Central

    2013-01-01

    Structure–activity profiles for the phytohormone auxin have been collected for over 70 years, and a number of synthetic auxins are used in agriculture. Auxin classification schemes and binding models followed from understanding auxin structures. However, all of the data came from whole plant bioassays, meaning the output was the integral of many different processes. The discovery of Transport Inhibitor-Response 1 (TIR1) and the Auxin F-Box (AFB) proteins as sites of auxin perception and the role of auxin as molecular glue in the assembly of co-receptor complexes has allowed the development of a definitive quantitative structure–activity relationship for TIR1 and AFB5. Factorial analysis of binding activities offered two uncorrelated factors associated with binding efficiency and binding selectivity. The six maximum-likelihood estimators of Efficiency are changes in the overlap matrixes, inferring that Efficiency is related to the volume of the electronic system. Using the subset of compounds that bound strongly, chemometric analyses based on quantum chemical calculations and similarity and self-similarity indices yielded three classes of Specificity that relate to differential binding. Specificity may not be defined by any one specific atom or position and is influenced by coulomb matrixes, suggesting that it is driven by electrostatic forces. These analyses give the first receptor-specific classification of auxins and indicate that AFB5 is the preferred site for a number of auxinic herbicides by allowing interactions with analogues having van der Waals surfaces larger than that of indole-3-acetic acid. The quality factors are also examined in terms of long-standing models for the mechanism of auxin binding. PMID:24313839

  18. Genetic analysis of bacteriophage lambda cIII gene: mRNA structural requirements for translation initiation.

    PubMed Central

    Kornitzer, D; Teff, D; Altuvia, S; Oppenheim, A B

    1989-01-01

    The bacteriophage lambda cIII gene product regulates the lysogenic pathway. The cIII gene is located in the leftward operon, which is transcribed from the pL promoter. We have previously shown (S. Altuvia and A. B. Oppenheim, J. Bacteriol. 167:415-419, 1986) that mutations that show elevated expression lie within the cIII coding sequence. We isolated mutants that show decreased CIII activity. All the mutations were found to cause a drastic reduction in the rate of initiation of cIII translation. Several mutations were found to be scattered within the first 40 nucleotides of the cIII coding region. Additional mutations affected the AUG initiation codon, the Shine-Dalgarno sequence, and the upstream RNaseIII processing site. Computer folding of the cIII mRNA suggested the presence of two alternative RNA structures. All the mutations within the coding region that reduce expression reduce the stability of one specific mRNA structure (structure B). Mutations that increase expression lie in the loops of this structure and may in fact stabilize it by interfering with the formation of the alternative structure (structure A). Thus, it appears that a specific mRNA secondary structure at the beginning of the cIII coding region is essential for efficient translation, suggesting that changes in mRNA structure regulate cIII expression. Images PMID:2523380

  19. Scandium(III)-zeolites as new heterogeneous catalysts for imino-Diels-Alder reactions.

    PubMed

    Olmos, Andrea; Louis, Benoit; Pale, Patrick

    2012-04-16

    This study demonstrates the first zeolite-catalyzed synthesis of piperidine derivatives, including peptidomimetics and indoloquinolizidine alkaloids. The approach developed utilizes a highly effective one-pot reaction cascade, through imine formation and imino-Diels-Alder reactions, promoted by scandium-loaded zeolites as a heterogeneous catalyst. The methodology described benefits from very low catalyst loadings (≤5 mol % of Sc(III) ), commercially and readily available starting materials, and mild reaction conditions. Furthermore, the Sc(III) -zeolite catalyst can be readily reused more than 10 times without any loss in efficiency.

  20. Ultrasmooth organic-inorganic perovskite thin-film formation and crystallization for efficient planar heterojunction solar cells.

    PubMed

    Zhang, Wei; Saliba, Michael; Moore, David T; Pathak, Sandeep K; Hörantner, Maximilian T; Stergiopoulos, Thomas; Stranks, Samuel D; Eperon, Giles E; Alexander-Webber, Jack A; Abate, Antonio; Sadhanala, Aditya; Yao, Shuhua; Chen, Yulin; Friend, Richard H; Estroff, Lara A; Wiesner, Ulrich; Snaith, Henry J

    2015-01-01

    To date, there have been a plethora of reports on different means to fabricate organic-inorganic metal halide perovskite thin films; however, the inorganic starting materials have been limited to halide-based anions. Here we study the role of the anions in the perovskite solution and their influence upon perovskite crystal growth, film formation and device performance. We find that by using a non-halide lead source (lead acetate) instead of lead chloride or iodide, the perovskite crystal growth is much faster, which allows us to obtain ultrasmooth and almost pinhole-free perovskite films by a simple one-step solution coating with only a few minutes annealing. This synthesis leads to improved device performance in planar heterojunction architectures and answers a critical question as to the role of the anion and excess organic component during crystallization. Our work paves the way to tune the crystal growth kinetics by simple chemistry.

  1. Stabilization of Submicron Calcium Oxalate Suspension by Chondroitin Sulfate C May Be an Efficient Protection from Stone Formation

    PubMed Central

    Li, Jun-Jun; Xue, Jun-Fa; Ouyang, Jian-Ming

    2013-01-01

    The influences of chondroitin sulfate C (C6S) on size, aggregation, sedimentation, and Zeta potential of sub-micron calcium oxalate monohydrate (COM) and calcium oxalate dihydrate (COD) crystallites with mean sizes of about 330 nm were investigated using an X-ray diffractometer, nanoparticle size Zeta potential analyzer, ultraviolet spectrophotometer, and scanning electron microscope, after which the results were compared with those of micron-grade crystals. C6S inhibited the conversion of COD to COM and the aggregation of COM and COD crystallitesis; it also decreased their sedimentation rate, thus increasing their stability in aqueous solution. The smaller the size of the COD crystallites, the easier they can be converted to COM. The stability of sub-micron COD was worse than that of micron-grade crystals. C6S can inhibit the formation of calcium oxalate stones. PMID:24382950

  2. IONIZED GAS KINEMATICS AT HIGH RESOLUTION. V. [Ne ii], MULTIPLE CLUSTERS, HIGH EFFICIENCY STAR FORMATION, AND BLUE FLOWS IN HE 2–10

    SciTech Connect

    Beck, Sara; Turner, Jean; Lacy, John; Greathouse, Thomas

    2015-11-20

    We measured the 12.8 μm [Ne ii] line in the dwarf starburst galaxy He 2–10 with the high-resolution spectrometer TEXES on the NASA IRTF. The data cube has a diffraction-limited spatial resolution of ∼1″ and a total velocity resolution, including thermal broadening, of ∼5 km s{sup −1}. This makes it possible to compare the kinematics of individual star-forming clumps and molecular clouds in the three dimensions of space and velocity, and allows us to determine star formation efficiencies. The kinematics of the ionized gas confirm that the starburst contains multiple dense clusters. From the M/R of the clusters and the ≃30%–40% star formation efficiencies, the clusters are likely to be bound and long lived, like globulars. Non-gravitational features in the line profiles show how the ionized gas flows through the ambient molecular material, as well as a narrow velocity feature, which we identify with the interface of the H ii region and a cold dense clump. These data offer an unprecedented view of the interaction of embedded H ii regions with their environment.

  3. A possible formation channel for blue hook stars in globular cluster II - Effects of metallicity, mass ratio, tidal enhancement efficiency and helium abundance

    NASA Astrophysics Data System (ADS)

    Lei, Zhenxin; Zhao, Gang; Zeng, Aihua; Shen, Lihua; Lan, Zhongjian; Jiang, Dengkai; Han, Zhanwen

    2016-09-01

    Employing tidally enhanced stellar wind, we studied in binaries the effects of metallicity, mass ratio of primary to secondary, tidal enhancement efficiency and helium abundance on the formation of blue hook (BHk) stars in globular clusters (GCs). Totally, 28 sets of binary models combined with different input parameters are studied. For each set of binary model, we presented the range of initial orbital periods which is needed to produce BHk stars in binaries. All the binary models could produce BHk stars within different range of initial orbital periods. We also compared our results with the observation in the Teff-logg diagram of GC NGC 2808 and ω Cen. Most of the BHk stars in these two GCs locate well in the region predicted by our theoretical models, especially when C/N enhanced model atmospheres is considered. We found that mass ratio of primary to secondary and tidal enhancement efficiency have little effects on the formation of BHk stars in binaries, while metallicity and helium abundance would play important roles, especially for helium abundance. Specifically, with helium abundance increasing in binary models, the space range of initial orbital periods needed to produce BHk stars becomes obviously wider, regardless of other input parameters adopted. Our results were discussed with recent observations and other theoretical models.

  4. Probing chromium(III) from chromium(VI) in cells by a fluorescent sensor

    NASA Astrophysics Data System (ADS)

    Hu, Xiangquan; Chai, Jie; Liu, Yanfei; Liu, Bin; Yang, Binsheng

    2016-01-01

    Cellular uptake of Cr(VI), followed by its reduction to Cr(III) with the formation of kinetically inert Cr(III) complexes, is a complex process. To better understand its physiological and pathological functions, efficient methods for the monitoring of Cr(VI) are desired. In this paper a selective fluorescent probe L, rhodamine hydrazide bearing a benzo[b]furan-2-carboxaldehyde group, was demonstrated as a red chemosensor for Cr(III) at about 586 nm. This probe has been used to probe Cr(III) which is reduced from Cr(VI) by reductants such as glutathione (GSH), vitamin C, cysteine (Cys), H2O2 and Dithiothreitol (DTT) by fluorescence spectra. Cr(VI) metabolism in vivo is primarily driven by Vc and GSH. Vc could reduce CrO42 - to Cr(III) in a faster rate than GSH. The indirectly detection limit for Cr(VI) by L + GSH system was determined to be 0.06 μM at pH = 6.2. Moreover, the confocal microscopy image experiments indicated that Cr(VI) can be reduced to Cr(III) inside cells rapidly and the resulted Cr(III) can be captured and imaged timely by L.

  5. Probing chromium(III) from chromium(VI) in cells by a fluorescent sensor.

    PubMed

    Hu, Xiangquan; Chai, Jie; Liu, Yanfei; Liu, Bin; Yang, Binsheng

    2016-01-15

    Cellular uptake of Cr(VI), followed by its reduction to Cr(III) with the formation of kinetically inert Cr(III) complexes, is a complex process. To better understand its physiological and pathological functions, efficient methods for the monitoring of Cr(VI) are desired. In this paper a selective fluorescent probe L, rhodamine hydrazide bearing a benzo[b]furan-2-carboxaldehyde group, was demonstrated as a red chemosensor for Cr(III) at about 586 nm. This probe has been used to probe Cr(III) which is reduced from Cr(VI) by reductants such as glutathione (GSH), vitamin C, cysteine (Cys), H2O2 and Dithiothreitol (DTT) by fluorescence spectra. Cr(VI) metabolism in vivo is primarily driven by Vc and GSH. Vc could reduce CrO4(2-) to Cr(III) in a faster rate than GSH. The indirectly detection limit for Cr(VI) by L+GSH system was determined to be 0.06 μM at pH=6.2. Moreover, the confocal microscopy image experiments indicated that Cr(VI) can be reduced to Cr(III) inside cells rapidly and the resulted Cr(III) can be captured and imaged timely by L.

  6. The EMPIRE Survey: Systematic Variations in the Dense Gas Fraction and Star Formation Efficiency from Full-disk Mapping of M51

    NASA Astrophysics Data System (ADS)

    Bigiel, Frank; Leroy, Adam K.; Jiménez-Donaire, Maria J.; Pety, Jérôme; Usero, Antonio; Cormier, Diane; Bolatto, Alberto; Garcia-Burillo, Santiago; Colombo, Dario; González-García, Manuel; Hughes, Annie; Kepley, Amanda A.; Kramer, Carsten; Sandstrom, Karin; Schinnerer, Eva; Schruba, Andreas; Schuster, Karl; Tomicic, Neven; Zschaechner, Laura

    2016-05-01

    We present the first results from the EMPIRE survey, an IRAM large program that is mapping tracers of high-density molecular gas across the disks of nine nearby star-forming galaxies. Here, we present new maps of the 3 mm transitions of HCN, HCO+, and HNC across the whole disk of our pilot target, M51. As expected, dense gas correlates with tracers of recent star formation, filling the “luminosity gap” between Galactic cores and whole galaxies. In detail, we show that both the fraction of gas that is dense, {f}{dense} traced by HCN/CO, and the rate at which dense gas forms stars, {{SFE}}{dense} traced by IR/HCN, depend on environment in the galaxy. The sense of the dependence is that high-surface-density, high molecular gas fraction regions of the galaxy show high dense gas fractions and low dense gas star formation efficiencies. This agrees with recent results for individual pointings by Usero et al. but using unbiased whole-galaxy maps. It also agrees qualitatively with the behavior observed contrasting our own Solar Neighborhood with the central regions of the Milky Way. The sense of the trends can be explained if the dense gas fraction tracks interstellar pressure but star formation occurs only in regions of high density contrast.

  7. The pam1 gene is required for meiotic bouquet formation and efficient homologous synapsis in maize (Zea mays L.).

    PubMed Central

    Golubovskaya, Inna N; Harper, Lisa C; Pawlowski, Wojciech P; Schichnes, Denise; Cande, W Zacheus

    2002-01-01

    The clustering of telomeres on the nuclear envelope (NE) during meiotic prophase to form the bouquet arrangement of chromosomes may facilitate homologous chromosome synapsis. The pam1 (plural abnormalities of meiosis 1) gene is the first maize gene that appears to be required for telomere clustering, and homologous synapsis is impaired in pam1. Telomere clustering on the NE is arrested or delayed at an intermediate stage in pam1. Telomeres associate with the NE during the leptotene-zygotene transition but cluster slowly if at all as meiosis proceeds. Intermediate stages in telomere clustering including miniclusters are observed in pam1 but not in wild-type meiocytes. The tight bouquet normally seen at zygotene is a rare event. In contrast, the polarization of centromeres vs. telomeres in the nucleus at the leptotene-zygotene transition is the same in mutant and wild-type cells. Defects in homologous chromosome synapsis include incomplete synapsis, nonhomologous synapsis, and unresolved interlocks. However, the number of RAD51 foci on chromosomes in pam1 is similar to that of wild type. We suggest that the defects in homologous synapsis and the retardation of prophase I arise from the irregularity of telomere clustering and propose that pam1 is involved in the control of bouquet formation and downstream meiotic prophase I events. PMID:12524364

  8. High-throughput analytical techniques for multiresidue, multiclass determination of 653 pesticides and chemical pollutants in tea--Part III: Evaluation of the cleanup efficiency of an SPE cartridge newly developed for multiresidues in tea.

    PubMed

    Pang, Guo-Fang; Fan, Chun-Lin; Chang, Qiao-Ying; Li, Yan; Kang, Jian; Wang, Wen-Wen; Cao, Jing; Zhao, Yan-Bing; Li, Nan; Li, Zeng-Yin; Chen, Zong-Mao; Luo, Feng-Jian; Lou, Zheng-Yun

    2013-01-01

    A comparative study was conducted over three stages on the cleanup efficiency of SPE cartridge Cleanert TPT, newly developed for multigroups of pesticide residues in tea. In Stage I, different SPE cartridges C18, graphite carbon black (GCB), primary secondary amine (PSA), and amino (NH2) were purchased and combined into 12 different sequences. Through the comparative test on cleanup efficiency of 84 representative pesticides in tea, Envi-Carb GCB + PSA with a good cleanup effect was selected. In Stage II, GC/MS test results from the comparative study of the extraction efficiency of 201 pesticides spiked into green tea and Woolong tea with Cleanert TPT and Envi-Carb + PSA SPE showed that average recoveries fell within 70-110% and RSD <20% for 193 and 184 pesticides, respectively, for green tea, accounting for 96.0 and 91.0% of the total number, respectively. GC/MS/MS test results also found 193 and 184 pesticides, respectively, meeting the recovery and RSD conditions, accounting for 96.0 and 91.5%, respectively, of the total number. For Woolong tea samples, GC/MS results showed that with Cleanert TPT and Envi-Carb + PSA SPE for cleanup, there were 192 and 177 pesticides, respectively, meeting the conditions, accounting for 95.5 and 88.1% of the total number, respectively. GC/MS/MS results demonstrated that there were 195 and 184 pesticides, respectively, meeting the conditions, accounting for 97.0 and 91.5% of the total number, respectively. It was seen that Cleanert TPT was superior to Envi-Carb + PSA in cleanup efficiency, whether for green or Woolong tea samples, or GC/MS or GC/MS/MS determination. In Stage III, 61104 results of the average content value of pesticides and RSD (two teas xtwo Youden pair concentrations x two kinds of SPE cartridges x two instruments x 19 tests x 201 pesticides) were derived from the 19 times stability tests over 3 months by paralleling three samples every 5 days via two instruments with two kinds of SPE cartridges for cleanup

  9. Herpes Simplex Virus 1 ICP22 but Not US1.5 Is Required for Efficient Acute Replication in Mice and VICE Domain Formation

    PubMed Central

    Mostafa, Heba H.

    2013-01-01

    The herpes simplex virus 1 (HSV-1) immediate-early protein, infected cell protein 22 (ICP22), is required for efficient replication in restrictive cells, for virus-induced chaperone-enriched (VICE) domain formation, and for normal expression of a subset of viral late proteins. Additionally, ICP22 is important for optimal acute viral replication in vivo. Previous studies have shown that the US1 gene that encodes ICP22, produces an in-frame, N-terminally truncated form of ICP22, known as US1.5. To date, studies conducted to characterize the functions of ICP22 have not separated its functions from those of US1.5. To determine the individual roles of ICP22 and US1.5, we made viral mutants that express either ICP22 with an M90A mutation in the US1.5 initiation codon (M90A) or US1.5 with three stop codons introduced upstream of the US1.5 start codon (3×stop). Our studies showed that, in contrast to M90A, 3×stop was unable to replicate efficiently in the eyes and trigeminal ganglia of mice during acute infection, to efficiently establish a latent infection, or to induce VICE domain formation and was only mildly reduced in its replication in restrictive HEL-299 cells and murine embryonic fibroblasts (MEFs). Both mutants enhanced the expression of the late viral proteins virion host shutoff (vhs) and glycoprotein C (gC) and inhibited viral gene expression mediated by HSV-1 infected cell protein 0 (ICP0). When we tested our mutants' sensitivity to type I interferon (beta interferon [IFN-β]) in restrictive cells, we noticed that the plating of the ICP22 null (d22) and 3×stop mutants was reduced by the addition of IFN-β. Overall, our data suggest that US1.5 partially complements the functions of ICP22. PMID:24089574

  10. QUANTIFYING THE SIGNIFICANCE OF THE MAGNETIC FIELD FROM LARGE-SCALE CLOUD TO COLLAPSING CORE: SELF-SIMILARITY, MASS-TO-FLUX RATIO, AND STAR FORMATION EFFICIENCY

    SciTech Connect

    Koch, Patrick M.; Ho, Paul T. P.; Tang, Ya-Wen

    2012-03-01

    Dust polarization observational results are analyzed for the high-mass star formation region W51 from the largest parent cloud ({approx}2 pc, James Clerk Maxwell Telescope) to the large-scale envelope ({approx}0.5 pc, BIMA array) down to the collapsing core e2 ({approx}60 mpc, Submillimeter Array). Magnetic field and dust emission gradient orientations reveal a correlation which becomes increasingly more tight with higher resolution. The previously developed polarization-intensity-gradient method is applied in order to quantify the magnetic field significance. This technique provides a way to estimate the local magnetic field force compared to gravity without the need of any mass or field strength measurements, solely making use of measured angles which reflect the geometrical imprint of the various forces. All three data sets clearly show regions with distinct features in the field-to-gravity force ratio. Azimuthally averaged radial profiles of this force ratio reveal a transition from a field dominance at larger distances to a gravity dominance closer to the emission peaks. Normalizing these profiles to a characteristic core scale points toward self-similarity. Furthermore, the polarization-intensity-gradient method is linked to the mass-to-flux ratio, providing a new approach to estimate the latter one without mass and field strength inputs. A transition from a magnetically supercritical to a subcritical state as a function of distance from the emission peak is found for the e2 core. Finally, based on the measured radius-dependent field-to-gravity force ratio we derive a modified star formation efficiency with a diluted gravity force. Compared to a standard (free-fall) efficiency, the observed field is capable of reducing the efficiency down to 10% or less.

  11. Sulfuric acid measurements in the exhaust plume of a jet aircraft in flight: Implications for the sulfuric acid formation efficiency

    NASA Astrophysics Data System (ADS)

    Curtius, J.; Arnold, F.; Schulte, P.

    2002-04-01

    Sulfuric acid concentrations were measured in the exhaust plume of a B737-300 aircraft in flight. The measurements were made onboard of the German research aircraft Falcon using the Volatile Aerosol Component Analyzer (VACA). The VACA measures total H2SO4, which is the sum of gaseous H2SO4 and aerosol H2SO4. Measurements took place at distances of 25-200 m behind the B737 corresponding to plume ages of about 0.1-1 seconds. The fuel sulfur content (FSC) of the fuel burned by the B737 engines was alternatively 2.6 and 56 mg sulfur per kilogram fuel (ppmm). H2SO4 concentrations measured in the plume for the 56 ppmm sulfur case were up to ~600 pptv. The average concentration of H2SO4 measured in the ambient atmosphere outside the aircraft plume was 88 pptv, the maximum ambient atmospheric H2SO4 was ~300 pptv. Average efficiencies ɛΔCO2 = 3.3 +/- 1.8% and ɛΔT = 2.9 +/- 1.6% for fuel sulfur conversion to sulfuric acid were inferred when relating the H2SO4 data to measurements of the plume tracers ΔCO2 and ΔT.

  12. Efficient Covalent Bond Formation in Gas-Phase Peptide-Peptide Ion Complexes with the Photoleucine Stapler

    NASA Astrophysics Data System (ADS)

    Shaffer, Christopher J.; Andrikopoulos, Prokopis C.; Řezáč, Jan; Rulíšek, Lubomír; Tureček, František

    2016-04-01

    Noncovalent complexes of hydrophobic peptides GLLLG and GLLLK with photoleucine (L*) tagged peptides G(L* n L m )K (n = 1,3, m = 2,0) were generated as singly charged ions in the gas phase and probed by photodissociation at 355 nm. Carbene intermediates produced by photodissociative loss of N2 from the L* diazirine rings underwent insertion into X-H bonds of the target peptide moiety, forming covalent adducts with yields reaching 30%. Gas-phase sequencing of the covalent adducts revealed preferred bond formation at the C-terminal residue of the target peptide. Site-selective carbene insertion was achieved by placing the L* residue in different positions along the photopeptide chain, and the residues in the target peptide undergoing carbene insertion were identified by gas-phase ion sequencing that was aided by specific 13C labeling. Density functional theory calculations indicated that noncovalent binding to GL*L*L*K resulted in substantial changes of the (GLLLK + H)+ ground state conformation. The peptide moieties in [GL*L*LK + GLLLK + H]+ ion complexes were held together by hydrogen bonds, whereas dispersion interactions of the nonpolar groups were only secondary in ground-state 0 K structures. Born-Oppenheimer molecular dynamics for 100 ps trajectories of several different conformers at the 310 K laboratory temperature showed that noncovalent complexes developed multiple, residue-specific contacts between the diazirine carbons and GLLLK residues. The calculations pointed to the substantial fluidity of the nonpolar side chains in the complexes. Diazirine photochemistry in combination with Born-Oppenheimer molecular dynamics is a promising tool for investigations of peptide-peptide ion interactions in the gas phase.

  13. Efficiently engineered cell sheet using a complex of polyethylenimine–alginate nanocomposites plus bone morphogenetic protein 2 gene to promote new bone formation

    PubMed Central

    Jin, Han; Zhang, Kai; Qiao, Chunyan; Yuan, Anliang; Li, Daowei; Zhao, Liang; Shi, Ce; Xu, Xiaowei; Ni, Shilei; Zheng, Changyu; Liu, Xiaohua; Yang, Bai; Sun, Hongchen

    2014-01-01

    Regeneration of large bone defects is a common clinical problem. Recently, stem cell sheet has been an emerging strategy in bone tissue engineering. To enhance the osteogenic potential of stem cell sheet, we fabricated bone morphogenetic protein 2 (BMP-2) gene-engineered cell sheet using a complex of polyethylenimine–alginate (PEI–al) nanocomposites plus human BMP-2 complementary(c)DNA plasmid, and studied its osteogenesis in vitro and in vivo. PEI–al nanocomposites carrying BMP-2 gene could efficiently transfect bone marrow mesenchymal stem cells. The cell sheet was made by culturing the cells in medium containing vitamin C for 10 days. Assays on the cell culture showed that the genetically engineered cells released the BMP-2 for at least 14 days. The expression of osteogenesis-related gene was increased, which demonstrated that released BMP-2 could effectively induce the cell sheet osteogenic differentiation in vitro. To further test the osteogenic potential of the cell sheet in vivo, enhanced green fluorescent protein or BMP-2-producing cell sheets were treated on the cranial bone defects. The results indicated that the BMP-2-producing cell sheet group was more efficient than other groups in promoting bone formation in the defect area. Our results suggested that PEI–al nanocomposites efficiently deliver the BMP-2 gene to bone marrow mesenchymal stem cells and that BMP-2 gene-engineered cell sheet is an effective way for promoting bone regeneration. PMID:24855355

  14. A physiologically based in silico model for trans-2-hexenal detoxification and DNA adduct formation in human including interindividual variation indicates efficient detoxification and a negligible genotoxicity risk.

    PubMed

    Kiwamoto, R; Spenkelink, A; Rietjens, I M C M; Punt, A

    2013-09-01

    A number of α,β-unsaturated aldehydes are present in food both as natural constituents and as flavouring agents. Their reaction with DNA due to their electrophilic α,β-unsaturated aldehyde moiety may result in genotoxicity as observed in some in vitro models, thereby raising a safety concern. A question that remains is whether in vivo detoxification would be efficient enough to prevent DNA adduct formation and genotoxicity. In this study, a human physiologically based kinetic/dynamic (PBK/D) model of trans-2-hexenal (2-hexenal), a selected model α,β-unsaturated aldehyde, was developed to examine dose-dependent detoxification and DNA adduct formation in humans upon dietary exposure. The kinetic model parameters for detoxification were quantified using relevant pooled human tissue fractions as well as tissue fractions from 11 different individual subjects. In addition, a Monte Carlo simulation was performed so that the impact of interindividual variation in 2-hexenal detoxification on the DNA adduct formation in the population as a whole could be examined. The PBK/D model revealed that DNA adduct formation due to 2-hexenal exposure was 0.039 adducts/10⁸ nucleotides (nt) at the estimated average 2-hexenal dietary intake (0.04 mg 2-hexenal/kg bw) and 0.18 adducts/10⁸ nt at the 95th percentile of the dietary intake (0.178 mg 2-hexenal/kg bw) in the most sensitive people. These levels are three orders of magnitude lower than natural background DNA adduct levels that have been reported in disease-free humans (6.8-110 adducts/10⁸ nt), suggesting that the genotoxicity risk for the human population at realistic dietary daily intakes of 2-hexenal may be negligible. PMID:23864024

  15. POPULATION III HYPERNOVAE

    SciTech Connect

    Smidt, Joseph; Whalen, Daniel J.; Wiggins, Brandon K.; Even, Wesley; Fryer, Chris L.; Johnson, Jarrett L.

    2014-12-20

    Population III supernovae have been of growing interest of late for their potential to directly probe the properties of the first stars, particularly the most energetic events that are visible near the edge of the observable universe. Until now, hypernovae, the unusually energetic Type Ib/c supernovae that are sometimes associated with gamma-ray bursts, have been overlooked as cosmic beacons at the highest redshifts. In this, the latest of a series of studies on Population III supernovae, we present numerical simulations of 25-50 M {sub ☉} hypernovae and their light curves done with the Los Alamos RAGE and SPECTRUM codes. We find that they will be visible at z = 10-15 to the James Webb Space Telescope and z = 4-5 to the Wide-Field Infrared Survey Telescope, tracing star formation rates in the first galaxies and at the end of cosmological reionization. If, however, the hypernova crashes into a dense shell ejected by its progenitor, it is expected that a superluminous event will occur that may be seen at z ∼ 20 in the first generation of stars.

  16. Efficient degradation of atrazine by magnetic porous copper ferrite catalyzed peroxymonosulfate oxidation via the formation of hydroxyl and sulfate radicals.

    PubMed

    Guan, Ying-Hong; Ma, Jun; Ren, Yue-Ming; Liu, Yu-Lei; Xiao, Jia-Yue; Lin, Ling-qiang; Zhang, Chen

    2013-09-15

    Magnetic porous copper ferrite (CuFe2O4) showed a notable catalytic activity to peroxymonosulfate (PMS). More than 98% of atrazine was degraded within 15 min at 1 mM PMS and 0.1 g/L CuFe2O4. In contrast, CuFe2O4 exhibited no obvious catalytic activity to peroxodisulfate or H2O2. Several factors affecting the catalytic performance of PMS/CuFe2O4 were investigated. Results showed that the catalytic degradation efficiency of atrazine increased with PMS and CuFe2O4 doses, but decreased with the increase of natural organic matters concentration. The catalytic oxidation also showed a dependence on initial pH. The presence of bicarbonate stimulated atrazine degradation by PMS/CuFe2O4 at low concentrations but inhibited the degradation at high concentrations. Furthermore, the reactive species for atrazine degradation in PMS/CuFe2O4 system were identified as hydroxyl radical (HO) and sulfate radical (SO4(·-)) through competition reactions of atrazine and nitrobenzene, instead of commonly used alcohol scavenging, which was not a reliable method in metal oxide catalyzed oxidation. Surface hydroxyl groups of CuFe2O4 were a critical part in radical generation and the copper on CuFe2O4 surface was an active site to catalyze PMS. The catalytic degradation of atrazine by PMS/CuFe2O4 was also effective under the background of actual waters.

  17. Cobalt(III) tetraaza-macrocyclic complexes as efficient catalyst for photoinduced hydrogen production in water: Theoretical investigation of the electronic structure of the reduced species and mechanistic insight.

    PubMed

    Gueret, Robin; Castillo, Carmen E; Rebarz, Mateusz; Thomas, Fabrice; Hargrove, Aaron-Albert; Pécaut, Jacques; Sliwa, Michel; Fortage, Jérôme; Collomb, Marie-Noëlle

    2015-11-01

    We recently reported a very efficient homogeneous system for visible-light driven hydrogen production in water based on the cobalt(III) tetraaza-macrocyclic complex [Co(CR)Cl2](+) (1) (CR=2,12-dimethyl-3,7,11,17-tetra-azabicyclo(11.3.1)-heptadeca-1(17),2,11,13,15-pentaene) as a noble metal-free catalyst, with [Ru(II)(bpy)3](2+) (Ru) as photosensitizer and ascorbate/ascorbic acid (HA(-)/H2A) as a sacrificial electron donor and buffer (PhysChemChemPhys 2013, 15, 17544). This catalyst presents the particularity to achieve very high turnover numbers (TONs) (up to 1000) at pH 4.0 at a relative high concentration (0.1mM) generating a large amount of hydrogen and having a long term stability. A similar activity was observed for the aquo derivative [Co(III)(CR)(H2O)2](3+) (2) due to substitution of chloro ligands by water molecule in water. In this work, the geometry and electronic structures of 2 and its analog [Zn(II)(CR)Cl](+) (3) derivative containing the redox innocent Zn(II) metal ion have been investigated by DFT calculations under various oxidation states. We also further studied the photocatalytic activity of this system and evaluated the influence of varying the relative concentration of the different components on the H2-evolving activity. Turnover numbers versus catalyst (TONCat) were found to be dependent on the catalyst concentration with the highest value of 1130 obtained at 0.05 mM. Interestingly, the analogous nickel derivative, [Ni(II)(CR)Cl2] (4), when tested under the same experimental conditions was found to be fully inactive for H2 production. Nanosecond transient absorption spectroscopy measurements have revealed that the first electron-transfer steps of the photocatalytic H2-evolution mechanism with the Ru/cobalt tetraaza/HA(-)/H2A system involve a reductive quenching of the excited state of the photosensitizer by ascorbate (kq=2.5×10(7) M(-1) s(-1)) followed by an electron transfer from the reduced photosensitizer to the catalyst (ket=1.4×10(9) M

  18. Acylation of Antioxidant of Bamboo Leaves with Fatty Acids by Lipase and the Acylated Derivatives' Efficiency in the Inhibition of Acrylamide Formation in Fried Potato Crisps.

    PubMed

    Ma, Xiang; Wang, Erpei; Lu, Yuyun; Wang, Yong; Ou, Shiyi; Yan, Rian

    2015-01-01

    This study selectively acylated the primary hydroxyl groups on flavonoids in antioxidant of bamboo leaves (AOB) using lauric acid with Candida antarctica lipase B in tert-amyl-alcohol. The separation and isolation of acylated derivatives were performed using silica gel column chromatography with a mixture of dichloromethane/diethyl ether/methanol as eluents. Both thin layer chromatography and high-performance liquid chromatography analyses confirmed the high efficiency of the isolation process with the purified orientin-6″-laurate, isoorientin-6″-laurate, vitexin-6″-laurate, and isovitexin-6″-laurate that were obtained. The addition of AOB and acylated AOB reduced acrylamide formation in fried potato crisps. Results showed that 0.05% AOB and 0.05% and 0.1% acylated AOB groups significantly (p < 0.05) reduced the content of acrylamide in potato crisps by 30.7%, 44.5%, and 46.9%, respectively. PMID:26098744

  19. Acylation of Antioxidant of Bamboo Leaves with Fatty Acids by Lipase and the Acylated Derivatives’ Efficiency in the Inhibition of Acrylamide Formation in Fried Potato Crisps

    PubMed Central

    Ma, Xiang; Wang, Erpei; Lu, Yuyun; Wang, Yong; Ou, Shiyi; Yan, Rian

    2015-01-01

    This study selectively acylated the primary hydroxyl groups on flavonoids in antioxidant of bamboo leaves (AOB) using lauric acid with Candida antarctica lipase B in tert-amyl-alcohol. The separation and isolation of acylated derivatives were performed using silica gel column chromatography with a mixture of dichloromethane/diethyl ether/methanol as eluents. Both thin layer chromatography and high-performance liquid chromatography analyses confirmed the high efficiency of the isolation process with the purified orientin-6″-laurate, isoorientin-6″-laurate, vitexin-6″-laurate, and isovitexin-6″-laurate that were obtained. The addition of AOB and acylated AOB reduced acrylamide formation in fried potato crisps. Results showed that 0.05% AOB and 0.05% and 0.1% acylated AOB groups significantly (p < 0.05) reduced the content of acrylamide in potato crisps by 30.7%, 44.5%, and 46.9%, respectively. PMID:26098744

  20. Structure of AscE and induced burial regions in AscE and AscG upon formation of the chaperone needle-subunit complex of ty